EP4137756A1

EP4137756A1 - Heat source unit, refrigeration cycle device, and refrigerator

Info

Publication number: EP4137756A1
Application number: EP20931630.6A
Authority: EP
Inventors: Yusuke Arii; Hiroki Sato; Kota Suzuki
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2020-04-14
Filing date: 2020-04-14
Publication date: 2023-02-22
Also published as: EP4137756A4; WO2021210064A1; JPWO2021210064A1; JP7330367B2

Abstract

A heat source unit (2) includes: a first flow path (80-83, 89) to be connected to a load device (3) so as to form a circulation flow path through which a refrigerant circulates; a compression device (10), an oil separator (20), and a condenser (30) that are disposed in the first flow path; a second flow path (91, 93) to return the refrigerant that has passed through the condenser (30) to the compression device (10) from an intermediate-pressure port (G3), the second flow path branching from a branch point in the first flow path; a second expansion device (LEV2) disposed in the second flow path; and an oil distributor (150) that is configured to return refrigerating machine oil discharged from an oil outlet of the oil separator (20) to the compression device (10). The oil distributor (150) is capable of changing a ratio at which the refrigerating machine oil is distributed to the intermediate-pressure port (G3) and the suction port (G1).

Description

TECHNICAL FIELD

The present disclosure relates to a heat source unit, a refrigeration cycle device, and a refrigerator.

BACKGROUND ART

The form of a housing of a compressor includes a low-pressure shell and a high-pressure shell. In the low-pressure shell, refrigerant and lubricating oil before compression are stored in a case. In the high-pressure shell, refrigerant and lubricating oil after compression are stored in a case. In a case where the compressor employs a low-pressure shell, oil is returned from an oil separator to a suction pipe of the compressor. However, in a case where the compressor employs a high-pressure shell, in some models, oil is returned from an oil separator to an intermediate-pressure port of the compressor in order to improve the performance of a refrigeration cycle device.
WO 2019/026270 A discloses a refrigeration cycle device that makes oil from an oil separator flow into an injection flow path for injecting a refrigerant into an intermediate-pressure port of a compressor.

CITATION LIST

PATENT LITERATURE

PTL 1: WO 2019/026270 A

SUMMARY OF INVENTION

TECHNICAL PROBLEM

In a case where the compressor is a high-pressure shell, when oil from the oil separator is returned to the injection flow path to the intermediate port, the oil on a side of a suction port of the compressor is diluted at the time of return of the liquid refrigerant (so-called liquid back), and the lubricity of scrolling of the compressor may be reduced.
However, if the oil in the oil separator is returned to the suction port of the compressor by giving priority to preventing the return of the liquid refrigerant, the liquid refrigerant returned together with the oil does not circulate through an indoor unit, and thus performance of the refrigeration cycle device is deteriorated.
A heat source unit of a refrigeration cycle device according to the present disclosure solves the above problem, and an object of the heat source unit is to solve a shortage of oil in a compressor while minimizing a decrease in performance of the refrigeration cycle device.

SOLUTION TO PROBLEM

The present disclosure relates to a heat source unit of a refrigeration cycle device to be connected to a load device including a first expansion device and an evaporator. The heat source unit includes: a first flow path to be connected to the load device so as to form a circulation flow path through which a refrigerant circulates; a compression device to suck the refrigerant from a suction port and an intermediate-pressure port and to discharge the refrigerant through a discharge port, the compression device being disposed in the first flow path; an oil separator disposed downstream of the compression device in the first flow path, and having a refrigerant inlet, a refrigerant outlet, and an oil outlet; a condenser disposed downstream of the oil separator in the first flow path; a second flow path to return the refrigerant that has passed through the condenser to the compression device from the intermediate-pressure port, the second flow path branching from a branch point downstream of the condenser in the first flow path in a direction in which the refrigerant circulates; a second expansion device disposed in the second flow path; and an oil distributor to return refrigerating machine oil discharged from the oil outlet of the oil separator to the compression device via the intermediate-pressure port and the suction port. The oil distributor is configured to change a ratio at which the refrigerating machine oil is distributed to the intermediate-pressure port and the suction port.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the heat source unit, the refrigeration cycle device, and the refrigerator of the present disclosure, it is possible to achieve both improvement in reliability in an abnormal operation mode in such a case in which liquid refrigerant returns, and improvement in performance in a normal operation when the liquid refrigerant does not return.

BRIEF DESCRIPTION OF DRAWINGS

Fig. 1 is a diagram illustrating a configuration of a first investigation example of an oil return path of a refrigeration cycle device having an intermediate-pressure injection flow path.
Fig. 2 is a diagram illustrating a configuration of a second investigation example of an oil return path of a refrigeration cycle device having an intermediate-pressure injection flow path.
Fig. 3 is an entire configuration diagram of a refrigeration cycle device 1 according to a first embodiment.
Fig. 4 is a diagram illustrating a control state of an electromagnetic valve of an oil distributor in the first embodiment.
Fig. 5 is a flowchart for describing control of the electromagnetic valve of the oil distributor executed by a control device in the first embodiment.
Fig. 6 is a diagram illustrating a control state of an electromagnetic valve of an oil distributor in a second embodiment.
Fig. 7 is a flowchart for describing control of the electromagnetic valve of the oil distributor executed by a control device in the second embodiment.
Fig. 8 is an entire configuration diagram of a refrigeration cycle device 201 according to a third embodiment.
Fig. 9 is a flowchart for describing control of the electromagnetic valve of the oil distributor executed by a control device in the third embodiment.
Fig. 10 is an entire configuration diagram of a refrigeration cycle device 301 according to a fourth embodiment.
Fig. 11 is a diagram illustrating a first example of a control state of a flow regulating valve of an oil distributor in the fourth embodiment.
Fig. 12 is a diagram illustrating a second example of a control state of a flow regulating valve of an oil distributor in the fourth embodiment.
Fig. 13 is an entire configuration diagram of a refrigeration cycle device 401 according to a fifth embodiment.
Fig. 14 is a diagram illustrating a control state of an electromagnetic valve of an oil distributor in the fifth embodiment.
Fig. 15 is a flowchart for describing control of the electromagnetic valve of the oil distributor executed by a control device in the fifth embodiment.
Fig. 16 is an entire configuration diagram of a refrigeration cycle device 501 according to a modification of the fifth embodiment.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention will be described in detail with reference to the drawings. Hereinafter, a plurality of embodiments will be described, but it is planned from the beginning of the application that configurations described in the embodiments are appropriately combined. The same or corresponding parts in the drawings are denoted by the same reference numerals, and descriptions thereof will not be repeated.

