JPH07215013A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To enhance maneuvering stability on a dry road surface and a wet road surface by forming slits at every other slit or every several slits into branching shapes among a plurality of slits provided at an equal space in the peripheral direction and extending obliquely toward both ends of a tread. CONSTITUTION:In a pneumatic tire provided with straight grooves 1a, 1b in the tire peripheral direction and a directional pattern wherein slits 3. 4 obliquely extending toward both ends of a tread from the straight groove 1a at a center part are provided at an equal space in the peripheral direction, one side slit 3 is formed into a branching type. Namely, the slit 3 is formed in such a manner as to have a branching oblique groove 3a extending branchedly in the same inclining direction as the slit 3 with an angle smaller than the slit 3 with respect to the grooves 1a, 1b. The branching oblique groove 3a is formed in such a manner as to intersect the other slit 4 without intersecting another groove 3a at least and extend to the next branching type slit 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire such as a high performance flat radial tire having a flatness of 60% or less.

[0002]

2. Description of the Related Art Pneumatic tires such as high-performance flat radial tires are required to have a high level of drainage performance on wet road surfaces as well as steering stability on dry road surfaces. Therefore, in order to achieve both these dry and wet performances, the directionality of straight grooves (vertical grooves) in the tire circumferential direction and inclined slits (horizontal grooves) arranged at approximately equal intervals in the circumferential direction is used. Various tread patterns, so-called directional patterns, have been proposed. In the case of a so-called flat tire having a flatness (flatness represented by a cross-sectional height with respect to the tire cross-sectional width) of 60% or less, the ground contact width may be larger than the tire height,
Most of them have at least three straight grooves.

For example, as a conventional general directional pattern, as shown in FIG. 7 (a), it has three straight grooves (11) in the circumferential direction, and at regular intervals in the tire circumferential direction. The straight groove (1
Based on a pattern in which slits (13) obliquely extending from 1) toward the tread end at a relatively large angle to the straight groove are provided, the straight groove (1
1) and the straight groove (11) from the shoulder portion, a relatively thin sub groove (1) having substantially the same width as the slit (13).
A pattern provided with 9) is known.

In such a tread pattern tire, if the angle (average angle) of the slit (13) with respect to the straight groove is set small with emphasis on the drainage property on a wet road surface, the rigidity of the block defined by the groove is increased. Is deteriorated and the performance on dry road surface is deteriorated. Further, if the angle of the slit (13) with respect to the straight groove is set to be large and the inclination with respect to the tire width direction is made gentle with an emphasis on steering stability on a dry road surface, there is a problem that drainage performance on a wet road surface is deteriorated. . Therefore, it has been extremely difficult to achieve both of these dry and wet performances at a high level.

Further, in the above-described directional pattern, for the purpose of improving both the dry and wet performances, for example, as shown in FIG. 8, the first slits () are alternately arranged in the circumferential direction. 13) and the second slit (1
In 4), the first slit (13) is directly crossed with the straight groove (11) in the center portion, and the second slit (14) is in the central portion inward of the straight groove (11) on both sides. In the area (12), bend it greatly,
The straight groove (11) at a relatively small angle with respect to the straight groove is allowed to intersect with the adjacent first slit (13) without intersecting with the straight groove (11) at the center portion, and the small inclined portion of the second slit (14). A pattern in which the tip of (14a) is terminated in the middle of the block or a pattern in which the straight groove (11) in the center portion is crossed as shown by the broken line in the figure is considered.

However, in the case of the pattern of FIG. 8, although the drainage performance on a wet road surface and the steering stability on a dry road surface are improved, the above-mentioned slits (13) (1) are used.
Due to the constitution of 4), the partition shape of the block of the part (a) in the central region (12) becomes large, and the circumference of the block,
Since the rigidity in the width direction increases, the difference in rigidity between the block row of the (a) part of the central area (12) and other block rows becomes large, and uneven wear easily occurs, which is also disadvantageous in reducing pattern noise. There is a problem such as becoming, and it is not satisfactory.

