GB2481128A

GB2481128A - Refrigeration air-conditioner and refrigerant charging method for the same

Info

Publication number: GB2481128A
Application number: GB1109605.4A
Authority: GB
Inventors: Osamu Morimoto; Hiroyuki Okano; Kosuke Tanaka
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2009-04-08
Filing date: 2009-04-08
Publication date: 2011-12-14
Anticipated expiration: 2029-04-08
Also published as: GB201109605D0; JPWO2010116496A1; WO2010116496A1; JP5306450B2; HK1162068A1; GB2481128B

Abstract

A refrigerant charging method for a refrigeration air-conditioner provided with a compressor (1) for sucking a refrigerant and discharging the refrigerant after compressing the refrigerant. The refrigerant discharged from the compressor (1) is returned to the suction side of the compressor (1) via an on-off valve (5), and a refrigerant is charged between the on-off valve (5) and the suction side of the compressor (1) from a refrigerant charging port (7) via a refrigerant charging on-off device (6).

Description

S

DESCRIPTON

Title of Invention: REFRIGERATION AIR-CONDITIONING APPARATUS AND

REFRIGERANT CHARGING METHOD THEREFOR

Technical Field

[0001] The present invention relates to a refrigeration air-conditioning apparatus in which an indoor unit and an outdoor unit are connected by a refrigerant pipeline and particularly to a technique of automatically charging the refrigerant.

Background Art

(0002] A technique of charging a refrigerant by estimating an excess or a shortage state of an amount of refrigerant in a refrigerant circuit of a refrigeration air-conditioning apparatus from an operation state of a refrigerating cycle has been proposed. (See Patent Literatures 1 and 2, for example).

Citation List Patent Literature [0003] Patent Literature 1: Japanese Unexamined Patent AppIicatior Publication No. 2008-64456 Patent Literature 2: Japanese Unexamined Patent Application Publication No. 2008-232579

Summary of Invention

Technical Problems (0004] However, hitherto, when the refrigerant charged into the refrigerant circuit is determined to be short and the refrigerant is charged, a liquid refrigerant is once charged into an aëcumulator. There are problems in that when the liquid refrigerant is charged into the accumulator, the refrigerant does not readily evaporate even if hot gas i.s blown into the accumulator because of the heat

I

S

radiated from the accumulator1 and in that it takes time for the liquid in the accumulator to be evaporated.

There are also problems in that when outside air temperature is low, it is difficult to determine whether or not the liquid in the accumulator has been evaporated, and in that as a result of determining the amount of refrigerant while the liquid refrigerant is still pooled in the accumulator, there is a possibility of the refrigerant being overcharged.

[0005] The present invention was made to address the above problems and an object thereof is to provide a refrigeration air-conditioning apparatus that can complete refrigerant charging more rapidly and more accurately.

Solution to Problem (0006] This invention is a refrigeration air-conditioning apparatus composed of at least a compressor, a condenser, a throttle device, and an evaporator, having a refrigerant circuit branching from a discharge side of the compressor and connected to a suction side of the compressor via opening/closing means, and a refrigerant charging port connected between the opening/closing means and the suction side of the compressor via a refrigerant charging on-off device.

(0007] Also the present invention is a refrigeration air-conditioning apparatus, in which a heal-source-side unit composed at least of a compressor, a heat-source-side heat exchanger, and a four-way valve, a load-side unit composed at least of a throttle device and a load-side heat exchanger, the heat-source-side unit, and the load-side unit are connected by an existing refrigerant pipeline.

A refrigerant circuit branching from a discharge side of the compressor and connected to a suction side of the compressor via opening/closing means,

I

and a refrigerant charging port connected between the opening/closing means and the suction side of the compressor via a refrigerant charging on-off device are provided.

[0008] -Also, the present invention is a refrigeration air-conditioning apparatus composed of a heat-source-side unit composed at least of a compressor, a heat-source-side heat exchanger, and a four-way valve, a load-side unit composed at least of a throttle device and a load-side heat exchanger, and a branch-flow controller having a bypass circuit that bypasses from a liquid portion to a low pressure portion via at least a gas-liquid separator, opening/closing means that switches between high and low pressures, and a bypass throttle device, the heat-source-side unit and the load-side unit are connected by two refrigerant pipelines via the branch-flow controller, having a refrigerant circuit branching from the discharge side of the compressor and connected to the suction side of the compressor via the opening/closing means; and a refrigerant charging port connected between the opening/closing means and the suction side of the compressor via a refrigerant charging on-off device.

E0009] Moreover, the present invention is a refrigeration air-conditioning apparatus composed of a heat-source-side unit composed at least of a compressor, a heat-source-side heat exchanger, a four-way valve, and a heat-source-side throttle device and a load-side unit composed at least of a load-side throttle device and a load-side heat exchanger, the heat-source-side unit and the load-side unit being connected to the heat-source-side heat exchanger and the load-side heat exchanger via a branch-flow kit, capable of switching between a high-pressure pipe and a low-pressure pipe, and the * heat-source-side throttle device and the load-side throttle device being connected by a liquid pipe, having a refrigerant circuit branching from -a discharge side of the compressor

S

and connected to a suction side of the compressor via opening/closing means, and a refrigerant charging port connected between the opening/closing means and the suctionside of the compressor via a refrigerant charging on-off device.

Advantageous Effects of Invention [0010] The refrigeration air-conditioning apparatus of the present invention can rapidly and accurately complete refrigerant charging without taking time in determining the amount of refrigerant in the refrigeration air-conditioning apparatus by, when charging the refrigerant, merging the liquid refrigerant to be charged with a discharge refrigerant (hot gas) discharged from a compressor so that the liquid refrigerant charged into a main refrigerant circuit is charged in an evaporated state by the heat of the hot gas.

Brief Description of Drawings

(0011] (Fig. 1] Fig. I is a refrigerant circuit diagram of a refrigeration air-conditioning apparatus according to Embodiment I of the present invention.

[Fig. 2] Fig. 2 is a control flowchart of a throttle device of the refrigeration air-conditioning apparatus according to Embodiment I of the present invention.

[Fig. 3] Fig. 3 is a control flowchart of automatic refrigerant charging of the refrigeration air-conditioning apparatus according to Embodiment 1 of the present invention.

[Fig. 4] Fig. 4 is a refrigerant circuit diagram of a refrigeration air-conditioning apparatus according to Embodiment 2 of the present invention.

[Fig. 5] Fig. 5 is a control flowchart of automatic refrigerant charging of the refrigeration air-conditioning apparatus according to Embodiment 2 of the present invention.

[Fig. 61 Fig. 6 is a control flowchart of automatic refrigerant charging of the refrigeration air-conditioning apparatus according to Embodiment 3 of the present invention.

S

(Fig. 7] Fig. 7 is a refrigerant circuit diagram of a refrigeration air-conditioning apparatus according to Embodiment 4 of the present invention.

[Fig. 8] Fig. 8 is a work flow chart relating to update of the refrigeration air-conditioning apparatus according to Embodiment 4 of the present invention.

[Fig. 9] Fig. 9 is a control flowchart of automatic refrigerant charging of the refrigeration air-conditioning apparatus during a cooling operation according to Embodiment 4 of the present invention.

[Fig. 10] Fig. 10 is a control flowchart of automatic refrigerant charging of the refrigeration air-conditioning apparatus during a heating operation according to Embodiment 4 of the present invention.

[Fig. 11] Fig. 11 is a refrigerant circuit diagram of a refrigeration air-conditioning apparatus according to Embodiment 5 of the present invention.

[Fig. 12] Fig. 11 is a control flowchart of automatic refrigerant charging of the refrigeration air-conditioning apparatus during a cooling operation according to Embodiment 5 of the present invention.

[Fig. 13] Fig. 13 is a refrigerant circuit diagram of a refrigeration air-conditioning apparatus according to Embodiment 6 of the present invention.

