Multi-connected refrigeration cycle device

Abstract

The present invention is provided with: a refrigerant circuit configured by connecting a heat source-side heat exchanger, a plurality of expansion valves, and a plurality of use-side heat exchangers by piping; and a control device. A heat source-side total expansion valve opening degree calculation unit that calculates the total expansion valve opening degree of an 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 the total expansion valve opening degree as a heat source-side total expansion valve opening degree; a second controller that calculates the total expansion valve opening of the expansion valves 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 the total expansion valve opening as a use-side total expansion valve opening; a maximum selector that selects either a heat source-side total expansion valve opening degree or a use-side total expansion valve opening degree; and a distribution controller that performs a process of distributing the maximum total expansion valve opening degree into the opening degrees of the respective expansion valves.

Description

Technical Field

[0001] The present technology relates to a multi-type refrigeration cycle device having a plurality of utilization-side heat exchangers, and particularly to expansion valve control based on a state value of a refrigerant after heat exchange. Background Art

[0002] Conventionally, there are multi-connected refrigeration cycle devices that are configured by connecting a plurality of pipes to a heat exchanger on the user side, which exchanges heat between a heat supply target such as hot air and a refrigerant. These multi-connected refrigeration cycle devices include a refrigerant circuit comprising a compressor, a heat source-side heat exchanger, a plurality of expansion valves connected in parallel, and a plurality of heat exchangers on the user side connected in series with each expansion valve. Furthermore, a control device controls the opening of each expansion valve to optimize the distribution of the refrigerant passing through the heat exchanger on the user side, thereby exchanging heat between the refrigerant and the heat exchanger (see, for example, Patent Document 1).

[0003] In such a multi-type refrigeration cycle device, during cooling operation, the control device varies the openings of the expansion valves to control the subcooling degree to a target subcooling degree. In this process, the control device distributes the total expansion valve opening, obtained by summing the openings of each expansion valve, according to the capacity ratio of the utilization-side heat exchangers. The control device controls the allocated openings of each expansion valve based on the difference between the superheat of the refrigerant passing through each utilization-side heat exchanger and the target superheat. Furthermore, if the control device determines that the superheat of the refrigerant in all utilization-side heat exchangers is greater than or less than the target superheat value, the control device changes the target subcooling degree.

[0004] During heating operation, the control device calculates the opening degrees of each expansion valve so that the degree of subcooling of the refrigerant passing through each indoor heat exchanger reaches a predetermined target degree of subcooling. Furthermore, if the control device determines that the degree of superheat in the outdoor heat exchanger is above the set value, it controls the airflow to lower the target degree of subcooling.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2002-054836 Summary of the Invention

[0008] Problems to be solved by the invention

[0009] In the multi-type refrigeration cycle device disclosed in Patent Document 1, a control device performs control to vary the target subcooling degree in order to prevent the superheat in the heat exchanger serving as the evaporator from exceeding the target superheat. However, this control method limits the variation of the expansion valve opening degree if the heat exchanger becomes insufficient for refrigerant and subcooling becomes completely uncontrollable, resulting in a problem of reduced operating efficiency.

[0010] On the other hand, during heating operation to heat a heat supply target, control is performed based on the subcooling degree of the control target, which is a significant noise source, while also varying the target subcooling degree based on the superheat of the outdoor heat exchanger. This increases the design burden of the control constants.

[0011] Therefore, in order to solve the above-mentioned problems, an object of the present invention is to provide a multi-type refrigeration cycle device that can be appropriately controlled based on the state of the refrigerant passing through the heat exchanger regardless of whether the refrigerant amount is large or small.

[0012] Solutions to Problems

[0013] The multi-type refrigeration cycle device involved in the present disclosure comprises a refrigerant circuit and a control device for controlling the devices in the device, wherein the refrigerant circuit is formed by connecting a compressor, a heat source side heat exchanger, a plurality of expansion valves, and a plurality of utilization side heat exchangers respectively connected in series with the expansion valves by using piping, so that the refrigerant circulates, and the control device comprises: a first controller, which calculates the total expansion valve opening of the expansion valve so that the heat source side state value of the refrigerant flowing out of the heat source side heat exchanger follows the heat source side target state value, and outputs it as the heat source side total expansion valve opening; a second controller, which calculates the total expansion valve opening of the expansion valve so that the heat source side state value of the refrigerant flowing out of the plurality of utilization side heat exchangers respectively follows the heat source side target state value; The total expansion valve opening of the expansion valve whose utilization side state value follows the utilization side target state value is output as the utilization side total expansion valve opening; a maximum selector, which selects either the heat source side total expansion valve opening and the utilization side total expansion valve opening as the maximum total expansion valve opening; and a distribution controller, which distributes the maximum total expansion valve opening into the expansion valve openings of each expansion valve, the distribution controller distributes the maximum total expansion valve opening based on a comparison between the utilization side state value of the refrigerant flowing out of each utilization side heat exchanger and a set threshold value, according to a distribution ratio that changes relatively with the opening of each expansion valve corresponding to each utilization side heat exchanger.

[0014] Effects of the Invention

[0015] According to the multi-type refrigeration cycle device disclosed in the present invention, in the control device, the first controller determines the heat source side total expansion valve opening obtained based on the heat source side state value of the refrigerant flowing out of the heat source side heat exchanger. In addition, the second controller determines the utilization side total expansion valve opening obtained based on the utilization side state value of the refrigerant flowing out of the utilization side heat exchanger. The distribution controller distributes the maximum total expansion valve opening selected by the maximum controller from the heat source side total expansion valve opening and the utilization side total expansion valve opening to each expansion valve, and determines the opening of each expansion valve. Therefore, the multi-type refrigeration cycle device can appropriately control the subcooling degree during operation with sufficient refrigerant, and can achieve energy saving with high efficiency. On the other hand, the multi-type refrigeration cycle device can automatically and continuously switch to superheat control during operation where the refrigerant is insufficient and the subcooling control is not established, and can appropriately control the subcooling degree. Therefore, efficient operation can be maintained regardless of the amount of refrigerant. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a diagram showing the configuration of an air-conditioning apparatus 1 according to Embodiment 1.

[0017] Figure 2 This is a diagram showing the configuration of the control device 400 in the air-conditioning apparatus 1 according to Embodiment 1.

[0018] Figure 3 This is a diagram showing the configuration of the control processing device 410 in the first embodiment.

[0019] Figure 4 This is a diagram showing the relationship between the degree of subcooling and the degree of superheat and time according to the first embodiment.

[0020] Figure 5 It is a diagram showing images related to the distribution processing operation in the air-conditioning apparatus 1 according to Embodiment 1.

[0021] Figure 6 This is a diagram showing the configuration of the control processing device 410 in the second embodiment.

[0022] Figure 7 This is a diagram showing the configuration of the control processing device 410 in the third embodiment. DETAILED DESCRIPTION

[0023] Hereinafter, the multi-type refrigeration cycle device involved in the embodiment will be described with reference to the accompanying drawings and the like. In the following drawings, the parts marked with the same figure mark are the same or equivalent parts, which are common throughout the entire text of the embodiment described below. In addition, in the drawings, the size relationship of each component is sometimes different from the actual one. Moreover, the form of the components shown in the entire specification is ultimately an example and is not limited to the form described in the specification. In particular, the combination of components is not limited to the combination in each embodiment, and the components described in other embodiments can also be applied to other embodiments. In addition, the high and low pressures and temperatures are not particularly determined in relation to absolute values, but are relatively determined in the state and action of the device, etc. In addition, with respect to multiple devices of the same type that are distinguished by subscripts, when there is no need to distinguish them specifically or in specific occasions, the subscripts are sometimes omitted and described.

[0024] Implementation method 1.

[0025] Figure 1 1 is a diagram showing the structure of an air conditioning apparatus 1 according to Embodiment 1. Here, as an example of a multi-type refrigeration cycle apparatus, an air conditioning apparatus 1 for conditioning indoor air as an air conditioning target space is described. In this case, the indoor air becomes the target of heat supply. Figure 1 As shown, the air-conditioning apparatus 1 of Embodiment 1 includes a heat source side unit 200, a utilization side unit 100, and a refrigerant piping 300. Furthermore, the refrigerant piping 300 connects the compressor 210, four-way valve 220, and heat source side heat exchanger 230 of the heat source side unit 200 with the utilization side heat exchanger 110 and expansion valve 120 of the utilization side unit 100, thereby forming a refrigerant circuit that circulates refrigerant to transport heat. Here, the air-conditioning apparatus 1 of Embodiment 1 is configured such that three utilization side units 100 are connected in parallel with respect to one heat source side unit 200 by piping. The number of connected units may be any number as long as two or more utilization side units 100 are connected in parallel by piping. Regarding control, the number of utilization side units 100 that are operated may also be one.

