Refrigeration cycle device and method for controlling same

Abstract

This refrigeration cycle device comprises: a refrigerant circuit in which a compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger are connected by piping, and in which a refrigerant circulates; a blowout temperature detection unit that detects a blowout temperature, which is the air temperature after passing through the indoor heat exchanger; and a control processing device that controls the expansion valve, the control processing device being provided with a blowout temperature control unit that calculates and outputs a blowout temperature control opening degree, which is the opening degree of the expansion valve for matching the blowout temperature with a preset blowout temperature target value, by means of a controller including at least an integrator, and the control processing device controlling the expansion valve so as to achieve the blowout temperature control opening degree that is output from the blowout temperature control unit.

Description

Refrigeration cycle device and control method thereof

[0001] The present disclosure relates to a refrigeration cycle apparatus including a refrigerant circuit through which a refrigerant circulates, and a control method thereof.

[0002] Conventionally, there has been an air conditioner as a type of refrigeration cycle apparatus. For example, in an air conditioner disclosed in Patent Document 1, a target value of the degree of superheat is determined based on the discharge temperature and the target value of the discharge temperature, and the opening of an expansion valve is controlled so that the degree of superheat reaches the target value, thereby causing the discharge temperature to reach the target value of the discharge temperature.

[0003] Japanese Patent Application Laid-Open No. 2000-74519

[0004] The air conditioner of Patent Document 1 controls the discharge temperature by controlling the degree of superheat through control of the opening of the expansion valve, that is, the discharge temperature is indirectly controlled by controlling the opening of the expansion valve. In the air conditioner of Patent Document 1, while indirectly controlling the discharge temperature, hunting is likely to occur due to the small difference between the time constant of the response of the degree of superheat due to the control of the opening of the expansion valve and the time constant of the response of the discharge temperature due to the control of the degree of superheat.

[0005] Furthermore, in refrigeration cycle devices, it is required to improve the tracking ability of the discharge temperature to follow a target value and maintain a stable air conditioning capacity.

[0006] The present disclosure has been made in consideration of the above-mentioned points, and aims to provide a refrigeration cycle device and a control method thereof that can suppress hunting and maintain stable air conditioning capacity.

[0007] The refrigeration cycle device of the present disclosure comprises a refrigerant circuit in which a compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger are connected by piping and in which a refrigerant circulates, a discharge temperature detection unit that detects the discharge temperature, which is the temperature of air after passing through the indoor heat exchanger, and a control processing device that controls the expansion valve, and the control processing device comprises a discharge temperature control unit that calculates and outputs a discharge temperature control opening, which is the opening of the expansion valve to match the discharge temperature to a predetermined discharge temperature target value, using a controller that includes at least an integrator, and controls the expansion valve to achieve the discharge temperature control opening output from the discharge temperature control unit.

[0008] The refrigeration cycle device and the control method thereof according to the present disclosure can suppress hunting and maintain stable air conditioning capacity.

[0009] FIG. 1 is a schematic diagram showing an example of the configuration of a refrigeration cycle apparatus according to Embodiment 1. FIG. 2 is a control block diagram showing the electrical configuration of the indoor unit of FIG. 1. FIG. 3 is a functional block diagram showing an example of a portion related to expansion valve opening control in a control processing device of a refrigeration cycle apparatus according to Embodiment 1. FIG. 4 is a block diagram showing the configuration of a discharge temperature control unit of the refrigeration cycle apparatus according to Embodiment 1. FIG. 5 is a flowchart of an expansion valve opening control method in a refrigeration cycle apparatus according to Embodiment 1. FIG. 6 is a functional block diagram showing an example of a portion related to expansion valve opening control in a control processing device of a refrigeration cycle apparatus according to Embodiment 2. FIG. 7 is a block diagram showing the configuration of a liquid backflow prevention control unit of a refrigeration cycle apparatus according to Embodiment 2. FIG. 8 is a flowchart of an expansion valve opening control method in a refrigeration cycle apparatus according to Embodiment 2. FIG. 9 is a functional block diagram showing an example of a portion related to expansion valve opening control in a control processing device of a refrigeration cycle apparatus according to Embodiment 3. FIG. 10 is a block diagram showing the configuration of an anti-freeze control unit of a refrigeration cycle apparatus according to Embodiment 3. FIG. 11 is a flowchart of an expansion valve opening control method in a refrigeration cycle apparatus according to Embodiment 3. FIG. 12 is a functional block diagram showing an example of a portion related to expansion valve opening control in a control processing device of a refrigeration cycle apparatus according to Embodiment 4. 16 is a functional block diagram showing another example of a part relating to the opening control of the expansion valve in the control processing device of the refrigeration cycle device according to embodiment 4. FIG. 17 is a schematic diagram showing an example of the configuration of a refrigeration cycle device according to embodiment 5. FIG. 18 is a control block diagram showing the electrical configuration of the indoor unit of FIG. 15. FIG. 19 is a functional block diagram showing an example of a part relating to the opening control of the expansion valve in the control processing device of the refrigeration cycle device according to embodiment 5. FIG. 20 is a block diagram showing the configuration of a refrigerant noise prevention control unit of the refrigeration cycle device according to embodiment 5. FIG. 21 is a flowchart of an expansion valve opening control method in the refrigeration cycle device according to embodiment 5.

[0010] Hereinafter, a refrigeration cycle apparatus according to an embodiment of the present disclosure will be described with reference to the drawings. In the following drawings, the same reference numerals denote the same or equivalent parts, and this applies throughout the entire specification.

[0011] [Embodiment 1] Fig. 1 is a schematic diagram showing an example of the configuration of a refrigeration cycle apparatus 1 according to Embodiment 1. As shown in Fig. 1, the refrigeration cycle apparatus 1 includes an outdoor unit 2 and an indoor unit 3. The outdoor unit 2 includes a compressor 6, a flow path switching device 7, an outdoor heat exchanger 8, and an outdoor blower 8a. The indoor unit 3 includes an expansion valve 9, an indoor heat exchanger 10, and an indoor blower 10a. The refrigeration cycle apparatus 1 includes a refrigerant circuit A in which the compressor 6, the flow path switching device 7, the outdoor heat exchanger 8, the expansion valve 9, and the indoor heat exchanger 10 are connected by piping 14, and in which a refrigerant circulates.

[0012] 1 is the minimum configuration for realizing the refrigeration cycle according to the present disclosure, and may include, as necessary, an accumulator that is a liquid reservoir for storing refrigerant that was not completely gasified and prevents it from being sucked into the compressor 6. The refrigeration cycle apparatus 1 may also include an injection circuit that suppresses an excessive rise in the discharge temperature of the compressor 6, and a receiver circuit or power receiver circuit that stores excess refrigerant.

[0013] Each of the devices constituting the refrigeration cycle device 1 will be described below.

[0014] The compressor 6 compresses and discharges the drawn refrigerant. The compressor 6 may have a capacity that can be changed by, for example, arbitrarily changing the drive frequency using an inverter circuit (not shown). The capacity is the amount of refrigerant discharged per unit time.

[0015] The flow path switching device 7 is connected to the discharge side of the compressor 6 and switches the flow of the refrigerant discharged from the compressor 6. The flow path switching device 7 is, for example, a four-way valve, and switches the circulation direction of the refrigerant discharged from the compressor 6 between cooling operation and heating operation. The flow path switching device 7 switches the direction of the refrigerant toward the outdoor heat exchanger 8 during cooling operation, and switches the direction of the refrigerant toward the indoor heat exchanger 10 during heating operation. The flow path switching device 7 switches the flow path so that the indoor heat exchanger 10 serves as an evaporator and the outdoor heat exchanger 8 serves as a condenser during cooling operation, and vice versa during heating operation.

[0016] The outdoor heat exchanger 8 is, for example, a fin-tube heat exchanger including pipes through which a refrigerant flows and fins into which the pipes are inserted. The outdoor blower 8a is a fan that blows air to the outdoor heat exchanger 8. The outdoor blower 8a may be a fan whose air volume can be changed by arbitrarily changing the drive rotation speed using, for example, an inverter circuit (not shown). The air volume is the amount of air sent out per unit time.

[0017] The indoor heat exchanger 10 is, for example, a fin-tube heat exchanger configured to include piping through which a refrigerant flows and fins into which the piping is inserted. The indoor blower 10a is a fan that blows air into the indoor heat exchanger 10. The indoor blower 10a may be configured to change its air volume by arbitrarily changing its drive rotation speed using, for example, an inverter circuit (not shown). The air volume is the amount of air blown out per unit time.

