JP6498560B2 - Motorcycle tires - Google Patents

Description

  The present invention relates to a motorcycle tire having a main groove and a shallow groove shallower than the main groove in a tread portion.

  Unlike a four-wheeled vehicle, it is necessary to tilt the vehicle body when turning a motorcycle, and motorcycle tires are required to improve handling performance when turning to realize stable handling of the motorcycle. . On the other hand, there is conventionally known a motorcycle tire in which a tread rubber in a tread portion is formed of two types of rubbers having different hardness to increase the turning force (see Patent Document 1).

  However, in the conventional motorcycle tire described in Patent Document 1, the gripping force or lateral force may change during turning due to a change in the hardness of the tread rubber, which may affect the handling performance. Therefore, the conventional motorcycle tire has room for improvement from the viewpoint of improving the handling performance during turning.

JP 2012-148680 A

  The present invention has been made in view of the above-described conventional problems, and an object thereof is to improve handling performance during turning of a motorcycle tire.

  The present invention is a motorcycle tire in which a tread rubber in a tread portion is formed with a main groove and a shallow groove shallower than the main groove. The tread rubber includes a center rubber including the tire equator, and two shoulder rubbers including the tread ends adjacent to both outer sides of the center rubber in the tire width direction. The tan δ at 30 ° C. of the shoulder rubber is larger than the tan δ at 30 ° C. of the center rubber. The contour shape of the tread surface of the tread portion in the cross section in the tire width direction is formed into a curved shape including a plurality of arc portions. A plurality of arc portions including a first arc portion including a tire equator; two second arc portions having a radius of curvature larger than the radius of curvature of the first arc portion adjacent to both outer sides of the first arc portion in the tire width direction; Have. A circumferential shallow groove extending in the tire circumferential direction is formed on the outer side in the tire width direction than the boundary between the center rubber and the shoulder rubber and the boundary between the first arc portion and the second arc portion.

  ADVANTAGE OF THE INVENTION According to this invention, the handling performance at the time of turning of the tire for motorcycles can be improved.

1 is a cross-sectional view in the tire width direction of a motorcycle tire of the present embodiment. 1 is a diagram showing a tread surface of a motorcycle tire according to an embodiment. FIG. 1 is a plan view showing a tread pattern of a motorcycle tire of the present embodiment.

An embodiment of a motorcycle tire of the present invention will be described with reference to the drawings.
A motorcycle tire (hereinafter, referred to as a tire) according to the present embodiment is a pneumatic tire mounted on a motorcycle, and is mounted on various motorcycle rims (front wheel rim, rear wheel rim).
FIG. 1 is a cross-sectional view of the tire 1 of the present embodiment in the tire width direction H, and shows a cross section of the normal tire 1 cut in the tire width direction H.

  Here, the normal state is a state when the tire 1 is mounted on the normal rim, the tire 1 is filled with the normal internal pressure, and the tire 1 is unloaded. The dimensions, positions, and the like related to the tire 1 are dimensions, positions, and the like in the tire 1 in a normal state. Further, the normal rim and the normal internal pressure are defined by the standards applied to the tire 1. For example, in JATMA YEAR BOOK (Japanese Automobile Tire Association Standard), the regular rim is a standard rim, and the regular internal pressure is the highest air pressure. When other standards are applied in the place of use or manufacturing place of the tire 1, the normal state of the tire 1 is defined according to each standard. Other standards are, for example, YEAR BOOK of TRA (The Tire and Rim Association Inc.) in the United States, and STANDARDS MANUAL of ETRTO (The European Tire and Rim Technical Organization) in Europe.

  As illustrated, the tire 1 includes an annular tread portion 2 that is in contact with the road surface, a pair of bead portions 3 that are located inside the tire radial direction K of the tread portion 2, an end portion of the tread portion 2, and a bead portion 3. A pair of sidewall portions 4 are provided between them. The tire 1 includes an annular bead core 5 disposed in the bead portion 3, a carcass 6, a belt 7 disposed in the tread portion 2, and a tread rubber 8. The carcass 6 is formed by one or more layers of carcass plies, and is arranged from one bead core 5 to the other bead core 5. The belt 7 has a plurality of cords arranged in parallel, and is disposed outside the carcass 6 in the tire radial direction K.

