JPH01144690A - Laminated piezoelectric actuator - Google Patents

Abstract

PURPOSE:To increase the stroke of a piezoelectric element while preventing a drift due to a temperature by installing a first sealing element at the other end of the columnar laminated piezoelectric element, one end of which is fixed, disposing a second sealing element adjacent to the sealing element and sealing a sealing liquid in liquid- seal space between both sealing elements. CONSTITUTION:A first sealing element (a diaphragm) having an effective area A1 is mounted at the other end of columnar laminated piezoelectric elements 101-103, one end of which is fastened, while a second sealing element (a bellows) 5 having an effective area A2 is arranged adjacent to the sealing element 10. A sealing liquid (such as silicone oil) 14 is sealed into liquid-seal space having volume V constituted between the sealing element 10 and the sealing element 5, and the elongation of the columnar laminated piezoelectric elements 101-103 is converted into the stroke of the sealing element 5 through the sealing liquid 14. It is preferable that A1>=A2 holds in the areas A1 and A2. When the linear expansion coefficient of the piezoelectric elements is represented by alpha, the linear expansion coefficient of a pipe by beta, the coefficient of cubic expansion of the sealing liquid by gamma, and the laminating length of the piezoelectric elements by L, it is preferable that the volume of the liquid-seal space having volume V satisfies Vgamma=LA/(beta-alpha).

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a laminated piezoelectric actuator, and in particular, expands the amount of expansion and contraction of a piezoelectric element using the principle of liquid leverage, and at the same time takes into account drift due to temperature changes by taking into account the volume of the sealed liquid. The present invention relates to a laminated piezoelectric actuator that is reduced in weight.

BACKGROUND ART A representative example of a recently developed multilayer piezoelectric actuator element (hereinafter referred to as piezoelectric element) is A manufactured by NEC Corporation.
There is EO505DIG. This piezoelectric element has external dimensions of 5
(W) X 5 (D) The plates and electrodes are sintered together.

This piezoelectric element is approximately 1
Extends by 6μm. If you restrain it so that it cannot stretch and apply voltage, it will generate a force of approximately 85 kgf. The withstand voltage of this piezoelectric element is 300V. The slight elongation of approximately 16 μm is
Although the extension stroke is optimal for mask alignment for IC manufacturing, it is too small for general use. For example, when trying to move a dot wire in a dot type printer, a stroke of approximately 100 times 16 μm is required. In order to magnify the deviation, a two-stage magnification lever of approximately 10 times x 1 time is used, and this has been put into practical use as a dot printer.

Also, unfortunately, the linear expansion coefficient α of the piezoelectric element is 6 PPM/
'C. Most ordinary materials have a positive coefficient of linear expansion, so it is extremely difficult to design them so that they are not affected by temperature.

As a typical method to improve this temperature characteristic, pipe 2
2 (see Figure 1B), a special material such as Invar with a low linear expansion coefficient β = 1.2 PPM/°C may be used, but even then the linear expansion coefficient α of the piezoelectric element is 6PP.
Since M/'C cannot be canceled out, for example, piezoelectric element ■0
1 (see Figure 1B) and used stainless steel 5US304 instead. Linear expansion coefficient β: 1.2PPM/°C
A method adapted to this is adopted. Instead, since the length of the piezoelectric element is shortened, the maximum deviation ΔLI1 naturally decreases.

Problems to be Solved by the Invention As mentioned above, a laminated piezoelectric actuator using a piezoelectric element cannot obtain a sufficient stroke because the elongation of the piezoelectric element is small, and the coefficient of linear expansion of the piezoelectric element is negative. Therefore, it was not possible to obtain a stable laminated piezoelectric actuator that is affected by temperature.

The present invention has been made in order to eliminate the disadvantage described in item 1 inherent in the prior art.Therefore, an object of the present invention is to increase the minute elongation of a piezoelectric element by using a liquid lever, and at the same time reduce the difference in linear expansion coefficient. An object of the present invention is to provide a novel laminated piezoelectric actuator that makes it possible to eliminate the temperature drift due to temperature drift by considering the volume of the sealed liquid.

