JP5844982B2 - tire - Google Patents

Description

  The present invention relates to a tire suitable for being mounted on a vehicle such as a truck or a bus, and particularly relates to a tire having a block pattern.

  In a pneumatic tire provided with a plurality of main grooves extending along the tire circumferential direction, a large number of tread surfaces are provided for the purpose of improving traction performance and WET performance (running performance on wet road surfaces). Blocks are defined.

  Conventionally, a technique has been developed that further improves the WET performance by further disposing a block circumferential groove that extends in the tire circumferential direction and divides the block into the block (for example, Patent Document 1). ).

  However, as in the technique described in Patent Document 1, providing a deep groove in the block, particularly in the circumferential end of the block, leads to a decrease in the rigidity of the block. Tires with small block rigidity are prone to cracks, and there are problems such as block flaking and chipping.

JP 2009-6877 A

  An object of the present invention is to solve the above-described problems, and to make the WET performance of a tire and the block peeling and chipping performance compatible with each other well.

As a result of diligent research to solve the above problems, the present inventor has found that when block circumferential grooves are provided in a tire block, the rigidity of the block is reduced at the end in the extending direction of the block circumferential grooves, and cracks are generated. As a result, it was found that block baldness and chipping occurred.
Therefore, the present inventor has achieved a good balance between tire WET performance and block flaking and chipping performance by making the groove depth of the block circumferential groove shallower at the end in the extending direction than at the center in the extending direction. The present inventors have found that this can be done and have completed the present invention.

The present invention is based on the above findings, and the gist of the present invention is as follows.
(1) A pair of first circumferential main grooves extending continuously along the tire circumferential direction across the tire equator in the tread portion, and a plurality of pieces extending in the tire width direction between the first circumferential main grooves A tire having a first width direction main groove and partitioning a plurality of central blocks, wherein the central block includes a block circumferential groove extending in the tire circumferential direction. grooves dividing the central blocks into small blocks, the groove depth of the block circumferential groove, than the extending direction central portion, rather shallow in the extending direction end portion, the central block, the extending in the tire width direction 1 block horizontal narrow groove, the groove depth of the first block horizontal narrow groove is shallower than the groove depth at the end position in the extending direction of the block circumferential groove, the first block horizontal narrow groove, How to extend the block circumferential groove whose extending direction is in the range of 0 to 20 ° with respect to the tire equatorial plane A tire characterized by extending across the central portion.

( 2 ) The tire according to (1) , wherein the block circumferential groove has a groove depth at an end portion in the extending direction in a range of 50 to 90% of a groove depth at a central portion in the extending direction.

( 3 ) The tire according to any one of the above (1) or (2) , wherein the central portion of the block circumferential groove includes the center position in the tire circumferential direction of the central block.

( 4 ) The block circumferential groove is any one of the above (1) to ( 3 ), wherein the extending length of the central portion in the extending direction is in a range of 10 to 50% of the length in the tire circumferential direction of the central block. The tire according to 1.

( 5 ) The tire according to any one of (1) to ( 4 ), wherein the block circumferential groove has a groove depth of 10 mm or more at a central position in the extending direction.

( 6 ) A pair of second circumferential main grooves positioned on the outer side in the tire width direction of the pair of first circumferential main grooves and extending continuously along the circumferential direction, and the first circumferential main grooves And a plurality of second width direction main grooves extending in the tire width direction between the second circumferential direction main grooves and a plurality of second width direction main grooves extending in the tire width direction between the second circumferential direction main grooves and the tread ends. A three-width direction main groove, and a plurality of intermediate blocks are defined by the first circumferential direction main groove, the second circumferential direction main groove, and the second width direction main groove, The tire according to any one of (1) to ( 5 ), wherein a plurality of side blocks are defined by a direction main groove, the tread end, and the third width direction main groove.

( 7 ) The tire according to ( 6 ), wherein the width of the central block is 180% or more of the width of the intermediate block.

( 8 ) The tire according to ( 6 ) or ( 7 ), wherein the blocks adjacent in the tire width direction are in a positional relationship shifted by a half pitch in the tire circumferential direction.

