U.S. patent application number 10/520825 was filed with the patent office on 2006-03-09 for piezo-electric compressor with displacement amplifier.
Invention is credited to Nam Trung Nguyen, Kim Tiow Ooi, Chen Zhao.
Application Number | 20060051232 10/520825 |
Document ID | / |
Family ID | 31974301 |
Filed Date | 2006-03-09 |
United States Patent
Application |
20060051232 |
Kind Code |
A1 |
Ooi; Kim Tiow ; et
al. |
March 9, 2006 |
Piezo-electric compressor with displacement amplifier
Abstract
A compressor (300) for successive suction and discharge of a
compressible fluid, thereby increasing fluid pressure of the
compressible fluid in a substantially closed chamber, the
compressor (300) comprising: at least one piezoelectric element
(22); a primary displacement member (46) coupled to the at least
one piezoelectric element (22); a secondary displacement member
(44) coupled to the piston (16); and a non-compressible fluid (45)
disposed to fill a fixed predetermined volume between the primary
displacement member (46) and the secondary displacement member
(44); wherein electrical actuation of the piezoelectric element
(22) is controllable to displace the primary displacement member
(46) by a predetermined distance, being coupled via the
noncompressible fluid (45) to displace the secondary displacement
member (44) by an amplified distance based upon the fixed
predetermined volume.
Inventors: |
Ooi; Kim Tiow; (Singapore,
SG) ; Zhao; Chen; (Singapore, SG) ; Nguyen;
Nam Trung; (Singapore, SG) |
Correspondence
Address: |
George D Liu;Lawrence Y D Ho & Associates
2101 Crystal Plaza Arc
Pmb 400
Arlington
VA
22202
US
|
Family ID: |
31974301 |
Appl. No.: |
10/520825 |
Filed: |
July 24, 2003 |
PCT Filed: |
July 24, 2003 |
PCT NO: |
PCT/SG03/00175 |
371 Date: |
July 28, 2005 |
Current U.S.
Class: |
418/229 |
Current CPC
Class: |
F04B 35/00 20130101;
F04B 35/04 20130101; F04B 17/003 20130101 |
Class at
Publication: |
418/229 |
International
Class: |
F04C 18/00 20060101
F04C018/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 4, 2002 |
SG |
200205376-7 |
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; a
primary displacement member coupled to said at least one
piezoelectric element; a secondary displacement member coupled to
said piston; and a non-compressible fluid disposed to fill a fixed
predetermined volume between said primary displacement member and
said secondary displacement member; wherein electrical actuation of
said at least one piezoelectric element is controllable to displace
said primary displacement member by a predetermined distance, said
primary displacement member being coupled via said non-compressible
fluid to displace said secondary displacement member by an
amplified distance based upon said fixed predetermined volume.
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 a 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, further comprising a
stopper and a piston spring, said piston spring disposed between
said stopper and said secondary displacement member.
6. A compressor in accordance to claim 1, wherein said
non-compressible fluid comprises hydraulic oil or compressor
lubricating oil.
7. A compressor in accordance to claim 1, wherein surface area of
said primary displacement member in contact with said
non-compressible fluid is larger than surface area of said
secondary displacement member in contact with said non-compressible
fluid.
8. 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 and cylinder assembly comprises a
piston, a cylinder, a suction plenum having a suction valve, and a
discharge plenum having a discharge valve, said compressor
comprising: at least one piezoelectric element; a primary
displacement member coupled to said at least one piezoelectric
element; a secondary displacement member coupled to said piston;
and a non-compressible fluid disposed to fill a fixed predetermined
volume between said primary displacement member and said secondary
displacement member; wherein, in response to electrical actuation
of said at least one piezoelectric element, displacement of said
secondary displacement member is amplified relative to displacement
of said primary displacement member, said displacements being based
upon said fixed predetermined volume and surface areas of said
primary displacement member and said secondary displacement member
in contact with said non-compressible fluid.
9. A compressor in accordance to claim 8, wherein said at least one
piezoelectric element is adapted to receive electrical signals for
electrical actuation.
10. A compressor in accordance to claim 9, wherein said electrical
signals comprises a series of voltage pulses.
11. A compressor in accordance to claim 9, wherein said electrical
signals comprises a series of current pulses.
12. A compressor in accordance to claim 8, further comprising a
stopper and a piston spring, said piston spring disposed between
said stopper and said secondary displacement member.
13. A compressor in accordance to claim 8, wherein said
non-compressible fluid comprises hydraulic oil or compressor
lubricating oil.
14. A compressor in accordance to claim 8, wherein surface area of
said primary displacement member in contact with said
non-compressible fluid is larger than surface area of said
secondary displacement member in contact with said non-compressible
fluid.
