JPS60148702A - Pneumatic tyre of vehicle - Google Patents

Abstract

PURPOSE:To improve the steering stability of a FF vehicle by specifically determining both the shoulder drop ratio at the tread side corner and the ratio of the curvature radius of the round shoulder at the tread side corner with respect to the maximum width of a tyre. CONSTITUTION:The titled tyre has a round shoulder 6 at the tread side corner part thereof and has such a section as that the crown periphery 7 is smoothly connected to the side periphery 8. The shoulder drop ratio D/C, namely, the ratio of the distance D measured from the line parallel to the revolutional axis of the tyre passing through the crown top T to the crossing point P, with respect to the distance C, measured from the tyre's equator line, of the crossing point P of both the extension lines from the crown periphery 7 and the side periphery 8 which are smoothly connected to each other to have therebetween the curved line of a round shoulder 6 having a radius of curvature indicated by R3, is specified to 0.05-0.09. And the ratio R3/W, namely, the ratio of said R3 with respect to the maximum width of the tyre is specified under 0.17.

Description

[Detailed Description of the Invention] (Technical Field) Among pneumatic tires for passenger cars, this invention relates to a device that is advantageously adapted to front-wheel drive (hereinafter abbreviated as FF) vehicles, in which the load burden on the rear wheels is much lower than on the front wheels. The technical content described in the specification is the result of development aimed at improving steering stability, which is a particular problem under the above-mentioned specificity of load bearing.

(Background technology) In general, the rear wheel load of FF cars is lower than the front wheel load, and as shown in Figure 1, which compares the surface load relationships for representative Japanese car models, these ratios are approximately equal to each other in the empty state. 40:60
It has become lower.

On the other hand, as shown in Figure 2, which shows an example of the relationship between the load and corner link power (hereinafter referred to as OP) of pneumatic υ ears for ordinary passenger cars, the air pressure (hereinafter referred to as OP) is When used in common, the OP of the rear wheels is much smaller than that of the front wheels, and therefore becomes a significant impediment to the steering stability of FF vehicles.

From Figure 2, it is clear that lowering the rear wheel machining can increase the ground contact area and increase OP, but this not only has the disadvantage of increased rolling resistance, but also requires troublesome maintenance, which greatly impairs practicality. Ru.

(Prior art and problems) Regarding the above-mentioned difficulties, attempts have been made to increase the OP by increasing the tread width of the tire and increasing the rigidity of the tread rubber, belt, and beads, but in general, the OP is low. Since the increase in Op under high load is more significant than the increase in Op under load, there is a risk that it may even have the opposite effect.In addition, it is likely to be accompanied by deterioration of living performance such as vibration and noise, and fuel efficiency, so it is difficult to apply these methods. It has limitations and is not practical.

(Objective of the invention) While maintaining the same load on the front wheels and rear wheels, - To greatly improve the grounding performance (ground contact width, ground contact area) of the rear wheel on the low load side compared to that of the front wheel on the high load side. ,
In other words, it is an object of the present invention to improve the steering stability of a front-wheel drive vehicle by leading to an improvement in the characteristics such that the load-〇p curve (■) shown in FIG.

(Misappropriation of inventions) The above purpose can be advantageously fulfilled by considering the following points. That is, - A pneumatic tire for a passenger car has a cross-sectional shape in which the tread side edge forms a round shoulder and the crown periphery smoothly connects with the side periphery, and the curve of the round shoulder with the radius of curvature of R8 is sandwiched. The ratio of the distance D from the straight line parallel to the axis of rotation of the tire passing through the crown top T to the distance O from the tire equatorial plane of the intersection point P on each extension of the periphery and the side periphery. In other words, shoulder drop ratio D10 is 0.0
5 to 0.09, and the ratio R8/w of R8 to the tire maximum width W is 0.17 or less.

The above relationship is generally illustrated in Fig. 4, where R□ is the crown radius of the center region of the pigeon tread, R8 is the crown radius of the side region connected to the round shoulder, R4 is the radius of curvature of the side periphery, and 0- 0 indicates the equatorial plane of the tire.

