pneumatic tires

Abstract

In a pneumatic tire, the tread is configured to have multiple blocks separated in the circumferential direction of the tire, thereby improving both handling performance and braking performance. [Solution] The pneumatic tire includes a tread, and the main rotation direction α of the tire is specified. The tread includes a plurality of blocks 33 that are separated in the circumferential direction of the tire by a plurality of grooves. The tread surface 43 of at least some of the blocks 33 is a protruding surface that projects outward in the radial direction of the tire. At least a portion or the apex of the ridge line Tm of the tread surface 43 is offset to the front side in the main rotation direction α of the tire with respect to the circumferential center C1 of the block 33.

Description

Technical Field

[0001] The present invention relates to pneumatic tires.

Background Art

[0002] In the tread of a pneumatic tire, there may be provided a plurality of blocks partitioned by a plurality of grooves. In this case, in order to make it easier to follow the unevenness of the road surface and to improve the grounding performance when the block falls over and thereby improve the driving performance, it is conceivable to provide a protruding surface that protrudes radially outward of the tire diameter on the tread surface of each block.

[0003] Patent Document 1 describes that in a pneumatic tire, each of a plurality of lands extending in the tire circumferential direction of the tread and separated in the tire axial direction has a protruding portion that protrudes substantially arcuately radially outward of the tire diameter from the profile line in the tire meridian cross-section, and the apex of the protruding portion is arranged outside the vehicle width direction from the center in the tire axial direction of the land.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the tread of a pneumatic tire, there are cases where multiple blocks are provided, separated by multiple grooves in the circumferential direction of the tire. In this case, in order to improve handling performance by making it easier to follow the unevenness of the road surface and improving contact when the blocks are tilted, it is conceivable to provide a projection surface with a circular arc cross-section that protrudes outward in the radial direction of the tire on the tread surface of each block. Furthermore, in this configuration, it is also conceivable to position the apex of the projection surface outward in the vehicle width direction, as described in Patent Document 1. However, this configuration has room for improvement in terms of improving braking performance. For this reason, it is desirable to improve both handling performance and braking performance in a configuration in which multiple blocks are provided in the tread, separated in the circumferential direction of the tire. [Means for solving the problem]

[0006] The pneumatic tire according to the present invention is a pneumatic tire having a tread, wherein the main direction of rotation of the tire is specified, and the tread includes a plurality of blocks separated in the circumferential direction of the tire by a plurality of grooves, the tread surface of at least some of the blocks is a projection that protrudes outward in the radial direction of the tire, and at least a portion of the ridge or apex of the tread surface is offset to the front side in the main direction of rotation of the tire with respect to the center of the block in the circumferential direction of the tire. [Effects of the Invention]

[0007] According to the pneumatic tire of the present invention, in a configuration in which a plurality of blocks separated in the circumferential direction of the tire are provided on the tread, the handling performance and braking performance can be improved. [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 cross-sectional 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] This figure corresponds to Figure 6 in the first comparative example, a pneumatic tire. [Figure 8] In the first 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 9] This figure corresponds to the enlarged view of the area near the contact point in Figure 8(b) of the pneumatic tire according to the embodiment. [Figure 10] This figure shows the results of a test conducted to determine the degree of deviation of the ridge line of the protruding surface from the center of the tire in the circumferential direction in the embodiment. It shows the results of measuring the portion of the contact area of ​​the pneumatic tire of the second comparative example where the contact pressure was above a predetermined value, at the initial braking stage (a) and the final braking stage (b). [Figure 11] In this embodiment, the figure shows the results of a test to determine the degree of deviation of the ridge of the protruding surface from the center of the tire in the circumferential direction, and is a figure showing the measurement results of the time change in the ratio of the contact area relative to the initial braking state for the contact area of ​​the pneumatic tire of the second comparative example, where the contact pressure of the contact area is above a predetermined value. [Figure 12] This figure corresponds to Figure 5, showing an alternative embodiment of a pneumatic tire. [Figure 13] This figure corresponds to Figure 9, showing an alternative embodiment of a pneumatic tire. [Figure 14] This figure corresponds to Figure 5, showing an alternative embodiment of a pneumatic tire. [Figure 15] This figure corresponds to Figure 9, showing an alternative embodiment of a pneumatic tire. [Figure 16] This figure shows cross-sections of the center block, mediate block, and shoulder block in a pneumatic tire of another embodiment, perpendicular to the tire axis, with their positions aligned in the tire circumferential direction. [Figure 17] In the pneumatic tire according to another example of the embodiment, it is a figure corresponding to FIG. 3.

