JPH034078A - Piezoelectric actuator - Google Patents

Abstract

PURPOSE:To simplify a structure and driving sequence by arranging a fixed side clamping piezoelectric element and a stroke piezoelectric element in the periphery of a plunger while setting the polarity of each clamping piezoelectric element in a reverse direction to each other and applying drive voltage from the respective drive circuit to each piezoelectric element so as to longitudinally actuate the plunger in the direction of an axial line. CONSTITUTION:Fixed and moving side clamping piezoelectric elements (e), (f) are connected in a parallel state further with the polarity in a reverse direction to each other. The fixed side clamping piezoelectric element (e), when positive voltage is applied, contracts an internal diameter to increase clamping force to a plunger P, while the moving side clamping piezoelectric element (f), when reverse voltage is applied, contracts an internal diameter to increase clamping force of the plunger P. While a stroke piezoelectric element (g) is extended in the direction of an axial line on the plunger P, in a non-voltage applied condition, and contracted in the direction of the axial line on the plunger P in a voltage applied condition. Thus, the plunger P is actuated to advance and retract in the direction of the axial line.

Description

[Detailed description of the invention] (b) Industrial application field The present invention relates to piezoelectric actuators.

(b) Conventional technology Conventionally, a plunger is disposed in a case so as to be movable on its axis, and a piezoelectric element for a fixed side clamp is attached to the outer periphery of the plunger, one end is fixed to the case, and a movable side clamp is attached to the other end. The piezoelectric element for stroke is fixed to the piezoelectric element for clamp, and
There is a piezoelectric actuator configured to move a plunger forward and backward in the axial direction by expanding and contracting each piezoelectric element by applying a driving voltage to each piezoelectric element. The drive circuit is connected, and according to the drive sequence, a voltage is applied to the piezoelectric element on the moving side to clamp the plunger, and then the applied voltage to the piezoelectric element on the fixed side is released to release the clamp on the plunger. A voltage is applied to the piezoelectric element for stroke to cause it to contract, and the plunger clamped by the piezoelectric element on the moving side is moved, and then a voltage is applied to the piezoelectric element on the fixed side to clamp the plunger, and then , release the applied voltage to the piezoelectric element on the moving side to release the clamp of the plunger, release the applied voltage to the piezoelectric element to cause it to expand, move only the piezoelectric element on the moving side to return to the initial state, By repeating the above operations, the plunger is moved a large amount.

In a piezoelectric actuator configured to provide a stroke piezoelectric element and apply a drive voltage from a drive circuit to each piezoelectric element to cause each piezoelectric element to expand and contract, thereby moving a plunger forward and backward in an axial direction, It is an object of the present invention to provide a piezoelectric actuator characterized in that the above piezoelectric clamping elements are connected to the same clamping drive circuit with polarities opposite to each other.

(c) Problems to be Solved by the Invention However, in the conventional configuration described above, a drive circuit is connected to each piezoelectric element, so three drive circuits are required, and the drive sequence is also complicated. There is.

(d) Means for Solving the Problems In the present invention, a plunger is disposed in a holder so as to be movable on its axis, a fixed-side clamping piezoelectric element is fixed to the outer periphery of the plunger, and one end is fixed to the holder, A piezoelectric element for clamping on the movable side is fixed to the other end (e) Function According to the present invention, two piezoelectric elements for clamping are connected to the same drive circuit with their characteristics in opposite directions, so that the piezoelectric elements for clamping can be driven in the same drive circuit. When a voltage is applied, the piezoelectric element on the moving side goes into a clamped state, and at the same time the piezoelectric element on the fixed side goes into an unclamped state.Next, voltage is applied to the stroke piezoelectric element to make it expand and contract, and the piezoelectric element on the moving side goes into an unclamped state. The element moves the clamped plunger, and then applies a driving voltage to the piezoelectric elements on the fixed side and the moving side to clamp the plunger with the piezoelectric element on the fixed side and at the same time release the clamp on the piezoelectric element on the moving side. By releasing the voltage applied to the piezoelectric element to cause it to expand and contract, moving only the piezoelectric element on the movable side to return to its initial state, and repeating the above operations, the plunger can be moved significantly.

(f) Effect Therefore, the drive circuit requires only two drive circuits, one connected to the stroke piezoelectric element and the other connected to the fixed side and moving side piezoelectric elements, compared to the conventional three drive circuits. Since only two items are required, the structure is simplified, and
This has the effect of simplifying the driving sequence.

(g) Example Embodiments of the present invention will be specifically described based on the accompanying drawings.

Figure 1 shows a piezoelectric actuator (^), in which a plunger (P) that can move forward and backward in the axial direction is arranged inside a cylindrical case (d) having front and rear walls (a) and (b). A ring-shaped fixed side clamping piezoelectric element (e), a moving side clamping piezoelectric element (f), and a stroke piezoelectric element (g) are disposed surrounding the plunger (P).

