JP7669770B2 - tire - Google Patents

Description

The present invention relates to a tire having a tread portion.

Conventionally, tires have been known in which the land area, divided by multiple circumferential grooves in the tread portion, includes blocks divided by multiple lateral grooves. For example, the tire in the following Patent Document 1 proposes a tire with slots in the middle blocks to improve performance on snow while maintaining steering stability.

Patent Publication 2018-134960

However, providing slots in the blocks to improve performance on snow tends to reduce the rigidity around the slots, resulting in poorer performance on dry tires and on ice, and further improvements were desired even for the tire of Patent Document 1.

The present invention was devised in light of the above-mentioned circumstances, and its main objective is to provide a tire that can improve dry performance, performance on ice, and performance on snow in a well-balanced manner.

The present invention is a tire having a tread portion, the tread portion including a plurality of circumferential grooves extending continuously in the tire circumferential direction and a land portion divided by the circumferential grooves, the land portion including a first land portion divided between a pair of the circumferential grooves, the first land portion including a plurality of first blocks divided by a plurality of first lateral grooves crossing the first land portion in the tire axial direction, the first block including a first edge portion extending in the tire circumferential direction on one side in the tire axial direction and a second edge portion bent so as to be recessed toward the first edge portion on the other side in the tire axial direction, the second edge portion being composed of a pair of gradually increasing portions that gradually increase the width of the first block from a narrowest portion where the axial width of the first block is smallest toward both ends in the tire circumferential direction.

In the tire of the present invention, it is preferable that the first edge portion extends in a straight line.

In the tire of the present invention, the land portion includes a second land portion adjacent to the second edge side of the first land portion, the second land portion includes a plurality of second blocks divided by a plurality of second lateral grooves that cross the second land portion in the tire axial direction, and it is preferable that the edge of the second block on the first land portion side extends linearly.

In the tire of the present invention, it is preferable that the second lateral groove opens into the circumferential groove at a position opposite the narrowest portion via the circumferential groove.

In the tire of the present invention, it is preferable that the first block and the second block each have a plurality of lateral sipes extending in the tire axial direction.

In the tire of the present invention, it is preferable that the first lateral groove has a different groove depth on the first edge side and the second edge side.

In the tire of the present invention, it is preferable that the first lateral groove includes a deep groove portion where the groove depth is large on the first edge side and a shallow groove portion where the groove depth is small on the second edge side.

In the tire of the present invention, it is preferable that the first lateral groove extends linearly in a direction inclined relative to the tire axial direction.

In the tire of the present invention, it is desirable that the distance in the tire circumferential direction between the narrowest portion and the end portion on one side of the second edge portion in the tire circumferential direction of the first block is 0.5 to 2.0 times the distance in the tire circumferential direction between the narrowest portion and the end portion on the other side of the second edge portion in the tire circumferential direction.

In the tire of the present invention, it is preferable that the first edge of the first block extends parallel to the tire circumferential direction.

In the tire of the present invention, the tread portion has an asymmetric tread pattern with a specified orientation when mounted on a vehicle, the circumferential groove includes an inner shoulder circumferential groove arranged on the innermost tread end side when mounted on a vehicle, and an inner crown circumferential groove arranged between the inner shoulder circumferential groove and the tire equator, and the first land portion is preferably an inner middle land portion divided by the inner shoulder circumferential groove and the inner crown circumferential groove.

In the tire of the present invention, the first block includes a first edge portion that extends circumferentially on one side in the tire axial direction, and a second edge portion that is bent so as to be recessed toward the first edge portion on the other side in the tire axial direction, and the second edge portion is composed of a pair of gradually increasing portions that gradually increase the width of the first block from a narrowest portion, where the axial width of the first block is the smallest, toward both ends in the tire circumferential direction.

Since the second edge of such a first block forms a slot portion in its entirety, it is possible to suppress local changes in rigidity and improve the tire's dry performance and performance on ice. In addition, this first block can generate a large snow column shear force due to the high rigidity of the gradually increasing portion, thereby improving the tire's performance on snow. Therefore, the tire of the present invention can improve dry performance, performance on ice, and performance on snow in a well-balanced manner.

1 is a development view showing one embodiment of a tread portion of a tire of the present invention. FIG. 2 is an enlarged view of a first land portion in FIG. 1 . FIG. 2 is an enlarged view of a third land portion and a fourth land portion of FIG. 1 .

