JPS59124409A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To improve the rigidity of a belt, fuel consumption, and durability by reducing the number of cords by specifying the volume fraction of steel cord in a crown belt layer, the diameter of steel filament, and the distribution coefficient between filaments each other. CONSTITUTION:In the range in the direction of thickness of two pieces of rubber-lined steel cord layers (a) and (b) which occupy a belt layer, namely in the range surrounded by the line connecting the closest points to a carcass out of the individual steel cords which constitute the layer (a) and the line connecting the closest points to a tread out of the steel cords in the layer (b), the volume fraction (f) of steel cord is specified to 10-35%, and the diameter (d) of the steel filament is specified to 0.06-0.40mm., and the distribution coefficient K in an equation representing the number N of contact points between steel filaments each other, in the belt layer, in the section perpendicular to the peripheral direction of a tire is set to 1 or less. Thus, the number of cords can be reduced, and fuel consumption and durability can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pneumatic radial tire.
This invention relates to a pneumatic radial tire that increases belt rigidity with a small number of coats and improves fuel efficiency and durability by increasing the degree of dispersion of steel filaments constituting reinforcing steel cords in the belt layer.

It is generally known that radial tires exhibit better maneuverability and better fuel efficiency than bias tires. These features of radial tires are achieved by having a carcass layer arranged in the radial direction and a belt layer surrounding the outer periphery of the crown of the carcass layer. Steel cords with high elastic modulus are used as the belt reinforcement material. It is even more effective when used.

Therefore, conventionally, steel cords are often used.

However, steel cord has a specific gravity of about 7.86°, which is several times heavier than synthetic fiber cords such as rayon, polyester, and Kevlar, so the use of steel cord increases the weight of the tire. An increase in the weight of tires and tires causes a deterioration in tire uniformity and an increase in the unsprung weight of the vehicle, which leads to a decrease in driving performance. Therefore, it is necessary to keep the amount of steel cord used to the minimum necessary.

The present invention has been made in view of the above-mentioned circumstances, and is a pneumatic radial that suppresses an increase in tire weight by using a small amount of steel cord, and improves durability and fuel efficiency during driving of an automobile. The purpose is to provide tires.

Therefore, the present invention provides a pneumatic radial tire having a carcass with a radial structure and a belt layer made of a rubberized steel cord layer surrounding the outer periphery of the crown portion of the carcass. The fraction f is 10 to 35%, and the diameter d of the steel filament constituting the steel cord is 0.06 to 0.40.
Furthermore, when the number of contact points between steel filaments in the cross section perpendicular to the tire circumferential direction of the belt layer is N (pieces/cTL2), (ru; belt number, 1; 1 from the inside of the tire The belt ply is characterized in that the dispersion coefficient k in the equation represented by θi: the angle of the steel cord arranged on the first belt ply with respect to the tire circumferential direction; k: the dispersion coefficient) is 1 or less.

Hereinafter, the present invention will be specifically explained based on the drawings.

FIG. 1 is a cross-sectional explanatory view of an example of a pneumatic tire of the present invention, in which 1 is a crown portion, 2 is a carcass with a radial structure in which cords are arranged in the radial direction, and in the crown portion 1, the outer circumference of this carcass 2 is A belt layer 3 made of a rubberized steel cord layer is arranged so as to surround the belt.

In the present invention, the volume fraction f of the steel cord in the belt layer 3 is 10 to 35%.

The reason for this limitation is that if the volume fraction f of the steel cord is less than 10%, it will not have enough strength as a belt reinforcement material for steel 2 shear tires, and there is a great risk that the belt layer will break while the car is running. On the other hand, if the volume fraction f in the belt layer becomes larger than 35%, the tire uniformity will be significantly deteriorated due to the increased weight of the crown portion. Therefore, the volume fraction of the steel cord in the belt layer is at least 10% and at most 3%.
It is necessary to limit it to 5%.

Moreover, the volume fraction is defined as follows. That is,
As shown in Fig. 2, when manufacturing a steel radial tire, two rubberized steel cord layers a and b, each having a thickness of hl and h2, are made to have an appropriate intersecting angle with each other. to form a belt layer.

Therefore, the thickness of the deposited body including the first layer a containing the rubber composition surrounding the steel cord and the second layer is h3.

However, when these two rubberized steel cord layers a and b form a tire, the first layer a is in contact with the carcass layer made of the rubberized synthetic fiber layer, while the second layer is in contact with the carcass layer made of the rubberized synthetic fiber layer. Contact with the tread rubber layer or trend rubber layer.

When looking at the two stacked rubberized steel cord layers a and b from a structural mechanics point of view, the area in the thickness direction is determined by h3 shown in the drawing, that is, the total thickness of the steel cord covering rubber layer. It is more reasonable to define it by the diagonally shaded area shown in the drawing, that is, the area from the upper end to the lower end where the steel wire exists.

The reason is that the tensile modulus of steel cord is 5000~
22000kgf/n is noni vs. vulcanized colloid A (
D The tensile modulus is extremely small, for example, 15 to 80 kg/crIL2 when expressed as a 100% modulus value, so two rubberized steel cord layers a.

This is because the mechanical properties of the composite layer consisting of b practically depend mostly on the spatial arrangement of the steel wires. The area in the thickness direction of the belt layer is defined by a line connecting the points closest to the carcass of the individual steel cords constituting the first layer a and a point closest to the tread of the individual steel cords constituting the second layer. It is defined as the part surrounded by the connecting line. Therefore,
The volume fraction f (%) of the steel cord in the belt layer is the ratio of the area occupied by the steel cord to the area considered to be the belt layer defined above in the cut plane perpendicular to the tire circumferential direction. It is defined as expressed as . Note that FIG. 3 is an explanatory plan view of the belt portion from the tire tread side. The steel cord a1 in the first layer a is inclined at an angle of θl with respect to the tire circumferential direction, and the steel cord b1 in the second layer is inclined at an angle of θ2 with respect to the tire circumferential direction.
is placed at an angle of

Further, in the present invention, the diameter d(-) of the steel filament constituting the steel cord is 0.06WI≦
d≦0.40m.

