JPH04110203A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE:To improve steering stability and prevent uneven abrasion of a pneumatic radial tire by forming in each of both side areas of a tread part after galvanization curing, from a side edge of an adjacent circumferential groove to a discontinuous area of auxiliary belt layers, an outwardly projecting portion of a tire which disappears when the tire is installed on a regular rim and filled with a regular internal pressure. CONSTITUTION:A projecting portion R projecting outward from a side edge portion E which faces an adjacent circumferential groove 1 to a discontinuous area P of auxiliary belt layers B-5 and B-6 is formed in each of both side areas Sh of a tread portion of a tire after curing in a galvanizing mold. In this case, the height (r) of the projection outward from a line l drawn from the edge portion E parallel to a tire rotation axis is made equal to about 0.1-0.4mm. When the tire is installed on a regular rim and filled with a regular internal pressure, this projecting port R disappears and forms a continuous wheel contour as shown by a solid line.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to an improvement of a pneumatic radial tire, and more particularly, a high-speed running door-filled radial tire with improved handling stability and uneven wear. It is related to.

(Prior art) In recent years, with the development of expressways and the increase in the output of vehicles, the operating speed of vehicles has become increasingly high. Performance passenger cars have also been realized.

Conventionally, the tread portion of a tire used for such high-speed running has a ground-contacting shape as shown in FIG. 2, and is usually provided with a reinforcing structure for the tread portion as shown in FIG. 3. That is, it is generally made of steel cord or aromatic polyamide fiber cord with a high modulus of elasticity, and has two main belt layers that intersect at a relatively small angle to the circumferential direction of the tire, and is in direct contact with the outer radial direction of this main belt layer. A belt structure consisting of an auxiliary belt layer is used.

In FIG. 2, the tread portion T of the tire includes two pairs of circumferential grooves 1 that extend symmetrically and substantially parallel to the circumferential direction of the tire.
．． 2.3 and 4, and these circumferential grooves divide the tread portion T into a central region Ce and both side regions sh.

Further, on the radially inner side of the tread portion T, a toroidal carcass C consisting of at least one ply of fiber cords arranged in a direction substantially perpendicular to the equatorial plane, and between the carcass C and the tread portion T, a toroidal carcass C is provided. Main belt layers B-1 and B-2 in which at least two plies of non-extensible cords are arranged in an inclined manner at a shallow angle to the plane are stacked so that the cords intersect with each other, and this main belt layer B-1,
Four auxiliary belt layers B-3, B-4, and B-5 each having heat-shrinkable cords arranged approximately parallel to the equatorial plane on the outer periphery of B-2.
and a belt structure consisting of B-6.

In order to ensure high-speed durability, both side areas sh of the tread portion T are further reinforced than the central area Ce by auxiliary belt layers B-5 and B-6, and the auxiliary belt layer B -5 and B-6 axially inner end b
1 and b2 are adjacent to the circumferential groove 1 in the both side areas S,
They form axially discontinuous areas P with mutual steps.

A pneumatic radial tire for high-speed running with such a configuration first laminates the inner liner, carcass, bead wire, and sidewall rubber on a cylindrical former, and then expands the laminate into a toroidal shape at that position. Then, the integrated belt structure and tread rubber layer are removed from the former and set on the crown of the carcass so that they are concentric, and then glued together to form a green tire. After getting
This green tire is manufactured by vulcanizing and curing it in a vulcanization mold under high temperature and pressure.

(Problem to be Solved by the Invention) However, in the above-mentioned conventional high-speed tire, especially the auxiliary belt layers B-5 and B-6 of the belt structure B
Due to the axially discontinuous area P, there was a problem in that the steering stability and uneven wear were likely to be adversely affected.

That is, in the conventional high-speed running tire, in order to strengthen both side regions sh of the tread portion T than the central region Ce, the axially inner end portions b1 and 2 of the auxiliary belt layers B-5 and B-6 in the belt structure B b2, a discontinuous area P having a step is formed near the edge of the circumferential groove 1, and the more reinforced both side areas sh reduce the internal pressure in the tire across the circumferential groove 1 that separates this area from the central area. When the tread was filled, the outer contour of the tread T tended to lack smoothness in the cross-sectional direction. When a load is applied to such a tire, a contact profile as shown in FIG. 2 occurs. The characteristic of the ground contact shape in this case is that both circumferential ends of both sides (white areas There was a problem that it was easy to cause.

When the ground contact shape and ground pressure become uneven in this way, uneven wear tends to occur on both sides sh of the tread portion T, resulting in insufficient ground contact area and uneven ground pressure distribution, which reduces steering stability. This caused the problem that isokinetic performance was inhibited.

The present invention was achieved as a result of studies to solve the problems of the conventional high-speed pneumatic tires described above.

Therefore, an object of the present invention is to provide a pneumatic radial tire for high-speed running that has improved handling stability and uneven wear.

