JPS61188203A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To enable the control stability at the time of cornering to be improved by specifying the ratio of radius of curvature between the bead side and the crown side at both ends of the maximum width of a carcass line for the inner and other sides of a radial tire for a passenger car when the tire is filled up to the standard air pressure. CONSTITUTION:When a tire is filled up to the standard air pressure, the radius of curvature for local areas between the end point A and B of the maximum width of a carcass line and a bead section 7 is expressed to be RCI and RCO, and the radius of curvature for local areas between the point A and B and a crown section 9 is expressed to be RCI' and RCO'. Then, a ratio RCI'/RCI and a ratio RCO'/RCO should be specified to be more than 0.9 and less than 0.8 respectively. This configuration enables the control stability at the time of cornering to be improved.

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to a pneumatic radial tire suitable for use in passenger cars, and in particular to an improved carcass shape that improves the handling characteristics when the vehicle turns. It is.

(Prior art) In a conventional pneumatic radial tire for a passenger car, the tire is mounted on a standard rim and filled with standard air pressure, and the carcass is moved from the carcass line's maximum width position toward the bead. The ratio of the radius of curvature Rc of the local line portion to the radius of curvature Rcl of the local carcass line portion from the same position toward the crown portion Rc'/R
c is 0.8 on either side of the tire equatorial plane.
~0.95, and the cross-sectional shape of the carcass line in the tire width direction was symmetrical with respect to the tire equatorial plane.

Such a known pneumatic radial tire has a reinforced structure in its bead portion and/or side portion, etc.
It is known that the vehicle exhibits excellent handling characteristics when turning.

(Problems to be Solved by the Invention) However, there is no end to the demand for turning performance of vehicles, coupled with the remarkable improvement in high-speed performance of vehicles in recent years.Especially during sports driving, there is a need to turn corners as quickly as possible. Moreover, there is always a desire for tires that can be driven safely.

Therefore, the inventors discovered that when a vehicle turns, the tires receive a much more severe mechanical input than the tires on the inside of the corner.
When we tried to analyze the force that acts on the belt and bead of the tire on the outside of the vehicle when turning, we found that the inner and outer sides of the vehicle are in completely opposite directions with the equatorial plane of the tire as the boundary. It turns out that there are factors that are affected by the force. Therefore, by applying an extra force to each half of the tire in the opposite direction to the external force that acts on each belt and bead when the vehicle turns, it is possible to counteract those external forces. , it is possible to advantageously improve the turning performance of the vehicle by canceling out at least a portion of those external forces and mitigating the tire deformation caused by the external forces.However, in the conventional tires described above, the belt and the belt on either side of the tire equatorial plane can be The bead parts also receive the same tension by filling them with air pressure, so
It has been impossible to bring about the effects based on the above-mentioned findings.

This invention improves the lateral rigidity of the tire by improving the shape of the carcass line to apply extra tension in advance to the belt and bead parts of the tire, where external forces in the compressive direction act especially when the vehicle turns. The present invention also provides air-filled tires with improved road grip.

(Means for Solving the Problems) The pneumatic radial tire of the present invention consists of cords that substantially extend in the radial direction of the tire, extending in a toroidal manner between a pair of bead cores, and the end portions of the cords extending in the radial direction of the tire. A carcass is provided around each bead core from the inside to the outside, and on the outer periphery of the crown part of this carcass, at least two tread reinforcing layers made of cords forming a relatively small angle with respect to the tire equatorial plane are provided. A belt made of at least two tread reinforcing layers is arranged, and a bead reinforcing layer made of cords forming an angle of 60 to 80 degrees with respect to the radial plane is provided at a position adjacent to the upper end of the carcass. In tires,
When the tire is mounted on a standard rim, and the tire is in a position filled with standard air pressure, the radius of curvature Rc of the local carcass line from the maximum width position of the carcass line toward the bead, and the local carcass line from that position toward the crown. The ratio Rc l/ to the radius of curvature P CI of the part
Rc is 0.9 on one side of the tire equatorial plane.
Above, the other side is 0.8 or less.

(Function) First, when we look at the effect that the lateral force acting on the tire when the vehicle turns has on the tire, its carcass, and belt, the carcass is shown in Fig. 2 (a) as a cross section in the width direction of the tire. As is clear from the figure, the lateral force causes the tire to be deformed from the solid line position to the broken line position, which is shown in the left half of the figure. ), the carcass bulges diagonally upward, and on the other side of the tire equatorial plane shown in the right half of the figure, that is, the outer part of the tire, the carcass is tilted and retracted downward, and as a result, the tire expands. In its inner part, the bead part is subjected to compression in its circumferential direction, and in its outer part, the bead part is subjected to circumferential tension.

On the other hand, as is clear from the in-plane elevation of the belt on the contact surface of the tire in Figure 2(b), the belt also moves from the solid line position to the dashed line position in the figure due to the action of lateral force. The inner part of the tire is deformed to the circumferential tension of the belt, and the outer part of the tire is
Each receives compression in the circumferential direction.

