JP2020152267A - tire - Google Patents

Abstract

To provide a tire capable of realizing both of on-snow performance and uneven wear performance.SOLUTION: A tire 1 includes a tread part 2. A crown land part 4A is formed at the tread part 2 in which the crown land part is separated by a pair of circumferential grooves 3 extending in a tire circumferential direction. The crown land part 4A includes a plurality of crown grooves 9 extending from the circumferential grooves 3 to inside of the crown land part 4A. The crown groove 9 comprises: an outer end part 9a having an aperture for the circumferential groove 3; and an inner end part 9b communicating with the crown groove 9 adjacent thereto in the tire circumferential direction. The crown land part 4A includes a plurality of side blocks 4b separated between the crown groove 9 and the circumferential groove 3. In the side block 4b, a first corner part 4d adjacent to the inner end part 9b and having a tapered acute angle is separated in a tread plan view. The first corner part 4d includes a step part 13 step-wisely extending to an inner side in the tire radial direction.SELECTED DRAWING: Figure 1

Description

The present invention relates to a tire having a tread portion having excellent snow performance.

Conventionally, tires having a tread portion suitable for traveling on a snowy road surface have been known. For example, Patent Document 1 below proposes a pneumatic tire having a tread portion divided into blocks by a plurality of main grooves continuously extending in a zigzag shape in the tire circumferential direction and a plurality of lateral grooves communicating between the main grooves. Has been done. The tire of Patent Document 1 exhibits a large traction when traveling on a snowy road surface, and has excellent on-snow performance.

JP-A-2017-128268

However, in the tire of Patent Document 1, heel-and-toe wear that partially wears in the tire circumferential direction may occur at the corners of the block divided by the main groove and the lateral groove, and there is room for improvement in uneven wear resistance performance. was there.

The present invention has been devised in view of the above circumstances, and a main object of the present invention is to provide a tire capable of achieving both snow performance and uneven wear resistance.

The present invention is a tire having a tread portion, and the tread portion is formed with a crown land portion divided by a pair of circumferential grooves extending in the tire circumferential direction, and the crown land portion has a pair. A plurality of crown grooves extending from the circumferential groove to the inside of the crown land portion are provided, and the crown groove communicates with an outer end portion opened in the circumferential groove and the crown groove adjacent to the tire circumferential direction. The land portion of the crown includes a plurality of side blocks divided between the crown groove and the circumferential groove, and the side block includes the inner end portion in a tread plan view. A first corner portion having a sharp angle and a tapered shape is divided adjacent to the tire, and the first corner portion is provided with a step portion extending in a stepwise manner inward in the radial direction of the tire.

In the tire of the present invention, the crown groove has a first inclined portion extending in an inclined direction with respect to the tire axial direction inside the tire axial direction and a first axial direction extending along the tire axial direction outside the tire axial direction. It is desirable to include the part.

In the tire of the present invention, it is desirable that a side tie bar is provided on the outer end side of the first axial direction portion.

In the tire of the present invention, it is desirable that the side tie bar is provided with a first tie bar sipe whose both ends are terminated in the side tie bar.

In the tire of the present invention, it is desirable that the groove width of the first axial portion is smaller than the groove width of the first inclined portion adjacent to the first axial portion.

In the tire of the present invention, it is desirable that a crown tie bar is provided on the inner end side of the first inclined portion.

In the tire of the present invention, it is desirable that the crown groove includes an arc portion extending in an arc shape.

In the tire of the present invention, the land portion of the crown includes a plurality of side blocks divided between the crown groove and the circumferential groove, and the side blocks have an acute angle adjacent to the inner end portion in a tread plan view. The first corner portion having a tapered shape is divided by, and the first corner portion is provided with a stepped portion extending in a stepwise manner inward in the radial direction of the tire.

In such a side block, the first corner portion bites into the snow when traveling on a snowy road surface, and the performance of the tire on the snow can be improved. In addition, this side block can increase the edge component when traveling on a snowy road surface while suppressing the tip of the first corner from touching the ground when traveling on a paved road surface due to the stepped portion. It is possible to achieve both snow performance and uneven wear resistance.

