pneumatic tires

Abstract

In pneumatic tires, the performance and braking performance are improved in a configuration in which sipes passing through the middle of the tire's circumferential direction are formed on the tread surface of the tread blocks. [Solution] The pneumatic tire includes a tread. The tread has a plurality of blocks 33 that are separated in the circumferential direction of the tire by a plurality of grooves. At least some of the blocks 33 have sipes 40 that pass through the middle of the circumferential direction of the tire and have a maximum depth shallower than the maximum depth of the plurality of grooves. The tread surfaces 43, 44 of the two regions 41, 42 separated by the sipes 40 of at least some of the blocks 33 are protruding surfaces that project outward in the radial direction of the tire, and the protrusion is greater in the middle of the circumferential direction of the tire than at both ends in the circumferential direction of the tire.

Description

Technical Field

[0001] The present invention relates to a pneumatic tire.

Background Art

[0002] Patent Document 1 describes that in a pneumatic tire, on both sides in the tire axial direction across the tire equator of the tread, an outer center land portion on the outer side of the vehicle and an inner center land portion on the inner side of the vehicle separated in the tire axial direction are provided. In a meridian cross section including the tire rotation axis, each center land portion has a tread surface convex in the radially outer direction of the tire, and a plurality of sipes are provided on the tread surface of each center land portion.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the tread of a pneumatic tire, there may be provided a plurality of blocks partitioned by a plurality of grooves and separated in the tire circumferential direction. In this case, in order to make it easier to follow the unevenness of the road surface or to improve the grounding property when the block falls down and improve the motion performance, a protruding surface that protrudes radially outward of the tire and has an arc shape in a cross section perpendicular to the tire axial direction is provided on the entire tread surface of each block. However, when forming a sipe that passes through the middle in the tire circumferential direction and crosses the protruding surface on the tread surface of the block, the grounding property of the block during braking may deteriorate. Thus, there is room for improvement in terms of enhancing the braking performance.

[0005] An object of the present invention is to improve the motion performance and braking performance in a configuration in which a sipe passing through the middle in the tire circumferential direction is formed on the tread surface of a block in a pneumatic tire.

Means for Solving the Problems

[0006] The pneumatic tire according to the present invention is a pneumatic tire. [Effects of the Invention]

[0007] According to the pneumatic tire of the present invention, in a configuration in which sipes passing through the middle of the tire's circumferential direction are formed on the tread surface of the blocks, the contact ability of the tread surface in each region separated by the sipes of the blocks can be improved, thereby improving both handling performance and braking performance. [Brief explanation of the drawing]

[0008] [Figure 1] This is a view from below of a pneumatic tire in one embodiment. [Figure 2] This is an enlarged view of section A in Figure 1. [Figure 3] Figure 2 is a cross-sectional view of BB. [Figure 4] This is a cross-sectional view taken from Figure 3 and enlarged to show one block. [Figure 5] Figure 4 is a perspective view of the block shown from the outside in the tire radial direction. [Figure 6] Figure 5 shows the block as viewed from the outside in the tire radial direction. [Figure 7] In the comparative example of a pneumatic tire, (a) is a schematic diagram showing the state of contact with the ground of one block of the tire when the tire is stationary, and (b) is a schematic diagram showing the state in which the block collapses when the vehicle is braking. [Figure 8A] This is a schematic diagram corresponding to Figure 7(b) in the pneumatic tire of the embodiment. [Figure 8B] This is an enlarged view of section C in Figure 8A. [Figure 9] This figure corresponds to Figure 5, showing an alternative embodiment of a pneumatic tire. [Figure 10] This is a view of one side of a pneumatic tire, separated by a block sipe, as seen from the radially outer side of the tire. [Figure 11]This figure corresponds to Figure 3, showing an alternative embodiment of a pneumatic tire. [Modes for carrying out the invention]

[0009] Hereinafter, embodiments of the pneumatic tire according to the present invention will be described in detail with reference to the drawings. The embodiments described below are merely examples, and the present invention is not limited to these embodiments. Furthermore, forms obtained by selectively combining each component of the embodiments described below are included in the present invention.

