tire

Abstract

To provide a tire improving braking performance while maintaining steering stability.SOLUTION: Provided is a tire with a tread part 2. The tread part 2 includes a pair of shoulder peripheral direction grooves 3A, a pair of crown peripheral direction grooves 3B, and a pair of middle land parts 4A. A plurality of middle sipes 15 are disposed on each of the middle land parts 4A. In the middle sipe 15, at least either of sipe edges on both sides thereof is formed on a chamfer part 20. The chamfer part 20 extends from the crown peripheral direction groove 3B to the shoulder peripheral direction groove 3A. A first chamfer width W3 at an end on the side of the crown peripheral direction groove 3B of the chamfer part 20 is greater than a second chamfer width W4 at an end on the side of the shoulder peripheral direction groove 3A of the chamfer part 20.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This disclosure relates to tires.

Background Art

[0002] Patent Document 1 below proposes a tire in which middle sipes are provided in each of a first middle land portion and a second middle land portion. The tire expects to improve noise performance and handling stability by the middle sipes.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, tires are required to improve braking performance and handling stability. As one means of improving braking performance, forming the siped edge of the middle sipes with a chamfered portion can be mentioned. The chamfered portion can equalize the ground pressure acting on the ground contact surface of the land portion around the sipes. Such an action helps to increase the frictional force in the tire circumferential direction provided by the land portion and improve the braking performance.

[0005] However, in order to further enhance the above-described effects, if the width of the chamfered portion is increased, the ground contact area of the land portion decreases, leading to deterioration of steering responsiveness, and ultimately there is a risk of deterioration of handling stability.

[0006] This disclosure has been devised in view of the above actual situation, and the main problem is to provide a tire that improves braking performance while maintaining handling stability.

Means for Solving the Problems

[0007] The present disclosure relates to a tire having a tread portion, the tread portion comprising four circumferential grooves extending continuously in the circumferential direction of the tire between two tread ends, and five land portions divided into the four circumferential grooves, the four circumferential grooves comprising a pair of shoulder circumferential grooves and a pair of crown circumferential grooves between the pair of shoulder circumferential grooves, the land portions comprising a pair of middle land portions divided between the shoulder circumferential grooves and the crown circumferential grooves, each of the middle land portions being provided with a plurality of middle sipes that completely traverse the middle land portion in the axial direction of the tire, the middle sipes having at least one of the sipe edges on both sides formed by a chamfer, the chamfer extending from the crown circumferential groove to the shoulder circumferential groove in a plan view of the tread, and the first chamfer width at the end of the chamfer on the crown circumferential groove side being greater than the second chamfer width at the end of the chamfer on the shoulder circumferential groove side. [Effects of the Invention]

[0008] By adopting the above configuration, the tire of this disclosure can improve braking performance while maintaining handling stability. [Brief explanation of the drawing]

[0009] [Figure 1] This is an exploded view of the tread portion showing one embodiment of the present disclosure. [Figure 2] Figure 1 shows enlarged views of the pair of middle and crown track areas. [Figure 3] Figure 2 is a magnified view of the 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] This is an enlarged view of the inner shoulder land area of ​​Figure 1. [Figure 7] This is an enlarged view of the outer shoulder land area of ​​Figure 1. [Figure 8] This is a plan view showing the contact surface shape of the tire in Figure 1. [Figure 9]This is an exploded view of the tread portion of another embodiment of the present disclosure. [Figure 10] This is a cross-sectional view along the longitudinal direction of a middle sipe of another embodiment of the present disclosure. [Figure 11] This is an enlarged view of the middle and crown sections of a pair of tires in the comparative example. [Modes for carrying out the invention]

[0010] 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 suitably used, for example, 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.

[0011] As shown in Figure 1, the tread portion 2 of the present disclosure includes four circumferential grooves 3 that extend continuously in the circumferential direction of the tire between two tread ends, and five land portions 4 divided into the four circumferential grooves 3. That is, the tire 1 of the present disclosure is configured as a so-called five-rib tire in which the tread portion 2 is composed of five land portions 4.

[0012] In this embodiment, the tread portion 2 has a specified orientation for mounting on a vehicle. As a result, the two tread ends include an inner tread end Ti that faces inward when the tire 1 is mounted on the vehicle, and an outer tread end To that faces outward when mounted on the vehicle. The mounting orientation is indicated, for example, by letters or symbols on the sidewall portion (not shown). However, the tire 1 of this disclosure is not limited to this configuration, and may not have a specified mounting orientation on the vehicle.

[0013] The inner tread edge Ti and the outer tread edge To correspond to the outermost contact points in the tire's axial direction when a normal load is applied to a tire 1 in its normal state, with a camber angle of 0°, and the tire is in contact with a flat surface.

