KR20120056209A - Heavy duty pneumatic tire - Google Patents

Abstract

An object of the present invention is to be able to reduce stone jam while maintaining drainage performance.
It is a heavy-load pneumatic tire 1 provided with at least 1 center main groove 3 which extends continuously in a zigzag form in center area Cr. The center main groove 3 includes a groove bottom 7 and a pair of groove walls 8A and 8B extending from the groove bottom 7 to the tread surface 2t. Each groove wall 8A, 8B extends to the tread surface 2t from the groove bottom side inclined portions 16A and 16B and the tire radially outer ends 16o and 16o of the groove bottom side steep inclined portions 16A and 16B. And tread surface side gentle slope portions 17A and 17B extending at angles α2 and α3 larger than the groove bottom side steep slope portions 16A and 16B. The groove width W1 of the groove bottom side steep slopes 16A and 16B is 2 mm to 8 mm. Each groove wall 8A, 8B includes an inward corner portion 11 of the center main groove 3 and an outward corner portion 12 that is bent to the opposite side to the groove center line 3c. The angles α2 and α3 of the tread surface side gentle slope portions 17A and 17B increase from the outward corner portion 12 to the inward corner portion 11.

Description

Heavy-duty pneumatic tires {HEAVY DUTY PNEUMATIC TIRE}

The present invention relates to a heavy duty pneumatic tire that can reduce stone pinching while maintaining drainage performance.

In order to ensure drainage performance, the tread portion of the pneumatic tire is provided with one to a plurality of relatively wide main grooves which extend continuously in the tire circumferential direction. This main groove is likely to cause so-called stone pinching, for example, in which gravel is kept open when traveling on a construction site or the like. Such pinching is particularly likely to occur in heavy-duty pneumatic tires having a large tread surface and a large groove depth, and there is a problem that rubber cracks and cracks are generated near the main groove.

As a technique for suppressing such pinching, as shown in FIG. 10, the protrusion 35 for preventing pinching is provided at a position apart from the groove wall surface on both sides of the main groove 3 in the longitudinal direction of the main groove as shown in FIG. 10. The technique is proposed (for example, refer patent document 1 below). Such projection 35 is deformed when the main groove 3 bites the gravel, and discharges the gravel from the main groove 3 by the restoring force, thereby reducing the pinching of the stone.

Patent Document 1: Japanese Patent Application Laid-Open No. 2008-296795

However, the above-mentioned projection 35 has a problem that it is easy to deform in contact with the groove wall surface by shrinkage of the main groove 3 at the time of grounding, and that the pinch cannot be sufficiently reduced. Moreover, the protrusion 35 also had the problem that drainage performance tends to decrease in order to reduce the groove volume of the main groove 3.

The present invention has been devised in view of the above facts, and the groove wall of the center main groove extends from the outer end of the groove bottom side steep slope and the groove bottom side steep slope to the tread surface and extends at a larger angle than the groove bottom side steep slope. It is a main object of the present invention to provide a heavy-load pneumatic tire which is configured of a tread surface side light inclined portion, and which is capable of reducing stone pinch while maintaining drainage performance on the basis of changing the angle of the tread surface side light inclined portion.

The invention according to claim 1 of the present invention has at least one center extending in a zigzag shape continuously in a tire circumferential direction with a plurality of bent portions in a center region which is a region of 10% of the tread width centered on the tire equator of the tread portion. A heavy-load pneumatic tire provided with a main groove, wherein the center main groove includes a groove bottom and a pair of groove walls extending from the groove bottom to the tread surface at a groove cross section perpendicular to the groove length direction, wherein each groove wall includes: A groove bottom side steep slope having a height of 10% to 35% of the depth of the groove from the groove bottom and having an angle of 0 ° to 5 ° with respect to the normal direction of the tread surface, and a radial outer end of the tire bottom side of the groove bottom side steep slope. And a tread surface side gentle slope that extends from the tread surface to the tread surface and extends at an angle greater than that of the groove bottom side steep slope. The groove width at the outer end of the inclined portion is 2 to 8 mm, and each of the groove walls is convex toward the zigzag groove center line of the center main groove so as to be bent toward the inward corner and to the opposite side to the groove center line. And an outward corner portion to be bent, wherein the angle of the tread surface side slow slope portion increases from the outward corner portion to the inward corner portion.

