Motorcycle tires

Abstract

To provide a tire for a motorcycle having a carcass of a bias structure and exhibiting excellent turning performance.SOLUTION: A tire for a motorcycle includes a tread part 2, a pair of sidewall parts 3, a pair of bead parts 4 and a carcass 6. The tread part 2 includes a crown area Cr, a pair of shoulder areas Sh and a pair of middle areas Mi. The carcass 6 includes a plurality of carcass cords. An angle θs of a carcass cord 13 with respect to the tire circumferential direction in a shoulder area Sh is larger than an angle θc of the carcass cord 13 with respect to the tire circumferential direction in the crown area Cr.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a tire for a motorcycle. [Background technology]

[0002] Patent Document 1 below proposes a bias tire for motorcycles. The tire includes a carcass ply with a bias structure in which carcass cords are arranged at an angle relative to the tire circumferential direction, and a band disposed inside the tread portion and outside the carcass. The carcass ply and the band are expected to reduce the tire's weight and improve handling stability. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-185511 Summary of the Invention [Problem to be solved by the invention]

[0004] Motorcycle tires including a carcass with a bias structure as described above tend to have small camber thrust when cornering at a relatively large camber angle, and improvements in cornering performance have been desired.

[0005] The present invention has been devised in view of the above circumstances, and has as its main object to provide a motorcycle tire having a bias structure carcass with excellent cornering performance. [Means for solving the problem]

[0006] The present invention is a motorcycle tire including a tread portion between a pair of tread ends, a pair of sidewall portions, a pair of bead portions, and a carcass with a bias structure extending from one of the bead portions to the other of the bead portions, wherein the tread portion includes a crown region that is the central region when the tread developed width between the pair of tread ends is divided into five equal parts in the tire axial direction, a pair of shoulder regions that include the pair of tread ends, and a pair of middle regions between the crown region and the pair of shoulder regions, and the carcass includes a plurality of carcass cords, and an angle θs of the carcass cords with respect to the tire circumferential direction in the shoulder regions is greater than an angle θc of the carcass cords with respect to the tire circumferential direction in the crown region.

[0007] In the crown region, the middle region and the shoulder region of the motorcycle tire of the present invention, the angle of the carcass cords with respect to the tire circumferential direction is preferably in the range of 20 to 65 degrees.

[0008] In the motorcycle tire of the present invention, the angle θc is preferably 0.35 to 0.90 times the angle θs.

[0009] In the motorcycle tire of the present invention, it is preferable that the tread portion includes a band layer arranged across the crown region, the middle region, and the shoulder region, the band layer includes a band ply in which band cords are arranged at an angle of 5° or less with respect to the tire circumferential direction, and the ends Em of the band cords in the middle region are larger than the ends Ec of the band cords in the crown region.

[0010] In the motorcycle tire of the present invention, the Ends Ec is preferably 0.50 to 0.90 times the Ends Em.

[0011] In the motorcycle tire of the present invention, it is desirable that the ends Es of the band cord in the shoulder region of the band ply be smaller than the ends Em.

[0012] In the motorcycle tire of the present invention, the ends Es are preferably 0.50 to 0.90 times the ends Em.

[0013] In the motorcycle tire of the present invention, it is preferable that θc×Ec / Em, obtained by multiplying the angle θc by the ratio of the ends Ec to the ends Em, is 10-55.

[0014] In the motorcycle tire of the present invention, θs×Es / Em, obtained by multiplying the angle θs by the ratio of the ends Es of the band cord in the shoulder region of the band ply to the ends Em, is preferably 10-55.

