JPS6146476A - Actuator device - Google Patents

Abstract

PURPOSE:To prevent overheat of a shape memory alloy with simple structure, by providing a positive-characteristics resistor layer through an insulating layer on a surface of a core made of a shape memory alloy, and covering the outer circumference of the resistor layer with an insulating layer. CONSTITUTION:An insulating layer 2 such as a silicone resin layer is provided on a shape memory alloy 1 such as a Ti-Ni-Cu alloy wire, and is solidified. Then, a positive-characteristics resistor layer 3 made of a mixture of conductive carbon and high molecular material is formed on the insulating layer 2. Electrodes are formed at fixed positions of the positive-characteristics resistor layer 3, and external terminals 5 are drawn out. The outer circumference of the layer 3 is covered with an insulating layer 4 such as a silicone resin layer to form an outer cover 10, thus constructing an actuator device. When engaged terminals 6 of the actuator device are engaged with operating portions of an actuator, and a power unit is connected to the external terminals 5, the outer cover 10 is heated to deform the shape memory alloy 1, thereby carrying out operation as the actuator.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an actuator element using a shape memory alloy.

Conventional Structure and Problems When a shape memory alloy (hereinafter referred to as SMA) is heated above its transformation temperature, it attempts to return to its memorized shape, causing displacement and generating force. In recent years, there has been active research and development into actuators that take advantage of this property.

Heating methods for operating this actuator include an indirect method and a direct method. The indirect method is a method in which the SMA is heated from the outside using a heater, hot air, or the like. Direct Hoke SM
This is a method that applies electricity to A and utilizes self-heating due to the electrical resistance of the SMA.

Since the characteristics of SMA deteriorate when it is overheated, it is necessary to ensure that the maximum operating temperature is not exceeded in any heating method. The maximum operating temperature is generally about 150'C when the SMA is a copper alloy, and about 20°C when the SMA is a Ni-Ti alloy. If the device is used at a temperature exceeding these temperatures, a change in the variable a temperature and a deterioration in the operational displacement will occur, making accurate control impossible.

The following two methods are known to avoid overheating. One is a lock method. In this method, after the SMA is activated by heating, the SMA's movable tt stopper is immediately locked to stop the heating.If the SMA operation is to be restored to its original state, the nutopper must be moved using another actuator. This is to release the lock.

The others are energized power control methods. In this method, the temperature of the heater or the temperature due to self-heating of the SMA is maintained at a constant temperature by controlling the current value or the interval between currents to be applied, respectively, using an electronic circuit.

These conventional methods have the following problems.

In the locking method, a locking actuator is required, resulting in a complicated structure, large size, and high cost. In the energized power control method, a separate electronic control circuit is required, which also increases the size of the system and increases the cost.

OBJECTS OF THE INVENTION The present invention solves these problems and aims to provide an actuator element that has a simple structure and prevents overheating of the SMA.

Structure of the Invention In order to achieve this object, the present invention provides a positive characteristic resistor layer on the surface of a core material made of a shape memory alloy through an insulating layer as an operating element of an actuator, and further covers the outer periphery with an insulating layer. The present invention provides a composite material in a coated configuration.

A positive characteristic resistor is a type of resistor whose electrical resistance suddenly increases by three to seven orders of magnitude when the temperature rises above the Curie temperature of the material, and is also called a PTC resistor or a PTC thermistor. Due to this property, the current flowing through the positive characteristic resistor is limited when the temperature exceeds one Curie temperature. For this reason, the temperature and rise due to self-heating of a positive characteristic resistor can be kept at a constant value of approximately one Curie temperature, and the current passing through a positive characteristic resistor is a small value corresponding to the resistance value determined by the temperature. becomes.

Barium titanate ceramics are well known as positive characteristic resistors, and mixtures of carbon and resin have also been put into practical use. In particular, the latter has a steady state resistance of 1/10
~1/100Ω, suitable for large current circuits. In either case, the Curie temperature can be changed by changing the composition and mixing ratio.

Therefore, since the heater that heats the SMA has no positive characteristic resistance, the SMA can be maintained at an appropriate temperature. Furthermore, when a positive characteristic resistor is directly electrically connected to the SMA and current is applied, the temperature of both the positive characteristic resistor and the SMA rises due to self-heating. The resistance value of the body increases suddenly, and as a result, the current flowing through the positive characteristic resistor and the SMAK decreases, self-heating is limited, and the SMA does not overheat.

