KR101940488B1 - Refrigerating cycle and method for operating the refrigerating cycle - Google Patents

Abstract

The present invention relates to a refrigeration cycle apparatus and a method of operating the refrigeration cycle apparatus. In the case of a refrigeration cycle in which a plurality of compressors are serially connected in series for multi-stage compression, the internal space of each compressor and the piping of the refrigeration cycle are connected to each other by an oil return pipe. In the pressure equalization process, So that the oil can be uniformly maintained in the plurality of compressors, thereby preventing the friction loss and the power consumption of the compressor caused by the oil shortage from being raised in advance In addition, it is possible to improve the cooling efficiency by simplifying the apparatus and the piping for eliminating the oil imbalance between the compressors.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a refrigeration cycle apparatus and a method of operating the same,

The present invention relates to a refrigeration cycle apparatus and a method of operating the refrigeration cycle apparatus, and more particularly to a refrigeration cycle apparatus having a plurality of compressors and a method of operating the refrigeration cycle.

Generally, the refrigeration cycle apparatus is a device for maintaining the inside of a refrigerator such as a refrigerator at a low temperature by using a refrigeration cycle including a compressor, a condenser, an inflator and an evaporator. The refrigeration cycle unit uses oil to protect the compressor from mechanical friction and the oil circulates in the refrigeration cycle together with the high temperature and high pressure refrigerant gas discharged from the compressor.

If the oil accumulates in the condenser, the evaporator or the cycle piping of the refrigeration cycle, the capacity of the refrigeration cycle is lowered and the amount of oil in the compressor becomes insufficient, causing the compressor to be burned.

In a refrigeration cycle with one compressor, the refrigerant is recovered and returned to the inlet, so that the amount of oil recovered can be known. Therefore, by controlling the operation of the compressor in consideration of the oil recovery amount, it is possible to prevent the degradation of the capacity of the refrigeration cycle or the failure of the compressor due to oil shortage.

However, in a refrigeration cycle having a plurality of compressors, the refrigerant and the oil may be heavily concentrated in one compressor depending on the operation mode, and thus the performance of the refrigeration cycle due to oil shortage or the failure of the compressor may occur in the other compressor .

In the conventional refrigeration cycle apparatus in which a plurality of compressors are connected to each other as described above, the oil filled in each compressor at the time of operation of the refrigeration cycle apparatus is discharged to the refrigeration cycle in the compressor together with the refrigerant, thereby causing an oil imbalance between the compressors I could. Particularly, when a plurality of compressors are connected in series to perform multi-stage compression of refrigerant, since the amount of movement of oil is different from each other, the oil is concentrated in one compressor and the friction loss and power consumption .

In addition, in the case of installing a separate microfluidic device outside the compressor in order to eliminate oil imbalance between the microfluidic devices in a refrigeration cycle device having a plurality of compressors, the space occupied by the installation of the microfluidic device is expanded, The piping for connection with the compressor becomes complicated and the flow resistance of the air increases, so that the cooling efficiency for the condenser is lowered.

An object of the present invention is to provide a compressor capable of preventing a refrigerating cycle from being operated in a state in which oil is concentrated in one compressor when a plurality of compressors are provided and preventing a friction loss or a power consumption from being increased due to oil shortage A refrigeration cycle device and a method of operating the refrigeration cycle device.

It is another object of the present invention to provide a refrigeration cycle apparatus having a plurality of compressors, which simplifies the apparatus and piping for eliminating the oil imbalance between the compressors, thereby reducing the space occupied by the apparatus for eliminating oil imbalances in the refrigeration cycle apparatus The present invention provides a refrigeration cycle apparatus and a method of operating the refrigeration cycle apparatus that can simplify the piping and reduce the flow resistance of the air to improve the cooling efficiency of the condenser.

In order to achieve the object of the present invention, there is provided a refrigeration cycle apparatus having a plurality of compressors including a predetermined amount of oil, wherein the determination unit determines whether the oil is biased by one compressor among the plurality of compressors; And an oil recovery unit that performs an equalizing operation by a pressure difference between a plurality of compressors in accordance with the contents determined by the determination unit.

In addition, a low-stage compressor and a high-stage compressor are connected in series, a condenser is connected to a discharge side of the high-stage compressor, a machine room fan is installed at one side of the condenser, a refrigerant switching valve is connected to an outlet of the condenser, Wherein the refrigerant switching valve includes a lower stage measuring outlet and a higher stage measuring rod so that the lower stage outlet is connected to the lower stage evaporator while the higher stage outlet is connected to the higher stage evaporator and the lower stage evaporator is connected to the suction side Stage compressor is connected to the suction side of the high-stage compressor, while the high-stage evaporator is connected to the suction side of the high-stage compressor, determining whether the equalizing operation is necessary between the low-stage compressor and the high- And performing a step of performing oil-lubricant transfer in which the oil is moved to a compressor having a small oil in an oil-rich compressor if the oil-equalizing operation is determined to be necessary. In the oil-equalizing operation, Opening both the low-stage measurement outlet of the refrigerant switching valve and the high-stage measurement outlet of the refrigerant switching valve for a predetermined time in a state where all of the compressors are stopped; A step of circulating the oil through the cycle, an operation of recovering oil by the low-stage compressor, and an operation of recovering oil by the high-stage compressor may be provided.

