JPH0671772B2 - Radial tire manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is a radial tire having a lug groove, in which peeling of the belt layer can be prevented by reducing the waviness of the shoulder portion, and the appearance of the completed tire is improved. Relates to a method for manufacturing a radial tire that can improve

[Conventional technology]

In radial tires, particularly radial tires for heavy loads such as trucks and buses, a lug groove is arranged in the tread portion, and the lug groove extends to the tread end.

Further, such a tread portion is conventionally wound around an outer peripheral surface of a tire base body with a raw rubber sheet a having a trapezoidal cross section and a uniform shape as shown in FIG. The lug groove was formed by vulcanizing with a rubber sheet and pressing the rubber sheet a against the tread pattern previously formed on the mold to deform the rubber sheet a.

[Problems to be Solved by the Invention]

By simultaneously forming the tread pattern during vulcanization as described above, as shown in FIG. 6, the block portion b is raised and the groove portion c is settled. Further, the shape of the rubber sheet a is changed by the pressing, and the belt layer d and the carcass e are corrugated between the block portion b and the groove portion c due to the change in the shape. Such waviness is remarkable in the shoulder portion, and as a result, the end portion of the belt layer d tends to peel off from the rubber layer, resulting in deterioration of durability of the tread portion. On the other hand, the lug groove extending in the tire axial direction causes the belt layer d to undulate in the tire circumferential direction, and this undulation causes undulation in the sidewall portion even in the tire appearance.

It may be possible to increase the thickness of the sidewall portion to prevent undulation of the sidewall portion, but the increase in the thickness increases the weight of the tire, resulting in an increase in cost and contributing to measures for preventing the peeling of the belt layer. I haven't.

The present invention is based on preliminarily forming a concave portion in the lug groove forming portion on the raw cover forming the tread portion prior to vulcanization thereof, which can prevent peeling of the belt layer end portion and enhance the durability of the tread portion. It is an object of the present invention to provide a method for manufacturing a radial tire that can improve the appearance of the tire.

[Means for Solving the Problems]

In the method of manufacturing a radial tire of the present invention for solving the above problems, a carcass that folds around the bead core of the bead part from the tread part to the sidewall part,
A radial tire having a belt layer arranged on the outer side in the radial direction of the carcass and on the inner side of the tread portion, and lug grooves and blocks protruding between the lug grooves are alternately arranged in parallel on the shoulder side of the tread portion. The method for manufacturing the tire, wherein a tread raw rubber sheet forming a tread portion is attached to the outer peripheral surface of the raw tire base to form a raw cover, and the tread width (TW) of the tire formed by vulcanization of the raw cover. Of the tread rubber contained in the lug groove portion (VG) between the position separating the tire axial direction by 3/8 times from the tire equator and the tread edge, and the rubber volume of the tread rubber contained in the block portion (VB ) And volume difference SO (= VB
~ VG) 0.8 times larger and 1.2 times smaller volume (S)
Prior to the vulcanization of the green cover, it is formed in advance in the tread raw rubber sheet at the lug groove forming portion of the vulcanizing die.

[Action]

Prior to the vulcanization of the raw cover, the recess is formed in advance in the tread raw rubber sheet forming the raw cover, so that the recess can be easily formed.

In addition, the volume S of the recess is restricted to 0.8 times to 1.2 times the volume difference between the lug groove portion and the block portion between the position separated from the tire equator 3/8 times the tread width TW and the tread edge. Even when the lug groove is formed by the vulcanization mold, the raw cover volume hardly changes. Therefore, since the belt layer does not have a wavy dent below the lug groove,
It is possible to improve the durability of the tread portion without peeling from the rubber layer at the belt end portion. Further, as described above, the waviness of the belt layer is reduced, so that the tread portion is not wavy, and the running stability is improved and the commercial value is increased.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

1 to 5, a radial tire manufacturing method of the present invention (hereinafter referred to as a manufacturing method) is a method of forming a concave portion in advance on a raw cover 3 forming a tread portion 2 of a radial tire 1 prior to vulcanization thereof. .

The radial tire 1 has a bead portion 6 through which a bead core 5 passes,
A sidewall 7 extending radially outward from the bead portion 6 is raised, and the tread portion 2 connecting the sidewall 7 is provided. Further, the radial tire 1 includes a carcass 9 which passes from the tread portion 2 through the sidewall 7 and is folded around the bead core 5 of the bead portion 6, and a plurality of belts outside the carcass 9 in the tire radial direction and inward of the tread portion 2. A belt layer 10 made of ply is provided.

