JPH0697529A - Differential strictive actuator - Google Patents

Abstract

PURPOSE:To realize linear control of high precision by providing a pair of striction bodies and a movable body which receives driving action in the mutually opposite directions by the strictive action of each striction body. CONSTITUTION:A movable body 23 which receives driving action in the mutually opposite direction by the strictive action of a pair of striction bodies 17, 18 is provided. In the case that the striction bodies 17, 18 are magnetostriction bodies, the strain inducing means are coils, and a first coil 15 and a second coil 16 are differentially excited by a first power supply circuit Ea and a second power supply circuit Db. In the case that the striction bodies 17, 18 are electrostriction bodies, the striction inducing means are a pair of DC voltage applying electrodes which constitute a pair sandwiching the electrostriction bodies. DC voltages are differentially applied to a first DC voltage applying electrode and a second DC voltage applying electrode from the first power supply circuit Ea and the second power supply circuit Eb. Thereby, in the strictive actuator, nonlinear characteristics of magnetostriction or electrostriction are improved, influence of temperature drift is eliminated, hysteresis characteristics are restrained, and excellence striction linearity can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a differential strain actuator.

[0002]

2. Description of the Related Art An actuator using a magnetostrictive element or an electrostrictive element has been conventionally proposed. FIG. 6A shows a magnetostrictive actuator, and the magnetostrictive body 1 is a terbium (T
e), iron (Fe), and dysprosium (Dy). A magnetic field is applied to the magnetostrictive body 1 by exciting the solenoid 2, and the magnetostrictive body 1 extends in the lengthwise direction by the applied magnetic field. Due to this extension, the drive lever 3 moves the preload spring 4
Driven against.

FIG. 7A shows an electrostrictive actuator,
The electrostrictive laminated body 5 is configured by alternately laminating the piezoelectric element layers 5a and the electrode layers 5b. The polarization direction of the piezoelectric element layer 5b is aligned with the voltage application direction (laminating direction), and when a DC voltage is applied to the electrode layer 5b, the electrostrictive body 5 extends in the laminating direction.

[0004]

The curve C ₁ of the graph of FIG. 6B represents the strain rate in the longitudinal direction of the magnetostrictive body 1 with respect to the strength of the magnetic field, and the curve C ₂ of the graph of FIG. 7B. Represents the strain rate in the stacking direction of the electrostrictive body 5 with respect to the strength of the voltage. As can be seen from both figures, the displacement characteristic of the magnetostrictive body 1 with respect to the applied magnetic field strength and the displacement characteristic of the electrostrictive body 5 with respect to the applied voltage strength are non-linear, and the hysteresis is large. Moreover, thermal expansion and changes in operating characteristics are significantly affected by changes in operating temperature,
There is a drawback related to the temperature drift phenomenon in which the amount of strain fluctuates due to temperature changes despite the same magnetic field strength. Therefore, it has been extremely difficult to use an actuator using a magnetostrictive body or an electrostrictive body as a precision actuator for controlling the flow rate or pressure in a high-performance minute positioning device, a spool valve, and a pilot valve.

It is an object of the present invention to provide a strain actuator capable of achieving highly accurate linear control by eliminating influences of non-linearity of magnetostrictive body and electrostrictive body, temperature drift and hysteresis as much as possible. .

[0006]

Therefore, according to the present invention,
A first power supply circuit that outputs a drive signal proportional to an input signal, and a second power circuit that outputs a drive signal inversely proportional to the input signal
Power supply circuit, first distortion inducing means for generating a distortion inducing force by the drive signal of the first power supply circuit, and second distortion inducing means for generating a distortion inducing force by the drive signal of the second power supply circuit. A differential including a pair of strain bodies that generate strain by the operation of the first strain inducing means and the second strain inducing means, and a movable body that receives a driving action in opposite directions due to the strain action of each strain body. Type strain actuator was constructed.

[0007]

When the strain body is a magnetostrictive body, the strain inducing means is a coil, and the first coil and the second coil are differentially excited by the first power supply circuit and the second power supply circuit. When the strain body is an electrostrictive body, the strain inducing body is a pair of direct current voltage applying electrodes sandwiching the electrostrictive body, and the first direct current voltage applying electrode and the second direct current voltage applying electrode pair are the first pair. Power supply circuit and second
A differential voltage is applied by the power supply circuit.

The differential excitation is excitation so that the magnetic fluxes of the pair of coils are generated in the directions in which they are mutually reduced. That is, when the magnetic flux of one coil increases, the magnetic flux of the other coil proportionally decreases. Differential voltage application is to increase the voltage between one DC voltage applying electrode pair and decrease the voltage between the other DC voltage applying electrode pair proportionally.

