Motorcycle tires

Abstract

To provide a motorcycle tire that enhances traction performance while suppressing a decrease in slide control performance during cornering. [Solution] This is a motorcycle tire 1. The first crown block 6 has a V-shaped leading edge 11. The leading edge 11 is inclined at an angle α1 of 10 degrees or more. The total number of first crown blocks 6 is 30% or more of the total number of crown blocks 4. The maximum length W1 in the tire axial direction of the first tread shape 6a is 60% to 70% of the tread width. The second tread shape 7a of the second crown block 7 has a maximum length WC in the tire axial direction that is smaller than the first tread shape 6a of the first crown block 6.

Description

Technical Field

[0001] The present invention relates to a tire for a motorcycle.

Background Art

[0002] Patent Document 1 below describes a pneumatic tire for a motorcycle for rough terrain travel provided with a plurality of blocks. The plurality of blocks include a plurality of crown blocks and a plurality of middle blocks. The crown block has a horizontally long block body and a convex portion protruding from the block body toward the trailing side in the rotational direction. In a block group consisting of one of the crown blocks and a pair of the middle blocks arranged on both sides thereof closest to this crown block, the center of gravity of the crown block is located on the trailing side in the rotational direction rather than each of the middle blocks.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Generally, in a tire for a motorcycle for rough terrain travel, when traveling straight, it is necessary to shear mud or the like on the road surface with the leading edge of the block in the tire rotational direction to obtain propulsion force (traction). However, when turning, since it is necessary to roll the motorcycle, simply increasing the traction causes a slide during the roll during turning, making it difficult to control the attitude of the motorcycle.

[0005] This invention was devised in view of the above-described circumstances, and its main objective is to provide a motorcycle tire that can improve traction performance while suppressing a decrease in slide control performance during cornering. [Means for solving the problem]

[0006] The present invention relates to a motorcycle tire for off-road riding having a tread portion with a specified tire rotation direction, wherein in a tread unfolded diagram, the tread portion includes a pair of tread ends, a tread width which is the distance in the tire axial direction between the pair of tread ends, a crown region which is a region of 40% of the tread width centered on the tire equator, and a plurality of blocks, wherein the plurality of blocks include a plurality of crown blocks whose center of gravity of the tread surface is located in the crown region, and the crown blocks include a plurality of first crown blocks having a first tread surface shape and a plurality of second crown blocks having a second tread surface shape A motorcycle tire comprising the following: the first tread shape is a V shape in which at least the leading edge in the tire rotation direction is inclined toward the leading edge in the tire rotation direction from the center in the tire axial direction toward both outward sides; the second tread shape has a maximum length WC in the tire axial direction that is smaller than that of the first tread shape; the total number of the first crown blocks is 30% or more of the total number of the crown blocks; the leading edge of the first tread shape is inclined at an angle of 10 degrees or more with respect to the tire axial direction; and the maximum length W1 in the tire axial direction of the first tread shape is 60% to 70% of the tread width. [Effects of the Invention]

[0007] By adopting the above-described configuration, the motorcycle tire of the present invention can enhance traction performance while suppressing a decrease in slide control performance. [Brief explanation of the drawing]

[0008] [Figure 1] This is a tread diagram showing one embodiment of the motorcycle tire of the present invention. [Figure 2]This is a cross-sectional view along line AA in Figure 1. [Figure 3] This is an enlarged view of Figure 1. [Figure 4] This is a cross-sectional view of line BB in Figure 3. [Figure 5] This is an enlarged view of Figure 1. [Figure 6] Figure 5 is a cross-sectional view of the CC line. [Figure 7] This is a tread diagram of another embodiment. [Modes for carrying out the invention]

[0009] Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. The drawings contain exaggerations and representations that differ from the actual structural dimensional ratios in order to aid in understanding the content of the present invention. Furthermore, the same or common elements are denoted by the same reference numerals throughout each embodiment, and redundant explanations may be omitted. Moreover, the specific configurations shown in the embodiments and drawings are for the purpose of understanding the content of the present invention. For this reason, the present invention is not limited to the specific configurations shown in the drawings.

[0010] Figure 1 is an exploded view (tread exploded view) of the tread portion 2 of the motorcycle tire 1 for off-road driving (hereinafter sometimes simply referred to as "tire") of this embodiment. Figure 2 is a cross-sectional view taken along line AA of Figure 1. Figure 2 shows the tire meridian cross-section of tire 1. Figures 1 and 2 also show tire 1 in its normal state. Here, "normal state" means that, in the case of tires for which various standards are defined, the tire is mounted on a normal rim (not shown), filled with the normal internal pressure, and is under no load. In the case of tires for which various standards are not defined, the normal state means a standard usage state according to the intended use of the tire, and is under no load. In this specification, unless otherwise specified, the dimensions of each part are values ​​measured in the normal state.

[0011] A "standard rim" is the rim defined for each tire within the standards system that the tire is based on. For example, it is the "standard rim" for JATMA, the "Design Rim" for TRA, and the "Measuring Rim" for ETRTO.

