JP2008128570A - Refrigerating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refrigerating apparatus, always supplying a suitable quantity of lubricating oil from an oil separator to a refrigerant sucked into a compressor to stably lubricate the compressor. <P>SOLUTION: This refrigerating apparatus includes the compressor 3, which is driven by an external driving source and whose rotational frequency depends on the external driving source, wherein the apparatus further includes: a lubricating oil retaining quantity estimating part 33 for estimating the retaining quantity of lubricating oil retained in a main refrigerant circuit 2 from the oil separator 4 to the compressor 3 and a hot gas bypass circuit 16; and a control part 32 for causing a refrigerant to flow through both the main refrigerant circuit 2 and the hot gas bypass circuit 16 to perform the lubricating oil recovery operation when the lubricating oil retaining quantity estimating part 33 estimates that a predetermined quantity or more lubricating oil retains the main refrigerant circuit 2 from the oil separator 4 to the compressor 3 and the hot gas bypass circuit 16. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention can be applied to a refrigeration apparatus having a compressor that is driven by an external drive source and whose rotational speed cannot be arbitrarily controlled, such as a transport refrigeration apparatus having a compressor that is driven by a vehicle traveling engine. It relates to the device.

In the vapor compression refrigeration system, the following method is employed as a lubrication method for lubricating the sliding portion of the compressor.
One is that an oil reservoir is provided in the compressor, the oil reservoir is filled with a certain amount of lubricating oil, and then the lubricating oil is supplied to a required sliding portion via an oil pump. In this method, the sliding portion is lubricated while circulating the lubricating oil. The other is that a predetermined amount of each of the refrigerant and the lubricating oil is sealed in the refrigeration cycle so that a certain proportion of the lubricating oil is contained in the refrigerant sucked into the compressor, and the lubricating oil is mixed with the refrigerant in the refrigeration cycle. This is a system in which each part of the compressor is lubricated by the lubricating oil contained in the refrigerant that is circulated and sucked into the compressor. Even in the former method, it is inevitable that a part of lubricating oil dissolved in the refrigerant discharged from the compressor is circulated in the refrigerant circuit.

  In the above refrigeration system, an oil separator is provided in the discharge pipe of the compressor, and the lubricating oil discharged together with the refrigerant from the compressor is separated by this oil separator, and the configuration in which the lubricating oil is returned to the compressor is widely put into practical use. Has been. This is to eliminate the poor lubrication that occurs when the compressor is in a state of lack of lubricating oil. In a transport refrigeration apparatus or a refrigerator refrigeration apparatus applied to a refrigeration vehicle or the like, Patent Document 1 discloses that the lubricating oil separated by an oil separator is returned to an oil sump of a compressor through an oil return circuit. A certain amount of lubricating oil is shown stored in the oil sump of the compressor. Patent Document 2 discloses a configuration in which the lubricating oil separated by the oil separator is recovered to the compressor side by performing an oil recovery operation.

However, in these refrigeration devices, the main refrigerant circuit side including the condenser, receiver and evaporator from the oil separator to the compressor, or the hot gas bypass circuit side provided by bypassing the condenser and receiver in the main refrigerant circuit, flows out, The lubricating oil staying there cannot be positively collected on the compressor side.
On the other hand, in a building air-conditioning air conditioner with a long refrigerant pipe, the cumulative outflow amount of lubricating oil flowing out from the compressor is calculated based on a predetermined formula, and this is set to a predetermined outflow amount limit value. For example, Patent Document 3 proposes a configuration in which an oil recovery operation is performed when the oil reaches the compressor and the lubricating oil is forcibly recovered in the compressor. In this case, the oil recovery operation is performed by controlling the rotational speed of the compressor to an arbitrary set rotational speed by an inverter and opening the expansion valve at the set opening.

Japanese Laid-Open Patent Publication No. 4-217761 JP-A-5-141792 JP 2005-351598 A

By the way, a transport refrigeration apparatus applied to a refrigeration vehicle or the like includes an independent engine (referred to as a sub-engine) or a sub-engine type in which a compressor is driven by a motor, and a vehicle travel engine. There is a direct connection type in which a compressor is driven. Among them, in the direct connection type, since the rotational speed of the compressor is determined by the speed of the vehicle or the transmission gear ratio, the rotational speed of the compressor cannot be arbitrarily controlled for the convenience of the refrigerator.
Therefore, in such a refrigeration system, the lubricating oil that flows out to the main refrigerant circuit and hot gas bypass circuit including the condenser, receiver, evaporator, etc. from the oil separator to the compressor and stays in these circuits is compressed. The oil cannot be recovered on the compressor side by the oil recovery operation performed by controlling the rotation speed of the machine.

