KR20190003661A - Pneumatic tire - Google Patents

Abstract

A center main groove formed in a central portion of the tread portion at a center of the tire; a shoulder main groove provided at an outer side in the tire width direction of the center main groove; And a plurality of chamfering portions provided in the center of the tire along the circumferential direction of the tire to change the position of the opening edge in an oblique direction with respect to the tire circumferential direction, A bending groove provided along the circumferential direction of the tire and bent in accordance with the shape of the chamfer of the chamfered portion and a shoulder groove formed between the shoulder groove and the bending groove in the center of the tire and crossing in the circumferential direction of the tire toward the bending groove And one end toward the curved groove is formed in the center portion And has a sub-groove that terminates.

Description

Pneumatic tire

The present invention relates to a pneumatic tire capable of preventing external defects while improving braking performance on a wet road surface and improving anti-abrasion performance.

Conventionally, for example, the pneumatic tire disclosed in Patent Document 1 has at least four circumferential main grooves extending in the tire circumferential direction, and a rib shape defined by the circumferential main grooves A tire according to any one of claims 1 to 3, wherein the tread portion is provided with a plurality of thick portions, and the second thick portion partitioned by the circumferential main groove on the outermost side in the tire width direction And a zigzag fine groove which divides the second thick portion in the tire width direction. According to the pneumatic tire disclosed in Patent Document 1, the edge portion of the tire ground plane is ensured and the braking performance on the wet road surface, which is the wet performance of the tire, is ensured because the second thick portion has the zig- .

Japanese Patent Publication No. 4905599

However, since the zigzag grooves have a bent portion, there is a possibility that a deficiency occurs in the thick portion at the time of removing the mold at the time of molding the tire, and there is a possibility that the appearance defect may occur. Further, since the zigzag grooves have bent portions, differences in stiffness are generated in the vicinity thereof, which may cause uneven wear.

The present invention has been made in view of the above, and an object thereof is to provide a pneumatic tire capable of improving the anti-abrasion performance while preventing defective appearance while ensuring braking performance on a wet road surface.

A pneumatic tire according to the present invention includes a tread portion having a first main groove extending in the tire circumferential direction at a central portion of a tread portion and a second main groove extending in a tire width direction outer side of the first main groove, A second main groove extending in the circumferential direction, a second main groove extending in the circumferential direction, a first main groove formed in the first main groove and the second main groove and continuous in the tire circumferential direction, and a second main groove formed in the peripheral edge of the first main groove And a plurality of chamfering portions which are arranged along the tire circumferential direction so as to vary the position of the opening edge in an oblique direction with respect to the circumferential direction of the tire, And the shape of the chamfer of the chamfered portion extends along the tire circumferential direction A second main groove formed in the second main groove and extending in the tire circumferential direction so as to extend in the tire circumferential direction and extending toward the bending groove, Is provided with a subsidiary groove which terminates in the above-mentioned thick portion.

According to this pneumatic tire, the edge component of the tire ground plane is secured by the bending grooves, and the braking performance on the wet road surface, which is the wet performance of the tire, is ensured. Further, the bending groove is provided to be bent in accordance with the shape of the chamfer of the chamfer provided at the opening edge of the first main groove, and one end of the bending groove terminating in the bending portion is provided. When the mold is released from the bending groove at the time of bending, the bending portion is deformed to the chamfered portion side and the bump groove side to widen the bending groove, so that the dropout of the mold is improved, It is possible to prevent defects from occurring and to prevent appearance defects. Further, the bending groove is bent in accordance with the shape of the chamfer of the chamfered portion provided at the opening edge of the first main groove, and one end toward the bending groove is provided with a groove for terminating in the bending portion. And the grounding pressure is made uniform, so that the anti-abrasion performance can be improved.

In the pneumatic tire of the present invention, it is preferable that the groove width (Wa) is formed in a range of 4% or more and 8% or less with respect to the tire widthwise dimension (W) .

If the groove width Wa of the bending groove is less than 4% with respect to the tire widthwise dimension W of the thick portion, the drainability of the bending groove is lowered and the contribution to braking performance on the wet road surface is reduced. On the other hand, when the groove width Wa of the bending groove exceeds 8% of the width W of the tire in the width direction of the tire, the stiffness of the heavy portion is lowered and the effect of improving the anti-abrasion performance is reduced. Therefore, in order to improve the anti-abrasion performance while ensuring the braking performance on the wet road surface, it is preferable that the groove width Wa of the bending groove is in the range of 4% to 8% with respect to the tire widthwise dimension W .

In the pneumatic tire according to the present invention, the tire widthwise dimension Wb from the chamfered portion to the edge of the chamfered portion at the center line is smaller than the tire widthwise dimension (W) To 20% or more and 45% or less with respect to the total area of the substrate.

If the tire width direction dimension Wb from the center line of the bending groove to the edge of the chamfered portion is less than 20% with respect to the tire widthwise dimension W of the thick portion, the bending groove becomes closer to the chamfered portion, The rigidity of the thick portion between them is lowered, and the effect of improving the anti-abrasion performance is reduced. On the other hand, when the tire width direction dimension Wb from the center line of the bending groove to the edge of the chamfered portion exceeds 45% with respect to the tire widthwise dimension W of the thick portion, It is difficult to secure the length of the groove, so that the drainage of the groove is reduced and the contribution to the braking performance on the wet road surface is reduced. Therefore, in order to improve the anti-abrasion performance while securing the braking performance on the wet road surface, it is preferable that the tire width direction dimension Wb from the center of the bending groove to the edge of the chamfered portion in the center of the bending groove is larger than the tire width direction Is preferably formed in a range of 20% or more and 45% or less with respect to the dimension (W).

In the pneumatic tire of the present invention, the groove depth Ha of the bending groove is formed in a range of 30% or more and 55% or less with respect to the groove depth (H) of the first main groove .

If the groove depth Ha of the bending groove is less than 30% of the groove depth H of the first main groove, the drainability of the bending groove is lowered and the contribution to braking performance on the wet road surface is reduced. On the other hand, when the groove depth Ha of the bending groove exceeds 55% of the groove depth H of the first main groove, the groove depth Ha of the bending groove approaches the groove depth H of the first main groove, When the molding die is released from the bending groove at the time of tire molding, the defects tend to occur in the thick portion and the effect of preventing appearance defects is reduced. Therefore, in order to prevent the appearance defect while securing the braking performance on the wet road surface, the groove depth Ha of the bending groove is formed in the range of 30% or more and 55% or less with respect to the groove depth H of the first main groove .

In the pneumatic tire of the present invention, the chamfer is formed in a triangular shape at the opening edge of the first main groove with a long side and a short side inclined with respect to the tire circumferential direction , The bent groove has a long first slope portion which is inclined in the tire circumferential direction along the long side of the chamfer and a second slope portion which is inclined in the tire circumferential direction along the short side of the chamfer Wherein the angle? Of the first inclined portion with respect to the tire circumferential direction is in a range of 2 占 to 7 占 and the angle? Of the second inclined portion with respect to the tire circumferential direction is 20 占 or more 60 DEG or less.

If the angle? Of the first inclined portion with respect to the tire circumferential direction is less than 2 占 or the angle? With respect to the tire circumferential direction of the second inclined portion is less than 20 占 the bending groove approaches the tire circumferential direction, The contribution to the braking performance on the wet road surface is reduced. On the other hand, if the angle? Of the first inclined portion with respect to the tire circumferential direction exceeds 7 degrees or the angle? With respect to the tire circumferential direction of the second inclined portion exceeds 60 degrees, The effect of improving the anti-abrasion performance is reduced. Further, when the molding die is removed from the bending groove at the time of tire forming, a deficiency is not caused in the thick portion It is easy to get up and the effect of preventing appearance failure is reduced. Therefore, in order to improve the anti-abrasion performance while preventing the appearance failure while securing the braking performance on the wet road surface, the angle? Of the first inclined portion with respect to the tire circumferential direction is in the range of 2 degrees or more and 7 degrees or less, The angle? Of the second inclined portion with respect to the tire circumferential direction is preferably in the range of 20 ° to 60 °.

In the pneumatic tire of the present invention, it is preferable that the chamfered portion has a dimension in the tire width direction (Wc) of 4% or more and 15% or less with respect to the dimension in the tire width direction (W) .

If the dimension Wc in the tire width direction of the chamfered portion is less than 4% with respect to the dimension W in the tire width direction of the thick portion, the drainability of the first main groove is lowered and the contribution to braking performance on the wet road surface is reduced. On the other hand, if the tire width direction dimension Wc of the chamfered portion exceeds 15% with respect to the tire width dimension W of the thick portion, the chamfer is notched significantly in the thick portion, The effect of improving the performance is reduced. Therefore, in order to improve the anti-abrasion performance while ensuring the braking performance on the wet road surface, the tire width direction dimension Wc of the chamfered portion is in the range of 4% or more and 15% or less with respect to the tire width direction dimension W As shown in Fig.

In the pneumatic tire according to the present invention, the chamfered portion is formed so that its tire diameter dimension Hb is in the range of 30% or more and 60% or less with respect to the groove depth (H) of the first main groove .

If the tire radial dimension Hb of the chamfered portion is less than 30% of the groove depth H of the first main groove, the drainability of the first main groove is lowered and the contribution to braking performance on the wet road surface is reduced. On the other hand, if the tire radial dimension (Hb) of the chamfered portion exceeds 60% of the groove depth (H) of the first main groove, the rigidity of the thick portion is lowered and the effect of improving the anti-abrasion performance is reduced. Therefore, in order to improve the anti-abrasion performance while ensuring the braking performance on the wet road surface, it is preferable that the tire radial dimension Hb of the chamfered portion is in the range of 30% or more and 60% or less with respect to the groove depth H of the first main groove As shown in Fig.

Further, in the pneumatic tire according to the present invention, it is preferable that, in a portion where the chamfered portion and the bent groove face each other in the tire width direction, a dimension (Wc) in the tire width direction of the chamfer at the chamfered portion, (Wd) in the tire width direction at the portion of the bending groove facing the tire in the tire width direction are the same, and the tire circumferential dimension (La) of one of the chamfers at the chamfer portion and the tire circumferential dimension The tire circumferential dimension Lb of one bending unit in the portion of the bending groove facing the tire width direction is formed to be the same.

According to this pneumatic tire, the tire width direction dimension Wc of the chamfer is equal to the tire width direction bending range Wd at the portion of the bending groove facing the tire width direction with respect to the chamfer, The tire circumferential dimension La and the tire circumferential dimension Lb of one bending unit in the portion of the bending groove facing the tire width direction are made equal to each other. The bending of the bending grooves becomes parallel, the difference in stiffness in the tire circumferential direction in the portion between the bending grooves is made uniform, and the effect of improving the internal uniaxial performance is remarkably obtained.

In the pneumatic tire of the present invention, it is preferable that the sub-grooves have a dimension in the tire width direction (We) of 40% or more and 50% or less with respect to the dimension in the tire width direction (W) .

If the tire width direction dimension (We) of the auxiliary groove is less than 40% of the tire width direction dimension (W) of the thick portion, the drainability of the subsidiary groove is lowered and the contribution to braking performance on the wet road surface is reduced. On the other hand, if the tire widthwise dimension We of the auxiliary groove exceeds 50% of the tire widthwise dimension W of the thick portion, the stiffness of the thick portion is lowered and the effect of improving the anti-abrasion performance is reduced. Therefore, in order to improve the anti-abrasion performance while securing the braking performance on the wet road surface, the tire widthwise dimension We in the width direction of the sub-grooves is preferably in the range of 40% to 50% .

In the pneumatic tire according to the present invention, the second main grooves are respectively provided on both sides in the tire width direction of the first main groove, and the second main grooves are formed on both sides of the first main groove in the tire width direction, Wherein the chamfered portion is provided at both opening edges of the first main groove, the curved groove is provided in each of the first and second main grooves, the groove is provided in each of the first and second main grooves, Wherein a groove opening area of the first main groove including the chamfered portion is smaller than a groove opening area excluding the chamfered portion in a state where the tread portion is grounded with the flat surface when the normal load is applied and 70% Is formed in a range of 15% or more and 20% or less with respect to a groove opening area of the first main groove.