The refrigeration cycle apparatus and the method of operating the refrigeration cycle apparatus according to the present invention can prevent the friction loss and the power consumption of the compressor caused by oil shortage from being raised by maintaining the oil uniformly in a plurality of compressors by using the operation algorithm can do.

In addition, the apparatus and piping for eliminating the oil imbalance between the compressors can be simplified to secure a wide mechanical space in which the compressor is installed, thereby enhancing the heat radiation effect of the condenser, thereby enhancing the cooling efficiency of the refrigeration cycle apparatus.

In addition, by performing the oil equalization operation periodically using the timer or the oil level sensor, it is possible to more effectively prevent the oil concentration between the compressors.

1 is a perspective view schematically illustrating a refrigerator for explaining a refrigeration cycle apparatus of the present invention,
FIG. 2 is a block diagram of a refrigeration cycle apparatus applied to the refrigerator of FIG. 1;
3 is a block diagram showing a control unit for controlling a refrigeration cycle according to the present embodiment.
FIG. 4 is a systematic diagram showing a refrigeration cycle controlled by the control unit according to FIG. 3;
FIG. 5 is a flowchart illustrating an operation algorithm of a refrigeration cycle according to an embodiment of the present invention,
FIG. 6 is a block diagram showing an embodiment of the equalizing operation in the flowchart according to FIG. 5;
FIG. 7 is a graph showing a change in pressure at the time of stoppage to explain the effect of the driving algorithm shown in FIG. 5,
Figs. 8 and 9 are front views showing respective embodiments of the oil level sensor according to the present embodiment,
FIG. 10 is a systematic diagram showing a refrigeration cycle having a high-stage oil recovery unit and a low-stage oil recovery unit in the refrigeration cycle according to FIG.
FIG. 11 is a block diagram showing another embodiment of the oil equalizing operation in the flowchart according to FIG. 5, and is a block diagram showing an algorithm for performing continuous equalizing operation by using a high stage oil recovery unit and a low stage oil recovery unit.
12 is a front view showing an embodiment of the oil recovery passage according to the present embodiment,
FIG. 13 is a front view showing the oil return valve of FIG. 12;
FIG. 14 is a front view showing another embodiment of the oil recovery passage according to the present embodiment. FIG.
Fig. 15 is a sectional view showing the operation of the oil recovery valve in the oil recovery passage according to Fig. 14,
16 is a front view showing another embodiment of the oil recovery passage according to the present embodiment,
FIG. 17 is a front view showing another embodiment of the oil recovery passage in FIG. 16;
18 is a front view showing another embodiment of the oil return passage according to the present embodiment,
19 and 20 are sectional views showing an oil separator applied to the oil recovery passage according to FIG. 18;
FIG. 21 is a flow diagram of the refrigeration cycle apparatus according to FIG. 2, showing a case where the refrigerant switching valve is a four-way valve;
22 is a sectional view showing an embodiment of a secondary compressor having an oil recovery passage in a refrigeration cycle apparatus according to the present invention.

Hereinafter, the refrigeration cycle apparatus and the operation method of the refrigeration cycle apparatus according to the present invention will be described in detail with reference to an embodiment shown in the accompanying drawings.

FIG. 1 is a perspective view schematically illustrating a refrigerator for explaining a refrigeration cycle apparatus of the present invention, and FIG. 2 is a system diagram of a refrigeration cycle apparatus applied to the refrigerator of FIG.

1 and 2, a refrigerator having a refrigeration cycle according to the present embodiment includes a refrigerator body 1 having a freezing chamber and a refrigerating chamber, a freezing chamber door 1 for opening and closing the freezing chamber and the refrigerating chamber of the refrigerator body 1, (2) and a refrigerator compartment door (3).

A machine room is provided on the lower side of the refrigerator main body 1 and a plurality of compressors 11 and 12 and a single condenser 13 in a refrigeration cycle for generating cold air are installed in the machine room. The plurality of compressors 11 and 12 are arranged such that the refrigerant compressed in one stage by the relatively low pressure primary compressor 11 is compressed in two stages by the relatively high pressure secondary compressor 12, Is connected to the inlet of the secondary compressor (12) by the first refrigerant pipe (21). The discharge port of the secondary compressor (12) is connected to the inlet of the condenser (13) by a second refrigerant pipe (22). The capacity of the primary compressor (11) and the secondary compressor (12) can be designed to be the same, but in the case of a refrigerator, the capacity of the secondary compressor (12) 11 can be designed to be approximately twice as large as the capacity of the first embodiment.

The refrigerant switching valve 16 for distributing the flow direction of the refrigerant in the direction of the first evaporator 14 or the second evaporator 15 to be described later is connected to the outlet of the condenser 13 by the third refrigerant pipe 23.

The refrigerant switching valve 16 may be a three-way valve. For example, the refrigerant switching valve 16 is provided with an inlet 16a connected to the outlet of the condenser 12, and is selectively connected to the inlet 16a of the refrigerant switching valve 16, A second outlet 16b and a second outlet 16c may be formed. A first branch tube (L1) is connected to the first outlet (16b), and a second branch tube (L2) is connected to the second outlet (16c).

