WO2021201143A1

WO2021201143A1 - Refrigeration device

Info

Publication number: WO2021201143A1
Application number: PCT/JP2021/013956
Authority: WO
Inventors: 和志久山; 正倫浮舟; 岡本　哲也; 大野　正雄; 柯壁陳
Original assignee: ダイキン工業株式会社
Priority date: 2020-03-31
Filing date: 2021-03-31
Publication date: 2021-10-07
Also published as: JP6897837B1; JP2021162236A

Abstract

A refrigeration device (10) is provided with: a refrigerant circuit (20) including a first compressor (21) and a second compressor (22) connected to the discharge side of the first compressor (21); and a control unit (100) for controlling the refrigerant circuit (20). The control unit (100) performs first control of increasing the differential pressure between the discharge side and the intake side of the first compressor (21) before or at the start of a second operation in which the first compressor (21) and a second compressor (22) are driven.

Description

Freezer

This disclosure relates to a freezing device.

Patent Document 1 discloses a freezing device including a refrigerant circuit including a first compressor and a second compressor connected to the discharge side of the first compressor. In this freezing device, it is possible to switch between the first operation in which the first compressor is stopped and the second compressor is driven, and the second operation in which the first compressor and the second compressor are driven. be.

Japanese Unexamined Patent Publication No. 2008-64421

The inventors of the present application are provided with a bypass pipe that bypasses the discharge side and the suction side of the first compressor and a check valve connected to the bypass pipe in order to switch between the first operation and the second operation. Was created. In the first operation, the refrigerant flowing out of the evaporator is sucked into the second compressor being driven via the bypass pipe. In the second operation, the check valve closes due to the increase in the differential pressure between the suction side and the discharge side of the first compressor, and the evaporated refrigerant is sent to the suction side of the first compressor without passing through the bypass pipe. Be done.

However, if the refrigerant pressure on the suction side is relatively low in the first compressor, the refrigerant pressure on the discharge side may also decrease accordingly. Therefore, even if the second operation is started, the differential pressure does not rise to the extent that the check valve is closed, and the refrigerant continues to be sucked into the second compressor via the bypass pipe. As a result, the check valve may not close after the start of the second operation.

An object of the present disclosure is to provide a refrigerating device that prevents the check valve connected to the bypass pipe from closing after the start of the second operation.

The first aspect of the present disclosure is
The first compressor (21) and the second compressor (22) connected to the discharge side of the first compressor (21) are included, and the first compressor (21) is stopped and the second compressor is stopped. It is possible to switch between the first operation of performing the refrigeration cycle in which (22) is driven and the second operation of performing the refrigeration cycle in which the first compressor (21) and the second compressor (22) are driven. Refrigerant circuit (20) and
A control unit (100) for controlling the refrigerant circuit (20) is provided.
The refrigerant circuit (20)
A bypass pipe (PB) connecting the suction side and the discharge side of the first compressor (21), and
It is connected to the bypass pipe (PB) and has a check valve (29) that limits the flow of refrigerant from the discharge side to the suction side of the first compressor (21).
The control unit (100) executes the first control for increasing the differential pressure between the discharge side and the suction side of the first compressor (21) before or at the start of the second operation.

In the first aspect, since the bypass pipe (PB) connects the suction side and the discharge side of the first compressor (21), the suction side and the discharge side of the first compressor (21) are connected by the first control. As the differential pressure increases, the differential pressure between the inflow side and the outflow side of the check valve (29) also increases. As a result, it is possible to prevent the check valve (29) from not closing after the start of the second operation.

A second aspect of the present disclosure is, in the first aspect, the first aspect.
The control unit (100) performs the first compressor (21) as the first control before starting the second operation from the stopped state of the first compressor (21) and the second compressor (22). 21) is driven.

In the second aspect, since the first compressor (21) is driven from the state where the first compressor (21) and the second compressor (22) are stopped, the refrigerant is the first compressor ( It is compressed by 21). As a result, the differential pressure between the suction side and the discharge side of the first compressor (21) increases. As a result, the differential pressure between the inflow side and the outflow side of the check valve (29) can be increased at the start of the subsequent second operation.

A third aspect of the present disclosure is the second aspect.
When the pressure difference between the discharge side and the suction side of the first compressor (21) becomes equal to or higher than a predetermined value while the first compressor (21) is driven by the first control, the control unit (100) , The second operation is executed.

In the third aspect, the second operation can be started after the differential pressure between the discharge side and the suction side of the first compressor (21) is increased to a predetermined value or more.

A fourth aspect of the present disclosure is the second aspect.
The control unit (100)
When the time for driving the first compressor (21) by the first control exceeds a predetermined time, the second operation is executed.

When a predetermined time elapses after the first compressor (21) is driven by the first control, the differential pressure between the suction side and the discharge side of the first compressor (21) rises to some extent. Therefore, in the fourth aspect, when a predetermined time elapses after the first compressor (21) is driven by the first control, the control unit (100) executes the second operation. As a result, the second operation can be started after the differential pressure between the suction side and the discharge side of the first compressor (21) is increased to some extent.

A fifth aspect of the present disclosure is, in any one of the first to fourth aspects,
The control unit (100) reduces the rotation speed of the second compressor (22) as the first control before switching from the first operation to the second operation.

In the fifth aspect, when the rotation speed of the second compressor (22) decreases, the pressure on the suction side of the second compressor (22) increases. Here, the suction side of the second compressor (22) and the discharge side of the first compressor (21) have substantially the same pressure. Since the first compressor (21) is stopped, the pressure on the discharge side and the suction side of the first compressor (21) are almost the same. Therefore, in the first operation, when the pressure on the suction side of the second compressor (22) rises, the pressure on the suction side of the first compressor (21) can be increased. As a result, the pressure on the discharge side of the first compressor (21) can be increased at the start of the second operation.

A sixth aspect of the present disclosure is, in the fifth aspect, the fifth aspect.
The control unit (100) has a predetermined value as an index indicating the pressure of the refrigerant on the suction side of the second compressor (22) while the rotation speed of the second compressor (22) is reduced by the first control. When the above is achieved, the second operation is executed.

In the sixth aspect, when the rotation speed of the second compressor decreases due to the first control, the pressure of the refrigerant on the suction side of the second compressor (22) increases. When the pressure of the refrigerant on the suction side of the second compressor (22) becomes a predetermined value or more, the pressure on the suction side of the discharge side of the first compressor (21) also becomes a predetermined value or more. The control unit (100) executes the second operation when the pressure on the suction side of the first compressor (21) becomes equal to or higher than a predetermined value. As a result, the second operation can be started after the differential pressure between the suction side and the discharge side of the first compressor (21) is increased to some extent.

