JPH0447618B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a passenger car in which a belt cover layer consisting of cords whose cord direction is approximately 0° with respect to the tire circumferential direction is disposed on the outermost layer of a belt reinforcing layer. The present invention relates to a method of manufacturing a pneumatic radial tire for use.

[Prior art]

Conventionally, in order to obtain a radial tire with excellent high-speed performance, as shown in Figs. On the carcass layer 4 in the tread portion 3, a plurality of belt reinforcing layers 5 are provided, which intersect with each other at cord angles of 10° to 30° with respect to the tire circumferential directions E and E'. Further, on the outermost layer 5u of the belt reinforcing layer 5, a belt cover layer 6 is arranged. In addition, in FIG. 5, 6a is a cord constituting the belt cover layer 6, 5a is a cord constituting the belt reinforcing layer 5, and 5d is a cord constituting the belt reinforcing layer 5.
represents the innermost layer of Bd is the width of the innermost layer 5d of the belt reinforcing layer 5.

The belt cover layer 6 has the function of reinforcing the belt reinforcing layer 5 to prevent the belt reinforcing layer 5 from curling up during high-speed running, and furthermore, together with the belt reinforcing layer 5, improves the rigidity in the tire circumferential direction. There is. The cord 6a of the belt cover layer 6 is generally a textile cord made of a heat-shrinkable material such as a nylon cord or a polyester cord.
It is located at approximately 0° with respect to E′.

By the way, in the manufacturing process of the tire equipped with the belt cover layer 6, after the belt reinforcing layer 5 is arranged, as shown in FIGS. 6a and 6b, the outermost layer of the belt reinforcing layer 5 is , code 6
A belt reinforcing layer 6 is arranged with a at approximately 0° with respect to the tire circumferential direction, and its terminal portions 62, 63 are arranged.
A splice portion 61 is formed by overlapping them. In this case, the length of the splice portion 61 of the belt cover layer 6 in the tire circumferential direction is represented by l ₁ (see FIG. 6a).

Next, tire constituent members such as the tread portion 3 are placed, and then this unvulcanized tire is pressurized and heated in a vulcanization mold (not shown) to vulcanize it into a product tire.

Here, the outer circumference of the unvulcanized tire before vulcanization is molded smaller than the inner circumference of the vulcanization mold, and during vulcanization, the unvulcanized tire is pressurized from the inside of the tire in the vulcanization mold to form a tire. , and its outer periphery is brought into close contact with the inner peripheral surface of the vulcanization mold. This is generally called lifting. Further, the value obtained by dividing the difference between the outer circumference of the unvulcanized tire before vulcanization and the outer circumference of the vulcanized tire after vulcanization by the outer circumference of the unvulcanized tire before vulcanization is called a lift ratio.

When lifted in this way, the carcass layer 4 and the belt reinforcing layer 5 can grow in outer circumference due to their structures, but the belt cover layer 6 has its cords extending in the tire circumferential direction as described above. Because it is located at almost 0°, it cannot grow. Therefore, as the belt cover layer 6 grows, each cord 6a constituting it stretches, and each end portion 6 at the splice portion 61 of the belt cover layer 6 grows.
The only reason is that 2 and 63 are shifted from each other.

However, since the adhesive strength of the splice portion 61 is small compared to the tensile strength of the cord 6a, most of the growth is due to the displacement of the splice portion 61. As a result, the splice portion 61 after vulcanization
The length l ₂ (see FIG. 6b) is shorter than the length l ₁ before vulcanization. As a result, most of the growth of the belt reinforcing layer 5 and the tread portion 3 will occur in the portions where they adhere to the splice portion 61 described above.

This causes uneven areas around the tire circumference,
This non-uniformity contributes to vehicle vibration when the automobile runs at high speed, and also causes deterioration in the high-speed durability of the tire.

This is because when a tire is mounted on a vehicle and a high-speed durability test is performed, the area around the splice part wears out abnormally quickly, and when an indoor high-speed durability test is performed, peeling failures occur mostly from the splice part. is also supported.

[Purpose of the invention]

The object of the present invention is to improve the uniformity of tires arranged with a belt cover layer in which splices are present,
Tire uniformity (especially RFV or
An object of the present invention is to provide a method for manufacturing a pneumatic radial tire with improved high-speed durability without deteriorating RRO.

