ES2879920T3 - Refrigeration appliance - Google Patents

Abstract

A refrigeration apparatus comprising: a refrigerant circuit (20) including a compressor (31a, 31b, 31c), a heat source side heat exchanger (33), a heat source side heat exchanger (61) a liquid refrigerant pipe (50) connecting a liquid end of the heat source side heat exchanger (33) to a liquid end of the utilization side heat exchanger (61), a pipe (54 injection ) connecting an intermediate portion (P1) of the liquid refrigerant pipe (50) to an intermediate port of the compressor (31a, 31b, 31c), a supercooling heat exchanger (34) connected to the pipe (50) of liquid refrigerant and the injection pipe (54) to exchange heat between a refrigerant flowing through the liquid refrigerant pipe (50) and a refrigerant flowing through the injection pipe (54), a valve (35 ) of supercooling expansion provided in a part of the injection pipe (54) between the intermediate part (P1) of the liquid refrigerant pipe (50) and the supercooling heat exchanger (34), and an expansion valve (36a, 36b, 36c) intermediate provided in a part of the injection pipe (54) between the supercooling heat exchanger (34) and the intermediate port of the compressor (31a, 31b, 31c); comprising a control section (13) configured to perform first and second opening degree adjustment operations in a cooling mode in which the refrigerant circuit (20) performs a refrigeration cycle in which the heat exchanger (33) The heat source side heat exchanger works as a condenser, the supercooling heat exchanger (34) works as a supercooling element, and the utilization side heat exchanger (61) works as an evaporator, adjusting an opening degree of the intermediate expansion valve (36a, 36b, 36c) in the first opening degree adjustment operation so that a temperature (Td) of a refrigerant discharged from the compressor (31a, 31b, 31c) is below a predetermined highest discharged refrigerant temperature threshold (Tdth), characterized in that an opening degree of the supercooling expansion valve (35) is set in the second operation opening degree adjustment so that a temperature of a refrigerant flows through a part of the injection pipe (54) between the supercooling heat exchanger (34) and the expansion valve (36a, 36b, 36c) intermedia is above a predetermined freezing temperature threshold (Tfth).

Description

DESCRIPTION

Refrigeration appliance

Technical field

The present disclosure relates to a refrigeration apparatus.

Background of the technique

A refrigeration apparatus using a refrigeration cycle is known in the art. Such a refrigeration apparatus has been widely used to cool the inside of a refrigerator and freezer and to condition the indoor air. For example, Patent Document 1 discloses a refrigeration apparatus including a refrigerant circuit that circulates a refrigerant through it to perform a refrigeration cycle. The refrigerant circuit includes a compressor, a heat source side heat exchanger, an expansion valve and a use side heat exchanger. The utilization side heat exchanger is provided in a freezer. The refrigeration apparatus of patent document 1 operates in the cooling mode. In cooling mode, the use-side heat exchanger allows a refrigerant to absorb heat from the indoor air and evaporate. Therefore, the air in the freezer becomes cold. The refrigerant circuit is provided with a supercooling heat exchanger and a supercooling expansion valve.

Furthermore, Patent Document 2 describes an air conditioner that is controlled such that when a first heat exchanger, i.e. a heat source side heat exchanger, acts as a condenser, as a refrigerant flows through through a first bypass pipe to an inlet side pipe for a compressor through impulse devices, said refrigerant also flows through a second bypass pipe through one of the impulse devices and is introduced into a compression chamber through an injection hole. When the heat source side heat exchanger acts as an evaporator, the air conditioner is controlled so that the refrigerant flows through the second bypass pipe through the pulse device mentioned above and into the chamber. compression through the injection port and the other impulse device either closes completely or closes so that almost no refrigerant flows through it. Patent Document 2 represents the closest prior art to the present invention.

Patent document 3 describes a container refrigeration device that includes a refrigerant circuit (20) configured to perform a refrigeration cycle and includes a main circuit (21) in which a compressor (30), a condenser (31) , an expansion valve (32), and an evaporator (33) are connected to each other in this order, and a hot gas bypass circuit (22) in which compressed refrigerant is supplied from the compressor (30) to the evaporator (33 ) without passing through the condenser (31) and the expansion valve (32); and a compressor control section (81) configured for, in a defrost operation in which the compressed refrigerant from the compressor (30) returns to the compressor (30) through the hot gas bypass circuit (22) and the evaporator (33) and the evaporator (33) is defrosted, control an operating speed of the compressor (30) so that a pressure of the compressed refrigerant of the compressor (30) reaches a target value.

List of references

Patent documents

[Patent Document 1] Japanese Unexamined Patent Publication No. 2009-287800

[Patent Document 2] WO 2015/029220 A1

[Patent Document 3] EP 2505 941 A1

Summary of the invention

Technical problem

In the refrigeration apparatus of patent document 1, the refrigerant circuit is provided with a liquid refrigerant pipe through which the liquid end of the heat source side heat exchanger and the liquid end of the heat exchanger Utilization side heat are connected to each other, and an injection pipe through which an intermediate part of the liquid refrigerant pipe and an intermediate port of the compressor are connected to each other. The supercooling heat exchanger is connected to the liquid refrigerant pipe and the injection pipe, and is configured to exchange heat between a refrigerant flowing through the liquid refrigerant pipe and a refrigerant flowing through the pipe. injection. The supercooling expansion valve is arranged in a part of the injection pipe between the intermediate part of the liquid refrigerant pipe and the supercooling heat exchanger.

In the cooling mode, the supercooling heat exchanger allows a refrigerant (high pressure refrigerant) that has flowed from the heat source side heat exchanger through the heat pipe. Liquid refrigerant to the supercooling heat exchanger has its heat absorbed by a refrigerant (intermediate pressure refrigerant) that has flowed from the supercooling expansion valve through the injection pipe to the supercooling heat exchanger and is going to be supercooled. This can improve the cooling capacity of the utilization side heat exchanger. The refrigerant (intermediate pressure refrigerant) is supplied from the supercooling heat exchanger through the injection pipe to the intermediate port of the compressor. This can reduce the temperature of the refrigerant in the compressor (specifically, the internal temperature of an intermediate pressure compression chamber) to reduce the temperature of the refrigerant discharged from the compressor. Therefore, the compressor can protect itself against abnormally high temperatures.

However, in the refrigeration apparatus of patent document 1, if the pressure of a refrigerant (intermediate pressure refrigerant) flowing from the supercooling expansion valve to the supercooling heat exchanger decreases in the injection pipe, so As the evaporation temperature of a refrigerant (intermediate pressure refrigerant) in the supercooling heat exchanger decreases, the temperature of a refrigerant moving from the supercooling heat exchanger to the intermediate orifice of the compressor may decrease in the injection and therefore the injection pipe may freeze. If the degree of freezing of the injection pipe increases, the ice formed in the injection pipe can cause the injection pipe to bend, or it can come into contact with any other component (for example, a housing) of the refrigeration appliance to create vibrations or noise.

Therefore, an object of the present disclosure is to provide a refrigeration apparatus that can protect a compressor against abnormally high temperatures and reduce the degree of freezing of an injection pipe.

Solution to the problem

The present invention, defined solely by the appended independent claim 1, is directed to a refrigeration apparatus including, inter alia, a refrigerant circuit (20) and a control section (13). The refrigerant circuit (20) includes a compressor (31a, 31b, 31c), a heat exchanger (33) on the heat source side, a heat exchanger (61) on the use side, a pipe (50) of liquid refrigerant connecting a liquid end of the heat source side heat exchanger (33) to a liquid end of the utilization side heat exchanger (61), an injection pipe (54) connecting a part ( P1) intermediate the liquid refrigerant pipe (50) to an intermediate port of the compressor (31a, 31b, 31c), a supercooling heat exchanger (34) connected to the liquid refrigerant pipe (50) and the pipe (54 injection) for exchanging heat between a refrigerant flowing through the liquid refrigerant line (50) and a refrigerant flowing through the injection line (54), a supercooling expansion valve (35) provided in a part of the injection pipe (54) in between the intermediate part (P1) of the liquid refrigerant pipe (50) and the supercooling heat exchanger (34) and an intermediate expansion valve (36a, 36b, 36c) provided in a part of the pipe (54) of injection between the supercooling heat exchanger (34) and the intermediate orifice of the compressor (31a, 31b, 31c). The control section (13) is configured to perform first and second opening degree adjustment operations in a cooling mode in which the refrigerant circuit (20) performs a refrigeration cycle where the heat exchanger (33) on the heat source side functions as a condenser, the supercooling heat exchanger (34) functions as a supercooling element, and the utilization side heat exchanger (61) functions as an evaporator. An opening degree of the intermediate expansion valve (36a, 36b, 36c) is adjusted in the first opening degree setting operation so that the temperature (Td) of a refrigerant discharged from the compressor (31a, 31b, 31c) is below a predetermined highest discharged refrigerant temperature threshold (Tdth). An opening degree of the supercooling expansion valve (35) is adjusted in the second opening degree setting operation so that a temperature of a refrigerant flowing through a part of the injection pipe (54) between The supercooling heat exchanger (34) and the intermediate expansion valve (36a, 36b, 36c) are above a predetermined freezing temperature threshold (Tfth).

