JPH1178418A - Pneumatic tire for two-wheeled vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire for a two-wheeled vehicle further improving gripping force and revolving performance at the time of giving a large camber angle by keeping a tire outer diameter within a JATMA standard and securing upright stability of the vehicle. SOLUTION: A tread outline of a tire cross-section charging air pressure of 0.5 kgf/cm<2> in a tire and rim assemble assembling a tire on a standard rim has a smooth composite circular arc shape made of three different curvature of radiuses of a circular arc of a curvature of a radius RC forming a tread central region, a circular arc of a curvature of a radius RM forming an intermediate region and a circular arc of a curvature of a radius RB forming tread both end part side regions, and the three different curvature radiuses satisfy a relation of RM<RC<RB.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire for a motorcycle, and more particularly to a radial ply tire for use in a sports motorcycle. The present invention relates to a pneumatic tire for a two-wheeled vehicle that exhibits highly excellent grip performance and cornering stability during cornering during vehicle running.

[0002]

2. Description of the Related Art Mainly, engine displacement 250 cc to 7
For radial ply tire of the sports system motorcycle pneumatic tire of 50cc class, while filled with air pressure of about 0.5 kgf / cm ² The tire assembly assembled to a standard rim, the tread surface The contour has a composite arc shape in which two or three arcs each having a different radius of curvature are smoothly connected in a tire cross section. Note that the air pressure filling state of about 0.5 kgf / cm ^2, and filled with approximately maximum air pressure to the assembly under vacuum in After sufficient fitting tires to rims, tire on the rim to hold the normal rim fitting state Means a state in which a normal shape is exhibited without distortion. The same applies hereinafter.

The contour shape of the tread will be described with reference to FIG. 2 which shows an outer contour of a cross section of a tire in which the assembly is filled with an air pressure of about 0.5 kgf / cm ² .
The first tread surface 11t has an arc of a radius of curvature _RC forming the tread surface 11t central region and an arc of a curvature radius R _M forming an intermediate region on both sides of the tread surface 11t central region, which is often omitted but exists in this case. When, with a composite arc shape of an arc having a curvature radius R _B to form a tread surface 11 both ends regions. However with the exception of the arc of curvature radius R _M forming the intermediate region is sometimes the two composite arcs.

[0004] As is clear from the contour of the tread surface 11t in FIG. 2, the magnitude relation of the radii of curvature R _C , R _M , and R _B of two to three (the example shown in FIG. 2) is determined by the three radii of curvature. In this case, R _C <R _M <R _B , and also in the case of two radii of curvature, R _C <R _B. In each case, adjacent arcs drawn by mutually different radii of curvature share a tangent line at their joint points and are smoothly connected.

Two wheels having a tread 11t contour shape shown in FIG.
Adds a large camber angle to pneumatic tires for automobiles
When turning a vehicle at a high speed and a small radius,
Has great gripping force (centripetal force) and highly excellent stability
Needless to say, this is required. To do that,
3, the radius of curvature R in the tread area 11t is determined. _B
As much as possible, and the tread surface 11t
The tangent line TL of the arc at the end P of the
The inclination angle θ formed by a straight line PL drawn in parallel with the
It needs to be as large as possible.

[0006]

Increasing as much as possible the ratio of the arc but the curvature radius R _B [0005], yet the inclination angle θ
When the tire and the rim assembly are filled with the maximum air pressure as shown in the left half contour diagram in FIG. 4, the tread surface 11 is greatly expanded and deformed, and the outer diameter is reduced to a contour shape 11a indicated by a two-dot chain line. Increase.

[0007] Such bulging deformation of the tread 11 causes instability in the upright running of the motorcycle, and sometimes JATMA.
YEAR BOOK (1997 edition, JATMA standard) defines the lower limit to the upper limit as a new dimension of the outer diameter, and even exceeds this upper limit. The JATMA standard is a problem because it is not limited to an organizational standard but is treated the same as the JIS standard.

