JPH03164305A - Radial tire for automobile - Google Patents

Abstract

PURPOSE:To improve hydroplaning resistance by dividing a tread section with the preset times of the tire maximum width into a center area and shoulder areas at the preset ratio with wide main grooves in the peripheral direction, forming lateral grooves with the preset inclination angle respectively, and setting the width of lateral grooves in shoulder areas wider toward the tread end section. CONSTITUTION:The width W of a tread section T is set to 0.6-0.7 with respect to the maximum width of a tire. Peripheral wide main grooves 1 and 1' are provided in parallel at an interval about 0.3-0.5 of the tread width W, and the tread section T is divided into a center area with the width (a) and shoulder areas with widths (b) and (b'). Peripheral grooves 4 with the average angle 65 deg. or above with respect to the equatorial plane O in shoulder areas. The width of lateral grooves 4 is gradually increased toward the tread end. Center lateral grooves are formed in the center area at the average angle smaller than the inclination angle of lateral grooves 4 in shoulder areas. The hydroplaning-resistant performance can be improved.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to the improvement of a radial tire for a passenger car, and more specifically to a passenger car with improved wet resistance performance during high-speed running, particularly hydroplaning resistance performance. This relates to radial tires.

(Conventional technology) Conventional radial tires for passenger cars have improved wet performance during high-speed driving, especially hydroplaning performance (due to high-speed driving, tires form on a water film on the road surface). In order to improve the phenomenon in which the friction coefficient between the road surface and the tread suddenly decreases due to the lifting of the tread, the tread has multiple linear grooves extending parallel to the circumferential direction and extending in a direction that intersects with these circumferential grooves. A large number of lateral grooves are formed.

The tread width of the above-mentioned conventional radial tires for passenger cars is usually 0.7 to 0.0 mm relative to the maximum width of the tire.
8 in width, and by arranging linear circumferential and lateral grooves at appropriate intervals and inclination angles on this tread, it was intended to improve drainage of the area in contact with the tread during high-speed running. .

(Problem to be Solved by the Invention) However, although the conventional radial tires for passenger cars described above can improve wet resistance performance and hydrobreening resistance performance to a certain extent by the linear circumferential grooves and lateral grooves, With the advancement of high-performance vehicles in recent years,
In particular, the current situation is that it is desired to further improve the hydrobraning resistance.

Therefore, an object of the present invention is to provide a radial tire for a passenger car that has improved wet resistance, particularly hydroplaning resistance, even more than ever before.

[Structure of the Invention] (Means for Solving the Problems) That is, the radial tire for a passenger car of the present invention has a pair of sidewalls and a tread portion extending between both sidewalls that are continuous in a toroidal manner, and a plurality of tread portions on the tread portion. In a tire having a land portion divided by a linear circumferential direction, a large number of lateral grooves and a group of grooves that intersect with the circumferential groove and the tread edge, the tread portion has a width of 0.6 with respect to the maximum width of the tire. A pair of wide main grooves are located in the part that separates the central region and both shoulder regions of the tread, and have a width of ~0.7, and are spaced apart from each other by approximately 0.3 to 0.5 of the tread width in the circumferential direction. The lateral groove extending to the shoulder area is inclined at an average angle of 65 degrees or more with respect to the equatorial plane of the tire, and has a groove width that increases from the axially inner position of the tire toward the tread edge, and has a groove width that increases from the axially inner position of the tire toward the tread edge. The transverse grooves in the region are characterized in that they have an average angle with respect to the equatorial plane that is smaller than the angle of inclination of said transverse grooves in the shoulder region.

(Function) The radial tire for a passenger car of the present invention has a pair of wide main grooves located in a portion that divides the central region and both shoulder regions of the tread as the main part of the linear circumferential groove, while extending into the shoulder region. The average inclination angle of the lateral force direction with respect to the equatorial plane of the tire is 65 degrees or more, and the groove width is expanded from the axially inner position of the tire toward the tread edge, so the drainage effect of the lateral grooves is improved. Furthermore, the tread width should be in the range of 0.6 to 0.7 with respect to the maximum width of the tire, and it is desirable that when the tire is mounted on a regular rim and the regular internal pressure and load are applied, In the contact area formed in a flat plate shape, the rectangular ratio defined as the ratio of the contact length at the 80% position of the tread width to the contact length at the center of the contact area is set in the range of 0.75 to 0.85. , the amount of water taken in when the tire is depressed is reduced, and the hydrobraning resistance can be further improved without sacrificing steering stability or uneven wear resistance.

