JP2005247061A - Tire for motorcycle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To sufficiently ensure a traction property at the time of turning while maintaining advantages of a parallel structure, and to improve turning performance. <P>SOLUTION: This tire for a motorcycle is equipped with a carcass 6 comprising one sheet of a carcass ply 6A for which a cord angle α is set to be 65 to 88°, and a band layer 7 comprising a band ply 7A which is spirally wound at a cord angle β of 5 or smaller. A folding back section 6b of the carcass 6 has an overlap section 20 which overlaps with the band layer 7. The overlap width Wa of the overlap section 20 is set to be 15 to 60 mm, and also, a distance La from a tread end Te at the tip of the folding back section 6b is set to be 16 to 25% of a tread width TW. Also, a tread thickness T from the band layer 7 to a tread surface 2S is made uniform or gradually reduced from a tire equator C toward the outside in the tire axial direction. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a motorcycle tire that is suitable as a rear wheel of a large motorcycle and has improved traction during turning and improved steering stability.

  In recent years, in order to improve high-speed performance in motorcycle tires, as a tread structure, a belt in which cords that are inclined and arranged at an angle of, for example, 15 to 30 ° with respect to the tire circumferential direction are crossed between plies. Instead of a so-called cross structure using layers, a shift to a so-called parallel structure using a band layer in which a cord is spirally wound along the tire circumferential direction is attempted.

  This is because the parallel structure increases the restraining force in the circumferential direction, while the tread bending rigidity is kept low, so that it is possible to secure a high ride comfort and to improve the disturbance absorption from the road surface. This is because it exhibits excellent effects in straight running stability and vibration suppression in the wobble mode.

  However, with the parallel structure, the cord is almost parallel to the tire equator, so when accelerating while tilting the tire on the winding road at a deep bank angle like circuit driving, lateral force acts on the band layer and traction There is a problem that the turning performance is inferior, for example, the performance is not sufficiently exhibited.

  Patent Document 1 discloses a tire having a parallel structure that improves the turning performance by increasing the rigidity of the tread shoulder region.

JP-A-5-330309

  The present invention extends the folded portion of the carcass to the lower part of the band layer, specifies the overlap width between the folded portion and the band layer, and arranges the carcass cords at a shallower angle than the conventional structure. To provide a motorcycle tire that can sufficiently ensure traction during turning and improve turning performance while maintaining excellent ride comfort, straight-line stability at high speed, and vibration characteristics, which are advantages. It is an object.

The invention of claim 1 of the present invention is a carcass in which a body portion extending from a tread portion through a sidewall portion to a bead core of a bead portion is provided with a series of folded portions that are folded back from the inner side in the tire axial direction around the bead core. A motorcycle tire having a band layer made of a band ply disposed inside the tread and outside the carcass and spirally wound with a band cord at an angle of 5 degrees or less with respect to the tire circumferential direction. There,
The carcass is composed of one carcass ply in which carcass cords are arranged at an angle of 65 to 88 ° with respect to the tire circumferential direction, and the folded portion has an overlapping portion that overlaps with the band layer on the inner side in the radial direction. And have a break
The overlapping width Wa in the tire axial direction along the band layer of the overlapping portion is 15 to 60 mm, and the distance La in the tire axial direction along the tread surface from the tread end at the tip of the folded portion is the tread surface between the tread ends. 16-25% of the tread width TW along,
Moreover, the tread thickness T from the band layer to the tread surface is constant or gradually decreased from the tire equator toward the tire axial direction outer side.

  In the invention of claim 2, the distance Lb in the tire axial direction along the tread surface from the tread end of the outer end of the band layer is set to 0 to 10 mm.

  According to a third aspect of the present invention, in the tire meridional section in which the tire is assembled on the regular rim and filled with the regular internal pressure, the tread surface has a tread radius Rc in the tread central region centered on the tire equator. It is characterized by being larger than the tread radius Rs in the outer tread side region.

