Multi-type refrigeration cycle apparatus

Abstract

This multi-type refrigeration cycle apparatus comprises: a refrigerant circuit formed by connecting, through piping, a heat source-side heat exchanger, a plurality of expansion valves, and a plurality of use-side heat exchangers; and a control device. The control device has a first controller that calculates a total expansion valve opening degree of the expansion valves for causing a heat source-side state value of a refrigerant flowing out from the heat source-side heat exchanger to follow a heat source-side target state value, and outputs the same as a heat source-side total expansion valve opening degree; a second controller that calculates a total expansion valve opening degree of the expansion valves for causing a use-side state value of the refrigerant flowing out from each of the use-side heat exchangers to follow a use-side target state value, and outputs the same as a use-side total expansion valve opening degree; a maximum selector that selects either one of the heat source-side total expansion valve opening degree or the use-side total expansion valve opening degree; and a distribution controller that performs a process for distributing a maximum total expansion valve opening degree to the opening degrees of the expansion valves.

Description

Multi-type refrigeration cycle equipment

[0001] The present technology relates to a multi-type refrigeration cycle apparatus having multiple user-side heat exchangers, and in particular to control of an expansion valve based on a state value of a refrigerant that has undergone heat exchange.

[0002] A multi-type refrigeration cycle apparatus is configured by connecting multiple user-side heat exchangers that exchange heat between a heat supply target, such as air, and a refrigerant. The multi-type refrigeration cycle apparatus has a refrigerant circuit that includes a compressor, a heat source-side heat exchanger, multiple expansion valves connected in parallel, and multiple user-side heat exchangers connected in series to each expansion valve. A control device controls the opening of each expansion valve to optimize the distribution of refrigerant passing through the user-side heat exchangers, causing the refrigerant to exchange heat in the user-side heat exchangers (see, for example, Patent Document 1).

[0003] In such a multi-type refrigeration cycle system, during cooling operation, the control device changes the opening of the expansion valves to control the degree of subcooling to a target degree of subcooling. The control device distributes the total expansion valve opening, calculated by summing the openings of the expansion valves, based on the capacity ratio of the user-side heat exchangers, and controls the opening of each expansion valve based on the difference between the superheat degree of the refrigerant passing through each user-side heat exchanger and the target degree of superheat. When the control device determines that the superheat degree of the refrigerant in all user-side heat exchangers has become greater or smaller than the target degree of superheat, it changes the target degree of subcooling.

[0004] On the other hand, in heating operation, the control device calculates the opening degree of each expansion valve so that the degree of subcooling of the refrigerant passing through each indoor heat exchanger becomes a predetermined target degree of subcooling. Then, when the control device determines that the degree of superheat of the outdoor heat exchanger is equal to or higher than the set degree of superheating, it performs control to reduce the target degree of subcooling.

[0005] Japanese Patent Application Laid-Open No. 2002-054836

[0006] In the multi-type refrigeration cycle system disclosed in Patent Document 1, the control device controls the target degree of subcooling so that the degree of superheat in the heat exchanger serving as the evaporator does not exceed the target degree of subcooling. However, with this type of control, when the heat exchanger experiences an excessive refrigerant shortage to the extent that the degree of subcooling becomes completely uncontrollable, the change in the expansion valve opening is limited, resulting in a problem of reduced operating efficiency.

[0007] On the other hand, in heating operation, which heats the heat supply target, control is performed based on the degree of subcooling, which is a control target subject to large disturbances, and the target degree of subcooling is changed according to the degree of superheating of the outdoor heat exchanger. This has led to the problem of a large design load for the control constants.

[0008] Therefore, in order to solve the above-mentioned problems, the object is to obtain a multi-type refrigeration cycle device that can more appropriately perform control based on the state of the refrigerant passing through the heat exchanger, regardless of whether the amount of refrigerant is excessive or insufficient.

[0009] The multi-type refrigeration cycle apparatus according to the present disclosure is configured by piping 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, and has a refrigerant circuit for circulating a refrigerant, and is equipped with a control device for controlling devices within the apparatus, wherein the control device includes a first controller that calculates a total expansion valve opening of the expansion valves that causes the heat source side state value of the refrigerant flowing out of the heat source side heat exchanger to follow the heat source side target state value, and outputs the calculated total expansion valve opening, and a total expansion valve opening of the expansion valves that causes the use side state value of the refrigerant flowing out of each of the plurality of use side heat exchangers to follow the use side target state value. The system includes a second controller that calculates the opening and outputs it as the user-side total expansion valve opening, a maximum selector that selects either the heat source-side total expansion valve opening or the user-side total expansion valve opening as the maximum total expansion valve opening, and a distribution controller that distributes the maximum total expansion valve opening to the expansion valve openings of each expansion valve, and the distribution controller distributes the maximum total expansion valve opening based on a distribution ratio that changes the opening of each expansion valve corresponding to each user-side heat exchanger relatively, based on a comparison between the user-side state value of the refrigerant flowing out from each user-side heat exchanger and a set threshold value.

[0010] According to the multi-type refrigeration cycle apparatus of the present disclosure, in the control device, the first controller determines the heat source-side total expansion valve aperture obtained from the heat source-side state value of the refrigerant flowing out of the heat source-side heat exchanger. The second controller determines the user-side total expansion valve aperture obtained from the user-side state value of the refrigerant flowing out of the user-side heat exchanger. The maximum controller selects the maximum total expansion valve aperture from the heat source-side total expansion valve aperture and the user-side total expansion valve aperture, and the distribution controller distributes the maximum total expansion valve aperture to each expansion valve to determine the aperture of each expansion valve. Therefore, when the multi-type refrigeration cycle apparatus is operating with sufficient refrigerant, it can appropriately control the degree of subcooling and achieve high-efficiency energy conservation. On the other hand, when the multi-type refrigeration cycle apparatus is operating with a shortage of refrigerant and subcooling control is not possible, it automatically and continuously switches to superheat control to appropriately control the degree of subcooling. Therefore, high-efficiency operation can be maintained regardless of the amount of refrigerant.

[0011] FIG. 1 is a diagram showing the configuration of an air conditioning apparatus 1 according to embodiment 1. FIG. 2 is a diagram showing the configuration of a control device 400 in the air conditioning apparatus 1 according to embodiment 1. FIG. 3 is a diagram showing the configuration of a control processing device 410 in embodiment 1. FIG. 4 is a diagram showing the relationship between the degree of subcooling and the degree of superheat and time in embodiment 1. FIG. 5 is a diagram showing an image relating to the distribution processing operation in the air conditioning apparatus 1 according to embodiment 1. FIG. 6 is a diagram showing the configuration of a control processing device 410 in embodiment 2. FIG. 7 is a diagram showing the configuration of a control processing device 410 in embodiment 3.

[0012] A multi-type refrigeration cycle apparatus according to an embodiment will be described below with reference to the drawings. In the following drawings, components with the same reference numerals are identical or equivalent and will be common throughout the following embodiments. The dimensional relationships between components in the drawings may differ from those in reality. The configurations of components shown throughout the specification are merely illustrative and are not limited to those described in the specification. In particular, the combinations of components are not limited to those in each embodiment; components described in other embodiments may be applied to other embodiments. Furthermore, the levels of pressure and temperature are not determined in relation to absolute values, but are determined relatively in terms of the state and operation of the apparatus. In addition, when multiple similar devices are distinguished by subscripts, the subscripts may be omitted if there is no need to distinguish or identify them.

[0013] Embodiment 1. FIG. 1 is a diagram showing the configuration of an air conditioner 1 according to Embodiment 1. Here, as an example of a multi-type refrigeration cycle apparatus, an air conditioner 1 that conditions the air of a room, which is a space to be air-conditioned, is described. In this case, the indoor air is the target for heat supply. As shown in FIG. 1 , the air conditioner 1 according to Embodiment 1 includes a heat source unit 200, a user unit 100, and refrigerant piping 300. The compressor 210, four-way valve 220, and heat source heat exchanger 230 of the heat source unit 200 are connected to the user unit 100's user heat exchanger 110 and expansion valve 120 via the refrigerant piping 300, forming a refrigerant circuit that circulates refrigerant to transport heat. Here, the air conditioner 1 according to Embodiment 1 is configured such that three user units 100 are connected in parallel to one heat source unit 200 via piping. The number of user units 100 connected in parallel may be two or more. Regarding control, the number of user side units 100 that are operated may be one.

[0014] The user-side units 100 (user-side units 100a to 100c) condition the air in a room to be air-conditioned by heating or cooling the air. Each user-side unit 100 has a user-side heat exchanger 110 (user-side heat exchanger 110a to 110c) and an expansion valve 120 (expansion valve 120a to 120c) as devices that make up the refrigerant circuit. Each user-side unit 100 also has an indoor fan 130 (indoor fan 130a to 130c).