According to a first advantageous aspect of the invention, the integrity of which is defined solely by the attached independent claim 1, the opening degree of the intermediate expansion valve (36a, 36b, 36c) can be adjusted in the first degree setting operation opening to adjust the flow rate (injection quantity) of the refrigerant flowing to the intermediate port of the compressor (31a, 31b, 31c). As a result, it can be adjusted how much the temperature of the refrigerant in the compressor will decrease (31a, 31b, 31c). This allows the temperature (Td) of the refrigerant discharged from the compressor (31a, 31b, 31c) to be adjusted. Adjusting the opening degree of the supercooling expansion valve (35) in the second opening degree setting operation allows the adjustment of the pressure of the refrigerant flowing from the supercooling expansion valve (35) to the exchanger (34 ) of supercooling heat in the injection pipe (54). Therefore, the temperature of the refrigerant flowing through the part of the injection pipe (54) between the supercooling heat exchanger (34) and the intermediate expansion valve (36a, 36b, 36c) can be adjusted.

According to a second aspect of the invention which is an embodiment of the first aspect, if the temperature (Td) of the refrigerant discharged from the compressor (31a, 31b, 31c) is below the threshold (Tdth) of the temperature of the highest discharged refrigerant, The control section (13) can perform the second operation of adjusting the opening degree, and if the temperature (Td) of the refrigerant discharged from the compressor (31a, 31b, 31c) is not found by Below the highest discharged refrigerant temperature threshold (Tdth), the control section (13) can increase the opening degree of the supercooling expansion valve (35).

According to the second aspect, increasing the opening degree of the supercooling expansion valve (35) can increase the flow rate of the refrigerant flowing from the supercooling expansion valve (35) to the supercooling heat exchanger (34) in the pipeline. (54), and thus can increase the flow rate (injection quantity) of the refrigerant flowing from the supercooling heat exchanger (34) through the intermediate expansion valve (36a, 36b, 36c) to the intermediate hole compressor (31a, 31b, 31c). This can increase how much the temperature of the refrigerant in the compressor (31a, 31b, 31c) will decrease and can reduce the temperature (Td) of the refrigerant discharged from the compressor (31a, 31b, 31c). Increasing the opening degree of the supercooling expansion valve (35) can increase the pressure of the refrigerant flowing from the supercooling expansion valve (35) to the supercooling heat exchanger (34) in the injection line (54). . Therefore, the temperature of the refrigerant flowing through the part of the injection pipe (54) between the supercooling heat exchanger (34) and the intermediate expansion valve (36a, 36b, 36c) can be increased.

According to a third aspect of the invention which is an embodiment of the first or second aspect, in the first operation of adjusting the degree of opening, if the temperature (Td) of the refrigerant discharged from the compressor (31a, 31b, 31c) is below of the highest discharged refrigerant temperature threshold (Tdth), the control section (13) can adjust the opening degree of the intermediate expansion valve (36a, 36b, 36c) so that a degree of overheating of the discharged refrigerant from the compressor (31a, 31b, 31c) is equal to a predetermined target degree of superheat, and if the temperature (Td) of the refrigerant discharged from the compressor (31a, 31b, 31c) is not below the threshold (Tdth) of temperature of the higher discharged refrigerant, the control section (13) can increase the opening degree of the intermediate expansion valve (36a, 36b, 36c).

According to the third aspect, increasing the opening degree of the intermediate expansion valve (36a, 36b, 36c) causes an increase in the flow rate (injection quantity) of the refrigerant that flows towards the intermediate orifice of the compressor (31a, 31b, 31c ). This can increase how much the temperature of the refrigerant will decrease in the compressor (31a, 31b, 31c) and can reduce the temperature (Td) of the refrigerant discharged from the compressor (31a, 31b, 31c).

According to a fourth aspect of the invention, which is an embodiment of any of the first to third aspects, in the second operation of adjusting the degree of opening, if the temperature of the refrigerant flowing through the part of the pipe (54) injection between the supercooling heat exchanger (34) and the intermediate expansion valve (36a, 36b, 36c) is above the freezing temperature threshold (Tfth), the control section (13) can reduce the degree opening of the supercooling expansion valve (35), and if the temperature of the refrigerant flowing through the part of the injection pipe (54) between the supercooling heat exchanger (34) and the valve (36a, 36b, 36c) of intermediate expansion is not above the freezing temperature threshold (Tfth), the control section (13) can increase the opening degree of the supercooling expansion valve (35).

According to the fourth aspect, reducing the degree of opening of the supercooling expansion valve (35) causes a reduction in the pressure of the refrigerant flowing from the supercooling expansion valve (35) to the supercooling heat exchanger (34) in the injection pipe (54). This can increase the degree of subcooling of the refrigerant in the supercooling heat exchanger (34). On the other hand, increasing the opening degree of the supercooling expansion valve (35) can increase the pressure of the refrigerant flowing from the supercooling expansion valve (35) to the supercooling heat exchanger (34) in the pipeline ( 54) injection. Therefore, the temperature of the refrigerant flowing through the part of the injection pipe (54) between the supercooling heat exchanger (34) and the intermediate expansion valve (36a, 36b, 36c) can be increased.

According to a fifth aspect of the invention, which is an embodiment of any one of the first to fifth aspects, the refrigerant circuit (20) may include an oil separator (41) configured to separate the oil in the refrigeration machine from the discharged refrigerant. of the compressor (31a, 31b, 31c), an oil return pipe (57) having two ends respectively connected to the oil separator (41) and an intermediate part of the injection pipe (54) between the exchanger (34) supercooling heat and intermediate expansion valve (36a, 36b, 36c), and an oil return expansion valve (42) provided in the oil return line (57), and in the cooling mode, the Control section (13) can perform a third opening degree adjustment operation in which an opening degree of the oil return expansion valve (42) is adjusted so that the temperature of a refrigerant flowing through of a pa rte of the injection pipe (54) between a union (P6) of the injection pipe (54) and the oil return pipe (57) and the intermediate expansion valve (36a, 36b, 36c) is located above threshold (Tfth) of freezing temperature.

According to the fifth aspect, adjusting the opening degree of the oil return expansion valve (42) in the third opening degree setting operation allows the adjustment of the refrigeration machine oil flow rate (refrigeration machine oil). relatively high temperature) flowing from the oil separator (41) through the oil return line (57) to the injection line (54). Therefore, the temperature of the coolant that flows through the part of the injection pipe (54) between the junction (P6) of the injection pipe (54) and the oil return pipe (57) and the expansion valve (36a, 36b, 36c) intermediate can be adjusted.

According to a sixth aspect of the invention which is an embodiment of the fifth aspect, in the third operation of adjusting the degree of opening, if the temperature of the refrigerant flowing through the part of the injection pipe (54) between the joint ( P6) of the injection pipe (54) and the oil return pipe (57) and the intermediate expansion valve (36a, 36b, 36c) is above the freezing temperature threshold (Tfth), section ( 13) can intermittently place the oil return expansion valve (42) in an open state so that the oil flow from the refrigeration machine passes through the oil return pipe (57) into the a predetermined unit time period is equal to a predetermined flow rate, and if the temperature of the refrigerant flowing through the part of the injection pipe (54) between the joint (P6) of the injection pipe (54) and the oil return line (57) and valve (36a, 36b, 36c) of intermediate expansion is not above the freezing temperature threshold (Tfth), the control section (13) may intermittently place the oil return expansion valve (42) in the open state so as to increase the flow rate of the cooling machine oil passing through the oil return line (57) within the predetermined unit time period.

According to the sixth aspect, increasing the flow rate of the refrigeration machine oil (relatively high temperature refrigeration machine oil) passing through the oil return line (57) within a predetermined unit time period causes an increase. at the temperature of the refrigerant flowing through the part of the injection pipe (54) between the joint (P6) of the injection pipe (54) and the oil return pipe (57) and the valve (36a, 36b, 36c) of intermediate expansion.

Advantages of the invention

According to the first aspect of the invention, an invention that is defined solely by the attached independent claim 1, adjusting the opening degree of an intermediate expansion valve (36a, 36b, 36c) in a first opening degree setting operation allows adjusting the temperature (Td) of a refrigerant discharged from a compressor (31a, 31b, 31c) so that the temperature (Td) is below a higher discharged refrigerant temperature threshold (Tdth). Therefore, the compressor (31a, 31b, 31c) can be protected against abnormally high temperatures. Furthermore, adjusting the opening degree of a supercooling expansion valve (35) in a second opening degree setting operation allows the temperature adjustment of a refrigerant flowing through a portion of a pipeline (54) of injection between a supercooling heat exchanger (34) and the intermediate expansion valve (36a, 36b, 36c) so that the temperature of the refrigerant is above a threshold (Tfth) of freezing temperature. This can reduce the degree of freezing of the injection line (54).

According to the second aspect of the invention, if the temperature (Td) of the refrigerant discharged from the compressor (31a, 31b, 31c) is not below the highest discharged refrigerant temperature threshold (Tdth), the increase in the degree of opening of the supercooling expansion valve (35) can reduce the temperature (Td) of the refrigerant discharged from the compressor (31a, 31b, 31c), and can increase the temperature of the refrigerant flowing through the part of the pipeline (54) injection between the supercooling heat exchanger (34) and the intermediate expansion valve (36a, 36b, 36c). Therefore, the compressor (31a, 31b, 31c) can be protected against abnormally high temperatures and the degree of freezing of the injection pipe (54) can be reduced.

According to the third aspect of the invention, in the first operation for adjusting the degree of opening, if the temperature (Td) of the refrigerant discharged from the compressor (31a, 31b, 31c) is not below the temperature threshold (Tdth) of the Higher discharged refrigerant, increasing the opening degree of the intermediate expansion valve (36a, 36b, 36c) can lower the temperature of the refrigerant discharged from the compressor (31a, 31b, 31c). Therefore, the compressor (31a, 31b, 31c) can be protected against abnormally high temperatures.

