pneumatic tires

Abstract

In pneumatic tires, a highly drainable configuration with a V-shaped pattern is used to suppress block deformation, thereby increasing the contact area with the ground. [Solution] The pneumatic tire has a designated main rotation direction α of the tire and includes a plurality of blocks 33 partitioned by a plurality of grooves. The plurality of grooves have a plurality of main grooves 20 that extend from the equator side toward the contact end side and have a greater inclination with respect to the tire axis on the equator side than on the contact end side, and sub-grooves 22 that connect adjacent main grooves 20 in the tire circumferential direction or in an inclined direction toward the tire circumferential direction. In at least one of the two adjacent main grooves 20 of a certain block 33, the bottom edge 33a that forms the bottom surface of the main groove 20 is longer than the tread side edge 33b that forms the tread side opening or the virtual tread side edge 38 with chamfering omitted, and has a shape that protrudes inward from one of the main grooves 20 in a plan view.

Description

Technical Field

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

Background Art

[0002] [[ID=1,12]]In order to exert the effect of the pattern formed on the tire surface, it is preferable to ground the pattern as much as possible. On the other hand, in actual use, when a load is applied to the block, the block is deformed so as to fall, and the contact area having a surface pressure of a predetermined value or more decreases, resulting in a decrease in performance. In particular, a large load is applied during vehicle braking. On the other hand, a V-shaped pattern in which the main rotation direction of the tire is specified may be formed on the tire surface.

[0003] Patent Document 1 describes that in a pneumatic tire, a V-shaped pattern having a main groove extending from the equator side toward the ground contact end side and having a larger inclination with respect to the tire axial direction on the equator side than on the ground contact end side is formed on the tire surface.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the configuration described in Patent Document 1, there is room for improvement in terms of enhancing drainage performance. For this reason, in a tire having a V-shaped pattern and high drainage performance, it is desired to increase the contact area during grounding by suppressing the collapse of the block.

[0006] An object of the present invention is to increase the contact area by suppressing the collapse of the block in a tire having a V-shaped pattern and high drainage performance.

Means for Solving the Problems

[0007] The pneumatic tire according to the present invention is a pneumatic tire having a tread, wherein the main rotation direction of the tire is specified, and the tread includes a plurality of blocks partitioned by a plurality of grooves, the plurality of grooves extending from the equator side toward the contact edge side, having a plurality of main grooves whose inclination with respect to the tire axis is greater on the equator side than on the contact edge side, and sub-grooves connecting adjacent main grooves in the tire circumferential direction or in an inclined direction toward the tire circumferential direction, and of at least one of the two adjacent main grooves of a certain block, the bottom edge forming the bottom surface of the wall surface forming the main groove is longer than the tread side edge forming the tread side opening, or the virtual tread side edge where the chamfer is omitted when a chamfer is connected to the tread side edge, and has a shape having a convex projection inward of one of the main grooves in a plan view. [Effects of the Invention]

[0008] According to the pneumatic tire of the present invention, in a highly drainable configuration having a V-shaped pattern, the contact area can be increased by suppressing the tilting of the blocks. [Brief explanation of the drawing]

[0009] [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 perspective view showing a single block taken from Figure 2 and enlarged. [Figure 5A] Figure 4 is an enlarged plan view of the block shown. [Figure 5B] This is an enlarged view of section C in Figure 5A. [Figure 5C] This is an enlarged view of section D in Figure 5A. [Figure 6]In the comparative example of a pneumatic tire, (a) is a schematic diagram showing the contact state 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 7] This figure corresponds to Figure 3, showing an alternative embodiment of a pneumatic tire. [Figure 8] The block shown in Figure 7 corresponds to the diagram in Figure 5. [Figure 9] This figure corresponds to Figure 5, showing an alternative embodiment of a pneumatic tire. [Figure 10] This figure corresponds to Figure 4, showing an alternative embodiment of a pneumatic tire. [Figure 11] The block shown in Figure 10 corresponds to the diagram in Figure 5. [Figure 12] This figure corresponds to Figure 5, showing an alternative embodiment of a pneumatic tire. [Figure 13] This is a view of a pneumatic tire in another embodiment, showing one block as seen from the radially outer side of the tire. [Figure 14] This figure corresponds to Figure 3, showing an alternative embodiment of a pneumatic tire. [Figure 15] This is an enlarged view corresponding to section E in Figure 1, showing another example of a pneumatic tire according to the embodiment. [Modes for carrying out the invention]

[0010] 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.

