JPH02267010A - Pneumatic tire having tread pattern with improved on-ice and on-snow performance - Google Patents

Abstract

PURPOSE:To improve the on-snow and on-ice performance of a tire having sipe-equipped ribs or blocks by adjusting the interval between or the depth of the sipes in ranges separated at a circumferential pitch corresponding to an arrangement pitch of a tread pattern so as to change the rigidity cyclically along the circumference. CONSTITUTION:For ribs 2b formed in the middle of a width center part C and a width end shoulder part E in segment ranges l separated at a circumferential pitch corresponding to an arrangement pitch of a treated pattern of a tire, the interval between sipes 3 is changed to change the rib rigidity cyclically along the tread circumference. In this case, it is possible to change the depth of the sipes instead. In this constitution, the number of the sipes can be increased without decreasing the rigidity, thereby the on-snow and on-ice performance can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) Tires used for running on snowy and/or icy roads, such as studless tires, are required to have high traction and braking performance on ice and snow.

This invention relates to pneumatic tires that are installed on particularly heavy vehicles such as trucks and buses in addition to general pneumatic tires for passenger cars, etc., and the present invention relates to pneumatic tires that are installed on particularly heavy vehicles such as trucks and buses. The aim is to make improvements and improvements.

(Prior Art) In order to improve the running performance of tires used for driving on snowy and/or icy roads, it is possible to reduce the edge component of the tire by providing a large number of sipes in the ridges that form part of the tread pattern. It has been well known in the past that it is effective to increase the

However, using a large number of sipes on the ridges on the tire tread surface not only reduces the rigidity of the tread and has a negative effect on traction on snowy roads.
As the bending deformation of the block increases, the contact area on the tread surface becomes smaller, and a large amount of water melts between the tire and the road surface due to a local pressure increase on the road surface. Deterioration of braking performance on icy roads is unavoidable.

Incidentally, Japanese Patent Laid-Open No. 56-21905 discloses a tire for winter running in which the protruding elements of the tire tread are divided by a number of mutually adjacent slits that are inclined with respect to the normal to the outer surface of the tire tread. However, even with such tires, deterioration in tire rigidity due to increased work and stiffness cannot be avoided, and it has not been possible to further improve driving performance.

(Problem B to be solved by the invention) It is possible to propose a pneumatic tire that can improve the performance on snow and ice by increasing the edge component of the tire without adversely affecting the preset rigidity of the tread surface. This is the object of this invention.

(Means for Solving the Problems) This invention has a groove disposed on a tread and ribs or blocks separated from each other by the groove, and the ribs or blocks are arranged at intervals from each other along the circumference of the tread. A pneumatic tire with a tread pattern divided into blades by sipes, wherein the ribs or protrusions are divided into segment areas with a circumferential pitch corresponding to the arrangement pitch of the tread pattern. This is a pneumatic tire having a tread pattern with improved performance on ice and snow, characterized by a sipe arrangement in which land portion stiffness changes periodically along the tread circumference due to a sequentially changing stiffness distribution.

Here, the above-mentioned sipe is defined as a narrow groove with a width of about 0.1 to 1.1 mm that closes within the ground contact surface of the tire.

In the present invention, it is preferable that the ribs on the tread surface of the tire configured as described above be located in a zone between the width center portion and the width end shoulder portion of the tread where the ground contact pressure is relatively high.

The segment region of the sipe arrangement is preferably structured such that groups of narrowly spaced sipes with the same cutting depth are unevenly distributed, or groups of sipes with gradually decreasing cutting depths are arranged.

Now, FIGS. 1(a) and 1(b) show the main parts of the tread part of the pneumatic tire according to the present invention for the left half of the tire. In the figures, 1 is a groove disposed on the tread T, and 2 is this groove 1. In this example, 2a indicates a rib, and 2b indicates a block, which are located in the middle zone between the width center C and the width end shoulder E of the tread T. The grooves 1 and the ridges 2 form a tread pattern.

