JP2018001930A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress deterioration of drainage property of a tread part, and improve steering stability.SOLUTION: A tire 1 comprises a center land part bottom-up part on a center land part which is closest to a tire equator surface, and a shoulder land part bottom-up part on a shoulder land part. The center land part bottom-up part and the shoulder land part bottom-up part are configured so that: a length in a tire circumferential direction of a part provided on a second groove is equal to a groove width of a second groove of the center land part; a length in a tire width direction projected in the tire circumferential direction is 50% or more and 150% or less of a groove width of a first groove; a maximum length in the tire width direction of a part provided on the first groove is 10% or more and 40% or less of a groove width of the first groove; and a maximum length of the tire circumferential direction is 100% or more and 300% or less of the length in the circumferential direction of the boundary. An average value in tire perimeter of a volume on the center land part bottom-up part is larger than an average value in tire perimeter of a volume on the shoulder land part bottom-up part.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 drainage of the tread portion is lowered depending on the size of the protrusion.

  This invention is made | formed in view of the above, Comprising: The objective is to provide the pneumatic tire which can aim at the improvement of steering stability performance, suppressing the fall of the drainage property of a tread part.

  In order to solve the above-described problems and achieve the object, a pneumatic tire according to an aspect of the present invention is partitioned by a plurality of first grooves extending in the tire circumferential direction and aligned in the tire width direction. A pneumatic tire having a plurality of land portions provided, wherein among the plurality of land portions, a center land portion that is a land portion closest to a tire equatorial plane is a plurality of the plurality of the second land sections that define the center land portion. Including a second groove of the center land portion provided in a row in the tire circumferential direction and a boundary portion communicating from the second groove of the center land portion to the first groove. A center land portion bottom-up portion provided across the first groove and the second groove of the center land portion, the groove bottom being raised to make the depth of the groove shallower than other portions, and The center land portion bottom raising portion is provided in the second groove of the center land portion. The length in the tire circumferential direction of the portion is equal to the groove width of the second groove of the center land portion, and the length in the tire width direction projected in the tire circumferential direction is the groove width of the first groove. And the maximum length in the tire width direction of the portion provided in the first groove is 10% or more and 40% or less of the groove width of the first groove, and A shoulder land portion that is a land portion that has a maximum length in the tire circumferential direction that is 100% or more and 300% or less of a circumferential length of the boundary portion, and is the outermost land portion in the tire width direction among the plurality of land portions. Is connected to the first groove defining the shoulder land portion, extends to the outside of the tire ground contact end portion, and a plurality of second grooves of the shoulder land portion provided side by side in the tire circumferential direction, and the shoulder Including a boundary portion that leads from the second groove of the land portion to the first groove; A shoulder land portion bottom-up portion that is provided across the groove and the second groove of the shoulder land portion, and has a groove bottom raised so that the depth of the groove is shallower than other portions, and the shoulder land portion The bottom raised portion has a length in the tire circumferential direction of a portion provided in the second groove of the shoulder land portion equal to the groove width of the second groove of the shoulder land portion, and is projected in the tire circumferential direction. The length in the tire width direction is not less than 50% and not more than 150% of the groove width of the first groove, and the maximum length in the tire width direction of the portion provided in the first groove is the first width. 10% or more and 40% or less of the groove width of the groove, and the maximum length in the tire circumferential direction is 100% or more and 300% or less of the circumferential length of the boundary portion, and the volume of the center land portion bottom-up portion The average value of the entire tire circumference is the volume of the shoulder land bottom raised portion. It is larger than the average value over the entire tire circumference.

  The average value of the volume of the center land portion bottom-up portion in the entire tire circumference is preferably 110% or more and 300% or less of the average value of the volume of the shoulder land portion bottom-up portion in the entire tire circumference.

  The center land portion bottom-up portion may have a cross-sectional area in the tire width direction that is larger than a cross-sectional area in the tire width direction of the shoulder land portion bottom-up portion.

  The center land portion bottom-up portion may have a height in the second groove that is higher than a height of the shoulder land portion bottom-up portion in the second groove.

  The center land portion bottom raising portion may have a maximum width in the second groove wider than a maximum width in the second groove of the shoulder land portion bottom raising portion.

  The center land portion bottom-up portion may have a maximum width in the first groove wider than a maximum width in the first groove of the shoulder land portion bottom-up portion.

  The center land portion bottom raised portion and the shoulder land portion raised portion are an upper surface, a first side wall surface from the upper surface toward the groove bottom of the first groove, and from the upper surface to the groove bottom of the second groove. And an angle formed between the upper surface of the center land portion bottom-up portion and the first side wall surface is formed by the upper surface of the shoulder land portion bottom-up portion and the first side wall surface. The angle formed between the upper surface of the center land portion bottom-up portion and the second side wall surface is smaller than the angle formed between the upper surface of the shoulder land portion bottom-up portion and the second side wall surface. May be.

  It is preferable that the portion provided in the first groove is in contact with at least a wall surface of the first groove having an acute angle with the wall surface of the second groove.

  A depth of the second groove, which is a length from a starting point of the shoulder land portion raised portion and the center land portion raised portion that rises in the second groove to a contact surface along a line parallel to the tire equator plane; The difference between the length of the portion provided in the second groove and the outermost position in the tire radial direction along the line parallel to the tire equatorial plane is the depth of the second groove. It is preferably 10% or more and 50% or less.

