Multi-type refrigeration cycle apparatus

Abstract

A refrigerant circuit and a controller are provided. The controller includes: a first controller that calculates a total expansion-valve opening degree for the expansion valves as a value for causing a heat-source-side state value of refrigerant to follow a target heat-source-side state value, and outputs the total expansion-valve opening degree as a total heat-source-side expansion-valve opening degree; a second controller that calculates the total expansion-valve opening degree for the expansion valves as a value for causing a use-side state value of refrigerant to follow a target use-side state value, and outputs the total expansion-valve opening degree as a total use-side expansion-valve opening degree; a maximum selector that selects one of the total heat-source-side expansion-valve opening degree and the total use-side expansion-valve opening degree; and a distribution controller that distributes the maximum total expansion-valve opening degree among the expansion valves.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a multi-type refrigeration cycle apparatus including a plurality of use-side heat exchangers, and more particularly, to control over expansion valves based on a state value of refrigerant subjected to heat exchange.BACKGROUND ART

[0002] In certain multi-type refrigeration cycle apparatuses, a plurality of use-side heat exchangers configured to cause heat exchange to be performed between refrigerant and a heat supply target such as air are connected by multiple pipes. Such a multi-type refrigeration cycle apparatus has a refrigerant circuit that includes, as components, a compressor, a heat-source-side heat exchanger, a plurality of expansion valves connected in parallel, and a plurality of use-side heat exchangers connected to the respective expansion valves in series. Furthermore, a controller controls the opening degree of each of the expansion valves to properly adjust the distribution of refrigerant that passes through an associated one of the use-side heat exchangers, and causes the use-side heat exchanger to perform heat exchange with the refrigerant (for example, see Patent Literature 1).

[0003] In such a multi-type refrigeration cycle apparatus, in a cooling operation, the controller changes the opening degree of each expansion valve to control the degree of subcooling to a target degree of subcooling. At this time, the controller distributes the total opening degree of the expansion valves, which is the sum of all the opening degrees of the expansion valves, based on the capacity ratios of the use-side heat exchangers, and controls the distributed opening degree of each expansion valve based on the difference between the degree of superheat of refrigerant that passes through an associated one of the use-side heat exchangers and a target degree of superheat. Then, the controller changes the target degree of subcooling when determining that the degree of superheat of the refrigerant in each of all the use-side heat exchangers exceeds or falls below the target degree of superheat.

[0004] In a heating operation, the controller calculates an opening degree of each expansion valve, which enables the degree of subcooling of refrigerant that passes through an associated one of indoor heat exchangers to reach a predetermined target degree of subcooling. Then, the controller lowers, as control, the target degree of subcooling when determining that the degree of superheat of an outdoor heat exchanger is higher than or equal to a set degree of superheat.CITATION LISTPatent LiteraturePatent Literature 1: Japanese Unexamined Patent Application Publication No. 2002-054836SUMMARY OF INVENTIONTechnical Problem

[0006] In the multi-type refrigeration cycle apparatus disclosed in Patent Literature 1, the controller performs control to change the target degree of subcooling so that the degree of superheat in a heat exchanger operating as an evaporator does not become higher than or equal to the target degree of superheat. However, in such a control, when the amount of refrigerant becomes excessively insufficient in the heat exchanger to the extent that the degree of subcooling becomes uncontrollable, the change in the opening degree of an expansion valve is restricted, and an operation efficiency lowers.

[0007] In a heating operation in which a heat supply target is heated, the target degree of subcooling is changed as a control based on the degree of superheat of the outdoor heat exchanger while performing a control based on the degree of subcooling, which is a control target subject to large disturbances. Consequently, the design burden of control parameters increases.

[0008] The present disclosure is applied to solve the above problems, and relates to a multi-type refrigeration cycle apparatus capable of performing a control more appropriately based on the state of refrigerant that passes through a heat exchanger regardless of excess or deficiency of the amount of refrigerant.Solution to Problem

[0009] A multi-type refrigeration cycle apparatus according to an embodiment of the present disclosure includes: a refrigerant circuit in which a compressor, a heat-source-side heat exchanger, a plurality of expansion valves, and a plurality of use-side heat exchangers connected in series to the respective expansion valves are connected by pipes, and refrigerant is circulated; and a controller configured to control components in the apparatus. The controller includes: a first controller configured to calculate a total expansion-valve opening degree for the expansion valves as a value for causing a heat-source-side state value of the refrigerant flowing out of the heat-source-side heat exchanger to follow a target heat-source-side state value, and output the total expansion-valve opening degree as a total heat-source-side expansion-valve opening degree; a second controller configured to calculate the total expansion-valve opening degree for the expansion valves as a value for causing a use-side state value of the refrigerant flowing out of each of the plurality of use-side heat exchangers to follow a target use-side state value, and output the total expansion-valve opening degree as a total use-side expansion-valve opening degree; a maximum selector configured to select one of the total heat-source-side expansion-valve opening degree and the total use-side expansion-valve opening degree, as a maximum total expansion-valve opening degree; and a distribution controller configured to perform processing to distribute the maximum total expansion-valve opening degree among the expansion valves as respective opening degrees thereof. The distribution controller is configured to distribute the maximum total expansion-valve opening degree at distribution ratios in which the opening degrees of the expansion valves associated with the respective use-side heat exchangers are relatively changed, based on comparison between the use-side state values of the refrigerant flowing out of the use-side heat exchangers and a set threshold.Advantageous Effects of Invention

[0010] In the multi-type refrigeration cycle apparatus according to an embodiment of the present disclosure, the first controller in the controller determines a total heat-source-side expansion-valve opening degree that can be obtained from a heat-source-side state value of refrigerant flowing out of the heat-source-side heat exchanger. The second controller determines a total use-side expansion-valve opening degree that can be obtained from use-side state values of refrigerant flow out of the use-side heat exchangers. The distribution controller distributes the maximum total expansion-valve opening degree, as which the maximum controller selects one of the total heat-source-side expansion-valve opening degree and the total use-side expansion-valve opening degree, among the expansion valves, and determines the opening degrees of the expansion valves. Thus, the multi-type refrigeration cycle apparatus is capable of properly controlling the degree of subcooling in an operation where the refrigerant is sufficient, thereby achieving a high efficiency operation and energy saving. By contrast, in an operation where the refrigerant is insufficient and a subcooling degree control cannot be performed, the multi-type refrigeration cycle apparatus can automatically and consecutively switch the control to a superheat degree control to properly control the degree of subcooling. Thus, regardless of the amount of refrigerant, a high efficiency operation can be maintained.BRIEF DESCRIPTION OF DRAWINGS

[0011] FIG. 1 illustrates a configuration of an air-conditioning apparatus 1 according to Embodiment 1.

[0012] FIG. 2 illustrates a configuration of a controller 400 in the air-conditioning apparatus 1 according to Embodiment 1.

[0013] FIG. 3 illustrates a configuration of a control processing device 410 in Embodiment 1.

[0014] FIG. 4 indicates relationships between time and the degree of subcooling and the degree of superheat in Embodiment 1.

[0015] FIG. 5 illustrates images regarding distribution processing operation in the air-conditioning apparatus 1 according to Embodiment 1.

[0016] FIG. 6 illustrates a configuration of a control processing device 410 in Embodiment 2.

[0017] FIG. 7 illustrates a configuration of a control processing device 410 in Embodiment 3.DESCRIPTION OF EMBODIMENTS

[0018] A multi-type refrigeration cycle apparatus according to each of embodiments will be described with reference to the drawings. In each of figures in the drawings that will be referred to below, components that are the same as or equivalent to those in a previous figure or previous figures are denoted by the same reference signs, and the same is true of the full text of the following descriptions concerning the embodiments. Furthermore, in each of the figures, a relationship or relationships in size between components may be different from actual ones. In additions, the configurations of the components described in the full text of the specification are each merely an example, and the descriptions concerning the configurations are not limiting. In particular, combinations of components are not limited to combinations of components described regarding the same embodiment, and a component or components in one embodiment may be applied to another embodiment. Furthermore, the level of each of pressures and that of each of temperatures are not determined in relation to any particular absolute value, but are relatively determined, for example, based on the state or operation of a device or devices. In addition, with regard to a plurality of components that are of the same type and are distinguished from each other by suffixes, the suffixes may be omitted if it is not necessary to distinguish between the plurality of components or specify one or ones of the plurality of components.Embodiment 1

[0019] FIG. 1 illustrates a configuration of an air-conditioning apparatus 1 according to Embodiment 1. The following description refers to, as an example of a multi-type refrigeration cycle apparatus, an air-conditioning apparatus 1 that air-conditions an indoor space that is an air-conditioning target space. In this case, the air in the indoor space is a heat supply target. As illustrated in FIG. 1, the air-conditioning apparatus 1 according to Embodiment 1 includes a heat-source-side unit 200, use-side units 100, and refrigerant pipes 300. A compressor 210, a four-way valve 220, and a heat-source-side heat exchanger 230 included in the heat-source-side unit 200, and a use-side heat exchanger 110 and an expansion valve 120 included in each of the use-side units 100 are connected by the refrigerant pipes 300, whereby a refrigerant circuit is formed in which refrigerant is circulated to carry heat. In this case, it is assumed that in the air-conditioning apparatus 1 according to Embodiment 1, three use-side units 100 are connected to one heat-source-side unit 200 in parallel by the pipes. It suffices that the number of use-side units 100 connected in parallel to the heat-source-side unit 200 by the pipes is two or more. Regarding control, only one use-side unit 100 that is to operate may be provided.

[0020] The use-side units 100 (use-side units 100a to 100c) each perform air-conditioning by heating or cool air in an indoor space that is an air-conditioning target space. The use-side units 100 include, as components included in the refrigerant circuit, respective use-side heat exchangers 110 (use-side heat exchangers 110a to 110c) and respective expansion valves 120 (expansion valves 120a to 120c). In addition, the use-side units 100 include respective indoor fans 130 (indoor fans 130a to 130c).

[0021] Each of the expansion valves 120, which serve as expansion devices, is a valve configured to decompress the refrigerant to expand the refrigerant. Each expansion valve 120 is, for example, an electronic expansion valve, and controls the amount of refrigerant passing through an associated one of the use-side heat exchangers 110 by adjusting the opening degree based on an instruction from a controller 400, which will be described later, to reduce the pressure of the refrigerant. The use-side heat exchanger 110 is a heat exchanger that causes heat exchange to be performed between air in an indoor space and the refrigerant to heat or cool the air. For example, in a heating operation in which the air is heated, the use-side heat exchanger 110 operates as a condenser, condenses the refrigerant, and causes the refrigerant to reject heat and thus liquefy to change into liquid-phase refrigerant. The liquid-phase refrigerant (hereinafter referred to as liquid refrigerant) then passes through the use-side heat exchanger 110. In a cooling operation in which the air is cooled, the use-side heat exchanger 110 operates as an evaporator, and causes the refrigerant to receive heat and thus evaporate to change into gas-phase refrigerant. The gas-phase refrigerant (hereinafter referred to as gas refrigerant) then passes through the use-side heat exchanger 110. Each of the indoor fans 130 causes air to pass through an associated one of the use-side heat exchangers 110 to accelerate heat exchange in the use-side heat exchanger 110, and supply the air that passes through the use-side heat exchanger 110 to the indoor space, which is the air-conditioning target space.

[0022] The heat-source-side unit 200 according to Embodiment 1 includes, as components included in the refrigerant circuit, a compressor 210, a four-way valve 220, a heat-source-side heat exchanger 230, and an accumulator 240. In addition, the heat-source-side unit 200 includes an outdoor fan 250. The compressor 210 compresses sucked refrigerant and discharges the refrigerant. The compressor 210 is, for example, a scroll compressor, a reciprocating compressor, a vane compressor, or another type of compressor. In this case, the compressor 210 can change the capacity (the amount of refrigerant to be delivered per unit time) of refrigerant to be discharged from the compressor 210 by a change in driving frequency that is made by an inverter circuit or a similar device.

[0023] The four-way valve 220, which serves as a flow switching device, is a valve configured to, for example, switch the flow of the refrigerant between that in the cooling operation and that in the heating operation. In the heating operation, the four-way valve 220 connects a discharge side of the compressor 210 and the use-side heat exchangers 110 and also connect a suction side of the compressor 210 and the heat-source-side heat exchanger 230. In the cooling operation, the four-way valve 220 connects the discharge side of the compressor 210 and the heat-source-side heat exchanger 230 and also connects the suction side of the compressor 210 and the use-side heat exchangers 110. The above description refers to by way of example the case where the four-way valve 220 is used as the flow switching device, but the flow switching device is not limited to the four-way valve 220. For example, the flow switching device may be, for example, a combination of multiple two-way valves.

[0024] The heat-source-side heat exchanger 230 is a heat exchanger configured to cause heat exchange to be performed between the refrigerant and an outdoor air. In the heating operation, the heat-source-side heat exchanger 230 of Embodiment 1 operates as an evaporator and evaporates the refrigerant to change it into gas refrigerant, which will pass through the heat-source-side heat exchanger 230. In the cooling operation, the heat-source-side heat exchanger 230 operates as a condenser and a subcooler and condenses refrigerant to change it into liquid refrigerant, which will pass through the heat-source-side heat exchanger 230. The configuration of the heat-source-side heat exchanger 230 will be described in detail later. Furthermore, the outdoor fan 250 is driven to generate a flow of air such that the air that flows from the outside of the heat-source-side unit 200 is made to pass through the heat-source-side heat exchanger 230 and flow out of the heat-source-side unit 200, thereby promoting heat exchange in the heat-source-side heat exchanger 230.

[0025] It should be noted that the components included in the refrigerant circuit in the air-conditioning apparatus 1 are not limited to those as illustrated in FIG. 1. The refrigerant circuit may include, for example, a capillary tube, as needed. In addition, although it is described that the use-side heat exchangers 110 and the heat-source-side heat exchanger 230 cause heat exchange to be performed between air and the refrigerant, it is not limiting. For example, these heat exchangers may cause heat exchange to be performed between water or geothermal heat and the refrigerant. Moreover, the heat-source-side unit 200 may be configured such that a pipe is branched and an expansion valve 120 is provided in the heat-source-side unit 200.

[0026] Next, an operation of each of the components in the air-conditioning apparatus 1 will be described based on the flow of refrigerant. First of all, an operation of each component in the refrigerant circuit in the heating operation will be described based on the flow of refrigerant. Dashed arrows in FIG. 1 indicate flows of the refrigerant in the heating operation. High-temperature and high-pressure gas refrigerant that is discharged from the compressor 210 after being obtained through compression thereby passes through the four-way valve 220 and flows into the use-side heat exchanger 110. The gas refrigerant is condensed and liquefied while passing through the use-side heat exchanger 110 and exchanging heat with, for example, air in the air-conditioning target space. The condensed and liquefied refrigerant passes through the expansion valve 120. The refrigerant is decompressed while passing through the expansion valve 120. After changing into two-phase gas-liquid refrigerant through decompression by the expansion valve 120, the refrigerant passes through the heat-source-side heat exchanger 230. In the heat-source-side heat exchanger 230, the refrigerant exchanges heat with an outdoor air sent by the outdoor fan 250 and is thus evaporated and gasified. The gasified refrigerant passes through the four-way valve 220 and the accumulator 240, and is re-sucked into the compressor 210. As described above, the refrigerant in the air-conditioning apparatus 1 circulates and performs air-conditioning for heating.

[0027] Next, the cooling operation will be described. The solid arrows in FIG. 1 indicate flows of the refrigerant in the cooling operation. High-temperature and high-pressure gas refrigerant that is discharged from the compressor 210 after being obtained through compression thereby passes through the four-way valve 220 and flows into the heat-source-side heat exchanger 230. Then, the refrigerant passes through the heat-source-side heat exchanger 230, exchanges heat with an outdoor air supplied by the outdoor fan 250, and is thus condensed and liquefied. The liquefied refrigerant passes through the expansion valve 120. While passing through the expansion valve 120, the refrigerant is decompressed to change into two-phase gas-liquid refrigerant. The two-phase refrigerant obtained through decompression by the expansion valve 120 passes through the use-side heat exchanger 110. Then, in the use-side heat exchanger 110, the refrigerant exchanges heat with air in the air-conditioning target space and is thus evaporated and gasified. The gasified refrigerant passes through the four-way valve 220, and is re-sucked into the compressor 210. As described above, the refrigerant in the air-conditioning apparatus 1 circulates and performs air-conditioning for cooling. With respect to Embodiment 1, a cooling operation in which the use-side heat exchanger 110 operates as an evaporator and the heat-source-side heat exchanger 230 operates as a condenser will be described.

[0028] The air-conditioning apparatus 1 according to Embodiment 1 includes a high-pressure sensor 510 and a low-pressure sensor 520 as pressure sensors. The high-pressure sensor 510 detects, as a high-pressure, the pressure of refrigerant discharged from the compressor 210, which is located on a high pressure side in the refrigerant circuit. The low-pressure sensor 520 detects, as a low-pressure, the pressure of refrigerant that flows into the accumulator 240, which is located on a low pressure side in the refrigerant circuit.

[0029] Furthermore, the air-conditioning apparatus 1 according to Embodiment 1 includes, for example, a heat-source-side heat exchanger gas-pipe temperature sensor 530, a heat-source-side heat exchanger liquid-pipe temperature sensor 540, use-side heat exchanger liquid-pipe temperature sensors 550, and use-side heat exchanger gas-pipe temperature sensors 560.

[0030] The heat-source-side heat exchanger gas-pipe temperature sensor 530 is provided at a pipe on a gas pipe side of the heat-source-side heat exchanger 230 and detects the temperature of gas refrigerant (including two-phase refrigerant) that flows into and out of the heat-source-side heat exchanger 230. The heat-source-side heat exchanger gas-pipe temperature sensor 530 detects, in the cooling operation, the temperature of refrigerant that flows into the heat-source-side heat exchanger 230, and detects, in the heating operation, the temperature of refrigerant that flows out of the heat-source-side heat exchanger 230. The heat-source-side heat exchanger liquid-pipe temperature sensor 540 is provided at a pipe on a liquid pipe side of the heat-source-side heat exchanger 230 and detects the temperature of liquid refrigerant (including two-phase refrigerant) that flows into and out of the heat-source-side heat exchanger 230. The heat-source-side heat exchanger liquid-pipe temperature sensor 540 detects, in the in the cooling operation, the temperature of refrigerant that flows out of the heat-source-side heat exchanger 230, and detects, in the heating operation, the temperature of refrigerant that flows into the heat-source-side heat exchanger 230.

