Air conditioner and method for controlling air conditioner

Abstract

To provide an air conditioner improving accuracy in a filling amount of refrigerant, and to provide a method for controlling the air conditioner.SOLUTION: An air conditioner is provided with: an indoor unit; a compressor; an outdoor heat exchanger; a supercooling heat exchanger; a first temperature sensor detecting a temperature of refrigerant flowing through a downstream of the outdoor heat exchanger; a first pressure sensor detecting a pressure of the refrigerant discharged from the compressor; an outdoor unit provided with a refrigerant filling port to which a refrigerant cylinder can be connected; and a control device. The control device includes: an operation part calculating a supercooling degree as a difference between a refrigerant saturation temperature estimated from the detection value of the first pressure sensor and the detection value of the first temperature sensor, and calculating a rate of the change in the supercooling degree with respect to a lapsed time from start of filling; a first determination part determining whether or not a first condition is satisfied, the first condition defined as a case in which the rate of change exceeds a prescribed first threshold value; and an operation control part operating the outdoor unit to finish the filling of the refrigerant when the first condition is satisfied.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to an air conditioner and a method for controlling an air conditioner. [Background technology]

[0002] Patent Document 1 discloses a technique for filling a refrigerant into an air conditioner having an indoor unit and an outdoor unit. In Patent Document 1, one of the conditions for completing the filling of the refrigerant is whether or not the degree of supercooling has reached a predetermined refrigerant filling completion specified value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2017-116156 A Summary of the Invention [Problem to be solved by the invention]

[0004] The present disclosure provides an air conditioner and a method for controlling an air conditioner that can improve the accuracy of the refrigerant filling amount. [Means for solving the problem]

[0005] The air conditioning apparatus of the present disclosure comprises an indoor unit, an outdoor unit equipped with a compressor, an outdoor heat exchanger, a subcooling heat exchanger, a first temperature sensor that detects the temperature of the refrigerant flowing downstream of the outdoor heat exchanger, a first pressure sensor that detects the pressure of the refrigerant discharged from the compressor, and a refrigerant filling port to which a refrigerant cylinder can be connected, and a control device, wherein the control device comprises a calculation unit that calculates a degree of subcooling, which is the difference between the saturation temperature of the refrigerant estimated from the detection value of the first pressure sensor and the detection value of the first temperature sensor, and calculates a rate of change in the degree of subcooling with respect to the elapsed time since filling begins, a first determination unit that determines whether the first condition is satisfied when the rate of change exceeds a predetermined first threshold, and an operation control unit that operates the outdoor unit to terminate filling of the refrigerant if the first condition is satisfied.

[0006] In addition, a control method for an air conditioning apparatus in the present disclosure is a control method for an air conditioning apparatus comprising an indoor unit, an outdoor unit comprising a compressor, an outdoor heat exchanger, a subcooling heat exchanger, a first temperature sensor that detects the temperature of the refrigerant flowing downstream of the outdoor heat exchanger, and a refrigerant filling port to which a refrigerant cylinder can be connected, the control method calculates a degree of subcooling, which is the difference between the saturation temperature of the refrigerant estimated from the detection value of a first pressure sensor that detects the pressure of the refrigerant discharged from the compressor and the detection value of the first temperature sensor, calculates a rate of change in the degree of subcooling with respect to the elapsed time since filling begins, determines whether the rate of change exceeds a predetermined first threshold value as a first condition, determines whether the first condition is satisfied, and if the first condition is satisfied, operates the outdoor unit to terminate filling of the refrigerant. Effect of the Invention

[0007] The air conditioner and the method of controlling the air conditioner according to the present disclosure control the charging of the refrigerant by taking into account the change in the degree of subcooling over time, thereby improving the accuracy of the charging amount of the refrigerant. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 shows the configuration of an air conditioning device. [Diagram 2]Block diagram showing the main parts of the control system for the outdoor unit and the indoor unit [Diagram 3] Ph diagram when the refrigerant charge is insufficient [Figure 4] Ph diagram when the refrigerant charge is appropriate [Diagram 5] Flowchart showing the operation of the first process [Figure 6] Flowchart showing the operation of the second process [Figure 7] Flowchart showing the operation of the third process [Figure 8] Graph showing time-dependent changes in degree of supercooling [Figure 9] Graph showing time change in superheat ratio DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] (The knowledge and other information that formed the basis of this disclosure) In an operation in which the refrigerant required for an air conditioner to satisfy its performance is filled using automatic control from a state where there is a shortage, and the valve is closed and the air conditioner automatically stops after a sufficient amount is filled, there was a problem that the accuracy was reduced if the indicator for determining the appropriate amount was the amount of change in the degree of subcooling at a specified refrigerant filling rate [kg / s] alone. Therefore, the subject of the present disclosure was formed in order to solve this problem. Therefore, the present disclosure provides an air conditioner and a control method for an air conditioner that can improve the accuracy of the refrigerant filling amount.

[0010] Hereinafter, the embodiments will be described in detail with reference to the drawings. However, in some cases, more detailed explanations than necessary may be omitted. For example, detailed explanations of already well-known matters or duplicate explanations of substantially the same configurations may be omitted. It should be noted that 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) [1-1. Configuration] [1-1-1. Air conditioning system configuration] The first embodiment will be described. FIG. 1 is a diagram showing the configuration of an air conditioning device 1.

[0012] As shown in FIG. 1, the air conditioner 1 includes an outdoor unit 4 and an indoor unit 2. The outdoor unit 4 includes a compressor 40, an accumulator 41, a four-way valve 42, an outdoor heat exchanger 43, and a subcooling heat exchanger 44. For example, the following description will be given based on the flow of refrigerant during cooling operation.

[0013] An accumulator 41 that supplies refrigerant to the compressor 40 is connected to the suction side of the compressor 40 by a pipe 77B. A four-way valve 42 is connected to the discharge side of the compressor 40 through a pipe 75A. An outdoor heat exchanger 43 is connected to the four-way valve 42 through a pipe 75B. The outdoor heat exchanger 43 is configured to exchange heat between the air sent by the fan and the refrigerant. The pipe 75A is also provided with a high pressure sensor 61, which will be described later.

[0014] The outdoor heat exchanger 43 has two stages. Two outdoor expansion valves 87U and 87D are provided between the outdoor heat exchanger 43 and the subcooling heat exchanger 44. The outdoor expansion valves 87U and 87D are solenoid valves that adjust the pressure of the refrigerant flowing out from the outdoor heat exchanger 43, etc.

[0015] The outdoor expansion valves 87U, 87D and the indoor unit 2 are connected by piping 78. An injection pipe 71 branching off from the pipe 78 is connected to the pipe 78 downstream of the subcooling heat exchanger 44. The injection pipe 71 passes through the subcooling heat exchanger 44 and is connected to an injection port 85 of the compressor 40. The injection pipe 71 and the injection port 85 constitute an injection mechanism.

[0016] As will be described later, the speed of refrigerant supply can be adjusted by changing the opening of a subcooling heat exchanger expansion valve 82, which is provided in the injection pipe 71 and adjusts the pressure of the refrigerant supplied to the subcooling heat exchanger 44. The subcooling heat exchanger expansion valve 82 corresponds to an example of an expansion valve.

[0017] A pipe 72 that branches off at a first branch point P1 is connected to the injection pipe 71, and the pipe 72 is connected to the upstream side of the accumulator 41. The pipe 72 is provided with a check valve 84, a refrigerant charging port 83, and an injection switching valve 81 in this order when viewed from the upstream side of the refrigerant, i.e., the subcooling heat exchanger 44 side.

[0018] The injection switching valve 81 can be switched to perform injection when closed and not to perform injection when open. That is, when the injection switching valve 81 is in the closed state, the refrigerant that has passed through the subcooling heat exchanger 44 flows to the injection port 85, and when the injection switching valve 81 is in the open state, the refrigerant that has passed through the subcooling heat exchanger 44 flows to the accumulator 41.

[0019] The refrigerant filling port 83 can be connected to a refrigerant cylinder 5 that is connected from outside the outdoor unit 4. The refrigerant cylinder 5 is equipped with a refrigerant supply pipe 5A. When filling the air conditioner 1 with refrigerant, the refrigerant supply pipe 5A is connected to the refrigerant filling port 83.

