tire

Abstract

To provide a tire improved in a snow-road performance.SOLUTION: A tire 1 has a tread part 2 provided with a block 3. A stair-shaped chamfering part 7, in which a height of the block is gradually reduced in a stair shape from a tread surface 3a toward a top part 3b, is formed at a block corner part 5 of the block 3. The stair-shaped chamfering part 7 includes a plurality of upper surfaces 10b which is in parallel to the tread surface 3a and a plurality of stair-shaped corner parts 12 in which the upper surfaces cross vertical surfaces 11a and 11b and the vertical surfaces cross the tread surface 3a to protrude toward outside of the block. In a vertical cross-sectional view of the block corner part 5 passing on the top part 3b, angles between virtual lines joining the stair-shaped corner parts 12 to each other and the tread surface 3a are 10-40 degrees.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a tire. [Background technology]

[0002] The following Patent Document 1 describes a pneumatic tire with blocks in the tread portion. The blocks include constricted blocks with recesses on the side surfaces in the tire axial direction. The recesses are defined by V-shaped edges that protrude toward the center of the block. When traveling on snow, these V-shaped recesses trap snow inside and compress and deform the trapped snow to form hard snow columns. For this reason, the pneumatic tire of Patent Document 1 is said to have excellent performance on snow. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-124504 A Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, there has been a demand for further improvement in the snow-covered road performance of tires. After carrying out various experiments, the inventors have discovered that snow-covered road performance can be improved by improving the block corners of the tread portion.

[0005] The present invention has been devised in view of the above circumstances, and has as its main object to provide a tire with improved snow-covered road performance. [Means for solving the problem]

[0006] The present invention is a tire including a tread portion, in which blocks having a tread surface are provided, and in a plan view of the tread, the blocks have block corner portions including apexes that are convex outwardly of the blocks, and the block corner portions are formed with a stepped chamfer in which the block height decreases in a stepped manner from the tread surface toward the apex, and the stepped chamfer portion includes a plurality of upper surfaces that are substantially parallel to the tread surface, a plurality of vertical surfaces that extend in the block height direction, and a plurality of stepped corner portions that are convex outwardly from the blocks where the upper surfaces, the vertical surfaces, and the vertical surfaces and the tread surface intersect, and in a vertical cross-sectional view of the block corner portions that pass through the apex, an angle between the tread surface and an imaginary straight line connecting each of the plurality of stepped corner portions is 10 to 40 degrees.

[0007] In the tire according to the present invention, it is desirable that the block corner portion is formed at an intersection between the tread surface, a wall surface of a longitudinal groove extending in the tire circumferential direction, and a wall surface of a lateral groove extending in the tire axial direction, and that the stepped chamfer portion straddles the wall surface of the longitudinal groove and the wall surface of the lateral groove.

[0008] In the tire according to the present invention, it is preferable that the stepped chamfered portion is provided with at least one rib extending in the block height direction.

[0009] In the tire according to the present invention, it is preferable that the rib extends in a zigzag shape.

[0010] In the tire according to the present invention, it is preferable that the rib has a plurality of zigzag corner portions, each of which is located at the step corner portion.

[0011] In the tire according to the present invention, it is preferable that a ratio of a width of the zigzag bend of the rib to an inclined piece of the stepped chamfered portion is 0.04 to 0.2.

[0012] In the tire according to the present invention, it is preferable that the height of the rib is 0.3 to 2.0 mm, and the width of the rib is 0.3 to 2.0 mm.

[0013] In the tire according to the present invention, it is preferable that the rib has a pair of rising surfaces rising from the upper surface, and in a cross-sectional view of the rib, an angle between an imaginary line connecting root side ends of the pair of rising surfaces and each of the rising surfaces is 30 to 90 degrees.

[0014] In the tire according to the present invention, it is preferable that the stepped chamfered portion is provided with a plurality of ribs extending in the block height direction, and the intervals between the respective ribs gradually increase outward in the block height direction. Effect of the Invention

[0015] By employing the above-mentioned configuration, the tire of the present invention can improve snowy road performance. [Brief description of the drawings]

[0016] [Figure 1] 1 is a partial perspective view of a block of a tire according to one embodiment of the present invention. [Diagram 2] 2 is a cross-sectional view taken along line AA in FIG. 1. [Diagram 3] FIG. 2 is a plan view of the block of FIG. 1. [Figure 4] FIG. 2 is a plan view of one embodiment of a tread portion. [Diagram 5] FIG. 2(a) is a cross-sectional view of one embodiment of a rib, and (b) is a cross-sectional view of another embodiment of a rib. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a partial perspective view of a block 3 provided in a tread portion 2 of a tire 1 of this embodiment. Fig. 1 shows the block 3 of a pneumatic tire 1 for passenger cars as a preferred embodiment. However, the present invention may also be applied to, for example, a pneumatic tire 1 for heavy loads or tires 1 of other categories.

