JP2024073985A - Pneumatic tires - Google Patents

Abstract

[Problem] To achieve excellent driving stability while ensuring good drainage. [Solution] A pneumatic tire 1 according to an embodiment is a tire having a tread 10 and a specified mounting direction for a vehicle. The tread 10 has main grooves extending in the tire circumferential direction, and mediate blocks 40 that are partitioned by the main grooves and are positioned on the outer side of the vehicle. An inclined surface 46 is formed on the axially outer side of the mediate block 40, and extends at an angle toward the main groove adjacent to the mediate block 40, and the inclined surface 46 extends along a direction inclined at a predetermined angle with respect to the tire circumferential direction. The rectangular ratio of the contact surface of the tread 10 is 0.55 to 0.85. [Selected Figure] Figure 2

Description

The present invention relates to pneumatic tires, and more specifically to tires with a specified mounting direction on a vehicle.

Conventionally, pneumatic tires with a tread having a main groove extending in the tire circumferential direction and a lateral groove extending in a direction intersecting the main groove and a specified mounting direction on a vehicle are widely known (see, for example, Patent Document 1). In the tread pattern disclosed in Patent Document 1, slopes are formed on the groove wall surfaces of the main grooves and the lateral grooves. By forming slopes on the groove wall surfaces, the groove area is increased, resulting in good drainage.

JP 2019-94004 A

However, as a result of the inventors' investigations, it was found that in tires with slopes formed on the groove walls, the block rigidity decreases and the handling stability decreases depending on the shape of the slope and the shape of the contact surface of the tread. It is an important challenge to realize a pneumatic tire that has excellent handling stability while ensuring good drainage.

The pneumatic tire according to the present invention is a pneumatic tire with a tread and a specified mounting direction relative to a vehicle, the tread has main grooves extending in the tire circumferential direction and mediate blocks partitioned by the main grooves and positioned on the outside of the vehicle, the axially outer side of the mediate blocks has a slope that extends at an angle toward the main groove side adjacent to the mediate blocks, the slope extends along a direction inclined at a predetermined angle relative to the tire circumferential direction, and the rectangular ratio of the contact surface of the tread is 0.55 to 0.85.

The pneumatic tire of the present invention provides excellent driving stability while ensuring good drainage.

1 is a perspective view of a pneumatic tire as an example of an embodiment. 1 is a plan view of a pneumatic tire as an example of an embodiment, showing an enlarged view of a portion of a tread. FIG. 2 is a plan view of a pneumatic tire according to an embodiment, illustrating an enlarged view of a first shoulder block. FIG. 2 is a perspective view of a pneumatic tire according to an embodiment, illustrating an enlarged view of a first shoulder block. 4 is a cross-sectional view taken along line AA in FIG. 3. 4 is a cross-sectional view taken along line BB in FIG. 3. 4 is a cross-sectional view taken along line CC in FIG. 3 . FIG. 2 is a plan view of a pneumatic tire according to an embodiment, showing a first mediate block. FIG. 2 is a perspective view of a pneumatic tire according to an embodiment, showing a first mediate block. 9 is a cross-sectional view taken along line DD in FIG. 8 . 9 is a cross-sectional view taken along line EE in FIG. 8 . 9 is a cross-sectional view taken along the line FF in FIG. 8 . FIG. 2 is a diagram showing a schematic shape of a ground contact surface of a tread. 1 is a perspective view of a pneumatic tire as an example of an embodiment, showing an outer side of a vehicle. FIG.

Below, an example of an embodiment of a pneumatic tire according to the present invention will be described in detail with reference to the drawings. The embodiment described below is merely an example, and the present invention is not limited to the following embodiment. In addition, the present invention includes forms that are formed by selectively combining the components of the embodiment described below.

Figure 1 is a perspective view showing a portion of a pneumatic tire 1, which is an example of an embodiment, and also shows the cross-sectional structure of the tire. As shown in Figure 1, the pneumatic tire 1 has a tread 10, which is the portion that comes into contact with the road surface. The tread 10 has a main groove extending in the tire circumferential direction, and a first shoulder block 30 and a first intermediate block 40 that are partitioned by the main groove, and is formed in an annular shape along the tire circumferential direction.

As will be described in more detail later, the axially inner side of the first shoulder block 30 and both axially opposite side of the first intermediate block 40 have slopes that extend obliquely toward the adjacent main groove. The slopes include a portion that extends along the circumferential direction of the tire and a portion that extends in a direction inclined at a predetermined angle to the circumferential direction of the tire. The rectangular ratio of the contact surface of the tread 10 is 0.55 to 0.85.

The pneumatic tire 1 is a tire with a specified mounting direction on the vehicle, and the mounting direction on the right and left sides of the vehicle is opposite. The tread 10 has different tread patterns on the left and right of the tire equator CL (see FIG. 2). The equator CL is an imaginary line along the tire circumferential direction that passes exactly in the center of the tire axial direction of the tread 10. For convenience of explanation, the terms "left and right" are used in this specification, and these left and right refer to the left and right in the direction of travel of the vehicle when the pneumatic tire 1 is mounted on the vehicle. The pneumatic tire 1 is suitable for summer tires, for example, for electric vehicles such as electric vehicles (EVs) and hybrid vehicles (HVs) with high acceleration performance, or for heavy sports utility vehicles (SUVs).

The tread 10 has multiple main grooves. There is no particular limit to the number of main grooves, but in this embodiment, four main grooves are formed: two center main grooves 21, 22 and two shoulder main grooves 20, 23. Having four main grooves further improves drainage.

Of the center main grooves 21, 22, the main groove located on the vehicle outer side is referred to as the first center main groove 21, and the main groove located on the vehicle inner side is referred to as the second center main groove 22. Also, of the shoulder main grooves 20, 23, the main groove located on the vehicle outer side is referred to as the first shoulder main groove 20, and the main groove located on the vehicle inner side is referred to as the second shoulder main groove 23. Each main groove is formed straight along the tire circumferential direction without bending in the tire axial direction. Each main groove may have the same width and depth, but in this embodiment, at least the widths of the first shoulder main groove 20 and the first center main groove 21 and the widths of the second shoulder main groove 23 and the second center main groove 22 are different from each other.

The tread 10 is defined by a first shoulder main groove 20 extending in the circumferential direction, and has a first shoulder block 30 located on the outer side of the vehicle, and a second shoulder block 70 located on the inner side of the vehicle, defined by a second shoulder main groove 23 extending in the circumferential direction. In other words, the pneumatic tire 1 is mounted on the vehicle so that the first shoulder block 30 is located on the outer side of the vehicle, and the second shoulder block 70 is located on the inner side of the vehicle. The block is a part that rises from a position corresponding to the bottom of the main groove toward the outer side in the tire radial direction, and is also called a land.

The tread 10 is partitioned by a first center main groove 21 and a second center main groove 22 that extend in the circumferential direction, and has a center block 50 located on the equator CL. The tread 10 also has a first intermediate block 40 formed between the first shoulder block 30 and the center block 50, and a second intermediate block 60 formed between the center block 50 and the second shoulder block 70.