In the present invention, since the SMA is in contact with the PTC resistor through the insulator, if the thickness of this insulator layer is made thin or a resin with good thermal conductivity is used, the SMA and the PTC resistor can be connected to each other through the insulator. The temperature of will be the same.

Therefore, as an actuator element operated by heating by energization, the actuator element has good responsiveness and can be miniaturized.

Description of examples Hereinafter, the present invention will be explained with reference to examples thereof.

FIG. 1 shows 1 of the actuator element in the present invention, 0
．． After setting and solidifying the silicone resin layer 3 with a thickness of 2 gg+, a positive characteristic resistor layer 3 made of a mixture of conductive carbon and a polymer material is formed, and electrodes are placed at predetermined locations on this positive characteristic resistor layer 3. The external terminals (not shown) were taken out. Then, the outer periphery of the actuator element was further covered with a silicone resin layer 4 to form an outer device 0.

FIG. 2 is an example of an external view of the same nactuator element. A linear TiN1Cu alloy wire 1 is formed with an outer device 0 including a positive characteristic resistor layer, and external terminals 5 are taken out from both ends of the outer device 0.

Locking terminals 6 are caulked at both ends of the TiN1Cu alloy wire 1. When the locking terminal 6t of this actuator element is locked to the operating part of the actuator, and the power supply is connected to the external terminal and energized, the external device 0 heats up by itself, and the TiN1Cu alloy wire 1 has a memory. It transforms into a shape, moves the operating part, and acts as an actuator.

FIG. 3 is an external view showing another actuator element of the present invention.

The one in the same figure is made of TiN1Cu with the entire coil shape as described.
An outer device including a positive characteristic resistor layer on an alloy wire 1.

The external terminals 5 are taken out from both ends of the external device 0. In this actuator element as well, the shape of the coil changes by supplying electricity to the external terminal 5, and it can be used as a driver of the actuator.

In these embodiments, only the positive characteristic resistor generates its own heat, but it is also possible to use one of the external terminals of the positive characteristic resistor by electrically connecting it to one end of the SMA. . In this case, the SMA may be used as the current passes through the positive characteristic resistor and the SMA.

Effects of the Invention Since the actuator element of the present invention integrates the SMA and the positive characteristic resistor, in a drive method that heats only the positive characteristic resistor or antibody, the heat of the positive characteristic resistor is immediately transferred to the SMA. It will be more responsive. In addition, in a drive method in which the SMA and the positive characteristic resistor are electrically connected in series and energized, the temperature rise due to the heat generated by the SMA itself is immediately transmitted to the positive characteristic resistor. Responsiveness of current control action is improved. Furthermore, in either system, overheating can be prevented by the current limiting action of the positive characteristic resistor. Furthermore, since the SMA and the positive characteristic resistor are integrated, the actuator can be made smaller, which is a practical advantage.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an actuator element of the present invention, FIG. 2 is an external view of the same actuator element, and FIG. 3 is an external view of an actuator element showing another embodiment of the present invention. 1.-1 shape memory alloy (SMA), 2.3-1 insulating layer, 4-11 positive characteristic resistor layer, 5-1 external terminal, 10-1 exterior. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2

Claims (3)

[Claims] (1) An actuator element in which a positive characteristic resistor layer is provided on the surface of a core material made of a shape memory alloy via an insulating layer, and the outer periphery is further covered with an insulating layer. (2) A positive characteristic resistor layer is provided on the surface of a core material made of a shape memory alloy via an insulating layer, the outer periphery of the positive characteristic resistor layer is further covered with an insulating layer, and current is applied between the electrodes of the positive characteristic resistor layer. The actuator element according to claim 1, which is used as a heating means for a memory alloy. (3) A positive characteristic resistor layer is provided on the surface of the core material made of a shape memory alloy through an insulating layer, and the outer periphery is further covered with an insulating layer, and one electrode of the positive characteristic resistor and a shape memory alloy layer are provided. 2. The actuator element according to claim 1, wherein the actuator element is used as heating means for the shape memory alloy by electrically connecting one end thereof and supplying current to the other electrode of the positive characteristic resistor and the other end of the shape memory alloy.