JP2011007379A - Air conditioner - Google Patents

Abstract

An air conditioner capable of avoiding bearing burnout due to lack of oil is provided.
The outdoor unit includes a compressor, an oil separator, a first electromagnetic on-off valve and a first electromagnetic valve. Provided with an oil return bypass circuit 10 that returns to the suction pipe 34 via the decompression device 9, the outdoor heat exchanger 3, and the outdoor electric expansion valve 5, and the indoor unit 30 includes an indoor heat exchanger 23, an indoor electric expansion And a gas bypass circuit 13 for returning the discharge gas to the suction pipe 34 via the second electromagnetic on-off valve 11 and the second pressure reducing device 12 at a position below the oil separator 2 and oil. It is provided in the return bypass circuit 10, and when the second electromagnetic on-off valve 11 is opened at the start of operation or the like, the flow rates of oil and liquid refrigerant returned from the oil separator 2 to the suction pipe 34 can be increased.
[Selection] Figure 1

Description

  The present invention relates to an air conditioner, and more particularly to an air conditioner equipped with a plurality of hermetic compressors, and relates to securing compressor oil at the start of operation.

  Conventionally, in this type of air conditioner, the oil inside the compressor is heated while the compressor is stopped in order to suppress the so-called “sleeping” in which the refrigerant dissolves in the oil inside the compressor while the compressor is stopped. Means are taken.

  FIG. 8 shows a flowchart of the preheating operation processing of the control unit in the conventional air conditioner. In the conventional air conditioner, when the outside air temperature is equal to or lower than a predetermined temperature, the compressor temperature is lowered and the refrigerant is compressed. There is one in which it is determined that the oil easily dissolves in the oil inside the machine, and the oil is heated by increasing the heating amount as the outside air temperature is lower (see, for example, Patent Document 1).

JP-A-8-114346

  However, in the configuration of the conventional air conditioner, the oil or liquid refrigerant inside the compressor is warmed to warm the bottom of the compressor, but it does not warm enough to the top of the compressor, and at the start of the compressor cylinder The gas refrigerant discharged from the refrigerant is condensed by exchanging heat with the compressor container having a relatively low temperature. The condensed liquid refrigerant was discharged together with oil from the compressor during the refrigeration cycle, and there was a problem that the oil inside the compressor was reduced.

  SUMMARY OF THE INVENTION The present invention solves the above-described conventional problems, and prevents the refrigerant from flowing out to a long pipe or an indoor unit even when a liquid refrigerant containing a large amount of oil is discharged from the compressor, and a bearing caused by a shortage of compressor oil. An object of the present invention is to provide an air conditioner that can avoid burning.

  In order to solve the above-described conventional problems, an air conditioner of the present invention includes an outdoor unit and a plurality of indoor units connected to the outdoor unit, and the outdoor unit includes a compressor, an oil separator, An oil return bypass circuit that returns from the oil separator to the suction pipe via the first electromagnetic on-off valve and the first pressure reducing device, an outdoor heat exchanger, an outdoor blower, an outdoor electric expansion valve, a four-way valve, A discharge superheat degree detection means; and a first supercooling degree detection means for detecting a supercooling degree of the outdoor heat exchanger. The indoor unit includes an indoor heat exchanger, an indoor blower, and an indoor electric expansion valve. And a second supercooling degree detection means for detecting the degree of supercooling of the indoor heat exchanger, and a gas for returning the discharge gas to the suction pipe via the second electromagnetic on-off valve and the second pressure reducing device The bypass circuit is installed below the oil separator and the bypass circuit is installed. In addition to the oil return bypass circuit, the second electromagnetic on-off valve is temporarily opened at the start of operation, etc., and the flow rate of oil and liquid refrigerant returned from the oil separator to the suction pipe is increased. The outflow of the liquid refrigerant containing oil to the outdoor heat exchanger or the like can be prevented, the oil can be efficiently returned to the compressor, and the reliability of the compressor can be improved.