First embodiment.

Fig. 1 is a diagram illustrating a configuration of a first investigation example of an oil return path of a refrigeration cycle device having an intermediate-pressure injection flow path. The refrigeration cycle device illustrated in Fig. 1 includes a main refrigerant flow path through which a refrigerant circulates in order of a discharge port G2 of a compression device 10, an oil separator 20, a condenser 30, a liquid receiver (receiver) 40, a first expansion device LEV1, an evaporator 60, and a suction port G1 of compression device 10, and an injection flow path through which the refrigerant is injected from an outlet portion of liquid receiver 40 to an intermediate-pressure port G3 of compression device 10 via a second expansion device LEV2.
In this configuration, oil separated in oil separator 20 is returned to suction port G1 of the compressor. Second expansion device LEV2 adjusts the flow rate of the refrigerant flowing through the injection flow path to control the discharge temperature of compression device 10.
As an advantage in this case, lubricity of the sliding portion in compression device 10 can be ensured. On the other hand, the refrigerant is also dissolved in the oil returned from oil separator 20 to compression device 10. Therefore, there is a disadvantage that an amount of refrigerant circulating on a side of evaporator 60 decreases by the amount of refrigerant dissolved in the oil, and capability and performance of the refrigeration cycle device decrease.
Fig. 2 is a diagram illustrating a configuration of a second investigation example of an oil return path of a refrigeration cycle device having an intermediate-pressure injection flow path.
There is a case, as in the refrigeration cycle device having the configuration illustrated in Fig. 2, in which oil separated from oil separator 20 is returned to intermediate-pressure port G3 of compression device 10. When oil is returned to intermediate-pressure port G3, refrigerant may be dissolved in the oil. However, the melted refrigerant can be used as a part of the refrigerant to be injected into compression device 10 in order to lower the discharge temperature. As a result, assuming that the discharge temperature of compression device 10 is the same, an opening degree of second expansion device LEV2 can be made lower in the configuration of Fig. 2 than in the configuration of Fig. 1, and an amount of liquid refrigerant circulated to evaporator 60 can be increased. Therefore, an energy loss is smaller in the configuration illustrated in Fig. 2 than in the oil return configuration illustrated in Fig. 1.
However, when the liquid refrigerant returns to suction port G1 of compression device 10, concentration of the oil decreases. Accordingly, lubrication may be insufficient inside compression device 10 from suction port G1 to intermediate-pressure port G3 in which the oil does not enter.
Refrigeration cycle device 1 according to a first embodiment can solve the problem in the above investigation examples.
Fig. 3 is an entire configuration diagram of refrigeration cycle device 1 according to the first embodiment. Fig. 1 functionally illustrates a connection relationship and an arrangement configuration of the devices in the refrigeration cycle device, and does not necessarily illustrate an arrangement in a physical space.
Referring to Fig. 3, refrigeration cycle device 1 includes a heat source unit 2, a load device 3, and extension pipes 84, 88. Since heat source unit 2 is usually disposed outside the room or outdoors, heat source unit 2 may be referred to as an outdoor unit or an exterior unit. In the present embodiment, heat source unit 2 operates as a cold source that discharges heat to the outdoors.
Heat source unit 2 of refrigeration cycle device 1 is connected to load device 3 by extension pipes 84, 88.
Heat source unit 2 includes compression device 10, oil separator 20, condenser 30, liquid receiver 40, and pipes 80 to 83 and 89. In the first embodiment, compression device 10 includes one compressor having three ports. Pipe 80 connects discharge port G2 of compression device 10 and oil separator 20. Pipe 81 connects oil separator 20 and condenser 30. Pipe 82 connects condenser 30 and liquid receiver 40. Pipe 83 connects liquid receiver 40 and a refrigerant outlet of heat source unit 2. Liquid receiver 40 is disposed between pipe 82 and pipe 83, and stores a refrigerant.
A flow path from pipe 89 to pipe 83 via compression device 10, pipe 80, oil separator 20, pipe 81, condenser 30, pipe 82, and liquid receiver 40, together with load device 3, forms a circulation flow path through which a refrigerant circulates. Hereinafter, this circulation flow path is also referred to as a "main circuit" of the refrigeration cycle.
Heat source unit 2 further includes pipes 91, 93, and second expansion device LEV2 disposed between pipe 91 and pipe 93. Pipe 91 causes the refrigerant to flow from pipe 83 connected to an outlet of liquid receiver 40 in the circulation flow path to second expansion device LEV2. Pipe 93 causes the refrigerant to flow from second expansion device LEV2 to compression device 10. Hereinafter, this flow path that branches from the main circuit and sends the refrigerant to compression device 10 via second expansion device LEV2 is referred to as an "injection flow path".
Load device 3 includes an electromagnetic valve 70, first expansion device LEV1, evaporator 60, and pipes 85, 86, 87. As first expansion device LEV1, for example, an expansion valve can be used. Preferably, first expansion device LEV1 is a temperature expansion valve controlled independently of heat source unit 2. Electromagnetic valve 70 is closed when a state on a side of load device 3 does not require a refrigerant.
Compression device 10 compresses the refrigerant sucked from pipe 89 and pipe 93, and discharges the compressed refrigerant to pipe 80. Compression device 10 includes suction port G1, discharge port G2, and intermediate-pressure port G3. Compression device 10 sucks the refrigerant having passed through evaporator 60 from suction port G1 and discharges the refrigerant from discharge port G2 toward condenser 30.
Pipe 93 causes the refrigerant to flow from an outlet of second expansion device LEV2 to intermediate-pressure port G3 of compression device 10. As second expansion device LEV2, for example, an expansion valve can be used. Preferably, second expansion device LEV2 is an electronic expansion valve whose opening degree is changed according to a signal given from outside.
Compression device 10 adjusts a rotational speed according to a control signal from a control device 100. A circulation amount of the refrigerant is adjusted by adjusting the rotation speed of compression device 10, and thus the refrigeration capacity of refrigeration cycle device 1 can be adjusted. As compression device 10, various types can be adopted, examples of which include a scroll type, a rotary type, a screw type, and the like.