The reason for this is that steel filaments thinner than O and Q5 wires have many difficulties in wire drawing, leading to increased costs, making them practically difficult to use on a commercial basis. On the other hand, 0
．． This is because a steel filament thicker than 40 m1 has a significant decrease in fatigue resistance and is not preferred in terms of tire durability.

Furthermore, in the present invention, when the number of contact points between steel filaments in a cross section perpendicular to the tire circumferential direction of belt layer B is N ((tFCrrL2),
.

The dispersion coefficient k in the formula expressed by is 1 or less (
In the formula, 1. θi is the same as defined above). This is due to the following reason.

Figure 4 shows a graph of the relationship between belt rigidity (belt rigidity increases as the number of steel cords is driven in) and transfer resistance when the number of steel cords in the belt layer is changed (index display). ).

As is clear from FIG. 4, it can be seen that the transfer resistance decreases as the belt rigidity increases, and it is expected that fuel efficiency will be improved by increasing the belt rigidity. In this way, it can be seen that an increase in belt rigidity improves fuel efficiency, but tires with increased belt rigidity by increasing the amount of steel cord used, as in these examples, suffer from uniformity as described above. becomes worse.

Therefore, in order to obtain a tire that satisfies all of the requirements of durability, fuel efficiency, and uniformity, it is necessary to use the minimum amount of steel cord necessary to ensure durability and to obtain as much tire rigidity as possible. desired. For this reason, we investigated the degree of dispersion of the steel cords in the belt layer and found that by using a belt layer in which the degree of dispersion coefficient k in the above formula (1) satisfies 1°0 or less,
They have discovered the surprising fact that it is possible to manufacture steel radial tires with increased durability and improved fuel efficiency without increasing tire weight.

Here, a steel cord with a k value of zero is one in which the strands of the cord are completely separate and have no contact points, and 1
．． Anything over 27 is a completely twisted cord with no gaps.

The effects of the present invention will be specifically explained below using Examples.

EXAMPLE In a 185 SR14 size radial tire for a passenger car equipped with a 2-ply polyester fiber cord as a carcass, tires were manufactured using various materials shown in Table 1 below as belt materials. The belt bendability was evaluated. Note that these evaluation conditions are as shown below.

Rolling resistance (a) Test conditions 2 methods Nidrum type Load: 300kg Air pressure: 1°7kg//crlL2 Speed: 60km/h ~ 150km/h (b) Rolling resistance value: Speed 60km/h ~ 150km/h The average value of h is expressed as an index with tire number 1 set as 100.

(a) Test conditions 2 methods: drum type load: 5
75kg Air pressure: 1.4kg/(m2 Slip angle: ±5° Camper: ±2° Speed: 20km/h Mileage: 1000 km (b) Display of belt breakage resistance After driving, disassemble the tire and remove the bare wire. The number of folds was counted. Displayed as an index with tire number 1 as 100. The smaller the index, the fewer the wires were folded, and the belt fold resistance was better.

(Left below) Table 1 The relationship between transfer resistance and dispersion coefficient is shown in Figure 5. In FIG. 5, A indicates the case where the volume fraction f is 14.1 to 15.5%, and B indicates the case where f is 25.0 to 26.7%. Further, the relationship between belt bendability and k is shown in Table 2 below.

Table 2 As can be seen from Figure 5 and Table 2, steel radial tires using belt materials where the constant k in equation (1) is k≦1.0 have good durability and fuel efficiency. That is clear.

As described above, the belt layer for a radial tire according to the present invention can improve rolling resistance without increasing the weight of the tire, and is particularly useful for improving the fuel efficiency of a radial tire for a passenger car.

Furthermore, since the belt layer for radial tires of the present invention has the effect of preventing the steel cord used from being damaged during running, its use in steel radial tires has the advantage of improving the durability of the tire. .

These effects are related to the placement of the steel cords in the belt material and are independent of tire size.

Therefore, the belt material of the present invention can also be used for large tires for trucks and buses.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional explanatory diagram of an example of a pneumatic tire of the present invention;
Figure 2 is a cross-sectional view of the belt layer perpendicular to the tire circumferential direction, Figure 3 is a plan view of the belt section viewed from the tire tread side, and Figure 4 is a graph showing the relationship between belt rigidity and rolling resistance. FIG. 5 is an explanatory diagram that graphically shows the relationship between the dispersion coefficient and the assembly resistance. DESCRIPTION OF SYMBOLS 1... Crown part, 2... Carcass, 6... Belt layer, a... First layer, b... Second layer. Agent Patent Attorney Shin Ogawa - Patent Attorney Masaru Noguchi Patent Attorney Kazuhiko Saishita Figure 1 Figure 2 Figure 1 Figure 4 Factor 5

Claims (1)

[Scope of Claims] A pneumatic radial tire having a carcass with a radial structure and a belt layer consisting of a rubberized steel cord layer surrounding the outer periphery of the crown portion of the carcass. Volume fraction f is 10-3
5% dust, the diameter d of the steel filaments constituting the steel cord is 0.06-0. (Set the number to N(pcs/c)
When a2), (rL: number of belts, i: first ply from the inside of the tire, θi: angle of the steel cord placed on the i-th belt ply with respect to the tire circumferential direction, k: dispersion coefficient)
A pneumatic radial tire in which the dispersion coefficient k in the formula expressed by is 1 or less.