JP5802079B2 - Method for manufacturing coil spring made of thermoplastic polymer - Google Patents

Description

The present invention relates to a coil spring made of a thermoplastic polymer.

  Conventionally, coils have been used as members of various appliances and devices such as automobiles, bedding, instruments, writing instruments, and pump dispensers for purposes such as shock absorption, energy storage, load adjustment, load detection, and vibration isolation. As a material of the coil, there are a material made of a metal such as a stainless steel material, a spring steel material, a piano wire material and a white wire material, and a material made of a non-metallic material such as a synthetic resin, FRP and synthetic fiber.

  In general, a metal coil has a higher elastic modulus than a synthetic resin, and can exhibit mechanical properties even with a member having a smaller cross-sectional area than a synthetic resin. In addition, since the physical properties are relatively stable with respect to operating environments such as temperature, the application range is wide. However, there are problems that it is inferior in durability such as being easily corroded by chemicals and easily rusting, and that it cannot be colored, and when used as a member in a resin product, it is difficult to separate and collect. Furthermore, there is a demand for weight reduction, and the development of non-metallic coils is underway.

  Synthetic resins are inferior in heat resistance and mechanical properties compared to metals, but they are superior in durability, such as lightness, wear resistance, and chemical resistance. It has features such as high insulation. Moreover, coloring can also be performed easily and special-shaped shaping | molding can be performed easily. Furthermore, when used as a member in a resin product, there is an advantage that it is easy to separate and collect.

  As such a synthetic resin coil, Patent Document 1 proposes a synthetic resin coil. Although it is almost impossible to separate metal coils incorporated in a synthetic resin product, this problem is solved by using synthetic resin-molded synthetic resin coils. Moreover, a required sufficient elasticity is ensured by combining a plurality of pieces in a spiral state and integrally forming them.

  Patent Document 2 proposes a coil spring using a carbon fiber reinforced resin using a carbon fiber having mechanical properties as a reinforcing material. Compared to resin coils, it has excellent mechanical properties.

These synthetic resin coil springs are manufactured by an integral molding method, a method in which a resin linear body is wound around a shaping shaft, and a method in which a resin linear body is wound around a heated shaping shaft. ing. In the integral molding method, there is a problem that not only a huge cost is required for producing a molding die, but also the strength of the obtained molded product is inferior. In addition, in the method of heating in a state where the resin linear body is wound around the upper shaping shaft and the method of winding the resin linear body around the heated shaping shaft, the shaping shaft having a spiral groove is used. It is difficult to respond to changes in diameter and coil pitch, and in particular, the method of heating with the resin wire wound around the top shaping shaft cannot adopt a continuous manufacturing process. There is a problem that it is difficult to obtain a molded product having uniform dimensional stability and shape stability because unevenness in the thermal history of the resin linear body is likely to occur.

  In Patent Document 3, as a method of manufacturing a synthetic resin coil having good dimensional stability and shape stability, a synthetic resin monofilament is advanced in a tension state and preheated to a temperature not lower than the melting point and not lower than the glass transition temperature of the monofilament material. Thereafter, a method has been proposed in which the wound monofilament is immediately wound on a rotating shaping shaft, and then the wound monofilament is rapidly cooled. However, in this method, there is a limit to the diameter of the monofilament to be used, and it is difficult to combine with other materials for providing other performance.

JP-A-10-73138 JP 07-42778 A JP-A-11-254520

An object of the present invention is a coil spring mainly using a non-metallic material, and can be easily and inexpensively molded without going through a complicated manufacturing process. An object of the present invention is to provide a coil spring that can flexibly cope with the situation.

This invention achieves the said subject, The summary is a manufacturing method of a coil spring,
A core-sheath type composite fiber in which a fiber converging body formed by converging a plurality of fibers is used, and the fibers constituting the fiber converging body include a low melting point polymer forming a sheath part and a high melting point polymer forming a core part. Consist only of
After winding the fiber bundling body into a predetermined spiral shape,
Production of a coil spring comprising a thermoplastic polymer, wherein the low-melting polymer constituting the fiber bundle is melted and heat-treated at a temperature at which the high-melting polymer does not melt, and then cooled. Is in the way.

  Hereinafter, the present invention will be described in detail.

