JP2006273249A - Pneumatic tire for motorcycle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire for a motorcycle suitable for a super-motored race. <P>SOLUTION: The pneumatic tire 10 for the motorcycle is provided with a bead core 12, a carcass 14, a tread rubber 18, a side rubber 26 and a cross belt 30. A carcass cord has tensile breaking strength of 4.7 cN/dtex or higher and is arranged at an angle of 0-35° relative to a tire equator plane CL. The belt cord has tensile breaking strength of 6.3 cN/dtex or higher and is arranged at an angle of 55-70° relative to the tire equator plane CL. A relationship of a radius of curvature CR of a tire crown center part 20A, the tire maximum width SW and tire section height SH from a bead base line BL to the outermost position in a tire radial direction along the tire radial direction satisfies (A) CR=50 mm-100 mm, (B) CR/SW=0.38-0.50 and (C) SH/SW=0.60-0.85. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pneumatic tire for two-wheeled vehicles, and more particularly to a pneumatic tire for two-wheeled vehicles that has improved running performance and steering stability performance on non-paved roads and paved roads.

  Motorcycle motorcycle races include “motocross races” that run on all unpaved roads and “road races” that run on all paved roads.

  The “motocross race” uses a pneumatic tire for a motocross race that emphasizes running performance and steering stability performance on all non-paved roads (see, for example, Patent Document 1), and the “road race” includes all paved roads. A pneumatic tire for road racing that emphasizes running performance and steering stability performance is used (see, for example, Patent Document 2).

  For example, in a pneumatic tire for a motocross race as described in Patent Document 1, a block pattern is adopted, and the negative rate of the tread portion is set to about 70% to 80%.

  Further, in a pneumatic tire for road racing as described in Patent Document 2, a slick pattern is adopted, and the negative rate of the tread portion is set to 0% (note that the negative rate is about 30 in rainy weather). Adopt a tread pattern set between% and 40%).

  On the other hand, recently, a new category of race called “Super Motard Race” that does not belong to any category of “Motocross Race” and “Road Race” has been held.

  This “Supermotard Race” was newly established with a strong demand for high-speed driving competition. For example, a motor in which approximately 70% of all courses are all paved roads and the remaining 30% is all unpaved roads. It is a cycle race.

In addition, in the “super motard race”, there may be a safe wet condition or a complete dry condition.
JP 2002-36823 A JP-A-10-67205

  The above-mentioned pneumatic tires for motocross races have a tread pattern in which the negative rate of the tread portion is set to about 70% to 80%. Taking advantage of this feature, the amount of biting into the soil (= dirt grip strength) Can be secured sufficiently, and is excellent in running performance and steering stability performance on all non-paved roads.

  However, in general, all paved roads are inferior in running performance and steering stability performance due to insufficient ground contact area with respect to the road surface, and further, the durability of the block (heat resistance, Inferior to wear.

  In addition, the pneumatic tire for road racing described above has a tread pattern in which the negative rate of the tread portion is set to 0% (in the case of rain, the negative rate is about 30% to 40%). Utilizing it, it is possible to secure sufficient frictional force against the road surface, so it has excellent running performance and steering stability performance on all paved roads.

  However, in general, for non-pavement roads, dart grip force cannot be sufficiently secured because of insufficient edges in the tread pattern and low ground pressure on the ground surface, so driving performance and steering stability performance. Inferior to

  Therefore, when the conventional pneumatic tire for motocross racing and the pneumatic tire for road racing are used in the above-mentioned super motard racing, sufficient running performance on the course including the non-paved road and the paved road and There is a problem that the steering stability performance cannot be exhibited.

  In addition, when the conventional pneumatic tire for motocross race is used for the super motard race described above, the durability (heat resistance, wear resistance) of the block can be ensured for running on the paved road. There is a problem that you can not.

  The present invention has been made in view of the above circumstances, and its purpose is to apply to super motorized racing, which is a new category of motorcycle racing, and traveling performance on non-paved roads and steering stability performance and traveling on paved roads. An object of the present invention is to provide a pneumatic tire for a two-wheeled vehicle capable of achieving both performance and steering stability performance and ensuring the durability (heat resistance and wear resistance) of a block.

  In order to solve the above-described problem, the invention according to claim 1 includes a pair of left and right bead cores extending along the tire circumferential direction, a toroidal shape between the pair of left and right bead cores, and portions on both ends in the tire width direction. A carcass composed of at least one layer of carcass plies formed by juxtaposing a plurality of carcass cords that are folded back and locked to each of the pair of left and right bead cores, and provided on the outer side in the tire radial direction of the carcass. The tread rubber constituting the tread portion, the pair of left and right side rubbers constituting the sidewall portion provided on the outer side in the tire axial direction of the carcass, and provided between the carcass and the tread rubber and covered with rubber A cross belt composed of at least two layers of belt plies formed in parallel with a plurality of belt cords; In the provided pneumatic tire for a motorcycle, the carcass cord has a tensile breaking strength of 4.7 cN / dtex or more and is disposed at an angle of 0 ° to 35 ° with respect to the tire equatorial plane. Is configured with a tensile breaking strength of 6.3 cN / dtex or more, is disposed at an angle of 55 ° to 70 ° with respect to the tire equator surface, is mounted on a standard rim, and is filled with a specified internal pressure. The relationship between the measured radius of curvature CR of the tire crown center portion in the tread portion, the maximum tire width SW, and the tire section height SH from the bead base line to the outermost position in the tire radial direction along the tire radial direction. CR = 50 mm to 100 mm (A), CR / SW = 0.38 to 0.50 (B), SH / SW = 0.60 to 0.85 (C) It is characterized by doing.

  Next, the operation of the invention described in claim 1 will be described.

  As in the first aspect of the invention, the tensile strength of the carcass cord provided in the carcass ply is 4.7 cN / dtex or more, and the carcass cord is at an angle of 0 ° to 35 ° with respect to the tire equatorial plane. An air for a motorcycle in which the tensile strength at break of the belt cord provided in the belt ply is 6.3 cN / dtex or more and the belt cord is arranged at an angle of 55 ° to 70 ° with respect to the tire equatorial plane. This tire is mounted on a standard rim, and the radius of curvature CR of the tire crown center portion in the tread portion measured with no specified internal pressure, the tire maximum width SW, and the bead base The relationship with the tire section height SH from the line along the tire radial direction to the outermost position in the tire radial direction is CR = 50 mm to 100 m. When configured so as to satisfy (A), CR / SW = 0.38 to 0.50 (B), SH / SW = 0.60 to 0.85 (C), unpaved road surface and pavement The contact surface pressure of the tread portion on both road surfaces can be optimized.

