JPS604405A - Pneumatic radial tire for passenger car - Google Patents

Abstract

PURPOSE:To contrive to reduce road noise while retaining stability in driving, by a method wherein the tire equivalent stiffness balance coefficient, which is the ratio of the equivalent stiffness of a side part to that of a tread part, of a radial tire is set in a specified range. CONSTITUTION:The pneumatic radial tire is provided with a carcass cord layer 4 between a left-right pair of bead parts 3, and a belt reinforcement layer 5 consisting of steel cords is provided between the tread part 1 and the carcass cord layer 4. In this case, the tire equivalent stiffness balance coefficient R, which is the ratio GS/GB, wherein GS is the equivalent stiffness of the side part represented by a predetermined formula as an equivalent evaluation of the stiffness of a tire region other than the tread part 1, namely, the region rang ing from a shoulder part through a side wall part 2 to the bead part 3, and GB is the equivalent stiffness of the tread part represented by a predetermined formula as an equivalent evaluation of the tread part 1, is set in the range of 0.17<=R<=0.34.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pneumatic shiracial tire for a passenger car, and more particularly to a pneumatic shiracial tire for a passenger car that reduces road noise without impairing handling stability.

Road noise is the noise generated when tires run on rough paved roads.Minor disturbances from the road surface induce vibrations in the tires, which vibrate various parts of the body through the suspension system, causing interior noise. This occurs as a result. Therefore, in order to reduce this phenomenon, it is necessary to reduce the vibration of each part of the body by absorbing and alleviating the disturbance from the road surface with the tires.

Conventionally, as a method for absorbing and alleviating this disturbance from the road surface on the tire side, many measures have been taken mainly to improve the tire material in pneumatic radial tires for passenger cars.

For example, specific measures for tire materials include using rubber with a high energy loss as tread rubber.
There are methods of increasing the energy loss in the tread portion by using rubber with a large an δ, or increasing the energy loss in this portion by increasing the mass of the tread rubber.

However, while these methods are sufficient as a countermeasure against road noise, it is a well-known fact that increasing the tan δ of the tread rubber significantly worsens the rolling resistance of the tire. No, no. Furthermore, increasing the mass of the tread rubber also leads to a worsening of rolling resistance, increases the weight of the tire, and is not an effective countermeasure from the viewpoint of material costs.

The present invention was developed in view of the above-mentioned circumstances, and an object of the present invention is to provide a pneumatic schiral tire for passenger cars that reduces road noise without impairing tire performance, particularly steering stability. shall be.

For this purpose, the present invention includes a pair of left and right bead portions, a pair of left and right sidewall portions connected to the bead portions, a tread portion located between the side wall portions, and a pair of left and right bead portions. In a pneumatic shiracial tire in which a carcass cord layer is installed between the tread portion and the carcass cord layer, and a belt reinforcing layer is arranged between the tread portion and the carcass cord layer, the side portion equivalent rigidity, (as’) and the tread portion equivalent rigidity Tire equivalent stiffness balance (5
) The gist of the present invention is a pneumatic schiral tire for a passenger car, characterized in that the coefficient (R) is 0.17≦R≦0.34.

EMBODIMENT OF THE INVENTION Hereinafter, the structure of this invention will be explained in detail by the Example shown in a figure.

FIG. 1 is an explanatory diagram of a calf cross-section of an example of a pneumatic tire according to the present invention. In Fig. 1, 1 is a tread portion;
Reference numeral 2 designates sidewall portions provided so as to extend on both sides of the tread portion 1, and reference numeral 6 designates bead wires embedded in the lower end portion of the oid wall portion 2 along the circumferential direction. A carcass cord layer 4 is provided to wrap around the bead wires 3 at both ends and along the inner surfaces of the sidewall section 2 and the tread section 1, and further between the carcass cord layer 4 and the tread section 1. A belt reinforcing layer 5 made of steel cord is interposed therebetween.

Carcass Cord Layer 40 As the carcass cord (6), general synthetic fibers such as nylon, rayon, and polyester are used. Furthermore, although steel cords are mainly used as cords for the belt reinforcing layer 5, aramid (aromatic polyamide fiber cords) may also be used. Furthermore, a nylon cord may be arranged as a secondary reinforcing material for the belt reinforcing layer 5 in parallel with the cord of the belt reinforcing layer 5 in the circumferential direction of the tire. In Figure 1, 6 is the bead filler, 7 is the rim part, sH is the tire cross-sectional height), l
represent the bead filler height and knot), respectively.

