Tire for a two-wheeled motor vehicle

Abstract

The present invention provides a tire for a two-wheeled motor vehicle, which has a carcass with a bias structure and can exhibit excellent cornering performance. The tire for a two-wheeled motor vehicle includes a tread portion (2), a pair of sidewall portions (3), a pair of bead portions (4), and a carcass (6). The tread portion (2) includes a crown region (Cr), a pair of shoulder regions (Sh), and a pair of intermediate regions (Mi). The carcass (6) includes a plurality of carcass cords. The angle (θs) of the carcass cords (13) in the shoulder region (Sh) with respect to the tire circumferential direction is larger than the angle (θc) of the carcass cords (13) in the crown region (Cr) with respect to the tire circumferential direction.

Description

Technical Field

[0001] The present invention relates to a tire for a two-wheeled motor vehicle. Background Art

[0002] In Patent Document 1 below, a bias tire for a two-wheeled motor vehicle is proposed. The tire has: a carcass ply having a bias structure, which is formed by arranging carcass cords obliquely with respect to the tire circumferential direction; and a belt, which is disposed inside the tread portion and outside the carcass. The tire expects weight reduction and improvement in handling stability through the carcass ply and the belt.

[0003] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2000-185511

[0004] A two-wheeled motor vehicle tire including a carcass having the above-described bias structure has a tendency of small camber thrust when turning at a relatively large camber angle, and improvement in turning performance is required. Summary of the Invention

[0005] The present invention has been made in view of the above actual situation, and its main object is to exhibit excellent turning performance in a two-wheeled motor vehicle tire having a carcass with a bias structure.

[0006] The present invention is a two-wheeled motor vehicle tire, which includes 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 bead portion to the other bead portion. The tread portion includes a crown region, a pair of shoulder regions, and a pair of intermediate regions between the crown region and the pair of shoulder regions. The crown region is a central region when the tread width between the pair of tread ends is divided into five equal parts in the tire axial direction. The pair of shoulder regions include the pair of tread ends. The carcass includes a plurality of carcass cords, and an angle θs of the carcass cords in the shoulder region with respect to the tire circumferential direction is larger than an angle θc of the carcass cords in the crown region with respect to the tire circumferential direction.

[0007] In the crown region, the intermediate region, and the shoulder region of the two-wheeled motor vehicle tire of the present invention, it is preferable that an angle of the carcass cords with respect to the tire circumferential direction is in a range of 20° to 65°.

[0008] In the two-wheeled motor vehicle tire of the present invention, it is preferable that the angle θc is 0.35 times 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 belt layer extending to the crown region, the intermediate region, and the shoulder region, the belt layer includes a belt ply formed by arranging belt cords at an angle of 5° or less with respect to the tire circumferential direction, and the number of cord ends Em of the belt cords in the intermediate region is larger than the number of cord ends Ec of the belt cords in the crown region.

[0010] In the motorcycle tire of the present invention, it is preferable that the number of cord ends Ec is 0.50 to 0.90 times the number of cord ends Em.

[0011] In the motorcycle tire of the present invention, it is preferable that the number of cord ends Es of the belt cords in the shoulder region of the belt ply is smaller than the number of cord ends Em.

[0012] In the motorcycle tire of the present invention, it is preferable that the number of cord ends Es is 0.50 to 0.90 times the number of cord 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 number of cord ends Ec to the number of cord ends Em is 10 to 55.

[0014] In the motorcycle tire of the present invention, it is preferable that θs × Es / Em obtained by multiplying the angle θs by the ratio of the number of cord ends Es of the belt cords in the shoulder region of the belt ply to the number of cord ends Em is 10 to 55.

[0015] In the motorcycle tire of the present invention, it is preferable that the belt ply is a seamless belt ply formed by spirally winding the belt cords.

[0016] By adopting the above structure, the motorcycle tire of the present invention can exhibit excellent turning performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a cross-sectional view showing an embodiment of the motorcycle tire of the present invention.