[0020] The refrigerant charging port 83 is equipped with a pressure reducing circuit 92. The pressure reducing circuit 92 reduces the pressure of the refrigerant being charged.

[0021] A second branch point P2 is provided in the piping 78 between the outdoor expansion valves 87U, 87D and the subcooling heat exchanger 44. The outdoor unit 4 includes a bypass pipe 76 that connects the second branch point P2 to the junction point P3. A bypass valve 90, a pressure reducing circuit 91, and a second temperature sensor 52 are provided in this order in the bypass pipe 76 from the second branch point P2 to the junction point P3.

[0022] A portion of the refrigerant that has passed through the outdoor expansion valves 87U, 87D is bypassed to the bypass pipe 76 when the bypass valve 90 is opened. The ratio of the bypassed refrigerant to the mainstream is, for example, 3%. The ratio of the bypassed refrigerant can be adjusted by adjusting the opening degree of the bypass valve 90.

[0023] The four-way valve 42 is connected to the accumulator 41 through a pipe 77A. The pipe 77A includes a junction P3. The pipe 77A includes a low pressure sensor 62 and a third temperature sensor 53, which will be described later.

[0024] The area through which the refrigerant detected by the high pressure sensor 61 passes, i.e., pipe 75A, and the area through which the refrigerant detected by the low pressure sensor 62 passes, i.e., pipe 77A, are separated by a constant pressure valve 86. The constant pressure valve 86 does not allow refrigerant to pass during normal refrigeration cycle operation or when the refrigerant is being charged. The constant pressure valve 86 functions as a safety valve that releases pressure when, for example, the detection value of the low pressure sensor 62 becomes abnormally large, i.e., when a high-pressure atmosphere is created near the low pressure sensor 62.

[0025] Hereinafter, each sensor provided in the outdoor unit 4 will be described. The first temperature sensor 51 is provided between the subcooling heat exchanger 44 of the pipe 78 and the indoor unit 2. The first temperature sensor 51 detects the temperature of the pipe 78. The first temperature sensor 51 outputs a detected value to the outdoor control device 400. This detected value corresponds to the temperature of the refrigerant flowing from the subcooling heat exchanger 44 to the indoor unit 2.

[0026] The second temperature sensor 52 is provided in the bypass pipe 76, and detects the temperature of the refrigerant after decompression flowing through the bypass pipe 76. The second temperature sensor 52 outputs a detected value to the outdoor control device 400.

[0027] The third temperature sensor 53 is provided between the indoor unit 2 and the junction P3, and detects the temperature of the refrigerant returning from the indoor unit 2 to the outdoor unit and back to the accumulator 41. Specifically, the third temperature sensor 53 is provided on the pipe 77A. The third temperature sensor 53 outputs a detection value to the outdoor control device 400. This detection value corresponds to the temperature of the return refrigerant returning from the indoor unit 2 to the outdoor unit 4.

[0028] The fourth temperature sensor 54 is provided outside the refrigeration cycle of the outdoor unit 4, and detects the outside air temperature outside the outdoor unit 4. The fourth temperature sensor 54 outputs a detected value to the outdoor control device 400.

[0029] The fifth temperature sensor 55U and the sixth temperature sensor 55D are provided upstream of the liquid pipe of the outdoor heat exchanger 43, and detect the temperature of the liquid pipe of the outdoor heat exchanger 43. The first temperature sensor 51 outputs a detection value to the outdoor control device 400. This detection value corresponds to the temperature of the refrigerant flowing into the outdoor heat exchanger 43.

[0030] The seventh temperature sensor 56U and the eighth temperature sensor 56D are provided downstream of the liquid pipe of the outdoor heat exchanger 43, and detect the temperature of the liquid pipe of the outdoor heat exchanger 43. The first temperature sensor 51 outputs a detection value to the outdoor control device 400. This detection value corresponds to the temperature of the refrigerant flowing out from the outdoor heat exchanger 43.

[0031] The high pressure sensor 61 is provided in the pipe 75, and detects the pressure of the refrigerant discharged from the compressor 40. The high pressure sensor 61 outputs a detected value to the outdoor control device 400. The high pressure sensor 61 corresponds to an example of a first pressure sensor.

[0032] The low pressure sensor 62 is provided in the pipe 77A, and detects the pressure of the refrigerant flowing from the indoor unit 2 toward the accumulator 41. The low pressure sensor 62 outputs a detected value to the outdoor control device 400. The low pressure sensor 62 corresponds to an example of a second pressure sensor.

[0033] The indoor unit 2 is connected to the outdoor unit 4 by a refrigerant piping, and the upstream side of the refrigerant piping is partitioned so as to be freely opened and closed by a gate valve 88, and the downstream side of the refrigerant piping is partitioned so as to be freely opened and closed by a gate valve 89. The air conditioner 1 circulates the refrigerant compressed by the outdoor unit 4 between the outdoor unit 4 and the indoor unit 2, and the indoor unit 2 conditions the conditioned room in which the indoor unit 2 is installed.

[0034] [1-1-2. Control system configuration] FIG. 2 is a block diagram showing the main parts of a control system for the outdoor unit 4 and the indoor unit 2. As shown in FIG. The outdoor control device 400 is a control device that controls each part of the outdoor unit 4. The outdoor control device 400 includes an outdoor processor 420, which is a processor such as a CPU (Central Processing Unit) or an MPU (Micro-Processing Unit), an outdoor memory 410, and an interface circuit for connecting other devices and sensors, and controls each part of the outdoor unit 4.

[0035] The outdoor memory 410 is a memory that stores programs and data. The outdoor memory 410 stores the outdoor control program 410, data to be processed by the outdoor processor 420, and detection values ​​detected by the detector group. The outdoor memory 410 has a non-volatile storage area. The outdoor memory 410 may also have a volatile storage area and constitute a work area for the outdoor processor 420. The outdoor memory 410 is constituted by, for example, a ROM or a RAM. The outdoor processor 420 reads and executes the outdoor control program 410 to function as an outdoor operation control unit 421, an outdoor communication control unit 422, a calculation unit 423, a first determination unit 424, a second determination unit 425, and a third determination unit 426. The outdoor control device 400 corresponds to an example of a control device.

[0036] The calculation unit 423 sets a first period which is a period for calculating the degree of subcooling. The duration of the first period is not necessarily constant, and is, for example, a period during which the degree of subcooling can be calculated about five times. The first period is set repeatedly within the time that has elapsed since the start of charging the refrigerant based on the setting of a first rate described later. Hereinafter, the time that has elapsed since the start of charging the refrigerant will be simply referred to as "elapsed time." Furthermore, the calculation unit 423 determines whether or not the latest first period has elapsed.

[0037] The calculation unit 423 acquires the saturation temperature estimated from the detection value detected by the high pressure sensor 61 during the first period and the detection value detected by the first temperature sensor 51.

[0038] Furthermore, the calculation unit 423 calculates the degree of subcooling, which is the difference between the saturation temperature estimated from the detection value detected by the high-pressure sensor 61 and the detection value detected by the first temperature sensor 51. The saturation temperature estimated from the detection value detected by the high-pressure sensor 61 is estimated by the calculation unit 423 taking into account pressure losses in each part of the air conditioning apparatus 1. In particular, the pressure loss of the refrigerant between the outdoor heat exchanger 43 and the outdoor expansion valves 87U, 87D is taken into account. The saturation temperature may be estimated by the calculation unit 423 based on data on the relationship between the refrigerant pressure and the saturation temperature stored in the storage unit 412.

[0039] The calculation unit 423 calculates a median value of the multiple degrees of supercooling within one first period, and then sets the median value as a representative value of the degrees of supercooling.

[0040] The representative value of the degree of supercooling corresponds to the representative degree of supercooling. When the number of degrees of supercooling calculated within one first period is an even number, the calculation unit 423 calculates the median value of the degrees of supercooling excluding the first calculated degree of supercooling. Since the representative degree of supercooling is selected from one of the degrees of supercooling actually calculated, there is an elapsed time when the degree of supercooling selected as the representative degree of supercooling was calculated. The elapsed time corresponds to an example of the elapsed time corresponding to the representative degree of supercooling.

