Refrigerator

Abstract

The invention provides a refrigerator capable of suppressing generation of surge. The refrigerator is a refrigerator that executes a refrigeration cycle. A condenser that condenses the compressed refrigerant; an expansion valve that expands the condensed refrigerant; an evaporator that evaporates the expanded refrigerant; a suction pipe that connects the evaporator and the compressor; and a second pipe that supplies the refrigerant after cooling the component to a suction pipe at a first position, and a third pipe that supplies the refrigerant after cooling the component to a second position included in the refrigerator, the second position being a position different from the first position.

Description

Technical Field

[0001] This invention relates to refrigeration machines. Background Technology

[0002] The refrigeration unit includes a compressor, a condenser, an expansion valve, and an evaporator. For example, a turbo compressor is sometimes used as the compressor. The turbo compressor has a rotating shaft, one end of which is equipped with an impeller, and the other end of the rotating shaft is located in the motor compartment (see, for example, Patent Document 1). In the turbo compressor described in Patent Document 1, low-temperature, low-pressure gas before pressurization is introduced into the motor compartment.

[0003] [Existing Technical Documents]

[0004] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 11-13697 Summary of the Invention

[0006] [The problem the invention aims to solve]

[0007] Compressors have various limitations that restrict their operational range. When these limitations are not met, the operation of the refrigeration unit becomes unstable. The object of this invention is to provide a refrigeration unit that expands the operational range of its compressor.

[0008] [Methods for solving the problem]

[0009] One aspect of the present invention relates to a refrigeration machine that performs a refrigeration cycle, comprising: a compressor for compressing refrigerant; a condenser for condensing the compressed refrigerant; an expansion valve for expanding the condensed refrigerant; an evaporator for evaporating the expanded refrigerant; a suction pipe connecting the evaporator and the compressor; a motor for driving the compressor; a first pipe for supplying refrigerant discharged from the condenser to a target component; a second pipe for supplying refrigerant after cooling the target component to the suction pipe at a first position; and a third pipe for supplying refrigerant after cooling the target component to a second position that is different from the first position and is included in the refrigeration machine.

[0010] In this type of refrigeration unit, the refrigerant after cooling the target component can be supplied to either the suction pipe at position 1 or position 2. The refrigeration unit can supply the refrigerant after cooling the target component to either position 1 or position 2. By selecting the target location for supplying the refrigerant after cooling the target component, the operating range of the compressor can be expanded.

[0011] In one aspect of the refrigeration machine of the present invention, the compressor may be a turbo compressor. In this refrigeration machine, by selecting the target location for refrigerant supply after cooling the component, and changing the operating state, surge can be suppressed.

[0012] In one aspect of the present invention, the object component in a refrigeration machine is a motor, or a bearing supporting the rotating shaft of a compressor, or a controller for the motor.

[0013] In this type of refrigeration unit, cooling the motor can suppress heat generation. Cooling the bearings can also suppress bearing burn-out. Finally, cooling the controller can prevent controller malfunctions.

[0014] In one aspect of the refrigeration machine according to the present invention, the second position can be an evaporator. In this aspect of the refrigeration machine, by returning the refrigerant after cooling the target component to the evaporator, the superheat of the refrigerant gas supplied to the compressor can be relatively low.

[0015] In one aspect of the present invention, the object component of the refrigerator is a motor, and a first piping can be connected to a flow path communicating with the inside of the motor housing. In this type of refrigerator, the motor can be directly cooled by supplying refrigerant into the motor housing. According to this type of refrigerator, cooling the motor can alleviate limitations related to motor temperature. Limitations related to motor temperature include the temperature conditions of the motor windings or magnets. Cooling the windings or magnets can expand the operating range of the compressor.

[0016] In one aspect of the refrigeration machine according to the present invention, the object component is a bearing supporting the rotating shaft of the compressor, and the bearing can be an oil-free bearing. In this type of refrigeration machine, a refrigerant can be used as the gas supplied to the oil-free bearing. According to this type of refrigeration machine, by cooling the oil-free bearing, the limitations related to bearing temperature can be alleviated. Therefore, the operating range of the compressor can be expanded. In this type of refrigeration machine, by using an oil-free bearing, bearings that use highly viscous fluids such as oil as working fluids can be eliminated. When using an oil-free bearing, bearing losses can be reduced even at high speeds. Therefore, the limitations related to the bearing rotation speed can be alleviated, and the operating range of the compressor can be expanded.

[0017] In one aspect of the present invention, the evaporator of the refrigerator can be an air heat exchanger that transfers heat between the refrigerant and air. In this type of refrigerator, air is cooled by heat exchange between the refrigerant and air. Air heat exchangers are more susceptible to temperature variations than water heat exchangers due to the influence of external air temperature. Therefore, the operating state of the compressor downstream of the air heat exchanger is more prone to change, and the required operating area is larger in refrigerators with air heat exchangers compared to those with water heat exchangers. The refrigerator of this aspect expands the operable area, thus being effective even in refrigerators with air heat exchangers where the operating state is easily varied.

[0018] One aspect of the present invention relates to a refrigeration unit that includes a first control valve provided on a second piping, a second control valve provided on a third piping, and a control unit for controlling the first and second control valves. In this refrigeration unit, the control unit can switch the refrigerant supply target after the cooling component is being cooled by controlling the opening and closing of the first and second control valves.

[0019] In one aspect of the present invention, in a refrigeration unit, a first operating mode can be executed by setting a first control valve to an open state and a second control valve to a closed state, and a second operating mode can be executed by setting the first control valve to a closed state and the second control valve to an open state.

[0020] In this type of refrigeration unit, by selecting the first operating mode, the refrigerant after cooling the target component can be returned to the compressor's suction pipe. This allows for a relatively high superheat of the refrigerant gas supplied to the compressor. Furthermore, by selecting the second operating mode, the refrigerant after cooling the target component can be supplied to a second location. According to this type of refrigeration unit, by selecting either the first or second operating mode, the superheat of the refrigerant gas supplied to the compressor can be changed, thereby expanding the compressor's operating range.

[0021] In the first operating mode, where the refrigerant, after cooling the components, returns to the compressor's suction line, the required compression power increases due to the increased superheat of the refrigerant. This results in a limitation on motor output at the operating point where high power is required. To avoid this limitation, the compressor can continue operating by switching from the first operating mode to the second operating mode. As a result, the operable operating range can be expanded.

[0022] In the second operating mode, where the refrigerant returns to the evaporator after cooling the target components, the cooling capacity decreases. In this second operating mode, to ensure cooling capacity, it is necessary to increase the required suction volume flow rate. Therefore, at operating points where high cooling capacity is required, a limitation on the compressor's rotational speed arises. To avoid this limitation, switching from the second operating mode to the first operating mode ensures cooling capacity while maintaining the compressor's rotational speed. This method allows switching from the first operating mode to the second operating mode, or vice versa, depending on the operating state, thus expanding the operable range.

[0023] In one aspect of the present invention, a refrigeration unit includes a control unit that controls the flow rate of refrigerant flowing in a third piping based on a surge line that delineates the boundary of a region in the compressor where surge occurs. In this refrigeration unit, by controlling the flow rate of the refrigerant flowing in the third piping based on the surge line, surge in the compressor can be suppressed.