Moreover, the invention of Claim 2 is the heavy-load pneumatic tire of Claim 1 whose said angle in the said outward corner part of the said tread surface side gentle slope part is 13 degrees-21 degrees.

Moreover, the invention of Claim 3 is the heavy-load pneumatic tire of Claim 1 or 2 whose said angle in the said inward corner part of the said tread surface side gentle slope part is 21 degrees-29 degrees.

The invention according to claim 4 is the heavy-load pneumatic tire according to claim 1, wherein the chamfered portion is provided at the inward corner portion at the corner of the tread surface side mild slope portion and the tread surface.

Moreover, the invention of Claim 5 is the heavy-load pneumatic tire of Claim 4 which becomes the maximum in the tire axial direction of the said chamfer part at the vertex of the said inward corner part.

The invention according to claim 6 is the heavy-load pneumatic tire according to any one of claims 1 to 5, wherein the groove wall includes a straight portion extending linearly between the inward corner portion and the outward corner portion.

The invention according to claim 7, wherein the groove bottom side steep slope portion is a heavy load according to any one of claims 1 to 6, wherein the inward corner portion and the outward corner portion include curved surfaces curved in an arc shape. It is a pneumatic tire.

In addition, in the invention according to claim 8, the tread portion is provided with at least one shoulder main groove extending continuously in a zigzag shape in the tire circumferential direction in a shoulder region which is an area on both sides of the tire axial direction of the center region. The zigzag amplitude of the shoulder main groove is the heavy-load pneumatic tire according to any one of claims 1 to 7 which is smaller than the zigzag amplitude of the center main groove.

In addition, according to the invention of claim 9, the tread portion is provided with a middle land portion extending in the tire circumferential direction between the center main groove and the shoulder main groove, and the center land portion and the center land portion are provided in the middle land portion. The heavy-load pneumatic tire of Claim 8 in which the middle horizontal groove which communicates between shoulder main grooves is provided.

The invention according to claim 10, wherein the shoulder main groove includes a shoulder groove bottom and a pair of shoulder groove walls extending from the shoulder groove bottom to a tread surface in a groove cross section perpendicular to the groove length direction. The shoulder groove wall includes a shoulder inward corner portion that is convex and curved toward the zigzag groove center line of the shoulder main groove, and a shoulder outward corner portion that is convexly curved to the opposite side to the groove center line, and the shoulder groove wall includes: The heavy-load pneumatic tire according to claim 8 or 9, comprising a shoulder straight portion extending linearly between the shoulder inward corner and the shoulder outward corner.

Moreover, the invention of Claim 11 is the heavy load pneumatic tire of Claim 10 which communicates between the said outward corner part of the said center main groove, and the said shoulder straight part.

In addition, in this specification, unless otherwise indicated, the dimension of each part of a tire shall be a value specified in the normal state of the no load which rim-assembled the normal rim and filled with normal internal pressure.

The term "regular rim" refers to a rim defined by each tire in a standard system including a standard followed by a tire, for example, a standard rim for JATMA, "Design Rim" for TRA, or "Measuring Rim" for ETRTO. do.

The above-mentioned "regular internal pressure" is the air pressure prescribed | regulated by the said tire for every tire, and it is set as the maximum air pressure in the case of JATMA, the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and "INFLATION PRESSURE" in case of ETRTO.

The heavy-load pneumatic tire of the present invention has at least one center main groove extending continuously in a zigzag direction in a tire circumferential direction with a plurality of bent portions in a center region, which is a region of 10% of the tread width centered on the tire equator of the tread portion. Is provided. The center main groove includes a groove bottom and a pair of groove walls extending from the groove bottom to the tread surface at the groove end surface perpendicular to the groove length direction.

Each groove wall has a height of 10% to 35% of the depth of the groove from the groove bottom and a radial direction of the tire bottom side of the groove bottom side inclined portion with an angle of 0 ° to 5 ° with respect to the normal direction of the tread surface, and the radial direction of the tire bottom side of the groove bottom side. And a tread surface side gentle slope that extends from the outer end to the tread surface and extends at an angle greater than that of the groove bottom side steep slope. The groove width at the outer end of the groove bottom steep slope is set to 2 mm to 8 mm. Since the center main groove is formed by the tread surface side slow slope portion, the center main groove reduces the contact area and the pressing force to the bite gravel, and sets the groove width at the outer end of the groove bottom side steep slope to be very small, between the groove bottom side steep slope portions. Since the pinching of stones can be suppressed, the pinching of stones can be reduced.

