Refrigeration apparatus having a four-way reversing valve

Abstract

A freezing device (100) includes a refrigerant circuit (90) and a control portion (9). The refrigerant circuit (90) has a compressor (11), a four-way reversing valve (12), and a connection flow path (91) connecting the compressor (11) and the four-way reversing valve (12). The refrigerant circuit (90) circulates a refrigerant (R). The control portion (9) performs switching of the four-way reversing valve (12) in order to change a circulation path of the refrigerant (R) in the refrigerant circuit (90). The control portion (9) performs the switching of the four-way reversing valve (12) in a case where a switching permission condition related to the refrigerant (R) in the connection flow path (91) is satisfied, and does not perform the switching of the four-way reversing valve (12) in a case where the switching permission condition is not satisfied.

Description

Technical Field

[0001] This disclosure relates to a refrigeration apparatus having a four-way reversing valve. Background Technology

[0002] The four-way reversing valve disclosed in Patent Document 1 (Japanese Patent Application Publication No. 63-015056) is installed in a refrigeration unit for switching the circulation direction of the refrigerant. This four-way reversing valve is a so-called differential pressure driven four-way reversing valve, which uses the pressure of the refrigerant passing through the valve chamber to move the valve core. Summary of the Invention

[0003] The technical problem that the invention aims to solve

[0004] Refrigerant passing through the four-way reversing valve may carry refrigeration oil into the valve chamber or narrow-bore pipe that makes up the four-way reversing valve. If the refrigeration oil remains inside the narrow-bore pipe, it will obstruct the movement of the valve core, potentially hindering the switching of the refrigerant circulation direction.

[0005] Technical solutions adopted to solve technical problems

[0006] The first-view refrigeration unit includes a refrigerant circuit and a control unit. The refrigerant circuit includes a compressor, a four-way reversing valve, and a connecting flow path connecting the compressor and the four-way reversing valve. The refrigerant circuit circulates refrigerant. The control unit switches the four-way reversing valve to change the circulation path of the refrigerant in the refrigerant circuit. The control unit switches the four-way reversing valve only when the switching allowable conditions related to the refrigerant in the connecting flow path are met; otherwise, it does not switch the four-way reversing valve.

[0007] According to this structure, the four-way directional valve will not switch if the state of the refrigerant in the connecting flow path does not meet the switching allowable conditions. Therefore, it can prevent switching failures or damage to the four-way directional valve caused by the switching action.

[0008] The second viewpoint of the refrigeration unit is based on the first viewpoint of the refrigeration unit. When the control unit receives a switching command to switch the four-way directional valve, it does not switch the four-way directional valve if the switching permission conditions are not met.

[0009] According to this structure, even if the control unit receives a switching command, it will not switch the four-way directional valve if the switching conditions are not met. Therefore, it can suppress situations where the switching action fails or the switching action damages the four-way directional valve.

[0010] The third viewpoint refrigeration unit is based on the first or second viewpoint refrigeration unit, but switches the permissible conditions related to the Froude number, an index representing the refrigerant circulation volume. The Froude number is represented by Fr as follows.

[0011] [Mathematical Expression 1]

[0012] Here, ρ G (kg / m 3 ρ is the density of the gaseous refrigerant. L (kg / m 3 U is the density of the liquid refrigerant. G (m / s) is the flow rate of the gaseous refrigerant. g (m / s) 2 ) is the acceleration due to gravity. D (m) is the inner diameter of the pipe that forms the connection path.

[0013] According to this structure, the switching permission condition is related to the refrigerant circulation rate. Therefore, it is possible to determine whether the switching of the four-way reversing valve is permitted or not based on the refrigerant circulation rate.

[0014] The fourth viewpoint's freezing device is based on the third viewpoint's freezing device, with the switching condition being that the Froude number is 1 or higher.

[0015] According to this structure, the switching condition is that the refrigerant circulation rate is above a specified value. Therefore, even when the refrigerant circulation rate is small and it is foreseeable that there is refrigeration oil retention in the connection flow path, it is possible to prevent switching failure or damage to the four-way reversing valve due to the presence of refrigeration oil that may hinder the switching operation.

[0016] The fifth viewpoint's refrigeration unit is based on any of the first to fourth viewpoints' refrigeration units. When the switching allowable conditions are not met, the control unit drives the compressor to perform an oil discharge operation that moves the refrigeration oil present in the connecting flow path downstream of the four-way reversing valve.

[0017] Based on this structure, oil drainage is performed when it is foreseeable that there will be refrigerant oil retention in the connecting flow path. Therefore, it is possible to prevent refrigerant oil residue that would hinder the switching action from remaining inside the four-way reversing valve.

[0018] The refrigeration unit of the sixth viewpoint is based on the refrigeration unit of the fifth viewpoint. In addition to switching the situation where the permissible conditions are not met, the control unit also performs oil drainage operation in at least one situation: immediately after the refrigeration unit is started and before it is stopped.

[0019] According to this structure, an oil draining operation is performed immediately after the refrigeration unit starts up or before it stops. This prevents refrigeration oil residue from remaining inside the four-way reversing valve.

[0020] The refrigeration device of the seventh viewpoint is based on the refrigeration device of any of the first to sixth viewpoints, with the connecting flow path having a U-shaped tube protruding downwards.