Mode 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 the following embodiments. Also, forms obtained by selectively combining the components of the embodiments described below are included in the present invention.

[0010] FIG. 1 is a view of a pneumatic tire 1 according to an example of the embodiment as seen from below. As shown in FIG. 1, the pneumatic tire 1 includes a tread 10 which is a portion that contacts the road surface. The tread 10 has a plurality of main grooves 20, 21 extending from the equator CL side toward the grounding ends E1, E2 sides, and the inclination angle with respect to the tire axial direction (the left-right direction in FIG. 1) is larger on the equator CL side than on the grounding ends E1, E2 sides; and a plurality of sub-grooves 22, 23 connecting the adjacent main grooves 20, 21 in the tire circumferential direction or in a direction inclined with respect to the tire circumferential direction; and a plurality of blocks 28 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 axial direction. Hereinafter, the pneumatic tire 1 will be referred to as tire 1.

[0011] The plurality of blocks 28 are formed along the main grooves 20, 21 and have blocks 30 on the vehicle outer side with respect to the tire equator and blocks 31 on the vehicle inner side with respect to the tire equator. The main groove 20 and the block 30 extend from the equator CL side toward the grounding end E1 side, and the main groove 21 and the block 31 extend from the equator CL side toward the grounding end E2 side.

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

[0013] Here, the "regular rim" is a rim defined by the tire specifications. In the case of JATMA, it is the "standard rim", and in the case of TRA and ETRTO, it is the "Measuring Rim". The "regular 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 regular internal pressure is usually 180 kPa for passenger car tires, but 220 kPa for tires marked as Extra Load or Reinforced. The "regular 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 regular 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 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 is provided.

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

[0016] The blocks 30 are formed along the main grooves 20 and are arranged alternately with the main grooves 20 in the circumferential direction of the tire. The blocks 30 include a center block 32 located on the equator CL side, a shoulder block 34 located on the 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 are formed, connecting two main grooves 20 in the circumferential direction of the tire or in an inclined direction relative to the circumferential direction of the tire. The sub-grooves 22 divide the block 30 into three blocks.

[0017] The blocks 31 are formed along the main grooves 21 and are arranged alternately with the main grooves 21 in the circumferential direction of the tire. The blocks 31 include a center block 35 located on the equator CL side, a shoulder block 37 located on the 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 are formed, connecting two main grooves 21 in the circumferential direction of the tire or in an inclined direction relative to the circumferential direction of the tire. The sub-grooves 23 divide the block 31 into three blocks.

[0018] As described above, the multiple blocks 30, 31 are separated in both the circumferential and axial directions of the tire by being partitioned by multiple main grooves 20, 21 and multiple sub-grooves 22, 23.

[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. In other words, the main grooves 20 and 21 gradually become more aligned with the tire axis as they move from the equator CL side toward the contact end E1 and E2, and the angle of 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] The tread surface, which is the outer surface of each block in the radial direction of the tire, is a projection that protrudes outward in the radial direction of the tire, and is a projection that has its maximum height at a position offset to the front side of the tire's main rotation direction α relative to the tire's circumferential center of each block.

[0031] The treads of the blocks will be explained in detail below using Figures 2 to 6. In the following, the tread 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.

[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 surface 43 of each mediate block 33 is a protruding surface that extends outward in the radial direction of the tire, and the protrusion is larger in the middle of the tire circumferential direction than at both ends in the circumferential direction of the tire.

[0034] As shown in Figure 4, the tread surface 43 of each mediate block 33 protrudes 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, E2 of the shoulder blocks 34, 37 on both sides of the tire axial direction, assuming that the main grooves 20, 21 and the secondary grooves 22, 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. The profile surface Sp does not include the protruding surfaces of the tread surfaces of each block 32, 33, 34, 35, 36, 37 that protrude radially outward from the tread.

