WO2020170466A1

WO2020170466A1 - Pneumatic tire

Info

Publication number: WO2020170466A1
Application number: PCT/JP2019/024251
Authority: WO
Inventors: 達也増山
Original assignee: 横浜ゴム株式会社
Priority date: 2019-02-20
Filing date: 2019-06-19
Publication date: 2020-08-27
Also published as: DE112019006446B4; DE112019006446T5; JP2020131944A; JP6631730B1

Abstract

Provided is a pneumatic tire with which it is possible to improve on-snow traction performance while maintaining good driving performance on an unpaved road. A plurality of central blocks 51 are partitioned toward the center of a tread portion 1 by lug grooves 20, 30 and a circumferential narrow groove 40 that are formed on an external surface of the tread portion 1, the central blocks 51 each including: on a leading side and a trailing side, a leading-side axial edge e1 and a trailing-side axial edge e2 that extend along a tire width direction across a tire equator CL; a pair of leading-side oblique edges e3, e4 that respectively extend obliquely from both ends of the leading-side axial edge e1 such that a block width gradually increases toward the trailing side; and a trailing-side oblique edge e5 that, in a region protruding from the tire equator CL, is inclined in a direction different from that of the leading-side oblique edge e3 and connects the leading-side oblique edge e3 with the trailing-side axial edge e2.

Description

Pneumatic tire

The present invention relates to a pneumatic tire suitable as a heavy duty pneumatic tire, and more particularly to a pneumatic tire capable of improving snow traction performance while maintaining good running performance on an unpaved road.

Heavy-duty pneumatic tires used for construction vehicles such as dump trucks are mainly required to have excellent running performance (traction performance) on unpaved roads. Therefore, a block-based tread pattern provided with a large number of lug grooves extending in the tire width direction is used (see, for example, Patent Document 1).

On the other hand, in recent years, the performance requirements for various tires have increased, and even with the tires mentioned above, it is required to improve not only the running performance on unpaved roads but also the snow traction performance.

Japanese Patent No. 4676959

An object of the present invention is to provide a pneumatic tire capable of improving snow traction performance while maintaining good running performance on an unpaved road.

A pneumatic tire for achieving the above object is a tread portion which extends in the tire circumferential direction and forms an annular shape, a pair of sidewall portions arranged on both sides of the tread portion, and a tire diameter of these sidewall portions. In a pneumatic tire having a pair of bead portions arranged on the inner side in the direction, the rotational direction is specified, on the outer surface of the tread portion, a plurality of lug grooves extending in the tire width direction, and a tire circumferential direction A circumferential narrow groove that connects the lug grooves adjacent to each other is formed, and a plurality of center blocks are defined on the center side of the tread portion by the lug groove and the circumferential narrow groove, and the center block is the tire equator. To the tire width direction including a first center block unevenly distributed on one side and a tire equator including a second center block unevenly distributed on the other side in the tire width direction, the first center block and the second center block. Are arranged alternately in the tire circumferential direction, each of the first center block and the second center block, the axial edge of the ground contact first side that extends along the tire width direction on the ground contact first side and straddles the tire equator. And an axial edge on the grounding landing side that extends along the tire width direction to the landing landing side and straddles the tire equator, and a block width from each end of the grounding landing side axial edge to the landing landing side. A pair of diagonal edges on the first-in-first-contact side that obliquely extend toward, and in a region protruding from the tire equator, inclines in a direction different from the first-side diagonal edge on the first-contact side and the first-side diagonal edge on the first-contact side. It is characterized by having an oblique edge on the post-grounding side that connects with an axial edge on the post-grounding side.

In the present invention, in a tire having a block-based tread pattern in which a plurality of blocks are divided by lug grooves and circumferential narrow grooves, by making the center block located near the tire equator have the above-described shape, the tire in the lug groove A groove component in the width direction can be sufficiently secured, and traction performance on unpaved roads (hereinafter referred to as off-road traction performance) and snow traction performance can be improved. In particular, since the center block near the tire equator has a plurality of axial edges and diagonal edges, it is possible to increase edge components in both the tire width direction and the tire circumferential direction, which contributes to improvement of snow traction performance. .. This makes it possible to maintain good off-road traction performance and improve snow traction performance as the number of edge components increases.

In the present invention, in each of the first center block and the second center block, the distance A from the connection point between the axial edge on the landing post-arrival side and the diagonal edge on the ground post-landing side to the tire equator, and The distance B from the connection point between the axial edge and the diagonal edge on the first landing side, which is not connected to the diagonal edge on the grounding side, to the tire equator satisfies the relationship of 0.40≦A/B≦0.68. It is preferable. This makes it possible to improve off-road traction performance and snow traction performance in a well-balanced manner.

In the present invention, the angle α formed by the oblique edge of the first center block or the second center block on the post-ground contact side and the axial edge of the second center block or the first center block on the pre-ground contact side is 55°≦α≦. It is preferably in the range of 75°. This makes it possible to improve off-road traction performance and snow traction performance in a well-balanced manner.