[0021] Based on this structure, the connecting flow path has a design that easily allows refrigeration oil to accumulate. Therefore, by performing an oil drain operation, refrigeration oil can be effectively removed from the connecting flow path and the four-way reversing valve.

[0022] The refrigeration device of the eighth viewpoint is based on the refrigeration device of any of the first to seventh viewpoints, and the refrigerant is carbon dioxide.

[0023] According to this structure, the refrigerant is carbon dioxide. When carbon dioxide is used as the refrigerant, the switching noise of the four-way reversing valve tends to increase. To reduce the switching noise, the circulation rate of carbon dioxide refrigerant is sometimes reduced, which results in refrigeration oil easily accumulating in the connecting flow path. Therefore, by performing an oil draining operation, refrigeration oil can be effectively removed from the connecting flow path and the four-way reversing valve.

[0024] The refrigeration unit of the ninth viewpoint is based on the refrigeration unit of any of the first to eighth viewpoints. The four-way reversing valve includes: a valve chamber, a valve core, a first pilot chamber, a second pilot chamber, a first port, a second port, a third port, and a fourth port formed in the valve chamber, a first pilot solenoid valve and a second pilot solenoid valve, a first flow path, a second flow path, and a third flow path. The valve core slides within the valve chamber. The first pilot chamber is formed at one end of the valve chamber. The second pilot chamber is formed at the end of the valve chamber opposite to the first pilot chamber. The first port receives refrigerant discharged from the compressor. The second port sprays refrigerant drawn into the compressor. The third port exchanges refrigerant with a heat exchanger. The fourth port exchanges refrigerant with a heat exchanger. The first and second pilot solenoid valves are separately configured from the valve chamber. The first flow path connects the first pilot chamber to the first pilot solenoid valve. The second flow path connects the second pilot chamber to the second pilot solenoid valve. The third flow path connects the connection path of the first pilot solenoid valve and the second pilot solenoid valve to the second port.

[0025] Based on this structure, the four-way directional valve has multiple flow paths connecting the pilot solenoid valve to the valve chamber. Therefore, by operating with oil drainage, it is possible to prevent refrigeration oil residue from remaining in multiple flow paths. Attached Figure Description

[0026] Figure 1 This is a circuit diagram showing the structure of the refrigeration unit 100.

[0027] Figure 2 This is a cross-sectional schematic diagram showing the four-way reversing valve 12 in operation during hot and cold water utilization.

[0028] Figure 3 This is another cross-sectional schematic diagram showing the four-way directional valve 12 in the transition state.

[0029] Figure 4 This is another cross-sectional schematic diagram showing the four-way reversing valve 12 in operation during heat utilization.

[0030] Figure 5 This is a block diagram showing the electrical system of the refrigeration unit 100.

[0031] Figure 6 This is a schematic diagram showing the connection piping between the compressor 11 and the four-way reversing valve 12.

[0032] Figure 7 This is a flowchart of the switching control of the four-way directional valve 12.

[0033] Figure 8 This is a flowchart of the oil discharge process.

[0034] Figure 9 This is a flowchart of the output processing of the switching control signal Q2. Detailed Implementation

[0035] <Implementation Method>

[0036] (1) Overall structure

[0037] Figure 1 The refrigeration unit 100 shown is used to provide users with hot heat or cold heat obtained from a heat source, and is configured as an air conditioning unit, for example. The refrigeration unit 100 is capable of performing hot / cold heat utilization operation to provide users with hot / cold heat and warm heat utilization operation to provide users with warm heat. In the case that the refrigeration unit 100 is an air conditioning unit, these are respectively equivalent to cooling operation and heating operation.

[0038] The refrigeration unit 100 includes a heat source unit 10, a utilization unit 20, a connecting pipe 30, and a communication line 35. These components together form a refrigerant circuit 90 that circulates refrigerant R and a control unit 9 that controls the refrigerant circuit 90.

[0039] As the refrigerant R, any refrigerant can be used, such as carbon dioxide. In the following description, refrigerant R is considered to be capable of undergoing a phase change to liquid, and terms such as "condensation," "evaporation," "liquid refrigerant," and "gas-liquid two-phase refrigerant" are used in the description. However, it should be noted that in the case of refrigerant R being carbon dioxide, there is no accompanying phase change to liquid, therefore, these terms are not strictly applicable.

[0040] (1-1) Heat source unit 10

[0041] The heat source unit 10 obtains heat or cold from a heat source such as outdoor air. The heat source unit 10 includes a compressor 11, a four-way reversing valve 12, a heat source heat exchanger 13, a heat source expansion valve 15, a storage tank 16, a liquid shut-off valve 17, and a gas shut-off valve 18, which are components of the refrigerant circuit 90. The heat source unit 10 also includes a heat source fan 14 located near the heat source heat exchanger 13. The heat source unit 10 also includes a heat source control unit 19, which is a component of the control unit 9. The heat source unit 10 also includes a low-pressure sensor S1, a high-pressure sensor S2, a heat source heat exchanger temperature sensor S3, and an external air temperature sensor S4.

[0042] (1-1-1) Compressor 11

[0043] The compressor 11 has a suction pipe 11a and a discharge pipe 11b. The compressor 11 compresses low-pressure gaseous refrigerant drawn in through the suction pipe 11a to generate high-pressure gaseous refrigerant, which is then discharged through the discharge pipe 11b. A low-pressure sensor S1 is provided on the suction side of the compressor 11, that is, near the suction pipe 11a. A high-pressure sensor S2 is provided on the discharge side of the compressor 11, that is, near the discharge pipe 11b. Both the low-pressure sensor S1 and the high-pressure sensor S2 measure the pressure of the refrigerant R.