  As described above, the air conditioner of the present invention makes it difficult for oil flowing out together with the liquid refrigerant from the compressor to flow out after the oil separator, and efficiently returns the liquid refrigerant containing oil to the compressor. The amount of oil in the compressor can be secured and the reliability of the compressor can be improved.

Refrigeration cycle diagram of the air-conditioning apparatus according to Embodiment 1 of the present invention The flowchart of the air conditioning apparatus in Embodiment 2 of this invention The flowchart of the air conditioning apparatus in Embodiment 3 of this invention. The flowchart of the air conditioning apparatus in Embodiment 4 of this invention Flowchart of the air-conditioning apparatus in Embodiment 5 of the present invention Flowchart of the air-conditioning apparatus according to Embodiment 6 of the present invention. Flowchart of the air conditioner in Embodiment 7 of the present invention Flow chart of preheating operation processing of control unit in conventional air conditioner

  The first invention is composed of an outdoor unit and a plurality of indoor units connected to the outdoor unit. The outdoor unit includes a compressor, an oil separator, and a first electromagnetic on-off valve from the oil separator. And an oil return bypass circuit that returns to the suction pipe via the first pressure reducing device, an outdoor heat exchanger, an outdoor fan, an outdoor electric expansion valve, a four-way valve, a discharge superheat degree detecting means, and the outdoor heat exchange A first supercooling degree detecting means for detecting a supercooling degree of the cooler, wherein the indoor unit includes an indoor heat exchanger, an indoor blower, an indoor electric expansion valve, and a supercooling degree of the indoor heat exchanger. And a second supercooling degree detecting means for detecting the gas bypass circuit for returning the discharged gas to the suction pipe via the second electromagnetic on-off valve and the second pressure reducing device, and the oil separator. In addition to the oil return bypass circuit. Liquid containing oil to the outdoor heat exchanger after the oil separator, etc. by temporarily opening the second electromagnetic on-off valve such as at the start and increasing the flow rate of oil and liquid refrigerant returning from the oil separator to the suction pipe The refrigerant can be prevented from flowing out, the oil can be efficiently returned to the compressor, and the reliability of the compressor can be improved.

  In the second invention, in particular, at the start of the heating operation of the first invention, the indoor electric expansion valve is closed until the indoor heat exchanger outlet temperature reaches a predetermined supercooled state using the second supercooling degree detecting means. The operation is started with the oil return bypass circuit and the gas bypass circuit opened and the outdoor electric expansion valve closed until the discharge pipe temperature reaches a predetermined overheat state using the discharge superheat degree detection means. As a result, the oil that flows out from the compressor together with the liquid refrigerant is less likely to flow out to the oil separator and later, and the liquid refrigerant containing the oil can be efficiently returned to the compressor, ensuring the amount of oil in the compressor. Thus, the reliability of the compressor can be improved.

  In the air conditioner of the second invention, particularly, the third invention operates the compressor at the maximum frequency at which the suction pressure becomes a predetermined set value at the start of the heating operation, and maximizes the overheating of the compressor. It can be shortened and heating start-up performance can be improved.

  In the fourth aspect of the invention, in particular, when the outdoor electric expansion valve of the second or third aspect of the invention is opened, the indoor electric expansion valve is also opened in advance, so that the compressor 1 can be overheated. The refrigerant can be immediately circulated to the indoor unit, the amount of oil in the compressor can be secured, and the reliability of the compressor can be improved, and the start-up performance of the heating can be improved.

In particular, the fifth invention includes a third electromagnetic on-off valve in parallel with the outdoor electric expansion valve of the first invention, and uses the first supercooling degree detection means at the start of the cooling operation to use the first heat exchanger outlet temperature. Until the third electromagnetic on-off valve and the outdoor electric expansion valve are closed until the predetermined supercooling state is reached, and the discharge pipe temperature becomes a predetermined superheated state using the discharge superheat degree detecting means of the compressor. Operation starts with the return bypass circuit and gas bypass circuit open and all indoor motor expansion valves closed, making it difficult for oil that flows out of the compressor along with the liquid refrigerant to flow after the oil separator. And the liquid refrigerant containing oil can be efficiently returned to the compressor, the amount of oil in the compressor can be secured, and the reliability of the compressor can be improved.

