Refrigerating machine

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a refrigerating machine having a refrigerant introducing unit for selectively introducing gas refrigerant separated in a gas-liquid separator into an intermediate pressure portion of a compressor.

2. Description of the Related Art

There is generally known a refrigerating machine equipped with a compressor, a radiator, a pressure-reducing device, a gas-liquid separator and a refrigerant introducing unit for selectively introducing gas refrigerant separated in the gas-liquid separator into an intermediate pressure portion (JP-A-2003-106693). In this type of refrigerating machine, the gas refrigerant separated in the gas-liquid separator is introduced into an intermediate pressure portion of the compressor while keeping the refrigerant under gas state, so that the efficiency of the compressor can be enhanced.

This type of refrigerating machine is equipped with a heat absorbing unit containing a heat absorber which selectively functions in each of different temperature zones in a refrigerating cycle in some cases.

For example, when the refrigerating machine as described above is applied to a refrigerator having a refrigerating chamber and a freezing chamber, a heat absorber functioning for refrigeration or freezing is disposed in a refrigerating cycle, and a refrigerating or freezing operation is carried out by using the function of any one heat absorber. In this case, it is important to carry out the operation with high efficiency without reducing the efficiency under any operation.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to provide a refrigerating machine in which when a heat absorbing unit selectively functioning in different temperature zones is provided in a refrigerating cycle, a high-efficiency operation can be performed in all the temperature zones without reducing the efficiency.

In order to attain the above object, a refrigerating machine comprising: a compressor; a radiator; a pressure-reducing device; a gas-liquid separator; a unit for introducing gas refrigerant separated in the gas-liquid separator into a first intermediate pressure portion of the compressor; a low pressure side circuit in which liquid refrigerant separated in the gas-liquid separator is circulated, the low pressure side circuit being equipped with an absorbing unit functioning selectively in different temperature zones; and a gas refrigerant introduction inhibiting/allowing switching unit for inhibiting introduction of the gas refrigerant separated in the gas-liquid separator into the intermediate pressure portion of the compressor when the heat absorbing unit is made to function in a higher temperature zone and allowing introduction of the gas refrigerant separated in the gas-liquid separator into a second intermediate pressure portion of the compressor which is lower in pressure than the first intermediate pressure portion of the compressor.

In the above refrigerating machine, a part of the gas refrigerant introduction inhibiting/allowing switching unit may be constructed by an opening/closing valve. Furthermore, another part of the gas refrigerant introduction inhibiting/allowing switching unit may be constructed by a three-way valve and a branched gas pipe.

In the above refrigerating machine, the heat absorbing unit may be equipped with plural heat absorbers each of which functions selectively and is equipped with a unit for guiding cold air passed through the heat absorber to a chamber which is controlled to the corresponding temperature zone. The heat absorbing unit may be equipped with one heat absorber which selectively functions in different temperature zones and is equipped with a unit for selectively guiding cold air passed through the heat absorber through a switching dumper to plural chambers which are respectively controlled to different temperature zones. The heat absorber may be disposed at a chamber which is controlled to a low temperature zone. In all the cases, refrigerant with which a high voltage side is set to supercritical pressure under operation may be filled in a refrigerant circuit.

Furthermore, the three-way valve and the branch gas pipe may constitute gas refrigerant introducing unit which can introduce the gas refrigerant separated in the gas-liquid separator to one of a first intermediate pressure portion of the compressor and a second intermediate pressure portion at a lower pressure suction side than the first intermediate pressure portion. When the heat absorbing unit is made to function in a low temperature zone, the gas refrigerant separated in the gas-liquid separator is introduced to the first intermediate pressure portion of the compressor. On the other hand, when the heat absorbing unit is made to function in a high temperature zone, the gas refrigerant is introduced to the second intermediate pressure portion of the compressor.

In this case, the heat absorbing unit may be provided with plural heat absorbers which function in different temperature zones, and each of the heat absorbers may function selectively and may be equipped with a unit for guiding cold air passed through the heat absorber concerned to a chamber which is controlled to the corresponding temperature zone. Furthermore, each of the heat absorbers may be disposed in a chamber which is controlled to the corresponding temperature zone.

Furthermore, the heat absorbing unit may be provided with one heat absorber which selectively functions in different temperature zones, and also with a unit for selectively guiding cold air therefrom through a switching dumper to plural chambers controlled to different temperature zones. In this case, the heat absorber may be disposed in a chamber controlled to a low temperature zone. In all the cases, carbon dioxide refrigerant with which the high pressure side is set to supercritical pressure under operation may be enclosed in the refrigerant circuit.

According to the present invention, the heat absorbing unit which selectively functions in different temperature zones is provided to the low pressure side circuit in which liquid refrigerant is circulated, and the refrigerating machine is provided with the gas refrigerant introduction inhibiting/allowing unit for inhibiting introduction of the gas refrigerant separated in the gas-liquid separator into the intermediate pressure portion of the compressor when the heat absorbing unit is made to function in a high temperature zone. Therefore, the high-efficient operation can be performed in the respective temperature zones.