[Structure of the Invention (Means for Solving the Problems) In other words, the pneumatic radial tire of the present invention has at least a pair of circumferential grooves extending substantially parallel to the circumferential direction of the tire in the tread surface, and a toroidal carcass comprising at least one ply of layers in which the tread portion is divided into a central region and both side regions by directional grooves, and fiber cords are arranged radially inside the tread portion in a direction substantially perpendicular to the equatorial plane; , a main belt layer in which at least two plies of non-stretchable cords are arranged at a shallow angle with respect to the equatorial plane between the carcass and the tread portion, and are stacked so that the cords intersect with each other; The belt structure includes a plurality of auxiliary belt layers each having heat-shrinkable cords arranged approximately parallel to the equatorial plane around the outer periphery of the main belt layer, and the auxiliary belt layers have areas on both sides compared to the central area of the tread portion. In a pneumatic tire which is reinforced with a tread and has axially discontinuous areas of the auxiliary belt layer in both side areas, both side areas of the tread portion after being vulcanized and cured using a vulcanization mold are: The tire, which has an outer profile that protrudes outward from the edge facing the adjacent circumferential groove to the discontinuous area of the auxiliary heald layer and has been vulcanized and hardened, is assembled on a regular rim, After filling the layer with internal pressure, the protruding outer contour shape of the tread region on both sides substantially disappears;
The present invention is characterized in that a continuous outer contour shape is formed.

(Function of the Invention) The pneumatic radial tire of the present invention has both sides of the tread portion, which has been vulcanized and hardened using a vulcanization mold, separated from the edge facing the adjacent circumferential groove by the auxiliary belt layer. After the tire is assembled to the regular rim and filled with the regular internal pressure, the protruding outer contour shape of the areas on both sides of the tread virtually disappears, and the continuous area is formed into an outwardly protruding shape. Since the outer contour shape is formed, a smooth ground contact shape can be obtained as a result, and a suitable ground contact pressure distribution can be obtained.

This advantageously suppresses uneven wear during driving, and also provides maneuverability such as steering stability.

(Description of Examples) Hereinafter, examples of the pneumatic radial tire of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a partial cross-sectional explanatory view showing the state of the pneumatic radial tire of the present invention after vulcanization and hardening but before internal pressure filling.

In FIG. 1, the pneumatic radial tire of the present invention (hereinafter simply referred to as a tire) has at least a pair of circumferential grooves (in the drawings, regions on both sides of the tire) extending substantially parallel to the circumferential direction of the tire in a tread surface T. The tread portion T is provided with a circumferential groove 1 adjacent to the central area Ce and one additional groove 2 indicated by the reference numeral 2 on the axially inner side of the circumferential groove 1. It is sectioned.

On the radially inner side of the tread portion T, a carcass C consisting of at least one ply of fiber cords arranged in a direction substantially perpendicular to the equatorial plane;
Main belt layers B, -1 and B-2 and this main belt layer B-1, B-2
From a plurality of auxiliary belt layers (four sheets B-3, B-4, B-5, and B6 in the drawing) consisting of heat-shrinkable cords typically made of nylon arranged approximately parallel to the circumferential direction on the outer periphery of the belt. It is equipped with a heald structure B.

Here, the auxiliary belt layers B-3 and B-4 are arranged radially outwardly and adjacent to the main belt layers B-1 and B-2, covering the entire area of the central area Ce and both side areas sh. .

In addition, the auxiliary belt layers B-5 and B-6 are arranged only in the outer side regions sh of the auxiliary belt layer B-4 in order to improve high-speed durability.

Therefore, the side areas sh of the tread portion T are further reinforced by the auxiliary belt layers B-5 and B-6 compared to the central area C, and the auxiliary belt layers B-5 and B-6 are The axially inner end ends b1 and b2 are near the circumferential groove 1 in the both side areas S, and form an axially discontinuous area P having a step difference.

In the state after being vulcanized and hardened using a vulcanization mold, the both side areas S of the tread portion T have an outer contour shape that is the first.
As shown in exaggerated dotted lines in the figure, adjacent circumferential grooves 1
From the edge E facing the above auxiliary belt layers B-5 and B-6
It has a protrusion R that protrudes outward toward the discontinuous area P, and the protrusion R is formed by giving the same shape to the vulcanization mold.

In addition, in FIG. 1, the protrusion R has an outward protrusion height r from a line g drawn parallel to the tire rotation axis from the edge E facing the circumferential groove 1 adjacent to which both side areas Sh are adjacent. Approximately 0.1~
0.41.

Furthermore, after this tire is assembled on a regular rim and filled with the regular internal pressure, the protrusions R on both side areas S of the tread portion virtually disappear, resulting in a continuous outer contour shape as shown by the solid line in FIG. form R'.

In this case, the continuous outer contour shape does not mean that the central area Ce and both side areas sh have the same radius of curvature, but in many cases, the radius of curvature of the central area Ce that is convex to the outside, Similarly, it refers to an outer contour in which the radius of curvature of the smaller convex areas on both sides are smoothly joined.

Of course, in some cases, both areas may be formed with outer contours having a plurality of decoding radii of curvature.

By doing this, after assembling the tire on the regular rim and filling it with the regular internal pressure, pressurize the tire on the flat plate and the second
In the figure, since there is no blank space indicated by the symbol X on both sides of the ground, a smooth contact surface can be obtained.