[0026] The user-side units 100 (user-side units 100a through 100c) perform air conditioning by heating or cooling the air within the indoor space serving as the air conditioning target space. Each user-side unit 100 includes a user-side heat exchanger 110 (user-side heat exchanger 110a through 110c) and an expansion valve 120 (expansion valve 120a through 120c) as components constituting the refrigerant circuit. Furthermore, each user-side unit 100 includes an indoor blower 130 (indoor blower 130a through 130c).

[0027] The expansion valve 120, which serves as a throttling device, is a valve that reduces the pressure of the refrigerant and expands it. The expansion valve 120 is, for example, an electronic expansion valve. Furthermore, the expansion valve 120 adjusts its opening based on instructions from the control device 400, described later, to reduce the pressure and control the amount of refrigerant passing through the corresponding user-side heat exchanger 110. Furthermore, the user-side heat exchanger 110 is a heat exchanger that heats or cools the indoor air by exchanging heat between the indoor air and the refrigerant. For example, during heating operation, which is heating operation, the user-side heat exchanger 110 functions as a condenser, condensing the refrigerant so that it dissipates heat and liquefies into a liquid refrigerant (hereinafter referred to as liquid refrigerant), which is then passed through. Furthermore, during cooling operation, which is cooling operation, the user-side heat exchanger 110 functions as an evaporator, causing the refrigerant to absorb heat and evaporate, thereby vaporizing into a gaseous refrigerant (hereinafter referred to as gaseous refrigerant), which is then passed through. The indoor air-sending device 130 causes air to pass 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 a room that is a space to be air-conditioned.

[0028] The heat source side unit 200 in Embodiment 1 includes a compressor 210, a four-way valve 220, a heat source side heat exchanger 230, and a liquid accumulator 240 as components constituting a refrigerant circuit. In addition, the heat source side unit 200 includes an outdoor blower 250. The compressor 210 compresses and discharges the sucked refrigerant. The compressor 210 is, for example, a scroll compressor, a piston compressor, or a vane compressor. Here, the compressor 210 can arbitrarily change the driving frequency using, for example, an inverter circuit, thereby changing the capacity of the refrigerant discharged by the compressor 210 (the amount of refrigerant delivered per unit time).

[0029] The four-way valve 220, which serves as a flow switching device, is a valve that switches the flow of refrigerant between cooling and heating operations, for example. During heating operation, the four-way valve 220 connects the discharge side of the compressor 210 to the utilization-side heat exchanger 110, and connects the suction side of the compressor 210 to the heat source-side heat exchanger 230. Furthermore, 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 utilization-side heat exchanger 110. While the example of using the four-way valve 220 is shown here, the flow switching device is not limited thereto. For example, the flow switching device may also be a combination of a plurality of two-way valves.

[0030] The heat source side heat exchanger 230 is a heat exchanger that performs heat exchange between the refrigerant and the outdoor air. The heat source side heat exchanger 230 of Embodiment 1 functions as an evaporator during heating operation, evaporating the refrigerant and allowing gaseous refrigerant to pass through. On the other hand, the heat source side heat exchanger 230 functions as a condenser and a subcooler during cooling operation, condensing the refrigerant and allowing liquid refrigerant to pass through. The structure of the heat source side heat exchanger 230 will be further described later. In addition, the outdoor blower 250 is driven to form an air flow in which air from the outside of the heat source side unit 200 passes through the heat source side heat exchanger 230 and flows out of the heat source side unit 200, thereby promoting heat exchange in the heat source side heat exchanger 230.

[0031] Here, the device configuration of the refrigerant circuit in the air conditioning apparatus 1 is not limited to Figure 1 The structure shown. The refrigerant circuit may also include a capillary tube or the like as needed. In addition, the utilization-side heat exchanger 110 and the heat source-side heat exchanger 230 have been described as structures in which the object of heat exchange is air and heat exchange is performed between air and refrigerant, but are not limited to this. For example, the heat exchanger may be a structure in which water or geothermal heat is used as the object of heat exchange with the refrigerant. In addition, the piping may be branched in the heat source-side unit 200 and the expansion valve 120 may be included in the heat source-side unit 200.

[0032] Next, the operation of each component in the air-conditioning apparatus 1 will be described based on the flow of the refrigerant. First, the operation of each component of the refrigerant circuit during heating operation will be described based on the flow of the refrigerant. Figure 1 The dotted arrows in the figure represent the flow of refrigerant during heating operation. The high-temperature and high-pressure gas refrigerant compressed and discharged by the compressor 210 passes through the four-way valve 220 and flows into the utilization-side heat exchanger 110. While passing through the utilization-side heat exchanger 110, the gas refrigerant is condensed and liquefied, for example, by exchanging heat with the air in the air-conditioned space. The condensed and liquefied refrigerant passes through the expansion valve 120. The refrigerant is decompressed while passing through the expansion valve 120. The refrigerant, which has been decompressed by the expansion valve 120 and has become a gas-liquid two-phase state, passes through the heat source-side heat exchanger 230. The refrigerant, which has evaporated and gasified through heat exchange with the outdoor air sent from the outdoor blower 250 in the heat source-side heat exchanger 230, passes through the four-way valve 220 and the accumulator 240 and is sucked into the compressor 210 again. As described above, the refrigerant circulates in the air conditioning device 1, performing air conditioning involving heating.

[0033] Next, the cooling operation will be described. Figure 1The solid arrows in the figure represent the flow of refrigerant during cooling operation. The 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, exchanges heat with the outdoor air supplied by the outdoor blower 250, and is thereby condensed and liquefied. The liquefied refrigerant then passes through the expansion valve 120. Here, the refrigerant is decompressed and becomes a gas-liquid two-phase state while passing through the expansion valve 120. The refrigerant, decompressed and becoming a gas-liquid two-phase state by the expansion valve 120, passes through the user-side heat exchanger 110. The refrigerant, which evaporates and gasifies in the user-side heat exchanger 110 through heat exchange with, for example, the air in the air-conditioned space, passes through the four-way valve 220 and is drawn back into the compressor 210. As described above, the refrigerant circulates in the air conditioning apparatus 1, performing air conditioning involving cooling. In the first embodiment, the description is given of a configuration in which cooling operation is performed in which the use-side heat exchanger 110 serves as an evaporator and the heat-source-side heat exchanger 230 serves as a condenser.

[0034] The air conditioning apparatus 1 in Embodiment 1 includes a high-pressure pressure sensor 510 and a low-pressure pressure sensor 520 as pressure sensors. The high-pressure pressure sensor 510 detects the pressure of the refrigerant discharged from the compressor 210, which is on the high-pressure side of the refrigerant circuit, as the high-pressure pressure. The low-pressure pressure sensor 520 detects the pressure of the refrigerant flowing into the accumulator 240, which is on the low-pressure side of the refrigerant circuit, as the low-pressure pressure.

[0035] In addition, the air conditioning device 1 in 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, a utilization side heat exchanger liquid pipe temperature sensor 550, and a utilization side heat exchanger gas pipe temperature sensor 560 as temperature sensors.

[0036] The heat source-side heat exchanger gas pipe temperature sensor 530 is installed 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 into and out of the heat source-side heat exchanger 230. During cooling operation, 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 and, during heating operation, detects the temperature of the refrigerant flowing out of the heat source-side heat exchanger 230. Furthermore, the heat source-side heat exchanger liquid pipe temperature sensor 540 is installed 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 into and out of the heat source-side heat exchanger 230. During cooling operation, 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 and, during heating operation, detects the temperature of the refrigerant flowing into the heat source-side heat exchanger 230.

