JPH0976708A - Pneumatic tire for motorcycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain excellent heat separation resistance at high speed running by avoiding additional arrangement of a member similar to a surplus reinforcing member, and providing specific circular arc territories on a carcass line. SOLUTION: In a carcass line CL on a section by a plane containing rotary axis of a tire and rim assembly, carcass lines CL of both side territories sandwiching tread end edges of a tread part 5 are formed out of circular arcs of radius of curvature R1 . Tire sectional height H measured from a rim diameter line RL is the sum of side height H1 from the rim diameter line RL to the tread end edge and crown height H2 from the tread end edge to the height H, and both side territories are set in the territories sandwiched between inside territories in the height range of 0.3H1 -0.8H1 and outside territories in the range of 0.6H1 -0.9H2 . When the carcass line CL in both side territories is formed out of a circular arc of radius of curvatue R, the ratio R1 /R of the radius of curvature R1 to the radius of curvature R is set so as to be in the range of 1.2-2.0.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a pair of bead portions, a pair of sidewall portions, and a toroidal tread portion continuous with both sidewall portions, and these portions are reinforced between bead cores embedded in the bead portion. Regarding a pneumatic tire for a two-wheeled motor vehicle comprising a radial carcass and a belt that reinforces the tread portion on the outer periphery of the carcass, excellent turning performance is achieved only by optimizing the carcass shape without adding extra constituent members. TECHNICAL FIELD The present invention relates to a pneumatic tire for a two-wheeled vehicle that is effective.

[0002]

2. Description of the Related Art The turning performance of a two-wheeled vehicle mainly depends on the camber thrust characteristics of a pneumatic tire mounted on the two-wheeled vehicle. Therefore, in order to improve the turning performance of the two-wheeled vehicle or to secure excellent turning performance, It is necessary to use tires that can obtain as large a camber thrust as possible when the vehicle turns.

When the pneumatic tire has a radial structure, it is a well known fact that the amount of camber thrust generated is smaller due to the lower lateral rigidity as compared with the bias structure. By additionally arranging a reinforcing member on the wall portion and the tread portion, the low lateral rigidity peculiar to the radial structure is compensated for, and a means for ensuring the required camber thrust characteristics has been adopted. Hereinafter, a pneumatic tire having a radial structure will be described.

[0004]

However, the above-mentioned additional arrangement of the reinforcing members causes the tread portion to increase in the amount of heat generated by the tread portion during running of the tire to deteriorate the heat generation characteristics. Any of these causes cracks at the edges and deteriorates the separation resistance, which causes the tire durability to decrease. Therefore, ensuring sufficient tire durability and compatibility with the camber thrust characteristics that satisfy the requirements have been accompanied by practically great difficulty.

Therefore, an object of the present invention is to fundamentally solve the above-mentioned contradictory problems, and while maintaining the tire durability at a high level including other various performances without additionally disposing an additional reinforcing member, It is an object of the present invention to provide a pneumatic tire for a two-wheeled vehicle that exhibits camber thrust characteristics that meet requirements.

[0006]

In order to achieve the above object, the present invention has been completed by focusing on the tension distribution acting on the carcass ply cord when the tire and the rim assembly are filled with the internal pressure. That is, the pneumatic tire for a two-wheeled vehicle according to the present invention is the tire described at the beginning, in which the tire is assembled to the applicable rim and filled with the reference internal pressure, and a carcass line having a cross section taken along a plane including the rotation axis of the rim assembly. Of these, the carcass lines in both regions sandwiching the tread edge of the tread portion are formed of an arc having a radius of curvature R ₁ , and the tire cross-section height H measured from the rim diameter line is calculated as the side height from the rim diameter line to the tread edge. H
₁ and the crown height H ₂ from the tread edge to the height H position, the both side areas are inner areas within the height range of 0.3H _{1 to} 0.8H _{1 based} on the rim diameter line. When,
The natural equilibrium shape of the radial carcass in another tire, which is a region sandwiched between the outside region within the height range of 0.6H _{2 to} 0.9H _{2 on the} basis of the above-mentioned height H position, and the pressure sharing ratio of the belt is matched. When the carcass lines in the both side regions obtained below are composed of arcs having a radius of curvature R, the value of the ratio R ₁ / R of the radius of curvature R _{1 to} the radius of curvature R is 1.
It is characterized by being in the range of 2 to 2.0.

In carrying out the present invention, it is preferable that the tread rubber gauge of the tread portion has a ratio T ₂ / T of the gauge T ₂ of the tread edge to the gauge T ₁ of the tire equatorial plane.
The value of ₁ is within the range of 1.1 to 1.5.

