JP2011240773A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire which excellently maintains on-snow performance and furthermore has enhanced uneven wear resistance.SOLUTION: The pneumatic tire includes a plurality of blocks 5, 6 which are divided by three main grooves 1, 2 and a plurality of lateral grooves 3 and lug grooves 4. In the pneumatic tire, the lug grooves 4 are arranged so as to extend within ±20° relative to the tire width direction, a bottom-up narrow groove 4a is formed in a communicative part of the lug grooves 4 relative to the outermost main groove 2. The groove depth D4a of this bottom-up narrow groove 4a is set to be 40-60% of the groove depth D2 of the outermost main groove 2, the groove width is set to be 30-50% of the maximum groove width of the lug grooves 4, and the length is set to be 20-40% of the length of the lug grooves 4.

Description

  The present invention relates to a pneumatic tire suitable for light trucks, and more particularly to a pneumatic tire that improves uneven wear resistance while maintaining good performance on snow.

  In a pneumatic tire, in order to improve performance on snow, the tread is provided with at least three main grooves extending in the tire circumferential direction and a plurality of horizontal grooves extending in the tire width direction, and a plurality of blocks are partitioned by the main grooves and the horizontal grooves. A tread pattern is employed (see, for example, Patent Document 1). Furthermore, the performance on snow can be further improved by providing sipes in each block. In such a tread pattern, traction performance on snow can be improved by increasing the number of lateral grooves and sipes.

  However, in such a tire, when focusing on the shoulder block, there is a problem that the block rigidity is lowered due to the formation of a large number of lug grooves and sipes for performance on snow, and uneven wear tends to occur. is there.

JP 2007-1484 A

  An object of the present invention is to provide a pneumatic tire that improves uneven wear resistance while maintaining good on-snow performance.

  In order to achieve the above object, the pneumatic tire of the present invention includes at least three main grooves extending in the tire circumferential direction in the tread portion, 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 lug groove that communicates with the outermost main groove and extends in the tire width direction toward the ground contact end side is provided, and a plurality of blocks are defined by the main groove, the lateral groove, and the lug groove. Is extended to within ± 20 ° with respect to the tire width direction, and the depth and width of the lug groove are communicated with the outermost main groove in comparison with other portions of the lug groove. A narrow bottom raised narrow groove portion is formed, the groove depth of the bottom raised narrow groove portion is 40 to 60% of the groove depth of the outermost main groove, and the groove width of the bottom raised narrow groove portion is the maximum groove width of the lug groove. 30-50% and the bottom raised narrow groove The length of the portion is 20-40% of the length from the main groove side end of the lug groove to the grounding end.

  In the present invention, since the lug grooves are arranged to extend within ± 20 ° with respect to the tire width direction, occurrence of uneven wear can be suppressed. Further, a bottom-up narrow groove portion having a groove depth and a groove width smaller than that of the other portion of the lug groove is formed at the communication portion with the outermost main groove of the lug groove, and the groove depth of the bottom-up narrow groove portion is set to the outermost portion. 40-60% of the groove depth of the main groove, the groove width is 30-50% of the maximum groove width of the lug groove, and the length of the bottom raised narrow groove portion is from the main groove side end of the lug groove to the ground end. Since it is 20 to 40% of the length, the rigidity difference between the blocks is reduced, and uneven wear can be suppressed. Therefore, it is possible to improve uneven wear resistance while maintaining good on-snow performance based on lug grooves.

  In the present invention, it is preferable to dispose a plurality of three-dimensional sipes extending in the tire width direction in each of the shoulder block defined by the lug groove and the outermost main groove. As described above, the performance on snow is improved by providing sipes on the shoulder block, but by making the sipes into a three-dimensional structure, the block can be prevented from falling.

  In the present invention, it is preferable to provide a chamfered portion at an acute edge of the shoulder block defined by the lug groove and the outermost main groove. Thereby, since it has an acute angle, the rigidity of the edge that is low in rigidity and difficult to wear uniformly can be increased, the wear of the block can be made uniform, and uneven wear can be suppressed.

