US20100175400A1 - Refrigeration apparatus - Google Patents

Refrigeration apparatus Download PDF

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Publication number
US20100175400A1
US20100175400A1 US12/667,016 US66701608A US2010175400A1 US 20100175400 A1 US20100175400 A1 US 20100175400A1 US 66701608 A US66701608 A US 66701608A US 2010175400 A1 US2010175400 A1 US 2010175400A1
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Prior art keywords
refrigerant
high pressure
superheat
degree
control
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US12/667,016
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English (en)
Inventor
Shinichi Kasahara
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Daikin Industries Ltd
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Daikin Industries Ltd
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Assigned to DAIKIN INDUSTRIES, LTD. reassignment DAIKIN INDUSTRIES, LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: KASAHARA, SHINICHI
Publication of US20100175400A1 publication Critical patent/US20100175400A1/en
Abandoned legal-status Critical Current

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B1/00—Compression machines, plants or systems with non-reversible cycle
    • F25B1/10—Compression machines, plants or systems with non-reversible cycle with multi-stage compression
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B41/00—Fluid-circulation arrangements
    • F25B41/30—Expansion means; Dispositions thereof
    • F25B41/39—Dispositions with two or more expansion means arranged in series, i.e. multi-stage expansion, on a refrigerant line leading to the same evaporator
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B49/00—Arrangement or mounting of control or safety devices
    • F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B9/00—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point
    • F25B9/002—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant
    • F25B9/008—Compression machines, plants or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant the refrigerant being carbon dioxide
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B13/00—Compression machines, plants or systems, with reversible cycle
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2309/00—Gas cycle refrigeration machines
    • F25B2309/06—Compression machines, plants or systems characterised by the refrigerant being carbon dioxide
    • F25B2309/061—Compression machines, plants or systems characterised by the refrigerant being carbon dioxide with cycle highest pressure above the supercritical pressure
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2313/00—Compression machines, plants or systems with reversible cycle not otherwise provided for
    • F25B2313/005—Outdoor unit expansion valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2313/00—Compression machines, plants or systems with reversible cycle not otherwise provided for
    • F25B2313/023—Compression machines, plants or systems with reversible cycle not otherwise provided for using multiple indoor units
    • F25B2313/0233—Compression machines, plants or systems with reversible cycle not otherwise provided for using multiple indoor units in parallel arrangements
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2313/00—Compression machines, plants or systems with reversible cycle not otherwise provided for
    • F25B2313/027—Compression machines, plants or systems with reversible cycle not otherwise provided for characterised by the reversing means
    • F25B2313/0272—Compression machines, plants or systems with reversible cycle not otherwise provided for characterised by the reversing means using bridge circuits of one-way valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2313/00—Compression machines, plants or systems with reversible cycle not otherwise provided for
    • F25B2313/027—Compression machines, plants or systems with reversible cycle not otherwise provided for characterised by the reversing means
    • F25B2313/02741—Compression machines, plants or systems with reversible cycle not otherwise provided for characterised by the reversing means using one four-way valve
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2313/00—Compression machines, plants or systems with reversible cycle not otherwise provided for
    • F25B2313/031—Sensor arrangements
    • F25B2313/0314—Temperature sensors near the indoor heat exchanger
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2313/00—Compression machines, plants or systems with reversible cycle not otherwise provided for
    • F25B2313/031—Sensor arrangements
    • F25B2313/0315—Temperature sensors near the outdoor heat exchanger
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
    • F25B2400/13—Economisers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2400/00—General features or devices for refrigeration machines, plants or systems, combined heating and refrigeration systems or heat-pump systems, i.e. not limited to a particular subgroup of F25B
    • F25B2400/23—Separators
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2600/00—Control issues
    • F25B2600/17—Control issues by controlling the pressure of the condenser
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2600/00—Control issues
    • F25B2600/21—Refrigerant outlet evaporator temperature
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2600/00—Control issues
    • F25B2600/25—Control of valves
    • F25B2600/2513—Expansion valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/19—Pressures
    • F25B2700/193—Pressures of the compressor
    • F25B2700/1931—Discharge pressures
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/19—Pressures
    • F25B2700/193—Pressures of the compressor
    • F25B2700/1933—Suction pressures
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/21—Temperatures
    • F25B2700/2102—Temperatures at the outlet of the gas cooler
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/21—Temperatures
    • F25B2700/2106—Temperatures of fresh outdoor air
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/21—Temperatures
    • F25B2700/2115—Temperatures of a compressor or the drive means therefor
    • F25B2700/21152—Temperatures of a compressor or the drive means therefor at the discharge side of the compressor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B2700/00—Sensing or detecting of parameters; Sensors therefor
    • F25B2700/21—Temperatures
    • F25B2700/2117—Temperatures of an evaporator
    • F25B2700/21174—Temperatures of an evaporator of the refrigerant at the inlet of the evaporator
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B49/00—Arrangement or mounting of control or safety devices
    • F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
    • F25B49/027—Condenser control arrangements

Definitions

  • the present disclosure relates to a refrigeration apparatus including a refrigerant circuit for performing a supercritical refrigeration cycle.
  • Patent Document 1 shows an example of the refrigeration apparatus.
  • PATENT DOCUMENT 1 Japanese Patent Publication No. 2002-22242
  • the refrigeration apparatus is configured to correct the control amount of the degree of opening of the expansion valve controlled by the expansion valve controller based on the capacity of the compressor, change of the degree of opening of the expansion valve leads to change of a circulation state of the refrigerant, thereby changing the low pressure of the refrigerant.
  • the compressor capacity controller adjusts the capacity of the compression mechanism.
  • the change of the capacity of the compressor involves re-correction of the control amount of the expansion valve controller.
  • a sequence of the correction of the control amount of the expansion valve controller, the change of the low pressure of the refrigerant, the change of the capacity of the compressor, and the re-correction of the control amount of the expansion valve controller occurs in a loop.
  • the control of the low pressure by the compressor, and the control of the degree of superheat by the expansion valve cannot be easily settled.
  • a refrigeration apparatus for performing a supercritical refrigeration cycle in which a high pressure of the refrigerant is equal to or higher than a critical pressure has a problem of difficulty in settling the control.
  • the present disclosure has been achieved by paying attention to a large variation of enthalpy of the refrigerant at an outlet of a gas cooler relative to the change of the high pressure of the supercritical refrigeration cycle.
  • the enthalpy of the refrigerant at the outlet of the gas cooler may greatly vary when the high pressure changes due to change of the low pressure. This leads to an event that is not caused by a subcritical refrigerant, i.e., the enthalpy of the refrigerant at an inlet of an indoor heat exchanger varies, thereby changing the degree of superheat of the refrigerant at an outlet of the indoor heat exchanger. As a result, the difficulty of settling of the control increases.
  • the enthalpy of the refrigerant at the outlet of the gas cooler may greatly vary due to the change of the high pressure. This leads to great fluctuation of indoor air heating capability, thereby changing the temperature of the indoor air, and changing a target value of the temperature of the refrigerant at the outlet of the gas cooler. This vicious circle further increases the difficulty of settling of the control.
  • CO 2 which is a supercritical refrigerant, shows greater variation in refrigerant density when it is superheated as compared with chlorofluorocarbons (e.g., when an evaporating temperature is 5° C., and the degree of superheat varies from 0° C.
  • a first aspect of the disclosure is directed to a refrigeration apparatus including: a refrigerant circuit ( 20 ) sequentially connecting a compression mechanism ( 21 ), a heat source side heat exchanger ( 23 ), an expansion mechanism ( 24 ), and a utilization side heat exchanger ( 27 ), and performing a supercritical refrigeration cycle in which a high pressure is a supercritical pressure of a refrigerant or higher; and a control section ( 40 ) for controlling a plurality of objects of control including at least the compression mechanism ( 21 ) and the expansion mechanism ( 24 ).
  • the control section ( 40 ) concurrently controls the plurality of objects of control, thereby concurrently controlling a predetermined physical value of the refrigeration apparatus, and the high pressure of the refrigeration cycle.
  • the predetermined physical value is controlled, while controlling the high pressure of the refrigeration cycle in the refrigerant circuit ( 20 ).
  • a different physical value can be controlled in consideration of the change of the high pressure of the refrigeration cycle, and the change of enthalpy of the refrigerant at an outlet of a gas cooler, due to adjustment of the objects of control.
  • the plurality of objects of control are concurrently controlled so as to concurrently control the high pressure of the refrigeration cycle and the predetermined physical value, thereby controlling the objects of control by taking into account the effect of their changes on the high pressure and the predetermined physical value.
  • control section ( 40 ) receives the predetermined physical value, and the high pressure of the refrigeration cycle as inputs, generates control signals each corresponding to the plurality of objects of control by associating the physical value and the high pressure with each other, and outputs the control signals to the corresponding objects of control, respectively, thereby concurrently controlling the predetermined physical value, and the high pressure of the refrigeration cycle.
  • control signals for controlling the plurality of objects of control are generated by associating the input predetermined physical value and high pressure of the refrigeration cycle with each other.
  • This allows for controlling the objects of control by taking both of the predetermined physical value and the high pressure into consideration, instead of controlling the objects of control by inputting any one of the predetermined physical value and the high pressure. Since the plurality of objects of control are concurrently controlled as described above, a control signal for one of the objects of control can be generated in consideration of the effect of adjustment of the other objects of control on the predetermined physical value and the high pressure.
  • the refrigeration apparatus further includes: a heat source side fan ( 28 ) for feeding air to the heat source side heat exchanger ( 23 ) in which the refrigerant exchanges heat with the air, wherein in cooling operation, the predetermined physical value includes an evaporating temperature of the refrigerant in the utilization side heat exchanger ( 27 ), and a degree of superheat of the refrigerant at an outlet of the utilization side heat exchanger ( 27 ), the objects of control further include the heat source side fan ( 28 ), and the control section ( 40 ) receives the evaporating temperature of the refrigerant, the degree of superheat of the refrigerant, and the high pressure of the refrigeration cycle as inputs, and concurrently controls the compression mechanism ( 21 ), the expansion mechanism ( 24 ), and the heat source side fan ( 28 ), thereby concurrently controlling the evaporating temperature of the refrigerant, the degree of superheat of the refrigerant, and the high pressure of the
  • the compression mechanism ( 21 ), the expansion mechanism ( 24 ), and the heat source side fan ( 28 ) are concurrently controlled, thereby concurrently controlling the high pressure of the refrigeration cycle, the evaporating temperature of the refrigerant, and the degree of superheat of the refrigerant.
