JP6631730B1 - Pneumatic tire - Google Patents

Abstract

An object of the present invention is to provide a pneumatic tire capable of improving traction performance on snow while maintaining good running performance on an unpaved road. A plurality of center blocks (51) are defined on the center side of the tread (1) by lug grooves (20, 30) and a circumferential narrow groove (40) formed on the outer surface of the tread (1). An axial edge e1 on the ground contact side and an axial edge e2 on the ground contact side that extend along the tire width direction and straddle the tire equator CL on the first arrival side and the late arrival side, and an axial edge on the first arrival side. A pair of oblique edges e3 and e4 on the first contact side extending obliquely so that the block width gradually increases from both ends of e1 toward the late contact side, and the oblique edge e3 on the first contact side in a region protruding from the tire equator CL. And an oblique edge e5 on the late arrival side of the ground connecting the oblique edge e3 on the first arrival side of the ground and the axial edge e2 on the late arrival side of the ground. [Selection] Figure 2

Description

  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 traction performance on snow while maintaining good running performance on unpaved roads.

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

  On the other hand, in recent years, the required performance of various tires has been increasing, and even in the above-described tires, it is required to improve not only the traveling performance on unpaved roads but also the traction performance on snow.

Japanese Patent No. 4676959

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

A pneumatic tire for achieving the above object has a ring-shaped tread extending in the tire circumferential direction, a pair of sidewalls disposed on both sides of the tread, and a tire diameter of these sidewalls. A pair of bead portions arranged on the inner side in the direction, and in a pneumatic tire in which the rotation direction is designated, on the outer surface of the tread portion, a plurality of lug grooves extending in the tire width direction; And a plurality of center blocks are defined on the center side of the tread portion by the lug grooves and the circumferential thin grooves, and the center blocks are separated by a tire equator. Including a first center block unevenly distributed on one side in the tire width direction and a second center block unevenly distributed on the other side in the tire width direction with respect to the tire equator, One center block and the second center block are alternately arranged in the tire circumferential direction, and each of the first center block and the second center block extends along the tire width direction on the ground contact first side and has a tire. The axial edge of the ground contact first side straddling the equator, the axial edge of the ground contact late side extending across the tire equator extending along the tire width direction to the ground contact late side, and the axial edge of the ground first arrival side. A pair of oblique edges on the first contact side extending obliquely so that the block width gradually increases toward the later contact side from both ends, and in a region protruding from the tire equator, inclined in a direction different from the oblique edge on the first contact side. the ground wherein the arrival side of the oblique edge connecting the axial edge of the ground after the called side possess a diagonal edge of the ground after the terminating axial edge and the tangent of the ground arrival side Te Angle with respect to each of the tire width direction of the axial edges of the trailing end is characterized in that in the range of -10 ° to 10 °.
Further, the pneumatic tire of the present invention includes a ring-shaped tread extending in the tire circumferential direction, a pair of sidewalls disposed on both sides of the tread, and a tire radially inner side of these sidewalls. In a pneumatic tire having a pair of bead portions arranged in the tire, the rotation direction is specified, in the outer surface of the tread portion, a plurality of lug grooves extending in the tire width direction, and adjacent to the tire circumferential direction. A circumferential narrow groove that connects the mating lug grooves 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. A first center block unevenly distributed on one side in the tire width direction and a second center block unevenly distributed on the other side in the tire width direction with respect to the tire equator; The blocks and the second center blocks are alternately arranged in the tire circumferential direction, and each of the first center block and the second center block extends along the tire width direction on the ground contact side and extends the tire equator. The axial edge of the ground contact first side straddling, the axial edge of the ground contact late side extending along the tire width direction to the ground contact late side and straddling the tire equator, from both ends of the axial edge of the ground first contact side A pair of oblique edges on the ground contact first side, each of which extends obliquely so that the block width gradually increases toward the ground contact late side, and is inclined in a direction different from the oblique edge on the ground first arrival side in a region protruding from the tire equator. A tread on one side with respect to the tire equator, having a diagonal edge on the ground first arrival side and a diagonal edge on the rear ground contact side connecting the axial edge on the ground last arrival side; A lug groove extending inward from the tread and intersecting the tire equator, and a lug groove extending inward from the tread end on the other side of the tire equator and intersecting the tire equator The lug grooves are arranged alternately in the tire circumferential direction, each lug groove intersects the tire equator and extends along the tire width direction, and the first groove portion extends from one end of the first groove portion. A second groove extending at an angle smaller than the first groove relative to the tire circumferential direction and extending to the tread end, the other end of the first groove being the second lug groove adjacent to the tire circumferential direction. In communication with the groove portion, the first groove portion is located closer to the ground contact than the end of the lug groove on the tread end side, the distance from the tire equator to the tread end is W, and in the tire width direction from the tire equator 0.5W away from the tire The region between the equator and the equator is defined as the inner region, and the region between the tread edge and the position 0.5 W apart from the tire equator in the tire width direction is defined as the outer region. The second groove is curved or bent so that the average angle of the second groove in the inner region with respect to the tire circumferential direction is smaller than the average angle with respect to the direction, and the maximum length of the center block in the tire width direction is smaller. It is characterized by being 25% to 35% of the tread development width.
Further, the pneumatic tire of the present invention has a tread portion extending in the tire circumferential direction and having an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and a tire radially inner side of these sidewall portions. In a pneumatic tire having a pair of bead portions arranged in the tire, the rotation direction is specified, in the outer surface of the tread portion, a plurality of lug grooves extending in the tire width direction, and adjacent to the tire circumferential direction. A circumferential narrow groove that connects the mating lug grooves 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. A first center block unevenly distributed on one side in the tire width direction and a second center block unevenly distributed on the other side in the tire width direction with respect to the tire equator; The blocks and the second center blocks are alternately arranged in the tire circumferential direction, and each of the first center block and the second center block extends along the tire width direction on the ground contact side and extends the tire equator. The axial edge of the ground contact first side straddling, the axial edge of the ground contact late side extending along the tire width direction to the ground contact late side and straddling the tire equator, from both ends of the axial edge of the ground first contact side A pair of oblique edges on the ground contact first side, each of which extends obliquely so that the block width gradually increases toward the ground contact late side, and is inclined in a direction different from the oblique edge on the ground first arrival side in a region protruding from the tire equator. The tread portion has an oblique edge on a ground first arrival side and an oblique edge on a late arrival ground connecting the axial edge on the late arrival ground side, and the tread portion is formed by the lug groove and the circumferential narrow groove. Is partitioned plurality of shoulder blocks in the shoulder side, it is characterized in that the shallow groove having at least one inflection point on each of the tread surface of the center block and the shoulder block is formed.