A first inflator 17 is connected to the first branch tube L1 and a fourth refrigerant tube 24 is connected to the outlet of the first inflator 17 and a fourth refrigerant tube 24 is connected to the fourth refrigerant tube 24 to cool the freezer compartment. The first evaporator 14 is connected.

The second inflator 18 is connected to the second branch pipe L2 and the fifth refrigerant pipe 25 is connected to the outlet of the second inflator 18. The fifth refrigerant pipe 25 cools the refrigerating compartment And the second evaporator 14 is connected.

Here, the first evaporator 14 and the second evaporator 15 may have the same capacity, but the second evaporator 15 may be formed in a larger capacity than the first evaporator 14 like a compressor. In addition, blowing fans 14a and 15a may be installed at one side of the first evaporator 14 and the second evaporator 15, respectively.

The outlet of the first evaporator 14 is connected to the suction side of the primary compressor 11 by the sixth refrigerant tube 26 while the outlet of the second evaporator 15 is connected to the suction side of the first compressor 11 by the seventh refrigerant tube 27 Is connected to the suction side of the secondary compressor (12). However, the seventh refrigerant tube 27 is not directly connected to the suction side of the secondary compressor 12 but is integrated in the middle of the first refrigerant tube 21 connected to the outlet of the primary compressor 11, (12). ≪ / RTI > Accordingly, the first evaporator 14 and the second evaporator 15 may be connected in parallel.

In the refrigerator having the refrigeration cycle according to the present embodiment as described above, the refrigerant switching valve is controlled in the direction of the first evaporator or the second evaporator in accordance with the operation mode of the refrigerator, thereby simultaneously operating both the refrigerating chamber and the freezing chamber. Or a freezing room operation in which only the freezing room is operated or a refrigerating room operation in which only the cold storage room is operated.

The first outlet 16b and the second outlet 16c of the refrigerant switching valve 16 are both opened to allow the refrigerant passing through the condenser 13 to flow through the first outlet 16b and the second outlet 16c, And moves in the direction of the first evaporator 14 and the second evaporator 15.

Then, the refrigerant sucked into the primary compressor 11 through the first evaporator 14 is compressed and discharged from the primary compressor 11 in one stage, and is discharged from the primary compressor 11, Is sucked into the secondary compressor (12). At this time, the refrigerant passing through the second evaporator 15 is moved to the first refrigerant pipe 21 through the seventh refrigerant pipe 27, mixed with the refrigerant compressed and discharged in the first compressor 11, And is sucked into the compressor (12).

Then, the refrigerant compressed in the first stage and the refrigerant having passed through the second evaporator 12 are compressed and discharged by the secondary compressor 12, and the refrigerant discharged from the secondary compressor 12 is moved to the condenser 13, And the refrigerant condensed in the condenser 13 is circulated in the direction of the first evaporator 14 and the second evaporator 15 in the refrigerant switching valve 16, and is repeated.

On the other hand, in the freezer compartment operation mode, the refrigerant switching valve 16 opens only the first outlet 16b, which is the refrigerating chamber side evaporator, that is, the second outlet 16c is blocked and the refrigerating chamber side evaporator is passed through the condenser 13 So that the refrigerant can move only in the direction of the first evaporator 14. The primary compressor 11 and the secondary compressor 12 operate at the same time and the refrigerant having passed through the first evaporator 14 passes through the primary compressor 11 and the secondary compressor 12, It is compressed and circulated.

On the other hand, in the refrigerating chamber operating mode, the refrigerant switching valve 16 blocks the first outlet 16b and opens the second outlet 16c. Then, the primary compressor (11) is stopped and only the secondary compressor (12) is started. Then, the refrigerant passing through the condenser 13 moves only in the direction of the second evaporator, is compressed by the second compressor 12 in one step, and is repeatedly moved to the condenser 13.

Here, when the primary compressor 11 and the secondary compressor 12 are connected in series by the first refrigerant pipe 21 to perform the two-stage compression operation, the oil of the primary compressor 11 as the low- The amount of oil discharged from the primary compressor 11 is larger than that of the recovered oil, so that efficiency deterioration due to oil shortage and parts damage occur . Therefore, the present invention is applicable to an oil equalizing apparatus for maintaining oil balance in a secondary compressor which is a high-stage compressor, a primary compressor which is a low-stage compressor, To operate effectively.

FIG. 3 is a block diagram showing a control unit for controlling the refrigeration cycle according to the present embodiment, and FIG. 4 is a systematic diagram showing a refrigeration cycle controlled by the control unit according to FIG.

As shown in the drawing, the oil equalizing apparatus according to the present embodiment includes a determination unit 30 for determining whether oil is biased by the secondary compressor 12, And an oil recovery unit 40 that performs an oil equalization action between the compressor 11 and the secondary compressor 12. [

The judging unit 30 can accumulate the operating time of the secondary compressor 12 as a high-stage compressor or the primary compressor as a low-stage compressor to detect whether the oil is biased by the secondary compressor 12, It is also possible to detect whether the oil level of the secondary compressor 12 is excessive or not by detecting the oil level of the primary compressor 12 or the primary compressor 11.

For example, a timer 35 may be provided in a refrigerator control unit or a compressor control unit (hereinafter abbreviated as a microcomputer) 31 in order to accumulate the operation time of the compressor to determine an oil imbalance. The microcomputer 31 may include an input unit 32, a determination unit 33, and an output unit 34 as shown in FIG.

