EP4632293A1

EP4632293A1 - Refrigeration device having four-way switching valve and shut-off valve

Info

Publication number: EP4632293A1
Application number: EP25721450.2A
Authority: EP
Inventors: Tomoya NISHIGUCHI; Masahiro Honda
Original assignee: Daikin Industries Ltd
Current assignee: Daikin Industries Ltd
Priority date: 2024-02-28
Filing date: 2025-02-03
Publication date: 2025-10-15
Also published as: JP7727225B1; WO2025182462A1; EP4632293A4; JP2025131415A

Abstract

A refrigeration apparatus (100) includes a refrigerant circuit (90), a control unit (9), and a first shutoff valve (41). The refrigerant circuit (90) includes a compressor (11), a four-way switching valve (12), a heat source heat exchanger (13), and a utilization heat exchanger (23). The compressor (11) has a suction port (11a) through which a refrigerant (R) is sucked and a discharge port (11b) through which the refrigerant is discharged. The control unit (9) switches a circulation path of the refrigerant (R) in the refrigerant circuit (90) by performing switching of the four-way switching valve (12). The first shutoff valve (41) is disposed between the four-way switching valve (12) and the utilization heat exchanger (23). The control unit (9) closes the first shutoff valve (41) before performing the switching of the four-way switching valve (12).

Description

TECHNICAL FIELD

The present disclosure relates to a refrigeration apparatus including a four-way switching valve and a shutoff valve.

BACKGROUND ART

A four-way switching valve disclosed in Patent Literature 1 ( JP S63-015056 A ) is mounted in a refrigeration apparatus to switch a circulation direction of a refrigerant.

SUMMARY OF THE INVENTION

Some of the refrigerants used in the refrigeration apparatus are of a type that involves a large pressure difference between a low-pressure gas refrigerant sucked into a compressor and a high-pressure gas refrigerant discharged from the compressor. Such a large pressure difference may cause an impact on and damage of the four-way switching valve at the time of switching of the four-way switching valve.

A refrigeration apparatus according to a first aspect includes a refrigerant circuit, a control unit, and a first shutoff valve. The refrigerant circuit includes a compressor, a four-way switching valve, a heat source heat exchanger, and a utilization heat exchanger. The compressor has a suction port through which a refrigerant is sucked and a discharge port through which the refrigerant is discharged. The control unit switches a circulation path of the refrigerant in the refrigerant circuit by performing switching of the four-way switching valve. The first shutoff valve is disposed between the four-way switching valve and the utilization heat exchanger. The control unit closes the first shutoff valve before performing the switching of the four-way switching valve.
In this configuration, by closing the first shutoff valve before performing the switching of the four-way switching valve, the refrigerant circuit around the four-way switching valve is shut off. Therefore, it is possible to reduce damage to the four-way switching valve due to a pressure difference of a large amount of the refrigerant.
A refrigeration apparatus according to a second aspect is the refrigeration apparatus according to the first aspect and further include a second shutoff valve. The second shutoff valve is disposed between the four-way switching valve and the heat source heat exchanger. The control unit further closes the second shutoff valve before performing the switching of the four-way switching valve.
In this configuration, not only the first shutoff valve but also the second shutoff valve contribute to blocking of the refrigerant circuit around the four-way switching valve. Therefore, damage to the four-way switching valve can be further reduced.
A refrigeration apparatus according to a third aspect is the refrigeration apparatus according to the second aspect and further include a bypass flow path and a pressure equalizing valve. The bypass flow path connects the suction port and the discharge port. The pressure equalizing valve is configured to open or close the bypass flow path. The control unit further opens the pressure equalizing valve before performing the switching.
In this configuration, the opened pressure equalizing valve reduces a pressure difference between the refrigerant at the suction port and the refrigerant at the discharge port. Therefore, damage to the four-way switching valve can be further reduced.
A refrigeration apparatus according to a fourth aspect is the refrigeration apparatus according to any one of the first to third aspects, in which the control unit performs the switching of the four-way switching valve after a predetermined time elapses after receiving a switch command of the four-way switching valve.
In this configuration, the pressure difference between the refrigerant at the suction port and the refrigerant at the discharge port can be expected to be eliminated by the elapse of the predetermined time. Therefore, damage to the four-way switching valve can be reduced.
A refrigeration apparatus according to a fifth aspect is the refrigeration apparatus according to any one of the first to fourth aspects, in which the control unit stops the compressor after receiving the switch command of the four-way switching valve.
In this configuration, the compressor is stopped at the time of the switching. It is therefore possible to avoid generation of a pressure difference between the refrigerant the suction port and of the refrigerant the discharge port.
A refrigeration apparatus according to a sixth aspect is the refrigeration apparatus according to the third aspect, in which the control unit closes the first shutoff valve or the second shutoff valve and opens the pressure equalizing valve before performing the switching of the four-way switching valve. The control unit performs the switching of the four-way switching valve in a state where the pressure equalizing valve is opened. After ending the switching of the four-way switching valve, the control unit closes the pressure equalizing valve and opens the first shutoff valve or the second shutoff valve.
In this configuration, the pressure equalizing valve is opened before the four-way switching valve is switched. Therefore, since the pressure difference between the refrigerant at the suction port and the refrigerant at the discharge port is eliminated, damage to the four-way switching valve can be suppressed.
A refrigeration apparatus according to a seventh aspect is the refrigeration apparatus according to the third aspect, in which the control unit closes the first shutoff valve or the second shutoff valve and opens the pressure equalizing valve before performing the switching of the four-way switching valve. The control unit closes the pressure equalizing valve when the pressure difference between the suction port and the discharge port becomes equal to or less than a predetermined value. The control unit performs the switching of the four-way switching valve in a state where the pressure equalizing valve is closed. After ending the switching of the four-way switching valve, the control unit opens the first shutoff valve or the second shutoff valve.
In this configuration, the pressure equalizing valve is closed before the four-way switching valve is switched. Therefore, when it can be determined that the pressure difference between the refrigerant at the suction port and the refrigerant at the discharge port is sufficiently small, the pressure equalizing valve can be quickly closed.
A refrigeration apparatus according to an eighth aspect is the refrigeration apparatus according to any one of the first to seventh aspects, in which the refrigerant includes carbon dioxide.
In this configuration, the refrigerant includes carbon dioxide. When carbon dioxide is used for the refrigerant, a switching noise of the four-way switching valve tends to be loud. Therefore, by operating the first shutoff valve and the like, an impact at the time of the switching is less likely to be transmitted to the outside.
A refrigeration apparatus according to a ninth aspect is the refrigeration apparatus according to the second or third aspect and further includes a heat source unit, a utilization unit, and a valve unit. The heat source unit has the compressor, the four-way switching valve, and the heat source heat exchanger. The utilization unit includes a utilization heat exchanger. The valve unit is disposed between the heat source unit and the utilization unit. The first shutoff valve or the second shutoff valve is disposed in the valve unit.
In this configuration, the first shutoff valve and the second shutoff valve are disposed in the valve unit. Therefore, when the first shutoff valve and the second shutoff valve are provided, it is not necessary to change a design of the refrigerant circuit of the heat source unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram showing a configuration of a refrigeration apparatus 100 according to a first embodiment.
FIG. 2 is a schematic sectional view showing a four-way switching valve 12 in a cold heat utilization operation.
FIG. 3 is another schematic sectional view showing the four-way switching valve 12 in a transient state.
FIG. 4 is another schematic sectional view showing the four-way switching valve 12 in a hot heat utilization operation.
FIG. 5 is a block diagram showing an electric system of the refrigeration apparatus 100.
FIG. 6 is a flowchart of switching control of the four-way switching valve 12.
FIG. 7 is a flowchart of output processing of a switch control signal Q2.
FIG. 8 is a flowchart of the switching control of the four-way switching valve 12 according to a second modification of the first embodiment.
FIG. 9 is a schematic sectional view showing a structure of the four-way switching valve 12 of a rotary type.
FIG. 10 is a flowchart of the switching control of the four-way switching valve 12 according to a third modification of the first embodiment.
FIG. 11 is a circuit diagram showing a configuration of the refrigeration apparatus 100 according to a second embodiment.