It is a developed view which shows one Embodiment of the tread part of the tire of this invention. It is an enlarged view of the center part of the crown land part. It is an enlarged view of the side block of the crown land part. It is an enlarged view of the circumferential groove. It is an enlarged view of the circumferential groove of another embodiment.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a development view showing a tread portion 2 of the tire 1 of the present embodiment. As shown in FIG. 1, the tire 1 of the present embodiment is suitably used as a pneumatic tire having a tread portion 2 suitable for traveling on a snowy road surface.

In addition to the snowy road surface, the tire 1 may be used as a pneumatic tire for traveling on an uneven terrain road surface such as a muddy land. Further, the tire 1 is not limited to a pneumatic tire, and may be, for example, a non-pneumatic tire in which the inside of the tire 1 is not filled with pressurized air.

The tread portion 2 of the present embodiment is formed with a plurality of circumferential grooves 3 extending in the tire circumferential direction and a plurality of land portions 4 separated by the circumferential grooves 3. For example, one circumferential groove 3 is formed between the tire equator C and the tread end Te.

Here, in the case of a pneumatic tire, the tread end Te is the most outer contact position in the tire axial direction when a normal load is applied to the tire 1 in the normal state and the tire 1 touches the plane at a camber angle of 0 °. The central position in the tire axial direction between the tread end Te is the tire equator C.

The "normal state" is a no-load state in which the tire 1 is rim-assembled on the normal rim and adjusted to the normal internal pressure. Hereinafter, unless otherwise specified, the dimensions and the like of each part of the tire 1 are values measured in this normal state.

A "regular rim" is a rim defined for each tire in the standard system including the standard on which the tire 1 is based. For example, "standard rim" for JATTA, "Design Rim" for TRA, and ETRTO. If so, it is "Measuring Rim".

"Regular internal pressure" is the air pressure defined for each tire in the standard system including the standard on which Tire 1 is based. For JATMA, "maximum air pressure", for TRA, the table "TIRE LOAD LIMITS" The maximum value described in "AT VARIOUS COLD INFLATION PRESSURES", or "INFLATION PRESSURE" for ETRTO.

"Regular load" is the load defined for each tire in the standard system including the standard on which Tire 1 is based. For JATMA, "maximum load capacity", for TRA, the table "TIRE LOAD" The maximum value described in "LIMITS AT VARIOUS COLD INFLATION PRESSURES", or "LOAD CAPACITY" for ETRTO.

The tread portion 2 of the present embodiment is formed with a crown land portion 4A divided by a pair of circumferential grooves 3 and a shoulder land portion 4B divided by the circumferential groove 3 and the tread end Te. As described above, the land portion 4 of the present embodiment includes the crown land portion 4A and the shoulder land portion 4B.

It is desirable that the circumferential groove 3 is formed in a zigzag shape in the tire circumferential direction. Such a circumferential groove 3 can improve the drainage property when traveling on a wet road surface while maintaining the traction when traveling on a snowy road surface, and achieves both the snow performance and the wet performance of the tire 1. be able to.

The crown land portion 4A of the present embodiment is provided with a plurality of crown grooves 9 extending inward from the pair of circumferential grooves 3 to the inside of the crown land portion 4A. Each of the plurality of crown grooves 9 includes, for example, an outer end portion 9a that opens in the circumferential groove 3 and an inner end portion 9b that communicates with the crown groove 9 adjacent in the tire circumferential direction. The crown groove 9 of the present embodiment is continuously extended in the tire circumferential direction as a whole by the plurality of crown grooves 9 without crossing the tire equator C.

The crown land portion 4A includes a center portion 4a divided between crown grooves 9 adjacent to each other in the tire axial direction, and a plurality of side blocks 4b divided between the crown groove 9 and the circumferential groove 3. Is desirable. In the present embodiment, one side block 4b is formed corresponding to one crown groove 9.

