JPS5818248B2 - Radial tires for passenger cars - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a radial tire for passenger cars with reduced rolling resistance.

When a passenger car is running, the power generated by the engine is finally transmitted to the tires through the power transmission mechanism of each part of the car, and the friction between the road surfaces drives the car. However, if the resistance to this drive is large, the fuel consumption increases. .

Recently, there has been a strong demand in the automobile industry to improve the running fuel efficiency of passenger cars from the viewpoint of energy saving and economic efficiency, and the present invention aims to reduce the rolling resistance of tires, which is one of the factors of running fuel efficiency.

- Energy loss associated with repeated deformation of tires during driving is an important factor that causes tire rolling resistance.

In other words, the tire undergoes compressive deformation and bending deformation due to the load applied, and when the vehicle runs, the deformation continuously moves along the circumference of the tire. At this time, various deformations and recoveries occur in each part of the tire. accompanied by mechanical energy loss during the repetition.

In other words, rubber-like substances, including tires, are so-called viscoelastic substances.
The relationship between stress and strain is non-linear, and strain shows a time delay in tracking stress.

Due to the tire's viscoelasticity, while the tire is running, deformation when it touches the ground and recovery when it leaves the ground are repeated, and at this time, a phase difference occurs in the relationship between stress and strain, resulting in hysteresis. Causes loss.

This is energy loss, and reducing the rolling resistance of the tire is nothing less than reducing such energy loss.

Conventionally, attempts have been made to reduce the above-mentioned energy loss, that is, transfer resistance, from the viewpoints of tread rubber compounding, sidewall rubber compounding, carcass materials, carcass rubber compounding, etc., but they have not been considered from a comprehensive perspective. Attempts to drastically reduce rolling resistance have resulted in the sacrifice of wet skid, which is an important characteristic for tires.

As a result of extensive research, the inventors found that the compression component and the bending component of the deformation behavior of the tread differ in the proportions that contribute to the rolling resistance of the tire, and that the tread composition and tread pattern are important for these. I discovered that.

In other words, when measuring on a 60-inch diameter drum, the contribution of the tread structure to rolling resistance is equivalent to approximately 40 times the contribution of the entire tire structure, and this 40% contribution is due to bending deformation. The ratio is about 30, and the ratio is about 10 due to compression deformation.

Based on this knowledge, the present invention considers both the composition of the tire tread and the pattern of the tread, and achieves a significant reduction in rolling resistance without impairing performance such as wet skids and with minimal sacrifice. be.

The present invention relates to a pair of bead wires and organic fiber cords arranged substantially parallel to the tire's radial direction, which are fixed to the bead wires, and are arranged straddling between a carcass and a sidewall made of polyester, 6-nylon, 6-row nylon, etc. In a radial tire for a passenger car comprising a tread portion and a breaker including at least one steel cord layer buried between the carcass and the tread portion, (1) the complex modulus of elasticity [E*] and loss elasticity of the tread rubber; rate CF '// l) and loss compliance [E''
/CE*)2]Each 30 surprises E*〈65 surprises 2 surprises E''〈10 surprises,' 0, 5 X 10-3crL'ky'4W'/ (E''
)2<4.0
A radial tire for a passenger car, characterized in that the value of the effective lateral groove index N, which is obtained by dividing the total sum for one rotation of the tire S) by the product of the tire outer diameter (D) and the tread cap, is within the range of be.

In the present invention, first, the viscoelastic properties of the tread rubber require that energy loss due to bending deformation and compressive deformation is small.

Here, if the bending deformation of the rubber is a constant strain behavior, the energy loss due to it is proportional to the loss modulus (E"), and if the compressive deformation is a constant stress behavior, the energy loss due to it is proportional to the loss compliance (E"). It is considered to be proportional to //(E*)2).

Therefore, it is desirable to reduce the loss elastic modulus (E') and loss compliance (E''/(E*)2) of the tread rubber. ) If 2) is made too small, the wet skid properties will be significantly reduced.