  According to the present invention, in a tire having a block-based tread pattern in which a plurality of blocks are partitioned by a lug groove and a circumferential narrow groove, the center block located near the tire equator has the above-described shape, so that the tire in the lug groove A sufficient groove component in the width direction can be ensured, and traction performance (hereinafter referred to as off-road traction performance) on unpaved roads and traction performance on snow 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 the edge components in both the tire width direction and the tire circumferential direction, contributing to improved traction performance on snow. . This makes it possible to maintain good off-road traction performance and to improve traction performance on snow with an increase in edge components.

  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 ground contact rear side and the oblique edge on the ground contact rear side to the tire equator, The distance B from the connection point between the axial edge and the diagonal edge on the first-ground contact side not connected to the diagonal edge on the late-contact ground side to the tire equator satisfies the relationship of 0.40 ≦ A / B ≦ 0.68. Is preferred. Thereby, off-road traction performance and snow traction performance can be improved in a well-balanced manner.

  In the present invention, the angle α between the oblique edge of the first center block or the second center block and the axial edge of the second center block or the first center block on the first ground contact side is 55 ° ≦ α ≦ Preferably it is in the range of 75 °. Thereby, off-road traction performance and snow traction performance can be improved in a well-balanced manner.

  In the present invention, the lug groove extends from one tread end to the tire equator inward in the tire width direction and crosses the tire equator, and the lug groove extends from the other tread end to the tire equator. It consists of lug grooves extending inward in the tire width direction and intersecting the tire equator, and these lug grooves are alternately arranged in the tire circumferential direction, and each lug groove intersects the tire equator and extends in the tire width direction. A first groove extending along the first groove, and a second groove extending from one end of the first groove to the tread end at an angle smaller than the first groove with respect to the tire circumferential direction. The other end communicates with the second groove of the lug groove adjacent in the tire circumferential direction, the first groove is located closer to the ground contact than the tread end of the lug groove, from the tire equator to the tread end. Distance is W, tire width from tire equator When the area between the position 0.5W away from the tire equator and the tire equator is the inner area, and the area between the position 0.5W away from the tire equator in the tire width direction and the tread edge is the outer area, 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 is smaller than the average angle of the second groove portion in the region with respect to the tire circumferential direction. The maximum length is preferably 25% to 35% of the tread development width. Since the lug groove including the first groove portion and the second groove portion is provided, low noise performance can be improved while improving off-road traction performance. That is, since the first groove portion extending along the tire width direction is arranged near the tire equator which largely contributes to the traction performance, and this first groove portion communicates with another lug groove (second groove portion), Traction performance can be efficiently improved. In addition, the length of the groove can be increased by bending or bending the second groove portion as described above, so that traction performance can be improved and generation of air column resonance can be suppressed. Further, by securing the maximum width of the center block appropriately, the rigidity of the block can be sufficiently secured and good traction performance can be exhibited.

