JP4649215B2 - Pneumatic tires for motorcycles - Google Patents

Description

  The present invention relates to a pneumatic tire for motorcycles, and more particularly to a pneumatic tire for motorcycles that achieves both drainage and wear resistance and improves steering stability.

  In recent years, motorcycles for racing are in the direction of higher horsepower and higher torque. For this reason, ensuring the drainage performance in high traction such as rainy weather is a major issue.

Conventionally, there are many tires having a circumferential groove in the crown center in order to ensure drainage performance and contact pressure within the contact surface (see, for example, Patent Document 1). On the other hand, as shown in FIG. 3, the main lug groove that exists at a minute distance from the circumferential groove has a large angle with respect to the tire equatorial plane in order to ensure drainage in the radial direction. .
JP 2000-142031 A

  As described above, since the angle of the main lug groove with respect to the tire equatorial plane is large, the drainage performance is excellent in the vicinity of the upright, but there is a problem that uneven wear occurs.

  In addition, due to insufficient block rigidity when standing upright, it has been difficult to achieve both stability during upright acceleration and cornering performance during cornering.

  In view of the above problems, an object of the present invention is to provide a pneumatic tire for a motorcycle that achieves both drainage and wear resistance and improves steering stability.

  In order to solve the above-mentioned problem, the feature of the present invention is that it extends in a toroid shape between bead cores embedded in a pair of bead parts, and extends from the inner side to the outer side in the tire width direction along the peripheral surface around the bead core. Alternatively, a carcass composed of at least one carcass ply, which is formed by winding from the outside to the inside, and in which textile cords formed by rubber coating in a range of 70 to 90 ° with respect to the tire equatorial plane are arranged in parallel, For motorcycles having a belt layer composed of at least two belt plies arranged between a carcass and a tread and arranged in parallel with a textile cord formed by rubber coating in a range of 20 to 40 ° with respect to the tire equatorial plane This pneumatic tire has a directional pattern on the tread, and the negative rate of the pattern is 20 to 40%. A central land portion formed by a pair of circumferential grooves in the central region of the tire, and the tread does not open to the pair of circumferential grooves, and extends from the central region toward the shoulder region, and the tire equator surface From the steeply inclined central portion where the inclination angle to the tire is 1 to 10 °, through the gentle inclination intermediate portion where the inclination angle to the tire equator surface is 15 to 50 °, the inclination angle to the tire equator surface is 55 to 90 ° It has an inclined main lug groove composed of an inclined side portion and a plurality of inclined sub lug grooves between the inclined main lug grooves, and the arrangement pitch of the inclined main lug grooves is a tire circumference x 10 to 20%, and The tires are rim-assembled on the rim used, and the ground contact length is 1.5 to 2.5 times that contacts the ground in the state where the used air pressure and load are applied. The groove width of the inclined main lug groove is half the tread width. If Tr is Tr, it is Tr × 3-6%, and the steep main lug groove is steep The central portion starts from the region of Tr × 5 to 15% from the circumferential groove and ends at the region of Tr × 20 to 40%, and the gently inclined middle portion of the inclined main lug groove is Tr × 45 to 75 from the circumferential groove. The steeply inclined central part of the inclined main lug groove is rim-assembled on the rim used, running on both side edges of the grounding point when the used air pressure, load 2000N, camper angle 0 ° The tread rubber on the tread surface side of the region corresponding to the middle portion of the steep slope substantially including the middle has a hardness of 40 to 55 degrees, and the tread rubber of the region corresponding to the middle portion of the gentle slope and the side portion of the fine slope is The gist of the present invention is a pneumatic tire for a motorcycle having a hardness smaller than that of the tread rubber in a region corresponding to the steeply inclined central portion. Here, “hardness” is a value measured at a test temperature of 24 ° C. in accordance with JIS K6253-1993 using a durometer hardness test and a type A tester.

  According to the pneumatic tire for a motorcycle according to the features of the present invention, it is possible to achieve both drainage and wear resistance and improve steering stability.

  In the pneumatic tire for motorcycles according to the features of the present invention, it is preferable that the tread rubber in the region corresponding to the moderately inclined middle portion and the slightly inclined side portion has a hardness of 30 to 45 degrees.