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 a tire 1 of this embodiment. As shown in Fig. 1, the tire 1 of this embodiment has a tread portion 2 that comes into contact with the road surface during driving. The tire 1 can be suitably adopted, for example, as a pneumatic tire for passenger cars used in winter. The tire 1 is not limited to such an embodiment, and may be adopted, for example, as a heavy load tire, a tire for two-wheeled vehicles, a non-pneumatic tire that is not filled with pressurized air inside, and the like.

The tread portion 2 of this embodiment includes a plurality of circumferential grooves 3 that extend continuously in the tire circumferential direction, a land portion 4 that is divided into the circumferential grooves 3, and a plurality of lateral grooves 5 that cross the land portion 4 in the tire axial direction. Such a tread portion 2 can generate snow column shear force with the circumferential grooves 3 and the lateral grooves 5, and the circumferential grooves 3 and the lateral grooves 5 can also exert an edge effect, which helps to improve the steering stability performance of the tire 1 when driving on snowy roads (hereinafter referred to as "snow performance") and the steering stability performance when driving on icy roads (hereinafter referred to as "ice performance").

The land portion 4 includes, for example, a first land portion 4A that is divided between a pair of circumferential grooves 3. The lateral groove 5 includes, for example, a first lateral groove 5A that is provided in the first land portion 4A. In this embodiment, the first land portion 4A includes a plurality of first blocks 6 that are divided by a plurality of first lateral grooves 5A that cross the first land portion 4A in the tire axial direction.

2 is an enlarged view of the first land portion 4A in FIG. 1. As shown in FIG. 2, the first block 6 of this embodiment includes a first edge portion 7 extending circumferentially on one side in the tire axial direction, and a second edge portion 8 bent so as to be recessed toward the first edge portion 7 on the other side in the tire axial direction. The second edge portion 8 is preferably composed of a pair of gradually increasing portions 8d, 8e that gradually increase the width of the first block 6 from a narrowest portion 8a, where the axial width W1 of the first block 6 is the smallest, toward both ends 8b, 8c in the tire circumferential direction.

Since the second edge portion 8 of this type of first block 6 forms a slot portion over its entirety, it is possible to suppress localized changes in rigidity and improve the steering stability performance (hereinafter referred to as "dry performance") of the tire 1 when traveling on dry roads and the performance on ice. Furthermore, this first block 6 can generate a large snow column shear force due to the high rigidity of the gradually increasing portions 8d, 8e, thereby improving the performance on snow of the tire 1. Therefore, the tire 1 of this embodiment can improve dry performance, performance on ice, and performance on snow in a well-balanced manner.

In a more preferred embodiment, the first edge 7 extends in a straight line. Such a first edge 7 improves the rigidity of the first block 6 and helps to improve the tire 1's dry performance, performance on ice, and performance on snow in a well-balanced manner.

The recess amount d of the second edge portion 8 is preferably 5% to 30% of the axial width W1 of the narrowest portion 8a of the first block 6. Such a first block 6 can generate a large snow column shear force while improving the ratio and rigidity of the first land portion 4A, and can improve the dry performance, ice performance, and snow performance of the tire 1 in a well-balanced manner.

The first block 6 preferably has a circumferential distance L1 between the narrowest portion 8a and the end 8b on one side of the second edge 8 in the tire circumferential direction, which is 0.5 to 2.0 times the circumferential distance L2 between the narrowest portion 8a and the end 8c on the other side of the second edge 8 in the tire circumferential direction. Such a first block 6 has an averaged rigidity, which can further improve the dry performance of the tire 1.

Here, when the section from the narrowest part 8a to the end 8b on one side is defined as a first gradually increasing section 8d, and the section from the narrowest part 8a to the end 8c on the other side is defined as a second gradually increasing section 8e, distance L1 is the length of the first gradually increasing section 8d in the tire circumferential direction. Distance L2 is the length of the second gradually increasing section 8e in the tire circumferential direction.

It is desirable for the first block 6 to have the first edge 7 extending parallel to the tire circumferential direction. Such a first block 6 prevents the rigidity of the first edge 7 side from decreasing, and can further improve the on-ice performance of the tire 1.

The first lateral groove 5A of this embodiment extends linearly in a direction inclined relative to the tire axial direction. The first lateral groove 5A has, for example, a first groove edge 9 on one side in the tire circumferential direction and a second groove edge 10 on the other side in the tire circumferential direction. It is desirable that at least one of the first groove edge 9 and the second groove edge 10 of the first lateral groove 5A extends linearly.

