JPS624604A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To improve the durability of a tire around its bead section by specifying a form index which is determined by both a ratio of the height of the maximum width of a tire when the tire is deflated to the height of the tire in cross section, and a ratio of the height of a bead filler to the said height of the tire in cross section in a pneumatic tire having the specified aspect ratio. CONSTITUTION:In a radial tire having an aspect ratio SH/SW of more than 90%, SDH represents the height of the maximum width when the tire is deflated, FH represents the height of a bead filler 6 in a tire cross section, and SH represents the height of the tire in cross section. And a form index A<2>/B<1/2> is hereby set to be 0.45-0.54 where A=SDH/SH, and B=FH/SH. This configuration enables the durability of the tire around the bead section to be improved with the provision of improved productivity.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention provides a radial tire with an aspect ratio of 90% or more, by defining the relationship between the tire maximum width position and the bead filler height within a certain range. , relates to a pneumatic tire with improved durability around the bead.

[Prior art]

Generally, when radial tires are used under high loads,
Stress tends to concentrate on the bead, and therefore there is a problem with its durability.

Among them, the aspect ratio (tire cross section height 5) I)
Radial tires in which the ratio of SH/SW to the tire cross-sectional width (S-) is 90% or more tend to cause stress concentration, and the durability of the bead portion is disadvantageous.

For this reason, in order to improve the durability of the bead part as mentioned above, reinforcing layers, reinforcing rubber, etc. have been added, but these have not been able to improve tire productivity. Also, there were major problems such as increased costs.

[Purpose of the invention]

This invention was devised by focusing on the conventional problems, and its purpose is to improve the durability of the bead area in radial tires with an aspect ratio of 90% or more that are used under high loads. To provide a pneumatic tire capable of improving tire productivity and reducing costs. It is something.

[Structure of the invention]

In order to achieve the above purpose, this invention
For radial tires with W) of 90% or more, the ratio of the height at the tire maximum width position (SDH) to the tire cross-sectional height (SR) at the time of deflation (A = SDI/SR)
The shape index (A2/σ) determined by the ratio (B=FII/SH) of the bead filler height FB) to the tire cross-sectional height (S11) was set in the range of 0.45 to 0.54. The gist of this is that

The present invention will be explained below based on the accompanying drawings.

FIG. 1 shows a front sectional view of essential parts of a pneumatic radial tire for a passenger car in which the present invention is implemented. A belt consisting of a tread 3 connected to a wall 2, a carcass cord 4 made of carbon fiber cord, and an upper belt reinforcing layer 5a and a lower belt reinforcing layer 5b between the side wall 2 and the carcass cord 4. It is constructed by arranging a layer 5.

Further, the turn-up portion X of the carcass cord 4 is arranged along the carcass cord layer so as to wrap around the bead filler 6.

Furthermore, in FIG. 1, SH is the cross-sectional height of the tire W, and S
DH indicates the height at the tire maximum width position, FH indicates the height of the bead filler, and SW indicates the cross-sectional width of the tire.

Next, we will explain the durability of the area around the bead of a radial tire, focusing on carcass cord 4.

The carcass cord 4 is 0. Generally, due to the nature of twisted cords, it is more advantageous for durability if tensile force is applied. Good. Therefore, for tires with an aspect ratio of 90% or more, which is disadvantageous in durability around the bead, we conducted an experiment to explain the layer by specifying the tire maximum width position (S D H) and bead filler height F H). It has become clear that it is possible to apply a tensile force to the bead carcass 4a during inflation (air filling).

The following is an explanation based on the results of the experiment.

First, the tensile force of the bead carcass 4a during inflation can be considered as follows.

If the tire maximum width position (S D I) acts upward (toward the shoulder side) from deflation (before air filling) to inflation, the bead carcass 4a will be pulled more, and the bead carcass 4a will inevitably exert a tensile force. will be working.

On the other hand, if the tire maximum width position (SDR) acts downward (towards the bead), a tensile force will act on the shoulder part of the carcass 4b, and less tensile force will act on the bead carcass 4a. Therefore, it is only necessary to control the movement of the tire maximum middle iZ (SDR) upward from deflation to inflation.

Figure 2 shows the relationship between the movement of the tire maximum width position (SDR) and the tire maximum width position (SDH) at the time of deflation (corresponding to the tire maximum width position in the mold width shape), and shows the relationship between the movement of the tire maximum width position (SDR) and the parameter. Tire cross section height S
Tire maximum width position at deflation (SD
R) ratio (A=SDR/RH) is taken.

As is clear from Figure 2, the tire cross-sectional height S H)
The ratio (A = SDR/SH) of the tire maximum width position (SDH) at deflation to ) movement is downward (towards the bead).

Furthermore, Figure 3 shows the influence of the bead filler height (FH), and the parameter is the ratio of the bead filler height (FH) to the tire cross-sectional height (SH) (B = FH/SH). ) is taken.