[0024] In one aspect of the present invention, a refrigeration unit controls the flow rate of the refrigerant flowing in the third piping based on an operating allowable limit line. This operating allowable limit line, relative to the surge line, represents the operating region on the side with a larger refrigerant flow rate, and is obtained after considering a margin for the surge line. In this refrigeration unit, by controlling the flow rate of the refrigerant flowing in the third piping based on the operating allowable limit line with a margin for the surge line, surge generation in the compressor can be effectively suppressed.

[0025] In one aspect of the present invention, in a refrigeration unit, the second position is an evaporator. The control unit predicts the compressor's operating point at a second point in time, after a specified period from the current first point in time. When the predicted operating point exists in a region close to the surge line above the operating allowable limit line, or in a region where surge occurs, the flow rate of the refrigerant flowing in the third piping is increased. In this type of refrigeration unit, the compressor's operating point at a second point in time after the current moment can be predicted, thus predicting the occurrence of surge. In this type of refrigeration unit, when the concern about surge is high, the occurrence of surge can be suppressed by increasing the flow rate of the refrigerant flowing in the third piping. Attached Figure Description

[0026] 【 Figure 1 [Image] represents a schematic diagram of a refrigeration machine according to one embodiment.

[0027] 【 Figure 2 [ ] represents a block diagram of the control section of a refrigeration unit.

[0028] 【 Figure 3 The diagram above represents the functional block diagram of the control unit of the refrigeration machine.

[0029] 【 Figure 4 The Morrill line diagram of the refrigeration cycle in a refrigeration machine.

[0030] 【 Figure 5 The graph represents the performance curve of the compressor.

[0031] 【 Figure 6 [A graph showing the relationship between volumetric flow rate and adiabatic efficiency in a compressor.]

[0032] 【 Figure 7 The diagram shows the control sequence in a refrigeration unit. Detailed Implementation

[0033] The embodiments are described with reference to the accompanying drawings, which are not intended to limit the invention. Furthermore, identical or corresponding parts or components in the drawings are given identical or corresponding reference numerals. Repeated descriptions of identical or corresponding parts or components are omitted below. Additionally, the parts or components in the drawings are not necessarily drawn to scale. Therefore, those skilled in the art can arbitrarily determine the specific dimensions by referring to the following non-limiting embodiments. Furthermore, the following embodiments are merely examples and are not intended to limit the invention. Moreover, the features and combinations thereof described in the embodiments are not necessarily the essential content of the invention.

[0034] [Overview of Refrigeration Machines]

[0035] Figure 1 The refrigeration unit 100 shown can be used, for example, in air conditioning units, refrigeration machines, and cold storage machines. The refrigeration unit 100 can also be used in other machines. The refrigeration unit 100 performs a refrigeration cycle. The refrigeration cycle of the refrigeration unit 100 is a vapor compression refrigeration cycle. The refrigeration unit 100 includes a compressor 10, a condenser 20, an expansion valve 30, and an evaporator 40.

[0036] There are no particular restrictions on the refrigerant used as the working fluid in the refrigeration unit 100. The compressor 10 compresses the refrigerant gas. The condenser 20 condenses the refrigerant gas compressed by the compressor 10. The expansion valve 30 expands the refrigerant condensed by the condenser 20. The evaporator 40 evaporates the refrigerant expanded by the expansion valve 30. The refrigerant gas evaporated by the evaporator 40 is drawn into the compressor 10.

[0037] Compressor 10 performs reversible adiabatic compression on the refrigerant gas. The refrigerant gas supplied to condenser 20 releases heat and liquefies under constant pressure. The liquefied refrigerant undergoes isenthalpic irreversible expansion through expansion valve 30, and a portion of the refrigerant evaporates. The refrigerant absorbs heat at constant pressure in evaporator 40.

[0038] The refrigeration unit 100 has refrigerant flow piping L11 to L14. Pipe L11 is the suction pipe connecting the evaporator 40 and the compressor 10. Pipe L12 connects the compressor 10 and the condenser 20. Pipe L13 connects the condenser 20 and the expansion valve 30. Pipe L14 connects the expansion valve 30 and the evaporator 40.

[0039] Refrigerant gas flows in pipe L11 and is drawn into compressor 10. The refrigerant gas compressed by compressor 10 flows in pipe L12 and is supplied to condenser 20. The refrigerant liquid liquefied in condenser 20 flows in pipe L13 and flows into expansion valve 30. The refrigerant expanded by expansion valve 30 flows in pipe L14 and is supplied to evaporator 40. The refrigerant gas that absorbs heat in evaporator 40 flows in pipe L11 and is supplied to compressor 10.

[0040] The compressor 10 is, for example, a turbo compressor. The compressor 10 includes a housing 11, an impeller 12, a drive shaft 13, a bearing 14, and a motor 50. The housing 11 houses the impeller 12, the drive shaft 13, the bearing 14, and the motor 50.

[0041] The housing 11 has a compression chamber 11a that houses the impeller 12 and a motor chamber 11b that houses the motor 50.

[0042] The impeller 12 is located at one end of the drive shaft 13. The other end of the drive shaft 13 is located inside the motor chamber 12b. The drive shaft 13 includes the rotating shaft of the motor 50.

[0043] Bearing 14 rotatably supports drive shaft 13. Bearing 14 is fixed to housing 11. Bearing 14 can be, for example, a radial bearing. Compressor 10 has multiple bearings 14. Bearing 14 can be, for example, an oilless bearing. Bearing 14 can be a sliding bearing or a rolling bearing.

[0044] The motor 50 is the drive source for the compressor 10. The motor 50 has a rotor and a stator. The rotor is fixed to the drive shaft 13 and rotates together with the drive shaft 13. The stator is fixed to the housing 11 and is disposed around the rotor.

[0045] The refrigeration unit 100 is equipped with an inverter 60. The inverter 60 controls the rotation speed of the motor 50. The inverter 60 is a controller that controls the operating frequency of the motor 50.

[0046] The impeller 12 of the compressor 10 rotates under the rotational driving force of the motor 50. The rotation of the impeller 12 compresses the refrigerant gas.

[0047] The compressor 10 is not limited to a turbo compressor (centrifugal compressor), but can also be a positive displacement compressor. Positive displacement compressors can be, for example, rotary, scroll, reciprocating, or screw compressors.

[0048] The condenser 20 is a heat exchanger that cools the high-temperature, high-pressure refrigerant vapor compressed by the compressor 10. The condenser 20 exchanges heat with the refrigerant, for example, through water or air, causing the refrigerant to condense. The heat exchanger in the condenser 20 can be, for example, water-cooled, air-cooled, evaporative, or other types. The heat exchanger can be shell-and-tube, double-tube, plate-fin, or other types.

[0049] Expansion valve 30 causes the high-pressure refrigerant liquid exiting condenser 20 to expand by throttling. The refrigerant passing through expansion valve 30 is in a low-pressure, low-temperature state. The refrigerant passing through expansion valve 30 is in a partially evaporated state, which is a state of wet vapor where saturated vapor and saturated liquid coexist.