[0044] (1-1-2) Four-way directional valve 12

[0045] The four-way reversing valve 12 switches the circulation direction of refrigerant R. The four-way reversing valve 12 has 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 connected to the discharge pipe 11b. The second port P2 is connected to a pipe connected to the storage tank 16. The third port P3 is connected to a pipe connected to the heat exchanger 13. The fourth port P4 is connected to a pipe connected to the gas shut-off valve 18.

[0046] When the refrigeration unit 100 is operating in a cold and heat utilization mode, such as Figure 1 As shown by the solid line, the four-way reversing valve 12 connects the first port P1 to the third port P3, and the second port P2 to the fourth port P4. When the refrigeration unit 100 is operating under heat utilization conditions, such as... Figure 1 As shown by the dashed line, the four-way directional valve 12 connects the first port P1 to the fourth port P4, and the second port P2 to the third port P3.

[0047] (1-1-3) Heat source heat exchanger 13

[0048] The heat source heat exchanger 13 facilitates heat exchange between outdoor air and refrigerant R. In operation for both cooling and heating, the heat source heat exchanger 13 functions as a condenser or radiator for refrigerant R; in operation for both warm and warm heating, it functions as an evaporator or absorber for refrigerant R. A heat source heat exchanger temperature sensor S3, located near the heat source heat exchanger 13, measures the condensation temperature, evaporation temperature, and other parameters of the refrigerant R within the heat source heat exchanger 13.

[0049] (1-1-4) Heat source fan 14

[0050] The heat source fan 14 promotes heat exchange in the heat source heat exchanger 13 by moving outdoor air through its interior. The temperature of the outdoor air is measured by the external temperature sensor S4.

[0051] (1-1-5) Heat source expansion valve 15

[0052] The heat source expansion valve 15 reduces the pressure of refrigerant R and regulates the flow rate of refrigerant R.

[0053] (1-1-6) Storage tank 16

[0054] Storage tank 16 stores the liquid refrigerant component mixed with the gaseous refrigerant and allows the gaseous refrigerant to pass through. Storage tank 16 is connected to the suction pipe 11a of compressor 11. Storage tank 16 prevents liquid refrigerant from being drawn into compressor 11.

[0055] (1-1-7) Liquid shut-off valve 17

[0056] The liquid shut-off valve 17 allows or interrupts the flow of liquid refrigerant or two-phase refrigerant. The opening and closing of the liquid shut-off valve 17 can be performed manually, for example, by the installation personnel of the refrigeration unit 100.

[0057] (1-1-8) Gas shut-off valve 18

[0058] The gas shut-off valve 18 allows or blocks the flow of low-pressure or high-pressure refrigerant. The opening and closing of the gas shut-off valve 18 is, for example, manually performed by the installation personnel of the refrigeration unit 100.

[0059] (1-1-9) Heat Source Control Department 19

[0060] The heat source control unit 19 acquires measured data from the low-pressure sensor S1, the high-pressure sensor S2, the heat source heat exchanger temperature sensor S3, and the external air temperature sensor S4. The heat source control unit 19 also controls the compressor 11, the four-way reversing valve 12, the heat source fan 14, and the heat source expansion valve 15.

[0061] (1-2) Using Unit 20

[0062] The utilization unit 20 provides warmth or cold to the user. As a component of the refrigerant circuit 90, the utilization unit 20 includes a utilization heat exchanger 23. The utilization unit 20 also includes a utilization fan 24 located near the utilization heat exchanger 23. The utilization unit 20 further includes a utilization control unit 29, which is a component of the control unit 9. The utilization unit 20 also includes a utilization heat exchanger temperature sensor S5 and a room temperature sensor S6. A remote control 27 is wired or wirelessly connected to the utilization control unit 29.

[0063] (1-2-1) Using heat exchanger 23

[0064] Heat exchanger 23 is used for heat exchange between indoor air and refrigerant R. In operation for both cooling and heating, heat exchanger 23 functions as an evaporator or absorber for refrigerant R; in operation for both warm and hot heating, it functions as a condenser or radiator for refrigerant R. A heat exchanger temperature sensor S5, located near heat exchanger 23, measures the condensation temperature, evaporation temperature, etc., of the refrigerant R within heat exchanger 23.

[0065] (1-2-2) Using fan 24

[0066] The fan 24 promotes heat exchange within the heat exchanger 23 by moving indoor air through it. The fan 24 also delivers the conditioned air from the heat exchanger 23 to the vicinity of the user. The indoor air temperature is measured by the room temperature sensor S6.

[0067] (1-2-3) Using the control unit 29

[0068] The control unit 29 acquires measured data from the heat exchanger temperature sensor S5 and the room temperature sensor S6. The control unit 29 also controls the fan 24. Furthermore, the control unit 29 communicates with the heat source control unit 19, forming a control unit 9 together with the heat source control unit 19. The control unit 29 also communicates with the remote controller 27.

[0069] (1-2-4) Remote Control 27

[0070] Remote controller 27 receives commands from the user and provides information to the user. The commands from the user include setting the target temperature, setting the airflow, and executing and switching between hot and cold operation and warm / hot operation.

