JP3075628B2 - Pneumatic tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire having a tread pattern that achieves both low noise and wet hydroplaning.

[0002]

2. Description of the Related Art Conventionally, in a tire whose rotation direction is specified, for example, a pair of circumferential straight grooves are sandwiched between the center of the tread and the equatorial plane of the tire, and between the circumferential grooves and both ends of the tread. Each has an intermediate circumferential straight groove, and, from both ends of the tread to the central circumferential groove, a large number of inclined lug grooves are arranged in a direction converging toward the center of the tread to form a land portion. A sectioned tread is known. In this case, the slanted lug grooves connecting the central circumferential groove and the intermediate circumferential groove have substantially the same width and depth at any position in the longitudinal direction.

[0003]

In the case of the above-mentioned treads known in the prior art, the circumferential straight groove has a groove width in which a step portion and a kick-out portion with respect to the ground contact surface during running are wider than the remaining ground contact center portion. It suddenly fluctuates in the direction of enlargement, and at that time, high frequency vibration is generated on the groove wall of the same direction groove, which causes a resonance effect on the air in the groove with the circumferential groove as a resonator, thereby deteriorating the noise effect. .

On the other hand, when the above-described inclined lug groove is opened in the circumferential direction, the air flow in the lug groove disturbs the air flow in the circumferential groove to some extent, so that a slight noise reduction effect is produced. There were problems such as insufficient.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a structure of a radial lug groove which communicates with a circumferential main groove in a tread. A pneumatic tire having a tread pattern that is configured to reduce tire noise by adopting a special structure while avoiding a decrease in hydroplaning performance and to achieve both low noise and wet hydroplaning performance. To be.

[0006]

In order to achieve the above object, in a pneumatic tire according to the present invention, a pair of sidewalls and a crown portion extending over both sidewalls are connected in a toroidal shape, and the crown portion is connected to a road surface. At least one circumferential groove extending substantially linearly in the circumferential direction at the center of the tread, a plurality of inclined lug grooves intersecting the groove from the outside in the axial direction, and In the tire including the land portion divided by the groove group, and the rotation direction is determined so that the axially inner end of the inclined lug groove contacts the ground before the outer end, the lug groove has an axially inner end. The present invention is characterized in that the cross-sectional area of the inclined lug groove is formed to be substantially equal by reducing the width of the groove on a plane as compared with the outer end in the axial direction and increasing the groove depth. It is.

[0007]

The operation of the pneumatic tire having the above-described structure will be described. 1) The radial lug grooves leading to the circumferential main grooves are tapered in the width direction toward the equatorial plane. Since the inclination angle (relative to the equatorial plane) of the land portion at the time of movement becomes small, the shape becomes sharp, so that it is possible to suppress the striking component at the stepping-side edge of the radial lug groove at the stepping portion. 2) Then, by increasing the volume in the depth direction at the outlet on the equatorial plane side of the radial lug groove, the medium flow in the circumferential main groove, that is, the air flow and the water flow, A jet is not formed at the exit on the equatorial plane side of the lug groove, and the generation of excessive peeling / vortex there can be suppressed. As a result, both low noise and wetness can be achieved.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a tread pattern of a pneumatic tire according to an embodiment of the present invention, and FIG. 2 is an enlarged view of an inclined lug groove in the tread pattern of the pneumatic tire of FIG. FIG. 3 is a view showing three different shapes of AA cross section of the inclined lug groove of FIG.

In FIG. 1, a pair of central circumferential grooves 2 on the left and right of the tread 1 with respect to the equatorial plane C, these central circumferential grooves 2 and intermediate circumferential grooves 3 at the center of both ends 4 of the tread, respectively. Is formed. The tread end 4 and the middle circumferential groove 3, the middle circumferential groove 3 and the center circumferential groove 23 are respectively connected, and the inclined lug grooves 5 extend so as to converge on the equatorial plane C, and are formed in an arrowhead shape. Have been. In the example shown in FIG. 1, a plurality of pairs of left and right central circumferential grooves 2 are formed, but of course one may be provided. Tilt lug grooves 5 of the equatorial plane C toward shown in FIG. 2 is gradually narrowed from the maximum width W ₁ in the vicinity of the intermediate portion circumferential groove 3 is narrowed in width toward the center circumferential direction grooves 2, Minimum width W near central circumferential groove 2
_{It is 2} . W ₁ / W ₂ is 1.2 to 3.0.

In measuring the widths W ₁ and W ₂ , the opening of the inclined lug grooves 5 into the circumferential grooves 2 and 3 is locally widened by chamfering or curving the corners of the land portion 8. In this case, an average groove wall is drawn with a straight line, and measurement is performed on this straight line (virtual line). The groove depth increases toward the central circumferential groove 2 so as to compensate for the decrease in groove volume due to the reduction of the width of the lug inclined groove 5, and the depth of the inclined lug groove 5 increases so that the cross-sectional areas are substantially equal. .

[0013] A- of the inclined lug grooves 5 in FIGS.
3A, the bottom 5B of the inclined lug groove 5 in the embodiment of FIG. 3A is shallower than the bottom 2B of the central circumferential groove 2 at the position facing the intermediate circumferential groove 3. The groove depth linearly increases in that direction, and at the position where it intersects with the central circumferential groove 2, the two depths are the same.

