pneumatic tires

Abstract

To provide a pneumatic tire having high design property and being excellent in durability and traction performance of a block constituting a tread pattern.SOLUTION: In a pneumatic tire 1 as an example of an embodiment, a tread 10 includes: a center block 40 having a trapezoidal shape in plan view and formed in a plural spaced in a tire circumferential direction; a first shoulder block 60 having a trapezoidal shape in plan view and formed so as to be arrayed alternately with the center block 40 in the tire circumferential direction; a main groove 30 formed between the center block 40 and the first shoulder block 60 and extending in the tire circumferential direction while bending repeatedly in a tire axis direction; and a second quarter block 70 formed between the center block 40 and the first shoulder block 60 along the main groove 30.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Conventionally, pneumatic tires having a tread with a plurality of grooves extending in the tire circumferential direction or the tire axial direction and a plurality of blocks defined by each groove have been widely known. For example, Patent Documents 1 and 2 disclose pneumatic tires in which a plurality of blocks that are trapezoidal in plan view are formed at the tire axial center of the tread. The pneumatic tires disclosed in Patent Documents 1 and 2 have a tread pattern that includes three main grooves extending straight in the tire circumferential direction and a plurality of trapezoidal blocks defined by each main groove, with the trapezoidal blocks arranged in two rows in the tire circumferential direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-154813 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-154815 Summary of the Invention [Problem to be solved by the invention]

[0004] In pneumatic tires, improving the durability and traction performance of the blocks that make up the tread pattern is an important issue. Furthermore, there is a demand for tires that not only have good performance but also have high design quality.

[0005] An object of the present invention is to provide a pneumatic tire that has a high design quality and in which the blocks that make up the red pattern have excellent durability and traction performance. [Means for solving the problem]

[0006] The pneumatic tire of the present invention is a pneumatic tire having a tread, the tread having: first blocks which are trapezoidal in plan view and formed at a plurality of intervals around the tire circumferential direction at the axial center of the tread; second blocks which are trapezoidal in plan view and formed at the axial ends of the tread so as to alternate with the first blocks around the tire circumferential direction; main grooves which are formed between the first blocks and the second blocks and extend around the tire circumferential direction while repeatedly bending in the axial direction; and third blocks which are formed along the main groove between the first blocks and the second blocks. [Effects of the Invention]

[0007] The pneumatic tire according to the present invention has a novel tread pattern characterized by an aggressive design, and is excellent in both durability and traction performance of the blocks that make up the tread pattern. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a perspective view of a pneumatic tire according to an embodiment, showing the internal structure of the tire. [Figure 2] 1 is a plan view of a pneumatic tire as an example of an embodiment. [Figure 3] FIG. 3 is a diagram showing a part of a cross section taken along the line AA in FIG. 2. [Figure 4] FIG. 4 is an enlarged view of a portion F1 in FIG. 3. [Figure 5] FIG. 4 is an enlarged view of a portion F2 in FIG. 3. [Figure 6] FIG. 3 is a diagram showing a part of a cross section taken along the line BB in FIG. 2. [Figure 7] FIG. 3 is a diagram showing a part of a cross section taken along the line CC in FIG. 2. [Figure 8] FIG. 3 is a cross-sectional view taken along the line DD in FIG. 2. [Figure 9] FIG. 10 is a diagram showing a modified example of a pneumatic tire. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an example of an embodiment of a pneumatic tire according to the present invention will be described in detail with reference to the drawings. The embodiment described below is merely an example, and the present invention is not limited to the following embodiment. Furthermore, the present invention includes configurations obtained by selectively combining the respective components of the multiple embodiments and modified examples described below.

[0010] FIG. 1 is a perspective view of a pneumatic tire 1 as an example of an embodiment. FIG. 1 also illustrates the internal structure of the pneumatic tire 1. As shown in FIG. 1, the pneumatic tire 1 has a tread 10, which is the portion that comes into contact with the road surface. The tread 10 has main grooves 20, 30 that extend in the tire circumferential direction and are formed in an annular shape along the tire circumferential direction. The main groove 20 does not bend in the tire axial direction, but is formed approximately straight along the tire circumferential direction. The main groove 30 extends in the tire circumferential direction while repeatedly bending in the tire axial direction.

[0011] The tread 10 has center blocks 40 (first blocks) that are trapezoidal in plan view, first shoulder blocks 60 (second blocks) that are trapezoidal in plan view and are arranged alternately with the center blocks 40 in the tire circumferential direction, and second quarter blocks 70 (third blocks) that are formed between the center blocks 40 and the first shoulder blocks 60 along the main grooves 30. A plurality of center blocks 40 are formed at the axial center of the tread 10 at intervals in the tire circumferential direction. The tread 10 further has first quarter blocks 50 and second shoulder blocks 80.

[0012] The pneumatic tire 1 is, for example, a tire with a specified mounting direction relative to a vehicle. The tread 10 has a tread pattern that is asymmetrical with respect to the tire equator CL (see FIG. 2 ), and the pneumatic tire 1 is mounted on the vehicle in opposite directions on the right and left sides. The equator CL refers to a line along the tire circumferential direction that passes through the exact center of the tread 10 in the tire axial direction. The pneumatic tire 1 is preferably mounted on a vehicle so that the first shoulder block 60 is located on the inside of the vehicle. For convenience of explanation, the terms "left and right" are used in this specification, and these left and right refer to the left and right when the tire is mounted on the vehicle and viewed in the direction of travel of the vehicle.