Next, looking at the effect that the deformation behavior of the tire due to lateral force has on the steering characteristics, the carcass, belt, and bead reinforcement layers provided at the bead all have sufficient resistance against force in the tensile direction. However, since the inner part of the tire cannot resist the force in the compression direction, there is insufficient tension in the bead reinforcing layer due to the compression in the circumferential direction of the bead part. The tire loses its rigidity and feels stiff, and in the outside part of the tire, due to the lack of tension due to circumferential compression of the belt, belt buckling occurs on the outside of the turn, resulting in loss of rigidity and ground contact. Both of these phenomena are negative factors for improving steering characteristics.

Therefore, in order to improve the handling characteristics of the vehicle, especially when turning, in order to eliminate these phenomena, the tension acting on the bead reinforcement layer on the inner side of the tire is increased when filling the tire with internal pressure, and the tire It is preferable to adopt a carcass line shape that increases belt tension in the outer part of the belt.

By the way, in this invention, the shape of the carcass line is determined by the radius of curvature R of the local part of the carcass line from the maximum width position of the carcass line toward the bead part when the tire is filled with internal pressure.
c and the radius of curvature Rc' of a local portion of the carcass line from that position toward the crown, the ratio Rc'/Rc is 0.9 on one side of the tire's equatorial plane, in other words, on the inner side of the tire. Above, preferably 1.0 or more, and 0.8 or less, preferably 0.0 in the outer part of the tire.
7 or less, in the inner part of the tire, the tension of the carcass increases in a part of the shoulder based on the internal pressure of the tire, increasing the circumferential tension of the bead part, and in the outer part of the tire, the tension in the carcass increases due to the internal pressure of the tire. The tension in the carcass decreases at a portion of the shoulder, and the tension in the circumferential direction of the belt increases.

To explain this in more detail based on FIG. 3, the above-mentioned radius of curvature ratio Rc
' Based on the specification of /Rc, a large force acts on the inner part of the tire in the direction of increasing the carcass tension in the shoulder part, as shown by the arrow in Fig. 3(a), and on the outer part of the tire, As shown by the arrow in FIG. 3(b), a large force acts in a direction that reduces the carcass tension in a portion of the shoulder. As a result, in the inner part of the tire,
The bead is also pulled in one direction of the shoulder, i.e. in the radial direction of the tire, resulting in an increase in the circumferential tension of the bead and thus an increase in the stiffness of the bead. The compressive force in the direction can be countered sufficiently effectively. On the other hand, in the outer part of the tire, the circumferential tension of the belt is increased to compensate for the decrease in the carcass tension of a part of the shoulder. The ground contact J3 and rigidity of the tire can always be maintained reliably.

(Example) The present invention will be explained below based on illustrated examples.

FIG. 1 is a cross-sectional view in the width direction of a tire showing an embodiment of the present invention, in which 1 is a carcass, and 2 is a belt consisting of at least two tread reinforcing layers arranged on the crown of the carcass 1. are shown respectively.

Here, the carcass 1 consists of an organic insulator or a steel insulator extending substantially in the radial direction of the tire, and this carcass 1 extends like a toroid between a pair of bead cores 3. , 1a are wound around the bead core 3.3 from the inside to the outside in the tire width direction and extend toward the shoulder portion 4.4.
Ru.

The reinforcing layer 2a of the belt 2 is made of a metal cord extending at a relatively small angle with respect to the tire equatorial plane x-X. 5b respectively.

And also here, the winding upper end portion 1a of the carcass 1,
A bead reinforcement H6 made of organic fiber or metal cord is provided adjacent to the inner side in the tire width direction, and the cord angle with respect to the radiation surface at the peripheral edge position passing through the radially outer edge of this reinforcement layer 6 is set to 80 to 60 degrees. do.

In the figure, 7 indicates a bead portion, 8 indicates a side portion, and 9 indicates a crown portion.

With this tire, when it is assembled on a standard rim and is not filled with air pressure, one side and the other side of the tire's equatorial plane are asymmetrical with respect to that plane. , and in a tire posture filled with standard air pressure, the radius of curvature ROI of the local portion of the carcass line from the maximum width of the carcass line 1 tA and B toward the bead portion 7 on the inner and outer sides of the tire,
Radius of curvature R'o1 of the local part of the ROO cass line. R
The ratios R'o□/Ro and R'CO/RcO are 0.9 or more and 0.8 or less, respectively.

Here, the reason why the ratio of curvature radii R'/IRo, R'Co/RcO is specified in this way is that in a so-called natural equilibrium shape, this ratio is 0.8.
~0.9, and at this time, the tension generated in the carcass is almost the same in both the shoulder part and the bead part, and the amount of protrusion when filling the internal pressure is also uniform, so in order to create tension deviation, the tension on the outside should be 0. This is because it is required to be 0.8 or less, and 0.9 or more on the inside.

