tire

Abstract

To provide a tire that can exert excellent on-snow performance, while maintaining steering stability on a dry road surface.SOLUTION: A tire has a tread part. The tread part includes a first tread end, a second tread end and a first middle land part. The first middle land part is provided with a plurality of middle lateral grooves 20 and a plurality of first middle sipes 31. Each of the plurality of middle lateral grooves 20 includes a first groove part 26, a second groove part 27 and a vertical groove part 28. The vertical groove part 28 includes a first vertical groove edge 28a and a second vertical groove edge 28b. Respective terminating ends 31a of the plurality of first middle sipes 31 are positioned closer to the second vertical edge 13b than the first vertical groove edge 28a.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] This disclosure relates to tires.

Background Art

[0002] In Patent Document 1 below, a tire is proposed in which a plurality of first middle lateral grooves and a plurality of second middle lateral grooves are provided in the middle land portion. This tire expects to achieve both driving stability on dry roads and performance on ice and snow by means of the first middle lateral grooves and the second middle lateral grooves.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] With the recent improvement in the performance of vehicles, there is an increasing demand for further improvement in the driving stability on dry roads and the performance on snow in tires.

[0005] This disclosure has been devised in view of the above actual situation, and the main problem is to provide a tire that can exhibit excellent snow performance while maintaining driving stability on dry roads.

Means for Solving the Problems

[0006] This disclosure relates to a tire having a tread portion, the tread portion including a first tread end, a second tread end, and a first middle land portion provided between the first tread end and the second tread end, the first middle land portion including a first longitudinal edge extending in the circumferential direction of the tire on the first tread end side, a second longitudinal edge extending in the circumferential direction of the tire on the second tread end side, and a tread surface between the first longitudinal edge and the second longitudinal edge, the first middle land portion having a plurality of middle transverse grooves that completely traverse the first middle land portion in the axial direction of the tire, and extending from the first longitudinal edge, Furthermore, the tire is provided with a plurality of first middle sipes having a broken end within the tread surface, each of the plurality of middle lateral grooves includes a first groove portion extending in the tire axial direction from the first longitudinal edge, a second groove portion extending in the tire axial direction from the second longitudinal edge, and a longitudinal groove portion communicating with the first groove portion and the second groove portion and extending in the tire circumferential direction, the longitudinal groove portion includes a first longitudinal groove edge on the first longitudinal edge side and a second longitudinal groove edge on the second longitudinal edge side, and the broken end of each of the plurality of first middle sipes is located on the second longitudinal edge side of the first longitudinal groove edge. [Effects of the Invention]

[0007] By adopting the above configuration, the tire disclosed herein can maintain handling stability on dry surfaces while exhibiting excellent performance on snow. [Brief explanation of the drawing]

[0008] [Figure 1] This is an exploded view of the tread portion showing one embodiment of the present disclosure. [Figure 2] This is an enlarged view of the first middle-distance track and field area in Figure 1. [Figure 3] Figure 2 shows a magnified view of the two middle lateral grooves and the first middle sipe. [Figure 4] This is a cross-sectional view along line AA in Figure 2. [Figure 5] Figure 2 is a cross-sectional view along line BB. [Figure 6] Figure 2 is a cross-sectional view along the CC line. [Figure 7]Figure 2 is a cross-sectional view along the DD line. [Figure 8] Figure 2 is a cross-sectional view along the EE line. [Figure 9] Figure 1 is an enlarged view of the Crown Land area. [Figure 10] Figure 9 shows enlarged views of the first, second, third, and fourth crown sipes. [Figure 11] This is an enlarged view of the second middle-distance track and field area in Figure 1. [Figure 12] Figure 11 is a cross-sectional view along the FF line. [Figure 13] Figure 11 is a cross-sectional view along the GG line. [Modes for carrying out the invention]

[0009] Hereinafter, one embodiment of the present disclosure will be described with reference to the drawings. Figure 1 is an exploded view of the tread portion 2 of a tire 1 showing one embodiment of the present disclosure. The tire 1 of this embodiment is, for example, a winter tire and is suitably used as a pneumatic tire for a passenger car. However, the present disclosure is not limited to this embodiment and may also be applied to pneumatic tires for heavy loads or non-pneumatic tires in which pressurized air is not filled inside the tire.

[0010] As shown in Figure 1, the tread portion 2 of the present disclosure includes a first tread end T1, a second tread end T2, a plurality of circumferential grooves 3 extending continuously in the circumferential direction of the tire between the first tread end T1 and the second tread end T2, and a plurality of land portions 4 divided by these circumferential grooves 3. In a preferred embodiment, the tire 1 of this embodiment is configured as a so-called five-rib tire in which the tread portion 2 is composed of four circumferential grooves 3 and five land portions 4.

[0011] The tread portion 2 of the present embodiment is, for example, specified in terms of the direction of attachment to a vehicle. As a result, the first tread end T1 is intended to be located on the outside of the vehicle when the tire is mounted on the vehicle. The second tread end T2 is intended to be located on the inside of the vehicle when the tire is mounted on the vehicle. The direction of attachment to the vehicle is, for example, indicated by letters or symbols on a sidewall portion (not shown). However, the tire 1 of the present disclosure is not limited to such a mode, and the direction of attachment to the vehicle may not be specified.

[0012] The first tread end T1 and the second tread end T2 respectively correspond to the ends of the ground contact surface when 70% of the normal load is applied to the tire 1 in the normal state and the tread portion 2 is grounded on a plane at a camber angle of 0°.

