US20070180854A1 - Expansion device - Google Patents
Expansion device Download PDFInfo
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- US20070180854A1 US20070180854A1 US11/701,497 US70149707A US2007180854A1 US 20070180854 A1 US20070180854 A1 US 20070180854A1 US 70149707 A US70149707 A US 70149707A US 2007180854 A1 US2007180854 A1 US 2007180854A1
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- United States
- Prior art keywords
- differential pressure
- spring
- pressure
- expansion device
- refrigerant
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B41/00—Fluid-circulation arrangements
- F25B41/30—Expansion means; Dispositions thereof
- F25B41/31—Expansion valves
- F25B41/33—Expansion valves with the valve member being actuated by the fluid pressure, e.g. by the pressure of the refrigerant
- F25B41/335—Expansion valves with the valve member being actuated by the fluid pressure, e.g. by the pressure of the refrigerant via diaphragms
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B41/00—Fluid-circulation arrangements
- F25B41/30—Expansion means; Dispositions thereof
- F25B41/31—Expansion valves
- F25B41/36—Expansion valves with the valve member being actuated by bimetal elements or shape-memory elements influenced by fluids, e.g. by the refrigerant
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2309/00—Gas cycle refrigeration machines
- F25B2309/06—Compression machines, plants or systems characterised by the refrigerant being carbon dioxide
- F25B2309/061—Compression machines, plants or systems characterised by the refrigerant being carbon dioxide with cycle highest pressure above the supercritical pressure
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2341/00—Details of ejectors not being used as compression device; Details of flow restrictors or expansion valves
- F25B2341/06—Details of flow restrictors or expansion valves
- F25B2341/068—Expansion valves combined with a sensor
- F25B2341/0683—Expansion valves combined with a sensor the sensor is disposed in the suction line and influenced by the temperature or the pressure of the suction gas
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2500/00—Problems to be solved
- F25B2500/18—Optimization, e.g. high integration of refrigeration components
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2600/00—Control issues
- F25B2600/25—Control of valves
- F25B2600/2505—Fixed-differential control valves
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B40/00—Subcoolers, desuperheaters or superheaters
Definitions
- the present invention relates to an expansion device, and more particularly to an expansion device for expanding refrigerant in a refrigeration cycle for an automotive air conditioner.
- a refrigeration cycle for an automotive air conditioner has been proposed from the viewpoint of global environmental problems, which uses carbon dioxide or the like as refrigerant for use in the refrigeration cycle.
- component elements have pressure resistant structures such that they can withstand high pressure, since the operating pressure of the refrigeration cycle using carbon dioxide is high.
- a compressor for compressing the refrigerant and an expansion device for expanding the compressed refrigerant when the high pressure of the refrigerant enters a dangerous region from a pressure-withstanding viewpoint, control for reducing the pressure is carried out, or the compressor and the expansion device are configured to be capable of lowering the pressure.
- an expansion device which is configured such that a high pressure-side pressure of refrigerant at an inlet of the refrigerant is compared with the atmospheric pressure, and when the high pressure-side pressure exceeds a predetermined pressure, the expansion device opens the valve to lower the high pressure-side pressure (see e.g. Japanese Unexamined Patent Publication No. 2004-142701 (FIGS. 2 and 5)).
- This expansion device comprises a bellows which externally receives the pressure of refrigerant introduced into the refrigerant inlet of the expansion device, for contracting as the pressure of refrigerant rises, and has an inside thereof open to the atmosphere, and a valve mechanism which opens as the bellows contracts.
- the bellows compares the high pressure-side pressure of refrigerant introduced into the refrigerant inlet of the expansion device with the atmospheric pressure, and when the pressure of refrigerant exceeds predetermined pressure, which is considered to be dangerous to the refrigeration cycle from the pressure-withstanding viewpoint, the bellows contracts, and the valve mechanism proportionally opens in response to the contraction of the bellows to lower the pressure.
- the bellows senses the high pressure-side pressure of refrigerant at the refrigerant inlet in terms of absolute pressure to control the valve mechanism, whereby prevention of the high pressure-side pressure of refrigerant at the refrigerant inlet from becoming higher than predetermined pressure can be effected to some extent.
- Japanese Unexamined Patent Publication No. 2004-142701 discloses another expansion device having the structure of a differential pressure control valve which does not sense the high pressure-side pressure in terms of absolute pressure, but operates in response to differential pressure between pressure at a refrigerant inlet and pressure at a refrigerant outlet.
- the expansion device is configured such that when the differential pressure between the pressure at the refrigerant inlet and the pressure at the refrigerant outlet exceeds a predetermined pressure, the expansion device opens the differential pressure control valve to lower the pressure at the refrigerant inlet.
- the expansion device is configured to limit pressure on the high-pressure side, there is no fear that the pressure on the high-pressure side becomes abnormally high. Further, the pressure on the high-pressure side is high when a high cooling power is demanded of the refrigeration cycle, and therefore in such a case, even if the compressor is operating with its maximum displacement, and the pressure on the high-pressure side exceeds the predetermined pressure, there is no need to control the discharge pressure such that it is lowered, on the compressor side, which makes it possible to operate the compressor efficiently at high discharge pressure, thereby enabling the refrigeration cycle to maintain a high cooling power.
- high pressure-side pressure is represented by a value obtained by adding low pressure side-pressure to the differential pressure between the pressure at the refrigerant inlet and the pressure at the refrigerant outlet, so that if the low pressure side-pressure undergoes a change, the high pressure-side pressure is directly influenced by the change, which makes it impossible to control the high pressure-side pressure in terms of absolute pressure.
- the present invention has been made in view of the above points, and an object thereof is to provide an expansion device which operates in response to differential pressure between pressure of refrigerant at an inlet and pressure of refrigerant at an outlet, and when pressure on a high-pressure side exceeds a predetermined pressure in terms of absolute pressure, functions as a pressure relief valve.
- the present invention provides 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 the spring urges the differential pressure control valve in a valve-closing direction, for opening the differential pressure control valve when the differential pressure becomes a value not lower than a predetermined value, and an actuator disposed on the downstream side, for correcting the predetermined value of the differential pressure at which the differential pressure control valve opens, according to a change in temperature or pressure of the refrigerant on the downstream side.
- 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. 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. 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.
- 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.
- the internal heat exchanger 6 is formed therein with a high-pressure passage for allowing high-pressure refrigerant introduced from the gas cooler 2 to flow therethrough, and a low-pressure passage for allowing low-pressure refrigerant introduced from the accumulator 5 to flow therethrough, and the expansion device 3 is disposed at the outlet of the high-pressure passage.
- the expansion device 3 disposed in the internal heat exchanger 6 has a body 21 .
- a central portion of the body 21 has a refrigerant-introducing groove 22 circumferentially formed in an outer periphery thereof, for introducing refrigerant from the high-pressure passage 12 .
- the refrigerant-introducing groove 22 is formed with a refrigerant inlet 23 which extends toward the center of the body 21 .
- a valve hole 24 in the center of a lower portion of the body 21 , there is axially formed a valve hole 24 , and the upstream side of the valve hole 24 is communicated with the refrigerant inlet 23 .
- a valve element 25 is axially movably disposed on the downstream side of the valve hole 24 , for opening and closing the valve hole 24 .
- the valve element 25 has an outer diameter larger than the inner diameter of the valve hole 24 such that the pressure of refrigerant introduced into the refrigerant inlet 23 is received in the valve-opening direction, and is urged in the valve-opening direction by a shape-memory alloy spring 26 forming a temperature-sensing section. It should be noted that the setting of the spring load of the shape-memory alloy spring 26 is adjusted by axially adjusting the position of a hollow cylindrical spring-receiving member 27 externally fixedly fitted on the valve element 25 , with respect to the valve element 25 . Furthermore, an orifice 28 is formed in the body 11 in a manner bypassing the valve hole 24 .
- the body 11 axially movably holds a shaft 29 extending along the axis thereof.
- the shaft 29 has a lower end, as viewed in FIG. 3 , which extends through the valve hole 24 and is rigidly press-fitted in the valve element 25 , and an upper end, as viewed in the figure, which is integrally formed with a large-diameter engaging portion for engagement with a spring-receiving member 30 .
- the shaft 29 is urged in the valve-closing direction via the spring-receiving member 30 by a spring 31 .
- the expansion device 3 forms a differential pressure control valve which opens and closes by the differential pressure between pressure on the upstream side of the valve hole 24 and pressure on the downstream side thereof.
- the shape-memory alloy spring 26 disposed on the low-pressure side of the differential pressure control valve has a feature that a spring load thereof is reversibly changed with respect to the cycle of temperature, and has characteristics that its spring load is small at temperature lower than the transformation temperature, whereas at temperature higher than the transformation temperature, the spring load becomes larger in proportion to a change in temperature. Therefore, the shape-memory alloy spring 26 serves as a temperature-sensing actuator which gives a spring load corresponding to the temperature of refrigerant on the low-pressure side to thereby control pressure on the high-pressure side, forming a low temperature-side temperature-sensing section.
- an O ring 32 is fitted on the outer periphery of the body 21 at a location below the refrigerant-introducing groove 22 , as viewed in FIG. 3 , for sealing between the high-pressure passage 12 and the pipe 14 when the expansion device 3 is mounted in the mounting hole 13 .
- an O ring 33 is disposed between the body 11 and the pipe 14 at a location inside the locking screws 15 screwed into the body 11 for fixing the pipe 14 , for sealing the low-pressure side of the expansion device 3 from the atmosphere.
- the expansion device 3 configured as above, when the differential pressure between pressure on the inlet side and pressure on the outlet side is small, the spring 31 is not bent by the differential pressure, and hence the differential pressure control valve remains closed. At this time, the high-pressure refrigerant having passed through the internal heat exchanger 6 flows through the orifice 28 , and when having flowed out from the orifice 28 , the refrigerant is adiabatically expanded to be changed into the low-pressure, low-temperature refrigerant, and is sent into the evaporator 4 via the pipe 14 .
- the expansion device 3 has a fixed restriction passage cross-sectional area determined by the cross-sectional area of the orifice 28 .
- the differential pressure control valve overcomes the urging force of the spring 31 in the valve-closing direction, to open.
