JPH05248342A - Shape memory alloy actuator - Google Patents

Abstract

PURPOSE:To provide a shape memory alloy actuator which can be directly put in turning motion, such as rotation, through the action of a shape memory alloy to restore its shape from a deformed state, without requiring a structure particularly for converting the rectilinear motion or oscillating motion of a crank or the like into rotary motion. CONSTITUTION:A shaft 3 is turnably held against a frame l at a fulcrum 5. Four shape memory springs SMA made of shape memory alloy are disposed radially at intervals of about 90 deg. with one end fixed at a position of a predetermined distance from the fulcrum 5 on the shaft 3 and the other end fixed to the frame 1, while the springs are expanded at room temperature from a fixed free length memorized when they are heated. Electricity is transmitted to the shape memory springs SMA in sequence around the shaft 3 to heat the shape memory springs SMA, so that tensile forces, with which the heated shape memory springs SMA return to the memorized free length, cause tilting of the shaft 3 in a corresponding direction, resulting in the spirally turning motion of the shaft 3 about the fulcrum 5.

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 shape memory alloy, and more particularly, it relates to a shape memory alloy actuator capable of rotating a shaft in a conical shape and rotating the shaft tip.

[0002]

2. Description of the Related Art Conventionally, a shape memory alloy: SMA (Shap
An actuator using e Memory Alloy) is known, and its mechanical principle model is shown in FIG. Figure 10
The one shown in (A) is a method in which after a predetermined shape is memorized in a shape memory alloy, deformation is applied by an external force in a low temperature martensite phase, and the shape is unidirectionally recovered by heating to recover the shape. , A so-called one-way type actuator.

The one shown in FIG. 10B is a so-called bias type which applies a biasing force for deformation, and is an actuator which is relatively frequently used as disclosed in, for example, Japanese Patent Laid-Open No. 2-308979. Since the shape memory alloy is easily deformed at low temperature, it is deformed by the biasing force of the spring, etc., and the restoring force of the shape memory alloy exceeds the biasing force at high temperature. .. Therefore, if a periodic heat cycle of heating-cooling is given to this mechanism, it is possible to perform continuous motion by deformation-shape recovery.

In the structure shown in FIG. 10C, one pair of shaped alloys is combined with each other, and one of them is heated and the other is combined by utilizing the fact that the recovery force during heating is larger than the force required for deformation at low temperature. This is a so-called differential type actuator that differentially extracts motion by cooling.

[0005]

However, the actuators of the above-described models are designed to move a driven member mainly in a straight line in order to open and close a ventilation valve or the like. It is possible to pull and rotate about a joint, but only a predetermined angle can provide a rotation range. Therefore, in order to obtain a revolving motion such as a rotating motion, a special structure for converting a linear motion of a gear or a crank or an oscillating motion of a predetermined angle into a rotary motion is required. come.

Since the shape memory alloy actuator itself has the function of an actuator, the shape memory alloy actuator is characterized in that it is mechanically simpler and more easily miniaturized than solenoids, motors, hydraulic actuators and the like. Therefore, it is considered effective to use as a microactuator, but as described above, a special structure is required to convert linear motion or swing motion of a predetermined angle into rotary motion, which hinders miniaturization. Since members such as gears and cranks are difficult to micronize, it is difficult to realize a microactuator that performs rotary motion.

Therefore, the present invention has an object to solve the above-mentioned problems, and does not require a special structure for converting linear motion or oscillating motion of gears, cranks or the like into rotary motion, and deformation of the shape memory alloy. -To provide a shape memory alloy actuator capable of directly performing a circular motion such as a rotary motion by a shape recovery operation.

[0008]

In order to achieve the above object, the present invention has the following constitution as means for solving the problems. That is, a frame serving as a fixed side is provided with a shaft rotatably held at a predetermined position in the longitudinal direction as a fulcrum, and at least three driving bodies made of a shape memory alloy are stored during heating. In a state of being compressed or expanded at room temperature from a certain free length, one end thereof is fixed at a position of a predetermined distance from the fulcrum on the shaft, and the other end is fixed to the frame and radially arranged. By driving the three driving bodies by sequentially energizing them around the shafts to heat the shafts, the shafts are driven by the heating force by the tension or biasing force to return to the stored free length of the heated driving bodies. The shape memory alloy actuator is characterized in that it is tilted in a direction corresponding to the body, and as a result, the shaft is caused to perform a conical orbital movement around the fulcrum. The configuration of the mediator is it.