[0008]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail below with reference to FIG. 1 which is a diagrammatic view of a left half portion of a cross section taken along a plane including a rotation axis of a tire and a rim assembly of one embodiment filled with a reference internal pressure. explain. The right half from the tire equatorial plane E is also shown in Figure 1.
Is the same as the left half part shown in Fig. 1, and in the figure, 1 is a pneumatic tire for a two-wheeled vehicle (hereinafter abbreviated as tire), 2 is J
It is an applicable rim of the tire 1 according to ATMEYEAR BOOK, and shows only its outer contour, and the tire 1 has a pair of bead portions 3 (only one side is shown), a pair of sidewall portions 4 (only one side is shown) and both sidewall portions 4 The toroidal tread portion 5 is connected to the. .

In FIG. 1, a carcass 6 is composed of one or more plies (two plies in the illustrated example) of a rubber-coated radial arrangement cord, and a pair of bead cores 7 embedded in the bead portion 3.
(Only one side is shown) Reinforce each part above each other.
A belt 7 that strengthens the tread portion 5 is arranged on the outer periphery of the carcass 6. The ply cord of the carcass 6 is made of organic fiber
It is usual to apply a cord, for example a nylon cord, and the belt 7 is also a spiral wound layer of an organic fiber cord, for example a Kevlar cord. Reference numeral 8 in the figure indicates an air impermeable inner liner.

According to the convention, the line connecting the centers of the ply thicknesses of the carcass 6 (thickness of 2 plies in the illustrated example) is called a carcass line CL, and this line CL is shown by a chain double-dashed line. Of the entire carcass line CL, the carcass lines CL on both sides sandwiching the end edge 5tE of the tread surface 5t of the tread portion 5 defined by the following are formed by an arc having a radius of curvature R ₁ .

Both side regions sandwiching the above-mentioned edge 5tE are defined as follows. That is, as shown in the figure, first, the sectional height H of the tire 1 measured from the rim diameter line RL determined by the rim 2
Is the sum of the side height H ₁ from the rim diameter line RL to the end edge 5tE of the tread 5t and the crown height H ₂ from the end edge 5tE to the sectional height H position, which are similarly measured.

Next, 0.3H _{1 based on the} rim diameter line RL
Within the height range of ~ 0.8H ₁ , the rim diameter line RL is shown in Fig. 1.
It is represented by the height H ₃ from the above, and the area included in the height H ₃ is called the inner area as viewed in the tire radial direction (hereinafter abbreviated as the radial direction), and the cross-sectional height H is 0.6H ₂ 〜.
The height range of 0.8H ₂ is represented by the height H ₄ which is opposite from the cross-section height H position to the inside, and the area included in the height H ₄ is also called the outer area when viewed in the radial direction. The area sandwiched between the outer area and the outer area is defined as the both side areas.

The radially outer position of the inner region is shown by a straight line L ₃ , and the radially inner position of the outer region is shown by a straight line L ₄ , where the intersection point P between the straight line L ₄ and the carcass line CL.
And a carcass line CL extending between the straight line L ₃ and the intersection Q of the carcass line CL are formed by an arc having a radius of curvature R ₁ of the center C ₁ .

Here, another tire is prepared in which the pressure sharing rate of the belt is matched with the above-mentioned tire, and this tire is assumed to have a natural equilibrium shape under the same internal pressure filling of the assembly with the rim, It is assumed that the carcass line obtained under this natural equilibrium shape is also an arc having a single radius of curvature R in both side regions defined above. At this time, the value of the ratio R ₁ / R of the radius of curvature R _{1 to} the radius of curvature R under the natural equilibrium shape needs to be within the range of 1.2 to 2.0. When the natural equilibrium shape of the radial carcass is determined, the pressure sharing rate of the belt has a great influence on the value of the radius of curvature of the both side regions described above, and therefore this is matched for both types of tires.

The ratio of curvature radii R ₁ / R is 1.2 to 2.
The reason for setting the value within the range of 0 will be described below. Fig. 2 shows the left half cross section of a conventional tire in which a two-ply radial carcass 6A (shown by a ply having a thickness) has a natural equilibrium shape. The numbers inside the tire are the rim points commonly used when setting the carcass line. Line R. P. It is the position number (No.) of the divided carcass line that divides the carcass line sandwiched between L and the equatorial plane of the tire into 10 equal parts. Further, FIG. 3 shows each position No. of the divided carcass line. The lateral rigidity (kgf-cm) that the sectioned plies in FEM (finite element method)
It is the diagram calculated | required by.

FIG. 3 is a so-called position sensitivity diagram showing the proportion of the divided ply to the lateral rigidity of the carcass ply. The carcass ply existing at 6 to 8 and positions on both sides thereof (positions surrounded by broken lines in the figure) has high sensitivity, and therefore, improving the ply tension at this position, more accurately, the ply cord tension, as a whole tire. It can be seen that it is effective in improving lateral rigidity.

