JP2001294018A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve gripping force, steering stability, and wear resistance during use in a flatly serviced dirt course. SOLUTION: In this pneumatic tire, a block B is partitioned in a tread surface 1A and a side protection part 7 comprising an annular irregular part extending in a tire circumferential direction is provided in a sidewall part 2. A ratio TW/SW of a width TW of the tread surface 1A and a tire maximum width SW at the sidewall part 2 is set at 0.850 to 1.000. An edge part 1b of a shoulder part 1B is chamfered into a circular arc with a radius R of 5 to 40 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire having improved grip force, steering stability and abrasion resistance, particularly when used on a flat dirt course. For entering tires.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 3, a pneumatic tire used in a dirt course competition is provided with a side protect portion 12 comprising an uneven portion extending in a tire circumferential direction on a sidewall portion 11 so as to prevent obstacles. On the other hand, the side wall portion 11 is protected. A large number of blocks 15 are defined on the tread surface 13 by circumferential grooves 14 and lateral grooves (not shown), and the edge portions 18 of the shoulder portions 17 of the tread portion 16 are squared (so-called sharp edges). The grip effect is ensured by those edge effects.

In recent years, the development of dirt courses has been progressing, and the number of courses on flat road surfaces with little gravel is increasing. In such a dirt course on a flat road surface, the pneumatic tire having the sharp edge described above is
Since the load on the shoulder portion 17 is greatly increased during cornering, the block 15a of the shoulder portion 17 is likely to fall down. As a result, the grip force is reduced, and the shoulder portion 17
Therefore, there is a problem that the progress of wear of the shoulder portion 17 is accelerated and the wear resistance is reduced. In addition, the sharp edge causes a discontinuity in the steering feeling (feeling of response) during cornering, which causes a problem that steering stability is deteriorated.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a pneumatic tire capable of improving grip force, steering stability and wear resistance when used on a flatly maintained dirt course. It is in.

[0005]

A pneumatic tire according to the present invention, which achieves the above object, has a block formed on a tread surface, and an uneven portion extending over one circumference of the tire in the tire circumferential direction on a sidewall portion. In a meridional section of a pneumatic tire provided with a side protect portion made of: a ratio TW / SW between a width TW of the tread surface and a maximum width SW of the tire at the sidewall portion is 0.850 to 1.00.
While being set to 0, the edge of the shoulder of the tread is chamfered with an arc having a radius of 5 to 40 mm.

By setting the ratio TW / SW between the width TW of the tread surface and the maximum width SW of the tire as described above, the width of the tread surface is made wider than in the prior art so that the tread surface in contact with the road surface is grounded. The area can be increased.
Therefore, on a flat dirt course,
Since the ground contact area exerts a greater effect on the grip force of the tire than the edge effect on the tread surface, a high grip force can be obtained through the frictional force due to the contact of the tread surface with the widened tread surface.

[0007] In addition to the above-mentioned wide grounding surface, by chamfering the edge portion of the shoulder portion as described above,
Since the fall of the block of the shoulder part can be suppressed, the load applied from the road surface to the tread surface can be distributed to the widened tread surface, so that early wear of the shoulder part is avoided, and the wear of the entire tread surface also progresses It becomes possible to suppress.

Further, by chamfering the edge portion of the shoulder portion as described above, the steering feeling during turning can be made continuous, so that the steering stability can be improved.

Here, the “tread surface width TW”, the “tire maximum width SW”, and the “radius of the edge portion of the shoulder portion” are respectively defined by mounting the tire on a rim specified in the 1999 edition of JATMA. This is a value when air is filled at an internal air pressure of 180 kPa.

[0010]

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

FIG. 1 shows an example of a pneumatic tire according to the present invention, wherein 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion. A carcass layer 4 is mounted between the left and right bead portions 3, and the end of the carcass layer 4 is wound around a bead core 5 embedded in the bead portion 3 from the inside of the tire to the outside. Outside the carcass layer 4 of the tread portion 1, two belt layers 6 are provided over one circumference of the tire in the tire circumferential direction. The tread surface 1A has a circumferential groove C
And a lateral groove (not shown) define a block B.

