JP5343429B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire suitable for off-road running, and more particularly to a pneumatic tire that improves off-road running performance while maintaining uneven wear resistance at an acceptable level.

  Pneumatic tires mounted on four-wheel drive vehicles such as pickup trucks are required to have good off-road driving performance typified by mud (muddy ground) driving performance and snow driving performance. As such a pneumatic tire, a tire in which a block pattern is provided by a circumferential main groove and a lug groove on a tread surface is known (for example, see Patent Document 1).

In the pneumatic tire having this block pattern, if the circumferential groove for dividing the block is further arranged in the shoulder region block to improve the off-road running performance, the shoulder region block rigidity to which a high load is applied during turning. Due to the reduction, uneven wear is likely to occur in the block in the shoulder region, and there is a problem that it is difficult to achieve both the off-road running performance and the uneven wear resistance, which are contradictory performances.
JP 2007-302071 A

  An object of the present invention is to provide a pneumatic tire capable of improving off-road running performance while maintaining uneven wear resistance at an acceptable level.

The pneumatic tire of the present invention that achieves the above object has a lug groove extending from the circumferential main groove extending in the tire circumferential direction to the shoulder region of the tread surface in the tire circumferential direction at a predetermined pitch in the tire circumferential direction. In a pneumatic tire in which a block is formed in a shoulder region by the circumferential main groove and the lug groove, front and rear auxiliary grooves extending into the block from lug grooves adjacent in the tire circumferential direction are provided in each block. , the intermediate region of the block positioned between the auxiliary groove after the front, both ends positioned in the block, the sipe independent away from the auxiliary groove to extend in the tire width direction, the sipes, the tire from the tire ground contact edge A main sipe portion that is located on the inner side in the width direction and extends in the tire width direction, and a first sub sipe that extends from one end of the main sipe portion to one side in the tire circumferential direction, and whose extension end is located in the block And extending from the other end to the other side in the tire circumferential direction, the extended end having a second sub-sipe portion located in the block, wherein the main sipe portion includes the circumferential main groove and the tire ground contact end. It is characterized by having a length of 40% to 60% of the distance W in the tire width direction .

  According to the above-described present invention, the front and rear auxiliary grooves are provided in the block so that the block is not divided. On the other hand, an independent sipe that extends in the tire width direction in the intermediate region between the front and rear auxiliary grooves and does not communicate with the groove. By providing, the groove component in the block can be effectively increased without significantly reducing the block rigidity. Therefore, it is possible to improve the off-road running performance while maintaining the uneven wear resistance of the block at an allowable level.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows an embodiment of a pneumatic tire according to the present invention, where 1 is a tread surface, CL is a tire equator surface, and T is a tire circumferential direction.

  The tread surface 1 is provided with four circumferential main grooves extending in a zigzag shape in the tire circumferential direction T. The four circumferential main grooves are two inner circumferential main grooves 2 arranged on both sides of the tire equatorial plane CL, and two outer circumferential main grooves 3 arranged on the outer side in the tire width direction. It consists of and. Between the outer circumferential main grooves 3 is a center region 1C of the tread surface 1, and the outer side in the tire width direction from the outer circumferential main grooves 3 is a shoulder region 1S of the tread surface 1. The circumferential main grooves 2 and 3 referred to here are circumferential grooves having a width of 6 to 10 mm and a depth of 8 to 12 mm.

  A rib 4 extending continuously in the tire circumferential direction T is provided between the two inner circumferential main grooves 2. The lug grooves 5 that are bent and extend between the circumferential main grooves 2 and 3 are arranged at a predetermined pitch in the tire circumferential direction T, and the plurality of blocks 6 are formed by the circumferential main grooves 2 and 3 and the lug grooves 5. A compartment is formed. Each block 6 extends in the tire circumferential direction T between the lug grooves 5, and is divided into an inner block 6 </ b> A and an outer block 6 </ b> B by a narrow groove 7 that is narrower and shallower than the lug groove 5.

  The bent lug groove 5 extends linearly between the inner lug groove portion 5X extending linearly between the inner circumferential main groove 2 and the narrow groove 7 and between the narrow groove 7 and outer circumferential main groove 3. An outer lug groove portion 5Y, and an intermediate lug groove portion 5Z that extends linearly in the tire circumferential direction T and connects the inner lug groove portion 5X and the outer lug groove portion 5Y, and the lug groove portions 5X, 5Y are in the tire circumferential direction T. Extending in one direction. The inner block 6A and the outer block 6B are arranged so as to be shifted from each other in the tire circumferential direction T by the lug groove 5 bent in this way. The inner block 6A and the outer block 6B are respectively provided with sipes 20 extending in the tire width direction and the circumferential direction.

