JPH0150198B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an actuator to which a shape memory alloy is applied, and in particular to this type of actuator suitable for use in high-speed operation cycles.

[Prior Art] In recent years, shape memory alloys have been used in various fields,
For example, by forming a Ni-Ti alloy into a coil spring shape,
A structure has been proposed that utilizes the one-way shape memory effect of heating by electric resistance heating or the like as a linear actuator and uses a bias coil spring made of ordinary spring steel or the like to recover from a deformed state. In this type of configuration, the resistance heating, etc. for actuating the actuator can achieve a high degree of linear position (stroke) accuracy by controlling, for example, pulse modulation, and can increase its response speed. It is.

[Problems to be Solved by the Invention] However, in the conventionally proposed linear actuator of this type, although the deformation recovery is provided with the bias coil spring, it is originally a unidirectional shape memory alloy. Since it depends on cooling, its response speed is extremely slow at the level of conventional natural cooling or external ventilation cooling, and increasing the surface area of the coil itself to improve this has been extremely difficult due to structural constraints. For this reason, this type of actuator is often applied in areas where the difference in response speed between heating and cooling, that is, activation and recovery, is only about 1 second, such as switching fire alarms, indoor air conditioning systems, etc. It has been limited to a few special applications, such as controlling the direction of air flow in a microwave oven and displaying the temperature of a microwave oven, and has not been able to be used in applications that require a small difference in response speed between reciprocations, such as high-speed switching valves that require high-speed switching.

The present invention was made in view of the slow cooling (return) response of the conventional actuator as described above, and an object of the present invention is to provide an actuator that has a fast heating/cooling response speed and a small difference in speed. It is said that

[Means for Solving the Problems] Therefore, in the present invention, the strands made of a unidirectional shape memory alloy that form the actuating coil spring of the actuator are bent, and a cooling medium is circulated through the wires. The purpose of the present invention is to achieve the above object by configuring the system to

[Example] (Structure) The present invention will be described below based on the drawings of the example. FIG. 1 is a longitudinal sectional view and a block diagram of a cooling system of an embodiment of a linear actuator according to the present invention. Reference numeral 1 designates an outer cylinder made of a non-conductive material, and 2 a plunger as an operating member made of a non-conductive material that slides in the inner diameter of the cylinder in the axial direction. It protrudes and can linearly drive a follower (not shown). The other end of the cylinder 1 is closed by a non-conductive end plug 3 via a gasket by screw fitting. A double actuator coil d formed by bending a thin hollow pipe-like wire made of a Ni-Ti unidirectional shape memory alloy is housed in the inner diameter bored in the axial direction of the plunger 2. and the outer coil 4a is connected to the inner coil 4.
b is continuous at the lower end of the plunger inner diameter,
The other ends of both coils 4a and 4b are fixed by a coil holder 5 made of a non-conductive material that passes through the end plug 3 and is embedded and fixed in the outer end of the end plug 3, so that each coil end forms a cylinder. It is led to the outside from 1. A terminal member 6 made of a conductive material is attached to each coil at the outlet end of the coil holder 5 at the end of each of these coils.
The coils 4 are configured to be heated by supplying current to the coils 4 from an external power source via lead wires 7 (V ₊ , V _- ), respectively. On the other hand, the operating end 2a of the plunger 2
A compression coil spring made of spring steel is interposed between the step shoulder provided on the side and the inward flange at the end of the cylinder 1, forming a bias coil spring 8 for restoring the stroke of the plunger 2.