[0015] The expansion valve 120, which functions as a throttle device or the like, is a valve that reduces the pressure of the refrigerant to expand it. The expansion valve 120 is, for example, an electronic expansion valve. The expansion valve 120 adjusts its opening based on instructions from a control device 400 (described later) or the like, reducing the pressure and controlling the amount of refrigerant passing through the corresponding user-side heat exchanger 110. The user-side heat exchanger 110 exchanges heat between the refrigerant and indoor air to heat or cool the indoor air. For example, during heating operation (heating operation), the user-side heat exchanger 110 functions as a condenser, condensing the refrigerant to release heat and liquefying it as a liquid refrigerant (hereinafter referred to as liquid refrigerant) for passage. During cooling operation (cooling operation), the user-side heat exchanger 110 functions as an evaporator, absorbing heat and evaporating the refrigerant, liquefying it as a gaseous refrigerant (hereinafter referred to as gaseous refrigerant) for passage. The indoor fan 130 passes air through the use-side heat exchanger 110 to promote heat exchange in the use-side heat exchanger 110, and supplies the air that has passed through the use-side heat exchanger 110 to the room, which is the space to be air-conditioned.

[0016] The heat source unit 200 in the first embodiment includes a compressor 210, a four-way valve 220, a heat source heat exchanger 230, and an accumulator 240 as components constituting a refrigerant circuit. The heat source unit 200 also includes an outdoor blower 250. The compressor 210 compresses and discharges the drawn refrigerant. The compressor 210 may be, for example, a scroll compressor, a reciprocating compressor, or a vane compressor. The compressor 210 can vary the volume of refrigerant discharged by the compressor 210 (the amount of refrigerant delivered per unit time) by varying the drive frequency as desired using, for example, an inverter circuit.

[0017] The four-way valve 220 serving as the flow path switching device is a valve that switches the flow of refrigerant between, for example, cooling operation and heating operation. During heating operation, the four-way valve 220 connects the discharge side of the compressor 210 to the user-side heat exchanger 110 and connects the suction side of the compressor 210 to the heat-source-side heat exchanger 230. During cooling operation, the four-way valve 220 connects the discharge side of the compressor 210 to the heat-source-side heat exchanger 230 and connects the suction side of the compressor 210 to the user-side heat exchanger 110. While the four-way valve 220 is used here as an example, the flow path switching device is not limited to this. For example, the flow path switching device may be configured by combining multiple two-way valves, etc.

[0018] The heat source-side heat exchanger 230 is a heat exchanger that exchanges heat between the refrigerant and outdoor air. In the first embodiment, the heat source-side heat exchanger 230 functions as an evaporator during heating operation, evaporating the refrigerant and passing a gas refrigerant. On the other hand, in cooling operation, the heat source-side heat exchanger 230 functions as a condenser and subcooler, condensing the refrigerant and passing a liquid refrigerant. The configuration of the heat source-side heat exchanger 230 will be described in further detail below. In addition, the outdoor blower 250, when driven, passes air from outside the heat source unit 200 through the heat source-side heat exchanger 230, forming an air flow that flows out of the heat source unit 200, thereby promoting heat exchange in the heat source-side heat exchanger 230.

[0019] Here, the equipment configuration of the refrigerant circuit in the air conditioning apparatus 1 is not limited to the configuration shown in FIG. 1 . The refrigerant circuit may, for example, include capillary tubes, etc., as necessary. Furthermore, the user-side heat exchanger 110 and the heat-source-side heat exchanger 230 are described as exchanging heat between air and a refrigerant, but this is not limiting. For example, the heat exchanger may exchange heat with water or geothermal heat, etc., as the refrigerant. Furthermore, the piping may be branched at the heat-source-side unit 200, and the expansion valve 120 may be included within the heat-source-side unit 200.

[0020] Next, the operation of each device in the air conditioner 1 will be described based on the flow of refrigerant. First, the operation of each device in the refrigerant circuit during heating operation will be described based on the flow of refrigerant. The dotted arrows in FIG. 1 indicate the flow of refrigerant during heating operation. High-temperature, high-pressure gas refrigerant compressed and discharged by the compressor 210 passes through the four-way valve 220 and flows into the user-side heat exchanger 110. While passing through the user-side heat exchanger 110, the gas refrigerant condenses and liquefies by, for example, exchanging heat with the air in the space to be air-conditioned. The condensed and liquefied refrigerant passes through the expansion valve 120. The refrigerant is decompressed as it passes through the expansion valve 120. The refrigerant, which has been decompressed by the expansion valve 120 and is now in a gas-liquid two-phase state, passes through the heat-source-side heat exchanger 230. In the heat source-side heat exchanger 230, the refrigerant evaporates by exchanging heat with the outdoor air sent from the outdoor blower 250, and the gasified refrigerant passes through the four-way valve 220 and the accumulator 240, and is again drawn into the compressor 210. In this way, the refrigerant in the air conditioner 1 circulates, and air conditioning related to heating is performed.

[0021] Next, cooling operation will be described. Solid arrows in FIG. 1 indicate the flow of refrigerant during cooling operation. High-temperature, high-pressure gas refrigerant compressed and discharged by the compressor 210 passes through the four-way valve 220 and flows into the heat-source-side heat exchanger 230. The refrigerant then passes through the heat-source-side heat exchanger 230 and condenses and liquefies by exchanging heat with outdoor air supplied by the outdoor blower 250. The liquefied refrigerant then passes through the expansion valve 120. As the refrigerant passes through the expansion valve 120, it is decompressed and reaches a two-phase gas-liquid state. The refrigerant decompressed and brought to a two-phase gas-liquid state by the expansion valve 120 passes through the user-side heat exchanger 110. The refrigerant then evaporates in the user-side heat exchanger 110 by exchanging heat with air in the space to be air-conditioned, for example. The gasified refrigerant then passes through the four-way valve 220 and is drawn back into the compressor 210. In this manner, the refrigerant circulates in the air-conditioning apparatus 1, performing air conditioning for cooling. In the first embodiment, a cooling operation will be described in which the utilization-side heat exchanger 110 functions as an evaporator and the heat-source-side heat exchanger 230 functions as a condenser.

[0022] The air conditioning apparatus 1 in Embodiment 1 has, as pressure sensors, a high-pressure pressure sensor 510 and a low-pressure pressure sensor 520. The high-pressure pressure sensor 510 detects, as the high-pressure pressure, the pressure of the refrigerant discharged from the compressor 210, which is the high-pressure side in the refrigerant circuit. The low-pressure pressure sensor 520 detects, as the low-pressure pressure, the pressure of the refrigerant flowing into the accumulator 240, which is the low-pressure side in the refrigerant circuit.

[0023] In addition, the air conditioning apparatus 1 in embodiment 1 has, for example, a heat source side heat exchanger gas pipe temperature sensor 530, a heat source side heat exchanger liquid pipe temperature sensor 540, a utilization side heat exchanger liquid pipe temperature sensor 550, and a utilization side heat exchanger gas pipe temperature sensor 560 as temperature sensors.

[0024] The heat source side heat exchanger gas pipe temperature sensor 530 is installed in the piping on the gas pipe side of the heat source side heat exchanger 230 and detects the temperature of the gas refrigerant (including two-phase refrigerant) flowing in and out of the heat source side heat exchanger 230. The heat source side heat exchanger gas pipe temperature sensor 530 detects the temperature of the refrigerant flowing into the heat source side heat exchanger 230 in cooling operation, and detects the temperature of the refrigerant flowing out of the heat source side heat exchanger 230 in heating operation. The heat source side heat exchanger liquid pipe temperature sensor 540 is installed in the piping on the liquid pipe side of the heat source side heat exchanger 230 and detects the temperature of the liquid refrigerant (including two-phase refrigerant) flowing in and out of the heat source side heat exchanger 230. The heat source side heat exchanger liquid pipe temperature sensor 540 detects the temperature of the refrigerant flowing out of the heat source side heat exchanger 230 in cooling operation, and detects the temperature of the refrigerant flowing into the heat source side heat exchanger 230 in heating operation.

