JPS59107894A - Actuator element made of shape memory alloy - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] The present invention relates to an actuator element using a coil made of a shape memory alloy, and in particular, the coil deformation based on shape recovery can be detected as a change in inductance without using an external sensor. It is something.

Various alloys are known as shape memory alloys, including (
All of them have the characteristic that when they are formed into a predetermined shape using an austenite phase, transformed into a martensite phase, and then heated, they recover to the predetermined shape formed using an austenite phase through martensitic transformation. Shape memory alloys are used in various actuator elements by taking advantage of these characteristics, and alloys made of bamboo with approximately 51 atm of Ni and the remainder of Ti, or a trace amount of additive elements are often used. Electrical heating is generally used to heat this alloy, and shape recovery begins when martensitic transformation begins due to heating, and the shape is recovered to a predetermined shape as the transformation ends, and shape recovery does not occur in the opposite direction. Therefore, in order to perform the reciprocating shape recovery operation, a reverse action spring (bias spring) is provided where the shape memory alloy is soft in the martensitic phase, and the reaustenite phase transforms into the martensitic phase due to temperature drop. The shape memory alloy is deformed again by a counteracting spring.

For shape memory alloys, especially Ni-Ti alloys, the shape recovery temperature (martensitic transformation temperature) k Ni content or N
Those adjusted by adjusting the i content and a trace amount of additive elements are used in various actuator elements, and coiled ones are the mainstream of actuator elements because they can obtain a large deformation amount. In order to perform accurate shape recovery using such an actuator element, it is necessary to detect the amount of shape recovery, and conventionally, external sensors have been used to control the shape recovery W. However, adding an external sensor to the actuator element not only prevents the actuator element from recovering its shape, but also makes it difficult to miniaturize the actuator and follow minute changes.

In view of this, as a result of various studies, the present invention is a shape memory alloy that can detect the amount of shape recovery of the shape memory alloy without measuring the amount of shape recovery using an external sensor, and can easily control the recovery #. This is a newly developed actuator element made of aluminum, which transforms into martensitic material by heating.
A high magnetic permeability member is provided inside a shape memory alloy coil that undergoes shape recovery, and coil deformation due to shape recovery is detected as a change in inductance.

This will be explained in detail using the drawings.

FIG. 1(a) shows an example of the basic structure of the device of the present invention.
A core (2) made of a high magnetic permeability material such as ferrite was inserted into the coil (1), which was formed by forming a wire rod consisting of at % and the remainder Ti into a tightly wound coil with an austenite phase and elongating it with a martensite phase. It is something.

The inductance of this coil (1) is a low value because the coil (1) is in an elongated state. When this coil (1) is fully energized and heated, the coil (1) undergoes mantenside transformation and recovers its shape into a tightly wound coil (1) formed from the austenite phase as shown in Figure 1 (b). ') will be concentrated on the core (2). As a result, the inductance of the coil (1') becomes a high value. Therefore, if the relationship between the inductance value and the amount of shape recovery is investigated in advance, it will be possible to detect the amount of shape recovery of the coil (1) by measuring the change in inductance using a bridge circuit, etc. The figure below shows an example of the amount of shape recovery, in which a tightly wound coil is formed in the austenite phase and N is stretched in the martensite phase.
A moving part (M) ffi made of i-Ti-based shape memory alloy wire was provided, and ferrite cores (2a) (2b) f were provided on the left and right sides of the moving part (M), located within coils (1a) (1b). It is something. This actuator has one coil (l
a) When electricity is applied, the coil (
As shown in Figure 2 (b), 1a) recovers its shape into a tightly wound coil core (al) formed from the austenite phase, and the movable part (M) moves to the right and concentrates on the core (2a). . As a result, the inductance of the coil (1a) becomes a high value, and the amount of shape recovery of the coil (1a) can be accurately controlled by measuring this inductance and controlling the amount of current on the basis of this measurement.

Next, when the other coil (lb')'fil- is heated with electricity, the coil (lb') changes shape due to martensitic transformation.
Raise Mt, move the movable part (M) f: to the left, and remove the coil (
la')k is stretched and returns to the state shown in FIG.

Figure 3 (A) shows another example of an actuator using the element of the present invention, in which Ni is formed into a tightly wound coil in the austenite phase and elongated in the martensitic phase as in the case in Figure 1. - A coil (1) made of a Ti-based shape memory alloy wire is arranged in a hanging manner, a ferrite core (2) is provided in the upper part of the coil (U), and a movable part (2) is provided at the lower end of the coil (1).
M) e installed. If this actuator is made to have a weight that allows the coil (1') whose shape has been recovered to be stretched again in the martensite phase, when the current is turned off and the temperature drops, the coil (1') will be stretched again and the third The state returns to the state shown in Figure (a). In such an actuator, if the amount of current is controlled by the inductance of the coil, the vertical movement of the movable part can be accurately controlled.

FIG. 4(a) shows still another example of an actuator using the element of the present invention, in which movable parts ( M
a) (Mb) k is provided between the inner actuating pieces (4a) (4b), and the Ni-4'i type shape is formed into a close-wound coil with an austenite phase and stretched with a martensitic phase as in the case of Fig. 1. The coil (1) made of shape memory wire is completely installed, the ferrite cores (2a) (2b) are provided on the inner working pieces (4a) and (4b) sides in the coil (1), and the inner working pieces (4
The reverse action spring (5) that opens in a V-shape is fully installed between the inner action pieces (4a) and (4b)'k between a) and (4b).

The file (1') is stretched again and the movable part (Ma) (M
b) Fi.

It will open. By repeating this, the movable part (Ma
) (Mb) will be repeatedly opened and closed, and if the energization is controlled by the inductance of the coil (1) during this repeated operation, the opening and closing of the movable part can be accurately controlled.

In both cases, we have explained an example in which a high magnetic permeability member is placed inside a coil made of a shape memory alloy, but the invention is not limited to this. A high magnetic permeability member should also be placed on the outer periphery of the coil, and when the coil is restored to its shape. If a magnetic closed circuit is formed using high magnetic permeability members inside and outside, leakage of magnetic flux will be reduced, and shape recovery of the coil can be detected as a clear increase in inductance. In addition, the device of the present invention performs Joule heating by energization to restore the shape of the coil and high-frequency energization for inductance detection. In this way, according to the device of the present invention, it is possible to control the amount of shape recovery by using the shape memory alloy itself as a sensor.・
This makes it possible to achieve significant industrial effects such as making the actuator smaller and making it easier to follow minute changes.

[Brief explanation of drawings]

Figures 1 (a) and 1 (b) show an example of the basic structure of the element of the present invention, (a) is an explanatory diagram of the element before shape recovery, and (b)
are explanatory diagrams after shape recovery, Figures 2 (a), (b), and 3 (
A) (B) and Figure 4 (A) (tllI) respectively show actuators using the element of the present invention, where 0) is an explanatory diagram before shape recovery, and (B) is an explanatory diagram after shape recovery. It is. 1, la, lb... Coil 1' before shape recovery
, 18', 1b'...Coil 2.2a after shape recovery,
2b... High permeability core 3...
・・・・・・・・・・・・Axis 4 ・・・・・・・・・・・・
・・・・・・・・・・・・ Actuation piece 5 ・・・・・・・・・
・・・・・・・・・Reverse action spring M, Ma, Mb・
····· movable part

Claims (1)

[Claims] A shape memory alloy actuator element characterized by providing a high magnetic permeability member inside a shape memory alloy coil that undergoes shape recovery due to martensitic transformation due to heating, and detecting coil deformation due to shape recovery as a change in inductance. .