The first lateral grooves 5A are linear, which helps maintain the high rigidity of the first blocks 6, and are inclined, which provides an edge effect in the tire circumferential and axial directions. As a result, the tire 1 of this embodiment can achieve a good balance between dry performance, performance on ice, and performance on snow.

It is desirable for the first transverse groove 5A to have different groove depths on the first edge 7 side and the second edge 8 side. The groove depth of such a first transverse groove 5A can be appropriately set according to the rigidity required for the first block 6 and the amount of snow compaction required for the first transverse groove 5A.

The first lateral groove 5A of this embodiment includes a deep groove portion 5a with a large groove depth on the first edge 7 side and a shallow groove portion 5b with a small groove depth on the second edge 8 side. Such a first lateral groove 5A can increase the rigidity of the second edge 8 side of the first block 6, where rigidity is likely to decrease with bending, and can further improve the on-ice performance of the tire 1. In addition, the first lateral groove 5A can strongly compact snow with the shallow groove portion 5b, generating a large snow column shear force, and can improve the on-snow performance of the tire 1.

It is desirable that the groove width W2 of the deep groove portion 5a of the first transverse groove 5A is larger than the groove width W3 of the shallow groove portion 5b. In the first transverse groove 5A of this embodiment, the first groove edge portion 9 extends linearly and the second groove edge portion 10 is formed in a stepped shape, so that the groove width W2 of the deep groove portion 5a is larger than the groove width W3 of the shallow groove portion 5b.

Such first lateral grooves 5A can pack more snow in the deep groove portion 5a, improving the on-snow performance of the tire 1. In addition, the first lateral grooves 5A are useful for increasing the rigidity of the second edge portion 8 side of the first block 6, which is prone to losing rigidity due to bending, thereby further improving the on-ice performance of the tire 1.

The first block 6 of this embodiment has multiple lateral sipes 11 extending in the tire axial direction. In this specification, a sipe is a cut that is perpendicular to the longitudinal direction and has a width of 2 mm or less. In this specification, unless otherwise specified, the dimensions of each part of the tire 1 are values measured in a normal state. In the case of a pneumatic tire, the "normal state" refers to an unloaded state in which the tire 1 is mounted on a normal rim and adjusted to the normal internal pressure.

A "genuine rim" is a rim that is determined for each tire by a standard system that includes the standard on which tire 1 is based, such as a "standard rim" for JATMA, a "design rim" for TRA, and a "measuring rim" for ETRTO. A "genuine rim" is a rim that is determined for each tire by the manufacturer, etc., when there is no standard system that includes the standard on which tire 1 is based.

"Normal internal pressure" is the air pressure set for each tire by each standard in the standard system including the standard on which tire 1 is based. For JATMA, it is the "maximum air pressure", for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and for ETRTO, it is the "INFLATION PRESSURE". "Normal internal pressure" is the air pressure set for each tire by the manufacturer, etc., if there is no standard system including the standard on which tire 1 is based.

For example, at least one of the lateral sipes 11 of the first block 6 is connected to the circumferential groove 3. In this embodiment, the lateral sipes 11 of the first block 6 extend in a zigzag pattern in a direction inclined to the tire axial direction. Such a first block 6 can further improve the on-ice performance of the tire 1 due to the edge effect of the lateral sipes 11. Note that the lateral sipes 11 of the first block 6 are not limited to this form, and for example, both ends may terminate within the first block 6, or they may extend in a straight line.

As shown in FIG. 1, it is preferable that the land portion 4 includes a second land portion 4B adjacent to the second edge portion 8 side of the first land portion 4A, and a third land portion 4C adjacent to the first edge portion 7 side of the first land portion 4A. The land portion 4 may further include, for example, a fourth land portion 4D adjacent to the third land portion 4C on the side opposite the first land portion 4A, and a fifth land portion 4E adjacent to the fourth land portion 4D on the side opposite the third land portion 4C.

The lateral grooves 5 include, for example, a second lateral groove 5B provided in the second land portion 4B, a third lateral groove 5C provided in the third land portion 4C, a fourth lateral groove 5D provided in the fourth land portion 4D, and a fifth lateral groove 5E provided in the fifth land portion 4E.

