Thermally actuated microvalve device Number:6,994,115 from the United States Patent and Trademark Office (PTO) owispatent

Title: Thermally actuated microvalve device

Abstract: A microvalve having a generally planar plate valve body defining a chamber and a plate valve member movable in the chamber about a pivot axis that is perpendicular to the valve body to control the flow of a fluid through the valve body. The plate valve member defines a pair of opposite faces, a first duct therethrough provides fluid communication between the opposite faces to equalize fluid pressures acting on the opposite faces in the region of the first duct. The plate valve member also has a second duct therethrough that provides fluid communication between the opposite faces to equalize fluid pressures acting on the opposite faces in the region of the second duct. The first duct and the second duct are equidistant from the pivot axis.

Patent Number: 6,994,115 Issued on 02/07/2006 to Hunnicutt

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Inventors:	Hunnicutt; Harry A. (Ann Arbor, MI)
Assignee:	Kelsey-Hayes Company (Livonia, MI)
Appl. No.:	041479
Filed:	January 24, 2005

Current U.S. Class:	137/625.65; 137/625.44; 251/11; 251/281
Current Intern'l Class:	F15B 13/04.4  (20060101); F16K 11/14    (20060101)
Field of Search:	137/62544,625.65 251/11,281

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Other References

"A Silicon Microvalve For The Proportional Control Of Fluids" by K.R. Williams, N.I. Maluf, E.N. Fuller, R.J. Barron, D.P. Jaeggi, and B.P. van Drieenhuizen, Transducers '99, Proc. 10.sup.th International Conference on Solid State Sensors and Actuators, held Jun. 7-10, 1999, Sendai, Japan, pp. 18-21. "Process for in-plane and out-of-plane single-crystal-silicon thermal microactuators"; J. Mark Noworolski, et al.; Sensors and Actuators A 55 (1996); pp. 65-69. Ayon et al., "Etching Characteristics and Profile Control in a Time Multiplexed ICP Etcher," Proc. Of Solid State Sensor and Actuator Workshop Technical Digest, Hilton Head SC, (Jun. 1998) pp. 41-44. Bartha et al., "Low Temperature Etching of Si in High Density Plasma Using SF.sub.6/O.sub.2," Microelectronic Engineering, Elsevier Science B.V., vol. 27, (1995) pp. 453-456. Fung et al., "Deep Etching of Silicon Using Plasma" Proc. Of the Workshop on Micromachining and Micropackaging of Transducers, (Nov. 7-8, 1984) pp. 159-164. IEEE Technical Digest entitled "Compliant Electro-thermal Microactuators", J. Jonsmann, O. Sigmund, S. Bouwstra, Twelfth IEEE International Conference on Micro Electro Mechanical Systems held Jan. 17-21, 1999, Orlando, Florida, pp. 588-593, IEEE Catalog No.: 99CH36291C. Klassen et al. "Silicon Fusion Bonding and Deep Reactive Ion Etching; A New Technology for Microstructures" Proc., Transducers 95 Stockholm Sweden (1995) pp. 556-559. Linder et al., "Deep Dry Etching Techniques as a New IC Compatible Tool for Silicon Micromachining," Proc,. Transducers, vol. 91, (Jun. 1991) pp. 524-527. Noworolski et al., "Process for in-plane and out-of-plane single-crystal-silicon thermal microactuators", Sensors and Actuators A. vol. 55, No. 1, 1996, pp. 65-69. Petersen et al. "Surfaced Micromachined Structures Fabricated with Silicon Fusion Bonding" Proc., Transducers 91, (Jun. 1992) pp. 397-399. Yunkin et al., "Highly Anisotropic Selective Reactive Ion Etching of Deep Trenches in Silicon," Microelectronic Enginineering, Elsevier Science B.V., vol. 23, (1994) pp. 373-376.

