Tire for rough terrain travel

Abstract

To provide a tire for off-road traveling which improves traction performance on an off-road.SOLUTION: A tire 1 for off-road travelling has a tread part 2. The tread part 2 is provided with a crown block 5. The crown block 5 includes a crown block body 10 which is formed in a V shape protruding toward a later landing side in a tire rotation direction N, and crown fin parts 11 projecting to the later landing side in the tire rotation direction N from the crown block body 10. The number of crown fin parts 11 is only two.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a tire for rough terrain driving.

Background Art

[0002] Patent Document 1 below describes a tire for rough terrain driving in which crown blocks are provided in the tread portion. The crown block includes a crown block main body portion and three crown fin portions protruding in the tire circumferential direction from the crown block main body portion. Such crown fin portions are said to be useful for enhancing traction performance.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When driving on a muddy road surface such as a muddy area with a tire as described above, mud and soil are likely to get stuck between the crown fin portions, and the stuck mud and soil are difficult to be discharged, so the traction tends to decrease.

[0005] The present disclosure has been devised in view of the above actual situation, and the main object is to provide a tire for rough terrain driving with improved traction performance on rough terrain.

Means for Solving the Problems

[0006] The present disclosure relates to a tire for rough terrain driving having a tread portion, wherein the tread portion has a specified tire rotation direction, and a plurality of crown blocks are provided on the tire equator in the tread portion. Each of the plurality of crown blocks includes a crown block body formed in a V shape that protrudes toward the trailing side in the tire rotation direction, and a crown fin portion that protrudes from the crown block body toward the trailing side in the tire rotation direction. The crown fin portion has only two, and it is a tire for rough terrain driving.

Effects of the Invention

[0007] By adopting the above configuration, the tire for rough terrain driving of the present disclosure can improve the traction performance on rough terrain.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Modes for Carrying Out the Invention

[0009] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. FIG. 1 is a cross-sectional view of an uneven terrain traveling tire (hereinafter sometimes simply referred to as "tire") 1 according to an embodiment of the present disclosure. FIG. 1 shows a tire meridian cross-section including a tire rotation axis (not shown) in the normal state of a pneumatic tire. FIG. 2 is a developed view of the tread portion 2 of the tire 1. The tire 1 of the present disclosure is suitable for motorcycles, but may also be adopted for passenger cars or heavy-duty vehicles. Further, the tire 1 of the present disclosure may be applied to a non-pneumatic tire not filled with compressed air.

[0010] The "normal state" is a no-load state in which the tire 1 is rim-mounted on a normal rim (not shown) and filled with a normal internal pressure. Hereinafter, unless otherwise specified, the dimensions and the like of each part of the tire are values measured in this normal state.

[0011] The "normal rim" is a rim defined for each tire in a standard system including the standard on which the tire 1 is based. For example, in the case of JATMA, it is the "standard rim", in the case of TRA, it is the "Design Rim", and in the case of ETRTO, it is the "Measuring Rim".

[0012] The "normal internal pressure" is the air pressure defined for each tire in a standard system including the standard on which the tire 1 is based. In the case of JATMA, it is the "maximum air pressure", in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in the case of ETRTO, it is the "INFLATION PRESSURE".

[0013] In the tire meridian cross-section, the outer surface of the tread portion 2 of the present embodiment is curved in an arc shape convex in the outer direction of the tire radius. Further, the tread portion 2 has a directional pattern in which the tire rotation direction (hereinafter sometimes simply referred to as the "rotation direction") N is specified.

[0014] In the tread portion 2 of the present embodiment, a plurality of crown blocks 5 are provided on the tire equator C. Each of the plurality of crown blocks 5 includes a crown block body 10 formed in a V shape that protrudes toward the trailing side in the rotational direction N, and a crown fin portion 11 that protrudes from the crown block body 10 toward the trailing side in the rotational direction N. Such a crown block 5 suppresses the tilting of the crown block body 10 toward the trailing side in the rotational direction N during grounding and exhibits a basic soil digging force, thereby enhancing the traction performance.

[0015] Only two crown fin portions 11 are provided per crown block 5. As a result, the region where soil is likely to accumulate (i.e., the region between the crown fin portions 11, 11) becomes one location per crown block 5, reducing soil accumulation, and thus the edge effect of the crown block body 10 can be highly exerted.

