JP2009150368A - Oil equalizing mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oil equalizing mechanism capable of equalizing oil in a plurality of compressors, capable of dealing with special compressors capable of conducting an unloading operation and capable of equalizing oil even in the case that it is difficult to detect a lowered oil level state. <P>SOLUTION: The oil equalizing mechanism is provided with oil level detection mechanisms 4 in the respective compressors 1, an oil return flow passages L for returning lubricating oil from an oil separator OS to the respective compressors 1, opening and closing valves V arranged in the respective oil return flow passages L and a control mechanism for controlling the opening and closing valves V. The control mechanism is provided with a normal control part for opening the opening and closing valves V corresponding to compressors of which oil levels are lowered and closing the opening and closing valves V corresponding to compressors of which oil levels are normal based on a detection signal from the oil level detection mechanism 4, an opening and closing cycle setting part for setting a peculiar opening and closing cycle and a peculiar opening and closing period ratio for each valve based on an opening and closing cycle and an opening and closing period ratio of each opening and closing valve V set by the normal control part and a special control part, used selectively from opening and closing valve control by the normal control part, for controlling the opening and closing valves V depending on the peculiar opening and closing cycles and the peculiar opening and closing period ratios. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an oil leveling mechanism in a refrigeration apparatus or an air conditioner having a plurality of compressors.

  As a conventional oil leveling system of this type, as described in Patent Document 1, an oil separator is connected between the discharge side confluence of a plurality of compressors and a four-way valve. A bypass passage is provided between the oil return pipe and each suction side of each compressor via an on-off valve, and the time during which any of the compressors is operated is integrated, and the integrated time reaches a predetermined time. When this is done, each on-off valve is closed and each compressor is operated to start a recovery operation for recovering the lubricating oil in the refrigerant circuit to each compressor. After a preset time has elapsed, each compressor is turned on. Stops one after another, opens the on-off valve corresponding to the stop compressor, returns the lubricating oil in the oil separator to the stop compressor, and controls the oil level of each compressor to be uniform. It has been.

JP 2004-116805 A

  However, since the above-mentioned one controls the on-off valve only at time intervals, there is a possibility that oil return corresponding to the actual oil level cannot be performed. Further, a stop compressor is required for the oil leveling operation, and the oil leveling cannot be performed during the operation of all the compressors. That is, one of the compressors must be stopped during the oil leveling operation, and there is a problem that the capacity is reduced accordingly.

  The present invention has been made in view of such problems, and the main problem is that in a refrigeration cycle having a plurality of compressors, only the compressor that is actually in a low oil amount state is returned to oil. To avoid wasteful oil return and to perform efficient oil leveling, and to eliminate the need to stop the compressor during the oil leveling operation and to prevent a decrease in capacity caused by it. It is to provide an oil leveling mechanism capable of Furthermore, an expected problem of the present invention is that the oil leveling mechanism can cope with a special compressor that can perform an unloading operation, and it is difficult to detect a low oil amount state of the compressor in a special operation situation. Even in such a case, the oil leveling may be performed in a state close to that during normal operation.

  That is, the oil leveling mechanism according to the present invention is applied to a refrigeration cycle having a plurality of compressors, and detects whether the amount of oil stored in each compressor is in a standard state or a reduced state. And an oil return passage for returning the lubricating oil from the oil separator to each compressor, an on-off valve provided in each oil return passage, and a control mechanism for opening and closing the on-off valve. Become. Based on the detection signal from the oil amount detection mechanism, the control mechanism opens the on-off valve corresponding to the compressor whose oil amount is in a lowered state, and opens and closes corresponding to the compressor whose oil amount is in a standard state. A normal control unit for closing the valve, and an open / close cycle setting unit for setting a specific open / close cycle and open / close period ratio for each open / close valve based on the open / close cycle and open / close period ratio of each open / close valve by the normal control unit; The on / off valve control by the normal control unit is selectively used, and when a predetermined switching event occurs for one on / off valve, the open / close cycle and the open / close period ratio set in the open / close cycle etc. setting unit And a special control unit that controls opening and closing of the on-off valve.