[0014] 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 the normal internal pressure, and moreover, it is in an unloaded 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 purpose of use of the tire, which means that the tire is not mounted on a vehicle and is in an unloaded state. In this specification, unless otherwise specified, the dimensions, etc. of each part of the tire are the values measured in the above-mentioned normal state.

[0015] The "normal rim" is the rim defined for each tire in a standard system including the standards based on which the tire is designed. For example, in the case of JATMA, it is the "standard rim"; in the case of TRA, it is the "Design Rim"; in the case of ETRTO, it is the "Measuring Rim".

[0016] The "normal internal pressure" is the air pressure defined for each tire in a standard system including the standards based on which the tire is designed. For example, in the case of JATMA, it is the "maximum air pressure"; in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; in the case of ETRTO, it is the "INFLATION PRESSURE".

[0017] The "normal load" means that in the case of a pneumatic tire with various standards defined, it is the load defined for each tire in a standard system including the standards based on which the tire is designed. For example, in the case of JATMA, it is the "maximum load capacity"; in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; in the case of ETRTO, it is the "LOAD CAPACITY". Also, in the case of a tire without various defined standards or a non-pneumatic tire, the "normal load" refers to the load acting on one tire in the standard mounting state of the tire. The above-mentioned "standard mounting state" means that the tire is mounted on a standard vehicle according to the purpose of use of the tire, and the vehicle is stationary on a flat road surface in a state where it can run.

[0018] The four circumferential grooves 3 include a pair of shoulder circumferential grooves 3A and a pair of crown circumferential grooves 3B arranged between the pair of shoulder circumferential grooves 3A. The shoulder circumferential grooves 3A of the present embodiment include, for example, an inner shoulder circumferential groove 5 arranged on the inner tread end Ti side and an outer shoulder circumferential groove 6 arranged on the outer tread end To side. The crown circumferential grooves 3B of the present embodiment include, for example, an inner crown circumferential groove 7 provided between the inner shoulder circumferential groove 5 and the tire equator C, and an outer crown circumferential groove 8 provided between the outer shoulder circumferential groove 6 and the tire equator C.

[0019] The distance L1 in the tire axial direction from the tire equator C to the groove center line of the shoulder circumferential groove 3A is preferably, for example, 25% to 35% of the tread width TW. The distance L2 in the tire axial direction from the tire equator C to the groove center line of the crown circumferential groove 3B is preferably, for example, 5% to 15% of the tread width TW. The tread width TW is the distance in the tire axial direction from the inner tread end Ti to the outer tread end To in the normal state.

[0020] Each circumferential groove 3 of the present embodiment extends linearly parallel to the tire circumferential direction, for example. Each circumferential groove 3 may extend in a wave shape, for example.

[0021] The groove width W1 of each circumferential groove 3 is preferably at least 3 mm or more. Also, the groove width W1 of each circumferential groove 3 is preferably, for example, 2.0% to 8.0% of the tread width TW. In the present embodiment, the outer shoulder circumferential groove 6 has the smallest groove width among the four circumferential grooves 3. However, the present disclosure is not limited to such an aspect. The depth of each circumferential groove 3 is preferably, for example, 5 to 10 mm in the case of a pneumatic tire for a passenger car.

[0022] The land portion 4 of this disclosure includes a pair of middle land portions 4A divided between the shoulder circumferential groove 3A and the crown circumferential groove 3B. The pair of middle land portions 4A of this embodiment include, for example, an inner middle land portion 12 and an outer middle land portion 13. The inner middle land portion 12 is divided, for example, between the inner shoulder circumferential groove 5 and the inner crown circumferential groove 7. The outer middle land portion 13 is divided, for example, between the outer shoulder circumferential groove 6 and the outer crown circumferential groove 8.

[0023] Furthermore, the land portion 4 of this embodiment includes a crown land portion 14, an inner shoulder land portion 10, and an outer shoulder land portion 11. The crown land portion 14 is divided between the inner crown circumferential groove 7 and the outer crown circumferential groove 8. The inner shoulder land portion 10 is divided on the tire axial side of the inner shoulder circumferential groove 5 and includes the inner tread end Ti. The outer shoulder land portion 11 is divided on the tire axial side of the outer shoulder circumferential groove 6 and includes the outer tread end To.

[0024] Figure 2 shows enlarged views of a pair of middle land sections 4A and crown land sections 14. As shown in Figure 2, each of the middle land sections 4A is provided with multiple middle sipes 15 that completely traverse the middle land section 4A in the tire axial direction.

[0025] In this specification, "sipe" refers to a small-width notch element in which a pair of sipe walls are arranged substantially parallel to each other, and the width between the two sipe walls is 1.5 mm or less. Preferably, the width is 0.5 to 1.5 mm. The opening of the sipe may be connected to a chamfered portion with a width exceeding 1.5 mm. The bottom of the sipe may be connected to a flask bottom with a width exceeding 1.5 mm.