[0018] Figure 2 is Figure 1 a developed view of the first carcass ply and the second carcass ply of

[0019] Figure 3 is Figure 1 a developed view of the first carcass ply of

[0020] Figure 4 is Figure 1 a developed view of the belt ply of

[0021] Description of Reference Numerals

[0022] 2: tread surface; 3: sidewall; 4: bead portion; 6: carcass; 13: carcass ply; Cr: crown region; Sh: shoulder region; Mi: intermediate region; θc: angle; θs: angle. Detailed Description of the Invention

[0023] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0024] Figure 1 is a tire meridian cross-section including the tire rotation axis in a normal state of the motorcycle tire 1 (hereinafter sometimes simply referred to as "tire") of the present embodiment. The tire 1 of the present embodiment is a tire for the front wheel of a motorcycle suitable for sporty driving on a road. However, the tire of the present invention is not limited to such a mode.

[0025] The "normal state" means that in the case of a motorcycle tire with various specifications determined, the tire is assembled on a normal rim, filled with a normal internal pressure, and in an unloaded state. In the case of a tire with undetermined various specifications, the above normal state means a standard use state corresponding to the use purpose of the tire, and means a state where it is not installed 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 above normal state.

[0026] The "normal rim" is a rim that determines the specification for each tire in a 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", and if it is ETRTO, it is the "Measuring Rim".

[0027] The "normal internal pressure" is the air pressure determined for each specification in a 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 described in the table "TIRE LOAD LIMITSAT VARIOUS COLD INFLATION PRESSURES", and if it is ETRTO, it is the "INFLATIONPRESSURE".

[0028] As Figure 1As shown, the tire 1 of the present 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 is curved in an arc shape with the outer surface 2s between one tread end Te and the other tread end Te protruding outward in the tire radius direction so as to obtain a sufficient ground contact area even when cornering with a large camber angle. In addition, the tread end Te corresponds to the end of the ground contact surface of the tread portion 2 when cornering with the maximum camber angle.

[0029] The tread portion 2 includes a crown region Cr, a pair of shoulder regions Sh, and a pair of intermediate regions Mi. The crown region Cr is the central region when the tread width TWe between the pair of tread ends Te is equally divided into five parts along the tire axial direction 5. The shoulder region Sh includes the tread end Te and is the region on both sides of the tread portion 2 in the tire axial direction when equally divided as above. The intermediate region Mi is divided between the crown region Cr and the pair of shoulder regions Sh. The boundary 10 of each region extends in a manner that equally divides the tread width TWe in a state where the tread portion 2 is developed into a plane, and in the tire meridian cross-section, it extends in the normal direction with respect to the outer surface 2s of the tread portion 2.

[0030] Moreover, the tire 1 of the present embodiment includes an annular 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. And the carcass 6 includes at least one carcass ply formed by coating multiple carcass cords with skim rubber. The carcass 6 of the present invention has a cross-ply structure in which the carcass cords extend obliquely with respect to the tire circumferential direction. The carcass cords are formed of organic fiber cords, for example.

[0031] The carcass 6 of the present embodiment is formed of, for example, a first carcass ply 11 and a second carcass ply 12 that overlap each other. In the present embodiment, in the tread portion 2, the first carcass ply 11 is disposed on the inner side in the tire radius direction of the second carcass ply 12. And the carcass 6 of the present embodiment includes a main body portion 6a and a return portion 6b. The main body portion 6a extends from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4. The return portion 6b is connected to the main body portion 6a and returns at the bead core 5 and extends outward in the tire radius direction.

[0032] Figure 2 An expanded view of the first carcass ply 11 and the second carcass ply 12 in the tread portion 2 is shown. And in Figure 3 , as a diagram showing the arrangement of the carcass cords 13, an expanded view of the first carcass ply 11 is shown. As Figure 2As shown, in the present embodiment, the carcass cords 13 of the first carcass ply 11 are inclined with respect to the tire axis in the first direction (in the figures of this specification, it is the upper right direction), and the carcass cords 13 of the second carcass ply 12 are inclined with respect to the tire axis in the second direction (in the figures of this specification, it is the lower right direction) opposite to the first direction. Thus, the first carcass ply 11 and the second carcass ply 12 overlap in the direction in which the carcass cords 13 that include each other cross.