In the present invention, the lug groove extends from the tread end on one side with respect to the tire equator toward the tire width direction inward and crosses the tire equator, and from the tread end on the other side with respect to the tire equator. Consisting of lug grooves extending inward in the tire width direction and intersecting the tire equator, these lug grooves are arranged alternately in the tire circumferential direction, and each lug groove intersects the tire equator in the tire width direction. The first groove portion that extends along the second groove portion that extends from one end of the first groove portion to the tread end with an angle smaller than the first groove portion with respect to the tire circumferential direction, and the first groove portion The other end communicates with the second groove portion of the lug groove adjacent in the tire circumferential direction, the first groove portion is located on the ground contact first side of the tread end side end portion of the lug groove, from the tire equator to the tread end. The distance is W, the area between the tire equator and the tire equator at a position 0.5 W away from the tire equator is the inner region, and the position is 0.5 W away from the tire equator at the tire width direction and the tread end. When the region of is the outer region, the second groove portion is curved or bent so that the average angle of the second groove portion in the inner region with respect to the tire circumferential direction becomes smaller than the average angle of the second groove portion in the outer region with respect to the tire circumferential direction. Therefore, the maximum length of the center block in the tire width direction is preferably 25% to 35% of the tread spread width. Since the lug groove including the first groove portion and the second groove portion is provided, it is possible to improve the low noise performance while improving the off-road traction performance. That is, the first groove portion extending along the tire width direction is arranged in the vicinity of the tire equator that greatly contributes to the traction performance, and the first groove portion communicates with another lug groove (second groove portion), The traction performance can be efficiently improved. In addition, the second groove portion is curved or bent as described above, so that the groove length can be increased, the traction performance can be improved, and the generation of air column resonance noise can be suppressed. Further, by appropriately securing the maximum width of the center block, it is possible to secure sufficient block rigidity and exhibit good traction performance.

In the present invention, a plurality of shoulder blocks are defined on the shoulder side of the tread portion by the lug groove and the circumferential narrow groove, and a shallow groove having at least one bending point is formed on each tread surface of the center block and the shoulder block. Preferably. Since the shallow groove has a bending point, the groove component in the tire circumferential direction and the groove component in the tire width direction can be increased in a balanced manner, and the snow traction performance in the tire circumferential direction and the width direction can be efficiently improved. it can.

In the present invention, one end of the shallow groove formed in each of the center blocks communicates with the circumferential narrow groove, the other end communicates with the lug groove, and the shallow groove formed in each of the center blocks faces the tire equator. The projected components of the shallow groove when projected do not overlap, and the shallow groove formed in the shoulder block has both ends terminating within the block, and the ground contact first side from the position of the apex of the shoulder block tread inner side in the tire width direction. Are preferably arranged in In this way, by providing the appropriately shaped shallow groove in the center block located near the tire equator, which greatly contributes to the traction performance, it is possible to effectively improve the snow traction performance. Further, by arranging so that the shallow grooves do not overlap as described above, avoiding excessive reduction in block rigidity over the entire circumference of the tire, and snow traction performance and off-road traction performance in the tire circumferential direction and It is possible to achieve a good balance and to achieve both of these performances at a high level. Further, the edge component can be increased on the first-in-ground contact side while suppressing the decrease in rigidity of the shoulder block, and the snow performance can be effectively improved. On the other hand, since there is no shallow groove on the post-grounding side and the block rigidity and the amount of rubber are secured, uneven wear (heel and toe wear) can be effectively suppressed.

In the present invention, the groove depth of the lug groove is preferably 15 mm to 28 mm. INDUSTRIAL APPLICABILITY The present invention can exhibit particularly excellent traction performance, anti-stone trapping performance and low noise performance in a heavy duty pneumatic tire having such characteristics.

In the present invention, the “tread ends” are both ends of the tread pattern portion of the tire in a state where the tire is assembled on a regular rim, the regular internal pressure is filled, and no load is applied (no load). The “distance W in the tire width direction from the tire equator to the tread end” in the present invention is a tread development width (specified by JATMA) which is a linear distance between the tread ends measured along the tire width direction in the above state. Equivalent to 1/2 of "tread width"). The "regular rim" is a rim that is defined for each tire in the standard system including the standard on which the tire is based. For example, in the case of JATMA, the standard rim, and in the case of TRA, "Design Rim" or ETRTO. If so, set it as “Measuring Rim”. "Regular internal pressure" is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. For JATMA, the maximum air pressure, and for TRA, the table "TIRE LOAD LIMITS AT VARIOUS" The maximum value described in COLD INFLUTION PRESSURES is "INFLATERATION PRESSURE" for ETRTO, but 180 kPa for tires for passenger cars.

FIG. 1 is a meridian sectional view of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a front view showing the tread surface of the pneumatic tire according to the embodiment of the present invention. FIG. 3 is a sectional view showing the center block formed on the tread surface of FIG. FIGS. 4A and 4B are front views showing another example of the center block formed on the tread surface.

