JPH07115569B2 - Pneumatic tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of the Invention The present invention relates to a pneumatic tire, particularly a high-performance pneumatic radial tire that is exposed to severe driving conditions, and in particular, improved uneven wear resistance and grip characteristics. It relates to the block pattern.

(Prior Art) As a pattern of a high-performance tire in recent years, generally, a plurality of circumferential main grooves substantially parallel to the tire circumferential direction and a large number of transverse directions extending obliquely with respect to the tire circumferential direction are provided. A block pattern is used which has a number of parallelogram blocks formed by grooves and in which the side walls of the blocks have a constant shape regardless of the circumferential position of the tire. In other words, the inclination angles of the side walls of the circumferential main groove and the transverse groove that partition each block with respect to the normal line standing on the block surface are constant. Further, in particular, in order to improve noise, noise, drainage characteristics, etc., the transverse groove is made relatively small with respect to the circumferential main groove.

(Problems to be solved by the invention) High-performance tires are exposed to more severe operating conditions than ordinary tires such as sudden start, sudden stop, and sharp turn. Has a problem that it is greatly deformed and uneven wear is likely to occur. That is, the parallelogram block divided by the circumferential main groove and the transverse groove generally has an acute-angled corner and an obtuse-angled corner. Since the transverse groove to be formed is arranged in a direction with a more obtuse angle with respect to the circumferential main groove, the rigidity of the acute angle corner is further reduced, and the acute angle corner of the block is deformed during sudden start, sudden stop or sudden turn. However, uneven wear occurs, and when a circumferential and transverse force is applied during traction, turning, etc.,
The block is too weak, and problems such as reduced maneuverability tend to occur.

In view of the above-mentioned problems, the present invention provides a block pattern for improving uneven wear and steerability of a tire without sacrificing noise characteristics and the like.

(Means for Solving the Problems) In view of the above-mentioned problems, the present inventors have improved the block rigidity of an acute-angled corner without changing the inclination angle of the transverse groove with respect to the tire circumferential main groove. As a result of various investigations to achieve this, the fact that the rigidity of the block sharp corner can be effectively increased by strengthening the block side wall facing the groove at the sharp corner of the block has been recognized.

For this reason, the present invention is based on the recognition of such a fact, for example, as shown in FIG. 1, a plurality of circumferential main grooves 2 extending substantially parallel to the tire circumferential direction A, and At least in a pneumatic tire having a block pattern formed by a large number of parallelogram blocks 4 that intersect with a circumferential main groove and are divided by a transverse groove 3 that extends obliquely to the circumferential main groove, At the sharp corners 4a of the block 4 of the tire tread both sides area 1a, the inclination angle of the block side wall 5 facing the transverse groove with respect to the normal line standing on the block surface is the same as the inclination of the block side wall 5 at the obtuse corner 4b. It is characterized by being larger than the angle.

(Operation) The block defined by the circumferential main groove and the transverse groove has alternating acute and obtuse corners in the circumferential direction. Therefore, by reinforcing the block side wall of the acute-angled corner facing the transverse groove by adjusting the inclination angle thereof with respect to the block surface normal, deformation of the acute-angled corner, especially under severe driving conditions, can be prevented. It becomes smaller, and uneven wear resistance and handling stability can be improved effectively.

Here, preferably, in the acute-angled corner portion of the block, the sidewall inclination angle is continuously changed along the groove, and more preferably, the sidewall inclination angle with respect to the normal line standing on the block surface is changed from the acute-angled corner to the obtuse-angled corner. 20 towards the corner
It is better to gradually decrease from ° to 5 °.

According to the present invention, the block side wall facing the circumferential main groove at the acute-angled corner may be inclined at the same inclination angle as described above. By strengthening the sidewalls of the sharp corners of the blocks in the areas on both sides of the tread that are exposed to severe conditions during turning, uneven wear during turning can be more effectively countered.

On the other hand, when the side wall of the block facing the transverse groove is reinforced, naturally, it is possible to particularly effectively counter uneven wear due to traction.

(Example) FIG. 1 shows a developed plan view of a part of a tire tread 1 according to an example of the present invention. In the example shown in FIG. 1, four circumferential main grooves 2 parallel to the tire circumferential direction A along the tire circumferential line are arranged at substantially equal intervals in the tread width direction and are inclined with respect to the tire circumferential direction. A plurality of transverse grooves 3 are arranged so as to intersect the circumferential main groove 2, and these grooves 2, 3 form a large number of parallelogram blocks 4. In this embodiment, both the circumferential main groove and the transverse groove are shown as straight examples, and the blocks divided by them are quadrilateral, but also in the block divided by the zigzag groove or the wavy groove in the design of the tread. It goes without saying that the same applies.