[0018] 1, in this embodiment, the block 3 includes a tread surface 3a that comes into contact with the road surface and, in a plan view of the tread, a peak 3b that protrudes outward from the block 3. The block 3 also includes a wall surface (first wall surface) 3c that extends in one direction from the peak 3b, and a wall surface (second wall surface) 3d that extends in the other direction from the peak 3b.

[0019] The block 3 of this embodiment has a block corner portion 5 including an apex 3b. The block corner portion 5 is formed with a stepped chamfered portion 7 in which the block height decreases in a stepped manner from the tread surface 3a to the apex 3b. Such a stepped chamfered portion 7 compacts snow and increases the snow column shear force. The stepped chamfered portion 7 is formed, for example, in a triangular shape in a plan view of the tread.

[0020] FIG. 2 is a vertical cross-sectional view (cross-sectional view taken along line AA in FIG. 1) of the block corner portion 5 passing through the top portion 3b. As shown in FIG. 2, the stepped chamfered portion 7 includes a plurality of upper surfaces 10, a plurality of vertical surfaces 11, and a plurality of stepped corner portions 12 that are convex toward the outside of the block. The upper surfaces 10 are formed substantially parallel to the tread surface 3a. When traveling on snow, such upper surfaces 10 can strongly pack snow to form a solid snow column. The vertical surfaces 11 extend in the block height direction. The stepped corner portions 12 are formed by the intersections of the upper surface 10 and the vertical surfaces 11, and the vertical surfaces 11 and the tread surface 3a.

[0021] The term "substantially parallel" includes a state in which, in a vertical cross-sectional view of the block corner portion 5 passing through the apex 3b, the angle (not shown) between the imaginary line n1 extended from the tread surface 3a and the imaginary line n2 extended from the top surface 10 is within 10 degrees. Additionally, "extending in the block height direction" includes a state in which the vertical surface 11 extends parallel to the block height direction (perpendicular to the tread surface 3a) as well as an angle (not shown) of 60 degrees or less with respect to the block height direction.

[0022] In this specification, the dimensions of each part of the tire 1 are values ​​measured when the tire 1 is mounted on a regular rim (not shown), inflated to the regular internal pressure, and in a regular condition with no load. The "regular rim" is a rim that is determined for each tire by a standard system that includes the standard on which the tire 1 is based, and is, for example, a "standard rim" for JATMA, a "design rim" for TRA, and a "measuring rim" for ETRTO.

[0023] The "normal internal pressure" is the air pressure determined for each tire by each standard in the standard system including the standard on which the tire 1 is based, and is the "maximum air pressure" in the case of JATMA, the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and "INFLATION PRESSURE" in the case of ETRTO. If the tire is for a passenger car, the normal internal pressure is 180 kPa.

[0024] The angle θ1 between the tread surface 3a and the virtual straight line n3 connecting each of the staircase corners 12 is set to 10 to 40 degrees. By setting the angle θ1 in the range of 10 to 40 degrees, the volume of the snow pillars formed by the step-like chamfered portion 7 and the effect of compacting the snow are both achieved, and a large snow pillar shear force can be exerted. In particular, on a packed snow road surface where the snow is compressed, the above action is exerted effectively. From this viewpoint, the angle θ1 is more preferably 15 degrees or more, even more preferably 20 degrees or more, still more preferably 30 degrees or less, and even more preferably 25 degrees or less. If it is not possible to connect each of the staircase corners 12 with a single straight line, the virtual straight line n3 is a virtual straight line (linear function) obtained by the least squares method using each of the staircase corners 12.

[0025] In this embodiment, the stepped chamfered portion 7 further includes a plurality of stepped recesses 13 that are recessed toward the inside of the block at the intersection of the upper surface 10 and the vertical surface 11. In this embodiment, the stepped recesses 13 are formed alternately with the stepped corner portions 12.

[0026] In this embodiment, the stepped chamfered portion 7 is formed by alternating upper surfaces 10 and vertical surfaces 11. The stepped chamfered portion 7 is formed, for example, by two or more and five or less upper surfaces 10 and vertical surfaces 11. The stepped chamfered portion 7 in this embodiment is formed by two upper surfaces 10 and three vertical surfaces 11. In the stepped chamfered portion 7, for example, the innermost vertical surface 11b in the block height direction forms the apex 3b.