  The tread rubber 8 is a portion in contact with the road surface of the tread portion 2 (outer peripheral portion of the tread portion 2), and is disposed outside the belt 7 in the tire radial direction K. The tread rubber 8 is disposed on the entire outer periphery of the tread portion 2, and the outer peripheral surface of the tread rubber 8 is a tread surface 9 of the tread portion 2. The tread surface 2 of the tread portion 2 is a ground contact surface (surface of the outer periphery of the tread portion 2) in contact with the road surface of the tread portion 2, and is located between the tread ends TE. The tread end TE is both ends of the tread surface 9 in the tire width direction H, and is located on the outermost side in the tire width direction H of the tread portion 2 (tread surface 9). The tire equator CL is located at the center in the tire width direction H of the tread surface 9 of the tread portion 2.

  The tread rubber 8 is composed of one center rubber 8A located in the center region of the tread surface 9 and two shoulder rubbers 8B located outside the center rubber 8A in the tire width direction H (shoulder portion side). The center rubber 8A is a portion including the tire equator CL of the tread rubber 8, and is located between the two shoulder rubbers 8B. The center of the center rubber 8A in the tire width direction H is located at the tire equator CL. The two shoulder rubbers 8B are portions including the tread ends TE of the tread rubber 8, and are adjacent to both outer sides in the tire width direction H of the center rubber 8A.

  The center rubber 8A and the shoulder rubber 8B are connected at the boundary between the center rubber 8A and the shoulder rubber 8B (rubber boundary 8C), and the tread rubber 8 is formed by the three rubbers 8A and 8B. Two rubber boundaries 8C are arranged at positions symmetrical with respect to the tire equator CL, and are respectively provided between the tire equator CL and the tread end TE. The rubber boundary 8 </ b> C is formed from the tread surface 9 to the belt 7, and partitions the tread rubber 8 in the tire width direction H. The center rubber 8A is a first rubber located between the two rubber boundaries 8C, and the shoulder rubber 8B is a second rubber located between the rubber boundary 8C and the outer tread end TE in the tire width direction H. .

  In the cross section of the tread portion 2 in the tire width direction H, the width (tread width) of the tread portion 2 along the surface (tread surface 9) of the tread portion 2 is W, and the half width of the tread portion 2 along the surface of the tread portion 2 ( Tread half width) is L. The tread width W is a distance (periphery length) along the surface of the tread portion 2 between the tread ends TE. The tread half width L is a distance along the surface of the tread portion 2 between the tire equator CL and the tread end TE, and is a half value (W / 2) of the tread width W. In this case, the rubber boundary 8C is an area between the position 0.55 × L away from the tire equator CL along the surface of the tread portion 2 and the position 0.85 × L away from the tire equator CL on both sides of the tire equator CL. Placed in.

  Within the tread rubber 8 of the tread portion 2, the two rubber boundaries 8 </ b> C are separated from the tire equator CL toward the outside in the tire width direction H by 0.55 × L (0.55 times the tread half width L). And 0.85 × L (0.85 times the tread half width L). The center rubber 8A is located in the center region (inner region in the tire width direction H) of the tread portion 2 between the two rubber boundaries 8C, and the shoulder rubber 8B is an outer tread edge in the tire width direction H from the rubber boundary 8C. It is located in the shoulder region (outer region in the tire width direction H) of the tread portion 2 up to TE. The width of the center rubber 8A along the surface of the tread portion 2 is wider than the width of the shoulder rubber 8B along the surface of the tread portion 2, and the widest center rubber 8A is disposed in the center region of the tread portion 2.

  The loss tangent (tan δ) of the shoulder rubber 8B is tan δ1, and the loss tangent (tan δ) of the center rubber 8A is tan δ2. In this case, tan δ1 at 30 ° C. of the shoulder rubber 8B is larger than tan δ2 at 30 ° C. of the center rubber 8A (tan δ1> tan δ2). The loss tangent (tan δ) is a ratio of the loss elastic modulus to the storage elastic modulus, and is measured by a loss tangent measuring device. Using shoulder rubber 8B and center rubber 8A having the same dimensions, tan δ1 and tan δ2 at 30 ° C. are measured under the same conditions.