[0018] The expansion valve 9 is provided in the piping on the refrigerant inlet side of the indoor heat exchanger 10 in the refrigerant flow during cooling operation. The expansion valve 9 expands the refrigerant. The expansion valve 9 is an electronic expansion valve with an adjustable opening. The opening of the expansion valve 9 is adjusted during cooling operation to adjust the evaporation temperature of the refrigerant in the indoor heat exchanger 10. By adjusting the evaporation temperature of the refrigerant, the degree of superheat SH of the refrigerant at the outlet of the indoor heat exchanger 10 is adjusted. Furthermore, the opening of the expansion valve 9 is adjusted during heating operation to adjust the condensation temperature of the refrigerant in the indoor heat exchanger 10. By adjusting the condensation temperature of the refrigerant, the degree of subcooling SC of the refrigerant at the outlet of the indoor heat exchanger 10 is adjusted. Note that, in the illustrated example, the expansion valve 9 is disposed in the indoor unit 3, but this is not limited to this configuration, and it may be disposed in the outdoor unit 2.

[0019] (Multiple Detectors) The refrigeration cycle apparatus 1 is equipped with multiple detectors. The refrigeration cycle apparatus 1 is equipped with a discharge temperature detector 11, a liquid pipe temperature detector 12, and a gas pipe temperature detector 13. The discharge temperature detector 11 is disposed at an air outlet (not shown) of the indoor unit 3, and detects the temperature of air discharged from the indoor unit 3. The discharge temperature detector 11 detects the discharge temperature, which is the temperature of air after passing through the indoor heat exchanger 10. The discharge temperature detector 11 is composed of a thermocouple, a thermistor, or the like. The detection result detected by the discharge temperature detector 11 is input to the indoor unit control device 5, which will be described later.

[0020] The liquid pipe temperature detection unit 12 is disposed in the indoor unit 3 and detects the temperature of the refrigerant flowing into the indoor heat exchanger 10 in the refrigerant flow direction during cooling operation, and detects the temperature of the refrigerant flowing out from the indoor heat exchanger 10 in the refrigerant flow direction during heating operation. The gas pipe temperature detection unit 13 is disposed in the indoor unit 3 and detects the temperature of the refrigerant flowing out from the indoor heat exchanger 10 in the refrigerant flow direction during cooling operation, and detects the temperature of the refrigerant flowing into the indoor heat exchanger 10 in the refrigerant flow direction during heating operation.

[0021] The liquid pipe temperature detection unit 12 and the gas pipe temperature detection unit 13 are configured with a thermocouple, a thermistor, etc. The results detected by these detection units are input to the indoor unit control device 5.

[0022] (Control Device) The refrigeration cycle apparatus 1 includes an outdoor unit control device 4 and an indoor unit control device 5. The outdoor unit control device 4 is disposed in the outdoor unit 2, and the indoor unit control device 5 is disposed in the indoor unit 3. The processing circuits of the outdoor unit control device 4 and the indoor unit control device 5 have the following configuration. The processing circuit of the control device is configured by dedicated hardware, or a CPU (Central Processing Unit, also called a central processing unit, processing device, arithmetic unit, microprocessor, microcomputer, or processor) that executes a program stored in memory.

[0023] When the processing circuit of the control device is dedicated hardware, the processing circuit may be, for example, a single circuit, a composite circuit, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof. In the control device, each functional unit realized by the processing circuit may be realized by a separate piece of hardware, or each functional unit may be realized by a single piece of hardware.

[0024] When the processing circuit of the control device is a CPU, each function executed by the processing circuit is realized by software, firmware, or a combination of software and firmware. The software and firmware are written as programs and stored in a memory unit. The CPU realizes each function of the processing circuit by reading and executing the programs stored in the memory unit. Note that some of the functions of the processing circuit may be realized by dedicated hardware and some by software or firmware.

[0025] As described above, the detection results of the detectors provided in the refrigeration cycle apparatus 1 are input to the indoor unit control device 5. Furthermore, the detection results are transmitted and received by wired or wireless communication between the control devices provided in the outdoor unit 2 and the indoor unit 3, and are shared. Although the above description shows a configuration in which each unit is provided with its own control device, this is not limiting. For example, the refrigeration cycle apparatus 1 may have the functions of each control device all installed in the outdoor unit 2 or the indoor unit 3.

[0026] Figure 2 is a control block diagram showing the electrical configuration of the indoor unit 3 of Figure 1. As shown in Figure 2, the indoor unit control device 5 is connected to a discharge temperature detection unit 11, a liquid pipe temperature detection unit 12, and a gas pipe temperature detection unit 13. The indoor unit control device 5 is configured to input the detection results of each of these detection units. In addition, user commands and the like are input to the indoor unit control device 5 via an operation unit (not shown).

[0027] The indoor unit control device 5 has a control processing device 51, a timing device 52, and a storage device 53. The control processing device 51 performs processes such as calculations and judgments based on the input temperature detection results, and controls the devices of the refrigeration cycle device 1, such as the expansion valve 9. The control processing device 51 performs an operation that maintains a stable air conditioning capacity without causing hunting of the discharge temperature. Details of this operation will be explained later.

[0028] The storage device 53 has data that is a program that describes the processing procedures to be performed by the control processing device 51. The storage device 53 has a volatile storage device (not shown) such as a random access memory (RAM) that can temporarily store data, a hard disk, and a non-volatile auxiliary storage device (not shown) such as a flash memory that can store data for the long term.

[0029] The timing device 52 is configured by, for example, a timer and is used for determining the time by the control processing device 51.

[0030] Each of the control processing device 51, the timing device 52, and the storage device 53 can be configured as dedicated equipment (hardware).

[0031] (Cooling Operation) The cooling operation of the refrigeration cycle apparatus 1 will be described with reference to Fig. 1. In the cooling operation, the flow path switching device 7 is switched to the state shown by the solid line in Fig. 1 .

[0032] The flow of the refrigerant will now be described. The gaseous refrigerant, compressed by the compressor 6 and becoming high-temperature and high-pressure, is discharged from the compressor 6 discharge port and flows into the outdoor heat exchanger 8. The gaseous refrigerant that flows into the outdoor heat exchanger 8 exchanges heat with air from the outdoor blower 8a, dissipates heat to the air, liquefies under high pressure, and flows out of the outdoor heat exchanger 8. The liquid refrigerant that flows out of the outdoor heat exchanger 8 is decompressed by the expansion valve 9, becomes a low-temperature two-phase refrigerant, and flows into the indoor heat exchanger 10. The low-temperature two-phase refrigerant that flows into the indoor heat exchanger 10 exchanges heat with air from the indoor blower 10a, absorbs heat from the air, vaporizes under low pressure, and flows out of the indoor heat exchanger 10. The gaseous refrigerant that flows out of the indoor heat exchanger 10 is drawn into the compressor 6 and compressed again. The refrigeration cycle apparatus 1 achieves the refrigeration cycle by repeating these operations.

[0033] (Heating Operation) The heating operation of the refrigeration cycle apparatus 1 will be described with reference to Fig. 1. In the heating operation, the flow path switching device 7 is switched to the state shown by the dotted line in Fig. 1 .

[0034] The flow of the refrigerant will now be described. The gaseous refrigerant, compressed by the compressor 6 and thus high in temperature and pressure, is discharged from the compressor 6's discharge port and flows into the indoor heat exchanger 10. The gaseous refrigerant that flows into the indoor heat exchanger 10 exchanges heat with air from the indoor blower 10a, dissipates heat to the air, liquefies under high pressure, and flows out of the indoor heat exchanger 10. The liquid refrigerant that flows out of the indoor heat exchanger 10 is decompressed by the expansion valve 9, becomes a low-temperature two-phase refrigerant, and flows into the outdoor heat exchanger 8. The low-temperature two-phase refrigerant that flows into the outdoor heat exchanger 8 exchanges heat with air from the outdoor blower 8a, absorbs heat from the air, vaporizes under low pressure, and flows out of the outdoor heat exchanger 8. The gaseous refrigerant that flows out of the outdoor heat exchanger 8 absorbs heat in the compressor 6 and is compressed again. The refrigeration cycle apparatus 1 achieves the refrigeration cycle by repeating these operations.