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; a primary
displacement member coupled to said at least one piezoelectric
element; a secondary displacement member coupled to said piston;
and a non-compressible fluid disposed to fill a fixed predetermined
volume between said primary displacement member and said secondary
displacement member; wherein, in response to electrical actuation
of said at least one piezoelectric element, displacement of said
secondary displacement member is amplified relative to displacement
of said primary displacement member, said displacements being based
upon said fixed predetermined volume and surface areas of said
primary displacement member and said secondary displacement member
in contact with said non-compressible fluid.
16. A fluid conveying apparatus in accordance to claim 15, 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 16, wherein
said electrical signals comprises a series of voltage pulses.
18. A fluid conveying apparatus in accordance to claim 16, wherein
said electrical signals comprises a series of current pulses.
19. A fluid conveying apparatus in accordance to claim 15, further
comprising a stopper and a piston spring, said piston spring
disposed between said stopper and said secondary displacement
member.
20. A fluid conveying apparatus in accordance to claim 15, wherein
said non-compressible fluid comprises hydraulic oil or compressor
lubricating oil.
21. A fluid conveying apparatus in accordance to claim 15, wherein
surface area of said primary displacement member in contact with
said non-compressible fluid is larger than surface area of said
secondary displacement member in contact with said non-compressible
fluid.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to fluid compressors. In
particular, this invention relates to use of a piezoelectric
apparatus 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. 1, 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 16
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,
cause excessive vibrations and noise. Furthermore, the above rotary
motor assembly is prone to mechanical failure due to wear and
tear.
[0008] An alternative to using a rotary motor assembly is to use a
linear actuator. Linear actuators are known in the art and many of
such actuators use piezoelectric elements. Generally, the
piezoelectric elements in such actuators convert electrical energy
into mechanical energy. In piezoelectric actuators, electrical
energy is applied to one or more piezoelectric elements to deform
the piezoelectric elements and thereby physically actuate at least
one other element. A limitation with existing piezoelectric
actuators is that physical deformation of piezoelectric elements is
relatively small. Consequently, applications using piezoelectric
actuators are limited to miniature devices. Typically, displacement
required in such miniature devices ranges from microns to
millimeters.
[0009] To overcome the relatively small displacement of
piezoelectric actuators, U.S. Pat. No. 5,063,542 Petermann et al.
describes a displacement amplifier that interconnects a
piezoelectric actuator with a displacement member. The
piezoelectric actuator has bellow members that define liquid-filled
expansible chambers and respond to linear displacement of
piezoelectric disks to provide an amplified linear displacement to
the displacement member. However, a problem with the displacement
amplifier of U.S. Pat. No. 5,063,542 Petermann et al is that the
expansible chambers are not fixed and precise control of the
amplified linear displacement is therefore difficult. This concept
of use of piezoelectric actuators in combination with hydraulic
displacement amplifiers are further described in U.S. Pat. No.
5,074,654 Alden et al. and U.S. Pat. No. 5,697,554 Auwaerter et al.
In Alden et al., a plurality of electrodistortive actuators coupled
to a hydraulic displacement amplifier are used for the controlling
of deformable mirrors. In Auwaerter et al., a metering valve for
metering fluid for fuel injection uses a piezoelectric element
coupled to a hydraulic displacement amplifier for the actuation of
a valve needle to control the amount of fuel injected.
[0010] Therefore, a need clearly exists for a linear motor that
applies piezoelectric elements having controllable displacement
amplifiers to overcome or at least alleviate the problems of
complexity, maintenance and mechanical failure in existing
reciprocating compressors.
SUMMARY OF THE INVENTION
[0011] The present invention seeks to provide a piezoelectric
apparatus for use in fluid compressors and pumps.
[0012] 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; a primary
displacement member coupled to the at least one piezoelectric
element; a secondary displacement member coupled to the piston; and
a non-compressible fluid disposed to fill a fixed predetermined
volume between the primary displacement member and the secondary
displacement member; wherein electrical actuation of the at least
one piezoelectric element is controllable to displace the primary
displacement member by a predetermined distance, the predetermined
distance being coupled via the non-compressible fluid to displace
the secondary displacement member by an amplified distance based
upon the fixed predetermined volume.
[0013] 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 and cylinder assembly comprises a
piston, a cylinder, a suction plenum having a suction valve, and a
discharge plenum having a discharge valve, the compressor
comprising: at least one piezoelectric element; a primary
displacement member coupled to the at least one piezoelectric
element; a secondary displacement member coupled to the piston; and
a non-compressible fluid disposed to fill a fixed predetermined
volume between the primary displacement member and the secondary
displacement member; wherein, in response to electrical actuation
of the at least one piezoelectric element, displacement of the
secondary displacement member is amplified relative to displacement
of the primary displacement member, the displacements being based
upon the fixed predetermined volume and surface areas of the
primary displacement member and the secondary displacement member
in contact with the non-compressible fluid.
