Refrigeration cycle system, and program

Abstract

To provide a refrigeration cycle system facilitating appropriate determination of a refrigerant amount.SOLUTION: A refrigeration cycle system includes: a compressor; a heat source-side heat exchanger; a supercooling heat exchanger having a main route and a cooling route; a supercooling expansion valve expanding refrigerant passing through the main route and passing the expanded refrigerant to the cooling route. The refrigerant cycle system includes a control part capable of executing a refrigerant amount determination operation. The control part executes a determination action of whether the refrigerant amount of the refrigeration cycle system is appropriate or not while the difference between supercooling degrees of the refrigerants at an inlet and an outlet of the cooling route is made constant and the refrigerant density at the outlet of the main route is made constant.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a refrigeration cycle system and a program. [Background technology]

[0002] Patent Document 1 discloses a refrigeration device that can determine the amount of refrigerant charged, which determines the amount of refrigerant charged using the temperature efficiency of a subcooler. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6590945 Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides a refrigeration cycle system that can facilitate appropriate determination of the amount of refrigerant. [Means for solving the problem]

[0005] The refrigeration cycle system of the present disclosure includes a compressor, a heat source side heat exchanger, a subcooling heat exchanger having a main path and a cooling path, and a subcooling expansion valve that expands refrigerant that has passed through the main path and passes it through the cooling path, and is equipped with a control unit capable of performing refrigerant amount determination operation, and in the refrigerant amount determination operation, the control unit performs an operation to determine whether the refrigerant amount in the refrigeration cycle system is appropriate while keeping the difference in the degree of subcooling of the refrigerant at the inlet and outlet of the cooling path constant and keeping the density of the refrigerant at the outlet of the main path constant.

[0006] The program disclosed herein is a program executable by a computer of a refrigeration cycle system including a compressor, a heat source side heat exchanger, a subcooling heat exchanger having a main path and a cooling path, and a subcooling expansion valve that expands refrigerant that has passed through the main path and passes it through the cooling path, and causes the computer to perform a refrigerant quantity determination operation that performs a determination operation on the refrigerant quantity of the refrigeration cycle system while keeping the difference in the degree of subcooling of the refrigerant at the inlet and outlet of the cooling path constant and keeping the density of the refrigerant at the outlet of the main path constant. [Effects of the Invention]

[0007] The refrigeration cycle system and the program according to the present disclosure can facilitate determination of the refrigerant amount in a refrigeration cycle system while suppressing the influence of the installation conditions and the environment of the refrigeration cycle system, thereby facilitating appropriate determination of the refrigerant amount in the refrigeration cycle system. [Brief explanation of the drawings]

[0008] [Figure 1] Air conditioner refrigeration cycle diagram [Figure 2] Air conditioner block diagram [Figure 3] Scatter diagram showing the relationship between the refrigerant circulation volume of an air conditioner and the arithmetic mean temperature difference [Figure 4] Flowchart showing the operation of the control unit [Figure 5] Flowchart showing the operation of the control unit DETAILED DESCRIPTION OF THE INVENTION

[0009] (Findings that formed the basis of this disclosure) At the time when the inventors came up with the idea of the present disclosure, methods for a system to determine the amount of refrigerant sealed in a refrigeration device included a technology for detecting by storing condensed liquid refrigerant in a high-pressure container such as a receiver, and a method for determining by detecting the supercooled state of the refrigerant at the condenser outlet. However, when a receiver is installed in a refrigeration unit, it is necessary to secure space for the receiver, which may lead to an increase in the size of the refrigeration unit's housing and an increase in weight and a decrease in economic efficiency due to the use of pressure-resistant materials.In addition, when determining the amount of refrigerant using an air heat exchanger, the state of the refrigeration cycle is greatly influenced by the installation conditions and the surrounding environment, making it difficult to properly determine the amount of refrigerant. Therefore, the present disclosure provides a refrigeration cycle system that can easily determine the amount of refrigerant in a refrigeration device regardless of the installation state.

[0010] Hereinafter, embodiments will be described in detail with reference to the drawings. However, unnecessary detailed description may be omitted. For example, detailed description of well-known matters or redundant description of substantially the same configuration may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. The accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0011] (Embodiment 1) Hereinafter, the first embodiment will be described with reference to the drawings. [1-1.Configuration] [1-1-1. Refrigeration cycle configuration] FIG. 1 is a refrigeration cycle diagram of an air conditioner 1 according to the first embodiment. The air conditioner 1 is an apparatus that performs air conditioning using a refrigeration cycle filled with a refrigerant. In this embodiment, the air conditioner 1 is a commercial multi-air conditioner. In this embodiment, an R410A refrigerant is used as the refrigerant. However, the refrigerant may be a refrigerant other than R410A, such as R32. The air conditioner 1 according to this embodiment is an example of a "refrigeration cycle system."

[0012] The air conditioner 1 has an outdoor unit 10 installed outdoors and an indoor unit 30 installed indoors. Although only one indoor unit 30 is shown in Fig. 1, the number of indoor units 30 may be two or more.

[0013] The outdoor unit 10 has a compressor 11, a four-way valve 13, and an outdoor heat exchanger 15. The compressor 11 is a device that sucks in, compresses, and discharges gas refrigerant. In this embodiment, the compressor 11 is a two-stage compressor. Also, in this embodiment, the compressor 11 has an injection port 11a that communicates with an intermediate pressure chamber that is at an intermediate pressure. The compressor 11 can lower the temperature of the refrigerant in the intermediate pressure chamber by taking in low-temperature refrigerant through the injection port 11a. Also, an accumulator 12 for preventing liquid compression is provided on the suction side of the compressor 11.

[0014] The four-way valve 13 is a device that switches between cooling operation and heating operation of the air conditioner 1 by switching the flow path. The four-way valve 13 is connected to the discharge side of the compressor 11 and the suction side of the accumulator 12 via refrigerant piping. During cooling operation, the four-way valve 13 causes the refrigerant discharged from the compressor 11 to flow to the outdoor heat exchanger 15, and returns the refrigerant flowing from the indoor unit 30 to the accumulator 12. During heating operation, the four-way valve 13 causes the refrigerant discharged from the compressor 11 to flow to the outdoor heat exchanger 15, and returns the refrigerant flowing from the indoor unit 30 to the accumulator 12.

[0015] The outdoor heat exchanger 15 exchanges heat between the refrigerant flowing therein and the outdoor air. The outdoor heat exchanger 15 is, for example, a fin-tube type heat exchanger. The outdoor heat exchanger 15 functions as a condenser during cooling operation. The outdoor heat exchanger 15 is provided in a position where it is exposed to the air flow from the outdoor blower 16. The outdoor blower 16 draws the outdoor air 1 into the outdoor unit 10, passes it through the outdoor heat exchanger 15, and then blows it out of the outdoor unit 10. In this embodiment, the outdoor blower 16 is a blower whose blowing volume can be controlled, for example, an axial flow blower. The outdoor heat exchanger 15 in this embodiment corresponds to the "heat source side heat exchanger" in this disclosure.

[0016] An outdoor expansion valve 17 is connected to the liquid side of the outdoor heat exchanger 15. The outdoor expansion valve 17 is a valve whose opening can be adjusted by electronic control. The outdoor expansion valve 17 expands the liquid refrigerant mainly during heating operation. In this embodiment, two outdoor expansion valves 17 are connected in parallel to the outdoor heat exchanger 15.

[0017] The outdoor expansion valve 17 is connected to one end of an indoor / outdoor connecting liquid pipe 21 via an outdoor liquid pipe 18. The outdoor liquid pipe 18 is a refrigerant pipe having a valve 22 for connection to the indoor / outdoor connecting liquid pipe 21. The indoor / outdoor connecting liquid pipe 21 is a refrigerant pipe that connects the outdoor unit 10 and the indoor unit 30. In other words, the indoor / outdoor connecting liquid pipe 21 is located closer to the indoor unit 30 than the outdoor expansion valve 17.

[0018] The other end of the indoor / outdoor connecting liquid pipe 21 is connected to an indoor expansion valve 31 of the indoor unit 30. The indoor expansion valve 31 is a valve whose opening can be adjusted by electronic control. The indoor expansion valve 31 expands the liquid refrigerant mainly during cooling operation.

[0019] The indoor expansion valve 31 is connected to the liquid side of the indoor heat exchanger 33. The indoor heat exchanger 33 is a heat exchanger that exchanges heat between the refrigerant flowing therethrough and the indoor air. The indoor heat exchanger 33 is, for example, a fin-tube heat exchanger. The indoor heat exchanger 33 functions as an evaporator during cooling operation of the air conditioner 1. The indoor heat exchanger 33 is provided in a position where it is exposed to the air flow generated by the indoor blower 34. The indoor blower 34 draws indoor air into the indoor unit 30 and then blows it into the room via the indoor heat exchanger 33. In this embodiment, the indoor blower 34 is a blower whose blowing volume can be adjusted electronically, such as a crossflow fan. One end of the indoor-external connecting gas pipe 23 is connected to the gas side of the indoor heat exchanger 33. This is a refrigerant pipe that connects the indoor unit 30 and the outdoor unit 10. The other end of the indoor / outdoor connecting gas pipe 23 is connected to the four-way valve 13 of the outdoor unit 10 .