[Structure of the invention]

The present invention provides a pneumatic radial tire in which a belt cover layer consisting of cords whose cord direction is approximately 0° with respect to the tire circumferential direction is arranged on the outside of a plurality of belt reinforcing layers in which cords intersect with each other between plies. When manufacturing the belt cover layer, a rubber tape in which a cord with an elongation rate higher than the lift rate during tire molding and vulcanization is embedded is placed on the belt reinforcing layer, and the side edges are butted against each other to create a substantially overlapping part. The rubber tape is constructed by winding the rubber tape in a spiral shape, and the ratio d/Bd of the width d of the rubber tape to the width Bd of the innermost layer of the belt reinforcing layer is
It is characterized by having a value of 0.03 to 0.15.

Hereinafter, the configuration of the present invention will be explained in detail with reference to the drawings.

In the present invention, as shown in FIGS. 4 and 5, the cord direction is approximately 0° (parallel ) When manufacturing a pneumatic radial tire equipped with a belt cover layer 6 made of cord, the belt cover layer 6 was formed as follows. Note that as the material of the cord constituting the carcass layer 4, chemical fibers such as nylon, rayon, and polyester are generally used. Steel cords are mainly used as cords for the belt reinforcing layer 5, but high-strength chemical fibers such as aromatic polyamide fiber cords can also be used.

(1) A rubber tape in which a cord with an elongation rate higher than the lift rate during tire molding and vulcanization is embedded is wound spirally on the belt reinforcing layer with the side ends abutted against each other without substantially overlapping portions. to constitute the belt cover layer. Here, the elongation rate refers to intermediate elongation. Intermediate elongation is measured according to JIS L1017.

By winding the rubber tape in a spiral manner on the belt reinforcing layer in this way, the start and end points of the rubber tape winding become terminals, and the splice part that spans the front width described above does not occur. , local deformation at the splice portion unlike in the prior art does not occur, and therefore non-uniformity on the tire circumference due to the arrangement of the belt cover layer is eliminated. In addition, when winding, it is preferable that the rubber tape is wound in the tire circumferential direction at the beginning and end, and at an angle of tan ⁻¹ (d/belt circumference) in the middle.

Rubber tape has a cord embedded in rubber that has a higher elongation rate than the lift rate during tire molding and vulcanization. The rubber used in this case may be a rubber composition commonly used for belt cover layers. Examples of the cord having a higher elongation rate than the lift rate during tire molding and vulcanization include cords made of nylon, polyester, and the like. The number of cords to be inserted may be the same as that for a normal belt cover layer, for example, approximately one cord per mm (0.8 to 1.2 cords/mm).

The reason why the cord constituting the rubber tape was made to have a higher elongation rate than the lift rate during tire molding and vulcanization is as follows.

For example, when vulcanization is performed using a two-split mold, the lift rate during tire molding and vulcanization must be approximately 3 to 4% due to problems with the operating mechanism of the mold. When two types of cords with different elongation rates are used as cords for the belt cover layer in such a mold, for example, with the nylon cord (elongation rate of about 5%), the tire uniformity is different from that of the conventional belt cover layer. It can be seen that the tire uniformity of the rayon cord (elongation rate of about 1 to 2%) is not improved compared to the conventional tire, although it is improved compared to the tire. In other words, as mentioned above, since there is no local deformation (so-called bumps) at the splice part, the amount of elongation (elongation rate) of the belt cover layer alone can compensate for the amount of elongation (equivalent to lift rate) during tire molding and vulcanization. This is because, when forming and vulcanizing a tire, it is necessary that the elongation rate of the cord of the belt cover layer is greater than the lift rate during forming and vulcanizing the tire.

(2) The ratio d/Bd of the width d of the rubber tape to the width Bd of the innermost layer of the belt reinforcing layer is 0.03 to 0.15.

