JPH1178433A - Heavy duty pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure excellent wet performance even after the disappearance of striations, not to mention under the presence of striations, by extending each striation and each sipe at an angle within a specified range to the circumferential direction of a tread, and opening one ends of the striation and sipe to a main groove. SOLUTION: A tread part is provided with main grooves 1 linearly in a circumferential direction, and ribs 2 are partitioned between these main grooves and between tread ends and the shoulder main grooves 1 positioned on the side end side. Each rib 2 is provided with striations 4 much shallower than the main grooves 1 and extended with circumferential spaces at an angle of 50-70 deg. to the circumferential direction of the tread, and the bottom of each striation 4 is provided with a sipe 5 extended along the striation 4. One ends of each striation 4 and sipe 5 are opened to the main groove 1 so as to realize smooth drainage and to improve wet performance. Excellent wet performance can therefore be ensured even after the disappearance of the striations 4 in association with wear.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heavy-duty pneumatic tire suitable for use in trucks, buses, and the like, and more particularly to an improvement in a tread pattern of the tire, which realizes excellent wet performance.

[0002]

2. Description of the Related Art As shown in FIG. 4, a rib-type tread pattern of a heavy-duty pneumatic tire has a plurality of ribs 42 having a plurality of circumferential main grooves 41 continuous in the tread circumferential direction. And ribs 42 other than the shoulder ribs 42 on the side of the tread are provided with sipes 43 which tend to extend in the tread width direction.
In each of the shoulder ribs 42, there is a sipe 44 having a tendency to extend in the circumferential direction of the tread and formed at intervals in the circumferential direction.

[0003] However, in this pneumatic tire in which both ends of the sipe are terminated in the ribs, the wet performance based on the cutting of the water film by the sipe edge and the incorporation of water into the sipe can be expected, but the pneumatic tire cannot be used on the road surface. When a large amount of water is present, in other words, when water is taken into the sipe and a large amount of water remains on the road surface, excellent wet performance cannot be expected.

Therefore, on the tread surface side of the sipe,
Attempts have also been made to form a plurality of thin grooves having an opening width to the tread tread portion of 2 to 3 mm and a depth of about 2 mm so as to improve wet performance by using the narrow grooves.

[0005]

With the proposed technique,
Although the wet performance is somewhat improved, both the sipe and the narrow groove end in the rib without communicating with the main groove, so that the wet performance is expected to be improved. In addition, there is a problem that a sudden decrease in wet performance when the narrow groove disappears due to wear of the tread tread portion is inevitable.

The present invention has been made as a result of studying to solve such problems of the prior art, and the purpose of the present invention is not only in the presence of narrow grooves, but also in It is an object of the present invention to provide a heavy-duty pneumatic tire capable of ensuring excellent wet performance by eliminating the narrow groove.

[0007]

A heavy-duty pneumatic tire according to the present invention has five ribs defined by, for example, four narrow grooves formed on a tread tread portion and extending continuously in a circumferential direction. Each of the ribs has a shallow depth that is much shallower than the main groove and extends at an angle in the range of 50 to 70 degrees with respect to the circumferential direction of the tread. A sipe extending along the sipe is formed, and at least one end of the narrow groove and the sipe is opened in the main groove.

In this pneumatic tire, at least one end, preferably both ends, of the narrow groove and the sipe are opened in the main groove to ensure smooth drainage from the narrow groove to the main groove.
It can greatly improve the wet performance of the tire,
In addition, even after the disappearance of the narrow groove, the drainage from the sipe to the main groove is sufficiently smoothed, and without the joy of a sudden decrease in wet performance, until the end of tread wear,
Good wet performance can be secured.

In this tire, each of the narrow groove and the sipe is extended at an angle in the range of 50 to 70 degrees with respect to the circumferential direction of the tread, so that the flow direction of the water in the ground contact surface is reduced. And the direction in which the drainage extends, the drainage performance can be further improved. That is, when the angle is out of the above range, the effect of improving the drainage performance is small.

[0010] Preferably, each of the narrow grooves and the sipe is bent at at least one position in the middle of its extension, thereby increasing the road grip force at the time of applying a slip angle to the tire.

[0011] More preferably, in such a pneumatic tire, the narrow grooves in adjacent ribs are mutually connected.
It is located almost on the virtual extension line, thereby, in addition to efficiently flowing the water discharged from the inside of the rib into the main groove, also flowing through the narrow groove in the adjacent rib, Drains out of the tread more quickly and smoothly.

