Tire for rough terrain

Abstract

The present application relates to an uneven ground running tire, and improves the traction performance on uneven ground. The uneven ground running tire (1) has a tread portion (2). A block (4) is provided on the tread portion (2) and protrudes from a tread base (2R). The block (4) includes a first side wall surface (11). The first side wall surface (11) includes: an outer side portion (13) extending in a straight line and inclined to a rear ground contact side in a tire rotation direction N; and an inner side portion (14) curved in an arc shape to connect the outer side portion (13) and the tread base (2R). A length (H1) of the outer side portion (13) in a tire radial direction is 30% to 70% of a block height (Ha).

Description

Technical Field

[0001] This disclosure relates to tires for driving on uneven terrain. Background Technology

[0002] Patent Document 1 describes a pneumatic tire with tread blocks provided in the tread area. The tread blocks include a first-contact side tread block wall located on the first-contact side in the tire's rotation direction. Furthermore, the tread block includes a first-contact edge where the first-contact side tread block wall intersects with the upper surface of the tread block. The first-contact edge is inclined towards the first-contact side, closer to the root of the tread block wall. Such tread blocks can improve road surface digging capacity by exerting large shear forces.

[0003] Patent Document 1: Japanese Patent No. 3384716

[0004] In recent years, there has been a desire to further improve the traction performance on uneven surfaces. Summary of the Invention

[0005] This disclosure is made in view of the above-mentioned practical situation, and its main purpose is to provide tires for driving on uneven surfaces that further improve traction performance on uneven surfaces.

[0006] This disclosure discloses a tire for driving on uneven surfaces, having a tread portion, wherein the tread portion is designated in the tire rotation direction, and a plurality of tread blocks raised from the tread base are provided on the tread portion, each of the plurality of tread blocks comprising: a tread surface having a first edge extending axially along the tire on the first contact side in the tire rotation direction; and a first sidewall extending radially inward from the first edge towards the tire. In a longitudinal section of the tread block along the tire circumference, the first sidewall includes: an outer portion extending linearly from the first edge towards the tire radially inward, and inclined towards the rear contact side in the tire rotation direction than the tread normal erected on the first edge; and an inner portion curved into an arc shape connecting the outer portion to the tread base, wherein the radial length of the outer portion is 30% to 70% of the tread block height in the tire radial direction from the tread base to the tread surface.

[0007] The tire for driving on uneven terrain disclosed herein, by adopting the above-described structure, can further improve traction performance on uneven terrain. Attached Figure Description

[0008] Figure 1 This is a top view showing the unfolded and enlarged tread of a tire for driving on uneven terrain according to an embodiment of the present disclosure.

[0009] Figure 2 yes Figure 1 A sectional view along line AA.

[0010] Figure 3 (a) to (c) are schematic diagrams showing the state of patterned block 4 deeply embedded in the road surface in a time sequence.

[0011] Figure 4 This is a top view of the tread area in this embodiment.

[0012] Figure 5 yes Figure 4 Enlarged view of the tread pattern on the tire crown.

[0013] Figure 6 yes Figure 4 Enlarged view of the tread pattern on the tire crown.

[0014] Figure 7 yes Figure 6 BB line section view.

[0015] Figure 8 yes Figure 4 A top view of the central patterned block.

[0016] Figure 9 yes Figure 4 A top view of the tire shoulder tread blocks.

[0017] Explanation of reference numerals in the attached figures

[0018] 1...Tire for driving on uneven ground; 2...Tread surface; 2R...Tread base; 4...Tread block; 11...First sidewall; 13...Outer side; 14...Inner side; H1...Length of the outer side; Ha...Tread block height; N...Tire rotation direction. Detailed Implementation

[0019] Hereinafter, an embodiment of the present disclosure will be described with reference to the accompanying drawings.

[0020] Figure 1 This is an enlarged top view of the tread portion 2 of a tire (hereinafter, sometimes simply referred to as "tire") 1 for driving on uneven terrain, representing an embodiment of this disclosure. The tire 1 of this disclosure is suitable, for example, for use in pneumatic tires for motorcycles. The tire 1 of this disclosure can also be applied to passenger car pneumatic tires, heavy-duty pneumatic tires, or non-pneumatic tires without compressed air.