In particular, as indicated by the broken line in the figure, the small inclined portion (1
When the tip of 4a) is crossed with the straight groove (11) of the center part, the rigidity of the block of the (b) part partitioned by this is not properly maintained, and the circumferential direction of the block of the (a) part is kept. The rigidity becomes more uneven, and the inner block row (15a) and the outer block row (1) in the central area (12) are
5b) also has a large difference in rigidity, which causes uneven wear and deterioration of pattern noise.

The present invention has been made in view of the above, and particularly, both steering stability on a dry road surface and drainage performance on a wet road surface without deteriorating uneven wear resistance and pattern noise performance. It is intended to provide a pneumatic tire that improves both of the above, and is capable of achieving both high performance levels.

[0009]

The pneumatic tire of the present invention for solving the above-mentioned problems has at least three straight grooves extending in the tire circumferential direction in the tread portion, and at least one straight groove is provided. In the pneumatic tire provided in the center portion, slits of substantially the same shape extending obliquely at a relatively large angle with respect to the straight groove from the straight groove of the center portion toward both ends of the tread are provided at substantially equal intervals in the circumferential direction, Among the slits, one slit or a plurality of slits existing as a plurality of slits are of a branch type, and an angle smaller than the angle of the slit with respect to the straight groove in the central region between the straight groove of the center part and the straight grooves on both sides of the straight groove. And a sloping groove extending in the same tilt direction as the slit is provided. By the intersection with other slits without intersecting rate groove extends to the slit of the next branch-shaped, characterized in that it cross contiguous with the slit.

According to a second aspect of the present invention, in the pneumatic tire, a plurality of straight grooves are provided at a center portion of the tread portion at a required interval, and the straight grooves are provided at substantially equal intervals in the circumferential direction. Each of the slits extends obliquely from the straight grooves on both sides of the center part toward both ends of the tread, and ribs are formed between the straight grooves of the center part.

[0011]

According to the pneumatic tire of the present invention described above, the tread pattern includes at least three straight grooves and a slit having a relatively large angle with respect to the straight grooves, that is, a slit having a relatively gentle inclination in the tire width direction. Since the basic pattern is a block that is divided by these straight grooves and slits, it has a shape that can maintain appropriate rigidity and contribute to steering stability on dry road surfaces, and the performance on dry road surfaces is improved. improves.

[0012] On the other hand, the branch slits having one or more slits each have a branch slant groove extending in the same inclination direction as the slit at a relatively small angle with respect to the straight groove.
The branched oblique groove allows quick drainage from the central region to the end portion on the tread side, whereby the drain angle is relatively large and the drainage disadvantage is compensated for, and a sufficient drainage can be secured.

Further, since the slit having a large angle in the low speed region and the branch oblique groove having a small angle in the high speed region share the drainage, a minimum groove space is required, and a sufficient ground contact area is secured accordingly. Yes, this also improves dry performance.

In particular, in the case of the present invention, a combination of slits having substantially the same shape and angle and arranged at substantially equal intervals in the circumferential direction and branched oblique grooves formed from one or more slits,
By extending the branched oblique groove to the next branched slit without intersecting with the straight groove of the center portion and continuously crossing it, in the central area between the straight groove of the center portion and the straight grooves on both sides of the straight groove. , The block will be divided into the inside and outside by the branch oblique groove, and the block will be divided and formed.
Therefore, there is almost no difference between the block rigidity in the central area and the block rigidity in the shoulder area, and the difference in rigidity between the inner block row and the outer block row in the central area does not become too large. Therefore, not only the pattern noise but also the performance against uneven wear is improved.

Further, as in the second aspect of the present invention, a plurality of straight grooves are provided in the center portion and ribs are formed between the grooves in the circumferential direction, and the slits and the branched oblique grooves are configured in the same manner as described above. In this case, as described above, the steering stability on dry road surface and the drainage performance on wet road surface can be improved without increasing the pattern noise and uneven wear, and in particular, the rib at the center part stabilizes straight running. The property is also improved.

[0016]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 shows a tread pattern of a tire according to an embodiment of the present invention. The internal reinforcing structure of the carcass, belt, etc. is the same as that of a normal tire,
The illustration and description thereof will be omitted.

