Piezoelectric actuator and pump using same

• US 20040021398A1
• Filed: 05/28/2003
• Published: 02/05/2004
• Est. Priority Date: 09/18/2000
• Status: Active Grant

• Current Assignee: Parker-Hannifin Corporation
• Original Assignee: Adaptivenergy, LLC
• Inventors: East, W. Joe
• Granted Patent: US 7,191,503 B2
• Time in Patent Office: Days
• US Class Current: 310/311
• CPC Class Codes: F04B 43/046 with piezoelectric drive
• CPC Class Codes: H10N 30/06 Forming electrodes or interconnections, e.g. leads or terminals
• CPC Class Codes: H10N 30/2047 Membrane type
• CPC Class Codes: H10N 30/802 Drive or control circuitry or methods for piezoelectric or electrostrictive devices not otherwise provided for
• CPC Class Codes: H10N 30/87 Electrodes or interconnections, e.g. leads or terminals
• CPC Class Codes: H10N 30/877 Conductive materials in general H01B1/00
• CPC Class Codes: Y10T 29/42 Piezoelectric device making
• CPC Class Codes: Y10T 29/49128 Assembling formed circuit to base

Abstract

A method of manufacturing piezoelectric actuators (14) is disclosed along with a minimum diaphragm pump (10) using the actuators. The object was an actuator which could be used in miniature diaphragm pumps and other applications and which would be smaller in size and simpler to manufacture than prior art actuators, yet would provide forces and displacements an order of magnitude higher than any previously known devices of similar size. The pump (10) incorporates the new actuator along with a novel one-way valve (200) and a small driver circuit (18). The pump is of direct application in the liquid cooling systems of small computers, and in other fluid systems.

Claims

1. [Amended] The method of making piezoelectric actuators 14 from piezoelectric wafers 38 wherein the improvement comprises the steps of:

a. cleaning the piezoelectric wafer 38 and enclosing metallic layers 40 and 42 using a solvent that does not leave a residue;

b. coating both sides of the piezoelectric wafer 38 with a thin layer, not more than 0.01 mm[0.005″

], of a high performance polyimide gel adhesive 41, the gel containing a minimum of 25% solids to allow sufficient material for a good bond after the solvent is driven off;

c. placing both sides of the piezoelectric wafer 38 under a standard heat lamp for about five minutes to remove most of the solvent from the gel and start the polyimide gel polymerization process;

d. once the adhesive is dry to the touch, placing the piezoelectric wafer 38 between the metallic layers 40 and 42 to form a piezoelectric actuator 14;

e. assembling a press comprising two 300 mm[12″

] square by 6 mm[¼

″

] thick plates of aluminum 101 held together with thumbscrews 102, at least two on each edge, covering the bottom plate 101 of the press with a sheet of polyimide film 104, placing multiple piezoelectric actuators 14 on the film and covering with a sheet of high temperature 3 mm[⅛

″

] thick rubber 106;

f. making the thumbscrews 102 finger tight;

g. placing the press 100 in a standard convection oven for about thirty minutes at about 200°

C.;

h. removing the press 100 from the oven, allowing it to cool to a safe temperature, and removing the actuators 14 from the press.

2. [Amended] A miniature diaphragm pump 10 for pumping fluids wherein the improvement comprises:

a pump body 12 having a pump chamber 30, an inlet 22, and an outlet 24;

a cover 16 for the pump body 12;

a piezoelectric actuator 14 fixed between the pump body 12 and the cover 16 as a diaphragm;

a one-way valve 200 located in one or both of the inlet 22 and the outlet 24 so that no part of the valve 200 protrudes into pump chamber 30; and

an electrical driver circuit 18 for the piezoelectric actuator 14 located in proximity to the pump 10.

3. The pump 10 of claim 2 further characterized in that the piezoelectric actuator comprises a layer of piezoelectric ceramic 38 between a substrate layer 40 of a first metal and an outer layer 42 of a second metal and bonded to each by an adhesive 41 in a press 100 at a temperature of about 200°

C.