[0011] FIG. 1 is a view seen from below of a pneumatic tire 1 which is an example of an embodiment. 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 extends from the equator CL side toward the ground contact ends E1 and E2 sides, and has a plurality of main grooves 20 and 21 in which 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 ground contact ends E1 and E2 sides. A plurality of sub - grooves 22 and 23 connect the adjacent main grooves 20 and 21 in the tire circumferential direction or in a direction inclined with respect to the tire circumferential direction. The tread 10 also has 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 the tire 1.

[0012] The plurality of blocks 28 are formed along the main grooves 20 and 21, and include a block 30 on the vehicle outer side with respect to the equator CL and a block 31 on the vehicle inner side with respect to the equator CL. The main groove 20 and the block 30 extend from the equator CL side toward the ground contact end E1 side, and the main groove 21 and the block 31 extend from the equator CL side toward the ground contact end E2 side.

[0013] 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 ground contact ends E1 and E2). In this specification, the ground contact ends E1 and E2 are defined as both ends in the tire axial direction of the region that contacts the flat road surface when a predetermined load is applied to an unused pneumatic tire 1 mounted on a standard rim and filled with air to a standard internal pressure. In the case of a passenger car tire, the predetermined load is a load corresponding to 88% of the standard load.

[0014] Here, "standard rim" refers to the rim defined by the tire standard; for JATMA, it is the "standard rim," and for TRA and ETRTO, it is the "Measuring Rim." "Standard internal pressure" refers to the "maximum air pressure" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "INFLATION PRESSURE" for ETRTO. The standard internal pressure is usually 180kPa for passenger car tires, but 220kPa for tires marked Extra Load or Reinforced. "Standard load" refers to the "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. For racing kart tires, the standard load is 392N.

[0015] Tire 1 is a directional tire with a specified main rotation direction. Figure 1 illustrates arrow α indicating the main rotation direction of the tire. In this specification, the "main rotation direction" of the tire means the direction of rotation when the vehicle on which the tire is mounted is moving forward. Since Figure 1 is a view of tire 1 from below, the main rotation direction of the tire α and the vehicle's direction of travel β are in opposite directions. It is preferable that the pneumatic tire 1 has an indication for the mounting direction relative to the vehicle. For example, at least one of letters and an arrow indicating the main rotation direction is provided on the side of the pneumatic tire 1.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] The main grooves 20 and blocks 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 grooves 21 and blocks 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 so that they are gradually positioned toward the rear in the main rotation direction α of the tire, starting from the axial center of the pneumatic tire 1 toward both sides of the axis. As a result, the tread 10 has a V-shaped pattern.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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 multiple main grooves 20, 21 and sub-grooves 22, 23. The maximum depth of each sipe 40 is, for example, between 40% and 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] Furthermore, as shown in Figure 2, chamfers 60, 61, and 62, which are roughly triangular in plan view in Figure 2, are formed on at least a portion of the corners of the treads of each block 32, 33, and 34. For example, chamfers 61 are formed on all four corners of the tread of mediate block 33. Chamfers are also formed on at least a portion of the corners of the treads of each block 35, 36, and 37, similar to blocks 32, 33, and 34.