[0010] Figure 1 is a view from below of a pneumatic tire 1, which is an example of an embodiment. As shown in Figure 1, the pneumatic tire 1 includes a tread 10, which is the part that contacts the road surface. The tread 10 has a plurality of main grooves 20, 21 that extend from the equator CL side toward the contact edges E1, E2 side, with a larger inclination angle with respect to the tire axis direction (left-right direction in Figure 1) on the equator CL side than on the contact edges E1, E2 side; a plurality of sub-grooves 22, 23 that connect adjacent main grooves 20, 21 in the tire rotation direction in the tire circumferential direction or in a direction inclined with respect to the tire circumferential direction; and a plurality of blocks 28 that are partitioned by the plurality of main grooves 20, 21 and the plurality of sub-grooves 22 and separated in both the tire circumferential direction and the tire axis direction. Hereinafter, the pneumatic tire 1 will be referred to as tire 1.

[0011] Multiple blocks 28 are formed along main grooves 20, 21, and include blocks 30 on the vehicle's outer side with respect to the equator CL, and blocks 31 on the vehicle's inner side with respect to the equator CL. The main grooves 20 and blocks 30 extend from the equator CL side to the ground end E1 side, while the main grooves 21 and blocks 31 extend from the equator CL side to the ground end E2 side.

[0012] The equator CL means a line along the circumferential direction of the tire passing through the center in the tire axial direction of the tread 10 (at a position equidistant from the grounding ends E1, E2). In this specification, the grounding ends E1, E2 are defined as the two ends in the tire axial direction of the region that contacts the flat road surface when a predetermined load is applied in a state where the unused pneumatic tire 1 is mounted on a standard rim and filled with air to reach the standard internal pressure. In the case of a passenger car tire, the predetermined load is a load corresponding to 88% of the standard load.

[0013] Here, the "standard rim" is a rim defined by the tire specifications. In the case of JATMA, it is the "standard rim"; in the case of TRA and ETRTO, it is the "Measuring Rim". The "standard internal pressure" is the "maximum air pressure" in the case of JATMA, the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and the "INFLATION PRESSURE" in the case of ETRTO. The standard internal pressure is usually 180 kPa for passenger car tires, but 220 kPa for tires marked as Extra Load or Reinforced. The "standard load" is the "maximum load capacity" in the case of JATMA, the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and the "LOAD CAPACITY" in the case of ETRTO. In the case of a racing kart tire, the standard load is 392 N.

[0014] The tire 1 is a directional tire with a specified main rotation direction. In FIG. 1, an arrow α indicating the main rotation direction of the tire is illustrated. In this specification, the "main rotation direction" of the tire means the rotation direction when the vehicle on which the tire is mounted moves forward. Since FIG. 1 is a view of the tire 1 seen from below, the tire main rotation direction α and the vehicle traveling direction β are in opposite directions. The pneumatic tire 1 preferably has a display for indicating the mounting direction with respect to the vehicle. On the side surface of the pneumatic tire 1, for example, at least one of characters and an arrow indicating the main rotation direction are provided.

[0015] The tread 10 has a tread pattern in which the blocks 30, 31 are arranged in a staggered manner along the tire circumferential direction. Most of the blocks 30, 31 are arranged separately on the left and right of the tread 10 with the equator CL in between.

[0016] The block 30 is formed along the main groove 20 and is arranged alternately with the main groove 20 in the tire circumferential direction. The block 30 includes a center block 32 located on the equator CL side, a shoulder block 34 located on the ground contact end E1 side, and a mediate block 33 sandwiched between the center block 32 and the shoulder block 34. Between the center block 32 and the mediate block 33, and between the mediate block 33 and the shoulder block 34, sub-grooves 22 that connect two main grooves 20 in the tire circumferential direction or in a direction inclined with respect to the tire circumferential direction are formed. The sub-grooves 22 divide the block 30 into three blocks.

[0017] The block 31 is formed along the main groove 21 and is arranged alternately with the main groove 21 in the tire circumferential direction. The block 31 includes a center block 35 located on the equator CL side, a shoulder block 37 located on the ground contact end E2 side, and a mediate block 36 sandwiched between the center block 35 and the shoulder block 37. Between the center block 35 and the mediate block 36, and between the mediate block 36 and the shoulder block 37, sub-grooves 23 that connect two main grooves 21 in the tire circumferential direction or in a direction inclined with respect to the tire circumferential direction are formed. The sub-grooves 23 divide the block 31 into three blocks.

