Expansion device

Abstract

To provide an expansion device which controls high pressure-side pressure such that the pressure does not exceed a predetermined pressure in terms of absolute pressure, while operating in response to differential pressure between pressure at an inlet thereof and pressure at an outlet thereof. An expansion device comprises an orifice for expanding refrigerant, a valve element disposed on a downstream side of a valve hole and urged by a shape-memory alloy spring in a valve-opening direction, a shaft disposed to extend through the valve hole and having one end thereof rigidly fixed to the valve element, and a spring provided at the other end of the shaft, for receiving load generated by differential pressure between pressure of refrigerant at an inlet of the device and pressure of refrigerant at an outlet thereof, in a valve-opening direction. The shape-memory alloy spring senses the temperature of refrigerant on the downstream side to perform temperature-dependent correction of a set value of the differential pressure for opening the valve element. Therefore, pressure on an upstream side of the valve hole is controlled as if by absolute pressure. Further, when the pressure on the upstream side exceeds a predetermined pressure, the spring is bent to open the expansion valve, and hence the pressure is prevented from rising above the predetermined pressure.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a system diagram showing a refrigeration cycle to which an expansion device according to a first embodiment is applied.

FIG. 2 is a diagram showing a Mollier chart of carbon dioxide.

FIG. 3 is a central longitudinal cross-sectional view of the arrangement of the expansion device according to the first embodiment.

FIG. 4 is a diagram showing a valve-opening characteristic of the expansion device according to the first embodiment.

FIG. 5 is a central longitudinal cross-sectional view of the arrangement of an expansion device according to a second embodiment.

FIG. 6 is a central longitudinal cross-sectional view of the arrangement of an expansion device according to a third embodiment.

FIG. 7 is a central longitudinal cross-sectional view of the arrangement of an expansion device according to a fourth embodiment.

FIG. 8 is a central longitudinal cross-sectional view of the arrangement of an expansion device according to a fifth embodiment.

FIG. 9 is a diagram showing a valve-opening characteristic of the expansion device according to the fifth embodiment.

FIG. 10 is a central longitudinal cross-sectional view of the arrangement of an expansion device according to a sixth embodiment.

FIG. 11 is a central longitudinal cross-sectional view of the arrangement of an expansion device according to a seventh embodiment.

FIG. 12 is a central longitudinal cross-sectional view of the arrangement of an expansion device according to an eighth embodiment.

FIG. 13 is a central longitudinal cross-sectional view of the arrangement of an expansion device according to a ninth embodiment.

FIG. 14 is a central longitudinal cross-sectional view of the arrangement of an expansion device according to a tenth embodiment.

FIG. 15 is a central longitudinal cross-sectional view of the arrangement of an expansion device according to an eleventh embodiment.

Claims

1. An expansion device for expanding refrigerant circulating through a refrigeration cycle, comprising: a differential pressure control valve for being opened by differential pressure between pressure of the refrigerant on an upstream side and pressure of the refrigerant on a downstream side;a spring disposed such that said spring urges said differential pressure control valve in a valve-closing direction, for opening said differential pressure control valve when the differential pressure becomes a value not lower than a predetermined value; andan actuator disposed on the downstream side, for correcting the predetermined value of the differential pressure at which said differential pressure control valve opens, according to a change in temperature or pressure of the refrigerant on the downstream side.

2. The expansion device according to claim 1, wherein said actuator is a low temperature-side temperature-sensing section which is disposed on the downstream side, for urging a valve element of said differential pressure control valve in a valve-opening direction, and corrects the predetermined value such that the predetermined value is made lower according to a rise in the temperature of the refrigerant on the downstream side.

3. The expansion device according to claim 2, wherein said low temperature-side temperature-sensing section is a shape-memory alloy spring whose load for correcting the predetermined value of the differential pressure at which said differential pressure control valve opens, is changed according to a change in the temperature of the refrigerant on the downstream side within a predetermined temperature range.

4. The expansion device according to claim 1, comprising an orifice provided parallel with a valve hole of said differential pressure control valve, for bypassing said differential pressure control valve.

5. The expansion device according to claim 2, comprising a shaft disposed in a manner extending through a valve hole and having one end thereof rigidly fixed to said valve element disposed on a downstream side of the valve hole, for transmitting a force generated by the differential pressure in a direction of opening or closing said valve element, and wherein the other end of said shaft is engaged with said spring disposed on an upstream side of the valve hole in a direction in which said spring is further bent as the differential pressure becomes higher, said spring receiving a load in a direction in which said spring is further bent as the temperature of the refrigerant on the downstream side becomes higher, via said shaft, whereby temperature-dependent correction is performed by said low temperature-side temperature-sensing section.

