JP3125109B2 - Pneumatic radial tires for passenger cars - 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 radial tire for a passenger car, which has both steering stability and ride comfort.

[0002]

2. Description of the Related Art Conventionally, as a means for improving the steering stability of a pneumatic radial tire for a passenger car, a reinforcing material is inserted into a sidewall portion or a height or hardness of a bead filler is increased to increase the tire's hardness. To increase the circumferential rigidity and lateral rigidity. However, when the circumferential stiffness and the lateral stiffness of the tire are increased, the steering stability is improved. On the other hand, the vertical stiffness is also increased, so that the riding comfort is reduced. Therefore, it is difficult to make the steering stability and the riding comfort compatible with each other. There was a problem.

[0003] In Japanese Patent Application Laid-Open No. 1-314611, an annular concave portion extending in the circumferential direction of the tire is formed in an upper region of the sidewall portion to increase the lateral spring constant (lateral rigidity) of the sidewall portion, thereby improving ride comfort. There has been proposed a pneumatic tire in which turning performance is improved without substantially reducing performance. However, this tire is passive because it does not substantially reduce ride comfort, and is not intended to actively improve it.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a pneumatic tire for a passenger car which improves both the riding comfort and the steering stability, which are difficult to achieve as described above.

[0005]

According to the present invention, which achieves the above object, when the surface length from a shoulder point P to a rim check line Q is L in a sidewall portion in a meridional section of a tire, In a region above the sidewall portion from the shoulder point P toward the rim check line Q to a length S defined by the following equation, a plurality of annular grooves extending in the tire circumferential direction and annular ribs between the annular grooves are provided. Wherein the upper part of the annular rib is projected from the surface of the side wall part.

0.10L <S <0.33L As described above, the present invention reduces longitudinal rigidity by providing a plurality of tire circumferential annular grooves in a region above a specific sidewall portion, thereby improving ride comfort. As well as improve
By protruding the upper portion of the annular rib formed between the plurality of annular grooves above the surface of the sidewall portion, the circumferential rigidity and the lateral rigidity can be increased, and the steering stability can be improved.

[0007] In the present invention, the shoulder point P is the intersection of an extension of the shoulder radius that defines the surface of the shoulder in a meridional section in the tire and an extension of the radius of the sidewall that defines the surface of the sidewall. Say. Further, the rim check line Q refers to an annular line in the tire circumferential direction formed at a position outside the bead portion released from contact with the rim.

FIG. 1 is a half sectional view of a pneumatic tire for a passenger car according to the present invention. In FIG. 1, 2 is a tread part, 3
Is a sidewall portion, 4 is a carcass layer, 5 is a bead portion,
8 indicates a rim, P indicates a shoulder point, and Q indicates a rim check line. As shown in FIG. 1, the intersection of the extension line (dashed line) of the shoulder radius Ra and the extension line (dotted line) of the sidewall radius Rb, that is, the surface length from the shoulder point P to the rim check line Q is denoted by L. In this case, a plurality of annular grooves 10 and annular ribs 11 extending in the tire circumferential direction are provided in the region above the sidewall portion from the shoulder point P toward the rim check line Q to the length S defined by the above equation. Is provided.
As shown in the partially enlarged view of FIG. 2, these annular grooves 10 have a groove depth d and a groove width w, and the annular ribs 11 formed between the annular grooves 10 have a protruding amount e at the top. It protrudes with.

The present inventors have divided the surface length L of the sidewall portion in the meridian section of the tire into approximately one-third equal portions, and have divided the surface length L from the shoulder point P toward the rim check line Q above the shoulder portion. region,
In the case where the center area and the lower area near the bead portion are set as 100, the case where the longitudinal stiffness, the lateral stiffness, and the circumferential stiffness of the tire in these areas are not substantially equal to 1/3 is 100, as shown in Table 1. I found that. Among these stiffnesses, the longitudinal stiffness affects ride comfort, while the circumferential stiffness and the lateral stiffness affect steering stability.

[0010] From Table 1, it can be seen that the upper region near the shoulder has the highest contribution to the circumferential stiffness, the lateral stiffness, and the vertical stiffness as compared with the other regions, and has the greatest effect on the steering stability and ride comfort. Therefore, if the structure of the upper region near the shoulder portion is devised, it is possible to improve both steering stability and ride comfort without substantially changing the structure of the other region.

