JPH0436234Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a drive element using a shape memory alloy, and particularly relates to an improvement in a heating means for heating a shape memory alloy member to restore it to a memorized shape. .

[Prior art]

A drive element using a shape memory alloy deforms a shape memory alloy member into a shape other than the memory shape at a temperature below the transformation point, and then heats it to a temperature above the transformation point.
It utilizes the force generated when the shape memory alloy member recovers to its memorized shape.

Conventionally, the shape memory alloy member in this type of drive element has generally been heated by directly applying electricity to the member. However, the electrical resistance value of shape memory alloy members is relatively small, for example, 0.2 mm in diameter.
To heat a Ni-Ti wire, a large current of approximately 2A must be passed through it.

In order to reduce the current used to heat the shape memory alloy member, it is possible to increase the electrical resistance value by reducing the cross-sectional area of the shape memory alloy member (reducing the wire diameter or thinning the plate thickness). Although this is necessary, there is a problem in that the force required to restore the shape memory alloy member to its memorized shape becomes smaller.

[Purpose of invention]

In view of the above problems, the purpose of this invention is to
A drive element using a shape memory alloy that can heat a shape memory alloy member to a temperature above its transformation point with a smaller current without reducing the shape memory recovery force of the shape memory alloy member (without reducing the cross-sectional area). It is about providing.

[Structure of the idea]

In order to achieve the above object, the present invention provides a planar heating element having a higher electrical resistance than the shape memory alloy member on the surface of the shape memory alloy member, which has a predetermined shape memorized, via a heat-resistant electrical insulating film. It is characterized by being attached.

[Effect]

This driving element using a shape memory alloy heats the shape memory alloy member with heat generated by heating the sheet heating element with electricity, rather than heating the shape memory alloy member with electricity. The sheet heating element is bonded to the shape memory alloy member via a thin heat-resistant electrical insulating film, and the state is almost the same as surface contact, so the heat transfer efficiency to the shape memory alloy member is extremely high. Since the electrical resistance value of the shape memory alloy member is made larger than that of the shape memory alloy member, it is possible to heat the shape memory alloy member to the memorized shape recovery temperature with a smaller current than when heating the shape memory alloy member directly.

Note that the shape to be memorized by the shape memory alloy member is determined depending on its use. For example, if you want to obtain linear motion, you can memorize a linear shape in a shape memory alloy member, bend it at a temperature below the transformation point,
It is sufficient to recover the linear shape by heating, or if rotational motion is to be obtained, the spiral shape is memorized in the shape memory alloy member, and the spiral shape is memorized by winding it at a temperature below the transformation point and by heating. All you have to do is restore it to its shape.

〔Example〕

1 and 2 show an embodiment of the present invention. This drive element includes, for example, a heat-resistant electrical insulating film 2 on both sides of a shape memory alloy plate 1 that has a linear shape memorized.
A planar heating element 3 is attached through the heating element 3, and a heat-resistant electrical insulating film 4 is attached to both sides of the heating element 3. Both ends 1a of the shape memory alloy plate 1 are exposed as connection parts with other members when constructing a drive device. 5 is a heat-resistant adhesive used for pasting.

A polyester film or the like can be used as the heat-resistant electrical insulating films 2 and 4. Further, the planar heating element 3 is formed by forming a metal foil such as aluminum foil into a meandering pattern. To form such a planar heating element 3, a metal foil is attached to the heat-resistant electrical insulating film 2 or 4, an etching resist is printed on the metal foil in a meandering pattern, and the exposed portion of the metal foil is dissolved by etching. and remove it.

A sheet heating element made of metal foil with polyester film attached to both sides can be heated to a temperature of 100 to 150°C, whereas the transformation point of a shape memory alloy is generally below about 100°C. A combination of the two is practically suitable.

Both ends 3a of the planar heating element 3 are projected as current-carrying terminals, and these ends 3a are attached to the projections of the heat-resistant electrical insulating film 2 for reinforcement.
Crimp-type connectors 6 are provided at both ends 3a of the sheet heating element 3.
A lead wire 7 is connected via. This drive element connects this lead wire 7 to a power source, causes the planar heating element 3 to generate heat, and heats the shape memory alloy plate 1 with the heat.