The second land portion 4B of this embodiment includes a plurality of second blocks 12 divided by a plurality of second lateral grooves 5B that cross the second land portion 4B in the tire axial direction. The second blocks 12 of this embodiment have an edge portion 13 on the first land portion 4A side that extends in a straight line. Such second blocks 12 suppress a decrease in rigidity on the first land portion 4A side, and can further improve the on-ice performance of the tire 1.

In this embodiment, the circumferential groove 3 between the first land portion 4A and the second land portion 4B has a smoothly changing groove width due to the second edge portion 8 of the first block 6 and the edge portion 13 of the second block 12. That is, the groove width of this circumferential groove 3 is largest at the narrowest portion 8a of the first block 6, gradually decreases due to the gradually increasing portions 8d and 8e of the second edge portion 8, and is smallest at the ends 8b and 8c of the first block 6. Such a circumferential groove 3 can generate a large snow column shear force by changing the groove width with the bending of the second edge portion 8, and can further improve the on-snow performance of the tire 1.

The second block 12 of this embodiment has a plurality of lateral sipes 14 extending in the tire axial direction. The lateral sipes 14 of the second block 12 are connected to the circumferential groove 3, for example. The lateral sipes 14 of the second block 12 of this embodiment extend in a zigzag shape in a direction inclined in the opposite direction to the lateral sipes 11 of the first block 6 with respect to the tire axial direction. The lateral sipes 14 of the second block 12 have, for example, an interrupted portion 14a that is interrupted midway in the longitudinal direction.

Such second blocks 12 can further improve the on-ice performance of the tire 1 due to the edge effect of the lateral sipes 14. Note that the lateral sipes 14 of the second blocks 12 are not limited to this form, and may, for example, terminate without communicating with the circumferential groove 3, extend in a straight line, or not have an interrupted portion 14a.

In this embodiment, the second lateral groove 5B extends linearly in a direction inclined in the opposite direction to the first lateral groove 5A. The second lateral groove 5B has, for example, a constant groove width W4. The linear shape of the second lateral groove 5B helps maintain high rigidity of the second block 12, and the inclination can provide an edge effect in the tire circumferential direction and the tire axial direction. Note that the second lateral groove 5B is not limited to this form, and may extend in a curved shape, or the groove width W4 may vary, for example.

The second lateral groove 5B preferably opens into the circumferential groove 3 at a position facing the narrowest part 8a of the second edge 8 of the first block 6 via the circumferential groove 3. Such second lateral groove 5B can cooperate with the second edge 8 of the first block 6 to generate a large snow column shear force, improving the on-snow performance of the tire 1.

Figure 3 is an enlarged view of the third land portion 4C and the fourth land portion 4D in Figure 1. As shown in Figure 3, the third land portion 4C is preferably divided by a pair of circumferential grooves 3. In this embodiment, the third land portion 4C includes a plurality of third blocks 15 divided by a plurality of third lateral grooves 5C that cross the third land portion 4C in the tire axial direction. The third lateral groove 5C has, for example, a third groove edge portion 16 on one side in the tire circumferential direction and a fourth groove edge portion 17 on the other side in the tire circumferential direction.

In this embodiment, the third groove edge 16 extends linearly. The fourth groove edge 17 preferably comprises a first portion 17a extending parallel to the third groove edge 16, and a second portion 17b extending from the first portion 17a so that the groove width gradually increases. For this reason, the fourth groove edge 17 extends in a bent manner due to the first portion 17a and the second portion 17b.

By varying the groove width, such third lateral grooves 5C can improve traction on snowy roads and improve the on-snow performance of the tire 1. In addition, since the third lateral grooves 5C do not add other slots or grooves to the third land portion 4C that the third lateral grooves 5C cross, it is possible to prevent a decrease in the ratio and rigidity of the third land portion 4C, and it is possible to improve the dry performance and on-ice performance of the tire 1. Therefore, the tire 1 of this embodiment can improve dry performance, on-ice performance, and on-snow performance in a balanced manner.

The third groove edge 16 preferably extends in a direction inclined relative to the tire axial direction. In this embodiment, the third groove edge 16 extends in a direction inclined in the opposite direction to the first lateral groove 5A. Such a third groove edge 16 can exert an edge effect in the tire circumferential direction and the tire axial direction, improving the on-ice performance of the tire 1.

