JP2002012012A - Pneumatic radial tire for passenger car - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic radial tire for a passenger car, having a rim guard capable of sufficiently securing protection of a rim and safety in limit running even if a flat ratio is not more than 55%. SOLUTION: In this pneumatic radial tire for a passenger car, an annular rim guard 3 formed by raising rubber outward in the tire axial direction is provided between the vicinity of the tire maximum width and the vicinity of a rim line. The meridional sectional shape of the rim guard 3 is approximately trapezoidal, the distance (h) between the top part 4 and an outermost layer carcass ply 2 is in the range of 10 to 17 mm, and the width in the tire radial direction of the top part 4 is in the range of 2 to 5 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire for a passenger car, and more particularly to a so-called flat tire (especially having a flatness of 55) which is mounted on a sporty passenger car in which sports driving performance and fashionability are emphasized. % Or less), which is a pneumatic radial tire for a passenger car with a rim guard that exhibits an excellent effect in the following.

[0002]

2. Description of the Related Art Conventionally, from the viewpoint of protection of a rim and safety at the time of limit running, an annular rim guard formed by protruding rubber outward in a tire axial direction is provided between a vicinity of a tire maximum width and a vicinity of a rim line. A flat pneumatic radial tire for a passenger car provided is widely and generally known. Here, the case where the safety at the time of the limit running is impaired is mainly the case where the rim touches the ground during cornering or when the steering wheel is suddenly turned, and the balance of the car is lost.

[0003]

However, the dimensions of the conventional rim guard in a flat pneumatic radial tire have not been strictly defined, and the rigidity of the rim guard has not been optimized. Therefore, especially in the case of a flat tire having an aspect ratio of 55% or less, it cannot be said that the conventional rim guard is not always specified so that the safety at the time of running at the protection limit is sufficient.

It is an object of the present invention to provide a pneumatic radial tire for a passenger car having a rim guard capable of sufficiently protecting the rim and ensuring the safety at the time of the limit running even if the flatness is 55% or less. It is in.

[0005]

The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that the above-mentioned object can be achieved by optimizing conditions such as dimensions of a rim guard. It was completed. That is, the present invention is as described below.

(1) In a pneumatic radial tire for a passenger car provided with an annular rim guard in which rubber is raised outward in the tire axial direction between the vicinity of the maximum width of the tire and the vicinity of the rim line, the rim guard has a substantially trapezoidal cross section. Wherein the distance (h) from the top to the outermost carcass ply is 10 to 17 mm, and the width of the top in the radial direction of the tire is 2 to 5 mm. It is.

(2) In the pneumatic radial tire for a passenger car of (1), the width in the tire radial direction of the rim guard at an intermediate point (h / 2) of a distance (h) from the top to the outermost carcass ply. (W) is 7-13mm
Is a pneumatic radial tire for a passenger car.

(3) In the pneumatic radial tire for a passenger car according to the above (1) or (2), the radius of curvature (R) of the outer side in the tire radial direction of the rim guard is 15 to 40 m.
m is a pneumatic radial tire for passenger cars.

(4) In the pneumatic radial tire for a passenger car according to any one of the above (1) to (3), at least 50% of the rubber constituting the annular rim guard has a hardness of 65 to 65% from the inside in the tire radial direction. This is a pneumatic radial tire for passenger cars made of 85 (Hs) hard rubber.

(5) In the pneumatic radial tire for a passenger car according to any one of the above (1) to (4), the flatness is 55
% Or less of a pneumatic radial tire for passenger cars.

In the pneumatic radial tire for a passenger car according to the present invention, the rim is not damaged even at the limit running, and the rim does not lose its balance due to contact with the ground at the limit running.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a meridional section of the annular rim guard 3 formed between the vicinity of the maximum width of the tire and the vicinity of the rim line by protruding rubber outward in the tire axial direction. Here, the tire maximum width is a maximum width measured excluding characters provided on a side portion, a white line, a side cut protector, and a rim guard for protecting a rim flange. Also, the rim line is a ridge that is provided on the surface of the bead portion of the tire in an annular shape, which is located slightly outside the rim flange in the tire radial direction when the tire is assembled to the rim, and the tire and the rim are concentric. This is a line for checking whether or not the parts are assembled.

In the present invention, the meridian section of the annular rim guard 3 is substantially trapezoidal, and the distance h from the top 4 to the outermost carcass ply 2 folded back by the bead core 1 is 10 to 17 mm, preferably. 12-16mm
And the width t of the top 4 in the tire radial direction is 2 to 5 m.
m, preferably 3-4 mm. When the distance h is less than 10 mm, the effect provided by the rim guard 3 is not sufficiently exerted, and the rim may come into contact with the ground at the time of running at the limit. On the other hand, if the distance h exceeds 17 mm, the rim guard 3 becomes too high, the rim guard 3 easily comes into contact with the ground, and abnormal wear of the rim guard 3 and rim guard breaking easily occur. If the width t is less than 2 mm, the top of the rim guard 3 is too thin, and the protection effect on the rim cannot be said to be sufficient. On the other hand, if it exceeds 5 mm, the upper width of the rim guard 3 becomes too wide, and as a result, the rigidity becomes too high, and the balance tends to be lost when it comes into contact with the ground. It also leads to an increase in weight.