[0020] The outdoor unit 10 is also provided with a subcooling heat exchanger 19. The subcooling heat exchanger 19 is a heat exchanger formed with a main path 19a through which the refrigerant flows and a cooling path 19b. The cooling heat exchanger 19 is disposed in a location that is less exposed to outside air, such as a machine room of the outdoor unit 10, and is therefore less susceptible to deterioration over time than the outdoor heat exchanger 15 and the indoor heat exchanger 33. The subcooling heat exchanger 19 exchanges heat between the refrigerant flowing through the main path 19a and the refrigerant flowing through the cooling path 19b. The main path 19a of the subcooling heat exchanger 19 is connected to a midpoint of the outdoor liquid pipe 18.

[0021] One end of the cooling path 19b is connected to the branch pipe 14. The branch pipe 14 is a refrigerant pipe that branches off from the outdoor liquid pipe 18 between the main path 19a of the subcooling heat exchanger 19 and the valve 22. The branch pipe 14 is provided with a subcooling expansion valve 14a. The subcooling expansion valve 14a is a valve whose opening can be adjusted by electronic control. Mainly during cooling operation, the subcooling expansion valve 14a expands the liquid refrigerant that flows from the outdoor liquid pipe 18 into the branch pipe 14, lowering its temperature, and then allows the liquid refrigerant to flow into the cooling path 19b. That is, the subcooling heat exchanger 19 cools the refrigerant flowing through the main path 19a with the refrigerant flowing through the cooling path 19b.

[0022] The other end of the cooling path 19b is connected to an injection pipe 25. The injection pipe 25 is a refrigerant pipe that injects the refrigerant from the cooling path 19b into the compressor 11 via the injection port 11a. A bypass pipe 27 that returns the refrigerant from the injection pipe 25 to the suction side of the accumulator 12 branches off from the injection pipe 25 in the middle. The bypass pipe 27 is provided with a bypass pipe opening / closing valve 28 that is electronically controlled and opens and closes.

[0023] The outdoor unit 10 is provided with an intake-side temperature sensor 41, a discharge-side temperature sensor 42, a main path inlet-side temperature sensor 43, a main path outlet-side temperature sensor 44, a cooling path inlet-side temperature sensor 45, and a cooling path outlet-side temperature sensor 46, which measure the refrigerant temperatures of various parts of the air conditioner 1. Each of the temperature sensors 41 to 46 is, for example, a thermistor.

[0024] The suction-side temperature sensor 41 measures a suction-side temperature T1, which is the refrigerant temperature on the suction side of the accumulator 12. The discharge-side temperature sensor 42 measures a discharge-side temperature T2, which is the refrigerant temperature on the discharge side of the compressor 11. The main path inlet-side temperature sensor 43 measures a main path inlet-side temperature T3, which is the refrigerant temperature between the outdoor expansion valve 17 and the main path 19a of the subcooling heat exchanger 19. The main path outlet-side temperature sensor 44 measures a main path outlet-side temperature T4, which is the refrigerant temperature between the main path 19a and the valve 22. The cooling path inlet-side temperature sensor 45 measures a cooling path inlet-side temperature T5, which is the refrigerant temperature between the cooling path 19b of the subcooling heat exchanger 19 and the subcooling expansion valve 14a. The cooling path outlet-side temperature sensor 46 measures a cooling path outlet-side temperature T6, which is the refrigerant temperature in the injection pipe 25.

[0025] When the outdoor heat exchanger 15 functions as a condenser, the main path inlet temperature T3 is the refrigerant temperature at the inlet side of the main path 19a, and the main path outlet temperature T4 is the refrigerant temperature at the outlet side of the main path 19a. Similarly, the cooling path inlet temperature T5 is the refrigerant temperature at the inlet side of the cooling path 19b, and the cooling path outlet temperature T6 is the refrigerant temperature at the outlet side of the cooling path 19b.

[0026] The air conditioner 1 is also provided with a suction-side pressure sensor 47 and a discharge-side pressure sensor 48. The suction-side pressure sensor 47 measures a suction-side pressure P7, which is the pressure of the refrigerant on the suction side of the accumulator 12, i.e., the suction side of the compressor 11. The discharge-side pressure sensor 48 measures a discharge-side pressure P8, which is the pressure on the discharge side of the compressor 11.

[0027] [1-1-2. Control system configuration] FIG. 2 is a diagram showing the configuration of a control system of the air conditioner 1.

[0028] 2, the air conditioner 1 has a notification unit 49. The notification unit 49 is a device that notifies specific content to people near the air conditioner 1. The notification unit 49 is, for example, a device that emits light such as an LED (Light Emitting Diode), a device that emits sound such as a speaker, or a display device such as a liquid crystal panel.

[0029] The air conditioner 1 has an operation unit 40. The operation unit 40 is a device that accepts various operations related to the air conditioner 1 from people near the air conditioner 1. The operation unit 40 is, for example, a switch, a button, or a touch panel.

[0030] The air conditioner 1 has a control device 50. In this embodiment, the control device 50 is provided in the outdoor unit 10. The control device 50 includes a processor 51 and a memory 52. The processor 51 is configured with a CPU (Central Processing Unit), an MPU (Micro-Processing Unit), or other arithmetic processing device. The memory 52 is a storage device that non-volatilely stores programs and data executed by the processor 51. The memory 52 is configured with a magnetic storage device, a semiconductor storage element, or other types of non-volatile storage device. Specifically, the memory 52 is configured with an HDD (Hard Disk Drive), a flash ROM (Read Only Memory), an SSD (Solid State Drive), or the like. The memory 52 may include RAM (Random Access Memory) that forms a work area for the processor 51. The processor 51 is an example of a "computer" in the present disclosure. The memory 52 is an example of a "storage unit" in the present disclosure.

[0031] The memory 52 stores a control program 54 executed by the processor 51. The control program 54 corresponds to the "program" in this disclosure. The memory 52 stores performance data 56. The memory 52 stores product characteristic data 58.

[0032] The performance data 56 includes information necessary for calculating the performance filling rate gradient, which will be described later, or information on the performance filling rate gradient itself. The performance data 56 is data that is stored in a non-volatile area of the memory 52 by performing the refrigerant amount determination operation, which will be described later, after the air conditioner 1 is installed. In other words, when the refrigerant amount determination operation has never been performed, such as immediately after the air conditioner 1 is installed, the performance data 56 is not stored in the memory 52. Details of the performance data 56 will be described later.

[0033] The product characteristic data 58 includes information necessary for calculating the product filling rate gradient, which will be described later, or information on the product filling rate gradient itself. The product characteristic data 58 is stored in the memory 52 when the air conditioner 1 is manufactured. The product characteristic data 58 may also be provided via the communications network NW or a portable storage medium after the air conditioner 1 is installed, and stored in a non-volatile area of the memory 52. Details of the product characteristic data 58 will be described later.

[0034] The control device 50 is provided with an outdoor unit I / F 59. The outdoor unit I / F 59 is an interface that enables the control device 50 to communicate with each part of the air conditioner 1 wirelessly or via a wired connection, and is equipped with hardware that complies with a predetermined communication standard. The control device 50 exchanges various signals and data with the various devices that are communicatively connected via the outdoor unit I / F 59.

[0035] The control device 50 is communicatively connected via the outdoor unit I / F 59 to various actuators of the air conditioner 1, such as the compressor 11, four-way valve 13, outdoor expansion valve 17, bypass pipe opening / closing valve 28, indoor expansion valve 31, and indoor blower 34. The control device 50 is also communicatively connected via the outdoor unit I / F 59 to the temperature sensors 41 to 46, pressure sensors 47 and 48, operation unit 40, and notification unit 49.

[0036] The control device 50 is also communicatively connected to an external communication device 90 via the outdoor unit I / F 59. The communication device 90 is connected to a communication network NW. The communication device 90 includes, for example, a connector for connecting a communication cable and an interface circuit for inputting and outputting signals through the connector. Furthermore, for example, the communication device 90 may be a wireless communication device that includes an antenna and a wireless circuit and is connected to the communication network NW via a wireless communication line.

[0037] The processor 51 includes, as a functional unit, a control unit 53. The control unit 53 is realized by the processor 51 executing a control program 54, through cooperation between software and hardware.

[0038] The control unit 53 operates various actuators that are communicatively connected to the control device 50, and operates the air conditioner 1. The control unit 53 also transmits and receives various signals or data to and from the sensors 41 to 48, the operation unit 40, and the communication device 90, and controls the operation of the air conditioner 1 based on the acquired signals or data.

