JP3467837B2 - Air conditioner - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-room type air conditioner having a plurality of indoor units with respect to one outdoor unit.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 6, a plurality of indoor units 200 are provided for one outdoor unit 100.
There is known a multi-room type air conditioner in which are branched and connected in parallel. In this multi-room air conditioner, the indoor heat exchanger 21 of the indoor unit 200 is switched by switching the circulation direction of the refrigerant discharged from the refrigerant compressor 110 with the four-way valve 120.
A cooling operation in which 0 is used as a refrigerant evaporator and a heating operation in which 0 is used as a refrigerant condenser can be performed.

However, in this air conditioner, the following problems occur when there is an indoor unit 200 whose operation is stopped. For example, considering the case where the operation of one indoor unit 200 is stopped, during the heating operation, the indoor heat exchanger 210 communicates with the refrigerant discharge side of the refrigerant compressor 110 via the gas side pipe 300 and the four-way valve 120. Therefore, the high-pressure gas refrigerant discharged from the refrigerant compressor 110 is condensed and accumulated in the stopped indoor heat exchanger 210, and
Refrigerating machine oil contained in the refrigerant also stays together with the refrigerant.

During cooling operation, the liquid-side pipe 400 is closed by closing the electromagnetic on-off valve 220 provided in the liquid-side pipe 400.
Refrigerating machine oil melts and stays in the liquid refrigerant inside. When the liquid refrigerant enters the indoor heat exchanger 210 due to the leakage of the electromagnetic opening / closing valve 220, the indoor heat exchanger 210 is connected to the gas side pipe 3
00 and the four-way valve 120 communicate with the refrigerant suction side of the refrigerant compressor 110, the refrigerant is sucked into the refrigerant compressor 110 as it is, but the flow velocity of the refrigerant due to the leakage of the electromagnetic opening / closing valve 220 is very small. Therefore, the refrigerating machine oil having a large viscosity adheres to the inner wall of the pipe of the indoor heat exchanger 210 and is retained therein without being sucked by the refrigerant compressor 110.

Gas shortage operation due to such refrigerant retention,
In order to eliminate insufficient lubrication of the refrigerant compressor due to retention of refrigerating machine oil, in JP-A-5-77945, an electric valve that acts as an expansion mechanism during cooling operation is provided, and the stop time of the indoor unit has passed a certain time. At times, there is disclosed a technique of opening the motor-operated valve for a predetermined time.

[0006]

However, according to the prior art disclosed in the above publication, depending on the length of the refrigerant pipe, the operating condition of the air conditioner, and the like, the hourly refrigeration to the indoor heat exchanger being stopped Machine oil retention changes. Further, in the multi-room air conditioner as described above, it is customary to install an oil separator in the refrigeration cycle, and the separation performance of this oil separator depends on the load conditions or the initial oil storage amount in the oil separator. The amount of oil accumulated per unit time in the stopped indoor heat exchanger varies greatly depending on the difference.

For this reason, for safety, it is necessary to open the motor-operated valve in a short cycle time and lengthen the valve-opening time. Therefore, when the motor-operated valve is opened, the refrigerant flows into the indoor heat exchanger that is stopped. As a result, there is a problem that the capacity of the indoor heat exchanger during operation is greatly reduced, and the balance of the refrigeration cycle is frequently lost due to opening and closing of the motor-operated valve, resulting in deterioration of air conditioning feeling. The present invention has been made based on the above circumstances, and an object thereof is to suppress a decrease in the capacity of an indoor heat exchanger during operation and to reduce an imbalance of a refrigeration cycle to improve an air conditioning feeling. The purpose is to provide an air conditioner that can

[0008]