Each groove wall further includes an inward corner portion that is convex toward the zigzag-shaped groove center line of the center main groove and an outward corner portion that is convex to the opposite side to the groove center line. And the angle of a tread surface side gentle slope part increases over an inward corner part from an outward corner part. Thereby, each groove wall makes the angle of the tread surface side slow slope part adjacent in the width direction of a center main groove different, and can further reduce the contact area and pressing force to gravel, and can effectively reduce the pinching of stones. In particular, as a result of various experiments, when the inward corner portion has a small rigidity, this portion has a function of holding gravel, and stones are easily caught. Therefore, by increasing the angle of the tread surface side mildly inclined portion of the inward corner portion, the bite of the stone can be more surely reduced while increasing the drainage performance.

In addition, since the center main groove can effectively reduce the pinching without providing a projection as in the related art, the drainage performance can be maintained.

BRIEF DESCRIPTION OF THE DRAWINGS The exploded view of the tread part of the heavy load pneumatic tire of this embodiment.
2 is a sectional view taken along the line AA in Fig.
3 is an enlarged view of FIG. 1.
4 is an expanded view showing an enlarged center main groove.
5 is a cross-sectional view taken along line BB of FIG. 4.
6A is a cross-sectional view taken along line CC of FIG. 4, and (b) is a cross-sectional view taken along line DD of FIG. 4.
7 is a perspective view illustrating the chamfer.
8 is an expanded view showing an enlarged shoulder main groove.
FIG. 9A is a cross-sectional view taken along line EE of FIG. 8, and FIG. 9B is a cross-sectional view taken along line FF of FIG. 8.
10 is a developed view of a tread portion of a conventional heavy-load pneumatic tire.

EMBODIMENT OF THE INVENTION Hereinafter, one Embodiment of this invention is described based on drawing.

As shown in FIG. 1, the heavy-duty pneumatic tire (henceforth simply a "tire") 1 of this embodiment, the tread part 2 is a tread centered around tire equator C. As shown in FIG. It is virtually divided into the center area | region Cr which is an area | region 10% of the width TW, and the shoulder area | regions Sh and Sh which are areas of both sides of the tire axial direction of the said center area | region Cr.

Here, the tread width TW is a tire axial distance between the tread ends 2e and 2e in the normal state. When the tread end 2e can be identified by a clear edge in appearance, the tread end 2e is a corresponding edge. However, when the tread end 2e cannot be identified, the tread end 2e is loaded with a normal load on the tire in the normal state and treaded at a camber angle of 0 °. When the part 2 is grounded to the plane, the ground end which is grounded to the plane at the outermost in the tire axial direction is determined as the tread end 2e.

The above-mentioned "normal load" is a load defined for each tire in the standard system including the standard followed by the tire, the maximum load capacity for JATMA, and the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA. If it is the maximum value described in the table and ETRTO, it is set as "LOAD CAPACITY".

In the tread portion 2, at least one extending continuously in a zigzag shape in the tire circumferential direction to the center region Cr, in this embodiment, one center main groove 3 and the shoulder regions Sh , Sh) is provided with at least one shoulder main groove 4 extending continuously in a zigzag shape in the tire circumferential direction, and in this embodiment. Accordingly, the tread portion 2 is divided into a center main groove 3 and a shoulder main groove 4 and extends in the tire circumferential direction, and the middle land portions Rm and Rm, the shoulder main groove 4 and the tread. Two shoulder ribs Rs and Rs, which are divided by the stage 2e and extend in the tire circumferential direction, are formed.

Further, whether the main grooves 3 and 4 belong to the center region Cr or the shoulder region Sh is determined by the amplitude of the groove center lines 3c and 4c of the center main groove 3 and the shoulder main groove 4. Based on the center position.

Further, in the middle land portions Rm and Rm, middle horizontal grooves 9 communicating between the center main groove 3 and the shoulder main groove 4 are spaced apart in the tire circumferential direction. As a result, the middle land portions Rm are formed as block rows. The shoulder ribs Rs and Rs are provided with lug grooves 10 for improving their wear resistance. As a result, the shoulder ribs Rs are formed as rib rows.

