JPH01100385A - Actuator - Google Patents

Abstract

PURPOSE:To obtain a varying actuating force in accordance with the amount of current supply in an actuator, which controls actions through electrical heating of an actuating spring consisting of shape memory alloy, by varying the electric resistance distribution of the shape memory alloy over the whole length of the actuating spring. CONSTITUTION:In an actuator a coil-shaped actuating spring 10 formed by winding a wire consisting of shape memory alloy and a coil-shaped bias spring 2 are fitted at the left and right sides of a flange 31 of an actuating rod 3. A current supply device 6 supplies current to this actuating spring 10 through an electrode plate 5, and thereby the spring 10 drives the actuating rod 3 to the right against the action of the bias spring 2. In this arrangement the section area of the actuating spring 10 is not uniform over the whole length, but a wire with thicker left end decreasing its dia. toward the right end is wound into a coil. Thereby an actuating force varying with the amount of current supply is obtained, which enhances the control accuracy.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention uses a shape memory alloy as an operation spring, and uses the shape recovery force of the shape memory alloy as an operation force by directly applying electric current to the operation spring to control the position. This invention relates to an actuator that performs load control, etc.

[Conventional technology]

As is well known, the crystal structure of shape memory alloys changes at temperatures above and below the transformation point temperature, and when deformed below the transformation point temperature, it returns to its original shape when heated above the transformation point temperature. It is an alloy with a shape memory effect that recovers.
Utilizing the characteristics of this shape memory effect, it has recently come to be applied in various fields.

Furthermore, as part of its application, the development of actuators using shape memory alloys is progressing. Actuators using such shape memory alloys have simple mechanisms, are compact, lightweight, and have excellent environmental resistance other than temperature, and have recently been used in various fields as actuators to replace conventional electromagnetic solenoids. has been reported.

Next, FIG. 10 shows a typical structural example of a conventional actuator using a shape memory alloy. In the figure, 1 is a coiled operating spring wound with a wire of a shape memory alloy of constant thickness such as NiTi alloy or tinol alloy, 2 is a coiled bias spring, and 3 is an operating rod. The operating springs 1.3 are located on both left and right sides of the rod flange 31. After the bias spring 2 is attached, the assembly of these parts is assembled into the frame 4 to constitute the actuator. Further, the operation spring 1 made of a shape memory alloy is directly energized by a current supply device 6 via electrode plates 5 arranged at both ends thereof.

With this configuration, at room temperature below the transformation point temperature of the shape memory alloy, the operating spring 1 is pushed to the left by the spring force of the bias spring 2 and deforms so as to contract, and the operating rod 3 is on standby in the state shown in the figure. Here, current is applied directly to the operating spring 1 via the electrode plate 5 from the current supply device 6, and when the shape memory alloy is heated to a temperature higher than the transformation point temperature, the shape is restored, and the operating spring 1 is operated against the bias spring 2. Drive rod 3 to the right. In other words, the operating rod 3 moves in two directions indicated by arrow A by controlling energization and de-energization.

In addition, the characteristics of the operation spring 1 made of NiTi alloy as the shape memory alloy mentioned above include the relationship between temperature T and load P when the spring is restrained and held in a constant deflection state, and the relationship between temperature T and load P when a constant load is applied to the spring. Temperature T and deflection δ when held at
The relationships between the two are shown in FIGS. 11 and 12, respectively. As is clear from this characteristic diagram, the characteristics of the operating spring made of a shape memory alloy change rapidly near the transformation point temperature of the shape memory alloy, and hardly change in other temperature ranges.

[Problem that the invention seeks to solve]

By the way, in the conventional actuator mentioned above, since the operating characteristics such as load and deflection change rapidly in a stepwise manner after reaching the transformation point temperature of the shape memory alloy, there is no problem when used as an on-off operation type actuator. However, in order to use it as a proportional actuator for position control, for example, extremely accurate temperature control is required in a narrow temperature range near the transformation point temperature of the shape memory alloy, and as it is, it is almost impossible to put it into practical use as a proportional actuator. I can't offer it.