[0013] The "normal state" means that in the case of a pneumatic tire with various standards defined, the tire is rim-mounted on a normal rim and filled with a normal internal pressure, and moreover, it is in a non-loaded state. In the case of a tire without various defined standards or a non-pneumatic tire, the "normal state" means a standard usage state according to the usage purpose of the tire, which is a state of not being mounted on a vehicle and being non-loaded. In this specification, unless otherwise specified, the dimensions and the like of each part of the tire are values measured in the above-mentioned normal state. Also, in this specification, unless otherwise specified, known methods can be appropriately applied to the measurement methods of the above-mentioned dimensions and material compositions.

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

[0015] "Normal internal pressure" is the air pressure defined for each tire in a standard system including the standards on which the tire is based. For JATMA, it is the "maximum air pressure"; for TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; and for ETRTO, it is the "INFLATION PRESSURE".

[0016] "Normal load" is, in the case of a pneumatic tire for which various standards are defined, the load defined for each tire in a standard system including the standards on which the tire is based. For JATMA, it is the "maximum load capacity"; for TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; and for ETRTO, it is the "LOAD CAPACITY". Also, in the case of a tire for which no various standards are defined, "normal load" refers to the maximum load applicable in using the tire, in accordance with the above standards.

[0017] The circumferential groove 3 includes the first shoulder circumferential groove 5 and the second shoulder circumferential groove 6, and the first crown circumferential groove 7 and the second crown circumferential groove 8 provided therebetween. The first shoulder circumferential groove 5 is provided closest to the first tread end T1 side among the plurality of circumferential grooves 3. The second shoulder circumferential groove 6 is provided closest to the second tread end T2 side among the plurality of circumferential grooves 3. The first crown circumferential groove 7 is provided between the first shoulder circumferential groove 5 and the tire equator C. The second crown circumferential groove 8 is provided between the second shoulder circumferential groove 6 and the tire equator C.

[0018] The axial distance L1 from the tire equator C to the groove centerline of the first shoulder circumferential groove 5 or the second shoulder circumferential groove 6 is preferably, for example, 25% to 35% of the tread width TW. The axial distance L2 from the tire equator C to the groove centerline of the first crown circumferential groove 7 or the second crown circumferential groove 8 is preferably, for example, 5% to 15% of the tread width TW. The tread width TW is the axial distance from the first tread end T1 to the second tread end T2 in the normal state described above.

[0019] In this embodiment, the second shoulder circumferential groove 6, the first crown circumferential groove 7, and the second crown circumferential groove 8 extend in a straight line or parallel to the tire circumferential direction. On the other hand, the groove edge of the first shoulder circumferential groove 5 on the tire equator C side extends in a zigzag shape. However, the shape of each circumferential groove 3 is not limited to these.

[0020] The groove width W1 of each circumferential groove 3 should preferably be at least 3 mm. Furthermore, the groove width W1 of each circumferential groove 3 should preferably be, for example, 3.0% to 7.0% of the tread width TW. The depth of each circumferential groove 3 is, for example, 5 to 10 mm in the case of pneumatic tires for passenger cars.

[0021] The land portion 4 of this embodiment includes a first middle land portion 13 provided between the first tread end T1 and the second tread end T2. In a preferred embodiment, the first middle land portion 13 is provided between the first tread end T1 and the tire equator C, and specifically, is divided between the first shoulder circumferential groove 5 and the first crown circumferential groove 7. The land portion 4 of this embodiment includes a first shoulder land portion 11, a second shoulder land portion 12, a second middle land portion 14, and a crown land portion 15. The first shoulder land portion 11 includes the first tread end T1 and is adjacent to the first middle land portion 13 via the first shoulder circumferential groove 5. The second shoulder land portion 12 includes the second tread end T2 and is divided on the tire axial side outward of the second shoulder circumferential groove 6. The second middle land portion 14 is provided between the second tread end T2 and the tire equator C, and specifically, is divided between the second shoulder circumferential groove 6 and the second crown circumferential groove 8. The crown land portion 15 is divided between the first crown circumferential groove 7 and the second crown circumferential groove 8. As a result, the crown land portion 15 is located on the tire equator C.

[0022] Figure 2 shows an enlarged view of the first middle section 13. As shown in Figure 2, the first middle section 13 includes a first longitudinal edge 13a extending in the circumferential direction of the tire on the first tread end T1 side, a second longitudinal edge 13b extending in the circumferential direction of the tire on the second tread end T2 side, and a tread surface 13s between the first longitudinal edge 13a and the second longitudinal edge 13b. The first middle section 13 is also provided with a plurality of middle lateral grooves 20 and a plurality of first middle sipes 31.

[0023] In this specification, "sipe" means a groove-like body having a small width (a recess having a longitudinal direction, including grooves and sipes), wherein the width between the two inner walls in the main body is 1.5 mm or less. The main body also means the portion where the two inner walls extend substantially parallel to each other in the tire radial direction. The main body may also extend in a zigzag pattern in the tire radial direction in the cross-section of the sipe. Furthermore, as will be described later, the sipe may include a chamfered portion. The sipe may also have a so-called flask bottom with an increased width at the bottom.

[0024] Figure 3 shows enlarged views of the two middle lateral grooves 20 and the first middle sipe 31. As shown in Figure 3, the middle lateral grooves 20 completely traverse the first middle tread 13 in the axial direction of the tire. The first middle sipe 31 extends from the first longitudinal edge 13a and has a broken end 31a within the tread surface 13s.