[0033] As Figure 3 shown, the angle θs of the carcass cords 13 in the shoulder region Sh with respect to the tire circumferential direction is larger than the angle θc of the carcass cords 13 in the crown region Cr with respect to the tire circumferential direction. By adopting the above structure, the tire 1 of the present invention can exhibit excellent turning performance. As a reason, the following mechanism can be considered.

[0034] By the above configuration of the carcass cords 13, the rigidity in the tire axial direction of the shoulder region Sh becomes relatively high. Therefore, during the process of grounding from the crown region Cr to the shoulder region Sh, the camber thrust and the cornering force gradually increase, and when cornering with the shoulder region Sh grounded, a sufficiently large camber thrust and cornering force can be obtained. On the other hand, in the crown region Cr, since the above angle of the carcass cords is small, the rigidity in the tire circumferential direction is high, and the braking performance is maintained. In the present invention, it is considered that excellent turning performance is exhibited through the above mechanism.

[0035] Hereinafter, a more detailed structure of the present embodiment will be described. In addition, each structure described below represents a specific embodiment of the present embodiment. Therefore, even if the present invention does not have the structures described below, of course, the above effects can still be exhibited. In addition, in the tire of the present invention having the above characteristics, even if any one of the structures described below is applied alone, an improvement in performance corresponding to each structure can be expected. Furthermore, in the case of a combined application of several of the structures described below, an improvement in combined performance corresponding to each structure can be expected.

[0036] As Figure 3 shown, in the crown region Cr, the intermediate region Mi, and the shoulder region Sh, the angle of the carcass cords 13 with respect to the tire circumferential direction is preferably in the range of 20° to 65°.

[0037] The angle θc of the carcass cords 13 in the crown region Cr with respect to the tire circumferential direction is, for example, 20° to 45°, preferably 25° to 40°. And the angle θm of the carcass cords 13 in the intermediate region Mi with respect to the tire circumferential direction is, for example, 25° to 60°, preferably 30° to 55°. The angle θs of the carcass cords 13 in the shoulder region Sh with respect to the tire circumferential direction is, for example, 25° to 65°, preferably 35° to 60°. However, the present invention is not limited to such an angle range.

[0038] The angle of the carcass cord 13 relative to the tire circumferential direction in each region preferably satisfies the relationship of the following formula (1). Moreover, the above-mentioned angle of the carcass cord 13 preferably continuously increases from the crown region Cr side toward the shoulder region Sh side. Thereby, the feel when the vehicle body tilts becomes linear, and the handling performance is improved.

[0039] θc < θm < θs…(1)

[0040] The above-mentioned angle θc of the carcass cord 13 in the crown region Cr is preferably 0.35 times or more, more preferably 0.50 times or more, preferably 0.90 times or less, and more preferably 0.75 times or less of the above-mentioned angle θs of the carcass cord 13 in the shoulder region Sh. Such an arrangement of the carcass cord 13 can prevent the feel of tilting from becoming heavy and can improve the turning performance.

[0041] The above-mentioned angle θm of the carcass cord 13 in the middle region Mi is preferably 0.75 times or more, more preferably 0.80 times or more, preferably 0.98 times or less, and more preferably 0.95 times or less of the above-mentioned angle θs of the carcass cord 13 in the shoulder region Sh. Such an arrangement of the carcass cord 13 can exhibit excellent handling performance when turning under a relatively large camber angle such that the middle region Mi or the shoulder region Sh contacts the ground.

[0042] The above arrangement of the carcass cord 13 is not only applicable to Figure 3 the carcass cord 13 of the first carcass ply 11 shown, but of course also applicable to the carcass cord of the second carcass ply 12. In addition, the angle of the carcass cord 13 in each of the above regions corresponds to the angle measured at the center position in the tire axial direction of each region.

[0043] As Figure 1 shown, the tread portion 2 of the present embodiment includes a belt layer 8 disposed to extend to the crown region Cr, the middle region Mi, and the shoulder region Sh. The belt layer 8 includes a belt ply 15 in which belt cords are arranged at an angle of 5° or less with respect to the tire circumferential direction. As a more preferred mode, the belt ply 15 of the present embodiment is configured as a seamless belt ply formed by helically winding belt cords.

