JP4448336B2 - Radial tires for passenger cars - Google Patents

Description

  The present invention relates to a radial tire for a passenger car that can reduce road noise.

  One of the noises caused by tires is road noise. It is considered that when the tire rolls, an impact received from the road surface vibrates the tread portion, and this vibration is transmitted from the rim to the chassis using the carcass as a medium and is generated as a resonance sound in the vehicle. Conventionally, in order to reduce road noise, means such as adopting a cord having low rigidity for the carcass as a vibration medium or improving the vibration transmission characteristics by reducing the number of cords to be driven is used. However, these methods have the disadvantage that the strength is insufficient and the durability is impaired.

The inventors repeated various experiments on a radial tire for a passenger car having a carcass ply folded around from the inner side in the tire axial direction around the bead core. Then, moving in the radially outer side than the conventional position of the bead core, and by moving to the inner side in the tire axial direction, reducing the inclination with respect to the tire axial direction of the profile of the carcass ply extending near the rim flange, road noise It has been found that the reduction effect is significantly obtained. As a prior art focusing on the position of the bead core, there is Patent Document 1 below, but this does not suggest a relationship with road noise.

Japanese Patent Laid-Open No. 10-181318

  As described above, an object of the present invention is to provide a radial tire for a passenger car that can change the profile of the carcass ply by improving the position of the bead core, and thus can reduce road noise.

The invention according to claim 1 of the present invention has a toroid-shaped main body extending between a pair of bead cores, and a folded-back portion connected to the main body and folded around the bead core from the inner side to the outer side in the tire axial direction. A radial tire for a passenger car equipped with a carcass ply, wherein the outermost position of the bead core in the tire axial direction is a tire meridian section in a normal state in which a normal rim is assembled and a rim is assembled and an internal pressure of 200 kPa is filled and a normal load is applied. In the normal state, a distance Y of 5.0 to 15.0 mm is spaced inward in the tire axial direction from the tire radial direction line passing through the rim width position, and the innermost position in the tire radial direction of the bead core is a bead baseline. at a distance X of 4.0 ～10.0Mm radially outward tire from, yet the sum of the distance X and the distance Y (X Y) is characterized by a 13.0~20.0mm der Rukoto.

The invention according to claim 2 is the radial tire for a passenger car according to claim 1 , wherein the sum (X + Y) is 15.5 to 19.0 mm .

In the invention according to claim 3, the bead core has a tire axial width of 4 to 12 mm and a tire radial height of 3 to 8 mm in the tire meridian section. This is a radial tire for passenger cars.

  By improving the position of the bead core as described above, the body portion of the carcass ply has a smaller inclination with respect to the tire axial direction of the profile in the vicinity of the rim flange (compared to that of conventional radial tires for passenger cars). Approach the direction.) Thereby, road noise is reduced.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a tire meridian cross-sectional view including a tire shaft of a passenger car radial tire of the present embodiment. A radial tire for a passenger car (hereinafter sometimes simply referred to as a “tire”) 1 includes a carcass 6 that extends from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4, and an outer side in the tire radial direction of the carcass 6. And the belt layer 7 distribute | arranged inside the tread part 2 is provided.

  The carcass 6 is composed of one or more radial structures in which carcass cords are arranged at an angle of, for example, 80 ° to 90 ° with respect to the tire equator C, in this example, one carcass ply 6A. As the carcass cord, a polyester cord is used in this example, but other than this, organic fiber cords such as nylon, rayon, aramid, and vinylon can be used.

  The carcass ply 6A includes a toroidal main body portion 6a extending between the pair of bead cores 5 and 5, and a turn-up portion 6b connected to the main body portion 6a and turned around the bead core 5 from the inner side to the outer side in the tire axial direction. It is. In the present embodiment, the bead core 5 is exemplified by a steel wire wound in a spiral shape and configured in a substantially rectangular cross section, but is not limited thereto. Further, a bead apex 8 made of hard rubber extending from the bead core 5 to the outer side in the tire radial direction is disposed between the main body portion 6a and the folded portion 6b of the carcass ply 6A. The rubber hardness of the bead apex rubber 8 is, for example, 70 to 99 degrees, more preferably 80 to 95 degrees in terms of JIS durometer A hardness.

