JPH0360909B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a shape memory alloy.

Shape memory alloys utilize the phenomenon that occurs when the low-temperature phase generated by thermoelastic martensitic transformation is deformed and then reversely transformed into the high-temperature phase by heating. It changes to an austenite structure at higher temperatures, and changes to a martensitic structure at lower temperatures. When this shape memory alloy is cooled from the high temperature side, the austenitic structure transforms to the martensitic structure, and it has superelasticity.On the other hand, when it is heated from the low temperature side, the martensitic structure transforms to the austenite structure, and the forming process It returns to the memorized shape. Known alloys that exhibit such a shape memory effect include nickel-titanium, copper-aluminum-nickel, and copper-aluminum, and when these shape memory alloys are used as a drive source, they must be heated and cooled from the outside. Therefore, it utilizes the displacement of the shape memory alloy. As a means for heating a shape memory alloy, a method is generally known in which a heater is wound around a valve drive element made of a shape memory alloy, as shown in Japanese Patent Laid-Open No. 57-25572. However, with such a structure, winding a coil around a wire made of a shape memory alloy is extremely inefficient, and heat conduction from the heater to the wire is applied from outside, and the valve drive element The disadvantage is that heat cannot be applied uniformly to the wire, and furthermore, the coil is easily disconnected due to being exposed to the outside.

The method for manufacturing a shape memory alloy according to the present invention has been devised in view of the above points, and is a method for manufacturing a shape memory alloy that makes it extremely easy to attach a heater to the wire and has excellent heating efficiency for the wire. It's about getting.

Next, a method for manufacturing a shape memory alloy according to the present invention will be explained with reference to the drawings. First, as shown in Figure 1,
is a material made of a shape memory alloy, and grooves 2A are carved over the entire length of the material to form the strands 2. Next, as shown in FIG. 2, the wire 2 is formed into a desired shape, such as an L-shape, and heat treated at a high temperature of 400 DEG C. for shape memory. Next, at the martensitic phase temperature where the composition of the shape memory alloy is in the martensitic phase (specifically, the martensitic transformation starting point (As point)
(Temperature below) Stretch it into a substantially straight line as shown in Figure 3. Next, as shown in FIG. 4, a heater 3 such as a nichrome wire is embedded in the groove 2A of the wire 2.

When the heater 3 is energized in such a state, the heater 3 self-generates heat, and this heat warms the wire 2 from inside, and most of the heat generated by the heater 3 is generated by surrounding most of the outer circumference with the wire 2. This allows efficient heat conduction and promotes temperature rise due to heating of the strands. When the temperature of the strand 2 reaches the reverse transformation start point (As point), it changes into the shape memorized in the previous heat treatment process, that is, the L-shape.

As described above, the method for manufacturing a shape memory alloy according to the present invention includes a first step of forming a material made of a shape memory alloy into a wire having a grooved cross section, and a heat treatment step to memorize the shape formed into a predetermined shape. , the second step of stretching the wire in a straight line at the martensitic phase temperature, and the third step of embedding the heater in the groove of the wire, so that the heater is completely inserted into the groove of the wire and the heater is The heat generated by the wire is transmitted from the inside of the wire, improving the heating efficiency for the shape memory alloy. Further, since the heater need only be simply inserted into the groove of the wire and does not need to be wound around the wire as in the prior art, the workability of attaching the heater to the wire can be improved. In addition, since the heater can be placed close to the center of the wire, even if the shape of the wire changes, the amount of displacement is relatively small, improving durability during repeated use. I was able to do that. Furthermore, since the heater can be placed inside the wire, the heater is less exposed directly to the outside, and in particular, the number of disconnections in the heater, which requires a thin wire diameter in terms of power consumption, is reduced.

[Brief explanation of drawings]

The figures show an example of the method for producing a shape memory alloy according to the present invention, in which Fig. 1 shows the first step, Fig. 2 shows the heat treatment step, and Fig. 3 shows the first step. This shows two steps, and FIG. 4 shows the third step. 2...Element wire, 2A...groove, 3...heater.

Claims (1)

[Claims] 1. A first step of forming a material made of a shape memory alloy into a wire with a grooved cross-sectional shape, a heat treatment step of forming it into a predetermined shape and memorizing the shape, and a second step of stretching it into a straight line at a martensitic phase temperature. A method for manufacturing a shape memory alloy, comprising a third step of embedding a heater in a groove of a wire.