JPH04238703A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To generate a turbulent flow while ensuring a wide area of radiating heat to thus promote temperature dropping action and to prevent generation of a crack by forming many recessed parts over a total unit in the peripheral direction of a tire in a fixed region opposed to a breaker buried in a tread part. CONSTITUTION:Two layers of breakers are arranged in the outside of a carcass in a tread part of a pneumatic tire 10. Here, many recessed parts 20 are formed over a total unit in the peripheral direction of the tire 10 in a fixed region 4 opposed to each breaker in a side surface of the tire 10. Each recessed part 20 is distributed in a range of 50 to 200 per 100cm<2> while setting respectively a depth (d) too 0.5 to 2mm further a diameter D to 5 to 10mm. On the other hand, in the above-mentioned region 4, its width (h) (between boundary lines S, P) is set to within a 10 to 60mm range in accordance with a size or the like of the tire. In this way, a wide area of radiating heat is ensured in the fixed region and also generating a turbulent flow thus to promote temperature dropping action, and generation of a crack in a breaker end part is effectively prevented.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a pneumatic tire having a breaker embedded in its tread.

0002

2. Description of the Related Art Conventionally, tires for four-wheeled vehicles have been reinforced with a plurality of layers of breakers (belts) embedded in the carcass layer of the tread portion. The side surface of the tire facing the breaker is usually formed as a flat surface, or has decorative grooves continuously formed in the circumferential direction.

0003

[Problems to be Solved by the Invention] With the above configuration, especially when driving at high speeds of 180 km/h or more, the tire is heated by frictional heat due to friction between the tire and the road surface, and thermal fatigue occurs due to the difference in thermal expansion between the rubber material and the breaker. This causes a problem in that cracks 80 are formed at the ends of the breakers 5 and 6 of the tire 10, as shown in FIG. As a countermeasure, it has been proposed to reduce the heat generation by reducing the thickness of the rubber in this part or by using low heat generation rubber in this part, but reducing the thickness is not recommended due to the strength of the tire. This is not preferable, and since the low heat generation rubber itself has low strength, there is a problem that the inside of the rubber may be damaged.

[0004] The present invention was made in order to eliminate such conventional drawbacks, and it is an object of the present invention to release heat from the breaker end with a simple structure and reliably prevent cracks from forming at the breaker end. The object of the present invention is to provide a pneumatic tire having a configuration that allows the following.

[0005]

[Means for Solving the Problems] This invention provides a pneumatic tire in which a breaker is embedded in the tread, and a number of recesses are formed over the entire circumferential direction in a certain area facing the breaker on the side surface of the pneumatic tire. It is something that exists.

[0006] The above-mentioned recess is formed to have a depth of 0.5 to 2 mm and a maximum diameter of 5 to 10 mm.
Preferably, ~200 recesses are arranged. Further, the width of the above region may be set to 10 to 60 mm.

[0007]

[Function] In the above configuration, since a large number of recesses are formed in a certain area of the side surface of the pneumatic tire facing the breaker, extending over the entire circumferential direction, a large heat dissipation area is formed in that area. A turbulent flow is generated, as a result of which a temperature-reducing effect is achieved, and crack initiation at the breaker end can be effectively achieved.

[0008]

[Embodiment] In FIG. 1, a pneumatic tire 10 consists of a tread portion 1, a sidewall portion 2, and a bead portion 3.
A bead 30 is embedded in the bead portion 3, a carcass 11 is embedded along the inner surfaces of the tread portion 1 and the sidewall portion 2, and the end portion of the carcass 11 is folded back at the bead portion 3. Two layers of breakers 5 and 6 are arranged in the tread portion 1 on the outside of the carcass 11.