[0031] In each block, of the two adjacent main grooves 20, 21, the bottom edge of the wall forming one of the main grooves, the main groove 20, 21 on the rear side in the main rotation direction α, is longer than the virtual tread-side edge where the chamfer is omitted when the chamfer is connected to the tread-side edge forming the opening on the tread surface 41, 42 side, and has a shape that protrudes inward in the width direction, more specifically, inward, of the main groove 20, 21 on the rear side in the main rotation direction α when viewed from above.

[0032] The following describes in detail the wall surfaces that form the main grooves of the blocks, using Figures 1 to 5C. In the following, we will mainly describe the wall surfaces that form the main grooves of the mediate block 33 of block 30, but the same applies to the wall surfaces that form the main grooves of 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.

[0033] 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. The tread surface of each mediate block 33 is a flat surface, but it may also be a protruding surface that extends outward in the radial direction of the tire.

[0034] Furthermore, as shown in Figures 3 to 5C, of ​​the two adjacent main grooves 20 of each mediate block 33, the bottom edge 33a that forms the bottom surface 20a of the wall surface 20b that forms one of the main grooves, the main groove 20 on the rear side in the main rotation direction α of the tire, is longer than the virtual tread-side edge 38 when the chamfer 61 is omitted, in the case where the chamfer 61 is connected to the tread-side edge 33b that forms the opening on the tread side 41. In addition, the bottom edge 33a has a shape that protrudes inward into the main groove 20 on the rear side in the main rotation direction α of the tire when viewed from above.

[0035] In the mediate block 33, chamfers 61 are connected to both longitudinal ends of the tread-side edge 33b. Therefore, the actual length of the tread-side edge 33b is the sum of the arc length of the intermediate section A1 in Figures 4 and 5A, the end A2 which is the tread-side edge of one chamfer 61 in Figure 5B, and the end A3 which is the tread-side edge of the other chamfer 61 in Figure 5C. For this reason, the actual length of the tread-side edge 33b is larger than when the chamfer 61 is not formed. However, the chamfer is formed only at the corners of the tread surface of the block, and the effect of the presence or absence of the chamfer on the block's tilting is almost negligible. For this reason, in cases where a chamfer 61 is connected to the tread-side edge 33b, as in this example, a virtual tread-side edge 38 without the chamfer 61 is defined, and the length of the virtual tread-side edge 38 is compared with the length of the bottom edge 33a.

[0036] As shown in Figures 5B and 5C, the virtual tread edge 38 is a virtual curve along the intermediate section A1, with the intersection points P1 and P2 of lines extending longitudinally from both sides of the intermediate section A1 of the actual tread edge 33b in a plan view of the mediate block 33, and lines extending longitudinally from both ends of the tread edge forming the sub-grooves 22 of the mediate block. Thus, the length of the virtual tread edge 38 is the sum of the length of the intermediate section A1, the first virtual end A4 connecting the intermediate section A1 and intersection point P1 (Figure 5B), and the second virtual end A5 connecting the intermediate section A1 and intersection point P2 (Figure 5C). In this example, the virtual tread edge 38 is longer than the bottom edge 33a. Note that in Figures 5B and 5C, the outline of the bottom surface of the chamfer 61 should actually be visible, but this outline has been omitted in order to make the virtual tread side edge 38 easier to understand.

[0037] In the examples shown in Figures 3 to 5C, both the bottom edge 33a and the tread edge 33b are approximately arc-shaped, with their longitudinal middle portions protruding inward toward the main groove 20. However, the bottom edge 33a protrudes more significantly inward toward the main groove 20 than the tread edge 33b. As a result, in the plan view shown in Figure 5A, the bottom edge 33a has a curved shape that protrudes more significantly inward toward the main groove 20 than the curved shape of the tread edge 33b. Therefore, the bottom edge 33a is longer than the tread edge 33b. In this case, in the plan view of the block, the maximum protrusion length La (Figure 5A) of the portion of the bottom edge 33a that protrudes more inward toward the main groove 20 than the tread edge 33b is preferably 15% to 25% of the groove width at the opening end of the main groove 20 on the tread side. This preferred configuration allows for greater suppression of block tilting, thereby increasing the contact area of ​​the block and making it easier to achieve improved braking performance. Furthermore, since the bottom edge 33a does not protrude excessively into the main groove 20, a decrease in drainage performance can be suppressed. On the other hand, if the maximum protrusion length La is less than 15% of the groove width, it becomes difficult to achieve the effect of improving braking performance by further suppressing block tilting. Conversely, if the maximum protrusion length La exceeds 25% of the groove width, there is a risk of decreased drainage performance due to a reduction in the volume of the main groove 20.