In order to achieve the above object, the present invention comprises the following technical means. In Claim 1, while having a plurality of indoor heat exchangers that are branched and connected in parallel to one or a plurality of refrigerant compressors, each of which is interposed in each refrigerant pipe leading to each of the indoor heat exchangers. , A refrigeration cycle provided with a plurality of opening / closing means for opening the refrigerant pipe in the open state and closing the refrigerant pipe in the closed state, and being interposed on the refrigerant discharge side of the refrigerant compressor in the refrigeration cycle, the refrigerant Refrigerating machine oil contained in the refrigerant discharged from the compressor is separated from the refrigerant, and an oil recirculation unit that recirculates to the refrigerant compressor, and an oil that detects the amount of refrigerating machine oil that recirculates to the refrigerant compressor by this oil recirculation unit. Amount detection means, comparison determination means for comparing the detection value of this oil amount detection means with a set value, and during operation of the refrigerant compressor,
The closed state determination means for determining whether there is the closed state opening / closing means among the plurality of opening / closing means, and the comparison in the case where the closed state determination means determines that there is the closed state opening / closing means When the determination unit determines that the detection value of the oil amount detection unit is less than or equal to the set value, the control unit performs an opening control for opening at least one of the opening / closing units in the closed state. .

Further, the control means, after executing the opening control, when the comparison determination means determines that the detection value of the oil amount detection means is larger than the set value, the opening state is determined by the opening control. The closing control is performed so that the opening / closing means is closed again.

The oil recirculation means separates the refrigerant and the refrigerating machine oil and stores the separated refrigerating machine oil, and one end is opened into the oil separator and the other end is the refrigerant compressor. And an oil recirculation pipe connected to the refrigerant suction port, and the oil amount detecting means has an oil temperature detecting means for detecting the temperature of the refrigerating machine oil flowing through the oil recirculating pipe. The amount of refrigerating machine oil flowing back from the oil separator to the refrigerant compressor is detected based on the detected value.

The oil reflux pipe has one end of the oil separator so that the gas refrigerant flows out of the oil separator together with the refrigerating machine oil when the refrigerating machine oil stored in the oil separator decreases by a predetermined amount. It is characterized by opening at a predetermined height position from the bottom surface.

The oil amount detecting means has a liquid level detecting means for detecting the liquid level of the refrigerating machine oil stored in the oil separator, and the oil separator detects the liquid level based on the detection value of the liquid level detecting means. It is characterized in that the amount of refrigerating machine oil flowing back to the refrigerant compressor is detected.

The indoor heat exchanger is a cooling heat exchanger for cooling air passing therethrough by heat exchange with a low-temperature low-pressure refrigerant flowing inside. Further, the indoor heat exchanger is a heating heat exchanger that heats air passing therethrough by heat exchange with a high-temperature and high-pressure refrigerant flowing inside.

The refrigeration cycle has a circulation direction switching means for switching the circulation direction of the refrigerant discharged from the refrigerant compressor in response to switching between the cooling operation and the heating operation, and the indoor heat exchanger is the cooling apparatus. A low-temperature low-pressure refrigerant is supplied during operation, and functions as a cooling heat exchanger that cools passing air by heat exchange with the low-temperature low-pressure refrigerant.
A high-temperature and high-pressure refrigerant is supplied during the heating operation, and it functions as a heating heat exchanger that heats passing air by heat exchange with the high-temperature and high-pressure refrigerant.

The opening / closing means is installed upstream of the indoor heat exchanger in the flow direction of the refrigerant. Further, the opening / closing means has a flow rate adjusting function for adjusting the flow rate of the refrigerant passing therethrough according to the valve opening degree, and by this flow rate adjusting function, the refrigerant supplied to the indoor heat exchanger during the cooling operation is decompressed and expanded. Is characterized by.

[0016]

According to the air conditioner of the present invention having the above-described structure, when it is determined that there is the opening / closing means in the closed state (the state in which the refrigerant pipe is closed) during the operation of the refrigerant compressor,
If the amount of refrigerating machine oil flowing back to the refrigerant compressor is less than the set value, it is judged that the refrigerating machine oil is staying in the cycle (especially in the indoor heat exchanger that is stopped), and the closed opening / closing means is opened. State. As a result, the refrigerant also flows through the stopped indoor heat exchanger, so that the refrigerating machine oil accumulated in the cycle can be returned to the refrigerant compressor. At this time, when there are two or more closed opening / closing means, all of the closed opening / closing means may be open, but at least one opening / closing means may be open.

Further, when the amount of the refrigerating machine oil flowing back to the refrigerant compressor increases and the detected value of the oil amount detecting means becomes larger than the set value after the closed opening / closing means is opened, the cycle When it is determined that the amount of refrigerating machine oil that remains is small or that it does not stay, the opening / closing means that has been opened is closed again.