  If it is such, based on the detection signal from the said oil amount detection mechanism, the opening / closing valve corresponding to the compressor in which the oil amount has fallen will be opened, and the opening valve corresponding to the other compressors will be closed. By doing so, the lubricating oil can be returned only to the compressor in which the amount of oil is reduced. Further, in this oil leveling operation, it is not necessary to stop the compressor in which the oil amount is reduced, so that the capacity of the entire compressor is not reduced.

  Furthermore, when there is a reason for switching to another control such that it is difficult to control by a normal control unit based on a signal from the oil amount detection mechanism for a certain on-off valve, switch to the control of the on-off valve by a special control unit It can respond by doing. Since the control of the on-off valve by the special control unit is performed based on the open / close cycle and the open / close period ratio of the control that the normal control unit has performed on the on-off valve, it is more than simply performing the open / close period of a fixed cycle. Oil leveling can be suitably performed.

  To prevent failure due to frequent opening and closing of the on-off valve while allowing an appropriate amount of oil to be returned to the compressor when a switching event occurs and the control is switched For the on-off valve whose opening / closing cycle by the normal control unit is less than a certain time, the open / close cycle setting unit substantially maintains the open / close period ratio inherent to the on-off valve at the on / off period ratio by the normal control unit, It is preferable that the opening / closing cycle unique to the opening / closing valve is set to be equal to or longer than the predetermined time.

  The oil amount detection mechanism of each compressor is preferably one that performs measurement by a single sensor for ensuring reliability, does not require heating of the refrigerant, and can accurately detect the oil amount with a simple configuration. As such, the compressor is of a low-pressure container type comprising a low-pressure container for storing lubricating oil and configured to connect a suction pipe for introducing refrigerant into the low-pressure container. The oil amount detection mechanism is configured so that the upper connection pipe and the lower connection pipe are drawn from the upper position and the lower position of the low pressure container, respectively, based on the oil level height at the time of the standard oil amount in the low pressure container, A communication pipe connected to the upper connection pipe and the lower connection pipe and configured such that the oil level in the internal space is displaced the same as the oil level in the low-pressure vessel, and the tip is branched from the suction pipe and the tip is connected to the communication pipe A branch pipe opened at a position higher than the oil level height at the time of the standard oil amount in the internal space, and a temperature sensor for measuring the surface temperature of the lower connection pipe, and depending on the temperature measured by the temperature sensor The amount of oil stored in the compressor is standard Those detectable configure or condition or degraded state and the like.

  It is preferable to easily determine whether or not a control switching event has occurred. As a specific aspect, if the oil amount state detected by the oil amount detection mechanism continues in the same state for a certain period or longer, it can be determined that a switching reason has occurred. .

When the compressor can be switched between a loading state that performs suction compression and an unloading state that does not perform suction compression while operating, the temperature measured by the temperature sensor is less likely to change in the unloading state. It is difficult to detect the amount of oil. Therefore, if the switching from the loading state to the unloading state is used as a switching reason, oil equalization can be suitably performed.

  When there are a plurality of compressors in which the lubricating oil is insufficient, in order to be able to return an appropriate amount of lubricating oil to each compressor, the opening control by the normal control unit and the special control unit is performed as follows: At the same time, it may be configured to be performed only for one on-off valve.

  For example, when the lubricating oil flowing out from the compressor is not sufficiently separated by the oil separator and a large amount of oil does not return to the compressor for a long time, the control by the normal control unit and the special control unit Oil return may not be sufficient. In order to solve such a problem, the control mechanism, when the oil amount reduction state continues longer than a predetermined time, when the oil amount reduction state occurs more than a predetermined number of times within a predetermined time, Or, when the oil level drop state occurs in more than a predetermined number of compressors at the same time, the compressor with the oil level in the standard state is operated and the on-off valve corresponding to the compressor is closed, and the oil level is reduced. What is necessary is just to further comprise the oil collection | recovery control part which stops the operation | movement of the compressor in a state and opens the on-off valve corresponding to this compressor.