In the modified example shown in FIGS. 3B and 3C, in FIG. 3B, the groove depth is closer to the end of the circumferential groove 3 than the bottom 3B of the circumferential groove 3. Starts from a shallow position, becomes slightly shallower toward the central circumferential groove 2, and then gradually becomes linearly deeper. Further, in FIG. 3C, FIG.
In the same manner as in the modified example, the groove depth of the inclined lug groove 5 becomes shallow for a while toward the central circumferential groove 2, then gradually increases to the center of the inclined lug groove 5, Groove 2
The same depth as the depth. In any case, if the width of the lug inclined groove 5 is compensated for by the depth of the inclined lug groove 5 in the transverse direction so as to compensate for the decrease in the groove volume due to the reduction of the width, and the cross-sectional area does not substantially change, It is still a thing which can produce the effect of. A central rib 6 is provided between the central circumferential grooves 2, a shoulder land portion 7 is provided between the inclined lug grooves 5 on the tread end 4 side, and the inclined lug grooves 5 provided on the central circumferential groove 2 side.
The portion between them is the central land portion 8.

Although the illustration of the pneumatic tire according to the embodiment of the present invention other than the tread is omitted, a known radial carcass and a similar known non-extensible belt layer are applied between the carcass and the tread. Of course, you can do that. Furthermore, as long as the circumferential grooves of the central circumferential groove 2 and the intermediate circumferential groove 3 are not completely straight lines as shown in the drawing, as long as the linearity is not impaired, for example,
It goes without saying that some ingress and egress may be provided on the left and right such as a shallow zigzag or a shallow deformed zigzag. In addition, deformation of the inclined lug groove is allowed as long as linearity is not impaired, including a slight curve shape, similarly to the circumferential groove.

Although the basic embodiment of the tread pattern of the pneumatic tire of the present invention has been described above, in order to eliminate the influence of the shoulder portion in the tire noise test, the inclined lug groove between the middle circumferential groove and the tread end is formed. The removed tread patterns of Examples and Comparative Examples of the present invention were applied to a test pneumatic tire, and an indoor unit test (automobile standard tire noise test method JASOC606) was performed.
At that time, the tire size of the pneumatic tire is 205 / 55R
At 16, the carcass has two polyester cord layers,
The belt layer is a tire having a common structure with two steel cord layers, the tread pattern is as shown in FIG. 4 (a), the circumferential groove is a straight groove, and the inclined lug groove is a second lug. 4 and FIG.
(A) and (b), and specific dimensions are as follows.

[0015]

1) Results of the indoor stand test (automobile standard tire noise test method JASOC606)

2) Wet Performance As a result of the test in 1), the decrease in the sound pressure level did not substantially change the groove volume of the lug groove, and it can be considered that the lug groove was improved. Therefore, the hydroplaning performance was maintained. It should be noted that the decrease in the groove width did not change the volume, pattern pitch, and the like of the inclined lug grooves, and did not worsen the water discharge.

[0018]

As described above in detail, the pneumatic tire of the present invention has a pair of sidewalls and a tread in which the crown portions extending over the both sidewalls are connected in a toroidal shape and the crown portions engage with the road surface. At least one circumferential groove in which the tread extends substantially linearly in the circumferential direction at the center thereof, a plurality of inclined lug grooves intersecting the groove in the shape of an arrow from the outside in the axial direction, and a land divided by the groove group. In the tire, the rotation direction is determined so that the axial inner end of the inclined lug groove is in contact with the outer end prior to the outer end, the lug groove has the axial inner end compared to the axial outer end. By reducing the groove width on a plane and increasing the groove depth by that amount, the cross-sectional area of the inclined lug groove is formed to be substantially equal, so that the noise is lower than that of a conventional pneumatic tire of this type. Not only superior in, while maintaining the wet resistance, in which the effect of such can be ensured a good operating in any state.

[Brief description of the drawings]

FIG. 1 is a diagram showing a tread pattern of a pneumatic tire according to an embodiment of the present invention.

FIG. 2A is an enlarged view of an inclined lug groove in a tread pattern of the pneumatic tire of FIG. 1; (B) is a perspective view of an inclined lug groove.

3A is a diagram showing an example of an AA cross section of the inclined lug groove of FIG. 2. FIG. (B) is a figure which shows another example of the AA cross section of the inclined lug groove of FIG. (C) is a figure which shows another example of the AA cross section of the inclined lug groove of FIG.

FIG. 4A is a diagram showing a tread pattern of a comparative example of a pneumatic tire subjected to a test on a stand alone. (B)
FIG. 2 is a view showing a tread pattern of an example of the present invention of a pneumatic tire subjected to a test on a single stand.

[Explanation of symbols]

Reference Signs List 1 tread 2 central circumferential groove 2B bottom of circumferential groove 3 middle circumferential groove 3B bottom of circumferential groove 4 tread end 5 inclined lug groove 5B bottom of inclined lug groove 6 central rib 7 shoulder land 8 central land Part W ₁ Maximum width near central circumferential groove 2 W ₂ Minimum width near central circumferential groove 3

Claims (1)

(57) [Claims] 1. A pair of sidewalls and a crown portion extending over both sidewalls are connected in a toroidal shape, and the crown portion is provided with a tread which engages with a road surface, and the tread is substantially linearly formed in a central portion thereof in a circumferential direction. At least one circumferential groove extending in the axial direction, a plurality of inclined lug grooves intersecting the groove from the outside in the axial direction, and a land portion divided by the groove group, and an axial inner end of the inclined lug groove. In a tire in which the rotation direction is determined such that the ground contact is made earlier than the outer end, the lug groove narrows the planar groove width at the axial inner end compared to the axial outer end, while increasing the groove depth. A pneumatic tire wherein the cross-sectional areas of the inclined lug grooves are formed to be substantially equal by increasing the depth.