Refrigeration device

Abstract

A refrigeration apparatus includes a refrigerant circuit (20) capable of being switched between a first operation in which a first compressor (21) is stopped and a second compressor (22) is driven and a second operation in which the first compressor (21) and the second compressor (22) are driven, and the refrigeration apparatus includes a suppression mechanism (50) that suppresses flow of refrigerant into the first compressor (21) when a first condition in which a pressure in the first compressor (21) is lower than an evaporation pressure of an evaporator (24, 27) is satisfied in the first operation.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a refrigeration device. BACKGROUND

[0002] Patent Document 1 discloses a refrigeration device having a refrigerant circuit including a first compressor and a second compressor connected to an injection side of the first compressor. In the refrigeration device, it is possible to switch between a first operation in which the first compressor is stopped and the second compressor is driven, and a second operation in which the first compressor and the second compressor are driven.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT DOCUMENT

[0005] Patent Document 1: Japanese Laid-Open Patent Publication No. 2008-64421 SUMMARY

[0006] PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] The present inventors have made a structure in which a bypass pipe is provided, which bypasses the injection side and the suction side of the first compressor, in order to switch between the first operation and the second operation. In the first operation, the refrigerant flowing out from the evaporator is sucked into the second compressor being driven via the bypass pipe. Thereby, the evaporated refrigerant is sent to the second compressor while bypassing the first compressor in the stopped state.

[0008] In such a refrigeration device, when the first operation is performed, if the evaporation temperature of the evaporator transiently rises, the in-machine temperature of the first compressor in the stopped state can sometimes be lower than the evaporation temperature of the evaporator. In this state, the in-machine pressure of the first compressor in the stopped state is lower than the evaporation pressure of the evaporator, and a problem arises in which a part of the refrigerant flowing out of the bypass pipe is sucked into the first compressor in the stopped state.

[0009] An object of the present disclosure is to provide a refrigeration device capable of suppressing the refrigerant flowing out of the bypass pipe from being sucked into the first compressor in the stopped state in the first operation in which the first compressor is stopped and the second compressor is driven.

[0010] TECHNICAL SOLUTION TO SOLVE THE PROBLEMS

[0011] A first aspect of the present disclosure is a refrigeration device,

[0012] The refrigeration device includes a refrigerant circuit 20, which includes a first compressor 21, a second compressor 22 connected to the discharge side of the first compressor 21, and evaporators 24 and 27. The refrigerant circuit 20 can switch between a first operation and a second operation. In the first operation, a refrigeration cycle is performed where the first compressor 21 is stopped and the second compressor 22 is driven. In the second operation, a refrigeration cycle is performed where both the first compressor 21 and the second compressor 22 are driven. Its characteristic is that:

[0013] The refrigerant circuit 20 has a bypass pipe PB connecting the suction side and the discharge side of the first compressor 21.

[0014] The refrigeration device includes a suppression mechanism 50, which, during the first operation, suppresses refrigerant from flowing into the first compressor 21 when a first condition indicating that the pressure inside the first compressor 21 is lower than the evaporation pressure of the evaporators 24 and 27 is met.

[0015] In the first aspect, when the first condition is met during the first operation, the suppression mechanism 50 suppresses the flow of refrigerant into the first compressor 21, which is in a stopped state.

[0016] The second aspect of this disclosure is based on the first aspect and is characterized in that:

[0017] The first condition is that the internal temperature of the first compressor 21 is lower than the evaporation temperature of the evaporators 24 and 27.

[0018] In the second aspect, if the internal temperature of the first compressor 21 is lower than the evaporation temperature of the evaporators 24 and 27, the suppression mechanism 50 suppresses the flow of refrigerant into the first compressor 21, which is in a stopped state.

[0019] The third aspect of this disclosure is based on the second aspect and is characterized in that:

[0020] The cooling device includes a first temperature sensor 48.

[0021] The first temperature sensor 48 detects the temperature of at least one of the following: the outer surface of the housing 21a of the first compressor 21, the interior of the housing 21a of the first compressor 21, the suction pipe 51 of the first compressor 21, the discharge pipe 52 of the first compressor 21, and the outdoor air.

[0022] The internal temperature of the first compressor 21 is based on the value detected by the first temperature sensor 48.

[0023] In the third aspect, the internal temperature of the first compressor 21 can be inferred based on the detection value of the first temperature sensor 48. It is also possible to determine whether the first condition is met based on the detection value of the first temperature sensor 48.

[0024] The fourth aspect of this disclosure is based on any one of the first to third aspects, and is characterized in that:

[0025] The suppression mechanism 50 has a valve 33 connected between the first compressor 21 and the outlet end of the bypass pipe PB.

[0026] When the first condition is met, the valve 33 is in the closed state.

[0027] In the fourth aspect, when the first condition is met, valve 33 is in the closed state. This prevents refrigerant that has flowed out from the bypass pipe PB from flowing into the first compressor 21 from the discharge side.

[0028] The fifth aspect of this disclosure is based on any one of the first to third aspects, and is characterized in that:

[0029] The suppression mechanism 50 includes a heating section 36 that heats the first compressor 21 when the first condition is met.

[0030] In the fifth aspect, if the first condition is met, the heating unit 36 ​​heats the first compressor 21. As a result, the internal temperature of the first compressor 21 rises. Consequently, it is possible to prevent the internal temperature of the first compressor 21 from falling below the evaporation temperatures of the evaporator 24 and the evaporator 27.

[0031] The sixth aspect of this disclosure is based on the fifth aspect and is characterized in that:

[0032] The heating unit 36 ​​includes a heater 37 disposed within the first compressor 21 and energized when the first condition is met.

[0033] In the sixth aspect, the heater 37 is heated by energizing it. This allows the first compressor 21 to be heated.

[0034] The seventh aspect of this disclosure is based on the fifth aspect and is characterized in that:

[0035] The heating unit 36 ​​includes an electric motor 21b disposed within the first compressor 21 and energized by a phase loss when the first condition is met.

[0036] In the seventh aspect, by energizing in the absence of a phase, the motor 21b heats up while the motor is stopped. This allows the first compressor 21 to be heated.

[0037] The eighth aspect of this disclosure is based on any one of the first to third aspects, and is characterized in that:

[0038] The suppression mechanism includes a pressure reduction mechanism 26 that reduces the evaporation pressure of the evaporators 24 and 27 when the first condition is met.