  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 of the center block and the tread surface of the shoulder block. Is preferred. 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 well-balanced manner, and the traction performance on snow 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 is directed toward the tire equator. The projection components of the shallow groove when projected do not overlap each other, the shallow groove formed in the shoulder block ends at the both ends in the block, and the shallow groove formed in the shoulder block is inside the tread surface of the shoulder block in the tire width direction. It is preferable to be arranged on the ground first arrival side with respect to the position of the vertex of. By providing a suitably shaped shallow groove in the center block located near the tire equator, which greatly contributes to traction performance, traction performance on snow can be effectively improved. In addition, by arranging the shallow grooves so as not to overlap as described above, the block stiffness is prevented from excessively decreasing over the entire circumference of the tire, and the traction performance on snow and the off-road traction performance in the tire circumferential direction are improved. And the performance can be highly compatible. Further, it is possible to increase the edge component on the side of first contact with the ground while suppressing the decrease in the rigidity of the shoulder block, and it is possible to effectively improve the performance on snow. On the other hand, since there is no shallow groove on the side where the ground contact is made, the block rigidity and the amount of rubber are ensured, and uneven wear (heel and toe wear) can be effectively suppressed.

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

  In the present invention, “tread ends” are both ends of a tread pattern portion of a tire in a state where a tire is assembled to a regular rim, a regular internal pressure is filled, and no load is applied (no load state). The “distance W in the tire width direction from the tire equator to the tread edge” in the present invention is the tread development width (defined by JATMA) which is the linear distance between the tread edges measured along the tire width direction in the above-described state. "Tread width"). The “regular rim” is a rim defined for each tire in a standard system including the standard on which the tire is based. For example, a standard rim for JATMA, a “Design Rim” for TRA, or an ETRTO In this case, “Measuring Rim” is set. “Normal internal pressure” is the air pressure specified for each tire in the standard system including the standard on which the tire is based. For JATMA, the maximum air pressure is used, and for TRA, the table “TIRE LOAD LIMITS AT VARIOUS” is used. The maximum value described in "COLD INFLATION PRESSURES" is "INFLATION PRESSURE" for ETRTO, but is 180 kPa when the tire is for a passenger car.

1 is a meridional section of a pneumatic tire according to an embodiment of the present invention. 1 is a front view showing a tread surface of a pneumatic tire according to an embodiment of the present invention. FIG. 3 is a sectional view showing a center block formed on a tread surface of FIG. 2. (A), (b) is a front view which shows the other example of the center block formed in 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, the pneumatic tire of the present invention includes a tread portion 1, a pair of sidewall portions 2 disposed on both sides of the tread portion 1, and a tire radially inner side of the sidewall portion 2. And a pair of bead portions 3. In FIG. 1, reference numeral CL indicates a tire equator, and reference numeral E indicates a tread end. In the illustrated example, the tread end E coincides with the outer edge in the tire width direction of the outermost block in the tire width direction (the edge formed by the tread surface of the outermost block in the tire width direction and the outer side surface in the tire width direction). ing. Although FIG. 1 is a meridian sectional view and is not drawn, 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. A basic structure is formed. Hereinafter, the description using FIG. 1 is basically based on the illustrated meridian cross-sectional shape, but each of the tire constituent members extends in the tire circumferential direction and forms an annular shape.

