JP6710995B2 - Pneumatic tire - Google Patents

Description

The present invention relates to a pneumatic tire having improved steering stability performance while maintaining a small tire mass.

Conventionally, it has been required to improve the steering stability of a pneumatic tire and suppress an increase in tire mass. Therefore, for example, a carcass including a pair of left and right split plies in which the central region including the tire equator has a hollow shape and a continuous ply that continuously extends in a toroidal shape between the bead cores arranged at the bead portions on both sides. Pneumatic tires have been proposed. In such a tire, both plies increase the lateral rigidity of the sidewall portion and the bead portion of the tire, so that the steering stability performance is improved and the hollow portion formed between the pair of split plies allows the tire to be The increase in mass is suppressed.

However, in recent years, it has been desired to further improve the steering stability performance while keeping the tire mass small.

JP, 2013-209092, A

The present invention has been devised in view of the above circumstances, and based on improving the structure of the carcass, to provide a pneumatic tire having excellent steering stability performance while maintaining a small tire mass. Is the main purpose.

The present invention is a pneumatic tire comprising a belt layer arranged in a tread portion and a carcass arranged inward of the belt layer in a tire radial direction, wherein the carcass comprises a layer of a first carcass cord. It includes a first ply and a pair of second plies that are formed of a layer of a second carcass cord and are spaced apart from each other on the left and right. The first ply has a toroidal shape between the bead cores disposed on the bead portions on both sides. It has a body portion that extends and a pair of folded portions that are connected to the body portion and that are folded back from the inner side in the tire axial direction around the bead core, and the outer ends of the folded portions are arranged on the bead portions. Located on the inner side in the tire radial direction than the outer end of the bead apex rubber in the tire radial direction, and the second plies from the first end located on the outer side in the tire radial direction from the outer end of the bead apex rubber. It extends inward in the tire radial direction and is folded back around the bead core and extends to a second end located radially outside the tire maximum width position, and the second carcass cord is higher than the first carcass cord. It is characterized by having rigidity.

In the pneumatic tire according to the present invention, it is desirable that the second carcass cord is aramid fiber.

In the pneumatic tire according to the present invention, the second ply has the first end located on the tire cavity side of the first ply, and the second end located on the tire outer surface side of the first ply. Is desirable.

In the pneumatic tire according to the present invention, it is desirable that the first end be located on the inner side in the tire radial direction with respect to the second end.

In the pneumatic tire according to the present invention, the separation distance between the second end and the outer end of the belt layer in the tire axial direction is preferably 10 to 40 mm.

In the pneumatic tire according to the present invention, the distance between the first end and the inner end of the bead core in the tire radial direction is preferably 40 to 60 mm in the tire radial direction.

In the pneumatic tire according to the present invention, it is preferable that a separation distance in the tire radial direction between the outer end of each of the folded portions and an inner end of the bead core in the tire radial direction is 10 to 30 mm.

The pneumatic tire of the present invention includes a belt layer arranged in the tread portion and a carcass arranged inside the belt layer in the tire radial direction. The carcass includes a first ply composed of a layer of the first carcass cord and a pair of second plies composed of a layer of the second carcass cord and arranged apart from each other on the left and right. The first ply has a main body portion that extends in a toroidal shape between the bead cores arranged on the bead portions on both sides, and a pair of folding portions that are continuous with the main body portion and that are folded back from the inner side in the tire axial direction around the bead core. doing. As described above, the carcass including the first ply and the second ply enhances the lateral rigidity of the sidewall portion and the bead portion of the tire. Therefore, the steering stability performance is improved. Further, since no ply is provided between the pair of second plies, it is possible to suppress an increase in the mass of the tire.

The outer end of the folded portion is located on the inner side in the tire radial direction with respect to the outer end of the bead apex rubber arranged in each bead portion in the tire radial direction. In this way, the outer end of the folded-back portion is kept small in height position in the tire radial direction, so that the mass of the tire is kept small.