In this invention, the ribs 2a have segment areas divided by a circumferential pitch corresponding to the arrangement pitch of the tread pattern of the tire! A large number of sipes 3 are arranged at appropriate intervals so that the rib rigidity changes periodically along the tread circumference due to the rigidity distribution that changes sequentially within the tread.

Figure 2 (a) and (b) show the segment area of the sipe array! Figures 3(a) and 3(b) show an example in which the rib rigidity is changed by unevenly distributing groups of narrowly spaced sipes 3 having the same cutting depth.
) show examples in which the rib rigidity is changed by gradually decreasing the cutting depth of the sipe 3.

In addition, although the above-mentioned pneumatic tire is exemplified in which the rib rigidity is changed, the sipes 3 can also be arranged so that the block rigidity is changed. Further, the internal structure of this tire is the same as that of a radial tire for boat fishing, and is not shown here.

(Function) In general, in order to improve driving force and braking performance when driving on snowy or icy roads, it is effective to increase the edge component of the tire by forming a large number of sipes on the ridges 2 of the trend surface. However, as mentioned above, excessive use of sipes leads to a decrease in the rigidity of the entire ridge, so there is a certain limit to the improvement in the performance of tires used on such road surfaces.

In this invention, in particular, the spacing and cutting depth of the sipes 3 are adjusted and arranged so that the rib 2a or the block stiffness changes periodically along the tread circumference, so the number of sipes is adjusted. Even if the sipes are increased, the resulting decrease in rigidity is compensated for by the area where the sipe spacing is large. Therefore, the stiffness of the ridge portion does not deteriorate over the entire circumference of the trend, and the traction and braking performance on snow and ice are advantageously improved by increasing the edge component.

(Example) A front-wheel drive 1800 cc tire with 2 passengers using sipe 175/70R13 tires in which the ribs 2a of the tread have the sipe arrangement as shown in FIGS. 1 and 2 above.
Driving performance was investigated by car on a mirror-like waterway surface with an air temperature of -7°C and a freezing temperature of -5°C, and on a compacted snow road surface.

In this investigation, the conventional tire shown in FIG. 4 was used as the reference tire. The results are shown in the following table, and it was confirmed that the tire according to the present invention exhibited higher performance than the tire used as a comparison tire, which was simply increased in sipes as shown in FIG.

Table (Effects of the Invention) Thus, according to the present invention, it is possible to increase the edge component and obtain high traction on snowy roads without causing deterioration of tire rigidity.

[Brief explanation of drawings]

Figures 1 (a) (b) to 3 (a) (b) are explanatory diagrams of the structure of a pneumatic tire according to the present invention, and Figures 4 (a) (b) and 5 (a) (b) are FIG. 2 is an enlarged view of the main parts of a conventional tire. 1... Groove 2... Ridge 2a... Rib 2b... Block 3... Sipe
! ...Segment area T...River Red Fig. 1 (a) Fig. 2 (a) (b) (a) Fig. 5

Claims (1)

[Claims] 1. A groove provided on the tread, and ribs or blocks spaced apart from each other by the groove, the ribs or blocks having sipes arranged at intervals along the circumference of the tread to form a blade. A pneumatic tire with a tread pattern, the ribs or blocks having a rigidity distribution that changes sequentially within segment areas that are divided by a circumferential pitch corresponding to the arrangement pitch of the tread pattern. A pneumatic tire having a tread pattern with improved performance on ice and snow, characterized by a sipe arrangement in which land part rigidity changes periodically along the tread circumference. 2. The pneumatic tire according to claim 1, wherein the ribs have a tread pattern located in an intermediate zone between the width center portion and the width end shoulder portions of the tread. 3. The pneumatic tire according to claim 1 or 2, wherein the segment area of the sipe arrangement has unevenly distributed groups of closely spaced sipes having the same cutting depth. 4. The pneumatic tire according to claim 1 or 2, wherein the segment area of the sipe arrangement consists of a group of sipes with a gradually decreasing cutting depth.