The pneumatic tire 1 comprises a pair of sidewalls 11 that bulge outward in the tire axial direction, and a pair of beads 12. The beads 12 are fixed to the rim of a wheel, and include, for example, a bead core and a bead filler. The sidewalls 11 and beads 12 are formed in an annular shape along the tire circumferential direction, and form the side surfaces of the pneumatic tire 1. The sidewalls 11 extend from both axial ends of the tread 10 toward the tire radial center.

The pneumatic tire 1 may have side ribs 13 formed between the ground contact ends E1, E2 (see FIG. 2) of the tread 10 and the part of the sidewall 11 that protrudes most axially outward. The ground contact end E1 is the ground contact end on the outer side of the vehicle, and the ground contact end E2 is the ground contact end on the inner side of the vehicle, and they are present in the first shoulder block 30 and the second shoulder block 70, respectively. The side ribs 13 protrude axially outward and are formed in an annular shape along the tire circumferential direction. The ground contact ends E1, E2 of the pneumatic tire 1, or the parts from their vicinity to the left and right side ribs 13, are also called shoulder or buttress regions.

The tread 10 and the sidewall 11 are generally made of different types of rubber. The side ribs 13 may be made of the same rubber as the ground contact surface of the tread 10, or may be made of a different rubber. In this specification, the ground contact ends E1 and E2 are defined as both axial ends of the area (ground contact surface) that contacts a flat road surface when an unused pneumatic tire 1 is mounted on a standard rim and filled with air to the standard internal pressure, and a specified load is applied. In the case of passenger car tires, the specified load is a load equivalent to 88% of the standard load.

Here, a "regular rim" is a rim determined by the tire standard, which is a "standard rim" for JATMA and a "Measuring Rim" for TRA and ETRTO. "Regular internal pressure" is the "maximum air pressure" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "INFLATION PRESSURE" for ETRTO. The regular internal pressure is usually 180 kPa for passenger car tires, but 220 kPa for tires labeled "Extra Load" or "Reinforced." "Normal load" is "maximum load capacity" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "LOAD CAPACITY" for ETRTO.

The pneumatic tire 1 comprises a carcass 14, an inner liner 15, and a belt 16. The carcass 14 is a cord layer covered with rubber, and forms the framework of the pneumatic tire 1 that can withstand loads, impacts, air pressure, etc. The inner liner 15 is a rubber layer provided on the inner peripheral surface of the carcass 14, and maintains the air pressure of the pneumatic tire 1. The belt 16 is a reinforcing band disposed between the rubber that constitutes the tread 10 and the carcass 14. The belt 16 tightens the carcass 14 to increase the rigidity of the pneumatic tire 1.

Since the pneumatic tire 1 is used as a tire with a specified mounting direction on the vehicle, it is preferable that the tire has a marking to indicate the mounting direction on the vehicle. The marking to indicate the mounting direction may be a letter, symbol, illustration, etc. indicating the inside or outside of the vehicle, and the configuration is not particularly limited. Generally, a symbol called a serial number is provided on the side of the pneumatic tire 1, but a serial number may also be used as a marking to indicate the mounting direction.

The serial number includes information such as a size code, time of manufacture (year and week of manufacture), and place of manufacture (manufacturing factory code). The mounting direction of the pneumatic tire 1 on the vehicle may be specified by providing a serial number only on the side (sidewall 11) of the pneumatic tire 1 facing the outside of the vehicle, or by providing different serial numbers on the side facing the outside and the side facing the inside of the vehicle. A specific example is providing a manufacturing factory code and a size code on both sides of the pneumatic tire 1, and providing the year and week of manufacture only on the side facing the outside of the vehicle.

The tread 10 of the pneumatic tire 1 will be described in detail below with reference to Figure 2. Figure 2 is a plan view of the pneumatic tire 1, showing a portion of the tread 10.

As shown in FIG. 2, the tread 10 has a center block 50 in the center in the tire axial direction, and has a tread pattern that is asymmetrical with respect to the equator CL. In the following, the region on the ground edge E1 side of the equator CL is referred to as the first region, and the region on the ground edge E2 side of the equator CL is referred to as the second region. When the tire is mounted on a vehicle so that the first region is located on the outer side of the vehicle and the second region is located on the inner side of the vehicle, the tread pattern of the pneumatic tire 1 can ensure good drainage while achieving excellent driving stability. As described above, the pneumatic tire 1 is a summer tire used on road surfaces without ice or snow, and is suitable for use as a tire for EVs, HVs, or SUVs.

In this embodiment, the axial center of the center block 50 is shifted toward the ground edge E1 from the equator CL. Therefore, the first center main groove 21 and the second center main groove 22, which are adjacent to each other on both sides of the center block 50 in the tire axial direction, are formed at positions at different distances from the equator CL.

Although the four main grooves may be formed with the same width, in this embodiment, the width _W22 of the second center main groove 22 and the width _W23 of the second shoulder main groove 23 formed in the second region are larger than the width _W20 of the first shoulder main groove 20 and the width _W21 of the first center main groove 21 formed in the first region. By making the main grooves formed in the second region wider, good drainage is ensured and wet braking performance is improved. In this specification, the groove width means the width along the profile surface α (see FIG. 5 described later) along the ground contact surface of the tread 10, unless otherwise specified.

The first center main groove 21 may be formed wider than the first shoulder main groove 20. The second center main groove 22 and the second shoulder main groove 23 may have the same width. For example, the groove widths are as follows: width _W20 is 12.0-13.5 mm, width _W21 is 14.5-16.0 mm, and widths _W22 and _W23 are 17.0-18.5 mm.

The four main grooves may be formed to the same depth, or the center main grooves 21, 22 may be formed deeper than the shoulder main grooves 20, 23. Unless otherwise specified, groove depth refers to the depth of the deepest part of the groove. More specifically, it refers to the shortest distance from the profile surface α at the deepest part to the bottom of the groove. An example of the depth of each main groove is 7 to 15 mm.

At least one of the four main grooves is generally provided with a wear indicator (not shown). The wear indicator is a protrusion located at the bottom of the groove that serves as an indicator for checking the wear level of the tread rubber.

In the first region of the tread 10, in order from the ground contact edge E1 side, a first shoulder block 30, a first intermediate block 40, and a center block 50 are formed. Also, in the first region, a first shoulder main groove 20 and a first center main groove 21 are formed. The first shoulder main groove 20 separates the first shoulder block 30 and the first intermediate block 40, and the first center main groove 21 separates the first intermediate block 40 and the center block 50.

In the second region of the tread 10, in order from the ground contact edge E2 side, a second shoulder block 70, a second intermediate block 60, and a center block 50 are formed. In addition, a second center main groove 22 and a second shoulder main groove 23 are formed in the second region. The second center main groove 22 separates the center block 50 and the second intermediate block 60, and the second shoulder main groove 23 separates the second intermediate block 60 and the second shoulder block 70.