  In particular, in a low-temperature refrigeration apparatus in which the cooling temperature is set low, the viscosity of the lubricating oil increases due to the low temperature. For this reason, it becomes difficult for the lubricating oil to circulate in the refrigeration cycle together with the refrigerant, and to stay on the refrigerant circuit side. Therefore, in a refrigeration system in which lubricating oil is circulated through a refrigeration cycle together with a refrigerant and each part of the compressor is lubricated by the lubricating oil contained in the refrigerant sucked into the compressor, the lubricating oil in the intended ratio is not necessarily provided. In some cases, the refrigerant is not contained in the suction refrigerant, and as a result, the compressor may be poorly lubricated.

  The present invention has been made in view of such circumstances, and can always supply an appropriate amount of lubricating oil from an oil separator into the refrigerant sucked into the compressor, thereby stably lubricating the compressor. An object is to provide a refrigeration apparatus.

In order to solve the above problems, the refrigeration apparatus of the present invention employs the following means.
That is, the refrigeration apparatus according to the present invention is driven by an external drive source and cools the compressor, the oil separator, the condenser, the receiver, the expansion valve, and the inside of the refrigerator whose rotation speed depends on the external drive source. Are connected in parallel to the condenser, the receiver, and the expansion valve via a bypass circuit solenoid valve and discharged from the compressor. A hot gas bypass circuit that bypasses the high-temperature and high-pressure refrigerant gas to the evaporator, and an oil return circuit that returns the lubricating oil separated by the oil separator to the suction pipe of the compressor, and the main refrigerant circuit includes a refrigerant. And a refrigeration apparatus in which a predetermined amount of lubricating oil is sealed, the main refrigerant circuit between the oil separator and the compressor, and the front A lubricating oil retention amount estimation unit that estimates a retention amount of the lubricating oil that is retained in a hot gas bypass circuit, and the main refrigerant circuit between the oil separator and the compressor, and the lubricating oil retention amount estimation unit, and When it is estimated that a predetermined amount or more of the lubricating oil stays in the hot gas bypass circuit, a controller that performs a lubricating oil recovery operation by flowing a refrigerant through both the main refrigerant circuit and the hot gas bypass circuit; It is characterized by having.

For example, in a transport refrigeration apparatus having a compressor driven by a vehicle travel engine, the rotational speed of the compressor is determined by the speed of the vehicle or the transmission gear ratio. For this reason, it is not possible to perform an oil recovery operation in which the rotational speed of the compressor is arbitrarily controlled to recover the lubricating oil staying in the refrigerant circuit.
However, according to the present invention, when it is estimated by the lubricating oil retention amount estimation unit that a predetermined amount or more of lubricating oil is retained in the main refrigerant circuit and the hot gas bypass circuit between the oil separator and the compressor, the control is performed. The refrigerant can be supplied to both the main refrigerant circuit and the hot gas bypass circuit by the unit, and the lubricating oil recovery operation can be performed. That is, by flowing the refrigerant through both the main refrigerant circuit and the hot gas bypass circuit, the density of the refrigerant sucked into the compressor is increased, and the refrigerant circulation amount is increased. Accordingly, the flow rate of the refrigerant can be increased, and the lubricating oil staying in the circuit can be conveyed by the refrigerant flow, and the lubricating oil can be recovered in the oil separator through the compressor. In addition, if the refrigerant flows through the evaporator from both the main refrigerant circuit and the hot gas bypass circuit in a state where the temperature in the refrigerator is low, the evaporation pressure of the evaporator becomes higher than the air temperature in the refrigerator, and the refrigerant condenses and liquids in the evaporator. A refrigerant is generated. This liquid refrigerant can be carried while washing away the lubricating oil adhering to the inner wall of the evaporator heat exchange tube or refrigerant pipe, etc., and can be recovered in the oil separator via the compressor. In addition, when the lubricant recovery operation is performed during defrost operation or heating operation in which the refrigerant is circulated through the hot gas bypass circuit, the lubricating oil remaining in the liquid refrigerant of the condenser and receiver should also be recovered. Can do. For this reason, in the refrigeration apparatus having a configuration in which the rotational speed of the compressor cannot be arbitrarily controlled, a proper lubricating oil recovery operation can be performed by appropriately performing a lubricating oil recovery operation and always ensuring an appropriate lubricating oil surface in the oil separator. Therefore, an appropriate proportion of lubricating oil can always be supplied from the oil return circuit to the refrigerant sucked into the compressor, and the lubrication failure of the compressor can be reliably eliminated.