DESCRIPTION OF EMBODIMENTS

(1) Overall configuration

FIG. 1 shows a refrigeration apparatus 100 according to a first embodiment. The refrigeration apparatus 100 is configured to provide a user with hot heat or cold heat acquired from a heat source, and is configured as an air conditioner, for example. The refrigeration apparatus 100 can perform a cold heat utilization operation for providing the user with cold heat and a hot heat utilization operation for providing the user with hot heat. When the refrigeration apparatus 100 is an air conditioner, these operations correspond to a cooling operation and a heating operation, respectively.
The refrigeration apparatus 100 includes a heat source unit 10, a plurality of utilization units 20, a connection piping 30, and a communication line 35. These components constitute a refrigerant circuit 90 that circulates a refrigerant R and a control unit 9 that controls the refrigerant circuit 90.
As the refrigerant R, any refrigerant can be used, but for example, carbon dioxide may be used. In the following description, the refrigerant R is treated as capable of undergoing a phase change to liquid, and terms such as "condensation", "evaporation", "liquid refrigerant", and "gas-liquid two-phase refrigerant" are used for description. However, it should be noted that when the refrigerant R includes carbon dioxide, there is no phase change to liquid, and therefore these terms do not apply strictly.

(1-1) Heat source unit 10

The heat source unit 10 acquires hot heat or cold heat from a heat source such as outdoor air. The heat source unit 10 includes, as components of the refrigerant circuit 90, a compressor 11, a four-way switching valve 12, a heat source heat exchanger 13, a heat source expansion valve 15, an accumulator 16, a liquid shutoff valve 17, a gas shutoff valve 18, a first shutoff valve 41, a second shutoff valve 42, and a pressure equalizing valve 43. The heat source unit 10 also includes a heat source fan 14 provided near the heat source heat exchanger 13. The heat source unit 10 further includes a heat source control unit 19 as a component of the control unit 9. The heat source unit 10 further includes a low pressure sensor S1 and a high pressure sensor S2.

(1-1-1) Compressor 11

The compressor 11 includes a suction port 11a and a discharge port 11b. The compressor 11 compresses a low-pressure gas refrigerant sucked from the suction port 11a, generates a high-pressure gas refrigerant, and discharges the refrigerant from the discharge port 11b. The low pressure sensor S1 is provided on a suction side of the compressor 11, in other words, near the suction port 11a. The high pressure sensor S2 is provided on a discharge side of the compressor 11, in other words, near the discharge port 11b. Both the low pressure sensor S1 and the high pressure sensor S2 measure a pressure of the refrigerant R.

