JP5416750B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire in which uneven wear of tread rubber is suppressed.

  In recent years, with higher performance of vehicles, further high-speed durability is required for pneumatic tires. For this reason, the tire which responded to the request | requirement of high performance is provided by providing the tread part with the belt layer which carries out the tagging of the carcass of radial structure, and improving the rigidity and durability of a tread part. However, such a radial tire has a problem that, when traveling at a high speed, lifting of both ends of the belt layer in the tire axial direction occurs and tread separation is likely to occur.

  In response to the above problems, a pneumatic tire has been proposed in which a shoulder band layer is provided at an outer end portion of the belt layer in the tire axial direction and lifting of the belt layer is suppressed. (For example, the following patent document 1).

JP 2009-241720 A

  However, in the pneumatic tire as described above, since the end of the belt layer is excessively tightened by the shoulder band layer, the crown land portion bulges due to the tire internal pressure filling and the centrifugal force during traveling. Compared to bulging, it becomes relatively large. For this reason, as shown in FIG. 4, in the shape of the contact surface, the maximum contact length a in the tire circumferential direction of the shoulder land portion A is smaller than the contact length b in the tire circumferential direction on the tire equator C. As a result, the ground contact pressure between the crown land portion and the shoulder land portion becomes uneven, and there is a problem that uneven wear occurs in the shoulder land portion, for example.

  The present invention has been devised in view of the above-described problems. A shoulder band layer disposed on both ends of the belt layer in the tire axial direction is provided, and the profile of the outer surface of the shoulder land portion is defined as a crown. The main object is to provide a pneumatic tire capable of suppressing the uneven wear of the shoulder land portion based on the fact that it protrudes outward in the tire axial direction from the profile of the land portion.

In order to achieve the above object, the invention of claim 1 of the present application is directed to a carcass extending from a tread portion to a bead portion through a sidewall portion, and to the outer side in the tire radial direction of the carcass, and a belt cord with respect to the tire equator. A belt layer composed of a belt ply inclined at an angle of 15 to 45 °, and a band ply arranged on the outer side in the tire radial direction of the belt layer and arranged with a band cord at an angle of 5 ° or less with respect to the tire circumferential direction a pneumatic tire comprising a band layer comprising, the band layer comprises a pair of shoulder band layer disposed on both end portions in the tire axial direction of the belt layer, disposed on the pair of shoulder band layers and a center band layer, your the meridian cross section including the tire rotational axis at regular state standard pressure One only mounted on a standard wheel rim is unloaded filled The tread rubber disposed in the tread portion includes a pair of shoulder land portions located on the outer side in the tire radial direction of the shoulder band layer, and a crown land portion between the shoulder land portions, and the shoulder land portion The outer surface profile of the outer surface of the crown land portion is 0.5 to 1.5 mm outward in the tire radial direction from the extension profile obtained by virtually extending the outer surface profile of the crown outward in the tire axial direction . A pair of shoulder main grooves extending continuously in the tire circumferential direction on the tread end side are provided, and the shoulder band layer and the center band layer have overlapping portions that overlap each other, and this overlapping portion is the shoulder main groove. It is provided in the area | region inside the tire radial direction of a groove | channel, It is characterized by the above-mentioned.

Further, in the invention of claim 2 , the shoulder land portion is formed between the tread end and the shoulder main groove, and the crown land portion is formed between the shoulder main groove. 1. The pneumatic tire according to 1.

  According to a third aspect of the invention, the shoulder band layer includes an outer band ply disposed on the outer side in the tire radial direction of the belt layer, an inner band ply disposed on the inner side in the tire radial direction of the belt layer, 3. The pneumatic tire according to claim 1, wherein the pneumatic tire has a fold structure having an inner band ply and a joint portion connecting the outer band ply.

  According to a fourth aspect of the present invention, in the profile of the outer surface of the shoulder land portion, the distance in the tire radial direction from the extended profile gradually decreases toward the outer side in the tire axial direction. The pneumatic tire described.