  Furthermore, in the refrigeration apparatus according to the present invention, in the refrigeration apparatus, the lubricating oil retention amount estimation unit includes a temperature sensor provided in the oil return circuit, and a detected value by the temperature sensor is substantially equal to a discharge pressure saturation temperature. Or the temperature of the substantially discharged refrigerant gas, and it is estimated whether or not the retention amount of the lubricating oil is equal to or greater than a predetermined amount.

  According to the present invention, since the lubricating oil retention amount estimation unit includes the temperature sensor provided in the oil return circuit, whether or not the lubricating oil is held in the oil separator from the detected value of the temperature sensor. Can be estimated. In other words, when the lubricating oil is flowing through the oil return circuit, the detected value of the temperature sensor is approximately the discharge pressure saturation temperature, and when the lubricating oil is flowing, it is approximately the discharged refrigerant gas temperature. By using this, when the circulation of the discharged refrigerant gas is detected, it can be determined that the lubricating oil is not held in the oil separator and the discharged refrigerant gas is circulating through the oil return circuit. . As a result, it can be estimated that a predetermined amount or more of the lubricating oil stays in the main refrigerant circuit and the hot gas bypass circuit between the oil separator and the compressor. In this case, the lubricating oil level can be quickly restored in the oil separator by causing the control unit to perform the lubricating oil recovery operation. Accordingly, an appropriate amount of lubricating oil can be supplied from the oil return circuit into the refrigerant sucked into the compressor, and the compressor can be continuously lubricated appropriately.

  Furthermore, in the refrigeration apparatus of the present invention, in the above refrigeration apparatus, the lubricating oil retention amount estimation unit holds a table that defines a relationship between an oil return circuit temperature and a degree of dilution of the lubricant in the oil separator by a refrigerant, Lubricating oil dilution is obtained from the oil return circuit temperature detected by the temperature sensor based on the table, and when the lubricating oil dilution is equal to or greater than a predetermined value, the bypass circuit solenoid valve is opened by the control unit. It is characterized by.

  If the amount of refrigerant dissolved in the lubricating oil in the oil separator is large, this expands and the temperature of the lubricating oil in the oil returning circuit decreases, so that the temperature of the lubricating oil flowing in the oil returning circuit is maintained in the oil separator. The degree of dilution of the lubricating oil with the refrigerant can be estimated. On the other hand, if the dilution of the lubricating oil with the refrigerant is high, it means that the ratio of the lubricating oil in the liquid flowing through the oil return circuit is small, which affects the lubrication of the compressor. According to the present invention, when the dilution degree of the lubricating oil in the oil separator is equal to or greater than a predetermined value, the refrigerant dissolved in the lubricating oil in the oil separator is quickly removed by opening the hot gas bypass circuit by the bypass circuit solenoid valve. Evaporation can reduce the dilution of the lubricating oil. Therefore, an appropriate amount of lubricating oil can always be supplied to the compressor, stable lubrication can be performed, and the reliability of the compressor can be improved.

  Furthermore, in the refrigeration apparatus of the present invention, in the above refrigeration apparatus, the lubricating oil retention amount estimation unit stores a lubricant oil removal amount per hour from the oil separator corresponding to each operation state obtained in advance. And determining whether or not the retention amount of the lubricating oil is greater than or equal to a predetermined amount based on the lubricant removal amount per hour stored in the storage unit and the operation continuation time in each operation state It is characterized by that.

  According to the present invention, the lubricating oil retention amount estimation unit includes the amount of lubricating oil removed from the oil separator corresponding to each operation state stored in the storage unit, and the operation duration time in each operation state. Based on the above, it can be estimated whether or not the retention amount of the lubricating oil is greater than or equal to a predetermined amount. That is, the main refrigerant circuit between the oil separator and the compressor is obtained when the result obtained by integrating the lubricant removal amount per time obtained in advance with the operation duration time in each operation state becomes an arbitrary ratio of the oil separator capacity. Further, it can be estimated that a predetermined amount or more of the lubricating oil stays in the hot gas bypass circuit. In this case, the lubricating oil surface can be quickly restored in the oil separator by performing the lubricating oil recovery operation by the control unit. Therefore, an appropriate amount of lubricating oil can be supplied into the refrigerant sucked into the compressor via the oil return circuit, and the compressor can be continuously lubricated appropriately. Moreover, since this lubricating oil retention amount estimation part does not require hardware devices, such as an oil return circuit temperature sensor, it can be implement | achieved at low cost.

  According to the present invention, even in a refrigeration apparatus equipped with a compressor that is driven by an external drive source and whose rotational speed depends on the external drive source, the lubricating oil recovery operation is performed as appropriate to the main refrigerant circuit and hot gas bypass circuit side. The refrigerant that has flowed out and stayed is collected in the oil separator, and an appropriate lubricating oil surface can be secured in the oil separator. Therefore, an appropriate proportion of lubricating oil can always be supplied from the oil return circuit to the refrigerant sucked into the compressor, and the lubrication failure of the compressor can be reliably eliminated.