[0035] (Outline of Control) During cooling operation, the refrigeration cycle device 1 performs the following control to maintain a stable air conditioning capacity without causing hunting of the discharge temperature. Here, an outline of the control will be described.

[0036] The refrigeration cycle device 1 has a discharge temperature T ｏ The target temperature of the outlet T ｔｇｔ The opening degree of the expansion valve 9 (hereinafter referred to as the blowout temperature control opening degree) U Ｔｏ Calculate the target outlet temperature T ｔｇｔ may be a set temperature set by a user or may be a temperature stored in advance in the storage device 53. The refrigeration cycle device 1 calculates the calculated blowout temperature control opening degree U Ｔｏ The expansion valve 9 is controlled so that

[0037] The above control is repeatedly performed at each sampling time. ｏ The target temperature of the outlet T ｔｇｔ Control is implemented to follow the

[0038] Next, a specific control configuration for carrying out the above control will be described.

[0039] Fig. 3 is a functional block diagram showing an example of a portion related to the opening control of the expansion valve 9 in the control processing device 51 of the refrigeration cycle apparatus 1 according to Embodiment 1. Fig. 4 is a block diagram showing the configuration of the discharge temperature control unit 501 of the refrigeration cycle apparatus 1 according to Embodiment 1. As shown in Fig. 3, the control processing device 51 includes the discharge temperature control unit 501.

[0040] The blowout temperature control unit 501 controls the blowout temperature T ｏ and the target outlet temperature T ｔｇｔ Based on this, the outlet temperature T ｏ The target temperature of the outlet T ｔｇｔ The outlet temperature control opening U ＴｏThe blowout temperature control unit 501 is configured with a controller 511 including at least an integrator 501a. In this example, the blowout temperature control unit 501 is configured with a PI controller including a proportional unit 501b and an integrator 501a.

[0041] The blowout temperature control unit 501 calculates the blowout temperature T ｏ and the target outlet temperature T ｔｇｔ The temperature deviation ΔT ｏ The blowout temperature control unit 501 calculates the blowout temperature deviation ΔT as shown in equation (2). ｏ Using the discharge temperature T ｏ The target temperature of the outlet T ｔｇｔ The opening degree U of the expansion valve 9 for controlling the blowout temperature is Ｔｏ Calculate.

[0042]

[0043]

[0044] Here, K ＰＴｏ is the proportional gain of the PI controller, and K ＩＴｏ is the integral gain of the PI controller. ＰＴｏ and K. ＩＴｏ may be changed according to the temperature of the refrigerant flowing into the indoor heat exchanger 10 detected by the liquid pipe temperature detection unit 12.

[0045] The blowout temperature control unit 501 may be configured with a discrete position or velocity PI controller. The blowout temperature control unit 501 is not limited to a PI controller, and may be configured with a controller that performs feedback control including an integrator such as PID control or model predictive control.

[0046] The integrator 501a may have upper and lower limit values ​​or anti-reset windup to stop integration as shown in Figure 4. Note that U in Figure 4 denotes the final output after selection control or upper and lower limit selection. The anti-reset windup shown in Figure 4 is an example and is not limited to the one shown.

[0047] The indoor unit control device 5 determines the air outlet temperature control opening degree U Ｔｏ The expansion valve 9 is controlled so that

[0048] In this way, the refrigeration cycle device 1 has a discharge temperature T ｏ In controlling the temperature of the air, the refrigeration cycle device 1 controls the temperature of the air by controlling the opening degree of the expansion valve 9. ..., the refrigeration cycle device 1 controls the temperature of the air, the refrigeration cycle device 1 controls the temperature of the air, the refrigeration cycle device 1 controls the temperature of the air, the refrigeration cycle device Ｔｏ That is, the refrigeration cycle device 1 uses the blowout temperature T ｏ Therefore, the refrigeration cycle device 1 controls the discharge temperature T ｏ The target value of the outlet temperature T ｏ This allows for stable air conditioning capacity without hunting.

[0049] In the illustrated example, the refrigeration cycle apparatus 1 is configured such that the indoor unit control device 5 includes the control processing device 51, but is not limited to this configuration. The refrigeration cycle apparatus 1 may also be configured such that the outdoor unit control device 4 includes the control processing device 51. This also applies to the embodiments described below.

[0050] FIG. 5 is a flowchart of a method for controlling the opening degree of the expansion valve in the refrigeration cycle apparatus 1 according to the first embodiment.

[0051] As described above, the control processing device 51 controls the blowout temperature control opening degree U Ｔｏ (Step S1), and the expansion valve 9 is set to the blowout temperature control opening degree U Ｔｏ (Step S2).

[0052] The above control is repeatedly performed at each sampling time. ｏ The target temperature of the outlet T ｔｇｔ Control is implemented to follow the

[0053] In the first embodiment, the case of cooling operation has been described, but the target air outlet temperature T ｔｇｔare applicable as well, although modifications are required.

[0054] [Effects of the Refrigeration Cycle Apparatus 1] The refrigeration cycle apparatus 1 of the first embodiment includes a refrigerant circuit A in which a refrigerant circulates, in which a compressor 6, an outdoor heat exchanger 8, an expansion valve 9, and an indoor heat exchanger 10 are connected by a pipe 14. The refrigeration cycle apparatus 1 has a discharge temperature T ｏ The control processing device 51 includes a discharge temperature control unit 501. The discharge temperature control unit 501 detects the discharge temperature T ｏ The preset target temperature value T ｔｇｔ The opening degree of the expansion valve 9 for matching the discharge temperature control opening degree U Ｔｏ The control processing device 51 calculates and outputs the blowout temperature control opening degree U output from the blowout temperature control unit 501. Ｔｏ The expansion valve 9 is controlled so that

[0055] With the above configuration, the refrigeration cycle device 1 has a discharge temperature T ｏ This allows for stable air conditioning capacity to be maintained without hunting, enabling stable air conditioning control.

[0056] [Embodiment 2] In embodiment 2, the liquid refrigerant is prevented from returning to the compressor 6, i.e., the liquid backflow, while the discharge temperature T ｏ The following description will focus on the configuration of the second embodiment that is different from the first embodiment, and the configuration not described in the second embodiment is the same as that of the first embodiment.

[0057] (Control Overview) The refrigeration cycle device 1 prevents liquid backflow while controlling the outlet temperature T ｏ In order to maintain stable air conditioning capacity without causing hunting, the following control is performed. An overview of the control is explained below.

[0058] During cooling operation, the refrigeration cycle device 1 is configured to adjust the superheat degree SH of the refrigerant flowing out from the indoor heat exchanger 10 to a predetermined liquid backflow prevention superheat degree SH.ｍｉｎ Based on this, the superheat degree SH is set to prevent liquid backflow. ｍｉｎ Liquid backflow prevention control opening U ＳＨ Calculate the liquid backflow prevention superheat SH ｍｉｎ is stored in advance in the storage device 53. To prevent liquid backflow, a superheat degree of 0°C or more is required. ｍｉｎ is set to, for example, 2°C or more, taking into consideration sensor errors. Since liquid backflow is more likely to occur as the degree of superheat SH decreases, the liquid backflow prevention degree SH ｍｉｎ is the lower limit of the degree of superheat SH at which liquid backflow can be prevented.

[0059] Here, the degree of superheat SH decreases when the expansion valve opening is increased, and increases when the expansion valve opening is decreased. In addition, liquid backflow is more likely to occur when the expansion valve opening is increased, and is less likely to occur when the expansion valve opening is decreased. For this reason, when the expansion valve opening is greater than the liquid backflow prevention control opening U ＳＨ Therefore, the refrigeration cycle device 1 prioritizes preventing the liquid backflow, and opens the expansion valve 9 at the discharge temperature control opening degree U Ｔｏ and liquid backflow prevention control opening U ＳＨ That is, the refrigeration cycle device 1 controls the opening degree to the smaller of the liquid backflow prevention control opening degree U ＳＨ is used as the upper limit of the expansion valve opening.

[0060] By the above control, the refrigeration cycle device 1 is Ｔｏ Liquid backflow prevention control opening U ＳＨ If the opening degree of the expansion valve is larger than the liquid backflow prevention control opening degree U ＳＨ This controls the flow rate to prevent liquid backflow.

[0061] In addition, the refrigeration cycle device 1 has a blowout temperature control opening degree U Ｔｏ Liquid backflow prevention control opening U ＳＨ If it is smaller than the opening degree of the expansion valve, the opening degree of the blowout temperature control Ｔｏ The outlet temperature T ｏ The target temperature of the outlet T ｔｇｔ This allows the refrigeration cycle device 1 to maintain a stable air conditioning capacity.

