JP2023062446A - tire - Google Patents

Abstract

To provide a tire which is excellent in a brake performance.SOLUTION: A tire includes a tread including two or more circumferential grooves, a first shoulder land part, and a second shoulder part. The first shoulder land part and the second shoulder land part have lateral grooves extending in a tire width direction. A first groove wall of the lateral grooves has a first region inclined so that a groove width is enlarged toward an opening of the lateral groove, and a second groove wall of the lateral groove has a second region inclined so that the groove width is enlarged toward the opening of the lateral groove. An inclination angle of the first region to a profile surface of the tread is smaller than an inclination angle of the second region to the profile surface. The first region is formed on the first direction side in the tire circumferential direction of the lateral grooves in the first shoulder land part, and is formed on the second direction side in the tire circumferential direction of the lateral grooves in the second shoulder land part.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a tire, and more particularly to a tire having a tread in which a plurality of circumferential grooves are formed.

Conventionally, a tire provided with a tread in which a plurality of circumferential grooves are formed is widely known. The tread has a plurality of land portions defined by circumferential grooves. In general, each land portion is formed with a lateral groove extending in the tire width direction. The groove wall of the lateral groove may be formed with an inclined region such that the groove width increases toward the opening of the groove.

Patent Document 1 discloses a tire having a plurality of lateral grooves that completely cross the shoulder land portion, and the upper portion of the groove wall is inclined at a predetermined angle so that the groove width expands toward the groove opening. . Patent Document 1 describes the effect of improving braking performance and wet performance on dry road surfaces.

JP 2020-69964 A

By the way, when the vehicle is braked, ground contact pressure may be concentrated near the groove walls of the lateral grooves, and sufficient braking performance may not be obtained. Since the coefficient of friction of rubber is inversely proportional to the contact pressure, concentration of the contact pressure on a portion of the tread lowers the coefficient of friction of rubber. Also, the concentration of contact pressure greatly deforms the rubber and reduces the contact area. Due to these factors, if the ground contact pressure concentrates on a portion of the tread, it is considered that the braking performance of the tire is greatly reduced.

In order to improve the braking performance of a tire, it is important to distribute and reduce the contact pressure while ensuring a large contact area. The tire disclosed in Patent Document 1 still has room for improvement in braking performance.

A tire according to the present invention includes two or more circumferential grooves, a first shoulder land portion formed on a first contact edge side, and a second shoulder land portion formed on a second contact edge side. The first shoulder land portion and the second shoulder land portion have lateral grooves extending in the tire width direction, and the first groove walls along the length direction of the lateral grooves are openings of the lateral grooves. to a depth of 2.0 mm, the first region is inclined so that the groove width increases toward the opening, and the second groove wall along the length direction of the lateral groove extends from the opening of the lateral groove to the depth In the range of 2.0 mm, it has a second region inclined so that the groove width expands toward the opening, and the width of the first region and the second region is the maximum, along the ground contact surface of the tread The inclination angle of the first region with respect to the tread profile surface is smaller than the inclination angle of the second region with respect to the tread profile surface, the first region is formed on the side of the lateral groove in the first direction in the tire circumferential direction in the first shoulder land portion, The second shoulder land portion is formed on the side of the lateral groove in the second direction in the tire circumferential direction.

The tire according to the present invention has excellent braking performance. ADVANTAGE OF THE INVENTION According to the tire which concerns on this invention, a large contact area can be ensured, and contact pressure can be distributed and reduced.

1 is a perspective view of a tire that is an example of an embodiment, and also shows the internal structure of the tire. FIG. It is a figure which shows a part of width direction cross section of the tire which is an example of embodiment. It is a top view of the tire which is an example of an embodiment, and is a figure showing a part of tread. FIG. 4 is a plan view showing part of the tread, showing an enlarged first region R1 positioned outside the vehicle from the tire equator. It is a top view which shows a part of tread, Comprising: The 2nd area|region R2 located inside a vehicle rather than a tire equator is expanded and shown. FIG. 4 is a perspective view of a portion of a first shoulder rib and a first intermediate rib located in a first region, viewed from the tire equator side; FIG. 5 is a perspective view of a portion of a second shoulder rib and a second intermediate rib located in a second region, viewed from the tire equator side; 4 is an enlarged view of lateral grooves formed in the first shoulder rib; FIG. FIG. 5 is a cross-sectional view taken along line AA in FIG. 4;

Hereinafter, an example of an embodiment of a tire according to the present invention will be described in detail with reference to the drawings. The embodiments described below are merely examples, and the present invention is not limited to the following embodiments. In addition, the present invention includes a form in which each constituent element of a plurality of embodiments and modified examples described below are selectively combined.

FIG. 1 is a perspective view of a tire 1 that is an example of an embodiment, and also illustrates the internal structure of the tire 1 . As shown in FIG. 1, the tire 1 has a tread 10 which is a portion that contacts the road surface. The tread 10 has a plurality of circumferential grooves and is annularly formed along the tire circumferential direction. The tread 10 is formed with four circumferential grooves 20, 21, 22, 23 extending parallel to each other along the tire circumferential direction. In this embodiment, the widths of the circumferential grooves are different from each other. Also, the groove depth is not the same for all circumferential grooves.

The tire 1 is a tire whose mounting direction with respect to the vehicle is designated. The tread 10 has a left-right asymmetrical tread pattern with respect to the tire equator CL, and the mounting direction of the tire 1 is opposite between the right side and the left side of the vehicle. The tire equator CL means a line along the tire circumferential direction passing through the center in the tire width direction. Although details will be described later, the tire 1 is configured so that the first circumferential groove 20, which has the shallowest depth and the narrowest width among the four circumferential grooves, is located outside the tire equator CL. is attached to the

In this specification, the terms "left and right" are used for the tire 1 and its constituent elements for convenience of explanation. The "right side" of the tire 1 means the right side when the tire 1 is mounted on the vehicle and viewed in the traveling direction (forward direction) of the vehicle, and the "left side" is the state of being mounted on the vehicle. means the left side of the tire 1 when viewed in the direction of travel of the vehicle. The drawings show arrows indicating the main tire rotation direction and left and right. The "main tire rotation direction" means the rotation direction of the tire 1 when the vehicle on which the tire 1 is mounted moves forward.

The tire 1 includes a pair of sidewalls 11 bulging most outward in the tire width direction, and a pair of beads 12 fixed to the rim of the wheel. The sidewall 11 and the bead 12 are annularly formed along the tire circumferential direction and constitute the side surface of the tire 1 . The sidewalls 11 extend in the tire radial direction from both widthwise ends of the tread 10 . The side rib 13 protrudes outward in the tire width direction and has an annular shape along the tire circumferential direction.

A tire 1 is a pneumatic tire filled with air of a predetermined pressure. The tread 10 and the sidewalls 11 are made of different types of rubber, for example. The portions from the vicinity of the ground contact edges E1, E2 of the tire 1 to the left and right side ribs 13 are generally called shoulders or buttress portions. The shoulder may be made of the same rubber as the contact surface of the tread 10, or may be made of a different rubber.

In this specification, the treads E1 and E2 refer to a state in which an unused tire 1 is mounted on a regular rim and inflated to a regular internal pressure, and a load of 70% of the regular load at the regular internal pressure is applied. It means both ends in the tire width direction of the area that touches the flat road surface when it is grounded.

Here, the "regular rim" is a rim defined by tire standards, such as "standard rim" for JATMA, "design rim" for TRA, and "measuring rim" for ETRTO. The "regular internal pressure" is the "maximum air pressure" for JATMA, the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and the "INFLATION PRESSURE" for ETRTO. The "regular load" is the "maximum load capacity" for JATMA, the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and the "LOAD CAPACITY" for ETRTO.