  Here, the “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based, for example, a standard rim for JATMA, “Design Rim” for TRA, Or ETRTO means “Measuring Rim”. The “regular internal pressure” is the air pressure specified by the tire for each tire. The maximum air pressure in the case of JATMA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in the case of TRA, If it is ETRTO, it means "INFLATION PRESSURE".

  Since the present invention is configured as described above, it is possible to sufficiently ensure the traction during turning while improving the turning performance while taking advantage of the parallel structure.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a meridional cross-sectional view of a motorcycle tire according to the present invention, and FIG. 2 is a diagram schematically showing the arrangement of carcass cords and band cords arranged on the tire in a plane.

  In FIG. 1, a motorcycle tire 1 (hereinafter referred to as a tire 1) has a tread portion 2 in which a tread surface 2S curves in a convex arc shape from the tire equator C to the tread end Te, and the tread end Te, Since the tire axial distance between Te forms the maximum tire width, turning at a large bank angle is enabled. Further, the tire 1 includes a carcass 6 extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and a band layer disposed on the inner side of the tread portion 2 and on the radially outer side of the carcass 6. 7 is arranged.

  The band layer 7 is composed of one or more band plies 7A having a parallel structure in which a band cord is spirally wound at an angle β of 5 degrees or less with respect to the tire circumferential direction. As the band cord, nylon, rayon, aromatic Organic fiber cords such as group polyamide and steel cords can be employed. In this example, the band layer 7 is composed of one band ply 7A using an aromatic polyamide cord having a single twist structure.

  In the band layer 7, the distance Lb in the tire axial direction along the tread surface 2S from the tread end Te at the outer end thereof is preferably in the range of 0 to 10 mm. By restraining and suppressing the change of the tire cross-sectional shape during running, the high-speed durability and high-speed running performance of the parallel structure are effectively exhibited. If the distance Lb exceeds 10 mm, the restraining force on the tread portion 2 is insufficient. Conversely, if the distance Lb is less than 0 mm, damage starting from the outer end of the band layer 7 is likely to occur.

  Next, the carcass 6 is composed of one carcass ply 6A in which carcass cords are arranged at an angle α of 65 to 88 ° with respect to the tire circumferential direction, and the carcass cords are made of organic materials such as nylon, rayon, and aromatic polyamide. Fiber cord is used. The carcass ply 6A includes a series of folded portions 6b that are folded from the inner side to the outer side in the tire axial direction around the bead core 5 at both ends of the main body portion 6a spanned between the bead cores 5 and 5. Between the bead core 6b and the folded portion 6b, an apex rubber rubber 8 for bead reinforcement extending in a radially outward direction from the bead core 5 is disposed. The radial height h1 of the apex rubber rubber 8 from the bead base line BL is smaller than the radial height he of the tread end Te. Preferably, the lower limit is 35% or more of the height he. Is 40% or more, and the upper limit is 70% or less, further 60% or less.

  The carcass 6 has a high turn-up structure in which the folded portion 6b passes through the sidewall portion 3 and is then sandwiched between the main body portion 6a and the band layer 7 and terminates in the tread portion 2. Thus, the folded portion 6b forms an overlapping portion 20 that overlaps with the band layer 7 on the inner side in the radial direction.

  Thus, the carcass 6 has a high turn-up structure having the overlapping portion 20, and the cord angle α is 65 to 88 °, and the carcass cord is at least 4 ° or more between the main body portion 6a and the folded portion 6b. By adopting a triangle structure that crosses and arranges at an angle, it is possible to obtain a high side rigidity comparable to that of two carcass plies, although the carcass ply 6A is one.

  Moreover, in the overlapping portion 20, a strong truss structure where the band cords intersect is formed, so that the tread rigidity in the tread shoulder region can be sufficiently increased. As a result, the shortage of traction during turning is resolved, and turning performance can be improved.

  And in order to exhibit such an effect effectively, the overlap width Wa of the tire axial direction along the band layer 7 of the said overlapping part 20 is the range of 15-60 mm, and the tread from the tread end Te of the front-end | tip of the said folding | turning part 6 is carried out. The distance La in the tire axial direction along the surface 2S is restricted to a range of 16 to 25% of the tread width TW along the tread surface 2S between the tread ends Te and Te.