[0041] The calculation unit 423 calculates the rate k of change in the degree of supercooling with respect to the elapsed time. In calculating the rate k of change, the calculation unit 423 uses the representative degree of supercooling and the elapsed time corresponding to the representative degree of supercooling.

[0042] Specifically, the calculation unit 423 calculates the rate of change k between the representative subcooling degree and the elapsed time corresponding to the representative subcooling degree in the most recent first period and the representative subcooling degree and the elapsed time corresponding to the representative subcooling degree in the first period immediately preceding the most recent one.

[0043] The calculation unit 423 sets a second period during which the first degree of superheat and the second degree of superheat are calculated. The second period is not necessarily constant, but is a period during which the first degree of superheat and the second degree of superheat can be calculated about five times. The second period is repeatedly set during the elapsed time from the start of charging of the refrigerant based on the setting of a second rate, which will be described later. The second period corresponds to the period during which the bypass valve 90 is open. Furthermore, the calculation unit 423 determines whether or not the latest second period has elapsed.

[0044] The calculation unit 423 acquires the saturation temperature estimated from the detection value detected by the low pressure sensor 62 during the second period and the detection value detected by the second temperature sensor 52.

[0045] Furthermore, the calculation unit 423 calculates a first degree of superheat, which is the difference between the saturation temperature estimated from the detection value detected by the low-pressure sensor 62 and the detection value detected by the second temperature sensor 52. The saturation temperature estimated from the detection value detected by the low-pressure sensor 62 is estimated by the calculation unit 423 based on the pressure loss in each part of the air conditioning device 1.

[0046] The saturation temperature may be estimated by the calculation unit 423 based on data on the relationship between the refrigerant pressure and the saturation temperature stored in the storage unit 412.

[0047] The calculation unit 423 acquires the saturation temperature estimated from the detection value detected by the low pressure sensor 62 during the second period and the detection value detected by the third temperature sensor 53.

[0048] Furthermore, the calculation unit 423 calculates a second degree of superheat, which is a value based on the difference between the saturation temperature estimated from the detection value detected by the low-pressure sensor 62 and the detection value detected by the third temperature sensor 53. The saturation temperature estimated from the detection value detected by the low-pressure sensor 62 is calculated by the calculation unit 423 based on the pressure loss in each part of the air conditioning device 1.

[0049] The saturation temperature may be estimated by the calculation unit 423 based on data on the relationship between the refrigerant pressure and the saturation temperature stored in the storage unit 412.

[0050] The first and second superheat degrees calculated multiple times in the second period are calculated at approximately the same elapsed time by the calculation unit 423. That is, the calculation unit 423 calculates two values, the first and second superheat degrees, corresponding to one elapsed time.

[0051] The calculation unit 423 calculates a superheat ratio, which is a ratio between the first superheat degree and the second superheat degree. The superheat ratio is obtained by dividing the first superheat degree by the second superheat degree. The superheat ratio is a ratio between the first superheat degree and the second superheat degree corresponding to approximately the same elapsed time. In this way, the calculation unit 423 calculates the superheat ratio multiple times within the second period. The superheat ratio corresponds one-to-one to the elapsed time.

[0052] The calculation unit 423 calculates a median value within one second period among the multiple superheat ratios calculated by the calculation unit 423. Furthermore, the calculation unit 423 sets the median value as a representative value of the superheat ratios. The representative value of the superheat ratios corresponds to the representative superheat ratio. When the number of superheat ratios calculated within one second period is an even number, the calculation unit 423 calculates the median value of the superheat ratios excluding the superheat ratio calculated first.

[0053] The calculation unit 423 sets a first rate, which is the time difference from the latest first period to the next first period. The calculation unit 423 decreases the first rate as the elapsed time increases. The first rate can also be said to be the time difference from one first period to the next first period.

[0054] The calculation unit 423 sets a second rate, which is the time difference from the latest second period to the next second period. The calculation unit 423 decreases the second rate as the elapsed time increases. The second rate can also be said to be the time difference from one second period to the next second period.

[0055] Furthermore, calculation unit 423 determines whether the most recent set first rate has elapsed, and also determines whether the most recent set second rate has elapsed.

[0056] The first determination unit 424 determines whether a first condition is satisfied. The first condition is that the rate of change k exceeds a predetermined first threshold value.

[0057] The second determination unit 425 determines whether a second condition is satisfied. The second condition is that the representative superheat ratio is lower than a predetermined second threshold value.

[0058] The third judgment unit 426 judges whether a third condition is satisfied. The third condition is that the representative degree of subcooling exceeds a predetermined third threshold. The third threshold is the degree of subcooling when the air conditioner 1 is charged with an appropriate amount of refrigerant. To the outdoor control device 400, the injection switching valve 81, the subcooling heat exchanger expansion valve 82, the outdoor expansion valves 87U and 87D, the four-way valve 42, the compressor 40, and a bypass valve 90 are connected. The outdoor operation control section 421 controls the operations of the injection switching valve 81, the subcooling heat exchanger expansion valve 82, the outdoor expansion valves 87U and 87D, the four-way valve 42, the compressor 40, and the bypass valve 90. The outdoor operation control unit 421 corresponds to an example of an operation control unit. Furthermore, a first temperature sensor 51, a second temperature sensor 52, a third temperature sensor 53, a high pressure sensor 61, and a low pressure sensor 62 are connected to the outdoor control device 400. These sensors may be collectively referred to as a detector group. Furthermore, the outdoor communication control unit 422 causes the outdoor communication unit 401 to transmit information held by the outdoor control device 400 to the indoor control device 300.

[0059] The outdoor operation control section 421 controls the operation of each section of the outdoor unit 4.

[0060] The outdoor communication control unit 422 communicates with the indoor control device 300 via the outdoor communication unit 401.

[0061] Next, the control configuration for the main parts of the indoor unit 2 will be described. The indoor unit 2 includes an indoor control device 300 and an indoor communication unit 301.

[0062] The indoor control device 300 is a control device that controls each part of the indoor unit 2. The indoor control device 300 is equipped with an indoor processor 320, which is a processor such as a CPU or MPU, an indoor memory 310, and an interface circuit for connecting other devices and sensors, and controls each part of the indoor unit 2.

[0063] The indoor memory 310 is a memory that stores programs and data. The indoor memory 310 stores the indoor control program 311 and data to be processed by the indoor processor 320. The indoor memory 310 has a non-volatile storage area. The indoor memory 310 may also have a volatile storage area and constitute a work area for the indoor processor 320. The indoor memory 310 is constituted by, for example, a ROM or a RAM.

[0064] The indoor communication unit 301 includes communication hardware such as a communication circuit, and communicates with the indoor control device 400 according to the control of the indoor control device 300. The communication standard of the indoor communication unit 301 may be a wireless communication standard or a wired communication standard.

[0065] The indoor processor 320 reads and executes the indoor control program 311 to function as an indoor operation control unit 321 and an indoor communication control unit 322 . The indoor communication control unit 322 communicates with the indoor control device 400 via the outdoor communication unit 401.

[0066] [1-1-3.Ph diagram] Figure 3 shows the Ph diagram when the refrigerant charge is insufficient. Figure 4 shows the Ph diagram when the refrigerant charge is appropriate. Note that the Ph diagrams in Figures 3 and 4 show the qualitative state of the refrigerant. The horizontal axis is the specific enthalpy of the refrigerant, in units of energy per unit mass [KJ / kg]. The vertical axis is the pressure of the refrigerant, in units of megapascals [MPa].

[0067] 3 and 4 show a saturated liquid line and a saturated vapor line 501, an isotherm line 503, and a specific volume line 505. Note that the specific volume increases as it moves downward on the vertical axis, that is, as the pressure decreases.

[0068] 1, when the bypass valve 90 is opened, only α% of the refrigerant in state N11 flows through the bypass pipe to the junction P3. The amount of refrigerant bypassed is, for example, 3%. The refrigerant flowing through the bypass pipe 76 is decompressed through a decompression circuit 91 formed in a capillary tube shape and reaches state N12. Furthermore, the refrigerant flowing through the bypass pipe 76 merges with the return refrigerant returning from the indoor unit 2 at the junction P3.

