JP2008189042A - Tire for motorcycle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire for a motorcycle capable of preventing wheel spin by ensuring sufficient traction performance when it runs straight on a wet road surface while maintaining satisfactory grip performance during its cornering on the wet road surface by making hardness of tread rubber proper. <P>SOLUTION: The tread part 3 is provided with a tread pattern having negative rate in a scope of 20-40% and having directivity and is constituted by at least four tread part regions having degrees of hardness of the rubber constituting adjacent regions being different from each other when viewed in a cross section in the direction of tire width. The degree of hardness of the rubber constituting the central tread part region 5 including an equatorial plane 4 of the tire among the tread part regions is higher than the degree of hardness of the rubber constituting the other tread part regions 6. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic tire for a motorcycle including a pair of bead portions in which a bead core is embedded, a pair of sidewall portions extending outward in the tire radial direction from the bead portion, and a tread portion extending between both sidewall portions. In particular, the present invention relates to a pneumatic tire for a motorcycle for traveling on a wet road, and the traveling performance of the pneumatic tire for a motorcycle on a wet road is improved.

  Generally, a pneumatic tire for a motorcycle turns by banking during cornering. At this time, the shoulder region of the tread portion is brought into contact with the road surface, and the frictional force between the shoulder region and the road surface is balanced against the centrifugal force, thereby achieving cornering traveling. Such frictional force correlates with the grip performance of a pneumatic tire for motorcycles. Therefore, grip performance is extremely important for motorcycle tires. Excellent grip performance can be obtained by configuring the tread portion with rubber having low rubber hardness. For this reason, pneumatic tires for motorcycles in which the rubber hardness of the entire tread portion is lowered have been used in racing tires where cornering performance is emphasized or cornering running is frequently used. However, with such a pneumatic tire for a motorcycle, the grip performance during cornering is sufficiently secured, but the traction performance may not be sufficiently obtained due to low rigidity in the tread contact area during straight traveling. .

  Thus, for example, as described in Patent Document 1, a tread composed of three tread regions including a central tread region including the tire equatorial plane and both shoulder tread regions positioned across the central tread region. The tread rubber in the center tread area is made of hard rubber, and the tread rubber in the shoulder tread area is made of soft rubber, ensuring grip performance with soft rubber when cornering, and straight running In addition, pneumatic tires for motorcycles that ensure traction performance with hard rubber have been developed. Further, in Patent Document 2, a tread portion is composed of left and right shoulder portions and a crown portion sandwiched between these shoulder portions, and an inner layer made of hard rubber and an outer layer made of soft rubber are laminated on the shoulder portion. A motorcycle tire is described in which the crown portion is made of hard rubber. According to this, the grip performance is secured by the soft rubber during cornering traveling, the traction performance is sufficiently secured by the hard rubber during straight traveling, and the rubber hardness of the inner layer is high. As a whole, the rigidity is increased and the steering stability is improved.

  In addition, as described in Patent Document 3, the center tread portion region, the shoulder tread portion region including the tread grounding end, and the intermediate tread portion region sandwiched between the center tread portion region and the shoulder tread portion region are provided. Provided with a tread part consisting of a tread part area, the rubber hardness of the middle tread part area is higher than that of the shoulder tread part area, and the rubber hardness of the central tread part area is higher than that of the intermediate tread part area. Pneumatic tires that improve and reduce road noise during cornering have been developed.

  When the road surface is wet due to rain or the like, the traction performance and cornering performance of the pneumatic tire are deteriorated as compared with the road surface in fine weather, and thus there is a risk of causing a slip accident during traveling. In particular, since motorcycles run cornering by banking the vehicle, they require a considerable grip performance in the tread area. Therefore, as a solution, for example, as described in Patent Document 4, the groove shape of the tread portion is optimized, and the rubber hardness of the tread rubber constituting the tread portion is remarkably reduced, thereby reducing drainage. A pneumatic tire for motorcycles has been developed that improves the grip performance during cornering while ensuring it.