[0039] In the eighth aspect, the evaporation pressure of the evaporator 24 and the evaporator 27 can be adjusted to below the internal pressure of the first compressor 21 by using the pressure reducing mechanism 26. Attached Figure Description

[0040] Figure 1 This is a piping diagram illustrating the configuration of the refrigeration device according to the first embodiment;

[0041] Figure 2 It is a block diagram showing the relationship between the control unit, various sensors, and refrigerant circuit components;

[0042] Figure 3 This indicates the flow of refrigerant during the first heating operation. Figure 1 A comparable diagram;

[0043] Figure 4 This indicates the flow of refrigerant during the second heating operation. Figure 1 A comparable diagram;

[0044] Figure 5 This indicates the flow of refrigerant during the first cooling operation (defrost operation). Figure 1 A comparable diagram;

[0045] Figure 6 This indicates the flow of refrigerant during the second cooling operation. Figure 1 A comparable diagram;

[0046] Figure 7 This is a graph showing the relationship between temperature and time when the first condition is met;

[0047] Figure 8 This is a flowchart of the actions performed by the control unit during the first heating operation;

[0048] Figure 9 This is a flowchart of the actions performed by the control unit during defrosting operation;

[0049] Figure 10 The refrigeration device involved in Modification 1 and Figure 1 A comparable diagram;

[0050] Figure 11 This is a flowchart of the operations performed by the control unit of the refrigeration device involved in Modification Example 1;

[0051] Figure 12This is a flowchart of the operations performed by the control unit of the refrigeration device involved in Modification Example 2;

[0052] Figure 13 This refers to the arrangement of the first temperature sensor in the refrigeration device according to other embodiments. Figure 1 A fairly accurate diagram. Detailed Implementation

[0053] The embodiments of this disclosure will now be described with reference to the accompanying drawings. It should be noted that the following embodiments are essentially preferred examples and are not intended to limit the scope of the invention, its application, or its uses. It should be noted that the arrows in the figures indicate the flow of refrigerant in the refrigerant circuit.

[0054] (First Implementation)

[0055] like Figure 1 As shown, the refrigeration apparatus 10 of this first embodiment heats the fluid to be heated. The fluid to be heated is water. The refrigeration apparatus 10 supplies the heated water to a hot water supply tank, a heating coil, a floor heating coil, or other similar equipment. The refrigeration apparatus 10 also cools the fluid to be heated. The fluid to be heated is water. The refrigeration apparatus 10 supplies the cooled water to a cooling coil or other similar equipment. The refrigeration apparatus 10 includes a refrigerant circuit 20, a suppression mechanism 50, and a control unit 100.

[0056] [Refrigerant circuit]

[0057] The refrigerant circuit 20 includes a first compressor 21, a second compressor 22, a four-way reversing valve 23, a heat source-side heat exchanger 24, a check valve bridge 25, an expansion valve 26, a utilization-side heat exchanger 27, a receiver 28, and a bypass check valve 29. The refrigerant circuit 20 is filled with refrigerant, and a refrigeration cycle is performed by circulating the refrigerant within the refrigerant circuit 20. Examples of refrigerants include R410A, R32, and R407C.

[0058] The refrigerant circuit 20 is capable of a first operation and a second operation. In the first operation, of the first compressor 21 and the second compressor 22, the second compressor 22 is driven while the first compressor 21 is stopped. In the second operation, both the first compressor 21 and the second compressor 22 are driven. It should be noted that the first and second operations will be described in detail below.

[0059] <First Compressor>

[0060] The first compressor 21 compresses the refrigerant that has been drawn in and then sprays out the compressed refrigerant. A first suction pipe 51 and a first discharge pipe 52 are connected to the first compressor 21.

[0061] The first compressor 21 is, for example, a scroll compressor. The first compressor 21 has a housing 21a, an electric motor 21b, a drive shaft 21c, a compression mechanism 21d, and a heater 37.

[0062] The casing 21a is cylindrical. The casing 21a is a pressure vessel. The interior of the casing 21a is the interior of the first compressor 21.

[0063] The electric motor 21b is arranged inside the housing 21a. The electric motor 21b has a stator and a rotor (not shown). The stator is fixed to the inner circumferential surface of the housing 21a. The rotor is disposed inside the stator. A coil is wound on the rotor.

[0064] The drive shaft 21c is arranged inside the housing 21a. The drive shaft 21c is fixed to the inside of the rotor. When the motor 21b is powered, the rotor of the drive shaft 21c rotates, thereby driving the shaft to rotate.

[0065] A compression mechanism 21d is arranged inside a housing 21a. The compression mechanism 21d has a stationary scroll and a moving scroll (not shown). The compression mechanism 21d is connected to a drive shaft 21c. The compression mechanism 21d is driven by the rotation of the drive shaft. When the compression mechanism 21d is driven, the low-pressure gaseous refrigerant drawn into the first compressor 21 is compressed, and high-pressure gaseous refrigerant is ejected.

[0066] The rotational speed of the first compressor 21 is variable. For example, the rotational speed of the motor 21b can be changed by altering the output frequency of the inverter (not shown) connected to the first compressor 21. As a result, the rotational speed (operating frequency) of the first compressor 21 changes.

[0067] <Second Compressor>

[0068] The second compressor 22 is located on the discharge side of the first compressor 21. The second compressor 22 compresses the incoming refrigerant and discharges the compressed refrigerant. The capacity of the second compressor 22 is larger than that of the first compressor 21. A second suction pipe 53 and a second discharge pipe 54 are connected to the second compressor 22. The second suction pipe 53 corresponds to the suction pipe. The inflow end of the second suction pipe 53 is connected to the outflow end of the first discharge pipe 52. The first compressor 21 and the second compressor 22 are connected in series.

[0069] The second compressor 22 is, for example, a scroll compressor. Like the first compressor 21, the second compressor 22 has a housing, drive shaft, and compression mechanism (not shown).

[0070] The speed of the second compressor 22 is variable. For example, the speed of the motor 21b can be changed by altering the output frequency of the inverter (not shown) connected to the second compressor 22. As a result, the speed (operating frequency) of the second compressor 22 changes.