[0069] When the refrigerant is insufficient, the pressure is reduced in a two-phase region in the process of reducing pressure from state N11 to state N12 on the outlet side of the outdoor heat exchanger 43 serving as a condenser. Since the pressure is reduced in a two-phase region, the refrigerant contains relatively more gas components than when the refrigerant charge amount is sufficient, and the flow rate tends to be faster, so the pressure difference between state N11 and state N12 tends to be larger.

[0070] The bypassed refrigerant after decompression is at or below the pressure of the return refrigerant of the evaporator and joins the return refrigerant at state N13 as gaseous refrigerant with a large specific volume.

[0071] State N14 shows a state after the return refrigerant and the bypassed refrigerant are merged. Since the bypassed refrigerant has a large specific volume, its effect on the return refrigerant flowing from the pipe 77A is relatively small.

[0072] On the other hand, when the amount of refrigerant charged is appropriate, a sufficient degree of subcooling is reached at the outlet side of the outdoor heat exchanger 43 serving as a condenser. Therefore, referring to Fig. 4, in the process of decompression from state N21 to state N22, decompression mainly occurs in the liquid phase region, so there is a tendency for the amount of gas components to be relatively smaller and the flow rate to be slower than when the amount of refrigerant charged is insufficient. Therefore, the pressure difference between state N21 and state N22 tends to be smaller than the pressure difference between state N11 and state N12.

[0073] The bypassed refrigerant after pressure reduction merges with the return refrigerant in state N23 as wet vapor with a smaller specific volume than the return refrigerant. State N24 shows the state of the return refrigerant before merging. As shown in state N24, the return refrigerant has a larger specific volume than the bypassed refrigerant in state N23.

[0074] State N25 shows the state of the refrigerant after merging. As shown in Fig. 4, when the amount of refrigerant charged is appropriate, the state changes greatly when the bypassed refrigerant merges with the returning refrigerant.

[0075] Therefore, the ratio of the degree of superheat of the refrigerant before merging, i.e., the second degree of superheat of the present disclosure, to the degree of superheat of the bypassed refrigerant, i.e., the first degree of superheat of the present disclosure, becomes large. Therefore, the influence on the refrigerant flowing from the pipe 77A becomes relatively large. In this way, when the representative superheat ratio falls below the second threshold, it can be determined whether the amount of refrigerant charged is appropriate. When the degree of subcooling is almost at the third threshold, the superheat ratio tends to be almost at the second threshold.

[0076] [1-2. Operation, etc.] [1-2-1. First process] FIG. 5 is a flowchart showing the operation of the first process. The first process is a process related to the degree of subcooling, and is executed in parallel with the second process and the third process, which will be described later, after the charging of the refrigerant starts.

[0077] The calculation unit 423 sets a first period (step S1). The first period is appropriately determined in consideration of the transient characteristics of the degree of subcooling.

[0078] The calculation unit 423 calculates the degree of subcooling a number of times (step S2). The number of times the degree of subcooling is calculated is appropriately determined in consideration of the transient characteristics of the degree of subcooling.

[0079] The calculation unit 423 determines whether or not the first period has elapsed (step S3). When the calculation unit 423 determines that the first period has not elapsed (step S3: NO), the calculation unit 423 executes the process of step S3 again.

[0080] If the calculation unit 423 determines that the first period has elapsed (step S3: YES), the calculation unit 423 further calculates a representative degree of subcooling (step S4), and sets an initial first rate (step S5).

[0081] Steps S1 to S5 show the process of calculating the first representative degree of subcooling after the start of charging of the refrigerant.

[0082] Next, the calculation unit 423 sets the next first period (step S10). The next first period is the first period immediately following the most recent first period among the completed first periods. The next first period is appropriately determined in consideration of the transient characteristics of the degree of supercooling.

[0083] The calculation unit 423 determines whether or not the first rate has elapsed (step S11). In step S11, the calculation unit 423 makes a determination based on the latest first rate. If the calculation unit 423 determines that the first rate has not elapsed (step S11: NO), it executes the process of step S11 again.

[0084] When the calculation unit 423 determines that the first rate has elapsed (step S11: YES), the calculation unit 423 further calculates the degree of subcooling a plurality of times (step S12). The number of times the calculation unit 423 calculates the degree of subcooling is appropriately determined in consideration of the transient characteristics of the degree of subcooling.

[0085] The calculation unit 423 determines whether or not the first period has elapsed (step S13). In step S13, the calculation unit 423 makes the determination based on the latest first period. If the calculation unit 423 determines that the first period has not elapsed (step S13: NO), it executes the process of step S13 again.

[0086] If the calculation unit 423 determines that the first period has elapsed (step S13: YES), the calculation unit 423 further calculates the representative degree of subcooling (step S14).

[0087] Next, the calculation unit 423 calculates the rate of change k (step S15).

[0088] The calculation unit 423 sets the first rate (step S16). The time duration of the first rate is set to be shorter than the past first rate.

[0089] Also, the change in the degree of subcooling over time is not a first-order change. Furthermore, the rate of change in the degree of subcooling over time increases as time passes after the start of charging the refrigerant. Therefore, the accuracy of the amount of refrigerant charged can be improved by setting the first rate to be shorter as time passes.

[0090] The first determination unit 424 determines whether or not the first condition is satisfied (Step S17). The third determination unit 426 determines whether or not the third condition is satisfied (Step S18). After step S18 is completed, the outdoor processor 420 transitions the process to step S10.

[0091] [1-2-2. Second Processing] FIG. 6 is a flowchart showing the operation of the second process. The second process is a process related to the superheat ratio, and is executed in parallel with the first process and the third process after the charging of the refrigerant starts. The second process is executed on the premise that the calculation unit 423 has set an initial second rate.

[0092] The calculation unit 423 sets the next second period (step S20). The next second period is the first period following the most recent second period among the completed second periods. If there is no completed second period, the next second period is the first second period. The second period is appropriately determined in consideration of the transient characteristics of the first degree of superheat and the second degree of superheat.

[0093] Next, the calculation unit 423 determines whether or not the second rate has elapsed (step S21). If the calculation unit 423 determines that the second rate has not elapsed (step S21: NO), the calculation unit 423 executes the process of step S21 again.

[0094] When the calculation unit 423 determines that the second rate has elapsed (step S21: YES), the outdoor operation control unit 421 closes the injection switching valve 81 (step S22) and opens the bypass valve 90 (step S23). By closing the injection switching valve 81, the state of the return refrigerant flowing from the indoor unit 2 at the junction P3 and the bypassed refrigerant can be detected by the detector group without mixing the refrigerant from the refrigerant cylinder 5.

[0095] The calculation unit 423 calculates the first superheat degree multiple times, calculates the second superheat degree multiple times, and calculates the superheat degree ratio multiple times (step S24).

[0096] At approximately the same elapsed time, one first degree of superheat and one second degree of superheat are calculated, and the superheat ratio is calculated as a ratio of these two values. The number of calculations is appropriately determined in consideration of the transient characteristics of the first degree of superheat and the second degree of superheat.

[0097] The calculation unit 423 determines whether or not the second period has elapsed (step S25). If the calculation unit 423 determines that the second period has not elapsed (step S25: NO), the calculation unit 423 executes the process of step S25 again.

[0098] If the calculation unit 423 determines that the second period has elapsed (step S25: YES), the outdoor operation control unit 421 opens the injection switching valve 81 (step S26) and closes the bypass valve 90 (step S27).

[0099] Next, the calculation unit 423 calculates the representative superheat ratio (step S28).

[0100] The calculation unit 423 sets a second rate, which is a time difference until the next second period (step S29). The time width of the second rate is set to be shorter than the past second rate. The change in the superheat ratio over time is not a first-order change. Also, the rate of change over time increases as time passes since the start of charging the refrigerant. Therefore, the accuracy of the charging amount of the refrigerant can be improved by setting the second rate to be shorter as time passes.

[0101] The second determination unit 425 determines whether or not the second condition is satisfied (Step S30).

[0102] [1-2-3.Third Processing] FIG. 7 is a flowchart showing the operation of the third process.

[0103] The outdoor operation control unit 421 determines whether the first condition, the second condition, and the third condition are satisfied (step S40). That is, the outdoor operation control unit 421 determines whether the first determination unit 424 determines that the first condition is satisfied, the second determination unit 425 determines that the second condition is satisfied, and the third determination unit 426 determines that the third condition is satisfied.

