JP3205395B2 - 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, and more particularly to a pneumatic tire having a low tread pattern with low noise and excellent wet performance.

[0002]

2. Description of the Related Art In order to improve the wet performance of a tire, particularly the hydroplaning resistance, and to reduce noise, a tread has a wide circumferential groove extending along the circumference thereof and a tire having an equatorial line. It is advantageous to arrange lateral grooves which extend at a strong inclination and intersect the circumferential grooves. In particular, when the ratio of the groove to the tread contact surface, that is, the negative ratio is increased, the wet performance is improved, but the noise characteristics are deteriorated.On the contrary, when the negative ratio is reduced, the noise characteristics are improved, but the wet performance is deteriorated. Will do.

[0003]

That is, in order to improve both wet performance and noise characteristics, it is not sufficient to simply adjust the negative ratio, and it is necessary to optimize the groove configuration and the inclination angle. is there. Therefore, an object of the present invention is to propose a tread pattern that can achieve both excellent wet performance and low noise characteristics.

[0004]

Means for Solving the Problems The inventors of the present invention have studied a tread pattern which can satisfy the above-mentioned object. They have found that they are advantageous and have completed the present invention. That is, the present invention has a tread pattern that is point-symmetrical with respect to a central circumferential groove disposed on the equator of the tire, and in one half of the tread half of the central circumferential groove, The land portion is defined by one peripheral groove extending along the equator of the tire in a divided region, and a number of lateral grooves extending from the tread end across the peripheral groove toward the central region,
In a pneumatic tire, the lateral groove is in the side area,
Extends at an angle of 60-120 ° to the equator of the tire,
It bends greatly in the vicinity of the circumferential groove, extends within the central region with an inclination of 5 to 30 ° with respect to the equator of the tire, and in the central region, a land portion continuous in the circumferential direction on both sides of the central circumferential groove. A pneumatic tire having a land portion crossed by the lateral groove, and a land portion defined by a sub-groove extending from the tread end to a circumferential groove in a side area and being substantially parallel to the lateral groove. In the implementation, it is advantageous that the lateral grooves and the sub-grooves extend substantially in the width direction of the tread in the side regions.

FIG. 1 shows a main part of a tread of a pneumatic tire according to the present invention. The tread is arranged along a central circumferential groove 1 provided on an equator (circumference at the center of the width of the tread) O of the tire. Tread ends T on both sides of this groove
From the center to the equator O, are divided into two side areas S and a central area C by the circumferential grooves 2 forming a pair at positions closer to 1/4 of the tread width in the illustrated example. Further, the lateral groove 3 extending from the tread end T across the peripheral groove 2 to the central area C, and the tread end T and the peripheral groove 2
By arranging the sub-grooves 4 connecting the two, land portions 5 and 6 are divided in the central region C, and land portions 7 long in the axial direction of the tire are divided in both side regions S.

The lateral grooves 3 and the sub-grooves 4 extend substantially in the width direction of the tread in both side regions S.
Is largely bent near the circumferential groove 2 in the central region C,
It extends to the vicinity of the central circumferential groove 1 with a small inclination with respect to the equator O. The tread shown in the drawing has a substantially point-symmetric pattern centered on a point on the equator O, as symbolized by the fact that the direction of the lateral groove 3 after bending is reversed on both sides of the equator O. A narrow groove 8 is formed between the tip of the lateral groove 3 and the bent portion of the adjacent lateral groove 3 spaced apart in the circumferential direction.
The rib-like land portion 5 and the block-like land portion 6 which are continuous in the circumferential direction on both sides of the central circumferential groove 1 are defined by the connection. Further, the land 6 is divided into two blocks 6a and 6b by a narrow groove 9, and these blocks 6a, 6b
The sipe 10 is provided on the land 7 so as to be closed in the ground contact surface so as to stop in the blocks 6a and 6b across the land 7. Reference numeral 11 denotes an auxiliary groove provided in a so-called buttress portion outside the tread contact edge.

Here, the inclination angle of the lateral groove 3 with respect to the equator O is different between the lateral area S and the central area C of the tread. First, an imaginary line connecting the groove width center point at the start point and the end point of the lateral groove 3 in the lateral area S Angle of intersection between the equator O and the equator O
It is important that the inclination angle α is in the range of 60 to 120 °, and that the inclination angle β in the central region C is in the range of 5 to 30 °, which is also defined in the same manner. The lateral groove 3 bends in the vicinity of the peripheral groove 2 and its inclination angle changes from α to β. Here, the bending angle γ of 75 ° or more ensures drainage of the groove. Preferred above.