[0018] As described above, the plurality of blocks 30, 31 are separated in both the tire circumferential direction and the tire axial direction by being partitioned by the plurality of main grooves 20, 21 and the plurality of sub-grooves 22, 23. Each of the main grooves 20, 21 corresponds to a first groove. Each of the sub-grooves 22, 23 corresponds to a second groove.

[0019] The tire 1 comprises a pair of sidewalls that bulge outward in the tire axial direction and a pair of beads. The beads are the portion that is fixed to the rim of the wheel and have a bead core and a bead filler. The sidewalls and beads are formed in an annular shape along the tire circumferential direction and form the side surface of the pneumatic tire 1. The sidewalls extend radially from both ends of the tread 10 in the tire axial direction.

[0020] The tread pattern of tire 1 will be described in detail below. The main grooves 20 are formed at arbitrary intervals in the circumferential direction of the tire. Similarly, the main grooves 21 are formed at arbitrary intervals in the circumferential direction of the tire. The tread 10 has a tread pattern in which most of the main grooves 20 and blocks 30 are located on the side of the equator CL towards the contact edge E1 (the left side of the tread 10), and most of the main grooves 21 and blocks 31 are located on the side of the equator CL towards the contact edge E2 (the right side of the tread 10). Blocks are portions that protrude outward in the radial direction of the tire.

[0021] In the tread 10, center blocks 32 and 35 are arranged alternately along the tire's circumferential direction, centered in the axial center of the tire. Furthermore, center blocks 32 and 35 are arranged in a staggered pattern along the equator CL.

[0022] The tread pattern of this embodiment is a pattern in which, in a plan view, blocks 30 and 31 are arranged symmetrically on the left and right sides, offset by a predetermined pitch in the tire circumferential direction with respect to the equator CL. The shape of block 30 is the same as the shape of block 31 when it is inverted with respect to the equator CL (the same applies to the main grooves 20 and 21). If block 31, which has been inverted at the equator CL, is slid in the tire circumferential direction, it will coincide with block 30. The tread pattern of this embodiment has good left-right balance and is effective in improving handling stability.

[0023] The main groove 20 and block 30 have a plan view shape that is curved so as to be convex toward the rear in the main rotation direction α of the tire. Similarly, the main groove 21 and block 31 also have a plan view shape that is curved so as to be convex toward the rear in the direction of tire rotation. The main grooves 20, 21 and blocks 30, 31 are inclined with respect to the tire axis direction so that they are gradually positioned toward the rear in the main rotation direction α of the tire, starting from the axial center side of the pneumatic tire 1 toward both sides of the axis.

[0024] As described above, the main grooves 20 and 21 have a greater angle of inclination with respect to the tire axis on the equator CL side than on the contact end E1 and E2 side. The angle of inclination of the main grooves 20 and 21 is determined by its relationship to a straight line connecting the centers of the main grooves 20 and 21. In other words, the main grooves 20 and 21 gradually become more aligned with the tire axis from the equator CL side toward the contact end E1 and E2, and the inclination with respect to the tire axis becomes gentler. The angle of inclination of the main grooves 20 and 21 with respect to the tire axis is, for example, 20° to 50° or 25° to 40° on the equator CL side.

[0025] The main groove 20 connects to the main groove 21 near the equator CL. The main groove 20 extends from the intersection with the main groove 21 toward the contact end E1 and extends beyond the contact end E1 to the left annular side rib (not shown). The main groove 21 extends from the intersection with the main groove 20 near the equator CL toward the contact end E2 and extends beyond the contact end E2 to the right annular side rib (not shown). Each side rib is formed at its respective end in the tire axial direction between the contact ends E1, E2 of the tread 10 and the part of the sidewall 11 that protrudes most outward in the tire axial direction. The side ribs protrude outward in the tire axial direction and are formed in an annular shape along the tire circumferential direction. The side ribs may be omitted.