JP-A-7-108805 JP 2005-271760 A JP 2003-326916 A JP 2000-1108 A

  However, the pneumatic tires described in Patent Documents 1 to 3 are intended only for improving the running performance on the dry road surface, and are not supposed to improve the running performance on the wet road surface. There is a high possibility that cornering performance and traction performance during straight running are not sufficiently secured. In addition, the tire disclosed in Patent Document 3 is optimized only for a pneumatic tire for a four-wheeled vehicle, and is optimized for a pneumatic tire for a motorcycle that turns by banking during cornering traveling. Absent. In addition, in a pneumatic tire for a motorcycle as described in Patent Document 4, although grip performance during cornering traveling can be sufficiently ensured on a wet road surface, the rubber hardness in the tread contact region during straight traveling decreases. Therefore, the shear rigidity in the tread portion is lowered, and foil spin is likely to occur, so that the traction performance may not be sufficiently ensured.

  Accordingly, an object of the present invention is to optimize the rubber hardness of the tread rubber constituting the tread portion, thereby maintaining the grip performance when cornering on a wet road surface, while traveling straight on a wet road surface. An object of the present invention is to provide a pneumatic tire for a motorcycle that prevents foil spin by ensuring sufficient traction performance.

  In order to achieve the above object, the present invention includes a pair of bead portions in which a bead core is embedded, a pair of side wall portions extending outward in the tire radial direction from the bead portion, and a tread portion extending between both side wall portions. The tread portion has a negative rate in the range of 20 to 40%, has a directional tread pattern, and the rubber hardness of the rubber constituting the adjacent region in the cross section in the tire width direction is mutually It is composed of at least four different tread regions, and the rubber hardness of the rubber constituting the central tread region, which is the tread region including the tire equatorial plane, constitutes the other tread regions. It is a pneumatic tire for motorcycles characterized by being larger than the rubber hardness of the rubber. With this configuration, the rubber hardness in the tread area during straight running can be sufficiently increased while ensuring sufficient grip performance during cornering on wet roads, increasing the shear rigidity at the tread. Thus, by improving the block rigidity with respect to the input direction, it is possible to effectively prevent foil spin and sufficiently ensure the traction performance on the wet road surface. Here, the “rubber hardness” refers to the rubber hardness of rubber measured at 24 ° C. based on the durometer type A spring test of the JIS K6253 vulcanized rubber physical test method.

  Moreover, it is preferable that the rubber hardness of the rubber which comprises a tread part area | region is so small that the tread part area | region located in a tire width direction outer side.

  Furthermore, it is preferable that the rubber hardness of the rubber constituting the other tread portion region is in the range of 50 to 95% of the rubber hardness of the rubber constituting the central tread portion region.

  Furthermore, it is preferable that the tread portion includes a central tread portion region, two shoulder tread portion regions including the tread grounding end, and two intermediate tread portion regions sandwiched between the central tread portion region and the shoulder tread portion region.

  In addition, the width of the central tread region is in the range of 0.15 to 0.35 times the tread width, and the sum of the widths of the two intermediate tread regions is 0.25 to 0.80 times the tread width. Preferably, the sum of the widths of the two shoulder tread region is within a range of 0.05 to 0.40 times the tread width. In the present specification, the tread width and the width of the tread portion region are distances measured along the periphery of the tread portion in the tire width direction cross section.

  In addition, it is preferable that the rubber hardness of the rubber constituting the shoulder tread portion region is in the range of 50 to 95% of the rubber hardness of the rubber constituting the intermediate tread portion region.

  According to the present invention, by optimizing the rubber hardness of the tread rubber constituting the tread portion, the traction performance when traveling straight on the wet road surface is maintained while maintaining the grip performance when cornering traveling on the wet road surface. By sufficiently ensuring the above, it becomes possible to provide a pneumatic tire for a motorcycle that prevents foil spin.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a tire width direction sectional view of a typical motorcycle pneumatic tire (hereinafter referred to as “tire”) according to the present invention, and FIG. 2 is a perspective view of the tire width direction section of the tire shown in FIG. 3 and 4 are sectional views in the tire width direction of other tires according to the present invention.

