Tire of two-wheeled vehicle for running on uneven ground

Abstract

The invention provides a two-wheeled vehicle tire used for running on rough ground, which can maintain impact absorption performance and simultaneously exert excellent roll characteristics. The present invention is a two-wheeled vehicle tire having a tread portion (2) for running on rough ground. The tread portion (2) includes a first tread end (T1), a second tread end (T2), a tread spread width (TWe), a tire equator (C), a crown region (6), and a side region (7). The tread portion (2) includes a plurality of crown blocks (10) and a plurality of outer blocks (20). The tread surface of each of the plurality of outer blocks (20) is a stepped surface (25) in which at least a narrow groove is formed or which includes a base surface (26) and a protruding surface (27) that partially protrudes outward in the block height direction with respect to the base surface (26). The tread surface of each of the plurality of crown blocks (10) is a non-stepped surface (28) in which a narrow groove (15) is formed and which does not have a protruding surface (27).

Description

Technical Field

[0001] The present invention relates to a two-wheeler tire for traveling on an uneven ground. Background Art

[0002] In Patent Document 1 described below, a motorcycle tire for traveling on an uneven ground is proposed, which has a plurality of first tread blocks provided on a tread surface. The first tread blocks include a pair of sipes that divide the tread surface and extend without crossing each other, a first portion formed between the pair of sipes, and a pair of second portions formed on both outer sides of the pair of sipes. In addition, the block height of the first portion is different from the block height of the pair of second portions. Further, in the specific embodiment shown in Patent Document 1, the intermediate tread block is configured as the above-described first tread block.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2020-179744 Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] In the tire as described above, when a fine groove or a stepped surface is formed on the tread surface of the tread block, the edge component of the tread block increases, thereby improving the traction performance and braking performance during straight running or turning.

[0008] However, when the above-described fine groove or stepped surface is used only for a part of the tread blocks, the edge components in each tread block are greatly different, and sometimes it may cause deterioration of the grip feeling or the transient characteristics of the response (hereinafter referred to as "roll characteristics") perceived by the driver during rolling.

[0009] In addition, when a stepped surface is formed on the tread block near the tire equator, the outer diameter of the tire increases compared with the case where no stepped surface is provided. Therefore, it is necessary to adjust the outer diameter of the tire to within the specification by using components other than the tread blocks. Therefore, for example, by adjusting such as reducing the block height or reducing the thickness of the tread rubber inside the tread block, it is also possible to impair the shock absorption of the tire.

[0010] The present invention has been made in view of the above actual situation, and its main problem is to provide a two-wheeler tire for traveling on an uneven ground that can exhibit excellent roll characteristics while maintaining shock absorption.

[0011] Technical Means for Solving the Problems

[0012] The present invention relates to a two-wheeler tire for traveling on an uneven ground, which has a tread surface. Among them, the tread surface includes a first tread end, a second tread end, a tread width extending from the first tread end to the second tread end, a tire equator, a crown region having a width of 20% of the tread width centered on the tire equator, and side regions on both outer sides of the crown region. The tread surface includes a plurality of crown tread blocks provided in the crown region and a plurality of outer tread blocks provided in the side regions. The tread surface of each of the plurality of outer tread blocks is a stepped surface formed with fine grooves or including a base surface and a protruding surface that locally protrudes outward in the tread block height direction with respect to the base surface. The tread surface of each of the plurality of crown tread blocks is a non-stepped surface formed with fine grooves and not having the protruding surface.

[0013] Effects of the Invention

[0014] By adopting the above structure, the two-wheeler tire for traveling on an uneven ground of the present invention can exhibit excellent roll characteristics while maintaining shock absorption. Description of the Drawings

[0015] Figure 1 It is a cross-sectional view of the tread surface of the two-wheeler tire for traveling on an uneven ground of the present embodiment.

[0016] Figure 2 It is Figure 1 an expanded view of the tread surface of

[0017] Figure 3 It is Figure 2 a sectional view taken along line B-B of

[0018] Figure 4 It is Figure 2 a sectional view taken along line C-C of

[0019] Figure 5 It is a sectional view of an outer tread block of another embodiment.

[0020] Figure 6 It is a sectional view of an outer tread block of another embodiment.

[0021] Figure 7 It is Figure 2 a sectional view taken along line D-D of

[0022] Figure 8 It is Figure 2 a sectional view taken along line E-E of

[0023] Figure 9 It is Figure 2 an enlarged view of a plurality of shoulder tread blocks of

[0024] Figure 10 It isFigure 2 Enlarged view of multiple intermediate tread blocks.

[0025] Figure 11 is Figure 2 Enlarged view of multiple crown tread blocks.

[0026] Figure 12 is a developed view of the tread surface of another embodiment of the present invention.

[0027] Figure 13 is a developed view of the tread surface of Comparative Example 1.

[0028] Figure 14 is an enlarged cross-sectional view of the crown tread block of Comparative Example 2.

[0029] Description of Reference Numerals

[0030] 2 Tread surface

[0031] 6 Crown area

[0032] 7 Side area

[0033] 10 Crown tread block

[0034] 15 Groove

[0035] 20 Outer tread block

[0036] 25 Step surface

[0037] 26 Base surface

[0038] 27 Protruding surface

[0039] 28 Non-step surface

[0040] T1 First tread end

[0041] T2 Second tread end

[0042] TWe Tread developed width Detailed Embodiment

[0043] Hereinafter, an embodiment of the present invention will be described based on the drawings. Although the drawings depict and include the features of the present invention, for the purpose of assisting in understanding the present invention, they sometimes include exaggerated representations or representations different from the actual structural dimensional ratios. In addition, in each embodiment, the same or common elements are denoted by the same reference numerals, and repeated descriptions are omitted.