[0021] like Figure 1 As shown, the tread portion 2 is designated with the tire rotation direction (hereinafter, sometimes simply referred to as "rotation direction") N. In this embodiment, the tread portion 2 is provided with a plurality of tread blocks 4 raised from the tread base 2R. The tread blocks 4 are not limited to the top view shape shown in the figure, but can adopt various top view shapes.

[0022] The plurality of tread blocks 4 each include: a tread surface 10 having a first edge 10e extending axially along the tire on the first contact side in the rotational direction N; and a first sidewall surface 11 extending radially inward from the first edge 10e toward the tire. The shape of the tread surface 10 of the tread block 4 is not limited to the structure shown in the figure, but can be adopted in various ways.

[0023] Figure 2 yes Figure 1 A sectional view along line AA. Figure 2 The diagram shows a longitudinal section of tread block 4 along the tire circumference. This longitudinal section represents the central position of tread block 4 along the tire axial direction. Figure 2 As shown, in the above longitudinal section, the first side wall 11 includes an outer side portion 13 and an inner side portion 14.

[0024] The outer portion 13 extends in a straight line from the first edge 10e toward the radially inward side of the tire, and extends obliquely toward the rear contact side in the direction of rotation N compared to the tread normal n erected on the first edge 10e. The inner portion 14 is curved into an arc shape to connect the outer portion 13 to the tread base 2R. Figure 3 (a) to (c) are schematic diagrams showing the patterned block 4 deeply embedded in the road surface f in this embodiment, presented in a time sequence. Figure 3 As shown in (a) to (c), this first sidewall 11, with the arc-shaped inner portion 14 as a fulcrum, transfers the rotational force from the tire's rotation to the outer portion 13, increasing the shear force. Therefore, the first sidewall 11 can deeply penetrate the road surface f. The term "straight line" in this specification naturally includes straight lines with an infinite radius of curvature, as well as arcs with a radius of curvature of 200 mm or more.

[0025] like Figure 2 As shown, the radial length H1 of the outer portion 13 is 30% to 70% of the radial tread height Ha of the tread block 4 from the tread base 2R to the tread surface 10. Since the length H1 of the outer portion 13 is more than 30% of the tread height Ha of the tread block 4, the outer portion 13 can deeply penetrate the road surface f. Since the length H1 of the outer portion 13 is less than 70% of the tread height Ha of the tread block 4, the inner portion 14 is prevented from becoming smaller, maintaining high rigidity of the inner portion 14, thus preventing the first sidewall 11 from collapsing towards the rear contact side in the rotation direction N. Furthermore, such a first sidewall 11 suppresses cracks and defects in the inner portion 14. Therefore, the tread block 4 of this embodiment can improve traction performance on uneven surfaces and maintain this effect over a long period. Additionally, such a tread block 4 improves instantaneity on uneven surfaces. From this perspective, the length H1 of the outer portion 13 is preferably more than 40% of the height Ha of the patterned block 4, and more preferably less than 60%.

[0026] In this specification, unless otherwise stated, the dimensions of all parts of tire 1 are values ​​measured under normal conditions. The term "normal conditions" refers to the unloaded state in which tire 1 is assembled on a normal rim (not shown) and filled with normal internal pressure.

[0027] "Standard rim" refers to a rim with a specified specification for each tire within a specification system that includes the specifications on which tire 1 is based. For example, if it is JATMA, it is "standard rim"; if it is TRA, it is "Design Rim"; and if it is ETRTO, it is "Measuring Rim".

[0028] "Standard internal pressure" refers to the air pressure specified for each tire in the specification system, including the specification on which tire 1 is based. If it is JATMA, it is "maximum air pressure". If it is TRA, it is the maximum value recorded in the table "TIRE LOAD LIMITS ATVARIOUS COLD INFLATION PRESSURES". If it is ETRTO, it is "INFLATION PRESSURE".

[0029] In this embodiment, the inner portion 14 is formed with a single radius of curvature. Such an inner portion 14 mitigates stress concentration acting on it, thus further improving traction performance. Alternatively, the inner portion 14 can be formed by arcs with multiple radii of curvature.

[0030] The radius of curvature R1 of the inner portion 14 is preferably 3 to 10 mm. Since the radius of curvature R is 3 mm or more, the stress concentration acting on the inner portion 14 is reduced. Since the radius of curvature R1 is 10 mm or less, the rigidity of the inner portion 14 is maintained at a high level. In the case where the inner portion 14 is formed by multiple arcs with different radii of curvature, the radius of curvature of the imaginary arc forming the outermost, innermost, and midpoint (not shown) of the tire radial direction of the inner portion 14 is adopted.

