JP2003276406A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire having improved muddy road travelling performance without worsening control stability and pattern noises on a dry road surface. <P>SOLUTION: The pneumatic tire comprises lug grooves 8 formed in a shoulder region on a tread portion 1. At least one protrusion 9 having a triangular cross section formed by cutting the lug groove 8 in its groove depth along the longitudinal direction is provided in the groove bottom of each lug groove 8. A relationship, h≤SGD/2, is established between a height h of the protrusion 9 and a groove depth SGD and a relationship, α<β≤90°, is established between an inclination α of a slope of the protrusion 9 on a tread center side and an inclination β of a slope the protrusion 9 outside a tread. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire suitable for running on muddy ground, and more particularly to a pneumatic tire for avoiding deterioration of performance of other tires when improving running performance on muddy ground. Containing tires.

[0002]

2. Description of the Related Art Mud running performance is one of the important performances for pneumatic tires classified as mud and snow. In order to improve this mud running performance,
Conventionally, methods such as increasing the groove area ratio in the tread portion and increasing the lug groove width have been proposed. However, increasing the groove area ratio or the lug groove width causes deterioration of steering stability and pattern noise on a dry road surface. Therefore, it is extremely difficult for both of these methods to achieve both the running performance on mud and other tires.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a pneumatic tire capable of improving the running performance on a muddy ground without deteriorating the steering stability and the pattern noise on a dry road surface. It is in.

[0004]

The pneumatic tire of the present invention for solving the above-mentioned problems is a pneumatic tire having a lug groove in a shoulder region of a tread portion, wherein the lug groove is formed at the bottom of the lug groove. Is provided with at least one protrusion having a triangular shape in a cross section cut out in the groove depth direction along the longitudinal direction, and the height h of the protrusion is h with respect to the groove depth SGD.
≤SGD / 2, and the inclination angle α of the slope on the tread center side of the projection and the inclination angle β of the slope on the tread outer side of the projection are in the relationship of α <β≤90 °. To do.

By providing at least one protrusion having a predetermined cross-sectional shape on the groove bottom of the lug groove in this way, it becomes possible to improve the earth scavenging property without unnecessarily widening the groove width of the lug groove. Become. Therefore, it is possible to improve the running performance on a muddy ground without deteriorating the steering stability and the pattern noise on the dry road surface. Further, since the height h of the protrusion is suppressed to be half or less of the groove depth SGD of the lug groove, the wet performance is not hindered.

In the present invention, the height h of the protrusion is the groove depth S.
It is preferable to have a relationship of SGD / 5 ≦ h ≦ SGD / 2 with respect to GD. Further, it is preferable that the inclination angle α of the slope of the protrusion on the tread center side and the inclination angle β of the slope of the protrusion on the outer side of the tread have a relationship of 30 ° ≦ α <β ≦ 90 °. Further, the inclination angle α of the slope on the tread center side of the protrusion and the inclination angle β of the slope on the outer side of the tread of the protrusion are β−
It is preferable to have a relationship of α ≧ 30 °. By satisfying these conditions, it becomes possible to obtain better soil repellency.

[0007]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows a pneumatic tire according to an embodiment of the present invention. In FIG. 1, 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion. A carcass layer 4 is mounted between the pair of left and right bead portions 3, 3. Both ends of the carcass layer 4 in the tire width direction are folded back around the bead core 5 from the tire inner side to the outer side. Further, a plurality of belt layers 6 are provided on the outer peripheral side of the carcass layer 4 in the tread portion 1. However,
These are merely examples, and the tire internal structure is not particularly limited.

A plurality of main grooves 7 extending in the tire circumferential direction are provided in the center region of the tread portion 1. On the other hand, the shoulder region of the tread portion 1 is provided with a plurality of lug grooves 8 extending in the tire width direction. These lug grooves 8 need to exist at least in the shoulder region, but may extend to the center side.
Further, the tread portion 1 may be provided with a lateral groove or sipe (not shown), and the ribs divided by the main groove 7 may be formed into blocks.

