JPS582846B2 - Tire tread pattern - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in the tread pattern of a tire, particularly a tread pattern of a passenger car tire, which has excellent drainage properties.

Conventionally, the tread of passenger car tires is of the so-called rib type, which consists of three or four circumferential grooves arranged in a zigzag pattern in the circumferential direction of the tire and circumferential ribs divided by these circumferential grooves. A so-called block type is known, which consists of a group of blocks further divided by a large number of lateral grooves extending in the direction of the rotational axis of the tire in addition to the above-mentioned circumferential grooves.

By the way, the cross-sectional shape of this type of tire has traditionally had a ratio of cross-sectional height to cross-sectional width of the tire of around 0.9.
There is a growing tendency for tire widths to become flattened to K0.8 or less, and tread widths are also becoming wider as tire widths increase.

With tires that have a flat tire shape and a wide tread width, the tread contact shape during driving is vertical, with the contact length being longer than the contact width with conventional tires. However, they have a rather wide shape, and if conventional glue-type or block-type patterns were applied to them, it became difficult to fully demonstrate tire performance, especially in rainy weather.

In other words, when conventional patterns are applied to flat tires, drainage performance during rain is improved by grooves that are relatively shortened in the vertical direction, but due to the rib or block arrangement based on the vertical direction (circumferential direction), The basic characteristics of a flat tire whose primary purpose is to improve high-speed performance, mainly on dry roads, by reducing the coefficient of friction between it and the road surface, which affects the longitudinal force generated by driving and braking. However, if the blocks are arranged so as to block the grooves that run straight in the circumferential direction of the tire, the frictional force in the longitudinal direction on dry roads will be improved, but on the other hand, the drainage in the contact patch on wet roads will be improved. Due to the wide ground contact width that accompanies the increase in tread width, the tire's surface contact ratio decreases significantly, making the tire susceptible to slipping when driving in the rain.

In addition to such a tread having grooves arranged mainly in the circumferential direction and/or width direction of the tire, there are other tire treads such as those disclosed in U.S. Pat. Nos. 3,705,613 and 3,674,077. A tread has been proposed that includes a large number of diagonally arranged grooves and blocks or ribs separated by these grooves.

Of these, the former has diagonal grooves that extend across the tread while increasing in width from one end of the tread to the other, while the latter has diagonal grooves that cross the center of the tread (only in one direction). ), and in one sense it can be said to be a tread that has improved the problems of the conventional tread.

According to experiments conducted by the inventors, the coefficient of friction during rainy weather decreases in a relatively low speed range of less than Lookkm/h in inverse proportion to the speed, albeit at a relatively gentle slope.

When the speed reaches a high speed range exceeding 100km/h, a wedge-shaped film of water begins to enter between the tread and the road surface within the contact patch.
The initial phenomenon of hydroplaning occurs, which causes a sudden drop in the coefficient of friction as the effective ground contact area decreases.

On the other hand, in such high-speed ranges, the tire's ground pressure distribution, which was relatively uniform across both ends of the tread, changes to a significantly higher convex distribution in the center of the tread due to centrifugal force caused by tire rotation. By utilizing the ground pressure that increases at the center, the water captured within the tread surface is guided diagonally from the center of the tread toward the ground contact edge at a predetermined angle, and is discharged, thereby preventing an abnormal decrease in the coefficient of friction. It has been found that it is effective in preventing water film from entering the contact area.

This invention was made based on such knowledge.

This will be explained below using the drawings.

FIG. 1 is a plan view of a tire tread showing one embodiment of the present invention.

Reference numeral 1 in the figure indicates a tread, and this tread includes main grooves 2 and 3, and a diamond-shaped block 4 divided by these main grooves,
Consists of 5 and 6.

The angle α between the center line j-J of the upward-right groove 2 and the center line l-l of the groove 3 with respect to the center line O-0 is 30°.
~50°.

The groove width gradually increases from the tread circumferential center line position toward both ends, so in this example, the width of the block is also 4.
It has decreased to 5 or 6.

With respect to the groove widths a and b of grooves 2 and 3, the corresponding groove widths a/ and b' at the tread edge are 1 at the tread surface position.
．． A range of 5 to 2.5 times is preferred.

