JP2015090226A - Freezer and method of controlling freezer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make compatible control over a pressure reducing mechanism for quick exiting from a predetermined gas-liquid two-phase state and normal stable control over the pressure reducing mechanism.SOLUTION: Indoor-side control devices 47, 57, and 67 are configured to control valve opening positions of indoor expansion valves 41, 51, and 61. When a current status quantity continuously has a predetermined value of overheating or overcooling at which output sides of respective indoor-side heat exchangers 42, 52, and 62 are determined to be in a gas-liquid two-phase state to exit from for a first set time or longer, the indoor-side control devices 47, 57, and 67 switch the control over valve opening positions from a first control state in which the control is normally performed not in the gas-liquid two-phase state to a second control state in which a speed of shifting the valve opening positions to smaller-opening positions is faster than that in the first control state.

Description

  The present invention relates to a refrigeration apparatus and a control method thereof, and more particularly to a refrigeration apparatus that performs a vapor compression refrigeration cycle by circulating a refrigerant and a control method thereof.

  A refrigerating apparatus such as an air conditioner has a compressor that compresses a refrigerant, a heat source side heat exchanger and a use side heat exchanger that perform heat exchange with the refrigerant, and a decompression mechanism that depressurizes the refrigerant. Is provided with a refrigerant circuit that performs a vapor compression refrigeration cycle by circulating the refrigerant. In such a refrigeration apparatus, for example, in order to improve the reliability of the compressor, it is important to suppress the liquid refrigerant sucked by the compressor. However, since it is difficult to directly detect the gas-liquid ratio of the refrigerant sucked by the compressor, the amount of liquid refrigerant sucked by the compressor is preferably detected from the state amount of the refrigerant circuit by detecting the state amount of the refrigerant circuit. An estimation is made as to whether or not a certain amount has not been reached.

  For example, in the air conditioner described in Patent Document 1 (Japanese Patent Laid-Open No. 10-38387), the first condition that the internal heat exchanger temperature (Te) of the indoor heat exchanger is 0 degrees or less, and the compressor If one of the second conditions that the discharge pipe temperature (Td) read this time is lower than the discharge pipe temperature (Td-1) read last time is satisfied, the motor-operated valve high-speed closing operation is controlled. An operation control device that performs control to enter is provided.

  The air conditioner described in Patent Document 2 (Japanese Patent Laid-Open No. 11-83205) is a case where the electronic expansion valve operates in the valve closing direction, and the discharge pipe temperature is equal to or higher than a predetermined value and the heat source. When the supply air volume to the side heat exchanger decreases rapidly and it is necessary to quickly close the electronic expansion valve to quickly shift to the optimal operating state, the electronic expansion valve can be connected to the electronic expansion valve regardless of the target operation amount. The expansion valve has a function of closing to a calculated opening obtained by multiplying the current opening of the expansion valve by a predetermined correction coefficient.

  However, when control such as the operation control apparatus of Patent Document 1 is performed, for example, even in a mild gas-liquid two-phase state in which the dryness is close to 1 and the ratio of liquid refrigerant in the refrigerant is small, the motorized valve speed is increased immediately. There is a possibility of entering into a closing operation, and in such a case, hunting may occur in which the valve opening and closing continues. Moreover, since the state determination of the conventional air-conditioning apparatus as described above is a look-ahead type (a type that is changed from the current state to a control suitable for a state that is estimated to occur in the future), a state that does not match the estimation occurs. For example, in the state judgment, the condition for changing the control is satisfied, but in reality, a state different from the estimated state may occur, and the situation may occur that inappropriate control change is performed from the result There is. In such a case, a sudden change of the control amount that is undesirable for the air conditioner occurs, and a problem that the state of the air conditioner becomes unstable is likely to occur.

  An object of the present invention is to detect that a predetermined gas-liquid two-phase state to be quickly escaped is generated at a specific predetermined position in a refrigeration apparatus that performs a vapor compression refrigeration cycle by circulating a refrigerant, and It is to achieve both the control of the decompression mechanism that promptly escapes from such a predetermined gas-liquid two-phase state and the control of the stable decompression mechanism during normal times.

  A refrigeration apparatus according to a first aspect of the present invention includes a compressor that compresses a refrigerant, a heat source side heat exchanger and a use side heat exchanger that perform heat exchange with the refrigerant, and a decompression of the refrigerant is adjusted by a valve opening degree. A refrigerant circuit that performs a vapor compression refrigeration cycle by circulating a refrigerant, and a use-side heat exchanger that is attached to the refrigerant circuit and is used to determine whether or not a gas-liquid two-phase state is used. A sensor for detecting the state quantity of the refrigerant in the refrigerant circuit in order to obtain the current state quantity at the outlet side of the heat source side heat exchanger or the suction side of the compressor, and the use side heat exchanger configured to be able to control the valve opening degree. Alternatively, when there is a continuation of the predetermined value of the current state quantity that can be judged to be in the gas-liquid two-phase state to be escaped at the outlet side of the heat source side heat exchanger or the suction side of the compressor for the first set time or longer. In addition, the control of the valve opening is not normally a gas-liquid two-phase state And a control device for the speed to reduce the valve opening is switched to the higher second control state than in the first control state from the first control state to be performed, but.

  In the refrigeration apparatus of the first aspect, since it is determined that the gas-liquid two-phase state should be escaped from the continuation of the predetermined value of the current state quantity for the first set time or longer, it is a gas-liquid two-phase state that does not need to escape. Nevertheless, it is possible to avoid making an erroneous determination that the gas-liquid two-phase state should be escaped promptly. This not only speeds up the escape from the gas-liquid two-phase state to be escaped, but also suppresses the switch to the second control state with a fast speed to reduce the valve opening in the gas-liquid two-phase state where it is not necessary to escape. Therefore, it is possible to prevent the occurrence of hunting by avoiding the second control state in which the valve opening is rapidly changed in the gas-liquid two-phase state that does not need to be escaped.

  The refrigeration apparatus according to the second aspect of the present invention is the refrigeration apparatus according to the first aspect, wherein the control device is a cooling unit as a predetermined value of the current state quantity for determining that it is a gas-liquid two-phase state to be escaped. Sometimes the condition that the calculated degree of superheat calculated for the refrigerant circuit is below the first threshold is used, or the condition that the calculated degree of supercooling calculated for the refrigerant circuit at the time of heating is below the second threshold is used , That is.

  In the refrigeration apparatus according to the second aspect, control is performed with the degree of superheat directly connected to the gas-liquid two-phase state during cooling, and control is performed with the degree of supercooling directly connected to the gas-liquid two-phase state during heating. It is possible to suppress erroneous determination that is not determined to be a gas-liquid two-phase state to be escaped even though the phase is in the state.

  A refrigeration apparatus according to a third aspect is the refrigeration apparatus according to the second aspect, wherein the control device is based on a deviation between the target superheat degree and the calculated superheat degree or a deviation between the target supercooling degree and the calculated subcooling degree in the first control state. PI control for changing the valve opening is performed, and in the second control state, the control is changed from PI control to control for reducing the valve opening based on the calculated degree of superheat or the calculated degree of supercooling.

  In the refrigeration apparatus of the third aspect, in the gas-liquid two-phase state, the deviation between the target superheat degree and the calculated superheat degree, or the deviation between the target supercooling degree and the calculated supercooling degree may be substantially equal to 0. However, it is possible to promptly escape from the gas-liquid two-phase state by reducing the valve opening based on the calculated degree of superheat or the calculated degree of supercooling.

  In the refrigeration apparatus according to the fourth aspect of the present invention, in the refrigeration apparatus according to the second aspect or the third aspect, the control device has a third threshold value smaller than the first threshold value during cooling even if the first set time has not elapsed. When the current state quantity is smaller than the fourth state, or when the current state quantity is smaller than the fourth threshold value that is smaller than the second threshold value during heating, the control of the valve opening degree is switched from the first control state to the second control state.

  In the refrigeration apparatus of the fourth aspect, a serious gas-liquid two-phase state that should be urgently escaped is obtained, and the current state quantity becomes smaller than the third threshold value that is smaller than the first threshold value during cooling, or the second state during heating. When the current state quantity becomes smaller than the fourth threshold value, which is smaller than the threshold value, it is possible to respond quickly without waiting for the first set time to elapse, and a serious gas-liquid two-phase state before the first set time elapses. Therefore, it is possible to prevent the occurrence of a problem that advances rapidly.

  The refrigeration apparatus according to the fifth aspect of the present invention is the refrigeration apparatus according to any one of the first to fourth aspects, wherein the control device switches to the second control state, and then the gas-liquid two to which the current state quantity is to escape. When the value is such that it can be determined that the phase state has been removed, the second control state is immediately switched to the first control state.

  In the refrigeration apparatus of the fifth aspect, it is better to control in the first control state when such a gas-liquid two-phase state is escaped than to the second control state to be used in the gas-liquid two-phase state to be escaped. Stabilize. In addition, even if the state immediately returns to the first control state, it is necessary to elapse the first set time to return to the second control state, so that hunting is also prevented.

  The refrigeration apparatus according to the sixth aspect of the present invention is the refrigeration apparatus according to the first to fifth aspects, wherein after the control device switches to the second control state, the gas-liquid should be allowed to escape for a predetermined second set time or more. When it is determined that the two-phase state has been continued, the control of the valve opening is switched to the third control state where the speed of reducing the valve opening is faster than that in the second control state.

  In the refrigeration apparatus of the sixth aspect, when it takes time to escape from the gas-liquid two-phase state even in the second control state, the escape from the gas-liquid two-phase state can be further accelerated in the third control state. When the state is insufficient, the escape time from the gas-liquid two-phase state can be shortened.

  A refrigeration apparatus according to a seventh aspect of the present invention is the refrigeration apparatus according to the sixth aspect, wherein the control device, in the third control state, increases the speed at which the valve opening is reduced stepwise according to the elapsed time. It is.

  In the refrigeration apparatus according to the seventh aspect, the speed at which the valve opening is reduced increases stepwise according to the elapsed time as time elapses in the third control state. It is possible to escape from the gas-liquid two-phase state more quickly than.

  The refrigeration apparatus according to the eighth aspect of the present invention is the refrigeration apparatus according to the seventh aspect, wherein the control device is configured such that the duration of each step is set shorter as the step proceeds.

  The refrigeration apparatus of the eighth aspect can escape from the gas-liquid two-phase state more quickly than when the time intervals of the steps are the same.