The present invention has been made in view of the above points, and its purpose is to provide an actuator that can be continuously controlled and can be applied as a proportional action actuator by improving an operating spring made of a shape memory alloy. It is in.

[Means for solving problems]

In order to solve the above-mentioned problems, according to the present invention, a shape memory alloy is used as an operation spring, and the required motion is controlled using the shape recovery force of the shape memory alloy as an operation force due to direct electrical heating to the operation spring. In the actuator, the electrical resistance value distribution of the shape memory alloy is changed continuously or stepwise over the entire length of the operating spring, so that an operating force that changes in accordance with the amount of energization is obtained.

[Effect]

With the above configuration, the cross-sectional area of the operating spring is changed continuously or stepwise along its longitudinal direction, so that a distribution of electrical resistance values corresponding to changes in the cross-sectional area is obtained.

When a current is supplied from a current supply device to an operating spring made of a shape memory alloy while changing the duty ratio using a pulse width modulation method, the temperature at which the operating spring generates heat due to Joule heat is uniformly electrical along the longitudinal direction. It changes with the temperature distribution corresponding to the resistance value distribution. As a result, the region exceeding the transformation point of the shape memory alloy changes continuously or stepwise, and the load generated by the operating spring as a whole can be controlled according to the amount of current applied.Therefore, the above operating spring is biased. By combining springs or by combining two shape memory alloy springs that are independently energized in opposite directions, highly accurate position control can be achieved depending on the amount of energization.
A proportional actuator that performs load control can be realized.

[Embodiment] FIGS. 1 and 2 each show an embodiment of a reciprocating single-rotation arm type actuator according to the present invention.

In FIG. 1, the same members corresponding to FIG. 10 are given the same reference numerals.

First of all, in Figure 1, the basic structure of the actuator is shown in Figure 1.
This is similar to Figure 0, in which the operating spring 10 made of a shape memory alloy has a cross-sectional area that is not as thick over its entire length, but is thicker at the left end and gradually becomes thinner toward the right end. It is made by winding wire into a coil. In addition, a step 41 is formed in the middle of the frame 4 to serve as a stopper, and the spring force of the bias spring 2 at room temperature causes each turn of the shape memory alloy operating spring 10 to come into contact and cause an electrical short circuit. 5. Efforts are made to prevent abnormal heat conduction.

Next, various operating characteristics of the operating spring 10 having the above configuration will be explained in comparison with the operating spring 1 having a uniform thickness shown in FIG. 10. First, Figures 3 and 4.

As shown in FIG. 5, coiled operation springs 1. and 1. are made of a shape memory alloy, each having a wire diameter di of -, where the coil diameter is r. Then, with a constant deflection δ0 applied to the coiled operation spring 10 made of a shape memory alloy whose wire diameter d2 changes continuously in the longitudinal direction, the current supply device 6 directly applies it to the operation spring via the electrode plate 5. Let us consider the loads PL and P2 that occur when electricity is applied and heated. In addition, operation spring 1.10
The wire diameters di and d2 shall be selected so that the operating spring as a whole generates the same load before and after the transformation point of the shape memory alloy.

Here, in FIG. 5, the resistance R (φ) of the minute portion of Δφ shown with diagonal lines in the middle of the coil wire of the operating spring in the longitudinal direction
If the core coil wire diameter is d, the coil diameter is r, and the specific resistance of the shape memory alloy is ρ, then R(φ)=ρ・rΔφ/r
t (d/2) ”-・・-・-(11.

Here, the operating spring I in Fig. 3 has a coil wire diameter d in its entire length region.
have the same wire diameter d1, so from equation (1) the electrical resistance value R(
The distribution of φ) is constant over the entire length of the coil wire, as shown by line (A) in FIG. Further, when the operating spring 1 is energized from the current supply device 6, the amount of heat generated in the minute portion Q (φ
), where the current is i9 and the energization time is t, Q(φn=i”Rφt−−−・−・・−・・・−・−
−−−−−−・−−−・−〜・・−・−・−−−−−+
21, and the distribution of heat generation over the entire length of the coil of the operating spring 1, that is, the distribution of temperature T(φ), is also as shown in line (A) in FIG.