[0037] The usage-side heat exchanger liquid pipe temperature sensors 550 (usage-side heat exchanger liquid pipe temperature sensors 550a through 550c) are installed in the liquid-side piping of the corresponding usage-side heat exchanger 110. Furthermore, the usage-side heat exchanger liquid pipe temperature sensors 550 detect the temperature of the liquid refrigerant (including two-phase refrigerant) flowing into and out of the usage-side heat exchanger 110. During cooling operation, the usage-side heat exchanger liquid pipe temperature sensors 550 detect the temperature of the refrigerant flowing into the corresponding usage-side heat exchanger 110, and during heating operation, they detect the temperature of the refrigerant flowing out of the corresponding usage-side heat exchanger 110. Furthermore, the usage-side heat exchanger gas pipe temperature sensors 560 (usage-side heat exchanger gas pipe temperature sensors 560a through 560c) are installed in the gas-side piping of the corresponding usage-side heat exchanger 110. Furthermore, the usage-side heat exchanger gas pipe temperature sensor 560 detects the temperature of the gas refrigerant (including two-phase refrigerant) flowing into and out of the usage-side heat exchanger 110. During cooling operation, the usage-side heat exchanger gas pipe temperature sensor 560 detects the temperature of the refrigerant flowing out of the corresponding usage-side heat exchanger 110, and during heating operation, detects the temperature of the refrigerant flowing into the corresponding usage-side heat exchanger 110.

[0038] Figure 2 1 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 for controlling the air conditioning apparatus 1. Figure 2 As shown, the control device 400 is connected to the various sensors described above, and receives input signals including data such as temperature and pressure. In addition, signals including user instructions are input to the control device 400 via an operation unit (not shown).

[0039] In addition, if Figure 2 As shown, the control device 400 includes a control processing device 410, a timing device 420, and a storage device 430. The control processing device 410 performs calculations and determinations based on temperature and other data contained in signals sent from various sensors, as well as user instructions, to control components such as the compressor 210, expansion valve 120, and outdoor fan 250 that make up the air conditioning system 1. The storage device 430 stores data required for the control processing device 410 to perform processing. The timing device 420 is a timer or other device that measures the time and duration required for the control processing device 410 to perform determinations and other processing.

[0040] Here, the control processing device 410 includes, for example, a microcomputer including a control calculation processing device such as a CPU (Central Processing Unit). However, the present invention is not limited thereto. The control processing device 410 may also be configured by combining dedicated components (hardware) as components. For example, the control processing device 410 may include a PI controller 417, described later, as a dedicated component.

[0041] The storage device 430 includes, for example, a ROM (Read Only Memory). Furthermore, the storage device 430 includes a storage device (not shown) such as a RAM (Random Access Memory) capable of temporarily storing data, or an auxiliary storage device (not shown) such as a flash memory or a solid-state drive. Furthermore, for example, the storage device 430 stores data that program the processing sequence performed by the control processing device 410. The control processing device 410 executes processing based on the program data to achieve device control, etc.

[0042] Figure 3 This is a diagram showing the configuration of the control processing device 410 in the first embodiment. Figure 3 4 shows a portion of the control of the air conditioning apparatus 1 by the control processing device 410 of the control device 400, which controls the expansion valve opening of each expansion valve 120. Figure 3 As shown, the control processing device 410 of the control device 400 in the first embodiment includes a first controller 411 , a second controller 412 , a maximum selector 413 , and a distribution controller 414 .

[0043] The first controller 411 calculates the heat source side state value of the refrigerant flowing out of the heat source side heat exchanger 230. Furthermore, the first controller 411 calculates the total expansion valve opening, which is the sum of the openings of the expansion valves 120 that follows the heat source side target state value, and outputs this as the heat source side total expansion valve opening. The air conditioning apparatus 1 in Embodiment 1 performs cooling operation. Therefore, the heat source side heat exchanger 230 functions as a condenser, and thus the heat source side state value becomes the subcooling degree (SC), and the heat source side target state value becomes the target subcooling degree. Furthermore, the first controller 411 includes a subcooling degree controller 415.

[0044] The subcooling controller 415 calculates the refrigerant's subcooling degree, calculates the total expansion valve opening degree required to adjust the refrigerant's subcooling degree to a target subcooling degree, and outputs the calculated value. In Embodiment 1, the subcooling controller 415 outputs signals from the high-pressure pressure sensor 510 and the heat source-side heat exchanger liquid pipe temperature sensor 540. Based on the high-pressure pressure signal from the high-pressure pressure sensor 510 and the refrigerant's physical properties, the subcooling controller 415 calculates the saturated liquid temperature at that pressure. Furthermore, the subcooling controller 415 calculates the difference between the saturated liquid temperature and the heat source-side liquid pipe temperature signal from the heat source-side heat exchanger liquid pipe temperature sensor 540 as the subcooling degree. However, the method for calculating the subcooling degree is not limited to this. For example, in the heat source-side heat exchanger 230, the subcooling degree may be calculated based on the difference between the temperature detected by a temperature sensor located in a portion where two-phase refrigerant flows and the heat source-side liquid pipe temperature. The target subcooling degree may be a constant value or a variable value set depending on the actual operating state. If the target subcooling degree is a variable value, for example, the target subcooling degree may be obtained by multiplying the difference between the condensing temperature and the ambient temperature of the heat exchanger serving as the condenser by a coefficient.

[0045] The second controller 412 calculates the heat source-side state value of the refrigerant flowing out of each user-side heat exchanger 110. Furthermore, the second controller 412 calculates the total expansion valve opening, which is the sum of the openings of each expansion valve 120 that follows the user-side target state value, and outputs this as the user-side total expansion valve opening. As described above, the air-conditioning apparatus 1 in Embodiment 1 performs cooling operation, with each user-side heat exchanger 110 functioning as an evaporator. Therefore, the user-side state value becomes the superheat (SH), and the user-side target state value becomes the target superheat. Furthermore, the second controller 412 includes a superheat controller 416.

[0046] The superheat controller 416 calculates the refrigerant's superheat, calculates the total expansion valve opening so that the refrigerant's superheat follows the set superheat upper limit, and outputs the result. In Embodiment 1, the superheat controller 416 outputs the total expansion valve opening so that the maximum superheat among the refrigerant superheats flowing out of each user-side heat exchanger 110 follows the superheat upper limit. The superheat upper limit can be determined, for example, based on hardware limitations or a value set based on empirical rules. The superheat controller 416 in Embodiment 1 receives input signals from the low-pressure pressure sensor 520 and the gas pipe temperature sensors 560 of each user-side heat exchanger. Based on the low-pressure pressure included in the signal from the low-pressure pressure sensor 520 and the physical properties of the refrigerant, the superheat controller 416 calculates the saturated gas temperature at that pressure. Furthermore, the superheat controller 416 calculates the difference between the saturated gas temperature and the user-side gas pipe temperature contained in the signal from each user-side heat exchanger gas pipe temperature sensor 560, and uses this difference as the superheat of the refrigerant flowing out of each user-side heat exchanger 110. However, the method for calculating the superheat is not limited to this. For example, in each user-side heat exchanger 110, the superheat can be calculated based on the difference between the temperature detected by a temperature sensor installed in a portion where two-phase refrigerant flows and the user-side gas pipe temperature. Furthermore, the control output of the superheat control is not limited to the maximum superheat; it can also be the minimum value. Furthermore, a statistical value obtained by statistically processing multiple superheats, such as an average or median value, can also be used. Furthermore, since the superheat does not take a value less than zero, values ​​below a certain threshold can also be treated as abnormal values.

[0047] The subcooling controller 415 and the superheat controller 416 each include a position-type PI controller 417. The PI controller 417 is a controller that performs feedback control based on proportional-integral control. Here, the PI controller 417 has an anti-integral windup function. This anti-integral windup function suppresses divergence in the value obtained by integration 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 the upper and lower limits of the expansion valve opening of the expansion valve 120. This anti-integral windup function is particularly effective when the control processing device 410 is configured with multiple PI controllers 417 connected in parallel and the value to be processed next is selected based on the output value of any one of the multiple PI controllers 417.

[0048] Here, in Embodiment 1, the subcooling controller 415 and the superheat controller 416 include PI controllers 417, but other controllers may also be used. For example, the subcooling controller 415 and the superheat controller 416 may include a P controller for proportional control, a PID controller for proportional-integral-derivative control, or a dynamic feedback controller such as a model predictive controller. Furthermore, the subcooling controller 415 and the superheat controller 416 may be dynamic or static controllers that perform control based on data pre-set in a table format, etc. Furthermore, the controllers may not be position-type controllers, but may be velocity-type controllers. However, even with velocity-type controllers, the subcooling controller 415 and the superheat controller 416 must output the total expansion valve opening to the maximum selector 413.

[0049] The maximum selector 413 compares the heat source side total expansion valve opening value outputted by the first controller 411 and the heat source side total expansion valve opening value outputted by the second controller 412 and outputs the larger value as the maximum total expansion valve opening.