[0035] As shown in Figure 4, the tread surface 43 of each mediate block 33 is a protruding surface that has a maximum projection height H2 from the profile surface Sp, located on a ridge line Tm (Figure 4) that is offset to the front side of the tire's main rotation direction α with respect to the tire's circumferential center C1 of each mediate block 33.

[0036] As shown in Figure 5, the tread surface 43 of the mediate block 33 is a curved surface on the radially outer side of the convex portion having a ridge line Tm in the direction along the main groove 20. In Figure 5, the front surface of the mediate block 33 in the plane of the paper is the cross-section shown in Figure 4. The ridge line Tm is at the maximum height position of the tread surface 43. As shown in Figure 4, when the tread 10 is cut in a cross-section perpendicular to the tire axis direction, the circumferential position of the ridge line Tm is shifted to the front side (right side in Figure 4) of the main rotation direction α of the tire, relative to the center C1 between the two adjacent main grooves 20 in the circumferential direction of the mediate block 33. In Figure 5, the circumferential position of the ridge line Tm is shown by a dashed line.

[0037] As shown in Figure 6, when viewing the tread surface 43 from the outside in the radial direction of the tire, consider a predetermined region 50 in the tire axial direction (the region indicated by arrow γ in Figure 6) between a straight line L1 perpendicular to the tire axial direction that passes through the intersection of the sub-groove 22 on the contact end E1 side and the main groove 20 on one side in the circumferential direction of the tire (upper side in Figure 6), and a straight line L2 perpendicular to the tire axial direction that passes through the intersection of the sub-groove 22 on the equator side CL and the main groove 20 on the other side in the circumferential direction of the tire (lower side in Figure 6). In this case, the portion of the ridge line Tm located in the predetermined region 50 is located in front of the center C1 in the circumferential direction of the tire along the main rotation direction α of the tread surface 43 (lower side in Figure 6). As a result, as will be described later, the dynamic performance and braking performance can be improved in a configuration in which multiple blocks separated in the circumferential direction of the tire are provided on the tread 10.

[0038] Furthermore, in this example, since the tread surface 43 is a convex portion with a ridge line Tm, it is possible to secure a contact area for both front and rear loads during straight-line driving. This makes braking performance more stable and higher.

[0039] Furthermore, in this example, the portion of the ridge line Tm of the tread surface 43 located in a predetermined region 50 is shifted to the front side of the tire's main rotation direction α by more than 7 / 10 of the distance between the two ends of the tire's circumferential direction in a cross section perpendicular to the tire axis. Therefore, when the circumferential length of the tire from the main groove 20 to the ridge line Tm on one side of the tire's circumferential direction (left side in Figure 4, upper side in Figure 6) is a1, and the circumferential length of the tire from the main groove 20 to the ridge line Tm on the other side of the tire's circumferential direction (right side in Figure 4, lower side in Figure 6) is a2, a1 and a2 satisfy the relationship a1 / (a1+a2)≧0.7.

[0040] Furthermore, the cross-sectional shape of the portion of the tread 43 located in a predetermined region 50, perpendicular to the tire axis direction, is as shown in Figure 4. In the region 44 located behind the ridge line Tm in the main tire rotation direction α, there is a curve formed by connecting two arcs R1 and R2, each with a radius of curvature increasing from the rear end wall surface 20a toward the front. In addition, the cross-sectional shape of the portion of the tread 43 located in a predetermined region 50, perpendicular to the tire axis direction, is a curve formed by a single arc R3 in the region 45 located in front of the ridge line Tm in the main tire rotation direction α. ​​The radius of curvature of arc R3 in region 45 is intermediate in size between the radii of curvature of the smallest arc R1 and the largest arc R2 in region 44. In this example, region 44 is formed by a shape connected by two arcs R1 and R2, but region 44 may also be a shape formed by connecting three or more arcs with a radius of curvature increasing from the rear end wall surface 20a toward the front.