  A control method for a refrigeration apparatus according to a ninth aspect of the present invention includes a compressor that compresses a refrigerant, a heat source side heat exchanger that performs heat exchange with the refrigerant, a use side heat exchanger, and a decompression of the refrigerant. A refrigerant circuit that performs a vapor compression refrigeration cycle by circulating a refrigerant, and a use-side heat that is attached to the refrigerant circuit and used to determine whether or not a gas-liquid two-phase state exists A method for controlling a refrigeration apparatus comprising a sensor for detecting a state quantity of a refrigerant in a refrigerant circuit in order to obtain a current state quantity on an outlet side of a exchanger or a heat source side heat exchanger or on a suction side of a compressor, The current state quantity that can be determined to be in the gas-liquid two-phase state to be escaped on the outlet side of the heat exchanger or the heat source side heat exchanger or the suction side of the compressor is continued for a first set time or more of a predetermined value. Judgment step to determine whether or not there was When it is determined in the determination step that the predetermined value of the current state quantity continues for the first set time or longer, the valve opening degree is controlled from the first control state that is performed in the normal time that is not the gas-liquid two-phase state. And a control operation changing step for switching to a second control state in which the valve opening degree is faster than that in the control state.

  In the refrigeration apparatus according to the ninth aspect, in the determination step, the predetermined value of the current state quantity can be determined as a gas-liquid two-phase state that should be escaped from the continuation of the first set time or more, and the gas-liquid that does not need to escape It is possible to avoid making a false determination that the gas-liquid two-phase state should be promptly escaped despite the two-phase state. This not only speeds up the escape from the gas-liquid two-phase state to be escaped, but also suppresses the switch to the second control state with a fast speed to reduce the valve opening in the gas-liquid two-phase state where it is not necessary to escape. Therefore, in the control operation changing step, in the gas-liquid two-phase state that does not need to be escaped, the second control state in which the valve opening is changed rapidly is avoided, and the occurrence of hunting is suppressed. Can do.

  In the refrigeration apparatus according to the first aspect of the present invention or the control method of the refrigeration apparatus according to the ninth aspect, it is detected that a predetermined gas-liquid two-phase state to be quickly escaped is detected, and such a predetermined Therefore, it is possible to achieve both the control of the pressure reducing mechanism for quickly escaping from the gas-liquid two-phase state and the control of the stable pressure reducing mechanism at the normal time.

  In the refrigeration apparatus according to the second aspect of the present invention, misjudgment that is not determined as the gas-liquid two-phase state to be escaped can be suppressed, and the gas-liquid two-phase state can be quickly performed in the gas-liquid two-phase state to be escaped. Thus, it is possible to reliably execute the control of the decompression mechanism that escapes from the vehicle.

  In the refrigeration apparatus according to the third aspect of the present invention, even if the deviation between the target superheat degree and the calculated superheat degree or the deviation between the target supercooling degree and the calculated supercooling degree is substantially equal to zero, A quick escape from the phase state can be performed.

  In the refrigeration apparatus according to the fourth aspect of the present invention, since the determination time can be changed according to the degree of the gas-liquid two-phase state, escape from the gas-liquid two-phase state can be accelerated.

  In the refrigeration apparatus according to the fifth aspect of the present invention, hunting can be suppressed while stabilizing the control.

  In the refrigeration apparatus according to the sixth aspect of the present invention, the escape time from the predetermined gas-liquid two-phase state can be further shortened by the third control state.

  In the refrigeration apparatus according to the seventh aspect of the present invention, the escape time from the predetermined gas-liquid two-phase state can be further shortened by a step-like change in speed at which the valve opening degree in the third control state is reduced.

  In the refrigeration apparatus according to the eighth aspect of the present invention, the escape time from the predetermined gas-liquid two-phase state is further increased by setting the time interval of each step of the step-like change in speed at which the valve opening degree in the third control state is reduced. It can be shortened.

The circuit diagram which shows the outline | summary of a structure of the air conditioning apparatus which concerns on this invention. The block diagram for demonstrating the control system of the air conditioning apparatus of FIG. The conceptual diagram for demonstrating the control example of the indoor side control apparatus which concerns on 1st Embodiment. The conceptual diagram for demonstrating the control example of the indoor side control apparatus which concerns on 2nd Embodiment. The conceptual diagram for demonstrating the control example of the indoor side control apparatus which concerns on 3rd Embodiment. The graph for demonstrating an example in case a gain magnification is changed in steps. The graph for demonstrating the other example in the case of changing gain magnification in a step shape. The graph for demonstrating the case where a gain magnification is increased linearly. The conceptual diagram for demonstrating the control example of the indoor side control apparatus which concerns on 4th Embodiment. The conceptual diagram for demonstrating the control example of the indoor side control apparatus which concerns on 5th Embodiment. The graph for demonstrating the change of the superheat degree in the case of controlling only in the 1st control state. The graph for demonstrating the change of the superheat degree in the case of switching and controlling between a 1st control state and a 2nd control state.

<First Embodiment>
(1) Configuration of Air Conditioner In the following description, an example of an air conditioner used for air conditioning in a building or the like by performing a vapor compression refrigeration cycle operation as the refrigeration apparatus according to the first embodiment. Are listed. FIG. 1 is a circuit diagram illustrating an outline of a configuration of an air conditioner that is a refrigeration apparatus according to a first embodiment of the present invention. An air conditioner 10 shown in FIG. 1 is mainly composed of an outdoor unit 20 as one heat source unit and a plurality of (three in the present embodiment) usage units connected in parallel thereto. And a liquid refrigerant communication pipe 71 and a gas refrigerant communication pipe 72 as refrigerant communication pipes connecting the outdoor unit 20 and the indoor units 40, 50, 60 to each other. That is, in the vapor compression refrigerant circuit 11 of the air conditioning apparatus 10 of the present embodiment, the outdoor unit 20, the indoor units 40, 50, and 60, the liquid refrigerant communication pipe 71, and the gas refrigerant communication pipe 72 are connected. Is made up of.

(1-1) Indoor unit The indoor units 40, 50, and 60 are installed in one room such as a conference room by embedding or hanging in a ceiling of a room such as a building, or hanging on a wall surface of the room. ing. Since the indoor units 40 and the indoor units 50 and 60 have the same configuration, only the configuration of the indoor unit 40 will be described here, and the configurations of the indoor units 50 and 60 are shown for each part of the indoor unit 40, respectively. The reference numbers 50 and 60 are used instead of the reference numbers 40 and description of each part is omitted.

  The indoor unit 40 mainly has an indoor refrigerant circuit 11a (a indoor refrigerant circuit 11b in the indoor unit 50 and an indoor refrigerant circuit 11c in the indoor unit 60) constituting a part of the refrigerant circuit 11. This indoor side refrigerant circuit 11a mainly has an indoor expansion valve 41 as an expansion mechanism and an indoor heat exchanger 42 as a use side heat exchanger. In the present embodiment, the indoor expansion valves 41, 51, 61 are provided in the indoor units 40, 50, 60, respectively, as the expansion mechanism. However, the present invention is not limited to this, and the expansion mechanism (including the expansion valve) is an outdoor unit. 20 may be provided, or may be provided in a connection unit independent of the indoor units 40, 50, 60 and the outdoor unit 20.

  The indoor expansion valve 41 is an electric expansion valve connected to the liquid side of the indoor heat exchanger 42 in order to adjust the flow rate of the refrigerant flowing in the indoor refrigerant circuit 11a, and blocks passage of the refrigerant. Is also possible.

  The indoor heat exchanger 42 is, for example, a cross fin type fin-and-tube heat exchanger configured by heat transfer tubes and a large number of fins. The indoor heat exchanger 42 is a heat exchanger that functions as a refrigerant evaporator during cooling operation to cool indoor air and functions as a refrigerant condenser during heating operation to heat indoor air.

  The indoor unit 40 sucks indoor air into the unit, exchanges heat with the refrigerant in the indoor heat exchanger 42, and then supplies the indoor air after heat exchange into the room as supply air. 43. The indoor fan 43 is a fan capable of changing the air volume supplied to the indoor heat exchanger 42 within a predetermined air volume range. For example, a centrifugal fan or a multiblade fan driven by a motor 43m formed of a DC fan motor or the like. Etc. In this indoor fan 43, a fixed air volume mode that sets three types of fixed air volumes, a weak wind with the smallest air volume, a strong wind with the largest air volume, and a medium wind between the weak wind and the strong wind, and the superheat degree SH and the supercooling. It is possible to select and set either an air volume automatic mode that automatically changes between low and high winds depending on the degree SC, or an air volume setting mode that is manually changed by an input device such as a remote controller. . That is, if the user selects one of “weak wind”, “medium wind”, and “strong wind” using a remote controller, for example, the air volume is fixed in the weak wind mode and “automatic” is selected. In this case, the air volume automatic mode in which the air volume is automatically changed according to the operation state is set. Here, a configuration in which the fan tap of the air volume of the indoor fan 43 is switched in three stages of “weak wind”, “medium wind”, and “strong wind” is described. The indoor fan air volume Ga, which is the air volume of the indoor fan 43, can be derived from, for example, calculation using the rotation speed of the motor 43m as a parameter. In addition, there are a method of deriving the indoor fan air volume Ga from a calculation based on the current value of the motor 43m, a method of deriving from a calculation based on a set fan tap, and the like.

  The indoor unit 40 is provided with various sensors. On the liquid side of the indoor heat exchanger 42, the refrigerant temperature (that is, the saturation temperature equivalent to the condensation pressure during heating operation (hereinafter referred to as the condensation temperature) Tc or the saturation temperature corresponding to the evaporation pressure during cooling operation (hereinafter referred to as the evaporation temperature). ) A liquid side temperature sensor 44 for detecting a refrigerant temperature corresponding to Te) is provided. A gas side temperature sensor 45 that detects the temperature of the refrigerant is provided on the gas side of the indoor heat exchanger 42. An indoor temperature sensor 46 that detects the temperature of indoor air flowing into the unit (that is, the indoor temperature Tr) is provided on the indoor air intake side of the indoor unit 40. As the liquid side temperature sensor 44, the gas side temperature sensor 45, and the room temperature sensor 46, for example, a thermistor can be used. The indoor unit 40 also includes an indoor side control device 47 that controls the operation of each part constituting the indoor unit 40. The indoor-side control device 47 includes an air-conditioning capacity calculation unit 47a that calculates the current air-conditioning capacity and the like in the indoor unit 40, and a required evaporation temperature Ter or a required condensing temperature required to exhibit the capacity based on the current air-conditioning capacity. And a required temperature calculation unit 47b for calculating Tcr (see FIG. 2). The indoor control device 47 includes a microcomputer, a memory 47c, and the like provided for controlling the indoor unit 40, and a remote controller (not shown) for individually operating the indoor unit 40. It is possible to exchange control signals and the like with each other, and exchange control signals and the like with the outdoor unit 20 via the transmission line 80a.

