JPH02241989A - Shape memory alloy actuator - Google Patents

Abstract

PURPOSE:To compact the size, reduce the weight, simplify the construction, and divide the operation into two strokes in one direction in which response speed is high, with regard to a shape memory alloy actuator, by balancing the elastic force of a SMA (shape memory alloy) with the energizing force of an elastic member in the course of a moving locus to stop a moving member. CONSTITUTION:A shape memory treatment is given to a SMA coil 1 in extended condition beforehand so that it may be extended gradually after inverse transformation start temperature is passed by heating. Meantime, a plate 2 is moved against an energizing force of a bias spring 5 to force its top end 2c near a block 11 and turn on a switch 8 by means of its slant surface 2d. Since a heating circuit 10 controls the electricity passing through the coil 1 by means of the signal to keep the temperature of the oil as it is, an object 12 can be carried by moving it together with a base. In addition, when the oil 1 is energized to be heated by the circuit 10, the plate 2 moves while rotating along a cam in clockwise direction to depart its top end 2c from the block 11. Accordingly, the object 12 is unloaded at a moved location of the base, a switch 9 is turned on by means of the top end 2c to stop the supply of electricity from the circuit 10 to the coil 1, and the plate 2 is also stopped by making contact with a stopper 6.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an actuator using a shape memory alloy (hereinafter referred to as SMA) used in small manipulators and the like.

Conventional technology In general, SMA actuators utilize the shape memory effect caused by the thermoelastic martensitic transformation of SMA to heat (cool) the SMA in a configuration consisting of an SMA and a bias spring, or a pair of competing SMAs. , the amount of deformation due to the temperature difference is extracted and used as an actuator. This is because the SMA, which has been previously subjected to shape memory treatment and deformed below the temperature at which the reverse transformation from thermoelastic martensite to the parent phase begins, completely returns to its original shape by being heated above the temperature at which the reverse transformation ends. It takes advantage of its ability to recover its shape. Therefore, compared to other actuators, it has the advantage of being extremely small and lightweight, and has an extremely simple configuration, and is expected to be applied to small manipulators and the like. However, since it is a temperature control system, it is difficult to keep the heating/cooling cycle within a short period of time.Especially when cooling, waiting for the temperature to drop naturally will slow down the response speed and make it impractical. The cycle cannot be obtained, and the functions required for various tasks, including basic manipulator movements such as grasping and immediately releasing an object, cannot be satisfied.

On the other hand, some proposals have been made, such as the SMA actuator shown in Japanese Patent Application Laid-Open No. 62-77882, in which a cooling member is purposely provided inside the SMA coil to speed up the response speed. There is.

Problems to be Solved by the Invention However, in the above-mentioned configuration, although it is sufficient to use only a cooling member, a device for cooling this member is additionally required (in the cited example, Freon gas is circulated by a compressor). This poses a problem in that the greatest features of the SMA actuator, such as being small, lightweight, and having a simple configuration, are lost.

In view of these points, the present invention provides a manipulator that can quickly grasp and quickly release an object without sacrificing the advantages of the SMA actuator, which are extremely small, lightweight, and extremely simple to configure. The purpose of the present invention is to provide an SMA actuator that can satisfy the functions required for various tasks, including basic operations.

Means for Solving the Problems The invention according to claim 1 includes a moving member whose movement locus is determined by a cam shape, and a moving member that is provided along the moving direction of the moving member and that is deformed by being heated and cooled. an SMA configured to operate the moving member; 1. The heating control means includes an elastic member that applies a bias force to the SMA and a heating control means that heats the SMA, and the heating control means balances the elastic force of the SMA and the biasing force of the elastic member during the movement trajectory of the moving member. According to claim 2, the movable member is configured such that the movable member is stopped, and two strokes are obtained in one direction: a first stroke before stopping and a second stroke after stopping. The invention of
A moving member whose movement trajectory is determined by a cam shape, and a plurality of SMAs arranged in series along the moving direction of this moving member and configured to deform when heated and cooled to operate the moving member. , an elastic member that applies a bias force to the plurality of SMAs, and a plurality of heating control means that heats the plurality of SMAs, and a part of the plurality of heating control means controls the corresponding plurality of SMAs. The movable member is configured to be heated to balance the elastic force of some of the plurality of SMAs and the biasing force of the elastic member to stop the movable member during the movement trajectory of the movable member. 1 stroke, and then the plurality of heating control means obtain a second stroke by heating all the corresponding plurality of SMAs, so that two strokes are obtained in one direction. shall be.