[0044] Figure 4 The developed view of the belt ply 15 is shown. In the present embodiment, the number of belt cords 16 of the belt ply 15 (the number of cords arranged per 5 cm width of the ply) varies according to each region. Thereby, improvement of various performances is expected.

[0045] Specifically, the number of cords Ec of the belt cords in the crown region Cr is, for example, 10 to 40, preferably 20 to 35. The number of cords Em of the belt cords in the intermediate region Mi is, for example, 20 to 60, preferably 30 to 55. The number of cords Es of the belt cords in the shoulder region Sh is, for example, 5 to 40, preferably 10 to 35.

[0046] The number of cords Em of the belt cords 16 in the intermediate region Mi is preferably larger than the number of cords Ec of the belt cords 16 in the crown region Cr. Specifically, the above-mentioned number of cords Ec in the crown region Cr is preferably 0.50 times or more, more preferably 0.60 times or more, preferably 0.90 times or less, and more preferably 0.80 times or less of the above-mentioned number of cords Em in the intermediate region Mi.

[0047] The number of cords Es of the belt cords 16 in the shoulder region Sh is preferably smaller than the number of cords Em of the belt cords 16 in the intermediate region Mi. Specifically, the above-mentioned number of cords Es in the shoulder region Sh is preferably 0.50 times or more, more preferably 0.60 times or more, preferably 0.90 times or less, and more preferably 0.80 times or less of the above-mentioned number of cords Em in the intermediate region Mi. Such an arrangement of the belt cords 16 can relatively relieve the rigidity in the tire circumferential direction of the shoulder region Sh and increase the contact ground surface of the shoulder region Sh, and thus can improve the grip performance during turning.

[0048] The inventors conducted various experiments and found that by establishing a relationship between the angle of the carcass cords 13 and the number of cords of the belt cords 16, the comprehensive performance of the tire such as the feel during tipping, the handling stability, and the turning performance can be improved.

[0049] Specifically, the above-mentioned angle θc of the carcass cords 13 in the crown region Cr ( Figure 3 as shown) multiplied by the ratio of the above-mentioned number of cords Ec of the belt cords 16 in the crown region Cr to the above-mentioned number of cords Em of the belt cords 16 in the intermediate region Mi, θc×Ec / Em, is preferably 10 or more, more preferably 15 or more, preferably 55 or less, and more preferably 50 or less. Such an arrangement of the carcass cords 13 and the belt cords 16 can maintain the handling stability in a turning state with a relatively small camber angle, and can evenly improve the wear resistance, the grip performance, and the turning performance.

[0050] From the same viewpoint, the above-mentioned angle θs of the carcass cords 13 in the shoulder region Sh ( Figure 3The θs×Es / Em obtained by multiplying the above-mentioned number of cords Es of the belt cords 16 in the shoulder region Sh by the ratio of the above-mentioned number of cords Es of the belt cords 16 in the shoulder region Sh to the number of cords Em of the belt cords 16 in the middle region Mi is preferably 10 or more, more preferably 15 or more, preferably 55 or less, and more preferably 50 or less. Such an arrangement of the carcass cords 13 and the belt cords 16 can maintain the handling stability in a turning state with a relatively large camber angle, and can evenly improve the wear resistance, the grip performance, and the turning performance.

[0051] The above has described in detail a motorcycle tire according to an embodiment of the present invention. However, the present invention is not limited to the above specific embodiment, and can be implemented in various ways.

[0052]

Examples

[0053] Based on the specifications in Tables 1 to 4, a motorcycle tire (front-wheel tire) with a nominal width of 120 mm, a flat rate of 70%, and a rim diameter of 17 inches having the Figure 1 basic structure was manufactured. And, as a comparative example, a tire was trial-produced in which the angle of the carcass cords with respect to the tire circumferential direction was constant over the entire range of the crown region, the middle region, and the shoulder region. In addition, the tire of the comparative example was substantially the same as the tire of the example except for the above matters. The turning performance, the grip performance, the handling stability, and the wear resistance of each test tire were tested. The common specifications and the test methods of each test tire are as follows.