[0044] Figure 1 shows a cross-sectional view of the tread surface 2 of the two-wheeled vehicle tire (hereinafter sometimes simply referred to as "tire") 1 for traveling on an uneven road surface in the standard state of the present embodiment. Figure 2 is a developed view of the tread surface 2 of the tire 1 unfolded on a plane.Figure 1 Equivalent to Figure 2 Cross-sectional view taken along line A-A

[0045] "Standard state" means that, in the case of tires with various specified specifications, the tire is assembled on a standard rim by the wheel rim, filled with the standard internal pressure, and in a load-free state. In the case of tires without various specified specifications, the "standard state" means the standard usage state corresponding to the usage purpose of the tire and in a load-free state. In this specification, unless otherwise specified, the dimensions and the like of each part are values measured in the above standard state.

[0046] "Standard rim" is the rim specified for each tire in the specification system including the specifications on which the tire is based. For example, if it is JATMA, it is the "standard rim"; if it is TRA, it is the "Design Rim"; if it is ETRTO, it is the "Measuring Rim".

[0047] "Standard internal pressure" is the air pressure specified for each tire in the specification system including the specifications on which the tire is based. If it is JATMA, it is the "maximum air pressure"; if it is TRA, it is the maximum value recorded in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; if it is ETRTO, it is the "INFLATION PRESSURE".

[0048] As Figure 1 shown, the tire 1 of the present embodiment is for a motorcycle and is, for example, suitable as a tire for a motorcycle cross-country race. The tire 1 of the present embodiment is, for example, suitable as a tire for the rear wheel of a motorcycle off-road vehicle. However, the present invention is not limited to such a manner. The outer surface of the tread portion 2 of the tire 1 of the present embodiment is curved outward in a convex arc shape in the cross section in the tire radial direction.

[0049] The tire 1 of the present embodiment, for example, has a carcass and a tread reinforcement layer (not shown). These can be appropriately adopted with existing structures. In addition, the tread portion 2 includes a plurality of tread blocks 5 that protrude from the tread bottom surface 4. When the tire 1 of the present embodiment travels on an uneven road surface, the tread blocks 5 penetrate into the road surface and exert a high reaction force. Therefore, the tread bottom surface 4 can also contact the road surface.

[0050] As Figure 2 shown, the tread portion 2 of the tire 1 of the present invention has a directional pattern specifying the rotation direction R. The rotation direction R is, for example, indicated by letters or marks on the sidewall portion 3 ( Figure 1 shown). However, the present invention is not limited to such a manner.

[0051] The tread surface portion 2 includes a first tread end T1, a second tread end T2, a tread width TWe from the first tread end T1 to the second tread end T2, and a tire equator C. The first tread end T1 and the second tread end T2 respectively refer to the outer edges in the tire axial direction of the tread surfaces of the tread blocks 5 included in the outermost tread block rows in the tire axial direction disposed on the tread surface portion 2.

[0052] The tread width TWe corresponds to the distance in the tire axial direction from the first tread end T1 to the second tread end T2 when the tread surface portion 2 is developed into a plane. The tire equator C is an imaginary line that extends parallel to the tire circumferential direction at the center position in the tire axial direction of the tread surface portion.

[0053] The tread surface portion 2 includes a crown region 6 and side regions 7. The crown region 6 has a width Wc of 20% of the tread width TWe centered on the tire equator C. The side regions 7 are regions disposed on both outer sides of the crown region 6. That is, the two side regions 7 are disposed with the crown region 6 therebetween. In Figure 2 it, the boundary 8 between the crown region 6 and the side regions 7 is indicated by a double-dashed line.

[0054] The tread surface portion 2 includes a plurality of crown tread blocks 10 provided on the crown region 6 and a plurality of outer tread blocks 20 provided on the side regions 7. In the developed view of the tread surface portion 2 of the present embodiment, on the tread surface of the tread block 5, the tread block through which the boundary 8 between the crown region 6 and the side regions 7 passes corresponds to the crown tread block 10. In other words, the entire tread surface of the outer tread block 20 is more on the outer side in the tire axial direction than the boundary 8. Further, the tread surface of the tread block refers to the region within the outer surface of the tread block that extends along the virtual tread bottom surface 4 passing through the root of the tread block. More specifically, it refers to the region with an angle of 30° or less with respect to the tread bottom surface 4.

[0055] The outer tread blocks 20 include a plurality of shoulder tread blocks 40 and a plurality of intermediate tread blocks 30, wherein the plurality of shoulder tread blocks 40 include the first tread end T1 or the second tread end T2, and the plurality of intermediate tread blocks 30 are disposed between the plurality of shoulder tread blocks 40 and the crown region 6. Figure 3 Shown Figure 2 is the cross-sectional view taken along line B-B as a view showing the cross-section of the shoulder tread block 40. Further, Figure 4 Shown Figure 2 is the cross-sectional view taken along line C-C as a view showing the cross-section of the intermediate tread block 30. Further, in the view showing the enlarged cross-section of the tread block of the present specification, for the sake of easy understanding of its features, the bending components included in the tread surface of the actual tread block are appropriately excluded for representation.

[0056] As Figure 3 and Figure 4As shown, the tread surfaces of the plurality of outer tread blocks 20 each form fine grooves 15 or stepped surfaces 25 including a base surface 26 and a protruding surface 27 that locally protrudes outward in the tread block height direction with respect to the base surface 26. Additionally, in the present embodiment, the entire protruding surface 27 protrudes outward in the tread block height direction with respect to the base surface 26. The fine grooves 15 refer to grooves with a groove width of 3.0 mm or less and include micro-grooves known as so-called knife grooves.

