JPH02293204A - Pneumatic tire for winter - Google Patents

Abstract

PURPOSE:To maintain a step fall quantity till the terminal period of abrasion so as to maintain the on-snow performance of a tire for heavy load such as a bus by defining and disposing a protrusion having a stepped surface which is grounded under the load between adjacent land parts by inclined thin grooves in such a way that the root width of the protrusion expands and that the width of the stepped surface is contracted. CONSTITUTION:A protrusion 4 is formed in a groove part 2 between adjacent land parts 3 along the periphery of a tread 1. This protrusion 4 has a stepped surface 4a, the stepped surface 4a is grounded under a load, and thin grooves 5 are provided adjacent to the land parts 3 to separate it from the land parts 3. In this case, the thin grooves 5 are formed inclined to expand a length l1 of the stepped surface 4a along the periphery of the tread 1 to the root of the protrusion to be a length l2. In this constitution, a step fall quantity can be maintained till the terminal period of abrasion, and the on-snow performance can be maintained for a long period.

Description

[Detailed Description of the Invention] (Industrial Application Field) It is an object of the present invention to propose a pneumatic tire for use on snowy roads, which improves the snow performance of pneumatic tires, especially pneumatic tires for heavy loads such as trucks and buses. It is something to do.

(Prior technology) In conventional winter running tires, grooves and land areas separated by the grooves are arranged on the entire surface of the tread to form an uneven pattern, and the area of the grooves is increased compared to general tires. Attempts have been made to lengthen the edges of the concave-convex pattern to improve the digging ability on snow and the drainage and drainage performance on ice.

(Problem to be Solved by the Invention) In order to obtain a larger driving force on a snow-covered road surface, especially on a compacted snow road surface, the shearing area of the snow column, that is, the tread By increasing the groove area, a certain effect can be obtained. However, braking performance, especially on icy roads, tends to deteriorate as the land area becomes smaller.

According to studies by the inventors, in addition to forming an uneven pattern, a large number of ridges having a step-down surface relative to the land surface are arranged in the grooves between adjacent land parts along the circumference of the tread. It has been discovered that by making the surface contact the ground under load, the edges of the uneven pattern that digs into the surface of the tire become longer, which helps the tire's performance on snow, and also increases the contact area and improves performance on ice.

In other words, for tires running on icy and snowy roads, driving force on snow is achieved by digging the land into the snow surface and shearing the snow pillars formed in the grooves, and control on ice by bringing more of the surface of the land into contact with the road surface. You can get power. In order to further improve on-ice performance, increasing the land surface area and increasing the contact area between the tread surface and the road surface can reduce ground contact pressure and reduce water surface melting due to pressure.

Note that if a ridge is provided in the groove, the area of the groove decreases and the driving performance on a snow-compacted road is reduced, but the amount of penetration of the land into the snow surface is extremely shallow, at most about IInII1, so it is difficult to drive on snow. No harm will occur.

If a ridge is provided in the tread groove that is one step lower than the tread surface, the ridge will also contact the ground on ice, increasing the contact area between the tread surface and the road surface and improving braking performance on ice.On the other hand, on compacted snow roads, the ground pressure of the ridge is low, does not dig into the snow surface and the shear area of the snow column does not decrease, so there is no reduction in driving performance on snow.

However, when driving on snow-removed or snow-free roads, the bumps created between the land sections and the level difference between the land sections are reduced due to land wear, leaving a problem in that stable performance cannot be maintained over a long period of time. .

In other words, in order for a ridge with a step surface relative to the land surface to be useful for increasing the shear force under the coining effect where the uneven pattern of the tre-nod is pushed into the compacted snow road surface, the step surface of the ridge relative to the land surface must be must be maintained until the tread is completely worn out. If the ridges in the above-mentioned technique were simply made to stand upright through the narrow gap between the groove bottom of the tread and the land area, they would easily bend and deform when they come into contact with a road surface free of snow, causing damage to the area around the tread. Even though the length of the circumference of the step surface imagined in is shorter than the length of the surface circumference of the land portion, wear of the step surface due to slip is difficult to occur, and wear of the land portion surface precedes.
As a result, after the stepped surface coincides with the worn surface, the wear progresses in substantially the same way on both surfaces, or the amount of stepped steps is reversed, making it impossible to maintain the above-mentioned step descending amount.

The purpose of this invention is to produce a similar wear rate on the step surface as on the land surface through the process of tire tread wear, thereby maintaining the amount of step descent until the end of wear and maintaining excellent snow performance. It is.

(Means for Solving the Problem) The present invention provides a pneumatic tire in which an uneven pattern is formed by disposing grooves and land areas separated by the grooves on the entire surface of the tread. In the groove between adjacent land parts, an anti-slip pattern is provided which has a step-down surface with respect to the surface of the land part and has a number of ridges that touch the ground under load, and a narrow strip that separates the ridges with respect to the land part. The gap slopes toward land in the direction of its depth,
A pneumatic tire for winter running, characterized in that the width along the inner periphery of the tread on the step surface of the ridge widens toward the base of the ridge, wherein It is further preferred that the facing edges are sharp and that the ridge has an extension that occupies a groove along the circumference of the tread, and that the extension is continuous along the circumference of the tread.

Now, Fig. 1 (a) and (b) show the protuberance according to the present invention in a cross section perpendicular to the axis of rotation of the tire, in which 1 is the tread, 2 is the groove forming the uneven pattern of the tread 1, and 3 is the same. This is the land area.