  In the air conditioner of the fifth invention, particularly, the sixth invention operates the compressor at the maximum frequency at which the suction pressure becomes a predetermined set value at the start of the cooling operation, and maximizes the overheating of the compressor. As a result, the cooling start-up performance can be improved.

  The seventh aspect of the invention is to open both the outdoor electric expansion valve and the third electromagnetic opening / closing valve in advance, particularly when the indoor electric expansion valve of the fifth or sixth invention is opened. If the compressor 1 is overheated, the refrigerant can be immediately circulated to the indoor unit, and the start-up performance of the heating can be improved while ensuring the amount of oil in the compressor and improving the reliability of the compressor 1.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the present invention is not limited to the present embodiment.

(Embodiment 1)
FIG. 1 is a refrigeration cycle diagram of the air-conditioning apparatus according to Embodiment 1 of the present invention.

  In FIG. 1, the air conditioner according to the present embodiment includes an outdoor unit 22 and a plurality of indoor units 30 connected to the outdoor unit 22 through connection pipes 35. The outdoor unit 22 includes the compressor 1, The oil separator 2, the oil return bypass circuit 10 that returns from the oil separator 2 to the suction pipe 34 via the first electromagnetic switching valve 8 and the first pressure reducing device 9, the outdoor heat exchanger 3, and the outdoor blower 4 And an outdoor electric expansion valve 5, a four-way valve 6, a discharge superheat degree detection means (not shown) for calculating the discharge superheat degree by the outdoor unit control device 21 using the discharge pressure detection means 15 and the discharge temperature detection means 14. The first supercooling degree detecting means (the outdoor heat exchanger temperature detecting means 17 and the outdoor heat exchanger outlet temperature detecting means 19 is used to calculate the degree of supercooling of the outdoor heat exchanger 3 by the outdoor unit controller 21). (Not shown) and the outdoor electric expansion valve 5 A third solenoid valve 20, the outside air temperature detecting means 18 for detecting the outside air temperature, and the accumulator 7, and a suction pressure detection means 16.

  The indoor unit 30 includes an indoor heat exchanger 23, an indoor blower 24, an indoor electric expansion valve 25, an indoor heat exchanger temperature detection unit 26, and an indoor heat exchanger outlet temperature detection unit 28. Second supercooling degree detecting means (not shown) for calculating the degree of supercooling of the indoor heat exchanger 23 and indoor intake air temperature detecting means 27 are provided.

  In the air conditioner in the present embodiment, the attachment position of the gas bypass circuit 13 that returns the discharge gas to the suction pipe 34 via the second electromagnetic on-off valve 11 and the second pressure reducing device 12 is located below the oil separator 2. In addition to the oil return bypass circuit 10, the second electromagnetic on-off valve 11 is temporarily opened such as at the start of operation to increase the flow rates of oil and liquid refrigerant returned from the oil separator 2 to the suction pipe 34. Can do.

  Thereby, the outflow of the liquid refrigerant containing oil to the outdoor heat exchanger 3, the connecting pipe 35, the indoor unit 30 and the like after the oil separator 2 can be prevented, and the oil can be efficiently returned to the compressor 1. The reliability of the compressor 1 can be improved.

(Embodiment 2)
FIG. 2 is a flowchart for explaining an operation control method for the air-conditioning apparatus according to Embodiment 2 of the present invention. In addition, the same code | symbol is attached | subjected to the same part as the air conditioning apparatus in the said Embodiment 1, and the description is abbreviate | omitted.

  In the figure, the air conditioner according to the present embodiment is provided with the oil return bypass circuit 10 when the heating is started, first, the outdoor electric expansion valve 5 is set to 0 (pls), the entire indoor electric expansion valve 25 is set to 0 (pls). The first electromagnetic on-off valve 8 is turned on, the second electromagnetic on-off valve 11 provided in the gas bypass circuit 13 is turned on, and the compressor 1 is started at a predetermined frequency F1 (Hz).

