WO2019093210A1

WO2019093210A1 - Refrigerating and air-conditioning apparatus

Info

Publication number: WO2019093210A1
Application number: PCT/JP2018/040568
Authority: WO
Inventors: 貴裕仲田; 伊藤　裕; 誠司岡; 智春芦澤; 幸正矢野
Original assignee: ダイキン工業株式会社
Priority date: 2017-11-09
Filing date: 2018-10-31
Publication date: 2019-05-16
Also published as: JP7048880B2; JP2019086260A

Abstract

This refrigerating and air-conditioning apparatus comprises: a refrigerant circuit that has a compressor (21), an outdoor heat exchanger, a pressure reducing mechanism (13), a liquid side stop valve, an indoor heat exchanger, and a gas side shutoff valve; an air sensor (28) that is attached to a suction side circuit of the compressor (21) and detects the entry of air into the refrigerant circuit; and a safe operation control unit (33) that controls the operation of the compressor (21) so as to stop the operation of the compressor (21) when the air sensor (28) detects the entry of air into the refrigerant circuit.

Description

Refrigeration air conditioner

The present disclosure relates to a refrigeration air conditioner.

The refrigeration air conditioning system includes a refrigerant circuit to which a compressor is connected. If the operation of the compressor is continued while the air is mixed in the refrigerant circuit for some reason, the temperature inside the compressor may abnormally increase, and the compressor may be damaged. As in the case of the refrigeration air conditioner (air conditioner) described in, for example, Patent Document 1, mixing of air into the refrigerant circuit is likely to occur during pump-down operation when the low pressure side pressure is lower than atmospheric pressure. For this reason, in the conventional refrigeration air conditioner described in Patent Document 1, the end of the pump-down operation is specifically abnormal when the operation state in which the possibility of air mixing is suspected in the pump-down operation is detected. In the case of prolonged operation, measures have been taken to forcibly stop the operation of the compressor.

JP, 2016-90223, A

However, the conventional air conditioner described in Patent Document 1 can detect the mixing of air in the normal air conditioning operation because it is a method of determining the mixing of air from the change of the operating condition in the pump-down operation. Not only was it impossible, but there was also the possibility of false detection.

An object of the present disclosure is to provide a refrigeration air conditioner capable of directly detecting the entry of air into a refrigerant circuit.

A refrigeration air conditioner according to a first aspect includes a refrigerant circuit including a compressor, an outdoor heat exchanger, a pressure reducing mechanism, a liquid side shut-off valve, an indoor heat exchanger, and a gas side shut-off valve, and a suction side circuit of the compressor. An air sensor attached to the refrigerant circuit for detecting the mixture of air in the refrigerant circuit, and the operation of the compressor being stopped when the air sensor detects the mixture of air in the refrigerant circuit And a safe operation control unit that controls the operation of the compressor.

In the present specification, the “freeze and air conditioning operation” refers to an air conditioning operation that adjusts the temperature, humidity, etc. of air in a living room such as a general household or office building or a work place in a factory, a cooling operation to cool the inside of a refrigerator, This refers to an operation in which a refrigeration cycle is applied, such as a freezing operation for freezing the inside of a freezer and a cooling operation for cooling lubricating oil of a machine tool. Moreover, a "freezer-air-conditioning apparatus" means the apparatus which performs a freezing air-conditioning operation which was illustrated here.

Further, in the present specification, the “air sensor” may be any sensor that can detect the mixture of air in the refrigerant circuit, and by detecting oxygen gas, carbon dioxide gas, nitrogen gas, etc., which are components of air, It may be something which detects the mixing of air. The air sensor is preferably one capable of detecting the concentration of air contained in the refrigerant in the refrigerant circuit.

According to the refrigeration air conditioning system of the first aspect, the mixing of air into the refrigerant circuit is directly detected regardless of whether the normal refrigeration air conditioning operation or the pump down operation, and the operation of the compressor is stopped. it can. In addition, since the air sensor is attached to the suction side circuit of the compressor, it can sensitively detect air mixing.

According to the refrigeration air conditioning system pertaining to the second aspect, the refrigerant circuit has a four-way switching valve capable of reversibly switching the refrigerant flow direction. The suction side circuit of the compressor has an accumulator. The air sensor is attached to a suction pipe that connects the accumulator and the four-way switching valve.