  A carcass layer 4 is mounted between the pair of right and left bead portions 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded from the inside to the outside of the vehicle around a bead core 5 arranged in each bead portion 3. Further, a bead filler 6 is arranged on the outer periphery of the bead core 5, and the bead filler 6 is wrapped around the main body and the folded portion of the carcass layer 4. On the other hand, a plurality of (four in FIG. 1) 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 cross 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 a range of, for example, 10 ° to 60 °. Although not employed in the pneumatic tire of FIG. 1, in the present invention, a belt reinforcing layer (not shown) may be further provided on the outer peripheral side of the belt layer 7. 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 of the carcass layer 4 (outside in the tire width direction) in the side wall portion 2. A rim cushion rubber layer 13 is disposed on the outer peripheral side (outside 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 (cap tread rubber layer and under tread rubber layer) having different physical properties 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. From the lug groove 20 intersecting the tire equator CL (hereinafter sometimes referred to as “one lug groove 20”) and the tread end E on the other side (left side in the figure) with respect to the tire equator CL. A lug groove 30 extending inward in the direction and intersecting the tire equator CL (hereinafter, may be referred to as “the other lug groove 30”) is provided. The one lug groove 20 and the other lug groove 30 are respectively provided in plural numbers.

  Each of the lug grooves 20, 30 intersects the tire equator CL and extends along the tire width direction, and one end of each of the first groove parts 21, 31 makes the tire more than the first groove parts 21, 31. The second groove portions 22 and 32 extend to the tread end E at a small angle with respect to the circumferential direction. More specifically, one lug groove 20 crosses the tire equator CL and extends along the tire width direction, and one end of the first groove 21 (one side of the tire equator (FIG. And the second groove portion 22 extending from the end portion on the right side) 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 the tire equator CL and extends along the tire width direction, and one end of the first groove 31 (the other side relative to the tire equator (the other side of the figure). The second groove 32 extends to the tread end E at an angle smaller than the first groove 31 with respect to the circumferential direction of the tire from the end (left side).

  One lug groove 20 and the other lug groove 30 are alternately arranged one by one 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 of the one lug groove 20 and the other 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 one side with respect to the tire equator CL, the second groove portions 22 of the one lug groove 20 are spaced apart in the tire circumferential direction. On the other side with respect to the tire equator CL, the second grooves 32 of the lug grooves 30 on the other side are arranged at intervals in the tire circumferential direction. In the present invention, if the first grooves 21 and 31 are alternately arranged and are adjacent to each other on the tire equator CL, it is regarded that the lug grooves 20 and 30 are alternately arranged unless otherwise specified. Shall be.

  The other ends of the first grooves 21, 31 of each lug groove 20, 30 communicate with the second grooves 32, 22 of another lug groove 30, 20 adjacent in the tire circumferential direction. That is, the first groove 21 of the one lug groove 20 communicates with the second groove 32 of the other lug groove 30 adjacent in the tire circumferential direction, and the first groove 31 of the other lug groove 30 is in the tire circumferential direction. Is connected to the second groove portion 22 of the one side lug groove 20 adjacent to the first lug groove 20.

  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 ends 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 each lug groove 20, 30 is defined as a whole with the rotation direction R from the tire equator CL side outward in the tire width direction. It has a shape inclined in the opposite direction.

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

  The circumferential narrow groove 40 is a groove having 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.

  The plurality of blocks 50 are defined by the lug grooves 20 and 30 and the circumferential narrow groove 40. Among the plurality of blocks 50, those located on the tire equator CL side (the center side of the tread portion 1) with respect to the circumferential narrow groove 40 are the center block 51, and the tread end E side (the tread portion) with respect to the circumferential narrow groove 40. 1 is located on the shoulder side). 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. In. That is, each of the first center block 51A and the second center block 51B has a shape that at least partially protrudes from the tire equator CL in the tire width direction. These first center blocks 51A and second center blocks 51B are alternately arranged 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 extends along the tire width direction on the ground contact side (stepping side), and extends along the tire equator CL. Side), the block width in the tire width direction from both ends of the axial edge e2 on the ground contact rear side and the axial edge e1 on the ground contact first side extending across the tire equator and extending across the tire equator. And a pair of oblique edges e3 and e4 on the first contact side extending obliquely so as to gradually increase toward the side, and in a region protruding from the tire equator CL, inclined in a direction different from the oblique edge e3 on the first contact side of the ground, and It has an oblique edge e5 on the back-to-ground side that connects the oblique edge e3 and the axial edge e2 on the back-to-ground side. In particular, it is preferable that the oblique edge e3 on the first-arrival side and the oblique edge e5 on the second-arrival side are inclined in opposite directions. In the illustrated example, in addition to the above-described edges e <b> 1 to e <b> 5, each center block 51 has an edge extending along the second groove portions 22 and 32 of the lug grooves 20 and 30, and a circumferential thin groove 40. And the oblique edge e3 on the ground first arrival side and the oblique edge e5 on the rear arrival ground side are inclined in directions opposite to each other. Further, in the illustrated example, all the edges forming each center block 51 are linear, but each center block 51 may include a curved or zigzag edge.