[0013] The pneumatic tire 1 includes a pair of sidewalls 11 that bulge outward in the tire axial direction, and a pair of beads 12. The beads 12 are fixed to the rim of a wheel and include a bead core 17 and a bead filler 18. The sidewalls 11 and the beads 12 are formed in an annular shape along the tire circumferential direction, and constitute the side surfaces of the pneumatic tire 1. The sidewalls 11 extend radially from both axial ends of the tread 10.

[0014] The pneumatic tire 1 may have side ribs 13 formed between the ground contact edges E1, E2 of the tread 10 and the portions of the sidewalls 11 that protrude most axially outward. The ground contact edge E1 is the ground contact edge on the first shoulder block 60 side, and the ground contact edge E2 is the ground contact edge on the second shoulder block 80 side. The side ribs 13 protrude axially outward and are formed in an annular shape along the circumferential direction of the tire. The portions of the pneumatic tire 1 from the ground contact edges E1, E2 or their vicinity to the left and right side ribs 13 are also called shoulder or buttress regions.

[0015] The tread 10 and the sidewall 11 are generally made of different types of rubber. The shoulder may be made of the same rubber as the tread 10, or a different rubber. In this specification, the contact edges E1 and E2 are defined as both axial ends of the area that comes into contact with a flat road surface when an unused pneumatic tire 1 is mounted on a standard rim and inflated to a standard internal pressure, and a predetermined load is applied. In the case of passenger car tires, the predetermined load is a load equivalent to 88% of the standard load.

[0016] Here, a "regular rim" is a rim specified by the tire standard, and is a "standard rim" for JATMA and a "measuring rim" for TRA and ETRTO. "Regular internal pressure" is the "maximum air pressure" for JATMA, the maximum value listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" table for TRA, and "INFLATION PRESSURE" for ETRTO. The regular internal pressure is usually 180 kPa for passenger car tires, but 220 kPa for tires labeled "Extra Load" or "Reinforced." "Regular load" is the "maximum load capacity" for JATMA, the maximum value listed in the "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" table for TRA, and "LOAD CAPACITY" for ETRTO. For racing kart tires, the regular load is 392 N.

[0017] The pneumatic tire 1 includes a carcass 14, a belt 15, and an inner liner 16. The carcass 14 is a cord layer coated with rubber, and forms the skeleton of the pneumatic tire 1 that can withstand loads, impacts, air pressure, etc. The belt 15 is a reinforcing band that is placed between the carcass 14 and the rubber that makes up the tread 10. The belt 15 tightly fastens the carcass 14, increasing the rigidity of the pneumatic tire 1. The inner liner 16 is a rubber layer provided on the inner surface of the carcass 14, and maintains the air pressure of the pneumatic tire 1.

[0018] When the pneumatic tire 1 is used as a directional tire with a specified mounting direction on a vehicle, the pneumatic tire 1 preferably has a marking for indicating the mounting direction on the vehicle. The marking for indicating the mounting direction may be an arrow indicating the main rotation direction of the tire, and its configuration is not particularly limited. Generally, symbols called serial numbers are provided on the side of the pneumatic tire 1, and serial numbers may also be used as a marking for indicating the mounting direction.

[0019] The serial number includes information such as a size code, manufacturing date (manufacturing year and week), and manufacturing location (manufacturing factory code). The mounting direction of the pneumatic tire 1 on the vehicle may be specified by providing a serial number only on the side (sidewall 11) of the pneumatic tire 1 facing outward from the vehicle, or by providing different serial numbers on the side facing outward and the side facing inward from the vehicle. A specific example is providing a manufacturing factory code and a size code on both sides of the pneumatic tire 1, and providing the manufacturing year and week only on the side facing outward from the vehicle.

[0020] The tread pattern of the pneumatic tire 1 will be described in detail below with reference to FIG. 2. FIG. 2 is a plan view of the pneumatic tire 1 (tread 10). In FIG. 2, the upper surface of each block is hatched with dots. The upper surface of the block is a surface along the profile surface α (see FIG. 4, etc.), and is the contact surface that comes into contact with the road surface in the range from the contact edge E1 to E2. The profile surface α is a surface along the outer peripheral surface of the tread 10.

[0021] As shown in Figure 2, the tread 10 has two main grooves 20, 30 extending in the tire circumferential direction, a groove-like depression 55 connected to the main groove 20, a secondary groove 75 extending from the tire axial center of the tread 10 toward the tread edge E1, and multiple blocks defined by each groove. The blocks are portions that protrude radially outward in the tire and are generally also called lands. The tread 10 has the following blocks: a center block 40, first quarter blocks 50, first shoulder blocks 60, second quarter blocks 70, and second shoulder blocks 80.

[0022] The main groove 20 is formed between the center block 40 and the second shoulder block 80 on the side of the ground contact edge E2, and extends approximately straight along the tire circumferential direction. In this embodiment, the center blocks 40 and the first quarter blocks 50 are arranged alternately in the tire circumferential direction on the equator CL, with recesses 55 interposed between them. The second shoulder blocks 80 are continuous blocks in the tire circumferential direction, and are formed parallel to the main groove 20 with a constant width. The main groove 20 is formed in the tread 10 so as to separate the center blocks 40 and the first quarter blocks 50 from the second shoulder blocks 80.

