JP2007130915A - Manufacturing method for air bladder for safety tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for an air bladder for a safety tire, which can reduce the fraction defective of a product by enabling the air bladder to be stably housed in a vulcanization mold even if rigidity is low when unvulcanized. <P>SOLUTION: This air bladder 1 for the safety tire is formed by vulcanization-molding a hollow annular member 2 which is composed of a rubber and a reinforcing material. The air bladder 1 is housed in the tire 4 and filled with internal pressure. In the normal state of the internal pressure of the tire 4, a space part S<SB>1</SB>is formed between the air bladder and an inner surface of the tire, and the air bladder is deformed in such a manner that a diameter is enlarged along with a decrease in the internal pressure of the tire, so as to bear a load in place of the tire. In the manufacture of the air bladder 1, after premolding is performed by applying the internal pressure to the member 2 under the unvulcanized state, vulcanization molding is performed by using the vulcanization mold. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is formed by vulcanizing and molding a hollow annular member made of rubber and a reinforcing material, accommodated in a tire and filled with an internal pressure. An air bladder for a safety tire that forms a space and expands and deforms as the internal pressure of the tire decreases, so that the load is supported from the tire, especially in the shape before and after vulcanization molding. It is related with the manufacturing method.

  Reinforcing members such as a reinforcing tube, reinforcing rubber, and reinforcing belt, or a foam, elastic body, medium, and the like as a safety tire that can travel a certain distance even in a run-flat state in which the tire internal pressure has suddenly decreased due to puncture etc In recent years, a tire containing a child has been known, and in recent years, from the viewpoint of suppressing manufacturing cost and mass increase, a space is formed at least between the tire inner surface when the tire has a normal internal pressure and a normal internal pressure. In a state in which the internal pressure of the tire is reduced, a safety tire that is expanded and deformed and accommodates an air bladder that replaces the load from the tire has been widespread (see, for example, Patent Document 1). Such an air bladder generally includes a hollow annular gas impermeable layer and a hoop reinforcing layer disposed on the crown portion of the gas impermeable layer and suppressing expansion of the diameter of the air bladder in a normal internal pressure state. It is. This hoop reinforcing layer is composed of a composite of rubber and non-woven fabric, and is attached to the gas-impermeable layer in an unvulcanized state and then vulcanized.

  In such an air bladder, in order to obtain a diameter expansion suppression effect by the hoop reinforcement layer, a plurality of layers of rubber and nonwoven fabric are laminated, which is a factor in increasing the mass and cost of the air bladder. It was. In view of this, the present applicant proposed in Japanese Patent Application No. 2004-142167 an air bladder that achieves weight reduction and cost reduction by forming a hoop reinforcement layer with a resin.

JP 2002-172918 A

  In an air bag as described in Patent Document 1, since a hoop reinforcing layer is attached to a gas-impermeable layer, it has a certain degree of rigidity even in an unvulcanized state and is close to the shape after vulcanization. It was. For this reason, there was no particular problem when accommodated in the vulcanization mold. However, an air bag as proposed in Japanese Patent Application No. 2004-142167 is formed by attaching a hoop reinforcing layer to a gas impermeable layer that has been vulcanized and molded, so that it has low rigidity in an unvulcanized state, and vulcanized. When housed in the mold, the shape was not stable, and a part of the air bladder was bitten into the mold, and there was a risk of air leakage from here.

  The object of the present invention is to solve such problems of the prior art, and the object is to achieve a stable vulcanization mold even when the rigidity in the unvulcanized state is low. An object of the present invention is to provide a method for producing a pneumatic tire bladder for safety tires that can be accommodated and can reduce the defective rate of products.

In order to achieve the above object, the present invention is formed by vulcanizing and molding a hollow annular member made of rubber and a reinforcing material, housed in a tire and filled with an internal pressure, and the tire has a normal internal pressure. Then, in producing a pneumatic bladder for a safety tire that forms a space between the inner surface of the tire and expands and deforms with a decrease in the internal pressure of the tire to support the load from the tire,
A method for producing an air bladder for a safety tire, characterized in that an internal pressure is applied to the uncured hollow annular member for pre-molding, followed by vulcanization molding using a vulcanization mold. . According to this, even if it is a hollow annular member with low rigidity in an unvulcanized state, the shape before vulcanization can be brought close to the shape after vulcanization, so that it is bitten when accommodated in the vulcanization mold. There is no fear of getting in.