[0071] (1-3) Connecting piping 30

[0072] The connecting piping 30 connects the heat source unit 10 to the utilization unit 20 to form a refrigerant circuit 90. The connecting piping 30 has a liquid connecting piping 31 and a gas connecting piping 32.

[0073] (1-3-1) Liquid connection piping 31

[0074] The liquid connecting pipe 31 connects the liquid shut-off valve 17 to the heat exchanger 23, allowing the liquid refrigerant or gas-liquid two-phase refrigerant to move.

[0075] (1-3-2) Gas connection piping 32

[0076] Gas connection piping 32 connects gas shut-off valve 18 and heat exchanger 23 to move low-pressure gas refrigerant or high-pressure gas refrigerant.

[0077] (1-4) Communication line 35

[0078] Communication line 35 connects heat source control unit 19 and utilization control unit 29 to form control unit 9. Communication line 35 transmits control signals, status, data and other signals between heat source control unit 19 and utilization control unit 29.

[0079] (2) Structure of the four-way reversing valve 12

[0080] Figure 2 The detailed structure of the four-way directional valve 12 is shown. The four-way directional valve 12 has a main valve section 50, a pilot valve section 60, and a small-diameter pipe assembly section 80.

[0081] (2-1) Main valve section 50

[0082] The main valve section 50 determines the circulation direction of the refrigerant R. The main valve section 50 includes a housing 51, a valve core 52, a first piston 53, and a second piston 54.

[0083] (2-1-1) Shell 51

[0084] The housing 51 is a cylindrical metal tube. The internal space of the housing 51 forms a valve chamber 51a. Four tubes, constituting a first port P1, a second port P2, a third port P3, and a fourth port P4, are connected to the housing 51. The fourth port P4, the second port P2, and the third port P3 are arranged in a row along the length of the housing 51. Furthermore, the first port P1 is located in a position not aligned with the other ports. The valve chamber 51a is filled with high-pressure gaseous refrigerant introduced through the first port P1.

[0085] (2-1-2) Valve core 52

[0086] The valve core 52 is a sliding component within the valve chamber 51a. The valve core 52 has: an arched valve body 52a; a first connecting portion 52b extending in one direction from the valve body 52a; and a second connecting portion 52c extending from the valve body 52a in the opposite direction to the first connecting portion 52b. The valve core 52 can... Figure 2Move left and right in the middle.

[0087] (2-1-3) First piston 53

[0088] The first piston 53 is fixed to the first connecting part 52b and moves together with the valve core 52. The first piston 53 forms a first pilot chamber 55 between the left end of the valve chamber 51a and the housing 51. A first piston hole 53a with a small diameter is formed on the first piston 53. The first pilot chamber 55 communicates with the first port P1 through the first piston hole 53a.

[0089] (2-1-4) Second piston 54

[0090] The second piston 54 is fixed to the second connecting part 52c and moves together with the valve core 52. The second piston 54 forms a second pilot chamber 56 between the right end of the valve chamber 51a and the housing 51. A second piston hole 54a with a smaller diameter is formed on the second piston 54. The second pilot chamber 56 communicates with the second port P2 through the second piston hole 54a.

[0091] (2-2) Pilot valve section 60

[0092] The pilot valve section 60 regulates the pressure inside the first pilot chamber 55 and the second pilot chamber 56 by controlling the refrigerant R moving into the first pilot chamber 55 and the second pilot chamber 56. The pilot valve section 60 includes a first pilot solenoid valve 61, a second pilot solenoid valve 62, and a connecting section 63.

[0093] (2-2-1) First pilot solenoid valve 61

[0094] The first pilot solenoid valve 61 controls whether the refrigerant R at the second port P2 reaches the first pilot chamber 55. The first pilot solenoid valve 61 has a first pilot valve core 71, a first cylinder 72, a first coil 73, and a first spring 74.

[0095] The first pilot valve core 71 is disposed inside the first cylinder 72, and can... Figure 2 The first pilot valve 71a is formed at the right end of the first pilot valve core 71. The restoring force of the first spring 74 acts to move the first pilot valve core 71 to the right. When current flows through the first coil 73, the first pilot valve core 71 is attracted by the first coil 73 to resist the restoring force of the first spring 74, and thus moves to the left.

[0096] (2-2-2) Second pilot solenoid valve 62

[0097] The second pilot solenoid valve 62 controls whether the refrigerant R at the second port P2 reaches the second pilot chamber 56. The second pilot solenoid valve 62 has a second pilot valve core 75, a second cylinder 76, a second coil 77, and a second spring 78.

[0098] The second pilot valve core 75 is disposed in the second cylinder 76, and can be used to... Figure 2 The second pilot valve 75 moves to the left and right. A second pilot valve 75a is formed at the left end of the second pilot valve core 75. The restoring force of the second spring 78 acts to move the second pilot valve core 75 to the left. When current flows through the second coil 77, the second pilot valve core 75 is attracted by the second coil 77 to resist the restoring force of the second spring 78, and thus moves to the right.

[0099] (2-2-3) Connecting part 63

[0100] The connecting part 63 is a component that connects the first pilot solenoid valve 61 and the second pilot solenoid valve 62. The connecting part 63 has a first pilot valve seat 65, a second pilot valve seat 66, a connecting passage 64, a first connection port 67, a second connection port 68, and a third connection port 69.