[0011] The present invention, as a device of such a structure,
In the upper region near the shoulder portion, a plurality of annular grooves extending in the circumferential direction of the tire are provided concentrically with respect to the tire axis in a region of the surface length S defined by the above-described formula, thereby reducing longitudinal rigidity. I did it. In addition, by making the upper part of the annular rib formed between the annular grooves thickened, the circumferential rigidity and the lateral rigidity are improved, and the steering stability is improved. When the area of the length S set in the area above the sidewall portion is 0.10 times or less of the surface length L, it is difficult to provide the annular groove, and it is difficult to improve the ride comfort by reducing the vertical rigidity. . On the other hand, the length S
When the length is 0.33 times or more the surface length L, the number of annular grooves increases, so that the peripheral rigidity and the lateral rigidity are excessively reduced and steering stability is deteriorated.

Further, the number of annular grooves formed in the region above the sidewall portion must be at least two, and it is difficult to sufficiently reduce the vertical rigidity with one. Further, if the number of the annular grooves is too large, the circumferential rigidity and the lateral rigidity will be reduced. The groove width w and the groove depth d of this annular groove
Is not particularly limited, but preferably the groove width w
Is 0.8 to 1.5 mm, and the groove depth d is 1.8 to 2.2 mm
It is preferable to reduce the longitudinal rigidity without impairing the required characteristics of the tire. The amount of protrusion e of the annular rib from the side wall surface is not particularly limited, but is preferably 0.6 to 0.9 mm to increase the circumferential rigidity and lateral rigidity without impairing the required characteristics of the tire. It should be done.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In a pneumatic radial tire having a profile in a meridional section shown in FIG. 1, a length S of a region above a sidewall portion, a ratio S / L of the length S to a surface length L of the sidewall portion, Inventive tires 1, 2, 3 and comparative tires 1, 2 in which the number of annular grooves was changed as shown in Table 2, respectively.

These five types of tire sizes were all the same 215 / 65R15, and the surface length L, the groove depth d of the annular groove, and the protrusion amount e of the annular rib were the same as described below. r = 62 mm, d = 1.5 mm, e = 1.5 mm. For comparison, a conventional tire having no annular groove and annular rib in the upper region of the sidewall portion was manufactured.

With respect to these six types of pneumatic tires, ride comfort and steering stability were evaluated by the following methods. The results are shown in Table 2. Evaluation method of ride comfort : An average value of five test drivers was evaluated by an actual vehicle sensory test on a general road. The evaluation results are shown as indices using the conventional tire as a reference (100). Driving stability evaluation method : An average value of five test drivers was evaluated by an actual vehicle sensory test at a circuit site. The evaluation results are shown as indices using the conventional tire as a reference (100).

[0016] As can be seen from Table 2, in the comparative tire 1, the length S of the region above the sidewall portion was set to 0.10 times or less of the surface length L and 1
The provision of these annular grooves has the same ride comfort as conventional tires, but has reduced steering stability. In addition, the comparative tire 2 has a length S
Is larger than 0.33 times the surface length L and five annular grooves are provided, so that the riding comfort is remarkably improved, but the steering stability is also significantly reduced.

On the other hand, all of the tires 1, 2, and 3 of the present invention have improved ride comfort and steering stability as compared with conventional tires.

[0018]

As described above, according to the present invention, a plurality of tire circumferential annular grooves are provided in a region above a specific sidewall portion to reduce longitudinal rigidity, and an upper portion of the annular rib in this region is formed. Since the peripheral rigidity and the lateral rigidity are increased by protruding from the side wall portion surface, it is possible to improve both ride comfort and steering stability.

[Brief description of the drawings]

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

FIG. 2 is a partially enlarged view of FIG.

[Description of Signs] 3 sidewall portion 8 rim 10 annular groove 11 annular rib P shoulder point Q rim check line L surface length S specific length of upper region of sidewall portion

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-314611 (JP, A) JP-A-61-71203 (JP, A) JP-A-58-112806 (JP, A) JP-A-62 143706 (JP, A) JP-A-63-130407 (JP, A) JP-A-3-208708 (JP, A) JP-A-47-44502 (JP, A) JP-A-62-1605 (JP, A) JP-A-61-81207 (JP, A) JP-A-3-82611 (JP, A) JP-A-2-88310 (JP, A) JP-B-45-30403 (JP, B1) (58) (Int.Cl. ⁷ , DB name) B60C 11/01 B60C 13/00-13/02

Claims (1)

(57) [Claims] When the surface length from the shoulder point P to the rim check line Q is L in the sidewall portion of the tire in the meridional section, the following formula is used from the shoulder point P toward the rim check line Q: A plurality of annular grooves extending in the circumferential direction of the tire and annular ribs between the annular grooves are provided in an upper region of the sidewall portion up to the defined length S, and an upper portion of the annular rib protrudes from the surface of the sidewall portion. Pneumatic radial tires for passenger cars. 0.10L <S <0.33L