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 middle land part. The first middle land part is provided with a plurality of middle lateral grooves 20 completely crossing the first middle land part, in a tire axial direction. At least one of the middle lateral grooves 20 includes a first groove part 26 extending in the tire axial direction from a first vertical edge 13a, and a second groove part 27 extending in the tire axial direction from a second vertical edge 13b. The first groove part 26 and the second groove part 27 are positionally shifted in a tire circumferential direction, so that a vertical groove edge 28e extending in the tire circumferential direction is formed between a groove edge 26e of the first groove part 26 and a groove edge 27e of the second groove part 27. A maximum depth of the first groove part 26 is different from a maximum depth of the second groove part 27.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] This disclosure relates to tires.

Background Art

[0002] In Patent Document 1 below, a pneumatic tire having a plurality of middle lateral grooves provided in each middle land portion is proposed. In the middle lateral groove, a rib having a raised groove bottom is provided. The pneumatic tire expects to maintain the handling stability on a dry road surface and improve the snow performance by the middle lateral groove and the rib.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] )]]In recent years, with the improvement of the performance of the power unit of vehicles, further improvement in handling stability on dry road surfaces and snow performance has been demanded.

[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 handling stability on a dry road surface.

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, a tire equator, and a first middle land portion provided between the first tread end and the tire equator, 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 being provided in the axial direction of the tire The tire is provided with a plurality of middle lateral grooves that completely traverse the direction, and at least one of the middle lateral grooves includes a first groove portion extending in the tire axial direction from the first longitudinal edge and a second groove portion extending in the tire axial direction from the second longitudinal edge, and a longitudinal groove edge extending in the tire circumferential direction is formed between the groove edge of the first groove portion and the groove edge of the second groove portion due to the displacement of the first groove portion and the second groove portion, and the maximum depth of the first groove portion is different from the maximum depth of the second groove portion. [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 enlarged views of the first and second middle transverse grooves. [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. [Figure 14] This is an enlarged view of the second middle track section of another embodiment of the present disclosure. [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 the orientation of mounting on a vehicle. Thereby, the first tread end T1 is intended to be located outside the vehicle when mounted on the vehicle. The second tread end T2 is intended to be located inside the vehicle when mounted on the vehicle. The orientation of mounting on the vehicle is, for example, indicated by characters or symbols on a sidewall portion (not shown). However, the tire 1 of the present disclosure is not limited to such a mode, and may be one in which the orientation of mounting on the vehicle is not specified.

[0012] The first tread end T1 and the second tread end T2 respectively correspond to the ends of the grounding 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 for which various standards are defined, the tire is rim - assembled 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 for which various standards are not defined or a non - pneumatic tire, the "normal state" means a standard use state according to the purpose of use of the tire, and it is a state where the tire is not mounted on a vehicle and is 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.

[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 JATMA, it is the "standard rim", in TRA, it is the "Design Rim", and in ETRTO, it is the "Measuring Rim".

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

[0016] "Regular load" refers to the load specified for each tire within the standard system, including the standard on which the tire is based, in the case of pneumatic tires for which various standards are defined. For example, it is the "maximum load capacity" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "LOAD CAPACITY" for ETRTO. For tires for which no various standards are defined, "regular load" refers to the maximum load that can be applied when using the tire, in accordance with the above standards.

[0017] The circumferential groove 3 includes a first shoulder circumferential groove 5 and a second shoulder circumferential groove 6, and a first crown circumferential groove 7 and a second crown circumferential groove 8 provided between them. The first shoulder circumferential groove 5 is provided furthest towards the first tread edge T1 among the multiple circumferential grooves 3. The second shoulder circumferential groove 6 is provided furthest towards the second tread edge T2 among the multiple 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 five land sections 4 of this disclosure include a first middle land section 13 located between the first tread end T1 and the tire equator C. The first middle land section 13 is divided between the first shoulder circumferential groove 5 and the first crown circumferential groove 7. The land section 4 of this embodiment includes a first shoulder land section 11, a second shoulder land section 12, a second middle land section 14, and a crown land section 15. The first shoulder land section 11 includes the first tread end T1 and is adjacent to the first middle land section 13 via the first shoulder circumferential groove 5. The second shoulder land section 12 includes the second tread end T2 and is divided on the tire axial side of the second shoulder circumferential groove 6. The second middle land section 14 is located 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.

[0023] Figure 3 shows an enlarged view of the two middle lateral grooves 20. Figure 3 is an enlarged view of the first middle lateral groove 21 and the second middle lateral groove 22, which will be described later. As shown in Figure 3, at least one of the middle lateral grooves 20 includes a first groove portion 26 and a second groove portion 27. The first groove portion 26 extends from the first longitudinal edge 13a in the tire axial direction. The second groove portion 27 extends from the second longitudinal edge 13b in the tire axial direction.