  As a result, with respect to the paved road surface, sufficient frictional force against the road surface can be secured, so that the running performance and the steering stability performance on the paved road surface are improved as compared with the conventional pneumatic tire for motocross races and the conventional road. This can be equivalent to a pneumatic tire for racing.

  At the same time, by optimizing the contact surface pressure of the tread, the durability (heat resistance and wear resistance) on the paved road surface is improved compared to conventional pneumatic tires for motocross races. At the same time, it can be made equivalent to a conventional pneumatic tire for road racing.

  Furthermore, with respect to the unpaved road surface, the amount of penetration into the soil (= dirt grip force) can be secured sufficiently, so that the running performance and steering stability performance on the unpaved road surface are compared to conventional pneumatic tires for road racing. Thus, it is possible to improve the performance of the conventional pneumatic tire for motocross racing.

  As described above, according to the invention described in claim 1, in order to be applied to a super motard race that is a new category of motorcycle racing, it is possible to achieve both running performance and steering stability performance on a non-paved road and a paved road. In addition to this, it is possible to ensure the durability (heat resistance and wear resistance) of the block.

  In addition, when the curvature radius CR of the above-mentioned tire crown center part is less than 50 mm, the curvature radius of a tire crown center part becomes too small. For this reason, the contact surface pressure in the central region of the tread portion becomes excessive, resulting in poor durability (heat resistance, wear resistance) on the paved road surface.

  In addition, since the radius of curvature of the tire crown center portion is too small, it is not possible to secure a sufficient frictional force on the paved road surface, and it becomes difficult to ensure traveling performance and steering stability performance on the paved road surface.

  Furthermore, when the radius of curvature CR of the tire crown center portion is larger than 100 mm, the radius of curvature of the tire crown center portion becomes excessive. For this reason, the contact surface pressure in the central area of the tread is too low, and the amount of penetration into the soil (= dirt grip force) on the unpaved road surface is insufficient, ensuring driving performance and steering stability performance on the unpaved road surface. Difficult to do.

  Further, when the value of CR / SW is less than 0.38, the radius of curvature of the tire crown center portion is relatively small. For this reason, the contact surface pressure in the central region of the tread portion becomes excessive, and the durability (heat resistance, wear resistance) on the paved road surface is inferior.

  Further, when the value of CR / SW is larger than 0.50, the radius of curvature of the tire crown center portion is relatively excessive. For this reason, the contact surface pressure in the center area of the tread is too low, especially due to insufficient edge effect on soil on unpaved road surface, dart grip force due to insufficient contact pressure on the road surface, and running performance on unpaved road surface. In addition, it is difficult to ensure the steering stability performance.

  In addition, when the SH / SW value is less than 0.60, that is, maintain the rigidity of the sidewall portion (depending on the height of the sidewall portion, if the height is low, the rigidity is relatively high). In this case, the radius of curvature of the tire crown center portion becomes relatively small. For this reason, the contact surface pressure in the central region of the tread portion becomes excessive, and in particular, the durability (heat resistance, wear resistance) on the paved road surface is inferior.

  Further, when the value of SH / SW is larger than 0.85, the radius of curvature of the tire crown center portion is relatively excessive. For this reason, the contact surface pressure in the center area of the tread is too low, especially due to insufficient edge effect on soil on unpaved road surface, dart grip force due to insufficient contact pressure on the road surface, and running performance on unpaved road surface. In addition, it is difficult to ensure the steering stability performance.

  The invention according to claim 2 is the pneumatic tire for a motorcycle according to claim 1, wherein the negative rate of the tread portion is set to 0% to 20% on an average of the entire tread portion. It is characterized by.

  Next, the operation of the second aspect of the invention will be described.

  As described in claim 2, in the pneumatic tire for a motorcycle according to claim 1, when the negative rate of the tread portion is set to 0% to 20% on the average of the entire tread portion, a sufficient contact area is secured. Therefore, a high grip force can be exhibited on the road surface in the dry condition.

  Therefore, the pneumatic tire for a motorcycle according to claim 2 can be suitably used as a dry condition tire.

  If the negative rate of the tread portion is set to be larger than 20% on the average of the entire tread portion, the land area in the tread portion becomes too small, resulting in poor durability such as wear resistance of the tread portion.

  The invention according to claim 3 is the pneumatic tire according to claim 1, wherein the negative rate of the tread portion is set to 30% to 40% on average of the entire tread portion. And

  Next, the operation of the third aspect of the invention will be described.

  As described in claim 3, in the pneumatic tire for a motorcycle according to claim 1, when the negative rate of the tread portion is set to 30% to 40% on the average of the entire tread portion, the drain groove volume of the tread portion is reduced. Since it is sufficiently secured, it is possible to exert a high grip force on the road surface in a wet condition.

  Therefore, the pneumatic tire for a motorcycle according to claim 3 can be suitably used as a tire for wet conditions.

  If the negative rate of the tread portion is set to be smaller than 30% on the average of the entire tread portion, the drain groove volume in the tread portion becomes too small, resulting in poor wet resistance performance.

  If the negative rate of the tread portion is set to be larger than 40% on the average of the entire tread portion, the area of the land portion in the tread portion becomes too small, resulting in poor durability such as wear resistance of the tread portion.

  According to a fourth aspect of the present invention, in the pneumatic tire for a motorcycle according to any one of the first to third aspects, a triangular cross section is formed on a tire radial outer side of the pair of left and right bead cores. Each of the bead epex rubbers is arranged, mounted on a standard rim, and measured at an unloaded condition filled with a specified internal pressure. The tire section height SH is measured from the bead base line to the tread end along the tire radial direction. Height WH, height CH from the bead base line to the carcass folding top along the tire radial direction, and height from the bead base line to the top of the bead apex rubber along the tire radial direction The relationship with EH is WH / SH = 0.38 to 0.55 (D), CH / WH = 0.55 to 0.90 (E), EH / WH = 0.1. And satisfies 0.35 ... the (F).

