Pneumatic tire

Abstract

To provide a pneumatic tire excellent in braking performance and driving performance.SOLUTION: A tread portion 10 includes a shoulder land portion 11 and a center land portion 12 adjacent to the shoulder land portion 11 via a circumferential groove 22. The shoulder land portion 11 includes a shoulder block 31 and a shoulder sipe 41 disposed in the shoulder block 31. The center land portion 12 includes a center block 32 and a center sipe 42 disposed in the center block 32. The shoulder sipe 41 is arranged in a kick-out side region 31k of the shoulder block 31, and is not arranged in a step-in side region 31s of the shoulder block 31. At least a part of the center sipe 42 is arranged on a bisecting line L32 bisecting the center block 32 in a tire circumferential direction or in a step-in side region center 32s of the center block 32.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to pneumatic tires.

Background Art

[0002] In a pneumatic tire having a tread pattern including blocks, an edge effect is exhibited during braking or driving, so that the braking performance and driving performance are excellent. When sipe is arranged in the block, although the edge component can be increased, the rigidity of the block is reduced, so that the block is likely to fall down when a load acts during braking or driving. When the block falls down and the grounding state deteriorates, the edge effect of the sipe is not properly exhibited, so that the effect of improving the braking performance and driving performance cannot be sufficiently obtained.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The ground contact pressure of the block during braking or driving tends to be relatively low on the stepping-in side (the front side in the tire rotation direction) and relatively high on the kicking-out side (the rear side in the tire rotation direction). Therefore, in order to suppress the falling down of the block, it is preferable to arrange the sipe close to the stepping-in side of the block. However, since the edge effect is small in the region of the stepping-in side where the ground contact pressure is low, the effect of improving the braking performance and driving performance is not sufficient. In addition, when the sipe is arranged uniformly shifted, a bias in pattern rigidity occurs, so it is also necessary to deal with this point.

[0005] Patent Document 1 describes a pneumatic tire with a sipe placed closer to the kicking-out side of the block, but it is for the purpose of suppressing uneven wear and does not suggest a solution for the technology to improve the braking performance and driving performance of the tire as described above.

[0006] The present disclosure has been made in view of the above circumstances, and its object is to provide a pneumatic tire excellent in braking performance and driving performance.

Means for Solving the Problems

[0007] In the pneumatic tire of the present disclosure, the tire rotation direction is specified, and the tread portion includes a shoulder land portion including a tread grounding end and a center land portion adjacent to the shoulder land portion via a circumferential groove. The shoulder land portion includes shoulder blocks arranged in the tire circumferential direction and a shoulder sipe arranged on the shoulder blocks. The center land portion includes center blocks arranged in the tire circumferential direction and a center sipe arranged on the center blocks. The shoulder sipe is arranged in the kicking-out side region of the shoulder block and is not arranged in the stepping-in side region of the shoulder block. At least a part of the center sipe is arranged on the bisecting line that bisects the center block in the tire circumferential direction or in the stepping-in side region of the center block.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0009] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings.

[0010] FIG. 1 is a plan development view showing an example of a tread portion 10 of a pneumatic tire T according to the present embodiment. The tire T is an automotive pneumatic tire including a pair of bead portions (not shown), a pair of sidewall portions (not shown) extending radially outward in the tire diameter direction from each of the pair of bead portions, and a tread portion 10 connected to the radially outer ends of each of the pair of sidewall portions in the tire diameter direction. The tire T shown in FIG. 1 is new, and the tread surface Tr forming the outer peripheral surface of the tread portion 10 is in an unworn state.

[0011] Arrow CD indicates the tire circumferential direction, which is the direction around the central axis (rotation axis) of the tire T. Arrow AD indicates the tire axial direction, which is a direction parallel to the central axis of the tire T. The side approaching the tire equator TC is the inner side AD1 in the tire axial direction, and the side away from the tire equator TC is the outer side AD2 in the tire axial direction. The tire equator TC is an imaginary line located at the center in the tire axial direction of the tire T and is orthogonal to the central axis of the tire T in plan view.

