JP2018001921A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress deterioration of wet brake performance, and improve other performances.SOLUTION: A pneumatic tire comprises: a first groove which is positioned on an outermost side of a ground plane in a tire width direction, and extends in a tire peripheral direction, in a tire meridian cross section; second grooves which are communicated to the first groove, extend to outside of a tire ground end part, and arranged in the tire peripheral direction; and bottom-up parts provided on the second groove, contact the boundary communicated to the first groove from the second groove, a groove bottom is elevated and a depth of the groove is made shallower than depth of other parts. The pneumatic tire has plural blocks divided by the first groove, tire ground end part, and the second grooves. In one set of blocks adjacent in the tire peripheral direction, a part provided on the first groove of the bottom-up part is configured so that, a volume of a part which contacts a block whose length of the tire peripheral direction is smaller, is larger than a volume of a part which contacts a block whose length of the tire peripheral direction is larger.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a pneumatic tire.

  A protrusion may be provided at the groove bottom of the tread portion of the tire. In the tire described in Patent Document 1, a protrusion is provided on the bottom of the main groove of the opening to the main groove of the lug groove.

Japanese Patent No. 5489782

  When the protrusion is provided at the bottom of the main groove as in the tire described in Patent Document 1, it is expected that the wet braking performance is lowered depending on the size of the protrusion.

  The present invention has been made in view of the above, and an object of the present invention is to provide a pneumatic tire capable of improving other performances such as uneven wear resistance and steering stability while suppressing a decrease in wet braking performance. Is to provide.

  In order to solve the above-described problems and achieve the object, a pneumatic tire according to an aspect of the present invention is located on the outermost side in the tire width direction of the ground contact surface in the tire meridional section and extends in the tire circumferential direction. A first groove, a second groove that extends to the outside of the tire ground contact end and that is provided side by side in the tire circumferential direction; and the first groove extends from the second groove to the first groove. A bottom raised portion that is provided across the first groove and the second groove, including a boundary portion that leads to the groove, and has a groove bottom raised to make the groove depth shallower than the other portions; A plurality of blocks that are partitioned by one groove, a tire ground contact end portion, and a plurality of the second grooves and are arranged in the tire circumferential direction, and the bottom raised portion is provided in the first groove A portion provided in the second groove, and a portion provided in the second groove. The length in the tire circumferential direction is equal to the groove width of the second groove, and the length in the tire width direction projected in the tire circumferential direction is 50% of the groove width of the first groove. % To 150% and the portion provided in the first groove has a maximum length in the tire width direction of 10% to 40% of the groove width of the first groove, and the tire The maximum circumferential length is not less than 100% and not more than 300% of the circumferential length of the boundary portion, and is provided in the first groove of the bottom raised portion in a set of blocks adjacent in the tire circumferential direction. The portion of the pair of blocks that is in contact with the block having the smaller length in the tire circumferential direction is in contact with the block having the larger length in the tire circumferential direction. It is larger than the volume.

The product M _i of the sum M _i (i is a natural number, hereinafter the same) of the circumferential lengths of a pair of blocks adjacent in the tire circumferential direction and the volume V _{i of the} raised portion provided between the pair of blocks. × minimum value of _{V i (M i × V i} ) min and a maximum value relationship between the _{(M i} × _{V i)} max _{is, 1.00 ≦ (M i × V} i) max / (M i × V i) It is preferable to satisfy min ≦ 1.05.

  It is preferable that the tire circumferential length of the block is the length of the block along the wall surface of the first groove.

  The length of the block in the tire circumferential direction is preferably the maximum value of the length of the block in the tire circumferential direction.

  The bottom raised portion provided between the set of blocks has a maximum length in the tire circumferential direction of a portion provided in the first groove, and the maximum length in the tire circumferential direction of the set of blocks. It is preferable that the block with the smaller maximum length in the tire circumferential direction is longer than the block with the larger.

  The bottom raised portion provided between the set of blocks has a maximum length in a tire width direction of a portion provided in the first groove, and a maximum length in a tire circumferential direction of the set of blocks. It is preferable that the block with the smaller maximum length in the tire circumferential direction is longer than the block with the larger.

  The bottom raised portion provided between the set of blocks has a maximum height in a tire radial direction of a portion provided in the first groove, and a maximum length in a tire circumferential direction of the set of blocks. It is preferable that the block with the smaller maximum length in the tire circumferential direction is higher than the block with the larger.

  The minimum of the product Xi × Yi between the area Xi in plan view of the block and the area Yi in plan view of the portion adjacent to the block among the portions provided in the first groove of the bottom raised portion The relationship between the value (Xi × Yi) min and the maximum value (Xi × Yi) max preferably satisfies 1.00 ≦ (Xi × Yi) max / (Xi × Yi) min ≦ 1.20.