[0026] Figure 3 shows an enlarged view of the middle sipe 15. Figure 4 shows a cross-sectional view of line AA in Figure 2. As shown in Figures 3 and 4, the middle sipe 15 has a chamfered portion 20 on at least one of its sipe edges. The chamfered portion 20 in this embodiment is, for example, composed of an inclined surface 20a extending between the ground contact surface and the sipe wall. This inclined surface 20a is, for example, positioned at an angle of 30 to 60° with respect to the tire normal passing through the ground contact surface. The depth of the chamfered portion 20 is, for example, 0.5 to 3.0 mm.

[0027] As shown in Figure 3, the chamfered portion 20 extends from the crown circumferential groove 3B to the shoulder circumferential groove 3A in a plan view of the tread. The first chamfer width W3 at the end of the chamfered portion 20 on the crown circumferential groove 3B side is greater than the second chamfer width W4 at the end of the chamfered portion 20 on the shoulder circumferential groove 3A side. In this disclosure, by adopting the above configuration, it is possible to improve braking performance while maintaining handling stability. The following mechanism is presumed to be the reason for this.

[0028] As shown in Figure 2, the middle ground section 4A of this disclosure has a middle sipe 15 with a chamfered portion 20 that suppresses distortion of the contact surface, and consequently equalizes the contact pressure acting on the contact surface. This improves braking performance and handling stability.

[0029] Furthermore, in areas such as the middle land portion 4A of this disclosure, the land portion positioned between the tire equator and the tread edge tends to experience greater ground pressure on the contact surface on the tire equator side. Taking this tendency into account, in this disclosure, the first chamfer width W3 (shown in Figure 3) at the end of the chamfer portion 20 on the crown circumferential groove 3B side is larger than the second chamfer width W4 (shown in Figure 3) at the end of the chamfer portion 20 on the shoulder circumferential groove 3A side. This ensures a sufficient chamfer width on the tire equator side where the ground pressure is relatively high, resulting in excellent braking performance. On the other hand, the chamfer width is smaller on the tread edge side where the ground pressure is relatively low, allowing for a larger contact area, thus effectively maintaining handling stability. It is inferred that the tire of this disclosure can improve braking performance while maintaining handling stability through the mechanism described above.

[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, the middle sipe 15 provided on one of the pair of middle land sections 4A and the middle sipe 15 provided on the other of the pair of middle land sections 4A are inclined in the same direction with respect to the tire axis. Specifically, the middle sipe 15 includes an outer middle sipe 16 provided on the outer middle land section 13 and an inner middle sipe 17 provided on the inner middle land section 12. The outer middle sipe 16 is inclined, for example, upward to the right with respect to the tire axis. Hereinafter, this direction of inclination may be referred to as "inclined in a first direction with respect to the tire axis." The inner middle sipe 17 is inclined, for example, in the same direction as the outer middle sipe 16 with respect to the tire axis. However, this disclosure is not limited to such embodiments. Unless otherwise specified, the features of the middle sipe 15 described herein can be applied to both the outer middle sipe 16 and the inner middle sipe 17.

[0032] The middle sipe 15 is, for example, angled at 20-30° relative to the tire axis. Such a middle sipe 15 can provide friction in the tire axis direction during wet driving, helping to improve handling stability.

[0033] The length of one pitch P1 in the tire circumferential direction of multiple middle sipes 15 is preferably greater than, for example, the width W5 in the tire axial direction of the contact surface of the middle ground portion 4A. Specifically, the length of one pitch P1 of the middle sipes 15 is 130% to 180% of the width W5 of the middle ground portion 4A. Such an arrangement of middle sipes 15 improves handling stability and wet performance in a balanced manner. Note that the length of one pitch refers to the distance in the tire circumferential direction between the sipe centerlines (lines that divide the sipe width in half) of two adjacent sipes in the tire circumferential direction.

[0034] As shown in Figure 3, the middle sipe 15 has chamfered portions 20 formed on each of its sipe edges. This further ensures the effects described above are achieved. Needless to say, the configuration of one chamfered portion 20 described herein can be applied to each of the two chamfered portions 20 provided on a single sipe.

[0035] The second chamfer width W4 is 30% to 60% of the first chamfer width W3. This provides a good balance of improved handling stability and braking performance.

[0036] Specifically, the first chamfer width W3 is preferably 1.5 to 3.0 mm. The second chamfer width W4 is preferably 0.5 to 1.5 mm. Furthermore, the minimum chamfer width of the chamfered portion 20 of the middle sipe 15 is preferably, for example, 0.3 to 1.0 mm. This suppresses uneven wear on the land surface while achieving the effects described above.

