JPH07290458A - Production of pneumatic tire - Google Patents

Abstract

PURPOSE:To enhance the capacity of a tire by obtaining the material physical properties of the respective regions of the product tire and enhancing the shape accuracy thereof by preliminarily vulcanizing a plurality of the local regions of the cross section of a green tire before finally vulcanizing the green tire. CONSTITUTION:When the shoulder part and bead part of a green tire 1 are preliminarily vulcanized by a preparatory vulcanizer 10, the rubber in the members constituting the preliminarily vulcanized shoulder and bead parts is vulcanized and cured to become high in modulus as compared with a preliminarily unvulcanized region and the nylon cord used in a ply cord generates heat shrinkage by the heat at the time of preliminary vulcanization and, therefore, the ply cord of the preliminarily unvulcanized region is changed to a stretched state. Next, when the preliminarily vulcanized green tire is charged in the mold mounted on a tire vulcanizer to be subjected to final vulcanization, the ply cord of the preliminarily unvulcanized region is largely stretched and the size of the green tire is fitted to the mold to perform final vulcanization.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire manufacturing technique for improving the performance of a tire by changing the material properties of each portion of a pneumatic tire used in various vehicles.

[0002]

2. Description of the Related Art As the performance requirements of tires have become more sophisticated, it has been attempted to divide the interior of the tire into smaller pieces and individually control the functions of various parts during tire manufacture or product manufacture. For example, the contour shape of the carcass ply code in the tire cross section is formed by connecting the curvatures taken by the respective parts of the carcass ply extending from the equatorial plane of the tire to the tire bead area. It has been attempted to improve various performances of tires by complexly combining the curvature values of each portion of the carcass ply cord shape to control the expansion amount of each portion at the time of filling with internal pressure. FIG. 5 exemplifies the case of the simplest carcass ply code shape, which is manufactured so that the shape in the mold has _three curvatures of R ₁ , R ₂ and R _3. To be done. In this case, the expansion of the tire center portion at the time of internal pressure is suppressed and the high speed performance of the tire is improved. However, as the shape of the carcass is complicated, it is very difficult to form each part of the carcass ply so as to have a desired curvature. For this reason, conventionally, complicated mechanisms such as using a specially shaped tire mold and a special bladder shape structure for pressing the green tire in the mold from the inner surface side of the tire during vulcanization have been added. Attempts have been made to devise a vulcanizing device, and further, a special material is applied to the inner surface of the tire to suppress the movement of the ply cord during vulcanization.

Further, when manufacturing a rug pattern tire for construction or agriculture in which large lug pattern blocks are intermittently arranged over the circumferential direction of the tire tread, a tire having a uniform thickness in the tire circumferential direction is usually used. The green tire with the tread rubber is put into a mold with engraved rug patterns with large irregularities and is vulcanized at high temperature and high pressure, so the tread rubber is put into the concave rug pattern with the mold. However, the tread rubber at the convex portion of the mold tends to be thinned due to fluidized suction, and the inner surface of the tire tends to be extremely uneven. For this reason, conventionally, the tread rubber has been made excessively thick to cope with the problem.

[0004]

In the state of the art described above, the tire manufacturing equipment and manufacturing method are complicated, the productivity is lowered, the manufacturing cost is increased, and the unsatisfactory design, There was a limit to the improvement of tire performance due to manufacturing compromise. For example, it is extremely difficult to change the track shape of the ply cord intricately in a narrow side area such as a flat tire by the conventional apparatus and manufacturing method, and the initially designed design shape must be corrected to a manufacturable degree. And in some cases, it causes the use of extra material and causes deterioration of the performance of other tires.In the case of the rug pattern tire for construction and agriculture, the height of the rug is limited. In addition, there are problems such as considering sacrifice in tire performance, and difficulty in solving the above-mentioned irregularities on the inner surface of the tire that tend to increase heat generation at the lug portion and cause fatigue cracks at the root of the lug.

Therefore, an object of the present invention is to perform vulcanization molding by previously changing the material physical properties at the time of vulcanization for a plurality of members in a specific local area in the radial cross section or the circumferential direction of the green tire. By doing so, the function of each part at the time of product is built in and the tire performance is improved.