[0015] In the motorcycle tire of the present invention, the band ply is preferably a jointless band ply in which the band cord is wound spirally. [Effects of the Invention]

[0016] The motorcycle tire of the present invention, by adopting the above-mentioned configuration, can exhibit excellent cornering performance. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a cross-sectional view showing an embodiment of a motorcycle tire of the present invention. [Figure 2] FIG. 2 is a development view of the first carcass ply and the second carcass ply of FIG. 1. [Figure 3] FIG. 2 is a development view of the first carcass ply of FIG. 1. [Figure 4] FIG. 2 is a development view of the band ply of FIG. 1. DETAILED DESCRIPTION OF THE INVENTION

[0018] An embodiment of the present invention will now be described with reference to the drawings. Fig. 1 is a cross-sectional view of a motorcycle tire 1 (hereinafter sometimes simply referred to as "tire") according to this embodiment, taken along the tire meridian including the tire rotation axis, in a normal state. The tire 1 according to this embodiment is a tire for the front wheel of a motorcycle suitable for on-road sports riding. However, the tire of the present invention is not limited to this embodiment.

[0019] "Normal condition" means, in the case of motorcycle tires for which various standards are established, that the tire is mounted on a normal rim, inflated to the normal internal pressure, and is in an unloaded state. In the case of tires for which various standards are not established, the normal condition means a standard use state according to the intended use of the tire, in which the tire is not mounted on a vehicle and is unloaded. In this specification, unless otherwise specified, the dimensions of each part of the tire are values measured in the normal condition.

[0020] A "genuine rim" is a rim that is defined for each tire by the standard system that includes the standard on which the tire is based. For example, in the case of JATMA, it is called a "standard rim," in the case of TRA, it is called a "design rim," and in the case of ETRTO, it is called a "measuring rim."

[0021] "Normal internal pressure" is the air pressure specified for each tire by each standard in the standard system, including the standard on which the tire is based. For JATMA, it is the "maximum air pressure," for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO, it is the "INFLATION PRESSURE."

[0022] As shown in Fig. 1, the tire 1 of this embodiment has a tread portion 2 between a pair of tread ends Te, a pair of sidewall portions 3, and a pair of bead portions 4. The tread portion 2 has an outer surface 2s between one tread end Te and the other tread end Te that is curved in an arc shape that is convex outward in the radial direction of the tire so as to ensure a sufficient contact area even when cornering at a large camber angle. The tread end Te corresponds to the end of the contact patch of the tread portion 2 when cornering at the maximum camber angle.

[0023] The tread portion 2 includes a crown region Cr, a pair of shoulder regions Sh, and a pair of middle regions Mi. The crown region Cr is the central region when the tread developed width TWe between the pair of tread edges Te is divided into five equal parts in the tire axial direction. The shoulder regions Sh include the tread edges Te and are regions on both sides of the tread portion 2 in the tire axial direction when the tread width TWe is divided into five equal parts. The middle regions Mi are separated between the crown region Cr and the pair of shoulder regions Sh. When the tread portion 2 is developed on a plane, the boundaries 10 of each region extend so as to divide the tread developed width TWe into five equal parts, and extend normal to the outer surface 2s of the tread portion 2 in the tire meridian cross section.

[0024] The tire 1 of this embodiment also includes a toroidal carcass 6. The carcass 6 extends from one bead portion 4 through one sidewall portion 3, the tread portion 2, and the other sidewall portion 3 to the other bead portion 4. The carcass 6 also includes at least one carcass ply in which a plurality of carcass cords are covered with a topping rubber. The carcass 6 of the present invention has a bias structure in which the carcass cords extend at an angle relative to the tire circumferential direction. The carcass cords are made of, for example, organic fiber cords.

[0025] The carcass 6 of this embodiment is composed of, for example, a first carcass ply 11 and a second carcass ply 12 that are overlapped with each other. In this embodiment, the first carcass ply 11 is arranged radially inward of the second carcass ply 12 in the tread portion 2. The carcass 6 of this embodiment also includes a main body portion 6a and a turned-up portion 6b. The main body portion 6a extends from the tread portion 2 through the sidewall portion 3 to the bead cores 5 of the bead portions 4. The turned-up portion 6b is continuous with the main body portion 6a, is turned up at the bead cores 5 and extends radially outward of the tire.