  Further, in the pneumatic tire for motorcycles according to the features of the present invention, the tread rubber in the region corresponding to the steeply inclined central portion is composed of two inner and outer rubber layers, and the outer rubber layer is 40 to 55 degrees. The inner rubber layer preferably has a higher hardness than the outer rubber layer.

  In the pneumatic tire for motorcycles according to the features of the present invention, the inner rubber layer preferably has a hardness of 50 to 65 degrees.

  According to the present invention, it is possible to provide a pneumatic tire for a motorcycle that achieves both drainage and wear resistance and improves steering stability.

  Next, embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and ratios of dimensions and the like are different from actual ones. Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

(Pneumatic tire structure)
As shown in FIG. 1, the pneumatic tire for a motorcycle according to the embodiment of the present invention extends between the pair of bead portions 1 and the pair of sidewall portions 2 and the sidewall portions 2 with respect to the tire equatorial plane CL. And a tread portion 3 connected in a toroidal shape. In FIG. 1, only the right side is shown, but it is of course that the configuration is usually symmetrical.

  The carcass 5 extends in a toroidal shape between the bead cores 4 embedded in the pair of bead portions 1, and is wound around the bead core along the circumferential surface from the inner side to the outer side in the tire width direction. A toroidal radial carcass that reinforces the portion 2 and the tread portion 3. The carcass may be configured by winding from the outside toward the inside. The carcass 5 is composed of at least one carcass ply in which textile cords coated with rubber in a range of 70 to 90 ° with respect to the tire equatorial plane are arranged in parallel. The textile cord used for the carcass is a highly elastic cord having a tensile breaking strength of 4.7 cN · dtex or more. “Tensile strength at break” is a value measured according to JIS K6251-1993 using a JIS No. 3 dumbbell-shaped test piece.

  The belt layers 6 a and 6 b are disposed between the carcass 5 and the tread portion 3 and reinforce the tread portion 3. The belt layers 6a and 6b are composed of at least two belt plies in which textile cords formed by rubber coating in a range of 20 to 40 ° with respect to the tire equatorial plane are arranged in parallel. The textile cord used for the belt layers 6a and 6b is a non-stretchable highly elastic cord having a tensile breaking strength of 6.3 cN · dtex or more. The widths of the belt layers 6a and 6b are substantially equal to the tread width.

  As shown in FIG. 2, the pneumatic tire for a motorcycle according to the present embodiment has a directional pattern on the tread. The negative rate of the pattern is 20-40%. Further, the rotation direction of the tire is an arrow A direction.

  A central land portion 19 formed by a pair of circumferential grooves 14 is provided in the central region of the tread. The central land portion 19 may have one circumferential groove, although not shown.

  The tread has an inclined main lug groove 16 and a plurality of inclined sub lug grooves 17 between the inclined main lug grooves 16.

  The inclined main lug groove 16 does not open to the pair of circumferential grooves 14 and extends from the central region of the tread toward the shoulder region. Further, the inclined main lug groove 16 is from a steeply inclined central portion S1 having an inclination angle α1 with respect to the tire equator plane CL of 1 to 10 ° to a moderately inclined intermediate portion having an inclination angle α2 with respect to the tire equator surface CL of 15 to 50 °. Through S2, it consists of a slightly inclined side portion S3 having an inclination angle α3 with respect to the tire equatorial plane CL of 55 to 90 °.

  The pitch L of the inclined main lug groove 16 (the circumferential length of the inclined main lug groove 16) is the tire circumferential length × 10 to 20%, and the tire is rim assembled to the used rim, and the used air pressure is set. The circumferential grounding length for grounding in a state where a load is applied is 1.5 to 2.5 times.

  Further, the groove width of the inclined main lug groove 16 is Tr × 3 to 6%, where Tr is half of the tread width.