[0024] In this disclosure, the first groove 26 and the second groove 27 are misaligned in the circumferential direction of the tire, so that a longitudinal groove edge 28e extending in the circumferential direction of the tire is formed between the groove edge 26e of the first groove 26 and the groove edge 27e of the second groove 27. Furthermore, the maximum depth of the first groove 26 is different from the maximum depth of the second groove 27. 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.

[0025] When driving on snow, the middle lateral grooves 20 compress the snow within them and shear it, thereby providing a large reaction force (hereinafter, such a reaction force may be referred to as "snow column shear force"). Furthermore, because the maximum depths of the first groove section 26 and the second groove section 27 are different, the groove with the smaller depth maintains the rigidity of the first middle land section 13 and maintains steering stability, while the groove with the larger depth can provide a large snow column shear force, improving snow performance.

[0026] Furthermore, the longitudinal groove edge 28e described above provides frictional force in the tire axial direction, which helps improve turning performance on snow. In addition, when the longitudinal groove edge 28e is combined with the first groove 26 and second groove 27 described above, snow that enters the groove with greater depth is more easily compressed in the tire axial direction, resulting in a greater snow column shear force. It is believed that the tire 1 of this disclosure can exhibit excellent snow performance while maintaining handling stability through this mechanism.

[0027] 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.

[0028] As shown in Figures 2 and 3, in this embodiment, each middle lateral groove 20 has the above-described characteristics. 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 (shown in Figure 2). The groove width W3 of the first groove 26 and the second groove 27 is, for example, 15% to 25% of the width W2 (shown in Figure 2) 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°.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] As shown in Figure 5, the second middle lateral groove 22 has a substantially inverted shape 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.

[0033] 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.

[0034] 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).

[0035] 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.

[0036] 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. The definition of "sipe" will be described later. Such groove bottom sipes 38 help to open the shallow groove section 36 appropriately and 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 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.

[0037] As shown in Figure 3, in this embodiment, each of the groove edges on both sides of one middle lateral groove 20 includes a longitudinal groove edge 28e. These two longitudinal groove edges 28e 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 positions the two longitudinal groove edges 28e so as to sandwich the tire axial center position of the tread surface 13s of the first middle land portion 13. Furthermore, the two longitudinal groove edges 28e each extend along the tire circumferential direction, and in a preferred embodiment, they extend parallel to each other. The angle of the longitudinal groove edges 28e with respect to the tire circumferential direction is, for example, 10° or less, and preferably 5° or less. The length L3 of the longitudinal groove edge 28e in the tire circumferential direction is preferably smaller than the maximum groove width in the first groove portion 26 and the second groove portion 27. Specifically, the length L3 is 75% to 95% of the groove width. Such longitudinal groove edges 28e can suppress uneven wear while improving turning performance when driving on snow.

[0038] The middle horizontal groove 20 includes a vertical groove 28 provided between the first groove 26 and the second groove 27. In this embodiment, for example, the region between one vertical groove edge 28e and a virtual extension line extending in the longitudinal direction thereof and the other vertical groove edge 28e and a virtual extension line extending in the longitudinal direction thereof is configured as the vertical groove 28.

[0039] 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.

[0040] 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.

[0041] In this specification, "sipe" means a small-width notch in which the width between two sipe walls is 1.5 mm or less in the sipe body. The sipe body also means the portion in which two sipe walls extend approximately parallel to each other in the tire radial direction. "Approximately parallel" means an embodiment in which the angle between the two sipe walls is 10° or less. 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. In this embodiment, the vertical sipe 30 extends with a constant width from the tread surface 13s of the first middle land portion 13 to the bottom.

[0042] 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.

[0043] 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.

[0044] As shown in Figure 2, the first middle section 13 is provided with a plurality of first middle sipes 31 and a plurality of second middle sipes 32. The first middle sipes 31 extend from the first longitudinal edge 13a and communicate with the longitudinal sipe 30. 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 in cooperation with the longitudinal sipe 30 to provide frictional force in multiple directions, further improving snow performance.

[0045] 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, 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 bite into the road surface more easily when driving on snow, resulting in excellent snow performance.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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°.

[0050] 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.

[0051] 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.

[0052] 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 the same applies hereafter). In this specification, the length of the sipe is measured from the center line of the sipe.

[0053] 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.

[0054] 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 44b of the fourth crown sipe 44 on the second longitudinal edge 15b side is preferably 10% or less of the circumferential pitch length P2 of the third crown sipe 43 (shown in Figure 9). This further improves wet performance.

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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).