  A tire radial direction along a line parallel to the tire equatorial plane of a portion provided in the first groove from the starting point of the shoulder land bottom raising portion and the center land bottom raising portion rising in the first groove. The tire equator of the portion provided in the second groove from the starting point of the shoulder land bottom raising part and the center land part bottom raising part that rises in the first groove. It is preferably 90% or more and 110% or less of the height to the outermost position in the tire radial direction along a line parallel to the surface.

  According to the pneumatic tire according to the present invention, it is possible to improve the steering stability performance while suppressing a decrease in drainage of the tread portion.

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 illustrating another example of the tread portion of the pneumatic tire according to the embodiment. FIG. 5 is an enlarged cross-sectional view of a part of the pneumatic tire according to the embodiment. FIG. 6 is a diagram illustrating an example of a tread portion of the pneumatic tire according to the embodiment. FIG. 7 is a diagram illustrating another example of the tread portion of the pneumatic tire according to the embodiment. FIG. 8 is a diagram showing the shape of the bottom raised portion in plan view. FIG. 9A is a diagram illustrating an example of another shape of the bottom-up portion. FIG. 9B is a diagram illustrating an example of another shape of the bottom raised portion. FIG. 9C is a diagram illustrating an example of another shape of the bottom raised portion. FIG. 9D is a diagram illustrating an example of another shape of the bottom raised portion. FIG. 9E is a diagram illustrating an example of another shape of the bottom raised portion. FIG. 10 is a diagram illustrating the height of a portion provided in the lug groove in the bottom raised portion. FIG. 11 is a diagram for explaining the height of the portion provided in the main groove and the lug groove in the bottom raised portion. FIG. 12 is a diagram for explaining the height of the portion provided in the main groove and the lug groove in the bottom raised portion. FIG. 13 is a view showing the length in the tire width direction of the portion provided in the main groove of the bottom raised portion. FIG. 14A is a cross-sectional view illustrating an example of a center land portion bottom-up portion. FIG. 14B is a cross-sectional view illustrating an example of a shoulder land portion bottom-up portion. FIG. 15A is a plan view illustrating an example of a center land portion bottom-up portion. FIG. 15B is a plan view illustrating an example of a shoulder land portion bottom-up portion. FIG. 16A is a plan view illustrating an example of a center land portion bottom-up portion. FIG. 16B is a plan view illustrating an example of a shoulder land portion bottom-up portion. FIG. 17A is a cross-sectional view illustrating an example of a center land portion bottom-up portion. FIG. 17B is a cross-sectional view illustrating an example of a shoulder land portion bottom-up portion. FIG. 18A is a cross-sectional view showing another example of the center land portion bottom raising portion. FIG. 18B is a cross-sectional view illustrating another example of the shoulder land portion bottom raising portion.

  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 21a and 21b can be referred to as first grooves extending in the tire circumferential direction. The lug groove 22 provided in the shoulder portion 12 can be said to be a second groove that extends to the outside of the tire ground contact end portion through the first groove.

  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 center land portion 30 _C that is the land portion closest to the tire equatorial plane CL includes a lug groove 22 and center land portion bottom-up portions SG _C1 and SG _C2 . Lug grooves 22 of the center land portion 30 _C is in communication with a plurality of main grooves 21 defining the center land portion 30 _C, are arranged side by side a plurality in the tire circumferential direction. The center land portion bottom raised portions SG _C1 and SG _C2 are provided across the main groove 21 and the lug groove 22 of the center land portion 30 _{C including} the boundary portion KK leading from the lug groove 22 of the center land portion 30 _C to the main groove 21. It is done. The center land portion bottom raised portions SG _C1 and SG _C2 are portions where the groove bottom is raised to make the groove depth shallower than other portions.

Further, the shoulder land portions 30 _S1 and 30 _S2 which are land portions located on the outermost side in the tire width direction include the lug groove 22 and the shoulder land portion bottom raised portions SG _S1 and SG _S2 . 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. The shoulder land portion bottom raised portions SG _S1 and SG _S2 include boundary portions KK that lead from the lug grooves 22 of 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 portions 30 _S1 and It is provided across the lug groove 22 of 30 _S2 . The shoulder land portion bottom raising portions SG _S1 and SG _S2 are portions where the groove bottom is raised to make the groove depth shallower than the other portions.

In the pneumatic tire 1 of this example, the volume of the center land portion bottom-up portion is larger than the volume of the shoulder land portion bottom-up portion. More specifically, the average value of the volume of the bottom raising portion in the tire entire circumference of the center land portion 30 _C is larger than the average value of the bottom-up volume in the tire entire circumference of the shoulder land portion 30 _S1, 30 _S2. That is, in FIG. 3, the average value of the volume of the raised portions SG _S1 provided in the tire circumferential direction is V _S1 , the average value of the volumes of the raised portions SG _C1 provided in the tire circumferential direction is V _C1 , and the tire circumference. When an average value of the volumes of the raised portions SG _S2 provided in the direction is V _S2 , V _C1 > V _S1 and V _C1 > V _S2 .

FIG. 4 is a diagram illustrating another example of the tread portion 6 of the pneumatic tire 1 according to the present embodiment. The tread portion 6 shown in FIG. 3 has bottom raised portions SG _C1 and SG _C2 provided on both sides of the center land portion 30 _C. In contrast, in FIG. 4, the bottom raised portion SG _C1 is provided only on one side of the center land portion 30 _C. A plurality of bottom raised portions SG _C1 are provided in the tire circumferential direction. The average value of the volumes of the raised portions SG _S1 provided in the tire circumferential direction is V _S1 , the average value of the volumes of the raised portions SG _C1 provided in the tire circumferential direction is V _C1 , and the plurality of values are provided in the tire circumferential direction. Assuming that the average value of the volume of the bottom raised portion SG _S2 is V _S2 , V _C1 > V _S1 and V _C1 > V _S1 .