A seventh aspect of the present disclosure is the first to sixth aspects.
At the start of the second operation, the control unit (100) measures the flow rate of the refrigerant of the second compressor (22) being driven as the first control of the first compressor (21) being driven. The rotation speed of at least one of the first compressor (21) and the second compressor (22) is adjusted so as to be equal to or less than the flow rate of the refrigerant of.

In the seventh aspect, at the start of the second operation (when the first compressor (21) is driven), the flow rate of the refrigerant flowing through the second compressor (22) is equal to or less than the flow rate flowing through the first compressor (21). Then, the pressure on the discharge side of the first compressor (21) rises. As a result, the pressure on the suction side of the first compressor (21) increases, so that the pressure difference between the discharge side and the suction side of the first compressor (21) can be increased.

The eighth aspect of the present disclosure is, in the seventh aspect, the seventh aspect.
At the start of the second operation, the control unit (100) measures the flow rate of the refrigerant of the second compressor (22) being driven as the first control of the first compressor (21) being driven. The rotation speed of the first compressor (21) is not changed so as to be equal to or less than the flow rate of the refrigerant of the above, and the rotation speed of the second compressor (22) is reduced.

In the eighth aspect, the flow rate of the refrigerant flowing through the second compressor (22) is set to be equal to or less than the flow rate flowing through the first compressor (21) without changing the rotation speed of the first compressor (21). Can be done.

A ninth aspect of the present disclosure is the seventh aspect of the present disclosure.
The control unit (100)
At the start of the second operation, as the first control, the flow rate of the refrigerant of the second compressor (22) being driven becomes equal to or less than the flow rate of the refrigerant of the first compressor (21) being driven. In addition, the rotation speed of the first compressor (21) is increased without changing the rotation speed of the second compressor (22).

In the ninth aspect, the flow rate of the refrigerant flowing through the second compressor (22) is set to be equal to or less than the flow rate flowing through the first compressor (21) without changing the rotation speed of the second compressor (22). Can be done.

A tenth aspect of the present disclosure is the first to ninth aspects.
The refrigerant circuit (20)
It has an injection mechanism (30) that introduces a refrigerant between the discharge side of the first compressor (21) and the suction side of the second compressor (22).
The control unit (100) first compresses the refrigerant by the injection mechanism (30) as the first control before switching from the first operation to the second operation or at the start of the second operation. It is introduced between the discharge side of the machine (21) and the suction side of the second compressor (22).

In the tenth aspect, the pressure of the refrigerant between the first compressor (21) and the second compressor (22) can be increased by the injection mechanism (30). As a result, the pressure on the discharge side of the first compressor (21) can be increased.

The eleventh aspect of the present disclosure is the first to tenth aspects.
The control unit (100) performs the first control when the outside air temperature is equal to or lower than a predetermined value.

In the eleventh aspect, it is possible to prevent the differential pressure between the suction side and the discharge side of the first compressor (21) from becoming small by performing the first control when the outside air temperature is equal to or lower than a predetermined temperature.

FIG. 1 is a piping diagram illustrating the configuration of the freezing device of the first embodiment. FIG. 2 is a block diagram showing the relationship between the control unit, various sensors, and the constituent devices of the refrigerant circuit. FIG. 3 is a view corresponding to FIG. 1 showing the flow of the refrigerant during the first heating operation. FIG. 4 is a view corresponding to FIG. 1 showing the flow of the refrigerant during the second heating operation. FIG. 5 is a view corresponding to FIG. 1 showing the flow of the refrigerant during the first cooling operation. FIG. 6 is a view corresponding to FIG. 1 showing the flow of the refrigerant during the second cooling operation. FIG. 7 is a flowchart of the operation performed by the control unit in the first operation. FIG. 8 is a flowchart of the operation performed by the control unit in the second operation. FIG. 9 is a block diagram showing the relationship between the control unit of the refrigerating apparatus according to the first modification, various sensors, and the constituent devices of the refrigerant circuit. FIG. 10 is a flowchart of an operation performed by the control unit of the refrigerating apparatus according to the first modification. FIG. 11 is a view corresponding to FIG. 7 performed by the control unit of the refrigerating apparatus according to the second modification. FIG. 12 is a view corresponding to FIG. 8 performed by the control unit of the refrigerating apparatus according to the third modification. FIG. 13 is a flowchart of an operation performed by the control unit of the refrigerating apparatus according to the modified example 4.

Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. It should be noted that the following embodiments are essentially preferred examples and are not intended to limit the scope of the present invention, its applications, or its uses. The arrows in the figure indicate the flow of the refrigerant in the refrigerant circuit.

<< Embodiment 1 >>
As shown in FIG. 1, the freezing device (10) of the first embodiment heats the target fluid. The target fluid is water. The refrigerating device (10) supplies the heated water to the equipment used such as a hot water supply tank, a coil for heating, and a coil for floor heating. The refrigerating device (10) cools the target fluid. The target fluid is water. The refrigerating device (10) supplies the cooled water to the utilization equipment such as a cooling coil. The refrigerating device (10) includes a refrigerant circuit (20) and a control unit (100).

[Refrigerant circuit]
The refrigerant circuit (20) includes a first compressor (21), a second compressor (22), a four-way switching valve (23), a heat source side heat exchanger (24), and a check valve bridge (25). ), An expansion valve (26), a user-side heat exchanger (27), an accumulator (28), and a bypass check valve (29). The refrigerant circuit (20) is filled with a refrigerant, and the refrigeration cycle is performed by circulating the refrigerant in the refrigerant circuit (20). The refrigerant is, for example, R410A, R32, R407C and the like.

The refrigerant circuit (20) can perform the first operation and the second operation. In the first operation, one of the second compressors (22) is driven and the first compressor (21) is stopped. In the second operation, both the first compressor (21) and the second compressor (22) are driven. The first operation and the second operation will be described in detail later.

<First compressor>
The first compressor (21) compresses the sucked refrigerant and discharges the compressed refrigerant. A first suction pipe (51) and a first discharge pipe (52) are connected to the first compressor (21). The first compressor (21) is, for example, a scroll type compressor. The first compressor (21) has a compression mechanism (not shown) and an electric motor (not shown) for driving the compression mechanism.

The motor of the first compressor (21) is a variable capacity type. Specifically, an inverter device is connected to the motor. The inverter device adjusts the output frequency of the electric power supplied from the power source to the motor. As a result, the rotation speed (operating frequency) of the electric motor of the first compressor (21) is adjusted.

<Second compressor>
The second compressor (22) is provided on the discharge side of the first compressor (21). The second compressor (22) compresses the sucked refrigerant and discharges the compressed refrigerant. The second compressor (22) has a larger capacity than the first compressor (21). In the second compressor (22), the second suction pipe (53) and the second discharge pipe (54) are connected. The inflow end of the second suction pipe (53) and the outflow end of the first discharge pipe (52) are connected. The first compressor (21) and the second compressor (22) are connected in series.