[0071] Four-way directional valve

[0072] The four-way directional valve 23 is an electrically operated directional valve. The four-way directional valve 23 is in its first state ( Figure 1 The state shown by the solid line) and the second state ( Figure 1 The system switches between states indicated by the dashed lines. In the first state, the first valve port P1 is connected to the fourth valve port P4, and the second valve port P2 is connected to the third valve port P3. In the second state, the first valve port P1 is connected to the third valve port P3, and the second valve port P2 is connected to the fourth valve port P4.

[0073] The first valve port P1 is connected to the outflow end of the second ejector pipe 54. The second valve port P2 is connected to the inflow end of the first suction pipe 51. The third valve port P3 is connected to the gas-side end of the heat source-side heat exchanger 24. The fourth valve port P4 is connected to the gas-side end of the utilization-side heat exchanger 27.

[0074] <Heat source side heat exchanger>

[0075] The heat source-side heat exchanger 24 allows the refrigerant to exchange heat with outdoor air (an example of a heat source-side fluid). The heat source-side heat exchanger 24 is an outdoor heat exchanger.

[0076] <Check valve bridge>

[0077] The check valve bridge 25 has four pipes and four check valves C connected to each pipe. The four check valves C are a first check valve C1, a second check valve C2, a third check valve C3, and a fourth check valve C4.

[0078] A main fluid pipe 55 is connected to the check valve bridge 25. Specifically, one end of the main fluid pipe 55 is connected to the inflow side of the second check valve C2 and the inflow side of the fourth check valve C4. The other end of the main fluid pipe 55 is connected to the outflow side of the first check valve C1 and the outflow side of the third check valve C3.

[0079] The check valve bridge 25 is connected to the liquid side end of the heat source-side heat exchanger 24 and the liquid side end of the utilization-side heat exchanger 27. Specifically, the outflow side of the second check valve C2 and the inflow side of the first check valve C1 are connected to the liquid side end of the heat source-side heat exchanger 24. The outflow side of the fourth check valve C4 and the inflow side of the third check valve C3 are connected to the liquid side end of the utilization-side heat exchanger 27.

[0080] The first to fourth check valves, C1 to C4, respectively allow refrigerant to flow into / out of the refrigerant. Figure 1 The refrigerant flows in the direction indicated by the arrow and restricts the flow of refrigerant in the opposite direction.

[0081] <Expansion Mechanism>

[0082] Expansion valve 26 expands the refrigerant to reduce its pressure. Expansion valve 26 corresponds to a pressure reducing mechanism. In this example, expansion valve 26 is a controllable expansion valve (e.g., an electronic expansion valve). Expansion valve 26 is connected to the main liquid line 55.

[0083] <Utilizing a side heat exchanger>

[0084] A heat exchanger 27 is used to exchange heat between refrigerant and water. The heat exchanger 27 has a first flow path 27a and a second flow path 27b. The first flow path 27a is for the refrigerant to flow through. The second flow path 27b is for the water to flow through. The second flow path 27b is connected midway through the utilization side loop 61 included in the utilization device. In the utilization side heat exchanger 27, the refrigerant flowing in the first flow path 27a exchanges heat with the water flowing in the second flow path 27b.

[0085] <Liquid Storage>

[0086] The receiver 28 is connected midway through the first suction pipe 51. The receiver 28 is a gas-liquid separator. Within the receiver 28, the refrigerant is separated into liquid and gaseous states. The receiver 28 is configured to allow only gaseous refrigerant to flow out.

[0087] Bypass circuit

[0088] The bypass circuit 60 has a bypass pipe PB and a bypass check valve 29. One end of the bypass pipe PB is connected to the outflow end of the first discharge pipe 52 and the inflow end of the second suction pipe 53. The other end of the bypass pipe PB is connected between the reservoir 28 in the first suction pipe 51 and the first compressor 21.

[0089] The bypass check valve 29 allows refrigerant to flow from the first suction pipe 51 to the inflow end of the second suction pipe 53, and restricts the flow of refrigerant in the opposite direction.

[0090] [Injection Circuit]

[0091] The injection circuit 30 is a circuit that supplies a portion of the refrigerant flowing in the main liquid line 55 to the suction side of the second compressor 22 during the second operation. The injection circuit 30 has an injection pipe PJ and an injection expansion valve 31.

[0092] One end of the injection pipe PJ is connected between the expansion valve 26 and the check valve bridge 25 in the main liquid pipe 55. The other end of the injection pipe PJ is connected to the second suction pipe 53.

[0093] The injection expansion valve 31 is connected upstream of the intermediate heat exchanger 40 in the injection pipe PJ. The injection expansion valve 31 reduces the pressure of the refrigerant flowing in the injection pipe PJ.

[0094] [Intermediate heat exchanger]

[0095] The intermediate heat exchanger 40 has a third flow path 40a and a fourth flow path 40b. The third flow path 40a is connected midway through the main liquid pipe 55. The fourth flow path 40b is connected midway through the injection pipe PJ. In the intermediate heat exchanger 40, the refrigerant flowing in the main liquid pipe 55 exchanges heat with the refrigerant flowing in the fourth flow path 40b.

[0096] 〔sensor〕

[0097] The refrigeration unit 10 has various sensors, such as temperature sensors that detect the temperature of the refrigerant, pressure sensors that detect the pressure of the refrigerant, etc. The detection results (signals) of various sensors are sent to the control unit 100. For example, the refrigeration unit 10 has an internal temperature sensor 43, a first refrigerant temperature sensor 41, a second refrigerant temperature sensor 42, and an external air temperature sensor 44.

[0098] Internal temperature sensor 43 corresponds to the first temperature sensor 48. Internal temperature sensor 43 is disposed on the outer surface of the housing 21a of the first compressor 21. Internal temperature sensor 43 detects the temperature of the outer surface of the housing 21a. The internal temperature Th1 of the first compressor 21 is calculated based on the temperature of the outer surface of the housing 21a. The internal temperature Th1 of the first compressor 21 is based on the detected value by internal temperature sensor 43.

[0099] The first refrigerant temperature sensor 41 is installed on the heat exchanger 24 on the heat source side. The first refrigerant temperature sensor 41 detects the temperature of the refrigerant inside the heat exchanger 24 on the heat source side. When the heat exchanger 24 on the heat source side functions as an evaporator, the first refrigerant temperature sensor 41 detects the evaporation temperature Te1 of the heat exchanger 24 on the heat source side.