  A depth of the second groove, which is a length from the starting point of the raised portion that rises in the second groove to a ground contact surface along a line parallel to the tire equatorial plane, and the second groove. The difference from the length to the outermost position in the tire radial direction along a line parallel to the tire equatorial plane is 20% or more and 70% or less of the depth of the second groove. It is preferable.

  According to the pneumatic tire concerning the present invention, improvement in other performance can be aimed at, suppressing the fall of the drainage of a tread part.

Drawing 1 is a sectional view showing an example of the pneumatic tire concerning an embodiment. FIG. 2 is an enlarged cross-sectional view of a part of the pneumatic tire according to the embodiment. FIG. 3 is a diagram illustrating an example of a tread portion of the pneumatic tire according to the embodiment. FIG. 4 is a diagram showing the shape of the bottom raised portion in plan view. FIG. 5 is a diagram for explaining the height of the raised portion in FIG. FIG. 6 is a diagram schematically showing a block defined by the main groove, the tire ground contact end portion, and the lug groove in FIG. 3. FIG. 7 is a plan view showing a bottom-up portion provided between a pair of adjacent blocks. FIG. 8 is a plan view showing a bottom-up portion provided between a pair of adjacent blocks. FIG. 9 is a plan view showing a bottom-up portion provided between a pair of adjacent blocks. FIG. 10 is a diagram of the block of FIG. 7 viewed from the direction of the arrow YA in FIG. FIG. 11A is a diagram illustrating an example of another shape of the bottom raised portion. FIG. 11B is a diagram illustrating an example of another shape of the bottom raised portion. FIG. 11C is a diagram illustrating an example of another shape of the bottom-up portion. FIG. 12 is a plan view of a raised bottom portion provided between a pair of adjacent blocks.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings, but the present invention is not limited thereto. The components of the embodiments described below can be combined as appropriate. Some components may not be used.

  In the following description, an XYZ orthogonal coordinate system is set, and the positional relationship of each part will be described with reference to this XYZ orthogonal coordinate system. One direction in the horizontal plane is defined as the X-axis direction, a direction orthogonal to the X-axis direction in the horizontal plane is defined as the Y-axis direction, and a direction orthogonal to each of the X-axis direction and the Y-axis direction is defined as the Z-axis direction. Further, the rotation (inclination) directions around the X axis, the Y axis, and the Z axis are the θX, θY, and θZ directions, respectively.

(Pneumatic tire structure)
FIG. 1 is a cross-sectional view illustrating an example of a pneumatic tire 1 according to the present embodiment. FIG. 2 is an enlarged cross-sectional view of a part of the pneumatic tire 1 according to the present embodiment. FIG. 3 is a diagram illustrating an example of the tread portion 6 of the pneumatic tire 1 according to the present embodiment. In the following description, the pneumatic tire 1 is appropriately referred to as a tire 1. Further, the tire 1 may be any of a passenger car, a heavy load, an industrial vehicle, and a motorcycle.

  The tire 1 is rotatable about a central axis (rotating axis) AX. 1 and 2 each show a meridional section passing through the central axis AX of the tire 1. A center axis AX of the tire 1 is orthogonal to the equator plane CL of the tire 1.

  In the present embodiment, the center axis AX and the Y axis of the tire 1 are parallel. That is, in the present embodiment, the direction parallel to the central axis AX is the Y-axis direction. The Y-axis direction is the width direction of the tire 1 or the vehicle width direction. The equatorial plane CL passes through the center of the tire 1 with respect to the Y-axis direction. The θY direction is the rotation direction of the tire 1 (center axis AX). The X-axis direction and the Z-axis direction are radial directions with respect to the central axis AX. The road surface (ground) on which the tire 1 travels (rolls) is substantially parallel to the XY plane.

  In the following description, the rotation direction of the tire 1 (center axis AX) is appropriately referred to as the circumferential direction, the radial direction with respect to the center axis AX is appropriately referred to as the radial direction, and the direction parallel to the center axis AX is appropriately determined as the width. It is called direction.

  The tire 1 includes a carcass portion 2, a belt layer 3, a belt cover 4, a bead portion 5, a tread portion 6, an inner liner 7, and a sidewall portion 8.

  Each of the carcass part 2, the belt layer 3, and the belt cover 4 includes a cord. The cord is a reinforcing material. The cord may be referred to as a wire. Each of the layers including the reinforcing material such as the carcass portion 2, the belt layer 3, and the belt cover 4 may be referred to as a cord layer or a reinforcing material layer.

  The carcass portion 2 is a strength member that forms the skeleton of the tire 1. The carcass part 2 includes a cord. The cord of the carcass portion 2 may be referred to as a carcass cord. The carcass part 2 functions as a pressure vessel when the tire 1 is filled with air. The carcass part 2 is supported by the bead part 5. The bead portion 5 is disposed on each of one side and the other side of the carcass portion 2 with respect to the Y-axis direction. The carcass portion 2 is folded back at the bead portion 5. The carcass portion 2 includes an organic fiber carcass cord and rubber covering the carcass cord. The carcass portion 2 may include a polyester carcass cord, a nylon carcass cord, an aramid carcass cord, or a rayon carcass cord.