[0104] If the outdoor operation control unit 421 determines that the first condition, the second condition, and the third condition are not satisfied (step S40: NO), the process of step S40 is executed again.

[0105] If the outdoor operation control unit 421 determines that the first condition, the second condition, and the third condition are satisfied (step S40: YES), the outdoor operation control unit 421 closes the injection switching valve 81 (step S41).

[0106] Next, the outdoor control device 400 stops the first process and the second process (step S42). In step S42, charging of the refrigerant is completed.

[0107] In addition, in step S40 of the third process, the determination may be made based on only the first condition, or based on only the first condition and the third condition.

[0108] [1-2-4. Changes in the degree of subcooling and superheat ratio over time] Next, an example of the change over time in the degree of subcooling and the change over time in the superheat ratio will be shown and the operation will be described. FIG. 8 is a graph showing the change in the degree of subcooling over time. The horizontal axis of the graph represents the elapsed time from the start of charging the refrigerant, in seconds [s]. The vertical axis of the graph is the degree of supercooling, measured in Kelvin [K].

[0109] After time TA1 has elapsed, the calculation unit 423 calculates the degree of subcooling multiple times during a first period SA1 set by the calculation unit 423. Plot group DA1 is a set of plots of the degree of subcooling calculated between time TA1 and time TA2, i.e., during the first first period SA1.

[0110] After the first period SA1 has elapsed, the calculation unit 423 sets the median value MA1 in the plot group DA1 as the representative degree of subcooling in the first first period SA1. Next, the calculation unit 423 sets a first rate HA1, which is the time until the next first period SA2. In Fig. 8, the first first rate HA1 is the time span from time TA1 to time TA3.

[0111] In a first period SA2 from time TA3 to time TA4, similarly to the first first period SA1, the calculation unit 423 calculates the degree of subcooling multiple times to obtain a plot group DA2. Next, after the first period SA2 has elapsed, the calculation unit 423 calculates a representative degree of subcooling MA2.

[0112] Furthermore, when the first period SA2 has elapsed, the calculation unit 423 calculates the rate of change k1 between the representative supercooling degree MA2 and the immediately preceding representative supercooling degree MA1. In the second and subsequent first periods SA3, SA4, SA5, SA6, SA7, and SA8, the rate of change k is calculated by the calculation unit 423 in the same manner as in the first first period SA2.

[0113] As shown in Fig. 8, the change in the degree of subcooling over time is not linear, but is a multi-order curve or an exponential function. Therefore, by setting the first rate to be shorter as the elapsed time increases, the rate of change k in a short time span can be calculated in the portion where the rate of change in the degree of subcooling over time is large. This improves the accuracy of the amount of refrigerant charged.

[0114] A two-dot chain line 511 indicates the third threshold. When the degree of supercooling changes over time as shown in Fig. 8, the representative degree of supercooling MA7 satisfies the third condition in the seventh first period SA7. Even if the third condition is satisfied, for example, when the rate of change k6 does not exceed the first threshold or when the representative degree of superheat ratio does not fall below the second threshold, the calculation unit 423 continues to calculate the degree of supercooling.

[0115] The first threshold value of the rate of change k is appropriately set based on the results of prior simulations and tests, from the perspective of whether the change in the degree of subcooling over time is such that it reaches the third threshold value, which is the target degree of subcooling, and from the perspective of improving the accuracy of the amount of refrigerant charged.

[0116] FIG. 9 is a graph showing the change in superheat ratio over time. The horizontal axis of the graph represents the elapsed time from the start of charging the refrigerant, in seconds [s]. The vertical axis of the graph is the superheat ratio and is dimensionless.

[0117] After the time TB1 has elapsed, the calculator 423 calculates the superheat ratio multiple times during a first second period SB1 set by the calculator 423. The plot group DB1 is a set of plots of the superheat ratios calculated between time TB1 and time TB2, i.e., during the first second period SB1.

[0118] When the second period SB ends, the calculation unit 423 sets the median value MB1 in the plot group DB1 as the representative superheat ratio in the first second period SB1. Next, the calculation unit 423 sets a second rate HB1, which is the time until the next second period SB2. In Fig. 9, the first second rate HB1 is the time width from time TB2 to time TB3.

[0119] In the second period SB2 from time TB3 to time TB4, similarly to the first second period SB1, the calculation unit 423 calculates the superheat ratio multiple times to obtain a plot group DB2. Next, the calculation unit 423 calculates a median value MB2 as a representative superheat ratio.

[0120] Fig. 9 shows a state in which the representative degree of supercooling MB7 is equal to or less than the second threshold value 512. When the superheat ratio changes over time as shown in Fig. 9, the second condition is satisfied after the seventh second period SB7 has elapsed.

[0121] As shown in Figures 8 and 9, the degree of subcooling and the superheat ratio have transient characteristics. Therefore, when determining the appropriate refrigerant amount, the accuracy of the refrigerant charging amount can be improved by using a representative value obtained for each period.

[0122] Also, the refrigerant charge amount 513 indicated by the dashed line does not increase linearly, but increases while being influenced by the pressure conditions at each location and the open / closed state of the injection switching valve 81 shown in Fig. 1. In particular, since the bypass valve 90 is open and the injection switching valve 81 is closed during the second period, the increase in the refrigerant charge amount 513 tends to stagnate.

[0123] The outdoor operation control unit 421 may adjust the opening degree of the subcooling heat exchanger expansion valve 82 based on the degree of supercooling, the first degree of superheat, the second degree of superheat, the superheat ratio, and the like. When the subcooling heat exchanger expansion valve 82 is opened, the refrigerant flowing from the subcooling heat exchanger 44 merges with the refrigerant supplied from the refrigerant cylinder 5. Since the pressure is higher upstream of the subcooling heat exchanger expansion valve 82 than near the injection switching valve 81, the speed of the refrigerant supply can be adjusted to be slower by opening the subcooling heat exchanger expansion valve 82. Since the opening degree of the subcooling heat exchanger expansion valve 82 can be changed by the outdoor operation control unit 421, the opening degree may be controlled so as to provide an appropriate speed of refrigerant supply.

[0124] [1-3. Effects, etc.] As described above, the air conditioning apparatus 1 comprises the indoor unit 2, the outdoor unit 4 equipped with the compressor 40, the outdoor heat exchanger 43, the subcooling heat exchanger 44, the first temperature sensor 51 that detects the temperature of the refrigerant flowing downstream of the outdoor heat exchanger 43, the high-pressure sensor 61 that detects the pressure of the refrigerant discharged from the compressor 40, and the refrigerant filling port 83 to which the refrigerant cylinder 5 can be connected, and the outdoor control device 400. The outdoor control device 400 comprises a calculation unit 423 that calculates the degree of subcooling, which is the difference between the saturation temperature of the refrigerant estimated from the detection value of the high-pressure sensor 61 and the detection value of the first temperature sensor 51, and calculates the rate of change k of the degree of subcooling with respect to the elapsed time since the start of filling, a first determination unit 424 that determines whether the first condition is satisfied when the rate of change k exceeds a predetermined first threshold value as a first condition, and an outdoor operation control unit 421 that operates the outdoor unit 4 to terminate filling of the refrigerant when the first condition is satisfied.

[0125] According to this, since the charging of the refrigerant is controlled taking into consideration the change in the degree of subcooling over time, the accuracy of the charging amount of the refrigerant is improved.

[0126] Moreover, the first temperature sensor 51 may be provided between the subcooling heat exchanger 44 and the indoor unit 2.

[0127] This makes it possible to calculate the degree of subcooling using the detection value of the refrigerant at the appropriate position.

[0128] In addition, the calculation unit 423 may set a predetermined first period, calculate the degree of supercooling multiple times within the first period, calculate a median of the multiple degrees of supercooling calculated within one first period, use the median as a representative supercooling degree that is a representative value of the degrees of supercooling, and use the representative supercooling degree and the elapsed time corresponding to the representative supercooling degree in calculating the rate of change k.

[0129] According to this, by using the median value of the degree of subcooling, the charging of the refrigerant is controlled taking into consideration the transient characteristics of the degree of subcooling, thereby improving the accuracy of the charging amount of the refrigerant.

[0130] Furthermore, the calculation unit 423 may set a first rate that is the time difference between the previous first period and the current first period, and may decrease the first rate as the elapsed time increases.