[0027] Fig. 3 is a plan view of the block corner portion 5 of Fig. 1. As shown in Fig. 3, the angle θ1 of the stepped chamfered portion 7 is an angle on a bisector c1 of an angle θa formed by the first wall surface 3c and the second wall surface 3d with the apex 3b as the center in a plan view of the tread. In the block corner portion 5 of this embodiment, the angle θ1 is 10 to 40 degrees in a vertical section parallel to the bisector c1, for example, in a vertical section T.

[0028] Although not particularly limited, in the block corner portion 5 where the stepped chamfered portion 7 is formed, the angle θa is desirably 30 degrees or more, more desirably 40 degrees or more, desirably 100 degrees or less, and more desirably 90 degrees or less.

[0029] 2, in the vertical cross-sectional view, for example, the upper surface 10 and the vertical surface 11 are each formed in a straight line. However, the upper surface 10 and the vertical surface 11 are not limited to this form, and may be, for example, an arcuate shape that is convex outward from the block 3, or an arcuate shape that is concave inward from the block 3.

[0030] Fig. 4 is a plan view showing one embodiment of the tread portion 2. As shown in Fig. 4, longitudinal grooves G1 extending in the tire circumferential direction and lateral grooves G2 extending in the tire axial direction are arranged in the tread portion 2. The longitudinal grooves G1 and the lateral grooves G2 define blocks 3.

[0031] The longitudinal groove G1 is, for example, a groove extending at an angle of 45 degrees or more with respect to the tire axial direction. The lateral groove G2 is, for example, a groove extending at an angle of less than 45 degrees with respect to the tire axial direction. In this specification, the longitudinal groove G1 and the lateral groove G2 are groove-shaped bodies having a groove width w of preferably 1.5 mm or more, more preferably 2.5 mm or more, and even more preferably 3.5 mm or more.

[0032] The blocks 3 include, for example, a crown block 3A disposed on the tire equator C, a pair of middle blocks 3B disposed on both axial sides of the crown block 3A, and a pair of shoulder blocks 3C disposed axially outboard of the middle block 3B. Note that the tread portion 2 is not limited to this embodiment, and various shapes can be adopted.

[0033] In this embodiment, each of the blocks 3A to 3C has a block corner portion 5 sandwiched between the longitudinal groove G1 and the lateral groove G2. In other words, in this embodiment, the block corner portion 5 is formed at the intersection of the tread surface 3a, the wall surface Ga of the longitudinal groove G1, and the wall surface Gb of the lateral groove G2.

[0034] In this embodiment, the stepped chamfered portion 7 is provided on the blocks 3A to 3C. In other words, the stepped chamfered portion 7 of this embodiment spans the wall surface Ga of the vertical groove G1 and the wall surface Gb of the horizontal groove G2. As a result, the snow pillars formed by the stepped chamfered portion 7 of this embodiment are smoothly discharged through the vertical groove G1 or the horizontal groove G2 during driving on snow. In this embodiment, the wall surface Ga of the vertical groove G1 constitutes the first wall surface 3c, and the wall surface Gb of the horizontal groove G2 constitutes the second wall surface 3d. Although not particularly limited, the height H (shown in FIG. 2) of the stepped chamfered portion 7 is preferably 25% or more of the groove depth (not shown) of the vertical groove G1 that forms the first wall surface 3c or the second wall surface 3d, more preferably 33% or more, more preferably 40% or less, and even more preferably 36% or less.

[0035] In order to exert a large snow column shear force while maintaining the rigidity of the block 3, the tire circumferential length L1 of the first wall surface 3c is desirably 10% or more of the tire circumferential length La of the block 3, more desirably 20% or more, desirably 50% or less, and more desirably 40% or less.

[0036] As shown in Fig. 1, the stepped chamfered portion 7 of this embodiment is provided with at least one rib 15 extending in the block height direction. This rib 15 helps form a strong snow column by blocking the snow on the stepped chamfered portion 7 without letting it escape when traveling on snow. Therefore, the rib 15 further improves snowy road performance.

[0037] For example, a plurality of ribs 15, three in this embodiment, are provided, so that snow between adjacent ribs 15 is more effectively blocked by the stepped chamfered portion 7, further improving snowy road performance.