Another tread pattern according to the present invention is shown in FIGS. The tread pattern shown in FIG.
In the tread pattern shown in FIG. 1, instead of the narrow grooves 8, 9 and the sipe 10, sipe 12a to 12c having different positions and directions are provided on the land portion 6, and sipe 13a and 13b are provided on the land portion 7, respectively. It is a thing.

Next, the tread pattern shown in FIG. 3 is different from the tread pattern shown in FIG. 1 in that the land portion 7 is not provided with the sipe 10, while the land portion 6 is provided with three narrow grooves 14a to 14c.
Is provided.

[0010]

Another structure of the tire according to the present invention is as follows.
Conventional tires may be used. For example, a carcass has at least one (at most three) turn-up ply wrapped around the bead core from the inside to the outside of the tire, and the ply is made of a fiber cord represented by rayon, nylon, and polyester. The belt layer is formed by arranging a non-extensible cord such as a steel cord or an aromatic polyamide fiber cord at 10 to 35 ° with respect to the equatorial plane of the tire using a material arranged in a direction (radial direction) substantially perpendicular to the equatorial plane. Over the entire width of the main belt layer, where at least two layers of the belt arranged at an angle of
At least one auxiliary belt layer in which a heat-shrinkable cord represented by a nylon cord is disposed substantially parallel to the equatorial plane of the tire, and a plurality of cords are formed along the circumference of the main belt layer in forming the auxiliary belt layer. Spirally wound ribbons are used depending on the state of the arranged ribbons. And on this belt layer,
The tread which becomes the above-mentioned tread pattern is arranged.

[0012]

The inclination of the lateral groove extending in the direction intersecting the circumferential groove on the tread surface with respect to the equator of the tire is made different in the side area and the central area of the tread mainly to achieve effective drainage. . That is, in the side region of the tread, the inclination angle α of the lateral groove is set in the range of 60 to 120 ° around 90 °, especially in the tread side region, it is necessary to quickly drain water in the ground contact surface to the ground end. If the inclination angle α is less than 60 ° or exceeds 120 °, the drainage performance is reduced. Further, when the inclination angle α is less than 60 ° or more than 120 °, the land portion surrounded by the lateral groove easily falls down to the groove side with respect to the input in the tire axial direction, so the grip force due to the decrease in the land portion rigidity. In addition, the groove is crushed and the width becomes narrow, which adversely affects drainage.

On the other hand, the inclination angle β of the lateral groove in the central region of the tread is intended to reduce the resistance of the water film when stepping on the ground and to advantageously carry the drainage from the central region of the tread to the side region. , 5 to 30 °. That is, if the inclination angle β is less than 5 °, the drainage efficiency to the tread side area deteriorates, while if it exceeds 30 °, the water film resistance increases remarkably.

Further, as described above, in order to exert different functions in the side area and the central area of the tread, it is necessary to sharply change the inclination angle of the lateral groove by largely bending it in the vicinity of the circumferential groove. If the bending angle γ is less than 75 °, the change in the inclination angle is too large, so it is preferable to secure 75 ° or more.

Further, it is known that the main cause of the pattern noise is an impact component when the tread is brought into contact with the rotating ground, and the influence is large in the central region of the tread. Therefore, in the pattern of the present invention, the horizontal grooves in the central region of the tread are steeply inclined at 5 ° to 30 °, thereby realizing a smooth rotary contact and reducing the impact component.

Further, when the ground shape matches the lateral groove, the pattern noise remarkably deteriorates. However, in the conventional pattern configuration in which the angle gradually changes in a curved manner from the center of the tread to the end, the tread width is reduced. The inclination around 1/4 point of
゜ There is a drawback that the average is obtained and it easily overlaps with the ground contact shape On the other hand, the pattern of the present invention greatly changes at the inflection point, has a small inclined portion near 45 °, and reduces the chance of coincidence with the grounding shape, which is advantageous in reducing the pattern noise.

[0017]

EXAMPLE According to the tread pattern shown in FIGS. 1 to 3, a pneumatic radial tire (tread width: 120 mm) having a tire size of 175/70 R13 was manufactured under the following specifications (1) to (3). Prototype.

(1) Test tire A (tread pattern in FIG. 1) The central circumferential groove 1 has a width of 6 mm and a depth of 8 mm, and the circumferential groove 2 has a width of:
5 mm and depth: 8 mm, and the lateral groove 3 is the width of the lateral area S:
5 mm and width of central area C: 1.5 to 4.5 mm and depth: 6.5
The angle of inclination α: 90 °, the angle of curvature γ: 130 °, and the angle of inclination β: 10 in mm, with the position where the distance t from the equator O is 20 mm as a bending point.
° extending. The width of the narrow grooves 8 and 9 is 1 mm.
The depth of the sipe 10 was 5 mm, the depth of the sipe 10 was 5 mm, and the width of the auxiliary groove was 2 mm and the depth was 3 mm.