  • the evaporating temperature and the degree of superheat of the refrigerant can be controlled with the high pressure of the refrigeration cycle stably controlled to a desired target value. This allows for an improved convergence rate of the control of the high pressure of the refrigeration cycle, the evaporating temperature of the refrigerant, and the degree of superheat of the refrigerant.
  • the predetermined physical value in heating operation, includes a degree of superheat of the refrigerant at an outlet of the heat source side heat exchanger ( 23 ), and the control section ( 40 ) receives the degree of superheat of the refrigerant, and the high pressure of the refrigeration cycle as inputs, and concurrently controls the compression mechanism ( 21 ) and the expansion mechanism ( 24 ), thereby concurrently controlling the degree of superheat of the refrigerant, and the high pressure of the refrigeration cycle.
  • the compression mechanism ( 21 ) and the expansion mechanism ( 24 ) are concurrently controlled, thereby concurrently controlling the high pressure of the refrigeration cycle, and the degree of superheat of the refrigerant.
  • the degree of superheat of the refrigerant can be controlled with the high pressure of the refrigeration cycle stably controlled to a desired target value. This allows for an improved convergence rate of the control of the high pressure of the refrigeration cycle, and the degree of superheat of the refrigerant.
  • the compression mechanism includes a first compressor ( 21 a ) for sucking and compressing a low pressure refrigerant, and a second compressor ( 21 b ) for further compressing and discharging the refrigerant discharged from the first compressor ( 21 a ),
  • the expansion mechanism includes a first expansion mechanism ( 24 ) for expanding a high pressure refrigerant, and a second expansion mechanism ( 26 ) for further expanding the refrigerant expanded to an intermediate pressure refrigerant by the first expansion mechanism ( 24 ).
  • the predetermined physical value includes an evaporating temperature of the refrigerant in the utilization side heat exchanger ( 27 ), a degree of superheat of the refrigerant at an outlet of the utilization side heat exchanger ( 27 ), and an intermediate pressure of the refrigeration cycle
  • the control section ( 240 ) receives the evaporating temperature of the refrigerant, the degree of superheat of the refrigerant, the intermediate pressure of the refrigeration cycle, and the high pressure of the refrigeration cycle as inputs, and concurrently controls the first and second compressors ( 21 a, 21 b ), and the first and second expansion mechanisms ( 24 , 26 ), thereby concurrently controlling the evaporating temperature of the refrigerant, the degree of superheat of the refrigerant, the intermediate pressure of the refrigeration cycle, and the high pressure of the refrigeration cycle.
  • the first and second compressors ( 21 a, 21 b ), and the first and second expansion mechanisms ( 24 , 26 ), are concurrently controlled, thereby concurrently controlling the high pressure of the refrigeration cycle, the evaporating temperature of the refrigerant, the degree of superheat of the refrigerant, and the intermediate pressure.
  • the evaporating temperature of the refrigerant, the degree of superheat of the refrigerant, and the intermediate pressure of the refrigeration cycle can be controlled with the high pressure of the refrigeration cycle stably controlled to a desired target value. This allows for an improved convergence rate of the control of the high pressure of the refrigeration cycle, the evaporating temperature of the refrigerant, the degree of superheat of the refrigerant, and the intermediate pressure of the refrigeration cycle.
  • the compression mechanism includes a first compressor ( 21 a ) for sucking and compressing a low pressure refrigerant, and a second compressor ( 21 b ) for further compressing and discharging the refrigerant discharged from the first compressor ( 21 a ),
  • the expansion mechanism includes a first expansion mechanism ( 24 ) for expanding a high pressure refrigerant, and a second expansion mechanism ( 26 ) for further expanding the refrigerant expanded to an intermediate pressure refrigerant in the first expansion mechanism ( 24 ).
  • the predetermined physical value includes an evaporating temperature of the refrigerant in the heat source side heat exchanger ( 23 ), a degree of superheat of the refrigerant at an outlet of the heat source side heat exchanger ( 23 ), and a gas cooler outlet temperature which is a temperature of the refrigerant at an outlet of the utilization side heat exchanger ( 27 ), and the control section ( 240 ) receives the evaporating temperature of the refrigerant, the degree of superheat of the refrigerant, the gas cooler outlet temperature of the refrigerant, and the high pressure of the refrigeration cycle as inputs, and concurrently controls the first and second compressors ( 21 a, 21 b ), and the first and second expansion mechanisms ( 24 , 26 ), thereby concurrently controlling the evaporating temperature of the refrigerant, the degree of superheat of the refrigerant, the gas cooler outlet temperature of the refrigerant, and the high pressure of the refrigeration cycle.
  • the first and second compressors ( 21 a, 21 b ), and the first and second expansion mechanisms ( 24 , 26 ), are concurrently controlled, thereby concurrently controlling the high pressure of the refrigeration cycle, the evaporating temperature of the refrigerant, the degree of superheat of the refrigerant, and the gas cooler outlet temperature.
  • the evaporating temperature of the refrigerant, the degree of superheat of the refrigerant, and the gas cooler outlet temperature can be controlled with the high pressure of the refrigeration cycle stably controlled to a desired target value. This allows for an improved convergence rate of the control of the high pressure of the refrigeration cycle, the evaporating temperature of the refrigerant, the degree of superheat of the refrigerant, and the gas cooler outlet temperature.
  • the predetermined physical value includes evaporating temperatures of the refrigerant in the utilization side heat exchangers ( 27 a, 27 b ), and degrees of superheat of the refrigerant at outlets of the utilization side heat exchangers ( 27 a, 27 b ), and the control section ( 340 ) receives the evaporating temperatures of the refrigerant, the degrees of superheat of the refrigerant in the utilization side heat exchangers ( 27 a, 27 b ), and the high pressure of the refrigeration cycle as inputs, and concurrently controls the compression mechanism ( 21 ), the plurality of utilization side heat expansion mechanisms ( 26 a, 26 b ), and the heat source side expansion mechanism ( 24 ), thereby concurrently controlling the evaporating temperatures of the refrigerant, and the degrees of superheat of the refrigerant in the utilization side heat exchangers ( 27 a, 27 b ), and the high pressure of the refrigeration cycle.
  • a plurality ones of the utilization side heat exchanger ( 27 a, 27 b ) are connected in parallel with each other, the expansion mechanism includes a plurality of utilization side expansion mechanisms ( 26 a, 26 b ) each corresponding to the utilization side heat exchangers ( 27 a, 27 b ), and a heat source side expansion mechanism ( 24 ) provided between the utilization side heat exchangers ( 27 a, 27 b ) and expansion mechanisms ( 26 a, 26 b ), and the heat source side heat exchanger ( 23 ).
  • the predetermined physical value includes a degree of superheat of the refrigerant at an outlet of the heat source side heat exchanger ( 23 ), and gas cooler outlet temperatures of the refrigerant which are temperatures of the refrigerant at outlets of the utilization side heat exchangers ( 27 a, 27 b ), and the control section ( 340 ) receives the degree of superheat of the refrigerant, the gas cooler outlet temperatures of the refrigerant in the utilization side heat exchangers ( 27 a, 27 b ), and the high pressure of the refrigeration cycle as inputs, and concurrently controls the compression mechanism ( 21 ), the plurality of utilization side expansion mechanisms ( 26 a, 26 b ), and the heat source side expansion mechanism ( 24 ), thereby concurrently controlling the degree of superheat of the refrigerant, the gas cooler outlet temperatures of the refrigerant in the utilization side heat exchangers ( 27 a, 27 b ), and the high pressure of the refrigeration cycle.
  • a plurality of objects of control i.e., the compression mechanism ( 21 ), the heat source side expansion mechanism ( 24 ), and the plurality of utilization side expansion mechanisms ( 26 a, 26 b ) are concurrently controlled, thereby concurrently controlling the high pressure of the refrigeration cycle, the degree of superheat of the refrigerant, and the gas cooler outlet temperatures at the utilization side heat exchangers ( 27 a, 27 b ).
  • the degree of superheat of the refrigerant, and the gas cooler outlet temperatures of the refrigerant at the utilization side heat exchangers ( 27 a, 27 b ) can be controlled with the high pressure of the refrigeration cycle stably controlled to a desired target value. This allows for an improved convergence rate of the control of the high pressure of the refrigeration cycle, the degree of superheat of the refrigerant, and the gas cooler outlet temperatures of the refrigerant at the utilization side heat exchangers ( 27 a, 27 b ).
  • a plurality of objects of control are concurrently controlled, thereby concurrently controlling the predetermined physical value of the refrigeration apparatus, and the high pressure of the refrigeration cycle. Therefore, the predetermined physical value, and the high pressure of the refrigeration cycle can be controlled concurrently while concurrently considering the predetermined physical value and the high pressure of the refrigeration cycle, and considering the effect of the plurality of objects of control on the predetermined physical value and the high pressure of the refrigeration cycle. This allows for an improved convergence rate of the control of the predetermined physical value and the high pressure of the refrigeration apparatus.
  • control signals for controlling the plurality of objects of control are generated by associating the input predetermined physical value and high pressure of the refrigeration cycle with each other. Therefore, a control signal for one of the objects of control can be generated in concurrent consideration of the predetermined physical value and the high pressure, and in consideration of the effect of adjustment of the other objects of control on the predetermined physical value and the high pressure. This allows for an improved convergence rate of the control of the predetermined physical value and the high pressure of the refrigeration apparatus.