[0025] Each of the multiple middle lateral grooves 20 includes a first groove portion 26 extending in the tire axial direction from a first longitudinal edge 13a, a second groove portion 27 extending in the tire axial direction from a second longitudinal edge 13b, and a longitudinal groove portion 28 communicating with the first groove portion 26 and the second groove portion 27 and extending in the tire circumferential direction. The longitudinal groove portion 28 also includes a first longitudinal groove edge 28a on the first longitudinal edge 13a side and a second longitudinal groove edge 28b on the second longitudinal edge 13b side. In this embodiment, the region between the first longitudinal groove edge 28a and a virtual extension line extending in its longitudinal direction, and the second longitudinal groove edge 28b and a virtual extension line extending in its longitudinal direction are configured as the longitudinal groove portion 28.

[0026] In this disclosure, the interrupted end 31a of each of the multiple first middle sipes 31 is located on the second longitudinal edge 13b side of the first longitudinal groove edge 28a. Furthermore, if the first longitudinal groove edge 28a is inclined with respect to the tire circumferential direction, the interrupted end 31a is located on the second longitudinal edge 13b side of the end of the first longitudinal groove edge 28a on the second longitudinal edge 13b side. By adopting the above configuration, the tire of this disclosure can exhibit excellent snow performance while maintaining handling stability on dry surfaces (hereinafter sometimes simply referred to as "handling stability"). The following mechanism is presumed to be the reason for this.

[0027] In the tire of this disclosure, the middle lateral groove 20 includes a first groove 26, a second groove 27, and a longitudinal groove 28. When driving on snow, the snow columns formed by such middle lateral groove 20 can exert large shear forces in multiple directions. Specifically, the portion of the snow column formed by the first groove 26 and the second groove 27 (hereinafter referred to as the first snow column portion) is supported by the portion formed by the longitudinal groove 28 (hereinafter referred to as the second snow column portion), providing a large reaction force in the circumferential direction of the tire when driving on snow. Similarly, the second snow column portion is supported by the first snow column portion, providing a large reaction force in the axial direction of the tire when driving on snow. Therefore, the above-described middle lateral groove 20 can significantly improve traction performance, braking performance, and cornering performance on snow.

[0028] On the other hand, the aforementioned first middle sipe 31 can provide frictional force when driving on snow while maintaining the rigidity of the first middle land section 13, thereby improving snow performance while maintaining handling stability on dry surfaces. In particular, because the interrupted end 31a of the first middle sipe 31 is located on the second longitudinal edge 13b side of the first longitudinal groove edge 28a of the longitudinal groove section 28, the first middle sipe 31 has sufficient length, which further enhances the edge effect performance on snow.

[0029] Furthermore, by specifying the interrupted end 31a of the first middle sipe 31 as described above, the land portion between the first groove 26 and longitudinal groove 28 of the middle lateral groove 20 and the first middle sipe 31 becomes more easily deformable. This effect helps prevent snow from accumulating inside the middle lateral groove 20 (especially the first groove 26 and longitudinal groove 28) when driving on snow. It is believed that this mechanism enables the tire 1 of this disclosure to continuously exhibit excellent snow performance.

[0030] The configuration of this embodiment will be described in more detail below. Note that each configuration described below represents a specific aspect of this embodiment. Therefore, it goes without saying that this disclosure can achieve the above-described effects even without the configurations described below. Furthermore, even if any one of the configurations described below is applied individually to a tire of this disclosure having the above-described features, an improvement in performance corresponding to each configuration can be expected. Moreover, if several of the configurations described below are applied in combination, a combined improvement in performance corresponding to each configuration can be expected.

[0031] As shown in Figure 2, in this embodiment, each middle lateral groove 20 has the characteristics described above. In addition, in a plan view of the tread, the first groove 26 and the second groove 27 extend in the tire axial direction with a constant groove width W3. The groove width W3 of the first groove 26 and the second groove 27 is, for example, 15% to 25% of the width W2 of the contact surface of the first middle land portion 13. The angle of the first groove 26 and the second groove 27 with respect to the tire axial direction is, for example, 25 to 35°. In this specification, unless otherwise specified, the angle and length of the grooves are measured at the groove centerline, and the groove width is measured as the width perpendicular to the groove centerline. The same applies to sipes.

[0032] In this embodiment, the first groove 26 and the second groove 27 have different cross-sectional shapes. As a result, the maximum depth of the first groove 26 is different from the maximum depth of the second groove 27. In this embodiment, the middle lateral groove 20 includes a plurality of first middle lateral grooves 21 and a plurality of second middle lateral grooves 22 with different depth distributions. The first middle lateral grooves 21 and the second middle lateral grooves 22 are arranged alternately, for example, in the circumferential direction of the tire.

[0033] Figure 4 shows a cross-sectional view along line AA in Figure 2. Figure 4 is a cross-sectional view of the first middle lateral groove 21 along the longitudinal direction of the groove. Figure 5 shows a cross-sectional view along line BB in Figure 2. Figure 5 is a cross-sectional view of the second middle lateral groove 22 along the longitudinal direction of the groove. As shown in Figures 4 and 5, the first groove portion 26 and the second groove portion 27 of the first middle lateral groove 21, and the first groove portion 26 and the second groove portion 27 of the second middle lateral groove 22, in this embodiment, each extend in the longitudinal direction of the groove to a certain depth.