Unlike a tire used for a vehicle having four or more wheels, a tire for a two-wheeled vehicle needs to have a remarkably large camber angle during turning, so that the tread width is significantly widened and the crown curvature radius is also increased. Generally, it is made extremely small. This allows a significantly larger camber angle to be achieved, resulting in a larger camber thrust and only the tread rubber contributing to wear.

Therefore, the position No. with high sensitivity to lateral rigidity is provided. 6
2 to 8 belong to a region that sandwiches the tread edge in the radial direction as shown in FIG. 2, and the carcass ply shape in this region is represented by a carcass line, and by setting the radius of curvature of the line as large as possible, It is possible to increase the tension of the ply cord when filling the internal pressure.

When setting a large radius of curvature, it is appropriate to use the radius of curvature R of the conventional natural equilibrium carcass line as a reference, and the ratio of the radiuses of curvature R ₁ / R is 1.2.
Within the range of 2.0 to 2.0, the position number. It is possible to further increase the tension of the carcass ply cords 6 to 8 and the vicinity thereof, and as a result, to significantly improve the lateral rigidity of the tire 1 as a whole. If the value of the ratio R ₁ / R is less than 1.2, it is impossible to obtain an effective lateral rigidity improving effect.

Further, in the above-mentioned both side regions sandwiching the edge 5tE.
Radially inner line CL connected to the carcass line CL
Is the point Q and the center C₁Center C on the line connecting₂Half with
Diameter R ₂Is formed by an arc of
Line CL is point P and center C ₁On the extension of the line segment connecting
Center C_ThreeRadius R with_ThreeIs formed. At this time
R₁If the value of / R exceeds 2.0, the above radius R₂And half
Diameter R_ThreeBecomes too small, resulting in a radius R₂And radius R
_ThreeCarcass ply in the CL area of the carcass line
The lateral stiffness component decreases, and the lateral stiffness is canceled out as a whole.
It is not possible to obtain favorable camber thrust characteristics.
It is possible.

The value of the ratio R ₁ / R of the above-mentioned radii of curvature is 1.2
The tire having the carcass line CL within the range of up to 2.0 has a crown shape in the widthwise both end regions of the tread from the tread edge toward the center when the tread portion has a conventional tread rubber gauge distribution. It is unavoidable to largely drop inward in the radial direction, and as a result, shoulder drop uneven wear due to running, so-called local drag wear, occurs in both end regions of the tread.

This uneven wear is caused by the gauge T ₁ of the tire equatorial plane E per gauge of the widthwise tread rubber 5g of the tread 5t.
The value of the ratio T ₂ / T ₁ Gauge T ₂ of the edge 5tE was in the range of 1.1 to 1.5, can be advantageously avoided by a tapered gauge distribution for. Where the ratio T ₂
If the value of / T ₁ is less than 1.1, the effect of suppressing the occurrence of drag uneven wear is insufficient and uneven wear resistance deteriorates. If it exceeds 1.5, the amount of heat generated near the edge 5tE increases and high speed is achieved. In any case, it is not preferable because the heat separation resistance during running is lowered.

[0023]

Example: Two-wheeled vehicle tire size 160/80
R16, and the tire configuration is in accordance with FIG. The radial carcass 6 is composed of two plies of 1260D / 2 nylon cord, and the belt 8 is composed of a spirally wound layer of 1500D / 2 Kevlar cord. The proper rim of this tire 1 is 3.50 in terms of rim width.

The sectional height H of the tire 1 is 127 mm, the side height H ₁ is 41 mm, and the crown height H ₂ is 86 m.
m. The height H ₃ related to the straight line L ₃ partitioning the inner sides in the radial direction of both sides of the tread edge 5 tE is 0.7 × H ₁ of 29 mm, and the height H ₄ related to the straight line L ₄ partitioning the outer side is 0. It is 57 mm of 66 × H ₂ .

Tires of Examples 1 to 3 were manufactured in which the ratio of curvature radii R ₁ / R and the ratio of gauges of tread rubber 5 g T ₂ / T ₁ were changed in common with the above. In order to verify the effect of improving the lateral rigidity, turning performance, uneven wear, and durability of each of the example tires, the value of the ratio R ₁ / R, the ratio T ₂ / T
Tires of the conventional example and the comparative example in which the value of ₁ was changed from those of the example were prepared, and comparative tests were performed under the following test conditions by using these tires as test tires.