It is desirable that the crown groove 9 is provided with a plurality of wide regions 9A having a large groove width and a plurality of narrow regions 9B having a small groove width alternately provided. In the crown groove 9 of the present embodiment, the outer end portion 9a is formed as a narrow region 9B, and the inner end portion 9b is formed as a wide region 9A. It is desirable that the crown groove 9 has at least one set of a wide region 9A and a narrow region 9B between the outer end portion 9a and the inner end portion 9b.

Such a crown groove 9 can reduce the viscosity of the groove wall of the crown groove 9 and the water in the crown groove 9, and can improve the wet performance of the tire 1. Further, since the wide region 9A and the narrow region 9B are repeated in the crown groove 9, the rigidity of the crown land portion 4A can be made uniform, and the uneven wear resistance performance of the tire 1 can be improved. it can.

It is desirable that at least one of the wide region 9A is formed as a changing region in which the groove width changes within the wide region 9A. Further, it is desirable that at least one of the narrow region 9B is formed as a changing region in which the groove width changes within the narrow region 9B. The wide region 9A and the narrow region 9B may include, for example, a constant region in which the groove width does not change within the respective ranges. The outer end portion 9a of the present embodiment is formed as a constant region. On the other hand, it is desirable that the inner end portion 9b is formed as a change region.

Here, the boundary between the wide region 9A and the narrow region 9B is a portion where at least one of the groove walls of the crown groove 9 is rapidly changing. Further, when both the wide region 9A and the narrow region 9B are formed as a change region, the boundary may be an intermediate portion between the wide region 9A and the narrow region 9B whose boundary changes gently. In such a wide region 9A and a narrow region 9B, the viscosity between the groove wall and water can be further reduced, and the wet performance of the tire 1 can be further improved.

FIG. 2 is an enlarged view of the center portion 4a of the crown land portion 4A. As shown in FIG. 2, it is desirable that the crown groove 9 is formed in a zigzag shape by a plurality of bent portions 9c. The crown groove 9 includes, for example, an arc portion 9d extending in an arc shape between the bent portions 9c. Here, the shape of the crown groove 9 is determined based on the center line in the groove width direction of the crown groove 9, and one of the groove walls changes like the boundary between the wide region 9A and the narrow region 9B. It is assumed that the center line of the part is unchanged.

Such a crown groove 9 can exhibit a large traction when traveling on a snowy road surface while suppressing pattern noise when traveling on a paved road surface, and achieves both snow performance and noise performance of the tire 1. be able to.

The center portion 4a of the present embodiment includes a center lateral groove 5 extending between the crown grooves 9 adjacent in the tire axial direction, a center sipe 6 extending between the crown grooves 9 adjacent in the tire axial direction, and a crown groove 9. A center notch 7 recessed inward in the tire axial direction is provided. Such a center portion 4a can increase the edge component when traveling on a snowy road surface while suppressing heel-and-toe wear and chipping when traveling on a paved road surface, and can improve the snow performance and uneven wear resistance of the tire 1. Can be compatible with each other.

The center portion 4a of the present embodiment is divided into a plurality of center blocks 4c by a plurality of center lateral grooves 5. It is desirable that each of the center blocks 4c is provided with a plurality of center sipes 6 and a plurality of center notches 7. Such a center block 4c can further increase the edge component when traveling on a snowy road surface, and can further improve the snow performance of the tire 1.

The center lateral groove 5 includes, for example, a pair of center end portions 5a communicating with the crown groove 9 adjacent in the tire axial direction. It is desirable that a center tie bar 8 is provided on at least one side of the pair of center end portions 5a of the center lateral groove 5. The center lateral groove 5 of the present embodiment is provided with center tie bars 8 at center end portions 5a on both sides. In such a center lateral groove 5, the rigidity of the center block 4c can be improved by the center tie bar 8, heel and toe wear and chipping of the center block 4c can be suppressed, and the uneven wear resistance performance of the tire 1 can be improved.