[0131] According to this, the rate of change of the degree of subcooling with respect to time increases as the elapsed time increases, so that the accuracy of the amount of refrigerant charged is further improved.

[0132] In addition, the calculation unit 423 may calculate the rate of change k between the representative subcooling degree and the elapsed time corresponding to the representative subcooling degree in the most recent first period and the representative subcooling degree and the elapsed time corresponding to the representative subcooling degree in the first period immediately preceding the most recent one.

[0133] Since the charging of the refrigerant is controlled taking into consideration the change in the degree of subcooling over time, the accuracy of the charging amount of the refrigerant is improved.

[0134] The outdoor unit 4 is provided with outdoor expansion valves 87U, 87D downstream of the outdoor heat exchanger 43, and is provided with an accumulator 41, a bypass pipe 76 connecting a first branch point P1 provided between the outdoor expansion valves 87U, 87D and the subcooling heat exchanger 44 and a junction point P3 provided between the accumulator 41 and the indoor unit 2, a second temperature sensor 52 that detects the temperature of the refrigerant flowing through the bypass pipe 76, a low pressure sensor 62 that detects the pressure of the refrigerant returning from the indoor unit 2 to the outdoor unit 4, and a third temperature sensor 53 that detects the temperature of the refrigerant returning from the indoor unit 2 to the outdoor unit 4. The calculation unit 423 calculates the temperature of the refrigerant from the detection value of the low pressure sensor 62. the outdoor control device 400 calculates a first degree of superheat which is the difference between the saturation temperature of the refrigerant estimated from the detection value of the low pressure sensor 62 and the detection value of the second temperature sensor 52, calculates a second degree of superheat which is the difference between the saturation temperature of the refrigerant estimated from the detection value of the low pressure sensor 62 and the detection value of the third temperature sensor 53, and calculates a superheat ratio which is the ratio of the first degree of superheat to the second degree of superheat. The outdoor control device 400 sets a second condition to a case where the superheat ratio is below a predetermined second threshold, and is provided with a second judgment unit 425 which judges whether or not the second condition is satisfied, and the outdoor operation control unit 421 may operate the outdoor unit 4 to terminate charging of the refrigerant when the second condition is satisfied in addition to the first condition.

[0135] This improves the accuracy of refrigerant charging because the states of the bypassed refrigerant in a high-pressure atmosphere and the refrigerant in a low-pressure atmosphere are detected. Also, the outdoor unit 4 can be made smaller because the appropriate amount of refrigerant to be charged is determined without using a container such as a receiver for receiving the refrigerant in a high-pressure atmosphere.

[0136] Furthermore, the calculation unit 423 may set a predetermined second period, calculate the superheat ratio multiple times within the second period, calculate a median of the multiple superheat ratios calculated within one second period, and set the median to a representative superheat ratio that is a representative value of the superheat ratios, and the second condition may be a case where the representative superheat ratio is lower than a predetermined second threshold value.

[0137] According to this, by using the median value of the superheat ratio for judgment, the charging of the refrigerant is controlled taking into consideration the transient characteristics of the superheat ratio, thereby improving the accuracy of the appropriate charging amount of the refrigerant.

[0138] Furthermore, the calculation unit 423 may set a second rate that is the time difference between the previous second period and the current second period, and may decrease the second rate as the elapsed time increases.

[0139] According to this, the rate of change of the degree of subcooling with respect to time increases as the elapsed time increases, so that the accuracy of the amount of refrigerant charged is further improved.

[0140] Furthermore, the bypass pipe 76 may include a bypass valve 90 capable of adjusting the amount of refrigerant branched off and flowing into the bypass pipe 76, and the outdoor operation control section 421 may open the bypass valve 90 during the second period.

[0141] According to this, since the amount of refrigerant to be bypassed can be adjusted by the bypass valve 90, an appropriate amount of refrigerant can be bypassed in calculation of the superheat ratio.

[0142] The outdoor unit 4 includes a compressor 40 having an injection mechanism for injecting the refrigerant that has passed through the subcooling heat exchanger 44, an injection pipe 71 that connects the subcooling heat exchanger 44 and the compressor 40, and a subcooling heat exchanger expansion valve 82 that adjusts the pressure of the refrigerant supplied to the subcooling heat exchanger 44. The injection pipe 71 includes a pipe 72 that branches off at a second branch point P2. The pipe 72 includes an injection switching valve 81 that can be switched to inject when closed and not inject when open, and a refrigerant filling port 83 between the second branch point P2 and the injection switching valve 81. The outdoor operation control unit 421 starts supplying the refrigerant from the refrigerant cylinder 5 by opening the injection switching valve 81, and ends supplying the refrigerant from the refrigerant cylinder 5 by closing the injection switching valve 81. The speed of supply of the refrigerant may be adjusted by changing the opening degree of the subcooling heat exchanger expansion valve 82.

[0143] This makes it possible to adjust the speed of the refrigerant without using a dedicated adjustment valve.

[0144] In addition, the outdoor control device 400 is provided with a third judgment unit 426 that determines whether or not the third condition is satisfied, where the degree of subcooling exceeds a predetermined third threshold, and the outdoor operation control unit 421 may terminate the supply of refrigerant from the refrigerant cylinder 5 when the third condition is satisfied in addition to the first and second conditions.

[0145] According to this, the charging of the refrigerant is controlled taking into consideration the value of the degree of subcooling in addition to the tendency of time-dependent change in the degree of subcooling and the value of the superheat ratio, so that the accuracy of the charging amount of the refrigerant is improved.

[0146] A control method for an air-conditioning apparatus (1) comprising an indoor unit (2), an outdoor unit (4) comprising a compressor (40), an outdoor heat exchanger (43), a subcooling heat exchanger (44), a first temperature sensor (51) for detecting the temperature of the refrigerant flowing downstream of the outdoor heat exchanger (43), and a refrigerant filling port (83) to which a refrigerant cylinder (5) can be connected, the control method for the air-conditioning apparatus (1) comprising the steps of: calculating a degree of subcooling which is the difference between the saturation temperature of the refrigerant estimated from the detection value of a high-pressure sensor (61) which detects the pressure of the refrigerant discharged from the compressor (40) and the detection value of the first temperature sensor (51); calculating a rate k of change in the degree of subcooling with respect to the elapsed time since filling started; determining whether or not the first condition is satisfied when the rate k of change exceeds a predetermined first threshold; and operating the outdoor unit (4) to terminate filling of the refrigerant if the first condition is satisfied.

[0147] According to this, since the charging of the refrigerant is controlled taking into consideration the change in the degree of subcooling over time, the accuracy of the charging amount of the refrigerant is improved.

[0148] (Other embodiments) As described above, the above-mentioned first embodiment has been described as an example 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. In addition, it is also possible to combine the components described in the above-mentioned first embodiment to create a new embodiment. Therefore, other embodiments will be exemplified below.

[0149] In the above-mentioned first embodiment, the calculation unit 423 is configured to calculate the rate k of change in the representative subcooling degree with respect to the elapsed time. In other embodiments, the calculation unit 423 may calculate an approximation formula using the representative subcooling degree and the elapsed time. Furthermore, the calculation unit 423 may calculate the rate of change at a point on the approximation formula calculated by the calculation unit 423.

[0150] In the above-mentioned embodiment 1, the calculation unit 423 is configured to set the first period and the second period. In another embodiment, a period setting unit may be provided, the period setting unit may set one predetermined period, and the first period and the second period may correspond to the predetermined period. In this case, the time widths of the first period and the second period in the same elapsed time are equal. Furthermore, in the above-mentioned embodiment 1, the calculation unit 423 is configured to set the first rate and the second rate. In another embodiment, the calculation unit 423 may be configured to set the rate, and the first rate and the second rate may correspond to the rate. In this case, the time widths of the first rate and the second rate in the same elapsed time are equal.

[0151] The outdoor processor 420 and the indoor processor 320 may be configured with a single processor or multiple processors. These processors may be hardware programmed to realize the corresponding functional units. In other words, these processors may be configured with, for example, an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array).