[0025] The use-side heat exchanger liquid pipe temperature sensors 550 (use-side heat exchanger liquid pipe temperature sensors 550a to 550c) are installed on the piping on the liquid pipe side of the corresponding use-side heat exchanger 110. The use-side heat exchanger liquid pipe temperature sensors 550 detect the temperature of liquid refrigerant (including two-phase refrigerant) flowing into and out of the use-side heat exchanger 110. In cooling operation, the use-side heat exchanger liquid pipe temperature sensors 550 detect the temperature of refrigerant flowing into the corresponding use-side heat exchanger 110, and in heating operation, they detect the temperature of refrigerant flowing out of the corresponding use-side heat exchanger 110. In addition, the use-side heat exchanger gas pipe temperature sensors 560 (use-side heat exchanger gas pipe temperature sensors 560a to 560c) are installed on the piping on the gas pipe side of the corresponding use-side heat exchanger 110. The use-side heat exchanger gas pipe temperature sensors 560 detect the temperature of the gas refrigerant (including two-phase refrigerant) flowing into and out of the use-side heat exchangers 110. In cooling operation, the use-side heat exchanger gas pipe temperature sensors 560 detect the temperature of the refrigerant flowing out of the corresponding use-side heat exchangers 110, and in heating operation, they detect the temperature of the refrigerant flowing into the corresponding use-side heat exchangers 110.

[0026] Fig. 2 is a diagram showing the configuration of the control device 400 in the air conditioning apparatus 1 according to embodiment 1. The control device 400 is a device that controls the air conditioning apparatus 1. As shown in Fig. 2, the various sensors described above are connected to the control device 400, and signals including data such as temperature and pressure are input. In addition, signals including user commands are input to the control device 400 via an operation unit (not shown).

[0027] 2, the control device 400 has a control processing device 410, a timing device 420, and a storage device 430. The control processing device 410 performs processing such as calculations and judgments based on data such as temperature contained in signals sent from various sensors and instructions from the user, and controls devices such as the compressor 210, expansion valve 120, and outdoor blower 250 that make up the air conditioning device 1. The storage device 430 is a device that stores data required for the control processing device 410 to perform processing. The timing device 420 is a device such as a timer that measures the time and period required for the control processing device 410 to perform processing such as judgment.

[0028] Here, the control processing device 410 may include, for example, a microcomputer having a control arithmetic processing device such as a CPU (Central Processing Unit). However, this is not limiting. The control processing device 410 may also be configured by combining dedicated devices (hardware) as constituent devices. For example, the control processing device 410 may include a PI controller 417 (described later) as a dedicated device.

[0029] The storage device 430 also includes, for example, a ROM (Read Only Memory). The storage device 430 also includes a storage device (not shown) such as a RAM (Random Access Memory) that can temporarily store data, or an auxiliary storage device (not shown) such as a flash memory or a solid state drive. The storage device 430 also includes, for example, program data that describes the processing procedures to be performed by the control processing device 410. The control processing device 410 then executes processing based on the program data to achieve device control, etc.

[0030] Fig. 3 is a diagram showing the configuration of the control processing device 410 in embodiment 1. Fig. 3 shows a portion of the control of the air conditioning device 1 performed by the control processing device 410 of the control device 400, which performs processing to control the expansion valve opening degree of each expansion valve 120. As shown in Fig. 3, the control processing device 410 of the control device 400 in embodiment 1 includes a first controller 411, a second controller 412, a maximum selector 413, and a distribution controller 414.

[0031] The first controller 411 calculates a heat source side state value of the refrigerant flowing out from the heat source side heat exchanger 230. The first controller 411 also calculates and outputs the total expansion valve opening, which is the sum of the openings of the expansion valves 120 that are made to follow the heat source side target state value, as the heat source side total expansion valve opening. The air conditioning apparatus 1 in embodiment 1 performs cooling operation. Therefore, because the heat source side heat exchanger 230 functions as a condenser, the heat source side state value becomes the degree of subcooling (SC), and the heat source side target state value becomes the target degree of subcooling. The first controller 411 then has a subcooling degree controller 415.

[0032] The subcooling degree controller 415 calculates the degree of subcooling of the refrigerant and performs calculations to output a total expansion valve opening degree that causes the degree of subcooling of the refrigerant to track a target degree of subcooling. The subcooling degree controller 415 in the first embodiment receives signals from the high-pressure sensor 510 and the heat-source-side heat exchanger liquid pipe temperature sensor 540. The subcooling degree controller 415 calculates the saturated liquid temperature at the high-pressure pressure contained in the signal from the high-pressure pressure sensor 510 using the physical properties of the refrigerant. The subcooling degree controller 415 then calculates the difference between the saturated liquid temperature and the heat-source-side liquid pipe temperature contained in the signal from the heat-source-side heat exchanger liquid pipe temperature sensor 540 as the degree of subcooling. However, the method for calculating the degree of subcooling is not limited thereto. For example, the degree of subcooling may be calculated from the difference between the temperature detected by a temperature sensor installed in a portion of the heat-source-side heat exchanger 230 where two-phase refrigerant flows and the heat-source-side liquid pipe temperature. The target degree of subcooling may be a constant value or a variable value that is set depending on the actual operating state. When the target degree of subcooling is a variable value, for example, the target degree of subcooling may be a value obtained by multiplying the difference between the condensing temperature and the ambient temperature of the heat exchanger serving as the condenser by a coefficient.

[0033] The second controller 412 calculates a heat source side state value of the refrigerant flowing out from each use side heat exchanger 110. The second controller 412 also calculates and outputs a total expansion valve opening, which is the sum of the openings of the expansion valves 120 that are made to follow the use side target state value, as a use side total expansion valve opening. As described above, the air conditioning apparatus 1 in Embodiment 1 performs cooling operation, and each use side heat exchanger 110 functions as an evaporator, so the use side state value is the degree of superheat (SH), and the use side target state value is the target degree of superheat. The second controller 412 then has a superheat degree controller 416.

[0034] The superheat controller 416 calculates the degree of superheat of the refrigerant and performs calculations to output a total expansion valve opening that causes the degree of superheat of the refrigerant to follow a set upper superheat limit value. In the first embodiment, the superheat controller 416 outputs a total expansion valve opening that causes the maximum degree of superheat of the refrigerant flowing out of each use-side heat exchanger 110 to follow the upper superheat limit value. The upper superheat limit value may be determined, for example, based on hardware constraints or may be set based on empirical rules. The superheat controller 416 in the first embodiment receives signals from the low-pressure pressure sensor 520 and each use-side heat exchanger gas pipe temperature sensor 560. The superheat controller 416 calculates the saturated gas temperature at the low-pressure pressure included in the signal from the low-pressure pressure sensor 520 using the physical properties of the refrigerant. The superheat controller 416 then calculates the difference between the saturated gas temperature and the use-side gas pipe temperature included in the signal from each use-side heat exchanger gas pipe temperature sensor 560 as the degree of superheat of the refrigerant flowing out of each use-side heat exchanger 110. However, the method for calculating the degree of superheat is not limited to this. For example, the degree of superheat may be calculated from the difference between the temperature detected by a temperature sensor installed in a portion of each use-side heat exchanger 110 where two-phase refrigerant flows and the use-side gas pipe temperature. Furthermore, the control output of the superheat control is not limited to the maximum value of the degree of superheat, but may also be the minimum value. Other statistical values ​​obtained by statistically processing multiple degrees of superheat, such as the average or median, may also be used. Note that because the degree of superheat does not take a value less than zero, values ​​below a certain threshold may be treated as outliers.

[0035] The subcooling degree controller 415 and the superheat degree controller 416 each have a position-type PI controller 417. The PI controller 417 is a controller that performs feedback control using proportional-integral control. Here, the PI controller 417 has an anti-reset windup function. The anti-reset windup function is a function that suppresses divergence of the integral value when the output value of the PI controller 417 differs from the actual expansion valve opening of the expansion valve 120 due to the selection of the maximum selector 413 or upper and lower limit constraints on the expansion valve opening of the expansion valve 120. A function such as anti-reset windup is particularly effective in a configuration such as the control processing device 410, in which multiple PI controllers 417 are configured in parallel and the next value to be processed is selected from the output value of one of the multiple PI controllers 417.

[0036] Here, although the subcooling degree controller 415 and the superheat degree controller 416 in the first embodiment include a PI controller 417, other controllers may also be used. For example, the subcooling degree controller 415 and the superheat degree controller 416 may include a P controller that performs proportional control, a PID controller that performs proportional-integral-derivative control, or a dynamic feedback controller such as a model predictive controller. Furthermore, the subcooling degree controller 415 and the superheat degree controller 416 may be dynamic or static controllers that perform control based on data set in advance in a table format or the like. Furthermore, the controllers do not have to be position-type controllers, but may also be speed-type controllers. However, even if they are speed-type controllers, the subcooling degree controller 415 and the superheat degree controller 416 must output the total expansion valve opening to the maximum selector 413.

[0037] The maximum selector 413 compares the value of the heat source side total expansion valve opening output by the first controller 411 with the value of the heat source side total expansion valve opening output by the second controller 412, and outputs the larger value as the maximum total expansion valve opening.

