JPH07223407A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To reduce conicity so as to improve straight advance stability by shifting the width center of a belt for reinforcing a tread part to the larger negative rate side from a tire equatorial face. CONSTITUTION:A pneumatic tire 1, in which a circumference directional groove 2a is formed in the left side area L of a tire equatorial face E while circumference directional grooves 2b, 2c are formed in a right side area R and different negative rates are provided on a tread part surface, is formed. A belt 8 is formed by laminating plys, in which steel cords arranged at angles of inclination of 24 deg. to the tire equatorial face E are coated with rubber, so that the cords are crossed by each other while putting the tire equatorial face E between them, and a belt reinforcing layer 9 covering the whole width of the belt 8 and a shoulder part reinforcing layer 10 are arranged. The belt width center B is not matched with the tire equatorial face E but is shifted to the right side area R with a larger negative rate. Therefore, conicity working on the basis of a difference in tread reaction force because of different negative rates can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire, and more particularly to a tire in which the negative ratio of the tread surface is different between the left and right sides of the tire equatorial plane.

[0002]

BACKGROUND ART Pneumatic radial tires usually have grooves on the tread surface to separate land portions. In recent years, the drainage of tires has been highlighted due to the speeding up of vehicles, and various proposals have been made on the pattern of the tread surface (especially in terms of the arrangement of grooves) as a method of improving this.

As one of them, the negative ratio of the tread surface is made to be different from each other across the tire equatorial plane so that the negative ratio of the inner tread surface when the vehicle is mounted is made larger than the negative ratio of the outer tread surface when the vehicle is mounted. There is a technique. As a result, the ground pressure of the inner portion when the vehicle is mounted becomes low especially during turning, so that the drainage performance is deteriorated by increasing the negative ratio.

[0004]

However, if the negative ratios are made different from each other across the tire equatorial plane as described above, the ground contact reaction force from the road surface is naturally small in the larger negative ratio, and the negative ratio However, the smaller one becomes, the larger it becomes. Therefore, even if the tire tries to go straight on the road surface, the difference in the ground contact reaction force always causes conicity, which is a factor that hinders straight running stability.

Therefore, an object of the present invention is to reduce the conicity in tires having different negative ratios as described above and improve straight running stability.

[0006]

SUMMARY OF THE INVENTION The present invention provides a pair of bead portions, sidewall portions extending radially outward from the bead portions, and a tread portion extending in a cylindrical shape across these sidewall portions. Having a belt inside to reinforce the tread portion, the tread portion surface has a plurality of grooves, further in the pneumatic radial tire different left and right negative ratio across the tire equatorial plane,
The pneumatic radial tire is characterized in that the center of width of the belt is deviated from the tire equatorial plane toward the larger negative ratio. Incidentally, the negative ratio is the ratio of the area of the groove portion to the total area of the tread,
Usually expressed as a percentage.

Here, it is preferable that the width center of the belt is displaced from the equatorial plane of the tire toward the larger negative ratio within a range of 1.5 mm or less.

[0008]

As described above, when the negative ratio of the tread surface is different between the left and right sides of the equatorial plane of the tire, the ground reaction force is also different when the tire rolls on the ground. However, in the present invention, the width center of the belt deviates from the tire equatorial plane to the side having a larger negative ratio, so that the area having a large negative ratio is reinforced as compared with the area having a small negative ratio as long as it is a belt. Therefore, it is possible to cancel the difference in the ground reaction force caused by the different negative ratios on the tread surface.

However, even if the negative ratios are made different, the negative ratios cannot be made extremely different in order to ensure the overall performance of the tire, and the ratio of the smaller negative ratio to the ratio of the larger negative ratio is higher. It can be suppressed to about 80% at best. Under this condition, also in the present invention, it is preferable that the width center of the belt is displaced from the equatorial plane of the tire by not more than 1.5 mm. Further, if the belt is further displaced, variations in tire manufacturing increase, which is not preferable.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. Shown in FIG. 1 is a size 2 to which the present invention applies.
The pattern of the pneumatic radial tire 1 of 35 / 45ZR17 is shown. As is apparent from FIG. 1, the left and right tread surfaces having the tire equatorial plane E had an asymmetric pattern.