[0101] The first pilot valve seat 65 receives the first pilot valve 71a. The first pilot valve seat 65 is connected to the first connection port 67. The first pilot solenoid valve 61 is closed when the first pilot valve 71a is in contact with the first pilot valve seat 65. At this time, the first connection port 67 is blocked by the first pilot valve 71a. The first pilot solenoid valve 61 is open when the first pilot valve 71a is separated from the first pilot valve seat 65. At this time, the first connection port 67 is opened.

[0102] The second pilot valve seat 66 receives the second pilot valve 75a. The second pilot valve seat 66 is connected to the second connection port 68. The second pilot solenoid valve 62 is closed when the second pilot valve 75a is in contact with the second pilot valve seat 66. At this time, the second connection port 68 is blocked by the second pilot valve 75a. The second pilot solenoid valve 62 is open when the second pilot valve 75a is separated from the second pilot valve seat 66. At this time, the second connection port 68 is opened.

[0103] The connecting path 64 connects the first pilot valve seat 65 and the second pilot valve seat 66. A third connection port 69 is formed on the connecting path 64. When the first pilot solenoid valve 61 is open, the first connection port 67 and the third connection port 69 are connected via the connecting path 64. When the second pilot solenoid valve 62 is open, the second connection port 68 and the third connection port 69 are connected via the connecting path 64.

[0104] (2-3) Small diameter pipe assembly 80

[0105] The narrow-diameter tube assembly 80 is an assembly of capillary tubes, having 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 to the first connection port 67. The second flow path 82 connects the second pilot chamber 56 to the second connection port 68. The third flow path 83 connects the second port P2 to the third connection port 69.

[0106] (3) Operation of the four-way directional valve 12

[0107] (3-1) Operating status of heating and cooling

[0108] Figure 2 The configuration of the various parts of the four-way directional valve 12 for hot and cold operation is shown. The valve core 52 is located on the left side. Thus, the valve core 52 connects the second port to the fourth port and connects the first port to the third port.

[0109] To position the valve core 52 on the left, the first pilot solenoid valve 61 is opened, and the second pilot solenoid valve 62 is closed. Thus, the second port P2 is connected to the first pilot chamber 55 via the third flow path 83, the third connection port 69, the connecting path 64, the first connection port 67, and the first flow path 81. Because the pressure of the gaseous refrigerant present in the second port P2 is low, the refrigerant R in the first pilot chamber 55 can be drawn to the second port P2. Furthermore, because the diameter of the first piston orifice 53a is small, the refrigerant R on both sides of the first piston will not immediately achieve equal pressure.

[0110] Because the second pilot solenoid 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 high-pressure gaseous refrigerant flowing in from the second piston hole 54a.

[0111] Under the pressure difference between the low-pressure refrigerant in the first pilot chamber 55 and the high-pressure refrigerant in the second pilot chamber 56, a force acts on the valve core 52 to move to the left. Therefore, the valve core 52 can be stably positioned on the left side.

[0112] (3-2) Transition state

[0113] Figure 3 The diagram illustrates the transition state of the four-way directional valve 12 when switching from cold / hot operation to warm / hot operation. To switch the four-way directional valve 12, the first pilot solenoid valve 61 is closed, and the second pilot solenoid valve 62 is opened. At this time, the second port P2 is connected to the second pilot chamber 56 via the third flow path 83, the third connection port 69, the connecting path 64, the second connection port 68, and the second flow path 82. High-pressure gaseous refrigerant in the second pilot chamber 56 can be drawn to the second port P2.

[0114] Since the first pilot solenoid valve 61 is closed, the first pilot chamber 55 is isolated from the second port P2. At this time, the first pilot chamber 55 is gradually filled with high-pressure gaseous refrigerant flowing in from the first piston hole 53a.

[0115] When the pressure of the gaseous refrigerant in the first pilot chamber 55 becomes greater than the pressure of the gaseous refrigerant in the second pilot chamber 56, a force that causes the valve core 52 to move to the right is applied to the valve core 52.

[0116] (3-3) The operating status of heat utilization

[0117] Figure 4 This refers to the configuration of the various parts of the four-way directional valve during heat recovery operation. Figure 3 Similarly, in the transition state, the first pilot solenoid valve 61 is closed, and the second pilot solenoid valve 62 is opened. The valve core 52 on the right connects the second port to the third port and the first port to the fourth port.

[0118] Under the pressure difference between the high-pressure refrigerant in the first pilot chamber 55 and the low-pressure refrigerant in the second pilot chamber 56, a force acts on the valve core 52 to move it to the right. Therefore, the valve core 52 can be stably positioned on the right side.

[0119] To resume cooling and heating operation, control is applied to open the first pilot solenoid valve 61 and close the second pilot solenoid valve 62. This, by filling the first pilot chamber 55 with low-pressure refrigerant and the second pilot chamber 56 with high-pressure refrigerant, generates a force that moves the valve core 52 to the left.

[0120] (4) Control of the four-way directional valve 12

[0121] (4-1) Electrical system of refrigeration unit 100

[0122] Figure 5 The electrical system of the refrigeration unit 100 is shown. Measurement data from the low-pressure sensor S1, high-pressure sensor S2, heat source heat exchanger temperature sensor S3, outside air temperature sensor S4, heat exchanger temperature sensor S5, and room temperature sensor S6, as well as user commands sent from the remote control 27, are input to the control unit 9. Furthermore, the control unit 9 outputs control signals for the compressor 11, four-way reversing valve 12, heat source fan 14, heat source expansion valve 15, and heat exchanger fan 24.

