JP2020083031A - Motorcycle tire - Google Patents

Abstract

To provide a motorcycle tire in which excellent transient characteristic and running stability are achieved.SOLUTION: A motorcycle tire 2 according to the present invention includes a recess 18 extending in a circumferential direction, in a boundary between a tread surface 20 and a side surface 28. It is preferable that the width of the recess 18 is 1.0 mm or more and 5.0 mm or less. It is preferable that the depth of the recess 18 is 0.5 mm or more and 3.0 mm or less. It is preferable that the shape of the recess 18 in a cross section perpendicular to the circumferential direction has a trapezoidal shape or an arc shape.SELECTED DRAWING: Figure 1

Description

The present invention relates to a motorcycle tire.

When the motorcycle travels straight, the motorcycle is almost upright. At this time, a large force is applied to the tire in the vertical direction. When the two-wheeled vehicle turns, the rider tilts the two-wheeled vehicle to obtain sufficient camber thrust. At this time, a large lateral force is applied to the tire. Tires for two-wheeled vehicles are required to have the ability to withstand these large forces and to make a stable and smooth transition from straight running to turning running. In other words, tires are required to achieve good transient characteristics and running stability. Japanese Patent Application Laid-Open No. 2017-052451 discloses a study on a tire for a two-wheeled vehicle that realizes excellent turning performance.

JP, 2017-052451, A

There is a demand for a tire for a two-wheeled vehicle, which has excellent transient characteristics and running stability.

An object of the present invention is to provide a tire for a two-wheeled vehicle, which has excellent transient characteristics and running stability.

The two-wheeled vehicle tire according to the present invention includes a circumferentially extending recess at the boundary between the tread surface and the side surface.

Preferably, in a cross section perpendicular to the circumferential direction, an intersection of the side surface and the recess has an outwardly pointed shape or an outwardly convex arcuate shape.

Preferably, in the cross section perpendicular to the circumferential direction, the intersection of the tread surface and the recess has an outwardly pointed shape or an outwardly convex arcuate shape.

Preferably, the width of the recess is 1.0 mm or more and 5.0 mm or less.

Preferably, the depth of the recess is 0.5 mm or more and 3.0 mm or less.

Preferably, in the cross section perpendicular to the circumferential direction, the shape of the recess is trapezoidal or arcuate.

The tire for a two-wheeled vehicle according to the present invention includes a recess extending in the circumferential direction at the boundary between the tread surface and the side surface. Due to this recess, even when the camber angle becomes deep during turning, the tire can flex flexibly. This contributes to good transient properties. Further, as a result, the tire has a good flexing feeling and a good ground contact feeling. This tire has excellent running stability.

FIG. 1 is a cross-sectional view showing a part of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view showing a part of the tire of FIG. FIG. 3 is an enlarged cross-sectional view showing a part of a pneumatic tire according to another embodiment of the present invention. FIG. 4 is an enlarged sectional view showing a part of a pneumatic tire according to still another embodiment of the present invention.

Hereinafter, the present invention will be described in detail based on preferred embodiments with reference to the drawings as appropriate.

FIG. 1 shows a pneumatic tire 2. In FIG. 1, the vertical direction is the radial direction of the tire 2, the horizontal direction is the axial direction of the tire 2, and the direction perpendicular to the paper surface is the circumferential direction of the tire 2. In FIG. 1, the alternate long and short dash line CL represents the equatorial plane of the tire 2. The shape of the tire 2 is symmetrical with respect to the equatorial plane CL except for the tread pattern.

The tire 2 includes a tread 4, a pair of sidewalls 6, a pair of wings 8, a pair of beads 10, a carcass 12, a band 14, an inner liner 16, a pair of chafers 17, and a pair of recesses 18. The tire 2 is a tubeless type. This tire 2 is for a two-wheeled vehicle. The tire 2 is mounted on the rear wheel of a two-wheeled vehicle.

The tread 4 has a shape that is convex outward in the radial direction. The outer surface of the tread 4 that can come into contact with the road surface is referred to as the tread surface 20. A groove 21 is carved on the tread surface 20. A tread pattern is formed by the groove 21. The tread 4 is made of crosslinked rubber having excellent wear resistance, heat resistance and grip.

As shown in FIG. 1, the contour of the tread surface 20 of the tire 2 is largely curved. In this tire 2, when traveling straight ahead, the peripheral portion of the tread surface 20 around the equator mainly contacts the road surface. When turning, the rider tilts the vehicle to run. Therefore, during turning, the portion of the tread surface 20 axially outside the peripheral portion of the equator mainly contacts the road surface.

Each of the sidewalls 6 extends substantially inward in the radial direction from the vicinity of the end of the tread 4. The sidewall 6 is made of a crosslinked rubber having excellent cut resistance and weather resistance. The sidewall 6 prevents the carcass 12 from being damaged.