Embodiments according to the present invention will be described below with reference to the drawings.
[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to FIG.
FIG. 1 shows a configuration diagram of a refrigeration apparatus 1 according to the present embodiment. The main refrigerant circuit 2 of the refrigeration apparatus 1 is discharged from the compressor 3 that compresses the refrigerant gas, the oil separator 4 that separates the lubricating oil contained in the refrigerant gas discharged from the compressor 3, and the compressor 3. A capacitor 5 that dissipates and condenses high-temperature and high-pressure refrigerant gas by heat exchange with the outside air, a receiver 6 that stores liquid refrigerant condensed by the capacitor 5, and a desiccant that removes moisture in the refrigerant circuit 2 are filled. The dryer 7, the sight glass 8 for monitoring the state of the refrigerant circulating in the refrigerant circuit 2, the gas-liquid heat exchanger 9 for exchanging heat between the liquid refrigerant and the gas refrigerant evaporated by the evaporator 11, and the liquid refrigerant. An expansion valve 10 for adiabatic expansion, an evaporator 11 for evaporating the refrigerant by exchanging heat between the adiabatic-expanded refrigerant and the internal air, and a liquid component in the vaporized gas refrigerant is separated to compress only the gas refrigerant. Suck into 3 And accumulator 12 to be constructed by connecting a refrigerant pipe 13 in this order.
The main refrigerant circuit 2 is filled with a predetermined amount of refrigerant and lubricating oil.

The refrigeration apparatus 1 is an engine direct-coupled transport refrigeration apparatus that is mounted on a refrigeration vehicle or the like and in which the compressor 3 is driven by a vehicle travel engine (not shown) via an electromagnetic clutch or the like. An evaporator unit 15 including the evaporator 11, the gas-liquid heat exchanger 9, the expansion valve 10, the accumulator 12, and the like is installed inside the refrigerator 14 shown by a two-dot chain line in FIG. The
The main refrigerant circuit 2 branches from the downstream refrigerant pipe 13 of the oil separator 4, the other end is connected to the inlet side of the evaporator 10, and the high-temperature and high-pressure refrigerant gas discharged from the compressor 3 is introduced into the evaporator 11. A hot gas bypass circuit 16 is provided for configuring a defrost cycle or a heating cycle. The hot gas bypass circuit 16 is provided with a bypass circuit solenoid valve 17, a drain pan heater 18 disposed below the evaporator 11, and a flow rate adjusting capillary tube 19.

  The refrigerant pipe 13 between the condenser 5 and the receiver 6 is provided with an electromagnetic valve 20 that is opened during the cooling operation and is controlled to be opened and closed by detecting the discharge pressure of the compressor 3 during the defrost or heating operation. The solenoid valve 20 is opened when the pressure detected by the discharge pressure sensor 28 is equal to or higher than a set pressure during defrosting or heating operation, and a part of the refrigerant in the defrosting cycle or heating cycle is passed through the condenser 5 to the receiver. 6 is charged. In addition, the refrigerant pipe 13 between the receiver 6 and the expansion valve 10 is opened during the cooling operation, and the discharge pressure of the compressor 3 is detected during the defrosting or heating operation, and the opening / closing control is performed continuously or intermittently. A solenoid valve 21 is provided. When the pressure detected by the discharge pressure sensor 28 is equal to or lower than the set pressure during defrost or heating operation, the solenoid valve 21 is continuously or intermittently opened, and the refrigerant in the receiver 6 is removed during the defrost cycle or heating cycle. To be released.

  A liquid bus path circuit 23 having an electromagnetic valve 22 is provided between the downstream refrigerant pipe 13 of the electromagnetic valve 21 and the downstream refrigerant pipe 13 of the accumulator 12. In the liquid bus path circuit 23, when the discharge refrigerant temperature of the compressor 3 detected by the discharge temperature sensor 29 is equal to or higher than a set value, the solenoid valve 22 is opened and a part of the liquid refrigerant is drawn into the intake refrigerant pipe of the compressor 3. 13 to bypass the compressor 3 and cool the compressor 3. Further, the suction refrigerant pipe 13 of the compressor 3 is provided with a pressure adjusting valve 24 that senses this when the discharge pressure of the compressor 3 rises and lowers the low pressure.