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

As shown in FIG. 1, a pneumatic tire of the present invention includes a tread portion 1, a pair of sidewall portions 2 arranged on both sides of the tread portion 1, and a sidewall portion 2 which is arranged inside a tire radial direction. And a pair of bead portions 3. In FIG. 1, reference symbol CL indicates the tire equator, and reference symbol E indicates the tread end. In the illustrated example, the tread edge E coincides with the tire width direction outer edge of the tire width direction outermost block (the edge portion formed by the tread surface of the tire width direction outermost block and the tire width direction outer side surface). ing. Although FIG. 1 is not drawn because it is a meridional cross-sectional view, the tread portion 1, the sidewall portion 2, and the bead portion 3 each extend in the tire circumferential direction to form an annular shape. The basic structure of the shape is constructed. Hereinafter, although the description with reference to FIG. 1 is basically based on the meridional cross-sectional shape shown in the drawing, each tire constituent member extends in the tire circumferential direction to form an annular shape.

A carcass layer 4 is mounted between the pair of left and right bead portions 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded back from the vehicle inside to the outside around the bead cores 5 arranged in each bead portion 3. A bead filler 6 is arranged on the outer periphery of the bead core 5, and the bead filler 6 is wrapped by the main body portion and the folded portion of the carcass layer 4. On the other hand, a plurality of layers (four layers in FIG. 1) of belt layers 7 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. Each belt layer 7 includes a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and the reinforcing cords are arranged so as to intersect each other between the layers. In these belt layers 7, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set in the range of, for example, 10° to 60°. Although not used in the pneumatic tire of FIG. 1, a belt reinforcing layer (not shown) may be further provided on the outer peripheral side of the belt layer 7 in the present invention. When the belt reinforcing layer is provided, the belt reinforcing layer includes, for example, an organic fiber cord oriented in the tire circumferential direction, and the angle of the organic fiber cord with respect to the tire circumferential direction can be set to, for example, 0° to 5°.

A tread rubber layer 11 is arranged on the outer peripheral side of the carcass layer 4 and the belt layer 7 in the tread portion 1. A side rubber layer 12 is arranged on the outer peripheral side (outer side in the tire width direction) of the carcass layer 4 in the sidewall portion 2. A rim cushion rubber layer 13 is arranged on the outer peripheral side (outer side in the tire width direction) of the carcass layer 4 in the bead portion 3. The tread rubber layer 11 may have a structure in which two types of rubber layers having different physical properties (cap tread rubber layer and undertread rubber layer) are laminated in the tire radial direction.

The present invention is applied to such a general pneumatic tire, but its cross-sectional structure is not limited to the basic structure described above.

As shown in FIG. 2, the surface of the tread portion 1 of the pneumatic tire of the present invention extends inward in the tire width direction from a tread end E on one side (right side in the figure) with respect to the tire equator CL. And a tire width from the tread end E on the other side (the left side in the drawing) with respect to the tire equator CL. A lug groove 30 (which may be referred to as "the other side lug groove 30" in the following description) that extends inward in the direction and intersects the tire equator CL is provided. A plurality of lug grooves 20 on one side and a plurality of lug grooves 30 on the other side are provided.

Each of the

lug grooves

20, 30 is a

first groove portion

21, 31 extending along the tire width direction so as to intersect with the tire equator CL, and one end of the

first groove portion

21, 31 is closer to the tire than the

first groove portion

21, 31. The

second groove portions

22 and 32 extend to the tread end E with a small angle with respect to the circumferential direction. More specifically, the lug groove 20 on one side intersects with the tire equator CL and extends along the tire width direction. The first groove portion 21 and one end of the first groove portion 21 (one side relative to the tire equator (see FIG. End portion (on the right side of) and a second groove portion 22 that extends to the tread end E at an angle smaller than the first groove portion 21 with respect to the tire circumferential direction. Similarly, the lug groove 30 on the other side intersects with the tire equator CL and extends along the tire width direction with a first groove portion 31 and one end of the first groove portion 31 (the other side with respect to the tire equator (in the figure). The second groove portion 32 extends from the end portion on the left side) to the tread edge E at an angle smaller than the first groove portion 31 with respect to the tire circumferential direction.

One lug groove 20 on the one side and one lug groove 30 on the other side are alternately arranged in the tire circumferential direction. However, since the

lug grooves

20 and 30 basically extend in the opposite directions from the tire equator CL, as described above, the first groove portion 21 and the other side of the lug groove 20 on one side on the tire equator CL. The first groove portions 31 of the lug grooves 30 are alternately arranged in the tire circumferential direction, but on the one side with respect to the tire equator CL, the second groove portions 22 of the one side lug groove 20 are spaced in the tire circumferential direction. On the other side of the tire equator CL, the second groove portions 32 of the lug groove 30 on the other side are arranged at intervals in the tire circumferential direction. In the present invention, if the

first groove portions

21 and 31 are alternately arranged and are adjacent to each other on the tire equator CL, it is considered that the

lug grooves

20 and 30 are alternately arranged unless otherwise specified. I shall.