[0016] The tread portion 2 includes, for example, a plurality of middle blocks 6 located outside the tire axial direction of each crown block 5, and a plurality of shoulder blocks 7 located outside the tire axial direction of each middle block 6. In the present embodiment, the middle blocks 6 are arranged on both sides of the crown block 5 in the tire axial direction. Each of the blocks 5 to 7 is partitioned by the tread base portion 2R.

[0017] Figure 3 is an enlarged view of the crown block 5. As shown in Figure 3, the crown block body 10 includes a tread surface 12, a leading-side block edge 13 that defines the leading side in the rotational direction N of the tread surface 12, and a trailing-side block edge 14 that defines the trailing side in the rotational direction N of the tread surface 12. The crown block body 10 further includes a pair of circumferential edges 15, 15 that connect the leading-side block edge 13 and the trailing-side block edge 14 and extend in the tire circumferential direction. The leading-side block edge 13, the trailing-side block edge 14, and the circumferential edge 15 are continuous with the block wall surface 8 of the crown block body 10 that extends radially outward from the tread base portion 2R in the tire radius direction. In this embodiment, the circumferential edge 15 extends linearly and parallel to the tire circumferential direction. Each circumferential edge 15 forms the outer end 10e of the crown block body 10 in the tire axial direction. The term "extends parallel" in this specification includes not only the case where the difference in angle between the two is 0 degrees, but also the case where the absolute value of the difference in the angle is 10 degrees or less.

[0018] In this embodiment, the leading-side block edge 13 and the trailing-side block edge 14 of the crown block are each inclined toward the trailing side in the rotational direction N from the center in the block width direction toward both outer sides in the block width direction. The leading-side block edge 13 and the trailing-side block edge 14 each have a trailing end 13e, 14e that is located on the most trailing side in the rotational direction N. Each trailing end 13e, 14e is located, for example, on the tire equator C.

[0019] The angle θ1 of the leading-side block edge 13 with respect to the tire axial direction is preferably 10 degrees or more, more preferably 15 degrees or more, preferably 45 degrees or less, and more preferably 35 degrees or less. The angle θ1 of the leading-side block edge 13 is the angle of the line segment connecting the trailing end 13e and the intersection position of the leading-side block edge 13 and the circumferential edge 15.

[0020] Figure 4 is an enlarged view of the crown block 5. As shown in Figure 4, the leading-side block edge 13 continuously inclines in the same direction with respect to the tire axis direction toward the trailing side in the rotational direction N from each circumferential edge 15 to the trailing end 13e. The leading-side block edge 13 includes a first outer portion 13a communicating with the circumferential edge 15, a first inner portion 13b including the trailing end 13e, and a first intermediate portion 13c connecting the first outer portion 13a and the first inner portion 13b. The first intermediate portion 13c inclines at a larger angle with respect to the tire axis direction than the first outer portion 13a and the first inner portion 13b. The first outer portion 13a and the first intermediate portion 13c extend linearly, for example. The first inner portion 13b extends in a V shape, for example.

[0021] The difference (θ1c - θ1a) between the angle θ1a of the first outer portion 13a and the angle θ1c of the first intermediate portion 13c is preferably, for example, 10 degrees or more, more preferably 15 degrees or more, preferably 35 degrees or less, and more preferably 30 degrees or less. The difference (θ1c - θ1b) between the angle θ1b of the first inner portion 13b and the angle θ1c of the first intermediate portion 13c is preferably, for example, 10 degrees or more, more preferably 15 degrees or more, preferably 35 degrees or less, and more preferably 30 degrees or less.

[0022] The trailing-side block edge 14 includes an inner edge portion 14A extending inward in the tire axis direction from the connection portion K between the crown block main body 10 and the crown fin portion 11, and an outer edge portion 14B extending outward in the tire axis direction from the connection portion K. The inner edge portion 14A includes the trailing end 14e, for example. The inner edge portion 14A extends in a V shape, for example. The outer edge portion 14B communicates with the circumferential edge 15 in the present embodiment. The outer edge portion 14B extends linearly, for example.