The oil separator 4 is provided with an oil return circuit 25 that returns the separated lubricating oil to the suction refrigerant pipe 13 of the compressor 3. The oil return circuit 25 is provided with a capillary tube 26 for flow rate adjustment and an oil return circuit temperature sensor 27.
Further, the suction refrigerant pipe 13 of the compressor 3 is provided with a low pressure sensor 30 and an intake gas temperature sensor 31. The detection values of the low pressure sensor 30 and the intake gas temperature sensor 31 and the discharge pressure sensor 28 and the discharge temperature sensor 29 described above are input to the control unit 32, respectively. The controller 32 controls opening / closing of the solenoid valves 17, 20, 21, and 22 as will be described later.

  Further, the detected value of the oil return circuit temperature sensor 27 is based on the detected value based on the detected amount of the lubricating oil staying in the main refrigerant circuit 2 and the hot gas bypass circuit 16 between the oil separator 4 and the compressor 3. This is input to the estimated lubricant retention amount estimation unit 33. When it is estimated that a predetermined amount or more of lubricating oil is retained in the main refrigerant circuit 2 and the hot gas bypass circuit 16 between the oil separator 4 and the compressor 3, the lubricating oil retention amount estimation unit 33 passes the control unit 32. Thus, the solenoid valves 17, 20, and 21 are opened, and the lubricant is supplied to both the main refrigerant circuit 2 and the hot gas bypass circuit 16 to execute the lubricant recovery operation.

Next, the operation of the refrigeration apparatus 1 according to the present embodiment will be described.
First, the cooling operation will be described. During the cooling operation, the refrigerant compressed by the compressor 3 flows into the oil separator 4 through the discharge refrigerant pipe 13. With this oil separator 4, most of the lubricating oil that dissolves in the refrigerant and is discharged from the compressor 3 together with the refrigerant is separated. The refrigerant from which the lubricating oil has been separated flows into the condenser 5 and is heat-exchanged with the outside air in the condenser 5 to be condensed and liquefied. This liquid refrigerant is guided to the receiver 6 through the electromagnetic valve 20 by the liquid refrigerant pipe 13. The refrigerant temporarily stored in the receiver 6 passes through the dryer 7, the sight glass 8, and the electromagnetic valve 21, and is heat-exchanged with the low-pressure gas refrigerant from the evaporator 11 in the gas-liquid heat exchanger 9. Led. This refrigerant is adiabatically expanded by the expansion valve 10 to become a low-temperature and low-pressure gas-liquid two-phase refrigerant and flows into the evaporator 11.

The refrigerant flowing into the evaporator 11 is heat-exchanged with the air in the cooler 14 circulated by an evaporator fan (not shown), and cools and evaporates the cooler air. As the cooling air is circulated in the cabinet, the inside of the refrigerator 14 is cooled to a predetermined temperature. The refrigerant evaporated in the evaporator 11 is guided to the compressor 3 through the gas-liquid heat exchanger 9 and the accumulator 12 through the suction refrigerant pipe 13.
As described above, when the refrigerant is circulated in the main refrigerant circuit 2, the cooling operation for cooling the inside of the refrigerator 14 is performed.

The defrosting operation or the heating operation is performed as follows. The defrost operation is an operation that heats and melts the frost formed on the evaporator 11 by the cooling operation, and the heating operation is an operation that heats (heats) the inside of the cooling chamber 14. These operations are performed by the same defrost cycle or heating cycle using the hot gas bypass circuit 16.
When a defrost operation or warming operation command is issued, the control unit 32 opens the bypass circuit electromagnetic valve 17 provided in the hot gas bypass circuit 16 and closes both the electromagnetic valve 20 and the electromagnetic valve 21. As a result, the high-temperature and high-pressure refrigerant (hot gas) discharged from the compressor 3 flows to the hot gas bypass circuit 16 side after the lubricating oil is separated by the oil separator 4, and further flows through the drain pan heater 18 and the capillary tube 19. Then, it flows into the evaporator 11. This refrigerant is dissipated in the evaporator 11 and is used for defrosting the evaporator 11 or heating (heating) in the refrigerator 14. The refrigerant that has flowed out of the evaporator 11 is guided to the compressor 3 through the gas-liquid heat exchanger 9 and the accumulator 12 through the suction refrigerant pipe 13.
By the above defrost cycle or heating cycle, the defrost operation for melting the frost formed on the evaporator 11 or the heating operation for heating (heating) the inside of the refrigerator 14 is performed.

  Further, during the defrosting operation or the heating operation, the discharge pressure is monitored by the discharge pressure sensor 28 so that the discharge pressure is within the set range, and when the discharge pressure rises to a set value or more, the solenoid valve 20 Is opened, and the refrigerant in the defrost cycle or the heating cycle is charged to the receiver 6 through the capacitor 5. Further, when the discharge pressure drops below the set value, the solenoid valve 21 is opened and the refrigerant held in the receiver 6 is released during the defrost cycle or the heating cycle. Thereby, an appropriate amount of the refrigerant can be circulated during the defrost cycle or the heating cycle, and a stable heating ability can be exhibited.