Therefore, in consideration of the fact that the energy loss due to bending deformation in the deformation of the tread portion contributes to the rolling resistance at a relatively high rate (approximately 30% of the total composition of the tire), the present invention has developed a loss modulus of elasticity related to bending deformation ( E tt ) is significantly lower in the comb, and conversely, the loss compliance (E / (E*)2) associated with the compressive deformation, which contributes to the transfer resistance, is relatively small.
), the aim was to maintain various performances such as wet skid without reducing them too much.

However, it is important that the complex modulus of elasticity (E*), loss modulus (E'), and loss compliance [E''/(E*)2] of the tread rubber of the radial tire according to the present invention are within the following ranges.

30 Surprising E*〈65 Surprising 2 Surprising E″〈10 Surprising 0.5X10-3cr; t/kg (E ″(E*)2
(4, OX 10-0-3ctV Here-, the complex modulus of elasticity (E*) and the loss modulus of elasticity (E") were measured using a viscoelastic spectrometer manufactured by Oiki Seisakusho.
The loss compliance (E"/ (E*)2) is obtained by calculating from the above measured values.

The present invention further requires that bending deformation be suppressed below a certain level from the viewpoint of the tread pattern.

For this purpose, the effective lateral groove finger MA) must exceed 1.1 and be less than 2.5.

Here, the effective lateral groove index p is determined by dividing the sum of the effective cross-sectional area S) in the width direction of the group portion of the tread pattern for one round of the tire by the product of the outside mD) of the tire and the tread width m.

That is.

Also, the sum of the effective cross-sectional areas in the width direction of the group parts (ΣS) is:
As shown in FIG. 1, grooves with a width of 1 mm or more (hereinafter simply referred to as grooves 5) 'G, , G2 and the grooves G1. Width direction component length of each center line of the groove (hereinafter referred to as siping) with width IWjrL or less connected to G2 1 t Ll
2 p Ll 3 ・””Ll n+ L21 +L2
21 L23 """L2n and 111, 1.12゜1
13°""'Z1mr z21 j z22 r 43
"・"・・・・・・Determine t2m, and connect this and groove G1
, G2, the product of the respective depths of siping Hl, H2,h, i.e. LlnHl, L2nH2, 71 m) 1.7
2mh is calculated, and the sum of these values for one round is obtained.

That is, the total effective cross-sectional area in the width direction (Σ5) nL 1nH12)::L2 nH2+:cz 1m
h+Σt2mh Here, for other tread patterns, the width direction component length of the groove G and siping Ll n t L2 n! '1
How to find m"2 m'- will be explained according to Figure 3. In Figure 3 A, 1 is the part that is effectively grounded, Go, G
2 is a groove, G is a siping that is connected to the groove, and 4 is a siping that is not connected to the groove.

Groove C1°G2 and the groove G1. The center line of the siping connected to G2 is shown in Figure 3.

Groove G1. Siping 4 that is not connected to G2 is particularly involved in the effects of the present invention, and therefore is excluded here.

Next, calculate the width direction component length from what is displayed at the end of Figure 3,
nt L"! Q t, '0mp -4□ is calculated and displayed as shown in FIG. 3.

Next, in the present invention, the tire outer diameter (2) refers to the outer diameter of the tire at the equatorial plane when the inner pressure is filled.

However, the effective lateral groove index N in the tread pattern according to the present invention is in the range of 141 to 2.5, preferably 15 to 2.0.
is within the range of

Here, if the effective lateral groove index N exceeds 2.5, the durability and wear resistance performance deteriorates significantly, and conversely, if it is 1.1 or less, no improvement in rolling resistance can be expected.

However. By combining the tread composition and tread pattern with a special configuration, the radial tire for passenger cars of the present invention maintains constant performance such as wear resistance, durability, and wet skid, and achieves a significant reduction in rolling resistance. This is what I did.