The second compressor (22) is, for example, a scroll type compressor. The second compressor (22) has a compression mechanism (not shown) and an electric motor (not shown) for driving the compression mechanism.

The motor of the second compressor (22) is a variable capacity type. Specifically, an inverter device is connected to the motor. The inverter device adjusts the output frequency of the electric power supplied from the power source to the motor. As a result, the rotation speed (operating frequency) of the electric motor of the second compressor (22) is adjusted.

<Four-way switching valve>
The four-way switching valve (23) is an electric switching valve. The four-way switching valve (23) is switched between a first state (a state shown by a solid line in FIG. 1) and a second state (a state shown by a broken line in FIG. 1). In the first state, the first port (P1) and the fourth port (P4) communicate with each other, and the second port (P2) and the third port (P3) communicate with each other. In the second state, the first port (P1) and the third port (P3) communicate with each other, and the second port (P2) and the fourth port (P4) communicate with each other.

The first port (P1) is connected to the outflow end of the second discharge pipe (54). The second port (P2) is connected to the inflow end of the first suction pipe (51). The third port (P3) communicates with the gas side end of the heat source side heat exchanger (24). The fourth port (P4) communicates with the gas side end of the user side heat exchanger (27).

<Heat source side heat exchanger>
The heat source side heat exchanger (24) exchanges heat between the refrigerant and the outdoor air (an example of the heat source side fluid). The heat source side heat exchanger (24) is an outdoor heat exchanger.

<Check valve bridge>
The check valve bridge (25) has four pipes and four check valves (C) connected to the respective pipes. The four check valves (C) include a first check valve (C1), a second check valve (C2), a third check valve (C3), and a fourth check valve (C4).

The main liquid pipe (55) is connected to the check valve bridge (25). Specifically, one end of the main liquid pipe (55) is connected to the inflow side of the second check valve (C2) and the inflow side of the fourth check valve (C4). The other end of the main liquid pipe (55) is connected to the outflow side of the first check valve (C1) and the outflow side of the third check valve (C3).

The check valve bridge (25) communicates with the liquid side end of the heat source side heat exchanger (24) and the liquid side end of the user side heat exchanger (27). Specifically, the outflow side of the second check valve (C2) and the inflow side of the first check valve (C1) communicate with the liquid side end of the heat source side heat exchanger (24). The outflow side of the fourth check valve (C4) and the inflow side of the third check valve (C3) communicate with the liquid side end of the utilization side heat exchanger (27).

Each of the first to fourth check valves (C1 to C4) allows the flow of the refrigerant in the direction indicated by the arrow in FIG. 1 and limits the flow of the refrigerant in the opposite direction.

<Expansion mechanism>
The expansion valve (26) expands the refrigerant to reduce the pressure of the refrigerant. The expansion valve (26) corresponds to the decompression mechanism. In this example, the expansion valve (26) is composed of an expansion valve (for example, an electronic expansion valve) whose opening degree can be adjusted. The expansion valve (26) is connected to the main liquid pipe (55).

<Heat exchanger on the user side>
The user-side heat exchanger (27) exchanges heat between the refrigerant and water. The user-side heat exchanger (27) has a first flow path (27a) and a second flow path (27b). The first flow path (27a) is a flow path through which the refrigerant flows. The second flow path (27b) is a flow path through which water flows. The second flow path (27b) is connected in the middle of the user side circuit (61) provided in the user equipment. In the user-side heat exchanger (27), the refrigerant flowing through the first flow path (27a) and the water flowing through the second flow path (27b) exchange heat.

<accumulator>
The accumulator (28) is connected in the middle of the first suction pipe (51). The accumulator (28) is a gas-liquid separator. In the accumulator (28), it is separated into a liquid refrigerant and a gas refrigerant. The accumulator (28) is configured such that only the gas refrigerant flows out of the accumulator (28).

<Bypass circuit>
The bypass circuit (60) has a bypass pipe (PB) and a bypass check valve (29). The bypass pipe (PB) connects the suction side and the discharge side of the first compressor (21). Specifically, one end of the bypass pipe (PB) is connected to the outflow end of the first discharge pipe (52) and the inflow end of the second suction pipe (53). The other end of the bypass pipe (PB) is connected between the accumulator (28) and the first compressor (21) in the first suction pipe (51).

The bypass check valve (29) limits the flow of refrigerant from the discharge side to the suction side of the first compressor (21), while allowing the flow of refrigerant in the opposite direction. Specifically blocking the absolute value [Delta] P _O of the differential pressure between the inlet side and the outlet side of the bypass check valve (29) is equal to or greater than [Delta] P _n is a predetermined pressure difference, the flow of the refrigerant in the bypass pipe (PB) The valve of the bypass check valve (29) closes so as to do so. Will be described later [Delta] P _O and [Delta] P _n.

[Injection mechanism]
The injection mechanism (30) introduces a refrigerant between the discharge side of the first compressor (21) and the suction side of the second compressor (22). Specifically, the injection mechanism (30) supplies a part of the refrigerant flowing through the main liquid pipe (55) to the suction side of the second compressor (22) in the second operation. The injection mechanism (30) has an injection pipe (PJ) and an injection expansion valve (31).

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

The injection expansion valve (31) is connected to the upstream side of the intermediate heat exchanger (40) in the injection pipe (PJ). The injection expansion valve (31) depressurizes the refrigerant flowing through the injection pipe (PJ).

[Intermediate heat exchanger]
The intermediate heat exchanger (40) has a third flow path (40a) and a fourth flow path (40b). The third flow path (40a) is connected in the middle of the main liquid pipe (55). The fourth flow path (40b) is connected in the middle of the injection pipe (PJ). In the intermediate heat exchanger (40), the refrigerant flowing through the main liquid pipe (55) and the refrigerant flowing through the fourth flow path (40b) exchange heat.

[Sensor]
The refrigerating apparatus (10) has various sensors such as a temperature sensor that detects the temperature of the refrigerant and the like, and a pressure sensor that detects the pressure of the refrigerant and the like. The detection results (signals) of various sensors are transmitted to the control unit (100). For example, the refrigerating device (10) has a first pressure sensor (41) and a second pressure sensor (42).

The first pressure sensor (41) is connected to the first suction pipe (51). The first pressure sensor (41) detects the pressure value P ₁ of the refrigerant in the first suction pipe (51). The pressure value P ₁ indicates the pressure value of the pressure on the suction side of the first compressor (21). The pressure value P ₁ indicates the pressure value on the inflow side of the bypass check valve (29).

The second pressure sensor (42) is connected to the second suction pipe (53). Second pressure sensor (42) detects the pressure value P ₂ of the refrigerant in the second suction pipe (53). The pressure value P ₂ indicates the pressure value on the suction side of the second compressor (22). The pressure value P ₂ indicates the pressure value on the discharge side of the first compressor (21). The pressure value P ₂ indicates the pressure value on the outflow side of the bypass check valve (29).