Further, the lubricating oil that has not been separated by the oil separator 4 during the cooling operation, defrosting operation, and heating operation described above flows out to the main refrigerant circuit 2 and hot gas bypass circuit 16 downstream of the oil separator 4. . The lubricating oil that has flowed out to the main refrigerant circuit 2 and the hot gas bypass circuit 16 circulates in the main refrigerant circuit 2 and the hot gas bypass circuit 16 together with the refrigerant, and returns to the compressor 3. In the main refrigerant circuit 2 and the hot gas bypass circuit 16 including the receiver 6, the gas-liquid heat exchanger 9, the evaporator 11, and the accumulator 12.
In particular, during the cooling operation, since the refrigerant flow rate in the evaporator 11 is slow and the refrigerant is circulated in the gas phase, the lubricating oil tends to stay in the evaporator 11. Further, during the defrosting operation and the heating operation, the lubricating oil flows from the branch portion of the hot gas bypass circuit 16 to the condenser 5 side and flows together with a part of the refrigerant naturally condensed in the condenser 5, and the oil-rich state in the liquid refrigerant The lubricating oil is retained.

In this way, the retention amount of the lubricating oil retained in the main refrigerant circuit 2 and the hot gas bypass circuit 16 increases with the passage of operation time. When the retention amount of the lubricating oil increases, the lubricating oil surface in the oil separator 4 is eventually lowered, and the lubricating oil disappears in the oil separator 4. If this happens, the lubricating oil cannot be supplied to the refrigerant sucked into the compressor 3 from the oil return circuit 25, and if this state continues, the lubricating oil in the compressor 3 becomes insufficient, resulting in poor lubrication.
The oil return circuit temperature sensor 27 detects the temperature of the oil return circuit 25 and inputs the detected value to the lubricating oil retention amount estimation unit 33. The lubricant retention amount estimation unit 33 estimates the retention amount of the lubricant remaining in the main refrigerant circuit 2 and the hot gas bypass circuit 16 from the detection value of the oil return circuit temperature sensor 27. That is, when the value detected by the oil return circuit temperature sensor 27 is filled with the lubricating oil in the oil return circuit 25, the discharge pressure saturation temperature is substantially reached, and when the lubricant is exhausted and the discharged refrigerant gas flows, It is possible to estimate whether or not the retention amount of the lubricating oil is equal to or greater than a predetermined amount by utilizing the fact that the refrigerant gas temperature is substantially discharged.

  As described above, when it is detected that the fluid flowing through the oil return circuit 25 uses the temperature difference due to the difference between the lubricating oil or the discharged refrigerant gas and the discharged refrigerant gas is flowing, Therefore, it can be determined that the lubricating oil is not retained and the discharged refrigerant gas flows through the oil return circuit 25 by bypass. Accordingly, it can be estimated that a predetermined amount or more of the lubricating oil is retained in the main refrigerant circuit 2 and the hot gas bypass circuit 16 between the oil separator 4 and the compressor 3. In this case, by using one or more of the discharge pressure sensor 28, the discharge temperature sensor 29, the low pressure sensor 30, and the intake gas temperature sensor 31, the remaining state quantities to be compared are set as the compressor efficiency and the theoretical refrigeration cycle. It can be estimated from characteristics and the like.

Thus, when it is estimated by the lubricating oil retention amount estimation unit 33 that a predetermined amount or more of the lubricating oil is retained in the main refrigerant circuit 2 and the hot gas bypass circuit 16 between the oil separator 4 and the compressor 3, the control is performed. The unit 32 performs a lubricant recovery operation.
The lubricating oil recovery operation is performed by simultaneously opening the solenoid valves 17, 20, and 21 and flowing the refrigerant through both the main refrigerant circuit 2 and the hot gas bypass circuit 16. When the refrigerant flows through both the main refrigerant circuit 2 and the hot gas bypass circuit 16, the density of the refrigerant sucked into the compressor 3 is increased, and the refrigerant circulation amount is increased. As a result, the flow rate of the refrigerant can be increased, so that the lubricating oil staying in the main refrigerant circuit 2 and the hot gas bypass circuit 16 is conveyed by this refrigerant flow, and this lubricating oil is passed through the compressor 3 to the oil. It can be recovered in the separator 4.

