JP2010173346A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire simultaneously improving steering stability on snow and steering stability on a dry road while maintaining a good wetting performance. <P>SOLUTION: In this pneumatic tire, at least three main grooves 1, 2 extending in a tire peripheral direction and a plurality of lateral grooves 3 extending in a tire width direction and communicated between the main grooves, and a plurality of blocks 5 is blocked by the main grooves 1, 2 and the lateral groove 3. A center main groove 1 positioned on a tire equator E among the main grooves 1, 2 is formed straight. The lateral groove 3 is arranged to be inclined at an angle of 40-60° relative to the tire peripheral direction, and a bottoming part 3a is formed at a portion communicated to the center main groove 1 of the lateral groove 3, so as to change the groove width of the lateral groove 3 in proportion to the groove depth. Groove depth D3a of the lateral groove 3 of the bottoming part 3a is made to 40-60% of the groove depth D1 of the center main groove 1, and the minimum groove with W3a of the lateral groove 3 is made to 30-50% of its maximum groove width W3. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a pneumatic tire suitable for a small truck, and more specifically, it is possible to simultaneously improve the handling stability on snow and the handling stability on a dry road surface while maintaining good wet performance. Related to pneumatic tires.

  In a pneumatic tire, a tread pattern in which at least three main grooves extending in the tire circumferential direction and a plurality of horizontal grooves extending in the tire width direction are provided in the tread portion and a plurality of blocks are partitioned by the main grooves and the horizontal grooves is adopted. Yes. In such a tread pattern, increasing the lateral groove component improves the traction performance on snow, but accordingly, the steering stability on the dry road surface decreases. In addition, when a part of the lateral groove is narrowed and formed into a sipe (see, for example, Patent Document 1), the handling stability on the dry road surface is improved, but the drainage performance and the traction performance on snow are reduced.

  On the other hand, in recent years, for example, for pneumatic tires for light trucks mounted on commercial vehicles, while maintaining good wet performance including drainage performance, on snow including traction performance and skid prevention performance on snow. Although it is required to improve the driving stability of the vehicle and improve the driving stability on the dry road surface, these requirements are not always satisfied.

JP 2004-345457 A

  An object of the present invention is to provide a pneumatic tire that can simultaneously improve the handling stability on snow and the handling stability on a dry road surface while maintaining good wet performance.

  In order to achieve the above object, a pneumatic tire according to the present invention is provided with at least three main grooves extending in the tire circumferential direction and a plurality of lateral grooves extending in the tire width direction and communicating between the main grooves. In a pneumatic tire in which a plurality of blocks are partitioned by a main groove and a lateral groove, a center main groove located on the tire equator of the main groove is formed in a straight shape, and the lateral groove is 40 ° to 60 ° with respect to the tire circumferential direction. It is arranged to be inclined at an angle of °, and a bottom raised portion is formed at the communication portion of the lateral groove with respect to the center main groove, the groove width of the lateral groove is changed in proportion to the groove depth, and the bottom raised portion is The groove depth of the transverse groove is 40% to 60% of the groove depth of the center main groove, and the minimum groove width of the transverse groove is 30% to 50% of the maximum groove width.

  In the present invention, by arranging a plurality of lateral grooves communicating between the main grooves so as to be inclined with respect to the tire circumferential direction, the lateral grooves having an extension component in the tire circumferential direction and an extension component in the tire width direction bite snow. This effectively suppresses longitudinal and lateral slipping of the vehicle when in the snow, so that the steering stability on snow can be improved. Further, a bottom raised portion is formed at the communication portion of the lateral groove with respect to the center main groove, and the groove width of the lateral groove is changed to be proportional to the groove depth, that is, the transverse groove is relatively narrowed at the bottom raised portion. The block rigidity at the site can be increased, and the steering stability on the dry road surface can be improved. Moreover, according to the method of increasing the block rigidity by relatively narrowing the horizontal groove at the bottom raised portion, the state where the horizontal groove communicates with the center main groove is secured, so that the wet performance including the drainage performance is improved. Can be maintained.