  Next, the indoor unit controller 29 uses the indoor heat exchanger temperature A1 detected by the indoor heat exchanger temperature detection means 26 and the indoor heat exchanger outlet temperature A2 detected by the indoor heat exchanger outlet temperature detection means 28. The heat exchanger supercooling degree ISC (= A1-A2) is calculated. The calculated ISC is compared with a predetermined set value T1, and if ISC> T1, the indoor electric expansion valve 25 is opened to the predetermined set value A (pls).

  Next, using the discharge temperature detected by the discharge temperature detecting means 14 and the discharge pressure detected by the discharge pressure detecting means 15, the outdoor unit control device 21 calculates the discharge superheat degree DSH. When the calculated DSH is compared with a predetermined set value T2 and DSH> T2, the first electromagnetic on-off valve 8 provided in the oil return bypass circuit 10 is provided with the outdoor electric expansion valve 5 at the predetermined set value B (pls). Is turned OFF, the second electromagnetic on-off valve 11 provided in the gas bypass circuit 13 is turned OFF, the compressor 1 is changed to a predetermined frequency F2 (Hz), and the routine proceeds to heating normal operation.

  Such an operation starting method, that is, when the outdoor electric expansion valve 5 is closed and the indoor electric expansion valve 25 is closed, the operation is started, and when the indoor heat exchanger is subcooled to some extent, the indoor electric expansion valve 25 is turned on. Opening and opening the outdoor electric expansion valve 5 when the degree of discharge superheat is achieved to some extent makes it difficult for oil flowing out of the compressor 1 together with the liquid refrigerant to flow out to the oil separator 2 and beyond, and two bypass circuits Since the compressor 1 can be overheated while efficiently returning the liquid refrigerant containing oil to the compressor 1, the amount of oil in the compressor 1 can be ensured and the reliability of the compressor 1 can be improved.

(Embodiment 3)
FIG. 3 is a flowchart for explaining an operation control method for the air-conditioning apparatus according to Embodiment 3 of the present invention. In addition, the same code | symbol is attached | subjected to the same part as the air conditioning apparatus in the said embodiment, and the description is abbreviate | omitted.

  In FIG. 3, when heating is started, first, the outdoor electric expansion valve 5 is set to 0 (pls), the all-door electric expansion valve 25 is set to 0 (pls), and the first electromagnetic on-off valve 8 provided in the oil return bypass circuit 10 is turned ON. The second electromagnetic on-off valve 11 provided in the gas bypass circuit 13 is turned on, and the compressor 1 is started at a predetermined frequency F1 (Hz).

  Next, the suction pressure Ps detected by the suction pressure detection means 16 is compared with a predetermined setting P1, and the frequency is increased until Ps <P1.

  Next, the indoor unit controller 29 uses the indoor heat exchanger temperature A1 detected by the indoor heat exchanger temperature detecting means 26 and the indoor heat exchanger outlet temperature A2 detected by the indoor heat exchanger outlet temperature detecting means 28 to The heat exchanger supercooling degree ISC (= A1-A2) is calculated. The calculated ISC is compared with a predetermined set value T1, and if ISC> T1, the indoor electric expansion valve 25 is opened to the predetermined set value A (pls).

Next, using the discharge temperature detected by the discharge temperature detecting means 14 and the discharge pressure detected by the discharge pressure detecting means 15, the outdoor unit control device 21 calculates the discharge superheat degree DSH. When the calculated DSH is compared with a predetermined set value T2 and DSH> T2, the first electromagnetic on-off valve 8 provided in the oil return bypass circuit 10 is provided with the outdoor electric expansion valve 5 at the predetermined set value B (pls). Is turned off, the second electromagnetic on-off valve 11 provided in the gas bypass circuit 13 is turned off, and the compressor 1 is turned on at a predetermined frequency F2.
Change to (Hz) and shift to heating normal operation.

  In addition to such an operation start method, that is, the start-up method of the second embodiment, the input of the compressor 1 which is an element for overheating the compressor 1 is maximized, so the amount of oil in the compressor 1 The rise performance of the heating can be improved while ensuring the reliability of the compressor 1 and improving the reliability.