  Further, when the refrigerant is allowed to flow through the evaporator 11 from both the main refrigerant circuit 2 and the hot gas bypass circuit 16 in a state where the temperature in the cooling chamber 14 is low, the evaporation pressure of the evaporator 11 becomes higher than the air temperature in the chamber. Then, the refrigerant is condensed and liquid refrigerant is generated. With this liquid refrigerant, the lubricating oil adhering to and staying on the heat exchange tube of the evaporator 11 or the refrigerant pipe 13 is conveyed while being washed away, and this lubricating oil can be recovered in the oil separator 4 via the compressor 3. Further, when the lubricating oil recovery operation is performed during the defrost operation or the heating operation in which the refrigerant is circulated through the hot gas bypass circuit 16, the lubricating oil that has remained in the liquid refrigerant of the capacitor 5 and the receiver 6 is retained. It can be recovered.

Thus, according to the present embodiment, the following effects can be obtained.
In the refrigeration apparatus 1 having a configuration in which the rotational speed of the compressor is arbitrarily controlled and the lubricating oil recovery operation cannot be performed, the lubricating oil recovery operation is appropriately performed, and an appropriate oil level of the lubricating oil is always provided in the oil separator 4. Can be secured.
Accordingly, since an appropriate ratio of lubricating oil can be supplied from the oil return circuit 25 to the refrigerant sucked into the compressor 3 and the compressor 3 can continue to be properly lubricated, the lubrication failure of the compressor 3 can be reliably ensured. Can be resolved.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIG.
The present embodiment is different from the first embodiment in that it has a function of reducing the dilution degree of the lubricating oil retained in the oil separator 4 by the refrigerant. The other points are the same as in the first embodiment, and a description thereof will be omitted.
In the present embodiment, the lubricating oil retention amount estimation unit 33 stores a table 34 that defines the relationship between the temperature of the oil return circuit 25 and the dilution of the lubricating oil in the oil separator 4 by the refrigerant. The dilution degree of the lubricating oil can be obtained based on the table 34 from the oil return circuit temperature detected by the oil return circuit temperature sensor 27. When the lubricating oil dilution is equal to or greater than a predetermined value, the control unit 32 opens the bypass circuit solenoid valve 17 of the hot gas bypass circuit 16.

  If the amount of refrigerant dissolved in the lubricating oil in the oil separator 4 is large, this expands and the temperature of the lubricating oil in the oil returning circuit 25 is lowered. The degree of dilution of the lubricating oil held in the refrigerant by the refrigerant can be estimated. On the other hand, if the degree of dilution of the lubricating oil with the refrigerant is high, the ratio of the lubricating oil in the liquid flowing through the oil return circuit 25 is reduced, which affects the lubrication of the compressor 3. According to the present embodiment, when the dilution of the lubricating oil in the oil separator 4 is equal to or greater than a predetermined value, the hot gas bypass circuit 16 is opened to quickly evaporate the refrigerant dissolved in the lubricating oil, so that the lubricating oil The degree of dilution can be reduced. As a result, an appropriate amount of lubricating oil can always be supplied to the compressor 3, stable lubrication can be performed, and the reliability of the compressor 3 can be improved.

[Third Embodiment]
Next, a third embodiment of the present invention will be described with reference to FIGS.
The present embodiment differs from the first embodiment in the configuration of the lubricating oil retention amount estimation unit 43. The other points are the same as in the first embodiment, and a description thereof will be omitted.
The lubricating oil retention amount estimation unit 43 of the present embodiment has a storage unit 44 that stores the amount of lubricating oil removed per hour from the oil separator 4 corresponding to each operation state obtained in advance. The lubricating oil retention amount estimation unit 43 is based on the lubricant removal amount per time stored in the storage unit 44 and the operation continuation time in each operation state, and the main refrigerant circuit 2 and the hot gas bypass circuit 16. It is estimated whether or not the retention amount of the lubricating oil retained in is not less than a predetermined amount.

  The lubricant removal amount per hour from the oil separator 4 is stored in the storage unit 44 in the form of a map. The lubricant removal amount per time is expressed as a function of the low pressure as shown in FIG. In other words, the actual removal amount of the lubricating oil is somewhere between the removal amount when the rotation speed of the compressor 3 is at the maximum rotation and the removal amount at the time of the minimum rotation. In the embodiment, the lubricant removal amount per hour at the time of maximum rotation at which the lubricant removal amount increases is set as a function expression with the low pressure. The main refrigerant circuit 2 between the oil separator 4 and the compressor 3 is obtained when the result of integrating the lubricant removal amount per time with the duration of each operation state becomes an arbitrary ratio of the capacity of the oil separator 4. Further, the amount of staying of the lubricating oil staying in the hot gas bypass circuit 16 is estimated to be a predetermined amount or more, and the solenoid valve 17, 20, 21 is opened by the control unit 32 to execute the lubricating oil recovery operation.