Furthermore, according to the present invention, the heat absorbing unit which selectively functions in different temperature zones is provided to the low pressure side circuit in which liquid refrigerant is circulated, and the refrigerating machine is provided with the gas refrigerant introducing unit for introducing the gas refrigerant into the first intermediate pressure portion of the compressor when the heat absorbing unit is made to function in a low temperature zone, and introducing the gas refrigerant into the second intermediate pressure portion of the compressor when the heat absorbing unit is made to function in a high temperature zone. Therefore, the high-efficient operation can be performed in the respective temperature zones.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a refrigerant circuit diagram showing a first embodiment of a refrigerating machine according to the present invention;

FIG. 2 is an enthalpy-pressure diagram of a refrigerating cycle;

FIG. 3 is a diagram showing an applied example to the first embodiment to a refrigerator;

FIG. 4 is a diagram showing an applied example to a refrigerator;

FIG. 5 is a refrigerant circuit diagram showing a modification of the first embodiment;

FIG. 6 is a diagram showing an applied example of the modification to a refrigerator;

FIG. 7 is a diagram showing an applied example to a refrigerator;

FIG. 8 is a refrigerant circuit diagram showing a second embodiment of the refrigerating machine according to the present invention;

FIG. 9 is an enthalpy-pressure diagram showing a refrigerating cycle;

FIG. 10 is a diagram showing an applied example of the second embodiment to a refrigerator, and corresponds to FIG. 3;

FIG. 11 is a diagram showing an applied example to a refrigerator and corresponds to FIG. 4;

FIG. 12 is a refrigerant circuit diagram showing a modification of the second embodiment, and corresponds to FIG. 5;

FIG. 13 is a diagram showing an applied example to a refrigerator, and corresponds to FIG. 6; and

FIG. 14 is a diagram showing an applied example to a refrigerator, and corresponds to FIG. 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments according to the present invention will be described hereunder with reference to the accompanying drawings.

FIG. 1 is a refrigerant circuit diagram showing a first embodiment according to the present invention. A refrigerating machine 30 is equipped with a compressor 1, a radiator 2, a first expansion valve (pressure-reducing device) 3 and a gas-liquid separator 4 which are connected to one another in this order. A part of the refrigerant circuit which extends from the compressor 1 through the radiator 2 to the inlet port of the first expansion valve 3 constitutes a high-pressure side circuit.

The compressor 1 is a two-stage compressor, and it includes a first-stage compressing portion 1A, a second-stage compressing portion 1B and an intermediate cooler 1C between the first-stage and second-stage compressing portions 1A and 1B. Reference numeral 8 represents a check valve. The refrigerating machine 30 is further equipped with a unit (gas refrigerant introduction inhibiting/allowing unit) 5 which selectively introducing gas refrigerant separated in the gas-liquid separator 4 into an intermediate pressure portion of the compressor 1. In this construction, the intermediate pressure portion is located between the intermediate cooler 1C and the second-state compressing portion 1B. The compressor 1 of the present invention is not limited to the two-stage compressor. If the compressor 1 is a one-stage compressor, the gas refrigerant introduction inhibiting/allowing unit 5 may be designed so as to return gas refrigerant to an intermediate pressure portion of the one-stage compressor. In this embodiment, the gas refrigerant introduction inhibiting/allowing unit 5 is constructed by a gas pipe 6 and an opening/closing valve 91 provided in the gas pipe 6. Accordingly, the introduction of the gas refrigerant into the intermediate pressure portion is started (allowed) or stopped (inhibited) by opening/closing the opening/closing valve 91.

Furthermore, the refrigerating machine 30 is provided with a low-pressure side circuit 9 for circulating liquid refrigerant separated in the gas-liquid separator 4, and the low-pressure side circuit 9 is provided with a heat absorbing unit 10 which selectively functions in different temperature zones. The heat absorbing unit 10 is constructed by a second expansion valve 11 and one heat absorber 14. By controlling the valve opening degree of the second expansion valve 11, the evaporating pressure in the heat absorber 14 is controlled. If the evaporating pressure is increased, the evaporating temperature is increased, and thus a refrigerating operation is carried out. On the other hand, if the evaporating pressure is reduced, the evaporating temperature in the heat absorber 14 is lowered, and thus a freezing operation is carried out. The refrigerant passed through the heat absorber 14 is passed through the check valve 8 and returned to the suction portion of the compressor 1.

In this embodiment, the heat absorber 14 is provided with a unit 23 for selectively guiding cold air passed through the heat absorber 14 to plural chambers (refrigerating chamber 21, freezing chamber 22) which are controlled to different temperature zones. The unit 23 contains an air flowing duct 24 and a switching dumper 25, and a controller 26 for switching the operation to one of the refrigerating and freezing operations is connected to the switching dumper 25.