4. The pump of claim 3 further characterized in that the substrate layer 40 is of stainless steel and the outer layer 42 is of aluminum.

5. The pump of claim 4 further characterized in that the adhesive 41 is a polyimide.

6. The pump of claim 5 further characterized in that the piezoelectric actuator 14 is flat.

7. The pump of claim 6 further characterized in that the press 100 comprises flat plates.

8. [Amended] The pump of claim 7 further characterized in that the piezoelectric actuator 14 is made by the following process:

a. clean a piezoelectric wafer 38 and enclosing metallic layers 40 and 42 using a solvent that does not leave a residue;

b. coat both sides of the piezoelectric wafer 38 with a thin layer, not more than 0.005″

, of a high performance polyimide gel adhesive 41 containing a minimum of 25% solids to allow sufficient material for a good bond after the solvent is driven off;

c. place both sides of the piezoelectric wafer 38 under a standard heat lamp for about five minutes to remove most of the solvent from the gel and start the polyimide gel polymerition process;

d. once the adhesive is dry to the touch, place the piezoelectric wafer 38 between the metallic layers 40 and 42 to from a piezoelectric actuator 14.

e. assemble a press 100 comprising two 12″

inch square by ¼

″

thick plates of aluminum 101 held together with thumbscrews 102, at least two on each edge, cover the bottom plate 101 of the press 100 with a sheet of polyimide film 104, place multiple piezoelectric actuators 14 on the film and cover with a sheet of high temperature ⅛

″

rubber sheet 106;

f. make the thumbscrews 102 finger tight;

g. place the press 100 in a standard convection oven for about thirty minutes at approximately 195°

C.;

h. remove the press 100 from the oven, allow it to cool to a safe temperature, and remove the actuators 14 from the press.

9. The pump 10 of claim 8 further characterized in that the pump body 12, cover 16, and piezoelectric actuator 14 are round and the piezoelectric actuator 14 is held in place between the pump body 12 and cover 16 by an o-ring 36 compressed between the cover 16 and the piezoelectric actuator 14, a plastic sealing washer 34 being interposed between the piezoelectric actuator 14 and the pump body 12.

10. The pump 10 of claim 9 further characterized in that the pump chamber 30 is only as deep as the thickness of the sealing washer 34.

11. The pump 10 of claim 9 further characterized in that the axes of the inlet 22 and outlet 24 are essentially perpendicular to the side of the pump body 12.

12. The pump 10 of claim 9 further characterized in that the axes of the inlet 22 and outlet 24 are essentially perpendicular to the plane of the piezoelectric actuator 14.

13. The pump 10 of claim 11 further characterized in that the substrate layer 40 faces the pump chamber 30.

14. The pump 10 of claim 13 further characterized in that the piezoelectric ceramic layer 38 is smaller in diameter than the substrate layer 40 and the outer layer 42 is smaller in diameter than the piezoelectric ceramic layer 38.

15. The pump 10 of claim 14 further characterized in that the compressed o-ring 36 acts only on the substrate layer 40 to fix the piezoelectric actuator 14 in place in the pump body 12.

16. The pump 10 of claim 15 further characterized in that the one-way valve 200 comprises a length of rigid tubing 204 connected to the inlet 22 or outlet 24, with one end of the rigid tubing 204 at an approximate 45°

angle with the axis of the rigid tubing 204 forming a slanted surface, and a thin disk 202 the same size and shape as the slanted surface affixed to the nether end 203 of the slanted surface acting as the working element of the one-way valve 200.

17. The pump 10 of claim 16 further characterized in that the thin disk 202 comprising the working element of the one-way valve 200 is formed of polyimide film.

18. The pump 10 of claim 17 further characterized in that a one-way valve 200 is located in both the inlet 22 and the outlet 24.

19. The pump 10 of claim 17 further characterized in that a one-way valve 200 is located only in the inlet 22.

20. The pump 10 of claim 19 further characterized in that no part of the one-way valve 200 is located in the pump chamber 30.