Reducing the width of the rubber tape improves tire uniformity and high-speed durability, but it also increases the number of times the rubber tape is wrapped around the belt reinforcement layer, making it difficult to wrap it with uniform tension and causing the rubber tapes to overlap each other when wrapping. Problems arise in terms of productivity, such as overlapping of documents. In particular, if d/Bd is less than 0.03, the above-mentioned problems become noticeable, which is not preferable. On the other hand, d/Bd
When exceeds 0.15, the width of the rubber tape becomes large;
Since the winding angle is no longer substantially 0° and becomes larger at the beginning and end of winding, the tire uniformity deteriorates, and furthermore, there is a problem that the hoop effect in the tire circumferential direction is reduced. Therefore, in the present invention, various effects of the width of the rubber tape and the width of the belt reinforcing layer on tire uniformity and high-speed durability are considered, and the belt cover layer 6 is configured in the tire structure shown in FIG. The ratio d/Bd of the width d of the rubber tape to the width Bd of the innermost layer 5d of the belt reinforcing layer 5 is set to 0.03 to 0.15. here,
The reason why the width Bd of the innermost layer 5d of the belt reinforcing layer 5 was used as a reference is because this width Bd is approximately constant in a tire.

〔Effect of the invention〕

According to the present invention, since the belt cover layer is defined as explained above, it is possible to significantly improve the uniformity of the tire, reduce vibrations especially during high-speed running, and improve riding comfort. High-speed durability can be improved without deteriorating uniformity.

Examples are shown below.

Example (1) Tire uniformity (RFV): Conducted in accordance with JASO C607 "Test method for uniformity of automobile tires".

The tire size is 185/70HR13, and the belt cover layer is constructed by wrapping a rubber tape embedded with a cord with a higher elongation rate than the lift rate during tire molding and vulcanization in a spiral shape on the belt reinforcing layer. Tires with various ratios of the width coefficient μ=d/Bd were made and measured, and the conventional tires were evaluated as 100. The results are shown in FIG.
In FIG. 2, the horizontal axis represents d/Bd, and the vertical axis represents RFV change (%).

As is clear from Figure 2, the ratio of d/Bd is
It can be seen that RFV is good when it is 0.15 or less.

(2) High-speed durability: The 185/70HR13 tires produced in (1) above were evaluated for indoor drum high-speed durability as follows.

After completing the JATMA high-speed performance test with a drum diameter of 1707 mm, the test was continued at an additional 10 km/h increments until the tire failed. The faster the speed at failure, the better the high-speed durability. The results are shown in FIG. 3, with the failure distance of the conventional tire set as 100.

In FIG. 3, the horizontal axis represents d/Bd, and the vertical axis represents change (%) in high-speed durability.

As is clear from Figure 3, the ratio of d/Bd is
It can be seen that high-speed durability is good when the value is 0.15 or less.

[Brief explanation of the drawing]

Fig. 1 is a developed plan view of the belt reinforcing layer and belt cover layer of an example of the tire of the present invention, and Fig. 2 shows the width d of the rubber tape and the width Bd of the innermost layer of the belt reinforcing layer.
Figure 3 shows the relationship between the ratio d/Bd and tire uniformity (RFV), and the width d of the rubber tape.
Figure 4 is a diagram showing the relationship between the ratio d/Bd of the width Bd of the innermost layer of the belt reinforcing layer and high-speed durability.
The figure is a developed plan view of a belt reinforcing layer and a belt cover layer of an example of a conventional tire, and FIGS. 6a and 6b are explanatory diagrams showing a splice portion of the belt cover layer of an example of a conventional tire. DESCRIPTION OF SYMBOLS 1...Bead part, 3...Tread part, 4...Carcass layer, 5...Belt reinforcement layer, 5u...Outermost belt reinforcement layer, 5d...Innermost belt reinforcement layer, 6
...Belt cover layer.

Claims (1)

[Claims] 1. When manufacturing a pneumatic radial tire in which a belt cover layer consisting of cords whose cord direction is approximately 0° with respect to the circumferential direction of the tire is arranged on the outside of a belt reinforcing layer of multiple layers in which cords intersect with each other between plies. , the belt cover layer is formed by spirally forming a rubber tape in which a cord having an elongation rate larger than the lift rate during tire molding and vulcanization is embedded, on the belt reinforcing layer, butting the side edges against each other without substantially creating an overlapping part. A method for manufacturing a pneumatic radial tire, which is constructed by winding the rubber tape in a shape, and the ratio d/Bd of the width d of the rubber tape to the width Bd of the innermost layer of the belt reinforcing layer is 0.03 to 0.15.