[0057] Each of the outer tread blocks 20 of the present embodiment has fine grooves 15 and a stepped surface 25 in which one surface divided by the fine grooves 15 constitutes the base surface 26 and the other surface constitutes the protruding surface 27. However, the present invention is not limited to such a manner. Figure 5 and 6 The cross-sectional view of the outer tread block 20 of another embodiment is shown. As Figure 5 shown, the outer tread block 20 of the present invention may also be provided with only fine grooves 15 where the two side surface portions of the fine grooves have the same height and do not form a stepped surface 25. Additionally, as Figure 6 shown, the outer tread block 20 of the present invention may also not be provided with fine grooves and form a stepped surface 25 including a base surface 26 and a protruding surface 27.

[0058] Figure 7 Shown Figure 2 is the cross-sectional view taken along the line D-D as a view showing the cross-section of the crown tread block 10. As Figure 7 shown, the tread surfaces of the plurality of crown tread blocks 10 each form fine grooves 15 and are non-stepped surfaces 28 that do not have the protruding surface 27 ( Figure 3 and Figure 4 shown). Additionally, the non-stepped surface 28 refers to a surface where the height of one surface divided by the fine grooves 15 and the height of the other surface are substantially the same and no step is formed. However, from the perspective of tolerating inevitable errors in a tire as a rubber product, a tire with a step of 0.5 mm or less is treated as a non-stepped surface.

[0059] By adopting the above structure, the tire of the present invention can exhibit excellent roll characteristics while maintaining shock absorption. The reasons are as follows.

[0060] As Figures 3 to 6 shown, in the tire of the present invention, the tread surfaces of the plurality of outer tread blocks 20 each form fine grooves 15 or are formed as stepped surfaces 25. Additionally, as Figure 7 shown, the tread surfaces of the plurality of crown tread blocks 10 are non-stepped surfaces 28 that form fine grooves 15 and do not have the protruding surface. Thus, as Figure 2 shown, the edge component of any tread block 5 is increased due to the fine grooves 15 or the stepped surface 25, and thus an improvement in roll characteristics can be expected.

[0061] On the other hand, in the prior art, when a stepped surface is formed on the tread blocks near the tire equator, the outer diameter of the tire increases compared to the case where no stepped surface is provided. Therefore, it is necessary to adjust the outer diameter of the tire within the specification by reducing the height of the tread blocks or the thickness of the tread rubber inside the tread blocks, etc. By these adjustments, the shock absorption of the tire may sometimes be impaired. In contrast, in the present invention, the tread surface of the crown tread block 10 is a non-stepped surface 28, so there is no need to increase the outer diameter of the tire, and the shock absorption can be maintained.

[0062] Hereinafter, a more detailed structure of the present embodiment will be described. In addition, the structure described below represents a specific manner of the present embodiment. Therefore, the present invention can of course exhibit the above-described effects even without the structure described below. In addition, in the tire 1 of the present invention having the above-described features, even if any one of the structures described below is applied alone, an improvement in the performance corresponding to each structure can be expected. Furthermore, when several of the structures described below are combined and applied, an improvement in the combined performance corresponding to each structure can be expected. In addition, hereinafter, the outer tread block 20 is shown as an example of a structure arranged on the side closer to the first tread end T1 than the tire equator C, but these structures can also be applied to the outer tread block 20 arranged on the side closer to the second tread end T2 than the tire equator C.

[0063] In the entire tread surface 2, the number N1 of the outer tread blocks 20 having the protruding surface 27 (both the shoulder tread blocks 40 and the intermediate tread blocks 30 in the present embodiment) is preferably 75% or less of the total number Nt of the crown tread blocks 10 and the outer tread blocks 20. As a more preferred mode, in the present embodiment, the number N1 is 60% to 70% of the total number Nt. By such an arrangement of the tread blocks, the roll characteristics can be further improved.

[0064] In the entire tread surface 2, the number N2 of the tread blocks 5 having the fine grooves 15 (in the present embodiment, all the tread blocks 5 have the fine grooves 15) is 40% to 200% of the number N1, preferably 130% to 170%. Such an arrangement of the tread blocks 5 can improve the roll characteristics while maintaining the wear resistance of the tread surface 2.

[0065] A reinforcing bridge 35 for connecting adjacent tread blocks 5 is provided on the tread surface 2 of the present embodiment. Figure 8 Shown Figure 2 The cross-sectional view taken along the E-E line is shown as an example of the reinforcing bridge 35. As Figure 2 And Figure 8 Shown, this reinforcing bridge 35 bulges locally from the tread bottom surface 4, and can improve the rigidity of the root part of the tread block. In addition, as Figure 8As shown, the raised height h1 of the reinforcing bridge 35 is less than 20% of the height of the adjacent tread blocks, specifically 1.0 to 2.5 mm. However, the reinforcing bridge 35 that connects the crown tread blocks 10 to each other is different in size from the above, which will be described later.

[0066] As Figure 2 shown, each of the plurality of crown tread blocks 10 is connected to an adjacent other crown tread block 10 and the outer tread block 20 by a reinforcing bridge 35. Each of the plurality of outer tread blocks 20 is connected to an adjacent other outer tread block 20 or crown tread block 10 by a reinforcing bridge 35. This can suppress the tipping of each tread block 5 and improve the traction performance and braking performance.

[0067] Figure 9 An enlarged view showing a plurality of shoulder tread blocks 40 is shown. As Figure 9 shown, on the tread surface of the shoulder tread block 40 of the present embodiment, there is provided a narrow groove 15 extending in the tire circumferential direction. The narrow groove 15 completely crosses the tread surface 40s of the shoulder tread block 40 in the tire circumferential direction, and divides the tread surface 40s into a base surface 26 disposed on the first tread end T1 side and a protruding surface 27 disposed on the tire equator C side.