(2) Test tire B (tread pattern in FIG. 2) The basic structure of the tread pattern is the same as that of the test tire A described above.
12a to 12c and 13a and 13b are cuts having a depth of 5 mm.

(3) Test tire C (tread pattern in FIG. 3) The lateral grooves 3 are arranged so as to extend at an inclination angle α: 75 °, a bending angle γ: 100 ° and an inclination angle β: 10 °. The tread pattern has a configuration substantially similar to that of the test tire A. The three narrow grooves 14a to 14c that divide the land portion 6 have a width of 2
mm and depth: 5 mm.

[0021]

As a comparison, a tire (comparative tire D) having the same size was also produced for the tread pattern shown in FIG. That is, the tread pattern shown in FIG. 4 has a pair of peripheral grooves 21 on both sides of the central peripheral groove 20 and a pair of peripheral grooves 22 on the outside thereof, respectively, and is inclined from the tread end T with respect to the equator O. A transverse groove 23 is provided which extends in a direction across the circumferential grooves 21 and 22 and is bent past the circumferential groove 22. The central peripheral groove 20 has a width of 4 mm and a depth of 8 mm, the peripheral groove 21 has a width of 6.5 mm and a depth of 8 mm, and the peripheral groove 22 has a width of 3
mm and depth: 8 mm, and the lateral groove 23 has a width: 3-6 mm
And depth: 6.5mm, tilt angle α: 45 °, bending angle γ: 95
° and the inclination angle β: arranged at 11 °.

Table 1 shows the results of subjecting these prototype tires to a hydroplaning test and a pattern noise test in straight running and cornering, respectively. The evaluation of each test was represented by an index when each test result of the comparative tire E was set to 100.

Here, in the hydroplaning test when traveling straight ahead, a tire having an internal pressure of 1.8 kgf / cm ² was mounted on a normal passenger car, and two people were riding on the tire.
The tread contact area was measured by photographing the tread when the vehicle was running straight at 90 km / h, and the residual ratio of the area was measured.

Next, in the hydroplaning test during turning, the peak lateral acceleration (grip limit) when traveling at a depth of 6 mm and a corner having a radius of 100 m at 50 to 90 km / h under the same conditions was determined. The change was measured.

In the pattern noise test, the feeling of the sound inside the vehicle when the vehicle was driven on a smooth road surface at 40 to 100 km / h under the same conditions was evaluated.

[0027]

[Table 1]

[0028]

According to the present invention, a tread pattern having both excellent wet performance and low noise characteristics can be provided, and it is conventionally difficult to achieve both by improving the tread pattern alone. High performance can be realized.

[Brief description of the drawings]

FIG. 1 is a development view of a tread pattern according to the present invention.

FIG. 2 is a development view of another tread pattern according to the present invention.

FIG. 3 is a development view of another tread pattern according to the present invention.

FIG. 4 is a development view of a tread pattern in comparison with the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Central peripheral groove 2 Peripheral groove 3 Lateral groove 4 Secondary groove 5 Land part 6 Land part 6a Block 6b Block 7 Land part 8 Narrow groove 9 Narrow groove 10 Sipe 11 Auxiliary groove 12a Sipe 12b Sipe 12c Sipe 13a Sipe 13b Sipe 14a Sipe 14b Sipe 14c Sipe 15 block 16a Narrow groove 16b Narrow groove 16c Narrow groove

Claims (2)

(57) [Claims] 1. A tread pattern which is point-symmetrical with respect to a central circumferential groove disposed on the equator of a tire, and which has a tread half on one side of the central circumferential groove, the tread half being laterally and centrally located. Pneumatically defined by one circumferential groove extending along the equator of the tire in sections and a number of transverse grooves extending from the tread end across the circumferential groove toward the central area. In the tire, the lateral groove extends in the side region with an inclination of 60 to 120 ° with respect to the equator of the tire, largely bends in the vicinity of the circumferential groove, and in the central region, with respect to the equator of the tire. It extends with an inclination of 5 to 30 °, and in the central region, a land portion continuous in the circumferential direction on both sides of the central circumferential groove, a land portion crossed by the lateral groove, and in the lateral region, the lateral groove and further from the tread end. An auxiliary that is connected to the circumferential groove and almost parallel to the lateral groove A pneumatic tire having land portions defined by grooves. 2. The pneumatic tire according to claim 1, wherein the lateral groove and the sub groove extend substantially in the width direction of the tread in the side area.