  Both the axial edge e1 on the ground contact first side and the axial edge e2 on the ground contact late side are arranged so as 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 a region of the center block 51 protruding from the tire equator CL. More specifically, as the cutout shape, the first groove 21 of the lug groove 20 on one side, the second groove 32 of the lug groove 30 on the other side adjacent in the tire circumferential direction, and the grounding of the first center block 51A A triangular area surrounded by the oblique edge e5 on the receiving side is formed. Also, the first groove 31 of the lug groove 30 on the other side, the second groove 22 of the one lug groove 20 adjacent in the tire circumferential direction, and the oblique edge e5 of the second center block 51B on the ground contacting side. An enclosed triangular area is formed. By forming such a triangular region, the groove volume of the lug grooves 20, 30 can be increased, and mud can be grasped on unpaved roads, while snow can be grasped on snowy roads. It can contribute to the improvement of off-road traction performance and snow traction performance.

  In the pneumatic tire described above, in a tire having a block-based tread pattern in which a plurality of blocks 50 are partitioned by the lug grooves 20 and 30 and the circumferential narrow groove 40, the center block 51 located near the tire equator CL is used as described above. By making the shape, the groove components in the tire width direction in the lug grooves 20 and 30 can be sufficiently ensured, and the off-road traction performance and snow traction performance can be improved. 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 edge components in both the tire width direction and the tire circumferential direction, and to improve traction performance on snow. Contribute. This makes it possible to maintain good off-road traction performance and to improve traction performance on snow with an increase in edge components.

  In addition, the presence of the circumferential narrow groove 40 disperses noise through the circumferential narrow groove 40, so that low noise performance can be improved. Further, since a circumferential groove component can be added by the circumferential narrow groove 40, the tire can be prevented from laterally shifting during traction and stability can be improved.

  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 ground contact rear side and the oblique edge e5 on the ground contact rear side is P1, and A connection point between the side axial edge e1 and the oblique edge e4 on the ground first arrival side is P2. The distance between the connection point P1 at the axial edge e2 on the ground contact side and the tire equator CL is distance A, and the distance between the connection point P2 at the axial edge e1 on the ground contact side and the tire equator CL is 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 appropriately setting the distance A with respect to the distance B, off-road traction performance and 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 if it is larger than 0.68, sufficient traction performance is obtained. Can not.

  Also, the angle formed between the oblique edge e5 on the ground contact rear side in the first center block 51A or the second center block 51B and the axial edge e1 on the ground contact side in the second center block 51B or the first center block 51A is an angle. Let it be α. This angle α is preferably set in the range of 55 ° ≦ α ≦ 75 °. In addition, the angle formed between the oblique edge e3 on the first ground contact side in the first center block 51A or the second center block 51B and the axial edge e2 on the second ground block in the second center block 51B or the first center block 51A is an angle. 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, off-road traction performance and snow traction performance can be improved in a well-balanced manner. Here, if the angle α or the angle β is out of the above-mentioned range, the effect of improving the traction performance cannot be sufficiently obtained. In addition, when the axial edge e1 on the ground contact side, the axial edge e2 on the ground contact side, the oblique edge e3 on the ground contact side, or the oblique edge e5 on the ground contact 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, 30 is defined as W, the distance in the tire width direction from the tire equator CL to the tread end E, and a distance of 0.50 W from the tire equator CL in the tire width direction and the tire equator CL. A region between the tread edge E and a position 0.50 W apart from the tire equator CL in the tire width direction is defined as an inner region Sa, and a second groove portion 22, 32 in the outer region Sb is defined as an outer region Sb. The second grooves 22, 32 are curved or bent so that the average angle θa of the second grooves 22, 32 in the inner area Sa with respect to the tire circumferential direction is smaller than the average angle θb with respect to the tire circumferential direction. In other words, the second grooves 22, 32 of the lug grooves 20, 30 are smoothly curved or have at least one bend so that the inclination angle with respect to the tire circumferential direction gradually decreases from the tread end E toward the tire equator CL. It is bent with points. In the center block 51, the maximum length L in the tire width direction is set to 25% to 35% of the tread development width TW.