The bead turning structure including the bead wire 3 and bead filler 6 can take various forms as shown in FIG. Figure 2 (A-1), (A-2), (A-3)
Figures 2 (B-1), (B-2) and (B- 3)
are carcass cord layer 4-1 in contact with the inner liner and carcass cord layer 4-1 not in contact with the inner liner.
2 (C-1), (C-2×(C'-3))
shows a structure in which the end of the carcass cord layer 4-1 is wound around the bead wire 3, and the bead wire 3 is wound approximately half a length from the outside to the inside in the carcass cord layer 4-2. In Fig. 2, 6-1 indicates the bead filler (hereinafter referred to as inner filler) sandwiched by the carcass cord layer 4-1, and 6-2 indicates the portion sandwiched by the carcass cord layer 4-1. Each represents the portion of the bead filler that is not filled in (hereinafter referred to as outer filler).

(1) The side portion equivalent rigidity (Gs) is expressed by the following formula.

In addition, the side part equivalent rigidity is an equivalent evaluation of the rigidity (tire radial direction rigidity) of the tire area other than the tread part 1, that is, the area from the shoulder part through the sidewall part 2 to the shoulder part. It is.

Ain, Ein: The cross-sectional area in the radial direction (recess 2) of the bead filler (inner filler 6-'1) in the part inserted and grooved by the carcass cord layer 4-1 in contact with the inner liner and 100% of the bead filler rubber % elongation modulus (kg/kg2) Aout, Eo
ut: carcass cord layer 4 in contact with the inner liner
-1 The cross-sectional area of the bead filler (outer filler 6-2) in the part not sandwiched by (-2) and the 100% elongation modulus of the bead filler rubber (kg/season 2) SR tire cross-sectional height -) l : Bead filler height and dark) d : Thickness of sidewall rubber part at maximum width of tire -) D : Tire circumferential direction (wrI) π : Pi (q) CDi=(AEc)i=ni (however, i =1 or 2)
(AEc)z: Tensile strength constant ni of the cord of the i@th carcass cord layer: Number of cords implanted per unit width of the j@th carcass cord layer (pieces/M) The outer filler 6-2 is the second As shown in the figure,
The rubber part that contacts the folded part of the carcass cord layer 4-1 that contacts the inner liner is basically different in type from the reed, sidewall rubber, and rim cushion rubber. 100% modulus is 9/1ran2 for O06
The above are used.

CDI is the carcass cord layer 4 in contact with the inner liner.
−1 is the carcass rigidity h, and CD2 is the carcass rigidity of the carcass cord layer 4-2 not in contact with the inner liner. As mentioned above, these are Cn1= (AEc)+=n
t (where i = 1 or 2). ni
is the number of cords per unit width in the circumferential direction of the bead core rotation of the carcass cord of the i-th carcass cord layer (cords /
謬).

This is the value calculated from the number of pieces with a width of 50 mm (10) It is.

The tensile strength constant of the carcass cord layer cord is defined by measuring the load-elongation curve of the cord using a method based on the JIS L 1017 chemical fiber and tire cord test method.
and the slope of the maximum load change of the curve. This is equivalent to the initial tensile resistance.

Furthermore, the modulus of bead filler rubber is defined as the stress at 100% elongation in the tensile test of JIS K6301 Vulcanized Rubber Physical Test Method.

The reason for determining the side part equivalent stiffness (Gs) as above is as follows.
The results of various experiments conducted by the present inventors show that it is necessary to reduce the stiffness in order to reduce slope noise, and in evaluating the stiffness, a bead rotation structure as shown in Fig. 2 was used. This is because it was discovered that the structure of each part of the tire, including the structure, must be considered.

It is preferable that the value of the side part equivalent stiffness (Gs) is within the range of 0.82 x 105≦G8≦1.51 x 165, and if it is within this range, road noise will be more satisfactory than conventional tires. can be reduced. In particular, if Gs is less than 0.82×10 5 , road noise is reduced, but the steering stability is inferior to that of conventional tires, which is not preferable.

(2) Tread portion equivalent rigidity (DB) is expressed by the following formula.

When considering the tire rigidity within the tire tread surface, in the case of a radial tire, belt rigidity as a tire hoop effect is important for tire performance. Therefore, when the equivalent rigidity of the tread portion, which is the rigidity in the circumferential direction of the tire, is evaluated using the rigidity of the belt reinforcing layer, it is expressed as follows.