It is desirable that the first portion 17a and the second portion 17b of the fourth groove edge 17 each extend linearly. Such a fourth groove edge 17 helps prevent a decrease in the rigidity of the third block 15 and improves the dry performance and ice performance of the tire 1.

The axial length L4 of the second portion 17b is preferably 50% to 200% of the axial length L3 of the first portion 17a. Such a fourth groove edge 17 provides an excellent balance between the first portion 17a and the second portion 17b, and helps to improve the dry performance, ice performance, and snow performance of the tire 1 in a well-balanced manner.

It is desirable that the groove depth of the third lateral groove 5C in the region R2 having the second portion 17b is greater than the groove depth of the third lateral groove 5C in the region R1 having the first portion 17a. Such a third lateral groove 5C can compact more snow in the region R2 having the second portion 17b, and can strongly compact snow in the region R1 having the first portion 17a, generating a large snow column shear force. Therefore, the tire 1 of this embodiment can further improve on-snow performance.

The groove depth of the third lateral grooves 5C in the region R2 having the second portion 17b is preferably 60% to 100% of the groove depth of the circumferential grooves 3. Such third lateral grooves 5C help prevent a decrease in the rigidity of the third blocks 15 and improve the dry performance and on-ice performance of the tire 1.

In this embodiment, the third land portion 4C has a circumferential narrow groove 18 that extends in the tire circumferential direction. It is preferable that the circumferential narrow groove 18 communicates with the first portion 17a. Such a circumferential narrow groove 18 can exert an edge effect while maintaining the high rigidity of the third land portion 4C, and can further improve the on-ice performance of the tire 1.

The third block 15 of this embodiment has a plurality of lateral sipes 19 extending in the tire axial direction. At least one of the lateral sipes 19 of the third block 15, for example, has at least one end connected to the circumferential groove 3. The lateral sipes 19 of the third block 15 of this embodiment extend in a zigzag shape in a direction inclined in the opposite direction to the lateral sipes 11 of the first block 6 with respect to the tire axial direction. The lateral sipes 19 of the third block 15, for example, have a discontinuous portion 19a that is interrupted without communicating with the circumferential narrow groove 18. That is, the circumferential narrow groove 18 of this embodiment is provided in the discontinuous portion 19a.

Such third blocks 15 can further improve the on-ice performance of the tire 1 due to the edge effect of the lateral sipes 19. Note that the lateral sipes 19 of the third blocks 15 are not limited to this form, and may, for example, terminate without communicating with the circumferential groove 3, extend linearly, or communicate with the circumferential narrow groove 18.

The third lateral groove 5C includes, for example, an opening 5c that opens into the circumferential groove 3 on the second portion 17b side. In this embodiment, the groove width W6 of the third lateral groove 5C at the opening 5c is larger than the groove width W5 of the third lateral groove 5C in the region R1 having the first portion 17a. Here, the groove width W6 of the third lateral groove 5C at the opening 5c is the maximum groove width of the third lateral groove 5C in the region R2 having the second portion 17b.

The fourth land portion 4D is preferably divided by a pair of circumferential grooves 3. In this embodiment, the fourth land portion 4D includes a plurality of fourth blocks 20 divided by a plurality of fourth lateral grooves 5D that cross the fourth land portion 4D in the tire axial direction. In this embodiment, the fourth lateral grooves 5D extend linearly in a direction that is inclined in the opposite direction to the third lateral grooves 5C.

The fourth lateral groove 5D in this embodiment has a constant groove width W7. The fourth lateral groove 5D is linear, which helps maintain the high rigidity of the fourth block 20, and is inclined, which provides an edge effect in the tire circumferential direction and tire axial direction. Note that the fourth lateral groove 5D is not limited to this form, and may extend in a curved shape, for example, or the groove width W7 may vary.

The fourth lateral groove 5D of this embodiment opens into the circumferential groove 3 at a position opposite the opening 5c of the third lateral groove 5C via the circumferential groove 3. Such third lateral groove 5C and fourth lateral groove 5D cooperate with each other to generate a large snow column shear force, improving the on-snow performance of the tire 1.

The groove width W6 of the third lateral groove 5C at the opening 5c is preferably equal to or less than the groove width W7 of the fourth lateral groove 5D. Such a third lateral groove 5C can suppress a decrease in the ratio and rigidity of the third land portion 4C, and can improve the dry performance and on-ice performance of the tire 1.