The difference between the strains of the pair of strain bodies due to the differential action remarkably improves the non-linearity due to the squared characteristic and the drift characteristic due to the influence of temperature, external magnetic field, and the like, and by applying an appropriate bias value. This brings about a substantially linear characteristic in which the hysteresis characteristic is suppressed. Therefore, the movable body is displaced in proportion to the difference between the strains of the two strain bodies, and the displacement of the movable body becomes substantially linear with respect to the input signal.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment embodying the present invention will be described below with reference to FIGS. Underframe 1 as shown in FIG.
0 has a pair of arms 10a and 10b, and mounting seats 11 and 12 are provided on the facing surfaces of both arms 10a and 10b.
Is fastened. Cylindrical yokes 13 and 14 are fixed on the mounting seats 11 and 12, respectively.
The coils 15 and 16 are housed therein. Coil 1
Magnetostrictive rods 17 and 18 are housed in 5 and 16. The magnetostrictive rods 17 and 18 are made of an alloy mainly containing terbium (Te), iron (Fe) and dysprosium (Dy).

Pressing plates 19, 20 are joined to the opposing surfaces of the magnetostrictive rods 17, 18, and preload springs 21, 22 are interposed between the pressing plates 19, 20 and the arms 10a, 10b. The pressing plates 19 and 20 are pressed against the magnetostrictive rods 17 and 18 by the pulling action of the preload springs 21 and 22.

Yokes 13, 14 and mounting seats 11, 12
The pressing plates 19 and 20 are both made of a ferromagnetic material, and a magnetic circuit is formed around the coils 15 and 16 by these members.

A lever 23 is interposed between the pressing plates 19 and 20. The lever 23 is tiltably supported by the underframe 10 via a support shaft 24, and both pressing plates 19 and 20 are in contact with the lever 23 via integrally formed spherical projections 19a and 20a.

Excitation of the coils 15 and 16 is performed by the drive circuit 25. The drive circuit 25 uses operational amplifiers 25a ₁ and 25b ₁ having excellent input / output linearity.
A power supply circuit Ea including an inverting amplifier circuit and an Eb including a non-inverting amplifier circuit are configured. Further, protective diodes 25a ₂ and 25b ₂ are provided in parallel with the coils 15 and 16 in order to suppress the induced voltage of the coils 15 and 16. Rb
₀ , Ra ₁ , Rb ₁ , Ra ₂ , Rb ₂ , Ra ₃ , Rb ₃
Is a resistor.

The straight lines L ₁ and L _{2 in} FIG. 2 show the input / output characteristics of the drive circuit 25. The horizontal axis of the coordinate axis is the drive circuit 25, 2
6 represents the control voltage signal Vin input to 6, and the vertical axis represents the output voltage. The output voltage represented by the straight line L ₁ and the output voltage represented by the straight line L ₂ are excitation voltages applied to the coils 15 and 16, and have characteristics opposite to each other. That is, the exciting voltages of the coils 15 and 16 are respectively Va and Vb.
Then, the exciting voltage Va monotonically increases with the same gradient with respect to the control voltage signal Vin, and the exciting voltage Vb monotonically decreases with the same gradient as the exciting voltage Va. Therefore, both excitation voltages Va and Vb
The value of the sum (Va + Vb) of V is always constant regardless of Vin. That is, the differential voltages Va and Vb are applied to the coils 15 and 16.

Curves C ₃ and C ₄ in FIG. 2 are magnetostrictive rods 17,
18 shows the distortion characteristics of 18. The coordinate axis of the strain characteristic of the magnetostrictive rod 18 represented by the curve C ₄ is vertically and horizontally inverted with respect to the coordinate axis of the strain characteristic of the magnetostrictive rod 17 represented by the curve C ₃ . The horizontal axis of the coordinate axes is the coils 15 and 16.
Represents the strength of the magnetic field generated by, and the vertical axis represents the strain rate. In this embodiment, the control voltage signal Vin is used in the range 0 to V ₁ in and the field strength ranges from 0 to e ₁ Oersted. Therefore, when the control voltage signal Vin is 0, the coil 1
The magnetic field generated by 5 is 0, and the magnetic field generated by the coil 16 is e ₁
Is. Coil 1 when the control voltage signal Vin is V ₁ in
The generated magnetic field of 5 is e ₁ and the generated magnetic field of the coil 16 is 0
Is.