As described above, according to the present invention, the opening / closing control of the opening / closing means is performed based on the amount of the refrigerating machine oil flowing back to the refrigerant compressor, so that the opening / closing means corresponding to the stopped indoor heat exchanger is required ( (When it is determined that the refrigerator oil is accumulated)
Can only be opened. Therefore, as compared with the conventional case where the motor-operated valve is uniformly opened when the stop time elapses for a fixed time, the frequency of opening the opening / closing means is reduced. As a result, it is possible to reduce the unbalance of the refrigeration cycle caused by the opening / closing means corresponding to the indoor heat exchanger being stopped being opened, so that the air conditioning feeling can be improved.

Further, when the detected value of the oil amount detecting means becomes larger than the set value as the amount of refrigerating machine oil flowing back to the refrigerant compressor increases, the opening / closing means is closed again to open the opening / closing means. It is possible to keep the open time to the minimum necessary. Therefore, it is possible to suppress the degree of decrease in the capacity of the operating indoor heat exchanger caused by the flow of the refrigerant to the indoor heat exchanger that is stopped.

The air conditioner of the present invention includes a cooling cycle in which the indoor heat exchanger is used as a cooling heat exchanger, a heating cycle in which the indoor heat exchanger is used as a heating heat exchanger, or a refrigerant compressor. By changing the circulation direction of the discharged refrigerant, it is used as a heat pump cycle that uses the indoor heat exchanger as a cooling heat exchanger during cooling operation and uses the indoor heat exchanger as a heating heat exchanger during heating operation. can do.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the air conditioner of the present invention will be described with reference to FIGS. FIG. 1 is an overall schematic diagram of an air conditioner. The air conditioner 1 of the present embodiment includes an outdoor unit 2 and an indoor unit 3 that form a refrigeration cycle, and a plurality of (two in the present embodiment) indoor units 3 are provided for one outdoor unit 2. is set up.

The outdoor unit 2 includes a refrigerant compressor 4, an oil recirculation means (which will be described later), a four-way valve 5, an outdoor heat exchanger 6, an outdoor throttle 7, an accumulator 8, and a refrigerant pipe (gas) for connecting these parts. It is composed of a side pipe 9 and a liquid side pipe 10). The indoor unit 3 is the indoor heat exchanger 1
1, indoor throttle 12, first solenoid valve 13 (opening / closing means of the present invention), second solenoid valve 14 (opening / closing means of the present invention), first check valve 15, second check valve 16, and each of these It is composed of a refrigerant pipe (gas side pipe 17 and liquid side pipe 18: both are refrigerant pipes of the present invention) for connecting components.

The refrigerant compressor 4 is rotationally driven by an external drive source (not shown) to compress and discharge the sucked gas refrigerant. The oil recirculation means separates refrigerating machine oil contained in the refrigerant discharged from the refrigerant compressor 4 from the refrigerant and recirculates it to the refrigerant compressor 4. The structure and operation of this oil recirculation means will be described later.

The four-way valve 5 is interposed in the gas side pipe 9,
The circulation direction of the refrigerant discharged from the refrigerant compressor 4 is switched according to the operation mode (cooling mode, heating mode). In FIG. 1, the flow of the refrigerant during the cooling operation is indicated by a solid arrow C, and the flow of the refrigerant during the heating operation is indicated by a broken arrow H. The outdoor heat exchanger 6 exchanges heat between the outdoor air and the refrigerant by receiving the air blown from the outdoor fan 19 arranged in front of the outdoor heat exchanger 6, and functions as a refrigerant condenser during the cooling operation to perform the heating operation. Sometimes it functions as a refrigerant evaporator.

The outdoor throttle 7 is provided in the liquid side pipe 10 and expands the refrigerant flowing out of the outdoor heat exchanger 6 during the cooling operation and the refrigerant flowing into the outdoor heat exchanger 6 during the heating operation under reduced pressure. In this embodiment, a capillary tube is used. The accumulator 8 is interposed in the gas side pipe 9 on the refrigerant intake side of the refrigerant compressor 4, stores the liquid refrigerant by separating the refrigerant flowing back to the refrigerant compressor 4 into a liquid refrigerant, and stores only the gas phase refrigerant in the refrigerant compressor. It sends it to 4.

