US5457956A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Microminiature stirling cycle cryocoolers and engines
Assignee: Sunpower Inc
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Filing: 1994-11-02
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Granted: 1995-10-17
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Expires: 2014-11-02
Abstract
Abstract A microminiature Stirling cycle engine or cooler is formed utilizing semiconductor, planar processing techniques. Such a Stirling cycle thermomechanical transducer has silicon end plates and an intermediate regenerator. The end plates are formed with diaphragms and backspaces, one end plate forming the expansion end and the opposite end plate forming the compression end, with the regenerator bonded in between. A control circuit apparatus is linked to the diaphragms for controlling the amplitude, phase and frequency of their deflections. The control circuit apparatus is adapted to operate the transducer above 500 Hz and the passages and the workspace, including those within the regenerator, expansion space and compression space, are sufficiently narrow to provide a characteristic Wolmersley number, which is characteristic of the irreversibilities generated by the oscillating flow of the working fluid in the workspace, below substantially 5 at the operating frequency above 500 Hz. Additionally, the amplitude of the vibrations of the diaphragm vibrations are sufficiently small to provide the working fluid a maximum Mach number below substantially 0.1 at an operating frequency above 500 Hz.
Inventors
- 👤 Lyn Bowman
- 👤 David M. Berchowitz
- 👤 Israel Urieli
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 14:45
CPC Classifications
F; F02; F02G; F02G1/00; F02G1/04; F02G1/043; F02G1/0435; F25; F25B; F25B9/00; F25B9/14; H; H10; H10W; H10W40/00; H10W40/30; H10W40/305; F02G2250/00; F02G2250/31; F02G2254/00; F02G2254/30; F02G2258/00; F02G2258/10; F25B2309/00; F25B2309/003; F25B2400/00; F25B2400/15; F25B2500/00; F25B2500/17; Y; Y10; Y10T; Y10T29/00; Y10T29/49; Y10T29/49229
Claims Analysis
Total Claims: 53
Claim 1
Independent Claim
293 words
An improved Stirling cycle thermomechanical transducer having (A) a pressure vessel defining an enclosed work space including fluid passages and containing a working fluid which is compressible and expansible fluid, the pressure vessel comprising: (a) a heat-accepting, fluid-expansion end having (i) an expansion space; (ii) a back space distal to the expansion space; (iii) a flexible expansion diaphragm forming a wall between the expansion space and the back space; and (iv) a heat-accepting heat exchanger proximally bounding the expansion space; and (b) a heat-ejecting, fluid-compression end having (i) a compression space; (ii) a back space distal to the compression (iii) a flexible, compression diaphragm forming a wall between the compression space and the back space; and (iv) a heat-ejecting heat exchanger proximally bounding the compression space; and (c) a heat regenerator interposed between said ends and including a perforate matrix in fluid communication with the expansion space and the compression space; and (B) a control circuit apparatus linked to the diaphragms for controlling the mode, amplitude, phase and frequency of the deflections of the diaphragms which alternately strain to provide periodic variations of the expansion space and compression space volumes and for maintaining a nominal 90° phase lead of the expansion space volume ahead of the compression space volume; wherein the improvement comprises the combination of: the control circuit apparatus being adapted to operate the transducer above 500 Hz; and the passages in the work space being sufficiently narrow to provide a Wolmersley number, which is characteristic of irreversibilities generated by the oscillating flow of the working fluid in the work space, below substantially 5 and the amplitude of diaphragm vibrations are sufficiently small to provide the working fluid a maximum Mach number below substantially 0.1 at an operating frequency above 500 Hz.