(1-1-2) Four-way switching valve 12

The four-way switching valve 12 switches a circulation path of the refrigerant R. The four-way switching valve 12 includes a first port P1, a second port P2, a third port P3, and a fourth port P4. The first port P1 is connected to a pipe communicating with the discharge port 11b. The second port P2 is connected to a pipe communicating with the accumulator 16. The third port P3 is connected to a pipe communicating with the heat source heat exchanger 13. The fourth port P4 is connected to a pipe communicating with the gas shutoff valve 18.
When the refrigeration apparatus 100 performs the cold heat utilization operation, in the four-way switching valve 12, the first port P1 and the third port P3 are connected, and the second port P2 and the fourth port P4 are connected as indicated by solid lines in FIG. 1. When the refrigeration apparatus 100 performs the hot heat utilization operation, in the four-way switching valve 12, the first port P1 and the fourth port P4 are connected, and the second port P2 and the third port P3 are connected as indicated by broken lines in FIG. 1.

(1-1-3) Heat source heat exchanger 13

The heat source heat exchanger 13 exchanges heat between the outdoor air and the refrigerant R. The heat source heat exchanger 13 functions as a condenser or a heat radiator for the refrigerant R in the cold heat utilization operation, and functions as an evaporator or a heat absorber for the refrigerant R in the hot heat utilization operation.

(1-1-4) Heat source fan 14

The heat source fan 14 promotes heat exchange in the heat source heat exchanger 13 by moving outdoor air to pass through the inside of the heat source heat exchanger 13.

(1-1-5) Heat source expansion valve 15

The heat source expansion valve 15 decompresses the refrigerant R and adjusts a flow rate of the refrigerant R.

(1-1-6) Accumulator 16

The accumulator 16 stores a liquid refrigerant component mixed in the gas refrigerant and allows the gas refrigerant to pass therethrough. The accumulator 16 is connected to the suction port 11a of the compressor 11. The accumulator 16 prevents the liquid refrigerant from being sucked into the compressor 11.

(1-1-7) Liquid shutoff valve 17

The liquid shutoff valve 17 passes or shuts off a liquid refrigerant, a gas-liquid two-phase refrigerant, and the like. The liquid shutoff valve 17 is opened and closed manually by, for example, an installation worker of the refrigeration apparatus 100.

(1-1-8) Gas shutoff valve 18

The gas shutoff valve 18 passes or shuts off a low-pressure gas refrigerant, a high-pressure gas refrigerant, or the like. The gas shutoff valve 18 is opened and closed manually by, for example, the installation worker of the refrigeration apparatus 100.

(1-1-9) First shutoff valve 41

The first shutoff valve 41 passes or shuts off the refrigerant R under the control of the control unit 9. The first shutoff valve 41 is disposed between the four-way switching valve 12 and a utilization heat exchanger 23 described later. Specifically, the first shutoff valve 41 is disposed between the fourth port P4 of the four-way switching valve 12 and the gas shutoff valve 18.

(1-1-10) Second shutoff valve 42

The second shutoff valve 42 passes or shuts off the refrigerant R under the control of the control unit 9. The second shutoff valve 42 is disposed between the third port P3 of the four-way switching valve 12 and the heat source heat exchanger 13.

(1-1-11) Pressure equalizing valve 43

The pressure equalizing valve 43 passes or shuts off the refrigerant R under the control of the control unit 9. The pressure equalizing valve 43 is disposed in a bypass flow path 95 that connects the suction port 11a and the discharge port 11b and bypasses the compressor 11. The pressure equalizing valve 43 is opened to reduce a pressure difference between the refrigerant at the suction port 11a and the refrigerant at the discharge port 11b.

(1-1-12) Heat source control unit 19

The heat source control unit 19 acquires measurement value data from the low pressure sensor S1 and the high pressure sensor S2. The heat source control unit 19 also controls the compressor 11, the four-way switching valve 12, the heat source fan 14, the heat source expansion valve 15, the first shutoff valve 41, the second shutoff valve 42, and the pressure equalizing valve 43.

(1-2) Utilization unit 20

The plurality of utilization units 20 has generally the same configuration. Hereinafter, one of the plurality of utilization units 20 will be described.
The utilization unit 20 provides the user with hot heat or cold heat. The utilization unit 20 includes the utilization expansion valve 22 and the utilization heat exchanger 23 as components of the refrigerant circuit 90. The utilization unit 20 also includes a utilization fan 24 provided near the utilization heat exchanger 23. The utilization unit 20 further includes a utilization control unit 29 as a component of the control unit 9. A remote controller 27 is connected to the utilization control unit 29 in a wired or wireless manner.

(1-2-1) Utilization expansion valve 22

The utilization expansion valve 22 decompresses the refrigerant R and adjusts the flow rate of the refrigerant R.

(1-2-2) Utilization heat exchanger 23

The utilization heat exchanger 23 exchanges heat between indoor air and the refrigerant R. The utilization heat exchanger 23 functions as an evaporator or a heat absorber for the refrigerant R in the cold heat utilization operation, and functions as a condenser or a heat radiator for the refrigerant R in the hot heat utilization operation.

(1-2-3) Utilization fan 24

The utilization fan 24 promotes heat exchange in the utilization heat exchanger 23 by moving indoor air to pass through the utilization heat exchanger 23. The utilization fan 24 also sends air conditioned by the utilization heat exchanger 23 to the vicinity of the user.

(1-2-4) Utilization control unit 29

The utilization control unit 29 acquires measurement value data from unillustrated sensors. The utilization control unit 29 also controls the utilization expansion valve 22 and the utilization fan 24. In addition, the utilization control unit 29 communicates with the heat source control unit 19 to constitute the control unit 9 together with the heat source control unit 19. The utilization control unit 29 further communicates with the remote controller 27.