  According to the present invention, the central block is a block circumferential groove extending in the tire circumferential direction by dividing the central block into small blocks, and the groove depth is longer than the central portion in the extending direction. By providing a shallow block circumferential groove at the portion, it is possible to improve the baldness and chipping performance of the block while maintaining the good WET performance of the tire.

FIG. 1 is a plan view showing a tread pattern of a tire according to the present invention. FIG. 2 (a) is a view showing a cross section taken along line XX of FIG. 1, and FIG. 2 (b) is a view of another embodiment of the tire according to the present invention cut in the same manner as FIG. 2 (a). FIG. 3 (a) and 3 (b) are schematic perspective views showing block peripheral grooves when one central block of the tire of Example 1 is extracted, and FIG. FIG. 3 (b) shows the state at the end of tire use. 4 (a) and 4 (b) are schematic perspective views showing block peripheral grooves when one central block of the tire of Comparative Example 1 is extracted, and FIG. FIG. 4 (b) shows the state at the end of tire use.

An embodiment of a tire of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing a tread pattern of a tire according to the present invention.
As shown in FIG. 1, the tire according to the present invention has a pair of first circumferential main grooves 1, 1 extending continuously along the tire circumferential direction across the tire equator, and the first tread portion 100. A plurality of first width direction main grooves 2 extending in the tire width direction are disposed between the circumferential direction main grooves 1 and 1, and a plurality of central blocks 3 are partitioned.
The central block 3 includes a block circumferential groove 4 extending in the tire circumferential direction. The block circumferential groove 4 divides the central block 3 into small blocks 3a and 3b. The groove depth of the block circumferential groove 4 is as follows. It is characterized by being shallower in the extending direction end portion 4b than in the extending direction central portion 4a, and by having such a configuration, the block has a good flaking and chipping performance while maintaining good tire WET performance. There is an effect that it can be improved.

  The central block 3 has a first block lateral narrow groove 5 extending in the tire width direction, and the groove depth of the first block lateral narrow groove 5 is a groove depth at the position of the end portion 4b of the block circumferential groove 4 in the extending direction. It is preferable to make it shallower. Here, the first block horizontal narrow groove 5 includes a horizontal groove having a groove width of 3 mm or less, a sipe that closes the opening when grounded, and the like. The edge component in the tire circumferential direction can be increased by providing the first block lateral narrow groove 5, preferably a sipe that closes the opening at the time of tire contact in the tire width direction. The term “when the tire is in contact with the ground” as used herein specifically refers to the time when the tire is mounted on a regular rim, set to a regular internal pressure, placed in a stationary state perpendicular to the flat plate, and loaded with a regular load. means. Here, the regular rim is “standard rim” defined by JATMA, “Design Rim” defined by TRA, or “Measuring Rim” defined by ETRTO. The normal internal pressure is “maximum air pressure” defined by JATMA, the maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “INFLATION PRESSURES” defined by ETRTO. The normal load is “maximum load capacity” defined by JATMA, the maximum value described in “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “LOAD CAPACITY” defined by ETRTO. Further, when the tire is worn, if the groove disappears at the end portion 4b in the extending direction of the block circumferential groove 4, stress concentrates on the sipe end, and cracks at the sipe end are likely to occur. Therefore, when comparing the groove depth of the first block lateral narrow groove 5 and the groove depth at the position of the end portion 4b in the extending direction of the block circumferential groove 4, the position of the end portion 4b in the extending direction of the block peripheral groove 4 is compared. It is preferable to set the groove depth to be larger.

  The first block lateral narrow groove 5 preferably extends across the central portion 4 a in the extending direction of the block circumferential groove 4. This is because the drainage performance is improved as compared with the case where the first block lateral narrow groove 5 extends across the end portion 4b of the block circumferential groove 4 in the extending direction.