Condenser 30 condenses the refrigerant discharged from compression device 10 and passed through oil separator 20, and flows the condensed refrigerant to pipe 82. Condenser 30 causes a high-temperature and high-pressure gas refrigerant discharged from compression device 10 to exchange heat with outside air. By this heat exchange, the refrigerant that has dissipated heat condenses and changes into a liquid phase. A fan (not illustrated) supplies condenser 30 with outside air with which the refrigerant exchanges heat in condenser 30. A refrigerant pressure PH of compression device 10 on discharge side can be adjusted by adjusting the rotational speed of the fan.
Heat source unit 2 further includes pressure sensors 110,111, temperature sensors 121,122, control device 100 that controls heat source unit 2, and an oil distributor 150 that distributes oil in oil separator 20.
Pressure sensor 110 detects a pressure PL of the refrigerant sucked into compression device 10, and outputs the detected value to control device 100. Pressure sensor 111 detects pressure PH of the refrigerant discharged from compression device 10, and outputs the detected value to control device 100.
Temperature sensor 121 detects a temperature T1 of the refrigerant discharged from compression device 10, and outputs the detected value to control device 100. Temperature sensor 122 detects a temperature T2 of the refrigerant sucked into compression device 10, and outputs the detected value to control device 100.
Oil distributor 150 includes a pipe 94, a pipe 95, a first valve SV1, and a second valve SV2. For example, electromagnetic valves can be used as first valve SV1 and second valve SV2. Pipe 94 connects an oil outlet of oil separator 20 and pipe 93. Pipe 95 connects the oil outlet of oil separator 20 and pipe 89. First valve SV1 is provided in pipe 94, and opens and closes a flow path of the oil and the refrigerant. Second valve SV2 is provided in pipe 95, and opens and closes the flow path of the oil and the refrigerant.
Control device 100 includes a CPU (Central Processing Unit) 102, a memory 104 (a ROM (Read Only Memory) and a RAM (Random Access Memory)), an input/output buffer (not shown) for inputting and outputting various signals, and the like. CPU 102 extracts programs stored in the ROM to a RAM or the like, and executes the programs. The programs stored in the ROM are programs in each of which a processing procedure of control device 100 is described. Control device 100 executes control of the devices in heat source unit 2 according to these programs. The control is not limited to software processing, but can be processed by dedicated hardware (electronic circuit).
In the present embodiment, oil distributor 150 is able to change a ratio at which the refrigerating machine oil is distributed to intermediate-pressure port G3 and suction port G1. Since oil distributor 150 changes the distribution by first valve SV1 and second valve SV2, the distribution ratio can be changed in three ways of (100%, 0%), (0%, 100%), and (0%, 0%) by a combination of (ratio% of intermediate-pressure port G3 and ratio% of suction port G1). For example, when an amount of oil in the compressor is excessive, both first valve SV1 and second valve SV2 can be closed to store refrigerating machine oil in oil separator 20.
As described above, heat source unit 2 of refrigeration cycle device 1 is provided with two oil return pipes from oil separator 20: pipe 95 connected to a suction pipe of compression device 10, and pipe 94 connected to intermediate-pressure port G3 of compression device 10. First valve SV1 and second valve SV2 are respectively provided in pipe 94 and pipe 95, and oil distributor 150 is able to switch the flow path for returning oil.
Fig. 4 is a diagram illustrating a control state of the electromagnetic valve of the oil distributor in the first embodiment. As illustrated in Fig. 4, in a normal state, first valve SV1 is opened and second valve SV2 is closed, to prioritize performance of refrigeration cycle device 1. On the other hand, when liquid refrigerant return to compression device 10 is detected, first valve SV1 is closed and second valve SV2 is opened. As a result, when liquid refrigerant return is detected, lubricity of compression device 10 is improved, and high-temperature oil and refrigerant return to the suction side of compression device 10, leading to elimination of an increase in suction superheat degree, that is, liquid refrigerant return.
Fig. 5 is a flowchart for describing control of the electromagnetic valve of the oil distributor executed by the control device in the first embodiment. In step S1, control device 100 determines whether or not liquid refrigerant return is detected.
The liquid refrigerant return can be detected by observing a decrease in the superheat degree (suction heat degree) of the refrigerant sucked by compression device 10. Since the suction heat degree is interlocked with the superheating degree of the refrigerant discharged from compression device 10 (discharge heat degree), a decrease in the discharge superheat degree may be detected.
Specifically, in step S1, control device 100 determines that the liquid refrigerant has returned when the suction heat degree or the discharge superheat degree falls below a certain threshold value.
The discharge superheat degree (T1-CT) is obtained from detected temperature T1 of temperature sensor 121 provided in a compressor discharge pipe as with a saturation temperature CT corresponding to pressure PH detected by pressure sensor 111 provided in the discharge pipe of compression device 10. The suction heat degree (T2-ET) is obtained from detection temperature T2 of temperature sensor 122 provided in a compressor suction pipe as with a saturation temperature ET corresponding to a detection pressure Pl of pressure sensor 110 provided in pipe 89 connected to suction port G1 of compression device 10.
When it is determined no liquid return is detected (NO in S1), control device 100 performs control to open first valve SV1 and close second valve SV2 in step S3. On the other hand, when it is determined that the liquid return is detected (YES in S1), control device 100 performs control to close first valve SV1 and open second valve SV2 in step S2.
As described above, by controlling oil distributor 150, the operation focusing on the capability and performance of refrigeration cycle device 1 is normally performed, but the operation can be switched to an operation prioritizing reliability of compression device 10 when the liquid refrigerant returns.
Instead of providing first valve SV1 and second valve SV2 as illustrated in Fig. 3, oil distributor 150 may be provided with a three-way valve to switch the flow path.