[0023] In the plan view of the tire, the crown fin portion 11 is formed in a parallelogram shape in the present embodiment. The crown fin portion 11 includes, for example, an outer edge 11e in the block width direction, an inner edge 11i in the block width direction, a leading edge 11a on the leading side in the rotational direction N, and a trailing edge 11b on the trailing side in the rotational direction N. The outer edge 11e and the inner edge 11i extend, for example, parallel to the tire circumferential direction. The leading edge 11a is arranged, for example, on the leading side in the rotational direction N with respect to the trailing side block edge 14. The leading edge 11a and the trailing edge 11b extend, for example, parallel to the outer edge portion 14B. The inner edge 11i, the outer edge 11e, the leading edge 11a, and the trailing edge 11b form an outer surface 11A facing the outside in the tire radial direction of the crown fin portion 11.

[0024] In the present embodiment, the outer surface 11A is located on the outside in the tire radial direction with respect to the tread surface 12 of the crown block body 10 (shown in FIG. 6). The outer surface 11A may be located, for example, in the same tire radial direction as the tread surface 12 of the crown block body 10.

[0025] The outer edges 11e in the block width direction of each of the two crown fin portions 11 are located inside in the block width direction with respect to both ends 10e, 10e in the tire axial direction of the crown block body 10. Thereby, the deformation of the crown fin portion 11 is maintained, and the mud clogged between the crown fin portions 11, 11 is smoothly discharged, so that the edge effect of the crown block body 10 is more effectively exerted.

[0026] As shown in FIG. 3, it is desirable that the separation distance La in the tire axial direction between the two crown fin portions 11 is 30% to 50% of the width W1 in the tire axial direction of the crown block body 10. Since the separation distance La is 30% or more of the width W1 of the crown block body 10, the discharge of mud becomes smooth. Since the separation distance La is 50% or less of the width W1 of the crown block body 10, the tilting of the crown block body 10 can be effectively suppressed. From such a viewpoint, it is more desirable that the separation distance La is 35% or more of the width W1 of the crown block body 10, and 45% or less is more desirable.

[0027] The separation distance Lb in the tire axial direction between the outer edge 11e of the crown fin portion 11 and one end 10e of the crown block body 10 is desirably 15% or more of the width W1 of the crown block body 10, more desirably 20% or more, desirably 35% or less, and more desirably 30% or less. Thereby, deformation of the crown fin portion 11 is ensured, and the effect of discharging mud is enhanced.

[0028] The width W2 of the crown fin portion 11 in the tire axial direction is desirably 5% or more of the width W1 of the crown block body 10, more desirably 10% or more, desirably 20% or less, and more desirably 15% or less. Since the width W2 of the crown fin portion 11 is 5% or more of the width W1 of the crown block body 10, the tilting of the crown block body 10 can be effectively suppressed. Since the width W2 of the crown fin portion 11 is 20% or less of the width W1 of the crown block body 10, an excessive increase in the rigidity of the crown fin portion 11 is suppressed, and the soil discharging property is maintained.

[0029] In order to suppress the tilting of the crown block body 10, the protrusion length Lc of the crown fin portion 11 in the tire circumferential direction from the crown block body 10 is desirably 50% or more of the length L1 of the crown block body 10 in the tire circumferential direction. If the protrusion length Lc of the crown fin portion 11 is excessively large, there is a risk that the soil discharging property will deteriorate. For this reason, the protrusion length Lc of the crown fin portion 11 is more desirably 60% or more of the length L1 of the crown block body 10, desirably 150% or less, and more desirably 110% or less.

[0030] FIG. 5 is an enlarged view of the crown block 5. As shown in FIG. 5, in the connection portion K between the crown block body 10 and the crown fin portion 11, a shallow groove 18 is formed to promote deformation on the side of the connection portion K of the crown fin portion 11. Such a shallow groove 18 helps to smoothly discharge the mud clogged between the crown fin portions 11.

[0031] The shallow groove 18 communicates with the inner edge portion 14A and the outer edge portion 14B so as to surround the connection portion K. The shallow groove 18 extends, for example, along the outer edge 11e, the inner edge 11i, and the leading edge 11a. Such a shallow groove 18 apparently separates the crown fin portion 11 and the crown block body 10 from each other, increasing the deformation of the crown fin portion 11, and thus enhancing the traction performance on uneven ground. In the present embodiment, the shallow groove 18 extends in a U shape convex on the leading side in the rotational direction N.