The indoor heat exchanger 11 exchanges heat between the refrigerant flowing inside and the air blown from the indoor fan 20, and functions as a refrigerant evaporator during cooling operation and as a refrigerant condenser during heating operation. To do. Indoor diaphragm 12
Is provided in the liquid side pipe 18 for decompressing and expanding the refrigerant flowing into the indoor heat exchanger 11 during the cooling operation and the refrigerant flowing out of the indoor heat exchanger 11 during the heating operation. In the present embodiment, Use a tube.

The first solenoid valve 13 is interposed in the liquid side pipe 18 and is opened (ON) by receiving energization (open state in the present invention) to open the liquid side pipe 18 and stop energization. (OFF) to close the valve (closed state in the present invention) to close the liquid side pipe 18. An indoor throttle 12 is provided between the first electromagnetic valve 13 and the indoor heat exchanger 11. The second solenoid valve 14 is interposed in the gas side pipe 17, and opens the gas side pipe 17 by being energized and opening by being energized in the same manner as the first solenoid valve 13, and the energization is stopped and closed. Then, the gas side pipe 17 is closed. In addition, the first solenoid valve 13 and the second
Each solenoid valve 14 is energized and controlled by the control device 21 (see FIG. 3).

The first check valve 15 is arranged in the first bypass 22 that bypasses the first electromagnetic valve 13, and discharges the refrigerant that has flowed out of the indoor heat exchanger 11 and is decompressed by the indoor throttle 12 during the heating operation. It can be passed (the direction of flow of the refrigerant is indicated by an arrow). The second check valve 16 is arranged in the second bypass 23 that bypasses the second electromagnetic valve 14, and the indoor heat exchanger 1 during the cooling operation.
It is possible to pass the refrigerant flowing out of 1 (the direction of the refrigerant flow is indicated by an arrow).

Each indoor unit 3 is branched and connected in parallel to the outdoor unit 2 by a liquid side communication pipe 24 and a gas side communication pipe 25.

As shown in FIG. 2, the oil recirculation means described above includes an oil separator 26 interposed in a gas side pipe 9 connected to the refrigerant discharge side of the refrigerant compressor 4, the oil separator 26 and the refrigerant. It is composed of two oil return pipes (a first oil return pipe 27 and a second oil return pipe 28) which communicate with a gas side pipe 9 connected to the refrigerant suction side of the compressor 4.

The oil separator 26 comprises a separation chamber 26a for centrifuging the refrigerant and the refrigerating machine oil, and a storage chamber 26b for storing the refrigerating machine oil separated in the separation chamber 26a. The separation chamber 26a is provided with an inlet 26c into which the gas refrigerant discharged from the refrigerant compressor 4 flows, and an outlet 26d from which the gas refrigerant obtained by separating the refrigerating machine oil in the separation chamber 26a flows out. The storage chamber 26b is located below the separation chamber 26a, and the refrigerating machine oil separated from the gas refrigerant in the separation chamber 26a falls by its own weight and is stored.

The first oil return pipe 27 has one end opened to the bottom surface of the oil separator 26 and the other end connected to the gas side pipe 9. One end of the second oil return pipe 28 is opened to the side surface of the oil separator 26 higher than the opening position of the first oil return pipe 27, and the other end is connected to the gas side pipe 9.

The first oil return pipe 27 and the second oil return pipe 28 are connected to the refrigerant compressor 4 from the oil separator 26.
To return the optimum amount of refrigerating machine oil to
a and 28a are provided. However, the resistance of each of the first oil return pipes 27 is smaller than that of the second oil return pipes 28 (that is, the first oil return pipes 27 are easier to flow than the second oil return pipes 28). 27
a and 28a are set.

The opening diameter of the second oil return pipe 28 opening on the side surface of the oil separator 26 is set larger than the opening diameter of the first oil return pipe 27 opening on the bottom surface of the oil separator 26. is there. The opening position (height H from the bottom surface of the oil separator 26) and the opening diameter of the second oil return pipe 28 are determined by the load condition that the air conditioner 1 can use and the size of the air conditioner 1. Has been done.