[0054] Rim size: MT3.50

[0055] Tire internal pressure: 250 kPa

[0056] Test vehicle: Displacement 1000 cc

[0057] <Turning performance, grip performance, handling stability>

[0058] The above test vehicle was run on a test course on a dry asphalt road surface, and each item was evaluated. In addition, the "turning performance" refers to the comprehensive turning performance from upright to full lean. And, the "grip performance" refers to the comprehensive grip performance in the entire driving region. The "handling stability" refers to the comprehensive handling stability including the controllability in the entire driving region. The results are expressed as a score out of 10, and the larger the value, the more excellent each evaluation item is.

[0059] <Wear resistance>

[0060] After the above test vehicle had run 15,000 km on a general road, the remaining amount of the tread rubber was measured. The results are an index with the remaining amount of the comparative example being 100, and the larger the value, the larger the remaining amount of the tread rubber and the more excellent the wear resistance.

[0061] The test results are shown in Tables 1 to 4.

[0062] [Table 1]

[0063]

[0064] [Table 2]

[0065]

[0066] [Table 3]

[0067]

[0068] [Table 4]

[0069]

[0070] The test results can confirm that the tires of the embodiments can exhibit excellent turning performance. In addition, it can be confirmed that the tires of the embodiments also improve the grip performance, handling stability, and wear resistance.

Claims

1. A tire for a motorized two-wheeler, which 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 cross-ply structure extending from one of the bead portions to the other bead portion. The tread surface portion includes a crown region, a pair of shoulder regions, and a pair of intermediate regions between the crown region and the pair of shoulder regions, wherein, The crown region is the central region when the tread width between the pair of tread ends is equally divided into five parts along the tire axis, and the pair of shoulder regions include the pair of tread ends. The carcass includes a plurality of carcass cords. The angle θs of the carcass cords in the shoulder region with respect to the tire circumferential direction is larger than the angle θc of the carcass cords in the crown region with respect to the tire circumferential direction. The tread portion includes a belt layer arranged to extend to the crown region, the intermediate region, and the shoulder region. The belt layer includes a belt ply formed by arranging belt cords at an angle of 5° or less with respect to the tire circumferential direction. The number of cords Em of the belt cords in the intermediate region is larger than the number of cords Ec of the belt cords in the crown region. The number of cords Es of the belt cords in the shoulder region of the belt ply is smaller than the number of cords Em. The angle θc of the carcass cords in the crown region with respect to the tire circumferential direction, the angle θm of the carcass cords in the intermediate region with respect to the tire circumferential direction, and the angle θs of the carcass cords in the shoulder region with respect to the tire circumferential direction satisfy the relationship of formula (1). θc < θm < θs … (1).

2. The tire for a motorized two-wheeler according to claim 1, wherein in the crown region, the intermediate region, and the shoulder region, the angle of the carcass cords with respect to the tire circumferential direction is in the range of 20° to 65°.

3. The tire for a motorized two-wheeler according to claim 1 or 2, wherein the angle θc is 0.35 times to 0.90 times the angle θs.

4. The tire for a motorized two-wheeler according to claim 1 or 2, wherein the number of cords Ec is 0.50 times to 0.90 times the number of cords Em.

5. The tire for a motorized two-wheeler according to claim 1 or 2, wherein the number of cords Es is 0.50 times to 0.90 times the number of cords Em.

6. The tire for a motorized two-wheeler according to claim 1 or 2, wherein θc × Ec / Em obtained by multiplying the angle θc by the ratio of the number of cords Ec to the number of cords Em is 10 to 55.

7. The tire for a motorized two-wheeler according to claim 1 or 2, wherein θs × Es / Em obtained by multiplying the angle θs by the ratio of the number of cords Es of the belt cords in the shoulder region of the belt ply to the number of cords Em is 10 to 55.

8. The tire for a motorized two-wheeler according to claim 1 or 2, wherein the belt ply is a seamless belt ply formed by spirally winding the belt cords.

Images