6. The expansion device according to claim 5, comprising a high temperature-side temperature-sensing section disposed in series with said spring, in a manner urging said differential pressure control valve in the valve-closing direction from the upstream side thereof, for shifting the predetermined value corrected by said low temperature-side temperature-sensing section, according to a change in the temperature of the refrigerant on the upstream side.

7. The expansion device according to claim 6, wherein said high temperature-side temperature-sensing section is a shape-memory alloy spring whose spring load changes according to the change in the temperature of the refrigerant on the upstream side.

8. The expansion device according to claim 7, wherein a biasing spring is disposed parallel with said shape-memory alloy spring.

9. The expansion device according to claim 7, comprising a first spring-receiving member disposed between said spring and said high temperature-side temperature-sensing section, and a stopper rigidly fixed to said shaft, and wherein when said high temperature-side temperature-sensing section senses a temperature not lower than the predetermined value, said stopper restricts an increase in the spring load of said first spring-receiving member.

10. The expansion device according to claim 9, wherein said shape-memory alloy spring is accommodated in a bottomed hollow cylindrical body in a state in which a spring load thereof is adjusted via a second spring-receiving member.

11. The expansion device according to claim 10, comprising a shaft disposed in a manner extending through the valve hole and the hollow cylindrical body, and having one end thereof rigidly fixed to said valve element, for transmitting a force generated by the differential pressure in the direction of opening said valve element, and wherein the other end of said shaft is engaged with said second spring-receiving member within said hollow cylindrical body in a direction in which said shape-memory alloy spring is further bent as the differential pressure becomes higher.

12. The expansion device according to claim 6, wherein said differential pressure control valve which is opened by bending of said spring occurring when the differential pressure becomes higher than the predetermined value is set to a predetermined very small opening degree when the differential pressure is not higher than the predetermined value.

13. The expansion device according to claim 5, comprising another spring disposed in series with said spring in a manner urging said differential pressure control valve in the valve-closing direction from the upstream side thereof, for progressively opening said differential pressure control valve from a set differential pressure lower than the predetermined value.

14. The expansion device according to claim 2, comprising another differential pressure control valve disposed such that said another differential pressure functions in parallel with said differential pressure control valve, for being opened by differential pressure lower than the predetermined value at which said spring opens said differential pressure control valve.

15. The expansion device according to claim 1, wherein said actuator is a low temperature-side pressure-sensing section which is disposed such that said actuator receives, via said spring, a valve element of said differential pressure control valve which is moved on the downstream side in a valve-opening direction by the differential pressure, and acts in a direction of decreasing a spring load of said spring according to a rise in the pressure of the refrigerant on the downstream side to thereby correct the predetermined value in a decreasing direction.

16. The expansion device according to claim 15, wherein said low temperature-side pressure-sensing section is a power element in which a diaphragm is hermetically held between a first housing having a center projected outward and a second housing having an opening in a center, and a disc spring provided within said first housing, for supporting, from inside, said diaphragm displaced in the valve-opening direction of said differential pressure control valve by the pressure of the refrigerant on the downstream side.

17. The expansion device according to claim 16, wherein a chamber of said power element within which said disc spring is accommodated is held under vacuum.

18. The expansion device according to claim 16, wherein a chamber of said power element within which said disc spring is accommodated is filled with gas, and a stopper is formed on the second housing, for restricting inflation of said diaphragm.

19. The expansion device according to claim 15, comprising another differential pressure control valve disposed such that said another differential pressure functions in parallel with said differential pressure control valve, for being opened by differential pressure lower than the predetermined value at which said spring opens said differential pressure control valve.

20. An expansion device for expanding refrigerant circulating through a refrigeration cycle, comprising: an orifice provided between a refrigerant inlet and a refrigerant outlet;a differential pressure control valve disposed parallel with said orifice, for being opened by differential pressure between pressure of the refrigerant at the refrigerant inlet and pressure of the refrigerant at the refrigerant outlet;a spring disposed such that said spring urges said differential pressure control valve in a valve-closing direction, for opening said differential pressure control valve when the differential pressure becomes not lower than a predetermined value; andset differential pressure-correcting means disposed at the refrigerant outlet, for correcting a set differential pressure by changing a load of said spring according to a change in temperature or pressure of the refrigerant at the refrigerant outlet, such that a pressure on an upstream side at which said differential pressure control valve opens is not changed.

21. The expansion device according to claim 20, wherein said set differential pressure-correcting means corrects the set differential pressure in a decreasing direction as the temperature or the pressure of the refrigerant at the refrigerant outlet becomes higher.