Means for Solving the Problems - In order to solve the problems of the prior art described above, a multilayer piezoelectric actuator according to the present invention has a columnar multilayer piezoelectric element (with one end fixed) as shown in FIG. 101,10
2, 103) attaching a first sealing element (diaphragm) with an effective area AI to the other end, and arranging a second sealing element 5 with an effective area A2 close to the first sealing element IO; The sealing element IO and the second sealing element (
A filling liquid (such as silicone oil) 14 is sealed in a liquid sealing space with a volume of V formed between bellows) 5, and the elongation of the columnar laminated piezoelectric elements (101, 102, 103) is controlled through the filling liquid 14. The horizontal formation converted into the stroke of the second sealing element 5 is used.

Preferably, the volume of the liquid seal space having the volume V is as described below (7)
Satisfies the relationship of Eq.

Embodiment FIGS. 1A and 1B are a plan view of an embodiment in which a laminated piezoelectric actuator according to the present invention is attached to a flow rate control valve, and a sectional view taken along line AA' in FIG. 1A. .

Referring to Figures 1A and 1B, reference numeral 1 is a block-shaped body with a large hole in the center for receiving a flow control mechanism. The flow rate Q enters through the inlet 2 and exits through the outlet 2'. 3 is a nozzle, and the gap between the nozzle 3 and the flapper 4 is changed by expansion and contraction of the bellows 5, and the flow rate Q is adjusted. A diaphragm 10 is sandwiched between the collar 8 and the flange 9 and welded at a joint 11, so that the collar 8 and the flange 9 are integrated. The upper end of the bellows 5 is in the center of the collar 8 with the partition plate 13 at the joint +2
It is welded with. A sealing liquid 14 such as silicone oil is sealed into a sealing space formed between the bellows 5 and the diaphragm IO from a sealing port (not shown).

When the flange 9 is tightened with the cap screw 15, 0
Ring IG, 17 collapses to prevent fluid leakage.

A piezoelectric element 10 is attached to the cap ILI- on the diaphragm lO.
1. Three pieces 102 and 103 are stacked and glue 19
It is glued with. Coating material 2 for piezoelectric element 103
0 is partially peeled off. Inside the piezoelectric element, several hundred thin PZT plates and positive and negative electrode plates 2I are stacked and sintered. Positive electrodes and negative electrodes are connected within the piezoelectric element. The applied driving voltage is directly applied to one PZT plate, resulting in a large electric field strength and generating piezoelectric strain in the thickness direction of the plate.

Reference number 22 is a pipe whose lower end is welded to the flange 9 at a joint 23. A thread is cut into the upper end of the pipe 22, and a head cap 24 is screwed into the pipe 22 so as to contact the upper end of the piezoelectric element 103. Reference number 25 is a lock nut for the bend cap 24, and reference number 26 is a positioning cap for the piezoelectric element +03.

Reference number 27 is a cushion material made of silicone rubber or the like. When the actuator falls off the desk, the cushion material 27 is used to prevent the piezoelectric element 101 from being damaged by the impact force.
- 103 and at the same time prevent piezoelectric element 1 from breaking.
Since 01-103 are connected in series and are longer,
This prevents the long columnar piezoelectric element from buckling due to compressive force.

Cushion material 27 is not necessarily an essential element.

The spring 6 pushing up the flapper 4 is filled with liquid 1
When the pressure in step 4 is to prevent negative pressure, a valve may be used at a pressure close to vacuum. In this case, if the spring 6 is not provided, air bubbles may be generated in the sealed liquid 14 and malfunction may occur, so the spring 6 is included to prevent this from occurring. This is not necessary if a completely vacuum degassed fill liquid 14 is used.