  Further, the steeply inclined central portion S1 of the inclined main lug groove 16 starts from a region of Tr × 5 to 15% from the circumferential groove 14 and ends in a region of Tr × 20 to 40%. Further, the gently inclined intermediate portion S2 of the inclined main lug groove 16 is disposed in a region of Tr × 45 to 75% from the circumferential groove 14. In addition, the steeply inclined central portion S1 of the inclined main lug groove 16 is substantially always during traveling while the rim is assembled on the rim used, and both side edges of the contact point when the used air pressure, the load is 2000 N, and the camper angle is 0 °. Including.

  Further, the inclined sub lug groove 17 starts from the region of Tr × 0 to 15% from the shoulder side end of the steeply inclined central portion S1 of the inclined main lug groove 16 and reaches the shoulder region.

(Structure and hardness of tread rubber)
Next, the structure and hardness of the tread rubber according to this embodiment will be described.

  As shown in FIG. 1, at least the tread rubber (A and B in FIG. 1) on the tread side has a hardness of 30 to 55 degrees.

  Further, the tread rubber A on the tread surface side in the region corresponding to the steeply inclined central portion S1 has a hardness of 40 to 55 degrees, and the tread rubber B in the region corresponding to the gently inclined intermediate portion S2 and the slightly inclined side portion S3 is The hardness of the region corresponding to the steeply inclined central portion S1 is smaller than that of the tread rubber. Specifically, it is preferable that the tread rubber in the region corresponding to the moderately inclined intermediate portion S2 and the slightly inclined side portion S3 has a hardness of 30 to 45 degrees.

  Further, the tread rubber in the region corresponding to the steeply inclined central portion S1 is composed of two inner and outer rubber layers. The outer rubber layer A (hereinafter referred to as “cap rubber layer”) has a hardness of 40 to 55 degrees, and the inner rubber layer C (hereinafter referred to as “base rubber layer”) is located on the outer side. Hardness greater than rubber layer A. Specifically, the inner rubber layer C preferably has a hardness of 50 to 65 degrees.

  The thickness of the base rubber layer C in the tire radial direction is 5 to 150% of the thickness of the cap rubber layer A in the tire radial direction.

  In addition, this embodiment is not restricted to this, The tread rubber in the area | region of the gentle inclination intermediate part S2 may be comprised by the rubber layer of two layers inside and outside.

(Action and effect)
According to the pneumatic tire for a motorcycle according to the present embodiment, the angle of the inclined main lug groove 16 with respect to the tire equatorial plane is small near the crown center and large near the shoulder, thereby achieving both drainage and wear resistance. be able to.

  Specifically, the inclined main lug groove 16 has a steeply inclined middle portion S2 having an inclination angle with respect to the tire equator plane of 15 to 50 ° from a steeply inclined central portion S1 having an inclination angle with respect to the tire equator surface of 1 to 10 °. And the fine slope side portion S3 having an inclination angle of 55 to 90 ° with respect to the tire equator plane.

  Further, a high elastic cord having a tensile breaking strength of 4.7 cN · dtex or more is used as a textile cord used for the carcass 5, and a tensile breaking strength of 6.3 cN · dtex or more is used as a textile cord used for the belt layers 6a and 6b. The non-extensible high elastic cord is used. Thus, by selecting a cord having a predetermined strength and arranging it in an appropriate structure to form a tire case, the amount of case members can be suppressed, high rigidity can be ensured, and wear resistance can be improved. In addition, an excessive weight increase can be prevented.

  In addition, by setting the negative rate of the tread pattern to 20 to 40%, it is possible to achieve both WET handling stability such as drainage and wear resistance. If it is less than 20%, it will be inferior to WET resistance, and if it exceeds 40%, it will be inferior to abrasion resistance.

  In addition, since the central land portion 19 formed by the pair of circumferential grooves 14 is formed in the steeply inclined central portion S1, the central land portion 19 is formed at a gentle angle with respect to the tire circumferential direction. In addition to ensuring tire rigidity at the time, it is possible to ensure drainage performance and contact pressure within the contact surface.