[0038] The distribution controller 414 distributes the maximum total expansion valve opening output from the maximum selector 413 to each expansion valve 120, and determines the opening of each expansion valve 120. Next, the distribution processing procedure performed by the distribution controller 414 in the first embodiment will be described. Set U = {1, 2, ..., n} is a set of use-side heat exchanger numbers. Here, n is the number of connected use-side heat exchangers 110. Also, V ⊂ U is a set of use-side heat exchanger numbers that are in operation. Then, A ⊂ V is a set of use-side heat exchanger numbers that are in operation and the superheat degree exceeds the upper limit superheat degree (SH ｉ >2, i∈V) is a set of user-side heat exchanger numbers. ｉ is the degree of superheat of the user side heat exchanger number i.

[0039] The distribution controller 414 determines the distribution ratio k ｉ where the distribution ratio k ｉ has the characteristics shown in the following equation (1).

[0040]

[0041] Then, the distribution controller 414 calculates the distribution ratio k ｉ Based on this, the expansion valve opening degree of each expansion valve 120 is calculated by the following equation (2): ｉ is the expansion valve opening degree of each expansion valve 120. ｔｏｔａｌ is the maximum total expansion valve opening output by the maximum selector 413. ｉ The initial value of is set to, for example, an equal value, or to be equal to the capacity ratio of the utilization side heat exchanger 110 .

[0042]

[0043] The distribution controller 414 calculates the distribution ratio k at one-minute intervals, for example. ｉThe distribution controller 414 determines whether to update the update information. However, the timing of the update process is not limited to this. For example, the distribution controller 414 does not necessarily need to execute the process at regular intervals, and can execute the process as soon as it detects a dry state. The distribution controller 414 can also execute the process as soon as it detects that the user-side unit 100 has started or stopped operating. Furthermore, the distribution controller 414 may execute the process by combining updates triggered by the detection of a dry state or the start or stop of operation of the user-side unit 100 with updates at regular intervals.

[0044] When the distribution controller 414 determines that the degree of superheat of a certain utilization side heat exchanger 110 is greater than a set superheat degree threshold (for example, 2K), it determines that the refrigerant flowing through that utilization side heat exchanger 110 is insufficient (is in a dry state). Then, the distribution controller 414 determines the distribution ratio k of the corresponding expansion valve 120. ｉ The current expansion valve opening of the expansion valve 120 is used as a reference, and the distribution ratio k ｉ The distribution ratio k ｉ When this value increases and the opening degree of the expansion valve 120 increases, the amount of refrigerant flowing through the user-side heat exchanger 110 increases.

[0045] Next, the distribution ratio k ｉ Here, the step at the timing of the previous update is k, and the step at the timing of the current update is k+1. First, when all the use-side heat exchangers 110 are in a dry state or when all the use-side heat exchangers 110 are not in a dry state, and A or A ｃ (A ｃ If A⊂V is the complement of the empty set, the distribution ratio k ｉ Therefore, the distribution ratio k ｉ (k+1) is the distribution ratio k for the previous update ｉ Using (k), it is expressed by the following equation (3).

[0046]

[0047] On the other hand, some of the user-side heat exchangers 110 are in a dry state, and A and A ｃIf both are not empty sets, the distribution ratio k ｉ (k+1) is expressed by the following equation (4) using the distribution ratio ki(k) related to the previous update: ｉ (k) is the distribution ratio k at the current expansion valve opening of the expansion valve 120 ｉ Formula (4) is a formula for updating the expansion valve opening of the expansion valve 120 corresponding to the user-side heat exchanger 110 in a dry state to increase the current expansion valve opening by 10%. ｉ If (k+1) is 0 or less or 1 or more, the distribution ratio k ｉ Therefore, the distribution ratio k ｉ (k+1) is expressed by the above-mentioned formula (3).

[0048]

[0049] As described above, the distribution controller 414 calculates the distribution ratio k ｉ By updating the opening ratio k of the expansion valve 120 corresponding to the use-side heat exchanger 110 in the dry state, the opening ratio k of the expansion valve 120 corresponding to the use-side heat exchanger 110 in the dry state is relatively increased, and the amount of refrigerant passing through the use-side heat exchanger 110 is increased, thereby eliminating the dry state. ｉ While maintaining the distribution ratio k for the total expansion valve opening ｉ Here, equation (4) shows that the expansion valve opening of the expansion valve 120 corresponding to the user-side heat exchanger 110 in the dry state is increased by 10%, but it is not limited to 10%. Furthermore, the rate of increase does not have to be constant.

[0050] Next, when the user side unit 100 that was operating stops, or when the user side unit 100 that was stopped starts operating, the distribution ratio k of each expansion valve 120 that is processed by the distribution controller 414 is ｉ Here, immediately after the user unit 100 is stopped or started, the state of the refrigerant in the refrigerant circuit is not stable, so the distribution controller 414 of the control device 400 determines the distribution ratio k based on the above-mentioned dry state. ｉUpdates will not be performed.

[0051] Here, M⊂V is a set of the numbers of the user-side heat exchangers 110 of the user-side units 100 that have been newly stopped. ｃ Let V(k) be the set of use side heat exchanger numbers of the use side heat exchangers 110 associated with the user side units 100 that have newly started operation. Furthermore, let V(k+1) be the set of use side heat exchanger numbers of the use side heat exchangers 110 associated with the user side units 100 that are in operation at the current time. Then, let V(k) be the set of use side heat exchanger numbers of the use side heat exchangers 110 associated with the user side units 100 that are in operation at the previous time. For example, when V(k) = {1, 3, 5, 7}, M = {3} and N = {2}, then V(k+1) = {1, 2, 5, 7}.

[0052] The distribution controller 414 sets the expansion valve opening of the expansion valve 120 of the stopped user unit 100 to a closed opening (opening 0). In addition, for the expansion valve opening of each expansion valve 120 of the user unit 100 other than the stopped user unit 100, the distribution ratio k ｉ The normal distribution ratio k is normalized based on the following equation (5) so that the sum of ｉ ' is calculated.

[0053]

[0054] Next, the distribution controller 414 calculates the normal distribution ratio k based on the following equation (6): ｉ Calculate the average of the normal distribution ratio k ′ corresponding to the user-side heat exchanger 110 that has started operation. ｉ Here, |V-M| is the number of elements in the set VM. Also, the minus sign in a set represents the difference set. Here, there is also a notation that uses a backslash instead of the minus sign, and in the formula, this notation is used.

[0055]

[0056] Then, the distribution controller 414 calculates the normal distribution ratio k ｉ Based on this, normalization is performed again, and the distribution ratio k ｉ (k+1) is calculated by the following equation (7).

[0057]

[0058] In this way, the distribution controller 414 calculates the distribution ratio k of the expansion valve opening of each expansion valve 120 when the user side unit 100 stops or starts operation. ｉ As described above, even if the operating state changes, the distribution ratio is maintained as much as possible, that is, by maintaining the distribution ratio between the expansion valve openings of the expansion valves 120 corresponding to the user-side heat exchangers 110 in the appropriate state, it is possible to suppress disturbances to control caused by changes in the operating state. ｉ The sum of the distribution ratio k is set to 1, but it does not necessarily have to be 1, and may be updated to a different value depending on the operating state. ｉ The calculation and determination method is an example, and the distribution controller 414 may use any method as long as it can obtain a solution similar to the above-mentioned method.

[0059] <Operational Overview> Figure 4 is a diagram showing the relationship between the degree of subcooling and the degree of superheat and time in the first embodiment. Figure 4(a) shows the degree of subcooling and the degree of superheat of the refrigerant when the amount of refrigerant in the refrigerant circuit is appropriate. As shown in Figure 4(a), when the refrigerant circuit is filled with an appropriate amount of refrigerant, the degree of subcooling of the refrigerant flowing out of the heat exchanger serving as a condenser converges to an optimal degree of subcooling over time. Also, the degree of superheat of the refrigerant flowing out of the heat exchanger serving as an evaporator converges to an optimal degree of superheat over time.

[0060] Figure 4(b) shows the degree of subcooling and the degree of superheat when the refrigerant in the refrigerant circuit is overfilled. When the refrigerant in the refrigerant circuit is overfilled, as shown in Figure 4(b), the degree of superheat of the refrigerant flowing out of the heat exchanger serving as an evaporator becomes uncontrollable. However, the degree of subcooling of the refrigerant flowing out of the heat exchanger serving as a condenser converges to the optimal degree of subcooling over time. In the control processing device 410 of the control device 400, the maximum selector 413 selects the larger total expansion valve opening, thereby enabling the total expansion valve opening to be distributed to the expansion valve openings of the expansion valves 120 with high precision, thereby enabling energy-saving control.