- the valve hole 24 of the differential pressure control valve has a sufficiently larger diameter than that of the orifice 28 , and therefore when the inlet pressure at the inlet of the expansion device 3 exceeds a valve-opening point, the restriction passage cross-sectional area of the expansion device 3 suddenly increases. This causes the inlet pressure to be always held not higher than the valve-opening point.
- the shape-memory alloy spring 26 is configured to generate a spring load corresponding to the pressure when the temperature is 10° C.
- the differential pressure control valve is so adjusted as to be opened by a differential pressure of 8.4 MPa.
- This causes the inlet pressure of the expansion device 3 to be specifically set to be 13 MPa, which is obtained by adding 8.4 MPa, which is a differential pressure as a relative value with respect to 4.6 MPa, which corresponds to the outlet temperature of refrigerant, to 4.6 MPa.
- pressure in the refrigeration cycle changes in the cycle of A-B-C-D-A.
- the spring load of the shape-memory alloy spring 26 is increased to act on the differential pressure control valve in the valve-opening direction.
- the differential pressure at which the differential pressure control valve opens is changed to approximately 7.15 MPa, as is apparent from FIG. 2 .
- the pressure of refrigerant is approximately 5.85 MPa, and hence the inlet pressure of the expansion device 3 is set to 13 MPa.
- pressure in the refrigeration cycle changes in the cycle of A′-B-C-D′-A′.
- the expansion device 3 senses the differential pressure between the inlet pressure and the outlet pressure, and the outlet temperature, and performs temperature-dependent correction of the differential pressure by adding the differential pressure to a pressure corresponding to the outlet temperature, whereby the expansion device 3 operates as if the inlet pressure is controlled by absolute pressure.
- the differential pressure control valve serves simply as a pressure relief valve to suddenly open, so that the inlet pressure is controlled to be held at 13 MPa, which prevents the inlet pressure from rising abnormally.
- FIG. 5 is a central longitudinal cross-sectional view of the arrangement of an expansion device according to a second embodiment.
- component elements identical or equivalent to those shown in FIG. 3 are designated by the same reference numerals, and detailed description thereof is omitted.
- the expansion device 3 a according to the second embodiment is distinguished from the expansion device 3 according to the first embodiment in that it is configured to sense the temperature of refrigerant at the inlet of the expansion device 3 such that the refrigeration cycle can be operated efficiently.
- the body 21 has an upper portion, as viewed in FIG. 5 , which has a tubular cylinder formed in one piece with therewith which accommodates the spring 31 that is bent by the inlet pressure exceeding 13 MPa to act on the differential pressure control valve to open the same, and a shape-memory alloy spring 41 for sensing the inlet temperature in a state arranged in series.
- a biasing spring 42 is arranged parallel with the shape-memory alloy spring 41 , for adjusting the characteristic of the shape-memory alloy spring 41 . More specifically, the shape-memory alloy spring 41 and the biasing spring 42 are arranged between the spring-receiving member 30 engaged with an engaging portion integrally formed with an upper end, as viewed in FIG.
- the adjustment member 44 is press-fitted into the cylinder until it reaches a position where it is brought into abutment with the spring 31 fully extended to a no spring-load status.
- the shape-memory alloy spring 41 senses the inlet temperature.
- the shape-memory alloy spring 41 has a small spring load, and therefore the synthetic load of the shape-memory alloy spring 41 and the spring 42 is small, and the setting differential pressure for opening the differential pressure control valve is set to a small value.
- the synthetic load of the shape-memory alloy spring 41 and the spring 42 becomes larger, and hence the setting differential pressure as well is set to a larger value, whereby the shape-memory alloy spring 41 is in a stiffened state between the spring-receiving member 30 and the spring-receiving member 43 when the inlet temperature is not lower than a predetermined temperature at which a change in the spring load of the shape-memory alloy spring 41 with respect to a change in the temperature is saturated.
- the temperature of refrigerant at the inlet of the expansion device 3 a is sensed by the shape-memory alloy spring 41 so as to shift a predetermined value of the differential pressure subjected to temperature-dependent correction by the shape-memory alloy spring 26 , according to a change in the inlet temperature.
- This makes it possible to control the temperature and pressure of refrigerant at the inlet of the expansion device 3 a , that is, a temperature and a pressure at a point C in FIG. 2 , along a control line CL approximated to an optimal control line that is considered to be capable of enhancing the cooling power of the refrigeration cycle while holding a high performance coefficient of the refrigeration cycle.
- the shape-memory alloy spring 41 when the inlet temperature is low, the shape-memory alloy spring 41 has a small spring load, and a valve-opening force of the valve element 25 , generated by the differential pressure between the inlet pressure and the outlet pressure is transmitted via the shaft 29 , the spring-receiving member 30 , the spring 31 , and the spring-receiving member 43 , to thereby bend the shape-memory alloy spring 41 , which causes the differential pressure control valve to be made open to a very small opening degree.
- the pressure of refrigerant at the inlet of the expansion device 3 b is controlled to a pressure which is determined by a pressure corresponding to the differential pressure across the differential pressure control valve and the outlet temperature.
- the temperature of refrigerant at the inlet of the expansion device 3 a is controlled by the shape-memory alloy spring 41 disposed at the inlet of the expansion device 3 a along the control line CL approximated to the optimal control line.
- the inlet pressure of refrigerant at the inlet of the expansion device 3 a when the spring 31 senses pressure exceeding 13 MPa, it causes the differential pressure control valve to be suddenly opened.
- FIG. 7 is a central longitudinal cross-sectional view of the arrangement of an expansion device according to a fourth embodiment.
- component elements identical or equivalent to those shown in FIG. 5 are designated by the same reference numerals, and detailed description thereof is omitted.
- the expansion device 3 c according to the fourth embodiment has the same basic construction as that of the expansion device 3 a according to the second embodiment, the expansion device 3 c is distinguished from the expansion device 3 a in that it is configured such that the spring 31 for sensing high pressures, the shape-memory alloy spring 41 , and the spring 42 can be easily assembled and adjusted.
- the spring-receiving member 43 through the center of which the shaft 29 loosely extends is integrally formed with a hollow cylindrical body accommodating the shape-memory alloy spring 41 and the spring 42 , and a stopper 45 for adjusting the spring loads of the shape-memory alloy spring 41 and the spring 42 via the spring-receiving member 30 is press-fitted into the hollow cylindrical body.
- the spring-receiving member 43 is placed on an upper portion, as viewed in FIG. 7 , of the spring 31 , and the adjustment member 44 is rigidly fixed to the body 21 such that the adjustment member 44 accommodates the spring 31 and the spring-receiving member 43 .
- the shape-memory alloy spring 41 and the spring 42 are assembled while adjusting the spring loads thereof in advance. More specifically, the shape-memory alloy spring 41 and the spring 42 , and the spring-receiving member 30 are placed in the hollow cylindrical body of the spring receiving member 43 in the mentioned order, and the stopper 45 is press-fitted into the hollow cylindrical body until it reaches a predetermined position, to thereby adjust the spring loads of the shape-memory alloy spring 41 and the spring 42 , whereby a high temperature-side temperature-sensing section is constructed. Then, the high temperature-side temperature-sensing section is placed on the spring 31 disposed in an upper space of the body 21 , as viewed in FIG.
- the adjustment member 44 having a hollow cylindrical shape and having an engaging portion with an upper portion thereof, as viewed in the figure, bent inward, is placed from above to cover them.
- the adjustment member 44 is further pushed down, as viewed in the figure, until the engaging portion is brought into abutment with an upper end, as viewed in the figure, of the spring-receiving member 43 , whereby the adjustment member 44 is fitted to the body 21 .
- the adjustment member 44 is pushed down, as viewed in the figure, as required, it is possible to adjust the spring load of the spring 31 .
- the shaft 29 is inserted from above, as viewed in the figure, and further, the differential pressure control valve is press-fitted by a predetermined amount into the valve element 25 to which is applied the adjusted spring load of the shape-memory alloy spring 26 , such that the differential pressure control valve is made open to a predetermined minimum opening degree by the shape-memory alloy spring 26 .
- the expansion device 3 c is assembled.
- the expansion device 3 c Since the expansion device 3 c has the same basic construction as that of the expansion device 3 a according to the second embodiment, the expansion device 3 c operates quite the same way as the expansion device 3 a.
- 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 the valve-opening characteristic of the expansion according to the fifth embodiment.
- component elements identical or equivalent to those shown in FIG. 7 are designated by the same reference numerals, and detailed description thereof is omitted.
- the expansion device 3 d according to the fifth embodiment is distinguished from the expansion device 3 c according to the fourth embodiment in that in place of the high temperature-side temperature-sensing section including the shape-memory alloy spring 41 and its biasing spring 42 of the expansion device 3 c , it is provided with a spring 42 a for opening the differential pressure control valve by a differential pressure lower than 13 MPa.
- the expansion device 3 d is characterized in that it has two valve-opening points at which the expansion device 3 d opens the differential pressure control valve in response to changes in the inlet pressure of refrigerant on the upstream side. More specifically, in a stage of low inlet pressure, the expansion device 3 d is made open to the predetermined minimum opening degree, and has a fixed restriction passage cross-sectional area. When the inlet pressure becomes higher, and first exceeds a predetermined value set by the spring 42 a , the spring 42 a is bent to open the differential pressure control valve. As the inlet pressure becomes higher, the restriction passage cross-sectional area increases proportionally. When the inlet pressure further increases to exceed 13 MPa, which is set by the spring 31 , the differential pressure control valve suddenly opens to lower the inlet pressure, thereby preventing the inlet pressure from rising above 13 MPa.
- FIG. 10 is a central longitudinal cross-sectional view of the arrangement of an expansion device according to a sixth embodiment.
- component elements identical or equivalent to those shown in FIG. 5 are designated by the same reference numerals, and detailed description thereof is omitted.
- the expansion device 3 e has the same basic construction as that of the expansion device 3 a according to the second embodiment, the expansion device 3 e is distinguished from the expansion device 3 a which has the high temperature-side temperature-sensing section that senses the temperature of refrigerant at the outlet of the internal heat exchanger 6 in that the expansion device 3 e has a high temperature-side temperature-sensing section that senses the temperature of refrigerant at the inlet of the internal heat exchanger 6 , that is, the temperature of refrigerant at the outlet of the gas cooler 2 .