[0006]

According to the method of manufacturing a pneumatic tire of the present invention, as described in claim 1, a preliminary vulcanization step of prevulcanizing a plurality of local areas of a green tire cross section, A main vulcanization step of main vulcanizing the green tire after completion of the preliminary vulcanization. A second aspect of the present invention is a method for manufacturing a most versatile tire in which the plurality of local areas are a tire bead area and a tire shoulder area. In the third aspect, in order to enhance the effect of the present invention, the vulcanization conditions at the time of the preliminary vulcanization are changed for each of the plurality of local areas.

A fourth aspect of the present invention is a method for producing a pneumatic tire of the present invention, which is applied when a plurality of local areas in which the physical properties of the material are required to be changed are present in the circumferential direction of the tire.
It is characterized in that a preliminary vulcanization step of pre-vulcanizing a plurality of local areas in the circumferential direction of the green tire and a main vulcanization of the green tire after completion of the preliminary vulcanization. Also, claim 5
In order to enhance the effect of the present invention, the vulcanization conditions at the time of the preliminary vulcanization are changed for each of the plurality of local areas.

In the above-mentioned present invention, the preliminary vulcanization is partially vulcanized only in the above-mentioned local area. However, in this vulcanization, a conventionally known tire vulcanizing machine is used in a conventional manner. The entire pneumatic tire is vulcanized. The vulcanization conditions are
It is determined by the pressure and temperature applied to the vulcanized member and its adaptation time.

[0009]

In the present invention, the inventors obtained the knowledge described below through repeated experiments for pre-vulcanizing green tires. That is, "at the pre-vulcanized green tire portion, the rubber constituting the tire member is vulcanized and hardened to make it difficult to stretch, and also in the organic fiber cords constituting the tire member, particularly nylon and polyester. In the case of heat-shrinkable materials such as the above, the cord shrinks due to the heat of vulcanization, making it difficult to stretch.
When the green tire provided with the portion where the material properties are changed in this manner is mainly vulcanized, the pressure medium (usually an inert gas or a mixed gas of an inert gas and a steam) is provided inside the tire in the mold. Tension acts on each member of the tire filled with, but the elongation of the member due to this tension is small in the pre-vulcanized part, while at the time of normal vulcanization in other parts that are not pre-vulcanized Similarly, the organic fiber cord and rubber constituting the member are stretched to a considerable extent by the above tension and vulcanized. As a result, in the product tire that has been vulcanized,
The modulus of the fiber cord at the portion stretched greatly during vulcanization becomes high, and the modulus of the fiber cord becomes low at the portion pre-vulcanized and less stretched at the time of vulcanization. "It has been found.

In view of this fact, when controlling the expansion amount of the carcass ply by combining the curvatures of the respective portions of the carcass ply code, it is not necessary to form an extremely complicated combination of the curvatures of the respective portions. The moduli of the ply code are changed based on the above findings, and the card of each part is changed.
It is possible to easily control the expansion amount of the cas ply, and it is possible to achieve higher tire performance.

Further, by pre-vulcanizing each part of the green tire corresponding to the position of the lug pattern arranged at a predetermined interval in the circumferential direction of the tire, the rubber on the tread portion of this part is vulcanized and cured. Since it becomes difficult to flow even at high temperature and high pressure during vulcanization, suction and inflow of rubber into the recess of the lug pattern of the mold described above is prevented, and the unevenness of the inner surface of the tire is eliminated and the durability of the tire is improved. improves. Further, the height of the lug can be designed higher than before, and the traction performance essential for the rug pattern can be improved.

[0012]

【Example】

[First Embodiment] A first embodiment of the present invention will be described with reference to FIGS.

FIG. 2 is a sectional view showing an example of a green tire 1 which is a toroidal pneumatic tire in a green state before vulcanization and molding. Inside the green tire 1, a pair of beads in the bead parts 5, 5'passes from the tire crown part 2 through both shoulder parts 3, 3'and both side parts 4, 4 '. A carcass ply code 7 is arranged to reach the cores 6 and 6 ', and both ends of the carcass ply code 7 are wound back around the bead cores 6 and 6'and locked. ing. Further, a belt layer 8 which is a reinforcing material for maintaining the basic tire shape when the product tire after vulcanization is filled with the internal pressure is disposed on the top of the carcass ply cord 7, and further, A tread rubber 9, which is a tread rubber that comes into contact with the road surface, is attached to the upper portion of the belt layer 8.