[0061] 4(c) shows the degree of subcooling and the degree of superheat when the amount of refrigerant in the refrigerant circuit is insufficient. When the amount of refrigerant in the refrigerant circuit is insufficient, as shown in FIG. 4(c), the degree of subcooling of the refrigerant flowing out of the heat exchanger serving as a condenser becomes uncontrollable. However, the degree of superheat of the refrigerant flowing out of the heat exchanger serving as an evaporator converges to the optimal degree of superheat over time. This allows the control device 400 to perform energy-saving control.

[0062] 5 is a diagram showing an image of the distribution processing operation in the air conditioning apparatus 1 of embodiment 1. In FIG. 5, at time T, the degree of superheat of the refrigerant flowing out of the use-side heat exchanger 110a exceeds a threshold value, and therefore the distribution ratio k of the refrigerant passing through each expansion valve 120 is ｉ is updated. The distribution controller 414 controls the opening of the expansion valve 120a to be 10% open. The distribution controller 414 also controls the opening of the expansion valves 120b and 120c to be, for example, 5% closed. In this way, the distribution controller 414 controls the distribution of the expansion valve openings of the expansion valves 120, so that the degree of superheat of the refrigerant flowing out from the use-side heat exchanger 110a decreases and converges to a value below the threshold, as shown in FIG. 5(a). On the other hand, as shown in FIGS. 5(b) and 5(c), the degree of superheat of the refrigerant flowing out from the use-side heat exchanger 110b and the use-side heat exchanger 110c increases slightly but converges below the threshold, and the state of the refrigerant stabilizes.

[0063] <Effects of the Air Conditioning Apparatus 1 in Embodiment 1> As described above, in the air conditioning apparatus 1 in Embodiment 1, in the control processing device 410 of the control device 400, the first controller 411 has a subcooling degree controller 415 and calculates the heat source side total expansion valve aperture based on the subcooling degree of the refrigerant flowing out of the heat source side heat exchanger 230. Furthermore, the second controller 412 has a superheat degree controller 416 and calculates the user side total expansion valve aperture based on the superheat degree of the refrigerant flowing out of each user side heat exchanger 110. The maximum selector 413 compares the value of the heat source side total expansion valve aperture with the value of the heat source side total expansion valve aperture and outputs the larger value as the maximum total expansion valve aperture. The distribution controller 414 distributes the maximum total expansion valve aperture to each expansion valve 120 and determines the aperture of each expansion valve 120. Therefore, the air conditioning apparatus 1 in Embodiment 1 can maintain highly efficient operation even under conditions where the amount of refrigerant is overfilled or insufficient.

[0064] For example, in a typical multi-type refrigeration cycle apparatus such as the air conditioner 1 having an accumulator 240 as in the first embodiment, the degree of subcooling of the refrigerant flowing through the corresponding user-side heat exchanger 110 is controlled by the expansion valve aperture of each expansion valve 120. However, if the amount of refrigerant in the refrigerant circuit is insufficient, reducing the expansion valve aperture of the expansion valve 120 will not determine the degree of subcooling, making the degree of subcooling uncontrollable. This makes it impossible to determine the appropriate degree of expansion valve aperture for the expansion valve 120. Furthermore, if the amount of refrigerant in the refrigerant circuit is insufficient, the amount of refrigerant flowing through the user-side heat exchanger 110, which serves as an evaporator, may be insufficient, resulting in insufficient capacity. Therefore, as in the air conditioner 1 of the first embodiment, the control processing device 410 of the control device 400 selects the total expansion valve aperture based on the degree of subcooling and the total expansion valve aperture based on the degree of superheat to determine the expansion valve aperture in the next step. Therefore, if there is sufficient refrigerant in the refrigerant circuit, the control device 400 can appropriately control the degree of subcooling, achieving highly efficient and energy-saving operation. On the other hand, even under operating conditions where the refrigerant is insufficient due to factors such as a long piping length and subcooling control is not possible, the control automatically and continuously switches to control based on the degree of superheat, thereby suppressing an increase in the degree of superheat. Furthermore, the control processing device 410 determines the expansion valve opening of each expansion valve 120 to suppress an increase in the degree of superheat, thereby maintaining stable and highly efficient operation.

[0065] Furthermore, the controller included in the control processing device 410 of the control device 400 in the first embodiment is a continuous controller with an anti-reset windup function. Therefore, even when the amount of refrigerant in the refrigerant circuit is moderate and operation is performed at a switching point between the degree of subcooling and the degree of superheat, hunting can be suppressed. This allows the air conditioning device 1 to operate stably. Furthermore, the degree of superheat can be controlled to the upper limit of superheat with high precision. This suppresses increases in the discharge temperature of the refrigerant discharged from the compressor 210, thereby protecting the equipment in the refrigerant circuit. In this way, by using continuous control such as PI control for not only the primary subcooling control but also secondary controls such as protection, and combining it with the maximum selector 413, the effects described above can be achieved.

[0066] As described above, the air conditioning apparatus 1 according to the first embodiment can maintain efficient operation even when the amount of refrigerant in the refrigerant circuit is insufficient. This indicates that highly efficient operation can be maintained even when the number of refrigerant circuits is reduced. Therefore, by reducing the amount of refrigerant, it is possible to provide a highly efficient multi-type refrigeration cycle apparatus at low cost.

[0067] Next, we will explain the case where the refrigerant circuit is overfilled. In a multi-type refrigeration cycle system, the degree of superheat is sometimes controlled by the expansion valve 120. However, if the refrigerant in the refrigerant circuit is overfilled, the degree of superheat cannot be controlled unless the expansion valve 120 is extremely throttled, resulting in reduced energy savings. When the refrigerant is overfilled, the heat source-side total expansion valve opening determined by the output of the subcooling degree controller 415, which is determined based on the degree of subcooling, is greater than the heat source-side total expansion valve opening determined by the output of the superheat degree controller 416, which is based on the degree of superheat. In the air conditioning apparatus 1 in embodiment 1, the distribution controller 414 distributes the expansion valve openings of the expansion valves 120 based on the larger total expansion valve opening selected by the maximum selector 413, thereby controlling the degree of subcooling. This allows for more efficient operation.

[0068] Furthermore, in the air conditioning apparatus 1 according to the first embodiment, the distribution ratio k ｉ is updated only when the degree of superheat of the refrigerant passing through the heat exchanger is greater than a predetermined threshold value. Generally, it is difficult to perform highly accurate superheat control in a multi-type refrigeration cycle apparatus. This is due to nonlinearity caused by changes in the number of operating units or load fluctuations of each use-side heat exchanger 110. Furthermore, this is because it is a multi-input, multi-output system in which the operation of a certain expansion valve 120 affects the degree of superheat of all use-side heat exchangers 110. Furthermore, the need to provide appropriate target values ​​for various operating states makes control design difficult. Therefore, in the air conditioning apparatus 1 of embodiment 1, the distribution controller 414 updates the distribution ratio k only when the degree of superheat is greater than a predetermined threshold value. ｉ is updated. In addition, a superheat controller 416, which controls the maximum, minimum, or average value of the superheat of the refrigerant passing through each user-side heat exchanger 110, is combined with the distribution controller 414. This increases robustness to environmental changes such as refrigerant amount, installation conditions, or operating state, and improves the stability of the superheat, thereby suppressing the occurrence of hunting. In this way, the configuration of the control processing device 410 itself is highly robust, so the control design load can be reduced. Furthermore, the designer only needs to provide a predetermined threshold value. This further reduces the design load. This is an effect that cannot be achieved when the superheat controller 416 or the distribution controller 414 is configured as a standalone unit.

[0069] In the air conditioning apparatus 1 according to the first embodiment, the control device 400 controls the expansion valve opening degree of each expansion valve 120 based on the distribution ratio k ｉ Since the expansion valve opening is controlled and managed by the distribution ratio k, the increase or decrease in the opening of each expansion valve can be controlled by the ratio. Therefore, the expansion valve opening can be maintained in a linear relationship with the refrigerant flow rate, making it easy to control. ｉBy managing the distribution ratios in this manner, it becomes easy to respond to the operation or stoppage of the user-side unit 100 having the user-side heat exchanger 110. In particular, by designing the distribution ratios between the expansion valves 120, which do not need to be changed, to be maintained as much as possible, it is possible to suppress disturbances to the refrigeration cycle caused by protective operations and changes in the operating state.

[0070] Furthermore, the first controller 411 and the second controller 412 each have a PI controller 417 and perform feedback control. A method for designing parameters for the PI controller 417, a controller established in control engineering, has already been established through numerous existing studies. Therefore, in the air conditioning apparatus 1 of embodiment 1, the design load of the controller that controls the degree of superheat or subcooling can be reduced. For example, a design method using system identification results based on step response can be considered as a method for designing the controller parameters. While parameters are generally calculated using mathematical procedures from characteristics obtained by system identification, the controller parameters can also be learned from input / output data input and output to the controller when the air conditioning apparatus 1 is actually operated. Here, system identification may be performed online or offline.