[0031] Each of the use-side heat exchanger liquid-pipe temperature sensors 550 (use-side heat exchanger liquid-pipe temperature sensors 550a to 550c) is provided at a pipe located on the liquid pipe side of an associated one of use-side heat exchangers 110. The use-side heat exchanger liquid-pipe temperature sensor 550 detects the temperature of liquid refrigerant (including two-phase refrigerant) that flows into and out of the associated use-side heat exchanger 110. The use-side heat exchanger liquid-pipe temperature sensor 550 detects, in the cooling operation, the temperature of refrigerant that flows into the associated use-side heat exchanger 110, and detects, in the heating operation, the temperature of refrigerant that flows out of the associated use-side heat exchanger 110. Furthermore, each of the use-side heat exchanger gas-pipe temperature sensors 560 (use-side heat exchanger gas-pipe temperature sensors 560a to 560c) is provided at a pipe located on the gas pipe side of an associated one of the use-side heat exchangers 110. The use-side heat exchanger gas-pipe temperature sensor 560 detects the temperature of gas refrigerant (including two-phase refrigerant) that flows into and out of the associated use-side heat exchanger 110. The use-side heat exchanger gas-pipe temperature sensor 560 detects, in the cooling operation, the temperature of refrigerant that flows out of the associated use-side heat exchanger 110, and detects, in the heating operation, the temperature of refrigerant that flows into the associated use-side heat exchanger 110.

[0032] FIG. 2 illustrates a configuration of a controller 400 in the air-conditioning apparatus 1 according to Embodiment 1. The controller 400 is a device configured to control the air-conditioning apparatus 1. As illustrated in FIG. 2, to the controller 400, the various sensors described above are connected, and signals including data on temperature and pressure are input. In addition, a signal including an instruction from a user is input to the controller 400 via an operation unit (not illustrated).

[0033] As illustrated in FIG. 2, the controller 400 includes a control processing device 410, a timing device 420, and a storage device 430. The control processing device 410 performs processing, such as calculation and determination, based on, for example, temperature data included in signals transmitted from various sensors and based on an instruction from the user, and controls components such as the compressor 210, the expansion valves 120, and the outdoor fan 250 included in the air-conditioning apparatus 1. The storage device 430 is a device that stores data required when the control processing device 410 performs processing. The timing device 420 is a device such as a timer that measures time and duration required when the control processing device 410 performs processing such as determination.

[0034] The control processing device 410 includes, for example, a microcomputer or a similar device including a control arithmetic processing device such as a central processing unit (CPU), but this is not limiting. The control processing device 410 may be formed in combination with a dedicated device (hardware) as a component. For example, the control processing device 410 may include, as a dedicated device, a PI controller 417, which will be described later.

[0035] The storage device 430 includes, for example, a read-only memory (ROM). In addition, the storage device 430 includes a storage unit (not illustrated), such as a random access memory (RAM) that can temporarily store data, or an auxiliary storage unit (not illustrated), such as a flash memory or a solid state drive. The storage device 430 also includes, for example, data in which the procedure of processing to be performed by the control processing device 410 is programmed. Then, the control processing device 410 executes processing based on the program data to achieve, for example, control of components.

[0036] FIG. 3 illustrates a configuration of the control processing device 410 in Embodiment 1. Of controls of the air-conditioning apparatus 1 that are performed by the control processing device 410 of the controller 400, a control of the opening degrees of the expansion valves 120 is performed by components as illustrated in FIG. 3. As illustrated in FIG. 3, the control processing device 410 of the controller 400 in Embodiment 1 includes a first controller 411, a second controller 412, a maximum selector 413, and a distribution controller 414.

[0037] The first controller 411 calculates a heat-source-side state value of refrigerant that flows out of the heat-source-side heat exchanger 230. In addition, the first controller 411 calculates and outputs a total expansion-valve opening degree, which is the sum of all the opening degrees of the expansion valves 120 and follows a target heat-source-side state value, as a total heat-source-side expansion-valve opening degree. The air-conditioning apparatus 1 according to Embodiment 1 performs the cooling operation. Thus, because the heat-source-side heat exchanger 230 operates as a condenser, the heat-source-side state value is a degree of subcooling (SC) and the target heat-source-side state value is a target degree of subcooling. In addition, the first controller 411 includes a subcooling degree controller 415.

[0038] The subcooling degree controller 415 calculates the degree of subcooling of refrigerant, and calculates and outputs the total expansion-valve opening degree as a value for causing the degree of subcooling of the refrigerant to follow the target degree of subcooling. To the subcooling degree controller 415 in Embodiment 1, signals from the high-pressure sensor 510 and the heat-source-side heat exchanger liquid-pipe temperature sensor 540 are input. The subcooling degree controller 415 calculates, from a high-pressure value included in a signal from the high-pressure sensor 510, a saturated liquid temperature at the pressure by using a physical property value of the refrigerant. The subcooling degree controller 415 then calculates, as a degree of subcooling, the difference between the saturated liquid temperature and a heat-source-side liquid pipe temperature, which is included in a signal from the heat-source-side heat exchanger liquid-pipe temperature sensor 540. However, a method for calculating the degree of subcooling is not limited to the above method. For example, in the heat-source-side heat exchanger 230, the degree of subcooling may be calculated from a difference between a heat-source-side liquid pipe temperature and a temperature detected by a temperature sensor installed at a portion where the two-phase refrigerant flows. In addition, the target degree of subcooling may be a constant value or a variable value to be set depending on an actual operating condition. In the case where a target degree of subcooling is a variable value, the target degree of subcooling may be a value obtained by multiplying a difference between a condensing temperature and an ambient temperature of a heat exchanger operating as a condenser by a coefficient.

[0039] The second controller 412 calculates a heat-source-side state value of refrigerant that flows out of each of the use-side heat exchangers 110. In addition, the second controller 412 calculates and outputs a total expansion-valve opening degree that is the sum of all the opening degrees of the expansion valves 120 and is a value for causing a use-side state value of the refrigerant to follow a target use-side state value, as a total use-side expansion-valve opening degree. As described above, because the air-conditioning apparatus 1 according to Embodiment 1 performs the cooling operation and each of the use-side heat exchangers 110 operates as an evaporator, the use-side state value is the degree of superheat (SH) and the target use-side state value is a target degree of superheat. In addition, the second controller 412 includes a superheat degree controller 416.

[0040] The superheat degree controller 416 calculates the degree of superheat of refrigerant, and calculates and outputs a total expansion-valve opening degree as a value for causing the degree of superheat of the refrigerant to follow a set upper limit degree of superheat. In Embodiment 1, the superheat degree controller 416 outputs a total expansion-valve opening degree as a value for causing the maximum one of the degrees of superheat of refrigerant that flows out of the use-side heat exchangers 110, to follow the upper limit degree of superheat. The upper limit degree of superheat may be determined based on a hardware restriction, for example, or may be set based on, for example, an experimental rule. To the superheat degree controller 416 in Embodiment 1, signals from the low-pressure sensor 520 and the use-side heat exchanger gas-pipe temperature sensors 560 are input. The superheat degree controller 416 calculates, from a low-pressure value included in a signal from the low-pressure sensor 520, a saturated gas temperature at the pressure by using a physical property value of the refrigerant. The superheat degree controller 416 then calculates, as the degree of superheat of refrigerant that flows out of each of the use-side heat exchangers 110, the difference between the saturated gas temperature and a use-side gas pipe temperature, which is included in a signal from each of the use-side heat exchanger gas-pipe temperature sensors 560. However, the method for calculating the degree of superheat is not limited to the above method. For example, in each of the use-side heat exchangers 110, the degree of superheat may be calculated from the difference between a use-side gas pipe temperature and a temperature detected by a temperature sensor installed at a portion where two-phase refrigerant flows. Furthermore, a control output of superheat degree control is not limited to the maximum degree of superheat. The control output may be a minimum value or another value, for example, a statistical value such as an average value or a median value that can be obtained by performing statistical processing on a plurality of degrees of superheat. It should be noted that because the degree of superheat does not fall below zero, the degree of superheat that is lower than or equal to a certain threshold may be treated as an outlier.

[0041] The subcooling degree controller 415 and the superheat degree controller 416 each include a position-type PI controller 417. The PI controller 417 is a controller configured to perform a feedback control by proportional-integral control. The PI controller 417 has an anti-reset windup function. The anti-reset windup function is a function of reducing occurrence of divergence of an integral value in the case where an output value of the PI controller 417 differs from an actual opening degree of an expansion valve 120 due to selection by the maximum selector 413 or upper or lower limit constraints imposed on the opening degree of the expansion valve 120. A function such as the anti-reset windup function is effective especially in a configuration in which a plurality of PI controllers 417 are arranged in parallel as in the control processing device 410 and a value to be processed next is selected from the output values of the plurality of PI controllers 417.

[0042] The subcooling degree controller 415 and the superheat degree controller 416 in Embodiment 1 include PI controllers 417, but may include other controllers instead of the PI controllers 417. For example, the subcooling degree controller 415 and the superheat degree controller 416 may each include a P controller configured to perform a proportional control, a PID controller configured to perform a proportional-integral-derivative control, or a dynamic feedback controller, such as a model predictive controller. In addition, each of the controllers of the subcooling degree controller 415 and the superheat degree controller 416 may be a dynamic or static controller configured to perform control based on data set in advance in a table format. Furthermore, the controller does not need to be a position-type controller but may be a speed-type controller. However, even when a speed-type controller is used, each of the subcooling degree controller 415 and the superheat degree controller 416 needs to output a total expansion-valve opening degree to the maximum selector 413.

[0043] The maximum selector 413 compares a value of a total heat-source-side expansion-valve opening degree output by the first controller 411 and a value of a total heat-source-side expansion-valve opening degree output by the second controller 412, and outputs the greater one of the above values as a maximum total expansion-valve opening degree.

[0044] The distribution controller 414 distributes the maximum total expansion-valve opening degree output from the maximum selector 413 among the expansion valves 120, and determines the opening degree of each of the expansion valves 120. Next, the procedure of distribution processing that is performed by the distribution controller 414 in Embodiment 1 will be described. It is assumed that U={1, 2, . . . , n} is a set of use-side heat exchanger numbers, where n is the number of use-side heat exchangers 110 that are connected; V⊂U is a set of the numbers of the use-side heat exchangers that are in in operation; and A⊂V is a set of the numbers of use-side heat exchangers in each of which the degree of superheat exceeds the upper limit degree of superheat (SHi>2, i∈V), where SHi is the degree of superheat of the use-side heat exchanger i.

[0045] The distribution controller 414 holds a distribution ratio ki (i∈V). The distribution ratio ki has a characteristic expressed by the following equation (1).[Math. 1]∑i∈𝒱ki=1(1)

[0046] Then, the distribution controller 414 calculates an opening degree of each of the expansion valves 120 based on the distribution ratio ki, according to equation (2), where Si is the opening degree of each expansion valve 120, and Stotal is a maximum total expansion-valve opening degree that is output by the maximum selector 413. Initial values of the distribution ratios ki are set, for example, equally among the expansion valves 120, or set in proportion to capability ratios of the use-side heat exchangers 110.[Math. 2]Si=ki*Stotal⁢ i∈𝒱(2)

[0047] The distribution controller 414 determines, for example, whether to update the distribution ratio ki at one-minute intervals, but this is not limiting. For example, the distribution controller 414 is not necessarily required to execute the processing at regular intervals. The distribution controller 414 is allowed to execute the processing upon detection of a dry state. Also, the distribution controller 414 is allowed to execute the processing upon detection of start or stop of the operation of the use-side unit 100. In addition, the distribution controller 414 may execute the processing by combining updates that are performed at regular intervals with updates triggered by events such as detection of a dry state or start / stop of the use-side unit 100.

[0048] When the distribution controller 414 determines that the degree of superheat of a use-side heat exchanger 110 is higher than a set superheat degree threshold (for example, 2K), it is determined that refrigerant that flows in the use-side heat exchanger 110 is insufficient (in a dry state). Then, the distribution controller 414 sets the distribution ratio ki of the expansion valve 120 to a higher distribution ratio ki in which the opening degree of the expansion valve 120 is increased from the current opening degree thereof. When the distribution ratio ki is increased and the opening degree of the expansion valve 120 is increased, the amount of the refrigerant flowing in the use-side heat exchanger 110 is increased.

[0049] Next, an example of updating the distribution ratio ki will be described. In the description, k is a step at the timing of performing the previous update and k+1 is a step at the timing of performing the present update. First, when all the use-side heat exchangers 110 are in a dry state or all the use-side heat exchanger 110 are not in a dry state, and A or Ac (Ac is a complement of A⊂V) is an empty set, the distribution ratio ki is not changed. Thus, the distribution ratio ki(k+1) of the present update is expressed by equation (3) by using the distribution ratio ki (k) of the previous update.[Math. 3]ki(k+1)=ki(k)⁢ i∈𝒱(3)

[0050] By contrast, when some of the use-side heat exchangers 110 are in a dry state and neither A nor Ac is an empty set, the distribution ratio ki(k+1) resulting from the present update is expressed by equation (4) by using the distribution ratio ki (k) resulting from the previous update. The distribution ratio ki (k) resulting from the previous update is the distribution ratio ki for the current opening degree of the expansion valve 120. The equation (4) is an equation for an update in which the opening degree of an expansion valve 120 associated with a use-side heat exchanger 110 that is in a dry state is increased by 10% with reference to the current opening degrees. It should be noted that when ki(k+1) is less than or equal to 0, or greater than or equal to 1, the distribution ratio ki is not changed. Thus, the distribution ratio ki(k+1) resulting from the present update is expressed by the above equation (3)[Math. 4]ki(k+1)={110100⁢ki(k)…⁢ i∈𝒜ki(k)-10100⁢ki(k)⁢∑i∈𝒜ki(k)∑i∈𝒜cki(k)…⁢ i∈𝒜c(4)

[0051] When the distribution controller 414 updates the distribution ratio ki as described above, the opening degree of an expansion valve 120 associated with a use-side heat exchanger 110 that is in a dry state is relatively increased and the amount of refrigerant passing through the use-side heat exchanger 110 is increased, whereby the dry state can be eliminated. In addition, the distribution ratio ki for the opening degree of an expansion valve 120 associated with a use-side heat exchangers 110 that is not in a dry state (proper state) is maintained and at the same time, the distribution ratio ki for the total expansion-valve opening degree can be reduced. Although the equation (4) indicates the case where the opening degree of an expansion valve 120 associated with a use-side heat exchanger 110 that is in a dry state is increased by 10%, the percent by which the opening degree is increased is not limited to 10%, and may be variable.

[0052] Next, it will be described how the distribution controller 414 performs processing for determining the distribution ratio ki of each expansion valve 120 in the case where the use-side unit 100 being in operation is stopped or the use-side unit 100 being in the stopped state is started. Here, the distribution controller 414 of the controller 400 does not update the distribution ratio ki based on the dry state described above, because the state of the refrigerant in the refrigerant circuit is unstable immediately after a stop or start of the operation of the use-side unit 100.

[0053] The following description is made on the assumption that M⊂V is a set of the numbers of the use-side heat exchangers 110 of use-side units 100 that are newly stopped; N⊂Vc is a set of the numbers of the use-side heat exchangers 110 of use-side units 100 that are newly started; V(k+1) is a set of the numbers of the use-side heat exchangers 110 of use-side units 100 that are in an operating state at the present time; and V(k) is a set of the numbers of the use-side heat exchangers 110 of use-side units 100 which were in an operating state at the previous time. For example, when V(k)={1, 3, 5, 7}, M={3} and N={2}, V (k+1)={1, 2, 5, 7}.

[0054] The distribution controller 414 causes the expansion valve 120 of a use-side unit 100 that is stopped to be fully closed (opening degree 0). In addition, for the opening degrees of the expansion valves 120 of the use-side units 100 excluding the use-side unit 100 that is stopped, distribution ratios kl′ that are normalized according to the following equation (5) such that that the sum of the distribution ratios ki for the previous update is 1 are calculated.[Math. 5]ki′=ki(k)∑i∈𝒱∖ℳki(k)⁢ i∈𝒱∖ℳ(5)

[0055] Next, the distribution controller 414 calculates an average of the normalized distribution ratios ki′ according to the following equation (6) and determines the average as a normalized distribution ratio ki′ for a use-side heat exchanger 110 that starts operating. It should be noted that |V−M| is the number of elements in a set V−M. In addition, a minus sign in a set indicates a difference set. It should also be noted that notation is present that uses a backslash instead of the minus sign. In the following equation, notation using a backslash is used.[Math. 6]ki′=∑i∈𝒱∖ℳki′<semantics definitionURL="">❘<annotation encoding="Mathematica">"\[LeftBracketingBar]"< / annotation>< / semantics>𝒱∖ℳ<semantics definitionURL="">❘<annotation encoding="Mathematica">"\[RightBracketingBar]"< / annotation>< / semantics>=1<semantics definitionURL="">❘<annotation encoding="Mathematica">"\[LeftBracketingBar]"< / annotation>< / semantics>𝒱∖ℳ<semantics definitionURL="">❘<annotation encoding="Mathematica">"\[RightBracketingBar]"< / annotation>< / semantics>⁢ i∈𝒩(6)

[0056] Then, the distribution controller 414 re-performs normalization based on the normalized distribution ratio ki′ and calculates a distribution ratio ki(k+1) for the present update, according to the following equation (7).[Math. 7]ki(k+1)=ki′∑i∈𝒱(k+1)ki′⁢ i∈𝒱⁡(k+1)(7)

[0057] As described above, when a use-side unit 100 is stopped or started, the distribution controller 414 can calculate and determine the distribution ratio ki for the opening degree of an associated one of the expansion valves 120. As described above, because distribution ratios are maintained as much as possible even when an operating condition is changed, that is, distribution ratios for the opening degrees of expansion valves 120 associated with use-side heat exchangers 110 that are in a proper state are maintained, it is possible to reduce occurrence of a disturbance of a control that is caused by a change in the operating condition. Although it is described that the sum of the distribution ratios ki is 1, it is not indispensable that the sum is 1, and the sum may be updated to another value depending on the operating condition. In addition, the above method for calculating and determining the distribution ratio ki is merely an example, and the distribution controller 414 can use any method as long as a solution similar to the solution obtained the above method is obtained.Operation Image

[0058] FIG. 4 illustrates graphs indicating respective relationships between time and the degree of subcooling and the degree of superheat in Embodiment 1. FIG. 4, (a), illustrates the degree of subcooling and the degree of superheat of refrigerant in the case where the amount of the refrigerant in the refrigerant circuit is appropriate. When an appropriate amount of refrigerant is filled in the refrigerant circuit, as time passes, the degree of subcooling of refrigerant that flows out of a heat exchanger operating as a condenser gradually converges to an optimal degree of subcooling, as illustrated in FIG. 4, (a). In addition, as time passages, the degree of superheat of refrigerant flowing out of a heat exchanger operating as an evaporator gradually converges to an optimal degree of superheat over time.

[0059] FIG. 4, (b), illustrates the degree of subcooling and the degree of superheat in the case where an excess amount of refrigerant is filled in the refrigerant circuit. When refrigerant is excessively filled in the refrigerant circuit, the degree of superheat of refrigerant flowing out of the heat exchanger operating as an evaporator cannot be controlled, as illustrated in FIG. 4, (b). By contrast, as time passes, the degree of subcooling of the refrigerant flowing out of the heat exchanger operating as a condenser gradually converges to the optimal degree of subcooling. In the control processing device 410 of the controller 400, when the maximum selector 413 selects a higher one of total expansion-valve opening degrees, the total expansion-valve opening degree can be highly accurately distributed among the expansion valves 120 as respective opening degrees thereof, and thus an energy saving control can be performed.