(1-2) Outdoor unit The outdoor unit 20 is installed outside a building or the like, and is connected to the indoor units 40, 50, and 60 via a liquid refrigerant communication pipe 71 and a gas refrigerant communication pipe 72. The refrigerant circuit 11 is configured together with the machines 40, 50 and 60. The outdoor unit 20 has an outdoor refrigerant circuit 11 d that constitutes a part of the refrigerant circuit 11. This outdoor refrigerant circuit 11d mainly includes a compressor 21, a four-way switching valve 22, an outdoor heat exchanger 23 as a heat source side heat exchanger, an outdoor expansion valve 38 as an expansion mechanism, an accumulator 24, A liquid side closing valve 26 and a gas side closing valve 27 are provided.

  The compressor 21 is a compressor whose operating capacity can be varied, and is a positive displacement compressor driven by a motor 21m whose rotation speed is controlled by an inverter. In addition, although the outdoor unit 20 shown here has one compressor 21, the number of compressors may be two or more when the number of indoor units connected is large.

  The four-way switching valve 22 is a valve for switching the direction of refrigerant flow. During the cooling operation, the outdoor heat exchanger 23 functions as a refrigerant condenser compressed by the compressor 21, and the indoor heat exchangers 42, 52, 62 serve as refrigerant evaporators condensed in the outdoor heat exchanger 23. In order to function, the discharge side of the compressor 21 and the gas side of the outdoor heat exchanger 23 are connected, and the suction side (specifically, the accumulator 24) of the compressor 21 and the gas refrigerant communication pipe 72 side are connected. Connected (cooling operation state: refer to the solid line of the four-way switching valve 22 in FIG. 1). On the other hand, during the heating operation, the indoor heat exchangers 42, 52, 62 function as the refrigerant condenser compressed by the compressor 21, and the refrigerant evaporator condensed in the indoor heat exchangers 42, 52, 62. In order to make the outdoor heat exchanger 23 function, the discharge side of the compressor 21 and the gas refrigerant communication pipe 72 side are connected, and the suction side of the compressor 21 and the gas side of the outdoor heat exchanger 23 are connected. (Heating operation state: see broken line of four-way switching valve 22 in FIG. 1).

  The outdoor heat exchanger 23 is, for example, a cross fin type fin-and-tube heat exchanger, and is a device for exchanging heat between air and a refrigerant in order to use air as a heat source. The outdoor heat exchanger 23 is a heat exchanger that functions as a refrigerant condenser during the cooling operation and functions as a refrigerant evaporator during the heating operation. The outdoor heat exchanger 23 has a gas side connected to the four-way switching valve 22 and a liquid side connected to the outdoor expansion valve 38.

  The outdoor expansion valve 38 is downstream of the outdoor heat exchanger 23 in the refrigerant flow direction in the refrigerant circuit 11 when performing a cooling operation in order to adjust the pressure, flow rate, and the like of the refrigerant flowing in the outdoor refrigerant circuit 11d. It is an electric expansion valve arrange | positioned in. That is, the outdoor expansion valve 38 is connected to the liquid side of the outdoor heat exchanger 23.

  The outdoor unit 20 has an outdoor fan 28 as a blower for sucking outdoor air into the unit, exchanging heat with the refrigerant in the outdoor heat exchanger 23, and then discharging it to the outside. The outdoor fan 28 is a fan capable of changing the air volume of air supplied to the outdoor heat exchanger 23, and is, for example, a propeller fan driven by a motor 28m composed of a DC fan motor or the like.

  The liquid side closing valve 26 and the gas side closing valve 27 are valves provided at connection ports with the liquid refrigerant communication pipe 71 and the gas refrigerant communication pipe 72. The liquid side shut-off valve 26 is disposed downstream of the outdoor expansion valve 38 and upstream of the liquid refrigerant communication pipe 71 in the refrigerant flow direction in the refrigerant circuit 11 when performing the cooling operation, and prevents passage of the refrigerant. It is possible to block. The gas side closing valve 27 is connected to the four-way switching valve 22 and can block the passage of the refrigerant.

  Further, the outdoor unit 20 includes a suction pressure sensor 29 that detects a suction pressure of the compressor 21 (that is, a refrigerant pressure corresponding to the evaporation pressure Pe during the cooling operation), and a discharge pressure of the compressor 21 (that is, a heating operation). A discharge pressure sensor 30 that detects a refrigerant pressure corresponding to the condensation pressure Pc at the time), a suction temperature sensor 31 that detects a suction temperature of the compressor 21, and a discharge temperature sensor 32 that detects a discharge temperature of the compressor 21. Is provided. An outdoor temperature sensor 36 for detecting the temperature of the outdoor air flowing into the unit (that is, the outdoor temperature) is provided on the outdoor air suction port side of the outdoor unit 20. A heat exchanger outlet temperature sensor 39 that detects the temperature of the refrigerant is provided on the outlet side of the outdoor heat exchanger 23. As the suction temperature sensor 31, the discharge temperature sensor 32, the outdoor temperature sensor 36, and the heat exchanger outlet temperature sensor 39, for example, a thermistor can be used. In addition, the outdoor unit 20 includes an outdoor control device 37 that controls the operation of each unit constituting the outdoor unit 20. As shown in FIG. 2, the outdoor side control device 37 determines a target evaporation temperature Tet or a target condensation temperature Tct (or a target evaporation temperature difference ΔTet or a target condensation temperature difference ΔTct) for controlling the operation capacity of the compressor 21. A target value determination unit 37a. The outdoor control device 37 includes a microcomputer (not shown) provided to control the outdoor unit 20, an inverter circuit that controls the memory 37b, the motor 21m, and the like. Control signals and the like can be exchanged between the 50 and 60 indoor control devices 47, 57 and 67 via the transmission line 80a. That is, the indoor control devices 47, 57, and 67, the outdoor control device 37, and the transmission line 80a that connects them constitute an operation control device 80 that performs operation control of the entire air conditioner 10. .

  As shown in FIG. 2, the operation control device 80 includes a suction pressure sensor 29, a discharge pressure sensor 30, a suction temperature sensor 31, a discharge temperature sensor 32, an outdoor temperature sensor 36, liquid side temperature sensors 44, 54 and 64, gas, The side temperature sensors 45, 55, 65 and the indoor temperature sensors 46, 56, 66 are connected so as to receive detection signals. In addition, the operation control device 80 can control the outdoor unit 20 and the indoor units 40, 50, 60 based on these detection signals and the like, the compressor 21, the four-way switching valve 22, the outdoor fan 28, the outdoor unit. The expansion valve 38, the indoor expansion valve, 41, 51, 61 and the indoor fans 43, 53, 63 are connected. Furthermore, various data for controlling the air conditioner 10 are stored in the memories 37b, 47c, 57c, and 67c constituting the operation control device 80.

(1-3) Refrigerant communication pipe The liquid refrigerant communication pipe 71 and the gas refrigerant communication pipe 72 are refrigerant pipes constructed on site when the air conditioner 10 is installed at an installation location such as a building. And what has various lengths and pipe diameters is used according to installation conditions, such as a combination of an outdoor unit and an indoor unit. For example, when the air conditioner 10 is newly installed in a building or the like, it is appropriate for the air conditioner 10 according to the installation conditions such as the length and pipe diameter of the liquid refrigerant communication pipe 71 and the gas refrigerant communication pipe 72. A sufficient amount of refrigerant is filled.

  As described above, the indoor refrigerant circuits 11a, 11b, and 11c, the outdoor refrigerant circuit 11d, the liquid refrigerant communication pipe 71, and the gas refrigerant communication pipe 72 are connected, and the refrigerant circuit 11 of the air conditioner 10 is configured. Has been. The air conditioner 10 is operated by switching the cooling operation and the heating operation by the four-way switching valve 22 by the operation control device 80 including the indoor side control devices 47, 57, 67 and the outdoor side control device 37. In addition, the control of each device of the outdoor unit 20 and the indoor units 40, 50, 60 is performed according to the operation load of each indoor unit 40, 50, 60.

(2) Operation of Air Conditioner (2-1) Cooling Operation First, the cooling operation will be described with reference to FIG. During the cooling operation, the four-way switching valve 22 is in the state shown by the solid line in FIG. 1, that is, the discharge side of the compressor 21 is connected to the gas side of the outdoor heat exchanger 23 and the suction side of the compressor 21 is the gas side. It is in a state where it is connected to the gas side of the indoor heat exchangers 42, 52, 62 via the closing valve 27 and the gas refrigerant communication pipe 72. Here, the outdoor expansion valve 38 is fully opened. The liquid side closing valve 26 and the gas side closing valve 27 are in an open state. The indoor expansion valve 41 is adjusted in opening degree so that the superheat degree SH1 of the refrigerant at the outlet of the indoor heat exchanger 42 (that is, the gas side of the indoor heat exchanger 42) becomes the target superheat degree SHt1, and the indoor expansion valve 51 The opening degree is adjusted so that the superheat degree SH2 of the refrigerant at the outlet of the indoor heat exchanger 52 (that is, the gas side of the indoor heat exchanger 52) becomes the target superheat degree SHt2, and the indoor expansion valve 61 is The opening degree of the refrigerant is adjusted so that the superheat degree SH3 of the refrigerant at the outlet 62 (that is, the gas side of the indoor heat exchanger 62) becomes the target superheat degree SHt3.

  Note that the target superheats SHt1, SHt2, and SHt3 are set to optimum values for the indoor temperatures Tr1, Tr2, and Tr3 to converge to the set temperatures Ts1, Ts2, and Ts3 within a predetermined superheat range. , 57, 67. The superheat degree SH1, SH2, SH3 of the refrigerant at the outlets of the indoor heat exchangers 42, 52, 62 is determined based on the refrigerant temperature values (Tg) detected by the gas side temperature sensors 45, 55, 65. It is detected by subtracting the refrigerant temperature value (corresponding to the evaporation temperature Te) detected by 44, 54, and 64, respectively. However, the superheat levels SH1, SH2, and SH3 of the refrigerant at the outlets of the indoor heat exchangers 42, 52, and 62 are not limited to being detected by the above-described method, but may be detected by the suction pressure sensor 29. The suction pressure may be converted into a saturation temperature value corresponding to the evaporation temperature Te and detected by subtracting the saturation temperature value of the refrigerant from the refrigerant temperature values detected by the gas side temperature sensors 45, 55, 65.