21. A pump 10 according to claim 20 further characterized in that the electrical driver for the piezoelectric actuator 14 comprises a 6-volt-d.c. power source and a circuit 18 for converting the 6-volts-d.c. to an a.c. voltage sufficient to drive the piezoelectric actuator 14 to a pumping condition.

22. A pump according to claim 21 further characterized in that the electrical driver comprises the circuit 18 shown in FIG. 4.

in which point A is connected to the substrate layer 40 of the piezoelectric actuator 14 and point B is connected to the outer layer 42 of the actuator 14;

in which the elements have the following values;

R18 to 20 MΩ

R28 to 20 MΩ

R3 

680 KΩ

R4 

 

1 MΩ

C1 

0.1 μ

FC2 

0.1 μ

FC3 

0.1 μ

F[200 v]C40.47 μ

F[200]L1 

680 μ

HD1BAS21 diode

and in which U1 is an IMP 528 chip designated an electroluminescent lamp driver and the values of R1 and R2 are chosen to vary the frequency of the output between about 35 Hz and about 85 Hz.

23. The pump 10 of claim 22 in which a square wave waveform is produced by the electrical driver circuit 18 of approximately 150 volts positive and 50 volts negative amplitude.

24. The pump 10 of claim 23 further characterized in that the electrical driver consists of miniaturized circuit elements and is contained in a box 302 mounted on the pump cover 16.

25. The pump 10 of claim 24 further characterized in that the output of the electrical driver circuit 18 is connected to the piezoelectric actuator 14 by means of spring loaded contacts 304 projecting through the pump cover 16.

26. The pump 10 of claim 25 further characterized in that two identical actuators 14 are positioned on either end of the pump body, the substrate layers 40 of each actuator 14 facing each other across the pump chamber 30.

27. The pump 10 of claim 25 further characterized in that two pump chambers 30 with associated piezoelectric actuators 14, inlets 22 and outlets 24, with one-way valves 200 in the inlets 22 only;

seals 34,36;

pump covers 16; and

drivers 18 are positioned side by side in one pump body, the two drivers 18 being in series electrically with the piezoelectric actuators 14 and operating in parallel fluidwise.

28. A miniature diaphragm pump 10 for pumping fluids wherein the improvement comprises;

a pump body 12 generally in the form of a disk measuring from about an inch to about an inch and a half across and from about a quarter inch to five-eighths inch thick with a generally circular pump chamber 30, and at least one opening in the pump body acting as an inlet 22 or outlet 24 and connected to a fluid system conduit 206;

a piezoelectric actuator 14 serving as the diaphragm of the pump 10, the actuator 14 being generally circular in shape and essentially flat and having been made of two metallic layers 40,42 sandwiching a layer of piezoelectric ceramic 38, the three layers being bonded together by a polyimide adhesive 41 in a flat press 100 at a temperature of about 200°

C.;

a pump cover 16;

the piezoelectric actuator 14 being sealed and held in place between the pump body 12 and the pump cover 16 by a sealing washer 34 and an o-ring seal 36, the pump cover 16 being fastened to the pump body 12 while under compression;

a one-way valve 200 positioned in the inlet 22 to allow flow of system fluid only into the pump 10, the valve 200 comprising a length of rigid tubing 204 with one end formed at about a 45°

angle to the axis of the tubing 204 and comprising a slanted end surface, with an elliptical disk 202 of polyimide film the same size and shape as the slanted end surface attached to the slanted end surface at the nether end 203 thereof, the valve 200 being mounted in the system conduit 206;

an electrical driver circuit 18 for the piezoelectric actuator 14 contained in a box 302 generally smaller in size than the pump body 12 mounted in proximity to the pump 10 and connected electrically to the piezoelectric actuator 14, the piezoelectric driver circuit 18 containing an integrated circuit device constituting an electroluminescent lamp driver, the piezoelectric driver circuit 18 producing a square wave of 150 volts positive to 50 volts negative across the piezoelectric actuator 14.