[0012] This tire T is a rotation direction specified type tire in which the tire rotation direction is specified. The specification of the tire rotation direction is performed, for example, by a display provided on the outer surface of the sidewall portion. Arrow RD1 indicates the front side (the forward direction of the vehicle) of the tire rotation direction, and arrow RD2 indicates the rear side of the tire rotation direction. The "indentation side" described later refers to the side where the block first contacts the road surface when the vehicle moves forward and corresponds to the front side RD1 of the tire rotation direction. Also, the "kicking-out side" described later refers to the side where the block contacts the road surface later when the vehicle moves forward and corresponds to the rear side RD2 of the tire rotation direction.

[0013] The tread ground contact ends TE1 and TE2 are the outermost positions in the tire axial direction of the ground contact surface in the normal state where the tire T mounted on the normal rim is filled with the normal internal pressure and placed perpendicular to the flat road surface and the normal load is applied. In addition, dimensions, angles, positional relationships, etc. of each part of the tire are defined in a no-load state where the tire T mounted on the normal rim is filled with the normal internal pressure unless otherwise specified.

[0014] The standard rim is the rim defined for each tire in a standard system including the standards on which the tire is based. For example, it is the standard rim in JATMA, and it is the "Measuring Rim" in TRA and ETRTO.

[0015] The standard internal pressure is the air pressure defined for each tire in a standard system including the standards on which the tire is based. In the case of truck and bus tires and light truck tires, it is the maximum air pressure in JATMA, the value corresponding to the Load Index described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in TRA, and the "INFLATION PRESSURE" in ETRTO. In the case of passenger car tires, it is usually 180 kPa, but it is 220 kPa for tires marked as Extra Load or Reinforced.

[0016] The standard load is the load defined for each tire in a standard system including the standards on which the tire is based. It is the "maximum load capacity" in JATMA, the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in TRA, and the "LOAD CAPACITY" in ETRTO. In the case of passenger car tires, it is the load corresponding to 88% of the above load.

[0017] As shown enlarged in FIG. 2, the tread portion 10 includes a shoulder land portion 11 including a tread contact end TE1, and a center land portion 12 adjacent to the shoulder land portion 11 via a circumferential groove 22. The shoulder land portion 11 includes a shoulder block 31 and a shoulder sipe 41 disposed in the shoulder block 31. The shoulder land portion 11 is formed by a block row in which the shoulder blocks 31 are arranged in the tire circumferential direction CD. The center land portion 12 includes a center block 32 and a center sipe 42 disposed in the center block 32. The center land portion 12 is formed by a block row in which the center blocks 32 are arranged in the tire circumferential direction CD.

[0018] In this embodiment, the center land portion 12 is divided into an outer center land portion 12a and an inner center land portion 12b by the circumferential groove 23. Therefore, the center land portion 12 includes the outer center land portion 12a and the inner center land portion 12b adjacent to the outer center land portion 12a via the circumferential groove 23. The depth of the circumferential groove 23 may be smaller than the depth of the circumferential groove 22. The outer center land portion 12a includes an outer center block 32a and an outer center sipe 42a disposed thereon. The inner center land portion 12b includes an inner center block 32b and an inner center sipe 42b disposed thereon. However, the present invention is not limited to this, and the center land portion 12 may be configured not to include the circumferential groove 23.

[0019] As shown in FIGS. 2 and 3, sipes such as the shoulder sipe 41 and the center sipe 42 are formed by small cuts. The width Ws of these sipes is set to be less than, for example, 1.6 mm, preferably less than 1.5 mm. The width Ws is obtained at a portion where the walls of the sipes extend substantially parallel to each other in the tire radial direction. In this example, a part of the center sipe 42 opens to the surface of the center block 32 via the chamfered portion 42f, and the chamfered portion 42f is formed by an inclined surface inclined in a direction to expand the opening of the sipe. However, a shape not including such a chamfered portion may also be used.