According to the first feature of the present invention, a moving member whose movement trajectory is determined by a cam shape is moved from S to S in the middle of its movement trajectory.
Since the elastic force of the MA and the biasing force of the elastic member can be balanced and stopped, the operation can be divided into two strokes in one direction with a fast response speed, and the cam shape can be adjusted to an appropriate one. This makes it possible to perform various tasks, including basic manipulator movements such as grasping and immediately releasing an object, without sacrificing the advantages of the SMA actuator, which are extremely small, lightweight, and extremely simple to configure. SMA that can satisfy the required functions
According to the second feature, the actuator moves a moving member whose movement trajectory is determined by the cam shape to a plurality of SMs in the middle of its movement trajectory.
It is possible to heat only a part of A and stop it by balancing the elastic force of those parts and the biasing force of the elastic member with simple temperature control. The SMA actuator can be divided into two strokes in the direction, and with a suitable cam shape, it can move the object without sacrificing the advantages of the SMA actuator, which are very small, lightweight, and extremely simple to configure. It is possible to provide an SMA actuator that can satisfy the functions required for various operations, including basic manipulator operations such as grasping and immediately releasing.

Embodiment FIG. 1 shows a configuration diagram of an SMA actuator (corresponding to the invention described in claim 1) in a first embodiment of the present invention. In Fig. 1, 1 is an SMA coil with one end fixed to a base (not shown) and the other end fixed to plate 2, 3.4 is a shaft fixed to the base, and 5 is one end fixed to the base. A bias spring whose other end is fixed to the plate 2, 6 a stopper fixed to the base, 8.9 a switch fixed to the base, and 10 a heating circuit.

Reference numeral 11 denotes a block fixed to the base, and is used to sandwich and fix the object 12 between it and the tip 2C of the plate 2. The plate 2 has a groove 2a that engages with the shaft 3, and a side surface 2b that contacts the shaft 4 from the biasing direction of the bias spring 5. When the plate 2 moves against the urging force of the bias spring 5, the slope portion 2d of the plate 2 connected to the side surface portion 2b comes into contact with the shaft 4. Therefore, the plate 2 can move while maintaining contact with the groove portion 2a, side surface portion 2b, and slope portion 2d and the respective shafts 3.4. In the state shown in the figure, both switches 8 and 9 are off, and the object 12 is not fixed to the block 11 either.

The operation of the SMA actuator of this embodiment configured as described above will be described below.

In this state, the heating circuit 10 connects the SMA coil 1 to
For example, heating is performed by applying electricity using a pulse width modulation (PWH) method. The SMA coil 1 has been subjected to shape memory treatment to be stretched in advance, and as a result of this heating, it gradually tries to stretch once the reverse transformation start temperature has passed. This shape recovery force is several times larger than the deformation stress at low temperature at the end temperature of reverse transformation.
Further, as the temperature increases, the force gradually increases, so that the plate 2 is eventually moved against the biasing force of the bias spring 5, and the tip end 2c of the plate 2 is brought closer to the block 11. The switch 8 is turned on by the slope portion 2d of the plate 2 when the tip portion 2c sandwiches and fixes the object 12 with the block 11. This state is shown by the solid line in FIG.

When the switch 8 is turned on, the heating circuit 10 controls the energization of the SMA coil 1 in response to the signal, and maintains the temperature as it is. As a result, a gripping operation can be performed between, for example, the tip 2c of the plate 2 and the block 11, and the object 12 can be carried by moving the base together.

On the other hand, from this state, the SM is further heated by the heating circuit 10.
When the A coil 1 is heated by electricity, the SMA coil 1 tends to expand further. However, since the side surface 2b of the plate 2 is connected to the slope 2d, the plate 2 gradually rotates clockwise along this cam shape and moves, and as a result, the tip 2C separates from the block 11. Become. Therefore, the gripping operation of the object 12 is released, and the object 12 can be placed at the moving location of the base. Here, the switch 9 is turned on by the tip 2c of the plate 2, and in response to the signal, the heating circuit 10 terminates the energization of the SMA coil 1, and the plate 2 also comes into contact with the stopper 6 and stops moving. This state is shown in FIG. 2 by a dashed line.

The SMA coil 1 that has been de-energized is eventually cooled down, and the biasing force of the bias spring 5 causes the plate 2 to return to its initial state (see FIG. 1).

