JPH07247954A - Shape memory actuator - Google Patents

Abstract

PURPOSE:To provide a shape memory actuator which does not prevent the deformation of the shape memory alloy without disconnection or plastic deformation of an electrothermal conversion element. CONSTITUTION:An actuator is provided with a flat plate shaped shape memory alloy where the bi-lateral shape memory treatment is realized, a flexible electrothermal conversion plate 14 which is arranged thereon in a stacked manner, and a working member 22 which is bent according to the deformation of the shape memory alloy 12. The working member 22 is provided with a pair of hinged structural bodies 24 connected in a bendable manner by a connecting and pivotably fitting part 26. The shape memory alloy 12 and a holding part 28 to hold the electrothermal conversion plate 4 in a slidable manner are provided at the end part of the respective hinged structural bodies 24. The electrothermal conversion plate 14 is provided with a metallic sheet resistor body which is a heating body, a flexible organic insulating film to cover the resistor body, and an electrode pad which is provided on the surface of the resistor body and electrically connected to the metallic film resistor body.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an actuator using a thermodynamic conversion element such as a shape memory alloy.

[0002]

2. Description of the Related Art Shape memory alloys are advantageous in terms of miniaturization because the material itself functions as an actuator, and are attracting attention as actuators in the field of micromachines. As the heating method of the shape memory alloy, there are a direct heating method in which an electric current is directly applied to the shape memory alloy and heating is performed by the generated Joule heat, and an indirect heating method in which an external temperature is changed or a heater provided separately is used. is there. An example of using the indirect heating method is, for example, JP-A-5-7.
As disclosed in Japanese Patent No. 4054, there is known a fiberscope in which a shape memory alloy and an electrothermal conversion element are inserted.

[0003]

Since the actuator using the shape memory alloy by the electric heating method uses Joule heat, the electric resistance of the shape memory alloy itself is sufficiently larger than that of the wiring supplying the current. Is desirable.
However, when the shape memory alloy is miniaturized, the electric resistance of the shape memory alloy is inevitably lowered, and thus it is difficult to form a wiring having an electric resistance sufficiently smaller than that. Moreover, since a current is directly applied to the shape memory alloy, it is necessary to insulate the shape memory alloy depending on the place of use.

Among the actuators using the indirect heating method, those that change the external temperature, such as utilizing the temperature difference between hot water and cold water, need to have a high temperature portion and a low temperature portion, so that the entire actuator is It gets bigger.
Further, since it is not possible to control only the temperature of the shape memory alloy and the entire temperature of the shape memory alloy is changed, the heat capacity is large and therefore the responsiveness as an actuator is poor. Furthermore, since it is necessary to greatly change the overall temperature, when various materials are used, problems such as deflection due to stress occur due to the difference in thermal expansion coefficient.

Further, as disclosed in Japanese Patent Publication No. 5-74054, in the case where the shape memory alloy and the heating wire are inserted in the fiberscope, the heat radiation from the heating wire to the fiberscope is large and the shape memory alloy is efficiently used. It is difficult to heat well. Further, four shape memory alloys are inserted around the center of the fiberscope body at intervals of 90 degrees, and there are two heating wires, each of which is along two shape memory alloys facing each other with respect to the center. Are provided in a loop. When a pair of shape memory alloys arranged along the heating wire is heated by reaching the transformation temperature by energizing one heating wire, each of the shape memory alloys is bent in a certain direction. Therefore, the strain due to the bending deformation of the shape memory alloy is likely to be directly transmitted to the heating wire, and the heating wire made of a general metal other than the shape memory alloy is likely to be plastically deformed or broken beyond the elastic deformation region. Further, when the heating wire is thick, for example, and is not subject to such deformation, the mechanical strength of the heating wire hinders the bending deformation of the shape memory alloy, so that the deformation force and the amount of deformation of the shape memory alloy can be efficiently externalized. Difficult to tell.

An object of the present invention is a shape memory actuator provided with a shape memory alloy and an electrothermal conversion element, wherein the electrothermal conversion element is free from disconnection or plastic deformation, and does not hinder the deformation of the shape memory alloy. It is to provide a memory actuator.

