JP7467955B2 - tire - Google Patents

Description

The present invention relates to a tire.

Patent Document 1 below proposes a pneumatic tire with inclined grooves in the tread portion. The pneumatic tire of Patent Document 1 is expected to improve wet performance by specifying the inclined grooves.

JP 2001-206020 A

Incidentally, it is known that increasing the rigidity of each land portion of the tread and generating a large cornering force is an effective way to improve the cornering performance of a tire on dry roads. On the other hand, if the number of grooves and sipes arranged on the land portion is reduced in order to increase the rigidity of the land portion, the drainage performance of the tread portion is not sufficiently ensured, and the cornering performance on wet roads (hereinafter referred to as "wet cornering performance") tends to be impaired. Therefore, in order to improve wet cornering performance, it is necessary to improve the rigidity of the land portion and ensure drainage performance.

The present invention was devised in consideration of the above problems, and its main objective is to provide a tire with improved wet cornering performance.

The present invention is a tire having a tread portion, the tread portion including a first land portion, the first land portion including a first longitudinal edge extending in the tire circumferential direction, a second longitudinal edge extending in the tire circumferential direction, and a tread surface therebetween, the first land portion being provided with a first sipe and a second sipe extending from the first longitudinal edge, and a lateral groove extending from the second longitudinal edge between the first sipe and the second sipe and terminating without reaching the first longitudinal edge, the groove width of the lateral groove being greater than the width of the first sipe and the second sipe, and the first sipe and the second sipe communicating with the lateral groove without directly communicating with the second longitudinal edge.

In the tire of the present invention, the lateral groove includes a discontinuous end that terminates within the tread surface of the first land portion, a first communicating portion with the first sipe, and a second communicating portion with the second sipe, and it is preferable that the first communicating portion and the second communicating portion are each located closer to the second longitudinal edge than the discontinuous end.

In the tire of the present invention, it is preferable that the first communicating portion and the second communicating portion are each located closer to the discontinuous end than the axial center position of the lateral groove.

In the tire of the present invention, it is preferable that the first communicating portion and the second communicating portion are located at the same position in the tire axial direction.

In the tire of the present invention, it is desirable that the minimum distance in the tire axial direction from the discontinuous end to the first communicating portion or the second communicating portion is 15% to 40% of the maximum distance in the tire axial direction from the first vertical edge to the first communicating portion or the second communicating portion.

In the tire of the present invention, it is preferable that the lateral groove includes a discontinuous end that terminates within the tread surface of the first land portion, and that the depth of the lateral groove gradually decreases toward the discontinuous end.

In the tire of the present invention, it is preferable that the bottom surface of the lateral groove is curved in an arc shape on the side of the discontinuous end in a cross section perpendicular to the longitudinal direction of the lateral groove.

In the tire of the present invention, it is desirable that the distance in the tire circumferential direction from the communication part of the first sipe at the first longitudinal edge to the groove center line of the lateral groove is 30% to 70% of the distance in the tire circumferential direction from the communication part of the first sipe at the first longitudinal edge to the communication part of the second sipe.

In the tire of the present invention, it is preferable that the first sipe and the second sipe each extend into the lateral groove without branching.

In the tire of the present invention, the first land portion includes a block piece surrounded by the first longitudinal edge, the first sipe, and the second sipe, and it is preferable that the length of the block piece in the tire axial direction is 30% to 70% of the length of the block piece in the tire circumferential direction.

In the tire of the present invention, it is preferable that the first sipe and the second sipe each include a lateral sipe portion extending in the tire axial direction and a longitudinal sipe portion extending in the tire circumferential direction.

In the tire of the present invention, it is desirable that the maximum depth of the longitudinal sipe portion is smaller than the maximum depth of the transverse sipe portion.

The tire of the present invention, by adopting the above-mentioned configuration, is able to exhibit excellent wet cornering performance.

1 is a development view of a tread portion of a tire according to one embodiment of the present invention. FIG. 2 is an enlarged view of a first land portion in FIG. 1 . FIG. 3 is an enlarged view of a first sipe, a second sipe, and a lateral groove in FIG. 2 . 4 is a cross-sectional view taken along line AA in FIG. 3. FIG. 2 is an enlarged view of a second land portion and a third land portion of FIG. 1 . 6 is a cross-sectional view taken along line BB in FIG. 5. 6 is a cross-sectional view taken along line CC of FIG. 5. FIG. 11 is an enlarged view of a first land portion according to another embodiment of the present invention. FIG. 4 is an enlarged view of a first land portion of a comparative example.

