pneumatic tires

Abstract

We provide pneumatic tires that offer a balance between handling performance and traction performance. [Solution] The tread 2 has a first main groove 11 and a second main groove 12 extending along the tire circumferential direction on the inner side in the tire axial direction, a narrow groove 13 extending along the tire circumferential direction on the outer side in the tire axial direction, a first shoulder rib 21 partitioned by the first main groove 11, a mediate rib 22 partitioned by the first main groove 11 and the second main groove 12, and a center rib 23 partitioned by the second main groove 12 and the narrow groove 13, with the groove volume ratio increasing in the order of the first shoulder rib 21, the mediate rib 22, and the center rib 23, and the center rib 23 and the mediate rib 22 protruding outward in the tire radial direction from the profile surface of the tread 2.

Description

Technical Field

[0001] The present disclosure relates to pneumatic tires.

Background Art

[0002] In pneumatic tires, tires with a rib pattern having main grooves, fine grooves, etc. along the tire circumferential direction are known (for example, Patent Document 1). Tires with a rib pattern have characteristics of low rolling resistance and low tire noise.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, in the above-described tire with a rib pattern, as one means for improving handling performance, it is conceivable to reduce the groove volume ratio of the center rib. However, by reducing the groove volume ratio of the center rib, the ground pressure dispersion will decrease. When the ground pressure dispersion decreases, the traction performance will decrease.

[0005] Therefore, an object of the present invention is to provide a pneumatic tire capable of achieving both handling performance and traction performance.

Means for Solving the Problems

[0006] The pneumatic tire according to the present invention is a pneumatic tire having a tread and a specified mounting direction for a vehicle, wherein the tread has a first main groove and a second main groove extending along the tire circumferential direction on the inner side in the tire axial direction, a fine groove extending along the tire circumferential direction on the outer side in the tire axial direction, a shoulder rib partitioned by the first main groove, a mediate rib partitioned by the first main groove and the second main groove, and a center rib partitioned by the second main groove and the fine groove, extending from the inner side to the outer side in the tire axial direction, wherein the groove volume ratio of the shoulder rib, mediate rib, and center rib is larger in the order of shoulder rib, mediate rib, and center rib, and the center rib and mediate rib protrude outward in the tire radial direction from the profile surface of the tread. [Effects of the Invention]

[0007] The pneumatic tire of the present invention makes it possible to achieve both handling performance and traction performance. [Brief explanation of the drawing]

[0008] [Figure 1] This is a cross-sectional view of a pneumatic tire, which is an example of an embodiment. [Figure 2] This is a plan view of the tread of a pneumatic tire, which is an example of an embodiment. [Figure 3] This diagram schematically shows the shape of the contact surface of the tread. [Modes for carrying out the invention]

[0009] An example of an embodiment of the present invention will be described in detail below. In the following description, specific shapes, materials, directions, numerical values, etc., are examples to facilitate understanding of the present invention and can be appropriately modified according to the application, purpose, specifications, etc.

[0010] [Air-filled tires] An example of an embodiment, a pneumatic tire 1, will be described using Figure 1.

[0011] The pneumatic tire 1 comprises a tread 2, which is the part that contacts the road surface; a sidewall 3, which forms the side of the tire; and a bead 4, which is the part that is fixed to the rim of the wheel. The pneumatic tire 1 is suitable, for example, as a semi-racing tire with high acceleration performance.

[0012] The pneumatic tire 1 is a tire with a specified mounting direction on the vehicle, meaning that the mounting direction is opposite on the right and left sides of the vehicle. In other words, the tread 2 has different tread patterns on the left and right sides of the tire equator CL. Here, the tire equator CL is a virtual line along the tire circumferential direction passing through the center of the tread 2 in the tire axial direction. Furthermore, for the sake of explanation, the term "left and right" is used in this specification, and this "left and right" refers to the left and right sides in the direction of travel of the vehicle when the pneumatic tire 1 is mounted on the vehicle.

[0013] The tread 2 is provided with a first main groove 11 and a second main groove 12 formed on the inner side in the tire axial direction, and a narrow groove 13 formed on the outer side in the tire axial direction. The first main groove 11, the second main groove 12, and the narrow groove 13 are formed straight along the tire circumferential direction without curving in the tire axial direction.

