JPH0349574A - Piezoelectric actuator having function of returning to operation origin - Google Patents

Abstract

PURPOSE:To surely return it to operation origin by providing a stopper which regulates the operation range mechanically. CONSTITUTION:For a piezoelectric actuator A, a plunger P as substance to be driven is attached freely in advance and retreat inside a casing c, and three pieces of piezoelectric elements e-g for clamping and stroke are arranged on the periphery. Moreover, clamping members k-l are stuck to the tops of elastic bridges i-j and a stopper S is formed at the inner face of the front wall of a casing, and this contacts with the bottom flange F of the plunger P and regulates the downward operation.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a piezoelectric actuator having an operation origin return function.

(Expression) Conventional technology Conventionally, there is a piezoelectric actuator as one form of pulse-driven actuator.The piezoelectric actuator has one side of a stroke piezoelectric element fixed to a fixed part, and a clamping piezoelectric element on the other side of the piezoelectric actuator. Attach the element, apply a pulse-like drive voltage to each piezoelectric element, clamp the plunger with the piezoelectric element for clamping, expand and contract the piezoelectric element for stroke to move the plunger forward and backward repeatedly, and move the plunger over a large distance. There are piezoelectric actuators that allow open-loop control because the amount of movement of the plunger is proportional to the drive voltage applied to the stroke piezoelectric element and the number of pulses.

However, there is a drawback that an error occurs in the position of the plunger due to an error in the driving voltage, a slip between the plunger and the piezoelectric element, and this error accumulates to become a large error.

Therefore, in order to solve this drawback, it is conceivable to provide the actuator with a position sensor that detects the position of the plunger to perform closed-loop operation control.

(c) Problems to be Solved by the Invention However, in order to control the operation of a closed loop, some kind of position sensor is required to detect the position of the plunger, which complicates the structure, control device, or control program. It also has the disadvantage of being expensive.

(2) Means for solving the problem In the fourth aspect of the present invention, a pulse voltage from a control device is applied to a piezoelectric element for clamping and a piezoelectric element for stroke to cause the plunger to reciprocate. In addition, in a piezoelectric actuator that performs open-loop plunger operation control, the actuator is provided with a stopper that mechanically restricts the operating range of the plunger, which serves as the plunger's operating origin, and the calculated position of the plunger is By outputting a pulse number greater than the number of pulses required to move the plunger from to the stopper to the piezoelectric actuator, and forcibly regulating the operation of the plunger with the stopper, the plunger is returned to its operating origin. It is an object of the present invention to provide a piezoelectric actuator having a characteristic return-to-origin function.

(E) Functions and Effects According to the present invention, the plunger is driven with an output of a number of pulses greater than the number of pulses required to move the plunger from its calculated position to the stopper, and the stopper forces the plunger to operate. The plunger can be reliably returned to its operating origin by regulating the movement of the plunger.

Note that the calculated position of the plunger is not determined when the power is turned on, such as during a power-on reset. By driving the stopper in one direction, the operation of the plunger is regulated by the stopper, so that the plunger can be reliably returned to the operating origin.

Thereafter, the operation of the plunger can be controlled in an open loop using the position returned to the operation origin as a reference.

The position of the plunger returned to its operating origin in this manner is extremely accurate, and as a result, the operation control of the plunger is also accurate.

(F) Embodiment An embodiment of the present invention will be described in detail based on the drawings. In FIG. 1, (A) shows a piezoelectric actuator as a pulse drive actuator, and a casing (e ), a plunger (P) as a drive body is mounted concentrically along the bracket line so as to move back and forth, and three piezoelectric elements (e) are mounted concentrically on the outer peripheral surface of the plunger (P). ) (f) (g) are installed.

In addition, (1) has its base end fixed to the support member (h), and (j) has its base end fixed to the stroke piezoelectric element (g), and its tips are directed toward the front and rear walls (a) and (b). It is an elastic bridge in the form of a cantilevered beam.

At the tip of the elastic bridge (1) (j), a clamping piezoelectric element (e) (') is attached to its outer circumferential surface, and a clamping member (k) (+) is fixed to its inner circumferential surface. ing.

In addition, a stopper (S) is formed on the inner surface of the front wall (a), and a flange (F) is formed at the lower end of the plunger (P).
The downward movement of the plunger (P) is restricted by contact with the plunger (P), and in this state, the plunger (P)
The position is set as the operating origin of the plunger (P).

Next, the action of each piezoelectric element (e) (f') (g) will be explained.Among the piezoelectric elements (e), (f), and (g), piezoelectric elements for clamping (e) and (f') are in a voltage applied state. Then, the inner diameter is reduced to clamp the plunger (P), and when no voltage is applied, the inner diameter is expanded to release the clamp on the plunger (P).

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

Next, the movement of the plunger (P) by the piezoelectric actuator (^) having such a configuration will be explained with reference to FIGS. 2 to 5.

A voltage is applied to the piezoelectric element (f') from a control device (C), which will be described later, according to a drive program, and as shown in FIG. 2, the plunger (P) is clamped and the piezoelectric element (e)
The clamp on the plunger (P) is released by releasing the voltage application to the plunger (P).

Next, as shown in Figure 3, when a voltage is applied to the piezoelectric element (g) to cause it to contract, the piezoelectric element (r) moves in the direction of the arrow, and along with this, the plunger (P) also moves in the direction of the arrow. Moving.