[0038] The ribs 15 extend, for example, in a zigzag shape. Such ribs 15 have a greater length than, for example, linearly extending ribs (not shown), and can therefore more effectively block snow. However, the ribs 15 are not limited to this form, and may extend, for example, in a wavy shape or linearly.

[0039] The rib 15 has a plurality of zigzag corners 16. Each zigzag corner 16 is located at a staircase corner 12. The zigzag corner 16 is located at a staircase recess 13. The rib 15 includes a first inclined portion 15a inclined toward either the first wall surface 3c or the second wall surface 3d toward the top 3b, and a second inclined portion 15b connected to the first inclined portion 15a and inclined toward the top 3b in the opposite direction to the first inclined portion 15a. The zigzag corners 16 are formed at the connection positions of the first inclined portion 15a and the second inclined portion 15b. This embodiment is useful for smoothly removing snow from the upper surface 10 and the vertical surface 11.

[0040] As shown in FIG. 3, in the plan view of the tread, the ratio (α / β) of the zigzag bending width α of the rib 15 to the inclined piece β of the stepped chamfered portion 7 is preferably 0.04 or more and 0.2 or less. Since the ratio (α / β) is 0.04 or more, the length of the rib 15 can be relatively long, and the effect of blocking snow is exhibited. If the ratio (α / β) exceeds 0.2, the effect of blocking snow is not large, and the snow discharge effect may be reduced. From this viewpoint, the ratio (α / β) is more preferably 0.06 or more and more preferably 0.16 or less. The bending width α is the length between adjacent vertices of the zigzag in a direction perpendicular to the center line 15c of the amplitude of the rib 15. The inclined piece β is the length on the first wall surface 3c or the length on the second wall surface 3d of the stepped chamfered portion 7.

[0041] Fig. 5(a) is a cross section of the rib 15. As shown in Fig. 5(a), the height h1 of the rib 15 is preferably 0.3 mm or more and 2.0 mm or less. Since the height h1 of the rib 15 is 0.3 mm or more, the effect of blocking snow is exhibited. Since the height h1 of the rib 15 is 2.0 mm or less, snow easily leaves the stepped chamfered portion 7 during driving on snow, and snow clogging is suppressed. From this viewpoint, the height h1 of the rib 15 is more preferably 0.6 mm or more and more preferably 1.7 mm or less.

[0042] The width w1 of the rib 15 is preferably 0.3 mm or more and 2.0 mm or less. Since the width w1 of the rib 15 is 0.3 mm or more, the rigidity of the rib 15 is maintained and snow can be effectively blocked. Since the width w1 of the rib 15 is 2.0 mm or less, the area of ​​the upper surface 10, etc., is secured in the stepped chamfered portion 7, and a large snow column can be formed. From this viewpoint, the width w1 of the rib 15 is more preferably 0.6 mm or more and more preferably 1.7 mm or less.

[0043] The rib 15 has a pair of rising surfaces 18 rising from the upper surface 10. In a cross-sectional view of the rib 15, the angle θ2 between each rising surface 18 and an imaginary straight line n4 connecting the root ends 18a of the pair of rising surfaces 18 is preferably 30 to 90 degrees. Since the angle θ2 is 30 degrees or more, the snow blocking effect is effectively exhibited. Since the angle θ2 is 90 degrees or less, a large volume of the snow pillar formed by the stepped chamfered portion 7 can be ensured.

[0044] In cross section, the rib 15 is formed into a triangle shape with the tips 18b of a pair of rising surfaces 18 connected to each other. Such a rib 15 forms a strong snow column and can ensure a large volume of the snow column. The rib 15 may be, for example, rectangular (not shown) with the angle θ2 of the pair of rising surfaces 18 being 90 degrees, or trapezoidal with the tips 18b of the pair of rising surfaces 18 connected by an outward surface 19 (shown in FIG. 5(b)) extending in the width direction of the rib 15.

[0045] As shown in Fig. 1, the rib 15 extends from the outermost vertical surface 11a in the block height direction to the innermost top surface 10b in the block height direction. More specifically, the rib 15 extends from the step corner portion 12 of the vertical surface 11a to the step corner portion 12 of the top surface 10b. Since such a rib 15 has a relatively large length, it has a large snow blocking effect. In this embodiment, the rib 15 is not formed on the innermost vertical surface 11b in the block height direction.

[0046] In this embodiment, the interval L2 between each rib 15 gradually increases toward the outside in the block height direction. Although not particularly limited, the minimum gap Lb between the ribs 15 is preferably 0.2 mm or more, more preferably 1 mm or more, more preferably 5 mm or less, and more preferably 3 mm or less. The minimum gap Lb between the ribs 15 is formed at the inner end of the rib 15 in the block height direction.