Preferably, a corner cut portion is provided at an acute angle side portion of the rib at an opening portion of the narrow groove to the main groove, and the corner cut portion allows water discharged from one narrow groove to be adjacent to the adjacent rib. In addition to making it easier to enter the narrow groove, the possibility of the narrow groove being blocked due to the elastic deformation of the acute-angled portion in the adjacent plane is eliminated, and the unevenness due to the presence of the acute-angled portion is eliminated. Prevent the occurrence of wear.

More preferably, the depth of the corner cut is
Deeper than that of the narrow groove, this makes it possible to secure the edge component even after the disappearance of the narrow groove,
Ensure smooth drainage from the remaining sipes to the main ditch.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a development view of a tread pattern showing one embodiment of the present invention. Here, the internal reinforcement structure of the tire is the same as that of a general heavy-duty radial tire, and is not shown.

Here, four main grooves 1 extending linearly and continuously in the circumferential direction are provided on the tread tread portion, and the shoulder main grooves 1 located between these main grooves and located at the most side end side are provided.
And a total of five ribs 2 are defined between the tread ends. In the shoulder main groove 1, as shown in a cross-sectional view in the cross direction of the main groove in FIG. 1B, the contour of the tread tread portion is stepped down, and is independent of the rib 2 and circumferentially. A continuous uneven wear sacrifice portion 3 can also be provided. The uneven wear sacrifice portion 3 comes into sliding contact with the road surface in the ground contact surface when a load is applied to the tire, and the uneven wear sacrifice portion 3 inevitably occurs on the tread tread portion. Function locally and without affecting tire performance.

Here, each of the ribs 2 has a depth much smaller than that of the main groove 1 and has a depth of 50 to 50 in the circumferential direction of the tread.
Narrow grooves 4 extending at an angle in the range of 70 degrees are provided at intervals in the circumferential direction, and a sipe 5 extending along the bottom of each narrow groove 4 is provided. FIG. 1C is a cross-sectional view of the intermediate rib 2 between the center rib and the shoulder rib, in which the narrow groove 4 has a much narrower groove width than the main groove 1. The radial inner end of the sipe 5 provided at the groove bottom reaches a position substantially equal to the radial position of the groove bottom of the main groove 1.

In the narrow groove 4 and the sipe 5, the one formed in the center rib 2 has a middle portion 6a overlapping the tire equator line in the middle of its extension, and a mutual portion from both ends of the center portion 6a. And a linear inclined portion 6b extending substantially parallel to the main groove 1 and opening to each main groove 1.
Also, those formed on the intermediate rib 1 have a substantially "F" shape or an inverted shape thereof having a peak or a valley deviated to the side end side of the rib 2, and the main groove 1 is formed at both ends thereof.
Open to

The narrow groove 4 provided on the shoulder rib 2
The sipe 5 has an end portion that opens to the main groove 1 at one end thereof and has an end portion bent in a direction approaching the tread width direction near the other end ending in the rib.

By the way, the extending angle of the narrow groove 4 and the sipe 5 having such a bent portion with respect to the tread circumferential direction is represented by the average value of the angles of the respective extending portions on the acute angle side with respect to the tread circumferential direction. In this case, the portion extending in the circumferential direction of the tread, such as the narrow groove 4 provided in the center rib 2 and the central portion 6a of the sipe 5,
It shall be excluded from the measurement object of the angle.

Further, in the illustrated example, each of the narrow grooves 4 of the adjacent ribs 2 is positioned substantially on an imaginary extension line thereof.
The corner notch 7 is provided in the acute angle side portion of the groove, more preferably, the depth of the corner notch 7 is made deeper than the depth of the narrow groove 4.

FIG. 2 is a view showing another embodiment of the present invention, in which the narrow groove 4 and the sipe 5 provided in the intermediate rib 2 are opened only in the main groove 1 on the tread end side. Is formed in a straight line substantially parallel to the linear inclined portion 6b of the center rib 2, and the other pattern configuration is the same as that described above.

According to the pneumatic tire configured as described above, the respective narrow grooves and sipes are opened in the main groove, so that the rapid change from the narrow groove 4 to the main groove 1 is achieved as described above. To achieve a smooth drainage and to greatly improve the wet performance.
Even after disappearance, good wet performance can be ensured. In addition, by setting the angle of the narrow groove 4 and the sipe 5 to the circumferential direction of the tread in a range of 50 to 70 degrees,
The drainage efficiency can be further increased, and the wet performance of the tire can be further improved.