[0031] In the first sidewall 11 of the aforementioned longitudinal section, the angle α of the first straight line X1 relative to the tread normal n erected on the first edge 10e is preferably 45 degrees or less. The first straight line X1 is a straight line connecting the first edge 10e to a position P1 that is 50% of the tread block height Ha, extending radially inward from the first edge 10e towards the tire. This ensures the rigidity of the tread block 4, allowing it to penetrate deeply into the first sidewall 11. If the angle α is small, the amount of soil excavated during shearing may be smaller. From this viewpoint, the angle α is preferably 5 degrees or more, preferably 35 degrees or less, and more preferably 25 degrees or less.

[0032] The tread 10 also has a second edge 10i extending axially along the tire on the rear contact side in the rotational direction N. Each tread block 4 also includes a second sidewall 12 extending radially inward from the second edge 10i towards the tire. Figure 1 (As shown).

[0033] In the aforementioned longitudinal section, the second sidewall 12 is inclined toward the rear contact side in the rotational direction N as it moves inward from the second edge 10i toward the radial direction of the tire. This second sidewall 12 increases the rigidity of the tread block 4 and prevents the tread block 4 from collapsing toward the rear contact side in the rotational direction N when it contacts the ground.

[0034] The second sidewall 12 includes, for example, a first portion 17 extending radially inward from the second edge 10i towards the tire; a second portion 18 connected to the first portion 17 and inclined more gently than the first portion 17; and a third portion 19 connecting the second portion 18 to the tread base 2R. In this embodiment, the first portion 17 and the second portion 18 extend in a straight line. The third portion 19 is curved in an arc shape. The third portion 19 is, for example, formed as an arc shape recessed towards the first contact side in the rotation direction N.

[0035] The radial length H2 of the tire in Part 17 is preferably 5% or more, more preferably 10% or more, and more preferably 25% or less, and more preferably 20% or less, of the tread block height Ha of the tread block 4. Furthermore, the radial length H3 of the tire in Part 28 is formed to be larger than the length H2 of Part 17. The length H3 of Part 28 is preferably 25% or more, more preferably 30% or more, and more preferably 45% or less, and more preferably 30% or less, of the tread block height Ha of the tread block 4.

[0036] The radius of curvature R2 of the third part 19 is formed to be larger than the radius of curvature R1 of the inner part 14. This further suppresses the collapse of the pattern block 4 during grounding. Although not particularly limited, the radius of curvature R2 of the third part 19 is preferably 10 mm or more, more preferably 15 mm or more, more preferably 30 mm or less, and more preferably 25 mm or less.

[0037] In the second sidewall 12 of the aforementioned longitudinal section, the angle β of the second straight line X2 relative to the tread normal n erected on the second edge 10i is preferably greater than the angle α. The second straight line X2 is a straight line connecting the second edge 10i to a position P2 that is 50% of the tread block height Ha from the second edge 10i radially inward towards the tire. This further suppresses the collapse of the tread block 4 upon contact with the ground.

[0038] In order to effectively perform the above-mentioned function, the angle β is preferably 5 degrees or more, more preferably 20 degrees or more, even more preferably 30 degrees or more, preferably 75 degrees or less, more preferably 60 degrees or less, and even more preferably 50 degrees or less.

[0039] Figure 4 This is a top view of the tread area 2 in this embodiment. Figure 4 As shown, the tread block 4 includes, for example, a crown tread block 5 disposed on the tire equator C; and an intermediate tread block 6 located axially outward of the crown tread block 5. In this embodiment, the tread block 4 includes a shoulder tread block 7 disposed axially outward of the intermediate tread block 6. The tread portion 2 has, for example, a shape symmetrical with respect to the tire equator C.

[0040] Furthermore, in this embodiment, each tread surface 10 of the tread block 5 and the intermediate tread block 6 has a first sidewall surface 11 including an outer portion 13 and an inner portion 14 as described above. The tread block 5 and the intermediate tread block 6 are primarily the tread blocks 4 that contact the ground during straight-line driving; therefore, the tire 1 of this embodiment particularly improves traction performance during straight-line driving. Also, each tread surface 10 of the tread block 5 and the intermediate tread block 6 in this embodiment has a second sidewall surface 12 as described above.

