WO2001001053A1

WO2001001053A1 - Electro-thermal expansion valve system

Info

Publication number: WO2001001053A1
Application number: PCT/US2000/018007
Authority: WO
Inventors: Roy R. Crawford; Donald S. Foreman; Theresa C. Jenne
Original assignee: Honeywell, Inc.
Priority date: 1999-06-29
Filing date: 2000-06-29
Publication date: 2001-01-04
Also published as: AU5780400A

Abstract

An electrically controlled electro-thermal expansion valve system (10) comprising a valve (14) which is opened or closed, partially or completely, by a diaphragm (18) that is part of a gas containing chamber (24) connected by a tube (26) to a thermal bulb (12) to which a temperature changing device (30) is attached. Under influence of the temperature changing device (30) which may be a thermal resistor (32) with an electric resistance heater or alternatively a thermopile (35), the pressure of the gas (25) is changed which moves the diaphragm (18). Another variant of the valve system has two thermal bulbs (12, 42) connected to two chambers (24, 28), respectively. The diaphragm (18) is a common wall of both chambers (24, 28). A thermopile (35) is used having one set of junctions (38) on one bulb (12) and another set (39) on the other bulb (42).

Description

ELECTRO-THERMAL EXPANSION VALVE SYSTEM BACKGROUND

The invention pertains to valves and particularly to expansion valves. More particularly, the invention pertains to electro-thermal expansion valves.

The present valve design has advantages over related art valves. For instance, stepper-motor driven valves have more moving parts, are more expensive, and are less reliable than the present valves . The stepper-motor valves require more complex electrical signals (i.e., synchronized electrical pulses) with more connections (typically four wires) than the present invention. The present valve requires only a simple analog voltage or current, or a pulse-width-modulated signal, requiring only two conductors.

Heat-driven valves (e.g., hot wax or heated bulbs) can typically open at a much higher rate than they can close. They are quite sensitive to ambient temperature conditions. These performance factors result in overall system performance worse than the present valves. Also, the heat- driven valves need more complex control algorithms to improve performance . Pulsed solenoid valves are typically pulse-width- modulated at a low frequency (e.g., six seconds per cycle), which results in the valve fully opening and closing during each cycle. Such operation results in a pulsed fluid (e.g., refrigerant) flow that often causes reliability problems with the valve and the associated system. The present valve system has a continuously modulated flow and smoother overall system operation.

SUMMARY OF THE INVENTION The invention is a mechanical thermostatic expansion valve (TEV) which may be electrically controlled. An electric resistance heater or thermopile is used to heat a thermal bulb having expanding gas going to a housed diaphragm that moves in reaction to the expanding gas. The diaphragm then drives the valve open so that refrigerant may flow. Heat conduction from the bulb through a thermal resistor to the refrigerant at the valve outlet cools the bulb so as to contract the gas against the diaphragm to drive the valve closed. The thermal resistor helps reduce the effects of ambient temperature conditions since thermal conduction between the bulb and existing refrigerant is the primary mechanism for cooling the bulb. The temperature difference between the bulb and the outgoing refrigerant is directly controlled by the heat supplied to the bulb from the heater in accordance with electrical power. This temperature difference directly determines the pressure difference across the diaphragm, which in turn determines the valve position for regulating the flow of refrigerant. In sum, the relative refrigerant flow rate, in terms of percent of full flow, is directly controlled by the electrical power supplied to the heater with minimal effects due to ambient temperature, inlet refrigerant temperature and pressure, and outlet refrigerant temperature and pressure .

Another variation of the invention is to use a thermoelectric device such as a thermopile, to control the temperature difference between the bulb and exiting refrigerant . Supplying an electrical current to the thermopile results in a direct heating or cooling of the thermal bulb due to the thermoelectric effect of passing an electrical current through dissimilar metals. Installation of the thermopile between the thermal bulb and the refrigerant outlet port, provides the benefit of providing a temperature difference that is in direct proportion to the electric power supplied to the thermopile.

Still another variant of the invention incorporates two thermal bulbs connected to two chambers, respectively, having a diaphragm as a common wall. One bulb is connected to one set of junctions of a thermopile and the other bulb is connected to the other set of thermopile junctions. One bulb is cooled and the other heated to result in a "push- pull" effect on the diaphragm that moves the valve. The flow is proportional to the temperature difference across the bulbs, which is proportional to the voltage applied to the thermopile.