The other ends of the

first groove portions

21, 31 of the

lug grooves

20, 30 communicate with the

second groove portions

32, 22 of the

other lug grooves

30, 20 adjacent in the tire circumferential direction. That is, the first groove portion 21 of the lug groove 20 on one side communicates with the second groove portion 32 of the lug groove 30 on the other side adjacent in the tire circumferential direction, and the first groove portion 31 of the lug groove 30 on the other side is in the tire circumferential direction. Is communicated with the second groove portion 22 of the lug groove 20 on the one side adjacent to.

The

first groove portions

21 and 31 of the

lug grooves

20 and 30 are located closer to the ground contact side (stepping side) than the end portions of the

lug grooves

20 and 30 on the tread end E side. That is, the pneumatic tire of the present invention is a tire in which the rotation direction R is designated, but the

lug grooves

20 and 30 as a whole have the rotation direction R from the tire equator CL side toward the tire width direction outer side. It has a shape inclined in the opposite direction.

In addition to

such lug grooves

20 and 30, circumferential narrow grooves 40 are provided. The circumferential narrow groove 40 is formed between the second groove portions adjacent to each other in the tire circumferential direction on one side of the tire equator CL, that is, the second lug groove 20 on one side adjacent to the tire equator CL in the tire circumferential direction on one side. The groove portions 22 extend in the tire circumferential direction so as to connect the groove portions 22 or the second groove portions 32 of the other side lug grooves 30 that are adjacent to each other in the tire circumferential direction on the other side with respect to the tire equator CL.

The circumferential narrow groove 40 has a smaller groove width than the

lug grooves

20 and 30. Specifically, the

lug grooves

20 and 30 have a groove width of, for example, 5 mm to 30 mm and a groove depth of, for example, 8 mm to 28 mm. In particular, when the tire is a heavy duty pneumatic tire, the groove depth may be, for example, 15 mm to 28 mm. On the other hand, the circumferential narrow groove 40 has a groove width of, for example, 7 mm to 11 mm and a groove depth of, for example, 15 mm to 20 mm.

A plurality of blocks 50 are defined by the

lug grooves

20, 30 and the circumferential narrow groove 40. Of the plurality of blocks 50, the one located on the tire equator CL side (center side of the tread portion 1) with respect to the circumferential narrow groove 40 is the center block 51, and the tread end E side with respect to the circumferential narrow groove 40 (tread portion). The one located on the shoulder side 1) is called a shoulder block 52. The center block 51 includes a first center block 51A unevenly distributed on one side in the tire width direction with respect to the tire equator CL, and a second center block 51B unevenly distributed on the other side in the tire width direction with respect to the tire equator CL. I'm out. That is, at least a part of each of the first center block 51A and the second center block 51B has a shape protruding from the tire equator CL in the tire width direction. The first center blocks 51A and the second center blocks 51B are arranged alternately in the tire circumferential direction.

As shown in FIG. 3, each center block 51 includes a plurality of edges e. More specifically, each center block 51 has an axial edge e1 on the first landing side that extends along the tire width direction on the first landing side (stepping side) and straddles the tire equator CL, and a rear landing side (kicking-out side). Side), which extends along the tire width direction and straddles the tire equator, and which has a block width in the tire width direction from both ends of an axial edge e2 on the landing rear end side and an axial edge e1 on the first landing side. A pair of diagonal edges e3, e4 on the grounding first arrival side that obliquely extend toward the side and a diagonal edge e3 on the grounding first arrival side in a region protruding from the tire equator CL. It has an oblique edge e3 and an oblique edge e5 on the post-grounding side that connects the axial edge e2 on the post-grounding side. In particular, it is preferable that the diagonal edge e3 on the first landing side and the diagonal edge e5 on the last landing side are inclined in opposite directions. In the illustrated example, each center block 51 has the edges e1 to e5, the edges extending along the

second groove portions

22 and 32 of the

lug grooves

20 and 30, and the circumferential narrow groove 40. The diagonal edge e3 on the first landing side and the diagonal edge e5 on the last grounding side are inclined in opposite directions. Further, in the illustrated example, all the edges forming each center block 51 are linear, but each center block 51 may include curved or zigzag edges.

The axial edge e1 on the first-to-ground landing side and the axial edge e2 on the last-to-ground landing side are both arranged to be -10° or more and 10° or less with respect to the tire width direction. In the illustrated example, both the axial edges e1 and e2 extend at 0° with respect to the tire width direction.

Since the center block 51 includes the plurality of edges e1 to e5 described above, a cutout shape is formed in the region of the center block 51 protruding from the tire equator CL. More specifically, as the notch shape, the first groove portion 21 of the lug groove 20 on one side, the second groove portion 32 of the lug groove 30 on the other side adjacent in the tire circumferential direction, and the first center block 51A after grounding. A triangular region surrounded by the landing side oblique edge e5 is formed. In addition, the first groove portion 31 of the lug groove 30 on the other side, the second groove portion 22 of the lug groove 20 on the one side that is adjacent in the tire circumferential direction, and the diagonal edge e5 of the second center block 51B on the post-grounding side. An enclosed triangular area is formed. By forming such a triangular region, the groove volume of the

lug grooves

20 and 30 can be increased, and mud can be grasped on an unpaved road while snow can be grasped on a snowy road. Therefore, it contributes to the improvement of off-road traction performance and snow traction performance.