One circumferential groove 2a is provided in the left side region L of the tire equatorial plane E (this side is the outside when the vehicle is mounted), and one circumferential groove 2b is provided in the right side region R (the inside is the side when the vehicle is installed). And 2c are arranged. Then, an inclined groove 3 extends from a position slightly leftward from the circumferential groove 2a toward the widthwise end SL of the tread, and the inclined groove 3 is branched from the middle into inclined grooves 3a and 3b. The tread surface on the left side of the circumferential groove 2a has a one-sided comb shape as a whole. On the other hand, the inclined groove 4 extends toward the widthwise end SR of the tread from a position slightly separated to the right of the circumferential groove 2a, and this inclined groove also branches from the middle to become inclined grooves 4a and 4b. But these inclined grooves 4a
, 4b intersect the circumferential grooves 2b, 2c, and thus partition a large number of blocks. In the pattern thus obtained, the negative ratio in the left side region L of the tire equatorial plane E was 34%, and the negative ratio in the right side region R was 42%. That is, the right side region R has a large negative ratio, and the ground reaction force at the time of grounding should be smaller in the right side region R than in the left side region L if only the negative ratio is focused on.

FIG. 2 is a sectional view of the meridian of the tread portion of the above embodiment. Shown here is a carcass 7 consisting of two plies rubber-coated with polyester cords arranged substantially in the radial direction of the tire, and rubber-coated steel cords arranged at an inclination angle of 24 ° with respect to the tire equatorial plane. A belt 8 consisting of two plies that are laminated so that the cords cross each other with the tire equatorial plane in between, and a ribbon made of several nylon cords covered with rubber to cover the entire width of the belt 8 A belt reinforcing layer 9 formed by winding from one end to the other in the width direction with a different lead angle, and a narrow shoulder reinforcing layer 10 formed similarly to the belt reinforcing layer 9 but reinforcing only the shoulder portion. . Here, the width center B of the belt does not coincide with the tire equatorial plane E, and is displaced to the right side region R having a large negative ratio. This amount of displacement is preferably 1.5 mm or less.

For comparison, a conventional example having the same size and structure as that of the above-mentioned embodiment was prepared except that the width center B of the belt coincides with the tire equatorial plane E. In the embodiment, the deviation amount between the belt width center B and the tire equatorial plane E is 1.0 mm.

These test examples were assembled on a size 8 1 / 2JJ rim, filled with an internal pressure of 2.0 kgf / cm ² , set on a uniformity machine, and a load of 500 kgf was applied to measure the conicity. The measurement of six test samples each showed an average value of 1.7 kgf in the example, and an average value of 7.5 kgf in the conventional example, demonstrating that conicity was reduced in the examples.

[0015]

According to the present invention, it is possible to reduce the conicity in a tire in which the left and right negative ratios are different from each other across the tire equatorial plane.

[Brief description of drawings]

FIG. 1 is a diagram showing a pattern of a pneumatic radial tire according to the present invention.

FIG. 2 is a meridian sectional view of the tread portion of the pneumatic radial tire according to the present invention.

[Simple explanation of symbols]

 1 Pneumatic radial tire 2a, 2b, 2c Circumferential groove 3,4 Inclined groove 7 Carcass 8 Belt 9 Belt reinforcement layer 10 Shoulder reinforcement layer E Tire equatorial plane L Tire left area R Tire right area SL, SR Tread width Direction edge B Belt width center

Claims (2)

[Claims] 1. A tread portion reinforcement, comprising a pair of bead portions, sidewall portions each extending radially outward from the bead portion, and a tread portion extending in a cylindrical shape across these sidewall portions. While arranging the belt inside, the tread portion surface has a plurality of grooves, further in the pneumatic radial tires with different left and right negative ratio across the tire equatorial plane, the width center of the belt, from the tire equatorial plane A pneumatic radial tire characterized by being shifted toward the larger negative ratio. 2. The pneumatic radial tire according to claim 1, wherein the width center of the belt is displaced from the equatorial plane of the tire toward the larger negative ratio within a range of 1.5 mm or less.