[0041] In this example, the upper end of the sipe 40 is located at the center C1 in the tire circumferential direction of the mediate block 33, but the sipe 40 may be formed at a position different from the center C1. Also, the sipe 40 may be omitted.

[0042] According to the tire 1 described above, in a configuration in which multiple blocks separated in the circumferential direction of the tire are provided on the tread 10, the tread surface of the block protrudes outward in the radial direction of the tire, making it easier to follow the unevenness of the road surface and improving the contact with the road when the block is tilted, thereby improving handling performance. Furthermore, a portion of the ridge of the tread surface of each block is shifted to the front side of the main rotation direction α of the tire with respect to the center C1 of the block in the circumferential direction of the tire. As a result, even though the contact portion of the block is inclined with respect to the road surface during braking, the contact area can be increased over a wide range from the front to the rear in the direction of vehicle travel β. This improves braking performance.

[0043] To explain this effect, we will first describe the state of the block tilt of the tire in the comparative example. Figure 7 is a diagram of tire 1a of the first comparative example, corresponding to Figure 6. Figure 8 shows tire 1a of the first comparative example, where (a) is a schematic diagram showing the state of one block of tire 1a in contact with the ground when tire 1a is stationary, and (b) is a schematic diagram showing the state in which the block tilts when the vehicle is braking. In Figures 7 and 8, the blocks are represented by mediate blocks 33a.

[0044] As shown in Figures 7 and 8(a), in the tire 1a of the first comparative example, the entire tread surface 43a of the mediate block 33a is a protruding surface that extends outward in the radial direction of the tire and has an arc shape in cross-section perpendicular to the tire axis. No sipes 40 are formed on the mediate block 33a that cross the tread surface 43a. The tread surface 43a is a convex surface having a ridge line Tm1 that extends along the longitudinal direction of the main groove 20. In this case, as shown in Figure 8(a), the contact portion of the mediate block 33a with the road surface 80 makes contact mostly near the center in the circumferential direction of the tire where the ridge line Tm1 is located.

[0045] On the other hand, as shown in Figure 8(b), in the first 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 point of the tread surface 43a moves to the front of the direction of travel β.

[0046] On the other hand, in the first comparative example, the ridge line Tm1 of the tread surface 43a of the mediate block 33a is located in the center of the tread surface 43a in the tire circumferential direction. Therefore, near the contact point, 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 curved surface with a circular arc cross-section is farther away from the road surface 80, and the contact area tends to be smaller. As a result, the comparative example has room for improvement in terms of improving braking performance.

[0047] Figure 9 is a diagram corresponding to the enlarged view of the area near the contact patch in Figure 8(b) of the tire 1 of the embodiment. According to the embodiment shown in Figure 9, the ridge line Tm of the tread surface 43 of the mediate block 33 is shifted to the front side of the main rotation direction α of the tire, i.e., to the rear side of the direction of travel β when the vehicle is moving forward, relative to the sipe 40 located in the center of the circumferential direction of the tread surface 43. This makes it easier for the tread surface 43 to make contact with the road surface 80 over a wide area in the longitudinal direction of the vehicle. Therefore, the contact area of ​​the tread surface 43 can be increased during braking, thereby improving braking performance.

[0048] In particular, in this embodiment, the portion of the ridge line Tm of the tread surface 43 located in a predetermined region 50 is shifted towards the front side of the main rotation direction α of the tire for more than 7 / 10 of the distance between the two ends in the tire circumferential direction of the cross section perpendicular to the tire axis. This makes it easier for the tread surface 43 to make contact with the road surface 80 over a wider area of ​​the tread surface 43 in the longitudinal direction of the vehicle. As a result, the contact area of ​​the tread surface 43 can be increased during braking, further improving braking performance.

[0049] Furthermore, as shown in Figure 9, in this embodiment, near the contact portion of the mediate block 33, a curved surface having a circular arc R1 with a small radius of curvature in its cross-sectional shape is provided near the wall surface 20a of the region 44 behind the ridge line Tm of the tread surface 43 in the main rotation direction α. ​​This makes it easier for the front end of the tread surface 43 in the direction of vehicle travel β to deform flexibly in accordance with the irregularities of the road surface 80, thereby increasing the contact area with the road surface 80. In addition, this front end is more likely to catch on the rear side of the protrusions 81 made of stone or the like on the road surface 80 in the direction of vehicle travel, further improving braking performance.