In the pneumatic tire described above, in the tire having a block-based tread pattern in which a plurality of blocks 50 are divided by the

lug grooves

20 and 30 and the circumferential narrow groove 40, the center block 51 located near the tire equator CL is described above. With the shape, it is possible to sufficiently secure the groove component in the tire width direction in the

lug grooves

20 and 30, and it is possible to improve the off-road traction performance and the snow traction performance. In particular, since the center block 51 near the tire equator CL has a plurality of axial edges and oblique edges, it is possible to increase the edge components in both the tire width direction and the tire circumferential direction, and improve snow traction performance. Contribute. This makes it possible to maintain good off-road traction performance and improve snow traction performance as the number of edge components increases.

Further, by having the circumferential narrow groove 40, noise is dispersed through the circumferential narrow groove 40, so that low noise performance can be improved. Furthermore, since the groove component in the tire circumferential direction can be added by the circumferential narrow groove 40, it is possible to prevent the tire from laterally shifting during traction and improve the stability.

In the pneumatic tire described above, in each of the first center block 51A and the second center block 51B, the connection point between the axial edge e2 on the post-grounding side and the diagonal edge e5 on the post-grounding side is P1, The connecting point between the axial edge e1 on the side and the diagonal edge e4 on the first-in-ground side is P2. The distance between the connection point P1 and the tire equator CL at the axial edge e2 on the landing-after-arrival side is defined as a distance A, and the distance between the connection point P2 and the tire equator CL at the axial edge e1 on the landing-first arrival side is defined as a distance B ( (See FIG. 3). At this time, it is preferable that the distance A and the distance B satisfy the relationship of 0.40≦A/B≦0.68. By properly setting the distance A with respect to the distance B, the off-road traction performance and the snow traction performance can be improved in a well-balanced manner. Here, if the ratio of the distance A to the distance B is smaller than 0.40, the block rigidity tends to decrease and the uneven wear resistance tends to deteriorate, and conversely, if it exceeds 0.68, sufficient traction performance can be obtained. I can't.

Further, the angle formed by the oblique edge e5 of the first center block 51A or the second center block 51B on the post-grounding side and the axial edge e1 of the second center block 51B or the first center block 51A on the first-grounding side of the ground is an angle. Let α. This angle α may be set in the range of 55°≦α≦75°. In addition, the angle formed by the diagonal edge e3 of the first center block 51A or the second center block 51B on the first landing side and the axial edge e2 of the second center block 51B or the first center block 51A on the last landing side of the ground is an angle. Let β. This angle β may be set in the range of 50°≦β≦60°. By appropriately setting the angle α or the angle β as described above, the off-road traction performance and the snow traction performance can be improved in a well-balanced manner. Here, if the angle α or the angle β deviates from the above range, the effect of improving the traction performance cannot be sufficiently obtained. In addition, when the axial edge e1 on the first landing side, the axial edge e2 on the first landing side, the diagonal edge e3 on the first grounding side, or the diagonal edge e5 on the last grounding side is not linear but curved or zigzag. The angle α or the angle β described above is measured based on a straight line connecting both ends of the edge.

In FIG. 2, each

lug groove

20 and 30 has a distance in the tire width direction from the tire equator CL to the tread end E as W, and a position apart from the tire equator CL in the tire width direction by 0.50 W and the tire equator CL. When the region between the tread end E and the position spaced from the tire equator CL in the tire width direction by 0.50 W is the outer region Sb, the

second groove portions

22, 32 in the outer region Sb are defined as the inner region Sa. The

second groove portions

22, 32 are curved or bent so that the average angle θa of the

second groove portions

22, 32 in the inner region Sa with respect to the tire circumferential direction becomes smaller than the average angle θb with respect to the tire circumferential direction. In other words, the

second groove portions

22 and 32 of the

lug grooves

20 and 30 are smoothly curved so that the inclination angle with respect to the tire circumferential direction gradually decreases from the tread end E side toward the tire equator CL side, or at least one bend. It has a point and is bent. Further, the maximum length L in the tire width direction of the center block 51 is set to 25% to 35% of the tread development width TW.

Since the tread pattern is configured as described above, it is possible to improve low-noise performance while improving off-road traction performance. That is, the

first groove portions

21 and 31 extending along the tire width direction are arranged in the vicinity of the tire equator CL, which greatly contributes to the traction performance, and the

first groove portions

21 and 31 are the first groove portions of the

other lug grooves

30 and 20. Since it communicates with the two

groove portions

32 and 22, the traction performance can be efficiently improved. In addition, the

second groove portions

22 and 32 are curved or bent as described above, so that the groove length can be increased, the traction performance can be improved, and the generation of air column resonance sound can be suppressed. Further, by appropriately securing the maximum width of the center block 51, it is possible to secure sufficient block rigidity and exhibit good traction performance. Here, if the magnitude relationship between the average angles θa and θb of the

second groove portions

22 and 32 is reversed, the curved or bent shape of the

second groove portions

22 and 32 becomes inappropriate, and the effect of improving traction performance is sufficiently obtained. Absent.