  Since the tread pattern is configured as described above, low noise performance can be improved while improving off-road traction performance. That is, the first groove portions 21 and 31 extending along the tire width direction are arranged near the tire equator CL which greatly contributes to the traction performance, and the first groove portions 21 and 31 are formed in the other lug grooves 30 and 20. Since it communicates with the two grooves 32, 22, traction performance can be efficiently improved. Further, since the second groove portions 22 and 32 are curved or bent as described above, the groove length can be increased, and traction performance can be improved, and generation of air column resonance can be suppressed. Further, by securing the maximum width of the center block 51 appropriately, the rigidity of the block can be sufficiently secured and good traction performance can be exhibited. Here, when 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 grooves 22, 32 of the lug grooves 20, 30 gradually decrease the angle with respect to the tire circumferential direction toward the tire equator CL as described above, and the average of the second grooves 22, 32 in the inner region Sa with respect to the tire circumferential direction. The angle θa is preferably 35 ° to 45 °, and the average angle θb of the second grooves 22, 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. Is advantageous. If the average angle θa of the second groove portions 22 and 32 is less than 35 °, the groove component in the tire width direction is reduced, so that it is difficult to sufficiently improve the traction performance. If 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 is reduced. Since it does not increase sufficiently, it becomes difficult to improve traction performance sufficiently. 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 Does not sufficiently increase, it becomes difficult to sufficiently improve the traction performance. If 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 bend or curve greatly, making it 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 a straight line connecting the midpoints of the lug grooves 20 and 30 in the groove width direction at the boundary position of each region with respect to the tire circumferential direction. Can be obtained as However, at the tire equator CL and the tread end E, as shown in the drawing, the midpoint at the tire equator CL or the tread end E of the extension of the second grooves 22, 32 drawn toward the tire equator CL or the tread end E is used. Shall be.

  As described above, the first groove portions 21 and 31 are provided for securing a groove component in the tire width direction mainly in the vicinity of the tire equator CL which largely contributes to traction performance. Therefore, it is preferable that the first grooves 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 set to 80 ° to 100 °. Thereby, traction performance can be efficiently improved by the first grooves 21 and 31. 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 increases, and the groove component in the tire width direction is sufficiently ensured. And the effect of improving traction performance is limited.

  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. 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 effect of providing the shallow groove 60 cannot be obtained because the shallow groove 60 is too shallow, and if the depth of the shallow groove 60 exceeds 3 mm, the block rigidity is reduced. The effect is greater. In the following description, the shallow groove 60 formed in the center block 51 is referred to as a center shallow groove 61, and the shallow groove 60 formed in the shoulder block 52 is referred to as 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. Although the number of shallow grooves 60 formed in each block 50 is not particularly limited, it is preferable to provide one shallow groove 60 in each block 50 as shown.

  According to 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 partitioned by the lug grooves 20 and 30 and the circumferential narrow grooves 40 as described above, each block 50 Since the shallow groove 60 having a 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 well-balanced manner, and the traction performance on snow in the tire circumferential direction and the width direction can be improved. It can be improved efficiently.

  Further, as shown in the figure, the center shallow groove 61 preferably has one end communicating with the circumferential narrow groove 40 and the other end communicating with the second grooves 22 and 32 of the lug grooves 20 and 30. The center shallow groove 61 may be 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. Furthermore, it is preferable that the projection components of the center shallow groove 61 do not overlap each other when the center shallow groove 61 is projected toward the tire equator CL. By providing the center block 51 located in the vicinity of the tire equator CL, which greatly contributes to traction performance, with the appropriately shaped center shallow groove 61, traction performance on snow can be effectively improved. Further, since the center shallow grooves 61 do not overlap as described above, the block rigidity is not excessively reduced over the entire circumference of the tire, and the balance between the snow traction performance and the off-road traction performance in the tire circumferential direction is prevented. And these performances can be highly compatible.

  On the other hand, both ends of the shoulder shallow groove 62 are preferably terminated in 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. Furthermore, the shoulder shallow groove 62 may be disposed on the stepping side of 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 a decrease in rigidity of the shoulder block 52, and it is possible to effectively improve the performance on snow. On the other hand, since there is no shallow groove on the kick-out side and the block rigidity and the rubber amount 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 of the lug grooves 20, 30 in the first groove portions 21, 31 is preferably set to 65% to 75% of the groove depth in the second groove portions 22, 32. Thereby, 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 traction performance.