  In addition, the inclined main lug groove 16 passes from a steeply inclined central portion S1 having an inclination angle with respect to the tire equator plane of 1 to 10 ° to a moderately inclined intermediate portion S2 having an inclination angle with respect to the tire equator surface of 15 to 50 °. It consists of the slightly inclined side part S3 whose inclination angle with respect to the tire equatorial plane is 55 to 90 °. If the angle S1 of the steep slope is less than 1 °, the effect of draining obliquely backward is inferior, and if it exceeds 10 °, the effect of draining backward during low camber / high-speed straight traveling is inferior. If the angle S2 of the gently inclined intermediate portion is less than 15 °, the traction property at the middle camber / high-speed cornering is inferior, and if it exceeds 50 °, the drainage property at the middle camber / high-speed cornering is inferior. When the angle of the slightly inclined side portion S3 is less than 55 °, the circumferential bending rigidity is too large, which is inferior to load holding (grounding property) at the time of large camber / cornering, and when it exceeds 90 °, the lateral / rear drainage property is inferior. .

  In addition, the pitch L of the inclined main lug grooves 16 is the tire circumferential length × 10 to 20%, and the ground is grounded in a state where the tire is rim-assembled on the used rim and loaded with the used air pressure and load. Length x 1.5 to 2.5 times. When the arrangement pitch L is less than 10% of the tire circumference, the blocks formed mainly between the steeply inclined portions become too fine and the rigidity is lowered, and the wear resistance and steering stability are inferior. , The distance between the inclined main lug grooves is too wide, and the drainage is inferior.

  The groove width of the inclined main lug groove 16 is Tr × 3 to 6%, where Tr is half of the tread width. If it is less than Tr x 3%, the groove width is too narrow and the drainage is inferior, and if it exceeds Tr x 6%, it is difficult to secure the block area formed between the inclined main lug grooves, resulting in wear resistance and handling stability. Inferior.

  The steeply inclined central portion S1 of the inclined main lug groove 16 starts from a region of Tr × 5 to 15% from the circumferential groove 14 and ends in a region of Tr × 20 to 40%. If the start end of the steeply inclined central portion S1 of the inclined main lug groove 16 is less than Tr × 5% from the circumferential groove 14, the land portion width therebetween becomes too thin, and the wear resistance and steering stability are inferior. If it exceeds 15%, the land width in between will become too wide, and the drainability of the tread central area during low camber / high-speed straight travel will be poor. In addition, if the end of the steeply inclined central portion S1 of the inclined main lug groove 16 is less than Tr × 20%, the groove area in the tread central region during low camber / high-speed straight traveling is insufficient, resulting in poor drainage, Tr × 40% If it exceeds 1, the groove area in the central region of the tread becomes excessive, and the wear resistance and steering stability are inferior.

  The moderately inclined intermediate portion S2 of the inclined main lug groove 16 is disposed in a region of Tr × 45 to 75% from the circumferential groove 14. If the position of the gently inclined intermediate portion S2 is less than Tr × 15%, the groove area of the grounding area is mainly insufficient during high-speed to low-speed cornering, resulting in poor drainage. If it exceeds Tr × 75%, high-speed to low-speed cornering Sometimes the groove area of the grounding area is too large and the grounding area is insufficient, resulting in poor wear resistance and steering stability.

  The steeply inclined central portion S1 of the inclined main lug groove 16 substantially includes both side edges of the ground contact point when the tire is rim-assembled on the used rim and the used air pressure, the load is 2000 N, and the camper angle is 0 ° during traveling. By this, it is excellent in WET road surface running performance such as drainage during straight traveling at high speed.

  Further, the inclined sub lug groove 17 starts from the region of Tr × 0 to 15% from the shoulder side end of the steeply inclined central portion S1 of the inclined main lug groove 16 and reaches the shoulder region. When the separation distance between the starting point position of the inclined sub lug groove 17 and the end point position of the inclined main lug groove 16 is less than Tr × 0%, the land portion formed between both grooves becomes too thin and wear resistance is increased. When the Tr × 15% is exceeded, the groove area in this region is insufficient and the drainage is inferior.

  Further, by having one circumferential groove in the central land portion 19, it is possible to further ensure drainage and ground pressure within the ground surface.

  By adopting the above-described tread pattern, it is possible to achieve both WET handling stability such as drainage and wear resistance. As described above, even harder wet roads can be run harder. As a result, even when driving wet wet roads, a certain level of wear resistance must be ensured, and further advanced maneuvering performance is required. It becomes. For this reason, it is necessary to develop and adopt an optimized tire structure that can maximize the performance of the tread pattern in response to further performance improvement needs. In the present invention, a tread structure having the following features is also employed.