The land portion 3 sandwiches a ridge 4 provided inside the groove portion 2 separating adjacent grooves 2 along the periphery of the tread 1, and the ridge 4 has a step of preferably about 1 mm compared to the surface of the land portion 3. It has a step surface 4a that slopes down.

An example of the arrangement of the protuberances 4 in the plane of the tread 10 is shown in the second example.
The case of the block arrangement tread pattern shown in the figure is shown.

In this invention, the ridge 4 is formed around the tread 1 on the stepped surface 4a of the ridge 4, with the slit 5 that separates it from the land portion 3 forming an inclination toward the land portion 3 in the depth direction. Follow me! 1 toward the base of bulge 4
It shall be expanded to 2. In addition to the case where the shape of the ridge 4 appearing on the development plane of the tread 1 is a parallelogram as shown in FIG. 2, several cases are summarized in FIG. ) ~ (f
), the ridges 4-1 are spaced apart like stepping stones (third
(see Figure (a)), or a dongbone-like arrangement (see Figure 3 (b)) that extends slightly along the vertical groove 2 along the trend 1 of the ridge 4-2, or the ridges i3, 4.
-5 having an extended portion 6 extending from the vertical groove 2 along the periphery of the tread 1 toward the horizontal groove 2 (see Fig. 3).
c) (see (e)), or those in which the extensions 6 of the ridges 4-4, 4-6 are connected by joints 7 in vertical or horizontal grooves (see Figures 3(d) and (f)). ) and other minor changes are also possible.

The internal structure of the pneumatic tire is the same as that of a typical heavy-duty pneumatic radial tire, and is not shown here.

(Function) The bending rigidity of the bump 4 that contacts the road surface in the contact area of the tread 1 is increased, making it difficult for deformation to occur.

The length of the circumference of the protuberance 4, which does not easily undergo such deformation, has a circumferential length whose radius is the distance from the center of rotation of the tire on the stepped surface 4a, compared to the similar circumferential length of the land portion 3. Since the height is short depending on the amount of drop, the step surface slips by the circumferential difference during one rotation of the tire, which causes wear that constantly precedes the surface wear of the land portion 3 of the tread 1.
The step-down amount will be held constant during the wear life of the tire.

Therefore, when the tire enters the compacted snow road surface while the step surface 4a of the bump 4 is maintained, the snow surface is compacted by the uneven pattern coining, which increases the shear resistance, and improves the tire's on-snow performance. When the tire enters an icy road surface, the protrusions make contact with the ground, so increasing the contact area of the tire can provide high braking performance.

In the above description, in any case, the above-mentioned slit 5
Due to the inclination, the edge of the land portion 3 facing the bulge 4 has an acute angle, thereby increasing the gripping force on a snow-packed road surface.

(Example) Tire size TBR10. A test tire of OOR20 was prepared according to Fig. 1(a) and Fig. 2;
The conventional tire has a general block type tread pattern as shown in Figure (a), and the spacing between the blocks shown in Figures 4(b) and (C) has been increased by approximately 20%, so that there is no step between them and the land area. We conducted traction tests on snowy roads and braking on icy roads with a comparison tire with an array of small protrusions.

On a snowy road, the driving force was measured using a load cell, and on an icy road, a ball brake was applied from a speed of 20 km/h on ice at -5°C, and the braking distance was measured.

The results are shown in the table below.

From the above table, it is clear that the tire according to the present invention improves the driving performance on snow and the control performance on ice at the same time.

In addition, the step-down distance used in the compliance example in the above table is 2ffI[I
The results of measuring the step down distance after driving on a paved road for 20,000 temples for tires with a cross section as shown in Figure 5, which have a similar tread pattern with a step down distance of 2 mm. , the tire according to the present invention can maintain the initial step-down distance, but as shown in FIG.
It was confirmed that in a tire with a structure in which the bumps are simply placed upright within the groove, the step surface of the bumps is at the same level as the land area, and the step cannot be maintained until the tire's wear life.

(Effects of the Invention) According to the present invention, a preset level difference can be maintained regardless of tire tread wear, and stable running can be realized until the end of tire wear.

[Brief explanation of drawings]

FIGS. 1(a), (b) and 2 are explanatory diagrams of the structure of a tire according to the present invention, and FIGS. 3(a) and (b). (C), (d), (e
), (f) are diagrams showing other examples of the tire according to the present invention; FIGS. 4(a), (b), and (C) are diagrams showing the tread outline of the conventional tire used in the example. FIG. 1... Tread 2... Groove 3... Block 4... Protuberance 5... Slit
4a...Step surface 1+,! 2z ・・・Length of crossing Bridges Co., Ltd.

Claims (1)

[Scope of Claims] 1. In a pneumatic tire in which an uneven pattern is formed by disposing grooves and land parts separated by the grooves on the entire surface of the tread, the land parts adjacent to each other along the circumference of the tread In the groove between them, an anti-slip pattern is provided which has a step-down surface with respect to the land surface and has a number of ridges that touch the ground under load, and the gap separating the ridge from the land surface has a depth of A pneumatic pump for winter running, characterized in that the ridge slopes toward the land in the direction of the ridge, and the width along the inner circumference of the tread on the stepped surface of the ridge widens toward the base of the ridge. tire. 2. The pneumatic tire according to claim 1, wherein the edge facing the protuberance of the land portion has an acute angle. 3. The pneumatic tire according to claim 1 or 2, wherein the ridge has an extension portion occupying a groove along the circumference of the tread. 4. The pneumatic tire according to claim 3, wherein the extension portion is continuous along the circumference of the tread.