Primary Examiner: Krishnamurthy; Ramesh
Attorney, Agent or Firm: MacMillan, Sobanski & Todd, LLC

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Parent Case Text

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CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No. 09/533,893, filed Mar. 22, 2000, now U.S. Pat. No. 6,845,962, the disclosures of which are incorporated herein by reference.

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Claims

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What is claimed is:

1. A microvalve comprising:

a generally planar plate valve body defining a chamber; and

a plate valve member movable in said chamber about a pivot axis perpendicular to said valve body to control the flow of a fluid through said valve body, said plate valve member defining a pair of opposite faces, a first duct therethrough providing fluid communication between said opposite faces to equalize fluid pressures acting on said opposite faces in the region of said first duct, and a second duct therethrough providing fluid communication between said opposite faces to equalize fluid pressures acting on said opposite faces in the region of said second duct, said first duct and said second duct being equidistant from said pivot axis.

2. The microvalve defined in claim 1, said valve body further defining a first port communicating with said chamber which is adapted to be connected to a source of high pressure fluid, and defining a second port communicating with said chamber which is adapted to be connected to a low pressure reservoir, said plate valve member being movable to a position in which said first duct is in fluid communication with said first port, and said second duct is in fluid communication with said second port.

3. The microvalve defined in claim 2, wherein said plate valve member is "T-shaped", comprising a main shaft connected to said pivot and a cross-member having a first end portion defining said first duct, a second end portion defining said second duct, and a middle portion between said first and second end portions fixed to said main shaft.

4. A micromachined device, comprising:

a body comprising a plurality of plates defining a plurality of parallel planes, said body defining a chamber within at least one intermediate plate and a fluid port communicating with said chamber; and

a member movable in said chamber within a plane parallel to said plurality of parallel planes, said member having a first portion and a second portion, said member being movable within a fixed range of movement such that only said first portion of the member is adjacent to said fluid port within said fixed range of movement, said member defining a pair of opposite faces, and further defining a vent through said second portion providing fluid communication between said opposite faces of said member to equalize fluid pressures acting on said opposite faces of said member.

5. The micromachined device defined in claim 4, wherein said member is a valve member movable to control the flow of a fluid through said fluid port.

6. The micromachined device defined in claim 5, wherein said valve member is "T-shaped", comprising a main shaft connected to a pivot and a cross-member comprising said first portion, and a third portion, said second portion being disposed between said first portion and said third portion, said first portion having a first duct defined therethrough, said third portion defining a second duct defined therethrough, said body defining a second fluid port in fluid communication with said chamber, only said third portion of said member being adjacent to said second fluid port within said fixed range of movement.

7. The micromachined device defined in claim 6, wherein said member is movable, within said fixed range of motion, to a first position in which said first duct is in unrestricted fluid communication with said fluid port and said second duct is in restricted fluid communication with said second fluid port, and movable to a second position in which said first duct is in restricted fluid communication with said fluid port and said second duct is in unrestricted fluid communication with said second fluid port.

8. The micromachined device defined in claim 6, wherein said vent is formed through said second portion adjacent said first duct, and further including a second vent defined through said second portion adjacent said second duct providing fluid communication between said opposite faces of said member to equalize fluid pressures acting on said opposite faces of said member.

9. The micromachined device defined in claim 6, wherein said vent is formed through said second portion adjacent said first duct, and further including a second vent defined through said second portion adjacent said vent providing fluid communication between said opposite faces of said member to equalize fluid pressures acting on said opposite faces of said member.

10. The micromachined device defined in claim 6, wherein said vent is formed through said second portion adjacent said first duct, and wherein said vent is one of a pair of laterally spaced apart vents formed through said second portion adjacent said first duct, and further including a second pair of laterally spaced apart vents defined through said second portion adjacent said second duct providing fluid communication between said opposite faces of said member to equalize fluid pressures acting on said opposite faces of said member.

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Description

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STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

REFERENCE TO A "MICROFICHE APPENDIX"

Not Applicable.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

This invention relates in general to semiconductor electromechanical devices, and in particular to a microvalve device having a pilot valve.