The first shoulder block 30, the first mediate block 40, the center block 50, the second mediate block 60, and the second shoulder block 70 are arranged parallel to one another across the main groove. In this embodiment, the width of the first shoulder block 30 is greater than the width of the second shoulder block 70. The width of the first mediate block 40 is greater than the width of the second mediate block 60. And the width of the center block 50 is the smallest of all the block widths.

As will be described in more detail later, the axially inner side of the first shoulder block 30 and the axially opposite side of the first intermediate block 40 have slopes 36, 46, 47 that extend at an angle toward the adjacent main groove. The slopes 36, 46, 47 include a portion that extends along the tire circumferential direction and a portion that extends in a direction inclined at a predetermined angle to the tire circumferential direction. The center block 50, the second intermediate block 60, and the second shoulder block 70 do not have slopes.

The first shoulder block 30 has multiple sipes formed along the tire circumferential direction. In this specification, a sipe means a narrow groove narrower than a lateral groove described later, with a groove width of 1.0 mm or less. Note that the groove width does not include the width of a step described later. In the pneumatic tire 1, the sipes, for example, play a role in adjusting the rigidity of the block, contributing to achieving both good ride comfort and braking performance. In this embodiment, the first shoulder block 30 has two longitudinal sipes 311, 312 formed along the tire circumferential direction.

The first shoulder block 30 has lateral sipes 32 and lateral grooves 33 extending axially outward from the longitudinal sipes 311. In this specification, the term "axially extending grooves" (similar to sipes) refers to both grooves extending along the axial direction of the tire and grooves extending at an inclination angle of 45° or less, preferably 30° or less, relative to the axial direction of the tire. The same applies to main grooves extending circumferentially, and the main grooves may be formed in a zigzag shape while curving at an inclination angle of 45° or less relative to the circumferential direction of the tire.

The lateral sipes 32 and lateral grooves 33 are alternately arranged at intervals in the circumferential direction of the tire. One end of the lateral sipes 32 and lateral grooves 33 opens into the longitudinal sipes 311, and the other end extends beyond the ground contact end E1 to the vicinity of the side rib 13. By extending the lateral sipes 32 and lateral grooves 33 to the vicinity of the side rib 13, drainage is improved.

The first shoulder block 30 is formed with sipes 35 that extend from the first shoulder main groove 20 toward the longitudinal sipe 312 at an inclination angle of approximately 45° with respect to the tire axial direction. A plurality of sipes 35 are formed at intervals in the tire circumferential direction. One end of the sipe 35 opens into the first shoulder main groove 20, and the other end opens into the longitudinal sipe 312. In this embodiment, the sipe 35 (and the other sipes as well) is formed in a straight line, but this is not limited thereto. For example, the sipe 35 may be formed in a curved line or may have a bent shape.

A step 34 is formed on one groove wall surface of the sipe 35, extending outward from the groove wall surface. In this specification, the step refers to a substantially flat portion of the block formed radially inward of the ground contact surface of the tread 10, other than the sipe and the lateral groove. The step 34 is formed continuously along the extension direction of the sipe 35. The width of the step 34 gradually increases toward the first shoulder main groove 20. The step 34 is also formed between the slope 36 and the first shoulder main groove 20.

The first intermediate block 40 has three longitudinal sipes 411, 412, and 413 formed along the tire circumferential direction. The first intermediate block 40 also has a sipe 451 formed from the first shoulder main groove 20 toward the longitudinal sipe 411 at an inclination angle of approximately 45° with respect to the tire axial direction. One end of the sipe 451 opens into the first shoulder main groove 20, and the other end opens into the longitudinal sipe 411. The first intermediate block 40 also has a sipe 452 formed from the first center main groove 21 toward the longitudinal sipe 413 at an inclination angle of approximately 45° with respect to the tire axial direction. One end of the sipe 452 opens into the first center main groove 21, and the other end opens into the longitudinal sipe 413.

It is preferable that the sipes 451 and 452 are formed on approximately the same straight line. It is even more preferable that the sipes 451 and 452 and the sipes 35 formed on the first shoulder block 30 are formed on approximately the same straight line. This improves drainage.

Steps 441, 442 are formed on one groove wall surface of sipes 451, 452, respectively, extending outward from the groove wall surface. Step 441 is formed continuously along the extension direction of sipe 451, and step 442 is formed continuously along the extension direction of sipe 452. The width of step 441 gradually increases toward first shoulder main groove 20, and is formed between slope 46 and first shoulder main groove 20. The width of step 442 gradually increases toward first center main groove 21, and is formed between slope 47 and first center main groove 21.

The steps 441 and 442 preferably have shapes that are point-symmetrical with respect to any point on the center line of the first intermediate block 40 in the tire axial direction. In addition, the step 441 and the step 34 formed on the axially inner side of the first shoulder block 30 are preferably formed to face each other across the first shoulder main groove 20. In addition, it is more preferable that the steps 441 and 34 have shapes that are point-symmetrical with respect to any point on the center line of the first shoulder main groove 20 in the tire axial direction. This allows for both good drainage and excellent handling stability.

Sipes 55 are formed in the center block 50, extending from the first center main groove 21 toward the inside of the center block 50 at an inclination angle of approximately 45° with respect to the tire axial direction. One end of the sipe 55 opens into the first center main groove 21, and the other end terminates inside the center block 50. The other end of the sipe 55 is located on the ground edge E2 side of the equator CL. It is preferable that the sipe 55 and the sipes 451, 452 formed in the first intermediate block 40 are formed on approximately the same straight line.

The center block 50 has a slope 56 formed from one groove wall surface of the sipe 55 toward the top surface of the center block 50. The slope 56 is formed along the extension direction of the sipe 55 and extends from the first center main groove 21 to the vicinity of the equator CL. The slope 56 may be formed from the middle of the groove wall surface of the sipe 55 toward the top surface, or from the groove bottom of the sipe 55 toward the top surface. The slope 56 may be formed on the groove wall surfaces of all the sipes 55, or may be formed on the groove wall surfaces of some of the sipes 55. By forming the slope 56, the rigidity of the center block 50 can be increased and uneven wear of the center block 50 can be suppressed.

Two longitudinal sipes 611, 612 are formed in the second intermediate block 60 along the tire circumferential direction. A sipe 651 is formed in the second intermediate block 60, extending from the second center main groove 22 toward the longitudinal sipe 611 at a predetermined inclination angle with respect to the tire axial direction. One end of the sipe 651 opens into the second center main groove 22, and the other end opens into the longitudinal sipe 611. In addition, a sipe 652 is formed in the second intermediate block 60, extending from the second shoulder main groove 23 toward the longitudinal sipe 612 at a predetermined inclination angle with respect to the tire axial direction. One end of the sipe 652 opens into the second shoulder main groove 23, and the other end opens into the longitudinal sipe 612.