[0038] The wall surface 20b between the bottom edge 33a and the tread edge 33b also has a cross-section perpendicular to the block height direction and is an arc shape that protrudes toward the inside of the main groove 20, with the amount of protrusion of its longitudinal middle portion increasing as it approaches the bottom surface of the main groove 20.

[0039] Furthermore, as shown in Figures 3 and 4, in each mediate block 33, the main groove 20 is formed on the rear side α in the main rotation direction of the tire, and the wall surface 20b connecting the bottom edge 33a and the tread edge 33b is inclined with respect to the tire radial direction in the middle of the longitudinal direction.

[0040] Furthermore, in this example, of the wall surfaces forming the main grooves 20 of each mediate block 33, only the bottom edge 33a of the wall surface 20b that forms the main groove 20 on the rear side in the main rotation direction α of the tire has a shape that protrudes inward into the main groove 20 when viewed from above, while the bottom edge 33c of the wall surface 20c that forms the main groove 20 on the front side in the main rotation direction α of the tire has a shape that is recessed toward the block side when viewed from above, and does not have a convex shape that protrudes inward into the main groove 20.

[0041] According to the above-described pneumatic tire 1, the tread 10 has a V-shaped pattern, and furthermore, adjacent main grooves are connected by sub-grooves in the tire circumferential direction or inclined relative to the tire circumferential direction, thereby improving drainage. Furthermore, in this configuration, the tread surface has a shape that is divided into multiple blocks in the tire axial direction from the equator side toward the contact edge side. Regardless of this shape with multiple blocks, according to the embodiment, of the two adjacent main grooves 20, 21 of each block, the bottom edge on the rear side in the tire's main rotation direction α is longer than the virtual tread side edge and has a shape that protrudes inward from the main groove 20, 21 on the rear side in the tire's main rotation direction α when viewed in plan. As a result, even when a bending load is applied to the block at the tire's contact point, the bottom edge, which is the root end of the block's wall surface, changes significantly from a straight shape along the longitudinal direction of the block, so the strain for bending the block increases, and the force required for bending increases. As a result, according to this embodiment, the tilting of each block can be suppressed, thereby increasing the contact area of ​​each block that has a surface pressure of a predetermined level or higher when it touches the ground. Therefore, both braking performance and driving performance can be improved. In particular, blocks are generally prone to tilting during braking, but according to this embodiment, the tilting of the blocks can be suppressed even during braking, thus improving braking performance.

[0042] Furthermore, according to the configuration of this example, the bottom edge of each block on the rear side α in the main rotation direction of the tire has a curved shape that protrudes significantly inward into the main groove compared to the curved shape of the tread edge when viewed from above. This allows for a larger component of the bottom edge that is significantly different from the longitudinal direction of the block. As a result, the tilting of each block can be further suppressed, the contact area of ​​each block can be increased, and braking performance can be further improved.

[0043] Furthermore, according to the configuration of this example, the main groove on the rear side α of the main tire rotation direction of each block, and the wall surface connecting the bottom edge and the tread edge, are inclined with respect to the tire radial direction at least in the middle of the longitudinal direction. This increases the resistance of each block to loads in a direction perpendicular to the tire radial direction, and increases the contact area, thereby improving braking performance.