  The belt layer 3 is a strength member that maintains the shape of the tire 1. The belt layer 3 includes a cord. The cord of the belt layer 3 may be referred to as a belt cord. The belt layer 3 is disposed between the carcass portion 2 and the tread portion 6. The belt layer 3 includes, for example, a belt cord made of metal fiber such as steel and rubber covering the belt cord. The belt layer 3 may include an organic fiber belt cord. In the present embodiment, the belt layer 3 includes a first belt ply 3A and a second belt ply 3B. The first belt ply 3A and the second belt ply 3B are laminated so that the cord of the first belt ply 3A and the cord of the second belt ply 3B intersect.

  The belt cover 4 is a strength member that protects and reinforces the belt layer 3. The belt cover 4 includes a cord. The cord of the belt cover 4 may be referred to as a cover cord. The belt cover 4 is disposed outside the belt layer 3 with respect to the central axis AX of the tire 1. The belt cover 4 includes, for example, a cover cord made of metal fiber such as steel and rubber covering the cover cord. The belt cover 4 may include an organic fiber cover cord.

  The bead portion 5 fixes the tire 1 to the rim. The bead portion 5 has a bead 50. The bead 50 is a strength member that fixes both ends of the carcass portion 2. The bead 50 is a bundle of steel wires. The bead 50 may be a bundle of carbon steel.

  The tread portion 6 includes a center portion 11 and shoulder portions 12 disposed on both sides of the center portion 11 in the Y-axis direction. The tread portion 6 protects the carcass portion 2. The tread portion 6 includes a grounding portion that comes into contact with the road surface.

  The tread portion 6 has a plurality of grooves 20 formed on the outer surface in the tire radial direction. The groove 20 includes a main groove 21 that extends in the circumferential direction of the tire 1 and a lug groove (lateral groove) 22 that extends at least partially in the width direction of the tire 1. A land portion is provided around the groove 20. The land portion is provided between the groove 20 and the groove 20 adjacent to the groove 20. The tread portion 6 includes a plurality of land portions arranged between the grooves 20. The main grooves 21, 21a, 21b can be referred to as first grooves extending in the tire circumferential direction. It can be said that the lug groove 22 provided in the shoulder portion 12 leads to the first groove and extends to the outside of the tire ground contact end portion.

  The main groove 21 is provided in the circumferential direction of the tire 1. At least a part of the main groove 21 is provided in the center portion 11 of the tread portion 6. The main groove 21 has a tread wear indicator inside. The treadwear indicator indicates the end of wear. The main groove 21 has a width of 4.0 mm or more and may have a depth of 5.0 mm or more. As shown in FIGS. 2 and 3, the tire 1 has four main grooves 21 in this example. In the present embodiment, of the four main grooves 21, the main groove 21 provided on the outermost side in the tire width direction is referred to as a main groove 21a and a main groove 21b.

  At least a part of the lug groove 22 is provided in the width direction of the tire 1. At least a part of the lug groove 22 is provided in the shoulder portion 12 of the tread portion 6. The shoulder portion 12 is disposed on each of one side (+ Y side) and the other side (−Y side) of the center portion 11 with respect to the width direction (Y-axis direction). The lug groove 22 has a width of 1.5 mm or more. The lug groove 22 may have a depth of 4.0 mm or more, and may partially have a depth of less than 4.0 mm.

  The inner liner 7 is a rubber layer having a high airtightness that is attached to the inner surface of the tire 1. The sidewall portion 8 protects the carcass portion 2. The sidewall portions 8 are disposed on one side and the other side of the tread portion 6 with respect to the Y-axis direction. The sidewall portion 8 includes sidewall rubbers disposed on one side and the other side of the tread portion 6 with respect to the Y-axis direction.

  In the present embodiment, the tread ground contact width is W. The tread contact width W is formed on a flat plate when the tire 1 is mounted on a specified rim and loaded in a vertical direction on the flat plate under a specified internal pressure, for example, an internal pressure condition of 200 kPa and 88% of a specified load. The longest straight line distance between the ground contact edge portions STA and STB in the direction parallel to the center axis AX (tire width direction) on the ground contact surface. The grounding end portions STA and STB are edge portions having a tread grounding width W.

As shown in FIG. 3, the tread portion 6 of the pneumatic tire 1 includes a plurality of main grooves 21, 21 a, 21 b extending in the tire circumferential direction. The center land portion 30 _C that is the land portion closest to the tire equator plane CL is defined by the main groove 21. The shoulder land portions 30 _S1 and 30 _S2 located on the outermost side in the tire width direction are partitioned by main grooves 21a and 21b, respectively. For this reason, the tread portion 6 of the pneumatic tire 1 has a plurality of land portions arranged side by side in the tire width direction.