[0050] 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 sequence performed by the distribution controller 414 in the first embodiment is described. Let the set U = {1, 2, ..., n} be the set of the serial numbers of the utilization side heat exchangers. Here, n is the number of connected utilization side heat exchangers 110. In addition, Set as the set of serial numbers of the heat exchangers on the utilization side that are in operation. If the superheat exceeds the upper superheat limit (SH i >2, i∈V) is the set of the serial numbers of the heat exchangers on the utilization side. i It is the superheat of the heat exchanger number i on the utilization side.

[0051] The distribution controller 414 maintains the distribution ratio k i (i∈V). Here, the distribution ratio k i It has the characteristics shown in the following formula (1).

[0052]

[0053] Furthermore, the distribution controller 414 calculates the distribution ratio k based on the distribution ratio k. i , the expansion valve opening of each expansion valve 120 is calculated according to the following formula (2). Here, S i is the expansion valve opening of each expansion valve 120. total is the maximum total expansion valve opening output by the maximum selector 413. iThe initial value of is set, for example, by setting it uniformly or setting it to be equal to the capacity ratio of the utilization side heat exchanger 110.

[0054]

[0055] The distribution controller 414 adjusts the distribution ratio k at intervals of, for example, 1 minute. i However, the timing of the update process is not limited to this. For example, the distribution controller 414 need not execute the process at regular intervals, but may execute the process upon detecting a dry state. Alternatively, the distribution controller 414 may execute the process upon detecting the start or stop of operation of the utilization-side unit 100. Furthermore, the distribution controller 414 may combine updates triggered by detection of a dry state or the start or stop of operation of the utilization-side unit 100 with updates at regular intervals.

[0056] If the distribution controller 414 determines that the superheat of a certain utilization side heat exchanger 110 is greater than the set superheat threshold (e.g., 2K), the refrigerant flowing to the utilization side heat exchanger 110 is insufficient (in a dry state). In addition, the distribution controller 414 uses the current expansion valve opening of the expansion valve 120 as a reference and adjusts the distribution ratio k of the corresponding expansion valve 120. i Set the distribution ratio k to be larger than the current expansion valve opening i If the distribution ratio k i As the expansion valve opening of the expansion valve 120 increases, the amount of refrigerant flowing to the utilization side heat exchanger 110 increases.

[0057] Next, the allocation ratio k i Here, the step at the time of the last update is set as k, and the step at the time of this update is set as k+1. First, when all the utilization side heat exchangers 110 are in a dry state or all the utilization side heat exchangers 110 are not in a dry state, and A or A c (A c yes When the complement of is an empty set, the distribution ratio k is not i Therefore, the distribution ratio k involved in this update i (k+1) uses the allocation ratio k involved in the last update i (k) is represented by the following formula (3).

[0058]

[0059] On the other hand, a portion of the utilization side heat exchanger 110 is in a dry state, and A and A cWhen neither is an empty set, the distribution ratio k involved in this update i (k+1) uses the allocation ratio k involved in the last update i (k) is expressed by the following equation (4). The distribution ratio k involved in the last update i (k) becomes 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 utilization side heat exchanger 110 in the dry state by increasing the expansion valve opening by 10% compared to the current expansion valve opening. i When (k+1) is less than 0 or greater than 1, the distribution ratio k is not used. i Therefore, the distribution ratio k involved in this update i (k+1) is represented by the above-mentioned formula (3).

[0060]

[0061] As described above, the distribution ratio k is updated by the distribution controller 414. i The expansion valve opening of the expansion valve 120 corresponding to the utilization side heat exchanger 110 in the dry state is relatively increased, and the amount of refrigerant passing through the utilization side heat exchanger 110 is increased, thereby eliminating the dry state. In addition, the distribution ratio k of the expansion valve opening of the expansion valve 120 corresponding to the utilization side heat exchanger 110 that is not in the dry state (appropriate state) can be maintained. i , and can reduce the distribution ratio k relative to the total expansion valve opening i Here, equation (4) shows the case where the expansion valve opening of the expansion valve 120 corresponding to the utilization side heat exchanger 110 in the dry state is increased by 10%, but it is not limited to 10%. In addition, the increase ratio does not need to be constant.

[0062] Next, the distribution ratio k at each expansion valve 120 processed by the distribution controller 414 when the utilization side unit 100 is stopped after operation or when the utilization side unit 100 starts operating after stopping is calculated. i Here, immediately after the operation of the utilization side unit 100 is stopped or just started, the state of the refrigerant in the refrigerant circuit is not stable, and therefore, the distribution controller 414 of the control device 400 does not execute the distribution ratio k based on the dry state. i Updates.

[0063] Here, Let be the set of the utilization side heat exchanger numbers of the utilization side heat exchangers 110 involved in the utilization side unit 100 that is newly stopped. Let V(k+1) be the set of the user-side heat exchanger numbers of the user-side heat exchangers 110 associated with the user-side unit 100 that has newly started operation. Furthermore, let V(k+1) be the set of the user-side heat exchanger numbers of the user-side heat exchangers 110 associated with the user-side unit 100 currently in operation. Furthermore, let V(k) be the set of the user-side heat exchanger numbers of the user-side heat exchangers 110 associated with the user-side unit 100 that was previously in operation. For example, when V(k) = {1, 3, 5, 7}, M = {3}, and N = {2}, then V(k+1) = {1, 2, 5, 7}.

[0064] The distribution controller 414 sets the expansion valve opening of the expansion valve 120 of the stopped usage-side unit 100 to the closed opening (opening 0). In addition, the expansion valve opening of each expansion valve 120 of the usage-side unit 100 other than the stopped usage-side unit 100 is set to the distribution ratio k related to the last update. i The sum of becomes 1, and the normalized distribution ratio k is calculated based on the following formula (5): i '.

[0065]

[0066] Next, the distribution controller 414 calculates the normal distribution ratio k based on the following equation (6): i ', and set it as the normal distribution ratio k corresponding to the utilization side heat exchanger 110 that starts operation i '. Here, |V - M| is the number of elements in the set V - M. Also, the minus sign in a set indicates the difference of sets. There are also notations that use a backslash instead of a minus sign, and this notation is used in the formula.

[0067]

[0068] Furthermore, the allocation controller 414 allocates the i ', normalize again and calculate the allocation ratio k involved in this update according to the following formula (7): i (k+1).

[0069]

[0070] As described above, the distribution controller 414 can calculate and determine the distribution ratio k of the expansion valve opening degree at each expansion valve 120 when the utilization side unit 100 stops or starts operating. iAs described above, even if the operating state changes, by maintaining the distribution ratio as much as possible, that is, maintaining the distribution ratio between the expansion valve openings of the expansion valve 120 corresponding to the appropriate state of the utilization side heat exchanger 110, the interference with the control caused by the change in the operating state can be suppressed. Here, as described above, the distribution ratio k i The sum of is set to 1, but it does not have to be 1, and can also be updated to different values ​​according to the operating state. i The calculation and determination method of is just one example, and the allocation controller 414 may use any method as long as the same solution as the above method can be obtained.

[0071] <Action Image>

[0072] Figure 4 This is a diagram showing the relationship between the degree of subcooling and the degree of superheat and time according to the first embodiment. Figure 4 (a) shows the subcooling and superheating of the refrigerant when the refrigerant quantity in the refrigerant circuit is appropriate. Figure 4 As shown in (a) of FIG1 , when the refrigerant circuit is appropriately charged with refrigerant, the subcooling degree of the refrigerant flowing out of the heat exchanger serving as the condenser converges to the optimal subcooling degree over time. Furthermore, the superheating degree of the refrigerant flowing out of the heat exchanger serving as the evaporator converges to the optimal superheating degree over time.

[0073] Figure 4 (b) shows the degree of subcooling and superheating when the refrigerant circuit is overcharged. Figure 4 If the refrigerant circuit is overfilled with refrigerant, as in (b), the superheat of the refrigerant flowing out of the heat exchanger serving as the evaporator becomes uncontrollable. However, the subcooling of the refrigerant flowing out of the heat exchanger serving as the condenser converges to the optimal subcooling over time. In the control processing unit 410 of the control device 400, the maximum selector 413 selects the larger total expansion valve opening, thereby accurately distributing the total expansion valve opening to the expansion valve openings of each expansion valve 120, enabling energy-saving control.