(Embodiment 4)
FIG. 4 is a flowchart for explaining an operation control method for the air-conditioning apparatus according to Embodiment 4 of the present invention. In addition, the same code | symbol is attached | subjected to the same part as the air conditioning apparatus in the said embodiment, and the description is abbreviate | omitted.

  In FIG. 4, when heating is started, the outdoor electric expansion valve 5 is first set to 0 (pls), the all-door electric expansion valve 25 is set to 0 (pls), and the first electromagnetic on-off valve 8 provided in the oil return bypass circuit 10 is turned ON. The second electromagnetic on-off valve 11 provided in the gas bypass circuit 13 is turned on, and the compressor 1 is started at a predetermined frequency F1 (Hz).

  Next, the indoor unit controller 29 uses the indoor heat exchanger temperature A1 detected by the indoor heat exchanger temperature detector 26 and the indoor heat exchanger outlet temperature A2 detected by the indoor heat exchanger outlet temperature detector 28. The indoor heat exchanger supercooling degree ISC (= A1-A2) is calculated.

  Furthermore, using the discharge temperature detected by the discharge temperature detecting means 14 and the discharge pressure detected by the discharge pressure detecting means 15, the outdoor unit control device 21 calculates the discharge superheat degree DSH.

  The calculated DSH is compared with a predetermined set value T1 (step 1), and the calculated ISC is compared with the predetermined set value T2 (step 2) until DSH> T1, and if ISC> T2. Then, the indoor electric expansion valve 25 is opened to a predetermined set value A (pls). Thereafter, DSH is compared with a predetermined set value T1 (step 3), and if DSH> T1, the outdoor electric expansion valve 5 is provided with the predetermined set value B (pls) and the first oil return bypass circuit 10 provided with the oil return bypass circuit 10. The electromagnetic on / off valve 8 is turned off, the second electromagnetic on / off valve 11 provided in the gas bypass circuit 13 is turned off, the compressor 1 is changed to a predetermined frequency F2 (Hz), and the operation is shifted to the normal heating operation.

  Note that DSH is compared with a predetermined set value T1 in Step 1, and if DSH> T1, Steps 2 and 3 are omitted, and the indoor electric expansion valve 25 is set to a predetermined set value A (pls) and outdoor electric expansion. The valve 5 is set to a predetermined set value B (pls), the first electromagnetic on-off valve 8 provided in the oil return bypass circuit 10 is turned off, the second electromagnetic on-off valve 11 provided in the gas bypass circuit 13 is turned off, and the compressor 1 is changed to a predetermined frequency F2 (Hz), and a transition is made to normal heating operation.

  In addition to such an operation start method, that is, the start-up method of the second embodiment, when the degree of discharge superheat is obtained to some extent, the outdoor electric expansion valve 5 and the indoor electric expansion valve are used regardless of the degree of subcooling of the indoor heat exchanger. By opening 25, the refrigerant can be immediately circulated to the indoor unit 30 if the compressor 1 is overheated, and the amount of oil in the compressor 1 is secured and the reliability of the compressor 1 is improved. Start-up performance can be improved.

(Embodiment 5)
FIG. 5 is a flowchart for illustrating an operation control method for the air-conditioning apparatus according to Embodiment 5 of the present invention. In addition, the same code | symbol is attached | subjected to the same part as the air conditioning apparatus in the said embodiment, and the description is abbreviate | omitted.

In FIG. 5, at the time of cooling start, first, the all-door electric expansion valve 25 is set to 0 (pls), the outdoor electric expansion valve 5 is set to 0 (pls), and the third electromagnetic opening / closing valve 20 attached to the outdoor electric expansion valve 5 is turned OFF. The first electromagnetic on-off valve 8 provided in the oil return bypass circuit 10 is turned on, the second electromagnetic on-off valve 11 provided on the gas bypass circuit 13 is turned on, and the compressor 1 is started at a predetermined frequency F1 (Hz). .