[0007]

A shape memory actuator of the present invention is a shape memory alloy plate that stores a shape memory so as to be deformed by a temperature change, and a flexibility for giving a temperature change to the shape memory alloy plate. And an operating member that bends according to the deformation of the shape memory alloy plate,
The actuating member is slidable in a state in which a pair of joint structures that are bendably connected by a connecting pivot portion and one shape memory alloy plate and one electrothermal conversion plate that are provided in each joint structure are overlapped. And a holding portion that holds the movable portion.

[0008]

In the shape memory actuator of the present invention, the strain applied to the electrothermal conversion plate is relieved by the sliding of the electrothermal conversion plate against the large deformation of the shape memory alloy plate. Therefore, the electrothermal conversion plate is not plastically deformed or broken. Moreover, the sliding effect of the electrothermal conversion plate and the holding portion has a small effect of hindering the deformation of the shape memory alloy plate,
Therefore, the deformation force and the deformation amount of the shape memory alloy plate can be efficiently transmitted to the outside. Furthermore, since the electrothermal conversion plate is not separated from the shape memory alloy by the plurality of holding portions, and the electrothermal conversion plate is not in direct contact with other than the holding portion,
The heat generated by the electrothermal conversion plate is efficiently transferred. This makes it possible to obtain an actuator with excellent responsiveness that can efficiently transmit the deformation force and the deformation amount of the shape memory alloy plate.

[0009]

Embodiments of the present invention will now be described with reference to the drawings. A shape memory actuator according to a first embodiment of the present invention will be described with reference to FIGS.

The shape memory actuator of this embodiment is
As shown in FIG. 1, it has a flat shape memory alloy 12, a flexible electrothermal conversion plate 14 placed on top of this, and an actuating member 22 that makes a bending motion according to the deformation of the shape memory alloy 12. ing.

The shape memory alloy 12 is made of Ti--Ni or Au--.
It has a composition such as Cd and is subjected to, for example, bidirectional shape memory processing. The actuating member 22 has a pair of joint structures 24 that are flexibly connected by a connecting pivot portion 26. At each end of each joint structure 24,
A holding portion 28 that slidably holds the shape memory alloy 12 and the electrothermal conversion plate 14 is provided.

As shown in FIG. 2, the electrothermal conversion plate 14 includes a metal thin film resistor 18 which is a heating element, a flexible organic insulating film 16 which covers the metal thin film resistor 18, and a metal thin film resistor 18 which is provided on the surface thereof. It has an electrode pad 20 electrically connected to. The flexible organic insulating film 16 is made of a material having heat resistance and mechanical strength, such as polyimide, and is used for the electrode pad 2
0 is made of a conductive metal material such as aluminum.
A lead wire (not shown) connected to a power supply device (not shown) is connected to the electrode pad 20 by wire bonding, soldering, or the like.

The metal thin film resistor 18 is made of, for example, Ti or P.
t, made of metal such as Ni-Cr, and as shown in FIG.
The shape memory alloy 12 is patterned in a loop shape so as to efficiently heat the shape memory alloy 12.

Next, the operation will be described. When power is supplied to the metal thin film resistor 18 via the lead wire from the above-described power supply device, the metal thin film resistor 18 generates Joule heat. The heat generated in the metal thin film resistor 18 is transmitted to the shape memory alloy 12 through the flexible organic insulating film 16 and heats it. As a result, the temperature of the shape memory alloy 12 rises, and when it reaches the transformation temperature, as shown in FIG. 4, the shape memory alloy 12 is deformed into the shape on the high temperature side stored in advance. This shape memory alloy 1
Due to the deformation of 2, the joint structure 24 rotates about the connecting and pivoting portion 26 as an axis, and the actuating member 22 is deformed into a dogleg shape as a whole.

Further, when the power supply to the metal thin film resistor 18 is stopped, the temperature of the shape memory alloy 12 and the electrothermal conversion plate 14 is lowered by heat radiation, and the shape memory alloy 12 is stored in the shape on the low temperature side stored in advance. Return to a straight shape. As a result, the operating member 22 returns to the straight shape as shown in FIG.