[Fig. 14] Fig. 14 is a control flowhad of automatic refrigerant charging of the refrigeration air-conditioning apparatus according to Embodiment 6 of the present invention.

Description of Embodiments

[0012] Embodiment 1.

Fig. I illustrates a refrigerant circuit diagram of a refrigeration air-conditioning apparatus according to Embodiment I of the present invention. In Fig. 1, reference numeral I denotes a compressor, 2 a! condenser, 3 a throttle device, and 4 an evaporator, and these components constitute a main refrigerant circuit. Also, a hot-gas bypass circuit (refrigerant circuit) is formed in which a

S

discharge side of the compressor I branches, and the branch line leads to the suction side of the compressor via an opening/closing valve 5 as channel opening/closing means. Moreover, the refrigerant circuit between the opening/closing valve 5 on the hot-gas bypass circuit and the suction side of the compressor branches, and a refrigerant charging port 7 is connected thereto via a.

refrigerant charging opening/closing valve 6. Reference numeral 8 denotes a pressure sensor that detects the pressure at a high-pressure portion in the discharge side of the compressor 1, and reference numeral 9 denotes a first temperature sensor that detects the temperature of the refrigerant on the discharge side of the compressor 1. Reference numeral 10 denotes a second temperature sensor that detects the temperature of the refrigerant at an outlet of the condenser 2, and reference numerals 11 and 12 denote third and fourth temperature sensors that detect temperatures of the refrigerant at an outlet and an inlet of the evaporator 4, respectively.

(0013] Subsequently, a flow of the refrigerant in the above-described refrigerant circuit refrigerant will be described. When the compressor I is driven, a high-temperature high-pressure gas refrigerant is discharged from the compressor and is liquefied by the condenser. The liquefied refrigerant is throttled down to a low temperature in the throttle device 3, evaporated and vaporized in the evaporator and returns to the compressor 1.

[0014] Control by the throttle device in the refrigeration cycle as above will be described by using Fig. 2. Fig. 2 is a flowchart illustrating an example of a control algorithm of the throttle device 3. In STEP 2, in order to obtain a control interval, waiting is performed for a predetermined time, and after the predetermined time has elapsed, the routine proceeds to STEP 3. In STEP 3, *the inlet/outlet temperature of the evaporator 4 is measured by the third and fourth temperature sensors. In STEP 4, a temperature difference Sil between an evaporator-inlet f temperature Tein and an evaporator outlit temperature Teout is calculated. In STEP 5, a correction value LEV of an opening-degree of the throttle device 3 is determined in accordance with the difference between SH calculated in STEP 4 and its target value SHm, and the setting is executed. In STEP 6, whether to end the operation or not is determined, and if it is to be ended, the routine proceeds to STEP 7, and if it is not to be ended, the routine returns to STEP 2.

(0015] In the refrigerating cycle in which the above operation is performed, a method of determining an amount of refrigerant and of automatically charging the refrigerant will be described by using Fig. 3. Fig. 3 is a flowchart illustrating an algorithm when the refrigerant is automatically charged. In Fig. 3, in a state in which a refrigerant supply cylinder charged with the refrigerant is connected to the refrigerant charging port 7, the operation of adjusting the amount of refrigerant is started in STEP 1. As a trigger to start the operation, a service switch, a remote controller, a contact point input from the outside, a control signal from a personal computer and the like is used provided at a portion of the outdoor unit. In STEP 2, in order to obtain a control interval, waiting is performed fOr a predetermined time, and after the predetermined time has elapsed, the routine proceeds to STEP 3. In STEP 3, the discharge pressure Pd of the compressor I and the refrigerant temperature at the outlet of a condenser 2 Tcout are detected. In STEP 4, the temperature difference SC between the saturated temperature Tsat (Pd) of the discharge pressure Pd and the refrigerant temperature at the outlet of the condenser 2 Tcout is calculated. In STEP 5, the calculated SC and its target value SCm are compared, and if SC »= SCm, then the routine proceeds to STEP 6, where the adjustment of the amount of refrigerant is finished. If SC < SCm, then the routine proceeds to STEP 7, where the refrigerant charging opening/closing valve 6 is kept open for predetermined time, and the refrigerant is charged into the refrigerant circuit from the refrigerant supply cylinder via the refrigerant charging port 7. In this step, the opening/closing valve 5 is also opened. After the

S

refrigerant is charged for a predetermined time in STEP 7, the routine proceeds to STEP 2. When the adjustment of the amount of refrigerant is finished, it is preferable that completion of the adjustment of the amount of refrigerant is notified to the outside by using a service display unit, a remote controller, personal computer for control, lamp display by an electric signal and the like.

[00161 As described above, by opening the opening/closing valve 5 at the same time as charging of the refrigerant in STEP 7, a high-temperature gas refrigerant discharged from the compressor I flows into the hot-gas bypass circuit, is mixed with the liquid refrigerant charged from the refrigerant supply cylinder and is evaporated and vaporized, and then merges with the refrigerant flowing throttled the main circuit on the suction side bf the compressor 1. The liquid does not flow back, and the liquid refrigerant can be rapidly evaporated, thereby determination of the amount of refrigerant can be completed rapidly. In addition, since dilution of lubricating oil or liquid compression in the compressor I does not occur, a system of high reliability can be realized.

(0017] Embodiment 2.

Fig. 4 shows a refrigerant circuit diagram according to Embodiment 2 of the present invention. A difference between Fig. 4 and Fig. 1 is that, instead of the refrigerant charging opening/closing valve 6, the refrigerant charging port 7 is connected between the opening/closing valve 5 on the hot-gas bypass circuit and the suction side of the compressor I via a second throttle valve 46 capable of flow-rate control.

[0018] In a refrigerating cycle as in Fig. 4, a method of determining an amount of refrigerant and of automatically charging the refrigerant will be described by using Fig. 5. Fig. 5 is a flowchart illustrating an algorithm when the refrigerant is automatically charged. In Fig. 5, in a state in which a refrigerant supply cylinder is connected to the refrigerant charging port 7, the operation of adjusting the amount of refrigerant is started in STEP 1. In STEP 2, in order to obtain a control interval, waiting is performed for a predetermined time, and after the predetermined time has elapsed, the routine proceeds to STEP 3. In STEP 3, the discharge pressure Pd of the compressor I and the refrigerant temperature at the outlet of the condenser 2 Tcout are detected. In STEP 4, the difference SC between the saturated temperature Tsat (Pd) of the discharge pressure Pd and the refrigerant temperature Tcout at the outlet of the condenser 2 is calculated. In STEP 5, the calculated SC and its target value SCm are compared, and if SC »= SCm, then the routine proceeds to STEP 6, where the adjustment of the amount of refrigerant is finished. If SC <SCm, then the routine proceeds to STEP 7, where the second throttle device 46 is opened, and the refrigerant is charged from the refrigerant supply cylinder into the refrigerant circuit via the refrigerant charging port 7. In this step, the opening/closing valve 5 is also opened. In STEP 8, the discharge pressure Pd of the compressor I and a discharge refrigerant terrperature Td of the compressor I are detected. In STEP 9, a temperature difference SHd between the discharge refrigerant temperature id of the compressor I and the saturated temperature Tsat (Pd) of the discharge pressure Pd of the compressor 1 is calculated. In STEP 10, in accordance with a difference between the calculated SHd and its target value SHdm, the opening-degree of the second throttle device 46 is corrected on the basis of LEV2, and the routine proceeds to STEP 11. In STEP 11, ii a predetermined time has elapsed, the routine returns to STEP 2, wñile if the predetermined time has not elapsed, the routine returns to STEP 7.

