JPS61202903A - Lug groove of pneumatic tire - Google Patents

Abstract

PURPOSE:To reduce the generation of sounds by vibration and air pumping by varying the form of a lug groove and making both a ground contacting front edge line and a ground contacting rear edge line deeply cross with said lug groove and allowing them to move from one end to the other end in order. CONSTITUTION:A fist reference line L1 is formed by connecting a groove center Po on a shoulder 12 to a groove center P1 at a distance of 1/10 the tread width B from the shoulder 12 along the tire meridian T, and its oblique angle alpha is set within the range of 15 deg., both clockwise and counterclockwise with respect to the tire meridian T, from the groove center Po toward the circumferential center line N respectively. The end part P1 of the first reference line L1 is connected to a groove center P2 at a distance of 1/3 the tread width B from the shoulder 12 along the tire meridian T, to form a second reference line L2, and its oblique angle beta to the tire meridian T is taken larger than the oblique angle alpha, and is set within the range of 15 to 45 deg., counterclockwise with respect to the tire meridian T, from the end part P1 of the first reference line L1 toward the circumferential center line N.

Description

Detailed Description of the Invention (Industrial Field of Application) This invention provides a pneumatic tire for automobiles having a plurality of lug grooves arranged on both sides of the circumferential center line intersecting the center line. It is related to the shape of.

(Prior Art) As a lug groove for a pneumatic tire, one shown in FIG. 4, for example, is generally known. That is, 1 is the tread, 2
is a shoulder, and a large number of lug grooves 3 are arranged on both left and right sides of the tire circumferential center line N, and one end thereof is the shoulder 2.
The other end of each lug groove 3 is opened toward the tire meridian T (the straight line 41i perpendicular to the tire circumferential center line) passing through the shoulder opening. It is tilted slightly counterclockwise. And each lug groove 3 is
It is formed by connecting a plurality of short straight grooves 3a, 3b, 3C in a zigzag shape.

(Problem to be Solved by the Invention) When the lug tire rotates as the car runs and the tread 1 moves upward (in the direction of the arrow) in FIG. The part between the leading edge line C of the ground contact and the upwardly curved trailing edge line of the ground contacts the ground, and this ground contact part moves downward in order. In other words, the tread l begins contacting the ground at the leading edge line C and ends contacting the trailing edge line C.

However, the conventional lug grooves 3 are formed in a zigzag shape, and both the left and right sides are inclined counterclockwise at a gentle angle with respect to the tire meridian T as described above. The grounding leading edge line C or the grounding trailing edge line crosses almost the entire area of the grounding line, and as a result, vibration noise due to the disconnection of grounding in the lug groove 3 portion and air bombing noise due to a sudden change in the volume of the lug groove 3 are generated. For example, the lug groove 3 on the left side facing the sidewalk slightly intersects with the leading edge line C of ground contact, but is almost parallel to the trailing edge line of ground contact. The ground trailing edge line passes through the entire length of 3 at almost the same time, and the vibration noise and air pumping noise mentioned above become significantly louder. In addition, since the left lug groove 3 is slightly inclined with respect to the ground contact leading edge line C, the ground contact leading edge line C passes from the end of the lug groove 3 closer to the circumferential center line N to the shoulder 2 side. However, since the above intersection is shallow, the vibration noise and air bombing noise generated are as follows:
On the other hand, the right lug groove 3 facing the center of the roadway is only slightly reduced compared to the one caused by the trailing edge line.
In contrast to the above, the noise based on the ground contact leading edge line C is significantly increased, and the noise based on the ground contact trailing edge line C is slightly reduced.

This invention changes the shape of the lug groove so that both the ground contact leading edge line C and the ground contact trailing edge line deeply intersect with the lug groove and move sequentially from one end to the other, thereby reducing vibration noise and air. This significantly reduces pumping noise.

(Means for Solving the Problems) As shown in FIGS. 1 and 2, lug grooves 13 are provided in a pneumatic tire that is provided laterally with respect to the center line N in the circumferential direction and has one end opened at the shoulder. , from the groove center P6 on the shoulder 12 (a point on the center line N of the lug groove 13) and 1/1 of the tread width B from the shoulder 12 along the tire meridian T.
The groove center R at a distance of 10 is connected with a straight line to form a first reference line, and its inclination angle α is set from the groove center line N on the shoulder 12 toward the tire circumferential direction center line N to the tire meridian. 1 each in the clockwise and counterclockwise directions of T.
5 degrees, and the tread width B is set along the tire meridian T from the edge R1 and the shoulder 12 of this first reference line.
The groove center P at a distance of 173 is connected with a straight line to form a second reference line, and the inclination angle β with respect to the tire meridian T is larger than the inclination angle α of the first reference line, and the above-mentioned 15 in the counterclockwise direction of the tire meridian T from the end P of the first reference line L1 toward the circumferential center line N.
Set in the range of ~45 degrees.

The lug grooves 13 may be either a plurality of short straight grooves connected together or a smooth curved groove.