According to the fourth aspect of the invention, in the second operation of adjusting the degree of opening, if the temperature of the refrigerant flowing through the part of the injection pipe (54) between the supercooling heat exchanger (34) and the intermediate expansion valve (36a, 36b, 36c) is above the freezing temperature threshold (Tfth), reducing the opening degree of the supercooling expansion valve (35) can increase the degree of subcooling of the refrigerant in the supercooling heat exchanger (34). This can improve the cooling capacity of the utilization side heat exchanger (61). On the other hand, if the temperature of the refrigerant flowing through the part of the injection pipe (54) between the supercooling heat exchanger (34) and the intermediate expansion valve (36a, 36b, 36c) is not found above the freezing temperature threshold (Tfth), the increase in the degree of opening of the supercooling expansion valve (35) causes an increase in the temperature of the refrigerant that flows through the part of the pipe (54) of injection between the supercooling heat exchanger (34) and the intermediate expansion valve (36a, 36b, 36c). This can reduce the degree of freezing of the injection line (54).

According to the fifth aspect of the invention, adjusting the opening degree of an oil return expansion valve (42) in a third opening degree adjusting operation allows adjustment of the temperature of a refrigerant flowing through a part of the injection pipe (54) between a joint (P6) of the pipe (54) of injection and an oil return pipe (57) and the intermediate expansion valve (36a, 36b, 36c) so that the temperature of the refrigerant is above the freezing temperature threshold (Tfth). This can reduce the degree of freezing of the injection line (54).

According to the sixth aspect of the invention, in the third operation of adjusting the degree of opening, if the temperature of the refrigerant that flows through the part of the injection pipe (54) between the joint (P6) of the pipe (54 ) injection and oil return pipe (57) and intermediate expansion valve (36a, 36b, 36c) is not above the freezing temperature threshold (Tfth), the increase in the flow rate of the machine oil from Refrigeration (relatively high temperature refrigeration machine oil) passing through the oil return line (57) within a predetermined unit time period causes an increase in the temperature of the refrigerant flowing through the part of the injection pipe (54) between the joint (P6) of the injection pipe (54) and the oil return pipe (57) and the intermediate expansion valve (36a, 36b, 36c). This can reduce the degree of freezing of the injection line (54).

Brief description of the drawings

[FIG. 1] Figure 1 is a pipe system diagram showing an exemplary configuration for a refrigeration apparatus according to an embodiment.

[FIG. 2] Figure 2 is a pipe system diagram for explaining an operation in a cooling mode.

[FIG. 3] Figure 3 is a pipe system diagram for explaining an operation in a defrost mode.

[FIG. 4] Figure 4 is a flow chart to explain how the opening degree of an intermediate expansion valve is adjusted.

[FIG. 5] Figure 5 is a flow chart to explain how the opening degree of a supercooling expansion valve is adjusted.

[FIG. 6] Figure 6 is a flow chart to explain how the opening degree of an oil return expansion valve is adjusted.

Detailed description

Embodiments of the present invention will now be described in detail with reference to the drawings. Note that the same reference characters denote the same or equivalent components in the drawings, and the description thereof will not be repeated.

(Refrigeration appliance)

Figure 1 shows an exemplary configuration for a refrigeration apparatus (10) according to one embodiment. The refrigeration apparatus (10) includes a heat source side unit (11), a plurality of (in this example, two) utilization side units (12) connected in parallel to the heat source side unit (11) heat source, and a controller (13). For example, the heat source side unit (11) is provided outdoors and the utilization side units (12) are provided indoors.

The heat source side unit (11) is provided with a heat source side circuit (21) and a heat source side fan (22). Each utilization-side unit (12) is provided with a utilization-side circuit (23), a utilization-side fan (24), and a drain pan (25). In this refrigeration apparatus (10), the circuit (21) on the heat source side of the unit (11) on the heat source side and the circuits (23) on the heat source side of the units (12) on the use side are connected to each other through a liquid interconnection pipe (14) and a gas interconnection pipe (15) to form a refrigerant circuit (20) that circulates a refrigerant through it to perform a vapor compression refrigeration cycle.

Specifically, the heat source side circuit (21) has liquid and gas ends respectively provided with a liquid stop valve (V1) and a gas stop valve (V2). The liquid stop valve (V1) and the gas stop valve (V2) are respectively connected to one end of the liquid interconnection pipe (14) and one end of the gas interconnection pipe (15). The liquid interconnection pipe (14) is connected to the liquid ends of the use side circuits (23), and the gas interconnection pipe (15) is connected to the gas ends of the circuits (23) on the utilization side.

<Heat source side circuit>

The heat source side circuit (21) includes first to third compressors (31 to-31c), a four-way valve (32), a heat source side heat exchanger (33), an exchanger (34 supercooling heat), a supercooling expansion valve (35), first to third intermediate expansion valves (36a-36c), a receiver (37), a heat source side expansion valve (38), valves (CV1-CV3) first to third check, an oil separator (41) and an oil return expansion valve (42). The circuit (21) on the side The heat source is provided with a discharge refrigerant pipe (51), a suction refrigerant pipe (52), a heat source side liquid refrigerant pipe (53), an injection pipe (54), a first connection pipe (55), a second connection pipe (56) and an oil return pipe (57). In the following description, the first to third compressors (31a-31c) are collectively referred to as "the compressor (31a, 31b, 31c)", and the first to third intermediate expansion valves (36a-36c) are collectively referred to as "the valve. (36a, 36b, 36c) of intermediate expansion ”.

«C om presors»

The compressor (31a, 31b, 31c) is configured to compress and discharge a refrigerant sucked into it. The compressor (31a, 31b, 31c) has a suction port, an intermediate port, and a discharge port. The suction port communicates with a compression chamber (that is, a compression chamber in a low pressure phase) during a suction stroke of the compressor (31a, 31b, 31c). The intermediate port communicates with a compression chamber (that is, a compression chamber in an intermediate pressure phase) in the middle of a compression stroke of the compressor (31a, 31b, 31c). The discharge port communicates with a compression chamber (that is, a compression chamber in a high pressure phase) during a discharge stroke of the compressor (31a, 31b, 31c). The compressor (31a, 31b, 31c) is configured, for example, as a scroll compressor that includes a compression chamber defined between a fixed scroll and an orbiting scroll, which mesh with each other.

Note that, in this example, the first compressor (31a) has a variable capacity. Specifically, changing the output frequency of an inverter (not shown) triggers a change in the rotational speed of an electric motor provided within the first compressor (31a). This causes the capacity of the first compressor (31a) to vary. The second and third compressors (31b, 31c) each have a fixed capacity. Specifically, the second and third compressors (31b, 31c) each include therein an electric motor that rotates at a constant rotational speed, and each has a constant capacity.

«V á lvu the four-way >>

The four-way valve (32) can toggle between a first state (indicated by the solid curves shown in Figure 1) and a second state (indicated by the broken curves shown in Figure 1). In the first state, a first hole communicates with a third hole and a second hole communicates with a fourth hole. In the second state, the first hole communicates with the fourth hole and the second hole communicates with the third hole.

The first port of the four-way valve (32) is connected to the discharge ports of the compressors (31a, 31b, 31c) through the discharge refrigerant line (51). The second port of the four-way valve (32) is connected to the suction ports of the compressors (31a, 31b, 31c) through the suction refrigerant line (52). The third port of the four-way valve (32) is connected to the gas end of the heat exchanger (33) on the heat source side. The fourth port of the four-way valve (32) is connected to the gas stop valve (V2).

<< Discharge refrigerant pipe, suction refrigerant pipe >>

In this example, the discharge refrigerant pipe (51) includes first, second and third discharge pipes (51a, 51b, 51c), one end of each of which is connected to the discharge port of an associated one of the compressors. (31a, 31b, 31c) first, second and third, and a discharge collection pipe (51 d) connecting the other end of each of the first, second and third discharge pipes (51a, 51b, 51c) to the first port of the four-way valve (32). The suction refrigerant pipe (52) includes first, second and third suction pipes (52a, 52b, 52c), one end of each of which is connected to the suction port of an associated one of the compressors (31a, 31b , 31c) first, second and third and a main suction pipe (52d) that connects the other end of each of the first, second and third suction pipes (52a, 52b, 52c) to the second port of the valve (32 ) four-way.

"Heat source side heat exchanger"

The heat source side heat exchanger (33) has its liquid end connected to one end of the heat source side liquid refrigerant pipe (53), and has its gas end connected to the third hole of the four-way valve (32). The heat source side fan (22) is arranged close to the heat source side heat exchanger (33). The heat source side heat exchanger (33) is configured to exchange heat between a refrigerant and the heat source side air (e.g., outdoor air) transferred by the heat source side fan (22). heat. The heat source side heat exchanger 33 is configured, for example, as a cross-finned tube and fin heat exchanger.

<< Heat source side liquid refrigerant piping >>

The heat source side liquid refrigerant pipe (53) has two ends respectively connected to the heat source side heat exchanger (33) and the liquid stop valve (V1). In this example, the Heat source side liquid refrigerant line (53) includes a first heat source side liquid line (53a) connecting the liquid end of the heat source side heat exchanger (33) to the receiver ( 37), a second heat source side liquid line (53b) connecting the receiver (37) to the supercooling heat exchanger (34), and a third heat source side liquid line (53c) connecting connects supercooling heat exchanger (34) to liquid stop valve (V1).

«Injection pipe»

The injection pipe (54) connects a first intermediate part (P1) of the heat source side liquid refrigerant pipe (53) to the intermediate ports of the compressors (31a, 31b, 31c). In this example, the injection pipe (54) includes a first main injection pipe (54m) connecting the first intermediate part (P1) of the heat source side liquid refrigerant pipe (53) to the exchanger (34) supercooling heat, a second main injection pipe (54n), one end of which is connected to the supercooling heat exchanger (34), and first, second and third injection branch pipes (54a, 54b, 54c) each connecting the other end of the second main injection pipe (54n) to the intermediate port of an associated one of the first, second and third compressors (31a, 31b, 31c). In the following description, the first, second, and third injection branch pipes (54a, 54b, 54c) are collectively referred to as "the injection branch pipe (54a, 54b, 54c)."