In the present invention, first, a fiber bundling body formed by bundling a plurality of fibers is prepared. In the present invention, since a coil spring is obtained using a thermoplastic polymer as a main material, a synthetic fiber made of a thermoplastic polymer is used as the fiber constituting the fiber bundle. Synthetic fibers can be preferably used because they can easily adjust the fineness and mechanical properties. Synthetic fibers include polyamide-based, aromatic polyester-based, aliphatic polyester-based, polyolefin-based and polyurethane-based synthetic fibers. Polyamide-based synthetic fibers are preferred because of their excellent wear resistance. Polyester-based synthetic fibers are preferred because of their excellent dimensional stability. In addition, if the coil is used for an application that is required to be naturally decomposed after use, it is preferable to use an aliphatic polyester-based synthetic fiber having biodegradability. Polyolefin-based synthetic fibers have a small specific gravity and are excellent in weight reduction. Therefore, they are preferably used for applications that require weight reduction. Further, depending on the application and purpose, a plurality of these synthetic fibers may be selected and arbitrarily combined to form a fiber bundle .

The fiber bundling body formed by bundling a plurality of fibers may be any fiber bundling as long as the fibers are bundled, a yarn obtained by arranging a plurality of fibers, a twisted yarn obtained by twisting a plurality of fibers, a spun yarn, Examples thereof include a twisted yarn obtained by combining drawn yarns and twisted yarns, a braid made using these yarns, a rope obtained by twisting, and the like. What is necessary is just to select suitably the thickness (wire diameter) of a fiber bundling body according to the magnitude | size etc. of the desired coil spring . In the present invention, the reason for using a fiber bundling body formed by bundling a plurality of fibers is that the fibers are simply bundled, so that there is flexibility between the fibers and it is very flexible. It is to be able to cope with various shapes. Therefore, according to the present invention, since the fiber bundling body itself has a large thickness, it has flexibility, so that it can be wound according to various winding diameters and winding pitches, and various forms of coil springs can be obtained. Can be easily obtained.

The fiber bundle is composed of a low melting point polymer and a high melting point polymer. The low-melting point polymer is melted and solidified by heat treatment later, and the fibers are fixed and integrated with each other to maintain a predetermined spiral shape. The high-melting point polymer is not melted by the heat treatment and is not melted. The form will be maintained and the mechanical properties of the coil spring will be borne. At this time, if the fiber bundle is formed only from the low melting point polymer, the low melting point polymer melts and flows during the heat treatment, and a predetermined spiral shape cannot be obtained. The mixing ratio of the low melting point polymer and the high melting point polymer is preferably about 10/90 to 70/30.

In the present invention, a composite fiber in which a low-melting polymer and a high-melting polymer are composited, and a fiber in which the low-melting polymer is arranged on at least the fiber surface is contained as a fiber constituting the fiber assembly. by, it forms a fiber aggregate by the low melting polymer and a high melting polymer. The composite fiber is also referred to as a composite binder fiber because it functions as a thermal binder by melting the low melting point polymer. In such a composite binder fiber, only the low melting point polymer is melted by heat treatment, and the fibers constituting the fiber bundle are fixed and integrated with each other, so that the fiber bundle becomes a rigid linear strip. A fiber collecting body, Ru is up the fiber bundle of only the composite binder fibers. As the composite binder fiber, a core-sheath type composite fiber in which a low melting point polymer forms a sheath part and a high melting point polymer forms a core part is used .

  As the low melting point polymer, any polymer having a spinning property by melt spinning may be used. For example, polyester polymer, polyamide polymer, polyolefin polymer, polybutyral polymer, polyacrylic polymer, polyethylene -A vinyl acetate copolymer, a polyurethane-type polymer, etc. are mentioned. The melting point of the low melting point polymer is preferably 20 ° C. or lower than the melting point of the high melting point polymer. This is because the high melting point polymer does not affect the physical properties by heat treatment. Further, the melting point of the low melting point polymer is preferably in the range of 80 to 160 ° C. in consideration of processability and physical properties. In consideration of adhesiveness, preferred combinations of the low melting point polymer / the high melting point polymer include low melting point polyester / high melting point polyester, low melting point polypropylene / high melting point polypropylene, polyethylene / polypropylene, low melting point nylon / high melting point nylon. The combination of these is mentioned. More specifically, a core-sheath type composite fiber in which a high melting point polyester having a melting point of 240 ° C. or higher is disposed in the core and a low melting point copolymer polyester having a melting point of 110 to 200 ° C. is disposed in the sheath, or a melting point of 180 ° C. or higher. A core-sheath type composite fiber in which a high melting point polyamide is disposed in the core and a low melting point polyamide having a melting point of 80 to 150 ° C. is disposed in the sheath is preferably used.

