JPH01144105A - Linear actuator - Google Patents

Abstract

PURPOSE:To attain a compact and lightweight structure and also the large driving force with a big stroke for a linear actuator by using a shape memory element as an energy source. CONSTITUTION:When a shape memory element 16 is energized and heated, the element 16 extends against the force of a coil spring 15 and a plunger 4 extrudes over a supporter 1. While the element 16 is turned into its original form when the energization is cut to the element 16 and the liquid nitrogen or the nitrogen gas is supplied to the element 16 via a nozzle 14 to cool the element 16. This restoring force of the element 16 moves the plunger 4 backward. Thus the spring 15 has just one function to give the restoring force to an inner case 2 owing to a fact that the plunger 4 has reciprocating motions only with deformation of the element 16. In such a constitution, a compact and lightweight structure and the large driving force with a big stroke are attained at one time for a linear actuator.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an air actuator using a shape memory element.

Conventional technology and its problems A solenoid is known as a typical linear actuator. This solenoid is used in many fields because there are no other effective alternatives, but it is generally considered to have the following disadvantages.

(1) In addition to the plunger, the coil and return spring are essential components, and since there are limits to the miniaturization of the coil, it is a national challenge to reduce the size and weight of the entire unit.

(2) Due to the presence of the return spring, a portion of the actuator's energy is canceled out, reducing the net effective output.

(3) The energizing voltage and current values are high, and it is necessary to constantly supply power while the actuator is in operation.
Energy saving cannot be achieved.

(4) The duty cycle is determined by the temperature rise associated with the energization of the coil, which limits long-term use.

(5) If you try to ensure a long stroke, the thrust will decrease exponentially as the plunger moves away from the coil, making it impossible to achieve a large stroke and large thrust at the same time.

(6) Since the axial length of the solenoid depends on the stroke of the plunger, there is a limit to the reduction in the axial length of the entire solenoid.

The present invention overcomes the various problems described above by using a shape memory element as an energy source, and provides a linear actuator that can replace conventional solenoids.

Means for Solving the Problems As shown in the embodiments, the linear actuator of the present invention includes a support body, a plunger supported so that the support body can reciprocate in a straight line, and a plunger between the support body and the plunger. Interposed therein, the unidirectional i& is composed of a coiled shape memory element with bidirectional operating characteristics.

Since the movement required for the plunger is bidirectional, forward movement and backward movement, if a unidirectional shape memory element is not used, it may be necessary to combine it with a mechanical coil spring, for example, or use a device with different characteristics. Two unidirectional shape memory elements are used.

When a unidirectional shape memory element and a mechanical coil spring are combined, for example, the forward movement of the plunger is performed by deforming the shape memory element due to heating, and the backward movement of the plunger is performed by the force of the coil spring (piascus). At the same time, the force of this coil spring deforms the shape memory element immediately before it is heated and deformed.

In addition, when two unidirectional shape memory elements are combined, the shape memory elements with different spring characteristics are held against each other, and one of the two shape memory elements is selectively deformed by heating. This allows the plunger to move back and forth.

When using a bidirectional shape memory element.

Since the element itself has bidirectional operating characteristics, this alone allows the plunger to reciprocate.

Embodiment Figure 1 (4), @ is a diagram showing a more specific embodiment of the present invention. Figure 1 (4) shows the state in which the plunger is not extended, and ■ in the same figure shows the state before the plunger is extended. Each state is shown.

In FIG. 1, 1 is a U-shaped support, and this support 1
An outer case 3 into which an inner case 2 is slidably inserted is attached.

Furthermore, a plunger 4 that penetrates the support body 1 is slidably inserted into the inner case 2.

In the case 2.3, a coil-shaped shape memory element 6 is disposed between the head portion 5 of the plunger 4 and the support body 1.
is interposed. As is clear from the figure, the shape memory element 6 is formed of the same wire in one or two steps so that its one end and the other end have different diameters. Note that another coil-shaped shape memory element 7 is interposed between the support body 1 and the inner case 2 via a spacer 8 so as to oppose the shape memory element 6.