  Next, the operation of the fourth aspect of the invention will be described.

  The pneumatic tire for a motorcycle according to any one of claims 1 to 3, wherein the tire is mounted on a standard rim and filled with a specified internal pressure, as measured in an unloaded state. When the relationship between the section height SH and the height WH from the bead base line to the tread end along the tire radial direction satisfies WH / SH = 0.38 to 0.55 (D), Since the height of the wall portion is an appropriate value for obtaining the rigidity of the sidewall portion, it is possible to optimally maintain the contact surface pressure of the tread portion on both the unpaved road surface and the paved road surface, Moreover, the unevenness absorbability (chattering resistance) from the road surface on a paved road can also be made favorable.

  Further, the relationship between the height WH from the bead base line to the tread end along the tire radial direction and the height CH from the bead base line to the carcass folding top along the tire radial direction is CH / WH = 0. .55 to 0.90 (E) is satisfied, since the reinforcing effect of the side wall portion by the folded portion obtained by folding the carcass back to the bead core is appropriately exhibited, so that the non-paved road surface and the paved road surface The contact surface pressure of the tread portion on both road surfaces can be maintained optimally, and the unevenness absorbability (chattering resistance) from the road surface on the paved road can be improved.

  Furthermore, since the flexible zone from the folded top of the carcass to the tread end is sufficiently secured, the behavior of the tire at cornering or the like can be stabilized.

  Also, the relationship between the height WH from the bead base line to the tread end along the tire radial direction and the height EH from the bead base line to the top of the bead epex rubber along the tire radial direction is EH / WH. = 0.18 to 0.35 (F) If the effect of reinforcing the bead portion by the bead epex rubber is moderately exhibited, this allows the non-paved road surface and the paved road surface on both road surfaces. The contact surface pressure of the tread portion can be optimally maintained, and the unevenness absorbability (chattering resistance) from the road surface on the paved road can be improved.

  In addition, when the value of WH / SH is less than 0.38, the height of the sidewall portion becomes too low, and the flexible zone of the sidewall portion is insufficient, so that both the unpaved road surface and the paved road surface are present. It becomes impossible to optimally maintain the contact surface pressure of the tread portion on the road surface, and at the same time, the result is inferior absorbability of unevenness (chattering resistance) from the road surface on the paved road.

  In addition, when the value of WH / CH is larger than 0.55, the height of the side wall portion becomes too high, and the rigidity of the side wall portion cannot be sufficiently secured. It becomes impossible to optimally maintain the contact surface pressure of the tread portion on both the road surface and the paved road surface.

  Furthermore, when the value of CH / WH is less than 0.55, the reinforcing effect of the side wall portion by the folded portion obtained by folding the carcass into the bead core is not exerted appropriately, and thereby, the non-paved road surface and the paved road surface It becomes impossible to optimally maintain the contact surface pressure of the tread portion on both road surfaces.

  Further, when the value of CH / WH is larger than 0.90, the reinforcing effect of the side wall portion by the folded portion where the carcass is folded back to the bead core becomes excessive, so the tread portion on both the non-paved road surface and the paved road surface. It is impossible to optimally maintain the ground contact surface pressure, and at the same time, the result is inferior absorbability of unevenness (chattering resistance) from the road surface on the paved road.

  Furthermore, since the flexible zone from the folded top of the carcass to the tread end becomes too small, the tire behavior at cornering or the like becomes abrupt.

  If the EH / WH value is less than 0.18, the bead epex rubber is not high enough to cause insufficient bead rigidity, and the tread on both the unpaved and paved road surfaces. It becomes impossible to maintain the contact surface pressure of the part optimally.

  In addition, when the value of EH / WH is larger than 0.35, the height of the bead epex rubber becomes too high, and the rigidity from the tire maximum width portion to the bead portion becomes excessive. In addition, it becomes impossible to optimally maintain the contact surface pressure of the tread portion on both road surfaces of the paved road surface, and at the same time, the result is inferior in unevenness absorption (chattering resistance) from the road surface on the paved road.

  The invention according to claim 5 is the pneumatic tire for a motorcycle according to any one of claims 1 to 4, wherein the pair of left and right bead cores has a triangular cross section on the outer side in the tire radial direction. Each bead epex rubber is arranged, mounted on a standard rim, and measured from an unloaded state filled with a specified internal pressure, the height BH from the bead base line to the top of the bead core along the tire radial direction, The height WH from the bead base line to the tread end along the tire radial direction, the height CH from the bead base line to the turn-up top of the carcass along the tire radial direction, and the tire radial direction from the bead base line , And the height EH to the top of the bead epex rubber is BH / WH = 0.11 to 0.14 (G), (EH-B ) / (CH-BH) = 0.11~0.30 ... and satisfying the (H).

  Next, the operation of the fifth aspect of the invention will be described.

  5. A pneumatic tire for a motorcycle according to any one of claims 1 to 4 as defined in claim 5, wherein the bead is mounted in a standard rim and is measured in a no-load state filled with a specified internal pressure. The height BH from the baseline to the top of the bead core along the tire radial direction (however, the distance between the bead seat of the standard rim and the bead core is maintained at the optimum dimension), and the tread along the tire radial direction from the bead base line If the relationship with the height WH to the end satisfies BH / WH = 0.11 to 0.14 (G), the size of the bead core is secured within the minimum necessary range. Thus, it is possible to prevent the tire from being detached from the rim and to suppress an increase in weight.

  In addition, the height BH from the bead base line to the top of the bead core along the tire radial direction is measured when mounted on the standard rim and filled with the specified internal pressure (however, the distance between the bead seat of the standard rim and the bead core) The distance from the bead base line to the carcass folding top along the tire radial direction, and the height from the bead base line to the top of the bead epex rubber along the tire radial direction. When the relationship with the EH satisfies (EH-BH) / (CH-BH) = 0.11 to 0.30 (H), the carcass folding top and the top of the bead epex rubber Since the distance is an appropriate value to obtain the rigidity of the sidewall portion, this can stabilize the behavior of the tire at cornering, etc. Qualitative can also be good.

  If the distance between the bead seat and the bead core of the standard rim is maintained at the optimum dimension and the BH / WH value is less than 0.11, the bead core becomes too small and the tire comes off the rim. There is a fear.