[0014] Furthermore, the tread 2 is provided with a first shoulder rib 21 demarcated by the first main groove 11, a median rib 22 demarcated by the first main groove 11 and the second main groove 12, a center rib 23 demarcated by the second main groove 12 and the narrow groove 13, and a second shoulder rib 24 demarcated by the narrow groove 13, extending from the inside to the outside in the axial direction of the tire. The first shoulder rib 21 and the second shoulder rib 24 are formed beyond the contact edges E1 and E2. A rib is a portion that rises outward in the radial direction of the tire from a position corresponding to the bottom of the first main groove 11 or the second main groove 12, and is also called a ridge.

[0015] Here, the contact points E1 and E2 of the pneumatic tire 1 are defined as the axial ends of the area (contact surface) that touches a flat road surface when a predetermined load is applied to an unused tire mounted on a regular rim and inflated to the normal internal pressure. The predetermined load is equivalent to 88% of the normal load.

[0016] Note that "standard rim" refers to the rim defined by the tire standard, which is "standard rim" for JATMA and "Measuring Rim" for TRA and ETRTO. Also, "standard internal pressure" is "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 standard internal pressure is usually 180kPa for passenger car tires, but it is 220kPa for tires marked Extra Load or Reinforced. "Standard 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.

[0017] As will be described in more detail later, the contact surface of the tread 2 in this embodiment has a relatively short contact length near the contact edges E1 and E2 compared to the length of the contact surface along the tire circumferential direction (contact length) on the tire equator CL, and the shape of the contact surface of the tread 2 is close to an ellipse shape. Specifically, the rectangularity ratio A of the contact surface of the tread 2 is designed to be 0.7 or more and 0.9 or less.

[0018] The sidewall 3 is disposed on both sides of the tread 2 and is formed in an annular shape along the tire circumferential direction. The sidewall 3 is the portion that protrudes most to the outside in the tire axial direction of the pneumatic tire 1, and is gently curved so as to be convex toward the outside in the tire axial direction. The sidewall 3 has a function of preventing damage to the carcass 5. The sidewall 3 is the portion that flexes most when the pneumatic tire 1 performs a cushioning action, and usually, a flexible rubber having fatigue resistance is adopted.

[0019] The bead 4 is disposed on the inner side in the tire radial direction of the sidewall 3 and is a portion fixed to the rim of the wheel. The bead 4 has a bead core 4A and a bead filler 4B. The bead core 4A is composed of a steel bead wire and is an annular member extending over the entire circumference in the tire circumferential direction, and is embedded in the bead 4. The bead filler 4B has a tip tapered shape extending to the outside in the tire radial direction and is an annular hard rubber member extending over the entire circumference in the tire circumferential direction.

[0020] The carcass 5 is spanned between a pair of beads 4 and is locked by being folded around the bead core 4A. The carcass 5 is composed of at least one carcass ply. The carcass ply is formed by coating a carcass cord made of organic fiber with a coating rubber. The carcass cord is disposed substantially perpendicular (for example, 80° or more and 90° or less) to the tire circumferential direction. Examples of the organic fiber used for the carcass cord include polyester fiber, rayon fiber, aramid fiber, and nylon fiber.

[0021] The inner liner 6 covers the inner surface of the tire between a pair of beads 4. The inner liner 6 is composed of an air permeation resistant rubber and has a function of maintaining the air pressure of the pneumatic tire 1.

[0022] The pneumatic tire 1 further includes a belt 7 disposed on the outer side in the tire radial direction of the carcass 5 and a cap ply 8 covering the outer side in the tire radial direction of the belt 7. The cap ply 8 has a function of reinforcing the belt 7. The number of the cap plies 8 may be one or two or more.

[0023] The belt 7 is disposed on the outer side in the tire radial direction of the top of the carcass 5 and is provided so as to overlap the outer peripheral surface of the carcass 5. The belt 7 is formed of a belt ply obtained by rubber-coating cords arranged in a direction inclined with respect to the tire circumferential direction. The material of the cords of the belt ply is not particularly limited, and examples thereof include organic fibers such as polyester, rayon, nylon, and aramid, or metals such as steel.

[0024] In the present embodiment, the belt 7 is composed of two belt plies 7A and 7B. The cords forming the two belt plies 7A and 7B are arranged so as to cross each other between the two belt plies 7A and 7B.

[0025] Here, the angle (belt angle) of the cords forming the two belt plies 7A and 7B with respect to the tire circumferential direction may be 20° or more and 30° or less. When the angle of the cords with respect to the tire circumferential direction is within the above range, it becomes easy to control the rectangularity ratio A of the grounding surface of the tread 2 to be 0.7 or more and 0.9 or less. Thereby, the drainage performance can be ensured.