In a large-scale refrigeration cycle, a plurality of outdoor units having one or a plurality of compressors may be provided. In this case, the lubricating oil is discharged from the refrigerant circuit in the outdoor unit to the external refrigerant circuit, and thus the outdoor unit. Compressor oil volume imbalance may occur between the two. To solve these problems,
The oil recovery control unit operates all the compressors when all the compressors of a certain outdoor unit have a reduced oil amount, and has an on-off valve corresponding to the compressor in which the oil amount is reduced. It is preferable that the on-off valve corresponding to the compressor that is opened and that has the oil amount in a standard state is closed.

  If it is an air conditioner equipped with such an oil leveling mechanism, it is possible to appropriately return oil to a compressor that lacks lubricating oil, without being accompanied by a reduction in the capacity of the compressor. Furthermore, even if a problem occurs in the detection of the oil amount by the oil amount detection mechanism, it is possible to switch to the control that can perform the oil equalization in a state close to that when the oil is operating normally.

  As described above, the present invention can return the lubricating oil to only the compressor without stopping the compressor in which the oil amount is reduced, and even if a failure occurs in the detection of the oil amount, Appropriate oil leveling can be performed by switching to a special control of a form close to that during operation.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, an oil equalizing mechanism 100 according to the present embodiment is applied to a power-heat conversion system (not shown) such as a refrigeration apparatus or an air conditioner having a plurality of compressors 1, and each compressor It operates to keep the oil amount of 1 at an appropriate amount. The compressor 1 according to this embodiment is a low-pressure container type compressor having a low-pressure container 2 for storing lubricating oil, and a suction pipe 3 for introducing a refrigerant is connected to the low-pressure container 2. It is.

  Thus, the oil leveling mechanism 100 returns the lubricating oil to the compressor 1 from the oil amount detection mechanism 4 that detects whether the amount of oil stored in each compressor 1 is in a standard state or a reduced state, and the oil separator OS. Oil return passages L, on-off valves V provided in the respective oil return passages L, and a control mechanism C that controls the opening / closing of the on-off valves V.

  More specifically, the oil amount detection mechanism 4 is arranged on the upper side of the low-pressure vessel 2 with reference to the oil level height in the low-pressure vessel 2 at the standard oil amount, as shown in FIGS. The upper connection pipe 54 and the lower connection pipe 53 drawn from the position and the lower position, respectively, and the upper connection pipe 54 and the lower connection pipe 53 are connected, and the oil level of the internal space is within the low pressure vessel 2. A communication pipe 52 configured to be displaced in the same manner as the oil level, and a tip branched from the suction pipe 3 and having a tip higher than the oil level height H (1) in the internal space of the communication pipe 52 at the time of the standard oil amount. A branch pipe 51 opened at a position, and a temperature sensor 6 for detecting the surface temperature of the lower connection pipe 53, and the stored oil in the compressor 1 is detected by the detected temperature detected by the temperature sensor 6. It is configured to detect whether the quantity is in a standard state or a reduced state

  The compressor 1 is a low-pressure container type compressor, and is configured to be switchable between a loading state in which a suction compression operation is performed and an unloading state in which the suction compression operation is not performed while being operated.

  The oil separator OS separates the refrigerant discharged from the compressor 1 and the lubricating oil, and flows the lubricating oil through the oil return passage L.

  The oil return flow path L connects the oil separator OS and a low-pressure pipe on the suction side of each compressor 1. The main flow portion L1 extends from the oil separator OS, and the branch flow portion L2 branches from the main flow portion L1 and connects to the low-pressure pipe on the suction side of each compressor 1.