(1) Lateral rigidity: A tire and a rim assembly filled with an internal pressure of 2.8 kgf / cm ² were given a camber angle of 30 °, and were laterally displaced by 5 mm under a load of 350 kgf. The force was measured. (2) Turnability: An actual vehicle feeling test by a skilled test driver. The tire internal pressure was according to the specified pressure of the vehicle, and the test result was based on the driver's rating. (3) Uneven wear: The amount of shoulder wear was measured by actually using it. (4) Durability: Similarly, the product was actually used, and the crack length at the end of the constituent member, which was the core of the separation generation, was measured. The above test results are represented by an index with the conventional example being 100. The higher the number, the better. The ratio of these indices is R ₁ /
The values of R and the ratio T ₂ / T ₁ are shown together in Table 1.

[0027]

[Table 1]

The following facts can be seen from the results shown in Table 1. That is, the comparative tires have improved lateral rigidity and therefore markedly improved turning performance, but on the other hand, they have uneven wear resistance, which is a level that may pose a practical problem. On the other hand, in Example 1, the lateral rigidity and the turning property are greatly improved without impairing the uneven wear resistance and the durability, that is, maintaining the level at which there is no problem in the market. Example 2 is Example 1
Compared with the above, the improvement in lateral rigidity and turning property is somewhat modest, and therefore, the uneven wear resistance shows superior performance. Although the durability of the third embodiment is slightly lower than that of the conventional example because the gauge ratio T ₂ / T ₁ is the limit value, the degree thereof is not a problem within a range that is sufficiently accepted in the market, and further, the other 3 performances In terms of occupying the most advantageous position, it can be said that the tire is suitable for turning and uneven wear resistance.

[0029]

According to the present invention, the additional heat-separation resistance during high-speed running is maintained by avoiding the additional arrangement of members similar to extra reinforcing members and providing a unique arc region for the carcass line. It is possible to improve the lateral rigidity of the tire by removing the humiliation of separation from cracks that tend to occur at the end of the additional member, and this makes it possible to dramatically improve the turning performance of the motorcycle. A pneumatic tire for a motorcycle can be provided.

[Brief description of drawings]

FIG. 1 is a left half sectional view including a rim of a pneumatic tire for a two-wheeled vehicle according to the present invention.

FIG. 2 is a left half sectional view of a conventional tire for explaining divisions of a carcass ply.

FIG. 3 is a diagram showing the distribution of lateral rigidity for each carcass ply section.

[Explanation of symbols]

1 Pneumatic Tire for Motorcycles 2 Applicable Rim 3 Bead Part 4 Sidewall Part 5 Tread Part 5g Tread Rubber 5t Tread 5tE Edge of Tread 6 Radial Carcass 7 Bead Core 8 Belt CL Carcass Line H Tire Section Height H ₁ Tread End Edge height H ₂ Height from the edge to the outer diameter position H ₃ Inner area height H ₄ Outer area height R ₁ Side area Carcass line curvature radius T ₁ Equatorial tread rubber gauge T ₂ Tread edge Tread rubber gauge

Claims (2)

[Claims] 1. A radial carcass consisting of a pair of beads, a pair of sidewalls, and a toroidal tread portion continuous to both sidewalls, and a radial carcass that reinforces each of the beads cores embedded in the beads.
A pneumatic tire for a two-wheeled vehicle, comprising: a belt for strengthening a tread portion on the outer periphery of the carcass, wherein the tire is assembled to its applicable rim and filled with a reference internal pressure, and a cross section taken along a plane including the rotation axis of the rim assembly. Of the carcass line, the carcass lines on both sides sandwiching the tread edge of the tread portion are formed of arcs with a radius of curvature (R ₁ ), and the tire section height (H) measured from the rim diameter line is calculated from the rim diameter line. As a sum of the side height (H ₁ ) to the tread edge and the crown height (H ₂ ) from the tread edge to the height (H) position, the both side areas are 0.3H on the basis of the rim diameter line. An inner region within the height range of _{1 to} 0.8H ₁ ,
Based on the above-mentioned height (H) position, it is defined as an area sandwiched between the outer area within the height range of 0.6H _{2 to} 0.9H ₂ and the natural carcass of the radial carcass in another tire is adjusted to match the pressure share of the belt. Assuming that the carcass lines on both sides obtained under the equilibrium shape are arcs having a radius of curvature (R), the ratio (R ₁ / R) of the radius of curvature (R ₁ ) to the radius of curvature (R) A pneumatic tire for a two-wheeled vehicle, having a value within a range of 1.2 to 2.0. _2. The ratio (T ₂ / T ₁ ) of the gauge (T ₂ ) of the tread edge to the gauge (T ₁ ) of the tire equatorial plane of the tread rubber gauge of the tread portion is 1.1 to 1. The tire according to claim 1, which is in a range of 5.