As shown in FIG. 2, the lug groove 8 has a plurality of protrusions 9 having a triangular shape in a cross section cut out in the groove depth direction along the longitudinal direction, as shown in FIG. It is provided. It is preferable that these protrusions 9 are formed over the entire width of the lug groove 8, but it is also possible to provide them in a part in the width direction. The height h of the projection 9 from the groove bottom satisfies the relationship of h ≦ SGD / 2, and more preferably SGD / 5 ≦ h ≦ SGD / 2, with respect to the groove depth SGD of the lug groove 8.
Also, the inclination angle α of the slope of the protrusion 9 on the tread center side
And the inclination angle β of the slope of the protrusion 9 on the outer side of the tread are α <
It satisfies the relation of β ≦ 90 °, more preferably 30 ° ≦ α <β ≦ 90 °. However, the inclination angles α and β of the slope of the protrusion 9 are angles with respect to the base of the triangle forming the protrusion 9.

As shown in FIG. 3A, when the tread portion 1 is not in contact with the ground, the groove bottom line 8A of the lug groove 8 is curved according to the tread radius. On the other hand, as shown in FIG. 3B, when the tread portion 1 is in contact with the ground, the groove bottom line 8A of the lug groove 8 is linear. In the present invention, by utilizing the change in the groove bottom radius when the tire is in contact with the ground and when the tire is not in contact with the ground,
It guides the mud clogged into the outside of the ditch.

Here, if the height h of the protrusion 9 is less than SGD / 5, the effect of improving the earth scavenging property becomes insufficient, and conversely SGD
If it exceeds / 2, the wet performance is deteriorated and the hydroplaning phenomenon is likely to occur. If the inclination angle β of the slope of the protrusion 9 on the outer side of the tread exceeds 90 °, the earth unloading property deteriorates.
The inclination angle α of the slope of the protrusion 9 on the tread center side is 30.
If it is less than °, the effect of improving the soil discharging property becomes insufficient, and if it is β or more, the soil discharging property deteriorates. In particular, if the relationship of β-α ≧ 30 ° is satisfied, it becomes possible to obtain better soil removal performance.

When the projection 9 having a predetermined cross-sectional shape is provided on the groove bottom of the lug groove 8 as described above, it becomes possible to improve the running performance on the mud ground due to the improvement of the soil discharging property, and the groove area ratio as in the conventional case. Since it is not necessary to increase the steering angle and the lug groove width, it is possible to avoid deterioration of steering stability and pattern noise on a dry road surface.

[0014]

EXAMPLES In a pneumatic tire having a tire size of 265 / 70R16 and having a plurality of lug grooves in the shoulder region of the tread portion, tires 1 to 1 of the present invention in which a plurality of protrusions having a triangular cross section are provided on the groove bottom of the lug groove 4 and comparative tires 1 to
3 and conventional tires 1 and 2 in which the groove bottom of the lug groove was flat were manufactured. Inventive tires 1 to 4 and comparative tire 1
3 to 3, as shown in Table 1, the groove depth SG of the height h of the protrusion
The ratio with respect to D, the inclination angle α of the slope on the tread center side of the protrusion, and the inclination angle β of the slope on the outside of the tread of the protrusion are variously changed. The conventional tire 2 has a wider lug groove width than the conventional tire 1. In Table 1, the lug groove width is an index value with the conventional tire 1 being 100.

With respect to these test tires, wet performance, running performance on muddy ground, steering stability on dry road surface, and pattern noise were evaluated under the following measurement conditions, and the results are shown in Table 1.
Are also shown.

Wet performance: A test tire was inflated to 200
The vehicle was mounted at kPa, traveled on a straight road provided with a pool having a water depth of 10 mm, the passing speed of the pool was gradually increased, and the speed at which the hydroplaning phenomenon occurred was measured. The evaluation results are shown by an index with the conventional tire 1 being 100. The larger the index value, the better the wet performance.