  Each block 6 is divided into two blocks 6A and 6B by a narrow groove 7 to reduce the block rigidity, while the blocks 6A and 6B are arranged to be shifted from each other in the tire circumferential direction T. The impact sound generated when the grounding is grounded is reduced, and the timing of the generation of the impact sound is made different so that the pattern noise caused by the block 6 is reduced.

  In each shoulder region 1S, lug grooves 8 extending beyond the tire ground contact end TE from the outer circumferential main groove 3 to the outer side in the tire width direction are arranged at a predetermined pitch in the tire circumferential direction T. A plurality of blocks 9 are partitioned by 3 and lug grooves 8. Each lug groove 8 has one bent portion 8x that is bent and extended in the tire circumferential direction on the inner side in the tire width direction from the tire ground contact end TE.

  A bottom raising portion 21 is provided at the groove bottom of the portion 8n of the lug groove 8 located on the inner side in the tire width direction from the bent portion 8x, that is, on the circumferential main groove 3 side from the position where the auxiliary groove 10 described later is provided. The blocks 9 in the circumferential direction are connected by a bottom raising portion 21 so as to increase the block rigidity on the circumferential main groove 3 side.

  Each block 9 is provided with one front and rear auxiliary groove 10 extending linearly into the block 9 from the bent portion 8x of the lug groove 8 adjacent in the tire circumferential direction. Each auxiliary groove 10 extends in the tire circumferential direction T while being inclined with respect to the tire circumferential direction T, has a narrower width than the lug groove 8, and a shallower depth than the lug groove 8. The two auxiliary grooves 10 extending in the tire circumferential direction front and rear from the bent portion 8x of the single lug groove 8 are provided symmetrically with respect to a point where the bent portion 8x is located.

  A single sipe 11 extending in the tire width direction is provided in an intermediate region 9M of the block 9 positioned between the front and rear auxiliary grooves 10. The sipe 11 extends inward in the tire width direction from the tire ground contact end TE, extends in the tire width direction, and extends from the one end of the main sipe portion 11A to one side in the tire circumferential direction. A first sub sipe portion 11B in which E1 is located in the block 9 and a second sub sipe in which the extending end E2 extends from the other end of the main sipe portion 11A to the other side in the tire circumferential direction. It has a portion 11 </ b> C, and both ends E <b> 1 and E <b> 2 are located in the block 9 and are formed in independent sipes that are separated from the front and rear auxiliary grooves 10. The first and second sub-sipe parts 11B and 11C extend to a position where they overlap the adjacent front and rear auxiliary grooves 10 in a side view.

The sipes 11, With such a configuration so as to have both parts and portions extending in the tire circumferential direction T that extends in the tire width direction, good off-road driving stability during turning and straight running To do. In addition, the sipe as used in the field of this invention means the notch whose width is 0.5-1.5 mm.

  In FIG. 1, a tread pattern in which the tire mounting direction is not specified is formed, and is a point-symmetric pattern with the intersection point G between the center line C of the inner lug groove portion 5X extending in a straight line and the tire equatorial plane CL as a symmetric point. Yes. In the figure, reference numeral 12 is a chamfered portion provided at the corner of the block 9, and reference numeral 13 is a notch groove provided on the outer side in the tire width direction from the tire ground contact end TE of the block 9.

  According to the present invention described above, the front and rear auxiliary grooves 10 are provided in the block 9 so that the block 9 is not divided. On the other hand, the intermediate region 9M between the front and rear auxiliary grooves 10 extends in the tire width direction and is formed in the groove. By providing an independent sipe 11 that does not communicate, the groove component in the block 9 can be effectively increased without greatly reducing the rigidity of the block 9. Therefore, it is possible to improve the off-road running performance while maintaining the uneven wear resistance of the block 9 at an allowable level.

  In the present invention, when the distance in the tire width direction between the circumferential main groove 3 and the tire ground contact end TE is W, the front and rear auxiliary grooves 10 are located in the region of 40% to 60% of the distance W from the circumferential main groove 3. Provided in R is preferable in terms of block rigidity. Note that the distance W in the case where the circumferential main groove 3 is in a zigzag shape shown in the figure is the length in the tire width direction at the shortest distance.