  If the overlap width Wa is less than 15 mm and the distance La is less than 16% of the tread width TW, the tread rigidity in the tread shoulder region is not sufficiently secured, and the traction particularly when turning in the full bank state is insufficient. Conversely, when the overlap width Wa is greater than 60 mm and the distance La is greater than 25% of the tread width TW, the tread rigidity is also increased in the tread central region, and disturbance absorption from the road surface and riding comfort are impaired. Reduces straight running stability during high-speed driving.

  If the cord angle α is larger than 88 °, both the side rigidity and the tread rigidity in the overlapping portion 20 are insufficient, and a satisfactory turning performance improvement effect cannot be obtained. On the other hand, if the angle is less than 65 °, the side rigidity becomes excessive and the excellent riding comfort unique to the radial tire cannot be exhibited. Accordingly, the upper limit of the cord angle α is preferably 85 ° or less, more preferably 80 or less, and the lower limit is preferably 72 ° or more.

  In the present invention, in order to further improve the turning performance, the tread thickness T from the band layer 7 to the tread surface 2S is made constant or gradually decreased from the tire equator C toward the outer side in the tire axial direction. As a result, the vehicle body can be smoothly brought down when shifting from straight running to turning, and smooth handling can be achieved. For this purpose, it is particularly preferable to gradually reduce the tread thickness T toward the outer side in the tire axial direction. At this time, the tread thickness Ts at the outer end of the band layer 7 is set to 60 to 90 of the tread thickness Tc at the tire equator C. More preferably, it is reduced to the range of%.

  Further, in this example, in order to further improve the steering stability during both straight travel and turning, as shown in FIG. 3, in the tire meridian section in the state where the tire is assembled on the regular rim and filled with the regular internal pressure. The tread radius Rc in the tread central region Yc of the tread surface 2S is set larger than the tread radius Rs in the outer tread side region Ys.

  The “tread central region Yc” is a region that mainly comes in contact with the vehicle when traveling straight ahead, and means a range of 20 to 40% of the tread width TW with the tire equator C as the center. Further, the “tread side region Ys” means a region outside the tread central region Yc that includes the tread shoulder region and contacts the ground during turning. The tread radii Rc and Rs mean arc radii when the regions Yc and Ys are each formed by a single arc, but are defined as follows when different from a single arc. The tread radius Rc is defined by the radius of an arc passing through the three points of the end points P1 and P1 of the tread central region Yc and the intermediate point P1m. The tread radius Rs passes through three points: a grounded outer end point Pe that is 5 to 12% of the tread width TW from the tread end Te, an inner end point P1 of the tread side region Ys, and an intermediate point Psm thereof. It is defined by the radius of the arc.

  As described above, by increasing the tread radius Rc in the tread central region Yc, the ground contact width during the straight traveling can be widened and the straight traveling stability can be improved. It also helps improve wear resistance. On the other hand, by making the tread radius Rs of the tread side region Ys relatively small, as shown in FIGS. 4 (A) and 4 (B), the contact pressure distribution in the contact surface during turning becomes uniform, The effect of improving traction can be exhibited more effectively. In order to exhibit such effects in a well-balanced manner, the tread radius ratio Rc / Rs is preferably in the range of 1.1 to 1.5. 4A shows the shape of the contact surface and the contact pressure distribution when Rc <Rs (Rc / Rs = 0.7), and FIG. 4B shows that Rc> Rs (Rc / Rs = 1. 4 shows the shape of the ground contact surface and the distribution of the contact pressure when it is defined as 4).