Further, the first oil return pipe 27 and the second oil return pipe 27
In the oil return pipe 28, as the oil amount detecting means of the present invention,
Temperature sensor 2 for detecting the temperature of the refrigerating machine oil flowing through the first oil return pipe 27 and the second oil return pipe 28, respectively.
9 and 30 are provided.

The control device 21 has a microcomputer (not shown) built therein, and the four-way valve 5, the outdoor fan 19, and the outdoor fan 19, so that a desired air-conditioning condition set by the operation panel 31 (see FIG. 3) can be obtained. Indoor fan 20, first
While controlling the energization of the solenoid valve 13 and the second solenoid valve 14, one of them is operated (at least 1 if three or more are used).
When the operation of the indoor unit 3 of the stand is stopped, refrigerating machine oil retention control (to be described later) for preventing the refrigerating machine oil from staying in the cycle is executed. Note that stopping the operation of the indoor unit 3 means stopping the operation of the indoor fan 20 and controlling the energization of the first solenoid valve 13 or the second solenoid valve 14 so that the refrigerant does not flow to the indoor heat exchanger 11. It is to do.

Next, the operation of this embodiment will be described. A) Cooling mode In the cooling mode, the refrigerant discharged from the refrigerant compressor 4 is
The oil separator 26 is guided to the four-way valve 5 and the outdoor heat exchanger 6, and the outdoor heat exchanger 6 blows air from the outdoor fan 19 to condense and liquefy it. After that, the outdoor heat exchanger 6 → the outdoor throttle 7 → the first solenoid valve 13 (at this time, the first solenoid valve 13: ON) →
The indoor throttle 12 is sent to the indoor heat exchanger 11. In this indoor heat exchanger 11, the low-temperature low-pressure refrigerant that has been decompressed and expanded in the outdoor throttle 7 and the indoor throttle 12 evaporates by heat exchange with the air blown by the indoor fan 20, and the air that passes through the indoor heat exchanger 11 To cool. After that, the indoor heat exchanger 11 → the second check valve 16 (at this time, the second solenoid valve 14: OF
F) → The four-way valve 5 → The accumulator 8 flows in this order, and the refrigerant is again sucked into the refrigerant compressor 4.

(B) Heating mode In the heating mode, the refrigerant discharged from the refrigerant compressor 4 is
The oil separator 26 → the four-way valve 5 → the second solenoid valve 14 (the second solenoid valve 14: ON at this time) → is guided to the indoor heat exchanger 11, and the indoor heat exchanger 11 blows air from the indoor fan 20. The condensed air is condensed and liquefied to heat the air passing through the indoor heat exchanger 11. Then, the heat is sent to the indoor heat exchanger 11 → the indoor throttle 12 → the first check valve 15 (the first electromagnetic valve 13: OFF at this time) → the outdoor throttle 7 → the outdoor heat exchanger 6. In the outdoor heat exchanger 6, the low-temperature low-pressure refrigerant that has been decompressed and expanded by the indoor throttle 12 and the outdoor throttle 7 evaporates by heat exchange with the air (outside air) blown by the outdoor fan 19. After that, it flows in the order of the outdoor heat exchanger 6-> the four-way valve 5-> the accumulator 8 and is again sucked into the refrigerant compressor 4.

In the above operation, the refrigerating machine oil contained in the gas refrigerant discharged from the refrigerant compressor 4 is separated from the gas refrigerant in the oil separator 26, but is not completely separated and a small amount of refrigeration is used. The machine oil circulates in the refrigeration cycle together with the gas refrigerant and returns to the refrigerant compressor 4 again. Therefore, when the operation of one of the indoor units 3 is stopped, the refrigerating machine oil accumulates in the stopped indoor unit 3 and the refrigerating machine oil runs short.

Therefore, in this embodiment, when the operation of any one of the indoor units 3 is stopped, the control device 21 performs the following refrigerating machine oil retention control. This refrigerating machine oil retention control will be described based on the flowchart shown in FIG.