[0037] The chamfered portion 20 includes, for example, a constant width portion 21, an inner widened portion 22, and an outer widened portion 23. The constant width portion 21 extends in the sipe length direction with a constant chamfer width. The inner widened portion 22 is, for example, connected to the crown circumferential groove 3B side of the constant width portion 21, and the chamfer width increases continuously from the constant width portion 21 to the crown circumferential groove 3B.

[0038] The outer widening portion 23 is, for example, connected to the shoulder circumferential groove 3A side of the fixed width portion 21, and the chamfer width increases continuously from the fixed width portion 21 to the shoulder circumferential groove 3A.

[0039] As described above, in this embodiment, the middle sipe 15 has chamfered portions 20 on each of its sipe edges, and the chamfered portions 20 include an inner widened portion 22 and an outer widened portion 23. In this embodiment, this configuration, combined with other factors, allows each middle ground section 4A to exhibit excellent ground contact even when the ground pressure changes significantly, thereby further improving steering stability and braking performance.

[0040] As shown in Figure 2, the fixed-width section 21 is located, for example, outside the tire axial direction of the center position of the middle ground section 4A in the tire axial direction. As a result, the tire axial length L3 of the inner widening section 22 is greater than the tire axial length L4 of the outer widening section 23. Specifically, the length L3 of the inner widening section 22 is 40% to 60% of the width W5 of the contact surface of the middle ground section 4A. The length L4 of the outer widening section 23 is 25% to 35% of the width W5 of the contact surface of the middle ground section 4A. As a result, the above-mentioned effect is reliably achieved even if the ground pressure acting on the middle ground section 4A changes.

[0041] Figure 5 shows a cross-sectional view of line BB in Figure 2. As shown in Figure 5, the maximum depth d1 of the inner widening portion 22 is greater than the maximum depth d2 of the outer widening portion 23. Specifically, the depth d2 of the outer widening portion 23 is 20% to 60% of the depth d1 of the inner widening portion 22. Furthermore, the depth d1 of the inner widening portion 22 and the maximum depth d2 of the outer widening portion 23 are, for example, 0.5 to 3.0 mm. Also, the minimum depth of the chamfered portion 20 is, for example, 0.3 to 1.0 mm.

[0042] The middle sipe 15 includes, for example, a middle tie bar 25 whose bottom is locally raised. The middle tie bar 25 is positioned, for example, in the central region when the middle sipe 15 is divided into three equal parts in the tire axial direction. The tire axial length L5 of the middle tie bar 25 is 30% to 50% of the tire axial width W5 (shown in Figure 2) of the contact surface of the middle ground 4A. The minimum depth d4 from the contact surface of the middle ground 4A to the outer surface of the middle tie bar 25 is, for example, 60% to 90% of the maximum depth d3 of the middle sipe 15, preferably 50% to 70%. The maximum depth d3 of the middle sipe 15 is, for example, 50% to 80% of the maximum depth of the shoulder circumferential groove 3A. Such a middle tie bar 25 helps maintain the rigidity of the middle ground 4A and provides a large cornering force.

[0043] As shown in Figure 2, the crown land area 14 has its center in the axial direction located on the outer tread edge To (shown in Figure 1) side of the tire equator C. As a result, in the crown land area 14, the width W6b of the contact patch in the outer region 14b on the outer tread edge To side of the tire equator C is greater than the width W6a of the contact patch in the inner region 14a on the inner tread edge Ti side of the tire equator C. Specifically, the width W6b of the outer region 14b is 51% to 55% of the width W6 of the contact patch of the crown land area 14. Such a crown land area 14 helps to linearize the change in cornering force with changes in steering angle, thereby improving handling stability and ride comfort.

[0044] The crown land area 14 is provided with a plurality of first crown sipes 31 and a plurality of second crown sipes 32. The first crown sipes 31 extend, for example, from the inner crown circumferential groove 7 and are interrupted within the crown land area 14. The second crown sipes 32 extend, for example, from the outer crown circumferential groove 8 and are interrupted within the crown land area 14. Such first crown sipes 31 and second crown sipes 32 can reduce rolling resistance while maintaining wet performance.

[0045] To ensure the above-mentioned effects are achieved, the first crown sipe 31 and the second crown sipe 32 do not cross the center position of the crown land area 14 in the tire axial direction, nor do they cross the tire equator C. The length L6 of the first crown sipe 31 or the second crown sipe 32 in the tire axial direction is, for example, 15% to 30% of the width W6 of the contact surface of the crown land area 14 in the tire axial direction.

[0046] The first crown sipe 31 and the second crown sipe 32 are inclined in the first direction with respect to the tire axis, for example. The angle of the first crown sipe 31 or the second crown sipe 32 with respect to the tire axis is, for example, 20 to 30°. In a more desirable embodiment, the angle difference between the first crown sipe 31 or the second crown sipe 32 and the outer middle sipe 16 is 10° or less. This suppresses uneven wear of the crown land portion 14.