DB=Σ(AEB)j=mj=CO84αj=WJ
j = 1 (Report B) j: Tensile spring constant of one cord of the j-th belt reinforcement layer (kg) Town = Number of cords driven per unit width of the j-th belt reinforcement layer (pieces/milk) αj: Cord angle (deg) of the j-th belt reinforcing layer with respect to the tire circumferential direction Wj: Belt width (neck) of the j-th belt reinforcing layer N: Number of stacked belt reinforcing layers Tensile shebane constant of one cord of the belt reinforcing layer ( kg) is defined by calculating a load-elongation curve using a method based on JISZ 2241 Tensile Shear Test for Metallic Materials and expressing it as the slope of this curve between 0.5% and 1.5% strain.

(3) The tire equivalent rigidity balance coefficient (R), which is the ratio (GS/DB) of the side part equivalent rigidity (Gs) to the tread part equivalent rigidity (DB), is set to 0.17≦R≦0.34.

When evaluating the steering stability of a tire, simply increasing the equivalent stiffness (Da) of the tread portion of a radial tire does not necessarily improve the steering stability.

Increasing the cornering power of a tire alone can be achieved by increasing the tread equivalent stiffness (DB) (13), but considering the function of the tire in terms of vehicle handling stability. However, it is not enough to simply increase the cornering power of a single tire.

Therefore, when considering the handling stability of the tire as a whole, it is divided into the tire tread part and the tire side part, and the balance of rigidity of these parts, that is, the tire equivalent rigidity balance coefficient (Gs R) The present inventors have discovered that =- is an indicator of the improvement in tire performance in terms of vehicle handling stability. As a result of prototyping and evaluating various tires, it was found that by setting the tire equivalent rigidity balance coefficient (R) to 0.17 ≦ R ≦ 0.34, it was possible to obtain a tire that could enjoy moderate handling stability. It has become possible.

If R is less than 0.17, for example, the side stiffness (G
When S) is held constant and the equivalent stiffness of the tread part ■B) is increased, the actual steering stability test (14) shows that there is a significant delay in the vehicle's response to steering, and sufficient steering stability cannot be obtained. . On the other hand, R is 0034'
For example, if the equivalent stiffness of the side part (GS) is increased while the equivalent stiffness of the tread part (DB) is constant, the balance between the size of the steering angle during steering and the movement of the car becomes worse, so the movement of the car in response to the steering becomes worse. If you don't look forward to it, you'll end up with a strange steering feel. Therefore, R must be within the above range.

The effects of the present invention will be specifically explained below with reference to experimental examples.

Experimental Example For the sample tire 165/705R13, various combinations of tires were prototyped by changing the side part equivalent stiffness (GS) by 6 levels and the tread part equivalent stiffness (DB) by 5 levels, and conducting an actual vehicle feeling test. The road noise performance and steering stability performance were evaluated. These results are listed in Table 1 below.

As a method of changing the side part equivalent stiffness (Gs),
The number of plies of the carcass cord layer, the material of the carcass cord, and the bead rotation structure corresponded to this.

In addition, the tread equivalent rigidity (DB) was changed by changing the material of the belt reinforcing layer, the belt cord angle, the belt width, etc.

The method for evaluating road noise performance and steering stability performance, as well as an example of calculating equal ethicality, are shown below.

(b) Actual vehicle road noise/feeling test method: To evaluate the absolute level of tire road noise performance,
Generally, this is done through sensory testing, but there is no established test method. However, in most cases this is done in the following way. Therefore, this method was used in this example as well. Attach the tires to be tested to the four wheels of the test vehicle and drive the vehicle at a speed of 50 to 60 km.
When driving at m/h on roads with large and small irregularities such as coarse-grained roads, Belgian roads, cracked roads, etc., passengers sensory-evaluate and score the noise level, sound quality, and degree of ear irritation generated inside the car. do.

The evaluation method is a 5-point system in which the reference tire is given a score of 0 in relative evaluation, and the rating scale is as follows. Note that REG (regular tires) were used as standard tires.

(b) Actual vehicle handling stability/feel test method: Evaluation of tire handling stability is generally performed by a sensory test conducted by a professional driver. Although there is no established test method, the following method is generally used. Therefore, this method was used in this example as well.

A test vehicle with test tires installed on its four wheels was driven in various driving modes such as lane shifting, steady circular turning, and slalom driving.
The driver performs a sensory evaluation and scores the vehicle's driving performance and steering feel.