FIG. 1 shows a shoulder of a green tire 1.
A pre-vulcanization device 10 for vulcanizing parts 3, 3'and bead parts 5, 5'is shown.

As shown in FIG. 1, the pre-vulcanizing device 10 is a pair of cylindrical bead supporting devices 11 each supporting a green tire 1 (only a part of which is shown in the drawing). Brackets 12A and 12B and the bracket 1 corresponding to the pair of brackets 12A and 12B, respectively.
Holding rings 13A, 13 screwed to 2A, 12B
B and. Then, between the bracket 12A and the sandwiching ring 13A and between the bracket 12B and the sandwiching ring 13B, the left and right base end sides of the bladder 14 having a U-shaped cross section are respectively formed. It is sandwiched.

The outer peripheral surface of the bladder 14 is a forming surface that abuts the inner surface side of the green tire 1 from the bead portions 5 and 5'of the green tire 1 to the shoulder portions 3 and 3 '. have.

A through hole (not shown) is formed in the bead supporting device 11, and the bladder 14 is inflated by filling the inside of the bladder 14 with air. . An O-ring 15 for preventing air leakage is arranged at each joint.

On the other hand, in the right side bracket 12A in the figure, a ring-shaped (only a part is shown in the figure) outer surface forming mould is formed.
The screw 16A is screwed. The outer surface forming mold 16A has a forming surface that abuts on the outer surface side of the green tire 1 from the bead portions 5 and 5'to the upper portions of the shoulder portions 3 and 3 '. There is.

This outer surface forming mold 16A is closer to the inner peripheral side (lower side in the figure), that is, the position corresponding to the bead portion 5'of the green tire, and further to the outer peripheral side (upper side in the figure), that is, the grease. At a position corresponding to the shoulder portion 3'of the tire, a block 18B containing electrothermal heaters 17B and 17S as a heating means formed in a ring shape along the circumferential direction of the outer surface forming mold 16A, and 18S is fixed. or,
On the outer peripheral side of the outer surface forming mold 16A, cooling water passages 20B and 20S which are ring-shaped cooling means having openings 19B and 19S for pouring and draining cooling water are formed.

In the portion of the outer surface forming mold 16A between the electric heating heaters 17B and 17S and the cooling water passages 20B and 20S, cooling fins 21 are formed in a ring shape. A plurality of outer surface forming molds 16A are formed so as to extend radially from the center of the outer surface 16A and have a constant interval in the circumferential direction.

On the other hand, on the left side of the bladder 14 in the figure, the tip of a cylinder rod 22 extending from a cylinder (not shown) as a driving means is located, and a connecting tool 23 is fixed to this tip. Further, the connector 23 has an outer surface forming mold having the same shape and structure as the outer surface forming mold 16A.
The field 16B is screwed and installed so as to oppose the outer surface forming mold 16A.

Therefore, by operating the cylinder, the position shown by the solid line in FIG. 1 for vulcanizing the green tire 1 and the left side of FIG. 1 for attaching and detaching the green tire 1 to the preliminary vulcanizing apparatus 10 are shown. The outer surface forming mold 16B reciprocates between itself and the position indicated by the chain double-dashed line.

Next, the vulcanization process of the green tire 1 according to this embodiment will be described. First, the cylinder rod 22 of the pre-vulcanization device 10 is contracted to the cylinder side, and the bead support device 11
Then, the outer surface forming mold 16B is separated from the outer surface forming mold 16B and moved to the position shown by the chain double-dashed line. Thereby, the bead supporting device 11
A space for inserting the green tire 1 is provided between the outer surface forming mold 16A and the outer surface forming mold 16B on the cylinder rod 22 side.

Next, an outer surface forming mode of the bead supporting device 11 is formed.
The green tire 1 is inserted between the sleeve 16A and the outer surface forming mold 16B on the cylinder rod 22 side. On this occasion,
The bladder-14 has shrunk, and there is no problem in the green tire 1
Can be inserted.