[0068] The narrow groove 15 preferably inclines toward the tire equator C side toward the first landing side (the first side in the tire circumferential direction) of the rotation direction R, for example. The angle θ1 of the narrow groove 15 with respect to the tire circumferential direction is, for example, 45° or less, preferably 5 to 15°. In addition, when the narrow groove 15 does not extend linearly, the angle θ1 represents the average angle of the narrow groove 15 with respect to the tire circumferential direction. The average angle is equivalent to dividing the narrow groove 15 into a plurality of minute regions, and dividing the sum of the angles of each minute region with respect to the tire circumferential direction by the number of the minute regions. Hereinafter, the angles of each part are measured in the same manner.

[0069] In a more preferred manner, it is preferable that the groove width of the narrow groove 15 continuously increases toward the first landing side of the rotation direction R over the entire length in the present embodiment. Thus, the maximum groove width is formed at the end on the first landing side of the narrow groove 15, and the minimum groove width is formed at the end on the second landing side (the second side in the tire circumferential direction) of the rotation direction R of the narrow groove 15. In addition, the minimum groove width is, for example, 65% to 80% of the maximum groove width. Such a narrow groove 15 can provide a large reaction force during braking, thereby improving the braking performance. As Figure 3 shown, the shoulder tread block 40 of the present embodiment is formed with a narrow groove 15, and the tread surface 40s is a stepped surface 25. In addition, the stepped surface 25 is provided with a base surface 26 on the first tread end T1 side and a protruding surface 27 on the tire equator C side. The height difference amount t1 between the base surface 26 and the protruding surface 27 is, for example, 1.0 to 2.0 mm. Such a shoulder tread block 40 helps to improve the turning performance.

[0070] As Figure 9 shown, the area of the base surface 26 in the shoulder tread block 40 is 55% to 65% of the total area of the tread surface 40s of the shoulder tread block 40 (the sum of the area of the base surface 26 and the area of the protruding surface 27, the same hereinafter). In addition, the area of the protruding surface 27 of the shoulder tread block 40 is 35% to 45% of the total area of the tread surface 40s. Thus, while maintaining the durability of the shoulder tread block 40, it is easy for the shoulder tread block 40 to sink into the road surface.

[0071] The shoulder tread block 40 includes a first shoulder tread block 41 and a second shoulder tread block 42 having different tread surface shapes. On the tread surface of the first shoulder tread block 41, two edges 41a extending in the tire axial direction are inclined in the same direction with respect to the tire axial direction. Specifically, the two edges 41a of the first shoulder tread block 41 are inclined from the first tread end T1 toward the rear landing side in the rotation direction R with respect to the tire equator C side. Such a first shoulder tread block 41 can exhibit excellent traction performance during turning.

[0072] On the tread surface of the second shoulder tread block 42, two edges 42a extending in the tire axial direction are inclined in different directions with respect to the tire axial direction. In a preferred embodiment, these two edges 42a are inclined so as to approach the tire equator C side. As a result, the length of the tread surface of the second shoulder tread block 42 in the tire circumferential direction continuously decreases toward the tire equator C side. Such a second shoulder tread block 42 has relatively high rigidity on the first tread end T1 side, which helps to improve the roll characteristics.

[0073] As Figure 2 shown, the first shoulder tread block 41 and the second shoulder tread block 42 are preferably connected to each other by a reinforcing bridge 35. In the present embodiment, these shoulder tread blocks 40 are also connected to a second intermediate tread block 32 described later by the reinforcing bridge 35. Thus, the shoulder tread blocks 40 are difficult to topple, and the traction performance and braking performance are improved. In addition, in Figure 9 , the reinforcing bridge 35 is omitted.

[0074] Figure 10 An enlarged view of a plurality of intermediate tread blocks 30 is shown. As Figure 10 shown, on the tread surface 30s of the intermediate tread block 30 in the present embodiment, a fine groove 15 is provided. The fine groove 15 extends in a curved manner so as to communicate with an edge extending in the tire axial direction and an edge extending in the tire circumferential direction in the outer peripheral edge of the tread surface 30s. Thus, the fine groove 15 divides the tread surface 30s of the intermediate tread block 30 into a base surface 26 and a protruding surface 27.

[0075] The narrow groove 15 extends, for example, from the trailing edge 30a that extends axially of the tire from the outer peripheral edge of the tread surface 30s on the trailing landing side in the rotational direction R to the equator side edge 30c that extends circumferentially of the tire on the tire equator C side. Further, the narrow groove 15 of the intermediate tread block 30 includes a first groove portion 16, a second groove portion 17, and a third groove portion 18. The first groove portion 16 extends circumferentially of the tire from the trailing edge 30a. The second groove portion 17 is connected to the first groove portion 16 and extends obliquely with respect to the tire axis. The third groove portion 18 extends axially of the tire from the second groove portion 17 to the equator side edge 30c. The angle θ2 between the first groove portion 16 and the third groove portion 18 is, for example, 70 to 110°, preferably 80 to 90°. Such a narrow groove 15 provides frictional forces in multiple directions and can evenly improve the roll characteristics and traction performance. Further, in the case where the first groove portion 16 and the third groove portion 18 are non-linear shapes, the angle θ2 is, for example, equivalent to the sum of the average angle of the first groove portion 16 with respect to an arbitrary reference line (for example, an imaginary straight line inclined at 45° with respect to the tire circumferential direction) and the average angle of the third groove portion 18 with respect to the reference line. The method for measuring the average angle is as described above. Further, the angle between two components described below can also be obtained by the same method.

[0076] In a preferred embodiment, the first groove portion 16 of the narrow groove 15 has a fixed groove width in its longitudinal direction. Further, it is preferable that the groove width of the narrow groove 15 continuously increases from the end portion on the first groove portion 16 side of the second groove portion 17 to the end portion on the equator side edge 30c side of the third groove portion 18. Thereby, the maximum groove width is formed at the end portion of the narrow groove 15 that communicates with the equator side edge 30c, and the minimum groove width is formed at the first groove portion 16 of the narrow groove 15. Further, the minimum groove width is, for example, 20% to 40% of the maximum groove width. Such a narrow groove 15 can further improve the roll characteristics.