Below, one embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a development view of a tread portion 2 of a tire 1 showing one embodiment of the present invention. The tire 1 of this embodiment is preferably used, for example, as a pneumatic tire for passenger cars. However, the present invention is not limited to such an embodiment, and may also be used in pneumatic tires for heavy loads and non-pneumatic tires that do not have pressurized air filled inside the tire.

As shown in FIG. 1, the tire 1 of the present invention has a tread portion 2 for which the orientation for mounting on a vehicle is specified. The tread portion 2 has a first tread edge Te1 intended to be located on the outer side of the vehicle when the tire 1 is mounted on the vehicle, and a second tread edge Te2 intended to be located on the inner side of the vehicle when the tire 1 is mounted on the vehicle. The orientation for mounting on the vehicle is indicated, for example, by letters or symbols on the sidewall portion (not shown). However, the tire 1 of the present invention is not limited to this aspect, and the orientation for mounting on the vehicle may not be specified.

In the case of pneumatic tires for which various standards are established, the first tread edge Te1 and the second tread edge Te2 are the axially outermost contact points when the tire 1 in a normal state is loaded with a normal load and contacts the ground on a flat surface with a camber angle of 0°. The normal state is when the tire is mounted on a normal rim, filled to the normal internal pressure, and unloaded. In this specification, unless otherwise specified, the dimensions of each part of the tire are values measured in the normal state.

A "genuine rim" is a rim that is determined for each tire by the standard system that includes the standard on which the tire is based. For example, in the case of JATMA, it is called a "standard rim," in the case of TRA, it is called a "design rim," and in the case of ETRTO, it is called a "measuring rim."

"Normal internal pressure" is the air pressure set for each tire by each standard in the standard system on which the tire 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." For ETRTO, it is the "INFLATION PRESSURE."

"Normal load" is the load that each standard specifies for each tire in the system of standards on which the tire 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."

In the case of tires for which no standards are established and non-pneumatic tires, the first tread edge Te1 and the second tread edge Te2 are the axially outermost contact points when a tire in standard use is loaded with a standard load and grounded on a flat surface with a camber angle of 0°. "Standard use condition" refers to a standard use condition according to the intended use of the tire, in which no load is applied. "Standard load" refers to a load of a standard magnitude applied to the tire in practical use. In addition, in the case of tires for which no standards are established and non-pneumatic tires, the tire dimensions described in this specification are applied as if they were measured in the standard use condition.

The tread portion 2 has a plurality of circumferential grooves 3 that extend continuously in the tire circumferential direction between the first tread edge Te1 and the second tread edge Te2, and a plurality of land portions 4 that are divided by the circumferential grooves 3.

The circumferential grooves 3 include, for example, a first circumferential groove 5, a second circumferential groove 6, a third circumferential groove 7, and a fourth circumferential groove 8. The first circumferential groove 5 is provided between the first tread edge Te1 and the tire equator C. The second circumferential groove 6 is provided between the first circumferential groove 5 and the tire equator C. The third circumferential groove 7 is provided between the tire equator C and the second tread edge Te. The fourth circumferential groove 8 is provided between the third circumferential groove 7 and the second tread edge Te2.

The axial distance L1 from the tire equator C to the groove centerline of the first circumferential groove 5 or the groove centerline of the fourth circumferential groove 8 is desirably, for example, 0.20 to 0.35 times the tread width TW. The axial distance L2 from the tire equator C to the groove centerline of the second circumferential groove 6 or the groove centerline of the third circumferential groove 7 is desirably, for example, 0.05 to 0.15 times the tread width TW. The tread width TW is the axial distance from the first tread edge Te1 to the second tread edge Te2 in the normal state.

In this embodiment, each circumferential groove 3 extends, for example, linearly in parallel to the tire circumferential direction. Each circumferential groove 3 may extend, for example, in a wavy manner.