Second embodiment.

In the case of a refrigerator used in a refrigeration warehouse or the like, as illustrated in Fig. 1, load device 3 and heat source unit 2 are connected by refrigerant extension pipes 84, 88. However, load device 3 and heat source unit 2 are not necessarily manufactured by the same manufacturer, and in many cases, load device 3 and heat source unit 2 are not connected by a communication line or the like. Therefore, when an interior of the refrigerator is sufficiently cooled on the side of load device 3, in order to prevent the interior of the refrigerator from being excessively cooled, electromagnetic valve 70 in load device 3 is closed, and the circulation of the refrigerant is blocked.
Then, as the operation of compression device 10 continues, the refrigerant in evaporator 60 and pipes 86 and 87 is sucked into compression device 10 and stored in liquid receiver 40. When pressure PL detected by pressure sensor 110 becomes lower than a threshold value, control device 100 stops the operation of compression device 10. Such an operation is also referred to as a pump down operation. When compression device 10 is stopped, as described above, pressure PL decreases more than usual, and a differential pressure between suction port G1 and discharge port G2 of compression device 10 increases. Since the compressor is in a state in which each port is internally shut off during the stop, the differential pressure is also maintained during the stop.
When it is necessary to restart compression device 10 due to a temperature rise on the side of load device 3 or the like, load device 3 opens electromagnetic valve 70. Then, since pressure PL increases, control device 100 activates compression device 10 accordingly.
However, depending on the compressor, it may be difficult to start up when the differential pressure between the suction port and the discharge port is large. It takes some time for the refrigerant to pass from liquid receiver 40 through first expansion device LEV1 and evaporator 60 to increase pressure PL. Therefore, in the refrigeration cycle device according to a second embodiment, starting performance of the compressor is improved using the oil return passage.
Fig. 6 is a diagram illustrating a control state of the electromagnetic valve of the oil distributor in the second embodiment. As illustrated in Fig. 6, in the normal state, control device 100 opens first valve SV1 and closes second valve SV2 in order to improve performance. On the other hand, when compression device 10 is activated, control device 100 closes first valve SV1 and opens second valve SV2. As a result, since the refrigerant on the discharge side of compression device 10 moves to the suction side, pressure PH decreases and pressure PL increases. When the pressure difference between the suction side and discharge side of compression device 10 decreases, torque required to rotate compression device 10 also decreases, and thus mobility of compression device 10 is improved. For example, in such a case where the difference between pressure PH and pressure PL before activation is larger than a threshold value, the control at the time of activation in Fig. 6 is performed.
Fig. 7 is a flowchart for describing control of the electromagnetic valve of the oil distributor executed by the control device in the second embodiment.
When stopping compression device 10, control device 100 simultaneously closes second valve SV2. First, in step S11, control device 100 determines whether or not it is the time of activation of compression device 10. For example, in such a case when the power is turned on, when pressure PL that has been less than or equal to a determination threshold for the stop rises above the determination threshold, or when the internal temperature rises above the threshold, control device 100 determines that it is time to start compression device 10.
When it is determined that it is the time of activation (YES in S11), in step S12, control device 100 determines whether or not the difference between pressure PH and pressure PL is larger than a threshold value Pth.
In a case where |PH-PL| > Pth is satisfied (YES in S12), in step S13, control device 100 closes first valve SV1 and opens second valve SV2. As a result, since the refrigerant on the discharge side of compression device 10 moves to the suction side, pressure PH decreases and pressure PL increases.
Subsequently, in step S14, control device 100 determines whether or not the difference between pressure PH and pressure PL is less than or equal to threshold value Pth. While the difference is not less than or equal to threshold value Pth, the processing remains in step S14, and waits for time.
In a case where it is determined in step S12 or step S14 that the difference between pressure PH and pressure PL is less than or equal to threshold value Pth (NO in S12 or YES in S14), in step S15, control device 100 opens first valve SV1 and closes second valve SV2. Then, in step S16, control device 100 activates compression device 10. Note that it is not always necessary to start compression device 10 after closing second valve SV2, and compression device 10 may be started in a state where second valve SV2 is opened.
As described above, by executing the control of oil distributor 150 at the time of starting compression device 10, compression device 10 is easily started as the starting time of compression device 10 is shortened and the torque required for starting is also reduced.