  Next, the outdoor unit controller 21 uses the outdoor heat exchanger temperature B1 detected by the outdoor heat exchanger temperature detection means 17 and the outdoor heat exchanger outlet temperature B2 detected by the outdoor heat exchanger outlet temperature detection means 19. An outdoor heat exchanger subcooling degree OSC (= B1-B2) is calculated. When the calculated OSC is compared with a predetermined set value T1, and OSC> T1, the outdoor electric expansion valve 5 is opened to the predetermined set value A (pls), and a third electromagnetic opening / closing function provided to the outdoor electric expansion valve 5 is provided. Turn on the valve 20.

  Next, using the discharge temperature detected by the discharge temperature detection means 14 and the discharge pressure detected by the discharge pressure detection means 15, the outdoor unit control device 21 calculates the discharge superheat degree DSH. When the calculated DSH is compared with a predetermined set value T2 and DSH> T2, the first electromagnetic on-off valve provided in the oil return bypass circuit 10 with the all-chamber electric expansion valve 25 set to the predetermined set value B (pls) 8 is turned OFF, the second electromagnetic on-off valve 11 provided in the gas bypass circuit 13 is turned OFF, the compressor 1 is changed to a predetermined frequency F2 (Hz), and the operation is shifted to the cooling normal operation.

  Such an operation start method, that is, when the outdoor electric expansion valve 5 is closed and the indoor electric expansion valve 25 is closed, the operation is started, and when the outdoor heat exchanger is subcooled to some extent, the outdoor electric expansion valve 5 is turned on. Opening and opening the indoor electric expansion valve 25 when the degree of discharge superheat is achieved to some extent makes it difficult for oil flowing out of the compressor 1 together with the liquid refrigerant to flow out to the oil separator 2 and beyond, and from two bypass circuits. Since the compressor 1 can be overheated while returning the liquid refrigerant containing oil to the compressor 1 efficiently, the amount of oil in the compressor 1 can be secured and the reliability of the compressor 1 can be improved.

(Embodiment 6)
FIG. 6 is a flowchart for illustrating an operation control method for the air-conditioning apparatus according to Embodiment 6 of the present invention. In addition, the same code | symbol is attached | subjected to the same part as the air conditioning apparatus in the said embodiment, and the description is abbreviate | omitted.

  In FIG. 6, at the time of cooling start, first, the all-door electric expansion valve 25 is set to 0 (pls), the outdoor electric expansion valve 5 is set to 0 (pls), and the third electromagnetic opening / closing valve 20 attached to the outdoor electric expansion valve 5 is turned OFF. The first electromagnetic on-off valve 8 provided in the oil return bypass circuit 10 is turned on, the second electromagnetic on-off valve 11 provided on the gas bypass circuit 13 is turned on, and the compressor 1 is started at a predetermined frequency F1 (Hz). .

  Next, the suction pressure Ps detected by the suction pressure detection means 16 is compared with a predetermined setting P1, and the frequency is increased until Ps <P1.

  Next, the outdoor unit controller 21 uses the outdoor heat exchanger temperature B1 detected by the outdoor heat exchanger temperature detection means 17 and the outdoor heat exchanger outlet temperature B2 detected by the outdoor heat exchanger outlet temperature detection means 19. Then, the degree of subcooling of the outdoor heat exchanger OSC (= B1-B2) is calculated. When the calculated OSC is compared with a predetermined set value T1, and OSC> T1, the outdoor electric expansion valve 5 is opened to the predetermined set value A (pls), and a third electromagnetic opening / closing function provided to the outdoor electric expansion valve 5 is provided. Turn on the valve 20.

  Next, using the discharge temperature detected by the discharge temperature detection means 14 and the discharge pressure detected by the discharge pressure detection means 15, the outdoor unit control device 21 calculates the discharge superheat degree DSH. When the calculated DSH is compared with a predetermined set value T2 and DSH> T2, the first electromagnetic on-off valve provided in the oil return bypass circuit 10 with the all-chamber electric expansion valve 25 set to the predetermined set value B (pls) 8 is turned OFF, the second electromagnetic on-off valve 11 provided in the gas bypass circuit 13 is turned OFF, the compressor 1 is changed to a predetermined frequency F2 (Hz), and the operation is shifted to the normal cooling operation.