[0026] [Rib shape] An example of the rib shape according to the embodiment will be described with reference to FIGS. 2 and 3.

[0027] The tread 2 has a tread pattern that is asymmetric with respect to the tire equator CL. The tread pattern of the pneumatic tire 1 exhibits the effects of the present invention remarkably when the tire is mounted on the vehicle such that the grounding end E1 side is located on the inner side of the vehicle and the grounding end E2 side is located on the outer side of the vehicle.

[0028] As described above, the tread 2 has a first main groove 11 and a second main groove 12 formed on the inner side in the tire axial direction, and a narrow groove 13 formed on the outer side in the tire axial direction. The first main groove 11 and the second main groove 12 are formed in the region on the contact edge E1 side of the tire equator CL, and the narrow groove 13 is formed in the region on the contact edge E2 side of the tire equator CL.

[0029] The first main groove 11, the second main groove 12, and the narrow groove 13 are formed straight along the circumferential direction of the tire without curving in the direction of the tire axis. In this case, water from the road surface can easily enter the first main groove 11, the second main groove 12, and the narrow groove 13, thereby improving drainage performance. At least one of the first main groove 11, the second main groove 12, and the narrow groove 13 may have a zigzag shape.

[0030] In this embodiment, the widths of the first main groove 11 and the second main groove 12 are formed to be greater than the width of the narrow groove 13. This improves drainage performance. The widths of the first main groove 11 and the second main groove 12 are the same. The widths of the first main groove 11 and the second main groove 12 may be, for example, 6 mm or more and 15 mm or less, and the width of the narrow groove 13 may be, for example, 5 mm or more and 14 mm or less. The width of the narrow groove 13 may be the same as the widths of the first main groove 11 and the second main groove 12, or it may be greater than the widths of the first main groove 11 and the second main groove 12. In this specification, unless otherwise specified, the width of the groove means the width on the profile surface α along the contact surface of the tread 2.

[0031] The sum of the widths of the three grooves may be, for example, 10% or more of the length W along the tire axis from contact point E1 to contact point E2 (hereinafter referred to as "contact width W"). This can improve drainage performance and achieve excellent handling stability.

[0032] The first main groove 11, the second main groove 12, and the narrow groove 13 may, for example, have the same depth. The depths of the first main groove 11, the second main groove 12, and the narrow groove 13 may be, for example, 2.5 mm or more and 6.0 mm or less. However, the depths of the first main groove 11, the second main groove 12, and the narrow groove 13 may be different.

[0033] A wear indicator (not shown) is generally provided in at least one of the first main groove 11, the second main groove 12, and the narrow groove 13. The wear indicator is a projection located at the bottom of the groove and serves as an indicator for checking the wear level of the tread rubber.

[0034] As described above, the tread 2 has a first shoulder rib 21 demarcated by the first main groove 11, a mediating rib 22 demarcated by the first main groove 11 and the second main groove 12, a center rib 23 demarcated by the second main groove 12 and the narrow groove 13, and a second shoulder rib 24 demarcated by the narrow groove 13, extending from the inside to the outside in the axial direction of the tire. The first shoulder rib 21, the mediating rib 22, the center rib 23, and the second shoulder rib 24 are formed continuously in the circumferential direction of the tire.

[0035] The groove volume ratio is largest for the first shoulder rib 21, mediate rib 22, and center rib 23, in that order. Here, the groove volume ratio is the groove volume ratio of each rib, and is the surface area of ​​the groove (excluding the first main groove 11, second main groove 12, fine groove 13, etc. adjacent to each rib, and referring to grooves such as slits formed in each rib) relative to the surface area of ​​each rib.

[0036] With the above configuration, the groove volume ratio of tread 2 increases in the axial direction of the tire from the tire equator CL towards the contact edge E1 (inside the vehicle). In other words, the groove volume ratio decreases in the axial direction of the tire from the contact edge E1 (inside the vehicle) towards the vicinity of the tire equator CL. This improves the handling performance of the pneumatic tire 1.

[0037] On the other hand, reducing the groove volume ratio of the center rib 23 and mediate rib 22 will decrease the distribution of ground pressure. This decrease in ground pressure distribution will reduce traction performance. Therefore, as will be described in detail later, the center rib 23 and mediate rib 22 are formed to protrude outward in the tire radial direction from the profile surface α of the tread 2. This suppresses the decrease in ground pressure distribution. As a result, the traction performance of the pneumatic tire 1 can be improved. In turn, it is possible to achieve both good handling performance and good traction performance.

