WO2004022973A1

WO2004022973A1 - Piezo-electric compressor

Info

Publication number: WO2004022973A1
Application number: PCT/SG2003/000176
Authority: WO
Inventors: Kim Tiow Ooi; Chen Zhao; Nam Trung Nguyen
Original assignee: Panasonic Refrigeration Devices Singapore Pte. Ltd.
Priority date: 2002-09-04
Filing date: 2003-07-24
Publication date: 2004-03-18
Also published as: AU2003253572A1

Abstract

A compressor (200) having a piston cylinder assembly for successive suction and discharge of a compressible fluid, thereby increasing fluid pressure of the compressible fluid in a substantially closed chamber, wherein the piston cylinder assembly comprises a piston (16), a cylinder (15), a cylinder bore (21), a suction plenum (11) having suction valve (13), and a discharge plenum (12) having a discharge valve (14), the compressor (200) comprising: at least one piezoelectric element (22); and at least one displacement amplifying means (32) coupled between piezoelectric element (22) and the piston; wherein electrical actuation of the piezoelectric element (22) by a predetermined distance displaces the piston (16) coupled via the displacement amplifying means (32) by an amplified distance.

Description

PIEZOELECTRIC COMPRESSOR

Field of the Invention

[0001] The present invention relates to fluid compressors. In particular, this invention relates to use of a piezoelectric elements in fluid compressors and pumps.

Background of the Invention [0002] Reciprocating compressors are positive displacement compressors. Positive displacement compressors take in successive volumes of a fluid which are confined within a substantially closed chamber and are forced to a higher pressure or undergoes compression. A reciprocating compressor achieves this by using a piston within a cylinder (piston cylinder assembly) as the compressing element. A fluid may be a gas or a liquid and may be both when referring to a refrigerant depending on the fluid pressure.

[0003] A reciprocating compressor uses at least two one-way valves in each cylinder that open only when a predetermined differential pressure is applied across such valves. Suction one-way valves (hereafter referred to as suction valves) open when fluid pressure in the cylinder decreases allowing a fluid to enter into the cylinder. Discharge one-way valves (hereafter referred to as discharge valves) open when at the end of the compression, fluid pressure in the cylinder increases to force the fluid out of the cylinder. This succession of suction and discharge of the fluid results in the fluid discharging at a higher pressure.

[0004] To achieve this succession of suction and discharge of fluid from the cylinder, the piston has to undergo a linear reciprocating movement in the cylinder. Referring to FIG.l, that shows a conventional reciprocating compressor, a piston cylinder assembly comprises a suction plenum 11, a discharge plenum 12, a suction valve 13, a discharge valve 14, a cylinder 15, a cylinder bore 21 and a piston 16. Such a piston cylinder assembly is known in the art. [0005] Linear reciprocating movement of the piston 16 for the operation of the reciprocating compressor in suction and discharge of fluid is provided by a mechanical assembly such as, for example, a rotary motor assembly. The rotary motor assembly comprises a rotary motor 19, a crank 18 and a connecting rod 17. Rotation of the rotary motor 19 is translated by the crank 18 and the connecting rod 17 into a linear up/down or forward/backward movement that provides the linear reciprocating movement required in the operation of the reciprocating compressor. A downward movement of the piston 16 decreases the pressure in the cylinder bore 21 to open the suction valve 13. Consequently, the fluid is drawn into the cylinder bore 21 through the suction plenum 11. This downward movement of the piston 16 is referred to as a suction stroke.

[0006] On the other hand, an upward movement of the piston compresses the fluid causing an increase in the fluid pressure and resulting in the suction valve 13 closing and the discharge valve 14 opening. As such, the fluid is forced from the cylinder bore 21 into the discharge plenum 12. This upward movement of the piston 16 is referred to as a discharge stroke.

[0007] The above rotary motor assembly makes use of several mechanical linkages and result in many moving parts. However, such a rotary motor assembly is unnecessarily complicated and requires extensive maintenance by way of lubrication and changing of linkages. Non-in-line mechanical forces acting on the piston 16 also cause excessive vibrations and noise. Furthermore, the above rotary motor assembly is prone to mechanical failure due to wear and tear.

[0008] Therefore, a need clearly exists for a linear motor that applies piezoelectric elements to overcome or at least alleviate the problems of complexity, maintenance and mechanical failure in existing reciprocating compressors. Summary of the Invention

[0009] The present invention seeks to provide a piezoelectric apparatus for use in fluid compressors and pumps.

[0010] Accordingly, in one aspect, the present invention provides a compressor having a piston cylinder assembly for successive suction and discharge of a compressible fluid, thereby increasing fluid pressure of the compressible fluid in a substantially closed chamber, wherein the piston cylinder assembly comprises a piston, a cylinder, a cylinder bore, a suction plenum having a suction valve, and a discharge plenum having a discharge valve, the compressor comprising: at least one piezoelectric element; and at least one displacement amplifying means coupled between the at least one piezoelectric element and the piston; wherein electrical actuation of the at least one piezoelectric element by a predetermined distance, displaces the piston coupled via the displacement amplifying means by an amplified distance.