The input unit 32 is electrically connected to the timer 35 or the oil level sensor 36. The output unit 34 controls the operation of each compressor and the flow direction of the refrigerant according to the contents determined by the determination unit 33 The secondary compressor 12, and the refrigerant switching valve 16 so that the refrigerant can be supplied to the primary compressor 11, the secondary compressor 12, and the refrigerant switching valve 16, respectively.

The oil recovery unit 40 includes an oil return pipe 42 connected to the shell internal space of the secondary compressor 12 to discharge the oil collected in the space inside the shell of the secondary compressor 12, 42 to prevent the oil from flowing back to the secondary compressor 12 from the second refrigerant pipe 22. The check valve 43 is installed outside the shell of the secondary compressor 12 not only to be immersed in oil but also to be advantageous for maintenance.

Here, the inlet end of the oil return pipe 42 is inserted so as to be positioned at an appropriate height of the oil level of the secondary compressor 12, that is, the height of the oil level of the oil filled amount, .

In the refrigerator having the refrigeration cycle according to the present embodiment as described above, the oil concentrated in the secondary compressor 12 can be sent to the primary compressor 11 by using the following algorithm. FIG. 5 is a flowchart illustrating an operation algorithm of a refrigeration cycle according to an embodiment of the present invention, and FIG. 6 is a block diagram illustrating an embodiment of the equalization operation in the flowchart of FIG.

5, the timer 35 provided in the microcomputer 31 during the normal operation of the refrigeration cycle accumulates the operation time of the secondary compressor 12, which is a high-stage compressor, and outputs the result to the secondary compressor 12 ) Exceeds the set normal operation time, it executes the oil equal operation.

Next, the equalizing operation time is accumulated by the timer 35 while the equalizing operation is performed, and when the equalizing operation time exceeds the set equalizing operation time, the series of operations for switching to the normal operation can be repeated.

Here, the operation of the oil equalizing operation is shown in FIG. At the same time, both the first outlet 16b and the second outlet 16c of the refrigerant switching valve 16 are opened to open the first and second compressors 11 and 16, So that the equalizing process is performed so that the pressure of the compressor 11 and the pressure of the secondary compressor 12 are equalized. (S12) Then, the oil, which has been concentrated into the inner space of the shell of the secondary compressor 12, Is discharged through the oil return pipe (42) to the second refrigerant pipe (22), that is, the refrigeration cycle by the compression period pressure difference. The pressure equalization process can be performed for about 5 minutes. FIG. 7 is a graph showing a change in pressure at the time of stoppage to explain the effect of the driving algorithm according to FIG. As shown in the figure, the pressure change is not so large at the time of stopping operation (normal cycle stop in the drawing) in a state where both the first outlet 16b and the second outlet 16c of the refrigerant switching valve 16 are closed . It can be seen that the discharge pressure of the secondary compressor 12, which is a high-stage compressor, is not significantly lowered. However, at the time of stopping the operation (in the drawing, stopping the oil recovery cycle) in the state where the first outlet 16b and the second outlet 16c of the refrigerant switching valve 16 are both opened, the discharge of the secondary compressor 12 The suction pressure of the primary compressor 11, which is a low-stage compressor, is greatly increased, and the pressure reversal between the secondary compressor and the primary compressor is generated, so that the oil in the secondary compressor 12 rapidly flows into the refrigeration cycle It can be seen that it flows out.

The first outlet 16b of the refrigerant switching valve 16 to the primary compressor 11 is opened and the second outlet 16c of the refrigerant switching valve 16 to the secondary compressor 12 is closed. At the same time, the oil recovery process for operating both the primary compressor 11 and the secondary compressor 12 is performed. (S13) Then, the oil that has flowed out in the refrigeration cycle is supplied to the primary evaporator (14) and then flows into the primary compressor (11) to prevent oil shortage in the primary compressor (11). At this time, it is preferable to cool the condenser 13 by operating the machine room fan installed in the machine room because the efficiency of the refrigeration cycle can be increased.

On the other hand, when the constant oil operation period set during the normal operation comes, the first compressor 11 and the second compressor 12 are both turned off. After a predetermined time, for example, 70 minutes, It may be preferable to perform the oil equalization operation after sufficiently cooling the interior of the refrigerator. If the oil equalization operation remains for less than a predetermined time during the pressure equalization process, the pressure equalization process can be performed and the oil recovery process can be performed at the same time. In addition, it is preferable to perform the oil equalizing operation after the defrosting operation is completed and the refrigeration cycle is restarted when the oil equalizing operation cycle comes during the defrosting operation to improve the efficiency of the refrigerator.

Meanwhile, the oil equalizing operation period can be controlled by integrating the operation time of the secondary compressor 12 using the timer 35 and controlling the oil equalizing operation timing based on the operation time of the secondary compressor 12, The oil equalizing operation period can be controlled by using the oil level sensors provided in the compressors 12 or installed in one of the compressors. The oil level sensor 36 may be a booster type as shown in FIG. 8 or a capacitance type as shown in FIG.