  At least the tread rubber (A and B in FIG. 1) on the tread side has a hardness of 30 to 55 degrees. If it is less than 30 degrees, it is too soft and inferior in wear resistance, and if it exceeds 55 degrees, it is too hard, especially on a WET road surface, and is inferior in grip.

  Further, the tread rubber A in the region corresponding to the steeply inclined central portion S1 has a hardness of 40 to 55 degrees. If it is less than 40 degrees, it is too soft and mainly has poor wear resistance in the central area of the tread during low camber / high-speed straight traveling, and if it exceeds 55 degrees, it is too hard and inferior in grip performance particularly in the WET road surface. .

  Further, the tread rubber B in the region corresponding to the gently inclined intermediate portion S2 and the slightly inclined side portion S3 has a hardness smaller than the tread rubber in the region corresponding to the steeply inclined central portion S1. Specifically, it is preferable that the tread rubber in the region corresponding to the moderately inclined intermediate portion S2 and the slightly inclined side portion S3 has a hardness of 30 to 45 degrees. If it is less than 30 degrees, it is too soft and is inferior in wear resistance in the same region, which is overused mainly during high-speed to medium-speed running, and if it exceeds 45 degrees, it is too hard and inferior in grip properties in the same region.

  The combined use of the tread structure described above makes it possible to use a wide range of motorcycles with a wide range of vehicle types / displacements. When used in many vehicle types, especially in high-performance motorcycles with high horsepower / torque, It is anticipated that further improvement in high-speed steering stability while ensuring wear resistance on a wet WET road surface will be required. In the present invention, as a further optimized tread structure, a cap / A base tread structure is also used.

  The tread rubber in a region corresponding to the steeply inclined central portion S1 is composed of the cap rubber layer A and the base rubber layer C. The cap rubber layer A has a hardness of 40 to 55 degrees. If it is less than 40 degrees, it is too soft and inferior in wear resistance, and if it exceeds 55 degrees, it is too hard, especially on a WET road surface, and grip properties are inferior.

  The base rubber layer C has a hardness of 50 to 65 degrees. If it is less than 50 degrees, it is too soft and inferior in the effect of reinforcing the tread crown, and the rigidity of the tread crown in the vehicle is insufficient, resulting in poor steering stability. On the other hand, if it exceeds 60 degrees, it is too hard and the flexibility of the tread crown portion is insufficient, and the grip performance on the WET road surface is particularly poor.

  Further, by disposing the cap / base tread structure only in the region corresponding to the steeply inclined central portion S1, the maneuverability (handling property) at the time of minute camber / high-speed cornering can be improved.

  Since the pneumatic tire for motorcycles according to the present embodiment is excellent in drainage and wear resistance, it is preferably used particularly in a high performance large displacement two-wheeled road race vehicle. Moreover, it can be suitably used even in rainy weather.

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.

In order to confirm the effect of the present invention, pneumatic tires according to Examples 1 and 2, Comparative Example 1, and Conventional Example 1 were prototyped. The size of each test tire was 190 / 650R16.5. The structure of each tire is as shown in Tables 1 and 2.

  In the test, each test tire was mounted on an actual vehicle, and in rainy weather, the grip evaluation and handling performance evaluation by a test rider and the amount of wear were confirmed on a circuit. The score is a maximum of 10 points, and a larger value indicates better performance.

(result)
The results are shown in Table 3.

  As compared with Conventional Example 1, Example 1 and Example 2 were superior in grip properties, wear resistance, and handling properties in a region having a straight advance and a small camper angle and a region having a large camber angle. Accordingly, the tread rubber in the region corresponding to the gently inclined intermediate portion S2 and the slightly inclined side portion S1 having the tread pattern shown in FIG. 2 has a hardness smaller than the tread rubber in the region corresponding to the steeply inclined central portion S1. Thus, it was found that both drainage and wear resistance are compatible, and the steering stability is improved.