(2) Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98

MEMS (MicroElectroMechanical Systems) is a class of systems that are physically small, having features with sizes in the micrometer range. These systems have both electrical and mechanical components. The term "micromachining" is commonly understood to mean the production of three-dimensional structures and moving parts of MEMS devices. MEMS originally used modified integrated circuit (computer chip) fabrication techniques (such as chemical etching) and materials (such as silicon semiconductor material) to micromachine these very small mechanical devices. Today there are many more micromachining techniques and materials available. The temm "microvalve" as used in this application means a valve having features with sizes in the micrometer range, and thus by definition is at least partially formed by micromachining. The term "microvalve device" as used in this application means a device that includes a microvalve, and that may include other components. It should be noted that if components other than a microvalve are included in the microvalve device, these other components may be micromachined components or standard sized (larger) components.

Various microvalve devices have been proposed for controlling fluid flow within a fluid circuit. A typical microvalve device includes a displaceable member or valve movably supported by a body and operatively coupled to an actuator for movement between a closed position and a fully open position. When placed in the closed position, the valve blocks or closes a first fluid port that is placed in fluid communication with a second fluid port, thereby preventing fluid from flowing between the fluid ports. When the valve moves from the closed position to the fully open position, fluid is increasingly allowed to flow between the fluid ports.

A typical valve consists of a beam resiliently supported by the body at one end. In operation, the actuator forces the beam to bend about the supported end of the beam. In order to bend the beam, the actuator must generate a force sufficient to overcome the spring force associated with the beam. As a general rule, the output force required by the actuator to bend or displace the beam increases as the displacement requirement of the beam increases.

In addition to generating a force sufficient to overcome the spring force associated with the beam, the actuator must generate a force capable of overcoming the fluid flow forces acting on the beam that oppose the intended displacement of the beam. These fluid flow forces generally increase as the flow rate through the fluid ports increases.

As such, the output force requirement of the actuator and in turn the size of the actuator and the power required to drive the actuator generally must increase as the displacement requirement of the beam increases and/or as the flow rate requirement through the fluid ports increases.

Accordingly, there is a need for a microvalve device capable of controlling relatively large flow rates and/or having a displaceable member capable of relatively large displacements with a relatively compact and low powered actuator.

BRIEF SUMMARY OF THE INVENTION

The invention relates to a microvalve device for controlling fluid flow in a fluid circuit. The microvalve device comprises a body having a cavity formed therein. The body further has first and second pilot ports placed in fluid communication with the cavity. The body also has first and second primary ports placed in fluid communication with the cavity. Each port is adapted for connection with a designated fluid source. In a preferred embodiment, one of the pilot ports and one of the primary ports may be in communication with a common fluid source. A pilot valve supported by the body is movably disposed in the cavity for opening and closing the first and second pilot ports. An actuator is operably coupled to the pilot valve for moving the pilot valve. A microvalve is positioned by the fluid controlled by the pilot valve. The microvalve is a slider valve having a first end and a second end. The slider valve is movably disposed in the cavity for movement between a first position and a second position. The first end of the slider valve is in fluid communication with the first and second pilot ports when the first and second pilot ports are open. The second end of the slider valve is in constant fluid communication with the first primary port. When moving between the first and second positions, the slider valve at least partially blocks and unblocks the second primary port for the purpose of variably restricting fluid flow between the primary ports.

In operation, the actuator controls the placement of the pilot valve. In turn, the placement of the pilot valve controls the fluid pressure acting on the first end of the slider valve. The difference between the fluid forces acting on the ends of the slider valve in turn controls the placement of the slider valve. The placement of the slider valve then controls the degree of fluid flow between the primary ports.

The force required to actuate the pilot valve is relatively small. Consequently, the actuator can be relatively compact with relatively low power requirements. Furthermore, the displacement of the slider valve and the flow rate between the primary ports can be relatively large because the fluid force differential associated with the fluid pressures of the fluid sources acting on the ends of the slider valve can be relatively large.