In the figure, (T) shows the tread portion, and (C) shows the center line thereof. In the case of this embodiment, the tread portion (T) has three straight grooves (1a) (1b) (1b) extending in the circumferential direction. That is,
One straight groove (1a) is provided in the center portion, and one straight groove (1b) (1b) is provided on each side of the tread portion (T). The straight groove (1a) of this center portion is provided. And the straight groove (1
A portion (b) (1b) and the central portion (2) are separated from other portions such as a shoulder portion outside the straight grooves (1b) (1b).

Then, the straight groove (1a) extending from the straight groove (1a) in the center portion toward both ends of the tread is used.
a) Slits (3) and (4) of substantially the same shape extending obliquely at a relatively large angle with respect to (1b), that is, at a relatively gentle inclination with respect to the tire width direction are provided at substantially equal intervals in the circumferential direction. .

As shown in the figure, these slits (3) and (4) intersect and are continuous with the straight groove (1a) in the center portion, and are straight upward in the central region (sloping upward from the front of the tire). The angle with respect to 1a) is slightly small, and the angle gradually increases toward the tread end so as to gradually increase.

The inclination angles of these slits (3) and (4) are 45 ° to 85 with respect to the straight grooves (1a) and (1b).
It is preferable to incline at an angle within the range of 0 °, particularly preferably within the range of 55 ° to 75 °, in order to secure the rigidity of the block partitioned by the groove and improve the drainage property.

Of the slits (3) and (4) described above, every other slit (3) is present as shown in FIG.
Is the central area (2) between the straight groove (1a) in the center portion and the straight grooves (1b) (1b) on both sides thereof.
At a substantially central position of the straight groove, a branched oblique groove (3a) extending at a much smaller angle than the slit (3) and extending in the same inclination direction as the slit (3) is provided. It is shaped.

The angle of the branched oblique groove (3a) is 4 ° to 15 ° with respect to the straight groove, particularly preferably 5 ° to 12 °.
This is preferable from the viewpoint of the effect of improving the drainage property by the branched oblique groove (3a).

The branched oblique groove (3a) is divided into two blocks (5) divided by the straight groove (1a) and the slits (3) (4) and the inside and outside blocks (5a) (5).
In such a manner that it is vertically divided so as to be divided into b), it does not intersect with the straight groove (1a) of the center portion but intersects with another slit (4) and extends to the next branched slit (3), It is continuous with the slit (3).

In the case of the figure, the tip of the branched oblique groove (3a) extends slightly beyond the slit (3) and terminates. Although this tip can be further extended, the gap between the next branched slit (3) and the branched oblique groove (3a) becomes small, which may lower the block rigidity. To end or slit (3)
It is preferable to terminate at the position.

When the tip end of the above-mentioned branched oblique groove (3a) is curved inward and intersects with the straight groove (1a) at the center, pattern noise increases due to the shape of the intersection. As described above, there is a problem that the block partitioned by the tip of the branched oblique groove (3a) becomes small, the block rigidity decreases, and the running performance on a dry road surface deteriorates. It is preferable to provide the straight groove (1a) without intersecting it.

The branch oblique groove (3a) is branched from the slit (3) at a substantially central portion of the central area (2).
At this time, the block (5) inside the branch oblique groove (3a) is
The rigidity ratio between the row of a) and the row of the outer block (5b) is
When the outer block row is 100, the branch position is preferably set so that the inner block row is 45 or more, that is, the difference in rigidity between both block rows is as small as possible. That is, if the rigidity of the inner block row is 45% or less with respect to the outer block row, uneven wear and pattern noise will be adversely affected. Therefore, it is desirable to set as described above.

Further, it is preferable from the viewpoint of drainage property that the branched oblique groove (3a) is formed to be slightly wider on the base side closer to the branched portion from the slit (3). At this time, it is desirable not to perform taper cut (corner drop) treatment on the acute corner portion (6) of the block (5a) in the branch portion from the slit (3). That is, when the corner portion (6) is taper cut, the straight groove (1a) in the center portion is cut.
The effluent flow is disturbed due to the merging of the effluent flow and the effluent flow of the branch oblique groove (3a), and the drainability is deteriorated.