[0050] Using Figures 10 and 11, we will explain the tests conducted in the embodiment to determine the degree of deviation of the ridge line Tm of the tread surface 43 from the tire circumferential center, which is 7 / 10 or greater.

[0051] The test was conducted using the tire of the second comparative example. The tire of the second comparative example has a tread with a basic shape similar to that of the embodiment, but the tread surface, which is the outer surface of each block in the radial direction of the tire, does not have a protruding surface that extends outward in the radial direction of the tire, and is a smooth surface along the profile surface of the tread. In addition, a sipe 40 extending along the longitudinal direction of the main groove is formed in the middle of the tread surface of each block in the circumferential direction of the tire, similar to the configuration in Figures 1 to 6.

[0052] Figure 10 shows the results of measuring the contact pressure of the tire contact area of ​​the second comparative example at the initial braking stage (a) and the final braking stage (b), where the contact pressure exceeds a predetermined value. In Figure 10, the right side is the front side in the direction of vehicle travel β. In Figure 10, the black areas indicate the portions of the tread where the contact pressure of the center block 35, mediate block 36, and shoulder block 37 on one side of the tire axial direction exceeds a predetermined value. These black areas are essentially the contact surface during braking.

[0053] From the measurement results shown in Figure 10, in the tire of the second comparative example, the effective contact area decreases by approximately 70% in both the front and rear regions of the vehicle direction β separated by the sipes 40 of each block at the end of braking compared to the initial braking stage. From this, it can be considered that, averaging the reduction in contact area of ​​each block during braking along the length direction of the main groove, approximately 70% of the main groove 21 or sipes 40 on the front side of the vehicle direction β is in effective contact with the rear side of the vehicle direction β in each region separated by the sipes 40 of each block. Furthermore, unlike the embodiment, in the second comparative example, the tread surface of the block does not protrude outward in the radial direction of the tire in a curved shape, so the contact performance at the rear end of the front region of the vehicle direction β separated by the sipes 40 is also worse, and consequently, the contact area at the front end of the rear region of the vehicle direction β separated by the sipes 40 is increased. On the other hand, in the tire of the first comparative example shown in Figure 8, the tread surface 43a of block 33a protrudes outward in the radial direction of the tire in a curved shape. Therefore, as each block 33a collapses during braking, it continuously contacts the front to rear of the vehicle in the direction of travel β, and in this case, it is thought that only about 70% of the area contacts the front to rear of the vehicle in the direction of travel β. This shows that it is effective to make approximately 70% of the area of ​​each block near the contact point during braking contact the front to rear of the vehicle in the direction of travel β more efficiently.

[0054] Figure 11 shows the measurement results of the change in the ratio of the contact area of ​​the tire in the second comparative example, where the contact pressure of the tire contact patch is above a predetermined value, relative to the initial braking state. From the measurement results shown in Figure 11, it can be seen that at the initial stage of braking, the tire's contact load becomes excessively high due to the sinking of the front of the vehicle, causing the contact area to increase from the standard value of 100%. Subsequently, as the sinking subsides and the blocks of the contact patch collapse, the contact area decreases, and it was confirmed that the ratio of this contact area becomes approximately 70% of the standard value. From this, it can be seen that, during braking, it is effective to make approximately 70% of the area from the front to the rear in the direction of vehicle travel β of each block near the contact patch more efficiently in contact with the road surface.

[0055] As in the embodiment, by configuring the degree of the bias towards the front in the main rotation direction of the tire to be 7 / 10 or more of the bias between the two ends in the circumferential direction of the tire, corresponding to the bias of the contact area towards the rear in the direction of vehicle travel of the ridge line Tm of the tread surface 43 relative to the tire circumferential center C1, the contact area can be increased more efficiently regardless of the collapse of the blocks near the contact area during braking.

