JPH09132011A - Heavy loading pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide both wear resistance and wet performance by making a negative ratio less than a specified value, and making a disposing shape for a main groove optimum. SOLUTION: Main grooves 4a and 4b are formed into a directional pattern while being spaced from each other, and a plurality of them are disposed therein, and the end terminals 5a and 5b of the main grooves are located in the area corresponding to the 25% of a tread width around a tire equator 3. In the area of a space enclosed between the tire equator 3 and at least the 25% position of the tread width, a crossed axes angle α formed by a tangent (m) which touches the circle of each main groove, and a tire equator surface, is gradually increased as the portion of each main groove is parted from the tire equator, and the continuous projected length in the width direction and projected length in the circumferential direction shall be equal to or more than 30%, and 70% of the tread width respectively.

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, which has a relatively small negative ratio to ensure good wear resistance and enhances groove disposition efficiency. The present invention relates to a heavy duty pneumatic tire having wet performance.

[0002]

2. Description of the Related Art In order to sufficiently exhibit wet performance such as driving and braking performance on a wet road surface, a tread portion of a tire extends in a main groove extending along a tire circumference and in a tire width direction. Various grooves such as auxiliary grooves are generally arranged as necessary. To improve wet performance,
It is useful to increase the proportion of the groove area on the tread surface, that is, the so-called negative ratio. On the contrary, in order to improve the wear resistance, it is preferable to reduce the proportion of the groove area on the tread surface. . Therefore, the wet performance and the wear resistance have a contradictory relationship, and it has been difficult to satisfy both of them.

[0003]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to set the negative ratio to a relatively small value of 0.3 or less to ensure sufficient wear resistance and to properly arrange the main groove. Thus, it is to provide a heavy duty pneumatic tire having good wet performance.

[0004]

In order to achieve the above object, the present invention has a tread portion which extends in a curved shape from both tread ends in a direction in which the tread ends converge on the tire equator, and the ends thereof are on the tire equator or the tire equator. In the vicinity area, a plurality of main grooves that are coincident with or apart from each other are arranged at intervals along the tire circumference, and the main grooves are sequentially arranged in the tire contact area from the end to the tread end. In a heavy-duty pneumatic tire having an entering directional pattern, the negative ratio is 0.3 or less, and the end of the main groove is within a region of 25% of the tread width W around the tire equator. In the area sandwiched between the equator and the position at least 25% of the tread width W from now on, the main groove portion is such that the intersection angle α between the tangent line m drawn to this and the tire equator plane is separated from the tire equator. According to Titrated becomes, the widthwise projected length L ₁ of consecutive main grooves, not less than 30% of the tread width W, continuous circumferential projection length L ₂ of the main groove is more than 70% of the tread width W Is a pneumatic tire for heavy loads. In addition, the tangent line m drawn to the above portion of the main groove
Specifically, means a tangent line drawn to an imaginary line passing through the groove width center of the main groove, and the continuous width-direction projected length L of the main groove.
₁ and the circumferential direction projected length L ₂ mean the length when an imaginary line passing through the groove width center of the main groove is projected on each of the lines along the width direction and the circumferential direction.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a partially developed tread portion of a typical heavy duty pneumatic tire according to the present invention. In the figure, reference numeral 1 is a tread portion, 2a and 2b are tread ends. 3 is a tire equator, 4a and 4b are main grooves, 5
a and 5b are the ends of the main groove.

In the tire having the tread pattern shown in FIG. 1, the tread portion 1 has curved ends extending from both tread ends 2a and 2b in a direction in which the tread ends 2a and 2b converge on the tire equator 3. A plurality of main grooves 4a and 4b, which are located at positions displaced from each other by a half pitch in the direction and at the same distance from the tire equator 3, are arranged at intervals along the tire circumference. Groove 4a
Or 4b from the end 5a or 5b to the tread end 2a
Alternatively, a directional pattern that sequentially enters the tire contact area toward 2b is formed.

The arrangement of the ends 5a, 5b of the main grooves 4a, 4b can be various modes other than the arrangement shown in FIG. For example, they may be arranged symmetrically with respect to the equatorial plane of the tire without being displaced from each other in the tire circumferential direction, or may be arranged so that the ends 5a and 5b coincide (that is, the main grooves 4a and 4b communicate with each other). 5a, 5b can also be arranged similar to the arrangement described above for the tire circumference at a position somewhat offset from the tire equator.

By setting the negative ratio to 0.3 or less,
Good wear resistance can be secured. Next, when the negative ratio was 0.3 or less, a study was conducted to obtain good drainage.