[0050] Evaporator 40 is a heat exchanger that exchanges heat between the expanded refrigerant exiting from expansion valve 30 and the fluid being cooled. The fluid being cooled is the fluid that is being cooled. The fluid being cooled can be, for example, air or water. The fluid being cooled can also be other fluids. In evaporator 40, the refrigerant, in a wet vapor state, evaporates by taking heat from the fluid being cooled. Evaporator 40 can be, for example, an air heat exchanger. An air heat exchanger transfers heat between the refrigerant and air.

[0051] Evaporator 40 can be, for example, dry type, flooded type, or liquid forced circulation type. Evaporator 40 can be, for example, plate-fin coil type or shell-and-tube type.

[0052] [Cooling mechanism]

[0053] Next, the cooling mechanism 200 will be described. The refrigerator 100 includes a cooling mechanism 200, which uses refrigerant discharged from the condenser 20 to cool the target component. The target component is, for example, a motor 50. The target component can be a bearing 14, or an inverter 60 that acts as a controller for the motor 50. The target component can also be other components. The cooling mechanism 200 can cool multiple target components. The cooling mechanism 200 can cool the motor 50, the bearing 14, and the inverter 60. For example, the cooling mechanism 200 can cool the motor 50 housed in the housing 11 via a cooling housing 11. The target component cooled by the cooling mechanism 200 can be the housing 11 of the compressor 10.

[0054] The component can be located separately from the compressor 10. The inverter 60 can be mounted on the compressor 10 or located separately from the compressor 10.

[0055] The cooling system 200 includes piping L21 to L24, an expansion valve V21, and control valves V23 and V24. Piping L21 connects the condenser 20 and the motor compartment 11b. Piping L21 connects to piping L13, which is connected to the outlet of the condenser 20, and to the motor compartment 11b. Piping L21 supplies refrigerant from the condenser 20 to the target component.

[0056] An expansion valve V21 is provided on pipe L21. Expansion valve V21 adjusts the flow rate and pressure of the refrigerant flowing in pipe L21. The refrigerant passing through expansion valve V21 is in a depressurized, low-temperature state. This low-temperature refrigerant flows in pipe L21 and is supplied to the target component. Pipe L21 is, for example, connected to the interior of the motor chamber 11b of housing 11. The refrigerant flowing in pipe L21 is supplied to the motor chamber 11b to cool the motor 50.

[0057] Pipe L22 is connected to the motor compartment 11b. The refrigerant cooling the motor 50 flows in pipe L22 and is discharged outside the motor compartment 11b. The outlet side of pipe L22 branches off and connects to pipes L23 and L24.

[0058] Pipe L23 connects pipe L22 and pipe L11. Pipe L24 connects pipe L22 and evaporator 40. Pipe L11 is the suction pipe at position 1. Evaporator 40 is an example of a second position different from position 1. Position 2 is a position included in refrigeration unit 100. Position 2 is not limited to evaporator 40, but can be other positions. For example, when compressor 10 is a multi-stage compressor, position 2 can be the inlet of the later stage compression mechanism (impeller). Furthermore, when compressor 10 is a multi-stage compressor, position 1 can be the suction pipe leading to the later stage compression mechanism. In refrigeration unit 100, position 1 can be multiple positions.

[0059] Pipe L21 is an example of a first pipe that supplies refrigerant discharged from condenser 20 to the target component. Pipe L23 is an example of a second pipe that supplies refrigerant after cooling the target component to the suction pipe (pipe L11) which is the first position. Pipe L24 is an example of a third pipe that supplies refrigerant after cooling the target component to a second position, which is different from the first position.

[0060] Control valve V23 is installed on pipe L23, and control valve V24 is installed on pipe L24. Control valve V23 is an example of the first control valve. Control valve V24 is an example of the second control valve. In the cooling mechanism 200, the target location for refrigerant supply after cooling motor 50 can be selected by controlling the opening and closing of control valves V23 and V24.

[0061] In the refrigeration unit 100, by opening control valve V23 and closing control valve V24, the first operating mode can be executed. In the first operating mode, the refrigerant after the cooling motor 50 can be returned to the suction pipe L11.

[0062] In the refrigeration unit 100, by closing control valve V23 and opening control valve V24, the second operating mode can be executed. In the second operating mode, the refrigerant after cooling motor 50 can return to evaporator 40. The connection target of piping L24 can be evaporator 40 or piping L14 connected to evaporator 40. The cooled refrigerant can be directly supplied to evaporator 40 or indirectly supplied to evaporator 40 through piping L14.

[0063] In the refrigeration unit 100, by controlling the opening and closing of control valves V23 and V24, the cooled refrigerant can be returned only to pipe L11, only to evaporator 40, or both pipe L11 and evaporator 40. Alternatively, the refrigeration unit 100 may not use control valves V23 and V24, but instead have control valves as three-way valves. Furthermore, in the refrigeration unit 100, control valve V23 may be installed on pipe L23, but not on pipe L24. Similarly, in the refrigeration unit 100, control valve V24 may be installed on pipe L24, but not on pipe L23.

[0064] [Swallowing]

[0065] Next, we will explain surge. Figure 5 It is a graph representing the performance curve of the compressor. Figure 5 In the diagram, the horizontal axis represents flow rate, and the vertical axis represents adiabatic head. Figure 6 In the diagram, the horizontal axis represents volumetric flow rate, and the vertical axis represents adiabatic efficiency. Figure 5 The diagram shows performance curves G1 to G3. Performance curves G1 to G3 represent the adiabatic pressure head at different rotational speeds.

[0066] In compressors used for various applications, such as axial compressors and centrifugal compressors, there is a concern about surge during operation. For example, in a centrifugal compressor, if the pressure is increased while the flow rate is reduced, rotating stall or surge may occur. Rotating stall typically occurs at low flow rates, eventually leading to surge.

[0067] For example, when a centrifugal compressor is running, if the flow rate decreases further after a certain threshold, a counter-current region is generated circumferentially inside the centrifugal compressor (turbomachinery). The generation of this counter-current region is called rotational stall. The phenomenon of counter-current region generation is a localized phenomenon within the circumferentially changing compressor.

[0068] When surge occurs inside the compressor, significant fluctuations in flow rate and pressure occur in the piping system connected to the compressor due to backflow and pulsation. This places a heavy load on all types of machinery, including the piping system, making it difficult for the compressor to continue operating.

[0069] For example, it is preferable to perform and confirm operational checks to predict surge, ensuring that the compressor's operating point does not enter the surge region, thus achieving a safety margin. In regions with higher flow rates than the operating point considering the safety margin, the compressor is operated to suppress surge.

[0070] For example, in variable drive operation using an inverter or similar device that allows the compressor's rotation speed to vary, the flow rate at which surge occurs at each rotation speed is determined. By connecting the operating points at which surge occurs at each rotation speed, the surge line (operating limit line) SL1, defined by the volumetric flow rate and adiabatic head, is determined.

[0071] Figure 5 The diagram illustrates the surge line SL1, the operating limit line SL2, and the rotational stall line SL3. The operating limit line SL2 is located in the operating region on the side with higher refrigerant flow relative to the surge line. The operating limit line SL2 is a line that takes into account the margin SR relative to the surge line SL1.

[0072] Figure 5 In the diagram, the area to the left of surge line SL1 is the surge-generating region. The area to the right of operating limit line SL2 is the operable region.