The controller 26 is also connected to the expansion valves 3 and 11 and the opening/closing valve 91. For example when the load of the freezing chamber 22 is tilted, the switching dumper 25 is inclined to a position indicated in FIG. 1 to guide cold air to the freezing chamber 22 (freezing operation). Under freezing operation, the opening/closing valve 91 is opened, and the gas refrigerant separated in the gas-liquid separator 4 is introduced into the intermediate pressure portion of the compressor 1 as indicated by a broken line. When the load of the refrigerating chamber 21 is increased, the switching dumper 25 is tilted to the opposite position to the position shown in FIG. 1 to guide cold air to the refrigerating chamber 21 (refrigerating operation) Under the refrigerating operation, the opening/closing valve 91 is closed, and the introduction of the gas refrigerant into the intermediate pressure portion of the compressor 1 is inhibited. The opening/closing valve 91 constitutes the gas refrigerant introduction inhibiting/allowing unit.

The refrigerant circuit is filled with such refrigerant that the high-pressure side of the refrigerant circuit is set to supercritical pressure under operation in accordance with a condition, for example, when the outside temperature is increased to 30° C. or more in summer season, when the load is increased or the like. Carbon dioxide refrigerant is filled as the above refrigerant. In place of carbon dioxide refrigerant, ethylene, diborane, ethane, nitrogen oxide or the like may be used as the refrigerant in which the high-pressure side circuit is operated under supercritical pressure.

In the above construction, even when the gas refrigerant separated in the gas-liquid separator 4 is circulated in the low-pressure side circuit 9, it cannot be used for cooling. Accordingly, if the gas refrigerant is turned to the suction port of the first-stage compressing portion 1A, it would reduce the efficiency of the refrigerating cycle.

Therefore, the gas refrigerant is introduced into the intermediate pressure portion of the compressor 1. In this embodiment, under the control of the controller 26 described above, introduction of the gas refrigerant into the intermediate pressure portion of the compressor 1 is allowed under freezing operation in which the temperature zone is low. On the other hand, introduction of the gas refrigerant into the intermediate pressure portion is inhibited under refrigerating operation in which the temperature zone is high.

FIG. 2 is an enthalpy-pressure (ph) diagram showing a two-stage compressor two-stage expansion cycle when gas refrigerant is introduced into the first intermediate pressure portion X of the compressor 1 under both the refrigerating operation and the freezing operation.

In FIG. 2, a cycle indicated by a solid line is formed during freezing operation (freezing around −26° C.). (1) represents the suction port of the first-stage compressor 1A, (2) represents the discharge port of the first-compressing portion 1A, (3) represents the suction port of the second-stage pressing portion 1B, and (4) represents the discharge port of the second-stage compressing portion 1A. The refrigerant discharged from the compressor 1 is circulated through the radiator 2 and cooled. (5) represents the inlet port of the first expansion valve 3, and (6) represents the outlet port of the first expansion valve 3. Under the state of (6), the refrigerant becomes two-phase mixture of gas/liquid.

The ratio of gas and liquid corresponds to the ratio of the length of the line segment of L1 (gas) and the length of the line segment of L2 (liquid). The refrigerant enters the gas-liquid separator 4 under the state that the refrigerant keeps the two-phase mixture. The gas refrigerant separated in the gas-liquid separator is introduced into the intermediate pressure portion of the compressor 1, that is, between the intermediate cooler 1C and the second-stage pressing portion 1B. (21) represents the outlet port of the gas-liquid separator 4. The refrigerant passed through the outlet port of the gas-liquid separator 4 reaches the suction port of the second-stage compressing portion 1B of (3), and then is compressed in the second-stage compressing portion 1B. The liquid refrigerant separated in the gas-liquid separator 4 is circulated in the low-pressure side circuit 9. (7) represents the outlet port of the gas-liquid separator 4, that is, the inlet port of the second expansion valve 11, (8) represents the outlet port of the second expansion valve 11 and (22) represents the outlet port of the heat absorber 14. The liquid refrigerant entering the heat absorber 14 evaporates to absorb heat. (1) represents the suction port of the first-stage compressing portion 1A.

On the other hand, a cycle indicated by a broken line is formed during refrigerating operation (refrigeration around −5° C.). That is, the state of the cycle is varied in the following order: (9) the suction port of the first-stage compressing portion 1A, (10) the discharge port of the first-stage compressing portion 1A, (11) the suction port of the second-stage compressing portion 1B, (12) the discharge port of the second-stage compressing portion 1B, (5) the inlet port of the first expansion valve 3, (13) the outlet port of the first expansion valve 3, (14) the outlet port of the gas-liquid separator 4 and thus the inlet port of the second expansion valve 11, (15) the outlet port of the second expansion valve 11 and (9) the suction port of the first-stage compressor 1A.