The groove width W5 of the third lateral groove 5C in the region R1 having the first portion 17a is preferably 30% to 50% of the groove width W7 of the fourth lateral groove 5D. Such a third lateral groove 5C can suppress a decrease in the ratio and rigidity of the third land portion 4C, and can improve the dry performance and on-ice performance of the tire 1.

The fourth block 20 of this embodiment has a plurality of lateral sipes 21 extending in the tire axial direction. For example, at least one end of the lateral sipes 21 of the fourth block 20 communicates with the circumferential groove 3. The lateral sipes 21 of the fourth block 20 of this embodiment extend in a zigzag shape in a direction inclined in the opposite direction to the lateral sipes 19 of the third block 15 with respect to the tire axial direction. The lateral sipes 21 of the fourth block 20 have, for example, an interrupted portion 21a that is interrupted midway in the longitudinal direction.

Such a fourth block 20 can further improve the on-ice performance of the tire 1 due to the edge effect of the lateral sipes 21. Note that the lateral sipes 21 of the fourth block 20 are not limited to this form, and may, for example, terminate without connecting to the circumferential groove 3, extend in a straight line, or not have an interrupted portion 21a.

As shown in FIG. 1, the fourth block 20 has a slot 23, for example, on the edge 22 on the fifth land portion 4E side. The slot 23 is preferably provided in a position facing the fifth lateral groove 5E via the circumferential groove 3. Such a slot 23 can cooperate with the fifth lateral groove 5E to generate a large snow column shear force, improving the on-snow performance of the tire 1.

The fifth land portion 4E of this embodiment includes a plurality of fifth blocks 24 divided by a plurality of fifth lateral grooves 5E that cross the fifth land portion 4E in the tire axial direction. The fifth blocks 24 of this embodiment have an edge 25 on the fourth land portion 4D side that extends in a straight line. Such fifth blocks 24 suppress a decrease in rigidity on the fourth land portion 4D side, and can further improve the on-ice performance of the tire 1.

The fifth lateral groove 5E of this embodiment extends linearly in a direction inclined in the opposite direction to the fourth lateral groove 5D. The fifth lateral groove 5E has, for example, a constant groove width W8. The fifth lateral groove 5E is linear, which helps maintain high rigidity of the fifth block 24, and is inclined, which can provide an edge effect in the tire circumferential direction and the tire axial direction. Note that the fifth lateral groove 5E is not limited to this form, and may extend in a curved shape, or the groove width W8 may vary, for example.

The fifth block 24 has a slot 26, for example, on the edge 25 on the fourth land portion 4D side. The slot 26 is preferably provided in a position facing the fourth lateral groove 5D via the circumferential groove 3. Such a slot 26 can cooperate with the fourth lateral groove 5D to generate a large snow column shear force, improving the on-snow performance of the tire 1.

The fifth block 24 of this embodiment has a plurality of lateral sipes 27 extending in the tire axial direction. At least one of the lateral sipes 27 of the fifth block 24 is connected to the circumferential groove 3, for example. The lateral sipes 27 of the fifth block 24 of this embodiment extend in a zigzag shape in a direction inclined in the opposite direction to the lateral sipes 21 of the fourth block 20 with respect to the tire axial direction. The lateral sipes 27 of the fifth block 24 have, for example, an interrupted portion 27a that is interrupted midway in the longitudinal direction.

The fifth block 24 can further improve the on-ice performance of the tire 1 due to the edge effect of the lateral sipes 27. Note that the lateral sipes 27 of the fifth block 24 are not limited to this form, and may, for example, terminate without communicating with the circumferential groove 3, extend in a straight line, or not have an interrupted portion 27a.

The tread portion 2 of this embodiment has an asymmetric tread pattern with a specified orientation for installation on a vehicle. The tread portion 2 includes, for example, an outer tread end To located on the outer side of the vehicle when installed on the vehicle, and an inner tread end Ti located on the inner side of the vehicle.

Here, in the case where the tire 1 is a pneumatic tire, the "outer tread end To" and the "inner tread end Ti" are the axially outermost contact points when the tire 1 in a normal state is loaded with a normal load and contacts a flat surface with a camber angle of 0°. The tire equator C is the central position in the tire axial direction between the outer tread end To and the inner tread end Ti.

"Normal load" is the load determined for each tire by the standard system including the standard on which tire 1 is based. For JATMA, it is "maximum load capacity." For TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." For ETRTO, it is "LOAD CAPACITY." "Normal load" is the load determined for each tire by the manufacturer, etc., when there is no standard system including the standard on which tire 1 is based.