[Control unit]
As shown in FIG. 2, the freezing device (10) has a control unit (100). The control unit (100) has a microcomputer and a memory device for storing software for operating the microcomputer.

The control unit (100) controls the refrigerant circuit (20) based on the signals of various sensors and the control signals from the outside. The control unit (100) includes a first compressor (21), a second compressor (22), a four-way switching valve (23), an expansion valve (26), an injection expansion valve (31), and various types. Includes multiple communication lines connecting to the sensor of.

The control unit (100) includes at least the first compressor (21), the second compressor (22), the four-way switching valve (23), the expansion valve (26), and the injection expansion valve (31). It has an output unit that outputs a control signal. The control unit (100) has an input unit into which the detection value of each sensor is input.

[Operating operation of refrigeration equipment]
In the freezing device (10) of the first embodiment, the first operation and the second operation are performed. The first operation includes a first heating operation and a first cooling operation. The second operation includes a second heating operation and a second cooling operation. In the second operation, the second compressor (22) functions as a high-stage compressor, and the first compressor (21) functions as a low-stage compressor.

<First heating operation>
As shown in FIG. 3, in the first heating operation, a refrigeration cycle is performed in which the utilization side heat exchanger (27) serves as a condenser (radiator) and the heat source side heat exchanger (24) serves as an evaporator. Specifically, the four-way switching valve (23) is set to the first state. The opening degree of the expansion valve (26) is adjusted as appropriate. The injection expansion valve (31) is set to the fully closed state. The first compressor (21) is stopped and the second compressor (22) is driven.

The refrigerant discharged from the second compressor (22) passes through the four-way switching valve (23), dissipates heat to water in the heat exchanger (27) on the user side, and condenses. The refrigerant flowing out of the heat exchanger (27) on the user side passes through the check valve bridge (25) and flows through the main liquid pipe (55). The refrigerant flowing through the main liquid pipe (55) is depressurized by the expansion valve (26), passes through the check valve bridge (25) again, and then evaporates in the heat source side heat exchanger (24). The refrigerant flowing out from the heat source side heat exchanger (24) passes through the four-way switching valve (23), the accumulator (28), and the bypass pipe (PB) in order, and is sucked into the second compressor (22) for compression. Will be done.

<Second heating operation>
As shown in FIG. 4, in the second heating operation, a refrigeration cycle is performed in which the heat exchanger (27) on the utilization side serves as a condenser (radiator) and the heat exchanger (24) on the heat source side serves as an evaporator. Specifically, the four-way switching valve (23) is set to the first state. The opening degree of the expansion valve (26) and the opening degree of the injection expansion valve (31) are appropriately adjusted. Both the first compressor (21) and the second compressor (22) are driven.

The refrigerant discharged from the second compressor (22) passes through the four-way switching valve (23), dissipates heat to water in the heat exchanger (27) on the user side, and condenses. The refrigerant flowing out of the heat exchanger (27) on the user side passes through the check valve bridge (25) and flows through the main liquid pipe (55). The refrigerant flowing through the main liquid pipe (55) dissipates heat to the refrigerant flowing through the fourth flow path (40b) in the third flow path (40a) of the intermediate heat exchanger (40) and is supercooled. After that, a part of the refrigerant flowing through the main liquid pipe (55) flows into the injection pipe (PJ), and the remaining refrigerant is depressurized by the expansion valve (26) of the main liquid pipe (55).

The decompressed refrigerant passes through the check valve bridge (25) and evaporates in the heat source side heat exchanger (24). The refrigerant flowing out of the heat source side heat exchanger (24) passes through the four-way switching valve (23) and the accumulator (28) in order, is sucked into the first compressor (21), and is compressed. The refrigerant discharged from the first compressor (21) is sucked into the second compressor (22) and compressed.

On the other hand, the refrigerant that has flowed into the injection pipe (PJ) is depressurized by the injection expansion valve (31) and flows from the refrigerant that flows through the third flow path (40a) in the fourth flow path (40b) of the intermediate heat exchanger (40). It absorbs heat and evaporates. After that, the refrigerant flowing through the injection pipe (PJ) is introduced into the second suction pipe (53) of the second compressor (22).

<First cooling operation>
As shown in FIG. 5, in the first cooling operation, a refrigeration cycle is performed in which the heat source side heat exchanger (24) serves as a condenser (radiator) and the user side heat exchanger (27) serves as an evaporator. Specifically, the four-way switching valve (23) is set to the second state. The opening degree of the expansion valve (26) is adjusted as appropriate. The injection expansion valve (31) is set to the fully closed state. The first compressor (21) is stopped and the second compressor (22) is driven.

The refrigerant discharged from the second compressor (22) passes through the four-way switching valve (23) and condenses in the heat source side heat exchanger (24). The refrigerant flowing out of the heat source side heat exchanger (24) passes through the check valve bridge (25) and flows through the main liquid pipe (55). The refrigerant flowing through the main liquid pipe (55) is depressurized by the expansion valve (26), passes through the check valve bridge (25) again, and then absorbs heat from water in the user side heat exchanger (27) and evaporates. The refrigerant flowing out from the heat exchanger (27) on the user side passes through the four-way switching valve (23), the accumulator (28), and the bypass pipe (PB) in order, and is sucked into the second compressor (22) for compression. Will be done.

<Second cooling operation>
As shown in FIG. 6, in the second cooling operation, a refrigeration cycle is performed in which the heat source side heat exchanger (24) serves as a condenser (radiator) and the user side heat exchanger (27) serves as an evaporator. Specifically, the four-way switching valve (23) is set to the second state. The opening degree of the expansion valve (26) and the opening degree of the injection expansion valve (31) are appropriately adjusted. Both the first compressor (21) and the second compressor (22) are driven.

The refrigerant discharged from the second compressor (22) passes through the four-way switching valve (23) and condenses in the heat source side heat exchanger (24). The refrigerant flowing out from the heat source side heat exchanger (24) passes through the check valve bridge (25) and flows through the main liquid pipe (55). The refrigerant flowing through the main liquid pipe (55) dissipates heat to the refrigerant flowing through the fourth flow path (40b) in the third flow path (40a) of the intermediate heat exchanger (40) and is supercooled. After that, a part of the refrigerant flowing through the main liquid pipe (55) flows into the injection pipe (PJ), and the remaining refrigerant is depressurized by the expansion valve (26) of the main liquid pipe (55).

The decompressed refrigerant passes through the check valve bridge (25), absorbs heat from water in the user heat exchanger (27), and evaporates. The refrigerant flowing out from the user-side heat exchanger (27) passes through the four-way switching valve (23) and the accumulator (28) in order, is sucked into the first compressor (21), and is compressed. The refrigerant discharged from the first compressor (21) is sucked into the second compressor (22) and compressed.