[0038] [First shoulder rib] The first shoulder rib 21 is positioned opposite the mediating rib 22 in the tire axial direction, with the first main groove 11 in between. The groove volume ratio of the first shoulder rib 21 is greater than that of the mediating rib 22 and the center rib 23, as described above. The width of the contact surface of the first shoulder rib 21 may be, for example, 10% or more and 30% or less of the contact width W.

[0039] Multiple slits 31 are formed in the first shoulder rib 21, spaced apart in the circumferential direction of the tire, and extending in a direction intersecting the first main groove 11. In this specification, a slit means a groove with a groove width of 2.0 mm or more.

[0040] The slit 31 does not communicate with the first main groove 11 and terminates inside the first shoulder rib 21. Therefore, the area of ​​the contact surface of the first shoulder rib 21 near the first main groove 11 is continuous in the circumferential direction of the tire. This significantly reduces the impact noise when the first shoulder rib 21 makes contact with the road surface. As a result, noise performance can be improved. In other words, if the slit 31 communicates with the first main groove 11, the contact surface of the first shoulder rib 21 becomes discontinuous in the circumferential direction of the tire, increasing the impact noise when the first shoulder rib 21 makes contact with the road surface and worsening noise performance.

[0041] The inner end of the slit 31 in the tire axial direction is positioned further inward than the contact patch E1 in the tire axial direction. The outer end of the slit 31 in the tire axial direction is positioned further outward than the contact patch E1 in the tire axial direction. In other words, the slit 31 is formed to straddle the contact patch E1.

[0042] The maximum width of the slit 31 may be 2.0 mm or more and 6.0 mm or less. The depth of the slit 31 at its deepest point may be approximately the same as the depth of the first main groove 11, or it may be 60% or more and 95% or less of the depth of the first main groove 11.

[0043] [Mediative Liver] The mediate rib 22 is positioned opposite the first shoulder rib 21 in the tire axial direction, straddling the first main groove 11, and opposite the center rib 23 in the tire axial direction, straddling the second main groove 12. The width W2 of the mediate rib 22 is, for example, 12% or more and 17% or less of the contact width W.

[0044] As described above, the groove volume ratio of the mediating rib 22 is smaller than that of the first shoulder rib 21 and larger than that of the center rib 23. This improves the handling performance of the pneumatic tire 1, as described above.

[0045] The mediating rib 22 protrudes radially outward from the profile surface α of the tread 2. Here, the profile surface α is the surface along the surface of the tread 2. Furthermore, the protrusion height of the mediating rib 22 from the profile surface α of the tread 2 is in the range of 0.5 to 1.0% of the width W2 of the mediating rib 22. This makes it possible to suppress the decrease in contact pressure distribution caused by reducing the groove volume ratio of the mediating rib 22, as described above. As a result, the traction performance of the pneumatic tire 1 can be improved.

[0046] The mediating rib 22 has multiple slits 32 and 33 formed therein, spaced apart in the circumferential direction of the tire, extending in directions that intersect with the first main groove 11 and the second main groove 12.

[0047] The slit 32 is formed from the first main groove 11 toward the tire equator CL and terminates inside the mediating rib 22. Alternatively, it may be formed from the first main groove 11 toward the second main groove 12.

[0048] The axial length of the slit 32 in the tire may be, for example, 10% or more and 30% or less of the width of the mediating rib 22. The maximum width of the slit 32 may be, for example, 2.0 mm or more and 6.0 mm or less. The slit 32 is generally formed to be shallower than the first main groove 11. The depth of the slit 32 may be, for example, 60% or more and 95% or less of the depth of the first main groove 10.

[0049] The slit 32 extends along a direction inclined toward one side in the circumferential direction of the tire with respect to the tire axis. The inclination angle of the slit 32 with respect to the tire axis may be, for example, 10° or more and 50° or less. The slit 32 may have a zigzag shape.

[0050] The slit 33 is formed from the second main groove 12 toward the grounding end E2 and terminates inside the mediating rib 22. Alternatively, the slit 33 may be formed from the second main groove 12 toward the first main groove 11.

[0051] The axial length of the slit 33 in the tire may be, for example, 30% or more and 80% or less of the width of the mediating rib 22. The width of the slit 33 may be, for example, 2.0 mm or more and 6.0 mm or less. The depth of the slit 33 may be, for example, 60% or more and 95% or less of the depth of the first main groove 11.

