JP2017001471A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire that makes abrasion resistance and wet performance compatible and further improves uneven abrasion resistance.SOLUTION: In a tread part 1, a plural rows of land parts 21-24 are partitioned by main grooves 11 extending in a tire circumference direction, where at respective land parts, lateral groove elements 30 extending in a tire width direction are formed. When an area ranging from a grounding end at the inside of a vehicle of the tread part 1 to a tire equator is set as a vehicle inside area Ain, an area ranging from a grounding end at the outside of the vehicle of the tread part 1 to the tire equator is set as a vehicle outside area Aout, and ratios of widths A-Ain a grounding area of each land part to widths B-Bin a grounding area of a part which extends continuously in the tire circumference direction without being divided by the lateral groove elements with a lateral width of more than 1.2 mm in each land part are set as continuous land part ratios, the continuous land part ratios of the tread part as a whole are set to 70% or more, the continuous land part ratios in the vehicle inside area are set larger than the continuous land part ratios in the vehicle outside area, and groove area ratios of the land parts 21 and 22 in the vehicle inside area are set larger than the groove area ratios of the land parts 23 and 24 in the vehicle outside area.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pneumatic tire in which a plurality of main grooves extending in the tire circumferential direction are provided in a tread portion, and more specifically, wear resistance and wet performance are balanced at a higher level, and moreover, uneven wear resistance. The present invention relates to a pneumatic tire that can improve the tire.

  In a pneumatic tire, generally, a plurality of main grooves extending in the tire circumferential direction are formed in the tread portion, and a plurality of rows of land portions extending in the tire circumferential direction are partitioned by these main grooves, and each land portion is divided. Transverse groove elements such as lug grooves and sipes extending in the tire width direction are formed.

  In the pneumatic tire having the above-described configuration, when the groove area of the tread portion is reduced (see, for example, Patent Documents 1 and 2), the rigidity of the tread portion is increased, so that the wear resistance can be improved. Although there is a problem, there is a problem that the wet performance is reduced accordingly. In addition, in a pneumatic tire in which the mounting direction with respect to the vehicle is specified, by making the pitch number and arrangement of the lug grooves different from each other in the vehicle inner region and the vehicle outer region, it is possible to make the tire performance in a trade-off relationship compatible (for example, However, it is difficult to achieve both wear resistance and wet performance with such a method.

JP 2014-166824 A JP 2014-184828 A JP 2013-244132 A JP 2012-236455 A JP 2011-255665A

  An object of the present invention is to provide a pneumatic tire that can achieve both wear resistance and wet performance at a higher level, and can further improve uneven wear resistance.

In order to achieve the above object, a pneumatic tire according to the present invention includes a tread portion that extends in the tire circumferential direction to form an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and the sidewall portions. In a pneumatic tire provided with a pair of bead portions arranged on the inner side in the tire radial direction of the tire, and a mounting direction for the vehicle is designated,
A plurality of main grooves extending in the tire circumferential direction are provided in the tread portion, a plurality of rows of land portions are partitioned by the main grooves, and a plurality of transverse groove elements extending in the tire width direction are formed in each land portion, and the tread The vehicle inner area extends from the ground contact edge on the inner side of the vehicle to the tire equator, and the vehicle outer area extends from the vehicle outer contact edge to the tire equator on the tread part. When the ratio of the width in the ground contact region of the portion extending continuously in the tire circumferential direction without being divided by the transverse groove element exceeding the groove width of 1.2 mm in the continuous land portion ratio is the whole of the tread portion The land portion ratio is 70% or more, the continuous land portion ratio in the vehicle inner region is larger than the continuous land portion ratio in the vehicle outer region, and the land portion groove is included in the vehicle inner region. Area ratio is the vehicle outer area Larger than the groove area ratio of land portions included it is characterized in.

  In the present invention, in the pneumatic tire in which the mounting direction with respect to the vehicle is specified, the continuous land portion ratio as a whole of the tread portion is set to 70% or more, so that the rigidity in the tire circumferential direction of the tread portion is increased and wear resistance is increased. Can be improved. Also, by increasing the ratio of the continuous land portion in the vehicle inner region to the continuous land portion ratio in the vehicle outer region, the effect of increasing the rigidity in the vehicle inner region that is likely to cause uneven wear is relatively increased. Uneven wear can be improved. Furthermore, by making the groove area ratio of the land portion included in the vehicle inner region larger than the groove area ratio of the land portion included in the vehicle outer region, drainage performance in the vehicle inner region where a relatively large load is applied during braking. Therefore, the wet performance (particularly, the braking performance on the wet road surface) can be improved.