[0077] As Figure 4 shown, the intermediate tread block 30 of the present embodiment is formed with the narrow groove 15, and the tread surface 30s is a stepped surface 25. The height difference t2 between the base surface 26 and the protruding surface 27 is, for example, 1.0 to 2.0 mm.

[0078] Further, as Figure 10As shown, the protruding surface 27 included in the stepped surface 25 is a surface surrounded by the fine groove 15, a part of the rear landing side edge 30a, and a part of the tire equator side edge 30c. In addition, the base surface 26 included in the stepped surface 25 is configured to surround a part of the protruding surface 27. Thus, the base surface 26 is a surface surrounded by the fine groove 15, the remainder of the rear landing side edge 30a and the remainder of the tire equator side edge 30c, the front landing side edge 30b extending in the tire axial direction on the front landing side in the rotational direction R, and the tread end side edge 30d extending in the tire circumferential direction on each tread edge side (in this case, the first tread end T1 side). Thus, the area of the protruding surface 27 in the tread surface 30s of the intermediate tread block 30 is smaller than the area of the base surface 26 of the tread surface 30s. Such an intermediate tread block 30 is easily inserted into an uneven ground and can exert a large reaction force. The area of the base surface 26 in the intermediate tread block 30 is 70% - 85% of the total area of the tread surface 30s of the intermediate tread block 30. In addition, the area of the protruding surface 27 in the intermediate tread block 30 is 15% - 30% of the total area of the tread surface 30s. Thus, the roll characteristics can be improved while maintaining the durability of the intermediate tread block 30.

[0079] Preferably, the front landing side edge 30b and the rear landing side edge 30a included in one intermediate tread block 30 are inclined in the same direction with respect to the tire axial direction. The angle θ3 of these edges with respect to the tire axial direction is, for example, 5 - 30°. In addition, in the present embodiment, the intermediate tread block 30 includes a tread block in which these edges are inclined to one side with respect to the tire axial direction and a tread block in which these edges are inclined to the other side with respect to the tire axial direction. That is, there are two types of intermediate tread blocks 30 with different inclination angles: the intermediate tread block 30 in which the front landing side edge 30b and the rear landing side edge 30a are inclined toward the rear landing side in the rotational direction R toward the first tread end T1 side, and the intermediate tread block 30 in which these edges are inclined toward the front landing side in the rotational direction R toward the first tread end T1 side, and they are arranged in a mixed manner in the tire circumferential direction. Even under various road surface conditions, such an arrangement of the intermediate tread block 30 can stably exert a reaction force and can further improve the roll characteristics.

[0080] The intermediate tread block 30, for example, includes a first intermediate tread block 31 and a second intermediate tread block 32 that are alternately arranged one by one in the tire circumferential direction in the present embodiment. As Figure 2 shown, the first intermediate tread block 31 is connected to the crown tread block 10 by a reinforcing bridge 35. The second intermediate tread block 32 is connected to the shoulder tread block 40 by a reinforcing bridge 35. The reinforcing bridge 35 connecting the first intermediate tread block 31 and the crown tread block 10 has the same raised height h1 as the above-mentioned reinforcing bridge 35 ( Figure 8As shown). By configuring the reinforcing bridge 35, the toppling tendency of the tread blocks of the first intermediate tread block 31 and the second intermediate tread block 32 is anisotropic. Therefore, when driving on a muddy road surface, these tread blocks are likely to topple in different directions, and thus it is difficult to retain mud around these tread blocks. Such an effect can continuously exhibit high grip performance. In addition, in Figure 10 these reinforcing bridges 35 are omitted.

[0081] In a preferred embodiment, one first intermediate tread block 31 is connected to the crown tread block 10 adjacent to one side in the tire circumferential direction and the crown tread block 10 adjacent to the other side in the tire circumferential direction by two reinforcing bridges 35. In addition, the reinforcing bridges 35 connecting the first intermediate tread block 31 and the crown tread block 10 include a manner in which its width continuously increases from the crown tread block 10 to the first intermediate tread block 31, a manner in which the width continuously decreases from the crown tread block 10 to the first intermediate tread block 31, and a manner in which the width is fixed. In this embodiment, these manners are distributed in the tire circumferential direction.

[0082] The second intermediate tread block 32 is connected to both the first shoulder tread block 41 and the second shoulder tread block 42. Specifically, the second intermediate tread block 32, the first shoulder tread block 41, and the second shoulder tread block 42 are connected by a reinforcing bridge 35 that bulges as a whole in the area surrounded by these tread blocks. Such an arrangement of the tread blocks and the reinforcing bridge can exhibit excellent roll characteristics and turning performance.

[0083] Figure 11 An enlarged view of a plurality of crown tread blocks 10 is shown. In addition, in Figure 11 the reinforcing bridges 35 connecting the first intermediate tread block 31 and the crown tread block 10 are omitted ( Figure 2 as shown). As Figure 11 shown, both ends of the fine groove 15 provided on the tread surface of the crown tread block 10 communicate with the outer peripheral edge of the tread surface 10s.

[0084] In each crown tread block 10, the fine groove 15 extends, for example, from the rear landing side edge 10a extending in the tire axial direction in the rear landing side in the rotational direction R in the outer peripheral edge of the tread surface to the tire equator side edge 10c extending in the tire circumferential direction on the tire equator C side. In addition, each fine groove 15 of the crown tread block 10 includes a longitudinal portion 23 extending in the tire circumferential direction and a transverse portion 24 extending in the tire axial direction. The longitudinal portion 23 extends in the tire circumferential direction from the rear landing side edge 10a. The transverse portion 24 extends from the longitudinal portion 23 to the tire equator side edge 10c. The angle θ4 between the longitudinal portion 23 and the transverse portion 24 is, for example, 70 to 90°. Thus, the fine grooves 15 of the crown tread blocks 10 provide frictional forces in multiple directions, and thus excellent roll characteristics and traction performance can be exhibited.