[0020] The indentation side region 31s is a region on the indentation side with respect to the bisecting line L31 that bisects the shoulder block 31 in the tire circumferential direction CD, and the kick-out side region 31k is a region on the kick-out side with respect to the bisecting line L31. The bisecting line L31 extends along the groove width center line 21c of a groove (the inclined groove 21 described later) that divides the shoulder block 31 in the tire circumferential direction CD, and is located in the middle of the pair of groove width center lines 21c. The surface of the shoulder block 31 is divided into an indentation side region 31s and a kick-out side region 31k with the bisecting line L31 as a boundary. The indentation side region 32s and the kick-out side region 32k of the center block 32 are also defined with the bisecting line L32 as a boundary in the same manner.

[0021] As shown in FIG. 2, the shoulder groove 41 is disposed in the kicking-out side region 31k of the shoulder block 31 and is not disposed in the stepping-in side region 31s of the shoulder block 31. The shoulder groove 41 is closer to the kicking-out side than the bisecting line L31. Further, at least a part of the center groove 42 is disposed on the bisecting line L32 that bisects the center block 32 in the tire circumferential direction or in the stepping-in side region 32s of the center block 32.

[0022] During braking, the contact pressure tends to be relatively high in the region AD2 on the outer side in the tire axial direction of the tread surface Tr and relatively low in the region AD1 on the inner side in the tire axial direction. Therefore, the contribution to the braking performance is greater for the shoulder land portion 11 than for the center land portion 12. Moreover, as described above, during braking, the contact pressure tends to be relatively high on the kicking-out side of the block. In the tire T of the present embodiment, since the shoulder groove 41 is disposed as described above in the shoulder land portion 11 where the contribution to the braking performance is large, the edge effect of the groove can be enhanced, and excellent braking performance can be exhibited.

[0023] During driving, the contact pressure tends to be relatively high in the region AD1 on the inner side in the tire axial direction of the tread surface Tr and relatively low in the region AD2 on the outer side in the tire axial direction. Therefore, the contribution to the driving performance is greater for the center land portion 12 than for the shoulder land portion 11. Moreover, as described above, during driving, the contact pressure tends to be relatively low on the stepping-in side of the block. In the tire T of the present embodiment, since the center groove 42 is disposed as described above in the center land portion 12 where the contribution to the driving performance is large, the collapse of the block can be suppressed, the unevenness of the pattern rigidity can be reduced, and excellent driving performance can be exhibited.

[0024] When a bisecting line L31k that bisects the kicking-out side region 31k in the tire circumferential direction CD is drawn following the bisecting line L31, it is preferable that the shoulder sip 41 is disposed on the stepping-in side rather than the bisecting line L31k. According to such a configuration, while the shoulder sip 41 is disposed in the kicking-out side region 31k, the shoulder sip 41 can be separated from the block edge on the kicking-out side, so that a decrease in the rigidity of the shoulder block 31 can be suppressed, and an effect of suppressing the collapse during braking and driving can be obtained.

[0025] In the present embodiment, although the end portion of the outer center sip 42a on the outer side AD2 in the tire axial direction is disposed in the kicking-out side region 32k, it gradually approaches the bisecting line L32 toward the inner side AD in the tire axial direction from the end portion, and the end portion of the outer center sip 42a on the inner side AD1 in the tire axial direction is disposed on the bisecting line L32. Further, the entire inner center sip 42b is disposed on the bisecting line L32. However, the present invention is not limited to this, and a part or all of the center sip 42 may be disposed in the stepping-in side region 32s.

[0026] In the present embodiment, the tread portion 10 includes inclined grooves 21 that extend while inclining toward the rear side RD2 in the tire rotation direction from the central portion in the tire axial direction of the tread portion 10 toward the tread ground contact end TE1. The inclined grooves 21 are repeatedly formed at intervals in the tire circumferential direction CD. The inclined grooves 21 are curved in a direction convex toward the rear side RD2 in the tire rotation direction. The inclined grooves 21 extend such that the angle with respect to the tire circumferential direction CD increases as they approach the tread ground contact end TE1. The inclined grooves 21 extend from the tire equator TC or its vicinity to the outer side AD2 in the tire axial direction and reach the tread ground contact end TE1.