In general, the accumulator is often mounted close to the compressor because it is a device associated with the compressor. In most cases, there is little extra space around the piping connecting the compressor and the accumulator. Therefore, it is difficult to secure a space for mounting the air sensor around the pipe connecting the compressor and the accumulator. On the other hand, the appendage of the four-way switching valve to the compressor is not as strong as that of the accumulator. Therefore, it is easy to secure an air sensor mounting space between the accumulator and the four-way switching valve in many cases where there is ample space.

According to the refrigeration air conditioner pertaining to the third aspect, in a state in which the liquid side shut-off valve is closed and the gas side shut-off valve is opened, the compressor and the pressure reducing mechanism are controlled to perform pump-down operation. The system further includes a pump down operation control unit configured to perform. The safe operation control unit is configured to stop the operation of the compressor when the air sensor detects air mixing in any of the normal refrigeration air-conditioning operation and the pump-down operation. .

According to this refrigeration air conditioning system, the operation of the compressor is controlled so that the operation of the compressor is stopped when the air sensor detects the presence of air in any of the normal refrigeration air conditioning operation and the pump down operation. Thus, damage to the compressor can be suppressed.

According to the refrigeration air conditioning system of the fourth aspect, the safe operation control unit is configured to immediately stop the operation of the compressor when the air sensor detects air mixing.
According to this refrigeration air conditioning system, since the operation of the compressor is immediately stopped when the air sensor detects the presence of air, damage to the compressor can be further suppressed.

According to the refrigeration air conditioning system of the fifth aspect, the refrigeration air conditioning system of the first to third aspects further includes a pressure sensor that detects a low pressure side pressure. The safe operation control unit is configured to stop the operation of the compressor when the low pressure side pressure is detected by the pressure sensor to be lower than the atmospheric pressure and the air sensor detects mixing of air. It is configured.

The mixing of air into the refrigerant circuit can not occur unless a portion below the atmospheric pressure is generated in the refrigerant circuit. Therefore, if it is added that the low pressure side pressure is lower than the atmospheric pressure as a condition for detecting the mixing of air and stopping the compressor as in this refrigeration air conditioner, false detection of air mixing by the air sensor is more It can be further suppressed.

The refrigeration air conditioning system according to the sixth aspect further includes a pump down operation control unit and an air mixing amount calculation unit. The pump-down operation control unit is configured to perform the pump-down operation by controlling the compressor and the pressure reducing mechanism in a state where the liquid side shut-off valve is closed and the gas side shut-off valve is opened. Ru. The air mixing amount calculation unit accumulates the amount of air mixed in the refrigerant circuit based on the air concentration in the refrigerant circuit measured by the air sensor and the rotational speed of the compressor in the case of the pump-down operation. It is configured to calculate a value. The safe operation control unit is configured to stop the operation of the compressor when a normal refrigeration air conditioning operation is performed when the air sensor detects air mixing, and the air sensor (28) When the pump down operation is performed when the air mixing is detected, the operation of the compressor is stopped when the air mixing amount calculating unit calculates the mixed air amount equal to or more than a preset threshold value. Is configured as.

According to this refrigeration air conditioning system, the operation of the compressor is stopped when the air sensor detects mixing of air during normal refrigeration air conditioning operation. Further, during the pump down operation, the operation of the compressor is stopped only when the accumulated air mixing amount becomes equal to or more than a preset threshold value. Therefore, it is possible to suppress useless system down due to false detection.

According to the refrigeration air conditioning system of the seventh aspect, in the refrigeration air conditioning system of the first and second aspects, the refrigeration air conditioning system further includes a pressure sensor that detects a low pressure side pressure. The safe operation control unit stops the operation of the compressor when the normal operation is performed when the pressure sensor detects that the pressure is lower than the atmospheric pressure and the air sensor detects the mixing of air. Configured such that the pressure sensor (29) detects that the pressure is lower than the atmospheric pressure and the air sensor (28) detects mixing of air, and when the pump-down operation is performed, the air The compressor is configured to stop the operation when the mixing amount calculation unit calculates the mixing air amount equal to or more than a preset threshold value.