The inclination angles of sipes 651 and 652 with respect to the tire axial direction may be the same or different. In addition, the inclination angles of sipes 651, 652 with respect to the tire axial direction may be smaller than the inclination angles of sipes 451, 452 formed in the first intermediate block 40 with respect to the tire axial direction. The inclination angles of sipes 651, 652 with respect to the tire axial direction are, for example, 20° to 50°.

One sipe 651 is formed between two adjacent lateral grooves 63 in the tire circumferential direction. The sipe 651 is preferably formed at a position that divides the space between the two adjacent lateral grooves 63 into approximately two equal parts in the tire circumferential direction. Two sipes 652 are formed between two adjacent lateral grooves 63 in the tire circumferential direction. The sipes 652 are preferably formed at a position that divides the space between the two adjacent lateral grooves 63 into approximately three equal parts in the tire circumferential direction.

The second intermediate block 60 has a lateral groove 63 formed therein, which extends from the second center main groove 22 toward the second shoulder main groove 23 at a predetermined inclination angle relative to the tire axial direction. One end of the lateral groove 63 opens into the second center main groove 22, and the other end opens into the second shoulder main groove 23. The inclination angle of the lateral groove 63 relative to the tire axial direction is approximately the same as that of the sipes 651, 652.

The groove width of the lateral grooves 63 varies along the tire axial direction. Specifically, the groove width of the lateral grooves 63 from the second center main groove 22 to the longitudinal sipe 612 is smaller than the groove width of the lateral grooves 63 from the longitudinal sipe 612 to the second shoulder main groove 23. The groove width of the lateral grooves 63 from the second center main groove 22 to the longitudinal sipe 612 is, for example, 30% to 70% of the groove width of the lateral grooves 63 from the longitudinal sipe 612 to the second shoulder main groove 23. By varying the groove width of the lateral grooves 63, the pumping noise generated from the lateral grooves 63 when the tire comes into contact with the ground can be reduced.

The second shoulder block 70 is formed with lateral sipes 72 and lateral grooves 73 that extend axially outward from the second shoulder main groove 23. A plurality of lateral sipes 72 and lateral grooves 73 are formed at intervals in the tire circumferential direction. Two lateral sipes 72 are formed between two adjacent lateral grooves 73. It is preferable that the lateral sipes 72 are formed at positions that divide the space between two adjacent lateral grooves 73 into approximately three equal parts in the tire circumferential direction. The inclination angles of the lateral sipes 72 and lateral grooves 73 with respect to the tire axial direction are approximately the same, for example, 5° to 20°.

One end of the lateral sipe 72 opens into the first center main groove 21, and the other end terminates within the second shoulder block 70. The other end of the lateral sipe 72 is preferably located outside the ground contact edge E2 in the axial direction of the tire. One end of the lateral groove 73 opens into the second shoulder main groove 23, and the other end extends beyond the ground contact edge E2 to the vicinity of the side rib 13. By extending the lateral groove 73 to the vicinity of the side rib 13, drainage is improved.

The lateral groove 73 includes a shallow groove portion 731 that is shallower than the rest of the lateral groove 73, and a narrow width portion 732 that is narrower than the rest of the lateral groove 73. The shallow groove portion 731 is formed near the connection position between the lateral groove 73 and the second shoulder main groove 23. The depth of the shallow groove portion 731 is, for example, 20% to 50% of the depth of the rest of the lateral groove 73. It is preferable that the groove wall surface of the shallow groove portion 731 is inclined so that the groove width narrows toward the groove bottom. By forming the shallow groove portion 731, the rigidity of the second shoulder block 70 can be increased, improving steering stability.

The narrow width portion 732 is formed axially outward of the shallow groove portion 731. The groove width of the narrow width portion 732 is, for example, 10% to 50% of the other portion of the lateral groove 73. By forming the narrow width portion 732, the rigidity of the second shoulder block 70 can be increased, improving steering stability.

The first shoulder block 30 will be described in detail below with reference to Figures 3 to 7. Figure 3 is a plan view showing the vicinity of the first shoulder block 30, and Figure 4 is an enlarged perspective view of the vicinity of the first shoulder block 30. Figures 5 to 7 are cross-sectional views taken along lines AA, BB, and CC in Figure 3, respectively.

As shown in Figures 3 and 4, the first shoulder block 30 has longitudinal sipes 311, 312 formed along the tire circumferential direction. In this embodiment, the groove width of the longitudinal sipes 311, 312 is approximately uniform in the tire radial direction except near the groove bottom, but is not limited to this. For example, the groove wall surface of the longitudinal sipes 311, 312 may be inclined so that the groove width narrows toward the groove bottom.

The groove wall surface of the longitudinal sipe 311 is formed with steps 37 extending toward the inside in the tire axial direction. The steps 37 are formed at a predetermined interval in the tire circumferential direction. The depth of the steps 37 is, for example, 10% to 50% of the depth of the longitudinal sipe 311. The width of the steps 37 in the tire axial direction is substantially uniform in the tire circumferential direction, and is, for example, substantially the same as the width of the longitudinal sipe 311. The length of the steps 37 in the tire circumferential direction is not particularly limited, and is, for example, substantially the same as the length of the interval between the steps 37 in the tire circumferential direction. By providing the steps 37 on the groove wall surface of the longitudinal sipe 311, the drainage performance of the longitudinal sipe 311 is improved. In this embodiment, the steps 37 are formed at a predetermined interval in the tire circumferential direction, but are not limited to this. For example, the steps 37 may be formed all around the tire circumferential direction.

The first shoulder block 30 is formed with lateral sipes 32 and lateral grooves 33 extending axially outward from the longitudinal sipes 311. One end of the lateral sipes 32 and lateral grooves 33 opens into the longitudinal sipes 311, and the other end extends to the vicinity of the side rib 13. The inclination angles of the lateral sipes 32 and lateral grooves 33 with respect to the axial direction of the tire are substantially the same, for example, 5° to 20°. The groove widths of the lateral sipes 32 (excluding the wide portion 321 described later) and lateral grooves 33 (excluding the wide portion 331 described later) are substantially uniform along the axial direction of the tire. The depths of the lateral sipes 32 (excluding the wide portion 321 described later) and lateral grooves 33 are not particularly limited, and are, for example, 50% to 150% of the depth of the longitudinal sipes 311.

The lateral sipe 32 includes a wide portion 321 that is shallower and wider than the other portions of the lateral sipe 32. The wide portion 321 is formed at the connection position between the lateral sipe 32 and the longitudinal sipe 311. The depth of the wide portion 321 is, for example, 10% to 50% of the depth of the other portions of the lateral sipe 32. The width of the wide portion 321 gradually increases toward the connection position between the lateral sipe 32 and the longitudinal sipe 311. The width of the wide portion 321 at the connection position between the lateral sipe 32 and the longitudinal sipe 311 is, for example, 200% to 500% of the width of the other portions of the lateral sipe 32. By forming the wide portion 321, the rigidity of the first shoulder block 30 can be increased, and the steering stability is improved.