Third embodiment.

In a third embodiment, an application example in the case of using two compressors connected in series will be described. When the compressor is used under a condition of a high compression ratio such as a condition where a ratio of a pressure on the high-pressure side to a pressure on the low-pressure side pressure is high, there is a case where two compressors are connected in series. Such a configuration is referred to as a two-stage compression configuration. The two-stage compression configuration is adopted, for example, for a heat source unit used in an ultra-low temperature state such as a freezing warehouse for fish, a heat source unit using a CO₂ refrigerant, and the like.
Fig. 8 is an entire configuration diagram of a refrigeration cycle device 201 according to the third embodiment. Refrigeration cycle device 201 includes a heat source unit 202, load device 3, and extension pipes 84, 88.
Heat source unit 202 is connected to load device 3 by extension pipes 84, 88. Load device 3 and extension pipes 84, 88 have the same configurations as those illustrated in Fig. 3, and thus the description thereof will not be repeated.
Heat source unit 202 includes a compression device 10A instead of compression device 10 in the configuration of heat source unit 2 illustrated in Fig. 3. Compression device 10A includes a first compressor 11, a second compressor 12, and a pressure sensor 112 connected in series. First compressor 11 sucks a refrigerant from pipe 89 and discharges the refrigerant to second compressor 12. Second compressor 12 discharges the sucked refrigerant to pipe 80. Pipe 93 as the injection flow path is connected to a connection portion between first compressor 11 and second compressor 12. Pressure sensor 112 detects a pressure PM of the connection portion.
First compressor 11 and second compressor 12 have separate housings. Each housing incorporates a motor and a compression unit. In order to perform two-stage compression, a compressor having one housing and one motor may be used. In this case, there are two discharge ports and two suction ports for low pressure and high pressure.
Such a two-stage compression configuration is adopted because when compression is performed at a high-pressure ratio by one compressor, the discharge temperature of the compressor becomes very high and the compressor may be damaged. Therefore, the discharge temperature is lowered by connecting two compressors in series and injecting the refrigerant therebetween.
In the case of the configuration as illustrated in Fig. 8, there is a possibility that a deviation occurs between an amount of oil in first compressor 11 and an amount of oil in second compressor 12. Therefore, each of first compressor 11 and second compressor 12 is provided with an oil amount sensor 131,132 that detects a degree of a level of the oil accumulated in a bottom portion of the housing. Then, an oil amount OL1 of first compressor 11 is detected by oil amount sensor 131, and an oil amount OL2 of second compressor 12 is detected by oil amount sensor 132.
When the oil amount of first compressor 11 is small, second valve SV2 is opened and first valve SV1 is closed. On the other hand, when the oil amount of second compressor 12 is small, the deviation in the oil amount is suppressed by opening first valve SV1 and closing second valve SV2.
Fig. 9 is a flowchart for describing control of the electromagnetic valve of the oil distributor executed by the control device in the third embodiment. First, in step S21, control device 100 determines whether or not oil amount OL1 of first compressor 11 is smaller than a determination threshold Th1.
When oil amount OL1 is smaller than determination threshold Th1 (YES in S21), control device 100 closes first valve SV1 and opens second valve SV2 in step 522. As a result, since the refrigerating machine oil is supplied from the oil separator to a side of the suction port of first compressor 11, oil amount OL1 increases.
On the other hand, when oil amount OL1 is greater than or equal to determination threshold Th1 (NO in S21), control device 100 determines whether or not oil amount OL2 of second compressor 12 is smaller than a determination threshold Th2 in step S23.
When oil amount OL2 is smaller than determination threshold Th2 (YES in S23), control device 100 opens first valve SV1 and closes second valve SV2 in step S24. As a result, since the refrigerating machine oil is supplied from the oil separator to a side of the suction port of second compressor 12, oil amount OL2 increases.
On the other hand, when oil amount OL2 is greater than or equal to determination threshold Th2 (NO in S23), control device 100 maintains current states of first valve SV1 and second valve SV2 without performing the process of step S24.
Since the amount of the refrigerating machine oil sealed inside is constant, when oil amount OL1 decreases, oil amount OL2 increases. Therefore, the processing in step S24 may be executed when it is determined to be NO in step S24 without performing the determination in step S23. Conversely, the determination in step S23 may be performed without performing the determination in step S21, and the process in step S22 may be performed when it is determined to be NO in step S23.
By controlling the oil distributor in this manner, it is possible to reduce the deviation of the refrigerating machine oil between first compressor 11 and second compressor 12.

Fourth embodiment.

