JPS599340B2 - How to mold radial tires - Google Patents

Description

[Detailed description of the invention] The present invention relates to an improvement in a method for molding radial tires.

There is a tire called a radial tire that has great practical value in terms of safety, economy, and durability.This radial tire has a bead built into the tire part that sits on the rim for mounting the tire. A carcass layer containing two sets of ring-shaped steel reinforcing bodies called ``ring-shaped steel reinforcing bodies'', a carcass layer containing reinforcing cords arranged radially or almost radially when viewed from the side of the tire that connects the beads, and a breaker placed on the outer peripheral surface of the carcass layer. It consists of a cylindrical reinforcing band called a layer, and an elastomer covering the outer surface of the layer.

Conventionally, in manufacturing this radial tire, the first step was to attach Kerr sply (corded rubber material for carcass) beads and other tire materials onto the first-stage molding drum to form a cylindrical carcass. Assemble the layers.

Next, in the second step, the carcass layer is transferred onto a second-stage forming drum, and the interval between both beads is gradually reduced to form a curved body having a predetermined large diameter.

Furthermore, as a third step, a corded rubber material called play couple is assembled onto the outer peripheral surface of the expanded carcass layer.

This assembly method involves wrapping multiple layers of play coupler around the outer circumferential surface of the carcass layer and pasting them together to form a cylindrical play force layer.In order to improve molding efficiency, multiple layers of play coupler are wrapped around the outer circumferential surface of the carcass layer to form a cylindrical play force layer. There is a method in which a play force layer is pre-caulked and pasted together in a cylindrical shape, and this is crimped onto the outer peripheral surface of the carcass layer.

Next, in the fourth step, the elastomer for the contact surface layer and other tire materials are pasted on top of it, and then it is removed from the molding drum and shaped into a raw rubber tire (green tire) that closely resembles the shape of the finished tire. ) is obtained.

Furthermore, in the fifth and final step, the raw rubber tire is heated and molded into the shape of a product tire using another molding device to undergo a chemical change, and then necessary finishing operations are performed to complete the product tire.

In general, a product tire must not only have its outer shape and dimensions, but also the distribution of the force acting on the internal cord, which is mechanically symmetrical with respect to the center cross section of the tire and uniform in the circumferential direction. This is important for the quality of the vehicle, and if these balances are disrupted, it is dangerous as it may cause vibrations while driving or worsen maneuverability.

In particular, compared to bias tires, the playing force layer is an important strength member in radial tires, but since the cord inside it does not reach the bead, the breaker layer is displaced during the third and subsequent steps. It is extremely important to ensure that the code angles are not distorted.

The play couple that makes up this play force layer is made by arranging textile cords (threads made of rayon, synthetic fibers, or other fibers twisted together) or steel cords (steel fibers twisted together) in parallel. It is coated with raw rubber and formed into a sheet shape, and the cords are connected only by the raw rubber.

Furthermore, at least one layer of the play couplers constituting the play force layer has a cord angle of around 15 degrees with respect to the length direction of the play couple, and the cord angles of the other play couplers vary depending on the number of layers and other factors, but It is determined so that the forces in the circumferential direction and the width direction are balanced.

For this reason, in the conventional method of bonding play couplers using a pair of crimping rollers to form a breaker layer, if the play couplers are strongly crimped with the pressure rollers, the play couplers will be stretched, especially in the case of play couplers with small contour angles. A play couple with a large cord angle is stretched a lot in the width direction, and a play couple with a large cord angle is stretched a lot in the circumferential direction, causing some slack and wrinkles in some areas, causing the cord angle of the play couple to change locally. A problem occurs.

This problem also occurs when a wide pressure roller is used because the elongation of the play couple in the circumferential direction is not improved.

It is conceivable to apply tension to the play couple and wrap it up in anticipation of the stretch of the play couple during the crimping process, but it is practically impossible to keep the tension constant at the beginning, middle, and end of the winding. Although this is possible, it has not been adopted because it causes local changes in the play coupler cord angle.

However, if you try to reduce the crimping force when crimping the play couplers to eliminate their elongation, the pressure bonding between the play couplers will be insufficient, and slippage may occur between the play couplers in the third step or a subsequent step. This causes problems such as air remaining.

In addition, from the perspective of improving the performance of product tires, special radial tires have been proposed that use a play couple that is only wider, with both ends folded back, or with a play couple that changes the cord angle across the width. However, it is nearly impossible to assemble such a play couple accurately using conventional molding methods.

As mentioned above, the breaker layer in a radial tire is an important strength member of the tire, and accurate assembly during molding is extremely important for the quality of the tire. During force layer assembly or subsequent processes, it is inevitable that the cord angles of the play couplers in the play force layer change or become disturbed, or that the play couplers are displaced relative to each other, thereby reducing the incidence of defective tires. It also had the disadvantage of being expensive.