[0039] The control unit 53 is configured to be able to perform a refrigerant amount determination operation in addition to the heating operation and cooling operation of the air conditioner 1. The refrigerant amount determination operation is an operation for determining the amount of refrigerant sealed in the refrigeration cycle of the air conditioner 1. The refrigerant amount determination operation will be described in detail later.

[0040] The air conditioner 1 is communicatively connected to a remote system 100 via a communication device 90 and a communication network NW. The remote system 100 is a device communicatively connected to the communication network NW. The remote system 100 is, for example, a server device equipped with a processor. The remote system 100 is configured to be able to transmit operation signals via the communication network NW that cause the air conditioner 1 to perform various operations.

[0041] The remote system 100 may be connected to multiple air conditioners 1. Hereinafter, when distinguishing between the air conditioners 1, they will be referred to as air conditioners 1A and 1B. The air conditioners 1A and 1B may be installed in different situations. For example, the length of the refrigerant piping of the air conditioners 1A and 1B, the number of indoor units 30, and the positional relationship between the outdoor unit 10 and the indoor units 30 may be different from each other. Furthermore, the environments in which the air conditioners 1A and 1B are installed, such as the ambient temperature, may be different from each other.

[0042] [1-2. Operation] The operation of the air conditioner 1 configured as described above will now be described. The control unit 53 is capable of executing a refrigerant amount determination operation, which is an operation for determining whether the amount of refrigerant filled in the air conditioner 1 is appropriate. During the refrigerant amount determination operation, the control unit 53 executes a determination operation for determining whether the refrigerant amount is appropriate while executing constant heating degree control and constant density control, in order to determine whether the refrigerant amount is appropriate while suppressing the effects of the installation conditions and environment of the air conditioner 1. Below, we will first explain constant heating degree control and constant density control, and then explain the principles of the determination operation and how to calculate an approximation formula for the filling rate gradient Y used in the determination operation. After that, we will explain a series of operations of the control unit 53, including constant heating degree control, constant density control, and the determination operation.

[0043] [1-2-1. Details of constant heating control and constant density control] The constant heating degree control is a control for maintaining a constant difference in the degree of subcooling of the refrigerant at the inlet and outlet of the cooling path 19b. The constant density control is a control for maintaining a constant density of the refrigerant at the outlet of the main path 19a. The constant heating degree control and constant density control are performed when the outdoor heat exchanger 15 functions as a condenser.

[0044] Constant degree of heating control is achieved by the control unit 53 controlling each unit of the air conditioner 1 so that the temperature difference T6-T5 between the cooling path inlet temperature T5 and the cooling path outlet temperature T6 is a constant value. Specifically, in constant degree of heating control, when the temperature difference T6-T5 becomes larger than a constant value, the control unit 53 increases the opening of the supercooling expansion valve 14a to increase the amount of refrigerant flowing into the cooling path 19b. Conversely, when the temperature difference T6-T5 becomes smaller than a constant value, the control unit 53 decreases the opening of the supercooling expansion valve 14a to decrease the amount of refrigerant flowing into the cooling path 19b.

[0045] Constant density control is achieved by the control unit 53 controlling each part of the air conditioner 1 so that the main path outlet temperature T4 remains constant. When the main path outlet temperature T4 is lower than the saturation temperature at the high-pressure side of the refrigeration cycle, the refrigerant at the outlet of the main path 19a is liquid refrigerant. In this state, the density of the liquid refrigerant at the outlet of the main path 19a can be calculated from the main path outlet temperature T4. In other words, by controlling the main path outlet temperature T4 to remain constant, the density of the refrigerant at the outlet of the main path 19a can be kept constant. Specifically, in the constant density control, when the main path outlet side temperature T4 drops below a constant value and the density increases, the control unit 53 increases the rotation speed of the compressor 11 and reduces the airflow rate of the outdoor blower 16. This increases the main path outlet side temperature T4 and reduces the refrigerant density. Conversely, when the main path outlet side temperature T4 rises above a constant value and the density decreases, the control unit 53 decreases the rotation speed of the compressor 11 and increases the airflow rate of the outdoor blower 16. This decreases the main path outlet side temperature T4 and increases the density.

[0046] When the constant heating degree control and the constant density control are being performed, it is possible to determine the amount of refrigerant while suppressing the influence of the environment.

[0047] [1-2-2. Principle of Judgment Operation] Figure 3 is a scatter diagram showing the relationship between the refrigerant circulation amount q of the air conditioner 1 and the arithmetic mean temperature difference ΔTm. Note that Figure 3 shows the relationship when constant heating control and constant density control are being executed. The graph in Figure 3 plots points for when the refrigerant amount is the appropriate amount, points for when it is 1 kg or 2 kg less than the appropriate amount, points for when it is 1 kg more than the appropriate amount, and points for when it is 70% of the appropriate amount.

[0048] As shown in Figure 3, the points where the amount of refrigerant is appropriate are located almost on line L1. In contrast, the points where the amount of refrigerant is 70% of the appropriate amount and the points where the amount is 1 kg more than the appropriate amount are located on curves L2 and L3, which are distant from the points where the amount is appropriate and line L1. Specifically, the points on the scatter plot where the amount of refrigerant is greater than the appropriate amount are located on the side of line L1 where the arithmetic mean temperature difference ΔTm is larger. The points on the scatter plot where the amount of refrigerant is less than the appropriate amount are located on the side of line L1 where the arithmetic mean temperature difference ΔTm is smaller.

[0049] In this way, when the refrigerant circulation volume q is within a predetermined range during execution of constant heating degree control and constant density control, it is known that if the amount of refrigerant filled in the air conditioner 1 is appropriate, the arithmetic mean temperature difference ΔTm can be approximated by a linear equation of the refrigerant circulation volume q. Conversely, if the refrigerant volume is not appropriate, it is known that the arithmetic mean temperature difference ΔTm cannot be approximated by a linear equation of the refrigerant circulation volume q. Hereinafter, the range of the refrigerant circulation volume q where the arithmetic mean temperature difference ΔTm can be approximated by a linear equation of the refrigerant circulation volume q when the amount of refrigerant filled in the air conditioner 1 is appropriate will be referred to as the effective circulation volume range Rq.

[0050] Hereinafter, the linear equation for the refrigerant circulation amount q, which approximates the arithmetic mean temperature difference ΔTm when the refrigerant amount is appropriate, will be referred to as the filling rate gradient Y. The above-mentioned straight line L1 is a plot of the filling rate gradient Y. The filling rate gradient Y is expressed by the following equation (A). Y=α*q+β (A) Hereinafter, α in formula (A) will be referred to as the packing rate gradient coefficient α, and β in formula (A) will be referred to as the packing rate gradient intercept β.

[0051] The determination operation of this embodiment utilizes this regularity to determine whether the amount of refrigerant in the air conditioner 1 is appropriate. That is, the set of the refrigerant circulation amount q and the arithmetic mean temperature difference ΔTm obtained during the refrigerant amount determination operation is compared with the filling rate gradient Y, and if there is a large deviation between them, it is determined that the amount of refrigerant in the air conditioner 1 is inappropriate.

[0052] The refrigerant circulation amount q is the mass of refrigerant discharged from the compressor 11 per unit time. The refrigerant circulation amount q is calculated using the compressor rotation speed, cylinder volume, mechanical efficiency, adiabatic efficiency, and compressor intake refrigerant density. Because a complex formula is required to calculate the compressor intake refrigerant density, a value converted from the compressor rotation speed may be used as the refrigerant circulation amount q.

[0053] The above-mentioned arithmetic mean temperature difference ΔTm is the arithmetic mean value of the difference in refrigerant temperature between the main path 19a and the cooling path 19b in the subcooling heat exchanger 19. In this embodiment, the arithmetic mean temperature difference ΔTm is calculated as the arithmetic mean value of the temperature difference T3-T6 between the main path inlet temperature T3 and the cooling path outlet temperature T6, and the temperature difference T4-T5 between the main path outlet temperature T4 and the cooling path inlet temperature T5. That is, the arithmetic mean temperature difference ΔTm is given by the following equation (B): ΔTm=(T3-T6+T4-T5) / 2 (B)

[0054] [1-2-3. How to calculate the filling rate gradient] The approximate equation for the filling rate gradient Y can be determined by calculating approximate values α0 and β0 of the filling rate gradient coefficient α and the filling rate gradient intercept β from the arithmetic mean temperature difference ΔTm and the refrigerant circulation rate q when the refrigerant amount is appropriate, and substituting these values into equation (A). The following describes how to determine the approximate equation for the filling rate gradient Y in this embodiment. In the following description, unless otherwise specified, it is assumed that constant heating degree control and constant density control are being executed and that the refrigerant circulation rate q is within the effective circulation rate range Rq.