- an O ring 47 is circumferentially formed on the outer periphery of the body 21 so as to prevent refrigerant in the refrigerant inlet passage 46 from leaking into the refrigerant inlet 23 in a state of the expansion device 3 e mounted to mounting hole 13 .
- the operation of the expansion device is the same as that of the expansion device 3 a except that the high temperature-side temperature-sensing section senses the temperature of refrigerant at the outlet of the gas cooler 2 in the refrigerant inlet passage 46 of the internal heat exchanger 6 .
- FIG. 11 is a central longitudinal cross-sectional view of the arrangement of an expansion device according to a seventh embodiment.
- component elements identical or equivalent to those shown in FIG. 10 are designated by the same reference numerals, and detailed description thereof is omitted.
- the expansion device 3 f according to the seventh embodiment is distinguished from the expansion device 3 e according to the sixth embodiment in that the construction of the high temperature-side temperature-sensing section that senses the temperature of refrigerant at the outlet of the gas cooler 2 is simplified. More specifically, the expansion device 3 f is configured such that the stopper 45 included in the high temperature-side temperature-sensing section of the expansion device 3 e is eliminated while arranging the shape-memory alloy spring 41 and the spring 42 in series with the spring 31 for sensing high pressure.
- the shape-memory alloy spring 41 acts in the direction of increasing the spring load of the high pressure-sensing spring 31 , and hence the expansion device 3 f has a characteristic that at a valve-opening point thereof, in response to changes in the inlet pressure, it opens the differential pressure control valve not sharply but a little more smoothly.
- FIG. 12 is a central longitudinal cross-sectional view of the arrangement of an expansion device according to an eighth embodiment.
- component elements identical or equivalent to those shown in FIG. 3 are designated by the same reference numerals, and detailed description thereof is omitted.
- the expansion device 3 g according to the eighth embodiment is distinguished from the expansion device 3 according to the first embodiment which has the high pressure-sensing spring 31 disposed on the upstream side in that the expansion device 3 g has the spring 31 disposed on the downstream side.
- the valve element 25 is disposed on the downstream side of the valve hole 24 formed through the body 21 , and the high pressure-sensing spring 31 is disposed to urge the piston 51 which is integrally formed with the valve element 25 and is axially and movably accommodated within the body 21 , in the valve-closing direction, while the shape-memory alloy spring 26 of the low temperature-side temperature-sensing section is disposed to urge the piston 51 in the valve-opening direction.
- the high pressure-sensing spring 31 has a spring load thereof adjusted by an adjustment screw 52 screwed into the body 21 .
- the spring 31 is bent in response to the differential pressure between the pressure of refrigerant on the upstream side and the pressure of refrigerant on the downstream side, whereby a predetermined value of the differential pressure, required for opening the differential pressure control valve, is subjected to correction dependent on the outlet temperature of refrigerant on the downstream side, sensed by the shape-memory alloy spring 26 , whereby when the pressure of refrigerant on the upstream side is high, the inlet pressure of refrigerant is always held at 13 MPa set by the spring 31 .
- the orifice 28 is formed through the valve element 25 , for allowing refrigerant to flow at a minimum flow rate when the differential pressure control valve is fully closed, and a strainer 53 is disposed on the upstream side of the valve hole thereof, for removing foreign matter from refrigerant.
- FIG. 13 is a central longitudinal cross-sectional view of the arrangement of an expansion device according to a ninth embodiment.
- component elements identical or equivalent to those shown in FIG. 12 are designated by the same reference numerals, and detailed description thereof is omitted.
- the expansion device 3 h according to the ninth embodiment is distinguished from the expansion device 3 g according to the eighth embodiment in that it is configured to incorporate a second differential pressure control valve in the differential pressure control valve (hereinafter referred to as “the first differential pressure control valve”) of the expansion device 3 g , such that two differential pressure control valves having different valve-opening points function in parallel.
- the first differential pressure control valve hereinafter referred to as “the first differential pressure control valve”
- the orifice 28 formed in the valve element 25 of the first differential pressure control valve serves as a valve hole of the second differential pressure control valve, with a valve element 61 being disposed on the downstream side, for opening and closing the valve hole, and a piston 62 integrally formed with the valve element is axially movably accommodated in the piston 51 of the first differential pressure control valve.
- the piston 62 is urged by the spring 63 in the valve-closing direction, and the spring load of the spring 63 is adjusted by an adjustment screw 64 screwed into the piston 51 .
- an orifice 65 for allowing refrigerant to flow at a minimum flow rate when the first and second differential pressure control valves are fully closed.
- the expansion device 3 h configured as above has a characteristic, as shown in FIG. 9 , that it has two valve-opening points at which the expansion device 3 h opens in response to changes in the inlet pressure of refrigerant on the upstream side. More specifically, in the expansion device 3 h , the shape-memory alloy spring 26 senses the outlet temperature of refrigerant on the downstream side to correct the predetermined value of differential pressure required for opening the first differential pressure control valve, whereby the inlet pressure of refrigerant is sensed as a pseudo absolute pressure.
- the expansion device 3 h has a fixed restriction passage cross-sectional area determined by the cross-sectional area of the orifice 65 of the second differential pressure control valve.
- the second differential pressure control valve opens, and as the differential pressure becomes higher, the restriction passage cross-sectional area increases proportionally. After that, when the inlet pressure reaches 13 MPa, the first differential pressure control valve starts to open. Further, when the inlet pressure increases to exceed 13 MPa set by the spring 31 , the first differential pressure control valve suddenly opens. This causes the inlet pressure to decrease, and hence prevents the same from increasing above 13 MPa.
- the low temperature-side temperature-sensing section is configured to correct the predetermined value of the valve-opening differential pressure for opening the differential pressure control valve according to changes in the temperature of refrigerant on the downstream side of the differential pressure control valve.
- the predetermined value of the valve-opening differential pressure can be corrected not only according to changes in the temperature of refrigerant on the downstream side of the differential pressure control valve but also according to changes in the pressure of refrigerant on the downstream side of the differential pressure control valve.
- an expansion device to have the same function as that of the expansion devices 3 to 3 h according to the first to ninth embodiments by configuring the expansion device such that in place of the low temperature-side temperature-sensing section, a low temperature-side pressure-sensing section senses the pressure of refrigerant at the outlet of the expansion device, to correct the predetermined value of the valve-opening differential pressure according to changes in the pressure of refrigerant on the downstream side of the differential pressure control valve.
- a low temperature-side pressure-sensing section senses the pressure of refrigerant at the outlet of the expansion device, to correct the predetermined value of the valve-opening differential pressure according to changes in the pressure of refrigerant on the downstream side of the differential pressure control valve.
- FIG. 14 is a central longitudinal cross-sectional view of the arrangement of an expansion device according to a tenth embodiment.
- component elements identical or equivalent to those shown in FIG. 12 are designated by the same reference numerals, and detailed description thereof is omitted.
- the expansion device 3 i according to the tenth embodiment is provided with a low temperature-side pressure-sensing section in place of the shape-memory alloy spring 26 as the low temperature-side temperature-sensing section of the expansion device 3 g according to the eighth embodiment. More specifically, the expansion device 3 i has a power element 71 fixed thereto by screwing an open end of a hollow cylindrical portion of the body 21 into the power element 71 .
- the power element 71 acts in the direction of decreasing the spring load of the high pressure-sensing spring 31 which sets the valve-opening differential pressure for opening the differential pressure control valve, to thereby serve as a pressure-sensing actuator that corrects a predetermined value of the valve-opening differential pressure in a decreasing direction.
- the power element 71 is formed by holding a diaphragm 74 made of a thin metal plate between an outer housing 72 having a center projected outward and an inner housing 73 having an opening in the center thereof and having a hub connected to the body 21 , and welding all the outer peripheries of the housings 72 and 73 and the diaphragm 74 under high-pressure gas or vacuum atmosphere along the whole circumferences thereof.
- a hermetically sealed space formed by the outer housing 72 and the diaphragm 74 accommodates a disc spring 75 , a spring 76 , and a spring receiving member 77 .
- the load of the disc spring 75 is adjusted by combining a plurality of disc springs (three in the illustrated example) having respective appropriate spring loads.
- the spring load of the spring 76 is adjusted by plastically inwardly deforming an end face of the outer housing 72 to change the position of the spring-receiving member 77 in the direction of compressing the spring 76 .
- a displacement-transmitting member 78 is disposed for transmitting the displacement of the diaphragm 74 to the spring 31 .
- a stopper 79 in the form of a step is formed on an inner wall of the housing 73 , for restricting the motion of the displacement-transmitting member 78 in the direction of increasing the spring load of the spring 31 . This inhibits the expansion device from correcting the predetermined value of the differential pressure when the compressor 1 is operating in a state in which the pressure of refrigerant on the downstream side of the differential pressure control valve is low.
- part of a screw thread of the body 21 which is screwed into the power element 71 , is cut such that the pressure of refrigerant on the downstream side of the differential pressure control valve easily reaches the diaphragm 74 , the cut part is not necessarily required since portions of the power element 71 and the body 21 screwed together are not completely hermetically sealed.
- the expansion device 3 i constructed as above, when the differential pressure between the pressure on the inlet side and the pressure on the outlet side is small, the spring 31 is not bent by the differential pressure, so that the differential pressure control valve is closed. At this time, high-pressure refrigerant having passed through the internal heat exchanger 6 flows through the orifice 28 , and when having flowed out from the orifice 28 , the refrigerant is adiabatically expanded to be changed into low-pressure, low-temperature refrigerant, and is sent to the evaporator 4 via the pipe 14 .
- the expansion device 3 i Until the inlet pressure of refrigerant at the inlet of the expansion device 3 i rises up to 13 MPa, which is the upper limit of the control range, the expansion device 3 i has a fixed restriction passage cross-sectional area determined by the cross-sectional area of the orifice 28 .
- the differential pressure control valve overcomes the urging force of the spring 31 in the valve-closing direction, to open.
- the valve hole 24 of the differential pressure control valve has a sufficiently larger diameter than that of the orifice 28 , and therefore when the inlet pressure at the inlet of the expansion device 3 i exceeds a valve-opening point, the restriction passage cross-sectional area of the expansion device 3 i suddenly increases. This causes the inlet pressure to be always held not higher than the valve-opening point.