[0023] The main groove 30 is formed between the center block 40 and the first shoulder block 60 on the side of the tread edge E1, and extends in the tire circumferential direction while repeatedly bending in the tire axial direction. In this embodiment, a first quarter block 50 and a second quarter block 70 are interposed between the center block 40 and the first shoulder block 60. The first quarter block 50 and the second quarter block 70 are circumferentially continuous blocks, and extend in the tire circumferential direction while bending in the tire axial direction so as to avoid the center block 40 and the first shoulder block 60. The main groove 30 is formed in the tread 10 so as to separate the first quarter block 50 and the second quarter block 70.

[0024] The main groove 20 includes a first portion 23, which is a portion including a plurality of narrow grooves 21 formed at a predetermined interval on the groove bottom, and a second portion 24, which is a portion without the plurality of narrow grooves 21 and is arranged alternately with the first portion 23 in the tire circumferential direction. The plurality of narrow grooves 21 formed at a predetermined interval on the groove bottom has the function of reducing noise generated from the tire while the vehicle is traveling. By arranging the first portions 23 of the main groove 20 at intervals in the tire circumferential direction, the noise reduction effect becomes more pronounced. In addition, the plurality of narrow grooves 21 enhances shadows, improving design and contributing to reducing the amount of rubber used.

[0025] Similar to the main groove 20, the main groove 30 has a first portion 33, which is a portion including a plurality of narrow grooves 31 formed at a predetermined interval at the groove bottom, and a second portion 34 where the plurality of narrow grooves 31 are not present. The main groove 30 is configured such that the first portions 33 and the second portions 34 are alternately arranged in the tire circumferential direction. The first portions 33 contribute to reducing tire noise, improving design, reducing the amount of rubber used, and the like. In this embodiment, the first portions 23 of the main groove 20 and the first portions 33 of the main groove 30 are arranged side by side in the tire axial direction. In this case, for example, the noise reduction effect becomes more pronounced, and the design becomes more cohesive, giving a sophisticated impression.

[0026] The tread 10 is formed with, in order from the ground contact edge E1, first shoulder blocks 60, second quarter blocks 70, first quarter blocks 50, center blocks 40, and second shoulder blocks 80. The center blocks 40 and first shoulder blocks 60 are not continuous in the tire circumferential direction, but are formed in multiples at intervals in the tire circumferential direction. The first quarter blocks 50, second quarter blocks 70, and second shoulder blocks 80 are continuous blocks in the tire circumferential direction and are formed in an annular shape along the tire circumferential direction.

[0027] The center blocks 40 and the first shoulder blocks 60 are trapezoidal blocks in a plan view and are arranged in a row at equal intervals in the tire circumferential direction. The first shoulder blocks 60 are formed at one axial end of the tread 10 on the contact edge E1 side so as to alternate with the center blocks 40 in the tire circumferential direction. Part of the center blocks 40 and part of the first shoulder blocks 60 overlap in the tire circumferential direction, and the first quarter blocks 50, second quarter blocks 70, and main grooves 30 are formed in a zigzag shape between the center blocks 40 and the first shoulder blocks 60.

[0028] The center blocks 40 and the first shoulder blocks 60 are arranged so that the short and long sides, which are the bases of the trapezoids, are aligned in the tire circumferential direction. That is, the hypotenuse of each trapezoid is inclined in the tire circumferential and axial directions. By aligning the trapezoidal blocks in this manner, stable traction performance is achieved. The short and long sides of the trapezoid are also called the upper base and lower base, respectively. Furthermore, the center blocks 40 and the first shoulder blocks 60 are arranged so that the short sides of each trapezoid face the main groove 30 side. This makes it easy to regularly arrange the center blocks 40 and the first shoulder blocks 60 in the tire circumferential direction.

[0029] The center block 40 may be the same size as the first shoulder block 60 or may be larger than the first shoulder block 60, but in this embodiment, it is formed slightly smaller than the first shoulder block 60. As will be described in detail later, a first slope 41, a second slope 42, and third slopes 43 and 44 are formed along the short sides, long sides, and oblique sides of the trapezoid of the center block 40, respectively. Similarly, a slope 61 is formed along the short side of the trapezoid of the first shoulder block 60.

[0030] The center block 40 is surrounded by a groove-shaped depression 55 and the main groove 20. The depression 55 is formed along the slopes 41, 43, and 44 in a roughly U-shape in plan view, and surrounds the center block 40 together with the main groove 20 extending along the slope 42. The slopes of the center block 40 form part of the groove wall and groove bottom of the depression 55 and the main groove 20. A first quarter block 50 is formed outside the depression 55 so as to sandwich the depression 55 with the center block 40.

[0031] Each first quarter block 50 includes a first zone 51 formed along a recess 55 so as to convex toward the ground contact edge E1, and a second zone 52 extending straight in the tire circumferential direction, with the first zones 51 and second zones 52 alternately repeated. The main groove 30 is formed along the first quarter block 50, and a second quarter block 70 is formed facing the first quarter block 50 across the main groove 30. Similar to the first quarter block 50, the second quarter block 70 includes a first zone 71 formed so as to convex toward the ground contact edge E1, and a second zone 72 extending straight in the tire circumferential direction. The first zone 71 is formed between adjacent first shoulder blocks 60 in the tire circumferential direction, extending beyond the ground contact edge E1.

[0032] A secondary groove 75 is formed in the tread 10 along the short sides and oblique sides of the trapezoid of the first shoulder block 60, surrounding three sides of the trapezoid. The secondary groove 75 is formed in a roughly U-shape in plan view and separates the first shoulder block 60 from the second quarter block 70. The secondary groove 75 extends axially outward from the equator CL side of the tread 10, extending beyond the ground contact edge E1. In other words, the trapezoid shape of the first shoulder block 60 is formed by the ground contact edge E1 and the secondary groove 75 connected to the ground contact edge E1.