[0085] In a preferred embodiment, the narrow groove 15 preferably extends from the end on the rear contact side edge 10a side to the end on the tire equator side edge 10c side with a fixed groove width. In a more preferred embodiment, when the narrow groove 15 is provided on the outer tread block 20 ( Figure 2 as shown), the average groove width of the narrow groove 15 provided on the crown tread block 10 is smaller than the average groove width of the narrow groove 15 provided on the outer tread block 20. Thereby, the roll characteristics are further improved. In addition, the average groove width is obtained by dividing the opening area of the narrow groove 15 by the length of the narrow groove 15 (the so-called edge length).

[0086] The tread surface 10s of the crown tread block 10 includes a first surface 36 and a second surface 37 divided by the narrow groove 15. The first surface 36 is surrounded by the narrow groove 15, a part of the rear contact side edge 10a, and a part of the tire equator side edge 10c. The second surface 37 is arranged so as to surround the first surface 36. Thereby, the second surface 37 is surrounded by the narrow groove 15, the remainder of the rear contact side edge 10a and the remainder of the tire equator side edge 10c, the leading contact side edge 10b extending in the tire axial direction on the leading contact side in the rotational direction R, and the tread end side edge 10d extending in the tire circumferential direction on the first tread end T1 side or the second tread end T2 ( Figure 2 as shown) side. Thereby, the second surface 37 of the crown tread block 10 has a larger area than the first surface 36.

[0087] The area of the first surface 36 of the crown tread block 10 is 10% to 30% of the total area of the tread surface 10s of one crown tread block 10 (the sum of the area of the first surface 36 and the area of the second surface 37). In addition, the area of the second surface 37 of the crown tread block 10 is 70% to 90% of the total area of the tread surface 10s. Thereby, the traction performance and the braking performance can be improved while maintaining the durability of the crown tread block 10.

[0088] The distance L2 in the tire circumferential direction from the center 38c of the imaginary tread surface 38 formed by the first surface 36, the narrow groove 15, and the second surface 37 to the center 36c of the first surface 36 is preferably 20% or more of the length L1 in the tire circumferential direction of the imaginary tread surface 38 at the center 38c of the imaginary tread surface 38, and more preferably 30% to 40%. Thereby, the deformation amount of the region including the first surface 36 becomes large, and the traction performance and the braking performance can be further improved.

[0089] As Figure 2 shown, in the entire tread surface portion 2, the sum of the area of the first surface 36 of the crown tread block 10 and the area of the protruding surface 27 of the outer tread block 20 is preferably 20% to 60% of the sum of the areas of the tread surfaces of the tread blocks 5. Thereby, the roll characteristics can be improved while maintaining the durability of the tread surface portion 2.

[0090] As Figure 11As shown in , the leading ground-contacting side edge 10b and the trailing ground-contacting side edge 10a included in a crown block 10 are preferably inclined in the same direction relative to the tire axial direction. The angle θ5 of these edges relative to the tire axial direction is, for example, 10 to 20°. In addition, in the present embodiment, there are two types of crown blocks 10 whose edges are inclined to opposite sides. That is, the crown blocks 10 whose leading ground-contacting side edge 10b and the trailing ground-contacting side edge 10a are inclined toward the trailing ground side in the lateral rotation direction R of the tire equator C and the crown blocks 10 whose edges are inclined toward the leading ground-contacting side in the lateral rotation direction R of the tire equator C are arranged in a mixed manner. As a result, the plurality of crown blocks 10 exert friction in multiple directions, thereby further improving the traction performance.

[0091] The angle θ6 between the first-contact side edge 10b and the lateral portion 24 is, for example, less than 20°, preferably 5 to 15°. Thus, these edges cooperate to provide greater friction, thereby improving traction performance and braking performance.

[0092] like Figure 2 As shown, the crown block 10 includes a first middle block 31 disposed on the leading ground contact side in the rotation direction R, a first crown block 11 connected by a reinforcing bridge 35, a first middle block 31 disposed on the trailing ground contact side in the rotation direction R, and a second crown block 12 connected by a reinforcing bridge 35. In addition, the crown block 10 of the present embodiment is composed of the first crown block 11 and the second crown block 12.

[0093] In the present embodiment, two first crown blocks 11 arranged across the tire equator C are connected by the reinforcing bridge 35, thereby forming a first crown block pair 46. In addition, two second crown blocks 12 arranged across the tire equator C are connected by the reinforcing bridge 35, thereby forming a second crown block pair 47. In addition, in the present embodiment, the first crown block pair 46 and the second crown block pair 47 are alternately arranged one after another in the tire circumferential direction. As a result, excellent traction performance and braking performance can be obtained under various road conditions.

[0094] As a more preferred mode, in the present embodiment, one first crown block pair 46 and one second crown block pair 47 are connected to the common first middle block 31 via the reinforcing bridge 35. Thus, on the tread portion 2, a plurality of imaginary annular bodies 45 having an annular shape in the tread top view are arranged in the tire circumferential direction through one first crown block pair 46, one second crown block pair 47, two first middle blocks 31, and the reinforcing bridge 35 connecting them. In addition, in one imaginary annular body 45, the second crown block pair 47 is arranged on the leading ground contact side in the rotation direction R than the first crown block pair 46.

[0095] likeFigure 7 As shown, the reinforcing bridge 35 included in two adjacent crown tread blocks 10 in the tire axial direction has a raised height h2 greater than that of the Figure 8 shown reinforcing bridge 35. The raised height h2 of this reinforcing bridge 35 is, for example, 20% to 50% of the height h3 of the crown tread block 10.