  Although not adopted in the present embodiment, a temperature sensor that detects the temperature of the refrigerant flowing in each of the indoor heat exchangers 42, 52, and 62 is provided and corresponds to the evaporation temperature Te detected by this temperature sensor. By subtracting the refrigerant temperature value from the refrigerant temperature value detected by the gas side temperature sensors 45, 55, and 65, the superheat degrees SH1, SH2, and SH3 of the refrigerant at the outlets of the indoor heat exchangers 42, 52, and 62, respectively. You may make it detect.

  When the compressor 21, the outdoor fan 28, and the indoor fans 43, 53, 63 are operated in the state of the refrigerant circuit 11, the low-pressure gas refrigerant is sucked into the compressor 21 and compressed to become a high-pressure gas refrigerant. Thereafter, the high-pressure gas refrigerant is sent to the outdoor heat exchanger 23 via the four-way switching valve 22, exchanges heat with the outdoor air supplied by the outdoor fan 28, and condenses to form a high-pressure liquid refrigerant. Become. Then, the high-pressure liquid refrigerant is sent to the indoor units 40, 50, 60 via the liquid side closing valve 26 and the liquid refrigerant communication pipe 71.

  The high-pressure liquid refrigerant sent to the indoor units 40, 50, 60 is decompressed to near the suction pressure of the compressor 21 by the indoor expansion valves 41, 51, 61, respectively, and becomes low-pressure gas-liquid two-phase refrigerant. Are sent to the indoor heat exchangers 42, 52, and 62, exchange heat with indoor air in the indoor heat exchangers 42, 52, and 62, respectively, and evaporate into low-pressure gas refrigerant.

  The low-pressure gas refrigerant is sent to the outdoor unit 20 via the gas refrigerant communication pipe 72 and flows into the accumulator 24 via the gas-side closing valve 27 and the four-way switching valve 22. Then, the low-pressure gas refrigerant that has flowed into the accumulator 24 is again sucked into the compressor 21. As described above, in the air conditioner 10, the outdoor heat exchanger 23 is condensed as a refrigerant condenser compressed in the compressor 21, and the indoor heat exchangers 42, 52, and 62 are condensed in the outdoor heat exchanger 23. It is possible to perform a cooling operation that functions as an evaporator for the refrigerant that is sent later through the liquid refrigerant communication pipe 71 and the indoor expansion valves 41, 51, 61. In the air conditioner 10, the indoor units 40, 50, 60 do not have a mechanism for adjusting the pressure of the refrigerant on the gas side of the indoor heat exchangers 42, 52, 62. , 52 and 62 are common pressures.

(2-2) Heating Operation Next, the heating operation will be described with reference to FIG. During the heating operation, the four-way switching valve 22 is in the state indicated by the broken line in FIG. 1 (heating operation state), that is, the discharge side of the compressor 21 is exchanged indoors via the gas side closing valve 27 and the gas refrigerant communication pipe 72. The compressor 42, 52, 62 is connected to the gas side, and the suction side of the compressor 21 is connected to the gas side of the outdoor heat exchanger 23. The opening of the outdoor expansion valve 38 is adjusted in order to reduce the refrigerant flowing into the outdoor heat exchanger 23 to a pressure at which the refrigerant can be evaporated in the outdoor heat exchanger 23 (that is, the evaporation pressure Pe). Yes. Moreover, the liquid side closing valve 26 and the gas side closing valve 27 are opened. The indoor expansion valves 41, 51, 61 are adjusted in opening degree so that the refrigerant subcooling degrees SC1, SC2, SC3 at the outlets of the indoor heat exchangers 42, 52, 62 become the target subcooling degrees SCt1, SCt2, SCt3, respectively. It has come to be. The target supercooling degrees SCt1, SCt2, and SCt3 are set so that the indoor temperatures Tr1, Tr2, and Tr3 converge to the set temperatures Ts1, Ts2, and Ts3 within the supercooling degree range that is specified according to the operation state at that time. The optimum temperature value is set. The subcooling degree SC1, SC2, SC3 of the refrigerant at the outlets of the indoor heat exchangers 42, 52, 62 sets the discharge pressure Pd of the compressor 21 detected by the discharge pressure sensor 30 to a saturation temperature value corresponding to the condensation temperature Tc. This is detected by subtracting the refrigerant temperature value detected by the liquid side temperature sensors 44, 54, and 64 from the saturation temperature value of the refrigerant.

  Although not adopted in the present embodiment, a temperature sensor that detects the temperature of the refrigerant flowing in each of the indoor heat exchangers 42, 52, and 62 is provided, and the refrigerant corresponding to the condensation temperature Tc detected by this temperature sensor. By subtracting the temperature value from the refrigerant temperature value detected by the liquid side temperature sensors 44, 54, 64, the subcooling degrees SC1, SC2, SC3 of the refrigerant at the outlets of the indoor heat exchangers 42, 52, 62 are detected. You may do it.

  When the compressor 21, the outdoor fan 28, and the indoor fans 43, 53, 63 are operated in the state of the refrigerant circuit 11, the low-pressure gas refrigerant is sucked into the compressor 21 and compressed to become a high-pressure gas refrigerant. It is sent to the indoor units 40, 50, 60 via the path switching valve 22, the gas side closing valve 27 and the gas refrigerant communication pipe 72. The high-pressure gas refrigerant sent to the indoor units 40, 50, 60 is condensed by exchanging heat with indoor air in the indoor heat exchangers 42, 52, 62, When passing through the indoor expansion valves 41, 51, 61, the pressure is reduced according to the opening degree of the indoor expansion valves 41, 51, 61.

  The refrigerant that has passed through the indoor expansion valves 41, 51, 61 is sent to the outdoor unit 20 via the liquid refrigerant communication pipe 71 and further depressurized via the liquid side closing valve 26 and the outdoor expansion valve 38. , Flows into the outdoor heat exchanger 23. The low-pressure gas-liquid two-phase refrigerant flowing into the outdoor heat exchanger 23 exchanges heat with the outdoor air supplied by the outdoor fan 28 to evaporate into a low-pressure gas refrigerant, and passes through the four-way switching valve 22. And flows into the accumulator 24. Then, the low-pressure gas refrigerant that has flowed into the accumulator 24 is again sucked into the compressor 21. In this air conditioner 10, since there is no mechanism for adjusting the refrigerant pressure on the gas side of the indoor heat exchangers 42, 52, 62, the condensation pressure Pc in all the indoor heat exchangers 42, 52, 62 is common. Pressure.

(3) Control of indoor expansion valve by indoor control device (3-1) During cooling In the following, the control during cooling of the indoor expansion valve 41 by the indoor side control device 47 will be described. Control of the indoor expansion valves 51 and 61 by the devices 57 and 67 is also performed. In the control of the indoor expansion valve 41, the indoor control device 47 selects either the normal first control state or the second control state in the gas-liquid two-phase state. In the first control state, for example, the control amount ΔEV of the valve opening degree of the indoor expansion valve 41 follows proportional integral (PI) control, as in the conventional case.

Deviation between the current superheating degree SH1 and the target degree of superheat SHT1 a (= SH1-SHt1) expressed as e, the previous error is expressed as e _prev, when the constant alpha and β and γ, ΔEV = α · (e- e _prev ) + β · e, the control amount ΔEV is determined. The calculation for determining the control amount ΔEV is performed, for example, every time a certain time elapses.

On the other hand, in the second control state, the control amount ΔEV is determined according to the equation: ΔEV = α · (e−e _prev ) + γ. When the time has elapsed with the outlet side of the indoor heat exchangers 42, 52, 62 being below the target superheat degree, there is almost no change in the superheat degree SH1, that is, (e−e _prev ) _≈0 , ΔEV≈γ in the second control state. When the outlet side of the indoor heat exchangers 42, 52, 62 remains below the target superheat degree, the superheat degree on the outlet side of the indoor heat exchangers 42, 52, 62 rapidly exceeds the target superheat degree. If the value of γ is set so that it can be shifted to a higher value, the time for shifting from the gas-liquid two-phase state to the dry state can be shortened. The setting that the superheat degree on the outlet side of the indoor heat exchangers 42, 52, 62 can be rapidly shifted to a value higher than the target superheat degree is that the speed at which the valve opening is made smaller than that in the first control state. That is, the setting is faster in the 2 control state. For example, if the relationship of γ> β · e is maintained until the superheat degree can shift to a value higher than the target superheat degree, (ΔEV in the second control state in the gas-liquid two-phase state)> (gas-liquid two-phase state [Delta] EV in the first control state), and the speed at which the valve opening is reduced is faster in the second control state than in the first control state. Information regarding the first control state and the second control state as described above is stored in the memory 47c of the indoor control device 47.

  The general control of the first control state and the second control state is as follows. That is, in the first control state, the control amount ΔEV is given by the function f having the deviation e between the target superheat degree SH1t and the superheat degree SH1 as a parameter, and ΔEV = f (e). On the other hand, in the second control state, the integral term of PI control is replaced with a constant, so that the control amount ΔEV is given by a function g having the superheat degree SH1 as a parameter, and ΔEV = g (SH1). That is, the optimal ΔEV is set to escape the gas-liquid two-phase state regardless of the target superheat degree SHt1 on the assumption that the second control state is the gas-liquid two-phase state. . For example, f (e) <g (SH1) is set in the range of the superheat degree SH1 considered that the suction side of the compressor 21 is in a gas-liquid two-phase state.

  In order to switch between the first control state and the second control state, it is important to determine the state on the outlet side of the indoor heat exchangers 42, 52, and 62. FIG. 3 is a conceptual diagram for explaining switching between the first control state and the second control state. The condition for switching from the first control state to the second control state shown in FIG. 3 (gas-liquid two-phase state determination condition) is a state where the superheat degree SH1 is 3.0 degrees or less (SH1 ≦ 3.0). Is for 60 seconds. Satisfying this condition means that a considerable time (predetermined time) out of the allowable time after a state in which the gas-liquid two-phase state must be promptly released (the gas-liquid two-phase state to be escaped) is allowed. It means that it has passed.

  On the other hand, the condition for switching from the second control state to the first control state (gas-liquid two-phase escape determination condition) is that a state in which the superheat degree SH1 exceeds 3.0 degrees (SH1> 3.0) has appeared. . Although the superheat degree SH1 was 3.0 degrees or less continuously for 60 seconds or more, the fact that it exceeds 3.0 degrees means that the outlet side of the indoor heat exchangers 42, 52, 62 must escape immediately. It can be judged that the gas-liquid two-phase state has been lost.