Various other objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiments, when read in light of the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1A is a top plan view of a first embodiment of a microvalve device according to this invention partly broken away to show the microvalve device in a first position.

FIG. 1B is a view similar to FIG. 1A, except with the microvalve device shown in a second position.

FIG. 2 is a sectional view of the microvalve device taken along the line 2—2 of FIG. 1A.

FIG. 3 is a sectional view of the microvalve device taken along the line 3—3 of FIG. 1A.

FIG. 4 is an enlarged view of a slider valve of the microvalve device illustrated in FIGS. 1A and 1B shown in an intermediate position.

FIG. 5A is a top plan view of a second embodiment of a microvalve device according to this invention partly broken away to show the microvalve device in a first position.

FIG. 5B is a view similar to FIG. 5A, except with the microvalve device shown in a second position.

FIG. 5C is a partial view of an alternate embodiment of the actuator illustrated in FIGS. 5A and 5B, showing pressure-reinforcing members thereof.

FIG. 5D is a partial view of an alternate embodiment of the actuator illustrated in FIGS. 1A and 1B, showing pressure-reinforcing members thereof.

FIG. 6 is an enlarged sectional view of the microvalve device taken along the line 6—6 of FIG. 5A.

FIG. 7 is a perspective view of a third plate of the microvalve device illustrated in FIGS. 5A and 5B, showing a bottom surface of the third plate.

FIG. 8 is an enlarged view of a slider valve of the microvalve device illustrated in FIGS. 5A and 5B shown in an intermediate position.

FIG. 9A is a top plan view of a third embodiment of a microvalve device according to this invention partly broken away to show the microvalve device in a first position.

FIG. 9B is a view similar to FIG. 9A, except with the microvalve device shown in a second position.

FIG. 10 is an enlarged view of a slider valve of the microvalve device illustrated in FIGS. 9A and 9B shown in the first position.

FIG. 11A is a top plan view of a fourth embodiment of a microvalve device according to this invention partly broken away to show the microvalve device in a first position.

FIG. 11B is a view similar to FIG. 11A, except with the microvalve device shown in a second position.

FIG. 12 is an enlarged view of a slider valve of the microvalve device illustrated in FIGS. 11A and 11B shown in the first position.

FIG. 13A is a top plan view of a fifth embodiment of a microvalve device according to this invention partly broken away to show the microvalve device in a first position.

FIG. 13B is a view similar to FIG. 13A, except with the microvalve device shown in a second position.

FIG. 14 is an enlarged view of a slider valve of the microvalve device illustrated in FIGS. 13A and 13B shown in the first position.

FIG. 15A is a schematic diagram of a first embodiment of a vehicular brake system including a microvalve unit having a normally open microvalve device and a normally closed microvalve device according to this invention shown in a normal operation mode.

FIG. 15B is a schematic diagram similar to FIG. 15A, except showing the vehicular brake system in a dump operation mode.

FIG. 15C is a schematic diagram similar to FIGS. 15A and 15B, except showing the vehicular brake system in a hold operation mode.

FIG. 16A is a schematic diagram of a second embodiment of a vehicular brake system including the microvalve device illustrated in FIGS. 13A and 13B configured as a two-position control valve shown in a normal operation mode.

FIG. 16B is a schematic diagram similar to FIG. 16A, except showing the vehicular brake system in a dump operation mode.

FIG. 17 is a schematic diagram of a third embodiment of a vehicular brake system including the microvalve device illustrated in FIGS. 13A and 13B configured as a proportional control valve shown in a normal operation mode.