  The block circumferential groove 4 preferably has a groove depth in the extending direction end portion 4b in a range of 50 to 90% of the groove depth in the extending direction central portion 4a. If the groove depth in the extending direction end portion 4b is less than 50% of the groove depth in the extending direction central portion 4a, the drainage property may be deteriorated, while the groove depth in the extending direction end portion 4b is not sufficient. This is because if it exceeds 90% of the groove depth in the central portion 4a in the extending direction, the rigidity is deteriorated, and baldness, chipping and the like may occur.

  FIG. 2 (a) is a view showing a cross section taken along line XX of FIG. 1, and FIG. 2 (b) is a view of another embodiment of the tire according to the present invention cut in the same manner as FIG. 2 (a). FIG. The groove depth at the end portion 4b in the extending direction of the block circumferential groove 4 refers to the groove depth indicated by reference numeral d from the block tread position in FIG. 2 (a). Further, as shown in FIG. 2B, even when the groove depth becomes deeper from the extending direction end 4b of the block circumferential groove 4 toward the extending direction central part 4a of the block circumferential groove 4, The groove depth at the end portion 4b in the extending direction of the block circumferential groove 4 refers to the groove depth indicated by the reference symbol d in FIG.

  If the disposition position of the block circumferential groove 4 is close to the end in the width direction of the central block 3, there is a possibility that cracks may occur from the end portion 4b in the extending direction, and from the viewpoint of uniform block rigidity after wear. The extending direction center portion 4a preferably includes the center position in the tire circumferential direction of the center block 3. Further, in the block circumferential groove 4, the extending length of the central portion 4 a in the extending direction is preferably in the range of 10 to 50% of the length in the tire circumferential direction of the central block 3. If the extension length of the central portion 4a in the extending direction is less than 10% of the length in the tire circumferential direction of the central block 3, a sufficient edge component may not be obtained, while the extension of the central portion 4a in the extending direction is likely to occur. This is because if the length exceeds 50% of the length in the tire circumferential direction of the central block 3, cracks tend to be generated from the end position of the central portion 4a in the extending direction.

  The block circumferential groove 4 preferably has a groove depth of 10 mm or more at the central portion 4a in the extending direction. This is because if the groove depth of the central portion 4a in the extending direction is less than 10 mm, an edge component may not be obtained in the late stage of tire wear.

  The tire according to the present invention is located on the outer side in the tire width direction of the pair of first circumferential main grooves 1 and has a pair of second circumferential main grooves 6 extending continuously along the circumferential direction, and a first circumference. Tire width direction between a plurality of second width direction main grooves 7 extending in the tire width direction between the direction main groove 1 and the second circumferential direction main groove 6, and between the second circumferential direction main groove 6 and the tread end 8. A plurality of third width direction main grooves 9 extending in the direction of the first circumferential direction main groove 1, the second circumferential direction main groove 6, and the second width direction main groove 7 are further provided. It is preferable to partition and form a plurality of side blocks 11 by the second circumferential main groove 6, the tread end 8 and the third width direction main groove 9. By having such a tread pattern, the edge component is sufficiently secured.

Width _{W 3} of the central block 3 is preferably at least 180% of the width _{W 10} of the intermediate block 10. If the width W ₃ of the central block 3 is less than 180% of the width W ₁₀ of the intermediate block 10, there is a possibility that the rigidity of the center block is deteriorated wear characteristics are reduced.

  It is preferable that the blocks adjacent in the tire width direction are in a positional relationship shifted by a half pitch in the tire circumferential direction. By adopting such a configuration, there is a noise reduction effect.