[0047] Figure 6 shows an enlarged view of the inner shoulder land portion 10. As shown in Figure 6, the inner shoulder land portion 10 is provided with a plurality of inner shoulder lateral grooves 35 and a plurality of inner shoulder sipes 36. In this embodiment, these are arranged alternately in the circumferential direction of the tire.

[0048] The inner shoulder lateral groove 35 extends from its inner end 35a, located between the inner tread edge Ti and the inner shoulder circumferential groove 5, to a position beyond the inner tread edge Ti. The inner shoulder lateral groove 35 crosses, for example, the axial center of the contact surface of the inner shoulder land portion 10. The axial length L7 of the inner shoulder lateral groove 35 at the contact surface of the inner shoulder land portion 10 is, for example, 70% to 90% of the axial width W7 of the contact surface of the inner shoulder land portion 10. Such an inner shoulder lateral groove 35 helps to improve braking performance while maintaining wet performance.

[0049] The inner shoulder lateral groove 35 is inclined, for example, downward to the right with respect to the tire axis. That is, in this embodiment, the inner shoulder lateral groove 35 is inclined in the opposite direction to the middle sipe 15 with respect to the tire axis. Hereinafter, this direction of inclination may be referred to as "inclined in a second direction with respect to the tire axis." The angle of the inner shoulder lateral groove 35 with respect to the tire axis is, for example, 5 to 15°. Such an inner shoulder lateral groove 35 can guide water inside towards the inner tread edge Ti side during wet driving, exhibiting excellent drainage performance.

[0050] The inner shoulder sipe 36 extends from the inner shoulder circumferential groove 5 to a position beyond the inner tread edge Ti. The inner shoulder sipe 36 extends linearly, for example, inclined in the second direction with respect to the tire axis. The angle of the inner shoulder sipe 36 with respect to the tire axis is, for example, 5 to 15°. The angle difference between the inner shoulder sipe 36 and the inner shoulder lateral groove 35 is preferably 10° or less, and in this embodiment, they extend parallel to each other. Such an inner shoulder sipe 36 can improve noise performance and ride comfort while suppressing uneven wear of the inner shoulder land portion 10.

[0051] It is preferable that the inner shoulder sipe 36 does not have a chamfered portion. That is, the inner shoulder sipe 36 has a sipe wall that is directly connected to the contact surface of the inner shoulder land portion 10 and extends along the radial direction of the tire. Such an inner shoulder sipe 36 can provide a large frictional force during wet driving due to its edge.

[0052] In this embodiment, the inner shoulder land portion 10 is provided with auxiliary sipes 37 that extend from the inner shoulder circumferential groove 5 to the inner end 35a of the inner shoulder transverse groove 35. Such auxiliary sipes 37 help maintain wet performance.

[0053] Figure 7 shows an enlarged view of the outer shoulder land portion 11. As shown in Figure 7, the outer shoulder land portion 11 is provided with a plurality of outer shoulder lateral grooves 41 and a plurality of outer shoulder sipes 42. In this embodiment, these are arranged alternately in the circumferential direction of the tire.

[0054] The outer shoulder lateral groove 41 extends from the outer shoulder circumferential groove 6 to a position beyond the outer tread edge To. The outer shoulder lateral groove 41 is inclined, for example, in the second direction with respect to the tire axis. That is, in this embodiment, the outer shoulder lateral groove 41 is inclined in the opposite direction to the middle sipe 15 with respect to the tire axis. The angle of the outer shoulder lateral groove 41 with respect to the tire axis is, for example, 5 to 15°. In a preferred embodiment, the angle difference between the outer shoulder lateral groove 41 and the inner shoulder lateral groove 35 (shown in Figure 6) is 10° or less, and more preferably 5° or less.

[0055] The outer shoulder sipe 42 extends from the outer shoulder circumferential groove 6 and has a discontinuous end 42a between the outer shoulder circumferential groove 6 and the outer tread end To. The axial length L8 of the outer shoulder sipe 42 is 40% to 60% of the axial width W8 of the contact surface of the outer shoulder land portion 11.

[0056] The outer shoulder sipe 42 is inclined, for example, in the second direction with respect to the tire axis. The angle of the outer shoulder sipe 42 with respect to the tire axis is, for example, 5 to 15°. The angle difference between the outer shoulder sipe 42 and the outer shoulder lateral groove 41 is preferably 10° or less, and in this embodiment, they extend parallel to each other. Such an outer shoulder sipe 42 can maintain wet performance while suppressing uneven wear of the outer shoulder land portion 11.

[0057] Furthermore, in this embodiment, the outer shoulder sipe 42 has chamfered portions 43 formed on each of its sipe edges. In a more desirable embodiment, the chamfered portion 43 has a wider chamfer width from the side of the interrupted end 42a toward the side of the outer shoulder circumferential groove 6. This equalizes the ground pressure acting on the outer shoulder land portion 11, improving steering stability and braking performance.