  In addition to such an operation start method, that is, the start-up method of the fifth embodiment, the input of the compressor 1 which is an element for overheating the compressor 1 is maximized, so the amount of oil in the compressor 1 As well as improving the reliability of the compressor 1, the cooling start-up performance can be improved.

(Embodiment 7)
FIG. 7 is a flowchart for explaining an operation control method for the air-conditioning apparatus according to Embodiment 7 of the present invention. In addition, the same code | symbol is attached | subjected to the same part as the air conditioning apparatus in the said embodiment, and the description is abbreviate | omitted.

  In FIG. 7, at the time of cooling start, first, the all-room electric expansion valve 25 is set to 0 (pls), the outdoor electric expansion valve 5 is set to 0 (pls), and the third electromagnetic opening / closing valve 20 provided to the outdoor electric expansion valve 5 is turned OFF. The first electromagnetic on-off valve 8 provided in the oil return bypass circuit 10 is turned on, the second electromagnetic on-off valve 11 provided on the gas bypass circuit 13 is turned on, and the compressor 1 is started at a predetermined frequency F1 (Hz). .

  Next, the outdoor unit controller 21 uses the outdoor heat exchanger temperature B1 detected by the outdoor heat exchanger temperature detection means 17 and the outdoor heat exchanger outlet temperature B2 detected by the outdoor heat exchanger outlet temperature detection means 19. An outdoor heat exchanger subcooling degree OSC (= B1-B2) is calculated. Furthermore, using the discharge temperature detected by the discharge temperature detecting means 14 and the discharge pressure detected by the discharge pressure detecting means 15, the outdoor unit control device 21 calculates the discharge superheat degree DSH.

  The calculated DSH is compared with a predetermined set value T1 (step 1), and the calculated OSC is compared with the predetermined set value T2 (step 2) until OSH> T2 until DSH> T1. Then, the outdoor electric expansion valve 5 is opened to a predetermined set value A (pls), and the third electromagnetic opening / closing valve 20 provided along with the outdoor electric expansion valve 5 is turned ON.

  Thereafter, DSH is compared with a predetermined set value T1 (step 3), and if DSH> T1, the all-chamber electric expansion valve 25 is provided with a predetermined set value B (pls) and the oil return bypass circuit 10 is provided. 1 is turned off, the second electromagnetic on-off valve 11 provided in the gas bypass circuit 13 is turned off, the compressor 1 is changed to a predetermined frequency F2 (Hz), and the operation is shifted to the normal cooling operation.

  Note that DSH is compared with a predetermined set value T1 in Step 1, and if DSH> T1, Steps 2 and 3 are omitted, and the outdoor electric expansion valve 5 is set to a predetermined set value A (pls) and outdoor electric expansion. The third electromagnetic on-off valve 20 attached to the valve 5 is turned on, the all-chamber electric expansion valve 25 is turned on at a predetermined set value B (pls), and the first electromagnetic on-off valve 8 provided in the oil return bypass circuit 10 is turned off. The second electromagnetic on-off valve 11 provided in the bypass circuit 13 is turned OFF, the compressor 1 is changed to a predetermined frequency F2 (Hz), and the operation is shifted to the normal cooling operation.

  In addition to such an operation start method, that is, the start-up method of the fifth embodiment, the outdoor electric expansion valve 5 and the all-indoor electric expansion valve 25 regardless of the degree of subcooling of the outdoor heat exchanger when the degree of discharge superheat is obtained to some extent. If the compressor 1 is overheated, the refrigerant can be immediately circulated to the indoor unit 30, and the amount of oil in the compressor 1 can be secured and the reliability of the compressor 1 can be improved, Start-up performance can be improved.