[0073] [Problems with existing technology]

[0074] Explain the problems with existing technology. For example, in the existing technology of air conditioners, when the flow rate becomes low (reduction in cooling capacity) and the high pressure head (high pressure difference), the operating point of the centrifugal compressor enters the region beyond the surge line SL1, and the centrifugal compressor cannot operate.

[0075] [Control Department]

[0076] Next, refer to Figure 2 This describes the control unit 210 of the refrigeration unit 100. Figure 2 This is a block diagram representing the control unit 210 of the refrigeration unit 100. Figure 2 This indicates the hardware structure of the control unit 210. For example... Figure 2 As shown, the control unit 210 is electrically connected to various sensors 220, inverter 60, expansion valve 30, expansion valve V21 and control valves V23 and V24.

[0077] Various sensors 220 can be, for example, temperature sensors (outdoor air temperature sensors) that measure the external temperature (outdoor air temperature) of the refrigeration unit 100, temperature sensors that measure the refrigerant temperature, pressure sensors that measure the refrigerant pressure, flow sensors that measure the refrigerant flow rate, etc. Various sensors 220 can also be sensors that acquire other information.

[0078] Various sensors 220 include, for example, an intake pressure sensor 221, an intake temperature sensor 222, an exhaust pressure sensor 223, an exhaust temperature sensor 224, and a water temperature sensor 225. The intake pressure sensor 221 detects the pressure of the refrigerant gas drawn into the compressor 10. The intake temperature sensor 222 detects the temperature of the refrigerant gas drawn into the compressor 10. The exhaust pressure sensor 223 detects the pressure of the refrigerant gas discharged from the compressor 10. The exhaust temperature sensor 224 detects the temperature of the refrigerant gas discharged from the compressor 10.

[0079] For example, when the evaporator is a water-heat exchanger, water temperature sensor 225 detects the temperature of the water flowing into the evaporator 40. Water temperature sensor 226 detects the temperature of the water flowing out of the evaporator 40. Control unit 210 inputs data detected by various sensors 220. Control unit 210 can use the data acquired by various sensors 220 to calculate various data. Control unit 210 can calculate the volumetric flow rate of refrigerant gas drawn into compressor 10 using the data acquired by water temperature sensors 225 and 226. Control unit 210 can calculate the volumetric flow rate of refrigerant gas based on the heat transfer in evaporator 40. Control unit 210 can calculate the volumetric flow rate of refrigerant gas based on the entropy in evaporator 40. In cases other than water-heat exchangers, the volumetric flow rate of refrigerant gas can be calculated using a flow meter that measures the refrigerant flow rate.

[0080] The control unit 210 includes a CPU 211 and a storage unit 212. The CPU (Central Processing Unit) 211 manages the overall processing of the refrigerator 100. The CPU 211 controls the rotation speed of the motor 50 via the inverter 60. The CPU 211 controls the opening and closing of the expansion valve 30. The CPU 211 controls the opening and closing of the expansion valve V21. The CPU 211 controls the opening and closing of the control valves V23 and V24.

[0081] The storage unit 212 includes a ROM (Read-Only Memory) 213 and a RAM (Random Access Memory) 214. The ROM 213 stores various programs used to enable the CPU 211 to perform control processing, as well as various data required for the operation of the refrigerator 100. The RAM 214 temporarily stores data acquired from the sensor 220.

[0082] [Function Block]

[0083] Next, refer to Figure 3 This describes the functional blocks in the control unit 210. Figure 3 This is a functional block diagram representing the control unit 210 of the refrigerator 100. The control unit 210, through the combination of hardware and software control units, constitutes a functional block that realizes the functions of the refrigerator 100.

[0084] In the refrigerator 100, each function of the embodiment can be implemented by one or more processing circuits. Here, "processing circuit" in this specification includes a processor programmed to perform each function by software, such as a processor implemented by a circuit, and devices such as ASICs (Application Integrated Circuits), DSPs (Digital Signal Processors), FPGAs (Field Programmable Gate Arrays), and conventional circuit modules designed to perform the functions described above.

[0085] The CPU 211 of the control unit 210 executes programs stored in the storage unit 212, such as ROM 213, to achieve the following: Figure 3 The functions of the motor control unit 231, expansion valve control unit 232, and valve control unit 233 shown are illustrated. Furthermore, external machines and sensors connected to the control unit 210 can also perform some of these functions. However, the functions of the control unit 210 are not limited to these.

[0086] The motor control unit 231 controls the rotation speed of the motor 50 via the inverter 60. The control unit 210 controls the rotation speed of the impeller 12 of the compressor 10 by controlling the rotation speed of the motor 50. The expansion valve control unit 232 controls the expansion valve 30 to control the pressure of the refrigerant after passing through the expansion valve 30.

[0087] Valve control unit 233 can control the opening and closing of expansion valve V21. Valve control unit 233 can control the opening and closing of control valve V23. Valve control unit 233 can control the opening and closing of control valve V24. Valve control unit 233 can control the opening and closing of expansion valve V21 to adjust the pressure of refrigerant supplied to motor 50.

[0088] The valve control unit 233 can switch the target location for supplying the cooled refrigerant by controlling the opening and closing of control valves V23 and V24. In the refrigeration unit 100, by setting the target location for supplying the cooled refrigerant to piping L11, a first operating mode can be executed. In the refrigeration unit 100, by setting the target location for supplying the cooled refrigerant to the evaporator 40, a second operating mode can be executed.

[0089] As described above, the motor control unit 231, the expansion valve control unit 232, and the valve control unit 233 can be implemented in software using the program stored in the storage unit 212. All or part of these motor control units 231, the expansion valve control unit 232, and the valve control unit 233 can be implemented in hardware using an IC (integrated circuit) or the like.

[0090] [Ph line chart]

[0091] Next, refer to Figure 4 This illustrates the Morrillon curve diagram in the refrigeration cycle of the refrigeration unit 100. Figure 4In the diagram, the horizontal axis represents enthalpy (h), and the vertical axis represents pressure (P). Graph Ph1 is the Ph graph for the first operating mode. Graph Ph2 is the Ph graph for the second operating mode.

[0092] The state change from "1 to 2" is an isentropic change resulting from the reversible adiabatic compression of compressor 10. The enthalpy change during this isentropic change is called the adiabatic head. The state change from "2 to 3" is an isobaric change in condenser 20, where the refrigerant is condensed and cooled. The state change from "3 to 4" is a proportional enthalpy change based on the throttling expansion of expansion valve 30. The state change from "4 to 1" is an isobaric change in evaporator 40, where the refrigerant is evaporated and heated. Furthermore, based on past experience, the actual compression process from "1 to 2" will deviate from reversible adiabatic compression. In a turbo compressor, under the same rotational speed and the same volumetric flow rate, the operating point of the compressor will exhibit the same adiabatic head characteristics. Therefore, this specification focuses on the reversible adiabatic compression process and the adiabatic head.

[0093] [Ph line graph in Operation Mode 1]

[0094] Diagram Ph1 shows the first operating mode, where the refrigerant after cooling the target component returns to pipe L11, which serves as the intake gas line. In the first operating mode, the superheat of the refrigerant gas drawn into the compressor 10 is relatively high. The cooled refrigerant flows from pipe L23 into pipe L11, thus the temperature of the compressed refrigerant gas discharged from the compressor 10 is higher compared to the second operating mode.