  • two objects of control i.e., the compression mechanism ( 21 ) and the expansion mechanism ( 24 ) are concurrently controlled in the heating operation, thereby concurrently controlling the high pressure of the refrigeration cycle, and the degree of superheat of the refrigerant. This allows for an improved convergence rate of the control of the high pressure of the refrigeration cycle, and the degree of superheat of the refrigerant.
  • four objects of control i.e., the first and second compressors ( 21 a, 21 b ), and the first and second expansion mechanisms ( 24 , 26 ), are concurrently controlled in the cooling operation in the refrigeration apparatus for performing a two-stage compression refrigeration cycle, thereby concurrently controlling the high pressure of the refrigeration cycle, the evaporating temperature of the refrigerant, the degree of superheat of the refrigerant, and the intermediate pressure of the refrigeration cycle.
  • This allows for an improved convergence rate of the control of the high pressure of the refrigeration cycle, the evaporating temperature of the refrigerant, the degree of superheat of the refrigerant, and the intermediate pressure of the refrigeration cycle.
  • four objects of control i.e., the first and second compressors ( 21 a, 21 b ), and the first and second expansion mechanisms ( 24 , 26 ), are concurrently controlled in the heating operation in the refrigeration apparatus for performing the two-stage compression refrigeration cycle, thereby concurrently controlling the high pressure of the refrigeration cycle, the evaporating temperature of the refrigerant, the degree of superheat of the refrigerant, and the gas cooler outlet temperature.
  • This allows for an improved convergence rate of the control of the high pressure of the refrigeration cycle, the evaporating temperature of the refrigerant, the degree of superheat of the refrigerant, and the gas cooler outlet temperature.
  • FIG. 1 is a piping diagram illustrating the structure of an air conditioner of a first embodiment.
  • FIG. 2 is a control block diagram of a controller in cooling operation.
  • FIG. 3 is a control block diagram of the controller in heating operation.
  • FIG. 6 is a control block diagram of the controller in heating operation.
  • FIG. 7 is a piping diagram illustrating the structure of an air conditioner of a third embodiment.
  • FIG. 9 is a control block diagram of the controller in heating operation.
  • FIG. 10 is a piping diagram illustrating the structure of an air conditioner of another embodiment.
  • FIG. 11 is a piping diagram illustrating the structure of an air conditioner of still another embodiment.
  • an air conditioner ( 10 ) of the present embodiment includes a refrigerant circuit ( 20 ), and a controller ( 40 ).
  • the refrigerant circuit ( 20 ) is a closed circuit filled with carbon dioxide (CO 2 ) as a refrigerant.
  • the refrigerant circuit ( 20 ) is configured to perform a vapor compression refrigeration cycle by circulating the refrigerant. Further, the refrigerant circuit ( 20 ) is configured to perform a supercritical refrigeration cycle in which a high pressure is equal to or higher than a supercritical pressure of carbon dioxide (i.e., a refrigeration cycle in which a vapor pressure is equal to or higher than a supercritical temperature of carbon dioxide).
  • the refrigerant circuit ( 20 ) connects a compressor ( 21 ), a four way switching valve ( 22 ), an outdoor heat exchanger ( 23 ), an outdoor expansion valve ( 24 ), and an indoor heat exchanger ( 27 ).
  • a discharge side of the compressor ( 21 ) is connected to a first port of the four way switching valve ( 22 ), and a suction side of the compressor ( 21 ) is connected to a second port of the four way switching valve ( 22 ).
  • the outdoor heat exchanger ( 23 ), the outdoor expansion valve ( 24 ), and the indoor heat exchanger ( 27 ) are sequentially arranged in a path from a third port to a fourth port of the four way switching valve ( 22 ).
  • the compressor ( 21 ) is configured as a fully sealed variable capacity compressor.
  • the compressor ( 21 ) sucks and compresses the refrigerant (carbon dioxide) to a supercritical pressure or higher, and then discharges the compressed refrigerant.
  • Changing a frequency of AC fed to a motor (not shown) of the compressor ( 21 ) changes a rotation speed, i.e., a capacity, of the compressor ( 21 ).
  • the compressor ( 21 ) constitutes a compression mechanism.
  • outdoor heat exchanger ( 23 ) outdoor air sucked by an outdoor fan ( 28 ) exchanges heat with the refrigerant.
  • indoor heat exchanger ( 27 ) indoor air sucked by an indoor fan ( 29 ) exchanges heat with the refrigerant.
  • the outdoor heat exchanger ( 23 ) constitutes a heat source side heat exchanger
  • the indoor heat exchanger ( 27 ) constitutes a utilization side heat exchanger.
  • the outdoor fan ( 28 ) constitutes a heat source side fan.
  • the four way switching valve ( 22 ) is switchable between a first state where the first and third ports communicate with each other, and the second and fourth ports communicate with each other (a state indicated by a solid line in FIG. 1 ), and a second state where the first and fourth ports communicate with each other, and the second and third ports communicate with each other (a state indicated by a broken line in FIG. 1 ).
  • the air conditioner ( 10 ) is able to switchably perform cooling operation and heating operation by switching the four way switching valve ( 22 ).
  • the four way switching valve ( 22 ) is set to the first state.
  • the outdoor heat exchanger ( 23 ) functions as a radiator (a gas cooler), and the indoor heat exchanger ( 27 ) functions as an evaporator to perform the refrigeration cycle.
  • the refrigerant in the supercritical state discharged from the compressor ( 21 ) flows into the outdoor heat exchanger ( 23 ), and dissipates heat to the outdoor air.
  • the refrigerant expands (decreases in pressure) as it passes through the outdoor expansion valve ( 24 ), and then flows into the indoor heat exchanger ( 27 ).
  • the refrigerant in the indoor heat exchanger ( 27 ) absorbs heat from the indoor air to evaporate, and the cooled indoor air is fed to the inside of the room.
  • the evaporated refrigerant is sucked into and compressed in the compressor ( 21 ).
  • the four way switching valve ( 22 ) is set to the second state.
  • the indoor heat exchanger ( 27 ) functions as a radiator (a gas cooler), and the outdoor heat exchanger ( 23 ) functions as an evaporator to perform the refrigeration cycle.
  • the refrigerant in the supercritical state discharged from the compressor ( 21 ) flows into the indoor heat exchanger ( 27 ), and dissipates heat to the indoor air.
  • the heated indoor air is fed to the inside of the room.
  • the refrigerant expands (decreases in pressure) as it passes through the outdoor expansion valve ( 24 ).
  • the refrigerant expanded by the outdoor expansion valve ( 24 ) flows into the outdoor heat exchanger ( 23 ), and absorbs heat from the outdoor air to evaporate.
  • the evaporated refrigerant is sucked into and compressed in the compressor ( 21 ).
  • the refrigerant circuit ( 20 ) includes an outdoor temperature sensor ( 30 ), an indoor temperature sensor ( 31 ), a low pressure sensor ( 32 ), a discharge temperature sensor ( 33 ), a high pressure sensor ( 34 ), a gas cooler outlet temperature sensor ( 37 ) for the heating operation, and a gas cooler outlet temperature sensor ( 39 ) for the cooling operation.
  • the outdoor temperature sensor ( 30 ) is a temperature sensing part for sensing the temperature of the outdoor air entering the outdoor heat exchanger ( 23 ).
  • the indoor temperature sensor ( 31 ) is a temperature sensing part for sensing the temperature of the indoor air entering the indoor heat exchanger ( 27 ).
  • the low pressure sensor ( 32 ) is a pressure sensing part for sensing the pressure of the refrigerant sucked into the compressor ( 21 ), i.e., the low pressure of the refrigeration cycle in the refrigerant circuit ( 20 ).
  • the discharge temperature sensor ( 33 ) is a temperature sensing part for sensing the temperature of the refrigerant discharged from the compressor ( 21 ).
  • the high pressure sensor ( 34 ) is a pressure sensing part for sensing the pressure of the refrigerant discharged from the compressor ( 21 ), i.e., the high pressure of the refrigeration cycle in the refrigerant circuit ( 20 ).
  • the gas cooler outlet temperature sensor ( 37 ) for the heating operation is a temperature sensing part for sensing the temperature of the refrigerant at an outlet of the indoor heat exchanger ( 27 ) when the refrigerant circulates in the refrigerant circuit ( 20 ) in a heating cycle.
  • the controller ( 40 ) is configured to receive output signals from the indoor temperature sensor ( 31 ), the low pressure sensor ( 32 ), the discharge temperature sensor ( 33 ), and the high pressure sensor ( 34 ), and to control an operation frequency of the compressor ( 21 ), the degree of opening of the outdoor expansion valve ( 24 ), and an operation frequency of the outdoor fan ( 28 ).
  • the controller ( 40 ) functions as a control section.
  • the target low pressure calculator ( 41 ) calculates the target low pressure P 1 s based on a temperature deviation et between a set temperature Ts and the output signal from the indoor temperature sensor ( 31 ) (i.e., an indoor temperature Ta).
  • the target discharge temperature calculator ( 43 ) calculates the target discharge temperature T 1 s based on the temperature deviation et, the output signal from the low pressure sensor ( 32 ) (i.e., an actual low pressure P 1 ), the output signal from the high pressure sensor ( 34 ) (i.e., an actual high pressure Ph), an operation frequency fc of the compressor ( 21 ), and the outdoor temperature TO. More specifically, the target discharge temperature calculator ( 43 ) calculates the target discharge temperature T 1 s corresponding to a target degree of superheat based on the temperature deviation et, the actual low pressure P 1 , the actual high pressure Ph, the operation frequency fc of the compressor ( 21 ), and the outdoor temperature T 0 .
  • the target low pressure calculator ( 41 ), the target high pressure calculator ( 42 ), and the target discharge temperature calculator ( 43 ) have maps and functions, respectively. Each of the calculators is configured to deliver an output value (a target value) corresponding to the input.
  • the control signal generator ( 49 ) has a plurality of PID control sections (p 1 a, p 2 a, . . . , p 1 b, p 2 b, . . . ) each having a control parameter corresponding to the input signal.
