JP2009126422A - Pneumatic tire for motorcycle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively enhance high speed stability in linear advancement traveling and traveling stability and grip performance at cornering traveling in a pneumatic tire for a motorcycle, in particular, for race traveling, by achieving a proper performance of a tread part structure. <P>SOLUTION: The pneumatic tire for the motorcycle is provided with: a carcass layer comprising a pair of bead parts buried with a bead core, a pair of side wall parts laid/extending to a space between the both side wall parts and constituted by a cord covered with a rubber; and a spiral belt layer constituted by helically and spirally winding a strip formed by covering one or a plurality of cords with a rubber in a tire circumferential direction. The pneumatic tire is provided with the carcass layer of three layers or four layers, and when a distance from a tire equator surface to a tread end is L and a distance from the tire equator surface to an end edge of the spiral belt layer is B at a cross section in a tire width direction, the distance B is within a range of 0.5L-0.8L. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention includes a pair of bead portions in which a bead core is embedded, a pair of sidewall portions extending from the bead portion to the outer side in the tire radial direction, and a tread portion extending between both sidewall portions. A configured carcass layer, and a spiral belt layer formed by spirally winding a strip formed by rubber coating one or more cords in the tire circumferential direction on the outer side in the tire radial direction of the carcass layer. The present invention relates to a pneumatic tire for a motorcycle, and aims to improve high-speed stability during straight traveling, traveling stability during cornering traveling, and grip performance.

  In recent years, motorcycles have become lighter and have higher performance, and in large displacement motorcycles, it has become more important to ensure running stability and grip performance during cornering and high-speed stability during straight running. . In particular, rear tires that are driven tires to which a large torque is applied are required to improve their performance. In order to ensure high-speed stability during straight traveling, a spiral belt layer is often disposed on a motorcycle tire as disclosed in Patent Document 1. By arranging the spiral belt layer, the change in shape in the tread contact area that contacts the road surface when traveling straight ahead is reduced compared to the inclined belt layer in which the cord direction is inclined at a constant angle with respect to the tire equator surface, and high speed Stability is improved. Moreover, since the change in shape in the tread contact area that contacts the road surface during straight traveling is reduced, uneven wear and heat generation during straight traveling can also be suppressed.

  In addition, as described in Patent Document 2, by making the carcass layer for motorcycles four or more layers, it is possible to optimize the bending rigidity in the tread contact area that contacts the road surface during cornering traveling, and to the road surface of the tread portion. While ensuring a sufficient contact area, it is possible to suppress excessive deformation in the tread contact area with the road surface and to ensure grip performance and running stability during cornering running including a large camber angle.

JP 09-118109 A JP-A-56-108302

  However, in the pneumatic tire for a motorcycle having the spiral belt layer described in Patent Document 1, the spiral belt layer is arranged in the entire tread portion, so that the bending rigidity in the tread contact area that contacts the road surface when traveling straight ahead is determined. The high-speed stability during straight running is improved, but the bending rigidity of the tread contact area that contacts the road surface during cornering is too high, so the running stability during cornering decreases. In addition, the area of the tread contact area that contacts the road surface may not be sufficiently secured, and grip performance may be deteriorated. In addition, since the contact pressure per unit volume in the tread contact area increases, the amount of wear increases and the wear resistance may deteriorate. If a rubber having low bending rigidity is used for the tread rubber for the purpose of improving the grip performance, the tread rubber is more likely to be worn, which is not preferable from the viewpoint of wear resistance. The pneumatic tire for a motorcycle having four or more carcass layers described in Patent Document 2 is provided with a cornering traveling including a large camber angle by sufficiently securing a bending rigidity in a tread contact area that contacts the road surface during cornering traveling. Although the grip performance and running stability at the time are improved, the bending rigidity of the tread contact area that touches the road surface during straight running does not improve sufficiently as with the spiral belt layer, and the tread shape changes Is too large, the high-speed stability may be reduced. Thus, it can be said that the improvement in high-speed stability during straight traveling and the improvement in running stability and grip performance during cornering are in a trade-off relationship.

  Accordingly, an object of the present invention is to optimize the tread structure, and particularly in a pneumatic tire for motorcycles for racing, high-speed stability during straight running, running stability during cornering, and grip. It is to improve performance.