The carcass 9 forms a radial array in which fiber cords made of steel, polyester, nylon or the like are arrayed at an angle of 70 to 90 ° with respect to the tire equator C. In the present embodiment, the belt layer 10 includes a first belt ply 21, a second belt ply 22, and a third belt ply 2 from the carcass 9 side toward the outside.
It consists of four belt plies arranged in the order of 3 and the fourth belt ply 24, and each belt ply has cords of steel nylon, polyester or the like arranged in a direction intersecting between adjacent belt plies. The carcass 9 and the belt layer 10 form the tire base 26 by coating the sidewall 7, the bead portion 6, and the outside thereof with rubber, and by providing the rubber layer 27 on the outside of the belt layer 10, the radial The tire 1 is formed.

The rubber layer 27 has a plurality of lug grooves 12 and a plurality of blocks 13 protruding between the lug grooves 12 and 12, as shown in FIG. And are arranged side by side alternately.

Since the belt layer 10 is arranged in such a manner that the cords of the belt plies 21, 22, 23, and 24 are arranged in a direction intersecting with each other, it exerts a hoop effect to enhance the rigidity of the tread portion 3, and the third belt ply 23 Is wide and the end portion F is extended to the vicinity of the tread edge D to maintain the rigidity of the shoulder 11 of the tread portion 2.

A breaker cushion 29 made of soft rubber is arranged outside the carcass 9 of the shoulder 11.

The rubber layer 27 is manufactured by the manufacturing process described below.

1) An unvulcanized tread raw rubber sheet 14 is formed which has a strip shape having a width dimension substantially equal to the tread width TW and has concave portions 4 on both side edges as shown in FIG.

2) The carcass 9 is formed in a toroidal shape and the belt layer 10 is attached, and the inner rubber 31 and the outer rubber 32 before vulcanization are attached to the inward and outward surfaces of the carcass 9 and the tread portion 2
The raw tire base 15 is formed by the breaker cushion 29. The raw tire base 15 can be vulcanized to form the tire base 26.

3) the tread raw rubber sheet 14 on the outer surface of the belt layer 10,
That is, it is wound around the outer peripheral surface 16 of the raw tire base 15. Therefore, the tread raw rubber sheet 14 forms the raw cover 3 attached to the raw tire base 15.

4) The raw tire base 15 to which the raw cover 3 is attached is charged into a vulcanization mold and vulcanized. The vulcanization mold is provided with a protrusion for forming the lug groove 12, and when the green cover 3 is vulcanized, a tire block pattern including the lug groove 12 is simultaneously formed. The raw cover 3 has the lug groove 12 formed on the outer peripheral surface and is vulcanized to form the rubber layer 27.

The position and size of the concave portion 4 provided on the tread raw rubber sheet 14 are set by the following method.

a) The volume of the recess 4 is the rubber volume of the tread rubber (hereinafter referred to as the rubber volume of the lug groove portion) VG contained in the lug groove 12 portion on the shoulder 11 side of the tread portion 2 and the block 13
It is set in relation to the volume difference SO between the rubber volume of the tread rubber contained in the portion (hereinafter referred to as the rubber volume of the block portion) VB.

b) By setting the shoulder 11 zone, the belt layer 10
It is possible to limit the remarkable range of the corrugation that occurs in 1) and the portion where the edge of the belt layer 10 is liable to peel due to the corrugation.

c) The rubber volume VG of the lug groove portion is calculated by the product of the distance from the 3/8 point P to the tread edge D and the thickness of the lug groove 12 from the groove bottom to the inner surface B, and also in the block The rubber volume VB of the part is calculated by the product of the distance from the 3/8 point P to the tread edge D and the thickness from the outer peripheral surface of the block 13 to the inner cavity B surface.

d) Further, the volume S of the concave portion 4 provided in the tread raw rubber sheet 14 is larger than 0.8 times the volume difference SO (= VB to VG) between the rubber volume VG of the lug groove portion and the rubber volume VB of the block portion, and
The volume S is smaller than 1.2 times, and the recess 4 is formed at the lug groove forming portion of the vulcanization mold.