  • the control signal generator ( 49 ) receives a low pressure deviation el between the target low pressure P 1 s calculated by the target low pressure calculator ( 41 ) and the actual low pressure P 1 from the low pressure sensor ( 32 ), a high pressure deviation e 2 between the target high pressure Phs calculated by the target high pressure calculator ( 42 ) and the actual high pressure Ph from the high pressure sensor ( 34 ), and a discharge temperature deviation e 3 between the target discharge temperature T 1 s calculated by the target discharge temperature calculator ( 43 ) and the output signal from the discharge temperature sensor ( 33 ) (i.e., an actual discharge temperature T 1 ).
  • Each of the first to ninth PID control sections (p 1 a, p 2 a, . . . ) delivers an output generated by multiplying the input deviation by a predetermined control parameter.
  • the control signal generator ( 49 ) generates a compressor frequency control signal ⁇ fc by adding the output signals from the first, fourth, and seventh PID control sections (p 1 a, p 4 a, p 7 a ), generates an expansion valve control signal ⁇ ev by adding the output signals from the second, fifth, and eighth PID control sections (p 2 a, p 5 a, p 8 a ), and generates a fan frequency control signal ⁇ ff by adding the output signals from the third, sixth, and ninth PID control sections (p 3 a, p 6 a, p 9 a ).
  • the compressor frequency control signal ⁇ fc, the expansion valve control signal ⁇ ev, and the fan frequency control signal ⁇ ff generated in this manner are output to the air conditioner ( 10 ).
  • a frequency of AC fed to the motor of the compressor ( 21 ) (i.e., the operation frequency) is set to a value corresponding to the compressor frequency control signal ⁇ fc, thereby changing the rotation speed of the compressor ( 21 ).
  • the capacity of the compressor ( 21 ) varies according to the compressor frequency control signal ⁇ fc.
  • a pulse number of the signal fed to the pulse motor of the outdoor expansion valve ( 24 ) is set to a value corresponding to the expansion valve control signal ⁇ ev.
  • the pulse motor of the outdoor expansion valve ( 24 ) rotates by an angle corresponding to the pulse number, thereby adjusting the degree of opening of the valve according to the expansion valve control signal ⁇ ev.
  • a frequency of AC fed to the motor of the outdoor fan ( 28 ) (i.e., the operation frequency) is set to a value corresponding to the fan frequency control signal ⁇ ff, thereby changing the rotation speed of the outdoor fan ( 28 ).
  • a flow rate of air fed from the outdoor fan ( 28 ) to the outdoor heat exchanger ( 23 ) varies according to the fan frequency control signal ⁇ ff.
  • the low pressure P 1 , the discharge temperature T 1 , and the high pressure Ph of the air conditioner ( 10 ) operated in this operation state are fed back to the controller ( 40 ) through the low pressure sensor ( 32 ), the discharge temperature sensor ( 33 ), and the high pressure sensor ( 34 ).
  • the controller ( 40 ) performs feed back control to set the low pressure P 1 (and an evaporating temperature), the discharge temperature T 1 (and the degree of superheat), and the high pressure Ph to the target values corresponding to the operation state, respectively.
  • each of the compressor frequency control signal ⁇ fc, the expansion valve control signal ⁇ ev, and the fan frequency control signal ⁇ ff is generated by associating the low pressure deviation e 1 , the high pressure deviation e 2 , and the discharge temperature deviation e 3 with each other.
  • the discharge temperature of the refrigerant is controlled by the outdoor expansion valve ( 24 )
  • the high pressure of the refrigeration cycle is controlled by the outdoor fan ( 28 )
  • objects of the control corresponding to the physical values, respectively, are not controlled independently.
  • each of the objects of the control i.e., the compressor ( 21 ), the outdoor expansion valve ( 24 ), and the outdoor fan ( 28 ) is controlled not only based on the changes of the low pressure, the high pressure, and the discharge temperature resulting from the control solely of the each of the objects of control, but is controlled based on the changes of the low pressure, the high pressure, and the discharge temperature resulting from the control of the other objects of control (in other words, the control parameters of the first to nine PID control sections (p 1 a, p 2 a, . . . ) are determined so as to take these changes into account).
  • control signal generator ( 49 ) receives the high pressure deviation e 2 between the target high pressure Phs calculated by the target high pressure calculator ( 42 ) and the actual high pressure Ph from the high pressure sensor ( 34 ), and the discharge temperature deviation e 3 between the target discharge temperature T 1 s calculated by the target discharge temperature calculator ( 43 ) and the actual discharge temperature T 1 of the discharge temperature sensor ( 33 ).
  • the control signal generator ( 49 ) In the heating operation, four PID control sections (p 1 b, p 2 b, . . . ) of the control signal generator ( 49 ) are operated. Specifically, the discharge temperature deviation e 3 input to the control signal generator ( 49 ) is input to the first and second PID control sections (p 1 b, p 2 b ), and the high pressure deviation e 2 is input to the third and fourth PID control sections (p 3 b, p 4 b ).
  • Each of the first to fourth PID control sections (p 1 b, p 2 b, . . . ) delivers an output generated by multiplying the input deviation by a predetermined control parameter.
  • the control signal generator ( 49 ) generates the compressor frequency control signal ⁇ fc by adding the output signals from the first and third PID control sections (p 1 b, p 3 b ), and generates the expansion valve control signal ⁇ ev by adding the output signals from the second and fourth PID control sections (p 2 b, p 4 b ).
  • the compressor frequency control signal ⁇ fc and the expansion valve control signal ⁇ ev generated in this manner are output to the air conditioner ( 10 ).
  • the capacity of the compressor ( 21 ) varies according to the compressor frequency control signal ⁇ fc, and the degree of opening of the outdoor expansion valve ( 24 ) is adjusted according to the expansion valve control signal ⁇ ev.
  • each of the compressor frequency control signal ⁇ fc and the expansion valve control signal ⁇ ev are generated by associating the high pressure deviation e 2 and the discharge temperature deviation e 3 with each other.
  • the objects of control corresponding to the physical values, respectively are not controlled independently.
  • the compressor ( 21 ) and the outdoor expansion valve ( 24 ) are concurrently controlled, thereby concurrently, or simultaneously controlling the high pressure and the discharge temperature.
  • each of the high pressure and the discharge temperature is not controlled by only one of the compressor ( 21 ) and the outdoor expansion valve ( 24 ), but is controlled by both of the compressor ( 21 ) and the outdoor expansion valve ( 24 ). More specifically, each of the objects of control, i.e., the compressor ( 21 ) and the outdoor expansion valve ( 24 ), is controlled not only based on the changes of the high pressure and the discharge temperature resulting solely from the control of the each of the objects of control, but is controlled based on the changes of the high pressure and the discharge temperature resulting from the control of the other objects of control (in other words, the control parameters of the first to fourth PID control sections (p 1 b, p 2 b, . . . ) are determined so as to take these changes into account).
  • three physical values i.e., the low pressure, the high pressure, and the discharge temperature
  • three objects of control i.e., the compressor ( 21 ), the outdoor expansion valve ( 24 ), and the outdoor fan ( 28 )
  • two physical values i.e., the high pressure and the discharge temperature
  • two objects of control i.e., the compressor ( 21 ) and the outdoor expansion valve ( 24 ).
  • some of the objects of control easily have an effect on the physical values, but some do not. That is, even when one of the objects of control is changed, some physical values are less susceptible to the change.
  • all the physical values to be controlled are input, and they are associated with each other to generate control signals each corresponding to the objects of control.
  • the degree of association of the certain physical value may be reduced or eliminated (specifically, among the PID control sections (p 1 a, p 1 b, . . .) for generating the control signal for the object of control to which a certain physical value is less susceptible, a control parameter of one of the PID control sections corresponding to the certain physical value may be reduced or reduced to zero).
  • An air conditioner ( 210 ) of the second embodiment is different from the air conditioner ( 10 ) of the first embodiment in that two expansion valves ( 24 , 26 ) are provided between an outdoor heat exchanger ( 23 ) and an indoor heat exchanger ( 27 ) of a refrigerant circuit ( 220 ), and that two compressors ( 21 a, 21 b ) are provided to perform a two-stage compression refrigeration cycle.
  • the air conditioner ( 210 ) includes a refrigerant circuit ( 220 ), and a controller ( 240 ).
  • the outdoor heat exchanger ( 23 ), the outdoor expansion valve ( 24 ), the gas-liquid separator ( 25 ), the indoor expansion valve ( 26 ), and the indoor heat exchanger ( 27 ) are sequentially arranged in a path from a third port to a fourth port of the four way switching valve ( 22 ).
  • the gas-liquid separator ( 25 ) is connected to the pipe connecting the first compressor ( 21 a ) and the second compressor ( 21 b ) through a first intermediate pressure refrigerant pipe ( 25 a ).
  • the first and second compressors ( 21 a, 21 b ) are the same as the compressor of the first embodiment.
  • the first and second compressors ( 21 a, 21 b ) constitute a compression mechanism.
  • Each of the outdoor expansion valve ( 24 ) and the indoor expansion valve ( 26 ) is comprised of an electronic expansion valve whose degree of opening is variable, and whose valve element (not shown) is driven by a pulse motor (not shown).
  • the outdoor expansion valve ( 24 ) constitutes a first expansion mechanism
  • the indoor expansion valve ( 26 ) constitutes a second expansion mechanism.
  • the gas-liquid separator ( 25 ) is a longitudinal, cylindrical hermetic container.
  • the gas-liquid separator ( 25 ) is connected to the outdoor expansion valve ( 24 ) and the indoor expansion valve ( 26 ) through a bridge circuit ( 50 ).
  • the other end of the refrigerant inlet pipe ( 25 d ) penetrates an upper surface of the hermetic container serving as the gas-liquid separator ( 25 ), and is positioned in an upper portion of space inside the container.
  • An end of a refrigerant outlet pipe ( 25 e ) is connected to a fourth terminal of the bridge circuit ( 50 ), and the other end of the refrigerant outlet pipe ( 25 e ) is connected to the gas-liquid separator ( 25 ).