[0055] In this embodiment, the approximate value α0 of the filling rate gradient coefficient α is calculated by the following formula (C). α0=(ΔTm1-ΔTm2) / (q1−q2) (C) The values q1 and q2 in equation (C) are different values of the refrigerant circulation volume q when the air conditioner 1 is filled with the appropriate amount of refrigerant. The values ΔTm1 and ΔTm2 are values of the arithmetic mean temperature difference corresponding to the values q1 and q2. In other words, the value Tm1 is the value of the arithmetic mean temperature difference ΔTm when the refrigerant circulation volume q is the value q1. Similarly, the value Tm2 is the value of the arithmetic mean temperature difference ΔTm when the refrigerant circulation volume q is the value q2. In other words, in this embodiment, the approximate value α0 of the filling rate gradient coefficient α is calculated by dividing the amount of change in the arithmetic mean temperature difference ΔTm over a specified period by the amount of change in the refrigerant circulation volume q over the same period.

[0056] In this embodiment, the approximate value β0 of the filling rate gradient intercept β is calculated based on the ambient temperature of the outdoor unit 10, the rotation speed of the compressor 11, the dilution rate of the refrigerating machine oil, and the like.

[0057] [1-2-4. Overview of refrigerant amount determination operation] FIG. 4 is a flowchart showing the operation of the control unit 53, and shows the operation during refrigerant quantity determination operation. The operation in FIG. 4 is executed when refrigerant is charged immediately after installation of the air conditioner 1, immediately after refrigerant is charged into the air conditioner 1, during regular inspection or simple inspection of the air conditioner 1, etc. The operation in FIG. 4 is executed when triggered by the control unit 53 detecting a first operation signal transmitted from the remote system 100, or by the control unit 53 detecting a first operation on the operation unit 40. The first operation signal is a signal that causes the air conditioner 1 to perform refrigerant quantity determination operation. The first operation is an operation that causes the air conditioner 1 to perform refrigerant quantity determination operation.

[0058] In step SA1, the control unit 53 controls the four-way valve 13 to connect the discharge side of the compressor 11 to the outdoor heat exchanger 15. By executing step SA1, the liquid refrigerant discharged from the compressor 11 and condensed in the outdoor heat exchanger 15 passes as a liquid through the main path 19a of the subcooling heat exchanger 19. Thereafter, part of the liquid refrigerant flows into the branch pipe 14, expands in the subcooling expansion valve 14a, becomes low-temperature flash gas, and flows into the cooling path 19b of the subcooling heat exchanger 19. As a result, in the subcooling heat exchanger 19, heat is transferred from the liquid refrigerant flowing through the main path 19a to the low-temperature refrigerant flowing through the cooling path 19b.

[0059] In this way, by executing step SA1, the outdoor heat exchanger 15 is brought into a state where it functions as a condenser. That is, by executing step SA1, the control unit 53 is able to execute the constant subcooling control and constant density control described above. After completing step SA1, the operation of the control unit 53 proceeds to step SA2.

[0060] In step SA2, the control unit 53 starts the constant supercooling control and constant density control described above. After completing step SA2, the operation of the control unit 53 proceeds to step SA3. Note that the control unit 53 continues the constant supercooling control and constant density control until the operation of the control unit 53 reaches step SA7.

[0061] In step SA3, control unit 53 executes an operation to determine the mode of the determination operation. Control unit 53 can execute the determination operation in a first determination mode that uses a past filling rate gradient that is an approximation formula of filling rate gradient Y based on past performance data 56, and a second determination mode that uses a product filling rate gradient that is an approximation formula of filling rate gradient Y based on product characteristic data 58. In step SA3, it is determined which of these two determination modes to execute the determination operation in.

[0062] In step SA3, the control unit 53 determines which determination mode to apply depending on whether the actual actual filling rate gradient is available. The state in which the control unit 53 can use the actual actual filling rate gradient means a state in which the actual filling rate gradient itself or data necessary for calculating the actual filling rate gradient is stored as performance data 56. If the control unit 53 determines that this data is stored (step SA3: YES), the operation of the control unit 53 proceeds to step SA12. If the control unit 53 determines that this data is not stored (step SA3: NO), the operation of the control unit 53 proceeds to step SA5.

[0063] As will be described later, when step SA4 is executed, control unit 53 executes the determination operation in the first determination mode, and when step SA5 is executed, it executes the determination operation in the second determination mode. That is, when control unit 53 can execute the determination operation in both the first determination mode and the second determination mode, it prioritizes execution of the determination operation in the first determination mode.

[0064] In step SA4, the control unit 53 acquires the actual filling rate gradient to be used in the determination operation. That is, the control unit 53 obtains an approximate value α0 of the filling rate gradient coefficient α and an approximate value β0 of the filling rate gradient intercept β from the actual data 56. The approximate value α0 obtained in step SA4 is referred to as the actual filling rate gradient coefficient. The actual data 56 includes data on the refrigeration cycles in refrigerant amount determination operations previously performed in each of the air conditioners 1A and 1B. That is, the actual data 56 is data specific to each of the air conditioners 1A and 1B, reflecting the installation conditions, etc., of each of the air conditioners 1A and 1B. Therefore, the actual data 56 of the air conditioner 1A differs from the actual data 56 of the air conditioner 1B.

[0065] For example, consider a case where the performance data 56 includes values q3 and q4, which are values of the refrigerant circulation amount q, acquired during a previously executed refrigerant amount determination operation, and values ΔTm3 and ΔTm4, which are values of the arithmetic mean temperature difference ΔTm when the refrigerant circulation amount q is the value q3 or q4. In this case, the control unit 53 substitutes the values q3, q4, ΔTm3, and ΔTm4 for the values q1, q2, ΔTm1, and ΔTm2 in equation (C), respectively, to calculate the performance filling rate gradient coefficient. Then, the control unit 53 calculates the approximate value β0 using the method described above. This allows the control unit 53 to calculate the performance filling rate gradient, completing step SA4. Alternatively, if the performance data 56 includes the performance filling rate gradient coefficient or performance filling rate gradient calculated using the values q3, q4, ΔTm3, and ΔTm4, the control unit 53 may use these data included in the performance data 56 as is. After step SA4 is executed, the control unit 53 proceeds to step SA6.

[0066] In step SA5, the control unit 53 acquires the product filling rate gradient to be used in the determination operation. That is, the control unit 53 obtains an approximate value α0 of the filling rate gradient coefficient α and an approximate value β0 of the filling rate gradient intercept β from the product characteristic data 58. The product characteristic data 58 is, for example, data obtained in a test in which the air conditioner 1 is made to perform a refrigerant amount determination operation. That is, the product characteristic data 58 is data common to each of the air conditioners 1A, 1B, and does not reflect the installation conditions, etc., of each of the air conditioners 1A, 1B.

[0067] For example, let us consider a case where product characteristic data 58 includes values q5 and q6, which are values of refrigerant circulation volume q obtained during a test in which air conditioner 1 is operated during refrigerant quantity determination, and values ΔTm5 and ΔTm6, which are values of the arithmetic mean temperature difference ΔTm when refrigerant circulation volume q is q5 and q6. In this case, control unit 53 substitutes values q5, q6, ΔTm5, and ΔTm6 for values q1, q2, ΔTm1, and ΔTm2 in equation (C), respectively, to obtain an approximate value α0 of the filling rate gradient coefficient α. Then, using the method described above, control unit 53 obtains an approximate value β0 of the filling rate gradient intercept β. This allows control unit 53 to obtain the actual filling rate gradient, completing step SA5. Alternatively, if product characteristic data includes an approximate value α0 of the filling rate gradient coefficient α or the product filling rate gradient obtained using values q5, q6, ΔTm5, and ΔTm6, control unit 53 may use these data included in product characteristic data 58 as is. By executing step SA5, the operation of the control unit 53 proceeds to step SA6.

[0068] In step SA6, the control unit 53 executes a determination operation regarding the amount of refrigerant in the air conditioner 1. By executing the determination operation, the control unit 53 obtains a determination result as to whether or not the amount of refrigerant in the air conditioner 1 is appropriate. Details of step SA6 will be described later.

[0069] In step SA7, the control unit 53 notifies the determination result of step SA6. The notification of the determination result may be executed, for example, by the control of the control unit 53, such that the notification unit 49 emits sound or light, or by the notification unit 49 performing a display. Furthermore, for example, the control unit 53 may notify the determination result to the remote system 100 via the communication device 90, the communication network NW, etc. When the execution of step SA4 is completed, the control unit 53 ends the refrigerant amount determination operation.

[0070] [1-2-3. Details of the judgment operation] Next, the determination operation in step SA6 will be described in detail.

[0071] FIG. 5 is a flowchart of the control unit 53, showing the details of the operation of the control unit 53 in step SA6.