-Issues at the start of the second operation-
If the outside air temperature is relatively low while the system of the refrigerating device (10) is stopped or the first operation is being executed, the pressure of the refrigerant on the suction side of the stopped first compressor (21) is also relatively low. It may be. In such a case, if the compression ratio of the first compressor (21) is constant, the absolute value of the differential pressure between the discharge side and the suction side of the first compressor (21) is relatively high at the start of the second operation. It becomes smaller. Therefore, the absolute value of the differential pressure between the inflow side and the outflow side of the bypass check valve (29) is relatively small, and even if the second operation is started, the refrigerant flowing through the first suction pipe (51) is the bypass pipe. It is sucked into the second compressor (22) via (PB).

If this state continues, the differential pressure of the first compressor (21) is less likely to rise, and the bypass check valve (29) closes even when the first compressor (21) reaches the normal rotation speed. Will remain absent. If the bypass check valve (29) is not closed continuously, some of the refrigerant will continue to be sucked into the second compressor (22) via the bypass pipe (PB) even after the start of the second operation. Two-stage compression of the refrigerant by the first compressor (21) and the second compressor (22) cannot be realized. As a result, there arises a problem that the capacity of the refrigerating apparatus (10) is reduced. In particular, since the first compressor (21) has a smaller compression ratio than the second compressor (22), this problem can occur remarkably.

In consideration of such a problem, the refrigerating apparatus (10) of the present embodiment suppresses that the bypass check valve (29) does not close after the start of the second operation. Specifically, the control unit (100) of the freezing device (10) executes the first control. The first control is a control that increases the differential pressure between the discharge side and the suction side of the first compressor (21) before the start of the second operation or at the start of the second operation.

In the present embodiment, the control unit (100) executes the first control in the first operation and the second operation. In the first operation, the first control is executed before the second operation is started from the stopped state of the first compressor (21) and the second compressor (22). In the second operation, the first control is executed before switching from the first operation to the second operation.

<First operation>
While the first compressor (21) and the second compressor (22) are stopped, when an operation command for executing the second operation is input to the control unit (100), the following first operation is performed.

The control unit (100) drives the first compressor (21) as the first control before starting the second operation from the stopped state of the first compressor (21) and the second compressor (22). The control unit (100) performs a second operation when the differential pressure between the discharge side and the suction side of the first compressor (21) exceeds a predetermined value while the first compressor (21) is driven by the first control. To execute. The first control in the first operation will be specifically described with reference to FIG. 7.

In step ST11, the control unit (100) executes the first control while the system of the refrigerating apparatus (10) is stopped. Specifically, the control unit (100) switches the four-way switching valve (23) to the first state. The control unit (100) stops the second compressor (22) and drives the first compressor (21). The control unit (100) appropriately adjusts the opening degree of the expansion valve (26) and sets the injection expansion valve (31) to the fully closed state.

When the first control is executed, the differential pressure between the suction side and the discharge side of the first compressor (21) increases. Along with this, the differential pressure between the inflow side and the outflow side of the bypass check valve (29) also increases. After executing the first control, step ST12 is executed.

In step ST12, the control unit (100), [Delta] P _O is the differential pressure between the discharge side and the suction side of the first compressor (21), it is determined whether the [Delta] P _n or more predetermined values. Specifically, the control unit (100) includes a pressure value P ₁ of the first pressure sensor (41) detects, seek [Delta] P _O from the difference between the pressure value P ₂ by the second pressure sensor (42) detects. Controller (100), [Delta] P _O is equal to or larger than [Delta] P _n. The pressure value P ₁ indicates the pressure on the inflow side of the bypass check valve (29), and the pressure value P ₂ indicates the pressure on the outflow side of the bypass check valve (29). Therefore, the differential pressure between the inflow side of the bypass check valve (29) and the outflow side the [Delta] P _O. Thus, if ΔP _O ≧ ΔP _n, it is possible to close the valve of the bypass check-valve (29).

When it is determined that the ΔP _O ≧ ΔP _n, step ST13 is executed. On the other hand, if [Delta] P _O is determined to be less than [Delta] P _n, since not close the valve of the bypass check valve (29), step ST11 is executed again.

In step ST13, the control unit (100) starts the second operation. Specifically, the control unit (100) drives the second compressor (22). At the start of the second operation, the differential pressure between the outflow side and the inflow side of the bypass check valve (29) is increased by the first control described above. Therefore, it is possible to prevent the bypass check valve (29) from not closing after the start of the second operation.

<Second operation>
If an operation command for executing the second operation is input to the control unit (100) before switching from the first operation to the second operation, the following second operation is performed. The control unit (100) reduces the rotation speed of the second compressor (22) as the first control before switching from the first operation to the second operation. When the index indicating the pressure of the refrigerant on the suction side of the second compressor (22) becomes equal to or higher than a predetermined value, the control unit (100) determines that the rotation speed of the second compressor (22) is reduced by the first control. The second operation is executed. The first control in the second operation will be specifically described with reference to FIG.

In step ST21, the control unit (100) starts the first operation. Specifically, the control unit (100) switches the four-way switching valve (23) to the first state. The control unit (100) stops the second compressor (22) and drives the first compressor (21). The control unit (100) appropriately adjusts the opening degree of the expansion valve (26) and sets the injection expansion valve (31) to the fully closed state. After the start of the first operation, step ST22 is executed.

In step ST22, the control unit (100) executes the first control. Specifically, the control unit (100) reduces the rotation speed of the second compressor (22). When the rotation speed of the second compressor (22) decreases due to the first control, the pressure on the discharge side of the second compressor (22) increases. The pressures on the discharge side of the second compressor (22) and the suction side of the first compressor (21) are almost the same. Since the first compressor (21) is stopped, the pressures on the discharge side and the suction side of the first compressor (21) are almost the same. As a result, the pressure on the suction side of the first compressor (21) also increases due to the decrease in the rotation speed of the second compressor (22).

In step ST23, the control unit (100) determines whether or not _{the pressure value P 2} is equal to or higher than the predetermined pressure value P _m. The indicator of the pressure on the suction side of the refrigerant of the second compressor (22), a pressure value P ₂ by the second pressure sensor (42) detects. The pressure value P _m _{is such that when the pressure value P 2} is equal to _{or higher than the pressure value P m} before the start of the second operation (driving the first compressor (21)), the pressure value P m starts the second operation (driving the first compressor (21)). ) at a value that is a ΔP _O ≧ ΔP _n. In other words, the bypass check valve (29) can be closed _{when P 2} ≧ P _m before the start of the second operation due to the decrease in the rotation speed of the second compressor (22).

If _{it is determined that P 2} ≧ P _m , step ST24 is executed. If _{it is determined that P 2} is _{less than P m} , step ST22 is executed.

In step ST24, the control unit (100) starts the second operation. Specifically, the control unit (100) drives the first compressor (21). At the start of the second operation, the differential pressure between the outflow side and the inflow side of the bypass check valve (29) is increased by the first control described above. Therefore, it is possible to prevent the bypass check valve (29) from not closing after the start of the second operation.