(Function) When the vehicle is running, the tread 11 (see Fig. 2) moves in the direction of arrow A as the tire rotates, and the portion between the trailing edge line C and the leading edge line C, as in the past, moves forward as the tire rotates. Ground. In this case, the inclination angle of the ground contact leading edge line C and the ground contact trailing edge line with respect to the tire meridian T is as follows, assuming that the positive direction is counterclockwise from the groove center on the shoulder 12 toward the tire circumferential direction center line N. The inclination angle θa at a distance from 12 to B/10 is +20 to +45 degrees or -20 to -45 degrees,
Since the inclination angle θb at the position at a distance of B/3 is O to +20 degrees or 0 to -20 degrees, the inclination angle α is -15 to +1
The first reference line Ll is 5 degrees, and the inclination angle β is +15 to +
The 45-degree second reference line never overlaps the leading edge line C or the trailing edge line C, but always intersects with them. In other words, the lug groove 13 is aligned with the leading edge line C. It does not have a part whose inclination angle coincides with any of the trailing edge line and the ground contact trailing edge line. Therefore, when the tread 11 moves in the direction of arrow A, the grounding flange line C or the trailing edge line does not lie across the entire length of the lug groove 13, and the lug groove 13 and the leading edge line C or the grounding edge line C do not lie across the entire length of the lug groove 13. The intersection with the trailing edge line is the lug groove 13
, which reduces both vibration and air-bumping noise.

Note that the inclination angle α of the first reference line is 115 degrees to +15 degrees.
Outside the range, noise reduction will be insufficient. In addition, if the inclination angle β of the second reference line C is less than +15 degrees, the intersection with the leading edge line C and the trailing edge line C will be shallow and will not be effective in reducing noise; If it exceeds this, uneven wear tends to occur in the lug portions between the adjacent lug grooves 13 and 13.

(Example) Size 1 having the tread pattern shown in Figures 1 and 2
0.00-20.14PR, rim 7.50 x 2G lug tire, the inclination angle α of the first reference line Ll and the inclination angle β of the second reference line Ll were changed variously to obtain JASO-C606 tires. A noise test was conducted using the stand-alone bench test method, and the results were as follows:
15 degrees (corresponding to β=6 degrees), a solid curve of the third WI was obtained. In addition, tires obtained by fixing α at 15 degrees and changing only β were installed on the front of a city bus, and a test was conducted to investigate the amount of uneven wear after traveling a certain distance. Difference between the amount of wear before and after the lug part (uneven wear amount) m
tt measurement, ratio m to uneven wear amount m of conventional lug tires
/-1, that is, the uneven wear index, the results shown by the dotted line in FIG. 3 were obtained. Note that point Q is a conventional lug tire (α = 15 degrees, β
= 6 degrees) and the uneven wear index.

As is clear from FIG. 3, as the inclination angle α of the first reference line increases, the noise increases, and this inclination angle α
At 18 degrees, which is larger than the upper limit of 15 degrees according to the present invention, there is no big difference from the conventional one, and as the inclination angle β of the second reference line increases, the noise decreases, but the uneven wear index increases, and this inclination If the angle β is less than the lower limit of 15 degrees, the noise will be on the same level as before, and if it exceeds the upper limit of 45 degrees, the amount of uneven wear will increase significantly. Note that as the amount of uneven wear increases, the noise also increases.

(Effect of the invention) According to this invention, the left and right lug grooves deeply intersect with both the ground contact leading edge line C and the ground contact trailing edge line, and the intersecting portion is formed in the longitudinal direction of the lug groove as the tire rotates. Since the lug groove portion moves in sequence, vibration noise caused by intermittent grounding of the lug groove portion and air pumping noise caused by changes in the volume of the lug groove are both reduced, and the amount of uneven wear is not much different from the conventional one.

[Brief explanation of the drawing]

FIG. 1 is an enlarged view of essential parts of an embodiment of the invention. FIG. 2 is a surface view of the tread of the above example, FIG. 3 is a graph showing the experimental results, and FIG. 4 is a surface view of the tread of a conventional lug tire. 11 Nidred, 12: Shoulder, 13: Lug groove, N:
Tire circumferential center line, T: Tire meridian, B: Dread width, I: First reference line, L: Second reference line, M: Groove center line, α, β: Inclination angle. 21st m

Claims (1)

[Scope of Claims] [1] In a lug groove of a pneumatic tire that is provided laterally with respect to the center line in the tire circumferential direction and has one end open to the shoulder, the groove center on the shoulder and the lug groove from the shoulder to the above-mentioned tire. The inclination angle with respect to the tire meridian of a first reference line that connects the groove center at a distance of 1/10 of the tread width along the tire meridian in the direction perpendicular to the circumferential center line from the groove center on the shoulder. The tread width is set in a range from 15 degrees clockwise to 15 degrees counterclockwise from the tire meridian toward the tire circumferential center line, and from the end of the first reference line and the shoulder along the tire meridian. 1
The inclination angle of the second reference line connecting the groove center at a distance of /3 with respect to the tire meridian is greater than the inclination angle of the first reference line, and from the end of the first reference line in the tire circumferential direction. A lug groove of a pneumatic tire, characterized in that the lug groove is set in a range of 15 to 45 degrees counterclockwise from the tire meridian toward the center line.