  Here, in order to help the understanding regarding the above-described control, a brief description will be given of the situation in which switching to the second control state is required. For example, even if the operation state of the outdoor unit 20 changes greatly, such as when the indoor unit 60 is thermo-off and the evaporation temperature drops rapidly, the indoor units 40 and 50 are in their respective internal states, that is, the indoor heat exchangers 42, The opening degree of the indoor expansion valves 41 and 51 is adjusted so that the change in the degree of superheat on the outlet side of 52 is detected and matched with the target degree of superheat. Therefore, when the indoor unit 60 is thermo-off and the evaporation temperature rapidly decreases, the indoor side control devices 47 and 57 of the indoor units 40 and 50 increase the degree of superheat on the outlet side of the indoor heat exchangers 42 and 52, so that the indoor expansion The opening degree of the valves 41 and 51 is increased. However, when the outdoor side control device 37 of the outdoor unit 20 starts the operation in which the thermo-off of the indoor unit 60 is incorporated, the openings of the indoor expansion valves 41 and 51 become too open, and the intake of the compressor 21 of the outdoor unit 20 is sucked. On the side, there is a possibility of falling into a gas-liquid two-phase state that should be escaped immediately. At this time, on the outlet side of the indoor heat exchangers 42 and 52, the degree of superheat may be significantly lower than the target degree of superheat. In addition, since the sensor attached to the refrigerant circuit 11 cannot accurately measure the distribution of the gas refrigerant and the liquid refrigerant in the pipe, the degree of superheat in the indoor heat exchangers 42, 52, 62, etc. is a certain value. In some cases, the liquid refrigerant flows out from the outlet side of the indoor heat exchangers 42, 52, and 62 and is in a gas-liquid two-phase state to be escaped. By investigating the relationship between the gas-liquid two-phase state to be escaped and the degree of superheat and supercooling in advance by tests and simulations with actual equipment, the gas-liquid two-phase to be escaped from the behavior of superheat and supercooling It becomes possible to determine whether or not it is in a state.

(3-2) During heating During heating, control based on the degree of supercooling SC1, SC2, SC3 is performed instead of control based on the degree of superheating SH1, SH2, SH3 performed during cooling. In the following, the control during heating of the indoor expansion valve 41 by the indoor side control device 47 will be described, but the same applies to the control of the indoor expansion valves 51 and 61 by the indoor side control devices 57 and 67. In the control of the indoor expansion valve 41, the indoor control device 47 selects either the first control state or the second control state. In the first control state, for example, the control amount ΔEV of the valve opening degree of the indoor expansion valve 41 follows proportional integral (PI) control, as in the conventional case.

If the deviation (= SC1-SCt1) between the current supercooling degree SC1 and the target supercooling degree SCt1 is represented by ew, the previous deviation is represented by ew _prev, and αw, βw, and γw are constants, ΔEV = αw · ( ew−ew _prev ) + βw · ew, the control amount ΔEV is determined. The calculation for determining the control amount ΔEV is performed, for example, every time a certain time elapses.

On the other hand, in the second control state, the control amount ΔEV is determined according to the formula: ΔEV = αw · (ew−ew _prev ) + γw. When the outlet side of the indoor heat exchangers 42, 52, 62 remains below the target supercooling degree, the superheat degree on the outlet side of the indoor heat exchangers 42, 52, 62 rapidly becomes the target superheat degree. If the value of γw is set so that it can be shifted to a higher value, the time required for shifting from the gas-liquid two-phase state to the dry state can be shortened. The setting is such that the supercooling degree on the outlet side of the indoor heat exchangers 42, 52, 62 can be rapidly shifted to a value higher than the target supercooling degree. This is a setting in which the second control state is faster than the state. For example, if the relationship of γw> βw · ew is maintained until the supercooling degree can shift to a value higher than the target supercooling degree, (ΔEV in the second control state in the gas-liquid two-phase state)> (gas-liquid two ΔEV in the first control state in the phase state), and the speed at which the valve opening is reduced is faster in the second control state than in the first control state. Information regarding the first control state and the second control state as described above is stored in the memory 47c of the indoor control device 47.

  During the heating operation, the decrease in the degree of supercooling causes the refrigerant state to become a gas-liquid two-phase when passing through the valve, resulting in an unstable flow rate of the refrigerant and a decrease in the stability of the refrigerant control. As described above, if the outlet side of the indoor heat exchangers 42, 52, and 62 can be rapidly transferred to a dry state, stability of refrigerant control during heating operation can be improved.

Further, in the outdoor expansion valve 38, by applying the same method as described above, the gas-liquid two-phase state to be escaped from the current state amount of the refrigerant on the suction side of the compressor 21 or the outlet side of the outdoor heat exchanger is determined. Switching from the first control state to the second control state when it occurs can be performed. At this time, for example, the current state quantity of the refrigerant calculated from the heat exchanger outlet temperature sensor 39 and the suction pressure sensor 29 or the suction temperature sensor 31 is used.
Second Embodiment
(4) Control of indoor expansion valve by indoor control device The air conditioner according to the second embodiment also has the configuration shown in FIG. 1 in the same manner as the air conditioner of the first embodiment. The difference between the air conditioner of the second embodiment and the air conditioner of the first embodiment is the control in the indoor control devices 47, 57, and 67 of the indoor units 40, 50, and 60. Therefore, description of the configuration of the air conditioner 10 of the second embodiment is omitted, and control in the indoor control devices 47, 57, and 67 will be described. As shown in FIG. 4, the control of the indoor side control devices 47, 57, and 67 in the second embodiment has a first control state in a normal state and a second control state in a gas-liquid two-phase state. This is the same, but the response to the gas-liquid two-phase state is made in two stages. That is, when the duration time of the gas-liquid two-phase state is long, the control mode is switched to the third control state in which the escape time from the gas-liquid two-phase state is shortened compared to the second control state.

  The first control state in the normal state and the second control state in the gas-liquid two-phase state are performed in the same manner as in the first embodiment in the second embodiment, and thus description thereof is omitted. The third control state for shortening the escape time is control in which the operation amount of the valve opening is made larger than that in the second control state.

For example, if the expression used in the second control state is ΔEV = α · (e−e _prev ) + γ, the third control state is realized by using an expression obtained by multiplying it by a coefficient (1 + ε) larger than 1. it can. However, ε> 0. That is, in the third control state, the control amount ΔEV is determined according to the equation: ΔEV = (1 + ε) · [α · (e−e _prev ) + γ].

  The relationship between the first control state, the second control state, the third control state, and the switching conditions between the states is as shown in FIG. Here, the switching conditions at the time of cooling the indoor unit 40 will be described, and the description of the switching conditions at the time of heating will be omitted. The switching conditions during cooling of the indoor units 50 and 60 and the switching conditions during heating are such that each parameter of the indoor unit 40 is replaced with a parameter of the indoor units 50 and 60, or the superheat degree SH during cooling is the supercooling degree during heating. What is necessary is just to replace with SC. At this time, it is not necessary to use the same numerical value as the switching condition for cooling and heating.

  FIG. 4 is a conceptual diagram for explaining switching between the first control state, the second control state, and the third control state. The conditions for switching from the first control state to the second control state (gas-liquid two-phase state determination condition) shown in FIG. 4 are a target superheat degree SH1t of 3.0 degrees or more and a superheat degree SH1 of 3.0. Or less (SH1 ≦ 3.0) for 60 seconds.

  The condition for switching from the gas-liquid two-phase second control state to the normal first control state (gas-liquid two-phase state determination cancellation condition) is a state where the superheat degree SH1 exceeds 3.0 degrees (SH1> 3.0). Has appeared, or the target superheat degree SH1t has become smaller than 3.0 degrees (SH1t <3.0). This condition is the same as the condition for switching from the third control state to the first control state.

Next, a condition for switching from the second control state corresponding to the gas-liquid two-phase state to the third control state corresponding to the liquid-rich gas-liquid two-phase state with a higher proportion of liquid refrigerant (liquid-rich gas-liquid two-phase state). The phase state determination condition) is that the state where the 60-second superheat degree SH1 is 3.0 degrees or less continues from the start point when the first control state is switched to the second control state. is there.
<Third Embodiment>
(5) Control of indoor expansion valve by indoor control device The air conditioner according to the third embodiment also has the configuration shown in FIG. 1, similarly to the air conditioner of the first embodiment. The difference between the air conditioner of the third embodiment and the air conditioner of the first embodiment is the control in the indoor control devices 47, 57, and 67 of the indoor units 40, 50, and 60. Therefore, description of the configuration of the air conditioner 10 of the third embodiment is omitted, and control in the indoor control devices 47, 57, and 67 will be described. As shown in FIG. 5, the control of the indoor side control devices 47, 57, 67 in the third embodiment is a multi-stage control in the liquid rich gas-liquid two-phase state of the control of the second embodiment. It has become what.

  Since the first control state in the normal state and the second control state in the gas-liquid two-phase state are the same as those in the second embodiment in the third embodiment, the description thereof will be omitted.

  Further, the switching conditions of the first control state, the second control state, and the third control state are as shown in FIG. Here, the switching conditions at the time of cooling the indoor unit 40 will be described, and the description of the switching conditions at the time of heating will be omitted. The switching conditions during cooling of the indoor units 50 and 60 and the switching conditions during heating are such that each parameter of the indoor unit 40 is replaced with a parameter of the indoor units 50 and 60, or the superheat degree SH during cooling is the supercooling degree during heating. What is necessary is just to replace with SC. At this time, it is not always necessary to use the same numerical value as the switching condition during cooling and heating.

  FIG. 5 is a conceptual diagram for explaining switching between the first control state, the second control state, and the third control state. As described above, the first control state is switched from the normal first control state shown in FIG. 5 to the gas-liquid two-phase state second control state (gas-liquid two-phase state determination condition) and the second control state. Conditions for switching to a state (gas-liquid two-phase state determination cancellation condition) and conditions for switching from the second control state of the gas-liquid two-phase state to the third control state of the liquid-rich gas-liquid two-phase state (liquid-rich gas-liquid two The phase state determination condition) is the same as in the second embodiment.

The first stage of the third control state is the same as the third control state of the second embodiment. In the first stage of the third control state, as shown in FIG. 6, the gain magnification is increased by (1 + ε) times. In this state, if the determination of the gas-liquid two-phase state continues even after 60 seconds of operation, the process proceeds to the second stage. In the second stage, as shown in FIG. 6, the gain magnification is further increased, and the gain magnification is increased to (1 + 2 · ε) times. That is, at this time, the control amount ΔEV is determined according to the equation: ΔEV = (1 + 2 · ε) · [α · (e−e _prev ) + γ].