  Here, the loss tangent (tan δ) is a loss tangent (tan δ) of a test piece (width: 5 mm, length: 30 mm, thickness: 2 mm) measured by a spectrometer (manufactured by Ueshima Seisakusho). (Initial strain: 150 μm, dynamic strain: 1%, frequency: 52 Hz, temperature 30 °). Using the test piece of the shoulder rubber 8B and the test piece of the center rubber 8A, the values of the loss tangent (tan δ) are measured, and the measured values are tan δ1 at 30 ° C. of the shoulder rubber 8B and tan δ2 of the center rubber 8A at 30 ° C. And

FIG. 2 is a diagram illustrating the tread surface 9 of the tire 1 of the present embodiment, and schematically illustrates the tread surface 9 between the tire equator CL and one tread end TE.
As illustrated, in the cross section in the tire width direction H of the tread portion 2, the contour shape 10 of the tread surface 9 of the tread portion 2 is formed in a curved shape including a plurality of arc portions 11 and 12. The contour shape 10 of the tread surface 9 is the shape of the tread surface 9 when the tread portion 2 has no tread pattern elements (grooves, convex portions, concave portions, etc.). The plurality of arc portions 11 and 12 are curved portions having predetermined curvature radii R1 and R2, respectively, and are connected at a boundary (arc boundary 13) between the arc portions 11 and 12. The contour shape 10 of the tread surface 9 is formed in a curved convex shape (convex curve) in which a plurality of arc portions 11 and 12 are smoothly connected.

  The plurality of arc portions 11 and 12 include one first arc portion 11 and two second arc portions 12 located outside the first arc portion 11 in the tire width direction H. The first arc portion 11 is a portion including the tire equator CL of the tread surface 9 and is located between the two second arc portions 12. The center of the first arc portion 11 in the tire width direction H is located at the tire equator CL. The two second arc portions 12 are adjacent to both outer sides in the tire width direction H of the first arc portion 11, and the curvature radius R2 of the second arc portion 12 is larger than the curvature radius R1 of the first arc portion 11 (R1). <R2).

  In the cross section of the tread portion 2 in the tire width direction H, the arc boundary 13 between the first arc portion 11 and the second arc portion 12 is 0. 0 along the surface of the tread portion 2 from the tire equator CL on both sides of the tire equator CL. It is arranged in a region between a position separated by 3 × L and a position separated by 0.7 × L. Within the tread surface 2 of the tread portion 2, the two arc boundaries 13 are respectively separated from the tire equator CL toward the outside in the tire width direction H by 0.3 × L (0.3 times the tread half width L). It is arrange | positioned between 0.7xL (0.7 times the tread half width L) and the position away.

  Here, the plurality of arc portions 11 and 12 include only one first arc portion 11 and two second arc portions 12, and the contour shape 10 of the tread surface 9 includes only three arc portions 11 and 12. It is formed in a curved shape. Two arc boundaries 13 are arranged at positions symmetrical with respect to the tire equator CL, and are respectively provided between the tire equator CL and the tread end TE. The first arc portion 11 is located between the two arc boundaries 13, and the second arc portion 12 is located between the arc boundary 13 and the outer tread end TE in the tire width direction H.

FIG. 3 is a plan view showing a tread pattern of the tire 1 of the present embodiment, and shows a part of the tire circumferential direction S of the tread portion 2 developed.
As illustrated, the tire 1 includes a plurality of main grooves 21 and 22 and a plurality of shallow grooves 31 to 33 on the tread surface 9 of the tread portion 2. The shallow grooves 31 to 33 are subgrooves shallower than the main grooves 21 and 22, and the main grooves 21 and 22 and the shallow grooves 31 to 33 are formed in the tread rubber 8 of the tread portion 2.

  The depths of all the shallow grooves 31 to 33 are shallower than the depths of all the main grooves 21 and 22, and the widths of all the shallow grooves 31 to 33 are narrower than the widths of all the main grooves 21 and 22. For example, the depth of the main grooves 21 and 22 is 2 to 7 mm, and the depth of the shallow grooves 31 to 33 is 0.1 to 1 mm. The shallow grooves 31 to 33 improve the drainage performance of the tire 1 while ensuring the rigidity of the tread portion 2.

  The plurality of main grooves 21 and 22 are inclined main grooves that extend in an inclined manner with respect to the tire circumferential direction S, and each extends in the tire circumferential direction S from one end on the tire equator CL side toward the other end on the tread end TE side. Inclined and extended. The main grooves 21 and 22 include a first main groove 21 and a second main groove 22. The first main grooves 21 and the second main grooves 22 are alternately arranged along the tire circumferential direction S on both sides of the tire equator CL. One end of the first main groove 21 is located on the inner side in the tire width direction H (the tire equator CL side) than one end of the second main groove 22, and the other end of the second main groove 22 is the first main groove 21. It is located on the outer side (tread end TE side) in the tire width direction H than the other end.