[0032] FIG. 6 is a cross-sectional view taken along line A-A of FIG. 5. As shown in FIG. 6, the groove depth d1 of the shallow groove 18 is desirably 5% or more, more desirably 10% or more, desirably 25% or less, and more desirably 20% or less of the block height H1 of the crown block 5. Also, as shown in FIG. 5, the width W3 of the shallow groove 18 is desirably 2% or more, more desirably 5% or more, desirably 15% or less, and more desirably 10% or less of the width W1 of the crown block body 10. Thereby, the above-described action is effectively exerted, and the rigidity of the crown fin portion 11 and the crown block body 10 is maintained, ensuring their high shear force.

[0033] The circumferential separation distance Ld between the leading-side end 18e of the shallow groove 18 in the rotational direction N and the trailing-side block edge 14 is desirably 60% or less of the length L1 of the crown block body 10. Thereby, the circumferential rigidity of the crown block body 10 is maintained, and the effect of suppressing the tilting when the crown block 5 contacts the ground is highly exerted.

[0034] Although not particularly limited, the width W1 of the crown block body 10 is desirably 20% or more, more desirably 25% or more, desirably 40% or less, and more desirably 35% or less of the tread deployment width TW. The tread deployment width TW is the distance in the tire axial direction between the tread ends Te, Te when the tread portion 2 is developed in a plane (shown in FIG. 2).

[0035] FIG. 7 is a cross-sectional view taken along line B-B of FIG. 5. As shown in FIG. 7, the block wall surface 8 of the crown block body 10 includes a first side wall surface 16 extending radially inward in the tire direction from the leading-side block edge 13 and a second side wall surface 17 extending radially inward in the tire direction from the trailing-side block edge 14. The first side wall surface 16 includes an outer portion 16a and an inner portion 16b in a longitudinal section.

[0036] The outer portion 16a extends linearly radially inward in the tire direction from the leading-side block edge 13 and extends inclined toward the trailing side in the rotational direction N with respect to the tread normal n erected on the leading-side block edge 13. The inner portion 16b is connected in an arc shape between the outer portion 16a and the tread base portion 2R. Such a first side wall surface 16 can penetrate deeply into the road surface. In this specification, the “linear shape” includes not only a straight line with an infinite radius of curvature but also an arc with a radius of curvature of 200 mm or more.

[0037] In this embodiment, the inner portion 16b is formed with a single radius of curvature. Such an inner portion 16b relaxes the stress concentration acting on the inner portion 16b, thereby further enhancing the traction performance. Note that the inner portion 16b may be formed of arcs with a plurality of radii of curvature.

[0038] The second side wall surface 17 includes, for example, a first portion 17a, a second portion 17b, and a third portion 17c. The first portion 17a extends radially inward in the tire direction from the trailing-side block edge 14. The second portion 17b is connected to the first portion 17a and is inclined more gently than the first portion 17a. The third portion 17c connects the second portion 17b and the tread base portion 2R. In this embodiment, the first portion 17a and the second portion 17b extend linearly. The third portion 17c is curved in an arc shape. The third portion 17c is formed, for example, in an arc shape concave toward the leading side in the rotational direction N.

[0039] FIG. 8 is an enlarged view of the vicinity of the middle block 6. As shown in FIG. 8, the middle block 6 includes a middle block body 20 that is inclined toward the leading side in the rotational direction N from the inner side to the outer side in the tire axial direction and has a parallelogram shape, and a middle fin portion 21 that protrudes from the middle block body 20 toward the trailing side in the rotational direction N.

[0040] The middle block body 20 includes a tread surface 22, a leading side middle edge 23 that defines the leading side in the rotational direction N of the tread surface 22, and a trailing side middle edge 24 that defines the trailing side in the rotational direction N of the tread surface 22. The middle block body 20 further includes a pair of circumferential middle edges 25 that extend from both ends of the leading side middle edge 23 toward the trailing side in the rotational direction N.

[0041] The pair of circumferential middle edges 25 includes an inner edge portion 25a that is adjacent to the crown block 5 in the tire axial direction and an outer edge portion 25b that is adjacent to the shoulder block 7 in the tire axial direction. The circumferential middle edge 25 extends linearly, for example.

[0042] The middle fin portion 21 is provided, for example, in two on the middle block body 20. The middle fin portion 21 includes an outer middle fin portion 21A that is connected to the outer edge portion 25b and an inner middle fin portion 21B that is arranged on the inner side in the tire axial direction than the outer middle fin portion 21A.

[0043] The outer middle fin portion 21A is directly connected to the middle block body 20. The outer edge 26 in the tire axial direction of the outer middle fin portion 21A and the outer edge portion 25b are formed by a single straight line.