[0062] Next, a specific control configuration for carrying out the above control will be described.

[0063] Fig. 6 is a functional block diagram showing an example of a portion related to the opening control of the expansion valve 9 in the control processing device 51 of the refrigeration cycle apparatus 1 according to embodiment 2. Fig. 7 is a block diagram showing the configuration of the liquid backflow prevention control unit 502 of the refrigeration cycle apparatus 1 according to embodiment 2. As shown in Fig. 6, the control processing device 51 includes a superheat degree calculation unit 500, a discharge temperature control unit 501, a liquid backflow prevention control unit 502, and a first selection unit 503.

[0064] The superheat degree calculation unit 500 calculates the superheat degree SH. The superheat degree calculation unit 500 calculates the superheat degree SH of the refrigerant flowing out from the indoor heat exchanger 10 during cooling operation. The superheat degree SH is calculated as the difference between the liquid pipe temperature detected by the liquid pipe temperature detection unit 12 and the gas pipe temperature detected by the gas pipe temperature detection unit 13. The superheat degree SH may be calculated as the difference between the compressor suction gas temperature, which is obtained by converting the pressure of the refrigerant suctioned into the compressor 6 into a saturated gas temperature, and the liquid pipe temperature or evaporation temperature detected by the liquid pipe temperature detection unit 12.

[0065] The liquid backflow prevention control unit 502 calculates the superheat degree SH and the liquid backflow prevention superheat degree SH. ｍｉｎ Based on this, the superheat degree SH is set to prevent liquid backflow. ｍｉｎ Liquid backflow prevention control opening U ＳＨ The backflow prevention control unit 502 is configured with a controller 512 including at least an integrator 502a. In this example, the backflow prevention control unit 502 is configured with a PI controller including a proportional unit 502b and an integrator 502a.

[0066] The liquid backflow prevention control unit 502 calculates the superheat degree SH and the liquid backflow prevention superheat degree SH as shown in equation (3). ｍｉｎ The liquid backflow prevention control unit 502 calculates the superheat degree deviation ΔSH between the liquid backflow prevention superheat degree SH and the liquid backflow prevention superheat degree SH by using the superheat degree deviation ΔSH as shown in equation (4). ｍｉｎ The expansion valve 9 is opened to prevent liquid backflow. ＳＨ Calculate.

[0067]

[0068]

[0069] Here, K ＰＳＨ is the proportional gain of the PI controller, and K ＩＳＨ is the integral gain of the PI controller.

[0070] The backflow prevention control unit 502 may be configured with a discrete position or velocity PI controller. The backflow prevention control unit 502 is not limited to a PI controller, and may be configured with a controller that performs feedback control including an integrator such as PID control or model predictive control.

[0071] The integrator 502a may have upper and lower limit values ​​or anti-reset windup that stop integration as shown in Figure 7. Note that U in Figure 7 denotes the final output after selection control or upper and lower limit selection. The anti-reset windup shown in Figure 7 is an example and is not limited to the one shown.

[0072] Liquid back prevention superheat degree SH ｍｉｎ may be set to different values ​​at the start-up and during normal operation of the refrigeration cycle apparatus 1. Specifically, the liquid backflow prevention superheat degree SH at the start-up ｍｉｎ is the liquid backflow prevention superheat degree SH during normal operation ｍｉｎ The liquid backflow prevention superheat degree SH may be set higher than the above. ｍｉｎ The liquid backflow prevention superheat degree SH may be changed based on the intake temperature detected by an intake temperature sensor (not shown) that detects the temperature of the indoor air being drawn into the indoor heat exchanger 10 and the set temperature set by the user. ｍｉｎ The liquid backflow prevention superheat degree SH may be set higher as the difference between the suction temperature and the set temperature increases. ｍｉｎ The higher the value is set, the greater the change in the expansion valve 9 becomes, and the refrigerant temperature stabilizes more quickly.

[0073] The first selection unit 503 is configured with a selector that selects the smaller of two input values. The first selection unit 503 selects the smaller of the two input values. Ｔｏand the liquid backflow prevention control opening degree U output from the liquid backflow prevention control unit 502. ＳＨ The first selection unit 503 selects and outputs the smaller of the expansion valve opening degree U Ｓ１ The indoor unit control device 5 outputs the expansion valve opening degree U Ｓ１ The expansion valve 9 is controlled so that

[0074] FIG. 8 is a flowchart of a method for controlling the opening degree of the expansion valve in the refrigeration cycle apparatus 1 according to the second embodiment.

[0075] As described above, the control processing device 51 controls the blowout temperature control opening degree U Ｔｏ (Step S11), and the liquid backflow prevention control opening degree U ＳＨ (Step S12). Ｔｏ and liquid backflow prevention control opening U ＳＨ In other words, the control processing device 51 selects the smaller of U Ｔｏ ≦U ＳＨ In this case, the outlet temperature control opening degree U Ｔｏ (Step S14), Ｔｏ >U ＳＨ In this case, the liquid backflow prevention control opening U ＳＨ (Step S15). Then, the control processing device 51 controls the expansion valve 9 to have the selected opening degree (Step S16).

[0076] The above control is repeatedly performed at each sampling time. As a result, the refrigeration cycle device 1 controls the expansion valve opening to the blowout temperature control opening U Ｔｏ and the expansion valve opening is controlled to the liquid backflow prevention control opening U ＳＨ The control to follow the temperature control opening U Ｔｏ and liquid backflow prevention control opening U ＳＨ The refrigeration cycle device 1 selectively performs the discharge temperature control opening degree U Ｔｏ and liquid backflow prevention control opening U ＳＨ In order to select the smaller of the two, the blowout temperature T ｏThis allows for stable air conditioning capacity to be maintained without hunting.

[0077] [Effects of the refrigeration cycle apparatus 1] As described above, in the refrigeration cycle apparatus 1 of the second embodiment, the control processing device 51 includes the superheat degree calculation unit 500. The superheat degree calculation unit 500 calculates the superheat degree SH of the refrigerant flowing out from the indoor heat exchanger 10 during cooling operation. The control processing device 51 also includes the discharge temperature control unit 501 and the liquid backflow prevention control unit 502 of the first embodiment. The liquid backflow prevention control unit 502 calculates the superheat degree SH by multiplying the superheat degree SH by a preset liquid backflow prevention superheat degree SH. ｍｉｎ The liquid backflow prevention control opening degree U is the opening degree of the expansion valve 9 for matching the liquid backflow prevention control degree U ＳＨ The control processing device 51 calculates and outputs the blowout temperature control opening degree U Ｔｏ and liquid backflow prevention control opening U ＳＨ The control processing device 51 controls the expansion valve 9 so that the opening degree is the opening degree output from the first selection unit 503.

[0078] With the above-described configuration, the refrigeration cycle device 1 of the second embodiment can prevent liquid backflow while maintaining the discharge temperature T ｏ Furthermore, in the refrigeration cycle apparatus 1, the liquid backflow prevention control section 502 is provided with the controller 512 including at least the integrator 502a, and in preventing liquid backflow, the controller 512 including the integrator 502a controls the degree of superheat SH, so that the degree of superheat SH has good follow-up to the target value, and liquid backflow can be stably prevented.

[0079] [Embodiment 3] In embodiment 3, the moisture in the air passing through the indoor heat exchanger 10 is prevented from freezing while the outlet temperature T ｏ The following description will focus on the configuration of the third embodiment that is different from the first embodiment, and the configuration not described in the third embodiment is the same as that of the first embodiment.

[0080] (Control Overview) In the refrigeration cycle device 1, if the temperature of the refrigerant passing through the heat transfer tube of the indoor heat exchanger 10, which functions as an evaporator, is too low during cooling operation, the moisture contained in the air may be cooled by the refrigerant in the heat transfer tube and freeze on the surface of the heat transfer tube. The refrigeration cycle device 1 prioritizes preventing such freezing while controlling the blowout temperature T ｏ In order to maintain stable air conditioning capacity without causing hunting, the following control is performed. An overview of the control is given below.