[0012] "Regular internal pressure" refers to the air pressure specified for each tire by each standard within the tire standard system, including the standard on which the tire is based. For JATMA, it is the "maximum air pressure," for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO, it is the "INFLATION PRESSURE."

[0013] The tire 1 of this embodiment is suitably used, for example, as a tire for motocross competitions. The tire 1 of this embodiment is suitably used, for example, as a rear tire for a motocross vehicle. However, the tire 1 is not limited to motocross competitions.

[0014] As shown in Figure 1 or Figure 2, the tread portion 2 of this embodiment has an outer surface that is curved in a convex arc shape outward in the tire radial direction in the tire meridian cross-section. Furthermore, the tread portion 2 has a specified tire rotation direction (hereinafter sometimes simply referred to as "rotation direction") R.

[0015] In the tread development diagram, the tread portion 2 in this embodiment includes a pair of tread ends Te and a tread width TW which is the distance between the pair of tread ends Te in the tire axial direction.

[0016] Furthermore, the tread section 2 includes a crown region Cr that is 40% of the tread width TW, centered on the tire equator C. The crown region Cr is mainly the area that makes contact with the road surface during straight-line driving, and is the area that does not make contact with the road surface during cornering with a large camber angle.

[0017] Furthermore, the tread portion 2 includes a plurality of blocks 3. The plurality of blocks 3 includes a plurality of crown blocks 4. Each crown block 4 is a block in which the center of gravity (centroid) 4c of its tread surface 4a is located in the crown region Cr. Note that the tread edge Te means the outer edge in the tire axial direction of the block located most outside in the tire axial direction among the blocks arranged in the tread portion 2.

[0018] The crown block 4 includes a plurality of first crown blocks 6 having a first tread shape 6a and a plurality of second crown blocks 7 having a second tread shape 7a. The first crown block 6 and the second crown block 7 have different tread shapes.

[0019] The first tread shape 6a is a V shape in which at least the leading edge 11 in the rotational direction R inclines toward the leading side in the rotational direction R from the center side in the tire axial direction toward both outer sides. Also, the leading edge 11 of the first tread shape 6a inclines at an angle α1 of 10 degrees or more with respect to the tire axial direction. Such a leading edge 11 increases the scraping force against the mud and effectively enhances the shear force in the crown region Cr where a relatively large ground contact pressure occurs, thereby improving the traction performance. Note that the angle α1 of the leading edge 11 is specified by a virtual straight line a1 (shown in FIG. 3). As shown in FIG. 3, the virtual straight line a1 is a straight line connecting an intersection point s1 and a first point s2 on the leading edge 11 where the angle α1 is the largest. The intersection point s1 is a point where a tire circumferential direction line c1 passing through the center of gravity 6c of the first tread shape 6a intersects the leading edge 11. Note that the angles of the other leading edges described later are specified in the same manner. Also, in this specification, the angle of each leading edge and the angle of each trailing edge described later are positive when they incline toward the leading side in the rotational direction R from the tire equator C side toward the tread edge Te side.

[0020] Also, as shown in FIG. 1, the total number of the first crown blocks 6 is 30% or more of the total number of the crown blocks 4. For this reason, the traction performance is sufficiently enhanced by the first crown blocks 6.

[0021] The maximum length W1 of the first crown block 6 in the axial direction of the tire should be set within the range of 60% to 70% of the tread width TW. Since the maximum length W1 of the first crown block 6 is 60% or more, the scratching force against mud can be greatly increased. To further increase this scratching force, the maximum length W1 of the first crown block 6 is preferably 62% or more of the tread width TW, and more preferably 64% or more. Since the maximum length W1 of the first crown block 6 is 70% or less, the lateral rigidity of the first crown block 6 is prevented from becoming excessively large, and the slide control performance is maintained at a high level. In order to effectively exert this effect, the maximum length W1 of the first crown block 6 is preferably 68% or less of the tread width TW, and more preferably 66% or less, in combination with any of the lower limits above. As an example, the maximum length W1 of the first crown block 6 is preferably 62% to 68% of the tread width TW, and more preferably 64% to 66%.

[0022] Furthermore, the second tread shape 7a of the second crown block 7 has a smaller maximum length WC in the tire axial direction than the first tread shape 6a. Such a second tread shape 7a moderately reduces the lateral stiffness of the crown region Cr.

[0023] Furthermore, the angle α1 of the leading edge 11 of the first tread shape 6a is preferably 45 degrees or less. This suppresses an excessive increase in shear force in the crown region Cr, and maintains high slide control performance. To improve traction performance while maintaining high slide control performance, the angle α1 is preferably 15 degrees or more, more preferably 20 degrees or more, more preferably 35 degrees or less, and even more preferably 25 degrees or less.