The second ply extends inward in the tire radial direction from a first end located outside the outer end of the bead apex rubber in the tire radial direction, and is folded back around the bead core to be outside the tire maximum width position in the tire radial direction. It extends to the second end located at. Since such a second ply can further increase the lateral rigidity of the sidewall portion and the bead portion in cooperation with the bead apex rubber, it exhibits excellent steering stability.

The second carcass cord has higher rigidity than the first carcass cord. Thereby, the lateral rigidity between the sidewall portion and the bead portion of the tire can be further increased. Further, since the layer of such a second carcass cord forms a pair of second plies, the second ply can be attached to the first ply with high precision without generating wrinkles or the like, thus obtaining high uniformity. It is possible to achieve excellent steering stability performance.

Therefore, the pneumatic tire of the present invention greatly improves the steering stability performance while maintaining a small tire mass.

It is a meridian sectional view of a pneumatic tire showing one embodiment of the present invention. FIG. 2 is a partially enlarged view of a bead portion and a sidewall portion on the right half of FIG. 1. It is a partial enlarged view of a bead part and a side wall part which shows other embodiments of the present invention.

An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a tire meridian sectional view in a normal state of a pneumatic tire (hereinafter, sometimes simply referred to as “tire”) 1 of the present embodiment. The tire 1 of this embodiment is suitable as a radial tire for passenger cars.

The "regular state" is an unloaded state in which the tire 1 is assembled on a regular rim (not shown) and filled with a regular internal pressure. In the present specification, unless otherwise specified, the dimensions and the like of each part of the tire 1 are values measured in this normal state.

The "regular rim" is a rim in which each standard is defined for each tire in a standard system including standards on which the tire is based. For example, "standard rim" for JATMA and "Design Rim" for TRA. , ETRTO is "Measuring Rim". In addition, "regular internal pressure" is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. For JATMA, the "maximum air pressure", and for TRA, the table "TIRE" Maximum value described in "LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", "INFLATION PRESSURE" for ETRTO. When the tire is for passenger cars, the normal internal pressure is 180 kPa.

The tire 1 of this embodiment includes a pair of bead cores 5 and 5, a pair of bead apex rubbers 8 and 8, a belt layer 7, a carcass 6, and an inner liner rubber 9. The bead core 5 is arranged in the bead portion 4. The bead apex rubber 8 extends outward from the bead core 5 in the tire radial direction. The belt layer 7 is arranged on the tread portion 2. The carcass 6 is arranged inside the belt layer 7 in the tire radial direction. The inner liner rubber 9 is arranged on the tire cavity side of the carcass 6 and forms a tire cavity surface 2b.

The belt layer 7 is composed of at least two belt cords in which belt cords are inclined with respect to the tire equator C at an angle of, for example, 10 to 40°, and in the present embodiment, two belt plies 7A and 7B inside and outside the tire radial direction. Has been done. The belt plies 7A and 7B are overlapped so that their width centers are aligned and the belt cords intersect each other. A steel cord is suitable as the belt cord. However, a highly elastic organic fiber cord such as aramid or rayon is also used as necessary.

In the present embodiment, the inner belt ply 7A is formed to have a larger width in the tire axial direction than the outer belt ply 7B. Therefore, both ends of the inner belt ply 7A constitute outer ends 7t of the belt layer 7 in the tire axial direction. The width Wa of the inner belt ply 7A in the tire axial direction is preferably 90% to 110% of the tread width TW. The belt layer 7 is not limited to such an aspect, and for example, the inner belt ply 7A may be formed to have a smaller width in the tire axial direction than the outer belt ply 7B.

The "tread width" TW is the tire axis between the tread ends Te and Te, which is the outermost ground contact position in the tire axial direction when the normal load is applied to the tire in a normal state and the tire is grounded on a flat surface at a camber angle of 0 degree. It is defined as the directional distance.