[0100] A second refrigerant temperature sensor 42 is provided on the utilization side heat exchanger 27. The second refrigerant temperature sensor 42 detects the temperature of the refrigerant flowing in the first flow path 27a of the utilization side heat exchanger 27. When the utilization side heat exchanger 27 functions as an evaporator, the second refrigerant temperature sensor 42 detects the evaporation temperature Te2 of the utilization side heat exchanger 27.

[0101] The external temperature sensor 44 detects the temperature of the outdoor air surrounding the refrigeration unit 10, i.e., the external temperature To. The external temperature sensor 44 is located outdoors.

[0102] [Suppression mechanism]

[0103] The refrigeration unit 10 has a suppression mechanism 50. The suppression mechanism 50 has a solenoid valve 33 and a control unit 100. The solenoid valve 33 corresponds to the valve of this disclosure. The solenoid valve 33 is connected between the first compressor 21 and the outlet end of the bypass pipe PB. The control unit 100 controls the solenoid valve 33. The control unit 100 switches the solenoid valve 33 between an open state and a closed state.

[0104] [Control Department]

[0105] like Figure 2 As shown, the refrigeration device 10 has a control unit 100. The control unit 100 has a microcomputer and a storage device for storing software for making the microcomputer work.

[0106] The control unit 100 controls the refrigerant circuit 20 based on signals from various sensors and control signals from external sources. The control unit 100 includes multiple communication lines that connect the first compressor 21, the second compressor 22, the four-way reversing valve 23, the expansion valve 26, the injection expansion valve 31, the solenoid valve 33, and various sensors.

[0107] The control unit 100 has at least an output unit that outputs control signals to the first compressor 21, the second compressor 22, the four-way reversing valve 23, the expansion valve 26, the injection expansion valve 31, and the solenoid valve 33. The control unit 100 also has an input unit that inputs the detection values ​​of each sensor.

[0108] [Operation of the refrigeration unit]

[0109] In the refrigeration apparatus 10 of the first embodiment, a first operation and a second operation are performed. The first operation includes a first heating operation and a first cooling operation. The second operation includes a second heating operation and a second cooling operation. In the second operation, the second compressor 22 functions as a high-level compressor, and the first compressor 21 functions as a low-level compressor. The refrigeration apparatus 10 performs a defrosting operation.

[0110] <First Heating Operation>

[0111] like Figure 3 As shown, in the first heating operation, a refrigeration cycle is performed where the heat exchanger on the utilization side 27 acts as a condenser (radiator) and the heat source side heat exchanger 24 acts as an evaporator. Specifically, the four-way reversing valve 23 is set to the first state. The opening of the expansion valve 26 is appropriately adjusted. The injection expansion valve 31 is set to the fully closed state. The first compressor 21 stops operating, and the second compressor 22 starts operating.

[0112] The refrigerant injected from the second compressor 22 passes through the four-way reversing valve 23 and condenses by dissipating heat to the water in the utilization-side heat exchanger 27. The refrigerant flowing out of the utilization-side heat exchanger 27 passes through the check valve bridge 25 and flows in the main liquid line 55. The refrigerant flowing in the main liquid line 55 is depressurized by the expansion valve 26, passes through the check valve bridge 25 again, and evaporates in the heat source-side heat exchanger 24. The refrigerant flowing out of the heat source-side heat exchanger 24 passes sequentially through the four-way reversing valve 23, the liquid receiver 28, and the bypass pipe PB, and is drawn into the second compressor 22 and compressed.

[0113] <Second heating operation>

[0114] like Figure 4 As shown, in the second heating operation, a refrigeration cycle is performed where the heat exchanger on the utilization side 27 acts as a condenser (radiator) and the heat source side heat exchanger 24 acts as an evaporator. Specifically, the four-way reversing valve 23 is set to the first state. The opening degree of the expansion valve 26 and the opening degree of the injection expansion valve 31 are appropriately adjusted. Both the first compressor 21 and the second compressor 22 operate.

[0115] The refrigerant injected from the second compressor 22 passes through the four-way reversing valve 23 and condenses by dissipating heat to water in the utilization-side heat exchanger 27. The refrigerant flowing out of the utilization-side heat exchanger 27 passes through the check valve bridge 25 and flows in the main liquid line 55. The refrigerant flowing in the main liquid line 55 is subcooled by dissipating heat to the refrigerant flowing in the fourth flow line 40b in the third flow path 40a of the intermediate heat exchanger 40. Afterwards, a portion of the refrigerant flowing in the main liquid line 55 flows into the injection pipe PJ, and the remaining refrigerant is depressurized by the expansion valve 26 of the main liquid line 55.

[0116] The depressurized refrigerant evaporates in the heat exchanger 24 on the heat source side after passing through the check valve bridge 25. The refrigerant flowing out of the heat exchanger 24 passes sequentially through the four-way reversing valve 23 and the receiver 28, and is then drawn into the first compressor 21 and compressed. The refrigerant ejected from the first compressor 21 is drawn into the second compressor 22 and compressed.

[0117] On the other hand, the refrigerant flowing into the injection pipe PJ is depressurized by the injection expansion valve 31. In the fourth flow path 40b of the intermediate heat exchanger 40, the depressurized refrigerant absorbs heat from the refrigerant flowing in the third flow path 40a and evaporates. Afterward, the refrigerant flowing in the injection pipe PJ is introduced into the second suction pipe 53 of the second compressor 22.

[0118] <First Cooling Operation>

[0119] like Figure 5As shown, in the first cooling operation, a refrigeration cycle is performed where the heat source-side heat exchanger 24 acts as a condenser (radiator) and the utilization-side heat exchanger 27 acts as an evaporator. Specifically, the four-way reversing valve 23 is set to the second state. The opening of the expansion valve 26 is appropriately adjusted. The injection expansion valve 31 is set to the fully closed state. The first compressor 21 stops operating, and the second compressor 22 starts operating.

[0120] The refrigerant injected from the second compressor 22 passes through the four-way reversing valve 23 and condenses in the heat source-side heat exchanger 24. The refrigerant flowing out of the heat source-side heat exchanger 24 passes through the check valve bridge 25 and flows in the main liquid line 55. The refrigerant flowing in the main liquid line 55 is depressurized by the expansion valve 26, passes through the check valve bridge 25 again, and evaporates by absorbing heat from water in the utilization-side heat exchanger 27. The refrigerant flowing out of the utilization-side heat exchanger 27 passes sequentially through the four-way reversing valve 23, the liquid receiver 28, and the bypass pipe PB, and is then drawn into the second compressor 22 and compressed.