[0047] Although the tire according to one embodiment of the present invention has been described in detail above, the present invention is not limited to the above specific embodiment and can be modified and carried out in various aspects. EXAMPLES

[0048] Tires of size 215 / 60R16 with the basic pattern shown in Figure 4 were prototyped based on the specifications in Table 1, and the snow-covered performance of each sample tire was tested. The common specifications and test methods for each sample tire are as follows. The height H of the stepped chamfer is the same for all examples. Height of stepped chamfer: 4mm

[0049] <Snowy road performance> Each sample tire was mounted on all wheels of a 1500cc front-wheel drive passenger vehicle under the following conditions, and a test driver drove the vehicle on a test course with a snowy road surface. The test driver evaluated the driving characteristics related to the steering response, traction, grip, etc. by sensory evaluation. The results are shown as a score with Comparative Example 1 being 100. The higher the value, the better the result. Rim (all wheels): 16 x 6.5J Internal pressure (all wheels): 240kPa

[0050] [Table 1]

[0051] As a result of the test, it was confirmed that the tires of the embodiment had excellent performance on snowy roads. [Explanation of symbols]

[0052] 1 Tire 2 Tread section 3 Blocks 3a Block tread 3b Top of block 5 Block corner 7 Step chamfer 10 Top side 11 Vertical surface 12 Staircase corner n3 Virtual line θ1 angle

Claims

1. A tire including a tread portion, The tread portion is provided with blocks having a tread surface, In a plan view of the tread, the block has a block corner portion including an apex portion that is convex outwardly of the block, The block corner portion is formed with a stepped chamfer portion in which the block height decreases in a stepped manner from the tread surface toward the apex, The stepped chamfer has a plurality of upper surfaces substantially parallel to the tread surface; A plurality of vertical surfaces extending in a height direction of the block; a plurality of staircase corners each of which is convex toward the outside of the block, the staircase corners being formed by intersecting the upper surface, the vertical surface, and the vertical surface and the tread surface; In a vertical cross-sectional view of the block corner portion passing through the apex, an angle between the tread surface and a virtual straight line connecting each of the plurality of stair corner portions is 10 to 40 degrees; The stepped chamfered portion is provided with a plurality of ribs extending in a height direction of the block, The spacing between each rib gradually increases toward the outside in the block height direction. tire.

2. the block corner portion is formed at an intersection between the tread surface, a wall surface of a longitudinal groove extending in a tire circumferential direction, and a wall surface of a lateral groove extending in an axial direction of the tire, The tire according to claim 1 , wherein the stepped chamfered portion spans a wall surface of the longitudinal groove and a wall surface of the lateral groove.

3. The tire according to claim 1 or 2, wherein the stepped chamfered portion is provided with at least one rib extending in a block height direction.

4. The tire of claim 3 wherein said ribs extend in a zigzag manner.

5. The rib has a plurality of zigzag corners, 5. A tire according to claim 3 or 4, wherein each zigzag corner is located at one of the stepped corners.

6. 6. The tire according to claim 3, wherein a ratio of a width of the zigzag bend of the rib to an inclined piece of the stepped chamfered portion is 0.04 to 0.

2.

7. The height of the rib is 0.3 to 2.0 mm; 7. The tire according to claim 3, wherein the rib has a width of 0.3 to 2.0 mm.

8. The rib has a pair of rising surfaces rising from the upper surface, 8. The tire according to claim 3, wherein, in a cross-sectional view of the rib, an angle between an imaginary line connecting root side ends of the pair of raised surfaces and each of the raised surfaces is 30 to 90 degrees.

9. A tire including a tread portion, The tread portion is provided with blocks having a tread surface, In a plan view of the tread, the block has a block corner portion including an apex portion that is convex outwardly of the block, The block corner portion is formed with a stepped chamfer portion in which the block height decreases in a stepped manner from the tread surface toward the apex, The stepped chamfer has a plurality of upper surfaces substantially parallel to the tread surface; A plurality of vertical surfaces extending in a height direction of the block; a plurality of staircase corners each of which is convex toward the outside of the block, the staircase corners being formed by intersecting the upper surface, the vertical surface, and the vertical surface and the tread surface; In a vertical cross-sectional view of the block corner portion passing through the apex, an angle between the tread surface and a virtual straight line connecting each of the plurality of stair corner portions is 10 to 40 degrees; The stepped chamfered portion is provided with at least one rib extending in the block height direction. tire.

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