  In the present invention, the groove area ratio in the ground contact region as a whole of the tread portion is preferably 30% or less. By defining the groove area ratio as a whole of the tread portion as described above, the effect of improving the wear resistance can be sufficiently obtained.

  Similarly, it is preferable that the groove area ratio in the contact area of the portion excluding the main groove of the tread portion is 10% or less. By defining the groove area ratio of the portion excluding the main groove of the tread portion as described above, the effect of improving the wear resistance can be sufficiently obtained.

  The difference between the groove area ratio of the land portion included in the vehicle inner region and the groove area ratio of the land portion included in the vehicle outer region is preferably 2% to 5%. By optimizing the difference between the two, it is possible to sufficiently improve the wet performance while maintaining good uneven wear resistance.

  The difference between the continuous land portion ratio in the vehicle inner region and the continuous land portion ratio in the vehicle outer region is preferably 5% to 15%. By optimizing the difference between the two, the effect of improving the uneven wear resistance can be sufficiently obtained.

  Moreover, it is preferable that the continuous land part ratio as a whole of a tread part is 70%-95%. By defining the upper limit value of the continuous land portion ratio as a whole of the tread portion, the wet performance can be favorably maintained.

  The present invention can be applied to a pneumatic tire mounted on various vehicles, but is particularly preferably applied to a pneumatic tire mounted on a passenger car. Since pneumatic tires for passenger cars are required to simultaneously improve wear resistance, wet performance, and uneven wear resistance, a remarkable effect can be expected in such applications.

  In the present invention, the ground contact area of the tread portion is the ground contact in the tire axial direction measured when a predetermined load is applied by placing the tire on a standard rim and filling the air pressure 230 kPa vertically on a plane. Identified based on width. The ground contact edge is the outermost position in the tire axial direction of the ground contact region. The “predetermined load” is a load corresponding to 70% of the maximum load capacity defined by each standard for each tire in the standard system including the standard on which the tire is based.

  The groove area ratio of the tread part or the land part is a ratio (%) of the area of the negative element to the sum of the area of the negative element and the area of the positive element on the tread part or the land part. The negative element means a groove part (including sipes), and the positive element means a land part.

It is meridian sectional drawing which shows the pneumatic tire which consists of embodiment of this invention. FIG. 2 is a development view showing a tread pattern of the pneumatic tire of FIG. 1.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. 1 to 2 show a pneumatic tire according to an embodiment of the present invention. This pneumatic tire is a tire in which the mounting direction of the tire front and back when the vehicle is mounted is designated. 1 to 2, IN is the inside of the vehicle when the vehicle is mounted, and OUT is the outside of the vehicle when the vehicle is mounted.

  As shown in FIG. 1, the pneumatic tire of the present embodiment includes a tread portion 1 that extends in the tire circumferential direction and has an annular shape, and a pair of sidewall portions 2, 2 disposed on both sides of the tread portion 1. And a pair of bead portions 3 and 3 disposed inside the sidewall portion 2 in the tire radial direction.

  A carcass layer 4 is mounted between the pair of bead portions 3 and 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded from the inside of the tire to the outside around the bead core 5 disposed in each bead portion 3. A bead filler 6 made of a rubber composition having a triangular cross-section is disposed on the outer periphery of the bead core 5.

  On the other hand, a plurality of belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 7 include a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and are arranged so that the reinforcing cords cross each other between the layers. In the belt layer 7, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set in a range of, for example, 10 ° to 40 °. A steel cord is preferably used as the reinforcing cord of the belt layer 7. For the purpose of improving high-speed durability, at least one belt cover layer 8 in which reinforcing cords are arranged at an angle of, for example, 5 ° or less with respect to the tire circumferential direction is disposed on the outer peripheral side of the belt layer 7. Yes. As the reinforcing cord of the belt cover layer 8, an organic fiber cord such as nylon or aramid is preferably used.

  In addition, although the tire internal structure mentioned above shows the typical example in a pneumatic tire, it is not limited to this.