  The extending direction of the block circumferential groove 4 is preferably in the range of 0 to 20 ° with respect to the tire equatorial plane. When the extending direction of the block circumferential groove 4 exceeds 20 ° with respect to the tire equatorial plane, an acute corner is formed in one of the small blocks 3a and 3b defined by the extending direction end 4b of the block circumferential groove 4. This is because uneven wear tends to occur. The extending shape of the block circumferential groove 4 may be formed by connecting the extending direction center portion 4a and both extending direction end portions 4b in a straight shape, but in particular, as shown in FIG. Connecting the extending direction center part 4a and both extending direction end parts 4b so as to extend in mutually different directions with respect to the tire circumferential direction and forming them in a zigzag shape increases the edge component. Is preferable. When the block circumferential groove 4 is formed in a zigzag shape, the angle of the extending direction of the block circumferential groove 4 with respect to the tire equatorial plane is a line passing through the groove width center of the block circumferential groove 4 as shown in FIG. The boundary position between the extending direction central portion 4a and both extending direction end portions 4b of the block circumferential groove 4 is defined as B and C, respectively, and both extending direction end portions 4b are first positions on the line. When the positions opened in the width direction main groove 2 are A and D, respectively, the extending direction of the line segment AB, line segment BC, and line segment CD is within a range of 0 to 20 ° with respect to the tire equator plane. It means that there is.

(Example 1)
As shown in FIG. 1, a pair of first circumferential main grooves (groove width: 7 mm, depth: 21 mm) and a plurality of first width direction main grooves (groove width: 8.5 mm, depth) are formed in the tread portion. Center block (width: 90 mm), a pair of first circumferential main grooves, a pair of second circumferential main grooves (groove width: 5 mm, depth: 20 mm) and a plurality of blocks An intermediate block (width: 40 mm) defined by two second width direction main grooves (groove width: 9.5 mm, depth: 20 mm), a tread edge and a third width direction main groove (groove width: 15 mm, In the central block of a tire having a plurality of side blocks (width: 45 mm) partitioned by a depth of 5 mm), a block circumferential groove (groove width at the center in the extending direction: 4 mm, depth: 15 mm) , Length: 14 mm, angle with respect to tire equator: 12 °, groove width at end of extending direction: 4 mm, depth: 8 mm, angle with respect to tire equator: −12 °) and central part of extending direction of block circumferential groove Extending across One block lateral narrow groove (groove width: 1 mm, depth: 1.5 mm) was provided to produce a truck / bus radial tire (315 / 80R225).

(Example 2)
A truck / bus radial tire (315 / 80R225) was produced in the same manner as in Example 1 except that the groove depth at the end in the extending direction of the block circumferential groove was 12 mm.

(Comparative Example 1)
A radial tire for trucks and buses (315 / 80R225) was produced in the same manner as in Example 1 except that the depth of the groove at the central end portion in the extending direction and the end portion in the extending direction of the block circumferential groove was 15 mm. ) Was produced.

  The tires of Examples 1 and 2 and Comparative Example 1 were mounted on a rim of size 9.0 × 22.5, the internal pressure was set to 830 kPa, and a running test on WET performance, block flaking, chipping performance, and the like was performed. Test conditions and evaluation criteria are as follows.

(WET performance)
The WET performance was evaluated in three stages according to the following evaluation criteria based on the driver's feelings as to whether or not slipping occurred by turning on three different road surfaces. Table 1 shows the evaluation results of the WET performance.
◎: When there is no slipping ○: Although slipping occurs, when the vehicle can travel without protruding from the road surface ×: When sliding occurs to the extent that it protrudes from the road surface

(Edge component of center block)
The edge component of the central block was measured by actually measuring the length of the edge portion in a specific range when the tire was new, 8 mm worn, and 12 mm worn. Table 1 shows the measurement result of the edge component of the central block. In addition, the numerical value of the edge component of the central block in Table 1 is indicated by an index ratio with the new edge component of Comparative Example 1 being 100, and the larger the numerical value, the larger the edge component of the central block. .

(Center block baldness, chipping performance)
The center block's baldness and chipping performance is evaluated in three stages according to the following evaluation criteria by having the same user use it in the actual vehicle, checking the state of the center block when 4mm wears, measuring the number of flakes and chips. did. Table 1 shows the evaluation results of the baldness and chipping performance of the central block.
◎: When there is no baldness or chipping ○: When there are less than 5 baldness and chippings in total ×: When there are 5 or more totaling baldness and chippings

  3 (a) and 3 (b) are schematic perspective views showing a block circumferential groove when one central block of the tire of Example 1 is extracted, and FIG. 3 (a) shows the tire. Fig. 3 (b) shows the state at the end of use of the tire. 4 (a) and 4 (b) are schematic perspective views showing block circumferential grooves when one central block of the tire of Comparative Example 1 is extracted, and FIG. 4 (a) shows the tire. Fig. 4 (b) shows the state at the end of tire use.