The magnetic field generated by the coil 15 acts on the magnetostrictive rod 17, and the magnetic field generated by the coil 16 acts on the magnetostrictive rod 18. Due to the action of these generated magnetic fields, both magnetostrictive rods 1
7, 18 are distorted, and this distorting force opposes via the lever 23. That is, as shown in FIG.
Forces F ₁ and F ₂ proportional to the strain rate are received from both magnetostrictive rods 17 and 18 via the spherical protrusions 19a and 20a on the shafts 9 and 20, respectively. When the control voltage signal Vin is V ₁ in / 2, both magnetostrictive rods 17 and 18 are subjected to the action of a magnetic field of the same strength, and the lever 23 exerts a force F of the same magnitude from both magnetostrictive rods 17 and 18.
Receive ₁ and F ₂ and equilibrate to the central position. That is, both magnetostrictive rods 17 and 18 have a total magnetic field e ₁ of 1 due to the bias current.
Upon receiving a magnetic bias of a value of / 2, the differential operation is performed with this state as a reference.

The curve C _{5 in} FIG. 2 shows the two magnetostrictive rods 17, 18.
Represents the differential output of the strain rate, and this strain curve C ₅ is the force F ₁ , F acting on the lever 23 from both magnetostrictive rods 17, 18.
The synthetic force of ₂ (F ₁ −F ₂ ) is also shown. Therefore, when the control voltage signal Vin is V ₁ in / 2 or less, the lever 23 tilts toward the magnetostrictive rod 17, and when the control voltage signal Vin is V ₁ in / 2 or more, the lever 23 moves toward the magnetostrictive rod 18 side. Lean. This inclination is influenced by the hysteresis characteristic of the distortion shown by the curve C ₅ , but this inclination displacement becomes almost linear.

The magnetostrictive rods 17 and 18 remarkably undergo thermal expansion and strain characteristic changes due to temperature changes. However, if the temperatures of both magnetostrictive rods 17 and 18 are the same, thermal expansion and strain of both magnetostrictive rods 17 and 18 occur in the directions opposite to each other.
Eighteen offset each other. Further, the lever 23 is always subjected to the force from the opposing direction by the magnetostrictive rods 17 and 18,
This has the effect of offsetting and reducing the hysteresis characteristics due to the backlash of each part.

The preload springs 21 and 22 have the function of improving the strain rate by the preload effect of the magnetostrictive alloy. The graph of FIG. 3 shows a method of significantly improving the hysteresis characteristic of the differential strain actuator of FIG.

In this system, the magnetic field generated in each of the magnetostrictive rods 17 and 18 is used in a range having a small hysteresis [e].
₂ , e ₃ ] and the value V of the control voltage signal Vin at which the value of the difference (Va-Vb) between the differential voltages Va and Vb becomes 0.
_By inputting ₂ in, both coils 15 and 16 have (e ₂ + e
A magnetic field having a strength of ₃ ) / 2 oersted is generated, and both magnetostrictive rods 17 and 18 receive a magnetic bias of this value and differentially operate with this state as a reference. The curve C ₆ represents the difference between the strain rates of the two magnetostrictive rods 17 and 18 in the magnetic field use range [e ₂ , e ₃ ]. As shown by the curve C ₆ , the hysteresis characteristic and linearity are greatly improved as compared with the case of FIG. Such improvement is obtained by specifying the range of use of the magnetic field to a range having a small hysteresis and applying the bias magnetic field.

It should be noted that when the intersections of the straight lines L ₁ and L ₂ representing the differential voltages Va and Vb in FIG. 2 are on the horizontal axis, that is, V
When the differential voltages Va and Vb such that a = Vb = 0 are output, the differential voltages Va and Vb take positive and negative values. When the differential voltages Va and Vb are positive and negative, the distortion rate has a minimum value,
The linearity of the synthetic distortion characteristics cannot be obtained. When a drive circuit that outputs differential voltages Va and Vb such that Va = Vb = 0 is used, a bias current is added to both coils 15 and 16 in advance so that both differential voltages Va and Vb are It should not be a negative value.

Alternatively, instead of applying a bias current, the yokes 13, 14, the mounting seats 11, 12 and the pressing plate 1
A permanent magnet may be interposed on the magnetic circuit composed of 9 and 20 so that the bias magnetic field acts on both magnetostrictive rods 17 and 18.

Next, a second embodiment embodying the present invention will be described with reference to FIG. A support 26a is integrally formed on the support 26, and a lever 26b is tiltably connected to the support 26a. Electrostrictive laminates 27 and 28 are erected on both sides of the pillar 26a.
The spherical protrusions 27a and 28a at the tips of the levers 7 and 28 are levers 26b.
Abuts on the fulcrum so as to take an exact symmetrical position.