  The plurality of shallow grooves 31 to 33 is a group of inclined grooves extending in an inclined manner with respect to the tire circumferential direction S as a whole, and is disposed so as to intersect with the main grooves 21 and 22. The shallow grooves 31 to 33 include a first shallow groove 31, a second shallow groove 32, and a third shallow groove 33. The first shallow groove 31 is formed between the first main groove 21 and the tire equator CL, and the second shallow groove 32 is formed between the first main groove 21 and the second main groove 22. The third shallow groove 33 is formed between the second main groove 22 and the tread end TE, and is located outside the first main groove 21 in the tire width direction H. A part of the third shallow groove 33 is a circumferential shallow groove 34 extending in the tire circumferential direction S, and the third shallow groove 33 includes the circumferential shallow groove 34 and other portions.

  The circumferential shallow groove 34 is formed on both sides of the tire equator CL from the boundary between the center rubber 8A and the shoulder rubber 8B (rubber boundary 8C) and the boundary between the first arc portion 11 and the second arc portion 12 (arc boundary 13). Is also formed outside the tire width direction H. The circumferential shallow groove 34 is formed in the shoulder rubber 8B positioned on the outer side in the tire width direction H with respect to the rubber boundary 8C, and on the second arc portion 12 positioned on the outer side in the tire width direction H with respect to the arc boundary 13. It is formed. Here, the plurality of shallow grooves 34 in the circumferential direction are spaced in parallel in the tire width direction H and extend linearly in the tire circumferential direction S. The length of the plurality of circumferential shallow grooves 34 in the tire circumferential direction S is the same length.

  In the cross section in the tire width direction H of the tread portion 2, the circumferential shallow groove 34 is 0.85 away from the tire equator CL along the surface of the tread portion 2 on both sides of the tire equator CL. It is formed only in the region between the positions separated by × L. Within the tread portion 2 of the tread portion 2, the circumferential shallow grooves 34 on one side and the other side in the tire width direction H are 0.3 × L (tread half-width) from the tire equator CL toward the outside in the tire width direction H, respectively. It is formed between a position separated by 0.3 times L and a position separated by 0.85 × L (0.85 times the tread half width L).

Next, the action and effect at the time of turning of the tire 1 described above will be described.
The tan δ1 at 30 ° C. of the shoulder rubber 8B is larger than tan δ2 at 30 ° C. of the center rubber 8A. Therefore, the energy loss of the shoulder rubber 8B is larger than the energy loss of the center rubber 8A, and the grip force of the shoulder rubber 8B is larger than the grip force of the center rubber 8A.

  When the tire 1 turns, the load applied to the front tire 1 increases due to braking. Further, the camber angle of the tire 1 gradually increases, and the region of the shoulder rubber 8B gradually increases with respect to the region of the center rubber 8A within the grounded portion of the tread portion 2. At that time, the grip performance required for the tire 1 is secured by the shoulder rubber 8B.

  Outside the rubber boundary 8C in the tire width direction H, the circumferential shallow groove 34 formed in the shoulder rubber 8B reduces the actual contact area of the shoulder rubber 8B and reduces the gripping force of the shoulder rubber 8B. Thereby, the change of the grip force accompanying the increase in the area | region of the shoulder rubber 8B is relieved. Further, the circumferentially shallow groove 34 reduces the rigidity and the lateral force at the grounded portion of the tread portion 2, and the change in the lateral force accompanying the increase in the region of the shoulder rubber 8 </ b> B is alleviated. As a result, the handling performance of the tire 1 is improved and the handling is stabilized.

  Thus, in the tire 1 of this embodiment, the handling performance at the time of turning of the tire 1 can be improved. Moreover, since the curvature radius R1 of the 1st circular arc part 11 is smaller than the curvature radius R2 of the 2nd circular arc part 12, the lightness at the time of a straight running and small camber is securable. Outside the arc boundary 13 in the tire width direction H, the circumferential shallow groove 34 reduces the bending rigidity of the tread surface 9 in the tire width direction H, and the curvature radius of the region where the circumferential shallow groove 34 is formed is substantially reduced. And the change in the radius of curvature associated with the ground contact of the second arc portion 12 is alleviated. Therefore, the handling performance of the tire 1 can be reliably improved.