[0011] In another aspect, the present invention provides a compressor having a piston cylinder assembly for successive suction and discharge of a compressible fluid, thereby increasing fluid pressure of the compressible fluid in a substantially closed chamber, wherein the piston cylinder assembly comprises a piston, a cylinder, a cylinder bore, a suction plenum having a suction valve, and a discharge plenum having a discharge valve, the compressor comprising: at least one piezoelectric element coupled to the piston; wherein electrical actuation of the at least one piezoelectric element by a predetermined distance also displaces the piston by the predetermined distance.

[0012] In yet another aspect, the present invention provides a fluid conveying apparatus having a piston cylinder assembly for successive suction and discharge of a fluid, wherein the piston and cylinder assembly comprises a piston, a cylinder, a suction plenum having a suction valve, and a discharge plenum having a discharge valve, the fluid conveying apparatus comprising: at least one piezoelectric element; and at least one displacement amplifying means coupled between the at least one piezoelectric element and the piston; wherein electrical actuation of the at least one piezoelectric element by a predetermined distance, displaces the piston coupled via the displacement amplifying means by an amplified distance.

[0013] In a further aspect, the present invention provides a fluid conveying apparatus having a piston cylinder assembly for successive suction and discharge of a fluid, wherein the piston and cylinder assembly comprises a piston, a cylinder, a suction plenum having a suction valve, and a discharge plenum having a discharge valve, the fluid conveying apparatus comprising: at least one piezoelectric element; and wherein electrical actuation of the at least one piezoelectric element by a predetermined distance also displaces the piston by the predetermined distance.

Brief Description of the Drawings

[0014] Two embodiments of the present invention will now be more fully described, by way of example, with reference to the drawings of which:

[0015] FIG.1 illustrates a prior art reciprocating compressor;

[0016] FIG. 2 illustrates a compressor in accordance with a first embodiment of the present invention; and

[0017] FIG. 3 illustrates a compressor in accordance with a second embodiment of the present invention;

Detailed description of the Drawings

[0018] Referring to FIG.2, a piezo-compressor 100 according to a first embodiment of the present invention is shown. The piezo-compressor 100 comprises a piston cylinder assembly similar to that of conventional reciprocating compressors as shown in FIG.l . However, instead of the conventional linear reciprocating movement supplied by a rotary motor 19, crank 18 and connecting rod 17, the present piezo-compressor 100 utilizes at least one piezoelectric element 22 coupled directly to the piston 16.

[0019] When actuating electrical signals are supplied to the piezoelectric element 22, the piezoelectric element 22 is deformed to displace the piston 16 linearly by a predetermined distance upward (discharge stroke). This increases the fluid pressure in the cylinder bore 21 and opens the discharge valve 14 to discharge the compressible fluid from the cylinder bore 21 into the discharge plenum 12. The subsequent actuating electrical signals electrically actuate the piezoelectric element 22 to deform in a manner that displaces the piston 16 linearly downward by a predetermined distance (suction stroke). This lowers the fluid pressure in the cylinder bore 21 and opens the suction valve 13 thereby drawing the compressible fluid from the suction plenum 11 into the cylinder bore 21.

[0020] The actuating electrical signals supplied to the piezoelectric element 22 are typically in accordance with specifications governing use of the piezoelectric element 22. Such actuating electrical signals comprise a series of voltage or current pulses of a predetermined amplitude for actuating of the piezoelectric element 22.

[0021] When such actuating electrical signals are supplied to the piezoelectric element 22 continuously, the piezoelectric element 22 is electrically actuated to reciprocally deform in a respective direction to execute either the suction stroke or the discharge stroke. This linear reciprocating movement of the piezoelectric element thus also causes the piston 16 to undergo the required linear reciprocating movement for the operation of the piezo-compressor 100. The operation of the piston cylinder assembly in the piezo-compressor 100 is similar to that of conventional reciprocating compressors. However, the piezo-compressor 100 advantageously has less moving parts and is less prone to mechanical failure. Such piezo-compressors could be advantageously utilized as mini or micro compressors for use in applications requiring continuous and constant dynamic operations while undergoing invariant loadings. Invariably, such piezo-compressors could also be advantageously utilized as fluid conveying apparatuses such as pumps. When used in applications as pumps, the fluid conveyed may be both compressible or non- compressible.