[0041] The first edge 10e of the tread block 5 is formed in a V-shape protruding towards the rear contact side in the direction of rotation N. This tread block 5 can exert a large shear force on the soil, thus improving traction performance.

[0042] The angle θ1 of the first edge 10e relative 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 25 degrees or less. This tread block 5 can concentrate the soil dug up by the first edge 10e at the center of the tread block width direction, thus exerting greater shear force. The angle θ1 is the angle of an imaginary straight line connecting the outer end e1 of the first edge 10e in the tire axial direction to the middle position e2 in the tire axial direction. The outer end e1 is located on the side of the first edge 10e that first touches the ground in the rotational direction N. The middle position e2 is located on the side of the first edge 10e that last touches the ground in the rotational direction N. Furthermore, in this embodiment, the middle position e2 is located on the tire equator C.

[0043] Each tread block 5 includes: a tread block body 20, which is formed in a V-shape protruding towards the rear contact side in the direction of rotation N; and tread fin portions 21, which protrude from the tread block body 20 towards the rear contact side in the direction of rotation N. For such a tread block 5, the tread fin portions 21 prevent the tread block body 20 from collapsing towards the rear contact side in the direction of rotation N upon contact with the ground, maintaining the digging force of the soil, thus improving traction performance. Each tread block 5 has only two tread fin portions 21.

[0044] Figure 5 This is an enlarged view of tread pattern block 5 on the tire crown. (See image below.) Figure 5As shown, the first edge 10e includes: a first outer portion 15a extending from its outer end e1; a first inner portion 15b including a middle position e2; and a first middle portion 15c connecting the first outer portion 15a and the first inner portion 15b. The first middle portion 15c is inclined at a greater angle relative to the tire axis than the first outer portion 15a and the first inner portion 15b. The first outer portion 15a and the first middle portion 15c extend, for example, in a straight line. The first inner portion 15b is bent into a V-shape, for example, at the middle position e2.

[0045] The second edge 10i includes: an inner edge portion 16A, which extends axially inward from the connection portion K between the tread block body 20 and the tread fin portion 21; and an outer edge portion 16B, which extends axially outward from the connection portion K. The inner edge portion 16A, for example, includes a rear contact end 16i in the rotational direction N of the second edge 10i. The inner edge portion 16A is, for example, bent into a V-shape. The outer edge portion 16B extends, for example, in a straight line.

[0046] In this embodiment, when the tire is viewed from above, the crown fin portion 21 is formed in a parallelogram shape. The crown fin portion 21 includes, for example, an outer edge 21e in the tread block width direction, an inner edge 21i in the tread block width direction, a first contact edge 21a on the first contact side in the rotational direction N, and a rear contact edge 21b on the rear contact side in the rotational direction N. The outer edge 21e and the inner edge 21i extend, for example, parallel to the tire circumferential direction. The first contact edge 21a is, for example, located on the first contact side in the rotational direction N, closer to the second edge 10i. The first contact edge 21a and the rear contact edge 21b extend, for example, parallel to the outer edge portion 16B. The inner edge 21i, the outer edge 21e, the first contact edge 21a, and the rear contact edge 21b form an outer surface 21A facing the radially outer side of the tire crown fin portion 21.

[0047] In this embodiment, the outer surface 21A is located radially outward from the tread surface 22 of the tread block body 20. Figure 7 (As shown). The outer surface 21A may also be located, for example, at the same radial position on the tire as the tread surface 22 of the tread block body 20.

[0048] The outer edge 21e of the tread fin portion 21 in the width direction is located inside the tread fin in the width direction, which is closer to the outer end 20e of the tread fin body 20 in the tire axial direction. Such a tread fin 5 maintains the deformation of the tread fin portion 21, which facilitates the removal of mud that is stuck between the tread fin portions 21, thus particularly improving the edge effect of the inner edge portion 16A of the tread fin body 20.

[0049] The tire axial separation distance Lb between the outer edge 21e of the tread fin portion 21 and the outer end 20e of the tread block body 20 is preferably 15% or more, more preferably 20% or more, more preferably 35% or less, and more preferably 30% or less of the width W1 of the tread block body 20. This ensures the deformation of the tread fin portion 21 and improves the mud removal effect.