[0014] 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; a primary displacement member coupled to the
at least one piezoelectric element; a secondary displacement member
coupled to the piston; and a non-compressible fluid disposed to
fill a fixed predetermined volume between the primary displacement
member and the secondary displacement member; wherein, in response
to electrical actuation of the at least one piezoelectric element,
displacement of the secondary displacement member is amplified
relative to displacement of the primary displacement member, the
displacements being based upon the fixed predetermined volume and
surface areas of the primary displacement member and the secondary
displacement member in contact with the non-compressible fluid.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] A preferred embodiment and two alternate embodiments of the
present invention is more fully described, by way of example, with
reference to the drawings of which:
[0016] FIG. 1 illustrates a prior art reciprocating compressor;
[0017] FIG. 2 illustrates a compressor in accordance with a first
alternate embodiment of the present invention;
[0018] FIG. 3 illustrates a compressor in accordance with a second
alternate embodiment of the present invention; and
[0019] FIG. 4 illustrates a compressor in accordance with a
preferred embodiment of the present invention.
DETAILED DESCRIPTION OF THE DRAWINGS
[0020] 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.
1. 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.
[0021] 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.
[0022] 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.
[0023] 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.
[0024] 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, a
displacement amplifying means such as a spring 32 is added. 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 the linear reciprocating movement of the piezoelectric
element 22 into an amplified linear reciprocating movement.
Consequently, the linear reciprocating movement of the piston 16 is
also amplified, thus increasing the volume of compressible fluid
handled at each suction or discharge stroke thereby increasing the
capacity of the piezo-compressor 200. However, the amplified linear
reciprocating movement provided by such a spring 32 may not be well
controlled and may develop harmonics which may eventually act
against the linear reciprocating movement of the piezoelectric
element 22. There is also dependency on the inherent mechanical
spring constant of the spring 32, which may deteriorate with
constant use.
[0025] Referring to FIG. 4, a super piezo-compressor 300 according
to a third embodiment of the present invention is shown. In
addition to a desirability for having larger linear reciprocating
movement of the piston 16, there is also a desirability for better
control over the linear reciprocating movement of the piston 16.
The super piezo-compressor 300 achieves this by utilizing a
hydraulic displacement amplifier. The hydraulic displacement
amplifier comprises a primary displacement member 46 coupled to the
piezoelectric element 22, a secondary displacement member 44
coupled to the piston 16, a non-compressible fluid 45 disposed to
fill a fixed predetermined volume between the primary displacement
member 46 and the secondary displacement member 44. The
non-compressible fluid 45 thus couples the primary displacement
member 46 to the secondary displacement member 44. An example of
such a non-compressible fluid 45 would be a hydraulic oil or a
compressor lubricating oil. The secondary displacement member 44 is
further coupled to the piston 16 by way of a piston rod 42. The
surface area of the primary displacement member 46 in contact with
the non-compressible fluid 45 is typically larger than that of the
surface area of the secondary displacement member 44 in contact
with the non-compressible fluid 45.
[0026] When actuating electrical signals are supplied to the
piezoelectric element 22, the piezoelectric element 22 deforms and
displaces the primary displacement member 46 by a small
predetermined distance. However, the secondary displacement member
44 is displaced by an amplified predetermined distance through
coupling with the non-compressible fluid 45 and thus also causes
the piston 16 to be displaced by an amplified predetermined
displacement via the piston rod 42. Amplification of displacement
of the secondary displacement member is based upon the fixed
predetermined volume and dimensions/surface area of said primary
displacement member and said secondary displacement member.
[0027] The relationship between the amplified displacement and the
surface areas of the primary displacement member 46, the
predetermined distance displaced by the primary displacement member
46 and the secondary displacement member 44 may be shown below: L =
A a .times. l ##EQU1##
[0028] Where L is the amplified displacement displaced by the
secondary displacement member 44 and l is the predetermined
distance displaced by the primary displacement member 46. Where A
is the surface area of the primary displacement member 46 in
contact with the non-compressible fluid 45 and a is the surface
area of the secondary displacement member in contact with the
non-compressible fluid 45.
[0029] A stopper 47 can further be coupled to a piston spring 43
which is further coupled to the secondary displacement member 44.
The stopper 47, together with the piston spring 43 serves to assist
in the linear reciprocating movement of the secondary displacement
member 44. Consequently, this also assists in the linear
reciprocating movement of the piston 16.
[0030] The hydraulic displacement amplifier does not merely provide
for amplification of the linear displacement of the piezoelectric
element 22. The hydraulic displacement amplifier also provides for
better control of the linear reciprocating movement of the piston
16.
[0031] The piezo-compressors 100, 200, 300 described in FIG. 2,
FIG. 3 and FIG. 4 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, 300 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.
* * * * *