As shown in FIG. 1, FIG. 2, the center main groove 3 and the shoulder main groove 4, for example, the groove width W1 in the direction perpendicular to the groove center lines 3c and 4c are 4 of the tread width TW. The groove depth D1 is set at about 3% to 15% of the tread width TW. The center main groove 3 and the shoulder main groove 4 help to improve the drainage performance while securing the pattern rigidity of the tread portion 2. In addition, in this embodiment, although the groove width W1 and the groove depth D1 are set similarly to the center main groove 3 and the shoulder main groove 4, of course, you may make them mutually different.

The center main groove 3 has a plurality of bent portions 13 and extends continuously in a zigzag shape in the tire circumferential direction. Since such zigzag grooves form edges of the tire axial component, the traction performance can be improved compared to, for example, straight grooves. 3 and 5, the center main groove 3 has a groove bottom 7 and a tread surface 2t from the groove bottom 7 in a groove end surface perpendicular to the groove length direction. It consists of a pair of groove wall 8A, 8B extended | stretched to the side.

As shown in Fig. 4, the groove walls 8A and 8B are inwardly cornered portions 11 that are convex and bent toward the zigzag-shaped groove center line 3c of the center main groove 3 in the plan view, and the The outward corner portions 12, which are convex toward the opposite side to the groove center line 3c, are curved, are alternately formed in the tire circumferential direction. Further, the inward corner portion 11 of one groove wall 8A and the outward corner portion 12 of the other groove wall 8B are adjacent in the tire axial direction, and the outward corner portion 12 of one groove wall 8A. ) And the inward corner 11 of the other groove wall 8B are formed adjacent to each other in the tire axial direction.

In FIG. 5, B-B sectional drawing of FIG. 4 is shown. As shown in FIG. 5, each of the groove walls 8A and 8B has a height H1 of 10% to 35% of the groove depth D1 from the groove bottom 7 and is normal to the tread surface 2t. Tread from groove bottom side steep inclined portions 16A, 16B having an angle α1 in the direction of 0 ° to 5 ° and outer end portions 16o, 16o in the radial direction of the groove bottom side steep inclined portions 16A, 16B. The tread surface side gentle slope portions 17A and 17B which extend to the surface 2t and extend at angles α2 and α3 larger than the groove bottom side steep slope portions 16A and 16B are included.

The groove width W2 at the outer ends 16o, 16o of the groove bottom side steep slopes 16A, 16B is set to 2 mm to 8 mm. Thus, by setting the groove width W2 very small, it is possible to suppress the entry of gravel between the groove bottom side steep slopes 16A and 16B, and to hold the angles α2 and α3 of the tread surface side gentle slope portions 17A and 17B. In doing so, it helps to suppress the excessively large groove width W1 of the center main groove 3.

The angles α2 and α3 of the tread surface side gentle slope portions 17A and 17B gradually increase from the outward corner portion 12 to the inward corner portion 11. That is, as shown in Fig. 4 and Figs. 6A and 6B, which are CC and DD cross-sectional views, for example, the angle of one tread surface side mild slope 17A between the bent portions 13A and 13B ( α2 increases from the outward corner portion 12 (angle α2o) over the inward corner portion 11 (angle α2i). Further, as shown in FIGS. 6B and 6A, the angle α3 of the other tread surface side mildly inclined portion 17B is also an inward corner portion from the outward corner portion 12 (angle α3o). It increases over (11) (angle (alpha) 3i). As a result, the tread surface side mildly inclined portions 17A and 17B can change the angles α2 and α3 in the longitudinal direction of the center main groove 3.

Thus, since the center main groove 3 is formed by the tread surface side mildly inclined portions 17A and 17B, most of the groove walls 8A and 8B can reduce the contact area and the pressing force to the bite gravel, and the stones become stuck. It can reduce stone jam. In addition, each groove wall 8A, 8B differs in the angle α2, α3 of the tread surface side mildly inclined portions 17A, 17B adjacent in the width direction of the center main groove 3, so that the contact area and the pressing force to the gravel are different. By making them different in each groove wall 8A, 8B, stone pinching can be reduced effectively.

Further, the tread surface side mildly inclined portions 17A and 17B have a larger rigidity than the outward corner portion 12 and have larger angles α2i and α3i at the inward corner portion 11, which is easier to have a function of holding gravel. By doing so, the bite of the stone can be reduced more reliably while increasing the drainage performance. In addition, since the center main groove 3 can effectively reduce the pinching without providing a projection as in the related art, the drainage performance can also be maintained.