According to this refrigeration air conditioning system, during normal operation, the pressure sensor detects that the pressure is lower than the atmospheric pressure, and when the air sensor detects air mixing, the operation of the compressor is stopped. Further, in the pump down operation, the operation of the compressor is stopped only when the accumulated air mixing amount becomes equal to or more than a preset threshold value. Therefore, it is possible to suppress useless system down due to false detection.

FIG. 2 is a refrigerant circuit diagram of the refrigeration air conditioning system according to the first embodiment. The block diagram which shows the peripheral device connected to the control apparatus of the same freezing air conditioning system. Correlation figure of aeration amount and possibility of compressor damage. The flowchart of the air mixing detection operation in the same refrigeration air conditioning system. FIG. 8 is a block diagram showing peripheral devices connected to the control device of the refrigeration air conditioning system according to Embodiment 2. The flowchart of the air mixing detection operation in the same refrigeration air conditioning system. 10 is a flowchart of an air mixing detection operation in the refrigeration air conditioning system according to the modification of the first embodiment. 16 is a flowchart of an air mixing detection operation in the refrigeration air conditioning system according to the modification of the second embodiment.

Hereinafter, a refrigeration air conditioner according to an embodiment of the present disclosure will be described. It is to be noted that the present disclosure is not limited to the examples described below, is shown by the claims, and is intended to include all modifications within the meaning and scope equivalent to the claims. Ru.

Embodiment 1
As shown in FIG. 1, in the air conditioner as the refrigeration air conditioning system according to the first embodiment, the indoor unit 1 installed indoors and the outdoor unit 2 installed outdoors are connected with the liquid side communication pipe L1. It is connected and constituted by gas side connecting piping L2. The air conditioner is a pair-type air conditioner in which the indoor unit 1 and the outdoor unit 2 are connected in a one-to-one manner. The indoor unit 1 is equipped with an indoor heat exchanger 11, an indoor fan 12, and an electric expansion valve 13 as an example of a pressure reducing mechanism. In the outdoor unit 2, a compressor 21, a four-way switching valve 22, an outdoor heat exchanger 23, a liquid side closing valve 24, a gas side closing valve 25, an accumulator 26, an outdoor fan 27 and the like are mounted. The liquid side shutoff valve 24 and the gas side shutoff valve 25 are manual on-off valves. Further, an air sensor 28 and a pressure sensor 29 are provided in a suction pipe that connects the accumulator 26 and the four-way switching valve 22.

The four-way switching valve 22 is configured to switch the refrigerant circuit between the cooling cycle and the heating cycle in a reversible manner. The air conditioner performs a cooling operation in the cooling cycle and performs a heating operation in the heating cycle. That is, during the cooling operation, as indicated by solid arrows in FIG. 1, the compressor 21, the four-way switching valve 22, the outdoor heat exchanger 23, the liquid side shutoff valve 24, the liquid side communication pipe L1, the electric expansion valve 13, A refrigerant circuit is formed that forms a cooling cycle in which the refrigerant is circulated in the order of the indoor heat exchanger 11, the gas side communication pipe L2, the gas side shut-off valve 25, the four-way switching valve 22, the accumulator 26, and the compressor 21. Further, during the heating operation, as shown by the broken line arrows in FIG. 1, the compressor 21, the four-way switching valve 22, the gas side shut-off valve 25, the gas side communication pipe L 2, the indoor heat exchanger 11, the electric expansion valve 13, A refrigerant circuit is formed that forms a heating cycle in which the refrigerant is circulated in the order of the liquid side communication pipe L1, the liquid side shut-off valve 24, the outdoor heat exchanger 23, the four-way switching valve 22, the accumulator 26, and the compressor 21.

In the air conditioner, in the cooling cycle, the outdoor heat exchanger 23 acts as a condenser, and the indoor heat exchanger 11 acts as an evaporator, whereby room air circulated by the indoor fan 12 is cooled and dehumidified. , The room is cooled. In the air conditioner, in the heating cycle, the outdoor heat exchanger 23 acts as an evaporator, and the indoor heat exchanger 11 acts as a condenser, so that the indoor air circulated by the indoor fan 12 is heated. And the room is heated.