(1-2-5) Remote controller 27

The remote controller 27 receives commands from the user and presents information to the user. The commands from the user include execution and switching of the cold heat utilization operation and the hot heat utilization operation in addition to setting of a target temperature and setting of an air volume.

(1-3) Connection piping 30

The connection piping 30 connects the heat source unit 10 and the utilization unit 20 to constitute the refrigerant circuit 90. The connection piping 30 includes a liquid connection pipe 31 and a gas connection pipe 32.

(1-3-1) Liquid connection pipe 31

The liquid connection pipe 31 connects the liquid shutoff valve 17 and the utilization heat exchanger 23, and moves the liquid refrigerant, the gas-liquid two-phase refrigerant, or the like.

(1-3-2) Gas connection pipe 32

The gas connection pipe 32 connects the gas shutoff valve 18 and the utilization heat exchanger 23, and moves the low-pressure gas refrigerant, the high-pressure gas refrigerant, or the like.

(1-4) Communication line 35

The communication line 35 connects the heat source control unit 19 and the utilization control unit 29 to constitute the control unit 9. The communication line 35 transmits a control signal, a status, data, and other signals between the heat source control unit 19 and the utilization control unit 29.

(2) Configuration of four-way switching valve 12

FIG. 2 shows a detailed configuration of the four-way switching valve 12. The four-way switching valve 12 is of a differential pressure-driven type. The four-way switching valve 12 includes a main valve portion 50, a pilot valve portion 60, and a small-diameter pipe group 80.

(2-1) Main valve portion 50

The main valve portion 50 determines the circulation direction of the refrigerant R. The main valve portion 50 includes a casing 51, a valve body 52, a first piston 53, and a second piston 54.

(2-1-1) Casing 51

The casing 51 is a cylindrical metal pipe. An internal space of the casing 51 constitutes a valve chamber 51a. Four pipes constituting the first port P1, the second port P2, the third port P3, and the fourth port P4 are connected to the casing 51. Among the ports, the fourth port P4, the second port P2, and the third port P3 are aligned in a line in that order in a longitudinal direction of the casing 51. The first port P1 is located at a position not aligned with the line of the other ports. The valve chamber 51a is filled with the high-pressure gas refrigerant introduced from the first port P1.

(2-1-2) Valve body 52

The valve body 52 is a member that slides in the valve chamber 51a. The valve body 52 includes a valve main body 52a having an arch shape, a first coupling portion 52b extending in one direction from the valve main body 52a, and a second coupling portion 52c extending from the valve main body 52a in a direction opposite to the first coupling portion 52b. The valve body 52 is movable in a left-right direction in FIG. 2.

(2-1-3) First piston 53

The first piston 53 is fixed to the first coupling portion 52b and moves together with the valve body 52. The first piston 53 forms a first pilot chamber 55 with the casing 51 at a left end of the valve chamber 51a. A first piston hole 53a having a small diameter is formed in the first piston 53. The first pilot chamber 55 communicates with the first port P1 through the first piston hole 53a.

(2-1-4) Second piston 54

The second piston 54 is fixed to the second coupling portion 52c and moves together with the valve body 52. The second piston 54 forms a second pilot chamber 56 with the casing 51 at a right end of the valve chamber 51a. A second piston hole 54a having a small diameter is formed in the second piston 54. The second pilot chamber 56 communicates with the second port P2 via the second piston hole 54a.

(2-2) Pilot valve portion 60

The pilot valve portion 60 adjusts the pressure inside the first pilot chamber 55 and the second pilot chamber 56 by controlling the refrigerant R moving to the first pilot chamber 55 and the second pilot chamber 56. The pilot valve portion 60 includes a first pilot electromagnetic valve 61, a second pilot electromagnetic valve 62, and a connecting portion 63.

(2-2-1) First pilot electromagnetic valve 61

The first pilot electromagnetic valve 61 controls whether to allow the refrigerant R in the second port P2 to reach the first pilot chamber 55. The first pilot electromagnetic valve 61 includes a first pilot valve body 71, a first cylinder 72, a first coil 73, and a first spring 74.
The first pilot valve body 71 is disposed in the first cylinder 72 and is movable in the left-right direction in FIG. 2. A first pilot valve 71a is formed at a right end of the first pilot valve body 71. A restoring force of the first spring 74 acts to move the first pilot valve body 71 to the right side. When a current flows through the first coil 73, the first pilot valve body 71 is attracted to the first coil 73 against the restoring force of the first spring 74, and thus moves to the left side.

(2-2-2) Second pilot electromagnetic valve 62

The second pilot electromagnetic valve 62 controls whether to allow the refrigerant R in the second port P2 to reach the second pilot chamber 56. The second pilot electromagnetic valve 62 includes a second pilot valve body 75, a second cylinder 76, a second coil 77, and a second spring 78.
The second pilot valve body 75 is disposed in the second cylinder 76 and is movable in the left-right direction in FIG. 2. A second pilot valve 75a is formed at a left end of the second pilot valve body 75. A restoring force of the second spring 78 acts to move the second pilot valve body 75 to the left side. When the current flows through the second coil 77, the second pilot valve body 75 is attracted to the second coil 77 against the restoring force of the second spring 78, and thus moves to the right side.