The depth of the center lateral groove 5 at the center end 5a is preferably 30% to 60% of the maximum depth of the crown groove 9. If the depth at the center end 5a is smaller than 30% of the maximum depth of the crown groove 9, the snow column formed by the center lateral groove 5 may become small, and the effect of improving the performance of the tire 1 on snow may be reduced. is there. If the depth at the center end 5a is larger than 60% of the maximum depth of the crown groove 9, the rigidity of the center block 4c may not be improved, and the effect of improving the uneven wear resistance performance of the tire 1 may be reduced. ..

The center sipe 6 has, for example, end portions 6a on both sides in the tire axial direction. It is desirable that at least one of the ends 6a of the center sipe 6 communicates with the center notch 7. Such a center sipe 6 can easily deform the center block 4c when the center block 4c touches the ground, improve the snow removal property of the crown groove 9, and improve the snow performance of the tire 1.

In the center sipe 6 of the present embodiment, the first center sipe 6A in which the end portions 6a on both sides communicate with the center notch portion 7 and one of the end portions 6a communicate with the center notch portion 7 and the other end portion 6a is bent. It includes a second center sipe 6B that communicates with section 9c. In such a center sipe 6, since the end portions 6a on both sides communicate with the center notch portion 7 or the bent portion 9c, the center block 4c can be more easily deformed, and the snow performance of the tire 1 can be further improved. ..

In the center sipe 6, for example, the depth of the end portions 6a on both sides is smaller than the maximum depth of the central portion of the center sipe 6. The depth of the end portion 6a of the center sipe 6 is preferably 20% to 40% of the maximum depth of the crown groove 9. If the depth of the end portion 6a is smaller than 20% of the maximum depth of the crown groove 9, it is difficult to be deformed even when the center block 4c touches the ground, and the snow removal property of the crown groove 9 may decrease. If the depth of the end portion 6a is larger than 40% of the maximum depth of the crown groove 9, the rigidity of the center block 4c is lowered, and heel-and-toe wear and chipping may occur.

It is desirable that the maximum depth of the center notch 7 is equal to or greater than the depth of the end 6a of the center sipe 6. If the maximum depth of the center notch 7 is smaller than the depth of the end 6a of the center sipe 6, the center notch 7 disappears earlier than the center sipe 6 due to wear during continuous use, and the crown groove 9 There is a risk that the snow removal performance of the car will decrease.

FIG. 3 is an enlarged view of the side block 4b of the crown land portion 4A. As shown in FIG. 3, the crown groove 9 that divides the side block 4b of the present embodiment has a first inclined portion 9C that extends inclined with respect to the tire axial direction inside the tire axial direction and a tire axial direction. Includes a first axial portion 9D extending outward along the tire axial direction.

It is desirable that the first inclined portion 9C extends in a zigzag shape from the inner end portion 9b along the tire circumferential direction. It is desirable that the first axial direction portion 9D extends linearly from the outer end portion 9a along the tire axial direction. In such a crown groove 9, since the first inclined portion 9C and the first axial direction portion 9D are bent, a strong snow column can be formed, and the snow performance of the tire 1 can be improved. ..

A crown tie bar 17 is provided on the inner end portion 9b side of the first inclined portion 9C of the present embodiment. The crown tie bar 17 is formed, for example, from the inner end portion 9b to the first side notch portion 16A described later. Such a crown tie bar 17 can increase the rigidity of the side block 4b and improve the uneven wear resistance performance of the tire 1.

The length of the crown tie bar 17 is preferably 20% to 40% of the pitch length between the crown tie bars 17 adjacent to each other in the tire circumferential direction. The height of the crown groove 9 of the crown tie bar 17 from the groove bottom is preferably 50% to 80% of the maximum depth of the crown groove 9. Therefore, the depth of the inner end portion 9b of the crown groove 9 is 20% to 50% of the maximum depth of the crown groove 9. Such a crown tie bar 17 can improve the rigidity of the side block 4b while maintaining excellent drainage property, and can achieve both wet performance and uneven wear resistance of the tire 1.

The first inclined portion 9C adjacent to the first axial direction portion 9D is preferably formed as a wide region 9A. Further, it is desirable that the first axial direction portion 9D is formed as a narrow region 9B. Such a first inclined portion 9C and a first axial direction portion 9D can suppress pattern noise when traveling on a paved road surface, and can improve the noise performance of the tire 1.

