JP2017001473A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire that is improved in abrasion resistance, wet performance and steering stability on a dry road surface.SOLUTION: In a tread part 1, a plurality of main grooves 11 extending in a tire circumference direction are provided and a plural rows of land parts 21-24 are partitioned, where at respective land parts, a plurality of lateral groove elements 30 extending in a tire width direction are formed. When an area closer to inside than center lines of a pair of outermost main grooves 11A and 11C positioned at the outermost side in a tire width direction, of the main grooves, is set as a center area Ce, areas ranging from the center lines to grounding ends are set as shoulder areas Sh, 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 center area are set larger than the continuous land part ratios in the shoulder area, and groove area ratios of the land parts in the center area are set larger than the groove area ratios of the land parts in the shoulder 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 further on a dry road surface. The present invention relates to a pneumatic tire that can improve steering stability.

  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. Further, in a pneumatic tire, by making the pitch number and arrangement of the lug grooves different between the vehicle inner region and the vehicle outer region, the tire performance having a trade-off relationship is made compatible (for example, refer to Patent Documents 3 to 5). However, it is difficult to achieve both wear resistance and wet performance with such a method.

JP 2014-166824 A JP 2014-184828 A JP2015-37945A JP 2014-162300 A JP 2013-154654 A

  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 further improve the handling stability on a dry road surface.

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
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 defined by the main grooves, and a plurality of transverse groove elements extending in the tire width direction are formed in each land portion, Among the grooves, the center region is the inner side in the tire width direction from the center line of the pair of outermost main grooves located on the outermost side in the tire width direction, and the shoulder region is from the center line of the outermost main groove to the ground contact end of the tread portion. And the width of each land portion in the ground contact region and the width of each land portion in the ground contact region continuously extending in the tire circumferential direction without being divided by the lateral groove element exceeding the groove width of 1.2 mm The continuous land portion ratio as a whole of the tread portion is 70% or more, and the continuous land portion ratio in the center region is higher than the continuous land portion ratio in the shoulder region. Large and the center area Groove area ratio of the land portion that includes and is characterized in that the larger than the groove area ratio of the land portions included in the shoulder region.

  In the present invention, in the pneumatic tire, by setting the continuous land portion ratio of the tread portion as a whole to 70% or more, the rigidity in the tire circumferential direction of the tread portion can be increased and the wear resistance can be improved. In addition, by increasing the ratio of the continuous land portion in the center region to the continuous land portion ratio in the shoulder region, the effect of increasing the rigidity in the center region, which greatly contributes to the handling stability on the dry road surface, is relatively increased. Therefore, the driving stability on the dry road surface can be improved. Furthermore, by making the groove area ratio of the land part included in the center area larger than the groove area ratio of the land part included in the shoulder area, drainage performance in the center area that contributes significantly to the wet performance during driving is good. Therefore, the wet performance (particularly, the traction 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 center region and the groove area ratio of the land portion included in the shoulder 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 steering stability on the dry road surface.

  The difference between the continuous land portion ratio in the center region and the continuous land portion ratio in the shoulder region is preferably 5% to 15%. By optimizing the difference between them, it is possible to sufficiently obtain the effect of improving the steering stability on the dry road surface.

  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 steering stability on dry road surfaces, 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.

  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 is located on the one side in the tire width direction from the tire equator CL, the main groove 11B located on the tire equator CL, and on the other side in the tire width direction from the tire equator CL. Main groove 11C. These main grooves 11A to 11C all extend linearly along the tire circumferential direction. The tread portion 1 includes a shoulder land portion 21 located on one side in the tire width direction with respect to the main groove 11A, a center land portion 22 located between the main groove 11A and the main groove 11B, and the main groove 11B. A center land portion 23 located between the main groove 11C and a shoulder land portion 24 located on the other side in the tire width direction from the main groove 11C is 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 center region Ce is an inner side in the tire width direction from the center line of the pair of main grooves 11A, 11C located on the outermost side in the tire width direction, and the shoulder line extends from the center line of these main grooves 11A, 11C to the ground contact end E of the tread portion 1. When the region Sh is set, the center land portions 22 and 23 are arranged in the center region Ce, and the shoulder land portions 21 and 24 are arranged in the shoulder region Sh. The center lines of the main grooves 11A and 11C are straight lines passing through the center position of the groove width.

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%. Further, the continuous land portion ratio xCe in the center area Ce _{[Xce = (B 2 + B 3} ) / (A 2 + A 3) × 100% ] of continuous land portion ratio XSH in the shoulder regions Sh [Xsh = (B ₁ + B ₄ ) / (A ₁ + A ₄ ) × 100%].

  Furthermore, the groove area ratio Rce of the land portions 22 and 23 included in the center region Ce is set to be larger than the groove area ratio Rsh of the land portions 21 and 24 included in the shoulder region Sh. Here, the groove area ratio Rce is the ratio (%) of the total area of the groove components included in the land portions 22 and 23 to the total area of the land portions 22 and 23, and the groove area ratio Rsh is the total area of the land portions 21 and 24. This is the ratio (%) of the total area of the groove components included in the land portions 21 and 24 to the area. As described above, when the continuous land portion ratio Xce in the center region Ce is larger than the continuous land portion ratio Xsh in the shoulder region Sh, the groove area ratio Rce is greater than the groove area ratio Rsh if the tread pattern is uniform. However, in the above pneumatic tire, the sipe 31 formed in the land portions 21 and 24 included in the shoulder region Sh is relatively reduced, and is formed in the land portions 22 and 23 included in the center region Ce. By relatively increasing the number of sipes 31, the groove area ratio Rce is made larger than the groove area ratio Rsh.