The tire 1 comprises a carcass 14, a belt 15 and an innerliner 16. The carcass 14 is a cord layer covered with rubber, and forms a frame of the tire 1 that withstands load, impact, air pressure, and the like. The belt 15 is a reinforcing band arranged between the rubber forming the tread 10 and the carcass 14 . The belt 15 strongly tightens the carcass 14 to increase the rigidity of the tire 1. - 特許庁The inner liner 16 is a rubber layer provided on the inner peripheral surface of the carcass 14 and maintains the air pressure of the tire 1 . The bead 12 also has a bead core 17 and a bead filler 18 .

It is preferable that the tire 1 is provided with a display for indicating the mounting direction with respect to the vehicle. A symbol called serial is generally provided on the side surface of the tire 1 . The serial includes information such as size code, manufacturing time (manufacturing year and week), and manufacturing place (manufacturing factory code). The mounting direction of the tire 1 with respect to the vehicle is specified by providing a serial only on the side (sidewall 11) of the tire 1 facing the outside of the vehicle, or by providing different serials on the side facing the outside and the side facing the inside of the vehicle. be done. As a specific example, a manufacturing factory code and a size code are provided on both side surfaces of the tire 1, and a manufacturing year week is provided only on the side surface facing the outside of the vehicle.

The rubber forming the tread 10 may have a multilayer structure. The tread rubber has, for example, a two-layer structure of a base rubber and a cap rubber forming a surface layer of the tread 10 . An example of a suitable hardness of the cap rubber is 65-75. In this case, since the rigidity of the tread 10 is likely to increase, it is effective in improving the limit performance. The hardness of rubber is measured with a type A durometer at a temperature of 23° C. in accordance with JIS K6253-3. Limit performance generally means performance under limit conditions under which a stable running state can be maintained.

Also, the 300% modulus of the cap rubber is, for example, 15 or less. In this case, since the rigidity of the tread 10 is likely to increase, it is effective in improving the limit performance. Although the lower limit of the 300% modulus of the cap rubber is not particularly limited, it is 10 as an example. The 300% modulus of rubber is measured under temperature conditions of 23° C. in accordance with JIS K6301. When the tread rubber has a single-layer structure, the physical properties of the tread rubber as a whole preferably satisfy the above conditions.

The tread 10 has land portions defined by four circumferential grooves. The land portion is a projecting portion projecting outward in the tire radial direction from the reference surface of the tread 10 . The reference plane is an imaginary plane along the bottom surface of the deepest circumferential groove, and means the outer peripheral surface of the tread 10 when no land portion exists. Four circumferential grooves 20, 21, 22 and 23 are formed in the tread 10 in this order from the outside of the vehicle. In other words, the tire 1 needs to be mounted on the vehicle such that the circumferential groove 20 is located on the outside of the vehicle and the circumferential groove 23 is located on the inside of the vehicle.

The tread 10 has a center rib 30, shoulder ribs 40, 50, and intermediate ribs 60, 70 as the land portions. The tread 10 does not have grooves crossing each land portion in the width direction, and each land portion is continuously formed in the shape of a rib in the tire circumferential direction. Forming each land portion in a rib shape suppresses collapse of the land portion (particularly lateral deformation) during high-speed turning and contributes to improvement of marginal performance.

The center rib 30 is arranged in the center portion of the tread 10 in the width direction. The shoulder ribs 40 and 50 are arranged on both sides of the tread 10 in the width direction. The ground contact edge E1 is present on the first shoulder rib 40 and the ground contact edge E2 is present on the second shoulder rib 50. As shown in FIG. Parts of the shoulder ribs 40, 50 extend to the side ribs 13 beyond the ground edges E1, E2. The first intermediate rib 60 is arranged between the center rib 30 and the shoulder ribs 40 , and the second intermediate rib 70 is arranged between the center rib 30 and the shoulder ribs 50 .

The center rib 30 is a land portion sandwiched between circumferential grooves 21 and 22 formed parallel to each other along the tire circumferential direction. The center rib 30 is separated from the intermediate rib 60 by the circumferential groove 21 and separated from the intermediate rib 70 by the circumferential groove 22 . The center rib 30 is formed on the tire equator CL. Below, in the tread 10, the area from the tire equator CL to the ground contact edge E1 located outside the vehicle is defined as a first area R1, and the area from the tire equator CL to the ground contact edge E2 located inside the vehicle is defined as a second area R2. and

The shoulder ribs 40 are formed in the first region R<b>1 , which is the region on the ground contact edge E<b>1 side of the tread 10 , and are separated from the intermediate ribs 60 by the circumferential grooves 20 . The shoulder rib 50 is formed in the second region R2, which is the region on the ground contact edge E2 side of the tread 10, and is separated from the intermediate rib 70 by the circumferential groove 23. As shown in FIG. The shoulder ribs 40, 50 have, for example, substantially the same width. Alternatively, the width of the shoulder ribs 40 may be slightly wider than the width of the shoulder ribs 50 .

The intermediate rib 60 is arranged adjacent to the shoulder rib 40 across the circumferential groove 20 and adjacent to the center rib 30 across the circumferential groove 21 in the first region R1 of the tread 10 . The intermediate rib 70 is arranged adjacent to the center rib 30 across the circumferential groove 22 and adjacent to the shoulder rib 50 across the circumferential groove 23 in the second region R2 of the tread 10 . . Mediate ribs 60 and 70 have, for example, substantially the same width as each other. Alternatively, the width of mediate rib 60 may be slightly wider than the width of mediate rib 70 .

Each rib is formed with a plurality of lateral grooves or sipes extending in the tire width direction. The shoulder ribs 40 have lateral grooves 41 and the shoulder ribs 50 have lateral grooves 51 . The ends of the lateral grooves 41, 51 on the tire equator CL side are preferably positioned within the shoulder ribs and are not connected to the circumferential grooves. The center rib 30 and the intermediate ribs 60, 70 are formed with sipes connected to the circumferential grooves. The sipes are arranged in a zigzag pattern along the tire circumferential direction in each rib.

Both the lateral grooves and the sipes are grooves extending in the width direction of the tire, but the lateral grooves are wide grooves and the sipes are fine linear grooves. It is generally recognized that these are different. In this specification, a groove having a groove width of 1.0 mm or less at a portion not including a tapered surface, which will be described later, is defined as a sipe, and a groove having a width exceeding 1.0 mm is defined as a lateral groove. Groove width means the shortest distance between opposing groove walls at any position of the groove walls along the length of the lateral groove or sipe. Hereinafter, the widths of lateral grooves and sipes mean their maximum values (maximum widths) unless otherwise specified.

Although the ratio of the groove area to the contact area of the tread 10 is not particularly limited, a preferred example is 33 to 40%. Securing a large contact area is effective in improving braking performance. The groove area is the area of the groove on the tread profile surface α along the ground contact surface of the tread 10, that is, the area at the opening of the groove, and includes the areas of circumferential grooves, lateral grooves, and sipes. In addition, the opening of the groove means the upper end opening of the groove facing outward in the tire radial direction.

The four circumferential grooves formed in the tread 10 will be described in detail below with reference to FIG. FIG. 2 is a view showing a part of the cross section of the tire 1 in the width direction. In FIG. 2, illustration of the carcass 14 and the like is omitted.

As shown in FIG. 2, of the four circumferential grooves, the first circumferential groove 20 positioned furthest to the outside of the vehicle has the shallowest depth and the narrowest width among the circumferential grooves. By forming the circumferential groove 20 with a shallow width and a narrow width, the rigidity of the tread 10 can be increased in the first region R1 of the tread 10 located on the outer side of the vehicle, and the marginal performance of steering stability on a dry road surface can be achieved. improves. The width W2 of the second circumferential groove 21 formed in the first region R1 of the tread 10 is wider than the width W1 of the circumferential groove 20, but the third and third grooves formed in the second region R2 of the tread 10 It is narrower than the widths W3 and W4 of the circumferential grooves 22 and 23 of No. 4.