"Regular load" is the load that each standard defines for each tire in the standard system including the standard on which the tire is based. For JATMA, "maximum load capacity", and for TRA, the table "TIRE LOAD The maximum value stated in "LIMITS AT VARIOUS COLD INFLATION PRESSURES" is "LOAD CAPACITY" for ETRTO. When the tire is for a passenger car, the regular load is a load equivalent to 88% of the above load.

In the present embodiment, the carcass 6 is composed of a first ply 6</b>A made of a layer of a first carcass cord (not shown) and a pair of second plies made of a layer of a second carcass cord (not shown) and separated left and right. It is composed of two plies 6B and 6B. In such a pair of second plies 6B and 6B, the increase in the mass of the tire is suppressed as compared with the continuous plies.

The first carcass cord and the second carcass cord are formed, for example, in a radial structure arranged at an angle of, for example, 75 to 90 degrees with respect to the tire circumferential direction.

The second carcass cord has higher rigidity than the first carcass cord. Thereby, the lateral rigidity of the sidewall portion 3 and the bead portion 4 of the tire 1 can be increased. Further, since such a layer of the second carcass cord forms the pair of second plies 6B, 6B, the bending stress generated in the second ply 6B can be reduced, so that wrinkles or the like do not occur in the first ply 6A. Can be pasted accurately. Therefore, high uniformity can be obtained, and excellent steering stability performance is exhibited.

The second carcass cord is preferably aramid such as Kevlar (registered trademark) in order to effectively exhibit the above-mentioned effects. As the first carcass cord, organic fibers such as nylon, rayon and polyester are suitable. When the first carcass cord and the second carcass cord are aramid, the rigidity of the carcass 6 becomes excessively high, and the first ply 6A and the second ply 6B do not extend during vulcanization in the tire manufacturing process, and the inner liner is not stretched. Only the rubber 9 extends. As a result, the inner liner rubber 9 may flow into the second ply 6B to reduce its thickness, which may reduce the lateral rigidity of the bead portion 4 and the sidewall portion 3.

The first ply 6A includes a main body portion 6a extending between the bead cores 5 and 5 in a toroidal shape, and a pair of folded-back portions 6b and 6b continuous with the main body portion 6a and folded back from the inner side to the outer side in the tire axial direction around the bead core 5. have. The first ply 6A as described above cooperates with the pair of second plies 6B and 6B to enhance the lateral rigidity of the sidewall portion 3 and the bead portion 4 of the tire 1. Therefore, the steering stability performance is improved.

As shown in FIG. 2, the outer end 6t of the folded-back portion 6b is located inside the tire radial direction outer end 8e of the bead apex rubber 8 in the tire radial direction. As a result, the above-described action is exhibited and the length of the first ply 6A is kept small, so that the increase in the mass of the tire 1 is suppressed.

The distance H1 in the tire radial direction between the outer end 6t of the folded-back portion 6b and the inner end 5i of the bead core 5 in the tire radial direction is preferably 10 to 30 mm. When the separation distance H1 is less than 10 mm, the carcass 6 is likely to come off and the steering stability may be deteriorated. If the separation distance H1 exceeds 30 mm, the mass of the first ply 6A becomes large, and thus the tire mass may not be kept small.

The second ply 6B has a first end 6e and a second end 6i. The first end 6e is located outside the outer end 8e of the bead apex rubber 8 in the tire radial direction. The second end 6i is located outside the tire maximum width position M in the tire radial direction. The second ply 6B extends inward in the tire radial direction from the first end 6e and is folded back around the bead core 5 to reach the second end 6i. Such a second ply 6B cooperates with the bead apex rubber 8 to effectively increase the rigidity of the bead portion 4 and the sidewall portion 3, so that the steering stability performance is further improved. Further, since such a second ply 6B generates a high pressing force on the bead core 5, for example, in the case where the bead core 5 is formed by winding a bead wire (not shown) a plurality of times, the bead wires are bundled. Wrapping can be eliminated. The "tire maximum width position" M is a position in the tire radial direction in which the main body portion 6a of the first ply 6A extends most outward in the tire axial direction in the normal state.

