JPH04123905A - Radial tire - Google Patents

Abstract

PURPOSE:To improve both operating stability and riding ability by severally specifying tire sectional width measured under an unloaded conditions, earthing width at the time of loading a fixed design normal load, and a distance between straight lines parallel to a rotary shaft, and additively providing a reinforcing ply. CONSTITUTION:A radial tire 1 is provided with a steel belt 3, and the nominal designation of a flattening ratio on a tire size marking is 60%. In this case, tire sectional width W measured under unloaded conditions is made smaller than the designation of sectional width on the tire size marking. A grounding width CM at the time of loading a fixed design normal load is established to be 0.6<=CW/W<=0.7. In addition to that, under the unloaded conditions, a distance (h) between a straight line (l1), which passes through the sectional center A of a belt 3 at a central position in the direction of the tire width and is parallel to the rotary shaft of the tire, and a straight line (l2), which passes through the sectional center B of the belt at the position of the grounding end at the time of loading and is parallel to the rotary axis of the tire, is established to be 0<=h/CM<=0.04. A reinforcing ply 6 is provided to reduce the radially outward displacement caused by centrifugal force of a tread shoulder to a central part.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention comprises a steel belt and has a nominal aspect ratio of 60%.
The aim is to improve both the handling stability and comfort of the radial tires.

(Conventional technology) In recent years, as vehicles have become more sophisticated and sophisticated, radial tires, which have become increasingly flat, are required to provide high-speed handling stability, while also requiring improved comfort. .

In order to improve the steering stability, it is necessary that changes in the shape of the tire's contact surface due to changes in the speed of the centrifugal force of the tire be small and stable.

Conventionally, therefore, a reinforcing ply was provided on the outer periphery of the belt, or the crown R of the tire was made smaller.

(Problem to be solved by the invention) However, the use of reinforcing ply increases the bending rigidity of the belt, which reduces the ability of the tire to wrap around unevenness on the road surface (enveloping property), and causes problems such as hersiconism, which makes it difficult to ride. decreases.

Also, when the crown R of the tire is made smaller, the Bell I
・There was also the problem that the envelope property deteriorated due to distortion in the tension distribution.

(Means for Solving the Problems) In view of the problems of the prior art described above, an object of the present invention is to provide a radial tire that can improve both steering stability and comfort.

A feature of the present invention is that a radial tire equipped with a steel belt (3), with a nominal aspect ratio of 60% on the tire size display, assembled on a predetermined standard rim and filled with a predetermined air pressure, can be used in an unloaded state. Tire cross-sectional width W measured at
is smaller than the nominal cross-sectional width indicated by the tire size, and CW is the ground contact width under load when a predetermined design normal load is applied, and 0.6≦CW/W≦0.7, and in the no-load state. , a straight line (11) passing through the cross-sectional center (A) of the belt (3) at the center position in the tire width direction and parallel to the tire rotation axis;
The distance between the ground contact end position under load and the straight line (!2) passing through the cross-sectional center (B) of the belt and parallel to the tire rotation axis is h, and 0≦h/CW≦0.04, and the tread shoulder A reinforcing ply (6) is provided to reduce radially outward displacement of the center portion due to centrifugal force.

(for production) The present invention is based on the following findings.

The solid line in Figure 4 shows the radial tire filled with air pressure.
It represents the shape of the ground contact surface when the speed is v-0, the horizontal axis direction is the tire rotation axis direction, and the vertical axis is along the tire equatorial plane.

In addition, Figure 5 shows the tension distribution of the steel belt of a conventional radial tire, and the vertical axis shows the belt tension (kg).
f), the horizontal axis shows the distance (mm) from the tread center in the direction of the tire rotation axis, the marks are the tension distribution when the tire is filled with air pressure and no load, and the marks are the tension distribution when the tire is filled with air pressure and the load is applied. is loaded to bring it into the ground state, and the speed V-
Tension distribution in the state of 0, ◇ mark is when the tire is filled with air pressure and a load is applied to the ground, and the speed is V = 1
The tension distribution at a speed of 20 km/h is shown. This tension distribution was obtained by analysis using the finite element method.

From FIG. 5, it can be seen that when the tire changes from an unloaded state to a ground contact state, the belt tension increases at the shoulder portion of the tread and decreases at the center portion.

This corresponds to the fact that the tread becomes a flat surface upon contact with the ground, the shoulder portions of the tread are stretched, and the center portion of the tread is compressed.

Furthermore, as the tire rotates, belt tension increases due to centrifugal force.

When the tire rotates, the ground contact area decreases due to deformation due to centrifugal force, but since the circumferential restraining force by the belt is smaller in the shoulder portion than in the center portion, the shoulder portion rises radially outward and the crown R becomes larger.

In this way, when the shoulder part rises radially outward and the crown R becomes larger, as shown by the broken line in Fig. 4, the ground contact surface during tire rotation is larger at the tread center part than at the shoulder part. The length becomes shorter, the self-lining torque decreases, and the steering stability decreases.