Size 175/7゜5R prototype made according to the configuration of this invention
Combining 18 tires with the same size conventional tires and regular size 5' rims, total weight 2.4 kg / ct
Comparison of tire cross-sectional contours when applying d
In the figure, the solid line represents the invention, and the imaginary line represents the conventional tire. In the figure, 1 is a tread portion, 2 is a side portion, 8 is a bead portion, 4 is a carcass, 5 is a belt, 6 is a round shoulder, 7 is a tarauchen periphery, and 8 is a side periphery.

Generally, the engineering p of this type of tire is 1.7~
The set load at this time is called the normal load, which is expressed as M. Figure 6 shows the relationship that the increase in load up to the normal load M has on the variation in the contact width of the tread. The value of the ratio B/A of the ground contact width B at a normal load M to that A at a normal load M is advantageously suitable when the value is between 0.9 and 1.0.

On the other hand, regarding the ground contact shape (footprint) of the tread under the regular load M, as shown in Fig. 7, I5 is the distance from the equator r to the ground contact width edge with respect to the ground contact length G along the tire equatorial plane 0-θ. The ratio F/G of the ground contact length F at a position of 0.9 times E is suitable within the range of 0.85 to 1.1, and if this ratio exceeds 1.1, shoulder wear may occur.

According to the results of actual measurements, under the above configuration 1 of the present invention, especially for the belt, in a so-called laminated structure of a separable belt, 0, 9 < B/A < 1-0, and 0.
．． The relationship of s, 5 ri'/g <1.1 is preferable.

Size 175/7oSR1 compared to Figure 5
The relationship between the load and contact width of the prototype tire ``8'' and the conventional tire 0 is as shown in Figure 8. R7゜〈0.9
0.94 in R7° according to this invention compared to the conventional tire of
Furthermore, as shown in Figure 9 regarding the relationship between load and ground contact area, the ground contact area is expanded to a much larger extent especially near the rear wheel load area than the ground contact area near the 1゛ζ front wheel load. Ta.

Install these tires on a 15000OFF small car,
When we conducted a feeling test by driving an actual vehicle on the applicant company's test course, concerns about the handling stability of the conventional 1゛ tire were completely eliminated with the example tire ■, and there were no problems with vibration or noise. Not accompanied.

In this test, the load burden was 250 to 9 on the front wheels and 15 on the rear wheels. By improving the C1 characteristics under low loads on the rear wheel side according to the present invention, the disadvantages in terms of steering stability performance that are specific to the above can be effectively improved without any disadvantages such as reduction.

[Brief explanation of drawings]

Figure 1 is a general trend graph of the load burden on the front and rear wheels of a FF vehicle, Figure 2 is a graph of the load-〇p relationship, and Figure 8 is a graph showing the target for improving the load-op relationship desirable for FF vehicles. Fig. 4 is a detailed explanatory diagram of the present invention, Fig. 5 is a comparison diagram between the embodiment and the conventional example, Fig. 6 is a graph of the relationship between load and ground contact width, and Fig. 7 shows evaluation criteria for ground contact shape. Fig. 8 is a comparison graph of the load-contact width relationship, and Fig. 9 is a comparison graph of the load-contact area relationship. ...Side periphery. Patent Applicant: Brideston Tire Co., Ltd. (Figure 1) FRONT Cargo (Figure 2)
fit> Fig. 3 f50 20θ 250 Kl Fig. 6 Fig. 7 Fig. 8 a+i love (#)) Fig. 9 1fI history (ni))

Claims (1)

[Claims] L A pneumatic tire for a passenger car has a cross-sectional shape in which the tread side edge forms a round shoulder and the crown periphery smoothly connects with the side periphery, and this is made by sandwiching the curve of the round shoulder with a radius of curvature of Rs. The distance D from the straight line parallel to the axis of rotation of the tire passing through the crown top T with respect to the distance O from the tire equatorial plane of the intersection point P on each extension of the crown periphery and side periphery that smoothly connect. Ratio, shoulder drop ratio is exactly 0.0
5 to 0.09 and a ratio of R8 to the tire maximum width W of 0.17 or less.