[0095] Furthermore, in the first operating mode, the pressure increase ΔP1 of compressor 10 is less than the pressure increase ΔP2 in the second operating mode. Moreover, in comparing the first and second operating modes, the rotational speed and volumetric flow rate of compressor 10 are the same. Similarly, in comparing with the prior art, the rotational speed and volumetric flow rate of compressor 10 are the same. The pressure increase ΔP1 is the difference between pressure P21 and pressure P1. The pressure increase ΔP2 is the difference between pressure P22 and pressure P1. The discharge pressure P21 of compressor 10 in the first operating mode is lower than the discharge pressure P22 of compressor 10 in the second operating mode.

[0096] In the first operating mode, when the required temperature difference ΔT in the refrigerator 100 is small, it can stop operating at the point of low adiabatic efficiency and continue operating at the point of high adiabatic efficiency. Therefore, compared to the past, the operating range of the refrigerator 100 can be expanded. This can suppress surge in the refrigerator 100 while simultaneously increasing its operating range.

[0097] Figure 5 It is a graph representing the performance curve of the compressor. Figure 5 In the diagram, the horizontal axis represents volumetric flow rate, and the vertical axis represents adiabatic efficiency. Figure 5 The figure shows performance curves G1 and G2. Performance curves G1 and G2 represent the adiabatic pressure head at different rotational speeds. Figure 5 The diagram shows the working points P21 and P22.

[0098] also, Figure 5 The diagram illustrates the surge line SL1. SL1 represents the line where surge occurs. Surge occurs when the volumetric flow rate is below the surge line SL1, resulting in unstable refrigerant gas flow.

[0099] Compared to operating point P22, operating point P21 has a higher volumetric flow rate and a lower adiabatic head. Compared to operating point P21, operating point P22 has a lower volumetric flow rate and a higher adiabatic head. Compared to operating points P21 and P22, operating point P23 has a lower volumetric flow rate and a higher adiabatic head. The volumetric flow rate at operating point P23 is below the surge line SL. Operating point P23 is a hypothetical operating point in the inoperable region.

[0100] Figure 6 It is a graph showing the relationship between volumetric flow rate and adiabatic efficiency in a compressor. Figure 6 In the diagram, the horizontal axis represents volumetric flow rate, and the vertical axis represents adiabatic efficiency. Figure 6 The diagram in Figure G3 illustrates this. The adiabatic efficiency at operating point P21 is lower than that at operating point P22. The adiabatic efficiency at operating point P22 is higher than that at operating point P21. The adiabatic efficiency at operating point P22 is close to the peak of the adiabatic efficiency of compressor 10.

[0101] In the refrigeration unit 100, the operating mode can be switched, and the operating point P21 and P22 can be changed. By switching to the operating point P21, which is farther from the surge line SL1, concerns about surge can be reduced. Furthermore, by switching the operating mode, the refrigeration unit 100 can select either the operating point P22 with higher adiabatic efficiency or the operating point P21 with lower adiabatic efficiency.

[0102] [Ph line graph in the second operating mode]

[0103] Line graph Ph2 represents the second operating mode, where the cooled refrigerant returns to the evaporator 40. In the second operating mode, the superheat of the refrigerant gas drawn into the compressor 10 is relatively low. The superheat of the refrigerant gas drawn into the compressor 10 in the second operating mode is lower than that in the first operating mode.

[0104] Furthermore, in the second operating mode, the pressure increase ΔP2 of the compressor 10 is greater than the pressure increase ΔP1 in the first operating mode. Therefore, in the second operating mode, the pressure can be increased to a pressure P22 that would otherwise be impossible to increase due to the limitation on the rotational speed of the drive shaft 13 in the compressor 10. The limitation on the rotational speed of the compressor 10 sometimes depends, for example, on the strength of the rotating body including the impeller 12, the drive shaft 13, and the motor 50. In addition, the limitation on the rotational speed of the compressor 10 sometimes depends, for example, on the shaft resonance of the rotating body. Furthermore, the limitation on the rotational speed of the compressor 10 sometimes depends, for example, on the strength of the bearing 14 supporting the drive shaft 13. In the refrigeration unit 100, by executing the second operating mode, the pressure of the refrigerant gas discharged from the compressor 10 can be increased compared to the conventional method at the same rotational speed and the same volumetric flow rate. As a result, the operating range of the refrigeration unit 100 can be expanded compared to the conventional method. Surge generation in the refrigeration unit 100 can be suppressed, while the operating range is expanded.

[0105] In the second operating mode, the circulating volumetric flow rate of the refrigerant in the refrigerator 100 is low, which can expand the operating range of the refrigerator 100 to areas that would otherwise be unable to operate due to entering a surge region.

[0106] Furthermore, in the second operating mode, the cooling capacity of the evaporator 40 is lower than that in the first operating mode. However, the cooling capacity of the evaporator 40 can be adjusted to maintain the same required temperature difference ΔT. For example, during heating operation of the refrigerator 100, the heating capacity can be maintained without affecting high-pressure operation.

[0107] [Comparison of Operation Mode 1 and Operation Mode 2]

[0108] The adiabatic head Δh1 based on compressor 10 in the first operating mode is the same as the adiabatic head Δh2 based on compressor 10 in the second operating mode.

[0109] The slope of the isentropic line in the first operating mode is different from that in the second operating mode. The slope of the isentropic line in the second operating mode is larger than that in the first operating mode. In the second operating mode, the pressure P22 of the compressed refrigerant gas based on compressor 10 is higher than the pressure P21 of the compressed refrigerant gas based on compressor 10 in the first operating mode.

[0110] The enthalpy h11 of state "1" when the compressor 10 is drawn into the compressor 10 in the first operating mode is higher than the enthalpy h12 of state "1" when the compressor 10 is drawn into the compressor 10 in the second operating mode. The superheat of the intake in the first operating mode is higher than the superheat of the intake in the second operating mode (Δh3=h11-h12).

[0111] In refrigerant properties, as the suction superheat increases, the slope of the isentropic line (1→2) decreases. That is, in compressor 10, under the same rotational speed and volumetric flow rate, the adiabatic heads Δh1 and Δh2 are the same, but the pressure rise ΔP1 and ΔP2 are different. The arrival pressure P22 in the second operating mode is higher than the arrival pressure P21 in the first operating mode. In other words, when the suction superheat is larger, the arrival pressure P21 of the compressed refrigerant in compressor 10 is lower than when the suction superheat is smaller (P21...). <P22)。

[0112] [The sequence of control in the refrigeration unit 100]

[0113] Next, refer to Figure 7 This explains the control sequence in the refrigeration unit 100. Figure 7 This is a flowchart showing the control sequence in the refrigeration unit 100.

[0114] First, the control unit 210 of the chiller 100 inputs various data. The control unit 210 inputs various data from various sensors 220. The control unit 210 can receive various signals from other input units and switches. The control unit 210 can input various data from external processing devices and terminals. For example, the control unit 210 can input data related to the external air temperature, data related to the heat load, and data related to the target water temperature (room temperature). The control unit 210 can calculate various data from the input data.

