JPH02101780A - Piezoelectric actuator - Google Patents

Abstract

PURPOSE:To enable the accurate operation of a piezoelectric actuator without decreasing the clamping force to a plunger by a method wherein, when the operating speed of the piezoelectric actuator is decreased, only the applied voltage to a piezoelectric element for stroke use is changed, and the applied voltage to a piezoelectric element for clamp use is kept constant. CONSTITUTION:In accordance with an input from a valve opening and shutting switch, a control signal is output to an actuator A of a diaphragm valve V1 from a control unit C, and drives each piezoelectric element to make said valve V1 execute an open and shut operation. At the time of operation speed control of the piezoelectric actuator, only the applied voltage to a piezoelectric element for stroke use is changed, and the applied voltage to a piezoelectric element for clamp use is kept constant. As a result, also when the operation speed is decreased, only the applied voltage to the element for stroke use is changed, and the applied voltage to the element for clamp use can be kept constant. Thereby, the clamping force to a plunger is not decreased, and the generation of plunger slip can be prevented, so that the accurate operation of piezoelectric actuator is enabled.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a piezoelectric actuator that can control the operating speed while preventing the driven member from slipping.

(b) Conventional technology Conventionally, as a form of piezoelectric actuator, one side of a piezoelectric element for stroke is fixed to a fixed part, a piezoelectric element for clamping is attached to the other side of the same element, and the piezoelectric element for clamping is A piezoelectric actuator that moves a plunger over a large distance by repeatedly moving the plunger forward and backward by clamping a plunger as a driven body and expanding and contracting a piezoelectric element for stroke, and a piezoelectric actuator for clamping and stroke. There is a piezoelectric element that generates ultrasonic vibrations and uses the vibrations to move a driven object.The actuator's operating speed can be controlled by changing the voltage applied to each piezoelectric element. There was one in which the amount of expansion and contraction of the element was changed each time.

(c) Problems to be Solved by the Invention However, in the above-mentioned prior art, the voltage applied to both piezoelectric elements for clamping and for stroke is changed in the same way, and in order to slow down the operating speed, When the voltage applied to each piezoelectric element is reduced, the clamping force of the clamping piezoelectric element is also reduced at the same time, causing the plunger as a driven member to slip, resulting in unstable operation.

(d) Means for Solving the Problems In the present invention, pulsed piezoelectricity is applied to a piezoelectric element for stroke and a piezoelectric element for clamping to cause the same elements to repeatedly perform forward and backward movement and clamping movement. In a piezoelectric actuator that operates a driven object, drive control configured to maintain the applied voltage for clamping constant while changing the applied voltage for changing the stroke when a signal is input. It is an object of the present invention to provide a piezoelectric actuator equipped with a piezoelectric actuator.

(E) Functions and Effects According to the present invention, in controlling the operating speed of a piezoelectric actuator, even when slowing down the operating speed, only the voltage applied to the piezoelectric element for stroke is changed, and the voltage applied to the piezoelectric element for clamping is changed. Since the applied voltage is kept constant, the clamping force on the plunger does not decrease, thus preventing the driven member from slipping and allowing the piezoelectric actuator to operate accurately.

Embodiment Embodiments of the present invention will be described in detail with reference to the drawings. In FIG. (C), a cylindrical plunger (d) as a driven body is installed concentrically and movably back and forth along the axis, and furthermore, four cylindrical plungers are installed concentrically on the outer peripheral surface of the cylindrical plunger (d). It is constructed by arranging a piezoelectric structure assembly consisting of piezoelectric elements (e), (f), (g), and (h).

In addition, (iHj) has its base end fixed to the piezoelectric elements (g) and (h) for stroke, and its tip end to the front and rear walls (a
)(b) is a cantilever-like elastic bridge extending toward

Piezoelectric elements (e) and (f) for clamping are attached to the outer peripheral surfaces of the tips of the elastic bridges (i) and (j), and brake shoes (k) (+) are fixed to the inner peripheral surfaces thereof. are doing.