That is, in the case (d), a holder (H) is fixed to the front wall (a), a plunger insertion hole (h) is bored in the holder (H), and the plunger (P) is inserted through the holder (H). , the base end of a clamp member (k) is fixed to the negative side surface of the holder (H), and a fixed-side clamping piezoelectric element (e) is connected to the tip of the clamp member (k).

Further, one end of a stroke piezoelectric element (g) is fixed to the other side of the holder (I1), and the base end of a clamp member (1) is fixed to the other end of the stroke piezoelectric element (g). A piezoelectric element (") for a movable side clamp is connected to the tip of the clamp member (1).

Each piezoelectric element (e) m (g) is constructed by laminating and bonding a large number of ring-shaped piezoelectric element pieces via a conductive adhesive such as silver base.

The material of each piezoelectric element piece is, for example, a ferroelectric material having an ABO3 perovskite crystal structure, PZT, etc.
(Pb (Zr, Ti)03) system, P LZT (
P b, La (Z r, Ti) Oa) system,
P T (P b T t Oa ) system or PZ
A three-component piezoelectric ceramic based on T can be used.

Next, the action of each piezoelectric element (e) (r) (g> will be explained.

Among the piezoelectric elements (θ) m (g), the piezoelectric elements (e) (D) for clamping the fixed side and the movable side clamp the plunger (P) with a predetermined force when no voltage is applied.

When a positive voltage is applied to the fixed side clamping piezoelectric element (e), the inner diameter is reduced to increase the clamping force on the plunger (P), and when a reverse voltage is applied, the inner diameter is expanded to release the clamp. .

On the other hand, when a positive voltage is applied to the movable-side clamping piezoelectric element (f), the inner diameter expands to release the clamp on the plunger (P), and when a reverse voltage is applied, the inner diameter is contracted to release the clamp from the plunger (P). clamping force increases.

Further, the stroke piezoelectric element (g) extends in the axial direction on the plunger (P) when no voltage is applied, and contracts in the axial direction on the plunger (P) when a voltage is applied.

Figure 2 shows the configuration of the control device (C), which includes a microprocessor (MPU) and a memory that stores the drive sequence of each piezoelectric element (e), (f), and (g). (M) and input/output interfaces (1) and (0), and the human interface (1) includes:
Switch (S) that operates the piezoelectric actuator (A)
The output interface (0) has a clamp drive circuit (D1) and a stroke drive circuit (D2).
) and are connected to.

Figure 3 shows the configuration of the clamp drive circuit and stroke drive circuit, and the clamp drive circuit (D1) includes four switching elements (S1) (82) (S3) (S
4) are bridge-connected, and the switching element (St
) and the switching element (S2) and between the switching element (S3) and the switching element (S4), the piezoelectric elements (e) and (f) for clamping the fixed side and the movable side are arranged in parallel, and the polarity are connected in opposite directions.

Then, the output from the control device (C) turns the switching element (SL) (S4) ONL and the switching element (S2
) When (S3) is turned off, each clamp piezoelectric element (
e) A positive voltage is applied to (f), and the switching element (S
1) Set (S4) to 0FFL, switching element (S2)
(83) is turned on, each clamp piezoelectric element (e) (
A reverse voltage is applied to f).

The stroke drive circuit (D2) has four switching elements (S5) (SS) (87) (S8) and two constant current circuits (It) (12) connected in a bridge in the same manner as described above. A stroke piezoelectric element (g
) is connected, and when switching elements (S5) and (S7) are turned ON and switching elements (8B and S8) are turned OFF by the output from the control device (C), a positive voltage is applied to the stroke piezoelectric element (g). is applied to the switching element (S5) (S?) to 0FFL, and the switching element (9B
) When (88) is turned ON, a reverse voltage is applied to the stroke piezoelectric element (g).

Figure 4 shows the timing of the drive voltage and each piezoelectric element (e).
(f) is a time chart showing the relationship with the operation of (g), in which drive voltages in the same direction are simultaneously applied to piezoelectric clamping elements (e) and (r);
e) (The polarities of D are opposite to each other, and when no voltage is applied to the clamping piezoelectric element (e) (H), the plunger (P) is clamped with a constant force. Therefore, when one clamping piezoelectric element strongly clamps the plunger (P), the other clamping piezoelectric element (e) (f) releases the clamp.

In addition, piezoelectric elements for clamping (e) (D are connected in parallel but in opposite directions, and both piezoelectric elements for clamping (
e) (Since a voltage equal to n is applied, even if the capacitances of both piezoelectric clamping elements (e) and (r) are unequal, the operations are performed in synchronization.

In addition, by connecting the constant current circuits (l1), (12), (13), and (14), the waveform of the drive voltage becomes approximately trapezoidal, and the acceleration of the operation of each piezoelectric element (e), m, and (g) is small. As a result, the piezoelectric actuator (^) operates quietly and smoothly.