  The tire shown in FIGS. 1 and 2 includes a pair of bead portions 1 in which bead cores are embedded, a pair of sidewall portions 2 extending from the bead portion 1 outward in the tire radial direction, and a tread extending between both sidewall portions 2. Part 3 is provided. The tread portion 3 has a negative rate in the range of 20 to 40%, has a directional tread pattern, and the rubber hardness of the rubber constituting the adjacent region in the cross section in the tire width direction is mutual. The tread portion regions 5 and 6 are different from each other. Of these tread region 5, 6, the central tread region 5, which is the tread region including the tire equatorial plane 4, has a rubber hardness larger than the rubber hardness of the rubber constituting the other tread region 6. Consists of rubber. Thus, the drainage performance and traction performance of a tire can be improved because the negative rate of the tread portion 3 is in the range of 20 to 40%. The reason for adopting this range is that when the negative rate of the tread part 3 is less than 20%, the tread contact area during cornering increases and grip performance is ensured, but the groove area of the tread part 3 is insufficient. As a result, the drainage performance of the tire is reduced, making it unsuitable for running on a wet road surface. On the other hand, when the negative rate of the tread portion 3 exceeds 40%, the traction performance and drainage performance are sufficiently secured. This is because the tread contact area during cornering running is insufficient, so that sufficient grip performance cannot be obtained, and it is also unsuitable for running on wet road surfaces. Moreover, the tread pattern arrange | positioned in the tread part 3 can improve the drainage performance of a tire by the structure which has the directionality. Furthermore, since the tread portion 3 is composed of at least four tread portion regions 5 and 6 having different rubber hardnesses, the rubber hardness in the tread contact region during cornering on a wet road surface is reduced. In addition, while ensuring sufficient grip performance of the tire, the rubber hardness in the tread area when driving straight on a wet road surface is increased, the shear rigidity of the tread is increased, and the block rigidity in the input direction is increased. By doing so, foil spin can be effectively prevented.

  Moreover, it is preferable that the rubber hardness of the rubber which comprises a tread part area | region is so small that the tread part area | region located in a tire width direction outer side. This is because, especially during cornering on wet road surfaces, the more the motorcycle is banked, the more the tread area located outside in the tire width direction will come into contact with the road surface, and the rubber hardness in such contact areas must be sufficiently small. This is because the frictional force with the road surface and the centrifugal force of the vehicle cannot resist and balance, and the tire may slip.

  Further, the rubber hardness of the rubber constituting the other tread portion region 6 is preferably in the range of 50 to 95%, more preferably 80 to 95% of the rubber hardness of the rubber constituting the central tread portion region 5. It is in the range. This is because when the rubber hardness of the rubber constituting the other tread portion region 6 is less than 50% of the rubber hardness of the rubber constituting the central tread portion region 5, Even if the traction performance can be ensured, during cornering running on the wet road surface, the rubber hardness is too small in the road surface contact area of the other tread area 6, so that the rubber is cracked and the crack progresses. As a result, part of the other tread part region 6 may be peeled off and the tread part 3 may be destroyed. On the other hand, the rubber hardness of the rubber constituting the other tread part region 6 constitutes the central tread part region 5. If the rubber hardness exceeds 95% of the rubber hardness, the traction performance of the central tread area 5 can not be secured when driving straight on a wet road surface. However, during cornering running on wet road surfaces, the rubber hardness in the road contact area of the other tread area 6 becomes too large, so that there is a possibility that the tire slips without obtaining a sufficiently high grip performance. It is.

