JPH0768941B2 - Actuator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention uses a shape memory alloy as an operation spring, and performs position control using the shape recovery force of the shape memory alloy by direct current heating to the device spring as an operation force, The present invention relates to an actuator that controls load.

[Conventional technology]

As is well known, the shape memory alloy changes its crystal structure above and below the transformation point temperature, and when the deformation given below the transformation point temperature is heated above the transformation point temperature, the original shape is restored. It is an alloy with a shape memory effect that recovers,
Utilizing the characteristics of the shape memory effect, it has recently been applied in various fields.

In addition, as part of its application, the development of actuators using shape memory alloys is in progress. An actuator using such a shape memory alloy has a simple mechanism, can be made small and lightweight, and has excellent environmental resistance other than temperature.As an actuator that replaces the conventional electromagnetic solenoid, it has recently been applied in various fields. Has been reported.

Next, FIG. 10 shows an example of a typical conventional structure of an actuator using a shape memory alloy. In the figure, 1 is Ni
A coil-shaped operation spring formed by winding a wire of a shape memory alloy having a constant thickness such as a Ti alloy (Nitinol alloy), 2 is a coil-shaped bias spring, and 3 is an operation rod.
On the other hand, the actuator spring 1 and the bias spring 2 are mounted on both left and right sides of the rod flange 31, and then the assembly of these parts is incorporated into the frame 4 to form an actuator. The operation spring 1 made of a shape memory alloy is directly energized by the current supply device 6 via the electrode plates 5 arranged at both ends thereof.

With such a structure, at room temperature below the transformation point temperature of the shape memory alloy, the operation spring 1 is deformed by the spring force of the bias spring 2 so as to be pushed and contracted to the left side, and the operation rod 3 stands by in the illustrated state. Here, the current supply device 6 directly energizes the operation spring 1 through the electrode plate 5 to recover the shape by heating the shape memory alloy to a temperature higher than the transformation point temperature, and the operation spring 1 operates against the bias spring 2. Drive the rod to the right. That is, the operating rod 3 moves in the two directions of arrow A by controlling the energization and de-energization.

As the characteristics of the operation spring 1 made of NiTi alloy as the shape memory alloy, the relationship between the temperature T and the load P when the spring is restrained and held in a constant flexure state, and a constant load is applied to the spring. The relationship between the temperature T and the deflection δ when held by holding is shown in FIGS. 11 and 12, respectively. As is apparent from this characteristic diagram, the characteristic of the operation spring made of the shape memory alloy changes rapidly near the transformation temperature of the shape memory alloy, and hardly changes in other temperature regions.

[Problems to be solved by the invention]

By the way, in the above-mentioned conventional actuator, the operating characteristics such as load and deflection suddenly change stepwise at the transformation point temperature of the shape memory alloy. Therefore, there is no problem in using it as an on-off actuator. However, for use as a proportional motion type actuator that performs position control, for example, extremely accurate temperature control is required in a narrow temperature region near the transformation temperature of the shape memory alloy,
As it is, it cannot be practically used as a proportional motion type actuator.

The present invention has been made in view of the above points, and an object thereof is to provide an actuator capable of continuous control which can be applied as a proportional motion type actuator by improving an operation 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 a required operation is controlled by using a shape recovery force of the shape memory alloy by direct current heating to the operation spring as an operation force. In the actuator, the electric resistance distribution of the shape memory alloy is continuously or stepwise changed over the entire length of the operation spring so as to obtain an operation force that changes corresponding to the amount of energization.

[Action]

With the above configuration, the operation spring changes the cross-sectional area continuously or stepwise along the longitudinal direction thereof to obtain the distribution of the electric resistance value corresponding to the change of the cross-sectional area.

When a current is supplied from a current supply device to the shape-memory alloy operation spring while changing the duty ratio by a pulse width modulation method, the heat generation temperature of the operation spring due to the Joule heat is not uniform along the longitudinal direction and is an electric current. It changes according to the temperature distribution corresponding to the resistance value distribution. Along with this, the region of the shape memory alloy that exceeds the transformation point temperature changes continuously or stepwise, and the load generated by the entire operation spring can be controlled according to the amount of energization. Therefore, by combining the above-mentioned operation spring with a bias spring, or by combining two shape memory alloy springs that are independently energized in opposite directions, highly precise position control and load control can be performed according to the amount of energization. It is possible to realize a proportional action type actuator that performs.

〔Example〕

1 and 2 show an embodiment of a reciprocating type actuator and a rotating arm type actuator according to the present invention, respectively.
In FIG. 1, the same members corresponding to those in FIG. 10 are designated by the same reference numerals.