[0121] <Second Cooling Operation>

[0122] like Figure 6 As shown, in the second cooling operation, a refrigeration cycle is performed where the heat source-side heat exchanger 24 becomes a condenser (radiator) and the side heat exchanger 27 becomes an evaporator. Specifically, the four-way reversing valve 23 is set to the second state. The opening degree of the expansion valve 26 and the injection expansion valve 31 are appropriately adjusted. Both the first compressor 21 and the second compressor 22 operate.

[0123] Refrigerant ejected from the second compressor 22 condenses in the heat source-side heat exchanger 24 via the four-way reversing valve 23. Refrigerant flowing out of the heat source-side heat exchanger 24 flows in the main liquid line 55 via the check valve bridge 25. The refrigerant flowing in the main liquid line 55 is subcooled by dissipating heat from the refrigerant flowing in the fourth flow line 40b through the third flow path 40a of the intermediate heat exchanger 40. Afterwards, a portion of the refrigerant flowing in the main liquid line 55 flows into the injection pipe PJ, while the remaining refrigerant is depressurized by the expansion valve 26 of the main liquid line 55.

[0124] The depressurized refrigerant passes through check valve bridge 25 and evaporates by absorbing heat from water in utilization-side heat exchanger 27. The refrigerant flowing out of utilization-side heat exchanger 27 passes sequentially through four-way reversing valve 23 and receiver 28, and is drawn into first compressor 21 and compressed. The refrigerant sprayed from first compressor 21 is drawn into second compressor 22 and compressed.

[0125] On the other hand, the refrigerant flowing into the injection pipe PJ is depressurized by the injection expansion valve 31. In the fourth flow path 40b of the intermediate heat exchanger 40, the depressurized refrigerant absorbs heat from the refrigerant flowing in the third flow path 40a and evaporates. Afterward, the refrigerant flowing in the injection pipe PJ is introduced into the second suction pipe 53 of the second compressor 22.

[0126] <Defrosting Operation>

[0127] like Figure 5 As shown, during defrosting operation, the same actions as in the first cooling operation are performed. During defrosting operation, a refrigeration cycle is performed where the heat source-side heat exchanger 24 becomes a condenser (radiator) and the utilization-side heat exchanger 27 becomes an evaporator. As a result, the lower portion of the surface of the heat source-side heat exchanger 24 is heated from the inside. The refrigerant used for defrosting the heat source-side heat exchanger 24, after evaporating in the utilization-side heat exchanger 27, is drawn into the first compressor 21 and compressed again.

[0128] - Technical problems during operation -

[0129] When the refrigeration unit 10 is in its first heating operation, the internal temperature of the first compressor 21, which is in a stopped state, is approximately equal to the external air temperature. Under normal operating conditions, because the external air temperature is higher than the evaporation temperature of the heat exchanger 24 on the heat source side, the evaporation pressure of the heat exchanger 24 on the heat source side is lower than the internal pressure of the first compressor 21 in the stopped state. Therefore, the refrigerant flowing in the bypass pipe PB flows into the suction side of the driven second compressor 22, while the refrigerant has difficulty flowing into the discharge side of the first compressor 21 in the stopped state.

[0130] However, as Figure 7 As shown, during the first heating operation, for example, on a morning when the outside temperature is extremely low, if the outside temperature rises sharply due to sudden sunlight, the evaporation pressure of the heat exchanger 24 on the heat source side will rise sharply. In contrast, the first compressor 21, in its stopped state, requires time for its internal temperature to rise to the same level as the outside temperature due to its heat capacity. At this time, sometimes the internal temperature of the first compressor 21 is lower than the evaporation temperature of the heat exchanger 24 on the heat source side. Figure 7 The diagram shows that during the period Δt from time t1 to time t2, the evaporation temperature Te1 of the heat exchanger 24 on the heat source side is higher than the internal temperature Th1 of the first compressor 21.

[0131] In this state, because the internal pressure of the first compressor 21 is lower than the evaporation pressure of the heat exchanger 24 on the heat source side, a portion of the refrigerant flowing in the bypass pipe PB flows into the discharge side of the first compressor 21, which has a lower pressure. If refrigerant flows into the first compressor 21, which is in a stopped state, the overall refrigerant supply in the refrigerant circuit 20 is insufficient, and the capacity of the refrigeration unit 10 decreases. If the first compressor 21 is driven during the first heating operation (switching to the second heating operation), the lubrication of the compression mechanism 21d of the first compressor 21 is impaired, and the reliability of the first compressor 21 is reduced.

[0132] The same phenomenon may occur during defrosting operation. If defrosting operation is performed at extremely low temperatures, the refrigerant that has dissipated heat in the heat source side heat exchanger 24 is depressurized by the expansion valve 26 and evaporates in the utilization side heat exchanger 27. Since the evaporation temperature of the utilization side heat exchanger 27 is transitionally higher than the internal temperature of the first compressor 21 at this time, refrigerant flows into the first compressor 21 during defrosting operation (first cooling operation).

[0133] Considering this problem, the refrigeration device 10 of this embodiment inhibits the flow of refrigerant into the first compressor 21 when a first condition is met. This first condition is that the internal pressure of the first compressor 21, which is in a stopped state during first operation, is lower than the evaporation pressure of the heat exchangers 24 and 27, which function as evaporators. Specifically, when the first condition is met, the inhibition mechanism 50 inhibits the flow of refrigerant that has flowed out from the bypass pipe PB into the discharge side of the first compressor 21.

[0134] Reference Figure 8 The operation of the suppression mechanism 50 during the first heating operation will be explained in detail.

[0135] In step ST1, the control unit 100 starts the first heating operation. Specifically, the control unit 100 switches the four-way reversing valve 23 to the first state. The control unit 100 sets the first compressor 21 to the stop state and drives the second compressor 22. The control unit 100 appropriately adjusts the opening of the expansion valve 26 and sets the injection expansion valve 31 to the fully closed state. If the first heating operation starts, step ST2 is executed.