  This preforming is preferably performed such that the outer diameter and inner diameter of the uncured hollow annular member are approximately the same as the outer diameter and inner diameter after vulcanization, respectively. As used herein, “substantially the same” means that with respect to the outer diameter, the value after preforming is in the range of 95 to 101%, preferably 98 to 100% of the value after vulcanization. As for the inner peripheral diameter, it means that the value after vulcanization is in the range of 80 to 100%, preferably 90 to 95% of the value after preforming, and measuring these diameters In other words, it is performed in a state where an internal pressure of 5 kPa is applied.

  Further, in the pre-molding, the uncured hollow annular member is accommodated in a preformer having a pair of mutually opposed substantially cylindrical inner and outer preformed surfaces, and the accommodated hollow annular member It is preferable to apply an internal pressure to the hollow annular member so as to be in contact with a pair of preformed surfaces of the preformer. The “substantially cylindrical” as used herein is not limited to a case where a single continuous surface forms a cylinder, but as described later, a plurality of surfaces are arranged side by side on the same circumference. The case where a cylinder is formed is included.

  Further, it is preferable that the preforming device is such that the inner peripheral preformed surface and / or the outer peripheral preformed surface can be expanded and contracted in the radial direction, and the outer peripheral and inner peripheral preformed surfaces are subjected to adhesion prevention processing.

  Furthermore, it is preferable to apply an anti-adhesive agent to the outer surface of the uncured hollow annular member prior to preforming.

  In addition, it is preferable to perform the preliminary molding until just before the vulcanization molding. The term "immediately before" here means that the time required to move to vulcanization molding is less than half of the time required for the preformed unvulcanized hollow annular member to be restored to its original shape. Preferably within 15 minutes, more preferably within 5 minutes.

  According to the present invention, by performing vulcanization molding after preforming, even when the rigidity of the unvulcanized hollow annular member is low, stable housing in the vulcanization mold is possible, and the product It is possible to provide a method for manufacturing a pneumatic tire bladder for safety tires that can reduce the defective rate.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view in the width direction showing a safety tire that accommodates air bladder and is assembled to a rim R in a state where the internal pressure is normal.

The air bladder 1 shown in FIG. 1 includes a hollow annular member 2 in which a gas-impermeable tube such as butyl rubber is covered with a composite material of rubber and a non-woven fabric, and a crown of the hollow annular member 2. And a hoop reinforcement layer 3 disposed in the section. The tire 4 and the air bladder 1 are each filled with an internal pressure. Generally, from the viewpoint of quickly expanding the air bladder 1 when the internal pressure is reduced, the tire 4 is stipulated in industrial standards and standards that are effective in the area where the tire is manufactured, sold, or used, such as JATMA, TRA, ETRTO, etc. Then, the internal pressure specified according to the load capacity is filled, and the air bladder 1 is filled with the internal pressure of the tire 4 within the range of 0 to 20%. As a result, the air bladder 1 tends to undergo diameter expansion deformation due to the internal pressure difference between the air bladder 1 and the tire 4, but the hoop reinforcement layer 3 bears the tension generated by the internal pressure difference, thereby suppressing the diameter expansion deformation. A space S ₁ is formed between the inner surface of the tire and a space S ₂ is formed inside the air bladder 1. When the internal pressure of the tire decreases due to puncture or the like, the hoop reinforcing layer 3 expands or breaks due to the increased internal pressure difference, and the air bladder 1 expands and deforms, thereby supporting the load from the tire.