[0096] As Figure 11 shown, the maximum width W2 in the tire axial direction of the second pair of crown tread blocks 47 (measured on the tread surface, the same applies hereinafter) is greater than the maximum width W1 in the tire axial direction of the first pair of crown tread blocks 46. Specifically, the maximum width W2 of the second pair of crown tread blocks 47 is 130% to 160% of the maximum width W1 of the first pair of crown tread blocks 46. Similarly, the width in the tire axial direction of the reinforcing bridge 35 included in the second pair of crown tread blocks 47 is greater than the width in the tire axial direction of the reinforcing bridge 35 included in the first pair of crown tread blocks 46. Thereby, when traveling on a muddy road surface, the imaginary annular body 45 can grasp a lot of mud, further improving the traction performance and braking performance.

[0097] Figure 12 is an expanded view of the tread surface portion 2 of another embodiment of the present invention. As Figure 12 shown, in this embodiment, no fine grooves are provided on the tread surface 20s of the outer tread block 20. The tread surface 20s of the outer tread block 20 in this embodiment is configured as a stepped surface 25, and the boundary 34 between the base surface 26 and the protruding surface 27 is indicated by a solid line. In such an embodiment, the protruding surface 27 can also provide a sufficient edge component, thereby being able to exhibit excellent roll characteristics.

[0098] As described above, although the preferred embodiments of the two-wheeled vehicle tire for traveling on an uneven road surface of the present invention have been described in detail, the present invention is not limited to the above specific embodiments and can be implemented in various modified forms.

[0099]

Examples

[0100] A rear wheel tire for a two-wheeled vehicle for traveling on an uneven road surface having the Figure 2 basic pattern was trial-produced. As Comparative Example 1, a tire having the Figure 13 shown pattern was trial-produced. The tread surface of each tread block a of the tire of Comparative Example 1 is not a protruding surface but a flat surface, and no fine grooves are arranged. In addition, as Comparative Example 2, a tire having the Figure 2 pattern and as Figure 14A tire having a tread block b with a stepped surface c is shown. In addition, in order to adjust the outer diameter of the tire within the specifications, in Comparative Example 2, the thickness of the tread rubber is slightly reduced on the radially inner side of the tread block b of the tire (illustration omitted). Except for the above matters, the tires of Comparative Examples 1 and 2 are substantially the same as the tires of the Examples. The roll characteristics, shock absorption, traction performance, and braking performance of these test tires were tested. The common specifications and test methods of each test tire are as follows.

[0101] Vehicle used: A 450 cc displacement motorcycle off-road racing vehicle

[0102] Tire size: 120 / 90-19

[0103] Rim size: 2.75WM

[0104] Internal pressure: 80 kPa

[0105] <Roll characteristics, shock absorption, traction performance, and braking performance>

[0106] The roll characteristics, shock absorption, traction performance, and braking performance during off-road motorcycle driving were evaluated by testing the rider's senses using the above test vehicle. The larger the value, the more excellent the various performances.

[0107] The test results are shown in Table 1.

[0108]

Table 1

[0109] Comparative Example 1 Comparative Example 2 Example Figure showing the tread pattern Figure 13 Figure 2 Figure 2 Figure showing the cross-section of the tread blocks - Figure 14 Figure 7 Cornering characteristics (rating) 100 100 104 Shock absorption (rating) 100 97 100 Traction performance (rating) 100 103 103 Braking performance (rating) 100 103 106

[0110] As shown in Table 1, it was confirmed that the tire of the Example exhibits excellent roll characteristics while maintaining shock absorption. In addition, it was confirmed that the traction performance and braking performance of the tire of the Example were also improved.

[0111] [Supplementary Note]

[0112] The present invention includes the following aspects.

[0113] [Invention 1]

[0114] A two-wheeled vehicle tire for driving on an uneven ground, having a tread portion, wherein,

[0115] The tread portion includes a first tread end, a second tread end, a tread width extending from the first tread end to the second tread end, a tire equator, a crown region having a width of 20% of the tread width centered on the tire equator, and side regions on both outer sides of the crown region,

[0116] The tread portion includes a plurality of crown tread blocks provided in the crown region and a plurality of outer tread blocks provided in the side regions,

[0117] The tread surface of each of the plurality of outer tread blocks is at least formed with fine grooves or a stepped surface including a base surface and a protruding surface that locally protrudes outward in the tread block height direction with respect to the base surface.

[0118] The tread surface of each of the plurality of crown tread blocks is a non-stepped surface formed with fine grooves and not having the protruding surface.

[0119] [Invention 2]

[0120] A two-wheeled vehicle tire for traveling on an uneven ground according to Invention 1, wherein

[0121] The rotation direction is specified.

[0122] The tread surface of at least one of the plurality of crown tread blocks includes a leading contact edge extending in the tire axial direction on the leading contact side in the rotation direction.

[0123] The fine grooves provided on the crown tread block having the leading contact edge include a lateral portion extending in the tire axial direction.

[0124] The angle between the leading contact edge and the lateral portion is 20° or less.

[0125] [Invention 3]

[0126] A two-wheeled vehicle tire for traveling on an uneven ground according to Invention 1 or 2, wherein

[0127] The tread surface of at least one of the plurality of crown tread blocks includes a first surface and a second surface having an area larger than that of the first surface, and the two ends of the fine grooves communicate with the outer peripheral edge of the tread surface.

[0128] The distance in the tire circumferential direction from the center of the imaginary tread surface composed of the first surface, the fine grooves, and the second surface to the center of the first surface is 20% or more of the length of the imaginary tread surface in the tire circumferential direction at the center of the imaginary tread surface.

[0129] [Invention 4]

[0130] A two-wheeled vehicle tire for traveling on an uneven ground according to any one of Inventions 1 to 3, wherein

[0131] The tread portion includes a tread bottom surface and a reinforcing bridge that locally bulges from the tread bottom surface and connects adjacent tread blocks.