  If the BH / WH value is larger than 0.14 while maintaining the distance between the bead seat and the bead core of the standard rim at an optimum dimension, the bead core becomes excessively larger than necessary, and the weight of the tire There arises a problem that the number increases more than necessary.

  Furthermore, when the value of (EH-BH) / (CH-BH) is less than 0.11, the distance between the folded top of the carcass and the top of the bead epex rubber becomes too long. The wall portion lacks rigidity and results in poor steering stability.

  When the value of (EH-BH) / (CH-BH) is greater than 0.30, the distance from the carcass folding top to the top of the bead epex rubber is too short. Since the rigidity of the sidewall portion changes abruptly between the tire and the top of the bead epex rubber, the behavior of the tire becomes abrupt and the steering stability is inferior.

  As described above in detail, according to the pneumatic tire for a motorcycle of the present invention, the running performance on the non-paved road, the driving stability performance, and the running on the paved road to be applied to the super motard race, which is a new category of motorcycle racing. In addition to achieving both performance and steering stability performance, it is possible to ensure the durability (heat resistance and wear resistance) of the block.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the members, configurations, arrangements, and the like described below do not limit the present invention, and it is needless to say that various modifications can be made in accordance with the spirit of the present invention.

  First, the configuration of the pneumatic tire 10 for a motorcycle according to the present embodiment will be described with reference to FIGS.

  The pneumatic tire 10 for a motorcycle according to the present embodiment is suitably used for a motorcycle for super motard racing, which is a new category of motorcycle racing, for example.

  The pneumatic tire 10 for a motorcycle according to the present embodiment is provided with a pair of left and right non-extendable bead cores 12 extending along the tire circumferential direction, and the carcass extends between the pair of left and right bead cores 12 in a toroidal shape. 14 is provided.

  The carcass 14 includes at least one layer (in this example, two layers) of carcass plies 14A formed by juxtaposing a plurality of carcass cords (not shown) made of rubber-coated high elastic textile cords. The portions on both ends in the direction are locked to the pair of bead cores 12 so as to be wound up from the inside to the outside.

  A carcass cord (not shown) provided on the carcass ply 14A is configured to have a tensile breaking strength of 4.7 cN / dtex or more and is disposed at an angle of 0 ° to 35 ° with respect to the tire equatorial plane CL. . As the carcass cord, rayon, nylon or the like is used.

  When rayon is used for the carcass cord, for example, the carcass ply 14A can be formed in two layers, and the inclination angle of the carcass cord with respect to the tire equatorial plane CL can be set to 30 °.

  Further, when nylon is used for the carcass cord, for example, the carcass ply 14A has one layer, the inclination angle of the carcass cord with respect to the tire equatorial plane CL is 0 °, or the carcass ply 14A has two layers. The inclination angle with respect to the tire equatorial plane CL can be set to 30 °.

  And the bead epex rubber 16 which makes a cross-sectional triangle shape is arrange | positioned at the tire radial direction outer side of a pair of right and left bead cores 12, respectively.

  A tread rubber 18 is provided on the outer side in the tire radial direction of the carcass 14, and thus a tread portion 20 is configured in the pneumatic tire 10 for a motorcycle according to this example.

  As shown in FIG. 2, a plurality of lug grooves 22 for exerting traction are provided in the central region of the tread portion 20. The lug groove 22 is formed to extend in the tire width direction in order to effectively exhibit traction.

  The negative rate of the tread portion 20 due to the provision of the lug groove 22 is set to 0% to 20% on an average of the entire tread portion 20 when the pneumatic tire 10 for a motorcycle is for dry condition. When the pneumatic tire 10 for use is for wet conditions, the average of the entire tread portion 20 is set to 30% to 40%.

  Although not related to the negative rate of the tread portion 20 in this example, an auxiliary groove 24 for promoting warming of the tread rubber 18 is provided in the shoulder region of the tread portion 20.

  As shown in FIG. 1, a side rubber 26 is provided on the outer side in the tire axial direction of the carcass 14, and thus, a sidewall portion 28 is configured in the pneumatic tire 10 for a motorcycle of this example.

  Between the carcass 14 and the tread rubber 18, at least two layers of a belt ply 30A (in this example) formed by juxtaposing a plurality of belt cords (not shown) made of rubber-coated non-extensible high-elastic textile cords. A two-layer cross belt 30 is provided. The cross belt 30 is disposed along the tread portion 20 so as to be substantially equal to the width of the tread portion 20.

  The belt cord (not shown) of the cross belt 30 has a tensile breaking strength of 6.3 cN / dtex or more and is disposed at an angle of 55 ° to 70 ° with respect to the tire equatorial plane CL. A Kevlar or the like is used as the belt cord.

  In the case where Kevlar is used for the belt cord, for example, the belt ply 30A has two layers, and the inclination angle of the belt cord with respect to the tire equatorial plane CL can be 57 °, 60 °, 63 °, or the like.

  In the pneumatic tire 10 for a motorcycle according to the present embodiment, the tire crown center portion 20A in the tread portion 20 is measured in a no-load state in which the pneumatic tire 10 for a motorcycle is mounted on the standard rim 40 and filled with a specified internal pressure. The relationship between the curvature radius CR, the tire maximum width SW, and the tire section height SH from the bead base line BL to the tire radial direction outermost position along the tire radial direction is CR = 50 mm to 100 mm (A), The dimensions are set so as to satisfy CR / SW = 0.38 to 0.50 (B) and SH / SW = 0.60 to 0.85 (C).

  At this time, if the CR / SW value is about 0.50, it is effective for non-paved road performance, and the SH / SW value is more effective for non-paved road performance as the value is larger within the above range.

  Further, in the pneumatic tire 10 for a motorcycle according to the present embodiment, the tire section height SH, the height WH from the bead base line BL to the tread end 20B along the tire radial direction, and the tire radial direction from the bead base line BL. The height CH from the bead base line BL to the top 16A of the bead epex rubber 16 along the tire radial direction is WH / SH = 0. .38 to 0.55 (D), CH / WH = 0.55 to 0.90 (E), EH / WH = 0.18 to 0.35 (F) ing.

  At this time, when the value of WH / SH is about 0.50, it is effective for pavement performance, and the value of EH / WH is more effective for pavement performance as the value is smaller within the above range.

