JPH0681519B2 - Piezoelectric actuator - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a piezoelectric actuator used for a precision positioning mechanism or the like, and more particularly to a piezoelectric actuator in which a piezoelectric element is combined with an elastic lever type displacement magnifying mechanism.

[Conventional technology]

The piezoelectric actuator is configured as shown in FIG. 5, and the displacement amount of the piezoelectric element 1 is enlarged by the elastic lever type displacement magnifying mechanism 2 and transmitted to the load 3.

In the conventional piezoelectric actuator described above, when no load is applied, a voltage is applied to the piezoelectric element 1 to cause an element displacement δ as shown in FIG. 6, which is displaced at a predetermined expansion rate of the elastic lever type displacement expansion mechanism 2. To do. However, when the load 3 is placed at the output end and is displaced as shown in FIG. 5, the static friction force Fs of the load 3 acts, so that the piezoelectric element 1
Even if a voltage is applied to the load 3, the load 3 does not move until the generated force at the output end reaches Fs. That is, as shown in FIG. 7, a dead zone occurs in the voltage-expansion displacement characteristic.

The following two means are conceivable in order to solve this and obtain a predetermined enlarged displacement.

One is to apply a bias voltage to a predetermined applied voltage for the dead zone. Two of them pre-load the elastic lever type displacement magnifying mechanism by the amount of static friction force Fs.
As a method for this, for example, there is a method in which a bolt having a small pitch is brought into contact with the proximal end side of the elastic lever type displacement magnifying mechanism and a preload is applied by this bolt.

[Problems to be Solved by the Invention]

However, even in the above two solutions, in the former case, the control range is reduced by the amount of the bias voltage applied, and in the latter case, when the preload amount is adjusted by micro displacement in micron units, the rotation angle of the bolt is extremely small. Becomes smaller,
Adjustment is difficult.

The present invention has been made in view of the above, and provides a piezoelectric actuator capable of eliminating the dead zone of the voltage-expansion displacement characteristic by finely adjusting the preload amount applied to the elastic lever type displacement amplification mechanism. It is what

[Means for Solving the Problems]

In order to achieve the above object, the piezoelectric actuator of the present invention is a combination of a piezoelectric element and an elastic lever type displacement magnifying mechanism,
The elastic lever type displacement magnifying mechanism is provided with a preload adjusting mechanism on the base end side thereof, which is flexibly deformed by an external force to increase the outer dimension.

[Action]

With the piezoelectric element incorporated in the elastic lever type displacement magnifying mechanism in contact with the preload adjusting mechanism and temporarily fixed, the tip of the deformation load section of the elastic lever type displacement magnifying mechanism is brought into contact with the load, and then an external force is applied to the preload adjusting mechanism. It is flexibly deformed to increase its outer dimension, which pushes the piezoelectric element to press the output end of the elastic lever type displacement magnifying mechanism to the load side to apply preload, and in this state, apply voltage to the piezoelectric element to load it. To drive.

〔Example〕

An embodiment of the present invention will be described with reference to FIGS. The same members as those of the conventional example shown in FIG.

Both ends of the piezoelectric element 1 are adhered to the plates 5 and 30, and one plate 5 thereof is fixed to the bracket 4 and the screw 31 so that the bracket 4, the plate 5, the piezoelectric element 1 and the plate 30 have an integrated structure. Is the screw 7 with the tip of the plate 30 in contact with the deformation load portion 9 via the pin 8.
Is incorporated in the elastic lever type displacement magnifying mechanism 2. The elastic lever displacement magnifying mechanism 2 is fixed to the frame 10 with bolts 11.

Reference numeral 12 is a preload adjusting mechanism provided at the base end of an elastic lever type displacement magnifying mechanism 2 incorporating the piezoelectric element 1. The preload adjusting mechanism 12 is as shown in FIG. The adjusting bolt 14 is penetrated through the frame body 13 and the one side member 14a of both side members 14a, 14b facing each other of the frame body 13, and the adjusting bolt 14 is screwed into the other side member 14b. When the adjusting bolt 14 is tightened, both side members 14a, 14b are bent toward each other in the facing direction, whereby the frame body 13 is deformed so that the outer dimension L of the other facing sides 15a, 15b is increased. It is supposed to do.
In this preload adjusting mechanism 12, one side of the deformed side members 15a, 15b is attached to the bracket 16 by a screw 17, and the bracket 16 is in contact with the bracket 4 on the opposite side of the deformed side member. In this state, it is fixed to the pedestal 10 with bolts 18.