  The groove depths of the lug grooves 20, 30 and the circumferential narrow groove 40 can be set in the above-described ranges, respectively. However, it is preferable that the circumferential narrow groove 40 be appropriately shallower than the lug grooves 20, 30. Specifically, the groove depth of the circumferential narrow groove 40 is preferably set to 75% to 85% of the groove depth of the second groove portions 22 and 32 of the lug grooves 20 and 30. By making the circumferential narrow groove 40 appropriately shallower than the second groove portions 22 and 32, the rigidity of the blocks (center block 51, shoulder block 52) adjacent to the circumferential narrow groove 40 can be increased, This is advantageous for improving traction performance.

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

  Regarding the “shape of the center block” in Table 1, the numbers of the corresponding drawings are described. The shape of the center block of the conventional example shown in FIG. 4A is greatly 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 the center block does not have a diagonal edge (edge e5 shown in FIG. 2) on the later-wear side.

  Further, the “change in the angle 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. The “angle near the tire equator in the lug groove” in Table 1 means whether or not the angle of the lug groove with respect to the tire circumferential direction is perpendicular 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 shown in Table 1.

Off-road traction performance:
A test course consisting of unpaved roads with the test tires assembled on wheels with a rim size of 22.5 x 9.00, with air pressure of 850 kPa, mounted on the drive shaft of a test vehicle (truck with an axle arrangement of 6 x 4) Was used for sensory evaluation by a test driver. The evaluation results were indicated by an index with the value of the conventional example being 100. The larger the index value, the better the off-road traction performance.

Traction performance on snow Each test tire is mounted on a wheel with a rim size of 22.5 × 9.00, the air pressure is set to 850 kPa, and the test tire is mounted on a drive shaft of a test vehicle (truck having an axle arrangement of 6 × 4). Sensory evaluation was performed by a test driver on a test course. The evaluation results were indicated by an index with the value of the conventional example being 100. The larger the index value, the better the traction performance on snow.

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

  On the other hand, in the comparative example, since each center block does not have the oblique edge on the side where the ground contact is made, the effect of improving the off-road traction performance and the snow traction performance cannot be sufficiently obtained.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall 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 end e Edge e1 Axial edge e2 on the ground contact side Axial edges e3 and e4 on the later-arriving ground side Diagonal edges e5 on the first-arriving ground side

Claims (9)