  If the determination of the gas-liquid two-phase state continues even after 60 seconds of operation in the second stage state, the process proceeds to the third stage. In the third stage, as shown in FIG. 6, the gain magnification is further increased, and the gain magnification is increased to (1 + 3 · ε) times. If the determination of the gas-liquid two-phase state continues even after 60 seconds of operation in the state of the third stage, the process proceeds to the fourth stage. In the fourth stage, as shown in FIG. 6, the gain magnification is further increased, and the gain magnification is increased to (1 + 4 · ε) times. Here, although the determination is made under the same condition for the continuation of the gas-liquid two-phase state determination condition, the determination condition is not necessarily the same, and the determination may be performed under different conditions in each stage.

  In the third control state, in any stage from the first stage to the fourth stage, the condition for switching to the normal first control state (gas-liquid two-phase state determination cancellation condition) is that the superheat degree SH1 is 3. A state exceeding 0 degrees (SH1> 3.0) has appeared, or the target superheat degree SH1t has become smaller than 3.0 degrees (SH1t <3.0). This condition is the same as the condition for switching from the second control state to the first control state.

  In the gain magnification switching shown in FIG. 6, the gain magnification increases by ε every 60 seconds, but the time interval TT (n) (n is a natural number) for increasing the gain magnification is , Not necessarily constant. This time interval TT (n) may use a recurrence formula or a function, or may be set individually. When the number of stages is small, it is easier to implement them individually.

  For example, as shown in FIG. 7, the time interval TT (n) can be gradually shortened. When the time interval TT (n) is shortened, the time until the gain magnification reaches a higher stage is shortened, whereby the gain magnification is also increased in a short time. Therefore, the amount of change in the valve opening increases in a short time, the valve closing speed becomes faster, and the time interval TT (n) from the gas-liquid two-phase state in a shorter time than when the time interval TT (n) is equal. Escape can be expected. In order to quickly escape from the gas-liquid two-phase state to be escaped, it is preferable that the time interval TT (n) is gradually shortened as shown in FIG. However, as the time interval TT (n) becomes shorter, overheating due to superheat is more likely to occur. Therefore, setting the time interval TT (n) causes overshoot while accelerating the escape from the gas-liquid two-phase state. It is adjusted to be difficult.

  In the control method shown in FIG. 6 and FIG. 7, the case where the gain magnification increases stepwise as time elapses in the third control state has been described. As shown in FIG. 8, it may be a smooth increase proportional to time. The change characteristic of the gain magnification indicated by the reference symbol L1 is that the gain magnification is not increased in the second control state, but is proportional to the elapsed time in the third control state.

At this time, the control amount ΔEV is determined according to the equation: ΔEV = (1 + ε (t)) · [α · (e−e _prev ) + γ]. In this case, ε (t) is a function of the elapsed time t after entering the third control state, and when proportional, ε (t) = φt (where φ is a constant). To be sure, in the second control state in this case, the control amount ΔEV is determined according to the equation: ΔEV = [α · (e−e _prev ) + γ]. Generally, in the above-described expression of the control amount ΔEV, it is sufficient that ε (t) is a monotonically increasing function that monotonously increases with time t.

When further generalized, it becomes a characteristic of a change in gain magnification indicated by a symbol L2. That is, in the second control state, the control amount ΔEV is determined according to the equation: ΔEV = (1 + ε ₂ (t ₂ )) · [α · (e−e _prev ) + γ], and in the second control state, ΔEV = (1 + ε ₃ (t ₃ )) · [α · (e−e _prev ) + γ], the control amount ΔEV is determined. In the case indicated by the symbol L2, ε ₂ (t ₂ ) is a function of the elapsed time t ₂ after entering the second control state, and ε ₂ (t ₂ ) = φ ₂ t ₂ (where φ ₂ is a constant), and ε ₃ (t ₃ ) is a function of the elapsed time t ₃ after entering the third control state, and ε ₃ (t ₃ ) = φ ₃ t ₃ (where φ _{3 3} is a constant). Also in this case, generally, in the above-described equation of the control amount ΔEV, ε ₂ (t ₂ ) may be a monotonically increasing function that monotonously increases with time t ₂ , and ε ₃ (t ₃ ) is time. Any monotonically increasing function that monotonously increases in accordance with t ₃ may be used.

As a special characteristic of the change in gain magnification indicated by the reference symbol L2, there is a characteristic having a change characteristic of gain magnification indicated by the reference symbol L3 when φ ₂ = φ ₃ . In this case, it is not necessary to distinguish between the second control state and the third control state. That is, it is the same as the case where the gain magnification is increased with the passage of time after entering the second control state in the second embodiment.

  When the gain magnification increases with time, there is a method of suppressing a sudden change in the control amount ΔEV when the first control state is changed to the second control state. In the description so far, it has been described that a predetermined constant γ is used to fix the integral gain of the integral term. However, a value that makes the value of the integral term the same when switching from the first control state to the second control state can be applied to the constant γ. That is, γ = β · e (where e is a value at the time of switching from the first control state to the second control state). By performing such switching, the sudden change of the control amount ΔEV when the first control state is changed to the second control state is eliminated, and the value of the integral term is set to increase with time regardless of the deviation. be able to. The same applies to the characteristics indicated by reference numerals L2 and L3, and the values C2 and C3 when switching are β · e (where e is the value when switching from the first control state to the second control state). Value). For this purpose, the values of β · e at the time of switching are calculated by the indoor side control devices 47, 57, and 67, and the indoor side control devices 47, 57, and 67 store the calculated values in the memories 47c, 57c, and 67c. Remember each. Instead of such a method, it is also possible to add an offset value that monotonically increases from 0 with the elapsed time, leaving the integral term. Since the value of the integral term is small in the gas-liquid two-phase state to be escaped, the value of the integral term immediately becomes sufficiently small with respect to the offset value, and the change of the integral term becomes negligible with respect to the offset value.

  Furthermore, in FIG. 6, the case where the first stage, the second stage, the third stage, and the fourth stage are increased by a constant value ε has been described. However, the value that is increased at each stage may not be constant. For example, the gain magnification in the first stage is (1 + ε), the gain magnification in the second stage is (1 + 3 · ε), the gain magnification in the second stage is (1 + 6 · ε), and the fourth It is also possible to change the increment at each stage such that the gain magnification at each stage is (1 + 10 · ε).

  In the above description, the integral gain and the proportional term are multiplied by the same gain magnification. However, the gain magnification multiplied by the integral term and the proportional term may be different. The integral term can be multiplied by the gain magnification of the solid line in FIG. 6, and the proportional term can be multiplied by the gain magnification of the two-dot chain line. Different gain magnifications can be applied to the integral term and the proportional term when the gain magnification is increased over time.

Also, two types of characteristics can be properly used according to the degree of the gas-liquid two-phase state. For example, the gain magnification change indicated by the symbol L3 can be switched when the characteristics of the change of the gain magnification indicated by the symbols L1 and L3 can be switched and the escape from the gas-liquid two-phase state should be accelerated. The change characteristics of When transitioning to the gas-liquid two-phase state while the proportional gain is increasing, IP control is performed when transitioning to the gas-liquid two-phase state within a predetermined time (for example, 120 seconds) after the increase of the proportional gain is canceled If the transition from the gas-liquid two-phase state to the normal state has never occurred since the start of IP control within a predetermined time (for example, 5 minutes), or during control other than IP control, In the case of transition to the phase state, it is determined that the gas-liquid two-phase state should be escaped immediately, and the change characteristic of the gain magnification indicated by the symbol L3 is used. Other than that, the change characteristic of the gain magnification indicated by the symbol L1 is used under the conditions described in FIG.
<Fourth embodiment>
(6) Control of indoor expansion valve by indoor control device The air conditioner according to the fourth embodiment also has the configuration shown in FIG. 1, similarly to the air conditioner of the first embodiment. The difference between the air conditioner of the fourth embodiment and the air conditioner of the first embodiment is the control in the indoor control devices 47, 57, and 67 of the indoor units 40, 50, and 60. Therefore, description of the configuration of the air conditioner 10 of the fourth embodiment is omitted, and control in the indoor side control devices 47, 57, and 67 will be described. As shown in FIG. 9, the control of the indoor side control devices 47, 57, and 67 in the fourth embodiment is performed in addition to the first control state in the normal state and the second control state in the gas-liquid two-phase state. When shifting from the second control state to the first control state, it is configured to return to the normal first control state through the fourth control state for once waiting for stability.

Since the first control state in the normal state and the second control state in the gas-liquid two-phase state are performed in the same manner as in the first embodiment in the fourth embodiment, the description thereof is omitted. The fourth control state for waiting for stability is control in which the amount of valve operation until it is determined that the gas-liquid two-phase state has been escaped and the state shifts from the second control state to the first control state is reduced. For example, if the expression used in the first control state is ΔEV = α · (e−e _prev ) + β · e, the fourth control state is a coefficient larger than 0 and smaller than 1 (0 <η <1 (Η is a real number)). That is, in the fourth control state, the control amount ΔEV is determined according to the equation: ΔEV = η · [α · (e−e _prev ) + β · e].

  The relationship between the first control state, the second control state, the fourth control state, and the switching conditions between the states is as shown in FIG. Here, the switching conditions at the time of cooling the indoor unit 40 will be described, and the description of the switching conditions at the time of heating will be omitted. Further, the switching conditions during cooling of the indoor units 50 and 60 and the switching conditions during heating are such that each parameter of the indoor unit 40 is replaced with a parameter of the indoor units 50 and 60, or the superheat degree SH during cooling is overheated during heating. The degree of cooling may be replaced with SC.

  FIG. 9 is a conceptual diagram for explaining switching between the first control state, the second control state, and the fourth control state. The condition for switching from the first control state to the second control state shown in FIG. 9 (gas-liquid two-phase state determination condition) is, for example, a state where the superheat degree SH1 is 3.0 degrees or less (SH1 ≦ 3.0) Is continued for 60 seconds, or the superheat degree SH1 is smaller than 1.0 degree.

  The condition for switching from the second control state to the first control state (gas-liquid two-phase state determination cancellation condition) starts, for example, when switching from the normal first control state to the second control state of the gas-liquid two-phase state As a point, the superheat degree SH1 becomes larger than 3.0 degrees (SH1> 3.0) before 15 seconds elapses from the start point. In this case, since it is relatively stable even when the second control state is returned to the first control state, the second control state is directly switched to the first control state without passing through the fourth control state.