  The width of each auxiliary groove 10 is 1.5 mm or more, preferably 2 mm or more, and the depth is preferably 30% or more of the depth of the circumferential main groove 3 from the viewpoint of off-road running performance. The upper limit of the width and depth of the auxiliary groove 10 is 5 mm or less, preferably 4 mm or less, and the depth is 70% or less of the depth of the circumferential main groove 3. Good in terms of sex. When the depth of the circumferential main groove 3 changes, the maximum depth is set as the depth of the circumferential main groove 3. The same applies to the following.

  The length Lg of each auxiliary groove 10 is preferably 20% or more of the block length Lb measured between the front and rear auxiliary grooves 10 from the viewpoint of off-road running performance. The upper limit value of the length Lg of the auxiliary groove 10 is preferably 30% or less of the block length Lb from the viewpoint of uneven wear resistance. Note that the length Lg and the block length Lb of the auxiliary groove 10 are measured on the center line 10C of the auxiliary groove 10.

  As described above, it is preferable that the auxiliary groove 10 extends while being inclined with respect to the tire circumferential direction T from the viewpoint of off-road steering stability during turning and straight traveling, but extends along the tire circumferential direction T. An existing configuration may be used. The inclination angle θ with respect to the tire circumferential direction T when the auxiliary groove 10 is inclined is preferably in the range of 5 ° to 20 °. When the inclination angle θ is 5 ° or less, it does not contribute to off-road steering stability during straight traveling. On the other hand, if the angle exceeds 20 °, the angle of the acute angle portion adjacent to the auxiliary groove 10 becomes small, and uneven wear tends to occur at the acute angle portion. More preferably, it is 5 to 10 °. As shown in the figure, the front and rear auxiliary grooves 10 are preferably in the same inclination direction with respect to the tire circumferential direction T, but may be inclined in opposite directions.

The length L s of the main sipe portions 11A is you more than 40% of the distance W from the viewpoint of off-road driving stability. Upper limit of the length Ls is, you below 60% in terms of block stiffness.

  The main sipe portion 11A preferably extends in the tire width direction within a range of ± 5 ° with respect to the tire width direction in order to contribute to off-road steering stability during straight traveling. On the other hand, the sub-sipe parts 11B and 11C preferably extend in the tire circumferential direction T within a range of ± 5 ° with respect to the tire circumferential direction T in order to contribute to off-road steering stability during turning.

  The depth of the sipe 11 is preferably in the range of 30% to 70% of the depth of the circumferential main groove 3. If the depth of the sipe 11 is shallower than 30% of the depth of the circumferential main groove 3, sufficient snow performance cannot be ensured. Conversely, if it exceeds 70%, the block rigidity is lowered.

  The height of the raised portion 21 from the groove bottom of the lug groove 8 may be 10% or more of the depth of the lug groove 8 in order to increase the rigidity of the block 9 to be connected. The upper limit value is preferably 30% or less of the depth of the lug groove 8 from the viewpoint of drainage and mud performance. The depth of the lug groove 8 can be 50% to 100% of the depth of the circumferential main groove 3.

  The lug groove 8 is not limited to the configuration having the bent portion 8x as described above, and may extend in the tire width direction without being bent. The angle α of the lug groove 8 with respect to the tire width direction is preferably in the range of 0 to 20 ° from the viewpoint of uneven wear resistance of the block 9. As shown in the figure, when the lug groove 8 is bent, the angle α is an angle of a portion extending in the tire width direction.

  In the tread pattern shown in FIG. 1, since the bottom raising portion 21 is provided to increase the block rigidity, a sipe 14 is further provided in the block 9 and a sipe 15 communicating with the notch groove 13 is provided from the vicinity of the tire ground contact TE. However, such sipes 14 and 15 may be provided in addition to the above-described sipes 11 according to the rigidity of the block 9.

  The present invention can be preferably used for a pneumatic tire for off-road running in which the air pressure is used in a range of 220 to 450 kPa and a high load acts on the shoulder region 1S, but it is not limited thereto.

  The tire contact point TE referred to in the present invention means that a tire is mounted on a standard rim specified by JATMA, filled with air pressure corresponding to the maximum load capacity specified by JATMA, and is 70% of the maximum load capacity. This is a ground contact end in the tread surface 1 in a state where a corresponding load is applied.