[0024] Furthermore, it is desirable that the total number of first crown blocks 6 be 70% or less of the total number of crown blocks 4. This prevents the shear force on the leading edge 11 of the first crown blocks 6 from becoming excessively large, and maintains high slide control performance. From this viewpoint, it is desirable that the total number of first crown blocks 6 be 40% or more of the total number of crown blocks 4, and more preferably 60% or less. In this embodiment, the total number of first crown blocks 6 is 50% of the total number of crown blocks 4. In this embodiment, the first crown blocks 6 and the second crown blocks 7 are arranged alternately in the circumferential direction of the tire.

[0025] As shown in Figure 2, in this specification, a block 3 is defined as a series of raised structures with a height H of 1.5 mm or more from the tread reference surface 2a. The tread reference surface 2a is a surface formed by smoothly connecting the outer surfaces Se of a pair of sidewall portions Sw, and is the surface from which the block 3 is raised. In this embodiment, the tread reference surface 2a is formed by a first circular arc Ra with radius R1 passing through the tire equator C, and a pair of second circular arcs Rb with radius R2 smaller than radius R1, which are smoothly connected to the first circular arc Ra. The tread edge Te is located on the normal to the second circular arcs Rb. Furthermore, each of the aforementioned "tread surfaces" is the outer surface of the block 3 excluding the wall surface 3w of the block 3. The wall surface 3w is a surface that extends from the tread reference surface 2a in the direction of the raised height. Figure 2 shows the wall surface 5w of the middle block 5, which will be described later, and the wall surface 9w of the shoulder block 9, which will be described later. The terms "tread" in the first tread shape 6a and the second tread shape 7a (shown in Figure 1) have the same meaning as the aforementioned tread. In this specification, each "edge" refers to the outer edge of each tread that appears in the tread development diagram.

[0026] Figure 3 is an enlarged view of Figure 1. As shown in Figure 3, the first crown block 6 includes a front-end edge 11, a rear-end edge 12 that extends in the tire axial direction, spaced apart from the front-end edge 11 in the tire circumferential direction, and a pair of connecting edges 13 that connect the front-end edge 11 and the rear-end edge 12. The front-end edge 11 extends, for example, in a zigzag shape. The intersection point s1 of the front-end edge 11 is located on the tire equator C. The rear-end edge 12 extends, for example, in a ridge shape with a larger amplitude than the front-end edge 11. In this embodiment, the rear-end edge 12 extends in a V-shape. The connecting edges 13 extend, for example, parallel to the tire circumferential direction.

[0027] The angle α2 of the rear-end edge 12 with respect to the tire axis is preferably 10 degrees or more, more preferably 15 degrees or more, preferably 45 degrees or less, and more preferably 35 degrees or less. Also, the absolute value of the difference between the angle α1 of the front-end edge 11 and the angle α2 of the rear-end edge 12, |α1-α2|, is preferably 20 degrees or less, and more preferably 10 degrees or less. The angle α2 is determined by a virtual straight line a2 connecting the intersection point s3 of the tire circumferential line c1 passing through the centroid 6c of the first tread shape 6a with the rear-end edge 12, and a second point s4 on the rear-end edge 12 where the angle α2 is largest. The angles of the other rear-end edges, which will be described later, are similar. In this embodiment, the centroid 6c of the first tread shape 6a is located on the tire equator C.

[0028] As shown in Figure 2 or Figure 3, the first tread shape 6a of the first crown block 6 includes a first tread portion 15, a second tread portion 16, and a third tread portion 17. The first tread portion 15 is formed with a first ridge height H1. The second tread portion 16 is formed with a second ridge height H2 which is smaller than the first ridge height H1. The third tread portion 17 is formed with a third ridge height H3 which is larger than the first ridge height H1. The first tread portion 15 also includes a central portion 18 located on the tire equator C, a pair of outer portions 19 located at both ends of the first tread shape 6a in the tire axial direction, and a rear-mount portion 20 positioned on the rear-mount side in the rotational direction R relative to the central portion 18. The second tread portion 16 includes a pair of first portions 21, a pair of second portions 22, and a plurality of third portions 23. Each first portion 21 is located between the central portion 18 and each outer portion 19 and is formed in a rectangular shape in the tread development diagram. Each second portion 22 is positioned between the central portion 18 and the rear contact portion 20 and is formed in a U-shape in the tread development diagram. The third portion 23 is connected to the outer portion 19 and is formed in an L-shape in the tread development diagram. The third portion 23 is positioned on the rear contact side of the outer portion 19 in the rotational direction R. The second ridge height H2a of the first portion 21 is formed to be smaller than, for example, the second ridge height H2b of the second portion 22 and the second ridge height H2c of the third portion 23. The second ridge height H2b of the second portion 22 is set to be the same as, for example, the second ridge height H2c of the third portion 23. The third tread portion 17 is connected to each third portion 23 and is formed in a rectangular shape in the tread development diagram. The rear landing portion 20 and the third tread portion 17 protrude further from the virtual straight line a2 towards the rear landing side in the rotational direction R.