The groove width W1 of each circumferential groove 3 is preferably, for example, 4.0% to 8.0% of the tread width TW. The depth of each circumferential groove 3 is preferably, for example, 5 to 10 mm in the case of a pneumatic tire for a passenger car.

The land portion 4 includes a first land portion 11, a second land portion 12, a third land portion 13, a fourth land portion 14, and a fifth land portion 15. That is, the tread portion 2 of this embodiment has a so-called five-rib pattern composed of the above-mentioned four circumferential grooves 3 and five land portions 4. However, the present invention is not limited to this aspect.

The first land portion 11 is divided between the first circumferential groove 5 and the second circumferential groove 6. The second land portion 12 is divided between the second circumferential groove 6 and the third circumferential groove 7. The third land portion 13 is divided between the third circumferential groove 7 and the fourth circumferential groove 8. The fourth land portion 14 is divided between the first tread edge Te1 and the first circumferential groove 5. The fifth land portion 15 is divided between the fourth circumferential groove 8 and the second tread edge Te2.

2 shows an enlarged view of the first land portion 11. As shown in FIG. 2, the first land portion 11 includes a first longitudinal edge 11a extending in the tire circumferential direction, a second longitudinal edge 11b extending in the tire circumferential direction, and a tread surface 11c therebetween. The first longitudinal edge 11a and the second longitudinal edge 11b are defined as the edges of the tread surface when the tire 1 in the normal state is loaded with the normal load and contacts the ground on a flat surface with a camber angle of 0°. For this reason, the first land portion 11 may be one in which the tread surface and the side surface are connected by a curved surface, or one in which a chamfered portion is formed between the tread surface and the side surface.

The first land portion 11 is provided with a first sipe 16, a second sipe 17, and a lateral groove 20. FIG. 3 shows an enlarged view of the first sipe 16, the second sipe 17, and the lateral groove 20. As shown in FIG. 3, the first sipe 16 and the second sipe 17 each extend from the first longitudinal edge 11a. The lateral groove 20 extends from the second longitudinal edge 11b between the first sipe 16 and the second sipe 17. The lateral groove 20 terminates without reaching the first longitudinal edge 11a. The groove width of the lateral groove 20 is larger than the width of the first sipe 16 and the second sipe 17. The first sipe 16 and the second sipe 17 are connected to the lateral groove 20 without directly connecting to the second longitudinal edge 11b.

In this specification, a sipe means a cut formed with such a small width that at least a portion of a pair of sipe walls contact each other on the ground surface when the tire is in the normal state and the normal load is applied. The width of the sipe is, for example, 1.5 mm or less, and preferably 1.0 mm or less. The width of the sipe means the width in the direction perpendicular to the length of the sipe at the portion where the pair of sipe walls extend parallel to each other.

The tire of the present invention, which has the above-mentioned configuration, is able to exhibit excellent wet cornering performance. The following mechanism is believed to be the reason for this.

The first sipes 16, the second sipes 17, and the lateral grooves 20 each serve to improve drainage. Meanwhile, the block pieces 24 divided into the first sipes 16 and the second sipes 17 can move slightly due to changes in ground pressure acting on the first land portion 11. As a result, for example, when traveling straight, the block pieces 24 move in the tire circumferential direction, closing at least one of the first sipes 16 and the second sipes 17, and the opposing sipe walls come into contact with each other. This increases the apparent rigidity of the first land portion 11.

In addition, when the first sipes 16 and second sipes 17 are closed during wet driving, the water inside them is discharged to the outside through the lateral grooves 20, providing excellent drainage. Furthermore, when cornering on wet roads, the block pieces 24 move in the tire axial direction, which more actively discharges the water in the first sipes 16, second sipes 17, and lateral grooves 20 to the outside. In the present invention, it is presumed that due to this action, the tire of the present invention can provide excellent wet cornering performance.

The following describes the detailed configuration of the tire 1 of this embodiment. The lateral groove 20 includes a discontinuous end 20c that terminates within the tread surface of the first land portion 11, a first communicating portion 20a with the first sipe 16, and a second communicating portion 20b with the second sipe 17.

The lateral grooves 20 are, for example, inclined with respect to the tire axial direction with a constant groove width, and extend from the second longitudinal edge 11b to the discontinuous end 20c. The angle of the lateral grooves 20 with respect to the tire axial direction is, for example, 10 to 20°. The axial length L3 of the lateral grooves 20 is, for example, 40% to 60% of the axial width W2 of the first land portion 11 (shown in FIG. 2, and the same applies below). Such lateral grooves 20 help improve wet cornering performance while maintaining the rigidity of the first land portion 11.

