JPH0326963Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to the tread groove shape of pneumatic tires used in automobiles and the like.

(Prior Art) An automobile tire has a tread portion in which a plurality of circumferentially continuous tread grooves are formed in the width direction.

This tread groove 11 generally has an outwardly expanding V-shape as shown in FIG. As the compression gradually becomes tighter, it becomes difficult to remove the groove, and it also causes damage such as cracks and damage to the bottom of the groove, causing a burst.

To easily remove trapped stones, use the tread groove 1.
The groove wall B of No. 1 is greatly inclined with respect to the groove center line C,
It would be fine if the outward spread angle was set large, but
If formed in this way, the groove width becomes too large, the effective ground contact area of the tread portion 1 becomes small, and the wear resistance decreases.

Therefore, conventionally, as disclosed in Japanese Patent Application Laid-open No. 50-98002 (FIG. 4), the tread groove 12 is formed so that the groove width differs in three steps in the depth direction, and the first groove 13 The second groove 14 and the third groove 15 are sequentially narrowed from the first groove wall 13B to the second groove wall 1.
4B and between the second groove wall 14B and the third groove wall 15B.
There are stepped portions 16 and 17, respectively, which are inclined toward the rear.
are connected and formed.

In addition, 3 disclosed in Special Publication No. 53-30202
In the step groove, the first groove has a deep and outwardly expanding inclined groove wall, the second groove also has an inclined groove wall, and the third groove is thin and straight and is formed discontinuously in the circumferential direction of the tread portion. , the second groove wall and the third groove wall are connected by an arcuate stepped surface.

(Problem to be Solved by the Invention) The former prior art (shown in FIG. 4) has a three-stage groove, but when the outer ends of the groove walls 13B, 14B, and 15B of each stage are sequentially connected, it becomes approximately V-shaped. So basically, V
Since the shape is the same as that of the groove, it is difficult to prevent stones from getting stuck in the groove, and since the step portions 16 and 17 are also inclined, it is difficult to prevent pebbles from entering the groove bottom and widening the groove.

In addition, in the latter conventional technology, the inclination angle of the first groove wall is small and the groove depth is deep, so it is difficult to expect the effect of preventing stones from entering, and the third groove is discontinuous and the tie rod is arranged. As the tread becomes worn, it becomes a pocket, making it easier to pick up stones. Furthermore, since the third groove wall has high rigidity and deforms little under load, it is difficult for the stone that has entered the pocket to come out of the groove, making it more likely that cracks will occur at the bottom of the groove.

(Means for Solving the Problems) In the present invention, in a three-stage groove, the groove depth 5A of the first groove 5 is about 20 to 50% of the total groove depth A, and that of the third groove 7 is about 20%. 40%, the first groove wall 5B is set at an inclination angle of about 20 to 45 degrees, the second groove wall 6B is set substantially parallel to the groove center line C, and the third groove 7 is set at an angle of about 1 to 40%. 4
The groove width is set to 7D of mm, and the second groove wall 6B and the third groove width are set to 7D.
By forming a flat step surface 8 substantially perpendicular to the groove center line C between the groove wall 7B, all of the problems of the prior art described above can be solved.

That is, the specific configuration of the problem solving means in the present invention is that a plurality of tread grooves 2, 3, and 4 are formed in the tire tread portion 1, and at least the tread groove 2 on the center side of the tread has three groove widths in the depth direction. In the tread groove shapes of different pneumatic tires, the first groove 5 on the tread surface side has a groove depth 5A set to approximately 20 to 50% of the total groove depth A, and a groove wall 5B that is oriented with respect to the groove center line C. The intermediate second groove 6 has a groove wall 6B that is inclined outward at an angle of approximately 20 to 45 degrees;
It is formed approximately parallel to the groove center line C from the back end of B; in the third groove 7 at the back, the groove depth 7A is the total groove depth A.
and the groove width 7D is approximately 1 to 4.
mm; a flat stepped surface 8 substantially perpendicular to the groove center line C is formed between the inner end of the second groove wall 6B and the outer end of the third groove wall 7B. be.

(Function) The first groove 5 on the tread surface side has a pair of groove walls 5B.
is spread outward at an inclination angle of 40 to 90 degrees,
This prevents foreign objects such as large stones from being bitten, and since the second groove 6 is a straight groove, small stones can enter, but the size of the intruding stones is limited, and even if stones enter, the groove is widened. The intrusion stones can be removed from the flat step surface 8.
to prevent entry into the third groove 7, and the third groove 7 has a groove width of 7.
D is narrow to prevent stones entering the second groove 6 from damaging the groove bottom.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

In Figures 1 and 2, 1 is the tread portion of a pneumatic tire, and three tread grooves 2, 3, and 4 connected in the circumferential direction are formed, and the present invention is applied only to the tread groove 2 at the center of the tread. Applied.

The tread groove 2 has three different groove widths in the depth direction, with the first groove 5 having the largest width on the tread surface side, the second groove 6 in the middle, and the third groove 7 having the smallest width at the back. .

The groove depth 5A of the first groove 5 is the total groove depth A of the tread groove 2.
is set to approximately 20 to 50%, that is, 0.2A≦5A≦0.5A.
It is inclined at an inclination angle θ of 45°, and the left and right groove walls 5B
It has a V-shape that expands outward at a wide angle of 40 to 90 degrees.

In the second groove 6, left and right groove walls 6B are formed substantially parallel to the groove center line C, each groove wall 6B is directly connected to the back end of the first groove wall 5B, and a stepped portion is not formed. Not yet. The groove depth of this second groove 6 is approximately 20 of the total groove depth A.
~60%, and preferably deeper than the third groove 7.