First, the closed state determination means of the control device 21 determines whether or not the operation of one of the indoor units 3 is stopped (step S1). This determination can be made by the operation signal output from the operation panel 31, but may be made by the energized state of the indoor fan 20, or when the cooling operation is performed, the first electromagnetic valve 13 and the heating operation are performed. If so, the determination may be made based on the energized state of the second solenoid valve 14.
That is, it can be determined that the operation of the indoor unit 3 is stopped when the indoor fan 20 is OFF, the first electromagnetic valve 13 is OFF during the cooling operation, and the second electromagnetic valve 14 is OFF during the heating operation. it can.

When the result of this determination is NO, that is, when the two indoor units 3 are both operating, there is no need to execute the refrigerating machine oil retention control, so the processing is stopped. When the determination result of step S1 is YES, that is, when the operation of one of the indoor units 3 is stopped,
The comparison and determination means of the control device 21 determines whether or not the difference (Ta-Tb) between the detection values of the temperature sensor 29 and the temperature sensor 30 is larger than the set value T1 (step S2).

Here, as the refrigerating machine oil accumulates in the indoor unit 3 that has stopped operation, the amount of refrigerating machine oil stored in the storage chamber 26b of the oil separator 26 gradually decreases.
The freezer oil level (position A in FIG. 2) of the storage chamber 26b is the upper end position of the opening of the second oil return pipe 28 (position B in FIG. 2).
When it goes down, the gas refrigerant is mixed in the refrigerating machine oil flowing out from the second oil reflux pipe 28. On the other hand, only the refrigerating machine oil flows out into the first oil return pipe 27 that opens at the bottom surface of the oil separator 26.

Since the gas refrigerant mixedly flowing in the refrigerating machine oil is decompressed by the resistance 28a provided in the second oil reflux pipe 28 and its temperature is lowered, it is installed in the first oil reflux pipe 27 through which only the refrigerating machine oil flows out. The detected value Tb of the temperature sensor 30 installed in the second oil recirculation pipe 28 becomes lower than the detected value Ta of the temperature sensor 29 thus set. Furthermore, as the refrigerating machine oil level decreases from B → C → D, the proportion of the gas refrigerant mixed in the second oil return pipe 28 increases, so that the detected value Tb of the temperature sensor 30 as shown in FIG. Gradually decreases, and the difference from the detection value Ta of the temperature sensor 29 increases. After that, when the refrigerating machine oil level in the storage chamber 26b drops below the opening lower end position (position D in FIG. 2) of the second oil reflux pipe 28, the detected value Tb of the temperature sensor 30 is changed to the second oil reflux pipe 2
It becomes constant at the temperature of the gas refrigerant flowing through 8.

Therefore, the temperature sensor 29 and the temperature sensor 3
When the difference between the detected values of 0 (Ta-Tb) is greater than or equal to the set value T1, it can be determined that the gas refrigerant is mixed with the refrigerating machine oil and flows out from the second oil reflux pipe 28. Therefore, if the determination result in step S2 is YES, the first solenoid valve 13 (during cooling operation) or the second solenoid valve 14 (in the cooling operation) of the indoor unit 3 that has stopped the operation in the process of step S3 (open control of the present invention). By temporarily turning on (during heating operation), the refrigerant can be caused to flow through the indoor heat exchanger 11 of the indoor unit 3 that is not in operation, and the refrigerating machine oil that has stagnated can be returned to the refrigerant compressor 4 together with the refrigerant. Note that step S
If the determination result of 2 is NO, step S2 is repeated until the determination result becomes YES.

Then, after executing step S3, the difference between the detected value Ta of the temperature sensor 29 and the detected value Tb of the temperature sensor 30 is set by the comparison / determination means T2 (however, T1>
It is determined whether it is smaller than T2) (step S4).
When this determination result is YES, that is, Ta-Tb <T2
In the case of, the refrigerating machine oil staying in the indoor unit 3 which is not operating recirculates with the opening of the first solenoid valve 13 or the second solenoid valve 14, and the refrigerating machine oil level in the oil separator 26 is changed. You can judge that it is rising.