As described above, according to this embodiment, the plate 2 whose movement trajectory is determined by the cam shape consisting of the side surface portion 2b and the slope portion 2d can be stopped in the middle of the movement trajectory by controlling the heating to the SMA coil 1. Due to this, the response speed is fast1
Divide the movement of plate 2 into two strokes in the direction,
It is possible to grasp the object 12 and immediately release it.

In this embodiment, the bias spring 5 is made of an ordinary spring, but it is also made of SMA, which is a type of elastic member, and is equipped with a new number and a heating circuit, so that the midway stop position can be controlled using two SMAs. They may be performed in an antagonistic manner. Further, although the block 11 fixed to the base is configured with one set of moving mechanisms including the plate 2, etc., it goes without saying that one more set of moving mechanisms may be provided in this embodiment. Further, although the intermediate stop position is configured by the switch 8, it can also be configured by using a pressure sensor or the like.

FIG. 3 shows a configuration diagram of an SMA actuator (corresponding to the invention set forth in claim 2) in a second embodiment of the present invention. In FIG. 3, 21a12lb are SMA coils connected in series, one end fixed to the base (not shown) and the other end locked to the plate 22, 23.24
25 is a shaft fixed to the base; 25 is a bias spring having one end fixed to the base and the other end locked to the plate 22; 26
29 is a stopper fixed to the base, 29 is a switch fixed to the base, and 30a130b is a heating circuit corresponding to the SMA coil 21a121b, respectively. Also 31
is a block fixed to the base, and is used to sandwich and fix the object 32 between it and the tip 22c of the plate 22.

In the plate 22, a groove 22a engages with the shaft 23, and a side surface 22b engages with the shaft 23 from the biasing direction of the bias spring 25.
It is in contact with 4. The plate 22 is the bias spring 2
When the plate 22 moves against the biasing force 5, the slope portion 22d of the plate 22 connected to the side surface portion 22 comes into contact with the shaft 24. Therefore, the plate 22 has a groove 22a and a side surface 2.
It is possible to move while maintaining contact between the shafts 23 and 2b and the slope portion 22d and the respective shafts 23 and 24. In the state shown in the figure, the switch 29 is off, and the object 3
2 is also not fixed to block 31.

The heating circuits 30a and 30b each have an SMA coil 21.
a and 21b can be heated individually.

The operation of the SMA actuator of this embodiment configured as described above will be described below.

In this state, the SMA coil 21 is heated by the heating circuit 30a.
(a) is electrically heated using, for example, a pulse width modulation (PWH) method. The SMA coil 21a has been subjected to shape memory treatment to be stretched in advance, and as a result of this heating, it gradually tries to stretch once the reverse transformation start temperature has passed. This shape recovery force is several times larger than the deformation stress at low temperatures at the reverse transformation end temperature, and gradually increases as the temperature rises, so that the plate 22 eventually moves against the biasing force of the bias spring 25. , the tip 22c of the plate 22 is brought close to the block 31. When the temperature reaches or exceeds the reverse transformation end temperature, the object 32 is stabilized in equilibrium with the biasing force of the bias spring 25, and the tip 22c sandwiches the object 32 with the block 31 and fixes it. This state is shown by the solid line in FIG.

The heating circuit 30a controls energization to the white MA coil 21a to maintain the temperature above the reverse transformation end temperature. As a result, for example, a gripping operation can be performed between the tip 22c of the plate 22 and the block 31, and if the entire base is moved, the object 3 can be gripped.
Can carry 2.

On the other hand, from this state, S
When the MA coil 21b is heated by electricity, the SMA coil 21
b tries to grow. However, the side surface 2 of the plate 22
2b is connected to the slope portion 22d, so the plate 22
moves while gradually rotating clockwise along the cam shape, and as a result, the tip 22c is separated from the block 31. Therefore, the gripping operation of the object 32 is released, and the object 32 can be placed at the moving location of the base.

Here, the tip 22c of the plate 22 causes the switch 2 to
9 is turned on, and the heating circuit 30a,
30b finishes energizing the SMA:I coil 21a121b, and the plate 22 also comes into contact with the stopper 26 and stops moving. This state is shown in FIG. 4 by a dashed line. The SMA coils 21a and 21b that have been de-energized are eventually cooled down, and the biasing force of the bias spring 25 forces the plate 22
returns to its initial state (see Figure 3).