(Example) Examples of the radial tire for passenger cars of the present invention will be described in detail below with reference to the drawings.

The drawing is a developed view of a tread portion of a radial tire for a passenger car according to the present invention.

In the drawings, parts other than the tread part are not shown, but the parts other than the shown parts, such as the crown part, sidewalls, radial carcass, and belt layer, have a well-known structure.

That is, a pair of sidewalls extending radially inward from both ends of a cylindrical crown section are connected in a toroidal manner, and the sidewalls and the crown section are made of organic fiber cords such as rayon or polyester that are substantially orthogonal to the equatorial plane. reinforced with a carcass of layers arranged in the direction of
The radially outer side is occupied by a tread portion that engages with the road surface.

Further, when the carcass has a so-called radial structure, a belt layer in which non-stretchable cords such as steel cords are arranged in an inclined manner is provided between the tread portion and the carcass.

In the drawings, the width W of the tread portion T of the radial tire for passenger cars of the present invention is 0.6 to 0.6 to the maximum width SW of the tire.
It has a width of 0.7 and is narrower than the conventional one.

In the present invention, the tire maximum width refers to the maximum width when filled with normal internal pressure, and the tread width refers to the ground contact width when the tire is pressurized with a normal load on a flat plate.

The tread portion T is provided with a pair of linear wide circumferential main grooves 1 and 1' at a distance of approximately 1/2 of the tread width W at a portion that separates the central region and both shoulder regions of the tread portion T. It is being That is, in the drawing, the interval a between the two circumferential main grooves 1, 1゛ (the width of the central region) and the tread width W are as follows:
a/W is approximately 0.3 to 0.5, which means that the widths b and b- of the shoulder region S are wider than in the past.

The groove width and groove depth of both circumferential main grooves 1 and 1' are the widest and deepest among the group, and the groove width is usually 7 to 10% of the tread width W, and the groove depth is 7%. It is set in the range of .0 to 9.0 open.

In addition to the two main circumferential grooves 1 and 1' mentioned above, for example, as shown in the figure, there is a central circumferential groove 2 with a relatively narrow groove width on the equatorial plane O of the tire, and a circumferential groove with an extremely narrow groove width in the shoulder area. It is also possible to provide auxiliary grooves 3, 3-.

On the other hand, a large number of lateral grooves that are inclined with respect to a line parallel to the tire's equator O are arranged in both the circumferential main full blooms, the circumferential main grooves, and the tread ends, and these full groups divide the land area. has been done.

Here, the shoulder lateral groove 4 extending in the shoulder area has an average angle (θ1) of 65 degrees or more with respect to the equatorial plane of the tire.
The width of the groove is formed in a trumpet shape that gradually increases from the position of both circumferential grooves 1 and 1' (inner position in the axial direction of the tire) toward the tread edge, thereby further enhancing the drainage effect. It is elevated.

Note that the shoulder instantaneous direction: a4 may have its base 4' extending to the tread center region as shown in the figure.

Further, the central lateral groove 5 extending in the central region of the tread is configured so that its average inclination angle (θ2) with respect to a line parallel to the equatorial plane is smaller than the inclination angle (θ1) of the shoulder lateral groove 4 in the shoulder region. It is located in

Here, the groove width of the central lateral groove 5 can be made almost the same as the groove width of the shoulder lateral groove 4, and the direction of the central lateral groove 5 is opposite to the direction of the shoulder lateral groove 4. It is also possible.

Furthermore, in the radial tire for passenger cars of the present invention,
It is desirable that the rectangularity ratio of the tire ground contact shape is in the range of 0.75 to 0.85, thereby further improving the hydrobraning resistance.