A ring-shaped tread portion extending in the tire circumferential direction, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed inside the sidewall portion in the tire radial direction. In the pneumatic tire with the 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 connecting the lug grooves adjacent in the tire circumferential direction are formed, and the lug groove and the circumferential groove 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 block is unevenly distributed on one side in the tire width direction with respect to the tire equator and 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 block and the second center block are alternately arranged in the tire circumferential direction,
Each of the first center block and the second center block extends along the tire width direction on the ground contact side, and extends along the tire equator. Extending along the tire and extending across the tire equator, and extending obliquely so that the block width gradually increases from both ends of the axial edge on the ground contact first side toward the ground contact late side. A pair of oblique edges on the first arrival side, and in a region protruding from the tire equator, inclined in a direction different from the oblique edge on the first arrival side, the oblique edge on the first arrival side and the axial edge on the late arrival side. possess a diagonal edge of the ground after the called side to connect, in the axial direction edges and scope angle of -10 ° to 10 ° with respect to the tire width direction of each of the axial edges of the ground after the terminating of the ground arrival side Ah Pneumatic tire, characterized in that that.   In each of the first center block and the second center block, a distance A from a connection point between the axial edge on the ground contact rear side and the oblique edge on the ground contact rear side to the tire equator, And the distance B from the connection point between the axial edge of the tire and the oblique edge on the ground first arrival side, which is not connected to the oblique edge on the late arrival 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 between the oblique edge of the ground contact rear side in the first center block or the second center block and the axial edge of the ground contact first side in the second center block or the first center block is 55 ° ≦ The pneumatic tire according to claim 1, wherein α ≦ 75 °. The lug groove extends inward in the tire width direction from one tread end to the tire equator and intersects the tire equator, and the lug groove extends from the other tread end to the tire equator in the tire width direction. It consists of lug grooves extending inward and crossing the tire equator, and these lug grooves are alternately arranged in the tire circumferential direction,
Each lug groove intersects the tire equator and extends along the tire width direction, and is inclined at a smaller angle to the tire circumferential direction than the first groove from one end of the first groove. A second groove extending to the tread end, the other end of the first groove communicates with the second groove of the lug groove adjacent in the tire circumferential direction, and the first groove is a tread end side of the lug groove. Is located closer to the ground than the end of the
The distance from the tire equator to the tread edge was W, the region between the tire equator and the position 0.5 W apart from the tire equator in the tire width direction was the inner region, and the distance from the tire equator was 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 of the second groove in the inner region with respect to the tire circumferential direction is smaller than the average angle of the second groove in the outer region with respect to the tire circumferential direction. The second groove is curved or bent so that
The pneumatic tire according to any one of claims 1 to 3, wherein a maximum length of the center block in the tire width direction is 25% to 35% of a 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 of the center block and the shoulder block. The pneumatic tire according to any one of claims 1 to 4, wherein 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 moved to the tire equator. Projection components of the shallow groove when projected toward each other do not overlap,
Both ends of the shallow groove formed in the shoulder block are terminated in the block, and the shallow groove formed in the shoulder block is closer to a ground contact side than a position of a vertex on a tread width side inner side of a tread surface of the shoulder block. The pneumatic tire according to claim 5, which is arranged.   The pneumatic tire according to any one of claims 1 to 6, wherein the lug groove has a maximum depth of 15 mm to 28 mm. A ring-shaped tread portion extending in the tire circumferential direction, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed inside the sidewall portion in the tire radial direction. In the pneumatic tire with the 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 connecting the lug grooves adjacent in the tire circumferential direction are formed, and the lug groove and the circumferential groove 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 block is unevenly distributed on one side in the tire width direction with respect to the tire equator and 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 block and the second center block are alternately arranged in the tire circumferential direction,
Each of the first center block and the second center block extends along the tire width direction on the ground contact side, and extends along the tire equator. Extending along the tire and extending across the tire equator, and extending obliquely so that the block width gradually increases from both ends of the axial edge on the ground contact first side toward the ground contact late side. A pair of oblique edges on the first arrival side, and in a region protruding from the tire equator, inclined in a direction different from the oblique edge on the first arrival side, the oblique edge on the first arrival side and the axial edge on the late arrival side. Having a diagonal edge on the grounding late arrival side to be connected,
The lug groove extends inward in the tire width direction from one tread end to the tire equator and intersects the tire equator, and the lug groove extends from the other tread end to the tire equator in the tire width direction. It consists of lug grooves extending inward and crossing the tire equator, and these lug grooves are alternately arranged in the tire circumferential direction,
Each lug groove intersects the tire equator and extends along the tire width direction, and is inclined at a smaller angle to the tire circumferential direction than the first groove from one end of the first groove. A second groove extending to the tread end, the other end of the first groove communicates with the second groove of the lug groove adjacent in the tire circumferential direction, and the first groove is a tread end side of the lug groove. Is located closer to the ground than the end of the
The distance from the tire equator to the tread edge was W, the region between the tire equator and the position 0.5 W apart from the tire equator in the tire width direction was the inner region, and the distance from the tire equator was 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 of the second groove in the inner region with respect to the tire circumferential direction is smaller than the average angle of the second groove in the outer region with respect to the tire circumferential direction. The second groove is curved or bent so that
The maximum length of the center block in the tire width direction is 25% to 35% of the tread development width. A ring-shaped tread portion extending in the tire circumferential direction, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed inside the sidewall portion in the tire radial direction. In the pneumatic tire with the 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 connecting the lug grooves adjacent in the tire circumferential direction are formed, and the lug groove and the circumferential groove 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 block is unevenly distributed on one side in the tire width direction with respect to the tire equator and 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 block and the second center block are alternately arranged in the tire circumferential direction,
Each of the first center block and the second center block extends along the tire width direction on the ground contact side, and extends along the tire equator. Extending along the tire and extending across the tire equator, and extending obliquely so that the block width gradually increases from both ends of the axial edge on the ground contact first side toward the ground contact late side. A pair of oblique edges on the first arrival side, and in a region protruding from the tire equator, inclined in a direction different from the oblique edge on the first arrival side, the oblique edge on the first arrival side and the axial edge on the late arrival side. Having a diagonal edge on the grounding late arrival side to be connected,
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 of the center block and the shoulder block. A pneumatic tire characterized in that:

Images