On the other hand, in the operating spring 10 shown in FIG. 4, the coil wire diameter d2 is not constant but changes continuously along the longitudinal direction. If , gradually increases, then equation (1) shows the distribution of electrical resistance and the heat generated by energization.

The temperature distribution will be represented by the (opening) line in FIG.

Next, the load P generated on the operating coils 1 and 10 due to the shape recovery force of the shape memory alloy due to energization will be considered. The deflection δ of the coiled operating spring is expressed as follows, where ω(φ) is the angular strain of the coil wire and r is the coil diameter. If n is the number of turns of the coil of the operating spring, φ0 is 2πn. Also, here the coil wire diameter is d.

If the rigidity of the shape memory alloy is G(φ), then ω(φl=
(32rP/π) ・(1/Δφ'・(dφ))・・
・・−・・・・・−・・−・−・−・・−・−
...(4). Therefore, the load P generated when the deflection of the operating springs 1 and 10 is maintained at 60 as shown in FIGS. 3 and 4 is as follows from (31, (412).

−・・・−−１−−−−−−・・−・−・−・・−・−
・-1-・-・-(5) Next, assuming that the R phase (rombohedral phase) transformation of the NiTi alloy is used to recover the shape of the shape memory alloy, the rigidity G (φ) of the shape memory alloy in the previous equation is
As shown in Figure 7, the transition temperature changes from GL to G to L at the transformation point temperature Tm.
Let us consider the generated load P of the operating spring assuming that it changes rapidly. In FIGS. 3 and 4, the current supply device increases the pulse width/period using the pulse width modulation method, that is, the duty ratio, from a state where the temperature of the operating spring 1.10 is sufficiently lower than the transformation point temperature of the shape memory alloy. When controlling the energization in step 6, first of all, in operating spring 1 in Fig. 3 where the coil wire diameter is constant, the temperature distribution becomes uniform over the entire length of the coil of the operating spring as shown in line (A) in Fig. 6. From equation (5), the relationship between the generated load P and the duty ratio is as shown in FIG. 8.

In other words, as shown in FIG. 7, below the transformation temperature Tm, G(φ
)-G, is heated to the transformation point temperature Tll and at the same time becomes G(φ
Since 1=Gn, when the duty ratio increases to a certain value in FIG. 8, the generated load P increases stepwise from PL to PH.

In other words, although the conventional actuator using the operating spring 1 shown in Fig. 3 can perform on/off operations as described above, it is not suitable for application to a proportional action type actuator that continuously controls the generated load. I understand.

On the other hand, in the operating spring 10 shown in Fig. 4, the temperature distribution over the entire length of the coil is not uniform and changes continuously, as shown by line (b) in Fig. 6. The relationship between the generated load P and the duty ratio is shown in FIG. 9 from equation (5). That is, as the duty ratio of the amount of current is gradually increased, the rigidity G (φl''GL) increases over the entire length of the coil wire of the operating spring 10.

Therefore, from the state where the generated load P=PL, first, the narrow region of the wire diameter d2 with high resistance in the operation spring 10 exceeds the transformation point temperature G (φl=G As a result, the generated load P of the operating spring 10 increases locally.Subsequently, as the duty ratio of the current is further increased, the area exceeding the transformation point temperature gradually increases, and along with this, the load P of the operating spring 10 as a whole increases. The generated load P gradually increases.Then, when the entire length of the coil wire of the operating spring 10 rises to the transformation point temperature, the overall rigidity increases to G.
(φ)=Gll, and the generated load becomes P-Pi.

In other words, the generated load does not change stepwise like the operation spring 1, but changes continuously in response to the duty ratio of the applied current.

As a result, in the actuator shown in FIG. 1 using the operation spring 10 shown in FIG. The shape recovery region of the spring 10 partially changes, and the load generated by the entire operating spring can be controlled continuously and accurately. In other words, by combining it with the bias spring 2 as shown in FIG. 1, it can be seen that continuous precision (proportional operation control) can be performed for position control and load control.