Here, the rectangular ratio of the tire contact shape refers to the squareness ratio of the tire contact shape when the tire is mounted on a regular rim and the contact surface is shaped like a ζF plate (the contact contour shown in the drawing) when the tire is mounted on a regular rim and the internal pressure and load are applied. It is defined as the ratio of the contact length L2 at 80% of the tread width to the contact length L1 at the center of the contact surface, and this rectangular ratio is defined by making the radius of curvature of the tread surface in the transverse direction relatively small, that is, at the tread edge. This can be obtained by adjusting the drop height of the cross-sectional profile.

As explained above, the radial tire for a passenger car of the present invention having a tread structure has excellent wet resistance, particularly hydrobraning resistance, and exhibits ideal drainage performance during high-speed running.

Next, the structure and effects of the radial tire for passenger cars of the present invention will be explained in more detail using test examples.

(Test example) Tire size: 175/70R13 82T, rim used: 5-1/2JX13, air pressure used: 2.0 kg
/ cd, the tread structure of the present invention described above was formed on the tread portion of a radial tire, and this tire was evaluated.

Note that other structures such as the radial carcass and belt layer of the tire and manufacturing conditions were similar to those of conventional tires, so details will be omitted.

That is, in Fig. 1, tread width W: 115 open, circumferential main groove width = 9, depth 2: 8.0 mm, groove width of central circumferential groove 2: 6 axes, depth: 8.0 mm, groove width of circumferential auxiliary groove 3: 2 mm, depth 26. Omm, a/W
:0. 5, W/SW 2 O. 6
5. Rectangular ratio: O. SO, groove width 5.5 mm in one corner direction of cylinder 3, depth: 8.0, θ1: 70 degrees, groove width of central lateral groove 5: 3.5 mm, depth +6.5 mm, θ2 :
A tire of the present invention was obtained by forming a tread portion at an angle of 45 degrees.

Regarding this tire of the present invention, the critical speed at which hydrobreening occurs when running at high speed on a test wet road surface with a water depth of 10 mm was determined to be 82.4 m.

On the other hand, for comparison, a/W: 0.65, W/SW: 0
．． 73, rectangular ratio: O. 9O, the average inclination angle θ1 of the shoulder direction 4: 45 degrees, and the average inclination angle θ2 of the central lateral groove 5: 67 degrees.The basic structure of ζ't was the same as above to obtain a comparative tire.

Regarding this comparative tire, the critical speed for hydroplaning was determined in the same manner as above, and it was found to be 73.4 km, which is inferior to the tire of the present invention.

[Effects of the Invention] As described above, the tire of the present invention can significantly improve hydroplaning resistance performance compared to conventional tires.

[Brief explanation of the drawing]

The drawing is a developed view of a tread portion of a radial tire for a passenger car according to the present invention. T...Tread section 1, 1-...
Straight wide circumferential main groove 2...Central circumferential groove 3, 3''...Circumferential auxiliary groove 4...Shoulder full circumferential groove 5...・・・
...Central lateral groove 0...Equatorial plane W...Tread width SW...Tire maximum width

Claims (2)

[Claims] (1) A pair of sidewalls and a tread section extending between both sidewalls are connected in a toroidal manner, and the tread section has a plurality of linear circumferential grooves, a large number of lateral grooves that intersect with the circumferential grooves and the tread ends, and In a tire having a land portion divided by groove groups, the tread portion has a width of 0.6 to 0.7 with respect to the tire maximum width, and the circumferential groove has a width of approximately 0.3 to 0.7 with respect to the maximum width of the tire. The tread includes a pair of wide main grooves located in the part that separates the central region of the tread and both shoulder regions with an interval of 0.5, and the lateral grooves extending to the shoulder regions are at an average angle of 65 degrees or more with respect to the equatorial plane of the tire. It has a groove width that is inclined and expands from the axially inner position of the tire toward the tread edge, and the lateral grooves in the central region of the tread are on average smaller than the inclination angle of the lateral grooves in the shoulder region with respect to the equatorial plane. A radial tire for a passenger car characterized by having an angle. (2) In the contact area formed in a flat plate shape when the tire is mounted on a regular rim and the regular internal pressure and load are applied, 80% of the tread width to the contact length at the center of the contact area
If the rectangular ratio defined by the ratio of the contact length at the position is 0.
Claim characterized in that it is in the range of 75 to 0.85 (
The radial tire for passenger cars described in 1).