First, in FIG. 1, the basic structure of the actuator is shown in FIG.
Similar to the figure, here the operation spring 10 made of a shape memory alloy has a uniform cross-sectional area throughout its entire length,
It is made by winding a wire rod that has a thick left end and gradually becomes thinner toward the right end. Frame 4
A step 41 serving as a stopper is formed in the middle part of
At normal temperature, the spring force of the bias spring 2 prevents contact between the turns of the shape memory alloy operation spring 10 to electrically short-circuit or to cause abnormal heat conduction.

Next, various operating characteristics of the operation spring 10 having the above structure will be described in comparison with the operation spring 1 having a uniform thickness shown in FIG. First, as shown in FIG. 3, FIG. 4, and FIG. 5, the coil-shaped operation spring 1 made of a shape memory alloy with a constant wire diameter d1 with the coil diameter r and the wire diameter d2 are continuous in the longitudinal direction. Coil spring made of shape memory alloy
Loads P1 and P2 generated when a current is supplied from the current supply device 6 directly to the operation spring through the electrode plate 5 to heat the operation spring while a constant deflection δ _{0 is applied} to 10 will be examined. The wire diameters d1 and d2 of the operating springs 1 and 10 are selected so that the operating springs as a whole generate the same load before and after the transformation point of the shape memory alloy.

Here, in FIG. 5, the resistance R (φ) of a small portion of Δφ indicated by diagonal lines in the middle of the coil wire longitudinal direction of the operation spring.
Is R (φ) = ρ · rΔφ / π (d / 2) ² (1), where d is the coil wire diameter, r is the coil diameter, and ρ is the specific resistance of the shape memory alloy. Become. Since the coil wire diameter d in the operation spring 1 of FIG. 3 is the same wire diameter d1 in the entire length region, the distribution of the electric resistance value R (φ) is expressed by the line (a) in FIG. 6 from the equation (1). Thus, it becomes constant over the entire length of the coil wire. Further, the heat generation amount Q (φ) generated in the minute portion when the operation spring 1 is energized by the current supply device 6 is Q (φ) = i ² Rφt (where i is the current and t is the energization time). 2) is the heat generation distribution in the entire coil length range of the operation spring 1,
That is, the distribution of the temperature T (φ) also becomes like the line (a) in FIG.

On the other hand, in the operation spring 10 shown in FIG. 4, since the coil wire diameter d2 is not constant and continuously changes along the longitudinal direction, the coil wire diameter d along φ in FIG. If becomes gradually larger, the distribution of the electric resistance value from Eq. (1),
In addition, the heat generation and temperature distribution due to energization are represented by the line (b) in FIG.

Next, the operation coil is operated by the shape recovery force of the shape memory alloy due to energization.
Consider the load P generated at 1, 10 by blowing. Deflection δ of the coil-shaped operation spring is given by ω (φ), the coil diameter is r, Becomes If the number of coil turns of the operation spring is n, then φ ₀ is 2πn. If the coil wire diameter is d and the rigidity of the shape memory alloy is G (φ), then ω (φ) = (32rP / π) · (1 / Δφ ⁴ · G (φ)).
… (4). Therefore, as shown in FIGS. 3 and 4, the operation spring 1,
The load P generated when the deflection of 10 is held at δ ₀ is given by the following equation from the equations (3) and (4).

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 modulus G (φ) of the shape memory alloy in the above equation is as shown in FIG.
Consider the generated load P of the operating spring on the assumption that it changes abruptly from _GL to _GH at Tm. In FIGS. 3 and 4, from the state where the temperature of the operating springs 1 and 10 is sufficiently lower than the transformation temperature of the shape memory alloy, the current supply device is arranged to increase the pulse width / cycle, that is, the duty ratio by the pulse width modulation method. 6
When the energization control is performed with, the temperature distribution of the operation spring 1 of FIG. 3 in which the coil wire diameter is constant becomes uniform over the entire coil length range of the operation spring as shown in line (a) of FIG. The relationship between the generated load P and the duty ratio is as shown in FIG. 8 from the equation (5). That is, as shown in FIG. 7, G (φ) = _GL at the transformation point temperature Tm or lower, but G (φ) over the entire length of the coil of the operation spring 1 at the same time when the temperature is raised to the transformation point temperature Tm. ) = G _H , the generated load P changes in a stepwise manner from P _L to P _H when the duty ratio rises to a certain value in FIG. That is, the conventional actuator using the operation spring 1 shown in FIG. 3 can be turned on and off as described above, but 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 operation spring 10 shown in FIG. 4, the temperature distribution in the entire coil length region is not uniform and changes continuously as shown by the line (b) in FIG. The relationship between the generated load P and the duty ratio is as shown in FIG. 9 from the equation (5). That is, gradually increased the duty ratio of the current amount, over the coil wire the entire length range of the operating spring 10 the shear modulus G (φ) = G _L, thus the state is generated load P = P _L, first operation A region of the spring 10 with a large wire diameter d2 having a large resistance exceeds the transformation point temperature before the region of a large wire diameter with a small resistance has G (φ) = _GH , and the generated load P of the operating spring 10 is locally Rise to. Subsequently, when the duty ratio of the energizing current is further increased, the region exceeding the transformation point temperature gradually increases, and the generated load P in the entire operation spring 10 is accordingly increased.
Will gradually rise. The rigidity of the whole when the coil wire the entire length range of the operating springs 10 is increased to transformation temperature is increased to G (φ) = G _H, the generated load becomes P = P _H. That is, the generated load does not change stepwise like the operation spring 1, but continuously changes corresponding to the duty ratio of the energized current.