  In the tire of the present embodiment, a reinforcing cord ply can be provided between the carcass 6 and the band layer 7 in order to increase the overall tread rigidity according to the use conditions. In such a case, a reinforcing cord ply in which reinforcing cords of organic fibers such as nylon, rayon, and aromatic polyamide are arranged at an angle of 45 to 72 ° with respect to the tire circumferential direction can be suitably used. At this time, the reinforcement effect can be enhanced by making the inclination direction of the reinforcement cord different from the inclination direction of the carcass cord of the carcass 6 and crossing each other. The ply width of the reinforcing cord ply along the reinforcing cord ply is preferably set to 60 to 95% of the tread width TW and smaller than the band width of the band layer 7.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

  A motorcycle tire (tire size 180 / 55ZR17) having the structure shown in FIG. 1 and the specifications shown in Table 1 was prototyped, and the high-speed stability, ride comfort, transient characteristics, and turning traction of the sample tire were evaluated by an actual vehicle running test. . Specifications other than those described in Table 1 are substantially the same as described in Table 2.

(1) Actual vehicle running test:
The tire is mounted on the rear wheel of a large motorcycle (750CC) under the conditions of a rim (MT5.5 × 17) and internal pressure (250 kPa), running on a dry asphalt tire test course, and high-speed stability at that time Riding comfort, transient characteristics, and turning traction were evaluated by a five-point method based on driver sensory evaluation. A larger index is better.

In the front wheel,
・ Tire size: 120 / 70ZR17,
Carcass: Number of plies (2 sheets), cord angle α (+ 88 ° / −88 °), cord (nylon, 1400 dtex / 2), cord end (41 pieces / 5 cm),
-Belt layer: Commercial tires with specifications of number of plies (2 sheets), cord angle (+ 17 ° / -17 °), cord (aromatic polyamide, 1670 dtex / 2), cord end (35 / 5cm), The rim (MT3.5 × 17) and the internal pressure (250 kPa) were used.

  As shown in Table 1, it can be confirmed that the tires of the examples have greatly improved turning traction while maintaining high-speed stability and riding comfort.

1 is a cross-sectional view showing an example of a motorcycle tire according to the present invention. FIG. 2 is a diagram schematically illustrating an arrangement state of carcass cords and band cords of the tire of FIG. It is a diagram which shows the outline shape of the tread surface in the state filled with normal internal pressure. (A) and (B) are diagrams illustrating the contact surface shape and the contact pressure distribution when the tread radius is Rc> Rs and Rc <Rs.

Explanation of symbols

2 tread portion 2S tread surface 3 side wall portion 4 bead portion 5 bead core 6 carcass 6A carcass ply 6a main body portion 6b folded portion 7 band layer 7A band ply 20 overlapping portion

Claims (3)

A carcass provided with a series of folded portions that are folded from the inner side to the outer side in the tire axial direction around the bead core in the main body portion that extends from the tread portion to the bead core through the sidewall portion, and the inside of the tread portion and the A motorcycle tire having a band layer made of a band ply arranged outside the carcass and spirally wound with a band cord at an angle of 5 degrees or less with respect to the tire circumferential direction;
The carcass is composed of one carcass ply in which carcass cords are arranged at an angle of 65 to 88 ° with respect to the tire circumferential direction, and the folded portion has an overlapping portion that overlaps with the band layer on the inner side in the radial direction. And have a break
The overlapping width Wa in the tire axial direction along the band layer of the overlapping portion is 15 to 60 mm, and the distance La in the tire axial direction along the tread surface from the tread end at the tip of the folded portion is the tread surface between the tread ends. 16-25% of the tread width TW along,
Moreover, the motorcycle tire is characterized in that the tread thickness T from the band layer to the tread surface is constant or gradually decreased from the tire equator toward the outer side in the tire axial direction.   The motorcycle tire according to claim 1, wherein a distance Lb in a tire axial direction along a tread surface from a tread end of an outer end of the band layer is set to 0 to 10 mm.   In a tire meridional section in a state where a tire is assembled with a normal rim and filled with a normal internal pressure, the tread surface has a tread radius Rc in a tread central region centered on the tire equator and a tread radius in an outer tread side region. The motorcycle tire according to claim 1 or 2, wherein the tire is larger than Rs.

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