  In the present invention, the opening for the outermost main groove of the lug groove is arranged at a position facing the opening for the outermost main groove of the lateral groove, and the opening of the lug groove with respect to the outermost main groove and the extension of the lateral groove The amount of deviation in the tire circumferential direction from the line is preferably 10% or less of the pitch length of the lateral groove. As a result, the lateral grooves and the lug grooves are substantially continuous in the tire width direction, so that the snow removal performance can be enhanced.

  In the present invention, the lateral groove is disposed so as to be inclined at 30 to 60 ° with respect to the tire circumferential direction, and the groove depth and groove are compared with other portions of the lateral groove at the communication portion with respect to the main groove on the center side of the lateral groove. A bottom raised narrow groove portion having a reduced width is formed, the groove depth of the bottom raised narrow groove portion is 40 to 60% of the groove depth of the main groove on the center side, and the groove width of the bottom raised narrow groove portion is 30 to the maximum groove width of the lateral groove. It is preferable to make it 50%. By arranging the lateral grooves in an inclined manner in this way, it is possible to improve steering stability under snow and wet conditions, and it is possible to improve uneven wear resistance by providing a bottom raised narrow groove portion.

  In this invention, it is preferable to arrange | position 4-6 three-dimensional sipes to each of the block of the center part partitioned by the horizontal groove and the main groove so that it may extend in a tire width direction. As described above, the performance on snow is improved by providing the sipe in the block of the center portion. However, by making the sipe into a three-dimensional structure, the collapse of the block can be suppressed.

It is an expanded view which shows the tread pattern of the pneumatic tire which consists of embodiment of this invention. It is an enlarged plan view which shows the block located in a shoulder part in the pneumatic tire of FIG. It is an enlarged side view which shows the block located in a shoulder part in the pneumatic tire of FIG. 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.

  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 CL 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 lateral grooves 3 that extend in the tire width direction and communicate between the main grooves 1 and 2, and a plurality that extend in the tire width direction from the outer main grooves 2 to the outside of the ground contact E A lug groove 4 is formed. The main grooves 1 and 2 and the lateral grooves 3 divide the two rows of blocks consisting of a plurality of blocks 5 in the center region, and the main grooves 2 and the lug grooves 4 constitute two rows of blocks consisting of a plurality of blocks 6 in the shoulder region. The column 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.

  The main grooves 1 and 2 are both formed in a straight shape to ensure good drainage performance. 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, and the lug groove 4 disposed in the shoulder region is the outer main groove 2. Communicating with Any number of the main grooves 1 and 2 may be provided as long as at least three are provided. When more than three are provided, the lug groove 4 is communicated with the outermost main groove 2.

  The lug grooves 4 are arranged so as to be inclined with respect to the tire width direction. The inclination angle α of the lug groove 4 with respect to the tire width direction is set within ± 20 °, preferably within ± 10 °. Here, the inclination angle α is an angle formed by the lug groove center line of the lug groove 4 with respect to the tire width direction (see FIG. 2). When this inclination angle α is out of the range of ± 20 °, the uneven wear resistance is lowered. If the inclination angle α of the lug groove 4 is ± 0 °, at least traction can be obtained, but the turning performance can be improved by inclining the lug groove 4 within the above range. It is preferable to incline with respect to.

  As shown in FIGS. 2 and 3, a bottom-up narrow groove portion 4 a is formed at a portion where the lug groove 4 communicates with the outer main groove 2. The bottom raised narrow groove portion 4 a is a portion formed so that the groove depth and the groove width are smaller than other portions of the lug groove 4. The length L4a of the bottom raised narrow groove portion 4a is set to 20 to 40% of the length L4 of the lug groove 4. Here, the length L4 of the lug groove is the length from the main groove side end of the lug groove 4 to the tire ground contact end E, and the length L4a of the bottom raised narrow groove 4a is the end of the lug groove 4 on the main groove side. , And the length measured along the center line of the groove width. Further, the groove width W4a of the bottom raised narrow groove portion 4a is set to 30 to 50% of the maximum groove width W4 of the lug groove 4, and the groove depth D4a of the bottom raised narrow groove portion 4a is set to 40 to 60% of the groove depth D2 of the main groove 2. Has been.