As mentioned above, an increase in the crown R of the tread while the vehicle is running reduces the steering stability. This will improve the As shown in Figure 6, by such measures to improve steering stability,
The shape of the ground contact surface during running, shown by the broken line, was supposed to have a smaller change in shape than the shape of the ground contact surface when the vehicle was stopped, shown by the solid line.

However, when the reinforcing ply is provided, the change in the shape of the ground contact surface due to centrifugal force can be reduced, but on the other hand, there is a problem of deterioration of the enveloping property due to an increase in belt bending rigidity.

On the other hand, if the crown R is set small, as shown in Fig. 7, the belt tension at the shoulder portion of the tread increases and the change in the contact surface shape can be reduced, but the enveloping effect due to the increase in the belt tension at the shoulder portion of the tread increases. The problem is a decrease in

Furthermore, if the crown R is set small, the belt tension at the center of I/Red will decrease, and belt compression force will be generated at the tread center, causing the ground surface to locally lift.
1- There is a risk of the buckling phenomenon occurring,
This will cause a decrease in steering stability.

Furthermore, Figure 7 shows the tension distribution of each steel belt in radial tires with different crown R.
The vertical axis shows the belt tension (kgf), and the horizontal axis shows the distance (mm) in the tire rotational axis direction from the l/red center. This tension distribution was obtained by analysis using the finite element method.

In contrast to the radial tire with the conventional structure as described above, the radial tire according to the present invention has a larger crown R compared to the radial tire with the conventional structure by setting 0≦h/CW≦0.04.

As a result, as shown in FIG. 2, the belt tension at the center portion of L and red is increased, and the belt tension at the shoulder portion is decreased, thereby reducing the difference in tension between the center portion and the shoulder portion.

Furthermore, in the radial tire according to the present invention, a reinforcing ply is provided to reduce the displacement of the L/Red shoulder part radially outward due to centrifugal force with respect to the center part, so that Even at high speeds, the belt tension difference between the sender part and the shoulder part is kept small.

This reduces the radially outward displacement of the center part of the tread shoulder area due to centrifugal force.
Changes in the shape of the ground contact surface due to changes in speed are reduced, improving steering stability at high speeds.

Furthermore, by reducing the difference in belt tension between the center portion and the shoulder portion of L/Red, the buckling phenomenon caused by the belt compression force in the center portion is prevented from occurring.

Further, the deterioration in envelope properties due to the provision of the reinforcing ply is prevented by reducing the belt tension at the shoulder portions of the tread.

In addition, FIG. 2 shows the tension distribution of the steel belt of the radial tire according to the present invention, where the vertical axis represents the belt tension (kgf), and the horizontal axis represents the distance from the tread center in the direction of the tire rotation axis (mm). ), the mark is the tension distribution when the tire is filled with air pressure and no load, the cross mark is the tension distribution when the tire is filled with air pressure and a load is applied to the ground, and the speed is V-0, ◇ mark is when the tire is filled with air pressure and a load is applied to make it in contact with the ground, and the speed V =
The tension distribution at a speed of 1.20 km/h is shown.

This tension distribution was obtained by analysis using the finite element method.

The reason why the belt of the radial tire according to the present invention is made of steel is because it is a common material including its cost.

As long as it is a steel belt, the number of plies, wire diameter, etc. are not limited.

The nominal aspect ratio of the tire size indication of the radial tire according to the present invention is 60%. This is because an aspect ratio other than this cannot produce the desired effect.

The radial tire according to the present invention has a tire cross-sectional width W measured in an unloaded state when assembled on a predetermined standard rim and filled with a predetermined air pressure, which is smaller than the nominal cross-sectional width indicated by the tire size. This is because the desired effect cannot be achieved with a cross-sectional width outside this range.

The radial tire according to the present invention has a ground contact width under load of CW, which satisfies 0.6≦CW/W≦0.7 when filled with the predetermined air pressure and loaded with a predetermined designed regular load.

0.6≦CW/W means that CW/W is 0.6
If it is less than this, the crown R becomes a reverse R when the tire is filled with a predetermined air pressure and no load is applied, making it impossible to fully demonstrate the performance of the tire. In Figure 3, the horizontal axis represents the aspect ratio and the vertical axis represents the value of CW/W, and the relationship with the crown R was determined through experiments. First, in the region below the broken line in the figure, the crown R has become an inverted R. From this, in order to prevent the crown R from becoming an inverted R, 0.6≦CW/W was set.

Also, CW/W≦0.7 is required because if CW/W exceeds 0.7, the ground contact width becomes too wide relative to the tire cross-sectional width, and the rigidity of the tread or side part becomes too large. This is because it becomes relatively too large and the ride comfort deteriorates.