As described above, since the electrothermal conversion plate 14 is not fixed to the shape memory alloy 12 and can slide, the shape memory alloy 12 and the electrothermal conversion plate 14 slide when the shape memory alloy 12 is heated. Transforms with. Shape memory alloy 12
Shows a larger strain deformation than a general metal, but since the shape memory alloy 12 and the electrothermal conversion plate 14 slide, an excessive force is not applied to the electrothermal conversion plate 14 due to the strain deformation of the shape memory alloy 12. Therefore, the electrothermal conversion plate 14 is not broken or plastically deformed. In other words, since the shape memory alloy 12 and the electrothermal conversion plate 14 slide, the mechanical strength of the electrothermal conversion plate 14 is determined by the shape memory alloy 1.
2 does not hinder the deformation of the shape memory alloy 12
The bending deformation force or the amount of bending deformation is efficiently transmitted to the outside.

Of course, the configuration of each part of this embodiment may be modified or changed as necessary. For example, in the embodiment, the two holding portions 28 are both the shape memory alloy 12 and the electrothermal conversion plate 14.
Although it was held slidably, one holding portion 28 may be fixed so as not to slide. With this configuration, the bending angle on the opposite side can be increased.
Alternatively, the shape memory alloy 12 may be a shape memory alloy plate that has undergone shape memory processing so as to expand and contract, and this may be fixed and held by the two holding portions 28. With this configuration,
The expansion and contraction deformation of the shape memory alloy can be converted into bending deformation.

Next, a shape memory actuator according to a second embodiment of the present invention will be described with reference to FIG. In this embodiment, as shown in FIG. 4, in addition to the structure of the first embodiment, a ring-shaped holding member 30 for holding the shape memory alloy 12 and the electrothermal conversion plate 14 between the two holding portions 28. Is provided. The holding member 30 includes two holding portions 2
It is preferable to be arranged in the middle of 8. Further, it may be mechanically bonded to either the shape memory alloy 12 or the electrothermal conversion plate 14.

By providing the holding member 30, the electrothermal conversion plate 14 does not separate from the shape memory alloy plate 12 when the shape memory alloy plate 12 is bent and deformed, and the electrothermal conversion plate 14 is always formed. Since it is slidably in contact with 12, the heat generated in the electrothermal conversion plate 14 is efficiently transferred to the shape memory alloy plate 12. Therefore, it is possible to obtain an actuator which is excellent in responsiveness and requires less power consumption of the electrothermal conversion plate 14.

The shape memory actuator of the third embodiment of the present invention will be described with reference to FIG. In the figure, members indicated by the same reference numerals as those in FIG. 1 are indicated as the same members as those described in the first embodiment.

The shape memory actuator of this embodiment is
As shown in FIG. 6, a flat shape memory alloy 12 subjected to a bidirectional shape memory treatment, a thin-film flexible electrothermal conversion plate 14, and an operation of bending according to the deformation of the shape memory alloy 12. It has a member 32.

The actuating member 32 has a pair of joint structures 34 that are rotatably connected by a connecting / pivoting portion 36. The joint structure 34 has a key-like holding portion 38 having a gap.
The shape memory alloy 12 and the electrothermal conversion plate 14 are slidably inserted into the gap.

When power is supplied to the electrothermal conversion plate 14 from a power supply device (not shown), the temperature of the shape memory alloy 12 rises, and when the transformation temperature is reached, the shape memory alloy 12 bends. After that, when the electrode supply is stopped and the temperature of the shape memory alloy 12 becomes lower than the transformation temperature, the shape memory alloy 12 returns to the straight state again. When the shape memory alloy 12 is deformed, the electrothermal conversion plate 14 is deformed while sliding on the contact surface of the shape memory alloy 12. Both ends of the joint structure 34 of the actuating member 32 move in the directions indicated by the arrows as the shape memory alloy 12 is curved and deformed.

In the actuator of this embodiment, as in the first embodiment, the electrothermal conversion plate 14 is free from the risk of being plastically deformed or damaged, and the deformation force and the deformation amount of the shape memory alloy 12 are the same as the bending force of the operating member 32. Efficiently converted to bending amount. Also,
When the joint structure 34 is composed of a tubular member, an optical fiber or a gripping tool can be inserted into the joint structure 34 to be used as a tubular manipulator.

