JPS61271104A - Vehicle pneumatic radial tire - Google Patents

Abstract

PURPOSE:To reduce noise due to the pattern of a radial tire during running of a vehicle, by forming a plurality of sub-grooves connecting among a plurality of straight main grooves at two kinds of different angles with respect to the circumferential direction of the tire, and by setting these angles in a specified range. CONSTITUTION:A plurality of annular straight main grooves 11-13, 11'-13' are formed in the tread surface of a tire in the circumferential direction E-E'. Further, these straight main grooves 11 and 11', 12 and 12', 13 and 13' are formed in symmetrical with each other with respect to the circumferential center line (m) of the tire, respectively. Further, there are formed sub-grooves 14 extending from the center section of the tread surface of the tire to the widthwise ground contact ends 15 of the tire. In this arrangement, the sub- grooves 14 are arranged at different angles theta1, theta2 alternately, with respect to the circumferential direction of the tire, and are connected to the straight main grooves 11-13, 11'-13. Further, the angles theta1, theta2 of the sub-grooves 14 are set in a range such as, 30 deg.<theta1, theta2<60 deg.. With this arrangement, noise due to the pattern of a tire may be reduced upon running of a vehicle without the wet skid performance of the tire being lowered.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a pneumatic radial tire for passenger cars that reduces noise (pattern noise) during running of the tire without impairing wet skid performance.

[Prior art]

BACKGROUND ART In recent years, as vehicles, especially passenger cars, have become more sophisticated, the structure of tires has changed from bias tires to radial tires, and the shape of tires has become flatter. By flattening the tire, the contact width of the tire tread becomes wider,
This increases cornering force and improves vehicle handling stability. However, as the tire becomes flatter, the contact length of the tire tends to gradually become shorter, resulting in a decrease in wet skid performance.

Conventionally, as a measure to prevent the deterioration of wet skid performance, the tread pattern formed on the tire tread surface was changed from a point-symmetrical pattern to a line-symmetrical pattern, thereby giving the tread pattern directionality and further limiting the direction of rotation of the tire. By doing so, the wet skid performance was improved.

However, giving direction to the tread pattern
Because the rigidity of the tire's ground contact area is increased (changed), it has been difficult to reduce pattern noise when the tire is running.

[Purpose of the invention]

The present invention is a pneumatic radial tire for passenger cars that has a directional tread pattern, and has the advantage of reducing pattern noise when running the tire without reducing its advantage of wet skid performance. The purpose is to provide

[Structure of the invention]

For this reason, the present invention provides a tire tread with a plurality of straight main grooves arranged in an annular manner in the tire circumferential direction symmetrically with respect to the tire circumferential center line, and extends these straight main grooves from the center of the tire tread to the tire widthwise ground contact edge. A tire that is connected to each other by a plurality of sub-grooves extending in the direction of the tire, the angle θ that each of the sub-grooves makes with the tire circumferential direction is two or more different angles, and these angles θ are 30° and θ<60 The gist of this invention is a pneumatic radial tire for passenger cars, which is characterized by a

Hereinafter, the configuration of the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a half-sectional perspective view of an example of a pneumatic radial tire for a passenger car according to the present invention. In this figure, a carcass layer 4 whose cord angle with respect to the tire circumferential direction EE' is substantially 90' is arranged between a pair of left and right bead portions 1.1.

Further, two belt layers 5 are arranged on the carcass layer 4 in the tread portion 3 over almost the entire area of the trend portion 3. Further, on this belt layer 5, a belt cover layer 6 is disposed over almost the entire area of the trend section 3. This belt cover layer 6 is provided to improve high-speed durability and does not necessarily need to be provided. In addition, 2
7 represents a sidewall portion, 7 represents a shoulder portion, and 8 represents a tire tread surface.

The carcass layer 4 has at least one layer, and its cord is made of nylon, polyester, aramid (
Chemical fibers such as aromatic polyamide fibers are generally used.