  From the evaluation results of Table 1, since both of Examples 1 and 2 have a reduced groove depth at the end in the extending direction of the block circumferential groove, almost no block flaking or chipping occurs due to a decrease in block rigidity. In addition, since the groove depth at the central portion in the extending direction of the block circumferential groove is sufficiently large, good results have been obtained for the WET performance.

  On the other hand, in Comparative Example 1, the peripheral groove of the block is formed with a constant groove depth at the end portion in the extending direction and the central portion in the extending direction. It turns out that the chipping performance is sacrificed.

  According to the present invention, the central block is a block circumferential groove extending in the tire circumferential direction, which divides the central block into small blocks, and the groove depth is longer in the extending direction than in the central part in the extending direction. By providing the shallow block circumferential groove at the portion, it is possible to improve the baldness and chipping performance of the block while maintaining the good WET performance of the tire.

DESCRIPTION OF SYMBOLS 1 1st circumferential direction main groove 2 1st width direction main groove 3 Central block 3a, 3b Small block 4 Block circumferential groove 4a Extension direction center part 4b Extension direction edge part 5 1st block horizontal narrow groove 6 2nd circumferential direction Main groove 7 Second width direction main groove 8 Tread end 9 Third width direction main groove 10 Intermediate block 11 Side block W ₃ Width of central block 3 W ₁₀ Width of intermediate block 10

Claims (8)

In the tread part,
A pair of first circumferential main grooves extending continuously along the tire circumferential direction across the tire equator;
A plurality of first width direction main grooves extending in the tire width direction between the first circumferential direction main grooves, and a tire formed by partitioning a plurality of central blocks,
The central block includes a block circumferential groove extending in the tire circumferential direction, and the block circumferential groove divides the central block into small blocks;
Groove depth of the block circumferential groove, than the extending direction central portion, rather shallow in the extending direction end portion,
The central block has a first block lateral narrow groove extending in the tire width direction, and the groove depth of the first block lateral narrow groove is greater than the groove depth at the end portion in the extending direction of the block circumferential groove. Shallow,
The first block transverse narrow groove extends across a central portion in the extending direction of the block circumferential groove whose extending direction is in a range of 0 to 20 ° with respect to the tire equatorial plane . 2. The tire according to claim 1 , wherein the block circumferential groove has a groove depth in an extending direction end portion in a range of 50 to 90% of a groove depth in an extending direction central portion. The tire according to claim 1 or 2 , wherein the block circumferential groove includes a center portion in the tire circumferential direction of the central block at a central portion in the extending direction. The tire according to any one of claims 1 to 3 , wherein the block circumferential groove has an extension length of a central portion in an extending direction in a range of 10 to 50% of a length in the tire circumferential direction of the central block. . The tire according to any one of claims 1 to 4 , wherein the block circumferential groove has a groove depth of 10 mm or more at a central position in the extending direction. A pair of second circumferential main grooves that are respectively located on the outer sides in the tire width direction of the pair of first circumferential main grooves and that extend continuously along the circumferential direction;
A plurality of second width direction main grooves extending in the tire width direction between the first circumferential direction main groove and the second circumferential direction main groove;
A plurality of third width direction main grooves extending in the tire width direction between the second circumferential direction main groove and the tread end;
A plurality of intermediate blocks are defined by the first circumferential main groove, the second circumferential main groove and the second width main groove;
The tire according to any one of claims 1 to 5 , wherein a plurality of side blocks are defined by the second circumferential main groove, the tread end, and the third width direction main groove. The tire according to claim 6 , wherein the width of the central block is 180% or more of the width of the intermediate block. The tire according to claim 6 or 7 , wherein blocks adjacent to each other in the tire width direction are in a positional relationship shifted by a half pitch in the tire circumferential direction.

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