Accordingly, the inventions described in claims 1 to 4 of the present invention have an outer diameter sufficiently falling within the JATMA standard,
An object of the present invention is to provide a pneumatic tire for a two-wheeled vehicle, which can improve the grip force and stability when a large camber is attached when turning a vehicle without impairing the upright running stability of the two-wheeled vehicle.

[0009]

In order to achieve the above object, the invention described in claim 1 of the present invention comprises a tread portion, a pair of side wall portions connected to both sides thereof, and a pair of bead portions connected to the tread portion. These parts are reinforced between the bead cores embedded in the bead part.
In a pneumatic tire for a two-wheeled vehicle including a radial carcass of ply or more and a belt that strengthens a tread portion at the outer periphery of the carcass, the tire and the rim assembly in which the tire is mounted on a standard rim and a rim assembly of 0.5 kgf / cm ² the tread portion profile tread of the tire cross-section filled with air pressure, the arc of curvature radius R _C to form a tread central region, and the arc of curvature radius R _M to form an intermediate region on both sides, the tread both ends regions has a smooth composite arc shape composed of three different radii of curvature of the arc of curvature radius R _B to form the three different radii of curvature, and satisfy the relationship of R _M <R _C <R _B Pneumatic tire for a two-wheeled vehicle.

Here, the standard rim is JATMA.
YEAR BOOK (1997 version) refers to an underlined rim among applicable rims described for each tire type and each tire size, and this is specified in the section of "General Information".

In practicing the invention described in claim 1, preferably, as in the invention described in claim 2, three different radii of curvature R _M , R _C , and R _B are each 40 (mm). _{) ≦ R M ≦ 90 (mm} ), 60 (mm) ≦ R C ≦ 110 (mm), a _{90 (mm) ≦ R B,} .

Furthermore, the engine displacement is mainly 250c.
In the tire to be mounted on the rear wheel of a two-wheeled motor vehicle of the c-750 cc class sport type, the half width W of the tread surface of the tread portion is 75 to 95 mm as in the invention described in claim 3.
In the case of a tire to be attached to both the front wheel and the rear wheel, the maximum camber angle attached to the tire during sports running is taken into consideration, as in the invention described in claim 4. The ratio C / W of the vertical distance C from the maximum diameter position on the tread portion tread surface to the tread edge and the half width W of the tread portion tread is in the range of 0.6 to 0.8. Is desirable.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. FIG. 1 shows a left half sectional view of a part of a pneumatic tire and a rim for a two-wheeled vehicle in which a tire and a rim assembly are filled with an air pressure of 0.5 kgf / cm ² , and a right half outer contour diagram of a tire section. It is explanatory drawing which also shows.

In FIG. 1, a pneumatic tire for a two-wheeled vehicle (hereinafter referred to as a tire) has a toroidal tread portion 1, a pair of sidewall portions 2 connected to both sides of the tread portion 1, and a pair of beads connected thereto. A carcass 5 of at least one ply (one ply in the illustrated example) for reinforcing these parts 1, 2, and 3 between bead cores 4 buried in a bead part 4, and a tread part at the outer periphery of the carcass 5. 1 that strengthens the belt.

The ply cord of the carcass 5 is an organic fiber cord, for example, a nylon 66 cord or a polyester cord.
A radial array that crosses within a range of 0 °. The belt 6 is a rubber-coated organic fiber cord cross layer of two or more layers (three layers in the illustrated example), and this cord is also compatible with nylon 66 cord and polyester cord. Note that the code intersection layer has a form in which the cords of layers adjacent to each other across the tire equatorial plane E intersect.

A tread rubber 7 is provided on the outer periphery of the belt 6, and the bottom surface of the tread rubber 7 is extended to the side wall 2 region as indicated by reference numeral 9. Note 8
Is the inner liner. In the case of a tubeless tire, an air-impermeable rubber is applied to the inner liner 8.