  In such an air bladder 1, the hoop reinforcement layer 3 is made of a resin such as polypropylene, polyethylene terephthalate, polycarbonate, etc., and compared with the air bladder in which the hoop reinforcement layer is constructed using a composite of conventional rubber and nonwoven fabric. It is possible to achieve weight reduction and cost reduction while maintaining the diameter expansion suppression effect at or above the same level. Since the conventional air hoop reinforcement layer contains rubber, it can be attached to an unvulcanized hollow annular member and bonded to the hollow annular member by vulcanizing the whole. As shown in FIG. 2, the hoop reinforcing layer made of resin is vulcanized and molded into a hollow elliptical member 2 having a flat elliptical cross-sectional shape close to the use state as shown in FIG. The part is bonded using an adhesive (not shown) or a double-sided tape. For this reason, in the unvulcanized state, the hoop reinforcing layer is not attached to the hollow annular member. Therefore, the hollow annular member has low rigidity and the shape is not stable. The unvulcanized hollow annular member is formed by a vulcanizing mold 6 formed by combining divided molds 5a, 5b and 5c as shown in FIG. 3, and accommodates the hollow annular member 2 therein. Then, the divided molds 5a to 5c are closed and vulcanization molding is performed, but it is difficult to uniformly accommodate the hollow annular member whose shape is not stable. In order to stabilize the shape, it is conceivable to apply a weak internal pressure of about several KPa to inflate the hollow annular member. However, when the internal pressure is applied without the hoop reinforcement layer, the hollow annular member Although the cross section is to be expanded so as to have a circular cross section, since the cross section of the inner space of the split mold is a flat elliptical shape, the expanded hollow annular member may be sandwiched between the split molds. When the hollow annular member is vulcanized in a non-uniformly contained state or sandwiched between split molds, it becomes a defective product having a low rigidity portion or a pinhole.

  Therefore, in the present invention, prior to vulcanization molding, while applying the internal pressure to the uncured hollow annular member, for example, constraining the outer surface thereof, for example, pre-molding that approximates the shape after vulcanization molding After that, the restraint is released, and this is accommodated in a vulcanization mold and vulcanized. The preformed hollow annular member maintains its shape over a certain period of time, so it can be easily accommodated uniformly in the vulcanization mold, and it is close to the shape after vulcanization molding, so it is between the split molds. There is no risk of being caught between the two. Furthermore, in the hollow annular member that is difficult to stabilize because the hoop reinforcing layer is not provided, it is difficult to automate the accommodation in the vulcanization mold. Since its shape is close to that after vulcanization molding, it can be automatically conveyed to a vulcanization mold using a loader.

  Preliminary molding is performed so that the cross-sectional shape of the hollow annular member can be uniformly accommodated in the vulcanization mold and can be prevented from being pinched between the split molds. Specifically, the cross-sectional shape of the hollow annular member after preforming is brought close to that after vulcanization molding, and in particular, the outer diameter and inner diameter of the uncured hollow annular member are vulcanized respectively. It is preferable to carry out so that it may become substantially the same as the subsequent outer diameter and inner diameter. The reason for setting the outer peripheral diameter and the inner peripheral diameter in this way is that when the hollow annular member is accommodated in the vulcanization mold, the outer peripheral diameter of the hollow annular member is larger than that after vulcanization molding, This is because if the inner peripheral diameter of the hollow annular member is smaller than that after vulcanization molding, the hollow annular member may protrude from the split molds and be bitten.

  Further, in the pre-molding, a hollow annular member 2 in an unvulcanized state is pre-molded as shown in FIG. 4 having a pair of generally cylindrical inner and outer peripheral preformed surfaces 7 and 8 facing each other. It is preferable to store the inside of the container 9 and apply an internal pressure to the stored hollow annular member 2 so that the hollow annular member 2 is expanded and brought into contact with the preformed surfaces 7 and 8. By thus constraining the inner and outer peripheral surfaces at the same time and performing preforming, a desired cross-sectional shape can be obtained relatively easily.

  The preformed surfaces 7 and 8 do not have to be a single continuous surface. As shown in FIG. 4, a plurality of segments are arranged side by side on the same circumference to form a cylindrical shape as a whole. Also good. At this time, it is preferable that there is no gap between adjacent segments. However, if the gap is as small as about 20 mm or less, the hollow annular member 2 can be satisfactorily preformed without protruding from here. Further, when the preforming surface is constituted by a plurality of segments in this way, the segment is moved in the radial direction by a segment driving means (not shown), so that the inner periphery preforming surface 7 and / or the outer periphery preforming surface 8 is moved. Can be expanded or contracted in the radial direction. Thereby, attachment of the hollow annular member 2 to the preformer 9 and removal of the hollow annular member 2 from the preformer 9 are facilitated. Further, in order to move the segment of the split mold in the radial direction, a well-known driving means can be used in tire manufacturing equipment such as a hydraulic cylinder and an air cylinder, so that the equipment can be made relatively simple.