[0044] To explain the effects of the embodiment, first, the tilting state of the blocks in the comparative example pneumatic tire will be described. Figure 6 shows a comparative example pneumatic tire 1a, where (a) is a schematic diagram showing the contact state of one block of the tire, the mediate block 33, when the tire is stopped, and (b) is a schematic diagram showing the state in which the mediate block 33 tilts when the vehicle is braking. In Figure 6, the tilting of the blocks is represented by the tilting of the mediate block 33.

[0045] In the comparative example pneumatic tire 1a shown in Figure 6(a), the lengths of the bottom edge forming the bottom surface of the main groove and the tread-side edge forming the tread-side opening are the same for each of the wall surfaces forming the two main grooves on both sides of the tire circumferential direction of the mediate block 33. A sipe 40 is formed on the tread surface 41 of the mediate block 33, passing through the middle in the tire circumferential direction.

[0046] In this comparative example, as shown in Figure 6(a), when the tire 1a is stopped, the tilting of the mediate block 33 can be ignored. Therefore, at the tread surface 41 of the contact area, each of the two regions 41a and 41b separated by the sipe can be easily brought into overall contact with the road surface 80.

[0047] On the other hand, as shown in Figure 5(b), when the vehicle is braking, the mediate block 33 tends to tilt downwards towards the rear in the direction of travel β at the contact point. In this case, the contact pressure tends to be lower in the rear portion of the tread surface 41 of the mediate block 33, as it moves away from the road surface 80. As a result, the contact area of ​​the tread surface 41 decreases, and there is room for improvement in terms of improving braking performance.

[0048] On the other hand, according to this embodiment, even during braking, the tilting of each block, such as the mediate block 33, can be suppressed, so the contact area can be increased. As a result, braking performance can be improved. In this example, each block has a chamfer connected to the wall surface 20b that forms the main grooves 20 and 21 on the rear side of the main rotation direction α of the tire. Furthermore, the bottom edge that forms the bottom surface of the main grooves 20 and 21 on the rear side of the main rotation direction α of each block is longer than the virtual tread-side edge that omits the chamfer of the tread-side edge that forms the tread-side opening, and has a shape that protrudes inward into the main grooves 20 and 21 on the rear side of the main rotation direction α in a plan view. On the other hand, in at least some of the blocks in this example, the wall surface 20b that forms the main grooves 20 and 21 on the rear side of the main rotation direction α of the tire may not have a chamfer connected to it. In this case, the bottom edge forming the bottom surface of the main groove on the rear side of the main rotation direction α of at least some of the blocks described above is made longer than the tread-side edge forming the tread-side opening, and has a shape that, in plan view, has a convex shape that protrudes inward into the main groove on the rear side of the main rotation direction α of the tire. With this configuration as well, similar to the configuration in this example, the contact area can be increased by suppressing the tilting of the blocks.

[0049] Figure 7 is a diagram of tire 1b, an alternative embodiment, corresponding to Figure 3. Figure 8 is a diagram of mediate block 33 shown in Figure 7, corresponding to Figure 5. In the embodiments described below, including this example, the case where there are no chamfers 60, 61, 62 (see Figure 2, etc.) at the corners of the tread surface of each block is described, but chamfers may be formed. In the configuration of this example, in each block such as mediate block 33, the bottom edge 33a that forms the bottom surface 20a of the main groove 20 of the main groove 20, which is part of the wall surface 20b that forms the main groove 20 on the rear side of the main rotation direction α of the tire, is longer than the tread-side edge 33b that forms the opening on the tread surface 41 side, and has a shape that, in plan view, has a convex shape that protrudes inward into the main groove 20 on the rear side of the main groove 20 on the rear side of the main rotation direction α of the tire. Furthermore, among the wall surfaces 20c1 that form the main groove 20 on the front side in the main rotation direction α of the tire, the bottom edge 33c1 that forms the bottom surface 20a of the main groove 20 is longer than the tread edge 33d that forms the opening on the tread surface 41, similar to the relationship between the bottom edge 33a and the tread edge 33b on the rear side in the main rotation direction α of the tire. In addition, the bottom edge 33c1 has a shape that protrudes inward into the main groove 20 on the front side in the main rotation direction α of the tire when viewed from above.