The driving body may be formed in a coil spring shape, a wave shape, or the like so that the entire length can be changed. According to the shape memory alloy actuator of the present invention having the above structure, when at least three driving bodies formed of a shape memory alloy are sequentially energized and heated around the shaft, the heated driving bodies are Attempts to return to the memorized free length produce tension when placed in the stretched state and bias when placed in the compressed state, with the shaft corresponding to its heated driver. In the case of tension, that is, in the case of tension, it is tilted toward the driver, while in the case of biasing force, it is tilted toward the opposite side. Since one end of each of these driving members is located at a predetermined distance from the fulcrum on the shaft and the other end is fixed to the frame and arranged radially, it is possible to repeat the deformation-shape recovery by heating in order as described above. Causes the shaft to perform a conical orbital movement around the fulcrum.

Therefore, if the shaft is rotated in a triangular pyramid shape by combining the displacements of the respective driving bodies, the tip of the shaft turns in a triangular shape. Orbit to. Further, the number of driving bodies may be increased and the driving bodies may be arranged in a circumferential shape, or the driving bodies may be, for example, 90
By controlling the energization timing even when four pieces are arranged at intervals, the shaft is made to move in a conical shape,
The tip can be circularly moved, or can be linearly reciprocated in any direction.

With such an actuator, it is possible to play a role of a so-called ant model leg and use it as a walking actuator. Alternatively, if the tip of the shaft is shaped to act as a blade and is rotated, it is possible to remove unnecessary substances attached to the inner wall of the capillary, for example. This is not limited to a cylindrical tube, but can be a tube having a triangular or quadrangular cross section. Since the present actuator can directly perform a circular motion such as a rotary motion by the deformation-shape recovery operation of the shape memory alloy, it is effectively used as a microactuator.

Further, a flange is provided at a position of a predetermined distance from the fulcrum of the shaft, and one end of the driver is fixed to the flange and the other end is fixed to the frame so that the driver is arranged substantially parallel to the shaft. Even if it does, it can be implemented similarly. In this case, the length of the driving body may be relatively short.

Furthermore, the shaft is held slidably in the longitudinal direction thereof, the fulcrums are sandwiched, and the driving bodies are arranged on both sides of the shaft in the longitudinal direction, respectively, and the driving bodies arranged on the same side are energized. The resulting tension or biasing force can also translate the shaft in the longitudinal direction. Therefore, it is possible to change the distance from the fulcrum to the tip of the shaft.
If it is a circular motion, its diameter can be reduced. For example, in the case of the above-mentioned ant model, if the length of the leg is shortened, it is convenient to pass through a narrow place, and the stroke of one step can be shortened.

[0014]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a schematic perspective view of a shape memory alloy actuator which is a first embodiment of the present invention. A shaft 3 is held on the frame 1 on the fixed side. Shaft 3
A predetermined position in the longitudinal direction of is a fulcrum 5, a spherical bearing 7 is fixed to the fulcrum 5, and the spherical bearing 7 is rotatably held by the frame 1. Therefore, shaft 3 has fulcrum 5
Is held rotatably with respect to the frame 1.

Further, four shape memory springs SMA1 to SMA1 as a driving body formed of a shape memory alloy in a coil spring shape.
The SMA 4 (distinguished by the number at the end) is fixed at one end at a predetermined distance from the fulcrum 5 of the shaft 3 toward the tip, and the other end is fixed to the frame 1 and arranged radially at intervals of about 90 degrees. Has been done. The shape memory spring SMA
As shown in FIG. 4, the 1 to SMA 4 may be fixed to the column portion 1 a protruding from the frame 1. Each shape memory spring S
MA1 to SMA4 are arranged in a stretched state at room temperature from a certain free length stored during heating.

