The present invention relates to a tire for motorcycles and a tire set for motorcycles.
Patent Document 1 listed below has proposed a bias tire for motorcycles. The tire includes a carcass ply having a bias structure in which carcass cords are arranged at an angle of 30 to 45 degrees with respect to a tire circumferential direction. In addition, the tire includes a band arranged inside a tread portion and outside a carcass. The band includes an endless band ply in which band cords are spirally wound in the tire circumferential direction. In the Patent Document 1, improvement in steering stability by the carcass ply and the band is expected.
Japanese Unexamined Patent Application Publication No.
2000-185511
Motorcycle tires having the above-described structure tend to impair ride comfort, and there has been a demand for improvements.
The present invention was made in view of the above, and a primary object thereof is to provide a tire for motorcycles and a tire set for motorcycles capable of exerting excellent steering stability while maintaining the ride comfort.
The present invention is a tire for motorcycles including a toroidal carcass and a band layer, wherein the carcass is formed by a plurality of carcass plies in which carcass cords are arranged in parallel, the carcass plies are overlapped so that the carcass cords cross each other, the carcass plies include at least one turned up ply which includes a main body portion extending between a tread portion and a bead core of a bead portion through a sidewall portion and a turned up portion connected with the main body portion and turned up around the bead core so as to extend outwardly in a tire radial direction, the carcass cords of the main body portion are arranged at an angle of 20 degrees or more and 70 degrees or less with respect to a tire equator, and the carcass cords of the turned up portion are arranged at an angle different from the carcass cords of the main body portion with respect to a tire circumferential direction, and the band layer is arranged radially outside the carcass and inside the tread portion, and includes a jointless band ply in which band cords are spirally arranged at angles of 5 degrees or less with respect to the tire circumferential direction.
In the tire for motorcycles according to the present invention, it is preferred that the angle of the carcass cords of the turned up portion are larger than the angle of the carcass cords of the main body portion.
In the tire for motorcycles according to the present invention, it is preferred that the angle of the carcass cords of the turned up portion are smaller than the angle of the carcass cords of the main body portion.
In the tire for motorcycles according to the present invention, it is preferred that no other cord reinforcing layer is provided between an outer surface of the tread portion and the band layer.
In the tire for motorcycles according to the present invention, it is preferred that a thickness of a side thinnest portion which has the smallest tire thickness in the sidewall portion and the bead portion is smaller than a thickness of the tread portion at the tire equator.
In the tire for motorcycles according to the present invention, it is preferred that the thickness of the side thinnest portion is 0.70 times or less the thickness of the tread portion.
In the tire for motorcycles according to the present invention, it is preferred that a radially outer end of the turned up portion is positioned radially outside the side thinnest portion.
In the tire for motorcycles according to the present invention, it is preferred that a radially outer end of the turned up portion is positioned radially inside an outer end in a tire axial direction of the band layer.
The second aspect of the present invention is a tire set for motorcycles including the above-described tires as a tire for a front wheel and a tire for a rear wheel, wherein the angle of the carcass cords of the main body portion of the tire for a front wheel are smaller than the angle of the carcass cords of the main body portion of the tire for a rear wheel.
The tire for motorcycles of the present invention can sufficiently secure rigidity of the tire by the above-described carcass and band layer, therefore, it is possible that excellent steering stability is exerted. On the other hand, in the tires having high rigidity, the ride comfort tends to be impaired. However, in the tire of the present invention, since the carcass cords of the turned up portion are arranged at an angle different from the carcass cords of the main body portion with respect to the tire circumferential direction, the rigidity in the tire radial direction can be moderated in parts in which the angle of the carcass cords with respect to the tire circumferential direction are relatively small (the main body portion or the turned up portion), therefore, the ride comfort can be maintained consequently.
An embodiment of the present invention will now be described in conjunction with accompanying drawings.
The “standard state” is a state in which the tire 1 is mounted on a standard rim (not shown), inflated to a standard inner pressure, and loaded with no tyre load. In this specification, dimensions and the like of various parts of the tire are those measured under the standard state, unless otherwise noted.
The “standard rim” is a wheel rim specified for the concerned tire by a standard included in a standardization system on which the tire is based, for example, the “normal wheel rim” in JATMA, “Design Rim” in TRA, and “Measuring Rim” in ETRTO.
The “standard inner pressure” is air pressure specified for the concerned tire by a standard included in a standardization system on which the tire is based, for example, the “maximum air pressure” in JATMA, maximum value listed in the “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” table in TRA, and “INFLATION PRESSURE” in ETRTO.
As shown in
The tire 1 of the present embodiment includes a toroidal carcass 6 and a band layer 7.
In
The band layer 7 is arranged radially outside the carcass 6 and inside the tread portion 2. The band layer 7 includes a jointless band ply (7a). In this jointless band ply (7a), band cords (7b) are spirally arranged at angles of 5 degrees or less with respect to the tire circumferential direction. The band layer 7 configured as such can effectively prevent the outer diameter from increasing when the tire rotates at a high speed, therefore, excellent high-speed stability and durability can be exerted.