The present inventors have proposed a new method for accurately and firmly crimping the cylindrical play force layer, but it is difficult to obtain a strong breaker layer without disturbance or displacement of the play coupler cords using this method. Even if it is possible, when pressing the carcass layer to the playing force layer, the cylindrical breaker layer is expanded in the radial direction as in the conventional method, the carcass layer is fitted into the inner peripheral surface of the cylindrical breaker layer, and then the breaker layer is The method of shrinking and pasting the breaker layer onto the outer circumferential surface of the carcass layer causes the following problems, and in the end it is impossible to obtain a green tire of good quality, and in turn, it is impossible to obtain a radial tire of good quality. was there.

In other words, when the cord angle of the play couple is close to 15 degrees, which is said to be suitable for the performance of the play force layer, when the play force layer is expanded in its radial direction, the stress generated in the raw rubber is large, making it difficult to expand uniformly. Not only is it extremely difficult, but once it is expanded, it will undergo permanent deformation and cannot be contracted to the specified diameter by its own restoring force, and if it is forcibly contracted, it will partially wrinkle. It has already been pointed out that sagging (sag) occurs, and there are methods to disperse this sag over the entire circumference as much as possible, but even if this can prevent the apparent sagging of the breaker layer, As a result, changes in local cord angles are increased.Furthermore, in the case of a playing force layer using steel cords, the adhesive strength between the raw rubber and steel cords is weak, resulting in local peeling inside. Phenomena may occur.

In addition, in the case of tires with small aspect ratios, it is known to use a pair of steel cylinders called play force rings for regulating the outer diameter of the carcass layer expansion, but after installing the play force layer on the carcass layer, When the play force ring is removed, the play force layer often slips and deviates from the center of the force residue layer, resulting in a problem that a satisfactory green tire cannot be formed.

The present invention was proposed for the purpose of solving the above-mentioned disadvantages of the conventional method. The breaker layer is held on the inner circumferential surface of an annular holder made of a rigid material that has a width approximately equal to the outer diameter of the playing force layer and slightly larger than that width, and that does not deform due to the pressure bonding of the carcass layer. On the inner peripheral surface of the shaped breaker layer,
A method for molding a radial tire, which comprises compressing the carcass layer to a cylindrical play layer by uniformly expanding the carcass layer in the radial direction using a suitable expansion means.

The present invention will be specifically described below with reference to the accompanying drawings.

In FIG. 1, D is a well-known tire-forming drum, which is supported by an outer shaft 2 and an inner shaft 7 of a headstock 1 containing a drive device, and includes a bead ring 3 10,
It includes a bladder clamp 59, a bladder 6 and a passageway 8 for supplying pressure fluid into the bladder 6, these parts being arranged in the relationship shown.

11 is a base, 12 is a guide member installed on the base 11, and 13 is a movable member installed on the base 11 to be guided by the guide member 12 and horizontally movable on the base 11 by a drive source (not shown). The annular holder 1 is placed on the moving table 13.
5 is fixed so that its center is on the axis X-X line of the outer shaft 2 and inner shaft 7 of the headstock 1,
This annular holder 15 and the moving table 13 form a breaker layer holder H.

The inner diameter of the annular holder 15 is approximately equal to the outer diameter of the breaker layer 14, which is pre-crimped and formed by pressure bonding with another device, and its width is formed to be somewhat thicker than the width of the breaker layer, and its inner periphery A protruding edge r is provided on one end edge of the surface.

Further, as shown in FIG.
15b and 15c, and a divided piece 15a
is fixed to the movable table 13, and its both ends are connected to the divided pieces ISB 15c by pins 16, and the divided pieces 15b and 15c can be connected or uncoupled in an interlocking manner.

That is, as shown in FIG. 2, the divided piece 15 of the divided piece 15b
A link 18 is rotatably supported by a pin 17 on a bracket 26 protruding outward near the joint with c.
The base of a hydraulic cylinder 210 is connected with a pin 2 to a bracket 28 protruding outward near the joint of the divided piece 15c with the divided piece 15b.
The tip of the link 18 is connected to one end of the link 18 by a pin 19.

When the hydraulic cylinder 210 rod 20 is extended and the link 18 is rotated about the pin 17, the pawl 24 provided on the link 18 engages with the convex piece 25 provided on the divided piece 15c. When the relationship is broken and the rod 20 is further extended, the link 18 rotates further, and the tip of the arm 27 provided on the link 18 hits the outer peripheral surface of the divided piece 15b, joining the divided piece 15b and the divided piece 15c. part is pin 1
It is designed to be opened around 6.

In addition, by reversing the above procedure, the divided piece 15b and the divided piece 15c are firmly connected at their joints, and form an integral annular holder 15 together with the divided piece 15a.

An example of a device for implementing the present invention is configured as described above, and in implementing the present invention,
First, the carcass layer 4 made with a pre-swaging device is attached to the tire-forming drum D as shown in FIG. Charge the play force layer 14 made with the device.