An energizing terminal 9 is provided on a portion of each shape memory spring SMA1 to SMA4 fixed to the frame 1.
The drive circuit 13 and the control circuit 15 are connected. In the present embodiment, the 1-2 phase excitation step motor drive method is used, an excitation signal is output from the control circuit 15, and the shape memory springs SMA1 to SMA1 are output from the unipolar drive circuit 13.
The voltage application to the SMA 4 is individually controlled to be turned on / off to supply a current.

Next, the operation of this embodiment will be described.
FIG. 2 is a time chart showing the energization states of the shape memory springs SMA1 to SMA4. The energization control shown in this time chart uses an energization pulse in which energization for the energization time T1 is periodically repeated at intervals of the non-energization time T2.
The four shape memory springs SMA1 to SMA4 are sequentially energized by shifting a predetermined phase.

Shape memory spring SMA heated by being energized
1 to SMA4 try to return to the stored free length, and in this embodiment, they try to contract and generate tension. Therefore, the shaft 3 is tilted toward the heated shape memory springs SMA1 to SMA4 springs. Then, when the energization is finished and the heat is dissipated, it stops in that state. It should be understood that by attaching a return spring or the like, the shape memory springs SMA1 to SMA4 can be configured to return to their original shapes and the shaft 3 to return to its original position.

In this embodiment, the shape memory springs SMA1 to SMA4 are sequentially heated around the shaft 3, and when only one phase is excited, the shape memory springs SMA1 to SMA4 are heated.
When two adjacent phases are excited in the direction of, a tension is generated in the intermediate direction between them. In this way, by sequentially heating and sequentially repeating the deformation and shape recovery of the shape memory springs SMA1 to SMA4, the shaft 3 makes a conical orbital movement about the fulcrum 5.

The cycle of heat generation and heat dissipation due to the energization described above varies depending on the transformation temperature of the shape memory springs SMA1 to SMA4, the wire diameter forming the coil spring, and the like. Therefore,
It is also possible to make the shaft 3 perform a circular motion close to a cone and to make the tip end circularly by adjusting the energization timing in advance by a feeling test or the like. Alternatively, it is also possible to perform an orbital motion close to a quadrangular pyramid. Also, the orbital speed itself can be changed.

Further, in addition to the orbital motion, for example, energization of only two adjacent shape memory springs SMA1 and SMA2 and two other shape memory springs SMA3 and SMA.
Energizing only 4 or facing shape memory spring SMA
By alternately energizing 1, SMA3 or SMA2, SMA4, the shaft 3 can be reciprocally rocked. In addition, four shape memory springs SMA1 to
If only three of the SMAs 4 are sequentially energized and the shaft 3 is rotated in a substantially triangular pyramid shape, the tip of the shaft 3 can be rotated in a substantially triangular shape.

Such an actuator plays the role of a so-called ant model leg as shown in FIG. 3 and can be used as a walking actuator. As shown in FIG. 3, two actuators sharing the frame 1 are prepared, and both ends of the shaft 3 are bent in the same direction to form four legs. Then, the shape memory spring SMA1 shown in FIG.
~ SMA4 is provided symmetrically on both sides of the frame 1 and supports 5
Shape memory springs SMA1 to S located at points symmetrical with respect to
The MA4 is excited at the same time. Therefore, tension acts on the shaft 3 in a point symmetrical manner about the fulcrum 5,
Both ends of the shaft 3 perform symmetrical orbital movement. Furthermore, the actuators corresponding to the front legs and the actuators corresponding to the rear legs can be caused to move in a manner similar to the walking motion of a four-legged animal by shifting the excitation timing by 180 degrees.

Further, as shown in FIG. 5, for example, six actuators shown in FIG. 4 are attached to form legs, respectively.
It is also possible to perform main leg walking. Since the present actuator can directly perform the circular motion such as the rotary motion by the deformation-shape recovery operation of the shape memory alloy, it can be easily micro-sized even when used as a walking actuator, and as a microactuator. Is expected to be used.