[0050] Figure 6 This is an enlarged view of tread pattern block 5 on the tire crown. (See image below.) Figure 6 As shown, a shallow groove 25 is formed at the connection portion K between the tread block body 20 and the tread fin portion 21 to promote deformation of the connection portion K side of the tread fin portion 21. Such a shallow groove 25 helps to smoothly drain the dirt that is blocked between the tread fin portions 21.

[0051] The shallow groove 25 communicates with the inner edge 16A and outer edge 16B of the tread block 5 in a manner that surrounds the connecting portion K. The shallow groove 25 extends, for example, along the outer edge 21e, inner edge 21i, and first-landing edge 21a. This shallow groove 25 makes the tread fin portion 21 appear independent from the tread block body 20, thus increasing the deformation of the tread fin portion 21 and further improving traction performance on uneven surfaces. In this embodiment, the shallow groove 25 extends in a U-shape, protruding towards the first-landing side in the rotation direction N.

[0052] Figure 7 yes Figure 6 A BB-line sectional view. For example... Figure 7 As shown, the groove depth d1 of the shallow groove 25 is preferably 5% or more of the tread block height Ha of the tread block 5, more preferably 10% or more, more preferably 25% or less, and more preferably 20% or less. Additionally, as... Figure 6 As shown, the width W3 of the shallow groove 25 is preferably 2% or more, more preferably 5% or more, more preferably 15% or less, and more preferably 10% or less, of the width W1 of the tread block body 20. This effectively achieves the aforementioned effect and maintains the rigidity of the tread fin portion 21 and the tread block body 20, ensuring their high shear strength.

[0053] The tire circumferential separation distance Ld between the first contact end 25e of the rotation direction N of the shallow groove 25 and the second edge 10i is preferably less than 60% of the length L2 of the tread block body 20. This maintains the tire circumferential rigidity of the tread block body 20, thus maximizing the effect of suppressing collapse when the tread block 5 contacts the ground.

[0054] Although not specifically limited, the width W1 of the tread block body 20 is preferably the tread unfolded width TW. Figure 4The tread width (TW) is 20% or more, more preferably 25% or more, and more preferably 40% or less, and more preferably 35% or less. The tread width TW is the axial distance between the tread ends Te and Te when the tread portion 2 is unfolded into a plane.

[0055] Figure 8 This is an enlarged top view of the area around the central patterned block 6. (Example) Figure 8 As shown, in this embodiment, the intermediate tread block 6 tilts towards the first contact side in the rotational direction N as it moves from the inner side of the tire axial direction towards the outer side. The intermediate tread block 6 includes, for example, a parallelogram-shaped intermediate tread block body 30 and an intermediate fin portion 31 protruding from the intermediate tread block body 30 towards the rear contact side in the rotational direction N.

[0056] The main body 30 of the intermediate tread block includes a pair of third edges 32 extending from both ends e3 of its first edge 10e toward the rear contact side in the direction of rotation N. The pair of third edges 32 are formed by a third inner edge 32a that is adjacent to the crown tread block 5 in the tire axial direction and a third outer edge 32b that is adjacent to the shoulder tread block 7 in the tire axial direction.

[0057] For example, two intermediate fin portions 31 are provided in the intermediate pattern block body 30. The intermediate fin portion 31 is composed of an outer intermediate fin portion 31A connected to the third outer edge 32b and an inner intermediate fin portion 31B disposed on the inner side of the tire axis than the outer intermediate fin portion 31A.

[0058] The outer intermediate fin portion 31A is directly connected to the intermediate tread block body 30. The outer edge 33 of the outer intermediate fin portion 31A along the tire axial direction and the third outer edge 32b are formed in a straight line.

[0059] The inner intermediate fin portion 31B is connected to the intermediate tread block body 30 via the intermediate shallow groove 36. The inner edge 37 of the inner intermediate fin portion 31B along the tire axial direction is separated from the third inner edge 32a by the intermediate shallow groove 36 in a straight line. Such an inner intermediate fin portion 31B facilitates deformation through the intermediate shallow groove 36, thus making it easier to remove dirt stuck between the two intermediate fin portions 31. The groove edge 36a, which extends along the length direction of the intermediate shallow groove 36 and is disposed on the first contact side in the rotation direction N, forms the second edge 10i of the intermediate tread block 6 in this embodiment.