-Effect of embodiment-
In the feature (1) of the embodiment, the refrigerant circuit (20) of the refrigerating apparatus (10) has a bypass pipe (PB) connecting the suction side and the discharge side of the first compressor (21) and a bypass pipe (PB). It has a check valve (29) that limits the flow of the refrigerant from the discharge side to the suction side of the first compressor (21). The refrigerating apparatus (10) includes a control unit (100) that controls the refrigerant circuit (20), and the control unit (100) discharges the first compressor (21) before or at the start of the second operation. The first control is performed to increase the differential pressure between the side and the suction side.

According to the feature (1) of the embodiment, the differential pressure between the suction side and the discharge side of the first compressor increases, and at the same time, the differential pressure between the inflow side and the outflow side of the bypass check valve (29) also increases. Therefore, it is possible to prevent the bypass check valve (29) from being closed after the second operation is started.

In addition, after the start of the second operation, it is suppressed that the refrigerant is sucked into the second compressor (22) via the bypass pipe (PB). As a result, the usual two-stage compression of the refrigerant by the first compressor (21) and the second compressor (22) can be realized, and the decrease in the capacity of the refrigerating device (10) can be suppressed.

In the feature (2) of the embodiment, the control unit (100) is first controlled as a first control before starting the second operation from the stopped state of the first compressor (21) and the second compressor (22). Drive the compressor (21).

According to the feature (2) of the embodiment, since the first compressor (21) is driven from the state where the first compressor (21) and the second compressor (22) are stopped, the refrigerant is the first 1 Compressed by the compressor (21). As a result, the differential pressure between the suction side and the discharge side of the first compressor (21) increases. As a result, the differential pressure between the inflow side and the outflow side of the bypass check valve (29) can be increased at the start of the subsequent second operation. As a result, it is possible to prevent the bypass check valve (29) from not closing after the start of the second operation.

In the feature (3) of the embodiment, the control unit (100) has a pressure difference between the discharge side and the suction side of the first compressor (21) while the first compressor (21) is driven by the first control. When the value exceeds the predetermined value, the second operation is executed.

According to a feature (3) of the embodiment, in the first operation, while the first compressor (21) is driven, the differential pressure [Delta] P _O between the discharge side and the suction side of the first compressor (21) is predetermined When the value _{becomes ΔP n} or more, the second operation can be started. When the differential pressure between the inflow side and the outflow side of the _{bypass check valve (29) increases to ΔP n} or more, the bypass check valve (29) can be closed. As a result, it is possible to prevent the bypass check valve (29) from not closing after the start of the second operation.

In the feature (4) of the embodiment, the control unit (100) reduces the rotation speed of the second compressor (22) as the first control before switching from the first operation to the second operation.

According to the feature (4) of the embodiment, in the second operation, when the rotation speed of the second compressor (22) decreases, the pressure on the suction side of the second compressor (22) increases, and at the same time, the first compressor The pressure on the discharge side of (21) also rises. In the first operation, the suction side and the discharge side of the first compressor (21) have substantially the same pressure, so the pressure on the suction side of the first compressor (21) is increased before switching to the second operation. be able to. As a result, when the second operation is started, the pressure of the refrigerant on the discharge side of the first compressor (21) rises. As a result, it increases [Delta] P _O is the second operation since the start of the bypass check-valve (29) can be prevented from not closed.

In the feature (5) of the embodiment, the control unit (100) applies the pressure of the refrigerant on the suction side of the second compressor (22) while the rotation speed of the second compressor (22) is reduced by the first control. When the indicated index exceeds a predetermined value, the second operation is executed.

According to the feature (5) of the embodiment, when the pressure value P ₂ on the suction side of the second compressor (22) becomes equal to or higher than the predetermined value P _{m before the start of the second operation by the first control,} The second operation can be started. When the pressure value P ₂ becomes the pressure value P _m _{or more, the pressure value P 1} indicating the pressure value on the suction side of the first compressor (21) also becomes the pressure value P _m or more. Pressure value _{P m} is a value [Delta] P _O is greater than or equal to [Delta] P _n. From this, it is possible to surely prevent the bypass check valve (29) from closing after the start of the second operation.

<< Modification 1 of Embodiment 1 >>
As shown in FIG. 9, the refrigerating apparatus (10) of the present modification 1 includes a first rotation detection unit (45), a second rotation detection unit (46), a first temperature sensor (47), and a second temperature sensor. Has (48). These detectors (45, 46) and sensors (47, 48) are connected to the control unit (100) by a communication line.

The first rotation detection unit (45) is provided in the first compressor (21). The first rotation detection unit (45) detects the rotation speed of the first compressor (21). The first rotation detection unit (45) is, for example, a current sensor that detects the current supplied to the first compressor (21). The rotation speed of the first compressor (21) is detected based on the current value detected by the current sensor.

The second rotation detection unit (46) is provided in the second compressor (22). The second rotation detection unit (46) detects the rotation speed of the second compressor (22). The second rotation detection unit (46) is, for example, a current sensor that detects the current supplied to the second compressor (22). The rotation speed of the second compressor (22) is detected based on the current value detected by the current sensor.

The first temperature sensor (47) is connected to the first suction pipe (51). The first temperature sensor (47) detects the temperature of the refrigerant sucked into the first compressor (21).

The second temperature sensor (48) is connected to the second suction pipe (53). The second temperature sensor (48) detects the temperature of the refrigerant sucked into the second compressor (22).

In the refrigerating apparatus (10) of the present modification 1, when an operation command for executing the second operation is input to the control unit (100), the following third operation is performed. In the third operation, the control unit (100) drives both the first compressor (21) and the second compressor (22) at the same time from the stopped state of the system of the refrigerating device (10), so that the second operation is performed. Start operation. The control unit (100) executes the first control at the start of the second operation. Specifically, as the first control, the first compressor ( The rotation rate of the second compressor (22) is reduced without changing the rotation rate of 21). The first control in the third operation will be described with reference to FIG.

In step ST31, the control unit (100) starts the second operation. Specifically, the control unit (100) switches the four-way switching valve (23) to the first state. The control unit (100) is the first compressor (21).
And the second compressor (22) are driven. The control unit (100) appropriately adjusts the opening degree of the expansion valve (26). After the start of the second operation, step ST32 is executed.

In step ST32, the control unit (100) executes the first control. By the first control, the rotation speed of the first compressor (21) is not changed, and the rotation speed of the second compressor (22) is reduced. Therefore, the flow rate of the refrigerant of the first compressor (21) does not change, but the flow rate of the refrigerant of the second compressor (22) decreases. The pressure on the suction side of the second compressor (22) and the pressure on the discharge side of the first compressor (21) increase.