[0060] FIG. 4, (c), illustrates the degree of subcooling and the degree of superheat in the case where the amount of the refrigerant in the refrigerant circuit is insufficient. When the amount of the refrigerant in the refrigerant circuit is insufficient, the degree of subcooling of the refrigerant flowing out of the heat exchanger operating as a condenser cannot be controlled, as illustrated in FIG. 4, (c). By contrast, as time passes, the degree of superheat of the refrigerant flowing out of the heat exchanger operating as an evaporator gradually converges to the optimal degree of superheat. Thus, the controller 400 can perform an energy saving control.

[0061] FIG. 5 illustrates images regarding distribution processing operation in the air-conditioning apparatus 1 according to Embodiment 1. Referring to FIG. 5, because the degree of superheat of the refrigerant flowing out of the use-side heat exchanger 110a exceeds a threshold, the distribution ratio ki for the refrigerant passing through each expansion valve 120 is updated at a time T. The distribution controller 414 performs control to increase the opening degree of the expansion valve 120a by 10%. In addition, the distribution controller 414 perform control to reduce the opening degrees of the expansion valves 120b and 120c by 5%. In such a manner, since the distribution controller 414 controls distribution of the opening degrees of the expansion valves 120, the degree of superheat of the refrigerant flowing out of the use-side heat exchanger 110a is reduced and converges to a value less than or equal to the threshold. By contrast, although, as illustrated in (b) and (c) in FIG. 5, the degrees of superheat of the refrigerant flowing out of the use-side heat exchanger 110b and the use-side heat exchanger 110c slightly increase, but converges to the threshold or converges below the threshold, and the state of the refrigerant is stabilized.Advantages of Air-Conditioning Apparatus 1 According to Embodiment 1

[0062] As described above, in the air-conditioning apparatus 1 according to Embodiment 1, in the control processing device 410 of the controller 400, the first controller 411 includes the subcooling degree controller 415 and calculates a total heat-source-side expansion-valve opening degree based on the degree of subcooling of refrigerant that flows out of the heat-source-side heat exchanger 230; and the second controller 412 includes the superheat degree controller 416 and calculates a total use-side expansion-valve opening degree based on the degrees of superheat of refrigerant that flows out of the use-side heat exchangers 110. The maximum selector 413 compares the total heat-source-side expansion-valve opening degree and the total heat-source-side expansion-valve opening degree with each other, and outputs the larger one of the total heat-source-side expansion-valve opening degree and the total heat-source-side expansion-valve opening degree as the maximum total expansion-valve opening degree. The distribution controller 414 distributes the maximum total expansion-valve opening degree among the expansion valves 120 to determine the opening degrees of the expansion valves 120. Thus, the air-conditioning apparatus 1 according to Embodiment 1 can maintain a highly efficient operation even under a condition where an excess or insufficient amount of refrigerant is supplied.

[0063] For example, in general, in a multi-type refrigeration cycle apparatus like the air-conditioning apparatus 1 including the accumulator 240 in Embodiment 1, the degree of subcooling of refrigerant that flows in each use-side heat exchanger 110 is controlled by control over the opening degree of an associated one of the expansion valves 120. However, when the amount of the refrigerant in the refrigerant circuit becomes insufficient, a degree of subcooling does is not obtained even when the opening degrees of the expansion valves 120 are reduced, as a result of which the degree of subcooling becomes uncontrollable, and it is therefore impossible to determine appropriate opening degrees of the expansion valves 120. In addition, when the amount of the refrigerant in the refrigerant circuit becomes insufficient, the amount of refrigerant flowing in a use-side heat exchanger 110 operating as an evaporator may become insufficient and the capability may thus become insufficient. In view of this, according to the air-conditioning apparatus 1 according to Embodiment 1, the control processing device 410 of the controller 400 selects a total expansion-valve opening degree for determining the opening degrees of the expansion valves in the next step, from a total expansion-valve opening degree based on the degree of subcooling and a total expansion-valve opening degree based on the degree of superheat. Therefore, when the refrigerant in the refrigerant circuit is sufficient, the controller 400 can achieve a high efficient and energy saving operation by appropriately controlling the degree of subcooling. In addition, even under an operation condition where the refrigerant is insufficient due to, for example, a long pipe length and the degree of subcooling cannot be controlled, the control is automatically and consecutively switched to a control based on the degree of superheat, and it is therefore possible to reduce an increase in the degree of superheat. Furthermore, because the control processing device 410 determines the opening degree of each expansion valve 120 for reduction of an increase in the degree of superheat, a stable and high efficient operation can be maintained.

[0064] Furthermore, a control unit included in the control processing device 410 of the controller 400 in Embodiment 1 is a control unit for consecutive control, which has an anti-reset windup function. With this configuration, even in an operation in which the amount of refrigerant in the refrigerant circuit is moderate and that is on a switching point between a subcooling degree control and a superheat degree control, it is possible to reduce an occurrence of hunting. Thus, the air-conditioning apparatus 1 can be stably operated. In addition, the degree of superheat can be highly accurately controlled to the upper limit degree of superheat. With this configuration, it is possible to reduce an increase in a discharge temperature of refrigerant that is discharged by the compressor 210 and to protect the components in the refrigerant circuit. Therefore, it is possible to obtain such advantages as described above by applying a consecutive control such as PI control, not only to a subcooling control that is a main control but also to a protection that is a secondary control, and by using the maximum selector 413 in combination with the above control.

[0065] As described above, in the air-conditioning apparatus 1 according to Embodiment 1, an efficient operation can be maintained even when the amount of the refrigerant in the refrigerant circuit is insufficient. This means that even in the case where the number of refrigerant circuits is reduced, a high efficient operation can be maintained. It is therefore possible to provide a multi-type refrigeration cycle apparatus that can highly efficiently operate while reducing the cost thereof by reducing the amount of refrigerant.

[0066] The following description is made with respect to the case where the refrigerant is excessively filled in the refrigerant circuit. In a multi-type refrigeration cycle apparatus, in some case, the degree of superheat is controlled by the expansion valve 120. However, in the case where the refrigerant is excessively filled in the refrigerant circuit, the degree of superheat cannot be controlled unless the opening degree of the expansion valve 120 is extremely reduced, and an energy saving performance is reduced. When the refrigerant is excessively filled, a total heat-source-side expansion-valve opening degree that is determined based on the degree of subcooling and output by the subcooling degree controller 415 becomes higher than a total heat-source-side expansion-valve opening degree that is determined based on the degree of superheat and output by the superheat degree controller 416. In the air-conditioning apparatus 1 according to Embodiment 1, a larger total expansion-valve opening degree selected by the maximum selector 413 is distributed among the expansion valves 120 as respective opening degrees thereof by the distribution controller 414, whereby the subcooling degree control is performed. With this configuration, a more efficient operation can be achieved.

[0067] Furthermore, in the air-conditioning apparatus 1 according to Embodiment 1, the distribution controller 414 updates the distribution ratio ki only when the degree of superheat of refrigerant passing through a heat exchanger is higher than a predetermined threshold. In general, it is difficult for a multi-type refrigeration cycle apparatus to perform a superheat degree control with high accuracy. This results from nonlinearity due to, for example, change in the number of use-side heat exchangers that are in operation or change in load of each use-side heat exchanger 110. It also results from adoption of a multi-input multi-output system in which an operation of one expansion valve 120 affects the degrees of superheat in all the use-side heat exchangers 110. In addition, it is necessary to give appropriate target values for various operation states, and this makes control design difficult. In view of this point, in the air-conditioning apparatus 1 according to Embodiment 1, the distribution controller 414 updates the distribution ratio ki only when the degree of superheat is higher than the predetermined threshold. In addition, the superheat degree controller 416 configured to control a maximum value, a minimum value, or an average value of the degrees of superheat of refrigerant passing through the use-side heat exchangers 110 is used in combination with the distribution controller 414. With this configuration, robustness against a change in environment, such as the amount of refrigerant, an installation condition, or an operation condition, is improved and the stability of the degree of superheat is thus improved. As a result, it is possible to reduce an occurrence of hunting. As described above, because the configuration of the control processing device 410 itself has high robustness, the load of the control design can be reduced. Furthermore, a designer has only to give a predetermined threshold. Therefore, it is possible to further reduce the load of design. This advantage cannot be obtained in the case where the superheat degree controller 416 and the distribution controller 414 are not used in combination.

[0068] Furthermore, in the air-conditioning apparatus 1 according to Embodiment 1, the controller 400 controls and manages the opening degree of each expansion valve 120 with respect to the distribution ratio ki, and it is therefore possible to control an increase and decrease in the opening degree of each expansion valve with respect to ratio. As a result, the opening degrees of the expansion valves can keep a linear relationship with the amount of the refrigerant, and can thus be controlled easily. Because the opening degrees of the expansion valves are managed by using the distribution ratio ki, the control of a start or stop of operation of each of use-side units 100 including the use-side heat exchangers 110 can be simplified. In particular, in a design, by setting that distribution ratios of expansion valves 120 for which the distribution ratios do not need to be changed such that the distribution ratios are kept as much as possible, it is possible to reduce occurrence of a disturbance on the refrigeration cycle that would be caused by a protective operation or a change in an operation state.

[0069] Furthermore, the first controller 411 and the second controller 412 include the PI controllers 417 and perform a feedback control. For the PI controller 417, which is an established controller in a control engineering field, methods for designing parameters have already been established by many existing studies. Therefore, in the air-conditioning apparatus 1 according to Embodiment 1, it is possible to reduce the load of designing a controller configured to control the degree of superheat or the degree of subcooling. For example, as a method for designing parameters for a controller, a design method that uses a system identification result by a step response can be considered. Basically, a parameter is calculated through a mathematical procedure from a characteristic obtained by a system identification, but a parameter for a controller can also be learned from input / output data that is input to or output from the controller when the air-conditioning apparatus 1 is actually operated. It should be noted that with respect to the system identification, it is not limited whether it is an online identification or an offline identification.Embodiment 2

[0070] FIG. 6 illustrates a configuration of the control processing device 410 in Embodiment 2. FIG. 6 illustrates a section that performs a control of the opening degree of each expansion valve, among controls of the air-conditioning apparatus 1 that are performed by the control processing device 410 of the controller 400. As illustrated in FIG. 6, as in Embodiment 1, the controller 400 according to Embodiment 2 includes the first controller 411, the second controller 412, the maximum selector 413, and the distribution controller 414. As in the case of Embodiment 1, the maximum selector 413 compares a value of a total heat-source-side expansion-valve opening degree output by the first controller 411 and a value of a total heat-source-side expansion-valve opening degree output by the second controller 412, and outputs the larger one of the value of the total heat-source-side expansion-valve opening degree and the value of the total heat-source-side expansion-valve opening degree as a maximum total expansion-valve opening degree.

[0071] The following description is made with respect to the case where the air-conditioning apparatus 1 according to Embodiment 2 performs a heating operation in which the use-side heat exchanger 110 operates as a condenser and the heat-source-side heat exchanger 230 operates as an evaporator. Thus, in the control processing device 410 of the controller 400 in Embodiment 2, the first controller 411 includes the superheat degree controller 416, and the second controller 412 includes the subcooling degree controller 415, as illustrated in FIG. 6.

[0072] The subcooling degree controller 415 in Embodiment 2 outputs a total expansion-valve opening degree as a value for causing the maximum one of the degrees of subcooling of refrigerant that flows out of the use-side heat exchangers 110 to follow a target degree of subcooling. To the subcooling degree controller 415 of Embodiment 2, signals from the high-pressure sensor 510 and the use-side heat exchanger liquid-pipe temperature sensors 550 are input. A control output for the subcooling degree control is not limited to the maximum degree of subcooling but may be a minimum value or another value, such as a statistical value that can be obtained through statistical processing on a plurality of degrees of subcooling as an average value or a median value, for example. It should be noted that because the degree of subcooling does not fall below zero, a degree of subcooling that is lower than a certain threshold may be treated as an outlier.

[0073] On the other hand, the superheat degree controller 416 in Embodiment 2, for example, calculates and outputs a total expansion-valve opening degree for causing the degree of superheat of refrigerant that flows out of the heat-source-side heat exchanger 230 to follow an upper limit degree of superheat. In addition, to the superheat degree controller 416 in Embodiment 1, signals from the low-pressure sensor 520 and the heat-source-side heat exchanger gas-pipe temperature sensor 530 are input.

[0074] As in Embodiment 1, the distribution controller 414 distributes the maximum total expansion-valve opening degree output from the maximum selector 413 among the expansion valves 120 to determine the opening degrees thereof. However, because the air-conditioning apparatus 1 of Embodiment 2 performs the heating operation, the distribution controller 414 executes processing different from that of Embodiment 1. A procedure of processes by the distribution controller 414 in Embodiment 2 will be described on the assumption that U={1, 2, . . . , n} is a set of use-side heat exchanger numbers, where n is the number of use-side heat exchangers 110 being connected; V⊂U is a set of use-side heat exchanger numbers of use-side heat exchangers that are in operation; A⊂V is a set of use-side heat exchanger numbers of use-side heat exchangers in which the degree of superheat is lower than a lower limit subcooling-degree threshold (SCi<2, i∈V); B⊂V is a set of use-side heat exchanger numbers of use-side heat exchangers in each of which the degree of subcooling exceeds an upper limit subcooling-degree threshold (SCi>9, i⊂V), where SCi is a degree of subcooling of the use-side heat exchanger I; and C={i∈V} is a set of use-side heat exchanger numbers of the use-side heat exchangers in which the degree of subcooling is within an appropriate range. It should be noted that i in the set C does not belong to set A or set B.

[0075] As in Embodiment 1, the distribution controller 414 holds distribution ratios ki (i∈V) having a characteristic expressed by the equation (1). Then, the distribution controller 414 calculates an opening degree of each expansion valve 120 based on the distribution ratios ki, according to the equation (2) described above.

[0076] Then, the distribution controller 414 updates the distribution ratio ki at, for example, one-minute intervals, but this is not limiting. When determining that the degree of subcooling of a use-side heat exchanger 110 is lower than the predetermined lower limit subcooling-degree threshold (for example, 2K), the distribution controller 414 determines that an excess amount of refrigerant flows in the use-side heat exchanger 110 and thus decreases the distribution ratio ki of an associated one of the expansion valves 120. When the distribution ratio ki is decreased, the opening degree of the expansion valve 120 is decreased and the amount of refrigerant that flows in the use-side heat exchanger 110 is thus decreased.

[0077] When determining that the degree of subcooling of a use-side heat exchanger 110 is higher than the predetermined upper limit subcooling-degree threshold (for example, 9K), the distribution controller 414 determines that a sufficient amount of refrigerant does not flow in the use-side heat exchanger 110 and thus increases the distribution ratio ki of an associated one of the expansion valves 120. When the +0 distribution ratio ki is increased, the opening degree of the expansion valve 120 is increased and the amount of the refrigerant flowing in the use-side heat exchanger 110 is thus increased.

[0078] Next, an example of updating of the distribution ratio ki will be described on the assumption that k is a step at the timing of the previous update and k+1 is a step at the timing of the present update. First, when all the use-side heat exchangers 110 are in the same state, the distribution ratios ki are not changed. The same state means V=A or V=B or V=C (this state will be referred to as condition a). The distribution ratio ki(k+1) resulting from the present update can be expressed by the equation (3) by using the distribution ratio ki (k) resulting from the previous update.

[0079] Meanwhile, when the use-side heat exchangers 110 do not satisfy the condition a and a use-side heat exchanger 110 in which the degree of subcooling falls within an appropriate range is not present, that is, when V≠A and V≠B and V≠C=Φ (empty set) are satisfied (this state will be referred to as condition b), the distribution ratio ki is determined by division by cases. The division by cases is carried out according to the number of elements.

[0080] In the case where |A|<|B|, the distribution ratio ki of the opening degree of the expansion valve 120 is updated based on the following equation (8).[Math. 8]ki(k+1)={90100⁢ki(k)…⁢ i∈𝒜ki(k)+10100⁢ki(k)⁢∑i∈𝒜ki(k)∑i∈ℬki(k)…⁢ i∈ℬ(8)

[0081] In the case where |A|≥|B|, the distribution ratio ki of the opening degree of the expansion valve 120 is updated based on the following equation (9).[Math. 9]ki(k+1)={110100⁢ki(k)…⁢ i∈ℬki(k)-10100⁢ki(k)⁢∑i∈ℬki(k)∑i∈𝒜ki(k)…⁢ i∈𝒜(9)

[0082] Finally, in the case where neither the condition a nor the condition b is satisfied, that is, in the case where V≠A, V≠B, V≠C, and C≠Φ, the distribution ratio ki of the opening degree of the expansion valve 120 is updated based on the following equation (10).[Math. 10]ki(k+1)={90100⁢ki⁢(k)…⁢ i∈𝒜110100⁢ki⁢(k)…⁢ i∈ℬki(k)+10100⁢ki(k)⁢∑i∈𝒜ki(k)∑i∈𝒞ki(k)-10100⁢ki(k)⁢∑i∈ℬki(k)∑i∈𝒞ki(k)…⁢ i∈𝒞(10)

[0083] When the distribution controller 414 updates the distribution ratio ki as described above, the opening degree of an expansion valve 120 associated with a use-side heat exchanger 110 in which the amount of the refrigerant is small is relatively increased and the amount of the refrigerant passing through the use-side heat exchanger 110 is increased. Thus, the opening degree of an expansion valve 120 associated with a use-side heat exchanger 110 in which the amount of the refrigerant is large is relatively decreased and the amount of the refrigerant passing through the use-side heat exchanger 110 is decreased. In addition, the opening degree of an expansion valve 120 associated with a use-side heat exchanger 110 in which the amount of refrigerant passing therethrough is not small or large and is proper is changed in such a manner as to maintain the total expansion-valve opening degree for the above expansion valves 120. Although the opening degree of the expansion valve 120 of the use-side heat exchanger 110 is increased or decreased by 10% in the equations (8) to (10), the percent by which the opening degree is increased or decreased is not limited to 10%, and needs not to be constant. In addition, although it is described above that regarding the condition b, depending on the number of elements in a set, case division is performed with respect to the method for determining a distribution ratio ki and the method is switched between plural methods. The conditions may be reversed and the method needs not to be switched depending on the number of elements.

