JPH1038708A - Shape memory alloy actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a shape memory alloy actuator in which the working temperature is widened while eliminating fluctuation in the working point due to temperature fluctuation by employing a shape memory alloy spring as one drive source and a parallel bias spring of a super resilient allay spring material and a resilient metal spring material as the other drive source. SOLUTION: A resilient alloy spring 12 is coupled in parallel with a super resilient alloy spring 13 to produce a bias spring 14. A shape memory allay spring 11 is composed of a Ti50Ni50 alloy and produced through ordinary hot working and cold working. A sample thereof is fixed at one end thereof and boded, at the other end thereof, to one end of the bias spring 14. The bias spring 14 is stretched and strain is applied to the shape memory alloy spring 11 and then the bias spring 14 is fixed at the other end thereof. Since a super resilient alloy element is employed in combination with a conventional spring material in the bias spring for recovering a shape memory alloy element, the working temperature can be set freely over a wide range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a shape memory alloy actuator.

[0002]

2. Description of the Related Art In recent years, actuators using a shape memory alloy element have received a great deal of attention, and various proposals have been made from ideas of heat engines and robot hands to practical products such as ventilation equipment for houses.

The operating principle of a shape memory alloy actuator is as follows. When a certain set temperature is reached, the shape memory alloy undergoes a reverse transformation of the martensitic transformation and recovers to a previously memorized shape. In other words, if the environmental temperature of the shape memory alloy itself or the shape memory alloy exceeds the set temperature,
It operates by generating a load difference with the shape recovery. If the actuator is used repeatedly,
A bias circuit is required for recovery after operation.

A feature of the shape memory alloy actuator is that the shape memory alloy element itself has both a temperature sensor function and an actuator function, so that the number of parts can be reduced, so that the actuator can be downsized. .

However, in spite of having such features, few of them are actually put to practical use.

[0006]

There are two main reasons why the practical application is delayed as described above. First
The reason is that the shape memory alloy slightly fluctuates in stress value due to a change in environmental temperature, and the length of the shape memory alloy element fluctuates accordingly, whereas the bias spring does not have such temperature characteristics. It is in.

That is, since the displacement due to the temperature change of the shape memory alloy becomes the displacement of the operating point as it is, it causes a malfunction as an actuator.

[0008] The second reason is that TiNi-based and Cu-based alloys are typical of shape memory alloys that have been put into practical use so far, and the transformation temperature of these alloys is minus 100 ° C to 80 ° C for TiNi-based. And a Cu-based alloy of 10 to 1
In addition to the temperature range of 60 ° C., when a bias circuit is provided, the shape memory alloy actuator (actually operates the shape memory alloy actuator) because the generated force (load difference) of the shape memory alloy is consumed to change the bias. The temperature range is narrowing.

That is, the use of a shape memory alloy as an actuator is limited to a certain limited temperature range.

The above two reasons are factors preventing the practical use of an actuator using a shape memory alloy. An object of the present invention is to provide a shape memory alloy actuator having a wide operating temperature range without displacement of an operating point due to a temperature change.

[0011]

According to the present invention, there is provided a shape memory alloy actuator which performs a reversible operation according to a temperature change, wherein one of the driving sources is constituted by a shape memory alloy spring having a shape memory effect, and A shape memory characterized in that the other of the sources is constituted by a bias spring comprising a parallel combination of a superelastic alloy spring material having a superelastic effect and an elastic metal spring material having a spring force selected according to a use temperature range. An alloy actuator is obtained.

According to the present invention, there is provided a shape memory alloy actuator characterized in that the superelastic alloy spring material is a superelastic alloy spring material whose spring force is adjustable.

[0013]

FIG. 1 shows a configuration of a shape memory alloy actuator according to an embodiment of the present invention. In the figure, 11 is a shape memory alloy spring, 12 is a conventionally used elastic alloy spring, and 13 is a superelastic alloy spring particularly used in the present invention. Elastic alloy spring 12 and superelastic alloy spring 1
3 are connected in parallel to form a bias spring 14.

The shape memory alloy spring 11 is made of Ti50Ni50
Alloy with a diameter of 75μ by normal hot working and cold working
m A line having a length of 50 mm was prepared. This line was linearly stored at a predetermined temperature for 30 minutes to prepare a sample.

One end of the sample is fixed, the other end is joined to one end of the bias spring 14, and the bias spring 14 is pulled. Fix the other end. The superelastic alloy spring 13 is made of Ti49Ni51 (φ40 μm, 40 m
m), the stress value required for distorting the shape memory alloy spring 11 by 1% is approximately 2%.
% In the range of 5% to 5%.

FIG. 2 shows the generated load of each of the above-mentioned springs. The generated load A of the superelastic alloy spring 13 increases almost linearly with an increase in temperature. When the elastic alloy spring 12 is, for example, a spring material made of stainless steel, the generated load B of the spring does not change with temperature. The sum of the generated loads of the two springs indicates the generated load C of the bias spring 14. D indicates the generated load of the shape memory alloy spring 11. The transformation temperature of the shape memory alloy spring 11 is martensite transformation start temperature Ms = 33 ° C., end temperature Mf = 14 ° C., reverse transformation start temperature As = 50 ° C., end temperature Af = 70 ° C.

By using the conventional spring material 12 and the superelastic alloy spring 13 in combination with the bias, the operating temperature T1 when the conventional spring material is used alone as the bias spring is reduced by T2. It will move up to. That is, the operating temperature range can be easily expanded by changing the spring force by changing the manufacturing conditions and the wire diameter.

The operating temperature can be changed even when the load generated by the shape memory alloy spring 11 is changed, and the operation has been conventionally performed. Even if the angle of the line D is changed by changing the load, the temperature does not change much from T1, so that the operating temperature range cannot be widened. Therefore, it is necessary to manufacture various elements having different temperature ranges. However, this diversification is not industrially favorable.

[0019]

As described above, in the actuator according to the present invention, by using a superelastic alloy element in combination with a conventional spring material as a bias for recovering after the shape memory alloy element is operated, The operating temperature can be set arbitrarily in a wide range.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between an operating temperature and a generated load in each configuration of the configuration example of FIG.

[Explanation of symbols]

 11 Shape memory alloy spring 12 Conventional spring 13 Super elastic alloy spring 14 Bias spring A Super elastic alloy spring B Conventional spring C Conventional spring + super elastic alloy spring D Shape memory alloy spring

Claims (2)

[Claims] 1. A shape memory alloy actuator performing a reversible operation according to a temperature change, wherein one of the drive sources is formed of a shape memory alloy spring, and the other of the drive sources is formed of a superelastic alloy spring material and an elastic metal spring material. A shape memory alloy actuator comprising a bias spring formed of a parallel combination. 2. The shape memory alloy actuator according to claim 1, wherein said superelastic alloy spring material is a superelastic alloy spring material whose spring force is adjustable.