  The belt layer 7 includes at least two belt plies 7A and 7B in which the belt cord is inclined and arranged at a small angle of, for example, 10 to 45 ° with respect to the tire equator C. The cords are superposed in a direction crossing each other. The belt cord employs a steel cord in this example, but a highly elastic organic fiber cord such as aramid or rayon can also be used as necessary.

  2 shows a tire meridian cross-sectional view of the bead portion in the normal state of the tire 1 of the present embodiment. Here, the “normal state” is a state in which the tire 1 is assembled on the normal rim 10 and filled with an internal pressure of 200 kPa and a normal load is applied. The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire 1 is based. For example, JAMMA is a standard rim, TRA is “Design Rim”, or ETRTO. If so, use "Measuring Rim". The regular rim 10 shown in this example is a 5 ° deep rim (hump type RH) defined by JATMA.

  The “regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. 80% of the maximum load capacity for JATMA and a table for TRA. TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES "80% of the value described in the value", and ETRTO, the load corresponding to 80% of "LOAD CAPACITY". Note that the tire 1 of the present embodiment is based on the JATMA standard.

  The inventors have conducted extensive research and have found that the profile of the main body portion 6a of the carcass ply 6A is important in order to reduce road noise. Specifically, in the normal state, it has been found that if the profile in the vicinity of the rim flange of the main body 6a is laid down, a road noise reduction effect can be obtained significantly. In order to lay the profile in the vicinity of the rim flange of the main body 6a without changing the maximum tire width or the like, it is possible to improve the position of the bead core 5 that holds the main body 6a. For example, when the main body portion 6a stands as shown in FIG. 3A, the force f input from the tread portion is easily transmitted so that the bead portion 4 directly pierces the rim flange. Therefore, vibration attenuation by the tire is small. On the other hand, when the main body 6a is sleeping, most of the force f is consumed by bending the bead portion 4 with the rim flange as a fulcrum, and transmission to the rim is reduced.

One method is to move the position of the bead core 5 outward in the tire radial direction as compared with the conventional method. Specifically, it is desirable to provide the innermost position in the tire radial direction of the bead core 5 with a distance X of 4.0 to 10.0 mm from the bead base line BL to the outer side in the tire radial direction. Here, the “bead base line” is a tire axial line passing through the rim diameter position of the regular rim 10.

When the distance X is less than 4 mm, there is no great difference from the structure of a conventional passenger car radial tire, and the effect of reducing road noise cannot be obtained . Conversely, when the distance X exceeds 10.0 mm, road noise can be greatly reduced, but the rubber volume between the bead core 5 and the rim seat increases, the seating performance of the bead portion 4 on the rim decreases, and steering stability is improved. Deteriorating. The regular rim 10 has a rim flange 10a height of 18 ± 1 mm in the JATMA standard. Therefore, when the distance X exceeds 10.0 mm, the function as the wall of the rim flange 10a for suppressing the rotational moment of the bead portion 4 with the bead core 5 as a fulcrum becomes small, and the rim may be detached. The bead core of the passenger car radial tire has a tire axial width a of 4 to 12 mm and a tire radial height b of 3 to 8 mm in the tire meridian cross section.

In addition , the position of the bead core 5 is moved inward in the tire axial direction as compared with the prior art. Specifically, the outermost position in the tire axial direction of the bead core 5 is provided at a distance Y of 5.0 to 15.0 mm from the tire radial direction line N passing through the position of the rim width RW to the inner side in the tire axial direction. It is.

  If the distance Y is less than 5.0 mm, there is no great difference from the structure of a conventional passenger car radial tire, and the effect of reducing road noise cannot be obtained. On the contrary, even if the distance Y exceeds 15.0 mm, the road noise reduction effect tends to reach its peak. If the distance Y exceeds 15.0 mm, the bead portion 4 may collide with the rim hump 11 to prevent accurate rim assembly. From such a viewpoint, the distance Y is preferably 6.0 mm or more, more preferably 8.0 mm or more, and the upper limit is 14.0 mm or less, more preferably 13.0 mm or less.