If the volume difference SO is smaller than 0.8 times, the rubber of the green cover 3 located in the vicinity of the concave portion 4 moves to the block 13 side when the tire is molded by the vulcanization mold, and the belt layer 10 is blocked by the block 13 by the movement. At this position, as shown in FIG. 6, a waviness that bends outward is generated. Further, when the volume difference S0 becomes larger than 1.2 times, the rubber of the green cover 3 moves from the block 13 side to the lug groove 12 portion at the time of molding, and the belt layer 10 becomes the sixth layer.
Contrary to the figure, rising undulations occur at the lug groove 12. The recess 4 is formed by using a tread raw rubber sheet.
At the time of molding 14, in addition to press molding with a die, it may be scraped off by cutting or the like.

As described above, in the manufacturing method of the present application, since the recess 4 is provided at the position corresponding to the lug groove 12 of the green cover 3 prior to the vulcanization of the tire and the configuration of the lug, the lug groove 12 can be formed with high accuracy. It is possible to prevent the corrugation of the belt layer 10 at the shoulder portion 11 and the peeling of the end portion of the belt layer 10.

By the way, the radial tire 1 manufactured by the manufacturing method of the present invention,
The wave height of the waviness at the end of the carcass 10 is reduced to 20% or less as compared with the tire manufactured by the related art in which no recess is provided. A radial tire 1 manufactured by the manufacturing method of the present invention was subjected to a running test in which a 100% load defined by JATMA was applied and the tire was run for a distance of 80 km. The result was that the heat generation temperature of the shoulder portion after running was about 5 degrees lower than that of the conventional manufacturing method. It has been found that since the amount of heat generated is small as described above, peeling of the end portion of the belt layer can be prevented and the durability of the tread portion is enhanced.

〔The invention's effect〕

As described above, the manufacturing method of the present invention is characterized in that a recess is formed in advance in a position where a lug groove is formed in a green cover forming a tread portion prior to vulcanization thereof, and therefore the conventional method tends to occur. It is possible to reduce the corrugation of the belt layer due to the lug groove forming and vulcanization.

Further, since the volume of the recess is regulated by the ratio to the volume difference between the lug groove portion and the block portion in the shoulder portion from 3/8 times the tread width to the outer edge, the waviness can be reduced more effectively and the amount of heat generated by running can be reduced. It is possible to prevent the peeling of the end portion of the belt layer from being reduced, thereby improving the durability of the tread portion and improving the appearance.

[Brief description of drawings]

FIG. 1 is a right half sectional view of a tire showing an embodiment of the present invention,
2 is a partial side view showing the lug groove on the shoulder side, FIG. 3 is a sectional view schematically showing a section taken along the line AA ′ of FIG. 2, and FIG.
2 is a cross-sectional view schematically showing a cross section taken along the line BB ′ of FIG. 2, FIG. 5 is a perspective view showing a tread raw rubber sheet, FIG. 6 is a cross-sectional view showing a conventional technique, and FIG. 7 is a conventional tread raw rubber. It is a perspective view showing a sheet. 1 ... Radial tire, 2 ... Tread part, 3 ... Raw cover, 4 ... Recessed part, 5 ... Bead core, 6 ... Bead part, 7 ... Sidewall part, 9 ... Carcass, 10 ... Belt Layer, 11 ... Shoulder, 12 ... Lag groove, 13 ... Block, 14 ... Tread raw rubber sheet, 15 ... Raw tire base, 16 ... Outer peripheral surface, C ... Tire equator, D ... Tread edge , S: concave volume, SO: volume difference, TW: tread width, VB: block volume, VG: lug groove volume.

Claims (1)

[Claims] 1. A carcass which folds back around a bead core of a bead part from a tread part to a sidewall part, and a belt layer which is arranged radially outside of the carcass and inside the tread part, A method for manufacturing a radial tire in which lug grooves and blocks rising between the lug grooves are alternately arranged in parallel on the shoulder side of the tread portion, wherein the tread raw rubber sheet forming the tread portion is provided on the outer peripheral surface of the raw tire base. The tread width (TW) of the tire formed by vulcanizing the raw cover while forming the attached raw cover.
Of the tread rubber contained in the lug groove portion (VG) between the position separating the tire axial direction by 3/8 times from the tire equator and the tread edge, and the rubber volume of the tread rubber contained in the block portion (VB ) And volume difference SO (= VB to VG)
Before the vulcanization of the green cover, a recess having a volume (S) larger than 0.8 times and smaller than 1.2 times is formed in the tread raw rubber sheet and at the lug groove forming portion of the vulcanizing die. A method for manufacturing a radial tire characterized by the above.