[0029] The first elevation height H1 is preferably 10 mm or more, more preferably 12 mm or more, preferably 18 mm or less, and even more preferably 16 mm or less. The second elevation height H2a of the first part 21 is preferably 1.5 mm or more, more preferably 2.0 mm or more, preferably 4.0 mm or less, and even more preferably 3.0 mm or less. The difference (H1-H2b) or (H1-H2c) between the second elevation height H2b of the second part 22 and the second elevation height H2c of the third part 23 and the first elevation height H1 is preferably 1.0 mm or more, more preferably 1.5 mm or more, preferably 3.0 mm or less, and even more preferably 2.5 mm or less. The difference (H3-H1) between the third elevation height H3 and the first elevation height H1 is preferably 0.5 mm or more, more preferably 1.0 mm or more, preferably 2.0 mm or less, and even more preferably 1.5 mm or less.

[0030] Figure 4 is a cross-sectional view along line BB in Figure 3. As shown in Figure 4, the first crown block 6 includes a front-end wall surface 25 extending from the front-end edge 11 to the tread reference surface 2a, and a rear-end wall surface 26 extending from the rear-end edge 12 to the tread reference surface 2a. The front-end wall surface 25 includes a first wall surface portion 25a extending from the front-end edge 11 toward the tread reference surface 2a toward the rear-end side in the rotational direction R, and a second wall surface portion 25b connected to the first wall surface portion 25a and extending toward the front-end side in the rotational direction R to the tread reference surface 2a. In this embodiment, the rear-end wall surface 26 extends continuously toward the rear-end side in the rotational direction R from the rear-end edge 12 to the tread reference surface 2a. Thus, the first crown block 6 has an acute-angled corner portion 11c of the leading edge 11 and an obtuse-angled corner portion 12c of the trailing edge 12. Such a first crown block 6 can increase the amount of mud scraped from the road surface at the leading wall surface 25. The first wall surface portion 25a includes, for example, a straight section m that extends in a straight line. The second wall surface portion 25b includes an arc-shaped section n that extends in an arc shape. The trailing wall surface 26 includes a straight section m and an arc-shaped section n.

[0031] Figure 5 is an enlarged view of Figure 1. As shown in Figure 5, the second crown block 7 includes a leading edge 31, a trailing edge 32, and a pair of connecting edges 33. The leading edge 31 is, for example, V-shaped, inclined toward the leading side in the rotational direction R from the center in the tire axial direction toward both outward sides. The trailing edge 32 extends, for example, linearly in the tire axial direction. In this embodiment, the trailing edge 32 extends continuously parallel to the tire axial direction. Each connecting edge 33 extends, for example, linearly. Each connecting edge 33 is inclined toward the leading side in the rotational direction R toward the outward side in the tire axial direction. In addition, the center of gravity 7c of the second tread shape 7a is located on the tire equator C in this embodiment.

[0032] The angle α3 of the leading edge 31 with respect to the tire axis and the angle α4 of the rear edge 32 with respect to the tire axis are each formed to be, for example, less than 10 degrees. Since such a second crown block 7 has high lateral rigidity, it can maintain high slide control performance. The angle α3 is, for example, 4 to 8 degrees. The angle α4 is, for example, 0 degrees.

[0033] As shown in Figure 4 or Figure 5, the second tread shape 7a of the second crown block 7 includes a fourth tread portion 34 with a fourth ridge height H4 and a fifth tread portion 35 with a fifth ridge height H5 that is smaller than the fourth ridge height H4. The fourth tread portion 34 includes a central portion 36 located at the tire equator C and a pair of outer portions 37 located on both sides of the central portion 36 in the tire axial direction. The fifth tread portion 35 is positioned between the central portion 36 and each of the outer portions 37. In the tread development diagram, the central portion 36, each of the outer portions 37, and the fifth tread portion 35 are formed in a rectangular shape.

[0034] In this embodiment, the fourth elevation height H4 is the same as the first elevation height H1. The difference between the fourth elevation height H4 and the fifth elevation height H5 (H4-H5) is preferably 3 mm or more, more preferably 4 mm or more, preferably 9 mm or less, and more preferably 8 mm or less. Such a second crown block 7 ensures shear force at the fourth tread portion 34 while suppressing a decrease in lateral rigidity.

[0035] The maximum width WC (shown in Figure 1) of the second crown block 7 is preferably 50% or more of the maximum length W1 (shown in Figure 1) of the first crown block 6, more preferably 55% or more, 70% or less, and even more preferably 65% ​​or less. Since such a second crown block 7 has appropriate lateral rigidity, it helps to improve traction performance while suppressing a decrease in slide control performance during cornering.

[0036] The second crown block 7 includes, for example, a first-contact side wall surface 38 extending from the first-contact side edge 31 to the tread reference surface 2a, and a second-contact side wall surface 39 extending from the second-contact side edge 32 to the tread reference surface 2a. In this embodiment, the first-contact side wall surface 38 is continuously inclined toward the first contact side in the rotational direction R from the first-contact side edge 31 to the tread reference surface 2a. In this embodiment, the second-contact side wall surface 39 is continuously inclined toward the second contact side in the rotational direction R from the second-contact side edge 32 to the tread reference surface 2a. The corner portion 31c of the first-contact side edge 31 and the corner portion 32c of the second-contact side edge 32 are each formed at an obtuse angle. In this embodiment, the first-contact side wall surface 38 and the second-contact side wall surface 39 each include a straight portion m and an arc portion n.