[0034] As shown in Figure 4, in the first middle lateral groove 21, the maximum depth d1 of the first groove 26 is smaller than the maximum depth d2 of the second groove 27. In the first middle lateral groove 21, the depth d2 of the second groove 27 is, for example, 60% to 80% of the depth dc of the first crown circumferential groove 7. Also, in the first middle lateral groove 21, the depth d1 of the first groove 26 is 40% to 60% of the depth dc of the first crown circumferential groove 7. Therefore, it is desirable that the depth d1 of the first groove 26 be 60% to 70% of the depth d2 of the second groove 27.

[0035] As shown in Figure 5, the second middle lateral groove 22 has a cross-sectional shape that is substantially the inverse of that of the first middle lateral groove 21. That is, in the second middle lateral groove 22, the maximum depth d1 of the first groove 26 is greater than the maximum depth d2 of the second groove 27. In the second middle lateral groove 22, the depth d1 of the first groove 26 is, for example, 60% to 80% of the depth dc of the first crown circumferential groove 7. Also, in the second middle lateral groove 22, the depth d2 of the second groove 27 is 40% to 60% of the depth dc of the first crown circumferential groove 7. Therefore, it is desirable that the depth d2 of the second groove 27 is 60% to 70% of the depth d1 of the first groove 26.

[0036] In this embodiment, by arranging the first middle lateral groove 21 and the second middle lateral groove 22 alternately in the circumferential direction of the tire, it is possible to improve both handling stability and snow performance in a balanced manner.

[0037] Figure 6 shows a cross-sectional view along line CC in Figure 2. Figure 6 is a cross-sectional view of the second groove 27 of the first middle lateral groove 21, or the first groove 26 of the second middle lateral groove 22 (hereinafter, these may be collectively referred to as the deep groove 37). Figure 7 shows a cross-sectional view along line DD in Figure 2. Figure 7 is a cross-sectional view of the first groove 26 of the first middle lateral groove 21, or the second groove 27 of the second middle lateral groove 22 (hereinafter, these may be collectively referred to as the shallow groove 36).

[0038] As shown in Figures 6 and 7, it is desirable that the deep groove 37 and the shallow groove 36 each open via a chamfered portion 25. The chamfered portion 25 includes an inclined surface 25s cut out between the tread surface and the groove wall of the land portion. In this embodiment, the inclined surface 25s is slightly curved in a direction that is convex outward in the radial direction of the tire. The inclined surface 25s may also be, for example, flat. Such a chamfered portion 25 helps to equalize the contact pressure acting on the tread surface 13s and improve resistance to uneven wear.

[0039] As shown in Figure 6, the deep groove section 37 is composed of, for example, a flat groove bottom section 37d. On the other hand, as shown in Figure 7, the shallow groove section 36 has a series of groove bottom sipes 38 that open at the groove bottom section 36d and extend in the radial direction of the tire. Such groove bottom sipes 38 make it easier to open the shallow groove section 36 appropriately, which helps to improve snow performance. Note that the depth d1 of the first groove section 26 of the first middle lateral groove 21 and the depth d2 of the second groove section 27 of the second middle lateral groove 22 mentioned above refer to depths that do not include the groove bottom sipes 38. Also, in Figures 4 and 5, the groove bottom sipes 38 are omitted. In a desirable embodiment, the total depth from the tread surface on land to the bottom of the groove bottom sipes 38 is also smaller than the depth of the deep groove section 37. This improves both handling stability and snow performance in a balanced way.

[0040] As shown in Figure 3, the first longitudinal groove edge 28a and the second longitudinal groove edge 28b in this embodiment are positioned, for example, in the central region when the tread surface 13s of the first middle land portion 13 is divided into three equal parts in the tire axial direction. This ensures that the first longitudinal groove edge 28a and the second longitudinal groove edge 28b are positioned so as to straddle the center position of the tread surface 13s of the first middle land portion 13 in the tire axial direction. Furthermore, the first longitudinal groove edge 28a and the second longitudinal groove edge 28b each extend along the tire circumferential direction, and in a preferred embodiment, they extend parallel to each other. The angle between the first longitudinal groove edge 28a and the second longitudinal groove edge 28b with respect to the tire circumferential direction is, for example, 10° or less, and preferably 5° or less. The length L3 of the first longitudinal groove edge 28a and the second longitudinal groove edge 28b in the tire circumferential direction is preferably smaller than the maximum groove width in the first groove 26 and the second groove 27. Specifically, the length L3 is 75% to 95% of the groove width. Such first longitudinal groove edges 28a and second longitudinal groove edges 28b can suppress uneven wear while improving turning performance when driving on snow.

[0041] As shown in Figures 4 and 5, the maximum depth d3 of the longitudinal groove 28 is smaller than the maximum depth d1 of the first groove 26 and the maximum depth d2 of the second groove 27. Specifically, the maximum depth d3 of the longitudinal groove 28 is 20% to 30% of the depth dc of the first crown circumferential groove 7. Such longitudinal grooves 28 increase the rigidity of the central part of the first middle ridge 13 and improve resistance to uneven wear.

[0042] As shown in Figure 2, it is desirable that the first middle section 13 is provided with at least one longitudinal sipe 30 extending in the circumferential direction of the tire. In this embodiment, the first middle section 13 has multiple longitudinal sipes 30 spaced apart in the circumferential direction of the tire. In this embodiment, the longitudinal sipes 30 extend from the tread surface 13s of the first middle section 13 to the bottom with a constant width.