[0064] 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.

[0065] This disclosure is not limited to the second middle tread 14 shown in Figure 11. Figure 14 shows an enlarged view of the second middle tread 14 in another embodiment of this disclosure. As shown in Figure 14, the second middle tread 14 of this embodiment is provided with a plurality of third middle sipes 33 and a plurality of fourth middle sipes 34, in addition to the third middle lateral grooves 23 and fourth middle lateral grooves 24 described above. The third middle sipes 33 extend from the second crown circumferential groove 8 and are interrupted within the tread surface of the second middle tread 14. The fourth middle sipes 34 extend from the second shoulder circumferential groove 6 and are interrupted within the tread surface. The third middle sipes 33 and the fourth middle sipes 34 are inclined, for example, in the same direction as the third middle lateral grooves 23 and fourth middle lateral grooves 24 with respect to the tire axis. The angle of these sipes with respect to the tire axis is, for example, 10 to 20°. The configuration of the first middle sipe 31 or the second middle sipe 32 described above can be applied to the third middle sipe 33 and the fourth middle sipe 34.

[0066] In another embodiment, in the second middle land section 14, for example, the middle sipe group 55 (shown in Figure 11) and the third middle sipe 33 and fourth middle sipe 34 shown in Figure 14 may be arranged between the third middle lateral groove 23 and the fourth middle lateral groove 24, which are adjacent in the circumferential direction of the tire (not shown). Such a sipe arrangement helps to further improve snow performance.

[0067] 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.

[0068] 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. [Examples]

[0069] A pneumatic tire of size 245 / 40ZR18 with the basic pattern shown in Figure 1 was prototyped. As a comparative example, a tire was prototyped in which the first middle land section had multiple middle lateral grooves extending inclined in the tire axial direction with a constant groove width, without including longitudinal grooves (not shown). The first middle land section of the comparative example extends in the tire axial direction to a constant depth. The depth of the middle lateral grooves in the comparative example was determined so that the groove volume was substantially the same as that of the middle lateral grooves in the embodiment. Except for the above, the embodiment and the comparative example have substantially the same configuration. The handling stability on dry surfaces and snow performance were tested for both the embodiment and the comparative example. The common specifications and test methods for each test tire are as follows. Mounted rim: 18×8.5J Tire pressure: 240kPa for all wheels Test vehicle: 2000cc engine, rear-wheel drive Tire mounting position: All wheels

[0070] <Handling stability on dry surfaces> The handling stability of the above test vehicle when driven on a dry surface was evaluated subjectively by the driver. The results are scored with the handling stability of the comparative example set at 100, and a higher number indicates better handling stability.

[0071] <Snow performance> The snow performance of the above test vehicles was evaluated subjectively by the drivers. The results are scored with the snow performance of the comparative example set at 100, and a higher number indicates better snow performance. The test results are shown in Table 1.

[0072] [Table 1]

[0073] The test results confirmed that the tires in this example exhibited excellent snow performance while maintaining handling stability on dry surfaces.

[0074] [Note] This disclosure includes the following aspects:

[0075] [Disclosure 1] A tire having a tread portion, The tread portion includes a first tread end, a second tread end, a tire equator, and a first middle land portion provided between the first tread end and the tire equator. 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 land portion is provided with a plurality of middle lateral grooves that completely traverse the first middle land portion in the direction of the tire axis, At least one of the middle lateral grooves includes a first groove portion extending in the tire axial direction from the first longitudinal edge and a second groove portion extending in the tire axial direction from the second longitudinal edge. As the first groove and the second groove are misaligned in the circumferential direction of the tire, a longitudinal groove edge extending in the circumferential direction of the tire is formed between the groove edge of the first groove and the groove edge of the second groove. The maximum depth of the first groove is different from the maximum depth of the second groove. tire. [Disclosure 2] The middle lateral groove includes a plurality of first middle lateral grooves in which the maximum depth of the first groove is less than the maximum depth of the second groove, and a plurality of second middle lateral grooves in which the maximum depth of the first groove is greater than the maximum depth of the second groove. The tire according to Disclosure 1, wherein the first middle lateral groove and the second middle lateral groove are alternately provided in the circumferential direction of the tire. [Disclosure 3] The tire according to disclosure 1 or 2, wherein the length of the longitudinal groove edge in the tire circumferential direction is smaller than the maximum groove width in the first groove and the second groove. [Disclosure 4] The aforementioned middle lateral groove includes a longitudinal groove provided between the first groove and the second groove, The tire according to any one of disclosures 1 to 3, wherein the maximum depth of the longitudinal groove is smaller than the maximum depth of the first groove and the maximum depth of the second groove. [Disclosure 5] The tire according to any one of disclosures 1 to 4, wherein the first middle land portion is provided with at least one longitudinal sipe that crosses the middle transverse groove in the tire circumferential direction. [Disclosure 6] The tire according to disclosure 5, wherein the first middle land portion is provided with at least one first middle sipe extending from the first longitudinal edge and communicating with the longitudinal sipe. [Disclosure 7] The tire according to disclosure 5 or 6, wherein the first middle land portion is provided with at least one second middle sipe extending from the second longitudinal edge and communicating with the longitudinal sipe. [Disclosure 8] The tread portion is specified in the orientation in which it is mounted on the vehicle. The first tread end is located on the outside of the vehicle when mounted on the vehicle, as described in any one of disclosures 1 to 7. [Explanation of Symbols]

