JPS631383A - Piezoelectric actuator - Google Patents

Abstract

PURPOSE:To position a piezoelectric actuator accurately at a high speed without necessity of controlling a closed loop by interposing a transmission member deformable by an external force between a piezoelectric element and a movable wall, and absorbing the displacement nonlinear characteristic of the element. CONSTITUTION:A piezoelectric actuator is composed by interposing a piezoelectric element 2 and a deformable transmission member 3 in series between the upper and lower walls of a holding member 1 which forms an elastic spring structure. The element 2 is displaced to be elongated by applying a voltage thereto, and a movable wall 13 is displaced under pressure through the member 3. At this time, the member 3 is elastically deformed by the pressure of the element 2 to absorb the displacement nonlinear characteristic of the element 2, thereby linearizing the displacing characteristic with respect to the wall 13.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a piezoelectric actuator applied to, for example, a precision positioning mechanism of an XY stage. 2. Prior Art> FIGS. 7 to 10 show common examples of this type of piezoelectric actuator.

Fig. 7 shows a movable body 6 directly mounted on a horizontal base 4 via a piezoelectric element 5, and Figs. ''), the piezoelectric element 5 is assembled into a holder 7 having a displacement magnifying mechanism 71, and the displacement of the piezoelectric element 5 is magnified in the opposite direction in Fig. 8, and in the orthogonal direction in Fig. 9. It expands and acts on movable objects.

Problems to be Solved by the Invention> However, these piezoelectric actuators have displacement characteristics shown in FIG. 10 with respect to applied voltage.

In the figure, the horizontal axis shows the applied voltage and the vertical axis shows the displacement of the actuator. This displacement characteristic has hysteresis and exhibits nonlinear characteristics both when the applied voltage increases and decreases, and this displacement Acts on moving objects. Therefore, when performing highly accurate positioning, it is necessary to provide a detection system to detect displacement and to feed back the detected displacement through closed-loop control, which results in problems such as the complexity and size of the device and the difficulty of high-speed positioning. was there.

Therefore, the present invention aims to achieve linearization of the displacement characteristics by disposing a movable body on the displacement output side of the piezoelectric actuator via a transmission member that absorbs the nonlinearity of the displacement characteristics of the actuator. ．． <Means for Solving the Problems> The means of the present invention for achieving the above object will be explained with reference to FIGS. 1 to 6 corresponding to the embodiments. A holder 1 has a movable wall 13 that transmits displacement to a movable part on the upper part of an extensible wall l2 installed vertically opposite to the holder 1, and a piezoelectric device whose one end is fixedly supported by the mounting wall 11 and which expands and contracts when voltage is applied. It consists of an element 2 and a transmission member 3 which is interposed between the other end of the piezoelectric element 2 and a movable wall 13 and is deformable in response to external force. <Operation> In FIG. 1, the piezoelectric element 2 is extended and displaced by voltage application, and the movable wall 13 is pressurized and displaced via the transmission member 3. At this time, the transmission member 3 is elastically deformed by the pressure applied by the piezoelectric element 2, absorbs and cancels the nonlinear displacement characteristic of the piezoelectric element 2, linearizes the displacement characteristic with respect to the movable wall 13, and detects displacement. This has the effect of realizing highly accurate positioning without requiring closed loop control for feedback.

<Embodiment> FIG. 1 shows an embodiment of a piezoelectric actuator according to the present invention.

The piezoelectric actuator includes a piezoelectric element 2 and a deformable transmission member 3 between the upper and lower walls of a holding member 1 having an elastic spring structure.
It is constructed by interposing them in series. The holding member 1 includes a telescopic wall 12.12 that is vertically disposed opposite to the horizontal mounting wall l1 and expands and contracts in the vertical direction, and a horizontal movable wall 13 that is parallel to the mounting wall l1 is integrally formed on the upper part of this telescopic wall. Both elastic walls 1
2.12, the mounting wall 11, the movable wall 13, and the connecting portions of the movable wall 13, as well as the thin portions 14 at appropriate locations, such as at the center of the height, to form an elastic spring structure.

The piezoelectric element 2 is a multilayer body of a plurality of plate-shaped piezo elements, the lower part of which is integrally bonded and fixed to the central part of the mounting wall 11 of the holding member 1, and the piezoelectric element 2 is It expands and contracts upward to pressurize the transmission member 3.

The transmission member 3 uses a steel ball in the embodiment, and has a lower spherical surface supported in spherical contact with the upper surface of the piezoelectric element 2, and an upper spherical surface bonded and fixed to the movable wall 13. Next, the operating principle of such a piezoelectric actuator will be explained. In FIG. 2, the amount of deformation δ of the steel ball constituting the transmission member 3 in response to an external force F is generally given by the following equation.

δ=C-F"...(1) However, C is the Young's modulus of the material that makes up the steel ball, and is a constant determined by the diameter of the steel ball. Transforming equation (1) above onto the vertical axis When shown in a characteristic diagram with the amount δ and the force F on the horizontal axis, the amount of deformation δ has a nonlinear relationship with the force F as shown in Figure 3. In Figure 1, when a voltage is applied to the piezoelectric element 2, When applied and extended and displaced, a force F=K − x acts on the transmission member 3 due to the rigidity K of the holding member 1 (X is the amount of displacement of the piezoelectric element).The force F acting on the transmission member 3 and the piezoelectric element The relationship between the applied voltage ■ and the force F is proportional to the amount of displacement The deformation occurs as given by the relational expression (1).The relationship between this amount of deformation δ and the voltage applied to the piezoelectric element 2 that generates the force F is expressed by the third
By combining the diagram and FIG. 4, the result is as shown in FIG. 5.