[0115] The control unit 210 determines whether to receive an end signal (step S12). For example, when the user ends the operation of the refrigerator 100, they operate the switch. The switch outputs an end signal. If the control unit 210 receives the end signal (step S12; yes), the process here ends. If the control unit 210 does not receive an end signal (step S12; no), the process in step S12 is executed.

[0116] Next, the control unit 210 confirms the operating point information of the compressor 10 after the next control (step S13).

[0117] Next, the control unit 210 calculates the adiabatic head and volumetric flow rate at the operating point (step S14). Using various input data, the control unit 210 can calculate the adiabatic head and volumetric flow rate at the operating point. Using the calculated adiabatic head and volumetric flow rate, the control unit 210 can calculate the future operating point after a specified time. For example, the control unit 210 can use... Figure 5 The chart shown calculates future working points.

[0118] Next, the control unit 210 determines whether the future operating point exceeds the allowable operating limit line SL2 (step S15). The control unit 210, for example, refers to... Figure 5The diagram shows how to determine if the future operating point exists in the region to the left of the operating allowable limit line SL2. When the control unit 210 anticipates that the future operating point exists in the region to the left of the operating allowable limit line SL2, it determines that the operating point exceeds the operating allowable limit line SL2. Compared to the state shown by the operating allowable limit line SL2, when the volumetric flow rate is lower, the operating point exists to the left of the operating allowable limit line SL2. Compared to the state shown by the operating allowable limit line SL2, when the volumetric flow rate is higher, the operating point exists to the right of the operating allowable limit line SL2.

[0119] If the future operating point exceeds the allowable operating limit line SL2 (step S15; yes), the control unit 210 executes the processing in step S18. If the future operating point does not exceed the allowable operating limit line SL2 (step S15; no), the control unit 210 executes the processing in step S16.

[0120] In step S16, the control unit 210 performs control. "Control" here includes, for example, controlling the rotation speed of the compressor 10 and controlling the valves. "Valves" here includes, for example, expansion valve 30, expansion valve V21, control valve V23, and control valve V24. The control unit 210 may also perform other controls. The control unit 210 performs various controls to operate the refrigeration unit 100.

[0121] Next, the control unit 210 confirms the operating point information of the refrigeration unit 100 under current control (step S17). The control unit 210 acquires various data to confirm the operating point information of the refrigeration unit 100 under current control. As operating point information, the control unit 210 confirms, for example, the suction pressure and suction temperature of the refrigerant gas drawn into the compressor 10, the discharge pressure and discharge temperature of the refrigerant gas discharged from the compressor 10, and the volumetric flow rate of the refrigerant gas drawn into the compressor 10.

[0122] After the processing in step S17 is executed, the control unit 210 repeats steps S13 to S15.

[0123] In step S18, the control unit 210 determines whether the intake gas can be returned to the target location and switched to the evaporator 40. Returning the intake gas to the target location means, for example... Figure 1 The refrigerant flowing in piping L22 is returned to its destination. The intake gas returns to its destination, for example, the evaporator 40 or piping L11.

[0124] When the current target location for the return of the intake gas is pipe L11 (step S18; Yes), the control unit 210 determines that the return location for the intake gas can be switched to the evaporator 40, and executes the processing in step S19.

[0125] If the current target location for the return of the inhaled gas is the evaporator 40 (step S18; no), the control unit 210 does not determine whether the return location for the inhaled gas can be switched to the evaporator 40, and executes step S20.

[0126] In step S19, the return target of the intake gas is switched from piping L11 to evaporator 40. In the refrigeration unit 100, the refrigerant flowing in piping L22 is supplied to evaporator 40. After the control unit 210 performs the processing of step S19, it repeats the processing of steps S17, S13, S14 and S15.

[0127] In step S20, the control unit 210 issues an error signal, ending the process here. After the process in step S20 is executed, the control unit 210 can execute a process to stop the operation of the refrigerator 100.

[0128] [The function and effect of refrigeration unit 100]

[0129] The refrigeration unit 100 according to this embodiment includes a pipe L23 that supplies refrigerant after cooling the motor 50 to a pipe (as a suction pipe in the first position) L11, and a pipe L24 that supplies refrigerant after cooling the motor 50 to an evaporator (second position) 40.

[0130] In this type of refrigeration unit 100, refrigerant after the target component is cooled can be supplied to either the piping L11 (position 1) or the evaporator 40 (position 2). The refrigeration unit 100 can supply refrigerant after the target component is cooled to both the piping L11 and the evaporator 40. By selecting the target location for refrigerant supply after the target component, the operating state of the refrigeration unit 100 can be changed, thus suppressing surge. Because the target location for refrigerant supply after the target component is selectable, the operable range of the refrigeration unit 100 can be expanded.

[0131] According to the refrigeration unit 100, even when the rotational speed of the compressor 10 is changed, the cooling capacity in the evaporator 40 can be adjusted by changing the target location of the cooled refrigerant supply. Furthermore, according to the refrigeration unit 100, by changing the target location of the cooled refrigerant supply, the operating range can be expanded, allowing operation even in pressure ranges that would otherwise be inoperable due to surge. In the refrigeration unit 100, by selecting the target location of the refrigerant supply after cooling the component, the operating state can be changed, thus suppressing the generation of surge.

[0132] In the refrigerator 100, the object component is the motor 50. In this type of refrigerator 100, cooling the motor 50 suppresses heat generation and improves its reliability. According to this type of refrigerator 100, cooling the motor 50 alleviates temperature-related limitations of the motor 50. Temperature-related limitations of the motor 50 include the temperature of its windings or magnets. By cooling the windings and magnets of the motor 50 in the refrigerator 100, the operating area of ​​the compressor 10 can be expanded.

[0133] In the refrigeration unit 100, the target component is not limited to the motor 50. In the refrigeration unit 100, the target component can be the bearing 14 that supports the drive shaft (rotation shaft) 13 of the compressor 10. In this structure of the refrigeration unit 100, by cooling the bearing 14, burn-out in the bearing 14 can be suppressed. According to this method, the refrigeration unit 100 can alleviate the limitations related to the temperature of the bearing 14. In the refrigeration unit 100, by cooling the bearing 14, the temperature rise of the bearing 14 can be suppressed, and the limitations related to the bearing 14 can be alleviated. Therefore, the area where the compressor 10 can operate can be expanded.

[0134] In the refrigerator 100, the target component can be the inverter 60, which serves as the controller for the motor 50. In this refrigerator 100 structure, by cooling the inverter 60, the occurrence of faults in the inverter 60 can be suppressed, thereby improving the reliability of the inverter 60.

[0135] In the refrigeration unit 100, the second position is the evaporator 40. In this type of refrigeration unit 100, by returning the refrigerant after cooling the target component to the evaporator 40, the superheat of the refrigerant gas supplied to the compressor 10 can be relatively low.

[0136] In the second operating mode, where the refrigerant, after cooling the target component, returns to the evaporator 40, the cooling capacity decreases. In this second operating mode, the required suction volume flow rate needs to be increased to ensure cooling capacity. Therefore, at operating points where high cooling capacity is required, a limitation on the compressor 10's rotational speed occurs. To avoid this limitation, switching from the second operating mode to the first operating mode ensures cooling capacity while maintaining the compressor 10's rotational speed.