Thereafter, as shown in Figure 4, a voltage is applied to the piezoelectric element (e) to clamp the plunger (P), and then the voltage applied to the piezoelectric element (') is released to unclamp the plunger (P). However, when the voltage applied to the piezoelectric element (g) is released, the piezoelectric element (g) expands and the piezoelectric element (r) returns to the position shown in FIG. 5.

After that, by repeating the above operation, the plunger (
P) can be moved like an inchworm 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.

The operation of the piezoelectric actuator (A) is controlled by a control device (C) shown in FIG.
It is composed of a microprocessor (MPU), an input/output interface (1) (0), and a memory (M) that stores a drive program. Sw) is connected to the output interface (0), and piezoelectric elements (e) (f') (g>) for clamping and stroke are connected to the output interface (0) via a drive circuit (D).

Then, when a control command from the switch (Sw) to the plunger (P) is manually input to the control device (C), a pulsed drive voltage is output according to the drive program, and the plunger (P) is actuated as described above. I can do it.

The embodiment of the present invention is configured as described above, and when the piezoelectric actuator (A) and the control device (C) are connected to a power source, a load is applied to the piezoelectric actuator (A) as part of a power-on reset. Before, Dan, Plunger (P
) is advanced until its operation is forcibly regulated by the stopper (S), and this position can be used as the origin of operation of the plunger (P).

The position of the plunger (P) that has returned to its operating origin in this way is extremely accurate because the operation of the plunger (P) is forcibly regulated by the stopper (S), and at the same time the plunger (P) in the memory (M) is By updating the position data of the plunger (P), it is possible to eliminate errors in the plunger (P) position data, which is a drawback of open loop control.

The current position data of the plunger (P) based on the position data of the plunger (P) updated in this way, and 1
By driving the plunger (P) with reference to the amount of movement of the plunger (P) per drive pulse, the operation of the plunger (P) can be controlled by a closed loop.

Returning the plunger (P) to its operating origin and updating the position data are always performed when the power is turned on as described above, but if necessary, the user can issue a command to the control device (C) to update the position data. You can set a timer during the control program and run it at regular intervals, or as described in the application example below, you can seize the opportunity to operate the plunger (P) until it is regulated by the stopper (S). Can be updated.

In addition, the driving of the plunger (P) toward the stopper (S) for return to the operating origin is the calculated plunger (P).
Since the number of pulses slightly greater than the number of pulses required to move the plunger (P) from the position to the stopper (S) is output, it is possible to prevent the plunger (P) from being forced to drive, and prevent clamping caused by forceful driving. piezoelectric element and plunger C
P) can prevent harmful effects such as wear.

The piezoelectric actuator (A) can connect various devices to the tip of the plunger (P) to accurately control the devices.

Figure 7 shows the above piezoelectric actuator (A) applied to control the operation of a diaphragm-type flow rate regulating valve (v).
v), which is configured to open/close and adjust the flow rate.

In the figure, (1) is the valve body, (2> is the inflow path, (3> is the outflow path, (4) is the main valve seat, (5) is the main valve body, (fs) is the pilot valve seat, and (7) is the main valve seat. ) indicates the diaphragm, (8) indicates the orifice, and <9) indicates the pilot valve body connected to the tip of the plunger (P). To open the valve body (1), press the plunger (P). Operate upward to remove the pilot valve seat (
6) is opened and closed by operating the plunger (P) downward to close the pilot valve seat (6).

In particular, when the valve body (1) is closed, the main valve body (5) is placed on the main valve seat (4), and the pilot valve body (9) connected to the tip of the plunger (P) is placed on the pilot valve seat (6). ), the downward movement of the plunger (P) is forcibly restricted, allowing it to act as a stopper and making this position the operating origin of the plunger (P). .

Therefore, the position data of the plunger (P) at the operating origin can be updated every time the main valve body (5) closes the valve.

In addition, since the position data of the plunger (P) is updated with the closed state of the main valve body (5) as the operating origin, the position data of the plunger (P) is updated with the closed state of the main valve body (5)
) and pilot valve body (9), etc., deviations in the valve closing position and opening degree due to fatigue are also automatically corrected.

As mentioned above, the position of the plunger (P) when the main valve body <5) is in the closed state is the operating origin, and since the position data of the plunger (P) is frequently updated, the plunger (P) It is possible to accurately control the position of the flow rate, and accurate flow rate adjustment can be performed.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional explanatory diagram of a piezoelectric actuator according to the present invention, FIGS. 2 to 5 are explanatory diagrams showing the operating order of the piezoelectric actuator, and FIG. 6 is a block diagram showing the configuration of a control device.
FIG. 7 is a cross-sectional explanatory diagram of the flow rate regulating valve. (A): Piezoelectric actuator (C) Two control devices (P): Plunger (S): Stopper (e) (f'): Piezoelectric element for clamping (g): Piezoelectric element for stroke Fig. 1

Claims (1)

[Claims] 1) The plunger is configured to reciprocate by applying a pulse voltage from a control device to the piezoelectric element for clamping and the piezoelectric element for stroke, and is configured to operate in an open loop. In a piezoelectric actuator that controls the operation of a plunger, the actuator is provided with a stopper that mechanically restricts the operating range of the plunger, which serves as the origin of the plunger's operation, and the plunger is moved from the calculated position of the plunger to the stopper. By outputting an output with a number of pulses greater than the number of pulses required to do this to the piezoelectric actuator, and forcibly regulating the operation of the plunger with the stopper,
A piezoelectric actuator having an operation origin return function characterized by returning a plunger to an operation origin.