When the groove opening area of the first main groove including the chamfered portion is larger than 15% of the groove opening area of the first main groove excluding the chamfered portion, the edge effect of the chamfer is lowered. Therefore, The contribution decreases. On the other hand, when the groove opening area of the first main groove including the chamfered portion is larger than 20% with respect to the groove opening area of the first main groove excluding the chamfer portion, the chamfer is largely notched in the thick portion, And the effect of improving the anti-irregular wear performance is reduced. Therefore, in order to improve the anti-abrasion performance while securing the braking performance on the wet road surface, it is preferable that the groove opening area of the first main groove including the chamfer is 15% or more and 20% Or less.

In the pneumatic tire according to the present invention, the second main grooves are respectively provided on both sides in the tire width direction of the first main groove, and the second main grooves are formed on both sides of the first main groove in the tire width direction, Wherein the chamfered portion is provided at both opening edges of the first main groove, the bent groove is provided in each of the first and second main grooves, the sub groove is provided in each of the first and second main grooves, Wherein each of the chamfered portions of both opening edges is provided with the chamfered portion continuous in the tire circumferential direction and a boundary portion in which the chamfered portion is continuous is provided so as to be offset from the tire circumferential direction at each opening edge of the first main groove do.

When the boundary portions in which the chamfers are continuous match each other at the opening edges of the first main groove in the tire circumferential direction, the chamfering does not exist in the circumferential direction of the tire, The contribution to the braking performance on the road surface is reduced, and the hydroplaning performance deteriorates. Therefore, since the chamfered portion is provided in the circumferential direction of the tire at each opening edge of the first main groove, the chamfered portion is always present in the tire circumferential direction, so that the braking performance on the wet road surface can be ensured.

In the pneumatic tire according to the present invention, the second main groove is provided on the outer side of each of the two first main grooves in the tire width direction, and the second main groove is formed on the outer side of the first main groove in the tire- Wherein the chamfered portion is formed only in the opening edge of the first main groove on the outer side in the tire width direction and the bent groove is provided in the first portion of the first main groove, Wherein a groove opening area of the first main groove including the chamfered portion is larger than a groove opening area of the chamfered portion in a state where the tread portion is grounded with the flat surface when the normal load is filled with 70% Is formed in a range of 8% or more and 13% or less with respect to a groove opening area of the first main groove excluding the groove portion.

If the groove opening area of the first main groove including the chamfered portion is larger than 8% with respect to the groove opening area of the first main groove excluding the chamfered portion, the edge effect of the chamfer is lowered. Therefore, The contribution decreases. On the other hand, when the groove opening area of the first main groove including the chamfered portion is larger than 13% with respect to the groove opening area of the first main groove excluding the chamfer portion, the chamfer is largely notched in the thick portion, And the effect of improving the anti-irregular wear performance is reduced. Therefore, in order to improve the anti-abrasion performance while ensuring the braking performance on the wet road surface, the groove opening area of the first main groove including the chamfer is 8% or more and 13% or less of the groove opening area of the first main groove excluding the chamfer, Or less.

In the pneumatic tire of the present invention, it is preferable that the rubber material constituting the tread surface in the tread portion has a rubber hardness at 20 ° C in a range of 62 to 68 inclusive.

If the rubber hardness is less than 62, the rubber strength is lowered and the wear resistance tends to deteriorate. On the other hand, if the rubber hardness exceeds 68, the flexibility of the rubber is lowered and the braking performance on the wet road surface tends to decrease. Therefore, it is desirable that the rubber hardness of the rubber material constituting the tread surface is in the range of 62 to 68 inclusive.

In the pneumatic tire of the present invention, it is preferable that the rubber material constituting the tread surface of the tread has a tan? In the range of 0.60 to 0.80 at 0 占 폚.

When tan? is less than 0.60, the wet performance tends to decrease, that is, the braking performance on a wet road surface. On the other hand, when tan? Exceeds 0.80, the rubber strength tends to decrease, and the toughness of the molded body tends to occur due to the mold removal during tire molding. Therefore, the tan δ at 0 캜 of the rubber material constituting the tread surface is preferably in the range of 0.60 or more and 0.80 or less.

In the pneumatic tire according to the present invention, it is preferable that an edge at an inner side of the tread width in contact with the tread surface in the second main groove and an edge at an end of the first main groove adjacent to the second main groove, The actual profile line in the thick portion formed by the first main groove and the second main groove protrudes outward in the tire radial direction with respect to the hypothetical profile line passing through the respective edge portions on both sides in the tire width direction in contact with the tread surface in the tire Is formed.

According to this pneumatic tire, the actual profile line in the thick portion protrudes outward in the tire radial direction from the hypothetical profile line, and the ground length in the tire circumferential direction in the ground region is increased . That is, the grounding region can be increased in the tire circumferential direction. As a result, the grounding property is improved and the braking performance on the wet road surface can be improved. In addition, since the grounding property is improved, the anti-abrasion performance can be improved.

The pneumatic tire according to the present invention can improve the anti-abrasion performance while preventing defective appearance while ensuring braking performance on a wet road surface.

1 is a plan view of a tread portion of a pneumatic tire according to Embodiment 1 of the present invention.
Fig. 2 is a partially enlarged plan view (Fig. 2 (a)) and a sectional view (Fig. 2 (b)) of the tread portion of the pneumatic tire according to Embodiment 1 of the present invention.
3 is a partially enlarged plan view of a tread portion of another example of a pneumatic tire according to Embodiment 1 of the present invention.
4 is a partially enlarged cross-sectional view of a tread portion of a pneumatic tire according to Embodiment 1 of the present invention.
5 is an explanatory view of a virtual profile line of a tread portion of a pneumatic tire according to Embodiment 1 of the present invention.
6 is a plan view of a tread portion of a pneumatic tire according to Embodiment 2 of the present invention.
Fig. 7 is a partially enlarged plan view (Fig. 7 (a)) and a sectional view (Fig. 7 (b)) of the tread portion of the pneumatic tire according to the second embodiment of the present invention.
8 is a partially enlarged plan view of a tread portion of another example of the pneumatic tire according to the second embodiment of the present invention.
9 is a partially enlarged sectional view of a tread portion of a pneumatic tire according to Embodiment 2 of the present invention.
10 is an explanatory view of a hypothetical profile line of a tread portion of a pneumatic tire according to Embodiment 2 of the present invention.
11 is a chart showing the results of the performance test of the pneumatic tire according to the embodiment of the present invention.
12 is a chart showing the results of the performance test of the pneumatic tire according to the embodiment of the present invention.
13 is a chart showing the results of the performance test of the pneumatic tire according to the embodiment of the present invention.
Fig. 14 is a chart showing the results of a performance test of pneumatic tires according to the embodiment of the present invention. Fig.
Fig. 15 is a chart showing the results of the performance test of the pneumatic tire according to the embodiment of the present invention. Fig.
16 is a chart showing the results of the performance test of the pneumatic tire according to the embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Incidentally, the present invention is not limited to this embodiment. Further, the constituent elements of this embodiment include those which are easily replaceable by those skilled in the art, or substantially the same ones. Further, a plurality of modified examples described in this embodiment can be arbitrarily combined within the range of a person skilled in the art.

[Embodiment 1]

1 is a plan view of a tread portion of a pneumatic tire according to the present embodiment. Fig. 2 is a partially enlarged plan view (Fig. 2 (a)) and a sectional view (Fig. 2 (b)) of the tread portion of the pneumatic tire according to the present embodiment. 3 is a partially enlarged plan view of a tread portion of another example of the pneumatic tire according to the present embodiment. 4 is a partially enlarged sectional view of the tread portion of the pneumatic tire according to the embodiment. 5 is an explanatory view of a hypothetical profile line of the tread portion of the pneumatic tire according to the present embodiment.

In the following description, the tire circumferential direction refers to the circumferential direction with the rotational axis (not shown) of the pneumatic tire 1 as the central axis. The tire width direction refers to a direction parallel to the rotation axis, and the inner side in the tire width direction refers to the side facing the tire equatorial plane (tire equatorial line) CL in the tire width direction and the tire widthwise outer side Refers to the side away from the tire equatorial plane CL. The tire radial direction refers to a direction orthogonal to the rotation axis, and the inner side of the tire radial direction refers to the side of the tire radial direction toward the rotary shaft, and the tire radial outer side refers to a side away from the rotary shaft in the tire radial direction. The tire equatorial plane CL is a plane passing through the center of the tire width of the pneumatic tire 1, as well as perpendicular to the rotation axis. The tire equator line refers to a line along the tire circumferential direction of the pneumatic tire 1 on the tire equatorial plane CL. In the present embodiment, the same symbol "CL" as the tire equatorial plane is attached to the tire equatorial line.

The pneumatic tire 1 of the present embodiment has a tread portion 2 as shown in Fig. The tread portion 2 is made of a rubber material and is exposed from the outermost side in the tire radial direction of the pneumatic tire 1 and the surface thereof becomes the contour of the pneumatic tire 1 as the tread surface 2a.

The tread portion 2 is provided with a plurality of circumferential main grooves 3 extending in the circumferential direction of the tire on the tread surface 2a side by side in the tire width direction . In the present embodiment, the circumferential main groove 3 at the center in the tire width direction is defined as the center groove (first main groove) 3A, and the circumferential main groove 3 is referred to as a shoulder main groove (second main groove) 3B. Note that the circumferential main groove 3 is a groove width of 5 mm or more and 20 mm or less and a groove depth of 5 mm or more and 15 mm or less (dimension from the opening position of the tread surface 2a to the groove bottom).

The center main groove 3A of the circumferential main groove 3 is arranged at the center of the ground in the ground region. The center central portion is an area in the vicinity of the tire equatorial plane CL and in this embodiment the center main groove 3A as the circumferential main groove 3 disposed at the center of the ground is located closest to the tire equatorial plane CL Circumferential main groove 3, and is disposed on the tire equatorial plane CL.

In addition, the grounding region is formed in such a manner that when the pneumatic tire 1 is rimmed in the normal rim and is filled with the normal internal pressure together with 70% of the normal load, the tread portion 2 of the pneumatic tire 1 Is a region where the tread surface 2a contacts the dry, flat road surface. Regular forest is the "standard forest" defined by JATMA, "Design Rim" defined by TRA, or "Measuring Rim" defined by ETRTO. In addition, the normal internal pressure is the maximum value listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or "INFLATION PRESSURES" prescribed by ETRTO. The normal load is the maximum value described in the "maximum load capacity" specified by JATMA, "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or "LOAD CAPACITY" prescribed by ETRTO.

The tread portion 2 is formed with a plurality of (four in this embodiment) sections in the tire width direction on the tread surface 2a by the circumferential main grooves 3. In this embodiment, the center ribs 4A are formed by the center ribs 3A and two rib-like ribs 4 formed by the shoulder ribs 3B on both outer sides of the tire widthwise direction. A rib-shaped bulged portion 4 disposed on the outer side in the tire width direction of each shoulder groove 3B is a shoulder portion 4B.

In the pneumatic tire 1 as described above, the center main groove 3A is formed at the opening edge of the center portion 4A on the side of the shoulder main groove 3B so that the position of the opening edge is changed obliquely with respect to the tire circumferential direction There are provided chamfer portions 5 in which a plurality of chamfer portions 5A are arranged along the tire circumferential direction. Since the center main groove 3A of the present embodiment is provided with the shoulder main grooves 3B at both outer sides of the tire width direction and the center portion 4A at both outer sides in the tire width direction, A base 5 is provided. As shown in Fig. 2 (b), the chamfer 5A is formed such that each corner of the opening edge of the center main groove 3A is notched in a triangular shape on the tread surface 2a of the center portion 4A, As shown in Fig. 2 (a) and Fig. 3, is formed as a triangular concave when viewed from the plane. Specifically, the chamfer 5A has a long side 5a and a short side 5b having different lengths inclined with respect to the tire circumferential direction, and is formed in a triangular shape at the opening edge of the center groove 3A. Incidentally, although not shown in the drawing, the chamfer 5A may be formed in a triangular shape at the opening edge of the center main groove 3A with two sides of the same length inclined with respect to the tire circumferential direction. Therefore, the center main groove 3A has an edge portion inclined with respect to the tire circumferential direction by the chamfered portion 5. Since the center chamfer 3A is formed such that the chamfer portions 5 provided at the opening edges on both sides in the tire width direction are inverted from each other by the chamfer 5A, And is formed in a zigzag shape in which a lightning-like shape in which a straight line is bent several times along the direction of the arrow. The chamfer 5A may be provided continuously in the tire circumferential direction as shown in Fig. 2 (a). As shown in Fig. 3, the chamfer 5A may be provided at intervals 5B in the tire circumferential direction It can be done.