  One on-off valve V is provided for each branch portion L2, and opens and closes the branch portion L2 in accordance with an opening / closing command from the control mechanism C.

  The control mechanism C has at least a hardware configuration including a CPU, a memory, various driver circuits, and the like, and the control mechanism C is changed in various ways by the cooperation of the CPU and peripheral devices in accordance with a program stored in the memory. Demonstrate the function.

  Therefore, in this embodiment, as shown in the functional block diagram of FIG. 4, at least the functions of the normal control unit C1, the opening / closing cycle setting unit C2, the special control unit C3, and the oil recovery control unit C4 are provided. The program is configured to demonstrate.

  Based on the detection signal from the oil amount detection mechanism 4, the normal control unit C1 opens the on-off valve V corresponding to the compressor 1 in which the oil amount is decreasing, and the oil amount is an appropriate amount. The on-off valve V corresponding to the compressor 1 in the standard state within the range is closed. Further, when it is detected that there are a plurality of compressors 1 whose oil amount has decreased, the opening / closing valves V corresponding to the respective compressors 1 are not simultaneously opened, but the opening times of the respective opening / closing valves V are shifted. It is also configured to open.

  The open / close cycle setting unit C2 is specific to each open / close valve V based on the open / close cycle and open / close period ratio of each open / close valve V in the normal control state in which the normal control unit C1 controls the open / close valve V. The open / close cycle and open / close period ratio are set. More specifically, the opening / closing cycle setting unit C2 measures and averages the actual cycle with the actual time when the normal control unit C1 opened the on-off valve V and the actual time closed as one cycle. Thus, the average opening / closing cycle is calculated. Further, the average opening / closing period ratio is set by averaging the actual opening / closing period ratio, which is the ratio between the actual time when the on-off valve V is open and the actual time when the opening / closing valve V is closed. Further, when the calculated average opening / closing cycle is shorter than the predetermined cycle stored in the memory, the corrected opening time is calculated by adding a plurality of opening times while maintaining the average opening / closing period ratio. The correction closing time is calculated by adding a plurality of closing times to be combined into one cycle (this specific example will be described later together with the operation).

  The special control unit C3 is that the compressor 1 is in the unloading operation, so that the refrigerant is not sucked and compressed, and the temperature sensor 6 does not significantly reduce the temperature. Can be switched from the normal control unit C1. Here, switching from the normal control unit C1 to the special control unit C3 is performed when there is no change in temperature for a time longer than the specified time stored in the memory by the signal from the temperature sensor 6. It is. The control of the special control unit C3 controls the open / close valve V based on the average open / close cycle and average open / close period ratio or the corrected open / close cycle and corrected open / close period ratio set by the open / close cycle etc. setting unit C2. It is configured. Further, even in the control of the special control unit C3, when opening the opening / closing valves V corresponding to the compressors 1, the opening times are set to be different so that the plurality of opening / closing valves V are not simultaneously opened. .

  For example, the oil recovery control unit C4 supplies the compressor 1 having a shortage of lubricating oil in a situation where the function of separating the lubricating oil by the oil separator is lowered and a large amount of oil does not return for a long time. It is for forcing oil equalization. The switching from the passage control unit or the special control unit C3 to the oil recovery control unit C4 is performed when the decrease in the oil amount of the compressor 1 is longer than the specified time stored in the memory. When the number of compressors 1 in which the oil amount is reduced is greater than or equal to a predetermined number when the number of compressors 1 is higher than a predetermined number in a certain time. The oil recovery unit control unit operates the compressor 1 in which the oil amount is in a standard state and closes the release valve corresponding to the compressor 1 and also operates the compressor 1 in which the oil amount is in a reduced state. While stopping, the on-off valve V corresponding to the compressor 1 is opened.

  The rough operation of the oil leveling mechanism 100 will be described first with reference to the flowchart of FIG. When the oil equalization mechanism 100 starts operation, first, the control valve C1 controls each on-off valve V (step S1). During the normal control period, the opening / closing cycle setting unit C2 calculates an average opening / closing period and an average opening / closing period ratio of each opening / closing valve V, and based on these values, calculates an opening / closing command value of the special control unit C3. It is generated (step S2).