[0019] As described above, when the refrigerant is charged from the refrigerant supply cylinder into the refrigerant circuit, liquid-back to the compressor I can be prevented in accordance with the disch'arge state of the compressor I by adjusting the charging flow rate with the second throttle device 46, and the charging flow rate can be maximized within its proper range when a

S

superheating-degree of the discharge from the compressor 1 is large by increasing the opening-degree of the throttle, and thus, rapid refrigerant charging can be realized. In this embodiment, a method is described in which the refrigerant flow rate charged. from the refrigerant supply cylinder is controlled so that the superheating-degree of the refrigerant discharged from the compressor 1.

will reach a predetermined target value set in advance, but the same effect can be obtained by using the superheating-degree of the refrigerant sucked into the compressor I as the index.

[0020] Embodiment 3.

Fig. 6 is a flowchart illustrating an algorithm when the refrigerant is automatically charged according to Embodiment 3 of the present invention. The configuration of the refrigerant circuit, here, is the same as Embodiment I. In Fig. 6, in a state in whicha refrigerant supply cylinder is connected to the refrigerant charging port 7, the operation of adjusting the amount of refrigerant is started in STEP I. In STEP 2, in order to obtain a control interval, waiting is performed for a predetermined time, and after the predetermined time has elapsed, the routine proceeds to STEP 3. In STEP 3, the discharge pressure Pd of the compressor I and the refrigerant temperature Tcout at the condenser outlet are detected. In STEP 4, a temperature difference SCi between the saturated temperature Tsat(Pd) of the discharge pressure Pd of the compressor 1 and the outlet refrigerant temperature Tcout of the condenser. 2 is calculated. In STEP 5, a temperature difference SC between the currently calculated SC1 and the previous calculation result SCi-1 is calculated. However, in the first detection, there is no previous value, and so the previous value is set at 0. In step 6, iSC is determined if it is "0" or not, and if "0" appears more than a predetermined number f times, which means the refrigerant has not been óharged, the routine proceeds to STEP 7, in which the refrigerant supply cylinder is considered as empty Or not connected, and a bomb replacement signal is emitted. A method of signaling may

S

be any of a service display unit, a remote controller, personal computer for control, lamp display. by an electric signal and the like. If SC = C is not detected a predetermined number of times, the routine proceeds to STEP 8. In STEP 8, the calculated SCi and its target value SCm are compared, and when SCi»= SCm, the routine proceeds.to STEP 9, in which the adjustment of the amount.of refrigerant is finished. When SCI < SCm, the routine proceeds to STEP 10. in which the refrigerant charging opening/closing valve 6 is kept open for a predetermined time, and the refrigerant is charged into the refrigerant circuit from the refrigerant supply cylinder via the refrigerant charging port 7. In this step, the. opening/closing valve 5 is also opened. After the refrigerant is charged for a predetermined time in STEP 10, the routine proceeds to STEP 2.

[0021] By means of the above operations, such a situation that the refrigerant supply cylinder is not connected to the refrigerant charging port 7 or the refrigerant charging operation is continued while the refrigerant supply cylinder is left empty can be prevented, and a system with high reliability in automatic refrigerant charging can be realized.

[0022] Embodiment 4.

Fig. 7 illustrates a refrigerant circuit diagram of a refrigeration air-conditioning apparatus according to Embodiment 4 of the present invention. In Fig. 7, reference numeral I denotes a compressor, 21 a four-way valve, 22 a heat-source-side heat exchanger, 23 an accumulator, 24 a refrigerant heat exchanger, 26 an outdoor throttle device, and 14 an opening/closing valve, which constitute a main refrigerant circuit of a heat-sOurce-side unit 51. Reference numeral 13 denotes an opening/closing valve on a circuit that bypasses the refrigerant heat exchanger 24. On the liquid side of the refrigerant heat exchanger 24, a portion between the refrigerant heat exchanger and the opening/closing valve 14 branches and merges with the refrigerant circuit between a gas pipe 102

S

on the gas side and the refrigerant heat exchanger 24 via a throttle device 17. A pipeline branching from a discharge pipeline of the compressor I merges with the refrigerant circuit between the four-way valve 21 and the accumulator 23 via the opening/closing valve 5, branches between the merged portion and the opening/closing valve 5 and connects to the refrigerant, charging port 7 via the refrigerant charging opening/closing valve 6.

The pipeline connected to the bottom of the accumulator 23 is connected to a recovering unit 25 via the opening/closing valve 15, and an upper part of the recovering unit 25 is connected to the refrigerant circuit between the four-way valve 21 and the accumulator 23 via the opening/closing valve 16. Also, the pipeline connected to the bottom of the accumulator 23 branches between the accumulator and the opening/closing valve 15 and is connected to the refrigerant circuit between the accumulator 23 and the compressor I via the opening/losing valve 19.

Moreover, reference numeral 8 denotes a pressure sensor that detects the pressure in a high-pressure portion in the discharge side of the compressor 1, and reference numeral 9 denotes a first temperature sensor that detects the temperature of the refrigerant on the discharge side of the compressor 1.

Reference numeral 10 denotes a second temperature sensor that detects the temperature of the refrigerant at the outlet of the heat-source-side heat exchanger 22. Reference numeral 18 denotes a fifth temperature sensor, which detects the temperature of the refrigerant, installed in a refrigerant circuit between the four-way valve 21 and the accumulator 23 and *n the downstream side from the merging point merging via the opening/closing valve 5 of the hot-gas bypass.

circuit. Also, reference numeral 20 is a second pressure sensor that detects the pressure of the refrigerant passing through a liquid pipe 101, and reference numeral 28 is a third pressure sensor that detects the pressure of the refrigerant passing through the refrigerant circuit between the four-way valve 21 and the accumulator 23: Here, the heat-source-side unit 51 is constituted by above

I

components.

[0023] On the other hand, reference characters 3a and 3b denote throttle devices, and reference characters 27a and 27b denote load-side heat exchangers.

5. Reference characters 11 a and 11 b denote third temperature sensors that detect the temperature of the refrigerant between the throttle devices 3a and 3b and the load-side heat exchangers 27a and 27b, and reference characters 1 2a and 1 2b are fourth temperature sensors that detect the temperature of the refrigerant between the load-side heat exchanger and a gas pipe 102. Above constitute the load-side units 52a and 52b. Suffixes a and b indicate a multiple-unit air-conditioning apparatus to which a plurality of indoor units are connected.

(0024] Also, reference numeral 101 denotes a liquid pipe and reference numeral 102 denotes a gas pipe, and pipelines used in an existing unit embedded in the ceiling can be allocated as theses pipes. The liquid pipe 101 and the gas pipe 102 connect the heat-source-side unit 51 and the load-side units 52a and 52b and [0025] A flow will be described with a flowchart in Fig. 8, of which foreign substances such as deteriorated lubricating oil used in an existing unit in the existing liquid pipe 101 and gas pipe 102 is removed prior to an air-conditioning operation using the unit as shown in Fig. 7. First, updating is started in STEP 1. In STEP 2, the existing units (the heat-source-side unit and the load-side unit) are removed. In STEP 3, new units are installed. In STEP 4, the new units and existing refrigerant pipelines are connected to each other. In STEP 5, after the liquid pipe 101, the gas pipe 102, the load-side units 52a and 52b are vacuumed, a refrigerant for the Ioad-sid unit is charged. In STEP 6, an amount of refrigeraht required for the system is determined, and an operation to recover the foreign substances is performed. In STEP 7, a cooling and heating operation and a

I

heating operation of an air-conditioning apparatus are checked, arid the updating is completed at STEP 8.