As shown in FIG. 5, when the height H1 of the said groove bottom side steep inclination part 16A, 16B is less than 10% of the groove depth D1 (shown in FIG. 2) of the center main groove 3, it is a middle land. There is a possibility that the stiffness of the portion Rm is lowered and the piece wear resistance performance is deteriorated. On the contrary, when the height H1 exceeds 35% of the groove depth D1, the groove volume of the center main groove 3 becomes excessively small, and there is a fear that the drainage performance may decrease. From this point of view, the height H1 is preferably 10% or more, more preferably 15% or more, more preferably 35% or less, more preferably of the groove depth D1. 30% or less is preferable.

From the same viewpoint, the angle α1 with respect to the normal direction of the tread surface 2t of the groove bottom side steep slopes 16A and 16B is preferably 0 ° or more, more preferably 1 ° or more, and , Preferably it is 5 degrees or less, More preferably, it is 4 degrees or less. In addition, the groove width W2 of the groove bottom side steep slopes 16A and 16B is preferably 2 mm or more, more preferably 4 mm or more, and preferably 8 mm or less, more preferably. 6 mm or less is preferable.

In addition, as shown to Fig.6 (a), (b), angle (alpha) 2o, (alpha) 3o in the outward corner part 12 of the said tread surface side gentle slope part 17A, 17B becomes like this. Preferably it is 13 degrees or more. More preferably, 15 degrees or more are preferable. If the angles α2o and α3o are too small, the contact area and the pressing force to the bite gravel may be large, and there is a possibility that the pinching cannot be sufficiently reduced. On the contrary, when the angles α2o and α3o are too large, the rigidity of the middle land portion Rm may be lowered, and the wear resistance and traction may be lowered. In view of this, the angles α2o and α3o are preferably 21 ° or less, more preferably 19 ° or less.

From the same point of view, the angles α2i and α3i at the inward corner portions 11 of the tread surface side mildly inclined portions 17A and 17B are preferably 21 ° or more, more preferably 23 ° or more. Preferably, it is 29 degrees or less, More preferably, it is 27 degrees or less.

In addition, in the corner portions 18 of the tread surface side mildly inclined portions 17A and 17B and the tread surface 2t, as shown in FIGS. 6A, 6B, and 7, the inward corner portion 11 is shown. In the present invention, it is preferable that the chamfer 20 is provided. Such a chamfer 20, in the bent portion 13 (shown in Fig. 4) of the center main groove 3, the groove width on the tread surface 2t side and the angle of the tread surface side gentle slope portions 17A, 17B substantially. By making it larger, the groove wall surface can be formed in a variety of surfaces, so that stone pinching and the stone discharge function can be improved. In addition, the chamfer 20 can suppress the grounding of the inward corner portion 11 having a sharp tip and a small rigidity, thereby improving the piece-wear resistance.

In order to exert such an effect effectively, as shown in FIGS. 4 and 6 (a) and (b), the width W3 in the tire axial direction of the chamfer 20 and the depth D2 in the tire radial direction ) And the angle α4 with respect to the normal direction of the tread surface 2t become the maximum at the vertex 11p of the inward corner portion 11.

The width W3 at the apex 11p of the chamfer 20 is preferably 10% or more, more preferably of the groove width W1 (shown in FIG. 1) of the center main groove 3. 30% or more is preferable. When the said width W3 is too small, there exists a possibility that stone pinching and uneven wear cannot fully be suppressed. On the contrary, when the width W3 is too large, the rigidity of the middle land portions Rm and Rm becomes excessively small, and there is a possibility that the wear resistance performance and the traction performance are deteriorated. From this point of view, the width W3 is preferably 90% or less, more preferably 70% or less of the tread width TW.

From the same viewpoint, the depth D2 at the apex 11p of the chamfer 20 is preferably 20% or more of the groove depth D1 (shown in FIG. 2) of the center main groove 3. More preferably, 30% or more is preferable, Furthermore, Preferably, it is 60% or less, More preferably, 50% or less is preferable. Similarly, the angle α4 with respect to the normal direction of the tread surface 2t at the apex 11p of the chamfer 20 is preferably 30 ° or more, more preferably 40 ° or more, Moreover, Preferably it is 80 degrees or less, More preferably, 70 degrees or less are preferable.

In addition, the chamfer 20 of this embodiment has the width W3, the depth D2, and the angle (alpha) 4 decreasing from the vertex 11p of the inward corner part 11 toward both sides of a tire circumferential direction. It has a cut surface. Such a chamfer 20 can secure the rigidity of the middle land part Rm (shown in FIG. 1), exhibiting the above effect | action.