  Furthermore, in the pneumatic tire 10 for a motorcycle according to the present embodiment, the pneumatic tire 10 for a motorcycle is mounted on the standard rim 40 and is measured in the tire radial direction from the bead base line BL measured in a no-load state filled with a specified internal pressure. Along the height BH to the top 12A of the bead core 12 (however, the distance between the bead seat 42 of the standard rim 40 and the bead core 12 is maintained at an optimum dimension), and the tread along the tire radial direction from the bead base line BL. The height WH to the end 20B, the height CH from the bead base line BL to the turn-up top 14B of the carcass 14 along the tire radial direction, and the bead apex rubber 16 from the bead base line BL along the tire radial direction. The relationship with the height EH up to the top 16A is BH / WH = 0.11 to 0.14 (G), (EH-BH It is dimensioned so as to satisfy the /(CH-BH)=0.11~0.30...(H).

  The prescribed internal pressure is an air pressure corresponding to the maximum load (maximum load capacity) of a single wheel in the applicable size described in the following standard.

  The standard is determined by an industrial standard effective in the region where the tire is produced or used.

  For example, in the United States it is “The Tire and Rim Association Inc. Year Book”, in Europe it is “The European Tire and Rim Technical Organization Standards Manual”, and in Japan it is the Japan Automobile Tire Association “JATMA Year Book”. It is specified.

  Further, the bead base line BL is a reference line on the bead portion 32 side when the tire section height (tire cross-section height) SH is measured, as shown in FIG.

  Next, the effect of the pneumatic tire 10 for a motorcycle according to this embodiment will be described.

  In the pneumatic tire 10 for a motorcycle according to the present embodiment, as described above, the tensile strength at break of the carcass cord provided in the carcass ply 14A is 4.7 cN / dtex or more, and the carcass cord is against the tire equatorial plane CL. The belt cord provided in the belt ply 30A has a tensile breaking strength of 6.3 cN / dtex or more, and the belt cord is 55 ° to the tire equatorial plane CL. It is arranged at an angle of 70 °.

  Then, as in this embodiment, the curvature of the tire crown center portion 20A in the tread portion 20 that is measured in a no-load state in which the pneumatic tire 10 for a motorcycle having the above-described configuration is mounted on the standard rim 40 and filled with the specified internal pressure. The relationship between the radius CR, the tire maximum width SW, and the tire section height SH from the bead base line BL to the outermost position in the tire radial direction along the tire radial direction is CR = 50 mm to 100 mm (A), CR / When configured to satisfy SW = 0.38 to 0.50 (B) and SH / SW = 0.60 to 0.85 (C), both the non-paved road surface and the paved road surface The contact surface pressure of the tread portion 20 can be optimized.

  As a result, with respect to the paved road surface, sufficient frictional force against the road surface can be secured, so that the running performance and the steering stability performance on the paved road surface are improved as compared with the conventional pneumatic tire for motocross races and the conventional road. This can be equivalent to a pneumatic tire for racing.

  At the same time, by optimizing the contact surface pressure of the tread portion 20, durability (heat resistance and wear resistance) on the paved road surface is improved compared to conventional pneumatic tires for motocross races. In addition, it is possible to make it equivalent to a conventional pneumatic tire for road racing.

  Furthermore, with respect to the unpaved road surface, the amount of penetration into the soil (= dirt grip force) can be secured sufficiently, so that the running performance and steering stability performance on the unpaved road surface are compared to conventional pneumatic tires for road racing. Thus, it is possible to improve the performance of the conventional pneumatic tire for motocross racing.

  As described above, according to this embodiment, it is possible to achieve both running performance and steering stability performance on a non-paved road and a paved road in order to be applied to a super motard race, which is a new category of motorcycle racing. The durability (heat resistance, wear resistance) of the block can be ensured.

  When the radius of curvature CR of the tire crown center portion 20A is less than 50 mm, the radius of curvature CR of the tire crown center portion 20A is too small. For this reason, the contact surface pressure in the central region of the tread portion 20 becomes excessive, resulting in poor durability (heat resistance, wear resistance) on the paved road surface.

  In addition, since the radius of curvature CR of the tire crown center portion 20A is excessively small, it becomes impossible to secure a sufficient frictional force against the paved road surface, and it becomes difficult to ensure the running performance and the steering stability performance on the paved road surface.

  Further, when the radius of curvature CR of the tire crown center portion 20A is larger than 100 mm, the radius of curvature CR of the tire crown center portion 20A becomes excessive. For this reason, the contact surface pressure in the central region of the tread portion 20 becomes too small, and the amount of biting into the soil (= dirt grip force) on the unpaved road surface is insufficient, so that the running performance and the steering stability performance on the unpaved road surface are improved. It becomes difficult to ensure.

  Further, when the CR / SW value is less than 0.38, the radius of curvature CR of the tire crown center portion 20A becomes relatively small. For this reason, the contact surface pressure in the central region of the tread portion 20 becomes excessive, and results in inferior durability (heat resistance, wear resistance) particularly on the paved road surface.

  Further, when the value of CR / SW is larger than 0.50, the radius of curvature CR of the tire crown center portion 20A is relatively excessive. For this reason, the contact surface pressure in the central region of the tread portion 20 becomes too small. In particular, the dart grip force is insufficient due to insufficient edge effect in the soil on the unpaved road surface, and insufficient ground pressure on the road surface, and traveling on the unpaved road surface. It becomes difficult to ensure performance and steering stability performance.

  When the value of SH / SW is less than 0.60, that is, the rigidity of the sidewall portion 28 (depending on the height of the sidewall portion 28, the rigidity becomes relatively high if the height is low). When trying to maintain, the radius of curvature CR of the tire crown center portion 20A is relatively small. For this reason, the contact surface pressure in the central region of the tread portion 20 becomes excessive, and in particular results in inferior durability (heat resistance, wear resistance) on the paved road surface.

  Further, when the value of SH / SW is larger than 0.85, the radius of curvature CR of the tire crown center portion 20A is relatively excessive. For this reason, the contact surface pressure in the central region of the tread portion 20 becomes too small. In particular, the dart grip force is insufficient due to insufficient edge effect in the soil on the unpaved road surface, and insufficient ground pressure on the road surface, and traveling on the unpaved road surface. It becomes difficult to ensure performance and steering stability performance.