The circumferential grooves 3 of this embodiment include an inner shoulder circumferential groove 3A arranged on the innermost tread edge Ti side when mounted on a vehicle, and an inner crown circumferential groove 3B arranged between the inner shoulder circumferential groove 3A and the tire equator C. It is preferable that the circumferential grooves 3 further include an outer crown circumferential groove 3C adjacent to the inner crown circumferential groove 3B across the tire equator C, and an outer shoulder circumferential groove 3D arranged on the outermost tread edge To side.

The inner shoulder circumferential groove 3A of this embodiment is a circumferential groove 3 between the second edge 8 of the first land portion 4A and the edge 13 of the second land portion 4B. Such an inner shoulder circumferential groove 3A can generate a large snow column shear force by changing the groove width as the second edge 8 bends, thereby further improving the on-snow performance of the tire 1.

It is desirable that the groove width of the inner crown circumferential groove 3B be greater than the groove width of the outer crown circumferential groove 3C. Such a tread portion 2 can pack more snow on the inside of the vehicle when mounted on the vehicle, improving the on-snow performance of the tire 1.

The first land portion 4A in this embodiment is an inner middle land portion divided by the inner shoulder circumferential groove 3A and the inner crown circumferential groove 3B. The second land portion 4B in this embodiment is an inner shoulder land portion divided between the inner shoulder circumferential groove 3A and the inner tread edge Ti. The third land portion 4C in this embodiment is a crown land portion divided by the inner crown circumferential groove 3B and the outer crown circumferential groove 3C and disposed on the tire equator C.

The fourth land portion 4D in this embodiment is an outer middle land portion divided by the outer crown circumferential groove 3C and the outer shoulder circumferential groove 3D. The fifth land portion 4E in this embodiment is an outer shoulder land portion divided between the outer shoulder circumferential groove 3E and the outer tread edge To.

As shown in Figures 1 and 2, in the first land portion 4A, it is desirable that the deep groove portion 5a of the first lateral groove 5A be located on the vehicle outer side of the shallow groove portion 5b when the tire is mounted on the vehicle. In this embodiment, the deep groove portion 5a of the first lateral groove 5A is located closer to the tire equator C than the shallow groove portion 5b. Such a first lateral groove 5A can compact more snow on the inner side in the tire axial direction, improving the on-snow performance of the tire 1.

As shown in Figures 1 and 3, in the third land portion 4C, the second portion 17b of the fourth groove edge portion 17 of the third lateral groove 5C of this embodiment is located on the vehicle outer side of the first portion 17a when mounted on the vehicle. Such a third lateral groove 5C can generate a larger snow column shear force on the vehicle outer side, improving the on-snow performance of the tire 1.

The second portion 17b is preferably disposed at a position straddling the tire equator C. Such third lateral grooves 5C have a gradually increasing groove width at the axial center of the tread portion 2, which can generate a larger snow column shear force and improve the on-snow performance of the tire 1.

The above describes in detail a particularly preferred embodiment of the present invention, but the present invention is not limited to the above-described embodiment and can be modified in various ways.

A prototype tire of the embodiment having the tread pattern of Figure 1 was produced based on the specifications of Table 1. As a comparative example, a prototype tire was produced in which a conventional partial slot was provided in the center of the first block in the tire circumferential direction. The slot of the comparative example has a slot width in the tire circumferential direction that is smaller than the slot length in the tire axial direction, and the slot length is equal to the recess amount d of Example 1. The prototype tire was used to test the dry performance, ice performance, and snow performance. The common specifications and test methods are as follows.

<Common specifications>
Tire size: 195/65R15
Rim size: 15 x 6.0JJ
Air pressure: 200kPa
Test vehicle: Front-wheel drive mid-size passenger car

<Dry performance>
The test vehicle was fitted with the prototype tires on all wheels, and the test driver evaluated the steering stability performance when the vehicle was driven on a test course on dry roads. Similar tests were performed by multiple test drivers, and the total score was calculated. The results were expressed as an index, with the total score of the comparative example being 100, and the higher the value, the better the dry performance.

<Ice performance>
A test vehicle fitted with prototype tires was driven on a test course on an icy road surface, and the steering stability performance was evaluated by the test driver's senses. Similar tests were conducted by multiple test drivers, and the total score was calculated. The results were expressed as an index, with the total score of the comparative example being 100, and the higher the value, the better the performance on ice.