  According to a fifth aspect of the present invention, in a load-load grounding state in which a normal load is applied to the tire in the normal state and grounded on a flat surface with a camber angle of 0 °, the grounding in the tire circumferential direction at the tire equator of the tread portion is performed. The pneumatic tire according to any one of claims 1 to 4, wherein a ratio Le / Ls between a length Le and a ground contact maximum length Ls in the tire circumferential direction of the shoulder land portion is 1.10 to 1.40. is there.

  In the pneumatic tire of the present invention, a pair of shoulder band layers are disposed on both ends of the belt layer in the tire radial direction and in the tire axial direction. As a result, lifting at both ends of the belt layer during high-speed running is suppressed, and high-speed durability is improved.

  Moreover, the profile of the outer surface of the shoulder land portion of the tread rubber is 0.5 to 1.5 mm outward in the tire radial direction from the extended profile obtained by virtually extending the profile of the outer surface of the crown land portion outward in the tire axial direction. . Thereby, the profile of the outer surface of a shoulder land part can be protruded ahead in the tire radial direction rather than the profile of a crown land part. When the tire is inflated when an internal pressure or a centrifugal force is applied to the tire, the protruding deformation of the crown land portion and the shoulder land portion is made uniform, so that the ground contact pressure is made uniform substantially over the entire tread portion. Accordingly, uneven wear of the shoulder land portion of the tread rubber is suppressed.

It is sectional drawing of the normal state which shows one Embodiment of the pneumatic tire of this invention. It is the elements on larger scale of the tread part of FIG. It is a top view which shows the contact surface shape of the pneumatic tire of FIG. It is a top view which shows the contact surface shape of the conventional pneumatic tire.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a tire meridian cross-sectional view including a tire shaft in a normal state of the pneumatic tire 1 of the present embodiment.

  The “normal state” means an unloaded state in which a tire is assembled on a normal rim and filled with a normal internal pressure. The “regular rim” is a rim determined for each tire in a standard system including a standard on which a tire is based. For example, JATMA is a standard rim, TRA is “Design Rim”, ETRTO Then "Measuring Rim". Furthermore, “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. The maximum air pressure is JATMA and the table “TIRE LOAD LIMITS AT” is TRA. Maximum value described in “VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” for ETRTO, but 180 kPa for tires for passenger cars.

  As shown in FIG. 1, the pneumatic tire 1 of the present embodiment includes a carcass 6 that extends from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and the carcass 6 is disposed on the outer side in the tire radial direction. The belt layer 7, the bead apex rubber 8 extending in a tapered manner from the bead core 5 toward the outer side in the tire radial direction, the outer side of the belt layer 7 in the tire radial direction and the both ends of the belt layer 7 in the tire axial direction. A thing for a passenger car comprising a pair of shoulder band layers 9 is shown.

  The carcass 6 includes, for example, two carcass plies 6 </ b> A and 6 </ b> B. And a folded portion 6b folded back from the inner side in the axial direction. The carcass plies 6A and 6B are cord plies in which a carcass cord is covered with a topping rubber. In the present embodiment, the carcass cord is disposed at an angle of, for example, 75 to 90 ° with respect to the tire equator C. ing. The carcass cord is preferably an organic fiber cord such as polyester cord, nylon, rayon, or aramid, and a steel cord can be adopted if necessary.

  The bead apex rubber 8 is made of hard rubber, is disposed between the main body portion 6a and the folded portion 6b, and extends in a tapered manner from the bead core 5 outward in the tire radial direction. Thereby, the bead part 4 and the sidewall part 3 are reinforced.

  The belt layer 7 is arranged at the outer side in the tire radial direction of the carcass 6 and has at least one belt cord inclined at an angle of 15 to 45 ° with respect to the tire equator C. The belt plies 7A and 7B are overlapped in a direction in which the cords cross each other. The belt cord is a steel cord in this embodiment. Thereby, the whole tread part 2 is reinforced strongly.

  The shoulder band layer 9 includes a band ply arranged at both ends in the tire radial direction and in the tire axial direction of the belt layer 7 and in which band cords are arranged at an angle of 5 ° or less with respect to the tire circumferential direction. The shoulder band layer 9 suppresses lifting of the end portion 7E in the tire axial direction of the belt layer 7 during high speed running, and improves high speed durability.