  Further, as described above, the bottom-up narrow groove portion 4a is formed at the communication portion of the lug groove 4 with respect to the outer main groove 2, and the groove width W4a and the groove depth D4a of the lug groove 4 are reduced, so that the vicinity of the bottom-up narrow groove portion 4a. The block rigidity can be increased and uneven wear can be prevented. In addition, since raising the bottom of the lug groove 4 and narrowing the width are combined, it is possible to ensure that the lug groove 4 communicates with the outer main groove 2 when increasing the block rigidity. Therefore, the drainage performance can be favorably maintained by the cooperation of the outer main groove 2 and the lug groove 4.

  At this time, by setting the length L4a of the bottom raised narrow groove portion 4a to 20 to 40% of the length L4 of the lug groove 4, uneven wear can be suppressed without deteriorating steering stability on snow. . If the length L4a of the bottom raised narrow groove portion 4a is smaller than 20% of the length L4 of the lug groove 4, the effect of suppressing uneven wear cannot be sufficiently obtained. Conversely, if the length L4a of the bottom raised narrow groove 4a is larger than 40% of the length L4 of the lug groove 4, the steering stability on snow is lowered.

  The groove depth D4a of the lug groove 4 in the bottom-up narrow groove portion 4a is 40 to 60% of the groove depth D2 of the main groove 2, but the groove depth D4a of the bottom-up narrow groove portion 4a with respect to the groove depth D2 of the main groove 2 If the ratio is less than 40%, the effect of suppressing uneven wear is improved, but drainage performance and snow drainage performance are degraded. Conversely, if the ratio is greater than 60%, the rigidity difference cannot be sufficiently reduced and sufficient uneven wear is achieved. The suppression effect cannot be obtained.

  The groove width W4a of the lug groove 4 in the bottom raised narrow groove portion 4a is 30 to 50% of the maximum groove width W4 of the lug groove 4, but the ratio of the groove width W4a of the bottom raised narrow groove portion 4a to the maximum groove width W4 of the lug groove 4 is If the ratio is less than 30%, the effect of suppressing uneven wear is improved, but drainage performance and snow drainage performance are deteriorated. Conversely, if the ratio is greater than 50%, the block rigidity does not change so much and the effect of suppressing uneven wear is obtained. I can't.

  Further, it is preferable to arrange 2 to 5 three-dimensional sipes 8 extending in the tire width direction in each block 6 formed by the outer main groove 2 and the lug groove 4. If a general two-dimensional sipe that bends only on the tread surface is provided on the block 6, it is possible to improve the performance on snow due to the edge effect of the sipe, but the block 6 is liable to fall down due to a decrease in block rigidity. It cannot be suppressed. On the other hand, a three-dimensional sipe that bends on the tread surface and also bends in the sipe depth direction can suppress the collapse of the block 6, thereby improving the performance on snow and suppressing uneven wear. It becomes possible. If the number of the three-dimensional sipes 8 is less than two, the collapse of the block cannot be sufficiently suppressed, and the effect of suppressing uneven wear cannot be obtained. On the contrary, if the number is greater than 5, the rigidity of the block 8 is lowered, so that the effect of suppressing uneven wear is lowered. As described above, the three-dimensional sipe 8 is a sipe that is deformed on the tread surface and is also deformed in the depth direction. For example, a pyramid sipe that forms a sipe by alternately combining triangular pyramidal blocks is cited. I can do it.