The cords constituting the belt layer 5 may be those commonly used for tires, preferably cords made of nylon or polyester, and cords made of steel, aramid, rayon, etc. can be used.

Nylon is generally used as the cord for the belt cover layer 6. The cord angle is substantially O' (parallel) to the tire circumferential direction EE''.

In the present invention, a tread pattern as shown in FIG. 2 is formed on the tire tread surface 8 of the pneumatic radial tire shown in FIG.

FIG. 2 is a plan view showing an example of the tire tread of the pneumatic radial tire for passenger cars of the present invention. In this FIG. 2, m indicates the center line of the tire tread in the tire circumferential direction,
11.12.13.11'.

12° and 13° are straight main grooves provided annularly in the tire circumferential direction EE''. Straight main grooves 11 and 11°,
12 and 12' and 13 and 13° are symmetrical with respect to the tire circumferential center line m, respectively. 14 are sub-grooves extending from the center of the tire tread to the ground contact edge 15 in the width direction of the tire, and these sub-grooves 14 are arranged alternately at different angles θ1 and '2 with respect to the tire circumferential direction, and the straight main grooves 11. 12.13.11° 12' and 13' are connected to each other. a, b, c.

d, e, f are blocks formed by these straight main grooves and sub-grooves, respectively. g represents center lip.

The tire having the tread pattern shown in FIG. 2 satisfies the following requirements (1) to (4).

(1) A plurality of straight main grooves 11.12.13.11'1 are provided on the tire tread surface 8 symmetrically about the tire circumferential center line m.
2' and 13'' are provided in an annular shape in the tire circumferential direction EE''.

This is because by providing a plurality of main grooves in this way, the see-through effect on the tire tread surface makes it easier for water that has entered from the front of the tire's ground contact area to escape to the rear of the ground contact area during driving.

(2) These straight main grooves are connected to each other by a plurality of sub-grooves 14 extending from the center of the tire tread 8 to the ground contact edge 15 in the tire width direction.

By connecting the straight main groove transversely with the sub-groove in this way, water that enters the straight main groove from the front of the tire's contact area during driving is easily drained through the sub-groove to a portion of both shoulders of the tire. This is because it will happen.

(3) The angle θ that each of the suffum grooves makes with the tire circumferential direction
must be two or more different angles.

The sound generated by tires while running, mainly pattern noise, is
Generally, this is caused by the fact that the rigidity of the tire ground contact portion changes along the tire circumferential direction. Therefore, in a tread pattern (block pattern) in which a plurality of main grooves are arranged annularly in the circumferential direction of the tire and sub-grooves connecting these main grooves, the tread rubber that is in contact with the road surface is interrupted by the grooves. When the part passes through the road surface, the trend stiffness (stiffness of the tire contact area) increases (changes) in the tire circumferential direction, and pattern noise occurs. As a result of various experiments, we have found that by bringing the angle between the sub-groove and the main groove closer to the circumferential direction, we can reduce the discontinuity in the stiffness of the entire tire road surface and reduce pattern noise. However, if the angle of the sub-grooves approaches the circumferential direction, the rigidity of each block composed of the sub-grooves becomes weaker, and although the discontinuity in rigidity is eliminated, the sub-grooves The total length of the tire becomes longer, and it takes too much time to drain the water that has entered from the main groove through the sub-groove to a portion of both sills of the tire, reducing wet skid performance, which is the advantage of a directional tread pattern. Resulting in.

In the present invention, in order to solve such problems, the main grooves and the sub-grooves connecting the main grooves are arranged at two or more different angles with respect to the tire circumferential direction, thereby easily achieving pitch variations. We learned that the same effect can be obtained when the sub-grooves are increased, and that it is possible to reduce the sound pressure level of pattern noise without impairing wet skid performance, which is an advantage of directional tread patterns. The angle θ formed by this is set to two or more different angles. For this reason, in FIG. 2, the sub-grooves are arranged at different angles θ1. They were arranged alternately at θ2.