[0043] The longitudinal sipes 30 are preferably positioned in the central region when the tread surface 13s of the first middle section 13 is divided into three equal parts in the axial direction of the tire. The angle of the longitudinal sipes 30 with respect to the circumferential direction of the tire is, for example, 10° or less, and preferably 5° or less. Such longitudinal sipes 30 can provide a large frictional force in the axial direction of the tire when driving on snow.

[0044] The longitudinal sipes 30, for example, cross the middle lateral grooves 20 in the circumferential direction of the tire. In a preferred embodiment, the longitudinal sipes 30 are arranged to cross the first middle lateral groove 21, and the longitudinal sipes 30 do not communicate with the second middle lateral groove 22. More specifically, the longitudinal sipes 30 cross the longitudinal groove portion 28 of the first middle lateral groove 21. As a result, the longitudinal sipes 30 are configured as groove bottom sipes at the bottom of the longitudinal groove portion 28. On the other hand, the second middle lateral groove 22 does not have such a configuration. This improves handling stability, snow performance, and resistance to uneven wear in a well-balanced manner.

[0045] As shown in Figure 3, the axial length L10 of the first middle sipe 31 is 40% to 60% of the axial width W2 (shown in Figure 2) of the first middle ground section 13. In a more desirable embodiment, the first middle sipe 31 in this embodiment extends from the first longitudinal edge 13a and communicates with the longitudinal sipe 30. Such a first middle sipe 31 helps to improve both handling stability and snow performance in a balanced way.

[0046] As shown in Figure 2, the first middle section 13 is provided with a plurality of second middle sipes 32 in addition to the first middle sipe 31 described above. The second middle sipes 32 extend from the second longitudinal edge 13b and communicate with the longitudinal sipe 30. In a preferred embodiment, the end of the first middle sipe 31 within the tread surface 13s communicates with one end of the longitudinal sipe 30 in the tire circumferential direction. The end of the second middle sipe 32 within the tread surface 13s communicates with the other end of the longitudinal sipe 30 in the tire circumferential direction. Such first middle sipes 31 and second middle sipes 32 work together with the longitudinal sipe 30 to provide frictional force in multiple directions, further improving snow performance. The second middle sipes 32 have the same tire axial length as the first middle sipe 31.

[0047] The first middle sipe 31 and the second middle sipe 32 are inclined, for example, in the same direction as the middle lateral groove 20 with respect to the tire axis. The angle of these sipes with respect to the tire axis is, for example, 10 to 50°, preferably 25 to 35°. In a preferred embodiment, the first middle sipe 31 and the longitudinal sipe 30 are connected such that the corner between them is acute. Similarly, the second middle sipe 32 and the longitudinal sipe 30 are connected such that the corner between them is acute. This allows the corners to easily bite into the road surface when driving on snow, resulting in excellent snow performance.

[0048] Figure 8 shows a cross-sectional view of line EE in Figure 2. Figure 8 is a cross-sectional view of the first middle sipe 31, and the configuration described below can also be applied to the second middle sipe 32. As shown in Figure 8, the first middle sipe 31 opens at the tread surface 13s via a chamfered portion 35. The chamfered portion 35 includes an inclined surface 35s cut out between the tread surface 13s and the sipe wall 31w. The inclined surface 35s in this embodiment is slightly curved in a direction that is convex outward in the radial direction of the tire. The inclined surface 35s may be, for example, flat. Such a chamfered portion 35 helps to equalize the contact pressure acting on the tread surface 13s, thereby improving handling stability and resistance to uneven wear.

[0049] As shown in Figure 2, it is desirable that the chamfered portion 35 of the first middle sipe 31 has a chamfer width that decreases toward the longitudinal sipe 30. Similarly, it is desirable that the chamfered portion 35 of the second middle sipe 32 has a chamfer width that decreases toward the longitudinal sipe 30. This ensures a contact area in the central part of the first middle ground portion 13, thereby maintaining steering stability. The chamfer width is the opening width of the chamfered portion in a plan view of the tread. Furthermore, the opening width refers to the width perpendicular to the longitudinal direction of the sipe.

[0050] The first middle sipe 31 and the second middle sipe 32 of this embodiment include a main body portion that extends linearly in the tire radial direction in its cross-section. However, these sipes are not limited to this configuration. In another embodiment, the first middle sipe 31 and the second middle sipe 32 may include a main body portion that extends in a zigzag pattern in the tire radial direction in its cross-section. In yet another embodiment, the first middle sipe 31 and the second middle sipe 32 may be configured as so-called 3D sipes that include a main body portion that extends in a zigzag pattern in the tire radial direction in its cross-section and also extends in a zigzag pattern in a tread plan view.

[0051] Figure 9 shows an enlarged view of the crown landing area 15 of Figure 1. The crown landing area 15 includes a first longitudinal edge 15a extending in the circumferential direction of the tire on the first tread end T1 side, a second longitudinal edge 15b extending in the circumferential direction of the tire on the second tread end T2 side, and a tread surface 15s between the first longitudinal edge 15a and the second longitudinal edge 15b. The crown landing area 15 is also provided with a plurality of first crown sipes 41, a plurality of second crown sipes 42, a plurality of third crown sipes 43, and a plurality of fourth crown sipes 44.