  Further, compared with Comparative Example 1, Example 1 and Example 2 were superior in grip properties, wear resistance, and handling properties in a region having a straight advance and a small camper angle and a region having a large camber angle. . Accordingly, the tread rubber in the region corresponding to the steeply inclined central portion S1 is composed of two inner and outer rubber layers, and the base rubber layer C has a hardness higher than that of the cap rubber layer A. It has been found that both the wear resistance and the handling stability are improved.

1 is a cross-sectional view including a tire rotation axis of a pneumatic tire for a motorcycle according to an embodiment. 1 is a plan view of a tread of a pneumatic tire for a motorcycle according to an embodiment. FIG. 6 is a tread plan view of a conventional pneumatic tire for a motorcycle.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Tread part, 2 ... Side wall part, 3 ... Tread part, 4 ... Bead core, 5 ... Carcass, 6a, 6b ... Belt layer, 14 ... Circumferential main groove, 16 ... Inclined main lug groove, 17 ... Inclined sub lug Groove, 19 ... Central land, CL ... Tire equator

Claims (4)

It extends in a toroid shape between bead cores embedded in a pair of bead portions, and is wound around the bead core along its peripheral surface from the inside in the tire width direction to the outside or from the outside to the inside, A carcass composed of at least one carcass ply in which textile cords coated with rubber in a range of 70 to 90 ° with respect to the tire equatorial plane are arranged in parallel;
A motorcycle provided with a belt layer made of at least two belt plies arranged between the carcass and the tread and arranged in parallel with a textile cord formed by rubber coating in a range of 20 to 40 ° with respect to the tire equatorial plane. Pneumatic tires for
The tread has a directional pattern, and the negative rate of the pattern is 20 to 40%,
In the central region of the tread, it has a central land portion formed by a pair of circumferential grooves,
From the steeply inclined central portion that does not open to the pair of circumferential grooves, extends from the central region toward the shoulder region, and has an inclination angle of 1 to 10 ° with respect to the tire equator surface, An inclined main lug groove formed of a slightly inclined side portion having an inclination angle of 55 to 90 ° with respect to the tire equator plane through a gentle inclination intermediate portion having an inclination angle of 15 to 50 ° with respect to the tire, and a plurality of spaces between the inclined main lug grooves And an inclined sub lug groove
The pitch of the inclined main lug groove is a tire circumferential length × 10 to 20%, and a circumferential grounding length × 1 in which the tire is rim-assembled on a working rim and is grounded in a state where a working air pressure and a load are applied. .5 to 2.5 times,
The groove width of the inclined main lug groove is Tr × 3 to 6%, where Tr is half of the tread width.
The steeply inclined central portion of the inclined main lug groove starts from a region of Tr × 5 to 15% from the circumferential groove and ends in a region of Tr × 20 to 40%.
The moderately inclined middle part of the inclined main lug groove is disposed in a region of Tr × 45 to 75% from the circumferential groove,
The steeply inclined central portion of the inclined main lug groove substantially includes both side edges of the ground contact point when the tire is rim-assembled on the used rim, and the used air pressure, the load is 2000 N, and the camper angle is 0 ° during traveling,
The tread rubber on the tread surface side in the region corresponding to the steeply inclined central portion has a hardness of 40 to 55 degrees, and the tread rubber in the region corresponding to the gently inclined intermediate portion and the slightly inclined side portion is the steeply inclined portion. A pneumatic tire for a motorcycle having a hardness smaller than that of a tread rubber in a region corresponding to a central portion.   2. The pneumatic tire for a motorcycle according to claim 1, wherein a tread rubber in a region corresponding to the gently inclined intermediate portion and the slightly inclined side portion has a hardness of 30 to 45 degrees.   The tread rubber in the region corresponding to the steeply inclined central portion is composed of two inner and outer rubber layers, the outer rubber layer has a hardness of 40 to 55 degrees, and the inner rubber layer is the outer rubber layer. The pneumatic tire for a motorcycle according to claim 1 or 2, wherein the pneumatic tire has a higher hardness than the rubber layer. The pneumatic tire for a motorcycle according to any one of claims 1 to 3, wherein the inner rubber layer has a hardness of 50 to 65 degrees.

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