[0037] As shown in Figure 1 or Figure 5, the tread portion 2 further includes a shoulder region Sh and a middle region Mi. The shoulder region Sh is the area extending 10% of the tread width TW from each tread edge Te. The middle region Mi is the area between the crown region Cr and each shoulder region Sh. The shoulder region Sh is the area that does not make contact with the road surface during straight-line driving, but makes contact with the road surface during cornering driving with a large camber angle. The middle region Mi is the area that does not make contact with the road surface during straight-line driving, but makes contact with the road surface during cornering driving.

[0038] Multiple blocks 3 include multiple middle blocks 5 and shoulder blocks 9 positioned outside the middle blocks 5 in the tire axis direction. Each middle block 5 has its center of gravity 5c of its tread surface 5a located in the middle region Mi. Each middle block 5 is positioned in each of the middle regions Mi. Each shoulder block 9 has its center of gravity 9c of its tread surface 9a located in the shoulder region Sh. Each shoulder block 9 is positioned in each of the shoulder regions Sh.

[0039] The tread portion 2 in this embodiment has a line-symmetric shape with respect to the tire equator C as the axis of symmetry. However, the tread portion 2 is not limited to this configuration.

[0040] Each of the middle blocks 5 is positioned closer to the second crown block 7 than to the first crown block 6 in the circumferential direction of the tire. Thus, the middle blocks 5 are positioned close to the second crown block 7, which has a maximum length WC in the axial direction of the tire that is smaller than that of the first tread shape 6a. Therefore, when the second crown block 7 is in contact with the ground, ease of roll control during cornering by the second crown block 7 is ensured, while the effect of increasing the shear force during cornering by the middle blocks 5 is achieved.

[0041] Furthermore, in the pair Pe of the middle block 5 and the second crown block 7 that are adjacent in the tire circumferential direction, the middle block 5 and the second crown block 7 are spaced apart in the tire circumferential direction. As a result, when turning, the shear force exerted by the edge 53 located on the inside of the middle block 5 in the tire axial direction is greatly increased, further suppressing the deterioration of slide control performance. Note that in this embodiment, the first crown block 6, the second crown block 7, and the middle block 5 are spaced apart in the tire circumferential direction.

[0042] In pair Pe, it is desirable that the center of gravity 5c of the tread surface 5a of the middle block 5 be located ahead of the center of gravity 7c of the tread surface 7a of the second crown block 7 in the rotational direction R. This makes it easier for the second crown block 7 and the middle block 5 to shift position in the tire circumferential direction, and the edge effect of the edge 53 located on the inside of the tire axial direction of the middle block 5 is exerted to a high degree, thus maintaining high slide control performance.

[0043] In the case of pair Pe and the first crown block 6 adjacent to pair Pe on the rearward side in the rotational direction R, the separation distance D2 is preferably 1.0 times or less of the separation distance D1 (shown in Figure 5). Separation distance D2 is the tire circumferential separation distance between the second crown block 7 and the middle block 5. Separation distance D1 is the tire circumferential separation distance between the first crown block 6 and the second crown block 7. If separation distance D2 exceeds 1.0 times separation distance D1, assuming that the tire circumferential separation distance D3 between the first crown block 6 and the middle block 5 remains unchanged, separation distance D1 will decrease, reducing the amount of mud scraped by the first crown block 6. This may prevent improvement in traction performance. For this reason, it is more desirable for separation distance D2 to be 0.8 times or less of separation distance D1, even more desirable for it to be 0.5 times or less, and even more desirable for it to be 0.2 times or less. While not particularly limited, the separation distance D2 is preferably 0.01 times or more the separation distance D1, and more preferably 0.03 times or more. In this embodiment, the second crown block 7 and the middle block 5 do not overlap in the circumferential direction of the tire.

[0044] Furthermore, as shown in Figure 1, in the pair Pe of this embodiment, if the separation distance D2 becomes excessively large, the lateral rigidity of the tread portion 2 will decrease, and it may become impossible to suppress the deterioration of slide control performance. For this reason, it is desirable that the separation distance D2 be smaller than the tire circumferential separation distance Da between the first crown block 6 adjacent to the leading side of the middle block 5 in the rotational direction R and the middle block 5, more preferably 5 mm or less, and even more preferably 3 mm or less.

[0045] As shown in Figure 5, the middle block 5 is provided in each of the pair of middle regions Mi. The middle block 5 in each of the two middle regions Mi is located at the same position in the tire circumferential direction. The center of gravity 5c of the tread surface 5a of the middle block 5 in each of the two middle regions Mi is located on the tire axial line Y1. The middle block 5 includes, for example, an overlapping portion 5d that overlaps with the first crown block 6 in the tire axial direction. The middle block 5 is also separated from the second crown block 7 in the tire axial direction.