The sidewall portion 2 is provided with a side protect portion 7 composed of an uneven portion extending over one circumference of the tire in the tire circumferential direction, and protects the sidewall portion 2 against obstacles during running. It has become. In the vicinity of the bead portion 3 of the side wall portion 2, a convex rim protect bar 8 extending over one circumference of the tire in the circumferential direction of the tire is provided so as to protect the mounted rim from obstacles during traveling. I have to.

The ratio TW / SW between the width TW of the tread surface 1A and the maximum width SW of the tire in the sidewall portion 2 is as follows:
It is set in the range of 0.850 to 1.000, and is set in the conventional (0.
716-0.840). The edge 1b of the shoulder 1B of the tread 1 is chamfered with an arc having a radius R of 5 to 40 mm.

Here, the width TW of the tread surface 1A is
As shown in FIG. 1, the side wall surface 2 a at the portion in contact with the chamfered portion m has a circular arc shape (curved shape) in the tire meridian direction.
, The tangents x1 and x2 to the sidewall surface 2a inclined at an angle of 20 ° with respect to the direction orthogonal to the tire axis, and the tread surface 1A (plurality) formed in an arc-shaped cross section in the tire meridian direction. In the case of being formed by a circular arc, a distance parallel to the tire axis between intersections z1 and z2 with extension lines y1 and y2 of the shoulder portion 1B).

As shown in FIG. 2, when the side wall surface 2a of the portion in contact with the chamfered portion m is linear in the tire meridian section, the extension lines s1, s2 and the extension line of the tread surface 1A are provided. Intersection points z1, z2 with y1, y2
Distance parallel to the tire axis.

The tire maximum width SW is the tire cross-section width of the widest part except for the rim protect bar 8 in the meridian direction.

As described above, in the present invention, the ratio TW / SW between the width TW of the tread surface 1A and the maximum tire width SW is set to be larger than that of the related art as described above, and the area of the tread surface 1A that contacts the road surface is reduced. Make it wider. In a flatly maintained dirt course, the contact area has a greater effect on the grip force of the tire than the edge effect of the tread surface. Therefore, it is necessary to secure a high grip force by the frictional force due to the surface contact of the wide tread surface 1A. Can be.

Further, in addition to the above-mentioned wide contact surface, the edge portion 1b of the shoulder portion 1B is chamfered as described above so as to prevent the block B of the shoulder portion 1B from falling down, so that the edge portion 1b is added to the tread surface 1A. Since the load can be distributed to the wide tread surface 1A, it is possible to prevent early wear of the shoulder portion 1B, and also to suppress progress of wear of the entire tread surface 1A, thereby improving wear resistance. Improvements are possible.

The ratio TW / SW between the width TW of the tread surface 1A and the maximum tire width SW of the sidewall portion 2 is 0.850.
If it is smaller, it is difficult to obtain the above-described improvement effect. Conversely, if it is larger than 1.000, the tread portion 1 becomes wider than the sidewall portion 2, so that the movement of the sidewall portion 2 becomes unstable, and the steering stability cannot be improved. Preferably, it is 0.900 to 1.000.

If the radius R of the edge portion 1b is less than 5 mm, the effect of suppressing the falling of the block B of the shoulder portion 1B is insufficient, while if it exceeds 40 mm, the contact length of the shoulder portion 1B becomes too short. However, it is difficult to obtain the effect of improving the steering stability. Preferably, 10 to 30
mm is better.

In the present invention, the edge portion 1b of the tread shoulder portion 1B may be configured to be chamfered in a polygonal or elliptical shape instead of the arc-shaped chamfer described above.

[0022]

EXAMPLE The tire 1 of the present invention having a tire size common to 205 / 65R15, a tire having the configuration shown in FIG. 1, a constant chamfer radius R at the edge portion of 30 mm, and a change in TW / SW as shown in Table 1. To 4 and comparative tires 1 and 2 were produced.

[0023] These tires have a rim size of 15 x 7.0.
It was mounted on a JJ rim, and an evaluation test of grip force and steering stability was performed under the following measurement conditions. Table 1 shows the results.