  In the present invention, the length of the bottom raised portion is preferably 20% to 50% of the length of the lateral groove. By increasing the length of the bottom raised part and increasing the block rigidity, it can be expected to improve the handling stability on the dry road surface, but if the length of the bottom raised part is excessive, the handling stability on the snow will decrease. become. By selecting the above range, it is possible to improve the driving stability on the dry road surface without reducing the driving stability on the snow.

  Each block adjacent to the center main groove is preferably provided with 4 to 6 sipes extending in the tire width direction. Sipes are necessary to improve the performance on snow, but if the number of sipes is excessive, the driving stability on the dry road surface will be reduced. By setting the number of sipes per block within the above range, both on-snow performance and steering stability on a dry road surface can be achieved.

  It is preferable to provide a chamfered portion at the edge of each block adjacent to the center main groove on the center main groove side, and to gradually increase the depth and width of the chamfered portion from the obtuse corner portion to the acute corner portion of the block. . Here, the maximum depth of the chamfered portion is preferably 30% to 50% of the depth of the center main groove. When the chamfered portion is provided at the edge on the center main groove side of each block, the wet performance can be improved by the edge effect.

  A plurality of narrow grooves on the tread surface of each block adjacent to the center main groove have a groove width of 0.1 mm to 0.8 mm, a groove depth of 0.1 mm to 0.8 mm, and are inclined with respect to the tire circumferential direction. Is preferably provided. By providing the narrow groove on the tread surface of each block, it is possible to improve the performance on snow in the initial use.

It is an expanded view which shows the tread pattern of the pneumatic tire which consists of embodiment of this invention. FIG. 2 is an enlarged plan view showing a block adjacent to a center main groove in the pneumatic tire of FIG. 1. FIG. 2 is an enlarged side view showing a block adjacent to a center main groove in the pneumatic tire of FIG. 1. FIG. 2 is an enlarged cross-sectional view showing a narrow groove formed on a tread surface of a block adjacent to a center main groove in the pneumatic tire of FIG. 1.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a tread pattern of a pneumatic tire according to an embodiment of the present invention, and FIGS.

  As shown in FIG. 1, the tread portion T has one center main groove 1 located on the tire equator E and extending in the tire circumferential direction, and located on both sides of the center main groove 1 in the tire circumferential direction. Two outer main grooves 2 that extend, a plurality of horizontal grooves 3 that extend in the tire width direction and communicate between the main grooves 1 and 2, and a plurality of horizontal grooves that extend from the outer main groove 2 to the outside of the ground contact end in the tire width direction 4 is formed. The main grooves 1 and 2 and the horizontal grooves 3 define two rows of block rows composed of a plurality of blocks 5 in the center region, and the main grooves 2 and the lateral grooves 4 constitute two rows of block rows composed of a plurality of blocks 6 in the shoulder region Is partitioned. The blocks 5 and 6 are provided with a plurality of sipes 7 and 8 each having a zigzag shape in plan view. However, the structure of the sipes 7 and 8 is not particularly limited.

  The main grooves 1 and 2 are both formed in a straight shape, but at least the center main groove 1 may be straight in order to ensure good drainage performance, and the outer main groove 2 may be in a zigzag shape. good. Further, in order to ensure good drainage performance, the lateral groove 3 disposed in the center region communicates with both the center main groove 1 and the outer main groove 2, but the lateral groove 4 disposed in the shoulder region is the outer main groove. The groove 2 may not be in communication.

  The lateral grooves 3 are arranged so as to be inclined with respect to the tire circumferential direction. The inclination angle θ of the lateral groove 3 with respect to the tire circumferential direction is set in a range of 40 ° to 60 °. Here, the inclination angle θ is an angle formed by the groove width center line of the lateral groove 3 with respect to the tire circumferential direction (see FIG. 2).

  As shown in FIGS. 2 and 3, a bottom raised portion 3 a is formed at a communication portion of the lateral groove 3 with respect to the center main groove 1. The bottom raised portion 3a is a portion raised to the bottom so that the groove depth is smaller than other portions of the lateral groove 3. The groove width of the lateral groove 3 changes so as to be proportional to the groove depth, and is relatively small at the bottom raised portion 3a. More specifically, the groove depth D3a of the lateral groove 3 in the bottom raised portion 3a is set in a range of 40% to 60% of the groove depth D1 of the center main groove 1. Further, the minimum groove width W3a of the lateral groove 3 is set in a range of 30% to 50% of the maximum groove width W3.