[0050] The tread-side edge 33d of the front wall surface 20c1 of each block in the main rotation direction α of the tire is an arc shape that is recessed inward in a plan view, while the bottom edge 33c1 has an arc shape that protrudes inward into the main groove 20. Furthermore, in the middle of the longitudinal direction, the bottom edge 33c1 is longer than the tread-side edge 33d because the amount by which it protrudes toward the main groove 20 is greater than the amount by which the tread-side edge 33d is recessed inward relative to a straight line extending in the longitudinal direction of the block. Also, as shown in Figure 7, the angle at which the wall surface 20c1 connecting the bottom edge 33c1 and the tread-side edge 33d is inclined with respect to the tire radial direction (vertical direction in Figure 7) is greater than the angle at which the rear wall surface in the main rotation direction α of the tire is inclined with respect to the tire radial direction.

[0051] As in the configuration of this example, if the bottom edge of each block has a shape where it is longer than the tread edge on both sides of the wall surface in the main tire rotation direction α, and has a convex shape that protrudes inward into the main groove in a plan view, the tilting of each block can be further suppressed. This allows the contact area of ​​each block to be further increased. In this example, the other configurations and functions are the same as those in Figures 1 to 5.

[0052] Figure 9 is a diagram corresponding to Figure 5, showing a different example of the embodiment, tire 1c. In this example, unlike the configurations in Figures 1 to 5, in each block such as the mediate block 33, the ends C1 and C2 of the wall surfaces along the block width direction, which are provided at both ends in the longitudinal direction of the block and protrude towards the main groove 20 side than the tread surface 41, are connected to both ends in the longitudinal direction of the wall surface 20b1 on the rear side in the main rotation direction α of the tire. At the bottom ends of each end C1 and C2, both ends of the bottom edge 33a1, which has a circular arc cross-section and protrudes significantly inward from the main groove 20 than the tread side edge 33b, are connected.

[0053] In this example, the bottom portion of the wall surface 20b1 protrudes significantly toward the main groove 20 without changing the shape of the arc-shaped portion of the bottom edge on the rear side of the main rotation direction α of the tire in each block. Therefore, the tilting of each block can be further suppressed. In this example, the other configurations and functions are the same as those in Figures 1 to 5, where chamfers are not connected to the tread-side edges of each block.

[0054] Figure 10 is a diagram of tire 1d, an alternative embodiment, corresponding to Figure 4. Figure 11 is a diagram of mediate block 33 shown in Figure 10, corresponding to Figure 5. In this example, unlike the configurations in Figures 1 to 5, in each block such as mediate block 33, the bottom edge 33a2 on the rear side in the main rotation direction α of the tire protrudes into the main groove 20 in a state where it changes in a wavy shape in the block width direction. Specifically, in a plan view of each block, the bottom edge 33a2 has a wavy shape with a valley connected between two peaks. Both ends of the bottom edge 33a coincide with both ends of the tread edge 33b in a plan view of each block. As a result, the bottom edge 33a2 is a wavy shape with two or more inflection points e1, e2, and e3. Therefore, in this example, since the shape of the bottom edge 33a2 is a more complex shape, the tilting of each block is further suppressed. In this example, the other configurations and functions are the same as those in Figures 1 to 5, where chamfers are not connected to the tread-side edges of each block.

[0055] Figure 12 is a diagram corresponding to Figure 5, showing tire 1e, an alternative embodiment. In this example, unlike the configurations in Figures 1 to 5, in each block such as mediate block 33, the ends C1 and C2 of the wall surfaces along the block width direction, which are provided at both ends in the longitudinal direction of the block and protrude towards the main groove 20 side from the tread surface 41, are connected to both ends in the longitudinal direction of the wall surface 20b3 on the rear side in the main rotation direction α of the tire. The ends of the bottom edge 33a3, which changes in a wavy shape in the block width direction, are connected to the tips of the bottom ends of each end C1 and C2.