In a fourth embodiment, another application example in a case where two compressors connected in series are used will be described. In the configuration illustrated in Fig. 8, if an electronic expansion valve, a capillary tube, or the like is used in the upstream side of second valve SV2, it is possible to operate first valve SV1 and second valve SV2 with both valves opened and to more finely adjust the oil amount.
Fig. 10 is an entire configuration diagram of a refrigeration cycle device 301 according to the fourth embodiment. Refrigeration cycle device 301 illustrated in Fig. 10 includes a heat source unit 302, load device 3, and extension pipes 84, 88.
Heat source unit 302 is connected to load device 3 by extension pipes 84, 88. Load device 3 and extension pipes 84, 88 have the same configurations as those illustrated in Fig. 3, and thus the description thereof will not be repeated.
Heat source unit 302 includes an oil distributor 150A instead of oil distributor 150 in the configuration of heat source unit 202 illustrated in Fig. 8. Other configurations of heat source unit 302 are similar to those of heat source unit 202 illustrated in Fig. 8, and thus the description thereof will not be repeated.
Oil distributor 150A further includes a flow regulating valve LEV3 in addition to the configuration of oil distributor 150. Flow regulating valve LEV3 and second valve SV2 are disposed in series with pipe 95. In Fig. 10, flow regulating valve LEV3 is disposed on an upstream side of second valve SV2, but an arrangement of these may be reversed. If flow regulating valve LEV3 can be fully closed, second valve SV2 may be omitted.
As flow regulating valve LEV3, an electronic expansion valve can be used. By using flow regulating valve LEV3, the distribution ratio of the oil to first compressor 11 and second compressor 12 can be finely controlled. For example, it is also possible to perform an equal amount of oil return to first compressor 11 and second compressor 12.
Fig. 11 is a diagram illustrating a first example of a control state of the flow regulating valve of the oil distributor in the fourth embodiment. In the first example, first valve SV1 and second valve SV2 are opened, and as illustrated in Fig. 11, when oil amount OL1 of first compressor 11 is large, the opening degree of flow regulating valve LEV3 is decreased, and when oil amount OL1 of first compressor 11 is small, the opening degree of flow regulating valve LEV3 is increased.
Since the amount of oil sealed in the refrigeration cycle device is constant, the amount of oil in second compressor 12 is also adjusted to an appropriate amount by adjusting the amount of oil in first compressor 11.
Fig. 12 is a diagram illustrating a second example of the control state of the flow regulating valve of the oil distributor in the fourth embodiment. In the first example illustrated in Fig. 11, the opening degree of flow regulating valve LEV3 is changed according to oil amount OL1 of first compressor 11. Instead, the opening degree of flow regulating valve LEV3 may be changed according to oil amount OL2 of second compressor 12. In the second example, first valve SV1 and second valve SV2 are opened, and as illustrated in Fig. 12, when oil amount OL2 of second compressor 12 is small, the opening degree of flow regulating valve LEV3 is decreased, and when oil amount OL2 of second compressor 12 is large, the opening degree of flow regulating valve LEV3 is increased.
Since the amount of oil sealed in the refrigeration cycle device is constant, the amount of oil in first compressor 11 is also adjusted to an appropriate amount by adjusting the amount of oil in second compressor 12.
In the fourth embodiment, the oil amounts of the two compressors can be controlled to appropriate amounts by controlling flow regulating valve LEV3 of oil distributor 150A.

Fifth embodiment.