Figure 4 shows a cross-sectional view taken along line A-A in Figure 3. Figure 4 corresponds to a cross-sectional view taken along the length of the lateral groove 20. As shown in Figure 4, the maximum depth d2 of the lateral groove 20 is 60% to 80% of the depth d1 of the second circumferential groove 6.

For example, the depth of the lateral groove 20 gradually decreases toward the discontinuous end 20c. In a more preferable embodiment, the bottom surface of the lateral groove 20 is curved in an arc shape on the side of the discontinuous end 20c. Such a lateral groove 20 guides water in the first sipe 16 and the second sipe 17 toward the second circumferential groove 6 during wet driving, further improving wet cornering performance.

As shown in FIG. 3, it is preferable that the first communicating portion 20a and the second communicating portion 20b are located closer to the second vertical edge 11b than the discontinuous end 20c. It is also preferable that the first communicating portion 20a and the second communicating portion 20b are located closer to the discontinuous end 20c than the axial center position of the lateral groove 20. As a more preferable aspect, in this embodiment, the first communicating portion 20a and the second communicating portion 20b are located at the same axial position. With this configuration, when the block piece 24 moves in the axial direction of the tire, the water in the first sipe 16 and the second sipe 17 is more easily discharged with stronger pressure toward the lateral groove 20.

The minimum axial distance L5 from the discontinuous end 20c to the first communicating portion 20a or the second communicating portion 20b is 15% to 40% of the maximum axial distance L4 from the first longitudinal edge 11a to the first communicating portion 20a or the second communicating portion 20b. Such lateral grooves 20 improve steering stability on dry roads and cornering performance on wet roads in a well-balanced manner.

From a similar viewpoint, the circumferential distance L7 from the communicating portion 16a of the first sipe 16 at the first longitudinal edge 11a to the groove centerline of the lateral groove 20 is preferably 30% or more, more preferably 40% or more, and preferably 70% or less, more preferably 60% or less of the circumferential distance L6 from the communicating portion 16a of the first sipe 16 at the first longitudinal edge 11a to the communicating portion 17a of the second sipe 17.

It is desirable that the first sipe 16 and the second sipe 17 extend to the lateral groove 20 without branching. This suppresses uneven wear of the first land portion 11.

The first sipe 16 includes a lateral sipe portion 26a extending in the tire axial direction and a vertical sipe portion 26b extending in the tire circumferential direction. The lateral sipe portion 26a and the vertical sipe portion 26b of the first sipe 16 are connected, for example, at an acute angle bend. Similarly, the second sipe 17 includes a lateral sipe portion 27a extending in the tire axial direction and a vertical sipe portion 27b extending in the tire circumferential direction. The lateral sipe portion 27a and the vertical sipe portion 27b of the second sipe 17 are connected, for example, at an obtuse angle bend. In this embodiment, the first sipe 16 and the second sipe 17 include the lateral sipe portions 26a, 27a, which makes it easier for the block piece 24 to move in the tire axial direction, thereby further enhancing the above-mentioned effect.

Each of the lateral sipe portions 26a, 27a is arranged at an angle of 45° or less with respect to the tire axial direction. The angle of the lateral sipe portions 26a, 27a with respect to the tire axial direction is, for example, 10 to 20°. In this embodiment, the lateral sipe portion 26a of the first sipe 16 and the lateral sipe portion 27a of the second sipe 17 are parallel to each other. In a more desirable embodiment, each of the lateral sipe portions 26a, 27a and the lateral groove 20 are arranged parallel to each other. Such lateral sipe portions 26a, 27a exert the above-mentioned effects while suppressing uneven wear of the first land portion 11.

The lateral sipe portions 26a, 27a cross, for example, the axial center position of the first land portion 11. The axial length L8 of the lateral sipe portions 26a, 27a is, for example, 55% to 80% of the axial width W2 of the first land portion 11. In a desirable embodiment, the axial length of the lateral sipe portion 26a of the first sipe 16 and the axial length of the lateral sipe portion 27a of the second sipe 17 are substantially the same. This improves the steering stability on dry roads and the cornering performance on wet roads in a well-balanced manner.