The air sensor 28 and the pressure sensor 29 are provided in a suction pipe that connects the accumulator 26 and the four-way switching valve 22 in the refrigerant circuit configured as described above. The air sensor 28 detects oxygen which is a component of air, that is, is an oxygen sensor, and detects the mixing of air by detecting oxygen in the intake gas. The pressure sensor 29 detects the refrigerant pressure of the suction pipe, that is, the low pressure side pressure.

Further, the present air conditioner is equipped with a control device 30 for controlling various operations as shown in FIG. Although the control device 30 is actually formed by the control unit mounted on the indoor unit 1 and the control unit mounted on the outdoor unit 2, since the control unit 30 operates functionally as one unit, Express and explain as an element.

As shown in FIG. 2, a compressor 21, a four-way switching valve 22, an electric expansion valve 13, an outdoor fan 27, an indoor fan 12, a liquid side closing valve 24 and a gas side closing valve 25 are connected to the control device 30. ing. More specifically, drive units of these devices are connected to the control device 30. In addition, the control device 30 includes an outdoor heat exchanger temperature sensor 41 and an outdoor air temperature sensor 42, an indoor heat exchanger temperature sensor 43, an indoor temperature sensor 44, an operation / stop switch 45, the aforementioned air sensor 28, and a pressure sensor. 29 are connected. Further, a remote controller 35 is connected to the control device 30 wirelessly.

In the above, the outdoor heat exchanger temperature sensor 41 is installed in the outdoor heat exchanger 23, and detects the temperature of the outdoor heat exchanger 23. The outside air temperature sensor 42 is installed in the outdoor unit 2 to detect the temperature of the outside air. The indoor heat exchanger temperature sensor 43 is installed in the indoor heat exchanger 11 and detects the temperature of the indoor heat exchanger 11. The indoor temperature sensor 44 is installed in the indoor unit 1 to detect the indoor air temperature. The operation / stop switch 45 is a switch for starting and stopping the pump down operation.

The remote control 35 functions as a drive operation unit for the air conditioner, and includes a drive switch for turning on and off the drive of the air conditioner, a drive mode selection unit, a setting unit for setting the set temperature of the indoor air, and normal heating The air volume setting part which sets the air volume of the indoor fan 12 at the time of driving | operation, the display part which displays indoor temperature, the air volume of the indoor fan 12, etc. are provided. The remote controller 35 is configured to wirelessly transmit the selected or set driving operation information to the control device 30.

The control device 30 includes a microcomputer, an input / output circuit and the like, and functionally configures the normal operation control unit 31, the pump-down operation control unit 32, and the safe operation control unit 33 by these functional components.

The normal operation control unit 31 detects an instruction from the remote control 35, an outdoor heat exchanger temperature detected by the outdoor heat exchanger temperature sensor 41, an outside air temperature detected by the outside air temperature sensor 42, and an indoor heat exchanger temperature sensor 43 Based on the indoor heat exchanger temperature, the indoor temperature detected by the indoor temperature sensor 44, and the like, arithmetic processing and judgment processing are performed to control the normal operation of the air conditioner. The command from the remote controller 35 includes an operation start command, an indoor temperature setting command, and the like.

The pump down operation control unit 32 controls the electric expansion valve 13 and the compressor 21 to perform the pump down operation when receiving a pump down operation command issued from the operation / stop switch 45.

That is, in the refrigerant circuit, when a refrigerant leak occurs in the indoor unit 1, or when relocation or repair of the air conditioner is performed, a pump-down operation is performed. When performing the pump-down operation, the pump-down operation control unit 32 of the control device 30 can be operated by pressing and holding the operation / stop switch 45 (see FIG. 2) provided in the indoor unit 1 or the outdoor unit 2. The start of forced operation is commanded. On the other hand, the worker closes the liquid side shut-off valve 24 and opens the gas side shut-off valve 25. Then, the motor-operated expansion valve 13 is fully opened by the pump-down operation control unit 32, the four-way switching valve 22 is switched to the cooling cycle side, and then the compressor 21 is driven at a predetermined frequency (for example, 50 Hz). A pump down operation is performed to recover the refrigerant on the indoor unit 1 side to the outdoor unit 2 side.