- the power element 71 disposed on the low-pressure side of the differential pressure control valve senses the outlet pressure of refrigerant having flowed out from the expansion device 3 i , and when the outlet pressure is high, the shape of a central portion of the disc spring 75 that receives the pressure via the diaphragm 74 is changed to be made concave inward (downward, as viewed in FIG. 14 ) such that the disc spring 75 acts in the direction of decreasing the valve-opening differential pressure, whereas when the outlet pressure is low, the shape of the central portion of the disc spring 75 is changed to be inflated outward (upward, as viewed in FIG. 14 ) such that the disc spring 75 acts in the direction of increasing the valve-opening differential pressure. That is, the power element 71 corrects the predetermined value of the valve-opening differential pressure, by applying load corresponding to the outlet pressure of the differential pressure control value to the valve element 25 in the valve-opening direction.
- the expansion device 3 i senses the differential pressure between the inlet pressure and the outlet pressure, and the outlet pressure, and pressure correction is performed by adding the differential pressure to the outlet pressure, whereby the expansion device 3 i operates as if it controlled the inlet pressure by absolute pressure.
- the differential pressure control valve suddenly opens, serving simply as a pressure relief valve, so that the inlet pressure is controlled to be held at 13 MPa, which prevents the inlet pressure from rising abnormally.
- the power element 71 can detect the outlet pressure of refrigerant at the outlet of the expansion device 3 i as an absolute value, and therefore it is possible to accurately monitor the inlet pressure of refrigerant at the inlet of the expansion device 3 i by the absolute pressure.
- the chamber accommodating the disc spring 75 is filled with a high-pressure gas, it is possible to employ a disc spring having a small spring load as the disc spring 75 since the high-pressure gas acts as an air spring.
- the stopper 79 restricts the motion of the displacement-transmitting member 78 such that when the expansion device 3 i is separately placed as a part, the high-pressure gas does not inflate the diaphragm 74 excessively toward the differential pressure control valve.
- FIG. 15 is a central longitudinal cross-sectional view of the arrangement of an expansion device according to an eleventh embodiment.
- component elements identical or equivalent to those shown in FIG. 13 are designated by the same reference numerals, and detailed description thereof is omitted.
- the shape-memory alloy spring 26 of the FIG. 13 expansion device 3 h according to the ninth embodiment is changed to the low temperature-side temperature-sensing section shown in FIG. 14 .
- the power element 71 which when sensing a high pressure, corrects the spring load of the spring 35 having been urging the first differential pressure control valve in the valve-closing direction, in the decreasing direction, is fitted to the hollow cylindrical portion of the body 21 by screwing the latter into the former.
- the orifice 28 of the valve element 25 of the first differential pressure control valve is provided with the orifice 65 for allowing refrigerant to flow at the minimum flow rate when the first and second differential pressure control valves are fully closed.
- the power element 71 senses the outlet pressure of refrigerant on the downstream side to correct the predetermined value of the differential pressure required for opening the first differential pressure control valve, whereby the inlet pressure of refrigerant is sensed as a pseudo absolute pressure.
- the expansion device 3 j has a fixed restriction passage cross-sectional area determined by the cross-sectional area of the orifice 65 of the second differential pressure control valve.
- the second differential pressure control valve opens, and as the differential pressure becomes higher, the restriction passage cross-sectional area increases proportionally.
- the first differential pressure control valve starts to open.
- the first differential pressure control valve suddenly opens. This causes the restriction passage cross-sectional area to suddenly increase, to lower the inlet pressure, and therefore the inlet pressure is prevented from rising above 13 MPa.
- the inlet pressure exceeds the predetermined pressure depending on the operating condition of the compressor, when the inlet pressure exceeds the predetermined pressure, the spring is bent to suddenly open the differential pressure control valve to reduce the inlet pressure. As a consequence, the inlet pressure is held at the predetermined pressure, which makes it possible to positively avoid a state in which pressure on the high-pressure side becomes abnormally high.
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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
- This application claims priority of Japanese Application No. 2006-29557 filed on Feb. 7, 2006, entitled “Expansion Device”, and No. 2006-254254 filed on Sep. 20, 2006, entitled “Expansion Device”.
- (1) Field of the Invention
- The present invention relates to an expansion device, and more particularly to an expansion device for expanding refrigerant in a refrigeration cycle for an automotive air conditioner.
- (2) Background Art
- A refrigeration cycle for an automotive air conditioner has been proposed from the viewpoint of global environmental problems, which uses carbon dioxide or the like as refrigerant for use in the refrigeration cycle. In the refrigeration cycle using carbon dioxide as refrigerant, component elements have pressure resistant structures such that they can withstand high pressure, since the operating pressure of the refrigeration cycle using carbon dioxide is high. Further, in a compressor for compressing the refrigerant and an expansion device for expanding the compressed refrigerant, when the high pressure of the refrigerant enters a dangerous region from a pressure-withstanding viewpoint, control for reducing the pressure is carried out, or the compressor and the expansion device are configured to be capable of lowering the pressure.
- For example, an expansion device is known which is configured such that a high pressure-side pressure of refrigerant at an inlet of the refrigerant is compared with the atmospheric pressure, and when the high pressure-side pressure exceeds a predetermined pressure, the expansion device opens the valve to lower the high pressure-side pressure (see e.g. Japanese Unexamined Patent Publication No. 2004-142701 (FIGS. 2 and 5)). This expansion device comprises a bellows which externally receives the pressure of refrigerant introduced into the refrigerant inlet of the expansion device, for contracting as the pressure of refrigerant rises, and has an inside thereof open to the atmosphere, and a valve mechanism which opens as the bellows contracts. With this arrangement, the bellows compares the high pressure-side pressure of refrigerant introduced into the refrigerant inlet of the expansion device with the atmospheric pressure, and when the pressure of refrigerant exceeds predetermined pressure, which is considered to be dangerous to the refrigeration cycle from the pressure-withstanding viewpoint, the bellows contracts, and the valve mechanism proportionally opens in response to the contraction of the bellows to lower the pressure. Thus, the bellows senses the high pressure-side pressure of refrigerant at the refrigerant inlet in terms of absolute pressure to control the valve mechanism, whereby prevention of the high pressure-side pressure of refrigerant at the refrigerant inlet from becoming higher than predetermined pressure can be effected to some extent.
- Further, Japanese Unexamined Patent Publication No. 2004-142701 discloses another expansion device having the structure of a differential pressure control valve which does not sense the high pressure-side pressure in terms of absolute pressure, but operates in response to differential pressure between pressure at a refrigerant inlet and pressure at a refrigerant outlet. The expansion device is configured such that when the differential pressure between the pressure at the refrigerant inlet and the pressure at the refrigerant outlet exceeds a predetermined pressure, the expansion device opens the differential pressure control valve to lower the pressure at the refrigerant inlet.
- As described above, since the expansion device is configured to limit pressure on the high-pressure side, there is no fear that the pressure on the high-pressure side becomes abnormally high. Further, the pressure on the high-pressure side is high when a high cooling power is demanded of the refrigeration cycle, and therefore in such a case, even if the compressor is operating with its maximum displacement, and the pressure on the high-pressure side exceeds the predetermined pressure, there is no need to control the discharge pressure such that it is lowered, on the compressor side, which makes it possible to operate the compressor efficiently at high discharge pressure, thereby enabling the refrigeration cycle to maintain a high cooling power.
- However, in the conventional expansion devices, although the expansion device using the bellows can sense high pressure-side pressure in terms of absolute pressure for control, it is necessary to take into account the pressure-withstanding property of the bellows that directly receives the high pressure, whereas in the case of the expansion device having the structure of a differential pressure control valve, high pressure-side pressure is represented by a value obtained by adding low pressure side-pressure to the differential pressure between the pressure at the refrigerant inlet and the pressure at the refrigerant outlet, so that if the low pressure side-pressure undergoes a change, the high pressure-side pressure is directly influenced by the change, which makes it impossible to control the high pressure-side pressure in terms of absolute pressure.
- The present invention has been made in view of the above points, and an object thereof is to provide an expansion device which operates in response to differential pressure between pressure of refrigerant at an inlet and pressure of refrigerant at an outlet, and when pressure on a high-pressure side exceeds a predetermined pressure in terms of absolute pressure, functions as a pressure relief valve.
- To solve the above problem, the present invention provides 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 the spring urges the differential pressure control valve in a valve-closing direction, for opening the differential pressure control valve when the differential pressure becomes a value not lower than a predetermined value, and an actuator disposed on the downstream side, for correcting the predetermined value of the differential pressure at which the differential pressure control valve opens, according to a change in temperature or pressure of the refrigerant on the downstream side.
- The above and other objects, features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example.
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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. - Hereafter, embodiments of the present invention will be described in detail with reference to the drawings showing expansion devices applied to a refrigeration cycle using carbon dioxide as refrigerant, by way of example.