As shown in
As shown in
As described above, the carcass 6 of the present embodiment has a so-called bias structure in which the carcass cords 20 are arranged at an angle with respect to the tire circumferential direction. In the carcass 6 having the bias structure, the carcass cords 20 have longer lengths between the bead core 5 on one side and the bead core 5 on the other side, therefore, binding force in the tire radial direction tends to be low. However, in the present invention, this disadvantage is compensated by the above-mentioned band layer. On the other hand, the tire provided with the band layer 7 has a small reaction force against torsional deformation of the ground contacting surface of the tread portion 2, and tends to have a small cornering force. Whereas, in the tire of the present invention, large camber thrust is easily generated by the carcass 6 having the bias structure, therefore, the disadvantage of the band layer 7 is compensated. As described above, in the tire 1 of the present invention, the disadvantages of various components can be compensated by applying the band layer 7 to the carcass 6 having the bias structure.
The tire 1 of the present invention can sufficiently secure rigidity of the tire by the above-mentioned carcass 6 and band layer 7, therefore, it is possible that excellent steering stability is exerted. On the other hand, in the tires having high rigidity, the ride comfort tends to be impaired. However, in the tire 1 of the present invention, since the carcass cords 20 of the turned up portion 17 are arranged as described above, the rigidity in the tire radial direction can be moderated in parts in which the angle of the carcass cords 20 with respect to the tire circumferential direction are relatively small (the main body portion 16 or the turned up portion 17), therefore, the ride comfort can be maintained consequently.
In the present embodiment, an angle θ4 of the carcass cords of the turned up portion 17 with respect to the tire circumferential direction are larger than an angle θ3 of the carcass cords 20 of the main body portion 16 with respect to the tire circumferential direction. Thereby, a large camber thrust is secured, and cornering performance is improved.
However, the present invention is not limited to the above embodiment. Therefore, the angle θ4 of the carcass cords of the turned up portion 17 with respect to the tire circumferential direction may be smaller than the angle θ3 of the carcass cords 20 of the main body portion with respect to the tire circumferential direction.
The angle difference between the carcass cords of the main body portion 16 and the carcass cords of the turned up portion 17 is 3 degrees or more and 15 degrees or less, for example, and preferably 5 degrees or more and 10 degrees or less. Accordingly, the response of the steering when the camber angle is increased becomes linear while the above-described effect is exerted.
As shown in
In
From the point of view of appropriately reinforcing the sidewall portion 3, it is preferred that an outer end (17o) of the turned up portion 17 in the tire radial direction is positioned radially outside the side thinnest portion 18. Further, it is preferred that the outer end (17o) of the turned up portion 17 is positioned radially inside an axially outer end (7o) of the band layer 7.
From the same point of view, it is preferred that a turned up height (h2) between a bead baseline and the outer end (17o) of the turned up portion 17 is 0.30 times or more and 0.50 times or less a tire height (h1) (shown in
The second aspect of the present invention is a tire set for motorcycles including the above-described tire 1 as a tire for a front wheel and a tire for a rear wheel. In this tire set, it is preferred that the angle of the carcass cords 20 of the main body portion 16 of the tire for a front wheel with respect to the tire circumferential direction are smaller than the angle of the carcass cords 20 of the main body portion 16 of the tire for a rear wheel with respect to the tire circumferential direction. The angle difference between them is, for example, 3 degrees or more and 20 degrees or less, and more preferably 5 degrees or more and 10 degrees or less. Thereby, the cornering force of the front wheel becomes relatively small, therefore, excellent straight running stability can be obtained.
While detailed description has been made of the tire for motorcycles according to an embodiment of the present invention, the present invention can be embodied in various forms without being limited to the illustrated embodiments.
Tires having the basic structure shown in
Rim size: MT3.50
Tire inner pressure: 250 kPa
Test vehicle: displacement of 1000 cc
While the above test vehicle was driven on an asphalt road surface of a curved road having a radius of curvature (R) of 400 meters at a speed of 220 km/h, reaction to disturbance was evaluated by the driver's feeling. The results are indicated by an evaluation point based on the Reference 1 being 100, wherein the larger the numerical value, the better the steering stability is.
When the above test vehicle was passing at a speed of 60 km/h through a bump having a height of 10 mm and a width of 30 mm, the magnitude of the impact and its convergence were evaluated by the driver's feeling. The results are indicated by an evaluation point based on the Reference 1 being 100, wherein the larger the numerical value, the better the ride comfort is.
While the above test vehicle was driven on an asphalt road surface of a winding mountain road, turn-in ability during cornering and easiness of leaning and steering were evaluated by the driver's feeling.
The results were indicated by an evaluation point based on the Reference 1 being 100, wherein the larger the numerical value, the better the steering lightness is.
The test results are shown in Table 1.
As shown in Table 1, the steering stability and the ride comfort were improved for the tires in each of the Examples compared with the tires in the Reference 1 (tires having a so-called radial structure). Further, when comparing the Examples and the References in which the angles of the carcass cords of the main body portions are common (for example, Examples 1 to 4 and Reference 3, Examples 6 to 8 and Reference 2), it was confirmed that the ride comfort was significantly improved. That is, it was confirmed that the tires for motorcycles in the Examples exerted excellent steering stability while maintaining the ride comfort. Furthermore, it was confirmed that the tires for motorcycles in the Examples also secured the steering lightness.
Number | Date | Country | Kind |
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2019-081190 | Apr 2019 | JP | national |