In step ST33, the control unit (100) determines whether or not the flow rate M2 of the refrigerant of the second compressor (22) is equal to or less than the flow rate M1 of the refrigerant of the first compressor (21). When the flow rate M2 becomes equal to or less than the flow rate M1, the pressures on the suction side of the second compressor (22) and the discharge side of the first compressor (21) increase, and the bypass check valve (29) can be closed. As a result, the differential pressure between the suction side and the discharge side of the first compressor (21) increases. When it is determined that the flow rate M1 ≥ the flow rate M2, the first control is released and the normal operation is started. The rotation speed of the second compressor (22) is adjusted according to the load of the equipment on the user side. If it is determined that the flow rate M1 is less than the flow rate M2, step ST32 is executed again.

Here, the control unit (100) obtains the flow rate M of the refrigerant of the compressor based on the rotation speed N of the compressor, the push-out volume (cylinder volume) V, and the suction density ρ. The flow rate M is a mass flow rate. Specifically, the flow rate M is obtained by M = N × V × ρ.

The rotation speed N is obtained by the rotation speed detection unit (45, 46). The suction density is determined by the temperature and pressure of the refrigerant sucked into each compressor (21, 22). The push-out volume V is set in advance in the control unit (100) according to the specifications of each compressor (21, 22).

Specifically, the control unit (100) obtains the rotation speed N1 of the first compressor (21) based on the detection value of the first rotation detection unit (45). The control unit (100) obtains the suction density ρ1 based on the detected value of the first pressure sensor (41) and the detected value of the first temperature sensor (47). The control unit (100) obtains the flow rate M1 of the refrigerant of the first compressor (21) based on the rotation speed N1, the suction density ρ1, and the push-out volume V1 of the first compressor (21).

The control unit (100) obtains the rotation speed N2 of the second compressor (22) based on the detection value of the second rotation detection unit (46). The control unit (100) obtains the suction density ρ2 based on the detected value of the second pressure sensor (42) and the detected value of the second temperature sensor (48). The control unit (100) obtains the flow rate M2 of the refrigerant of the second compressor (22) based on the rotation speed N2, the suction density ρ2, and the push-out volume V2 of the second compressor (22).

According to this modification, in the third operation, the flow rate of the refrigerant flowing through the second compressor (22) flows through the first compressor (21) without changing the rotation speed of the first compressor (21). It can be less than or equal to the flow rate. Since it is only necessary to control the rotation speed of the second compressor (22), the first control can be easily executed.

In addition, the first control can shorten the time until the flow rate of the first compressor (21) becomes equal to or higher than the flow rate of the second compressor (22). Thus, it is possible to quickly be at least [Delta] P _n differential pressure [Delta] P _O between the discharge side and the suction side of the first compressor (21). As a result, it is possible to prevent the bypass check valve (29) from not closing after the start of the second operation.

<< Modification 2 of the embodiment >>
In the second modification of the embodiment, the determination method after the first control in the first operation is different from that of the above embodiment. Specifically, it will be described with reference to FIG.

In step ST41, the control unit (100) executes the same first control as in step ST11 of the first embodiment.

In step ST42, the control unit (100) determines whether or not the time for driving the first compressor (21) exceeds a predetermined time. When the time for driving the first compressor (21) exceeds a predetermined time, the differential pressure between the suction side and the discharge side of the first compressor (21) increases. When the control unit (100) determines that the predetermined time has elapsed, step ST43 is executed. If the control unit (100) determines that the predetermined time has not elapsed, step ST42 is executed again.

In step ST43, the control unit (100) drives the second compressor (22) to execute the second operation, as in step ST13 of the first embodiment.

In this modification, the control unit (100) determines whether or not a predetermined time has elapsed after the first compressor (21) is driven. It is not necessary to detect the differential pressure [Delta] P _O between the discharge side and the suction side of the first compressor (21), it can be easily prevented that the second operation since the start of the bypass check-valve (29) is not closed.

<< Modification 3 of the embodiment >>
The first control according to the third modification of the embodiment is different from the first control of the above embodiment in the second operation. In this modification, the control unit (100) uses the injection mechanism (30) to discharge the refrigerant to the discharge side of the first compressor (21) and the first control before switching from the first operation to the second operation. 2 Introduce between the compressor (22) and the suction side. Specifically, it will be described with reference to FIG.

In step ST51, the control unit (100) executes the first operation in the same manner as in step ST21 of the first embodiment.

In step ST52, the control unit (100) executes the first control. The opening degree of the injection expansion valve (31) is adjusted by the first control. In the first operation, a part of the refrigerant flowing through the main liquid pipe (55) flows into the injection pipe (PJ) and is depressurized by the injection expansion valve (31). The decompressed refrigerant undergoes heat exchange in the intermediate heat exchanger (40) and then flows into the second suction pipe (53). As a result, in the first operation, the pressure on the suction side of the second compressor (22) rises, and at the same time, the pressure on the suction side of the first compressor (21) also rises.

In step ST53, the control unit (100) determines whether or not _{the detected value P 2 of} the first pressure sensor (41) is P _{m or more, as in step ST23 of the first embodiment.}

In step ST54, the control unit (100) executes the second operation in the same manner as in step ST24 of the first embodiment.

In this modification, the refrigerant can be injected from the injection pipe (PJ) into the second suction pipe (53) by opening the injection expansion valve (31). As a result, the pressure of the refrigerant on the suction side of the first compressor (21) can be easily increased before switching from the first operation to the second operation.

<< Modification 4 of the embodiment >>
The refrigerating apparatus (10) according to the fourth modification of the embodiment has an outside air temperature sensor (not shown) for detecting the outside air temperature. The outside air temperature sensor is connected to the control unit (100) by a communication line.

The first control of this modification is different from the first control of the above embodiment in the first operation to the third operation. Hereinafter, the first control according to the present modification in the first operation will be described with reference to FIG.

In step ST61, the control unit (100) determines whether the temperature value T outside air temperature sensor detects is equal to or less than T _O is a predetermined value. Here, if the second operation is performed in a state where the temperature value T detected by the outside air temperature sensor is relatively low, the pressure (evaporation pressure) of the refrigerant sucked into the first compressor (21) becomes low. In this state, the differential pressure between the discharge side and the suction side of the first compressor (21) is relatively low, so that the bypass check valve (29) does not close. Therefore, when the temperature value T is equal to or less than the predetermined value T _O, the first control is executed in step ST61. When the temperature value T is determined to be higher than the predetermined value T _O, step ST63 is executed.

In step ST62, the control unit (100) executes the first control in the same manner as in step ST11 of the first embodiment.

In step ST63, the control unit (100) as in step ST12 of the first embodiment, it is determined whether [Delta] P _O is not less than [Delta] P _n.

In step ST64, the control unit (100) starts the second operation in the same manner as in step ST13 of the first embodiment.