[0072] At the beginning of step SA6, in step SA11, control unit 53 samples a pair of value qi of refrigerant circulation amount q and value ΔTmi of arithmetic mean temperature difference ΔTm when refrigerant circulation amount q is value qi. Control unit 53 obtains value qi using the rotation speed of compressor 11, etc. Control unit 53 also obtains value ΔTmi by substituting the measured values of each temperature sensor 43-46 when refrigerant circulation amount q is value qi into equation (B). Note that in step SA11, control unit 53 controls the rotation speed of compressor 11, etc., to set value qi within effective circulation amount range Rq.

[0073] In this embodiment, control unit 53 samples multiple pairs of values qi of refrigerant circulation amount q and values ΔTmi of arithmetic mean temperature difference ΔTm when refrigerant circulation amount q is value qi. That is, control unit 53 samples value qi and value ΔTmi corresponding to value qi multiple times while controlling the rotation speed of compressor 11 and changing refrigerant circulation amount q within effective circulation amount range Rq. After completing sampling of value qi and value ΔTmi corresponding to value qi, control unit 53 proceeds to step SA12.

[0074] In step SA12, the control unit 53 executes a determination based on the filling rate gradient Yi for determination. The filling rate gradient Yi for determination is a linear expression for the value qi, and is given by the following equation (D). Yi=α0*qi+β0 (D) In equation (D), control unit 53 uses α0, the approximation value of the filling rate gradient coefficient α obtained in step SA4 or step SA5, as the coefficient of the value qi of the refrigerant circulation amount q. Control unit 53 also uses β0, the approximation value of the filling rate gradient intercept β obtained in step SA4 or step SA5, as the constant term of equation (D). That is, when performing the determination operation in the first determination mode, control unit 53 uses the actual filling rate gradient obtained in step SA4 as the determination filling rate gradient Yi. When performing the determination operation in the second determination mode, control unit 53 uses the product filling rate gradient obtained in step SA5 as the determination filling rate gradient Yi.

[0075] In step SA12, the control unit 53 determines whether the magnitude of the difference between the value ΔTmi when the refrigerant circulation amount q sampled in step SA11 is the value qi and the filling rate gradient Yi for determination corresponding to the value qi is equal to or smaller than the confidence interval θ. That is, it determines whether the following inequality (E) is satisfied. |(α0*qi+β0)-ΔTmi|≦θ (E) The confidence interval θ is a value that is set appropriately. When the confidence interval θ is a small value, the range of the refrigerant amount in the air conditioner 1, over which the control unit 53 will not determine that the refrigerant amount in the air conditioner 1 is inappropriate, is smaller than when the confidence interval θ is a large value.

[0076] In this embodiment, in step SA11, since only a plurality of pairs of values qi and ΔTmi are sampled, the control unit 53 determines whether or not the inequality (E) holds for all the sampled pairs.

[0077] In this embodiment, if there is one or more pairs of values qi and ΔTmi for which inequality (E) holds (step SA12: YES), the operation of control unit 53 proceeds to step SA13. If inequality (E) does not hold for all pairs (step SA12: NO), control unit 53 determines that the amount of refrigerant in the air conditioner 1 is inappropriate, and the operation of control unit 53 proceeds to step SA16.

[0078] In step SA13, the control unit 53 determines whether constant heating control is being maintained. When the amount of refrigerant charged in the air conditioner 1 is significantly less than the appropriate amount, the volume of the entire refrigeration cycle of the air conditioner 1 is constant, resulting in a large refrigerant specific volume. Therefore, when the amount of refrigerant charged is significantly less than the appropriate amount, the refrigerant temperature is higher than when the amount of refrigerant is the appropriate amount under the same pressure conditions, resulting in a larger specific enthalpy. Therefore, when the amount of refrigerant charged is significantly less than the appropriate amount, the proportion of gaseous refrigerant increases when the subcooling expansion valve 14a is decompressed. This requires increasing the opening of the subcooling expansion valve 14a, which prevents the refrigerant from being completely throttled, resulting in a small amount of pressure reduction. In this case, the constant heating control described above cannot be continued. In other words, when the amount of pressure reduction in the subcooling expansion valve 14a is smaller than a predetermined value, it can be determined that constant heating control is not being maintained.

[0079] That is, the control unit 53 determines whether the difference between the injection pressure Pm, which is the pressure in the injection pipe 25 after passing through the supercooling expansion valve 14a, and the high-pressure pressure Ph is equal to or less than the reference differential pressure ΔP. The high-pressure pressure Ph is the pressure at a point in the refrigeration cycle of the air conditioner 1 where the refrigerant pressure becomes high. The high-pressure pressure Ph is, for example, the pressure on the discharge side of the compressor 11, the pressure of the outdoor heat exchanger 15 which serves as a condenser, etc. That is, in step SA13, the control unit 53 determines whether the following inequality (F) is true. Ph-Pm≧ΔP (F) The reference differential pressure ΔP is stored, for example, in the memory 52. The reference differential pressure ΔP is set to the minimum value of the differential pressure between the high pressure Ph and the injection pressure Pm while constant heating degree control can be continued, for example, during a test using the air conditioner 1.

[0080] In this embodiment, the value of the high-pressure pressure Ph is the discharge-side pressure P8 measured by the discharge-side pressure sensor 48. In this embodiment, the value of the injection pressure Pm is the saturation pressure converted from the cooling path inlet temperature T5 measured by the cooling path inlet temperature sensor 45.

[0081] If formula (F) is true, the operation of the control unit 53 proceeds to step SA14. If formula (F) is not true, the control unit 53 determines that the amount of refrigerant in the air conditioner 1 is inappropriate, and the operation of the control unit 53 proceeds to step SA16.

[0082] In step SA14, the control unit 53 determines whether the various parameters of the air conditioner 1 are within their reference ranges. For example, even if the control unit 53 determines that the refrigerant amount is appropriate in steps SA12 and SA13, if the operation of the various actuators of the air conditioner 1 is outside the expected operating range, it is considered that the determination was incorrect. To address such a case, in step SA14, the control unit 53 of this embodiment determines whether the various parameters whose values change depending on the operation of the various actuators are within their respective reference value ranges. Specifically, in this embodiment, the control unit 53 determines whether the heating degree on the discharge side of the compressor 11, the heating degree on the suction side of the compressor 11, the subcooling degree in the condenser, the opening degree of the evaporator expansion valve, and the discharge temperature of the compressor 11 are each within their respective reference value ranges.

[0083] In this embodiment, the control unit 53 uses, as the heating degree on the discharge side of the compressor 11, a value obtained by subtracting the saturation temperature converted from the discharge side pressure P8 measured by the discharge side pressure sensor 48 from the discharge side temperature T2 measured by the discharge side temperature sensor 42. When the heating degree on the discharge side of the compressor 11 is equal to or greater than a predetermined reference value, the control unit 53 determines that the heating degree is outside the range of the reference value.

[0084] The control unit 53 uses, as the degree of heating on the suction side of the compressor 11, a value obtained by subtracting the saturation temperature converted from the suction side pressure P7 measured by the suction side pressure sensor 47 from the suction side temperature T1 measured by the suction side temperature sensor 41. When the degree of heating on the suction side of the compressor 11 is equal to or greater than a predetermined reference value, the control unit 53 determines that the degree of heating is outside the range of the reference value.

[0085] The control unit 53 uses, as the degree of subcooling in the condenser, a value obtained by subtracting the main path inlet side temperature T3 or the main path outlet side temperature T4 measured by the main path inlet side temperature sensor 43 or the main path outlet side temperature sensor 44 from the saturation temperature converted from the discharge side pressure P8. When the degree of subcooling in the condenser is equal to or less than a predetermined reference value, the control unit 53 determines that it is outside the range of reference values.

[0086] The control unit 53 uses the opening degree of the indoor expansion valve 31 as the opening degree of the expansion valve for the evaporator. When the opening degree of the expansion valve for the evaporator is equal to or greater than a predetermined reference value determined for each air conditioning load, the control unit 53 determines that the opening degree is outside the range of the reference value.

[0087] The control unit 53 uses the discharge-side temperature T2 measured by the discharge-side temperature sensor 42 as the discharge temperature of the compressor 11. When the discharge temperature of the compressor 11 is equal to or higher than a predetermined reference value, the control unit 53 determines that the discharge temperature is outside the range of the reference value.

[0088] If it is determined in step SA14 that all of the parameters are within the reference value range, the operation of the control unit 53 proceeds to step SA15. If it is determined in step SA14 that one or more parameters are outside the reference value range, the control unit 53 determines that the amount of refrigerant in the air conditioner 1 is inappropriate, and the operation of the control unit 53 proceeds to step SA15.

[0089] In step SA15, the control unit 53 finalizes the determination result of the determination operation as a result that the amount of refrigerant in the air conditioner 1 is appropriate. After completing step SA15, the operation of the control unit 53 proceeds to step SA17.