When each of the narrow groove 4 and the sipe 5 is bent at at least one position in the middle of the extension, the road surface grip component is applied to the road surface input component in the tread width direction when the vehicle turns. In particular, when the narrow grooves of the adjacent ribs are substantially located on their virtual extension lines, in particular, from one narrow groove, the adjacent ribs The drainage flow into the narrow groove can be smoothed, and the drainage efficiency can be further improved. Further, the improvement of the drainage efficiency becomes more remarkable due to the formation of the corner cut portions 7.

(Embodiment) An embodiment of the present invention will be described below in relation to braking performance and turning performance on a wet road surface. The standard rim is mounted on a tire of size 295/80 R22.5, and the vehicle is driven with the maximum air pressure when a single wheel is mounted. h), and evaluate by measuring the distance slipped from when the brake is applied to when the vehicle stops.
The evaluation was made by measuring a turning time and a lateral acceleration when a circular turning with a radius of 0 to 30 m was performed.

Here, the tire 1 of the embodiment has the tread pattern shown in FIG. 1, and has a tread tread width of 118.5 mm and main groove widths of 15.0 and 14.5 m.
m, the depth of the main groove is 17.4 mm, the width of the narrow groove is 3.0 mm, the depth of the narrow groove is 2.0 mm, and the sipe depth from the bottom of the narrow groove is 13.1 mm. Of the tread in the circumferential direction were set to 70 degrees for the center rib, 60 degrees for the intermediate rib, and 50 degrees for the shoulder rib.

Example tire 2 had the tread pattern shown in FIG. 2, and had the dimensions specified in Example tire 1 except that the angle between the narrow groove of the intermediate rib and the circumferential direction of the sipe was 70 degrees. Is the same as

The comparative tire has the tread pattern shown in FIG. 3, and differs from the tire 1 of the embodiment in that all the narrow grooves and sipes are terminated in the ribs. .

The conventional tire has a tread pattern shown in FIG. Here, the width and depth of the circumferential main groove are 13.5 mm and 14.7 mm, respectively.
And

The braking performance and turning performance of each of these tires were evaluated as indices using the conventional tire as a control, and the results are as shown in Table 1. The larger the index value in the table, the better the result.

[0030]

[Table 1]

[0031]

As is apparent from the above embodiment, according to the present invention, the angle of the narrow groove and the sipe with respect to the circumferential direction of the tread is in the range of 50 to 70 degrees, and at least one end thereof is formed in the main groove. By opening to the, it is possible to achieve a significant improvement in wet performance, and after the disappearance of the narrow groove, still under the opening to the main groove of the sipe,
Good wet performance can be secured.

[Brief description of the drawings]

FIG. 1 is a tread pattern developed view showing one embodiment of the present invention.

FIG. 2 is a tread pattern developed view showing another embodiment of the present invention.

FIG. 3 is a tread pattern developed view showing a comparative tire.

FIG. 4 is a tread pattern developed view showing a conventional tire.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main groove 2 Rib 3 Uneven wear sacrificed part 4 Narrow groove 5 Sipe 6a Central part 6b Inclined part 7 Corner cut

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI B60C 11/13 B60C 11/04 H 11/11 11/06 B

Claims (5)

[Claims] 1. Each of a plurality of ribs formed on a tread tread portion and defined by a main groove extending continuously in a circumferential direction has a depth much smaller than that of the main groove, and the rib has a depth substantially smaller than that of the main groove. A narrow groove extending at an angle in the range of 50 to 70 degrees, and a sipe extending along the bottom of each narrow groove is formed, and at least one end of the narrow groove and the sipe is opened in the main groove. Heavy load pneumatic tire. 2. The heavy-duty pneumatic tire according to claim 1, wherein each of the narrow grooves and the sipe is bent at at least one position in the middle of its extension. 3. The heavy-duty pneumatic tire according to claim 1, wherein the narrow grooves of the adjacent ribs are located substantially on a virtual extension line thereof. 4. The heavy duty pneumatic tire according to claim 1, wherein a corner cut portion is provided at an acute angle side portion of the rib at an opening portion of the narrow groove to the main groove. 5. The pneumatic tire for heavy load according to claim 4, wherein the depth of the corner cut portion is not deeper than the narrow groove.