  In the example shown in FIGS. 2, 3 and 4, the number of main grooves 21 is an even number. The number of main grooves 21 is not limited to an even number, and may be an odd number. FIG. 5 is an enlarged cross-sectional view of a part of the pneumatic tire according to the present embodiment. FIG. 6 is a diagram illustrating an example of a tread portion of the pneumatic tire according to the present embodiment. As shown in FIGS. 5 and 6, the tire 1 has three main grooves 21. Of the three 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.

5 and 6 show an example in which the center of the tread portion 6 in the tire width direction coincides with the tire equatorial plane CL. Also in the example illustrated in FIG. 6, the land portions closest to the tire equatorial plane CL among the plurality of land portions of the tread portion 6 are the center land portions 30 _C1 and 30 _C2 . The center land portion 30 _C1 includes the lug groove 22 and the center land portion bottom raised portions SG _C1 and SG _C2 . Center land part 30 _C2 has lug groove 22 and center land part bottom raising part SG _C3 , SG _C4 . A plurality of center land portion bottom raised portions SG _C1 , SG _C2 , SG _C3 , and SG _C4 are provided side by side in the tire circumferential direction.

Lug grooves 22 of the center land portion _{30 C1} is in communication with a plurality of main grooves 21,21a partitioning the center land portion _{30 C1,} are arranged side by side a plurality in the tire circumferential direction. Lug grooves 22 of the center land portion _{30 C2} communicates with a plurality of main grooves 21,21b partitioning the center land portion _{30 C2,} are arranged side by side a plurality in the tire circumferential direction.

Center land portion raised bottom portion _{SG C1} is provided astride the lug groove 22 of the main groove 21a and the center land portion _{30 C1} contains boundary KK leading from the lug grooves 22 of the center land portion _{30 C1} to the main groove 21a. The center land portion bottom raising portion SG _C2 is provided across the main groove 21 and the lug groove 22 of the center land portion 30 _{C1 including} the boundary portion KK leading from the lug groove 22 of the center land portion 30 _C1 to the main groove 21.

The center land portion bottom raising portion SG _C3 is provided across the main groove 21 and the lug groove 22 of the center land portion 30 _{C2 including} the boundary portion KK leading from the lug groove 22 of the center land portion 30 _C2 to the main groove 21. Center land portion raised bottom portion _{SG C4} is provided astride the lug groove 22 of the main groove 21b and the center land portion _{30 C2} include boundary KK leading from the lug grooves 22 of the center land portion _{30 C2} to the main groove 21b.

The land portions located on the outermost side in the tire width direction are shoulder land portions 30 _S1 and 30 _S2 . The shoulder land portion 30 _S1 includes a lug groove 22 and a shoulder land portion bottom raised portion SG _S1 . The shoulder land portion 30 _S2 includes a lug groove 22 and a shoulder land portion bottom raised portion SG _S2 . A plurality of shoulder land portion bottom raising portions SG _S1 and SG _S2 are provided side by side in the tire circumferential direction.

Lug grooves 22 of the shoulder land portion _{30 S1,} through the main groove 21a defining the shoulder land portion _{30 S1,} and extends to the outside of the tire ground contact ends STA. A plurality of lug grooves 22 of the shoulder land portion _30S1 are provided side by side in the tire circumferential direction. Lug grooves 22 of the shoulder land portion _{30 S2,} through the main groove 21b defining the shoulder land portion _{30 S2,} and extends to the outside of the tire ground contact end STB. A plurality of lug grooves 22 of the shoulder land portion _30S2 are provided side by side in the tire circumferential direction.

The shoulder land portion bottom raising portion SG _S1 is provided across the main groove 21a and the lug groove 22 of the shoulder land portion 30 _{S1 including} the boundary portion KK leading from the lug groove 22 of the shoulder land portion 30 _S1 to the main groove 21 a. The shoulder land portion bottom raising portion SG _S2 is provided across the main groove 21b and the lug groove 22 of the shoulder land portion 30 _{S2 including} the boundary portion KK leading from the lug groove 22 of the shoulder land portion 30 _S2 to the main groove 21 b.

As described above, in the pneumatic tire 1 of this example, the volume of the center land portion bottom-up portion closest to the tire equatorial plane CL is larger than the volume of the shoulder land portion bottom-up portion. That is, in FIG. 6, the average value of the volume of the shoulder land portion bottom raising portion SG _S1 provided in the tire circumferential direction is V _S1 , and the average value of the volume of the center land portion bottom raising portion SG _C2 provided in the tire circumferential direction. V _C2 , the average value of the volume of the center land portion bottom raised portion SG _C3 provided in the tire circumferential direction is V _C3 , and the average value of the volume of the shoulder land portion bottom raised portion SG _S2 provided in the tire circumferential direction is V _{Assuming S2} , V _C2 > V _S1 and V _C3 > V _S2 . The volume of the average value V _C1 of the center land portion raised bottom portion SG _{C1 and,} for the average value V _C4 of the volume of the center land portion raised bottom portion SG _C4, the magnitude of the average value of the volume of the other raised portion both Absent.

