JP2012116405A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire that achieves improvement in wear performance by suppressing wiping deformation caused by an in-plane contraction force during grounding.SOLUTION: The pneumatic tire is configured so that a belt layer 3 is arranged at the outer peripheral side of a carcass layer 2 in a tread 1. The belt layer 3 includes: a first belt ply 7; a second belt ply 8 arranged at the outer peripheral side of the first belt ply 7; and a third belt ply 9 arranged at the outer peripheral side of the second belt ply 8. The third belt ply 9 has: a center reinforcing part 91 located at the center side in the tread width direction and having a cord angle of smaller than 45° with respect to the tire circumferential direction; and shoulder reinforcing parts 92 located at both end sides in the tread width direction and having cord angles of larger than 45° with respect to the tire circumferential direction.

Description

  The present invention relates to a pneumatic tire in which a belt layer is disposed on the outer peripheral side of a carcass layer in a tread portion.

  Usually, a main groove extending along the tire circumferential direction is formed on a tread surface of a pneumatic tire, and a land portion is partitioned into a plurality of portions by the main groove. As a result of repeated research by the present inventor, when the tire is in contact with the ground, a force called in-plane contraction force acts on the ground contact surface, and the deformation of the land portion resulting from it has a considerable adverse effect on the wear performance. I understand. In this specification, such deformation of the land portion is called wiping deformation.

  The in-plane contraction force acts from the periphery of the contact surface toward the center, and the stronger the force the closer to the periphery, the more wiping deformation along the tire circumferential direction becomes dominant at the center in the tread width direction. The wiping deformation along the tire width direction is dominant at both ends in the tread width direction. As a result, early progress of wear is promoted and the occurrence of uneven wear such as center wear, shoulder wear, heel and toe wear is promoted, so there is a possibility that wear performance can be improved by suppressing such wiping deformation. found.

  The following Patent Document 1 describes a pneumatic tire in which a reinforcing layer (cap layer) is disposed in the inner area of a rib that is a land portion, and the following Patent Document 2 describes an inner area of a main groove. A pneumatic tire provided with a reinforcing layer (additional protective layer) is described. However, in these tires, the cord included in the reinforcing layer extends uniformly at or near the tire circumferential direction, so that wiping deformation along the tire width direction cannot be suppressed, and wear performance is improved with respect to the above viewpoint. It is thought that the effect to do is scarce.

Japanese Utility Model Publication No. 3-123702 JP 2008-285059 A

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a pneumatic tire capable of improving wear performance by suppressing wiping deformation caused by in-plane contraction force at the time of ground contact.

  The above object can be achieved by the present invention as described below. That is, the pneumatic tire according to the present invention is a pneumatic tire in which a belt layer is disposed on the outer peripheral side of the carcass layer of the tread portion, and the belt layer includes the first belt ply and the first belt ply. A second belt ply disposed on the outer circumferential side; and a third belt ply disposed on the outer circumferential side of the second belt ply, wherein the third belt ply is in the tread width direction. A center reinforcing portion located at the center of the tire and having a cord angle with respect to the tire circumferential direction of less than 45 °, and a shoulder located at both ends in the tread width direction and having a cord angle with respect to the tire circumferential direction exceeding 45 ° And a reinforcing portion.

  In this pneumatic tire, the belt layer includes the third belt ply as described above, and at the center side in the tread width direction where wiping deformation along the tire circumferential direction is dominant, the cord is in the tire circumferential direction. Alternatively, a shoulder reinforcement portion having a center reinforcement portion extending at an angle close to that and extending at an angle close to or close to the tire width direction on both ends in the tread width direction where wiping deformation along the tire width direction is dominant Therefore, the wiping deformation caused by the in-plane contraction force at the time of ground contact can be suppressed and the wear performance can be improved.

  In the present invention, it is preferable that the angle of the cord with respect to the tire circumferential direction at the center reinforcing portion is 0 to 35 °, and the angle of the cord with respect to the tire circumferential direction at the shoulder reinforcing portion is 70 to 90 °. According to this configuration, the cord angle of the center reinforcing portion is brought closer to the tire circumferential direction, and it becomes easy to suppress wiping deformation at the center side in the tread width direction, and the cord angle of the shoulder reinforcing portion is brought closer to the tire width direction. Thus, it is easy to suppress wiping deformation at both ends in the tread width direction, so that the wear performance can be effectively improved.