(2-2-3) Connecting portion 63

The connecting portion 63 is a member that connects the first pilot electromagnetic valve 61 and the second pilot electromagnetic valve 62. The connecting portion 63 includes a first pilot valve seat 65, a second pilot valve seat 66, a communication path 64, a first connecting port 67, a second connecting port 68, and a third connecting port 69.
The first pilot valve seat 65 receives the first pilot valve 71a. The first pilot valve seat 65 communicates with the first connecting port 67. The first pilot electromagnetic valve 61 being closed means that the first pilot valve 71a comes into contact with the first pilot valve seat 65. At this time, the first connecting port 67 is closed by the first pilot valve 71a. The first pilot electromagnetic valve 61 being opened means that the first pilot valve 71a is separated from the first pilot valve seat 65. At this time, the first connecting port 67 is opened.
The second pilot valve seat 66 receives the second pilot valve 75a. The second pilot valve seat 66 communicates with the second connecting port 68. The second pilot electromagnetic valve 62 being closed means that the second pilot valve 75a comes into contact with the second pilot valve seat 66. At this time, the second connecting port 68 is closed by the second pilot valve 75a. The second pilot electromagnetic valve 62 being opened means that the second pilot valve 75a is separated from the second pilot valve seat 66. At this time, the second connecting port 68 is opened.
The communication path 64 communicates the first pilot valve seat 65 and the second pilot valve seat 66. A third connecting port 69 is formed in the communication path 64. When the first pilot electromagnetic valve 61 is opened, the first connecting port 67 and the third connecting port 69 communicate with each other via the communication path 64. When the second pilot electromagnetic valve 62 is opened, the second connecting port 68 and the third connecting port 69 communicate with each other via the communication path 64.

(2-3) Small-diameter pipe group 80

The small-diameter pipe group 80 is an assembly of capillary tubes, and includes a first flow path 81, a second flow path 82, and a third flow path 83. The first flow path 81 connects the first pilot chamber 55 and the first connecting port 67. The second flow path 82 connects the second pilot chamber 56 and the second connecting port 68. The third flow path 83 connects the second port P2 and the third connecting port 69.

(3) Operation of four-way switching valve 12

(3-1) State of cold heat utilization operation

FIG. 2 shows an arrangement of each part of the four-way switching valve 12 for performing the cold heat utilization operation. The valve body 52 is located on the left side. As a result, the valve body 52 allows the second port to communicate with the fourth port and allows the first port to communicate with the third port.
In order to position the valve body 52 on the left side, the first pilot electromagnetic valve 61 is opened and the second pilot electromagnetic valve 62 is closed. As a result, the second port P2 communicates with the first pilot chamber 55 via the third flow path 83, the third connecting port 69, the communication path 64, the first connecting port 67, and the first flow path 81. Since the pressure of the gas refrigerant existing in the second port P2 is low, the refrigerant R in the first pilot chamber 55 can be sucked into the second port P2. Since the diameter of the first piston hole 53a is small, the refrigerant R on both sides of the first piston is not immediately equalized.
Since the second pilot electromagnetic valve 62 is closed, the second pilot chamber 56 is isolated from the second port P2. At this time, the second pilot chamber 56 is filled with the high-pressure gas refrigerant flowing in from the second piston hole 54a.
A pressure difference between the low-pressure gas refrigerant in the first pilot chamber 55 and the high-pressure gas refrigerant in the second pilot chamber 56 causes a force to act so as to move the valve body 52 to the left. Accordingly, the valve body 52 can be stably located on the left side.

(3-2) Transient state

FIG. 3 shows a transient state of the four-way switching valve 12 at the time of switching from the cold heat utilization operation to the hot heat utilization operation. In order to switch the four-way switching valve 12, the first pilot electromagnetic valve 61 is closed and the second pilot electromagnetic valve 62 is opened. At this time, the second port P2 communicates with the second pilot chamber 56 via the third flow path 83, the third connecting port 69, the communication path 64, the second connecting port 68, and the second flow path 82. The high-pressure gas refrigerant in the second pilot chamber 56 can be sucked into the second port P2.
Since the first pilot electromagnetic valve 61 is closed, the first pilot chamber 55 is isolated from the second port P2. At this time, the first pilot chamber 55 becomes filled with the high-pressure gas refrigerant flowing in from the first piston hole 53a.
When the pressure of the gas refrigerant in the first pilot chamber 55 becomes larger than the pressure of the gas refrigerant in the second pilot chamber 56, a force acts so as to move the valve body 52 to the right.

(3-3) State of hot heat utilization operation

FIG. 4 is an arrangement of each part of the four-way switching valve when the hot heat utilization operation is performed. As in the transient state in FIG. 3, the first pilot electromagnetic valve 61 is closed and the second pilot electromagnetic valve 62 is opened. The valve body 52 located on the right side allows the second port to communicate with the third port and allows the first port to communicate with the fourth port.
A pressure difference between the high-pressure gas refrigerant in the first pilot chamber 55 and the low-pressure gas refrigerant in the second pilot chamber 56 causes a force acts so as to move the valve body 52 to the right. Accordingly, the valve body 52 can be stably located on the right side.
In order to perform the cold heat utilization operation again, control is performed so as to open the first pilot electromagnetic valve 61 and close the second pilot electromagnetic valve 62. Accordingly, by filling the first pilot chamber 55 with the low-pressure gas refrigerant and filling the second pilot chamber 56 with the high-pressure gas refrigerant, a force is generated so as to move the valve body 52 to the left.