  In this embodiment, two conditions (gas-liquid two-phase escape determination conditions) for switching from the next second control state to the fourth control state waiting for stability are prepared. That is, when the first condition or the second condition of the gas-liquid two-phase escape determination condition is satisfied, the second control state is switched to the fourth control state. The first condition of the gas-liquid two-phase escape judgment condition is that when the first control state is switched to the second control state, the superheat degree SH1 is more than 3.0 degrees after 15 seconds from the start point. It has increased. In addition, the second condition of the gas-liquid two-phase escape determination condition is that the superheat degree SH1 (n) starts after 15 seconds have elapsed from the start point when the first control state is switched to the second control state. Is larger than 1.0 degree and the superheat degree SH1 (n) is larger than the previous superheat degree SH1 (n-1) added by 0.1 degree for 30 seconds or more. Here, n of SH (n) is a natural number, and SH (n) indicates the degree of superheat SH1 calculated from the nth measurement result.

  A condition for switching from the fourth control state waiting for stability to the second control state of the gas-liquid two-phase state (gas-liquid two-phase state re-determination condition) is, for example, that the superheat degree SH1 is smaller than 1.0 degree. . Alternatively, the state where the superheat degree SH1 is 3.0 ° C. or lower continues for 45 seconds or more. Other examples of the gas-liquid two-phase state redetermination condition include that the relative superheat degree RSH1 is smaller than a predetermined value, or that the decrease in the opening of the indoor expansion valve 41 is continued for a predetermined time. . The relative superheat RSH1 here is obtained by dividing the superheat SH1 of the indoor heat exchanger 42 by the temperature of the intake air (indoor air) of the indoor heat exchanger 42, that is, the temperature difference between the indoor temperature Tr1 and the refrigerant temperature Te1. Value. If the relative superheat degree RSH1 is described by an equation, RSH1 = SH1 ÷ (Tr1−Te1).

The condition for switching from the fourth control state waiting for stability to the normal first control state (first control state return condition) starts, for example, when the second control state switches to the fourth control state. Either 80 seconds or more have elapsed since the point, or the relative superheat RSH1 is greater than 0.5 degrees (RSH1> 0.5).
<Fifth Embodiment>
(7) Control of Indoor Expansion Valve by Indoor Control Device The air conditioner according to the fifth embodiment has the configuration shown in FIG. 1 as with the air conditioner of the first embodiment. The difference between the air conditioner of the fifth embodiment and the air conditioner of the first embodiment is the control in the indoor control devices 47, 57, and 67 of the indoor units 40, 50, and 60. Therefore, the description of the configuration of the air conditioner 10 of the fifth embodiment is omitted, and the control in the indoor control devices 47, 57, and 67 will be described. Control of the indoor side control devices 47, 57, and 67 in the fifth embodiment is a combination of the controls of the second and fourth embodiments, as shown in FIG.

  The first control state in the normal state and the second control state in the gas-liquid two-phase state are the same as in the first embodiment in the fifth embodiment, and the liquid-rich gas-liquid two with a higher liquid refrigerant ratio. The third control state in the phase state is the same as that of the second embodiment, and the fourth control state waiting for stability is the same as that of the fourth embodiment, and thus description thereof is omitted.

  Further, the relationship between the first control state, the second control state, the third control state, the fourth control state, and the switching conditions between the states is as shown in FIG. Here, the switching conditions at the time of cooling the indoor unit 40 will be described, and the description of the switching conditions at the time of heating will be omitted. The switching conditions during cooling of the indoor units 50 and 60 and the switching conditions during heating are such that each parameter of the indoor unit 40 is replaced with a parameter of the indoor units 50 and 60, or the superheat degree SH during cooling is the supercooling degree during heating. What is necessary is just to replace with SC. At this time, it is not necessary to use the same numerical value as the switching condition for cooling and heating.

  FIG. 10 is a conceptual diagram for explaining switching between the first control state, the second control state, the third control state, and the fourth control state. Conditions for switching from the normal first control state shown in FIG. 10 to the second control state of the gas-liquid two-phase state (gas-liquid two-phase state determination condition) and conditions for switching from the second control state to the first control state ( Gas-liquid two-phase state determination cancellation condition) and conditions for switching from the second control state corresponding to the gas-liquid two-phase state to the third control state corresponding to the liquid-rich gas-liquid two-phase state (liquid-rich gas-liquid two-phase The condition determination condition is the same as in the second embodiment.

  In the fifth embodiment, the condition (gas-liquid two-phase escape determination condition) for switching from the second control state in the gas-liquid two-phase state to the fourth control state waiting for stability is, for example, from the first control state to the second control state. The superheat degree SH1 becomes greater than 3.0 degrees after 15 seconds have elapsed from the start point, starting from the time when the control state is switched. A condition for switching from the fourth control state waiting for stability to the second control state of the gas-liquid two-phase state (gas-liquid two-phase state re-determination condition) is, for example, that the superheat degree SH1 is smaller than 1.0 degree. . Alternatively, starting from the time when the second control state is switched to the fourth control state, the state where the superheat degree SH1 is 3.0 degrees or less continues for 60 seconds or more from the start point.

  In the fifth embodiment, the condition for switching from the third control state corresponding to the liquid-rich gas-liquid two-phase state to the fourth control state waiting for stability (the liquid-rich gas-liquid two-phase escape determination condition) is, for example, The superheat degree SH1 is greater than 3.0 degrees. In the fifth embodiment, the fourth control state is not switched to the third control state, but is temporarily returned to the second control state.

  The condition for switching from the fourth control state waiting for stability to the normal first control state (first control state return condition) is 80 seconds or more from the start point, starting at the time of switching to the fourth control state. Or the relative superheat RSH1 is larger than 0.5 degree (RSH1> 0.5).

(8) Features (8-1)
In each of the above embodiments, during cooling, each liquid side temperature sensor 44, from the refrigerant temperature value detected by each gas side temperature sensor 45, 55, 65 in the indoor side control devices 47, 57, 67 (example of control device). The superheat degrees SH1, SH2, and SH3 (examples of the current state quantity and the calculated superheat degree) are detected by subtracting the refrigerant temperature values detected by 54 and 64. When it is determined that the superheat degrees SH1, SH2, SH3 are 3.0 degrees or less (an example of a predetermined value) continues for 60 seconds (example of the first set time) or more, the normal first control is performed. The state is switched to the second control state of the gas-liquid two-phase state. In the state switched in this way, the speed at which the valve opening is reduced (squeezed) is higher in the second control state than in the first control state that is performed in a normal state that is not a gas-liquid two-phase state. Here, the gas side temperature sensors 45, 55, and 65 and the liquid side temperature sensors 44, 54, and 64 are examples of sensors of the refrigeration apparatus according to the first aspect.

  FIG. 11 shows the overheating when the control is performed only in the first control state and the switching from the first control state to the second control state is not performed even if it is determined that the gas-liquid two-phase state to be escaped is reached. It is a graph which shows the relationship between a degree and a valve opening degree. On the other hand, FIG. 12 is a graph showing the relationship between the degree of superheat and the valve opening in each of the above embodiments in which switching between the first control state and the second control state is performed. FIG. 11 and FIG. 12 describe that the degree of superheat, the valve opening degree, and the time per length are the same for the vertical axis and the horizontal axis. It can be seen that the slope at which the valve opening shown in FIG. 12 is reduced is larger than the slope at which the valve opening shown in FIG. 11 is reduced. Therefore, the time in which the degree of superheat is below the threshold value for determining whether or not the gas-liquid two-phase state to be escaped is shorter in the graph of FIG. 12 than in the graph of FIG. .

  During heating, the indoor side control devices 47, 57, and 67 (examples of control devices) convert the discharge pressure Pd of the compressor 21 detected by the discharge pressure sensor 30 into a saturation temperature value corresponding to the condensation temperature Tc. By subtracting the refrigerant temperature value detected by the liquid side temperature sensors 44, 54 and 64 from the saturation temperature value of the refrigerant, the subcooling degrees SC1, SC2 and SC3 (examples of the current state quantity and the calculated subcooling degree) are respectively obtained. can get. When it is determined that the state where the supercooling degrees SC1, SC2, SC3 are 3.0 degrees or less (an example of a predetermined value) continues for 60 seconds (an example of the first set time) or more, the normal first The control state is switched to the second control state of the gas-liquid two-phase state. In the state switched in this way, the speed at which the valve opening is reduced (squeezed) is higher in the second control state than in the first control state that is performed in a normal state that is not a gas-liquid two-phase state. Here, the discharge pressure sensor 30 and the liquid side temperature sensors 44, 54, and 64 are examples of sensors of the refrigeration apparatus according to the first aspect.

  It is determined that the gas-liquid two-phase state should be escaped from the continuation of the superheat degrees SH1, SH2, SH3 and the supercool degrees SC1, SC2, SC3 of 3.0 degrees or less for 60 seconds or more. Therefore, it is possible to avoid making an erroneous determination that the gas-liquid two-phase state should be promptly escaped despite the gas-liquid two-phase state that does not need to be escaped. In this way, in the gas-liquid two-phase state where not only the escape from the gas-liquid two-phase state to be escaped is accelerated, but also the switching to the second control state where the valve opening degree is reduced is not required to escape. It is suppressed. As a result, it is possible to suppress the occurrence of hunting by avoiding the second control state in which the valve opening is rapidly changed in the gas-liquid two-phase state that does not need to be escaped. As a result, it is detected that the gas-liquid two-phase state that should be promptly escaped is detected, and the control of the decompression mechanism that promptly escapes from the gas-liquid two-phase state that should be escaped and stable in normal times. It is possible to achieve both control of the decompression mechanism.

  In particular, control is performed with superheats SH1, SH2, SH3 (examples of calculated superheat degrees) that are directly connected to the gas-liquid two-phase state during cooling, and supercooling degrees SC1, SC2, SC3 (calculated) that are directly connected to the gas-liquid two-phase state during heating. By controlling with the example of the degree of supercooling), it is possible to suppress erroneous determination that is not determined to be a gas-liquid two-phase state to be escaped although it is in a gas-liquid two-phase state to be escaped. And the control of the decompression mechanism which escapes from a gas-liquid two-phase state rapidly in the gas-liquid two-phase state which should be made to escape can be performed reliably.

  In the outdoor expansion valve 38, the same method as described above is applied, and the gas-liquid two-phase state to be escaped from the current state quantity of the refrigerant on the suction side of the compressor 21 or the outlet side of the outdoor heat exchanger is determined. Switching from the first control state to the second control state when it occurs can be performed. At this time, for example, the heat exchanger outlet temperature sensor 39 and the suction pressure sensor 29 or the suction temperature sensor 31 are examples of the refrigeration apparatus sensor according to the first aspect, and the outdoor control device 37 is an example of the control device.