In this way, when the temperature difference between the room temperature and the temperature of the indoor heat exchanger 11 continues to fall below the predetermined temperature difference by performing the pump-down operation, the pump-down is substantially ended. It is judged that When the pump-down is substantially completed, the refrigerant in the indoor heat exchanger 11 becomes lean and substantially no heat exchange takes place. As a result, the temperature difference between the indoor temperature and the temperature of the indoor heat exchanger 11 falls below the predetermined temperature difference. When such a state is reached, the operator is notified by a command from the pump-down operation control unit 32 that the substantial end of the pump-down is performed by lighting the end lamp (not shown) or the like. Is operated at a predetermined frequency. Then, the worker closes the gas side shut-off valve 25 and operates the operation / stop switch 45 to stop the compressor 21. Thus, the pump down operation is completed.

The safe operation control unit 33 operates the compressor 21 so as to avoid damage to the compressor 21 based on at least the low pressure side pressure detected by the pressure sensor 29 and the presence or absence of air mixing by the air sensor 28. Control.

If the operation of the compressor 21 is continued with the air being mixed into the refrigerant circuit, the temperature inside the compressor 21 rises. As shown in FIG. 3, the potential for compressor damage increases as the amount of oxygen in the refrigerant circuit increases. Therefore, in the present air conditioner, the safe operation control unit 33 operates at the same time when the operation is started, and the operation of detecting air mixing in the refrigerant circuit and the coping operation at the time of air mixing detection are performed.

Next, as an operation of the air conditioner according to the present embodiment, a detection operation of air mixing into the refrigerant circuit by the safe operation control unit 33 and a coping operation upon air mixing detection will be described in detail based on FIG. .

As shown in FIG. 4, simultaneously with the start of the refrigeration air conditioning operation, the pressure sensor 29 monitors the low pressure side pressure in the suction pipe of the compressor 21 and detects whether the low pressure side pressure has become lower than atmospheric pressure (step S11). The lowest refrigerant pressure in the refrigerant circuit is the low pressure side pressure in the suction pipe of the compressor 21. Therefore, the aeration of the refrigerant circuit may occur usually after the low pressure side pressure becomes lower than the atmospheric pressure.

Then, when the low pressure side pressure becomes lower than the atmospheric pressure (in the case of YES in step S11), the safe operation control unit 33 proceeds to the next step S12. In the case where the low pressure side pressure exceeds the atmospheric pressure (in the case of NO in step S11), there is no possibility of air mixing into the refrigerant circuit, so the check as to whether the low pressure side pressure is lower than atmospheric pressure is repeated. .

In the next step S12, in view of the possibility of air mixing into the refrigerant circuit, the safe operation control unit 33 determines whether air mixing is detected in the suction side circuit of the compressor 21 by the air sensor 28. To check. The suction side circuit of the compressor 21 is a circuit extending from the four-way switching valve 22 to the compressor 21 as shown in FIG. In this embodiment, the detection of aeration by the air sensor 28 is performed by determining whether or not the intake gas refrigerant contains oxygen. When the air sensor 28 detects that air is mixed in the refrigerant circuit (YES in step S12), the safe operation control unit 33 immediately stops the operation of the compressor 21 and forces the normal operation. End control and end control.

The detection operation of air mixing in the refrigerant circuit by the safe operation control unit 33 described above and the coping operation at the time of air mixing detection are started simultaneously with the start of the refrigeration air conditioning operation. Then, it is performed in parallel with the control of the refrigeration air conditioning operation by the normal operation control unit 31. In addition, it is comprised so that it may operate | move in parallel, also when the pump down driving | operation controlled by the pump down driving | operation control part 32 is started during normal driving | operating. Therefore, if air is detected by the air sensor 28 in this pump-down operation (YES in step S12), the safe operation control unit 33 immediately stops the operation of the compressor 21 (step S13), The normal operation is forcibly ended and the control is ended.

(Advantages of Embodiment 1)
The air conditioner as the refrigeration air conditioning system according to the first embodiment is configured as described above, so that the following effects can be obtained.

(1) According to the present air conditioner, regardless of whether the normal refrigeration air conditioning operation or the pump down operation, when the low pressure side pressure of the compressor 21 is lower than the atmospheric pressure, the mixing of air into the refrigerant circuit is detected In this case, since the operation of the compressor 21 is stopped, damage to the compressor 21 can be suppressed.

(2) Moreover, since the air sensor 28 is attached to the suction side circuit of the compressor 21, it is possible to sensitively detect air mixing.
(3) Since the air sensor 28 is attached around the pipe connecting the compressor 21 and the accumulator 26, it is easy to secure a mounting space for the air sensor 28.