  Furthermore, as shown in FIG. 3, the tread portion 3 is sandwiched between a central tread portion region 5, two shoulder tread portion regions 7 including the tread grounding end, and the central tread portion region 5 and the shoulder tread portion region 7. It is preferable that the intermediate tread region 8 is formed. This is because, if the rubber hardness of the rubber constituting the central tread portion region 5 is the largest and the traction performance during straight running is sufficiently secured, the tire width increases as the motorcycle is banked by cornering. Since it is necessary to reduce the rubber hardness of the tread portion region on the outer side in the direction, the rubber hardness constituting the intermediate land portion region 8 is made smaller than the central tread portion region 5, and the shoulder tread portion region 7 is made smaller than the intermediate tread portion region 8. This is because, by reducing the rubber hardness that constitutes the height, it is possible to ensure a high grip performance in proportion to the camber angle of banking.

  In addition, the width of the central tread portion region 5 is preferably in the range of 0.15 to 0.35 times the tread width, and more preferably in the range of 0.20 to 0.30 times. The sum of the widths of the two intermediate tread portion regions 8 is preferably in the range of 0.25 to 0.80 times the tread width, and more preferably in the range of 0.35 to 0.70 times. . Furthermore, the sum of the widths of the two shoulder tread region 7 is preferably in the range of 0.05 to 0.40 times the tread width, more preferably in the range of 0.08 to 0.20 times. . This is because, when they are out of the respective ranges, the balance between the traction performance and the grip performance on the wet road surface is biased, and the running performance on the wet road surface may be deteriorated.

  In addition, the rubber hardness of the rubber constituting the shoulder tread portion region 7 is preferably in the range of 50 to 95% of the rubber hardness of the rubber constituting the intermediate tread portion region 8, more preferably 60 to 85. %. This is because when the rubber hardness of the rubber constituting the shoulder tread portion region 7 is less than 50% of the rubber hardness of the rubber constituting the intermediate tread portion region 5, the shoulder tread portion region 7 is road surface during cornering running on a wet road surface. Even if it is grounded, the rubber hardness is too small, so that the rubber is cracked, and the progress of the crack may cause a part of the shoulder tread part region 7 to peel off and cause the tread part 3 to break. On the other hand, when the rubber hardness of the rubber constituting the shoulder tread portion region 7 exceeds 95% of the rubber hardness of the rubber constituting the intermediate tread portion region 8, the shoulder tread portion region 7 is Even if it touches the road surface, its rubber hardness is too high, so that sufficient grip performance is not obtained and the tire slips. This is because there is a possibility that up.

  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. 4, the tread portion 1 is sandwiched between the left and right shoulder tread portion regions 7 made of rubber having a relatively small rubber hardness, and the shoulder tread portion region 7. A central tread portion region 5 made of rubber having a rubber hardness greater than that of the constituting rubber is provided, and a surface rubber layer 9 is laminated on the outer side in the tire width direction of the shoulder tread portion region 7 and on the outer side in the tire radial direction. It is also possible. The surface rubber layer is made of rubber having a lower rubber hardness than the rubber constituting the shoulder tread portion region 7. Similar to the tire shown in FIG. 3 in which the tread portion is divided into five tread regions, such a tire ensures grip performance when cornering on a wet road surface, and sufficiently secures traction performance when traveling straight on a wet road surface. Is done. Furthermore, since the rubber hardness of the shoulder tread portion region 7 where the surface rubber layer 9 is laminated is large, the rigidity of the tread portion 1 as a whole is increased, and the steering stability performance is improved.

  Next, a tire according to the present invention was prototyped and the running performance on a wet road surface was evaluated, which will be described below.

  Example tires 1 and 2, as shown in FIG. 3, the tread portion is composed of five tread portion regions, and the tread portion has a tread pattern in which a drainage groove having directionality is disposed. This is a pneumatic tire for motorcycles having a negative rate of 35%, a rubber hardness of 55 ° in the central tread region, and a tire size of 190 / 650R16.5, and has the specifications shown in Table 1. At this time, the numerical value of the rubber hardness in Table 1 is calculated by converting the rubber hardness in the central tread portion region of the example tire as a reference value 100 and expressing the rubber hardness in other tread portion regions as a relative value.

  For comparison, the following conventional tires 1 and 2 were also prototyped. The conventional tire 1 has the configuration shown in FIG. 5, has a negative rate of 35%, and has the specifications shown in Table 1. Furthermore, the conventional tire 2 has the configuration shown in FIG. 6, has a negative rate of 35%, and has the specifications shown in Table 1.