  The tire 1 of the present invention (the first embodiment) having the configuration shown in FIG. 1 except that the tire size is the same for 205R16C 110 / 108S and the sipe 11 of the shoulder region block is composed of only the main sipe portion, 1 of the present invention having the configuration of FIG. 1 having a main sipe portion and both sub-sipe portions 11 (this embodiment 2), and a comparative tire 1 in which the main sipe portion communicates with the circumferential main groove in the present tire 1 (comparison) Example 1), a comparative tire 2 in which both sub-sipe parts communicate with the lug groove in the tire 2 of the present invention (Comparative Example 2), and a reference tire without the sipe 11 in the tire 1 of the present invention (reference example) are used as test tires, respectively. Produced.

  In each test tire, the auxiliary groove is located in the range of 40% to 60% of the distance W from the circumferential main groove, the auxiliary groove width is 3 mm, and the depth is 50% of the circumferential main groove depth. Is 25% of the block length Lb. The inclination angle of the auxiliary groove is 10 °, the length of the main sipe part is 50% of the distance W, and the height of the bottom raised part is 30% of the depth of the lug groove.

  Each of these test tires is assembled to a wheel with a rim size of 16 × 6J, and the air pressure is 260 kPa for the front tire and 400 kPa for the rear tire. As a result of the evaluation test, the results shown in Table 1 were obtained.

Off-road driving performance In the off-road test course, a sensory test of off-road running performance was performed by a test driver. The evaluation result is indicated by an index value where the reference tire is 100. The larger the index value, the better the off-road driving performance.

Uneven wear resistance After running a traveling distance of 8000 km (mountain road: 59%, paved road: 41%), the amount of heel and toe wear (mm) in the shoulder region block was measured. The evaluation result is indicated by an index value where the reference tire is 100. The larger the index value, the better the uneven wear resistance. An index value of 97 or more is an allowable level.

  From Table 1, it can be seen that the tire of the present invention can improve off-road running performance while maintaining uneven wear resistance at an acceptable level.

1 is a partial development view of a tread surface showing an embodiment of a pneumatic tire of the present invention.

Explanation of symbols

1 tread surface 1S shoulder region 2,3 circumferential main groove 8 lug groove 9 block 9M intermediate region 10 auxiliary groove 11 sipe 11A main sipe portion 11B first sub sipe portion 11C second sub sipe portion R region T tire circumferential direction TE tire Ground end

Claims (6)

Lug grooves extending outward in the tire width direction from circumferential main grooves extending in the tire circumferential direction in the shoulder region of the tread surface are arranged at a predetermined pitch in the tire circumferential direction, and the circumferential main grooves and the lug grooves In pneumatic tires with blocks in the shoulder area,
Each block is provided with front and rear auxiliary grooves extending in the block from lug grooves adjacent to the front and rear in the tire circumferential direction, and both ends are located in the block in the middle region of the block located between the front and rear auxiliary grooves. An independent sipe that is spaced apart from the groove extends in the tire width direction, the sipe is positioned on the inner side in the tire width direction from the tire ground contact end, and extends from the one end of the main sipe portion to the tire width direction. A first sub-sipe portion that extends to one side in the circumferential direction and whose extension end is located in the block, and a first sub-sipe portion that extends from the other end to the other side in the tire circumferential direction, and whose extension end is located in the block. A pneumatic tire having two sub-sipe parts, wherein the main sipe part has a length of 40% to 60% of a distance W in the tire width direction between the circumferential main groove and the tire ground contact end. .   2. The front and rear auxiliary grooves are provided in a region of 40% to 60% of the distance W from the circumferential main groove, where W is the distance in the tire width direction between the circumferential main groove and the tire ground contact edge. Pneumatic tire described in 2.   The pneumatic tire according to claim 1 or 2, wherein the front and rear auxiliary grooves have a width of 1.5 mm to 5.0 mm and a depth of 30% to 70% of the depth of the circumferential main groove.   The pneumatic tire according to claim 1, 2 or 3, wherein a length Lg of the front and rear auxiliary grooves is 20% to 30% of a block length Lb measured between the front and rear auxiliary grooves.   5. The front and rear auxiliary grooves extend while being inclined with respect to the tire circumferential direction, and an inclination angle θ of the auxiliary grooves with respect to the tire circumferential direction is 5 ° to 20 °. Pneumatic tires. The pneumatic tire according to any one of claims 1 to 5, wherein the first and second auxiliary sipe portions extend to positions where they overlap with adjacent auxiliary grooves in a side view.

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