[0136] In step ST2, the control unit 100 determines whether a first condition is met. The first condition indicates that the internal pressure of the first compressor 21 is lower than the evaporation pressure of the heat exchanger 24 on the heat source side. Here, the relationship between the internal pressure of the first compressor 21 and the evaporation pressure of the heat exchanger 24 on the heat source side is related to the relationship between the internal temperature of the first compressor 21 and the evaporation temperature of the heat exchanger 24 on the heat source side. Therefore, if the internal temperature Th1 of the first compressor 21 is lower than the evaporation temperature Te1 of the heat exchanger 24 on the heat source side, the control unit 100 considers the first condition to be met. If the first condition is determined to be met, step ST3 is executed. If the first condition is determined not to be met, step ST4 is executed.

[0137] In step ST3, the suppression mechanism 50 operates. Specifically, the control unit 100 sets the solenoid valve 33 to the closed state. When the solenoid valve 33 is set to the closed state, the discharge side of the first compressor 21 is disconnected from the suction side of the second compressor 22 and the outlet end of the bypass pipe PB. Thus, under the condition that the first condition is met, it is possible to prevent the refrigerant that has flowed out of the bypass pipe PB from being drawn into the first compressor 21. After step ST3 is completed, step ST2 is executed again.

[0138] In step ST4, the suppression mechanism 50 is deactivated. Specifically, the control unit 100 sets the solenoid valve 33 to the open state. After step ST4 is completed, step ST5 is executed.

[0139] In step ST5, the control unit 100 determines whether to start the second heating operation. If it determines that the second heating operation should not be started, the first heating operation continues, and step ST2 is executed again. If it determines that the second heating operation should be started, the control unit 100 drives the first compressor 21.

[0140] Next, refer to Figure 9 The operation of the suppression mechanism 50 during defrosting is explained in detail.

[0141] In step ST11, the control unit 100 initiates the first cooling operation, i.e., defrosting operation. Specifically, the control unit 100 switches the four-way reversing valve 23 to the second state. The control unit 100 sets the first compressor 21 to the stop state and drives the second compressor 22. The control unit 100 appropriately adjusts the opening of the expansion valve 26 and sets the injection expansion valve 31 to the fully closed state. If defrosting operation has started, step ST12 is executed.

[0142] In step ST12, the control unit 100 determines whether the first condition is met. Similar to step ST2 above, if the internal temperature Th1 of the first compressor 21 is lower than the evaporation temperature Te2 of the utilization-side heat exchanger 27, the control unit 100 considers the first condition to be met. If the first condition is determined to be met, step ST13 is executed. If the first condition is determined to be unmet, step ST14 is executed.

[0143] In step ST13, the suppression mechanism 50 operates. Specifically, the control unit 100 sets the solenoid valve 33 to the closed state. After step ST13 is completed, step ST12 is executed again.

[0144] In step ST14, the suppression mechanism 50 is deactivated. Specifically, the control unit 100 sets the solenoid valve 33 to the open state. After step ST14 is completed, step ST15 is executed.

[0145] In step ST15, the control unit 100 determines whether to terminate the defrosting operation. If it determines that the defrosting operation should not be terminated, the defrosting operation continues, and step ST12 is executed again. If it determines that the defrosting operation should be terminated, the process ends.

[0146] -Effects of the implementation method-

[0147] In feature (1) of the embodiment, the refrigeration device 10 includes a suppression mechanism 50, which, during the first operation of a refrigeration cycle in which the first compressor 21 is stopped and the second compressor 22 is driven, suppresses the flow of refrigerant into the first compressor 21 when a first condition indicating that the internal pressure of the first compressor 21 is lower than the evaporation pressure of the evaporators 24 and 27 is met.

[0148] According to feature (1) of the embodiment, during the first heating operation, when the first condition is met, the flow of refrigerant flowing in the bypass pipe PB into the ejection side of the first compressor 21 is suppressed. Because the flow of refrigerant into the first compressor 21 in the stopped state can be suppressed, the shortage of refrigerant during the first operation can be suppressed. As a result, during the first heating operation, for example, in the early morning when the outside temperature is extremely low, even if the outside temperature rises sharply due to sudden sunlight, the decrease in the capacity of the refrigeration unit 10 can be suppressed.

[0149] In addition, because the flow of refrigerant into the first compressor 21 in the stopped state can be suppressed, the dissolution of oil in the first compressor 21 in the stopped state into the refrigerant can be suppressed. As a result, when switching from the first heating operation to the second heating operation, damage to the lubrication of the compression mechanism 21d inside the first compressor 21 can be suppressed.

[0150] In feature (2) of the implementation, the first condition is that the internal temperature of the first compressor 21 is lower than the evaporation temperature of the heat exchanger 24 (evaporator) on the heat source side.

[0151] According to feature (2) of the implementation method, by detecting the internal temperature Th1 of the first compressor 21 and the evaporation temperature Te1 of the heat source side heat exchanger 24, it is possible to determine whether the first condition is met.

[0152] In feature (3) of the implementation, the internal temperature sensor 43 detects the temperature of the outer surface of the housing 21a of the first compressor 21, and the internal temperature of the first compressor 21 is based on the value detected by the internal temperature sensor 43.

[0153] According to feature (3) of the implementation method, the internal temperature Th1 of the first compressor 21 can be inferred based on the detection value of the internal temperature sensor 43.

[0154] In feature (4) of the embodiment, the suppression mechanism 50 has a solenoid valve 33 (valve) connected between the first compressor 21 and the outlet end of the bypass pipe PB, and the solenoid valve 33 is in a closed state when the first condition is met.

[0155] According to feature (4) of the embodiment, when the first condition is met, the control unit 100 sets the solenoid valve 33 to the closed state. As a result, it is possible to suppress the flow of refrigerant from the bypass pipe PB into the first compressor 21 when the first condition is met.

[0156] (Modification 1 of the first embodiment)

[0157] like Figure 10 As shown, in the refrigeration apparatus 10 of the first embodiment, the first compressor 21 has a heater 37 but no solenoid valve 33. The heater 37 is arranged in an oil reservoir (not shown) of the housing 21a. The oil reservoir is formed at the bottom of the housing 21a. The heater 37 is an electric heater that heats up by receiving power from the power source S. The heater 37 inhibits the dissolution of oil into the refrigerant by heating the oil reservoir.