Further, as in the illustrated embodiment, in each block row in the circumferential direction, the slits (3) and (4) separated by the straight grooves are located on the left and right sides in front of and behind the ground or behind and in the front. It is preferable to form them by shifting. That is, since the left and right positions of the slits (3) and (4) are displaced,
It is possible to prevent the air in the slits (3) and (4) from being discharged to the left and right simultaneously, and further improve the performance against pattern noise.

In particular, as described above, even if the slits (3) and (4) are continuous from the straight groove (1a) in the center portion toward both ends of the tread, the drained water is actually the slit (3). 3) Since it does not flow in the groove of (4), even if there is a phase difference between the left and right slits as described above, the drainage effect does not change and the wet performance does not deteriorate.

At the intersection of the slits (3) and (4) and the straight grooves (1b) and (1b) on both sides, the block (5b) inside the straight groove (1b).
It is preferable to taper-cut the acute-angled corner portion (7) in order to increase the block rigidity and improve the steering stability.

In the tire having the directional pattern having the above-described structure, every other one of the slits (3) and (4) having substantially the same shape provided at substantially equal intervals in the circumferential direction is present. The branched slit (3) is provided with the branched oblique groove (3a) branched in the central area (2) as described above, and particularly the block (5) in the central area (2) is longitudinally cut. The blocks (5a) (5) inside and outside the branched oblique groove (3a) in the central area (2) are
b) has moderately high rigidity, the difference in rigidity between the inner and outer block rows is small, and there is almost no difference in block rigidity between the central area and the shoulder area, increasing uneven wear and pattern noise. It is possible to improve the performance of dry road surface.

Moreover, the branched oblique grooves (3a) branched from every other slit (3) extend to the position of the next branched slit (3) without intersecting with the straight groove (1a) in the center portion. By suppressing the increase of pattern noise, all slits (3) (4)
Is connected to the straight groove (1a) in the center portion, and the branched oblique groove (3a) extends long in the tire circumferential direction at a relatively small angle with respect to the straight groove, so that the performance on a dry road surface is improved. Also, drainage performance on wet road surfaces can be improved without impairing the effect of preventing pattern noise and uneven wear.

In FIGS. 2 to 5, slits (3) and (4) similar to those described above are provided at equal intervals in the circumferential direction.
In a pattern in which every other slit (3) is provided with a branched oblique groove (3a), two straight grooves (1a) (1a) (1a) (1a) having a slightly small groove width are provided at a center portion of the tread portion (T). ) Is provided, and the slits (3) and (4) are obliquely extended from the straight grooves (1a) (1a) on both sides toward the tread end, and the straight grooves (1
The case where straight ribs (8) are formed between a) and (1a) is shown.

The straight rib (8) in the center portion is continuous in the circumferential direction as shown in FIGS. 2 and 3, and is also circumferentially formed by crossing the slits (3) and (4) as shown in FIGS. 4 and 5. In some cases, it may be divided.

In any of these examples, similarly to the above, it is possible to improve performance such as running performance on dry road surface and drainage performance on wet road surface without impairing uneven wear resistance and pattern noise performance. Of course, the straight ribs (8) at the center can improve the straight running stability. Although not shown,
Even when three or more straight grooves are provided in the center portion in parallel to each other at a required interval and straight ribs are formed between the straight grooves of the center portion, and slits and branched oblique grooves are provided in the same manner as described above, the same result is obtained. Produce an effect.

In the above-mentioned embodiment, the case where every other slit (3) is provided and the branch oblique groove (3a) is provided therein, however, every other slit is provided as shown in FIG. For example, a plurality of branched slits (3) are arranged, and this slit (3) is crossed with another slit (4) in the same manner as described above and is crossed with the next branched slit (3). It is also possible to implement by providing a branched oblique groove (3a), and in this case also,
The same effect as the above is produced. It is preferable that the number of the plurality of lines is 5 or less from the viewpoint of drainage effect.

The following is a comparative test between the tires of the examples of the present invention and conventional tires in terms of steering stability on dry road surfaces, steering stability on wet road surfaces (drainability), and pattern noise and abrasion resistance. Will be described.

The tires used in the tests were all 205/55 R16 in size and had a tread width of 184 mm, and the carcass, the belt and the like had the same internal structure.