DETAILED DESCRIPTION OF THE INVENTION

A first embodiment of a microvalve device for controlling fluid flow in a fluid circuit is shown generally at 10 in FIG. 1A. The microvalve device 10 includes a body indicated generally at 12. The body 12 includes first, second and third plates 14, 16 and 18, respectively, as best shown in FIGS. 2 and 3. The second plate 16 is attached to and between the first and third plates 14, 18. Preferably, each plate 14, 16, 18 is made of semiconductor material, such as silicon. Alternatively, the plates 14, 16, 18 may be made of any other suitable material, such as glass, ceramic, aluminum, or the like. The description regarding the materials of the plates 14, 16, 18 also applies to the alternate embodiments of microvalve devices disclosed below.

It should be understood that the term "fluid source" as used in this application only means a quantity of fluid. The fluid source may be at a relatively "high pressure", such as the discharge of a running pump, in which case fluid will tend to flow from that fluid source to the area of interest. Alternatively, the fluid may be of relatively "low pressure", such as the suction of a running pump, in which case the fluid will tend to flow from the area of interest to the fluid source. The term "non-planar" as used in this application means that the fluid flow, force, or other subject of the term has a significant component acting perpendicular to the parallel planes defined by the plates 14, 16, and 18. Other terms which may be used in this application include upper, lower, above, below, up, down and the like. These terms are defined in this application with respect to an arbitrary frame work in which the direction perpendicular to the second plate 16 toward the first plate 14 is defined as "down" and the direction perpendicular to the second plate 16 toward the third plate 18 is defined as "up". This convention is for ease of discussion and is not intended as a limitation to the orientation of the devices described herein in actual use or as a limitation to the claims. The terms "inner" and "outer" are defined with respect to the relative closeness of the component under discussion to the longitudinal axis generally defined by the assembly (generally a valve) under discussion, with an inner component being relatively closer to the axis than an outer component.

In this disclosure, reference is sometimes made to a valve being "closed" or a port being "covered or "blocked". It should be understood that these terms mean that flow through the valve or the port is reduced sufficiently that any leakage flow remaining will be relatively insignificant in applications in which the microvalve devices described herein should be employed.

Referring to FIGS. 1A, 1B, and 2, the first plate 14 defines a first pilot port 20 and a second pilot port 22. The first pilot port 20 is adapted for connection with one of a "low pressure" fluid medium or source (not shown) and a "high pressure" fluid medium or source (not shown). The second pilot port 22 is adapted for connection with the other of the "low pressure" fluid source and the "high pressure" fluid source. The first plate 14 also defines a first exhaust port 24 and a second exhaust port 26. Each exhaust port 24, 26 is adapted for connection with a common fluid source (not shown).

Referring also to FIG. 3, the first plate 14 further defines a first primary port 28 and a second primary port 30. The primary ports 28 and 30 are each adapted for connection with a different respective fluid source (not shown).

Referring again to FIG. 2, the third plate 18 defines a first pilot port 20′ opposing the first pilot port 20 and a second pilot port 22′ opposing the second pilot port 22. The pilot ports 20′ and 22′ are adapted for connection with the fluid sources associated with the first and second pilot ports 20 and 22, respectively. The third plate 18 also defines a first exhaust port 24′ opposing the first exhaust port 24 and a second exhaust port 26′ opposing the second exhaust port 26. The exhaust ports 24′, 26′ are adapted for connection with the fluid source associated with the exhaust ports 24 and 26.

Referring again to FIG. 3, the third plate 18 further defines a first primary port 28′ opposing the first primary port 28 and a second primary port 30′ opposing the second primary port 30. The primary ports 28′ and 30′ are adapted for connection with the fluid sources associated with the primary ports 28 and 30, respectively. The purpose of having opposing ports is discussed below.

Additionally, the third plate 18 includes a pair of electrical contacts 32a and 32b disposed in corresponding openings formed in the third plate 18. The electrical contacts 32a, 32b contact the second plate 16 and are adapted for connection to a suitable power source (not shown) for providing an electrical current between the contacts 32a and 32b. The electrical contacts 32a, 32b are illustrated as solder joints, but may be wire leads or the like. Additionally, it should be appreciated that one or both of the electrical contacts 32a and 32b may be placed in the first plate 14.