Next, a shape memory actuator of a fourth embodiment of the present invention will be described with reference to FIG. In the figure, the members denoted by the same reference numerals as those in FIG. 6 are the same members as those in the third embodiment.

The shape memory actuator of this embodiment is
As shown in FIG. 7, a flat shape memory alloy 12 that has been subjected to bidirectional shape memory processing, a thin-film flexible electrothermal conversion plate 14, and an operation that bends according to the deformation of the shape memory alloy 12. It has a member 32.

The actuating member 32 has a pair of joint structures 34 that are rotatably connected by a connecting pivot 36. The shape memory alloy 12 and the electrothermal conversion plate 14 are joint structures 3
4 is arranged on the outer side of the sheet 4 and is held by a coil spring 40 surrounding it. Of course, the shape memory alloy 12 has a deforming force larger than the elastic force of the coil spring 40.

In the actuator of this embodiment, the elastic force of the coil spring 40 hinders the deformation from the straight state on the low temperature side to the bent state on the high temperature side.
When deforming from a bent state on the high temperature side to a straight shape on the low temperature side, it assists the deformation and speeds up the deformation. Other than that, the same effect as the third embodiment can be obtained.

Modifications of the shape memory alloy 12 and the electrothermal conversion plate 14 in the above-mentioned four embodiments will be described below with reference to FIGS. 8 to 10. That is, the modifications described below can be applied to any of the above-described embodiments.

First, the first modification will be described with reference to FIG. In this modification, an oil-based lubricant 42 is filled between the shape memory alloy plate 12 and the electrothermal conversion plate 14.
As the oily lubricant 42, one having good thermal conductivity is preferable, and as such an example, for example, silicon grease can be cited.

The oil-based lubricant 42 reduces the sliding resistance between the shape memory alloy plate 12 and the electrothermal conversion plate 14, contributes to the improvement of the responsiveness of the actuator, and the shape memory alloy plate 1
2 and the electrothermal conversion plate 14 are brought into close contact with each other to prevent separation due to bending deformation.

Next, a second modification will be described with reference to FIG. In this modification, the electrothermal conversion plate 14 is provided with the solid lubricant 44. Examples of the solid lubricant 44 include a metal thin film and an organic coating film. The metal thin film is formed by depositing nickel, for example, by electroless plating. Examples of the material of the organic coating film include polyparaxylylene.

Since the sliding resistance of a solid is affected by the hardness of the surface, by providing the solid lubricant 44 on the flexible organic insulating film 16 which is soft such as polyimide, the shape memory alloy plate 12 and the electrothermal conversion can be converted. The sliding resistance of the plate 14 is reduced, and the deformation force and the deformation amount generated in the shape memory alloy plate 12 can be transmitted to the outside with low loss. Further, by providing the solid lubricant 44, it is possible to prevent the flexible organic insulating film 16 from being broken due to sliding and breaking the metal thin film resistor 18 or causing an electrical short circuit.

Next, a third modification will be described with reference to FIG. In this modification, a metal film 46 having an appropriate film thickness and good thermal conductivity is joined to the electrothermal conversion plate 14. The metal film 46 is formed by depositing copper or the like by electroless plating or the like. The film thickness is optimized by the amount of strain applied to the metal thin film resistor 18.

By the way, the electric resistance of the metal thin film resistor 18 changes due to the strain. Therefore, the metal thin film resistor 18 can be used as a strain gauge by sensing the change in the electric resistance.
However, in the structure as in the first embodiment, since the shape memory alloy plate 12 and the electrothermal conversion plate 14 slide, the metal thin film resistor 18 bends and deforms, but is located at the bending center of the electrothermal conversion plate 14. Not distorted to do.

By providing the metal film 46 on the electrothermal conversion plate 14 as in this modification, the metal thin film resistor 18 is distorted by the bending deformation of the shape memory alloy plate 12. Therefore, the amount of strain can be measured by sensing the electrical resistance change of the metal thin film resistor 18.

Since the electric resistance of the metal thin film resistor 18 is affected by temperature, it is desirable to provide a plurality of metal thin film resistors 18 to form a bridge circuit and measure temperature-compensated strain. In that case, since it can also be used as a temperature sensor, the temperature of the electrothermal conversion plate 14 can also be measured.