Referring to FIG. 2, the pressure (13) of the outlet port of the first expansion valve 3 in the broken-line cycle (under refrigerating operation) is remarkably higher than the pressure (6) of the outlet port of the first expansion valve 3 under the solid-line cycle (under freezing operation). When the pressure of the outlet port of the first expansion valve 3 is increased, the amount of the gas component in the refrigerant before the refrigerant enters the gas-liquid separator 4 is reduced. This is because the ratio between gas and liquid at the inlet port of the gas-liquid separator 4 corresponds to the ratio of L1 (gas) and L2 (liquid) or the ratio of L3 (gas) and L4 (liquid) as described above. In conformity with this, a large amount of gas refrigerant is introduced into the intermediate pressure portion of the compressor 1 under the solid-line cycle (freezing operation), however, the amount of gas refrigerant to be introduced into the intermediate pressure portion is very small under the broken-line cycle (refrigerating operation).

That is, under freezing operation, the amount of the gas refrigerant introduced into the intermediate pressure portion of the compressor 1 is increased, and the efficiency of the refrigerating cycle can be enhanced by some degree because the gas component which does not contribute to cooling is not circulated in the low pressure circuit 9.

Particularly in the above construction, since carbon oxide refrigerant is filled in the refrigerant circuit, the amount of the gas component is larger as compared with chlorofluorocarbon (Freon) type refrigerant. Accordingly, a higher efficiency can be achieved by introducing a larger amount of gas component into the intermediate pressure portion of the compressor 1. On the other hand, under refrigerating operation in which the temperature zone is high, the occurrence amount of gas refrigerant to be introduced into the intermediate pressure portion of the compressor 1 itself is small, and thus even when the gas refrigerant is introduced into the intermediate pressure portion, the efficiency of the refrigerating cycle cannot be so enhanced as compared with complication in pipe construction, etc.

According to this embodiment, introduction of gas refrigerant into the intermediate pressure portion of the compressor 1 is allowed only under freezing operation because of the effect of introducing the gas refrigerant is higher. On the other hand, under refrigerating operation in which the temperature zone is high, introduction of gas refrigerant into the intermediate pressure portion of the compressor 1 is inhibited. Therefore, the variable cycle can be implemented and the efficiency of the refrigerating cycle is enhanced by a simple pipe construction and simple control.

Furthermore, according to this embodiment, all the parts of the heat absorbing unit 10 which selectively function in different temperature zones, that is, the second expansion valve 11 and the heat absorber 14 are provided to the low pressure side circuit 9. Therefore, for example when the refrigerating operation is carried out and when the freezing operation is carried out, the remarkably highly efficient operation can be performed without reducing the efficiency.

FIG. 3 shows an applied example of the refrigerating machine of the above embodiment to a refrigerator.

A refrigerator (fridge) 40 has a refrigerating chamber 41 at the upper stage and a freezing chamber 42 at the lower stage. An inner partition wall 43 is provided at the inner back side of the freezing chamber 42, and the heat absorber 14 described above is provided in an air flow path 44 partitioned by the inner partition wall 43. A first switching dumper 45 is disposed at the inlet port A of the air flow path 44, and the first switching dumper 45 is switched between a closing position (broken-line position) for closing the inlet port A of the air flow path 44 and an opening position (solid-line position) for opening the inlet port A of the air flow path 44. A back side air flow path 46 is formed on the back wall 47 of the refrigerator 40. When the first switching dumper 45 is switched to the broken-line position, the inlet port 4 of the air flow path 44 and the refrigerating chamber 41 intercommunicate with each other through the back side air flow path 46. Furthermore, a fan 48 and a second switching dumper 49 are disposed at the outlet port B of the air flow path 44, and the second switching dumper 49 is switched between a closing position (broken-line position) for closing the outlet port B of the air flow path 44 and an opening position (solid-line position) for opening the outlet port B of the air flow path 44. At the solid-line position, the second switching dumper 49 closes an opening 51 formed in an intermediate partition wall 50.

In the above construction, during freezing operation, the compressor 1 is turned on, the fan 48 is turned on, the opening/closing valve 91 is opened, and each of the dumpers 45 and 49 is switched to the solid-line position. Accordingly, air in the freezing chamber 42 is circulated in the heat absorber 14, and supplied to the freezing chamber 42. During refrigerating operation, the opening/closing valve 91 is closed, and each of the dumpers 45 and 49 is switched to the broken-line position. Accordingly, air in the refrigerating chamber 41 enters the air flow path 44 through the back side air flow path 46, and it is circulated in the heat absorber 14 and then supplied to the refrigerating chamber 41.

FIG. 5 shows a refrigerant circuit of a modification of the first embodiment.