The pneumatic tire 1 of the present embodiment is formed with the bending grooves 6 and the groove 7 in the center portion 4A formed by dividing the center main groove 3A and the shoulder main groove 3B.

The bending grooves 6 are arranged side by side in the tire width direction of the opening edge having the chamfered portion 5 of the center main groove 3A and extending in the tire circumferential direction. The bending groove 6 is formed by bending by being inclined in conformity with the shape of the chamfer 5A of the chamfer 5. [ Concretely, as shown in Figs. 2 (a) and 3, the bending groove 6 has a long first inclined portion 6a inclined in the tire circumferential direction along the long side 5a of the chamfer 5A, And a short second inclined portion 6b which is inclined in the tire circumferential direction along the short side 5b of the chamfer 5A. Since the bending grooves 6 are provided along the tire circumferential direction in conformity with the shape of the triangular chamfer 5A, they are formed in a continuous zigzag shape in which the straight lines are bent several times along the tire circumferential direction have. In the pneumatic tire 1 shown in Fig. 3, since the chamfer 5A is provided so as to extend in the tire circumferential direction with the opening edge of the center groove 3A at the interval 5B in the tire circumferential direction, The bending groove 6 has an intermediate portion 6c extending in the tire circumferential direction and not inclined. The bending grooves 6 divide the center portion 4A into a first center portion 4Aa on the side of the center spur 3A and a second center portion 4Ab on the side of the shoulder spur 3B. Incidentally, the bending groove 6 is a groove width of 1.5 mm or more, less than the circumferential main groove 3, and a groove depth less than the circumferential main groove 3.

The groove 7 is formed between the shoulder groove 3B and the bending groove 6 so as to cross the tire circumferential direction. As shown in Fig. 2 (a) and Fig. 3, the auxiliary groove 7 is formed in such a manner that one end 7a extends in the direction of the bending groove 6 and has an interval between the center and the bending groove 6 4A (the second center-of-gravity portion 4Ab). Specifically, the groove 7 is provided with one end 7a directed toward the short second inclined portion 6b having a large bend of the bending groove 6. [ The other end 7b of the auxiliary groove 7 extends in the direction of the shoulder main groove 3B and communicates with the shoulder main groove 3B. Although not shown in the drawing, the groove 7 is terminated in the center portion 4A (the second center portion 4Ab) so that the other end 7b is spaced from the shoulder groove 3B It can be done. Incidentally, the groove 7 is a groove width of 1.5 mm or more and less than the circumferential main groove 3, and a groove depth less than the circumferential main groove 3.

Thus, the pneumatic tire 1 of the present embodiment has a center main groove (first main groove) 3A extending in the tire circumferential direction at the center of the ground of the tread portion 2, A shoulder main groove 3B extending along the tire circumferential direction on the outside of the tire width direction and a center portion 4A formed by the center main groove 3A and the shoulder main groove 3B and continuous in the tire circumferential direction And a chamfer 5A which is provided at an opening edge of the center main groove 3A on the side of the center portion 4A and which changes the position of the opening edge obliquely with respect to the tire circumferential direction, And the chamfered portion 5 extending in the tire circumferential direction and juxtaposed in the tire width direction of the opening edge provided at the center vertical portion 4A and having the chamfer portion 5 of the center circumferential groove 3A, The shape of the chamfer 5A And is provided between the shoulder main groove 3B and the bending groove 6 in the center portion 4A so as to intersect the tire circumferential direction and extend toward the bending groove 6. The bending groove 6, , And one end (7a) facing the bending groove (6) has a groove (7) terminating in the center portion (4A).

According to this pneumatic tire 1, the edge component of the tire ground plane is secured by the bending grooves 6, and the braking performance on the wet road surface, which is the wet performance of the tire, is ensured. The bent groove 6 is bent in accordance with the shape of the chamfer 5A of the chamfered portion 5 provided at the opening edge of the center main groove 3A and one end 7a facing the bent groove 6 The center portion 4A of the center portion 4A having the bent groove 6 is formed in the center portion 4A of the center portion 4A when the mold is released from the curved groove 6 at the time of tire formation, The center portion 4Aa and the second center portion 4Ab are deformed toward the chamfered portion 5 side and the side groove 7 side so that the bending groove 6 is widened, It is possible to prevent defects in the center portion (4A) at the time and to prevent appearance defects. The bent groove 6 is bent in accordance with the shape of the chamfer 5A of the chamfered portion 5 provided at the opening edge of the center main groove 3A and one end 7a facing the bent groove 6 The rigidity difference of the center portion 4A having the bending grooves 6 is suppressed and the grounding pressure is made uniform by providing the groove 7 that terminates in the center portion 4A of the center portion 4A, .

In the pneumatic tire 1 of the present embodiment, as shown in Figs. 2 (a) and 3, the groove width (opening width) Wa of the bending groove 6 is smaller than the center width 4A to 8% or less with respect to the tire width direction W of the tire.

When the groove width Wa of the bending groove 6 is less than 4% with respect to the tire widthwise dimension W of the center portion 4A, the drainability of the bending groove 6 is lowered, The contribution decreases. On the other hand, when the groove width Wa of the bending groove 6 exceeds 8% of the width W of the center portion 4A in the tire width direction, the rigidity of the center portion 4A is lowered, . Therefore, in order to improve the anti-abrasion performance while ensuring the braking performance on the wet road surface, the groove width Wa of the bending groove 6 is set to be 4% or less of the width W of the center portion 4A in the tire width direction, Or more and 8% or less. The groove width Wa of the bending groove 6 is set to be smaller than the groove width W of the center thick portion 4A in the tire width direction dimension W (W) in order to obtain the effect of improving the anti-abrasion performance while ensuring the braking performance on the wet road surface. ) Is preferably in the range of 5% or more and 7% or less.

In the pneumatic tire 1 of the present embodiment, as shown in Figs. 2 (a) and 3, the bending grooves 6 are formed at the centers of the chamfered portions 5 at the center line S thereof It is preferable that the tire width direction dimension Wb to the edge 5c in the thick portion 4A is formed in the range of 20% or more and 45% or less with respect to the tire width direction dimension W of the center thick portion 4A desirable.

The center line S of the bending groove 6 is a straight line passing through the center of the groove width Wa of the bending groove 6. [ The edge 5c at the center portion 4A of the chamfered portion 5 is formed such that the chamfer 5A of the chamfered portion 5 is located at the edge of the largest notch of the tread surface 2a of the center thick portion 4A to be.

The tire width direction dimension Wb from the center portion 4A of the chamfer 5 to the edge 5c at the center line S of the bending groove 6 is smaller than the tire width direction Wb of the center portion 4A If it is less than 20% of the dimension W, the bending groove 6 becomes closer to the chamfered portion 5, and the rigidity of the center portion 4A between the bending grooves 6 is lowered and the effect of improving the anti-abrasion performance is reduced. The tire width direction dimension Wb from the center portion 4A of the beveled portion 5 to the edge 5c at the center line S of the bending groove 6 is smaller than the dimension Wb of the center portion 4A If the width of the groove 7 exceeds 45% of the widthwise dimension W, the range of arrangement of the groove 7 becomes narrow and the length of the groove 7 becomes difficult to secure. Therefore, the drainability of the groove 7 decreases, The contribution to the braking performance is reduced. The edge 5c at the center portion 4A of the chamfered portion 5 at the center line S of the bending groove 6 is set to be smaller than the edge 5c at the center line S of the bending groove 6, Is preferably formed in a range of 20% or more and 45% or less with respect to the tire width direction dimension (W) of the center thick portion 4A. In order to obtain the effect of improving the anti-abrasion performance while securing the braking performance on the wet road surface, the center portion S of the beveled portion 5 in the center line S of the bending groove 6, It is preferable that the tire width direction dimension Wb to the edge 5c of the center portion 4A is formed in the range of 25% or more and 35% or less with respect to the tire width direction dimension W of the center portion 4A.

2 (b), the groove depth Ha of the bending groove 6 in the pneumatic tire 1 of the present embodiment is set to be equal to the groove depth H of the center main groove 3A ) Is preferably in the range of 30% or more and 55% or less.

If the groove depth Ha of the bending groove 6 is less than 30% of the groove depth H of the center bump 3A, the drainability of the bending groove 6 is lowered and the contribution to braking performance on the wet road surface Lt; / RTI > On the other hand, when the groove depth Ha of the bending groove 6 exceeds 55% of the groove depth H of the center main groove 3A, the groove depth Ha of the bending groove 6 is larger than the groove depth Ha of the center main groove 3A When the molding die is released from the bending grooves 6 at the time of tire formation, the center portion 4A tends to be defected easily and the effect of preventing appearance defects is reduced. The groove depth Ha of the bending groove 6 is preferably not less than 30% and not more than 55% of the groove depth H of the center main groove 3A in order to prevent the appearance failure while securing the braking performance on the wet road surface. Is preferably formed in a range. It is preferable that the groove depth Ha of the bending groove 6 is 35% or more of the groove depth H of the center groove 3A in order to obtain the effect of preventing the appearance defect while ensuring the braking performance on the wet road surface. Or more and 50% or less.

2 (a) and 3, the chamfered portion 5 is formed such that the chamfer 5A is inclined to the long side 5a (5a), which is inclined with respect to the tire circumferential direction, in the pneumatic tire 1 of the present embodiment, Of the chamfer 5A and the short side 5b are formed in the shape of a triangle at the opening edge of the center main groove 3A and the bending groove 6 is formed in a shape of a long length extending in the tire circumferential direction along the long side 5a of the chamfer 5A Is formed by bending a first inclined portion 6a and a short second inclined portion 6b which is inclined in the tire circumferential direction along the short side 5b of the chamfer 5A and the first inclined portion 6a The angle? Of the second inclined portion 6b with respect to the tire circumferential direction is in a range of 20 degrees or more and 60 degrees or less .

If the angle? Of the first inclined portion 6a with respect to the tire circumferential direction is less than 2 占 or the angle? With respect to the tire circumferential direction of the second inclined portion 6b is less than 20 占, 6 are brought close to the tire circumferential direction and the edge effect is lowered, so that the contribution to the braking performance on the wet road surface is reduced. On the other hand, when the angle? Of the first inclined portion 6a with respect to the tire circumferential direction exceeds 7 degrees or the angle? With respect to the tire circumferential direction of the second inclined portion 6b exceeds 60 degrees The rigidity of the center portion 4A is lowered and the effect of improving the anti-abrasion resistance is reduced. Further, since the bending grooves 6 The defects tend to occur in the center portion 4A and the effect of preventing appearance defects is reduced. Therefore, in order to improve the anti-abrasion performance while preventing the appearance defects while securing the braking performance on the wet road surface, it is preferable that the angle? Of the first inclined portion 6a with respect to the tire circumferential direction is not less than 2 degrees and not more than 7 degrees Of the second inclined portion 6b and the angle beta of the second inclined portion 6b with respect to the tire circumferential direction is in the range of 20 DEG to 60 DEG. In order to obtain the effect of improving the anti-abrasion performance while preventing the appearance failure while ensuring the braking performance on the wet road surface, it is preferable that the angle? Of the first inclined portion 6a with respect to the tire circumferential direction is 3 And the angle of the second inclined portion 6b with respect to the tire circumferential direction is preferably in the range of 30 DEG to 45 DEG.

2 (a) and Fig. 3, the chamfered portion 5 of the pneumatic tire 1 according to the present embodiment is formed such that the tire width direction dimension Wc thereof is larger than the center portion 4A, Is preferably formed in a range of 4% or more and 15% or less with respect to the tire width direction dimension (W) of the tire.