Of the plurality of land portions of the tread portion 6, the shoulder land portions 30 _S1 and 30 _S2 which are the land portions located on the outermost side in the tire width direction include the lug groove 22 and the raised portions SG _a1 and SG _b1. . Lug grooves 22 of the shoulder land portion ₃₀ S1, _{30 S2} is the main grooves 21a defining the shoulder land portion ₃₀ S1, _{30 S2,} leading to 21b, extend tire ground contact end STA, to the outside of the STB, the tire circumferential direction Are provided side by side. A plurality of blocks B11, B12, B13, B14, B15... Arranged in the tire circumferential direction are defined by the main groove 21a, the ground contact end portion STA, and the plurality of lug grooves 22. A plurality of blocks B21, B22, B23, B24, B25... Arranged in the tire circumferential direction are defined by the main groove 21b, the ground contact end portion STB, and the plurality of lug grooves 22.

(Bottom raised part)
The bottom raised portions SG _a1 and SG _b1 include the boundary grooves KK that lead from the lug grooves 22 of the blocks B11 and B21 constituting the shoulder land portions 30 _S1 and 30 _S2 to the main grooves 21 a and 21 b, and the main grooves 21 a and 21 b and the shoulder land It is provided across the lug grooves 22 of the portions 30 _S1 and 30 _S2 . The raised bottom portions SG _a1 and SG _b1 are portions where the groove bottom is raised to make the groove depth shallower than the other portions. Hereinafter, for convenience of description, the raised portions SG _a1 and SG _b1 may be collectively referred to as a raised portion SG.

  FIG. 4 is a diagram showing the shape of the raised bottom SG in plan view. As shown in FIG. 4, the raised portion SG has a portion SG21 provided in the main grooves 21, 21a, and 21b that are the first grooves and a lug groove 22 that is the second groove, with the boundary portion KK interposed therebetween. And part SG22 provided in the. The lug groove 22 is a groove between the first block B1 and the second block B2 adjacent in the circumferential direction. The end portion 111 is a corner portion of the tread surface on the block B1 side of the boundary portion KK that leads from the lug groove 22 to the main grooves 21, 21a, and 21b. The end 121 is a corner of the tread surface on the block B2 side of the boundary KK that leads from the lug groove 22 to the main grooves 21, 21a, 21b.

  In FIG. 4, the portion SG22 provided in the lug groove 22 of the bottom raised portion SG has a tire circumferential direction length L2 equal to the groove width of the lug groove 22 and is projected in the tire circumferential direction. The length L5 is not less than 50% and not more than 150% of the groove width L1 of the main groove 21, for example.

  The portion SG21 provided in the main grooves 21, 21a, 21b of the bottom raised portion SG has a maximum length L4 in the tire width direction of, for example, 10% or more and 40% or less of the groove width L1 of the main grooves 21, 21a, 21b. The maximum length L3 in the tire circumferential direction is, for example, 100% or more and 300% or less of the length L2 in the tire circumferential direction of the boundary portion KK.

  Moreover, the bottom raising effect can be effectively obtained by providing the bottom raising portion SG communicating with the main grooves 21, 21a, 21b, and the reduction of the groove volume and the deterioration of drainage can be minimized. The above dimensional range is considered optimal from the balance between the block rigidity and drainage of the shoulder.

(Height of the raised part, etc.)
FIG. 5 is a diagram illustrating the height of the bottom raising portion SG in FIG. In FIG. 5, the starting point that rises in the lug groove 22 of the bottom raised portion SG is P1, and the starting point that rises in the main groove 21a of the bottom raised portion SG is P2.

  From the lug groove 22 toward the boundary KK with the main groove 21a, a height H1 from the starting point P1 of the raised portion SG rising in the lug groove 22 to the point P3 of the ground contact surface along a line parallel to the tire equatorial plane is set. And the depth of the lug groove 22. In addition, the length from the bottom raised portion SG to the outermost position in the tire radial direction along the line parallel to the tire equator plane, that is, the height from the point P4 to the point P5 is defined as H2. When the upper surface of the raised portion SG is not flat (for example, when there is unevenness), the highest position of the upper surface of the raised portion SG is the point P4.

  At this time, the difference between the height H1 and the height H2 is, for example, 20% to 70% of the depth (height H1) of the lug groove 22. When the height of the bottom raised portion SG is less than 20% of the depth of the lug groove 22, the effect of the bottom raised portion SG is not sufficiently obtained. Conversely, when the height exceeds 70%, the drainage performance is deteriorated.