In the example shown, the side walls 5 facing the transverse groove 3 of the sharp corners 4a of each block 4 in the tread flank areas 1a, in particular, of the blocks in the tire tread are, as illustrated in FIG. It is inclined at an inclination angle α with respect to the normal line B standing upright. As shown in FIGS. 2 to 4, which are sectional views taken along the lines II-II, III-III and IV-IV in FIG. It decreases continuously from ° to 5 °. For example, in Fig. 2, α ₁ is 20 °, β
₁ is 5 °, in FIG. 3 α ₂ = β ₂ , 12 °, and in FIG. 4, α ₃
Is 5 ° and β ₃ is 20 °. The inclination angle of the block side wall may be changed stepwise instead of being continuously changed as shown in the above-mentioned example.

In the embodiment shown in FIG. 1, the block side wall of the central block row is not provided with an inclination angle, but it is needless to say that the block side wall of the central block row can be provided with an inclination angle in the same manner. The inclination angle can be made stronger or weaker depending on the block row and the shape of the block.

FIG. 5 shows an embodiment of a tread pattern having directionality, that is, in the case where the rotation direction is specified. In this example, as the inclination angles of the side walls 6 and 5 of the block 4 facing the circumferential main groove 2 and the transverse groove 3 in the acute corner 4a of the block 4 approach the obtuse corner 4b, respectively. Has been gradually reduced. For example, FIGS. 6 and 7 shown as cross-sectional views taken along line VI-VI and VII-VII in FIG.
In the figure, the angle θ is the same and 10 °, the side wall of the block is inclined at an acute angle corner 4a shown in FIG. 6 with an inclination angle α ₁ of 20 °, and the middle portion 4c of both corners is shown in FIG. The inclination angle α ₂ is 15 °.

(Effects of the Invention) Table 1 shows the effects of the present invention in comparison with those of the prior art.

The tread pattern used in this comparative experiment is the tread pattern shown in FIG. 5 for both the present invention and the conventional tire.
As the conventional tire, the same tire as the tire of the present invention was used except that the side wall angles of the transverse groove and the circumferential main groove were not changed. That is, the sidewall inclination angle of the transverse groove of the conventional tire is α ₂ shown in FIG. 3 is 12 °, and the sidewall inclination angle of the circumferential main groove is α ₂ shown in FIG. It is constant. On the other hand, the sidewall inclination angle of the main groove of the tire of the present invention used the one illustrated in FIG.

Noise is measured by a general measuring device, and uneven wear is a measure of how much a step is formed from the outer surface compared to the adjacent block after constant running. Steering stability is straight forward slalom, sudden start, After making a sudden stop, the feeling was evaluated.

As is clear from Table 1, according to the present invention, it is possible to reduce the uneven wear of the tire tread and to improve the steerability of the vehicle.

[Brief description of drawings]

1 is a partially developed plan view of a tire tread according to the present invention, FIG. 2 is a sectional view taken along line II-II in FIG. 1, FIG. 3 is a sectional view taken along line III-III in FIG. 1, and FIG. Is a sectional view taken along the line IV-IV in FIG. 1, FIG. 5 is a partially developed plan view showing another embodiment of the tire tread according to the present invention, and FIG. 6 is a sectional view taken along the line VI-VI in FIG. FIG. 7 is a sectional view taken along the line VII-VII in FIG. 1 ... Tire tread, 1a ... Both sides of tread 2 ... Circumferential main groove, 3 ... Transverse groove 4 ... Block, 4a ... Block sharp corner 4b ... Block obtuse corner, 5, 6 ... … Block side wall

Claims (2)

[Claims] 1. A plurality of circumferential main grooves extending substantially parallel to a tire circumferential direction, and a transverse groove that is inclined with respect to the tire circumferential direction and extends intersecting the circumferential main groove. In a pneumatic tire having a block pattern formed by a large number of substantially parallelogram-shaped blocks partitioned by and, at least one of a circumferential main groove and a transverse groove of a block on both sides of a tire tread is provided. A pneumatic tire characterized in that an angle of inclination of a facing side wall of a block with respect to a normal line standing on the surface of the block is made larger at an acute-angled corner of the block than at an obtuse-angled corner. 2. The pneumatic tire according to claim 1, wherein the inclination angle of the side wall of the block is gradually reduced from an acute-angled corner portion of the block toward an obtuse-angled corner portion.