  When a special control unit switching reason is detected in a compressor 1 that the signal from the temperature sensor 6 indicates the same value for a longer time than a predetermined period stored in the memory (step S3), the compressor The control of the on-off valve V corresponding to 1 is switched so as to be performed by the special control unit C3. When the signal from the temperature sensor 6 of the compressor 1 no longer shows the same value, the control of the on-off valve V is returned to the normal control unit C1 (step S4).

  Further, the oil amount decrease time of the compressor 1 is longer than the specified time stored in the memory, and the frequency of the oil amount decrease of the compressor 1 is high and the predetermined number of times stored in the memory within a predetermined time or more. When an oil recovery control unit switching event is detected, that is, the occurrence of an oil reduction, or the number of compressors 1 in a reduced oil quantity is greater than the predetermined number stored in the memory (step S5), each opening and closing The control of the valve V is switched from the normal control unit C1 or the special control unit C3 to the control by the oil recovery control unit C4 (step S6). If the oil recovery control part C4 switching reason is eliminated, the control of each compressor 1 is returned to the control by the normal control part C1 or the special control part C3.

  Next, the oil amount detection in step S1 and the oil leveling operation by the normal control unit C1 will be described in detail with reference to the flowchart of FIG.

  When an appropriate amount of lubricating oil is contained in the compressor 1, as shown in FIG. 2, the lower connection pipe 53 provided with the temperature sensor 6 of the oil amount detecting mechanism 4 has a high temperature lubricating oil. Are in contact with each other, the temperature detected by the temperature sensor 6 varies at a high temperature. Next, when the amount of oil decreases and the oil level becomes H (2) with the oil level lowered as shown in FIG. 3, the lower connecting pipe 53 passes through the low-temperature gas refrigerant and generates heat. Since it is taken away, the temperature detected by the temperature sensor 6 decreases. The oil amount detection mechanism 4 detects the oil drop state of each compressor 1 depending on whether or not the detected temperature is lower than a predetermined temperature (step S11).

  When this oil drop state is detected in a certain compressor 1, the normal control opens only the on-off valve V corresponding to the corresponding compressor 1, and the compressor 1 in which the other appropriate oil amount is maintained. Keep the open valve closed. Then, the lubricating oil separated from the oil separator OS flows only into the compressor 1 in which the oil amount is reduced (step S13).

  If it is detected by the oil amount detection mechanism 4 that there are a plurality of compressors 1 having a reduced oil amount in the stage before step S13, the opening time of the on-off valve V corresponding to each compressor 1 is set. As shown in FIG. 7, the setting is shifted by a predetermined time (step S12).

  When the oil amount detection mechanism 4 detects that the lubricating oil has returned to the compressor 1, the normal control unit C1 closes the open valve that has been opened, and returns to step S11.

Next, the oil leveling operation by the special control unit C3 in step S4 will be described in detail.
In the normal control unit C1, as shown in FIG. 8, a case where the opening / closing control of the opening / closing valve V is performed at a cycle shorter than a predetermined period is taken as an example.

  In this case, as shown in FIG. 8, the open / close cycle setting unit C2 maintains the average open / close period ratio of the control of the open / close valve V performed by the normal control unit C1, as shown in FIG. The corrected opening / closing cycle is set in the special control unit C3 so that the opening / closing frequency of the opening / closing valve V is reduced with time. The special control unit C3 controls the on-off valve V according to time so that the corrected open / close cycle and the average open / close period ratio, thereby performing oil equalization.

  Thus, according to the present embodiment, based on the detection signal from the oil amount detection mechanism 4, the on-off valve V corresponding to the compressor 1 in which the oil amount has decreased is opened, and the other compressors 1 are opened. By closing the release valve corresponding to, the lubricating oil can be returned only to the compressor 1 in which the amount of oil is reduced. Further, in this oil leveling operation, it is not necessary to stop the compressor 1 to be leveled, so that a reduction in capacity does not occur.