[0026] Here, details of the operation of recovering the foreign substances will be described. First, a flow of the refrigerant when the foreign-substance recovering operation is performed in the cooling mode Will be described. The high-temperature high-pressure gas refrigerant discharged from the compressor I reaches the heat-source-side heat exchanger 22 via the four-way valve 21 and is condensed and liquefied. The condensed and liquefied liquid refrigerant is throttled by the outdoor throttle device 26 so that a detected value of a second pressure sensor 20 is under a withstanding pressure of the existing refrigerant pipeline and so that the liquid refrigerant is of an intermediate pressure, is cooled in the refrigerant heat exchanger 24, and is flowed into the liquid pipe 101 via the opening/closing valve 14. The liquid refrigerant having flowed into the liquid pipe 101 flows into the load-side unit while peeling off the foreign substances in the liquid pipe 101 with the refrigerant flow. The liquid refrigerant containing the foreign substances flowing into the load-side unit is throttled by the throttle devices 3a and 3b to a low pressure, takes heat away from around the load-side heat exchangers 27a and 27b, is evaporated so as to perform cooling, and flows into the gas pipe 102 turned into a two-phase refrigerant containing a liquid refrigerant. The gas-liquid two-phase refrigerant having flowed into the gas pipe 102 flows into the heat-source-side unit 51 while also peeling off the foreign substances in the gas pipe 102. The gas-liquid two-phase refrigerant containing.

foreign substances, having returned to the heat-source-side unit 51, exchanges heat with the high-pressure liquid refrigerant in the refrigerant heat exchanger 24 arid becomes a full gas refrigerant and flows into the accumulator 23 via the four-way valve 21. The gas refrigeraht containing the foreign substances that have flowed into the accumulator 23 has the foreign substances separated in the accumulator 23, and the gas refrigerant returns to the compressor 1. The foreign substances having been separated in the accumulator 23 flow into the recovering unit 25 via the opening/closing valve 15 and are collected in the recovering unit 25.

On this occasion, a part of the dynamic pressure of the refrigerant changes to a static pressure in the accumulator 23, and the pressure in the recovering unit 25 becomes lower than the pressure of the accumulator 23 by the opening of the opening/closing valve 16, thus a flow of the foreign substances is generated from the accumulator 23 to the recovering unit 25 in accordance with the differential pressure. Quality of wet vapor of the gas-liquid two-phase refrigerant at the outlet of the load-side unit is controlled by controlling the throttle devices 3a and 3b s.c that the superheating-degree of. the refrigerant at the suction portion of the accumulator 23 calculated from the fifth temperature sensor 18 and a third pressure sensor 28 is constant.

(0027] * After the above operation is performed for a predetermined time, the control of the refrigeration air-conditioning apparatus is changed as follows, and the amount of refrigerant is checked. The high-temperature high-pressure gas refrigerant discharged from the compressor I reaches the heat-source-side heat exchanger 22 via the four-way valve 21 and is condensed and liquefied. The condensed and liquefied liquid refrigerant is throttled by the outdoor throttle device 26 so that a detected value of the second pressure sensor 20 is under a withstanding pressure of the existing refrigerant pipeline and so that the liquid refrigerant is of an intermediate pressure. is cooled in the refrigerant heat exchanger 24 until it is supercooled, while a part is cooled to a low pressure through the throttle device 17 and merges with the gas refrigerant flowing through a low-pressure gas part. The remaining liquid refrigerant flows into the liquid pipe 101 via the opening/closing valve 14. The liquid refrigerant having flowed into the liquid pipe 101 flows to the load-side unit; the liquid refrigerant having flowed into the load-side unit is throttled to a low pressure by the throttle devices 3a and 3b, takes heat away from around the load-side heat exchangers 27a and 27b, is * 15 evaporated.so as to perform cooling, is controlled so that the superheating-degree of the outlet refrigerant of the load-side heat exchanger acquired as a difference in the detected values between the third temperature sensors lie and lib and the fourth temperature sensors 12a and 12b is constant, is gasified, and is flown into the gas pipe 102. The gas refrigerant having flowed into.the gas pipe 102 flows into the heat-source-side unit 51. The gas refrigerant having returned to the heat-source-side unit 51 merges with the low-temperature gas-liquid two-phase refrigerant that has flowed through the bypass circuit provided with the throttle * device 17, and then, exchanges heat with the high-pressure liquid refrigerant in the refrigerant heat exchanger 24 and becomes a full gas refrigerant and flows into the accumulator 23 via the four-way valve 21. The gas refrigerant having flowed into the accumulator 23 returns to the compressor 1. At this time, the opening/closing valve 15 installed in a pipeline connected to the bottom of the accumulator 23 is closed so as to keep the foreign substances in, and the 15. opening/closing valve 19 is opened so that the lubricating oil in the compressor I taken out with the refrigerant flows into a suction pipe of the compressor 1 via the opening/closing valve 19 so as to return the oil. As above, by changing the refrigerant control method after the foreign substances are recovered, the refrigerant in the liquid pipe 101 enters a full liquid state and the refrigerant in the gas pipe 102 enters a full gas refrigerant state, which is a refrigerant distribution state in performing an air conditioning operation, thus enabling accurate determination of the amount of refrigerant.

[0028] Subsequently, a method of automatically charging a refrigerant during the foreign-substance recovering operation in cooling will be described using a flowchart in Fig. 9. In Fig. 9, the foreign-substance recovering operation is started in STE? 1, and the compressor 1 is started. In STEP 2, the temperature Td of the refrigerant discharged from the compressor 1 is detected. In STEP 3, particularly in the initial state, since only the refrigerant charged into the heat-source-side unit in advance and the refrigerant for the load-side unit charged after vacuuming have been charged into the refrigerant circuit, the refrigerant is short in many cases; the detected discharge temperature Td and an upper limit value Tdmax of the discharge temperature set in advance are compared with each other, and 5. when Td > Tdmax, it is determined that the refrigerant is short, and the routine proceeds to STEP 5, in which the refrigerant charging opening/closing valve 6 is opened together with the opening/closing valve 5 so that the refrigerant is charged. When Td Tdmax in STEP 3, the routine proceeds to STEP 4, in which whether the predetermined time has elapsed or not is determined. If the predetermined time has elapsed in STEP 4, the routine proceeds to STEP 6, while if the predetermined time has not elapsed, the routine returns to STEP 2. In STEP 6, as described above, the control method is changed, and the operation of superheating the refrigerant at the load-side unit outlet is performed. In STEP 7, whether the predetermined time has elapsed or not is determined once more, and-if the predetermined time has elapsed, the routine proceeds to STEP 8, in which the discharge pressure Pd of the refrigerant discharged from the compressor I and the outlet temperature Tcout of the heat-source-side heat exchanger 22 are detected. In STEP 9, the driference SC between the saturated temperature Tsat(Pd) of Pd and Tcout is calculated, and in STEP 10, SC and the target value SCm of SC are compared, and when SC SCm, the routine proceeds to STEP 11, in which the foreign-substance recovering operation is completed. If SC < SCm, the routine proceeds to STEP 12, opens the opening/closing valve 5 and the refrigerant charging opening/closing valve 6 for a predetermined time to charge the refrigerant form the refrigerant charging port 7; then, the routine returns to ST.EP 7.

(0029] Subsequently, a flow of the refrigerant when recovery of foreign substance is operated while preforming a heating mode will be described on the basis of Fig. 7 The high-temperature high-pressure gas refrigerant discharged a from the compressor I flows into the refrigerant heat exchanger 24 via the four-way valve 21, is cooled in the refrigerant heat exchanger 24, becomes a high-pressure gas-liquid two-phase refrigerant, and flows into the gas pipe 102. At this time, the high pressure is controlled to a pressure no more than the withstanding pressure of the. existing pipeline by capacity control of the compressor I or the like. The gas-liquid two-phase refrigerant having flowed into the gas pipe 102 flows into the load-side unit while peeling off the foreign substances in the gas pipe 102. The gas-liquid two-phase refrigerant containing the foreign substances that has flowed into the load-side unit radiates heat to around the load-side heat exchangers 27a and 27b, is condensed so as to perform heating, is liquefied, and then, is throttled by the throttle devices 3a and 3b to an intermediate pressure, is turned into a two-phase refrigerant containing the foreign substances, and is flown into the liquid pipe 101. The gas-liquid two-phase refrigerant having flowed into the liquid pipe 101 flows into the heat-source-side unit 51 while also peeling off the foreign substances in the liquid pipe 101. The gas-liquid two-phase refrigerant containing the foreign substances having returned to the heat-source-side unit 51 flows into the refrigerant heat exchanger 24 via the opening/closing valve 14, exchanges heat with the high-pressure gas refrigerant and becomes a two-phase refrigerant with a high quakty of wet vapor and is throttled by the outdoor throttle device 26 to a low pressure and then, flows through the heat-source-side heat exchanger 22 and is fully vaporized therein and flows into the accumulator 23 via the four-way valve 21.