[0071] Embodiment 2. Figure 6 is a diagram showing the configuration of a control processing device 410 in embodiment 2. Figure 6 shows the portion of the control of the air conditioning apparatus 1 performed by the control processing device 410 of the control device 400 that controls the aperture of each expansion valve. As shown in Figure 6, the control device 400 of embodiment 2 includes a first controller 411, a second controller 412, a maximum selector 413, and a distribution controller 414, similar to embodiment 1. As described in embodiment 1, the maximum selector 413 compares the value of the heat source side total expansion valve aperture output by the first controller 411 with the value of the heat source side total expansion valve aperture output by the second controller 412, and outputs the larger value as the maximum total expansion valve aperture.

[0072] Here, the air conditioning apparatus 1 in the second embodiment will be described as performing heating operation in which the user-side heat exchanger 110 serves as a condenser and the heat-source-side heat exchanger 230 serves as an evaporator. For this reason, the control device 400 in the second embodiment has a control processing device 410 in which a first controller 411 has a superheat controller 416 and a second controller 412 has a subcool controller 415, as shown in FIG.

[0073] The subcooling degree controller 415 in the second embodiment outputs a total expansion valve opening degree that causes the maximum subcooling degree among the subcooling degrees of the refrigerant flowing out of each use-side heat exchanger 110 to follow the target subcooling degree. The subcooling degree controller 415 in the second embodiment receives signals from the high-pressure sensor 510 and each use-side heat exchanger liquid pipe temperature sensor 550. The control output of the subcooling degree control is not limited to the maximum subcooling degree, but may also be the minimum value, or other statistical values ​​obtained by statistically processing multiple subcooling degrees, such as the average or median. Note that the subcooling degree does not take a value less than zero, so values ​​below a certain threshold may be treated as outliers.

[0074] On the other hand, the superheat controller 416 in the second embodiment performs calculations and outputs the total expansion valve opening degree that causes the superheat degree of the refrigerant flowing out of the heat source side heat exchanger 230 to follow the superheat degree upper limit value. The superheat controller 416 in the first embodiment receives signals from the low-pressure pressure sensor 520 and the heat source side heat exchanger gas pipe temperature sensor 530.

[0075] As in the first embodiment, the distribution controller 414 distributes the maximum total expansion valve opening output from the maximum selector 413 to each expansion valve 120 and determines the expansion valve opening for each expansion valve 120. However, because the air conditioning apparatus 1 in the second embodiment performs heating operation, the distribution controller 414 performs processing different from that in the first embodiment. The distribution processing procedure performed by the distribution controller 414 in the second embodiment will be described. Let U = {1, 2, ..., n} be a set of use-side heat exchanger numbers. Here, n is the number of connected use-side heat exchangers 110. Let V ⊂ U be a set of use-side heat exchanger numbers that are in operation. Let A ⊂ V be a set of use-side heat exchanger numbers whose subcooling degree is less than the lower subcooling degree threshold (SCi < 2, i ∈ V). Let B ⊂ V be a set of use-side heat exchanger numbers whose subcooling degree is greater than the upper subcooling degree threshold (SCi > 9, i ∈ V). Here, SCi is the subcooling degree of the heat exchanger with the i-th heat exchanger number. Let C = {i∈V} be the set of heat exchanger numbers with subcooling degrees within an appropriate range. In this case, i in set C does not belong to set A or set B.

[0076] As in the first embodiment, the distribution controller 414 controls the distribution ratio k ｉ (i∈V). The distribution controller 414 then calculates the distribution ratio k ｉ Based on this, the expansion valve opening degree of each expansion valve 120 is calculated using the above-mentioned formula (2).

[0077] Then, the distribution controller 414 calculates the distribution ratio k at intervals of, for example, one minute. ｉ However, the timing of the update process is not limited to this. When the distribution controller 414 determines that the degree of subcooling of a certain use-side heat exchanger 110 is smaller than the set lower limit subcooling threshold (for example, 2K), it determines that an excessive amount of refrigerant is flowing through that use-side heat exchanger 110, and updates the distribution ratio k of the corresponding expansion valve 120. ｉ Reduce the distribution ratio k ｉ When the pressure difference between the expansion valve 120 and the user side heat exchanger 110 decreases, the opening degree of the expansion valve 120 decreases, and the amount of refrigerant flowing through the user side heat exchanger 110 decreases.

[0078] When the distribution controller 414 determines that the degree of subcooling of a certain use-side heat exchanger 110 is greater than the set upper limit subcooling threshold (for example, 9 K), it determines that a sufficient amount of refrigerant is not flowing through that use-side heat exchanger 110, and reduces the distribution ratio k of the corresponding expansion valve 120. ｉ Increase the distribution ratio k ｉ When the value of the expansion valve 120 increases, the opening degree of the expansion valve 120 increases, and the amount of refrigerant flowing into the user-side heat exchanger 110 increases.

[0079] Next, the distribution ratio k ｉ Here, the step at the timing of the previous update is assumed to be k, and the step at the timing of the current update is assumed to be k+1. First, when all the utilization side heat exchangers 110 belong to the same state, the distribution ratio k ｉ The distribution ratio k for this update is not changed. The state is the same when V = A, V = B, or V = C (this is called condition a). ｉ (k+1) is the distribution ratio k for the previous update ｉ Using (k), it can be expressed by the above-mentioned formula (3).

[0080] On the other hand, if the use side heat exchanger 110 does not satisfy the condition a and there is no use side heat exchanger 110 whose degree of subcooling is within an appropriate range, that is, if V≠A, V≠B, and V≠C=φ (empty set) are satisfied (this is called condition b), the distribution ratio k ｉ The case is determined by dividing the cases according to the number of elements.

[0081] In the case where |A|<|B|, the distribution ratio k of the expansion valve opening of each expansion valve 120 is calculated based on the following equation (8). ｉ Update.

[0082]

[0083] Next, in the case of |A|≧|B|, the distribution ratio k of the expansion valve opening of each expansion valve 120 is calculated based on the following equation (9). ｉ Update.

[0084]

[0085] Finally, if neither condition a nor condition b is met, that is, if V≠A, V≠B, V≠C, and C≠φ, the distribution ratio k of the expansion valve openings of the expansion valves 120 is calculated based on the following equation (10): ｉ Update.

[0086]

[0087] As described above, the distribution controller 414 calculates the distribution ratio k ｉ By updating , the expansion valve opening of the expansion valve 120 corresponding to the use-side heat exchanger 110 in a state where the refrigerant is low increases relatively, and the amount of refrigerant passing through the use-side heat exchanger 110 increases. Therefore, the expansion valve opening of the expansion valve 120 corresponding to the use-side heat exchanger 110 in a state where the refrigerant is high decreases relatively, and the amount of refrigerant passing through the use-side heat exchanger 110 decreases. Furthermore, the expansion valve opening of the expansion valve 120 corresponding to the use-side heat exchanger 110 in an appropriate state where the amount of refrigerant passing through is neither too little nor too much changes so as to maintain the total expansion valve opening while maintaining the opening ratio of the expansion valves 120. Here, in equations (8) to (10), the expansion valve opening of the expansion valve 120 corresponding to the use-side heat exchanger 110 is increased or decreased by 10%, but this is not limited to 10%. Furthermore, the rate of increase or decrease does not have to be constant. Furthermore, in condition b, the distribution ratio k ｉ Although the method for determining the number of elements is described as being switched depending on the case, the present invention is not limited to this. The conditions may be reversed, and the method does not need to be switched depending on the number of elements.

[0088] When the user-side unit 100 that was operating stops, or when the user-side unit 100 that was stopped starts operating, the distribution ratio k ｉThe process of determining the refrigerant amount is the same as that described in the first embodiment. However, in heating operation, if the expansion valve opening of the expansion valve 120 corresponding to the stopped use-side heat exchanger 110 is completely closed, the refrigerant may accumulate in the use-side heat exchanger 110. For this reason, the expansion valve opening of the expansion valve 120 may be slightly opened. There is no problem if the expansion valve opening of the expansion valve 120 is slightly opened to the extent that it has almost no effect on the amount of refrigerant passing through the use-side heat exchanger 110 of the operating use-side unit 100. If the effect cannot be ignored, the distribution ratio k according to the slightly opened opening may be set. ｉ Set the distribution ratio k ｉ We will aim to expand the method of determining this.

[0089] <Effects of the Air Conditioning Apparatus 1 in Embodiment 2> As described above, in the air conditioning apparatus 1 in Embodiment 2, the control processing device 410 of the control device 400 has a subcooling degree controller 415 and a distribution controller 414. By configuring the subcooling degree controller 415 and the distribution controller 414 in combination, it is possible to control the maximum, minimum, or average value of each subcooling degree using the total expansion valve opening. As a result, the subcooling degree of each use-side heat exchanger 110 can be maintained within an appropriate range, thereby achieving highly efficient operation. This is an effect that cannot be achieved when the subcooling degree controller 415 or the distribution controller 414 is configured as a standalone unit.