BRIEF DESCRIPTION OF THE DRAWING Figure 1 shows an electro-thermal expansion valve using an electric resistance heater and a thermal resistance cooler.

Figure 2 reveals a valve like that of figure 1 except it uses a thermopile.

Figure 3 reveals a similar valve mechanism except it has a dual thermal bulb temperature sensing mechanism with a thermopile situated on both bulbs.

DESCRIPTION OF THE EMBODIMENTS In Figure 1 is an electro-thermal expansion valve assembly 10. Valve assembly 10 is used for electronically controlling the flow of refrigerant. A liquid refrigerant 11 enters port 13 of valve assembly 10 and goes between valve 14 and valve seat 15 when valve 14 is open, that is, it is not up against seat 15. Refrigerant 11 exits valve assembly out from port 16. The movement, that is, the closing or opening of valve 14 against seat 15, is controlled by valve stem 17 which in turn is moved by diaphragm 18 of a chamber or diaphragm housing 19. Valve 14 is normally closed because of spring 20. Spring 20 has one end situated on support 21 that is part of and attached to a fixture 22 of valve assembly 10. The other end of spring 20 is situated against a ring 23 that is attached firmly to valve stem 17. Spring 20 is under compression of only a few pounds or ounces, depending on the size of valve 14, just enough to close the valve when gas 25 pressure is at a minimal level for valve closure; and with no other forces acting on valve 14, closes valve 14 by pulling it up against valve seat 15.

Valve 14 is lifted off of valve seat 15 by diaphragm 18 via stem 17. Pressure of a gas 25 in a chamber 24 of diaphragm housing 19 increases to a value sufficient to push diaphragm 18 and valve stem 17 to overcome the tension of the compression of spring 20. A typical gas 25 pressure of 50 psi can open valve 14 from seat 15. This pushing of stem 17 lifts valve 14 off of seat 15 and permits refrigerant 11 to flow between seat 15 and valve 14 into port 16. Refrigerant 11 then exits port 16 of valve assembly 10.

When refrigerant 11 enters port 13, it is relatively warm (e.g., 90 degrees F) and at a high pressure (i.e., 100 to 300 psi) . Refrigerant 11 entering port 13 is a liquid. When refrigerant 11 exits port 16, it is relatively cool (i.e. -20 to 20 degrees F) and at a low pressure (i.e., 0 to 50 psi) . Refrigerant 11 exiting port 13 is a liquid vapor mixture .

Bulb 12 contains either a liquid refrigerant or a solid adsorbent material. In either situation, heating the liquid or solid generates additional gas, which increases the pressure over the diaphragm. Cooling it causes gas to be adsorbed, thus decreasing the pressure. The gas is not really expanding or contracting, but is being generated or removed by the solid adsorbent or the liquid adsorbent. Either approach (solid or liquid) can be used in this valve system.

Bulb 12 contains gas 25 that increases or decreases in pressure. Gas 25 enters chamber 24 of diaphragm housing 19 from bulb 12 via a tube pipe 26 and increases the pressure in chamber 24 when gas 25 is heated. This is when valve 14 is opened. Pipe 26 needs to be only a few inches long, though it can be a few feet long, because bulb 12 is placed close to valve 14, within a few inches. Gas 25 exits chamber 24 of diaphragm housing 19 into bulb 12 via pipe 26 and decreases the pressure in chamber 24 when gas 25 is cooled. Pipe 27 connects port 16 with chamber 28 in diaphragm housing 19. Chamber 28 is opposite of chamber 24 relative to diaphragm 18. Pipe 27 equalizes the pressure between chamber 28 and the backside of valve 14, so there is no need for refrigerant to seep around the valve stem supports 20 and 29 of valve assembly fixture 22.