[0052] The slit 33 includes a slit 33A that extends in a direction inclined toward one side in the circumferential direction of the tire with respect to the tire axis, and a slit 33B that bends in the middle and extends in a direction inclined toward the other side in the circumferential direction of the tire. The inclination angle of slit 33A with respect to the tire axis may be, for example, 30° or more and 70° or less. The inclination angle of slit 33B with respect to the tire axis may be, for example, 10° or more and 50° or less.

[0053] [Center Rib] The center rib 23 is formed on the tire equator CL. In this embodiment, the axial center of the center rib 23 is positioned closer to the contact end E2 than the tire equator CL. The width of the center rib 23 is, for example, 15% or more and 20% or less of the contact width W.

[0054] As described above, the groove volume ratio of the center rib 23 is smaller than that of the first shoulder rib 21 and the mediating rib 22. This improves the handling performance of the pneumatic tire 1, as described above.

[0055] The center rib 23 protrudes outward in the tire radial direction from the profile surface α of the tread 2. Furthermore, the protrusion height of the center rib 23 from the profile surface α of the tread 2 is in the range of 0.5 to 1.0% of the width W3 of the center rib 23. This makes it possible to suppress the decrease in contact pressure distribution caused by reducing the groove volume ratio of the center rib 23, as described above. As a result, the traction performance of the pneumatic tire 1 can be improved.

[0056] Slits 34 are formed in the center rib 23. The slits 34 are formed at predetermined intervals in the circumferential direction of the tire. The slits 34 are formed from the narrow groove 13 toward the tire equator CL and terminate inside the center rib 23. The slits 34 also have a length that does not reach the tire equator CL from the narrow groove 13. However, the slits 34 may have a length that reaches the tire equator CL from the narrow groove 13, or they may be formed from the narrow groove 13 toward the second main groove 12.

[0057] The axial length of the slit 34 in the tire may be, for example, 20% or more and 60% or less of the width W3 of the center rib 23. The width of the slit 34 may be, for example, 2.0 mm or more and 6.0 mm or less. The depth of the slit 34 may be, for example, 60% or more and 95% or less of the depth of the second main groove 12.

[0058] The slit 34 extends along a direction inclined toward one side in the circumferential direction of the tire with respect to the tire axis. The inclination angle of the slit 34 with respect to the tire axis may be, for example, 10° or more and 50° or less. The slit 34 may have a zigzag shape.

[0059] [Second shoulder rib] The second shoulder rib 24 is positioned opposite the center rib 23 in the tire axial direction, with the narrow groove 13 in between. The width W4 of the contact surface of the second shoulder rib 24 may be, for example, 20% or more and 50% or less of the contact width W.

[0060] Multiple slits 35 are formed on the inner side of the second shoulder rib 24 in the direction of the tire axis, spaced apart in the tire circumferential direction, and extending in a direction intersecting the narrow groove 13. Additionally, multiple slits 36 are formed on the outer side of the second shoulder rib 24 in the direction of the tire axis, spaced apart in the tire circumferential direction, and extending in a direction intersecting the narrow groove 13.

[0061] The slits 35 are formed at predetermined intervals in the circumferential direction of the tire. The slits 35 are formed from the narrow groove 13 toward the contact end E2 and terminate inside the second shoulder rib 24. The slits 35 also have a length that does not reach the contact end E2 from the narrow groove 13.

[0062] The axial length of the slit 35 in the tire may be, for example, 10% or more and 40% or less of the width W4 of the second shoulder rib 24. The width of the slit 35 may be, for example, 2.0 mm or more and 6.0 mm or less. The depth of the slit 35 may be, for example, 60% or more and 95% or less of the depth of the second main groove 12.

[0063] The slit 35 extends along a direction inclined toward one side in the circumferential direction of the tire with respect to the tire axis. The inclination angle of the slit 35 with respect to the tire axis may be, for example, 10° or more and 50° or less. The slit 35 may have a zigzag shape.

[0064] The slit 36 ​​does not communicate with the narrow groove 13 and terminates inside the second shoulder rib 24. Therefore, the area of ​​the contact surface of the second shoulder rib 24 near the narrow groove 13 is continuous in the circumferential direction of the tire. This significantly reduces the impact noise when the second shoulder rib 24 contacts the road surface. As a result, noise performance can be improved. In other words, if the slit 36 ​​communicates with the narrow groove 13, the contact surface of the second shoulder rib 24 becomes discontinuous in the circumferential direction of the tire, increasing the impact noise when the second shoulder rib 24 contacts the road surface and worsening noise performance.

