JPS6181207A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To increase the longitudinal deflection of a pneumatic tire with the actual ground area ratio of 40-65% and improve the running characteristics and resistance to cut by forming a preset number of circumferential grooves at the specific height position of a side wall section. CONSTITUTION:A pneumatic tire is provided with a pair of bead section 2 and filler 3, a carcass layer 4, a tread section 5, and a side wall between the bead section 2 and the tread section 5. In such a pneumatic tire with the actual ground area ratio of 40-65%, three or more circumferential grooves 10 are formed at the side wall section 6 located at the 30-75% position from the bead section 2 side for the tire cross-sectional height SH. These circumferential grooves 10 are formed within the ranges of 2.0mm or more and less than 7.0mm in depth and 2.5mm or more and less than 15mm or less in picks. Besides, the circumferential grooves 10 are all formed in cross-sectional waveforms consisting of protrusions 11 and recesses 12 with roundnesses.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a pneumatic tire, and more particularly to an improvement in a pneumatic tire suitable for use as a rally tire running on irregular roads.

[Conventional technology]

Traditionally, tire sidewalls have been formed relatively flat without large irregularities, and rally tires have a similar structure.

When tires with such a profile are driven on uneven roads, they hit rocks, stones, etc. and are susceptible to side cuts, which often results in errors from cuts.

For this reason, rally tires and other tires that run on uneven roads must be reinforced by using stronger carcass materials, thickening the rubber gauge in the sidewalls, and inserting reinforcement into the sidewalls due to the structure of the tires. I was going.

As a result, although the cut resistance of the sidewall portion is improved, the tire rigidity, that is, the spring constant of the tire and the impact force against the protrusions are increased, and the steering stability, which is the original function of the tire, may be impaired.

In addition, as tires have become flatter in recent years, the flex zone of the tire has become narrower, and if the structure is designed with cut resistance in mind, such as rally tires, the tire side rigidity will further increase, and when riding over a large protrusion, the flex zone of the tire will become narrower. , the input applied to the vehicle's suspension becomes large, and there is a lot of damage to the vehicle.

On the other hand, when a load is applied to the tire and the tire deflects, the surface strain of the sidewall rubber will be:

It is known that the tire price increases by about 15% compared to before putting air into the tire, and when driving on an uneven road in the rain,
This strain and the lubrication effect of moisture caused the cut resistance to deteriorate significantly.

[Purpose of the invention]

An object of the present invention is to provide an excellent pneumatic tire that eliminates the above-mentioned conventional drawbacks and can improve stable running performance and cut resistance.

[Structure of the invention]

That is, the present invention provides a pneumatic tire with an actual ground contact area ratio of 40 to 65%, in which three or more circumferential grooves are formed in the sidewall portion at a position of 30 to 75% from the bead side with respect to the tire cross-sectional height. The gist of this article is a pneumatic tire characterized by the following.

Hereinafter, the present invention will be specifically described by way of examples with reference to the drawings.

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

In the figure, reference numeral 1 denotes a pneumatic tire according to an embodiment of the present invention, which includes a pair of bead parts 2 and a filler 3, a carcass layer 4 connecting these, and a cylindrical tread part 5 in the center. A sidewall portion 6 is arranged between the bead portion 2 and the bead portion 2 .

A belt layer 7 is arranged in the tread portion 5 with a width of 85 to 115% of the tread width. This belt layer 7 is made of reinforcing cords made of non-stretchable cords such as steel cords and aromatic polyamide fiber cords.
Two or more sheets are stacked one on top of the other, intersecting each other at an angle of 27°.

Further, these heald layers 7 are entirely covered with tread rubber 8.

On the other hand, the side wall portion 6 includes the tread portion 5 and the bead portion 2.
0, and is covered with side tread rubber 9 on the outside of the carcass layer 4.

Reference numeral 10 in the figure indicates a circumferential groove disposed in the sidewall portion 6, which is disposed at a position 30% to 75% from the bead side of the tire cross-sectional height SH shown in FIG.

The circumferential grooves 10 preferably have a depth of 2.01 mm or more and 7.0 mm or less, a pitch of 2,5111 mm or more and 15 mm or less, and at least three grooves are arranged.

FIG. 3 shows an example of the shape of the circumferential groove 10 described above.
In (A), both the convex portion 11 and the concave portion 12 of the circumferential groove 10 are rounded, and the cross section is wavy.

In (B), only the concave portions 12 are rounded, and the surfaces of the convex portions 11 are flat. (C) shows the convex portion 11. Both of the recesses 12 are angular. Example (D) is similar to example (B) in that only the concave portion 12 is rounded, but the surface of the convex portion 110 coincides with the tire profile line and is simply grooved. (
E) is an example in which the bottom of the recess 12 is flat, but the corners are rounded.