  In the pneumatic tire, a chamfered portion 6a is formed at at least an acute edge on the outer main groove 2 side of each block 8 adjacent to the outer side of the outer main groove 2 in the tire width direction. Edges with sharp angles are less rigid, force is easy to escape when touching, and it is difficult to wear evenly. Therefore, by providing a chamfer 6a at least at the edges with sharp angles, the block wear becomes uniform and uneven wear. Can be suppressed. The chamfered portion 6a may have any shape as long as it can suppress a decrease in rigidity of the edge having an acute angle.

  In the pneumatic tire, the opening of the lug groove 4 with respect to the outer main groove 2 is preferably disposed at a position facing the opening of the lateral groove 3 with respect to the outer main groove 2, and in particular, the opening of the lug groove 4 with respect to the outer main groove 2. The amount of deviation in the tire circumferential direction between the portion and the extension line of the lateral groove 3 is preferably 10% or less of the pitch length of the lateral groove 3. Thereby, since the lug groove 4 and the horizontal groove 3 come to continue substantially, snow removal performance can be improved. More preferably, the opening of the lug groove 4 with respect to the outer main groove 2 is disposed on the extension line of the lateral groove 3.

  The lateral grooves 3 communicating between the main grooves 1 and 2 are preferably arranged so as to be inclined with respect to the tire circumferential direction. In particular, the inclination angle β of the lateral grooves 3 with respect to the tire circumferential direction is preferably 30 to 60 °, and more preferably the inclination angle β is 40 to 50 °. Here, the inclination angle β is an angle formed by the groove width center line of the lateral groove with respect to the tire circumferential direction (see FIG. 4).

  As shown in FIGS. 4 and 5, it is preferable that a bottom raised narrow groove 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 narrow groove portion 3a is a portion formed so that the groove depth and the groove width are smaller than other portions of the lateral groove 3. The length L3a of the bottom raised narrow groove portion 3a is preferably set to 20 to 40% of the length L3 of the lateral groove 3. Here, the length L3 of the lateral groove is the length from the end of the lateral groove 3 on the center main groove 1 side to the end of the outer main groove 2 side, and the length L3a of the bottom raised narrow groove portion 3a is the center of the lateral groove 3 These are lengths from the end on the main groove 1 side, and are all measured along the groove width center line. Further, the groove depth D3a of the bottom raised narrow groove portion 3a is 40 to 60% of the groove depth D1 of the center main groove 1, and the groove width W3a of the bottom raised narrow groove portion 3a is 30 to 50% of the maximum groove width W3 of the lug groove 3. It is preferable that it is set.

  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. The lateral groove 3 having an extending component in the tire width direction can effectively suppress slippage in the longitudinal direction and the lateral direction of the vehicle. As a result, it is possible to improve the steering stability on snow or under wet conditions.

  Further, it is preferable to form a bottom-up narrow groove portion 3a at a portion where the lateral groove 3 communicates with the center main groove 1, and to reduce the groove depth D3a and the groove width W3a of the lateral groove 3, thereby blocking in the vicinity of the bottom-up narrow groove portion 3a. The rigidity becomes high and uneven wear can be suppressed. Moreover, since the bottom raising of the lateral groove 3 and the narrowing 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.

  As described above, the inclination angle β of the lateral grooves 3 with respect to the tire circumferential direction is preferably 30 to 60 °. However, if the inclination angle β is smaller than 30 °, the traction performance on snow cannot be sufficiently improved. . On the contrary, if the inclination angle β is larger than 60 °, the performance of preventing skidding on snow cannot be sufficiently improved.

  As described above, the length L3a of the bottom raised narrow groove portion 3a is preferably set to 20 to 40% of the length L3 of the lateral groove 3, thereby improving uneven wear resistance without deteriorating steering stability on snow. Can be improved. If the length L3a of the bottom raised narrow groove portion 3a is smaller than 20% of the length L3 of the lateral groove 3, the effect of suppressing uneven wear becomes insufficient, and conversely the length L3a of the bottom raised narrow groove portion 3a is equal to the length L3 of the lateral groove 3. If it is larger than 40%, the steering stability on snow cannot be improved sufficiently.