The construction of this modification is different from the construction shown in FIG. 1 in the construction of the heat absorbing unit 10. The heat absorbing unit 10 of this modification comprises a three-way valve 11, a first capillary tube 12, a heat absorber 57 for refrigeration which is connected to the first capillary tube 12 in series, a second capillary tube 13 which is connected to the first capillary tube 12 and the heat absorber 57, and a heat absorber 58 for freezing which is connected to the second capillary tube 13 in series. Reference numeral 59 represents a check valve. When the refrigerant is made to flow into the first capillary tube 12 by switching the three-way valve 11, the flow amount of the refrigerant flowing in the heat absorber 57 is increased, and the refrigerating operation is carried out. Furthermore, when the refrigerant is made to flow into the second capillary tube 13 by switching the three-way valve 11, the flow amount of the refrigerant flowing in the heat absorber 58 is increased (the flow amount of the refrigerant flowing in the heat absorber 57 is reduced), and thus the freezing operation is carried out.

FIG. 6 shows an applied example of the modification to a refrigerator (fridge).

The refrigerator 40 has a refrigerating chamber 41 at the upper stage, and a freezing chamber at the lower stage. Inner partition walls 61 and 62 are provided at the inner back sides of the respective chambers 41 and 42. The heat absorber 57, 58 and the fan 63, 64 are disposed in an air flow path 44 partitioned by the inner partition wall 61, 62. In this construction, the three-way valve 11 is switched in accordance with thermo-on, thermo-off of the refrigerating operation and the freezing operation to make the refrigerant flow into any one of the heat absorbers 57 and 58, and the corresponding one of the fans 62 and 63 is driven.

FIG. 7 shows another modification of the first embodiment.

This construction of this modification is different from the construction of FIG. 6 in the construction of the heat absorbing unit 10. In the heat absorbing unit 10 of this modification, the three-way valve is omitted, and electrical motor operated valves 65 and 66 are connected to the capillary tubes 12 and 13 in series, respectively. In this construction, the electrical motor operated valves 65 and 66 are turned on or off in accordance with thermo-on, thermo-off of the refrigerating operation and the freezing operation to make the refrigerant selectively flow into any one of the heat absorbers 57 and 58, and the corresponding one of the fans 62 and 63 is driven. In these embodiments, substantially the same effects can be achieved.

The present invention is not limited to the above embodiments, and various modifications may be made without departing from the subject matter of the present invention. In the above embodiments, the gas refrigerant introduction inhibiting/allowing unit is constructed by the opening/closing valve 91, however, the present invention is not limited to the opening/closing valve 91. For example, a circuit construction achieved by combining a check valve, etc. may be used insofar as it introduces the gas component of the refrigerant into the intermediate pressure portion of the compressor 1 under freezing operation while the introduction of the gas component is inhibited under refrigerating operation.

Furthermore, in the above embodiments, carbon dioxide refrigerant is enclosed in the refrigerant circuit. However, the present invention is not limited to carbon dioxide refrigerant, and it is needless to say that chlorofluorocarbon (freon) type refrigerant or the like may be enclosed in the refrigerant circuit in place of carbon dioxide refrigerant. Furthermore, the specific construction of the gas refrigerant introducing unit 5 and the place from which the gas component is introduced are not limited to specific ones, and they may be arbitrarily determined insofar as it can introduced the gas component of the refrigerant into the intermediate pressure portion of the compressor 1 in accordance with the operation condition.

In the above embodiments, the introduction of the gas refrigerant into the intermediate pressure portion is inhibited on the assumption that the occurrence amount (L3) of the gas refrigerant introduced into the intermediate portion of the compressor 1 is small during refrigerating operation in which the temperature zone is high. However, when the occurrence amount (L3) of the gas refrigerant is not small to the extent that it cannot be neglected, the refrigeration efficiency can be further enhanced by designing the refrigerating machine so that the gas refrigerant which does not contribute to cooling is prevented from being circulated in the low-pressure circuit side.

Next, an embodiment in which the gas refrigerant is introduced into the compressor 1 under refrigerating operation to further enhance the efficiency of the refrigerating cycle.

FIG. 8 is a refrigerant circuit diagram showing a second embodiment of the present invention. A refrigerating machine 130 of this embodiment has the same refrigerant circuit as the first embodiment except for apart of the construction. In the following description, the different construction from the first embodiment will be mainly described. The same or corresponding constituent elements are represented by the same references, and the detailed description thereof is omitted.

The refrigerating machine 130 is equipped with a refrigerant gas introducing unit 105 for selectively introducing gas refrigerant separated in the gas-liquid separator 4 into one of a first intermediate pressure portion X of the compressor 1 and a second intermediate pressure portion Y which is nearer to the low pressure suction side than the first intermediate pressure portion X. In this construction, the first intermediate pressure portion X is located between the intermediate cooler 1C and the second-stage compressing portion 1B, and the second intermediate pressure portion Y is located at some midpoint of the first-stage compressing portion 1A. In this embodiment, the compressor 1 comprises a two-stage compressor, however, the compressor 1 is not limited to the two-stage compressor.