Next, another embodiment is shown in FIGS. First
The same members as those in the embodiment are designated by the same reference numerals and detailed description thereof will be omitted. However, the shape memory springs are collectively referred to simply as SMA (same for the third and subsequent embodiments). First, a second embodiment will be described with reference to FIG. The shaft 3 is held by a sliding bearing 21 so as to be slidable in the longitudinal direction. And
The sliding bearing 21 is supported from four sides by elastic spring bodies 23 whose one end is fixed to the frame 1, and is configured to allow the above-mentioned conical movement of the shaft 3.

Shape memory springs SMA are arranged on both sides of the shaft 3 in the longitudinal direction with the fulcrum 5 interposed therebetween. Therefore, the shaft 3 can be translated in the longitudinal direction by the tension generated by energizing the shape memory springs SMA arranged on the same side (for example, the left side of the frame 1 in FIG. 6A). Therefore, as shown by the chain double-dashed line in FIG. 6A, the distance from the fulcrum 5 to the tip of the shaft 3 can be changed. Can be increased or decreased. Therefore, in the case of the above-mentioned ant model, if the length of the leg is shortened, it is convenient to pass through a narrow place. Also, the stroke of one step can be changed.

Next, a third embodiment will be described. As shown in FIG. 7, the frame 1 is formed in a bottomed cylindrical shape, and the shape memory spring SMA is arranged substantially orthogonal to the shaft 3 and fixed to the side wall 31 of the frame 1. The shaft 3 is fixed to the frame 1 via an elastic spring body 33, and is configured to allow the above-mentioned conical movement of the shaft 3. In this case, the elastic spring body 33
Is the fulcrum 5. In this case, the length of the shape memory spring SMA may be relatively shorter than that of the first embodiment.

Next, a fourth embodiment will be described. As shown in FIG. 8, the shaft 3 is fixed to the frame 1 via the elastic spring body 43, and the elastic spring body 43 serves as the fulcrum 5. A flange 41 is provided on the shaft 3 at a predetermined distance from the fulcrum 5, and one end of the shape memory spring SMA is fixed to the flange 41 so that the shape memory spring SMA is arranged substantially parallel to the shaft 3. The other end is fixed to the frame 1.

In this case, the shape memory spring SMA is contracted in order, so that the collar portion 41 as shown by the two-dot chain line in the figure.
The shaft 3 makes a conical orbital movement around the fulcrum 5 via the. In this case as well, the length of the shape memory spring SMA may be relatively shorter than that of the first embodiment.

Next, a fifth embodiment will be described with reference to FIG. As shown in the figure, this embodiment is a combination of the above-mentioned second and fourth embodiments. The shaft 3 is held slidably in the longitudinal direction by a sliding bearing 51,
The sliding bearing 51 is an elastic spring body 5 fixed to the frame 1.
It is supported from all sides by 3 and allows the conical movement of the shaft 3. Then, with the fulcrum 5 sandwiched between the fulcrums 5 on both sides in the longitudinal direction of the shaft 3, the collar portions 55 are respectively provided, and the shape memory spring SMA is arranged so as to be arranged substantially parallel to the shaft 3. One end is fixed to the collar 55 and the other end is fixed to the frame 1.

In this case, the length of the shape memory spring SMA may be relatively shorter than that of the second embodiment. In addition, in the fifth embodiment, the collar portions 55 are provided on both sides and relatively large as a whole, but the moment of inertia of the collar portion 55 increases and the role of the flywheel causes the velocity fluctuation during the orbital movement. There is also an advantage that the movement is reduced and the movement becomes smooth.

In any of the above-mentioned embodiments, a special structure for converting linear motions or swing motions of gears and cranks into rotary motions is not required, and the deformation-shape recovery operation of the shape memory alloy is performed. It is possible to directly perform a circular motion such as a rotary motion. The present invention is not limited to the embodiments as described above, and can be implemented in various modes without departing from the gist of the present invention. For example, in the above embodiment, four shape memory springs SMA1 to SMA are used.
The case of using MA4 has been described, but if three or more,
The shaft 3 can be caused to perform a conical orbital movement around the fulcrum 5. Further, a larger number of shape memory springs SMA may be arranged circumferentially to perform a smoother conical movement.