FIG. 4 shows the position of the circumferential groove 10 in the width direction.
), the tire profile line 13 is the convex part 11 and the concave part 1
In (B), the tire profile line 13 is in contact with the surface of the convex portion 11. In this way, in the present invention, the profile line of the tire is aligned with the circumferential groove 1.
It is preferable that the depth is in the range of 0.

Next, the effects of the present invention will be explained with reference to the drawings.

Figure 5 is a graph showing the relationship between the vertical load and vertical deflection of a tire size 1655R13, air pressure 1.9° rim 5 1/2 Jx13, where curve A shows the product of the present invention and curve B shows the conventional product. ing.

As shown in FIG. 5, the tire of the present invention having circumferential grooves 10 has a larger amount of vertical deflection than a conventional tire without circumferential grooves, and has a greater vertical spring constant than conventional tires. Appropriate values can be obtained.

Especially for rally tires that run on rough roads, in consideration of cut resistance, cords with high cutting strength are used in the carcass layer, the number of carcass layers is increased, and the sidewall part has high rigidity. , the amount of vertical deflection decreases, the tire's vertical spring constant becomes extremely high, and the input to the vehicle suspension also increases.

FIG. 6 shows the relationship between vertical impact force and speed in the case of running over a protrusion, and FIG. 7 shows the relationship between longitudinal impact force and speed.

From the figure, it can be seen that product A of the present invention has a vertical impact force that is approximately 15% lower than conventional product B, and has improved handling stability and ride comfort.

FIG. 8 is a graph showing the relationship between the vertical load and the ground contact area, and it can be seen that the product A of the present invention has a larger ground contact area under the same load than the conventional product.

Therefore, the traction of the tire while driving.

Braking performance and cornering characteristics are improved.

Figure 9 is a diagram showing the degree of tire deflection under load and under no load, where the solid line a represents the shape of the tire under no load, the dotted line represents the shape of the tire under load, and Ra and Rh represent the curvature of the tire under no load and under load, respectively. It represents the radius.

As shown in FIG. 9, when a load is applied to the tire, the tire deflects, and the radius of curvature of the side wall portion becomes smaller. For this reason, the outer covering rubber (side rubber) in the sidewall section is subjected to tension and causes distortion, and the distortion is maximum at the surface. This side rubber is arranged for the purpose of preventing damage to the tire, and is an important constituent material especially for rally tires that run on rough roads.

Therefore, the side rubber of a rally tire is thicker than that of a general passenger car radial tire, and when a vertical load is applied to the tire and deflection occurs, surface strain on the side portion tends to increase.

It is known that the surface distortion of the sidewall section generally increases by about 15% when the vertical deflection of the tire is around 20II11 compared to when it is unloaded, but for rally tires with thick side rubber, etc. This distortion increases.

However, by arranging the circumferential grooves 10 in the range shown in Fig. 2, when a vertical load is applied to the tire, the surface strain due to deflection is separated by the circumferential grooves, and the surface of the side protrusions is Since distortion can be significantly reduced, side cuts can be prevented.

〔Effect of the invention〕

As mentioned above, the present invention has an actual ground contact area ratio of 40 to 65%.
In pneumatic tires, there is a
Since more than one circumferential groove is formed, the vertical deflection of the tire can be increased.

As a result, it is possible to effectively alleviate the excessively high side rigidity of a tire structure such as a rally tire that emphasizes cut resistance.

In addition, it is possible to reduce the protrusion impact force, and also to reduce the surface distortion caused by the deflection of the sidewall portion, so it is possible to significantly improve the tire running characteristics and cut resistance.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional explanatory diagram showing a pneumatic tire according to an embodiment of the present invention, Fig. 2 is a graph showing the relationship between circumferential groove load and vertical deflection, and Fig. 6 is a vertical impact force of the tire. Figure 7 is a graph showing the relationship between speed and speed.
Fig. 8 is a graph showing the relationship between impact force and speed, Fig. 8 is a graph showing the relationship between tire vertical load and ground contact area, and Fig. 9 is an explanatory diagram showing the degree of tire deflection under load. 1-tire, 2-bead part, 3-filler, 4--carcass layer, 5--tread part, 6-sidewall part,
7-Belt layer, 8-) Red rubber, 9-Side tread rubber, 10-Circumferential groove, 11-Protrusion, 12-Four parts, 13
- Tire profile line.

Claims (1)

[Claims] A pneumatic tire with an actual ground contact area ratio of 40 to 65%, characterized in that three or more circumferential grooves are formed in the sidewall portion at a position of 30 to 75% from the bead side with respect to the tire cross-sectional height. pneumatic tires.