FIG. 6 schematically shows blocks B11, B12, B13, B14, B15... Partitioned by the main groove 21a, which is the first groove, the ground end STA, and the lug groove 22, which is the second groove. FIG. FIG. 6 schematically shows the main groove 21 a and the lug groove 22. In FIG. 6, one of the groove walls of the main groove 21a is indicated by a broken line. As shown in FIG. 6, a plurality of lug grooves 22 are provided side by side in the tire circumferential direction. For example, the plurality of lug grooves 22 may be provided with a constant pitch length along the tire circumferential direction, or may be provided with a plurality of types of pitch lengths along the tire circumferential direction. A plurality of blocks B11, B12, B13, B14, B15,... Are partitioned by the main groove 21a, the ground contact end portion STA, and the plurality of lug grooves 22. A plurality of blocks B11, B12, B13, B14, B15... Are provided side by side in the tire circumferential direction. Between a pair of blocks adjacent to each other in the tire circumferential direction, bottom-up portions SG _a1 , SG _a2 , SG _a3 , SG _a4 ... _Are provided. The raised portions SG _a1 , SG _a2 , SG _a3 , SG _a4 ... Are composed of a portion provided in the lug groove 22 between a pair of blocks and a portion provided in the main groove 21a. The portion provided in the main groove 21a is in contact with each set of blocks. For this reason, bottom raising part _SGa1 , _SGa2 , _SGa3 , _SGa4 ... is substantially T-shaped by planar view.

Here, FIG. 7, FIG. 8 and FIG. 9 are plan views showing the raised bottom SG provided between a pair of adjacent blocks. 7, FIG. 8, and FIG. 9 schematically show the blocks B11 and B12 and the bottom raised portion SG. In FIG. 7, FIG. 8, and FIG. 9, the bottom raising portion SG is provided across the boundary portion KK between a pair of adjacent blocks B11 and B12. 7, 8, and 9, the portion of the bottom raised portion SG that is in contact with the block B <b> 11 among the portions SG <b> 21 provided in the main groove 21 a that is the first groove is a surface along the line 112. a portion cut along a (a surface along the tire radial direction) is defined as a portion S _a. Among the partial SG21, defines a portion taken along a plane along the portion in contact with the block B12 in line 122 (the surface along the tire radial direction) and the partial S _b. The line 112 is a line starting from the end 111 on the block B11 side and extending parallel to the tire width direction. The line 122 is a line that starts from the end 121 on the block B12 side and extends parallel to the tire width direction.

(Volume of bottom raised part)
7, among the partial SG21, the relationship between the volume of a portion S _a of the volume and the partial S _b, than the volume of the portion corresponding to the block is larger maximum value of the tire circumferential length, the tire circumferential direction length The volume of the portion corresponding to the block with the smallest maximum value is larger. For example, than the maximum value of the tire circumferential length of the block B12, when the maximum value of the tire circumferential length of the block B11 is small, it is larger in volume of a portion S _a than the volume of the portion S _b. In other words, the volume of the portion S _a in contact with the pair of blocks B11, B12 tire circumferential direction of the smaller block lengths of the (small block side), in the tire circumferential direction length larger of greater than the volume of the portion S _b in contact with the block (large block side).

When adjusting the relationship between the volume of a portion S _a of the volume and the partial S _b, may adjust the tire circumferential direction of the length of the portion S _a and part S _b. In FIG. 8, it is assumed that the maximum length in the tire circumferential direction of the block B12 is longer than the maximum length in the tire circumferential direction of the block B11. That is, the small block B11 side is longer than the large block B12 side in the tire circumferential direction length of the portion SG21 provided in the main groove 21a of the bottom raised portion SG. In part SG21, the portion _{S a} of the tire circumferential direction of the maximum length L31, part by longer than the tire circumferential direction of the maximum length L32 of the _{S b,} than the volume of the portion _{S a} of the volume portion _{S b} Can be bigger.

When adjusting the relationship between the volume of a portion S _a of the volume and the partial S _b, may adjust the length of the tire width direction of a portion S _a and part S _b. In FIG. 9, it is assumed that the maximum length in the tire circumferential direction of the block B12 is longer than the maximum length in the tire circumferential direction of the block B11. That is, the small block B11 side is longer than the large block B12 side in the tire width direction length of the portion SG21 provided in the main groove 21a of the bottom raised portion SG. In part SG21, the tire width direction maximum length L41 of the portion _{S a,} portion by longer than the tire width direction maximum length L42 of the _{S b,} than the volume of the portion _{S a} of the volume portion _{S b} Can be bigger.