A displacement H obtained by subtracting the deformation amount δ of the transmission member 3 from the displacement amount X of the piezoelectric element 2 appears on the displacement surface A of the holding member 1. Since this displacement H is the displacement that acts on the movable part,
When determining the relationship between the displacement H and the applied voltage ■ to the piezoelectric element 2, if we calculate H=x−δ from FIGS. 3 and 5, we get
The linear characteristics shown in the figure are obtained, and the linearity of the deformation H and voltage (2) is improved compared to the conventional displacement characteristic (FIG. 10).

Note that the transmission member 3 is not limited to steel balls, but may also be a member that exhibits nonlinear displacement characteristics as shown in FIG. 3 in response to external force F. shape. Of course, any material is fine. <Effects of the Invention> As described above, the present invention includes a movable wall 13 that transmits displacement to a movable part on the upper part of the extensible wall 12 that is vertically installed opposite to the mounting wall 11.
A piezoelectric element 2 whose one end is fixedly supported on a mounting wall 11 and expands and contracts when a voltage is applied, and a transmission member 3 that is interposed between the piezoelectric element 2 and the movable wall 13 and is deformable by external force. Since the actuator is configured, in the present invention,
The transmission member 3 absorbs and cancels the non-linear displacement characteristics of the piezoelectric element 2, improving the displacement linearity of the movable part, thereby eliminating the need for closed-loop control that detects and feeds back displacement, resulting in high-speed and This has the effect of realizing highly accurate positioning.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the piezoelectric actuator according to the present invention, FIG. 2 is a diagram showing the state of deformation of the transmission member in response to external force, and FIG. 3 is a characteristic diagram showing the relationship between the external force and the amount of deformation of the transmission member. , Fig. 4 is a characteristic diagram showing the relationship between the force applied to the transmission member and the voltage applied to the piezoelectric element, Fig. 5 is a characteristic diagram showing the relationship between the applied voltage to the piezoelectric element and the amount of deformation of the transmission member, and Fig. 6. is a characteristic diagram showing the displacement obtained by subtracting the amount of deformation of the transmission member from the displacement of the piezoelectric element, Figures 7 to 9 are diagrams showing the conventional example, and Figure 10 is a diagram showing the displacement characteristics of the piezoelectric element in the conventional example. be. 1...Holder 11...Mounting wall 12.
... Telescopic wall 13 ... Movable wall 2 ...
Piezoelectric element 3...Transmission member patent applicant
Tateishi Electric Co., Ltd.'lr2+B ainipts-ytn-tHbi
s*itt. (t; a↓ bone m) Z mark r41 pressure V procedure chief official text <spontaneous> 1. Indication of the incident: Patent Application No. 143810/1982 2. Title of the invention Piezoelectric actuator 3. Relationship with the case of the person making the amendment Patent applicant address: 10 Hanazono Tsuchido-cho, Ukyo-ku, Kyoto-shi, 616 Name (2)
94) Tateishi Electric Co., Ltd. Representative Takao Tateishi 4. Agent 5. Target of amendment "Claims of the specification" Scope of claims ■ Mounting wall A holder having a movable wall that transmits displacement to a movable part and one end attached to the upper part of a telescopic wall installed vertically facing the soil. a piezoelectric element that is fixedly supported on a wall and expands and contracts by applying a voltage, and is interposed between the other end of the piezoelectric element and the movable wall,
A piezoelectric actuator comprising a transmission member that can be deformed by external force. (2) The piezoelectric actuator according to claim 1, wherein the piezoelectric element is a piezo element that expands and contracts when a voltage is applied. (2) The piezoelectric actuator according to claim 1, wherein the transmission member is a member that absorbs and linearizes the nonlinearity of the displacement characteristics of the piezoelectric element. (2) The piezoelectric actuator according to claim 1, wherein the transmission member is a sphere, or at least a member whose contact surface with the piezoelectric element is formed into a spherical surface.

Claims (4)

[Claims] (1) A holder that has a movable wall that transmits displacement to the movable part on the top of an extensible wall that is vertically installed facing each other on the mounting wall, and a piezoelectric device that has one end fixedly supported on the mounting wall and that expands and contracts when voltage is applied. A piezoelectric actuator comprising a piezoelectric element and an electric member interposed between the other end of the piezoelectric element and a movable wall and deformable by external force. (2) The piezoelectric actuator according to claim 1, wherein the piezoelectric element is a piezo element that expands and contracts when a voltage is applied. (3) The piezoelectric actuator according to claim 1, wherein the transmission member is a member that absorbs and linearizes nonlinearity in the displacement characteristics of the piezoelectric element. (4) The piezoelectric actuator according to claim 1, wherein the transmission member is a sphere, or at least a member whose contact surface with the piezoelectric element is formed into a spherical surface.