Both ends of the shape memory elements 6 and 7 are connected to a switch 9.
10 and variable resistors 11.12 to a DC power source 13, and by switching a switch 9.10, either one of the shape memory elements 6.7 can be selectively heated with electricity.

Reference numeral 14 denotes a support IK shadow forming nozzle for introducing a cooling medium such as nitrogen gas or liquid nitrogen in order to accelerate cooling of the shape memory element 6 after being electrically heated.

Therefore, according to the structure of the above embodiment, as shown in FIG. Accordingly, the inner case 2 extends from the outer case 3, and the plunger 4 projects from the support body 1 while compressing and deforming the shape memory element 7.

On the other hand, when the switch 10 is turned on instead of the switch 9 from the state shown in FIG. 1(4), the shape memory element 7 is heated by electricity. As a result, the shape memory element 7 returns to its original state, that is, the expanded state, and the inner case 2 is pushed back as shown in FIG. 1 (8), thereby compressing the shape memory element 6. Plunger 4 retreats. In this case, it is desirable to supply, for example, liquid nitrogen or nitrogen gas from the nozzle 14 in order to accelerate the temperature reduction of the shape memory element 6.

Please note that the shape memory elements 6.7 in Figure 1 (4) and (9)
Either one of them can be replaced with a mechanical coil spring. For example, if the shape memory element 7 is not replaced with a coil spring, the shiblunger 4 is extended by heating the shape memory element 6 with electricity, and the shape memory element 6 is
By cutting off the current supply to the plunger 4, the plunger 4 retreats due to the restoring force of the coil spring.

FIG. 2 shows another embodiment of the present invention. In this embodiment, a bidirectional shape memory element 16 and a mechanical coil spring 15 are combined.
One end of the plunger 6 is mechanically connected to the support IK, and the other end is mechanically connected to the head portion 5 of the plunger 4. The bidirectional shape memory element 16 is made by strongly processing the shape alloy itself.
Alternatively, it can be submerged by heat treatment in a restrained state, memorize the shape on the high temperature side and the low temperature side, and repeatedly deform into the shape on the high temperature side when the temperature is high and the shape on the low temperature side when the temperature is low.

To be careful, in the case of FIG. 2, the shape memory element 16 is heated by electricity, so that the shape memory element 16 extends against the force of the coil spring 15, and the plunger 4 protrudes from the support l. . On the other hand, if the power to the shape memory element 16 is cut off and, for example, liquid phoneme or nitrogen gas is supplied from the nozzle 14 to cool the shape memory element 16, the shape shown in FIG. 2 is obtained. The plunger 4 retreats due to its restoring force. In other words, according to this embodiment, if the plunger 4 reciprocates only due to the deformation of the shape memory element 16, the coil spring 15 only has the function of imparting restoring force to the inner case 2. In the case of this embodiment, there is an advantage that the stroke L of the plunger 4 can be ensured to be larger than the stroke t shown in FIG.

Effects of the Invention As described above, since the linear actuator of the present invention uses a shape memory element as an energy source, it can be made smaller and lighter than conventional solenoids.

A large stroke and large thrust can be achieved at the same time.

[Brief explanation of the drawing]

Fig. 1 (4) is a cross-sectional view showing an embodiment of the present invention, with the plunger in a non-protruding state, Fig. 1 (4) is a cross-sectional view of the plunger in Fig. 1 (4) in a retracted state, and Fig. 2 FIG. 3 is an explanatory cross-sectional view showing another embodiment of the present invention. 1... Support body, 2... Inner case, 3...
・-Outer case, 4... Plunger, 6, 7...
・Shape memory element, 15・■Coil spring, 16・
...Shape memory element. 2 people outside

Claims (1)

[Claims] (1) A support body, a plunger supported by the support body so as to be capable of linear reciprocating movement, and a coil-shaped plunger interposed between the support body and the plunger that has unidirectional or bidirectional operating characteristics. A linear actuator comprising a shape memory element.