When adjusting the relationship between the volume of a portion S _a of the volume and the partial S _b, may adjust the maximum height in the tire radial direction of a portion S _a and part S _b. FIG. 10 is a view of the blocks B11 and B12 in FIG. 7 as viewed from the direction of the arrow YA in FIG. In FIG. 10, the bottom raising part SG is provided between a pair of adjacent blocks B11 and B12. 10, of the raised bottom portion SG, among the partial SG21 provided in the main groove 21a is a first groove, to define a portion in contact with the block B11 and parts _{S a.} Portion _{S a,} among the parts SG21, a portion taken along the plane along the line 113 passing through the end portion 111 (the surface along the tire width direction). Among the partial SG21, define the portion contacting to the block B12 and parts _{S b.} Part S _b, among the parts SG21, a part of the portion taken along a plane along a line 123 passing through the end portion 121 (the surface along the tire width direction).

In FIG. 10, it is assumed that the maximum length in the tire circumferential direction of block B12 is longer than the maximum length in the tire circumferential direction of block B11. That is, the small block B11 side is higher than the large block B12 side with respect to the height in the tire radial direction of the portion SG21 provided in the main groove 21a of the bottom raised portion SG. In part SG21, the maximum height H11 tire radial direction of the portion _{S a,} by higher than the maximum height H12 tire radial direction of the portion _{S b,} than the volume of the portion _S volume portions of _{a S b} Can be bigger. In addition, about the tire circumferential direction length of a block, it can define as the length of this block along the wall surface of a 1st groove | channel, for example. Further, the tire circumferential length of the block may be defined as, for example, the maximum value of the block circumferential length of the block.

Returning to FIG. 6, the lengths of the blocks B11, B12, B13, B14, B15... In the tire circumferential direction are a length a, a length b, a length b, a length c, and a length b, respectively. . The length a is the largest and the length c is the smallest. The length b is smaller than the length a and larger than the length c. The length of the block in the tire circumferential direction is, for example, the length of the block along the wall surface 210 of the main groove 21. Further, the length of the block in the tire circumferential direction may be, for example, the maximum value of the length of the block in the tire circumferential direction. The raised portions SG _a1 , SG _a2 , SG _a3 , SG _a4 ... _Have volumes of volume V ₁ , volume V ₂ , volume V ₃ , and volume V ₄ , respectively.

As shown in FIG. 6, the sum M ₁ (i is a natural number, hereinafter the same) of the circumferential lengths of a pair of adjacent blocks is the sum of the length a of the block B11 and the length b of the block B12, the sum M the sum of the length b of ₂ block B12 of length b and the block B13, the sum of the length c of length b and the block B14 of the sum _{M 3} are block B13, the length of the sum _{M 4} is a block B14 c And the length b of the block B15. Similarly, the sum M _i of the circumferential lengths of a pair of blocks adjacent in the tire circumferential direction can be calculated for other blocks not shown.

In this example, the product M _i × V _i of the sum M _i of the circumferential lengths of a pair of blocks adjacent in the tire circumferential direction and the volume Vi of the raised portion provided between the sets of blocks is all It is assumed that it is within ± 5% between these blocks. That is, the relationship between the minimum value (M _i × V _i ) min and the maximum value (M _i × V _i ) max of the product M _i × V _i is
1.00 ≦ (M _i × V _i ) max / (M _i × V _i ) min ≦ 1.05
Satisfy the relationship. If this relationship is satisfied, in the portion where the circumferential length of the block is small and the rigidity is low, it is possible to increase the volume of the raised portion to improve uneven wear resistance and steering stability. On the contrary, in the place where the circumferential length of the block is large and the rigidity is high, the volume of the bottom raised portion can be reduced to improve drainage. In FIG. 6, the block defined by the main groove 21, the ground end STA, and the plurality of lug grooves 22 has been described. However, the main groove 21, the ground end STB, and the plurality of lug grooves 22 are described. The same applies to the blocks partitioned by.

(Other shapes of bottom raised part)
Examples of other shapes of the bottom raised portion will be described with reference to FIGS. 11A to 11C. 11A to 11C are diagrams illustrating examples of other shapes of the bottom-up portion. 11A to 11C all show the shape of the raised portion in plan view.

  The bottom raised portion SG1 shown in FIG. 11A is in contact with the wall surface having an acute angle 211 and the obtuse angle 212 of the wall surface 210 of the main groove 21 with respect to the wall surface of the lug groove 22. The portion SG21 provided in the main groove 21 of the bottom raised portion SG1 has a shape in which the length in the tire circumferential direction increases as the distance from the wall surface 210 increases. Therefore, the maximum length of the bottom raised portion SG1 in the tire circumferential direction is the length of the portion farthest from the wall surface 210.

  The bottom raised portion SG2 shown in FIG. 11B is in contact with the wall surface 210 having the acute angle 211 and the wall surface having the obtuse angle 212 with respect to the wall surface of the lug groove 22 among the wall surfaces 210 of the main groove 21. The portion SG21 provided in the main groove 21 of the bottom raised portion SG2 is semicircular and has a shape in which the length in the tire circumferential direction becomes shorter as the distance from the wall surface 210 increases. Accordingly, the maximum length of the bottom raised portion SG2 in the tire circumferential direction is the length of the portion closest to the wall surface 210.