[0033] Hereinafter, each component of the tread pattern will be described in further detail with reference to Figures 3 to 7 as appropriate in addition to Figure 2. Figures 3, 6, and 7 are partial cross-sections taken along lines AA, BB, and CC, respectively, in Figure 2. Figure 4 is an enlarged view of a portion F1 in Figure 3, and Figure 5 is an enlarged view of a portion F2 in Figure 3.

[0034] [Main groove 20,30] As shown in FIG. 2 , the main grooves 20, 30 are formed on both sides of the equator CL and extend in the tire circumferential direction without intersecting the equator CL. The main grooves 20, 30 are formed to sandwich the center block 40 and the first quarter block 50, which are located at the axial center of the tread 10. As described above, the main groove 20 is formed substantially straight along the tire circumferential direction, while the main groove 30 extends in a zigzag pattern along the tire circumferential direction. The depth of the main grooves 20, 30 is not constant along the tire circumferential direction; for example, shallow and deep portions are regularly repeated. The deepest points of the main grooves 20, 30 are deeper than the deepest points of the recesses 55 and the secondary grooves 75.

[0035] The main groove 20 has a plurality of narrow grooves 21 formed at its bottom, and the first portion 23, which functions to reduce tire noise, is formed slightly wider than the second portion 24. The first portion 23 includes a first region 25a in which the plurality of narrow grooves 21 are formed, and a second region 25b that slopes so as to become gradually deeper toward the first region 25a. The first region 25a is formed adjacent to the second shoulder block 80, and the second region 25b is formed adjacent to the first region 25a on the equator CL side. The first region 25a is formed in a trapezoidal shape in a plan view that is elongated along the main groove 20, with the base of the trapezoid parallel to the tire circumferential direction and the short side facing the equator CL. The inclination angle of the second region 25b with respect to the profile surface α of the tread 10 is, for example, 30° to 70°.

[0036] Each first portion 23 of the main groove 20 is adjacent to the second zone 52 of the first quarter block 50, and each second portion 24 is adjacent to the center block 40. That is, the first portion 23 and the second portion 24 of the main groove 20 are formed along the tire circumferential direction at the same repeating unit length (pitch) as the block at the axial center of the tread 10. Similarly, the first portion 33 and the second portion 34 of the main groove 30 are formed at the same pitch as the block at the axial center of the tread 10.

[0037] The main groove 30 is formed wider in a first portion 33, where a plurality of narrow grooves 31 are formed at the groove bottom, than in a second portion 34. The plurality of narrow grooves 31 are formed across the entire width of the main groove 30, and the first portion 33 is formed as a trapezoid in a plan view as a whole. The trapezoid of the first portion 33 has a base parallel to the tire circumferential direction and a short side facing the equator CL. The second portion 34 is a narrow groove portion extending along the first zone 51 of the first quarter block 50, and is formed in a generally U-shape in a plan view so as to be convex toward the tread edge E1.

[0038] The multiple fine grooves 21, 31 may be formed in a random pattern, for example, with different groove widths and in different directions. However, to achieve a stable noise reduction effect and enhance design, it is preferable that they be formed with a certain degree of regularity. The fine grooves 21, 31 may extend in a direction intersecting the tire axial direction and circumferential direction, but in this embodiment, they are formed along the tire axial direction or circumferential direction. Noise generated by a pneumatic tire 1 is broadly divided into road noise and pattern noise. The fine grooves 21, 31 reduce noise generated by the tire by shifting the frequency band of pattern noise.

[0039] The multiple narrow grooves 21 are formed, for example, parallel to one another, and the first portion 23 has an uneven groove bottom structure formed by alternating narrow grooves 21 and ribs 22 sandwiched between the multiple narrow grooves 21 (the same applies to the narrow grooves 31). The narrow grooves 21, 31 extend in the tire axial direction at the tire circumferential center of the first portion 23, 33, and extend in the tire circumferential direction at both ends of the first portion 23, 33. In this case, the frequency band of pattern noise can be shifted more effectively, resulting in a more pronounced noise reduction effect. The design also gives an impression of novelty and sophistication. The narrow grooves 21, 31 may be bent midway and have a portion extending in the tire circumferential direction and a portion extending in the tire axial direction.

[0040] As shown in FIGS. 3 to 5 , the second portion 24 of the main groove 20 and the second portion 34 of the main groove 30 are arranged side by side in the tire axial direction, separated by the center block 40, the recess 55, and the first quarter block 50. The second portion 24 of the main groove 20 has a slope 26 that gradually deepens toward the tread edge E1, and a side groove 27 that extends along the second shoulder block 80. The side groove 27 extends straight in the tire circumferential direction and, like the second portion 34 of the main groove 30, is formed with a narrow width and deep depth. In this embodiment, the bottom of the side groove 27 and the bottom of the narrow groove 21 are formed to the same depth, forming the deepest portion of the main groove 20. Furthermore, the bottom of the narrow groove 31 of the main groove 30 and the bottom of the second portion 34 are formed to the same depth, forming the deepest portion of the main groove 30.

[0041] The depth of the groove in the second portion 24 gradually deepens from the center block 40 side toward the second shoulder block 80 side. The slope 42 of the center block 40 that forms the groove wall of the second portion 24 is inclined at an angle θ2 with respect to the profile plane α. The slope 26 is formed from the lower end of the slope 42 to the side groove 27, with a width exceeding 50% of the width of the second portion 24. The slope 26 is inclined at an angle θ5 with respect to a plane β that is parallel to the profile plane α. The angle θ5 is smaller than the angle θ2, making the slope 26 more gentle than the slope 42.