Grip force : Each test tire was attached to a cornering tester, air pressure was 230 kPa, and load was 3.
The cornering force was measured under the conditions of 5 kN, a slip angle of 3 °, and a camber angle of 0 °, and the result was evaluated by an index using the comparative tire 1 as 100. The larger this value, the better the grip force.

Driving stability : Each test tire was subjected to an air pressure of 230
Attach it to a 2.0 liter front and rear wheel drive car at kPa, and perform a feeling test with five trained test drivers on a hard dirt course of 2.6 km per round, which is maintained flat, and evaluated on a five-point scale did.
The evaluation results were shown as an average value of five persons (rounded off to the nearest whole number). The larger this value, the better the ride comfort.

[0026]

[Table 1]

From Table 1, TW / SW is set to 0.850-1.
When it is set to 000 (the tires of the present invention 1 to 4), it is understood that both the grip force and the steering stability are excellent as compared with the cases outside of this range (the comparative tires 1 and 2).

The tire size is made common to 205 / 65R15, and the TW / S
Inventive tires 5 to 9 and comparative tire 3 in which W was fixed at 0.900 and the chamfer radius R of the edge portion was changed as shown in Table 2.
To 4 were respectively produced.

Each of these tires has a rim size of 15 × 7.0.
Attached to the JJ rim, the grip force and the steering stability were evaluated in the same manner as described above, and the wear resistance was evaluated as described below. Table 2 shows the results.

Abrasion resistance : Each test tire was subjected to an air pressure of 230 k.
Attach to 2.0 liter front and rear wheel drive car to Pa,
After running 13 km on a hard dirt course having a circumference of 2.6 km and being flatly maintained, the wear amount of the shoulder portion was measured, and the comparative tire 3 was evaluated as 1 on a three-point scale. The larger the value, the better the wear resistance.

[0031]

[Table 2]

As is clear from the table, the radius R is 5 to 40.
When the thickness is set to mm (the tires of the present invention 5 to 9), the grip force, the steering stability, and the wear resistance are all superior to those outside the above range (comparative tires 3 to 4).

[0033]

As described above, according to the present invention, the ratio TW / SW of the width TW of the tread surface to the maximum width SW of the tire and the chamfer radius R of the shoulder edge portion are specified as described above, so that the flatness is reduced. Grip force, handling stability, and wear resistance when used on a maintained dirt course can be improved.

[Brief description of the drawings]

FIG. 1 is a tire meridian direction sectional view showing an example of a pneumatic tire of the present invention.

FIG. 2 is a sectional view of a main part showing another example of the tire of FIG. 1;

FIG. 3 is a schematic cross-sectional view in the tire meridian direction showing an example of a conventional pneumatic tire.

[Explanation of symbols]

 Reference Signs List 1 tread portion 1A tread surface 1B shoulder portion 1b edge portion 2 sidewall portion 3 bead portion 4 carcass layer 5 bead core 6 belt layer 7 side protect portion 8 rim protect bar B block R radius SW tire maximum width TW tread surface width m chamfering Department

Claims (5)

[Claims] In a meridional section of a pneumatic tire, a block is formed on a tread surface, and a sidewall portion is provided with a side protect portion formed of an uneven portion extending over one circumference of the tire in a circumferential direction of the tire. The ratio TW / SW of the width TW of the tread surface to the tire maximum width SW in the sidewall portion is 0.850 to
A pneumatic tire in which the edge of the shoulder of the tread is chamfered with an arc having a radius of 5 to 40 mm while being set to 1.000. 2. The method according to claim 1, wherein the radius is 10 to 30 mm.
The pneumatic tire as described. 3. The ratio TW / SW is 0.900 to 1.0.
The pneumatic tire according to claim 1, wherein the value is 00. 4. The shoulder portion edge portion having a radius of 5
The pneumatic tire according to claim 1 or 3, wherein a chamfer is formed in a polygonal shape or an elliptical shape instead of the configuration in which the chamfer is formed with a 40 mm arc. 5. The pneumatic tire according to claim 1, wherein a convex rim protect bar extending over one circumference of the tire in the tire circumferential direction is provided near a bead part of the sidewall part.