The

second groove portions

22 and 32 of the

lug grooves

20 and 30 are averaged with respect to the tire circumferential direction of the

second groove portions

22 and 32 in the inner region Sa when gradually decreasing the angle with respect to the tire equator CL with respect to the tire circumferential direction as described above. The angle θa is preferably 35° to 45°, and the average angle θb of the

second groove portions

22 and 32 in the outer region Sb with respect to the tire circumferential direction is preferably 70° to 85°. Thereby, the angle in each part of the

second groove portions

22 and 32 becomes good, and the curved or bent shape of the

second groove portions

22 and 32 becomes good, so that the lug groove length is increased and the traction performance is improved. Will be advantageous. When the average angle θa of the

second groove portions

22 and 32 is less than 35°, it is difficult to sufficiently improve the traction performance because the groove component in the tire width direction is reduced. When the average angle θa of the

second groove portions

22 and 32 exceeds 45°, the difference from the average angle θb becomes small, and the

second groove portions

22 and 32 cannot be bent or curved sufficiently, and the lug groove length becomes longer. Since it does not increase sufficiently, it becomes difficult to sufficiently improve the traction performance. If the average angle θb of the

second groove portions

22 and 32 is less than 70°, the difference from the average angle θa becomes small and the

second groove portions

22 and 32 cannot be bent or curved sufficiently, and the lug groove length is increased. Does not increase sufficiently, it becomes difficult to sufficiently improve the traction performance. When the average angle θb of the

second groove portions

22 and 32 exceeds 85°, the difference from the average angle θa becomes large and the

second groove portions

22 and 32 are largely bent or curved, and it is difficult to secure a good groove shape. Become.

The average angle of the

second groove portions

22 and 32 of the

lug grooves

20 and 30 is the angle formed by the straight line connecting the midpoints of the groove width directions of the

lug grooves

20 and 30 at the boundary positions of the regions with respect to the tire circumferential direction. Can be asked as However, at the tire equator CL and the tread end E, as shown in the figure, the midpoint of the extension line of the

second groove portions

22, 32 drawn toward the tire equator CL or the tread end E at the tire equator CL or the tread end E is used. I shall.

As described above, the

first groove portions

21 and 31 are provided to secure the groove component in the tire width direction mainly in the vicinity of the tire equator CL, which largely contributes to the traction performance. Therefore, it is preferable that the

first groove portions

21 and 31 extend in a direction substantially perpendicular to the tire circumferential direction. Specifically, the angle θc of the

first groove portions

21 and 31 with respect to the tire circumferential direction is preferably 80° to 100°. Thereby, the

first groove portions

21 and 31 can efficiently improve the traction performance. When the angle θc of the

first groove portions

21 and 31 is less than 80° or more than 100°, the inclination of the

first groove portions

21 and 31 with respect to the tire width direction becomes large, and a sufficient groove component in the tire width direction is ensured. Cannot be achieved, and the effect of improving traction performance is limited.

Further, in FIG. 2, a shallow groove 60 having at least one bending point is formed on the tread surface of each block 50. The shallow groove 60 is a groove having a smaller groove depth than the

lug grooves

20, 30 and the circumferential narrow groove 40, and the groove depth is preferably set to 1 mm to 3 mm and the groove width is set to, for example, 1 mm to 3 mm. it can. If the depth of the shallow groove 60 is less than 1 mm, the shallow groove 60 is too shallow to obtain the effect of providing the shallow groove 60, and if the depth of the shallow groove 60 exceeds 3 mm, the block rigidity is increased. The impact will increase. In the following description, the shallow groove 60 formed in the center block 51 is called a center shallow groove 61, and the shallow groove 60 formed in the shoulder block 52 is called a shoulder shallow groove 62. In the illustrated example, both the center shallow groove 61 and the shoulder shallow groove 62 have one bending point. The number of shallow grooves 60 formed in each block 50 is not particularly limited, but it is preferable to provide one shallow groove 60 in each block 50 as illustrated.

In the present invention, in order to ensure off-road traction performance, in the tire having a block-based tread pattern in which a plurality of blocks 50 are divided by the

lug grooves

20, 30 and the circumferential narrow grooves 40 as described above, each block 50 Since the shallow groove 60 having the bending point is provided on the tread surface of the tire, the groove component in the tire circumferential direction and the groove component in the tire width direction can be increased in a balanced manner, and the snow traction performance in the tire circumferential direction and the width direction can be improved. It can be improved efficiently.

Further, as shown, the center shallow groove 61 may have one end communicating with the circumferential narrow groove 40 and the other end communicating with the

second groove portions

22, 32 of the

lug grooves

20, 30. The center shallow groove 61 is preferably bent along the outer edge of the center block 51 on the stepping side or the kicking side. At this time, the center shallow groove 61 is preferably arranged within a range of ±5 mm in the tire circumferential direction from the center position of the center block 51 in the tire circumferential direction. Further, it is preferable that the projection components of the center shallow groove 61 when the center shallow groove 61 is projected toward the tire equator CL do not overlap. By providing the center shallow groove 61 having an appropriate shape in the center block 51 located near the tire equator CL, which greatly contributes to the traction performance, it is possible to effectively improve the snow traction performance. Further, since the center shallow grooves 61 do not overlap as described above, the block rigidity is prevented from being excessively reduced over the entire circumference of the tire, and a balance between snow traction performance and off-road traction performance in the tire circumferential direction is avoided. Can be improved, and these performances can be highly compatible.