(4) Control of four-way switching valve 12

(4-1) Electrical system of refrigeration apparatus 100

FIG. 5 shows an electric system of the refrigeration apparatus 100. Measurement value data of the low pressure sensor S1 and the high pressure sensor S2 and commands from the user transmitted from the remote controller 27 of each of the plurality of utilization units 20 are input to the control unit 9. The control unit 9 also outputs control signals to the compressor 11, the four-way switching valve 12, the heat source fan 14, the heat source expansion valve 15, and the utilization expansion valve 22 and the utilization fan 24 that belong to each of the plurality of utilization units 20.
The commands transmitted from the remote controller 27 include a switch command Q1 for the four-way switching valve 12. For example, when the user inputs to the remote controller 27 to execute the hot heat utilization operation while the refrigeration apparatus 100 is executing the cold heat utilization operation, the remote controller 27 transmits the switch command Q1 to the control unit 9 in order to perform the switching of the four-way switching valve 12 and thereby to execute the hot heat utilization operation. Alternatively, when the user inputs to the remote controller 27 to execute the cold heat utilization operation while the refrigeration apparatus 100 is executing the hot heat utilization operation, the remote controller 27 transmits the switch command Q1 to the control unit 9 in order to perform the switching of the four-way switching valve 12 and thereby to execute the cold heat utilization operation.
Upon receiving the switch command Q1, the control unit 9 performs a predetermined calculation to output a switch control signal Q2 to the four-way switching valve 12. Specifically, the switch control signal Q2 is an open/close control signal to the first pilot electromagnetic valve 61 and the second pilot electromagnetic valve 62.

(4-2) Switching control

FIG. 6 is a flowchart of a main routine of switching control of the four-way switching valve 12. In step S100, the switching control is started.
In step S101, it is confirmed whether a normal state of the refrigerant circuit 90 is realized in which the first shutoff valve 41 and the second shutoff valve 42 are opened and the pressure equalizing valve 43 is closed. When the normal state is not realized (S101: NO), the processing proceeds to error processing in step S191. On the other hand, when the normal state is realized (S101: YES), the processing proceeds to step S102.
In step S102, it is confirmed whether the control unit 9 has received the switch command Q1. When the switch command Q1 has not been received (S102: NO), the processing proceeds to the error processing in step S191. On the other hand, when the switch command Q1 has been received (S102: YES), the processing proceeds to step S103.
In step S103, the control unit 9 stops the compressor 11. In step S104, the control unit 9 closes the first shutoff valve 41 and the second shutoff valve 42 and opens the pressure equalizing valve 43. In this manner, preparation of the refrigerant circuit 90 for switching the four-way switching valve 12 is made.
In step S111, a count value of a timer of the control unit 9 is reset to zero. In step S112, the control unit 9 starts clocking of the timer. In step S113, the control unit 9 refers to a value measured by the timer, and confirms whether a predetermined time has elapsed. The predetermined time is, for example, five seconds. When the predetermined time has not elapsed (S113: NO), the processing returns to step S113. On the other hand, when the predetermined time has elapsed (S113: YES), the processing proceeds to step S114. In step S114, the control unit 9 ends the clocking of the timer. As a result, since a predetermined time has elapsed after the preparation of the refrigerant circuit 90 for switching the four-way switching valve 12, the state of the refrigerant R is expected to be stabilized.
In step S121, the control unit 9 closes the pressure equalizing valve 43.
In step S131, the control unit 9 executes a subroutine for outputting the switch control signal Q2 to the four-way switching valve 12. The subroutine for outputting the switch control signal Q2 will be described later.
After the switching control of the four-way switching valve 12 ends, in step S141, the control unit 9 restores the connection of the refrigerant circuit 90 other than the four-way switching valve 12 by opening the first shutoff valve 41 and the second shutoff valve 42. Next, in step S142, the control unit 9 restarts the operation of the compressor 11.
Thereafter, in step S114, the main routine of the switching control of the four-way switching valve 12 ends.
Step S191 is the error processing. In this step, the control unit 9 returns the refrigerant circuit 90 to the normal state by opening the first shutoff valve 41 and the second shutoff valve 42 and closing the pressure equalizing valve 43. In step S192, the control unit 9 ends the main routine of the switching control with an error.
FIG. 7 is a flowchart of a subroutine of output processing of the switch control signal Q2. In step S200, the output of the switch control signal Q2 is started. In step S201, the control unit 9 confirms a content of the switch command Q1 already received. When the content of the switch command Q1 is to request execution of the cold heat utilization operation (step S201: cold heat utilization operation), the processing proceeds to step S202. In step S202, the control unit 9 outputs the switch control signal Q2 to open the first pilot electromagnetic valve 61 and close the second pilot electromagnetic valve 62. Thereafter, in step S204, the output processing of the switch control signal Q2 ends.
On the other hand, when the content of the switch command Q1 is to request execution of the hot heat utilization operation (step S201: hot heat utilization operation), the processing proceeds to step S203. In step S203, the control unit 9 outputs the switch control signal Q2 to close the first pilot electromagnetic valve 61 and open the second pilot electromagnetic valve 62. Thereafter, in step S204, the output processing of the switch control signal Q2 ends.