  The raised portion SG3 shown in FIG. 11C is in contact with the wall surface having an acute angle 211 and the wall surface having an acute angle 213 with respect to the wall surface of the lug groove 22 among the wall surfaces 210 of the main groove 21. As shown in FIG. 11C, when the angle between the wall surface 210 of the main groove 21 and the wall surface of the lug groove 22 is an acute angle on both sides of the lug groove 22, the bottom raising portion SG <b> 3 is the wall surface having the acute angle 211 and the acute angle 213. A bottom raising portion SG3 is provided so as to contact both of the wall surfaces. The portion SG21 provided in the main groove 21 of the bottom raised portion SG3 is rectangular, and has a shape in which the length in the tire circumferential direction does not change even if the portion is separated from the wall surface 210.

FIG. 12 is a plan view of a bottom raised portion SG provided between a pair of adjacent blocks B1 and B2. In FIG. 12, the end portion 111 on the block B1 side of the opening portion to the main groove 21a of the lug groove 22 and the end portion 112 on the block B2 side of the opening portion to the main groove 21a of the lug groove 22 are defined and raised to the bottom. among parts SG, in part SG21 provided to the main groove 21a, a portion S _a in contact with the block B1, taken in a plane along a line 112 extending parallel to the tire width direction end portion 111 as a start point, end part 121 when defining a portion S _b in contact with the block B2 taken in a plane along a line 122 extending parallel to the tire width direction as a starting point, the area by the plan view of a portion S _a Y1, planar portion S _b Regarding the area Y2 in view, the area X1 of the block B1 in plan view, and the area X2 of the block B2 in plan view, the ratio of the maximum value to the minimum value of the product is within 1.2. desirable.

That is, the relationship between the maximum product value (Xi × Yi) max and the minimum value (Xi × Yi) min (i is a natural number, the same shall apply hereinafter) is
1.0 ≦ (Xi × Yi) max / (Xi × Yi) min ≦ 1.2
Meet. That is, when the relationship between the minimum value and the maximum value of Xi × Yi satisfies the condition of 100% or more and 120% or less, the rigidity in the tire circumferential direction can be made more uniform.

(Example)
A pneumatic tire with a size of 195 / 65R15 91H is assembled to a wheel with a size of 15 × 6J, the air pressure is set to 230 kPa, and “wet braking performance”, “uneven wear resistance performance”, “steering stability performance” A test was conducted. The results are shown in Tables 1 and 2. Table 1 shows test results (Example 1 to Example 13) when the length of the block along the wall surface 210 of the main groove 21 is defined as the length of the block in the tire circumferential direction. Table 2 shows the test results (Example 14 to Example 26) when the maximum value of the length of the block in the tire circumferential direction is defined as the length of the block in the tire circumferential direction.

  In Tables 1 and 2, “wet braking performance” was measured on a wet road surface with a water film of 1 mm from the initial speed of 100 km / h until braking and stopping. Using the reciprocal of the measured value, comparison was made with an index. “Uneven wear resistance performance” was measured by measuring the amount of uneven wear generated on the shoulder land after running 10,000 km after mounting on a test vehicle. Using the reciprocal of the measured value, comparison was made with an index. The “steering performance” was displayed as an index after sensory evaluation by a panelist using a 1.8L FF vehicle. The calculation of the bottom-up volume was performed by casting the bottom-up portion with clay.

In Tables 1 and 2, the index of the conventional example is set to “100”, and the index value is preferably as large as possible. As a conventional example, the lug groove is provided with a bottom raised portion, the main groove does not have a bottom raised portion, the length L5 / length L1 is 150%, and the relationship between the minimum value and the maximum value of M _i × V _i is 5 A tire was prepared in which the ratio of the difference between the height H1 and the height H2 with respect to the height H1 is 50% or more and within 10%. Further, as a comparative example, a tire having no raised portion in the lug groove and the main groove was prepared.

As can be seen from Example 1 to Example 26 shown in Table 1 and Table 2, the lug groove and the main groove are provided with bottom raised portions, and the length L5 / length L1 is 50% or more and 150% or less When length L4 / length L1 is 10% or more and 40% or less, and when length L3 / length L2 is 100% or more and 300% or less, the minimum value and the maximum value of M _i × V _i When the relationship is within 5%, if the small block side is larger than the large block side with respect to the volume of the portion provided in the main groove of the bottom raised portion, the tire circumferential length of the portion provided in the main groove of the bottom raised portion When the small block side is longer than the large block side, the tire width direction length of the portion provided in the main groove of the bottom raised part is provided in the main groove of the bottom raised part when the small block side is larger than the large block side. Tire diameter When the small block side is larger than the large block side with respect to the height, when the relationship between the minimum value and the maximum value of Xi × Yi is 100% or more and 120% or less, the height H1 and the height H2 with respect to the height H1 Preferred characteristics were obtained when the difference ratio was 20% or more and 70% or less.