The lateral groove 33 includes a wide portion 331 that is wider than the remaining portion of the lateral groove 33. The width of the wide portion 331 gradually increases toward the connection position between the lateral groove 33 and the longitudinal sipe 311. The width of the wide portion 331 at the connection position between the lateral groove 33 and the longitudinal sipe 311 is, for example, 110 to 200% of the width of the remaining portion of the lateral groove 33. The depth of the wide portion 331 is not particularly limited, and is approximately the same as the depth of the lateral groove 33 in this embodiment. By forming the wide portion 331, the volume of the lateral groove 33 can be increased, improving drainage.

A slope 36 is formed on the axially inner side of the first shoulder block 30, extending at an angle toward the first shoulder main groove 20. The slope 36 includes a first slope 361 extending along the tire circumferential direction and a second slope 362 extending in a direction inclined at a predetermined angle relative to the tire circumferential direction.

As shown in Fig. 3, the inclination angle _θ1 of the second inclined surface 362 with respect to the tire circumferential direction is preferably 1° or more, and more preferably 3° or more. By setting the inclination angle _θ1 to 1° or more, drainage performance can be improved. Moreover, the inclination angle _θ1 is preferably 30° or less, and more preferably 20° or less. By setting the inclination angle _θ1 to 30° or less, a decrease in rigidity of the first shoulder block 30 can be suppressed, and steering stability can be ensured. Thus, an example of a suitable range for the inclination angle _θ1 is 1° to 30°, and more preferably 3° to 20°.

As will be described in more detail later, when the rectangular ratio of the contact surface of the tread 10 is between 0.55 and 0.85, the end of the contact surface intersects with the second slope 362 at a substantially right angle in a plan view. As a result, during sudden braking or acceleration, the second slope 362 comes into contact with the road surface, preventing the blocks from collapsing, reducing the ground pressure at the end of the blocks, and improving cornering performance during turns.

The first shoulder block 30 is formed with a sipe 35 that extends from the first shoulder main groove 20 toward the longitudinal sipe 312 at an inclination angle of approximately 45° with respect to the tire axial direction. One end of the sipe 35 opens into the first shoulder main groove 20, and the other end opens into the longitudinal sipe 312. The groove width and depth of the sipe 35 are approximately uniform along the extension direction of the sipe 35.

A step 34 extending outward from the sipe 35 is formed on the groove wall surface of the sipe 35 on the side adjacent to the second slope 362. The step 34 includes a portion formed along the sipe 35 and a portion formed between the second slope 362 and the first shoulder main groove 20. The width of the portion of the step 34 formed along the sipe 35 (the width in the direction perpendicular to the extension direction of the sipe 35) gradually increases toward the first shoulder main groove 20 in the extension direction of the sipe 35. In addition, the width of the portion of the step 34 formed between the second slope 362 and the first shoulder main groove 20 (the width in the tire axial direction) gradually decreases in the tire circumferential direction as it moves away from the adjacent sipe 35.

FIG. 5 is a cross-sectional view of line AA in FIG. 3, and is a cross-sectional view of the first inclined surface 361. As shown in FIG. 5, the inclination angle θ ₃₆₁ of the first inclined surface 361 with respect to the profile surface α along the ground contact surface of the tread 10 is preferably 30° or more, more preferably 40° or more. By setting the inclination angle θ ₃₆₁ to 30° or more, the groove volume can be increased and the drainage performance can be improved. Moreover, the inclination angle θ ₃₆₁ of the first inclined surface 361 is preferably 60° or less, more preferably 50° or less. By setting the inclination angle θ ₃₆₁ to 60° or less, the reduction in the surface area of the block of the first shoulder block 30 due to the formation of the first inclined surface 361 can be suppressed, and the wear resistance performance and the grip performance can be ensured. Therefore, an example of a suitable range of the inclination angle θ 361 of the first inclined surface ₃₆₁ is 30° to 60°, more preferably 40° to 50°.

In the present embodiment, the inclination angle θ ₃₆₁ of the first slope 361 (similarly for the second slope 362) is uniform in the tire radial direction, but is not limited thereto. For example, the first slope 361 may include a plurality of slopes inclined at different angles with respect to the profile surface α. Also, for example, the first slope 361 may include a curved slope. Also, in the present embodiment, the inclination angle θ ₃₆₁ of the first slope 361 is uniform in the tire circumferential direction, but is not limited thereto. For example, the inclination angle θ ₃₆₁ of the first slope 361 may increase or decrease as it approaches the connection position between the first slope 361 and the second slope 362.

The depth H ₃₆₁ of the first sloping surface 361 is preferably 10% or more of the depth H ₂₀ of the first shoulder main groove 20, and more preferably 25% or more. By making the depth H ₃₆₁ of the first sloping surface 361 10% or more of the depth H ₂₀ of the first shoulder main groove 20, the volume of the groove can be increased and the drainage can be improved. Moreover, the depth H ₃₆₁ of the first sloping surface 361 is preferably 70% or less of the depth H ₂₀ of the first shoulder main groove 20, and more preferably 60% or less. By making the depth H ₃₆₁ of the first sloping surface 361 70% or less of the depth H ₂₀ of the first shoulder main groove 20, the reduction in the volume of the block of the first shoulder block 30 due to the formation of the first sloping surface 361 can be suppressed. As a result, the reduction in the rigidity of the first shoulder block 30 is suppressed, and the steering stability is improved. Therefore, an example of a suitable range for the depth _H361 of the first sloping surface 361 is 10% to 70% of the depth H20 of the first shoulder main groove ₂₀ , and more preferably 25% to 60%. The depth _H361 of the first sloping surface 361 means the shortest distance from the profile surface α to the deepest part of the first sloping surface 361.

In the present embodiment, the depth H ₃₆₁ of the first slope 361 (the same applies to the second slope 362) is uniform in the tire circumferential direction, but is not limited thereto. For example, the depth H ₃₆₁ of the first slope 361 may increase or decrease as it approaches the connection position between the first slope 361 and the second slope 362.

The width W ₃₆₁ of the first sloping surface 361 is preferably 20% or more of the width W ₂₀ of the first shoulder main groove 20, more preferably 25% or more. By making the width W ₃₆₁ of the first sloping surface 361 20% or more of the width W ₂₀ of the first shoulder main groove 20, the groove volume can be increased and the drainage can be improved. Moreover, the width W ₃₆₁ of the first sloping surface 361 is preferably 50% or less of the width W ₂₀ of the first shoulder main groove 20, more preferably 45% or less. By making the width W ₃₆₁ of the first sloping surface 361 50% or less of the width W ₂₀ of the first shoulder main groove 20, the reduction in the surface area of the blocks of the first shoulder block 30 caused by the formation of the first sloping surface 361 can be suppressed, and the wear resistance and grip performance can be ensured. Thus, an example of a suitable range of the width W ₃₆₁ of the first sloping surface 361 is 20% to 50% of the width W ₂₀ of the first shoulder main groove 20, more preferably 25% to 45%. The width of the first inclined surface means the length in a direction perpendicular to the direction in which the adjacent main grooves extend in a plan view, and the width of the main groove means the length between the intersection points of the profile surface α and imaginary lines extending from both groove walls toward the profile surface α.