In the tread 10, two circumferential grooves are formed in each of the first region R1 and the second region R2. In comparison, it is smaller in the first region R1. The ground contact area of the first region R1 is larger than the ground contact area of the second region R2. Also, the total volume of the circumferential grooves is smaller in the first region R1 than in the second region R2. In this case, the marginal performance of steering stability on dry road surfaces is more effectively improved. The tire 1 is suitable as a tire for a high-output, high-performance car (UHP tire) that requires high marginal performance.

When the rigidity of the first region R1 is increased, it becomes difficult for the tire to absorb the impact received from the road surface, and it is assumed that the ride comfort will be poor especially when traveling on a rough road surface. Although details will be described later, the tire 1 achieves both steering stability and ride comfort by devising the sipe shape of the mediate rib 60 adjacent to the circumferential groove 20 .

In this embodiment, the three circumferential grooves 21, 22, 23 except for the circumferential groove 20 have approximately the same depth. In this specification, the groove depth means the length from the tread profile surface α along the contact surface of the tread 10 to the groove bottom. The groove bottoms of the circumferential grooves 21, 22, 23 are formed substantially flat. The groove walls of the circumferential grooves 21, 22, and 23 are formed at an angle close to perpendicular to the profile plane α, but are inclined so that the groove width becomes slightly narrower toward the groove bottom. Each groove wall is slightly curved in the vicinity of the groove bottom.

The circumferential groove 20 is curved such that the groove bottom is convex inward in the tire radial direction. The groove bottom of the circumferential groove 20 has little or no flat area. The groove wall 20a of the circumferential groove 20 on the tire equator CL side has a smaller inclination angle with respect to the profile surface α than the groove walls of the other circumferential grooves. On the other hand, the groove wall on the ground contact end E1 side of the circumferential groove 20 has a larger angle with respect to the profile surface α than the groove wall 20a and the groove walls of the other circumferential grooves. are formed substantially vertically. That is, the depth of the circumferential groove 20 gradually changes from the upper end of the groove wall toward the groove bottom on the tire equator CL side, and changes sharply on the ground contact edge E1 side.

The depth D1 of the circumferential groove 20 is preferably 50 to 80% of the depth of the deepest circumferential groove. If the depth D1 is within this range, it is possible to effectively improve steering stability on dry road surfaces while ensuring good drainage performance and ride comfort, provided that other components are appropriately controlled. . In this embodiment, the depths of the circumferential grooves 21, 22, 23 other than the circumferential groove 20 are substantially the same, but the depths D2, D3 of the circumferential grooves 21, 22 are substantially the same, The depth D4 of the directional groove 23 may be slightly shallower than the depths D2 and D3.

The depth D1 of the circumferential groove 20 is preferably 50 to 80% of the depths D2 and D3 of the circumferential grooves 21 and 22. The depth D1 is more preferably 55 to 70% of the depths D2 and D3, and the relationship between the depths of the four circumferential grooves is, for example, D1<D4≤D2=D3.

An example of the depth D1 of the circumferential groove 20 is 4.5 mm. An example of the depth D3 of the circumferential groove 22 is 7.6 mm. The depth of the circumferential groove means the depth of the deepest portion unless otherwise specified. Further, unless otherwise specified, the width of the circumferential groove means the width at the opening of the groove, in other words, the length of the profile surface α along the tire width direction. In this embodiment, the width of each circumferential groove is substantially constant, and the width of each rib is also substantially constant.

The width W1 of the circumferential groove 20 is preferably 60% or less of the width W3 of the circumferential groove 22 having the widest width among the circumferential grooves. The width W1 of the circumferential groove 20 is more preferably 50% or less of the width W3 of the circumferential groove 22, and particularly preferably 30 to 50% of the width W3. If the widths W1 and W3 have such a relationship, it is possible to effectively improve steering stability on a dry road surface while ensuring good drainage performance and ride comfort performance, provided that other configurations are appropriately controlled. It can be improved. An example of width W1 is 7.0 to 8.0 mm.

In the present embodiment, groove walls 20a of the circumferential groove 20, groove walls of the circumferential groove 21 on the tire equator CL side, and groove walls of the circumferential groove 23 on the tire equator CL side are provided with respect to the profile surface α. A region Rz inclined at an angle of 60° or less is formed. In other words, the regions Rz are formed along the tire circumferential direction at the edges of the center rib 30 and the intermediate rib 60 on the side of the ground contact E1 and the edge of the intermediate rib 70 on the side of the ground contact E2. For example, the region Rz is formed at an inclination angle of 20 to 50° with respect to the profile surface α in a depth range within 20% of the depth of the circumferential groove from the upper end of each groove wall.

The width W2 of the circumferential groove 21 is larger than the width W1 of the circumferential groove 20 and smaller than the widths W3, W4 of the circumferential grooves 22,23. The width W2 is preferably 1.3 to 2.5 times the width W1 of the circumferential groove 20, more preferably 1.5 to 2.2 times. The width W2 is preferably 55 to 90% of the width W3 of the circumferential groove 22, more preferably 65 to 80%. Also, the width W4 of the circumferential groove 23 is larger than the widths W1 and W2 of the circumferential grooves 20 and 21 and smaller than the width W3 of the circumferential groove 22 . The width W4 of the circumferential groove 23 is, for example, 1.1 to 1.5 times the width W2 of the circumferential groove 21 and 75 to 95% of the width W3 of the circumferential groove 22.

In other words, the relationship between the widths of the four circumferential grooves is W1<W2<W4<W3. In this case, it becomes easy to achieve both steering stability and riding comfort while ensuring good drainage performance. Note that the groove wall of the circumferential groove 22 is not formed with an inclined surface like the region Rz.

In the tread 10, as described above, the total widths W1 and W2 of the circumferential grooves 20 and 21 formed in the first region R1 are equal to the widths W3 and W3 of the circumferential grooves 22 and 23 formed in the second region R2. It is smaller than the sum of W4. Therefore, the center in the width direction of the center rib 30 is located closer to the ground contact edge E1 than the tire equator CL. In addition, the distance from the intermediate rib 60 in the first region R1 to the grounding end E1 is slightly shorter than the distance from the intermediate rib 70 to the grounding end E2 in the second region R2.

The widths of the center rib 30 and the intermediate ribs 60, 70 may be the same or different. In the present embodiment, the width of the rib means the length of the ground contact surface of the rib along the tire width direction. The width of the mediate rib 60 is slightly larger than the width of the center rib 30 and the mediate rib 70, for example. The center rib 30 and the intermediate rib 70 have substantially the same width.

Hereinafter, the lateral grooves and sipes formed in each land portion will be described in detail with reference to FIGS. 3 to 5. FIG. FIG. 3 is a plan view showing part of the tread 10. FIG. FIG. 4 is an enlarged plan view showing the first region R1, and FIG. 5 is an enlarged plan view showing the second region R2. In FIG. 3, the upper surface of each land portion is indicated by dot hatching (the same applies to FIG. 8).