[0060] The width W4 of the intermediate shallow groove 36 is preferably 80% or more, more preferably 90% or more, and preferably 125% or less, more preferably 110% or less, of the width W3 of the shallow groove 25 of the tread block 5. The depth of the intermediate shallow groove 36 (not shown) is preferably 5% or more, more preferably 10% or more, and preferably 20% or less, more preferably 15% or less, of the height of the tread block body 30 (not shown). The width W5 of the intermediate tread block body 30 is preferably the tread width TW. Figure 4 (as shown) 5% or more, more preferably 10% or more, more preferably 25% or less, more preferably 20% or less.

[0061] like Figure 4 As shown, the first edge 10e of the intermediate tread block 6 is located, for example, on an imaginary straight line X3 formed by extending the first edge 10e of the crown tread block 5 outward in the tire axial direction. Thus, the first edge 10e of the intermediate tread block 6 and the first edge 10e of the crown tread block 5 appear to form a single edge, thereby generating a large shear force and improving traction performance. In this specification, the term "single edge" naturally includes the case where the first edge 10e of the intermediate tread block 6 coincides with the imaginary straight line X3, and also includes the case where the maximum circumferential separation distance Le between the first edge 10e of the intermediate tread block 6 and the imaginary straight line X3 is 3 mm or less.

[0062] Figure 9 This is a top view of tire shoulder tread block 7. (Example) Figure 9 As shown, when viewed from above, the shoulder tread block 7 is formed, for example, in a quadrilateral shape. In this embodiment, the shoulder tread block 7 is formed in a trapezoidal shape. The tread surface 7a of the shoulder tread block 7 includes an outer edge 41, an inner edge 42, a rear contact side edge 43, and a first contact side edge 44. The outer edge 41 extends, for example, outward from the tire axial direction along the tire circumferential direction. In this embodiment, the outer edge 41 forms the tread end Te. The inner edge 42 extends, for example, inward from the tire axial direction than the outer edge 41 along the tire circumferential direction. In this embodiment, the rear contact side edge 43 connects the outer edge 41 and the inner edge 42 and extends parallel to the tire axial direction. In this embodiment, the rear contact side edge 43 defines the rear contact side of the rotation direction N of the shoulder tread block 7. In this embodiment, the first contact side edge 44 connects the outer edge 41 and the inner edge 42 and is inclined relative to the tire axial direction. In this embodiment, the first-to-ground edge 44 defines the first-to-ground side of the rotation direction N of the tire shoulder tread block 7.

[0063] In this embodiment, the shoulder tread block 7 has a shoulder groove 45. When viewed from above, the shoulder groove 45 extends in a V-shape. Such a shoulder groove 45 promotes the deformation of the shoulder tread block 7, making it easier to remove mud that is stuck between the shoulder tread block 7 and the intermediate tread block 6.

[0064] The shoulder groove 45 includes a circumferential portion 46 extending along the tire circumference and an axial portion 47 extending along the tire axis. The circumferential portion 46 extends at an angle of less than 45 degrees relative to the tire circumference. The axial portion 47 is inclined at an angle of more than 45 degrees relative to the tire circumference.

[0065] In this embodiment, the circumferential portion 46 extends parallel to the tire circumferential direction from the rear contact edge 43 toward the first contact side in the rotational direction N, and forms an end within the shoulder tread block 7. In this embodiment, the axial portion 47 extends from the inner edge 42 toward the outer side of the tire axial direction and connects to the end of the circumferential portion 46. In this embodiment, the axial portion 47 extends parallel to the first contact edge 44. Such a shallow shoulder groove 45 further promotes the deformation of the shoulder tread block 7.

[0066] The width W6 of the shoulder shallow groove 45 is preferably 5% or more, more preferably 10% or more, and more preferably 25% or less, and more preferably 20% or less, of the tire axial width W7 of the shoulder tread block 7. The depth of the shoulder shallow groove 45 (not shown) is preferably 5% or more, more preferably 10% or more, and more preferably 20% or less, and more preferably 15% or less, of the tread block height (not shown). The width W7 of the shoulder tread block 7 is preferably 5% or more, more preferably 7% or more, and more preferably 20% or less, and more preferably 15% or less, of the tread width TW.

[0067] For tread rubber with 5 to 7 such patterned blocks (illustration omitted), the rubber hardness is preferably 70 degrees or higher, and more preferably 90 degrees or lower. In this specification, the rubber hardness is based on the A hardness of a durometer measured by JIS-K6253 at 23°C.

[0068] The preferred embodiments of this disclosure have been described in detail above, but this disclosure is not limited to the illustrated embodiments and can be implemented in various ways. All front wheel tires have the same tread pattern.