  In the present invention, the shoulder reinforcing portion is arranged in a region reaching from the end portion of the third belt ply to the inner region of the shoulder main groove located on the outermost side in the tread width direction formed on the tread surface. Is preferred. In the main groove formation location, because of the lack of rubber, in-plane contraction force in the tire width direction with the groove bottom as the starting point is likely to act, and this tendency is particularly pronounced in the outermost shoulder main groove Therefore, according to the above configuration, wiping deformation along the tire width direction can be effectively suppressed by the shoulder reinforcement portion.

  In the present invention, the cord constituting the third belt ply is preferably made of steel. According to such a configuration, it is possible to increase the strength of the third belt ply cord and enhance the effect of suppressing wiping deformation.

Tire meridian cross-sectional view showing an example of a tread portion of a pneumatic tire according to the present invention 1 is a plan view of a belt layer provided in the tire of FIG. Sectional view showing the periphery of the shoulder main groove

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The tire T shown in FIG. 1 is a pneumatic radial tire for a small truck, and a belt layer 3 is disposed on the outer peripheral side of the carcass layer 2 of the tread portion 1. The carcass layer 2 is constituted by a toroidal-shaped carcass ply including a cord extending substantially at right angles to the tire circumferential direction, and reaches a tread portion 1 through a sidewall portion 4 from a pair of bead portions (not shown). Is configured.

  The belt layer 3 is laminated on the outer periphery of the carcass layer 2 and reinforces the carcass layer 2 with an effect. A tread rubber 5 is provided on the outer peripheral side of the belt layer 3, and the outer peripheral surface of the tread rubber 5 constitutes a tread surface Tr. The tread surface Tr is provided with a plurality of (four in the present embodiment) main grooves 6a to 6d extending in the tire circumferential direction and a land portion 10 partitioned by them. The land portion 10 of the present embodiment is composed of a plurality of blocks divided by a lateral groove (not shown).

  The belt layer 3 is disposed on the belt ply 7 (first belt ply), the belt ply 8 (second belt ply) disposed on the outer peripheral side of the belt ply 7, and the outer peripheral side of the belt ply 8. Belt ply 9 (third belt ply). In the present embodiment, the belt ply 7 is laminated on the outer periphery of the carcass layer 2, the belt ply 8 is laminated on the outer periphery of the belt ply 7, and the belt ply 9 is laminated on the outer periphery of the belt ply 8. Each belt ply includes a plurality of cords arranged in parallel in a hook shape, and is formed by covering them with rubber.

  FIG. 2 is a plan view of the belt layer 3, but the codes in the drawing are conceptually described, and the actual arrangement pitch becomes denser. The belt plies 7 and 8 include cords C7 and C8 extending at an angle of θ7 and θ8 with respect to the tire circumferential direction (vertical direction in FIG. 2), respectively, and the cords C7 and C8 are opposite to each other. It is arranged to intersect. The angles θ7 and θ8 are set to 15 to 35 °, for example.

  The belt ply 9 is located on the center side in the tread width direction and the center reinforcing portion 91 where the angle θ9c of the cord C9 with respect to the tire circumferential direction is less than 45 °, and on both ends in the tread width direction and on the tire circumference A shoulder reinforcing portion 92 having an angle θ9s of the cord C9 with respect to the direction exceeding 45 °. In the present embodiment, an example in which the angle θ9c is 0 ° is shown. The belt ply 9 is closest to the land portion 10 among the belt plies constituting the belt layer 3, and has a large contribution to suppression of wiping deformation.

  As described above, the belt ply 9 has a cord C9 extending at or near the tire circumferential direction at the center in the tread width direction where wiping deformation along the tire circumferential direction is dominant, and along the tire width direction. Further, at both ends in the tread width direction where wiping deformation is dominant, the cord C9 extends at an angle close to or in the tire width direction. With such a configuration, it is possible to suppress the wiping deformation caused by the in-plane contraction force at the time of contact and improve the wear performance.