[0026] The width of the main grooves 20 and 21 may be constant along their entire length, but in this embodiment, it gradually increases from the equator CL side toward the ground contact ends E1 and E2. The width of the main grooves 20 and 21 may be maximum, for example, at or near the ground contact ends E1 and E2, or at or near the intersection with the secondary grooves 22 and 23. In this case, drainage performance is improved, and the snow column shear force that grips and compacts the snow is also improved, resulting in good snow performance. The main grooves 20 and 21 are formed to the same depth, for example.

[0027] The sub-grooves 22 and 23 are narrower in width (maximum width) than the main grooves 20 and 21. The sub-groove 22 extends in the circumferential direction of the tire or in a direction inclined with respect to the circumferential direction of the tire, dividing the block 30 and connecting adjacent main grooves 20. In the example shown in Figure 1, the sub-groove 22 is inclined with respect to the circumferential direction of the tire so as it moves gradually away from the contact edge E1 from the front to the rear in the main rotation direction α of the tire. Similarly, the sub-groove 23 divides the block 31 and connects adjacent main grooves 21, and is inclined with respect to the circumferential direction of the tire so as it moves gradually away from the contact edge E2 from the front to the rear in the main rotation direction α of the tire. The sub-grooves 22 and 23 may be shallower or deeper than the main grooves 20 and 21, but it is preferable that they be formed to the same depth as the main grooves 20 and 21. In this case, compared to when the groove depth changes, the water flow for drainage is not disturbed, thus improving drainage performance.

[0028] Each block 32, 33, 34, 35, 36, 37 may have a slit formed along the main grooves 20, 21. The slit may terminate within each block 32, 33, 34, 35, 36, 37 without dividing the block. This increases the edge area and improves the snow performance of tire 1. The slit may also penetrate each block 30, 31. In this case, it is possible to improve the snow performance and drainage performance of tire 1.

[0029] Furthermore, within the tread surface of each block 32, 33, 34, 35, 36, 37, a sipe 40 is formed that passes through the middle of the tire's circumferential direction and has a maximum depth shallower than the maximum depth of the multiple main grooves 20, 21 and sub-grooves 22, 23. The maximum depth of each sipe 40 is, for example, 40% to 95% of the maximum depth of the main grooves 20, 21. The sipes 40 formed on the center blocks 32, 35 and mediate blocks 33, 36 are aligned along the longitudinal direction of each block so as to reach two adjacent sub-grooves 22, 23 at both ends of the tire axial direction of the respective block. The sipes 40 formed on the shoulder blocks 34, 37 are aligned along the longitudinal direction of the shoulder blocks 34, 37 so that one end reaches an adjacent sub-groove 22, 23 on the inner side of the shoulder block 34, 37 in the tire axial direction, while the other end terminates within the shoulder block 34, 37.

[0030] Each block's sipe 40 divides the tire circumferentially into two regions, and the tread surface of each region is a protruding surface that extends outward in the radial direction of the tire, with the protrusion being larger in the middle of the tire circumferential direction than at both ends.

[0031] The tread surfaces of the blocks will be explained in detail below using Figures 2 to 6. In the following, the tread surface of the mediate block 33 of block 30 will be mainly explained, but the same applies to the mediate block 36 of block 31, the center blocks 32 and 35 of each block 30 and 31, and the shoulder blocks 34 and 37, which are divided in the circumferential direction of the tire by the sipes 40.

[0032] As shown in Figure 2, each mediate block 33 is separated from the other blocks 32, 33, and 34 by two main grooves 20 spaced apart in the circumferential direction of the tire, and two spaced secondary grooves 22 that intersect each of the main grooves 20. The distance between the two secondary grooves 22 is longer than the distance between the two main grooves 20.

[0033] Furthermore, as shown in Figures 3 to 6, the tread surfaces 43 and 44 of the two regions 41 and 42 separated in the tire circumferential direction by the sipes 40 of each mediate block 33 are protruding surfaces that project outward in the tire radial direction, and the protrusion is larger in the middle of the tire circumferential direction than at both ends.

[0034] As shown in Figure 4, the tread surfaces 43 and 44 of each region 41 and 42 protrude radially outward from the profile surface Sp of the tread 10. The profile surface Sp is a hypothetical surface along the tread near the contact ends E1 and E2 of the shoulder blocks 34 and 37 on both sides of the tire axial direction, assuming that the main grooves 20 and 21 and the secondary grooves 22 and 23 do not exist. It is a hypothetical surface formed by the continuous profile line, which is a hypothetical contour in the tire meridian cross-section where multiple arcs of curvature are smoothly continuous, extending around the entire circumference of the tire in the circumferential direction. The profile surface Sp does not include the protruding surfaces of the tread surfaces of each block 32, 33, 34, 35, 36, and 37 that protrude radially outward from the tread.