On the other hand, the shoulder shallow groove 62 is preferably terminated at both ends inside the shoulder block 52, as shown in the figure. Further, the shoulder shallow groove 62 may be bent along the outer edge of the shoulder block 52 on the stepping side. Further, the shoulder shallow groove 62 is preferably arranged on the stepping side with respect to the position of the apex of the tread surface of the shoulder block 52 on the inner side in the tire width direction. By providing the shoulder shallow groove 62 in this way, it is possible to increase the edge component on the stepping side while suppressing the decrease in rigidity of the shoulder block 52, and to effectively improve the snow performance. On the other hand, since there is no shallow groove on the kicking side and the block rigidity and the amount of rubber are secured, uneven wear (heel and toe wear) can be effectively suppressed.

The

lug grooves

20 and 30 may have a uniform groove depth as a whole, but it is preferable that the

first groove portions

21 and 31 be appropriately shallower than the

second groove portions

22 and 32. Specifically, the groove depth in the

first groove portions

21, 31 of the

lug grooves

20, 30 is preferably 65% to 75% of the groove depth in the

second groove portions

22, 32. Accordingly, the rigidity of the block (center block 51) adjacent to the

first groove portions

21 and 31 can be increased, which is advantageous for improving the traction performance.

The groove depths of the

lug grooves

20 and 30 and the circumferential narrow groove 40 can be set within the ranges described above, but it is preferable that the circumferential narrow groove 40 be appropriately shallower than the

lug grooves

20 and 30. Specifically, the groove depth of the circumferential narrow groove 40 is preferably 75% to 85% of the groove depth of the

second groove portions

22, 32 of the

lug grooves

20, 30. In this way, by making the circumferential narrow groove 40 appropriately shallower than the

second groove portions

22, 32, the rigidity of the blocks (center block 51, shoulder block 52) adjacent to the circumferential narrow groove 40 can be increased, It is advantageous to improve the traction performance.

The tire size is 315/80R22.5 and has the basic structure illustrated in FIG. 1. The tread portion has a plurality of lug grooves extending in the tire width direction and lug grooves adjacent to each other in the tire circumferential direction. In a pneumatic tire in which a circumferential narrow groove to be connected is formed, and a plurality of center blocks are defined on the center side of the tread portion by the lug groove and the circumferential narrow groove, the shape of the center block, the diagonal of the landing post-arrival side Presence/absence of edges, presence/absence of axial edges on the landing first-arrival side and landing-after landing side, ratio of distance A to distance B (A/B), inclination angle α of diagonal edge on landing-after-landing side, angle change of lug groove, Conventional examples, comparative examples and Examples 1 to 6 in which the angle near the equator of the tire in the lug groove, the presence or absence of opening of the lug groove to other lug grooves, and the arrangement of shallow grooves in each block are set as shown in Table 1, respectively. The pneumatic tire of was produced.

Regarding "Shape of center block" in Table 1, the corresponding drawing numbers are listed. The shape of the center block of the conventional example shown in FIG. 4(a) is significantly different from the shape of FIG. 2, but each part is made to correspond to FIG. 2 as described in the figure. Further, the shape of the center block of the comparative example shown in FIG. 4B is different from the shape of FIG. 2 in that it does not have a diagonal edge (edge e5 shown in FIG. 2) on the landing/arrival side.

In addition, the “angle change of the lug groove” in Table 1 means that the inclination angle of the lug groove with respect to the tire circumferential direction gradually decreases from the tread end side toward the tire equator side. Further, the “angle in the lug groove near the tire equator” in Table 1 means whether or not the angle of the lug groove with respect to the tire circumferential direction is vertical near the tire equator.

For these pneumatic tires, off-road traction performance and snow traction performance were evaluated by the following evaluation methods, and the results are also shown in Table 1.

Off-road traction performance:
Each test tire was mounted on a wheel with a rim size of 22.5×9.00, the air pressure was set to 850 kPa, the tire was mounted on the drive shaft of a test vehicle (a truck with an axle arrangement of 6×4), and the test course consisted of an unpaved road. Sensory evaluation was performed by a test driver. The evaluation results are shown by an index with the value of the conventional example being 100. The larger the index value, the better the off-road traction performance.

Snow traction performance Each test tire was mounted on a wheel with a rim size of 22.5 x 9.00, the air pressure was set to 850 kPa, and it was mounted on the drive shaft of a test vehicle (a truck with an axle arrangement of 6 x 4) to consist of a snowy road. Sensory evaluation was performed by a test driver on the test course. The evaluation results are shown by an index with the value of the conventional example being 100. The larger the index value, the better the snow traction performance.