FIG. 7 is a diagram illustrating another example of the tread portion 6 of the pneumatic tire 1 according to the present embodiment. The tread portion 6 shown in FIG. 6 has center land portion bottom raised portions SG _C1 and SG _C2 provided on both sides of the center land portion 30 _C1 . Moreover, the tread portion 6 illustrated in FIG. 6 includes center land portion bottom raised portions SG _C3 and SG _C4 provided on both sides of the center land portion 30 _C2 . On the other hand, in FIG. 7, the center land portion bottom raised portion SG _C1 is provided only on one side of the center land portion 30 _C1 , and the center land portion raised portion SG _C4 is provided only on one side of the center land portion 30 _C2 . A plurality of center land portion bottom raised portions SG _C1 and SG _C4 are provided in the tire circumferential direction. The average value of the volume of the shoulder bottom raising portion SG _S1 provided in the tire circumferential direction is V _S1 , the average value of the volume of the center land portion raising portion SG _C1 provided in the tire circumferential direction is V _C1 , and the tire circumferential direction. Assuming that the average value of the volume of the plurality of center land portion bottom raised portions SG _C4 provided is V _C4 and the average value of the volume of the shoulder land portion bottom raised portions SG _S2 provided in the tire circumferential direction is V _S2 , V _C1 > V _S1 and V _C4 > V _S2 .

In FIG. 6 and FIG. 7, when the distance from the distance and the equatorial plane CL from the equatorial plane CL to the central land portion 30 _C1 to center land portion 30 _C2 are equal, the closest land portion to the equatorial plane CL is the center It becomes the land part 30 _C1 and the center land part 30 _C2 . When the distance from the equator plane CL is not equal, the land portion closest to the equator plane CL is either the center land portion 30 _C1 or the center land portion 30 _C2 .

(Bottom raised part)
As described above, the pneumatic tire 1 includes the center land portion bottom raised portions SG _C1 and SG _C2 and the shoulder land portion bottom raised portions SG _S1 and SG _S2 . Hereinafter, for the convenience of explanation, these raised portions may be collectively referred to as a raised portion SG.

  FIG. 8 is a diagram showing the shape of the raised bottom SG in plan view. As shown in FIG. 8, the bottom-up 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.

  A 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 a tire length direction maximum length L5 projected in the tire circumferential direction. For example, it is 50% or more and 150% or less of the groove width L1 of the main groove 21.

  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.

  By raising the corners of the shoulder blocks that are likely to be deformed, it is possible to improve the rigidity as compared with the case where only the lug grooves 22 are provided with a raised bottom. Moreover, the bottom raising effect can be effectively obtained by providing the bottom raising that communicates 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.

(Relation with wall angle)
The bottom raised portion SG is preferably in contact with the wall surface 210 of the main grooves 21, 21 a, 21 b that has an acute angle with the wall surface with the lug groove 22. By providing the bottom raising portion SG on the acute angle side where the block is likely to be deformed, the effect of raising the bottom can be obtained effectively. For this reason, it is preferable that bottom raising part SG is provided so that the angle with the wall surface with the lug groove 22 may be an acute angle among the wall surfaces 210 of the main grooves 21, 21a, 21b.

(Other shapes of bottom raised part)
Examples of other shapes of the bottom raised portion will be described with reference to FIGS. 9A to 9E. 9A to 9E are diagrams illustrating examples of other shapes of the bottom-up portion. 9A to 9E all show the shape of the raised portion in plan view.

  9A 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 grooves 21, 21a, 21b. The portion SG21 provided in the main grooves 21, 21a, 21b of the bottom raised portion SG1 is rectangular, and has a shape in which the length in the tire circumferential direction does not change even if it is separated from the wall surface 210.

  9B, of the wall surfaces 210 of the main grooves 21, 21a, and 21b, the bottom raised portion SG2 is in contact with the wall surface having an acute angle 211 with the wall surface of the lug groove 22, and is not in contact with the wall surface having the obtuse angle 212. The portion SG21 provided in the main grooves 21, 21a, 21b of the bottom raised portion SG2 has a shape in which the length in the tire circumferential direction decreases 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.

  9C is in contact with the wall surface having an acute angle 211 and the obtuse angle 212 with respect to the wall surface of the lug groove 22 among the wall surfaces 210 of the main grooves 21, 21a, and 21b. The portion SG21 provided in the main grooves 21, 21a, 21b of the bottom raised portion SG3 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 SG3 in the tire circumferential direction is the length of the portion farthest from the wall surface 210.

  The bottom raised portion SG4 shown in FIG. 9D is in contact with a wall surface having an acute angle 211 and an obtuse angle 212 with respect to the wall surface 210 of the lug groove 22 among the wall surfaces 210 of the main grooves 21, 21a, 21b. A portion SG21 provided in the main grooves 21, 21a, 21b of the bottom raised portion SG4 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. Therefore, the maximum length of the bottom raised portion SG4 in the tire circumferential direction is the length of the portion closest to the wall surface 210.

  The bottom raised portion SG5 shown in FIG. 9E 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 grooves 21, 21a, and 21b. As shown in FIG. 9E, when the angle between the wall surface 210 of the main grooves 21, 21a and 21b and the wall surface of the lug groove 22 is an acute angle on both sides of the lug groove 22, the wall surface is an acute angle 211 and the wall surface is an acute angle 213. The bottom raising portion SG5 is provided so as to contact both of the above. The portion SG21 provided in the main grooves 21, 21a, 21b of the bottom raised portion SG5 is rectangular, and has a shape in which the length in the tire circumferential direction does not change even if it is separated from the wall surface 210.

  As described above, the portion SG21 provided in the main grooves 21, 21a, 21b of the bottom raised portions SG1 to SG5 is at least an angle with the wall surface of the lug groove 22 among the wall surfaces 210 of the main grooves 21, 21a, 21b. Touches the wall with an acute angle.