  In order to enhance the effect of suppressing wiping deformation, the angle θ9c of the cord C9 in the center reinforcing portion 91 is preferably 0 to 35 °, and more preferably 0 to 15 °. Further, the angle θ9s of the cord C9 in the shoulder reinforcing portion 92 is preferably 70 to 90 °, and more preferably 80 to 90 °. When the cord C9 of the center reinforcing portion 91 is inclined with respect to the tire circumferential direction (that is, when θ9c> 0 °), the center reinforcing portion 91 and the shoulder reinforcing portion 92 have the same inclination direction. This is advantageous in terms of uneven wear performance in the tire width direction because the difference in rigidity between the center side and both end sides can be suppressed.

  The width W9 of the belt ply 9 is preferably set to 70 to 110% of the ground contact width TW. If this is less than 70%, the belt ply 9 becomes narrow and the effect of improving the wear performance due to the suppression of wiping deformation tends to decrease. On the other hand, if it exceeds 110%, the belt ply 9 becomes wider, and a useless portion that does not contribute to suppression of wiping deformation in the ground contact surface increases. Note that the width W9 is more preferably set to 90 to 100% of the grounding width TW from the viewpoint of accurately suppressing wiping deformation within the grounding surface.

  The ground contact TE is the outermost position in the tire axial direction where the rim is assembled on a regular rim, the tire is placed vertically on a flat road surface filled with a regular internal pressure, and grounded on the road surface when a regular load is applied, The distance in the tire axial direction between the ground contact ends TE is the ground contact width TW. The normal load and the normal internal pressure are the maximum load (design normal load in the case of passenger car tires) specified in JIS D4202 (specifications of automobile tires) and the air pressure corresponding to the maximum load. The standard rim specified in The widths W9 and W91 are also obtained under the same conditions.

  At the locations where the main grooves 6a to 6d are formed, since the rubber is missing, an in-plane shrinkage force in the tire width direction with the groove bottom as a base point is likely to act, and the shoulder main groove 6a located on the outermost side in the tread width direction. , 6d, the tendency is particularly remarkable. Therefore, in the present embodiment, the shoulder reinforcing portion 92 is arranged in a region reaching from the end portion of the belt ply 9 to the inner region of the shoulder main grooves 6a and 6d, thereby wiping deformation along the tire width direction. The shoulder reinforcement portion 92 can be effectively suppressed.

  From the viewpoint of sufficiently suppressing the wiping deformation from the groove bottom of the shoulder main groove 6a as the base point, when the shoulder reinforcing portion 92 is projected onto the groove bottom height BL of the main groove shown in FIG. Preferably occupies a region that is 250% or more of the groove width W6 of the main groove 6a. The same applies to the shoulder main groove 6d. The groove width W6 is measured by the groove bottom height BL with reference to the extension line EL of the groove wall. The groove bottom height BL is a height at which the deepest end of the main groove 6 is located, and extends with the same curvature as the tread surface Tr.

  The width W91 of the center reinforcing portion 91 is preferably set to 40 to 70% of the ground contact width TW. When this is 40% or more, wiping deformation along the tire circumferential direction is accurately suppressed, which is beneficial for preventing the occurrence of heel and toe wear and the early progression of wear. In addition, the area where the shoulder reinforcing portion 92 is disposed is ensured by being 70% or less, and the wiping deformation along the tire width direction is accurately suppressed by the shoulder reinforcing portion 92, so that the center wear and the shoulder wear are generated. Useful for prevention.

  In the present embodiment, the belt ply 9 is laminated on the outer periphery of the belt ply 8 so that the tread portion 1 can be easily formed. However, the present invention is not limited to this, and the belt ply 9 may be offset to the tread surface Tr side to enhance the wiping deformation suppressing action. In that case, it is sufficient if the belt ply 9 is buried in the vicinity of the groove bottom height BL. In the case of a general tread rubber having a cap / base structure, since the interface between the cap rubber and the base rubber is formed at a height equivalent to the groove bottom height BL, the belt ply 9 is interposed at the interface. May be.

  The cords C7 and C8 included in the belt plies 7 and 8 are preferably made of steel in order to enhance the reinforcing effect on the carcass layer 2. Further, the cord C9 included in the belt ply 9 is also preferably made of steel from the viewpoint of enhancing the effect of suppressing wiping deformation, and may be another material having strength equivalent to steel.