8 may be a negative electrode plate (or a positive electrode plate) fixed to an appropriate height from the bottom surface of the shell so that the positive electrode plate (or the negative electrode plate) 37 may be a fixed electrode, ) 38 is formed to move along the oil surface between the bottom surface of the shell and the positive electrode plate 37, which is the fixed electrode, so as to form the movable electrode. 9 (a) and 9 (b), the negative electrode plate 38, which is a movable electrode, is detached from the positive electrode plate 37 while moving in the up-and-down direction, Can be detected. The negative electrode plate 38, which is a movable electrode, is preferably formed of a material that can float well on the oil. In the case of metal, a floating member such as a ball can be coupled to the negative electrode plate 38 as a movable electrode.

On the other hand, the capacitive-type oil level sensor 36 shown in Fig. 9 has a structure in which both the positive electrode plate 37 and the negative electrode plate 38 are fixed electrodes, and depending on whether oil exists between the positive electrode plate 37 and the negative electrode plate 38, The height of the oil level can be detected by using the characteristic that the capacitance value is changed.

Here, the oil level sensor 36 is different from the embodiment in which the timer is used only in detecting the oil level of the compressor and determining whether the oil level operation is necessary, but the actual oil level operation can be performed in the same manner as the above-described embodiment. A detailed description thereof will be omitted.

On the other hand, under normal operating conditions, the oil is mainly supplied to the secondary compressor (12), so that the space between the shell of the secondary compressor (12) and the discharge pipe of the secondary compressor is connected to an oil return pipe ) May be connected. However, since the oil may be biased to the primary compressor 11 in an overcasting condition where the ambient temperature is higher than the normal operating condition, the space inside the shell of the primary compressor 11 and the discharge of the primary compressor 11 A lower stage oil recovery unit 45 consisting of an oil recovery pipe (hereinafter referred to as a lower stage oil recovery pipe) 46 and a check valve 47 may be installed between the first refrigerant pipes 21 connected to the pipe.

10 is a schematic diagram showing a refrigeration cycle having a high-stage oil recovery unit and a low-stage oil recovery unit in the refrigeration cycle according to FIG.

As shown in the figure, the high-stage oil recovery unit 41 is provided to communicate with the internal space of the shell of the secondary compressor 12 to recover the oil collected in the space inside the shell of the secondary compressor 12, Stage check valve 43 installed between the pipe 42 and the high-stage oil return pipe 42 to prevent the oil from flowing backward from the second refrigerant pipe 22 to the secondary compressor 12 can do.

The lower-stage oil recovery unit 45 is provided with a low-stage oil recovery pipe 46 which is provided so as to communicate with the internal space of the shell of the primary compressor 11 and discharges the oil collected in the space inside the shell of the primary compressor 11, And a low-stage check valve 47 installed in the middle of the low-stage measurement oil return pipe 46 to prevent the oil from flowing back to the primary compressor 11 from the first refrigerant pipe 21. [

Here, the inlet ends of the high-stage oil return pipe 42 and the low-stage oil return pipe 46 are connected to an appropriate oil level height of the secondary compressor 12 as the high-stage compressor and the primary compressor 11 as the low- That is, to be positioned at the height of the oil level of the oil sealed amount, is preferable because oil can be prevented from flowing out excessively during the oil equalizing process. The height of the inlet end of the high-stage oil return pipe 42 inserted into the secondary compressor 12 and the height of the low-stage measured oil return pipe 46 inserted into the primary compressor 11 may be different from each other . For example, the inlet end height of the high-stage oil return pipe 42 is inserted far away from the bottom of the shell in the secondary compressor 12 having a relatively large amount of oil filling, while the primary compressor 11, The height of the inlet end of the oil return pipe 46 can be inserted close to the bottom surface of the shell.

In the refrigerator having the refrigerating cycle according to the present embodiment as described above, the oil equalizing operation period can be controlled according to the above-described embodiment, that is, the algorithm shown in FIG. A description thereof will be omitted.

In this embodiment, the oil equalization operation for the secondary compressor for recovering the oil of the secondary compressor to the primary compressor and the oil equalization operation for the primary compressor for recovering the oil of the primary compressor to the secondary compressor are independently performed However, it is preferable to continuously perform the oil equalizing operation for the secondary compressor and the oil equalizing operation for the primary compressor because the oil leaking phenomenon to the compressor, which may occur under various conditions, can be prevented .

FIG. 11 is a block diagram showing another embodiment of the oil equalizing operation in the flowchart according to FIG. 5, and is a block diagram showing an algorithm for performing continuous equalizing operation using a high stage oil recovery unit and a low stage oil recovery unit.

As shown in the figure, after the constant-temperature operation for the secondary compressor is performed for a predetermined time (for example, about 5 minutes), the constant-temperature operation for the primary compressor is performed for a predetermined time (for example, 1 minute and 30 seconds) .

First, the oil equalizing operation for the secondary compressor can proceed based on the procedure shown in FIG. At the same time, both the first outlet 16b and the second outlet 16c of the refrigerant switching valve 16 are opened to open the first and second compressors 11 and 16, So that the equalizing process is performed so that the pressure of the compressor 11 and the pressure of the secondary compressor 12 are equalized. (S12) Then, the oil, which has been concentrated into the inner space of the shell of the secondary compressor 12, The refrigerant flows out through the high-stage measurement oil return pipe 42 to the second refrigerant pipe 22, that is, the refrigerating cycle by the compression period pressure difference. The pressure equalization process can be performed for about 5 minutes.