  Since the oil detection mechanism can detect the oil amount with only one temperature sensor 6, it is more reliable than a method using a plurality of sensors.

  Even if the compressor 1 is performing an unloading operation in which it is difficult to detect a decrease in the oil amount, the normal control based on the oil amount detection is switched to the special time control based on the time, so that the oil can be appropriately leveled. it can. Moreover, since the special control is set based on the open / close cycle and the open / close period ratio of the open / close valve V during normal control, it is possible to perform oil equalization very close to that during normal operation. Furthermore, when the opening / closing cycle is too short, the opening / closing cycle is changed to an appropriate length while maintaining the opening / closing period ratio, so that early failure of the opening / closing valve V due to frequent opening / closing can be prevented.

  In the control of the on-off valve V by the normal control unit C1 and the special control unit C3, when it is difficult to eliminate the oil amount decrease state, the control is switched to the oil recovery control unit C4, and the compressor 1 in which the oil amount is decreased is switched. By stopping and opening the corresponding on-off valve V, the oil amount can be set to an appropriate value.

The present invention is not limited to the above embodiment.
You may use the oil equalization mechanism of the said embodiment for an air conditioning apparatus.
As a switching reason for switching the control from the normal control unit to the special control unit, it is conceivable that the oil amount detection mechanism breaks down and control by the oil amount detection cannot be performed. Also in this case, for example, the fact that only a constant value is always output due to the failure of the temperature sensor may be used as a failure detection condition to switch control.

When the refrigeration cycle includes a plurality of outdoor units having one or a plurality of compressors, and the oil recovery control unit causes all the compressors to have a reduced oil amount in all the compressors of a certain outdoor unit. The on-off valve corresponding to the compressor whose oil amount is in a lowered state is opened, and the on-off valve corresponding to the compressor whose oil amount is in a standard state may be closed. If this is the case, even if a reduction in the amount of oil in the compressor occurs in units of outdoor units, leveling is performed between outdoor units that are difficult to perform leveling with the control of the normal control unit and special control unit. be able to.

  The special control unit may record the control of the normal control unit for a predetermined time and reproduce the open / close cycle and the open / close ratio as they are. Even in such a case, it is possible to perform the oil leveling operation in accordance with the tendency of the oil amount of the compressor to decrease.

  The oil amount detection mechanism may use a plurality of temperature sensors. In that case, the control may be switched when the output of at least one temperature sensor shows the same value for a long time.

  In addition, the present invention is not limited to the above-described embodiment and the like, and it goes without saying that various modifications can be made without departing from the spirit of the present invention.

The typical schematic diagram showing the oil equalization mechanism in one embodiment of the present invention. The typical schematic diagram which shows the oil level detection mechanism etc. at the time of the standard oil amount in the same embodiment. The typical schematic diagram which shows the oil level detection mechanism etc. at the time of the low oil amount in the same embodiment. The functional block diagram of the embodiment. The flowchart which shows the oil equalization control of the embodiment. The flowchart which shows the oil equalization control by the normal control part in the embodiment. The open time graph which shows the relationship between the some open valves in the embodiment. The graph which shows the opening / closing control of the special control part when opening / closing is repeated with the short cycle in the same embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Oil equalization mechanism 1 ... Compressor 2 ... Low pressure vessel 3 ... Suction pipe 54 ... Upper connection pipe 53 ... Lower connection pipe 52 ... Communication pipe 51 ... Branch pipe 6 ... Temperature sensor OS ... Oil separator L ... Oil return channel V ... Open / close valve C ... Control mechanism C1 ... Normal control unit C2 ... Open / close cycle, etc. Part C3 ... Special control part C4 ... Oil recovery control part H (1) ... Oil level at standard oil level