[0084] In the case where a use-side unit 100 that is in operation is stopped or a use-side unit 100 that is in a stopped state is stated, the processing for determining the distribution ratio ki for an associated expansion valve 120 by the distribution controller 414 is the same as that in Embodiment 1. However, in the heating operation, when the expansion valve 120 associated with the use-side heat exchanger 110 that is in the stopped state is completely closed, the refrigerant may remain in the use-side heat exchanger 110. Thus, the expansion valve 120 may be slightly opened. Even when the expansion valve 120 is slightly opened, it is not a problem as long as it has little effect on the amount of refrigerant passing through the use-side heat exchanger 110 of the use-side unit 100 that is in operation. If the effect cannot be ignored, the distribution ratio ki is set according to the slight opening of the expansion valve 120 to extend the determination method of the distribution ratio ki.Advantages of Air-Conditioning Apparatus 1 According to Embodiment 2

[0085] As described above, in the air-conditioning apparatus 1 according to Embodiment 2, the control processing device 410 of the controller 400 includes the subcooling degree controller 415 and the distribution controller 414. By using the subcooling degree controller 415 and the distribution controller 414 in combination, a maximum value, a minimum value, or an average value of the degrees of subcooling can be controlled based on the total expansion-valve opening degree. Therefore, the degree of subcooling of each use-side heat exchanger 110 can be kept in an appropriate range, and a high efficiency operation can thus be achieved. This advantage cannot be obtained unless the subcooling degree controller 415 and the distribution controller 414 are used in combination.

[0086] In the air-conditioning apparatus 1 according to Embodiment 2, the distribution controller 414 updates the distribution ratio ki only when the degree of subcooling of refrigerant passing through a heat exchanger does fall within the predetermined range. In general, in a multi-type refrigeration cycle apparatus, it is hard to perform a subcooling degree control with high accuracy. This is caused by, for example, nonlinearity due to a change in the number of use-side units 100 that are in operation or a change in load of each use-side heat exchanger 110. This is also because the multi-type refrigeration cycle apparatus uses a multi-input multi-output system in which the operation of the expansion valve 120 affects the degrees of subcooling of all the use-side heat exchangers 110. Moreover, because appropriate target values are required to be set for various operation states, it makes control design difficult. In view of these points, in the air-conditioning apparatus 1 according to Embodiment 2, the distribution controller 414 updates the distribution ratio ki only when the degree of subcooling does not fall within the predetermined range. In addition, the subcooling degree controller 415 configured to control the maximum value, the minimum value, or the average value of the degrees of subcooling of refrigerant passing through the use-side heat exchangers 110 is used in combination with the distribution controller 414. Thus, robustness for changes in environment, such as the amount of the refrigerant, an installation condition, or an operation condition, is improved and the stability of degree of subcooling is thus improved. As a result, an occurrence of hunting can be reduced. In such a manner, because the robustness is improved by the configuration of the control processing device 410 itself, the load of designing control can be reduced. Furthermore, a designer only has to set a predetermined threshold. Accordingly, it is possible to further reduce the load of design.Embodiment 3

[0087] FIG. 7 illustrates a configuration of the control processing device 410 in Embodiment 3. FIG. 7 illustrates a section that performs a control of the opening degree of each expansion valve, among controls of the air-conditioning apparatus 1 that are performed by the control processing device 410 of the controller 400. Referring to FIG. 7, components that are denoted by the same reference signs as in Embodiment 1 described with reference to FIG. 3 basically perform the same processing operations as described regarding Embodiment 1. As illustrated in FIG. 7, the controller 400 of Embodiment 3, as well as the controller 400 of Embodiment 1, includes the first controller 411, the second controller 412, the maximum selector 413, and the distribution controller 414.

[0088] The subcooling degree controller 415 of the first controller 411 in Embodiment 3 has a validity / invalidity determination function. When the degree of subcooling is higher than a predetermined set subcooling-degree threshold (for example, 2K), the subcooling degree controller 415 determines that a condition is valid, and when the degree of subcooling is equal to or lower than the set subcooling-degree threshold, the subcooling degree controller 415 determines that the condition is invalid. The superheat degree controller 416 of the second controller 412 in Embodiment 3 also has the validity / invalidity determination function. When the degree of superheat is higher than a set superheat degree set threshold (for example, 2K), the subcooling degree controller 415 determines that a condition is valid, and when the degree of superheat is equal to or lower than the threshold, the subcooling degree controller 415 determines that the condition is invalid.

[0089] In addition, the controller 400 of Embodiment 3 further includes a throttling controller 418. The throttling controller 418 has a function of performing a control to decrease the total expansion-valve opening degree by feedforward control. For example, when the total expansion-valve opening degree is required to be changed at a constant speed, the throttling controller 418 calculates the total expansion-valve opening degree based on the following equation (11), where ΔS is a predetermined opening-degree change amount, k is a step at the timing of the previous update, and k+1 is a step at the timing of the present update. Data on step k is stored in, for example, the storage device 430.[Math. 11]Stotal(k+1)=Stotal(k)-Δ⁢S(11)

[0090] Furthermore, the throttling controller 418 also has the validity / invalidity determination function. For example, when the subcooling degree controller 415 and the superheat degree controller 416 both determine that the conditions are invalid, the throttling controller 418 determines that a condition is valid; otherwise, the throttling controller 418 determines that the condition is invalid. When the determinations made by the subcooling degree controller 415 and the superheat degree controller 416 each transition from the determination that the condition is invalid to the determination that the condition is valid, the subcooling degree controller 415 and the superheat degree controller 416 adjust, for example, an integral value so that the transition occurs in a bumpless manner.

[0091] The above equation (11) is an example of a calculation where ΔS is a constant value and the opening degree of an expansion valve is changed at a constant speed. However, it is not indispensable that the opening degree of the expansion valve is changed at the constant speed. For example, a convergence time T may be set for a start opening degree Ss and a converged opening degree St, and the opening-degree change amount ΔS may be calculated by the following equation (12), where Tc is a control cycle. By setting the opening-degree change amount ΔS as indicated by the equation (12), a time period from start to convergence can be designed.[Math. 12]Δ⁢S=Ss-StT⁢Tc(12)

[0092] The converged opening degree St in the equation (12) is actually an unknown value. Thus, the throttling controller 418 estimates the converged opening degree St from a calculation based on the equation (13), for example. A refrigerant flow rate G is expressed by the equation (13) by using an expansion-valve opening degree S, a differential pressure dP, an expansion-valve inlet refrigerant density ρl, a compressor rotation speed F, a compressor suction refrigerant density ρg, and constants (C1, C2).[Math. 13]G=C1*S*dP*ρl=C2*F*ρg(13)

[0093] From the equation (13), the expansion-valve opening degree S is expressed by equation (14), where C is a constant.[Math. 14]S=C⁢F*ρgdP*ρl(14)

[0094] Since the compressor rotation speed F is controlled by the controller 400, the throttling controller 418 can obtain the compressor rotation speed F from internal information. In addition, dP, ρg, and ρl can be estimated by using a design value, the compressor rotation speed F, suction temperature conditions of the heat exchangers, thermal resistances of the heat exchangers, and other factors. For example, when a suction temperature of the condenser is high and a suction temperature of the evaporator is low, the differential pressure dP increases. The differential pressure dP also increases when the thermal resistance of the heat exchanger is high. Furthermore, the differential pressure dP also increases when the compressor rotation speed F is high. In addition, when the compressor rotation speed F is high, when the suction temperature of the evaporator is low, or when the thermal resistance of the evaporator is high, the compressor suction refrigerant density ρg, decreases.

[0095] As described above, parameters are estimated based on operation conditions. When the compressor rotation speed F or the compressor suction refrigerant density ρg, increases, the converged opening degree St is set high. When the compressor rotation speed F or the compressor suction refrigerant density ρg decreases, the converged opening degree St is set low. In addition when the differential pressure dP increases, the converged opening degree St is set low, and when differential pressure dP decreases, the converged opening degree St is set high.

[0096] As described above, the converged opening degree St can be estimated. In this case, it should be noted that if the compressor rotation speed F is allowed to change moment by moment, the converged opening degree St also changes over time, and as a result, the opening-degree change amount ΔS also changes over time.

[0097] Next, an example where a throttling speed is not constant will be described. As a characteristic of an expansion valve 120, the higher the opening degree S of the expansion valve, the smaller the effect of the expansion valve 120 on the system. For example, assuming that the opening degree S of the expansion valve falls within the range of 0 to 1000, changing of the opening degree S of the expansion valve from 10 to 11 has a larger effect on the system than changing of the opening degree S of the expansion valve from 900 to 901. Accordingly, the opening-degree change amount ΔS is conceivable to be increased when the opening degree S of the expansion valve is high, and to be decreased when the opening degree S of the expansion valve is low. For example, based on the equation (15), the opening-degree change amount ΔS is updated in such a manner as to be proportional to the current opening degree S of the expansion valve.[Math. 15]Δ⁢S=-S⁡(k)*(eα-1)(15)α=-TcT⁢log⁢SsSt

[0098] By calculating the opening-degree change amount ΔS as indicated by the equation (15), the obtained opening-degree change amount ΔS is proportional to the current opening degree S of the expansion valve, and the effect on the system can be kept constant. Furthermore, by setting a as indicated in the equation (15), time T required to obtain a converged opening degree from the start can be designed. Although the above description is made with respect to the case where the air-conditioning apparatus 1 performs the cooling operation, the above processing can also be applied to the heating operation.

[0099] Furthermore, in addition to the technique described in the above descriptions, the opening-degree change amount ΔS may be determined based on the temperature of the refrigerant. For example, when the air-conditioning apparatus 1 is started, a discharge temperature of the compressor 210 may suddenly rise after starting of the air-conditioning apparatus 1 due to an initial refrigeration distribution or a starting opening degree. Thus, when the controller 400 detects that the discharge temperature suddenly rises, the throttling controller 418 may reduce sudden rising of the opening-degree change amount ΔS such that the opening-degree change amount ΔS gently varies. By causing the opening-degree change amount ΔS to be gently changed, it is possible to achieve a prompt and stably operation, without occurrence of stopping of the operation that would be caused by an excessive rise in the discharge temperature.Advantages of Air-Conditioning Apparatus 1 According to Embodiment 3

[0100] As described above, in the air-conditioning apparatus 1 according to Embodiment 3, the control processing device 410 of the controller 400 includes the throttling controller 418 configured to control the opening-degree change amount ΔS of the total expansion-valve opening degree. When it is determined that the total expansion-valve opening degree based on the degree of subcooling or superheat, which is output by the first controller 411 or the second controller 412, is invalid, a control of the total expansion-valve opening degree is performed by the throttling controller 418. Thus, the air-conditioning apparatus 1 according to Embodiment 3 can shorten a time period that is required from the start of the operation until the operation is stabilized, and can promptly perform heating or cooling. For example, in a multi-type refrigeration cycle apparatus that controls the degree of subcooling or the degree of superheat, it is hard to achieve a quick responsiveness because the degree of subcooling or the degree of superheat does not fall below zero. However, in the air-conditioning apparatus 1 according to Embodiment 3, the control processing device 410 of the controller 400 can obtain a desired responsiveness by using the valid / invalid determination functions of the throttling controller 418, the first controller 411, and the second controller 412.INDUSTRIAL APPLICABILITY

[0101] Regarding Embodiments 1 to 3, although the air-conditioning apparatus is described as an example of a multi-type refrigeration cycle apparatus, the present disclosure is not limited to the air-conditioning apparatus. The present disclosure can be applied to another multi-type refrigeration cycle apparatus, such as a refrigeration apparatus or a cooling apparatus configured to cool a heat supply target.REFERENCE SIGNS LIST1: air-conditioning apparatus, 100, 100a, 100b, 100c: use-side unit, 110, 110a, 110b, 110c: use-side heat exchanger, 120, 120a, 120b, 120c: expansion valve, 130, 130a, 130b, 130c: indoor fan, 200: heat-source-side unit, 210: compressor, 220: four-way valve, 230: heat-source-side heat exchanger, 240: accumulator, 250: outdoor fan, 300: refrigerant pipe, 400: controller, 410: control processing device, 411: first controller, 412: second controller, 413: maximum selector, 414: distribution controller, 415: subcooling degree controller, 416: superheat degree controller, 417: PI controller, 418: throttling controller, 420: timing device, 430: storage device, 510: high-pressure sensor, 520: low-pressure sensor, 530: heat-source-side heat exchanger gas-pipe temperature sensor, 540: heat-source-side heat exchanger liquid-pipe temperature sensor, 550, 550a, 550b, 550c: use-side heat exchanger liquid-pipe temperature sensor, 560, 560a, 560b, 560c: use-side heat exchanger gas-pipe temperature sensor

Examples

embodiment 1

[0019]FIG. 1 illustrates a configuration of an air-conditioning apparatus 1 according to Embodiment 1. The following description refers to, as an example of a multi-type refrigeration cycle apparatus, an air-conditioning apparatus 1 that air-conditions an indoor space that is an air-conditioning target space. In this case, the air in the indoor space is a heat supply target. As illustrated in FIG. 1, the air-conditioning apparatus 1 according to Embodiment 1 includes a heat-source-side unit 200, use-side units 100, and refrigerant pipes 300. A compressor 210, a four-way valve 220, and a heat-source-side heat exchanger 230 included in the heat-source-side unit 200, and a use-side heat exchanger 110 and an expansion valve 120 included in each of the use-side units 100 are connected by the refrigerant pipes 300, whereby a refrigerant circuit is formed in which refrigerant is circulated to carry heat. In this case, it is assumed that in the air-conditioning apparatus 1 according to Embo...

embodiment 2

[0070]FIG. 6 illustrates a configuration of the control processing device 410 in Embodiment 2. FIG. 6 illustrates a section that performs a control of the opening degree of each expansion valve, among controls of the air-conditioning apparatus 1 that are performed by the control processing device 410 of the controller 400. As illustrated in FIG. 6, as in Embodiment 1, the controller 400 according to Embodiment 2 includes the first controller 411, the second controller 412, the maximum selector 413, and the distribution controller 414. As in the case of Embodiment 1, the maximum selector 413 compares a value of a total heat-source-side expansion-valve opening degree output by the first controller 411 and a value of a total heat-source-side expansion-valve opening degree output by the second controller 412, and outputs the larger one of the value of the total heat-source-side expansion-valve opening degree and the value of the total heat-source-side expansion-valve opening degree as a...

embodiment 3

[0087]FIG. 7 illustrates a configuration of the control processing device 410 in Embodiment 3. FIG. 7 illustrates a section that performs a control of the opening degree of each expansion valve, among controls of the air-conditioning apparatus 1 that are performed by the control processing device 410 of the controller 400. Referring to FIG. 7, components that are denoted by the same reference signs as in Embodiment 1 described with reference to FIG. 3 basically perform the same processing operations as described regarding Embodiment 1. As illustrated in FIG. 7, the controller 400 of Embodiment 3, as well as the controller 400 of Embodiment 1, includes the first controller 411, the second controller 412, the maximum selector 413, and the distribution controller 414.

[0088]The subcooling degree controller 415 of the first controller 411 in Embodiment 3 has a validity / invalidity determination function. When the degree of subcooling is higher than a predetermined set subcooling-degree th...

TECHNICAL FIELD

[0001] The present disclosure relates to a multi-type refrigeration cycle apparatus including a plurality of use-side heat exchangers, and more particularly, to control over expansion valves based on a state value of refrigerant subjected to heat exchange.BACKGROUND ART

[0002] In certain multi-type refrigeration cycle apparatuses, a plurality of use-side heat exchangers configured to cause heat exchange to be performed between refrigerant and a heat supply target such as air are connected by multiple pipes. Such a multi-type refrigeration cycle apparatus has a refrigerant circuit that includes, as components, a compressor, a heat-source-side heat exchanger, a plurality of expansion valves connected in parallel, and a plurality of use-side heat exchangers connected to the respective expansion valves in series. Furthermore, a controller controls the opening degree of each of the expansion valves to properly adjust the distribution of refrigerant that passes through an associated one of the use-side heat exchangers, and causes the use-side heat exchanger to perform heat exchange with the refrigerant (for example, see Patent Literature 1).

[0003] In such a multi-type refrigeration cycle apparatus, in a cooling operation, the controller changes the opening degree of each expansion valve to control the degree of subcooling to a target degree of subcooling. At this time, the controller distributes the total opening degree of the expansion valves, which is the sum of all the opening degrees of the expansion valves, based on the capacity ratios of the use-side heat exchangers, and controls the distributed opening degree of each expansion valve based on the difference between the degree of superheat of refrigerant that passes through an associated one of the use-side heat exchangers and a target degree of superheat. Then, the controller changes the target degree of subcooling when determining that the degree of superheat of the refrigerant in each of all the use-side heat exchangers exceeds or falls below the target degree of superheat.

[0004] In a heating operation, the controller calculates an opening degree of each expansion valve, which enables the degree of subcooling of refrigerant that passes through an associated one of indoor heat exchangers to reach a predetermined target degree of subcooling. Then, the controller lowers, as control, the target degree of subcooling when determining that the degree of superheat of an outdoor heat exchanger is higher than or equal to a set degree of superheat.CITATION LISTPatent LiteraturePatent Literature 1: Japanese Unexamined Patent Application Publication No. 2002-054836SUMMARY OF INVENTIONTechnical Problem

[0006] In the multi-type refrigeration cycle apparatus disclosed in Patent Literature 1, the controller performs control to change the target degree of subcooling so that the degree of superheat in a heat exchanger operating as an evaporator does not become higher than or equal to the target degree of superheat. However, in such a control, when the amount of refrigerant becomes excessively insufficient in the heat exchanger to the extent that the degree of subcooling becomes uncontrollable, the change in the opening degree of an expansion valve is restricted, and an operation efficiency lowers.

[0007] In a heating operation in which a heat supply target is heated, the target degree of subcooling is changed as a control based on the degree of superheat of the outdoor heat exchanger while performing a control based on the degree of subcooling, which is a control target subject to large disturbances. Consequently, the design burden of control parameters increases.

[0008] The present disclosure is applied to solve the above problems, and relates to a multi-type refrigeration cycle apparatus capable of performing a control more appropriately based on the state of refrigerant that passes through a heat exchanger regardless of excess or deficiency of the amount of refrigerant.Solution to Problem

[0009] A multi-type refrigeration cycle apparatus according to an embodiment of the present disclosure includes: a refrigerant circuit in which a compressor, a heat-source-side heat exchanger, a plurality of expansion valves, and a plurality of use-side heat exchangers connected in series to the respective expansion valves are connected by pipes, and refrigerant is circulated; and a controller configured to control components in the apparatus. The controller includes: a first controller configured to calculate a total expansion-valve opening degree for the expansion valves as a value for causing a heat-source-side state value of the refrigerant flowing out of the heat-source-side heat exchanger to follow a target heat-source-side state value, and output the total expansion-valve opening degree as a total heat-source-side expansion-valve opening degree; a second controller configured to calculate the total expansion-valve opening degree for the expansion valves as a value for causing a use-side state value of the refrigerant flowing out of each of the plurality of use-side heat exchangers to follow a target use-side state value, and output the total expansion-valve opening degree as a total use-side expansion-valve opening degree; a maximum selector configured to select one of the total heat-source-side expansion-valve opening degree and the total use-side expansion-valve opening degree, as a maximum total expansion-valve opening degree; and a distribution controller configured to perform processing to distribute the maximum total expansion-valve opening degree among the expansion valves as respective opening degrees thereof. The distribution controller is configured to distribute the maximum total expansion-valve opening degree at distribution ratios in which the opening degrees of the expansion valves associated with the respective use-side heat exchangers are relatively changed, based on comparison between the use-side state values of the refrigerant flowing out of the use-side heat exchangers and a set threshold.Advantageous Effects of Invention

[0010] In the multi-type refrigeration cycle apparatus according to an embodiment of the present disclosure, the first controller in the controller determines a total heat-source-side expansion-valve opening degree that can be obtained from a heat-source-side state value of refrigerant flowing out of the heat-source-side heat exchanger. The second controller determines a total use-side expansion-valve opening degree that can be obtained from use-side state values of refrigerant flow out of the use-side heat exchangers. The distribution controller distributes the maximum total expansion-valve opening degree, as which the maximum controller selects one of the total heat-source-side expansion-valve opening degree and the total use-side expansion-valve opening degree, among the expansion valves, and determines the opening degrees of the expansion valves. Thus, the multi-type refrigeration cycle apparatus is capable of properly controlling the degree of subcooling in an operation where the refrigerant is sufficient, thereby achieving a high efficiency operation and energy saving. By contrast, in an operation where the refrigerant is insufficient and a subcooling degree control cannot be performed, the multi-type refrigeration cycle apparatus can automatically and consecutively switch the control to a superheat degree control to properly control the degree of subcooling. Thus, regardless of the amount of refrigerant, a high efficiency operation can be maintained.BRIEF DESCRIPTION OF DRAWINGS

[0011] FIG. 1 illustrates a configuration of an air-conditioning apparatus 1 according to Embodiment 1.