(8-2)
In the first control state, the indoor side control devices 47, 57, and 67 have a deviation e between the target superheat degrees SHt1, SHt2, and SHt3 and the calculated superheat degrees SH1, SH2, and SH3, or the target supercool degrees SCt1, SCt2, and SCt3, and the calculated supercool degrees. PI control is performed to change the valve opening based on the deviation of degrees SC1, SC2, SC3. In each of the above-described embodiments, in the second control state, the calculated superheat degree SH1, SH2, SH3 or the calculated supercooling degree SC1 is calculated from the PI control using, for example, the equation ΔEV = g (SH) or ΔEV = g (SC). , SC2 and SC3 are changed to control for reducing the valve opening. In the gas-liquid two-phase state, the deviation between the target superheating degree SHt1, SHt2, SH3t and the calculated superheating degree SH1, SH2, SH3 or the deviation between the target supercooling degree SCt1, SCt2, SCt3 and the calculated supercooling degree SC1, SC2, SC3 is zero. In some cases, the valve opening degree is reduced based on the calculated superheat degree or the calculated supercooling degree, so that the quick escape from the gas-liquid two-phase state can be performed.

(8-3)
Even if 60 seconds have not passed, the indoor side control devices 47, 57, and 67 have a superheat degree of 1.0 degree (third threshold value) smaller than the superheat degree of 3.0 degrees (example of the first threshold value) during cooling. Superheat degree SH1, SH2, SH3 is smaller than example) or supercooling degree is less than 3.0 degree (example of second threshold value) during heating, and is less than 1.0 degree (example of fourth threshold value) When the degree of supercooling SC1, SC2, SC3 is small, the valve opening degree control is switched from the first control state to the second control state. It becomes a serious gas-liquid two-phase state that should be escaped urgently, and the superheat degree SH1, SH2, SH3 is smaller than 1.0 degree during cooling, or the supercool degree SC1, SC2, SC3 is overcooled during heating When the degree becomes smaller than 1.0 degree, it is possible to respond quickly without waiting for 60 seconds. Thereby, it is possible to prevent the occurrence of a problem that rapidly advances due to a serious gas-liquid two-phase state until 60 seconds elapses. Since the time taken for the determination can be changed according to the degree of the gas-liquid two-phase state, the escape from the gas-liquid two-phase state can be accelerated.

(8-4)
After switching to the second control state, the indoor side control devices 47, 57, and 67 have a superheat degree SH1, SH2, SH3 or a supercool degree SC1, SC2, SC3 larger than 3.0 degrees (the air to be escaped). When the value reaches an example in which it can be determined that the liquid two-phase state has been released, the second control state is immediately switched to the first control state. Control in the first control state is more stable when the gas-liquid two-phase state is escaped than in the second control state to be used in the gas-liquid two-phase state to be escaped. In addition, even if the state immediately returns to the first control state, it is necessary to pass another 60 seconds to return to the second control state, so that hunting can be suppressed while stabilizing the control.

(8-5)
After switching to the second control state, the indoor side control devices 47, 57, and 67 continue for 60 seconds (an example of the second set time) for more than the degree of superheat SH1, SH2, SH3 or the degree of supercooling SC1, SC2, When the state where SC3 is 3.0 degrees or less (the gas-liquid two-phase state where the outlet side of the use side heat exchanger should be escaped) is continued, the speed at which the valve opening is made smaller than in the second control state is third. Switch the valve opening control to the control state. When it takes time to escape from the gas-liquid two-phase state even in the second control state, the escape from the gas-liquid two-phase state can be further accelerated in the third control state, and when the second control state is insufficient, The escape time from the predetermined gas-liquid two-phase state can be further shortened by the three control states.

(9) Modification (9-1) Modification 1A
In each of the above embodiments, the air conditioner in which a plurality of indoor units 40, 50, 60 are connected to one outdoor unit 20 has been described. However, the present invention is directed to one indoor unit per one outdoor unit. It can also be applied to an air conditioner to which is connected.

(9-2) Modification 1B
If it is limited to the air conditioner in which one indoor unit is connected to one outdoor unit 20, the information on the outdoor unit can also be used for the judgment for shifting to the second control state. For example, a period in which the discharge temperature of the compressor 21 is smaller than a predetermined value set in advance continues for a predetermined period, the discharge temperature continuously decreases for a predetermined period, or the degree of superheat (discharge temperature and refrigerant) For example, a period in which the difference from the condensing temperature is smaller than a predetermined value set in advance continues for a predetermined period. As a specific example, a period in which the superheat degree of the discharge unit of the compressor 21 is smaller than 5.0 continues for 60 seconds or more.

(9-3) Modification 1C
In each of the above embodiments, the case of PI control has been described as an example of the first control state, but other control methods such as PID (proportional-integral-derivative) control can also be used for the first control state.

(9-4) Modification 1D
In each of the above-described embodiments, the control that leaves the proportional term such as ΔEV = α · (e−e _prev ) + γ has been described as the second control state. However, for example, the proportional term such as ΔEV = γ is used. If the speed of reducing the valve opening is faster in the second control state than in the first control state in the gas-liquid two-phase state, the degree of superheat is changed to a proportional term. Other functions with SH as a parameter can also be used.

(9-5) Modification 1E
In each of the above embodiments, the case where the decompression mechanism is the indoor expansion valve 41, 51, 61 or the outdoor expansion valve 38 has been described. However, the place where the decompression mechanism is installed is not limited to these, and may be placed in another place. The present invention can be applied to a case where control is performed so that the degree of superheat or supercooling of an object to be controlled by the valve of the installed pressure reducing mechanism does not become too low.

DESCRIPTION OF SYMBOLS 10 Air conditioning apparatus 11 Refrigerant circuit 20 Outdoor unit 21 Compressor 23 Outdoor heat exchanger 30 Discharge pressure sensor 38 Outdoor expansion valve 40, 50, 60 Indoor unit 41, 51, 61 Indoor expansion valve 42, 52, 62 Indoor heat exchanger 44, 54, 64 Liquid side temperature sensor 45, 55, 65 Gas side temperature sensor 46, 56, 66 Indoor temperature sensor 47, 57, 67 Indoor side control device

Japanese Patent Laid-Open No. 10-38387 JP-A-11-83205

Claims (9)

The compressor (21) that compresses the refrigerant, the heat source side heat exchanger (23) and the use side heat exchanger (42, 52, 62) that perform heat exchange with the refrigerant, and the decompression of the refrigerant by the valve opening degree. A refrigerant circuit (11) having an adjustable pressure reducing mechanism (38, 41, 51, 61) and circulating a refrigerant to perform a vapor compression refrigeration cycle;
To obtain the current state quantity on the outlet side of the use side heat exchanger or the heat source side heat exchanger or the suction side of the compressor, which is attached to the refrigerant circuit and used for determining whether or not it is in a gas-liquid two-phase state Sensors (29, 30, 31, 39, 44, 54, 64, 45, 55, 65) for detecting the state quantity of the refrigerant in the refrigerant circuit;
The valve opening degree is configured to be controllable, and it is determined that a gas-liquid two-phase state to be escaped at the outlet side of the use side heat exchanger or the heat source side heat exchanger or the suction side of the compressor is determined. When the predetermined value of the current state quantity to be obtained continues for a first set time or more, the control of the valve opening degree is performed from the first control state to the first control state, which is performed at a normal time that is not a gas-liquid two-phase state. And a control device (47, 57, 67) for switching to the second control state where the speed of reducing the valve opening is fast,
A refrigeration apparatus comprising: The control device calculates a degree of superheat calculated for the refrigerant circuit during cooling as a predetermined value of the current state quantity for determining that the gas-liquid two-phase state to be escaped is equal to or less than a first threshold value. Using a condition that the calculated supercooling degree calculated for the refrigerant circuit during heating is less than or equal to a second threshold value,
The refrigeration apparatus according to claim 1. In the first control state, the control device performs PI control to change the valve opening based on a deviation between the target superheat degree and the calculated superheat degree or a deviation between the target supercool degree and the calculated supercool degree. In the two-control state, the control is changed from the PI control to a control for reducing the valve opening based on the calculated superheat degree or the calculated supercooling degree.
The refrigeration apparatus according to claim 2. Even if the first set time has not elapsed, the control device has a fourth threshold value that is smaller than the third threshold value that is smaller than the first threshold value during cooling or smaller than the second threshold value during heating. When the current state quantity is smaller than the control of the valve opening from the first control state to the second control state,
The refrigeration apparatus according to claim 2 or claim 3. The control device immediately switches from the second control state to the first state when the current state quantity reaches a value that can be determined to have escaped from the gas-liquid two-phase state to be escaped after switching to the second control state. Switch to control state,
The refrigeration apparatus according to any one of claims 1 to 4. The control device controls the valve opening when the control device determines that the gas-liquid two-phase state to be escaped is continued for a second set time or more after switching to the second control state. Switching to the third control state where the speed of reducing the valve opening is faster than in the control state;
The refrigeration apparatus according to any one of claims 1 to 5. In the third control state, the control device increases the speed at which the valve opening is decreased stepwise according to the elapsed time.
The refrigeration apparatus according to claim 6. In the control device, the duration of each step (TT (n)) is set shorter as the step progresses.
The refrigeration apparatus according to claim 7. The compressor (21) that compresses the refrigerant, the heat source side heat exchanger (23) and the use side heat exchanger (42, 52, 62) that perform heat exchange with the refrigerant, and the decompression of the refrigerant by the valve opening degree. A refrigerant circuit (11) having an adjustable pressure reducing mechanism (41, 51, 61) and performing a vapor compression refrigeration cycle by circulating the refrigerant; and whether the gas-liquid two-phase state is attached to the refrigerant circuit. A sensor for detecting a state quantity of the refrigerant in the refrigerant circuit in order to obtain a current state quantity on the outlet side of the use side heat exchanger or the heat source side heat exchanger or the suction side of the compressor, A control method for a refrigeration apparatus (10) comprising:
A first value of a predetermined value of the current state quantity that can be determined to be a gas-liquid two-phase state to be escaped on the outlet side of the use side heat exchanger or the heat source side heat exchanger or on the suction side of the compressor. A determination step for determining whether or not there has been a continuation of a set time or more;
When it is determined in the determination step that the predetermined value of the current state quantity has continued for the first set time or longer, the control of the valve opening is performed in a normal time that is not a gas-liquid two-phase state. A control operation changing step for switching from a state to a second control state in which the valve opening degree is faster than that in the first control state;
A method for controlling a refrigeration apparatus.

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