Fig. 6 is a cross-sectional view taken along line BB in Fig. 3, and is a cross-sectional view of the second inclined surface 362. As shown in Fig. 6, the inclination angle θ ₃₆₂ of the second inclined surface 362 with respect to the profile surface α may be substantially the same as or different from the inclination angle θ ₃₆₁ (see Fig. 5) of the first inclined surface 361. From the same viewpoint as the inclination angle θ ₃₆₁ of the first inclined surface 361, the inclination angle θ ₃₆₂ of the second inclined surface 362 is preferably 30° to 60°, and more preferably 40° to 50°.

The depth H ₃₆₂ of the second slant surface 362 may be substantially the same as or different from the depth H ₃₆₁ of the first slant surface 361 (see FIG. 5). From the same viewpoint as the depth H _{361 of the first slant surface 361, the depth H 362} of the second slant surface ₃₆₂ is preferably 10% to 70% of the depth H ₂₀ of the first shoulder main groove 20, and more preferably 25% to 60%. In addition, a step 34 is formed between the second slant surface 362 and the first shoulder main groove 20. Therefore, the depth H ₃₆₂ of the second slant surface 362 is equal to the distance from the profile surface α to the step 34.

In this embodiment, the step 34 is formed substantially parallel to the profile surface α, but is not limited thereto. For example, the step 34 may have a slope that extends at an angle toward the first shoulder main groove 20. The slope angle of the slope formed in the step 34 may be substantially the same as or different from the slope angle θ ₃₆₂ of the second slope 362. The slope formed in the step 34 may include a curved slope.

The width of the second slope 362 may be substantially the same as or different from the width _W361 (see FIG. 5) of the first slope 361. From the same viewpoint as the width _W361 of the first slope 361, the width of the second slope 362 is preferably 20% to 50% of the width _W20 of the first shoulder main groove 20, and more preferably 25% to 45%. Note that the width of the second slope 362 means the width along the direction perpendicular to the extension direction of the second slope 362.

FIG. 7 is a cross-sectional view of the line CC in FIG. 3, and is a cross-sectional view of the sipe 35 and the step 34. The depth H ₃₅ of the sipe 35 is not particularly limited, and may be approximately the same as the depth H ₂₀ of the first shoulder main groove 20 (see FIG. 5), or may be 70% to 95% of the depth H ₂₀ of the first shoulder main groove 20. In this embodiment, the groove wall surface near the groove bottom of the sipe 35 is curved, but is not limited to this. For example, the groove wall surface and the groove bottom surface of the sipe 35 may be connected at approximately right angles. In this embodiment, the groove width of the sipe 35 is approximately uniform in the tire radial direction, but is not limited to this. For example, the groove width of the sipe 35 may be formed so that the groove width narrows toward the groove bottom. In addition, the groove wall surface of the sipe 35 may be formed with a slope having a predetermined inclination angle with respect to the profile surface α.

The first mediate block 40 will be described in detail below with reference to Figures 8 to 12. Figure 8 is a plan view showing the vicinity of the first mediate block 40, and Figure 9 is an enlarged perspective view of the vicinity of the first mediate block 40. Figures 10 to 12 are cross-sectional views taken along lines DD, EE, and FF in Figure 8, respectively.

Three longitudinal sipes 411, 412, 413 are formed in the first intermediate block 40 along the tire circumferential direction. In this embodiment, the groove width of the longitudinal sipes 411, 412, 413 is approximately uniform in the tire radial direction except near the groove bottom, but is not limited to this. For example, the groove wall surface of the longitudinal sipes 411, 412, 413 may be inclined so that the groove width narrows toward the groove bottom.

The vertical sipe 412 has a plurality of widened portions 412A with an expanded groove width. The maximum groove width of the widened portions 412A is not particularly limited, but is, for example, 200 to 500% of the width of the remaining portions of the vertical sipe 412. By forming the widened portions 412A, heat that accumulates in the center of the first intermediate block 40 in the tire axial direction can be cooled. In this embodiment, the groove wall surface of the widened portions 412A is formed in an arch shape, but is not limited to this. For example, it may be formed in a U-shape or a wave shape.

A slope 46 is formed on the axially outer side of the first intermediate block 40, extending at an angle toward the first shoulder main groove 20. The slope 46 includes a first slope 461 extending along the tire circumferential direction and a second slope 462 extending in a direction inclined at a predetermined angle to the tire circumferential direction. In addition, a slope 47 is formed on the axially inner side of the first intermediate block 40, extending at an angle toward the first center main groove 21. The slope 47 includes a first slope 471 extending along the tire circumferential direction and a second slope 472 extending in a direction inclined at a predetermined angle to the tire circumferential direction, like the slope 46.

As shown in Fig. 8, the inclination angle θ ₂ of the second inclined surface 462 with respect to the tire circumferential direction and the inclination angle θ ₃ of the second inclined surface 472 with respect to the tire circumferential direction may be different from the inclination angle θ ₁ (see Fig. 3), but are preferably substantially the same. From the same viewpoint as the inclination angle θ ₁ , an example of a suitable range for the inclination angles θ ₂ and θ ₃ is 1° to 30°, and more preferably 3° to 20°.

As will be described in more detail later, when the rectangular ratio of the ground contact surface of the tread 10 is 0.55 to 0.85, the end of the ground contact surface intersects with the second slopes 462, 472 at approximately right angles in a plan view. As a result, during sudden braking or acceleration, the second slopes 462, 472 come into contact with the road surface, preventing the blocks from collapsing, reducing the ground contact pressure at the block ends, and improving steering stability during normal driving.

The first intermediate block 40 is formed with a sipe 451 extending from the first shoulder main groove 20 toward the longitudinal sipe 411 at an inclination angle of approximately 45° with respect to the tire axial direction. One end of the sipe 451 opens into the first shoulder main groove 20, and the other end opens into the longitudinal sipe 411. The first intermediate block 40 is also formed with a sipe 452 extending from the first center main groove 21 toward the longitudinal sipe 413 at an inclination angle of approximately 45° with respect to the tire axial direction. One end of the sipe 452 opens into the first center main groove 21, and the other end opens into the longitudinal sipe 413. The groove width and depth of the sipes 451, 452 are approximately uniform along the extension direction of the sipes 451, 452.

Steps 441, 442 extending outward are formed on the groove wall surfaces of the sipes 451, 452 on the side closest to the second slopes 462, 472. The step 441 includes a portion formed along the sipe 451 and a portion formed between the second slope 462 and the first shoulder main groove 20. The step 442 includes a portion formed along the sipe 452 and a portion formed between the second slope 472 and the first center main groove 21.