The gas refrigerant introducing unit 105 comprises a gas pipe 6, a three-way valve 81 provided in the gas pipe 6 and two branch gas pipes 82 and 83 branched from the three-way valve 81. One branch gas pipe 82 is connected to the first intermediate pressure portion X, and the other branch gas pipe 83 is connected to the second intermediate pressure portion Y. Here, the three-way valve 81 and the branch gas pipe 83 constitutes the gas refrigerant introducing unit. Accordingly, when the gas pipe 6 and the branch gas pipe 82 intercommunicate with each other by switching the three-way valve 81, the gas refrigerant is introduced into the first intermediate pressure portion X as indicated by an broken-line arrow. When the gas pipe 6 and the branch gas pipe 83 intercommunicate with each other by switching the three-way valve 81, the gas refrigerant is introduced into the second intermediate pressure portion Y. Here, the three-way valve 81 is not limited to an electromagnetic type, and a differential pressure driving type or the like. Furthermore, the first intermediate pressure portion X corresponds to the intermediate pressure portion in the first embodiment.

The controller 26 is connected to the compressor 1, the expansion valves 3 and 11 and the three-way valve 81. For example, when the load of the freezing chamber 22 is increased, the valve opening degree of the second expansion valve 11 is increased, the flow amount flowing in the heat absorber 14 is increased, and the switching dumper 25 is tilted to the position shown in FIG. 8 to thereby guide cold air to the freezing chamber 22 (freezing operation). During freezing operation, the three-way valve 81 is switched to make the gas pipe 6 and the branch gas pipe 82 intercommunicate with each other, so that the gas refrigerant separated in the gas-liquid separator 4 is introduced into the first intermediate pressure portion X as indicated by the broken-line arrow. Furthermore, when the load of the refrigerating chamber 21 is increased, the switching dumper 25 is tilted to the opposite position to the position shown in FIG. 8 to guide cold air to the refrigerating chamber 21 (refrigerating operation). During refrigerating operation, the three-way valve 81 is switched to make the gas pipe 6 and the branch gas pipe 83 intercommunicate with each other, and the gas refrigerant is introduced into the second intermediate pressure portion Y.

As in the case of the first embodiment, the refrigerant circuit is filled with such refrigerant that the high-pressure side of the refrigerant circuit is set to supercritical pressure under operation in accordance with a condition, for example, when the outside temperature is increased to 30° C. or more in summer season, when the load is increased or the like. Carbon dioxide refrigerant is filled as the above refrigerant. In place of carbon dioxide refrigerant, ethylene, diborane, ethane, nitrogen oxide or the like may be used as the refrigerant in which the high-pressure side circuit is operated under supercritical pressure.

In the above construction, even when the gas refrigerant separated in the gas-liquid separator 4 is circulated in the low pressure side circuit 9, it is not usable for cooling. Therefore, if the gas refrigerant concerned is returned to the suction port of the first-stage compressing portion 1A, the efficiency of the refrigerating cycle would be reduced. Therefore, the gas refrigerant is introduced into the intermediate pressure portion of the compressor 1. However, as described with reference to the first embodiment, when the occurrence amount (L3) of the gas refrigerant is small, even if the gas refrigerant is circulated in the low pressure side circuit 9, it hardly affects the efficiency of the refrigerating cycle. In other words, even when such a small amount of gas refrigerant is introduced into the intermediate pressure portion of the compressor, it does not enhance the efficiency of the refrigerating cycle. Accordingly, in this embodiment, under the control of the controller 26 described above, the gas refrigerant is introduced into the first intermediate pressure portion X of the compressor 1 under freezing operation in which the temperature zone is low, and the gas refrigerant is introduced into the second intermediate pressure portion Y nearer to the low-pressure suction side of the compressor 1 than the first intermediate pressure portion X under refrigerating operation in which the temperature zone is high, whereby the efficiency of the refrigerating cycle is further enhanced.

FIG. 9 is an enthalpy-pressure (ph) diagram showing the two-stage compression two-stage expansion cycle when the gas refrigerant is introduced into the first intermediate pressure portion X of the compressor 1 under freezing operation in which the temperature zone is low while the gas refrigerant is introduced into the second intermediate pressure portion Y of the compressor 1 under refrigerating operation in which the temperature zone is high. Here, the ph diagram of FIG. 9 is compared with the ph diagram of FIG. 2 when the gas refrigerant is introduced into the first intermediate pressure portion X of the compressor 1 in both the refrigerating and freezing operations.

In FIGS. 2 and 9, the refrigerating cycle indicated by a solid line is formed during freezing operation (freezing around −26° C.). (1) represents the suction port of the first-stage compressing portion 1A, (2) represents the discharge port of the first-stage compressing portion 1A, (3) represents the suction port of the second-stage compressing portion 1B, and (4) represents the discharge port of the second-stage pressing portion 1B. The refrigerant discharged from the compressor 1 is circulated through the radiator 2 to be cooled. (5) represents the inlet port of the first expansion valve, and (6) represents the outlet port of the first expansion valve 3. Under this state, the refrigerant becomes two-phase mixture of gas and liquid.