The groove width of the first axial direction portion 9D is preferably 25% to 75% of the groove width of the first inclined portion 9C adjacent to the first axial direction portion 9D. Such a first axial direction portion 9D can suppress pattern noise while maintaining the rigidity of the side block 4b, and can achieve both noise performance and uneven wear resistance of the tire 1.

A side tie bar 11 is provided on the outer end portion 9a side of the first axial direction portion 9D of the present embodiment. Such a side tie bar 11 can further improve the rigidity of the side block 4b while suppressing pattern noise, and can achieve both noise performance and uneven wear resistance of the tire 1.

The height of the crown groove 9 of the side tie bar 11 from the groove bottom is preferably 50% to 80% of the maximum depth of the crown groove 9. Therefore, the depth of the crown groove 9 at the outer end portion 9a is 20% to 50% of the maximum depth of the crown groove 9. Such a side tie bar 11 can improve the rigidity of the side block 4b while suppressing pattern noise, and can achieve both the noise performance of the tire 1 and the uneven wear resistance performance.

It is desirable that the side tie bar 11 be provided with a first tie bar sipe 12 whose ends end within the side tie bar 11. Such a first tie bar sipe 12 can increase the edge component when traveling on a snowy road surface without increasing the pattern noise when traveling on a paved road surface, and can improve the snow performance and noise performance of the tire 1. It can be compatible.

The depth of the first tie bar sipe 12 is preferably 75% to 100% of the height of the crown groove 9 of the side tie bar 11 from the groove bottom. Such a first tie bar sipe 12 is suitable for improving the snow performance and noise performance of the tire 1 in a well-balanced manner.

FIG. 4 is an enlarged view of the circumferential groove 3. As shown in FIG. 4, the angle θ1 with respect to the tire axial direction at the outer end portion 9a of the crown groove 9 is preferably 5 to 10 °. If the angle θ1 is smaller than 5 °, the pattern noise becomes large, and the effect of improving the noise performance of the tire 1 may be reduced. If the angle θ1 is larger than 10 °, the snow removal property of the crown groove 9 is lowered, and the effect of improving the snow performance of the tire 1 may be reduced.

As shown in FIG. 3, it is desirable that the side block 4b is provided with a side lateral groove 10 extending inward in the tire axial direction from the circumferential groove 3 and terminating within the side block 4b. The side lateral groove 10 of the present embodiment has a second inclined portion 10A extending inclining with respect to the tire axial direction inside the tire axial direction and a second axial portion extending along the tire axial direction outside the tire axial direction. Includes 10B and. In such a side lateral groove 10, since the second inclined portion 10A and the second axial direction portion 10B are bent, a strong snow column can be formed, and the snow performance of the tire 1 can be improved. ..

In the tread plan view, the side block 4b of the present embodiment has a first corner portion having an acute angle and a taper shape adjacent to the inner end portion 9b of the crown groove 9 by two crown grooves 9 adjacent to each other in the tire circumferential direction. It is desirable that 4d be classified. Such a first corner portion 4d can bite into the snow when traveling on a snowy road surface, and can improve the performance of the tire 1 on the snow.

The first corner portion 4d of the present embodiment is provided with a step portion 13 extending stepwise inward in the radial direction of the tire. The step portion 13 has two or more steps, and in the present embodiment, the step portion 13 has three steps. Such a stepped portion 13 can increase the edge component when traveling on a snowy road surface while suppressing the tip of the first corner portion 4d from touching the ground when traveling on a paved road surface, and the tire 1 can be on snow. It is possible to achieve both performance and uneven wear resistance.

The side block 4b is formed with a first side wall 4e extending along the circumferential groove 3. The first side wall 4e is provided with a step portion 14 extending stepwise inward in the radial direction of the tire. The step portion 14 has, for example, a three-step portion. It is desirable that the step portion 14 is provided adjacent to the outer end portion 9a of the crown groove 9. Such a step portion 14 can increase the edge component in the tire axial direction when traveling on a snowy road surface, and can improve the performance of the tire 1 on snow. Further, the step portion 14 can reduce the viscosity with water in the crown groove 9 and further improve the wet performance of the tire 1.