The tire of Example 1 had the pattern shown in FIG. 1, and the width of the straight groove in the center portion was: 6.
The width was 6 mm, the width of the straight groove on both sides was 9.7 mm, the width of the slit (average) was 4.1 mm, and the width of the branched oblique groove (average) was 4.0 mm.

The tire of Example 2 has the pattern shown in FIG. 2, and the width of the straight groove in the center portion is: 5.
3 mm, width of straight rib: 16 mm, width of straight groove on both sides: 7.7 mm, width of slit (average):
It was 4.1 mm, and the width (average) of the branched oblique grooves was 4.0 mm.

Comparative Example 1 corresponds to the conventional example shown in FIG.
The tire having the pattern (a), Comparative Example 2 is shown in FIG.
The tire having the pattern of (b) and the tire having the pattern of FIG. 8 were used in Comparative Example 3.

Test Method For steering stability on dry and wet road surfaces,
By the actual running of the test course under the normal load and the normal internal pressure, the driver's feeling is evaluated, and the pattern noise is evaluated by the waveform at 40 to 120 km / h on the noise test drum,
The wear resistance was evaluated by measuring the friction energy of each block.

The results of the comparison test are shown in Table 1 below as an index with Comparative Example 1 corresponding to the conventional tire as 100. The larger the index value, the better the result.

[0045]

[Table 1]

As is clear from the above test results, in the case of Comparative Example 2 in which the drainage property is taken into consideration, the drainage property on the wet road surface is good because there are many straight grooves having a large groove width corresponding to the main groove. While the steering stability is improved, the ground contact area is reduced, and the steering stability on dry road surface is lower than that of Comparative Example 1 of the conventional tire.

On the other hand, the tires of Example 1 and Example 2 of the present invention did not deteriorate the performance against pattern noise and the wear resistance, and the steering stability on dry road surface and the steering stability on wet road were stable. Both performances (drainability) could be improved as compared with Comparative Example 1 of the conventional tire.

[0048]

As described above, according to the present invention, the contradictory characteristics of steering stability on dry road surface and drainage performance on wet road surface without impairing the performance against pattern noise and wear resistance (uneven wear). Both performances can be improved, and both can be achieved at a high level.

Particularly, according to the second aspect of the present invention, the straight running property can be improved in addition to the improvement of both the dry and wet performances.

[Brief description of drawings]

FIG. 1 is a front view of a tread pattern according to an embodiment of the present invention.

FIG. 2 is a front view of a tread pattern of another embodiment.

FIG. 3 is a front view of a tread pattern of another embodiment.

FIG. 4 is a front view of a tread pattern of another embodiment.

FIG. 5 is a front view of a tread pattern of another embodiment.

FIG. 6 is a front view of a tread pattern according to still another embodiment.

7 (a) and 7 (b) are front views showing examples of tread patterns of conventional tires.

FIG. 8 is a front view showing another conventional tread pattern example.

[Explanation of symbols]

 (T) Tread (1a) Center straight groove (1b) (1b) Both sides straight groove (2) Center area (3) Branch slit (3a) Branch oblique groove (4) Other slit ( 5) Block (5a) Inner block (5b) Outer block

Claims (2)

[Claims] 1. A tread portion having at least three straight grooves extending in the tire circumferential direction, at least one straight groove being provided in a center portion, and straight from the straight groove of the center portion toward both ends of the tread. In a pneumatic tire in which slits of substantially the same shape extending obliquely at a relatively large angle with respect to a groove are provided at substantially regular intervals in the circumferential direction, among the slits, one or more slits are present as a branched type. In the central area between the straight groove of the center part and the straight grooves on both sides of the straight groove, a branched oblique groove extending at a smaller angle to the straight groove than the slit and branching in the same inclination direction as the slit is provided. This branched oblique groove intersects at least the straight groove of the center part and intersects with other slits so that the next branched type groove is formed. A pneumatic tire that extends to a slit and is continuous with the slit. 2. The center portion of the tread portion is provided with a plurality of straight grooves with a required interval, and the slits at substantially equal intervals in the circumferential direction are directed from the straight grooves on both sides of the center portion to both ends of the tread. 2. The pneumatic tire according to claim 1, wherein the pneumatic tire extends obliquely, and ribs are formed between the straight grooves of the center portion.