In the present embodiment, the second ply 6B includes a lumen side portion 6c extending from the first end 6e to the bead core 5 and a tire extending from the lumen side portion 6c to the second end 6i and extending from the lumen side portion 6c to the tire. The outer portion 6d is arranged on the outer surface side.

In the present embodiment, the first end 6e of the second ply 6B is located on the tire cavity side of the first ply 6A. That is, in the present embodiment, the inner cavity side portion 6c is located on the tire inner cavity side of the main body portion 6a of the first ply 6A. Further, the second end 6i of the present embodiment is located on the tire outer surface side of the first ply 6A. As a result, the second ply 6B having the second carcass cord with high rigidity has a larger radius of curvature around the bead core 5 than the first ply 6A. As a result, the second ply 6B can be formed with high precision, so that the steering stability performance is kept high.

In the present embodiment, the outer portion 6d having high rigidity is arranged on the tire outer surface side with respect to the first ply 6A. Therefore, the cut resistance is improved.

In the present embodiment, the first end 6e is located on the inner side in the tire radial direction with respect to the second end 6i. As a result, the height of the inner cavity side portion 6c of the second ply 6B in the tire radial direction can be suppressed to be small, so that the tire mass can be kept small.

The distance H2 in the tire radial direction between the first end 6e and the inner end 5i of the bead core 5 in the tire radial direction is preferably 40 to 60 mm. If the separation distance H2 is less than 40 mm, it may not be possible to cooperate with the bead apex rubber 8 and the lateral rigidity of the bead portion 4 may not be improved. If the separation distance H2 exceeds 60 mm, the mass of the tire 1 may increase. Also, during vulcanization, the inner liner rubber 9 may flow into the inner cavity side portion 6c to a large extent, and the lateral rigidity may be reduced.

In order to effectively exhibit the above-described action, the distance H3 between the first end 6e and the outer end 8e of the bead apex rubber 8 in the tire radial direction is preferably 5 to 20 mm.

The second end 6i is preferably located outside the outer end 7t of the belt layer 7 in the tire axial direction. When the second end 6i is located inside the outer end 7t of the belt layer 7 in the tire axial direction, the tire mass may be excessively large. Moreover, since the second end 6i damages the belt plies 7A and 7B, the steering stability may be rather deteriorated.

The distance L between the second end 6i and the outer end 7t of the belt layer 7 in the tire axial direction is preferably 10 to 40 mm. If the separation distance L is less than 10 mm, the second end 6i may contact the belt layer 7 and the mass of the tire 1 may increase. If the separation distance L exceeds 40 mm, the lateral rigidity of the sidewall portion 3 may not be sufficiently enhanced.

The thickness D of the first ply 6A and the second ply 6B is preferably about 0.75 to 1.25 mm, for example.

FIG. 3 shows an enlarged view of the bead portion 4 and the sidewall portion 3 in the right half of the tire 1 according to another embodiment of the present invention. The tire 1 has the same structure as the above-described tire 1 except for the arrangement of the first ply 6A and the second ply 6B, and thus the description thereof will be omitted.

In the tire 1 of this embodiment, the inner cavity side portion 6c is arranged closer to the tire outer surface side than the main body portion 6a of the first ply 6A. As a result, the inflow of the inner liner rubber 9 to the second ply 6B side is more effectively suppressed, so that the lateral rigidity of the bead portion 4 can be maintained high even when the second carcass cord is aramid. ..

Although the embodiments of the present invention have been described in detail above, it is needless to say that the present invention is not limited to the illustrated embodiments and can be modified into various modes for implementation.