[0081] The refrigeration cycle device 1 detects the liquid pipe temperature T ＥＫＩ and the preset anti-freeze temperature EKI ｍｉｎ Based on this, the liquid pipe temperature T ＥＫＩ The anti-freeze temperature EKI ｍｉｎ Anti-freeze control opening U to match ＥＫＩ The liquid pipe temperature T detected by the liquid pipe temperature detection unit 12 is calculated. ＥＫＩ is the temperature of the refrigerant flowing through the indoor heat exchanger 10 during cooling operation. ｍｉｎ is stored in advance in the storage device 53. The liquid pipe temperature must be kept at 0°C or higher to prevent the moisture in the air from freezing. ｍｉｎ If the sensor error is taken into consideration, it must be set to 2 to 3°C. The freezing of moisture contained in the air passing through the indoor heat exchanger 10 occurs when the liquid pipe temperature T ＥＫＩ Since it is more likely to occur as the anti-freeze temperature EKI ｍｉｎ is the liquid pipe temperature T at which freezing can be prevented. ＥＫＩ is the lower limit of

[0082] Here, when the expansion valve opening is reduced, the evaporation temperature of the indoor heat exchanger 10 decreases, making it easier for the moisture contained in the air passing through the indoor heat exchanger 10 to freeze, whereas when the expansion valve opening is increased, the evaporation temperature of the indoor heat exchanger 10 increases, making it less likely to freeze. ＥＫＩ Therefore, the refrigeration cycle device 1 opens the expansion valve 9 at the outlet temperature control opening degree U Ｔｏ and anti-freeze control opening U ＥＫＩThat is, the refrigeration cycle device 1 controls the opening degree to the larger of the anti-freeze control opening degree U ＥＫＩ is used as the lower limit of the expansion valve opening.

[0083] By the above control, the refrigeration cycle device 1 is Ｔｏ is the anti-freeze control opening U ＥＫＩ If the opening degree of the expansion valve is smaller than the anti-freeze control opening degree U ＥＫＩ This is controlled to prevent freezing.

[0084] In addition, the refrigeration cycle device 1 has a blowout temperature control opening degree U Ｔｏ is the anti-freeze control opening U ＥＫＩ If it is greater than , the expansion valve opening is set to the blowout temperature control opening U Ｔｏ The outlet temperature T ｏ The target temperature of the outlet T ｔｇｔ This allows the refrigeration cycle device 1 to maintain a stable air conditioning capacity.

[0085] Next, a specific control configuration for carrying out the above control will be described.

[0086] Fig. 9 is a functional block diagram showing an example of a portion related to the opening control of the expansion valve 9 in the control processing device 51 of the refrigeration cycle apparatus 1 according to embodiment 3. Fig. 10 is a block diagram showing the configuration of the anti-freeze control unit 504 of the refrigeration cycle apparatus 1 according to embodiment 3. As shown in Fig. 9, the control processing device 51 includes a discharge temperature control unit 501, an anti-freeze control unit 504, and a second selection unit 505.

[0087] The anti-freezing control unit 504 detects the liquid pipe temperature T ＥＫＩ and anti-freeze temperature EKI ｍｉｎ Based on this, the anti-freeze control opening degree U ＥＫＩ The anti-freezing control unit 504 is configured with a controller 513 including at least an integrator 504a. In this example, the anti-freezing control unit 504 is configured with a PI controller including a proportional unit 504b and an integrator 504a.

[0088] The anti-freeze control unit 504 calculates the liquid pipe temperature T ＥＫＩ and anti-freeze temperature EKIｍｉｎ Liquid pipe temperature deviation ΔT ＥＫＩ The anti-freeze control unit 504 calculates the liquid pipe temperature deviation ΔT as shown in equation (6). ＥＫＩ Using the liquid pipe temperature T ＥＫＩ The anti-freeze temperature EKI ｍｉｎ The anti-freeze control opening degree U of the expansion valve 9 is set to match the ＥＫＩ Calculate.

[0089]

[0090]

[0091] Here, K ＰＥＫＩ is the proportional gain of the PI controller, and K ＩＥＫＩ is the integral gain of the PI controller.

[0092] The anti-freeze control unit 504 may be configured with a discrete position or velocity PI controller. The anti-freeze control unit 504 is not limited to a PI controller, and may be configured with a controller that performs feedback control including an integrator, such as PID control or model predictive control.

[0093] The integrator 504a may have upper and lower limit values ​​or anti-reset windup that stop integration as shown in Figure 10. Note that U in Figure 10 denotes the final output after selection control or upper and lower limit selection. The anti-reset windup shown in Figure 10 is an example and is not limited to the one shown.

[0094] The second selection unit 505 is configured with a selector that selects the larger of two input values. The second selection unit 505 selects the larger of the two input values. Ｔｏ and the antifreeze control opening degree U output from the antifreeze control unit 504. ＥＫＩ The second selection unit 505 selects and outputs the larger of the expansion valve opening degree U Ｓ２ The indoor unit control device 5 outputs the expansion valve opening degree U Ｓ２ The expansion valve 9 is controlled so that

[0095] FIG. 11 is a flowchart of a method for controlling the opening degree of the expansion valve in the refrigeration cycle apparatus 1 according to the third embodiment.

[0096] As described above, the control processing device 51 controls the blowout temperature control opening degree U Ｔｏ (Step S21), and the anti-freeze control opening degree U ＥＫＩ (Step S22). Ｔｏ and anti-freeze control opening U ＥＫＩ In other words, the control processing device 51 selects the larger of U Ｔｏ ≧U ＥＫＩ In this case, the outlet temperature control opening degree U Ｔｏ (Step S24), Ｔｏ <U ＥＫＩ In this case, the anti-freeze control opening U ＥＫＩ (Step S25). Then, the control processing device 51 controls the expansion valve 9 to have the selected opening degree (Step S26).

[0097] The above control is repeatedly performed at each sampling time. Ｔｏ and anti-freeze control opening U ＥＫＩ In order to select the larger of the two, the outlet temperature T ｏ This allows for stable air conditioning capacity to be maintained without hunting.

[0098] [Effects of the Refrigeration Cycle Apparatus 1] As described above, in the refrigeration cycle apparatus 1 of the third embodiment, the control processing device 51 includes the discharge temperature control unit 501 and the anti-freeze control unit 504 of the first embodiment. The anti-freeze control unit 504 controls the liquid pipe temperature T ＥＫＩ The preset anti-freeze temperature EKI ｍｉｎ Anti-freeze control opening U to match ＥＫＩ The control processing device 51 calculates and outputs the blowout temperature control opening degree U Ｔｏ and anti-freeze control opening UＥＫＩ The control processing device 51 controls the expansion valve 9 so that the opening degree output from the second selection unit 505 is the larger of the two.

[0099] With the above configuration, the refrigeration cycle device 1 of the third embodiment prevents freezing while maintaining the outlet temperature T ｏ In addition, the refrigeration cycle device 1 can maintain a stable air conditioning capacity without causing hunting, and can perform stable air conditioning control. ＥＫＩ In order to control the liquid pipe temperature T ＥＫＩ It has good tracking ability to the target value, and can prevent freezing stably.

[0100] [Embodiment 4] Embodiment 4 corresponds to a combination of the above-described Embodiments 2 and 3. In Embodiment 4, the outlet temperature T ｏ The following description will focus on the configuration of the fourth embodiment that differs from the second and third embodiments, and the configuration not described in the fourth embodiment is the same as that of the second and third embodiments.

[0101] (Control Overview) The refrigeration cycle device 1 prioritizes either freezing prevention or liquid backflow prevention. When prioritizing freezing prevention, the refrigeration cycle device 1 adjusts the outlet temperature control opening degree U Ｔｏ and liquid backflow prevention control opening U ＳＨ and the smaller of the two and the anti-freeze control opening U ＥＫＩ The expansion valve 9 is controlled so that the opening degree is the larger of the two.

[0102] By the above control, the refrigeration cycle device 1 performs anti-freezing in an operating condition where freezing occurs, and performs liquid backflow prevention in an operating condition where freezing does not occur but liquid backflow occurs. In an operating condition where neither freezing nor liquid backflow occurs, the refrigeration cycle device 1 operates to make the discharge temperature follow the target value.

[0103] Next, a specific control configuration for carrying out the above control will be described.

[0104] Fig. 12 is a functional block diagram showing an example of a portion related to the opening control of the expansion valve 9 in the control processing device 51 of the refrigeration cycle apparatus 1 according to Embodiment 4. As shown in Fig. 12, the control processing device 51 includes a superheat degree calculation unit 500, a discharge temperature control unit 501, a liquid backflow prevention control unit 502, a first selection unit 503, a freeze prevention control unit 504, and a third selection unit 521.