The width of the portion of the step 441 formed along the sipe 451 (the width in a direction perpendicular to the extension direction of the sipe 451) gradually increases in the extension direction of the sipe 451 toward the first shoulder main groove 20. In addition, the width of the portion of the step 441 formed between the second slope 462 and the first shoulder main groove 20 (the width in the tire axial direction) gradually increases in the tire circumferential direction as it moves away from the connection position between the first slope 461 and the second slope 462.

As with step 441, the width of step 442 (the width in the direction perpendicular to the extension direction of sipe 452) of the portion formed along sipe 452 of step 442 gradually increases in the extension direction of sipe 452 toward first center main groove 21. Also, the width of the portion formed between second slope 472 of step 442 and first center main groove 21 (width in the tire axial direction) gradually increases in the tire circumferential direction as it moves away from the connection position between first slope 471 and second slope 472.

Hereinafter, the cross-sectional shapes of the first inclined surface 461, the second inclined surface 462, and the sipe 451 will be described with reference to FIGS. 10 to 12. Note that the description of the first inclined surface 471, the second inclined surface 472, and the sipe 452 will be omitted, but they can be formed in a similar manner. FIG. 10 is a cross-sectional view taken along line DD in FIG. 8, and is a cross-sectional view of the first inclined surface 461. The inclination angle θ ₄₆₁ of the first inclined surface 461 with respect to the profile surface α along the ground contact surface of the tread 10 may be different from the inclination angle θ ₃₆₁ of the first inclined surface 361 formed in the first shoulder block 30 with respect to the profile surface α, but is preferably approximately the same. Also, from the same viewpoint as the inclination angle θ ₃₆₁ , an example of a suitable range of the inclination angle θ ₄₆₁ of the first inclined surface 461 is 30° to 60°, and more preferably 40° to 50°.

In the present embodiment, the inclination angle θ ₄₆₁ of the first slope 461 (similarly for the second slope 462) is uniform in the tire radial direction, but is not limited thereto. For example, the first slope 461 may include a plurality of slopes inclined at different angles with respect to the profile surface α. Also, for example, the first slope 461 may include a curved slope. Also, in the present embodiment, the inclination angle θ ₄₆₁ of the first slope 461 is uniform in the tire circumferential direction, but is not limited thereto. For example, as the connection position between the first slope 461 and the second slope 462 approaches, the inclination angle θ ₄₆₁ of the first slope 461 may increase or decrease.

The depth H ₄₆₁ of the first sloping surface 461 may be different from the depth H ₃₆₁ of the first sloping surface 361 formed in the first shoulder block 30, but is preferably approximately the same. From the same viewpoint as the depth H ₃₆₁ of the first sloping surface 361, an example of a suitable range of the depth H 461 of the first sloping surface 461 of the first sloping surface ₄₆₁ is preferably 10% to 70% of the depth H ₂₀ of the first shoulder main groove 20, and more preferably 25% to 60%.

In the present embodiment, the depth H ₄₆₁ of the first slope 461 (the same applies to the second slope 462) is uniform in the tire circumferential direction, but is not limited thereto. For example, the depth H ₄₆₁ of the first slope 461 may increase or decrease as the connection position between the first slope 461 and the second slope 462 approaches.

The width _W461 of the first sloping surface 461 may be different from the width _W361 of the first sloping surface ₃₆₁ formed in the first shoulder block 30, but is preferably approximately the same. From the same viewpoint as the width W361 of the first sloping surface 361, an example of a suitable range of the width _W461 of the first sloping surface 461 of the first sloping surface 461 is preferably 20% to 50% of the width _W20 of the first shoulder main groove 20, and more preferably 25% to 45%.

Fig. 11 is a cross-sectional view taken along line CC in Fig. 8, and is a cross-sectional view of the second inclined surface 462. As shown in Fig. 11, the inclination angle θ ₄₆₂ of the second inclined surface 462 with respect to the profile surface α may be substantially the same as or different from the inclination angle θ ₄₆₁ (see Fig. 10) of the first inclined surface 461. From the same viewpoint as the inclination angle θ ₄₆₁ of the first inclined surface 461, the inclination angle θ ₄₆₂ of the second inclined surface 462 is preferably 30° to 60°, and more preferably 40° to 50°.

The depth H ₄₆₂ of the second slant surface 462 may be substantially the same as or different from the depth H ₄₆₁ of the first slant surface 461 (see FIG. 10). From the same viewpoint as the depth H 461 of the first slant surface 461, the depth H ₄₆₂ of the second slant surface ₄₆₂ is preferably 10% to 70% of the depth H ₂₀ of the first shoulder main groove 20, and more preferably 25% to 60%. In addition, a step 441 is formed between the second slant surface 462 and the first shoulder main groove 20. Therefore, the depth H ₄₆₂ of the second slant surface 462 coincides with the distance from the profile surface α to the step 441.

In this embodiment, the step 441 is formed substantially parallel to the profile surface α, but is not limited thereto. For example, the step 441 may have a slope that extends at an angle toward the first shoulder main groove 20. The slope angle of the slope formed in the step 441 may be substantially the same as or different from the slope angle θ ₄₆₂ of the second slope 462. In addition, the slope formed in the step 441 may include a curved slope.

The width of the second slope 462 may be substantially the same as or different from the width _W461 (see FIG. 10) of the first slope 461. From the same viewpoint as the width _W461 of the first slope 461, the width of the second slope 462 is preferably 20% to 50% of the width _W20 of the first shoulder main groove 20, and more preferably 25% to 45%. Note that the width of the second slope 462 means the width along a direction perpendicular to the extension direction of the second slope 462.

FIG. 12 is a cross-sectional view of the line CC in FIG. 8, and is a cross-sectional view of the sipe 451 and the step 441. The depth H ₄₅₁ of the sipe 451 is not particularly limited, and may be approximately the same as the depth H ₂₀ of the first shoulder main groove 20, or may be 70% to 95% of the depth H ₂₀ of the first shoulder main groove 20. In this embodiment, the groove wall surface near the groove bottom of the sipe 451 is curved, but is not limited to this. For example, the groove wall surface and the groove bottom surface of the sipe 451 may be connected at approximately right angles. In this embodiment, the groove width of the sipe 451 is approximately uniform in the tire radial direction, but is not limited to this. For example, the groove width of the sipe 451 may be inclined so that the groove width narrows toward the groove bottom. In addition, the groove wall surface of the sipe 451 may be formed with a slope having a predetermined inclination angle with respect to the profile surface α.

The shape of the ground contact surface of the tread 10 will be described in detail below with reference to Figures 13 and 14. Figure 13 is a diagram that shows a schematic of the shape of the ground contact surface of the tread 10, and Figure 14 is a perspective view of the pneumatic tire 1, and an enlarged view showing the outside of the vehicle.