The air conditioner of the present invention temporarily opens the second electromagnetic on-off valve, such as at the start of operation, and increases the flow rates of oil and liquid refrigerant returned from the oil separator to the suction pipe to increase the outdoor heat after the oil separator. This system can prevent outflow of liquid refrigerant containing oil to the exchanger, etc., can efficiently return oil to the compressor, and can improve the reliability of the compressor. The present invention is not limited to a device, and can be applied to an outdoor multi-type air conditioner in which a plurality of outdoor units are connected.

DESCRIPTION OF SYMBOLS 1 Compressor 2 Oil separator 3 Outdoor heat exchanger 4 Outdoor blower 5 Outdoor electric expansion valve 6 Four-way valve 7 Accumulator 8 First electromagnetic on-off valve 9 First pressure-reducing device 10 Oil return bypass circuit 11 Second electromagnetic on-off valve 12 Second pressure reducing device 13 Gas bypass circuit 14 Discharge temperature detection means 15 Discharge pressure detection means 16 Suction pressure detection means 17 Outdoor heat exchanger temperature detection means 18 Outdoor air temperature detection means 19 Outdoor heat exchanger outlet temperature detection means 20 Third Electromagnetic on-off valve 21 Outdoor unit control device 22 Outdoor unit 23 Indoor heat exchanger 24 Indoor fan 25 Indoor electric expansion valve 26 Indoor heat exchanger temperature detection means 27 Indoor intake air temperature detection means 28 Indoor heat exchanger outlet temperature detection means 29 Indoor unit control device 30 Indoor unit 34 Suction pipe 35 Connection pipe

Claims (7)

The outdoor unit includes an outdoor unit and a plurality of indoor units connected to the outdoor unit. The outdoor unit includes a compressor, an oil separator, a first electromagnetic on-off valve from the oil separator, and a first pressure reducing device. An oil return bypass circuit that returns to the suction pipe via the outdoor heat exchanger, an outdoor fan, an outdoor electric expansion valve, a four-way valve, a discharge superheat degree detection means, and a degree of supercooling of the outdoor heat exchanger. A first subcooling degree detecting means for detecting, and the indoor unit detects a subcooling degree of the indoor heat exchanger, the indoor blower, the indoor electric expansion valve, and the indoor heat exchanger. A supercooling degree detecting means, and a gas bypass circuit for returning the discharge gas to the suction pipe via a second electromagnetic on-off valve and a second pressure reducing device is located below the oil separator, and Air conditioning characterized by an oil return bypass circuit Location. At the start of heating operation, the second supercooling degree detecting means is used to close the indoor electric expansion valve until the indoor heat exchanger outlet temperature reaches a predetermined supercooling state, and the discharge superheat degree detecting means is used to discharge the pipe temperature. 2. The air conditioner according to claim 1, wherein the operation is started with the oil return bypass circuit and the gas bypass circuit in an open state and the outdoor electric expansion valve in a closed state until a predetermined overheat state is reached. The air conditioner according to claim 2, wherein the compressor is operated at a maximum frequency at which the suction pressure becomes a predetermined set value at the start of the heating operation. The air conditioner according to claim 2 or 3, wherein when the outdoor electric expansion valve is in a condition to be opened, the indoor electric expansion valve is also opened in advance. A third electromagnetic on-off valve is provided in parallel with the outdoor electric expansion valve. When the cooling operation is started, the third supercooling degree detection means is used until the outdoor heat exchanger outlet temperature reaches a predetermined supercooling state. Close the electromagnetic on-off valve and outdoor electric expansion valve, and open the oil return bypass circuit and gas bypass circuit until the discharge pipe temperature reaches the predetermined overheat state using the discharge superheat degree detection means of the compressor, and all The air conditioner according to claim 1, wherein the operation is started with the indoor electric expansion valve of the engine closed. 6. The air conditioner according to claim 5, wherein at the start of the cooling operation, the compressor is operated at a maximum frequency at which the suction pressure becomes a predetermined set value. The air conditioner according to claim 5 or 6, wherein both the outdoor electric expansion valve and the third electromagnetic on-off valve are opened in advance when the indoor electric expansion valve is opened.