[0035] As shown in Figures 2, 5, and 6, the tread surfaces 43 and 44 of the two regions 41 and 42 are mountain-shaped, with vertices Tm1 and Tm2 located between the main groove 20 and the sipe 40, and between the two secondary grooves 22. As shown in Figure 6, vertices Tm1 and Tm2 are located in the center of the tread surfaces 43 and 44 when viewed from the outside in the radial direction of the tire. Vertex Tm1 is located closer to the equator CL than vertex Tm2. Each tread surface 43 and 44 has single curved surfaces S1, S2, S3, and S4 extending from each of the four edges that are in contact with the main groove 20, the sipe 40, and each secondary groove 22, respectively, which intersect at vertices Tm1 and Tm2.

[0036] As shown in Figures 4 and 6, when the tread 10 is cut in a cross section perpendicular to the tire axis direction so as to pass through the apex Tm1 of one of the tread surfaces 43, 44, the circumferential position of the apex Tm1 is located in the center between the main groove 20 and the sipe 40 adjacent to the mediate block 33. In other words, the circumferential length a1 from the main groove 20 to the apex Tm1 on one side of the tire's circumferential direction (left side in Figure 4, upper side in Figure 6) is approximately equal to the circumferential length a2 from the sipe 40 to the apex Tm1.

[0037] As shown in Figure 6, when the tread 10 is cut in a cross section perpendicular to the tire axis direction so as to pass through the apex Tm2 of the other tread surface 44 of each tread surface 43, 44, the circumferential position of the apex Tm2 is located in the center between the main groove 20 and the sipe 40 adjacent to the mediate block 33. In other words, the circumferential length b2 from the main groove 20 to the apex Tm2 on the other side of the tire's circumferential direction (lower side in Figure 6) is approximately equal to the circumferential length b1 from the sipe 40 to the apex Tm2.

[0038] In the above-described pneumatic tire 1, a sipe 40 is formed on the tread surface of each block, such as the mediate block 33, passing through the middle of the tire's circumferential direction. As a result, the tread surfaces 43 and 44 of each region 41 and 42, separated by the sipe 40 on the tread surface of each block, protrude outward in the tire's radial direction. This makes it easier to follow the unevenness of the road surface and improves contact with the road when the block is tilted, thereby improving handling performance. Furthermore, despite the sipe 40 being formed on the tread surfaces 43 and 44 of the blocks passing through the middle of the tire's circumferential direction, the tread surfaces 43 and 44 of each region 41 and 42 are protruding in a way that is larger in the middle of the tire's circumferential direction than at both ends. This improves the contact ability of the tread surfaces 43 and 44 of each region 41 and 42, thereby improving braking performance. Thus, both handling performance and braking performance can be improved.

[0039] To explain this effect, we will first describe the tilting state of the blocks in the comparative example pneumatic tire. Figure 7 shows the comparative example pneumatic tire 1a, where (a) is a schematic diagram showing the contact state of one block of the tire, the mediate block 33a, when the tire is stopped, and (b) is a schematic diagram showing the state in which the mediate block 33a tilts when the vehicle is braking. In Figure 7, the tilting of the blocks is represented by the tilting of the mediate block 33a.

[0040] As shown in Figure 7(a), in the comparative example pneumatic tire 1a, the entire tread surface 45 of the mediate block 33a protrudes outward in the radial direction of the tire and has an arc-shaped projection in a cross section perpendicular to the tire axis. Furthermore, a sipe 40 is formed on the tread surface 45 of the mediate block 33a, passing through the middle of the tire circumferential direction and crossing the projection. In this case, each of the two regions of the tread surface 45 separated by the sipe 40 of the mediate block 33a has a projection that protrudes the most at the end on the sipe 40 side in the tire circumferential direction. In this state, the contact portion of the mediate block 33a with the road surface 80 makes most contact near the center of the tire circumferential direction, with the sipe 40 in between.