  As shown in FIG. 2, the tread portion 1 is formed with three main grooves 11 extending in the tire circumferential direction. Here, the main groove is a circumference having a groove width of 3.0 mm or more, preferably 3.0 mm to 8.0 mm, and a groove depth of 4.0 mm or more, preferably 4.0 mm to 8.0 mm. Means directional groove. That is, a circumferential groove having a groove width of less than 3.0 mm or a groove depth of less than 4.0 mm does not correspond to the main groove. The main groove 11 includes a main groove 11A located on the vehicle inner side than the tire equator CL, a main groove 11B located on the tire equator CL, and a main groove 11C located on the vehicle outer side than the tire equator CL. . These main grooves 11A to 11C all extend linearly along the tire circumferential direction. The tread portion 1 includes an inner shoulder land portion 21 located on the vehicle inner side than the main groove 11A, an inner center land portion 22 located between the main groove 11A and the main groove 11B, a main groove 11B, and a main groove 11B. An outer center land portion 23 positioned between the groove 11C and an outer shoulder land portion 24 positioned on the vehicle outer side than the main groove 11C are partitioned.

  A plurality of transverse groove elements 30 extending in the tire width direction are formed in each of the land portions 21 to 24. The transverse groove element 30 includes a sipe (or narrow groove) 31 having a groove width of 1.2 mm or less and a lug groove 32 having a groove width exceeding 1.2 mm. The lug groove 32 having a groove width exceeding 1.2 mm substantially divides the continuity of the land portions 21 to 24 in the tire circumferential direction, but the sipe (or narrow groove) having a groove width of 1.2 mm or less. 31 does not substantially divide the continuity of the land portions 21 to 24 in the tire circumferential direction. The pitch in the tire circumferential direction and the length in the tire width direction of the transverse groove element 30 including the sipe 31 and the lug groove 32 are individually set in the land portions 21 to 24.

  The vehicle inner region Ain is defined as the vehicle inner region Ain from the vehicle inner grounding edge Ein of the tread portion 1 to the tire equator CL, and the vehicle outer region Aout from the vehicle outer grounding end Eout of the tread 1 to the tire equator CL. The groove pattern at and the groove pattern at the vehicle outer side area Aout are asymmetric with each other.

As shown in FIG. 2, the widths of the land portions 21 to 24 in the ground contact area are A ₁ , A ₂ , A ₃ , and A ₄ , respectively. In the land portions 21 to 24, the width in the ground contact region of the portion continuously extending in the tire circumferential direction without being divided by the lateral groove element 30 (that is, the lug groove 32) exceeding the groove width of 1.2 mm is respectively set. B _1, a _{B 2, B 3, B 4} . These land portions 21 to 24 continuously extend in the tire circumferential direction without being divided by the lateral groove elements 30 exceeding the groove width of 1.2 mm in the widths A _{1 to} A ₄ and the land portions 21 to 24 in the ground contact area. The continuous land portion ratio is calculated based on the widths B _{1 to} B ₄ in the contact area of the portion.

In the pneumatic tire, the continuous land portion ratio Xt [Xt = (B ₁ + B ₂ + B ₃ + B ₄ ) / (A ₁ + A ₂ + A ₃ + A ₄ ) × 100%] of the tread portion 1 as a whole is 70%. As described above, it is more preferably set in the range of 70% to 95%. The continuous land portion ratio Xin [Xin = (B ₁ + B ₂ ) / (A ₁ + A ₂ ) × 100%] in the vehicle inner region Ain is the continuous land portion ratio Xout [Xout = (B _{3 + B 4) / (A} 3 + A 4) is set to be greater than × 100%].

  Further, the groove area ratio Rin of the land portions 21 and 22 included in the vehicle inner area Ain is set to be larger than the groove area ratio Rout of the land portions 23 and 24 included in the vehicle outer area Aout. Here, the groove area ratio Rin is a ratio (%) of the total area of the groove components included in the land parts 21 and 22 to the total area of the land parts 21 and 22, and the groove area ratio Rout is the total area of the land parts 23 and 24. This is the ratio (%) of the total area of the groove components included in the land portions 23 and 24 to the area. As described above, when the continuous land portion ratio Xin in the vehicle inner region Ain is larger than the continuous land portion ratio Xout in the vehicle outer region Aout, the groove area ratio Rin is equal to the groove area ratio if the tread pattern is uniform. Although smaller than Rout, in the pneumatic tire, the sipe 31 formed in the land portions 21 and 22 included in the vehicle inner region Ain is relatively increased, and the land portions 23 and 24 included in the vehicle outer region Aout. The groove area ratio Rin is made larger than the groove area ratio Rout by relatively reducing the number of sipes 31 formed in the groove.