  Further, in the present embodiment, the shoulder band layer 9 includes an outer band ply 9a disposed on the outer side in the tire radial direction of the belt layer 7, an inner band ply 9b disposed on the inner side in the tire radial direction of the belt layer 7, This is a fold structure having the inner band ply 9b and a joint portion 9c that joins the outer band ply 9a. Thereby, the restraining force at the end portion 7E of the belt layer 7 that is easily lifted can be intensively increased by the outer band ply 9a and the inner band ply 9b, and the outer diameter growth of the shoulder land portion 11 can be suppressed uniformly.

  In the present embodiment, the center band layer 10 is provided between the pair of shoulder band layers 9 and 9 and outside the belt layer 7 in the tire radial direction. The center band layer 10 is also composed of a band ply in which band cords are arranged at an angle of 5 ° or less with respect to the tire circumferential direction. Thereby, the rigidity and durability of the crown land portion 12 are further improved.

In this embodiment, an organic fiber cord is used for the band cord of the shoulder band layer 9, while a steel cord is used for the band cord of the center band layer 10. Thereby, at the time of tire molding, distortion or undulation of the band cord in the vicinity of the tread end portion Te is suppressed, and productivity can be improved. The present invention is not limited to such embodiments, but may be an organic fiber cord is used in both sheet Yorudabando layer 9 and a center band layer 10. In this case, the rigidity from the crown land portion 12 to the shoulder land portion 11 is further improved.

  Further, the shoulder band layer 9 and the center band layer 10 have overlapping portions 10E that overlap each other, but this position is arranged inward in the tire radial direction of the side wall 13s of the shoulder main groove 13 as in this embodiment. More preferably, it is desirable to be provided at the inner side in the tire radial direction of the groove bottom 13b of the shoulder main groove 13. Accordingly, the overlapping portion 10E is prevented from being provided inward in the tire radial direction of the shoulder land portion 11, the ground pressure acting on the overlapping portion 10E that tends to be a separation starting point is reduced, and the separation is suppressed.

  In the present invention, the inner end 9e in the tire axial direction of the shoulder band layer 9 and the outer end 10e in the tire axial direction of the center band layer 10 may be in contact with each other or separated from each other. As a result, the outer surfaces in the tire radial direction of the shoulder band layer 9 and the center band layer 10 are flattened, the rubber distribution in the tire axial direction is averaged, and steering stability during turning is improved.

  The tread rubber 2 </ b> G disposed in the tread portion 2 includes a pair of shoulder land portions 11 positioned on the outer side in the tire radial direction of the shoulder band layer 9, and a crown land portion 12 between the shoulder land portions 11.

  In the present invention, the shoulder land portion 11 includes a land portion between the tire radial direction line L1 extending outward in the tire radial direction through the inner end 9e in the tire axial direction of the shoulder band layer 9, and the tread end Te. means. The crown land portion 12 means a land portion provided between the tire radial direction lines L1 and L1.

  Further, the tread end Te means an outermost ground contact end in the tire axial direction when a normal load is applied to the tire in the normal state and is grounded on a plane with a camber angle of 0 degree. Further, the “regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. The maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES”. If ETRTO, “LOAD CAPACITY”.

  In the present embodiment, the tread rubber 2G disposed in the tread portion 2 is provided with a pair of shoulder main grooves 13 extending continuously in the tire circumferential direction on the tread end Te side. Thereby, the water film which generate | occur | produced between the crown land part 12 and the road surface at the time of wet driving | running | working can be drained appropriately. In order to effectively exhibit such an effect, the shoulder main groove 13 has a tread width TW of 30 in which the tire axial distance between the groove center and the tire equator C is the tire axial distance between the tread ends Te and Te. It is desirable to be provided at a position of ~ 35%.

  In the present embodiment, the shoulder main groove 13 is provided on the tire radial direction line L1. Therefore, the shoulder land portion 11 is formed as a land portion between the tread end Te and the shoulder main groove 13, and the crown land portion 12 is formed as a land portion between the shoulder main grooves 13 and 13. As a result, most of the ground contact pressure of the tire acts on the crown land portion 12 reinforced by the belt layer 7 and the center band layer 10 and can further prevent separation from the end portion 7E of the belt layer 7. .