Next, the movement of the plunger (P) by the piezoelectric actuator (^) having such a configuration will be explained with reference to FIGS. 5 to 8.

A reverse voltage is applied from the control device (C) to the piezoelectric elements (e) and (f) for the fixed side and moving side clamps according to the drive sequence, as shown in FIG. ) to release the clamp on the plunger (P), and at the same time release the plunger (P) using the moving side clamp piezoelectric element ('').
Clamp P).

Next, as shown in FIG.
) is contracted by applying a positive voltage, the movable clamping piezoelectric element ( ) moves in the direction of the arrow, and the same piezoelectric element (1
The plunger (P) clamped by ') also moves in the direction of the arrow.

Thereafter, as shown in FIG. 7, a positive voltage is applied to the piezoelectric element (e) (H) for fixed side and moving side clamps, and the plunger (P) is clamped by the piezoelectric element (e) for fixed side clamps. When the moving-side clamping piezoelectric element (') is unclamped and a reverse voltage is applied to the stroke piezoelectric element (g) as shown in Figure 8, the stroke piezoelectric element (
g) expands, and the piezoelectric element (r) for the movable side clamp,
Return to the pre-operation position shown in FIG.

After that, by repeating the above operation, the plunger (
P) can be moved in a linear manner with a stroke on the μm order or sub-μm order, and various actuating devices connected to the tip of the plunger (P) can be precisely operated.

Next, an example of how the piezoelectric actuator (^) is used will be explained.

Figure 9 shows an automatic valve m configured to drive a diaphragm-type valve body (v) with a piezoelectric actuator (^) of the present invention.
), and (io) is a valve box, which has an inflow passage (H) and an outflow passage (H) that are connected to the secondary piping and the secondary piping, respectively.
12). In addition, in the valve box (10), between the inflow path (H) and the outflow path (12), there is a main valve hole (
13) is formed, and a main valve seat (14) is formed at the periphery of the upper end opening of the main valve hole (13).

A diaphragm (I5), which also serves as a main valve element for opening and closing the main valve hole (13), is disposed on the main valve seat (14) so as to be able to move toward and away from the main valve seat (14).

Above the diaphragm (15) is the diaphragm back chamber (■
6) is formed, and the diaphragm back chamber (1B) is formed with an orifice (1B) provided at the periphery of the diaphragm (15).
7) and communicates with the inflow path (H).

(18) is a pilot valve hole bored in the diaphragm (15), which connects the diaphragm back chamber (IB) and the outflow path (12).
) are in communication.

Above the pilot valve hole (18), a pilot valve body (19) provided at the lower end of the plunger (P) of the piezoelectric actuator (^) is placed opposite, and the pilot valve hole (18) is opened by the operation of the piezoelectric actuator (^). open and close.

With the above configuration, the automatic valve m) uses the self-servo action of the diaphragm-type valve body (v), and the diaphragm (1)
5) follows the movement of the plunger (P) of the piezoelectric actuator (A) to open and close the main valve seat (14).

(20) is a flange that limits the vertical stroke of the plunger (P), and (21) is a seal with a Y-shaped cross section.

Figure 10 shows a temperature control valve (v2) constructed using two automatic valves (v1) shown in Figure 9, and a hot water supply pipe (
31) and the water supply pipe (32) to adjust the temperature of the mixed hot water discharged from the mixed hot water pipe (33).

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional explanatory diagram of a piezoelectric actuator according to the present invention, Fig. 2 is a block diagram showing the configuration of the control device, Fig. 3 is a circuit diagram showing the configuration of the drive circuit, and Fig. 4 shows the drive voltage and each piezoelectric actuator. Time chart showing the relationship with element operation, Figure 5~
FIG. 8 is an explanatory diagram of the operation of the same piezoelectric actuator, FIG. 9 is a cross-sectional explanatory diagram of a single-valve type automatic valve using the same piezoelectric actuator, and FIG. 10 is a cross-sectional explanatory diagram of the same double-valve type automatic valve. Piezoelectric actuator (old): Drive circuit for clamp Drive circuit for stroke Plunger case Piezoelectric element for fixed side clamp Piezoelectric element for moving side clamp Piezoelectric element for stroke

Claims (1)

[Claims] 1) A plunger (P) is disposed on the holder (H) so as to be movable on its axis, and a fixed-side clamping piezoelectric element (e) is attached to the outer periphery of the plunger (P), and one end is attached to the holder (H). ), and a stroke piezoelectric element (g) with a moving side clamping piezoelectric element (f) fixed at the other end, each piezoelectric element (
e) A piezoelectric device configured to actuate each piezoelectric element (e), (f), and (g) by applying a driving voltage to each of (f) and (g) to move the plunger (P) forward and backward in the axial direction. A piezoelectric actuator (A) characterized in that the clamping piezoelectric elements (e) and (f) are connected to the same clamping drive circuit (D1) with polarities opposite to each other.