[0012] FIG. 2 illustrates a configuration of a controller 400 in the air-conditioning apparatus 1 according to Embodiment 1.

[0013] FIG. 3 illustrates a configuration of a control processing device 410 in Embodiment 1.

[0014] FIG. 4 indicates relationships between time and the degree of subcooling and the degree of superheat in Embodiment 1.

[0015] FIG. 5 illustrates images regarding distribution processing operation in the air-conditioning apparatus 1 according to Embodiment 1.

[0016] FIG. 6 illustrates a configuration of a control processing device 410 in Embodiment 2.

[0017] FIG. 7 illustrates a configuration of a control processing device 410 in Embodiment 3.DESCRIPTION OF EMBODIMENTS

[0018] A multi-type refrigeration cycle apparatus according to each of embodiments will be described with reference to the drawings. In each of figures in the drawings that will be referred to below, components that are the same as or equivalent to those in a previous figure or previous figures are denoted by the same reference signs, and the same is true of the full text of the following descriptions concerning the embodiments. Furthermore, in each of the figures, a relationship or relationships in size between components may be different from actual ones. In additions, the configurations of the components described in the full text of the specification are each merely an example, and the descriptions concerning the configurations are not limiting. In particular, combinations of components are not limited to combinations of components described regarding the same embodiment, and a component or components in one embodiment may be applied to another embodiment. Furthermore, the level of each of pressures and that of each of temperatures are not determined in relation to any particular absolute value, but are relatively determined, for example, based on the state or operation of a device or devices. In addition, with regard to a plurality of components that are of the same type and are distinguished from each other by suffixes, the suffixes may be omitted if it is not necessary to distinguish between the plurality of components or specify one or ones of the plurality of components.Embodiment 1

[0019] FIG. 1 illustrates a configuration of an air-conditioning apparatus 1 according to Embodiment 1. The following description refers to, as an example of a multi-type refrigeration cycle apparatus, an air-conditioning apparatus 1 that air-conditions an indoor space that is an air-conditioning target space. In this case, the air in the indoor space is a heat supply target. As illustrated in FIG. 1, the air-conditioning apparatus 1 according to Embodiment 1 includes a heat-source-side unit 200, use-side units 100, and refrigerant pipes 300. A compressor 210, a four-way valve 220, and a heat-source-side heat exchanger 230 included in the heat-source-side unit 200, and a use-side heat exchanger 110 and an expansion valve 120 included in each of the use-side units 100 are connected by the refrigerant pipes 300, whereby a refrigerant circuit is formed in which refrigerant is circulated to carry heat. In this case, it is assumed that in the air-conditioning apparatus 1 according to Embodiment 1, three use-side units 100 are connected to one heat-source-side unit 200 in parallel by the pipes. It suffices that the number of use-side units 100 connected in parallel to the heat-source-side unit 200 by the pipes is two or more. Regarding control, only one use-side unit 100 that is to operate may be provided.

[0020] The use-side units 100 (use-side units 100a to 100c) each perform air-conditioning by heating or cool air in an indoor space that is an air-conditioning target space. The use-side units 100 include, as components included in the refrigerant circuit, respective use-side heat exchangers 110 (use-side heat exchangers 110a to 110c) and respective expansion valves 120 (expansion valves 120a to 120c). In addition, the use-side units 100 include respective indoor fans 130 (indoor fans 130a to 130c).

[0021] Each of the expansion valves 120, which serve as expansion devices, is a valve configured to decompress the refrigerant to expand the refrigerant. Each expansion valve 120 is, for example, an electronic expansion valve, and controls the amount of refrigerant passing through an associated one of the use-side heat exchangers 110 by adjusting the opening degree based on an instruction from a controller 400, which will be described later, to reduce the pressure of the refrigerant. The use-side heat exchanger 110 is a heat exchanger that causes heat exchange to be performed between air in an indoor space and the refrigerant to heat or cool the air. For example, in a heating operation in which the air is heated, the use-side heat exchanger 110 operates as a condenser, condenses the refrigerant, and causes the refrigerant to reject heat and thus liquefy to change into liquid-phase refrigerant. The liquid-phase refrigerant (hereinafter referred to as liquid refrigerant) then passes through the use-side heat exchanger 110. In a cooling operation in which the air is cooled, the use-side heat exchanger 110 operates as an evaporator, and causes the refrigerant to receive heat and thus evaporate to change into gas-phase refrigerant. The gas-phase refrigerant (hereinafter referred to as gas refrigerant) then passes through the use-side heat exchanger 110. Each of the indoor fans 130 causes air to pass through an associated one of the use-side heat exchangers 110 to accelerate heat exchange in the use-side heat exchanger 110, and supply the air that passes through the use-side heat exchanger 110 to the indoor space, which is the air-conditioning target space.

[0022] The heat-source-side unit 200 according to Embodiment 1 includes, as components included in the refrigerant circuit, a compressor 210, a four-way valve 220, a heat-source-side heat exchanger 230, and an accumulator 240. In addition, the heat-source-side unit 200 includes an outdoor fan 250. The compressor 210 compresses sucked refrigerant and discharges the refrigerant. The compressor 210 is, for example, a scroll compressor, a reciprocating compressor, a vane compressor, or another type of compressor. In this case, the compressor 210 can change the capacity (the amount of refrigerant to be delivered per unit time) of refrigerant to be discharged from the compressor 210 by a change in driving frequency that is made by an inverter circuit or a similar device.

[0023] The four-way valve 220, which serves as a flow switching device, is a valve configured to, for example, switch the flow of the refrigerant between that in the cooling operation and that in the heating operation. In the heating operation, the four-way valve 220 connects a discharge side of the compressor 210 and the use-side heat exchangers 110 and also connect a suction side of the compressor 210 and the heat-source-side heat exchanger 230. In the cooling operation, the four-way valve 220 connects the discharge side of the compressor 210 and the heat-source-side heat exchanger 230 and also connects the suction side of the compressor 210 and the use-side heat exchangers 110. The above description refers to by way of example the case where the four-way valve 220 is used as the flow switching device, but the flow switching device is not limited to the four-way valve 220. For example, the flow switching device may be, for example, a combination of multiple two-way valves.

[0024] The heat-source-side heat exchanger 230 is a heat exchanger configured to cause heat exchange to be performed between the refrigerant and an outdoor air. In the heating operation, the heat-source-side heat exchanger 230 of Embodiment 1 operates as an evaporator and evaporates the refrigerant to change it into gas refrigerant, which will pass through the heat-source-side heat exchanger 230. In the cooling operation, the heat-source-side heat exchanger 230 operates as a condenser and a subcooler and condenses refrigerant to change it into liquid refrigerant, which will pass through the heat-source-side heat exchanger 230. The configuration of the heat-source-side heat exchanger 230 will be described in detail later. Furthermore, the outdoor fan 250 is driven to generate a flow of air such that the air that flows from the outside of the heat-source-side unit 200 is made to pass through the heat-source-side heat exchanger 230 and flow out of the heat-source-side unit 200, thereby promoting heat exchange in the heat-source-side heat exchanger 230.

[0025] It should be noted that the components included in the refrigerant circuit in the air-conditioning apparatus 1 are not limited to those as illustrated in FIG. 1. The refrigerant circuit may include, for example, a capillary tube, as needed. In addition, although it is described that the use-side heat exchangers 110 and the heat-source-side heat exchanger 230 cause heat exchange to be performed between air and the refrigerant, it is not limiting. For example, these heat exchangers may cause heat exchange to be performed between water or geothermal heat and the refrigerant. Moreover, the heat-source-side unit 200 may be configured such that a pipe is branched and an expansion valve 120 is provided in the heat-source-side unit 200.

[0026] Next, an operation of each of the components in the air-conditioning apparatus 1 will be described based on the flow of refrigerant. First of all, an operation of each component in the refrigerant circuit in the heating operation will be described based on the flow of refrigerant. Dashed arrows in FIG. 1 indicate flows of the refrigerant in the heating operation. High-temperature and high-pressure gas refrigerant that is discharged from the compressor 210 after being obtained through compression thereby passes through the four-way valve 220 and flows into the use-side heat exchanger 110. The gas refrigerant is condensed and liquefied while passing through the use-side heat exchanger 110 and exchanging heat with, for example, air in the air-conditioning target space. The condensed and liquefied refrigerant passes through the expansion valve 120. The refrigerant is decompressed while passing through the expansion valve 120. After changing into two-phase gas-liquid refrigerant through decompression by the expansion valve 120, the refrigerant passes through the heat-source-side heat exchanger 230. In the heat-source-side heat exchanger 230, the refrigerant exchanges heat with an outdoor air sent by the outdoor fan 250 and is thus evaporated and gasified. The gasified refrigerant passes through the four-way valve 220 and the accumulator 240, and is re-sucked into the compressor 210. As described above, the refrigerant in the air-conditioning apparatus 1 circulates and performs air-conditioning for heating.

[0027] Next, the cooling operation will be described. The solid arrows in FIG. 1 indicate flows of the refrigerant in the cooling operation. High-temperature and high-pressure gas refrigerant that is discharged from the compressor 210 after being obtained through compression thereby passes through the four-way valve 220 and flows into the heat-source-side heat exchanger 230. Then, the refrigerant passes through the heat-source-side heat exchanger 230, exchanges heat with an outdoor air supplied by the outdoor fan 250, and is thus condensed and liquefied. The liquefied refrigerant passes through the expansion valve 120. While passing through the expansion valve 120, the refrigerant is decompressed to change into two-phase gas-liquid refrigerant. The two-phase refrigerant obtained through decompression by the expansion valve 120 passes through the use-side heat exchanger 110. Then, in the use-side heat exchanger 110, the refrigerant exchanges heat with air in the air-conditioning target space and is thus evaporated and gasified. The gasified refrigerant passes through the four-way valve 220, and is re-sucked into the compressor 210. As described above, the refrigerant in the air-conditioning apparatus 1 circulates and performs air-conditioning for cooling. With respect to Embodiment 1, a cooling operation in which the use-side heat exchanger 110 operates as an evaporator and the heat-source-side heat exchanger 230 operates as a condenser will be described.

[0028] The air-conditioning apparatus 1 according to Embodiment 1 includes a high-pressure sensor 510 and a low-pressure sensor 520 as pressure sensors. The high-pressure sensor 510 detects, as a high-pressure, the pressure of refrigerant discharged from the compressor 210, which is located on a high pressure side in the refrigerant circuit. The low-pressure sensor 520 detects, as a low-pressure, the pressure of refrigerant that flows into the accumulator 240, which is located on a low pressure side in the refrigerant circuit.

[0029] Furthermore, the air-conditioning apparatus 1 according to Embodiment 1 includes, for example, a heat-source-side heat exchanger gas-pipe temperature sensor 530, a heat-source-side heat exchanger liquid-pipe temperature sensor 540, use-side heat exchanger liquid-pipe temperature sensors 550, and use-side heat exchanger gas-pipe temperature sensors 560.

[0030] The heat-source-side heat exchanger gas-pipe temperature sensor 530 is provided at a pipe on a gas pipe side of the heat-source-side heat exchanger 230 and detects the temperature of gas refrigerant (including two-phase refrigerant) that flows into and out of the heat-source-side heat exchanger 230. The heat-source-side heat exchanger gas-pipe temperature sensor 530 detects, in the cooling operation, the temperature of refrigerant that flows into the heat-source-side heat exchanger 230, and detects, in the heating operation, the temperature of refrigerant that flows out of the heat-source-side heat exchanger 230. The heat-source-side heat exchanger liquid-pipe temperature sensor 540 is provided at a pipe on a liquid pipe side of the heat-source-side heat exchanger 230 and detects the temperature of liquid refrigerant (including two-phase refrigerant) that flows into and out of the heat-source-side heat exchanger 230. The heat-source-side heat exchanger liquid-pipe temperature sensor 540 detects, in the in the cooling operation, the temperature of refrigerant that flows out of the heat-source-side heat exchanger 230, and detects, in the heating operation, the temperature of refrigerant that flows into the heat-source-side heat exchanger 230.

[0031] Each of the use-side heat exchanger liquid-pipe temperature sensors 550 (use-side heat exchanger liquid-pipe temperature sensors 550a to 550c) is provided at a pipe located on the liquid pipe side of an associated one of use-side heat exchangers 110. The use-side heat exchanger liquid-pipe temperature sensor 550 detects the temperature of liquid refrigerant (including two-phase refrigerant) that flows into and out of the associated use-side heat exchanger 110. The use-side heat exchanger liquid-pipe temperature sensor 550 detects, in the cooling operation, the temperature of refrigerant that flows into the associated use-side heat exchanger 110, and detects, in the heating operation, the temperature of refrigerant that flows out of the associated use-side heat exchanger 110. Furthermore, each of the use-side heat exchanger gas-pipe temperature sensors 560 (use-side heat exchanger gas-pipe temperature sensors 560a to 560c) is provided at a pipe located on the gas pipe side of an associated one of the use-side heat exchangers 110. The use-side heat exchanger gas-pipe temperature sensor 560 detects the temperature of gas refrigerant (including two-phase refrigerant) that flows into and out of the associated use-side heat exchanger 110. The use-side heat exchanger gas-pipe temperature sensor 560 detects, in the cooling operation, the temperature of refrigerant that flows out of the associated use-side heat exchanger 110, and detects, in the heating operation, the temperature of refrigerant that flows into the associated use-side heat exchanger 110.

[0032] FIG. 2 illustrates a configuration of a controller 400 in the air-conditioning apparatus 1 according to Embodiment 1. The controller 400 is a device configured to control the air-conditioning apparatus 1. As illustrated in FIG. 2, to the controller 400, the various sensors described above are connected, and signals including data on temperature and pressure are input. In addition, a signal including an instruction from a user is input to the controller 400 via an operation unit (not illustrated).

[0033] As illustrated in FIG. 2, the controller 400 includes a control processing device 410, a timing device 420, and a storage device 430. The control processing device 410 performs processing, such as calculation and determination, based on, for example, temperature data included in signals transmitted from various sensors and based on an instruction from the user, and controls components such as the compressor 210, the expansion valves 120, and the outdoor fan 250 included in the air-conditioning apparatus 1. The storage device 430 is a device that stores data required when the control processing device 410 performs processing. The timing device 420 is a device such as a timer that measures time and duration required when the control processing device 410 performs processing such as determination.

[0034] The control processing device 410 includes, for example, a microcomputer or a similar device including a control arithmetic processing device such as a central processing unit (CPU), but this is not limiting. The control processing device 410 may be formed in combination with a dedicated device (hardware) as a component. For example, the control processing device 410 may include, as a dedicated device, a PI controller 417, which will be described later.

[0035] The storage device 430 includes, for example, a read-only memory (ROM). In addition, the storage device 430 includes a storage unit (not illustrated), such as a random access memory (RAM) that can temporarily store data, or an auxiliary storage unit (not illustrated), such as a flash memory or a solid state drive. The storage device 430 also includes, for example, data in which the procedure of processing to be performed by the control processing device 410 is programmed. Then, the control processing device 410 executes processing based on the program data to achieve, for example, control of components.

[0036] FIG. 3 illustrates a configuration of the control processing device 410 in Embodiment 1. Of controls of the air-conditioning apparatus 1 that are performed by the control processing device 410 of the controller 400, a control of the opening degrees of the expansion valves 120 is performed by components as illustrated in FIG. 3. As illustrated in FIG. 3, the control processing device 410 of the controller 400 in Embodiment 1 includes a first controller 411, a second controller 412, a maximum selector 413, and a distribution controller 414.

[0037] The first controller 411 calculates a heat-source-side state value of refrigerant that flows out of the heat-source-side heat exchanger 230. In addition, the first controller 411 calculates and outputs a total expansion-valve opening degree, which is the sum of all the opening degrees of the expansion valves 120 and follows a target heat-source-side state value, as a total heat-source-side expansion-valve opening degree. The air-conditioning apparatus 1 according to Embodiment 1 performs the cooling operation. Thus, because the heat-source-side heat exchanger 230 operates as a condenser, the heat-source-side state value is a degree of subcooling (SC) and the target heat-source-side state value is a target degree of subcooling. In addition, the first controller 411 includes a subcooling degree controller 415.

[0038] The subcooling degree controller 415 calculates the degree of subcooling of refrigerant, and calculates and outputs the total expansion-valve opening degree as a value for causing the degree of subcooling of the refrigerant to follow the target degree of subcooling. To the subcooling degree controller 415 in Embodiment 1, signals from the high-pressure sensor 510 and the heat-source-side heat exchanger liquid-pipe temperature sensor 540 are input. The subcooling degree controller 415 calculates, from a high-pressure value included in a signal from the high-pressure sensor 510, a saturated liquid temperature at the pressure by using a physical property value of the refrigerant. The subcooling degree controller 415 then calculates, as a degree of subcooling, the difference between the saturated liquid temperature and a heat-source-side liquid pipe temperature, which is included in a signal from the heat-source-side heat exchanger liquid-pipe temperature sensor 540. However, a method for calculating the degree of subcooling is not limited to the above method. For example, in the heat-source-side heat exchanger 230, the degree of subcooling may be calculated from a difference between a heat-source-side liquid pipe temperature and a temperature detected by a temperature sensor installed at a portion where the two-phase refrigerant flows. In addition, the target degree of subcooling may be a constant value or a variable value to be set depending on an actual operating condition. In the case where a target degree of subcooling is a variable value, the target degree of subcooling may be a value obtained by multiplying a difference between a condensing temperature and an ambient temperature of a heat exchanger operating as a condenser by a coefficient.