  In the pneumatic tire 10 for a motorcycle having the above-described configuration as in the present embodiment, when the negative rate of the tread portion 20 is set to 0% to 20% on the average of the entire tread portion 20, a sufficient contact area is ensured. Therefore, a high grip force can be exhibited on the road surface in the dry condition.

  Therefore, the pneumatic tire 10 for a motorcycle configured in this way can be suitably used as a dry condition tire.

  In addition, when the negative rate of the tread portion 20 is set to be larger than 20% on the average of the tread portion 20 as a whole, the area of the land portion in the tread portion 20 becomes too small, and the durability of the tread portion 20 such as wear resistance is inferior. It becomes.

  Moreover, in the pneumatic tire 10 for a motorcycle having the above-described configuration as in the present embodiment, when the negative rate of the tread portion 20 is set to 30% to 40% on the average of the entire tread portion 20, the drainage groove of the tread portion 20. Since the volume is sufficiently secured, a high grip force can be exhibited on the road surface in the wet condition.

  Therefore, the pneumatic tire 10 for motorcycles configured in this way can be suitably used as a tire for wet conditions.

  In addition, when the negative rate of the tread part 20 is set to be smaller than 30% on the average of the entire tread part 20, the drain groove volume in the tread part 20 becomes too small, resulting in poor wet resistance.

  Moreover, when the negative rate of the tread portion 20 is set to be larger than 40% on the average of the tread portion 20 as a whole, the area of the land portion in the tread portion 20 becomes too small, resulting in inferior durability such as wear resistance of the tread portion 20. It becomes.

  Then, as in this embodiment, the pneumatic tire 10 for a motorcycle having the above-described configuration is mounted on the standard rim 40, and the tire section height SH measured in a no-load state filled with the specified internal pressure and the bead base line BL are used. When the relationship with the height WH up to the tread end 20B along the tire radial direction satisfies WH / SH = 0.38 to 0.55 (D), the height of the sidewall portion 28 becomes the side It is an appropriate value for obtaining the rigidity of the wall portion 28.

  Thereby, the contact surface pressure of the tread portion 20 on both the unpaved road surface and the paved road surface can be optimally maintained, and the unevenness absorption (chattering resistance) from the road surface on the paved road is also good. be able to.

  Further, the relationship between the height WH from the bead base line BL to the tread end 20B along the tire radial direction and the height CH from the bead base line BL to the turn-up top 14B of the carcass 14 along the tire radial direction is: When CH / WH = 0.55 to 0.90 (E) is satisfied, the reinforcing effect of the sidewall portion 28 by the folded portion obtained by folding the carcass 14 to the bead core 12 is appropriately exhibited.

  Thereby, the contact surface pressure of the tread portion 20 on both the unpaved road surface and the paved road surface can be optimally maintained, and the unevenness absorption (chattering resistance) from the road surface on the paved road is also good. be able to.

  Further, since the flexible zone from the turn-up top portion 14B of the carcass 14 to the tread end 20B is sufficiently secured for the sidewall portion 28, the behavior of the tire at cornering or the like can be stabilized.

  Further, the relationship between the height WH from the bead base line BL to the tread end 20B along the tire radial direction and the height EH from the bead base line BL to the top 16A of the bead apex rubber 16 along the tire radial direction. However, if EH / WH = 0.18 to 0.35 (F) is satisfied, the reinforcement effect of the bead portion 32 by the bead epex rubber 16 is appropriately exhibited.

  Thereby, the contact surface pressure of the tread portion 20 on both the unpaved road surface and the paved road surface can be optimally maintained, and the unevenness absorption (chattering resistance) from the road surface on the paved road is also good. be able to.

  In addition, when the value of WH / SH is less than 0.38, the height of the sidewall portion 28 becomes too low, and the flexible zone of the sidewall portion 28 is insufficient, so that the non-paved road surface and the paved road surface. It becomes impossible to optimally maintain the contact surface pressure of the tread portion 20 on both road surfaces, and at the same time, the result is inferior absorbability of unevenness (chattering resistance) from the road surface on the paved road.

  In addition, when the value of WH / CH is larger than 0.55, the height of the sidewall portion 28 becomes too high, and the rigidity of the sidewall portion 28 cannot be sufficiently secured. It becomes impossible to optimally maintain the contact surface pressure of the tread portion 20 on both the non-paved road surface and the paved road surface.

  Furthermore, when the value of CH / WH is less than 0.55, the reinforcing effect of the side wall portion 28 by the folded portion obtained by folding the carcass 14 to the bead core 12 is not adequately exhibited. It becomes impossible to optimally maintain the contact surface pressure of the tread portion 20 on both road surfaces of the paved road surface.

  Further, when the value of CH / WH is larger than 0.90, the reinforcing effect of the sidewall portion 28 by the folded portion where the carcass 14 is folded back to the bead core 12 becomes excessive, and therefore both the unpaved road surface and the paved road surface. It becomes impossible to optimally maintain the contact surface pressure of the tread portion 20 at the same time, and at the same time, the unevenness absorption from the road surface on the paved road (chattering resistance) is inferior.

  Further, with respect to the sidewall portion 28, since the flexible zone from the folded top portion 14B of the carcass 14 to the tread end 20B becomes too small, the behavior of the tire at cornering or the like becomes abrupt.

  Further, when the value of EH / WH is less than 0.18, the bead epex rubber 16 is insufficient in height so that the rigidity of the bead portion 32 becomes insufficient, and both the unpaved road surface and the paved road surface. It is impossible to optimally maintain the contact surface pressure of the tread portion 20.

  When the value of EH / WH is larger than 0.35, the height of the bead epex rubber 16 becomes too high, and the rigidity from the tire maximum width portion to the bead portion 32 in the sidewall portion 28 is increased. As a result, it becomes impossible to maintain the optimum contact surface pressure of the tread portion 20 on both the unpaved road surface and the paved road surface. This results in inferior chattering).