If the dimension Wc in the tire width direction of the chamfered portion 5 is less than 4% with respect to the dimension W in the tire width direction of the center portion 4A, the drainability of the center groove 3A is deteriorated and the braking performance Lt; / RTI > On the other hand, if the tire width direction dimension Wc of the chamfered portion 5 exceeds 15% with respect to the tire width direction dimension W of the center portion 4A, the chamfer 5A is formed in the center portion 4A, The rigidity of the center portion 4A is lowered, and the effect of improving the anti-abrasion performance is reduced. Therefore, in order to improve the anti-abrasion performance while ensuring the braking performance on the wet road surface, the tire width direction dimension Wc of the chamfered portion 5 is set to 4 % Or more and 15% or less. Also. The dimension Wc in the tire width direction of the chamfered portion 5 is smaller than the dimension W in the tire width direction of the center thick portion 4A in order to remarkably obtain the effect of improving the anti-abrasion performance while ensuring the braking performance on the wet road surface. , Preferably not less than 6% and not more than 8%.

2 (b), in the chamfered portion 5, the tire radial dimension Hb of the pneumatic tire 1 of the present embodiment is smaller than the groove depth of the center main groove 3A Is preferably 30% or more and 60% or less with respect to the height (H).

When the tire radial dimension Hb of the chamfered portion 5 is less than 30% with respect to the groove depth H of the center groove 3A, the drainability of the center groove 3A is decreased and the braking performance on the wet road surface The contribution decreases. On the other hand, when the tire radial dimension Hb of the chamfered portion 5 exceeds 60% with respect to the groove depth H of the center main groove 3A, the rigidity of the center portion 4A is lowered, . Therefore, in order to improve the anti-abrasion performance while ensuring the braking performance on the wet road surface, the tire radial dimension Hb of the chamfered portion 5 is preferably not less than 30% of the groove depth H of the center main groove 3A And preferably 60% or less. In order to obtain the effect of improving the anti-abrasion performance while ensuring the braking performance on the wet road surface, the tire radial dimension Hb of the chamfered portion 5 is set to be equal to the groove depth H of the center main groove 3A, , Preferably not less than 40% and not more than 55%.

In the pneumatic tire 1 of the present embodiment, as shown in Fig. 2 (a) and Fig. 3, in the portion where the chamfered portion 5 and the bending groove 6 face each other in the tire width direction, The width Wc in the tire width direction of the chamfer 5A in the chamfered portion 5 and the width Wc in the tire width direction in the portion of the bending groove 6 facing the tire widthwise direction with respect to the chamfer 5A And the chamfer 5A of the chamfer 5A and the bending groove 6 facing the chamfer 5A in the tire width direction have the same width Wd, It is preferable that the tire circumferential dimension Lb of one bending unit at the portion of the tire circumferential direction Lb is the same.

With this pneumatic tire 1, the dimension Wc in the tire width direction of the chamfer 5A and the dimension Wc in the tire width direction of the portion of the bending groove 6 facing the tire width direction with respect to the chamfer 5A The bending range Wd of the chamfer 5A is the same and the dimension La of the chamfer 5A in the tire circumferential direction is smaller than the size of one bending unit La in the portion of the bending groove 6 facing the tire width direction with respect to the chamfer 5A. The edge shape of the chamfer 5A and the bending of the bending groove 6 become parallel to each other so that the center of the center portion 4A in the tire circumferential direction So that the effect of improving the anti-abrasion performance can be remarkably obtained.

In the pneumatic tire 1 of the present embodiment, as shown in Fig. 2 (a) and Fig. 3, the groove 7 has a dimension in the tire width direction We, Is preferably formed in a range of 40% or more and 50% or less with respect to the tire width direction dimension (W).

The dimension in the tire width direction We of the groove 7 is the dimension in the tire width direction when the groove 7 is projected in the tire circumferential direction.

When the tire widthwise dimension We of the groove 7 is less than 40% of the tire widthwise dimension W of the center portion 4A, the drainability of the groove 7 is lowered and the braking performance The contribution decreases. On the other hand, when the tire widthwise dimension We of the groove 7 exceeds 50% of the center width W of the center portion 4A in the tire width direction, the rigidity of the center portion 4A is lowered, The effect becomes smaller. Therefore, in order to improve the anti-abrasion performance while ensuring the braking performance on the wet road surface, the tire widthwise dimension We of the groove 7 is set to 40% of the tire widthwise dimension W of the center- Or more and 50% or less. In order to obtain the effect of improving the anti-abrasion performance while ensuring the braking performance on the wet road surface, the tire width direction dimension We of the groove 7 is larger than the tire width direction dimension W ) To 43% or more and 46% or less.

In the pneumatic tire 1 of the present embodiment, as shown in Fig. 2 (a) and Fig. 3, the groove 7 is formed so as to extend from the end toward the bending groove 6 to the bending groove 6 It is preferable that the shortest dimension Wf is formed in a range of 7% or more and 20% or less with respect to the tire width direction dimension W of the center thick portion 4A.

If the shortest dimension Wf between the end portion of the groove 7 facing the bending groove 6 and the bending groove 6 is less than 7% with respect to the tire width direction dimension W of the center portion 4A, 4A) is lowered and the effect of improving the anti-abrasion resistance is reduced. On the other hand, when the shortest dimension Wf between the end portion of the groove 7 facing the bending groove 6 and the bending groove 6 exceeds 20% with respect to the tire width direction dimension W of the center portion 4A, The stiffness of the thick portion 4A is increased and the center portion 4A is more likely to be defected when the forming die is out of the bending groove 6 at the time of tire formation and the effect of preventing appearance defects is reduced. Therefore, in order to prevent the appearance failure and improve the anti-abrasion performance, the shortest dimension Wf between the end portion of the groove 7 facing the bending groove 6 and the bending groove 6 is larger than the short dimension Wf of the center portion 4A Is preferably formed in a range of 7% or more and 20% or less with respect to the tire widthwise dimension (W). The minimum length Wf between the end portion of the groove 7 facing the bending groove 6 and the bending groove 6 is smaller than the center of the center of the bending groove 6, Is preferably in the range of 10% or more and 15% or less with respect to the tire widthwise dimension (W) of the thick portion (4A). In order to obtain the same effect, it is preferable that the shortest dimension Wf between the end portion of the groove 7 facing the bending groove 6 and the bending groove 6 is in the range of 2 mm to 5 mm , And more preferably in the range of 3 mm or more and 4 mm or less.

In the pneumatic tire 1 of the present embodiment, as shown in Figs. 1 to 3, shoulder main grooves 3B are respectively provided on both outer sides of the center main grooves 3A in the tire width direction, 4A are divided into a center main groove 3A and a shoulder main groove 3B on both sides in the tire width direction of the center main groove 3A and chamfer portions 5 are provided at both opening edges of the center main groove 3A, The center grooves 4A are provided with the bending grooves 6 and the central grooves 4A are provided with the groove grooves 7. The grooves 7 are provided in the regular rims so as to fill the normal inner pressure, The groove opening area of the center spiral groove 3A including the chamfered portion 5 is set to be smaller than the center opening width of the center portion excluding the chamfered portion 5 in a state where the tread portion 2 is grounded with the flat surface, Is preferably formed in a range of 15% or more and 20% or less with respect to the groove opening area of the main groove (3A).

When the groove opening area of the center main groove 3A including the chamfered portion 5 is larger than 15% with respect to the groove opening area of the center main groove 3A excluding the chamfered portion 5, The edge effect is lowered, so that the contribution to the braking performance on the wet road surface is reduced. On the other hand, when the groove opening area of the center main groove 3A including the chamfered portion 5 is larger than 20% with respect to the groove opening area of the center main groove 3A excluding the chamfered portion 5, Is largely notched in the center portion 4A, the rigidity of the center portion 4A is lowered and the effect of improving the anti-abrasion performance is reduced. Therefore, in order to improve the anti-abrasion performance while securing the braking performance on the wet road surface, the groove opening area of the center groove 3A including the chamfered portion 5 is larger than the center groove 3A (excluding the chamfered portion 5) In the range of not less than 15% and not more than 20% with respect to the groove opening area of the groove. In order to obtain the effect of improving the anti-abrasion performance while ensuring the braking performance on the wet road surface, the groove opening area of the center groove 3A including the chamfered portion 5 is set to be smaller than the chamfered portion 5 Is preferably formed in a range of 17% or more and 19% or less with respect to the groove opening area of the center main groove 3A.

2 (a), in the pneumatic tire 1 of the present embodiment, shoulder main grooves 3B are respectively provided on both sides in the tire width direction of the center main grooves 3A, 4A are divided into a center main groove 3A and a shoulder main groove 3B on both sides in the tire width direction of the center main groove 3A and chamfer portions 5 are provided at both opening edges of the center main groove 3A, The center portion 4A has a curved groove 6 and the central portion 4A has a groove 7. The chamfered portions 5 of both opening edges of the center groove 3 A It is preferable that the chamfer 5A is continuously provided in the tire circumferential direction and the boundary portion A in which the chamfer 5A is continuous is provided to be offset from the tire circumferential direction at each opening edge of the center groove 3A Do.

The chamfer 5A does not exist in the circumferential direction of the tire when the boundary portion A in which the chamfer 5A continues is coincident with the circumferential direction of the tire at the opening edge of the center main groove 3A, The drainage performance deteriorates only in that portion, so that the contribution to the braking performance on the wet road surface is reduced and the hydro-building performance deteriorates. Therefore, since the chamfered portion 5A is always present in the tire circumferential direction because the boundary portion A in which the chamfer 5A continues is shifted from the circumferential direction of the tire at each opening edge of the center groove 3A, The braking performance can be secured.

In the present embodiment, each of the shoulder portions 4B has three circumferential grooves 8 extending in the circumferential direction of the tire along the shoulder groove 3B. Each of the shoulder leg portions 4B is divided into the first shoulder portion 4Ba on the side of the shoulder main groove 3B and the second shoulder portion 4Bb on the outer side in the tire width direction. In addition, the circumferential groove 8 is a groove width of 1.5 mm or more and less than the circumferential main groove 3, and a groove depth of less than the circumferential main groove 3.

Each shoulder portion 4B has a shoulder groove 9 that intersects the tire circumferential direction on the second shoulder portion 4Bb. One end of the shoulder groove 9 passes through the three circumferential grooves 8 and terminates in the first shoulder portion 4Ba and the other end extends outwardly of the tread surface 2a in the tire width direction. Incidentally, the shoulder groove 9 is a groove width of 1.5 mm or more and less than the circumferential main groove 3, and a groove depth less than the circumferential main groove 3.

Each shoulder portion 4B has a shoulder groove 10 formed in the second shoulder portion 4Bb so as to intersect in the tire circumferential direction. The shoulder groove (10) has one end communicating with the circumferential directional groove (8) and the other end extending in the tire width direction outer side of the tread surface (2a). Incidentally, the shoulder grooves 10 are in the range of 0.4 mm or more and 1.2 mm or less, and are formed as so-called sipes.

4 and 5, in the pneumatic tire 1 of the present embodiment, the tread surface 2a of the shoulder main groove 3B in the tire widthwise direction, which is in contact with the tread surface 2a, And an imaginary profile line passing through respective edge portions 3Aa and 3Aa on both sides in the tire width direction in contact with the tread surface 2a in the center main groove 3A adjacent to the shoulder main groove 3B It is preferable that the actual profile line LB in the center portion 4A formed by the center main groove 3A and the shoulder main groove 3B is formed protruding outward in the radial direction of the tire.

The hypothetical profile line LA has an edge section 3Ba on the inner side in the tire width direction in contact with the tread surface 2a of the shoulder main groove 3B and a shoulder main groove 3Ba on the meridional section as described above, 3A and 3Aa on both sides in the tire width direction in contact with the tread surface 2a in the center main groove 3A adjacent to the tread surface 2a and a curvature (Radius of curvature). Further, the virtual profile line LA may have the center point on the tire equatorial plane CL. The actual profile line LB has an edge section 3Ba on the inner side in the tire width direction in contact with the tread surface 2a in the shoulder main groove 3B and an edge section 3Ba on the shoulder main groove 3B adjacent to the shoulder main groove 3B Refers to an arc having a center point on the inner side of the tread surface 2a of the tread surface 2a after passing an edge 3Aa on the side of the shoulder main groove 3B in contact with the tread surface 2a in the center main groove 3A.