[0056] Figure 12 is a diagram of tire 1b in another embodiment, corresponding to Figure 5. Figure 13 is a diagram of tire 1b in another embodiment, corresponding to Figure 9. In the configuration of this example, in each block such as mediate block 33b, the shape of the cross section perpendicular to the tire axis direction in the portion located in a predetermined region 50 (see Figure 6) of the tread surface 43b has a curve formed by a first circular arc R4 in the region 44b behind the ridge line Tm in the main tire rotation direction α. ​​Also, the shape of the cross section perpendicular to the tire axis direction in the portion located in the predetermined region 50 of the tread surface 43b has a curve formed by a second circular arc R5 in the region 45b in front of the ridge line Tm in the main tire rotation direction α. ​​The radius of curvature of the first circular arc R4 is greater than the radius of curvature of the second circular arc R5.

[0057] According to the configuration of this example, as shown in Figure 13, during braking, the radius of curvature of the front side of the tread surface 43b of the block in the direction of vehicle travel β can be made larger overall from the ridge line Tm of the tread surface 43b at the contact point, thereby increasing the contact area with the road surface 80 and further improving braking performance. In addition, unlike the configuration shown in Figure 9, the radius of curvature of the curve at the front end of the tread surface 43b in the direction of vehicle travel β can be made larger in this configuration, so that the tilting of the block toward the rear side of the tread surface β in the direction of vehicle travel can be suppressed. As a result, the part of the tread surface 43b that is toward the rear side of the tread surface β in the direction of vehicle travel can be brought closer to the road surface 80 from the ridge line Tm, thereby increasing the effective contact area. This further improves braking performance. Furthermore, by making the radius of curvature of the second arc R5 of the part of the tread surface 43b that is toward the rear side of the tread surface β in the direction of vehicle travel larger than the radius of curvature of the third arc R3 in the configuration of Figure 4, the effective contact area can be increased further, and braking performance can be further improved. In this example, the other configurations and functions are the same as those in Figures 1 to 6.

[0058] Figure 14 is a diagram of another example of the embodiment of tire 1c, corresponding to Figure 5. Figure 15 is a diagram of another example of tire 1c, corresponding to Figure 9. In the configuration of this example, in each block such as the mediate block 33c, the shape of the cross section perpendicular to the tire axis direction in the portion located in a predetermined region 50 (see Figure 6) of the tread surface 43c is such that it exhibits braking force in a state that can easily flexibly respond to various road surface angle movements in the region 44c behind the ridge line Tm in the main rotation direction α of the tire. Specifically, in region 44c, multiple curved surfaces S1, S2...S5 are connected via boundary lines, and one end of each boundary line is located near a point Pm on the ridge line Tm. Each curved surface S1, S2...S5 becomes lower as it moves away from the ridge line Tm. Furthermore, while the curved surfaces S1 and S5, which have portions along the ridge line Tm, are gently sloping surfaces, the other curved surfaces S2, S3, and S4 slope sharply as they move away from the ridge line Tm until near the wall surface of the groove 20, and then slope gently. In the region 45c in front of the ridge line Tm in the main rotation direction α of the tire, the surface is similar to the region 45 of the tread surface 43 shown in Figures 4 and 5. In this example, in the cross section visible on the front side of the page in Figure 14, in region 44c, a circular arc R7 with a large radius of curvature is connected to the ridge line Tm, and a circular arc R6 with a smaller radius of curvature than arc R7, which is recessed toward the inside of the mediate block 33c, is connected to the wall surface of the groove 20.

[0059] According to the configuration of this example, as shown in Figure 15, during braking, the area 44c of the tread surface 43c that is in front of the ridge line Tm in the direction of vehicle travel can flexibly respond to changes in the unevenness of the road surface 80 and easily increase the contact area, thereby increasing the braking force on road surfaces 80 with large changes in unevenness. In this example, the other configurations and operations are the same as those in Figures 1 to 6.

[0060] Figure 16 is a diagram showing cross-sections of the center block 32, mediate block 33, and shoulder block 34 in a tire of another embodiment, perpendicular to the tire axis direction, with their positions in the tire circumferential direction aligned.