  Since the uncured hollow annular member is mainly composed of raw rubber, it adheres to the pre-molder 9 and tends to be difficult to take out after pre-molding. From the viewpoint of preventing such adhesion, it is preferable to perform adhesion prevention processing such as Teflon (registered trademark) coating on the inner and outer periphery preformed surfaces of the preformer. Alternatively, prior to preforming, a powdery adhesion preventive agent such as talc or a liquid adhesion preventive agent (external liquid for mold release) such as stearic acid may be applied to the outer surface of the uncured hollow annular member. Good.

  Thus, even in the case of a hollow annular member that has undergone a pre-molding step, the difference in cross-sectional shape from that after vulcanization molding increases with time due to the resilience of the material constituting it. As a result, the possibility of being bitten by the split mold increases with time. Therefore, it is preferable to perform vulcanization molding in as short a time as possible after completion of the preliminary molding. Specifically, vulcanization molding is preferably performed within 15 minutes after completion of the pre-molding, and more preferably vulcanization molding is performed within 5 minutes.

  Note that the above description shows only a part of the embodiment of the present invention, and these configurations can be combined with each other or various modifications can be made without departing from the gist of the present invention. . For example, FIG. 4 shows a mode in which the hollow annular member 2 is placed vertically, but it is hollow as shown in FIG. 5 in accordance with the shape of the vulcanizing mold to be used and the loader used for transporting it. The annular member 2 can also be placed horizontally.

  As is clear from the above description, according to the present invention, by performing vulcanization molding after preforming, even when the rigidity of an unvulcanized hollow annular member is low, it is possible to stabilize the vulcanization mold. It has become possible to provide a method for producing a pneumatic tire bladder for safety tires that can be accommodated and reduce the defective rate of products.

FIG. 3 is a cross-sectional view in the width direction showing a safety tire that contains an air bladder and is assembled to a rim in a state where the internal pressure is normal. It is a cross-sectional schematic diagram which shows the procedure which affixes a hoop reinforcement layer on a hollow annular member. It is a cross-sectional schematic diagram of a typical vulcanization mold used in the present invention, and shows a hollow annular member accommodated and closed. It is a perspective view of the typical preformer used for this invention, accommodates a hollow annular member, and shows it in the closed state. It is a perspective view of the other preforming device used for this invention, accommodates a hollow annular member, and shows it in the open state.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Air bladder 2 Hollow annular member 3 Hoop reinforcement layer 4 Tire 5a, 5b, 5c Division mold 6 Vulcanization mold 7 Inner circumference preforming surface 8 Outer circumference preforming surface 9 Preformer

Claims (8)

A hollow annular member made of rubber and reinforcing material is formed by vulcanization molding, and is stored in the tire and filled with the internal pressure. When the internal pressure of the tire is normal, a space is formed between the inner surface of the tire and the tire. In the production of an air bladder for a safety tire that expands and deforms as the internal pressure of the tire decreases and replaces the load from the tire,
A method for producing an air bladder for a safety tire, characterized in that an internal pressure is applied to the uncured hollow annular member for preforming, followed by vulcanization molding using a vulcanization mold.   The manufacturing method according to claim 1, wherein preforming is performed such that an outer peripheral diameter and an inner peripheral diameter of the hollow annular member in an unvulcanized state are substantially the same as an outer peripheral diameter and an inner peripheral diameter after vulcanization, respectively.   The unvulcanized hollow annular member is housed in a pair of generally cylindrical inner and outer preforming surfaces facing each other, and an internal pressure is applied to the housed hollow annular member, The manufacturing method according to claim 1 or 2, wherein the hollow annular member is expanded and brought into contact with the pair of preforming surfaces to perform preforming.   The manufacturing method according to claim 3, wherein an inner peripheral preforming surface of the preformer can be expanded and contracted in a radial direction.   The manufacturing method according to claim 3 or 4, wherein an outer peripheral preformed surface of the preformer can be expanded and contracted in a radial direction.   The manufacturing method as described in any one of Claims 3-5 using the preformer formed by giving an adhesion prevention process to an outer periphery and an inner periphery preforming surface.   The manufacturing method as described in any one of Claims 3-6 which apply | coats an adhesion inhibitor to the outer surface of the said hollow annular member of an unvulcanized state prior to preforming. The manufacturing method as described in any one of Claims 1-7 which preforms until just before a vulcanization molding.

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