  The groove depth D3a of the lateral groove 3 in the bottom-up narrow groove portion 3a is preferably 40 to 60% of the groove depth D1 of the center main groove 1, but the groove of the bottom-up narrow groove portion 3a with respect to the groove depth D1 of the center main groove 1 If the ratio of the depth D3a is smaller than 40%, the effect of suppressing uneven wear becomes insufficient. Conversely, if the ratio is larger than 60%, the snow drainage performance cannot be sufficiently improved.

  The groove width W3a of the lateral groove 3 in the bottom raised narrow groove portion 3a is preferably 30 to 50% of the maximum groove width W3 of the lateral groove 3, but the ratio of the groove width W3a of the bottom raised narrow groove portion 3a to the maximum groove width W3 of the lateral groove 3 is If it is less than 30%, the snow drainage performance cannot be sufficiently improved. Conversely, if the ratio is more than 50%, the movement of the block is increased and the uneven wear resistance cannot be sufficiently improved.

  Moreover, it is preferable to arrange 4 to 6 three-dimensional sipes 7 extending in the tire width direction in each block 5 formed by the center main groove 1 and the lateral groove 3. If the block 5 is provided with a general two-dimensional sipe that bends only on the tread surface, it is possible to improve the performance on snow due to the edge effect of the sipe, but the block rigidity is lowered, so the block 5 is likely to fall down and uneven wear is caused. It cannot be suppressed. On the other hand, a three-dimensional sipe that bends on the tread surface and also in the sipe depth direction can suppress the collapse of the block 5, thereby improving the performance on snow and suppressing uneven wear. It becomes possible. If the number of the three-dimensional sipes 7 is less than four, the collapse of the block 5 cannot be sufficiently suppressed, and the effect of suppressing uneven wear cannot be obtained. On the other hand, if the number is greater than 6, the rigidity of the block 5 is reduced, and the effect of suppressing uneven wear is reduced.

  The tire size is 195 / 75R16C, and three main grooves extending straight in the tire circumferential direction and a plurality of lateral grooves and lug grooves extending in the tire width direction are provided in the tread portion, and these main grooves, lateral grooves, and lug grooves are provided. In a pneumatic tire in which a plurality of blocks are partitioned, four sipes are provided in the center block, and three sipes are provided in the shoulder block, the inclination angle α of the lug groove with respect to the tire width direction, the lug groove Dimension of bottom raised narrow groove (length L4a / L4 and groove depth D4a / D4), type of sipe provided in shoulder block, presence of chamfered portion for sharp edge of shoulder block, presence of lug groove on lateral groove extension line 10 types of tires of conventional examples, comparative examples 1 to 5, and examples 1 to 4 as shown in Table 1 were prepared. As the sipe, a two-dimensional sipe (2D) having a zigzag shape on the tread surface or a three-dimensional sipe (3D) having a zigzag shape on the tread surface and also having a zigzag shape in the sipe depth direction was employed.

  The conventional example is an example having no features of the present invention. Comparative Example 1 is an example in which only the lug groove angle is within the scope of the present invention, and the bottom raised narrow groove portion is not provided. Comparative Examples 2 and 3 are examples in which, in addition to Comparative Example 1, only a portion having a narrow groove width is provided. In Comparative Examples 4 and 5, in addition to Comparative Example 2, the bottom is further raised to provide a bottom raised narrow groove, but the depth of the bottom raised narrow groove is outside the scope of the present invention.