[0046] In this embodiment, the middle block 5 includes a leading edge 51, a trailing edge 52, an inner joint edge 53, and an outer joint edge 54. The leading edge 51 is inclined towards the leading side in the rotational direction R, for example, from the tire equator C to the tread edge Te. The trailing edge 52 is continuously inclined towards the leading side in the rotational direction R, from the tire equator C to the tread edge Te. The inner joint edge 53 is continuously inclined towards the trailing side in the rotational direction R, from the tire equator C to the tread edge Te. Such an inner joint edge 53 exhibits a large shear force. The outer joint edge 54 is continuously inclined towards the leading side in the rotational direction R, from the tire equator C to the tread edge Te.

[0047] Figure 6 is a cross-sectional view along line CC of Figure 5. As shown in Figure 5 or Figure 6, the tread surface 5a of the middle block 5 includes a sixth tread portion 56 with a sixth ridge height H6, a seventh tread portion 57 with a seventh ridge height H7 which is smaller than the sixth ridge height H6, and an eighth tread portion 58 with an eighth ridge height H8 (shown in Figure 2) which is larger than the sixth ridge height H6. The sixth tread portion 56 includes a leading edge 51 and an outer connecting edge 54, and is formed in an L-shape in the tread development diagram. The seventh tread portion 57 is connected to the rearward side of the sixth tread portion 56 in the rotational direction R, and is formed in an L-shape in the tread development diagram. The eighth tread portion 58 is located on the rearward side of the seventh tread portion 57 in the rotational direction R and on the tire equator C side, and is formed in a rectangular shape in the tread development diagram.

[0048] In this embodiment, the sixth elevation height H6 is the same as the first elevation height H1. The difference between the sixth elevation height H6 and the seventh elevation height H7 (H6-H7) is the same as the difference between the first elevation height H1 and the second elevation height H2b of the second part 22 (H1-H2b). The difference between the eighth elevation height H8 and the sixth elevation height H6 (H8-H6) is the same as the difference between the first elevation height H1 and the third elevation height H3 (H3-H1).

[0049] The maximum length W2 of the middle block 5 in the tire axial direction is smaller than the maximum length W1 of the first crown block 6 (shown in Figure 3). The maximum length W2 of the middle block 5 is preferably 15% or more of the maximum length W1 of the first crown block 6, more preferably 20% or more, more preferably 30% or less, and more preferably 25% or less. The maximum length W2 of the middle block 5 is formed by the leading edge 51. Such a middle block 5 can obtain a large shear force and maintain high slide control performance.

[0050] The middle block 5 includes, for example, a front-end wall surface 61 extending from the front-end edge 51 to the tread reference surface 2a, and a rear-end wall surface 62 extending from the rear-end edge 52 to the tread reference surface 2a. In this embodiment, the front-end wall surface 61 is continuously inclined toward the front end in the rotational direction R from the front-end edge 51 to the tread reference surface 2a. In this embodiment, the rear-end wall surface 62 is continuously inclined toward the rear end in the rotational direction R from the rear-end edge 52 to the tread reference surface 2a. The corner portion 51c of the front-end edge 51 and the corner portion 52c of the rear-end edge 52 are both formed at an obtuse angle. In this embodiment, each of the front-end wall surface 61 and the rear-end wall surface 62 includes a straight portion m and an arc portion n.

[0051] As shown in Figure 1 or Figure 5, the shoulder blocks 9 are provided in each of the pair of shoulder regions Sh. The shoulder blocks 9 in both shoulder regions Sh are located at the same position in the circumferential direction of the tire. The center of gravity 9c of the tread surface 9a of the shoulder blocks 9 in both shoulder regions Sh is located on the tire axial line Y2.

[0052] The shoulder block 9 includes a first overlapping portion K1 that overlaps with the first crown block 6 in the tire circumferential direction, and a second overlapping portion K2 that overlaps with the second crown block 7 in the tire circumferential direction. Such a shoulder block 9 helps to moderately increase the lateral rigidity of the tire 1 and maintain high slide control performance.

[0053] The shoulder block 9 includes a leading edge 71, a trailing edge 72, an inner joint edge 73, and an outer joint edge 74. The leading edge 71 and the trailing edge 72 are, for example, linear and extend in the tire axial direction. In this embodiment, the leading edge 71 is continuously inclined toward the leading side in the rotational direction R, from the tire equator C to the tread end Te. In this embodiment, the trailing edge 72 is continuously inclined toward the trailing side in the rotational direction R, from the tire equator C to the tread end Te. The inner joint edge 73 includes a first edge portion 73a extending from the inner end of the leading edge 71 in the tire axial direction, a second edge portion 73b extending from the inner end of the trailing edge 72 in the tire axial direction, and a third edge portion 73c connecting the first edge portion 73a and the second edge portion 73b. The first edge portion 73a and the second edge portion 73b are continuously inclined toward the rear end in the rotational direction R, from the tire equator C toward the tread edge Te. The third edge portion 73c extends in a convex arc toward the rear end in the rotational direction R. The outer joint edge 74 overlaps with the tread edge Te.