As shown in FIGS. 3 to 5, the center rib 30 has sipes 31 and 32 formed thereon. The first sipe 31 extends in the tire width direction from the circumferential groove 21 located on the ground contact end E1 side and terminates within the center rib 30 . The second sipe 32 extends in the tire width direction from the circumferential groove 22 located on the ground contact end E2 side and terminates within the center rib 30 . That is, the sipes 31 and 32 have a first lengthwise end (hereinafter sometimes referred to as a "starting end") communicating with the circumferential groove, and a second end (hereinafter sometimes referred to as a "terminating end") in the center. Located within rib 30 . In addition, the sipes 31 and 32 are inclined with respect to the tire width direction so that the ends on the right side in the traveling direction of the vehicle are located forward of the ends on the left side in the main rotation direction of the tire.

The sipe 31 is formed with a length extending from the circumferential groove 21 over the tire equator CL, and the sipe 32 is formed with a length extending from the circumferential groove 22 over the tire equator CL. The sipes 31 and 32 are alternately arranged along the tire circumferential direction and extend in substantially the same direction at substantially the same inclination angle with respect to the tire width direction. In addition, the sipes 31 and 32 are formed in the same number at approximately equal intervals along the tire circumferential direction. In this embodiment, the number of sipes formed in each of the center rib 30 and the intermediate ribs 60, 70 is the same.

The length of the sipe 31 is longer than the length of the sipe 32, eg, 2-4 times, or 2-3 times the length of the sipe 32. Unless otherwise specified, the length of the sipe means both the length along the sipe from the start end to the end of the sipe and the length along the tire width direction in plan view of the tread 10 (the length of the lateral groove (same for ). The sipes 31 and 32 are shallow in the vicinity of the terminal ends, and have a depth of 2.0 mm or less, for example. It is preferable that portions of the sipes 31 and 32 that exceed 2.0 mm in depth do not overlap in the tire circumferential direction.

The depth of the sipe 31 is preferably shallower than the depth of the circumferential groove 21 . Similarly, the depth of sipe 32 is preferably shallower than the depth of circumferential groove 22 . In this embodiment, the depths of the sipes 31, 32 are, for example, substantially the same and constant over the length of the sipes. The depth of the sipes 31, 32 is preferably 70 to 95% of the depth of the circumferential grooves 21, 22 except for shallow portions near the ends. An example of the depth (depth of the deepest part) of the sipes 31 and 32 is 5.8 mm.

It is preferable that the groove walls of the sipes 31 and 32 have a tapered surface, which is an area slanted so that the width of the groove increases toward the opening of the sipe, within a range of 2.0 mm deep from the opening of each sipe. In this embodiment, the sipe 31 has a first tapered surface 31A and a second tapered surface 31B, and the sipe 32 has a tapered surface 32A. That is, the sipe 31 has tapered surfaces on both sides in the width direction, and the sipe 32 has tapered surfaces on only one side in the width direction. Each tapered surface is formed, for example, over a depth range of 0.8 to 2.0 mm from the opening of the sipe.

The first tapered surface 31A is formed on the first groove wall along the length direction of the sipe 31, and the second tapered surface 31B is formed on the second groove wall along the length direction of the sipe 31. there is The first and second groove walls are arranged to face each other in the tire circumferential direction. The first groove wall of the sipe 31 extends longer toward the circumferential groove 22 than the second groove wall, and the first tapered surface 31A is longer than the second tapered surface 31B. Each tapered surface is formed from a position in contact with the circumferential groove 21, but the second tapered surface 31B does not reach the tire equator CL. On the other hand, the first tapered surface 31A extends toward the circumferential groove 22 beyond the tire equator CL.

32 A of taper surfaces are formed in the 1st groove wall along the length direction of the sipe 32. As shown in FIG. The tapered surface 32A is arranged on the same side as the first tapered surface 51A of the lateral groove 51 and the tapered surface 72A of the sipe 72, which will be described later. A second groove wall of the sipe 32 facing the first groove wall is formed substantially perpendicular to the profile plane α. The tapered surface 32A extends from the circumferential groove 22 toward the circumferential groove 21 across the tire equator CL, and overlaps the first tapered surface 31A of the sipe 31 in the tire circumferential direction.

The two tapered surfaces of the sipe 31 may have the same inclination angle with respect to the profile surface α and may be formed with the same width. It is slightly smaller than the inclination angle of the second tapered surface 31B. Also, the maximum width of the first tapered surface 31A is slightly larger than the maximum width of the second tapered surface 31B. Each of the tapered surfaces has curved portions 33A and 33B in the intermediate portions in the length direction, and the direction in which the tapered surfaces face changes slightly across the curved portions 33A and 33B. The width of each tapered surface also changes at the bends 33A and 33B. The width of each tapered surface gradually decreases from the bent portions 33A and 33B toward the terminal end of the sipe 31 .

The maximum width of the first tapered surface 31A is, for example, 1.05 to 1.30 times the maximum width of the second tapered surface 31B. At the portion where the width of each tapered surface is maximum, the inclination angle of the first tapered surface 31A with respect to the profile surface α is preferably 15 to 60°, and the inclination angle of the second tapered surface 31B with respect to the profile surface α is preferably 15 to 60°. preferable. The angle of inclination of each tapered surface with respect to the profile surface α may be substantially constant over the entire length of the tapered surface.

The width of the first tapered surface 31A is maximum in the range from the starting end of the sipe 31 to the bent portion 33A. On the other hand, the second tapered surface 31B has the maximum width at the bent portion 33B. The bent portion 33B is located closer to the tire equator CL than the bent portion 33A. The relationship between the tapered surface of the sipe 31 and the tapered surface of the sipe 32, such as the inclination angle and the width, is not particularly limited. The maximum width of the tapered surface 32A of the sipe 32 is, for example, substantially the same as the maximum width of the second tapered surface 31B. Also, the inclination angle of the tapered surface 32A with respect to the profile surface α may be the same as the inclination angle of the second tapered surface 31B with respect to the profile surface α.

Each tapered surface of the center rib 30 contributes to dispersion of the ground contact pressure together with the tapered surfaces of the other land portions. The configuration in which the sipe 31 has two tapered surfaces and the sipe 32 has one tapered surface is effective in ensuring a large ground contact area while distributing and reducing ground contact pressure to improve braking performance. Since the configuration of the center rib 30 greatly affects the braking performance especially during straight running, the shape, size, positional relationship, etc. of each tapered surface of the center rib 30 greatly contribute to the improvement of the braking performance. In this embodiment, from the viewpoint of improving braking performance, the configuration of the tapered surface of each land portion is designed so that the tread 10 as a whole exhibits more effective functions.

Widths of the plurality of sipes 31 may be slightly different. For example, the sipes 31 adjacent in the tire circumferential direction have different widths, and the center rib 30 is formed with sipes 31 having two to six different widths. The two to six types of sipes 31 may be arranged so that the width gradually increases along the tire circumferential direction. Regarding the sipe 32, the sipes of other ribs, and the lateral grooves 41, 51, the groove widths adjacent to each other in the tire circumferential direction may be different.

Hereinafter, the sipes formed in the intermediate ribs 60 and 70 will be described in detail with appropriate reference to FIGS. 6 and 7 together with FIGS. FIG. 6 is a perspective view of a portion of the first intermediate rib 60 and the first shoulder rib 40 located in the first region R1, viewed from the tire equator CL side. FIG. 7 is a perspective view of a portion of the second intermediate rib 70 and the second shoulder rib 50 located in the second region R2 as seen from the tire equator CL side.

As shown in FIGS. 3 and 4 , sipes 61 and 62 are formed in the mediate rib 60 adjacent to the circumferential groove 20 . The first sipe 61 extends in the tire width direction from the circumferential groove 21 located on the tire equator CL side and terminates within the intermediate rib 60 . The second sipe 62 extends in the tire width direction from the circumferential groove 20 located on the ground contact end E1 side and terminates within the intermediate rib 60 . That is, the sipes 61 and 62 have their first lengthwise ends communicating with the circumferential grooves and their second ends located within the intermediate ribs 60 . A sipe 61 extending from the tire equator CL side is longer than a sipe 62 extending from the ground contact edge E1 side.