In this state, the cylinder rod 22 is extended to move the outer surface forming mold 16B to the bead supporting device 11 side, and the outer surface forming mold 16B is brought into contact with the holding ring 13B and stopped. Then, the bladder 14 is expanded to form a pair of side surfaces of the bladder 14 and the outer surface forming mold 16.
The bead portions 5 and 5'of the green tire 1 are sandwiched and fixed between A and 16B (position indicated by the solid line in FIG. 1).

Next, the blocks 18B and 18S, which are heating areas of the outer surface forming molds 16A and 16B, are electrically heated.
The rubber and ply cord around the bead cores 6 and 6'and the rubber and ply cord around the shoulder portions 3 and 3'are vulcanized by heating with the heat of 17B and 17S. Simultaneously with this, cooling water is made to respectively flow into the cooling water passages 20B and 20S at the side portions of the outer surface forming molds 16A and 16B and the outer ends of the shoulder portions to form the outer surface forming molds 16A other than the above-mentioned heating area.
16B is cooled and outer surface forming molds 16A, 1
With the fins 21 arranged between the inner and outer circumferences of 6B, the heat transmitted from the blocks of the heating area is radiated to the outside to insulate the outer surface forming molds 16A, 16B other than the heating area, and the bead core 6, Prevent vulcanization in parts other than near 6 "and the shoulder part.

After the predetermined time has elapsed and the pre-vulcanization of the bead portion and the shoulder portion is completed, the following operation is performed.

Bladder by removing air from the bladder 14.
And the side surface of the bladder 14 and the outer surface forming mold 16 are reduced.
Bead portion 5 of the green tire 1 between A and 16B,
Release the 5 ”clamp. After this, the cylinder rod 22 is contracted to move the outer surface forming mold 16B from the position indicated by the solid line to the position indicated by the alternate long and two short dashes line. In this state, the green tire 1 is removed from the pre-vulcanization device 10 and the pre-vulcanization step is completed. Then, the main vulcanization of the entire green tire 1 is carried out by a known vulcanization molding machine.

Next, a change in material physical properties of the member in each cross-sectional area of the green tire and effects based on the change due to the vulcanization process from the above-mentioned preliminary vulcanization to the main vulcanization will be described below. .

When the shoulder portion and the bead portion of the green tire are prevulcanized as in this embodiment, as shown in FIG. 3 (a), the prevulcanized shoulder portion and bead portion are beaded. Among the members constituting the cord portion, the rubber has a higher modulus than the portion which is vulcanized and hardened and is not prevulcanized, and the nylon cord used in the ply cord in this embodiment is prevulcanized. The heat causes heat shrinkage, which changes the ply cord of the portion which is not prevulcanized to the stretched state.

Next, when the green tire which has been changed to such a state by the preliminary vulcanization is put into a mold attached to a known tire vulcanizer to carry out the main vulcanization, FIG. As shown in FIG. 3, each part of the green tire is stretched in the mold so as to conform to the shape of the mold. At this time, the member of the pre-vulcanized part has a high rubber modulus and is difficult to be stretched.Therefore, the ply cord of the part which is not pre-vulcanized is largely stretched, and the size of the green tire is considered to be suitable for the mold. Then, the main vulcanization is performed.

In the product tire after the main vulcanization, as shown in FIG. 3 (C), the ply cord is already greatly extended in the tire crown portion and the tire side portion. -High domodulus. On the other hand, the pre-vulcanized tire shoulder and bead parts are
It has a built-in allowance that allows the cord to extend with respect to external force during use without being stretched, so to speak, the cord modulus is low.

When the product tire thus manufactured is put to practical use, since the ply cord is difficult to expand at the tire crown portion, the outer shape growth of the crown portion is small at the time of filling the inner pressure of the tire and at the time of high speed running, and the durability of the tire is reduced. Performance is improved. or,
Since the ply cord modulus of the tire side portion is high, the side rigidity is increased and it becomes easy to improve the steering stability performance of the tire. On the other hand, since the rubber modulus of the bead part is high during this main vulcanization, the bead shape is manufactured uniformly over the tire circumferential direction, improving the uniformity performance of the product tire and improving the tire vibration comfort. Performance is improved.