Claim 2
Dependent Claim
293 words
An improved Stirling cycle thermomechanical transducer having (A) a pressure vessel defining an enclosed work space including fluid passages and containing a working fluid which is compressible and expansible fluid, the pressure vessel comprising: (a) a heat-accepting, fluid-expansion end having (i) an expansion space; (ii) a back space distal to the expansion space; (iii) a flexible expansion diaphragm forming a wall between the expansion space and the back space; and (iv) a heat-accepting heat exchanger proximally bounding the expansion space; and (b) a heat-ejecting, fluid-compression end having (i) a compression space; (ii) a back space distal to the compression (iii) a flexible, compression diaphragm forming a wall between the compression space and the back space; and (iv) a heat-ejecting heat exchanger proximally bounding the compression space; and (c) a heat regenerator interposed between said ends and including a perforate matrix in fluid communication with the expansion space and the compression space; and (B) a control circuit apparatus linked to the diaphragms for controlling the mode, amplitude, phase and frequency of the deflections of the diaphragms which alternately strain to provide periodic variations of the expansion space and compression space volumes and for maintaining a nominal 90° phase lead of the expansion space volume ahead of the compression space volume; wherein the improvement comprises the combination of: the control circuit apparatus being adapted to operate the transducer above 500 Hz; and the passages in the work space being sufficiently narrow to provide a Wolmersley number, which is characteristic of irreversibilities generated by the oscillating flow of the working fluid in the work space, below substantially 5 and the amplitude of diaphragm vibrations are sufficiently small to provide the working fluid a maximum Mach number below substantially 0.1 at an operating frequency above 500 Hz.
Claim 3
Dependent Claim
28 words
A transducer in accordance with claim 1 wherein at least one of said ends of the pressure vessel is an integral plate comprising a high thermal conductivity material.
Claim 4
Dependent Claim
45 words
A transducer in accordance with claim 2 wherein the expansion end of the pressure vessel is an integral plate comprising a high thermal conductivity material and the compression end of the pressure vessel is a spaced, parallel integral plate comprising a high thermal conductivity material.
Claim 5
Dependent Claim
39 words
A transducer in accordance with claim 3 further including a plurality of said pressure vessels arranged in a parallel two dimensional array, their expansion ends being integrally formed as one plate and their compression ends formed as another plate.
Claim 6
Dependent Claim
17 words
A transducer in accordance with claim 2 wherein said high thermal conductivity material is a silicon plate.
Claim 7
Dependent Claim
22 words
A transducer in accordance with claim 5 wherein the silicon plate comprises a plurality of laminated, etched silicon wafers joined together in-the-plane.
Claim 8
Dependent Claim
16 words
A transducer in accordance with claim 6 wherein said wafers are joined by silicon fusion bonding.
Claim 9
Dependent Claim
18 words
A transducer in accordance with claim 6 wherein said wafers are joined by an intermediary film of glass.
Claim 10
Dependent Claim
17 words
A transducer in accordance with claim 6 wherein said wafers are joined by an intermediary metal film.
Claim 11
Dependent Claim
33 words
A transducer in accordance with claim 6 wherein at least one of said heat exchangers comprises a region of at least one of said silicon wafers, said region being formed with transverse perforations.
Claim 12
Dependent Claim
22 words
A transducer in accordance with claim 3 wherein the integral end plates and the regenerator are joined together into an integral structure.
Claim 13
Dependent Claim
21 words
A transducer in accordance with claim 11 wherein the end plates are joined to the regenerator by an intermediary metal film.
Claim 14
Dependent Claim
21 words
A transducer in accordance with claim 11 wherein the end plates are joined to the regenerator by an intermediary glass film.
Claim 15
Dependent Claim
20 words
A transducer in accordance with claim 11 wherein the end plates are joined to the regenerator by an anodic bond.
Claim 16
Dependent Claim
21 words
A transducer in accordance with claim 2 or 3 or 4 wherein the interposed regenerator comprises a low thermal conductivity material.
Claim 17
Dependent Claim
19 words
A transducer in accordance with claim 15 wherein the low thermal conductivity material of the regenerator comprises a ceramic.
Claim 18
Dependent Claim
19 words
A transducer in accordance with claim 15 wherein the low thermal conductivity material of the regenerator comprises a glass.
Claim 19
Dependent Claim
36 words
A transducer in accordance with claim 15 wherein the perforate matrix of the regenerator is comprised of a reticulated foam with continuously connected voids along the entire length of the working fluid flow through the regenerator.