The sipes 61 and 62 are alternately arranged along the tire circumferential direction and extend in substantially the same direction at substantially the same inclination angle with respect to the tire width direction. In addition, the sipes 61 and 62 are arranged in the same number at approximately equal intervals along the tire circumferential direction. Although the details will be described later, the sipes 61 and 62 are formed with a length such that portions exceeding 2.0 mm in depth do not overlap in the tire circumferential direction. Forming each sipe with such a length from both sides of the mediate rib 60 in the width direction suppresses deformation of the mediate rib 60 during high-speed turning and braking, and the tire has high rigidity in the first region R1. In 1, good ride comfort performance can be ensured. That is, it is possible to effectively achieve both steering stability (limit performance) and ride comfort performance.

As shown in FIGS. 3 and 5, sipes 71 and 72 are formed in the mediate rib 70 of the second region R2. The first sipe 71 extends in the tire width direction from the circumferential groove 22 positioned on the tire equator CL side and terminates within the intermediate rib 70 . The second sipe 72 extends in the tire width direction from the circumferential groove 23 located on the ground contact end E2 side and terminates within the intermediate rib 70 . That is, the sipes 71 , 72 have first longitudinal ends communicating with the circumferential grooves and second ends located within the intermediate ribs 70 . A sipe 71 extending from the tire equator CL side is longer than a sipe 72 extending from the ground contact edge E2 side. In addition, the sipe 71 has a bent portion 71C that is greatly bent.

The sipes 71 and 72 are alternately arranged along the tire circumferential direction, similarly to the sipes 61 and 62 . In addition, the sipes 71 and 72 are arranged in the same number at approximately equal intervals along the tire circumferential direction. In the present embodiment, the sipe 72 has substantially the same inclination angle with respect to the tire width direction as the sipe 61 and the sipe 31 of the center rib 30 and is formed to be positioned on an extension line of the sipes 31 , 61 . In other words, the sipes 31, 61, 72 are arranged substantially on the same straight line. Although the sipe 71 is bent, a part of the sipe 71 is formed so as to be positioned on an extension line of the sipe 62 and the sipe 32 of the center rib 30 .

The groove wall of each sipe of the mediate ribs 60 and 70 has a tapered surface, which is an area slanted so that the width of the groove increases toward the opening, within a range of 2.0 mm deep from the opening of each sipe. The sipes 61 and 71 are formed with tapered surfaces on both sides in the width direction, and the sipes 62 and 72 are formed on only one side in the width direction of each sipe. Each tapered surface is formed, for example, over a depth range of 0.8 to 2.0 mm from the opening of the sipe.

The tapered surfaces of the sipes 62 , 72 are formed on the first direction side of the sipe 62 in the tire circumferential direction at the intermediate rib 60 , and are formed on the second direction side of the sipe 72 in the tire circumferential direction at the intermediate rib 70 . . In the tire 1 mounted on the left side of the vehicle, the tapered surface 62A of the sipe 62 is formed in the groove wall on the rear side of the groove wall of the sipe 62 in the main rotation direction of the tire. It is formed in the groove wall on the front side in the main rotation direction of the tire among the groove walls. In this case, the ground pressure can be distributed in a well-balanced manner over the entire tread 10, and the effect of improving braking performance and steering stability becomes more pronounced.

As shown in FIGS. 4 and 6, the sipe 61 formed in the intermediate rib 60 has a first tapered surface 61A and a second tapered surface 61B. Sipe 62 has tapered surface 62A as described above. 61 A of 1st taper surfaces are formed in the 1st groove wall along the length direction of the sipe 61, and the 2nd taper surface 61B faces the 1st groove wall along the length direction of the sipe 61. It is formed in the second groove wall. The first groove wall of the sipe 61 extends longer toward the circumferential groove 20 than the second groove wall, and the first tapered surface 61A is longer than the second tapered surface 61B. Both tapered surfaces of the sipes 61 and 62 are narrowed from the starting end of the sipe toward the terminal end.

The two tapered surfaces of the sipe 61 may have different angles of inclination with respect to the profile plane α, but in this embodiment they have substantially the same angle of inclination. Also, the maximum widths of the two tapered surfaces are substantially the same. At the portion where the width of each tapered surface is maximum, the inclination angle of each tapered surface with respect to the profile surface α is preferably 15 to 60°. The inclination angles of the first tapered surface 61A and the second tapered surface 61B with respect to the profile surface α may be substantially constant over the entire length of the tapered surfaces.

A tapered surface 62A of the sipe 62 is formed on the first groove wall along the length direction of the sipe 62 . 62 A of taper surfaces are arrange|positioned at the same side as 41 A of 1st taper surfaces of the lateral groove 41 mentioned later. A second groove wall of the sipe 62 facing the first groove wall is formed substantially perpendicular to the profile plane α. The relationship between the tapered surface 62A and the tapered surface of the sipe 61, such as the inclination angle and the width, is not particularly limited. The maximum width of the tapered surface 62A is larger than the maximum width of the tapered surface of the sipe 61, for example. In the tire 1 mounted on the left side of the vehicle, the first groove walls of the sipes 61 and 62 are located on the rear side of the sipe 61 in the main rotation direction of the tire.

Sipe 61 is longer than sipe 62 as described above. The length of the sipe 61 is preferably 1.1 to 2.5 times the length of the sipe 62, more preferably 1.2 to 2.0 times. The sipes 61 and 62 are formed so that portions exceeding 2.0 mm in depth (hereinafter referred to as "first portions") do not overlap in the tire circumferential direction. A predetermined space S1 exists between the end of the first portion of the sipe 61 and the end of the first portion of the sipe 62 in the tire width direction. The interval S1 is substantially equal to the distance along the tire width direction between the groove bottom of the sipe 61 and the groove bottom of the sipe 62 . In addition, the sipes 61 and 62 have a shallow depth in the vicinity of the terminal ends, for example, 2.0 mm or less (this portion is hereinafter referred to as a "second portion").

The total length of the sipes 61 and 62 along the tire width direction is preferably 60-90%, more preferably 70-80%, of the width of the mediate rib 60 . That is, the spacing S1 is preferably 10 to 40%, more preferably 20 to 30%, of the width of the mediate rib 60. As shown in FIG. In this case, it is possible to more effectively improve the marginal performance of steering stability on dry road surfaces while ensuring good ride comfort performance. For example, the length of the sipe 61 is 50 to 65% or more and the length of the sipe 62 is 30 to 45% or more of the width of the mediate rib 60 . The second portions of the sipes 61 and 62 may overlap in the tire circumferential direction, but in the present embodiment, each sipe including the second portions is formed with a length that does not overlap in the tire circumferential direction.

The depth of the sipe 61 is preferably shallower than the depth of the circumferential groove 21 . The depth of sipe 62 is preferably shallower than the depth of circumferential groove 20 . Although the depths of the sipes 61 and 62 may be the same, in the present embodiment, since the depth D1 of the circumferential groove 20<the depth D2 of the circumferential groove 21, the depth of the sipe 61>the sipe 62 is the depth of The depth of the sipe 61 (first portion) is, for example, 70-95% of the depth D2 of the circumferential groove 21 . The depth of the sipe 62 (first portion) is, for example, 70-95% of the depth D1 of the circumferential groove 20 .