[0158] In this modified example, the suppression mechanism 50 includes a heater 37 and a control unit 100. The heater 37 corresponds to the heating unit 36. If the first condition is met, the heater 37 heats the first compressor 21. Specifically, the heater 37, which receives power from the control unit 100, heats the interior of the first compressor 21. (See reference...) Figure 11 The operation of the suppression mechanism 50 in Modified Example 2 will be explained.

[0159] In step ST21, the control unit 100 performs the same operation as in step ST1 of the first embodiment.

[0160] In step ST22, similar to step ST2 in the first embodiment, the control unit 100 determines whether the first condition is met. If the first condition is met, step ST23 is executed. If the first condition is not met, step ST24 is executed.

[0161] In step ST23, the suppression mechanism 50 operates. Specifically, the control unit 100 energizes the heater 37. The energized heater 37 generates heat, heating the interior of the first compressor 21. After executing step ST23, step ST22 is executed again.

[0162] In step ST24, the operation of the suppression mechanism 50 is deactivated. Specifically, the control unit 100 stops energizing the heater 37.

[0163] In step ST25, the control unit 100 determines whether to start the second heating operation. If it determines that the second heating operation should not be started, the first heating operation continues, and step ST22 is executed again. If it determines that the second heating operation should be started, the control unit 100 drives the first compressor 21.

[0164] According to this modified example, if the first condition is met during the first operation, the internal temperature of the first compressor 21 will rise due to the heating of the heater 37. Therefore, it is possible to prevent the internal temperature Th1 of the first compressor 21 from falling below the evaporation temperature Te1 of the heat exchanger 24, which functions as an evaporator. As a result, it is possible to prevent refrigerant from flowing into the first compressor 21 during the first operation.

[0165] In addition, the heater 37 can also be used as the heating and suppression mechanism 50 for the oil storage section. Since it is not necessary to install a component like the solenoid valve 33 in the first embodiment as the suppression mechanism 50 in the refrigeration device 10, the increase in manufacturing cost of the refrigeration device 10 can be suppressed.

[0166] In addition, since power is only required when the first condition is met, it can suppress the increase in power consumption and also suppress the increase in the operating cost of the refrigeration device 10.

[0167] (Modification 2 of the first embodiment)

[0168] The refrigeration apparatus 10 in the first embodiment, variant 2, does not have a solenoid valve 33. In this variant, the suppression mechanism 50 has an expansion valve 26 and a control unit 100. The expansion valve 26 corresponds to the pressure reducing mechanism. When a first condition is met, it reduces the evaporation pressure of the evaporator. (See reference...) Figure 12 The operation of the control unit 100 in this modified example will be explained.

[0169] In step ST31, the control unit 100 performs the same operation as in step ST1 of the first embodiment.

[0170] In step ST32, similar to step ST2 in the first embodiment, the control unit 100 determines whether the first condition is met. If the first condition is met, step ST33 is executed. If the first condition is not met, step ST34 is executed.

[0171] In step ST33, the suppression mechanism 50 operates. Specifically, the control unit 100 adjusts the opening of the expansion valve 26 to reduce the pressure on the refrigerant. After step ST33 is executed, step ST32 is executed again.

[0172] In step ST34, the suppression mechanism 50 is released. Specifically, the control unit 100 stops adjusting the opening of the expansion valve 26. After step ST34, step ST35 is executed.

[0173] In step ST35, the control unit 100 determines whether to start the second heating operation. If it determines that the second heating operation should not be started, the first heating operation continues, and step ST32 is executed again. If it determines that the second heating operation should be started, the control unit 100 drives the first compressor 21.

[0174] According to this modified example, when the first condition is met, the control unit 100 adjusts the opening of the expansion valve 26 to reduce the opening. As a result, the refrigerant pressure is reduced, and the evaporation temperature Te1 in the heat exchanger 24 on the heat source side decreases. If the evaporation temperature Te1 decreases, the evaporation pressure in the heat exchanger 24 on the heat source side also decreases. Consequently, because the evaporation pressure can be made lower than the internal pressure of the first compressor 21, the inflow of refrigerant into the first compressor 21 during the first operation can be suppressed.

[0175] In addition, the expansion valve 26 can be used as both the refrigeration cycle operation and the suppression mechanism 50 of the refrigeration device 10. Therefore, it is not necessary to install a component like the solenoid valve 33 of the first embodiment as the suppression mechanism 50 in the refrigeration device 10, so it is possible to suppress the increase in the manufacturing cost of the refrigeration device 10.

[0176] (Other implementation methods)

[0177] The above implementation method can also adopt the following structure.

[0178] like Figure 13 As shown, the first temperature sensor 48 of the refrigeration device 10 can also be at least one of the following: internal temperature sensor 43, internal temperature sensor 45, suction pipe temperature sensor 47, and external air temperature sensor 44.

[0179] An internal temperature sensor 45 is disposed inside the housing 21a. The internal temperature sensor 45 detects the temperature inside the housing 21a. An inhalation tube temperature sensor 47 is connected to the first inhalation tube 51. The inhalation tube temperature sensor 47 detects the temperature of the first inhalation tube 51. An ejection tube temperature sensor 46 is connected to the first ejection tube 52. The ejection tube temperature sensor 46 detects the temperature of the first ejection tube 52.

[0180] In other words, the first temperature sensor 48 can also be a sensor that detects the temperature of at least one of the following: the interior of the housing 21a, including the outer surface of the housing 21a in the first embodiment; the first suction pipe 51; the first discharge pipe 52; and the outdoor air. The internal temperature of the first compressor 21 is based on the detection value detected by the first temperature sensor 48.

[0181] The heating element 36 can also be an electric motor 21b mounted on the first compressor 21. The electric motor 21b is energized with a single phase loss when the first condition is met. Single phase loss energization refers to an energized state where, for example, one or more phases of the three-phase power supply S are not operating. Therefore, although the electric motor 21b is not driven, it remains energized. If this state continues, the coils of the electric motor 21b heat up, and the internal temperature of the first compressor 21 rises. This prevents the internal temperature of the first compressor 21 from falling below the evaporation temperature of the evaporators 24 and 27. As a result, it prevents refrigerant from flowing into the first compressor 21 during the first operation.