  In order to achieve the above object, a pneumatic tire for a motorcycle according to the present invention spans a pair of bead portions in which a bead core is embedded, a pair of sidewall portions extending outward from the bead portion in the tire radial direction, and both sidewall portions. A carcass layer composed of a rubber tread, and a strip formed by rubber coating one or more cords on the outer side of the carcass layer in the tire radial direction. A spiral belt layer formed by spiral winding, the carcass layer is three or four layers, and in the tire width direction cross section, the distance from the tire equatorial plane to the tread edge is L, When the distance from the tire equatorial plane to the edge of the spiral belt layer is B, the distance B is in the range of 0.5L to 0.8L.In such pneumatic tires for motorcycles, the spiral belt layer is arranged in the central area of the tread part including the tire equatorial plane, so that the bending rigidity of the tread contact area that comes in contact with the road surface during straight running is sufficiently high, and high speed. Stability can be improved effectively. In addition, since the spiral belt layer is not provided on both sides of the tread portion, a tread portion region in which only three or four carcass layers are provided instead of the spiral belt layer during cornering traveling is provided. Make contact with the road surface. As a result, the bending rigidity in the tread contact area is improved and the change in the tread shape does not become too large compared to the case where the area having two or less carcass layers is grounded. Can be improved. In addition, as the area where the spiral belt layer is placed at the time of cornering is grounded, the bending rigidity does not become too high and a sufficient contact area to the road surface is secured, so grip performance during cornering Can be improved. The “distance from the tire equator plane to the tread edge” here means the length measured along the periphery from the tire equator plane to the tread portion surface in the tire width direction cross section. The “distance from the surface to the edge of the spiral belt layer” refers to the length measured from the tire equator surface to the edge along the periphery of the spiral belt layer in the cross section in the tire width direction.

  Moreover, it is preferable to provide an intersecting belt layer in which a plurality of cords are covered with rubber between the carcass layer and the spiral belt layer, and the cords intersect with each other across the tire equator plane.

  Furthermore, the cord constituting the carcass layer is preferably inclined within a range of 40 to 90 °, more preferably within a range of 60 to 90 ° with respect to the tire circumferential direction.

  Furthermore, the cord constituting the carcass layer is preferably a nylon cord, and the cord constituting the cross belt layer is preferably an aramid cord.

  According to the present invention, by optimizing the structure of the tread portion, particularly in a pneumatic tire for motorcycles for racing, high speed stability during straight running, running stability during cornering running, and grip performance can be achieved. It becomes possible to improve.

  Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 are sectional views in the tire width direction of a typical pneumatic tire for a motorcycle (hereinafter referred to as “tire”) according to the present invention.

  As shown in FIG. 1, a motorcycle tire according to the present invention includes a pair of bead cores 2, a pair of bead portions 3, 3, and a pair of sidewalls extending outward from the bead portion 3 in the tire radial direction. And tread portions 5 extending between the side wall portions 4 and 4. Further, the motorcycle tire 1 is constituted by a rubber-coated cord, and a main body portion 6 extending in a toroid shape over a tread portion 5 extending between both sidewall portions 4 and 4, and the main body portion 6. 3 layers of carcass layers 8 that extend from the inner side in the tire width direction toward the outer side around the bead core 2 and the outer side in the tire radial direction of the carcass layer 8 is covered with rubber. And a spiral belt layer 9 formed by continuously winding the strip in the tire circumferential direction. At this time, the distance B measured along the periphery from the tire equatorial plane CL to the edge 10 of the spiral belt layer 9 is measured along the periphery from the tire equatorial plane CL to the tread edge 11 in the tire width direction cross section. The distance L is in the range of 0.5 to 0.8 times. In such a tire 1 for a motorcycle, during straight running, the tread portion region where the spiral belt layer 9 is disposed contacts the road surface, and the bending rigidity of the tread contact region that contacts the road surface can be increased. As a result, high-speed stability can be effectively improved. The main cause of the decrease in high-speed stability during straight running is due to the standing wave phenomenon. The standing wave phenomenon is caused by the fact that the tread rubber on the rear side of the tire contact surface, that is, the kicking end side of the contact surface, is caused by friction with the road surface because the bending rigidity of the tread contact area that contacts the road surface during straight running is insufficient. Deformation excessively means that the side wall portion 4 in the vicinity thereof is continuously bent and deformed to be in a wavy state. If bending deformation continuously occurs in the sidewall portion 4, vibration is generated, and rubber forming the sidewall portion 3 is repeatedly deformed to generate heat, and excessive heat accumulation may cause a tire burst. Moreover, since it is a phenomenon that easily occurs during high-speed running, it can be said to be very dangerous because it is likely to occur during races that frequently run at high speeds. Further, when cornering running with the vehicle banked, the tread portion region where only the three carcass layers 8 are disposed instead of the spiral belt layer 9 contacts the road surface. Cornering driving without excessive bending rigidity in the tread contact area and excessive tread shape change during cornering driving, as in the case where only the tread area where only the carcass layer is arranged touches the road surface The running stability at the time is improved. In addition, the bending rigidity of the tread contact area becomes too high, as in the case where the tread portion area where the spiral belt layer 9 is disposed during cornering travel is grounded to the road surface, and the area of the tread contact area that contacts the road surface is small. The grip performance during cornering can be effectively ensured without becoming too much. When the distance B is less than 0.5 times the distance L, the area where the spiral belt layer 9 is arranged is insufficient in the tread contact area that contacts the road surface during straight traveling, and the road surface contacts the road surface during straight traveling. Since the bending rigidity in the tread contact area is not sufficiently ensured, the high-speed stability during straight running decreases. On the other hand, when the distance B exceeds 0.8 times the distance L, the spiral belt layer 9 is disposed excessively large up to the bead portion 3 side. Therefore, it is difficult to make cornering traveling at a large camber angle where high grip performance and traveling stability are required. As shown in FIG. 2, the carcass layer 8 can be increased to four layers according to the desired performance, and the bending rigidity of the tread contact area that contacts the road surface during cornering can be further increased. On the other hand, when the carcass layer 8 has five or more layers, the bending rigidity in the tread contact area that contacts the road surface during cornering traveling becomes too high, and the grip performance and traveling stability may not be sufficiently improved. Although illustration is omitted, if at least two of the three or four carcass layers 8 are locked to the bead core 1, the locking force to the bead core 2 is sufficiently secured, and the remaining carcass layers If it extends to at least the vicinity of the bead core 2, the running stability and grip performance during cornering running can be sufficiently secured.