As shown in FIGS. 5 and 7, the sipe 71 formed in the intermediate rib 70 has a first tapered surface 71A and a second tapered surface 71B, and the sipe 72 has a tapered surface 72A. 71 A of 1st taper surfaces are formed in the 1st groove wall along the length direction of the sipe 71, and the 2nd taper surface 71B faces the 1st groove wall along the length direction of the sipe 71. It is formed in the second groove wall. The sipe 71 has an intermediate portion that is greatly bent so as to protrude in the tire circumferential direction. The sipe 71 is longer than the sipe 72 in both the length along the tire width direction and the length along the sipe.

The sipe 71 has a bent portion 71C, and for example, the first and second groove walls are bent at an angle of 90 to 120° at the bent portion 71C. The bent portion 71C is formed at or near the longitudinal central portion of the sipe 71 . The sipe 71 is gently curved such that a portion from the bent portion 71</b>C to the terminal end is convex toward the starting end of the sipe 71 . The sipes 71 are formed so as to protrude in the same direction in the tire circumferential direction as the direction in which the width of the recessed portions 53 of the shoulder ribs 50 , which will be described later, is reduced.

The two tapered surfaces of the sipe 71 may have the same inclination angle with respect to the profile surface α and may have the same width, but in the present embodiment, the inclination angles and widths are different from each other. The relationship between the inclination angle and the width of the two tapered surfaces varies between the range from the starting end of sipe 71 to bent portion 71C and the range from bent portion 71C to the terminal end of sipe 71 . That is, the inclination angle and the width of each tapered surface change greatly with the bent portion 71C as a boundary.

In the range from the starting end of the sipe 71 to the bent portion 71C, the inclination angle of the first tapered surface 71A with respect to the profile surface α is smaller than the inclination angle of the second tapered surface 71B with respect to the profile surface α, and is the maximum of the first tapered surface 71A. The width is greater than the maximum width of the second tapered surface 71B. The width of each tapered surface gradually decreases from the starting end of the sipe 71 toward the bent portion 71C.

In the range from the bent portion 71C to the terminal end of the sipe 71, the inclination angle of the first tapered surface 71A with respect to the profile surface α is larger than the inclination angle of the second tapered surface 71B with respect to the profile surface α, and is the maximum of the first tapered surface 71A. The width is smaller than the maximum width of the second tapered surface 71B. In a predetermined range from the end of sipe 71, the depth of sipe 71 is shallow, and first tapered surface 71A and second tapered surface 71B are connected.

A tapered surface 72A of the sipe 72 is formed on the first groove wall along the length direction of the sipe 72 . A second groove wall of the sipe 72 facing the first groove wall is formed substantially perpendicular to the profile plane α. The relationship between the two tapered surfaces of the tapered surface 72A and the sipe 71, such as the inclination angle and the width, is not particularly limited. It's becoming In addition, in the tire 1 mounted on the left side of the vehicle, the first groove walls of the sipes 71 and 72 are located on the front side of the sipe 71 in the main rotation direction of the tire.

As with the sipes of the mediate rib 60, the portions (first portions) of the sipes 71 and 72 each having a depth exceeding 2.0 mm do not overlap in the tire circumferential direction. A gap S2 exists between the end of the first portion of the sipe 71 and the end of the first portion of the sipe 72 in the tire width direction. The interval S2 is the distance between the ends of the first portions (groove bottoms) of the sipes 71 and 72 along the tire width direction. In addition, the sipes 71 and 72 have a shallow depth in the vicinity of the terminal ends, and have a depth of 2.0 mm or less, for example.

The portions (second portions) where the depth of the sipes 71 and 72 is reduced to 2.0 mm or less may overlap in the tire circumferential direction. The relationship between the intervals S1 and S2 in the mediate ribs 60 and 70 is not particularly limited, but in the present embodiment, the interval S1>the interval S2. The total length of the groove bottoms of the sipes 71 and 72 along the tire width direction is preferably 80 to 99% of the width of the mediate rib 70 . That is, the interval S2 is preferably 1 to 20% of the width of the mediate rib 70. As shown in FIG.

The depth of the sipe 71 is preferably shallower than the depth of the circumferential groove 22 . Similarly, the depth of sipe 72 is preferably shallower than the depth of circumferential groove 23 . In this embodiment, the depths of sipes 71, 72 are, for example, substantially the same and constant over the length of the sipes. The depth of the sipes 71, 72 (first portion) is preferably 70 to 95% of the depths D2, D3 of the circumferential grooves 21, 22.

The configuration of each sipe formed in the intermediate ribs 60, 70, particularly the sipes 61, 62 of the intermediate rib 60, for example, suppresses large deformation of the ribs during high-speed turning and braking, and improves ride comfort performance. substantially improve. The first region R1 of the tread 10 has a large contact area and high rigidity, and the tire 1 is excellent in marginal performance of steering stability, but such a tire tends to have poor ride comfort performance. However, according to the tire 1, both steering stability and ride comfort performance are highly compatible. In addition, the tapered surface of each sipe ensures a large contact area while distributing contact pressure in a well-balanced manner, greatly contributing to improvements in braking performance and steering stability.

Hereinafter, the lateral grooves formed in the shoulder ribs 40 and 50 will be described in detail with reference to FIGS. 8 and 9 together with FIGS. FIG. 8 is an enlarged perspective view showing one lateral groove 41 formed in the shoulder rib 40. As shown in FIG. FIG. 9 is a cross-sectional view taken along line AA in FIG. 4, which is a cross-sectional view in the width direction of the lateral groove 41 at a portion where the width of each tapered surface of the lateral groove 41 is maximum.

As shown in FIGS. 3, 4 and 6, lateral grooves 41 extending in the tire width direction are formed in the shoulder ribs 40 of the first region R1. The lateral groove 41 is formed over the side rib 13 from a position away from the edge of the shoulder rib 40 beyond the ground contact edge E1. The lateral groove 41 is not connected to the circumferential groove 20 , and the starting end of the lateral groove 41 on the tire equator CL side is positioned within the shoulder rib 40 . In this case, the reduction in ground contact area due to deformation of the shoulder ribs 40 is suppressed, and good steering stability and braking performance are obtained.

The lateral grooves 41 are formed in the same number as the sipes of the mediate rib 60 at substantially equal intervals along the tire circumferential direction. The lateral grooves 41 are inclined in the same direction as the sipes of the intermediate ribs 60 with respect to the tire width direction, but the angle of inclination is smaller than that of the sipes of the intermediate ribs 60 . Further, the lateral groove 41 bends slightly near the starting end, and the depth gradually decreases from the bent portion 41C toward the starting end. The depth of the lateral groove 41 is the deepest at the bent portion 41C. The depth of the lateral groove 41 gradually becomes shallower from the bent portion 41C toward the ground contact edge E1, and becomes even shallower as the side rib 13, which is the terminal position, is approached beyond the ground contact edge E1.

The groove wall of the lateral groove 41 has a tapered surface, which is an area slanted so that the groove width increases toward the opening in a range of 2.0 mm deep from the opening of the lateral groove 41 . The lateral groove 41 has a first tapered surface 41A and a second tapered surface 41B. The first tapered surface 41A (first region) is formed in the first groove wall along the length direction of the lateral groove 41, and the second tapered surface 41B (second region) is formed along the length direction of the lateral groove 41. Also, it is formed on the second groove wall facing the first groove wall. The two tapered surfaces are formed over the entire length of the lateral groove 41 on both sides in the width direction of the lateral groove 41 . Each tapered surface is formed over a depth range of 0.8 to 2.0 mm from the opening of the lateral groove 41, for example.

As shown in FIGS. 3, 5, and 7, lateral grooves 51 extending in the tire width direction are formed in the shoulder ribs 50 of the second region R2. As with the lateral grooves 41 of the shoulder ribs 40 , the lateral grooves 51 are formed over the side ribs 13 from a position away from the edge of the shoulder ribs 50 beyond the ground contact edge E<b>2 . The lateral groove 51 is not connected to the circumferential groove 23 , and the starting end of the lateral groove 51 on the tire equator CL side is positioned within the shoulder rib 50 . The lateral grooves 41 , 51 are not aligned in the tire width direction, and the lateral groove 51 is arranged on the extension line of the lateral groove 41 in the longitudinal direction.