Further, in the above embodiment, the shape memory spring S is used.
The MA is arranged in a stretched state at room temperature from a certain free length stored during heating, so that tension is generated by heating, but conversely, at a room temperature below a certain free length stored during heating. It may be arranged in a compressed state and heated to generate a biasing force. In this case, the shaft 3 is merely biased in the opposite direction of the heated shape memory spring SMA, resulting in a conical orbital movement similar to that of the above-described embodiment.

Further, the shape memory spring SMA may be formed in the same manner as long as it is formed in a wavy shape in addition to the coil shape so long as the length of the entire shape is changed by the shape recovery operation.

[0034]

As described above in detail, according to the shape memory alloy actuator of the present invention, the driving body formed of the shape memory alloy is sequentially energized and heated around the shaft to deform and recover the shape. By repeating, the shaft
Performs a conical orbital movement around a fulcrum. Therefore, it is possible to obtain a circular motion such as a circular motion at the tip of the shaft, and a special structure for converting linear motion or swing motion such as gear or crank into rotary motion is not required, and deformation of the shape memory alloy -By the shape recovery operation, it is possible to directly perform a circular motion such as a rotary motion, and it is very effective for use as a microactuator.

[Brief description of drawings]

FIG. 1 is a schematic perspective view of a shape memory alloy actuator that is a first embodiment of the present invention.

FIG. 2 is a time chart showing an energized state of a shape memory spring.

FIG. 3 is a schematic perspective view when used as a walking actuator that functions as a leg of an ant model.

FIG. 4 is a schematic perspective view showing a modified example of the shape memory alloy actuator.

FIG. 5 is a schematic perspective view when used as a six-legged walking actuator.

FIG. 6A is a partially cutaway side view of the second embodiment, and FIG.
Is also a front view.

FIG. 7 is a partially cutaway perspective view showing a third embodiment.

FIG. 8 is a schematic perspective view showing a fourth embodiment.

FIG. 9 is a schematic perspective view showing a fifth embodiment.

FIG. 10 is a diagram showing a mechanical principle model of an actuator using a conventional shape memory alloy, in which (A) is a unidirectional type,
(B) is a bias type and (C) is a differential type.

[Explanation of symbols]

1 ... frame, 3 ... shaft, 5 ... fulcrum,
7 ... Spherical bearing 13 ... Drive circuit, 15 ... Control circuit, 21, 5
1 ... Sliding bearing, 41, 55 ... Collar part, SMA, S
MA1 to SMA4 ... Shape memory spring

Claims (3)

[Claims] 1. A frame, which is a fixed side, is provided with a shaft rotatably held at a predetermined position in the longitudinal direction as a fulcrum, and at least three driving bodies made of a shape memory alloy are provided,
In a state of being compressed or expanded at room temperature from a certain free length stored during heating, one end of the shaft is fixed at a predetermined distance from the fulcrum on the shaft, and the other end is fixed to the frame to be radial. By arranging and heating the at least three driving bodies by sequentially energizing them around the shafts, the shafts are driven by tension or biasing force to return to the stored free length of the heated driving bodies. A shape memory alloy actuator characterized in that it is tilted in a direction corresponding to the heated driving body, and as a result, causes the shaft to perform a conical orbital movement about the fulcrum. 2. A flange is provided on the shaft at a position a predetermined distance from the fulcrum, and one end of the driver is fixed to the flange so that the driver is arranged substantially parallel to the shaft. The shape memory alloy actuator according to claim 1, wherein the other end is fixed to the frame. 3. The shaft is held slidably in the longitudinal direction thereof, and the driving bodies are arranged on both sides in the longitudinal direction of the shaft with the fulcrum interposed therebetween, and the driving bodies arranged on the same side. The shape memory alloy actuator according to claim 1 or 2, wherein the shaft is translated in the longitudinal direction by a tension or a biasing force generated by the energization.