[0123] The commands sent from the remote controller 27 include a switching command Q1 for the four-way reversing valve 12. For example, when the refrigeration unit 100 is operating in both heating and cooling mode, if the user inputs a command to the remote controller 27 indicating that heating and cooling mode should be operated, the remote controller 27 sends a switching command Q1 to the control unit 9 indicating that the four-way reversing valve 12 should be switched to operate in both heating and cooling mode. Alternatively, when the refrigeration unit 100 is operating in both heating and cooling mode, if the user inputs a command to the remote controller 27 indicating that heating and cooling mode should be operated, the remote controller 27 sends a switching command Q1 to the control unit 9 indicating that the four-way reversing valve 12 should be switched to operate in both heating and cooling mode.

[0124] When the control unit 9 receives the switching command Q1, it performs a predetermined calculation and outputs a switching control signal Q2 for the four-way directional valve 12. Specifically, the switching control signal Q2 refers to the opening and closing control signal for the first pilot solenoid valve 61 and the second pilot solenoid valve 62.

[0125] (4-2) Connecting flow path 91

[0126] Figure 6 The connecting piping between compressor 11 and four-way reversing valve 12 is shown. The discharge pipe 11b of compressor 11 is connected to the first port P1 of four-way reversing valve 12 by a connecting flow path 91. Connecting flow path 91 includes a filter 92 and a downwardly projecting U-shaped pipe 93. In the U-shaped pipe 93, refrigeration oil supplied by refrigerant R is easily stored due to gravity.

[0127] The following situation may occur: a portion of the refrigeration oil stored in the U-shaped pipe 93 may enter the four-way reversing valve 12 from the first port P1 through the high-pressure refrigerant discharged from the discharge pipe 11b. The refrigeration oil in the four-way reversing valve 12 may block the first flow path 81, the second flow path 82, the third flow path 83, the first piston hole 53a, and the second piston hole 54a, thereby potentially hindering the operation of the valve core 52, the first piston 53, and the second piston 54. Thus, the refrigeration oil may impede the operation of the four-way reversing valve 12 in switching the circulation direction of the refrigerant R.

[0128] (4-3) Switching control

[0129] Figure 7 This is a flowchart of the main routine for the switching control of the four-way directional valve 12. In step S100, the switching control begins. In step S101, the control unit 9 checks whether it has received the switching command Q1 issued from the remote controller 27 based on user input. If it has not been received (S101: No), the process returns to step S101. If it has been received (S101: Yes), the process proceeds to step S102.

[0130] In step S102, the control unit 9 confirms whether the switching permission conditions are met. The switching permission conditions are related to the Froude number, which represents the refrigerant circulation quantity. The Froude number is represented by the following formula: Fr.

[0131] [Mathematical Expression 1]

[0132] Here, ρ G (kg / m 3 ρ is the density of the gaseous refrigerant. L (kg / m 3 U is the density of the liquid refrigerant. G(m / s) is the flow velocity of the gaseous refrigerant in the flow path 91, g(m / s) 2 ) is the acceleration due to gravity, and D(m) is the inner diameter of the pipe that forms the connecting flow path 91.

[0133] Where, ρ G (kg / m 3 ), ρ L (kg / m 3 ) and g(m / s 2 Since is a constant, it can be pre-input into control unit 9. Furthermore, D(m) is a design value, and therefore, it can also be pre-input into control unit 9. G (m / s) can be calculated based on the speed parameter of the compressor 11 output by the control unit 9.

[0134] For example, the switching conditions can be set as follows.

[0135] [Mathematical Expression 2]

[0136] This means that the refrigerant circulation rate in the connecting flow path 91 is above the specified value.

[0137] If the handover permission condition is met (S102: Yes), the process proceeds to step S104. On the other hand, if the handover permission condition is not met (S102: No), the process proceeds to step S103.

[0138] In step S103, a subroutine for oil drainage is executed. Oil drainage refers to the operation of using high-pressure refrigerant gas discharged from compressor 11 to purge the refrigeration oil present in the connecting flow path 91, causing the refrigeration oil to move downstream of the four-way reversing valve 12. The subroutine for oil drainage will be described later. After the oil drainage operation is completed, the process proceeds to step S104.

[0139] In step S104, the control unit 9 executes a subroutine for outputting a switching control signal Q2 to the four-way directional valve 12. The subroutine for outputting the switching control signal Q2 will be described later.

[0140] Subsequently, in step S105, the switching control of the four-way directional valve 12 ends.

[0141] Figure 8This is a flowchart of the subroutine for oil discharge operation. In step S200, oil discharge operation begins. In step S201, the control unit 9 checks whether the compressor 11 is running. If the compressor 11 is running (S201: Yes), the process proceeds to step S203. On the other hand, if the compressor 11 is not running (S201: No), the process proceeds to step S202. In step S202, the compressor 11 begins operation. As a result, high-pressure gaseous refrigerant is supplied from the discharge pipe 11b.

