JPS61157401A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To improve high-speed durability and steering stability by specifying the relations between the contact position between the tread center pat and the right and left side pats, between-edge distance in the both-edge reinforcement pats oaf a belt, and the length of the reinforcement pat, in a tire having the tread constituted with two kinds of curved surfaces. CONSTITUTION:The distance Lp between the contact point P between the center pat constituted with the radius R1 curvature forming a tread and the both side pats constituted with the radius R2 of curvature and the center edge pat (a) of the reinforcement pat A constituted by bending the right and left sides of a belt layer V is made 1/4 of more of the length La of the reinforcement part, when the contact point P is on the tread center C side in comparison with the center edge pat (a) of the reinforcement pat A. When the contact point P is on a shoulder pat S side in comparison with the center edge part (a) of the reinforcement pat A, the distance Lp is made 1/5 or more of the length La of the reinforcement part A. With such constitution, high-speed durability and steering stability can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement of a pneumatic radial tire, which is used as a tire for passenger cars and the like.

[Prior art] ゛ ・ As a means of improving the high-speed durability of pneumatic radial tires, both left and right ends of the steel belt that constitute the belt layer are bent toward the center of the tire, so that both left and right ends of the belt layer are bent. A so-called steel folded belt structure is being considered to improve the rigidity of the steel.

However, in this steel folded belt structure, there is a large difference in rigidity between the left and right ends of the belt layer, which are reinforced at the bent parts (hereinafter referred to as reinforcing parts), and the central part of the belt layer, which is not reinforced. Strain was concentrated near the side ends of the parts, and as a result, there was a risk that the reinforcing cords near these ends would break.

This tendency becomes particularly noticeable in the case of tires (two-stage radius tread tires) in which the radius of curvature of the tread is different from the radius of curvature forming the central part of the tread and the radius of curvature forming the left and right sides of the tread. be.

Therefore, as a result of repeated experiments and studies described below, the inventor of the present invention found that the tread is a two-stage radius tread, and
In the case of pneumatic radial tires that have reinforced left and right sides of the belt layer, the point of contact between the radius of curvature that forms the center of the tread and the radius of curvature that forms both left and right sides of the tread is determined by the reinforced part that reinforces both the left and right sides of the belt layer. It has been found that the above-mentioned problems can be solved by setting the position from the positional relationship with the tire center side end.

[Purpose of the invention]

The present invention was made based on the above-mentioned knowledge, and aims to provide an excellent pneumatic radial tire that can significantly improve high-speed durability and also improve handling stability. .

[Structure of the invention]

That is, in the present invention, the radius of curvature of the tread T is composed of the radius of curvature R1 forming the central portion of the tread and the radius of curvature R2 forming the left and right side portions, and the belt layer V using steel cords as reinforcing cords. A pneumatic radial tire reinforced on both left and right sides of the belt layer V, where La is the distance between the tire center side end a and the shoulder side end of the reinforcing part A that reinforces the left and right sides of the belt layer V. , the tire center side end a of the reinforcing portion A and the radius of curvature R1
If the distance between and the contact point P of the radius of curvature R2 is Lp,
(a) If the contact point P is located closer to the tread center C than the tire center side end a of the reinforcing part A,
p≧La/4 伽) The above contact point P is located at the tire center side end a of the reinforcing portion A.
If it is located closer to the shoulder part S than 1"
The gist of the present invention is a pneumatic radial tire characterized in that tp≧La15.

Hereinafter, the present invention will be specifically described by way of examples with reference to the drawings.

FIG. 1 is an explanatory cross-sectional view showing the main parts of the first embodiment, FIG. 2 is an explanatory cross-sectional view showing the main parts of the second embodiment, and FIGS.
e) is an explanatory cross-sectional view showing a main part of an example of the structure of the belt layer, and FIG. 4 is a view showing the results of an experiment.

In the figure, E denotes a pneumatic radial tire according to an embodiment of the present invention, in which the radius of curvature of the tread T is composed of a radius of curvature R1 forming the center portion of the tread T and a radius of curvature R2 forming the left and right side portions, Moreover, it is constructed by reinforcing both left and right sides of the belt layer V using steel cords as reinforcing cords.