[0044] The inner middle fin portion 21B is connected to the middle block body 20 via the middle shallow groove 30. The inner edge 27 in the tire axial direction of the inner middle fin portion 21B and the inner edge portion 25a are formed in a straight line with the middle shallow groove 30 therebetween. Such an inner middle fin portion 21B is promoted to deform by the middle shallow groove 30, so as to smoothly remove the mud clogged between the two middle fin portions 21. The groove edge 30a extending in the longitudinal direction of the middle shallow groove 30 and arranged on the leading side in the rotational direction N forms the trailing side middle edge 24 in the present embodiment.

[0045] The groove width W4 of the middle shallow groove 30 is desirably 80% or more, more desirably 90% or more, desirably 125% or less, and more desirably 110% or less of the groove width W3 of the shallow groove 18 of the crown block 5. The groove depth (not shown) of the middle shallow groove 30 is desirably 5% or more, more desirably 10% or more, desirably 20% or less, and more desirably 15% or less of the block height (not shown) of the middle block body 20. The width W5 of the middle block body 20 is desirably 5% or more, more desirably 10% or more, desirably 25% or less, and more desirably 20% or less of the tread development width TW.

[0046] FIG. 9 is a plan view of the shoulder block 7. As shown in FIG. 9, the shoulder block 7 is formed, for example, in a rectangular shape in a tread plan view. In this embodiment, the shoulder block 7 is formed in a trapezoidal shape. The tread surface 7a of the shoulder block 7 includes an outer edge 41, an inner edge 42, a trailing-side edge 43, and a leading-side edge 44. The outer edge 41 extends, for example, in the tire circumferential direction on the outer side in the tire axial direction of the tread surface 7a. In this embodiment, the outer edge 41 forms the tread end Te. The inner edge 42 extends, for example, in the tire circumferential direction on the inner side in the tire axial direction of the tread surface 7a. The trailing-side edge 43 joins the inner edge 42 and the outer edge 41 in this embodiment and extends parallel to the tire axial direction. The trailing-side edge 43 of this embodiment defines the trailing side in the rotational direction N of the shoulder block 7. The leading-side edge 44 joins the inner edge 42 and the outer edge 41 in this embodiment and is inclined with respect to the tire axial direction. The leading-side edge 44 of this embodiment defines the leading side in the rotational direction N of the shoulder block 7.

[0047] In this embodiment, the shoulder block 7 has a shoulder shallow groove 45. In a tread plan view, the shoulder shallow groove 45 extends in a V shape. Such a shoulder shallow groove 45 promotes the deformation of the shoulder block 7 and smooths the discharge of the mud clogged between the shoulder block 7 and the middle block 6.

[0048] The shoulder shallow groove 45 includes a circumferential portion 46 extending in the tire circumferential direction and an axial portion 47 extending in the tire axial direction. The circumferential portion 46 extends at an angle of 45 degrees or less with respect to the tire circumferential direction. The axial portion 47 is inclined at an angle exceeding 45 degrees with respect to the tire circumferential direction.

[0049] The circumferential portion 46 of the present embodiment extends parallel to the tire circumferential direction from the trailing edge 43 toward the leading side in the rotational direction N and terminates within the shoulder block 7. The axial portion 47 of the present embodiment extends from the inner edge 42 toward the outside in the tire axial direction and is connected to the end of the circumferential portion 46. In the present embodiment, the axial portion 47 extends parallel to the leading edge 44. Such a shoulder shallow groove 45 further promotes the deformation of the shoulder block 7.

[0050] The groove width W6 of the shoulder shallow groove 45 is desirably 5% or more, more desirably 10% or more, desirably 25% or less, and more desirably 20% or less of the width W7 of the shoulder block 7 in the tire axial direction. The groove depth (not shown) of the shoulder shallow groove 45 is desirably 5% or more, more desirably 10% or more, desirably 20% or less, and more desirably 15% or less of the block height (not shown) of the shoulder block 7. The width W7 of the shoulder block 7 is desirably 5% or more, more desirably 7% or more, desirably 20% or less, and more desirably 15% or less of the tread development width TW.

[0051] The tread rubber 2G (shown in FIG. 1) in which such blocks 5 to 7 are formed desirably has a rubber hardness of 70 degrees or more and desirably 90 degrees or less. In this specification, the rubber hardness is the durometer A hardness measured in an environment of 23°C based on JIS-K6253.