[0142] In step S203, the count value of the timer in control unit 9 is reset to zero. In step S204, control unit 9 starts the timer. In step S205, control unit 9 checks the timer's count value to confirm whether a predetermined time has elapsed. The predetermined time is, for example, 5 seconds. If the predetermined time has not elapsed (S205: No), the process returns to step S205. On the other hand, if the predetermined time has elapsed (S205: Yes), the process proceeds to step S206. In step S206, control unit 9 stops the timer. In step S207, the oil draining subroutine ends.

[0143] Figure 9 This is a flowchart of a subroutine for processing the output of the switching control signal Q2. In step S300, the output of the switching control signal Q2 begins. In step S301, the control unit 9 confirms the content of the received switching command Q1. If the content of the switching command Q1 requests the execution of hot / cold utilization operation (step S301: Hot / Cold Utilization Operation), the process proceeds to step S302. In step S302, the control unit 9 outputs the switching control signal Q2, indicating that the first pilot solenoid valve 61 is opened and the second pilot solenoid valve 62 is closed. Then, in step S304, the output processing of the switching control signal Q2 ends.

[0144] On the other hand, if the switching instruction Q1 requests the execution of heat utilization operation (step S301: heat utilization operation), the process proceeds to step S303. In step S303, the control unit 9 outputs a switching control signal Q2 indicating that the first pilot solenoid valve 61 is closed and the second pilot solenoid valve 62 is opened. Then, in step S304, the output processing of the switching control signal Q2 ends.

[0145] (5) Characteristics

[0146] (5-1)

[0147] If the state of the refrigerant R in the connecting flow path 91 does not meet the switching allowable conditions, the four-way directional valve 12 will not be switched. Even if the control unit 9 receives the switching command Q1, it will not switch the four-way directional valve 12 if the switching allowable conditions are not met. Therefore, it is possible to suppress the possibility of switching failure or damage to the four-way directional valve 12.

[0148] (5-2)

[0149] The switching conditions are related to the refrigerant circulation rate. Therefore, the switching of the four-way reversing valve 12 can be determined based on the rate at which the refrigerant R can be blown away from the refrigeration oil.

[0150] (5-3)

[0151] The switching condition is that the Froude value related to the circulation volume of refrigerant R is a specified value, i.e., 1 or higher. Therefore, when the circulation volume of refrigerant R is small and it is foreseeable that there is refrigeration oil retention in the connecting flow path 91, it is possible to prevent the switching operation from failing due to the presence of refrigeration oil that may become a resistance to the switching operation, or the four-way reversing valve 12 from being damaged.

[0152] (5-4)

[0153] In cases where refrigerant oil is foreseeably retained in the connection flow path 91, the compressor 11 is driven to perform oil discharge operation before the four-way reversing valve 12 switches. Therefore, the refrigerant oil residue inside the four-way reversing valve 12 that would otherwise hinder the switching operation can be suppressed.

[0154] (5-5)

[0155] Because of the downward-protruding U-shaped tube 93, the connecting flow path 91 has a structure that easily allows refrigeration oil to accumulate. Therefore, by performing an oil draining operation, refrigeration oil can be effectively removed from the connecting flow path 91 and the four-way reversing valve 12.

[0156] (5-6)

[0157] The refrigerant R can be carbon dioxide. When carbon dioxide is used as the refrigerant R, the switching noise of the four-way reversing valve 12 tends to increase. To reduce the switching noise, the circulation rate of carbon dioxide refrigerant is sometimes reduced, which results in the accumulation of refrigeration oil in the connecting flow path 91. Therefore, by performing an oil draining operation, refrigeration oil can be effectively removed from the connecting flow path 91 and the four-way reversing valve 12.

[0158] (5-7)

[0159] The four-way directional valve 12 has a first flow path 81, a second flow path 82, and a third flow path 83 that connect the first pilot solenoid valve 61 or the second pilot solenoid valve 62 to the valve chamber 51a. Therefore, by operating the oil draining valve, it is possible to suppress the presence of refrigerant oil in the relatively narrow flow paths such as the first flow path 81, the second flow path 82, and the third flow path 83.

[0160] (6) Variations

[0161] (6-1) First variation

[0162] In the above embodiment, the oil draining operation is performed when the switching command Q1 is issued. Alternatively, or based on this, the oil draining operation can also be performed immediately after the refrigeration unit 100 is started or before it stops. In this case, it is possible to further suppress the accumulation of refrigeration oil inside the four-way reversing valve 12.

[0163] (6-2) Second variation

[0164] In the above embodiment, the first pilot solenoid valve 61 and the second pilot solenoid valve 62 open when current flows through the first coil 73 or the second coil 77, respectively. Alternatively, the first pilot solenoid valve 61 and the second pilot solenoid valve 62 may also close when current flows through the first coil 73 or the second coil 77, respectively.

[0165] (6-3) Third variation

[0166] In the above embodiment, the switching command Q1 is issued by the remote controller 27. Alternatively, the switching command Q1 can be issued by other parts. For example, the switching command Q1 can be triggered by the output of the heat source heat exchanger temperature sensor S3. When the refrigeration unit 100 is in heat utilization operation, if the control unit 9 detects that condensation is forming on the heat source heat exchanger 13 based on the measured value of the heat source heat exchanger temperature sensor S3, the control unit 9 can initiate defrosting operation by issuing a switching control signal Q2 to the four-way reversing valve 12 to perform heat utilization operation.