  Then, as in this embodiment, the two-wheeled pneumatic tire 10 having the above-described configuration is mounted on the standard rim 40 and is measured along the tire radial direction from the bead base line BL measured in a no-load state filled with the specified internal pressure. A height BH to the top portion 12A of the bead core 12 (however, the distance between the bead seat 42 of the standard rim 40 and the bead core 12 is maintained at an optimum dimension), and a tread end 20B along the tire radial direction from the bead base line BL. Since the size of the bead core 12 is ensured within the minimum necessary range when the relationship with the height WH satisfies BH / WH = 0.11 to 0.14 (G) Thus, it is possible to prevent the tire from being detached from the rim and to suppress an increase in weight.

  Further, a height BH from the bead base line BL, which is mounted on the standard rim 40 and measured in an unloaded state filled with the specified internal pressure, to the top 12A of the bead core 12 along the tire radial direction (however, the bead of the standard rim 40) The distance between the seat 42 and the bead core 12 is maintained at an optimum dimension), the height CH from the bead base line BL to the turn-up top 14B of the carcass 14 along the tire radial direction, and the tire radial direction from the bead base line BL. When the relationship with the height EH up to the top portion 16A of the bead epex rubber 16 is satisfied to satisfy (EH-BH) / (CH-BH) = 0.11 to 0.30 (H) The distance between the folded top portion 14B of the carcass 14 and the top portion 16A of the bead epex rubber 16 is an appropriate value for obtaining the rigidity of the sidewall portion 28.

  Thereby, the behavior of the tire at cornering or the like can be stabilized, and the steering stability can be improved.

  If the distance between the bead seat 42 of the standard rim 40 and the bead core 12 is maintained at an optimum dimension and the value of BH / WH is less than 0.11, the bead core 12 becomes too small, and the tire May come off the rim.

  Further, when the distance between the bead seat 42 of the standard rim 40 and the bead core 12 is maintained at the optimum size and the value of BH / WH is larger than 0.14, the bead core 12 becomes excessively larger than necessary. There arises a problem that the weight of the tire increases more than necessary.

  Furthermore, when the value of (EH-BH) / (CH-BH) is less than 0.11, the distance between the folded top portion 14B of the carcass 14 and the top portion 16A of the bead epex rubber 16 becomes too long. As a result, the rigidity of the sidewall portion 28 is insufficient, resulting in poor steering stability.

  Further, when the value of (EH-BH) / (CH-BH) is larger than 0.30, the distance from the folded top portion 14B of the carcass 14 to the top portion 16A of the bead epex rubber 16 is too short. Since the rigidity of the sidewall portion 28 changes abruptly between the folded top portion 14B of the carcass 14 and the top portion 16A of the bead epex rubber 16, the behavior of the tire becomes abrupt and results in poor steering stability. .

  As described above in detail, according to the pneumatic tire 10 for a motorcycle according to the present embodiment, in order to be applied to a super motard race that is a new category of motorcycle racing, traveling performance and steering stability performance and pavement on a non-paved road. It is possible to achieve both driving performance and steering stability performance on the road and to ensure the durability (heat resistance and wear resistance) of the block.

  Next, performance evaluation of the pneumatic tire for a motorcycle according to the present embodiment will be described.

  In order to confirm the effect of the present invention, performance evaluation is performed on the pneumatic tire for a motorcycle according to the present embodiment to which the present invention is applied and the pneumatic tire for a motorcycle according to a comparative example.

  Performance evaluation is performed for each pneumatic tire by performing each performance evaluation of paved road high-speed straight running stability, paved road high-speed turning stability, and non-paved road turning stability (both feeling evaluation). The performances of the pneumatic tire for a motorcycle and the pneumatic tire for a motorcycle according to a comparative example will be compared.

  The larger the evaluation value, the better the paving road high-speed turning stability.

  Four types of pneumatic tires for motorcycles according to the present embodiment are prepared, and two types of pneumatic tires for motorcycles according to the comparative example are prepared. Table 1 shows details of the pneumatic tire for a motorcycle according to this example and the pneumatic tire according to a comparative example.

  The motorcycle according to Example 1 and Example 2 is equipped with a 125 / 600R17 size pneumatic tire for motorcycles applied to the present invention only on the front, and the test rim has a size of MT3.50 × 17. Use one.

  In addition, the motorcycles according to Example 3 and Example 4 are equipped with motorcycle / pneumatic tires of the size of 125 / 600R16.5 to which the present invention is applied on the front and rear, and MT3. Use a 50 × 16.5 size.

  The configuration of the pneumatic tire for a motorcycle according to the above-described embodiment is applied to the pneumatic tire for a motorcycle according to Examples 1 to 4.

  A motorcycle pneumatic tire 50 (size: 80 / 100R21) shown in FIGS. 3 and 4 is attached only to the front of the motorcycle according to Comparative Example 1, and the test rim has a size of MT1.60 × 21. Use things.

  As shown in FIG. 3, the pneumatic tire 50 for a motorcycle according to the comparative example 1 has a configuration in which a cross belt is omitted from the pneumatic tire for a motorcycle to which the present invention is applied. The configuration of the basic members is the same as that of the pneumatic tire for a motorcycle according to the first to fourth embodiments (however, the dimensions of each part are different as shown in Table 1).

  In the pneumatic tire for a motorcycle according to Comparative Example 1, the same reference numerals are used for members having the same functions as those of the pneumatic tire for a motorcycle according to Example 1 to Example 4, and the description thereof is omitted.

  In the pneumatic tire 50 for a motorcycle according to the comparative example 1, as shown in FIG. 4, a plurality of blocks 52 are formed in the tread portion 20, and the negative rate is set to 80% on the average of the entire tread portion. ing.

  Furthermore, in the pneumatic tire for a motorcycle according to Comparative Example 1, as shown in Table 1, polyester (tensile breaking strength: cN / dtex) is used for the carcass cord, and the inclination angle of the carcass cord with respect to the tire equatorial plane is used. Is 40 °, which is outside the numerical range of the present invention in this respect.

  In the pneumatic tire for a motorcycle according to Comparative Example 1, as shown in Table 1, although the CR value is within the numerical range of the present invention, CR / SW, SH / SW, WH / SH, CH / WH, EH / WH, BH / WH, (EH-BH) / (CH-BH), and the negative rate of the tread portion are outside the numerical range of the present invention.

  As in Example 1 and Example 2, the motorcycle according to Comparative Example 2 was fitted with a 125 / 600R17 size pneumatic tire for a motorcycle only on the front, and the test rim had an MT of 3.50 × 17. Use a size.