  Also, as shown in FIGS. 3 and 4, a plurality of cords extending between the carcass layer 8 and the spiral belt layer 9 and extending toward the bead portion 3 are covered with rubber. It is preferable to provide an intersecting belt layer 11 in which the cords intersect with each other across the tire equator plane. By adopting such a configuration, it is possible to improve the shear rigidity of the tread portion region where the cross belt layer 11 comes into contact with the road surface during cornering traveling, and to effectively secure the desired canvas last.

  Furthermore, the cords constituting the carcass 8 layer are preferably inclined within a range of 40 to 90 °, more preferably within a range of 60 to 90 ° with respect to the tire circumferential direction. This is because, when the cords constituting the carcass layer 8 are inclined at less than 40 ° with respect to the tire circumferential direction, the bending rigidity in the tire circumferential direction in the tread contact area that contacts the road surface during cornering traveling is improved. There is a possibility that the bending stability in the tire width direction is insufficient and the deformation in the tire width direction of the tread portion 5 due to the friction with the road surface cannot be sufficiently suppressed, and the steering stability is lowered. Because there is.

  Further, the cord constituting the carcass layer 8 is made of nylon cord having a low elastic modulus so that the side wall portion 4 can be easily deformed and the carcass layer 8 can withstand failure due to separation or the like when repeatedly deformed. It is preferable that Further, the cord constituting the cross belt layer 11 is an aramid cord having a high elastic modulus in order to ensure sufficient bending rigidity in a region where the spiral belt layer 9 is not disposed in the tread portion 5. preferable.

  The above description shows only a part of the embodiment of the present invention, and these configurations can be combined alternately or various changes can be made without departing from the gist of the present invention. For example, as shown in FIG. 5, a protective belt layer 12 extending in a direction orthogonal to the tire circumferential direction and coated with an aramid cord may be disposed outside the spiral belt layer 9 in the tire radial direction.

  Next, a tire according to the present invention in which the carcass layer and the distance B satisfy the conditions of the present invention (comparative tires 1 to 8) and the tire according to the present invention in which the carcass layer and the distance B satisfy the conditions of the present invention (Examples) Tires 1 to 6) were made as tires with a tire size of 190 / 55R17M / C, and their performance was evaluated.

  Example tires 1 to 4 are motorcycle tires having a carcass layer of 3 to 4 layers and a distance B in a range of 0.5 L to 0.8 L and having a spiral belt layer. Moreover, the comparative example tires 1 to 6 have an automatic spiral belt layer in which the carcass layer is 3 to 4 layers and the distance B is not in the range of 0.5 L to 0.8 L. This is a tire for motorcycles. Example tires 5 and 6 are motorcycle tires having a carcass layer of 3 to 4 and a distance B in a range of 0.5 L to 0.8 L and having a cross belt layer and a spiral belt layer. It is. Further, in the comparative tires 7 and 8, the intersecting belt layer and the spiral belt layer that do not satisfy the condition that the carcass layer is 3 to 4 layers and the distance B is in the range of 0.5L to 0.8L. This is a motorcycle tire comprising In any of these tires, the cords constituting the carcass layer are inclined within a range of 40 to 90 ° with respect to the tire circumferential direction, and have the specifications shown in Table 1, respectively.