[0090] In the air conditioning apparatus 1 according to the second embodiment, the distribution ratio k ｉ is updated only when the degree of subcooling of the refrigerant passing through the heat exchanger is outside a set predetermined range. Generally, it is difficult to perform highly accurate control of the degree of subcooling in a multi-type refrigeration cycle apparatus. This is due to nonlinearity caused by changes in the number of operating units or load fluctuations of each use-side heat exchanger 110. Furthermore, this is because it is a multi-input, multi-output system in which the operation of a certain expansion valve 120 affects the degree of subcooling of all use-side heat exchangers 110. In addition, the need to provide appropriate target values ​​for various operating states makes control design difficult. Therefore, in the air conditioning apparatus 1 of embodiment 2, the distribution controller 414 updates the distribution ratio k only when the degree of subcooling is outside a set predetermined range.ｉ is updated. In addition, a subcooling degree controller 415 that controls the maximum, minimum, or average value of the subcooling degree of the refrigerant passing through each user-side heat exchanger 110 is combined with the distribution controller 414. This increases robustness to environmental changes such as refrigerant amount, installation conditions, or operating state, and improves the stability of the subcooling degree, thereby suppressing the occurrence of hunting. In this way, the configuration of the control processing device 410 itself is highly robust, making it possible to reduce the control design load. Furthermore, the designer only needs to provide a predetermined threshold value. This further reduces the design load.

[0091] Embodiment 3. Figure 7 is a diagram showing the configuration of a control processing device 410 in embodiment 3. Figure 7 shows the part of the control of the air conditioning device 1 performed by the control processing device 410 of the control device 400 that controls the opening degree of each expansion valve. In Figure 7, devices and the like that are given the same reference numerals as in Figure 3 basically perform the same processing operations as those described in embodiment 1. As shown in Figure 7, the control device 400 of embodiment 3 also includes a first controller 411, a second controller 412, a maximum selector 413, and a distribution controller 414, just like the control device 400 of embodiment 1.

[0092] Here, the subcooling degree controller 415 of the first controller 411 in the third embodiment has a valid / invalid determination function. The subcooling degree controller 415 determines the subcooling degree to be valid if the degree is greater than a set subcooling degree threshold (for example, 2 K), and determines the subcooling degree to be invalid if the degree is equal to or less than the supercooling degree threshold. The superheating degree controller 416 of the second controller 412 in the third embodiment also has a valid / invalid determination function. The subcooling degree controller 415 determines the subcooling degree to be valid if the degree is greater than a set superheating degree threshold (for example, 2 K), and determines the subcooling degree to be invalid if the degree is equal to or less than the superheating degree threshold.

[0093] The control device 400 of the third embodiment further includes a throttle controller 418. The throttle controller 418 has a function of controlling the throttle of the total expansion valve opening by feedforward control. For example, when it is desired to change the total expansion valve opening at a constant rate, the throttle controller 418 calculates the total expansion valve opening based on the following equation (11): where ΔS is a preset amount of change in opening. Furthermore, the step at the timing of the previous update is defined as k, and the step at the timing of the current update is defined as k+1. Data relating to step k is stored, for example, in the storage device 430.

[0094]

[0095] The throttle controller 418 also has a valid / invalid determination function. If the superheat controller 416 and the subcooling controller 415 both determine that they are invalid based on the valid / invalid determination described above, the throttle controller 418 determines that they are valid; otherwise, the throttle controller 418 determines that they are invalid. The subcooling controller 415 and the subcooling controller 416 adjust their integral values, etc., so that there is a bumpless change when they transition from an invalid determination to an valid determination.

[0096] Here, the above-mentioned formula (11) is an example of a calculation in which ΔS is a constant value and the expansion valve opening is changed at a constant speed. However, the speed does not necessarily have to be constant. For example, when the start opening S ｓ and convergence opening S ｔ A convergence time T may be set for the valve opening, and the valve opening change amount ΔS may be calculated by the following equation (12). ｃ is the control period. By setting the opening change amount ΔS as in equation (12), it is possible to design the time from start-up to convergence.

[0097]

[0098] Convergence opening S in equation (12) ｔ is actually an unknown value. Therefore, the aperture controller 418 calculates the convergence aperture S based on, for example, the following equation (13): ｔ The refrigerant flow rate G is calculated based on the expansion valve opening S, the pressure difference dP, and the refrigerant density ρ at the expansion valve inlet. ｌ , compressor rotation speed F, compressor intake refrigerant density ρ ｇand a constant (C １ , C ２ ), it is expressed by the following equation (13).

[0099]

[0100] From equation (13), the expansion valve opening degree S is expressed by the following equation (14): where C is a constant.

[0101]

[0102] Since the compressor rotation speed F is controlled by the control device 400, the throttle controller 418 can obtain it from internal information. ｇ , ρ ｌ ) can be estimated using the design value, compressor rotation speed F, the suction temperature conditions of each heat exchanger, the thermal resistance of the heat exchanger, etc. For example, when the suction temperature of the condenser is high and the suction temperature of the evaporator is low, the high-low differential pressure dP becomes large. Also, when the thermal resistance of the heat exchanger is large, the high-low differential pressure dP becomes large. Furthermore, when the compressor rotation speed F is high, the high-low differential pressure dP becomes large. Also, when the compressor rotation speed F is high, the suction temperature of the evaporator is low, or the thermal resistance of the evaporator is large, the compressor suction refrigerant density ρ ｇ becomes smaller.

[0103] As described above, the parameters are estimated from the operating state, and the compressor rotation speed F or the compressor intake refrigerant density ρ ｇ When becomes larger, the convergence opening S ｔ is set to a large value, and the compressor rotation speed F or the compressor intake refrigerant density ρ ｇ When becomes smaller, the convergence opening S ｔ When the differential pressure dP increases, the convergence opening S ｔ is set to a small value, and when the differential pressure dP is small, the convergence opening St is set to a large value.

[0104] From the above, the convergence opening S ｔ If the compressor rotation speed F and other factors are allowed to change from moment to moment, the convergence opening S ｔIt should be noted that the value of also changes over time, and as a result, the opening change amount ΔS also changes over time.

[0105] Next, an example in which the throttling speed is not constant will be described. A characteristic of the expansion valve 120 that it imparts to the system is that the larger the expansion valve opening S, the smaller the impact on the system tends to be. For example, assuming that the expansion valve opening S ranges from 0 to 1000, changing the expansion valve opening S from 10 to 11 will have a greater impact on the system than changing the expansion valve opening S from 900 to 901. Therefore, it is conceivable to increase the opening change amount ΔS when the expansion valve opening S is large, and to decrease the opening change amount ΔS when the expansion valve opening S is small. For example, the opening change amount ΔS is updated so as to be proportional to the current expansion valve opening S based on the following equation (15):

[0106]

[0107] By calculating the opening change amount ΔS according to equation (15), the opening change amount ΔS becomes proportional to the current expansion valve opening amount S, and the effect on the system can be kept constant. Furthermore, by setting α according to equation (15), it is possible to design the time T from start-up until the convergent opening amount is reached. Here, the case where the air conditioning apparatus 1 performs cooling operation has been described, but the same can also be applied to heating operation.

[0108] Furthermore, in addition to the above, the opening change amount ΔS may be determined based on the refrigerant temperature. For example, when the air conditioning apparatus 1 is started, the discharge temperature of the compressor 210 may rise sharply after start-up depending on the initial refrigerant distribution or the start-up opening amount. Therefore, when the control device 400 detects a sudden rise in the discharge temperature, the throttle controller 418 may take measures such as gradually reducing the opening change amount ΔS. By gradually reducing the opening change amount ΔS, stable operation can be achieved quickly without causing an operation shutdown due to an excessive rise in the discharge temperature.

[0109] Effect of the Air Conditioning Apparatus 1 in Embodiment 3 As described above, according to the air conditioning apparatus 1 in Embodiment 3, the control processing device 410 of the control device 400 includes a throttle controller 418 that controls the opening change amount ΔS of the total expansion valve opening. When the total expansion valve opening based on the subcooling and superheat degrees by the first controller 411 and the second controller 412 is disabled, control is performed using the throttle controller 418. Therefore, the air conditioning apparatus 1 in Embodiment 3 can shorten the time from startup to stabilization and perform fast heating or cooling. For example, in a multi-type refrigeration cycle apparatus that controls the subcooling degree or superheat degree, it is difficult to achieve fast responsiveness because the subcooling degree or superheat degree does not take a value less than 0. As with the air conditioning apparatus 1 in Embodiment 3, the control processing device 410 of the control device 400 can achieve the desired responsiveness by utilizing the enable / disable determination function of the throttle controller 418 and the first controller 411 and the second controller 412.