A temperature changing device, such as a thermoelectric cooler or an electric resistance heater 30, is connected to an electrical power supply via a control switch by conductors 31. A thermoelectric cooler can heat or cool. The thermoelectric cooler may be a solid-state heat pump. When a voltage is applied to the thermoelectric cooler, one side gets hot and the other side gets cold. In figure 1, resistance heater 30 is attached to thermal bulb 12 via a thermal resistor 32. When a voltage is applied across conductors 31, heater 30 heats the thermal bulb 12 and thus gas 25 in thermal bulb 12. The heat from the heater is also transferred through the thermal resistance to tube 16 such that a temperature difference is maintained between the bulb and outlet pipe that is directly proportional to the heater power. Gas 25 expands and opens valve 14 to permit the passage of refrigerant 11 from port 13 to port 16, in the manner as described above. When the voltage is removed from across conductors 31 of heater 30, then heat conduction from bulb 12 through thermal resistor 32 to refrigerant 11 at valve assembly 10 output 16, cools bulb 12 and gas 25. The ensuing gas 25 pressure results in the closure of valve 14 as described above . The integrated design of bulb heater 30 and thermal resistor 32 characteristics provide for appropriate valve action and dynamic characteristics. Thermal resistor 32 may be made from brass or other materials selected for particular thermal conduction between bulb 12 and exiting refrigerant 11. Thermal resistor 32 reduces the effect of ambient temperature conditions.

In summary, the temperature difference between bulb 12 and outlet refrigerant 11, which is controlled by heat supplied to bulb 12, directly determines the pressure difference across diaphragm 18, which in turn determines the valve 14 position. The overall effect is that the relative refrigerant 11 flow rate (in percent of full flow) through and by valve 14 is directly controlled by the electrical power supplied to heater 30 with minimal effects due to ambient temperature, inlet refrigerant 11 temperature and pressure, or outlet refrigerant 11 temperature and pressure. Effectively, one has an electro-thermal expansion valve assembly 10 that uses electrical resistance heating and thermal resistance cooling.

Figure 2 shows an electro-thermal expansion valve assembly 40 that uses a thermoelectric device (thermopile) 35 for heating or cooling thermal bulbs 12 and enclosed gas 25. Supplying an electrical current to thermopile 35 results in direct heating or cooling of bulb 12 due to the thermoelectric effect of passing an electrical current through connected dissimilar metals 36 and 37, having junctions 38 and 39, respectively. Placing thermopile 35 between bulb 12 and refrigerant exit port 16, a temperature difference is provided that is in proportion to the electrical power supplied to thermopile 35. To open valve 14, junctions 38 become hotter while junctions 39 become cooler. Gas 25 in bulb 12 increases in pressure thereby affecting diaphragm 18 and opening valve 14 as explained above. To close valve 14, junctions 38 become cooler while junctions 39 become hotter. Gas 25 in bulb 12 then decreases in pressure thereby affecting diaphragm 18 and closing valve 14 as explained above. Whether junctions 39 and 38 become cooler and hotter, respectively, or vice versa, depends on the direction of the electric current applied to terminals 33 and 34 of thermopile 35. The metals used for strips 36 and 37, respectively, may be for example iron and copper.

Even though electro-thermal valve assembly 40 is slightly more complex than valve assembly 10, it tends to have better electrical thermal performance characteristics if made appropriately.

For an electro-thermal expansion valve assembly 50 in figure 3, two bulbs 12 and 42 provide a pressure difference of gases 25 and 45, respectively, across diaphragm 18 that is proportional to the temperature difference of bulbs 12 and 42. With current applied to terminals 33 and 34 of thermopile 35, junctions 38 heat bulb 12 and junctions 39 cool bulb 42. The pressure of gas 25 increases and the pressure of gas 45 decreases. Bulbs 12 and 42 are connected to chambers 24 and 28 by tubes 26 and 46, respectively. That pressure differential causes diaphragm 18 to move valve stem 17 so as to open valve 14 relative to valve seat 15 so that refrigerant 11 can flow by valve 14 from port 13 to port 16. With the current flow to terminals 33 and 34 reversed, junctions 38 cool bulb 12 and junctions 39 heat bulb 42. The pressure of gas 25 decreases and the pressure of gas 45 increases. That pressure differential causes diaphragm 18 to move valve stem 17 so as to close valve 14 relative to valve seat 15 to prevent refrigerant 11 from flowing from port 13 to port 16.

The temperature difference across charge bulbs 12 and 42 is proportional to the voltage applied across terminals 33 and 34 (or proportional to the magnitude of the current flowing through thermopile 35) . The pressure difference between gases 25 and 45 in chambers 24 and 28, respectively, is proportional to the temperature difference. The deflection of diaphragm 18 is proportional to the pressure difference. The opening of valve 15 relative to valve seat 14 is proportional to the deflection of diaphragm 18. The flow of refrigerant 11 from port 13 to port 16 is proportional to the opening of valve 15. Therefore, the flow of refrigerant 11 is proportional to the voltage applied across terminals 33 and 34, where the pressure of gas 25 in chamber 24 is greater or equal to the pressure of gas 45 in chamber 28.