The cross-sectional shape of the groove can be U-shaped, V-shaped, etc., and in addition to being suitable for tilting, thin cuts known as sipes can be added to the periphery or center of each block as appropriate.

FIG. 2 is a plan view of a tire tread showing another embodiment.

In this embodiment, the main grooves 7 and 8 that intersect in different directions meander toward the tread ends E-E and E'-E' along a broken line, and merge into the end main grooves 9 and 10.

The portion divided by these grooves forms a relatively large U-shaped block 16 by crank-shaped block blocks 11, 12, 13 and auxiliary grooves 14, 15.

The auxiliary grooves 14,15 begin on a circumferential line that is substantially the same as the circumferential line passing through the position where the main grooves 7, 8 join the end main grooves 9, 10 and open only to the sides of the tire.

This auxiliary groove adjusts the excessive area of the outer surface of the relatively large block 16, and makes the ratio of the area of the outer surface of the block portion to the area of the groove portion larger at the center than at both ends.

When the main grooves 7 and 8 extend in a broken line pattern like this, the line m
and lines j-j, l-l passing through the middle of the meandering amplitude of the center line of the main groove portion indicated by n (in this example, passing through the origin C of the main groove on the center line O-0) and the tread. Let angles α and β formed with the circumferential center line 0-0 be the inclination angle of the main groove.

In this invention, when the inclined main groove is arranged in a broken line shape,
The maximum amplitude g does not exceed 10% of the tread width W.

In the embodiment shown in Fig. 1, the grooves and blocks are arranged symmetrically with respect to the center line O-0, but in the embodiment shown in Fig. 2, the arrangement is not symmetrical with respect to the center line. .

However, each block as an element constituting the tread is arranged in the same shape in both the left and right regions, so that the surface area of the block that contacts the road surface, that is, the effective ground contact area, is substantially equal between the left and right regions. In that sense, it can be said that the left and right sides are substantially symmetrical.

Further, in the illustrated example, the inclined main grooves 2, 3 and 7, 8 communicate with each other in the left and right directions across the center line O-0, but they may be discontinuous in the left and right directions as long as the purpose is not impaired.

The tread of the present invention constructed in this way has an inclined main groove extending in a mesh shape with the groove width increasing from the center toward both ends, so that the main groove opens around the ground surface. Since rainwater can be collected and drained, the drainage effect during rainy weather is high. Also, due to the shape and arrangement of the grooves, the area of the protrusions on the tread surface, that is, the area of the outer surface of the block portion, is smaller than the area of the grooves. By making the ratio larger in the center than at both ends, the convex distribution of the tire's ground pressure in the center, which is high in the high speed range, becomes a gentler distribution, which improves wear in the center. Even when applied to a tire with a flat cross-sectional shape and a wide tread width, the driving and braking characteristics of the tire can be effectively maintained due to the action of the blocks divided by the inclined main grooves.

[Brief explanation of the drawing]

FIGS. 1 and 2 are developed views of a tread showing an embodiment of the present invention. 1... Tread, 2, 3, 7, 8...
Main groove, 4, 5, 6, 11, 12, 13, 16...
・Block group.

Claims (1)

[Scope of Claims] 1. In a flat tire in which the ratio of the cross-sectional height to the cross-sectional width of the tire is 0.8 or less, a cross-sectional pattern extending from the circumferential center line of the tread in a diagonal pattern toward the tread edge. It consists of a main groove and a block group divided by these main grooves, and the block group is arranged almost symmetrically with respect to the circumferential center line of the tread, and the main groove forming the above-mentioned mesh pattern is located at the circumferential center of the tread. The main groove intersects with the line at an average inclination angle of 30° to 50°, and the groove width of the main groove becomes wider from the circumferential center line position of the tread to both ends, and is compared with the groove width on the circumferential center line. A tire tread pattern in which the groove width is 1.5 to 2.5 times as wide at both ends. 2. The tread pattern according to claim 1, wherein the main groove extends meanderingly in a polyline pattern that goes in and out over a range not exceeding 10% of the tread width with respect to the diagonal direction toward the tread end. 3. The tread pattern according to claim 1, wherein the main groove communicates from one end of the tread to the other end. 4. According to claim 2, the tread has auxiliary grooves that open only to the sides of the tread to form a U-shape, and blocks that are relatively large compared to the blocks in the center of the tread are arranged in the circumferential direction. tread pattern.