"Supercooling heat exchanger"

The supercooling heat exchanger (34) is connected to the heat source side liquid refrigerant pipe (53) and the injection pipe (54), and is configured to exchange heat between a refrigerant flowing through the heat source side liquid refrigerant pipe 53 and a refrigerant flowing through injection pipe 54. In this example, the supercooling heat exchanger (34) has first channels (34a) connected between the second heat source side liquid line (53b) and the third heat source side liquid line (53c) and second channels (34b) connected between the first main injection line (54m) and the second line Main injection channel (54n), and is configured to exchange heat between a refrigerant flowing through the first channels (34a) and a refrigerant flowing through the second channels (34b). s supercooling is configured as, for example, a plate heat exchanger.

"Supercooling expansion valve"

The supercooling expansion valve (35) is provided in a part of the injection pipe (54) between the first intermediate part (P1) of the heat source side liquid refrigerant pipe (53) and the exchanger (34 ) from supercooling heat (in this example, in the first main injection pipe (54m)). The supercooling expansion valve (35) has an adjustable opening degree. The supercooling expansion valve (35) is configured, for example, as an electronic expansion valve (motor-operated valve).

«Intermediate expansion valves»

The intermediate expansion valve (36a, 36b, 36c) is arranged in a part of the injection pipe (54) between the supercooling heat exchanger (34) and the intermediate port of the compressor (31a, 31b, 31c). In this example, the first, second, and third intermediate expansion valves (36a, 36b, 36c) are associated with the first, second, and third compressors (31a, 31b, 31c), respectively, and are provided in the lines (54a, 54b, 54c) of first, second and third injection branch, respectively. The intermediate expansion valves (36a, 36b, 36c) also have an adjustable degree of opening. The intermediate expansion valves (36a, 36b, 36c) are configured, for example, as electronic expansion valves (motor-operated valves).

<<Receiver>>

The receiver (37) is connected to a part of the heat source side liquid refrigerant pipe (53) between the heat source side heat exchanger (33) and the supercooling heat exchanger (34), and is capable of temporarily storing a condensed refrigerant in the condenser (specifically, the heat source side heat exchanger (33) or the utilization side heat exchangers (61)). In this example, the receiver (37) has its top and bottom respectively connected to the first and second heat source side liquid pipes (53a, 53b).

<< Connection pipes >>

The first connecting pipe (55) connects the second and third intermediate parts (P2, P3) of the heat source side liquid refrigerant pipe (53) together. The second intermediate part (P2) is a part of the heat source side liquid refrigerant pipe (53) between the first intermediate part (P1) and the liquid stop valve (V1), and the third part (P3 ) intermediate is a part of the liquid refrigerant pipe (53) on the side heat source between the liquid end of the heat source side heat exchanger (33) and the receiver (37).

The second connecting pipe (56) connects the fourth and fifth intermediate parts (P4, P5) of the heat source side liquid refrigerant pipe (53) together. The intermediate fourth part (P4) is a part of the heat source side liquid refrigerant pipe (53) between the supercooling heat exchanger (34) and the first intermediate part (P1), and the fifth part (P5 Intermediate is a part of the heat source side liquid refrigerant pipe (53) between the liquid end of the heat source side heat exchanger (33) and the third intermediate part (P3).

«Heat source side expansion valve >>

The heat source side expansion valve (38) is provided in the second connecting pipe (56). The heat source side expansion valve (38) has an adjustable degree of opening. The heat source side expansion valve (38) is configured, for example, as an electronic expansion valve (motor-operated valve).

"Retention valves"

The first check valve (CV1) is provided in a part of the heat source side liquid refrigerant pipe (53) between the third and fifth intermediate parts (P3, P5), and is configured to allow a refrigerant to flow only in one direction from the middle fifth part (P5) to the middle third part (P3). The second check valve (CV2) is provided in a part of the heat source side liquid refrigerant pipe (53) between the first and second intermediate parts (P1, P2), and is configured to allow a refrigerant to flow only in one direction from the first intermediate part (P1) towards the second intermediate part (P2). The third check valve (CV3) is provided in the first connection pipe (55) and is configured to allow a refrigerant to flow only in one direction from the second intermediate part (P2) to the third intermediate part (P3) of the heat source side liquid refrigerant pipe (53).

"Oil separator"

The oil separator (41) is provided in the discharge refrigerant pipe (51) (in this example, the discharge collection pipe (51 d)), and is capable of separating the refrigeration machine oil from a refrigerant discharged from the compressors (31a, 31b, 31c) and store the refrigeration machine oil therein.

<< Oil return pipe >>

The oil return pipe (57) is used to supply the refrigeration machine oil (relatively high temperature refrigeration machine oil) stored in the oil separator (41) to the injection pipe (54), and has two ends respectively connected to the oil separator (41) and an intermediate part of the injection pipe (54) between the supercooling heat exchanger (34) and the intermediate expansion valves (36a, 36b, 36c) (in this example , an intermediate part of the second main injection pipe (54n)).

<< Oil return expansion valve >>

The oil return expansion valve (42) is provided in the oil return line (57). The oil return expansion valve (42) has an adjustable opening degree. The oil return expansion valve (42) is configured, for example, as an electronic expansion valve (motor-operated valve).

<Usage side circuits>

Each use-side circuit (23) includes a use-side heat exchanger (61), a use-side open / close valve (62) and a use-side expansion valve (63). The use-side circuit (23) is provided with a use-side liquid refrigerant pipe (71) and a use-side gaseous refrigerant pipe (72).

<< Utilization side heat exchanger >>

The utilization side heat exchanger (61) has its liquid end connected to the liquid interconnection pipe (14) through the utilization side liquid refrigerant pipe (71), and has its gas end connected to the gas interconnection pipe (15) through the gaseous refrigerant pipe (72) of the use side. The fan (24) on the use side is arranged close to the heat exchanger (61) on the use side. The utilization-side heat exchanger (61) is configured to exchange heat between a refrigerant and utilization-side air (eg, indoor air) transferred by the utilization-side fan (24). The utilization side heat exchanger (61) is configured, for example, as a cross-finned tube and fin heat exchanger.

"Liquid refrigerant piping on the use side, gaseous refrigerant piping on the use side"

One end of the use-side liquid refrigerant pipe (71) is connected to the liquid interconnection pipe (14), and the other end thereof is connected to the liquid end of the side heat exchanger (61). of use. In this example, the use-side liquid refrigerant pipe (71) includes a first use-side liquid pipe (71a), one end of which is connected to the interconnecting liquid pipe (14), a pipe (71b) one end of which is connected to the other end of the first use-side liquid pipe (71a), and a second use-side liquid pipe (71c) that connects the other end of the drain pan pipe (71b) to the liquid end of the utilization side heat exchanger (61). One end of the utilization side gaseous refrigerant pipe (72) is connected to the gas end of the utilization side heat exchanger (61), and the other end of it is connected to the interconnection pipe (15) Of gas.

«Opening / closing valve on the operating side, expansion valve on the operating side»

The utilization side on / off valve (62) and utilization side expansion valve (63) are arranged in series in the utilization side liquid refrigerant line (71) (in this example, the second line (71c) of liquid from the use side.

The utilization side on / off valve (62) can switch between an open state and a closed state. The use-side on / off valve (62) is configured, for example, as a solenoid valve. The utilization side expansion valve (63) has an adjustable opening degree. In this example, the utilization side expansion valve (63) is configured as an externally equalized thermostatic expansion valve. Specifically, the utilization side expansion valve (63) includes a feeler bulb (63a) provided in the utilization side gaseous refrigerant line (72) and an equalizer (63b) connected to an intermediate portion of the line (72 ) of gaseous refrigerant on the use side, and has its opening degree adjusted according to the temperature of the probe bulb (63a) and the pressure of a refrigerant in the equalizer (63b).

<Drain pan>

The drain pan (25) is disposed below the utilization side heat exchanger (61) and is configured to collect condensed and frozen water falling from the surface of the utilization side heat exchanger (61). The drain pan pipe (71b) which is a part of the use-side liquid refrigerant pipe (71) is arranged in the drain pan (25).

<Liquid refrigerant piping>

In the refrigerant circuit (20), the heat source side liquid refrigerant pipe (53) and the liquid interconnection pipe (14) form a liquid refrigerant pipe (50). That is, the liquid end of the heat source side heat exchanger (33) is connected to the liquid refrigerant pipe (50). The use-side liquid refrigerant pipe (71) connects the liquid end of the use-side heat exchanger (61) to the liquid refrigerant pipe (50). The injection pipe (54) connects an intermediate part (the first intermediate part (P1)) of the liquid refrigerant pipe (50) to the intermediate ports of the compressors (31a, 31b, 31c). The supercooling heat exchanger (34) is connected to the liquid refrigerant pipe (50) and the injection pipe (54), and is configured to exchange heat between a refrigerant flowing through the refrigerant pipe (50). liquid and a refrigerant flowing through the injection line (54).

<< Various sensors >>

The refrigeration apparatus (10) is provided with various sensors such as first to third discharged refrigerant temperature sensors (81a-81c) and an injection refrigerant temperature sensor (82). In the following description, the first to third discharged refrigerant temperature sensors (81a-81c) are collectively referred to as "the discharged refrigerant temperature sensor (81a, 81b, 81c)."