  It is preferable to use similar fibers as the fibers constituting the fiber bundle. Since the low-melting-point polymer and the high-melting-point polymer have good thermal adhesiveness, the fibers can be firmly fixed and integrated with each other, and a more rigid linear body can be obtained. In addition, using similar fibers is also preferable from the viewpoint of recycling. Therefore, when using a fiber other than the heat-sealing fiber, it is important to select a fiber that is excellent in the melting component and adhesion of the heat-sealing fiber during the heat treatment.

The fineness of the fibers constituting the fiber bundling body only needs to be flexible when spirally wound, and is preferably about 3 to 20 dtex. Further, the fineness of the fiber bundling body may be flexible as long as it is wound in a spiral shape. Also, since the fineness of the filaments constituting the coil spring is selected, it may be appropriately selected according to the use of the coil spring. The lower limit is preferably about 500 dtex, and the upper limit is preferably about 5 million dtex. The fiber bundling body may be obtained by bundling 25 to several million fibers.

  Although the form of the fiber which comprises a fiber bundling body may be a short fiber or a continuous fiber, a continuous fiber is preferable. Since continuous fibers do not have fluff, fluff is not formed on the surface of the filaments obtained by stiffening the fiber bundle by heat treatment.

  In addition, you may add suitably to the fiber to be used in the range which does not impair the effect of this invention, such as a flame retardant, a coloring agent, a pigment, a lubricant, a weathering agent, antioxidant, and a heat-resistant agent generally used. Further, the fiber cross-sectional shape may be any of a round cross section, an irregular cross section, a hollow cross section, and the like. Moreover, the fiber which gave processing, such as false twist processing and taslan processing, to a fiber can also be used.

  In the present invention, after winding the above-described fiber bundled body into a predetermined spiral shape, the low-melting polymer is melted and heat-treated at a temperature at which the high-melting polymer does not melt, and then cooled. Then, the low-melting polymer obtained by melting and solidifying the fibers in the fiber bundle is fixed and integrated, so that the fiber bundle becomes a rigid linear body, the helical shape is fixed, and is made of a thermoplastic polymer. A coil can be obtained.

In winding the fiber bundle so as to have a spiral shape, a predetermined shaping axis may be used. In the present invention, since the fiber bundling body has flexibility between fibers, any shape can be supported. Therefore, in order to obtain a desired coil spring , it can be set as appropriate according to the diameter of the shaping shaft, the pitch of the spiral, various cross-sectional shapes of the shaft, and according to changes in the shaft diameter and pitch. Moreover, the heating method is not particularly limited, but a known means such as an iron, a hot air welder, a hot air dryer, or a tenter machine may be used. The heat treatment temperature may be appropriately set in relation to the heat treatment time, but is set to a temperature not lower than the melting point of the high melting point polymer and not lower than the melting point of the high melting point polymer.

Cool after heat treatment. By cooling, the melted low-melting point polymer is solidified, and the fibers constituting the fiber bundle are fixed and integrated, and the fiber bundle becomes a rigid linear body (rigid straight line body). By this treatment, a coil spring in which the rigid linear strip formed of the thermoplastic polymer has an arbitrary spiral shape is obtained. As a cooling means, known means such as air cooling or water cooling may be used.

In the present invention, a flexible fiber bundling body formed by bundling a plurality of specific fibers is wound into an arbitrary spiral shape, and then subjected to heat treatment to form a fiber bundling body. The coil spring is obtained as a rigid linear strip by fixing and integrating the space, and the rigid linear strip exhibiting a spiral shape, various diameter thickness, spiral shape, spiral pitch, etc. Any desired helical shape can be applied as desired. In addition, a coil spring made of a thermoplastic polymer can be easily formed into a spiral shape at low cost without going through a complicated manufacturing process.

