JPH0798988B2 - Shape memory alloy tension coil spring manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to an improvement in a method of manufacturing a shape memory alloy tension coil spring used for various applications.

"Prior Art" Conventionally, when manufacturing a shape memory alloy tension coil spring, as is apparent from JP-A-61-13038 and JP-A-61-28925, nickel-titanium-based materials are used. A shape memory alloy wire rod made of an alloy or the like is used to integrally form a coiled body of the closely wound coil and hook portions at both ends in advance, and then the molded body having the hook portion is set in a heat treatment die to form a die. It has been common to manufacture a shape memory alloy tension coil spring in which a desired shape is memorized by performing heat treatment together under predetermined conditions.

[Problems to be Solved by the Invention] Therefore, in the conventional manufacturing method, the shape memory alloy tension coil springs must be manufactured one by one.
Needless to say, it is unsuitable for mass production, but particularly in a heat treatment die for memorizing the shape, since both end hook portions are integrally formed in advance with the molded body, Since a corresponding mold part is required, the mold itself is naturally complicated, and there is a big problem that the cost of the mold rises unnecessarily, and the work of setting it in the mold is also complicated and there is a dislike. . Therefore, a manufacturing method disclosed in Japanese Utility Model Laid-Open No. 60-56131 is also proposed.

In this manufacturing method, a shape-memory alloy wire rod is used to form a tightly wound coil body, and the shape of the coil body is first stored in the coil body by heat treatment, and then hook portions are formed at both ends of the coil body. Therefore, if only the shape of the mold for heat treatment is grasped, the mold part of the hook part is certainly unnecessary, and the above-mentioned improvement of the mold surface can be expected.

However, under the manufacturing method, in order to form the hook portions on both ends of the heat-treated coil body, the both ends must be rounded and formed in the opposite direction to the coil winding direction. However, it is technically difficult to form the reverse hook portion or the hook portion varies in shape, and the free length of the coil body may become unstable.

Therefore, after forming the hook portion, it is necessary to separately perform processing such as immersing the hook portion in hot water to correct the shape of the hook portion. Therefore, from the viewpoint of mass productivity, it can be said that the manufacturing method is also preferable. There wasn't.

"Means for Solving Problems" The present invention was developed in order to effectively solve the problems of these conventional manufacturing methods. A coil body is formed from a shape memory alloy wire rod. , The close-wound shape of the coil body is stored in advance by heat treatment using a mold, and then only the both ends of the coil body are subjected to cold impact processing so that the shape memory characteristic of the both ends of the coil body disappears. After that, both ends are raised to form the hook.

[Operation] According to the present invention, therefore, the coil body formed of the shape memory alloy wire is first heat-treated in advance to memorize its shape, and then only the both ends of the coil body are shot. By performing cold impact processing such as peening to eliminate the shape memory characteristic of both ends of the coil body, and then raising both ends of the coil body later to form the hook portion, Since we can manufacture alloy tension coil springs,
Since the die used for the heat treatment need only memorize the coil shape, the die shape becomes simpler than the conventional die, and the die cost for heat treatment can be reduced.

[Examples] Hereinafter, the present invention will be described in detail based on an illustrated example. In the manufacturing method according to the example, first, a shape-memory alloy wire rod of a nickel-titanium-based alloy is used to form a closely wound coil. The coil body 1 is molded, and the closely wound shape of the coil body 1 is stored in advance by heat treatment using a mold.

Therefore, it is sufficient for the mold (not shown) used in such a heat treatment step to be able to store the shape of the closely wound winding. Therefore, it is necessary to store the shape of the hook together with the conventional mold. In comparison, the mold shape becomes extremely simple.

Then, as shown in FIG. 1, a core metal 3 is inserted into the inside of the coil body 1 in which the closely wound shape is stored, and both ends of the coil body 1 (in the embodiment, two windings at each end are wound). Min) Masking 4 is applied to the outer periphery except 2.2 to expose only both ends 2.2 of the coil body 1.