[0052] As described above, the particularly preferred embodiments of the present disclosure have been described in detail. However, the present disclosure is not limited to the illustrated embodiments and can be implemented in various forms.

Example

[0053] A rear wheel tire for a motorcycle for rough terrain travel having the basic pattern of FIG. 2 was prototyped based on the specifications in Table 1. Then, tests were conducted on the traction performance, braking performance, and overall performance of each test tire. The front wheel tires are the same in all examples. The common specifications and test methods of each test tire are as follows. Vehicle in use: Motocross racing vehicle with a displacement of 450 cc Tire sizes (front and rear wheels): 80 / 100 - 21, 120 / 80 - 19 Rim sizes (front and rear wheels): 21×1.60, 19×2.15 Inner pressure: 80 kPa The test method is as follows.

[0054] <Traction performance, braking performance, overall performance> When the test vehicle was driven on an uneven ground covered with mud, the traction performance and braking performance were evaluated by the senses of the test rider. Here, the "traction performance" was evaluated by the senses of the test rider based on the smoothness of the driving when accelerating during straight - line driving and turning driving. The "braking performance" was evaluated by the senses of the test rider based on the stability of the driving when decelerating during straight - line driving and turning driving. The "overall performance" was evaluated by the senses of the test rider based on the stability of the driving when accelerating and decelerating during straight - line driving and turning driving. Each test was shown by a 10 - point method with a full score of 10 points. The test results are shown in Table 1.

[0055]

Table 1

[0056] As a result of the test, it is understood that the tire of the example has improved traction performance on uneven ground compared to the tire of the comparative example. Also, it is understood that the tire of the example has improved braking performance compared to the tire of the comparative example.

[0057] [Appendix] This disclosure includes the following aspects.

[0058] [This Disclosure 1] A tire for driving on uneven ground having a tread portion, wherein the tread portion has a specified tire rotation direction, In the tread portion, a plurality of crown blocks are provided on the tire equator. Each of the plurality of crown blocks includes a crown block body formed in a V shape that protrudes toward the trailing side in the tire rotation direction, and a crown fin portion that protrudes from the crown block body toward the trailing side in the tire rotation direction. There are only two of the crown fin portions. Tire for rough terrain driving. [Disclosure 2] The outer edge in the block width direction of each of the two crown fin portions is located inside the block width direction from both ends in the tire axis direction of the crown block body, and the tire for rough terrain driving according to Disclosure 1. [Disclosure 3] The separation distance in the tire axis direction between the two crown fin portions is 30% to 50% of the width in the tire axis direction of the crown block body, and the tire for rough terrain driving according to Disclosure 1 or 2. [Disclosure 4] The width in the tire axis direction of each crown fin portion is 5% to 20% of the width in the tire axis direction of the crown block body, and the tire for rough terrain driving according to any one of Disclosures 1 to 3. [Disclosure 5] The protrusion length in the tire circumferential direction of the crown fin portion from the crown block body is 50% or more of the length in the tire circumferential direction of the crown block body, and the tire for rough terrain driving according to any one of Disclosures 1 to 4. [Disclosure 6] In the connection portion between the crown block body and the crown fin portion, a shallow groove is formed to promote deformation on the side of the connection portion of the crown fin portion, and the tire for rough terrain driving according to any one of Disclosures 1 to 5. [Disclosure 7] The crown block body includes a tread surface and a trailing side block edge that defines the trailing side in the rotation direction of the tread surface. The trailing side block edge includes an inner edge portion that extends inward in the tire axis direction from the connection portion and an outer edge portion that extends outward in the tire axis direction from the connection portion. The shallow groove surrounds the connecting portion and communicates with the inner edge portion and the outer edge portion. The tire for rough terrain driving according to Disclosure 6 of the present disclosure. [Disclosure 8 of the present disclosure] The groove depth of the shallow groove is 5% to 25% of the block height of the crown block body. The tire for rough terrain driving according to Disclosure 6 or 7 of the present disclosure. [Disclosure 9 of the present disclosure] The width of the shallow groove is 2% to 15% of the width in the tire axial direction of the crown block body. The tire for rough terrain driving according to any one of Disclosures 6 to 8 of the present disclosure. [Disclosure 10 of the present disclosure] The crown block body includes a tread surface and a trailing-side block edge that defines the trailing side in the rotational direction of the tread surface. The circumferential separation distance between the leading end of the shallow groove in the tire rotational direction and the trailing-side block edge is 60% or less of the circumferential length of the crown block body. The tire for rough terrain driving according to any one of Disclosures 6 to 9 of the present disclosure. [Disclosure 11 of the present disclosure] The crown block body includes a tread surface and a leading-side block edge that defines the leading side in the rotational direction of the tread surface. The angle of the leading-side block edge with respect to the tire axial direction is 10 to 45 degrees. The tire for rough terrain driving according to any one of Disclosures 1 to 10 of the present disclosure.