(Height of the raised part, etc.)
FIG. 10 is a diagram for explaining the height of the portion SG22 provided in the lug groove 22 in the bottom raised portion. In FIG. 10, the starting point rising in the lug groove 22 of the bottom raised portion SG is P1, and the starting point rising in the main grooves 21, 21a, 21b of the bottom raised portion SG is P2.

  From the lug groove 22 to the main grooves 21, 21a, 21b, 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 equator plane, The depth of the lug groove 22 is assumed. Further, of the portion SG22 provided in the lug groove 22 of the bottom raised portion SG, the length to the outermost position in the tire radial direction along the line parallel to the tire equator plane, that is, from the point P4 to the point P5. Let the height be 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, 10% to 50% of the depth (height H1) of the lug groove 22. If the height of the portion SG22 provided in the lug groove 22 of the bottom raised portion SG is less than 10% of the depth of the lug groove 22, the effect of the raised portion SG cannot be obtained sufficiently, and conversely if it exceeds 50%. The drainage performance is reduced.

  11 and 12 are diagrams illustrating the heights of the portions SG21 and SG22 provided in the main grooves 21, 21a, and 21b and the lug groove 22 in the bottom raised portion. In FIG. 11 and FIG. 12, along the line parallel to the tire equator plane of the portion SG21 provided in the main grooves 21, 21a, 21b from the starting point P2 of the raised bottom SG that rises in the main grooves 21, 21a, 21b. The height to the outermost position P6 in the tire radial direction is defined as H4. Further, the outermost position P4 in the tire radial direction along the line parallel to the tire equatorial plane of the portion SG22 provided in the lug groove 22 from the starting point P2 of the raised portion SG rising in the main grooves 21, 21a, 21b. The height up to is H3. At this time, the height H4 is not less than 90% and not more than 110% of the height H3. That is, it is preferable that the height H3 of the portion SG22 provided in the lug groove 22 is equal to the height H4 of the portion SG21 provided in the main grooves 21, 21a, 21b. By making the height of the portion SG22 provided in the lug groove 22 and the portion SG21 provided in the main grooves 21, 21a, 21b equal, it is possible to achieve both the block rigidity and the drainage in a balanced manner. it can.

  FIG. 11 shows a case where the height H4 of the part SG21 provided in the main grooves 21, 21a, 21b is lower than the height H3 of the part SG22 provided in the lug groove 22. FIG. 12 shows a case where the height H4 of the portion SG21 provided in the main grooves 21, 21a, 21b is higher than the height H3 of the portion SG22 provided in the lug groove 22.

  FIG. 13 is a diagram illustrating the length in the tire width direction of the portion SG21 provided in the main grooves 21, 21a, 21b of the bottom raised portion SG. As shown in FIG. 13, the bottom raised portion SG of this example has a length L6 in the tire width direction of the portion SG21 provided in the main grooves 21, 21a, 21b from the end portion P7 on the upper surface of the bottom raised portion SG to the main groove. It increases as it approaches the point P2 at the groove bottom of 21, 21a, 21b. Thus, the drainage effect of the main grooves 21, 21a, 21b is sufficiently reduced by reducing the area of the raised portion SG (part SG21) occupying the main grooves 21, 21a, 21b (area projected in the tire circumferential direction). Can demonstrate.

(Volume of bottom raised part)
The volume of the center land portion bottom raised portions SG _C1 and SG _C2 is different from the volume of the shoulder land portion bottom raised portions SG _S1 and SG _S2 . The volume of the center land portion raised bottom portion _SG C1, _{SG C2} is greater than the volume of the shoulder land portion raised bottom portion _SG S1, _{SG S2.} The volume of the bottom raised portion may be based on the average value of the volumes of the bottom raised portions provided in the tire circumferential direction, or may be based on the total volume that is the sum of the volumes of the bottom raised portions.

As described above, at the block angle of the shoulder portion where deformation is likely to occur, by providing a bottom raising portion straddling the main grooves 21a, 21b and the lug groove 22, the rigidity is higher than that provided only the lug groove 22 is raised. Improvement is possible. Furthermore, in the center land portion that greatly affects the steering stability performance, the bottom raising volume is increased in order to increase the block rigidity, and in the shoulder land portion having a low contribution, the bottom raising volume is reduced so as not to reduce the drainage. That is, by making the volume of the center land portion bottom raising portion SG _C1 larger than the volume of the shoulder land portion bottom raising portion SG _S1 , it is possible to improve the steering stability performance while suppressing a decrease in drainage.

In order to make the volume of the center land portion bottom raising portion SG _C1 larger than the volume of the shoulder land portion bottom raising portion SG _S1 , for example, it is conceivable to adjust the height of the bottom raising portion.

Figure 14A is a cross-sectional view showing an example of a center land portion raised bottom portion _{SG C1.} FIG. 14B is a cross-sectional view illustrating an example of the shoulder land portion bottom raising portion SG _S1 . As shown in FIGS. 14A and 14B, the height (H1-H2) of the center land portion bottom raised portion SG _{C1 in} the lug groove 22 is the height (H1-H2) of the shoulder land portion bottom raised portion SG _S1 in the lug groove 22. Higher than.

The height of the center land portion raised bottom portion SG _C1 in the lug groove 22 by higher than the height of the shoulder land portion raised bottom portion SG _S1, the volume of the volume of the center land portion raised bottom portion SG _C1 shoulder land portion raised bottom portion SG _S1 The steering stability performance can be improved while suppressing a decrease in drainage of the tread portion.

In order to make the volume of the center land portion bottom raising portion SG _C1 larger than the volume of the shoulder land portion bottom raising portion SG _S1 , for example, it is conceivable to adjust by changing the width of the bottom raising portion in the lug groove 22.