  In the pneumatic tire configured as described above, the plurality of lateral grooves 3 communicating between the main grooves 1 and 2 are arranged so as to be inclined with respect to the tire circumferential direction. When the lateral groove 3 having the extending component in the tire width direction bites snow, it is possible to effectively suppress the vehicle slip in the front-rear direction and the lateral direction. Thereby, steering stability on snow can be improved.

  In addition, the bottom raised portion 3a is formed at the communication portion of the horizontal groove 3 with respect to the center main groove 1, and the groove width of the horizontal groove 3 is changed in proportion to the groove depth, thereby increasing the block rigidity in the vicinity of the raised portion 3a. In addition, the handling stability on the dry road surface can be improved. In addition, since the bottom raising and the narrowing of the lateral groove 3 are combined, it is possible to ensure that the lateral groove 3 communicates with the center main groove 1 when increasing the block rigidity. Therefore, the drainage performance can be favorably maintained by the cooperation of the center main groove 1 and the lateral groove 3.

  The inclination angle θ of the lateral grooves 3 with respect to the tire circumferential direction is set to 40 ° to 60 °. If the inclination angle θ is less than 40 °, the traction performance on the snow is deteriorated. The anti-skid performance is reduced.

  The groove depth D3a of the horizontal groove 3 in the bottom raised portion 3a is 40% to 60% of the groove depth D1 of the center main groove 1, but the ratio of the groove depth D3a of the horizontal groove 3 to the groove depth D1 of the center main groove 1 If it is less than 40%, the drainage performance and the snow drainage performance will be reduced. Conversely, if it exceeds 60%, the effect of improving the steering stability on the dry road surface will be insufficient.

  The minimum groove width W3a of the horizontal groove 3 is set to 30% to 50% of the maximum groove width W3. If the ratio of the minimum groove width W3a to the maximum groove width W3 of the horizontal groove 3 is less than 30%, drainage performance and snow drainage performance. On the contrary, if it exceeds 50%, the block rigidity does not change so much and the effect of improving the steering stability on the dry road surface becomes insufficient.

  In the pneumatic tire described above, the length L3a of the bottom raised portion 3a may be set in the range of 20% to 50%, more preferably in the range of 30% to 40% of the length L3 of the lateral groove 3. Here, the length L3a of the bottom raised portion 3a and the length L3 of the lateral groove 3 are lengths measured along the groove width center line of the lateral groove 3. By setting the length L3a of the bottom raised portion 3a within the above range, the steering stability on the dry road surface can be improved without reducing the steering stability on the snow. If the length L3a of the bottom raised portion 3a is too small, the effect of improving the steering stability on the dry road surface is insufficient, and conversely if too large, the steering stability on the snow is lowered.

  Moreover, it is preferable to arrange four to six sipes 7 extending in the tire width direction in each block 5 adjacent to the center main groove 1. This makes it possible to achieve both snow performance and driving stability on a dry road surface. If the number of sipes 7 provided in each block 5 is less than 4, the performance on snow is lowered, and if it exceeds 6, the steering stability on the dry road surface is lowered.

  In the pneumatic tire, a chamfered portion 5 a is formed at an edge of each block 5 adjacent to the center main groove 1 on the center main groove side. The depth (dimension in the tire radial direction) and width (dimension in the tire width direction) of the chamfered portion 5a gradually increase from the obtuse corner portion of the block 5 toward the acute corner portion. Thereby, wet performance can be improved by the edge effect of the chamfer 5a. Here, the maximum depth D5a of the chamfered portion 5a is preferably 30% to 50% of the groove depth D1 of the center main groove 1. If the ratio of the maximum depth D5a of the chamfered portion 5a to the groove depth D1 of the center main groove 1 is less than 30%, the effect of improving the wet performance becomes insufficient, and conversely if it exceeds 50%, the block rigidity decreases. Steering stability on dry roads is reduced.