The discharged refrigerant temperature sensor (81a, 81b, 81c) is configured to detect the temperature of a refrigerant discharged from the compressor (31a, 31b, 31c) (hereinafter referred to as the discharged refrigerant temperature (Td)). In this example, the first, second and third discharged refrigerant temperature sensors (81a, 81b, 81c) are respectively associated with the first, second and third intermediate expansion valves (36a, 36b, 36c) and are installed close to the discharge ports of the first, second and third compressors (31a, 31b, 31c) and detect the temperatures of the refrigerants at their respective installation locations as the temperatures (Td) of the discharged refrigerant).

The injection refrigerant temperature sensor (82) is configured to detect the temperature of a refrigerant flowing through a portion of the injection pipe (54) between the supercooling heat exchanger (34) and the valves (36a , 36b, 36c) of intermediate expansion (beneficially, between a joint (P6) of the injection pipe (54) and the oil return pipe (57) and the intermediate expansion valves (36a, 36b, 36c)). In this example, the injection refrigerant temperature sensor (82) is installed in a part of the second main injection pipe (54n) between the junction (P6) and the expansion valves (36a, 36b, 36c). intermediate to detect the temperature of a refrigerant in its place of installation as the temperature of a refrigerant flowing through a part of the second main injection pipe (54n) between the union (P6) and the valves (36a, 36b, 36c) intermediate expansion (hereinafter referred to as the injection coolant temperature (Tinj)).

<Controller (control section)>

The controller (13) controls the components of the refrigeration apparatus (10) to control the operations of the refrigeration apparatus (10). Specifically, the controller (13) controls the compressors (31a, 31b, 31c), the various fans (the fan (22) on the heat source side and the fans (24) on the utilization side) and the various valves (the four-way valve (32), supercooling expansion valve (35), intermediate expansion valves (36a, 36b, 36c), heat source side expansion valve (38), valve (42) oil return expansion valve, and the operating side opening / closing valves (62)), based on values detected by the various sensors (the discharged refrigerant temperature sensors (81a, 81b, 81c), the sensor ( 82) of injection coolant temperature and other sensors). Note that the refrigeration apparatus (10) operates in a cooling mode in which the indoor air is cooled, or in a defrost mode in which the utilization side heat exchangers (61) are defrosted. For a refrigeration appliance according to the present invention, the controller is configured as described by the attached independent claim 1.

<Cooling mode>

Next, an operation in a cooling mode will be described with reference to Figure 2. In the cooling mode, the refrigerant circuit (20) performs a refrigeration cycle in which the heat exchanger (33) on the cooling side The heat source functions as a condenser, the supercooling heat exchanger (34) functions as a supercooling element and the utilization side heat exchangers (61) function as evaporators.

Specifically, the four-way valve (32) is placed in the first state. This allows the discharge ports of the compressors (31a, 31b, 31c) to communicate with the gas end of the heat exchanger (33) on the heat source side, and allows the suction ports of the compressors (31a , 31b, 31c) communicate with the gas interconnection pipe (15). The compressors (31a, 31b, 31c), the fan (22) on the heat source side and the fans (24) on the utilization side are started. In addition, the opening degrees of the supercooling expansion valve (35) and the intermediate expansion valves (36a, 36b, 36c) are adjusted, the heat source side expansion valve (38) is placed in a state fully closed, and the oil return expansion valve (42) is intermittently placed in an open state. In each utilization-side unit (12), the utilization-side open / close valve (62) is placed in an open state or a closed state, depending on the load required to cool the indoor air and the degree of opening. of the expansion valve (63) on the utilization side is adjusted according to the temperature of the probe bulb (63a) and the pressure of a refrigerant in the equalizer (63b), so that the degree of overheating of a refrigerant at an outlet of the Use side heat exchanger (61) is equal to a predetermined degree of superheat. Note that Figure 2 shows a situation where the use-side open / close valves (62) of all the use-side units (12) are placed in the open state.

A refrigerant discharged from the compressors (31a, 31b, 31c) passes through the oil separator (41) in the discharge refrigerant pipe (51), then flows through the four-way valve (32) to the exchanger Heat source side heat (33) dissipates the heat to heat source side air (eg, outdoor air) in the heat source side heat exchanger (33) and condenses. The refrigerant (high pressure refrigerant) that has flowed out of the heat source side heat exchanger (33) passes through the first check valve (CV1) in the first source side liquid pipe (53a) heat, then passes through the receiver (37) and the second heat source side liquid pipe (53b) in this order, flows into the first channels (34a) of the supercooling heat exchanger (34), and It is supercooled by causing its heat to be absorbed by a refrigerant (intermediate pressure refrigerant) that flows through the second channels (34b) of the supercooling heat exchanger (34). The refrigerant that has flowed out of the first channels (34a) of the supercooling heat exchanger (34) flows into the third heat source side liquid pipe (53c). Part of the refrigerant that has entered the third heat source side liquid pipe (53c) flows to the first main injection pipe (54m). The remaining part passes through the second check valve (CV2) in the third heat source side liquid pipe (53c) and then flows through the liquid stop valve (V1) into the pipe (14 ) liquid interconnection.

The refrigerant that has entered the first main injection pipe (54m) is decompressed in the supercooling expansion valve (35), flows into the second channels (34b) of the supercooling heat exchanger (34) and absorbs heat from the refrigerant (high pressure refrigerant) flowing through the first channels (34a) of the supercooling heat exchanger (34). The refrigerant that has flowed out of the second channels (34b) of the supercooling heat exchanger (34) flows through the second main injection pipe (54n) to the injection branch pipes (54a, 54b, 54c). The refrigerant that has entered each injection branch pipe (54a, 54b, 54c) is decompressed in one of the associated valves (36a, 36b, 36c) intermediate expansion and flows into the intermediate orifice of one associated of the compressors (31a, 31b, 31c). The refrigerant that has flowed through the intermediate port into the compressor (31a, 31b, 31c) mixes with a refrigerant in the compressor (31a, 31b, 31c) (specifically, a refrigerant in the compression chamber). That is, the refrigerant in the compressor (31a, 31b, 31c) is compressed while cooling.

Meanwhile, the refrigerant that has entered the liquid interconnection pipe (14) flows to the first liquid pipe (71a) on the use side of the unit (12) on the use side that has its valve (62) positioned operating side opening / closing in open state. In the utilization-side unit (12) having its utilization-side opening / closing valve (62) set in the open state, the refrigerant that has entered the first utilization-side liquid pipe (71a) flows through the drain pan line (71b) into the second utilization side liquid line (71c). The refrigerant that has entered the second utilization side liquid line (71c) passes through the utilization side open / close valve (62) and is then decompressed in the utilization side expansion valve (63). of use. The decompressed refrigerant flows to the use-side heat exchanger (61) and absorbs heat from the use-side air (eg, indoor air) into the use-side heat exchanger (61) to evaporate. Therefore, the air on the use side is cooled. The refrigerant that has flowed out of the utilization side heat exchanger (61) passes through the utilization side gaseous refrigerant pipe (72), the gas interconnection pipe (15), the valve (V2) of gas stop, the four-way valve (32) and the suction refrigerant pipe (52) in this order, and is sucked through the suction ports of the compressors (31a, 31b, 31c).

The oil separator (41) separates the refrigeration machine oil from the refrigerant (that is, the refrigerant discharged from the compressors (31a, 31b, 31c)) and stores the refrigeration machine oil therein. Then, if the oil return expansion valve (42) is placed in the open state, the refrigeration machine oil (relatively high temperature refrigeration machine oil) stored in the oil separator (41) flows through from the oil return pipe (57) to the second main injection pipe (54n). The refrigeration machine oil flow that has entered the second main injection line (54n) merges with the flow of a refrigerant flowing through the second main injection line (54n). Then, the fused refrigerant flows through the intermediate expansion valves (36a, 36b, 36c) in the injection branch pipes (54a, 54b, 54c) to the intermediate ports of the compressors (31a, 31b, 31c).

In the cooling mode, the flow rate (injection quantity) of the refrigerant flowing to the intermediate port of the compressor (31 a, 31 b, 31c) can be adjusted by adjusting the opening degree of the valve (36a, 36b, 36c) intermediate expansion. Therefore, it is possible to adjust how much the temperature of a refrigerant in the compressor is going to decrease (31a, 31b, 31c). As a result, the temperature of the refrigerant discharged from the compressor (31a, 31b, 31c) (that is, the temperature (Td) of the discharged refrigerant) can be adjusted. Next, how the opening degree of the intermediate expansion valve (36a, 36b, 36c) is adjusted in the cooling mode will be described in detail.

In the cooling mode, the pressure of the refrigerant flowing through the supercooling expansion valve (35) into the second channels (34b) of the supercooling heat exchanger (34) in the injection pipe (54) can be adjust by adjusting the opening degree of the supercooling expansion valve (35). This allows adjustment of the degree of supercooling of the refrigerant in the supercooling heat exchanger (34) (specifically, the degree of supercooling of the refrigerant flowing out of the first channels (34a) of the supercooling heat exchanger (34)) and the temperature of the refrigerant flowing between the supercooling heat exchanger (34) and the intermediate expansion valves (36a, 36b, 36c) in the injection pipe (54). The flow rate of the refrigerant flowing through the supercooling expansion valve (35) into the second channels (34b) of the supercooling heat exchanger (34) in the injection pipe (54) can be adjusted by adjusting the opening degree of the supercooling expansion valve (35). This allows adjustment of the flow rates (injection quantities) of the refrigerant flowing from the second channels (34b) of the supercooling heat exchanger (34) through the intermediate expansion valves (36a, 36b, 36c) towards the orifices. intermediate of the compressors (31a, 31b, 31c). Next, how the opening degree of the supercooling expansion valve 35 is adjusted in the cooling mode will be described in detail.