  Moreover, as shown in Table 1, the two-wheeled pneumatic tire according to Comparative Example 2 has only the value of EH / WH outside the numerical range of the present invention.

  Furthermore, in the pneumatic tire for a motorcycle according to Comparative Example 2, since a slick tire is employed, the negative rate of the tread portion is set to 0% on the average of the entire tread portion.

  Note that the internal pressures of the pneumatic tires for motorcycles according to Examples 1 to 4, Comparative Example 1 and Comparative Example 2 are all 150 kPa.

  Table 2 shows the results of performance evaluations of the pneumatic tire for a motorcycle according to this example and the pneumatic tire for a motorcycle according to a comparative example.

  From the results of Table 2, although the pneumatic tire for motorcycles according to Comparative Example 1 was excellent in non-paved road turning stability, it resulted in poor paved road high-speed straight running stability and paved road high-speed turning stability.

  Therefore, the pneumatic tire for a motorcycle according to Comparative Example 1 is excellent in the steering stability performance on the non-paved road, but is inferior in the running performance and the steering stability performance on the paved road. It can be said that the running performance and the steering stability performance are not compatible.

  Moreover, although the pneumatic tire for two-wheeled vehicles which concerns on the comparative example 2 was excellent in the paved road high-speed straight running stability and paved road high-speed turning stability, it resulted in inferior non-paved road turning stability.

  Therefore, the pneumatic tire for a motorcycle according to Comparative Example 2 is excellent in running performance and steering stability performance on a paved road, but is inferior in steering stability performance on an unpaved road. It can be said that the running performance and the steering stability performance are not compatible.

  On the other hand, although the pneumatic tire for a motorcycle of Example 4 is slightly inferior in turning stability on a non-paved road, the pneumatic tire for a motorcycle according to Examples 1 to 3 to which the present invention is applied is not paved. Road turning stability, paved road high-speed straight running stability and paved road high-speed turning stability were all excellent.

  Therefore, the pneumatic tires for motorcycles according to Examples 1 to 3 are compatible with both the steering stability performance on the non-paved road, the running performance and the steering stability performance on the paved road, and are a new category of motorcycle racing. It can be said that it is a tire that can be suitably used for a super motard race.

FIG. 1 is a cross-sectional view showing a configuration of a pneumatic tire for a motorcycle according to the present embodiment. FIG. 2 is a view showing a tread portion of the pneumatic tire for a motorcycle according to the present embodiment. FIG. 3 is a cross-sectional view showing the configuration of the pneumatic tire for a motorcycle according to Comparative Example 1. 4 is a view showing a tread portion of a pneumatic tire for a motorcycle according to Comparative Example 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Pneumatic tire for motorcycles 12 Bead core 12A Top part 14 Carcass 14A Carcass ply 14B Folding top part 16 Bead Epex rubber 16A Top part 18 Tread rubber 20 Tread part 20A Tire crown center part 20B Tread end 26 Side rubber 28 Side wall part 30 Cross belt 30A Belt Ply 40 Standard Rim BL Bead Baseline

Claims (5)

A pair of left and right bead cores extending along the tire circumferential direction;
A carcass formed by arranging a plurality of rubber-coated carcass cords in parallel between the pair of left and right bead cores, in which a portion on both ends in the tire width direction is folded and locked to each of the pair of left and right bead cores. A carcass comprising at least one ply layer;
A tread rubber provided on the outer side in the tire radial direction of the carcass and constituting a tread portion;
A pair of left and right side rubbers that are provided on the outer side in the tire axial direction of the carcass and constitute sidewall portions;
A cross belt comprising at least two layers of belt plies provided between the carcass and the tread rubber and formed in parallel with a plurality of rubber-coated belt cords;
In a pneumatic tire for a motorcycle equipped with
The carcass cord has a tensile breaking strength of 4.7 cN / dtex or more and is disposed at an angle of 0 ° to 35 ° with respect to the tire equatorial plane.
The belt cord has a tensile breaking strength of 6.3 cN / dtex or more and is disposed at an angle of 55 ° to 70 ° with respect to the tire equatorial plane.
The radius of curvature CR of the tire crown center portion in the tread portion, the tire maximum width SW, and the tire diameter along the tire radial direction from the bead base line, measured in a no-load state that is mounted on a standard rim and filled with a specified internal pressure. The relationship with the tire section height SH up to the outermost position in the direction is
CR = 50mm-100mm ......... (A)
CR / SW = 0.38-0.50 (B)
SH / SW = 0.60-0.85 (C)
A pneumatic tire for motorcycles that satisfies the requirements.   2. The pneumatic tire for a motorcycle according to claim 1, wherein the negative rate of the tread portion is set to 0% to 20% on an average of the entire tread portion.   2. The pneumatic tire according to claim 1, wherein the negative rate of the tread portion is set to 30% to 40% on an average of the entire tread portion. On the outer side in the tire radial direction of the pair of left and right bead cores, bead epex rubber having a triangular cross section is disposed,
The tire section height SH, a height WH from the bead base line to the tread end along the tire radial direction, and a height CH from the bead base line to the turn-up top of the carcass along the tire radial direction; The relationship with the height EH from the bead base line to the top of the bead epex rubber along the tire radial direction is as follows:
WH / SH = 0.38-0.55 (D)
CH / WH = 0.55-0.90 (E)
EH / WH = 0.18 to 0.35 (F)
The pneumatic tire for a motorcycle according to any one of claims 1 to 3, wherein the pneumatic tire is satisfied. On the outer side in the tire radial direction of the pair of left and right bead cores, bead epex rubber having a triangular cross section is disposed,
A height BH from the bead base line to the top of the bead core along the tire radial direction, measured in a no-load state that is mounted on a standard rim and filled with a specified internal pressure, and along the tire radial direction from the bead base line The height WH to the tread end, the height CH from the bead base line to the folded top portion of the carcass along the tire radial direction, and the top portion of the bead apex rubber along the tire radial direction from the bead base line The relationship with the height EH is
BH / WH = 0.11 to 0.14 (G)
(EH-BH) / (CH-BH) = 0.11 to 0.30 (H)
The pneumatic tire for a motorcycle according to any one of claims 1 to 4, wherein the pneumatic tire is satisfied.

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