Next, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. Moreover, about the coil spring obtained in the Example, the spring characteristic was evaluated by the following.
<Spring constant>
In accordance with JIS B2704, the spring constant (N / mm) was calculated by the following equation using two types of loads A and B with a deflection of 30 to 70% of the natural height when a load was applied. .
C = (MA-MB) / (LA-LB)
(C: spring constant,
MA: Mass of load A (N),
MB: Mass of load B (N),
LA: Deflection when load A is applied (mm),
LB: Deflection when load B is applied (mm))

Example 1
As the fiber constituting the fiber bundle, only a concentric core-sheath type composite fiber (binder fiber) in which a low melting point polymer is arranged in the sheath part and a high melting point polymer is arranged in the core part was used. The core-sheath type composite fiber is a copolymer of 12 mol% of ε-caprolactone with respect to the total number of moles of ε-caprolactone and the total alkylene terephthalate unit whose sheath is composed of ethylene terephthalate and butylene terephthalate (molar ratio 1/1). Copolyester (melting point: 161 ° C.), polyethylene terephthalate (melting point: 260 ° C.) at the core, and composite spinning with a core / sheath mass ratio of 2.7 / 1. 1670 decitex / 192f multifilament yarn was prepared.

  The multifilament yarn was used to form a string with eight corners to obtain a braid having an outer diameter of 1.4 mm, which was used as a fiber bundle.

A fiber bundling body (braid) is wound around a metal shaft, and in this wound state, hot air treatment is performed under conditions of 180 ° C. × 10 minutes, demolded after air cooling, an inner diameter of 9.5 mm, a natural height of 10 mm, A coil spring composed of a thermoplastic polymer having 5 effective windings was obtained. The spring constant of the obtained coil spring was 0.032 N / mm.

Example 2
Using the core-sheath type composite fiber used in Example 1, as a multifilament yarn of 1100 dtex / 96f, the multifilament yarn was used to form a string with eight corners to obtain a braid having an outer diameter of 1.1 mm, This was used as a fiber bundle.
A coil spring constituted by a thermoplastic polymer having an inner diameter of 9.5 mm, a natural height of 10 mm, and an effective winding number of 5 was obtained in the same manner as in Example 1 by using the obtained fiber bundle (braid). The spring constant of the obtained coil spring was 0.022 N / mm.

Example 3
Using the core-sheath type composite fiber used in Example 1, as a multifilament yarn of 560 decitex / 48f, the multifilament yarn was used to form a string with eight corners, and a braid having an outer diameter of 0.7 mm was obtained. This was used as a fiber bundle.
A coil spring constituted by a thermoplastic polymer having an inner diameter of 9.5 mm, a natural height of 10 mm, and an effective winding number of 5 was obtained in the same manner as in Example 1 by using the obtained fiber bundle (braid). The spring constant of the obtained coil spring was 0.0051 N / mm.

Comparative Example As a fiber constituting the fiber bundle, only a binder fiber composed only of a low-melting polymer is used, and the binder fiber is composed of an entire alkylene terephthalate unit composed of ethylene terephthalate and butylene terephthalate (molar ratio 1/1). 1100 decitex / 120f multifilament composed of a copolyester (melting point 161 ° C.) obtained by copolymerizing 12 mol% of ε-caprolactone with respect to the total number of moles of ε-caprolactone. Yarn was prepared. This multifilament yarn was used to form a string with eight corners to obtain a braid with an outer diameter of 1.1 mm, which was used as a fiber bundle.
When the obtained fiber bundle (braid) was heat-treated in the same manner as in Example 1, all the fibers were melted, and the melt flowed down from the metal shaft, thereby obtaining a coil spring. could not.

Claims (3)

A manufacturing method of a coil spring,
A core-sheath type composite fiber in which a fiber converging body formed by converging a plurality of fibers is used, and the fibers constituting the fiber converging body include a low melting point polymer forming a sheath part and a high melting point polymer forming a core part. Consist only of
After winding the fiber bundling body into a predetermined spiral shape,
Production of a coil spring comprising a thermoplastic polymer, wherein the low-melting polymer constituting the fiber bundle is melted and heat-treated at a temperature at which the high-melting polymer does not melt, and then cooled. Method. 2. The fiber bundle is formed into a rigid straight strip by heat-treating and fixing and integrating the fibers in the fiber bundle by melting and solidifying a low melting point polymer. A manufacturing method of a coil spring made of the thermoplastic polymer. The method for producing a coil spring comprising a thermoplastic polymer according to claim 1 or 2, wherein the fibers constituting the fiber assembly are continuous fibers.