[0074] Figure 4 (c) shows the degree of subcooling and superheating when the amount of refrigerant in the refrigerant circuit is insufficient. Figure 4 As in (c) of Figure 1, if the refrigerant quantity in the refrigerant circuit is insufficient, the subcooling of the refrigerant flowing out of the heat exchanger serving as the condenser becomes uncontrollable. However, the superheat of the refrigerant flowing out of the heat exchanger serving as the evaporator converges to the optimal superheat over time. Therefore, the controller 400 can perform energy-saving control.

[0075] Figure 5: is a diagram showing an image of the distribution processing operation in the air conditioning apparatus 1 according to Embodiment 1. Figure 5 At time T, the superheat of the refrigerant flowing out of the utilization side heat exchanger 110a exceeds the threshold value, and therefore, the distribution ratio k of the refrigerant passing through each expansion valve 120 is updated. i The distribution controller 414 controls the expansion valve 120a to open by 10%. In addition, the distribution controller 414 controls the expansion valve 120b and the expansion valve 120c to close by 5%, for example. In this way, the distribution controller 414 controls the distribution of the expansion valve openings at each expansion valve 120, such as Figure 5 As shown in (a), the superheat of the refrigerant flowing out of the utilization side heat exchanger 110a decreases and converges to a value below the threshold. Figure 5 (b) and Figure 5 As shown in (c), the superheat of the refrigerant flowing out of the use-side heat exchanger 110b and the use-side heat exchanger 110c increases slightly, but converges below the threshold value, and the state of the refrigerant is stable.

[0076] <Effects of the air-conditioning apparatus 1 in Embodiment 1>

[0077] As described above, in the air-conditioning apparatus 1 according to Embodiment 1, within the control processing unit 410 of the control device 400, the first controller 411 includes a subcooling controller 415 that calculates the heat-source-side total expansion valve opening based on the subcooling of the refrigerant flowing out of the heat-source-side heat exchanger 230. Furthermore, the second controller 412 includes a superheat controller 416 that calculates the utilization-side total expansion valve opening based on the superheat of the refrigerant flowing out of each utilization-side heat exchanger 110. The maximum selector 413 compares the heat-source-side total expansion valve opening with the heat-source-side total expansion valve opening and outputs the larger value as the maximum total expansion valve opening. The distribution controller 414 distributes the maximum total expansion valve opening to each expansion valve 120, thereby determining the opening of each expansion valve 120. Therefore, the air-conditioning apparatus 1 according to Embodiment 1 can maintain efficient operation even under conditions of overcharging or undercharging of the refrigerant.

[0078] For example, typically, in a multi-type refrigeration cycle system such as an air-conditioning apparatus 1 having an accumulator 240 as in Embodiment 1, the subcooling of the refrigerant flowing to the corresponding utilization-side heat exchanger 110 is controlled based on the expansion valve opening of each expansion valve 120. However, if the amount of refrigerant in the refrigerant circuit is insufficient, even if the expansion valve opening of expansion valve 120 is reduced, the subcooling will not be increased, and subcooling control becomes impossible. Consequently, the appropriate expansion valve opening of expansion valve 120 cannot be determined. Furthermore, if the amount of refrigerant in the refrigerant circuit is insufficient, the amount of refrigerant flowing to the utilization-side heat exchanger 110, which serves as the evaporator, is insufficient, potentially leading to capacity deficiency. Therefore, as in the air-conditioning apparatus 1 of Embodiment 1, the control processing unit 410 of the control device 400 selects a total expansion valve opening for determining the expansion valve opening in the next step based on the total expansion valve opening based on the subcooling and the total expansion valve opening based on the superheat. Therefore, if there is sufficient refrigerant in the refrigerant circuit, the control device 400 appropriately controls the subcooling degree, achieving highly efficient and energy-saving operation. On the other hand, under operating conditions where subcooling control is not possible due to insufficient refrigerant, for example due to long piping lengths, the control automatically and continuously switches to superheat-based control, suppressing increases in superheat. Furthermore, because the control processing device 410 determines the expansion valve opening of each expansion valve 120 to suppress increases in superheat, stable and efficient operation can be maintained.

[0079] In addition, the controller included in the control processing device 410 of the control device 400 in embodiment 1 is a continuous controller with an anti-integral windup function. Therefore, even when the amount of refrigerant in the refrigerant circuit is moderate and the object to be controlled is at the switching point between subcooling and superheating, the occurrence of instability can be suppressed. Therefore, the air conditioning device 1 can be operated stably. In addition, the superheat can be controlled to the upper limit superheat with high precision. Therefore, the rise in the discharge temperature of the refrigerant discharged by the compressor 210 can be suppressed, and the protection of the components in the refrigerant circuit can be achieved. In this way, not only the main subcooling control, but also the secondary control such as protection can be achieved by setting a continuous control such as PI control and combining the maximum selector 413, thereby achieving the above-mentioned effect.

[0080] Thus, in the air-conditioning apparatus 1 according to Embodiment 1, efficient operation can be maintained even when the refrigerant amount in the refrigerant circuit is insufficient. Furthermore, this demonstrates that efficient operation can be maintained even when the refrigerant circuit is reduced. Therefore, by reducing the refrigerant amount, an inexpensive and efficient multi-type refrigeration cycle apparatus can be provided.

[0081] Next, the case where the refrigerant circuit is overfilled with refrigerant will be described. In a multi-type refrigeration cycle device, superheat is sometimes controlled by the expansion valve 120. However, if the refrigerant in the refrigerant circuit is overfilled, the superheat cannot be controlled without extremely throttling the expansion valve 120, and energy saving will be reduced. If the refrigerant is overfilled, the total expansion valve opening on the heat source side obtained by the output of the subcooling controller 415, which is determined based on the subcooling, is larger than the total expansion valve opening on the heat source side obtained by the output of the superheat controller 416 based on the superheat. In the air conditioning device 1 in embodiment 1, the distribution controller 414 distributes the expansion valve openings of each expansion valve 120 based on the larger total expansion valve opening selected by the maximum selector 413, thereby performing subcooling control. As a result, more efficient operation can be achieved.

[0082] Furthermore, in the air conditioning apparatus 1 according to the first embodiment, the distribution ratio k performed by the distribution controller 414 is i The update is performed only when the superheat of the refrigerant passing through the heat exchanger is greater than the set threshold value. Generally speaking, it is difficult to perform high-precision superheat control in a multi-type refrigeration cycle device. The reasons for this include nonlinearity caused by changes in the number of operating units or load changes of each utilization-side heat exchanger 110. Furthermore, this is because it is a multi-input and multi-output system in which the action of a certain expansion valve 120 affects the superheat of all utilization-side heat exchangers 110. In addition, appropriate target values ​​need to be assigned to various operating states, which also makes control design difficult. Therefore, the air-conditioning device 1 of embodiment 1 updates the distribution ratio k by the distribution controller 414 only when the superheat is greater than the specified threshold value. i . In addition, the superheat controller 416 that controls the maximum value, minimum value or average value of the superheat of the refrigerant passing through each utilization side heat exchanger 110 is combined with the distribution controller 414. Therefore, the robustness against environmental changes such as the refrigerant amount, setting conditions or operating status becomes higher, and the stability of the superheat is improved, thereby suppressing the occurrence of instability. In this way, since high robustness can be obtained by relying on the structure of the control processing device 410 itself, the control design burden can be reduced. In addition, the designer only needs to assign a specified threshold value. Therefore, the design burden can be further reduced. This is an effect that cannot be achieved when the superheat controller 416 or the distribution controller 414 is set as a single structure.

[0083] In the air conditioning apparatus 1 according to the first embodiment, the control device 400 uses the distribution ratio k i By controlling and managing the expansion valve opening of each expansion valve 120, the increase or decrease of the expansion valve opening can be controlled proportionally. Therefore, the expansion valve opening can maintain a linear relationship with the refrigerant flow rate, making it easy to control. iManaging the expansion valve openings simplifies responding to the operation or shutdown of the utilization-side unit 100 having the utilization-side heat exchanger 110. In particular, by designing the expansion valves 120 to maintain the distribution ratio as much as possible without requiring a change in the distribution ratio, it is possible to minimize disturbances to the refrigeration cycle caused by protective actions and changes in operating conditions.

[0084] In addition, the first controller 411 and the second controller 412 have a PI controller 417 for performing feedback control. In controllers such as the PI controller 417 that are established in control engineering, the method of designing parameters has been established through a large amount of existing research. Therefore, in the air-conditioning device 1 of embodiment 1, the design burden of the controller that controls superheat or subcooling can be reduced. For example, as a design method for controller parameters, a design method that relies on the results of system equivalence recognition of step responses can be considered. Basically, the parameters are calculated in a mathematical order based on the characteristics obtained through system equivalence recognition, but the parameters of the controller can also be learned based on the input and output data input and output in the controller when the air-conditioning device 1 is actually operating. Here, regarding system equivalence recognition, it is not limited to online equivalence recognition or offline equivalence recognition.