[0039] The second controller 412 calculates a heat-source-side state value of refrigerant that flows out of each of the use-side heat exchangers 110. In addition, the second controller 412 calculates and outputs a total expansion-valve opening degree that is the sum of all the opening degrees of the expansion valves 120 and is a value for causing a use-side state value of the refrigerant to follow a target use-side state value, as a total use-side expansion-valve opening degree. As described above, because the air-conditioning apparatus 1 according to Embodiment 1 performs the cooling operation and each of the use-side heat exchangers 110 operates as an evaporator, the use-side state value is the degree of superheat (SH) and the target use-side state value is a target degree of superheat. In addition, the second controller 412 includes a superheat degree controller 416.

[0040] The superheat degree controller 416 calculates the degree of superheat of refrigerant, and calculates and outputs a total expansion-valve opening degree as a value for causing the degree of superheat of the refrigerant to follow a set upper limit degree of superheat. In Embodiment 1, the superheat degree controller 416 outputs a total expansion-valve opening degree as a value for causing the maximum one of the degrees of superheat of refrigerant that flows out of the use-side heat exchangers 110, to follow the upper limit degree of superheat. The upper limit degree of superheat may be determined based on a hardware restriction, for example, or may be set based on, for example, an experimental rule. To the superheat degree controller 416 in Embodiment 1, signals from the low-pressure sensor 520 and the use-side heat exchanger gas-pipe temperature sensors 560 are input. The superheat degree controller 416 calculates, from a low-pressure value included in a signal from the low-pressure sensor 520, a saturated gas temperature at the pressure by using a physical property value of the refrigerant. The superheat degree controller 416 then calculates, as the degree of superheat of refrigerant that flows out of each of the use-side heat exchangers 110, the difference between the saturated gas temperature and a use-side gas pipe temperature, which is included in a signal from each of the use-side heat exchanger gas-pipe temperature sensors 560. However, the method for calculating the degree of superheat is not limited to the above method. For example, in each of the use-side heat exchangers 110, the degree of superheat may be calculated from the difference between a use-side gas pipe temperature and a temperature detected by a temperature sensor installed at a portion where two-phase refrigerant flows. Furthermore, a control output of superheat degree control is not limited to the maximum degree of superheat. The control output may be a minimum value or another value, for example, a statistical value such as an average value or a median value that can be obtained by performing statistical processing on a plurality of degrees of superheat. It should be noted that because the degree of superheat does not fall below zero, the degree of superheat that is lower than or equal to a certain threshold may be treated as an outlier.

[0041] The subcooling degree controller 415 and the superheat degree controller 416 each include a position-type PI controller 417. The PI controller 417 is a controller configured to perform a feedback control by proportional-integral control. The PI controller 417 has an anti-reset windup function. The anti-reset windup function is a function of reducing occurrence of divergence of an integral value in the case where an output value of the PI controller 417 differs from an actual opening degree of an expansion valve 120 due to selection by the maximum selector 413 or upper or lower limit constraints imposed on the opening degree of the expansion valve 120. A function such as the anti-reset windup function is effective especially in a configuration in which a plurality of PI controllers 417 are arranged in parallel as in the control processing device 410 and a value to be processed next is selected from the output values of the plurality of PI controllers 417.

[0042] The subcooling degree controller 415 and the superheat degree controller 416 in Embodiment 1 include PI controllers 417, but may include other controllers instead of the PI controllers 417. For example, the subcooling degree controller 415 and the superheat degree controller 416 may each include a P controller configured to perform a proportional control, a PID controller configured to perform a proportional-integral-derivative control, or a dynamic feedback controller, such as a model predictive controller. In addition, each of the controllers of the subcooling degree controller 415 and the superheat degree controller 416 may be a dynamic or static controller configured to perform control based on data set in advance in a table format. Furthermore, the controller does not need to be a position-type controller but may be a speed-type controller. However, even when a speed-type controller is used, each of the subcooling degree controller 415 and the superheat degree controller 416 needs to output a total expansion-valve opening degree to the maximum selector 413.

[0043] The maximum selector 413 compares a value of a total heat-source-side expansion-valve opening degree output by the first controller 411 and a value of a total heat-source-side expansion-valve opening degree output by the second controller 412, and outputs the greater one of the above values as a maximum total expansion-valve opening degree.

[0044] The distribution controller 414 distributes the maximum total expansion-valve opening degree output from the maximum selector 413 among the expansion valves 120, and determines the opening degree of each of the expansion valves 120. Next, the procedure of distribution processing that is performed by the distribution controller 414 in Embodiment 1 will be described. It is assumed that U={1, 2, . . . , n} is a set of use-side heat exchanger numbers, where n is the number of use-side heat exchangers 110 that are connected; V⊂U is a set of the numbers of the use-side heat exchangers that are in in operation; and A⊂V is a set of the numbers of use-side heat exchangers in each of which the degree of superheat exceeds the upper limit degree of superheat (SHi>2, i∈V), where SHi is the degree of superheat of the use-side heat exchanger i.

[0045] The distribution controller 414 holds a distribution ratio ki (i∈V). The distribution ratio ki has a characteristic expressed by the following equation (1).[Math. 1]∑i∈𝒱ki=1(1)

[0046] Then, the distribution controller 414 calculates an opening degree of each of the expansion valves 120 based on the distribution ratio ki, according to equation (2), where Si is the opening degree of each expansion valve 120, and Stotal is a maximum total expansion-valve opening degree that is output by the maximum selector 413. Initial values of the distribution ratios ki are set, for example, equally among the expansion valves 120, or set in proportion to capability ratios of the use-side heat exchangers 110.[Math. 2]Si=ki*Stotal⁢ i∈𝒱(2)

[0047] The distribution controller 414 determines, for example, whether to update the distribution ratio ki at one-minute intervals, but this is not limiting. For example, the distribution controller 414 is not necessarily required to execute the processing at regular intervals. The distribution controller 414 is allowed to execute the processing upon detection of a dry state. Also, the distribution controller 414 is allowed to execute the processing upon detection of start or stop of the operation of the use-side unit 100. In addition, the distribution controller 414 may execute the processing by combining updates that are performed at regular intervals with updates triggered by events such as detection of a dry state or start / stop of the use-side unit 100.

[0048] When the distribution controller 414 determines that the degree of superheat of a use-side heat exchanger 110 is higher than a set superheat degree threshold (for example, 2K), it is determined that refrigerant that flows in the use-side heat exchanger 110 is insufficient (in a dry state). Then, the distribution controller 414 sets the distribution ratio ki of the expansion valve 120 to a higher distribution ratio ki in which the opening degree of the expansion valve 120 is increased from the current opening degree thereof. When the distribution ratio ki is increased and the opening degree of the expansion valve 120 is increased, the amount of the refrigerant flowing in the use-side heat exchanger 110 is increased.

[0049] Next, an example of updating the distribution ratio ki will be described. In the description, k is a step at the timing of performing the previous update and k+1 is a step at the timing of performing the present update. First, when all the use-side heat exchangers 110 are in a dry state or all the use-side heat exchanger 110 are not in a dry state, and A or Ac (Ac is a complement of A⊂V) is an empty set, the distribution ratio ki is not changed. Thus, the distribution ratio ki(k+1) of the present update is expressed by equation (3) by using the distribution ratio ki (k) of the previous update.[Math. 3]ki(k+1)=ki(k)⁢ i∈𝒱(3)

[0050] By contrast, when some of the use-side heat exchangers 110 are in a dry state and neither A nor Ac is an empty set, the distribution ratio ki(k+1) resulting from the present update is expressed by equation (4) by using the distribution ratio ki (k) resulting from the previous update. The distribution ratio ki (k) resulting from the previous update is the distribution ratio ki for the current opening degree of the expansion valve 120. The equation (4) is an equation for an update in which the opening degree of an expansion valve 120 associated with a use-side heat exchanger 110 that is in a dry state is increased by 10% with reference to the current opening degrees. It should be noted that when ki(k+1) is less than or equal to 0, or greater than or equal to 1, the distribution ratio ki is not changed. Thus, the distribution ratio ki(k+1) resulting from the present update is expressed by the above equation (3)[Math. 4]ki(k+1)={110100⁢ki(k)…⁢ i∈𝒜ki(k)-10100⁢ki(k)⁢∑i∈𝒜ki(k)∑i∈𝒜cki(k)…⁢ i∈𝒜c(4)

[0051] When the distribution controller 414 updates the distribution ratio ki as described above, the opening degree of an expansion valve 120 associated with a use-side heat exchanger 110 that is in a dry state is relatively increased and the amount of refrigerant passing through the use-side heat exchanger 110 is increased, whereby the dry state can be eliminated. In addition, the distribution ratio ki for the opening degree of an expansion valve 120 associated with a use-side heat exchangers 110 that is not in a dry state (proper state) is maintained and at the same time, the distribution ratio ki for the total expansion-valve opening degree can be reduced. Although the equation (4) indicates the case where the opening degree of an expansion valve 120 associated with a use-side heat exchanger 110 that is in a dry state is increased by 10%, the percent by which the opening degree is increased is not limited to 10%, and may be variable.

[0052] Next, it will be described how the distribution controller 414 performs processing for determining the distribution ratio ki of each expansion valve 120 in the case where the use-side unit 100 being in operation is stopped or the use-side unit 100 being in the stopped state is started. Here, the distribution controller 414 of the controller 400 does not update the distribution ratio ki based on the dry state described above, because the state of the refrigerant in the refrigerant circuit is unstable immediately after a stop or start of the operation of the use-side unit 100.

[0053] The following description is made on the assumption that M⊂V is a set of the numbers of the use-side heat exchangers 110 of use-side units 100 that are newly stopped; N⊂Vc is a set of the numbers of the use-side heat exchangers 110 of use-side units 100 that are newly started; V(k+1) is a set of the numbers of the use-side heat exchangers 110 of use-side units 100 that are in an operating state at the present time; and V(k) is a set of the numbers of the use-side heat exchangers 110 of use-side units 100 which were in an operating state at the previous time. For example, when V(k)={1, 3, 5, 7}, M={3} and N={2}, V (k+1)={1, 2, 5, 7}.

[0054] The distribution controller 414 causes the expansion valve 120 of a use-side unit 100 that is stopped to be fully closed (opening degree 0). In addition, for the opening degrees of the expansion valves 120 of the use-side units 100 excluding the use-side unit 100 that is stopped, distribution ratios kl′ that are normalized according to the following equation (5) such that that the sum of the distribution ratios ki for the previous update is 1 are calculated.[Math. 5]ki′=ki(k)∑i∈𝒱∖ℳki(k)⁢ i∈𝒱∖ℳ(5)

[0055] Next, the distribution controller 414 calculates an average of the normalized distribution ratios ki′ according to the following equation (6) and determines the average as a normalized distribution ratio ki′ for a use-side heat exchanger 110 that starts operating. It should be noted that |V−M| is the number of elements in a set V−M. In addition, a minus sign in a set indicates a difference set. It should also be noted that notation is present that uses a backslash instead of the minus sign. In the following equation, notation using a backslash is used.[Math. 6]ki′=∑i∈𝒱∖ℳki′<semantics definitionURL="">❘<annotation encoding="Mathematica">"\[LeftBracketingBar]"< / annotation>< / semantics>𝒱∖ℳ<semantics definitionURL="">❘<annotation encoding="Mathematica">"\[RightBracketingBar]"< / annotation>< / semantics>=1<semantics definitionURL="">❘<annotation encoding="Mathematica">"\[LeftBracketingBar]"< / annotation>< / semantics>𝒱∖ℳ<semantics definitionURL="">❘<annotation encoding="Mathematica">"\[RightBracketingBar]"< / annotation>< / semantics>⁢ i∈𝒩(6)

[0056] Then, the distribution controller 414 re-performs normalization based on the normalized distribution ratio ki′ and calculates a distribution ratio ki(k+1) for the present update, according to the following equation (7).[Math. 7]ki(k+1)=ki′∑i∈𝒱(k+1)ki′⁢ i∈𝒱⁡(k+1)(7)

[0057] As described above, when a use-side unit 100 is stopped or started, the distribution controller 414 can calculate and determine the distribution ratio ki for the opening degree of an associated one of the expansion valves 120. As described above, because distribution ratios are maintained as much as possible even when an operating condition is changed, that is, distribution ratios for the opening degrees of expansion valves 120 associated with use-side heat exchangers 110 that are in a proper state are maintained, it is possible to reduce occurrence of a disturbance of a control that is caused by a change in the operating condition. Although it is described that the sum of the distribution ratios ki is 1, it is not indispensable that the sum is 1, and the sum may be updated to another value depending on the operating condition. In addition, the above method for calculating and determining the distribution ratio ki is merely an example, and the distribution controller 414 can use any method as long as a solution similar to the solution obtained the above method is obtained.Operation Image

[0058] FIG. 4 illustrates graphs indicating respective relationships between time and the degree of subcooling and the degree of superheat in Embodiment 1. FIG. 4, (a), illustrates the degree of subcooling and the degree of superheat of refrigerant in the case where the amount of the refrigerant in the refrigerant circuit is appropriate. When an appropriate amount of refrigerant is filled in the refrigerant circuit, as time passes, the degree of subcooling of refrigerant that flows out of a heat exchanger operating as a condenser gradually converges to an optimal degree of subcooling, as illustrated in FIG. 4, (a). In addition, as time passages, the degree of superheat of refrigerant flowing out of a heat exchanger operating as an evaporator gradually converges to an optimal degree of superheat over time.

[0059] FIG. 4, (b), illustrates the degree of subcooling and the degree of superheat in the case where an excess amount of refrigerant is filled in the refrigerant circuit. When refrigerant is excessively filled in the refrigerant circuit, the degree of superheat of refrigerant flowing out of the heat exchanger operating as an evaporator cannot be controlled, as illustrated in FIG. 4, (b). By contrast, as time passes, the degree of subcooling of the refrigerant flowing out of the heat exchanger operating as a condenser gradually converges to the optimal degree of subcooling. In the control processing device 410 of the controller 400, when the maximum selector 413 selects a higher one of total expansion-valve opening degrees, the total expansion-valve opening degree can be highly accurately distributed among the expansion valves 120 as respective opening degrees thereof, and thus an energy saving control can be performed.

[0060] FIG. 4, (c), illustrates the degree of subcooling and the degree of superheat in the case where the amount of the refrigerant in the refrigerant circuit is insufficient. When the amount of the refrigerant in the refrigerant circuit is insufficient, the degree of subcooling of the refrigerant flowing out of the heat exchanger operating as a condenser cannot be controlled, as illustrated in FIG. 4, (c). By contrast, as time passes, the degree of superheat of the refrigerant flowing out of the heat exchanger operating as an evaporator gradually converges to the optimal degree of superheat. Thus, the controller 400 can perform an energy saving control.

[0061] FIG. 5 illustrates images regarding distribution processing operation in the air-conditioning apparatus 1 according to Embodiment 1. Referring to FIG. 5, because the degree of superheat of the refrigerant flowing out of the use-side heat exchanger 110a exceeds a threshold, the distribution ratio ki for the refrigerant passing through each expansion valve 120 is updated at a time T. The distribution controller 414 performs control to increase the opening degree of the expansion valve 120a by 10%. In addition, the distribution controller 414 perform control to reduce the opening degrees of the expansion valves 120b and 120c by 5%. In such a manner, since the distribution controller 414 controls distribution of the opening degrees of the expansion valves 120, the degree of superheat of the refrigerant flowing out of the use-side heat exchanger 110a is reduced and converges to a value less than or equal to the threshold. By contrast, although, as illustrated in (b) and (c) in FIG. 5, the degrees of superheat of the refrigerant flowing out of the use-side heat exchanger 110b and the use-side heat exchanger 110c slightly increase, but converges to the threshold or converges below the threshold, and the state of the refrigerant is stabilized.Advantages of Air-Conditioning Apparatus 1 According to Embodiment 1

[0062] As described above, in the air-conditioning apparatus 1 according to Embodiment 1, in the control processing device 410 of the controller 400, the first controller 411 includes the subcooling degree controller 415 and calculates a total heat-source-side expansion-valve opening degree based on the degree of subcooling of refrigerant that flows out of the heat-source-side heat exchanger 230; and the second controller 412 includes the superheat degree controller 416 and calculates a total use-side expansion-valve opening degree based on the degrees of superheat of refrigerant that flows out of the use-side heat exchangers 110. The maximum selector 413 compares the total heat-source-side expansion-valve opening degree and the total heat-source-side expansion-valve opening degree with each other, and outputs the larger one of the total heat-source-side expansion-valve opening degree and the total heat-source-side expansion-valve opening degree as the maximum total expansion-valve opening degree. The distribution controller 414 distributes the maximum total expansion-valve opening degree among the expansion valves 120 to determine the opening degrees of the expansion valves 120. Thus, the air-conditioning apparatus 1 according to Embodiment 1 can maintain a highly efficient operation even under a condition where an excess or insufficient amount of refrigerant is supplied.

[0063] For example, in general, in a multi-type refrigeration cycle apparatus like the air-conditioning apparatus 1 including the accumulator 240 in Embodiment 1, the degree of subcooling of refrigerant that flows in each use-side heat exchanger 110 is controlled by control over the opening degree of an associated one of the expansion valves 120. However, when the amount of the refrigerant in the refrigerant circuit becomes insufficient, a degree of subcooling does is not obtained even when the opening degrees of the expansion valves 120 are reduced, as a result of which the degree of subcooling becomes uncontrollable, and it is therefore impossible to determine appropriate opening degrees of the expansion valves 120. In addition, when the amount of the refrigerant in the refrigerant circuit becomes insufficient, the amount of refrigerant flowing in a use-side heat exchanger 110 operating as an evaporator may become insufficient and the capability may thus become insufficient. In view of this, according to the air-conditioning apparatus 1 according to Embodiment 1, the control processing device 410 of the controller 400 selects a total expansion-valve opening degree for determining the opening degrees of the expansion valves in the next step, from a total expansion-valve opening degree based on the degree of subcooling and a total expansion-valve opening degree based on the degree of superheat. Therefore, when the refrigerant in the refrigerant circuit is sufficient, the controller 400 can achieve a high efficient and energy saving operation by appropriately controlling the degree of subcooling. In addition, even under an operation condition where the refrigerant is insufficient due to, for example, a long pipe length and the degree of subcooling cannot be controlled, the control is automatically and consecutively switched to a control based on the degree of superheat, and it is therefore possible to reduce an increase in the degree of superheat. Furthermore, because the control processing device 410 determines the opening degree of each expansion valve 120 for reduction of an increase in the degree of superheat, a stable and high efficient operation can be maintained.

[0064] Furthermore, a control unit included in the control processing device 410 of the controller 400 in Embodiment 1 is a control unit for consecutive control, which has an anti-reset windup function. With this configuration, even in an operation in which the amount of refrigerant in the refrigerant circuit is moderate and that is on a switching point between a subcooling degree control and a superheat degree control, it is possible to reduce an occurrence of hunting. Thus, the air-conditioning apparatus 1 can be stably operated. In addition, the degree of superheat can be highly accurately controlled to the upper limit degree of superheat. With this configuration, it is possible to reduce an increase in a discharge temperature of refrigerant that is discharged by the compressor 210 and to protect the components in the refrigerant circuit. Therefore, it is possible to obtain such advantages as described above by applying a consecutive control such as PI control, not only to a subcooling control that is a main control but also to a protection that is a secondary control, and by using the maximum selector 413 in combination with the above control.