(5) Characteristics

(5-1)
By closing the first shutoff valve 41 and the second shutoff valve 42 before performing the switching of the four-way switching valve 12, the refrigerant circuit 90 around the four-way switching valve 12 is shut off. Therefore, it is possible to reduce damage to the four-way switching valve 12 due to a pressure difference of a large amount of the refrigerant R.
(5-2)
The pressure equalizing valve 43 is opened to reduce the pressure difference between the refrigerant R at the suction port 11a and the refrigerant R at the discharge port 11b. Therefore, damage to the four-way switching valve 12 can be further reduced.
(5-3)
After receiving the switch command Q1 of the four-way switching valve, the control unit 9 performs the switching for the four-way switching valve 12 after a predetermined time has elapsed. Therefore, it can be expected that the pressure difference between the refrigerant R at the suction port 11a and the refrigerant R at the discharge port 11b is eliminated by the elapse of the predetermined time, and thus, damage to the four-way switching valve 12 can be reduced.
(5-4)
After receiving the switch command Q1 for the four-way switching valve 12, the control unit 9 stops the compressor 11 in step S103. It is therefore possible to avoid generation of a pressure difference between the refrigerant R the suction port 11a and of the refrigerant R the discharge port 11b.
(5-5)
Before switching the four-way switching valve 12 in step S131, the pressure equalizing valve 43 is closed in step S121. Therefore, when it can be determined that the pressure difference between the refrigerant R at the suction port 11a and the refrigerant R at the discharge port 11b is sufficiently small, the pressure equalizing valve 43 can be quickly closed.

In particular, in a case where the four-way switching valve 12 is of a differential pressure-driven type as shown in FIGS. 2 to 4, the pressure equalizing valve 43 can be closed even before the switching of the four-way switching valve 12 when the pressure difference decreases to some extent due to pressure equalization.
(5-6)
The refrigerant R may include carbon dioxide. When carbon dioxide is used for the refrigerant, a switching noise of the four-way switching valve 12 tends to be loud. Therefore, by closing the first shutoff valve 41 and the second shutoff valve 42, an impact at the time of switching of the four-way switching valve 12 is less likely to be transmitted to the outside.

(6) Modifications

(6-1) First modification

In the embodiment described earlier, the control unit 9 closes both the first shutoff valve 41 and the second shutoff valve 42 before the switching operation of the four-way switching valve 12. Alternatively, the control unit 9 may close one of the first shutoff valve 41 or the second shutoff valve 42 before the switching operation of the four-way switching valve 12.

(6-2) Second modification

In the embodiment described earlier, as shown in FIG. 6, after receiving the switch command Q1 for the four-way switching valve 12, the control unit 9 performs the switching of the four-way switching valve 12 after a predetermined time has elapsed. Alternatively, after receiving the switch command Q1 for the four-way switching valve 12, the control unit 9 may calculate the pressure difference between the refrigerant R on the suction side and the refrigerant R on the discharge side of the compressor 11 from the measurement values of the low pressure sensor S1 and the high pressure sensor S2, and perform the switching of the four-way switching valve 12 after confirming that the pressure difference is small.
FIG. 8 is a flowchart of the main routine of the switching control of the four-way switching valve 12 according to a second modification. In step S302, the control unit 9 confirms that the switch command Q1 has been received. Thereafter, in step S304, the control unit 9 opens the pressure equalizing valve 43. In step S313, the control unit 9 calculates a pressure difference between a high pressure side and a low pressure side from the measurement values of the low pressure sensor S1 and the high pressure sensor S2, and confirms whether the pressure difference is smaller than a predetermined value. When, with the pressure difference being not smaller than the predetermined value (S313: NO), a predetermined time has elapsed (S314: YES), the processing proceeds to error processing in step S391. On the other hand, when the pressure difference is smaller than the predetermined value (S313: YES), the processing proceeds via steps S316 and S321 to step S331. In step S331, the switching of the four-way switching valve 12 is performed.

(6-3) Third modification

In the embodiment described earlier, the four-way switching valve 12 is of a differential pressure-driven type as shown in FIGS. 2 to 4. Alternatively, the four-way switching valve 12 may be of a rotary type.
The four-way switching valve 12 of a rotary type shown in FIG. 9 includes a cylindrical casing 251 and a valve seat 255 provided on a bottom surface of the casing 251. The valve seat 255 is provided with the first port P1, the second port P2, the third port P3, and the fourth port P4 through which the refrigerant R passes. A valve body 252 having a round column shape is rotatably disposed in the casing 251. The valve body 252 is provided with a high-pressure side groove 252a and a low-pressure side groove 252b. The valve body 252 can rotate by 90° by an action of a coil and an unillustrated permanent magnet. In FIG. 9, 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. When the valve body 252 rotates 90° from the state in FIG. 9, the first port P1 and the fourth port P4 can communicate with each other, and the second port P2 and the third port P3 can communicate with each other.
FIG. 10 is a flowchart of the main routine of the switching control of the four-way switching valve 12 of a rotary type. Unlike the control of the four-way switching valve 12 of a differential pressure-driven type in FIG. 6, in the case of the control of the four-way switching valve 12 of a rotary type in FIG. 10, the pressure equalizing valve 43 is opened when the four-way switching valve 12 is switched in step S431.
Specifically, prior to the switching of the four-way switching valve 12, the control unit 9 closes the first shutoff valve 41 and the second shutoff valve 42 and opens the pressure equalizing valve 43 in step S404. Thereafter, in step S431, the control unit 9 performs the switching of the four-way switching valve 12 in a state where the pressure equalizing valve 43 is opened. After the end of the switching of the four-way switching valve 12, the control unit 9 closes the pressure equalizing valve 43 and opens the first shutoff valve 41 and the second shutoff valve 42 in step S441.
The switching of the four-way switching valve 12 of a rotary type is difficult to perform when there is a large pressure difference between the high pressure side and the low pressure side. Therefore, the switching of the four-way switching valve 12 is often desirably performed in a state where the pressure equalizing valve 43 is reliably opened.