According to such an air-inlet tire 1, the actual profile line LB in the center-of-gravity portion 4A protrudes outward in the tire radial direction from the virtual profile line LA, Direction grounding length can be increased compared to the case of the hypothetical profile line LA. That is, the grounding region can be increased in the tire circumferential direction. As a result, the grounding property is improved and the braking performance on the wet road surface can be improved. In addition, since the grounding property is improved, the anti-abrasion performance can be improved. The actual profile line LB is formed so as to protrude outward in the tire radial direction from the imaginary profile line LA in the center portion 4A on both sides in the tire width direction with the tire equatorial plane CL sandwiched therebetween. The effect can be remarkably obtained.

The actual profile line LB in the center-of-gravity portion 4A is larger than the virtual profile line LA in the case of 70% of the normal load along with the normal- The maximum protruding amount Ga protruding outward in the direction is preferably 0.1 mm or more and 0.5 mm or less.

When the maximum projecting amount Ga in the center portion 4A is less than 0.1 mm, the projecting amount of the center portion 4A is small, and it becomes difficult to improve the grounding property. On the other hand, when the maximum projecting amount Ga of the center portion 4A exceeds 0.5 mm, the projecting amount of the center portion 4A becomes excessively large and the grounding length at the center portion of the center portion becomes too large, This causes early wear of the same type of uneven wear. Therefore, in order to improve the braking performance and the anti-abrasion performance on the wet road surface, it is preferable to set the maximum protruding amount Ga outward in the tire radial direction of the center portion 4A to 0.1 mm or more and 0.5 mm or less Do.

5, in the pneumatic tire 1 according to the present embodiment, the ground end T and the tread surface 2a contacting the tread surface 2a in the shoulder main groove 3B are formed on the meridional end face, On the imaginary profile line LA 'continuing to the imaginary profile line LA after passing through the edge sections 3Ba and 3Bb on both sides in the width direction of the shoulder main groove 3B in the tire width direction outer side of the shoulder main groove 3B It is preferable that the profile lines are formed to coincide with each other. That is, the thicker portion projecting outward in the tire radial direction than the hypothetical profile line LA is the center portion 4A on the side of the tire equatorial plane CL rather than the shoulder groove 3B. The circumferential bending grooves 6 are provided in the center portion 4A defined by the center main groove 3A and the shoulder main groove 3B so that the grounding property in the vicinity of the center of the center portion 4A tends to deteriorate The center portion 4A of the tire equator line CL tends to have a low contact pressure with respect to the shoulder portion 4B and therefore the portion of the thick portion protruding outward in the tire radial direction from the hypothetical profile line LA, It is preferable that only the center portion 4A on the tire equatorial plane CL side of the shoulder main groove 3B is preferable.

The ground end T is a tread portion 2 of the pneumatic tire 1 when the pneumatic tire 1 is rimmed in the normal rim and a normal load is applied together with the normal internal pressure, The tread surface 2a of the tread surface 2a contacts the outermost ends of the tire in the tire width direction and continues in the tire circumferential direction.

However, in the present embodiment, the rubber material constituting the tread surface 2a of the tread portion 2 has rubber hardness (JIS-A hardness in accordance with JIS-K6253 under 20 DEG C) Or less. If the rubber hardness is less than 62, the rubber strength is lowered and the wear resistance tends to deteriorate. On the other hand, if the rubber hardness exceeds 68, the flexibility of the rubber is lowered and the braking performance on the wet road surface tends to decrease. Therefore, it is preferable that the rubber hardness of the rubber material constituting the tread surface 2a is in the range of 62 or more and 68 or less.

It is preferable that the rubber material constituting the tread surface 2a of the tread portion 2 has tan? (Tangent loss) at 0.degree. C. of 0.60 or more and 0.80 or less. When tan? is less than 0.60, the wet performance tends to decrease, that is, the braking performance on a wet road surface. On the other hand, when tan? Exceeds 0.80, the rubber strength tends to decrease and the tends to be easily caused by the mold removal during tire molding. Therefore, the tan δ at 0 캜 of the rubber material constituting the tread surface 2a preferably ranges from 0.60 to 0.80.

[Embodiment 2]

6 is a plan view of the tread portion of the pneumatic tire according to the present embodiment. Fig. 7 is a partially enlarged plan view (Fig. 7 (a)) and a sectional view (Fig. 7 (b)) of the tread portion of the pneumatic tire according to the present embodiment. 8 is a partially enlarged plan view of a tread portion of another example of the pneumatic tire according to the present embodiment. 9 is a partially enlarged sectional view of the tread portion of the pneumatic tire according to the embodiment. 10 is an explanatory view of a hypothetical profile line of the tread portion of the pneumatic tire according to the present embodiment.

In the following description, the tire circumferential direction refers to the circumferential direction with the rotational axis (not shown) of the pneumatic tire 11 as the central axis. The tire width direction refers to a direction parallel to the rotation axis, and the inner side in the tire width direction refers to the side facing the tire equatorial plane (tire equatorial line) CL in the tire width direction and the tire widthwise outer side Refers to the side away from the tire equatorial plane CL. The tire radial direction refers to a direction orthogonal to the rotation axis, and the inner side of the tire radial direction refers to the side of the tire radial direction toward the rotary shaft, and the tire radial outer side refers to a side away from the rotary shaft in the tire radial direction. The tire equatorial plane CL is a plane passing through the center of the tire width of the pneumatic tire 11, as well as perpendicular to the rotation axis. The tire equator line refers to a line along the tire circumferential direction of the pneumatic tire 11 on the tire equatorial plane CL. In the present embodiment, the same symbol "CL" as the tire equatorial plane is attached to the tire equatorial line.

The pneumatic tire 11 of the present embodiment has a tread portion 2 as shown in Fig. The tread portion 2 is made of a rubber material and is exposed from the outermost side in the tire radial direction of the pneumatic tire 11 and the surface thereof becomes the contour of the pneumatic tire 11 as the tread surface 2a.

The tread portion 2 is provided with a plurality of circumferential main grooves 3 extending in the circumferential direction of the tire on the tread surface 2a side by side in the tire width direction . In the present embodiment, the two circumferential main grooves 3 at the center in the tire width direction with the tire equatorial plane CL sandwiched therebetween are defined as the center grooves (first main grooves) 3A, Each of the circumferential main grooves 3 on the outer side in the tire width direction is referred to as a shoulder main groove (second main groove) 3B. Note that the circumferential main groove 3 is a groove width of 5 mm or more and 20 mm or less and a groove depth of 5 mm or more and 15 mm or less (dimension from the opening position of the tread surface 2a to the groove bottom).

Each of the center main grooves 3A of the circumferential main groove 3 is disposed at the center of the ground in the ground region. The center main groove 3A as the circumferential main groove 3 disposed in the center of the ground in the present embodiment is a region in the vicinity of the tire equatorial plane CL, Direction main groove (3).

In addition, the grounding region is formed in such a manner that when the pneumatic tire 11 is rimmed in the normal rim and a normal internal pressure is applied together with 70% of the normal load, the tread portion 2 of the pneumatic tire 11 Is a region where the tread surface 2a contacts the dry, flat road surface. Regular forest is the "standard forest" defined by JATMA, "Design Rim" defined by TRA, or "Measuring Rim" defined by ETRTO. In addition, the normal internal pressure is the maximum value listed in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or "INFLATION PRESSURES" prescribed by ETRTO. The normal load is the maximum value described in the "maximum load capacity" specified by JATMA, "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or "LOAD CAPACITY" prescribed by ETRTO.

The tread portion 2 is formed with a plurality of (five in this embodiment) sections in the tire width direction on the tread surface 2a by the circumferential main grooves 3. In this embodiment, one rib-shaped thick portion 41 partitioned between the center main grooves 3A is referred to as a center thick portion 41A. The two rib-like thick portions 41 formed by dividing the center main groove 3A and the shoulder main groove 3B outside the tire width direction are referred to as a middle portion 41B. The rib-shaped thick portion 41 disposed on the outer side in the tire width direction of each shoulder groove 3B is the shoulder thick portion 41C.

In the pneumatic tire 11 as described above, the center main groove 3A is formed at the opening edge of the middle portion 41B of the shoulder main groove 3B side so that the position of the opening edge is changed obliquely with respect to the tire circumferential direction There are provided chamfer portions 5 in which a plurality of chamfer portions 5A are arranged along the tire circumferential direction. Since the center main groove 3A of the present embodiment is provided with the shoulder main groove 3B on the outer side in the tire width direction and the middle portion 41B on the outer side in the tire width direction, And a chamfered portion 5 is provided. 7 (b), the chamfer 5A is formed such that each corner of the opening edge of the center main groove 3A on the tread surface 2a of the middle portion 41B is notched in a triangular shape, As shown in Fig. 7 (a) and Fig. 8, is formed as a triangular concave when viewed from the plane. Specifically, the chamfer 5A has a long side 5a and a short side 5b having different lengths inclined with respect to the tire circumferential direction, and is formed in a triangular shape at the opening edge of the center groove 3A. Incidentally, although not shown in the drawing, the chamfer 5A may be formed in a triangular shape at the opening edge of the center groove 3A with two sides of the same length, which are inclined with respect to the tire circumferential direction. Therefore, the center main groove 3A has an edge portion inclined with respect to the tire circumferential direction by the chamfered portion 5. The chamfer 5A may be provided continuously in the tire circumferential direction as shown in Fig. 7 (a). As shown in Fig. 8, the chamfer 5A may be provided at intervals 5B in the tire circumferential direction It can be done.

The pneumatic tire 11 of the present embodiment has the bending groove 6 and the groove 7 formed in the middle portion 41B formed by the center main groove 3A and the shoulder main groove 3B.

The bending grooves 6 are arranged side by side in the tire width direction of the opening edge having the chamfered portion 5 of the center main groove 3A and extending in the tire circumferential direction. The bending groove 6 is formed by bending by being inclined in conformity with the shape of the chamfer 5A of the chamfer 5. [ Specifically, as shown in Figs. 7 (a) and 8, the bending groove 6 has a long first inclined portion 6a which is inclined in the tire circumferential direction along the long side 5a of the chamfer, (6b) inclined in the tire circumferential direction along the short side (5b) of the tire (5A). Since the bending grooves 6 are provided along the tire circumferential direction in conformity with the shape of the triangular chamfer 5A, they are formed in a continuous zigzag shape in which the straight lines are bent several times along the tire circumferential direction have. In addition, in the pneumatic tire 11 shown in Fig. 8, since the chamfer 5A is provided so as to extend along the circumferential direction of the tire with the opening edge of the center groove 3A at the interval 5B in the tire circumferential direction, The bending groove 6 has an intermediate portion 6c extending in the tire circumferential direction and not inclined. The bending groove 6 divides the middle portion 41B into a first middle portion 41Ba on the side of the center groove 3A and a second middle portion 41Bb on the side of the shoulder main groove 3B. Incidentally, the bending groove 6 is a groove width of 1.5 mm or more, less than the circumferential main groove 3, and a groove depth less than the circumferential main groove 3.

The groove 7 is formed between the shoulder groove 3B and the bending groove 6 so as to cross the tire circumferential direction. As shown in Figs. 7 (a) and 8 (b), the groove 7 is formed so that one end 7a is extended toward the bending groove 6 and has a gap between the bending groove 6 and the middle portion 41B (the second middle part 41Bb). Specifically, the groove 7 is provided with one end 7a directed toward the short second inclined portion 6b having a large bend of the bending groove 6. [ The other end 7b of the auxiliary groove 7 extends in the direction of the shoulder main groove 3B and is connected to the shoulder main groove 3B. Incidentally, although not shown in the drawing, the groove 7 is terminated in the middle portion 41B (second middle portion 41Bb) such that the other end 7b has a gap with the shoulder groove 3B It may be installed. Incidentally, the groove 7 is a groove width of 1.5 mm or more and less than the circumferential main groove 3, and a groove depth less than the circumferential main groove 3.