[0022] Referring to FIG.3, an improved piezo-compressor 200 according to a second embodiment of the present invention is shown. In addition to utilizing at least one piezoelectric element 22, at least one displacement amplifying means such as a spring 32 is added. The spring 32 is coupled between the piezoelectric element 22 and the piston 16. Typical linear displacement achieved by piezoelectric elements are in the range of microns to millimeters. In certain applications, such small displacements do not constitute sufficient reciprocating linear movement to operate a piezo-compressor 100 at a high enough capacity. The spring 32 acts as a displacement amplifier that translates predetermined linear distance displaced by the piezoelectric element 22 into an amplified distance. Consequently, the piston 16 which is coupled to the spring 32 is also displaced by an amplified distance. Correspondingly, the linear reciprocating movement of the piezoelectric element 22 also results in the piston 16 undergoing an amplified linear reciprocating movement which increases the volume of compressible fluid handled at each suction or discharge stroke thereby increasing the capacity of the piezo- compressor 200 and improving the piezo-compressor' s performance..

[0023] The piezo-compressors 100, 200, described in FIG.2, and FIG.3 have been depicted and described in a vertical layout. They have also been described singularly. However, it would be obvious to a person skilled in the art to operate the described piezo-compressors 100, 200 in other orientations without departing from the scope of the invention. Further, that the piezo-compressors could also be used in plurality, in a variety of arrangements, and in applications other than compressors and pumps, without departing from the scope of the invention. It will be appreciated that various modifications and improvements can be made by a person skilled in the art without departing from the scope of the present invention.

Claims

1. A compressor having a piston cylinder assembly for successive suction and discharge of a compressible fluid, thereby increasing fluid pressure of said compressible fluid in a substantially closed chamber, wherein said piston cylinder assembly comprises a piston, a cylinder, a cylinder bore, a suction plenum having a suction valve, and a discharge plenum having a discharge valve, said compressor comprising: at least one piezoelectric element; and at least one displacement amplifying means coupled between said at least one piezoelectric element and said piston; wherein electrical actuation of said at least one piezoelectric element by a predetermined distance, displaces said piston coupled via said displacement amplifying means by an amplified distance.

2. A compressor in accordance to claim 1, wherein said at least one piezoelectric element is adapted to receive electrical signals for electrical actuation.

3. A compressor in accordance to claim 2, wherein said electrical signals comprises

series of voltage pulses.

4. A compressor in accordance to claim 2, wherein said electrical signals comprises a series of current pulses.

5. A compressor in accordance to claim 1, wherein said displacement amplifying means comprises a spring.

6. A fluid conveying apparatus having a piston cylinder assembly for successive suction and discharge of a fluid, wherein said piston and cylinder assembly comprises a piston, a cylinder, a suction plenum having a suction valve, and a discharge plenum having a discharge valve, said fluid conveying apparatus comprising: at least one piezoelectric element; and at least one displacement amplifying means coupled between said at least one piezoelectric element and said piston; wherein electrical actuation of said at least one piezoelectric element by a predetermined distance, displaces said piston coupled via said displacement amplifying means by an amplified distance.

7. A fluid conveying apparatus in accordance to claim 8, wherein said at least one piezoelectric element is adapted to receive electrical signals for electrical actuation.

8. A fluid conveying apparatus in accordance to claim 9, wherein said electrical signals comprises a series of voltage pulses.

9. A fluid conveying apparatus in accordance to claim 9, wherein said electrical signals comprises a series of current pulses.

10. A compressor having a piston cylinder assembly for successive suction and discharge of a compressible fluid, thereby increasing fluid pressure of said compressible fluid in a substantially closed chamber, wherein said piston cylinder assembly comprises a piston, a cylinder, a cylinder bore, a suction plenum having a suction valve, and a discharge plenum having a discharge valve, said compressor comprising: at least one piezoelectric element coupled to said piston; wherein electrical actuation of said at least one piezoelectric element by a predetermined distance also displaces said piston by said predetermined distance.

1 1. A compressor in accordance to claim 14, wherein said at least one piezoelectric element is adapted to receive electrical signals for electrical actuation.

12. A compressor in accordance to claim 15, wherein said electrical signals comprises a series of voltage pulses.

13 A compressor in accordance to claim 15, wherein said electrical signals comprises a series of current pulses.

14. A compressor in accordance to claim 14, wherein said displacement amplifying means comprises a spring.

15. A fluid conveying apparatus having a piston cylinder assembly for successive suction and discharge of a fluid, wherein said piston and cylinder assembly comprises a piston, a cylinder, a suction plenum having a suction valve, and a discharge plenum having a discharge valve, said fluid conveying apparatus comprising: at least one piezoelectric element; and wherein electrical actuation of said at least one piezoelectric element by a predetermined distance also displaces said piston by said predetermined distance.

16. A fluid conveying apparatus in accordance to claim 19, wherein said at least one piezoelectric element is adapted to receive electrical signals for electrical actuation.

17. A fluid conveying apparatus in accordance to claim 20, wherein said electrical signals comprises a series of voltage pulses.

18. A fluid conveying apparatus in accordance to claim 20, wherein said electrical signals comprises a series of current pulses.