[0042] 7, the first portion 23 of the main groove 20 and the first portion 33 of the main groove 30 are arranged side by side in the tire axial direction, separated by the second zone 52 of the first quarter block 50. In the first portions 23, 33, the narrow grooves 21, 31 are formed to the same depth, and the ribs 22, 32 are formed to the same height.

[0043] The tread 10 is provided with a wear indicator (not shown). The wear indicator is a protrusion disposed on the bottom of at least one of the main grooves 20, 30, and serves as an indicator for checking the wear level of the tread rubber. The height of the ribs 22, 32 is preferably equal to or less than the height of the wear indicator, and is particularly preferably equal to the height of the wear indicator. In this case, even if the tread rubber wears down to the height of the wear indicator, the noise reduction function, i.e., the uneven structure of the groove bottom, can be maintained.

[0044] [Center Block 40] As shown in FIG. 2, the center block 40 is a trapezoidal block in a plan view formed at the axial center of the tread 10, with slopes along each side of the trapezoid. The center block 40 may have any shape as long as its top surface (contact surface) is trapezoidal. The trapezoid may be substantially trapezoidal, for example, it may be approximately trapezoidal with rounded corners. The center block 40 is arranged with its short side facing the contact edge E1 and its long side facing the contact edge E2, with the short side and long side parallel to the tire circumferential direction. The long side of the trapezoid of the center block 40 is located closer to the equator CL than the short side.

[0045] The trapezoidal hypotenuse of the center block 40 is inclined with respect to the tire circumferential direction and the axial direction. The two hypotenuses of the trapezoid are inclined away from each other in the tire axial direction from the ground contact edge E1 to the ground contact edge E2, but for example, the inclination angle of each hypotenuse with respect to the tire axial direction is the same, and the lengths of each hypotenuse are also the same. Third inclined surfaces 43, 44 are formed along the trapezoidal hypotenuses at both ends of the center block 40 in the tire circumferential direction. The inclined surfaces 43, 44 are formed to be the same size as each other.

[0046] As described above, the center blocks 40 are arranged in a row in the tire circumferential direction at equal intervals. Here, "equal intervals" includes not only completely equal intervals but also cases where they are considered to be substantially equal intervals. By arranging the center blocks 40 at equal intervals, stable traction performance can be ensured. The distance between adjacent center blocks 40 in the tire circumferential direction (the shortest distance between the slope 43 of the first center block 40 and the slope 44 of the second center block 40) is, for example, longer than the length of the short side of the trapezoid of the center block 40 and shorter than the length of the long side of the trapezoid. An example number of center blocks 40 along the tire circumferential direction is 20 to 30.

[0047] As shown in FIGS. 4 to 6, the inclination angles of the slopes relative to the profile surface α along the outer peripheral surface of the tread 10 gradually increase in the order of the third slopes 43 and 44, the first slope 41, and the second slope 42 (θ3, θ4 < θ1 < θ2). The inclination angles θ3 and θ4 of the slopes 43 and 44 relative to the profile surface α may be different from each other, but are the same in this embodiment. That is, the slopes 43 and 44 facing the tire circumferential direction have a gentle inclination, while the slopes 41 and 42 facing the tire axial direction have a steep inclination. In this case, traction performance can be improved while maintaining good ride comfort. In particular, increasing the inclination angle θ2 of the slope 42 facing outward from the vehicle improves cornering power (CP), for example.

[0048] The inclination angle θ1 of the slope 41 with respect to the profile surface α is preferably 30° to 70°, and more preferably 40° to 60°. The inclination angle θ2 of the slope 42 with respect to the profile surface α is preferably 60° to 80°, and more preferably 65° to 75°. The inclination angle θ3 of the slope 43 with respect to the profile surface α is preferably 20° to 50°, and more preferably 25° to 45°. If the inclination angle of each slope of the center block 40 is within this range, good ride comfort and traction performance can be achieved more effectively.

[0049] [1st Quarter Block 50] As shown in FIG. 2 , the first quarter blocks 50 are formed to surround the center blocks 40 on three sides, with recesses 55 between them, and are continuous in the tire circumferential direction along the main grooves 30. The first zones 51 of the first quarter blocks 50 are formed in the shape of narrow strips with a constant width, and extend along the shorter sides and two oblique sides of the trapezoid of the center blocks 40, separated by the recesses 55. The first zones 51 are formed in a generally U-shape in plan view, convex toward the tread edge E1. The second zones 52 of the first quarter blocks 50 extend in the tire circumferential direction between the center blocks 40, connecting the two first zones 51.

[0050] The height of the first quarter block 50 is preferably equal to or less than the height of the center block 40 and higher than the height of the wear indicator. In this specification, the height of the block means the shortest distance from the reference surface of the tread 10 along the deepest part of the main grooves 20, 30 to the top surface of the block (the same applies to the wear indicator). In this embodiment, the first quarter block 50 is formed at the same height as the center block 40, and the top surface of the first quarter block 50 forms the contact surface that comes into contact with the road surface.

[0051] As shown in Figures 3 and 4, the first zone 51 of the first quarter block 50 is sandwiched between the main groove 30 and the recess 55. By providing the first quarter block 50 between the main groove 30 and the recess 55, the overall block rigidity of the tread 10 can be increased while ensuring good drainage. The contact area is also increased, improving, for example, traction performance and braking performance. The width of the first zone 51 is not particularly limited, but in this embodiment, it is narrower than the width of the recess 55 and wider than the width of the second portion 34 of the main groove 30.