Of these piezoelectric elements (e), (f), (g), and (h), the piezoelectric elements (e) and (f) for clamping function as clamp members, and when the power is turned on, the piezoelectric elements for stroke The piezoelectric elements (a) and (h) are configured to contract when turned off.

That is, the piezoelectric elements (e) and (f) for clamping contract in the energized state and act in a direction to reduce the inner diameter, increasing the clamping force of the cylindrical plunger (d), while in the non-energized state Then, the clamping force of the cylindrical first langeer (d) is reduced by acting in a direction in which the inner diameter expands. on the other hand,
The stroke piezoelectric elements (g) and (h) are in a contracted state on the cylindrical plunger (d) in the axial direction when not energized, and extend over the cylindrical plunger (d) when energized. The total length in the axial direction is increased.

The cylindrical plunger (d) controls the four piezoelectric elements (e) (f) ((J) and (h) by a control device (
C), it can be moved in the axial direction.

Each piezoelectric element (e) (f) (+;+) (h) is formed by laminating a large number of piezoelectric element pieces in the axial direction of the cylindrical plunger (d), as shown in FIGS. 2 and 5. It is a cylindrical element with electrodes provided at both ends of the cylinder, and by applying a voltage to both ends, it is configured to contract by an amount approximately proportional to the applied voltage, reducing the clamping force and stroke. The amount can be controlled by the applied voltage.

Note that the piezoelectric element piece can be made of, for example, piezoelectric ceramics, and examples of such piezoelectric ceramics include AB
PZT[Pb(Zr.

Ti') 03 ] system, and PLZT [Pb, La
(Zr.

A three-component system based on Ti ) Oa ], PT (PbTiOa ), or PZT can be used.

Furthermore, as shown in Fig. 3, the piezoelectric elements (e), (f), (g), and (tl) are formed by forming a large number of thin ring-shaped piezoelectric element pieces in the radial direction around the axis of the cylindrical plunger (d). It can also be formed by laminating. In this case, the applied force direction of the voltage is 9
It will change by 0 degrees.

Note that in the above configuration, piezoelectric elements (e) (f) (g)
(h) can have not only a circular cross section but also a rectangular cross section, for example, and can also be formed from divided pieces as shown in FIGS. 4 and 5.

Moreover, the cylindrical plunger (d) has a brake shoe (kH
Since the material is clamped many times by I), it is desirable to use a material with a small coefficient of linear expansion, high hardness, strength, creep resistance, and wear resistance, and high processing accuracy. For example, a material made of ceramic material is desirable. I can think of things.

Next, the movement of the cylindrical plunger (d) by the piezoelectric actuator (^) having such a configuration will be explained with reference to FIGS. 6 to 8.

When a voltage is applied to the piezoelectric element (e) from a control device (C), which will be described later, according to a drive program, as shown in FIG. While increasing the clamping force, the voltage of the piezoelectric element (f) is released to expand the diameter of the piezoelectric element (f), thereby reducing the clamping force of the cylindrical plunger (d) by the piezoelectric element (f).

Next, as shown in FIG. 7, when a voltage is applied to the piezoelectric elements (g) and (h) to cause them to expand, the piezoelectric elements (e) and (f) move in the direction of the arrow, and as a result, the piezoelectric elements Since the clamping force of (e) is larger than the clamping force of the piezoelectric element (f), the cylindrical plunger (d) also moves in the direction of the arrow 6:' by slipping on the clamping portion of the piezoelectric element (f).

Thereafter, as shown in FIG. 8, a voltage is applied to the piezoelectric element (f) to increase the clamping force of the cylindrical plunger (d), and then the voltage applied to the piezoelectric element (e) is released to increase the clamping force in the radially expanding direction. When the clamping force of the cylindrical first langeer (d) is reduced and the voltage applied to the piezoelectric element (+I+) (h) is released, the piezoelectric elements (a) and (h) shorten in the direction of the arrow. The cylindrical plunger (d) further moves in the direction of the arrow.