A pneumatic tire of size 265/65R17 having the basic structure of FIG. 1 was prototyped based on the specifications of Table 1, and the mass and steering stability performance of each test tire were tested. The main common specifications and test methods for each sample tire are as follows.
Belt layer width Wa: 192 mm
Tread width TW: 202mm
Belt layer width Wa/tread width TW: 95%
Separation distance H1: 20 mm
First carcass cord: polyester

<Steering stability>
Test tires were installed on all wheels of a 3000 cc passenger car under the following conditions. A test driver runs this vehicle on a test course on a dry asphalt road, and the steering stability performance regarding grip, stability, rigidity, etc. at that time was evaluated by the test driver's sensory. The results are displayed as a score with Comparative Example 1 as 100, and the larger the value, the better.
Rim: 7.5JJ×17.0
Internal pressure: 200kPa

<Tire mass>
The mass per tire is measured, and the index is represented by an index in which the reciprocal of Comparative Example 1 is 100. The larger the number, the better.
The test results are shown in Table 1. In Table 1, "POL" represents polyester and "ARA" represents aramid.

As a result of the test, it was confirmed that the tires of the examples had improved steering stability performance as compared with the comparative examples.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 6 Carcass 6A 1st ply 6B 2nd ply 6a Body part 6b Folding part 6t Outer end of folding part 6e First end 6i Second end 7 Belt layer 8 Bead apex rubber 8e Outer end of bead apex rubber

Claims (9)

A pneumatic tire comprising a belt layer arranged on the tread portion and a carcass arranged on the inner side in the tire radial direction of the belt layer (excluding a run flat tire having a reinforcing rubber layer having a crescent cross section) . There
The carcass includes a first ply made of a layer of a first carcass cord and a pair of second plies made of a layer of a second carcass cord and arranged apart from each other on the left and right,
The first ply includes a main body portion that extends in a toroidal shape between bead cores arranged on the bead portions on both sides, and a pair of folding portions that are continuous with the main body portion and that are folded back from the inner side to the outer side in the tire axial direction around the bead core. Has and
The outer end of each folded-back portion is located on the tire radial direction inner side than the outer end of the bead apex rubber arranged in each bead portion in the tire radial direction,
Each of the second plies extends inward in the tire radial direction from a first end of the bead apex rubber located outside of the outer end of the tire in the tire radial direction and is folded back around the bead core so that the tire is wider than the tire maximum width position. Extends to the second end located radially outward,
The second carcass cord is aramid,
The pneumatic tire according to claim 1, wherein the first carcass cord is any one of nylon, rayon, and polyester . The second ply extends to the inner side of the cavity extending from the first end to the bead core, is connected to the side of the inner cavity, extends to the second end, and is arranged closer to the tire outer surface than the side of the inner cavity. The pneumatic tire according to claim 1 , which is composed of an outer side portion . The inner cavity side portion is located closer to the tire inner cavity side than the main body portion,
The pneumatic tire according to claim 2 , wherein the outer portion is located closer to the tire outer surface side than the folded portion . The lumen side portion is located on the tire outer surface side with respect to the main body portion,
The pneumatic tire according to claim 2, wherein the outer portion is located closer to the inner side of the tire than the folded portion. The pneumatic tire according to claim 1 , wherein the first end is located on the inner side in the tire radial direction with respect to the second end . The pneumatic tire according to any one of claims 1 to 5, wherein the second end is located outside the outer end of the belt layer in the tire axial direction in the tire axial direction . The pneumatic tire according to claim 6, wherein the distance between the second end and the outer end of the belt layer in the tire axial direction is 10 to 40 mm. The pneumatic tire according to any one of claims 1 to 7 , wherein a separation distance in the tire radial direction between the first end and an inner end of the bead core in the tire radial direction is 40 to 60 mm . The pneumatic tire according to any one of claims 1 to 8 , wherein a distance in the tire radial direction between the outer end of each of the folded portions and an inner end of the bead core in the tire radial direction is 10 to 30 mm .

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