[0054] As shown in Figure 5 or Figure 6, the tread surface 9a of the shoulder block 9 includes a ninth tread portion 75 with a ninth ridge height H9, a tenth tread portion 76 with a tenth ridge height H10 which is smaller than the ninth ridge height H9, and an eleventh tread portion 77 with an eleventh ridge height H11 which is larger than the ninth ridge height H9. The ninth tread portion 75 includes a first-contact portion 79 located on the first-contact side in the rotational direction R, and a second-contact portion 80 located on the second-contact side in the rotational direction R than the first-contact portion 79. In the tread development diagram, the first-contact portion 79 is formed in a rectangular shape, and the second-contact portion 80 is formed in an L-shape. The eleventh tread portion 77 is located between the first-contact portion 79 and the second-contact portion 80. In the tread development diagram, the eleventh tread portion 77 is formed in a rectangular shape. The tenth tread portion 76 includes a first portion 82 located between the first portion 79 and the eleventh tread portion 77, and a second portion 83 located between the second portion 80 and the eleventh tread portion 77. The tenth ridge height H10a of the first portion 82 is smaller than the tenth ridge height H10b of the second portion 83. In the tread development diagram, the first portion 82 is formed in a rectangular shape, and the second portion 83 is formed in an L-shape.

[0055] In this embodiment, the ninth elevation height H9 is the same as the first elevation height H1. The difference between the ninth elevation height H9 and the tenth elevation height H10a of the first part 82 (H9-H10a) is the same as the difference between the fourth elevation height H4 and the fifth elevation height H5 (H4-H5). The difference between the ninth elevation height H9 and the tenth elevation height H10b of the second part 83 (H9-H10b) is the same as the difference between the first elevation height H1 and the second elevation height H2b of the second part 22 (H1-H2b). The difference between the eleventh elevation height H11 and the ninth elevation height H9 (H11-H9) is the same as the difference between the first elevation height H1 and the third elevation height H3 (H3-H1).

[0056] The shoulder block 9 includes, for example, a front-end wall surface 85 extending from the front-end edge 71 to the tread reference surface 2a, and a rear-end wall surface 86 extending from the rear-end edge 72 to the tread reference surface 2a. In this embodiment, the front-end wall surface 85 is continuously inclined toward the front end in the rotational direction R from the front-end edge 71 to the tread reference surface 2a. In this embodiment, the rear-end wall surface 86 is continuously inclined toward the rear end in the rotational direction R from the rear-end edge 72 to the tread reference surface 2a. The corner portion 71c of the front-end edge 71 and the corner portion 72c of the rear-end edge 72 are each formed at an obtuse angle. In this embodiment, the front-end wall surface 85 and the rear-end wall surface 86 each include a straight portion m and an arc portion n.

[0057] As shown in Figure 4 or Figure 6, in the cross-section of each block 3, only the corner portion 11c of the leading edge 11 of the first crown block 6 is formed at an acute angle. Such a corner portion 11c helps to increase the amount of scratching against the mud. On the other hand, the corner portion 12c of the rearing edge 12 of the first crown block 6 is obtuse. Also, the corner portions 31c, 51c, and 71c of the leading edges 31, 51, and 71 of the second crown block 7, middle block 5, and shoulder block 9, and the corner portions 32c, 52c, and 72c of the rearing edges 32, 52, and 72c of the rearing edges 32, 52, and 72c are obtuse. This increases the rigidity of each block 6, 7, 5, and 9.

[0058] As shown in Figure 2, the tire 1 of this embodiment includes a tread rubber Tg comprising a plurality of blocks 3. The rubber hardness of the tread rubber Tg at 25°C is preferably 50 or higher, more preferably 70 or higher, preferably 80 or lower, and more preferably 78 or lower. The rubber hardness is measured in accordance with JIS-K6253 using a durometer at a 25°C environment.

[0059] Figure 7 is a tread unfolded view of the tread portion 2 of another embodiment. As shown in Figure 7, in pair Pe, the middle block 5 and the second crown block 7 may overlap in the tire circumferential direction. The ratio SC / WC obtained by dividing the tread surface area SC of the second crown block 7 by the maximum length WC of the second crown block 7 is the longitudinal length LC (not shown) of the second crown block 7. In this case, the overlapping distance DO in the tire circumferential direction between the middle block 5 and the second crown block 7 is preferably 0.5 times or less of the longitudinal length LC, and more preferably 0.3 times or less. The tread surface area SC is the area of ​​the second tread shape 7a. Since the overlapping distance DO is 0.5 times or less of the longitudinal length LC, the edge effect of the middle block 5 is exerted during cornering, so that high slide control performance can be maintained. Note that the longitudinal length LC is smaller than the maximum length La of the second crown block 7 in the tire circumferential direction.