[0058] The chamfer width of the chamfered portion 43 of the outer shoulder sipe 42 increases continuously, for example, from the side of the interrupted end 42a toward the side of the outer shoulder circumferential groove 6. The maximum chamfer width W9 of the chamfered portion 43 is, for example, 2.0 to 4.0 mm. In this embodiment, the maximum chamfer width W9 is formed at the end of the outer shoulder sipe 42 on the side of the outer shoulder circumferential groove 6.

[0059] In a more desirable embodiment, the maximum chamfer width W9 of the outer shoulder sipe 42 is smaller than the first chamfer width W3 (shown in Figure 3) of the chamfered portion 43 of the middle sipe 15, and larger than the second chamfer width W4 (shown in Figure 3). This suppresses uneven wear in each part.

[0060] In this embodiment, no other grooves or sipes are provided in each land area, except for the grooves and sipes described above. This allows the various performance characteristics described above to be exhibited in a well-balanced manner. However, this disclosure is not limited to this embodiment.

[0061] Figure 8 shows the contact surface shape when 50% of the normal load is applied to the tire 1 in the normal state (hereinafter sometimes referred to as the "50% load state"). As shown in Figure 8, in the 50% load state, it is desirable that the width W11 in the tire axial direction of the contact surface of the outer shoulder land area 11 is 114% to 124% of the width W10 in the tire axial direction of the contact surface of the crown land area 14.

[0062] Similarly, the width W12 in the axial direction of the contact surface of the outer middle land portion 13 is preferably 85% to 115% of the width W10 in the axial direction of the contact surface of the crown land portion 14. Furthermore, the width W12 in the axial direction of the contact surface of the outer middle land portion 13 is preferably greater than the width W13 in the axial direction of the contact surface of the inner middle land portion 12. Specifically, the width W12 of the outer middle land portion 13 is preferably 105% to 115% of the width W13 of the inner middle land portion 12. In addition, the width W13 in the axial direction of the contact surface of the inner middle land portion 12 and the width W14 in the axial direction of the contact surface of the inner shoulder land portion 10 are preferably 80% to 100% of the width W10 in the axial direction of the contact surface of the crown land portion 14. As a result, when the tire 1 of this embodiment is applied to all wheels of a vehicle, the front and rear wheels can exert cornering force in a balanced manner, and consequently, excellent handling stability is achieved.

[0063] Figure 9 shows an exploded view of the tread portion 2 in another embodiment of the present disclosure. As shown in Figure 9, in this embodiment, compared to the embodiment shown in Figure 1, the outer middle sipe 16 and the first and second crown sipes 31 and 2 crown sipes 32 are inclined in the second direction with respect to the tire axis. As a result, the middle sipe 15 provided on one of the pair of middle land portions 4A and the middle sipe 15 provided on the other of the pair of middle land portions 4A are inclined in opposite directions with respect to the tire axis. Such an embodiment helps to increase the conicity of the tire. The configuration described in the embodiments shown in Figures 1 to 8 can be applied to the embodiment in Figure 9.

[0064] Figure 10 shows a cross-sectional view along the longitudinal direction of the middle sipe 15 in another embodiment of the present disclosure. As shown in Figure 10, the middle sipe 15 in this embodiment includes a middle tie bar 25 with a locally raised bottom. The middle tie bar 25 in this embodiment is located, for example, on the side of the crown circumferential groove 3B rather than the center of the tire axial direction of the contact surface of the middle ground 4A. Specifically, the middle tie bar 25 is raised including the tire axial end of the middle sipe 15. Such a middle tie bar 25 helps to increase the rigidity of the middle ground 4A on the crown circumferential groove 3B side, thereby providing excellent handling stability.

[0065] In yet another embodiment, the middle tie bar 25 may be located, for example, on the side of the shoulder circumferential groove 3A rather than the center position in the tire axial direction of the contact surface of the middle ground portion 4A (not shown). In such an embodiment, the rigidity of the middle ground portion 4A on the shoulder circumferential groove 3A side is improved, and consequently the steering response during turning becomes more linear.

[0066] The axial length L5 of the middle tie bar 25 is 30% to 50% of the axial width W5 (shown in Figure 2) of the contact surface of the middle ground section 4A. If the axial length of the middle tie bar 25 changes in the radial direction of the tire, the length L5 shall be measured at the center position in the radial direction of the tire. The minimum depth d4 from the contact surface of the middle ground section 4A to the outer surface of the middle tie bar 25 is, for example, 60% to 90% of the maximum depth d3 of the middle sipe 15, preferably 50% to 70%. The maximum depth d3 of the middle sipe 15 is, for example, 50% to 80% of the maximum depth of the shoulder circumferential groove 3A. Such a middle tie bar 25 helps to improve handling stability and wet performance in a balanced way.