  • the other end of the refrigerant outlet pipe ( 25 e ) penetrates the upper surface of the hermetic container of the gas-liquid separator ( 25 ), and is positioned in a lower portion of the space inside the container.
  • the four way switching valve ( 22 ) is set to the first state.
  • the outdoor heat exchanger ( 23 ) functions as a radiator (a gas cooler), and the indoor heat exchanger ( 27 ) functions as an evaporator to perform the refrigeration cycle.
  • an intermediate pressure refrigerant discharged from the first compressor ( 21 a ) is compressed in the second compressor ( 21 b ) to the supercritical state.
  • the supercritical refrigerant flows into the outdoor heat exchanger ( 23 ), and dissipates heat to the outdoor air.
  • the intermediate pressure gaseous refrigerant flows from the upper portion in the space inside the gas-liquid separator ( 25 ) to the suction side of the second compressor ( 21 b ) through the first intermediate pressure refrigerant pipe ( 25 a ), merges with the intermediate pressure gaseous refrigerant discharged from the first compressor ( 21 a ), and is sucked into the second compressor ( 21 b ).
  • the intermediate pressure liquid refrigerant is temporarily stored in the lower portion of the space inside the gas-liquid separator ( 25 ), and then exits from the lower portion of the space to pass through the refrigerant outlet pipe ( 25 e ), the bridge circuit ( 50 ), and the third intermediate pressure refrigerant pipe ( 25 c ).
  • the intermediate pressure liquid refrigerant expands (decreases in pressure) in the indoor expansion valve ( 26 ) to become a gas-liquid two phase low pressure refrigerant, and flows into the indoor heat exchanger ( 27 ).
  • the indoor heat exchanger ( 27 ) the refrigerant absorbs heat from the indoor air to evaporate, and the cooled indoor air is fed to the inside of the room. The evaporated refrigerant is sucked into and compressed in the first compressor ( 21 a ).
  • the four way switching valve ( 22 ) is set to the second state.
  • the indoor heat exchanger ( 27 ) functions as a radiator (a gas cooler), and the outdoor heat exchanger ( 23 ) functions as an evaporator to perform the refrigeration cycle.
  • an intermediate pressure gaseous refrigerant discharged from the first compressor ( 21 a ) is compressed in the second compressor ( 21 b ) to the supercritical state.
  • the supercritical refrigerant flows into the indoor heat exchanger ( 27 ), and dissipates heat to the indoor air.
  • the heated indoor air is fed to the inside of the room.
  • the intermediate pressure gaseous refrigerant flows from the upper portion of the space inside the gas-liquid separator ( 25 ) to the suction side of the second compressor ( 21 b ) through the first intermediate pressure refrigerant pipe ( 25 a ), merges with the intermediate pressure gaseous refrigerant discharged from the first compressor ( 21 a ), and is sucked into the second compressor ( 21 b ).
  • the intermediate pressure liquid refrigerant is temporarily stored in the lower portion of the space inside the gas-liquid separator ( 25 ), and then flows from the lower portion of the space to the outdoor expansion valve ( 24 ) through the refrigerant outlet pipe ( 25 e ), the bridge circuit ( 50 ), and the second intermediate pressure refrigerant pipe ( 25 b ).
  • the intermediate pressure liquid refrigerant expands (decreases in pressure) as it passes through the outdoor expansion valve ( 24 ) to become a gas-liquid two phase low pressure refrigerant, and flows into the outdoor heat exchanger ( 23 ).
  • the refrigerant absorbs heat from the outdoor air to evaporate.
  • the evaporated refrigerant is sucked into and compressed in the first compressor ( 21 a ).
  • the high pressure sensor ( 34 ) is a pressure sensing part for sensing the pressure of the refrigerant discharged from the second compressor ( 21 b ), i.e., the high pressure of the refrigeration cycle in the refrigerant circuit ( 220 ).
  • the suction temperature sensor ( 35 ) is a temperature sensing part for sensing the temperature of the refrigerant sucked into the first compressor ( 21 a ).
  • the intermediate pressure saturation temperature sensor ( 36 ) is arranged in the refrigerant outlet pipe ( 25 e ) connecting the bridge circuit ( 50 ) and the gas-liquid separator ( 25 ), and functions as a temperature sensing part for sensing the temperature of the intermediate pressure refrigerant, i.e., the intermediate pressure saturation temperature of the refrigeration cycle.
  • the gas cooler outlet temperature sensor ( 37 ) for the heating operation is a temperature sensing part for sensing the temperature of the refrigerant at an outlet of the indoor heat exchanger ( 27 ) when the refrigerant circulates in the refrigerant circuit ( 220 ) in a heating cycle.
  • the controller ( 240 ) is configured to receive output signals from the indoor temperature sensor ( 31 ), the low pressure sensor ( 32 ), the high pressure sensor ( 34 ), the suction temperature sensor ( 35 ), the intermediate pressure saturation temperature sensor ( 36 ), and the gas cooler outlet temperature sensor ( 37 ) for the heating operation, and to control the operation frequencies of the first and second compressors ( 21 a, 21 b ), and the degrees of opening of the outdoor and indoor expansion valves ( 24 , 26 ).
  • the controller ( 240 ) includes, as shown in FIGS. 5 and 6 , a target low pressure calculator ( 41 ) for calculating a target low pressure P 1 s which is a target value of the low pressure of the refrigeration cycle, a target high pressure calculator ( 42 ) for calculating a target high pressure Phs which is a target value of the high pressure of the refrigeration cycle, a target superheat degree calculator ( 44 ) for calculating the target degree of superheat SHs of the refrigerant which is a target value of the degree of superheat of the refrigerant, an actual superheat degree calculator ( 45 ) for calculating the actual degree of superheat SH of the refrigerant, a target intermediate pressure saturation temperature calculator ( 46 ) for calculating a target intermediate pressure saturation temperature T 3 s which is a target value of the intermediate pressure saturation temperature of the refrigerant, a target gas cooler outlet temperature calculator ( 47 ) for calculating a target gas cooler outlet temperature T 4 s which is a target value of the temperature of the ref
  • the target superheat degree calculator ( 44 ) calculates the target degree of superheat SHs of one of the outdoor heat exchanger ( 23 ) and the indoor heat exchanger ( 27 ) functioning as an evaporator based on a temperature deviation et between a set temperature Ts and an indoor temperature Ta from the indoor temperature sensor ( 31 ).
  • the target superheat degree calculator ( 44 ) calculates the target degree of superheat SHs based on the temperature deviation et and an outdoor temperature T 0 from the outdoor temperature sensor ( 30 ).
  • the actual superheat degree calculator ( 45 ) calculates the actual degree of superheat SH of the refrigerant at an outlet of a heat exchanger functioning as an evaporator of the outdoor heat exchanger ( 23 ) and the indoor heat exchanger ( 27 ) based on an actual low pressure P 1 from the low pressure sensor ( 32 ) and an actual suction temperature T 2 from the suction temperature sensor ( 35 ).
  • the target intermediate pressure saturation temperature calculator ( 46 ) calculates the target intermediate pressure saturation temperature T 3 s based on at least one of the outdoor temperature TO from the outdoor temperature sensor ( 30 ), the indoor temperature Ta from the indoor temperature sensor ( 31 ), an actual high pressure Ph from the high pressure sensor ( 34 ), the actual low pressure P 1 from the low pressure sensor ( 32 ), the target high pressure Phs calculated by the target high pressure calculator ( 42 ), and the target low pressure P 1 s calculated by the target low pressure calculator ( 41 ).
  • the target gas cooler outlet temperature calculator ( 47 ) calculates the target gas cooler outlet temperature T 4 s, which is a target value of the temperature of the refrigerant at the outlet of the indoor heat exchanger ( 27 ) when the indoor heat exchanger ( 27 ) functions as a radiator, based on the temperature deviation et.
  • the target superheat degree calculator ( 44 ), the actual superheat degree calculator ( 45 ), and the target intermediate pressure saturation temperature calculator ( 46 ) have maps and functions, respectively. Each of them is configured to deliver an output value (a target value) corresponding to the input.
  • the control signal generator ( 249 ) has a plurality of PID control sections (p 1 a, p 2 a, p 1 b, p 2 b, . . . ) each having a control parameter corresponding to the input signal.
  • the control signal generator ( 49 ) receives a low pressure deviation el between the target low pressure P 1 s calculated by the target low pressure calculator ( 41 ) and the actual low pressure P 1 from the low pressure sensor ( 32 ), a high pressure deviation e 2 between the target high pressure Phs calculated by the target high pressure calculator ( 42 ) and the actual high pressure Ph from the high pressure sensor ( 34 ), a superheat degree deviation e 4 between the target degree of superheat SHs calculated by the target superheat degree calculator ( 44 ) and the actual degree of superheat SH calculated by the actual superheat degree calculator ( 45 ), and an intermediate pressure saturation temperature deviation e 5 between the target intermediate pressure saturation temperature T 3 s calculated by the target intermediate pressure saturation temperature calculator ( 46 ) and the output signal from the intermediate pressure saturation temperature sensor ( 36 ) (i.e., an actual intermediate pressure saturation temperature T 3 ).
  • Each of the first to sixteenth PID control sections (p 1 c, p 2 c, . . . ) delivers an output generated by multiplying the input deviation by a predetermined control parameter.
  • the control signal generator ( 249 ) generates a first compressor frequency control signal ⁇ fc 1 by adding the output signals from the first, fifth, ninth, and thirteenth PID control sections (p 1 c, p 5 c, p 9 c, p 13 c ), generates a second compressor frequency control signal ⁇ fc 2 by adding the output signals from the second, sixth, tenth, and fourteenth PID control sections (p 2 c, p 6 c, p 10 c, p 14 c ), generates an outdoor expansion valve control signal ⁇ ev 1 by adding the output signals from the third, seventh, eleventh, and fifteenth PID control sections (p 3 c, p 7 c, p 11 c, p 15 c ), and generates an indoor expansion valve control signal ⁇ ev
  • the capacity of the first compressor ( 21 a ) varies to a value corresponding to the first compressor frequency control signal Me 1
  • the capacity of the second compressor ( 21 b ) varies to a value corresponding to the second compressor frequency control signal ⁇ fc 2 .