[0041] On the other hand, as shown in Figure 7(b), in the comparative example, when the vehicle is braked, the area of ​​the mediate block 33a that contacts the road surface 80 tilts downward so as to face the rear of the vehicle's direction of travel β. As a result, in the area of ​​the mediate block 33a that is in front of the direction of travel β and behind the main rotation direction α of the tire, the contact area of ​​the tread surface 45 tends to move forward of the direction of travel β, and the contact area tends to increase.

[0042] On the other hand, in the comparative example, near the contact point of the mediate block 33a, in the region on the front side of the main tire rotation direction α, which is on the rear side of the direction of travel β, the tread surface 45 is a curved surface with a large radius of curvature in its cross-section, forming an arc shape. Except for the vicinity of the sipe 40, which is the front end of the direction of travel β, the contact area tends to be small as it is far away from the road surface 80. As a result, the comparative example has room for improvement in terms of improving braking performance.

[0043] Figure 8A is a schematic diagram of the pneumatic tire according to the embodiment, corresponding to Figure 7(b). Figure 8B is an enlarged view of section C in Figure 8A. According to the embodiment shown in Figure 8A, the tread surfaces 43 and 44 of the two regions 41 and 42 separated by the sipe 40 of the mediate block 33 are protruding surfaces that protrude more significantly in the middle of the tire circumferential direction than at both ends in the tire circumferential direction. As a result, in the region 41 on the rear side of the main tire rotation direction α, which is the front side of the direction of travel β, the tread surface 44 approaches a flat state more easily than in the comparative example shown in Figure 7(b), so that the contact area of ​​the tread surface 43 can be made larger than in the comparative example.

[0044] Furthermore, near the contact point of the mediate block 33, in the region 42 on the front side of the main tire rotation direction α, which is behind the direction of travel β, a curved surface with a small radius of curvature and a circular arc shape is formed on the sipe 40 side of the tread surface 44, which is a protruding surface. As a result, the tire makes greater contact with the road surface behind the direction of travel β from near the sipe 40, and the contact area can be increased compared to the comparative example shown in Figure 7(b).

[0045] Furthermore, as shown in Figure 8B, in this embodiment, unlike the comparative example shown in Figure 7, near the contact area of ​​the mediate block 33, curved surfaces with a small radius of curvature and a substantially arc-shaped cross-section are easily formed on both ends of the tread surfaces 44 and 43 in the front and rear regions 42 and 41, respectively, in the direction of the main rotation α of the tire. As a result, each tread surface 44 and 43 can be easily deformed flexibly in accordance with the irregularities of the road surface 80, thereby increasing the contact area with the road surface 80. As a result, braking performance can be improved in this embodiment.

[0046] Furthermore, in this embodiment, each block, such as the mediate block 33 having tread surfaces 43 and 44, is separated from other blocks by two main grooves 20 and 21 and two sub-grooves 22 and 23. In addition, at least one of the tread surfaces 43 and 44 of the two regions 41 and 42 of each block is shaped like a mountain, with peaks Tm1 and Tm2 between the main grooves 20 and 21 and the sipe 40, and between the two sub-grooves 22 and 23. This makes it easier for the tread surfaces 43 and 44 of each region to deform to follow the road surface when a lateral force is applied to the tire from the road surface during cornering. This improves cornering performance.

[0047] Furthermore, the distance between the two sub-grooves 22 and 23 that define the axial ends of each block having tread surfaces 43 and 44 is longer than the distance between the two main grooves 20 and 21 in the circumferential direction of the tire. In this case, the tread surfaces 43 and 44 of the two regions 41 and 42 of each block are protruding surfaces with multiple inclined surfaces of different inclination angles located on different sides. This makes it easier for the tire to withstand lateral forces from the road surface more smoothly during cornering, improving cornering stability and enhancing braking performance.

[0048] Figure 9 is a diagram corresponding to Figure 5, showing a pneumatic tire in another embodiment. In this example, the tread surfaces 43a and 44a of the two regions 41a and 42a separated by the sipes 40 of each block, such as the mediate block 33b, are convex portions having ridges Tma and Tmb in directions along the main groove 20 and the sipes 40, respectively. The ridges Tma and Tmb are located at the maximum height position of the tread surfaces 43a and 44a. When the tread 10 is cut in a cross section perpendicular to the tire axis direction so as to pass through the ridges Tma and Tmb of each tread surface 43a and 44a, the circumferential position of the ridges Tma and Tmb is located in the center between the main groove 20 and the sipes 40 adjacent to the mediate block 33.