In the present invention, in particular, the distance between the tire center side end part a and the shoulder part side end part A of the reinforcing part A reinforcing both left and right sides of the belt layer V is set as La, and the reinforcing part A Let Lp be the distance between the tire center side end a and the point of contact P between the radius of curvature R1 and the radius of curvature R2, then the position of this point of contact P is: (a) The point of contact P is If it is located closer to the tread center C than the tire center side edge a, <
LD≧La/4 (b) When the above contact point P is located closer to the shoulder portion S than the tire center side end a of the reinforcing portion A, Lp
≧La15.

To further explain this structure, in the first embodiment shown in FIG. 1 and the second embodiment shown in FIG. 2, the belt layer V and the tread side belt v1 are laminated on the tread side of the carcass side belt V2, respectively. Along with this tread side belt v
This is an example in which both left and right sides of the tire 1 are bent toward the tread center C side, and these left and right bent portions are respectively used as the above-mentioned reinforcing portions A.

In the case of the first embodiment shown in FIG. 1, the point of contact P between the radius of curvature R1 and the radius of curvature R2 is positioned closer to the tread center C than the end a of the reinforcing portion A on the tire center side. In the case of the second embodiment shown in FIG. 2, the position of the contact point P between the radius of curvature R1 and the radius of curvature R2 is set to This is an example in which it is located closer to the shoulder portion S than the shoulder portion S.

Of course, in the case of the first embodiment described above, the tire center side end a of the reinforcing portion A, the radius of curvature R1 and the radius of curvature R2
Lp is set within the range of tp≧La/4, and in the case of the second embodiment, Lp is
It is set within the range of ≧La15.

From the results of experiments described below, this is true in the case of the first example.
That is, when the point of contact P between the radius of curvature R1 and the radius of curvature R2 of the tread is located closer to the tread center C than the tire center side end a of the reinforcing portion A, Lp is less than La/4. In the case of the second embodiment, the contact point P between the radius of curvature R1 and the radius of curvature R2 of the tread may break.
is located closer to the shoulder portion S than the tire center side end a of the reinforcing portion A, Lp is La15
If it is less than that, there is a risk that the steel cord constituting the belt will break, which will both impede the high-speed durability of this type of pneumatic radial tire.

Furthermore, as described above, the present invention allows the radius of curvature of the trailer T to be formed into a so-called two-stage radius consisting of the radius of curvature R1 forming the center portion of the tread and the radius of curvature R2 forming the left and right side portions. Therefore, it is possible to improve steering stability during high-speed driving, especially cornering characteristics.

Next, structural examples of the belt layer V shown in FIGS. 3(a) to 3(e) will be described.

FIG. 3(a) shows a structure similar to the first and second embodiments described above.

In Fig. 3), the tread side belt v1 is laminated on the tread side of the carcass side belt v2, and the left and right sides of the carcass side belt v2 are bent toward the tread center C side, and the left and right bent portions are reinforced as described above. This is an example of section A.

In FIG. 3(C), the tread side belt v1 is laminated on the tread side of the carcass side belt v2, and the tread center C side is stacked so as to cover both left and right sides of the carcass side belt V2 and both left and right sides of the tread side belt Vt. This is an example in which the left and right bent portions are respectively used as the above-mentioned reinforcing portions A.

FIG. 3(d) shows that the tread side belt v1 is laminated on the tread side of the carcass side belt v2, and one side of the shoulder part side of each of the belts v and v2 is bent toward the tread center C side, and This is an example in which each of the bent portions is the reinforcement portion A described above.

In Fig. 3+8), the tread side belt v1 is laminated on the tread/throat side of the carcass side belt v2, and the belt reinforcing layer K is arranged so as to cover both left and right sides of each of these belts v1 and v2 from the tread side. This is an example in which the left and right belt reinforcing layers K are the above-mentioned reinforcing portions A.

[Experiment example]

In this experimental example, the radius of curvature of the tread T is composed of a radius of curvature R1 forming the center portion of the tread T and a radius of curvature R2 forming the left and right side portions.
As in the second embodiment, a belt layer V using steel cord as a reinforcing cord and a tread side belt V are laminated on the tread side of the carcass side belt (2),
The left and right sides of this tread side belt v1 are bent toward the tread center C side, and the left and right bent portions are respectively reinforcing portions A.
Using a pneumatic radial tire with
The position of the contact point P of the radius of curvature R2 was varied variously, and the relationship between the position of the contact point P with respect to the position of the tire center side end a of the reinforcing part A and the bending of the steel cord constituting the belt was investigated. .