Next, to explain the effect, if the length of three piezoelectric elements of 20 mm length stacked is L, then l, = GOnon. Maximum elongation Δ when applying maximum drive voltage 150VDC
Lm is: ΔLm=IGμo+X3=48μzoos (1) The diaphragm IO with the effective area AI is pushed downward by this maximum extension ΔLll+: 48μm. Since the bulk elastic modulus of the filled liquid 14 is very large, the volumetric compression of the filled liquid 14 can be ignored. Therefore, if the effective area of the bellows 5, which is the second sealing element, is A2, then the downward deflection ΔLl of the flapper 4 can be approximately expressed as ΔLl −MoΔL (
AI /A2 ) ・ ・ Fist (2) In the case of Fig. 1B, the effective area AI of the diaphragm lO is approximately 10 times the effective area A2 of the bellows 5, so the downward deviation of the flapper 4 ΔLl is multiplied by 10 and becomes ΔL1=ΔLo+ X1O=480m X1O=480
urn: 0.48+++m...# (3) A deflection of the flapper 4 of about 0.5 mm is obtained. With this much stroke, it can be used for most purposes.

On the other hand, due to ease of welding, etc., stainless steel 5US304 is often used for the pipe 22. The linear expansion coefficient β of stainless steel 5US304 is 18.4.
PPm/℃. Piezoelectric elements 101, 102, 10
Since the linear expansion coefficient α of 3 is -6PP+++/'C,
When the temperature of the piezoelectric elements 101, 102, and 103 is increased by Δt°C under a constant driving voltage, the increase deviation ΔL2 due to the temperature at the lower end of the piezoelectric element is ΔL2=L(β−α)Δt (4) When the temperature rises by Δt=10° C. to about Δt−30° C., the -1-increase deviation ΔL2 due to the temperature at the lower end of the piezoelectric element becomes about the same as the maximum elongation ΔLm when a driving voltage is applied. In other words, with a driving voltage of 150V, the lower end of the piezoelectric element extended 48μm downward,
An increase in temperature of 30° C. causes a similar upward deviation, and the elongation ΔLm of the voltage element due to the drive voltage is canceled out. The temperature-induced deviation ΔL2 at the lower end of the piezoelectric element due to this temperature rise is absorbed by the volumetric expansion of the sealed liquid 14.

To simplify the explanation, it is assumed that the piezoelectric element pillar is removed. If the volume of the filled liquid is V and the coefficient of volumetric expansion is γ, then the volume is ΔV=γVΔt when the temperature of Δt'C increases - ΔV=γVΔt
increase in height. If the flapper 4 is fixed, the effective area of the diaphragm 10 is AI, so the deviation ΔLd of the diaphragm is ΔLd=γVΔt
/Al (5) If the deviation ΔL2 of the lower end of the piezoelectric element in equations (4) and (, 5) is designed to be equal to the deviation ΔLd of the diaphragm, the following relationship is obtained.

L(β-α)=γV/A+ (6) If this functional relationship is maintained, the influence of temperature will be canceled out.

If equation (6) is solved with respect to V, LA / (β-α) V-□ ... (7) γ As an example, the effective diameter of the diaphragm 10 is 1.50n+
Silicone oil 5 manufactured by Toray Co., Ltd. was used as the binding and sealing liquid.
11200 (100cs), γ
:9[1l10PP/'C. Although the enclosed volume (2) is a little too small, it is easy to put a dead spacer etc. into the liquid to make the enclosed space as described above.

Note that a diaphragm lO is used as a sealing element on the piezoelectric element side.
The reason for using the bellows is to save space and reduce the cost, and of course it does not matter if it is a bellows. The same thing can be said about the bellows 5 on the nozzle side. Of course, a diaphragm could be used instead of the bellows, or since the stroke of this part is large, a bellows would have lower stress and be easier to design. Although the strokes of the diaphragm 0 and the bellows 5 were made in the same direction up and down, the bellows 5 may be turned sideways to perform work in the lateral direction.

A valve with a structure as shown in FIG. 1B is called a normally open type. This is because the nozzle 3 and flapper 4 are opened when the power is turned off. By changing the structure, it can be easily changed to a normally closed type.