[0026] Fig. 2 shows a developed view of the first carcass ply 11 and the second carcass ply 12 in the tread portion 2. Fig. 3 shows a developed view of the first carcass ply 11 as a diagram illustrating the arrangement of the carcass cords 13. As shown in Fig. 2, in this embodiment, the carcass cords 13 of the first carcass ply 11 are inclined in a first direction (upward and to the right in each drawing in this specification) with respect to the tire axial direction, and the carcass cords 13 of the second carcass ply 12 are inclined in a second direction (downward and to the right in each drawing in this specification) that is opposite to the first direction with respect to the tire axial direction. As a result, the first carcass ply 11 and the second carcass ply 12 are overlapped in such a way that the carcass cords 13 included in each ply intersect.

[0027] 3, the angle θs of the carcass cord 13 in the shoulder region Sh relative to the tire circumferential direction is larger than the angle θc of the carcass cord 13 in the crown region Cr relative to the tire circumferential direction. By adopting the above-described configuration, the tire 1 of the present invention can exhibit excellent cornering performance. The following mechanism is thought to be the reason for this.

[0028] The above-described arrangement of the carcass cords 13 relatively increases the axial rigidity of the shoulder region Sh. Therefore, as the crown region Cr moves from the shoulder region Sh to the ground, the camber thrust and cornering force gradually increase, and sufficient camber thrust and cornering force are obtained during cornering when the shoulder region Sh contacts the ground. Meanwhile, in the crown region Cr, the carcass cord angle is small, so the circumferential rigidity of the tire is high, maintaining braking performance. It is believed that the present invention achieves excellent cornering performance due to the above-described mechanism.

[0029] The following describes the configuration of this embodiment in more detail. Note that each configuration described below represents a specific aspect of this embodiment. Therefore, it goes without saying that the present invention can achieve the above-described effects even if it does not have the configuration described below. Furthermore, even if any one of the configurations described below is applied alone to a tire of the present invention having the above-described characteristics, an improvement in performance corresponding to each configuration can be expected. Furthermore, when several of the configurations described below are applied in combination, an improvement in combined performance corresponding to each configuration can be expected.

[0030] As shown in FIG. 3, the angle of the carcass cords 13 relative to the tire circumferential direction is preferably in the range of 20 to 65 degrees in the crown region Cr, the middle region Mi, and the shoulder region Sh.

[0031] The angle θc of the carcass cords 13 in the crown region Cr relative to the tire circumferential direction is, for example, 20 to 45°, and preferably 25 to 40°. The angle θm of the carcass cords 13 in the middle region Mi relative to the tire circumferential direction is, for example, 25 to 60°, and preferably 30 to 55°. The angle θs of the carcass cords 13 in the shoulder region Sh relative to the tire circumferential direction is, for example, 25 to 65°, and preferably 35 to 60°. However, the present invention is not limited to these angle ranges.

[0032] The angle of each region of the carcass cord 13 relative to the tire circumferential direction preferably satisfies the relationship of the following formula (1). Furthermore, it is desirable that the angle of the carcass cord 13 continuously increases from the crown region Cr side toward the shoulder region Sh side. This makes the response when leaning the vehicle body linear, improving handling performance. θc<θm<θs…(1)

[0033] The angle θc of the carcass cords 13 in the crown region Cr is preferably 0.35 or more, more preferably 0.50 or more, and preferably 0.90 or less, more preferably 0.75 or less, of the angle θs of the carcass cords 13 in the shoulder region Sh. Such an arrangement of the carcass cords 13 can improve cornering performance while preventing the tire from feeling heavy when leaning over.

[0034] The angle θm of the carcass cords 13 in the middle region Mi is preferably 0.75 or more times, more preferably 0.80 or more times, and preferably 0.98 or less times, more preferably 0.95 or less times, of the angle θs of the carcass cords 13 in the shoulder regions Sh. Such an arrangement of the carcass cords 13 allows excellent handling performance to be exhibited during cornering at a relatively large camber angle where the middle region Mi or the shoulder regions Sh come into contact with the ground.

[0035] It goes without saying that the arrangement of the carcass cords 13 described above is applied not only to the carcass cords 13 of the first carcass ply 11 shown in Fig. 3 but also to the carcass cords of the second carcass ply 12. The angles of the carcass cords 13 in each of the above-described regions correspond to those measured at the center position of each region in the axial direction of the tire.