It is desirable that the side block 4b is provided with a plurality of side sipes 15 extending from the circumferential groove 3 to the crown groove 9 and a side notch 16 recessed outward from the crown groove 9 in the tire axial direction. In the side sipe 15, for example, the end portion 15a on the side of the crown groove 9 communicates with the side notch portion 16. Such a side sipe 15 can easily deform the side block 4b when the side block 4b touches the ground, improve the snow removal property of the crown groove 9, and improve the snow performance of the tire 1.

The side sipe 15 preferably includes a first side sipe 15A extending from the first side wall 4e. It is desirable that the side notch 16 includes a first side notch 16A through which the first side sipe 15A communicates. Since both sides of the first side sipe 15A communicate with the first side wall 4e and the side cutout portion 16, the side block 4b can be more easily deformed and the performance of the tire 1 on snow can be further improved.

As shown in FIG. 1, the shoulder land portion 4B includes, for example, a shoulder lateral groove 18 extending from the circumferential groove 3 to the tread end Te, and a shoulder land portion 4B extending outward in the tire axial direction from the circumferential groove 3. A terminating shoulder sipe 19 is provided.

The shoulder land portion 4B of the present embodiment is divided into shoulder blocks 4f by a plurality of shoulder lateral grooves 18. It is desirable that each of the shoulder blocks 4f is provided with a plurality of shoulder sipes 19. Such a shoulder block 4f can increase the edge component when traveling on a snowy road surface, and can improve the snow performance of the tire 1.

It is desirable that the shoulder lateral groove 18 is formed in a zigzag shape. Such a shoulder lateral groove 18 can reduce pattern noise when traveling on a paved road surface and improve the noise performance of the tire 1.

As shown in FIG. 4, the shoulder lateral groove 18 includes a shoulder end portion 18a communicating with the circumferential groove 3 at a position where at least a part overlaps the outer end portion 9a in the tire circumferential direction. Such a shoulder lateral groove 18 is smoothly continuous with the crown groove 9 via the circumferential groove 3, and a strong snow column can be formed at the intersection with the circumferential groove 3, so that the tire 1 can be formed on snow. Performance can be improved.

The length of the overlapping portion of the shoulder end portion 18a and the outer end portion 9a in the tire circumferential direction is preferably 25% or less of the length of the outer end portion 9a in the tire circumferential direction. Such shoulder lateral grooves 18 and crown grooves 9 have few portions that come into contact with each other at the same time during traveling, and the noise performance of the tire 1 can be improved.

It is desirable that a shoulder tie bar 20 is provided on the shoulder end 18a side of the shoulder lateral groove 18. Such a shoulder tie bar 20 can improve the rigidity of the shoulder land portion 4B while maintaining excellent drainage, and can achieve both wet performance and uneven wear resistance of the tire 1.

The height of the shoulder lateral groove 18 of the shoulder tie bar 20 from the groove bottom is preferably 50% to 80% of the maximum depth of the shoulder lateral groove 18. Such a shoulder tie bar 20 can improve the rigidity of the shoulder land portion 4B while suppressing pattern noise, and can achieve both the noise performance of the tire 1 and the uneven wear resistance performance.

The angle θ2 of the shoulder lateral groove 18 at the shoulder end 18a with respect to the tire axial direction is preferably 5 to 10 °. If the angle θ2 is smaller than 5 °, the pattern noise becomes large, and the effect of improving the noise performance of the tire 1 may be reduced. If the angle θ2 is larger than 10 °, the snow removal property is lowered, and the effect of improving the performance of the tire 1 on snow may be reduced.