[0132] Each of the plurality of crown tread blocks is connected to other adjacent crown tread blocks and the outer tread blocks through the reinforcing bridge.

[0133] The plurality of outer tread blocks are respectively connected to other adjacent outer tread blocks or the crown tread blocks through the reinforcing bridges.

[0134] [Invention 5]

[0135] For the two-wheeled vehicle tire for traveling on an uneven ground according to Invention 4, wherein

[0136] The outer tread blocks include a plurality of shoulder tread blocks including the first tread end and a plurality of intermediate tread blocks disposed between the plurality of shoulder tread blocks and the crown region,

[0137] The plurality of intermediate tread blocks alternately include a first intermediate tread block connected to the crown tread block through the reinforcing bridge and a second intermediate tread block connected to the shoulder tread block through the reinforcing bridge in the tire circumferential direction.

[0138] [Invention 6]

[0139] For the two-wheeled vehicle tire for traveling on an uneven ground according to any one of Inventons 1 to 5, wherein

[0140] The plurality of crown tread blocks include a first surface and a second surface having an area larger than that of the first surface through both ends of the narrow groove communicating with the outer peripheral edge of the tread,

[0141] The tread surface of each of the plurality of outer tread blocks is the stepped surface including the protruding surface,

[0142] In the whole of the tread portion, the sum of the area of the first surface and the area of the protruding surface is 20% to 60% of the total area of the tread surfaces of the crown tread blocks and the outer tread blocks.

[0143] [Invention 7]

[0144] For the two-wheeled vehicle tire for traveling on an uneven ground according to any one of Inventons 1 to 6, wherein

[0145] In the whole of the tread portion, the number N1 of the outer tread blocks having the protruding surface is 75% or less of the total number Nt of the crown tread blocks and the outer tread blocks.

[0146] [Invention 8]

[0147] For the two-wheeled vehicle tire for traveling on an uneven ground according to Invention 7, wherein

[0148] In the whole of the tread portion, the number N2 of the tread blocks having the narrow groove is 40% to 200% of the number N1.

Claims

1. A two-wheeled vehicle tire for running on uneven ground, having a tread portion, characterized in that: The tread portion includes a tire equator, a first tread end disposed on one axial side of the tire equator, a second tread end disposed on the other axial side of the tire equator, a tread development width from the first tread end to the second tread end, a crown region centered at the tire equator and having a width of 20% of the tread development width, and side regions on both outer sides of the crown region. The tread portion includes a plurality of crown blocks disposed in the crown region and a plurality of outer side blocks disposed in the side region. Each of the plurality of outer tread blocks has at least a fine groove or a step surface formed thereon, the step surface including a base surface and a protruding surface partially protruding outward in the tread block height direction relative to the base surface. Each tread surface of the plurality of crown blocks is a non-step surface having fine grooves formed therein and having no protruding surface.

2. The tire for a two-wheeled vehicle for running on uneven terrain according to claim 1, characterized in that: The direction of rotation is specified, The tread surface of at least one of the plurality of crown blocks includes a leading ground contact side edge extending along the tire axial direction on the leading ground contact side in the rotation direction, The thin groove provided on the crown block having the first ground contacting side edge includes a transverse portion extending in the axial direction of the tire, The angle between the first-landing side edge and the lateral portion is less than 20°.

3. The tire for a two-wheeled vehicle for running on uneven terrain according to claim 1 or 2, characterized in that: The tread surface of at least one of the plurality of crown blocks includes a first surface and a second surface having an area larger than that of the first surface, wherein both ends of the thin groove are connected to the outer peripheral edge of the tread surface. A distance in the tire circumferential direction from a centroid of an imaginary tread surface formed by the first surface, the narrow groove, and the second surface to a centroid of the first surface is equal to or greater than 20% of a tire circumferential length of the imaginary tread surface at the centroid of the imaginary tread surface.

4. The tire for a two-wheeled vehicle for running on uneven terrain according to claim 1 or 2, characterized in that: The tread portion includes a tread bottom surface and a reinforcement bridge partially raised from the tread bottom surface and connecting adjacent pattern blocks. The plurality of crown blocks are connected to other adjacent crown blocks and the outer side blocks through the reinforcement bridges, The plurality of outer side blocks are respectively connected to other adjacent outer side blocks or the crown block via the reinforcing bridges.

5. The tire for a two-wheeled vehicle for running on uneven terrain according to claim 4, characterized in that: The outer pattern blocks include a plurality of shoulder pattern blocks including the first tread end and a plurality of middle pattern blocks arranged between the plurality of shoulder pattern blocks and the crown area, The plurality of middle blocks alternately include, in the tire circumferential direction, first middle blocks connected to the crown blocks via the reinforcing bridges and second middle blocks connected to the shoulder blocks via the reinforcing bridges.

6. The tire for a two-wheeled vehicle for running on uneven terrain according to claim 1 or 2, characterized in that: The plurality of crown blocks are connected to the outer peripheral edge of the tread surface through both ends of the thin groove and include a first surface and a second surface having an area larger than that of the first surface. The tread surface of each of the plurality of outer tread blocks is the step surface including the protruding surface. In the entire tread portion, a total of an area of ​​the first surface and an area of ​​the protruding surface is 20% to 60% of a total area of ​​the tread surfaces of the crown block and the outer block.

7. The tire for a two-wheeled vehicle for running on uneven terrain according to claim 1 or 2, characterized in that: In the entire tread portion, the number N1 of the outer blocks having the protruding surface is equal to or less than 75% of the total number Nt of the crown blocks and the outer blocks.

8. The tire for a two-wheeled vehicle for running on uneven terrain according to claim 7, characterized in that: In the entire tread portion, the number N2 of the blocks having the thin grooves is 40% to 200% of the number N1.

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