[0137] In the refrigerator 100, the object component is the motor 50, and the piping L21 connects to a flow path communicating with the motor chamber 11b. The piping L21 may include a flow path communicating with the motor chamber 11b. The flow path communicating with the motor chamber 11b includes a flow path penetrating the housing 11. In this type of refrigerator 100, refrigerant can be supplied to the interior of the motor chamber 11b, directly cooling the rotating shaft, rotor, and stator of the motor 50 inside the housing 11. In this type of refrigerator 100, as described above, the limitations related to the temperature of the motor 50 can be alleviated, thereby expanding the area where the compressor 10 can operate.

[0138] In the refrigeration unit 100, the object component can be the bearing 14 supporting the drive shaft 13 of the compressor 10, and the bearing 14 can be an oil-free bearing. In this type of refrigeration unit 100, refrigerant can be used as the gas supplied to the oil-free bearing. Therefore, by using an oil-free bearing, the wear resistance and erosion resistance of the bearing 14 can be improved. In addition, by using an oil-free bearing, the maintenance of the bearing 14 can be reduced.

[0139] According to the refrigeration unit 100 of this embodiment, by cooling the oil-free bearing, the limitations related to the temperature of the bearing 14 can be alleviated. This expands the operating range of the compressor 10. In the refrigeration unit 100 of this embodiment, by employing an oil-free bearing, bearings that use highly viscous fluids such as oil as the working fluid can be eliminated. When using an oil-free bearing, bearing losses are reduced even at high speeds. Therefore, the limitations related to the rotational speed of the bearing 14 can be alleviated, and the operating range of the compressor 10 can be expanded.

[0140] In the refrigeration unit 100, the evaporator 40 is an air heat exchanger that transfers heat between the refrigerant and the air. In this type of refrigeration unit 100, air can be cooled by heat exchange between the refrigerant and the air. The refrigeration unit 100 can be applied to air conditioning systems, for example, for adjusting the temperature of indoor air in a residence.

[0141] Air heat exchangers are affected by the outside air temperature, resulting in greater temperature variations compared to water heat exchangers. Therefore, the operating state of the compressor 10 downstream of the air heat exchanger is more prone to change, and the required operating area is larger in a refrigerator 100 equipped with an air heat exchanger compared to a refrigerator equipped with a water heat exchanger. The refrigerator 100 of this type expands the operable area, making it effective in refrigerators equipped with air heat exchangers where operating states are prone to change.

[0142] The refrigeration unit 100 includes a control valve V23 located on pipe L23, a control valve V24 located on pipe L24, and a control unit 210 that controls the control valves V23 and V24. In this type of refrigeration unit 100, the control unit 210 controls the opening and closing of the control valves V23 and V24, thereby allowing the refrigerant supply target after the cooling component to be switched.

[0143] In the refrigeration unit 100, the control unit 210 can execute the first operating mode by opening the control valve V23 and closing the control valve V24, and can execute the second operating mode by closing the control valve V23 and opening the control valve V24.

[0144] In this type of refrigeration unit 100, by selecting the first operating mode, the refrigerant after cooling the target component can be returned to the suction pipe L11 of the compressor 10. This allows for a relatively high superheat of the refrigerant gas supplied to the compressor 10. Furthermore, in this type of refrigeration unit 100, by selecting the second operating mode, the refrigerant after cooling the target component can be supplied to the evaporator 40, which serves as a second location. According to this type of refrigeration unit 100, by selecting either the first or second operating mode, the superheat of the refrigerant gas supplied to the compressor 10 can be changed, thus suppressing surge. The range of adjustable operation can be expanded in the refrigeration unit 100.

[0145] In the first operating mode, after the refrigerant has cooled the components, it returns to the suction pipe L11 of the compressor 10. Due to the increased superheat of the refrigerant, the required compression power in the compressor 10 increases. Therefore, at the operating point where high power is required, limitations related to motor output arise. To avoid such limitations related to motor output, the operation mode is switched from the first to the second operating mode, thereby allowing the compressor 10 to continue operating. As a result, the operable range can be expanded.

[0146] In this method, by switching from the second operating mode to the first operating mode, the rotational speed limitation of the compressor 10 can be avoided, and the cooling capacity can be ensured while maintaining the rotational speed of the compressor 10. According to the refrigeration unit 100, it is possible to switch from the first operating mode to the second operating mode or from the second operating mode to the first operating mode depending on the operating state, thereby expanding the operable range.

[0147] The refrigerator 100 according to the embodiment may include a control unit 210 that controls the flow rate of refrigerant flowing in the third piping L24 based on a surge line SL1, which indicates the boundary of the region where surge occurs in the compressor 10. In this type of refrigerator 100, by controlling the flow rate of refrigerant flowing in the piping L24 based on the surge line SL1, surge in the compressor 10 can be suppressed.

[0148] In the refrigeration unit 100 of the embodiment, the control unit 210 controls the flow rate of the refrigerant flowing in the piping L24 based on the operating allowable limit line SL2. The operating allowable limit line is the operating region on the side with a larger refrigerant flow rate relative to the surge line SL1, and is obtained by taking into account the margin SR relative to the surge line SL1. In the refrigeration unit 100 of this embodiment, the flow rate of the refrigerant flowing in the piping L24 is controlled based on the operating allowable limit line SL2 with a margin SR relative to the surge line SL1, thereby effectively suppressing the generation of surge in the compressor 10.

[0149] In the refrigeration unit 100 of this embodiment, the second position is the evaporator. The control unit 210 predicts the operating point of the compressor 10 at a second point in time after a specified period from the current first point in time. When the predicted operating point is in a region closer to the surge line SL1 than the operating allowable limit line SL2, or in a region where surge occurs, the flow rate of the refrigerant flowing in the piping L24 can be increased. In this type of refrigeration unit 100, the operating point of the compressor 10 at a second point in time after the current moment can be predicted, thus predicting the occurrence of surge. In this type of refrigeration unit, when there is a high concern about surge, the occurrence of surge can be suppressed by increasing the flow rate of the refrigerant flowing in the piping L24.

[0150] In the refrigeration unit 100 of this embodiment, the return target of the refrigerant gas can be switched from a state where the refrigerant gas is returned to the piping L11, which serves as the suction side of the compressor 10, to the evaporator 40. In such a refrigeration unit 100, the pressure boost based on the compressor 10 can be increased at the same rotational speed and volumetric flow rate. Furthermore, in the refrigeration unit 100, due to the reduction in superheat, the slope of the isentropic line becomes steeper, and the reaching pressure can be increased at the same adiabatic head.

[0151] Furthermore, in this type of refrigerator 100, the return destination of the refrigerant gas is switched to the evaporator 40, thereby reducing the cooling capacity. In this type of refrigerator 100, part of the enthalpy change inside the evaporator 40 is unusable for cooling, thus reducing the cooling capacity. Therefore, in the refrigerator 100, the cooling capacity can be reduced without reducing the flow rate of the compressor 10.

[0152] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the above embodiments. Various modifications and substitutions are applicable to the above embodiments without departing from the scope of the present invention. Furthermore, the features described separately can be combined as long as they do not create technical contradictions.