Here, the contour of the tread 1t of the tread 1 is
As viewed in the width direction of the tread surface 1t, forming an arc of curvature radius R _C to form a tread surface 1t central region, and the arc of curvature radius R _M which forms a tread surface 1t intermediate region on both sides, the tread 1t both side end regions It shall have a composite arc shape of an arc having a curvature radius R _B. The composite arc shape has a shape in which arcs having three different radii of curvature are smoothly connected to each other. Desirably, adjacent arcs of the composite arc are inscribed or circumscribed with each other. The center of the curvature radius _RC is located on the tire equatorial plane E.

The radius of curvature R _C, R _M, the value of R _B is tripartite cross, required to be set to satisfy the relation R _M <R _C <R _B, that is, the curvature radius R _M Arc is radius of curvature R
The arc of _C arc and the radius of curvature R _B is that inscribed respectively.

The tire provided with the tread portion 1 having the tread surface 1t having the composite arc shape described above has a tangent line T shown in FIG.
L tilt angle θ is taken large, and even when the arc chord length of curvature radius R _B form set sufficiently large, out excessive external径膨like tread 11a of the two-dot chain line shown in FIG. 4 Can be suppressed, and the radius of curvature R _C forming an arc in the central region of the tread 1t can be set sufficiently large.

As a result, the tire outer diameter can be sufficiently kept within the JATMA standard, the running stability of the two-wheeled vehicle in the upright posture can be improved, and a large camber angle can be provided for the vehicle. When turning with
It is possible to improve grip force and turning stability of the tire. Here, the grip force refers to a lateral force generated from the tire, that is, a force mainly based on the camber thrust and dependent on the cornering force.

In the case of sports-type two-wheel vehicle tires mainly having an engine displacement of 250 cc to 750 cc, the width 2 × W of the tread 1 t is practically 150 mm to 190 mm.
The range of mm is suitable.

Further, the maximum diameter position of the tread surface 1t of the tread portion 1, which is the position T of the tread surface 1t intersecting with the tire equatorial plane E as shown in FIG.
The vertical distance C and the half width W are set such that the value of the ratio C / W between the vertical distance C to the t-edge P and the half width W of the tread 1t is in the range of 0.6 to 0.8. This greatly contributes to an improvement in tire grip force and an improvement in turning stability when turning with a large camber angle. Positions P to Q
The space between them is a chamfer.

[0023]

[Example] Radial ply tire 6 for motorcycle
0 series ZR type for road use, 160 / 60R in size
17 is a tire mounted on a two-wheeled vehicle with a displacement of 250 cc. The carcass 5 has one ply, and the ply cord is a radial arrangement of a nylon 66 cord of 1500 D / 2 (90 in the tire equatorial plane E). ° orthogonal). The belt 6 has three cord crossing layers, and the cords of each layer are arranged at an inclination of 30 ° with respect to the tire equatorial plane E. JIS A at 100 ° C.
A rubber having a hardness of 39 ° was applied.

The tire is mounted on its standard rim 10 with an MT of 4.50.
When the air pressure of 0.5 kgf / cm ^{2 is applied to} this, the half width W of the tread 1t is 84 mm, and the vertical distance C from the maximum diameter position T of the tread 1t to the edge P of the tread 1t is measured.
Was 54.9 mm, and the value of the ratio C / W was 0.654. The height H from the rim diameter line RL to the tread edge 1t edge P is 38.2 mm.

In common with the above description, for the composite arc forming the tread surface 1t, in the embodiment, the radius of curvature R _C =
75 mm, the radius of curvature R _M = 60 mm, the radius of curvature R _B = 3
70 mm. Conventional Example For this example, the radius of curvature R _C = 63 mm, the curvature radius R _M = 85 mm, the curvature radius R _B = 250 mm.