[0060] Although particularly preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described above and can be implemented in various modified forms. [Examples]

[0061] A motorcycle tire with the basic tread pattern shown in Figure 1 was prototyped based on the specifications in Table 1. Traction performance and slide control performance during cornering were tested using the prototype test tire. The common specifications and test methods for each test tire are as follows.

[0062] <Common Specifications> Tire size: 140 / 80-18 Rim size: 2.15×18 Air pressure: 80kPa Carcass structure: Bias Test vehicle: 450cc 4-stroke engine vehicle Test course: Muddy off-road course Total number of crown blocks: Same for each comparative example and each example.

[0063] <Traction performance and slide control performance during cornering> Using a test vehicle equipped with a test tire on the rear wheel, the traction performance and slide control performance during cornering were evaluated subjectively by a test rider while driving on a test course. The results are presented on a 10-point scale.

[0064] The test results are shown in Table 1. [Table 1]

[0065] The test results confirmed that the motorcycle tire in the example demonstrated a reduced decrease in slide control performance and improved traction performance compared to the motorcycle tire in the comparative example.

[0066] [Note] The present invention includes the following embodiments.

[0067] [Invention 1] A motorcycle tire for off-road riding having a tread portion with a specified tire rotation direction, In the tread development diagram, The tread portion includes a pair of tread ends, a tread width which is the distance in the tire axial direction between the pair of tread ends, a crown region which is 40% of the tread width centered on the tire equator, and a plurality of blocks. The plurality of blocks include a plurality of crown blocks whose center of gravity of the tread surface is located in the crown region, The crown block includes a plurality of first crown blocks having a first tread shape and a plurality of second crown blocks having a second tread shape. The first tread shape is a V-shape in which at least the leading edge in the tire rotation direction is inclined from the center in the tire axial direction toward both outward sides toward the leading edge in the tire rotation direction. The second tread shape has a tire axial maximum length WC that is smaller than that of the first tread shape. The total number of the first crown blocks is 30% or more of the total number of crown blocks. The leading edge of the first tread shape is inclined at an angle of 10 degrees or more with respect to the tire axis, The maximum length W1 in the axial direction of the first tread shape is 60% to 70% of the tread width. Motorcycle tires. [Invention 2] The motorcycle tire according to the present invention 1, wherein the total number of the first crown blocks is 70% or less of the total number of the crown blocks. [Invention 3] The motorcycle tire according to invention 1 or 2, wherein the leading edge of the first tread shape is inclined at an angle of 45 degrees or less with respect to the tire axis. [4th Invention] The motorcycle tire according to any one of inventions 1 to 3, wherein the maximum length WC is 50% to 60% of the maximum length W1 of the first tread shape. [5th ​​Invention] The motorcycle tire according to any one of inventions 1 to 4, wherein the second crown block and the first crown block are arranged alternately in the circumferential direction of the tire. [Invention 6] The tread rubber includes the tread rubber that forms the plurality of blocks, The motorcycle tire according to any one of invention 1 to 5, wherein the rubber hardness of the tread rubber at 25°C is 50 to 80. [Explanation of Symbols]

[0068] 1. Motorcycle tires 4 Crown Block 6. First Crown Block 6a 1st tread shape 7. Second Crown Block 7a Second tread shape 7a 11 First-come, first-served edge

Claims

1. A motorcycle tire for off-road riding having a tread portion with a specified tire rotation direction, In the tread development diagram, The tread portion includes a pair of tread ends, a tread width which is the distance in the axial direction of the tire between the pair of tread ends, a crown region which is 40% of the tread width centered on the tire equator, and a plurality of blocks. The plurality of blocks include a plurality of crown blocks whose center of gravity of the tread surface is located in the crown region, The crown block includes a plurality of first crown blocks having a first tread shape and a plurality of second crown blocks having a second tread shape. The first tread shape is a V-shape in which at least the leading edge in the tire rotation direction is inclined from the center in the tire axial direction toward both outer sides toward the leading edge in the tire rotation direction, The second tread shape has a tire axial maximum length WC that is smaller than that of the first tread shape. The total number of the first crown blocks is 30% or more of the total number of crown blocks. The leading edge of the first tread shape is inclined at an angle of 10 degrees or more with respect to the tire axis. The maximum length W1 in the axial direction of the first tread shape is 60% to 70% of the tread width. Motorcycle tires.

2. The motorcycle tire according to claim 1, wherein the total number of the first crown blocks is 70% or less of the total number of the crown blocks.

3. The motorcycle tire according to claim 1, wherein the leading edge of the first tread shape is inclined at an angle of 45 degrees or less with respect to the tire axis.

4. The motorcycle tire according to any one of claims 1 to 3, wherein the maximum length WC is 50% to 60% of the maximum length W1 of the first tread shape.

5. The motorcycle tire according to any one of claims 1 to 3, wherein the second crown block and the first crown block are arranged alternately in the circumferential direction of the tire.

6. The tread rubber includes the tread rubber that forms the plurality of blocks, The motorcycle tire according to any one of claims 1 to 3, wherein the rubber hardness of the tread rubber at 25°C is 50 to 80.

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