[0153] In the above embodiments, the compressor 10 can be a single-stage compressor or a multi-stage compressor with multiple impellers 12. For example, in a multi-stage compressor, the cooled refrigerant can be supplied to the impeller (compression mechanism) in the later stage.

[0154] In the above embodiment, cooled refrigerant is supplied to the evaporator 40, which serves as the second position. However, refrigerant can be supplied to any position on the evaporator 40, and cooled refrigerant can be supplied to the upstream piping L14 connected to the evaporator 40. Furthermore, there can be multiple second positions. For example, in the refrigeration unit 100, cooled refrigerant can be supplied to multiple positions for the evaporator 40.

[0155] One aspect of the present invention is as follows.

[0156] <1> A refrigeration machine that performs a refrigeration cycle.

[0157] The refrigeration unit is equipped with...

[0158] Compressor that compresses refrigerant,

[0159] The condenser of the compressed refrigerant,

[0160] An expansion valve that expands the condensed refrigerant.

[0161] An evaporator that causes the expanded refrigerant to evaporate.

[0162] The suction pipe connecting the evaporator and the compressor,

[0163] The motor that drives the compressor,

[0164] The first piping supplyes the refrigerant discharged from the condenser to the target component.

[0165] The second piping supplies the refrigerant, after cooling the object component, to the suction piping at the first location, and

[0166] The third piping supplies the refrigerant, after cooling the object component, to the second position contained in the refrigeration unit, which is a different position from the first position.

[0167] <2> According to the above <1> The compressor in the aforementioned refrigeration unit is a turbo compressor.

[0168] <3> According to the above <1> or <2> The refrigeration machine, wherein the object component is the motor, or the bearing supporting the rotating shaft of the compressor, or the controller of the motor.

[0169] <4> According to the above <1> ~ <3> The second position is the evaporator in any of the aforementioned refrigeration machines.

[0170] <5> According to the above <1> ~ <4> In any one of the aforementioned refrigeration machines, the object component is the motor.

[0171] The first piping is connected to a flow path that leads to the housing of the motor.

[0172] <6> According to the above <1> ~ <5> In any of the aforementioned refrigeration machines, the object component is a bearing that supports the rotating shaft of the compressor.

[0173] The bearing is an oil-free bearing.

[0174] <7> According to the above <1> ~ <6> The evaporator is an air heat exchanger that transfers heat between the refrigerant and the air, in any of the aforementioned refrigeration machines.

[0175] <8> According to the above <1> ~ <7> Any of the aforementioned refrigeration units, comprising,

[0176] The first control valve is located on the second piping.

[0177] The second control valve located on the third piping, and

[0178] A control unit that controls the first control valve and the second control valve.

[0179] <9> According to the above <8> The refrigeration unit, the control unit

[0180] This allows the first control valve to be in the open state and the second control valve to be in the closed state, thus executing the first operating mode.

[0181] It can close the first control valve and open the second control valve to execute the second operating mode.

[0182] <10> According to the above <1> ~ <9> The refrigeration unit of any one of the refrigeration units described herein includes a control unit that controls the flow rate of the refrigerant flowing in the third piping based on a surge line that represents the boundary of the region in which surge occurs in the compressor.

[0183] <11> According to the above <10> In the refrigeration unit, the control unit controls the flow rate of the refrigerant flowing in the third piping based on the operating allowable limit line. The operating allowable limit line is obtained by taking a margin from the surge line in the operating region on the side with a larger flow rate of the refrigerant.

[0184] <12> According to the above <11> The refrigeration unit described above, wherein the second position is the evaporator.

[0185] The control unit predicts the operating point of the compressor from the current first time point through a specified second time point.

[0186] When the predicted operating point exists in a region closer to the surge line than the operating allowable limit line, or in the region where surge occurs, the flow rate of the refrigerant flowing in the third piping is increased.

[0187] This international application claims priority based on Japanese Patent Application No. 2023-058725, filed on March 31, 2023, and incorporates the entire contents of Japanese Patent Application No. 2023-058725 into this international application.

[0188] [Attached image labels]

[0189] 100 Refrigeration unit

[0190] 10 Compressors

[0191] 13. Drive shaft (rotary shaft)

[0192] 14. Bearings (object component, oil-free bearings)

[0193] 20 Condenser

[0194] 30 Expansion Valve

[0195] 40 Evaporator (Position 2, Air Heat Exchanger)

[0196] 50 Motor (Object Component)

[0197] 60 Inverter (motor controller)

[0198] 210 Control Department

[0199] L11 piping (suction piping, position 1)

[0200] L21 piping (1st piping)

[0201] L23 piping (2nd piping)

[0202] L24 piping (3rd piping)

[0203] V23 Control Valve (First Control Valve)

[0204] V24 Control Valve (Second Control Valve)

Claims

1. A refrigeration machine that performs a refrigeration cycle, The refrigeration unit includes: Compressor that compresses refrigerant, The condenser of the compressed refrigerant, An expansion valve that expands the condensed refrigerant. An evaporator that causes the expanded refrigerant to evaporate. The suction pipe connecting the evaporator and the compressor, The motor that drives the compressor, The first piping supplyes the refrigerant discharged from the condenser to the target component. The second piping supplies the refrigerant, after cooling the object component, to the suction piping at the first location, and... The third piping supplies the refrigerant, after cooling the object component, to a second position within the refrigeration unit, which is a position different from the first position.

2. The refrigeration machine according to claim 1, wherein the compressor is a turbo compressor.

3. The refrigeration machine according to claim 1 or 2, wherein the object component is the motor, or a bearing supporting the rotating shaft of the compressor, or a controller of the motor.

4. The refrigeration machine according to any one of claims 1 to 3, wherein the second position is the evaporator.

5. The refrigeration machine according to any one of claims 1 to 4, wherein the object component is the motor. The first piping is connected to a flow path that leads to the housing of the motor.

6. The refrigeration machine according to any one of claims 1 to 5, wherein the object component is a bearing supporting the rotating shaft of the compressor. The bearing is an oil-free bearing.

7. The refrigeration machine according to any one of claims 1 to 6, wherein the evaporator is an air heat exchanger that transfers heat between the refrigerant and the air.

8. The refrigeration machine according to any one of claims 1 to 7, comprising: The first control valve is located on the second piping. The second control valve located on the third piping, and A control unit that controls the first control valve and the second control valve.

9. The refrigeration unit according to claim 8, wherein the control unit is capable of opening the first control valve and closing the second control valve to execute the first operating mode. The control unit can close the first control valve and open the second control valve to execute the second operating mode.

10. The refrigeration machine according to any one of claims 1 to 9, comprising a control unit that controls the flow rate of the refrigerant flowing in the third piping based on a surge line indicating the boundary of the region in which surge occurs in the compressor.

11. The refrigeration unit according to claim 10, wherein the control unit controls the flow rate of the refrigerant flowing in the third piping based on an operating allowable limit line, the operating allowable limit line being obtained by taking a margin relative to the surge line in the operating region on the side with a larger flow rate of the refrigerant.

12. The refrigeration unit according to claim 11, wherein the second position is the evaporator. The control unit predicts the operating point of the compressor from the current first time point through a specified second time point. When the predicted operating point exists in a region closer to the surge line than the operating allowable limit line, or in the region where surge occurs, the flow rate of the refrigerant flowing in the third piping is increased.

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