Claims (9)

It is applied to a refrigeration cycle equipped with a plurality of compressors,
An oil amount detection mechanism that detects whether the amount of stored oil in each compressor is in a standard state or a reduced state, an oil return channel for returning lubricating oil from the oil separator to each compressor, and each oil return channel Comprising an on-off valve provided and a control mechanism for controlling on-off of the on-off valve,
The control mechanism is
Based on a detection signal from the oil amount detection mechanism, a normal control unit that opens the on-off valve corresponding to the compressor whose oil amount is low and closes the on-off valve corresponding to the compressor whose oil amount is in the standard state When,
An open / close cycle setting unit for setting an open / close cycle and open / close period ratio specific to each open / close valve based on the open / close cycle and open / close period ratio of each open / close valve by the normal control unit;
The on / off valve control by the normal control unit is selectively used, and when a predetermined switching event occurs for one on / off valve, the specific on / off period and the specific on / off period ratio set in the on / off cycle setting unit are used. And a special control unit that controls opening and closing of the on-off valve.   For the open / close valve whose open / close cycle by the normal control unit falls below a certain time, the open / close cycle setting unit substantially maintains the open / close period ratio inherent to the open / close valve at the open / close period ratio by the normal control unit, and 2. The oil leveling mechanism according to claim 1, wherein an opening / closing cycle unique to the valve is set to be equal to or longer than the predetermined time. The compressor is of a low-pressure vessel type comprising a low-pressure vessel for storing lubricating oil, and configured to connect a suction pipe for introducing a refrigerant into the low-pressure vessel;
The oil amount detection mechanism includes an upper connection pipe and a lower connection pipe drawn from an upper position and a lower position of the low pressure container, respectively, with reference to an oil level height at the time of a standard oil amount in the low pressure container; A connecting pipe connected to the connecting pipe and the lower connecting pipe, and configured so that the oil level of the internal space is displaced the same as the oil level in the low-pressure vessel; and the tip of the connecting pipe is branched from the suction pipe A branch pipe that is opened at a position higher than the oil level height at the time of the standard oil amount in the internal space, and a temperature sensor that measures the surface temperature of the lower connecting pipe, and depending on the temperature measured by the temperature sensor, The oil leveling mechanism according to claim 1 or 2, wherein the oil leveling mechanism is configured to detect whether the amount of stored oil in the compressor is in a standard state or a reduced state.   The oil leveling system according to any one of claims 1 to 3, wherein the switching reason is that the oil amount state detected by the oil amount detecting mechanism continues for a certain period or longer in the same state. The compressor is switchable between a loading state in which suction compression action is performed and an unloading state in which suction compressor action is not performed while operating,
The oil leveling mechanism according to claim 3, wherein the switching reason is that the loading state is switched to the unloading state.   The oil leveling mechanism according to any one of claims 1 to 4, wherein the opening control by the normal control unit and the special control unit is performed on only one on-off valve at the same time. The control mechanism is
If the oil level has been reduced for a longer time than the specified time, if the oil level has been reduced more than a predetermined number of times within a certain period of time, or if more than a predetermined number of compressors have been simultaneously reduced In such a case, the compressor in which the oil amount is in a standard state is operated, the on-off valve corresponding to the compressor is closed, and the operation of the compressor in which the oil amount is in a reduced state is stopped and the compressor is The oil leveling mechanism according to any one of claims 1 to 6, further comprising an oil recovery control unit that opens a corresponding on-off valve. The refrigeration cycle comprises a plurality of outdoor units having one or more compressors,
The oil recovery control unit operates all the compressors when all the compressors of a certain outdoor unit have a reduced oil amount, and has an on-off valve corresponding to the compressor in which the oil amount is reduced. The oil leveling mechanism according to claim 7, wherein the on-off valve corresponding to the compressor that is open and has an oil amount in a standard state is closed.   An air conditioner comprising the oil leveling mechanism according to any one of claims 1 to 8.