(4) As a condition for detecting the mixing of air and stopping the compressor 21, in addition to the detection of the mixing of air by the air sensor 28, it is added that the low pressure side pressure is lower than the atmospheric pressure by the pressure sensor 29. Therefore, the possibility of false detection is reduced as compared with the case where the detection of air mixing is performed by the air sensor 28 alone.

Second Embodiment
Next, an air conditioner as a refrigeration air conditioner according to Embodiment 2 will be described based on FIGS. 5 and 6.

The air conditioner according to the second embodiment relates to the detection operation of air mixing into the refrigerant circuit and the coping operation upon air mixing detection, in the detection operation and coping operation after the detection during the normal operation and the pump down operation. The contents are different. Compared to the case of the first embodiment, the operation in the normal operation is the same, but the operation in the pump-down operation is different. Because, in the pump-down operation, the operation is performed until the low pressure side pressure becomes lower than the atmospheric pressure, and therefore, the detection of the low pressure side pressure by the pressure sensor 29 is almost only meaningful as a condition to stop the compressor 21 Because there is no Therefore, in the air conditioner, in order to further increase the certainty, it is confirmed that the cumulative amount of air mixed in the refrigerant circuit becomes equal to or more than a predetermined value, and erroneous detection is eliminated.

As a configuration according to the second embodiment, differences from the first embodiment will be described.
As shown in FIG. 5, a major difference from the first embodiment is that the control device 30 is provided with the aeration amount calculation unit 34. The aeration amount calculation unit 34 calculates the amount of refrigerant sucked into the compressor 21 in consideration of changes in the rotational speed and low pressure side pressure of the compressor 21, and further, in the gas refrigerant sucked into the compressor 21. Air concentration calculated from oxygen concentration is grasped including its change. The air mixing amount calculation unit 34 is configured to calculate the cumulative air mixing amount accumulated in the outdoor unit 2 based on these pieces of information. Therefore, the pump-down operation control unit 32 outputs the information on the rotational speed of the compressor 21 and the low pressure side pressure of the refrigerant circuit to the aeration amount calculation unit 34 in order to enable the calculation in the aeration amount calculation unit 34. Configured as. Further, in order to detect the oxygen concentration in the inhaled gas, for the oxygen sensor as the air sensor 28, one capable of detecting the oxygen concentration in the inhaled gas is used. The oxygen concentration detected by the air sensor 28 is output to the aeration amount calculation unit 34 via the safe operation control unit 33.

Next, as the operation according to the second embodiment configured as described above, the operation of detecting air mixing in the refrigerant circuit and the coping operation at the time of detecting air mixing will be described in detail based on FIG.
As shown in FIG. 6, the low pressure side pressure in the suction piping of the compressor 21 is monitored by the pressure sensor 29 simultaneously with the start of the refrigeration air conditioning as in the case of the first embodiment, and the low pressure side pressure is below atmospheric pressure. It is detected whether it has become (step S21).

When the low pressure side pressure becomes lower than the atmospheric pressure (YES in step S21), the safe operation control unit 33 proceeds to the next step S22. When the low pressure side pressure exceeds the atmospheric pressure (in the case of NO at step S21), the check of whether the low pressure side pressure is equal to or less than the atmospheric pressure is repeated.

In the next step S22, the safe operation control unit 33 checks whether the air sensor 28 detects air mixing in the suction side circuit of the compressor 21. In this embodiment, the detection of aeration by the air sensor 28 is performed by determining whether oxygen is contained in the suction gas refrigerant and measuring the oxygen concentration in the suction gas. If the air sensor 28 does not detect the mixing of air into the refrigerant circuit (NO in step S22), the safe operation control unit 33 returns to step S21. On the other hand, when the air sensor 28 detects mixing of air into the refrigerant circuit (in the case of YES at step S22), the safe operation control unit 33 proceeds to step S23 to determine whether it is a pump down operation or a normal operation. Do.