Referring to FIGS. 1A and 1B, the second plate 16 includes the following main components: a fixed portion 34; a first microvalve embodied as a pilot valve 36 supported by the fixed portion 34 for fully opening and closing the pilot ports 20, 20′, 22, 22′; an actuator 38 for moving the pilot valve 36; and a second microvalve embodied as a slider valve 40 for controlling fluid flow between the first primary ports 28, 28′ and the second primary ports 30, 30′. These components along with the other components of the second plate 16 are described below.

The microvalve device 10 may have gaps (not shown) between the first and/or third plates 14, 18 and each of the moving elements of the second plate 16 including the pilot valve 36, the actuator 38, and the slider valve 40. These gaps may be formed by thinning the moving elements 36, 38, 40 and/or by forming a recess in the first and third plates 14, 18 adjacent the moving elements 36, 38, 40. The sizes of the gaps formed between the pilot ports 20, 20′, 22, 22′ and the pilot valve 36 immediately around the pilot ports 20, 20′, 22, 22′ are small enough to adequately restrict fluid from leaking past the pilot valve 36 when the pilot ports 20, 20′, 22, 22′ are blocked by the pilot valve 36. Preferably, these gaps are approximately 1 micron in size. Similarly, the sizes of the gaps formed between the slider valve 40 and the associated ports 24, 24′, 26, 26′, 28, 28′, 30, 30′ immediately around the associated ports 24, 24′, 26, 26′, 28, 28′, 30, 30′ are small enough to adequately restrict fluid from leaking past the slider valve 40 when the associated ports 24, 24′, 26, 26′, 28, 28′, 30, 30′ are blocked by the slider valve 40. Preferably, these gaps also are approximately 1 micron in size. The gap sizes of the gaps of all other areas between the first and third plates 14, 18 and the moving elements 36, 38, and 40 are sufficiently large enough to provide free movement of the moving elements 36, 38, and 40. Preferably, these gaps are approximately 10 microns in size.

The fixed portion 34 defines a cavity 42 and is fixedly attached to the first and third plates 14, 16.

The pilot valve 36 is a microvalve formed as an longitudinally elongate beam having an end flexibly attached to the fixed portion 34 by an elongate flexure beam 36a. The flexure beam 36a acts as a hinge for mounting the pilot valve 26 in the cavity 42 of the valve body formed by the first, second, and third plates 14, 16, 18. The flexure beam 36a forms a reduced-width generally longitudinally extending extension of the pilot valve 36. The pilot valve 36 is movably disposed in the cavity 42 for pivotal movement between a first position and a second position, the flexure beam 36a bending as the pilot valve 36 moves. As the pilot valve 36 pivots, it defines a plane within which the pilot valve 36 is moving. Preferably, the pilot valve 36 is of a uniform thickness. Within the plane of movement of the pilot valve 36, the pilot valve 36 defines a first transverse width. The flexure beam 36a defines a second transverse width that is less than said first transverse width. FIGS. 1A and 1B show the pilot valve 36 in the first and second positions, respectively. In the first position, the pilot valve 36 blocks or substantially closes the second pilot ports 22, 22′ and unblocks or fully opens the first pilot ports 20, 20′. By opening the first pilot ports 20, 20′, the pilot valve 36 provides fluid communication between the first pilot ports 20, 20′ and a fluid passage 47 connecting the pilot valve 36 and the slider valve 40. In the second position, the pilot valve 36 unblocks or fully opens the second pilot ports 22, 22′ and blocks or substantially closes the first pilot ports 20, 20′. By opening the second pilot ports 22, 22′, the pilot valve 36 provides fluid communication between the second pilot ports 22, 22′ and the fluid passage 47. As will be more fully described below, during use the pilot valve 36 selectively directs "high pressure" fluid into the fluid