[0027] The circumferential grooves 22 and 23 each extend along the tire circumferential direction CD and are connected to a pair of inclined grooves 21 adjacent to the tire circumferential direction CD. The circumferential groove 22 divides between the shoulder block 31 and the center block 32, and the circumferential groove 23 divides between the outer center block 32a and the inner center block 32b. The circumferential grooves 22 and 23 are each inclined outward in the tire axial direction AD2 toward the front side RD1 in the tire rotation direction. Since the circumferential grooves 22 and 23 inclined in this way include an edge component with respect to the tire circumferential direction CD, it is convenient for improving braking performance and driving performance.

[0028] The shoulder block 31 and the center block 32 (outer center block 32a, inner center block 32b) are each divided in the tire circumferential direction by the inclined groove 21. Between a pair of inclined grooves 21 adjacent to the tire circumferential direction CD, the shoulder block 31, the outer center block 32a, and the inner center block 32b are arranged in this order toward the inner side AD1 in the tire axial direction, and this combination of blocks is repeatedly provided in the tire circumferential direction CD. In this example, each block is formed in a quadrangle (quadrilateral) in plan view, but it is not limited to this.

[0029] In order to prevent the block from falling over, it is desirable to minimize the reduction in rigidity due to the sipe. From this viewpoint, the number of shoulder sipes 41 arranged for one shoulder block 31 is preferably 2 or less, and more preferably 1 as in this embodiment. The same applies to the number of center sipes 42 arranged for one center block 32. In this embodiment, in the shoulder block 31, the outer center block 32a, and the inner center block 32b, only one sipe is arranged for each block.

[0030] In the present embodiment, since the shoulder sip 41 is connected to the circumferential groove 22 and reaches the tread ground end TE1, the edge component by the shoulder sip 41 is set to be long. However, it is not limited to this. For example, the shoulder sip 41 may be separated from the circumferential groove 22 and / or the tread ground end TE1 and terminated within the block to suppress the reduction in the rigidity of the block due to the sip. Alternatively, in order to ensure the rigidity of the block while setting the edge component to be long, it is also effective to relatively reduce the depth of the shoulder sip 41 at the connection portion between the shoulder sip 41 and the circumferential groove 22.

[0031] In the present embodiment, the outer center sip 42a is connected to each of the circumferential groove 22 and the circumferential groove 23, and the inner center sip 42b is also connected to the circumferential groove 23, and the edge component is set to be long. However, it is not limited to this. The center sip 42 may be separated from the circumferential groove 22 and / or the circumferential groove 23 and terminated within the block to suppress the reduction in the rigidity of the block due to the sip. Alternatively, as described in the explanation of the shoulder sip 41, the depth of the center sip 42 may be relatively reduced at the connection portion between the center sip 42 and the circumferential grooves 22, 23.

[0032] In the kicking-out side region 31k of the shoulder block 31, since the rigidity is reduced by the arrangement of the shoulder sip 41, if a sip having a surface shape including a bent portion, such as a corrugated sip often adopted in a studless tire, is arranged, stress may concentrate on the bent portion. Therefore, the shoulder sip 41 preferably has a surface shape that does not include a portion bent at an angle of less than 150 degrees, and more preferably has a surface shape extending linearly or in an arc shape. The same applies to the center sip 42. In the present embodiment, the shoulder sip 41 has an arc-shaped surface shape that gently curves along the inclined groove 21.

[0033] The angle θ formed between the block edge 31e of the shoulder block 31 facing the circumferential groove 22 and the shoulder side 41 is preferably 90 ± 10 degrees. According to such a configuration, it is possible to prevent the rigidity of the corner portion formed by the block edge 31e and the shoulder side 41 from excessively decreasing, which is advantageous for suppressing the collapse of the block. The same applies to the block edge of the center block 32 facing the circumferential grooves 22 and 23. In the present embodiment, the length of the block edge 31e of the shoulder block 31 is smaller than the length of the block edge of the shoulder block 31 facing the inclined groove 21.