Claim 20
Dependent Claim
22 words
A transducer in accordance with claim 15 wherein the perforate matrix of the regenerator comprises a plurality of parallel, spaced, planar walls.
Claim 21
Dependent Claim
21 words
A transducer in accordance with claim 15 wherein the perforate matrix of the regenerator comprises a plurality of spaced, concentric tubes.
Claim 22
Dependent Claim
29 words
A transducer in accordance with claim 15 wherein the regenerator comprises a spirally wound, low thermal conductivity, solid film having projections formed in the film to space its layers.
Claim 23
Dependent Claim
20 words
A transducer in accordance with claim 15 wherein the perforate matrix of the regenerator comprises a plurality of parallel tubes.
Claim 24
Dependent Claim
35 words
A transducer in accordance with claim 15 wherein the perforate matrix of the regenerator comprises a plurality of spaced, parallel walls defining passages between the walls having a cross-sectional aspect ratio greater than approximately 8.
Claim 25
Dependent Claim
17 words
A transducer in accordance with claim 2 or 3 or 4 wherein said diaphragms are flat sheets.
Claim 26
Dependent Claim
17 words
A transducer in accordance with claim 2 or 3 or 4 wherein said diaphragms have annular corrugations.
Claim 27
Dependent Claim
26 words
A transducer in accordance with claim 2 or 3 or 4 wherein said diaphragms have at least one thickened region forming a boss of additional mass.
Claim 28
Dependent Claim
37 words
A transducer in accordance with claim 1 or 2 or 3 or 4 wherein the control circuit apparatus includes a pair of electromechanical actuators, a different one of which is mechanically connected to each of the diaphragms.
Claim 29
Dependent Claim
44 words
A transducer in accordance with claim 27 wherein at least one of the electromechanical actuators includes a thin film of piezoelectric material mounted on the diaphragm for applying a mechanical stress to the diaphragm when the piezoelectric material is driven by an electrical signal.
Claim 30
Dependent Claim
76 words
A transducer in accordance with claim 27 wherein at least one of the electromechanical transducers comprises a pair of electrically conducting thin film electrodes, one of said electrodes being attached to a diaphragm and the other electrode being spaced from the first electrode and attached to the pressure vessel end for applying a mechanical stress to the diaphragm in response to an electrostatic force between the electrodes when the electrodes are driven by an electrical signal.
Claim 31
Dependent Claim
70 words
A transducer in accordance with claim 27 wherein at least one of the electromechanical transducers comprises a pair of electrically conducting thin film coils, one of the coils being attached to a diaphragm and the other coil being attached to the pressure vessel end for applying a mechanical stress to the diaphragm in response to an electromagnetic force between the coils when the coils are driven by an electrical signal.
Claim 32
Dependent Claim
43 words
A transducer in accordance with claim 3 wherein the control means includes a pair of electromechanical actuators, a different one of which is mechanically connected to each of the diaphragms and wherein electrical conductors are connected to the diaphragm actuators through the plate.
Claim 33
Dependent Claim
27 words
A transducer in accordance with claim 2 or 3 or 4 wherein at least one diaphragm is resonant at substantially the operating frequency of the thermomechanical transducer.
Claim 34
Dependent Claim
53 words
A transducer in accordance with claim 32 wherein the back space adjacent a resonant diaphragm forms a gas spring having a characteristic spring constant and acting upon the diaphragm and wherein the diaphragm mass and the spring constant are selected to resonate the diaphragm at substantially the operating frequency of the thermomechanical transducer.
Claim 35
Dependent Claim
54 words
A transducer in accordance with claim 32 wherein the back space adjacent a resonant diaphragm is sufficiently large to have a spring constant of substantially zero and wherein the resonant diaphragm mass is selected to resonate with the spring constant of the silicon diaphragm itself at substantially the operating frequency of the thermomechanical transducer.
Claim 36
Dependent Claim
60 words
A transducer in accordance with claim 32 wherein the back space forms a gas spring having a characteristic spring constant and wherein a resonant diaphragm has a characteristic second spring constant and wherein the diaphragm mass, the diaphragm spring constant and the gas spring constant are selected to resonate the diaphragm at substantially the operating frequency of the thermomechanical transducer.