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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. - As shown in
FIG. 1 , the refrigeration cycle comprises acompressor 1 for compressing refrigerant, agas cooler 2 for cooling the compressed refrigerant, anexpansion device 3 for throttling and expanding the cooled refrigerant, anevaporator 4 for evaporating the expanded refrigerant, anaccumulator 5 for storing surplus refrigerant in the refrigeration cycle and separating refrigerant in a gaseous phase from the evaporated refrigerant to send the separated refrigerant to thecompressor 1, and aninternal heat exchanger 6 for performing heat exchange between refrigerant flowing from thegas cooler 2 to theexpansion device 3 and refrigerant flowing from theaccumulator 5 to thecompressor 1. InFIG. 1 , arrows indicate flows of refrigerant. - As indicated by A-B-C-D-A in
FIG. 2 , the refrigeration cycle operates such that refrigerant in a gaseous phase is compressed into high-temperature, high-pressure refrigerant by the compressor 1 (A-B); the high-temperature, high-pressure refrigerant is cooled by the gas cooler 2 (B-C); the cooled refrigerant is throttled and expanded to be changed into low-temperature, low-pressure refrigerant by the expansion device 3 (C-D); and the low-temperature, low-pressure refrigerant is evaporated by the evaporator 4 (D-A). In the process in which refrigerant is expanded by theexpansion device 3, when the pressure of the refrigerant becomes lower than the saturated vapor line SL, the refrigerant is changed into a two-phase gas-liquid state, and when the refrigerant in the two-phase gas-liquid state is evaporated by theevaporator 4, it cools air in the vehicle compartment by depriving the air of latent heat of vaporization. - Further, in the refrigeration cycle using carbon dioxide as refrigerant, it is a common practice to dispose the
internal heat exchanger 6 that performs heat exchange between refrigerant at an outlet port of thegas cooler 2 and refrigerant at the outlet of theevaporator 4, so as to lower the enthalpy of refrigerant at the inlet of theevaporator 4 to thereby enhance the cooling power of the refrigeration cycle. - The
internal heat exchanger 6 is formed therein with a high-pressure passage for allowing high-pressure refrigerant introduced from thegas cooler 2 to flow therethrough, and a low-pressure passage for allowing low-pressure refrigerant introduced from theaccumulator 5 to flow therethrough, and theexpansion device 3 is disposed at the outlet of the high-pressure passage. - More specifically, as shown in
FIG. 3 , abody 11 of theinternal heat exchanger 6 is formed therein with the high-pressure passage 12 for allowing the high-pressure refrigerant introduced from thegas cooler 2 to flow therethrough to the outlet thereof, and has amounting hole 13 formed at an end of the high-pressure passage 12, for having theexpansion device 3 mounted therein. In a state of theexpansion device 3 being mounted in themounting hole 13, apipe 14 communicating with theevaporator 14 is fitted to an open end of themounting hole 13 withlocking screws 10 which are screwed into thebody 11. Thepipe 14 is formed to have an inner diameter slightly smaller than the outer diameter of theexpansion device 3 such that theexpansion device 3 is prevented from being removed from themounting hole 13 by the high-pressure refrigerant. - The
expansion device 3 disposed in theinternal heat exchanger 6 has abody 21. A central portion of thebody 21 has a refrigerant-introducinggroove 22 circumferentially formed in an outer periphery thereof, for introducing refrigerant from the high-pressure passage 12. The refrigerant-introducinggroove 22 is formed with arefrigerant inlet 23 which extends toward the center of thebody 21. Further, in the center of a lower portion of thebody 21, there is axially formed avalve hole 24, and the upstream side of thevalve hole 24 is communicated with therefrigerant inlet 23. Further, avalve element 25 is axially movably disposed on the downstream side of thevalve hole 24, for opening and closing thevalve hole 24. Thevalve element 25 has an outer diameter larger than the inner diameter of thevalve hole 24 such that the pressure of refrigerant introduced into therefrigerant inlet 23 is received in the valve-opening direction, and is urged in the valve-opening direction by a shape-memory alloy spring 26 forming a temperature-sensing section. It should be noted that the setting of the spring load of the shape-memory alloy spring 26 is adjusted by axially adjusting the position of a hollow cylindrical spring-receivingmember 27 externally fixedly fitted on thevalve element 25, with respect to thevalve element 25. Furthermore, anorifice 28 is formed in thebody 11 in a manner bypassing thevalve hole 24. - Further, the
body 11 axially movably holds ashaft 29 extending along the axis thereof. Theshaft 29 has a lower end, as viewed inFIG. 3 , which extends through thevalve hole 24 and is rigidly press-fitted in thevalve element 25, and an upper end, as viewed in the figure, which is integrally formed with a large-diameter engaging portion for engagement with a spring-receivingmember 30. Theshaft 29 is urged in the valve-closing direction via the spring-receivingmember 30 by aspring 31. Thus, theexpansion device 3 forms a differential pressure control valve which opens and closes by the differential pressure between pressure on the upstream side of thevalve hole 24 and pressure on the downstream side thereof. It should be noted that thespring 31 is set to such a spring load as will bend to open the differential pressure control valve when the pressure on the inlet side of theexpansion device 3 exceeds an upper limit of a control range of the spring load, e.g. 13 MPa. The setting of the spring load is adjusted by the amount of press-fitting of theshaft 29 into thevalve element 25. - The shape-
memory alloy spring 26 disposed on the low-pressure side of the differential pressure control valve has a feature that a spring load thereof is reversibly changed with respect to the cycle of temperature, and has characteristics that its spring load is small at temperature lower than the transformation temperature, whereas at temperature higher than the transformation temperature, the spring load becomes larger in proportion to a change in temperature. Therefore, the shape-memory alloy spring 26 serves as a temperature-sensing actuator which gives a spring load corresponding to the temperature of refrigerant on the low-pressure side to thereby control pressure on the high-pressure side, forming a low temperature-side temperature-sensing section. - It should be noted that an
O ring 32 is fitted on the outer periphery of thebody 21 at a location below the refrigerant-introducinggroove 22, as viewed inFIG. 3 , for sealing between the high-pressure passage 12 and thepipe 14 when theexpansion device 3 is mounted in the mountinghole 13. Similarly, an O ring 33 is disposed between thebody 11 and thepipe 14 at a location inside the locking screws 15 screwed into thebody 11 for fixing thepipe 14, for sealing the low-pressure side of theexpansion device 3 from the atmosphere. - In the
expansion device 3 configured as above, when the differential pressure between pressure on the inlet side and pressure on the outlet side is small, thespring 31 is not bent by the differential pressure, and hence the differential pressure control valve remains closed. At this time, the high-pressure refrigerant having passed through theinternal heat exchanger 6 flows through theorifice 28, and when having flowed out from theorifice 28, the refrigerant is adiabatically expanded to be changed into the low-pressure, low-temperature refrigerant, and is sent into theevaporator 4 via thepipe 14. - Until the inlet pressure of refrigerant at the inlet of the
expansion device 3 rises up to 13 MPa, which is the upper limit of the control range, as shown inFIG. 4 , theexpansion device 3 has a fixed restriction passage cross-sectional area determined by the cross-sectional area of theorifice 28. When the inlet pressure at the inlet of theexpansion device 3 has reached 13 MPa, the differential pressure control valve overcomes the urging force of thespring 31 in the valve-closing direction, to open. Thevalve hole 24 of the differential pressure control valve has a sufficiently larger diameter than that of theorifice 28, and therefore when the inlet pressure at the inlet of theexpansion device 3 exceeds a valve-opening point, the restriction passage cross-sectional area of theexpansion device 3 suddenly increases. This causes the inlet pressure to be always held not higher than the valve-opening point. - On the other hand, the shape-
memory alloy spring 26 disposed on the low-pressure side of the differential pressure control valve senses the outlet temperature of refrigerant having flowed out from theexpansion device 3, and when the outlet temperature is high, the shape-memory alloy spring 26 acts on the differential pressure control valve in the valve-opening direction, whereas when the outlet temperature of refrigerant is low, it acts on the differential pressure control valve in the valve-closing direction. More specifically, when the outlet temperature of refrigerant is higher than martensitic transformation temperature of the shape-memory alloy spring 26, the shape-memory alloy spring 26 is changed into an austenite phase in which it has a characteristic that its spring load is largely changed according to temperature. As a result, the shape-memory alloy spring 26 has a spring load that changes according to a change in the outlet temperature of refrigerant, to thereby apply load corresponding to the outlet temperature to thevalve element 25 in the valve-opening direction. - For example, when the outlet temperature of the
expansion device 3 is 10° C., according to theFIG. 2 Mollier chart, the low pressure side-pressure is approximately 4.6 MPa. Therefore, the shape-memory alloy spring 26 is configured to generate a spring load corresponding to the pressure when the temperature is 10° C. At this time, the differential pressure control valve is so adjusted as to be opened by a differential pressure of 8.4 MPa. This causes the inlet pressure of theexpansion device 3 to be specifically set to be 13 MPa, which is obtained by adding 8.4 MPa, which is a differential pressure as a relative value with respect to 4.6 MPa, which corresponds to the outlet temperature of refrigerant, to 4.6 MPa. At this time, pressure in the refrigeration cycle changes in the cycle of A-B-C-D-A. - Here, assuming that the outlet temperature of the
expansion device 3 has risen to 20° C., the spring load of the shape-memory alloy spring 26 is increased to act on the differential pressure control valve in the valve-opening direction. At this time, the differential pressure at which the differential pressure control valve opens is changed to approximately 7.15 MPa, as is apparent fromFIG. 2 . When the outlet temperature of theexpansion device 3 is 20° C., the pressure of refrigerant is approximately 5.85 MPa, and hence the inlet pressure of theexpansion device 3 is set to 13 MPa. At this time, pressure in the refrigeration cycle changes in the cycle of A′-B-C-D′-A′. - As described above, when a high cooling power is demanded, and the
compressor 1 is operating with its maximum displacement, theexpansion device 3 senses the differential pressure between the inlet pressure and the outlet pressure, and the outlet temperature, and performs temperature-dependent correction of the differential pressure by adding the differential pressure to a pressure corresponding to the outlet temperature, whereby theexpansion device 3 operates as if the inlet pressure is controlled by absolute pressure. Moreover, when the inlet pressure exceeds 13 MPa, the differential pressure control valve serves simply as a pressure relief valve to suddenly open, so that the inlet pressure is controlled to be held at 13 MPa, which prevents the inlet pressure from rising abnormally. -
FIG. 5 is a central longitudinal cross-sectional view of the arrangement of an expansion device according to a second embodiment. InFIG. 5 , component elements identical or equivalent to those shown inFIG. 3 are designated by the same reference numerals, and detailed description thereof is omitted. - The
expansion device 3 a according to the second embodiment is distinguished from theexpansion device 3 according to the first embodiment in that it is configured to sense the temperature of refrigerant at the inlet of theexpansion device 3 such that the refrigeration cycle can be operated efficiently. - More specifically, in the
