Resilient tires and wheels – Tires – resilient – Anti-skid devices
Patent
1985-11-08
1988-04-12
Ball, Michael
Resilient tires and wheels
Tires, resilient
Anti-skid devices
B60C 1106
Patent
active
047367822
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a pneumatic tire. More particularly, the present invention relates to a ribbed pneumatic tire for high speed driving, which is used for a heavy-load vehicle such as a heavy truck, a bus or a light truck.
BACKGROUND ART
In the field of ribbed pneumatic tires for high-speed driving in heavy-load vehicles, trials have been carried out to improve braking capacity on a wet road, that is, the wet braking capacity, without reduction of the abrasion resistance by making complex tread patterns.
These trials are roughly divided into the following two means.
(1) Many continuous zigzag grooves extending in the circumferential direction of a tire are formed on the tread surface of the tire while leaving spaces in the lateral direction.
(2) The point height Hm of the many zigzag grooves formed on the tread surface of a tire is increased.
However, these means involve problems as described below.
(a) In the above-mentioned means (1), the braking effect depends on the number and width of the zigzag grooves arranged on the tread surface of the tire. Accordingly, if many grooves having a broad width are arranged in a limited ground-contacting region to improve the braking effect, the actual ground-contacting area of the tire T is decreased and the abrasion resistance is reduced. Furthermore, if the groove width is increased, abnormal abrasion, known as "rib punching", occurs and the abrasion resistance of the tire is drastically reduced.
(b) The above-mentioned means (2) is advantageous over the means (1) in that the braking effect can be improved without increasing the number and width of the grooves. However, since the width of ribs Rs formed on the side of the shoulder portion is greatly changed with the increase of the point height Hm of the grooves, abnormal abrasion, known as "wavy abrasion", occurs, also, in the means (2), the abrasion resistance of the tire is drastically reduced. Moreover, the riding comfort and driving stability are reduced.
DISCLOSURE OF THE INVENTION
It is a primary object of the present invention to provide a pneumatic tire in which the wet braking capacity is improved without reduction of the abrasion resistance.
More specifically, in accordance with the present invention, there is provided a pneumatic tire having at least 3 zigzag grooves continuous in the circumferential direction of the tire, which are formed on the tread surface of the tire while leaving spaces in the lateral direction, wherein, in the zigzag groove located on the side of the shoulder portion, the ratio of the point height Hs to the tread width W is in the range of from 2% to 4%, and in the zigzag groove located on the side of the tread center portion, the ratio of the point height Hc to the tread width W is in the range of from 6% to 10%.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a development diagram of the tread pattern of a conventional pneumatic tire having many zigzag grooves formed on the tread surface;
FIG. 2 is a development diagram of the tread pattern of a conventional pneumatic tire having zigzag grooves having a large point height, which are formed on the tread surface of the tire;
FIG. 3A is a development diagram of the pattern showing abnormal abrasion (especially rib punching) caused in the conventional pneumatic tire shown in FIG. 1;
FIG. 3B is a diagram illustrating the section (main part only) of a part of the tire of FIG. 3A seen along the line A--A in FIG. 3A;
FIG. 4A is a graph illustrating the relationship between the ratio Wm/W (%) of the groove width Wm of the tire to the tread width W and the abrasion quantity d (mm) of rib punching caused in the rib Rc on the side of the center portion Tc of the tire T;
FIG. 4B is a graph illustrating the relationship between the ratio Wm/W (%) of the groove width Wm of the tire to the tread width W and the wet braking capacity (index);
FIG. 5A is a development diagram of a pattern showing abnormal abrasion (especially wavy abrasion) caused in the conventional pneumatic tire shown in FIG. 2;
FIG. 5B is a
REFERENCES:
patent: 3450182 (1969-06-01), Verdier
patent: 3831654 (1974-08-01), Boileau
patent: 4122879 (1978-10-01), Takigawa et al.
Ball Michael
The Yokohama Rubber Co. Ltd.
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