  In the pneumatic tire described above, by setting the continuous land portion ratio Xt of the tread portion 1 as a whole to 70% or more, the rigidity of the tread portion 1 in the tire circumferential direction can be increased and the wear resistance can be improved. Here, if the continuous land portion ratio Xt of the tread portion 1 as a whole is smaller than 70%, the effect of improving the wear resistance becomes insufficient. In particular, the continuous land portion ratio Xt of the tread portion 1 as a whole is preferably set in the range of 70% to 95%. If the continuous land portion ratio Xt as a whole of the tread portion 1 is larger than 95%, the groove area becomes small and the effect of improving the wet performance is lowered.

  Further, in the above-described pneumatic tire, the rigidity in the vehicle inner region Ain, which tends to cause uneven wear, is set by making the continuous land portion ratio Xin in the vehicle inner region Ain larger than the continuous land portion ratio Xout in the vehicle outer region Aout. Since the effect of increasing is relatively increased, it is possible to improve uneven wear resistance.

  The difference (Xin−Xout) between the continuous land portion ratio Xin in the vehicle inner region Ain and the continuous land portion ratio Xout in the vehicle outer region Aout is preferably set in a range of 5% to 15%. Thereby, the effect of improving uneven wear resistance can be sufficiently obtained. If the difference between the continuous land portion ratio Xin and the continuous land portion ratio Xout (Xin−Xout) is smaller than 5%, the rigidity in the vehicle inner area Ain is insufficient, and the effect of improving uneven wear resistance becomes insufficient. On the other hand, if it exceeds 15%, the rigidity difference between the vehicle inner side area Ain and the vehicle outer side area Aout becomes excessive, and the effect of improving uneven wear resistance decreases.

  Further, in the pneumatic tire described above, the groove area ratio Rin of the land portions 21 and 22 included in the vehicle inner area Ain is made larger than the groove area ratio Rout of the land portions 23 and 24 included in the vehicle outer area Aout. Since the drainage performance in the vehicle inner area Ain where a relatively large load is applied during braking is improved, the wet performance (particularly, the braking performance on the wet road surface) can be improved.

  The difference (Rin−Rout) between the groove area ratio Rin of the land portions 21 and 22 included in the vehicle inner area Ain and the groove area ratio Rout of the land portions 23 and 24 included in the vehicle outer area Aout is 2% to 5%. Set to a range. Thereby, the improvement effect of wet performance can fully be acquired, maintaining uneven wear resistance favorably. If the difference (Rin−Rout) between the groove area ratio Rin and the groove area ratio Rout is less than 2%, the effect of improving the wet performance is reduced. Conversely, if the difference is greater than 5%, the vehicle inner area Ain and the vehicle outer area Aout are reduced. Therefore, the effect of improving uneven wear resistance is reduced.

  Further, the groove area ratio Rt in the ground contact region as a whole of the tread portion 1 is 30% or less, preferably 20% to 30%. Thereby, the effect of improving the wear resistance can be sufficiently obtained. If the groove area ratio Rt in the ground contact region as a whole of the tread portion 1 is larger than 30%, the effect of improving uneven wear resistance is lowered.

  Similarly, the groove area ratio Rr in the ground contact region of the portion (that is, the land portions 21 to 24) excluding the main groove 11 of the tread portion 1 is 10% or less, preferably 5% to 10%. . Thereby, the effect of improving the wear resistance can be sufficiently obtained. If the groove area ratio Rr of the portion excluding the main groove 11 of the tread portion 1 is larger than 10%, the effect of improving uneven wear resistance is lowered.

  Although the embodiment depicted in FIGS. 1 and 2 relates to a pneumatic tire for passenger cars, the present invention can also be applied to pneumatic tires for other uses.

  In a pneumatic tire having a tire size of 155 / 65R14, a tread portion, a pair of sidewall portions, and a pair of bead portions, and a mounting direction with respect to the vehicle is designated, a plurality of main tires extending in the tire circumferential direction on the tread portion A plurality of lateral groove elements extending in the tire width direction are formed in each land portion, a continuous land portion ratio Xt as a whole of the tread portion, a vehicle inner region The continuous land portion ratio Xin in the vehicle, the continuous land portion ratio Xout in the vehicle outer region, the groove area ratio Rt in the ground contact region as a whole of the tread portion, and the ground contact region of the portion excluding the main groove in the tread portion Conventional example, comparative examples 1 and 2 in which the groove area ratio Rr, the groove area ratio Rin of the land portion included in the vehicle inner region, and the groove area ratio Rout of the land portion included in the vehicle outer region are set as shown in Table 1 Example 1 8 tires were produced.