[0061] The following describes blocks 32, 33, and 34 of block 30, but blocks 35, 36, and 37 of block 31 are similar, except that they are symmetrical to block 30 with respect to the equator CL.

[0062] The center block 32, mediate block 33, and shoulder block 34 each have tread surfaces 43d, 43e, and 43f, respectively. In the tread surface 43d of the center block 32, the cross-sectional shape perpendicular to the tire axis in the intermediate region in the tire axis direction, which is a predetermined region in the tire axis direction, is the same as the cross-sectional shape perpendicular to the tire axis in the predetermined region 50 of the mediate block 33 shown in Figures 1 to 6.

[0063] Furthermore, in each block 32, 33, and 34, the edges Tm2, ​​Tm3, and Tm4 of the tread surfaces 43d, 43e, and 43f in the predetermined intermediate tire axial region are biased towards the front side of the tire's main rotation direction α for more than 7 / 10 of the distance between the two ends in the tire circumferential direction of the cross section perpendicular to the tire axial direction. Moreover, the bias of the edges Tm2, ​​Tm3, and Tm4 of the tread surfaces 43d, 43e, and 43f in the predetermined intermediate tire axial region of each block 32, 33, and 34 with respect to the tire's main rotation direction α is different from that of the others.

[0064] Specifically, in this example, in the intermediate tire axial region of each block 32, 33, and 34, the forward bias of the ridges Tm4, Tm3, and Tm2 of the tread surfaces 43f, 43e, and 43d toward the front in the main rotation direction α of the tire increases in the order of shoulder block 34, mediate block 33, and center block 32.

[0065] Furthermore, the maximum protrusion heights H2, H2a, and H2b of the tread surfaces 43d, 43e, and 43f extending radially outward from the profile surface Sp in the intermediate tire axial region, which is a predetermined area in each block 32, 33, and 34, are different from each other.

[0066] Specifically, in this example, in the intermediate axial region of each block 32, 33, and 34, the maximum protrusion heights H2b, H2a, and H2 of the tread surfaces 43f, 43e, and 43d increase in the order of shoulder block 34, mediate block 33, and center block 32.

[0067] Generally, in each block 32, 33, and 34, the ground contact load increases during braking in the order of shoulder block 34, mediate block 33, and center block 32. Therefore, during braking, blocks 34, 33, and 32 tend to tilt significantly and have a smaller contact area in that order. For this reason, as in this example, by increasing the forward bias of the ridges Tm4, Tm3, and Tm2 of the tread surfaces 43f, 43e, and 43d in the order of shoulder block 34, mediate block 33, and center block 32, in the direction of the tire's main rotation α, the contact area can be increased more efficiently in each block 32, 33, and 34 over a wide range from the front to the rear in the direction of vehicle travel.

[0068] Furthermore, as in this example, by increasing the maximum protrusion heights H2b, H2a, and H2 of the tread surfaces 43f, 43e, and 43d in the order of shoulder block 34, mediate block 33, and center block 32, the contact of blocks 34, 33, and 32 with the road surface can be increased in this order. In Figure 16, the overall height is shown to increase in the order of shoulder block 34, mediate block 33, and center block 32, but it is sufficient that the height from the profile surface Sp is increased, and the overall block height may be lower, for example, for the shoulder block 34 than for the mediate block 33 and center block 32. This further improves braking performance. In this example, the other configurations and functions are the same as those in Figures 1 to 6.

[0069] Figure 17 is a diagram of a tire in another embodiment, corresponding to Figure 3. 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.

