JP2900260B2 - Pneumatic radial tire - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pneumatic radial tire having improved steering stability and ride comfort by increasing the tire circumferential rigidity of side portions.

[Conventional technology]

In general, in order to improve the performance of a radial tire, optimization of a spring constant representing the casing rigidity of the tire is one of important items. As shown in FIG. 2, the spring constant (vertical direction of the tire rotation axis), the lateral direction (tire width direction) of the spring constant (L), and the circumferential direction (tire circumferential direction) are shown in FIG. Spring constant (θ)
Can be divided into In the radial tire, the rigidity of the side portion 4 in the tire circumferential direction, that is, the circumferential spring constant (θ) is generally low, which is disadvantageous in steering stability. Second
In the figure, 2 is a bead core, and T is a tread portion.

Conventionally, various reinforcements (bead filler, chafer, etc.) are added to the bead to increase the circumferential spring constant (θ), and the cord angle of the carcass layer with respect to the tire circumferential direction is about 87 ° (half-radial structure) And that. However, in this case, since both the vertical spring constant (V) and the horizontal spring constant (L) increase, the ride comfort deteriorates.

[Problems to be solved by the invention]

The present invention improves steering stability and ride comfort by increasing the circumferential spring constant (θ) without substantially increasing the longitudinal spring constant (V) and the lateral spring constant (L). An object of the present invention is to provide a pneumatic radial tire.

The balanced carcass theory is applied to the tire profile currently used in order to reduce the distortion at the time of filling the internal pressure and to give the tire an outer shape excellent in durability. In the carcass line in this case, that is, the balanced carcass line, tires having the same outer width can have an infinite number of shapes, and an optimum shape is selected to satisfy various performances. However, the relationship between the shape of the carcass line and the shape of the tire surface has not been sufficiently studied at the time of designing a tire profile. Therefore, the present invention provides a carcass line shape and a tire surface shape that can increase the circumferential spring constant (θ) without substantially affecting the vertical spring constant (V) and the horizontal spring constant (L). It was done as a result of studying the relationship with.

[Means for solving the problem]

The present invention provides a pneumatic radial tire in which a carcass layer is mounted between a pair of left and right bead portions, and an end portion of the carcass layer is turned up around the bead core from the inside to the outside of the tire and wound up. JI between the tire maximum width position and the carcass layer turn-up winding terminal
A tire with a S hardness of 80 or more has a crescent-shaped rubber filler in the meridian direction section, and is assembled on a regular rim.When the regular internal pressure is filled, the height a from the rim at the tire maximum width position on the tire surface is the carcass layer. The height b of the tire from the rim at the maximum width position is smaller than the height b, and the relationship between these heights and the tire section height c satisfies the following expression.

(B / c) − (a / c) ≧ 0.03 Hereinafter, this means will be described in detail with reference to the drawings.

FIG. 1 is a meridional section explanatory view showing an example of the pneumatic radial tire of the present invention. In FIG. 1, a carcass layer 3 is mounted on a pair of right and left beads 1.
The end of the carcass layer 3 is wound around the bead core 2 from the inside to the outside of the tire. 4 is a side part and 5 is a rim. In Fig. 1, it is assembled on a regular rim,
4 shows a tire when a normal internal pressure is charged. Here, the regular rim refers to a standard rim defined by JATMA. Specifically, the regular rim was published on April 1, 1988. Refers to the rim of the JATMA standard (Japan Automobile Tire Association standard) described in Chapter A of "JATMA YEAR BOOK". Further, "filled with the normal internal pressure" means that the tire has been filled with air so as to have the normal internal pressure. Normal internal pressure is the same as “JA
Refers to JATMA standard air pressure described in Chapter A of TMA YEAR BOOK.

(1) In the present invention, in the tire shown in FIG.
The height a of the tire surface from the rim 5 at the tire maximum width position is the height b of the carcass layer 3 from the rim 5 at the tire maximum width position.
(A <b).

Here, the position of the rim 5 serving as a height base is a rim surface corresponding to the outer diameter of the rim.

The reason that a <b is satisfied is that the larger the b is, the lower the vertical spring constant (V) and the horizontal spring constant (L) are, but there is almost no influence on the circumferential spring constant (θ), and a
This is because by setting <b, a reinforcing effect for increasing the circumferential spring constant can be obtained.

(2) Further, in the present invention, the relationship between these heights a and b and the tire section height c satisfies the following expression.

(B / c) − (a / c) ≧ 0.03 The tire section height c is the height of the tread surface from the rim 5 that is the highest.

For the rigidity due to the shape effect of the carcass profile of the tire, if b / c is increased, the longitudinal spring constant (V)
And the lateral spring constant (L) decreases. Conversely, these constants can be increased by reducing b / c. The circumferential spring constant (θ) is hardly affected by b / c, but is affected by the reinforcing material.