Thereafter, by repeating the above operation, the cylindrical plunger (d) can be moved in a lengthwise manner with a stroke on the μm order or sub-μm order, and the cylindrical plunger (
d) Various actuating devices connected to the tip can be operated precisely.

Next, an ultrasonic linear motor (B), which is another form of the piezoelectric actuator, will be described as a second embodiment with reference to FIGS. 9 to 11.

The ultrasonic linear motor (B) shown in FIG. 9 has front and rear walls (a
Cylindrical actuator gauging (C
) is equipped with a plunger (d) that can move forward and backward along the axis, and a vibrating body (
n), and a pressing member (P) and a pressing sliding member (Pl) for pressing the 1 langeer (d) are provided on opposite sides, and the pressing member (P) applies an appropriate pressure via a spring (fl). A flat piezoelectric element (V) (w) (x) (X) ( y) A plurality of (y) are provided at regular intervals in the axial direction, and each piezoelectric element (
v) (w) (x) (X) (y) (y) are respectively connected to a drive circuit (D).

And piezoelectric element (v) (w) (x) (X) (y)
The material for (y) is a ferroelectric material with an ABOa lobskite crystal structure, PZT [Pb (Z
r, Ti ) Oa ] system, PLZT [Pb, La
(Zr.

Ti)Oa], PT[PbTi0a] system, or PZ
A three-component system based on T can be used.

Therefore, each piezoelectric element (V) n) is controlled by the drive circuit (D).
When voltage is applied to (x) (X) (y) (y), each piezoelectric element (v) (W) (x) (X) (y) (y) causes ultrasonic vibration with different phases, By vibrating the vibrating body (n), the vibrating body (n) can move one rungeer (d) forward and backward with a stroke on the μm order or sub-μm order, and when the applied voltage is released, the spring (Q) Since the plunger (d) can be advanced by the urging force of the plunger (d), by repeatedly performing such forward and backward movement, various actuating devices connected to the plunger head (dl) at the tip of the plunger (d) can be precisely operated. This means that you will be able to do so.

(S) is a plunger (d) provided on the inner peripheral surface of the vibrating body (n).
), (r) and (r') are plate vibrating elastic bodies that absorb the vibrations of the vibrating body (n).

In addition, as shown in FIGS. 10 and 11, a vibrating body (n)
A pair of piezoelectric elements (V) and (W) for clamping are arranged on the back surface of the same, and two pairs of piezoelectric elements for stroke (
X)(X)(V)(V) are arranged at respective lateral positions of the piezoelectric elements (t) and (u).

Each piezoelectric element (xHx) (y) (y) has the following restrictions.
A drive pulse controlled according to a drive program stored in advance in the device (C) is applied, and the pulse generates approximately trochoid-shaped waves on the sliding surface (p) of the vibrating body (n). , a large number of vibration transmitting protrusions (S) provided on the sliding contact surface (p) are each caused to make approximately elliptical movements as shown in FIG.

The plunger (d) is in pressure contact with the vibration transmission protrusion (S) which is moving approximately in an ellipse, but since the sliding surface (p) is vibrating approximately in a trochoidal shape as described above, the vibration is not transmitted. A pressure contact state occurs only when the protrusion (S) is located at the top of the same waveform, so the plunger (d) is sent only in one direction, and this is repeated to move the plunger (d) forward and backward. .

In particular, the wave height (α) of the vibration transmission protrusion (S), that is, the clamp force is approximately proportional to the voltage applied to the piezoelectric elements (V) (W) for clamping, and therefore, each piezoelectric element (V )
(W) (x) (x) (y) By controlling the voltage applied to (y), the clamping force and rotation speed can be controlled.