  When the length of the block in the tire circumferential direction is defined as the length of the block along the wall surface of the first groove (Example 1 to Example 13), the maximum value of the length in the tire circumferential direction of the block In any case, the same effect can be obtained in each of the examples (Examples 14 to 26).

DESCRIPTION OF SYMBOLS 1 Tire 2 Carcass part 3 Belt layer 3A, 3B Belt ply 4 Belt cover 5 Bead part 6 Tread part 7 Inner liner 8 Side wall part 11 Center part 12 Shoulder part 20 Groove 21 Main groove 22 Lug groove 50 Bead 111, 121 End part 210 Wall surface B1, B11-B15, B2, B21-B25 Block CL Equatorial plane SG, SG1-SG3, _SGa1 , _SGb1 bottom raised part

Claims (9)

In the tire meridional section, a first groove that is located on the outermost side in the tire width direction of the contact surface and extends in the tire circumferential direction;
A second groove extending through the first groove and extending to the outside of the tire ground contact end and provided in a plurality in the tire circumferential direction;
The boundary between the second groove and the first groove is included and the first groove and the second groove are provided, and the groove bottom is raised so that the depth of the groove is higher than that of other portions. With a shallow raised bottom,
A plurality of blocks that are partitioned by the first groove, the tire ground contact end portion, and the plurality of second grooves, and are arranged side by side in the tire circumferential direction;
With
The bottom raised portion includes a portion provided in the first groove and a portion provided in the second groove, and the portion provided in the second groove is in a tire circumferential direction. Is equal to the groove width of the second groove, and the length in the tire width direction projected in the tire circumferential direction is not less than 50% and not more than 150% of the groove width of the first groove,
The portion provided in the first groove has a maximum length in the tire width direction of 10% to 40% of a groove width of the first groove, and a maximum length in the tire circumferential direction is 100% or more and 300% or less of the circumferential length of the boundary part,
In a set of blocks adjacent to each other in the tire circumferential direction, a portion provided in the first groove of the bottom raised portion contacts a block having a smaller length in the tire circumferential direction of the set of blocks. A pneumatic tire in which the volume of the portion that is in contact is larger than the volume of the portion that is in contact with the larger block in the circumferential direction of the tire. The product M of the sum M _i (i is a natural number, hereinafter the same) of the tire circumferential direction lengths of a pair of blocks adjacent in the tire circumferential direction and the volume V _{i of the} raised portion provided between the pair of blocks. the minimum value of _{i × V i (M i ×} V i) min and the maximum value is the relationship between the _{(M i × V i) max} ,
1.00 ≦ (M _i × V _i ) max / (M _i × V _i ) min ≦ 1.05
The pneumatic tire according to claim 1, wherein   The pneumatic tire according to claim 1 or 2, wherein a tire circumferential length of the block is a length of the block along a wall surface of the first groove.   The pneumatic tire according to claim 1 or 2, wherein the tire circumferential length of the block is a maximum value of the length of the block in the tire circumferential direction.   The bottom raised portion provided between the set of blocks has a maximum length in the tire circumferential direction of a portion provided in the first groove, and the maximum length in the tire circumferential direction of the set of blocks. The pneumatic tire according to any one of claims 1 to 4, wherein a block having a smaller maximum length in the tire circumferential direction is longer than a block having a larger tire length.   The bottom raised portion provided between the set of blocks has a maximum length in a tire width direction of a portion provided in the first groove, and a maximum length in a tire circumferential direction of the set of blocks. The pneumatic tire according to any one of claims 1 to 4, wherein a block having a smaller maximum length in the tire circumferential direction is longer than a block having a larger tire length.   The bottom raised portion provided between the set of blocks has a maximum height in a tire radial direction of a portion provided in the first groove, and a maximum length in a tire circumferential direction of the set of blocks. The pneumatic tire according to any one of claims 1 to 4, wherein a block having a smaller maximum length in the tire circumferential direction is higher than a block having a larger tire length. The minimum of the product Xi × Yi between the area Xi in plan view of the block and the area Yi in plan view of the portion adjacent to the block among the portions provided in the first groove of the bottom raised portion The relationship between the value (Xi × Yi) min and the maximum value (Xi × Yi) max is
1.00 ≦ (Xi × Yi) max / (Xi × Yi) min ≦ 1.20
The pneumatic tire according to any one of claims 1 to 7, wherein: A depth of the second groove, which is a length from the starting point of the raised portion that rises in the second groove to a ground contact surface along a line parallel to the tire equatorial plane, and the second groove. The difference from the length to the outermost position in the tire radial direction along a line parallel to the tire equatorial plane is 20% or more and 70% or less of the depth of the second groove. The pneumatic tire according to any one of claims 1 to 8.

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