As shown in FIGS. 2, 3, and 4(a), in a certain region 4 on the side surface of the tire 10 facing the breakers 5, 6, there are a number of recesses 20 throughout the circumferential direction of the tire. is formed, and the depth d of the recess 20 is 0.
．． The diameter D is 5 to 10 mm, and the radius of curvature R of the bottom is set to 0.5 to 10 mm. Also, the distribution of this recess 20 is 100 cm2 (10 cm square)
50 to 200 contact recesses 20 may be arranged. Further, the width h (between the boundary lines S and P) of the region 4 may be set in the range of 10 to 60 mm depending on the tire size and the like. The recesses 20 are formed in a symmetrical arrangement on both left and right sides of the tire 10 in FIG.

The purpose of the recess 20 is to increase the area of the region 4 on the side surface of the tire and to generate turbulence to promote heat dissipation, so the depth of the recess 20 is 0.5 mm.
If the depth is less than 2 mm, there will be no effect of forming the recess.
Exceeding this is not preferable because it weakens the strength of the tire. Moreover, if the diameter D and distribution of the recess 20 are outside the above range,
In terms of heat dissipation, the function of the recess cannot be fully demonstrated. Further, if the radius of curvature R is smaller than 0.5 mm, cracks are likely to occur, which has a negative effect on the strength of the tire, while if it is larger than 10 mm, the recess 20 becomes close to a smooth surface, and the above-mentioned function as a recess cannot be achieved. Area 4
The width h may be appropriately set within the above range depending on the size of the tire; if it is smaller than that range, the heat dissipation effect will be insufficient, and if it is larger than the above range, unevenness will be formed in the extra area. This is not desirable.

[0011] The recess 20 is not limited to the circular shape described above, but may also be a rectangular recess 30 as shown in FIG. 4(b), or various other shapes. The ranges of depth d and plane dimension D for these various shapes may be set in the same manner as described above.

FIG. 5(a) shows a temperature curve in region 4 of the tire side surface when running at a speed of 180 km/h, a curve 50 is a temperature curve when region 4 is a smooth surface, and a curve 40 is a temperature curve in region 4 of the tire side surface. A temperature curve is shown in the case where the recess 20 is formed. In the latter case, the width h of the area in FIGS. 1 and 2 is 50 mm, the depth of the recess 20 is 1 mm, and FIG. 5(b)
Four recesses 20 were distributed within a range where the length w of one side was 20 mm. As is clear from this result, the temperature is lower when the predetermined recess 20 is formed (curve 40) than when the tire side surface is smooth (curve 50), and the temperature is lower in the area inside the point P. It is shown that the temperature is low, clearly demonstrating the effect of this invention.

As described above, in the present invention, since a recess is formed in a predetermined area 4 on the side surface of the tire 10 to effectively dissipate heat, the edge of the breaker is provided with a recess as shown in FIG.
The occurrence of cracks 80 as shown in FIG. 1 is reliably prevented.

[0014]

As explained above, according to the present invention, a large number of recesses are formed over the entire circumferential direction in a certain area of the side surface of the pneumatic tire facing the breaker. A large heat dissipation area is formed and turbulent flow occurs, resulting in a temperature reduction effect.
It is possible to effectively prevent the occurrence of cracks at the end of the breaker.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a tire to which the present invention is applied.

FIG. 2 is a partial front view of the vicinity of the outer circumference of the tire.

FIG. 3 is a cross-sectional view of a recess.

FIG. 4 is a plan view of a recess.

FIG. 5 is a comparison diagram of temperature curves with and without recesses and a distribution diagram of recesses.

[Explanation of symbols]

1 Tread part 2 Side wall 3 Bead part 4 Area where recesses are formed 10 Tires 20 Recessed part 30 Recessed part D Diameter of recess h Area width

Claims (3)

[Claims] 1. A pneumatic tire comprising a pneumatic tire with a breaker embedded in the tread, and a pneumatic tire having a number of recesses formed over the entire circumferential direction in a certain area facing the breaker on the side surface of the pneumatic tire. tire. [Claim 2] The depth of the recess is 0.5 to 2 mm.
2. The pneumatic tire according to claim 1, wherein the pneumatic tire has a maximum diameter of 5 to 10 mm, and 50 to 200 recesses are arranged per 100 mm2. 3. The pneumatic tire according to claim 1, wherein the width of the region is set to 10 to 60 mm.