  • the degree of opening of the outdoor expansion valve ( 24 ) is adjusted according to the outdoor expansion valve control signal ⁇ ev 1
  • the degree of opening of the indoor expansion valve ( 26 ) is also adjusted according to the indoor expansion valve control signal ⁇ ev 2 .
  • each of the first and second compressor frequency control signals ⁇ fc 1 and ⁇ fc 2 , and the outdoor and indoor expansion valve control signals ⁇ ev 1 and ⁇ ev 2 are generated by associating the low pressure deviation e 1 , the high pressure deviation e 2 , the superheat degree deviation e 4 , and the intermediate pressure saturation temperature deviation e 5 with each other.
  • the objects of control each corresponding to the physical values are not controlled independently, but the first and second compressors ( 21 a, 21 b ), and the outdoor and indoor expansion valves ( 24 , 26 ) are controlled concurrently, thereby concurrently, or simultaneously controlling the low pressure, the high pressure, the degree of superheat, and the intermediate pressure saturation temperature.
  • each of the objects of control i.e., the first and second compressors ( 21 a, 21 b ), and the outdoor and indoor expansion valves ( 24 , 26 ), is controlled not only based on the changes of the low pressure, the high pressure, the degree of superheat, and the intermediate pressure saturation temperature resulting solely from the control of the each of the objects of control, but is controlled based on the changes of the low pressure, the high pressure, the degree of superheat, and the intermediate pressure saturation temperature resulting from the control of the other objects of control (in other words, the control parameters of the first to sixteenth PID control sections (p 1 c, p 2 c, . . . ) are determined so as to take these changes into account).
  • sixteen PID control sections (p 1 d, p 2 d, . . . ) of the control signal generator ( 249 ) different from those operated in the cooling operation are operated.
  • the high pressure deviation e 2 input to the control signal generator ( 249 ) is input to the first to the fourth PID control sections (p 1 d -p 4 d )
  • the intermediate pressure saturation temperature deviation e 5 is input to the fifth to the eighth PID control sections (p 5 d -p 8 d )
  • the gas cooler outlet temperature deviation e 6 is input to the ninth to twelfth PID control sections (p 9 d -p 12 d )
  • the superheat degree deviation e 4 is input to the thirteenth to sixteenth PID control sections (p 13 d -p 16 d ).
  • the high pressure Ph, the suction temperature T 2 , the intermediate pressure saturation temperature T 3 , and the gas cooler outlet temperature T 4 in the air conditioner ( 210 ) operated in this operation state are fed back to the controller ( 240 ) through the high pressure sensor ( 34 ), the suction temperature sensor ( 35 ), the intermediate pressure saturation temperature sensor ( 36 ), and the gas cooler outlet temperature sensor ( 37 ) for the heating operation.
  • the controller ( 240 ) performs feed back control to set the high pressure Ph, the degree of superheat SH, the intermediate pressure saturation temperature T 3 , and the gas cooler outlet temperature T 4 to target values corresponding to the operation state, respectively.
  • each of the high pressure, the degree of superheat, the intermediate pressure saturation temperature, and the gas cooler outlet temperature is not controlled only by one of the first and second compressors ( 21 a, 21 b ), and the outdoor and indoor expansion valves ( 24 , 26 ), but is controlled by all the first and second compressors ( 21 a, 21 b ), and the outdoor and indoor expansion valves ( 24 , 26 ).
  • the plurality of objects of control e.g., the first compressor ( 21 a ), the outdoor expansion valve ( 24 ), etc.
  • the plurality of objects of control are simultaneously controlled in such a manner that the high pressure of the refrigeration cycle, and the predetermined physical value of the air conditioner ( 210 ) are adjusted to the predetermined target values corresponding to the operation state.
  • each of the objects of control is controlled in consideration of the changes of the physical value and the high pressure of the refrigeration cycle resulting from the control of the plurality of objects of control.
  • all the physical values to be controlled are input, and they are associated with each other to generate control signals each corresponding to the objects of control.
  • the degree of association of the certain physical value may be reduced or eliminated (specifically, among the PID control sections (p 1 c, p 1 d, . . . ) for generating the control signal for the object of control to which a certain physical value is less susceptible, a control parameter of one of the PID control sections corresponding to the certain physical value may be reduced or reduced to zero.
  • An air conditioner ( 310 ) of the third embodiment is different from the air conditioner ( 10 ) of the first embodiment in that a plurality of indoor heat exchangers ( 27 a, 27 b ) are provided in a refrigerant circuit ( 320 ).
  • the air conditioner ( 310 ) includes a refrigerant circuit ( 320 ), and a controller ( 340 ) as shown in FIG. 7 .
  • a discharge side of the compressor ( 21 ) is connected to a first port of the four way switching valve ( 22 ), and a suction side of the compressor ( 21 ) is connected to a second port of the four way switching valve ( 22 ).
  • the outdoor heat exchanger ( 23 ), the outdoor expansion valve ( 24 ), the receiver ( 25 ), the two indoor expansion valves ( 26 a, 26 b ), and the two indoor heat exchangers ( 27 a, 27 b ) are sequentially arranged in a path from a third port to a fourth port of the four way switching valve ( 22 ).
  • the first and second indoor heat exchangers ( 27 a, 27 b ) are provided with first and second indoor fans ( 29 a, 29 b ), respectively.
  • the air conditioner ( 310 ) is able to switchably perform cooling operation and heating operation by switching the four way switching valve ( 22 ).
  • the four way switching valve ( 22 ) is set to the first state.
  • the outdoor heat exchanger ( 23 ) functions as a radiator
  • the first and second indoor heat exchangers ( 27 a, 27 b ) function as evaporators to perform the refrigeration cycle.
  • the refrigerant in the supercritical state discharged from the compressor ( 21 ) flows into the outdoor heat exchanger ( 23 ), and dissipates heat to the outdoor air. After the heat dissipation, the refrigerant expands (decreases in pressure) as it passes through the outdoor expansion valve ( 24 ).
  • the expanded refrigerant passes through the receiver ( 25 ), and is branched, and the branched flows of the refrigerant pass through the first and second indoor expansion valves ( 26 a, 26 b ). At this time, the refrigerant further expands (decreases in pressure), and flows into the first and second indoor heat exchangers ( 27 a, 27 b ). That is, the refrigerant flowing between the outdoor expansion valve ( 24 ) and the indoor expansion valves ( 26 a, 26 b ), and in the receiver ( 25 ) is at an intermediate pressure. In the first and second indoor heat exchangers ( 27 a, 27 b ), the refrigerant absorbs heat from the indoor air to evaporate, and the cooled air is fed to the inside of the room. The evaporated refrigerant is sucked into and compressed in the compressor ( 21 ).
  • the four way switching valve ( 22 ) is set to the second state.
  • the first and second indoor heat exchangers ( 27 a, 27 b ) function as radiators
  • the outdoor heat exchanger ( 23 ) functions as an evaporator to perform the refrigeration cycle.
  • the refrigerant discharged from the compressor ( 21 ) in the supercritical state is branched, and the branched flows of the refrigerant enter the first and second indoor heat exchangers ( 27 a, 27 b ), respectively, and dissipate heat to the indoor air.
  • the heated indoor air is fed to the inside of the room.
  • the refrigerant expands (decreases in pressure) as it passes through the second indoor expansion valves ( 26 a, 26 b ).
  • the expanded refrigerant passes through the receiver ( 25 ), and then further expands (decreases in pressure) as it passes through the outdoor expansion valve ( 24 ). That is, the refrigerant flowing between the first and second indoor expansion valves ( 26 a, 26 b ) and the outdoor expansion valve ( 24 ), and in the receiver ( 25 ) is at the intermediate pressure.
  • the refrigerant expanded by the outdoor expansion valve ( 24 ) flows into the outdoor heat exchanger ( 23 ), and absorbs heat from the outdoor air to evaporate. The evaporated refrigerant is sucked into and compressed in the compressor ( 21 ).
  • the air conditioner ( 310 ) configured in this manner includes, in the refrigerant circuit ( 320 ), first and second indoor temperature sensors ( 31 a, 31 b ), a low pressure sensor ( 32 ), a high pressure sensor ( 34 ), a suction temperature sensor ( 35 ), first and second gas cooler outlet temperature sensors ( 37 a, 37 b ) for the heating operation, first and second evaporator outlet temperature sensors ( 38 a, 38 b ), and a gas cooler outlet temperature sensor ( 39 ) for the cooling operation.
  • the first and second indoor temperature sensors ( 31 a, 31 b ) are sensing parts for sensing the temperatures of the flows of the indoor air entering the first and second indoor heat exchangers ( 27 a, 27 b ), and are provided for the first and second indoor heat exchangers ( 27 a, 27 b ), respectively.
  • the first and second gas cooler outlet temperature sensors ( 37 a, 37 b ) for the heating operation are temperature sensing parts for sensing the temperatures of the refrigerant at the outlets of the first and second indoor heat exchangers ( 27 a, 27 b ), respectively, when the refrigerant circulates in the refrigerant circuit ( 320 ) in the heating cycle.
  • the controller ( 340 ) is configured to receive output signals from the first and second indoor temperature sensors ( 31 a, 31 b ), the low pressure sensor ( 32 ), the high pressure sensor ( 34 ), the suction temperature sensor ( 35 ), the first and second gas cooler outlet temperature sensors ( 37 a, 37 b ) for the heating operation, and the first and second evaporator outlet temperature sensors ( 38 a, 38 b ), and to control the operation frequency of the compressor ( 21 ), and the degrees of opening of the outdoor, first, and second indoor expansion valves ( 24 , 26 a, 26 b ).