[0059] 1 Tire for rough terrain driving 2 Tread portion 5 Crown block 10 Crown block body 11 Crown fin portion N Tire rotational direction

Claims

1. A tire for rough terrain travel having a tread portion, wherein the tread portion has a specified tire rotation direction, and a plurality of crown blocks are provided on the tire equator in the tread portion, each of the plurality of crown blocks includes a crown block body formed in a V shape that protrudes toward the trailing side in the tire rotation direction, and a crown fin portion that protrudes from the crown block body toward the trailing side in the tire rotation direction, there are only two crown fin portions, the crown block body includes a tread surface, a leading side block edge that defines the leading side in the tire rotation direction of the tread surface, a trailing side block edge that defines the trailing side in the tire rotation direction of the tread surface, and a pair of circumferential edges that connect the leading side block edge and the trailing side block edge and extend in the tire circumferential direction, the leading side block edge is inclined in the same direction with respect to the tire axial direction toward the trailing side in the tire rotation direction from each circumferential edge to the trailing end located on the most trailing side in the tire rotation direction, the leading side block edge includes a first outer portion that communicates with each circumferential edge, a first inner portion that extends in a V shape including the trailing end, and a first intermediate portion that connects the first outer portion and the first inner portion, an angle θ1c of the first intermediate portion with respect to the tire axial direction is larger than an angle θ1a of the first outer portion with respect to the tire axial direction and an angle θ1b of the first inner portion with respect to the tire axial direction, A tire for rough terrain travel.

2. The tire for rough terrain travel according to claim 1, wherein outer edges in the block width direction of each of the two crown fin portions are located inside in the block width direction than both ends in the tire axial direction of the crown block body.

3. The tire for rough terrain travel according to claim 1 or 2, wherein a separation distance in the tire axial direction between the two crown fin portions is 30% to 50% of a width in the tire axial direction of the crown block body.

4. The tire for rough terrain travel according to any one of claims 1 to 3, wherein a width in the tire axial direction of each crown fin portion is 5% to 20% of a width in the tire axial direction of the crown block body.

5. The protruding length in the tire circumferential direction of the crown fin portion from the crown block body is 50% or more of the length of the crown block body in the tire circumferential direction. The tire for rough terrain driving according to any one of claims 1 to 4.

6. In the connecting portion between the crown block body and the crown fin portion, a shallow groove is formed to promote deformation on the side of the connecting portion of the crown fin portion. The tire for rough terrain driving according to any one of claims 1 to 5.

7. The crown block body includes a tread surface and a trailing side block edge that defines the trailing side in the rotational direction of the tread surface. The trailing side block edge includes an inner edge portion extending inward in the tire axial direction from the connecting portion and an outer edge portion extending outward in the tire axial direction from the connecting portion. The shallow groove communicates with the inner edge portion and the outer edge portion so as to surround the connecting portion. The tire for rough terrain driving according to claim 6.

8. The groove depth of the shallow groove is 5% to 25% of the block height of the crown block body. The tire for rough terrain driving according to claim 6 or 7.

9. The width of the shallow groove is 2% to 15% of the width of the crown block body in the tire axial direction. The tire for rough terrain driving according to any one of claims 6 to 8.

10. The crown block body includes a tread surface and a trailing side block edge that defines the trailing side in the rotational direction of the tread surface. The separation distance in the tire circumferential direction between the leading end on the leading side in the tire rotational direction of the shallow groove and the trailing side block edge is 60% or less of the length of the crown block body in the tire circumferential direction. The tire for rough terrain driving according to any one of claims 6 to 9.

11. The crown block body includes a tread surface and a leading side block edge that defines the leading side in the rotational direction of the tread surface. The angle of the leading side block edge with respect to the tire axial direction is 10 to 45 degrees. The tire for rough terrain driving according to any one of claims 1 to 10.

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