In the case of a radial tire, the rigidity of the belt portion and the bead portion is set to be high, and the region between the bead cores from the maximum tire cross-sectional width determined by b / c is a region where the reinforcing layer can be added. In other words, by increasing b / c for the carcass profile and decreasing a / c for the profile of the tire surface, the cross-sectional area on the bead portion increases, and the increase in the bead portion rigidity due to the longitudinal and lateral In the direction, the profile effect is canceled out and suppressed, and in the circumferential direction, the rigidity can be increased by the effect of the reinforcing material.

For the ratio of a / c and b / c, it is possible to take different values because it is determined by the tire flatness, size, and required performance, the effect of the present invention, a / c and b / c c
Is determined by the difference between B / c = a / c for conventional tires
And the difference is 0. When (b / c) − (a / c) ≧ 0, the intended effect of the present invention is exhibited. Because the rigidity of tire reinforcement is limited by durability, cost, etc., (b /
Experiments have shown that it is possible to increase the circumferential rigidity when the difference is c) − (a / c) ≧ 0.03.

(3) In the present invention, in order to further improve the steering stability performance, the JIS is provided between the tire maximum width position 10 of the carcass layer 3 and the turn-up winding terminal 11 of the carcass layer 3.
A rubber filler d having a hardness of 80 or more and a crescent-shaped cross section in the tire meridian direction is arranged.

Thereby, the volume and hardness of the lower portion of the side portion 4 are increased, and the circumferential spring constant (θ) is further increased. In FIG. 1, reference symbol e denotes a rubber reinforcing member disposed from the side portion to the bead portion.

 Examples and comparative examples are shown below.

(Examples, Comparative Examples)

For each tire A~D shown in Table 1, the longitudinal spring constant (hereinafter, referred to as S _V), lateral spring constant (hereinafter, referred to as S _L), the circumferential spring rate (hereinafter, referred to as S _O), steering stability (Steerability, stability) and ride comfort (strength per hit, convergence) were measured. Table 2 shows the results. Each tire has a tire size of 205/60 R15, air pressure of 2.0 kg / cm ² , R
IM 15 × 6JJ.

Measurement method of S _V , S _L , S _O : To remove the influence of the rigidity of the belt part, fix the tire surface with an annular ring to measure the rigidity of only the side part, Displacement was performed, and the displacement and force were measured to calculate respective spring constants. The results are shown in Table 2 by indexes. The higher the value, the higher the rigidity.

Measuring method of steering stability (steerability, stability): A sensory test by five panelists on a test course. Lane change test for each speed range, steady turning test, control
A drive test and a transient response test were performed and evaluated.

The steerability relates to the dynamic performance of the vehicle, and refers to the effectiveness, response, and response performance of the rudder.

Stability refers to the stability of the vehicle to steering motion and the stability of the vehicle to disturbances.

 The results are shown in Table 2 by indexes. Higher numbers are better.

Measuring method of ride comfort (strength of hit, convergence): It is a sensory test on various rough road surfaces installed on the test course.

The hit strength is the magnitude of the input from the road surface felt by the panelists.

The convergence refers to a performance of attenuating an input from a road surface.

 The results are shown in Table 2 by indexes. Higher numbers are better.

As can be seen from Table 1, the tires A and B do not satisfy the relationship of (b / c)-(a / c) ≧ 0.03 in the present invention and have no rubber filler d. It satisfies the relationship of (b / c)-(a / c) ≧ 0.03 in the invention, but has no rubber filler d.
As is clear from Table 2, the tire D (Example 1) of the present invention is superior in the handling stability and the riding comfort as compared with the tires A, B, and C (Comparative Examples 1 to 3). I understand.

〔The invention's effect〕

As described above, according to the present invention, a crescent-shaped rubber filler having a JIS hardness of 80 or more in a meridian section is arranged between the tire maximum width position of the carcass layer and the carcass layer turn-up winding terminal, and a regular rim. to set, when filled with the normal inner pressure, (a / c) together with the a <b - because of the (a / c) ≧ 0.03, without increasing the S _V and S _L substantially the S _O The driving stability and the riding comfort can be improved.

[Brief description of the drawings]

FIG. 1 is a half-sectional view in the meridian direction showing an example of the pneumatic radial tire of the present invention, and FIG. 2 is a longitudinal spring constant (V), a lateral spring constant (L), and a circumferential spring constant (θ). FIG. 3 is an explanatory view showing a half section in the tire meridian direction showing the relationship of FIG. 1 ... beat part, 2 ... bead core, 3 ... carcass layer, 4 ... side part, 5 ... rim, T ... tread part.

Claims (1)

(57) [Claims] 1. A radial tire in which a carcass layer is mounted between a pair of left and right bead portions, and an end of the carcass layer is turned up around a bead core from the inside to the outside of the tire and wound up. JIS hardness 80 between the maximum width position and the carcass layer turn-up winding terminal
When the rubber filler having a crescent cross section in the tire meridian direction described above is arranged and assembled on a regular rim and filled with a regular internal pressure, the height a from the rim at the tire maximum width position on the tire surface is adjusted to the tire maximum of the carcass layer. A pneumatic radial tire characterized in that the height b is smaller than the height b from the rim at a large position, and the relationship between these heights and the tire section height c satisfies the following expression. (B / c)-(a / c) ≧ 0.03