As a result, in the actuator of FIG. 1 using the operation spring 10 of FIG. 4, by appropriately controlling the current flowing through the operation spring 10 by the pulse width modulation method, the shape memory alloy operation corresponding to the energization amount can be obtained. The shape recovery region of the spring 10 is partially changed, and the load generated as the entire operation spring can be accurately and continuously controlled. That is, it can be seen that by combining with the bias spring 2 as shown in FIG. 1, proportional motion control can be continuously and accurately performed with respect to position control and load control.

In the above-mentioned embodiment, the operating spring 10 has been described as having a coil wire diameter that changes continuously, but even if the coil wire diameter is changed stepwise along its longitudinal direction, substantially the same effect can be obtained. it can. Further, in the embodiment of FIG. 1, the bias spring 2 is replaced with a spring made of a shape memory alloy from a normal spring material, and its energization is controlled in the opposite direction to that of the operation spring 1, whereby the proportionality in the two directions of arrow A is obtained. It becomes possible to perform operation control.

Next, FIG. 2 shows an actuator according to another embodiment of the present invention. This embodiment is a rotary arm type actuator for rotating the movable arm 73 in the direction of arrow B in the arm mechanism 7 in which the movable arm 73 is connected to the tip of the fixed arm 71 via the pivot 72. Here, a wire-shaped operation spring 8 made of a shape memory alloy whose wire diameter is gradually increased is stretched on the back side of the entire length area from the fixed arm 71 to the movable arm 73 via the pulley 74 provided on the pivot 72. , The operation spring 8
On the opposite side, a coil-shaped operating spring 9 made of a shape memory alloy, which straddles between the fixed arm 71 and the movable arm 73 and whose coil wire diameter changes continuously or stepwise as in the previous embodiment.
Is installed diagonally. The operating springs 8 and 9 are individually heated by the electric current supply device 6 to directly energize them.

With this configuration, the operating spring 8 is energized and heated to recover its shape from the illustrated state, so that the movable arm 73 rotates counterclockwise in accordance with the amount of energization. On the contrary, if the operation spring 9 is electrically heated, the movable arm 73 rotates clockwise. Moreover, the rotation angle can be continuously and accurately controlled by appropriately controlling the amount of current flowing through the operation springs 8 and 9 during this operation.

As described above, according to the present invention, the shape memory alloy is used as the operation spring, and the required operation is controlled by using the shape recovery force of the shape memory alloy by the direct current heating to the operation spring as the operation force. In the actuator to be performed, the electric resistance value distribution of the shape memory alloy is continuously or stepwise changed over the entire length of the operation spring so as to obtain an operation force that changes according to the amount of energization. As the proportional motion type actuator, which could not be achieved by the above, it is possible to perform position control and load control with high accuracy, and it is possible to expand its applications.

[Brief description of drawings]

1 and 2 are configuration diagrams of reciprocating type and arm rotating type actuators showing different embodiments of the present invention, respectively.
FIGS. 4, 5, and 6 are side views, a partial front view, and a front view of a shape memory alloy operating spring whose coil wire diameter is constant and whose coil wire diameter is continuously changed, which are shown for explaining the operation. Is a distribution diagram of electric resistance and temperature over the entire length of the coil wire of the operation spring corresponding to FIGS. 3 and 4, FIG. 7 is a relational diagram of rigidity and temperature of shape memory alloy, FIG. 8 and FIG. The figures show the relationship between the load generated by the operating spring and the duty ratio of the energizing current, which correspond to Figures 3 and 4, respectively. Figure 10 shows the configuration of a typical conventional actuator, and Figures 11 and 12 show FIG. 10 is a diagram showing the relationship between the load, the deflection, and the temperature of the shape memory alloy operating spring shown in FIG. 10. In each drawing, 1,8,9,10: shape memory alloy operating spring, 2: bias spring, 3: operating rod, 5: electrode plate, 6: current supply device, 7: arm mechanism.

Claims (2)

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