The first outlet 16b of the refrigerant switching valve 16 to the primary compressor 11 is opened and the second outlet 16c of the refrigerant switching valve 16 to the secondary compressor 12 is closed. At the same time, the oil recovery process for operating both the primary compressor 11 and the secondary compressor 12 is performed. (S13) Then, the oil that has flowed out in the refrigeration cycle is supplied to the primary evaporator (14) and then flows into the primary compressor (11) to prevent oil shortage in the primary compressor (11). At this time, it is preferable to cool the condenser 13 by operating the machine room fan installed in the machine room because the efficiency of the refrigeration cycle can be increased.

Next, the first outlet 16b of the refrigerant switching valve 16, which is directed to the primary compressor 11, is opened and the second outlet 16c of the refrigerant switching valve 16, which is directed to the secondary compressor 12, The refrigerant discharged from the secondary compressor 12 is discharged from the first outlet 16b of the refrigerant switching valve 16 to the second compressor 12 through the first outlet 16b of the refrigerant switching valve 16, To the primary compressor (11), thereby increasing the pressure in the space inside the shell of the primary compressor (11), thereby pushing out the oil that has been poured into the primary compressor (11). The oil that has been poured into the space inside the shell of the primary compressor 11 flows out to the first refrigerant pipe 21 through the low-stage oil return pipe 46. The oil flows through the suction pipe of the secondary compressor 12 The refrigerant flows into the space inside the shell of the compressor 12 so that the oil balance is established between the primary compressor 11 and the secondary compressor 12. [

Meanwhile, another embodiment of the oil return pipe in the refrigeration cycle apparatus according to the present invention is as follows.

That is, in the above-described embodiments, the oil return pipe is connected between the shell internal space of the secondary compressor and the discharge pipe, or between the internal space of the shell of the primary compressor and the discharge pipe. In this embodiment, The oil balance between the compressors can be eliminated by connecting the compressors directly with an oil return pipe.

12, the oil return pipe 61 can connect the inside of the shell of the secondary compressor 12 with the inside of the shell of the primary compressor 11. As shown in FIG. Both ends of the oil return pipe (61) are respectively connected to the shell bottom of the secondary compressor (12) and the shell bottom of the primary compressor (11).

An oil return valve (62) for selectively opening and closing the oil return pipe (61) may be installed at both ends of the oil return pipe (61). The oil return valve 62 is composed of a bore 65 that ascends and descends according to the amount of oil and a valve member 66 that is coupled to the bore 65 and opens and closes both ends of the oil return pipe 61, .

The bail 65 is integrally coupled to a support member 67 hinged to be rotatable on the bottom surface of the compressors 11 and 12 and the valve member 66 is coupled to the bail 65 or the support member 67 The oil return pipe 61 can be integrally formed or assembled with the bore 62 or the support member 67 so as to open and close the end of the oil return pipe 61 while rotating together. The valve member 66 may be formed in a flat plate shape, but may be formed in a wedge shape to increase the sealing force.

However, the oil return valve 62 may be installed in the middle of the oil return pipe 61 at the outside of the compressor. FIG. 14 is a front view showing another embodiment of the oil recovery passage according to the present embodiment, and FIG. 15 is a sectional view showing the operation of the oil recovery valve in the oil recovery passage according to FIG.

14, a valve space 71a is formed in the middle of the oil return pipe 71 so that the piston valve 72 is slidably received, and a secondary compressor 12 is provided on the upper surface of the valve space 71a. Or the discharge pipe of the primary compressor (11) and the gas guide pipe (73). An elastic member 72a for resiliently supporting the valve member 72 is provided in the valve space portion 71a at the bottom of the valve member 72, that is, on the opposite side of the gas guide pipe 73, The stopper surface 71b may be protruded or stepped at a predetermined height on the inner circumferential surface of the oil return pipe 71a so that the valve member 72 can block the oil return pipe 71 when the valve member 72 is lowered.

15 (a), during the operation of the refrigeration cycle, that is, during operation of the compressor, high-pressure refrigerant is introduced into the oil return pipe 71 through the gas guide pipe 73 through the discharge pipe of the compressor And the high-pressure refrigerant pressurizes the valve member 72 to block the oil return pipe 71 while the valve member 72 is lowered. As a result, pressure leakage between both compressors is prevented to maintain the pressure difference required for the two-stage compression while the oil remains stagnant inside the shells of both compressors.

25 (b), when the refrigerating cycle is stopped or operated at a low capacity, the valve member 72 is lifted by the elastic force of the elastic member 72a and the oil return pipe 71 is opened So that the oil in both compressor shells moves in accordance with the internal pressure difference of the shell, thereby achieving oil balance between the compressors.

On the other hand, the oil return pipe may connect the inside of the shell of the secondary compressor and the suction pipe of the primary compressor. FIG. 16 is a front view showing another embodiment of the oil recovery passage according to the present embodiment, and FIG. 17 is a front view showing another embodiment of the oil recovery passage in FIG.

16, the oil return pipe 81 is connected to the middle of the suction pipe of the primary compressor 11 through the shell of the secondary compressor 12, and in the middle of the oil return pipe 81, And an oil return valve 82 for selectively opening and closing the oil return valve 81 can be provided.