The gas refrigerant containing the foreign substances that have flowed into the accumulator 23 has the foreign substances separated in the accumulator 23, and the gas refrigerant returns to the compressor 1. The foreign substances having been separated in the accumulator 23 flow into the recovering unit 25 via the openingfclosing valve 15 and are collected in the recovering unit 25. On this occasion, a part of the dynamic pressure of the refrigerant changes to a static pressure in the accumulator 23, and the pressure in the recovering unit 25 becomes lower than the pressure of the accumulator 23 by the opening of the opening/closing valve 16, thus a flow of the foreign substances is generated from the accumulator 23 to. the recovering unit 25 in accordance with the differential pressure. The superheating-degree of the refrigerant at the outlet of the heat-source-side heat exchanger 22 is controlled by the outdoor throttle device 26.

[0030] After the above operation is performed for a predetermined time, the control of the refrigeration air-conditioning apparatus is changed as follows, and the amount of refrigerant is checked. The high-temperature high-pressure gas refrigerant discharged from the compressor I flows into the refrigerant heat exchanger 24 via the four-way valve 21, but since the refrigerant is not allowed to flow to the low-pressure side, heat exchange is not performed,and thus the refrigerant flows into the gas pipe 102 still in the superheated gas state. At this time, the high pressure is controlled to a pressure no more than the withstanding pressure of the existing pipeline by capacity control of the compressor 1 or the like.

The high-temperature gas refrigerant having flowed into the gas pipe 102 flows into the load-side unit. The high-temperature gas refrigerant that has flowed into the load-side unit radiates heat to around the load-side heat exchangers 27a and 27b, is condensed so as to perform heating, is liquefied, and then, is throttled by the throttle devices 3a and 3b to an intermediate pressure, is turned into a two-phase refrigerant containing the foreign substances, and is flown into the liquid pipe 101. The gas-liquid two-phase refrigerant having flowed into the liquid pipe 101 flows into the heat-source-side unit 51. The gas-liquid two-phase refrigerant containing the foreign substances having returned to the heat-source-side unit 51 flows through the opening/closing valve 13 bypassing the refrigerant heat exchanger 24 and is throttled by the outdoor throttle device 26 and then, flows through the heat-source-side heat exchanger 22 and is fully vaporized therein and flows into the accumulator 23 via the four-way valve 21. As

O

above, by changing the refrigerant control method after the foreign substances are recovered, the state of the refrigerant in the liquid pipe 101 becomes the same as that in the usual heating operation or slightly close to a liquid and the refrigerant in the gas pipe 102 enters a full gas refrigerant state, which is a refrigerant distribution state in performing an air conditioning operation, thus enabling accurate determination of the amount of refrigerant.

[0031] Subsequently, a method of automatically charging a refrigerant during a foreign-substance recovering operation in heating will be described by using a flowchart in Fig. 10. In Fig. 10, the foreign-substance recovering operation is started in STEP 1, and the compressor I ts started. In STEP 2, the temperature Id of the refrigerant discharged from the compressor I is detected. In STEP 3, particularly in the initial state, since only the refrigerant charged into the heat-source-side unit 51 in advance and the refrigerant for the load-side unit charged after vacuuming have been charged into the refrigerant circuit, the refrigerant is short in many cases; the detected discharge temperature Td and an upper limit value Tdmax of the discharge temperature set in advance are compared with each other, and when Id > Tdmax, it is determined that the refrigerant is short, and the routine proceeds to STEP 5, in which the refrigerant charging opening/closing valve 6 is opened together with the opening/closing valve 5 so that the refrigerant is charged from the refrigerant charging port 7.

When Id »= Idmax in STEP 3, the routine proceeds to STEP 4, in which whether the predetermined time has elapsed or not is determined. If the predetermined time has elapsed in STEP 4, the routine proceeds to STEP 6, while if the predetermined time has not elapsed, the routine returns to STEP 2. In STEP 6, as described above, the control method is changed, and the operation of bypassing the refrigerant heat exchanger 24 on the low-pressure side is performed. In STEP 7, whether the predetermined time has elapsed or not is determined once more, and if the predetermined time has elapsed, the routine proceeds to STEP 8, in which the discharge pressure Pd of the refrigerant discharged from the compressor 1 and an average value Tcoutave of the outlet temperature of the load-side heat exchangers 27a and 27b are detected and calculated. In STEP 9, the difference SC between the saturated temperature Tsat(Pd) of Pd and Tcout..ave is calculated, and at STEP I 0, SC and the target value SCm of SC are compared, and in the case of SC SCm, the routine proceeds to STEP 11, in which the foreign-substance recovering operation is completed. If SC < SCm, the routine proceeds to STEP 12, opens the opening/closing valve 5 and the refrigerant charging opening/closing valve 6 for a predetermined time to charge the refrigerant form the refrigerant charging port 7; then, the routine returns to STEP 7.

(0032] By means of the above operations, if the unit is renewed using the existing refrigerant pipeline, even if the existing pipeline is in a state embedded in a wall or a ceiling, the amount of refrigerant can be accurately determined by the unit itself, and the refrigerant can be charged, and thus, construction time can be reduced, and the amount of refrigerant can be determined regardless of whether it is in cooling or heating Therefore, regardless of the season, a system with high reliability in terms of amount of refrigerant can be obtained.

[0033] In this embodiment, the example having two indoor units is described, but it is self-apparent that similar effects can be obtained with a system with three indoor units. Also, even with a plurality of heat-source-side units connected, similar control method can be applied by use of a similar method such as processing the average of the state of the outlet refrigerant of the heat-source-side heat exchanger.

[b034] Embodiment 5.

Fig. II. illustrates a refrigerant circuit diagram of a refrigeration air-conditioning apparatus according to Embodiment 5 of the present invention.

This device is provided with a heat-source-side, unit 51, load-side units 52a and 52b, and a branch-flow controller 53.

First, a configuration of the heat-source-side unit 51 will be described.

Reference numeral I denotes a compressor, 21 a four-way valve, 22 a.

heat-source-side heat exchanger, 23 an accumulator, and 32a, 32b, 32c, and 32d check valves, which are connected so as to constitute a main refrigerant circuit of the heat-source-side unit 51. Also, a pipeline branching from a discharge pipeline of the compressor I merges with the refrigerant circuit between the four-way valve 21 and the accumulator 23 via the opening/closing valve 5, branches between the merged portion and the opening/closing valve 5 and connects to the refrigerant charging port 7 via the refrigerant charging opening/closing valve 6.

* Moreover, reference numeral 8 denotes a pressure sensor that detects the pressure in a high-pressure portion in the discharge side of the compressor 1, and reference numeral 9 denotes a first temperature sensor that detects the temperature of the refrigerant on the discharge side of the compressor 1. The heat-source-side unit 51 is constituted by above components.

10035] Subsequently, a configuration of the load-side unit will be described.

Reference characters 3a and 3b denote throttle devices, and 27a and 27b load-side heat exchangers. Reference characters ha and lib denote third temperature sensors that detect the temperature of the refrigerant between the throttle devices 3a and 3b and the load-side heat exchangers 27a and 27b, and reference characters 12a and 12b are fourth temperature sensors that detect the temperature of the refrigerant between the load-side heat exchanger and a gas pipe. Above constitute the load-side units 52a and 52b. Suffixes a and b indicate a multiple-unit air-conditioning apparatus to which a plurality of indoor units are connected.