Therefore, the first solenoid valve 13 that has been turned on once
(During the cooling operation) or the second solenoid valve 14 (during the heating operation) is turned off (step S5, the closing control of the present invention), and the normal operation mode is restored. In addition, when the determination result of step S4 is NO, it returns to step S3 and the open state of the 1st solenoid valve 13 or the 2nd solenoid valve 14 is maintained until the determination result of step S4 becomes YES.

As described above, in this embodiment, the first electromagnetic valve 13 (during cooling operation) or the second electromagnetic valve 13 is operated only when the shortage of the refrigerating machine oil flowing back to the refrigerant compressor 4 from the oil separator 26 is detected.
Since the opening / closing control of the solenoid valve 14 (during the heating operation) can be performed, the frequency of opening the first solenoid valve 13 or the second solenoid valve 14 decreases. As a result, the refrigeration cycle balance is not frequently collapsed when the first solenoid valve 13 or the second solenoid valve 14 is opened, so that the air conditioning feeling is improved.

In this embodiment, the load condition, the pipe length,
Regardless of the number of indoor units 3, differences in the operating state of the air conditioner 1, and variations in the leakage of the first solenoid valve 13 and the second solenoid valve 14, a shortage of refrigerating machine oil in the refrigerant compressor 4 is stable and Can be prevented.

[Modification] In this embodiment, the oil separator 2 is used.
Although the amount of refrigerating machine oil flowing back to the refrigerant compressor 4 from 6 is determined based on the detection values of the two temperature sensors 29 and 30, a liquid for detecting the liquid level of the refrigerating machine oil stored in the oil separator 26. It is also possible to provide the surface detection means and judge whether the refrigerator oil amount is insufficient based on the detection value of the liquid level detection means.

In this embodiment, the heat pump type refrigeration cycle in which the circulation direction of the refrigerant discharged from the refrigerant compressor 4 is switched by the four-way valve 5 in accordance with the operation mode has been described. It can also be applied to a cooling cycle in which the heat exchanger 11 is used as a heat exchanger for cooling (refrigerant evaporator) or a heating cycle in which the indoor heat exchanger 11 is used as a heat exchanger for heating (refrigerant condenser).

In this embodiment, the outdoor diaphragm 7 and the indoor diaphragm 12 are arranged.
Although the two pressure reducing means are provided, the outdoor throttle 7 and the indoor throttle 1 are provided by providing the first solenoid valve 13 with the pressure reducing and expanding function.
2 can be abolished. That is, the first solenoid valve 13
Has a structure in which the flow rate of the refrigerant passing therethrough can be adjusted according to the valve opening degree, and the flow rate adjusting function decompresses and expands the refrigerant supplied to the indoor heat exchanger 11 during the cooling operation.

In this embodiment, the case where two indoor units 3 are installed is illustrated, but when three or more indoor units 3 are installed, even if there are two or more indoor units 3 that have stopped operation, at least one indoor unit 3 is installed. The refrigerating machine oil retention control can be executed for the unit 3. Of course, it is needless to say that the lack of refrigerating machine oil can be eliminated early by executing the refrigerating machine oil retention control for all the indoor units 3 that have stopped operation.

[Brief description of drawings]

FIG. 1 is an overall schematic diagram of an air conditioner.

FIG. 2 is a schematic diagram of an oil return means.

FIG. 3 is a block diagram relating to a control system of this embodiment.

FIG. 4 is a flowchart showing the operation of this embodiment.

FIG. 5 is a graph showing the relationship between the position of the oil level of the refrigerator in the oil separator and the sensor temperature.

FIG. 6 is a schematic diagram of an air conditioner according to a conventional technique.

[Explanation of symbols] 1 Air conditioner 4 Refrigerant compressor 5 4-way valve (circulation direction switching means) 11 Indoor heat exchanger 13 1st solenoid valve (opening / closing means) 14 Second solenoid valve (opening / closing means) 17 Gas side piping (refrigerant piping) 18 Liquid side piping (refrigerant piping) 21 Control device (control means) 26 Oil separator (oil recirculation means) 27 1st oil return pipe (oil return means) 28 Second oil return pipe (oil return means) 29 Temperature sensor (oil amount detection means) 30 Temperature sensor (oil amount detection means)

─────────────────────────────────────────────────── ─── Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) F25B 1/00 387 F25B 13/00 104 F25B 43/02