As described above, the pneumatic tire 11 of the present embodiment has the center main groove (first main groove) 3A extended in the tire circumferential direction at the center of the ground of the tread portion 2, A shoulder main groove 3B extending along the tire circumferential direction on the outer side in the tire width direction and a shoulder main groove 3B extending in the tire circumferential direction and formed by a center main groove 3A and a shoulder main groove 3B, And a chamfer 5A which is provided at an opening edge of the center main groove 3A on the side of the middle portion 41B and which changes the position of the opening edge at an angle with respect to the tire circumferential direction, And the chamfered portion 5 extending in the tire circumferential direction and juxtaposed in the tire width direction of the opening edge provided at the middle portion 41B and having the chamfer portion 5 of the center groove 3A, Of the chamfer (5A) And the shoulder groove 3B and the bending groove 6 in the middle portion 41B so as to intersect the bending groove 6 in the tire circumferential direction , And one end (7a) facing the bending groove (6) has a groove (7) terminating in the middle portion (41B).

According to the pneumatic tire 11, the edge component of the tire ground plane is secured by the bending grooves 6, and the braking performance on the wet road surface, which is the wet performance of the tire, is ensured. The bent groove 6 is bent in accordance with the shape of the chamfer 5A of the chamfered portion 5 provided at the opening edge of the center main groove 3A and one end 7a facing the bent groove 6 And a groove 7 terminating in the middle portion 41B of the middle portion 41B is provided in the middle portion 41B of the middle portion 41B. When the molding die is released from the bending groove 6 at the time of tire formation, The middle portion 41Ba and the second middle portion 41Bb are deformed toward the chamfered portion 5 side and the side groove 7 side so that the bending groove 6 is widened, It is possible to prevent defects in the middle portion 41B and to prevent appearance defects. The bent groove 6 is bent in accordance with the shape of the chamfer 5A of the chamfered portion 5 provided at the opening edge of the center main groove 3A and one end 7a facing the bent groove 6 The provision of the auxiliary grooves 7 terminating in the middle portion 41B allows the rigidity difference of the middle portion 41B having the bending grooves 6 to be suppressed and the grounding pressure to be uniform so that the anti- .

In the pneumatic tire 11 of the present embodiment, as shown in Figs. 7 (a) and 8, the groove width (opening width) Wa of the bending groove 6 is larger than the width 41B is preferably in the range of 4% or more and 8% or less with respect to the tire width direction W of the tire.

If the groove width Wa of the bending groove 6 is less than 4% with respect to the tire widthwise dimension W of the middle portion 41B, the drainability of the bending groove 6 is lowered and the braking performance on the wet road surface The contribution decreases. On the other hand, when the groove width Wa of the bending groove 6 exceeds 8% with respect to the tire width direction dimension W of the middle portion 41B, the rigidity of the middle portion 41B is lowered and the effect of improving the anti- . Therefore, in order to improve the anti-abrasion performance while ensuring the braking performance on the wet road surface, the groove width Wa of the bending groove 6 is set to 4% of the dimension W in the tire width direction of the middle- Or more and 8% or less. The groove width Wa of the bending groove 6 is set to be smaller than the width dimension W of the middle portion 41B in the tire width direction W ) Is preferably in the range of 5% or more and 7% or less.

In the pneumatic tire 11 of the present embodiment, as shown in Fig. 7 (a) and Fig. 8, the bending groove 6 is formed in the center line S of the chamfered portion 5, The tire width direction dimension Wb from the thick portion 41B to the edge 5c is formed in the range of 20% or more and 45% or less with respect to the tire width direction dimension W of the middle portion 41B desirable.

The center line S of the bending groove 6 is a straight line passing through the center of the groove width Wa of the bending groove 6. The edge 5c of the chamfered portion 5 at the middle portion 41B is formed so that the chamfer 5A of the chamfered portion 5 is located at the edge of the portion where the tread face 2a of the middle portion 41B is notched most to be.

The tire width direction dimension Wb from the center line S of the bending groove 6 to the edge 5c at the middle portion 41B of the chamfered portion 5 is smaller than the tire width direction Wb of the middle portion 41B If it is less than 20% of the dimension W, the bending groove 6 becomes closer to the chamfered portion 5, and the rigidity of the middle portion 41B between the bending groove 6 and the chamfered portion decreases. On the other hand, the tire width direction dimension Wb from the middle portion 41B of the beveled portion 5 to the edge 5c in the center line S of the bending groove 6 is smaller than the tire width direction If the width of the groove 7 exceeds 45% of the widthwise dimension W, the range of arrangement of the groove 7 becomes narrow and the length of the groove 7 becomes difficult to secure. Therefore, the drainability of the groove 7 decreases, The contribution to the braking performance is reduced. The edge 5c at the middle portion 41B of the beveled portion 5 at the center line S of the bending groove 6 is set to be smaller than the edge 5c of the beveled portion 5, Is preferably formed in a range of 20% or more and 45% or less with respect to the tire width direction dimension W of the middle portion 41B. In order to obtain the effect of improving the anti-abrasion performance while ensuring the braking performance on the wet road surface, it is preferable that the center portion S of the bending groove 6 is formed in the middle portion 41B of the beveled portion 5 It is preferable that the tire width direction dimension Wb to the edge 5c of the middle portion 41B is formed in the range of 25% or more and 35% or less with respect to the tire width direction dimension W of the middle portion 41B.

7 (b), in the pneumatic tire 11 of the present embodiment, the groove depth Ha of the bending groove 6 is smaller than the groove depth H of the center main groove 3A ) Is preferably in the range of 30% or more and 55% or less.

If the groove depth Ha of the bending groove 6 is less than 30% of the groove depth H of the center bump 3A, the drainability of the bending groove 6 is lowered and the contribution to braking performance on the wet road surface Lt; / RTI > On the other hand, when the groove depth Ha of the bending groove 6 exceeds 55% of the groove depth H of the center main groove 3A, the groove depth Ha of the bending groove 6 is larger than the groove depth Ha of the center main groove 3A When the mold is released from the bending grooves 6 at the time of tire forming, the middle portion 41B is liable to be defected and the effect of preventing the appearance failure is reduced. The groove depth Ha of the bending groove 6 is preferably not less than 30% and not more than 55% of the groove depth H of the center main groove 3A in order to prevent the appearance failure while securing the braking performance on the wet road surface. Is preferably formed in a range. It is preferable that the groove depth Ha of the bending groove 6 is 35% or more of the groove depth H of the center groove 3A in order to obtain the effect of preventing the appearance defect while ensuring the braking performance on the wet road surface. Or more and 50% or less.

In the pneumatic tire 11 of the present embodiment, as shown in Fig. 7 (a) and Fig. 8, the chamfered portion 5 is formed such that the chamfer 5A is inclined to the long side 5a Of the chamfer 5A and the short side 5b are formed in the shape of a triangle at the opening edge of the center main groove 3A and the bending groove 6 is formed in a shape of a long length extending in the tire circumferential direction along the long side 5a of the chamfer 5A Is formed by bending a first inclined portion 6a and a short second inclined portion 6b which is inclined in the tire circumferential direction along the short side 5b of the chamfer 5A and the first inclined portion 6a The angle? Of the second inclined portion 6b with respect to the tire circumferential direction is in a range of 20 degrees or more and 60 degrees or less .

If the angle? Of the first inclined portion 6a with respect to the tire circumferential direction is less than 2 占 or the angle? With respect to the tire circumferential direction of the second inclined portion 6b is less than 20 占, 6 are close to the tire circumferential direction, the edge effect is lowered, so that the contribution to the braking performance on the wet road surface is reduced. On the other hand, when the angle? Of the first inclined portion 6a with respect to the tire circumferential direction exceeds 7 degrees or the angle? With respect to the tire circumferential direction of the second inclined portion 6b exceeds 60 degrees The rigidity of the middle portion 41B is lowered and the effect of improving the anti-abrasion resistance is reduced. Further, since the bending grooves 6 The defects tend to occur in the middle portion 41B and the effect of preventing appearance defects is reduced. Therefore, in order to improve the anti-abrasion performance while preventing the appearance defects while securing the braking performance on the wet road surface, it is preferable that the angle? Of the first inclined portion 6a with respect to the tire circumferential direction is not less than 2 degrees and not more than 7 degrees Of the second inclined portion 6b and the angle beta of the second inclined portion 6b with respect to the tire circumferential direction is in the range of 20 DEG to 60 DEG. In order to obtain the effect of improving the anti-abrasion performance while preventing the appearance failure while ensuring the braking performance on the wet road surface, it is preferable that the angle? Of the first inclined portion 6a with respect to the tire circumferential direction is 3 And the angle of the second inclined portion 6b with respect to the tire circumferential direction is preferably in the range of 30 DEG to 45 DEG.

In the pneumatic tire 11 of the present embodiment, as shown in Figs. 7 (a) and 8, the chamfered portion 5 is formed so that its tire width direction dimension Wc is smaller than the width of the middle- Is preferably formed in a range of 4% or more and 15% or less with respect to the tire width direction dimension (W) of the tire.

If the tire width direction dimension Wc of the chamfered portion 5 is less than 4% with respect to the tire width direction dimension W of the middle portion 41B, the drainability of the center groove 3A is lowered, Lt; / RTI > On the other hand, if the tire width direction dimension Wc of the chamfered portion 5 exceeds 15% with respect to the tire width direction dimension W of the middle-heavy portion 41B, the chamfer 5A is greatly formed in the middle portion 41B The rigidity of the middle portion 41B is lowered, and the effect of improving the anti-abrasion performance is reduced. Therefore, in order to improve the anti-abrasion performance while ensuring the braking performance on the wet road surface, the tire width direction dimension Wc of the chamfered portion 5 is set to 4 % Or more and 15% or less. In order to obtain the effect of improving the anti-abrasion performance while securing the braking performance on the wet road surface, the tire width direction dimension Wc of the chamfered portion 5 is preferably set to the tire width direction dimension W) of 6% or more and 8% or less.

7 (b), in the chamfered portion 5, the tire radial dimension Hb of the pneumatic tire 11 of the present embodiment is smaller than the groove depth of the center main groove 3A Is preferably 30% or more and 60% or less with respect to the height (H).

When the tire radial dimension Hb of the chamfered portion 5 is less than 30% with respect to the groove depth H of the center groove 3A, the drainability of the center groove 3A is decreased and the braking performance on the wet road surface The contribution decreases. On the other hand, when the tire radial dimension Hb of the chamfered portion 5 exceeds 60% of the groove depth H of the center main groove 3A, the rigidity of the middle portion 41B is lowered, . Therefore, in order to improve the anti-abrasion performance while ensuring the braking performance on the wet road surface, the tire radial dimension Hb of the chamfered portion 5 is preferably not less than 30% of the groove depth H of the center main groove 3A And preferably 60% or less. In order to obtain the effect of improving the anti-abrasion performance while ensuring the braking performance on the wet road surface, the tire radial dimension Hb of the chamfered portion 5 is set to be equal to the groove depth H of the center main groove 3A, , Preferably not less than 40% and not more than 55%.

In the pneumatic tire 11 of the present embodiment, as shown in Fig. 7 (a) and Fig. 8, in the portion where the chamfered portion 5 and the bending groove 6 face each other in the tire width direction, The width Wc in the tire width direction of the chamfer 5A in the chamfered portion 5 and the width Wc in the tire width direction in the portion of the bending groove 6 facing the tire widthwise direction with respect to the chamfer 5A And the chamfer 5A of the chamfer 5A and the bending groove 6 facing the chamfer 5A in the tire width direction have the same width Wd, It is preferable that the tire circumferential dimension Lb of one bending unit at the portion of the tire circumferential direction Lb is the same.

With this pneumatic tire 11, the dimension Wc in the tire width direction of the chamfer 5A and the dimension Wc in the tire width direction in the portion of the bending groove 6 facing the tire width direction with respect to the chamfer 5A The bending range Wd of the chamfer 5A is the same and the dimension La of the chamfer 5A in the tire circumferential direction is smaller than the size of one bending unit La in the portion of the bending groove 6 facing the tire width direction with respect to the chamfer 5A. The edge shape of the chamfer 5A and the bending of the bending groove 6 are made parallel to each other and the tire circumferential direction dimension Lb of the middle portion 41B So that the effect of improving the anti-abrasion performance can be remarkably obtained.