(1) Configuration

FIG. 11 shows the refrigeration apparatus 100 according to a second embodiment. The refrigeration apparatus 100 is different from the refrigeration apparatus according to the first embodiment in that each of the plurality of utilization units 20 can individually select the cold heat utilization operation or the hot heat utilization operation. In order to enable such individual selection, the connection piping 30 includes three pipes, namely, a liquid connection pipe 31, a low pressure gas connection pipe 32, and a high pressure and low pressure gas connection pipe 33. The heat source unit 10 includes two four-way switching valves, namely, a first four-way switching valve 12a and a second four-way switching valve 12b, and two gas shutoff valves, namely, a first gas shutoff valve 18a and a second gas shutoff valve 18b. Furthermore, a valve unit 40 is disposed between the heat source unit 10 and each of the utilization units 20.
Each valve unit 40 includes two first shutoff valves 41 and a valve control unit 49. One of the two first shutoff valves 41 passes or shuts off the refrigerant R between the low pressure gas connection pipe 32 and the utilization heat exchanger 23, and the other passes or shuts off the refrigerant R between the high pressure and low pressure gas connection pipe 33 and the utilization heat exchanger 23. The valve control units 49 constitute the control unit 9 of the refrigeration apparatus 100 together with the heat source control unit 19 and the utilization control units 29.

(2) Characteristics

When the switch command Q1 for the first four-way switching valve 12a or the second four-way switching valve 12b is issued from the remote controller 27 of any of the utilization units 20, the control unit 9 closes both of the two first shutoff valves 41 included in each of the valve units 40 as in the first embodiment before the switching operation is performed. This configuration reduces damage to the first four-way switching valve 12a or the second four-way switching valve 12b due to the pressure difference of the refrigerant R.

(3) Modifications

In the embodiment described earlier, the second shutoff valve 42 is provided in the heat source unit 10. Alternatively, the pipe of the refrigerant circuit 90 may be designed such that the second shutoff valve 42 is provided in the valve unit 40.

The embodiment of the present disclosure has been described above. It is understood that various changes to modes and details should be available without departing from the gist and scope of the present disclosure recited in the claims.

REFERENCE SIGNS LIST

9: control unit
10: heat source unit
11: compressor
11a: suction port
11b: discharge port
12: four-way switching valve
13: heat source heat exchanger
19: heat source control unit
20: utilization unit
23: utilization heat exchanger
27: remote controller
29: utilization control unit
30: connection piping
35: communication line
40: valve unit
41: first shutoff valve
42: second shutoff valve
43: pressure equalizing valve
49: valve control unit
90: refrigerant circuit
95: bypass flow path
100: refrigeration apparatus
Q1: switch command
Q2: switch control signal
R: refrigerant

CITATION LIST

PATENT LITERATURE

Patent Literature 1: JP S63-015056 A

Claims

A refrigeration apparatus (100) comprising:
a refrigerant circuit (90) including:
a compressor (11) including a suction port (11a) through which a refrigerant (R) is sucked and a discharge port (11b) through which the refrigerant is discharged,

a four-way switching valve (12),

a heat source heat exchanger (13), and

a utilization heat exchanger (23);

a control unit (9) that switches a circulation path of the refrigerant in the refrigerant circuit by performing switching of the four-way switching valve; and

a first shutoff valve (41) disposed between the four-way switching valve and the utilization heat exchanger, wherein

the control unit closes the first shutoff valve before performing the switching of the four-way switching valve.
The refrigeration apparatus according to claim 1, further comprising
a second shutoff valve (42) disposed between the four-way switching valve and the heat source heat exchanger, wherein

the control unit further closes the second shutoff valve before performing the switching of the four-way switching valve.
The refrigeration apparatus according to claim 2, further comprising:
a bypass flow path (95) that connects the suction port and the discharge port; and

a pressure equalizing valve (43) configured to open or close the bypass flow path, wherein

the control unit further opens the pressure equalizing valve before performing the switching.
The refrigeration apparatus according to any one of claims 1 to 3, wherein the control unit performs the switching of the four-way switching valve after a predetermined time elapses after receiving a switch command (Q1) of the four-way switching valve.
The refrigeration apparatus according to any one of claims 1 to 4, wherein the control unit stops the compressor after receiving the switch command (Q1) of the four-way switching valve.
The refrigeration apparatus according to claim 3, wherein
the control unit

closes the first shutoff valve or the second shutoff valve and opens the pressure equalizing valve before performing the switching of the four-way switching valve,

performs the switching of the four-way switching valve in a state where the pressure equalizing valve is opened, and

closes the pressure equalizing valve and opens the first shutoff valve or the second shutoff valve after ending the switching of the four-way switching valve.
The refrigeration apparatus according to claim 3, wherein
the control unit

closes the first shutoff valve or the second shutoff valve and opens the pressure equalizing valve before performing the switching of the four-way switching valve,

closes the pressure equalizing valve when a pressure difference between the suction port and the discharge port becomes equal to or less than a predetermined value,

performs the switching of the four-way switching valve in a state where the pressure equalizing valve is closed, and

opens the first shutoff valve or the second shutoff valve after ending the switching of the four-way switching valve.
The refrigeration apparatus according to any one of claims 1 to 7, wherein the refrigerant includes carbon dioxide.
The refrigeration apparatus according to claim 2 or 3, further comprising:
a heat source unit (10) including the compressor, the four-way switching valve, and the heat source heat exchanger;

a utilization unit (20) including the utilization heat exchanger; and

a valve unit (40) disposed between the heat source unit and the utilization unit, wherein

the first shutoff valve or the second shutoff valve is disposed in the valve unit.