As shown in FIG. 8, the tire according to the present invention consists of a carcass 8 in which organic fiber cords are arranged in the radial direction, and at least one steel cord layer (in FIG.
layers are shown.

) The breaker structure of the tire according to the present invention has an auxiliary layer 11 made of an organic fiber cord such as nylon or polyester at the end of the breaker 10, as shown in FIG. In addition, as shown in Fig. 10, a steel cord breaker 10 and nylon,
Various aspects such as a combination structure with an organic fiber cord layer 11 such as Kevlar can be adopted.

Table 1 shows the values of the effective lateral groove fingers MA) for the various tread patterns shown in Figure 5 and Figure 6 shows the relationship between the rolling resistance index and the bending deformation strain index for these tread patterns. Shown below.

Here, the transfer resistance index and bending deformation strain index are the values of transfer resistance and compressive strain of the tread pattern shown in Figure 5 A.
This is the relative value when .

As is clear from Fig. 6, the tread pattern with the larger effective lateral groove finger (MA) in Table 1 has a lower bending deformation strain index.
The transfer resistance index is also low.

The rolling resistance was measured by placing a 60-inch diameter curvature drum 5 and a rotatably supported test tire 6 side by side in contact with each other, and applying a constant load to the test tire 6 from the F direction. When rotating the drum, the torque applied to the drum was measured and the transfer resistance was calculated from this.

The bending deformation strain shown in FIG. 6 is the strain on the tire surface when the tire 6 is loaded with a load on the drum 5, and the bending deformation strain is the maximum at a position 30 to 40 degrees away from the contact surface. is the value of

The present invention will be described below with reference to Examples.

Example 1 A steel breaker tire with a tire size of 165SR13 and the structure shown in FIG.
Four types of tires were prototyped with combinations of formulas ■) and (II) shown in the table, with tread patterns of Figure 5 Mouth and Figure 5 Part 2, and their rolling resistance performance and wet grip performance were measured. .

Transfer resistance performance is determined by tire internal pressure of 1. ．． Measurements were made on a 60 inch diameter drum under conditions of 9%, a load per tire of 420 to 9, and a running speed of 80 km/h.

In addition, the wet grip performance is a porta-pull kid on wet roads.

The friction coefficient was measured using a resistance tester and is expressed as a relative value to the value of Comparative Example 1.

The measurement results of the performance are shown in Table 3.

From the same table, it is recognized that the present invention significantly improves both rolling resistance performance and wet grip performance.

[Brief explanation of the drawing]

Figure 1, Figure 2, Figure 3 Figure 3 C is a reference diagram for calculating the effective cross-sectional area in the width direction, Figure 4 is a cross-sectional view of the tire, Figure 5
Figure 2 shows examples of tread patterns according to the present invention. Figure 5 C shows comparative example 1. Figure 6 shows the displacement resistance index and bending deformation strain index for the various tread patterns shown in Figure 5. 7 is a reference diagram of the transfer resistance measurement method, FIG. 8 is a cross section of the tire according to the present invention, and FIGS. 9 and 10 are the curve breaker structure of the tire according to the present invention. show.

Claims (1)

[Scope of Claims] 1: a carcass made of organic fiber cords fixed to the bead wires and arranged substantially parallel to the radial direction of the tire; a tread portion spanning between sidewalls; In a radial tire for a passenger car made of a plaaker including at least one steel cord layer buried between the tread portions, ■ the complex elastic claw [“E*]” loss modulus (H)° and loss compliance of the tread pattern; E′/(E*)
2] are 30 extra〈E ku65 surprise 2 surprise E"〈10 surprise 0.5X10-3gJ㉙〈E" / (E *) 2 (4, O
The dynamic characteristic value is within the range of X 10" crA/kg, and Effective transverse groove index A obtained by dividing by the product of
A radial tire for a passenger car, characterized in that it is in the range of 1.1 <A=::S/ CD XW) <2.5.