When a length of the pipe connecting the outdoor unit and the indoor unit is long, a larger amount of oil may be sealed in consideration of the pipe length. However, depending on the operation state, the amount of oil may be excessive and the amount of oil accumulated in the compressor may increase. In this case, an accumulator may be used as an oil reservoir to store excess refrigerant.
Fig. 13 is an entire configuration diagram of a refrigeration cycle device 401 according to a fifth embodiment. Refrigeration cycle device 401 illustrated in Fig. 13 includes a heat source unit 402, load device 3, and extension pipes 84, 88.
Heat source unit 402 is connected to load device 3 by extension pipes 84, 88. Load device 3 and extension pipes 84, 88 have the same configurations as those illustrated in Fig. 3, and thus the description thereof will not be repeated.
Heat source unit 402 further includes an accumulator 22, a pipe 96, a third valve SV3, and an oil amount sensor 130 in the configuration of heat source unit 2 illustrated in Fig. 3. Other configurations of heat source unit 402 are similar to those of heat source unit 2 illustrated in Fig. 3, and thus the description thereof will not be repeated. For example, an electromagnetic valve can be used as third valve SV3.
Accumulator 22 is disposed in the middle of pipe 89. Oil amount sensor 130 detects an oil amount OL of compression device 10.
In the fifth embodiment, an oil distributor 150C is used. Oil distributor 150C includes pipes 94 to 96, first valve SV1, second valve SV2, and third valve SV3. Pipe 94 connects an oil outlet of oil separator 20 and pipe 93. First valve SV1 is provided in pipe 94, and opens and closes a flow path of the oil and the refrigerant. Second valve SV2 is provided in pipe 95, and opens and closes the flow path of the oil and the refrigerant. Pipe 96 branches from a portion upstream of first valve SV1 in pipe 95 and joins pipe 89 on a side of an inlet of accumulator 22. Third valve SV3 is disposed in the middle of pipe 96.
In the fifth embodiment, third valve SV3 is provided in addition to second valve SV2, to switch between a case of directly returning the oil to compression device 10 and a case of storing the oil in accumulator 22.
Fig. 14 is a diagram illustrating a control state of the electromagnetic valve of the oil distributor in the fifth embodiment. As illustrated in Fig. 14, in the normal case, performance is prioritized, and open first valve SV1 and close second valve SV2 and third valve SV3. When the liquid refrigerant return is detected, second valve SV2 is opened and first valve SV1 and third valve SV3 are closed since there is a possibility of insufficient lubrication in the compressor. Even in the normal case where liquid refrigerant return is not detected, when oil amount OL in compression device 10 is larger than the determination threshold, third valve SV3 is opened, first valve SV1 and second valve SV2 are closed, and oil is accumulated in the accumulator.
Accordingly, the capability and performance of the refrigeration cycle device, lubrication of the compressor oil, and discharge of the surplus oil from the compressor can be balanced.
Fig. 15 is a flowchart for describing control of the electromagnetic valve of the oil distributor executed by the control device in the fifth embodiment. First, in step S31, control device 100 determines whether or not liquid refrigerant return is detected.
As in the first embodiment, the liquid refrigerant return can be detected by observing a decrease in the superheat degree (suction heat degree) or a decrease in the discharge superheat degree of the refrigerant sucked by compression device 10.
When it is determined that the liquid return is detected (YES in S31), control device 100 opens second valve SV2 and closes first valve SV1 and third valve SV3 in step S32.
On the other hand, when it is determined no liquid return is detected (NO in S31), control device 100, in step S33, determines whether or not oil amount OL of compression device 10 is larger than a determination threshold Th.
When oil amount OL is larger than determination threshold Th (YES in S33), control device 100 opens third valve SV3 and closes first valve SV1 and second valve SV2 in step S34. As a result, the refrigerating machine oil is changed to be supplied from oil separator 20 supplied to the suction port of compression device 10 to the side of the inlet of accumulator 22, so that oil amount OL decreases.
On the other hand, when oil amount OL is less than determination threshold Th (NO in S33), control device 100 opens first valve SV1 and closes second valve SV2 and third valve SV3 in step S35.
As described above, by controlling oil distributor 150C, the operation is normally performed with emphasis on the capability and performance of refrigeration cycle device 1, but the operation can be switched to the operation in which the reliability of compression device 10 is prioritized in such a case when the liquid refrigerant returns or when the amount of oil of the compressor is excessive.
Fig. 16 is an entire configuration diagram of a refrigeration cycle device 501 according to a modification of the fifth embodiment. Refrigeration cycle device 501 includes a heat source unit 502, load device 3, and extension pipes 84, 88.
Heat source unit 502 is connected to load device 3 by extension pipes 84, 88. Load device 3 and extension pipes 84, 88 have the same configurations as those illustrated in Fig. 3, and thus the description thereof will not be repeated.
Heat source unit 502 includes compression device 10A instead of compression device 10 in the configuration of heat source unit 402 illustrated in Fig. 13. Other configurations of heat source unit 502 are similar to those of heat source unit 402 illustrated in Fig. 13, and the configurations of compression device 10A is similar to the configuration of Fig. 8.
When it is indicated that oil amount OL1 of first compressor 11 is short, control device 100 opens second valve SV2 and closes first valve SV1 and third valve SV3. When it is indicated that oil amount OL2 of second compressor 12 is short, first valve SV1 is opened, and second valve SV2 and third valve SV3 are closed. When none of oil amounts OL1 and OL2 is indicated to be short, third valve SV3 is opened, and first valve SV1 and second valve SV2 are closed.
With such control, even in a configuration in which two compressors connected in series are used, excessive oil can be stored in accumulator 22.
An oil amount sensor may also be provided in accumulator 22, and the oil amount of the accumulator may also be added as a control parameter. Since the amount of the refrigerating machine oil sealed in refrigeration cycle device 501 is constant, similar control can be performed by detecting the amounts of at least two of first compressor 11, second compressor 12, and accumulator 22.
In addition, in order to improve accuracy in detection by the oil amount sensor described above, in order to exclude a case where the liquid refrigerant is sucked, it is possible to the suction superheating degree or the discharge superheat degree of the compressor together using a temperature sensor and a pressure sensor to determine the oil amount in combination with an output of the oil amount sensor.

(Summary)

The embodiments described above will be described again with reference to the drawings.
As shown in Fig. 3, the present disclosure relates to heat source unit 2 of refrigeration cycle device 1 connected to load device 3 including first expansion device LEV1 and evaporator 60. Heat source unit 2 includes: a first flow path (80 to 83, 89) to be connected to load device 3 so as to form a circulation flow path through which a refrigerant circulates; compression device 10 to suck the refrigerant from suction port G1 and intermediate-pressure port G3 and discharge the refrigerant through discharge port G2, the compression device being disposed in the first flow path; oil separator 20 disposed downstream of compression device 10 in the first flow path and having a refrigerant inlet, a refrigerant outlet, and an oil outlet; condenser 30 disposed downstream of the oil separator in the first flow path; a second flow path (91, 93) to return the refrigerant that has passed through condenser 30 to compression device 10 from intermediate-pressure port G3, the second flow path branching from a branch point downstream of condenser 30 in the first flow path in a direction in which the refrigerant circulates; second expansion device LEV2 disposed in the second flow path; and oil distributor 150 to return refrigerating machine oil discharged from the oil outlet of the oil separator 20 to compression device 10 via intermediate-pressure port G3 and suction port G1. Oil distributor 150 is able to change a ratio at which the refrigerating machine oil is distributed to intermediate-pressure port G3 and suction port G1.
Oil distributor 150 includes first valve SV1 to cause the oil outlet of oil separator 20 and intermediate-pressure port G3 to communicate with each other; and second valve SV2 to cause the oil outlet of oil separator 20 and suction port G1 to communicate with each other.
Heat source unit 2 further includes control device 100 to control first valve SV1 and second valve SV2. As illustrated in Figs. 4 and 5, when the amount of the liquid refrigerant return to suction port G1 is larger than the determination value, control device 100 opens second valve SV2 and closes first valve SV1.
Heat source unit 2 further includes control device 100 to control first valve SV1 and second valve SV2. As illustrated in Figs. 6 and 7, when pressure difference |PH-PL| between discharge port G2 and suction port G1 is larger than determination value Pth in activating compression device 10, control device 100 opens second valve SV2 to reduce the pressure difference.
As illustrated in Fig. 8, compression device 10A includes first compressor 11 to suck the refrigerant from the suction port and to discharge the refrigerant to a pipe connected to the intermediate-pressure port, and second compressor 12 to suck the refrigerant from the pipe connected to the intermediate-pressure port and to discharge the refrigerant through the discharge port.
As illustrated in Fig. 10, oil distributor 150A includes a first valve SV1 to cause the oil outlet of oil separator 20 and the intermediate-pressure port to communicate with each other, and flow regulating valve LEV3 to cause the oil outlet of oil separator 20 and the suction port to communicate with each other.
As shown in Fig. 13, heat source unit 402 further includes an accumulator 22 disposed upstream of compression device 10 in the first flow path. Oil distributor 150C includes: first valve SV1 to cause the oil outlet of oil separator 20 and intermediate-pressure port G3 to communicate with each other; second valve SV2 to cause the oil outlet of oil separator 20 and suction port G1 to communicate with each other; and third valve SV3 to cause the oil outlet of oil separator 20 and the inlet of accumulator 22 to communicate with each other.
Another aspect of the present disclosure relates to refrigeration cycle device 1, 201, 301, 401, 501 including: heat source unit 2, 202, 302, 402, 502 according to any one of the above described heat source units; and load device 3.
Yet another aspect of the present disclosure relates to a refrigerator including refrigeration cycle device 1, 201, 301, 401, 501.
The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims instead of the descriptions of the embodiments stated above, and it is intended that meanings equivalent to the claims and all modifications within the scope are included.