From a similar perspective, the depth of the lateral sipe portions 26a, 27a is, for example, 80% to 120% of the depth of the lateral groove 20.

The vertical sipe portions 26b, 27b are arranged, for example, at an angle of less than 45° with respect to the tire circumferential direction. The angle of the vertical sipe portions 26b, 27b with respect to the tire circumferential direction is preferably 15° or less. In this embodiment, the vertical sipe portions 26b, 27b extend parallel to the tire circumferential direction. Furthermore, the vertical sipe portion 26b of the first sipe 16 and the vertical sipe portion 27b of the second sipe 17 are located at the same position in the tire axial direction and are arranged on the same straight line. As a result, the two vertical sipe portions 26b, 27b work together to exert a frictional force in the tire axial direction, improving wet cornering performance.

The maximum depth of the longitudinal sipe portions 26b, 27b is, for example, smaller than the maximum depth of the lateral grooves 20. Also, it is desirable that the maximum depth of the longitudinal sipe portions 26b, 27b is smaller than the maximum depth of the lateral sipe portions 26a, 27a. Specifically, the maximum depth of the longitudinal sipe portions 26b, 27b is 25% to 50% of the maximum depth of the lateral sipe portions 26a, 27a. Such longitudinal sipe portions 26b, 27b are useful for improving wet cornering performance while suppressing excessive reduction in rigidity of the first land portion 11.

The first land portion 11 includes a block piece 24 surrounded by a first vertical edge 11a, a first sipe 16, and a second sipe 17. The axial length L9 of the block piece 24 is 60% to 90% of the axial width W2 of the first land portion 11. In addition, the axial length L9 of the block piece 24 is 30% to 70% of the circumferential length L10 of the block piece 24.

It is desirable that the circumferential length L10 of the block piece 24 is greater than the axial width W2 of the first land portion 11. Specifically, the circumferential length L10 of the block piece 24 is 1.30 to 1.50 times the axial width W2 of the first land portion 11. Such a block piece 24 has high circumferential rigidity and helps improve traction performance on dry road surfaces.

As shown in FIG. 2, the first land portion 11 of this embodiment is provided with a plurality of first groove elements 18 in the tire circumferential direction, each of which is composed of the above-mentioned lateral grooves 20, first sipes 16, and second sipes 17. In addition, the first land portion 11 is provided with second groove elements 19 between adjacent first groove elements 18 in the tire circumferential direction. In other words, the first land portion 11 is provided with the first groove elements 18 and the second groove elements 19 alternately in the tire circumferential direction.

The second groove element 19 includes a constant width portion 19a that extends at a constant width from the first longitudinal edge 11a, and a narrow width portion 19b that extends from the constant width portion 19a to the second longitudinal edge 11b at a width smaller than that of the constant width portion 19a. In this embodiment, the narrow width portion 19b is configured as, for example, a sipe.

The axial length L11 of the constant width portion 19a is, for example, smaller than the axial length of the lateral groove 20. The length L11 of the constant width portion 19a is also smaller than the axial length of the lateral sipe portions 26a, 27a. The constant width portion 19a does not cross the axial center position of the first land portion 11. Specifically, the length L11 of the constant width portion 19a is 25% to 35% of the axial width W2 of the first land portion 11. Such a constant width portion 19a is useful for improving steering stability and wet cornering performance in a well-balanced manner.

For example, the narrow portion 19b crosses the axial center position of the first land portion 11. The axial length L12 of the narrow portion 19b is greater than the axial length L3 of the lateral groove 20. Specifically, the length L12 of the narrow portion 19b is 65% to 75% of the axial width W2 of the first land portion 11.

The second groove elements 19 are inclined, for example, in the same direction as the lateral grooves 20 with respect to the tire axial direction. The angle of the second groove elements 19 with respect to the tire axial direction is, for example, 5 to 25 degrees.

The maximum depth of the second groove element 19 is preferably greater than the maximum depth of the longitudinal sipe portions 26b and 27b. Such second groove elements 19 provide greater friction in the circumferential direction of the tire on wet road surfaces, which helps to improve traction performance on wet road surfaces.