In the above embodiment, the operating spring 10 has a coil wire diameter that changes continuously, but substantially the same effect can be obtained even if the coil wire diameter is changed stepwise along its longitudinal direction. can. Furthermore, in the embodiment shown in FIG.
By replacing the bias spring 2 with a shape memory alloy spring instead of a normal spring material and controlling its energization in the opposite direction to the operation spring 1, it is possible to perform proportional operation control in the two directions of arrow A. Become.

Next, FIG. 2 shows an actuator according to a different embodiment of the present invention. In this embodiment, a pivot portion 72 is provided at the tip of the fixed arm 71.
This is a rotary arm type actuator that rotates the movable arm 73 in the direction of arrow B in the arm mechanism 7 that connects the movable arm 73 via the arm mechanism 7. Here, a wire-shaped operation spring 8 made of a shape memory alloy whose wire diameter gradually increases is stretched on the back side of the entire length region from the fixed arm 71 to the movable arm 73 via a pulley 74 provided on the pivot portion 72. On the opposite side of the operating spring 8, there is a coiled operating coil made of a shape memory alloy, which extends between the fixed arm 71 and the movable arm 73 and whose coil wire diameter changes continuously or stepwise as in the previous embodiment. A spring 9 is installed diagonally. Further, each of the operating springs 8 and 9 is heated and controlled by being individually energized directly by the current supply device 6.

With this configuration, by heating the operating spring 8 from the illustrated state to restore its shape, the movable arm 73 rotates counterclockwise in response to the amount of current applied. Conversely, if the operation spring 9 is energized and heated, the movable arm 73 rotates clockwise. Furthermore, by appropriately controlling the amount of current flowing through the operating spring 8.9 during this operation, the rotation angle can be continuously and accurately controlled.

〔Effect of the invention〕

As described above, according to the present invention, in an actuator that uses a shape memory alloy as an operation spring and controls a required operation using the shape recovery force of the shape memory alloy as an operation force by direct electric heating to the operation spring, By changing the electrical resistance value distribution of the shape memory alloy continuously or stepwise over the entire length of the operating spring, the structure is configured to obtain an operating force that changes in response to the amount of current, which cannot be achieved with conventional actuators. As a proportional operation type actuator, position control and load control can be performed with high precision, and its uses can be expanded.

[Brief explanation of the drawing]

1 and 2 are configuration diagrams of a reciprocating type actuator and an arm rotation type actuator showing different embodiments of the present invention, respectively.
Figures 4 and 5 are a side view, a partial front view, and a partial front view of an operation spring made of a shape memory alloy in which the coil wire diameter is constant and the coil wire diameter changes continuously, for the purpose of explaining the operation. 3 and 4 are electrical resistance and temperature distribution diagrams over the entire length of the coil wire of the operating spring, Figure 7 is a diagram of the relationship between the rigidity of the shape memory alloy and temperature, and Figures 8 and 9 The diagrams show the relationship between the load generated by the operating spring and the current duty ratio corresponding to Figures 3 and 4, Figure 10 is a configuration diagram of a typical conventional actuator, and Figures 11 and 12 are FIG. 10 is a relationship diagram of the load, deflection, and temperature of the shape memory alloy operating spring in FIG. 10, respectively. In each figure, 1.8.9. io: Operation spring made of shape memory alloy, 2: Bias spring, 3: Stainless steel, 5: Electrode plate, Fig. 1 Fig. 2 Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 9

Claims (1)

[Scope of Claims] 1) In an actuator that uses a shape memory alloy as an operation spring and controls a required operation using the shape recovery force of the shape memory alloy by direct electric heating to the operation spring as an operation force, the operation spring is An actuator characterized in that the electric resistance value distribution of a shape memory alloy is changed continuously or stepwise over the entire length region to obtain an operating force that changes in response to the amount of current applied. 2) The actuator according to claim 1, wherein the cross-sectional area of the operating spring changes continuously or stepwise along its longitudinal direction.