[0052] As shown in Figure 6, on the equator CL of the tread 10, second zones 52 of center blocks 40 and first quarter blocks 50 are alternately arranged along the tire circumferential direction, separated by recesses 55. The length of the center blocks 40 along the tire circumferential direction is longer on the main groove 20 side and shorter on the main groove 30 side, while the length of the second zones 52 along the tire circumferential direction is shorter on the main groove 20 side and longer on the main groove 30 side. Also, on the equator CL, the length of the center blocks 40 along the tire circumferential direction is longer than the length of the second zones 52 along the tire circumferential direction.

[0053] As shown in FIG. 7 , the second zone 52 of the first quarter block 50 is sandwiched on both sides in the tire axial direction by the first portions 23, 33, where the main grooves 20, 30 are wider. The distance between the main grooves 20, 30 is minimized in the first portions 23, 33. The second zone 52 is formed wider than the first portions 23, 33. In this case, the block rigidity of the tread 10 is increased in the area where the two main grooves are closer to each other, effectively improving the durability of the blocks. Furthermore, the second zone 52 is reinforced by the ribs 22, 32 formed in the first portions 23, 33.

[0054] [Recess 55] As shown in FIG. 2 , the recess 55 is formed between the center block 40 and the first quarter block 50, surrounding the center block 40 on three sides like a moat. The recess 55 extends like a groove along the short sides and oblique sides of the trapezoid of the center block 40, forming a roughly U-shape in plan view. Both ends of the recess 55 on the ground-contact edge E2 side are connected to the main groove 20, allowing rainwater and other water around the center block 40 to flow into the main groove 20. The recess 55 is wider along the slopes than along the short sides of the trapezoid of the center block 40, and the width gradually increases as it approaches the main groove 20. This improves drainage at the axial center of the tread 10.

[0055] The recesses 55 extend from the main groove 20 toward the ground contact edge E1 and are formed in the tire circumferential direction to positions that overlap with the secondary grooves 75. The secondary grooves 75 are formed at one axial end of the tread 10 at intervals in the tire circumferential direction, and the recesses 55 are formed so as to enter between the secondary grooves 75 that are adjacent in the tire circumferential direction. By arranging the recesses 55 and the secondary grooves 75 so that they overlap in the tire circumferential direction, drainage can be more effectively improved.

[0056] As shown in Figures 3, 4, and 6, the depth of the recess 55 is shallower than the main grooves 20 and 30 and gradually deepens as it approaches the main groove 20. In this case, drainage can be improved while ensuring the durability of the center block 40 and the first quarter block 50. The widthwise depth of the recess 55 gradually deepens along the trapezoidal slope of the center block 40, reaching its deepest point at the bottom end of the slope. It is preferable that the shallowest portion of the recess 55 be deeper than the top surface of the wear indicator.

[0057] [First Shoulder Block 60] As shown in FIG. 2, the first shoulder block 60 is a trapezoidal block formed at one axial end of the tread 10 in a plan view, and has a slope 61 along at least its short side. The pneumatic tire 1 is preferably mounted on a vehicle so that the first shoulder block 60 is located on the inside of the vehicle. The first shoulder block 60 only needs to have a shape whose contact patch is recognized as substantially trapezoidal. The short sides and oblique sides of the trapezoid of the first shoulder block 60 are formed by the secondary groove 75, and the contact edge E1 is the long side of the trapezoid.

[0058] The first shoulder blocks 60 are arranged with the short sides of the trapezoids facing the equator CL and the short and long sides parallel to the tire circumferential direction. As with the center blocks 40, the hypotenuses of the trapezoids of the first shoulder blocks 60 are inclined with respect to the tire circumferential direction and the axial direction. The two hypotenuses of the trapezoid are inclined away from each other in the axial direction from the equator CL toward the tread edge E1. However, for example, the inclination angle of each hypotenuse with respect to the axial direction is the same, and the lengths of each hypotenuse are also the same. A slope may be formed along the hypotenuse of the trapezoid of the first shoulder blocks 60.

[0059] The first shoulder blocks 60 are formed between adjacent center blocks 40 in the tire circumferential direction, spanning positions that overlap with the center blocks 40 in the tire circumferential direction. In this case, the block rigidity of the tread 10 as a whole can be increased, achieving stable block durability and traction performance. The ground contact area of ​​the first shoulder blocks 60 may be larger than that of the center blocks 40, for example, 1.1 to 1.5 times. The first shoulder blocks 60 are formed in the same number and at the same pitch as the center blocks 40 in the tire circumferential direction.

[0060] As shown in FIG. 7 , the slope 61 along the short side of the trapezoid of the first shoulder block 60 may be formed to a depth equal to or greater than the depth of the ribs 22, 32 of the main grooves 20, 30. The slope 61 forms the groove wall and groove bottom of the secondary groove 75, which is deepest at the bottom end of the slope 61. The inclination angle of the slope 61 with respect to the profile plane α may be greater than the inclination angle of the second region 25b of the main groove 20 and less than the inclination angle θ2 of the slope 42 of the center block 40. Increasing the inclination angle of the slope 61 facing outward from the vehicle can improve, for example, the CP characteristics.