  In the present embodiment, the crown land portion 12 is provided with crown main grooves 14 that are arranged on both outer sides of the tire equator C in the tire axial direction and extend continuously in the tire circumferential direction. Further, the crown main groove 14 is provided at a position where the distance in the tire axial direction from the tire equator C is 10 to 15% of the tread width TW.

FIG. 2 shows an enlarged cross-sectional view of the tread portion 2.
As shown in FIG. 2, the pneumatic tire 1 of the present invention is an extension in which the profile S1 of the outer surface of the shoulder land portion 11 is virtually extended outward in the tire axial direction from the profile S2 of the outer surface of the crown land portion 12. It is 0.5 to 1.5 mm outward in the tire radial direction from the profile iS2. Thereby, the profile S1 of the outer surface of the shoulder land portion 11 can be projected in advance in the tire radial direction outside the profile S2 of the crown land portion 12. When the tire is inflated due to internal pressure or centrifugal force, the crown land portion 12 having a large protrusion balances with the shoulder land portion 11 having a small protrusion, and the protrusion deformation of the tread portion is made uniform, so that the contact pressure is increased. It becomes uniform over almost the entire area of the tread portion 2. Therefore, uneven wear of the shoulder land portion 11 is suppressed.

  The profile S1 means the contour shape of the outer surface between the tread end Te and the inner end 11e of the ground contact surface of the shoulder land portion 11 in the tire axial direction. Further, the extension profile iS2 is an extension line of an arc having a radius of curvature R passing through the outer surface of the crown land portion 12 and the intersection P1 of the tire equator C and the outer end 12e of the ground contact surface of the crown land portion 12 in the tire axial direction. Means. Further, the inner end 11e and the outer end 12e mean an inner end and an outer end in a grounded state in which a normal load is applied.

  In the profile S1, the distance d in the tire radial direction from the extended profile iS2 needs to be in the range of 0.5 to 1.5 mm. If the distance d is less than 0.5 mm, the contact pressure between the crown land portion 12 and the shoulder land portion 11 cannot be made uniform, and the uneven wear of the shoulder land portion 11 cannot be sufficiently suppressed. On the other hand, when the distance d exceeds 1.5 mm, the ground contact pressure of the shoulder land portion 11 becomes excessive, and uneven wear occurs in the crown land portion 12. From such a viewpoint, the profile S1 is more preferably 0.8 to 1.2 mm outward in the tire radial direction than the extended profile iS2.

  Moreover, it is desirable that the distance d gradually decreases toward the outer side in the tire axial direction. Thereby, the profile S1 approaches the extended profile iS2 toward the outer side in the tire axial direction. Therefore, in addition to improving the impact mitigation performance when riding a kite on the ground contact side, the ground contact surface shape of the shoulder land portion 11 is necessary when the ground contact load of the tire moves outward in the tire axial direction at the time of turning, for example. It changes smoothly according to and exhibits stable turning performance.

  As described above, in the pneumatic tire 1 of the present invention, the profile S1 of the shoulder land portion 11 is on the outer side in the tire radial direction than the extended profile iS2 of the crown land portion 12. For this reason, in the contact surface shape, the contact length in the tire circumferential direction of the shoulder land portion 11 can be relatively increased.

  FIG. 3 shows the shape of the ground plane when a normal load is applied. As shown in FIG. 3, the tire according to this embodiment includes a contact length Le in the tire circumferential direction at the tire equator C of the tread portion 2, and a maximum contact length Ls in the tire circumferential direction of the shoulder land portion 11. The ground plane shape in which the ratio Le / Ls is set to 1.10 to 1.40 can be obtained.

  When the ratio Le / Ls exceeds 1.40, the ground contact area of the shoulder land portion 11 is reduced, and particularly the stability during turning is impaired, and the contact surface shape of the entire tread portion 2 is the outer side in the tire axial direction. It becomes a substantially oval shape that becomes smaller toward, and the amount of slip between the shoulder land portion 11 and the road surface increases, and uneven wear of the shoulder land portion 11 is likely to occur. On the other hand, if the ratio Le / Ls is less than 1.10, the ground contact area of the crown land portion 12 is relatively small, and there is a risk of deteriorating the straight running stability. The amount of sliding with the road surface increases, and uneven wear of the crown land portion 12 is likely to occur.