[0036] Finally, a configuration of a branch-flow controller 53 arranged between the heat-source-side unit 51 and the load-side units 52a and 52b will be described.

Reference numeral 33 denotes a gas-liquid separator, in which an upper part of the gas-liquid separator 33 is connected to opening/closing valves 41a and 41b for high pressure, while a lower part of the gas-liquid separator 33 is connected to a first refrigerant heat exchanger 35. The other end of the first refrigerant heat exchanger 35 is connected to check valves 39a and 39b and a second refrigerant heat exchanger 36 via a throttle device 34. Also1 the other end of the second refrigerant heat exchanger 36 is connected to the check valves 40a and 40b which are connected, to the throttle devices 3a and 3b of the load-side unit. Also, the refrigerant circuit (bypass circuit) branching from between the second refrigerant heat exchanger 36 and the check valves 40a and 40b is connected to the low-pressure sides of the second refrigerant circuit 36 and the first refrigerant heat exchanger 35 via a throttle device 37, and then, connected to the inlet of a low-pressure pipe 104. Moreover1 the gas-side pipelines of the load-side heat exchangers 27a and 27b are connected to an upper-part pipeline of the gas-liquid separator 33 via the opening/closing valves 41a and 41b for high pressure and also connected to the low-pressure pipe 104 via the opening/closing valves 42a and 42b for low-pressure.

[0037] The heat-source-side unit 51 and the load-side units 52a and 52b are connected via the branch-flow controller 53. At this time, the heat-source-side unit 51 and the branch-flow controller 53 are connected by a high-pressure pipe 103 and the low-pressure pipe 104, and the branch-flow controller 53 and the load-side units 52a and 52b are connected via the liquid pipe and the gas pipe.

[0038] In a multipl'e-unit system having the above configuration, the flow of the refrigerant when the amount of refrigerant is adjusted, and the refrigerant is automatically charged as necessary will be described. The operation mode is set such that afl the indoor units perform cooling. At this time, when the compressor I is operated, a high-temperature high-pressure gas refrigerant passes through the four-way vale 21 and is condensed and vaporized in the heat-source-side heat exchanger 22 and is brought into a liquid state. However, the refrigerant at the outlet, of the condenser (heat-source-side heat exchanger 22) will not be in a supercooled state, as for the high-pressure pipe 103 has, considering pressure loss during heating, a large diameter and the entire pipeline is not filled with refrigerant as to be refrigerant-sealed, in many cases. In this case, a gas-liquid twa-phase refrigerant containing some gas flows through the high-pressure pipe 103 and flows into the gas-liquid separator 33. The gas-liquid two-phase refrigerant that has flowed into the gas-liquid separator 33 flows to the first refrigerant heat exchanger 35 from the lower part of the gas-liquid separator 33 is throttled by the throttle device 34 to an intermediate pressure, and is cooled by the second refrigerant heat exchanger 36 till it is fully condensed. And a part thereof is throttled by the throttle device 37 to a low pressure, flows through the low-pressure sides of the second refrigerant heat exchanger 36 and the first refrigerant head exchanger 35, exchanges heat with the intermediate-pressure gas-liquid two-phase refrigerant flowing through the high-pressure side, is evaporated and vaporized, merges with the refrigerant flowing through the main circuit, and flows into the low-pressure pipe 104. At this time, the throttle device 37 detects the superheating-degree of the refrigerant by a difference in temperature of a temperature sensor 44 installed at the inlet of the second refrigerant heat exchanger 36 and a temperature sensor 45 installed on the outlet side of the first refrigerant heat exchanger 35, and controls such that the superheating-degree is constant. The remaining liquid refrigerant having been supercooled in the second refrigerant heat exchanger 36 flows into the load-side unit via the check valves 40a and 40b. Then, the refrierant is throttled by the throttle devices ha and iib to a low pressure, takes heat from around the load-side heat exchangers 27a and 27b so as to perform cooling, is evaporated and vaporized, flows to the

O

low-pressure pipe 104 via the opening/closing valves 42a and 42b, and returns to the heat-source-side unit 51. The gas refrigerant having returned to the heat-source-side unit 51 returns to the compressor I via the check valve 32b, the four-way valve 21 and the accumulator 23.

[0039].

A method of determining that a state of a refrigerant is short and automatically charging a refrigerant1 during the cooling operation performed as above, will be described using a flowchart in Fig. 12. In Fig. 12, in a state in which a refrigerant supply cylinder is connected to the refrigerant charging port 7, the operation of adjusting the amount of refrigerant is started in STEP 1. As a starting trigger, a service switch, a remote controller, a contact point input from the outside a control signal from a personal computer and the like is used provided at an outdoor unit. In STEP 2, in order to obtain a control interval, waiting is performed for a predetermined time, and after the predetermined time has elapsed, the routine proceeds to STEP 3. In STEP 3, an intermediate pressure Pm of the branch-flow controller 53 and a refrigerant temperature Trout in the second refrigerant heat exchanger 36 are detected. In STEP 4, the temperature difference SC between the saturated temperature Tsat(Pm) of Pm and the outlet refrigerant temperature Trout of the second refrigerant heat exchanger 36 is calculated. In STEP 5, the calculated SC and its target value SCm are compared, and if SC »= SCm, then the routine proceeds to STEP 6, where the. adjustment of the amount of refrigerant is finished. If SC <SCm, then the routine proceeds to STEP 7, where the refrigerant charging openinglclosing valve 6 is kept open for a predetermined time, and the refrigerant is charged into the refrigerant circuit from the refrigerant supply cylinder via the refrigerant charging port 7. In this step, the opening/closing valve 5 is also opened. After the refrigerant is charged for a predetermined time in STEP 7, the routine proceeds to STEP 2.

[0040] Subsequently, an operation of the above refrigeration air-conditioning apparatus during a usual air conditioning operation will be described. First, a cooling only operation in which all the load-side units perform a cooling operation will be described. A high-temperature high-pressure gas refrigerant discharged from the compressor I is condensed at.the heat-source-side heat exchanger 22 and then, reaches the gas-liquid separator 33 in the branch-flow controller 53 via the check valve 32a and the high-pressure pipe 103. The liquid refrigerant that has reached the gas-liquid separator 33 flows to the first refrigerant heat exchanger 35 from the lower part of the gas-liquid separator 33, is throttled by the throttle device 34 to an intermediate pressure, is cooled by the second refrigerant heat exchanger 36 to increase the supercooling-degree, and a. part of the refrigerant reaches the load-side units 52a and 52b via the check valves 40a and 40b. The liquid refrigerant having reached the load-side units 52a and 52b is throttled by the throttle devices 3a and 3b to a low pressure, is turned into a low-temperature gas-liquid two-phase refrigerant and flows into the load-side heat exchangers 27a and 27b, takes heat from around to perform cooling, is evaporated and vaporized, and flows into the low-pressure pipe 104 via the opening/closing valves 42a and 42b. On the other hand, the remaining liquid refrigerant having its supercooling-degree increased at the second refrigerant heat exchanger 36 is throttled by the throttle device 37 and is turned into a low-temperature gas-liquid two-phase refrigerant, flows into the second refrigerant heat exchanger 36 and the first refrigerant heat exchanger 35, exchanges heat with the liquid refrigerant flowing from the other channel in the gas-liquid separator 33, is evaporated and vaporized, merges with the gas refrigerant evaporated and vaporized in the load-side heat exchangers 27a and 27b, and then, flows through the low-pressure pipe 104 and returns to the compressor I via the check valve 32b, the four-way valve 21, and the accumulator 23.