[0065] As described above, in the air-conditioning apparatus 1 according to Embodiment 1, an efficient operation can be maintained even when the amount of the refrigerant in the refrigerant circuit is insufficient. This means that even in the case where the number of refrigerant circuits is reduced, a high efficient operation can be maintained. It is therefore possible to provide a multi-type refrigeration cycle apparatus that can highly efficiently operate while reducing the cost thereof by reducing the amount of refrigerant.

[0066] The following description is made with respect to the case where the refrigerant is excessively filled in the refrigerant circuit. In a multi-type refrigeration cycle apparatus, in some case, the degree of superheat is controlled by the expansion valve 120. However, in the case where the refrigerant is excessively filled in the refrigerant circuit, the degree of superheat cannot be controlled unless the opening degree of the expansion valve 120 is extremely reduced, and an energy saving performance is reduced. When the refrigerant is excessively filled, a total heat-source-side expansion-valve opening degree that is determined based on the degree of subcooling and output by the subcooling degree controller 415 becomes higher than a total heat-source-side expansion-valve opening degree that is determined based on the degree of superheat and output by the superheat degree controller 416. In the air-conditioning apparatus 1 according to Embodiment 1, a larger total expansion-valve opening degree selected by the maximum selector 413 is distributed among the expansion valves 120 as respective opening degrees thereof by the distribution controller 414, whereby the subcooling degree control is performed. With this configuration, a more efficient operation can be achieved.

[0067] Furthermore, in the air-conditioning apparatus 1 according to Embodiment 1, the distribution controller 414 updates the distribution ratio ki only when the degree of superheat of refrigerant passing through a heat exchanger is higher than a predetermined threshold. In general, it is difficult for a multi-type refrigeration cycle apparatus to perform a superheat degree control with high accuracy. This results from nonlinearity due to, for example, change in the number of use-side heat exchangers that are in operation or change in load of each use-side heat exchanger 110. It also results from adoption of a multi-input multi-output system in which an operation of one expansion valve 120 affects the degrees of superheat in all the use-side heat exchangers 110. In addition, it is necessary to give appropriate target values for various operation states, and this makes control design difficult. In view of this point, in the air-conditioning apparatus 1 according to Embodiment 1, the distribution controller 414 updates the distribution ratio ki only when the degree of superheat is higher than the predetermined threshold. In addition, the superheat degree controller 416 configured to control a maximum value, a minimum value, or an average value of the degrees of superheat of refrigerant passing through the use-side heat exchangers 110 is used in combination with the distribution controller 414. With this configuration, robustness against a change in environment, such as the amount of refrigerant, an installation condition, or an operation condition, is improved and the stability of the degree of superheat is thus improved. As a result, it is possible to reduce an occurrence of hunting. As described above, because the configuration of the control processing device 410 itself has high robustness, the load of the control design can be reduced. Furthermore, a designer has only to give a predetermined threshold. Therefore, it is possible to further reduce the load of design. This advantage cannot be obtained in the case where the superheat degree controller 416 and the distribution controller 414 are not used in combination.

[0068] Furthermore, in the air-conditioning apparatus 1 according to Embodiment 1, the controller 400 controls and manages the opening degree of each expansion valve 120 with respect to the distribution ratio ki, and it is therefore possible to control an increase and decrease in the opening degree of each expansion valve with respect to ratio. As a result, the opening degrees of the expansion valves can keep a linear relationship with the amount of the refrigerant, and can thus be controlled easily. Because the opening degrees of the expansion valves are managed by using the distribution ratio ki, the control of a start or stop of operation of each of use-side units 100 including the use-side heat exchangers 110 can be simplified. In particular, in a design, by setting that distribution ratios of expansion valves 120 for which the distribution ratios do not need to be changed such that the distribution ratios are kept as much as possible, it is possible to reduce occurrence of a disturbance on the refrigeration cycle that would be caused by a protective operation or a change in an operation state.

[0069] Furthermore, the first controller 411 and the second controller 412 include the PI controllers 417 and perform a feedback control. For the PI controller 417, which is an established controller in a control engineering field, methods for designing parameters have already been established by many existing studies. Therefore, in the air-conditioning apparatus 1 according to Embodiment 1, it is possible to reduce the load of designing a controller configured to control the degree of superheat or the degree of subcooling. For example, as a method for designing parameters for a controller, a design method that uses a system identification result by a step response can be considered. Basically, a parameter is calculated through a mathematical procedure from a characteristic obtained by a system identification, but a parameter for a controller can also be learned from input / output data that is input to or output from the controller when the air-conditioning apparatus 1 is actually operated. It should be noted that with respect to the system identification, it is not limited whether it is an online identification or an offline identification.Embodiment 2

[0070] FIG. 6 illustrates a configuration of the control processing device 410 in Embodiment 2. FIG. 6 illustrates a section that performs a control of the opening degree of each expansion valve, among controls of the air-conditioning apparatus 1 that are performed by the control processing device 410 of the controller 400. As illustrated in FIG. 6, as in Embodiment 1, the controller 400 according to Embodiment 2 includes the first controller 411, the second controller 412, the maximum selector 413, and the distribution controller 414. As in the case of Embodiment 1, the maximum selector 413 compares a value of a total heat-source-side expansion-valve opening degree output by the first controller 411 and a value of a total heat-source-side expansion-valve opening degree output by the second controller 412, and outputs the larger one of the value of the total heat-source-side expansion-valve opening degree and the value of the total heat-source-side expansion-valve opening degree as a maximum total expansion-valve opening degree.

[0071] The following description is made with respect to the case where the air-conditioning apparatus 1 according to Embodiment 2 performs a heating operation in which the use-side heat exchanger 110 operates as a condenser and the heat-source-side heat exchanger 230 operates as an evaporator. Thus, in the control processing device 410 of the controller 400 in Embodiment 2, the first controller 411 includes the superheat degree controller 416, and the second controller 412 includes the subcooling degree controller 415, as illustrated in FIG. 6.

[0072] The subcooling degree controller 415 in Embodiment 2 outputs a total expansion-valve opening degree as a value for causing the maximum one of the degrees of subcooling of refrigerant that flows out of the use-side heat exchangers 110 to follow a target degree of subcooling. To the subcooling degree controller 415 of Embodiment 2, signals from the high-pressure sensor 510 and the use-side heat exchanger liquid-pipe temperature sensors 550 are input. A control output for the subcooling degree control is not limited to the maximum degree of subcooling but may be a minimum value or another value, such as a statistical value that can be obtained through statistical processing on a plurality of degrees of subcooling as an average value or a median value, for example. It should be noted that because the degree of subcooling does not fall below zero, a degree of subcooling that is lower than a certain threshold may be treated as an outlier.

[0073] On the other hand, the superheat degree controller 416 in Embodiment 2, for example, calculates and outputs a total expansion-valve opening degree for causing the degree of superheat of refrigerant that flows out of the heat-source-side heat exchanger 230 to follow an upper limit degree of superheat. In addition, to the superheat degree controller 416 in Embodiment 1, signals from the low-pressure sensor 520 and the heat-source-side heat exchanger gas-pipe temperature sensor 530 are input.

[0074] As in Embodiment 1, the distribution controller 414 distributes the maximum total expansion-valve opening degree output from the maximum selector 413 among the expansion valves 120 to determine the opening degrees thereof. However, because the air-conditioning apparatus 1 of Embodiment 2 performs the heating operation, the distribution controller 414 executes processing different from that of Embodiment 1. A procedure of processes by the distribution controller 414 in Embodiment 2 will be described on the assumption that U={1, 2, . . . , n} is a set of use-side heat exchanger numbers, where n is the number of use-side heat exchangers 110 being connected; V⊂U is a set of use-side heat exchanger numbers of use-side heat exchangers that are in operation; A⊂V is a set of use-side heat exchanger numbers of use-side heat exchangers in which the degree of superheat is lower than a lower limit subcooling-degree threshold (SCi<2, i∈V); B⊂V is a set of use-side heat exchanger numbers of use-side heat exchangers in each of which the degree of subcooling exceeds an upper limit subcooling-degree threshold (SCi>9, i⊂V), where SCi is a degree of subcooling of the use-side heat exchanger I; and C={i∈V} is a set of use-side heat exchanger numbers of the use-side heat exchangers in which the degree of subcooling is within an appropriate range. It should be noted that i in the set C does not belong to set A or set B.

[0075] As in Embodiment 1, the distribution controller 414 holds distribution ratios ki (i∈V) having a characteristic expressed by the equation (1). Then, the distribution controller 414 calculates an opening degree of each expansion valve 120 based on the distribution ratios ki, according to the equation (2) described above.

[0076] Then, the distribution controller 414 updates the distribution ratio ki at, for example, one-minute intervals, but this is not limiting. When determining that the degree of subcooling of a use-side heat exchanger 110 is lower than the predetermined lower limit subcooling-degree threshold (for example, 2K), the distribution controller 414 determines that an excess amount of refrigerant flows in the use-side heat exchanger 110 and thus decreases the distribution ratio ki of an associated one of the expansion valves 120. When the distribution ratio ki is decreased, the opening degree of the expansion valve 120 is decreased and the amount of refrigerant that flows in the use-side heat exchanger 110 is thus decreased.

[0077] When determining that the degree of subcooling of a use-side heat exchanger 110 is higher than the predetermined upper limit subcooling-degree threshold (for example, 9K), the distribution controller 414 determines that a sufficient amount of refrigerant does not flow in the use-side heat exchanger 110 and thus increases the distribution ratio ki of an associated one of the expansion valves 120. When the +0 distribution ratio ki is increased, the opening degree of the expansion valve 120 is increased and the amount of the refrigerant flowing in the use-side heat exchanger 110 is thus increased.

[0078] Next, an example of updating of the distribution ratio ki will be described on the assumption that k is a step at the timing of the previous update and k+1 is a step at the timing of the present update. First, when all the use-side heat exchangers 110 are in the same state, the distribution ratios ki are not changed. The same state means V=A or V=B or V=C (this state will be referred to as condition a). The distribution ratio ki(k+1) resulting from the present update can be expressed by the equation (3) by using the distribution ratio ki (k) resulting from the previous update.

[0079] Meanwhile, when the use-side heat exchangers 110 do not satisfy the condition a and a use-side heat exchanger 110 in which the degree of subcooling falls within an appropriate range is not present, that is, when V≠A and V≠B and V≠C=Φ (empty set) are satisfied (this state will be referred to as condition b), the distribution ratio ki is determined by division by cases. The division by cases is carried out according to the number of elements.

[0080] In the case where |A|<|B|, the distribution ratio ki of the opening degree of the expansion valve 120 is updated based on the following equation (8).[Math. 8]ki(k+1)={90100⁢ki(k)…⁢ i∈𝒜ki(k)+10100⁢ki(k)⁢∑i∈𝒜ki(k)∑i∈ℬki(k)…⁢ i∈ℬ(8)

[0081] In the case where |A|≥|B|, the distribution ratio ki of the opening degree of the expansion valve 120 is updated based on the following equation (9).[Math. 9]ki(k+1)={110100⁢ki(k)…⁢ i∈ℬki(k)-10100⁢ki(k)⁢∑i∈ℬki(k)∑i∈𝒜ki(k)…⁢ i∈𝒜(9)

[0082] Finally, in the case where neither the condition a nor the condition b is satisfied, that is, in the case where V≠A, V≠B, V≠C, and C≠Φ, the distribution ratio ki of the opening degree of the expansion valve 120 is updated based on the following equation (10).[Math. 10]ki(k+1)={90100⁢ki⁢(k)…⁢ i∈𝒜110100⁢ki⁢(k)…⁢ i∈ℬki(k)+10100⁢ki(k)⁢∑i∈𝒜ki(k)∑i∈𝒞ki(k)-10100⁢ki(k)⁢∑i∈ℬki(k)∑i∈𝒞ki(k)…⁢ i∈𝒞(10)

[0083] When the distribution controller 414 updates the distribution ratio ki as described above, the opening degree of an expansion valve 120 associated with a use-side heat exchanger 110 in which the amount of the refrigerant is small is relatively increased and the amount of the refrigerant passing through the use-side heat exchanger 110 is increased. Thus, the opening degree of an expansion valve 120 associated with a use-side heat exchanger 110 in which the amount of the refrigerant is large is relatively decreased and the amount of the refrigerant passing through the use-side heat exchanger 110 is decreased. In addition, the opening degree of an expansion valve 120 associated with a use-side heat exchanger 110 in which the amount of refrigerant passing therethrough is not small or large and is proper is changed in such a manner as to maintain the total expansion-valve opening degree for the above expansion valves 120. Although the opening degree of the expansion valve 120 of the use-side heat exchanger 110 is increased or decreased by 10% in the equations (8) to (10), the percent by which the opening degree is increased or decreased is not limited to 10%, and needs not to be constant. In addition, although it is described above that regarding the condition b, depending on the number of elements in a set, case division is performed with respect to the method for determining a distribution ratio ki and the method is switched between plural methods. The conditions may be reversed and the method needs not to be switched depending on the number of elements.

[0084] In the case where a use-side unit 100 that is in operation is stopped or a use-side unit 100 that is in a stopped state is stated, the processing for determining the distribution ratio ki for an associated expansion valve 120 by the distribution controller 414 is the same as that in Embodiment 1. However, in the heating operation, when the expansion valve 120 associated with the use-side heat exchanger 110 that is in the stopped state is completely closed, the refrigerant may remain in the use-side heat exchanger 110. Thus, the expansion valve 120 may be slightly opened. Even when the expansion valve 120 is slightly opened, it is not a problem as long as it has little effect on the amount of refrigerant passing through the use-side heat exchanger 110 of the use-side unit 100 that is in operation. If the effect cannot be ignored, the distribution ratio ki is set according to the slight opening of the expansion valve 120 to extend the determination method of the distribution ratio ki.Advantages of Air-Conditioning Apparatus 1 According to Embodiment 2

[0085] As described above, in the air-conditioning apparatus 1 according to Embodiment 2, the control processing device 410 of the controller 400 includes the subcooling degree controller 415 and the distribution controller 414. By using the subcooling degree controller 415 and the distribution controller 414 in combination, a maximum value, a minimum value, or an average value of the degrees of subcooling can be controlled based on the total expansion-valve opening degree. Therefore, the degree of subcooling of each use-side heat exchanger 110 can be kept in an appropriate range, and a high efficiency operation can thus be achieved. This advantage cannot be obtained unless the subcooling degree controller 415 and the distribution controller 414 are used in combination.

[0086] In the air-conditioning apparatus 1 according to Embodiment 2, the distribution controller 414 updates the distribution ratio ki only when the degree of subcooling of refrigerant passing through a heat exchanger does fall within the predetermined range. In general, in a multi-type refrigeration cycle apparatus, it is hard to perform a subcooling degree control with high accuracy. This is caused by, for example, nonlinearity due to a change in the number of use-side units 100 that are in operation or a change in load of each use-side heat exchanger 110. This is also because the multi-type refrigeration cycle apparatus uses a multi-input multi-output system in which the operation of the expansion valve 120 affects the degrees of subcooling of all the use-side heat exchangers 110. Moreover, because appropriate target values are required to be set for various operation states, it makes control design difficult. In view of these points, in the air-conditioning apparatus 1 according to Embodiment 2, the distribution controller 414 updates the distribution ratio ki only when the degree of subcooling does not fall within the predetermined range. In addition, the subcooling degree controller 415 configured to control the maximum value, the minimum value, or the average value of the degrees of subcooling of refrigerant passing through the use-side heat exchangers 110 is used in combination with the distribution controller 414. Thus, robustness for changes in environment, such as the amount of the refrigerant, an installation condition, or an operation condition, is improved and the stability of degree of subcooling is thus improved. As a result, an occurrence of hunting can be reduced. In such a manner, because the robustness is improved by the configuration of the control processing device 410 itself, the load of designing control can be reduced. Furthermore, a designer only has to set a predetermined threshold. Accordingly, it is possible to further reduce the load of design.Embodiment 3

[0087] FIG. 7 illustrates a configuration of the control processing device 410 in Embodiment 3. FIG. 7 illustrates a section that performs a control of the opening degree of each expansion valve, among controls of the air-conditioning apparatus 1 that are performed by the control processing device 410 of the controller 400. Referring to FIG. 7, components that are denoted by the same reference signs as in Embodiment 1 described with reference to FIG. 3 basically perform the same processing operations as described regarding Embodiment 1. As illustrated in FIG. 7, the controller 400 of Embodiment 3, as well as the controller 400 of Embodiment 1, includes the first controller 411, the second controller 412, the maximum selector 413, and the distribution controller 414.

[0088] The subcooling degree controller 415 of the first controller 411 in Embodiment 3 has a validity / invalidity determination function. When the degree of subcooling is higher than a predetermined set subcooling-degree threshold (for example, 2K), the subcooling degree controller 415 determines that a condition is valid, and when the degree of subcooling is equal to or lower than the set subcooling-degree threshold, the subcooling degree controller 415 determines that the condition is invalid. The superheat degree controller 416 of the second controller 412 in Embodiment 3 also has the validity / invalidity determination function. When the degree of superheat is higher than a set superheat degree set threshold (for example, 2K), the subcooling degree controller 415 determines that a condition is valid, and when the degree of superheat is equal to or lower than the threshold, the subcooling degree controller 415 determines that the condition is invalid.

[0089] In addition, the controller 400 of Embodiment 3 further includes a throttling controller 418. The throttling controller 418 has a function of performing a control to decrease the total expansion-valve opening degree by feedforward control. For example, when the total expansion-valve opening degree is required to be changed at a constant speed, the throttling controller 418 calculates the total expansion-valve opening degree based on the following equation (11), where ΔS is a predetermined opening-degree change amount, k is a step at the timing of the previous update, and k+1 is a step at the timing of the present update. Data on step k is stored in, for example, the storage device 430.[Math. 11]Stotal(k+1)=Stotal(k)-Δ⁢S(11)

[0090] Furthermore, the throttling controller 418 also has the validity / invalidity determination function. For example, when the subcooling degree controller 415 and the superheat degree controller 416 both determine that the conditions are invalid, the throttling controller 418 determines that a condition is valid; otherwise, the throttling controller 418 determines that the condition is invalid. When the determinations made by the subcooling degree controller 415 and the superheat degree controller 416 each transition from the determination that the condition is invalid to the determination that the condition is valid, the subcooling degree controller 415 and the superheat degree controller 416 adjust, for example, an integral value so that the transition occurs in a bumpless manner.