The flow from the nozzle 3 toward the flapper 4 as shown in FIG. 1B is called outward flow. If it flows in the opposite direction, it will flow inward. It may flow in either direction depending on the application. The effect is the same even if a poppet valve or the like is operated instead of the flapper.

1A and 1B merely illustrate a flow control valve as one embodiment of the present invention. For example, bellows 5
The dot matrix printing dot wire may be operated with a stroke of .

If the gap between the nozzle 3 and the flapper 4 is intentionally made small and an excessive driving voltage is applied to the piezoelectric element, the nozzle 3 and the flapper 4 will come into contact with each other, and the sealed liquid pressure will rise and become overpressure, causing the bellows and May damage the diaphragm. In addition to limiting the maximum voltage electrically, care must also be taken in mechanical assembly. If necessary, safety devices can be added to prevent excessive force from being generated.

Effects of the Invention The present invention is constructed and operates as described above.According to the present invention, the stroke of the piezoelectric element can be easily increased, and drift due to temperature can be reduced by adjusting the volume of the sealed liquid. It is possible to obtain an actuator that does not cause this phenomenon, and has a very large practical effect.

Production-L is also advantageous in that it does not use special materials such as Invar. It is superior to conventional electromagnetic actuators in that it has a conversion efficiency of nearly 50% from electrical energy to mechanical energy, generates less heat, and has a faster response.

[Brief explanation of the drawing]

FIG. 1A is a plan view showing an embodiment of the present invention, and FIG. 1B is a sectional view taken along line AA' in FIG. 1A and viewed in the direction of the arrow. 101. Body, 2-,,'? a Person hole, 2',, outflow hole 311. nozzle, 4. ,, flapper, 5. ,, bellows 611. Spring, 8. ,,color,900. Flange, 10. , , diaphragm, +1.12. ,,joint,138. , partition plate, 14. , , fill liquid, +5. ,
, cap screw, l1li, 1.7. ,, O-ring, +8. ,, Cap, 191. , adhesive, 20. ,
, coating material, 21. ,, electrode plate, 22. ,, pipe, 23. ,, welded part, 24. ,, head cap, 2
5. ,,Lock nut, 2Ei,,,Cap 27,,
, cushion material, +01, +02, +031. ,,
Laminated piezoelectric element, A1. , , Effective area of the first sealing element (diaphragm), A2 , , Effective area of the second sealing element (bellows), Q, , Flow rate, L, , , Length of stacked piezoelectric elements, ΔLm, ,,maximum elongation,ΔL,1
．． Downward deflection of flamper 4, ΔL2. ．． ．． Deflection of the lower end of the piezoelectric element, V, , Filled liquid volume, ΔLd. 9. Diaphragm deflection

Claims (4)

[Claims] (1). A first sealing element having an effective area A1 is attached to the other end of the columnar laminated piezoelectric element having one end fixed.
A second seal element having an effective area A2 is disposed adjacent to the seal element, and the sealed liquid is contained in a liquid seal space having a volume V formed between the first seal element and the second seal element. A laminated piezoelectric actuator characterized in that the elongation of the columnar laminated piezoelectric element is converted into the stroke of the second sealing element via the sealed liquid. (2). In the multilayer piezoelectric actuator according to claim (1), the linear expansion coefficient of the piezoelectric element is α
, the linear expansion coefficient of the pipe is β, the volumetric expansion coefficient of the sealed liquid is γ, and the stacking length of the columnar laminated piezoelectric element is L, the volume of the liquid seal space with the volume V is expressed by the following formula V = { A laminated piezoelectric actuator further characterized in that it satisfies the following relationship: LA/(β-α)}/γ. (3). The laminated piezoelectric actuator according to claim (1) or (2), further characterized in that the effective area A1≧effective area A2. (4). In the laminated piezoelectric actuator according to claim (1), (2) or (3),
A laminated piezoelectric actuator further characterized in that the flow rate is controlled by operating a flapper and a nozzle with the stroke of the second sealing element.