  From such a viewpoint, the ratio Le / Ls is more preferably set to 1.15 to 1.25. Thereby, the contact surface shape of the entire tread portion 2 becomes a substantially square shape, the contact pressure between the crown land portion 12 and the shoulder land portion 11 becomes uniform, and uneven wear of the shoulder land portion 11 is suppressed, and is excellent. Straight running stability and turning stability are exhibited.

  As mentioned above, although the pneumatic tire of this invention was demonstrated in detail, it cannot be overemphasized that this invention can be changed into various aspects, without being limited to said specific embodiment.

   A pneumatic tire of size 235 / 50R18 having the basic structure shown in FIG. 1 was prototyped based on the specifications shown in Table 1, and its durability was measured. The test method is as follows.

<Durability>
The test tire was run on the drum at a speed of 70 km / h under the conditions of a rim of 18 × 7 JJ, an internal pressure of 180 kPa, and a load of 6.15 kN, and the running distance until the shoulder land portion was damaged was measured. A result is an index | exponent which set the comparative example 1 to 100, and shows that durability is so high that a numerical value is large.
The test results are shown in Table 1.

  As a result of the test, it can be confirmed that the tires of Examples 1 to 9 have improved durability as compared with the tires of Comparative Examples 1 and 2.

2 Tread portion 3 Side wall portion 4 Bead portion 6 Carcass 7 Belt layer 9 Shoulder band layer 10 Center band layer 11 Shoulder land portion 12 Crown land portion 13 Shoulder main groove 14 Crown main groove

Claims (5)

The carcass leading from the tread part to the bead part through the sidewall part,
A belt layer comprising a belt ply disposed on the outer side in the tire radial direction of the carcass and having a belt cord inclined at an angle of 15 to 45 ° with respect to the tire equator;
A pneumatic tire comprising a band layer including a band ply arranged on the outer side in the tire radial direction of the belt layer and arranged with a band cord at an angle of 5 ° or less with respect to the tire circumferential direction,
The band layer includes a pair of shoulder band layers disposed at both ends in the tire axial direction of the belt layer, and a center band layer disposed between the pair of shoulder band layers,
In the meridian cross section including the tire rotation axis in the normal state in which the rim is assembled to the normal rim and the normal internal pressure is filled and no load is applied,
The tread rubber disposed in the tread portion includes a pair of shoulder land portions located on the outer side in the tire radial direction of the shoulder band layer, and a crown land portion between the shoulder land portions,
The profile of the outer surface of the shoulder land portion is 0.5 to 1.5 mm in the tire radial direction outer side than the extended profile obtained by virtually extending the profile of the outer surface of the crown land portion outward in the tire axial direction ,
The tread portion is provided with a pair of shoulder main grooves extending continuously in the tire circumferential direction on the most tread end side,
The shoulder band layer and the center band layer have overlapping portions that overlap each other, and the overlapping portions are provided in a region radially inward of the tire main groove in the tire radial direction. tire.
The shoulder land portion is formed between the tread edge and the shoulder main grooves and the crown land portion, the pneumatic tire according to claim 1, wherein formed between the shoulder main grooves.
  The shoulder band layer includes an outer band ply disposed on the outer side in the tire radial direction of the belt layer, an inner band ply disposed on the inner side in the tire radial direction of the belt layer, and the inner band ply and the outer band ply. The pneumatic tire according to claim 1, wherein the pneumatic tire has a fold structure having a joint portion for joining the tire.   4. The pneumatic tire according to claim 1, wherein a profile of an outer surface of the shoulder land portion is such that a distance in a tire radial direction from the extension profile gradually decreases toward an outer side in a tire axial direction. In a load-load grounding state in which a normal load is applied to the tire in the normal state and grounded to a plane with a camber angle of 0 °,
The ratio Le / Ls between the contact length Le in the tire circumferential direction at the tire equator of the tread portion and the maximum contact length Ls in the tire circumferential direction of the shoulder land portion is 1.10 to 1.40. The pneumatic tire in any one of 4 thru | or 4.

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