  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.

  In the pneumatic tire described above, by making the continuous land portion ratio Xce in the center region Ce larger than the continuous land portion ratio Xsh in the shoulder region Sh, the center region has a large contribution to the handling stability on the dry road surface. Since the effect of increasing the rigidity in Ce is relatively increased, the steering stability on the dry road surface can be improved.

  The difference (Xce−Xsh) between the continuous land portion ratio Xce in the center region Ce and the continuous land portion ratio Xsh in the shoulder region Sh is preferably set in the range of 5% to 15%. Thereby, the improvement effect of the steering stability on a dry road surface can fully be acquired. If the difference between the continuous land portion ratio Xce and the continuous land portion ratio Xsh (Xce−Xsh) is smaller than 5%, the rigidity in the center region Ce is insufficient, and the effect of improving the driving stability on the dry road surface is insufficient. On the contrary, if it is larger than 15%, the rigidity difference between the center region Ce and the shoulder region Sh becomes excessive, so that the effect of improving the steering stability on the dry road surface is lowered.

  Further, in the pneumatic tire described above, driving is performed by making the groove area ratio Rce of the land portions 22 and 23 included in the center region Ce larger than the groove area ratio Rsh of the land portions 21 and 24 included in the shoulder region Sh. Since the drainage performance in the center region Ce that greatly contributes to the wet performance at the time becomes good, the wet performance (particularly, the traction performance on the wet road surface) can be improved.

  The difference (Rce−Rsh) between the groove area ratio Rce of the land portions 22 and 23 included in the center region Ce and the groove area ratio Rsh of the land portions 21 and 24 included in the shoulder region Sh is in the range of 2% to 5%. It is good to set. As a result, it is possible to sufficiently improve the wet performance while maintaining good steering stability on the dry road surface. If the difference (Rce-Rsh) between the groove area ratio Rce and the groove area ratio Rsh is smaller than 2%, the effect of improving the wet performance is reduced. Conversely, if the difference is larger than 5%, the rigidity in the center region Ce is insufficient. Therefore, the effect of improving the handling stability on the dry road surface 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 and having a tread portion, a pair of sidewall portions, and a pair of bead portions, a plurality of main grooves extending in the tire circumferential direction are provided in the tread portion, and a plurality of these main grooves are provided. The land portion of the row is partitioned, and a plurality of transverse groove elements extending in the tire width direction are formed in each land portion, the continuous land portion ratio Xt as a whole of the tread portion, the continuous land portion ratio Xce in the center region, the shoulder region The continuous land portion ratio Xsh in the tread portion, the groove area ratio Rt in the ground contact region as a whole of the tread portion, the groove area ratio Rr in the ground contact region of the portion excluding the main groove of the tread portion, the land included in the center region The tires of conventional examples, comparative examples 1 and 2 and examples 1 to 8 in which the groove area ratio Rce of the portion and the groove area ratio Rsh of the land portion included in the shoulder region are set as shown in Table 1 were manufactured.

  These test tires were evaluated for wear resistance, handling stability on a dry road surface, 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.

Steering stability on dry roads:
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. Evaluation was performed. The evaluation results are shown as an index with the conventional example being 100. The larger the index value, the better the steering stability on the dry road surface.

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. It accelerated and measured the driving distance until it reached 50 km / 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 in comparison with the conventional example, and also the driving stability on the dry road surface. Improvement effect was obtained. On the other hand, in Comparative Example 1, although the continuous land portion ratio Xce in the center region is larger than the continuous land portion ratio Xsh in the shoulder region, the groove area ratio Rce of the land portion included in the center region is accordingly accompanied. Is smaller than the land area ratio Rsh of the land portion included in the shoulder region, the wet performance was insufficient. In Comparative Example 2, although the land area groove area ratio Rce included in the center area is larger than the land area groove area ratio Rsh included in the shoulder area, the continuous land area in the center area is accordingly accompanied. Since the portion ratio Xce is smaller than the continuous land portion ratio Xsh in the shoulder region, the steering stability on the dry road surface was 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 Ce Center area | region Sh Shoulder 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 the provided pneumatic tire,
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 defined by the main grooves, and a plurality of transverse groove elements extending in the tire width direction are formed in each land portion, Among the grooves, the center region is the inner side in the tire width direction from the center line of the pair of outermost main grooves located on the outermost side in the tire width direction, and the shoulder region is from the center line of the outermost main groove to the ground contact end of the tread portion. And the width of each land portion in the ground contact region and the width of each land portion in the ground contact region continuously extending in the tire circumferential direction without being divided by the lateral groove element exceeding the groove width of 1.2 mm The continuous land portion ratio as a whole of the tread portion is 70% or more, and the continuous land portion ratio in the center region is higher than the continuous land portion ratio in the shoulder region. Large and the center area A pneumatic tire, wherein a groove area ratio of the land portion is larger than the groove area ratio of land portions included in the shoulder region 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 center region and the groove area ratio of the land portion included in the shoulder region is 2% to 5%. The described pneumatic tire.   The pneumatic tire according to any one of claims 1 to 4, wherein a difference between a continuous land portion ratio in the center region and a continuous land portion ratio in the shoulder region is 5% to 15%.   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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