[0052] Figure 10 shows enlarged views of the first crown sipe 41, the second crown sipe 42, the third crown sipe 43, and the fourth crown sipe 44. As shown in Figure 10, these sipes are inclined in the same direction with respect to the tire axis. In a preferred embodiment, these sipes are inclined in the same direction with respect to the tire axis as the middle lateral groove 20 (shown in Figure 2). The angle of these sipes with respect to the tire axis is, for example, 25 to 35°.

[0053] The first crown sipe 41 extends from the first longitudinal edge 15a and has a cut-off end 41a within the tread surface 15s. The second crown sipe 42 extends from the second longitudinal edge 15b and has a cut-off end 42a within the tread surface 15s. The third crown sipe 43 extends from the first longitudinal edge 15a and has a cut-off end 43a within the tread surface 15s. In a plan view of the tread, the third crown sipe 43 has a different shape from the first crown sipe 41. The fourth crown sipe 44 extends from the second longitudinal edge 15b and has a cut-off end 44a within the tread surface 15s. In a plan view of the tread, the fourth crown sipe 44 has a different shape from the second crown sipe 42.

[0054] The circumferential distance L4 between the outer end 41b of the first crown sipe 41 on the side of the first longitudinal edge 15a and the outer end 42b of the second crown sipe 42 on the side of the second longitudinal edge 15b is preferably 10% or less of the circumferential pitch length P1 of the first crown sipe 41 (shown in Figure 9). This makes it easier for water pushed aside by the crown land portion 15 during wet driving to be guided to the outer end of either sipe, thereby improving wet performance.

[0055] The axial length L6 of the first crown sipe 41 is, for example, 40% to 60% of the axial width W5 of the tread surface 15s of the crown land portion 15 (shown in Figure 9, and similarly hereafter).

[0056] The second crown sipe 42 is preferably positioned across the center of the tread surface 15s of the crown base 15 in the tire axial direction. The interrupted end 42a of the second crown sipe 42 is located closer to the first longitudinal edge 15a than the interrupted end 41a of the first crown sipe 41. The axial length L7 of the second crown sipe 42 is preferably greater than the axial length L6 of the first crown sipe 41. Specifically, the length L7 of the second crown sipe 42 is 65% to 85% of the width W5 of the tread surface 15s of the crown base 15. Such a second crown sipe 42 can improve snow performance and wet performance while maintaining handling stability.

[0057] The circumferential distance L5 between the outer end 43b of the third crown sipe 43 on the first longitudinal edge 15a side and the outer end b of the fourth crown sipe 44 on the second longitudinal edge 15b side should preferably be 10% or less of the circumferential pitch length P2 of the third crown sipe 43 (shown in Figure 9). This further improves wet performance.

[0058] The axial length L8 of the third crown sipe 43 is smaller than the length L7 of the second crown sipe 42 and smaller than the length L6 of the first crown sipe 41. Furthermore, the end 43a of the third crown sipe 43 is located closer to the first longitudinal edge 15a than the end 44a of the fourth crown sipe 44. In a more desirable embodiment, the end 43a of the third crown sipe 43 is located closer to the second longitudinal edge 15b than the end 42a of the second crown sipe 42. The length L8 of the third crown sipe 43 is 25% to 45% of the width W5 of the tread surface 15s of the crown land portion 15. Such a third crown sipe 43 helps to balance handling stability with snow performance and wet performance.

[0059] From a similar viewpoint, the axial length L9 of the fourth crown sipe 44 is, for example, smaller than the length L7 of the second crown sipe 42 and smaller than the length L6 of the first crown sipe 41. Specifically, the length L9 of the fourth crown sipe 44 is 25% to 45% of the width W5 of the tread surface 15s of the crown land portion 15.

[0060] The first crown sipe 41, the second crown sipe 42, the third crown sipe 43, and the fourth crown sipe 44 each open on the tread surface 15s via a chamfered portion 45. This equalizes the ground pressure acting on the tread surface 15s of the crown land portion 15, improving steering stability and resistance to uneven wear. The chamfered portion 45 of these sipes can be made using the same configuration as the chamfered portion 35 of the first middle sipe 31 (shown in Figure 8), and a detailed explanation is omitted here.

[0061] As shown in Figure 9, it is desirable that the entire length of the first crown sipe 41 and the second crown sipe 42 opens to the tread surface via a chamfered portion 45. Furthermore, it is desirable that the chamfer width W6 of the chamfered portion 45 of the first crown sipe 41 and the chamfer width W7 of the chamfered portion 45 of the second crown sipe 42 are constant in the longitudinal direction of the sipe. In addition, the chamfer width W7 of the chamfered portion 45 of the second crown sipe 42 is 80% to 120% of the chamfer width W6 of the chamfered portion 45 of the first crown sipe 41, and in this embodiment, these are substantially the same. This suppresses uneven wear around these sipes.

[0062] It is desirable that the chamfer width of the chamfered portion 45 of the third crown sipe 43 continuously decreases from the first longitudinal edge 15a toward the interrupted end 43a. It is also desirable that the chamfer width of the chamfered portion 45 of the fourth crown sipe 44 continuously decreases from the second longitudinal edge 15b toward the interrupted end 44a. This ensures sufficient contact area in the central part of the crown land portion 15 and reliably maintains steering stability. In this embodiment, the chamfered portion of the third crown sipe 43 is substantially gone at the interrupted end 43a, but the embodiment is not limited to this configuration, and the chamfered portion 45 may remain at the interrupted end 43a. The same applies to the fourth crown sipe 44.