Each end of the hollow pipe forming the actuator coil 4 is connected to a cooling device 12 and configured to allow a cooling medium such as Freon gas, low temperature air, etc. to be circulated inside the pipe at high speed. It has been done. Piping joints 9 and 10 are screwed on the outside of the cylinder 1, and are connected via piping 11.
It is connected to the high speed pump 13 of the cooling device 12. An outer circumferential groove 2b is formed on the plunger 2 near the inner end thereof, and the piping joints 9, 10 are formed at a position corresponding to the stroke S end when the actuator coil 9 is heated and expanded by electricity. It communicates with the hole to allow circulation of the cooling medium.
The configuration is such that communication is blocked by the outer circumferential surface of the plunger at positions other than this position. high speed pump 1
3 is intended to be driven and controlled by the control device 12 to circulate the low-temperature cooling medium from the cooler 15 at high speed through the inner diameter of the pipe of the actuator coil 4 during the restoring stroke of the plunger 2. . 1a is a ventilation hole for preventing the generation of vacuum or pressure inside the cylinder 1 when the plunger 2 moves.

(Operation) Next, the operation of the above configuration will be explained. Second
The figure shows a block diagram of the structure of the embodiment. 20 is a power source, 21 is a heating device, and resistance heating device 23
is precisely controlled by a pulse modulator 22. Further, the cooler 15 includes a compressor 24,
It consists of a capacitor 25 and a switching valve 26.

Referring to FIG. 1 and FIG. 2, first, selector valve 2
6 (this high-speed switching valve can also apply the actuator type of the above embodiment) is closed to interrupt the circulation of the cooling medium, and when the actuator coil 4 is resistance heated by the heating device 21 from the power source 20, the coil 4 is extended, and the plunger 2 is extended to the operating position on the left side of FIG. 1 (in the direction of the solid line arrow) against the biasing force of the bias coil spring 8, thereby driving a follower (not shown). At this time, the holes in the piping joints 9 and 10 on the cylinder 1 are connected to the circumferential groove 2b on the plunger 2.
Matches the section. In this state, when heating to the actuator coil 4 is stopped and the switching valve 26 is opened to circulate the cooling medium inside the pipe of the actuator coil 4 at high speed, the coil quickly returns to its original temperature in a short period of time. Then, due to the biasing force of the bias coil spring 8, the plunger 2 contracts and restores to its restoring position (in the direction of the dotted line arrow in FIG. 1).

Another method of operation is to maintain the plunger in the restored state shown in FIG. 1 by constantly circulating the cooling medium without passing through the joints 9 and 10.
It is also possible to perform a high-speed operation cycle of the plunger by repeatedly applying resistance heating to heat the cooling medium and the actuator coil in this state, and then cutting off the voltage and repeating cooling by the cooling medium.
At this time, the switching valve 26 is not necessary.

In either case, the response of the plunger during the restoring cycle is extremely fast, and the actuator can be applied to high-speed operation applications.

[Other Examples] The actuator coil in the above example was of a double coil type, but depending on the application, the inner coil may be formed into a straight line so as to slide through the coil holder. It is also possible.

[Effects of the Invention] As explained above, according to the present invention, the wire of the actuator coil made of a shape memory alloy is formed into a hollow pipe shape, and the cooling medium is circulated at high speed through the inner diameter thereof. The response of the cooling and restoring operation of the actuator has been significantly sped up and the difference from the heating operation has been reduced, making it possible to apply high-speed cycles to this type of actuator.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view and a block diagram of a cooling system of an embodiment of a linear actuator according to the present invention, and FIG. 2 is a block diagram of its configuration. 1... Cylinder, 2... Plunger (operating member), 4... Actuator coil, 4a/4b
...Outer/inner coil, 8...Bias coil spring,
12... Cooling device, 21... Heating device.

Claims (1)

[Scope of Claims] 1. A hollow cylinder having an opening at one end and a closed end at the other end, an actuating member housed within the cylinder and having its tip portion inserted through the opening of the cylinder; A spring is disposed between the cylinder and the actuating member and biases the actuating member to the restoring position, and a hollow pipe-like wire made of a shape memory alloy is bent into a coil shape, and the proximal end of the actuating member and the cylinder an actuator coil disposed between the actuator coil and the actuator coil whose extension moves the actuating member to the actuating position;
A shape memory characterized by comprising: a heating device that resistively heats the actuator coil by applying current to it; and a cooling device that cools the actuator coil by circulating a cooling medium through the inner diameter of the pipe of the actuator coil. Alloy applied actuator.