One end (high-stage compressor side) of the oil return pipe 81 may be connected to the bottom of the shell of the compressor or may be extended to abut the bottom of the shell.

The oil recovery valve 82 may be a solenoid valve electrically connected to the microcomputer 31 or may be a check valve or the like for allowing the oil to move only in the direction of the primary compressor 11 from the secondary compressor 12 Or a safe valve that opens when a certain pressure is reached.

However, as shown in Fig. 17, the capillary 83 may be provided in the middle of the oil return pipe 81 instead of the oil return valve. In the case of the capillary 83, even if the oil return pipe 81 can not be completely shut off during operation of the refrigeration cycle apparatus, the oil discharged from the secondary compressor 12 can be easily returned to the primary compressor 11 It is preferable that the flow path resistance is formed so as not to move.

On the other hand, the oil return pipe may be connected to the discharge pipe of the secondary compressor and the inside of the shell of the primary compressor. In such a case, the oil return pipe may further include an oil separator.

FIG. 18 is a front view showing another embodiment of the oil recovery passage according to the present embodiment, and FIGS. 19 and 20 are sectional views showing an oil separator applied to the oil recovery passage according to FIG.

18, in this embodiment, the oil return pipe 91 is connected to the discharge pipe of the primary compressor 11 and the suction pipe of the secondary compressor 12, and in the middle of the oil return pipe 91, The oil is separated from the refrigerant discharged through the discharge pipe of the compressor 12 and the refrigerant gas (dotted arrow) is separated into the secondary compressor 12 and the separated oil (solid line arrow) is recovered by the primary compressor 11 An oil separator 92 is provided.

19, the oil separator 92 includes a separation vessel 93 having a predetermined internal space, an oil separation net 94 provided inside the separation vessel 93 for separating oil from the refrigerant, And an oil return valve 95 so that the oil separated by the separation net 94 can be selectively moved in the direction of the primary compressor.

The separation vessel 93 has an inlet 96 connected to the discharge pipe of the secondary compressor 12 and a first outlet 97 connected to the inlet of the condenser 13, The second outlet 98 communicating with the inside of the shell of the primary compressor 11 is formed below the oil separation net 94 and the second outlet 98 communicating with the interior of the shell of the primary compressor 11 is formed at the upper half of the separation vessel 93 That is, on the bottom surface of the separation vessel 93.

The oil separation net 94 may be installed laterally at an intermediate height so as to divide the inner space of the separation vessel 93 into an upper half portion and a lower half portion. In this case, the inlet 96 and the first outlet 97 may be formed to communicate with each other above the oil separation net 94 and the second outlet 98 to communicate with the oil separation net 94, respectively. However, as shown in FIG. 20, the oil separation net 94 may be installed so as to surround the inlet 96 of the separation vessel 93. In this case, the first outlet 97 can be formed to communicate with the upper half of the separation vessel 93, and the second outlet 98 can communicate with the lower half (for example, the bottom) of the separation vessel 93.

The refrigerant discharged from the secondary compressor 12 toward the condenser 13 flows into the separation vessel 93 of the oil separator 92 and flows into the separation vessel 93 of the oil separator 92, The refrigerant passes through the oil separation net 94 in the oil separator 93 to separate the oil, and the separated oil is accumulated on the bottom surface of the separation vessel 93. The refrigerant moves to the condenser 13 through the first outlet 97. When the separated oil accumulates a certain amount, the bail 95a of the oil return valve 95 is lifted to open the wedge-shaped valve member 95b do. The oil is then recovered into the shell of the primary compressor through the open oil return tube (91).

As described above, since the oil separator is directly connected between the compressors, the separated oil is recovered in the primary compressor without being left in the piping of the refrigeration cycle, so that the oil recovery effect is high and the piping can be simplified.

In the meantime, all of the driving algorithms of the above-described embodiments have been described with respect to the case where the refrigerant switching valve is a three-way valve. However, in the present embodiment, even when the refrigerant switching valve 16 is a four- Can be similarly applied.

However, in the above-described embodiment, the first outlet 16b of the refrigerant switching valve 16 is opened when the oil flowing out in the cycle of the oil-equalizing operation to the secondary compressor 12 is led to the primary compressor 11 However, in this embodiment, the oil can be led to the primary compressor by using the third outlet 16d of the refrigerant switching valve 16 which is a four-way valve.

An oil guide pipe 19 is connected to the third outlet 16d of the refrigerant switching valve 16 and the oil guide pipe 19 is connected to the outlet of the first evaporator 14 And may be connected between the suction side of the compressor 11 and the sixth refrigerant pipe 26.

Accordingly, in the refrigeration cycle having the refrigerant switching valve 16 and the oil guide pipe 19 of the four-way valve, the first outlet 16b of the refrigerant switching valve 16 or the first outlet 16b of the refrigerant switching valve 16 in the above- The second outlet 16c is closed and only the third outlet 16d to which the oil guide pipe 19 is connected is opened so that the oil in the refrigeration cycle flows through the refrigerant switching valve 16 and the oil guide pipe 19, (11).