The ratio of gas and liquid corresponds to the ratio of the length of the line segment of L1 (gas) and the length of the line segment of L2 (liquid). The refrigerant enters the gas-liquid separator 4 under the state that the refrigerant is the two-phase mixture. The gas refrigerant separated in the gas-liquid separator 4 is introduced into the intermediate portion of the compressor 1, that is, between the intermediate cooler 1C and the second-stage compressing portion 1B. (21) represents the outlet port of the gas-liquid separator 4. The refrigerant passed through the gas-liquid separator 4 reaches the first intermediate pressure portion X, that is, the suction port of the second-stage compressing portion 1B of (3), and compressed in the second-stage compressing portion 1B. On the other hand, the liquid refrigerant separated in the gas-liquid separator 4 is circulated in the low pressure side circuit 9. (7) represents the outlet port of the gas-liquid separator 4, and thus the inlet port of the second expansion valve, (8) represents the outlet port of the second expansion valve 11, and (22) represents the outlet port of the heat absorber 14. The liquid refrigerant entering the heat absorber 14 evaporates and absorbs heat. (1) represents the suction port of the first-stage compressing portion 1A.

On the other hand, the cycle indicated by a broken line is formed under refrigerating operation (refrigeration around −5° C.). That is, in FIG. 9, the state is varied in the following order: (9) the suction port of the first-stage compressing portion 1A, (11) the second intermediate pressure portion Y, that is, the intermediate portion of the first-stage pressure compressing portion 1A, (12) the discharge port of the first-stage compressing portion 1A and thus the inlet port of the intermediate cooler 1C, (13) the outlet port of the intermediate cooler 1C and thus the suction port of the second-stage compressing portion 1B, (14) the discharge port of the second-stage compressing portion 1B, (5) the inlet port of the first expansion valve 3, (15) the outlet port of the first expansion valve, (16) the outlet port of the gas-liquid separator 4 and thus the inlet port of the second expansion valve 11, (17) the outlet port of the second expansion valve 11, and (9) the suction port of the first-stage compressing portion 1A.

In FIG. 2, the gas refrigerant is introduced into the first intermediate pressure portion X of the compressor 1, and thus the state is varied in the following order: (9) the suction port of the first-stage compressing portion 1A, (10) the discharge port of the first-stage compressing portion 1A, (11) the first intermediate pressure portion X, that is, the outlet port of the intermediate cooler 1C, and thus the suction port of the second-stage compressing portion 1B, (12) the discharge port of the second-stage compressing portion 1B, (5) the inlet port of the first expansion valve 3, (13) the outlet port of the first expansion valve 3, (14) the outlet port of the gas-liquid separator 4, that is, the inlet port of the second expansion valve 11, (15) the outlet port of the second expansion valve 11 and the suction port of the first-stage compressing portion 1A.

When comparing the cases of FIGS. 2 and 9, the gas refrigerant is introduced into the first intermediate pressure portion X of the compressor 1 under freezing operation in which the temperature zone is low in both the cases. Accordingly, under freezing operation, substantially the same cycle indicated by the solid line is formed in FIGS. 2 and 9.

On the other hand, under the refrigerating operation in which the temperature zone is high, the gas refrigerant is introduced into the second intermediate pressure portion Y nearer to the low voltage suction side than the first intermediate pressure portion X in FIG. 9 whereas the gas refrigerant is introduced into the first intermediate pressure portion X of the compressor 1 in FIG. 2. The pressure of the second intermediate pressure portion Y is lower than the pressure of the first intermediate pressure portion X. Accordingly, when the gas refrigerant is introduced into the second intermediate pressure portion Y having the lower pressure, the pressure at the outlet port of the first expansion valve 3 can be reduced as compared with the case where the gas refrigerant is introduced into the first intermediate pressure portion X.

That is, under refrigerating operation, the pressure of the line segments L5 and L6 (FIG. 9) is lower than the pressure of the line segments L3 and L4 (FIG. 2) in the cycle indicated by the broken line. When the pressure at the outlet port of the first expansion valve 3 is reduced, the amount of the gas component of the refrigerant before it enters the gas-liquid separator 4 is increased. This is also apparent from the fact that the line segment L5 is longer than the line segment L3. As described above, the ratio of gas and liquid at the inlet port of the gas-liquid separator 4 corresponds to the ratio of L5 (gas) and L6 (liquid) in FIG. 9, and also corresponds to the ratio of L3 (gas) and L4 (liquid) in FIG. 2. Accordingly, the amount of the gas refrigerant introduced into the intermediate pressure portion of the compressor 1 is larger as compared with FIG. 2, and thus it cannot be neglected. Therefore, the efficiency of the refrigerating cycle can be enhanced by the degree corresponding to the effect achieved when the gas component which does not contribute to cooling is prevented from being circulated in the low pressure circuit 9. Particularly, in the above construction, carbon dioxide refrigerant is enclosed in the refrigerant circuit, and thus the amount of the gas component of the refrigerant is larger in the ratio of gas and liquid separated in the gas-liquid separator 4 as compared with chlorofluorocarbon (Freon) type refrigerant, and a larger amount of gas component is introduced to the intermediate pressure portion o the compressor 1, whereby the efficiency of the refrigerating cycle can be more enhanced.