[0036] As shown in Fig. 1, the tread portion 2 of this embodiment includes a band layer 8 arranged across the crown region Cr, the middle region Mi, and the shoulder region Sh. The band layer 8 includes a band ply 15 in which band cords are arranged at an angle of 5° or less with respect to the tire circumferential direction. In a more preferable embodiment, the band ply 15 of this embodiment is configured as a jointless band ply in which the band cords are wound spirally.

[0037] 4 shows a developed view of the band ply 15. In this embodiment, the ends (the number of cords arranged per 5 cm of ply width) of the band cords 16 of the band ply 15 are different in each region, which is expected to improve various performances.

[0038] Specifically, the ends Ec of the band cord in the crown region Cr is, for example, 10 to 40, and preferably 20 to 35. The ends Em of the band cord in the middle region Mi is, for example, 20 to 60, and preferably 30 to 55. The ends Es of the band cord in the shoulder region Sh is, for example, 5 to 40, and preferably 10 to 35.

[0039] The ends Em of the band cord 16 in the middle region Mi is preferably larger than the ends Ec of the band cord 16 in the crown region Cr. Specifically, the ends Ec in the crown region Cr is preferably 0.50 times or more, more preferably 0.60 times or more, and preferably 0.90 times or less, more preferably 0.80 times or less, of the ends Em in the middle region Mi.

[0040] The ends Es of the band cords 16 in the shoulder regions Sh are preferably smaller than the ends Em of the band cords 16 in the middle region Mi. Specifically, the ends Es in the shoulder regions Sh are preferably 0.50 or more times, more preferably 0.60 or more times, and preferably 0.90 or less, more preferably 0.80 or less times the ends Em in the middle region Mi. Such an arrangement of the band cords 16 relatively reduces the circumferential rigidity of the shoulder regions Sh and increases the contact patch of the shoulder regions Sh, thereby improving grip performance during cornering.

[0041] As a result of various experiments, the inventors have found that by relating the angle of the carcass cord 13 to the ends of the band cord 16, it is possible to improve the overall performance of the tire, such as the response when leaning, handling stability, cornering performance, etc.

[0042] Specifically, θc×Ec / Em, which is obtained by multiplying the angle θc (shown in FIG. 3) of the carcass cords 13 in the crown region Cr by the ratio of the ends Ec of the band cords 16 in the crown region Cr to the ends Em of the band cords 16 in the middle region Mi, is preferably 10 or more, more preferably 15 or more, and is preferably 55 or less, more preferably 50 or less. Such an arrangement of the carcass cords 13 and the band cords 16 can improve wear resistance, grip performance, and cornering performance in a balanced manner while maintaining handling stability in cornering conditions with a relatively small camber angle.

[0043] From a similar viewpoint, θs×Es / Em, which is obtained by multiplying the angle θs (shown in FIG. 3) of the carcass cords 13 in the shoulder regions Sh by the ratio of the ends Es of the band cords 16 in the shoulder regions Sh to the ends Em of the band cords 16 in the middle regions Mi, is desirably equal to or greater than 10, more desirably equal to or greater than 15, and is desirably equal to or less than 55, more desirably equal to or less than 50. Such an arrangement of the carcass cords 13 and the band cords 16 can improve wear resistance, grip performance, and cornering performance in a balanced manner while maintaining handling stability in cornering conditions with a relatively large camber angle.

[0044] Although a motorcycle tire according to one embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiment described above, and can be modified and implemented in various aspects. [Example]

[0045] A motorcycle tire (front tire) having the basic structure of Fig. 1, a nominal width of 120 mm, an aspect ratio of 70%, and a rim diameter of 17 inches was manufactured based on the specifications in Tables 1 to 4. As a comparative example, a tire was manufactured in which the angle of the carcass cords relative to the tire circumferential direction was constant throughout the crown region, middle region, and shoulder region. The comparative tire was substantially the same as the example tire, except for the above-mentioned points. Each test tire was tested for cornering performance, grip performance, handling stability, and wear resistance. The common specifications and test methods for each test tire are as follows: Rim size: MT3.50 Tire pressure: 250kPa Test vehicle: 1000cc

[0046] <Cornering performance, grip performance, handling stability> The above test vehicle was driven on a test course with a dry asphalt surface, and each item was evaluated. "Cornering performance" refers to the overall cornering performance from upright to full banking. "Grip performance" refers to the overall grip performance over the entire driving range. "Handling stability" refers to the overall handling stability, including handling performance over the entire driving range. The results are shown on a scale of 10, with the higher the number, the better the evaluation item.