The operation of the piezoelectric actuator (A) and the ultrasonic linear motor (8) is controlled by a control device (C) shown in FIG. 13, which is controlled by a microprocessor.
(HPU), input/output interface (I) (0),
It is composed of a memory (M) that stores the drive program, and the input interface (1) is connected to the operating speed setting device (Vs) and the valve open/close switch (Sw).
A voltage control circuit (V) for controlling the voltage applied to the clamp and stroke drive circuits (DC) (DS) and the stroke drive circuit (Ds) are connected to the output interface (0). ing.

In addition, each drive circuit (DC) (Os) is connected to a drive power source (S), and in particular, the drive circuit for stroke (Ds)
is connected to the drive power source (S) via the voltage control circuit (V) mentioned above, and controls the applied voltage output to the stroke drive circuit (Os) by the voltage control signal from the control device (C). That's what I do.

As mentioned above, in order to change the operating speed of the actuator, the voltage applied to the stroke piezoelectric elements (a) (h) and piezoelectric elements (x) (x) (y) (y) is raised and lowered by the voltage control circuit. However, piezoelectric elements (a) (h) for clamping
) and piezoelectric elements (V) (W), the same electrode piezoelectric elements (a), (h) and (V) (
W), a sufficient rung force can always be generated, preventing slippage and allowing the actuator to operate accurately.

As shown in FIGS. 1 and 9, the piezoelectric actuator (A) and ultrasonic linear motor (B) have a diaphragm valve (vl) at the tip of a plunger (dl) (d2) as a driven body. v2) Nohirot valve body (Pl) (P
2) can be connected in series to open and close the diaphragm valves (Vl) (V2) and adjust the flow rate.

In addition, in Fig. 1 and Fig. 9, (1) and (1) indicate the valve body, (
2) (2) is the inflow path, (3) (3) is the outflow path, (4) (
4) is the main valve seat, (5) (5) is the pilot valve seat, (6H
6) is the diaphragm, (7) (7) is the orifice, f
8) (8) indicates a seal.

Embodiments of the present invention are configured as described above, and in particular:
The control device (
A control signal is output from C) to the actuator (^) (B) of the diaphragm valve (Vl) (V2), and each piezoelectric element is operated as described above to open and close the volume valve (Vl) (V2). When controlling the operating speed of the piezoelectric actuator, only the voltage applied to the piezoelectric element for stroke is changed, and the voltage applied to the piezoelectric element for clamping is kept constant. Even when slowing down the speed, only the voltage applied to the piezoelectric element for stroke is changed, and the voltage applied to the piezoelectric element for clamping can be kept constant, so the clamping force on the plunger does not decrease. , Therefore, occurrence of plunger slip is prevented,
This has the effect that the piezoelectric actuator can be operated accurately.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional explanatory diagram of a piezoelectric actuator according to the present invention. FIG. 2 is a sectional view taken along the line II in FIG. 1. 3 to 5 are explanatory diagrams of other specific examples of piezoelectric elements. FIGS. 6 to 8 are explanatory diagrams showing the order of operation of the piezoelectric actuator. FIG. 9 is a cross-sectional explanatory diagram of the ultrasonic linear motor. FIG. 10 is a sectional view of the vibrating body. FIG. 11 is a sectional view taken along the line ■-■ in FIG. 10. FIG. 12 is an explanatory diagram showing the operation of the ultrasonic linear motor. FIG. 13 is a block diagram showing the configuration of the control device. (A): Piezoelectric actuator (B): Ultrasonic linear motor (C) Two control devices (Dc): Drive circuit for clamp Ds): Drive circuit for stroke V: Voltage control circuit d: Plan as driven object Jar e(f): piezoelectric element for the flang q(h): piezoelectric element for the stroke V(W) piezoelectric element for the clamp

Claims (1)

[Claims] (1) A piezoelectric actuator that operates a driven body by applying pulsed piezoelectricity to a piezoelectric element for stroke and a piezoelectric element for clamping, and causing the same elements to repeatedly perform forward and backward movement and clamping movement. A piezoelectric actuator comprising a drive control section configured to maintain an applied voltage for clamping constant while changing an applied voltage for an actuation speed change stroke when a signal is input.