[0061] [Second Quarter Block 70] As shown in FIG. 2 , the second quarter blocks 70 are formed to surround the first shoulder blocks 60 on three sides, with the secondary grooves 75 separating them. Like the first quarter blocks 50, the second quarter blocks 70 are formed along the main grooves 30 and are continuous in the tire circumferential direction. The first zones 71 of the second quarter blocks 70 extend from the equator CL toward the ground contact edge E1, between the first shoulder blocks 60 adjacent in the tire circumferential direction, and beyond the ground contact edge E1. The second zones 72 of the second quarter blocks 70 extend in the tire circumferential direction between the center blocks 40, connecting the two first zones 71.

[0062] The second quarter blocks 70 are formed to the same height as the center blocks 40 and first shoulder blocks 60, and the top surfaces of the second quarter blocks 70 form the contact surface that comes into contact with the road surface. The first zone 71 of the second quarter blocks 70 includes a first portion that gradually expands in the circumferential direction of the tire from the contact edge E1 side toward the equator CL side, and a second portion that branches off from the first portion along the main groove 30.

[0063] As shown in FIG. 7 , the second zone 72 of the second quarter block 70 is sandwiched between the first portion 33 of the main groove 30 and the secondary groove 75, and is formed parallel to the second zone 52 of the first quarter block 50. The width of the second zone 72 is, for example, equal to the width of the secondary groove 75 and narrower than the width of the first portion 33. In this embodiment, the second zones 52 and 72 are connected by the rib 32 of the first portion 33. In addition, the sidewalls of the second zone 72, which form the groove wall and groove bottom of the secondary groove 75, are gently inclined toward the first shoulder block 60. This ensures high block durability even in the wider groove width portion.

[0064] [minor groove 75] As shown in FIG. 2 , the secondary grooves 75 extend along the short sides and oblique sides of the trapezoid of the first shoulder block 60 and are formed in a roughly U-shape in plan view. The secondary grooves 75 are formed wider between the short sides of the trapezoid and the second quarter block 70 than in other portions. The secondary grooves 75 are formed at equal intervals around the tire circumference and are not connected around the tire circumference or to the main grooves 30. The secondary grooves 75 extend from the tire axial center of the tread 10 to a position beyond the contact edge E1, allowing rainwater and the like to be easily drained from the center. This ensures high block rigidity while achieving good drainage.

[0065] In this embodiment, as described above, portions of the recesses 55 and portions of the sub-grooves 75 overlap in the tire circumferential direction, and the recesses 55 and the sub-grooves 75 are formed so as to be alternately aligned in the tire circumferential direction. That is, the recesses 55 and the sub-grooves 75 are arranged in a staggered pattern along the tire circumferential direction, similar to the arrangement of the center blocks 40 and the first shoulder blocks 60. Furthermore, the main grooves 30 are formed between the recesses 55 and the sub-grooves 75, with the first quarter blocks 50 and the first shoulder blocks 60 interposed therebetween. This makes it easy to achieve both high block rigidity and good drainage.

[0066] As shown in Figure 7, in the wider portion of the secondary groove 75, i.e., the portion located between the short side of the trapezoid of the first shoulder block 60 and the second quarter block 70, slopes are formed from both sides of the width of the secondary groove 75 toward the groove bottom. These slopes are slopes 61 formed along the short side of the first shoulder block 60 and the side wall of the second zone 72 of the second quarter block 70. The slopes 61 have a larger inclination angle with respect to the profile plane α than the side wall of the second zone 72.

[0067] [Second Shoulder Block 80] As shown in FIG. 2, the second shoulder blocks 80 are formed at the other axial end of the tread 10, extending from a position adjacent to the main groove 20 to a position beyond the contact edge E2. Although FIG. 2 does not show grooves in the second shoulder blocks 80, for example, grooves extending in the axial direction of the tire may be formed. The shape of the grooves formed in the second shoulder blocks 80 is not particularly limited. As described above, the second shoulder blocks 80 are formed with a constant width parallel to the main groove 20.

[0068] 8 shows a part of a tire circumferential cross section (cross section taken along line DD in FIG. 2) of the first portion 23 of the main groove 20. The cross-sectional structure of the first portion 33 of the main groove 30 is also similar to the cross-sectional structure shown in FIG.

[0069] As shown in Figure 8, the first portion 23 (first region 25a) of the main groove 20 has multiple narrow grooves 21 formed at a predetermined interval at the groove bottom, and the narrow grooves 21 and ribs 22 are arranged alternately to form an uneven groove bottom shape. The multiple narrow grooves 21 formed at a predetermined interval shift the noise frequency band, reducing noise generated by the tire, and also enhance the shadows in the design, giving a more sophisticated impression. Furthermore, this contributes to reducing the amount of rubber used.

[0070] An example of the depth Dp of the narrow groove 21 is 0.5 mm to 2 mm. In other words, the depth Dp of the narrow groove 21 is the height of the rib 22 from the bottom of the narrow groove 21. The upper surface of the rib 22 is formed to a depth approximately equal to that of the slope 26 of the second portion 24 of the main groove 20, for example, and can be considered as the first groove bottom of the main groove 20. The upper surface of the rib 22 may be inclined like the second region 25b, but in this embodiment, it is formed parallel to the profile surface α. The bottom of the narrow groove 21 is approximately equal to the depth of the bottom of the side groove 27 of the second portion 24, and can be considered as the second groove bottom. In other words, the main groove 20 is formed to a depth of at least two stages.