[0067] 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]

[0068] A 235 / 45R19 size tire with the basic pattern shown in Figure 1 was prototyped based on the specifications in Table 1. As a comparative example, a tire with a pair of middle sections a shown in Figure 11 was also prototyped. The middle section a of the comparative tire is provided with a middle sipe b having a chamfered section c extending with a certain chamfer width. Except for the above, the comparative tire is substantially the same as the one shown in Figure 1. The handling stability and braking performance of each test tire were tested. The common specifications and test methods for each test tire are as follows. Mounted rim: 19×8.0J Tire pressure: 230kPa Test vehicle: 2000cc engine, four-wheel drive Tire mounting position: All wheels

[0069] <Handling Stability> 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.

[0070] <Braking performance> The above test vehicles were driven on dry roads, and their braking performance in various conditions was evaluated subjectively by the drivers. The results are scored with the braking performance of the comparative example set at 100, and a higher number indicates better braking performance. The test results are shown in Table 1.

[0071] [Table 1]

[0072] As shown in Table 1, the tires of the embodiment maintain handling stability at 101-104 points while improving braking performance to 104-108 points. In other words, it was confirmed that the tires of this disclosure improve braking performance while maintaining handling stability.

[0073] [Note] This disclosure includes the following aspects.

[0074] [Disclosure 1] A tire having a tread portion, The tread portion includes four circumferential grooves that extend continuously in the circumferential direction of the tire between two tread ends, and five land portions divided by the four circumferential grooves. The four circumferential grooves include a pair of shoulder circumferential grooves and a pair of crown circumferential grooves between the pair of shoulder circumferential grooves. The land portion includes a pair of middle land portions separated between the shoulder circumferential groove and the crown circumferential groove, Each of the aforementioned middle land sections is provided with a plurality of middle sipes that completely traverse the middle land section in the direction of the tire axis, The middle sipe has at least one of its sipe edges on both sides formed with a chamfered portion. The chamfered portion extends from the crown circumferential groove to the shoulder circumferential groove in a plan view of the tread. The first chamfer width at the end of the chamfered portion on the crown circumferential groove side is greater than the second chamfer width at the end of the chamfered portion on the shoulder circumferential groove side. tire. [Disclosure 2] The tire according to Disclosure 1, wherein the middle sipe is formed by the chamfered portion on each of the sipe edges on both sides. [Disclosure 3] The tire according to disclosure 1 or 2, wherein the chamfered portion includes an inner widening portion in which the chamfer width continuously increases toward the crown circumferential groove. [Disclosure 4] The tire according to disclosure 3, wherein the chamfered portion includes an outer widening portion in which the chamfered width continuously increases toward the shoulder circumferential groove. [Disclosure 5] The chamfered portion includes a fixed-width portion extending at a constant width between the inner widened portion and the outer widened portion. The tire according to disclosure 4, wherein the fixed-width portion is located outward in the tire axial direction from the center position in the tire axial direction of the middle land portion. [Disclosure 6] The tire according to disclosure 4 or 5, wherein the length in the tire axial direction of the inner widening portion is greater than the length in the tire axial direction of the outer widening portion. [Disclosure 7] The tire according to any one of disclosures 4 to 6, wherein the maximum depth of the inner widening portion is greater than the maximum depth of the outer widening portion. [Disclosure 8] The tire according to any one of disclosures 1 to 7, wherein the second chamfer width is 30% to 60% of the first chamfer width. [Disclosure 9] The tire according to any one of disclosures 1 to 8, wherein the middle sipe provided on one of the pair of middle land sections and the middle sipe provided on the other of the pair of middle land sections are inclined in opposite directions with respect to the tire axis. [Disclosure 10] The tire according to any one of disclosures 1 to 8, wherein the middle sipe provided on one of the pair of middle land sections and the middle sipe provided on the other of the pair of middle land sections are inclined toward each other in the same direction with respect to the tire axis. [Disclosure 11] The tread portion includes the outer tread end, which becomes the outer side of the vehicle when mounted on the vehicle, depending on the orientation of mounting on the vehicle. The five land areas include the outer shoulder land area which includes the outer tread end, The tire according to disclosure 10, wherein the outer shoulder land portion is provided with a plurality of outer shoulder lateral grooves and a plurality of outer shoulder sipes that are inclined in the opposite direction to the middle sipe with respect to the tire axis. [Disclosure 12] The tread portion includes an inner tread end that faces inward when mounted on a vehicle, depending on the orientation of mounting on the vehicle. The five land areas include the inner shoulder land area which includes the inner tread end, The tire according to disclosure 10 or 11, wherein the inner shoulder land portion is provided with a plurality of inner shoulder lateral grooves and a plurality of inner shoulder sipes that are inclined in the opposite direction to the middle sipe with respect to the tire axis. [Disclosure 13] The tire according to any one of disclosures 1 to 12, wherein the maximum depth of the middle sipe is 50% to 80% of the maximum depth of the shoulder circumferential groove. [Disclosure 14] The tire according to any one of disclosures 1 to 13, wherein the middle sipe includes a middle tie bar with a locally raised bottom. [Disclosure 15] The tire according to disclosure 14, wherein the minimum depth from the contact surface of the middle land portion to the outer surface of the middle tie bar is 60% to 90% of the maximum depth of the middle sipe. [Disclosure 16] The tire according to disclosure 14 or 15, wherein the length of the middle tie bar in the tire axial direction is 30% to 50% of the width of the contact surface of the middle land portion in the tire axial direction. [Explanation of Symbols]