  • the controller ( 340 ) includes, as shown in FIGS. 8 and 9 , a target low pressure calculator ( 41 ) for calculating a target low pressure P 1 s which is a target value of the low pressure of the refrigeration cycle, a target high pressure calculator ( 42 ) for calculating a target high pressure Phs which is a target value of the high pressure of the refrigeration cycle, an actual superheat degree calculator ( 45 ) for calculating the actual degree of superheat SH which is the actual degree of superheat of the refrigerant, a target first superheat degree calculator ( 44 a ) for calculating a target first degree of superheat SHas which is a target value of the degree of superheat of the refrigerant at the outlet of the first indoor heat exchanger ( 27 a ) in the cooling operation, a target second superheat degree calculator ( 44 b ) for calculating a target second degree of superheat SHbs which is a target value of the degree of superheat of the refrigerant at the outlet of the
  • the target low pressure calculator ( 41 ) calculates the target low pressure P 1 s of the air conditioner ( 310 ) as a whole based on a temperature deviation eta between a set temperature Tsa of the first indoor heat exchanger ( 27 a ) and an indoor temperature Taa from the first indoor temperature sensor ( 31 a ), and a temperature deviation etb between a set temperature Tsb of the second indoor heat exchanger ( 27 b ) and an indoor temperature Tab from the second indoor temperature sensor ( 31 b ).
  • the target high pressure calculator ( 42 ) calculates the target high pressure Phs of the air conditioner ( 310 ) based on an outdoor temperature TO from the outdoor temperature sensor ( 30 ), and a gas cooler outlet temperature T 4 from the gas cooler outlet temperature sensor ( 39 ) for the cooling operation.
  • the target second superheat degree calculator ( 44 b ) calculates the target second degree of superheat SHbs based on the temperature deviation etb of the second indoor heat exchanger ( 27 b ).
  • the actual superheat degree calculator ( 45 ) calculates the actual degree of superheat SH, which is the actual degree of superheat of the refrigerant at the outlet of the outdoor heat exchanger ( 23 ), based on the actual low pressure P 1 from the low pressure sensor ( 32 ), and the actual suction temperature T 2 from the suction temperature sensor ( 35 ).
  • the target first gas cooler outlet temperature calculator ( 47 a ) calculates the target first gas cooler outlet temperature T 4 as based on the temperature deviation eta of the first indoor heat exchanger ( 27 a ).
  • the target low pressure calculator ( 41 ), the target high pressure calculator ( 42 ), the target first superheat degree calculator ( 44 a ), the target second superheat degree calculator ( 44 b ), the target superheat degree calculator ( 44 ), the target first gas cooler outlet temperature calculator ( 47 a ), and the target second gas cooler outlet temperature calculator ( 47 b ) have maps and functions, respectively. Each of them is configured to output an output value corresponding to the input.
  • the control signal generator ( 349 ) has PID control sections (p 1 e, p 2 e, p 1 f, p 2 f, . . . ) each having a control parameter corresponding to the input signal.
  • the control signal generator ( 349 ) receives a low pressure deviation el between the target low pressure P 1 s calculated by the target low pressure calculator ( 41 ) and the actual low pressure P 1 from the low pressure sensor ( 32 ), a high pressure deviation e 2 between the target high pressure Phs calculated by the target high pressure calculator ( 42 ) and the actual high pressure Ph from the high pressure sensor ( 34 ), a first superheat degree deviation e 4 a between the target degree of superheat SHas calculated by the target first superheat degree calculator ( 44 a ) and the actual first degree of superheat SHa of the first indoor heat exchanger ( 27 a ) calculated by the actual superheat degree calculator ( 45 ), and the second superheat degree deviation e 4 b between the target degree of superheat SHbs calculated by the target second superheat degree calculator ( 44 b ) and the actual second degree of superheat SHb of the second indoor heat exchanger ( 27 b ) calculated by the actual superheat degree calculator ( 45 ).
  • sixteen PID control sections (p 1 e, p 2 e, . . . ) of the control signal generator ( 349 ) are operated. Specifically, the low pressure deviation el input to the control signal generator ( 349 ) is input to the first to fourth PID control sections (p 1 e -p 4 e ), the high pressure deviation e 2 is input to the fifth to eighth PID control sections (p 5 e -p 8 e ), the first superheat degree deviation e 4 a is input to the ninth to twelfth PID control sections (p 9 e -p 12 e ), and the second superheat degree deviation e 4 b is input to the thirteenth to sixteenth PID control sections (p 13 e -p 16 e ).
  • Each of the first to sixteenth PID control sections (p 1 e, p 2 e, . . . ) delivers an output generated by multiplying the input deviation by a predetermined control parameter.
  • the control signal generator ( 349 ) generates a compressor frequency control signal ⁇ fc by adding output signals from the first, fifth, ninth, and thirteenth PID control sections (p 1 e, p 5 e, p 9 e, p 13 e ), generates an outdoor expansion valve control signal ⁇ ev 1 by adding output signals from the second, sixth, tenth, and fourteenth PID control sections (p 2 e, p 6 e, p 10 e, p 14 e ), generates a first indoor expansion valve control signal ⁇ ev 2 a by adding output signals from the third, seventh, eleventh, and fifteenth PID control sections (p 3 e, p 7 e, p 11 e, p 15 e ), and generates a second indoor expansion valve control signal ⁇ ev 2
  • the compressor frequency control signal ⁇ fc, the outdoor expansion valve control signal ⁇ ev 1 , the first indoor expansion valve control signal ⁇ ev 2 a, and the second indoor expansion valve control signal ⁇ ev 2 b are output to the air conditioner ( 310 ).
  • the capacity of the compressor ( 21 ) varies to a value corresponding to the compressor frequency control signal ⁇ fc.
  • the low pressure P 1 , the high pressure Ph, the first evaporator outlet temperature T 5 a of the first indoor heat exchanger ( 27 a ), and the second evaporator outlet temperature T 5 b of the second indoor heat exchanger ( 27 b ) of the air conditioner ( 310 ) operated in this operation state are fed back to the controller ( 340 ) through the low pressure sensor ( 32 ), the high pressure sensor ( 34 ), and the first and second evaporator outlet temperature sensors ( 38 a, 38 b ).
  • the controller ( 340 ) performs feed back control to set the low pressure P 1 , the high pressure Ph, and the first and second degrees of superheat SHa and SHb to target values corresponding to the operation state, respectively.
  • each of the compressor frequency control signal ⁇ fc, and the outdoor, first indoor, and second indoor expansion valve control signals ⁇ ev 1 , ⁇ ev 2 a, and ⁇ ev 2 b is generated by associating the low pressure deviation e 1 , the high pressure deviation e 2 , the first superheat degree deviation e 4 a, and the second superheat degree deviation e 4 b with each other.
  • the objects of control each corresponding to the physical values are not controlled independently, but the compressor ( 21 ), the outdoor expansion valve ( 24 ), and the first and second indoor expansion valves ( 26 a, 26 b ) are controlled concurrently, thereby concurrently, or simultaneously controlling the low pressure, the high pressure, the first degree of superheat, and the second degree of superheat.
  • each of the low pressure, the high pressure, the first degree of superheat, and the second degree of superheat is not controlled only by one of the compressor ( 21 ), the outdoor expansion valve ( 24 ), and the first and second indoor expansion valves ( 26 a, 26 b ), but is controlled by all the compressor ( 21 ), the outdoor expansion valve ( 24 ), and the first and second indoor expansion valves ( 26 a, 26 b ).
  • each of the objects of control i.e., the compressor ( 21 ), the outdoor expansion valve ( 24 ), and the first and second indoor expansion valves ( 26 a, 26 b ) is not controlled not only based on the changes of the low pressure, the high pressure, the first degree of superheat, and the second degree of superheat resulting from the control of the each of the objects of control, but is controlled based on the changes of the low pressure, the high pressure, the first degree of superheat, and the second degree of superheat resulting from the control of the other objects of control (in other words, the control parameters of the first to sixteenth PID control sections (p 1 e, p 2 e, . . . ) are determined so as to take these changes into account).
  • the control signal generator ( 349 ) receives a high pressure deviation e 2 between the target high pressure Phs calculated by the target high pressure calculator ( 42 ) and the actual high pressure Ph from the high pressure sensor ( 34 ), a superheat degree deviation e 4 between the target degree of superheat SHs calculated by the target superheat degree calculator ( 44 ) and the actual degree of superheat SH calculated by the actual superheat degree calculator ( 45 ), a first gas cooler outlet temperature deviation e 6 a between the target first gas cooler outlet temperature T 4 as calculated by the target first gas cooler outlet temperature calculator ( 47 a ) and the actual first gas cooler outlet temperature T 4 a from the first gas cooler outlet temperature sensor ( 37 a ) for the heating operation, and a second gas cooler outlet temperature deviation e 6 b between the target second gas cooler outlet temperature T 4 bs calculated by the target second gas cooler outlet temperature calculator ( 47 b ) and the actual second gas cooler outlet temperature T 4 b from the second gas cooler outlet temperature sensor ( 37 b ) for the heating
  • sixteen PID control sections (p 1 f, p 2 f, . . . ) of the control signal generator ( 349 ) different from those operated in the cooling operation are operated.
  • the high pressure deviation e 2 input to the control signal generator ( 349 ) is input to the first to fourth PID control sections (p 1 f -p 4 f )
  • the first gas cooler outlet temperature deviation e 6 a is input to the fifth to the eighth PID control sections (p 5 f -p 8 f )
  • the second gas cooler outlet temperature deviation e 6 b is input to the ninth to the twelfth PID control sections (p 9 f -p 12 f )
  • the superheat degree deviation e 4 is input to the thirteenth to sixteenth PID control sections (p 13 f -p 16 f ).
  • Each of the first to sixteenth PID control sections (p 1 f, p 2 f, . . . ) delivers an output generated by multiplying the input deviation by a predetermined control parameter.