[Specifications of tires used in the experiment]

Tire size: 195/70RH14 (radial tire) Carcass: Two layers using polyester cord as reinforcement cord.

Belt layer: As described above.

[Experiment conditions]

Air pressure・・・・・・・・・2゜Okg/d,
.

Load・・・・・・・・・・・・4 per diamond
00 kg.

[Experiment method]

10% gravel roads, 90% paved roads (30% of which are curved roads)
The vehicle was driven on the same road for 60,000 hours at an average speed of 601 n/hr, and then the tire was cut open and the number of belt cords broken was measured.

The results of the experiment are shown in Figure 4.

Note that the vertical axis is an index, where 100 is the number of belt cord breaks in a conventional tire whose tread is formed with one radius of curvature.

In addition, on the horizontal axis, O indicates the case where the position of the tire center side end a of the reinforcing part A and the position of the contact point P between the radius of curvature R1 and the radius of curvature R2 coincides, and on the right side, When the position of the contact point P is located closer to the tread center C than the end a on the tire center side of the reinforcing part A, Lp is taken as (+), and the position of the contact point P is taken as (+) on the left side. , when the reinforcing portion A is located closer to the shoulder portion S than the tire center side end a, Lp is taken as (-).

From FIG. 4, when the contact point P between the radius of curvature R1 and the radius of curvature R2 of the tread is located closer to the tread center C than the tire center side end a of the reinforcement part A,
If Lp is less than La/4, there is a risk that the steel cord constituting the belt will break, and the position of the point of contact P between the radius of curvature R1 and the radius of curvature R2 of the dou red is set at the center of the tire in the reinforcing portion A. If it is located closer to the shoulder S than the side edge A, if Lp is less than La15, there is a risk that the steel cord that makes up the belt will break, and this will reduce the high-speed durability of this type of pneumatic radial tire. It is known to inhibit sex.
)1 Therefore, in the case of a pneumatic radial tire with a two-stage radius tread and reinforced belt layers on both left and right sides, (a) the above contact point P is lower than the end a on the tire center side of the reinforced part A; If it is located on the tread center C side,
p≧La/4, middle) The above contact point P is located at the tire center side end a of the reinforcing portion A.
If it is located closer to the shoulder part S than Lp≧L
It can be seen that if the tire is set to a15, it is possible to significantly prevent cord bending of the belt layer during running, and it is possible to improve the high-speed durability of a pneumatic radial tire with a two-stage tread radius.

〔Effect of the invention〕

Since the present invention is configured as described above, cord bending of the belt layer during running can be significantly prevented, and the high-speed durability of a pneumatic radial tire with a two-stage tread radius can be greatly improved. At the same time, it is possible to improve steering stability during driving, especially cornering characteristics.

[Brief explanation of the drawing]

FIG. 1 is an explanatory cross-sectional view showing the main parts of the first embodiment, FIG. 2 is an explanatory cross-sectional view showing the main parts of the second embodiment, and FIGS.
e) is an explanatory cross-sectional view showing a main part of an example of the structure of the belt layer, and FIG. 4 is a view showing the results of an experiment. - T...Tread, ■...Belt layer, A...Reinforcement part, a...'tire center side end of reinforcement part, P...Curvature radius Ri and curvature radius constituting the tread Contact point with R2 -□

Claims (1)

[Claims] The radius of curvature of the tread T is a radius of curvature R_1 forming the central part of the tread and a radius of curvature R_2 forming the left and right sides of the tread.
A pneumatic radial tire is constructed of a pneumatic radial tire in which both left and right sides of a belt layer V are reinforced using steel cords as reinforcing cords, and the reinforcing portion A that reinforces both left and right sides of the belt layer V is located at the center of the tire. The distance between the end a and the shoulder side end b is La, and the tire center side end a of the reinforcement part A, the radius of curvature R_1, and the radius of curvature R
If the distance between _2 and contact P is Lp, then this contact P
(a) The above contact point P is located at the tire center side end a of the reinforcing portion A.
If it is located closer to the tread center C than the tread center, Lp≧
La/4 (b) The above contact point P is located at the tire center side end a of the reinforcing portion A.
If it is located closer to the shoulder part S than Lp≧La
A pneumatic radial tire characterized by being positioned at /5.