Figure 15A is a plan view showing an example of a center land portion raised bottom portion _{SG C1.} FIG. 15B is a plan view showing an example of the shoulder land portion bottom raising portion SG _S1 . As shown in FIGS. 15A and 15B, the maximum width of the center land portion bottom raised portion SG _C1 (the maximum length L5 in the tire width direction) in the lug groove 22 as the second groove is the shoulder land portion bottom raised in the lug groove 22. It is wider than the maximum width of portion SG _S1 (maximum length L5 in the tire width direction).

By making the maximum width of the center land portion bottom raised portions SG _C1 and SG _C2 in the lug groove 22 wider than the maximum width of the shoulder land portion bottom raised portions SG _S1 and SG _S2 , the volume of the center land portion raised portions SG _C1 and SG _C2 is increased. Can be made larger than the volume of the shoulder land portion bottom raising portions SG _S1 and SG _S2 , and the steering stability performance can be improved while suppressing a decrease in drainage of the tread portion.

In order to make the volume of the center land portion bottom raised portions SG _C1 and SG _C2 larger than the volume of the shoulder land portion bottom raised portions SG _S1 and SG _S2 , for example, the width of the bottom raised portions in the main grooves 21, 21a, and 21b is changed and adjusted. It is also possible to do.

Figure 16A is a plan view showing an example of a center land portion raised bottom portion _{SG C1.} FIG. 16B is a plan view showing an example of a shoulder land portion bottom raising portion SG _S1 . As shown in FIGS. 16A and 16B, a first groove in which the main grooves 21, 21a, the maximum width of the center land portion raised bottom portion _{SG C1} in 21b (maximum length L4 in the tire width direction), the main grooves 21, It is wider than the maximum width (maximum length L4 in the tire width direction) of the shoulder land portion bottom raised portion SG _S1 in 21a and 21b.

By making the maximum width of the center land portion bottom raised portions SG _C1 and SG _C2 in the main grooves 21a and 21b wider than the maximum width of the shoulder land portion bottom raised portions SG _S1 and SG _S2 , the center land portion bottom raised portions SG _C1 and SG _C2 Is made larger than the volume of the shoulder land portion bottom raising portions SG _S1 and SG _S2 , and the steering stability performance can be improved while suppressing the decrease in drainage of the tread portion.

In order to make the volume of the center land portion bottom raised portions SG _C1 , SG _C2 larger than the volume of the shoulder land portion bottom raised portions SG _S1 , SG _S2 , for example, the grooves of the main grooves 21, 21 a, 21 b from the upper surface and the upper surface of the bottom raised portion It is also possible to adjust the volume so that the angle formed between the bottom or the side wall surface of the lug groove 22 toward the groove bottom differs between the center land portion bottom raised portions SG _C1 and SG _C2 and the shoulder land portion raised portions SG _S1 and SG _S2. Conceivable.

Figure 17A is a cross-sectional view showing an example of a center land portion raised bottom portion _{SG C1.} FIG. 17B is a cross-sectional view illustrating an example of the shoulder land portion bottom raising portion SG _S1 . As shown in FIGS. 17A and 17B, the angle formed between the upper surface 23 of the center land portion bottom raised portion SG _C1 and the side wall surface 25 from the upper surface 23 toward the groove bottom of the main groove 21 is an angle θ1c, and the shoulder land portion raised portion SG _S1. angle angle? 1s, the side wall surface extending from the top surface 23 and upper surface 23 of the center land portion raised bottom portion SG _C1 to the groove bottom of the lug groove 22 formed from the upper surface 24 and top surface 24 and side wall surface 26 toward the groove bottom of the main groove 21a of the 27 and of the angle of the angle Shita2c, angle angle between the side wall surface 28 extending from the top surface 24 and upper surface 24 of the shoulder land portion raised bottom portion _{SG S1} to the groove bottom of the lug groove 22? 2s, to.

  At this time, the angle θ1c and the angle θ1s correspond to each other. The angle θ1c is smaller than the angle θ1s. For example, the angle θ1s is 112 degrees and the angle θ1c is 99 degrees. Further, the angle θ2c and the angle θ2s have a corresponding positional relationship. The angle θ2c is smaller than the angle θ2s. For example, the angle θ2s is 148 degrees and the angle θ2c is 118 degrees.

As described above, when the angles formed by the corresponding surfaces of the center land portion bottom raising portions SG _C1 and SG _C2 and the shoulder land portion bottom raising portions SG _S1 and SG _S2 are compared, the center land portion bottom raising portions SG _C1 and SG _C2 are compared. The angle of the tire width direction side wall of is smaller than the angle of the tire width direction side walls of the shoulder land portion bottom raised portions SG _S1 and SG _S2 . That is, the center land portion bottom raised portions SG _C1 , SG _C2 and the shoulder land portion bottom raised portions SG _S1 , SG _S2 are the upper surfaces 23, 24 and the sides from the upper surfaces 23, 24 toward the groove bottoms of the main grooves 21, 21 a, 21 b. Wall surfaces 25 and 26 and side wall surfaces 27 and 28 from the upper surfaces 23 and 24 toward the groove bottom of the lug groove 22 are provided. Then, the angle formed between the side wall surface 25 toward the groove bottom of the upper surface 23 and the main groove 21 of the center land portion raised bottom portion _SG C1, _{SG C2,} top 24 and the main groove 21a of the shoulder land portion raised bottom portion _SG S1, _{SG S2} The angle formed between the upper surface 23 of the center land portion bottom raised portions SG _C1 and SG _C2 and the side wall surface 27 toward the groove bottom of the lug groove 22 is smaller than the angle formed with the side wall surface 26 toward the groove bottom. It is smaller than the angle formed by the upper surface 24 of the land portion raised portions SG _S1 and SG _S2 and the side wall surface 28 facing the groove bottom of the lug groove 22. In this case, it can be larger than the volume of the center land portion raised bottom portion _SG C1, shoulder land portion raised bottom portion the volume of the _{SG C2 SG} S1, _{SG S2.}