By using this modified example, when used in a shape memory actuator having a joint structure as in the third embodiment, for example, the bending angle of the joint structure can be calculated from the amount of distortion, so that the positioning accuracy is good. Operation becomes possible. Further, since the metal film 46 is provided, the heat of the electrothermal conversion plate 14 is uniformly transferred to the shape memory alloy plate 12,
There is also an advantage that the positional deformation irregularity and the temporal deformation irregularity of the shape memory alloy plate 12 become small, and the operation as an actuator becomes smooth.

Considering the above-mentioned four embodiments, the present invention can be summarized as follows. 1. A shape memory alloy plate that has a shape memory so as to be deformed by a temperature change, a flexible electrothermal conversion plate for giving a temperature change to the shape memory alloy plate, and a shape memory alloy plate that bends according to the deformation of the shape memory alloy plate. And a shape memory alloy plate and an electrothermal converter, each of which is provided with a pair of joint structures that are flexibly connected by a connecting and pivoting portion. A shape memory actuator, comprising: a holding portion that slidably holds the plates in a stacked state.

With this configuration, the strain applied to the electrothermal conversion plate by sliding the electrothermal conversion plate against the large deformation of the shape memory alloy plate is alleviated. Therefore, the electrothermal conversion plate is not plastically deformed or broken. Further, sliding of the electrothermal conversion plate and the holding portion has a small effect of hindering the deformation of the shape memory alloy plate, so that the deforming force and the amount of deformation of the shape memory alloy plate can be efficiently transmitted to the outside. Furthermore, since the electrothermal conversion plate is not separated from the shape memory alloy by the plurality of holding parts and the electrothermal conversion plate is not in direct contact with other parts than the holding parts, the heat generated by the electrothermal conversion plate is efficiently transferred. . This makes it possible to obtain an actuator with excellent responsiveness that can efficiently transmit the deformation force and the deformation amount of the shape memory alloy plate.

2. The shape memory actuator according to claim 1, further comprising a holding member that holds the shape memory alloy and the electrothermal conversion plate between the two holding portions in a fixed or slidable manner.

By providing the holding member in this way,
When the shape memory alloy plate is deformed, it is possible to prevent the shape memory alloy plate and the electrothermal conversion plate from being separated from each other at a portion which is not held by the holding portion, thereby lowering the thermal conductivity. Thereby, the heat generated in the electrothermal conversion plate is efficiently transferred to the shape memory alloy plate.

3. The shape memory actuator according to claim 1 or 2, wherein a lubricating material that reduces friction is provided between the shape memory alloy plate and the electrothermal conversion plate. By providing the lubricating material in this manner, sliding friction between the shape memory alloy plate and the electrothermal conversion plate is reduced. As a result, the force required for flexural deformation is reduced, smooth operation is obtained, and the generated force and deformation amount of the shape memory alloy plate are efficiently transmitted to the outside.

4. The shape memory actuator according to claim 3, wherein the lubricating material is an oil-based lubricant. By filling the space between the shape memory alloy and the electrothermal conversion plate with the oil-based lubricant, the two do not come into direct contact with each other, so that the lubricity is improved and the sliding resistance is reduced. Thereby, a smooth operation is obtained, and the generated force and the deformation amount of the shape memory alloy plate are efficiently transmitted to the outside. In addition, since the oil-based lubricant makes the shape memory alloy plate and the electrothermal conversion plate adhere to each other, the heat generated by the electrothermal conversion plate can be efficiently shaped, especially when silicon grease having high thermal conductivity is used as the oil-based lubricant. It is transmitted to the memory alloy plate. This is preferable for improving the response of the actuator and reducing the power consumption.

5. The shape memory actuator according to claim 3, wherein the lubricating material is a metal thin film coated on the electrothermal conversion plate. In general, by coating the electrothermal conversion plate whose surface is a flexible organic insulating film with a metal thin film, sliding friction between the shape memory alloy plate and the electrothermal conversion plate is reduced. As a result, the force required for flexural deformation is reduced, smooth operation is obtained, and the generated force and deformation amount of the shape memory alloy plate are efficiently transmitted to the outside. Further, since the solid lubrication is used, the effect is semipermanently maintained, so that the durability as an actuator is improved.