Generally, slippery on a wet road surface is caused by the fact that when the tire rolls under load, water on the road surface located in front of the tire penetrates between the tire tread and the ground,
This is because the contact area where the tire tread comes into direct contact with the ground (hereinafter referred to as “actual contact area”) is reduced, which reduces wet performance.

A tire having a conventional pattern such as a rib pattern or a block pattern can be used to remove water that has entered the contact area.
Although discharged through the groove, in the case of such a tire, since the main groove is arranged along the tire circumference, the water that has infiltrated into the contact area is in front of the tire along the arrangement direction of the main groove. As a result, the tires can step on the pushed water again, resulting in a reduction in the actual ground contact area and a reduction in wet performance. In particular, the deterioration of braking performance during high-speed running was remarkable.

Therefore, in the heavy-duty tire of the present invention, the main grooves are formed so as to sequentially enter the tire contact area from the end to the tread end, and the main grooves 4a and 4b end 5a,
5b is arranged in the area of 25% of the tread width centering on the tire equator, and the area between the tire equator and the position of at least 25% of the tread width is the main groove portion. Angle α between the tangent line m and the equatorial plane of the tire
However, by gradually increasing the distance from the tire equator, and preferably in the range of 5 to 25 °, the water that has entered the contact area is pushed out to the side of the tire along the arrangement direction of the main groove. As a result, the tire does not step on the pushed water again, and it is possible to suppress the reduction of the actual ground contact area and improve the wet performance.

Further, by making the continuous widthwise projected length of the main groove 30% or more of the tread width and the continuous circumferentially projected length of the main groove 70% or more of the tread width, the contact area is infiltrated. The drained water is efficiently drained. This is because if the continuous width-direction projected length of the main groove is less than 30% and the continuous circumferential-direction projected length of the main groove is less than 70%, drainage becomes insufficient.

Further, the negative ratio is preferably in the range of 0.25 to 0.29 in view of satisfying both the wear resistance and the wet performance in the best balance.

In FIG. 1, auxiliary grooves 6a to 6e opening in the two main grooves and two to three cutting sipes 7 are provided at the end of the block land portion facing the main groove. Auxiliary groove 6a
Reference numerals 6e to 6e are provided for improving driving / braking during wet conditions, and the cut sipe 7 is provided for equalizing the ground contact pressure on the land portion of the block, and are provided as necessary.

Therefore, in the tire of the present invention, by optimizing the disposition shape of the main groove in this way, when the wet performance is made equal to that of the conventional tire, the negative ratio is 0.3 or less. It is possible to obtain a sufficient wear resistance because it can be made considerably smaller than the above. Further, when the negative ratio is 0.3 or less, as shown in FIG. 2, the wet performance of the tire having the conventional block pattern is significantly deteriorated, whereas the tire having the pattern of the present invention is deteriorated in wet performance. Since the ratio is small, the advantage of the present invention is also high.

[0016]

EXAMPLE A specific example of the pneumatic tire according to the present invention will be described with reference to FIG. -Examples The heavy duty pneumatic tires used in the examples have the tread pattern shown in Fig. 1, and the tire size is 11R2.
2.5, and both tread ends 2a, 2 on the tread portion 1
b extending in a curved shape in a direction converging to the tire equator 3, and their ends 5a, 5b are displaced from each other by a half pitch (50 mm) in the tire circumferential direction, and are equal distances from the tire equator 3, respectively. A plurality of main grooves 4a, 4b located at a distance of (8 mm) are arranged at intervals along the tire circumference 6, and the main grooves 4a or 4b extend from the end 5a or 5b to the tread end 2a or 2b. A directional pattern was formed to sequentially enter the tire contact area. The negative ratio was 0.27.

The tire equator 3 and the tread width 2 from now on
In the area sandwiched between the 5% position and the main groove 4a, 4b, the intersection angle α between the tangent line m drawn to the main groove 4a, 4b and the tire equatorial plane 3 is 5 ° at the end points 5a, 5b. The distance from the equator 3 was set to 25 ° at a position of 25% of the tread width and gradually increased as the tire was separated from the equator 3. Furthermore, the continuous width-direction projected length L ₁ of the main grooves 4a and 4b was set to 48% of the tread width, and the continuous circumferential-direction projected length L ₂ of the main grooves 4a and 4b was set to 105% of the tread width. The main groove has a groove depth of 16.5 mm and a groove width of 5a at the end position.
Alternatively, it was 2.5 mm at 5b and 7 mm at the tread end 2a or 2b position.