[0105] The first selection unit 503 is configured as a selector that selects the smaller of the two input values ​​as described above. The first selection unit 503 selects the smaller of the two input values ​​as the air outlet temperature control opening degree U Ｔｏ and the liquid backflow prevention control opening degree U output from the liquid backflow prevention control unit 502. ＳＨ The smaller of these is selected, and the selected expansion valve opening degree U Ｓ１ Output.

[0106] The third selection unit 521 is configured as a selector that selects the larger of two input values. The third selection unit 521 selects the expansion valve opening degree U Ｓ１ and the antifreeze control opening degree U output from the antifreeze control unit 504. ＥＫＩ The larger of these is selected, and the selected expansion valve opening degree (hereinafter referred to as expansion valve opening degree U Ｓ３ The indoor unit control device 5 outputs the expansion valve opening degree U Ｓ３ The expansion valve 9 is controlled so that

[0107] FIG. 13 is a flowchart of a method for controlling the opening degree of the expansion valve in the refrigeration cycle apparatus 1 according to the fourth embodiment.

[0108] As described above, the control processing device 51 controls the blowout temperature control opening degree U Ｔｏ (Step S31) and the liquid backflow prevention control opening degree U ＳＨ (step S32), and then the antifreeze control opening degree U ＥＫＩ (Step S33). The calculation order is not limited to this order.

[0109] The control processing device 51 controls the air outlet temperature control opening degree U Ｔｏ and liquid backflow prevention control opening U ＳＨ In other words, the control processing device 51 selects the smaller of U Ｔｏ ≦U ＳＨ In this case, the outlet temperature control opening degree U Ｔｏ (Step S35), Ｔｏ >U ＳＨ In this case, the liquid backflow prevention control opening U ＳＨ Next, the control processing device 51 selects the air outlet temperature control opening degree U Ｔｏ and liquid backflow prevention control opening U ＳＨ The expansion valve opening degree U Ｓ１ and anti-freeze control opening U ＥＫＩ In other words, the control processing device 51 selects the larger of U Ｓ１ ≧U ＥＫＩ In this case, the expansion valve opening degree U Ｓ１ (Step S38), Ｓ１ <U ＥＫＩ In this case, the anti-freeze control opening U ＥＫＩ (Step S39). Then, the control processing device 51 controls the expansion valve 9 to have the selected opening degree (Step S40).

[0110] The above control is repeated at each sampling time. In the refrigeration cycle device 1, when priority is given to the prevention of freezing between the prevention of freezing and the prevention of liquid backflow, the blowout temperature control opening degree U Ｔｏ and liquid backflow prevention control opening U ＳＨ and the smaller of the two and the anti-freeze control opening U ＥＫＩ In this way, the refrigeration cycle device 1 can prevent liquid backflow and perform stable air conditioning control while prioritizing prevention of freezing.

[0111] Although the case where priority is given to prevention of freezing has been described here, the refrigeration cycle apparatus 1 may also prioritize prevention of liquid backflow. Fig. 14 is a functional block diagram of the refrigeration cycle apparatus 1 when priority is given to prevention of liquid backflow.

[0112] 14 is a functional block diagram showing another example of the part related to the opening control of the expansion valve 9 in the control processing device 51 of the refrigeration cycle device 1 according to the fourth embodiment. Ｔｏ and anti-freeze control opening U ＥＫＩ The second selection unit 505 selects the larger of the two, and sets the selected expansion valve opening degree (hereinafter, expansion valve opening degree U Ｓ１１ The control processing device 51 outputs the expansion valve opening degree U Ｓ１１ and the liquid backflow prevention control opening degree U output from the liquid backflow prevention control unit 502. ＳＨ The fourth selection unit 522 selects the smaller of the two, and the selected expansion valve opening degree (hereinafter, the expansion valve opening degree U Ｓ３１ ) is output.

[0113] With the above configuration, the refrigeration cycle device 1 prevents liquid backflow when the operating condition is such that liquid backflow occurs, and prevents freezing when the operating condition is such that liquid backflow does not occur but freezing occurs. The refrigeration cycle device 1 operates to make the discharge temperature follow the target value when the operating condition is such that neither liquid backflow nor freezing occurs.

[0114] [Effects of Refrigeration Cycle Apparatus 1] As described above, in the refrigeration cycle apparatus 1 of the fourth embodiment, the control processing device 51 includes the degree-of-superheat calculation unit 500. The degree-of-superheat calculation unit 500 calculates the degree of superheat SH of the refrigerant flowing out from the indoor heat exchanger 10 during cooling operation. The control processing device 51 also includes the discharge temperature control unit 501 of the first embodiment, the liquid backflow prevention control unit 502 of the second embodiment, and the anti-freeze control unit 504 of the third embodiment.

[0115] The control processing device 51 controls the air outlet temperature control opening degree U Ｔｏ and liquid backflow prevention control opening U ＳＨ a first selection unit 503 that selects and outputs the smaller of the opening degree U ＥＫＩand a third selection unit 521 that selects and outputs the larger of the two. The control processing device 51 controls the expansion valve 9 so that the opening degree is the one output from the third selection unit 521. Alternatively, the control processing device 51 controls the expansion valve 9 so that the opening degree is the one output from the third selection unit 521. Ｔｏ and anti-freeze control opening U ＥＫＩ a second selection unit 505 that selects and outputs the larger of the opening degree output from the second selection unit 505 and the liquid backflow prevention control opening degree U ＳＨ and a fourth selection unit 522 that selects and outputs the smaller opening degree between the first and second selection units 521 and 522. The control processing device 51 controls the expansion valve 9 so that the opening degree is the opening degree output from the fourth selection unit 522.

[0116] With the above-described configuration, the refrigeration cycle device 1 of the fourth embodiment performs liquid return and freeze prevention, while maintaining the discharge temperature T ｏ In order to prevent liquid backflow, the refrigeration cycle device 1 controls the superheat degree SH by the controller 512 including at least the integrator 502a, so that the superheat degree SH can follow the target value well and liquid backflow can be prevented stably. In order to prevent freezing, the refrigeration cycle device 1 controls the liquid pipe temperature T by the controller 513 including at least the integrator 504a. ＥＫＩ In order to control the liquid pipe temperature T ＥＫＩ It has good tracking ability to the target value, and can prevent freezing stably.

[0117] [Embodiment 5] In embodiment 5, the blowout temperature T ｏ The following description will focus on the configuration of the fifth embodiment that is different from the first embodiment, and the configuration not described in the fifth embodiment is the same as that of the first embodiment.

[0118] FIG. 15 is a schematic diagram showing an example of the configuration of a refrigeration cycle apparatus 1 according to a fifth embodiment. As shown in FIG. 15, the refrigeration cycle apparatus 1 of the fifth embodiment has a configuration in which a refrigerant pressure detection unit 15 is further provided in addition to the refrigeration cycle apparatus 1 of the first embodiment shown in FIG. The refrigerant pressure detection unit 15 is disposed in the indoor unit 3 and detects the pressure of the refrigerant flowing into the indoor heat exchanger 10 during heating operation. The refrigerant pressure detection unit 15 is composed of a pressure sensor. The detection result detected by the refrigerant pressure detection unit 15 is input to the indoor unit control device 5.

[0119] (Control Overview) In the refrigeration cycle apparatus 1, if sufficient supercooling cannot be achieved at the refrigerant outlet of the indoor heat exchanger 10 during heating operation, the refrigerant flows into the expansion valve 9 in a two-phase state, causing refrigerant noise in the expansion valve 9. The refrigeration cycle apparatus 1 performs the following control to prevent refrigerant noise from occurring in the expansion valve 9 during heating operation. An overview of the control will now be described.

[0120] The refrigeration cycle device 1 calculates the degree of supercooling SC of the refrigerant flowing out from the indoor heat exchanger 10 and the refrigerant noise prevention degree SC ｍｉｎ Based on this, the subcooling degree SC is set to the refrigerant noise prevention subcooling degree SC ｍｉｎ Refrigerant noise prevention control opening U to match ＳＣ Calculate the refrigerant noise prevention supercooling degree SC ｍｉｎ is stored in advance in the storage device 53. Refrigerant noise is likely to occur when the degree of supercooling SC is 0°C. For this reason, the degree of supercooling SC needs to be kept higher than 0°C. Furthermore, by setting the degree of supercooling SC to an appropriate value, the refrigeration cycle device 1 can improve energy saving performance and stabilize the controllability of the discharge temperature. For this reason, the refrigerant noise prevention subcooling degree SC ｍｉｎ is set to, for example, 2°C or more, taking into consideration sensor errors. Since refrigerant noise is more likely to occur as the degree of supercooling SC decreases, the refrigerant noise prevention subcooling degree SC ｍｉｎ is the lower limit of the degree of supercooling SC at which the generation of refrigerant noise can be suppressed.