As shown in FIG. 4, it is preferable that the said groove wall 8A, 8B contains the straight part 22 extended linearly between the inward corner part 11 and the outward corner part 12. As shown in FIG. Such a straight portion 22 can smoothly guide the water film on the road surface along the center main groove 3, and can improve drainage performance.

The groove bottom side steep slopes 16A and 16B include a curved surface 23 curved in an arc shape in the inward corner portion 11 and the outward corner portion 12, and are zigzag in the tire circumferential direction. It is preferable to extend continuously. Such curved surface 23 disperses the distortion that tends to concentrate on the groove bottom side steep slopes 16A, 16B in the inward corner portion 11 and the outward corner portion 12, and can effectively suppress stone pinching. have. In particular, in the inward corner portion 11, since the increase of the angles α2i and α3i of the tread surface side gentle slope portions 17A and 17B becomes gentle, the rigidity is not excessively increased by the formation of the chamfer portion 20. It is possible to form the chamfer 20.

In order to exert such an effect effectively, the radius of curvature R1 of the groove bottom side steep slopes 16A and 16B is preferably 5 mm or more, more preferably 10 mm or more, and preferably 25 Mm or less, More preferably, 20 mm or less is preferable.

Next, as shown in Fig. 8 and Figs. 9A and 9B which are EE and FF sectional drawing, the said shoulder main groove 4 is a shoulder groove bottom in the groove cross section orthogonal to a groove length direction. (26) and a pair of shoulder groove walls 27A, 27B extending from the shoulder groove bottom 26 to the tread surface 2t.

The shoulder groove walls 27A and 27B are also convex toward the groove center line 4c (shown in FIG. 1) of the shoulder main groove 4, and the shoulder inward corner portion 28 and the groove center line 4c are curved. Includes a shoulder outward corner portion 29 that is convex and curved to the opposite side. In addition, the shoulder main groove 4 also has shoulder inward corners 28 and shoulder outward corners 29 formed alternately in the tire circumferential direction on the shoulder groove walls 27A and 27B. It extends continuously in a zigzag shape in the tire circumferential direction.

The shoulder main groove 4 has a smaller contribution to traction performance than the center main groove 3. For this reason, as shown in FIG. 3, in this embodiment, while setting the zigzag pitch P2 of the shoulder main groove 4 to the same as the zigzag pitch P1 of the center main groove 3, The zigzag amplitude V2 can be made smaller than the zigzag amplitude V1 of the center main groove 3, so that the drainage performance and the wear resistance performance can be improved.

Since such an effect can be exhibited effectively, the zigzag amplitude V2 is preferably 60% or more, more preferably 70% or more, and preferably 100% or less of the zigzag amplitude V1, More preferably, 90% or less is preferable. The zigzag amplitude V1 of the center main groove 3 is, for example, about 4% to 10% of the tread width TW (shown in FIG. 1), and the zigzag pitch P1 is 300% of the zigzag amplitude V1. It is preferably set to about 600%.

In addition, as shown in FIG. 8, the shoulder groove walls 27A and 27B include a shoulder straight portion 31 that extends linearly between the shoulder inward corner portion 28 and the shoulder outward corner portion 29. . Such a shoulder straight portion 31 can also guide the water film on the road surface smoothly.

In addition, the shoulder groove walls 27A and 27B of the present embodiment have an angle α5 of 15 ° to 30 ° with respect to the normal direction of the tread surface 2t, as shown in FIGS. 9A and 9B. Is inclined to. Such shoulder main groove 4 can set the groove volume larger than the center main groove 3, and can improve the drainage performance more effectively.

Moreover, in the shoulder inward corner part 28 in the shoulder inward corner part 28 among the pair of shoulder groove walls 27A and 27B, the shoulder groove wall 27B of the tire axial direction outer side and the tread surface 2t are shoulder chamfered parts. It is preferable that 33 is provided. Such a shoulder chamfer 33 can also effectively prevent the pinching of stones that are likely to occur at the shoulder inward corner 28, and at the time of turning to increase the ground pressure of the shoulder rib Rs (shown in FIG. 1), the tip is sharp. In addition, by suppressing the grounding of the shoulder inward corner portion 28 having a small rigidity, it is possible to improve the wear resistance performance.