In the cooling mode, intermittently placing the oil return expansion valve (42) in the open state allows the refrigeration machine oil stored in the oil separator (41) to intermittently flow into the return line (57). of oil. Therefore, the refrigeration machine oil can be efficiently returned to the compressors (31a, 31b, 31c). Next, it will be described in detail how the opening degree of the oil return expansion valve (42) in the cooling mode is adjusted.

<Defrost mode>

Next, an operation in a defrost mode will be described with reference to Figure 3. In the defrost mode, the refrigerant circuit (20) performs a refrigeration cycle in which the heat exchangers (61) on the The utilization functions as condensers and the heat exchanger (33) on the heat source side functions as an evaporator.

Specifically, the four-way valve (32) is placed in the second state. This allows the compressor discharge ports (31a, 31b, 31c) to communicate with the gas interconnecting pipe (15) and allows the compressor suction ports (31a, 31b, 31c) to communicate with the gas end of the heat exchanger (33) from the heat source side. The compressors (31a, 31b, 31c) and the fan (22) on the heat source side are turned on and the fan (24) on the utilization side is turned off. Furthermore, the supercooling expansion valve (35) is placed in a fully closed state. The intermediate expansion valves (36a, 36b, 36c) are placed in a fully closed state. The degree of opening of the heat source side expansion valve (38) is adjusted so that the degree of superheating of the refrigerant at the outlet of the heat source side heat exchanger (33) is equal to one degree target overheating. The oil return expansion valve (42) is placed in a fully closed state. In each utilization-side unit (12), the utilization-side opening / closing valve (62) is placed in the open state, and the utilization-side expansion valve (63) is placed in the fully open state. .

The refrigerant discharged from the compressors (31a, 31b, 31c) passes through the oil separator (41) in the discharge refrigerant pipe (51), then passes through the four-way valve (32) and the valve (V2) gas stop in this order, and flows into the gas interconnection pipe (15). The refrigerant that has entered the gas interconnection pipe (15) flows into the gaseous refrigerant pipes (72) on the use side of the units (12) on the use side. In each utilization-side unit (12), the refrigerant that has entered the utilization-side gaseous refrigerant pipe (72) flows to the utilization-side heat exchanger (61) and dissipates the heat in the exchanger ( 61) heat from the utilization side to condense it. Therefore, the frost formed on the utilization side heat exchanger (61) is heated to melt. The refrigerant that has flowed out of the utilization-side heat exchanger (61) flows into the second utilization-side liquid line (71c), passes through the utilization-side expansion valve (63) fully open and the utilization side on / off valve (62) open in this order, passes through the drain pan line (71b) and the first utilization side liquid line (71a) in this order, and flows towards the liquid interconnection pipe (14).

The refrigerant that has entered the liquid interconnection line (14) flows through the liquid stop valve (V1) to the third heat source side liquid line (53c). The refrigerant that has entered the third heat source side liquid pipe (53c) flows into the first connection pipe (55), passes through the third check valve (CV3) in the first pipe (55) connection point and flows into the first heat source side liquid pipe (53a). The refrigerant that has entered the first heat source side liquid line (53a) passes through the receiver (37), the second heat source side liquid line (53b), the first channels (34a) from the supercooling heat exchanger (34) in this order, and flows to the third heat source side liquid pipe (53c). The refrigerant that has entered the third heat source side liquid pipe (53c) flows into the second connecting pipe (56). The refrigerant that has entered the second connecting pipe (56) is decompressed in the expansion valve (38) on the heat source side and flows to the first liquid pipe (53a) on the heat source side. The refrigerant that has entered the first heat source side liquid pipe (53a) flows into the heat source side heat exchanger (33) and absorbs heat from the heat source side air (for example, outdoor air) into the heat exchanger (33) on the heat source side to evaporate it. The refrigerant that has flowed out of the heat source side heat exchanger (33) passes through the four-way valve (32) and the suction refrigerant pipe (52) in this order, and is sucked into the suction ports of the compressors. (31a, 31b, 31c).

In the defrost mode, a refrigerant (high temperature refrigerant) that has flowed out of the utilization side heat exchanger (61) that functions as a condenser flows through the drain pan pipe (71b). This allows the refrigerant flowing through the drain pan pipe (71b) to heat up and melt the frost remaining in the drain pan (25) (i.e. the accumulated frost on the drain pan (25) and blocks of ice resulting from the freezing of condensed water). Note that the water resulting from the melting of the remaining frost is discharged through a drain pipe (not shown).

[Adjusting the opening degrees of intermediate expansion valves]

Next, how the opening degree of the intermediate expansion valve (36a, 36b, 36c) is adjusted in the cooling mode will be described with reference to Figure 4. The controller (13) performs a first degree adjustment operation. opening (stages (ST11 -ST13)) each time a predetermined operating time elapses in the cooling mode. In the first operation of adjusting the opening degree, the controller (13) adjusts the opening degree of the intermediate expansion valve (36a, 36b, 36c) so that the temperature (Td) of the discharged refrigerant is below a predetermined higher discharged refrigerant temperature threshold (Tdth). In this example, the controller (13) performs the first opening degree adjustment operation for each of the first to third intermediate expansion valves (36a-36c). For example, the controller (13) performs the first opening degree adjustment operation for the first intermediate expansion valve (36a) associated with the first compressor (31a), based on the value detected by the first sensor (81 a) temperature of the discharged refrigerant. In the first operation of adjusting the degree of opening, the procedures indicated below are carried out.

<Stage (ST11)>

First, the controller (13) determines whether the temperature (Td) of the discharged refrigerant is below the highest discharged refrigerant temperature threshold (Tdth) (step (ST11)). The highest discharged refrigerant temperature threshold (Tdth) is set to be, for example, the threshold (higher value, such as 105 ° C) of the discharged refrigerant temperature (Td) which can be considered as not causing the compressor (31a, 31b, 31c) have an abnormally high temperature. If the temperature (Td) of the discharged refrigerant is below the highest discharged refrigerant temperature threshold (Tdth), the procedure advances to step (ST12). If not, the procedure advances to step (ST13).

<Stage (ST12): checking the degree of overheating of the discharged refrigerant>

If the temperature (Td) of the discharged refrigerant is below the highest discharged refrigerant temperature threshold (Tdth), the controller (13) adjusts the opening degree of the intermediate expansion valve (36a, 36b, 36c) from so that the superheat degree of the refrigerant discharged from the compressor (31a, 31b, 31c) (hereinafter referred to as the discharged superheat degree) is equal to a predetermined target superheat degree (for example, 15 ° C).

Specifically, if the discharged superheat degree is above the target superheat degree, the controller (13) increases the opening degree of the intermediate expansion valve (36a, 36b, 36c). This increases the flow rate (injection quantity) of the refrigerant flowing into the intermediate port of the compressor (31a, 31b, 31c), thereby increasing the amount of temperature of the refrigerant in the compressor (31a, 31b, 31c) that must decrease . As a result, the temperature of the refrigerant discharged from the compressor (31a, 31b, 31c) (that is, the temperature (Td) of the discharged refrigerant) can be lowered, thereby reducing the degree of superheat discharged.

On the other hand, if the discharged superheat degree is below the target superheat degree, the controller (13) reduces the opening degree of the intermediate expansion valve (36a, 36b, 36c). This increases the flow rate (injection quantity) of the refrigerant flowing into the intermediate port of the compressor (31a, 31b, 31c), thereby reducing how much the temperature of the refrigerant in the compressor (31a, 31b, 31c) will decrease. As a result, the temperature of the refrigerant discharged from the compressor (31a, 31b, 31c) (that is, the temperature (Td) of the discharged refrigerant) can be increased, thereby increasing the degree of superheat discharged.

If, in this way, the degree of opening of the intermediate expansion valve (36a, 36b, 36c) is adjusted so that the degree of superheating of the refrigerant discharged from the compressor (31a, 31b, 31c) is equal to the degree of superheating predetermined target, the flow rate (injection amount) of the refrigerant flowing to the intermediate port of the compressor (31a, 31b, 31c) can be appropriately adjusted.

<Stage (ST13)>

If the temperature (Td) of the discharged refrigerant is not below the highest discharged refrigerant temperature threshold (Tdth) (NO in step (ST11)), the controller (13) increases the valve opening degree ( 36a, 36b, 36c) of intermediate expansion a predetermined amount. This increases the flow rate (injection quantity) of the refrigerant flowing into the intermediate port of the compressor (31a, 31b, 31c), thereby increasing the amount of temperature of the refrigerant in the compressor (31a, 31b, 31c) that must decrease . As a result, the temperature of the refrigerant discharged from the compressor (31a, 31b, 31c) (that is, the temperature (Td) of the discharged refrigerant) can be lowered.

If, in step ST13, the intermediate expansion valve 36a, 36b, 36c has a maximum opening degree (for example, a fully open state), the controller 13 maintains the opening degree of the valve. (36a, 36b, 36c) of intermediate expansion at the maximum opening degree.

[Setting the opening degree of the supercooling expansion valve]

Next, how the opening degree of the supercooling expansion valve (35) is adjusted in the cooling mode will be described with reference to Figure 5. The controller (13) performs the procedure shown in Figure 5 (steps ( ST20-ST24)) each time a predetermined operating time elapses in cooling mode.

<Stage (ST20)>

First, the controller (13) determines whether the discharged refrigerant temperature (Td) is below the highest discharged refrigerant temperature threshold (Tdth). If the temperature (Td) of the discharged refrigerant is below the highest discharged refrigerant temperature threshold (Tdth), the procedure advances to step (ST21). If not, the procedure advances to step ST24.