[0065] The inner end of the slit 36 ​​in the tire axial direction is positioned further inward than the contact patch E2 in the tire axial direction. The outer end of the slit 36 ​​in the tire axial direction is positioned further outward than the contact patch E2 in the tire axial direction. In other words, the slit 36 ​​is formed to straddle the contact patch E2.

[0066] The maximum width of the slit 36 ​​may be 2.0 mm or more and 6.0 mm or less. The depth of the slit 36 ​​at its deepest point may be approximately the same as the depth of the narrow groove 13, or it may be 60% or more and 95% or less of the depth of the second main groove 12.

[0067] [summary] This disclosure is further illustrated by the following embodiments. Configuration 1: A pneumatic tire having a tread and a specified mounting direction for the vehicle, The tread has a first main groove and a second main groove extending along the tire circumferential direction on the inner side in the tire axial direction, a narrow groove extending along the tire circumferential direction on the outer side in the tire axial direction, a shoulder rib partitioned by the first main groove, a median rib partitioned by the first main groove and the second main groove, and a center rib partitioned by the second main groove and the narrow groove, extending from the inner side to the outer side in the tire axial direction. The shoulder rib, mediate rib, and center rib have a larger groove volume ratio in the order of shoulder rib, mediate rib, and center rib. The center rib and the mediating rib protrude outward in the tire radial direction from the profile surface of the tread. Pneumatic tires. Configuration 2: The pneumatic tire described in Configuration 1, The projection height of the center rib from the tread profile surface is in the range of 0.5 to 1.0% of the width of the center rib, and the projection height of the mediating rib from the tread profile surface is in the range of 0.5 to 1.0% of the width of the mediating rib. Pneumatic tires. Configuration 3: The pneumatic tire described in Configuration 1, The ratio of the width of the center rib to the width of the tread is 15% to 20%. Pneumatic tires. Configuration 4: The pneumatic tire described in Configuration 1, The ratio of the width of the mediating rib to the width of the tread is 12% to 17%. Pneumatic tires.

[0068] It should be noted that the present invention is not limited to the embodiments and their modifications described above, and various changes and improvements are possible within the scope of the claims of this application. [Explanation of Symbols]

[0069] 1 Pneumatic tire, 2 Tread, 3 Sidewall, 4 Bead, 4A Bead core, 4B Bead filler, 5 Carcass, 6 Inner liner, 7 Belt, 7A, 7B Belt ply, 8 Cap ply, 11 First main groove, 12 Second main groove, 13 Minor groove, 21 First shoulder rib, 22 Mediate rib, 23 Center rib, 24 First shoulder rib, 31 Slit, 32 Slit, 33 Slit, 33A Slit, 33B Slit, 34 Slit, 35 Slit, 36 Slit, CL Tire equator, E1 Contact edge, E2 Contact edge, W Contact width, W1 Width of first shoulder rib, W2 Width of mediate rib, W3 Width of center rib, W4 Width of second shoulder rib, α Profile surface

Claims

1. A pneumatic tire having a tread and a specified mounting direction for the vehicle, The tread has a first main groove and a second main groove extending along the tire circumferential direction on the inner side in the tire axial direction, a narrow groove extending along the tire circumferential direction on the outer side in the tire axial direction, a shoulder rib partitioned by the first main groove, a median rib partitioned by the first main groove and the second main groove, and a center rib partitioned by the second main groove and the narrow groove, extending from the inner side to the outer side in the tire axial direction. The shoulder rib, mediate rib, and center rib have a larger groove volume ratio in the order of shoulder rib, mediate rib, and center rib. The center rib and the mediating rib protrude outward in the tire radial direction from the profile surface of the tread. Pneumatic tires.

2. A pneumatic tire according to claim 1, The projection height of the center rib from the tread profile surface is in the range of 0.5 to 1.0% of the width of the center rib, and the projection height of the mediating rib from the tread profile surface is in the range of 0.5 to 1.0% of the width of the mediating rib. Pneumatic tires.

3. A pneumatic tire according to claim 1, The ratio of the width of the center rib to the width of the tread is 15% to 20%. Pneumatic tires.

4. A pneumatic tire according to claim 1, The ratio of the width of the mediating rib to the width of the tread is 12% to 17%. Pneumatic tires.

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