[0085] Implementation method 2.

[0086] Figure 6 This is a diagram showing the configuration of the control processing device 410 in the second embodiment. Figure 6 The control processing unit 410 of the control device 400 controls the opening of each expansion valve. Figure 6 As shown, 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, similarly to Embodiment 1. As described in the first embodiment, the maximum selector 413 compares the heat source side total expansion valve opening value output by the first controller 411 with the heat source side total expansion valve opening value output by the second controller 412, and outputs the larger value as the maximum total expansion valve opening.

[0087] Here, in the air conditioning apparatus 1 in the second embodiment, a case where the heating operation is performed in which the utilization side heat exchanger 110 functions as a condenser and the heat source side heat exchanger 230 functions as an evaporator is described. Figure 6 As shown, in the control processing device 410 , the first controller 411 includes a superheat controller 416 , and the second controller 412 includes a subcooling controller 415 .

[0088] The subcooling controller 415 in Embodiment 2 outputs a total expansion valve opening that causes the maximum subcooling degree among the subcooling degrees of the refrigerant flowing out of each utilization-side heat exchanger 110 to track the target subcooling degree. Furthermore, the subcooling controller 415 in Embodiment 2 receives input signals from the high-pressure pressure sensor 510 and the liquid pipe temperature sensors 550 of each utilization-side heat exchanger. Furthermore, the control output of the subcooling control is not limited to the maximum subcooling degree; it can also be the minimum value. Alternatively, a statistical value obtained by statistically processing multiple subcooling degrees, such as an average value or median value, can be used. Furthermore, since the subcooling degree does not assume a value less than zero, values ​​below a certain threshold can also be treated as abnormal values.

[0089] On the other hand, the superheat controller 416 in the second embodiment performs calculations and outputs a total expansion valve opening that causes the superheat of the refrigerant flowing out of the heat source side heat exchanger 230 to track the superheat upper limit. Furthermore, the superheat controller 416 in the first embodiment receives input signals from the low pressure sensor 520 and the heat source side heat exchanger gas pipe temperature sensor 530.

[0090] The distribution controller 414 distributes the maximum total expansion valve opening output from the maximum selector 413 to each expansion valve 120 in the same manner as in the first embodiment, and determines the expansion valve opening at each expansion valve 120. However, since the air conditioning apparatus 1 of the second embodiment performs heating operation, the distribution controller 414 performs processing different from that of the first embodiment. The distribution processing sequence performed by the distribution controller 414 in the second embodiment will be described. Set U = {1, 2, ..., n} is set as the set of serial numbers of the utilization side heat exchangers. Here, n is the number of connected utilization side heat exchangers 110. In addition, Let be the set of serial numbers of the heat exchangers on the utilization side that are in operation. Let be the set of the serial numbers of the heat exchangers on the utilization side whose subcooling degree is less than the lower subcooling degree threshold (SCi<2, i∈V). Let C = {i∈V} be the set of user-side heat exchanger numbers whose subcooling exceeds the upper subcooling threshold (SCi>9, i∈V). Here, SCi is the subcooling of user-side heat exchanger number i. Furthermore, let C = {i∈V} be the set of user-side heat exchanger numbers whose subcooling falls within the appropriate range. Here, i in set C does not belong to set A or set B.

[0091] The distribution controller 414 maintains the distribution ratio k having the characteristic represented by equation (1) as in the first embodiment. i (i∈V). And, the allocation controller 414 allocates the i , the expansion valve opening of each expansion valve 120 is calculated according to the aforementioned formula (2).

[0092] Furthermore, the distribution controller 414 updates the distribution ratio k at intervals of, for example, 1 minute. i However, the timing of the update process is not limited to this. If the distribution controller 414 determines that the subcooling degree of a certain utilization side heat exchanger 110 is smaller than the set lower limit subcooling degree threshold (for example, 2K), then if there is an excess amount of refrigerant flowing in the utilization side heat exchanger 110, the distribution ratio k of the corresponding expansion valve 120 is reduced. i When the distribution ratio ki decreases, the expansion valve opening of the expansion valve 120 decreases, and the amount of refrigerant flowing to the utilization side heat exchanger 110 decreases.

[0093] If the distribution controller 414 determines that the degree of subcooling of a certain utilization side heat exchanger 110 is greater than the set upper limit of subcooling (e.g., 9K), it means that there is insufficient refrigerant flow in the utilization side heat exchanger 110, and increases the distribution ratio k of the corresponding expansion valve 120. i If the distribution ratio k i As the pressure increases, the expansion valve opening of the expansion valve 120 increases, thereby increasing the amount of refrigerant flowing to the utilization side heat exchanger 110.

[0094] Next, the allocation ratio k i Here, the step at the time of the last update is set as k, and the step at the time of this update is set as k+1. First, when all the utilization side heat exchangers 110 are in the same state, the distribution ratio k is not set. i The same state means that V=A or V=B or V=C (this is condition a). The distribution ratio k involved in this update i (k+1) can use the allocation ratio k involved in the last update i (k) is represented by the aforementioned formula (3).

[0095] On the other hand, when the utilization side heat exchanger 110 does not satisfy condition a and there is no utilization side heat exchanger 110 with a subcooling degree within the appropriate range, that is, when V≠A, V≠B, and V≠C=φ (empty set) are satisfied (this is referred to as condition b), the distribution ratio k is determined according to the case. i . The distinction is made based on the number of elements.

[0096] When |A|<|B|, the distribution ratio k of the expansion valve opening degree at each expansion valve 120 is updated based on the following equation (8): i .

[0097]

[0098] Next, when |A|≥|B|, the distribution ratio k of the expansion valve opening degree at each expansion valve 120 is updated based on the following equation (9): i .

[0099]

[0100] Finally, when neither condition a nor condition b is satisfied, that is, when V≠A and V≠B and V≠C and C≠φ, the distribution ratio k of the expansion valve opening at each expansion valve 120 is updated based on the following equation (10): i .

[0101]

[0102] As described above, the distribution ratio k is updated by the distribution controller 414. i , the expansion valve opening of the expansion valve 120 corresponding to the utilization side heat exchanger 110 in a state with less refrigerant is relatively increased, and the amount of refrigerant passing through the utilization side heat exchanger 110 is increased. Therefore, the expansion valve opening of the expansion valve 120 corresponding to the utilization side heat exchanger 110 in a state with more refrigerant is relatively decreased, and the amount of refrigerant passing through the utilization side heat exchanger 110 is reduced. In addition, the expansion valve opening of the expansion valve 120 corresponding to the utilization side heat exchanger 110 in an appropriate state where the amount of refrigerant passing through is neither too much nor too little is changed in a manner that maintains the mutual opening ratio and maintains the total expansion valve opening. Here, in equations (8) to (10), it is set to increase or decrease the expansion valve opening of the expansion valve 120 corresponding to the utilization side heat exchanger 110 by 10%, but it is not limited to 10%. In addition, the ratio of increase or decrease may not be constant. In addition, the distribution ratio k according to the number of elements of the set under condition b is explained. i The method of determining the situation is distinguished by the occasion to switch the method, but it is not limited to this. The conditions can also be reversed, and switching can also be performed not based on the number of elements.

[0103] When the utilization side unit 100 is stopped after operation or when the utilization side unit 100 starts to operate after stopping, the distribution ratio k at each expansion valve 120 is determined by the distribution controller 414. iThe determination and other processes are the same as those described in the first embodiment. However, during the heating operation, if the expansion valve opening of the expansion valve 120 corresponding to the stopped utilization-side heat exchanger 110 is completely closed, the refrigerant may sometimes accumulate in the utilization-side heat exchanger 110. Therefore, the expansion valve opening of the expansion valve 120 may sometimes become slightly open. Even if the expansion valve opening of the expansion valve 120 is slightly open, there is no problem as long as it has almost no effect on the amount of refrigerant passing through the utilization-side heat exchanger 110 of the utilization-side unit 100 in operation. In cases where the influence cannot be ignored, the distribution ratio k corresponding to the slightly open opening is set. i , achieving the distribution ratio k i Extension of the determination method.