[0056] The bottom edge 33a3 is a waveform that changes on both sides relative to the arc-shaped curve (dotted line γ in Figure 12) that protrudes inward from the tip of the bottom end of C1 and C2 at each end, to the tip of the main groove 20 to which both ends are connected.

[0057] Furthermore, in a plan view of each block, the minimum protrusion height d1 of the wave-like shape from the tread-side edge 33b to the bottom edge 33a3 is 0 or greater and 0.20% or less of the width of the main groove 20. Also, in a plan view of each block, the maximum protrusion height of the wave-like shape from the tread-side edge 33b to the bottom edge 33a3 is 5% to 25% of the width of the main groove 20. This allows the tread-side edge 33b to be wave-like while protruding significantly inward from the main groove 20 in a plan view. In this example, the other configurations and functions are the same as those in Figures 1 to 5, where chamfers are not connected to the tread-side edges of each block, or the configuration in Figure 9, or the configurations in Figures 10 and 11.

[0058] In the configurations of the above examples, a sipe 40 is formed along the longitudinal direction of the block at the center of the tire circumferential direction of each block. Each sipe 40 extends in the radial direction of the tire, but each sipe may be inclined with respect to the radial direction of the tire. Also, sipes may be omitted in each block.

[0059] Figure 13 is a view of a mediate block 36, which is a single block, from the radially outer side of the tire in a tire 1f of another embodiment. In the configuration of this example, the wall surface forming the main groove of the mediate block 36 of block 31 will be mainly described with reference to Figure 1, but the same applies to the wall surfaces forming the main grooves of the mediate block 33 of block 30, the center blocks 32 and 35 of each block 30 and 31, and the shoulder blocks 34 and 37.

[0060] In this example, no sipes are formed on each block. Furthermore, of the wall surfaces 21b and 21c that form the main grooves 21 on both sides of the main tire rotation direction α of each block, the bottom edge 36a and 36c that form the bottom surface of the main groove 21 are longer than the tread edge 36b and 36d that form the opening on the tread surface 42 side, and have a shape that protrudes inward into the main groove 21 in a plan view. More specifically, each bottom edge 36a and 36c protrudes inward into the main groove 21 in a wave shape, and the wave has five inflection points f1 to f5. As a result, in this example, the shape of the bottom edge 36a and 36c is more complexly changed, further suppressing the tilting of each block. In this example, the other configurations and functions are the same as those in Figures 1 to 5, where chamfers are not connected to the tread edge of each block, or the configuration in Figure 8, or the configuration in Figure 12.

[0061] Figure 14 is a diagram corresponding to Figure 3, showing a different example of tire 1g in the embodiment. In the configurations shown in Figures 1 to 5, as shown in Figure 3, the longitudinal middle portion of the wall surface 20b that forms the main groove 20 on the rear side of the main rotation direction α of each block such as the mediate block 33 is inclined linearly with respect to the tire radial direction. On the other hand, in the configuration of this example, the longitudinal middle portion of the wall surface 20b4 that forms the main groove 20 on the rear side of the main rotation direction α of each block such as the mediate block 33 and connects the bottom edge 33a4 and the tread edge 33b is inclined curvely with respect to the tire radial direction so as to be inward toward the inside of the main groove. In this example, the other configurations and operations are the same as in the configurations of Figures 1 to 5, in which chamfers are not connected to the tread edge of each block.

[0062] Figure 15 is an enlarged view corresponding to section C in Figure 1, showing tire 1h, another embodiment of the model. In this example, similar to the configurations in Figures 1 to 5, the bottom edges 52, 53, and 54 that form the bottom surface of the main groove 20 on the rear side of the main rotation direction α of each center block 32, each mediate block 33, and each shoulder block 34 of the block 30 are longer than the tread-side edges 32b, 33b, and 34b that form the tread-side opening. Furthermore, the bottom edges 52, 53, and 54 have a shape that protrudes inward into the main groove 20 on the rear side of the main rotation direction α in a plan view.