Mud running performance: test tire pressure 20
It was mounted on a vehicle at 0 kPa, traveled on a mud, and the amount of adhered mud after running was measured. The evaluation results are shown by an index with the conventional tire 1 being 100. The larger the index value, the better the running performance on the mud.

Steering stability on dry road surface: A test tire was mounted on a vehicle at an air pressure of 200 kPa, and a feeling test was conducted by a test driver on a dry paved road surface. The evaluation results are shown by an index with the conventional tire 1 being 100. The larger this index value, the better the steering stability on dry road surface.

Pattern noise: test tire with air pressure 20
It was mounted on a vehicle at 0 kPa, and the noise level due to pattern noise when the vehicle passed through a dry paved road surface was measured. The evaluation results are shown by an index with the conventional tire 1 being 100, using the reciprocal of the measured value. A larger index value means less pattern noise.

[0020]

[Table 1]

As can be seen from Table 1, the tire 1 of the present invention
All of Nos. 4 to 4 had good running performance on muddy ground, and were able to maintain the wet performance, steering stability on dry road surface, and pattern noise at the same level as the conventional tire 1. On the other hand, the tire 2 of the related art has a wide lug groove width, so that although it has good running performance on mud and wet performance, the steering stability and pattern noise on dry road surfaces deteriorated. Since the comparative tire 1 had α> β, the running performance on the mud was deteriorated. Since the comparative tire 2 had β> 90 °, the running performance on the muddy ground was deteriorated. Comparative tire 3 is h
> SGD / 2, so the wet performance deteriorated.

[0022]

As described above, according to the present invention, in the pneumatic tire having the lug groove in the shoulder region of the tread portion, the lug groove is formed along the longitudinal direction at the groove bottom of the lug groove. At least one protrusion having a triangular shape in a cross section cut in the direction is provided, and the height h of the protrusion has a relationship of h ≦ SGD / 2 with respect to the groove depth SGD, and the protrusion has a tread center side. The inclination angle α of the slope and the inclination angle β of the slope outside the tread of the protrusion are α <β ≦ 90 °
It becomes possible to improve the soil discharge performance (mud performance) without unnecessarily widening the groove width of the lug groove, and as a result, steering stability and pattern noise on dry road surface are deteriorated. It is possible to improve the running performance on the mud ground without causing it.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a pneumatic tire according to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of a portion A of FIG.

FIG. 3 shows a protrusion provided in a lug groove, (a) is a contour diagram when the tread portion is not grounded, and (b) is a contour diagram when the tread portion is grounded.

[Explanation of symbols]

1 tread section 2 Side wall part 3 bead part 4 carcass layers 5 bead core 6 belt layers 7 main groove 8 lug grooves 9 protrusions h Height of protrusion Groove depth of SGD lug groove Angle of inclination of the slope on the tread center side of the α protrusion Inclination angle of the slope outside the tread of the β protrusion

Claims (5)

[Claims] 1. A pneumatic tire having a lug groove in a shoulder region of a tread portion, wherein a groove bottom of the lug groove is provided.
The lug groove is provided with at least one protrusion having a triangular shape in a cross section cut out in the groove depth direction along the longitudinal direction, and the height h of the protrusion is h ≦ SGD / 2 with respect to the groove depth SGD. And the inclination angle α of the slope of the projection on the tread center side and the inclination angle β of the slope of the projection on the outer side of the tread are in the relationship of α <β ≦ 90 °. 2. The pneumatic tire according to claim 1, wherein the height h of the protrusion has a relationship of SGD / 5 ≦ h ≦ SGD / 2 with respect to the groove depth SGD. 3. The inclination angle α of the slope of the protrusion on the tread center side and the inclination angle β of the slope of the protrusion on the outer side of the tread have a relationship of 30 ° ≦ α <β ≦ 90 °. The pneumatic tire according to 2. 4. The inclination angle α of the slope of the protrusion on the tread center side and the inclination angle β of the slope of the protrusion on the outer side of the tread have a relationship of β-α ≧ 30 °. Pneumatic tire described. 5. The pneumatic tire according to claim 1, which is for running on muddy ground.