Then, in such a state, cold impact processing such as shot peening, dry honing and liquid honing is performed. In the present embodiment, masking 4 is applied to all parts that do not require impact processing. However, without masking, both ends 2.2 of the coil body 1 are Partial application of the cold impact working is also optional depending on the implementation.

Then, whichever method is adopted, as shown in FIG. 2, only the both ends 2 and 2 of the exposed coil body 1 are subjected to cold impact working to be hardened, and the shape obtained by the heat treatment is obtained. Since the memory characteristic is completely lost, both ends 2
Raise 2 to the desired shape by bending it in the coil winding direction,
By molding the hook portion 12, the desired shape memory alloy tension coil spring 11 shown in FIG. 3 is manufactured.

The shape memory characteristics are not lost by merely raising both ends 2 and 2 of the heat-treated coil body 1 to form the hook portions 12. Therefore, in this embodiment, the heat-treated shape memory alloy is used. Focuses on the fact that, when subjected to severe impact processing such as shot peening, it hardens and loses its shape memory characteristics, so cold impact processing such as shot peening is an extremely important step in manufacturing. Needless to say.

Therefore, the tension coil spring 11 manufactured by the above process
However, when it operates according to temperature change, the hook portion 12 that has lost the shape memory characteristic due to impact processing is not deformed at all,
Since only the tightly wound coil portion main body expands and contracts to operate, reliable operation is always guaranteed.

Further, as shown in the drawing, if the hook portion 12 is raised at the first winding after cold impact processing and the remaining first winding is located at both ends of the coil body, the hook where stress is easily concentrated Since it effectively suppresses the settling of the part 12,
This also contributes to the improvement of the durability of the tension coil spring 11 itself.

Although the above embodiment describes the manufacture of one tension coil spring 11, the coil body 1 is preliminarily formed into a long length and heat-treated, and the core metal 3 is inserted as shown in FIG. A masking 4 is intermittently applied to the attached long coil body 1, and a portion where the masking 4 is not applied is sequentially cut, and a tension spring 11 is manufactured from each of the cut bodies in the same manner as described above. Then, mass productivity is improved, and an inexpensive tension coil spring can be provided.

[Advantages of the Invention] As described above, according to the present invention, by adopting the above-mentioned configuration, it is possible to use a die for heat treatment that only memorizes the shape of the closely wound coil.
Compared with the conventional mold, which requires you to memorize the hook shape as well, the mold shape is much simpler and can greatly contribute to the reduction of mold cost, and the setting work for the mold is also great. Since this is easy, mass productivity is also greatly improved.

In addition, even when the hooks are formed on both ends of the coil body, cold impact processing is applied to both ends of the coil body to eliminate its shape memory characteristic, so that the both ends are raised in the coil winding direction. Since it is possible to easily mold the hook portion, it is possible to always provide a tension coil spring made of a shape memory alloy that is highly reliable in operation without worrying about variations in the shape of the hook portion. became.

Further, if only a predetermined portion of the long coil body is subjected to cold impact processing, the impact processed portion is sequentially cut, and both ends of each cut body are raised to form the hook portion, Since mass production of shape memory alloy tension coil springs is possible,
Along with the cost reduction of the die, the tension coil spring itself is very inexpensive.

[Brief description of drawings]

FIG. 1 is an explanatory view of a main part showing an example in which both ends of a coil body are subjected to cold impact working in a manufacturing method according to an embodiment of the present invention, and FIG. 2 is a cross section showing a coil body subjected to cold impact working. FIG. 3 and FIG. 3 are cross-sectional views showing a tension coil spring made of a shape memory alloy as a final product, and FIG. 4 is an explanatory view of main parts showing another example in which a coil body is subjected to cold impact working. 1 ... Coil body, 2 ... Coil body end, 11 ... Shape memory alloy tension coil spring, 12 ... Hook part.

Claims (1)

[Claims] 1. A coil body is formed from a shape memory alloy wire rod,
The close-wound shape of the coil body was stored in advance by heat treatment using a mold, and then only the both ends of the coil body were subjected to cold impact processing to eliminate the shape memory characteristic of both ends of the coil body. Then, the method for producing a tension coil spring made of a shape memory alloy is characterized in that the both ends are raised to form the hook part.