The operation in the above configuration will be described for the case of driving the load 3.

First, the preload adjusting mechanism 12 is fixed to the mount 10 with the bolt 18. Next, the piezoelectric element 1 is assembled in the elastic lever type displacement magnifying mechanism 2 and temporarily fixed by the bolt 7, and in this state, the bracket 4 is pressed so as to come into contact with the preload adjusting mechanism 12, and the bolt 11
And fix it to the stand 10. . Here, the gantry 10 is moved together so that the output end of the deformation load unit 9 of the elastic lever type displacement magnifying mechanism 2 is brought into contact with the load 3 and the gantry 10 is attached to the body (not shown) of the positioning device or the like by the bolt 19. Fix it.

By tightening the adjusting bolt 14 of the preload adjusting mechanism 12 in this state, the frame body 13 of the preload adjusting mechanism 12 is deformed, whereby the deformation load portion 9 is pushed through the bracket 4, the piezoelectric element 1, and the pin 8. It tries to push the load 3 by displacing the output end. However, as described above, since static load acts on the load 3, the load 3 cannot be pushed, and it bends to the opposite side as shown by the chain double-dashed line in FIG. 1. This amount of deflection is the preload amount. Therefore, as shown in FIG. 8, the preload amount and the displacement amount of the deformation load portion 9 are calibrated in advance, and the preload amount can be confirmed by detecting the displacement amount by the displacement sensor 20 during the adjustment. .

When the preload is adjusted, the bolt 7 is tightened to fix the bracket 4 with the piezoelectric element 1 to the displacement magnifying mechanism 2.

By the above operation, the setting of the piezoelectric actuator to the load 3 is completed, and in this state, a predetermined voltage is applied to the piezoelectric element 1 to operate as a piezoelectric actuator.

FIG. 3 shows the piezoelectric actuator according to the present invention as a hydraulic pressure adjusting valve.
In this embodiment, the output end of the deformation load section 9 of the elastic lever type displacement magnifying mechanism 2 is in contact with the operating pin 22 of the hydraulic pressure adjusting valve 21. By pushing the deformation load portion 9 at the output end, the poppet valve 24 is opened against the return spring 23. Reference numeral 25 is a magnetoresistive displacement sensor.

At this time, as shown in FIG. 9, the initial setting force (kgf) (preload) of the return spring 23 is the static friction force Fs in the previous example.
Therefore, the amount of the dead zone is determined by this, and the displacement amount due to the application of the same voltage is also different as shown in FIG.

The initial setting force (kgf) is based on the relationship shown in FIG.
(Spring natural length-spring set length) x spring constant.

Note that the above-mentioned preload amount is the cover 26 that receives the return spring 23.
Adjustment can be performed by inserting a shim 27 into the spring and changing the spring set length, but by using the preload adjusting mechanism 12, the preload amount can be set easily and accurately.

〔The invention's effect〕

According to the present invention, the amount of preload applied to the elastic lever type displacement magnifying mechanism 2 can be adjusted extremely finely, and the voltage-
The dead zone of the enlarged displacement characteristic can be eliminated.

[Brief description of drawings]

1 to 4 show an embodiment of the present invention.
FIG. 2 is a front view, FIG. 2 is a front view showing a preload adjusting mechanism, FIG. 3 is an embodiment diagram when applied to a hydraulic pressure adjusting valve, and FIG. 4 is an output with respect to an applied voltage to a piezoelectric element at different preload amounts. FIG. 5 is a diagram showing a displacement, FIG. 5 is a front view showing a conventional piezoelectric actuator, FIGS. 6 and 7 are diagrams showing a displacement amount with respect to a voltage applied to a piezoelectric element, and FIG. 8 is a displacement magnifying mechanism. FIG. 9 is a diagram showing the relationship between the amount of deflection at the output end and the preload, and FIG. 9 is an explanatory diagram of the initial setting force of the return spring of the hydraulic control valve. Reference numeral 1 is a piezoelectric element, 2 is an elastic lever type displacement magnifying mechanism, 10 is a body, and 12 is a preload adjusting mechanism.

Claims (1)

[Claims] 1. A piezoelectric element 1 and an elastic lever type displacement magnifying mechanism 2 are combined, and a base end side of the elastic lever type displacement magnifying mechanism 2 is provided.
A piezoelectric actuator comprising a preload adjusting mechanism (12) which is flexibly deformed by an external force and whose outer dimension is increased.