  In the pneumatic tire, a plurality of narrow grooves 9 that are inclined with respect to the tire circumferential direction are formed on the tread surface of each block 5 adjacent to the center main groove 1. As shown in FIG. 4, the narrow groove 9 has a groove width w of 0.1 mm to 0.8 mm and a groove depth d of 0.1 mm to 0.8 mm. These narrow grooves 9 are fine grooves shallower than the sipe 7. By providing the narrow groove 9 on the tread surface of each block 5, the water film generated between the icy and snowy road surface and the tread surface is effectively removed by the fine groove 9, improving on-ice performance and on-snow performance in the initial use. can do. Further, when the fine narrow grooves 9 are provided on the tread surface of the block 5, the presence of these fine grooves 9 promotes the peeling of the tread surface, so that the time until the original characteristics of the tread rubber are exhibited is shortened. Can also be obtained.

  Here, if the groove width w is less than 0.1 mm, the narrow groove 9 has insufficient water film removal effect and snow removal performance, and conversely if it exceeds 0.8 mm, the road surface and contact area decrease. As a result, the effect of improving the performance on ice and the performance on snow is reduced. On the other hand, if the groove depth d of the narrow groove 9 is less than 0.1 mm, the effect of removing the water film becomes insufficient. Sex is reduced.

  The pitch p of the fine grooves 9 is preferably in the range of 2.5 mm to 5.0 mm. When the pitch p of the narrow grooves 9 is set to be relatively large as described above, the narrow grooves 9 are reliably prevented from being crushed when a high load is applied to the tire, and even on high load conditions, It is possible to improve the performance and performance on snow. If the pitch p of the narrow grooves 9 is less than 2.5 mm, the effect of improving the performance on ice and the performance on snow under high load conditions decreases, and conversely if it exceeds 5.0 mm, the effect of removing the water film becomes insufficient.

  The inclination angle α of the narrow groove 9 with respect to the tire circumferential direction is preferably set in a range of 40 ° to 60 °. If the inclination angle α of the fine groove 9 is less than 40 °, the edge of the fine groove 9 hardly contributes to braking / driving, and conversely if it exceeds 60 °, the edge of the fine groove 9 hardly contributes to prevention of skid.

  In the embodiment described above, the case where three main grooves are provided in the tread portion has been described. However, in the present invention, the number of main grooves can be increased according to the tread width. For example, five main grooves including a center main groove may be provided in the tread portion.

  The tire size is 195 / 75R16C 107 / 105R, and three main grooves extending straight in the tire circumferential direction and a plurality of horizontal grooves extending in the tire width direction are provided in the tread portion, and a plurality of blocks are formed by the main grooves and the horizontal grooves. In pneumatic tires with multiple sipes in each block, the inclination angle of the lateral groove with respect to the tire circumferential direction, the presence or absence of a raised portion of the lateral groove, the presence or absence of a chamfer, the presence or absence of fine groove processing, the maximum groove of the lateral groove The ratio of the minimum groove width to the width (W3a / W3 × 100%), the ratio of the groove depth of the horizontal groove at the bottom raised portion to the groove depth of the center main groove (D3a / D1 × 100%), the bottom raised portion to the length of the horizontal groove Tires of conventional examples, comparative examples 1 to 3 and examples 1 to 4 having the length ratio (L3a / L3 × 100%) set as shown in Table 1 were prepared.

  In addition, the bottom raising part was formed in the communicating part with respect to the center main groove of a horizontal groove. The chamfered portion is provided at the edge of each block adjacent to the center main groove on the center main groove side, and the depth and width gradually increase from the obtuse corner to the acute corner of the block. The depth was 40% of the depth of the center main groove. For the narrow grooves, the groove width was 0.4 mm, the groove depth was 0.4 mm, the pitch was 4.0 mm, and the inclination angle with respect to the tire circumferential direction was 50 °.

  These tires were evaluated for steering stability on a dry road surface, steering stability on a wet road surface, and steering stability on snow by the following evaluation methods, and the results are also shown in Table 1.