For the evaluation method, we adopted the same method as in the case of road noise.

Example of calculating equal ethicality: ! 6F) Calculating the tire (165/70 SR13) results in the following.

r 17
B) 1 = (AEB) 2 = 3625 kg Number of cords driven (unit width) m1 = m2 = 0°8 (40 cords 15°) Belt cord angle α1 = α2 = 27° Belt width W, = 125 hp W2 = 115 Theory DB '=
3625 'X O,8X 'CO8' 27°X
125 +3625X O,8X'CO3'27°X
115 = 4387'
Number of 0 code inputs n1 = 1.1 (55 pieces, 1150 old) Therefore, CDI = (AE (1 I x nl = 9
5.7 X 1.1 Structural form of the pedestal (Fig. 2 (A)
-2)) (18) Ain = 1682, Aout = 106 tran2
゜1ijn = 0.99kg/mm2. Eout=0
．． 618ky7h2.

SH=120.4. mn l = 45 d = 3゜0 concave D = 13X25゜4 trunk π = 3゜1415
(Left below) Table 1 (19) As is clear from Table 1, the equivalent stiffness of the side part (Gs)
It can be seen that when the tire diameter is less than 0.82X105, road noise is reduced, but the steering stability is inferior to that of conventional tires.

FIG. 3 shows the relationship between the results of the actual vehicle road noise and feeling test and the side equivalent stiffness (GS). From FIG. 3, it can be seen that when Gs is 1°51×105 kg or less, the road noise feeling test results are generally better than those of conventional tires.

FIG. 4 shows the relationship between the quality of the results of the actual vehicle handling stability/feeling test and the tire equivalent rigidity balance coefficient (R). According to Figure 4, 0.17≦R
It can be seen that good steering stability can be obtained when ≦0.34.

As explained above, according to the present invention, road noise can be reduced without impairing steering stability.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is an explanatory diagram of a meridional cross section of an example of the pneumatic siracial (21) (20) tire for passenger cars of the present invention, Fig. 2 is a structural diagram of the bead rotation of the same tire, and Fig. 3 Figure 4 is a relationship diagram between road noise quality and side part equivalent rigidity (G, q), and Figure 4 is a relationship diagram between handling stability quality and tire equivalent rigidity balance coefficient (R). 1...Tread part, 2 ...Side wall section, 3.
...Bead wire, 4...Carcass cord layer, 5"'
Belt reinforcing layer, 6... Bead filler, 7... Rim portion. Agent: Patent Attorney Shin Ogawa − Patent Attorney Ken Noguchi Patent Attorney Kazuhiko Saishita (9)

Claims (1)

[Claims] Consisting of a pair of left and right bead portions, a pair of left and right sidewall portions connected to the bead portions, and a tread portion located between the sidewall portions, a carcass is provided between the pair of left and right bead portions. In a pneumatic shiracial tire on which a cord layer is mounted and a belt reinforcing layer is arranged between the tread section and the carcass cord layer, the side section equivalent stiffness (Gs) and the tread section equivalent stiffness (DB) are The tire equivalent rigidity balance coefficient (R), which is the ratio (Os/Dn), is 0.17≦R≦0.
34 A pneumatic shiracial tire for a passenger car, characterized by: However, Gs and DB are expressed by the following formula (1) p (2). Ain+Ein: radial cross-sectional area of the bead filler in the portion sandwiched by the carcass cord layer in contact with the inner liner (f=-”) and 100% of the bead filler rubber
% extension modulus (kg/wn”) Aout, Eou
t: Cross-sectional area of the bead filler in the part not sandwiched by the carcass cord layer in contact with the inner liner (-2) and 100% elongation modulus of the bead filler rubber (kyM2) SH: Tire cross-sectional height theory) l: Bead filler d: Thickness of the sidewall rubber at the widest part of the tire) D: Tire rim diameter (throat) π: Circumference ratio CD1=(AEc)+・ni (however, i=1 or 2)
(AEc)H: Tensile strength constant ni of the cord of the first carcass cord layer: Number of cords per unit width light beam of the j-th carcass cord layer (pieces/old) (AEn)j: j-th belt reinforcement layer Tensile strength constant of one cord (kg) ITlj , : Number of cords per unit width of the j-th belt reinforcing layer (pieces/old) αj : Cord angle of the j-th belt reinforcing layer with respect to the tire circumferential direction ( deg) Wjmj Belt width (side) of the belt reinforcing layer N": Number of layers of the belt reinforcing layer