In the above configuration, the material for the carcass C is organic fiber such as rayon or polyester, and the material for the main belt layers B-1 and B-2 of the belt structure B is, for example, steel cord or Kevlar (aromatic polyamide). At least two non-stretchable cords such as fiber cords are stacked so that each cord intersects with the other.
Further, as the material for the auxiliary belt layers B-3, B-4, B-5 and B-6, it is preferable to use heat-shrinkable cords such as nylon arranged substantially parallel to the circumferential direction. .

The structure and effects of the pneumatic tire of the present invention will be further explained with reference to test examples below.

(Test Example) A pneumatic radial tire with a tire rotation axis of 255/40ZR17 was provided with the structure shown in FIG. 1 or 3 above, and a tire of the present invention was manufactured.

That is, as the main belt layers B-1 and B-2, steel cords (IX
5) A metal belt layer in which two layers were crossed with each other was used.

Further, an auxiliary belt in which wide nylon cords are arranged radially outwardly and adjacent to the main belt layers B-1 and B-2 and substantially parallel to the tire circumferential direction over the entire area of the central area Ce and both side areas sh. In addition to arranging the layers B-3 and B-4, similar auxiliary belt layers B-5 and B-6 were also arranged from the outer side areas sh to part of the central area Ce. The edges b1 and B2 of the layers B5 and B-6 facing the circumferential groove 1 were arranged so as to be offset by 10 degrees in the axial direction and to form a discontinuous area P having a step.

When forming the tire, the outward protrusion height r from a line g drawn parallel to the tire rotation axis from the edge E facing the circumferential groove 1 adjacent to both side areas Sh is approximately 0. 2m
Using a vulcanization mold that can form a protrusion R such that
A tire of the present invention was manufactured. After the tire of the present invention was assembled on a regular rim and filled with a regular internal pressure (2.6 kg/cd), the protrusion R disappeared and a continuous outer contour shape R' was exhibited.

On the other hand, for comparison, a conventional tire was obtained in the same manner except that the shape of the molding die was the same as that of the conventional tire and the formation of the protrusion R was omitted.

Regarding the tire of the present invention and the conventional tire thus obtained, rim used: 9, internal pressure: 2.6 kg/cd, load:
Under the condition of 560 kg, uneven wear occurrence status (ground contact shape and ground contact pressure) and steering stability (slalom running, 100 mph ~
250 km/h), the results of the feeling evaluation are shown in the table below.

Table [Effects of the Invention] As explained above in detail, the pneumatic radial tire of the present invention has both side regions of the tread portion, after being vulcanized and hardened using a vulcanization mold, formed into adjacent circumferential grooves. It has an outer contour that protrudes outward from the facing edge to the discontinuous area of the auxiliary heald layer, and after the vulcanized and hardened tire is assembled on the regular rim and filled with the regular internal pressure, the above tread part Since the protruding outer contour shape of both side regions is substantially eliminated and a continuous outer contour shape is formed, a smooth ground contact shape and ground contact pressure can be maintained during load transfer of the tire.

Therefore, the pneumatic radial tire of the present invention does not cause uneven wear during running, and has performance as a high-speed tire that is advantageous in terms of maneuverability such as steering stability.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional explanatory diagram showing the state of the pneumatic radial tire of the present invention before and after vulcanization and curing, Fig. 2 is a developed view showing the contact print of a conventional pneumatic radial tire, and Fig. 3 is the same (conventional FIG. 1 is an explanatory cross-sectional view showing a pneumatic radial tire. T...Tread section C...Central area S...Both sides area 1...Circumferential groove C...Carcass B...Belt Structures B-1, B-2...Main belt layer B-3 to B-6...Auxiliary belt layer

Claims (1)

[Scope of Claims] The tread surface has at least a pair of circumferential grooves extending substantially parallel to the circumferential direction of the tire, and the circumferential grooves divide the tread portion into a central area and both side areas; a toroidal carcass comprising at least one ply of fiber cords arranged radially inside the tread in a direction substantially perpendicular to the equatorial plane, and a non-stretchable carcass at a shallow angle to the equatorial plane between the carcass and the tread; a main belt layer in which at least two plies of sex cords are stacked on top of each other so that the cords intersect with each other, and heat-shrinkable cords are arranged around the outer periphery of the main belt layer approximately parallel to the equatorial plane. The belt structure includes a plurality of auxiliary belt layers, the auxiliary belt layer having both side areas reinforced compared to the central area of the tread portion, and an axis of the auxiliary belt layer in the both side areas. In a pneumatic tire having a directionally discontinuous region, the regions on both sides of the tread portion after being vulcanized and cured using a vulcanization mold are discontinuous in the auxiliary belt layer from the edge facing the adjacent circumferential groove. After the tire is assembled to the regular rim and filled with the regular internal pressure, the protruding outer contour shape of the regions on both sides of the tread virtually disappears, and the tire is continuous. A pneumatic radial tire characterized by forming an outer contour shape.