[0071] The widths of the multiple narrow grooves 21 may be different from one another, but in this embodiment, each narrow groove 21 is formed with the same width W. An example of the width of the narrow groove 21 is 0.1 mm to 0.5 mm. The width of the rib 22 may be equal to or less than the width W of the narrow groove 21, but in this embodiment, it is larger than the width W of the narrow groove 21. The rib 22 may include a first rib 22a having a width W1 and a second rib 22b having a width W2, or may include three or more types of ribs having different widths. Alternatively, the widths of the ribs 22 may be the same. From the standpoint of design, block durability, and the like, a suitable example of a groove bottom uneven structure is a structure in which the intervals between the narrow grooves 21 are uniform (the width of the ribs 22 is constant) and the width of the ribs 22 is larger than the width of the narrow grooves 21.

[0072] The side walls of the rib 22 (groove walls of the narrow groove 21) are inclined so that the width increases toward the lower end of the rib 22. The inclination angles θa and θb of the side walls with respect to an imaginary line perpendicular to the bottom of the narrow groove 21 are, for example, 1° or more, and preferably 1° to 5°. The lower end portions of the side walls of the rib 22 may be curved toward the inside of the rib 22. When the rib 22 has such a side wall shape, it can be easily released from the mold during tire manufacturing. The multiple narrow grooves 21 may be formed at intervals equivalent to at least 10% of the groove width from the side walls of the main groove 20. In this case, the load transmitted from the block to the rib 22 is reduced, and the stability of the groove bottom uneven shape is improved.

[0073] As described above, the pneumatic tire 1 has a highly aesthetic design and the blocks that make up the tread pattern have excellent durability and traction performance. The pneumatic tire 1 has a tread pattern in which trapezoidal center blocks 40 and first shoulder blocks 60 in a plan view are arranged alternately in the circumferential direction of the tire, with main grooves 30 and second quarter blocks 70 extending in a zigzag pattern interposed between them, resulting in an innovative and sophisticated design.

[0074] The tread pattern of the pneumatic tire 1 also has first quarter blocks 50 formed to surround three sides of the center block 40, and groove-like depressions 55 formed between the center block 40 and the first quarter blocks 50. The tread pattern of the pneumatic tire 1 has an aggressive and innovative design, while the blocks are highly durable and achieve excellent traction performance. The pneumatic tire 1 also has good drainage and excellent wet grip performance, for example.

[0075] The above-described embodiment can be appropriately modified in design without impairing the object of the present invention. As shown in Fig. 9, the tread pattern according to the present invention may have main grooves 20x, 30x that do not have a region (first portion) where a plurality of fine grooves are arranged at a predetermined interval at the groove bottom.

[0076] The depth of the main grooves 20x, 30x may be constant along the tire circumferential direction. The main groove 20x does not have to have a side groove 27 formed along the second shoulder block 80. In the configuration illustrated in FIG. 2, for example, the center block 40 and the first shoulder block 60 may be moved toward the second shoulder block 80, so that the width of the main groove 30x is approximately the same as or greater than the width of the main groove 20x. The tread may have one main groove 30, or three or more main grooves.

[0077] In the tread pattern according to the present invention, the configuration of the first quarter blocks 50 and recesses 55 surrounding the center block 40 on three sides is useful for improving the durability and traction performance of the blocks, as described above. However, the object of the present invention can be achieved by changing the configuration of the blocks other than the center block 40, first shoulder blocks 60, and second quarter blocks 70. [Explanation of symbols]

[0078] 1 pneumatic tire, 10 tread, 11 sidewall, 12 bead, 13 side rib, 14 carcass, 15 belt, 16 inner liner, 17 bead core, 18 bead filler, 20, 30 main groove, 21, 31 narrow groove, 22, 32 rib, 22a first rib, 22b second rib, 23, 33 first portion, 24, 34 second portion, 25a first region, 25b second region, 26, 41, 42, 43, 44, 61 slope, 27 side groove, 40 center block, 50 first quarter block, 51, 71 first zone, 52, 72 second zone, 55 recess, 60 first shoulder block, 70 second quarter block, 75 secondary groove, 80 second shoulder block, CL equator, E1, E2 ground contact edge

Claims

1. A pneumatic tire having a tread, The tread is a plurality of first blocks each having a trapezoidal shape in a plan view and spaced apart from one another in the tire circumferential direction at the tire axial center of the tread; second blocks each having a trapezoidal shape in a plan view and formed at an axial end of the tread so as to alternate with the first blocks in the tire circumferential direction; a main groove formed between the first block and the second block, the main groove extending in the tire circumferential direction while repeatedly bending in the tire axial direction; a third block formed along the main groove between the first block and the second block; a fourth block formed continuously in an annular shape in the tire circumferential direction between the first block and the main groove; A pneumatic tire having

2. The pneumatic tire according to claim 1 , wherein the first block and the second block have trapezoidal short sides and long sides aligned in the tire circumferential direction, and the short sides are disposed on the main groove side.

3. The pneumatic tire according to claim 1 or 2, wherein the tread has a sub-groove formed along a short side and an oblique side of the trapezoid of the second block so as to surround three sides of the trapezoid.

4. The pneumatic tire according to claim 3 , wherein the auxiliary groove is formed wider between the short side of the second block and the third block than in other portions.

5. The pneumatic tire according to claim 4 , wherein the widened portion of the sub-groove has slopes formed from both sides in the width direction of the sub-groove toward the groove bottom.

6. 6. The pneumatic tire according to claim 1, wherein the tread has a groove-like depression formed between the first block and the fourth block so as to surround three sides of the trapezoid of the first block.

Images