[0075] 2 Tread section 3 Circumferential groove 3A Shoulder circumferential groove 3B Crown circumferential groove 4 Land 4A Middle Track and Field Club 15 Middle Sipe 20 Chamfered section W3 First chamfer width W4 Second chamfer width

Claims

1. A tire having a tread portion, The tread portion includes four circumferential grooves that extend continuously in the circumferential direction of the tire between the two tread ends, and five land portions divided by the four circumferential grooves. The four circumferential grooves include a pair of shoulder circumferential grooves and a pair of crown circumferential grooves between the pair of shoulder circumferential grooves. The land portion includes a pair of middle land portions separated between the shoulder circumferential groove and the crown circumferential groove, Each of the aforementioned middle land sections is provided with a plurality of middle sipes that completely traverse the middle land section in the direction of the tire axis, The aforementioned middle sipe has chamfered edges on both sides. The chamfered portion extends from the crown circumferential groove to the shoulder circumferential groove in a plan view of the tread. Each of the two chamfered portions has a first chamfer width at the end of the chamfered portion on the crown circumferential groove side that is greater than the second chamfer width at the end of the chamfered portion on the shoulder circumferential groove side. tire.

2. The tire according to claim 1, wherein the chamfered portion includes an inner widening portion in which the chamfered width continuously increases toward the crown circumferential groove.

3. The tire according to claim 2, wherein the chamfered portion includes an outer widening portion in which the chamfer width continuously increases toward the shoulder circumferential groove.

4. The chamfered portion includes a fixed-width portion extending at a constant width between the inner widening portion and the outer widening portion, The tire according to claim 3, wherein the fixed-width portion is located outward in the tire axial direction from the center position in the tire axial direction of the middle land portion.

5. The tire according to claim 3 or 4, wherein the length of the inner widened portion in the tire axial direction is greater than the length of the outer widened portion in the tire axial direction.

6. The tire according to any one of claims 4 to 5, wherein the maximum depth of the inner widening portion is greater than the maximum depth of the outer widening portion.

7. The tire according to any one of claims 1 to 6, wherein the second chamfer width is 30% to 60% of the first chamfer width.

8. The tire according to any one of claims 1 to 7, wherein the middle sipe provided on one of the pair of middle land sections and the middle sipe provided on the other of the pair of middle land sections are inclined in opposite directions with respect to the tire axis.

9. The tire according to any one of claims 1 to 7, wherein the middle sipe provided on one of the pair of middle land sections and the middle sipe provided on the other of the pair of middle land sections are inclined in the same direction with respect to the tire axis.

10. The tread portion includes an outer tread end that is on the outside of the vehicle when mounted on the vehicle, depending on the orientation of mounting on the vehicle. The five land areas include the outer shoulder land area which includes the outer tread end, The tire according to claim 9, wherein the outer shoulder land portion is provided with a plurality of outer shoulder lateral grooves and a plurality of outer shoulder sipes that are inclined in the opposite direction to the middle sipe with respect to the tire axis.

11. The tread portion includes an inner tread end that is on the inside of the vehicle when mounted on the vehicle, depending on the orientation of mounting on the vehicle. The five land areas include the inner shoulder land area which includes the inner tread end, The tire according to claim 9 or 10, wherein the inner shoulder land portion is provided with a plurality of inner shoulder lateral grooves and a plurality of inner shoulder sipes that are inclined in the opposite direction to the middle sipe with respect to the tire axis.

12. The tire according to any one of claims 1 to 11, wherein the maximum depth of the middle sipe is 50% to 80% of the maximum depth of the shoulder circumferential groove.

13. The tire according to any one of claims 1 to 12, wherein the middle sipe includes a middle tie bar whose bottom is locally raised.

14. The tire according to claim 13, wherein the minimum depth from the contact surface of the middle land portion to the outer surface of the middle tie bar is 60% to 90% of the maximum depth of the middle sipe.

15. The tire according to claim 13 or 14, wherein the length of the middle tie bar in the tire axial direction is 30% to 50% of the width of the contact surface of the middle land portion in the tire axial direction.

Images