In the present invention, the distance h from the top 4 of the annular rim guard 3 to the outermost carcass ply 2 is h.
The width W of the annular rim guard 3 in the tire radial direction at the intermediate point (h / 2) is preferably 7 to 13 mm, more preferably 9 to 12 mm. If the width W is less than 7 mm, the rim guard 3 becomes too thin, and the protective effect on the rim cannot be said to be sufficient. On the other hand, if it exceeds 13 mm, the rigidity of the rim guard 3 becomes too high, and when the rim guard 3 comes into contact with the ground, the balance tends to be lost, and the weight increases.

Further, in the present invention, the radius of curvature R of the outer side of the rim guard 3 in the tire radial direction is preferably 1
It is 5 to 40 mm, more preferably 20 to 30 mm.
This radius of curvature R has the same meaning as in the case of the width W,
If this value is less than 15 mm, the rim guard 3 becomes too thin, and the protective effect on the rim cannot be said to be sufficient.
On the other hand, if it exceeds 40 mm, the rigidity of the rim guard 3 becomes too high, and when the rim guard 3 comes into contact with the ground, the balance tends to be lost and the weight increases.

Furthermore, in the present invention, an area S surrounded by A, B, C, and D in FIG. 2 (a virtual line (dashed line in the figure) assuming a tire having no rim guard between D and A).
In the rubber constituting the annular rim guard 3 defined by the above, the hatched area U surrounded by B, C, D, and E made of hard rubber having a hardness of 65 to 85 (Hs) is 50% or more. Preferably, there is. As a result, the rigidity of the rim guard 3 can be maintained, and an effect excellent in wear resistance can be obtained.
It is possible to prevent abnormal wear of the rim guard, breakage of the rim guard, and the like, and it is possible to ensure the permanence of the effects of the present invention. Here, the hardness is a hardness based on JIS spring A type hardness.

As described above, the present invention is characterized by the size and hardness of the rim guard and exerts particularly excellent effects on a flat tire having a flatness of 55% or less.
It should be noted that the structure and material other than the rim guard are not particularly limited, and can be determined according to a common use.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments. Conventional Example, Examples 1-4, Comparative Example Pneumatic radial tire for passenger cars (size: 215 / 45R) equipped with a rim guard satisfying the conditions shown in Table 1 below
17) were prototyped, mounted on standard rims specified by JATMA, and filled with air pressure corresponding to the maximum load capacity specified by JATMA. Thereafter, the test tire was mounted on a vehicle (Artezza manufactured by Toyota Co., Ltd.), and a limit running feeling test was performed. In this test, three drivers traveled on a winding road, and the average score of the 10-point evaluation was used as the evaluation result. In addition, in the limit running feeling test, the presence or absence of rim damage and rim guard abnormality were also examined. The results obtained are shown in Table 1 below.

[0019]

[Table 1]

1) Rubber area S constituting the entire rim guard
Is the ratio of the region U where the hard rubber having a hardness of 78 (Hs) exists from the inside in the tire radial direction. 2) It was "9" when the tire was new, but 1000km
After running, the score was "7" (in other examples, there was no change in the score even after running 1000 km). 3) Rim guard wear was observed after traveling 1000 km. 4) The tip was chipped.

[0021]

In the pneumatic radial tire for a passenger car according to the present invention, the dimensions of the rim guard are optimized, so that the flat tire does not damage the rim at the time of the limit running, and the balance of the vehicle is improved. The vehicle can be safely driven without breaking and without damage to the rim guard. It is also effective for fashionability and weight reduction. Therefore, excellent effects are exhibited in vehicles such as sports cars that require sporty running.

[Brief description of the drawings]

FIG. 1 is an enlarged partial sectional view showing a rim guard according to the present invention.

FIG. 2 is an enlarged partial cross-sectional view showing rubber regions having different hardnesses in a rim guard.

[Explanation of symbols]

 1 bead core 2 outermost carcass ply 3 rim guard 4 top

Claims (5)

[Claims] 1. A pneumatic radial tire for a passenger car having an annular rim guard formed by rubber raised outside in the tire axial direction between the vicinity of a maximum width of a tire and the vicinity of a rim line, wherein the rim guard has a substantially trapezoidal cross section. And the distance (h) from the top to the outermost carcass ply is 1
A pneumatic radial tire for a passenger car, wherein the width of the top portion in the tire radial direction is 2 to 5 mm. 2. A tire radial direction width (W) of the annular rim guard at an intermediate point (h / 2) of a distance (h) from the top to the outermost carcass ply is 7 to 13 mm. Pneumatic radial tire for passenger cars. 3. The rim guard according to claim 1, wherein a radius of curvature of a radially outer side of the rim guard is 15 to 40 mm.
The pneumatic radial tire for a passenger car according to the description. 4. The rubber constituting the rim guard,
The pneumatic radial tire for a passenger car according to any one of claims 1 to 3, wherein at least 50% of the region from the radially inner side of the tire is made of a hard rubber having a hardness of 65 to 85 (Hs). 5. The flattening rate is 55% or less.
The pneumatic radial tire for a passenger car according to any one of the above.