As shown in FIG. 1, the planar heating element 3 can have a small cross-sectional area and a long length by forming thin metal foil into a meandering pattern, and therefore has shape memory. Since the electrical resistance value can be made sufficiently larger than that of the alloy plate 1, the shape memory alloy plate 1 can be heated with a smaller current than when the shape memory alloy plate 1 is directly heated with electricity. Therefore, the thickness and width of the shape memory alloy plate 1 can be freely selected according to the required driving force without considering the electrical resistance value of the plate itself.

FIG. 3 shows another embodiment of the invention. This drive element is made up of two shape memory alloy plates 1 and three planar heating elements 3 stacked in a plurality of layers in an alternating arrangement. Of course, a heat-resistant electrical insulating film 2 is interposed between the shape memory alloy plate 1 and the planar heating element 3, and a heat-resistant electrical insulating film 4 is also pasted on the outermost surface. By using a plurality of shape memory alloy plates in this way, it is possible to obtain a large driving force.

FIG. 4 shows yet another embodiment of the present invention. This drive element is constructed by arranging a plurality of shape memory alloy wires 8 in parallel as a shape memory alloy member. The rest of the structure is the same as the embodiment shown in FIGS. 1 and 2.

FIG. 5 shows how the driving element of the present invention is used.
Reference numeral 9 indicates a drive element of the present invention in which a sheet heating element is attached to a shape memory alloy member. Both ends of this drive element 9 are rotatably attached to a stator 10 and a movable element 11. Also, in parallel with this, the stator 10
A coil spring 12 is stretched between the movable element 11 and the movable element 11. The movable element 11 is guided by the stator 10 and is slidable in the direction of arrow S. The lead wire 7 of the drive element 9 is drawn out of the stator 10 and connected to a power source.

When the shape memory alloy member is not heated, the drive element 9 is deformed into an arcuate shape by the tension of the coil spring 12 as shown, and the movable element 11 is in the retracted position. When the shape memory alloy member is heated by the planar heating element, the member exerts a force to restore the memorized shape (linear shape), so the drive element 9 overcomes the tension of the coil spring 12 and returns to the linear shape. This moves the mover 11 forward. When heating by the planar heating element is stopped, the shape memory recovery force of the shape memory alloy member is lost, and the tension of the coil spring 12 causes the movable element 11 to return to its original retracted position.

Although metal foil was used as the planar heating element in the above embodiment, the present invention may also use other planar heating elements such as rubber or plastic sheet mixed with carbon powder. Further, the planar heating element may be attached to only one side of the shape memory alloy plate.

[Effect of idea]

As explained above, according to the present invention, a shape memory alloy member is heated by applying current to a planar heating element that is attached to the shape memory alloy member and has a higher electric resistance value than that of the shape memory alloy member. Since the heat is transferred to the shape memory alloy member, the shape memory alloy member can be heated to a temperature equal to or higher than the transformation point with a smaller current than when heating the shape memory alloy member with electricity. Moreover, since the shape memory alloy member itself is not heated by electricity, the cross-sectional area of the shape memory alloy member can be selected regardless of the electrical resistance value, and the required driving force (memory shape recovery force) can be easily obtained. be able to.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway plan view showing one embodiment of the drive element of the present invention, FIG. 2 is an enlarged cross-sectional view taken along the line - - of FIG. 1, and FIGS. 3 and 4 are other embodiments of the present invention, respectively. FIG. 5 is a cross-sectional view showing the driving element of the present invention in use. DESCRIPTION OF SYMBOLS 1... Shape memory alloy plate, 2... Heat resistant electrical insulating film, 3... Planar heating element, 4... Heat resistant electrical insulating film, 8... Shape memory alloy wire.

Claims (1)

[Claims for Utility Model Registration] (1) Shape memory alloy member 1 that memorizes a predetermined shape
A driving element using a shape memory alloy, characterized in that a sheet heating element 3 having a higher electrical resistance value than the shape memory alloy member 1 is pasted on the surface of the shape memory alloy member 1 via a heat-resistant electrical insulating film 2. (2) The drive element according to claim 1, in which the shape memory alloy member 1 and the planar heating element 3 are alternately stacked in a plurality of layers. (3) The driving element according to claim 1 of the utility model registration claim, in which the shape memory alloy member 1 is plate-shaped. (4) Utility model registration The drive element according to claim 1, which is composed of a plurality of shape memory alloy wires in which shape memory alloy members are arranged in parallel.