[0090] In step SA16, the control unit 53 finalizes the determination result of the determination operation as a result that the amount of refrigerant in the air conditioner 1 is not appropriate. After completing step SA16, the operation of the control unit 53 proceeds to step SA17.

[0091] As described above, in this embodiment, the control unit 53 independently determines the amount of refrigerant in the air conditioner 1 in steps SA12 to SA14. When the control unit 53 determines that the amount of refrigerant is inappropriate in one or more of the determinations, it reports in step SA7 that the amount of refrigerant in the air conditioner 1 is inappropriate. Furthermore, when the control unit 53 does not determine that the amount of refrigerant is inappropriate in all of the determinations, it determines in step SA7 that the amount of refrigerant in the air conditioner 1 is appropriate. In this embodiment, the accuracy of the determination by the control unit 53 is ensured by combining multiple determinations in this way.

[0092] In step SA17, control unit 53 stores each value qi and ΔTmi sampled in step SA11, or an approximate value α0 of the filling rate gradient coefficient α and an approximate value β0 of the filling rate gradient intercept β calculated using formula (C) and each value qi and ΔTmi. Completion of step SA17 enables control unit 53 to use the actual filling rate gradient based on the current data in the next and subsequent refrigerant amount determination operations. Completion of step SA17 causes control unit 53 to end the determination operation in step SA6 and proceed to the operation of step SA7 in FIG. 4.

[0093] [1-3. Effects, etc.] As described above, in this embodiment, the air conditioner 1 is equipped with a compressor 11, an outdoor heat exchanger 15, a subcooling heat exchanger 19 having a main path 19a and a cooling path 19b, and a subcooling expansion valve 14a which expands the refrigerant that has passed through the main path 19a and passes it through the cooling path 19b, and is equipped with a control unit 53 that is capable of performing refrigerant amount determination operation, and in the refrigerant amount determination operation, the control unit 53 performs a determination operation as to whether the refrigerant amount in the air conditioner 1 is appropriate, while keeping the difference in the degree of subcooling of the refrigerant at the inlet and outlet of the cooling path 19b constant and keeping the density of the refrigerant at the outlet of the main path 19a constant. This makes it easier to determine the amount of refrigerant in the air conditioner 1 while suppressing the effects of installation conditions and the environment. Therefore, it becomes easier to determine the amount of refrigerant in the air conditioner 1 appropriately.

[0094] As in this embodiment, the air conditioner 1 may be configured to include an operation unit 40 that accepts operations, and the control unit 53 may be configured to execute the refrigerant amount determination operation when the operation unit 40 accepts a first operation. This allows an operator or the like to determine the amount of refrigerant in the air conditioner 1 at any time. Therefore, for example, when filling the air conditioner 1 with refrigerant, it is easy to check whether the appropriate amount of refrigerant has been filled.

[0095] As in this embodiment, the air conditioner 1 may be configured such that, when the control unit 53 receives a first operation signal from the remote system 100, it executes the refrigerant amount judging operation. This makes it possible to automatically and periodically determine the amount of refrigerant in the air conditioner 1 from a remote system. This makes it easier to monitor for refrigerant leaks in the air conditioner 1, for example.

[0096] As in this embodiment, the control unit 53 may be configured to use the temperature difference between the refrigerant flowing into the main path 19a and the refrigerant flowing out from the main path 19a to perform the determination operation during the refrigerant amount determination operation. This allows the determination operation to be performed using the temperature of the refrigerant in the subcooling heat exchanger 19, which is less susceptible to deterioration over time, making it easier to determine the amount of refrigerant in the air conditioner 1 while suppressing the effects of the installation conditions and environment of the air conditioner 1. This makes it easier to appropriately determine the amount of refrigerant in the air conditioner 1.

[0097] As in this embodiment, the control unit 53 may be configured to determine in the judgment operation that the amount of refrigerant in the air conditioner 1 is inappropriate if the combination of the value qi of the refrigerant circulation amount q in the air conditioner 1 and the value ΔTmi of the arithmetic mean temperature difference ΔTm between the refrigerant in the main path 19a and the refrigerant in the cooling path 19b is outside the range of the confidence interval θ centered on the judgment filling rate gradient Yi. This allows the determination operation to be performed using the temperature of the refrigerant in the subcooling heat exchanger 19, which is less susceptible to deterioration over time, making it easier to determine the amount of refrigerant in the air conditioner 1 while suppressing the effects of the installation conditions and environment of the air conditioner 1. This makes it easier to appropriately determine the amount of refrigerant in the air conditioner 1.

[0098] As in the present embodiment, the judgment operation may include a first judgment mode, and when the control unit 53 performs the judgment operation in the first judgment mode, the actual filling rate gradient may be used as the judgment filling rate gradient Yi, the actual filling rate gradient may be calculated as a linear equation for the refrigerant circulation amount q with the actual filling rate gradient coefficient as a first-order coefficient, and the actual filling rate gradient coefficient may be a value obtained by dividing the amount of change in the arithmetic mean temperature difference ΔTm during the execution of a refrigerant amount judgment operation that was previously performed by the amount of change in the refrigerant circulation amount q. This allows the refrigerant amount in the air conditioner 1 to be determined based on data from previous refrigerant amount determination operations, reflecting conditions specific to each air conditioner 1A, 1B. This makes it easier to accurately determine whether the refrigerant amount in the air conditioner 1 is appropriate. Specifically, immediately after installing the air conditioner 1 and properly charging it with refrigerant, a refrigerant amount determination operation is performed to obtain values for the refrigerant circulation amount q and the arithmetic mean temperature difference ΔTm. These values are then used to calculate the actual filling rate gradient coefficient, which can be used in the determination operation of the first determination mode. This makes it easier to compare the current refrigerant amount in the air conditioner 1 with the appropriate refrigerant amount in the past, making it easier to determine whether the air conditioner 1 is leaking refrigerant.

[0099] As in this embodiment, the judgment operation may include a second judgment mode, and when the control unit 53 performs the judgment operation in the second judgment mode, the control unit 53 may use the product filling rate gradient as the judgment filling rate gradient Yi, and the product filling rate gradient may be a linear expression for the refrigerant circulation amount q based on the product characteristic data 58 pre-stored in the memory 52. This makes it easier to determine whether the amount of refrigerant in the air conditioner 1 is appropriate using data stored in advance in memory 52. Therefore, even in cases where the actual filling rate gradient cannot be used, it is easier to appropriately determine the amount of refrigerant in the air conditioner 1. Specifically, for example, when installing the air conditioner 1 using existing piping whose piping length is unknown, the refrigerant amount determination operation is performed, and the refrigerant is charged while determining whether the amount of refrigerant is appropriate in the second determination mode, making it easier to appropriately charge the refrigerant into the air conditioner 1.

[0100] As in this embodiment, the control unit 53 may be configured to perform the determination operation in the first determination mode when the actual filling rate gradient is available, and to perform the determination operation in the second determination mode when the actual filling rate gradient is unavailable. This allows for preferential use of the actual filling rate gradient, which is more likely to reflect the installation conditions of each of the air conditioners 1A, 1B, etc. This makes it easier to determine the amount of refrigerant in the air conditioner 1 appropriately.

[0101] As in this embodiment, the air conditioner 1 may be configured to have an injection pipe 25 that injects the refrigerant that has passed through the cooling path 19b into the compressor 11, and the control unit 53 may determine in the determination operation that the amount of refrigerant in the air conditioner 1 is inappropriate when the differential pressure between the pressure in the injection pipe 25 and the pressure on the discharge side of the compressor 11 is equal to or less than the reference differential pressure ΔP. This makes it easier to determine whether the amount of refrigerant in the refrigeration cycle system is appropriate, even when it is difficult to continue the refrigerant amount determination operation.

[0102] As in this embodiment, the control unit 53 may be configured to determine that the amount of refrigerant in the air conditioner 1 is inappropriate if, in the judgment operation, the degree of superheat on the discharge side and suction side of the compressor 11, the degree of subcooling in the outdoor heat exchanger 15, the temperature on the discharge side of the compressor 11, or the opening degree of the indoor expansion valve 31 are outside the range of reference values. This makes it easier to determine whether or not an appropriate amount of refrigerant is sealed in the air conditioner 1, even when the various actuators operate outside their expected operating ranges.

[0103] In addition, in this embodiment, the control program 54 is a program that can be executed by the processor 51 of the air conditioner 1 that is equipped with a compressor 11, an outdoor heat exchanger 15, a subcooling heat exchanger 19 having a main path 19a and a cooling path 19b, and a subcooling expansion valve 14a that expands the refrigerant that has passed through the main path 19a and passes it through the cooling path 19b, and causes the processor 51 to perform a refrigerant quantity determination operation that performs a determination operation on the refrigerant quantity of the air conditioner 1 while keeping the difference in the degree of subcooling of the refrigerant at the inlet and outlet of the cooling path 19b constant and keeping the density of the refrigerant at the outlet of the main path 19a constant. This makes it easier to determine the amount of refrigerant in the air conditioner 1 while suppressing the effects of installation conditions and the environment. Therefore, it becomes easier to determine the amount of refrigerant in the air conditioner 1 appropriately.