[0182] The control unit 100 may also include a refrigerant pressure sensor (not shown) for detecting the evaporation pressure of the refrigerant circuit 20 and an internal pressure sensor (not shown) for detecting the internal pressure of the first compressor 21. During the first operation, when the pressure value detected by the internal pressure sensor is lower than the evaporation pressure detected by the refrigerant pressure sensor, the control unit 100 can determine that a first condition has been met. Since the evaporation pressure of the evaporator and the internal pressure of the first compressor 21 are directly detected, it is possible to reliably prevent the evaporation pressure from exceeding the internal pressure.

[0183] The control unit 100 can also determine the evaporator pressure based on the temperature detected by the first temperature sensor 48. Specifically, the control unit 100 can determine the evaporation pressure of the heat source-side heat exchanger 24 based on the saturation pressure corresponding to the temperature detected by the first refrigerant temperature sensor 41. The control unit 100 can also determine the evaporation pressure of the utilization-side heat exchanger 27 based on the saturation pressure corresponding to the temperature detected by the second refrigerant temperature sensor 42. The control unit 100 can determine the value of the internal pressure of the first compressor 21 based on data (information) representing the relationship between the internal temperature of the first compressor 21 and the first compressor 21.

[0184] The suppression mechanism 50 can also begin operating before the first condition is met. In this case, the control unit 100, for example, predicts the evaporation temperature of the evaporator and the internal temperature of the first compressor 21 based on the degree of rise in the external temperature, and infers whether the first condition is met. For example, in Figure 7 In this scenario, if the first condition is presumed to be met at time t1, the suppression mechanism 50 operates before time t1. Therefore, it is possible to reliably suppress the flow of refrigerant into the first compressor 21 at the point in time (time t1) when the first condition is met.

[0185] The suppression mechanism 50 can also be activated during the period Δt in which the first condition is met, or during a portion of the period Δt. When the suppression mechanism 50 is activated during the period Δt, the flow of refrigerant into the first compressor 21 can be reliably suppressed.

[0186] The suppression mechanism 50 can also continue to operate after the period Δt (after time t2). This reliably suppresses the flow of refrigerant into the first compressor 21.

[0187] Valve 33 can be a flow regulating valve or an expansion valve.

[0188] The pressure reducing mechanism 26 can also be an expander, a capillary tube, etc. In the case where the pressure reducing mechanism 26 is a capillary tube, a valve (not shown) and a branch pipe (not shown) bypassing the valve are provided on the main liquid pipe 55 of the refrigerant circuit 20. The capillary tube is connected to this branch pipe.

[0189] The first compressor 21 and the second compressor 22 can also be other compressors such as rotary, oscillating piston, turbine, screw, etc.

[0190] In the refrigerant circuit 20, a compressor may also be further connected to the discharge side of the second compressor 22. In other words, the refrigerant circuit 20 can also perform a multi-stage compression refrigeration cycle with more than three compressors.

[0191] The above describes the embodiments and variations, but it is understood that various changes can be made to the scheme and specific circumstances without departing from the spirit and scope of the claims. As long as the function of the object of this disclosure is not affected, the above embodiments and variations can be appropriately combined or substituted. The use of "first," "second," etc., as described above is used to distinguish the terms assigned to these descriptions and is not limited to the number or order of these terms.

[0192] -Industry Applicability-

[0193] In summary, this disclosure is useful for refrigeration devices.

[0194] - Symbol Explanation -

[0195] 10 Refrigeration unit

[0196] 20 Refrigerant Circuit

[0197] 21 First Compressor

[0198] 21a Casing

[0199] 21b Electric motor

[0200] 22 Second compressor

[0201] 26. Expansion valve (pressure reducing mechanism)

[0202] 33. Solenoid valve (valve)

[0203] 36 Heating section

[0204] 37 Heater

[0205] 48 First Temperature Sensor

[0206] 50 Suppression mechanism

[0207] 51 First suction tube (suction tubing)

[0208] 52 First ejection pipe (ejection conduit)

Claims

1. A refrigeration apparatus including a refrigerant circuit (20) including a first compressor (21), a second compressor (22) connected to a discharge side of the first compressor (21), and an evaporator (24, 27), the refrigerant circuit (20) being capable of switching between a first operation in which a refrigeration cycle in which the first compressor (21) is stopped and the second compressor (22) is driven is performed, and a second operation in which a refrigeration cycle in which the first compressor (21) and the second compressor (22) are driven is performed, characterized by: the refrigerant circuit (20) having a bypass pipe (PB) connecting a suction side and a discharge side of the first compressor (21), the refrigeration apparatus including a suppression mechanism (50) that, in the first operation, suppresses flow of refrigerant that has flowed out from the bypass pipe (PB) into the discharge side of the first compressor (21) when a first condition in which a pressure in the first compressor (21) is lower than an evaporation pressure of the evaporator (24, 27) is satisfied.

2. The refrigeration apparatus according to claim 1, characterized in that: the first condition is a condition in which a temperature in the first compressor (21) is lower than an evaporation temperature of the evaporator (24, 27).

3. The refrigeration apparatus according to claim 2, characterized in that: the refrigeration apparatus includes a first temperature sensor (48), the first temperature sensor (48) detects a temperature of at least one of an outer surface of a casing (21a) of the first compressor (21), an inside of the casing (21a) of the first compressor (21), a suction pipe (51) of the first compressor (21), a discharge pipe (52) of the first compressor (21), and outdoor air, and the temperature in the first compressor (21) is a value based on a detection value detected by the first temperature sensor (48).

4. The refrigeration apparatus according to any one of claims 1 to 3, characterized in that: the suppression mechanism (50) has a valve (33) connected between the first compressor (21) and a flow-out end of the bypass pipe (PB), and the valve (33) is in a closed state when the first condition is satisfied.

5. The refrigeration apparatus according to any one of claims 1 to 3, characterized in that: the suppression mechanism (50) includes a heating portion that heats the first compressor (21) when the first condition is satisfied.

6. The refrigeration apparatus according to claim 5, characterized in that: the heating portion (36) includes a heater (37) provided in the first compressor (21) and energized when the first condition is satisfied.

7. The refrigeration apparatus according to claim 5, characterized in that: the heating portion (36) includes a motor (21b) provided in the first compressor (21) and energized with a phase missing when the first condition is satisfied. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 8. The refrigerating apparatus according to any one of claims 1 to 3, characterized by: the suppression mechanism includes a pressure reducing mechanism (26) that reduces the evaporation pressure of the evaporator (24, 27) when the first condition is established.

Images