  As the camber angle of the tire 1 increases, a higher grip performance is required. Therefore, the circumferential shallow groove 34 should not be formed outside the tire width direction H from a position 0.85 × L away from the tire equator CL. preferable. Further, when the circumferential shallow groove 34 is formed on the inner side in the tire width direction H than the position 0.3 × L away from the tire equator CL, the wear resistance performance of the tire 1 may be affected.

  Therefore, in the tire 1, the circumferential shallow groove 34 is only in a region between a position 0.3 × L away from the tire equator CL along the surface of the tread portion 2 and a position 0.85 × L away. Forming. Thereby, the circumferential shallow groove 34 is formed inside the tire width direction H from the position 0.85 × L away from the tire equator CL, and more than the position 0.3 × L away from the tire equator CL. It is formed outside the tire width direction H. As a result, the grip performance at the time of turning of the tire 1 can be ensured, and a decrease in the wear resistance performance of the tire 1 can also be suppressed.

  The circumferential shallow groove 34 is formed only in a region between a position separated by 0.65 × L and a position separated by 0.85 × L along the surface of the tread portion 2 from the tire equator CL. More preferred. Thereby, the fall of the abrasion resistance performance of the tire 1 can be suppressed more reliably. The center rubber 8A is preferably a rubber having higher wear resistance than the shoulder rubber 8B. By doing in this way, the abrasion resistance performance of the tire 1 can be improved.

  The plurality of arc portions that define the contour shape 10 of the tread surface 9 may have at least the first arc portion 11 and the second arc portion 12. Therefore, the plurality of arc portions may have only the first arc portion 11 and the second arc portion 12. In addition to the first arc portion 11 and the second arc portion 12, the plurality of arc portions have one arc portion or a plurality of arc portions outside the second arc portion 12 in the tire width direction H. You may do it. The radius of curvature of the outer arc portion of the second arc portion 12 in the tire width direction H may be larger than the radius of curvature R2 of the second arc portion 12 or may be smaller than the radius of curvature R2 of the second arc portion 12.

  DESCRIPTION OF SYMBOLS 1 ... Tire, 2 ... Tread part, 3 ... Bead part, 4 ... Side wall part, 5 ... Bead core, 6 ... Carcass, 7 ... Belt, 8 ... Tread rubber, 8A ... center rubber, 8B ... shoulder rubber, 8C ... rubber boundary, 9 ... tread surface, 10 ... contour shape, 11 ... first arc portion, 12 ... 2nd arc part, 13 ... arc boundary, 21 ... 1st main groove, 22 ... 2nd main groove, 31 ... 1st shallow groove, 32 ... 2nd shallow groove, 33. ··· Third shallow groove, 34 ... circumferential shallow groove, CL ... tire equator, H ... tire width direction, K ... tire radial direction, L ... tread half width, S ... Tire circumferential direction, TE ... tread edge, W ... tread width.

Claims (3)

A tire for a motorcycle in which a tread rubber in a tread portion is formed with a main groove and a shallow groove shallower than the main groove,
The tread rubber is composed of a center rubber including the tire equator, and two shoulder rubbers including the tread ends adjacent to both outer sides of the center rubber in the tire width direction,
Tan δ at 30 ° C. of the shoulder rubber is larger than tan δ at 30 ° C. of the center rubber,
The contour shape of the tread surface of the tread portion in the cross section in the tire width direction is formed into a curved shape composed of a plurality of arc portions,
A plurality of arc portions including a first arc portion including a tire equator; two second arc portions having a radius of curvature larger than the radius of curvature of the first arc portion adjacent to both outer sides of the first arc portion in the tire width direction; Have
A motorcycle tire in which a circumferential shallow groove extending in the tire circumferential direction is formed on the outer side in the tire width direction from the boundary between the center rubber and the shoulder rubber and the boundary between the first arc portion and the second arc portion. The motorcycle tire according to claim 1,
In the cross section in the tire width direction of the tread portion, when the half width of the tread along the surface of the tread portion is L, the circumferential shallow groove is separated from the tire equator by 0.3 × L along the surface of the tread portion; A motorcycle tire formed only in a region between 0.85 × L distances. The motorcycle tire according to claim 1,
In the cross section of the tread portion in the tire width direction, when the tread half width along the surface of the tread portion is L, the boundary between the first arc portion and the second arc portion is 0. 0 along the tread portion surface from the tire equator. A motorcycle tire disposed in a region between a position 3 × L apart and a location 0.7 × L apart.

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