[0104] (Other embodiments) As described above, the first embodiment has been described as an example of the technology disclosed in the present application. However, the technology in the present disclosure is not limited to this, and can be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are made. Furthermore, it is also possible to combine the components described in the first embodiment above to create new embodiments. Therefore, other embodiments will be exemplified below.

[0105] In the first embodiment, the air conditioner 1 has been described as an example of a refrigeration cycle system, but the refrigeration cycle system is not limited to the air conditioner 1. For example, the refrigeration cycle system may be a refrigerator or a freezer showcase. Furthermore, the freezer showcase may have a separate outdoor unit or may have a built-in refrigeration cycle.

[0106] In the first embodiment, the control unit 53 is described as executing steps SA12, SA13, and SA14 as an example of the determination operation, but this is just one example. For example, the control unit 53 may be configured not to execute steps SA13 and SA14 in the determination operation. In this case, if the control unit 53 does not determine in step SA12 that the amount of refrigerant in the air conditioner 1 is inappropriate, the control unit 53 may be configured to execute step SA15 and confirm the determination result of the determination operation as being that the amount of refrigerant in the air conditioner 1 is appropriate.

[0107] In the first embodiment, it has been described that the approximate value α0 of the filling rate gradient coefficient α is calculated using formula (C). Also, in the first embodiment, it has been described that the approximate value β0 of the filling rate gradient intercept β is calculated based on the ambient temperature of the outdoor unit 10, the rotation speed of the compressor 11, the dilution rate of the refrigeration oil, etc. However, the method of calculating the approximate values α0 and β0 is not limited to the above. For example, the control unit 53 may be configured to calculate the approximate values α0 and β0 by performing regression analysis using the least squares method, maximum likelihood estimation method, or the like on multiple pairs of values of the refrigerant circulation amount q and values of the arithmetic mean temperature difference ΔTm.

[0108] In the first embodiment, it has been described that the control unit 53 samples a plurality of pairs of the value qi and the value ΔTmi in step SA11, and determines whether or not the inequality (E) holds for all the sampled pairs in step SA12. However, this is merely an example. The control unit 53 may make the determination using the inequality (E). For example, the control unit 53 may be configured to determine whether or not the inequality (E) holds for any number of pairs of the value qi and the value ΔTmi that are sampled in step SA12, the number being one or more. Furthermore, for example, the control unit 53 may be configured to sample only one pair in step SA11, as long as the number is any number greater than one.

[0109] In the first embodiment, it has been explained that the control unit 53 determines that the amount of refrigerant in the air conditioner 1 is inappropriate if, in step SA12, inequality (E) is not satisfied for any of the pairs of values qi and ΔTmi for which it has determined whether inequality (E) is satisfied, the control unit 53 determines that the amount of refrigerant in the air conditioner 1 is inappropriate. However, this is just one example. The control unit 53 may be configured to determine that the amount of refrigerant in the air conditioner 1 is inappropriate if, in step SA12, inequality (E) is not satisfied for any number of pairs of values qi and ΔTmi for which it has determined whether inequality (E) is satisfied.

[0110] The various parameters of the refrigeration cycle, such as the refrigerant temperature and pressure, used for various operations such as determination by the control unit 53 may be values measured directly by various sensors, or may be values converted from the measurements of the various sensors. Furthermore, the various parameters may be measured at any location in the refrigeration cycle of the air conditioner 1, as long as the parameters have values equivalent to those described in the first embodiment.

[0111] The units shown in FIG. 2 are merely examples, and the specific implementation form is not particularly limited. In other words, it is not necessary to implement hardware corresponding to each unit individually, and it is of course possible to configure the units so that their functions are realized by a single processor executing a program. Furthermore, some of the functions realized by software in the above-described embodiments may be implemented as hardware, or some of the functions realized by hardware may be implemented by software. The specific detailed configurations of the air conditioner 1, communication device 90, remote system 100, and other devices may also be changed as desired without departing from the spirit of this disclosure.

[0112] Furthermore, the step units of operation shown in Figures 4 and 5 are divided according to the main processing content to make it easier to understand the operation of the air conditioner 1, and this disclosure is not limited by the way the processing units are divided or their names.

[0113] It should be noted that the above-described embodiments are intended to illustrate the technology of the present disclosure, and various modifications, substitutions, additions, omissions, etc. may be made within the scope of the claims or their equivalents.

[0114] (Addendum) The above description of the embodiments discloses the following techniques. (Technology 1) A refrigeration cycle system including a compressor, a heat source side heat exchanger, a subcooling heat exchanger having a main path and a cooling path, and a subcooling expansion valve that expands refrigerant that has passed through the main path and passes it through the cooling path, and further including a control unit capable of performing a refrigerant amount determination operation, wherein the control unit, during the refrigerant amount determination operation, performs an operation of determining whether the amount of refrigerant in the refrigeration cycle system is appropriate while keeping the difference in the degree of subcooling of the refrigerant at the inlet and outlet of the cooling path constant and keeping the density of the refrigerant at the outlet of the main path constant. This makes it easier to determine the amount of refrigerant in the refrigeration cycle system while suppressing the effects of installation conditions and the environment, thereby facilitating appropriate determination of the amount of refrigerant in the refrigeration cycle system.

[0115] (Technical 2) The refrigeration cycle system according to Technical 1, further comprising an operation unit that accepts an operation, wherein the control unit executes the refrigerant amount determining operation when the operation unit accepts a first operation. This allows an operator or the like to determine the amount of refrigerant in the refrigeration cycle system at any time, making it easier to check whether an appropriate amount of refrigerant is being charged, for example, when charging the refrigeration cycle system with refrigerant.

[0116] (Technical Aspect 3) The refrigeration cycle system according to Technical Aspect 1 or 2, wherein the control unit executes the refrigerant amount determining operation when a first operation signal is received from a remote system. This allows the amount of refrigerant in the refrigeration cycle system to be determined automatically and periodically from a remote system, making it easier to monitor, for example, refrigerant leakage from the refrigeration cycle system.

[0117] (Technology 4) A refrigeration cycle system according to any one of technologies 1 to 3, wherein the control unit uses the temperature difference between the refrigerant flowing into the main path and the refrigerant flowing out of the main path to perform the determination operation during the refrigerant amount determination operation. The determination can be performed using the temperature of the refrigerant in the subcooling heat exchanger, which is less susceptible to deterioration over time, and the amount of refrigerant in the refrigeration cycle system can be easily determined while suppressing the influence of the installation conditions and environment of the refrigeration cycle system. Therefore, it is easy to appropriately determine the amount of refrigerant in the refrigeration cycle system.

[0118] (Technology 5) A refrigeration cycle system described in any one of Technologies 1 to 4, wherein, in the judgment operation, the control unit judges that the amount of refrigerant in the refrigeration cycle system is inappropriate if the set of the amount of refrigerant circulating in the refrigeration cycle system and the arithmetic mean temperature difference between the refrigerant in the main path and the refrigerant in the cooling path is outside the range of a confidence interval centered on a judgment filling rate gradient. This allows the determination operation to be performed using the refrigerant temperature in the subcooling heat exchanger, which is less susceptible to deterioration over time, making it easier to determine the amount of refrigerant in the air conditioner 1 while suppressing the effects of the installation conditions and environment of the refrigeration cycle system. This makes it easier to appropriately determine the amount of refrigerant in the refrigeration cycle system.

[0119] (Technology 6) A refrigeration cycle system described in any one of Technologies 1 to 5, wherein the judgment operation includes a first judgment mode, and when the control unit performs the judgment operation in the first judgment mode, the control unit uses an actual filling rate gradient as the judgment filling rate gradient, and the actual filling rate gradient is calculated as a linear equation for the refrigerant circulation amount with an actual filling rate gradient coefficient as a first-order coefficient, and the actual filling rate gradient coefficient is a value obtained by dividing the change in arithmetic mean temperature difference during the execution of the refrigerant amount judgment operation performed in the past by the change in the refrigerant circulation amount. This allows the refrigerant amount of a refrigeration cycle system to be determined based on data from previously performed refrigerant amount determination operations, reflecting conditions specific to each refrigeration cycle system. This makes it easier to accurately determine whether the refrigerant amount in a refrigeration cycle system is appropriate. Specifically, immediately after installing a refrigeration cycle system and properly charging it with refrigerant, a refrigerant amount determination operation is performed to obtain values for the refrigerant circulation amount and the arithmetic mean temperature difference. These values are used to calculate an actual filling rate gradient coefficient, which can be used in the determination operation of the first determination mode. This makes it easier to compare the current refrigerant amount in the refrigeration cycle system with the appropriate refrigerant amount in the past, making it easier to determine whether the refrigerant in the refrigeration cycle system is leaking.