Each wing 8 is located between the tread 4 and the sidewall 6. The wings 8 are joined to the tread 4 and the sidewalls 6, respectively. The wings 8 are made of crosslinked rubber having excellent adhesiveness.

Each bead 10 is located inside the sidewall 6 in the radial direction. The bead 10 includes a core 22 and an apex 24. The core 22 has a ring shape and includes a wound non-stretchable wire. A typical material for the wire is steel. The apex 24 extends radially outward from the core 22. The apex 24 is tapered outward in the radial direction. The apex 24 is made of high hardness crosslinked rubber.

The carcass 12 includes a carcass ply 26. In this tire 2, the carcass 12 is composed of one carcass ply 26. The carcass ply 26 is bridged between the beads 10 on both sides and extends along the tread 4 and the sidewall 6. The carcass ply 26 is folded around the core 22 from the inner side to the outer side in the axial direction. The carcass 12 may be composed of two or more carcass plies 26.

Although not shown, the carcass ply 26 includes a large number of cords and a topping rubber arranged in parallel. The absolute value of the angle formed by each code with respect to the equatorial plane CL is 75° to 90°. In other words, this carcass 12 has a radial structure. The cord is made of organic fiber. Examples of preferable organic fibers include polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers and aramid fibers.

The band 14 is located inside the tread 4 in the radial direction. The band 14 is laminated on the outer side of the carcass 12 in the radial direction. Although not shown, the band 14 includes a cord and a topping rubber. The cord is spirally wound. The band 14 has a so-called jointless structure. The cord extends substantially in the circumferential direction. The angle of the cord with respect to the circumferential direction is 5° or less, and further 2° or less. The cord is made of organic fiber. Examples of preferable organic fibers include nylon fibers, polyester fibers, rayon fibers, polyethylene naphthalate fibers and aramid fibers.

The inner liner 16 is located inside the carcass 12. The inner liner 16 is joined to the inner surface of the carcass 12. The inner liner 16 is made of a crosslinked rubber having an excellent air shielding property. A typical base rubber for the inner liner 16 is butyl rubber or halogenated butyl rubber. The inner liner 16 holds the internal pressure of the tire 2.

Each chafer 17 is located near the bead 10. When the tire 2 is incorporated into the rim, the chafer 17 contacts the rim. This contact protects the vicinity of the bead 10. In this embodiment, the chafer 17 is made of cloth and rubber impregnated in the cloth. The chafer 17 may be made of crosslinked rubber.

In this tire 2, the outer surface of the tire 2 located inside the tread surface 20 in the radial direction and visible from the axial direction is referred to as a side surface 28. As shown in FIG. 1, the axial width of the tire 2 becomes maximum at the position of the boundary between the tread surface 20 and the side surface 28. The position of the boundary between the tread surface 20 and the side surface 28 is the maximum width position of the tire 2.

The recess 18 is located at the boundary between the tread surface 20 and the side surface 28, as shown in FIG. 1. The tire 2 has a recess 18 at the maximum width position. The recess 18 extends in the circumferential direction. FIG. 2 is an enlarged sectional view showing the recess 18 of FIG. As shown in FIG. 2, in this cross section, the recess 18 has an arc shape. An intersection 30 between the side surface 28 and the recess 18 has a shape that is sharpened outward. The intersection 32 between the tread surface 20 and the recess 18 also has a shape that is pointed outward.

The effects of the present invention will be described below.

The two-wheeled vehicle tire 2 according to the present invention is provided with the recess 18 extending in the circumferential direction at the boundary between the tread surface 20 and the side surface 28. The recess 18 appropriately suppresses the vertical spring constant even when the camber angle becomes deep during turning. Even when the camber angle becomes deep due to the recess 18, the tire 2 can flex flexibly. As a result, the two-wheeled vehicle equipped with the tire 2 can be smoothly tilted at an appropriate speed from an upright posture to a posture in which the camber angle is deep. The tire 2 has excellent transient characteristics.

The tire 2 can flex flexibly when it is upright and when the camber angle becomes deep. The tire 2 has a good flexing feeling. Furthermore, this contributes to a good feeling of touching the ground. In this tire 2, good running stability is realized.

As shown in FIG. 2, the recess 18 preferably has an arc shape in a cross section perpendicular to the circumferential direction. Due to the arcuate recess 18, the tire 2 can flex flexibly even when the camber angle becomes deep during turning. The tire 2 has excellent transient characteristics. Further, the recess 18 contributes to a good bending feeling and a good ground contact feeling. In this tire 2, good running stability is realized. Furthermore, the recess 18 having an arc shape is easy to process. With this tire 2, excellent productivity is maintained.