When it is determined in step S23 that the normal operation is performed, the safe operation control unit 33 immediately stops the compressor 21 as in the case of the first embodiment (step S26). Therefore, when mixing of air is detected in normal operation, it becomes substantially the same as that of the first embodiment. However, if it is determined in step S23 that the pump-down operation is being performed, there is no mixing of air during the normal operation, but the current operation enters the pump-down operation and the low pressure side pressure of the compressor 21 is It is presumed that the pump down operation has advanced to such an extent that the pressure is lower than the atmospheric pressure. Moreover, it is inferred that the infiltration of air arose after becoming in this state. Here, when based only on the detection result of the air sensor 28, there is a possibility that the determination of the compressor stop may be mistaken based on the erroneous detection of the air sensor 28. In view of such circumstances, in the present embodiment, the aeration amount calculation unit 34 includes the number of revolutions of the compressor 21, the low pressure side pressure of the compressor 21, the oxygen concentration in the intake gas detected by the air sensor 28, The accumulated amount of air is calculated from the passage of time (step S24). Then, when the accumulated mixing amount exceeds a preset threshold (in the case of YES in step S25), the safe operation control unit 33 stops the operation of the compressor 21 (step S26). It should be noted that in step S25, if the accumulated mixing amount of air does not exceed the preset threshold value, it is determined that there is no mixing of air that would damage the compressor 21, and the operation of the compressor 21 continues as it is (In the case of NO at step S25).

(Advantages of Embodiment 2)
Since the air conditioner as the refrigeration air conditioner according to Embodiment 2 is configured as described above, in addition to the following effects, the effects of (2) and (3) can also be exhibited. it can.

(5) During normal operation, when the low pressure side pressure decreases and the air sensor 28 detects mixing of air into the refrigerant circuit, the operation of the compressor 21 is immediately stopped, so damage to the compressor 21 is caused. Can be suppressed. Further, the possibility of erroneous detection is reduced as compared with the case where the detection of air mixing is performed by the air sensor 28 alone.

(6) During the pump down operation, the low pressure side pressure is reduced, and the air sensor 28 detects that air is mixed in the refrigerant circuit, and the accumulated amount of air mixed in the refrigerant circuit is set in advance. It may exceed the threshold value. In such a case, since the operation of the compressor 21 is stopped on the assumption that the mixing of air into the refrigerant circuit has been confirmed, the risk of erroneous detection is reduced.

(Modification)
The above description of each embodiment is an exemplification of a form which the refrigeration and air conditioning device according to the present disclosure can take, and is not limited to the form. Note that at least two modifications that do not contradict each other may be combined.

In the first embodiment, as a detection condition of air mixing into the refrigerant circuit, it can be omitted that the low pressure side pressure becomes equal to or less than the atmospheric pressure. In this case, the detection operation of air mixing and the coping operation at the time of air mixing detection omit the detection of the low-pressure side pressure in step S11 in the procedure in the first embodiment shown in FIG. Just follow the steps. That is, as shown in FIG. 7, when the air sensor 28 detects air mixing into the refrigerant circuit (YES in step S12), the operation of the compressor 21 is immediately stopped (step S13). The operation may be forced to end. In this case, the attachment of the pressure sensor 29 itself can be omitted.

In the second embodiment, as a detection condition of air mixing into the refrigerant circuit, it can be omitted that the low pressure side pressure becomes lower than the atmospheric pressure. In this case, the detection operation of air mixing and the coping operation at the time of air mixing detection omit the detection of the low-pressure side pressure in step S21 in the procedure in the second embodiment shown in FIG. Just follow the steps. That is, as shown in FIG. 8, when mixing of air into the refrigerant circuit is detected by the air sensor 28 (YES in step S22), it is determined whether the current operation is the pump down operation or the normal operation ( Step S23). If it is determined in step S23 that the current operation is the normal operation, the compressor 21 is immediately stopped (step S26). On the other hand, if it is determined in step S23 that the current operation is pump-down operation, compression is performed if the cumulative amount of air mixed into the refrigerant circuit exceeds a preset threshold (YES in step S25). The operation of the machine 21 is stopped (step S26). In this case, the attachment of the pressure sensor 29 itself can be omitted.

In the embodiment described above, the oxygen sensor is used as the air sensor 28, but the air sensor 28 may detect carbon dioxide or nitrogen gas which is an air component.
In the first embodiment, the mounting position of the air sensor 28 is a low-pressure pipe connecting the four-way switching valve 22 and the accumulator 26. However, if space permits, the accumulator 26 and the compressor 21 can be used. It may be a suction pipe to be connected. In this case, since the mixing of air is detected at a position closer to the suction port of the compressor 21, the mixing of air into the refrigerant circuit can be detected more accurately.