As described above, according to this embodiment, by heating only the SMA coil 21a and stopping the plate 22 whose movement trajectory is determined by the cam shape consisting of the side surface portion 22b and the slope portion 22d in the middle of the movement trajectory, The plate 22 can be moved in two directions in one direction with simple temperature control and fast response speed.
It is possible to divide the stroke into two strokes, such as grasping the object 32 and immediately releasing it.

In this embodiment, the bias spring 25 is an ordinary spring.
However, this may also be made of SMA, which is a type of elastic member, and a heating circuit may be newly provided to control the midway stop position by having the SMAs compete against each other. Further, although the block 31 is constructed of an object fixed to the base, it goes without saying that one more set of moving mechanisms of this embodiment may be provided.

Further, as in the case described in the first embodiment, the intermediate stop position may be detected using a switch, a pressure sensor, or the like.

As described in detail, according to the invention described in claim 1, the elastic force of the SMA and the biasing force of the elastic member are applied to the moving member whose movement trajectory is determined by the cam shape in the middle of the movement trajectory. Since it is possible to balance and stop, the operation can be divided into two strokes in one direction with a fast response speed, and by making the cam shape appropriate, it is extremely small and lightweight. In addition, the SMA actuator can satisfy the functions required for various tasks, including the basic operation of a manipulator such as grasping an object and immediately releasing it, without sacrificing the advantage of the SMA actuator that it has an extremely simple configuration. According to the invention described in claim 2, the moving member whose movement trajectory is determined by the cam shape is moved in the middle of its movement trajectory,
It is possible to heat only some of the multiple SMAs and stop them by balancing their elastic forces and the biasing force of the elastic member with simple temperature control, so the operation can be controlled by reducing the response speed. SMA can be divided into two strokes in one fast direction, and by choosing an appropriate cam shape, it is extremely small, lightweight, and extremely easy to configure.
We can provide an SMA actuator that can satisfy the functions required for various tasks, including basic manipulator operations such as grasping an object and immediately releasing it, without sacrificing the advantages of the actuator. The effect is strong.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a shape memory alloy actuator in a first embodiment of the present invention, FIG. 2 is an explanatory diagram of the operation of the same shape memory alloy actuator, and FIG. 3 is a shape memory in a second embodiment of the present invention. FIG. 4 is a block diagram of the alloy actuator, and is an explanatory diagram of the operation of the same shape memory alloy actuator. 1... Shape memory alloy coil, 2... Plate, 2a
81. Groove portion, 2 b, , Side portion, 2 d, Slope portion, 3.4... Shaft, 5... Bias spring, 8... Switch, 10... Heating circuit, 21 a121 b.
...Shape memory alloy coil, 22-...Plate, 2
2a, , groove portion, 22b, . Side part, 22 d, slope part, 23. 24...Axis,...Bias spring, 0a1 30b...Heating circuit.

Claims (4)

[Claims] (1) A moving member whose movement trajectory is determined by a cam shape, and a shape that is provided along the moving direction of this moving member and is configured to deform when heated and cooled to operate the moving member. A memory alloy, an elastic member that applies a bias force to the shape memory alloy, and a heating control means for heating the shape memory alloy, the heating control means controlling the shape memory alloy during the movement trajectory of the moving member. The movable member is configured to be stopped by balancing the elastic force of the alloy and the biasing force of the elastic member, and the movable member is configured to have a first stroke before stopping and a second stroke after stopping.
A shape memory alloy actuator characterized in that it obtains two strokes in two directions. (2) A movable member whose movement locus is determined by a cam shape, and a movable member arranged in series along the moving direction of the movable member, and configured to deform when heated and cooled to operate the movable member. a plurality of shape memory alloys, an elastic member that applies a bias force to the plurality of shape memory alloys, and a plurality of heating control means for respectively heating the plurality of shape memory alloys; By heating a corresponding part of the plurality of shape memory alloys, the elastic force due to the part of the plurality of shape memory alloys and the elastic member are reduced during the movement trajectory of the moving member. The movable member is configured to be stopped by balancing the biasing force of the movable member to obtain a first stroke, and then the plurality of heating control means heat all of the corresponding shape memory alloys to obtain a first stroke. A shape memory alloy actuator characterized in that it is configured to obtain two strokes, and is configured to obtain two strokes in one direction. (3) The shape memory alloy actuator according to claim 1 or 2, wherein the cam shape is configured such that the moving member approaches a certain point in the first stroke and moves away from it in the second stroke. . (4) The heating control means has a detection member for detecting a position at which the moving member should stop, and is configured to perform heating control based on a signal from the detection member. shape memory alloy actuator.