Steering stability on dry roads:
The test tire is assembled to a wheel with a rim size of 16 × 5 1 / 2J and mounted on a vehicle (van) with a maximum loading capacity of 3.5 tons. The front wheel pressure is 280 kPa and the rear wheel pressure is 450 kPa. The steering stability was evaluated in the speed range of / h. 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.

Steering stability on wet surfaces:
The test tire is assembled on a wheel with a rim size of 16 × 5 1 / 2J and mounted on a vehicle (van) with a maximum loading capacity of 3.5 tons. The front wheel pressure is 280 kPa and the rear wheel pressure is 450 kPa. The steering stability was evaluated in the speed range of / h. 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 wet road surface.

Steering stability on snow:
The test tire is assembled on a wheel with a rim size of 16 × 5 1 / 2J and mounted on a vehicle (van) with a maximum loading capacity of 3.5 tons. The front wheel pressure is 280 kPa and the rear wheel pressure is 450 kPa. The steering stability was evaluated in the speed range of / h. The evaluation results are shown as an index with the conventional example being 100. The larger the index value, the better the handling stability on snow.

  As is clear from Table 1, the tires of Examples 1 to 4 all maintain the steering stability on the wet road surface better than the conventional example, and the steering stability on the snow and the steering on the dry road surface. Stability could be improved at the same time. In particular, in Examples 3 and 4 in which the chamfered portion was provided, the steering stability on the wet road surface was also improved.

  On the other hand, since the tire of Comparative Example 1 does not have a bottom raised portion in the lateral groove, the effect of improving the steering stability on the dry road surface was insufficient. In the tire of Comparative Example 2, since the ratio of the minimum groove width to the maximum groove width of the horizontal groove and the ratio of the groove depth of the lateral groove at the bottom raised portion to the groove depth of the center main groove are too small, the handling stability on snow is improved. The effect was insufficient. In the tire of Comparative Example 3, the ratio of the minimum groove width to the maximum groove width of the horizontal groove and the ratio of the groove depth of the lateral groove at the bottom raised portion to the groove depth of the center main groove are too large. The improvement effect was insufficient.

1, 2 Main groove 3, 4 Horizontal groove 5, 6 Block 7, 8 Sipe 9 Narrow groove T Tread part E Tire equator

Claims (6)

  In a pneumatic tire in which a tread portion is provided with at least three main grooves extending in the tire circumferential direction and a plurality of lateral grooves extending in the tire width direction and communicating between the main grooves, and a plurality of blocks are defined by the main grooves and the lateral grooves. A center main groove located on the tire equator of the main grooves is formed in a straight shape, and the lateral grooves are arranged so as to be inclined at an angle of 40 ° to 60 ° with respect to the tire circumferential direction. A bottom raised portion is formed at a communication portion with respect to the main groove, the groove width of the horizontal groove is changed to be proportional to the groove depth, and the groove depth of the horizontal groove in the bottom raised portion is set to the groove depth of the center main groove. A pneumatic tire characterized in that it is 40% to 60%, and the minimum groove width of the lateral groove is 30% to 50% of the maximum groove width.   2. The pneumatic tire according to claim 1, wherein a length of the raised bottom portion is 20% to 50% of a length of the lateral groove.   The pneumatic tire according to claim 1 or 2, wherein each block adjacent to the center main groove is provided with four to six sipes extending in a tire width direction.   A chamfered portion is provided at the edge of each block adjacent to the center main groove on the center main groove side, and the depth and width of the chamfered portion are gradually increased from the obtuse corner portion to the acute corner portion of the block. The pneumatic tire according to any one of claims 1 to 3.   The pneumatic tire according to any one of claims 1 to 4, wherein a maximum depth of the chamfered portion is 30% to 50% of a groove depth of the center main groove.   A plurality of narrow grooves on the tread surface of each block adjacent to the center main groove, having a groove width of 0.1 mm to 0.8 mm, a groove depth of 0.1 mm to 0.8 mm, and inclined with respect to the tire circumferential direction The pneumatic tire according to claim 1, wherein the pneumatic tire is provided.

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