JPH0519994B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a minute displacement element using a piezoelectric (electrostrictive) material, and more particularly to a piezoelectric actuator that eliminates the influence of hysteresis.

<Prior Art> When an electric field is applied to a piezoelectric (electrostrictive) material, distortion occurs due to the reverse piezoelectric effect. As a piezoelectric element utilizing this piezoelectric inverse effect, one shown in a cross-sectional view in FIG. 4 is conventionally known. In FIG. 4, 1 is a piezoelectric element formed by laminating rectangular piezoelectric materials 2. In FIG. Piezoelectric material 2 is made by adding an appropriate amount of binder, plasticizer, and dispersant to ceramic calcined powder, mixing it in an organic solvent, forming a thin film with a thickness of about 0.1 mm, and drying it. Internal electrodes are formed on one or both sides of the material 2 by coating or the like. Reference numeral 4 denotes insulators arranged to insulate internal electrodes alternately from opposing surfaces. External electrodes are formed on the side surfaces of the laminate including these insulators, and piezoelectricity is generated by applying a voltage to the external electrodes. A voltage is applied to both sides of each material 2.

<Problems to be Solved by the Invention> Incidentally, the relationship between applied voltage and displacement in such a piezoelectric element is as shown in FIG. In other words, the direction in which the voltage is increased (indicated by line segment A)
When a voltage of 50V is applied, the displacement is a little more than 4μm, and when a voltage of 100V is applied, the displacement is about 8μm.What should be noted here is that hysteresis occurs, for example, when the voltage is lowered. In the case of the direction (indicated by the line segment B), the change is about 5.5 μm, and a hysteresis of about 0.5 μm occurs. If such hysteresis exists, there is a problem that accurate displacement control cannot be performed.

The present invention has been made in view of the problems of the above-mentioned conventional technology, and includes storing the above-mentioned conventional pressure-sensitive element in a container,
The container is configured to be displaced in accordance with the displacement of the pressure-sensitive element, the displacement is detected by a thin film strain gauge formed on the container, and a voltage is applied in accordance with the displacement to perform accurate displacement control. With the goal.

<Means for solving the problems> The configuration of the present invention for solving the above problems is as follows:
A piezoelectric element in which an electrode is formed on at least one side of a piezoelectric material processed into a sheet, a plurality of piezoelectric materials are laminated, and a constant elastic material has a surface that accommodates the piezoelectric element and is displaced in accordance with the displacement of the piezoelectric element. a container, two first strain gauges arranged on the displacing surface of the container so that the displacement is felt to the maximum, and two second strain gauges arranged so that the displacement is felt to the minimum. , displacement detection means for detecting the displacement of the container from the outputs of these strain gauges; and the output from the displacement detection means is used as one input, and the output is applied to the piezoelectric element based on the setting input input from the other terminal. The strain gauge comprises a voltage applying means for applying a voltage, the setting input is based on the output of the displacement detecting means, and the strain gauge is formed as a thin film strain gauge using a thin film forming technique. .

<Example> Figures 1 to 3 show an example of the piezoelectric actuator of the present invention. Figure 1 is a perspective view of the piezoelectric actuator, and Figure 2 is a partially enlarged view of the strain gauge portion of Figure 1. The sectional view and FIG. 3 are electrical circuit diagrams. In these figures, 10 is a container that houses the piezoelectric actuator 1, and in this embodiment, the piezoelectric actuator 1 is housed in a container 1 having a rectangular cross section.
It is press-fitted in contact with the upper and lower parts of 0. For this reason, a constant pressure is applied to the left and right support plates (the middle part is hollowed out in the figure) in a state where no voltage is applied to the piezoelectric actuator. On this support plate, when the piezoelectric actuator is displaced in the direction of arrow B, first thin film strain gauges 11 are formed at two places on the left and right along the longitudinal direction (direction of arrow C) where the displacement is felt the most. Second thin film strain gauges 12 are formed at two locations, upper and lower, along the transverse direction where almost no stress is felt. In addition,
As the material for the container 10, a constant elastic material such as Nicepan C (trade name) is used. Figure 2 is an enlarged cross-sectional view of a thin film strain gauge formed on _one side of the container.
Form a Ni-Cr-Si thin film and use it as a strain gauge. FIG. 3 shows the electrical circuit of this piezoelectric actuator. In the figure, 30 is a displacement detection means, which includes the first and second strain gauges 11,
12 are connected to face each other as a bridge, and the output difference between them is detected by the first amplifier 20. The output of this amplifier 20 is the second
is connected to one input terminal of the amplifier 21, and a setting input is connected to the other input terminal. Second
The amplifier 21 controls the voltage applied to the piezoelectric actuator so that the output from the first amplifier 20 and the setting input match. Note that the output of the bridge is 0 when the voltage applied to the piezoelectric actuator 1 is 0, and the output is maximum when a voltage of 100 V is applied and the displacement is maximum, for example,
The setting input to the second amplifier 21 is the maximum output of this bridge measured in advance. Therefore, if the setting input is set to, for example, 50%, the second amplifier 21 controls the applied voltage by mechanical feedback so that the piezoelectric actuator 1 has a maximum displacement of 50%.

According to the above configuration, an electric signal corresponding to the displacement of the piezoelectric actuator measured in advance is used as a setting signal, and a voltage corresponding to the setting signal is applied to the piezoelectric actuator, so that the influence of hysteresis can be removed.

<Effects of the Invention> As described above in detail with the embodiments, according to the present invention, the applied voltage is controlled in accordance with the displacement, so accurate displacement control without hysteresis can be performed. Further, in the present invention, since the strain gauge is formed of a thin film, for example,
Compared to the case where a separately prepared strain gauge is attached to the side of a piezoelectric actuator to form a bridge, this method has the advantage that it is not affected by the creep, lifespan, heat resistance, etc. of the adhesive itself.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of the piezoelectric actuator of the present invention, FIG. 2 is a partially enlarged cross-sectional view of the strain gauge portion of FIG. 1, FIG. 3 is an electric circuit diagram, and FIG. 4 is a diagram showing a conventional example. FIG. 5 is a diagram showing the relationship between applied voltage and displacement in a piezoelectric element. 1... Piezoelectric actuator, 10... Container, 1
DESCRIPTION OF SYMBOLS 1...First strain gauge, 12...Second strain gauge, 30...Displacement detection means, 31...
Voltage application means.

Claims (1)

[Claims] 1. A piezoelectric element in which an electrode is formed on at least one side of a piezoelectric material processed into a sheet, a plurality of sheets of the piezoelectric material are laminated, and a constant elastic material having a surface that accommodates the piezoelectric element and is displaced in accordance with displacement of the piezoelectric element. a container consisting of a container, two first strain gauges arranged on the displacing surface of the container so that the displacement is felt to the maximum, and two second strain gauges arranged so that the displacement is felt to the minimum. and displacement detection means for detecting the displacement of the container from the outputs of these strain gauges, and the output from the displacement detection means is used as one input, and a voltage is applied to the piezoelectric element based on the setting input input from the other terminal. The displacement sensor comprises a voltage applying means for applying a voltage, the setting input is based on the output of the displacement detecting means, and the strain gauge is formed as a thin film strain gauge using a thin film forming technique. piezoelectric actuator.