[0034] As shown in FIG. 2, the center side 42 (specifically, the outer center side 42a) is smoothly continuous with the shoulder side 41 via the circumferential groove 22. By providing a pseudo - continuity of the sides between the shoulder block 31 and the center block 32 (specifically, the outer center block 32a) in this way, stress is more likely to be evenly transmitted between the blocks, which is advantageous for improving braking performance and driving performance. In the present embodiment, an example is shown in which a bridge 22b that rises from the groove bottom of the circumferential groove 22 and connects the shoulder block 31 and the center block 32 is provided, but it is not limited to this.

[0035] In the present embodiment, further, the inner center side 42b is smoothly continuous with the outer center side 42a via the circumferential groove 23. The outer center side 42a is arranged so as to smoothly connect between the shoulder side 41 arranged in the kick - out side region 31k and the inner center side 42b arranged on the bisector L32. In the region sandwiched by the pair of inclined grooves 21 adjacent to the tire circumferential direction CD, the shoulder side 41, the outer center side 42a, and the inner center side 42b gradually approach the stepped - in side region in this order.

[0036] The fact that two circumferential grooves are smoothly continuous through the circumferential grooves means that a virtual line extending one of them in its longitudinal direction and a virtual line extending the other in its longitudinal direction overlap within the circumferential groove or are close to each other such that the separation distance in the tire circumferential direction is negligible (for example, 2.0 mm or less).

[0037] In the present embodiment, the shoulder circumferential groove 41 is formed as a two-dimensional circumferential groove whose shape does not change along the depth direction. However, the present invention is not limited to this, and the shoulder circumferential groove 41 may be formed as a three-dimensional circumferential groove including a portion whose shape changes along the depth direction. The same applies to the center circumferential groove 42.

[0038] As shown in FIG. 1, the tread portion 10 further includes a shoulder land portion 13 including the tread ground contact end TE2 and a center land portion 14 adjacent to the shoulder land portion 13 via the circumferential groove 24. The shape of the tread half-region including these land portions corresponds to the shape obtained by inverting the tread half-region (see FIG. 2) including the shoulder land portion 11 and the center land portion 12 with respect to the tire equator TC. Since the above-described matters also apply to the shoulder land portion 13 and the center land portion 14, redundant descriptions are omitted.

[0039] In the present embodiment, the characteristic configuration regarding the tread portion 10 as described above is applied to both of the pair of tread half-regions, that is, the tread half-region (see FIG. 2) including the shoulder land portion 11 and the center land portion 12 and the tread half-region including the shoulder land portion 13 and the center land portion 14. However, the present invention is not limited to this, and a configuration applied to only one of the pair of tread half-regions may also be used.

[0040] Those skilled in the art will understand that the above-described embodiments are specific examples of the following aspects.

[0041] [1] The pneumatic tire of the present disclosure has a specified tire rotation direction, and the tread portion includes a shoulder land portion including a tread grounding end and a center land portion adjacent to the shoulder land portion via a circumferential groove. The shoulder land portion includes shoulder blocks arranged in the tire circumferential direction and a shoulder sipe arranged in the shoulder blocks. The center land portion includes center blocks arranged in the tire circumferential direction and a center sipe arranged in the center blocks. The shoulder sipe is arranged in the kicking-out side region of the shoulder block and is not arranged in the stepping-in side region of the shoulder block. At least a part of the center sipe is arranged on the bisecting line that bisects the center block in the tire circumferential direction or in the stepping-in side region of the center block. According to such a configuration, a pneumatic tire excellent in braking performance and driving performance can be provided.

[0042] [2] In the pneumatic tire of the above [1], the tread portion may include an inclined groove that extends obliquely rearward in the tire rotation direction from the central portion in the tire axial direction of the tread portion toward the tread grounding end, and the shoulder block and the center block may each be divided in the tire circumferential direction by the inclined groove. In such a case, it will have a tread pattern suitable as a rotation direction specified type tire.