In FIG. 2, a double-headed arrow W indicates the width of the recess 18. The width W is the distance between the intersection 30 between the recess 18 and the side surface 28 and the intersection 32 between the recess 18 and the tread surface 20. The width W is preferably 1.0 mm or more. By setting the width W to 1.0 mm or more, the tire 2 can flexibly bend even when the camber angle becomes deep during turning. The tire 2 has excellent transient characteristics. Further, the recess 18 contributes to a good bending feeling and a good ground contact feeling. In this tire 2, good running stability is realized. From this viewpoint, the width W is more preferably 2.0 mm or more.

The width W is preferably 5.0 mm or less. By setting the width W to be 5.0 mm or less, the rigidity is appropriately maintained in the tire 2 in the vicinity of the boundary between the tread surface 20 and the side surface 28. The tire 2 is prevented from being excessively bent. This contributes to excellent transient characteristics. Furthermore, this contributes to a good bending feeling and a feeling of ground contact. In this tire 2, good running stability is realized. From this viewpoint, the width W is more preferably 4.0 mm or less.

In FIG. 2, a double-headed arrow D indicates the depth of the recess 18. The depth D is the maximum value of the distance from the straight line connecting the intersection 30 between the recess 18 and the side surface 28 and the intersection 32 between the recess 18 and the tread surface 20 to the bottom of the recess 18. The depth D is preferably 0.5 mm or more. By setting the depth D to 0.5 mm or more, the tire 2 can flex flexibly even when the camber angle becomes deep during turning. The tire 2 has excellent transient characteristics. Further, the recess 18 contributes to a good bending feeling and a good ground contact feeling. In this tire 2, good running stability is realized. From this viewpoint, the depth D is more preferably 0.8 mm or more.

The depth D is preferably 3.0 mm or less. By setting the depth D to 3.0 mm or less, in the tire 2, the rigidity is appropriately maintained in the vicinity of the boundary between the tread surface 20 and the side surface 28. The tire 2 is prevented from being excessively bent. This contributes to excellent transient characteristics. Furthermore, this contributes to a good bending feeling and a feeling of ground contact. In this tire 2, good running stability is realized. From this viewpoint, the depth D is more preferably 2.0 mm or less.

In the present invention, the size and angle of each member of the tire 2 are measured in a state where the tire 2 is incorporated in a regular rim and the tire 2 is filled with air so as to have a regular internal pressure. No load is applied to the tire 2 during the measurement. In the present specification, the regular rim means a rim defined in the standard on which the tire 2 depends. The “standard rim” in the JATMA standard, the “Design Rim” in the TRA standard, and the “Measuring Rim” in the ETRTO standard are regular rims. In the present specification, the normal internal pressure means the internal pressure defined in the standard on which the tire 2 depends. The "maximum air pressure" in the JATMA standard, the "maximum value" listed in "TIRE LOAD LIMITSAT VARIOUS COLD INFLATION PRESSURES" in the TRA standard, and the "INFLATION PRESSURE" in the ETRTO standard are normal internal pressures. This also applies to the following tires.

FIG. 3 shows a part of a tire 40 according to another embodiment of the present invention. This is a cross section perpendicular to the circumferential direction of the tire 40. The tire 40 has a recess 46 at the boundary between the tread surface 42 and the side surface 44. The recess 46 extends in the circumferential direction. In FIG. 3, the recess 46 is shown enlarged. The tire 40 is the same as the tire 2 of FIG. 1 except for the shape of the recess 46.

As shown in FIG. 3, in the tire 40, the recess 46 has an arc shape in a cross section perpendicular to the circumferential direction. An intersection 48 between the side surface 44 and the recess 46 has an outwardly convex arc shape. An intersection 50 between the tread surface 42 and the recess 46 also has an outwardly convex arc shape.

In the tire 40, the recess 46 appropriately suppresses the vertical spring constant even when the camber angle becomes deep during turning. Due to this recess 46, the tire 40 can flex flexibly even when the camber angle becomes deep. As a result, the two-wheeled vehicle equipped with the tires 40 can smoothly lean from an upright posture to a posture in which the camber angle is deep at an appropriate speed. The tire 40 has excellent transient characteristics. Further, the recess 46 contributes to a good flexing feeling and a good ground contact feeling. The tire 40 achieves good running stability.

FIG. 4 shows a part of a tire 52 according to still another embodiment of the present invention. This is a cross section perpendicular to the circumferential direction of the tire 52. The tire 52 has a recess 58 at the boundary between the tread surface 54 and the side surface 56. The recess 58 extends in the circumferential direction. In FIG. 4, this recess 58 is shown enlarged. The tire 52 is the same as the tire 2 of FIG. 1 except for the shape of the recess 58.