[0152] The configurations of the outdoor unit 4, outdoor control device 400, indoor control device 300, and indoor unit 2 shown in Fig. 2 are merely examples, and the specific implementation form is not particularly limited. In other words, it is not necessarily necessary to implement hardware that corresponds to each unit individually, and it is also possible to implement a configuration in which one processor executes a program to realize the functions of each unit. Also, some of the functions realized by software in the above-mentioned embodiment may be hardware, or some of the functions realized by hardware may be software.

[0153] At least one of the calculation unit 423, the first determination unit 424, the second determination unit 425, and the third determination unit 426 provided in the outdoor control device 400 may be provided in the indoor control device 300. Also, the indoor operation control unit 321 may function as the outdoor operation control unit 421.

[0154] The step units of the operations shown in Figures 5, 6, and 7 are divided according to the main processing contents in order to make the operations easier to understand, and the operation is not limited by the manner in which the processing units are divided or the names of the processing units. The operations may be divided into more step units according to the processing contents. Furthermore, one step unit may be divided so as to include more processing. Furthermore, the order of the steps may be appropriately changed within a range that does not interfere with the purpose of this disclosure.

[0155] 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, and the like can be made within the scope of the claims or their equivalents.

[0156] (Additional Note) The above description of the embodiments discloses the following techniques.

[0157] (Technology 1) An air conditioning apparatus comprising: an indoor unit; an outdoor unit equipped with a compressor, an outdoor heat exchanger, a subcooling heat exchanger, a first temperature sensor that detects the temperature of refrigerant flowing downstream of the outdoor heat exchanger, a first pressure sensor that detects the pressure of refrigerant discharged from the compressor, and a refrigerant filling port to which a refrigerant cylinder can be connected; and a control device, wherein the control device comprises: a calculation unit that calculates a degree of subcooling, which is the difference between a saturation temperature of the refrigerant estimated from the detection value of the first pressure sensor and the detection value of the first temperature sensor, and calculates a rate of change in the degree of subcooling with respect to the elapsed time since filling begins; a first determination unit that determines whether or not the first condition is satisfied, wherein a first condition is defined as a case in which the rate of change exceeds a predetermined first threshold; and an operation control unit that operates the outdoor unit to terminate filling of the refrigerant if the first condition is satisfied. According to this, since the charging of the refrigerant is controlled taking into consideration the change in the degree of subcooling over time, the accuracy of the charging amount of the refrigerant is improved.

[0158] (Technical 2) The air conditioner according to Technical 1, wherein the first temperature sensor is provided between the subcooling heat exchanger and the indoor unit. This makes it possible to calculate the degree of subcooling using the detection value of the refrigerant at the appropriate position.

[0159] (Technology 3) The air conditioning apparatus described in Technology 2, wherein the calculation unit sets a predetermined first period, calculates the degree of supercooling a plurality of times within the first period, calculates a median of the plurality of degrees of supercooling calculated within one of the first periods, sets the median as a representative degree of supercooling that is a representative value of the degrees of supercooling, and uses the representative degree of supercooling and the elapsed time corresponding to the representative degree of supercooling in calculating the rate of change. According to this, by using the median value of the degree of subcooling, the charging of the refrigerant is controlled taking into consideration the transient characteristics of the degree of subcooling, thereby improving the accuracy of the charging amount of the refrigerant.

[0160] (Technology 4) The air conditioning apparatus according to Technology 3, wherein the calculation unit sets a first rate which is a time difference between the previous first period and the current first period, and reduces the first rate as the elapsed time increases. According to this, the rate of change of the degree of subcooling with respect to time increases as the elapsed time increases, so that the accuracy of the amount of refrigerant charged is further improved.

[0161] (Technology 5) The air conditioning apparatus described in Technology 4, wherein the calculation unit calculates the ratio of change between the representative supercooling degree and the elapsed time corresponding to the representative supercooling degree in the most recent first period and the representative supercooling degree and the elapsed time corresponding to the representative supercooling degree in the first period immediately preceding the most recent one. Since the charging of the refrigerant is controlled taking into consideration the change in the degree of subcooling over time, the accuracy of the charging amount of the refrigerant is improved.

[0162] (Technique 6) The outdoor unit includes an outdoor expansion valve downstream of the outdoor heat exchanger, an accumulator, and a bypass pipe connecting a first branch point provided between the outdoor expansion valve and the subcooling heat exchanger and a junction point provided between the accumulator and the indoor unit, and includes a second temperature sensor that detects the temperature of the refrigerant flowing through the bypass pipe, a second pressure sensor that detects the pressure of the refrigerant returning from the indoor unit to the outdoor unit, and a third temperature sensor that detects the temperature of the refrigerant returning from the indoor unit to the outdoor unit, and the calculation unit calculates a saturation temperature of the refrigerant estimated from a detection value of the second pressure sensor. and the detection value of the second temperature sensor; calculate a first degree of superheat which is the difference between the saturation temperature of the refrigerant estimated from the detection value of the second pressure sensor and the detection value of the third temperature sensor; calculate a superheat ratio which is the ratio of the first degree of superheat to the second degree of superheat; the control device sets a second condition to a case where the superheat ratio is below a predetermined second threshold, and includes a second determination unit which determines whether or not the second condition is satisfied; and the operation control unit operates the outdoor unit to terminate charging of the refrigerant when a second condition is satisfied in addition to the first condition. This improves the accuracy of refrigerant charging because the state of the bypassed refrigerant in a high-pressure atmosphere and the state of the low-pressure refrigerant are detected. Also, the outdoor unit can be made smaller because the appropriate amount of refrigerant to be charged is determined without using a container such as a receiver to receive the refrigerant in a high-pressure atmosphere.

[0163] (Technique 7) The air conditioning apparatus described in Technique 6, wherein the calculation unit sets a predetermined second period, calculates the superheat ratio a plurality of times within the second period, calculates a median of the plurality of superheat ratios calculated within one of the second periods, and sets the median as a representative superheat ratio that is a representative value of the superheat ratios, and the second condition is a case where the representative superheat ratio is lower than a predetermined second threshold value. According to this, by using the median value of the superheat ratio for judgment, the charging of the refrigerant is controlled taking into consideration the transient characteristics of the superheat ratio, thereby improving the accuracy of the appropriate charging amount of the refrigerant.

[0164] (Technology 8) The air conditioning apparatus according to Technology 7, wherein the calculation unit sets a second rate which is a time difference between the previous second period and the current second period, and reduces the second rate as the elapsed time increases. According to this, the rate of change of the degree of subcooling with respect to time increases as the elapsed time increases, so that the accuracy of the amount of refrigerant charged is further improved.

[0165] (Technology 9) The air conditioning apparatus described in Technology 8, wherein the bypass pipe is provided with a bypass valve capable of adjusting the amount of refrigerant branched off and flowing into the bypass pipe, and the operation control unit opens the bypass valve during the second period. According to this, since the amount of refrigerant to be bypassed can be adjusted by the bypass valve, an appropriate amount of refrigerant can be bypassed in calculation of the superheat ratio.

[0166] (Technology 10) The outdoor unit includes the compressor having an injection mechanism that injects refrigerant that has passed through the subcooling heat exchanger, an injection piping that connects the subcooling heat exchanger and the compressor, and an expansion valve that adjusts the pressure of the refrigerant supplied to the subcooling heat exchanger, the injection piping including a branch piping that branches off at a second branch point, the branch piping including an injection switching valve that can be switched to inject in a closed state and not inject in an open state, and the refrigerant filling port between the second branch point and the injection switching valve, and the operation control unit starts supplying refrigerant from the refrigerant cylinder by opening the injection switching valve, stops supplying refrigerant from the refrigerant cylinder by closing the injection switching valve, and adjusts the speed of refrigerant supply by changing the opening degree of the expansion valve. An air conditioning apparatus as described in any one of Technologies 1 to 9. This makes it possible to adjust the speed of the refrigerant without using a dedicated adjustment valve.

[0167] (Technology 11) An air conditioning apparatus as described in any of Technologies 1 to 9, wherein the control device defines a third condition as a case in which the degree of subcooling exceeds a predetermined third threshold, and includes a third judgment unit that judges whether the third condition is satisfied, and the operation control unit terminates the supply of refrigerant from the refrigerant cylinder when the third condition is satisfied in addition to the first condition and the second condition. According to this, the charging of the refrigerant is controlled taking into consideration the value of the degree of subcooling in addition to the tendency of time-dependent change in the degree of subcooling and the value of the superheat ratio, so that the accuracy of the amount of refrigerant charged is improved.