[0070] In the examples above, we described a configuration in which the tread surface of all blocks is a projection that protrudes outward in the radial direction of the tire, and a portion of the ridge is offset to the front side in the main rotation direction of the tire with respect to the center of the block in the circumferential direction of the tire. On the other hand, the tread surface of only a portion of the blocks of the tread may be a projection that protrudes outward in the radial direction of the tire, and a portion of the ridge is offset to the front side in the main rotation direction of the tire with respect to the center of the block in the circumferential direction of the tire. Furthermore, the ridge of the tread surface of only a portion of the blocks of the tread may be offset to the front side in the main rotation direction of the tire by 7 / 10 or more of the distance between the two ends of the cross section perpendicular to the tire axis in the circumferential direction of the tire. In addition, in some or all of the blocks of the tread, at least all of the ridge of the tread surface may be offset to the front side in the main rotation direction of the tire with respect to the center of the block in the circumferential direction of the tire. Furthermore, the tread may have a shape in which some or all of the block surfaces have a highest point in one part, and the highest point is offset to the front side in the main rotation direction of the tire with respect to the center of the block in the tire circumferential direction, or it may be offset to the front side in the main rotation direction of the tire for 7 / 10 or more of the distance between the two ends of the cross section perpendicular to the tire axis in the tire circumferential direction. [Explanation of symbols]

[0071] 1,1a,1b,1c Pneumatic tire (tire), 10,10a Tread, 11 Sidewall, 20,21 Main groove, 22,23 Secondary groove, 28,30,31 Block, 32,35 Center block, 33,36 Mediate block, 34,37 Shoulder block, 40,40a Sipes, 43,43a~43f Tread, 44,44b,44c,45,45b,45c Area, 50 Designated area, 80 Road surface, 81 Protrusion, CL Equator, E1,E2 Contact edge.

Claims

1. A pneumatic tire having a tread, The main rotation direction of the tire is specified, and 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 tread surfaces of the aforementioned blocks are protruding surfaces that project outward in the radial direction of the tire, A pneumatic tire in which at least a portion or the apex of the ridge of the tread surface is offset to the front side in the main rotational direction of the tire with respect to the center of the block in the circumferential direction of the tire.

2. At least a portion of the ridge of the tread surface or the apex is shifted to the front side in the main rotation direction of the tire for 7 / 10 or more of the distance between the two ends in the circumferential direction of the tire in a cross-section perpendicular to the tire axis. The pneumatic tire according to claim 1.

3. The shape of the cross-section in at least a portion of the tread surface has a curve formed by connecting multiple circular arcs in the region behind the ridge or vertex in the main rotation direction of the tire, where the radius of curvature increases from the rear end wall towards the front, and a curve formed by a single circular arc in the region in front of the ridge or vertex in the main rotation direction of the tire. The pneumatic tire according to claim 2.

4. The shape of the cross-section in at least a portion of the tread surface has a curve formed by a first circular arc in the region behind the ridge or vertex in the main rotation direction of the tire, and a curve formed by a second circular arc in the region in front of the ridge or vertex in the main rotation direction of the tire, wherein the radius of curvature of the first circular arc is greater than the radius of curvature of the second circular arc. The pneumatic tire according to claim 2.

5. The aforementioned plurality of blocks include a center block, a mediate block, and a shoulder block, arranged in order from the tire equator toward the tire axial outward. Each of the center block, mediate block, and shoulder block has at least a portion of the ridge of the tread surface or the vertex of which is shifted to the front side in the main rotation direction of the tire by 7 / 10 or more of the distance between the two ends of the tire circumferential direction of the cross section perpendicular to the tire axis, The bias of at least a portion of the ridge line or the apex of the tread surface in each of the center block, mediate block, and shoulder block with respect to the main rotation direction of the tire is different from that of the others. The pneumatic tire according to claim 1.

6. The shoulder block, mediate block, and center block are in a sequence in which the bias toward the front in the main rotation direction of the tire is increasing, at least a portion of the ridge of the tread or the apex. The pneumatic tire according to claim 5.

7. The aforementioned plurality of blocks include a center block, a mediate block, and a shoulder block, arranged in order from the tire equator toward the tire axial outward. Each of the center block, mediate block, and shoulder block has at least a portion of the ridge of the tread surface or the apex offset to the front side in the main rotation direction of the tire with respect to the center of the block in the circumferential direction of the tire. The maximum protrusion heights of the center block, mediate block, and shoulder block from the profile surface of the tread outward in the tire radial direction are different from each other. The pneumatic tire according to claim 1.

8. The maximum protruding height of the tread increases in the order of the shoulder block, the mediate block, and the center block. The pneumatic tire according to claim 7.

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