  Each of these test tires is attached to a rim of size MT6.00-17 to form a tire wheel, and is mounted on a motorcycle for racing with a displacement of 1000 cc as a rear tire under the condition of applying a pneumatic pressure of 200 kPa (relative pressure) and running straight High-speed stability during running, running stability during cornering, and grip performance were evaluated. The front tire was mounted on a vehicle by attaching a motorcycle tire of size 120 / 70R17M / C to a rim of size MT3.50-17 under the condition of applying air pressure: 210 kPa (relative pressure).

  High-speed stability during straight running is the result of painting the tire wheels, reducing the air pressure on the drum tester, and applying the load to the tire when rotating at a speed equivalent to 300 km / h. The surface was photographed with a camera and evaluated by whether or not a standing wave was generated. The evaluation results are shown in Table 1.

  The grip performance during cornering was evaluated by feeling the above vehicle running on a circuit by a professional rider. In the table, “sufficient” is described when the grip performance during cornering is sufficiently ensured, and “insufficient” is indicated when the grip performance is not sufficiently ensured. The evaluation results are shown in Table 1.

  The running stability during cornering running was evaluated by a professional rider running on a circuit with a feeling of 10 points. The larger the numerical value, the better the running stability during cornering running. If it is 7 points or more, it indicates that the running stability during cornering running is sufficiently secured. The evaluation results are shown in Table 1. Show.

  As is clear from the results in Table 1, the comparative example tires having 3 to 4 carcass layers and not satisfying the condition that the distance B is in the range of 0.5 L to 0.8 L are obtained during cornering running. None of the running stability, grip performance during cornering, and high-speed stability during straight running were improved. On the other hand, each performance of Example tires 1 to 6 having 3 to 4 carcass layers and a distance B in the range of 0.5 L to 0.8 L was effectively ensured.

  As is clear from the above, by optimizing the tread structure, especially in pneumatic tires for motorcycles for racing, high-speed stability during straight traveling, traveling stability during cornering traveling, and Grip performance can be improved effectively.

1 is a sectional view in the tire width direction of a typical tire according to the present invention. FIG. 5 is a sectional view in the tire width direction of another typical tire according to the present invention. FIG. 5 is a sectional view in the tire width direction of another typical tire according to the present invention. FIG. 5 is a sectional view in the tire width direction of another typical tire according to the present invention. FIG. 5 is a sectional view in the tire width direction of another typical tire according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tire 2 Bead core 3 Bead part 4 Side wall part 5 Tread part 6 Main part 7 Folding part 8 Carcass layer 9 Spiral belt layer 10 Edge of spiral belt layer 11 Cross belt layer 12 Protective belt layer L From tire equatorial surface to tread edge Distance B Distance from the tire equatorial plane to the edge of the spiral belt layer CL Tire equatorial plane

Claims (5)

A carcass comprising a pair of beads embedded with a bead core, a pair of sidewalls extending from the bead to the outside in the tire radial direction, and a tread extending between both sidewalls, and a cord covered with rubber And a spiral belt layer formed by spirally winding a strip formed by rubber coating one or more cords on the outer side in the tire radial direction of the carcass layer in the tire circumferential direction. In pneumatic tires for motorcycles,
3 or 4 carcass layers,
In the cross section in the tire width direction, when the distance from the tire equator plane to the tread edge is L and the distance from the tire equator plane to the edge of the spiral belt layer is B, the distance B is 0.5L to 0.8L. A pneumatic tire for a motorcycle, characterized by being in the range.   2. The belt according to claim 1, wherein a plurality of cords are rubber-coated between the carcass layer and the spiral belt layer, and the belt includes a cross belt layer in which the cords intersect with each other across the tire equatorial plane. Pneumatic tire for motorcycles.   The pneumatic tire for a motorcycle according to claim 1 or 2, wherein the cord constituting the carcass layer is inclined within a range of 40 to 90 ° with respect to a tire circumferential direction.   The pneumatic tire for a motorcycle according to any one of claims 1 to 3, wherein the cord constituting the carcass layer is a nylon cord.   The pneumatic tire for a motorcycle according to any one of claims 2 to 4, wherein the cord constituting the intersecting belt layer is an aramid cord.

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