[0104] <Effects of the Air Conditioning Apparatus 1 in Embodiment 2>

[0105] As described above, in the air-conditioning apparatus 1 according to Embodiment 2, the control processing unit 410 of the control device 400 includes a subcooling controller 415 and a distribution controller 414. By combining the subcooling controller 415 and the distribution controller 414, it is possible to control the maximum, minimum, or average value of each subcooling degree according to the total expansion valve opening. Consequently, the subcooling degree of each utilization-side heat exchanger 110 can be maintained within an appropriate range, enabling efficient operation. This is an effect that cannot be achieved when the subcooling controller 415 or the distribution controller 414 is configured as a single unit.

[0106] In the air conditioning apparatus 1 according to the second embodiment, the distribution ratio k i The update is performed only when the subcooling degree of the refrigerant passing through the heat exchanger is outside the set prescribed range. Generally speaking, it is difficult to perform high-precision subcooling control in a multi-type refrigeration cycle device. The reasons for this include nonlinearity caused by changes in the number of operating units or load changes of each utilization-side heat exchanger 110. Furthermore, this is because it becomes a multi-input and multi-output system in which the action of a certain expansion valve 120 affects the subcooling degree of all utilization-side heat exchangers 110. In addition, appropriate target values ​​need to be assigned to various operating states, which also makes control design difficult. Therefore, the air-conditioning device 1 of embodiment 2 updates the distribution ratio k by the distribution controller 414 only when the subcooling degree is outside the prescribed range. i. In addition, a subcooling controller 415 for controlling the maximum value, minimum value or average value of the subcooling of the refrigerant passing through each utilization side heat exchanger 110 is combined with the distribution controller 414. Therefore, the robustness against environmental changes such as the refrigerant amount, setting conditions or operating status becomes higher, and the stability of the subcooling is improved, thereby suppressing the occurrence of instability. In this way, since high robustness can be obtained by relying on the structure of the control processing device 410 itself, the control design burden can be reduced. In addition, the designer only needs to assign a specified threshold value. Therefore, the design burden can be further reduced.

[0107] Implementation method 3.

[0108] Figure 7 This is a diagram showing the configuration of the control processing device 410 in the third embodiment. Figure 7 FIG. 4 shows a portion of the control of the air conditioning apparatus 1 by the control processing device 410 of the control device 400, which controls the opening degree of each expansion valve. Figure 7 Regarding the Figure 3 The components with the same reference numerals basically perform the same processing operations as those described in the first embodiment. Figure 7 As shown, the control device 400 according to the third embodiment also includes a first controller 411 , a second controller 412 , a maximum selector 413 , and a distribution controller 414 , similarly to the control device 400 according to the first embodiment.

[0109] Here, the subcooling controller 415 of the first controller 411 in Embodiment 3 has a validity determination function. The subcooling controller 415 determines that the controller is valid if the subcooling degree is greater than a set subcooling degree threshold (e.g., 2K), and invalid if the subcooling degree is below the set subcooling degree threshold. Furthermore, the superheat controller 416 of the second controller 412 in Embodiment 3 also has a validity determination function. The subcooling controller 415 determines that the controller is valid if the superheat degree is greater than a set superheat degree threshold (e.g., 2K), and invalid if the superheat degree is below the set superheat degree threshold.

[0110] In addition, the control device 400 of embodiment 3 further includes a throttling controller 418. The throttling controller 418 has a function of controlling the throttling 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 throttling controller 418 calculates the total expansion valve opening based on the following equation (11). Here, ΔS is a predetermined amount of change in the opening. In addition, the step at the time of the previous update is set to k, and the step at the time of this update is set to k+1. The data related to step k is stored, for example, in the storage device 430.

[0111] S total (k+1)=Stotal (k)-ΔS …(11)

[0112] Throttle controller 418 also has a validity / invalidity determination function. Based on the aforementioned validity / invalidity determination, if both superheat controller 416 and subcooling controller 415 are determined to be invalid, the controller is determined to be valid. Otherwise, the controller is determined to be invalid. Furthermore, when the subcooling controller 415 and the superheat controller 416 transition from invalid to valid, the controller adjusts the integral value, etc., to produce a bumpless change.

[0113] Here, the above formula (11) is an example of calculation in which ΔS is a constant value and the expansion valve opening is changed at a constant speed. However, it is not necessary to have a constant speed. For example, it is also possible to change the expansion valve opening S with respect to the starting opening S. s and convergence opening S t Set the convergence time T and calculate the opening change ΔS according to the following formula (12). c By setting the opening change ΔS as in equation (12), the time from start-up to convergence can be designed.

[0114]

[0115] The convergence opening S in formula (12) t It is actually an unknown value. Therefore, the throttle controller 418 estimates and calculates the convergence opening S based on the following equation (13), for example. t The refrigerant flow rate G is calculated by the expansion valve opening S, the high and low pressure difference dP, and the refrigerant density ρ at the expansion valve inlet. l , compressor speed F, compressor suction refrigerant density ρ g And constants (C1, C2) are expressed by the following formula (13).

[0116]

[0117] Based on equation (13), the expansion valve opening S is expressed by the following equation (14): Here, C is a constant.

[0118]

[0119] Since the compressor speed F is controlled by the control device 400, the throttle controller 418 can obtain it from the internal information. g , ρ l), can be estimated using the design value, compressor 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 pressure difference dP becomes larger. In addition, when the thermal resistance of the heat exchanger is large, the high-low pressure difference dP also becomes larger. Furthermore, when the compressor speed F is high, the high-low pressure difference dP also becomes larger. In addition, when the compressor speed F is high, when the suction temperature of the evaporator is low, or when the thermal resistance of the evaporator is large, the compressor suction refrigerant density ρ g Become smaller.

[0120] As described above, the parameters are estimated based on the operating state, and the compressor speed F or the compressor suction refrigerant density ρ g When it becomes larger, the opening S will converge t If the setting is large, the compressor speed F or the compressor suction refrigerant density ρ g When it becomes smaller, the opening S will converge t In addition, when the high and low pressure difference dP becomes larger, the convergence opening S t If the setting is small, the opening S will be narrowed when the high and low pressure difference dP becomes smaller. t Set it big.

[0121] According to the above configuration, the convergence opening S can be estimated. t Here, if the compressor speed F and other parameters are allowed to change at any time, the convergence opening S t The value of also changes with time. As a result, it should be noted that the opening change amount ΔS also changes with time.

[0122] Next, an example in which the throttling speed is not constant is described. As a characteristic of the expansion valve 120 that is brought to the system, there is a tendency that the larger the expansion valve opening S is, the smaller the impact on the system is. For example, if the expansion valve opening S adopts a value of 0 to 1000, the impact on the system will be greater when the expansion valve opening S is changed from 10 to 11 than when the expansion valve opening S is changed from 900 to 901. Therefore, it is considered to increase the opening change ΔS when the expansion valve opening S is large, and to reduce the opening change ΔS when the expansion valve opening S is small. For example, based on the following formula (15), the opening change ΔS is updated in a manner proportional to the current expansion valve opening S.

[0123] ΔS=-S(k)*(e α -1) …(15)

[0124]

[0125] By calculating the opening change ΔS as shown in equation (15), the opening change ΔS is proportional to the current expansion valve opening S, and the impact on the system can be kept constant. Furthermore, by setting α as shown in equation (15), the time T from startup to reaching a convergent opening can be designed. While the description herein is based on the case where the air-conditioning apparatus 1 is performing cooling operation, the application is also possible for heating operation.

[0126] Furthermore, in addition to the above, the opening change ΔS can also be determined based on the refrigerant temperature. For example, when the air-conditioning apparatus 1 is started up, the discharge temperature of the compressor 210 may rise sharply after startup, depending on the initial refrigerant distribution or the startup opening. Therefore, when the control device 400 detects a sharp rise in the discharge temperature, the throttle controller 418 can also respond by, for example, slowing down the opening change ΔS. By slowing down the opening change ΔS, operation stops due to excessive increases in discharge temperature are avoided, and stable operation can be quickly achieved.