Claim 37
Dependent Claim
55 words
A transducer in accordance with claims 2 or 3 or 4 wherein the expansion end is formed as a plate and wherein the control circuit apparatus includes a motive power means for driving at least one of the diaphragms for operating the transducer as a refrigerator for lowering the temperature of the expansion end plate.
Claim 38
Dependent Claim
30 words
A transducer in accordance with claim 36 wherein an electronic device is thermally linked to the expansion end plate so that a low temperature is produced in the electronic device.
Claim 39
Dependent Claim
30 words
A transducer in accordance with claim 36 wherein an electronic device is integrally fabricated in the expansion end plate so that a low temperature is produced in the electronic device.
Claim 40
Dependent Claim
34 words
A transducer in accordance with claim 36 wherein electronic devices are fabricated in films attached and thermally linked to the expansion end plate so that a low temperature is produced in the electronic devices.
Claim 41
Dependent Claim
27 words
A transducer in accordance with claim 36 wherein the interior of a compartment is thermally linked to the expansion end plate for containing and cooling an object.
Claim 42
Dependent Claim
50 words
A transducer in accordance with claim 2 or 3 or 4 wherein a thermal energy source is thermally linked to the expansion end and the control means includes an energy conveying link from the compression diaphragm to a load for operating the transducer as an engine to drive the load.
Claim 43
Dependent Claim
14 words
A transducer in accordance with claim 41 wherein said load is an electrical generator.
Claim 44
Dependent Claim
14 words
A transducer in accordance with claim 41 wherein said load is a fluid pump.
Claim 45
Dependent Claim
34 words
A transducer in accordance with claim 41 wherein a transparent sheet forming a window is mounted to the expansion end in juxtaposition to the expansion diaphragm for admitting solar radiation onto the expansion diaphragm.
Claim 46
Dependent Claim
23 words
A transducer in accordance with claim 44 wherein said transparent sheet is contoured as a lense to focus concentrated light upon the diaphragm.
Claim 47
Independent Claim
191 words
A method for constructing a Stirling cycle thermomechanical transducer comprising: (a) forming a cooperating diaphragm, back space, expansion space and heat exchanger for each of a plurality of spaced apart, heat-accepting, fluid-expansion ends of a plurality of Stirling transducer pressure vessels by etching away selected portions of silicon wafers and then aligning and joining the wafers together in the plane as an integral, expansion end plate; (b) forming a cooperating diaphragm, back space, compression space and heat exchanger for each of a plurality of spaced apart, heat ejecting, fluid compression ends of a plurality of Stirling transducer pressure vessels by etching away selected portions of silicon wafers and then aligning and joining the wafers together in the plane as an integral compression end plate; (c) forming a plurality of heat regenerators joined together as an integral regenerator plate, each regenerator having fluid openings on opposite sides of the regenerator plate, the openings being spaced apart for registration with said end plates; and (d) interposing, aligning and joining the regenerator plate between the expansion end plate and the compression end plate to form a unitary structure comprising a plurality of Stirling transducers.
Claim 48
Independent Claim
191 words
A method for constructing a Stirling cycle thermomechanical transducer comprising: (a) forming a cooperating diaphragm, back space, expansion space and heat exchanger for each of a plurality of spaced apart, heat-accepting, fluid-expansion ends of a plurality of Stirling transducer pressure vessels by etching away selected portions of silicon wafers and then aligning and joining the wafers together in the plane as an integral, expansion end plate; (b) forming a cooperating diaphragm, back space, compression space and heat exchanger for each of a plurality of spaced apart, heat ejecting, fluid compression ends of a plurality of Stirling transducer pressure vessels by etching away selected portions of silicon wafers and then aligning and joining the wafers together in the plane as an integral compression end plate; (c) forming a plurality of heat regenerators joined together as an integral regenerator plate, each regenerator having fluid openings on opposite sides of the regenerator plate, the openings being spaced apart for registration with said end plates; and (d) interposing, aligning and joining the regenerator plate between the expansion end plate and the compression end plate to form a unitary structure comprising a plurality of Stirling transducers.