The electrostrictive laminates 27 and 28 are piezoelectric element layers 27.
b and 28b and electrode layers 27c and 28c are alternately adhered to form a laminated structure. One DC voltage V of the drive circuit 25
a is applied between the adjacent electrode layers 27c, and the other DC voltage Vb of the drive circuit 25 is applied between the adjacent electrode layers 28c. Piezoelectric element layer 2
The polarization directions of 7b and 28b and the voltage application direction are made to coincide with each other, and DC voltage Va, is applied to the electrode layers 27c and 28c.
When Vb is applied, the piezoelectric element layers 27b and 28b are strained and expanded in the thickness direction according to the applied voltage values Va and Vb. Therefore, the entire electrostrictive laminates 27 and 28 extend in the laminating direction, and the lever 26b receives the strain acting force of both electrostrictive laminates 27 and 28.

The strain characteristics of both electrostrictive laminates 27 and 28 are shown in FIG.
As shown by the curve C ₂ in (b), the DC voltages Va and Vb are differentially applied and the differential strain output is used to generate the electrostrictive laminate 27, as in the case of FIG. 2 or 3. It is possible to remarkably improve the non-linearity and temperature drift of the composite strain characteristic of No. 28, and reduce the hysteresis characteristic.

FIG. 5 shows an embodiment in which two or more sets of the electrostrictive actuators of FIG. 4 are combined, and the working tips of the levers 26b of both electrostrictive actuators are coupled to each other to form a spring 26c by narrowing the cross section near the center. is doing. Reference numeral 29 is an object to be positioned in the vertical direction of the drawing, such as a discharge electrode. When the lever 26b has a single action while the acting force of the lever 26b is doubled by a plurality of such actuator configurations. The arc motion of is improved, and the vertical straight line motion can be accurately performed.

[0028]

As described in detail above, the differential strain actuator of the present invention remarkably improves the non-linear characteristic of magnetostriction or electrostriction and the influence of temperature drift, suppresses the hysteresis characteristic, and achieves good strain linearity. It has an excellent effect that it can be obtained.

[Brief description of drawings]

FIG. 1 is a combination diagram showing a structure and a drive circuit of a differential magnetostrictive actuator.

FIG. 2 is a graph showing magnetostriction hysteresis characteristics and input / output characteristics of a drive circuit.

FIG. 3 is a graph showing magnetostrictive hysteresis characteristics and input / output characteristics of a drive circuit.

FIG. 4 is a combination diagram showing a structure and a drive circuit of a differential electrostrictive actuator.

FIG. 5 is a combination diagram showing another example of the structure of the differential electrostrictive actuator and the drive circuit.

FIG. 6A is a simplified diagram showing a structure of a conventional magnetostrictive actuator, and FIG. 6B is a graph showing a hysteresis characteristic of magnetostriction.

FIG. 7A is a simplified diagram showing a structure of a conventional electrostrictive actuator, and FIG. 7B is a graph showing a hysteresis characteristic of electrostriction.

[Explanation of symbols]

15, 16 ... Coil, 17, 18 ... Magnetostrictive rod, 25 ...
Drive circuit, 27, 28 ... Electrostrictive laminated body, Ea, Eb ... Power supply circuit.

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[Procedure amendment]

[Submission date] November 12, 1992

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1]

Claims (3)

[Claims] 1. A drive signal (V) proportional to an input signal (Vin).
a) a first power supply circuit (Ea), a second power supply circuit (Eb) which outputs a drive signal (Va) inversely proportional to the input signal (Vin), and a first power supply circuit (Ea) ) A first distortion inducing means (15 or 27) for generating a distortion inducing force by the drive signal (Ea).
c) and the second distortion inducing means (16 or 28) for generating the distortion inducing force by the drive signal (Eb) of the second power supply circuit (Eb).
c), a pair of strain bodies (17, 18 or 27b, 28b) that generate strain by the operation of the first strain inducing means (15 or 27c) and the second strain inducing means (16 or 28c), and each strain. A movable body (23) which receives a driving action in mutually opposite directions by a straining action of the body (17, 18 or 27b, 28b).
Or 26b), a differential strain actuator. 2. The differential strain actuator according to claim 1, wherein the strain inducing means (15, 16) is a coil, and the strain body (17, 18) is a magnetostrictive body. 3. The strain inducing means (27c, 28c) is a pair of DC voltage applying electrodes sandwiching the strain body (27b, 28b), and the strain body (27b, 28b) is an electrostrictive body. 1. The differential strain actuator according to 1.