[0110] In the first to third embodiments, an air conditioner has been described as an example of a multi-type refrigeration cycle apparatus, but the present invention is not limited to this and can also be applied to other multi-type refrigeration cycle apparatuses, such as a refrigeration system or a cooling system that cools a heat supply target.

[0111] 1 Air conditioning apparatus, 100, 100a, 100b, 100c User side unit, 110, 110a, 110b, 110c User side heat exchanger, 120, 120a, 120b, 120c Expansion valve, 130, 130a, 130b, 130c Indoor blower, 200 Heat source side unit, 210 Compressor, 220 Four-way valve, 230 Heat source side heat exchanger, 240 Accumulator, 250 Outdoor blower, 300 Refrigerant piping, 400 Control device, 410 Control processing device, 411 First controller, 412 Second controller, 413 Maximum selector, 414 Distribution controller, 415 Subcooling degree controller, 416 Superheating degree controller, 417 PI controller, 418 Throttle controller, 420 Timer, 430: Memory 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 sensors, 560, 560a, 560b, 560c: Use side heat exchanger gas pipe temperature sensors.

Claims

1. A refrigerant circuit is configured by piping-connecting 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 each of the expansion valves, and circulating a refrigerant, a control device for controlling equipment in the apparatus, and is provided with, the control device, a first controller that calculates the total expansion valve opening degree of the expansion valve that causes the heat source side state value of the refrigerant flowing out from the heat source side heat exchanger to follow the heat source side target state value, and outputs it as the heat source side total expansion valve opening degree; a second controller that calculates the total expansion valve opening degree of the expansion valve that causes the use side state value of the refrigerant flowing out from each of the plurality of use side heat exchangers to follow the use side target state value, and outputs it as the use side total expansion valve opening degree; a maximum selector that selects either one of the heat source side total expansion valve opening degree and the use side total expansion valve opening degree as the maximum total expansion valve opening degree; and a distribution controller that performs a process of distributing the maximum total expansion valve opening degree to the expansion valve opening degrees of each of the expansion valves. The distribution controller is a multi-type refrigeration cycle apparatus that distributes the maximum total expansion valve opening degree according to a distribution ratio in which the opening degrees of the respective expansion valves corresponding to the respective use side heat exchangers change relatively based on a comparison between the use side state value of the refrigerant flowing out from each of the use side heat exchangers and a set threshold value.

2. In a cooling operation for cooling a heat supply target by heat exchange between the refrigerant in the use side heat exchanger, the first controller calculates the heat source side total expansion valve opening degree using the degree of subcooling of the refrigerant flowing out from the heat source side heat exchanger as the heat source side state value, the second controller calculates the use side total expansion valve opening degree that causes the maximum value or minimum value of the superheat degrees of the refrigerant flowing out from each of the plurality of use side heat exchangers, or a statistical value obtained by statistically processing the plurality of superheat degrees, to follow the upper limit superheat degree, using a value obtained from the superheat degrees of the refrigerant flowing out from each of the plurality of use side heat exchangers as the use side state value, the maximum selector compares the heat source side total expansion valve opening degree and the use side total expansion valve opening degree, and if the heat source side total expansion valve opening degree is larger, selects the heat source side total expansion valve opening degree as the maximum total expansion valve opening degree, and if the use side total expansion valve opening degree is larger, selects the use side total expansion valve opening degree as the maximum total expansion valve opening degree. The multi-type refrigeration cycle device according to claim 1, wherein the distribution controller sets the distribution ratio such that the opening degree of the expansion valve corresponding to the utilization-side heat exchanger in which the superheat degree of the refrigerant flowing out is equal to or higher than the threshold value relatively increases.

3. In a heating operation for heating a heat supply target by heat exchange between the refrigerant in the utilization-side heat exchanger, the first controller calculates the total expansion valve opening degree on the heat source side that follows the upper limit superheat degree, using the superheat degree of the refrigerant flowing out from the heat source-side heat exchanger as the heat source-side state value; the second controller calculates the total expansion valve opening degree on the utilization side that follows the lower limit subcooling degree, using, as the utilization-side state value, a value obtained from the subcooling degrees of the refrigerants flowing out from the plurality of utilization-side heat exchangers, and taking, among the subcooling degrees of the refrigerants flowing out from the plurality of utilization-side heat exchangers, the maximum value or the minimum value, or a statistical value obtained by statistically processing the plurality of subcooling degrees; the maximum selector compares the total expansion valve opening degree on the heat source side and the total expansion valve opening degree on the utilization side, and if the total expansion valve opening degree on the utilization side is larger, selects the total expansion valve opening degree on the utilization side as the maximum total expansion valve opening degree, and if the total expansion valve opening degree on the heat source side is larger, selects the total expansion valve opening degree on the heat source side as the maximum total expansion valve opening degree; The multi-type refrigeration cycle device according to claim 1, wherein the distribution controller sets the distribution ratio such that the opening degree of the expansion valve corresponding to the utilization-side heat exchanger is relatively increased or decreased so that the subcooling degree of the refrigerant flowing out falls within a range of a set upper limit subcooling degree threshold value and a lower limit subcooling degree threshold value.

4. In the cooling operation, for the expansion valve corresponding to the utilization-side heat exchanger in which the superheat degree is greater than a set superheat degree threshold value, the distribution controller increases the distribution ratio so as to increase the expansion valve opening degree based on the current expansion valve opening degree, and for the expansion valve opening degrees of the other expansion valves, while maintaining the relationship of the distribution ratios among the other expansion valves, decreases the distribution ratio with respect to the total expansion valve opening degree. The multi-type refrigeration cycle device according to claim 2.

5. In the heating operation, for the expansion valve corresponding to the user-side heat exchanger where the degree of subcooling is less than the lower limit subcooling threshold value, the expansion valve opening degree of the expansion valve is set as the expansion valve opening degree that reduces the distribution ratio so as to reduce the expansion valve opening degree based on the current expansion valve opening degree. For the expansion valve corresponding to the user-side heat exchanger where the degree of subcooling is greater than the upper limit subcooling threshold value, the expansion valve opening degree of the expansion valve is increased by increasing the distribution ratio so as to increase the expansion valve opening degree based on the current expansion valve opening degree. For the other expansion valves that do not fall into either category, the distribution ratio for the total expansion valve opening degree is decreased while maintaining the relationship of the distribution ratios among the other expansion valves. The multi-type refrigeration cycle apparatus according to claim 3.

6. For the expansion valve corresponding to the user-side heat exchanger that stops heat exchange, the distribution controller changes the distribution ratio so that the expansion valve opening degree becomes the closed opening degree. For the expansion valve corresponding to the user-side heat exchanger that starts heat exchange, the distribution ratio is set such that the expansion valve opening degree becomes the average value of the distribution ratios. The multi-type refrigeration cycle apparatus according to any one of claims 1 to 5.

7. The control device has a throttle controller that reduces the total expansion valve opening degree by feedforward control. The first controller and the second controller have a valid / invalid determination function that determines them to be valid if the degree of subcooling or superheat is greater than the set threshold value, and invalid if it is below the set threshold value. The throttle controller has the valid / invalid determination function, and determines to be valid when both the first controller and the second controller are determined to be invalid, and invalid otherwise. The maximum selector selects the largest value among the outputs of the first controller, the second controller, and the throttle controller that are determined to be valid as the maximum total expansion valve opening degree. The multi-type refrigeration cycle apparatus according to any one of claims 1 to 5.

8. The throttle controller according to claim 7 performs control to decrease the expansion valve opening degree of the expansion valve at a constant speed. The multi-type refrigeration cycle apparatus according to claim 7.

9. The throttle controller according to claim 8 calculates a convergence opening degree and calculates the constant speed based on the time to the set convergence opening degree. The multi-type refrigeration cycle apparatus according to claim 8.

10. The multi-type refrigeration cycle apparatus according to claim 7, wherein the throttle controller increases the throttle width when the opening degree of the expansion valve is large, and decreases the throttle width when the opening degree of the expansion valve is small.

11. The multi-type refrigeration cycle apparatus according to claim 10, wherein the throttle controller calculates a convergence opening degree and determines a slope of the throttle width based on the time until the set convergence opening degree.

12. The multi-type refrigeration cycle apparatus according to claim 9, wherein the throttle controller calculates the convergence opening degree based on the rotational speed of the compressor, the refrigerant density at the compressor inlet of the compressor, the differential pressure between high and low levels in the refrigerant circuit, and the refrigerant density at the expansion valve inlet flowing into the expansion valve.