In the pneumatic tire 11 of the present embodiment, as shown in Fig. 7 (a) and Fig. 8, the groove 7 has a dimension in the tire width direction We, Is preferably formed in a range of 40% or more and 50% or less with respect to the tire width direction dimension (W).

The tire width direction dimension We of the groove 7 is a dimension in the tire width direction when the groove 7 is projected in the tire circumferential direction.

If the tire widthwise dimension We of the groove 7 is less than 40% of the tire widthwise dimension W of the middle-heavy portion 41B, the drainability of the groove 7 is lowered and the braking performance The contribution decreases. On the other hand, when the tire widthwise dimension We of the groove 7 exceeds 50% of the width W of the middle portion 41B in the tire width direction, the rigidity of the middle portion 41B is lowered, The effect becomes smaller. Therefore, in order to improve the anti-abrasion performance while ensuring the braking performance on the wet road surface, the tire widthwise dimension We of the groove 7 is set to 40% of the tire widthwise dimension W of the middle- Or more and 50% or less. In order to obtain the effect of improving the anti-abrasion performance while ensuring the braking performance on the wet road surface, the tire width direction We of the groove 7 is set to be smaller than the tire width direction dimension W ) To 43% or more and 46% or less.

In the pneumatic tire 11 of the present embodiment, as shown in Fig. 7 (a) and Fig. 8, the groove 7 is formed in such a manner that the end portion of the groove 7 facing the bending groove 6 and the bending groove 6 It is preferable that the shortest dimension Wf is formed in a range of 7% or more and 20% or less with respect to the tire width direction dimension W of the middle portion 41B.

If the shortest dimension Wf between the end portion of the groove 7 facing the bending groove 6 and the bending groove 6 is less than 7% with respect to the tire width direction dimension W of the middle portion 41B, 41B is lowered and the effect of improving the anti-abrasion resistance is reduced. On the other hand, when the shortest dimension Wf between the end portion of the groove 7 facing the bending groove 6 and the bending groove 6 exceeds 20% with respect to the tire width direction dimension W of the middle portion 41B, The stiffness of the thick portion 41B is increased and the middle portion 41B is liable to be damaged when the forming die is released from the bending groove 6 at the time of tire formation and the effect of preventing defective appearance is reduced. Therefore, in order to prevent the appearance failure and improve the anti-abrasion performance, the shortest dimension Wf between the end portion of the groove 7 facing the bending groove 6 and the bending groove 6 is larger than the minimum dimension Wf of the middle portion 41B Is preferably formed in a range of 7% or more and 20% or less with respect to the tire widthwise dimension (W). It is preferable that the shortest dimension Wf between the end portion of the groove 7 facing the bending groove 6 and the bending groove 6 is larger than the width Wf of the middle groove 7 in order to obtain the effect of improving the anti- Is preferably in the range of 10% or more and 15% or less with respect to the tire width direction dimension (W) of the thick portion 41B. In order to obtain the same effect, it is preferable that the shortest dimension Wf between the end portion of the groove 7 facing the bending groove 6 and the bending groove 6 is in the range of 2 mm to 5 mm , And more preferably in the range of 3 mm or more and 4 mm or less.

In the pneumatic tire 11 of the present embodiment, as shown in Figs. 6 to 8, shoulder main grooves 3B are provided outside each of the two center main grooves 3A in the tire width direction, The outer circumferential groove 41B is divided into a center circumferential groove 3A and a shoulder circumferential groove 3B at the outer side in the tire width direction of the center circumferential groove 3A and the chamfered portion 5 is formed only at the outer circumferential edge of the center circumferential groove 3A in the tire width direction. A bent groove 6 is provided in each middle portion 41B and a groove 7 is provided in each middle portion 41B so that the groove is rimmed in the normal rim and is filled with the normal internal pressure The groove opening area of the center spiral groove 3A including the chamfered portion 5 is larger than the groove opening area of the chamfered portion 5 in a state where the tread portion 2 is grounded with the flat surface when 70% In the range of 8% or more and 13% or less with respect to the groove opening area of the center main groove 3A excluding the bar Preferable.

When the groove opening area of the center main groove 3A including the chamfered portion 5 is larger than 15% with respect to the groove opening area of the center main groove 3A excluding the chamfered portion 5, The edge effect is lowered, so that the contribution to the braking performance on the wet road surface is reduced. On the other hand, when the groove opening area of the center main groove 3A including the chamfered portion 5 is larger than 20% with respect to the groove opening area of the center main groove 3A excluding the chamfered portion 5, Is largely notched in the middle portion 41B, the rigidity of the middle portion 41B is lowered and the effect of improving the anti-abrasion performance is reduced. Therefore, in order to improve the anti-abrasion performance while securing the braking performance on the wet road surface, the groove opening area of the center groove 3A including the chamfered portion 5 is larger than the center groove 3A (excluding the chamfered portion 5) In the range of not less than 8% and not more than 13% with respect to the groove opening area of the groove. In order to obtain the effect of improving the anti-abrasion performance while ensuring the braking performance on the wet road surface, the groove opening area of the center groove 3A including the chamfered portion 5 is set to be smaller than the chamfered portion 5 Is preferably formed in a range of 9% or more and 11% or less with respect to the groove opening area of the center main groove (3A).

Incidentally, in the present embodiment, each of the shoulder leg portions 41C has three circumferential grooves 8 extending in the tire circumferential direction along the shoulder groove 3B. The shoulder thick portions 41C are divided by the circumferential grooves 8 into the shoulder main portion 41Ca on the shoulder main groove 3B side and the second shoulder thick portion 41Cb on the outer side in the tire width direction at most. In addition, the circumferential groove 8 is a groove width of 1.5 mm or more and less than the circumferential main groove 3, and a groove depth of less than the circumferential main groove 3.

Each shoulder thick portion 41C has a shoulder groove 9 that intersects the tire circumferential direction on the second shoulder thick portion 41Cb. One end of the shoulder groove 9 passes through the three circumferential grooves 8 and terminates in the first shoulder portion 41Ca and the other end extends outwardly of the tread surface 2a in the tire width direction. Incidentally, the shoulder groove 9 is a groove width of 1.5 mm or more and less than the circumferential main groove 3, and a groove depth less than the circumferential main groove 3.

Each shoulder thick portion 41C has a shoulder groove 10 formed in the second shoulder thick portion 41Cb so as to intersect in the tire circumferential direction. The shoulder groove (10) has one end communicating with the circumferential directional groove (8) and the other end extending in the tire width direction outer side of the tread surface (2a). Incidentally, the shoulder grooves 10 are in the range of 0.4 mm or more and 1.2 mm or less, and are formed as so-called sipes.

9 and 10, in the pneumatic tire 11 of the present embodiment, the tread surface 2a of the shoulder main groove 3B on the meridional end face in the tire width direction inner side in contact with the tread surface 2a And a virtual profile line (3A) passing through respective edge portions 3Aa and 3Aa on both sides in the tire width direction in contact with the tread surface 2a in the center main groove 3A adjacent to the shoulder main groove 3B It is preferable that the actual profile line LB in the middle portion 41B formed by the center main groove 3A and the shoulder main groove 3B is formed protruding outward in the radial direction of the tire.

The hypothetical profile line LA has an edge section 3Ba on the inner side in the tire width direction in contact with the tread surface 2a of the shoulder main groove 3B and a shoulder main groove 3Ba on the meridional section as described above, 3A and 3Aa on both sides in the tire width direction in contact with the tread surface 2a in the center main groove 3A adjacent to the tread surface 2a and a curvature Circle of radius. Further, the virtual profile line LA may have the center point on the tire equatorial plane CL. The actual profile line LB has an edge section 3Ba on the inner side in the tire width direction in contact with the tread surface 2a in the shoulder main groove 3B and an edge section 3Ba on the shoulder main groove 3B adjacent to the shoulder main groove 3B Refers to an arc having a center point on the inner side of the tread surface 2a of the tread surface 2a after passing an edge 3Aa on the side of the shoulder main groove 3B in contact with the tread surface 2a in the center main groove 3A.

According to the pneumatic tire 11 as described above, the actual profile line LB of the middle portion 41B protrudes outward in the tire radial direction from the virtual profile line LA, Direction grounding length can be increased compared to the case of the hypothetical profile line LA. That is, the grounding region can be increased in the tire circumferential direction. As a result, the grounding property is improved and the braking performance on the wet road surface can be improved. In addition, since the grounding property is improved, the anti-abrasion performance can be improved. The actual profile line LB is formed protruding outward in the tire radial direction from the hypothetical profile line LA in the middle portion 41B on both sides in the tire width direction with the tire equatorial plane CL therebetween. The effect can be remarkably obtained.

The actual profile line LB in the middle part 41B is smaller than the actual profile line LB in the tire circumferential direction in comparison with the hypothetical profile line LA when the normal rim is rimmed and the normal internal pressure is filled with 70% The maximum protruding amount Ga protruding outward in the direction is preferably 0.1 mm or more and 0.5 mm or less.

When the maximum protruding amount Ga in the middle thick portion 41B is less than 0.1 mm, the protruding amount of the middle thick portion 41B becomes small, and it becomes difficult to improve the grounding property. On the other hand, when the maximum protruding amount Ga of the middle portion 41B exceeds 0.5 mm, the projecting amount of the middle portion 41B becomes excessively large and the grounding length at the center portion of the center portion becomes too large, It causes the same type of uneven wear as abrasion. Therefore, in order to improve the braking performance and the anti-abrasion performance on the wet road surface, it is preferable that the maximum protruding amount Ga toward the tire radial outer side in the middle portion 41B is 0.1 mm or more and 0.5 mm or less Do.

9 and 10, in the pneumatic tire 11 of the present embodiment, the pneumatic tire 11 of the present embodiment is arranged such that the tire width direction in contact with the tread surface 2a in each center main groove 3A, The actual profile line LD in the center portion 41A of the center portion defined by the center groove 3A in each of the virtual profile lines LA passing through the respective edge portions 3Aa and 3Aa on both sides It is preferable that they are formed to protrude.

According to such an air inlet tire 11, the actual profile line LD in the center portion 41A protrudes outward in the tire radial direction from the virtual profile line LA, Direction grounding length can be increased compared to the case of the hypothetical profile line LA. That is, the grounding region can be increased in the tire circumferential direction. As a result, the grounding property is improved and the braking performance on the wet road surface can be improved. In addition, since the grounding property is improved, the anti-abrasion performance can be improved.

When the normal load is applied and 70% of the normal load is applied to the normal rim, the actual profile line LD of the center thick portion 41A is set to be smaller than the hypothetical profile line LA of the actual profile line LD, The maximum protrusion amount Gc protruding outward in the direction is preferably 0.1 mm or more and 0.5 mm or less.

If the maximum projecting amount Gc of the center thick portion 41A is less than 0.1 mm, the projecting amount of the center thick portion 41A becomes small, and it becomes difficult to improve the grounding property. On the other hand, when the maximum protrusion amount Gc of the center-of-gravity portion 41A exceeds 0.5 mm, the amount of projection of the center-of-gravity portion 41A becomes excessively large and the grounding length at the center portion of the center portion becomes too large, It causes the same type of uneven wear as abrasion. Therefore, in order to improve the braking performance and the anti-abrasion performance on the wet road surface, it is preferable that the maximum projecting amount Gc of the center portion 41A toward the tire radial outside is 0.1 mm or more and 0.5 mm or less Do.