As shown in FIG. 4, in the tire 52, the recess 58 has a trapezoidal shape in a cross section perpendicular to the circumferential direction. An intersection 60 between the side surface 56 and the recess 58 has an outwardly pointed shape. The intersection 62 between the tread surface 54 and the recess 58 also has a shape that is sharply outward.

In the tire 52, the trapezoidal recess 58 appropriately suppresses the vertical spring constant even when the camber angle becomes deep during turning. Due to the recess 58, the tire 52 can flex flexibly even when the camber angle becomes deep. As a result, the two-wheeled vehicle equipped with the tires 52 can be smoothly tilted at an appropriate speed from an upright posture to a posture in which the camber angle is deep. The tire 52 has excellent transient characteristics. In addition, the recess 58 contributes to a good flexing feeling and a good ground contact feeling. The tire 52 achieves good running stability. Furthermore, the trapezoidal recess 58 is easy to process. The tire 52 maintains excellent productivity.

Although not shown, the shape of the recess is not limited to the arc shape and the trapezoid shape in the cross section perpendicular to the circumferential direction. The shape of the recess may be triangular or rectangular. The shape of the recess may be another polygonal shape.

Hereinafter, the effects of the present invention will be clarified by examples, but the present invention should not be limitedly interpreted based on the description of the examples.

[Example 1]
A two-wheeled vehicle tire of Example 1 having the structure shown in FIG. 1 was obtained. In this example, two types of tires, a front tire and a rear tire, were produced. The size of the front tire was 120/70ZR17. The size of the rear tire was 200/55ZR17. The specifications of the recesses of these tires are shown in Table 1. In the cross section perpendicular to the circumferential direction, the recessed portion of each tire has an arc shape. This is shown as "arc" in the column of "depression shape" in Table 1. In each tire, the intersection of the side surface and the recess has a shape that is sharply outward. The intersection of the tread surface and the recess also has an outwardly pointed shape.

[Comparative Example 1]
Rear tires and front tires were obtained in the same manner as in Example 1 except that each of them had no recessed portion.

[Example 2]
Rear and front tires were obtained in the same manner as in Example 1 except that the shape of the recess was trapezoidal.

[Example 3-6]
Rear tires and front tires were obtained in the same manner as in Example 1 except that the width W of the recess was set to the value shown in Table 1.

[Examples 7-10]
Rear tires and front tires were obtained in the same manner as in Example 1 except that the depth D of the recess was set to the value shown in Table 2.

[Transient characteristics, deflection, ground contact]
The front tire was mounted on a regular rim (rim size=MT3.50×17) and mounted on the front wheel of a two-wheeled vehicle with a displacement of 1000 cc. Air was filled so that the internal pressure was 250 kPa. The rear tire was mounted on a regular rim (rim size=MT6.00×17) and mounted on the rear wheel of this two-wheeled vehicle. Air was filled so that the internal pressure was 290 kPa. This motorcycle was run on a dry asphalt road surface, and sensory evaluation was performed by a rider. The evaluation items are the transient characteristics, the feeling of bending, and the feeling of touching the ground. The results are shown in Table 1-2 as an index with Comparative Example 1 being 100. In each case, the larger the value, the more preferable.

As shown in Table 1-2, the tires of Examples are totally superior to the tires of Comparative Example. From this evaluation result, the superiority of the present invention is clear.

The tire described above can be applied to various motorcycles.

2, 40, 52... Tire 4... Tread 6... Sidewall 8... Wing 10... Bead 12... Carcass 14... Band 16... Innerliner 17... Chafer 18, 46, 58... Cavity 20, 42, 54... Tread surface 22... Core 24... Apex 26... Carcass ply 28, 44, 56... Side surface 30 , 50, 60... Intersection between side surface and recess 32, 48, 62... Intersection between tread surface and recess

Claims (6)

A two-wheeled vehicle tire having a circumferentially extending recess at the boundary between the tread surface and the side surface. The tire for a two-wheeled vehicle according to claim 1, wherein an intersection of the side surface and the recess has a shape that is sharply outward or an arc that is outwardly convex in a cross section perpendicular to the circumferential direction. The tire for a two-wheeled vehicle according to claim 1 or 2, wherein, in a cross section perpendicular to the circumferential direction, an intersection of the tread surface and the recess has an outwardly pointed shape or an outwardly convex arcuate shape. The tire for a two-wheeled vehicle according to any one of claims 1 to 3, wherein the width of the recess is 1.0 mm or more and 5.0 mm or less. The tire for a two-wheeled vehicle according to any one of claims 1 to 4, wherein the depth of the recess is 0.5 mm or more and 3.0 mm or less. The motorcycle tire according to any one of claims 1 to 5, wherein the recess has a trapezoidal shape or an arc shape in a cross section perpendicular to the circumferential direction.

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