As shown in FIG. 13, the contact surface of the tread 10 has a shape close to an ellipse, with a contact length (L2) near the contact end being relatively short compared to the contact length (L1) which is the length of the contact surface along the tire circumferential direction on the equator CL. Here, the contact length (L1) is the length of the contact surface along the tire circumferential direction on the equator CL when an unused pneumatic tire is mounted on a regular rim and filled with air to a specified internal pressure, and a load equivalent to 70.4% of the regular load is applied. The contact length (L2) is the length of the contact surface along the tire circumferential direction at a position 10 mm axially inward from both ends of the contact surface determined under the above measurement conditions. The specified internal pressure under the above measurement conditions is 200 kPa when the aspect ratio of the tire is 60% or more, and 220 kPa when the aspect ratio is less than 60%. In addition, for tires that are described as Extra Load, the specified internal pressure under the above measurement conditions is 240 kPa when the aspect ratio is 60% or more, and 260 kPa when the aspect ratio is less than 60%.

In this specification, L2/L1 is defined as the rectangular ratio of the contact surface of the tread 10. In this embodiment, the contact length (L2) is substantially the same length on the left and right sides of the tread 10.

The rectangular ratio of the ground contact surface of the tread 10 is 0.55 to 0.85. In the tread pattern of this embodiment, if the rectangular ratio under the above conditions is 0.55 to 0.85, as shown in FIG. 13, in a plan view, the end of the ground contact surface and the second slope 462 formed on the first intermediate block 40 intersect at approximately right angles. This improves drainage to the outside in the axial direction of the tire. In addition, during sudden braking and acceleration, the second slope 462 comes into contact with the road surface, reducing the ground contact pressure at the block end, suppressing lifting of the ground contact surface, and improving steering stability during normal driving.

The rectangular ratio of the contact surface is more preferably 0.60 to 0.80, even more preferably 0.65 to 0.75, and particularly preferably 0.68 to 0.72. In the tread pattern of this embodiment, if the rectangular ratio of the contact surface is less than 0.55, the handling stability decreases, making it difficult to achieve both good drainage and excellent handling stability. On the other hand, if the rectangular ratio of the contact surface exceeds 0.85, the drainage decreases, making it difficult to achieve both good drainage and excellent handling stability.

Below, we will explain the belt reinforcement 17 and belt angle of this embodiment as a form for achieving a rectangular ratio of the contact surface of 0.55 to 0.85.

First, the belt reinforcement 17 will be described. As shown in FIG. 14, the belt reinforcement 17 is disposed between the belt 16 and the tread 10. The belt reinforcement 17 is disposed to improve durability and reduce road noise during driving. The belt reinforcement 17 has, for example, a two-layer structure and includes a cap ply 18 and an edge ply 19. Note that the configuration of the belt reinforcement 17 is not limited to this. For example, it may be configured not to include the cap ply 18, or may be configured to have two layers of edge ply 19.

The cap ply 18 extends in the axial direction of the tire between the left and right side ribs 13. The cap ply 18 is made of an insulating organic fiber layer, such as polyamide fiber, and is covered with a topping rubber.

The edge ply 19 is disposed at each end of the belt 16 in the tire axial direction. As shown in FIG. 14, it is preferable that the inner end 19A of the edge ply 19 is located outside the outer end 462A of the second slope 462 formed on the first mediate block 40 in the tire axial direction. This makes it easy to set the rectangular ratio of the ground contact surface to 0.55 to 0.85. The inner end 19A refers to the end of the edge ply 19 located most inside in the tire axial direction. The outer end 462A of the second slope 462 refers to the most outside position in the tire axial direction among the intersections between the second slope 462 and the profile surface α along the ground contact surface of the tread 10.

Next, the belt angle will be described. The belt angle is the angle of the belt cord relative to the tire circumferential direction. The belt angle is preferably 21° to 27°. Within this range, it is easy to achieve a rectangular ratio of the contact surface of 0.55 to 0.85. If the belt angle is smaller than 21°, the binding force of the belt 16 becomes strong, and the rectangular ratio of the contact surface exceeds 0.85. On the other hand, if the belt angle is larger than 27°, the binding force of the belt 16 becomes weak, and the rectangular ratio of the contact surface becomes smaller than 0.55. The belt angle is more preferably 22° to 26°, and even more preferably 23° to 25°.

As described above, the pneumatic tire 1 having the above configuration can achieve excellent driving stability while ensuring good drainage. The second slope 462 is formed on the axially outer side of the first intermediate block 40, extending at an angle toward the first shoulder main groove 20 and in a direction inclined at a predetermined angle with respect to the tire circumferential direction, and the rectangular ratio of the contact surface of the tread 10 is set to 0.55 to 0.85. During sudden braking and acceleration, the second slope 462 comes into contact with the road surface, reducing the contact pressure at the block end, suppressing lifting of the contact surface, and improving driving stability during normal driving.

The above embodiment can be modified as appropriate within the scope of the present invention. In the above embodiment, a first slope extending along the tire circumferential direction and a second slope extending along a direction inclined at a predetermined angle to the tire circumferential direction are formed, but for example, the first slope does not have to be formed. Also, in the above embodiment, a step is formed between the second slope and the main groove, but for example, the step does not have to be formed. Note that the number and shape of the lateral grooves and sipes formed in each block may be changed within the scope of the present invention.

1 Pneumatic tire, 10 Tread, 11 Sidewall, 12 Bead, 13 Side rib, 14 Carcass, 15 Inner liner, 16 Belt, 17 Belt reinforcement, 18 Cap ply, 19 Edge ply, 20 First shoulder main groove, 21 First center main groove, 22 Second center main groove, 23 Second shoulder main groove, 30 First shoulder block, 32, 72 Lateral sipe, 33, 63, 73 Lateral groove, 34, 37, 441, 442 Step, 35, 55, 451, 452, 651, 652 Sipe, 36, 46, 47 Slope, 40 First intermediate block, 50 Center block, 60 Second intermediate block, 70 Second shoulder block, 311, 312, 411, 412, 413, 611, 612 Longitudinal sipe, 321 Wide section, 361, 461, 471 First slope, 362, 462, 472 Second slope, 412A Wide section, 462A Outer end, 731 Shallow groove section, 732 Narrow section

Claims (4)

A pneumatic tire having a tread and a specified mounting direction on a vehicle,
The tread is
A main groove extending in a tire circumferential direction;
A mediate block defined by the main groove and disposed on the outer side of the vehicle;
having
A slope is formed on a side surface of the mediate block on an outer side in the tire axial direction, the slope extending toward a main groove adjacent to the mediate block,
The inclined surface extends along a direction inclined at a predetermined angle with respect to the tire circumferential direction,
The pneumatic tire has a rectangular ratio of the ground contact surface of the tread of 0.55 to 0.85. The pneumatic tire according to claim 1, wherein the width of the slope is 20% or more of the groove width of the adjacent main groove. Belt and
An edge ply provided at an end of the belt in the tire axial direction and disposed on an outer side of a vehicle;
Further comprising:
The pneumatic tire according to claim 1 , wherein an axially inner end of the edge ply is disposed outwardly of an axially outer end of the slope. Further comprising a belt;
The pneumatic tire according to claim 1 or 2, wherein the belt angle of the belt is from 21° to 27°.

Images