  These test tires were evaluated for wear resistance, uneven wear resistance, and wet performance by the following test methods, and the results are also shown in Table 1.

Abrasion resistance:
Each test tire is mounted on a wheel with a rim size of 14 x 4.5 J and mounted on a light vehicle with a displacement of 660 cc. The estimated wear life (km) was calculated from the remaining amount. The evaluation results are shown as an index with the conventional example being 100. A larger index value means better wear resistance.

Uneven wear resistance:
Each test tire is mounted on a wheel with a rim size of 14 x 4.5 J and mounted on a light vehicle with a displacement of 660 cc. The level difference of the heel and toe wear in the shoulder land portion was measured. The evaluation results are shown as an index with the conventional example being 100, using the reciprocal of the measured value. The larger the index value, the better the uneven wear resistance.

Wet performance:
Each test tire is mounted on a wheel with a rim size of 14 x 4.5 J and mounted on a light vehicle with a displacement of 660 cc. The braking distance was measured by applying a brake from the running state of h. The evaluation results are shown as an index with the conventional example being 100, using the reciprocal of the measured value. The larger the index value, the better the wet performance.

  As can be seen from Table 1, all of the tires of Examples 1 to 8 have improved wear resistance and wet performance at the same time as compared with the conventional example, and also have an improvement effect on uneven wear resistance. It was obtained. On the other hand, in Comparative Example 1, although the continuous land portion ratio Xin in the vehicle inner region is larger than the continuous land portion ratio Xout in the vehicle outer region, the land portion groove included in the vehicle inner region accordingly. Since the area ratio Rin is smaller than the groove area ratio Rout of the land portion included in the vehicle outer region, the wet performance was insufficient. In Comparative Example 2, the land area groove area ratio Rin included in the vehicle inner area is larger than the land area groove area ratio Rout included in the vehicle outer area. Since the continuous land portion ratio Xin is smaller than the continuous land portion ratio Xout in the vehicle outer region, the uneven wear resistance is insufficient.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 11 Main groove 21, 22, 23, 24 Land part 30 Horizontal groove element 31 Sipe 32 Lug groove Ain Vehicle inside area Aout Vehicle outside area CL Tire equator

Claims (7)

An annular tread portion extending in the tire circumferential direction, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the inner side in the tire radial direction of the sidewall portions. In a pneumatic tire with a specified mounting direction for the vehicle,
A plurality of main grooves extending in the tire circumferential direction are provided in the tread portion, a plurality of rows of land portions are partitioned by the main grooves, and a plurality of transverse groove elements extending in the tire width direction are formed in each land portion, and the tread The vehicle inner area extends from the ground contact edge on the inner side of the vehicle to the tire equator, and the vehicle outer area extends from the vehicle outer contact edge to the tire equator on the tread part. When the ratio of the width in the ground contact region of the portion extending continuously in the tire circumferential direction without being divided by the transverse groove element exceeding the groove width of 1.2 mm in the continuous land portion ratio is the whole of the tread portion The land portion ratio is 70% or more, the continuous land portion ratio in the vehicle inner region is larger than the continuous land portion ratio in the vehicle outer region, and the land portion groove is included in the vehicle inner region. Area ratio is the vehicle outer area A pneumatic tire and greater than the groove area ratio of land portions included.   2. The pneumatic tire according to claim 1, wherein a groove area ratio in the contact area as a whole of the tread portion is 30% or less.   The pneumatic tire according to claim 1 or 2, wherein a groove area ratio in a ground contact region of a portion excluding the main groove of the tread portion is 10% or less.   The difference between the groove area ratio of the land portion included in the vehicle inner region and the groove area ratio of the land portion included in the vehicle outer region is 2% to 5%. The pneumatic tire according to Crab.   The air according to any one of claims 1 to 4, wherein a difference between a continuous land portion ratio in the vehicle inner region and a continuous land portion ratio in the vehicle outer region is 5% to 15%. tire.   The pneumatic tire according to any one of claims 1 to 5, wherein a ratio of a continuous land portion as a whole of the tread portion is 70% to 95%.   The pneumatic tire according to claim 1, wherein the pneumatic tire is mounted on a passenger car.

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