[0063] The maximum chamfer width W8 of the chamfered portion 45 of the third crown sipe 43 is smaller than the chamfer width W6 of the chamfered portion 45 of the first crown sipe 41. Specifically, the chamfer width W8 of the third crown sipe 43 is 75% to 90% of the chamfer width W6 of the first crown sipe 41. Similarly, the maximum chamfer width W9 of the chamfered portion 45 of the fourth crown sipe 44 is smaller than the chamfer width W7 of the chamfered portion 45 of the second crown sipe 42. Specifically, the chamfer width W9 of the fourth crown sipe 44 is 75% to 90% of the chamfer width W7 of the second crown sipe 42. Such third crown sipes 43 and fourth crown sipes 44 help to balance and enhance handling stability and snow performance.

[0064] Each crown sipe in this embodiment includes a main body that extends linearly in the tire radial direction in its cross-section. However, these sipes are not limited to this configuration. In another embodiment, each crown sipe may include a main body that extends in a zigzag pattern in the tire radial direction in its cross-section. In yet another embodiment, each crown sipe may be configured as a so-called 3D sipe that includes a main body that extends in a zigzag pattern in the tire radial direction in its cross-section and also extends in a zigzag pattern in a tread plan view.

[0065] Figure 11 shows an enlarged view of the second middle tread section 14. As shown in Figure 11, the second middle tread section 14 has a third middle lateral groove 23 and a fourth middle lateral groove 24 alternately arranged in the circumferential direction of the tire. The third middle lateral groove 23 and the fourth middle lateral groove 24 have a common shape in a plan view of the tread and completely cross the second middle tread section 14 in the axial direction of the tire. In addition, the third middle lateral groove 23 and the fourth middle lateral groove 24 are inclined in the same direction as the middle lateral groove 20 (shown in Figure 2) with respect to the axial direction of the tire. The angles of the third middle lateral groove 23 and the fourth middle lateral groove 24 with respect to the axial direction of the tire are smaller than the angles of the middle lateral groove 20 (shown in Figure 2) with respect to the axial direction of the tire, and are smaller than the angles of each sipe provided on the crown tread section 15 (shown in Figure 9) with respect to the axial direction of the tire. Specifically, the angles of the third middle lateral groove 23 and the fourth middle lateral groove 24 with respect to the axial direction of the tire are, for example, 10 to 20°. On the other hand, the third middle horizontal groove 23 and the fourth middle horizontal groove 24 have different internal structures.

[0066] Figure 12 shows a cross-sectional view along the FF line of Figure 11. As shown in Figure 12, the third middle lateral groove 23 has a shallow groove portion 46 on the second crown circumferential groove 8 side and a deep groove portion 47 on the second shoulder circumferential groove 6 side. Figure 13 shows a cross-sectional view along the GG line of Figure 11. As shown in Figure 13, the fourth middle lateral groove 24 has a substantially inverted shape of the third middle lateral groove 23. That is, the fourth middle lateral groove 24 has a deep groove portion 47 on the second crown circumferential groove 8 side and a shallow groove portion 46 on the second shoulder circumferential groove 6 side. In this embodiment, by alternately providing such third middle lateral grooves 23 and fourth middle lateral grooves 24 in the circumferential direction of the tire, resistance to uneven wear and handling stability are improved.

[0067] The shallow groove portions 46 of the third middle lateral groove 23 and the fourth middle lateral groove 24 can be configured with the same configuration as the shallow groove portion 36 of the middle lateral groove 20 (shown in Figure 7). Similarly, the deep groove portions 47 of the third middle lateral groove 23 and the fourth middle lateral groove 24 can be configured with the same configuration as the deep groove portion 37 of the middle lateral groove 20 (shown in Figure 6).

[0068] As shown in Figure 11, the second middle section 14 is provided with multiple middle sipe groups 55 in the tire circumferential direction, each consisting of multiple bent sipes 56 arranged in the tire axial direction. In this embodiment, the middle sipe groups 55 are formed by arranging multiple bent sipes 56 so as to overlap in the tire axial direction. The bent sipes 56 include a portion that protrudes on one or the other side in the tire circumferential direction. Such middle sipe groups 55 are difficult to open during braking and driving, so snow and ice are less likely to accumulate inside when driving on snow, and excellent snow performance can be sustained.

[0069] As shown in Figure 1, the first shoulder land portion 11 is provided with a plurality of first shoulder lateral grooves 51 and first shoulder sipes 52. The first shoulder lateral grooves 51 and first shoulder sipes 52 extend, for example, from the first shoulder circumferential groove 5 to at least the first tread edge T1. The second shoulder land portion 12 is provided with a plurality of second shoulder lateral grooves 53 and a shoulder sipe group 60 in which a plurality of bent sipes 61 are arranged in the tire axial direction. The shoulder sipe group 60 has substantially the same configuration as the middle sipe group 55 described above. These lateral grooves and sipes help to further improve snow performance.

[0070] Although a tire according to one embodiment of the present disclosure has been described in detail above, the present disclosure is not limited to the specific embodiment described above and can be implemented in various modified forms.

