JPH06138264A - Actuator - Google Patents

Abstract

PURPOSE:To prevent fluctuation of an operating point by using a shape memory material with superelastic characteristics as the return spring of an actuator driven by the shape memory material. CONSTITUTION:An actuator comprises a shape memory alloy 1 and a superelastic material 2 both of which have one end secured and are joined together at the other ends in such a manner as to pull a weight 3 from each other. The shape memory alloy 1 is composed of Ti 50 and Ni 50 and is fabricated by hot and cold working so as to have a diameter of about 75mu and a length of about 50mm and by processing for 30 minutes. The superelastic material 2 is composed of Ti 49 and Ni 51 and about 40mu in diameter and about 40mm in length, having the stress value required for deflecting the alloy 1 by 10% and showing superelasticity in the range of about 2 to 5% of the amount of deflection, while matching with the stress values in the range where it shows superelasticity. When current is made to flow through the alloy 1, the alloy 1 is heated to provide a certain generative force and the spring action of the superelastic material 2 enables effective use of the generative force, so that the operating point of the actuator is seldom varied even with changes in ambient temperature and that the actuator exhibits stable characteristics.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to actuators.

[0002]

2. Description of the Related Art In recent years, shape memory alloy elements (hereinafter referred to as SMA
It is activated by applying an electric current to
Actuators for driving weights have recently attracted attention from various fields. For example, when this actuator is applied to automobile parts, it also functions as a temperature sensor, so there are many proposals from which large effects can be expected in the sense of reducing the number of parts. The reality is that very few are present.

The operating principle of an actuator using SMA will be described. When the operating temperature is near room temperature, the reverse transformation point start temperature As when heating the SMA by passing an electric current through it
It does not operate up to the vicinity of the point, but operates due to a large stress difference (stress difference generated before and after energization of SMA, in other words, load difference) in the range from that temperature to the reverse transformation point end temperature Af. To do.

Further, generally, a stainless spring is used as a bias spring for recovering the original position after the actuator is operated.

[0005]

However, when a stainless spring whose size and shape hardly change due to temperature change is used, the generated force that can be used when the SMA is actually operated (heating method depends on energization). In some cases, the stress difference or load difference before and after energization is also used for deforming the stainless spring, so that there is a drawback in that the generated force for driving the weight becomes considerably small.

In addition, the stress value of SMA fluctuates due to the change of environmental temperature, and the length of SMA fluctuates accordingly.
On the other hand, since the stainless steel spring does not have such temperature characteristics, there is a drawback that a change in displacement due to the temperature of the SMA directly causes a change in the operating point (the operating position and the joint portion), which causes a malfunction.

Therefore, a technical object of the present invention is to obtain an actuator in which the generated force for driving the weight can be effectively utilized and the operating point hardly changes even when the environmental temperature changes.

[0008]

According to the present invention, a member made of a shape memory alloy whose shape changes with temperature changes is used as a drive source for displacing a driven part, and a spring for restoring the drive source is used. In the actuator provided, an actuator characterized in that a shape memory material having superelasticity is used as the spring is obtained.

In this actuator, an actuator is obtained, characterized in that the member is a shape memory alloy which itself generates heat when an electric current is applied to the member and exhibits a shape memory effect.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An actuator according to an embodiment of the present invention will be described below with reference to the drawings.

With reference to FIG. 1, an actuator according to an embodiment of the present invention has a shape memory alloy material 1 in which one end is fixed and the other end is joined so as to hold a weight (load) 3 respectively.
And a super elastic material 2.

The shape memory alloy material 1 is an alloy of Ti50Ni50, and is φ75 μ × 50 by ordinary hot working and cooling working.
It is manufactured by treating the wire with a linear shape of mm for 30 minutes.

On the other hand, the super elastic material 2 is made of Ti49Ni51.
(Φ40 μ × 40 mm), which has a stress value (load value) necessary for straining the shape memory alloy material 1 by 1% and exhibits superelasticity in a strain amount range of about 2% to 5%. It is made to match the stress value in the range of the state showing superelasticity.

When an electric current is passed through the shape memory alloy material 1, heat is generated in the shape memory alloy material 1 itself, and a certain generated force (80 g) in the shape memory alloy material 1 is obtained. The value of the electric current passed at this time is shown in Table 1 in comparison with that of the conventional stainless spring. Since the stainless steel spring has a spring constant of 10 gf / mm and hardly changes even when the temperature changes, the position of the above-mentioned joint hardly changes in the operating temperature range.

[0015]

[Table 1]

The actuator according to the embodiment of the present invention is
The change in the position of the operating point when the temperature was changed from 50 ° C to 50 ° C was also tested with the position at 25 ° C as the reference point. The shape memory alloy material 1 has a transformation point at a temperature M at which the transformation from the austenite state to the martensite state starts.
s point = 33 ° C., temperature at which this transition ends Mf point = 14 ° C.,
A temperature at which the reverse transformation, which is a transformation from the martensite state to the austenite state, starts at As point = 50 ° C. and Af point at which this transformation ends = 70 ° C. was used.

The results are shown in Table 2 below. "+" Indicates that the neutral point has shifted to the shape memory alloy material 1 side, and "-" indicates that it has shifted to the opposite side.

[0018]

[Table 2]

Comparing the embodiment of the present invention with the stainless steel of the comparative example, it is apparent that the working point (origin position for actuation) of the present invention is remarkably changed in spite of the fact that the embodiment of the present invention is changed. It can be seen that the actuator according to (1) hardly changes and is very stable even if the environmental temperature changes.

[0020]

According to the present invention, by using a super elastic material as a bias spring for recovering the original position after the operation, the generated force for driving the weight can be effectively utilized, and the ambient temperature can be effectively used. Has the effect of exhibiting stable characteristics with almost constant load and displacement characteristics, with almost no change in the operating point.

[Brief description of drawings]

FIG. 1 is a principle diagram of an actuator according to an embodiment of the present invention.

[Explanation of symbols]

 1 Shape memory alloy material 2 Super elastic material 3 Weight (load)

Claims (2)

[Claims] 1. An actuator comprising a member made of a shape memory alloy, the shape of which changes with temperature change, as a drive source for displacing a driven part, and a spring for restoring the drive source, wherein the spring is An actuator characterized by using a shape memory material having elastic characteristics. 2. The actuator according to claim 1, wherein the member is a shape memory alloy exhibiting a shape memory effect by itself generating heat when an electric current is applied to the member.