Furthermore , it is desirable to determine the position of the bead core 5 so as to satisfy both the specifications of the distance X and the distance Y. That is, the tire 1 in which the distance X is 4.0 to 10.0 mm and the distance Y is 5.0 to 15.0 mm is desirable. At this time, more preferable ranges of the distances X and Y can be combined. The distance X is set to 4.0 to 10.0 mm, and the sum (X + Y) with the distance Y is set to 13.0 to 20.0 mm. Thus, by securing the distance X at a constant amount and regulating the sum (X + Y) of both distances within a certain range, it is possible to reduce the risk of rim disengagement while ensuring the effect of reducing road noise.

As described above, by improving the position of the bead core 5, the portion near the rim flange of the main body portion 6a can be tilted in the direction of laying down without changing the maximum tire width. As an example, the intersection point between the tire axial direction line of the bead core 5 in the tire radial direction and the main body portion 6a is P1, and the intersection point P2 between the tire radial direction line N passing through the position of the rim width RW and the main body portion 6a. The inclination line K connecting the tires is 30 to 63 ° with respect to the tire axial direction. More preferably, the angle α is set to 50 to 63 °. In a conventional tire, the angle α is about 64 to 70 °.

  Further, it is desirable that the folded portion 6b of the carcass ply 6A has a small height at the end 6be. Thereby, the rigidity of bead part 4 falls, vibration absorption nature is raised, and a road noise reduction effect is raised further. As an example, the height h of the folded portion 6b from the bead base line BL is desirably about 50 to 90% of the height G of the rim flange 10a. When the bending rigidity of the bead part 4 is lowered, the strain acting on the bead part 4 is increased. However, since such a height position is hardly affected by the distortion, looseness at the outer end 6be of the folded part 6b, etc. Can be effectively prevented.

  A radial tire for a passenger car having a tire size of 195 / 60R15 88H having the basic structure shown in FIG. Then, road noise and anti-rim removal performance were tested and compared. Each tire changes the distances X and Y and the angle α of the main body, and the other configurations are substantially the same. The bead core had the width a = 5 mm and the height b = 5 mm. A test was also conducted for a conventional passenger car radial tire (comparative example). The test method is as follows.

<Road noise performance>
Each tire is mounted on all wheels of a 2000cc domestic FF passenger car with a rim (15 x 6 JJ) and internal pressure (200 kPa), running on a smooth road surface for measuring road noise at a speed of 60 km / h. The overall noise level dB (A) was measured at the position of the right ear of the seat. The evaluation is shown as the amount of change from the comparative example, and the minus display indicates that the road noise is smaller than that of the comparative example 1.

<Rim resistance>
A bead unsheeting test was performed in accordance with JIS D4230. The larger the value, the better. Table 1 shows the test results.

  As a result of the test, it was confirmed that the tire of the example significantly reduced road noise. It was also confirmed that the standard value 8890N was cleared with respect to the anti-rim removal performance.

It is sectional drawing of the radial tire for passenger cars which shows embodiment of this invention. It is a fragmentary sectional view which expands and shows the bead part of the regular state. (A), (B) is sectional drawing of a bead part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Passenger car radial tire 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 6a Main part 6b Folding part 7 Belt layer X Distance Y Distance

Claims (3)

A radial tire for a passenger car comprising a toroidal main body portion extending between a pair of bead cores, and a carcass ply that is continuous with the main body portion and is folded around the bead core from the inner side to the outer side in the tire axial direction. ,
In the tire meridian cross section in a normal state in which a normal rim is assembled and the inner pressure is 200 kPa and a normal load is applied,
In the normal state, the outermost position of the bead core in the tire axial direction separates a distance Y of 5.0 to 15.0 mm from the tire radial direction line passing through the rim width position inward in the tire axial direction,
The innermost position in the tire radial direction of the bead core is separated by a distance X of 4.0 to 10.0 mm from the bead base line to the outer side in the tire radial direction .
Moreover passenger radial tire for the sum of the distance X and the distance Y (X + Y) is characterized 13.0~20.0mm der Rukoto. The radial tire for a passenger car according to claim 1, wherein the sum (X + Y) is 15.5 to 19.0 mm . 3. The radial tire for a passenger car according to claim 1, wherein the bead core has a tire axial width of 4 to 12 mm and a tire radial height of 3 to 8 mm in a tire meridian cross section .

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