Further, an auxiliary groove 6a opened to the two main grooves
~ 6e or 2-3 at the end of the block land facing the main groove
Book cut sipe 7 was provided. The carcass consists of one ply of a rubberized layer in which steel cords are radially arranged, the belt has a laminated arrangement of four cord rubberized layers, and the angle of the cords of the rubberized layer with respect to the tire circumference is The first layer rises to the right 50 °, the second layer rises to the right 18 °, the third layer rises to the left 18 °, the fourth layer rises to the left 1
8 °, that is, the second layer and the third layer are in a cross cord arrangement. Other tire structures are almost the same as the conventional tire.

COMPARATIVE EXAMPLE The tire used in the comparative example has a tangent line drawn with the main grooves 4a and 4b in the region sandwiched between the tire equator 3 and the position of 25% of the tread width. The intersection angle α between m and the tire equatorial plane 3 is 15 ° at the ends 5a and 5b, and 1 at a position of 25% of the tread width from the tire equatorial line 3 respectively.
The tire is substantially the same as the tire used in the example, except that the tire is linearly extended from the tire equator 3 toward the tread edge at a constant inclination angle of 5 °.

Conventional Example The tire used in the conventional example is a conventional tire having the block pattern shown in FIG. 4, and the negative ratio is 0.32.
It is.

Test Method In the test, the above-mentioned test tire was used to evaluate wet performance and wear resistance. Wet performance, running on a wet road surface at a constant speed of 40 km / h and 60 km / h,
The braking distance when the brake was applied was measured, and the reciprocal of the braking distance was indexed to obtain a braking index, which was evaluated. The larger the brake index, the better the wet performance.
FIG. 3 shows the test results for Examples and Comparative Examples. From this result, the example is superior in wet performance to any traveling speed as compared with the comparative example.

The wear resistance was measured by measuring the amount of wear of the tread rubber after running an actual vehicle for 80,000 km. From the measured amount of wear, 1
mm The running distance (km) when worn was calculated, and this running distance was converted into an index ratio to obtain a wear resistance index, which was evaluated. The larger the abrasion resistance index, the better the abrasion resistance. As a result,
When the wear resistance index of the conventional example is 100, the comparative example is 120,
The example is 133, and the example has the best wear resistance.

[0023]

According to the present invention, the water that has entered the contact area is pushed out to the side of the tire along the arrangement direction of the main groove, and as a result, it is pushed out like a conventional tire. The tire will not be able to step on the water again, and it is possible to suppress the reduction of the actual ground contact area and improve the wet performance. Further, even if the negative ratio is considerably smaller than that of the conventional tire, sufficient wet performance can be obtained, and therefore the wear resistance is also excellent. From the above, the present invention makes it possible to provide a heavy-duty pneumatic tire satisfying both wet performance and wear resistance, which could not be achieved by a tire having a conventional pattern.

[Brief description of the drawings]

FIG. 1 is a developed view of a part of a tread portion of a typical pneumatic tire for heavy load according to the present invention.

FIG. 2 is a diagram plotting braking performance during wet when the negative ratio is changed.

FIG. 3 is a diagram showing a relationship between a traveling speed on a wet road surface and a brake index.

FIG. 4 is a developed view of a part of a tread portion of a conventional tire.

[Explanation of symbols]

1 Tread part 2a, 2b Tread edge 3 Tire equator 4a, 4b Main groove 5a, 5b End of main groove 6a ~ 6e Auxiliary groove 7 Cut sipe 8 Tire rotation direction m Tangent line α to the main groove m and tire equatorial plane Crossing angle with 3 W tread width L ₁ Continuous width projected length of main groove L ₂ Continuous projected length of main groove in circumferential direction

Claims (1)

[Claims] 1. A tread portion extends in a curved shape from both tread ends in a direction in which it converges on the tire equator, and its ends are located at positions which are coincident with or apart from each other on or near the tire equator. A plurality of main grooves are arranged at intervals along the circumference of the tire, and the main grooves form a directional pattern that sequentially enters the tire contact area from the end to the tread end. , The negative ratio is 0.3 or less, and the end of the main groove is within the region of 25% of the tread width (W) centered on the tire equator. %, The area between the main groove and the main groove is the intersection angle (α) between the tangent line (m) drawn to this and the tire equatorial plane.
Is gradually increased as the distance from the tire equator increases, and the continuous width-direction projected length (L ₁ ) of the main groove is 30% or more of the tread width (W). A heavy duty pneumatic tire having a length (L ₂ ) of 70% or more of a tread width (W).