Here, there may be a case where there is no corner between the upper surface and the side wall surface, and the upper surface and the side wall surface are connected by a curved surface. Figure 18A is a cross-sectional view showing another example of the center land portion raised bottom portion SG _C1. FIG. 18B is a cross-sectional view showing another example of the shoulder land portion bottom raising portion SG _S1 .

As shown in FIG. 18A, and the side wall surface 25 extending from the top surface 23 and upper surface 23 of the center land portion raised bottom portion _{SG C1} to the groove bottom of the main groove 21 are connected by a curved face 31. Further, the side wall surface 27 extending from the top surface 23 and upper surface 23 of the center land portion raised bottom portion SG _C1 to the groove bottom of the lug groove 22 are connected by a curved surface 32. An angle formed by the upper surface 23 and the side wall surface 25 connected by the curved surface 31 is an angle θ1c. The angle formed by the upper surface 23 and the side wall surface 27 connected by the curved surface 32 is an angle θ2c.

As shown in FIG. 18B, the side wall surface 26 extending from the top surface 24 and upper surface 24 of the shoulder land portion raised bottom portion _{SG S1} to a groove bottom of the main groove 21a are connected by a curved surface 33. Further, the side wall surfaces 28 extending from the top surface 24 and upper surface 24 of the shoulder land portion raised bottom portion SG _S1 to the groove bottom of the lug groove 22 are connected by a curved surface 34. The angle formed by the upper surface 24 and the side wall surface 26 connected by the curved surface 33 is an angle θ1s. The angle formed by the upper surface 24 and the side wall surface 28 connected by the curved surface 34 is an angle θ2s.

Even when the upper surfaces 23 and 24 and the side wall surfaces 25, 26, 27 and 28 are connected by the curved surfaces 31, 32, 33 and 34, the upper surface 23 and the side wall surface 25 of the center land portion bottom raised portions SG _C1 and SG _C2 . The volume of the center land portion bottom raised portions SG _C1 and SG _C2 is increased by making the angle 27 smaller than the angle between the upper surface 24 and the side wall surfaces 26 and 28 of the shoulder land portion raised portions SG _S1 and SG _S2. The volume of the parts SG _S1 and SG _S2 can be made larger.

(Example)
A pneumatic tire with a size of 195 / 65R15 91H was assembled to a wheel with a size of 15 × 6J, the air pressure was set to 230 kPa, and “WET braking performance” and “steering stability performance” were tested on the test course. The results are shown in Tables 1 to 3.

  In Tables 1 to 3, “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.

  The “steering stability performance” was calculated by comparing an index by driving a FF vehicle with a displacement of 1.8 liters fitted with pneumatic tires 1 and panelists performing sensory evaluations.

  The volume of the bottom raised portion was calculated by pressing the clay against the bottom raised portion to mold, and calculating the volume of the recess formed in the clay mold.

  In the embodiment, the case where the main grooves 21a and 21b do not have the bottom raised portion SG and the lug groove 22 has the bottom raised portion SG is defined as Conventional Example 1. A case in which the main grooves 21, 21 a, 21 b and the lug grooves 22 do not have the bottom raised portion SG was set as Comparative Example 1. The main grooves 21a, 21b and lug grooves 22 have bottom raised portions SG. The average value of the center land portion bottom raised portion volume over the entire tire circumference / the shoulder land portion bottom raised portion volume average value over the entire tire circumference is 100%. The length L5 / length L1 of the bottom raised portion (Sh) is 100%, the length L5 / length L1 of the center land raised portion (Ce) is 100%, the center land raised portion and the shoulder land raised portion Length L4 / length L1 is 30%, length L3 / length L2 of the center land bottom raising portion and shoulder land bottom raising portion is 200%, and the height H1-height of the shoulder land bottom raising portion (Sh) H2) / height H1 is 30%, center land bottom raised part (Ce) (height H1-height H2) / height H1 is 30%, center land part raised part and shoulder land part raised part height H4 / height H3 The case of a 100% sample of Comparative Example 2.

  In Tables 1 to 3, the index of Conventional Example 1 is set to “100”, and the larger the index value, the better the performance.

  As can be seen from Example 1 to Example 21 shown in Table 1 to Table 3, the lug groove and the main groove are provided with a raised portion, and the average value of the volume of the center land portion raised portion over the entire tire circumference is the shoulder. A favorable characteristic was obtained when the volume of the land bottom raised portion was larger than the average value of the entire tire circumference. The length L5 / length L1 is 50% to 150%, the length L4 / length L1 is 10% to 40%, the length L3 / length L2 is 100% to 300%, and the height H1. On the other hand, when the difference between the height H1 and the height H2 is 10% or more and 50% or less and the height H4 / height H3 is 90% or more and 110% or less, preferable characteristics were obtained. Furthermore, preferable characteristics were obtained when the average value of the volume of the center land portion bottom-up portion in the entire tire circumference was 110% to 300% of the average value of the volume of the shoulder land portion bottom-up portion in the tire circumference.