[0121] Here, the degree of subcooling SC decreases as the expansion valve opening degree is increased, and increases as the expansion valve opening degree is decreased. Therefore, refrigerant noise is more likely to occur as the expansion valve opening degree is increased, and is less likely to occur as the expansion valve opening degree is decreased. Since refrigerant noise is more likely to occur as the expansion valve opening degree is increased, when the expansion valve opening degree is increased, the refrigerant noise prevention control opening degree U ＳＣ If the opening degree of the expansion valve 9 is larger than the opening degree of the outlet temperature control U Ｔｏ and refrigerant noise prevention control opening U ＳＣ That is, the refrigeration cycle device 1 controls the refrigerant noise prevention control opening degree U ＳＣ is used as the upper limit of the expansion valve opening.

[0122] By the above control, the refrigeration cycle device 1 is Ｔｏ Refrigerant noise prevention control opening degree U ＳＣ If it is larger than the refrigerant noise prevention control opening degree U ＳＣ This controls the temperature to suppress the generation of refrigerant noise.

[0123] In addition, the refrigeration cycle device 1 has a blowout temperature control opening degree U Ｔｏ Refrigerant noise prevention control opening degree U ＳＣ If it is smaller than the opening degree of the expansion valve, the opening degree of the blowout temperature control Ｔｏ The outlet temperature T ｏ The target temperature of the outlet T ｔｇｔ This allows the refrigeration cycle device 1 to maintain a stable air conditioning capacity. Ｔｏ is the outlet temperature T ｏ The target temperature for the outlet during heating operation is T ｔｇｔ This is the opening to match the

[0124] Next, a specific control configuration for carrying out the above control will be described.

[0125] Figure 16 is a control block diagram showing the electrical configuration of the indoor unit 3 of Figure 15. The indoor unit 3 of embodiment 5 has a refrigerant pressure detection unit 15 added to the indoor unit 3 of embodiment 1 shown in Figure 2. The detection result detected by the refrigerant pressure detection unit 15 is input to the indoor unit control device 5.

[0126] Fig. 17 is a functional block diagram showing an example of a portion related to the opening control of the expansion valve 9 in the control processing device 51 of the refrigeration cycle apparatus 1 according to embodiment 5. Fig. 18 is a block diagram showing the configuration of the refrigerant noise prevention control unit 507 of the refrigeration cycle apparatus 1 according to embodiment 5. As shown in Fig. 17, the control processing device 51 includes a degree-of-subcooling calculation unit 506, a discharge temperature control unit 501, a refrigerant noise prevention control unit 507, and a fifth selection unit 523.

[0127] The subcooling degree calculation unit 506 calculates the subcooling degree SC of the refrigerant flowing out of the indoor heat exchanger 10 during heating operation. The subcooling degree SC is calculated based on the liquid pipe temperature detected by the liquid pipe temperature detection unit 12 and the condensing temperature. The condensing temperature may be a value obtained by converting the pressure detected by the refrigerant pressure detection unit 15 into a saturation value, or may be a value detected by a thermistor or thermocouple temperature sensor installed in the two-phase region of the indoor heat exchanger 10 functioning as a condenser.

[0128] The refrigerant noise prevention control unit 507 calculates the supercooling degree SC and the refrigerant noise prevention supercooling degree SC ｍｉｎ Based on this, the subcooling degree SC is set to the refrigerant noise prevention subcooling degree SC ｍｉｎ The refrigerant noise prevention control opening degree U of the expansion valve 9 to match ＳＣ The refrigerant noise prevention control unit 507 is configured with a controller 514 including at least an integrator 507a. In this example, the refrigerant noise prevention control unit 507 is configured with a PI controller including a proportional unit 507b and an integrator 507a.

[0129] The refrigerant noise prevention control unit 507 calculates the refrigerant noise prevention subcooling degree SC as shown in equation (7). ｍｉｎThe refrigerant noise prevention control unit 507 calculates the subcooling degree deviation ΔSC between the refrigerant noise prevention subcooling degree SC and the refrigerant noise prevention subcooling degree SC by using the subcooling degree deviation ΔSC as in equation (8). ｍｉｎ The refrigerant noise prevention control opening degree U of the expansion valve 9 to match ＳＣ Calculate.

[0130]

[0131]

[0132] Here, K ＰＳＣ is the proportional gain of the PI controller, and K ＩＳＣ is the integral gain of the PI controller.

[0133] The refrigerant noise prevention control unit 507 may be configured with a discrete position or velocity PI controller. The refrigerant noise prevention control unit 507 is not limited to a PI controller, and may be configured with a controller that performs feedback control including an integrator, such as PID control or model predictive control. The integrator 507a may have upper and lower limit values ​​or anti-reset windup that stop integration, as shown in FIG. 18. Note that U in FIG. 18 is written to mean the final output after selective control or upper and lower limit selection. The anti-reset windup shown in FIG. 18 is an example and is not limited to the one shown.

[0134] The fifth selection unit 523 is configured with a selector that selects the smaller of two input values. Ｔｏ and the refrigerant noise prevention control opening degree U output from the refrigerant noise prevention control unit 507. ＳＣ The fifth selection unit 523 selects and outputs the smaller of the expansion valve opening degree U Ｓ４ The indoor unit control device 5 outputs the expansion valve opening degree U Ｓ４ The expansion valve 9 is controlled so that

[0135] FIG. 19 is a flowchart of a method for controlling the opening degree of the expansion valve in the refrigeration cycle apparatus 1 according to the fifth embodiment.

[0136] As described above, the control processing device 51 controls the blowout temperature control opening degree U Ｔｏ (Step S41), and the refrigerant noise prevention control opening degree U ＳＣ (Step S42). Ｔｏ and refrigerant noise prevention control opening U ＳＣ In other words, the control processing device 51 selects the smaller of U Ｔｏ ≦U ＳＣ In this case, the outlet temperature control opening degree U Ｔｏ (Step S44), Ｔｏ >U ＳＣ In this case, the refrigerant noise prevention control opening degree U ＳＣ (Step S45). Then, the control processing device 51 controls the expansion valve 9 to have the selected opening degree (Step S46).

[0137] The above control is repeatedly performed at each sampling time. Ｔｏ and refrigerant noise prevention control opening U ＳＣ In order to select the smaller of the two, the refrigerant noise is prevented while the blowout temperature T ｏ This allows for stable air conditioning capacity to be maintained without hunting.

[0138] [Effects of the Refrigeration Cycle Apparatus 1] As described above, the refrigeration cycle apparatus 1 of the fifth embodiment can prevent refrigerant noise while maintaining the discharge temperature T ｏ Furthermore, in order to prevent refrigerant noise, the refrigeration cycle device 1 controls the degree of supercooling SC using the controller 514 including at least the integrator 507a, and therefore has good follow-up ability to the target value of the degree of supercooling SC, thereby enabling stable suppression of refrigerant noise.

[0139] REFRIGERATED CYCLE DEVICE, 2 OUTDOOR UNIT, 3 INDOOR UNIT, 4 OUTDOOR UNIT CONTROL DEVICE, 5 INDOOR UNIT CONTROL DEVICE, 6 COMPRESSOR, 7 FLOW CHANNEL SWITCHING DEVICE, 8 OUTDOOR HEAT EXCHANGER, 8a OUTDOOR BLOWER, 9 EXPANSION VALVE, 10 INDOOR HEAT EXCHANGER, 10a INDOOR BLOWER, 11 OUTPUT TEMPERATURE DETECTION DEVICE, 12 LIQUID PIPE TEMPERATURE DETECTION DEVICE, 13 GAS PIPE TEMPERATURE DETECTION DEVICE, 14 PIPING, 15 REFRIGERATED REFRIGERATED PRESSURE DETECTION DEVICE, 51 CONTROL PROCESSING DEVICE, 52 TIMING DEVICE, 53 MEMORY DEVICE, 500 SUPERHEAT DEGREE DETECTION DEVICE, 501 OUTPUT TEMPERATURE CONTROL DEVICE, 501a INTEGRATOR, 501b PROPORTIONER, 502 LIQUID BACK ANTI-FREEZE CONTROL DEVICE, 502a INTEGRATOR, 502b PROPORTIONER, 503 FIRST SELECTION DEVICE, 504 ANTI-FREEZE CONTROL DEVICE, 504a INTEGRATOR, 504b PROPORTIONER, 505 FIRST SELECTION DEVICE, 506 Subcooling degree calculation unit, 507 refrigerant noise prevention control unit, 507a integrator, 507b proportioner, 511 controller, 512 controller, 513 controller, 514 controller, 521 third selection unit, 522 fourth selection unit, 523 fifth selection unit, A refrigerant circuit.