expansion device 3 a, thebody 21 has an upper portion, as viewed inFIG. 5 , which has a tubular cylinder formed in one piece with therewith which accommodates thespring 31 that is bent by the inlet pressure exceeding 13 MPa to act on the differential pressure control valve to open the same, and a shape-memory alloy spring 41 for sensing the inlet temperature in a state arranged in series. A biasingspring 42 is arranged parallel with the shape-memory alloy spring 41, for adjusting the characteristic of the shape-memory alloy spring 41. More specifically, the shape-memory alloy spring 41 and the biasingspring 42 are arranged between the spring-receivingmember 30 engaged with an engaging portion integrally formed with an upper end, as viewed inFIG. 5 , of theshaft 29, and a spring-receivingmember 43 through the center of which theshaft 29 loosely extends, and thespring 31 is disposed between the spring-receivingmember 43 and the bottom of the tubular cylinder. An upward motion, as viewed inFIG. 6 , of the spring-receivingmember 43 is restricted by anadjustment member 44 press-fitted into the cylinder, and a downward motion thereof, as viewed inFIG. 6 , is restricted by astopper 45 rigidly fixed to theshaft 29. - The
adjustment member 44 is press-fitted into the cylinder until it reaches a position where it is brought into abutment with thespring 31 fully extended to a no spring-load status. With this arrangement, even when a force of the inlet pressure in the valve-opening direction acts on thespring 31 via theshaft 29, and the shape-memory alloy spring 41 and the biasingspring 42, thespring 31 is not bent is so for as the inlet pressure is not higher than 13 MPa, and when the inlet pressure exceeds 13 MPa, thespring 31 is bent to quickly open the differential pressure control valve. - On the other hand, the shape-
memory alloy spring 41 senses the inlet temperature. When the inlet temperature is low, the shape-memory alloy spring 41 has a small spring load, and therefore the synthetic load of the shape-memory alloy spring 41 and thespring 42 is small, and the setting differential pressure for opening the differential pressure control valve is set to a small value. As the inlet temperature becomes higher, the synthetic load of the shape-memory alloy spring 41 and thespring 42 becomes larger, and hence the setting differential pressure as well is set to a larger value, whereby the shape-memory alloy spring 41 is in a stiffened state between the spring-receivingmember 30 and the spring-receivingmember 43 when the inlet temperature is not lower than a predetermined temperature at which a change in the spring load of the shape-memory alloy spring 41 with respect to a change in the temperature is saturated. - According to the
expansion device 3 a, when the inlet temperature is low, the spring loads of the shape-memory alloy spring 41 and the biasingspring 42 which act on the differential pressure control valve in the valve-closing direction are small, and hence the differential pressure control valve is made open to a very small opening degree corresponding to theorifice 28 by the differential pressure between the inlet pressure and the outlet pressure, whereby refrigerant is allowed to flow, causing adiabatic expansion of refrigerant. At this time, similarly to theexpansion device 3 according to the first embodiment, the pressure of refrigerant at the inlet of theexpansion device 3 a is controlled to a pressure which is determined by the differential pressure across the differential pressure control valve and a pressure corresponding to the outlet temperature. - On the other hand, the temperature of refrigerant at the inlet of the
expansion device 3 a is sensed by the shape-memory alloy spring 41 so as to shift a predetermined value of the differential pressure subjected to temperature-dependent correction by the shape-memory alloy spring 26, according to a change in the inlet temperature. This makes it possible to control the temperature and pressure of refrigerant at the inlet of theexpansion device 3 a, that is, a temperature and a pressure at a point C inFIG. 2 , along a control line CL approximated to an optimal control line that is considered to be capable of enhancing the cooling power of the refrigeration cycle while holding a high performance coefficient of the refrigeration cycle. - Of course, also in the
expansion device 3 a, when the inlet pressure has risen to exceed 13 MPa, thespring 31 bends to suddenly open the differential pressure control valve, which prevents the inlet pressure from rising above the valve-opening point. -
FIG. 6 is a central longitudinal cross-sectional view of the arrangement of an expansion device according to a third embodiment. InFIG. 6 , component elements identical or equivalent to those shown inFIG. 5 are designated by the same reference numerals, and detailed description thereof is omitted. - The
expansion device 3 b according to the third embodiment is distinguished from theexpansion device 3 a according to the second embodiment in that the positional relationship between thespring 31, the shape-memory alloy spring 41, and thespring 42 is reversed. - According to the
expansion device 3 b, when the inlet temperature is low, the shape-memory alloy spring 41 has a small spring load, and a valve-opening force of thevalve element 25, generated by the differential pressure between the inlet pressure and the outlet pressure is transmitted via theshaft 29, the spring-receivingmember 30, thespring 31, and the spring-receivingmember 43, to thereby bend the shape-memory alloy spring 41, which causes the differential pressure control valve to be made open to a very small opening degree. At this time, similarly to theexpansion devices expansion device 3 b is controlled to a pressure which is determined by a pressure corresponding to the differential pressure across the differential pressure control valve and the outlet temperature. Further, the temperature of refrigerant at the inlet of theexpansion device 3 a is controlled by the shape-memory alloy spring 41 disposed at the inlet of theexpansion device 3 a along the control line CL approximated to the optimal control line. As to the inlet pressure of refrigerant at the inlet of theexpansion device 3 a, when thespring 31 senses pressure exceeding 13 MPa, it causes the differential pressure control valve to be suddenly opened. -
FIG. 7 is a central longitudinal cross-sectional view of the arrangement of an expansion device according to a fourth embodiment. InFIG. 7 , component elements identical or equivalent to those shown inFIG. 5 are designated by the same reference numerals, and detailed description thereof is omitted. - Although the
expansion device 3 c according to the fourth embodiment has the same basic construction as that of theexpansion device 3 a according to the second embodiment, theexpansion device 3 c is distinguished from theexpansion device 3 a in that it is configured such that thespring 31 for sensing high pressures, the shape-memory alloy spring 41, and thespring 42 can be easily assembled and adjusted. - More specifically, in the
expansion device 3 c, the spring-receivingmember 43 through the center of which theshaft 29 loosely extends is integrally formed with a hollow cylindrical body accommodating the shape-memory alloy spring 41 and thespring 42, and astopper 45 for adjusting the spring loads of the shape-memory alloy spring 41 and thespring 42 via the spring-receivingmember 30 is press-fitted into the hollow cylindrical body. Further, the spring-receivingmember 43 is placed on an upper portion, as viewed inFIG. 7 , of thespring 31, and theadjustment member 44 is rigidly fixed to thebody 21 such that theadjustment member 44 accommodates thespring 31 and the spring-receivingmember 43. - When the
expansion device 3 c is assembled, first, the shape-memory alloy spring 41 and thespring 42 are assembled while adjusting the spring loads thereof in advance. More specifically, the shape-memory alloy spring 41 and thespring 42, and the spring-receivingmember 30 are placed in the hollow cylindrical body of thespring receiving member 43 in the mentioned order, and thestopper 45 is press-fitted into the hollow cylindrical body until it reaches a predetermined position, to thereby adjust the spring loads of the shape-memory alloy spring 41 and thespring 42, whereby a high temperature-side temperature-sensing section is constructed. Then, the high temperature-side temperature-sensing section is placed on thespring 31 disposed in an upper space of thebody 21, as viewed inFIG. 7 , and theadjustment member 44 having a hollow cylindrical shape and having an engaging portion with an upper portion thereof, as viewed in the figure, bent inward, is placed from above to cover them. In a state in which an upper portion of thebody 21 is partially press-fitted into a lower portion, as viewed in the figure, of theadjustment member 44, theadjustment member 44 is further pushed down, as viewed in the figure, until the engaging portion is brought into abutment with an upper end, as viewed in the figure, of the spring-receivingmember 43, whereby theadjustment member 44 is fitted to thebody 21. Furthermore, if theadjustment member 44 is pushed down, as viewed in the figure, as required, it is possible to adjust the spring load of thespring 31. Finally, theshaft 29 is inserted from above, as viewed in the figure, and further, the differential pressure control valve is press-fitted by a predetermined amount into thevalve element 25 to which is applied the adjusted spring load of the shape-memory alloy spring 26, such that the differential pressure control valve is made open to a predetermined minimum opening degree by the shape-memory alloy spring 26. Thus, theexpansion device 3 c is assembled. - Since the
expansion device 3 c has the same basic construction as that of theexpansion device 3 a according to the second embodiment, theexpansion device 3 c operates quite the same way as theexpansion device 3 a. -
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 the valve-opening characteristic of the expansion according to the fifth embodiment. InFIG. 8 , component elements identical or equivalent to those shown inFIG. 7 are designated by the same reference numerals, and detailed description thereof is omitted. - The
expansion device 3 d according to the fifth embodiment is distinguished from theexpansion device 3 c according to the fourth embodiment in that in place of the high temperature-side temperature-sensing section including the shape-memory alloy spring 41 and its biasingspring 42 of theexpansion device 3 c, it is provided with aspring 42 a for opening the differential pressure control valve by a differential pressure lower than 13 MPa. - Referring to
FIG. 9 , theexpansion device 3 d is characterized in that it has two valve-opening points at which theexpansion device 3 d opens the differential pressure control valve in response to changes in the inlet pressure of refrigerant on the upstream side. More specifically, in a stage of low inlet pressure, theexpansion device 3 d is made open to the predetermined minimum opening degree, and has a fixed restriction passage cross-sectional area. When the inlet pressure becomes higher, and first exceeds a predetermined value set by thespring 42 a, thespring 42 a is bent to open the differential pressure control valve. As the inlet pressure becomes higher, the restriction passage cross-sectional area increases proportionally. When the inlet pressure further increases to exceed 13 MPa, which is set by thespring 31, the differential pressure control valve suddenly opens to lower the inlet pressure, thereby preventing the inlet pressure from rising above 13 MPa. -
FIG. 10 is a central longitudinal cross-sectional view of the arrangement of an expansion device according to a sixth embodiment. InFIG. 10 , component elements identical or equivalent to those shown inFIG. 5 are designated by the same reference numerals, and detailed description thereof is omitted. - Although the
expansion device 3 e according to the sixth embodiment has the same basic construction as that of theexpansion device 3 a according to the second embodiment, theexpansion device 3 e is distinguished from theexpansion device 3 a which has the high temperature-side temperature-sensing section that senses the temperature of refrigerant at the outlet of theinternal heat exchanger 6 in that theexpansion device 3 e has a high temperature-side temperature-sensing section that senses the temperature of refrigerant at the inlet of theinternal heat exchanger 6, that is, the temperature of refrigerant at the outlet of thegas cooler 2. - In the