[0069] Example

[0070] Based on the specifications in Table 1, a trial production was carried out with... Figure 4 The test tires were rear wheel tires for motorcycles designed for use on uneven terrain. Then, the traction / instantaneous performance and overall performance of each tire were tested. The front wheel tires were identical in all cases. The common specifications and test methods for all test tires are as follows.

[0071] Vehicle used: 450cc off-road racing motorcycle

[0072] Tire sizes (front and rear): 80 / 100-21, 120 / 80-19

[0073] Wheel rim dimensions (front and rear): 21×1.60, 19×2.15

[0074] Internal pressure: 80 kPa

[0075] The testing method is as follows.

[0076] <Traction performance / Instantaneous performance>

[0077] The traction and instantaneous acceleration performance of the test vehicles were evaluated using rider sensory assessments on uneven terrain with mud. Here, "traction performance" refers to the smoothness of acceleration response when the accelerator is engaged at a certain speed while traveling straight and turning (the smoothness of acceleration as speed increases further from a fully increased state). "Instantaneous acceleration performance" refers to the smoothness of acceleration response when the accelerator is engaged at low speeds during start-up, straight-line travel, and turning (the smoothness of acceleration as speed increases from a low state). "Overall performance" refers to the smoothness of riding and the comfort of handlebar response during acceleration while traveling straight and turning, evaluated using rider sensory assessments. Each test was scored out of 10.

[0078] The test results are shown in Table 1. In Table 1, "A" indicates that the first edge of the center tread block is located on an imaginary straight line formed by extending the first edge of the crown tread block axially outwards from the tire.

[0079] Table 1

[0080]

[0081] The test results indicate that the tires of the embodiments demonstrate improved traction performance on uneven surfaces compared to the comparative tires. Furthermore, it can be understood that the tires of the embodiments exhibit improved instantaneous performance compared to the comparative tires.

[0082] [Postscript]

[0083] This disclosure includes the following methods.

[0084] [This disclosure 1]

[0085] A tire for driving on uneven surfaces has a tread portion, wherein the tread portion is designated in the tire rotation direction, and a plurality of tread blocks raised from the tread base are provided on the tread portion. Each of the plurality of tread blocks includes: a tread surface having a first edge extending axially along the tire on the first contact side in the tire rotation direction; and a first sidewall extending radially inward from the first edge. In a longitudinal section of the tread block along the tire circumference, the first sidewall includes: an outer portion extending linearly from the first edge radially inward and inclined towards the rear contact side in the tire rotation direction than the tread normal erected on the first edge; and an inner portion curved into an arc shape connecting the outer portion to the tread base. The radial length of the outer portion is 30% to 70% of the tread block height in the tire radial direction from the tread base to the tread surface.

[0086] [This disclosure 2]

[0087] In the tire for driving on uneven terrain as described in this disclosure 1, the aforementioned longitudinal section is the longitudinal section at the central position of the tire axial direction of the aforementioned tread block.

[0088] [This disclosure 3]

[0089] In the tires for driving on uneven terrain described in disclosure 1 or 2,

[0090] The radius of curvature of the inner part is 3 to 10 mm.

[0091] [This disclosure 4]

[0092] In any one of the tires for driving on uneven terrain disclosed herein, in the first sidewall of the longitudinal section, the angle α between the first edge and the position 50% of the height of the tread block that is radially inward from the first edge of the tire and the tread normal erected on the first edge is 45 degrees or less.

[0093] [This disclosure 5]

[0094] In any one of the tires for driving on uneven terrain disclosed herein, the tread further has a second edge extending axially along the rear contact side in the tire rotation direction, and each of the plurality of tread blocks further includes a second sidewall extending radially inward from the second edge toward the inner side of the tire. In the longitudinal section, the second sidewall is inclined toward the rear contact side in the tire rotation direction as it moves radially inward from the second edge toward the inner side of the tire.

[0095] [This disclosure 6]

[0096] In the tire for driving on uneven terrain as described in this disclosure 5, in the first sidewall and the second sidewall of the longitudinal section, the angle β of the second straight line connecting the second edge to a position 50% of the height of the tread block in the radial direction inward from the second edge relative to the tread normal line erected on the second edge is greater than the angle α of the first straight line connecting the first edge to a position 50% of the height of the tread block in the radial direction inward from the first edge relative to the tread normal line erected on the first edge.