  • the control signal generator ( 349 ) generates a compressor frequency control signal ⁇ fc by adding output signals from the first, fifth, ninth, and thirteenth PID control sections (p 1 f, p 5 f, p 9 f, p 13 f ), generates an outdoor expansion valve control signal ⁇ ev 1 by adding output signals from the second, sixth, tenth, and fourteenth PID control sections (p 2 f, p 6 f, p 10 f, p 14 f ), generates a first indoor expansion valve control signal ⁇ ev 2 a by adding output signals from the third, seventh, eleventh, and fifteenth PID control sections (p 3 f, p 7 f, p 11 f, p 15 f ), and generates a second indoor expansion valve control signal ⁇ ev 2
  • the compressor frequency control signal ⁇ fc, the outdoor expansion valve control signal ⁇ ev 1 , the first indoor expansion valve control signal ⁇ ev 2 a, and the second indoor expansion valve control signal ⁇ ev 2 b generated in this manner are output to the air conditioner ( 310 ).
  • the capacity of the compressor ( 21 ) varies to a value corresponding to the compressor frequency control signal ⁇ fc.
  • the degree of opening of the outdoor expansion valve ( 24 ) is adjusted according to the outdoor expansion valve control signal ⁇ ev 1
  • the degree of the first indoor expansion valve ( 26 a ) is adjusted according to the first indoor expansion valve control signal ⁇ ev 2 a
  • the degree of opening of the second indoor expansion valve ( 26 b ) is adjusted according to the second indoor expansion valve control signal ⁇ ev 2 b.
  • Each of the compressor frequency control signal ⁇ fc, the outdoor expansion valve control signal ⁇ ev 1 , and the first and second indoor expansion valve control signals ⁇ ev 2 a and ⁇ ev 2 b is generated by associating the high pressure deviation e 2 , the superheat degree deviation e 4 , the first gas cooler outlet temperature deviation e 6 a, and the second gas cooler outlet temperature deviation e 6 b with each other.
  • the objects of control each corresponding to the physical values are not controlled independently, but the compressor ( 21 ), the outdoor expansion valve ( 24 ), and the first and second indoor expansion valves ( 26 a, 26 b ), are controlled concurrently, thereby concurrently, or simultaneously controlling the high pressure, the degree of superheat, the first gas cooler outlet temperature, and the second gas cooler outlet temperature.
  • each of the high pressure, the degree of superheat, the first gas cooler outlet temperature, and the second gas cooler outlet temperature is not controlled only by one of the compressor ( 21 ), the outdoor expansion valve ( 24 ), and the first and second indoor expansion valves ( 26 a, 26 b ), but is controlled by all the compressor ( 21 ), the outdoor expansion valve ( 24 ), and the first and second indoor expansion valves ( 26 a, 26 b ).
  • the objects of control i.e., the compressor ( 21 ), the outdoor expansion valve ( 24 ), and the first and second indoor expansion valves ( 26 a, 26 b ) is controlled not only based on the changes of the high pressure, the degree of superheat, the first gas cooler outlet temperature, and the second gas cooler outlet temperature resulting from the control of the each of the objects of control, but is controlled based on the changes of the high pressure, the degree of superheat, the first and second gas cooler outlet temperatures resulting from the control of the other objects of control (in other words, the control parameters of the first to sixteenth PID control sections (p 1 f, p 2 f, . . . ) are determined so as to take these changes into account).
  • the plurality of objects of control e.g., the compressor ( 21 ), the outdoor expansion valve ( 24 ), etc.
  • the predetermined physical value of the air conditioner ( 310 ) are adjusted to the predetermined target values corresponding to the operation state.
  • each of the objects of control is controlled in consideration of the changes of the physical value and the high pressure of the refrigeration cycle resulting from the control of the plurality of objects of control.
  • the capability of the air conditioner ( 310 ) e.g., the low pressure, the degree of superheat, etc. in the cooling operation
  • the capability of the air conditioner ( 310 ) can be controlled with the high pressure stably kept to the target value corresponding to the operation state.
  • four physical values i.e., the low pressure, the high pressure, the first degree of superheat, and the second degree of superheat, are controlled by the four objects of control, i.e., the compressor ( 21 ), the outdoor expansion valve ( 24 ), and the first and second indoor expansion valves ( 26 a, 26 b ), in the cooling operation.
  • four physical values i.e., the high pressure, the first gas cooler outlet temperature, the second gas cooler outlet temperature, and the degree of superheat, are controlled by four objects of control, i.e., the compressor ( 21 ), the outdoor expansion valve ( 24 ), and the first and second indoor expansion valves ( 26 a, 26 b ).
  • some of the objects of control easily have an effect on the physical values, but some do not. That is, even when one of the objects of control is changed, some physical values are less susceptible to the change.
  • all the physical values to be controlled are input, and they are associated with each other to generate control signals each corresponding to the objects of control.
  • the degree of association of the certain physical value may be reduced or eliminated (specifically, among the PID control sections (p 1 e, p 1 f, . . . ) for generating the control signal for the object of control to which a certain physical value is less susceptible, a control parameter of one of the PID control sections corresponding to the certain physical value may be reduced or reduced to zero).
  • the control signals for the first and second compressors ( 21 a, 21 b ), the first and second indoor expansion valves ( 26 a, 26 b ), and the outdoor expansion valve ( 24 ) are generated, i.e., the first and second compressors ( 21 a, 21 b ), the first and second indoor expansion valves ( 26 a, 26 b ), and the outdoor expansion valve ( 24 ) are controlled, in such a manner that the high pressure, the low pressure, the first evaporator outlet temperature, the second evaporator outlet temperature, and the intermediate pressure saturation temperature are set to predetermined target values, respectively, when adjustment of all the first and second compressors ( 21 a, 21 b ), the first and second indoor expansion valves ( 26 a, 26 b ), and the outdoor expansion valve ( 24 ) is done.
  • the disclosed technique may be applied to a multi-type air conditioner ( 510 ) which performs a two-stage compression refrigeration cycle, and includes an internal heat exchanger ( 51 ) between the outdoor heat exchanger ( 23 ) and the outdoor expansion valve ( 24 ), and a plurality of indoor units.
  • a multi-type air conditioner ( 510 ) which performs a two-stage compression refrigeration cycle, and includes an internal heat exchanger ( 51 ) between the outdoor heat exchanger ( 23 ) and the outdoor expansion valve ( 24 ), and a plurality of indoor units.
  • an outdoor expansion valve ( 24 ) is provided in the connection pipe ( 52 ) to be positioned closer to the receiver ( 25 ) than to the junction with the bypass pipe ( 53 ).
  • a receiver pressure saturation temperature sensor ( 55 ) is arranged at the connection pipe ( 52 ) closer to the receiver ( 25 ) than to the outdoor expansion valve ( 24 ).
  • An intermediate pressure saturation temperature sensor ( 36 ) is arranged at the bypass pipe ( 53 ) downstream of the internal heat exchanger ( 51 ).
  • the air conditioner ( 510 ) configured in this manner, for example, the high pressure, the low pressure, the first evaporator outlet temperature, the second evaporator outlet temperature, the intermediate pressure saturation temperature, and an internal pressure of the receiver sensed by the receiver pressure saturation temperature sensor ( 55 ) are input, and these physical values are associated with each other to generate control signals for controlling the first and second compressors ( 21 a, 21 b ), the first and second indoor expansion valves ( 26 a, 26 b ), the outdoor expansion valve ( 24 ), and the bypass expansion valve ( 54 ), respectively.
  • the control signals for the first and second compressors ( 21 a, 21 b ), the first and second indoor expansion valves ( 26 a, 26 b ), the outdoor expansion valve ( 24 ), and the bypass expansion valve ( 54 ), respectively, are generated, i.e., the first and second compressors ( 21 a, 21 b ), the first and second indoor expansion valves ( 26 a, 26 b ), the outdoor expansion valve ( 24 ), and the bypass expansion valve ( 54 ) are controlled in such a manner that the high pressure, the low pressure, the first evaporator outlet temperature, the second evaporator outlet temperature, the intermediate pressure saturation temperature, and the internal pressure of the receiver are set to the predetermined target values, respectively, when adjustment of all the first and second compressors ( 21 a, 21 b ), the first and second indoor expansion valves ( 26 a, 26 b ), the outdoor expansion valve ( 24 ), and the bypass expansion valve ( 54 ) is done.
  • two compressors ( 21 a, 21 b ), and two expansion valves ( 24 , 26 ) are provided to perform a two-stage compression refrigeration cycle.
  • a single compressor may be provided, and gas injection may be performed during the compression in the compressor.
  • the number of objects of control is three including the single compressor and the two expansion valves ( 24 , 26 ). Therefore, the number of physical values to be controlled is preferably three in total (including at least the high pressure of the refrigeration cycle).
  • a plurality of physical values is input, and outputs generated by multiplying the input physical values by control parameters, respectively, are added to generate a control signal for one object of control.
  • the disclosed technique is not limited to this configuration.
  • a plurality of physical values may be input, and they may be multiplied by a matrix constituted of the control parameters, to calculate a plurality of control signals as outputs based on a dynamic model of the refrigeration cycle in each of the refrigerant circuits.
  • the input physical values are associated with each other to generate the control signal for the objects of control.
  • concurrent control of the plurality of objects of control allows for concurrent control of the plurality of physical values, thereby allowing for an improved convergence rate of the control of each of the physical values.
  • the expansion valve is employed as the expansion mechanism.
  • the disclosed technique is not limited thereto, and an expansion unit may be used.
  • the outdoor fan ( 28 ) is controlled as the object of control.
  • the outdoor fan ( 28 ) may be used in combination to perform control of the high pressure and the capability of the apparatus.
  • Outdoor fan heat source side fan

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JP2007173372A JP2009014210A (ja) 2007-06-29 2007-06-29 冷凍装置
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EP2175212B1 (fr) 2020-02-12
EP2175212A4 (fr) 2014-10-08
CN101688700A (zh) 2010-03-31
AU2008272365A1 (en) 2009-01-08
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KR20100036345A (ko) 2010-04-07
JP2009014210A (ja) 2009-01-22

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