The lateral grooves 51 are formed in the same number as the sipes of the mediate rib 70 at approximately equal intervals along the tire circumferential direction. In this embodiment, the number of lateral grooves 41, 51, the number of sipes of the center rib 30, and the number of sipes of the mediate ribs 60, 70 are the same. Similar to the lateral groove 41, the lateral groove 51 bends slightly near the starting end, and the depth gradually decreases from the bent portion 51C toward the starting end. The depth of the lateral groove 51 gradually becomes shallower from the bent portion 51C toward the ground contact edge E2, and becomes even shallower as the side rib 13, which is the terminal position, is approached beyond the ground contact edge E2.

A groove wall of the lateral groove 51 has a tapered surface, which is an area slanted so that the groove width increases toward the opening in a range of 2.0 mm deep from the opening of the lateral groove 51 . The lateral groove 51 has a first tapered surface 51A and a second tapered surface 51B. The first tapered surface 51A (first region) is formed in the first groove wall along the length direction of the lateral groove 51, and the second tapered surface 51B (second region) is formed along the length direction of the lateral groove 51. Also, it is formed on the second groove wall facing the first groove wall. The two tapered surfaces are formed over the entire length of the lateral groove 51 on both sides in the width direction of the lateral groove 51 . Each tapered surface is formed over a depth range of 0.8 to 2.0 mm from the opening of the lateral groove 51, for example.

Although details will be described later, the first tapered surface 41A of the lateral groove 41 is wider than the second tapered surface 41B and has a smaller inclination angle with respect to the profile surface α. Similarly, the first tapered surface 51A of the lateral groove 51 is wider than the second tapered surface 51B and has a smaller inclination angle with respect to the profile surface α. In this embodiment, the first tapered surface is formed on the side of the lateral groove 41 of the shoulder rib 40 in the first direction in the tire circumferential direction, and is formed on the side of the lateral groove 51 of the shoulder rib 50 in the second direction in the tire circumferential direction. there is

In the tire 1 that is mounted on the left side of the vehicle, the first tapered surface 41A of the lateral groove 41, like the tapered surface 62A of the intermediate rib 60, is located on the rear side of the groove wall of the lateral groove 41 in the main rotation direction of the tire. formed. Like the tapered surface 72A of the intermediate rib 70, the first tapered surface 51A of the lateral groove 51 is formed on the groove wall of the lateral groove 51 on the front side in the main rotation direction of the tire. In this case, the ground pressure can be distributed in a well-balanced manner over the entire tread 10, and the effect of improving braking performance and steering stability becomes more pronounced.

The shoulder rib 50 has a generally triangular concave portion 53 formed in the edge along the circumferential groove 23 . Although the second region R2 of the tread 10 has a smaller contact area than the first region R1, the recesses 53 increase the grip on the road surface and contribute to the improvement of steering stability. The recessed portion 53 is formed, for example, with a depth exceeding the tapered surface of the lateral groove 51 from the upper end opening of the circumferential groove 23 . The depth of the concave portion 53 is preferably shallower than the depth of the lateral groove 51 . The number of recesses 53 is smaller than the number of lateral grooves 51 and is formed at approximately equal intervals in the tire circumferential direction. The number of recesses 53 is, for example, half the number of lateral grooves 51, and is formed so as to be positioned between two lateral grooves 51 in the tire circumferential direction.

The recessed portion 53 is arranged so as to be aligned with the sipe 71 of the intermediate rib 70 in the tire width direction. A portion of the groove wall of the circumferential groove 23 forming the side wall of the shoulder rib 50 is recessed inside the rib, and the width of the recess 53 changes along the tire circumferential direction so as to have a generally triangular shape in plan view. are doing. The width of the concave portion 53 gradually decreases in the same direction as the direction in which the sipe 71 protrudes. The depth of the recessed portion 53 is constant over the entire length in the tire circumferential direction.

Hereinafter, the configuration of the tapered surface will be described in more detail, taking the lateral groove 41 as an example. The configurations of the first tapered surfaces 41A and 51A are the same except that the directions with respect to the tire circumferential direction are opposite to each other (the same applies to the second tapered surfaces 41B and 51B).

As shown in FIGS. 8 and 9, the maximum width Wa of the first tapered surface 41A of the lateral groove 41 is larger than the maximum width Wb of the second tapered surface 41B. The width of each of the two tapered surfaces is substantially constant and maximizes between the bent portion 41C of the lateral groove 41 and the ground contact edge E1. The width of each tapered surface gradually decreases from the bent portion 41C of the lateral groove 41 toward the starting end, and slightly decreases from the ground contact end E1 toward the side rib 13. As shown in FIG. On the outer side in the tire width direction of the ground contact edge E1, the width of each tapered surface may be approximately the same, and the width of the second tapered surface 41B may be larger than the width of the first tapered surface 41A.

The maximum width Wa of the first tapered surface 41A is preferably 1.5 to 3.0 times, more preferably 1.8 to 2.5 times, the maximum width Wb of the second tapered surface 41B. In this case, the contact pressure can be distributed more effectively in good balance while ensuring a large contact area of the tread 10 . When the maximum width Wa is less than 1.5 times the maximum width Wb, the effect tends to be small. On the other hand, when the maximum width Wa exceeds 3.0 times the maximum width Wb, the effect of reducing the ground pressure tends to decrease.

The maximum width Wa of the first taper surface 41A is preferably 30 to 50% of the maximum width W of the lateral groove 41, more preferably 35 to 45%. The total maximum width of the first tapered surface 41 a and the second tapered surface 41 b is preferably 50% or more of the maximum width W of the lateral groove 41 . In this case, it becomes easier to distribute the contact pressure in a well-balanced manner while ensuring a large contact area of the tread 10, and the effect of improving steering stability and braking performance becomes more pronounced. The total maximum width of the two tapered surfaces is, for example, 50-80% or 55-70% of the maximum width W.

At the portion where the widths of the first tapered surface 41A and the second tapered surface 41B are maximum, the inclination angle θa of the first tapered surface 41A with respect to the profile surface α is smaller than the inclination angle θb of the second tapered surface 41B with respect to the profile surface α. It's becoming Since the two tapered surfaces have the maximum width between the bent portion 41C of the lateral groove 41 and the ground contact edge E1, the angle θa<angle θb at least within this range. It should be noted that the angle θa>angle θb may be satisfied at the outer side in the tire width direction of the ground contact edge E1.

The difference between the inclination angle θa of the first tapered surface 41A and the inclination angle θb of the second tapered surface 41B is preferably 10° or more. In this case, the contact pressure can be distributed more effectively in good balance while ensuring a large contact area of the tread 10 . A preferable example of the inclination angle θa of the first tapered surface 41A with respect to the profile surface α is 20 to 40°, more preferably 25 to 35°. A preferable example of the inclination angle θb of the second tapered surface 41B with respect to the profile surface α is 30 to 60°, more preferably 40 to 50°.

If the inclination angles θa and θb of the respective tapered surfaces are too large beyond the above range, the effect of reducing the contact pressure tends to decrease. On the other hand, if the inclination angles θa and θb of the respective tapered surfaces are too small beyond the above range, it becomes difficult to secure a large contact area. Preferably, each tapered surface has an inclination angle θa, θb within the above range, and a difference (θb−θa) between the angle θa and the angle θb is 10° or more. An example of a preferable range of the difference between the angles θa and θb is 10 to 25° or 15 to 20°.