[0120] (Technology 7) A refrigeration cycle system described in Technology 5 or 6, wherein the judgment operation includes a second judgment mode, and when the control unit performs the judgment operation in the second judgment mode, the control unit uses a product filling rate gradient as the judgment filling rate gradient, and the product filling rate gradient is a linear equation for the refrigerant circulation amount based on product characteristic data pre-stored in a memory unit. This makes it easier to determine whether the amount of refrigerant in the refrigeration cycle system is appropriate using data stored in advance in the storage unit. Therefore, even when the actual filling rate gradient cannot be used, it is easier to appropriately determine the amount of refrigerant in the refrigeration cycle system. Specifically, for example, when a refrigeration cycle system is installed using existing piping whose piping length is unknown, the refrigerant amount determination operation is performed, and the refrigerant is charged while determining whether the amount of refrigerant is appropriate in the second determination mode, thereby making it easier to appropriately charge the refrigerant into the refrigeration cycle system.

[0121] (Technology 8) A refrigeration cycle system according to Technology 7, wherein the control unit performs the judgment operation in the first judgment mode when the actual filling rate gradient is available, and performs the judgment operation in the second judgment mode when the actual filling rate gradient is unavailable. This allows the use of a performance filling rate gradient that more easily reflects the installation status of each refrigeration cycle system, etc., with priority, thereby making it easier to appropriately determine the amount of refrigerant in the refrigeration cycle system.

[0122] (Technology 9) A refrigeration cycle system according to any one of technologies 1 to 8, further comprising an injection pipe for injecting the refrigerant that has passed through the cooling path into the compressor, and wherein the control unit determines in the judgment operation that the amount of refrigerant in the refrigeration cycle system is inappropriate when the differential pressure between the pressure in the injection pipe and the high-pressure pressure is equal to or less than a reference differential pressure. This makes it easier to determine whether the amount of refrigerant in the refrigeration cycle system is appropriate, even when it is difficult to continue the refrigerant amount determination operation.

[0123] (Technology 10) A refrigeration cycle system described in any one of Technologies 1 to 9, wherein the control unit determines that the amount of refrigerant in the refrigeration cycle system is inappropriate if, in the judgment operation, the degree of superheat on the discharge side and suction side of the compressor, the degree of subcooling in the condenser, the temperature on the discharge side of the compressor, or the opening degree of the expansion valve of the evaporator are outside the range of reference values. This makes it easier to determine whether an appropriate amount of refrigerant is sealed in the refrigeration cycle system even when various actuators operate outside their expected ranges.

[0124] (Technology 11) A program executable by a computer for a refrigeration cycle system including a compressor, a heat source side heat exchanger, a subcooling heat exchanger having a main path and a cooling path, and a subcooling expansion valve that expands refrigerant that has passed through the main path and passes it through the cooling path, the program causing the computer to execute a refrigerant amount determination operation that determines the amount of refrigerant in the refrigeration cycle system while keeping the difference in the degree of subcooling of the refrigerant at the inlet and outlet of the cooling path constant and keeping the density of the refrigerant at the outlet of the main path constant. This makes it easier to determine the amount of refrigerant in the refrigeration cycle system while suppressing the effects of installation conditions and the environment, thereby facilitating appropriate determination of the amount of refrigerant in the refrigeration cycle system. [Industrial Applicability]

[0125] The present disclosure is applicable to refrigeration cycle systems, specifically to various devices that constitute a refrigeration cycle, such as air conditioners, commercial refrigerators, showcases, and the like. [Explanation of symbols]

[0126] 1, 1A, 1B Air conditioner 10 Outdoor unit 11 Compressor 11a injection port 12 Accumulator 13 Four-way valve 14 Branch piping 14a Cooling expansion valve 15 Outdoor heat exchanger (heat source side heat exchanger) 16 Outdoor blower 17 Outdoor expansion valve 18 Outdoor liquid pipe 19 Subcooling heat exchanger 19a Main Route 19b Cooling path 21 Internal and external connecting liquid pipe 22 valves 23 Internal and external gas pipe connection 25 Injection piping 27 Bypass pipe 28 Bypass pipe on-off valve 30 Indoor unit 31 Indoor expansion valve 33 Indoor heat exchanger 34 Indoor fan 39 Control section 40 Control section 41 Intake side temperature sensor 42 Discharge side temperature sensor 43 Main path inlet temperature sensor 44 Main path outlet temperature sensor 45 Cooling path inlet temperature sensor 46 Cooling path outlet temperature sensor 47 Intake side pressure sensor 48 Discharge side pressure sensor 49 Information Department 50 Control device 51 Processor (computer) 52 Memory (storage section) 53 Control Unit 54 Control Program 56 Performance Data 58 Product characteristics data 59 Outdoor unit I / F 90 Communication Equipment 100 Remote System

Claims

1. A compressor; a heat source side heat exchanger; a subcooling heat exchanger having a main path and a cooling path; a subcooling expansion valve for expanding the refrigerant that has passed through the main path and passing it through the cooling path, A control unit capable of executing a refrigerant amount determination operation is provided, The control unit, in the refrigerant amount determination operation, performs a determination operation as to whether the amount of refrigerant in the refrigeration cycle system is appropriate, while keeping a difference in the degree of subcooling of the refrigerant at the inlet and the outlet of the cooling path constant and keeping a density of the refrigerant at the outlet of the main path constant. Refrigeration cycle system.

2. An operation unit that accepts operations is provided, the control unit executes the refrigerant amount determining operation when the operation unit receives a first operation. The refrigeration cycle system according to claim 1 .

3. the control unit executes the refrigerant amount determination operation when a first operation signal is received from the remote system. The refrigeration cycle system according to claim 1 .

4. The control unit uses a temperature difference between the refrigerant flowing into the main path and the refrigerant flowing out from the main path to perform the determination operation in the refrigerant amount determination operation. The refrigeration cycle system according to claim 1 .

5. In the determination operation, the control unit When a set of a refrigerant circulation amount in the refrigeration cycle system and an arithmetic mean temperature difference between the refrigerant in the main path and the refrigerant in the cooling path is outside a range of a confidence interval centered on a filling rate gradient for judgment, it is determined that the refrigerant amount in the refrigeration cycle system is inappropriate. The refrigeration cycle system according to claim 1 .

6. the determination operation includes a first determination mode, the control unit uses an actual filling rate gradient as the filling rate gradient for determination when performing the determination operation in the first determination mode, the actual filling rate gradient is calculated as a linear equation for the refrigerant circulation amount, with an actual filling rate gradient coefficient as a linear coefficient; The actual filling rate gradient coefficient is a value obtained by dividing the amount of change in the arithmetic mean temperature difference during the execution of the refrigerant amount determination operation that was previously executed by the amount of change in the refrigerant circulation amount. The refrigeration cycle system according to claim 5 .

7. the determination operation includes a second determination mode, the control unit uses a product filling rate gradient as the filling rate gradient for determination when performing the determination operation in the second determination mode, The product filling rate gradient is a linear expression for the refrigerant circulation amount based on product characteristic data pre-stored in a storage unit. The refrigeration cycle system according to claim 6.

8. The control unit When the actual filling rate gradient is available, the determination operation is performed in the first determination mode; When the actual filling rate gradient is unavailable, the determination operation is performed in the second determination mode. The refrigeration cycle system according to claim 7.

9. an injection pipe that injects the refrigerant that has passed through the cooling path into the compressor; In the determination operation, the control unit determines that the amount of refrigerant in the refrigeration cycle system is inappropriate when a differential pressure between the pressure in the injection pipe and a high-pressure pressure is equal to or less than a reference differential pressure. The refrigeration cycle system according to claim 1 .

10. In the determination operation, the control unit determines that the amount of refrigerant in the refrigeration cycle system is inappropriate when the degree of superheat on the discharge side and the suction side of the compressor, the degree of subcooling in the condenser, the temperature on the discharge side of the compressor, or the opening degree of the expansion valve of the evaporator are outside of a range of reference values. The refrigeration cycle system according to claim 9.

11. A computer-executable program for a refrigeration cycle system including a compressor, a heat source-side heat exchanger, a subcooling heat exchanger having a main path and a cooling path, and a subcooling expansion valve that expands a refrigerant that has passed through the main path and passes it through the cooling path, causing the computer to execute a refrigerant amount determination operation for determining the amount of refrigerant in the refrigeration cycle system while maintaining a constant difference in the degree of subcooling of the refrigerant at the inlet and outlet of the cooling path and a constant density of the refrigerant at the outlet of the main path; program.

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