Fig. 5 shows an enlarged view of the second land portion 12 and the third land portion 13. As shown in Fig. 5, the second land portion 12 is provided with a plurality of interrupted grooves 30 that extend from the third circumferential groove 7 and terminate within the second land portion 12. In this embodiment, the interrupted grooves 30 include a plurality of first interrupted grooves 31 that cross the tire equator C, and a plurality of second interrupted grooves 32 that terminate closer to the third circumferential groove 7 than the first interrupted grooves 31. The first interrupted grooves 31 and the second interrupted grooves 32 are alternately provided in the tire circumferential direction.

The interrupted grooves 30 are, for example, inclined with respect to the tire axial direction. The interrupted grooves 30 are inclined with respect to the tire axial direction in the same direction as the lateral grooves 20 (shown in FIG. 2) provided in the first land portion 11. It is desirable that the maximum angle of the interrupted grooves 30 with respect to the tire axial direction is greater than the maximum angle of the lateral grooves with respect to the tire axial direction. The angle of the interrupted grooves 30 with respect to the tire axial direction is, for example, 35 to 55 degrees. Such interrupted grooves 30 can further improve wet cornering performance.

Figure 6 shows a cross-sectional view of line B-B in Figure 5. As shown in Figure 6, the depth of the interrupted groove 30 gradually decreases, for example, from the third circumferential groove 7 toward the second circumferential groove 6. The maximum depth of the interrupted groove 30 is 80% to 120% of the depth of the lateral groove 20 provided in the first land portion 11. In this embodiment, the depth of the interrupted groove 30 is the same as the depth of the lateral groove 20. This makes the progress of wear uniform between the first land portion 11 and the second land portion 12, suppressing uneven wear.

As shown in FIG. 5, it is preferable that the second land portion 12 is provided with a connecting sipe 33 extending from the second interrupted groove 32 to the second circumferential groove 6. Such a connecting sipe 33 is useful for improving wet performance.

The third land portion 13 is provided with a plurality of inclined transverse grooves 35 that extend at an angle from the third circumferential groove 7 to the fourth circumferential groove 8. The inclined transverse grooves 35 are inclined, for example, in the same direction as the interrupted grooves 30 provided in the second land portion 12 with respect to the tire axial direction. During wet driving, such inclined transverse grooves 35, together with the interrupted grooves 30, guide water in the grooves toward the second tread edge Te2, improving wet performance.

The inclined transverse groove 35 includes, for example, two gently sloping portions 35a arranged on both sides in the tire axial direction, and a steeply sloping portion 35b arranged between them. The angle of the steeply sloping portion 35b relative to the tire axial direction is greater than the angle of the gently sloping portion 35a relative to the tire axial direction. The angle of the gently sloping portion 35a relative to the tire axial direction is, for example, 15 to 25 degrees. The angle of the steeply sloping portion 35b relative to the tire axial direction is, for example, 40 to 50 degrees. Such an inclined transverse groove 35 improves traction performance and cornering performance on wet road surfaces in a well-balanced manner.

Figure 7 shows a cross-sectional view taken along line CC in Figure 5. As shown in Figure 7, the depth of the gentle slope portion 35a on the fourth circumferential groove 8 side and the depth of the steep slope portion 35b are smaller than the depth of the gentle slope portion 35a on the third circumferential groove 7 side. Such an inclined cross groove 35 provides the above-mentioned effects while maintaining steering stability on dry road surfaces.

In a more desirable embodiment, the gentle slope portion 35a and the steep slope portion 35b on the fourth circumferential groove 8 side are provided with groove bottom sipes (not shown) that open at the groove bottom and extend along the length of the inclined transverse groove 35. Such groove bottom sipes are useful for improving the steering stability on dry road surfaces and the cornering performance on wet roads in a well-balanced manner.

As shown in FIG. 5, it is desirable that the region in which the end of the inclined cross groove 35 on the third circumferential groove 7 side extends parallel to the tire axial direction does not overlap with the end of the interrupted groove 30 on the third circumferential groove 7 side provided in the second land portion 12. This suppresses uneven wear of the second land portion 12 and the third land portion 13.