Claims (10)

(57) [Claims] 1. An a) having a plurality of indoor heat exchangers that are branched and connected in parallel to one or a plurality of refrigerant compressors, and interposed in each refrigerant pipe leading to each of the indoor heat exchangers. A refrigeration cycle having a plurality of opening / closing means for opening the refrigerant pipe in the open state and closing the refrigerant pipe in the closed state; and b) interposing on the refrigerant discharge side of the refrigerant compressor in the refrigeration cycle. An oil recirculation means for separating refrigerating machine oil contained in the refrigerant discharged from the refrigerant compressor from the refrigerant and returning it to the refrigerant compressor; and c) refrigeration for returning to the refrigerant compressor by the oil recirculation means. An oil amount detecting means for detecting the amount of machine oil; d) a comparing and judging means for comparing the detected value of the oil amount detecting means with a set value; and e) closing the plurality of opening / closing means when the refrigerant compressor is in operation. State of the A closed state judging means for judging whether or not there is an opening / closing means, and f) in the case where the closed state judging means judges that there is the opening / closing means in the closed state, the comparison judging means judges whether the oil amount detecting means An air conditioner comprising: a control unit that performs open control to open at least one of the opening / closing units in the closed state when it is determined that the detected value is equal to or less than the set value. 2. The control means, after executing the opening control, if the comparison determination means determines that the detection value of the oil amount detection means is larger than the set value, the open state is determined by the opening control. The air conditioner according to claim 1, wherein the closing control is performed to close the opened and closed means again. 3. The oil recirculation means separates the refrigerant and the refrigerating machine oil and stores the separated refrigerating machine oil, and one end is opened in the oil separator and the other end is the refrigerant. An oil recirculation pipe connected to the refrigerant suction port of the compressor, and the oil amount detection means has an oil temperature detection means for detecting the temperature of the refrigerating machine oil flowing through the oil recirculation pipe. The air conditioner according to claim 1 or 2, wherein the amount of refrigerating machine oil flowing back to the refrigerant compressor from the oil separator is detected based on the detection value of the means. 4. The oil separation pipe has one end for separating the oil so that a gas refrigerant flows out from the oil separator together with the refrigerating machine oil when the refrigerating machine oil stored in the oil separator decreases by a predetermined amount. The air conditioner according to claim 3, wherein the air conditioner is opened at a predetermined height position from the bottom surface of the vessel. 5. The oil amount detecting means has a liquid level detecting means for detecting the liquid level of the refrigerating machine oil stored in the oil separator, and the oil separating means is based on the detection value of the liquid level detecting means. The air conditioner according to claim 3 or 4, wherein an amount of refrigerating machine oil flowing back to the refrigerant compressor from a refrigerator is detected. 6. The indoor heat exchanger is a cooling heat exchanger for cooling air passing therethrough by heat exchange with a low-temperature low-pressure refrigerant flowing inside. The air conditioner according to 1. 7. The indoor heat exchanger is a heating heat exchanger for heating air passing therethrough by heat exchange with a high-temperature and high-pressure refrigerant flowing inside. The air conditioner according to 1. 8. The refrigeration cycle has a circulation direction switching means for switching the circulation direction of the refrigerant discharged from the refrigerant compressor according to switching between cooling operation and heating operation, and the indoor heat exchanger comprises: A low-temperature low-pressure refrigerant is supplied during the cooling operation, and functions as a cooling heat exchanger that cools passing air by heat exchange with the low-temperature low-pressure refrigerant, and a high-temperature high-pressure refrigerant is supplied during the heating operation. Has been
The air conditioner according to any one of claims 1 to 5, which functions as a heating heat exchanger that heats passing air by heat exchange with the high-temperature and high-pressure refrigerant. 9. The air conditioner according to claim 1, wherein the opening / closing means is installed upstream of the indoor heat exchanger in the flow direction of the refrigerant. 10. The opening / closing means has a flow rate adjusting function for adjusting the flow rate of the refrigerant passing therethrough according to the valve opening degree, and the flow rate adjusting function reduces the pressure of the refrigerant supplied to the indoor heat exchanger during cooling operation. The air conditioner according to claim 6 or 8, wherein the air conditioner expands.