There may or may not be a spacing between bulbs 12 and 42. Or there may be some sort of thermal resistor between the bulbs, depending on the various design parameters for valve assembly 50.

In diaphragm housing 19, chambers 24 and 28 are designed to have equivalent volumes when the pressures in the chambers are the same. (Equivalent volumes are not necessary.) Placement of barrier 43 establishes the amount of volume for chamber 28. Seal 44 around stem 17 prevents gas 45 from leaking out of chamber 28. Seal 44 may be constructed to be an ordinary seal around stem 17 or a small diaphragm attached around stem 17 and to barrier 43. Movement of such diaphragm would have negligible effect upon the volume of chamber 28. Alternatively, barrier 43 may be replaced with a diaphragm across fixture 22 and be attached to the end of a shortened valve stem 17. In the latter configuration, stem 17 would no longer be present in chamber 28 nor be attached to diaphragm 18. Various other ways may be utilized for effectuating the dual chambers in valve assembly 50.

Though the invention has been described with respect to specific embodiments, many variations and modifications will become apparent to those skilled in the art upon reading the present description. It is therefore the intention that the appended claims be interpreted as broadly as possible in view of the prior art to include all such variations and modifications .

Claims

THE CLAIMS

1. An electro-thermal expansion valve system comprising: a conveyance device; a valve situated in said conveyance device; a valve actuator connected to said valve; a bulb connected to said valve actuator; and a temperature changing device proximate to said bulb.

2. The valve system of claim 1, wherein said bulb contains a gas and an adsorbent, which has a change of pressure upon a change of temperature of said bulb.

3. The valve system of claim 2, wherein the change of pressure causes said valve actuator to open or close said valve .

4. The valve of claim 3, wherein opening or closing of said valve affects a flow of a fluid through said conveyance device .

5. The valve system of claim 4, wherein said bulb is proximate to an output of said conveyance device.

6. The valve system of claim 5, wherein: said valve actuator has a housing that has a diaphragm which moves upon a change of the pressure of the gas from said tube connected to the housing; and said valve is connected to the diaphragm.

7. The valve system of claim 6, wherein said bulb is attached to a thermal resistor, and the thermal resistor is attached to said conveyance device proximate to the output .

8. The valve system of claim 7, wherein said temperature changing device is a resistance heater.

9. The valve system of claim 8, wherein said fluid is a refrigerant that, upon the opening of said valve, flows from an input to the output of said conveyance device.

10. The valve system of claim 9, wherein said conveyance device is a pipe-like structure.

11. An electro-thermal expansion valve system comprising: a valve assembly having an input port, an output port and a valve ; a valve actuator connected to said valve assembly; a thermal bulb connected to said valve actuator; and a temperature changing device proximate to said thermal bulb.

12. The valve system of claim 11, wherein: a temperature change of said thermal bulb causes said valve actuator to open or close the valve; and said thermal bulb is situated proximate to the output port of said valve assembly.

13. The valve system of claim 12, wherein said temperature changing device is a thermopile attached to said thermal bulb and the output port of said valve assembly.

14. The valve assembly of claim 13, wherein: said valve actuator is a chamber having a diaphragm attached to the chamber at its perimeter; the chamber is connected to said thermal bulb; and the diaphragm is connected to the valve.

15. The valve assembly of claim 14, wherein: said thermal bulb and the chamber are filled with a gas and an adsorbent, which have changes in pressure with temperature changes of said bulb; the changes in pressure of the gas result in changes of position of the diaphragm; and the changes of position of the diaphragm result in opening and closing the valve.

16. The valve assembly of claim 15, wherein the opening and closing of the valve regulates an amount of a fluid flowing from the input port to the output port .

17. The valve assembly of claim 16, wherein the fluid is a refrigerant .

18. An electro-thermal expansion valve system, comprising: a valve assembly having a first port, a second port, and a valve for regulating an amount of fluid flow from the first port to the second port; a valve actuator connected to the valve of said valve assembly; a first thermal bulb connected to said valve actuator; and a second thermal bulb connected to said valve actuator.

19. The valve system of claim 18, wherein: said valve actuator has a first chamber and a second chamber separated by a diaphragm; the diaphragm is connected to said valve; the first thermal bulb is connected to the first chamber; and the second thermal bulb is connected to the second chamber .