[0167] (6-4) Fourth variation

[0168] In the above embodiments, Figure 8 During the oil discharge operation shown, the operation of compressor 11 is not significantly different from normal operation. In other words, the oil discharge operation involves not controlling the first pilot solenoid valve 61 and the second pilot solenoid valve 62 for a specified period of time. Alternatively, the operation of compressor 11 can be changed to something different from normal operation during the oil discharge operation. For example, the speed of compressor 11 can be reduced to a specified lower value or increased to a specified higher value during the oil discharge operation.

[0169] <Conclusion>

[0170] The embodiments of this disclosure have been described above, but it should be understood that various changes in form and detail can be made without departing from the spirit and scope of this disclosure as set forth in the claims.

[0171] Symbol Explanation

[0172] 9. Control Department; 10 Heat source units; 11. Compressor; 11a Inhalation tube; 11b Discharge pipe; 12. Four-way directional valve; 13. Heat source heat exchanger; 15. Heat source expansion valve; 19. Heat Source Control Department; 20. Utilization Unit; 23. Utilize heat exchangers; 29. Utilize the control unit; 30 Connecting piping; 50 Main valve section; 51. Shell; 51a Valve chamber; 52 Valve core; 52a Valve body; 52b First connecting part; 52c Second connecting part; 53 First piston; 53a First piston bore; 54. Second piston; 54a Second piston bore; 55 First Pilot Room; 56. Second pilot room; 60. Pilot valve section; 61 First pilot solenoid valve; 62 Second pilot solenoid valve; 63: Connecting part 64 Connecting path; 65 First pilot valve seat; 66 Second pilot valve seat; 67 First connection port; 68 Second connection port; 69. Third connection port; 71 First pilot valve core; 71a First pilot valve; 75 Second pilot valve core; 75a Second pilot valve; 80mm narrow-diameter pipe assembly; 81 First flow path; 82 Second flow path; 83 Third flow path; 90. Refrigerant circuit; 91 Connect the flow path; 93 U-shaped tube; 100 Refrigeration unit; P1 is the first port; P2 Second Port; P3 Third Port; P4 fourth port; Q1 Switching command; Q2 switches the control signal; R is the refrigerant.

[0173] Existing technical documents

[0174] Patent documents

[0175] Patent Document 1: Japanese Patent Application Publication No. 63-015056

Claims

1. A refrigeration apparatus (100), characterized in that, include: A refrigerant circuit (90) having a compressor (11), a four-way reversing valve (12), and a connecting flow path (91) connecting the compressor and the four-way reversing valve, and circulating refrigerant (R); and Control unit (9), which switches the four-way reversing valve to change the circulation path of the refrigerant in the refrigerant circuit. The control unit performs the switching of the four-way reversing valve when the switching allowable conditions related to the refrigerant in the connection flow path are met; otherwise, the switching of the four-way reversing valve is not performed.

2. The refrigeration apparatus according to claim 1, characterized in that, When the control unit receives a switching command (Q1) to switch the four-way directional valve, it will not switch the four-way directional valve if the switching permission conditions are not met.

3. The refrigeration apparatus according to claim 1 or 2, characterized in that, The switching allowance is related to the Froude number, an index representing the amount of refrigerant circulating. The Fr number is represented by the following formula: [Mathematical Expression 1] Here, ρ G (kg / m 3 ρ is the density of the gaseous refrigerant. L (kg / m 3 U is the density of the liquid refrigerant. G (m / s) is the flow rate of the gaseous refrigerant, g(m / s) 2 ) is the acceleration due to gravity, and D(m) is the inner diameter of the pipe that forms the connecting flow path.

4. The refrigeration apparatus according to claim 3, characterized in that, The switching condition is that the Froude number is 1 or more.

5. The refrigeration apparatus according to any one of claims 1 to 4, characterized in that, If the switching permission condition is not met, the control unit drives the compressor to perform an oil discharge operation that moves the refrigeration oil present in the connecting flow path downstream of the four-way reversing valve.

6. The refrigeration apparatus according to claim 5, characterized in that, Except in cases where the switching permission conditions are not met, the control unit also performs the oil draining operation in at least one of the following situations: immediately after the refrigeration unit is started or before it is stopped.

7. The refrigeration apparatus according to any one of claims 1 to 6, characterized in that, The connecting flow path has a U-shaped tube (93) that protrudes downward.

8. The refrigeration apparatus according to any one of claims 1 to 7, characterized in that, The refrigerant is carbon dioxide.

9. The refrigeration apparatus according to any one of claims 1 to 8, characterized in that, The four-way directional valve has: Valve chamber (51a); The valve core (52) slides in the valve chamber; A first pilot chamber (55) is formed at the end of the valve chamber; A second pilot chamber (56) is formed at the end of the valve chamber opposite to the first pilot chamber. The valve chamber has a first port (P1), a second port (P2), a third port (P3), and a fourth port (P4). The first port receives the refrigerant discharged from the compressor, the second port sprays out the refrigerant drawn into the compressor, the third port exchanges the refrigerant with a heat source heat exchanger, and the fourth port exchanges the refrigerant with a heat exchanger. A first pilot solenoid valve (61) and a second pilot solenoid valve (62) are configured separately from the valve chamber. The first flow path (81) connects the first pilot chamber to the first pilot solenoid valve. The second flow path (82) connects the second pilot chamber to the second pilot solenoid valve; and A third flow path (83) that connects the first pilot solenoid valve and the second pilot solenoid valve (64) to the second port.

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