[0097] [This disclosure 7]

[0098] In the tire for driving on uneven terrain described in this disclosure 6, the aforementioned angle β is 5 to 75 degrees.

[0099] [This disclosure is 8]

[0100] In any one of the tires for driving on uneven terrain disclosed herein 1 to 7, the plurality of tread blocks include a crown tread block disposed on the tire equator, wherein the first edge of the crown tread block is formed in a V-shape protruding toward the rear contact side in the direction of tire rotation.

[0101] [This disclosure is number 9]

[0102] In the tire for driving on uneven terrain as described in this disclosure 8, the angle between the first edge of the tread pattern block and the tire axial direction is 10 to 45 degrees.

[0103] [This disclosure is number 10]

[0104] In the tire for driving on uneven surfaces as described in disclosure 8 or 9, the tread blocks include an intermediate tread block located axially outward from the crown tread blocks, and the first edge of the intermediate tread block is located on an imaginary straight line formed by extending the first edge of the crown tread block axially outward from the tire.

Claims

1. A tire for driving on uneven terrain, having a tread pattern, characterized in that, The tread section is designated to indicate the tire's rotation direction. The tread surface is provided with multiple tread blocks that rise from the base of the tread. The plurality of tread blocks each include: a tread surface having a first edge extending axially along the tire on the first contact side in the tire rotation direction; and a first sidewall extending radially inward from the first edge. In the longitudinal section along the tire circumference of the tread block, the first sidewall includes: an outer portion extending linearly from the first edge toward the radially inward side of the tire, and inclined at an angle toward the rear contact side in the tire rotation direction than the tread normal erected at the first edge; and an inner portion curved into an arc shape connecting the outer portion to the tread base. The radial length of the outer portion of the tire is 30% to 70% of the radial height of the tread block, from the tread base to the tread surface. The plurality of tread blocks include tread blocks arranged on the tire equator. The first edge of the tread pattern block is formed in a V-shape protruding towards the rear contact side in the direction of tire rotation. The tread pattern blocks each include: a tread pattern block body, formed in a V-shape protruding towards the rear contact side in the direction of tire rotation; and tread fin portions, protruding from the tread pattern block body towards the rear contact side in the direction of tire rotation. The outer surface of the tread fin portion facing the radial outer side of the tire is located radially outer than the tread surface of the tread block body.

2. The tire for driving on uneven terrain according to claim 1, characterized in that, The longitudinal section is the longitudinal section at the center position of the tire axial direction of the tread block.

3. The tire for driving on uneven terrain according to claim 1 or 2, characterized in that, The radius of curvature of the inner part is 3~10mm.

4. The tire for driving on uneven terrain according to claim 1 or 2, characterized in that, In the first sidewall of the longitudinal section, the angle α of the first straight line connecting the first edge to a position 50% of the height of the tread block in the radially inward direction from the first edge relative to the tread normal erected on the first edge is less than 45 degrees.

5. The tire for driving on uneven terrain according to claim 1 or 2, characterized in that, The tread also has a second edge extending axially along the rear contact side in the tire rotation direction. Each of the plurality of tread blocks further includes a second sidewall extending radially inward from the second edge toward the inner side of the tire. In the longitudinal section, the second sidewall is inclined toward the rear contact side in the tire rotation direction as it moves inward from the second edge toward the radial direction of the tire.

6. The tire for driving on uneven terrain according to claim 5, characterized in that, In the first and second sidewalls of the longitudinal section, the angle β of the second straight line connecting the second edge to a position 50% of the height of the tread block in the radially inward direction of the tire relative to the tread normal on the second edge is greater than the angle α of the first straight line connecting the first edge to a position 50% of the height of the tread block in the radially inward direction of the tire relative to the tread normal on the first edge.

7. The tire for driving on uneven terrain according to claim 6, characterized in that, The angle β is 5 to 75 degrees.

8. The tire for driving on uneven terrain according to claim 1, 2 or 7, characterized in that, The angle between the first edge of the tread pattern block and the tire axial direction is 10 to 45 degrees.

9. The tire for driving on uneven terrain according to claim 1, 2 or 7, characterized in that, The tread blocks include intermediate tread blocks located axially outward from the crown tread blocks. The first edge of the intermediate tread block lies on an imaginary straight line formed by extending the first edge of the tread block outward in the tire axial direction.

Images