[0041] Subsequently, a cooling-main operation, in which a cooling operation and* a heating operation are present at the same time and a cooling load is larger than a heating load, wilt be described. A high-temperature high-pressure gas refrigerant discharged from the compressor 1 is partially condensed at the heat-source-side heat exchanger 22 and becomes a high-temperature high-pressure gas-liquid two-phase refrigerant and then, reaches the gas-liquid separator 33 in the branch-flow controller 53 via the check valve 32a and the high-pressure pipe 103. Here, it is assumed that the load-side unit 52a is performing a heating operation and the load-side unit 52b is performing a cooling operation. The gas-liquid two-phase refrigerant having reached the gas-liquid separator 33 has its gas refrigerant separated in the upper part of the gas-liquid separator 33; the gas refrigerant flows to the load-side heat exchanger 27a via the opening/closing valve 41a, radiates heat.to around so as to perform heating, is condensed and liquefied, is throttled by the throttle device 3a to an intermediate pressure, and returns to the branch-flow controller 53. After the liquid refrigerant having returned to the branch-flow controller 53 merges with the liquid refrigerant that has been separated by the gas-liquid separator 33, that has had its supercooling increased at the first refrigerant heat exchanger 35, and that has been throttled by the throttle device 34 to an intermediate pressure, the liquid refrigerant further increases its supercooling-degree in the second refrigerant heat exchanger 36 and then, flows a part thereof to the load-side unit 52b via the check valve 40b, while the remaining liquid refrigerant flows to the throttle valve 37. The liquid refrigerant having reached the load-side unit 52b is throttled by the throttle device 3b to a low pressure, is turned into a low-temperature gas-liquid two-phase refrigerant and flows into the load-side heat exchanger 27b, takes heat from around to perform cooling, is evaporated and vaporized, and flows into the low-pressure pipe 104 via the opening/closing valve 42b. On the other hand, the liquid refrigerant having flowed to the throttle device 37is throttled by the throttle device 37 and is *turned into a low-temperature gas-liquid two-phase refrigerant, flows into the second refrigerant heat exchanger 36 and the first refrigerant heat exchanger 35, exchanges heat with the liquid refrigerant having flowed from the gas-liquid separator 33, is evaporated and vaporized, merges with the gas refrigerant evaporated and vaporized in the load-side heat exchanger 27b, and returns 10 the compressor I via the check valve 32b, the four-way valve 21, and the accumulator 23 [00421 Subsequently, a heating-main operation in which a cooling operation and * a heating operation are present at the same time and a heating load is larger than a cooling load will be described. The high-temperature high-pressure gas refrigerant discharged from the compressor I flows to the high-pressure pipe 103 via the four-way valve 21 and the check valve 32c and reaches the gas-liquid separator 33 in the branch-flow controller 53. Here, it is assumed that the load-side unit 52a is performing a heating operation and the load-side unit 52b is performing a cooling operation. The high-temperature high-pressure gas refrigerant having reached the g2s-liquid separator 33 flows to the load-side heat exchanger 27a via the opening/closing yalve 41a from the upper part of the gas-liquid separator 33, radiates heat to around so as to perform heating, is condensed and liquefied, is throttled by the throttle device Sa to an intermediate pressure, and returns to the branch-flow controller 53. A part of the liquid refrigerant having returned to the branch-flow controller 53 is cooled by the second refrigerant heat exchanger 36 and then, flows to the load-side unit 52b via the check valve 40b. The liquid refrigerant having reached the load-side unit 52b is throttled by the throttle device 3b to a low pressure, is turned into a low-temperature gas-liquid two-phase refrigerant and flows into the load-side heat exchanger 27b, takes heat from around to perform cooling, is evaporated and vaporized, and flows into the low-pressure pipe 104 via the opening/closing valve 42b. The remaining liquid that has returned to the branch-flow 6ontroller 53 is throttled by the throttle device 37 to a low pressure, merges with the gas refrigerant evaporated and vaporized in the load-side heat exchanger 52b, flows through the low-pressure pipe 104, is evaporated and vaporized in the heat-Source-Side heat exchanger 22 and returns to the compressor I via the four-way valve 21 and the accumulator 23.

[00431 Finally, a heating only operation in which all the load-side units perform a heating operation will be described. The high-temperature high-pressure gas refrigerant discharged from the compressor I flows to the high-pressure pipe 103 via the four-way valve 21 and the check valve 32c and reaches the gas-liquid separator 33 in the branch-flow controller 53. The high-temperature high-pressure gas refrigerant having reached the gas-liquid separator 33 flows to the load-side heat exchangers 27a and 27b via the opening/closing valves 41a and 41b from the upper part of the gas-liquid separator 33, radiates heat to around so as to perform heating, is condensed and liquefied, is throttled by the throttle device 3a and 3b to an intermediate pressure, and returns to the branch-flow controller 53.

The liquid refrigerant having returned to the branch-flow controller 53 is throttled by the throttle device 37 to a low pressure, merges with the gas refrigerant evaporated and vaporized in the load-side heat exchanger 52b, flows through the tow-pressure pipe 104, is evaporated and vaporized in the heat-source-side heat exchanger 22 and returns to the compressor I via the four-way valve 21 and the accumulator 23.

[0044] By means of the configuration and the operation as above, even in a double-pipe type system having a thick high-pressure pipe 103 capable of simultaneous heating and cooling operations, it becomes possible to appropriately determine the refrigerant and to perform automatic refrigerant charging if the refrigerant is short. Also, even if the refrigerant cannot be overcooled in the heat-source-side heat exchanger 22, an appropriate amount of refrigerant can be determined and the refrigerant can be charged with accuracy by the supercooling-degree at the outlets of the refrigerant heat exchangers 35 and 36, and thus, the refrigerant is not overcharged and a system with high reliability can be obtained.

[0045] Embodiment 6.

Fig. 13 illustrates a refrigerant circuit diagram of a refrigeration air-conditioning apparatus according to Embodiment 6 of the present invention.

This apparatus is provided with the heat-source-side unit 51, the load-side units 52a and 52b, and branch-flow kits 54a and 54b.

The configuration of the heat-source-side unit 51 is as follows. Reference numeral I denotes a compressor, 22 a heat-source-side heat exchanger, 23 an accumulator, and 26 an outdoor throttle device. A discharge pipeline of the compressor I is connected to the heat-source-side heat exchanger 22 via an opening/closing valve 29b and is also connected to the high-pressure pipe 103 by branching from the middle thereof. An inflow pipe of the accumulator 23 is connected to the refrigerant circuit between the opening/closing valve 29b and the heat-source-side heat exchanger 22 via the opening/closing valve 29a and is also connected to the low-pressure pipe 104 by branching from the middle thereof.

Also, the other end of the heat-source-side heat exchanger 22 is connected to the liquid pipe 101. Moreover, a pipeline branching from the discharge pipeline of the compressor 1 is merged with the refrigerant circuit between the four-way valve 21 and the accumulator 23 via the opening/closing valve 5 and is connected to the refrigerant charging port 7 via the refrigerant charging opening/closing valve 6 between the merging portion and the opening/closing valve 5. Moreover, reference numeral 8 denotes a pressure sensor that detects the pressure at a high-pressure portion in the discharge side of the compressor 1, and reference numeral 9 denotes a first temperature sensor that detects the temperature of the refrigerant at a high-pressure portion on the discharge side of the compressor 1.

The heat-source-side unit 51 is constituted by above components.

[0046] Subsequently, a configuration of the load-side unit will be described.

Reference characters 3a and 3b denote throttle devices, arid 27a and 27b load-side heat exchangers. Reference characters lie and lib are third temperature sensors that detect the temperature of the refrigerant between the throttle devices 3a and 3b and the load-side heat exchangers 27a and 27b, and reference characters 12a arid 12b are fourth temperature sensors that detect the temperature of the refrigerant between the load-side heat exchangers 27a and 27b and the branch-flow kits 54a and 54b. Above constitute the load-side units 52a and 52b. Suffixes a and b indicate a multiple-unit air-conditioning apparatus to which a plurality of indoor units are connected.