  As described above, according to the present embodiment, the result of integrating the amount of lubricant oil removed per hour from the oil separator 4 obtained in advance with the operation duration time in each operation state is an arbitrary ratio of the oil separator capacity. Then, it is estimated that a predetermined amount or more of the lubricating oil stays in the main refrigerant circuit 2 and the hot gas bypass circuit 16 between the oil separator 4 and the compressor 3, and the lubricating oil recovery operation can be performed. By this lubricating oil recovery operation, the oil level of the lubricating oil can be quickly restored in the oil separator 4 as in the first embodiment. Therefore, an appropriate amount of lubricating oil can always be supplied into the refrigerant sucked into the compressor 3 via the oil return circuit 25, and the compressor 3 can be continuously lubricated appropriately. Further, the lubricant retention amount estimation unit 43 of the present embodiment does not require a hardware device such as a temperature sensor, and can be realized in software, and thus can be realized at low cost.

  In each of the embodiments described above, sensors such as the discharge pressure sensor 28, the discharge temperature sensor 29, the low pressure sensor 30, and the intake gas temperature sensor 31 other than the oil return circuit temperature sensor 27 provided in the oil return circuit 25 are as follows. In general, it is provided as an indispensable component device in the refrigeration apparatus, and does not need to be newly provided in the present invention, and an existing sensor can be used.

It is a block diagram of the freezing apparatus which concerns on 1st and 2nd embodiment of this invention. It is a block diagram of the control part of the freezing apparatus which concerns on 3rd Embodiment of this invention. It is a figure of the map which shows the relationship between the low pressure pressure used for 3rd Embodiment of this invention, and the amount of lubricant oil removal per time.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Refrigeration apparatus 2 Main refrigerant circuit 3 Compressor 4 Oil separator 5 Capacitor 6 Receiver 10 Expansion valve 11 Evaporator 13 Refrigerant piping 14 Cooling chamber 16 Hot gas bypass circuit 17 Bypass circuit solenoid valves 20 and 21 Solenoid valve 25 Oil return circuit 27 Oil return Circuit temperature sensor 32 Control unit 33, 43 Lubricating oil retention amount estimation unit 34 Table 44 Storage unit (map)

Claims (4)

A compressor that is driven by an external drive source and whose rotation speed depends on the external drive source, an oil separator, a condenser, a receiver, an expansion valve, and an evaporator that cools the inside of the refrigerator are sequentially connected by a refrigerant pipe. A main refrigerant circuit composed of
A hot gas bypass circuit that is connected in parallel to the condenser, the receiver, and the expansion valve via a bypass circuit solenoid valve, and that bypasses high-temperature and high-pressure refrigerant gas discharged from the compressor to the evaporator;
An oil return circuit for returning the lubricating oil separated by the oil separator to the suction pipe of the compressor,
A refrigerating apparatus in which a predetermined amount of refrigerant and lubricating oil are sealed in the main refrigerant circuit,
A lubricating oil retention amount estimation unit for estimating a retention amount of the lubricating oil remaining in the main refrigerant circuit and the hot gas bypass circuit between the oil separator and the compressor;
When the lubricating oil retention amount estimation unit estimates that a predetermined amount or more of the lubricating oil is retained in the main refrigerant circuit and the hot gas bypass circuit between the oil separator and the compressor, the main refrigerant A refrigerating apparatus comprising: a controller that performs a lubricant recovery operation by flowing a refrigerant through both the circuit and the hot gas bypass circuit. The lubricating oil retention amount estimation unit includes a temperature sensor provided in the oil return circuit,
2. The method according to claim 1, further comprising: determining whether a detected value by the temperature sensor is a substantially discharge pressure saturation temperature or a substantially discharge refrigerant gas temperature, and estimating whether or not the retention amount of the lubricating oil is a predetermined amount or more. The refrigeration apparatus described in 1. The lubricating oil retention amount estimation unit holds a table that defines the relationship between the oil return circuit temperature and the dilution of the lubricating oil in the oil separator by the refrigerant,
Lubricating oil dilution is obtained from the oil return circuit temperature detected by the temperature sensor based on the table, and when the lubricating oil dilution is equal to or greater than a predetermined value, the bypass circuit solenoid valve is opened by the control unit. The refrigeration apparatus according to claim 2. The lubricating oil retention amount estimation unit includes a storage unit that stores the amount of lubricating oil removed per hour from the oil separator corresponding to each operation state obtained in advance.
Based on the lubricant removal amount per time stored in the storage unit and the operation continuation time in each operation state, it is estimated whether or not the retention amount of the lubricant is equal to or greater than a predetermined amount. The refrigeration apparatus according to claim 1.

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