<Stages (ST21-ST23): second opening degree setting operation>

If the temperature (Td) of the discharged refrigerant is below the highest discharged refrigerant temperature threshold (Tdth), the controller (13) performs a second opening degree adjustment operation. In the second operation of adjusting the opening degree, the controller (13) adjusts the opening degree of the supercooling expansion valve (35) so that the temperature of a refrigerant flowing through a part of the pipe ( 54) injection between the supercooling heat exchanger (34) and the intermediate expansion valves (36a, 36b, 36c) (in this example, the temperature (Tinj) of the injection refrigerant) is above a threshold ( Tfth) of default freezing temperature. The freezing temperature threshold (Tfth) is set to be, for example, the threshold (lower value, such as 02C) of the injection refrigerant temperature (Tinj) which can be considered as not causing the pipe (54) to injection is frozen. In the second operation of adjusting the degree of opening, the procedures indicated below are carried out.

<< Stage (ST21) >>

Specifically, the controller (13) determines whether the temperature (Tinj) of the injection coolant is above the freezing temperature threshold (Tfth). If the temperature (Tinj) of the injection refrigerant is above the freezing temperature threshold (Tfth), the procedure advances to step (ST22). If not, the procedure advances to step (ST23).

<< Stage (ST22) >>

If the temperature (Tinj) of the injection refrigerant is above the freezing temperature threshold (Tfth), the controller (13) reduces the opening degree of the supercooling expansion valve (35) by a predetermined amount (stage ( ST22)). This can reduce the pressure of the refrigerant flowing from the supercooling expansion valve (35) into the second channels (34b) of the supercooling heat exchanger (34) in the injection line (54). As a result, the degree of subcooling of the refrigerant in the supercooling heat exchanger (34) can be increased.

<< Stage (ST23) >>

On the other hand, if the temperature (Tinj) of the injection refrigerant is not above the freezing temperature threshold (Tfth), the controller (13) increases the opening degree of the supercooling expansion valve (35) one predetermined amount (step (ST23)). This can increase the pressure of the refrigerant flowing from the supercooling expansion valve (35) into the second channels (34b) of the supercooling heat exchanger (34) in the injection line (54). As a result, the temperature of the refrigerant flowing through a portion of the injection pipe (54) between the supercooling heat exchanger (34) and the intermediate expansion valves (36a, 36b, 36c) (in this example, the temperature (Tinj) of the injection coolant) can be increased.

<Stage (ST24)>

If the temperature (Td) of the discharged refrigerant is not above the threshold (Tdth) of the temperature of the highest discharged refrigerant (NO in step (ST20)), the controller (13) increases the degree of opening of the valve ( 35) of supercooling expansion a predetermined amount without performing the second opening degree adjustment operation (steps (ST21-ST23)). This can increase the flow rate of the refrigerant flowing from the supercooling expansion valve (35) into the second channels (34b) of the supercooling heat exchanger (34) in the injection pipe (54), and can increase the flow rate ( injection quantity) of the refrigerant that flows through each intermediate expansion valve (36a, 36b, 36c) to the intermediate orifice of an associated one of the compressors (31a, 31b, 31c). As a result, it is possible to increase how much the temperature of the refrigerant in each compressor (31a, 31b, 31c) will decrease, and the temperature of the refrigerant discharged from the compressor (31a, 31b, 31c) (that is, the temperature (Td) of the discharged refrigerant) can be reduced. Increasing the degree of opening of the supercooling expansion valve (35) can increase the pressure of the refrigerant flowing from the supercooling expansion valve (35) into the second channels (34b) of the supercooling heat exchanger (34). in the injection pipe (54). As a result, the temperature of the refrigerant flowing through a portion of the injection pipe (54) between the supercooling heat exchanger (34) and the intermediate expansion valves (36a, 36b, 36c) (in this example, the temperature (Tinj) of the injection coolant) can be increased.

If, in step ST22, the supercooling expansion valve (35) has a minimum opening degree (for example, a fully closed state), the controller (13) maintains the opening degree of the valve (35) of supercooling expansion at minimum opening degree. If, in stages (ST23, ST24), the supercooling expansion valve (35) has a maximum opening degree (for example, a fully open state), the controller (13) maintains the valve opening degree ( 35) of supercooling expansion at maximum opening degree.

[Oil return expansion valve opening degree adjustment]

Next, it will be described how the opening degree of the oil return expansion valve (42) is adjusted in the cooling mode with reference to Figure 6. The controller (13) performs a third operation of adjusting the degree of return. opening (stages (ST31-ST33)) each time a predetermined operating time elapses in cooling mode. In the third operation of adjusting the opening degree, the controller (13) adjusts the opening degree of the oil return expansion valve (42) so that the temperature of the refrigerant flowing through a part of the pipe (54) between the union (P6) of the injection pipe (54) and the oil return pipe (57) and the intermediate expansion valves (36a, 36b, 36c) (in this example, the temperature ( Tinj) of the injection coolant) is above the freezing temperature threshold (Tfth). In the third operation for adjusting the degree of opening, the procedures indicated below are carried out.

<Stage (ST31)>

First, the controller (13) determines whether the temperature (Tinj) of the injection coolant is above the freezing temperature threshold (Tfth). If the temperature (Tinj) of the injection refrigerant is above the freezing temperature threshold (Tfth), the procedure advances to step (ST32). If not, the procedure advances to step ST33.

<Stage (ST32)>

If the temperature (Tinj) of the injection refrigerant is above the freezing temperature threshold (Tfth), the controller (13) intermittently places the oil return expansion valve (42) in an open state so that the cooling machine oil flow rate passing through the oil return pipe (57) within a predetermined unit time period (i.e. the amount of oil return) is equal to a predetermined flow rate (a normal flow rate). ). Specifically, the controller (13) intermittently places the oil return expansion valve (42) in the open state, so that the period of time during which the oil return expansion valve (42) is placed in the Open state within a predetermined period of time is equal to a predetermined period of time (a normal period of time). Alternatively, the controller (13) sets the opening degree of the open oil return expansion valve (42) to be at a predetermined opening degree (a normal opening degree).

<Stage (ST33)>

If the temperature (Tinj) of the injection refrigerant is not above the freezing temperature threshold (Tfth), the controller (13) intermittently places the oil return expansion valve (42) in an open state, so that the flow rate of refrigeration machine oil passing through the oil return line (57) within a predetermined unit time period (i.e. the amount of oil return) increases by a predetermined rate (step (ST33 )). Specifically, the controller (13) intermittently places the oil return expansion valve (42) in the open state so that the period of time during which the oil return expansion valve (42) is placed in the open state. open within a predetermined period of time increases. Alternatively, the controller (13) may increase the opening degree of the open oil return expansion valve (42). Increasing the flow rate of the refrigeration machine oil (relatively high temperature refrigeration machine oil) passing through the oil return line (57) within a predetermined unit time period can increase the temperature of the refrigerant that flows through the part of the injection pipe (54) between the junction (P6) of the injection pipe (54) and the oil return pipe (57) and the expansion valves (36a, 36b, 36c) (in this example, the temperature (Tinj) of the injection coolant).

If, in step ST33, the flow rate of the cooling machine oil passing through the oil return pipe 57 within a predetermined unit time period (i.e. the amount of oil return) is higher, the controller (13) controls the opening / closing of the oil return expansion valve (42) to keep the amount of oil return at the highest flow rate. Specifically, if a period of time during which the oil return expansion valve (42) is in the open state within a predetermined unit time period is longer (for example, equal to the unit time period), the Controller (13) controls the opening / closing of the oil return expansion valve (42) to keep the period of time during which the valve is in the open state for the longest period of time. Alternatively, if the opening degree of the open oil return expansion valve (42) is higher (for example, in the fully open state), the controller (13) can control the opening / closing of the valve (42 ) oil return expansion valve to keep the opening degree of the oil return expansion valve (42) open at the highest opening degree.

[Advantages of the realization]

As can be seen from the above description, adjusting the opening degree of the intermediate expansion valve (36a, 36b, 36c) in the first opening degree setting operation allows the temperature (Td) of the refrigerant discharged from the compressor (31a, 31b, 31c) is set to be below the highest discharged refrigerant temperature threshold (Tdth). Therefore, the compressor (31a, 31b, 31c) can be protected against abnormally high temperatures. Adjusting the opening degree of the supercooling expansion valve (35) in the second opening degree setting operation allows the temperature of the refrigerant flowing through a part of the injection pipe (54) between the exchanger (34) supercooling heat and intermediate expansion valves (36a, 36b, 36c) are adjusted to be above the freezing temperature threshold (Tfth). This can reduce the degree of freezing of the injection line 54 (specifically, the degree of progression of freezing).

If the temperature (Td) of the refrigerant discharged from the compressor (31a, 31b, 31c) is not below the threshold (Tdth) of the temperature of the highest discharged refrigerant, the increase in the degree of opening of the expansion valve (35) Supercooling can lower the temperature. of the refrigerant discharged from the compressor (31a, 31b, 31c), and can increase the temperature of the refrigerant that flows through a part of the injection pipe (54) between the supercooling heat exchanger (34) and the valves ( 36a, 36b, 36c) of intermediate expansion. This allows the compressors (31a, 31b, 31c) to be protected against abnormally high temperatures and reduces the degree of freezing of the injection pipe (54).

In the first operation of adjusting the degree of opening, if the temperature (Td) of the refrigerant discharged from the compressor (31a, 31b, 31c) is not below the threshold (Tdth) of the temperature of the highest discharged refrigerant, the increase of the The degree of opening of the intermediate expansion valve (36a, 36b, 36c) can reduce the temperature of the refrigerant discharged from the compressor (31a, 31b, 31c). Therefore, the compressor (31a, 31b, 31c) can be protected against abnormally high temperatures.