[0047] <Wear resistance> After the test vehicle was driven 15,000 km on public roads, the remaining amount of tread rubber was measured. The results were expressed as an index, with the remaining amount of the comparative example being 100. A larger index indicates a larger amount of remaining tread rubber and better wear resistance. The test results are shown in Tables 1-4.

[0048] [Table 1]

[0049] [Table 2]

[0050] [Table 3]

[0051] [Table 4]

[0052] As a result of the test, it was confirmed that the tires of the examples exhibited excellent cornering performance. In addition, it was confirmed that the tires of the examples also had improved grip performance, handling stability, and wear resistance. [Explanation of symbols]

[0053] 2 Tread section 3 Sidewall 4 Bead section 6. Carcass 13 Carcass cord Cr Crown region Sh Shoulder region Mi middle range θc angle θs angle

Claims

1. A tire for a motorcycle, The tire includes a tread portion between a pair of tread ends, a pair of sidewall portions, a pair of bead portions, and a carcass having a bias structure extending from one of the bead portions to the other of the bead portions, The tread portion includes a crown region that is a central region when a tread developed width between the pair of tread edges is divided into five equal parts in the tire axial direction, a pair of shoulder regions that include the pair of tread edges, and a pair of middle regions between the crown region and the pair of shoulder regions, The carcass includes a plurality of carcass cords, an angle θs of the carcass cord with respect to the tire circumferential direction in the shoulder region is larger than an angle θc of the carcass cord with respect to the tire circumferential direction in the crown region, In a developed view of the carcass cord, the carcass cord extends so as to smoothly convex toward one side in the tire circumferential direction between the tire equator and one of the pair of tread ends, and extends so as to smoothly convex toward the other side in the tire circumferential direction between the tire equator and the other of the pair of tread ends. Tires for motorcycles.

2. A motorcycle tire as described in claim 1, wherein the angle of the carcass cord relative to the tire circumferential direction in the crown region, the middle region and the shoulder region is in the range of 20 to 65 degrees.

3. A motorcycle tire as described in claim 1 or 2, wherein the angle θc is 0.35 to 0.90 times the angle θs.

4. A motorcycle tire as described in any one of claims 1 to 3, wherein the angle θc of the carcass cord in the crown region is 25 to 40°.

5. The tread portion includes a band layer disposed across the crown region, the middle region, and the shoulder region, the band layer includes a band ply in which band cords are arranged at an angle of 5° or less with respect to the tire circumferential direction, The motorcycle tire according to claim 1 , wherein an end Em of the band cord in the middle region is greater than an end Ec of the band cord in the crown region.

6. A motorcycle tire as described in claim 5, wherein Ends Ec is 0.50 to 0.90 times Ends Em.

7. A motorcycle tire as described in claim 5 or 6, wherein the ends Es of the band cord in the shoulder region of the band ply are smaller than the ends Em.

8. A motorcycle tire as described in claim 7, wherein Ends Es is 0.50 to 0.90 times Ends Em.

9. A motorcycle tire as described in any one of claims 5 to 8, wherein θc × Ec / Em, obtained by multiplying the angle θc by the ratio of the ends Ec to the ends Em, is 10 to 55.

10. A motorcycle tire as described in any one of claims 5 to 9, wherein θs × Es / Em, obtained by multiplying the angle θs by the ratio of the ends Es of the band cord in the shoulder region of the band ply to the ends Em, is 10 to 55.

11. A motorcycle tire as described in any one of claims 5 to 10, wherein the band ply is a jointless band ply in which the band cord is wound spirally.

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