FIG. 5 is an enlarged view of the circumferential groove 3 of another embodiment. Components having the same functions as those in the above-described embodiment are designated by the same reference numerals, and the description thereof will be omitted. As shown in FIG. 5, the shoulder lateral groove 18 of this embodiment is formed in the circumferential groove 3 at a position overlapping with 50% or more of the length of the outer end portion 9a of the crown groove 9 in the tire circumferential direction in the tire circumferential direction. Includes a communicating shoulder end 18a. Since such a shoulder lateral groove 18 can form a stronger snow column at the intersection with the circumferential groove 3 in cooperation with the crown groove 9, the snow performance of the tire 1 can be further improved.

A shoulder tie bar 21 is provided on the shoulder end 18a side of the shoulder lateral groove 18 of this embodiment. It is desirable that the shoulder tie bar 21 be provided with a second tie bar sipe 22 whose ends end within the shoulder tie bar 21. Such a second tie bar sipe 22 can increase the edge component when traveling on a snowy road surface without increasing the pattern noise, and can achieve both the snow performance and the noise performance of the tire 1.

The depth of the second tie bar sipe 22 is preferably 75% to 100% of the height of the shoulder lateral groove 18 of the shoulder tie bar 21 from the groove bottom. Such a second tie bar sipe 22 is suitable for improving the snow performance and noise performance of the tire 1 in a well-balanced manner.

Although the particularly preferable embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and can be modified into various embodiments.

A tire having the basic pattern shown in FIG. 1 was prototyped based on the specifications shown in Tables 1 and 2. The snow performance and uneven wear resistance of each prototype tire were tested. The common specifications and test methods for each prototype tire are as follows.

<Common specifications>
Tire size: 265 / 65R17 112S
Rim size: 17 x 8.0J
Air pressure: 220 kPa

<Snow performance>
One test driver boarded a medium-sized SUV test vehicle with prototype tires mounted on all wheels, and the distance when accelerating from 5 mph to 20 mph on a snow-packed course was measured. The result is represented by an index with a comparative example of 100, and the larger the value, the shorter the distance and the better the performance on snow.

<Uneven wear resistance>
The wear energy of each part of the tread part of the prototype tire was measured using the wear energy measuring device. The result is represented by an index with Comparative Example as 100, and the larger the value, the smaller the variation in wear energy and the better the uneven wear resistance performance.

The test results are shown in Tables 1 and 2.

As a result of the test, it was confirmed that the tires of the examples had improved snow performance and uneven wear resistance performance as compared with the comparative example, and had both snow performance and uneven wear resistance.

1 Tire 2 Tread part 3 Circumferential groove 4A Crown land part 4b Side block 4d First corner part 9 Crown groove 9a Outer end part 9b Inner end part 13 Step part

Claims (7)

A tire with a tread
The tread portion is formed with a crown land portion divided by a pair of circumferential grooves extending in the tire circumferential direction.
The crown land portion is provided with a plurality of crown grooves extending inward of the crown land portion from the pair of circumferential grooves.
The crown groove includes an outer end portion that opens in the circumferential groove and an inner end portion that communicates with the crown groove adjacent to the tire circumferential direction.
The crown land portion includes a plurality of side blocks divided between the crown groove and the circumferential groove.
In the tread plan view, the side block is adjacent to the inner end portion and is divided into an acute-angled and tapered first corner portion.
The first corner portion is provided with a step portion extending in a stepwise manner inward in the radial direction of the tire.
tire. The crown groove includes a first inclined portion extending inward in the tire axial direction and inclined with respect to the tire axial direction, and a first axial portion extending in the outer side in the tire axial direction along the tire axial direction. Item 1. The tire according to item 1. The tire according to claim 2, wherein a side tie bar is provided on the outer end side of the first axial direction portion. The tire according to claim 3, wherein the side tie bar is provided with a first tie bar sipe whose both ends are terminated in the side tie bar. The tire according to any one of claims 2 to 4, wherein the groove width of the first axial direction portion is smaller than the groove width of the first inclined portion adjacent to the first axial direction portion. The tire according to any one of claims 2 to 5, wherein a crown tie bar is provided on the inner end side of the first inclined portion. The tire according to any one of claims 1 to 6, wherein the crown groove includes an arc portion extending in an arc shape.

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