20. The valve system of claim 19, further comprising a temperature changing device proximate to said first and second thermal bulbs .

21. The valve system of claim 20, wherein said temperature changing device affects temperatures of said first and second thermal bulbs by approximately simultaneously increasing the temperature of said first thermal bulb and decreasing the temperature of said second thermal bulb, and vice versa.

22. The valve system of claim 21, further comprising: a first gas and adsorbent in said first thermal bulb and the first chamber; and a second gas and adsorbent in said second thermal bulb and the second chamber.

23. The valve system of claim 22, wherein: the approximately simultaneously increasing the temperature of said first thermal bulb and decreasing the temperature of said second thermal bulb, causes the first gas to increase in pressure and the second gas to decrease in pressure, thereby resulting in movement of the diaphragm which opens the valve; and the approximately simultaneously decreasing the temperature of said first thermal bulb and increasing the temperature of said second thermal bulb, causes the first gas to decrease in pressure and the second gas to increase in pressure, thereby resulting in movement of the diaphragm which closes the valve.

24. The valve system of claim 23, wherein a position of the valve controls a flow rate of a fluid going through said valve assembly from the first port to the second port.

25. The valve system of claim 24, wherein said temperature changing device is a thermopile having a first set of junctions proximate to said first thermal bulb and a second set of junctions proximate to said second thermal bulb.

26. The valve system of claim 25, wherein the fluid is a refrigerant .

27. An electro-thermal expansion valve system comprising: a valve assembly having a valve, and input and output ports connected to the valve; a housing and a diaphragm forming a first chamber that is variable in volume according to movement of the diaphragm; and a first thermal bulb connected to the first chamber; and wherein : the diaphragm is connected to the valve; the movement of the diaphragm results in opening or closing the valve; said first thermal bulb and the first chamber contain a first gas that results in a change of volume with a change of temperature; and the change of volume causes a movement of the diaphragm.

28. The valve system of claim 27, further comprising a temperature changing device proximate to said first thermal bulb.

29. The valve system of claim 28, wherein: said first thermal bulb is proximate to the output port ; and the valve regulates a flow of a fluid through the valve assembly.

30. The valve system of claim 29, further comprising: a thermal resistor situated between and in contact with the output port and said temperature changing device; and wherein: said temperature changing device is an electric resistance heater; and the fluid is a refrigerant.

31. The valve system of claim 30, further comprising a tube connected between a second chamber formed by said housing and diaphragm, and the output port .

32. The valve system of claim 27, further comprising a temperature changing device proximate to said first thermal bulb and the output port .

33. The valve system of claim 32, wherein: said temperature changing device is a thermopile having a first set of junctions proximate to said first thermal bulb and a second set of junctions proximate to the output port ; and the valve regulates a flow of fluid between the input and output ports.

34. The valve system of claim 33, further comprising: a tube connected to a second chamber formed by said housing and diaphragm, and to the output port; and wherein the fluid is a refrigerant .

35. The valve system of claim 27, further comprising: a second chamber formed by said housing and diaphragm; a second thermal bulb connected to said second chamber; and wherein: said second thermal bulb and the second chamber contain a second gas that results in a change of volume with a change of temperature; and the change of volume causes a movement of the diaphragm.

36. The valve system of claim 35, further comprising a temperature changing device proximate to said first and second thermal bulbs .

37. The valve system of claim 36, wherein: said temperature changing device is a thermopile having a first set of junctions proximate to said first thermal bulb and a second set of junctions proximate to said second thermal bulb; and the valve controls a flow of fluid between the input and output ports.

38. The valve system of claim 37, wherein the fluid is a refrigerant .

39. An electro-thermal expansion valve system, comprising: a means for controlling a flow of fluid; an input means, connected to said means for controlling the flow of fluid, for providing an entry for fluid to said means for controlling the flow of fluid; an output means, connected to said means for controlling the flow of fluid, for providing an exit for fluid from said means for controlling the flow of fluid; an actuating means, connected to said means for controlling the flow of fluid, for actuating said means for controlling the flow of fluid in accordance with a pressure of a gas; a temperature sensing means, connected to said actuating means, for sensing a temperature and providing the pressure of the gas, representative of the temperature, to said actuating means; a temperature changing means, connected to said temperature sensing means, for changing the temperature of said temperature sensing means.

40. The valve system of claim 39, wherein the gas is associated with an adsorbent .

41. The valve system of claim 40, wherein said fluid is a refrigerant .