internal heat exchanger 6, in the high-pressure passage 12 formed in thebody 11, arefrigerant inlet passage 46 into which high-pressure refrigerant is introduced from thegas cooler 2 is formed such that it passes in the vicinity of the mountinghole 13 to which theexpansion device 3 e is mounted. The mountinghole 13 is formed to extend to therefrigerant inlet passage 46 such that when theexpansion device 3 e is mounted to the mountinghole 13, the high temperature-side temperature-sensing section thereof is located within therefrigerant inlet passage 46. Further, in theexpansion device 3 e, anO ring 47 is circumferentially formed on the outer periphery of thebody 21 so as to prevent refrigerant in therefrigerant inlet passage 46 from leaking into therefrigerant inlet 23 in a state of theexpansion device 3 e mounted to mountinghole 13. - Also in this construction of the
expansion device 3 e, the operation of the expansion device is the same as that of theexpansion device 3 a except that the high temperature-side temperature-sensing section senses the temperature of refrigerant at the outlet of thegas cooler 2 in therefrigerant inlet passage 46 of theinternal heat exchanger 6. -
FIG. 11 is a central longitudinal cross-sectional view of the arrangement of an expansion device according to a seventh embodiment. InFIG. 11 , component elements identical or equivalent to those shown inFIG. 10 are designated by the same reference numerals, and detailed description thereof is omitted. - The
expansion device 3 f according to the seventh embodiment is distinguished from theexpansion device 3 e according to the sixth embodiment in that the construction of the high temperature-side temperature-sensing section that senses the temperature of refrigerant at the outlet of thegas cooler 2 is simplified. More specifically, theexpansion device 3 f is configured such that thestopper 45 included in the high temperature-side temperature-sensing section of theexpansion device 3 e is eliminated while arranging the shape-memory alloy spring 41 and thespring 42 in series with thespring 31 for sensing high pressure. As a result, when the temperature and the pressure of refrigerant at the outlet of thegas cooler 2 are high, the shape-memory alloy spring 41 acts in the direction of increasing the spring load of the high pressure-sensingspring 31, and hence theexpansion device 3 f has a characteristic that at a valve-opening point thereof, in response to changes in the inlet pressure, it opens the differential pressure control valve not sharply but a little more smoothly. -
FIG. 12 is a central longitudinal cross-sectional view of the arrangement of an expansion device according to an eighth embodiment. InFIG. 12 , component elements identical or equivalent to those shown inFIG. 3 are designated by the same reference numerals, and detailed description thereof is omitted. - The
expansion device 3 g according to the eighth embodiment is distinguished from theexpansion device 3 according to the first embodiment which has the high pressure-sensingspring 31 disposed on the upstream side in that theexpansion device 3 g has thespring 31 disposed on the downstream side. - More specifically, in the
expansion device 3 g, thevalve element 25 is disposed on the downstream side of thevalve hole 24 formed through thebody 21, and the high pressure-sensingspring 31 is disposed to urge thepiston 51 which is integrally formed with thevalve element 25 and is axially and movably accommodated within thebody 21, in the valve-closing direction, while the shape-memory alloy spring 26 of the low temperature-side temperature-sensing section is disposed to urge thepiston 51 in the valve-opening direction. The high pressure-sensingspring 31 has a spring load thereof adjusted by anadjustment screw 52 screwed into thebody 21. With this arrangement, thespring 31 is bent in response to the differential pressure between the pressure of refrigerant on the upstream side and the pressure of refrigerant on the downstream side, whereby a predetermined value of the differential pressure, required for opening the differential pressure control valve, is subjected to correction dependent on the outlet temperature of refrigerant on the downstream side, sensed by the shape-memory alloy spring 26, whereby when the pressure of refrigerant on the upstream side is high, the inlet pressure of refrigerant is always held at 13 MPa set by thespring 31. - Further, in the
expansion device 3 g, theorifice 28 is formed through thevalve element 25, for allowing refrigerant to flow at a minimum flow rate when the differential pressure control valve is fully closed, and astrainer 53 is disposed on the upstream side of the valve hole thereof, for removing foreign matter from refrigerant. -
FIG. 13 is a central longitudinal cross-sectional view of the arrangement of an expansion device according to a ninth embodiment. InFIG. 13 , component elements identical or equivalent to those shown inFIG. 12 are designated by the same reference numerals, and detailed description thereof is omitted. - The
expansion device 3 h according to the ninth embodiment is distinguished from theexpansion device 3 g according to the eighth embodiment in that it is configured to incorporate a second differential pressure control valve in the differential pressure control valve (hereinafter referred to as “the first differential pressure control valve”) of theexpansion device 3 g, such that two differential pressure control valves having different valve-opening points function in parallel. - More specifically, in the
expansion device 3 h, theorifice 28 formed in thevalve element 25 of the first differential pressure control valve serves as a valve hole of the second differential pressure control valve, with avalve element 61 being disposed on the downstream side, for opening and closing the valve hole, and apiston 62 integrally formed with the valve element is axially movably accommodated in thepiston 51 of the first differential pressure control valve. Thepiston 62 is urged by thespring 63 in the valve-closing direction, and the spring load of thespring 63 is adjusted by anadjustment screw 64 screwed into thepiston 51. Further, in thevalve element 61 as well, there is formed anorifice 65 for allowing refrigerant to flow at a minimum flow rate when the first and second differential pressure control valves are fully closed. - The
expansion device 3 h configured as above has a characteristic, as shown inFIG. 9 , that it has two valve-opening points at which theexpansion device 3 h opens in response to changes in the inlet pressure of refrigerant on the upstream side. More specifically, in theexpansion device 3 h, the shape-memory alloy spring 26 senses the outlet temperature of refrigerant on the downstream side to correct the predetermined value of differential pressure required for opening the first differential pressure control valve, whereby the inlet pressure of refrigerant is sensed as a pseudo absolute pressure. Here, in a stage of low inlet pressure, theexpansion device 3 h has a fixed restriction passage cross-sectional area determined by the cross-sectional area of theorifice 65 of the second differential pressure control valve. When the inlet pressure becomes higher, and first, the differential pressure between the inlet pressure on the upstream side and the outlet pressure on the downstream side exceeds a pressure set by thespring 63, the second differential pressure control valve opens, and as the differential pressure becomes higher, the restriction passage cross-sectional area increases proportionally. After that, when the inlet pressure reaches 13 MPa, the first differential pressure control valve starts to open. Further, when the inlet pressure increases to exceed 13 MPa set by thespring 31, the first differential pressure control valve suddenly opens. This causes the inlet pressure to decrease, and hence prevents the same from increasing above 13 MPa. - In the aforementioned first to ninth embodiments, the low temperature-side temperature-sensing section is configured to correct the predetermined value of the valve-opening differential pressure for opening the differential pressure control valve according to changes in the temperature of refrigerant on the downstream side of the differential pressure control valve. However, the predetermined value of the valve-opening differential pressure can be corrected not only according to changes in the temperature of refrigerant on the downstream side of the differential pressure control valve but also according to changes in the pressure of refrigerant on the downstream side of the differential pressure control valve. This is because refrigerant is in a saturated liquid state at the outlet of the expansion device, and in this saturated liquid state, the temperature and the pressure of refrigerant are constant without undergoing any change, as shown by line D-A or D′-A′ of the
FIG. 2 Mollier chart, and therefore if the temperature is determined, the pressure is determined. As described above, in theevaporator 4 on the outlet side of the expansion device, the evaporation pressure of refrigerant is constant, and moreover the temperature and the pressure have a linear relation therebetween, so that it is possible to consider that sensing of the pressure of refrigerant at the outlet of the expansion device is equivalent to sensing of the temperature of refrigerant at the outlet of the expansion device. This makes it possible to cause an expansion device to have the same function as that of theexpansion devices 3 to 3 h according to the first to ninth embodiments by configuring the expansion device such that in place of the low temperature-side temperature-sensing section, a low temperature-side pressure-sensing section senses the pressure of refrigerant at the outlet of the expansion device, to correct the predetermined value of the valve-opening differential pressure according to changes in the pressure of refrigerant on the downstream side of the differential pressure control valve. Hereinafter, a detailed description will be given of constructions provided with such a low temperature-side pressure-sensing section. -
FIG. 14 is a central longitudinal cross-sectional view of the arrangement of an expansion device according to a tenth embodiment. InFIG. 14 , component elements identical or equivalent to those shown inFIG. 12 are designated by the same reference numerals, and detailed description thereof is omitted. - The
expansion device 3 i according to the tenth embodiment is provided with a low temperature-side pressure-sensing section in place of the shape-memory alloy spring 26 as the low temperature-side temperature-sensing section of theexpansion device 3 g according to the eighth embodiment. More specifically, theexpansion device 3 i has apower element 71 fixed thereto by screwing an open end of a hollow cylindrical portion of thebody 21 into thepower element 71. When high pressure is sensed, thepower element 71 acts in the direction of decreasing the spring load of the high pressure-sensingspring 31 which sets the valve-opening differential pressure for opening the differential pressure control valve, to thereby serve as a pressure-sensing actuator that corrects a predetermined value of the valve-opening differential pressure in a decreasing direction. - The
power element 71 is formed by holding adiaphragm 74 made of a thin metal plate between anouter housing 72 having a center projected outward and aninner housing 73 having an opening in the center thereof and having a hub connected to thebody 21, and welding all the outer peripheries of thehousings diaphragm 74 under high-pressure gas or vacuum atmosphere along the whole circumferences thereof. A hermetically sealed space formed by theouter housing 72 and thediaphragm 74 accommodates adisc spring 75, aspring 76, and aspring receiving member 77. The load of thedisc spring 75 is adjusted by combining a plurality of disc springs (three in the illustrated example) having respective appropriate spring loads. The spring load of thespring 76 is adjusted by plastically inwardly deforming an end face of theouter housing 72 to change the position of the spring-receivingmember 77 in the direction of compressing thespring 76. On a side of thediaphragm 74 opposite to a side thereof where thedisc spring 75 is disposed, a displacement-transmittingmember 78 is disposed for transmitting the displacement of thediaphragm 74 to thespring 31. Astopper 79 in the form of a step is formed on an inner wall of thehousing 73, for restricting the motion of the displacement-transmittingmember 78 in the direction of increasing the spring load of thespring 31. This inhibits the expansion device from correcting the predetermined value of the differential pressure when thecompressor 1 is operating in a state in which the pressure of refrigerant on the downstream side of the differential pressure control valve is low. - It should be noted that although in the present embodiment, part of a screw thread of the