In order to effectively exert this action, the width W4 in the tire axial direction, the depth D3 in the radial direction of the tire, and the tread surface 2t at the apex 28p of the shoulder inward corner portion 28 are in the normal direction. The relative angle α6 is preferably formed to be equal to the width W3, the depth D2, and the angle α4 of the chamfer 20 of the center main groove 3 shown in FIG. 6A. .

As shown in FIG. 3, the middle lateral groove 9 communicates between the outward corner portion 12 and the shoulder straight portion 31 of the center main groove 3. Such middle lateral grooves 9 substantially increase the groove width of the center main grooves 3 together with the chamfers 20 in the bent portions 13 of the center main grooves 3 to more effectively block the stones. Can be.

In addition, the middle lateral groove 9 can reduce the ground area of the outward corner portion 12, which is relatively rigid, and can effectively prevent uneven wear of the middle land portion Rm (shown in FIG. 1). In addition, since the middle lateral groove 9 opens at the shoulder straight portion 31 which shifted the position slightly in the tire circumferential direction from the shoulder outward corner portion 29, the shoulder groove wall of the inner side of the tire axial direction having a relatively small ground pressure ( In 27A), the edge component of the shoulder inward corner portion 28 can be exhibited, and the traction performance can be improved.

In addition, the middle lateral groove 9 of the present embodiment has a slim groove portion 9a having a groove width W5 of about 2 mm to 12 mm, and an outward corner of the center main groove 3 from both ends of the slim groove portion 9a. It is comprised including the diameter expansion parts 9b and 9b which diameter expand toward the part 12 and the shoulder straight part 31, respectively. In addition, the middle lateral groove 9 has an angle α7 of the slim groove portion 9a with respect to the tire circumferential direction set to 20 ° to 40 °, and the groove depth D4 (shown in FIG. 2) is the center main groove ( It is set to about 5% to 50% of the groove depth D1 of 3). The middle lateral groove 9 can secure the rigidity of the middle land portion Rm while exhibiting the above action.

As mentioned above, although especially preferable embodiment of this invention was described in detail, this invention can be modified and implemented in various aspects, without being limited to embodiment shown.

[Example]

The tire which comprises the basic structure shown in FIG. 1, and has the center main groove tread part shown in Table 1 was manufactured, and their performance was evaluated. In addition, as a comparison, the tire (comparative example 1) which has the tread part provided with the protrusion (length: 6.5 mm, width: 3.0 mm, height: 3.5 mm) for preventing stones shown in FIG. 10, and the angle of the tread surface side gentle slope part Similarly, the tires (comparative example 2) which grew from the inward corner part to an outward corner part were tested similarly. In addition, the common specification is as follows.

Tire size: 11.00R20

Rim size: 8.0 V x 20

Tread Width (TW): 226 mm

Center Main Home:

Groove width (W1): 16 mm

Groove depth (D1): 17 mm

Zigzag amplitude (V1): 16 mm

Ratio (V1 / TW): 7%

Zigzag pitch (P1): 79 mm

Ratio (P1 / V1): 494%

Shoulder main groove:

Groove width (W1): 16 mm

Groove depth (D1): 17 mm

Angle (α5): 19 °

Shoulder Chamfer:

Width at vertex (W4): 7 mm

Ratio (W4 / W1): 43.8%

Depth at Vertex (D3): 8 mm

Ratio (D3 / D1): 47.1%

Angle at vertex (α6): 40 °

Middle Groove:

Groove width (W5): 4 mm

Angle (α7): 28 °

Groove depth (D4): 2 mm

Ratio (D4 / D1): 11.8%

The test method is as follows.

<My stone jamming performance>

Each sample tire is rim-assembled on the rim, filled with internal pressure of 830 kPa, mounted on the rear wheel of a 10-ton loading 2-DD car (without load), and the road including Sarido has a speed of 40 km / h? 60 km. After running 2000 km / h, the number of stones bite in the center main groove of the rear wheel was examined. The result is an index display in which the number of stone jams in Comparative Example 1 is set to 100, and the smaller the numerical value, the better.

<My Wear Wear Performance>

After each sample tire was rim-assembled on the above conditions, mounted on the rear wheel of the vehicle, and after running 30,000 km in general / high speed, the amount of wear of the middle land part was measured. The amount of abrasion measured the difference of the abrasion amount in the inward corner part of a middle land part, and the abrasion amount of the other part, and was represented by the index which makes the value of the comparative example 1 100. The smaller the value, the better.