In this embodiment, the third land portion 13 is provided with a plurality of first interrupted sipes 36 and a plurality of second interrupted sipes 37. The first interrupted sipes 36 extend from the third circumferential groove 7 and are interrupted within the third land portion 13. The second interrupted sipes 37 extend from the fourth circumferential groove 8 and are interrupted within the third land portion 13. Such first interrupted sipes 36 and second interrupted sipes 37 help to improve traction performance on wet road surfaces while maintaining the rigidity of the third land portion 13.

As shown in FIG. 1, the fourth land portion 14 is provided with, for example, a plurality of first outer shoulder lateral grooves 41 and a plurality of second outer shoulder lateral grooves 42. The first outer shoulder lateral groove 41 extends, for example, from the first circumferential groove 5 to the first tread edge Te1. The second outer shoulder lateral groove 42 preferably extends, for example, from the first tread edge Te1 and is interrupted within the fourth land portion 14.

The first outer shoulder lateral groove 41 includes, for example, a narrow groove portion 41a that communicates with the first circumferential groove 5. In this embodiment, it is desirable that the narrow groove portion 41a smoothly continues with the constant width portion 19a of the second groove element 19 provided in the first land portion 11 via the first circumferential groove 5. Note that "smoothly continuing through the circumferential groove" means that the minimum distance in the circumferential groove between the region in which the groove or sipe that communicates with the edge on one side of the circumferential groove is extended along its length and the region in which the groove or sipe that communicates with the edge on the other side of the circumferential groove is extended along its length is 2.0 mm or less. In this embodiment, the minimum distance between the narrow groove portion 41a and the constant width portion 19a is 0 (i.e., the regions overlap). Such a groove arrangement can further improve wet performance.

The fourth land portion 14 is provided with a plurality of outer shoulder sipes 43 extending from the first circumferential groove 5 to the first tread edge Te1. The outer shoulder sipes 43 are smoothly connected to, for example, the first sipes 16 or the second sipes 17 provided in the first land portion 11 via the first circumferential groove 5. This makes it easier for each sipe to open appropriately, and makes it easier for the edges of the sipes to exert a large frictional force.

The fifth land portion 15 has a plurality of inner shoulder lateral grooves 45 and a plurality of inner shoulder sipes 46. The inner shoulder lateral grooves 45 extend, for example, from the fourth circumferential groove 8 to the second tread edge Te2. The inner shoulder sipes 46 extend, for example, from the fourth circumferential groove 8 to the second tread edge Te2.

The inner shoulder lateral groove 45 is preferably smoothly connected to the inclined transverse groove 35 provided in the third land portion 13 via the fourth circumferential groove 8. The inner shoulder sipe 46 is preferably smoothly connected to the second interrupted sipe 37 provided in the third land portion 13 via the fourth circumferential groove 8. Such an arrangement of grooves and sipes further improves wet cornering performance.

Figure 8 shows an enlarged view of the first land portion 11 of another embodiment of the present invention. In Figure 8, the same reference numerals are used for the configurations common to those described above, and the description here is omitted. As shown in Figure 8, the first sipe 16 and the second sipe 17 of this embodiment extend linearly from the first longitudinal edge 11a to the lateral groove 20, inclined in the tire axial direction. The first sipe 16 and the second sipe 17 are inclined at an angle of, for example, 25 to 50 degrees with respect to the tire axial direction. This embodiment can also achieve the above-mentioned effects. In addition, in this embodiment, the first sipe 16 and the second sipe 17 do not include a bent portion, so the wear resistance of the first land portion 11 is improved.

The tire according to one embodiment of the present invention has been described in detail above, but the present invention is not limited to the specific embodiment described above and can be modified and implemented in various ways.

A tire of size 225/45R18 having the basic pattern of FIG. 1 was prototyped. As a comparative example, a tire having a first land portion a shown in FIG. 9 was prototyped. As shown in FIG. 9, in the first land portion a of the comparative tire, the first sipe b and the second sipe c do not communicate with the lateral groove d, but cross the first land portion a. The pattern elements of the comparative tire are substantially the same as those shown in FIG. 1, except for the above-mentioned points. The wet cornering performance and handling stability of each test tire were tested. The common specifications and test methods of each test tire are as follows.
Rim: 18x8.0
Tire pressure: front wheel 220kPa, rear wheel 250kPa
Test vehicle: 2000cc displacement, rear-wheel drive Tire mounting position: all wheels

<Wet cornering performance>
The test vehicle was driven on a circuit with a wet road surface, and the wet cornering performance was evaluated by the driver. The results are expressed as a score based on the comparative example being 100, with a higher score indicating better wet cornering performance.