Claims

1. A refrigeration cycle device comprising: a refrigerant circuit in which a compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger are connected by piping and in which a refrigerant circulates; a discharge temperature detection unit that detects the discharge temperature, which is the temperature of air after passing through the indoor heat exchanger; and a control processing device that controls the expansion valve, wherein the control processing device comprises a discharge temperature control unit that calculates and outputs, by a controller including at least an integrator, a discharge temperature control opening, which is the opening of the expansion valve to match the discharge temperature to a predetermined discharge temperature target value, and controls the expansion valve to achieve the discharge temperature control opening output from the discharge temperature control unit.

2. The control processing device comprises: a superheat degree calculation unit that calculates the degree of superheat of the refrigerant flowing out from the indoor heat exchanger during cooling operation; a liquid backflow prevention control unit that calculates and outputs a liquid backflow prevention control opening, which is the opening of the expansion valve for matching the degree of superheat to a predetermined liquid backflow prevention superheat degree, using a controller including at least an integrator; and a first selection unit that selects and outputs the smaller of the discharge temperature control opening and the liquid backflow prevention control opening, and controls the expansion valve to achieve the opening output from the first selection unit.

3. The control processing device comprises: an anti-freeze control section that calculates and outputs an anti-freeze control opening degree using a controller including at least an integrator to make the temperature of the refrigerant flowing through the indoor heat exchanger during cooling operation coincide with a preset anti-freeze temperature; and a second selection section that selects and outputs the larger opening degree of the discharge temperature control opening degree and the anti-freeze control opening degree, and controls the expansion valve to achieve the opening degree output from the second selection section. Refrigeration cycle device according to claim 1.

4. The control processing device comprises: a superheat degree calculation unit that calculates the superheat degree of refrigerant flowing out from the indoor heat exchanger during cooling operation; a liquid backflow prevention control unit that calculates and outputs a liquid backflow prevention control opening, which is the opening of the expansion valve for making the superheat degree equal to a predetermined liquid backflow prevention superheat degree, using a controller including at least an integrator; an anti-freeze control unit that calculates and outputs an anti-freeze control opening, which is the opening of the expansion valve for making the temperature of the refrigerant flowing through the indoor heat exchanger during cooling operation equal to a predetermined anti-freeze temperature, using a controller including at least an integrator; a first selection unit that selects and outputs the smaller of the discharge temperature control opening and the liquid backflow prevention control opening; and a third selection unit that selects and outputs the larger of the opening output from the first selection unit and the anti-freeze control opening, and the control unit controls the expansion valve to achieve the opening output from the third selection unit.

5. The control processing device comprises: a superheat degree calculation unit that calculates the superheat degree of refrigerant flowing out from the indoor heat exchanger during cooling operation; a liquid backflow prevention control unit that calculates and outputs a liquid backflow prevention control opening, which is the opening of the expansion valve for making the superheat degree equal to a predetermined liquid backflow prevention superheat degree, using a controller including at least an integrator; an anti-freeze control unit that calculates and outputs an anti-freeze control opening, which is the opening of the expansion valve for making the temperature of the refrigerant flowing through the indoor heat exchanger during cooling operation equal to a predetermined anti-freeze temperature, using a controller including at least an integrator; a second selection unit that selects and outputs the larger of the discharge temperature control opening and the anti-freeze control opening; and a fourth selection unit that selects and outputs the smaller of the opening output from the second selection unit and the liquid backflow prevention control opening, and controls the expansion valve to achieve the opening output from the fourth selection unit.

6. The refrigerant circuit comprises a flow path switching device that switches the flow path so that the indoor heat exchanger functions as an evaporator and the outdoor heat exchanger functions as a condenser during cooling operation, and vice versa during heating operation; and the control processing device comprises: a subcooling degree calculation unit that calculates the degree of subcooling of refrigerant flowing out from the indoor heat exchanger that functions as a condenser during heating operation; a refrigerant noise prevention control unit that calculates and outputs a refrigerant noise prevention control opening, which is the opening of the expansion valve for matching the degree of subcooling to a preset refrigerant noise prevention subcooling degree, using a controller including at least an integrator; and a fifth selection unit that selects and outputs the smaller of the discharge temperature control opening and the refrigerant noise prevention control opening, and controls the expansion valve to achieve the opening output from the fifth selection unit.

7. A control method for a refrigeration cycle device having a refrigerant circuit in which a compressor, an outdoor heat exchanger, an expansion valve, and an indoor heat exchanger are connected by piping and in which a refrigerant circulates, the control method comprising the steps of: calculating, by a controller including at least an integrator, a discharge temperature control opening, which is the opening of the expansion valve for making the discharge temperature, which is the temperature of air after passing through the indoor heat exchanger, equal to a predetermined target discharge temperature value; and controlling the expansion valve so that the opening of the expansion valve becomes the discharge temperature control opening.

8. A control method for a refrigeration cycle device as described in claim 7, comprising the steps of: calculating, by a controller including at least an integrator, a liquid backflow prevention control opening, which is the opening of the expansion valve for matching the superheat of the refrigerant flowing out of the indoor heat exchanger during cooling operation to a predetermined liquid backflow prevention superheat; and controlling the expansion valve so that the opening becomes the smaller of the discharge temperature control opening and the liquid backflow prevention control opening.

9. A control method for a refrigeration cycle device as described in claim 7, comprising the steps of: calculating, by a controller including at least an integrator, an anti-freeze control opening for matching the temperature of the refrigerant flowing through the indoor heat exchanger during cooling operation to a preset anti-freeze temperature; and controlling the expansion valve so that the opening becomes the larger of the discharge temperature control opening and the anti-freeze control opening.

10. A control method for a refrigeration cycle device as described in claim 7, comprising the steps of: calculating, by a controller including at least an integrator, a liquid backflow prevention control opening, which is the opening of the expansion valve for making the superheat of the refrigerant flowing out of the indoor heat exchanger during cooling operation coincide with a predetermined liquid backflow prevention superheat; calculating, by a controller including at least an integrator, a freeze prevention control opening, which is the opening of the expansion valve for making the temperature of the refrigerant flowing through the indoor heat exchanger during cooling operation coincide with a predetermined freeze prevention temperature; and controlling the opening of the expansion valve to be the larger of the smaller of the discharge temperature control opening and the liquid backflow prevention control opening, and the freeze prevention control opening.

11. A control method for a refrigeration cycle device as described in claim 7, comprising the steps of: calculating, by a controller including at least an integrator, a liquid backflow prevention control opening, which is the opening of the expansion valve for matching the superheat of the refrigerant flowing out of the indoor heat exchanger during cooling operation to a predetermined liquid backflow prevention superheat; calculating, by a controller including at least an integrator, a freeze prevention control opening, which is the opening of the expansion valve for matching the temperature of the refrigerant flowing through the indoor heat exchanger during cooling operation to a predetermined freeze prevention temperature; and controlling the opening of the expansion valve to be the smaller of the larger of the discharge temperature control opening and the freeze prevention control opening, or the liquid backflow prevention control opening.

12. A control method for a refrigeration cycle device as described in claim 7, wherein the refrigerant circuit is provided with a flow path switching device that switches the flow path so that the indoor heat exchanger functions as an evaporator and the outdoor heat exchanger functions as a condenser during cooling operation, and vice versa during heating operation; the method further comprises a step of calculating, by a controller including at least an integrator, a refrigerant noise prevention control opening, which is the opening of the expansion valve for making the degree of subcooling of the refrigerant flowing out of the indoor heat exchanger that functions as a condenser during heating operation coincide with a preset refrigerant noise prevention subcooling degree; and the control method controls the opening of the expansion valve so that it becomes the smaller of the discharge temperature control opening and the refrigerant noise prevention control opening.

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