According to the tire 1 configured as described above, it is possible to effectively disperse the contact pressure while ensuring a large contact area, thereby achieving excellent braking performance. In addition, excellent steering stability is obtained, especially on dry road surfaces. If the contact pressure is concentrated on a part of the tread, the coefficient of friction of the rubber is lowered, and the rubber is greatly deformed to reduce the contact area. In the tire 1, for example, the tapered surfaces of the lateral grooves 41 and 51 formed in the shoulder ribs 40 and 50 and the synergistic effect of the tapered surfaces of the sipes formed in the center rib 30 and the mediate ribs 60 and 70 provide It suppresses the concentration of the ground pressure and effectively reduces the ground pressure.

As described above, the tire 1 has high rigidity in the first region R1 of the tread 10 located on the outer side of the vehicle, and is excellent in steering stability during high-speed turning and braking. In the tire 1, the circumferential grooves 20 in the first region R1 are particularly formed shallow and narrow, and the lateral grooves 41 of the shoulder ribs 40 are separated from the circumferential grooves 20, thereby increasing the rigidity of the shoulder ribs 40 and enabling high-speed turning. This suppresses large deformation of the shoulder ribs 40 during driving and braking. Furthermore, sipes 61 and 62 having tapered surfaces formed from both sides in the width direction of the mediate rib 60 secure the rigidity of the first region R1 and achieve good ride comfort.

As described above, the tire 1 is excellent in braking performance, has high marginal performance in steering stability, and is suitable for a UHP tire. The tire 1 is also excellent in ride comfort performance. Tire 1 is a novel high-performance tire having excellent braking performance, steering stability performance, and ride comfort performance.

It should be noted that the above-described embodiment can be appropriately modified in design within the scope of the present invention. For example, the land portions are preferably formed in a rib shape, but lateral grooves or sipes that cross the land portions may be formed as long as the desired rigidity of the tread 10 can be ensured. Moreover, in the above-described embodiment, four circumferential grooves having different widths are formed in the tread 10, but the configuration of the circumferential grooves is not limited to this.

In the above-described embodiment, the synergistic effect of the tapered surfaces of the shoulder ribs 40, 50, the center rib 30, and the intermediate ribs 60, 70 effectively distributes the contact pressure. You may change the structure of a taper surface in the range which can ensure an effect. For example, a sipe that does not have a tapered surface may be formed in the center rib or intermediate rib.

In the above embodiment, the maximum width Wa of the first tapered surface 41A of the lateral groove 41 is greater than the maximum width Wb of the second tapered surface 41B, and the inclination angle θa of the first tapered surface 41A is the inclination angle of the second tapered surface 41B. Although it is smaller than θb, it is possible to satisfy the maximum width Wa<maximum width Wb and the angle θa<angle θb as long as the desired effect of reducing the ground contact area and contact pressure can be ensured.

1 tire, 10 tread, 11 sidewall, 12 bead, 13 side rib, 14 carcass, 15 belt, 16 inner liner, 17 bead core, 18 bead filler, 20, 21, 22, 23 circumferential groove, 30 center rib, 31, 32, 61, 62, 71, 72 Sipe 31A, 41A, 51A, 61A, 71A First tapered surface 31B, 41B, 51B, 61B, 71B Second tapered surface 32A, 62A, 72A Tapered surface 40, 50 Shoulder rib 41, 51 Lateral groove 41C, 51C, 71C Bent portion 53 Concave portion 60, 70 Mediate rib CL Tire equator E1, E2 Ground contact edge R1 First region R2 Second region

Claims (13)

A tire having a tread including two or more circumferential grooves, a first shoulder land portion formed on a first contact edge side, and a second shoulder land portion formed on a second contact edge side. There is
The first shoulder land portion and the second shoulder land portion have lateral grooves extending in the tire width direction,
The first groove wall along the length direction of the lateral groove has a first region inclined so that the groove width expands toward the opening in a range of 2.0 mm deep from the opening of the lateral groove,
The second groove wall along the length direction of the lateral groove has a second region inclined so that the groove width expands toward the opening in a range of 2.0 mm in depth from the opening,
In the portion where the widths of the first region and the second region are maximum, the inclination angle of the first region with respect to the tread profile surface along the ground contact surface of the tread is the inclination of the second region with respect to the tread profile surface. less than the angle
The first region is formed at the first shoulder land portion on the first direction side of the lateral groove in the tire circumferential direction, and is formed at the second shoulder land portion on the second direction side of the lateral groove in the tire circumferential direction. There are tires. In the portion where the widths of the first region and the second region are maximum, the inclination angle of the first region with respect to the tread profile surface is 20 to 40°, and the inclination of the second region with respect to the tread profile surface. The tire according to claim 1, wherein the angle is between 30 and 60 degrees and is 10 degrees or more greater than the inclination angle of the first region. 3. The tire according to claim 1 or 2, wherein ends of the lateral grooves on the tire equator side are positioned within the first and second shoulder land portions. The tire according to any one of claims 1 to 3, wherein the ratio of groove area to contact area of the tread is 33-40%. The tire according to any one of claims 1 to 4, wherein the maximum width of the first region is 30-50% of the maximum width of the lateral grooves. The tread includes a first intermediate land portion arranged adjacent to the first shoulder land portion through the circumferential groove, and an intermediate land portion arranged adjacent to the second shoulder land portion through the circumferential groove. and a second mediate land portion,
The first intermediate land portion and the second intermediate land portion include a first sipe extending from the circumferential groove located on the tire equator side and terminating within each land portion, and the first sipe located on the ground contact end side. forming a second sipe extending from the circumferential groove and terminating within each of the land portions;
A tire according to any preceding claim, wherein the first sipe is longer than the second sipe. The groove walls of the first sipe and the second sipe have an inclined region within a depth of 2.0 mm from the opening of each sipe so that the groove width increases toward the opening,
7. The tire of claim 6, wherein the slanted regions are formed on both widthwise sides of the first sipe and only on one widthwise side of the second sipe. The inclined region of the second sipe is formed on the first direction side of the second sipe in the tire circumferential direction in the first intermediate land portion, and the second sipe in the second intermediate land portion of the tire. The tire according to claim 7, which is formed on the second direction side in the circumferential direction. The tire is a tire whose mounting direction with respect to the vehicle is specified,
According to any one of claims 6 to 8, the first sipe formed in the second intermediate land portion arranged inside the vehicle from the tire equator has an intermediate portion bent so as to protrude in the tire circumferential direction. A tire according to any one of the preceding paragraphs. The tire is a tire whose mounting direction with respect to the vehicle is specified,
The second shoulder land portion, which is arranged on the inner side of the vehicle with respect to the tire equator, has a generally triangular concave portion in a plan view formed on an edge along the circumferential groove,
The tire according to any one of claims 1 to 9, wherein the number of recesses is smaller than the number of the lateral grooves and is formed at approximately equal intervals in the tire circumferential direction. The tread includes a center land portion formed on the tire equator,
The center land portion includes a first sipe extending from the circumferential groove located on the first ground contact end side and terminating within the center land portion, and the circumferential groove located on the second ground contact end side. forming a second sipe extending from and terminating within the center land portion;
11. Tire according to claim 10, wherein said first sipe is longer than said second sipe. The groove walls of the first sipe and the second sipe have an inclined region within a depth range of 2.0 mm from the opening of each sipe so that the sipe width increases toward the opening,
12. The tire of claim 11, wherein the slanted regions are formed on both sides of the first sipe in the width direction and only on one side of the second sipe in the width direction. The tire according to any one of claims 1 to 12, wherein the 300% modulus of the rubber forming the surface layer of the tread is 15 or less.

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