[0076] 2 Tread section 13. 1st Middle Track and Field Club 13a First longitudinal edge 13b Second vertical edge 13s tread 20 Middle Horizontal Groove 26. First groove 27 Second groove 28e Longitudinal groove edge T1 First tread end T2 Second tread end C Tire Equator

Claims

1. A tire having a tread portion, The tread portion includes a first tread end, a second tread end, a tire equator, and a first middle land portion provided between the first tread end and the tire equator. 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 land portion is provided with a plurality of middle lateral grooves that completely traverse the first middle land portion in the direction of the tire axis, At least one of the middle lateral grooves includes a first groove portion extending in the tire axial direction from the first longitudinal edge and a second groove portion extending in the tire axial direction from the second longitudinal edge. As the first groove and the second groove are misaligned in the circumferential direction of the tire, a longitudinal groove edge extending in the circumferential direction of the tire is formed between the groove edge of the first groove and the groove edge of the second groove. The maximum depth of the first groove is different from the maximum depth of the second groove. The length of the longitudinal groove edge in the tire circumferential direction is smaller than the maximum groove width in the first groove and the second groove. tire.

2. The tire according to claim 1, wherein the first middle land portion is provided with at least one longitudinal sipe that crosses the middle transverse groove in the circumferential direction of the tire.

3. A tire having a tread portion, The tread portion includes a first tread end, a second tread end, a tire equator, and a first middle land portion provided between the first tread end and the tire equator. 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 land portion is provided with a plurality of middle lateral grooves that completely traverse the first middle land portion in the tire axial direction, at least one longitudinal sipe that crosses the middle lateral grooves in the tire circumferential direction, and at least one first middle sipe that extends from the first longitudinal edge and communicates with the longitudinal sipe. At least one of the middle lateral grooves includes a first groove portion extending in the tire axial direction from the first longitudinal edge and a second groove portion extending in the tire axial direction from the second longitudinal edge. As the first groove and the second groove are misaligned in the circumferential direction of the tire, a longitudinal groove edge extending in the circumferential direction of the tire is formed between the groove edge of the first groove and the groove edge of the second groove. The maximum depth of the first groove is different from the maximum depth of the second groove. tire.

4. A tire having a tread portion, The tread portion includes a first tread end, a second tread end, a tire equator, and a first middle land portion provided between the first tread end and the tire equator. 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 land portion is provided with a plurality of middle lateral grooves that completely traverse the first middle land portion in the tire axial direction, at least one longitudinal sipe that crosses the middle lateral grooves in the tire circumferential direction, and at least one second middle sipe that extends from the second longitudinal edge and communicates with the longitudinal sipe. At least one of the middle lateral grooves includes a first groove portion extending in the tire axial direction from the first longitudinal edge and a second groove portion extending in the tire axial direction from the second longitudinal edge. As the first groove and the second groove are misaligned in the circumferential direction of the tire, a longitudinal groove edge extending in the circumferential direction of the tire is formed between the groove edge of the first groove and the groove edge of the second groove. The maximum depth of the first groove is different from the maximum depth of the second groove. tire.

5. The middle lateral groove includes a plurality of first middle lateral grooves in which the maximum depth of the first groove portion is less than the maximum depth of the second groove portion, and a plurality of second middle lateral grooves in which the maximum depth of the first groove portion is greater than the maximum depth of the second groove portion. The tire according to any one of claims 1 to 4, wherein the first middle lateral groove and the second middle lateral groove are alternately provided in the circumferential direction of the tire.

6. The middle horizontal groove includes a vertical groove provided between the first groove and the second groove, The tire according to any one of claims 1 to 5, wherein the maximum depth of the longitudinal groove is smaller than the maximum depth of the first groove and the maximum depth of the second groove.

7. The tread portion is specified in the direction in which it is mounted on the vehicle. The tire according to any one of claims 1 to 6, wherein the first tread end is located on the outside of the vehicle when mounted on the vehicle.

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