JPH01145202A - Pneumatic tyre - Google Patents

Abstract

PURPOSE:To reduce the partial abrasion of shoulder portions by respectively specifying the ratio of the radius of curvature of a surface contour in a tread to a tyre maximum value and the ratio of the wall thickness of the tread in a tyre equatorial surface to the wall thickness of the tread in a belt layer end. CONSTITUTION:A pneumatic tyre respectively has a carcass 2 whose both ends are turned up around a pair of right and left bead cores so as to be linked and a belt layer 3 outside the carcass 2 and a tread 4 outside the belt layer 3. In this case, the ratio of the radius of curvature TR of a surface contour in the tread 4 to a tyre maximum width SW is set within a range of 1.5-2.0. Also, the ratio of the wall thickness TC of the tread 4 in a tyre equatorial surface to the wall thickness TS of the tread 4 in the end portion P of the belt layer 3 is set within a range of 0.9-1.1. With this arrangement, the partial abrasion of shoulder portions is reduced on every condition in consideration of the difference of wheel alignment and the size of horizontal swing G and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pneumatic tire in which uneven wear is reduced by optimizing the radius of curvature of the tread surface and the tread wall pressure.

[Conventional technology]

Front tires of automobiles tend to suffer from shoulder drop wear on the outside or inside shoulders of the vehicle due to vehicle alignment, lateral forces during turns, road gradients, etc.For this reason, the tread radius of the tires has traditionally been reduced. By reducing the difference in outer diameter between a part of the tread center and a part of the tread shoulder, the ground contact pressure of the shoulder part is increased, and slippage between the shoulder part and the road surface is suppressed, thereby reducing uneven wear. However, although this method is very effective when the alignment (toe amount) of the vehicle is small, when the turning machine G is small, and when there is a lot of straight running, it is not effective when the amount of toe-in and toe-out is large and When the turning frequency is high and the turning machine G is large, it is difficult to suppress uneven wear on a part of the shoulder.

[Problems to be solved]

The present invention proposes a pneumatic tire having an appropriate tread radius that reduces uneven wear on a part of the shoulder under all conditions, taking into consideration the differences in wheel alignment, the size of the swing machine G, etc. .

[Technical means]

The present invention comprises a carcass 2 which is secured by folding both ends around a pair of left and right bead cores 1, a belt 713 disposed outside the carcass, and a tread 4 disposed further outside the belt layer 3. and the ratio TR/SW of the radius of curvature TR of the contour of the surface of the tread 4 and the maximum tire width SW.
The value of is 1.5 or more and 2.0 or less, and the value of the ratio TS/TC of the tread thickness TC at the tire equatorial plane to the tread thickness TS at the belt layer end P is 0.9 or more and This is a pneumatic tire characterized by a diameter of 1°1 or less.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a cross-sectional view of the tire of the present invention when it is filled with the normal internal pressure. The contour shape of the tire tread 4 surface is formed by a circular arc with a single radius of curvature TR, and the ratio TR/SW of the radius of curvature TR to the tire maximum width SW must be 1.5 to 2.0. It comes out.

Tires with the structure shown in FIG. 1 and the specifications shown in Table 1 were prototyped, and the relationships between abrasion properties and TR/SW and T S /T C were evaluated. First, the relationship between TR/SW and wear energy ratio (sillder part/crown part) is calculated based on slip angle and camber.
Figure 2 shows the results of measurements with different angles.If TR/SW is smaller than 1.5, the wear energy ratio at a slip angle and camber angle of 0 degrees decreases rapidly, and therefore the crown The amount of wear on the shoulder is greater than the amount of friction on the shoulder. On the other hand, TR/SW is 2.0
If it exceeds 2°, the wear energy ratio at a slip angle of 2° and a camber angle of 1° increases rapidly, and therefore the amount of wear on a portion of the shoulder becomes larger than the amount of friction on the crown portion. Therefore, within the slip angle and camber angle ranges described above, the abrasion energy of the shoulder and crown portions is approximately uniform when TR/SW is within the above range. In addition, since the rear tire has a slip angle and a camber angle of 0°,
On the other hand, the front tire has a predetermined slip angle and camber angle, so the wear tendency corresponds to the curve ■ in Figure 2.
! It shows a wear tendency corresponding to No. 11.

Next, Figure 3 shows the ratio TS/T of the tread thickness TC at the tire equatorial plane and the tread thickness TS at the belt layer end P.
It is a graph showing the relationship between C and the wear amount ratio (shielder part/crown part). Here, the belt layer end P is defined as the end of the belt ply in the radial direction.From figure 0, the wear ratio of the rear tire (slip angle 0°, camber angle 0°) is approximately regardless of the TS/TC value. constant, while for front tires (slip angle 2°, camber angle 1°) TS/TC
As the value of increases, the wear ratio gradually approaches 1.
Furthermore, Fig. 4 shows the relationship between the value of TS/TC and the buckling (degree of deformation) of the belt wi3, and it shows that when the value of TS/TC exceeds 1.1, the degree of deformation of the belt layer 3 suddenly increases. Become.

From these facts, it can be seen that a value of TS/TC in the range of 0.9 to 1.1 is most effective in preventing uneven wear and bankling of the belt li3.

In the present invention, the carcass cord is made of organic fiber cords such as polyester, rayon, aramid, nylon, etc. arranged at an angle of 70° to 90° with respect to the tire circumferential direction, while the belt M3 is made of steel cord, aramid, etc. It is constructed by laminating a plurality of plies in which highly elastic inorganic or organic fiber cords are arranged at an angle of 10 to 30 degrees with respect to the circumferential direction of the tire. Further, in the area above the bead core 1 surrounded by the carcass 2 and its folded part 2a, a bead epex 5 is provided which extends in the direction of the sidewall with gradually decreasing wall pressure.
This Bead Epex 5 has a JIS hardness of 75.
A range of 95° is preferable.

〔Effect of the invention〕

In the present invention, the contour shape of the tread surface has a specific radius of curvature as described above, so even under driving conditions where the slip angle and camber angle change, uniform wear at the tread crown and part of the tread shoulder is maintained. For example, as shown in Fig. 5, the contact surface of a tire having a slip angle of θ with respect to the traveling direction is divided into a sticky area X on the stepping side and a slipping area Y on the kicking side. In the invention, in the slip area Y, the amount of slip in the cylinder part and the crown part is approximately equal, and uneven wear does not occur. Since the ratio is set to the above-mentioned structure, the problem of buff clinging of the belt layer does not occur.

[Brief explanation of the drawing]

Figure 1 is a sectional view of the tire of the present invention, Figures 2 and 3 are the relationship between the wear energy ratio and TR/SW, the amount of wear and T
A diagram showing the relationship between R/SW, FIG. 4 is a graph showing the relationship between belt layer buckling and TS/TC, and FIG. 5 is a schematic diagram showing the ground contact surface when the tire is running. Patent Applicant Sumitomo Rubber Industries Co., Ltd. Agent Patent Attorney Tadashi Naemura Figure 2 Figure 4 [ Figure 3

Claims (1)

[Claims] (1) A carcass that is secured by folding both ends around a pair of left and right bead cores, a belt layer disposed outside the carcass, and a tread disposed further outside the belt layer, the tread Radius of curvature TR of surface contour
The value of the ratio TR/SW between the tire maximum width SW and the tire maximum width SW is 1.5 or more and 2.0 or less, and the ratio TS/TC between the tread thickness TC at the tire equatorial plane and the tread thickness TS at the end of the belt layer. A pneumatic tire characterized in that the value of is 0.9 or more and 1.1 or less.