According to this modification, by performing the first control when the outside air temperature is below a predetermined temperature, the differential pressure between the suction side and the discharge side of the first compressor (21) at the start of the second operation becomes smaller. Can be suppressed. As a result, it is possible to reliably prevent the bypass check valve (29) from closing after the start of the second operation.

<< Other Embodiments >>
The above embodiment may have the following configuration.

In the first operation, the control unit (100) does not have to make the determination in step ST12. Specifically, the control unit (100) may drive the second compressor (22) after executing the first control (step ST11) (step ST13).

In step ST32 of the third operation, at the start of the second operation, the control unit (100) sets the flow rate of the refrigerant of the second compressor (22) being driven as the first control to the first compressor being driven. The rotation speed of at least one of the first compressor (21) and the second compressor (22) may be adjusted so as to be equal to or less than the flow rate of the refrigerant of (21).

For example, the control unit (100) may increase the rotation speed of the first compressor (21) without changing the rotation speed of the second compressor (22). Since it is only necessary to adjust the rotation speed of the first compressor (21), the first control can be easily executed.

Further, the control unit (100) may adjust the rotation speeds of both the first compressor (21) and the second compressor (22). In this case, the control unit (100) adjusts so as to increase the rotation speed of the first compressor (21) and decrease the rotation speed of the second compressor (22). As a result, the flow rate M2 of the refrigerant of the second compressor (22) can be set to be equal to or less than the flow rate M1 of the refrigerant of the first compressor (21) in a shorter time.

In the second modification of the embodiment, the control unit (100) may execute the first control at the start of the second operation.

In the third modification of the embodiment, the control unit (100) may execute the first control even in the second operation and the third operation when the outside air temperature is equal to or less than a predetermined value.

In the first modification of the embodiment, the first control may be performed at the start of the second operation in which the first compressor (21) is driven and then the second compressor (22) is driven.

The refrigerating apparatus (10) includes a first temperature sensor (not shown) that detects the temperature of the refrigerant on the suction side of the first compressor (21), and a discharge side (second compressor (22)) of the first compressor (21). ) May be provided with a second temperature sensor (not shown) that detects the temperature of the refrigerant on the suction side). Pressure value P ₁ on the suction side of the first compressor (21) may be determined based on the saturation pressure corresponding to the temperature detected in the first temperature sensor. Pressure value P ₂ of the suction side of the discharge side and the second compressor (22) of the first compressor (21) may be determined based on the saturation pressure corresponding to the temperature detected in the second temperature sensor.

The first compressor (21) and the second compressor (22) may be a rotary type compressor, a swing piston type compressor, or a turbo type compressor. It may be another compressor.

The first rotation detection unit (45) and the second rotation detection unit (46) may be devices for detecting the torque value of the compressor (21, 22), respectively, or the rotation of the compressor (21, 22). It may be a device for detecting a number.

Although the embodiments and modifications have been described above, it will be understood that various modifications of the forms and details are possible without departing from the purpose and scope of the claims. Further, the above embodiments and modifications may be appropriately combined or replaced as long as the functions of the subject of the present disclosure are not impaired.

As explained above, this disclosure is useful for freezing equipment.

20 Refrigerant circuit 21 1st compressor 22 2nd compressor PB Bypass piping 29 Bypass check valve (check valve)
30 Injection mechanism 100 Control unit

Claims

The first compressor (21) and the second compressor (22) connected to the discharge side of the first compressor (21) are included, and the first compressor (21) is stopped and the second compressor is stopped. It is possible to switch between the first operation of performing the refrigeration cycle in which (22) is driven and the second operation of performing the refrigeration cycle in which the first compressor (21) and the second compressor (22) are driven. Refrigerant circuit (20) and
A control unit (100) for controlling the refrigerant circuit (20) is provided.
The refrigerant circuit (20)
A bypass pipe (PB) connecting the suction side and the discharge side of the first compressor (21), and
It is connected to the bypass pipe (PB) and has a check valve (29) that limits the flow of refrigerant from the discharge side to the suction side of the first compressor (21).
The control unit (100) is characterized in that it executes the first control for increasing the differential pressure between the discharge side and the suction side of the first compressor (21) before or at the start of the second operation. Refrigeration equipment.
In claim 1,
The control unit (100) performs the first compressor (21) as the first control before starting the second operation from the stopped state of the first compressor (21) and the second compressor (22). A freezing device characterized by driving 21).
In claim 2,
When the pressure difference between the discharge side and the suction side of the first compressor (21) becomes equal to or higher than a predetermined value while the first compressor (21) is driven by the first control, the control unit (100) , A refrigerating apparatus characterized in that the second operation is executed.
In claim 2,
The control unit (100)
A refrigerating apparatus characterized in that when the time for driving the first compressor (21) by the first control exceeds a predetermined time, the second operation is executed.
In any one of claims 1 to 4,
The control unit (100) is a refrigerating device characterized in that the rotation speed of the second compressor (22) is reduced as the first control before switching from the first operation to the second operation.
In claim 5,
The control unit (100) has a predetermined value as an index indicating the pressure of the refrigerant on the suction side of the second compressor (22) while the rotation speed of the second compressor (22) is reduced by the first control. When the above is achieved, the refrigerating apparatus is characterized in that the second operation is executed.
In any one of claims 1 to 6,
At the start of the second operation, the control unit (100) measures the flow rate of the refrigerant of the second compressor (22) being driven as the first control of the first compressor (21) being driven. A refrigerating apparatus characterized in that the rotation speed of at least one of the first compressor (21) and the second compressor (22) is adjusted so as to be equal to or less than the flow rate of the refrigerant of.
In claim 7,
At the start of the second operation, the control unit (100) measures the flow rate of the refrigerant of the second compressor (22) being driven as the first control of the first compressor (21) being driven. A refrigerating apparatus characterized in that the rotation speed of the first compressor (21) is not changed so as to be equal to or less than the flow rate of the refrigerant of the above, and the rotation speed of the second compressor (22) is reduced.
In claim 7,
The control unit (100)
At the start of the second operation, as the first control, the flow rate of the refrigerant of the second compressor (22) being driven becomes equal to or less than the flow rate of the refrigerant of the first compressor (21) being driven. In addition, a refrigerating apparatus characterized in that the rotation speed of the first compressor (21) is increased without changing the rotation speed of the second compressor (22).
In any one of claims 1 to 9,
The refrigerant circuit (20)
It has an injection mechanism (30) that introduces a refrigerant between the discharge side of the first compressor (21) and the suction side of the second compressor (22).
The control unit (100) first compresses the refrigerant by the injection mechanism (30) as the first control before switching from the first operation to the second operation or at the start of the second operation. A freezing device that is installed between the discharge side of the machine (21) and the suction side of the second compressor (22).
In any one of claims 1 to 10,
The control unit (100) is a freezing device that performs the first control when the outside air temperature is equal to or lower than a predetermined value.