The tires of the embodiment and the conventional example are mounted on the rear wheels of a two-wheeled Japanese motorcycle having an engine displacement of 250 cc, and a skilled test driver repeatedly turns on a dry road surface of a test course. The driver rated the grip force and stability of the tire by feeling evaluation. The score is out of 10 and the higher the value, the better. Each tire was filled with an air pressure of 2.3 kgf / cm ² .

The results of the evaluation by the test driver's feeling evaluation are as follows. Example tire: 7 points for both grip force and stability Conventional tire: 6 points for both grip force and stability In addition, it was confirmed that the outer diameter of each tire was within the range defined by the JATMA standard before the test run, and the upright stability of the vehicle during the run test was sufficient.

From these results, the tire of the present invention satisfies the outer diameter dimension defined by the JATMA standard, maintains sufficient uprightness of the vehicle, and exhibits excellent turning performance exceeding the grip force and stability of the conventional tire. You can see that there is.

[0029]

According to the invention described in claims 1 to 4 of the present invention, the outer diameter dimension satisfying the JATMA standard is satisfied,
Provided is a pneumatic tire for a two-wheeled vehicle, which can sufficiently maintain upright running stability, which is a basic performance of a two-wheeled vehicle, and can improve grip force and stability when a large camber is attached when turning the vehicle. be able to.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a tire section according to an embodiment of the present invention, in which a left half is a cross-sectional view and a right half is an outer contour view together with a part of a rim.

FIG. 2 is an explanatory diagram showing a partial cross section of a rim and an outer contour diagram of a cross section of a conventional tire together.

FIG. 3 is a partially enlarged view of FIG. 2;

FIG. 4 is an explanatory diagram of a change in tread surface before and after filling a conventional tire with a maximum air pressure.

[Explanation of symbols]

Reference Signs List 1 tread portion 1t tread surface 2 side wall portion 3 bead portion 4 bead core 5 carcass 6 belt 7 tread rubber 8 inner liner 9 groove bottom line 10 rim _RC radius of curvature of circular arc in center region of tread surface R _M radius of curvature of circular arc in middle region of tread surface tread from the vertical distance RL rim diameter line H rim diameter line between the R _B tread side end portions arc of curvature radius W tread half width P tread edge T tread maximum diameter position C tread maximum diameter position and tread edge region Edge height E Tire equatorial plane

Claims (4)

[Claims] An at least one ply radial carcass comprising a tread portion, a pair of sidewall portions connected to both sides thereof, and a pair of bead portions connected to the tread portion, and reinforcing each of these portions between bead cores embedded in the bead portion. And a pneumatic tire for a two-wheeled vehicle including a belt for strengthening a tread portion on the outer periphery of the carcass, wherein a tire and a rim assembly having the tire mounted on a standard rim were filled with an air pressure of 0.5 kgf / cm ² . The contour of the tread surface of the tread of the tire cross section is defined by an arc having a radius of curvature (R _C ) forming a center region of the tread surface, an arc having a radius of curvature (R _M ) forming an intermediate region on both sides thereof, and regions at both end portions of the tread surface. It has a smooth composite arc shape consisting of three different radii of curvature with the arc of the radius of curvature (R _B ) to form, and the three different radii of curvature are related to the relationship of R _M <R _C <R _B A pneumatic tire for a two-wheeled vehicle, characterized by satisfying a relationship. 2. Three different radii of curvature (R _M ),
(R _C ) and (R _B ) are 40 (mm) ≦ R _M ≦ 90 (mm), 60 (mm) ≦ R _C ≦ 110 (mm), and 90 (mm) ≦ R _B , respectively. The tire described in 1. 3. The half width (W) of the tread portion of the tread portion is 75 to
The tire according to claim 1 or 2, wherein the thickness is within a range of 95 mm. 4. The ratio (C / W) of the vertical distance (C) from the maximum diameter position on the tread portion tread surface to the tread edge and the half width (W) of the tread portion tread is 0.6. The tire according to any one of claims 1 to 3, which is in a range of -0.8.