[0127] <Effects of the air-conditioning apparatus 1 in Embodiment 3>

[0128] As described above, in the air-conditioning apparatus 1 of Embodiment 3, the control processing unit 410 of the control device 400 includes a throttle controller 418 for controlling the opening variation ΔS of the total expansion valve opening. Furthermore, when the total expansion valve opening based on the subcooling and superheating values ​​obtained by the first controller 411 and the second controller 412 is invalid, the throttle controller 418 controls the total expansion valve opening. Consequently, the air-conditioning apparatus 1 of Embodiment 3 can shorten the time from startup to stabilization of operation, enabling rapid heating or cooling. For example, in a multi-type refrigeration cycle apparatus that controls subcooling or superheating, rapid responsiveness is difficult to achieve because these values ​​do not take values ​​less than 0. However, as in the air-conditioning apparatus 1 of Embodiment 3, the control processing unit 410 of the control device 400 effectively utilizes the throttle controller 418 and the validity / invalidity determination functions of the first controller 411 and the second controller 412, thereby achieving desired responsiveness.

[0129] Industrial Applicability

[0130] In Embodiments 1 to 3, an air conditioning apparatus is described as an example of a multi-type refrigeration cycle apparatus, but the present invention is not limited thereto and can be applied to other multi-type refrigeration cycle apparatuses such as refrigeration apparatuses and cooling apparatuses that cool heat supply objects.

[0131] Description of Reference Signs

[0132] 1 Air conditioning device, 100, 100a, 100b, 100c utilization side unit, 110, 110a, 110b, 110c utilization 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 piping, 400 control device, 410 control processing device, 411 first controller, 412 second controller Controller, 413 maximum selector, 414 distribution controller, 415 subcooling controller, 416 superheat controller, 417 PI controller, 418 throttling controller, 420 timing device, 430 storage device, 510 high-pressure pressure sensor, 520 low-pressure 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 utilization side heat exchanger liquid pipe temperature sensor, 560, 560a, 560b, 560c utilization side heat exchanger gas pipe temperature sensor.

Claims

1. A multi-type refrigeration cycle device, comprising a refrigerant circuit and a control device for controlling components within the device, wherein the refrigerant circuit is configured by connecting a compressor, a heat source side heat exchanger, a plurality of expansion valves, and a plurality of utilization side heat exchangers connected in series to the expansion valves via piping, thereby circulating the refrigerant. The control device has: a first controller that calculates a total expansion valve opening of the expansion valve so that a heat source side state value of the refrigerant flowing out of the heat source side heat exchanger follows a heat source side target state value, and outputs the calculated total expansion valve opening as a heat source side total expansion valve opening; a second controller for calculating the total expansion valve opening of the expansion valves so that the utilization-side state value of the refrigerant flowing out of each of the plurality of utilization-side heat exchangers follows a utilization-side target state value, and outputting the calculated total expansion valve opening as the utilization-side total expansion valve opening; a maximum selector for selecting one of the heat source side total expansion valve opening and the utilization side total expansion valve opening as a maximum total expansion valve opening; as well as a distribution controller for distributing the maximum total expansion valve opening to the expansion valve openings of the respective expansion valves; The distribution controller distributes the maximum total expansion valve opening based on a comparison between the utilization side state value of the refrigerant flowing out of each of the utilization side heat exchangers and a set threshold value, and according to a distribution ratio that relatively changes in the opening of each of the expansion valves corresponding to each of the utilization side heat exchangers.

2. The multi-type refrigeration cycle device according to claim 1, wherein: During the cooling operation in which the heat supply target is cooled by heat exchange with the refrigerant in the utilization side heat exchanger, The first controller calculates the opening of the heat source side total expansion valve using the subcooling degree of the refrigerant flowing out of the heat source side heat exchanger as the heat source side state value. The second controller uses a value obtained based on the superheat of the refrigerant flowing out of the plurality of the utilization-side heat exchangers as the utilization-side state value, and calculates the utilization-side total expansion valve opening so that the maximum value or the minimum value among the superheats of the refrigerant flowing out of the plurality of the utilization-side heat exchangers, or a statistical value obtained by statistically processing the plurality of superheats, follows an upper limit superheat. The maximum selector compares the heat source side total expansion valve opening with the utilization side total expansion valve opening. If the heat source side total expansion valve opening is larger, the heat source side total expansion valve opening is selected as the maximum total expansion valve opening. If the utilization side total expansion valve opening is larger, the utilization side total expansion valve opening is selected as the maximum total expansion valve opening. The distribution controller sets the distribution ratio so that the opening degree of the expansion valve corresponding to the usage-side heat exchanger from which the degree of superheat of the refrigerant flowing out is equal to or greater than the threshold value is relatively increased.

3. The multi-type refrigeration cycle device according to claim 1, wherein: During the heating operation in which the heat supply target is heated by heat exchange with the refrigerant in the utilization side heat exchanger, The first controller uses the superheat of the refrigerant flowing out of the heat source side heat exchanger as the heat source side state value and calculates the opening of the heat source side total expansion valve so as to follow the upper limit of superheat. The second controller uses a value obtained based on the subcooling degree of the refrigerant flowing out of the plurality of the utilization-side heat exchangers as the utilization-side state value, and calculates the utilization-side total expansion valve opening so that the maximum value or the minimum value among the subcooling degrees of the refrigerant flowing out of the plurality of the utilization-side heat exchangers, or a statistical value obtained by statistically processing the plurality of subcooling degrees, follows the lower limit subcooling degree. The maximum selector compares the heat source side total expansion valve opening with the utilization side total expansion valve opening. If the utilization side total expansion valve opening is larger, the utilization side total expansion valve opening is selected as the maximum total expansion valve opening. If the heat source side total expansion valve opening is larger, the heat source side total expansion valve opening is selected as the maximum total expansion valve opening. The distribution controller sets the distribution ratio so as to relatively increase or decrease the opening of the expansion valve corresponding to the utilization-side heat exchanger so that the subcooling degree of the outflowing refrigerant is within a range of a set upper subcooling degree threshold and a lower subcooling degree threshold.

4. The multi-type refrigeration cycle device according to claim 2, wherein: During the cooling operation, the distribution controller increases the distribution ratio of the expansion valve opening of the expansion valve corresponding to the utilization-side heat exchanger having a superheat greater than the set superheat threshold so as to increase the expansion valve opening based on the current expansion valve opening, maintains the relationship between the expansion valve openings of the other expansion valves and reduces the distribution ratio relative to the total expansion valve opening.

5. The multi-type refrigeration cycle device according to claim 3, wherein: During the heating operation, the distribution controller is configured to reduce the distribution ratio so as to reduce the expansion valve opening based on the current expansion valve opening for the expansion valve opening corresponding to the utilization-side heat exchanger whose supercooling degree is smaller than the lower-limit supercooling degree threshold, and to increase the distribution ratio so as to increase the expansion valve opening based on the current expansion valve opening for the expansion valve opening corresponding to the utilization-side heat exchanger whose supercooling degree is larger than the upper-limit supercooling degree threshold. For the expansion valve openings of other expansion valves that do not fall into the above-mentioned situations, the relationship between the distribution ratios of the other expansion valves is maintained, and the distribution ratio relative to the total expansion valve opening is reduced.

6. The multi-type refrigeration cycle device according to any one of claims 1 to 5, wherein: The distribution controller changes the distribution ratio for the expansion valve corresponding to the utilization-side heat exchanger that stops heat exchange so that the expansion valve opening becomes a closed opening, and sets the distribution ratio for the expansion valve corresponding to the utilization-side heat exchanger that starts heat exchange so that the expansion valve opening becomes an average value of the distribution ratio.

7. The multi-type refrigeration cycle device according to any one of claims 1 to 6, wherein: The control device includes a throttling controller for throttling the opening of the total expansion valve by feedforward control. The first controller and the second controller have a validity determination function, which determines that the controller is valid if the degree of supercooling or superheating is greater than a set threshold, and invalid if the degree of supercooling or superheating is less than the set threshold. The throttle controller has the above-mentioned validity judgment function, and judges it as valid when both the first controller and the second controller are judged to be invalid, and judges it as invalid otherwise. The maximum selector selects a maximum value of the outputs of the first controller, the second controller, and the throttle controller, which are determined to be valid, as the maximum total expansion valve opening.

8. The multi-type refrigeration cycle device according to claim 7, wherein: The throttle controller performs control to reduce the expansion valve opening of the expansion valve at a constant speed.

9. The multi-type refrigeration cycle device according to claim 8, wherein: The throttle controller calculates a convergence opening, and calculates the constant speed based on a time until the set convergence opening is reached.

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

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

12. The multi-type refrigeration cycle device according to claim 9 or 11, wherein: The throttle controller calculates the convergent opening based on the rotation speed of the compressor, the density of the refrigerant sucked into the compressor, the high and low pressure difference in the refrigerant circuit, and the density of the refrigerant at the expansion valve inlet flowing into the expansion valve.

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