(4) The angle θ of these sub-grooves is 30°〈θ〈60
(In FIG. 2, the angles θ1 and θ2 of these sub-grooves 14 are 30°<θ1, θ2 and 60°).

This is a value obtained as a result of an experiment, and this value is necessary in order to achieve the purpose of the present invention.

〔Effect of the invention〕

As explained above, according to the present invention, since the tread pattern is defined as described above, pattern noise can be reduced without deteriorating wet skid performance.

EXAMPLES The effects of the present invention will be specifically explained below with reference to Examples.

Example (1) Tires having the tread bar turn shown in Fig. 2 were manufactured with various single sub-groove angles θ (θ1 = θ2), and the wet skid performance and tire running performance were evaluated. Pattern noise (JASO standard (C60B-81
) was evaluated.

The test conditions are tire size: 205/60R158
9B.

Tire internal pressure; 2. Okg/aJ, RIM ;6-JJ
X15, number of pitches: 60 pitches, groove width: main groove 4-911
1111% sub grooves 3 to 6 Illll. The results are shown in index form in FIG. In FIG. 3, l represents pattern noise and n represents wet skid performance.

As can be seen from FIG. 3, when the sub-groove angle is less than 30°, the pattern noise is excellent, but the wet skid performance is not at a practical level. Also, sub groove angle 6
When the angle exceeds 0°, the wet skid performance is at an acceptable level, but the pattern noise is not at a practical level. Therefore, the range that satisfies both wet skid performance and pattern noise is that the sub-groove angle θ is 30°<θ<60°.
This is the case.

(2) A tire having a tread pattern shown in FIG. 2, in which the sub-groove angles θ1 to θ6 shown in FIG.
Tires were manufactured with the following changes as shown in the table (Comparative Tires 1 to 2, Invention Tires 1 to 4), and these tires were:
Tire size; 205/60R1589H, tire internal pressure; 2. Okg/cd, RIM, 6-JJ
X15, number of pitches; 60 pitches - groove width; main grooves 4 to 911
The 111% sub-groove is 3 to 6 mm.

For these tires, wet skid performance and pattern noise during tire running were evaluated in the same manner as described above. The results are shown in Table 1 below as an index. In Table 1, the smaller the value of pattern noise, the better the value, and the larger the value, the better the wet skid performance.

(Margins below this page) From Table 1, when the sub-groove angle θ is set to two or more different angles at 30° < θ < 60° (inventive tires 1 to 4), pattern noise and wet skid It can be seen that both performance is excellent.

[Brief explanation of drawings]

FIG. 1 is a half-sectional perspective view of an example of a pneumatic radial tire for a passenger car according to the present invention, FIG. 2 is a plan view showing an example of the tire tread of the pneumatic radial tire for a passenger car according to the present invention, and FIG. FIG. 4 is an explanatory diagram showing the relationship between groove angles, wet skid performance, and pattern noise. FIG. 4 is an explanatory diagram showing sub-groove angles in the tread pattern of the tire tread. 1...Bead part, 2...Side wall part, 3...
・Trend part, 4... Carcass layer, 5... Belt layer, 6... Belt cover single layer, 7... Shoulder part, 8
...Tire tread, 11.12, 13.11', 12'
, 13'...Straight main groove, 14...Sub groove, 1
5...Tread width direction ground contact edge. Figure 1 E Figure 2 F' Figure 3 Figure 4

Claims (1)

[Claims] A plurality of straight main grooves are provided on the tire tread in an annular manner in the tire circumferential direction symmetrically with respect to the tire circumferential center line, and these straight main grooves are provided with a plurality of sub-grooves extending from the center of the tire tread to the tire widthwise contact edge. The angle θ that each of the sub-grooves makes with the tire circumferential direction is
are two or more different angles, and these angles θ are 3
A pneumatic radial tire for a passenger car, characterized in that 0°<θ<60°.