[0071] [Note] This disclosure includes the following aspects:

[0072] [Disclosure 1] A tire having a tread portion, The tread portion includes a first tread end, a second tread end, and a first middle land portion provided between the first tread end and the second tread end. The first middle section includes a first longitudinal edge extending in the circumferential direction of the tire at the first tread end, a second longitudinal edge extending in the circumferential direction of the tire at the second tread end, and a tread surface between the first longitudinal edge and the second longitudinal edge. The first middle section is provided with a plurality of middle lateral grooves that completely traverse the first middle section in the tire axial direction, and a plurality of first middle sipes that extend from the first longitudinal edge and have interrupted ends within the tread surface. Each of the aforementioned middle lateral grooves includes a first groove portion extending in the tire axial direction from the first longitudinal edge, a second groove portion extending in the tire axial direction from the second longitudinal edge, and a longitudinal groove portion communicating with the first groove portion and the second groove portion and extending in the tire circumferential direction. The longitudinal groove portion includes a first longitudinal groove edge on the first longitudinal edge side and a second longitudinal groove edge on the second longitudinal edge side. Each of the aforementioned interrupted ends of the plurality of first middle sipes is located on the second longitudinal edge side of the first longitudinal groove edge. tire. [Disclosure 2] The tire according to Disclosure 1, wherein one first middle sipe is provided between two adjacent middle lateral grooves in the circumferential direction of the tire. [Disclosure 3] The first middle sipe has a chamfered portion formed therein. The tire according to disclosure 1 or 2, wherein the chamfer width of the chamfered portion of the first middle sipe decreases toward the interrupted end of the first middle sipe. [Disclosure 4] The tire according to any one of disclosures 1 to 3, wherein the length of the first middle sipe in the tire axial direction is 40% to 60% of the maximum width of the tread surface in the tire axial direction of the first middle land portion. [Disclosure 5] The first middle section is provided with a plurality of second middle sipes that extend from the second longitudinal edge and have a broken end within the tread surface. The tire according to any one of disclosures 1 to 4, wherein the interrupted end of the second middle sipe is located on the first longitudinal edge side of the second longitudinal groove edge. [Disclosure 6] The tire according to disclosure 5, wherein only one second middle sipe is provided between two adjacent middle lateral grooves in the circumferential direction of the tire. [Disclosure 7] The second middle sipe has a chamfered portion formed therein. The tire according to disclosure 5 or 6, wherein the chamfer width of the chamfered portion of the second middle sipe decreases toward the interrupted end of the second middle sipe. [Disclosure 8] The tire according to any one of disclosures 5 to 7, wherein the interrupted end of the second middle sipe is located on the first longitudinal edge side than the interrupted end of the first middle sipe. [Explanation of Symbols]

[0073] 2 Tread section 13. 1st Middle Track and Field Club 20 Middle Horizontal Groove 26. First groove 27 Second groove 28. Longitudinal grooves 28a First longitudinal groove margin 28b Second longitudinal groove margin 31. First Middle Sipe 31a Interrupted end T1 First tread end T2 Second tread end

Claims

1. A tire having a tread portion, The tread portion includes a first tread end, a second tread end, and a first middle land portion provided between the first tread end and the second tread end. The first middle section includes a first longitudinal edge extending in the circumferential direction of the tire at the first tread end, a second longitudinal edge extending in the circumferential direction of the tire at the second tread end, and a tread surface between the first longitudinal edge and the second longitudinal edge. The first middle section is provided with a plurality of middle lateral grooves that completely traverse the first middle section in the tire axial direction, and a plurality of first middle sipes that extend from the first longitudinal edge and have interrupted ends within the tread surface. Each of the aforementioned middle lateral grooves includes a first groove portion extending in the tire axial direction from the first longitudinal edge, a second groove portion extending in the tire axial direction from the second longitudinal edge, and a longitudinal groove portion communicating with the first groove portion and the second groove portion and extending in the tire circumferential direction. The longitudinal groove portion includes a first longitudinal groove edge on the first longitudinal edge side and a second longitudinal groove edge on the second longitudinal edge side. Each of the aforementioned interrupted ends of the plurality of first middle sipes is located on the second longitudinal edge side of the first longitudinal groove edge, The first middle land portion is provided between the first shoulder circumferential groove, which is located closest to the first tread end T1, and the first crown circumferential groove, which is located between the first shoulder circumferential groove and the tire equator. Between two adjacent middle lateral grooves in the circumferential direction of the tire, only one of the first middle sipes is provided. tire.

2. The first middle sipe has a chamfered portion formed therein. The tire according to claim 1, wherein the chamfer width of the chamfered portion of the first middle sipe decreases toward the interrupted end of the first middle sipe.

3. The tire according to claim 1 or 2, wherein the length of the first middle sipe in the tire axial direction is 40% to 60% of the maximum width in the tire axial direction of the tread surface of the first middle land portion.

4. The first middle land portion is provided with a plurality of second middle sipes extending from the second longitudinal edge and having a discontinuous end within the tread surface, The tire according to any one of claims 1 to 3, wherein the interrupted end of the second middle sipe is located on the first longitudinal edge side of the second longitudinal groove edge.

5. The tire according to claim 4, wherein only one second middle sipe is provided between two adjacent middle lateral grooves in the circumferential direction of the tire.

6. The second middle sipe has a chamfered portion formed therein. The tire according to claim 4 or 5, wherein the chamfer width of the chamfered portion of the second middle sipe decreases toward the interrupted end of the second middle sipe.

7. The tire according to any one of claims 4 to 6, wherein the interrupted end of the second middle sipe is located on the first longitudinal edge side than the interrupted end of the first middle sipe.

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