[0043] [3] In the pneumatic tire of the above [1] or [2], the center sipe may be smoothly continuous with the shoulder sipe via the circumferential groove. According to such a configuration, stress is likely to be uniformly transmitted between the shoulder block and the center block, which is convenient for improving braking performance and driving performance.

[0044] [4] In any one of the pneumatic tires [1] to [3] above, the shoulder sidewall may have a surface shape extending linearly or arcuately. Thereby, it is possible to avoid that a portion where stress is likely to concentrate during braking or driving is formed by the shoulder sidewall.

[0045] [5] In any one of the pneumatic tires [1] to [4] above, the shoulder sidewall is connected to the circumferential groove, and the angle formed by the block edge of the shoulder block facing the circumferential groove and the shoulder sidewall may be 90 ± 10 degrees. According to such a configuration, it is possible to prevent the rigidity of the corner portion formed by the block edge and the shoulder sidewall from excessively decreasing, which is convenient for suppressing the collapse of the block.

[0046] The pneumatic tire of the present disclosure can be configured equivalently to a normal pneumatic tire except that the tread portion is configured as described above, and any of conventionally known materials, shapes, structures, manufacturing methods, etc. can be adopted.

[0047] Although the embodiments of the present disclosure have been described with reference to the drawings, the specific configuration should be considered not to be limited to this embodiment. The scope of the present disclosure is shown not only by the description of the above-described embodiment but also by the claims, and further includes all modifications within the meaning and scope equivalent to the claims.

[0048] The pneumatic tire of the present disclosure is not limited to the above-described embodiments at all, nor is it limited to the above-described effects. The pneumatic tire of the present disclosure can be variously improved and modified without departing from the gist thereof. Also, it is possible to arbitrarily combine and adopt each configuration employed in the above-described embodiments.

Explanation of Reference Numerals

[0049] 10 tread portion, 11 shoulder land portion, 12 center land portion, 12a outer center land portion, 12b inner center land portion, 21 inclined groove, 22 circumferential groove, 23 circumferential groove, 31 shoulder block, 31e block edge, 31k kick-out side region, 31s indentation side region, 32 center block, 32a outer center block, 32b inner center block, 32k kick-out side region, 32s indentation side region, 41 shoulder sipe, 42 center sipe, 42a outer center sipe, 42b inner center sipe, TE1 tread ground contact end, L31 bisector, L32 bisector

Claims

1. The tire rotation direction is specified, The tread portion includes a shoulder land portion including a tread ground contact end and a center land portion adjacent to the shoulder land portion via a circumferential groove, The shoulder land portion includes shoulder blocks arranged in the tire circumferential direction and a shoulder sipe arranged in the shoulder blocks, The center land portion includes center blocks arranged in the tire circumferential direction and a center sipe arranged in the center blocks, The shoulder sipe is arranged in the kicking-out side region of the shoulder block and is not arranged in the stepping-in side region of the shoulder block, At least a part of the center sipe is arranged on a bisecting line that bisects the center block in the tire circumferential direction or in the stepping-in side region of the center block, a pneumatic tire.

2. The tread portion includes an inclined groove that extends obliquely rearward in the tire rotation direction from the central portion in the tire axial direction of the tread portion toward the tread ground contact end, The shoulder block and the center block are each divided in the tire circumferential direction by the inclined groove, the pneumatic tire according to Claim 1.

3. The center sipe is smoothly continuous with the shoulder sipe via the circumferential groove, the pneumatic tire according to Claim 1.

4. The shoulder sipe has a surface shape that does not include a portion bent at an angle less than 150 degrees, the pneumatic tire according to Claim 1.

5. The shoulder sipe is connected to the circumferential groove, The angle formed by the block edge of the shoulder block facing the circumferential groove and the shoulder sipe is 90 ± 10 degrees, the pneumatic tire according to any one of Claims 1 to 4.

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