<Snow performance>
The test vehicle was fitted with the prototype tires on all wheels, and the steering stability performance was evaluated by the test driver's senses when the vehicle was driven on a test course on snowy roads. Similar tests were performed by multiple test drivers, and the total score was calculated. The results were expressed as an index, with the total score of the comparative example being 100, and the higher the index value, the better the performance on snow.

The results of the tests are shown in Table 1.

The test results confirmed that the Example tires had better dry performance, ice performance, and snow performance than the Comparative Example tires, and that the overall performance, determined by the sum of these values, was also improved, resulting in a well-balanced improvement in dry performance, ice performance, and snow performance.

Reference Signs List 1 Tire 2 Tread portion 3 Circumferential groove 4 Land portion 4A First land portion 5A First lateral groove 6 First block 7 First groove edge portion 8 Second groove edge portion 8a Narrowest portion 8b End portion 8c End portion 8d Gradually increasing portion 8e Gradually increasing portion

Claims (9)

A tire having a tread portion,
The tread portion includes a plurality of circumferential grooves extending continuously in a tire circumferential direction and a land portion divided by the circumferential grooves,
The land portion includes a first land portion partitioned between the pair of circumferential grooves,
The first land portion includes a plurality of first blocks divided by a plurality of first lateral grooves that cross the first land portion in the tire axial direction,
The first block includes a first edge portion extending in a tire circumferential direction on one side in the tire axial direction and a second edge portion bent so as to be recessed toward the first edge portion on the other side in the tire axial direction,
the second edge portion is composed of a pair of gradually increasing portions that gradually increase the width of the first block from a narrowest portion, where the width of the first block in the tire axial direction is smallest, toward both ends in the tire circumferential direction,
the land portion includes a second land portion adjacent to the first land portion on the second edge portion side,
The second land portion includes a plurality of second blocks divided by a plurality of second lateral grooves that cross the second land portion in the tire axial direction,
The second block has an edge portion on the first land portion side extending linearly,
The second lateral groove opens into the circumferential groove at a position facing the narrowest portion with the circumferential groove interposed therebetween.
tire. The tire according to claim 1 , wherein the first block and the second block each have a plurality of lateral sipes extending in an axial direction of the tire. A tire having a tread portion,
The tread portion includes a plurality of circumferential grooves extending continuously in a tire circumferential direction and a land portion divided by the circumferential grooves,
The land portion includes a first land portion partitioned between the pair of circumferential grooves,
The first land portion includes a plurality of first blocks divided by a plurality of first lateral grooves that cross the first land portion in the tire axial direction,
The first block includes a first edge portion extending in a tire circumferential direction on one side in the tire axial direction and a second edge portion bent so as to be recessed toward the first edge portion on the other side in the tire axial direction,
the second edge portion is composed of a pair of gradually increasing portions that gradually increase the width of the first block from a narrowest portion, where the width of the first block in the tire axial direction is smallest, toward both ends in the tire circumferential direction,
The first transverse groove has a different groove depth between the first edge portion side and the second edge portion side .
tire. The tire according to claim 3 , wherein the first lateral groove includes a deep groove portion having a larger groove depth on the first edge side and a shallow groove portion having a smaller groove depth on the second edge side. 5. The tire according to claim 1 , wherein the first edge portion extends in a straight line. The tire according to claim 1 , wherein the first lateral groove extends linearly in a direction inclined with respect to the tire axial direction. 7. The tire according to claim 1, wherein the first block has a circumferential distance between the narrowest portion and the end portion on one side in the tire circumferential direction of the second edge portion that is 0.5 to 2.0 times the circumferential distance between the narrowest portion and the end portion on the other side in the tire circumferential direction of the second edge portion . The tire according to claim 1 , wherein the first edge portion of the first block extends parallel to the tire circumferential direction. The tread portion has an asymmetric tread pattern with a specified orientation for mounting on a vehicle,
the circumferential groove includes an inner shoulder circumferential groove disposed on an innermost tread end side when mounted on a vehicle, and an inner crown circumferential groove disposed between the inner shoulder circumferential groove and a tire equator,
The tire according to claim 1 , wherein the first land portion is an inner middle land portion divided by the inner shoulder circumferential groove and the inner crown circumferential groove.

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