  Each of these test tires is attached to a rim of size 6.25 × 16.5 to form a tire wheel, which is attached to a test vehicle, applied with air pressure: 220 kPa (relative pressure) and tire load 1.5 kN, and wet road surface. The traction performance and grip performance during running were evaluated. The grip performance during cornering running on a wet road surface is a feeling evaluation by a rider rising from a cornering running at a camber angle of 30 to 45 ° (small camber angle: around 30 °, large camber angle: around 45 °), and Evaluation is based on slip rate data from actual vehicle measurement using an on-vehicle measuring instrument, and the traction performance when traveling straight on a wet road surface is evaluated by the rider's feeling evaluation during high-speed straight traveling at a camber angle of 0 °, and on-vehicle measurement. Evaluation was made based on slip rate data obtained by actual vehicle measurement using a measuring instrument.

  In addition, the numerical value of evaluation of various tests is evaluated as a full scale of 10 points, and the evaluation result is shown in Table 2.

  As is clear from the results in Table 2, the traction performance during straight running and the grip performance during cornering running on the wet road surface of Example tires 1 and 2 are maintained at a higher level than the conventional tires 1 and 2. I understand that.

  As is apparent from the above, the present invention optimizes the rubber hardness of the tread rubber constituting the tread portion, thereby maintaining the grip performance when cornering the wet road surface while maintaining the wet road surface. It has become possible to provide a pneumatic tire for a motorcycle that prevents foil spin by ensuring sufficient traction performance when traveling straight ahead.

1 is a sectional view in the tire width direction of a typical tire according to the present invention. It is a one part perspective view of the tire width direction cross section of the tire shown in FIG. 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. It is a tire width direction sectional view of a conventional example tire. It is a tire width direction sectional view of a conventional example tire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bead part 2 Side wall part 3 Tread part 4 Tire equatorial plane 5 Central tread part area | region 6 Other tread part area | region 7 Shoulder tread part area | region 8 Middle tread part area | region 9 Surface rubber layer

Claims (6)

A pair of bead portions in which a bead core is embedded, a pair of sidewall portions extending outward in the tire radial direction from the bead portion, and a tread portion extending between both sidewall portions;
The tread portion has a negative rate in a range of 20 to 40%, has a directional tread pattern, and the rubber hardness of the rubber constituting the adjacent region when viewed in a cross section in the tire width direction is mutually It is composed of at least four different tread region, and the rubber hardness of the rubber constituting the central tread region which is the tread region including the tire equatorial plane is different from the other tread regions. A pneumatic tire for a motorcycle, characterized by being larger than the rubber hardness of the rubber constituting the motorcycle.   The pneumatic tire for a motorcycle according to claim 1, wherein the rubber hardness of the rubber constituting the tread portion region is smaller in the tread portion region located on the outer side in the tire width direction.   The air for a motorcycle according to claim 1 or 2, wherein a rubber hardness of the rubber constituting the other tread portion region is in a range of 50 to 95% of a rubber hardness of the rubber constituting the central tread portion region. Enter tire.   The tread portion includes the central tread portion region, two shoulder tread portion regions including a tread grounding end, and two intermediate tread portion regions sandwiched between the central tread portion region and the shoulder tread portion region. The pneumatic tire for a motorcycle according to any one of 3 above.   The width of the central tread portion region is in the range of 0.15 to 0.35 times the tread width, and the sum of the widths of the two intermediate tread portion regions is in the range of 0.25 to 0.80 times the tread width. The pneumatic tire for a motorcycle according to claim 4, wherein the sum of the widths of the two shoulder tread portion regions is in a range of 0.05 to 0.40 times the tread width.   The pneumatic for motorcycles according to claim 4 or 5, wherein a rubber hardness of the rubber constituting the shoulder tread portion region is in a range of 50 to 95% of a rubber hardness of the rubber constituting the intermediate tread portion region. tire.

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