10, in the pneumatic tire 11 according to the present embodiment, the ground end T and the tread surface 2a contacting the tread surface 2a in the shoulder main groove 3B, On the hypothetical profile line LA 'continuing to the virtual profile line LA after passing through the edge portions 3Ba and 3Bb on both sides in the width direction and on the shoulder thick portion 41C outside the tire width direction of the shoulder main groove 3B It is preferable that the profile lines are formed to coincide with each other. That is, the thick portion projecting outward in the tire radial direction from the virtual profile line LA is the middle portion 41B on the tire equatorial plane CL side of the shoulder groove 3B or the center portion 41A furthermore . The middle portion 41B divided by the center main groove 31A and the shoulder main groove 31B is provided with the circumferential bending groove 6 so that the grounding property near the center of the middle portion 41B tends to deteriorate The middle portion 41B of the tire equatorial line CL tends to have a low contact pressure with respect to the shoulder portion 41C and therefore a portion of the thick portion projecting outward in the tire radial direction from the hypothetical profile line LA, It is preferable that it is the middle portion 41B on the tire equatorial plane CL side of the shoulder main groove 3B or the center portion 41A.

The ground end T is a tread portion 2 of the pneumatic tire 11 when the pneumatic tire 11 is rimmed in the normal rim and a normal load is applied together with the normal internal pressure, The tread surface 2a of the tread surface 2a contacts the outermost ends of the tire in the tire width direction and continues in the tire circumferential direction.

However, in the present embodiment, the rubber material constituting the tread surface 2a of the tread portion 2 has rubber hardness (JIS-A hardness in accordance with JIS-K6253 under 20 DEG C) Or less. If the rubber hardness is less than 62, the rubber strength is lowered and the wear resistance tends to deteriorate. On the other hand, if the rubber hardness exceeds 68, the flexibility of the rubber is lowered and the braking performance on the wet road surface tends to decrease. Therefore, it is preferable that the rubber hardness of the rubber material constituting the tread surface 2a is in the range of 62 or more and 68 or less.

It is preferable that the rubber material constituting the tread surface 2a of the tread portion 2 has tan? (Tangent loss) at 0.degree. C. of 0.60 or more and 0.80 or less. When tan? is less than 0.60, the wet performance tends to decrease, that is, the braking performance on a wet road surface. On the other hand, when tan? Exceeds 0.80, the rubber strength tends to decrease and the tends to be easily caused by the mold removal during tire molding. Therefore, the tan δ at 0 캜 of the rubber material constituting the tread surface 2a preferably ranges from 0.60 to 0.80.

Example

In this embodiment, a performance test was conducted on the braking performance, the anti-abrasion performance on the wet road surface, and the vulcanization failure (appearance defect) in addition to the plural types of test tires having different conditions (see Figs. 11 to 16).

In this performance test, the pneumatic tire of the tire size of 195/65 R15 was used as the test tire 1 in the pneumatic tires of the types shown in Figs. 1 and 2 corresponding to the above-mentioned first embodiment. The test tire 1 is assembled and mounted on a regular rim of 15 × 6J, filled with a normal internal pressure (200 kPa), and mounted on a test vehicle (1400 cc · front engine front drive vehicle). In the pneumatic tires of Figs. 6 and 7 corresponding to the second embodiment described above, the pneumatic tire of the tire size 215/45 R17 was used as the test tire 2. The test tire 2 is assembled and mounted on a regular rim of 17 × 7J, filled with a normal internal pressure (200 kPa), and mounted on a test vehicle (1400 cc · front engine front drive vehicle).

The braking performance evaluation method on the wet road surface measures the braking distance from 100 km / h per hour on the wet road surface test course of 1 mm in depth with the above test vehicle. Based on the measurement results, an exponent evaluation is performed based on Conventional Examples 1 and 2 as the reference (100). This evaluation is preferable as the numerical value is larger.

The method for evaluating the anti-abrasion performance is such that the abrasion type is visually confirmed after running the test vehicle on the dry road surface test course at an average speed of 80 km / h for 10,000 km. Based on the visual confirmation result, an exponent evaluation is performed based on Conventional Examples 1 and 2 with reference (100). This evaluation is preferable as the numerical value is larger.

In the evaluation method of the vulcanization failure, 200 test tires 1 and 2 are vulcanized, and the appearance defects of the defects and cracks of the parts are visually confirmed. Based on the visual confirmation result, an exponent evaluation is performed based on Conventional Examples 1 and 2 with reference (100). This evaluation is preferable as the numerical value is larger.

In the embodiment shown in Figs. 11 to 13, the test tire 1 based on the pneumatic tire of the type shown in Figs. 1 and 2 was applied. In the pneumatic tire of Conventional Example 1, the chamfered portion is not provided in the first main groove and the straight groove extending in the tire circumferential direction is provided instead of the bent groove, in contrast to the shapes shown in Figs. 1 and 2 have. The pneumatic tire of Comparative Example 1 has no chamfer portion in the first main groove with respect to the shapes shown in Figs. 1 and 2. On the other hand, the pneumatic tires of Embodiments 1 to 40 are of the shapes shown in Figs. 1 and 2, and a chamfer portion is provided in the first main groove, and a bending groove and a minor groove are also provided.

As shown in the test results of Figs. 11 to 13, the pneumatic tires of Examples 1 to 40 are improved in braking performance on the wet road surface and improved in the anti-abrasion performance and vulcanization failure (outer appearance failure) .

In the embodiment shown in Figs. 14 to 16, the test tire 2 based on the pneumatic tire of the type shown in Figs. 6 and 7 was applied. In the pneumatic tire of Conventional Example 2, the chamfered portion is not provided in the first main groove as compared with the shapes shown in Figs. 6 and 7, and a straight groove extending in the tire circumferential direction is provided instead of the bent groove have. The pneumatic tire of Comparative Example 2 is not provided with chamfer portions in the first main grooves with respect to the shapes shown in Figs. 6 and 7. On the other hand, the pneumatic tires of Examples 41 to 79 are of the types shown in Figs. 6 and 7, and the chamfer portion is provided in the first main groove, and the bending groove and the minor groove are also provided.

As shown in the test results of Figs. 14 to 16, the pneumatic tires of Examples 41 to 79 are improved in braking performance on the wet road surface and improved in the anti-abrasion performance and vulcanization failure (appearance defect) .

1: Pneumatic tire
2: tread portion
2a: Tread face
3A: Center main groove (1st main groove)
3B: Shoulder groove (2nd main groove)
4A: Center of Central (Heavy)
5: Chamfer
5A: Chamfer
5a: Long side
5b: short side
5c: Edge
6: curved groove
6a: first inclined portion
6b: second inclined portion
7: Sub-groove
7a: Once
7b: the other end
A:
S: centerline
11: Pneumatic tire
41B: Middle height (Heavy)

Claims (15)

A first main groove formed to extend along a circumferential direction of the tire at a ground central portion of the tread portion,
A second main groove extending in the tire width direction outside the first main groove along the tire circumferential direction,
A main portion formed by the first main groove and the second main groove and continuing in the tire circumferential direction;
A chamfered portion provided at the opening edge of the first main groove and arranged in plural along the tire circumferential direction so as to change the position of the opening edge diagonally with respect to the tire circumferential direction,
A bending groove provided in the longitudinal section of the first main groove, the bending groove extending in the tire width direction of the opening edge of the first main groove and extending along the tire circumferential direction and bent in accordance with the shape of the chamfer,
A second main groove formed in the second main groove and extending in the tire circumferential direction so as to extend in the direction of the bending groove and an end portion of the second main groove intersecting the bending groove in the tire circumferential direction,
And a pneumatic tire. The method according to claim 1,
Wherein the groove has a groove width (Wa) of 4% or more and 8% or less with respect to a tire width direction dimension (W) of the tire. 3. The method according to claim 1 or 2,
Wherein the bending groove has a dimension in the tire width direction Wb from the center line to the edge in the thick portion of the chamfered portion is 20% or more and 45% or less Of the total length of the pneumatic tire. 4. The method according to any one of claims 1 to 3,
Wherein the bending groove has a groove depth Ha in a range of 30% or more and 55% or less with respect to a groove depth (H) of the first main groove. 5. The method according to any one of claims 1 to 4,
Wherein the chamfer has a long side and a short side where the chamfer is inclined with respect to the tire circumferential direction and is formed in a triangular shape at an opening edge of the first main groove, And a second inclined portion which is inclined in the circumferential direction of the tire along the short side of the chamfer and which is formed by bending the first inclined portion and the second inclined portion which are inclined in the circumferential direction of the tire along the short side of the chamfer, The angle? Of the inclined portion with respect to the tire circumferential direction is in the range of 2 占 to 7 占 and the angle? Of the second inclined portion with respect to the tire circumferential direction is in the range of 20 占 to 60 占Features pneumatic tires. 6. The method according to any one of claims 1 to 5,
Wherein the chamfered portion has a dimension Wc in the tire width direction in a range of 4% or more and 15% or less with respect to a dimension (W) in the tire width direction of the heavy portion. 7. The method according to any one of claims 1 to 6,
Wherein the chamfered portion has a tire radial dimension (Hb) in a range of 30% or more and 60% or less with respect to a groove depth (H) of the first main groove. 8. The method according to any one of claims 1 to 7,
Wherein the chamfered portion has a width Wc in the tire width direction and a width Wc of the chamfer in the widthwise direction of the tire, Of the chamfered portion in the tire width direction is the same as the bending width Wd in the tire width direction of the chamfered portion and the dimension La of the chamfer in the circumferential direction of the tire in the chamfered portion, Is formed to have the same tire circumferential dimension (Lb) of one bending unit in the portion of the tire (A). 9. The method according to any one of claims 1 to 8,
Wherein the groove has a dimension in the tire width direction (We) in a range of 40% or more and 50% or less with respect to a dimension (W) in the tire width direction of the heavy portion. 10. The method according to any one of claims 1 to 9,
Wherein the second main grooves are respectively provided on both sides in the tire width direction of the first main grooves and the first main grooves and the second main grooves are formed on both sides in the tire width direction of the first main groove, Wherein the chamfered portion is provided at both opening edges of the main groove, the curved groove is provided in each of the thick portions, the sub-grooves are provided in each of the thick portions,
Wherein the grooved opening area of the first main groove including the chamfered portion is smaller than the groove opening area of the first main groove including the chamfered portion when the tread portion is grounded with the flat surface when the normal rim is rimmed, Is formed in a range of 15% or more and 20% or less with respect to a groove opening area of the first main groove excluding the chamfered portion. 11. The method according to any one of claims 1 to 10,
Wherein the second main grooves are respectively provided on both sides in the tire width direction of the first main grooves and the first main grooves and the second main grooves are formed on both sides in the tire width direction of the first main groove, Wherein the chamfered portion is provided at both opening edges of the main groove, the curved groove is provided in each of the thick portions, the sub-grooves are provided in each of the thick portions,
Wherein each of the chamfered portions of both the opening edges of the first main groove is provided with the chamfer continuously in the circumferential direction of the tire, and the boundary portion in which the chamfer is continuous is offset from the circumferential direction of the tire at the opening edge of the first main groove And the pneumatic tire is a pneumatic tire. 10. The method according to any one of claims 1 to 9,
Wherein the second main groove is provided on an outer side of each of the two first main grooves in a tire width direction and the thick portion is defined by the first main groove and the second main groove on the outer side in the tire width direction of the first main groove, Wherein the chamfered portion is provided only at an opening edge of the main groove in the tire outer side in the tire width direction, the bent groove is provided in the thick portion, and the sub-
Wherein the grooved opening area of the first main groove including the chamfered portion is smaller than the groove opening area of the first main groove including the chamfered portion when the tread portion is grounded with the flat surface when the normal rim is rimmed, Is formed in a range of 8% or more and 13% or less with respect to a groove opening area of the first main groove excluding the chamfered portion. 13. The method according to any one of claims 1 to 12,
Characterized in that the rubber material constituting the tread surface in the tread portion has a rubber hardness at 20 DEG C in a range of 62 to 68 inclusive. 14. The method according to any one of claims 1 to 13,
Wherein the rubber material constituting the tread surface of the tread has a tan? At 0 占 폚 of 0.60 or more and 0.80 or less. 15. The method according to any one of claims 1 to 14,
The tire according to any one of claims 1 to 3, wherein an end edge of the tire circumferential side in contact with the tread surface in the second main groove and an end edge of the tire circumferential direction in contact with the tread surface in the first main groove Wherein an actual profile line of the thick section formed by the first main groove and the second main groove is formed protruding outward in the tire radial direction with respect to a virtual profile line passing through each edge of the tire, .

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