Claim 49
Dependent Claim
21 words
A method in accordance with claim 46 further comprising separating the unitary structure between selected transducers to form arrays of transducers.
Claim 50
Dependent Claim
22 words
A method in accordance with claim 47 further comprising separating the unitary structure between transducers to form a plurality of individual transducers.
Claim 51
Dependent Claim
54 words
A method in accordance with claim 46 wherein the integral regenerator plate is formed by: (a) forming a plurality of individual, substantially identical regenerators; (b) aligning the individual regenerators in a parallel, laterally spaced array for registration with said end plates; and (c) mechanically connecting the individual regenerators together to form said regenerator plate.
Claim 52
Dependent Claim
266 words
An improved Stirling cycle thermomechanical transducer having: (A) a pressure vessel defining an enclosed work space including fluid passages and containing a compressible and expansible fluid, the pressure vessel comprising: (a) a heat-accepting, fluid expansion region having (i) an expansion region (ii) a flexible expansion diaphragm forming a wall of the expansion space; and (iii) a heat-accepting, heat exchanger bounding the expansion space; and (b) a heat-ejecting, fluid compression region having: (i) a compression space; (ii) a flexible compression diaphragm forming a wall of the compression space; and (iii) a heat-ejecting, heat exchanger bounding the compression space; and (c) a heat regenerator interposed between said regions and including a perforate matrix in fluid communication with the expansion space and the compression space; and (B) a control circuit apparatus linked to the diaphragms for controlling the mode, amplitude, phase and frequency of the deflections of the diaphragms which alternately strain to provide periodic variations of the expansion space and compression space volumes and for maintaining a nominal 90° phase lead of the expansion space volume ahead of the compression space volume; wherein the improvement comprises the combination of: the control circuit apparatus being adapted to operate the transducer above 500 Hz; and the passages in the work space being sufficiently narrow to provide a Wolmersley number, which is characteristic of the irreversibilities generated by the oscillating flow of the working fluid in the work space, being below substantially 5 and the amplitude of diaphragm vibrations are sufficiently small to provide the working fluid a maximum Mach number below substantially 0.1 at an operating frequency above 500 Hz.
Claim 53
Dependent Claim
266 words
An improved Stirling cycle thermomechanical transducer having: (A) a pressure vessel defining an enclosed work space including fluid passages and containing a compressible and expansible fluid, the pressure vessel comprising: (a) a heat-accepting, fluid expansion region having (i) an expansion region (ii) a flexible expansion diaphragm forming a wall of the expansion space; and (iii) a heat-accepting, heat exchanger bounding the expansion space; and (b) a heat-ejecting, fluid compression region having: (i) a compression space; (ii) a flexible compression diaphragm forming a wall of the compression space; and (iii) a heat-ejecting, heat exchanger bounding the compression space; and (c) a heat regenerator interposed between said regions and including a perforate matrix in fluid communication with the expansion space and the compression space; and (B) a control circuit apparatus linked to the diaphragms for controlling the mode, amplitude, phase and frequency of the deflections of the diaphragms which alternately strain to provide periodic variations of the expansion space and compression space volumes and for maintaining a nominal 90° phase lead of the expansion space volume ahead of the compression space volume; wherein the improvement comprises the combination of: the control circuit apparatus being adapted to operate the transducer above 500 Hz; and the passages in the work space being sufficiently narrow to provide a Wolmersley number, which is characteristic of the irreversibilities generated by the oscillating flow of the working fluid in the work space, being below substantially 5 and the amplitude of diaphragm vibrations are sufficiently small to provide the working fluid a maximum Mach number below substantially 0.1 at an operating frequency above 500 Hz.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1998-10-16 | 1999-04-17 | 1999-10-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2002-10-16 | 2003-04-17 | 2003-10-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2006-10-16 | 2007-04-17 | 2007-10-17 | $7700.00 | Window Closed / Lapsed |