[0063] On the other hand, in this example, the ratio of the length D2 of the bottom edge 52, 53, 54 to the length D1 of the tread side edge 32b, 33b, 34b (D2 / D1) increases in the order of shoulder block 34, mediate block 33, and center block 32.

[0064] According to the configuration of this example, the tilting of the shoulder block 34, which tends to experience large loads during braking, can be suppressed, thereby improving braking performance. Furthermore, in the center block 32, the complex shape of the wall surface forming the main groove 20 can be suppressed, and the narrowing of the cross-sectional shape along the width direction of the main groove 20 can be suppressed. This suppresses the deterioration of hydroplaning resistance, which is greatly affected by the volume and drainage of the groove in the central part of the tire's axial direction. In this example, the other configurations and functions are the same as those in Figures 1 to 5. In addition, in the configuration of this example, the bottom edges 52, 53, and 54 can also be made corrugated, as shown in the configurations in Figures 10 to 13.

[0065] Furthermore, in the configurations of the above examples, the bottom edge of each block may be longer than the tread edge only on the front main groove side of the tire's main rotation direction α, and the bottom edge may have a shape in which it protrudes inward into the main groove on the front side of the tire's main rotation direction α when viewed from above.

[0066] Furthermore, in some of the blocks forming the tread, the bottom edge of the wall forming at least one of the two adjacent main grooves is longer than the tread edge, and the block has a shape that protrudes inward into one of the main grooves when viewed from above. [Explanation of Symbols]

[0067] 1,1a~1h Pneumatic tire (tire), 10,10a Tread, 11 Sidewall, 20,21 Main groove, 22,23 Secondary groove, 28,30,31 Block, 32,35 Center block, 32b,33b Tread edge, 33,36 Mediate block, 33a,33a1~33a4,33c,33c1 Bottom edge, 33b,33d Tread edge, 36a,36c Bottom edge, 36b,36d Tread edge, 34,37 Shoulder block, 40 Sipe, 41,42 Tread, 52,53,54 Bottom edge, 60,61,62 Chamfer, 80 Road surface, 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 partitioned by a plurality of grooves, The plurality of grooves extend from the equator towards the contact end, and each groove has a plurality of main grooves that are more inclined with respect to the tire axis on the equator side than on the contact end side, and sub-grooves that connect adjacent main grooves in the tire circumferential direction or in an inclined direction with respect to the tire circumferential direction. In at least one of the two adjacent main grooves of a portion of the block, the bottom edge forming the bottom surface of the main groove is longer than the tread-side edge forming the tread-side opening, or the virtual tread-side edge where the chamfer is omitted when a chamfer is connected to the tread-side edge, and has a shape that protrudes inward into one of the main grooves in a plan view. Pneumatic tires.

2. The bottom edge, in a plan view, has a curved shape that protrudes significantly inward from one of the main grooves compared to the curved shape of the tread edge. The pneumatic tire according to claim 1.

3. The wall surface that forms one of the main grooves and connects the bottom edge and the tread edge is inclined with respect to the tire radial direction at least in the middle of the longitudinal direction. The pneumatic tire according to claim 1.

4. The bottom edge has a waveform with two or more inflection points. The pneumatic tire according to claim 1.

5. In a plan view, the minimum protrusion height of the wave from the tread edge is 0 or greater and 20% or less of the width of one of the main grooves, and in a plan view, the maximum protrusion height of the wave from the tread edge is 5% or more and 25% or less of the width of one of the main grooves. The pneumatic tire according to claim 4.

6. The plurality of blocks include a center block, a mediate block, and a shoulder block, arranged in order from the equator side toward the tire axial side outwards. The ratio of the length of the bottom edge to the length of the tread edge increases in the order of the shoulder block, the mediate block, and the center block. The pneumatic tire according to claim 1.

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