In this case, the joint between the divided pieces 15b and 15c of the annular holder 150 is opened and the breaker layer 14 is inserted, and then both the divided pieces 15b and 15c are connected, so that the loading operation can be easily performed.

In this case, the ridge r provided on the annular holder 15 is useful for positioning the play force layer 14 when it is inserted.

Next, the drive source of the moving table 13 is activated, and the annular holder 15
After being moved until the center plane Z-Z of the playing force layer 14 inserted therein coincides with the center plane of the drum D, that is, the center plane Y-Y of the carcass layer 4, it is fixed at that position.

(See Figure 3) Next, pressure fluid is supplied from the pressure fluid passage 8 to the bladder 6 to gradually inflate the bladder 6, and as usual, the bead rings 3, 10 and the bladder clamps 5, 9 are synchronously brought closer together. As a result, the carcass layer 4 begins to expand, and the central portion of its outer circumferential surface comes into contact with the central portion of the inner circumferential surface of the playing force layer 14.

Therefore, when the carcass layer 4 continues to expand, the carcass layer 4 uses internal pressure due to the expansion of the bladder 6 to expel the air from both sides of the play force layer 14 from the inner periphery and center of the play force layer 14, as shown in FIG. Firmly crimped and bonded to the inner circumferential surface.

When the carcass layer 4 is crimped onto the inner circumferential surface of the play force layer 14 in this way, the annular holder 150 divided piece 15b 1
5c is released and the movable table 13 is returned to the position shown in FIG.
After supplying and bonding the elastomer for the ground contact layer and other tire materials to the outer periphery of the tires 4, the tire molding drum D is shrunk in the usual manner and removed from the drum D to obtain a desired green tire.

In the above example, a tire-forming drum D with a bladder was used to support and expand the carcass layer 4 formed by a pre-caulking device. A type of drum for assembling and expanding the drum or a type called a metallic drum may also be used.

In summary, the present invention provides the following steps when pressing a carcass layer onto the inner circumferential surface of a cylindrical play force layer which has been pre-crimped and press-molded.
The cylindrical play force layer was held on the inner circumferential surface of an annular holder made of a rigid material that was approximately equal to the outer diameter of the play force layer and had a width slightly larger than that width, and that did not deform due to the pressure bonding of the carcass layer. A radial tire characterized in that the carcass layer is compressed to the cylindrical play layer by uniformly expanding the carcass layer in the radial direction on the inner circumferential surface of the cylindrical play force layer using an appropriate expansion means. Therefore, according to the present invention, (1) when pressing the carcass layer 4 onto the inner circumferential surface of the play force layer 14, the play force can be reduced by simply expanding the carcass layer 4; To prevent layer 14 from expanding or contracting, breaker layer 140
There is no risk of local sagging or changes in the cord angle of each play couple, and especially in the case of play couplers using steel cords, there is no risk of local peeling.

Therefore, good green tires with uniform quality can be obtained.

(2) Also, since the playing force layer 14 is firmly held by the annular holder 15 during the expansion of the carcass layer 4, the playing force layer 14 is firmly held even in tires with small aspect cradle.
There is no risk of slippage between the carcass layer 4 and the carcass layer 4, and the two are firmly bonded by pressure.

(3) Also, the play force layer 1 held within the annular holder 15
Since the carcass layer 4 is bonded to the inner circumferential surface of the carcass layer 4 while being expanded, the playing force layer 14 does not stretch in the width direction.

Therefore, from this point of view as well, the code angle of the play couple does not change.

(4) When the carcass layer 4 is expanded, it is bonded to the play force layer 14 from the center toward both sides while expelling air interposed between the play force layer and the play force layer, so there is no risk of air being trapped between both layers. , both layers are reliably and firmly bonded.

The following practical effects can be mentioned.

[Brief explanation of the drawing]

The figures are schematic explanatory diagrams of an example of an apparatus for carrying out the present invention.
The cross-sectional view taken along the line 1, 3, 4, and 5 are explanatory views of the operating state of the main parts. H: Playing force layer holder consisting of moving table 13 and annular holder 15, D: Drum, 4: Carcass layer, 14: Braking force layer.

Claims (1)

[Claims] 1. When pressing the carcass layer onto the inner circumferential surface of the cylindrical playing layer that has been pre-crimped and crimped, the cylindrical playing layer should have a diameter that is approximately equal to the outer diameter of the playing layer and slightly larger than its width. While the carcass layer is held on the inner circumferential surface of the annular holder, which has a large width and is made of a rigid material that does not deform when the carcass layer is crimped, the carcass layer is radially applied to the inner circumferential surface of the cylindrical play force layer using an appropriate expanding means. 1. A method for forming a radial tire, comprising compressing the carcass layer to a cylindrical play layer by uniformly expanding the carcass layer.