In the second operation of adjusting the degree of opening, if the temperature of the refrigerant flowing through the part of the injection pipe (54) between the supercooling heat exchanger (34) and the valves (36a, 36b, 36c ) of intermediate expansion is above the freezing temperature threshold (Tfth), reducing the degree of opening of the supercooling expansion valve (35) increases the degree of subcooling of the refrigerant in the heat exchanger (34) of supercooling. This can improve the cooling capacity of the utilization side heat exchanger (61). On the other hand, if the temperature of the refrigerant flowing through the part of the injection pipe (54) between the supercooling heat exchanger (34) and the intermediate expansion valves (36a, 36b, 36c) is not found Above the freezing temperature threshold (Tfth), increasing the degree of opening of the supercooling expansion valve (35) can increase the temperature of the refrigerant flowing through the part of the injection pipe (54) between the supercooling heat exchanger (34) and the intermediate expansion valves (36a, 36b, 36c). This can reduce the degree of freezing of the injection line (54).

Adjusting the opening degree of the oil return expansion valve (42) in the third opening degree adjusting operation allows the refrigeration machine oil flow rate (relatively high temperature refrigeration machine oil) flowing from the oil separator (41) through the oil return pipe (57) into the injection pipe (54) is fitted. Therefore, the temperature of the refrigerant flowing through the part of the injection pipe (54) between the joint (P6) of the injection pipe (54) and the oil return pipe (57) and the valves ( 36a, 36b, 36c) intermediate expansion joints can be adjusted.

In the third operation of adjusting the degree of opening, if the temperature of the refrigerant flowing through the part of the injection pipe (54) between the joint (P6) of the injection pipe (54) and the pipe (57 ) oil return and intermediate expansion valves (36a, 36b, 36c) is not above the freezing temperature threshold (Tfth), the increase in the flow rate of the refrigeration machine oil (refrigeration machine oil) relatively high temperature) that passes through the oil return pipe (57) within a predetermined unit time period triggers an increase in the temperature of the refrigerant that flows through the part of the injection pipe (54) between the junction (P6) of the injection pipe (54) and the oil return pipe (57) and the intermediate expansion valves (36a, 36b, 36c). This can reduce the degree of freezing of the injection line (54).

(Other realizations)

In the above description, an exemplary refrigeration apparatus (10) includes two utilization-side units (12). However, the number of units 12 on the use side can be one, three or more.

The exemplary refrigerant circuit (20) includes three compressors (compressors (31 to-31c) first through third). However, the number of compressors can be one, two, four or more.

Note that the foregoing description of the embodiment is merely a beneficial example in nature, and is not intended to limit the scope, application, or uses of the present invention as defined solely by the appended claims.

Industrial applicability

As can be seen from the above description, the above-mentioned refrigeration apparatus is useful as a refrigeration apparatus that cools an internal space, etc.

Description of the reference characters

10 Refrigeration appliance

11 Heat source side unit

12 Utilization side unit

13 Controller (control section)

20 Refrigerant circuit

21 Heat source side circuit

22 Heat source side fan

23 Operating side circuit

24 Usage side fan

25 Drain pan

31st First compressor

31b Second compressor

31c Third compressor

32 Four-way valve

33 Heat source side heat exchanger

34 Supercooling heat exchanger

35 Supercooling Expansion Valve

36a First intermediate expansion valve

36b Second intermediate expansion valve

36c Third intermediate expansion valve

37 Receiver

38 Heat source side expansion valve

41 Oil separator

42 Oil return expansion valve

50 Liquid refrigerant piping

51 Discharge refrigerant piping

52 Suction refrigerant piping

53 Heat source side liquid refrigerant piping 54 Injection piping

55 First connection pipe

56 Second connecting pipe

57 Oil return line

61 Use side heat exchanger

62 Operating side on / off valve

63 Utilization side expansion valve

71 Utilization side liquid refrigerant piping 72 Utilization side gaseous refrigerant piping

Claims (6)

1. A refrigeration apparatus comprising: a refrigerant circuit (20) including a compressor (31a, 31b, 31c), a heat exchanger (33) on the heat source side, a heat exchanger (61) on the use side, a pipe (50) of liquid refrigerant connecting a liquid end of the heat source side heat exchanger (33) to a liquid end of the utilization side heat exchanger (61), an injection pipe (54) connecting a part (P1) intermediate the liquid refrigerant pipe (50) to an intermediate port of the compressor (31a, 31b, 31c), a supercooling heat exchanger (34) connected to the liquid refrigerant pipe (50) and the pipe ( 54) injection for exchanging heat between a refrigerant flowing through the liquid refrigerant line (50) and a refrigerant flowing through the injection line (54), a supercooling expansion valve (35) provided in a part of the injection pipe (54) n between the intermediate part (P1) of the liquid refrigerant pipe (50) and the supercooling heat exchanger (34), and an intermediate expansion valve (36a, 36b, 36c) provided in a part of the pipe (54 ) injection between the supercooling heat exchanger (34) and the intermediate orifice of the compressor (31a, 31b, 31c); that understands a control section (13) configured to perform first and second opening degree adjustment operations in a cooling mode in which the refrigerant circuit (20) performs a refrigeration cycle wherein the heat exchanger (33) of the The heat source side functions as a condenser, the supercooling heat exchanger (34) functions as a supercooling element, and the heat exchanger (61) on the utilization side functions as an evaporator, adjusting an opening degree of the intermediate expansion valve (36a, 36b, 36c) in the first operation of adjusting the degree of opening so that a temperature (Td) of a refrigerant discharged from the compressor (31a, 31b, 31c) is below a threshold ( Tdth) of default highest discharged refrigerant temperature, characterized by what An opening degree of the supercooling expansion valve (35) is adjusted in the second opening degree setting operation so that a temperature of a refrigerant flows through a part of the injection pipe (54) between the Supercooling heat exchanger (34) and intermediate expansion valve (36a, 36b, 36c) is above a predetermined freezing temperature threshold (Tfth). 2. The refrigeration apparatus according to claim 1, wherein If the temperature (Td) of the refrigerant discharged from the compressor (31a, 31b, 31c) is below the highest discharged refrigerant temperature threshold (Tdth), the control section (13) performs the second degree setting operation. opening, and if the temperature (Td) of the refrigerant discharged from the compressor (31a, 31b, 31c) is not below the highest discharged refrigerant temperature threshold (Tdth), the control section (13) increases the degree opening of the supercooling expansion valve (35). The refrigeration apparatus according to claim 1 or 2, wherein In the first operation of adjusting the degree of opening, if the temperature (Td) of the refrigerant discharged from the compressor (31a, 31b, 31c) is below the threshold (Tdth) of the temperature of the highest discharged refrigerant, the section (13 ) control adjusts the opening degree of the intermediate expansion valve (36a, 36b, 36c) so that a superheat degree of the refrigerant discharged from the compressor (31a, 31b, 31c) is equal to a predetermined target superheat degree, and if the temperature (Td) of the refrigerant discharged from the compressor (31a, 31b, 31c) is not below the highest discharged refrigerant temperature threshold (Tdth), the control section (13) increases the opening degree of the intermediate expansion valve (36a, 36b, 36c). The refrigeration apparatus according to any of claims 1-3, wherein In the second operation of adjusting the degree of opening, if the temperature of the refrigerant flowing through the part of the injection pipe (54) between the supercooling heat exchanger (34) and the valve (36a, 36b, 36c ) of intermediate expansion is above the freezing temperature threshold (Tfth), the control section (13) reduces the opening degree of the supercooling expansion valve (35), and if the temperature of the refrigerant flowing to through the part of the injection pipe (54) between the supercooling heat exchanger (34) and the intermediate expansion valve (36a, 36b, 36c) is not above the freezing temperature threshold (Tfth), The control section (13) increases the opening degree of the supercooling expansion valve (35). The refrigeration apparatus according to any of claims 1-4, wherein The refrigerant circuit (20) includes an oil separator (41) configured to separate the refrigeration machine oil from the refrigerant discharged from the compressor (31a, 31b, 31c), an oil return pipe (57) having two ends respectively connected to the oil separator (41) and an intermediate part of the injection pipe (54) between the supercooling heat exchanger (34) and the expansion valve (36a, 36b, 36c) intermediate, and an oil return expansion valve (42) provided in the oil return line (57) and In the cooling mode, the control section (13) performs a third opening degree adjustment operation in which an opening degree of the oil return expansion valve (42) is adjusted so that a temperature of a refrigerant flowing through a part of the injection pipe (54) between a joint (P6) of the injection pipe (54) and the oil return pipe (57) and the valve (36a, 36b, 36c ) of intermediate expansion is above the freezing temperature threshold (Tfth). The refrigeration apparatus according to claim 5, wherein In the third operation of adjusting the degree of opening, if the temperature of the refrigerant flowing through the part of the injection pipe (54) between the joint (P6) of the injection pipe (54) and the pipe (57 ) return oil and the intermediate expansion valve (36a, 36b, 36c) is above the freezing temperature threshold (Tfth), the control section (13) intermittently places the return expansion valve (42) of oil in an open state such that a flow rate of refrigeration machine oil passing through the oil return line (57) within a predetermined unit time period is equal to a predetermined flow rate, and if the temperature of the refrigerant flowing through the part of the injection pipe (54) between the joint (P6) of the injection pipe (54) and the oil return pipe (57) and the valve (36a, 36b, 36c ) of intermediate expansion is not above the threshold (Tfth) of tem freezing temperature, the control section (13) intermittently places the oil return expansion valve (42) in the open state so that the flow rate of the cooling machine oil passing through the Oil return within the predetermined unit time period increases.