-In the above embodiment, although a separate type air conditioner was listed as a refrigeration air conditioner, the refrigeration air conditioner is an integrated air conditioner, a cooling device for cooling the inside of a refrigerator, and a freezing device for freezing the inside of a freezer, It may be a device that performs other types of refrigeration cycle application operation such as a cooling device that cools the lubricating oil of a machine tool.

While the embodiments have been described above, it will be appreciated that various changes in form and detail may be made without departing from the spirit and scope of the claims.

Claims

A refrigerant circuit having a compressor (21), an outdoor heat exchanger (23), a pressure reducing mechanism (13), a liquid side shutoff valve (24), an indoor heat exchanger (11), and a gas side shutoff valve (25);
An air sensor (28) attached to a suction side circuit of the compressor (21) for detecting air mixing in the refrigerant circuit;
A safety operation control unit for controlling the operation of the compressor (21) to stop the operation of the compressor (21) when the air sensor (28) detects the mixing of air into the refrigerant circuit (33) and a refrigeration air conditioner.
The refrigerant circuit has a four-way switching valve (22) capable of reversibly switching the refrigerant flow direction,
The suction circuit of the compressor (21) comprises an accumulator (26)
The refrigeration air conditioning system according to claim 1, wherein the air sensor (28) is attached to a suction pipe that connects the accumulator (26) and the four-way switching valve (22).
The refrigeration air conditioner according to claim 1 or 2
With the liquid side shutoff valve (24) closed and the gas side shutoff valve (25) opened, the pump (21) and the pressure reducing mechanism (13) are controlled to perform a pump-down operation. Further comprising a pump down operation control unit (32) configured as
The safe operation control unit (33) operates the compressor (21) when the air sensor (28) detects the mixing of air in either the normal refrigeration air conditioning operation or the pump down operation. A refrigeration air conditioner that is configured to stop.
The safe operation control unit (33) is configured to immediately stop the operation of the compressor (21) when the air sensor (28) detects the mixing of air. Refrigeration air conditioner according to any one of the above.
The refrigeration air conditioner according to any one of claims 1 to 3.
It further comprises a pressure sensor (29) for detecting the low pressure side pressure,
When the low pressure side pressure is detected by the pressure sensor (29) to be lower than the atmospheric pressure and the air sensor (28) detects that the air is mixed, the safe operation control unit (33) Refrigerating air conditioner configured to stop operation of a compressor (21).
The refrigeration air conditioner according to claim 1 or 2
With the liquid side shutoff valve (24) closed and the gas side shutoff valve (25) opened, the pump (21) and the pressure reducing mechanism (13) are controlled to perform a pump-down operation. A pump down operation control unit (32) configured as
In the case of the pump-down operation, the cumulative value of the amount of air mixed in the refrigerant circuit is calculated from the air concentration in the refrigerant circuit measured by the air sensor (28) and the rotational speed of the compressor (21). Further comprising an aeration amount calculation unit (34) configured to calculate
The safe operation control unit (33) is configured to stop the operation of the compressor (21) when the normal refrigeration air conditioning operation is performed when the air sensor (28) detects the mixing of air. When the pump down operation is performed when the air sensor (28) detects air mixing, the air mixing amount calculation unit (34) sets the amount of mixed air equal to or greater than a preset threshold value. Refrigerated air conditioner configured to stop operation of the compressor (21) when calculated.
In the refrigeration air conditioner according to claim 6,
It further comprises a pressure sensor (29) for detecting the low pressure side pressure,
The normal operation is performed when the safe operation control unit (33) detects that the pressure sensor (29) is lower than atmospheric pressure and the air sensor (28) detects mixing of air. The pressure sensor (29) detects that the pressure is lower than the atmospheric pressure and the air sensor (28) detects mixing of air, and the operation of the compressor (21) is stopped. When the pump-down operation is being performed, the operation of the compressor (21) is configured to be stopped when the air mixing amount calculation unit (34) calculates the amount of mixed air equal to or greater than a preset threshold. A refrigeration air conditioner.