[0049] According to the configuration in this example, a larger contact area can be secured for the front and rear loads during straight-line driving compared to the configurations in Figures 1 to 6, thus enabling more stable and higher braking performance. In this example, the other configurations and operations are the same as those in Figures 1 to 6.

[0050] Figure 10 is a view of one region 41b of a block divided by a sipe, as seen from the radially outer side of the tire, in a pneumatic tire of another embodiment. In the configuration of this example, in each block such as the mediate block 33c, the tread surface 43b of each region 41b divided by the sipe 40 is formed when two single curved surfaces S1a, S2a extending from two regions divided in the longitudinal direction of the main groove 20, and three single curved surfaces S3a, S4a, S5a extending from three regions divided in the longitudinal direction of the sipe 40 intersect at vertex Tm3. Each of the two curved surfaces S3a and S5a is in contact with the sub-groove 22 on the side where the curved surfaces S3a and S5a are located. In this case, the curved surface S4a and parts of the curved surfaces S3a and S5a are arranged on the front side of region 41b in the main tire rotation direction α, and the curved surfaces S1a and S2a and the remaining parts of the curved surfaces S3a and S5a are arranged on the rear side of region 41b in the main tire rotation direction α. ​​Figure 10 shows only one side of region 41b divided by the block's sipes 40, but the tread surface of the other side of region (not shown) also has multiple curved surfaces, similar to the tread surface of region 41b, and the relationship between these multiple curved surfaces and the main tire rotation direction is the same as that of region 41b.

[0051] In the configuration of Figure 10, the curved surfaces S1a and S2a can also be the same single curved surface. Parts or all of each curved surface S1a, S2a, S3a, S4a, and S5a can also be planes. In this example, the other configurations and functions are the same as those in Figures 1 to 6.

[0052] Figure 11 is a diagram corresponding to Figure 3, showing a pneumatic tire of another embodiment. In this example, in the tread 10a, the sipes 40a in each block, such as the mediate block 33, are inclined with respect to the tire's radial direction. More specifically, each sipe 40a is inclined toward the inside in the tire's radial direction, towards the front of the tire's main rotation direction α. ​​In this example, the other configurations and functions are the same as those in Figures 1 to 6. [Explanation of symbols]

[0053] 1,1a pneumatic tire (tire), 10,10a tread, 11 sidewall, 20,21 main groove, 22,23,22a secondary groove, 28 ground, 30,31 blocks, 32,35 center block, 33,33a,36 mediate block, 34,37 shoulder block, 40,40a sipe, 41,42,41a,42a,41b,41c,42c area, 43,44,45,43a,44a,43b,43c,44c tread, 51 first end, 52 second end, 53,54 tangent, 80 road surface, CL equator, E1,E2 contact end.

Claims

1. A pneumatic tire having a tread, The tread includes a plurality of blocks separated in the circumferential direction of the tire by a plurality of grooves, At least some of the aforementioned blocks have sipes that pass through the middle of the tire circumferential direction and have a maximum depth shallower than the maximum depth of the plurality of grooves. A pneumatic tire in which the tread surfaces of at least some of the blocks, each of the two regions separated by the sipes, are protruding surfaces that project outward in the radial direction of the tire, and which protrude more significantly in the middle of the tire circumferential direction than at both ends in the circumferential direction of the tire.

2. The block having the tread surface in the two regions is separated from other blocks by two first grooves spaced apart in the circumferential direction of the tire and two spaced second grooves intersecting each of the first grooves. The tread surface of at least one of the two regions is mountain-shaped, having a peak between the first groove and the sipe, and between the two second grooves. The pneumatic tire according to claim 1.

3. The distance between the two second grooves is longer than the distance between the two first grooves. The pneumatic tire according to claim 2.

4. The tread surface of at least one of the two regions is a protruding surface having a plurality of inclined surfaces with different inclination angles arranged on different sides. A pneumatic tire according to claim 1 or claim 2.

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