6. The shape memory actuator according to claim 3, wherein the lubricating material is an organic coating film coated on the electrothermal conversion plate. Generally, by coating the electrothermal conversion plate whose surface is a flexible organic insulating film with an organic coating film, sliding friction between the shape memory alloy plate and the electrothermal conversion plate is reduced. As a result, the force required for flexural deformation is reduced, smooth operation is obtained, and the generated force and deformation amount of the shape memory alloy plate are efficiently transmitted to the outside. In particular, when a hard organic material having excellent insulating properties such as polyparaxylylene is used as the material of the organic coating film, it is effective in preventing a leak current from a pinhole or a crack of the flexible organic insulating film.

7. The shape memory actuator according to any one of claims 1 to 6, wherein a surface of the electrothermal conversion plate that contacts the shape memory alloy plate is plated with a metal film. When the electrothermal conversion plate is deformed according to the deformation of the shape memory alloy, the metal thin film resistor, which is the heating element of the electrothermal conversion plate, is distorted by being removed from the bending center due to the thickness of the metal film provided on the electrothermal conversion plate. Receive. Since the electric resistance of the metal thin film resistor changes due to this strain, it can be used as a strain gauge by sensing the electric resistance change. Therefore, since the bending deformation amount of the actuator can be calculated from the strain by measuring the strain of the electrothermal conversion plate, accurate position control becomes possible.

8. The shape memory actuator according to any one of claims 1 to 7, wherein the electrothermal conversion plate includes a metal thin film resistor and a flexible organic insulating film that covers the metal thin film resistor. The flexible organic insulating film preferably has heat resistance, and examples of such a material include polyimide. Since the metal thin film resistor is covered with the organic insulating film, the electrothermal conversion plate can be placed in contact with the shape memory alloy plate that has not been subjected to insulation treatment, and heat can be efficiently transferred. Further, since the electrothermal conversion plate is in the form of a thin film, it has a low mechanical strength, and since it has flexibility, it has a small effect of hindering the deformation of the shape memory alloy plate. As a result, the deformation force and the deformation amount of the shape memory alloy plate can be efficiently transmitted to the outside, and thus an actuator having excellent responsiveness can be obtained.

[0049]

According to the present invention, a shape memory actuator excellent in responsiveness is provided, in which the deformation force and the amount of deformation of the shape memory alloy plate are efficiently transmitted without the electrothermal conversion element being plastically deformed or broken. To be done.

[Brief description of drawings]

FIG. 1 is a perspective view of a shape memory actuator according to a first embodiment of the present invention.

FIG. 2 is a side sectional view in which a part of the shape memory actuator of FIG. 1 is cut away.

3 is a transparent top view of the electrothermal conversion plate shown in FIG.

FIG. 4 is a diagram showing a state when the shape memory alloy of FIG. 1 is bent and deformed.

FIG. 5 is a perspective view of a shape memory actuator according to a second embodiment of the present invention.

FIG. 6 is a perspective view of a shape memory actuator according to a third embodiment of the present invention.

FIG. 7 is a perspective view of a shape memory actuator according to a fourth embodiment of the present invention.

FIG. 8 is a diagram showing a first modification of the shape memory alloy and the electrothermal conversion plate applicable to the first to fourth embodiments.

FIG. 9 is a diagram showing a second modification of the shape memory alloy and the electrothermal conversion plate applicable to the first to fourth embodiments.

FIG. 10 is a view showing a third modification of the shape memory alloy and the electrothermal conversion plate applicable to the first to fourth embodiments.

[Explanation of symbols]

12 ... Shape memory alloy, 14 ... Electrothermal conversion plate, 22 ... Actuating member, 24 ... Joint structure, 26 ... Connection pivot part, 28 ... Holding part.

Claims (1)

[Claims] 1. A shape memory alloy plate that is shape-memorized so as to be deformed by a temperature change, a flexible electrothermal conversion plate for giving a temperature change to the shape memory alloy plate, and a shape memory alloy plate for deformation. An actuating member is provided, wherein the actuating member comprises a pair of joint structures that are bendably connected by a connecting and pivoting portion, and one shape memory alloy provided for each joint structure. A shape memory actuator having a plate and an electrothermal conversion plate that are slidably held in a stacked state.