  Examples 1 to 4 are all examples in which the lug groove angle is 10 °, the groove length of the bottom raised narrow groove portion is 30% of the distance from the main groove to the grounding end, and the groove depth is 50% of the main groove depth. It is. The first embodiment is an example in which a three-dimensional sipe is provided as a sipe. Example 2 is an example in which chamfering is further applied to the acute angle portion with respect to Example 1. The third embodiment is an example in which the lug grooves are further arranged on the extended lines of the narrow grooves as compared with the second embodiment. The fourth embodiment is an example in which the sipe is a two-dimensional sipe with respect to the third embodiment.

  These ten types of tires were evaluated for uneven wear resistance and snow handling stability by the following evaluation methods, and the results are also shown in Table 1.

Uneven wear resistance A test tire was 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. Later, the state of wear was compared. Relative evaluation was performed using an index with the conventional example as 100. The larger the index value, the better the uneven wear resistance.

Performance on snow 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 300 kPa and the rear wheel pressure is 480 kPa. The sensory evaluation was performed. The evaluation results are shown by a 100-point method in which Conventional Example 1 is taken as 100. The larger the index value, the better the performance on snow.

  The conventional example is the standard. Comparative Examples 1 to 5 can slightly improve only the wear resistance, but the performance on snow is maintained at the conventional level or is lower than the conventional example. On the other hand, all of Examples 1 to 4 improved the uneven wear resistance and the performance on snow, and highly compatible these performances.

1, 2 Main groove 3 Horizontal groove 3a Bottom raised narrow groove portion 4 Lug groove 4a Bottom raised narrow groove portion 5, 6 Block 7, 8 Sipe T Tread portion CL Tire equator E Tire ground contact edge

Claims (6)

At least three main grooves extending in the tire circumferential direction in the tread portion, a plurality of lateral grooves extending in the tire width direction and communicating between the main grooves, and communicating with the outermost main groove and toward the grounding end side In a pneumatic tire provided with a lug groove extending in the tire width direction and partitioning a plurality of blocks by these main groove, lateral groove, and lug groove,
The lug groove is disposed so as to extend within ± 20 ° with respect to the tire width direction, and the depth of the lug groove in the communication portion with respect to the outermost main groove of the lug groove as compared with other portions of the lug groove and A bottom raised narrow groove portion having a reduced groove width is formed, the groove depth of the bottom raised narrow groove portion is 40 to 60% of the groove depth of the outermost main groove, and the groove width of the bottom raised narrow groove portion is the maximum of the lug groove. 30 to 50% of the groove width, and the length of the bottom raised narrow groove portion is set to 20% to 40% of the length from the main groove side end portion of the lug groove to the ground contact end. .   The plurality of three-dimensional sipes are arranged so as to extend in the tire width direction in each of the shoulder block defined by the lug groove and the outermost main groove. Pneumatic tire.   3. The pneumatic tire according to claim 1, wherein a chamfered portion is provided at an edge at an acute angle of a block of a shoulder portion defined by the lug groove and the outermost main groove.   An opening for the outermost main groove of the lug groove is disposed at a position facing the opening for the outermost main groove of the lateral groove, and an opening of the lug groove with respect to the outermost main groove and the lateral groove The pneumatic tire according to claim 1, 2 or 3, wherein the amount of deviation in the tire circumferential direction from the extension line is 10% or less of the pitch length of the lateral groove.   The lateral groove is disposed so as to be inclined at 30 to 60 ° with respect to the tire circumferential direction, and a groove depth and a groove width are formed in a communication portion with respect to the main groove on the center side of the lateral groove as compared with other portions of the lateral groove. A narrow bottom raised narrow groove portion is formed, the groove depth of the bottom raised narrow groove portion is 40 to 60% of the groove depth of the main groove on the center side, and the groove width of the bottom raised narrow groove portion is 30% of the maximum groove width of the lateral groove. The pneumatic tire according to any one of claims 1 to 4, wherein the pneumatic tire is -50%.   The pneumatic according to any one of claims 1 to 5, wherein four to six three-dimensional sipes are arranged so as to extend in the tire width direction in each of the blocks of the center section defined by the lateral grooves and the main grooves. tire.

Images