<Handling stability>
The steering stability when traveling on a general road consisting of a dry road surface was evaluated by the driver's senses. The results are expressed as a score based on the comparative example being 100, with a higher score indicating better steering stability.
The results of the tests are shown in Table 1.

As a result of the tests, it was confirmed that the tires of the examples exhibited excellent wet cornering performance. In particular, it was confirmed that not only the embodiment shown in FIG. 2 (Examples 1 to 9), but also the embodiment shown in FIG. 8 (Example 10) exhibited excellent wet cornering performance. As described above, it was confirmed that the present invention can provide a tire with improved wet cornering performance.

In addition to the above-mentioned effects, it was also confirmed that the tires of Examples 1 to 10 maintained steering stability.

2 tread portion 11 first land portion 11a first longitudinal edge 11b second longitudinal edge 11c tread surface 16 first sipe 17 second sipe 20 lateral groove

Claims (10)

A tire having a tread portion,
The tread portion includes a first land portion,
The first land portion includes a first longitudinal edge extending in a tire circumferential direction, a second longitudinal edge extending in a tire circumferential direction, and a tread surface therebetween,
The first land portion is provided with a first sipe and a second sipe extending from the first longitudinal edge, and a lateral groove extending from the second longitudinal edge between the first sipe and the second sipe and terminating without reaching the first longitudinal edge,
A groove width of the lateral groove is larger than a width of the first sipe and a width of the second sipe,
The first sipe and the second sipe communicate with the lateral groove without directly communicating with the second longitudinal edge ,
the lateral groove includes a discontinuous end that terminates within a tread surface of the first land portion, a first communicating portion with the first sipe, and a second communicating portion with the second sipe,
the first communicating portion and the second communicating portion are each located closer to the second vertical edge than the discontinuous end;
tire. The tire according to claim 1 , wherein the first communicating portion and the second communicating portion are each located closer to the discontinuous end than a center position of the lateral groove in an axial direction of the tire. The tire according to claim 1 , wherein the first communicating portion and the second communicating portion are located at the same position in the tire axial direction. 4. The tire according to claim 1, wherein a minimum distance in the tire axial direction from the discontinuous end to the first communicating portion or the second communicating portion is 15% to 40% of a maximum distance in the tire axial direction from the first vertical edge to the first communicating portion or the second communicating portion. A tire having a tread portion,
The tread portion includes a first land portion,
The first land portion includes a first longitudinal edge extending in a tire circumferential direction, a second longitudinal edge extending in a tire circumferential direction, and a tread surface therebetween,
The first land portion is provided with a first sipe and a second sipe extending from the first longitudinal edge, and a lateral groove extending from the second longitudinal edge between the first sipe and the second sipe and terminating without reaching the first longitudinal edge,
A groove width of the lateral groove is larger than a width of the first sipe and a width of the second sipe,
The first sipe and the second sipe communicate with the lateral groove without directly communicating with the second longitudinal edge,
The lateral groove includes an end that is interrupted within the tread surface of the first land portion,
The lateral grooves have a depth that gradually decreases toward the end.
tire. 6. The tire according to claim 1, wherein the circumferential distance from the first sipe communicating portion at the first longitudinal edge to the groove center line of the lateral groove is 30% to 70% of the circumferential distance from the first sipe communicating portion at the first longitudinal edge to the second sipe communicating portion. The tire according to claim 1 , wherein the first sipe and the second sipe each extend into the lateral groove without branching. The first land portion includes a block piece surrounded by the first longitudinal edge, the first sipe, and the second sipe,
8. The tire according to claim 1, wherein a length of the block piece in the tire axial direction is 30% to 70% of a length of the block piece in the tire circumferential direction. The tire according to claim 1 , wherein the first sipe and the second sipe each include a lateral sipe portion extending in an axial direction of the tire and a longitudinal sipe portion extending in a circumferential direction of the tire. The tire of claim 9 , wherein a maximum depth of the longitudinal sipes is less than a maximum depth of the transverse sipes.

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