In the third groove 7, the groove wall 7A is approximately 20 to 40% of the total groove depth A.
That is, it is set to 0.2A≦7A≦0.4A, the groove width 7D is approximately 1 to 4 mm, and the left and right groove walls 7B are straight groove walls parallel to the groove center line C, similar to the second groove wall 6B. It's summery. The back of this third groove 7 is an arc-shaped groove bottom.

The outer end width 5D of the first groove 5 is determined by considering the wear resistance of the tread portion 1, and the inclination angle θ and the groove depth 5D of the first groove 5 are determined in consideration of the wear resistance of the tread portion 1.
A is set, and the groove width 7A of the third groove 7 is set so that a pebble that has entered the second groove 6 does not enter the third groove 7, and even if the tip of a pebble enters the third groove 7, the groove The groove depth is set so as not to cause damage or cracks to the bottom, and the groove width 6D of the second groove 6 is also determined by these values.

This second groove 6 allows pebbles to enter, but since it is a straight groove, it is unlikely to be enlarged by intruding stones, and stones can be ejected from the groove when the second groove wall 6B is elastically deformed. be. This second groove 6 and the third groove
A flat step surface 8 is formed between the groove 7 and the groove 7 . Since both the second groove wall 6B and the third groove wall 7B are parallel to the groove center line C, a flat step surface 8 exists to connect both the groove walls 6B and 7B, and this flat step surface 8
is approximately perpendicular to the groove center line C, and the second
Pebbles that have entered the groove 6 are caught and prevented from entering the third groove 7.

In the first groove 5, if the groove depth 5A is made shallower than 0.2A, the tread groove 2 becomes essentially a two-step groove, and the effect of preventing stones from entering becomes lower.
When the groove is made deeper, the groove width 5D becomes wider, but the inclination angle θ becomes smaller, making it easier for stones to enter and enter the groove bottom. If the inclination angle θ is smaller than 20°, the effect of preventing stones from entering will decrease, and if it is larger than 45°, the groove width 5D will become too wide or the second
The groove 6 and the third groove 7 become too narrow, leading to a decrease in wear resistance or a decrease in drainage performance.

In the third groove 7, if the groove depth 7A is made shallower than 0.2A, it becomes easy to damage the groove bottom.
If it is deeper than 0.4A, multiple small stones will enter and damage the bottom of the groove, and if the groove width 7D is narrower than 1.0mm, the drainage performance in rainy weather will be poor.
If it is wider than mm, pebbles will easily enter the groove and reach the bottom of the groove and cause damage.

The tread groove 3, which is away from the center of the tread,
4 is a two-stage groove in which a first groove 5 and a second groove 6 of the tread groove 2 are formed, and the third groove 7 is not formed. Stones are likely to get stuck in the center of the tread portion 1, so the present invention should be adopted at least in the groove in the center of the tread, but the left and right tread grooves 3,
4 may also be provided with the third groove 7.

(Effects of the invention) According to the invention described in detail above, the tread groove 2 in which the groove width in the depth direction differs in three steps is such that the first groove 5 on the tread surface side has a groove depth of 5A that is the full groove depth. About A
Since the groove wall 5B is set at 20 to 40% and is inclined outward at an angle of about 20 to 45 degrees with respect to the groove center line C,
It is possible to prevent foreign objects such as relatively large stones from getting caught, and the intermediate second groove 6 is formed so that the groove wall 6B is approximately parallel to the groove center line C from the inner end of the first groove wall 5B. , the penetration of relatively small stones is allowed, but the expansion of the groove is reduced, and the deep third groove 7 has a groove depth 7A set to about 20 to 40% of the total groove depth A and a groove width 7D. Since it is set to approximately 1 to 4 mm, it is possible to prevent cracks in the groove bottom while ensuring drainage performance, and furthermore, there is no space between the inner end of the second groove wall 6B and the outer end of the third groove wall 7B. Since the flat step surface 8 is formed substantially perpendicular to the groove center line C, it is possible to prevent pebbles from entering the third groove 7 from the second groove 6, thereby improving the wear resistance of the tread portion 1. While ensuring drainage performance, it is possible to prevent stones from getting stuck, and the stones that are stuck can also be discharged by deforming the groove wall B, making it possible to reduce damage to the bottom of the groove.

[Brief explanation of the drawing]

Figures 1 and 2 show an embodiment of the present invention, Figure 1 is a sectional view taken along the line shown in Figure 2, Figure 2 is a plan view of the tread portion, and Figures 3 and 4 are two examples of the prior art. FIG. 1...Tread portion, 2...Tread groove, 5...
1st groove, 6...2nd groove, 7...3rd groove, 8...flat stepped surface, A...total groove depth, B...groove wall, C...groove center line, D...groove width , θ...Inclination angle.

Claims (1)

[Scope of claim for utility model registration] A plurality of tread grooves 2 in the tire tread portion 1,
3 and 4 are formed, and at least the tread groove 2 on the tread center side has three groove widths in the depth direction.The first groove 5 on the tread surface side has a groove depth of 5A. is set at about 20 to 50% of the total groove depth A, and the groove wall 5B is inclined outward at an angle of about 20 to 45 degrees with respect to the groove center line C; is the first groove wall 5
It is formed approximately parallel to the groove center line C from the back end of B; in the third groove 7 at the back, the groove depth 7A is the total groove depth A.
and the groove width 7D is approximately 1 to 4.
mm; a flat stepped surface 8 substantially perpendicular to the groove center line C is formed between the inner end of the second groove wall 6B and the outer end of the third groove wall 7B. The characteristic tread groove shape of pneumatic tires.