<Drainage performance>

The vehicle was rim-assembled under the above conditions and mounted on the rear wheel of the vehicle, and the vehicle was gradually increased on a course in which a pond having a depth of 5 mm and a length of 20 m was provided on an asphalt road surface having a radius of 100 m. The horizontal acceleration (horizontal G) was measured, and the average horizontal G of the front wheel at the speed of 50 km / h-80 km / h was calculated. The result was represented by the index which makes comparative example 1 100. The larger the value, the better.

The results of the test are shown in Table 1.

As a result of the test, it was confirmed that the tire of the example can reduce stone pinching while maintaining drainage performance.

1 tire 2 tread section
3 center home 7 home floor
8A, 8B groove wall 11 inward corner
12 Outward corners 13 Bends
16A, 16B Groove steep slope 17A, 17B Tread surface mild slope

Claims (11)

A heavy-load pneumatic tire having a plurality of bent portions and one or more center main grooves continuously extending in a zigzag shape in a tire circumferential direction in a center region, which is an area of 10% of the tread width centered on the tire equator of the tread portion,
The center main groove includes a groove bottom and a pair of groove walls extending from the groove bottom to the tread surface at a groove cross section perpendicular to the groove length direction,
Each groove wall has a groove bottom side steep slope having a height of 10% to 35% of the groove depth from the groove bottom and an angle of 0 ° to 5 ° with respect to the normal direction of the tread surface;
And a tread surface side gentle slope that extends from the radially outer end of the groove bottom side steep slope to the tread surface and extends at an angle greater than the groove bottom side steep slope,
The groove width at the outer end of the groove bottom side steep slope is 2 mm to 8 mm,
Each of the groove walls includes an inward corner portion that is convex and curved toward the zigzag groove center line of the center main groove, and an outward corner portion that is convex and curved toward the opposite side to the groove center line,
The angle of the tread surface side mild inclined portion gradually increases from the outward corner portion to the inward corner portion. The heavy-load pneumatic tire according to claim 1, wherein the angle at the outward corner portion of the tread surface side gentle slope portion is 13 ° to 21 °. The heavy-load pneumatic tire according to claim 1 or 2, wherein the angle at the inward corner portion of the tread surface side gentle slope portion is 21 ° to 29 °. The heavy-load pneumatic tire according to claim 1, wherein a chamfer portion is provided at the inward corner portion at the corner portion of the tread surface side mild slope portion and the tread surface. The heavy-duty pneumatic tire according to claim 4, wherein a width in the tire axial direction of the chamfer portion becomes maximum at a vertex of the inward corner portion. 6. The heavy load air according to any one of claims 1, 2, 4 or 5, wherein the groove wall includes a straight portion extending linearly between the inward corner portion and the outward corner portion. tire. The said groove bottom side steep inclination part contains the curved surface curved in arc shape in the said inward corner part and the said outward corner part, The said inclined floor part of Claim 1, 2, 4 or 5 characterized by the above-mentioned. Heavy duty pneumatic tires. The said tread part is zigzag-shaped in a tire circumferential direction to the shoulder area | region which is the area | region of the both sides of the tire axial direction of the said center area | region in the said tread part. One or more shoulder main grooves are provided to extend continuously,
The heavy-duty pneumatic tire of which the zigzag amplitude of the said shoulder main groove is smaller than the zigzag amplitude of the said center main groove. The said tread part is provided with the middle land part extended in a tire circumferential direction between the center main groove and the shoulder main groove,
The middle land portion is a heavy-duty pneumatic tire that is provided with a middle horizontal groove communicating between the center main groove and the shoulder main groove. 10. The shoulder main groove according to claim 9, wherein the shoulder main groove includes a shoulder groove bottom and a pair of shoulder groove walls extending from the shoulder groove bottom to a tread surface at a groove cross section perpendicular to the groove length direction.
Each shoulder groove wall includes a shoulder inward corner portion that is convex and curved toward the zigzag groove center line of the shoulder main groove, and a shoulder outward corner portion that is convexly curved toward the opposite side to the groove center line,
And the shoulder groove wall includes a shoulder straight portion extending linearly between the shoulder inward corner and the shoulder outward corner. The heavy duty pneumatic tire according to claim 10, wherein the middle lateral groove communicates between the outward corner portion of the center main groove and the shoulder straight portion.

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