  In this embodiment, although the example which connected the edge part of the shoulder reinforcement part 92 to the edge part of the center reinforcement part 91 is shown, you may isolate | separate these. When connecting both reinforcing portions as in the present embodiment, the ends of the center reinforcing portion 91 and the shoulder reinforcing portion 92 that are separately manufactured may be brought into contact with each other and may be pressure-bonded by a zipper joint or the like. The ends may be overlapped and joined so as not to overlap.

  The pneumatic tire of the present invention is the same as a normal pneumatic tire except that the belt layer includes the third belt ply as described above, and all of the conventionally known materials, shapes, structures, manufacturing methods, etc. It can be employed in the invention.

  In order to specifically show the configuration and effects of the present invention, the following wear performance was evaluated and will be described.

(1) Wear resistance (wear life)
After wearing a tire on a real vehicle and running on a general road for 50000 km, measure the amount of wear (decrease in main groove depth) at the center and both ends in the tread width direction, and calculate the reciprocal of the maximum value of the amount of wear. Calculated. Evaluation is shown by an index when Comparative Example 1 is set to 100, and the larger the value, the better the performance.

(2) Uneven wear performance (center wear, shoulder wear)
In the tire after running, the ratio (center wear amount / shoulder wear amount) between the wear amount (center wear amount) on the center side in the tread width direction and the wear amount (shoulder wear amount) on both ends was measured. The closer this ratio is to 1.0, the more uniform wear tends to be, and the better the performance.

(3) Heel and toe wear performance In the above-mentioned tire after running, the height of the stepping side and the kicking side of the block, which is the land portion provided at the center in the tread width direction, is measured, and the reciprocal of the difference in height is calculated. Calculated. Evaluation is shown by an index when Comparative Example 1 is set to 100, and the larger the value, the better the performance.

  In the tire having the structure shown in FIG. 1 (size LT265 / 70R17), the third belt ply includes a cord (made of nylon) that extends in parallel and uniformly with the tire circumferential direction. 2 includes a cord (steel) that extends uniformly at 45 ° with respect to the comparative example 2 and includes a center reinforcing portion and a shoulder reinforcing portion as shown in FIG. 2, and an angle θ9c of the cord (steel) included therein , Θ9s were set to 0 ° and 80 °, respectively, as Example 1. The evaluation results are shown in Table 1.

  In Comparative Example 1, since the suppression of wiping deformation along the tire width direction is not sufficient, the partial wear performance is relatively low, and the wear resistance performance is also inferior. In Comparative Example 2, since both wiping deformation along the tire circumferential direction and wiping deformation along the tire width direction cannot be suppressed, the partial wear performance and the heel and toe wear performance are inferior. On the other hand, in Example 1, while being relatively excellent in uneven wear performance and heel and toe wear performance, the wear resistance performance can also be improved.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Carcass layer 3 Belt layer 6a Shoulder main groove 6d Shoulder main groove 7 1st belt ply 8 2nd belt ply 9 3rd belt ply 91 Center reinforcement part 92 Shoulder reinforcement part C9 3rd belt ply Constructing code Tr Tread surface

Claims (4)

In the pneumatic tire in which the belt layer is disposed on the outer peripheral side of the carcass layer of the tread portion,
The belt layer includes a first belt ply, a second belt ply disposed on the outer peripheral side of the first belt ply, and a third belt disposed on the outer peripheral side of the second belt ply. Belt ply and
The third belt ply is located on the center side in the tread width direction and the center reinforcing portion has a cord angle of less than 45 ° with respect to the tire circumferential direction, and is located on both ends in the tread width direction and on the tire circumference. A pneumatic tire, comprising: a shoulder reinforcing portion in which an angle of the cord with respect to the direction exceeds 45 °.   The pneumatic tire according to claim 1, wherein an angle of the cord with respect to the tire circumferential direction at the center reinforcing portion is 0 to 35 °, and an angle of the cord with respect to the tire circumferential direction at the shoulder reinforcing portion is 70 to 90 °. .   The shoulder reinforcing portion is disposed in a region reaching from the end portion of the third belt ply to an inner region of a shoulder main groove located on the outermost side in the tread width direction formed on the tread surface. Or the pneumatic tire of 2.   The pneumatic tire according to any one of claims 1 to 3, wherein a cord constituting the third belt ply is made of steel.

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