In the radial tire according to the present invention, in an unloaded state filled with the predetermined air pressure, a straight line (see Fig. 1 11) and a straight line (1!2 in Figure 1) that passes through the cross-sectional center of the belt (point B in Figure 1) and is parallel to the tire rotation axis at the load contact end position (h), 0
≦h/CW≦0.04.

The reason why 0≦h/CW is set is that if Ii/CW becomes 0 or less, the crown R of the tire will obviously become an inverted R.

Also, h/CW≦0.04 is h/CW
This is because if it exceeds 0.04, the desired effect cannot be achieved sufficiently.

The belt reinforcing ply may be one that reduces radially outward displacement of the center portion of the shoulder portion of the tread due to centrifugal force; for example, one or two gap plies may be provided to cover the entire belt; One cap ply may be used to cover the entire belt, and one edge ply may be provided at each end to cover both ends of the belt. Alternatively, as shown in FIG. It may be covered with a sheet of edge ply 6.

In addition, the aspect ratio and cross-sectional width of the tire size display are I
This is a unified name based on SO, JIS, the following Japan Automobile Tire Association standards, etc.

In addition, the predetermined standard rim, predetermined air pressure, and predetermined design regular load are those stipulated by the standards established by the Japan Automobile Tire Association (JATMA) (Japan Automobile Tire Association Standards) (JATMA YEARBOOK, 19
1990 edition, Chapter A).

This means that if the rim width (indicated by R in Fig. 1), air pressure, and applied load are different, even if the aspect ratio is the same, the tire cross-sectional width (indicated by W in Fig. 1) and the ground contact width under load (indicated by 11 in Fig. 1) will change. ) are different, so we decided to use the Japan Automobile Tire Association standard as a standard for numerically limiting these tire cross-sectional widths, etc.

In this Japan Automobile Tire Association standard, standard rims are defined according to tire size, and a design regular load is defined as a load corresponding to when the tire is filled with a predetermined air pressure.

(Example) Fig. 1 shows a part of a cross section including the rotating shaft of a radial tire according to an example of the present invention, in which 1 is a tread, 2 is a carcass ply, 3 is a two-ply steel belt, 4 is peed core, 5 is bead filler, 6 is edge ply,
7 is a side wall.

Table 1 below shows data for Examples and Comparative Examples.

In addition, the size of the radial tire of each Example and Comparative Example in Table 1 is 205/60R]5.

Further, the ground contact length is the circumferential length at the tread center, and the numerical value (%) in parentheses indicates the rate of change in the ground contact length during running, with the time at rest being 100%.

Furthermore, high-speed stability and comfort are shown in the results of a feeling test, with the results of Comparative Example 2 being set as an index of 100, and the larger the index, the better.

In addition, the feeling of response is the feeling of response when steering,
The hardness of the hit corresponds to the envelope property, and the damping is the ease with which vibration subsides.

(Hereinafter referred to as "next leaf") Table (hereinafter referred to as "adult leaf") From Table 1 above, according to the present example, the steering stability is better than the comparative example not only in the feeling test but also because the rate of change in ground contact length is small. I understand that.

Further, according to this example, the envelope property is also better than that of the comparative example.

In other words, it is confirmed that both steering stability and livability are optimized.

(Effects of the Invention) According to the radial tire according to the present invention, it is possible to improve both steering stability and livability due to the novel configuration not seen in the past.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the cross-sectional structure of a radial tire according to an embodiment of the present invention, Fig. 2 is a diagram showing the tension distribution of the belt of the radial tire according to the present invention, and Fig. 3 is a diagram showing the aspect ratio and CW/W. A diagram showing the relationship with crown R, Figure 4 is a diagram showing the shape of the contact patch of a radial tire, Figure 5 is a diagram showing the tension distribution of the belt of a conventional radial tire, and Figure 6 is a diagram showing the shape of the contact patch of the radial tire. FIG. 7 is a diagram showing the tension distribution of the belt of a radial tire. 3... Steel belt, 6... Edge ply (reinforced ply). Su□ri A-

Claims (1)

[Claims] (1) Tire cross-sectional width measured under no-load conditions for a radial tire equipped with a steel belt (3), with a nominal aspect ratio of 60% on the tire size display, assembled on a specified standard rim and filled with a specified air pressure. W is smaller than the nominal cross-sectional width indicated by the tire size, and CW is the ground contact width under load when a predetermined design normal load is applied, and 0.6≦CW/W
≦0.7, and in the no-load state, a straight line (l_1) passing through the cross-sectional center (A) of the belt (3) at the center position in the tire width direction and parallel to the tire rotation axis, and at the ground contact end position under load. The distance from the belt cross-sectional center (B) to the straight line (l_2) parallel to the tire rotation axis is h, 0≦h/CW≦
0.04, and is characterized in that a reinforcing ply (6) is provided to reduce radially outward displacement of the shoulder portion of the tread due to centrifugal force with respect to the center portion.