Here, more preferably, the ratio R'o/Ro of the radius of curvature of the inner part of the tire is set to 1.0 or more, and the ratio R'co/Rco of the outer part is set to 0.7 or less. , the thickness distribution from the sidewall to the bead can be maintained appropriately.

In addition, the heights 11□ and ho in the tire cross section at the maximum width positions A and B of the carcass line are 50 to 65% and 26 to 53% of the maximum cross-sectional height of the tire, respectively. It is preferable to set the ratio Rc'/R'C to 0.9 or more on one side and 0.8 or less on the other side.

Furthermore, with this tire, it is necessary to fill the sleeve with standard air pressure.
However, in the inner part of the tire, the maximum protrusion position of the carcass line is at the maximum width position of the carcass line after air filling or closer to the crown, and in the outer part, the maximum protrusion position of the carcass line is at the maximum width position of the carcass line after air filling or closer to the crown. □
Although it may be slightly off-center, this is a characteristic phenomenon that occurs in the tire constructed according to the present invention.

A comparative test was conducted between the tire according to the present invention and a conventional tire under the following conditions.

Tire specifications size: P, S 205/60 R15 carcass:
Polyester cord tsood/2.2 pieces Belt: Steel cord 0.23φ x 5 Intersection angle with respect to the equatorial plane 20° Cap and layer: Nylon cord 1250d/2 1 layer each.

Intersection angle O between the equatorial plane.

Bead reinforcing layer: Steel cord 0.23φX5 Cord angle 66° with respect to the radiation surface The various dimensions after filling the tire with the standard air pressure are as shown in the table below.

Test Conditions Various tires were mounted on a domestically produced 2000 cc sport-type passenger car and the test was run around a circuit with one lap of 2.04 KIIl.

-14=Result The average lap time of the earliest 3 laps of the 5 laps was 1'16''83 for the conventional tie V, whereas it was 1'16''34 for the tire of the present invention, and the average lap time of the tire of the present invention was 1'16''34. is 0.49 seconds faster than that of conventional tires. Note that when this is converted into distance, it becomes a difference of 27 meters at a speed of 200 km/h.

(Effects of the Invention) As is clear from the above, according to the present invention, the shape of the carcass line is changed asymmetrically between the inner part and the outer part of the tire, and in the inner part, the shape of the carcass line is changed asymmetrically between the inner part and the outer part of the tire. By increasing the directional tension and also by increasing the belt tension in the outer portion, the lateral stiffness of the tire and the road grip are increased, especially when the vehicle is turning, resulting in an effective improvement in the handling characteristics.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view in the width direction of a tire showing an embodiment of the present invention, Fig. 2 is a route diagram showing the state of deformation of the carcass and belt due to lateral force, and Fig. 3 shows a portion where carcass tension is increased according to the invention. It is a diagram. 1... Carcass 1a... End portion 2... Bell 1 to 2a... Tread reinforcing layer 3... Bead core 4... Shoulder part 6... Bead reinforcing layer 7... Bead portion "CI'RcI'R'Co
, RcO...radius of curvature R'/R, R'co/
Rco...Ratio CI CI h, ho...Maximum width position height of carcass line Fig. 2 (a) (b) Fig. 3 (a) (b)

Claims (1)

[Claims] 1. Consisting of a cord that substantially extends in the radial direction of the tire, extending in a toroidal manner between a pair of bead cores, and extending the end portion around the bead cores from the inside in the width direction of the tire. A carcass that is each rolled up toward the outside; at least two tread reinforcing layers made of cords arranged on the outer periphery of the crown portion of the carcass and forming a relatively small angle with respect to the tire equatorial plane; and an upper end of the carcass. In a tire that has an adjacent bead reinforcing layer made of cords forming an angle of 60 to 80 degrees with respect to the radial plane, when the rim is assembled on a standard rim and the tire is in a position filled with standard air pressure, the carcass line is at its maximum. The ratio Rc'/Rc of the radius of curvature Rc of the local part of the carcass line going from the wide position to the bead part and the radius of curvature Rc' of the local part of the carcass line going from the same position to the crown part, is calculated on one side with the tire equatorial plane as the boundary. 0.9 or more on one side, and on the other side
A pneumatic radial tire characterized in that the tire has a diameter of 0.8 or less. 2. The ratio Rc'/Rc of the radius of curvature is 1.0 or more on the one side bordering the tire equatorial plane and 0.7 on the other side.
The tire according to item 1 below. 3. As the standard air pressure is filled, the maximum protrusion position of the carcass line is on the one side bordering the tire equatorial plane.
2. The tire according to item 1 or 2, wherein the carcass line is located at the maximum width position or closer to the crown portion than the maximum width position, and the other side is located at the maximum width position of the carcass line or closer to the bead portion.