DESCRIPTION OF SYMBOLS 1 Pneumatic 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, 21a, 21b Main groove 22 Lug groove 30 _C , 30 _C1 , 30 _C2 center land portion 30 _S1 , 30 _S2 shoulder land portion 50 bead 210 wall surface 211, 213 acute angle 212 obtuse angle CL equatorial plane SG, SG1-SG5 bottom raised portion SG _C1 , SG _C2 , SG _C3 , SG _C4 center Land part bottom raising part SG _S1 , SG _S2 shoulder land part bottom raising part

Claims (10)

A pneumatic tire defined by a plurality of first grooves extending in the tire circumferential direction and having a plurality of land portions arranged side by side in the tire width direction,
Among the plurality of land portions, the center land portion that is the land portion closest to the tire equator plane communicates with the plurality of first grooves that define the center land portion, and a plurality of center land portions are provided side by side in the tire circumferential direction. Including the second groove of the center land portion and the boundary portion leading from the second groove of the center land portion to the first groove, and straddling the first groove and the second groove of the center land portion. And a center land portion bottom-up part that raises the groove bottom and makes the groove depth shallower than other parts,
The center land portion raising portion is
The length in the tire circumferential direction of the portion provided in the second groove of the center land portion is equal to the groove width of the second groove in the center land portion, and in the tire width direction projected in the tire circumferential direction. The length is 50% or more and 150% or less of the groove width of the first groove,
The maximum length in the tire width direction of the portion provided in the first groove is not less than 10% and not more than 40% of the groove width of the first groove, and the maximum length in the tire circumferential direction is the boundary. 100% or more and 300% or less of the circumferential length of the part,
Of the plurality of land portions, a shoulder land portion which is a land portion located on the outermost side in the tire width direction communicates with the first groove defining the shoulder land portion and extends to the outside of the tire ground contact end portion. And a plurality of second grooves of the shoulder land portion provided side by side in the tire circumferential direction, and a boundary portion that leads from the second groove of the shoulder land portion to the first groove, and A shoulder land bottom raising portion provided across the second groove of the shoulder land portion, the groove bottom being raised to make the groove depth shallower than other portions,
The shoulder land portion bottom raising portion is
The length in the tire circumferential direction of the portion provided in the second groove of the shoulder land portion is equal to the groove width of the second groove in the shoulder land portion, and in the tire width direction projected in the tire circumferential direction. The length is 50% or more and 150% or less of the groove width of the first groove,
The maximum length in the tire width direction of the portion provided in the first groove is not less than 10% and not more than 40% of the groove width of the first groove, and the maximum length in the tire circumferential direction is the boundary. 100% or more and 300% or less of the circumferential length of the part,
A pneumatic tire in which an average value of the volume of the center land portion bottom-up portion in the entire tire circumference is larger than an average value of the volume of the shoulder land portion bottom-up portion in the tire circumference.   2. The pneumatic tire according to claim 1, wherein an average value of the volume of the center land portion bottom-up portion in the entire tire circumference is 110% or more and 300% or less of an average value of the volume of the shoulder land portion bottom-up portion in the tire circumference. .   2. The pneumatic tire according to claim 1, wherein the center land portion bottom-up portion has a cross-sectional area in the tire width direction larger than a cross-sectional area in the tire width direction of the shoulder land portion bottom-up portion.   2. The pneumatic tire according to claim 1, wherein the center land portion bottom-up portion has a height in the second groove that is higher than a height in the second groove of the shoulder land portion bottom-up portion.   2. The pneumatic tire according to claim 1, wherein the center land portion bottom raised portion has a maximum width in the second groove wider than a maximum width in the second groove of the shoulder land portion bottom raised portion.   2. The pneumatic tire according to claim 1, wherein the center land portion bottom raised portion has a maximum width in the first groove wider than a maximum width in the first groove of the shoulder land portion bottom raised portion. The center land portion bottom raised portion and the shoulder land portion raised portion are an upper surface, a first side wall surface from the upper surface toward the groove bottom of the first groove, and from the upper surface to the groove bottom of the second groove. Each having a second side wall surface,
An angle formed between the upper surface of the center land portion bottom-up portion and the first side wall surface is smaller than an angle formed between the upper surface of the shoulder land portion bottom-up portion and the first side wall surface, and the center land portion. The pneumatic tire according to claim 1, wherein an angle formed by the upper surface of the bottom raised portion and the second side wall surface is smaller than an angle formed by the upper surface of the shoulder land bottom raised portion and the second side wall surface.   The part provided in the said 1st groove | channel contacts the wall surface whose angle with the wall surface of the said 2nd groove | channel is an acute angle at least among the wall surfaces of the said 1st groove | channel. A pneumatic tire given in any 1 paragraph.   A depth of the second groove, which is a length from a starting point of the shoulder land portion raised portion and the center land portion raised portion that rises in the second groove to a contact surface along a line parallel to the tire equator plane; The difference between the length of the portion provided in the second groove and the outermost position in the tire radial direction along the line parallel to the tire equatorial plane is the depth of the second groove. The pneumatic tire according to any one of claims 1 to 8, wherein the pneumatic tire is 10% or more and 50% or less.   A tire radial direction along a line parallel to the tire equatorial plane of a portion provided in the first groove from the starting point of the shoulder land bottom raising portion and the center land bottom raising portion rising in the first groove. The tire equator of the portion provided in the second groove from the starting point of the shoulder land bottom raising part and the center land part bottom raising part that rises in the first groove. The pneumatic tire according to any one of claims 1 to 9, wherein the pneumatic tire has a height that is 90% or more and 110% or less of a height to the outermost position in the tire radial direction along a line parallel to the surface.

Images