As is clear from Table 1, in each of Examples 1 to 6, the off-road traction performance and the snow traction performance were improved as compared with the conventional example.

On the other hand, in the comparative example, since each center block does not have a diagonal edge on the landing side after landing, it was not possible to sufficiently obtain the effect of improving off-road traction performance and snow traction performance.

1 Tread Part 2 Sidewall Part 3

Bead Part

20, 30 Lug Groove 40 Circumferential Narrow Groove 51 Center Block 51A First Center Block 51B Second Center Block CL Tire Equator E Tread Edge e Edge e1 Axial Edge e2 on First Grounding Side Axial edges e3, e4 on the landing post-arrival side Diagonal edge e5 on the landing landing side Diagonal edge on the landing landing side

Claims

An annular tread portion extending in the tire circumferential direction, a pair of sidewall portions arranged on both sides of the tread portion, and a pair of bead portions arranged on the tire radial inner side of these sidewall portions. In a pneumatic tire with a specified rotation direction,
On the outer surface of the tread portion, a plurality of lug grooves extending in the tire width direction and a circumferential narrow groove that connects the lug grooves adjacent to each other in the tire circumferential direction are formed, and the lug groove and the circumference are formed. A plurality of center blocks are defined on the center side of the tread portion by the direction narrow groove, and the center blocks are unevenly distributed on one side in the tire width direction with respect to the tire equator. , Including a second center block unevenly distributed on the other side, the first center blocks and the second center blocks are arranged alternately in the tire circumferential direction,
Each of the first center block and the second center block has an axial edge on the first landing side that extends along the tire width direction on the first landing side and straddles the tire equator, and a tire width direction on the last landing side. And an axial edge of the grounding rear-end side that extends along the tire equator, and diagonally extends from both ends of the axial edge of the ground-contacting first-arrival side so that the block width gradually increases toward the ground-contacting rear-end side. A pair of diagonal edges on the first landing side, the diagonal edge on the first landing side and the axial edge on the last landing side on the ground inclining in a direction different from the diagonal edge on the first landing side in the region protruding from the tire equator. A pneumatic tire having an oblique edge on the grounding/adhering side to be connected.
In each of the first center block and the second center block, the distance A from the connection point between the axial edge on the landing rear landing side and the diagonal edge on the landing landing side to the tire equator, and the ground landing first side And the distance B from the connection point between the axial edge of the tire and the diagonal edge on the first landing side which is not connected to the diagonal edge on the grounding side to the tire equator is 0.40≦A/B≦0.68. The pneumatic tire according to claim 1, wherein the relationship is satisfied.
The angle α formed by the oblique edge of the first center block or the second center block on the post-grounding side and the axial edge of the second center block or the first landing side of the ground on the first landing side is 55°≦. The pneumatic tire according to claim 1 or 2, wherein α is in the range of 75°.
The lug groove, the lug groove extending inward in the tire width direction from the tread end on one side with respect to the tire equator and intersecting the tire equator, and the tire width direction from the tread end on the other side with respect to the tire equator. It consists of lug grooves that extend inward and intersect the tire equator, and these lug grooves are arranged alternately in the tire circumferential direction,
Each lug groove, a first groove portion that extends along the tire width direction intersecting the tire equator, and inclined from the one end of the first groove portion at a smaller angle with respect to the tire circumferential direction than the first groove portion. The second groove portion extending to the tread end, the other end of the first groove portion communicates with the second groove portion of the lug groove adjacent in the tire circumferential direction, the first groove portion is the tread end side of the lug groove. It is located on the grounding first-arrival side than the end of
The distance from the tire equator to the tread edge is W, the region between the tire equator and the tire equator at a distance of 0.5 W in the tire width direction is the inner region, and the tire equator is at a distance of 0.5 W in the tire width direction. When the region between the position and the tread end is the outer region, the average angle with respect to the tire circumferential direction of the second groove portion in the inner region is smaller than the average angle with respect to the tire circumferential direction of the second groove portion in the outer region. So that the second groove portion is curved or bent,
The pneumatic tire according to any one of claims 1 to 3, wherein the maximum length of the center block in the tire width direction is 25% to 35% of the tread development width.
A plurality of shoulder blocks are defined on the shoulder side of the tread portion by the lug groove and the circumferential narrow groove, and a shallow groove having at least one bending point is formed on each tread surface of the center block and the shoulder block. The pneumatic tire according to any one of claims 1 to 4, characterized in that:
One end of the shallow groove formed in each of the center blocks communicates with the circumferential narrow groove, the other end communicates with the lug groove, and the shallow groove formed in each of the center blocks is connected to the tire equator. The projected components of the shallow groove when projected toward each other do not overlap,
The shallow groove formed in the shoulder block has both ends terminating inside the block, and is arranged on a ground contact first side with respect to a position of an apex of the tread surface of the shoulder block on the inner side in the tire width direction. The pneumatic tire according to item 5.
The pneumatic tire according to any one of claims 1 to 6, wherein the maximum depth of the lug groove is 15 mm to 28 mm.