In this embodiment, all the elements of the heat absorbing unit 10 which selectively functions in different temperature zones, that is, the second expansion valve 11 and the heat absorber 14 are provided to the low pressure side circuit 9. Therefore, in both the case where the refrigerating operation is carried out and the case where the freezing operation is carried out, the highly efficient operation can be performed without reducing the efficiency.

The refrigerating machine may be designed so that the gas refrigerant introduction inhibiting/allowing unit 5 according to the first embodiment and the gas refrigerant introducing unit 105 according to the second embodiment is connected to each other in series. In this case, both the units are switched to each other in accordance with the reduction of the efficiency of the refrigerating cycle which is caused by the occurrence amount of the gas refrigerant under refrigerating operation. Specifically, the gas refrigerant introduction inhibiting/allowing unit 5 is secured to the gas refrigerant discharge side of the gas-liquid separator 4, and the gas refrigerant introducing unit 105 is secured to the output side of the gas refrigerant introduction inhibiting/allowing unit 5.

The gas refrigerant introducing unit 105 may be designed so as to introduce the refrigerant into the first intermediate pressure portion of the compressor 1 or the second intermediate pressure portion nearer to the suction side of the compressor 1 than the first intermediate pressure portion in accordance with the operating condition, and the specific construction thereof and the introducing position thereof are determined freely.

FIGS. 10 to 14 show examples when the above embodiment is applied to a refrigerator, and correspond to FIGS. 3 to 7 when the gas refrigerant introduction inhibiting/allowing unit 5 is changed to the gas. refrigerant introducing unit 105. Each operation in the refrigerator is identical to the corresponding operation described with reference to FIGS. 3 to 7, and the duplicative description thereof is omitted.

As described above, according to the present invention, under freezing operation having a higher effect, the gas refrigerant is introduced into the intermediate pressure portion (first intermediate pressure portion) of the compressor 1, and under refrigerating operation in which the temperature zone is high, the gas refrigerant is introduced into the intermediate pressure portion (second intermediate pressure portion) at the lower pressure side than the first intermediate pressure portion. Therefore, the variable cycle can be implemented and the efficiency of the refrigerating cycle can be enhanced by a simple pipe construction and a simple control operation.

The gas refrigerant introducing inhibiting/allowing unit of the first embodiment and the gas refrigerant introducing unit of the second embodiment may be used independently of each other, however, a combination thereof may be arranged a gas refrigerant introduction inhibiting/allowing switching unit having both the functions thereof in the gas pipe 6 between the gas-liquid separator 4 and the compressor 1. In this case, the gas refrigerant introduction inhibiting/allowing unit 5 is provided at the gas-liquid separator 4 side while the gas refrigerant introducing unit 105 is disposed between the gas refrigerant introduction inhibiting/allowing unit 5 and the compressor 1. Furthermore, under freezing operation, the gas refrigerant introduction inhibiting/allowing unit and the gas refrigerant introducing unit are operated so that the gas refrigerant from the gas-liquid separator 4 is passed through the gas refrigerant introduction inhibiting/allowing unit, and further passed through the gas refrigerant introducing unit to the first intermediate pressure portion X of the compressor 1. On the other hand, under refrigerating operation, the gas refrigerant introduction inhibiting/allowing unit and the gas refrigerant introducing unit are selectively operated so that the gas refrigerant from the gas-liquid separator 4 is inhibited from being introduced to the compressor by the gas refrigerant introduction inhibiting/allowing unit or allowed to be introduced to the compressor through the gas refrigerant introduction inhibiting/allowing unit, passed through the gas refrigerant introducing unit and then introduced to the second intermediate pressure portion Y of the compressor in accordance with the condition such as the gas refrigerant amount at the outlet port of the first expansion valve 3 or the like.

The present invention is not limited to the above embodiments, and various modifications may be made without departing from the subject matter of the present invention. For example, in the above construction, carbon dioxide refrigerant is enclosed in the refrigerant circuit, however, the present invention is not limited to carbon dioxide refrigerant. For example, chlorofluorocarbon (Freon) type refrigerant or the like may be enclosed in the refrigerant circuit in place of carbon dioxide refrigerant.

Number	Date	Country	Kind
P2004-79341	Mar 2004	JP	national
P2004-79342	Mar 2004	JP	national

Refrigerating machine

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CPC

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