REFERENCE SIGNS LIST

1, 201, 301, 401, 501: refrigeration cycle device, 2, 202, 302, 402, 502: heat source unit, 3: load device, 10, 10A: compression device, 11: first compressor, 12: second compressor, 20: oil separator, 22: accumulator, 30: condenser, 40: liquid receiver, 60: evaporator, 70: electromagnetic valve, 80 to 83, 85 to 87, 89, 91, 93 to 96: pipe, 84, 88: extension pipe, 100: control device, 104: memory, 110 to 112: pressure sensor, 121, 122: temperature sensor, 130 to 132: oil amount sensor, 150, 150A, 150C: oil distributor, G1: suction port, G2: discharge port, G3: intermediate-pressure port, LEV1: first expansion device, LEV2: second expansion device, LEV3: flow regulating valve, SV1: first valve, SV2: second valve, SV3: third valve

Claims

A heat source unit of a refrigeration cycle device to be connected to a load device including a first expansion device and an evaporator, the heat source unit comprising:
a first flow path to be connected to the load device so as to form a circulation flow path through which a refrigerant circulates;

a compression device to suck the refrigerant from a suction port and an intermediate-pressure port and to discharge the refrigerant through a discharge port, the compression device being disposed in the first flow path;

an oil separator disposed downstream of the compression device in the first flow path, and having a refrigerant inlet, a refrigerant outlet, and an oil outlet;

a condenser disposed downstream of the oil separator in the first flow path;

a second flow path to return the refrigerant that has passed through the condenser to the compression device from the intermediate-pressure port, the second flow path branching from a branch point downstream of the condenser in the first flow path in a direction in which the refrigerant circulates;

a second expansion device disposed in the second flow path; and

an oil distributor to return refrigerating machine oil discharged from the oil outlet of the oil separator to the compression device via the intermediate-pressure port and the suction port, wherein

the oil distributor is configured to change a ratio at which the refrigerating machine oil is distributed to the intermediate-pressure port and the suction port.
The heat source unit according to claim 1, wherein
the oil distributor includes:
a first valve to cause the oil outlet of the oil separator and the intermediate-pressure port to communicate with each other; and

a second valve to cause the oil outlet of the oil separator and the suction port to communicate with each other.
The heat source unit according to claim 2, further comprising a control device to control the first valve and the second valve, wherein
when an amount of liquid refrigerant return to the suction port is larger than a determination value, the control device opens the second valve and closes the first valve.
The heat source unit according to claim 2, further comprising a control device to control the first valve and the second valve, wherein
when a pressure difference between the discharge port and the suction port is larger than a determination value in activating the compression device, the control device opens the second valve to reduce the pressure difference.
The heat source unit according to claim 1, wherein
the compression device includes:
a first compressor to suck the refrigerant from the suction port and to discharge the refrigerant to a pipe connected to the intermediate-pressure port; and

a second compressor to suck the refrigerant from the pipe connected to the intermediate-pressure port and to discharge the refrigerant through the discharge port.
The heat source unit according to claim 5, wherein
the oil distributor includes:
a first valve to cause the oil outlet of the oil separator and the intermediate-pressure port to communicate with each other; and

a flow regulating valve to cause the oil outlet of the oil separator and the suction port to communicate with each other.
The heat source unit according to claim 1, further comprising an accumulator disposed upstream of the compression device in the first flow path, wherein
the oil distributor includes:
a first valve to cause the oil outlet of the oil separator and the intermediate-pressure port to communicate with each other;

a second valve to cause the oil outlet of the oil separator and the suction port to communicate with each other; and

a third valve to cause the oil outlet of the oil separator and an inlet of the accumulator to communicate with each other.
A refrigeration cycle device comprising the heat source unit according to any one of claims 1 to 7 and the load device.
A refrigerator comprising the refrigeration cycle device according to claim 8.