[0168] (Technology 12) A control method for an air-conditioning apparatus comprising an indoor unit, an outdoor unit comprising a compressor, an outdoor heat exchanger, a subcooling heat exchanger, a first temperature sensor that detects the temperature of refrigerant flowing downstream of the outdoor heat exchanger, and a refrigerant filling port to which a refrigerant cylinder can be connected, the control method for an air-conditioning apparatus comprising the steps of: calculating a degree of subcooling, which is the difference between the saturation temperature of the refrigerant estimated from the detection value of a first pressure sensor that detects the pressure of the refrigerant discharged from the compressor and the detection value of the first temperature sensor; calculating a rate of change in the degree of subcooling with respect to the elapsed time since filling begins; determining whether the rate of change exceeds a predetermined first threshold value as a first condition; determining whether the first condition is satisfied; and, if the first condition is satisfied, operating the outdoor unit to terminate filling of the refrigerant. According to this, the same actions and effects as those of the first technique are achieved. [Industrial Applicability]

[0169] INDUSTRIAL APPLICABILITY As described above, the air conditioner and the method for controlling the air conditioner according to the present invention can be used in applications where refrigerant is charged at the time of installation work. [Explanation of symbols]

[0170] 1. Air conditioning equipment 2 Indoor unit 4 Outdoor unit 5 Refrigerant Cylinder 40 Compressor 41 Accumulator 43 Outdoor heat exchanger 44 Subcooling heat exchanger 51 First temperature sensor 52 Second temperature sensor 53 3rd temperature sensor 61 High pressure sensor (first pressure sensor) 62 Low pressure sensor (second pressure sensor) 71 Injection piping 76 Bypass Pipe 81 Injection switching valve 82 Expansion valve for subcooling heat exchanger (expansion valve) 83 Refrigerant charge port 85 Injection port 90 Bypass valve 400 Outdoor control device (control device) 421 Outdoor operation control unit (operation control unit) 423 Arithmetic section 424 1st Judgment Department 425 Second Judgment Department 426 Third Judgment Section P1 First branch point P2 Second branch point P3 confluence

Claims

1. The present invention relates to a cooling system for a refrigerant tank that is provided with an indoor unit, an outdoor unit including a compressor, an outdoor heat exchanger, a subcooling heat exchanger, a first temperature sensor that detects the temperature of a refrigerant flowing downstream of the outdoor heat exchanger, a first pressure sensor that detects the pressure of the refrigerant discharged from the compressor, and a refrigerant filling port to which a refrigerant cylinder can be connected; and a control device. The control device includes: Calculating a degree of subcooling, which is a difference between a saturation temperature of the refrigerant estimated from a detection value of the first pressure sensor and a detection value of the first temperature sensor; A calculation unit that calculates a rate of change in the degree of subcooling with respect to an elapsed time from the start of filling; a first determination unit that determines whether or not a first condition is satisfied when the rate of change exceeds a predetermined first threshold; and an operation control unit that operates the outdoor unit to finish charging the refrigerant when the first condition is satisfied. Air conditioning units.

2. The first temperature sensor is provided between the subcooling heat exchanger and the indoor unit. The air conditioning apparatus according to claim 1.

3. The calculation unit is A predetermined first period is set; Calculating the degree of subcooling a plurality of times within the first period; A median value of the plurality of degrees of supercooling calculated within one of the first periods is calculated, and the median value is set as a representative degree of supercooling that is a representative value of the degrees of supercooling; In calculating the rate of change, the representative degree of supercooling and the elapsed time corresponding to the representative degree of supercooling are used. The air conditioning apparatus according to claim 2.

4. The calculation unit is a first rate is set as a time difference between the previous first period and the current first period, and the first rate is made smaller as the elapsed time increases; The air conditioning apparatus according to claim 3.

5. The calculation unit is Calculating a ratio of change between the representative subcooling degree and the elapsed time corresponding to the representative subcooling degree in the latest first period and the representative subcooling degree and the elapsed time corresponding to the representative subcooling degree in the first period immediately before the latest one; The air conditioning apparatus according to claim 4.

6. The outdoor unit is an outdoor expansion valve is provided downstream of the outdoor heat exchanger; an accumulator; and a bypass pipe connecting a first branch point provided between the outdoor expansion valve and the subcooling heat exchanger and a junction point provided between the accumulator and the indoor unit; a second temperature sensor for detecting a temperature of the refrigerant flowing through the bypass pipe; a second pressure sensor that detects a pressure of the refrigerant returning from the indoor unit to the outdoor unit, and a third temperature sensor that detects a temperature of the refrigerant returning from the indoor unit to the outdoor unit, The calculation unit is Calculating a first degree of superheat, which is a difference between a saturation temperature of the refrigerant estimated from a detection value of the second pressure sensor and a detection value of the second temperature sensor; Calculating a second degree of superheat, which is a difference between a saturation temperature of the refrigerant estimated from a detection value of the second pressure sensor and a detection value of the third temperature sensor; Calculating a superheat ratio which is a ratio between the first superheat and the second superheat; The control device includes: A second determination unit that determines whether or not a second condition is satisfied, the second condition being determined as a case in which the superheat ratio is lower than a predetermined second threshold value, The operation control unit operates the outdoor unit to finish charging the refrigerant when a second condition is satisfied in addition to the first condition. The air conditioning apparatus according to claim 1.

7. The calculation unit is Setting a second predetermined period; Calculating the superheat ratio a plurality of times within the second period; A median value of the plurality of superheat ratios calculated within one of the second periods is calculated, and the median value is set as a representative superheat ratio that is a representative value of the superheat ratios; The second condition is a case where the representative superheat ratio is lower than a predetermined second threshold value. The air conditioning apparatus according to claim 6.

8. The calculation unit is a second rate is set as a time difference between the previous second period and the current second period, and the second rate is made smaller as the elapsed time increases; The air conditioning apparatus according to claim 7.

9. the bypass pipe is provided with a bypass valve capable of adjusting the amount of refrigerant branched and flowing into the bypass pipe, The operation control unit opens the bypass valve during the second period. The air conditioning apparatus according to claim 8.

10. The outdoor unit includes a compressor having an injection mechanism that injects the refrigerant that has passed through the subcooling heat exchanger; An injection pipe connecting the subcooling heat exchanger and the compressor; an expansion valve for adjusting the pressure of the refrigerant supplied to the subcooling heat exchanger, The injection pipe includes a branch pipe branched at a second branch point, the branch pipe includes an injection switching valve that can be switched so as to perform injection in a closed state and not to perform injection in an open state, and the refrigerant filling port is provided between the second branch point and the injection switching valve; The operation control unit is The injection switching valve is opened to start supplying the refrigerant from the refrigerant cylinder; The injection switching valve is closed to stop the supply of the refrigerant from the refrigerant cylinder. The speed of supplying the refrigerant is adjusted by changing the opening degree of the expansion valve. An air-conditioning apparatus according to any one of claims 1 to 9.

11. The control device includes a third determination unit that determines whether or not a third condition is satisfied when the degree of subcooling exceeds a predetermined third threshold value, the operation control unit terminates the supply of the refrigerant from the refrigerant cylinder when the third condition is satisfied in addition to the first condition and the second condition. An air-conditioning apparatus according to any one of claims 1 to 9.

12. A method for controlling an air conditioner including an indoor unit, a compressor, an outdoor heat exchanger, a subcooling heat exchanger, a first temperature sensor that detects the temperature of a refrigerant flowing downstream of the outdoor heat exchanger, and an outdoor unit that includes a refrigerant filling port to which a refrigerant cylinder can be connected, A control method for an air-conditioning apparatus, comprising: calculating a degree of subcooling, which is the difference between a saturation temperature of the refrigerant estimated from a detection value of a first pressure sensor that detects the pressure of the refrigerant discharged from the compressor and the detection value of the first temperature sensor; calculating a rate of change in the degree of subcooling with respect to the elapsed time since filling begins; determining whether or not the first condition is satisfied, when the rate of change exceeds a predetermined first threshold; and, when the first condition is satisfied, operating the outdoor unit to terminate filling of the refrigerant.

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