[0091] The above equation (11) is an example of a calculation where ΔS is a constant value and the opening degree of an expansion valve is changed at a constant speed. However, it is not indispensable that the opening degree of the expansion valve is changed at the constant speed. For example, a convergence time T may be set for a start opening degree Ss and a converged opening degree St, and the opening-degree change amount ΔS may be calculated by the following equation (12), where Tc is a control cycle. By setting the opening-degree change amount ΔS as indicated by the equation (12), a time period from start to convergence can be designed.[Math. 12]Δ⁢S=Ss-StT⁢Tc(12)

[0092] The converged opening degree St in the equation (12) is actually an unknown value. Thus, the throttling controller 418 estimates the converged opening degree St from a calculation based on the equation (13), for example. A refrigerant flow rate G is expressed by the equation (13) by using an expansion-valve opening degree S, a differential pressure dP, an expansion-valve inlet refrigerant density ρl, a compressor rotation speed F, a compressor suction refrigerant density ρg, and constants (C1, C2).[Math. 13]G=C1*S*dP*ρl=C2*F*ρg(13)

[0093] From the equation (13), the expansion-valve opening degree S is expressed by equation (14), where C is a constant.[Math. 14]S=C⁢F*ρgdP*ρl(14)

[0094] Since the compressor rotation speed F is controlled by the controller 400, the throttling controller 418 can obtain the compressor rotation speed F from internal information. In addition, dP, ρg, and ρl can be estimated by using a design value, the compressor rotation speed F, suction temperature conditions of the heat exchangers, thermal resistances of the heat exchangers, and other factors. For example, when a suction temperature of the condenser is high and a suction temperature of the evaporator is low, the differential pressure dP increases. The differential pressure dP also increases when the thermal resistance of the heat exchanger is high. Furthermore, the differential pressure dP also increases when the compressor rotation speed F is high. In addition, when the compressor rotation speed F is high, when the suction temperature of the evaporator is low, or when the thermal resistance of the evaporator is high, the compressor suction refrigerant density ρg, decreases.

[0095] As described above, parameters are estimated based on operation conditions. When the compressor rotation speed F or the compressor suction refrigerant density ρg, increases, the converged opening degree St is set high. When the compressor rotation speed F or the compressor suction refrigerant density ρg decreases, the converged opening degree St is set low. In addition when the differential pressure dP increases, the converged opening degree St is set low, and when differential pressure dP decreases, the converged opening degree St is set high.

[0096] As described above, the converged opening degree St can be estimated. In this case, it should be noted that if the compressor rotation speed F is allowed to change moment by moment, the converged opening degree St also changes over time, and as a result, the opening-degree change amount ΔS also changes over time.

[0097] Next, an example where a throttling speed is not constant will be described. As a characteristic of an expansion valve 120, the higher the opening degree S of the expansion valve, the smaller the effect of the expansion valve 120 on the system. For example, assuming that the opening degree S of the expansion valve falls within the range of 0 to 1000, changing of the opening degree S of the expansion valve from 10 to 11 has a larger effect on the system than changing of the opening degree S of the expansion valve from 900 to 901. Accordingly, the opening-degree change amount ΔS is conceivable to be increased when the opening degree S of the expansion valve is high, and to be decreased when the opening degree S of the expansion valve is low. For example, based on the equation (15), the opening-degree change amount ΔS is updated in such a manner as to be proportional to the current opening degree S of the expansion valve.[Math. 15]Δ⁢S=-S⁡(k)*(eα-1)(15)α=-TcT⁢log⁢SsSt

[0098] By calculating the opening-degree change amount ΔS as indicated by the equation (15), the obtained opening-degree change amount ΔS is proportional to the current opening degree S of the expansion valve, and the effect on the system can be kept constant. Furthermore, by setting a as indicated in the equation (15), time T required to obtain a converged opening degree from the start can be designed. Although the above description is made with respect to the case where the air-conditioning apparatus 1 performs the cooling operation, the above processing can also be applied to the heating operation.

[0099] Furthermore, in addition to the technique described in the above descriptions, the opening-degree change amount ΔS may be determined based on the temperature of the refrigerant. For example, when the air-conditioning apparatus 1 is started, a discharge temperature of the compressor 210 may suddenly rise after starting of the air-conditioning apparatus 1 due to an initial refrigeration distribution or a starting opening degree. Thus, when the controller 400 detects that the discharge temperature suddenly rises, the throttling controller 418 may reduce sudden rising of the opening-degree change amount ΔS such that the opening-degree change amount ΔS gently varies. By causing the opening-degree change amount ΔS to be gently changed, it is possible to achieve a prompt and stably operation, without occurrence of stopping of the operation that would be caused by an excessive rise in the discharge temperature.Advantages of Air-Conditioning Apparatus 1 According to Embodiment 3

[0100] As described above, in the air-conditioning apparatus 1 according to Embodiment 3, the control processing device 410 of the controller 400 includes the throttling controller 418 configured to control the opening-degree change amount ΔS of the total expansion-valve opening degree. When it is determined that the total expansion-valve opening degree based on the degree of subcooling or superheat, which is output by the first controller 411 or the second controller 412, is invalid, a control of the total expansion-valve opening degree is performed by the throttling controller 418. Thus, the air-conditioning apparatus 1 according to Embodiment 3 can shorten a time period that is required from the start of the operation until the operation is stabilized, and can promptly perform heating or cooling. For example, in a multi-type refrigeration cycle apparatus that controls the degree of subcooling or the degree of superheat, it is hard to achieve a quick responsiveness because the degree of subcooling or the degree of superheat does not fall below zero. However, in the air-conditioning apparatus 1 according to Embodiment 3, the control processing device 410 of the controller 400 can obtain a desired responsiveness by using the valid / invalid determination functions of the throttling controller 418, the first controller 411, and the second controller 412.INDUSTRIAL APPLICABILITY

[0101] Regarding Embodiments 1 to 3, although the air-conditioning apparatus is described as an example of a multi-type refrigeration cycle apparatus, the present disclosure is not limited to the air-conditioning apparatus. The present disclosure can be applied to another multi-type refrigeration cycle apparatus, such as a refrigeration apparatus or a cooling apparatus configured to cool a heat supply target.REFERENCE SIGNS LIST1: air-conditioning apparatus, 100, 100a, 100b, 100c: use-side unit, 110, 110a, 110b, 110c: use-side heat exchanger, 120, 120a, 120b, 120c: expansion valve, 130, 130a, 130b, 130c: indoor fan, 200: heat-source-side unit, 210: compressor, 220: four-way valve, 230: heat-source-side heat exchanger, 240: accumulator, 250: outdoor fan, 300: refrigerant pipe, 400: controller, 410: control processing device, 411: first controller, 412: second controller, 413: maximum selector, 414: distribution controller, 415: subcooling degree controller, 416: superheat degree controller, 417: PI controller, 418: throttling controller, 420: timing device, 430: storage device, 510: high-pressure sensor, 520: low-pressure sensor, 530: heat-source-side heat exchanger gas-pipe temperature sensor, 540: heat-source-side heat exchanger liquid-pipe temperature sensor, 550, 550a, 550b, 550c: use-side heat exchanger liquid-pipe temperature sensor, 560, 560a, 560b, 560c: use-side heat exchanger gas-pipe temperature sensor

Examples

embodiment 1

[0019]FIG. 1 illustrates a configuration of an air-conditioning apparatus 1 according to Embodiment 1. The following description refers to, as an example of a multi-type refrigeration cycle apparatus, an air-conditioning apparatus 1 that air-conditions an indoor space that is an air-conditioning target space. In this case, the air in the indoor space is a heat supply target. As illustrated in FIG. 1, the air-conditioning apparatus 1 according to Embodiment 1 includes a heat-source-side unit 200, use-side units 100, and refrigerant pipes 300. A compressor 210, a four-way valve 220, and a heat-source-side heat exchanger 230 included in the heat-source-side unit 200, and a use-side heat exchanger 110 and an expansion valve 120 included in each of the use-side units 100 are connected by the refrigerant pipes 300, whereby a refrigerant circuit is formed in which refrigerant is circulated to carry heat. In this case, it is assumed that in the air-conditioning apparatus 1 according to Embo...

embodiment 2

[0070]FIG. 6 illustrates a configuration of the control processing device 410 in Embodiment 2. FIG. 6 illustrates a section that performs a control of the opening degree of each expansion valve, among controls of the air-conditioning apparatus 1 that are performed by the control processing device 410 of the controller 400. As illustrated in FIG. 6, as in Embodiment 1, the controller 400 according to Embodiment 2 includes the first controller 411, the second controller 412, the maximum selector 413, and the distribution controller 414. As in the case of Embodiment 1, the maximum selector 413 compares a value of a total heat-source-side expansion-valve opening degree output by the first controller 411 and a value of a total heat-source-side expansion-valve opening degree output by the second controller 412, and outputs the larger one of the value of the total heat-source-side expansion-valve opening degree and the value of the total heat-source-side expansion-valve opening degree as a...

embodiment 3

[0087]FIG. 7 illustrates a configuration of the control processing device 410 in Embodiment 3. FIG. 7 illustrates a section that performs a control of the opening degree of each expansion valve, among controls of the air-conditioning apparatus 1 that are performed by the control processing device 410 of the controller 400. Referring to FIG. 7, components that are denoted by the same reference signs as in Embodiment 1 described with reference to FIG. 3 basically perform the same processing operations as described regarding Embodiment 1. As illustrated in FIG. 7, the controller 400 of Embodiment 3, as well as the controller 400 of Embodiment 1, includes the first controller 411, the second controller 412, the maximum selector 413, and the distribution controller 414.

[0088]The subcooling degree controller 415 of the first controller 411 in Embodiment 3 has a validity / invalidity determination function. When the degree of subcooling is higher than a predetermined set subcooling-degree th...

Claims

1. A multi-type refrigeration cycle apparatus comprising:a refrigerant circuit in which a compressor, a heat-source-side heat exchanger, a plurality of expansion valves, and a plurality of use-side heat exchangers connected in series to the respective expansion valves are connected by pipes, and refrigerant is circulated; anda controller configured to control components in the apparatus,wherein the controller includesa first controller configured to calculate a total expansion-valve opening degree for the expansion valves as a value for causing a heat-source-side state value of the refrigerant flowing out of the heat-source-side heat exchanger to follow a target heat-source-side state value, and output the total expansion-valve opening degree as a total heat-source-side expansion-valve opening degree,a second controller configured to calculate the total expansion-valve opening degree for the expansion valves as a value for causing a use-side state value of the refrigerant flowing out of each of the plurality of use-side heat exchangers to follow a target use-side state value, and output the total expansion-valve opening degree as a total use-side expansion-valve opening degree,a maximum selector configured to select one of the total heat-source-side expansion-valve opening degree and the total use-side expansion-valve opening degree, as a maximum total expansion-valve opening degree, anda distribution controller configured to perform processing to distribute the maximum total expansion-valve opening degree among the expansion valves as respective opening degrees thereof, andwherein the distribution controller is configured to distribute the maximum total expansion-valve opening degree at distribution ratios in which the opening degrees of the expansion valves associated with the respective use-side heat exchangers are relatively changed, based on comparison between the use-side state values of the refrigerant flowing out of the use-side heat exchangers and a set threshold.

2. The multi-type refrigeration cycle apparatus of claim 1, whereinin the cooling operation in which a heat supply target is cooled by heat exchange with the refrigerant in each of the use-side heat exchangers,the first controller calculates the total heat-source-side expansion-valve opening degree by using a degree of subcooling of the refrigerant flowing out of the heat-source-side heat exchanger as the heat-source-side state value,the second controller calculates the total use-side expansion-valve opening degree as a value for causing a maximum value or a minimum value of the degrees of superheat of the refrigerant flowing out of the use-side heat exchangers, or a statistical value obtained through statistical processing on the degrees of superheat to follow an upper limit degree of superheat, while using a value obtained from the degree of superheat of the refrigerant flowing out of each of the use-side heat exchangers, as the use-side state value,the maximum selector compares the total heat-source-side expansion-valve opening degree and the total use-side expansion-valve opening degree; and selects the total heat-source-side expansion-valve opening degree as the maximum total expansion-valve opening degree, when the total heat-source-side expansion-valve opening degree is higher than the total use-side expansion-valve opening degree, and selects the total use-side expansion-valve opening degree as the maximum total expansion-valve opening degree, when the total use-side expansion-valve opening degree is higher than the total heat-source-side expansion-valve opening degree, andthe distribution controller determines, as the distribution ratios, distribution ratios in which the opening degrees of the expansion valves associated with use-side heat exchangers in each of which the degree of superheat of the refrigerant flowing out thereof is higher than or equal to the threshold are relatively increased.

3. The multi-type refrigeration cycle apparatus of claim 1, whereinin the heating operation in which a heat supply target is heated by heat exchange with the refrigerant in each of the use-side heat exchangers,the first controller calculates the total heat-source-side expansion-valve opening degree as a value for causing a degree of superheat of the refrigerant flowing out of the heat-source-side heat exchanger to follow an upper limit degree of superheat, as the heat-source-side state value,the second controller calculates the total use-side expansion-valve opening degree as a value for causing a maximum value or a minimum value of the degrees of subcooling of the refrigerant flowing out of the use-side heat exchangers, or a statistical value obtained through statistical processing on the degrees of subcooling to follow a lower limit degree of superheat, while using a value obtained from the degree of subcooling of the refrigerant flowing out of each of the plurality of use-side heat exchangers, as the use-side state value,the maximum selector compares the total heat-source-side expansion-valve opening degree and the total use-side expansion-valve opening degree; and selects the total use-side expansion-valve opening degree as the maximum total expansion-valve opening degree, when the total use-side expansion-valve opening degree is higher than the total heat-source-side expansion-valve opening degree, and selects the total heat-source-side expansion-valve opening degree as the maximum total expansion-valve opening degree, when the total heat-source-side expansion-valve opening degree is higher than the total use-side expansion-valve opening degree, andthe distribution controller determines, as the distribution ratios, distribution ratios in which the opening degrees of the expansion valves associated with use-side heat exchangers are relatively increased or decreased such that the degrees of subcooling of the refrigerant flowing out thereof each fall within a range of a set upper limit subcooling-degree threshold to a lower limit subcooling-degree threshold.

4. The multi-type refrigeration cycle apparatus of claim 2, whereinthe distribution controller is configured to, in the cooling operation, increase the distribution ratio with respect to the opening degree of the expansion valve associated with a use-side heat exchanger in which the degree of superheat is higher than a set superheat degree threshold, such that the opening degree of the expansion valve is increased with reference to a current opening degree of the expansion valve, and decrease the distribution ratio for the total expansion-valve opening degree while maintaining a relationship in distribution ratio between the other expansion valves.

5. The multi-type refrigeration cycle apparatus of claim 3, whereinthe distribution controller is configured to, in the heating operation, decrease the distribution ratio with respect to the opening degree of the expansion valve associated with a use-side heat exchanger in which the degree of subcooling is lower than the lower limit subcooling-degree threshold, such that the opening degree of the expansion valve is decreased with reference to a current opening degree of the expansion valve, increase the distribution ratio with respect to the opening degree of the expansion valve associated with a use-side heat exchanger in which the degree of subcooling is higher than the upper limit subcooling-degree threshold, such that the opening degree of the expansion valve is increased with reference to a current opening degree of the expansion valve, and decrease the distribution ratio for the total expansion-valve opening degree while maintaining a relationship in distribution ratio between the other expansion valves.

6. The multi-type refrigeration cycle apparatus of claim 1, whereinthe distribution controller is configured to change the distribution ratio, with respect to the expansion valve associated with the use-side heat exchanger in which heat exchange is stopped, such that the opening degree of the expansion valve is set to an opening degree at which the expansion valve is closed, and change the distribution ratio, with respect to the expansion valve associated with the use-side heat exchanger in which heat exchange is started, such that the opening degree of the expansion valve is set to an average value of the distribution ratios.

7. The multi-type refrigeration cycle apparatus of claim 1, whereinthe controller includes a throttling controller configured to reduce the total expansion-valve opening degree by a feedforward control,the first controller and the second controller each have a validity / invalidity determination function of determining that a condition is valid when the degree of subcooling or superheat is higher than a set threshold, and determining that the condition is invalid when the degree of subcooling or superheat is lower than or equal to the set threshold,the throttling controller has the valid / invalid determination function of determining that a condition is valid when the first controller and the second controller each determine that the condition is invalid; otherwise, determining that the condition is invalid, andthe maximum selector is configured to select a greatest one of values that are output as determinations that the conditions are valid, by the first controller, the second controller, and the throttling controller, as the maximum total expansion-valve opening degree.

8. The multi-type refrigeration cycle apparatus of claim 7, whereinthe throttling controller is configured to perform a control to reduce the opening degree of the expansion valve at a constant speed.

9. The multi-type refrigeration cycle apparatus of claim 8, whereinthe throttling controller is configured to calculate and set a converged opening degree and calculate the constant speed based on a time period required to achieve the converged opening degree.

10. The multi-type refrigeration cycle apparatus of claim 7, whereinthe throttling controller is configured to increase a throttle range when the opening degree of the expansion valve is high, and decrease the throttle range when the opening degree of the expansion valve is low.

11. The multi-type refrigeration cycle apparatus of claim 10, whereinthe throttling controller is configured to calculate and set a converged opening degree and determine a throttle range slope based on a time period required to achieve the set converged opening degree.

12. The multi-type refrigeration cycle apparatus of claim 9, whereinthe throttling controller is configured to calculate the converged opening degree based on a rotation speed of the compressor, a density of refrigerant that is sucked into the compressor, a differential pressure in the refrigerant circuit, and a density of refrigerant at an inlet of the explanation valve that flows into the expansion valve.

13. The multi-type refrigeration cycle apparatus of claim 2, whereinthe distribution controller is configured to change the distribution ratio, with respect to the expansion valve associated with the use-side heat exchanger in which heat exchange is stopped, such that the opening degree of the expansion valve is set to an opening degree at which the expansion valve is closed, and change the distribution ratio, with respect to the expansion valve associated with the use-side heat exchanger in which heat exchange is started, such that the opening degree of the expansion valve is set to an average value of the distribution ratios.

14. The multi-type refrigeration cycle apparatus of claim 3, whereinthe distribution controller is configured to change the distribution ratio, with respect to the expansion valve associated with the use-side heat exchanger in which heat exchange is stopped, such that the opening degree of the expansion valve is set to an opening degree at which the expansion valve is closed, and change the distribution ratio, with respect to the expansion valve associated with the use-side heat exchanger in which heat exchange is started, such that the opening degree of the expansion valve is set to an average value of the distribution ratios.

15. The multi-type refrigeration cycle apparatus of claim 4, whereinthe distribution controller is configured to change the distribution ratio, with respect to the expansion valve associated with the use-side heat exchanger in which heat exchange is stopped, such that the opening degree of the expansion valve is set to an opening degree at which the expansion valve is closed, and change the distribution ratio, with respect to the expansion valve associated with the use-side heat exchanger in which heat exchange is started, such that the opening degree of the expansion valve is set to an average value of the distribution ratios.

16. The multi-type refrigeration cycle apparatus of claim 5, whereinthe distribution controller is configured to change the distribution ratio, with respect to the expansion valve associated with the use-side heat exchanger in which heat exchange is stopped, such that the opening degree of the expansion valve is set to an opening degree at which the expansion valve is closed, and change the distribution ratio, with respect to the expansion valve associated with the use-side heat exchanger in which heat exchange is started, such that the opening degree of the expansion valve is set to an average value of the distribution ratios.

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