As is clear from Figure 3, the height of the bead filler is F
As H) becomes higher, the tire maximum width position (SDH) moves upward (towards the shoulder) during inflation.

From the above results, when organized using the shape index A''/'l/i, the results are shown in Figure 4.In other words, by specifying the shape index A''/f°, the tire maximum width position can be determined. (SDH) movement can be controlled, and tensile force can be applied by the bead portion carcass 4a.

In addition, the value of the shape index A''/fi is such that the amount of movement at the tire maximum width position (SDR) is 0III1 to 51m1m.
You can set it so that

If the amount of movement of the tire maximum width position (SDR) is less than
A tensile force acts downward, and the bead portion carcass 4a
There is not much tensile force applied to the

Further, if the amount of movement of the tire maximum width position (SDR) is 51 or more, the upward movement is too large and the tread radius becomes too large, causing a problem of uneven wear.

[Embodiments of the invention]

Hereinafter, the present invention will be explained based on embodiments.

Table 1 below shows Examples 1 and 2 of the present invention and Comparative Example 1.
The shape index and durability evaluation results of No. 2 are shown below.

(Left below) Size is 135/95R12LT with an aspect ratio of 95%.
The basic structure is that the carcass is made of two pieces of polyester and the belt is made of two pieces of steel.

Durability was evaluated using an indoor drum test, and the test conditions were JI
According to the S durability performance test, the distance traveled was expressed as an index.

Comparison 1.2 has a large shape index At1fi of 0.58, and the tire maximum width position from deflation to inflation (
The movement of S D H) is -1.5 mm, which is a downward movement.

In Comparison 2, a reinforcing layer was added to the bead portion to improve durability.

On the other hand, in Example 1.2, the shape index A''/f is 0.49.
The movement of the tire maximum width position (S D H) is +
It moves upward by 3.5mm, and the bead part carcass 4a
A tensile force is exerted by the

The durability of Example 1 is higher than that of Comparison 2 in which a bead reinforcement layer is added.
It can be seen that this is clearly improved over Comparison 1.

Further, in Example 2, the JIS hardness of the bead filler 6 was increased, and Comparative 2. Although inferior to Example 1, it is superior to Comparison 1.

The JIS hardness of this bead filler 6 is preferably 90 degrees or less, and if it exceeds that, the durability will decrease significantly.

On the other hand, B (=FH/SH) representing the height of the bead filler
are all 0.25 or more, but if it is less than 0.25, the bead filler 6 is too small, resulting in vertical deflection.

Width deflection becomes too large, and problems arise with the static load radius and the spacing between two wheels when using two wheels.

〔Effect of the invention〕

As mentioned above, the aspect ratio (SH/SW) of this invention is 90.
% or more, the ratio of the height 5D) l) of the tire maximum width position at deflation to the tire cross-sectional height (SH) (A = SDI / SH) and the bead filler height (FH) of the tire. Section height (SH)
The shape index (A2/f) determined by the ratio (B=FH/5ll) is set in the range of 0.45 to 0.54. This has the effect of improving the durability around the bead, thereby improving tire productivity and reducing costs.

[Brief explanation of drawings]

Figure 1 is a front cross-sectional view of the main parts of a pneumatic radial tire for passenger cars in which the present invention is implemented, and Figure 2 is the maximum tire width position (S
Regarding the movement of DR), a graph explanatory diagram showing the relationship between the tire maximum middle position at the time of deflation (SDR), Fig. 3 is a graph explanatory diagram showing the influence of the bead filler height (FH), and Fig. 4 FIG. 1 is a graph explanatory diagram showing experimental results of the present invention. SDI...height at maximum tire width position, FH...height of bead filler, SH...tire cross-sectional height, SW.
...Tire cross-sectional width, A...Tire cross-sectional height SR at the height of the tire maximum width position at deflation (5DI)
), B... Bead filler height (FH
) to the tire cross-sectional height (SH), S) l/S
W...Aspect ratio. 1st W: J1 Procedural Amendment 1. Case description 1985 Patent Application No. 14058
8 No. 2, Name of the invention Pneumatic tire 3, Relationship with the case of the person making the amendment H person's address (residence) Name Kanne) (671) Yokohama Rubber Co., Ltd. 4, Agent

Claims (1)

[Claims] 1. In a radial tire with an aspect ratio (SH/SW) of 90% or more, the ratio (A= SDH/SH), and bead filler height (F
H) to the tire cross-sectional height (SH) (B=FH
/SH), the shape index (A^2/√B) determined by
．． A pneumatic tire characterized in that the pneumatic tire is set in a range of 45 to 0.54. However, the above-mentioned aspect ratio (SH/SW) refers to the ratio of the tire cross-sectional height (SH) to the tire cross-sectional width (SW). 2. The ratio (B=FH/SH) of the height (FH) of the bead filler to the tire cross-sectional height (SH) is 0.2
5 or more, and the JIS hardness of the bead filler rubber is 90 degrees or less.