[0047] Regarding the heat-source-side unit 51 and the load-side unit 52 having the above configurations, the heat-source-side heat exchanger 22 and the throttle devices 3a and 3b are connected via the liquid pipe 101, and the load-side heat exchangers 27a and 27b are connected to the high-pressure pipe 103 and the low-pressure pipe 104 via the branch-flow kits 54a and 54b. Regarding the branch-flow kits 54a and 54b, the high-pressure pipe 103 is connected to the load-side heat exchangers 27a and 27b via the opening/closing valves 30a and 30b, and the low-pressure pipe 104 is connected to the toad-side heat exchangers 27a and 27b via the opening/closing valves 31a and 31b.

f0048J In the multiple-unit system having the above configuration, a flow of the refrigerant when the amount of refrigerant is adjusted, and the refrigerant is automatically charged as necessary will be described. First, an operation mode in which all the load-side units perform cooling will be described. At this time, when the compressor 1 is operated, the high-temperature high-pressure gas refrigerant flows to the heat-source-side heat exchanger 22 via the opening/closing valve 29b and is condensed and liquefied. The liquefied liquid refrigerant having flowed to the liquid pipe 101, flows to the load-side units 52a and 52b, is throttled by the

S

throttle devices 3a and 3b to a low pressure, takes heat from around the load-side heat exchangers 27a and 27b so as to perform cooling, is evaporated and vaporized, flows to the low-pressure pipe 104 via the opening/closing valves 31 a and 32b, and returns to the heat-source-side unit 51. The gas refrigerant having* returned to the heat-source-side unit 51 returns to the compressor I via the accumulator 23.

[0049] Subsequently, an operation mode in which cooling and heating are present at the same time, and a cooling load is larger than a heating load will be described. Here, it is assumed that the load-side unit 52a is performing a heating operation and the load-side unit 52b is performing a cooling operation. When the compressor I is operated, a high-temperature high-pressure gas refrigerant discharged from the compressor I flows to the heat-source side heat exchanger 22 via the opening/closing valve 29b and also flows toward the load-side unit through the high-pressure pipe 103. The gas refrigerant having flowed to the heat-source-side heat exchanger 22 radiates heat and is condensed and liquefied, and the liquefied refrigerant is throttled by the outdoor throttle device 26 to an intermediate pressure, flows through the liquid pipe 101 and flows toward the load-side unit. On the other hand, the gas refrigerant having flowed through the high-pressure pipe 103 flows to the load-side heat exchanger 27a via the opening/closing valve 30a, radiates heat to around so as to perform heating, is condensed and liquefied, and then, is throttled by the throttle device 3a to an intermediate pressure, merges with the liquid refrigerant having flowed through the liquid pipe 101, and flows to the load-side unit 52b. The liquid refrigerant having flowed to the load-side unit 52b is throttled by the throttle device 3b to a low pressure, takes heat from the periphery so as to perform cooling in the Toad-side heat exchanger 27b, is evaporated and vaporized and flows to the low-pressUre pipe 104 via the opening/closing valve 31b and returns to the heat-source-side unit 51 and returns to the compressor I via the accumulator 23.

S

[0050] Subsequently an operation mode in which a cooling operation and a heating operation are present at the same time and a heating load is larger will be described. Here, it is assumed that the load-side unit 52a is performing a heating operation and the load-side unit 52b is performing a cooling operation. When the compressor I is..operated, a high-temperature high-pressure gas refrigerant discharged from the compressor I flows to the load-side unit through the high-pressure pipe 103. The gas refrigerant having flowed through the high-pressure pipe 103 flows to the load-side heat exchanger 27a via the opening/closing valve 30a, radiates heat to around so as to perform heating, is condensed and liquefied, and then, is throttled by the throttle device 3a to an intermediate pressure, and a part thereof flows to the load-side unit 52b, while the remaining liquid refrigerant flows through the liquid pipe 101 and flows to the heat-source-side unit 51. The liquid refrigerant having flowed to the load-side unit 52b is throttled by the throttle device 3b to a low pressure, takes heat from the periphery so as to perform cooling in the load-side heat exchanger 27b, is evaporated and vaporized and flows to the low-pressure pipe 104 via the opening/closing valve 31b and returns to the heat-source-side unit 51. Also, the liquid refrigerant having flowed through the liquid pipe 101 and returned to the heat-source-side unit 51 is throttled by the outdoor throttle device 26 to a low pressure, exchanges heat with the outside air in the heat-source-side heat exchanger 22, is evaporated and vaporized, merges with the gas refrigerant having flowed through the low-pressure pipe 104 via the opening/closing valve 29a, and returns to the compressor I via the accumulator 23.

[0051] Subsequenhiy, a method of determining that a state of a refrigerant is short and automatically charging a refrigerant, during a cooling operation or a cooling-main operation, will be described using a flowchart in Fig. 14. In Fig. 14, in a state in which a refrigerant supply cylinder is connected to the refrigerant

I

charging prt 7, the operation of adjusting the amount of refrigerant is started in STEP 1. As a starting trigger, a service switch, a remote controller, a contact point input from the outside, a control signal from a personal computer and the like is used provided at an outdoor unit. In STEP 2, in order to obtain a control interval, waiting is performed for a predetermined time, and after the predetermined time has elapsed, the routine proceeds to STEP 3. In STEP 3, the discharge pressure Pd of the compressor I and the refrigerant temperature Tcout at the outlet of the heat-source-side heat exchanger 22 are detected. In STEP 4, the temperature.

difference SC between the saturated temperature Tsat(Pd) of Pd and the outlet refrigerant temperature Tcout of the heat-source-side heat exchanger 22 is calculated. In STEP 5, the calculated SC and its target value SCm are compared, and if SC »= SCm, then the routine proceeds to STEP 6, where the adjustment of the amount of refrigerant is finished. If SC < SCm, then the routine proceeds to STEP 7, where the refrigerant charging opening/closing valve 6 is kept open for a predetermined time, and the refrigerant is charged into the refrigerant circuit from the refrigerant supply cylinder via the refrigerant charging port 7. In this step, the opening/closing valve 5 is also opened. After the refrigerant is charged for a predetermined time in STEP 7, the routine proceeds to STEP 2.

[0052] By means of the above configuration and operation, even in a triple-pipe-type refrigerating air-conditioning system capable of simultaneous operation of cooling and heating, an appropriate amount of refrigerant is rapidly determined, and a refrigerant can be charged as necessary, and thus, accurate refrigerant charging can be completed quickly.

Reference Signs List [0053] 1 compressor, 2 condenser, 3, 3a, 3b throttle device, 4 evaporator, 5 opening/closing valve, 6 refrigerant charging opening/closing valve, 7 refrigerant charging port, 8 pressure sensor, 9 first temperature sensor, 10 second temperature sensor, 11, ha, lib third temperature sensor, 12, 12a, 12b fourth temperature sensor, 13 opening/closing valve, 14 opening/closing valve, 15 opening/closing valve, 16 opening/closing valve, 17 throttle device, 18 fifth temperature sensor, 19 opening/closing valve, 20 second pressure sensor, 21 four-way valve, 22 heat-source-side heat exchanger, 23 accumulator, 24 refrigerant heat exchanger, 25 recovering unit, 26 outdoor throttle device, 27a, 27b load-side heat exchanger, 28 third pressure sensor, 29a, 29b opening/closing valve, 30a, 30b opening/closing valve, 31a, 31b opening/closing valve, 32a, 32b, 33c, 33d check valve, 33 gas-liquid separator, 34 throttle device, 35 first refrigerant heat exchanger, 36 second refrigerant heat exchanger, 37 throttle device, 38 temperature sensor, 39a, 39b check valve, 40a, 40b check valve, 41a, 41b opening/closing valve for high pressure, 42a, 42b opening/closing valve for low pressure, 43 pressure sensor, 44 temperature sensor, 45 temperature sensor, 46 second throttle device, 51 heat-source-side unit, 52a, 52b load-side unit, 53 branch-flow controller, 54 branch-flow kit, 101 liquid pipe, 102 gas pipe, 103 high-pressure pipe, 104 low-pressure pipe.