body 21, which is screwed into thepower element 71, is cut such that the pressure of refrigerant on the downstream side of the differential pressure control valve easily reaches thediaphragm 74, the cut part is not necessarily required since portions of thepower element 71 and thebody 21 screwed together are not completely hermetically sealed. - In the
expansion device 3 i constructed as above, when the differential pressure between the pressure on the inlet side and the pressure on the outlet side is small, thespring 31 is not bent by the differential pressure, so that the differential pressure control valve is closed. At this time, high-pressure refrigerant having passed through theinternal heat exchanger 6 flows through theorifice 28, and when having flowed out from theorifice 28, the refrigerant is adiabatically expanded to be changed into low-pressure, low-temperature refrigerant, and is sent to theevaporator 4 via thepipe 14. - Until the inlet pressure of refrigerant at the inlet of the
expansion device 3 i rises up to 13 MPa, which is the upper limit of the control range, theexpansion device 3 i has a fixed restriction passage cross-sectional area determined by the cross-sectional area of theorifice 28. When the inlet pressure at the inlet of theexpansion device 3 i has reached 13 MPa, the differential pressure control valve overcomes the urging force of thespring 31 in the valve-closing direction, to open. Thevalve hole 24 of the differential pressure control valve has a sufficiently larger diameter than that of theorifice 28, and therefore when the inlet pressure at the inlet of theexpansion device 3 i exceeds a valve-opening point, the restriction passage cross-sectional area of theexpansion device 3 i suddenly increases. This causes the inlet pressure to be always held not higher than the valve-opening point. - On the other hand, the
power element 71 disposed on the low-pressure side of the differential pressure control valve senses the outlet pressure of refrigerant having flowed out from theexpansion device 3 i, and when the outlet pressure is high, the shape of a central portion of thedisc spring 75 that receives the pressure via thediaphragm 74 is changed to be made concave inward (downward, as viewed inFIG. 14 ) such that thedisc spring 75 acts in the direction of decreasing the valve-opening differential pressure, whereas when the outlet pressure is low, the shape of the central portion of thedisc spring 75 is changed to be inflated outward (upward, as viewed inFIG. 14 ) such that thedisc spring 75 acts in the direction of increasing the valve-opening differential pressure. That is, thepower element 71 corrects the predetermined value of the valve-opening differential pressure, by applying load corresponding to the outlet pressure of the differential pressure control value to thevalve element 25 in the valve-opening direction. - With this arrangement, when a high cooling power is demanded and the
compressor 1 is operating with its maximum displacement, theexpansion device 3 i senses the differential pressure between the inlet pressure and the outlet pressure, and the outlet pressure, and pressure correction is performed by adding the differential pressure to the outlet pressure, whereby theexpansion device 3 i operates as if it controlled the inlet pressure by absolute pressure. Moreover, when the inlet pressure exceeds 13 MPa, the differential pressure control valve suddenly opens, serving simply as a pressure relief valve, so that the inlet pressure is controlled to be held at 13 MPa, which prevents the inlet pressure from rising abnormally. - It should be noted that in the case where a chamber accommodating the
disc spring 75 is under vacuum, thepower element 71 can detect the outlet pressure of refrigerant at the outlet of theexpansion device 3 i as an absolute value, and therefore it is possible to accurately monitor the inlet pressure of refrigerant at the inlet of theexpansion device 3 i by the absolute pressure. Further, in the case where the chamber accommodating thedisc spring 75 is filled with a high-pressure gas, it is possible to employ a disc spring having a small spring load as thedisc spring 75 since the high-pressure gas acts as an air spring. In this case, thestopper 79 restricts the motion of the displacement-transmittingmember 78 such that when theexpansion device 3 i is separately placed as a part, the high-pressure gas does not inflate thediaphragm 74 excessively toward the differential pressure control valve. -
FIG. 15 is a central longitudinal cross-sectional view of the arrangement of an expansion device according to an eleventh embodiment. InFIG. 15 , component elements identical or equivalent to those shown inFIG. 13 are designated by the same reference numerals, and detailed description thereof is omitted. - In the expansion device 3 j according to the eleventh embodiment, the shape-
memory alloy spring 26 of theFIG. 13 expansion device 3 h according to the ninth embodiment is changed to the low temperature-side temperature-sensing section shown inFIG. 14 . More specifically, in the expansion device 3 j, thepower element 71, which when sensing a high pressure, corrects the spring load of the spring 35 having been urging the first differential pressure control valve in the valve-closing direction, in the decreasing direction, is fitted to the hollow cylindrical portion of thebody 21 by screwing the latter into the former. Further, theorifice 28 of thevalve element 25 of the first differential pressure control valve is provided with theorifice 65 for allowing refrigerant to flow at the minimum flow rate when the first and second differential pressure control valves are fully closed. - According to the expansion device 3 j constructed as above, the
power element 71 senses the outlet pressure of refrigerant on the downstream side to correct the predetermined value of the differential pressure required for opening the first differential pressure control valve, whereby the inlet pressure of refrigerant is sensed as a pseudo absolute pressure. Here, in a stage of low inlet pressure, the expansion device 3 j has a fixed restriction passage cross-sectional area determined by the cross-sectional area of theorifice 65 of the second differential pressure control valve. When the inlet pressure becomes higher, and first, the differential pressure between the inlet pressure on the upstream side and the outlet pressure on the downstream side exceeds a pressure set by thespring 63, the second differential pressure control valve opens, and as the differential pressure becomes higher, the restriction passage cross-sectional area increases proportionally. After that, when the inlet pressure reaches 13 MPa, the first differential pressure control valve starts to open. Further, when the inlet pressure increases to exceed 13 MPa set by thespring 31, the first differential pressure control valve suddenly opens. This causes the restriction passage cross-sectional area to suddenly increase, to lower the inlet pressure, and therefore the inlet pressure is prevented from rising above 13 MPa. - The expansion device according to the present invention is configured such that it corrects the predetermined value of the differential pressure at which the differential pressure control valve opens, according to a change in the temperature or pressure of the refrigerant on the downstream side, detected by the actuator, that is, it corrects the set differential pressure of the differential pressure control valve by using the temperature or pressure on the low-pressure side. This enables the differential pressure control valve to operate as if it sensed the inlet pressure on the high-pressure side in terms of absolute pressure, without being influenced by the pressure on the low pressure side in spite of the differential pressure control valve operating in response to the differential pressure.
- Further, even if the inlet pressure exceeds the predetermined pressure depending on the operating condition of the compressor, when the inlet pressure exceeds the predetermined pressure, the spring is bent to suddenly open the differential pressure control valve to reduce the inlet pressure. As a consequence, the inlet pressure is held at the predetermined pressure, which makes it possible to positively avoid a state in which pressure on the high-pressure side becomes abnormally high.
- The foregoing is considered as illustrative only of the principles of the present invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and applications shown and described, and accordingly, all suitable modifications and equivalents may be regarded as falling within the scope of the invention in the appended claims and their equivalents.
Claims (21)
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; and
an 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; and
set 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.
Applications Claiming Priority (4)
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JP2006-029557 | 2006-02-07 | ||
JP2006029557 | 2006-02-07 | ||
JP2006-254254 | 2006-09-20 | ||
JP2006254254A JP2007240138A (en) | 2006-02-07 | 2006-09-20 | Expansion device |
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US20070180854A1 true US20070180854A1 (en) | 2007-08-09 |
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US11/701,497 Abandoned US20070180854A1 (en) | 2006-02-07 | 2007-02-02 | Expansion device |
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EP (1) | EP1816417A2 (en) |
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Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20080202156A1 (en) * | 2007-02-26 | 2008-08-28 | Youngkee Baek | Air-conditioning system for vehicles |
US20130248020A1 (en) * | 2010-11-30 | 2013-09-26 | Claus Thybo | Expansion valve with variable opening degree |
Families Citing this family (3)
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---|---|---|---|---|
JP5209412B2 (en) * | 2008-08-22 | 2013-06-12 | サンデン株式会社 | Vapor compression refrigeration cycle |
JP5338611B2 (en) * | 2009-10-19 | 2013-11-13 | 株式会社大林組 | Vertical seismic isolation device |
JP2011133139A (en) * | 2009-12-22 | 2011-07-07 | Fuji Koki Corp | Expansion valve |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH08320171A (en) * | 1995-05-25 | 1996-12-03 | Fuji Koki Seisakusho:Kk | Opening/closing valve and freezing system using it |
JP2000241048A (en) * | 1999-02-24 | 2000-09-08 | Saginomiya Seisakusho Inc | Temperature-sensitive expansion valve |
JP2001153499A (en) * | 1999-11-30 | 2001-06-08 | Saginomiya Seisakusho Inc | Control valve for refrigerating cycle |
-
2006
- 2006-09-20 JP JP2006254254A patent/JP2007240138A/en active Pending
-
2007
- 2007-02-02 US US11/701,497 patent/US20070180854A1/en not_active Abandoned
- 2007-02-06 EP EP07002526A patent/EP1816417A2/en not_active Withdrawn
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20080202156A1 (en) * | 2007-02-26 | 2008-08-28 | Youngkee Baek | Air-conditioning system for vehicles |
US20130248020A1 (en) * | 2010-11-30 | 2013-09-26 | Claus Thybo | Expansion valve with variable opening degree |
US9170039B2 (en) * | 2010-11-30 | 2015-10-27 | Danfoss A/S | Expansion valve with variable opening degree |
US20160018142A1 (en) * | 2010-11-30 | 2016-01-21 | Danfoss A/S | Expansion valve with variable opening degree |
Also Published As
Publication number | Publication date |
---|---|
JP2007240138A (en) | 2007-09-20 |
EP1816417A2 (en) | 2007-08-08 |
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Owner name: TGK CO., LTD., JAPAN Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:HIROTA, HISATOSHI;TSUGAWA, TOKUMI;TONEGAWA, MASAAKI;AND OTHERS;REEL/FRAME:018962/0509 Effective date: 20061222 |
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