In this embodiment, the prevulcanization is carried out by using a shoulder.
The vulcanization conditions of the part and the bead part were the same, but the vulcanization conditions can be changed for each pre-vulcanization area. For example, when the wall thickness of the bead portion is extremely thicker than that of the shoulder portion, the vulcanization time of the bead portion is lengthened or the electric heating temperature is set high. Further, in this embodiment, only the shoulder portion and the bead portion of the tire were pre-vulcanized, but if necessary, the tire cross section may be further finely divided to pre-vulcanize three or more areas. Can be done.

[Second Embodiment] In the second embodiment, as shown in FIG.
As shown in (a) and (b), it is a manufacturing method of pre-vulcanizing the part 25 of the green tire corresponding to the position of the lug pattern 24 arranged at constant intervals in the circumferential direction of the tire.

That is, in accordance with the lug pitch P of the lug tire shown in FIG. 4 (a), as shown in FIG. 4 (b), a preliminary addition of a predetermined length in the circumferential direction is carried out at every P ′ on the circumference of the green tire. Apply sulfur. Next, the green tire thus pre-vulcanized is put into a mold attached to a known vulcanizer to perform main vulcanization.

In the pre-vulcanized green tire, the rubber is vulcanized and hardened at each position of the lug pattern to increase the modulus, and therefore the ply cord coated with the hardened rubber is also less likely to be stretched. . Therefore, even when the rubber around the lug pattern flows and flows into the recess of the lug during the main vulcanization, the ply cord at this portion is difficult to stretch and the cord is sucked into the recess of the lug. This is extremely small, and the occurrence of irregularities on the inner surface of the tire as shown in FIG. 4B is prevented. Further, it has become possible to reduce the thickness of the tread rubber, which has been set to be thick to prevent the unevenness.

[0037]

According to the present invention, since necessary vulcanization of the green tire is preliminarily vulcanized and physical properties of the material are changed to perform the main vulcanization, a complicated carcass contour shape required for a high performance tire is obtained. It is easy to build and the degree of freedom in tire shape design increases. Moreover, since unnecessary movement of the member is prevented during the main vulcanization, the thickness of the excess rubber can be reduced, and the weight of the tire can be reduced. Further, since the shape of the bead portion is manufactured uniformly and accurately, the uniformity of the tire is improved.

[Brief description of drawings]

FIG. 1 is a sectional view of a preliminary vulcanizing apparatus according to a first embodiment.

FIG. 2 is a cross-sectional view of a green tire.

FIG. 3 is a diagram showing changes in material properties at various parts of the tire due to preliminary vulcanization.

FIG. 4 is an explanatory diagram of preliminary vulcanization of a lug tire according to a second embodiment.

FIG. 5 is a diagram illustrating a conventional carcass shape setting example.

[Explanation of symbols]

1 Green Tire 2 Crown Part 3, 3'Shoulder Part 4, 4'Side Part 5, 5'Bead Part 6, 6'Bead Core 7 Carcass Ply Code 8 Belt Layer 9 Tread Rubber 10 Preliminary Addition Sulfurizing device 11 Bead supporting device 12A, 12B Bracket 13A, 13B Clamping ring 14 Bladder 15 O-ring 16A, 16B Outer surface forming mold 17B, 17S Electric heating heater 18B, 18S block 19B, 19S Opening 20B , 20S Cooling water passage 21 Fin 22 Cylinder rod 23 Connecting tool 24 Lug pattern 25 Green tire part corresponding to the position of the lug pattern

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display area B29L 30:00

Claims (5)

[Claims] 1. A pre-vulcanization step of pre-vulcanizing a plurality of local areas of a green tire cross section, and a main vulcanization step of main-vulcanizing the green tire after completion of the pre-vulcanization. A method for manufacturing a pneumatic tire, comprising: 2. A bead area and a shoulder of a green tire.
A method for producing a pneumatic tire, characterized in that the green tire is subjected to main vulcanization after preliminary vulcanization of the area and the area. 3. The method for producing a pneumatic tire according to claim 1, wherein a plurality of local areas of the cross section of the green tire are prevulcanized under different vulcanization conditions. 4. A pre-vulcanization step of pre-vulcanizing a plurality of local areas in the circumferential direction of the green tire, and a method of manufacturing a pneumatic tire for permanently vulcanizing the green tire after the pre-vulcanization. . 5. The method for producing a pneumatic tire according to claim 4, wherein a plurality of local areas in the circumferential direction of the green tire are prevulcanized under different vulcanization conditions.