On the other hand, when the oil of the secondary compressor is moved in the direction of the condenser of the refrigeration cycle by using the above-described driving algorithm, the oil passage may be formed differently depending on the compressor. In other words, a connecting type reciprocating compressor mainly used for converting the rotational motion of the motor into linear motion and a vibrating reciprocating compressor using the linear motion of the motor are applied to the refrigerator. In these connection type reciprocating compressors and vibratory reciprocating compressors, all the discharge pipes are directly connected to the discharge side of the compression mechanism section, and the refrigerant discharged from the compression mechanism section is directly transferred to the condenser of the refrigeration cycle without passing through the internal space of the shell. . Therefore, in the case of these low-pressure compressors, in order to move the oil in the space inside the shell to the refrigeration cycle, an oil recovery channel such as the above-described oil recovery pipe may be required.

However, even in the case of a high-pressure compressor in which the discharge pipe communicates with the inner space of the shell, a separate oil return flow passage may be required since the discharge pipe is generally arranged higher than the oil level. For example, a rotary compressor or a scroll compressor (particularly, a high-pressure scroll compressor in which a discharge pipe communicates with a shell inner space), which is mainly applied to an air conditioner, is arranged such that the discharge pipe is higher than the oil level. Therefore, in this case also, the high-stage compressor may require an oil return flow path for moving the oil in the shell internal space to the refrigeration cycle.

22 is a sectional view showing an embodiment of a secondary compressor having an oil recovery passage in a refrigeration cycle apparatus according to the present invention.

As shown in the figure, the secondary compressor according to the present embodiment has a structure in which the frame 120 is resiliently installed in the inner space of the closed shell 110, the reciprocating motor 130 and the cylinder 140 are installed in the frame 120, And a piston 150 coupled to a mover 133 of the reciprocating motor 130 is inserted into the cylinder 140 so as to reciprocate and the piston 150 is coupled to both sides of the piston 150 in the direction of movement of the piston 150. [ A plurality of resonance springs 161 and 162 for inducing a resonance motion of the resonator 150 are respectively installed.

A compression space 141 is formed in the cylinder 140. A suction channel 151 is formed in the piston 150. A suction valve 171 for opening and closing the suction channel 151 is provided at the end of the suction channel 151. [ And a discharge valve 142 for opening and closing the compression space 141 of the cylinder 140 is provided on the end surface of the cylinder 140.

A suction pipe 111 connected to a discharge pipe (not shown) of the primary compressor 11 is connected to the inner space of the shell 110. A suction pipe 111 is connected to one side of the suction pipe 111, And a discharge pipe 112 connected to the discharge pipe 112 is connected.

The oil return pipe 42 is connected to one side of the shell 110 through an oil return pipe 42 which communicates with the inner space through the shell 110. Oil flows into the oil return pipe 42, A check valve 43 is provided to block the check valve 43 from being operated.

One end of the oil return pipe 42 is connected to the middle of the discharge pipe 112 from the outside of the shell of the secondary compressor 12 while the other end of the oil return pipe 42 is inserted into the shell 110, As shown in FIG. The lower end of the oil return pipe 42 may be formed to be bent in the direction of the reciprocating motor in consideration of the shape of the shell 110. On the bottom surface of the shell 110 contacting the lower end of the oil return pipe 42, An oil flange (not shown) may be installed so as to be filtered.

The check valve 43 may be a check valve or a safety valve that is automatically opened when the internal pressure of the shell rises above a predetermined pressure, but may be an electronic solenoid valve. When the check valve 43 is a solenoid valve, the check valve 43 can be electrically connected to the microcomputer controlling the refrigeration cycle so that the check valve 43 can be associated with the operation state of the refrigeration cycle apparatus.

Meanwhile, the oil return pipe may be connected to the discharge pipe in the inner space of the shell 110 of the secondary compressor 12, and the check valve 43 may be installed in the inner space of the shell 110. In this case, the space occupied by the refrigeration cycle unit can be reduced and the piping can be simplified.

In the drawing, reference numeral 135 denotes a coil.

In the secondary compressor according to the present embodiment as described above, when power is applied to the coil 135 of the reciprocating motor 130, the motor 133 of the reciprocating motor 130 reciprocates. The piston 150 coupled to the muffler 133 reciprocates linearly in the cylinder 140 while compressing the refrigerant in the primary compressor 11 through the suction pipe 111 to discharge the refrigerant into the shell Inhale. The refrigerant in the space inside the shell 110 is sucked into the compression space 141 of the cylinder 140 through the suction passage 151 of the piston 150 and the refrigerant in the compression space 141 during the forward movement of the piston 150 And is discharged to the condenser 13 of the refrigeration cycle through the discharge pipe 112.

Referring to FIG. 4, in the primary compressor 11, the oil is discharged together with the refrigerant and moves into the shell 110 of the secondary compressor 12, so that the oil of the secondary compressor 12 increases In the refrigeration cycle as in the present embodiment, the primary compressor (11) is supplied with the oil leaned by the secondary compressor (12) through the primary compressor (11) So that the primary compressor 11 and the secondary compressor 12 maintain the oil balance, thereby enhancing the efficiency and reliability of the compressor as well as the performance of the refrigeration cycle apparatus.

The oil contained in the inner space of the shell 110 of the secondary compressor 12 is guided to the discharge pipe 112 through the oil return pipe 42 penetrating to the outside from the internal space of the shell 110, Cycle.

11, 12: compressor 13: condenser
14, 15: evaporator 16: refrigerant switching valve
16b: first outlet 16c: second outlet
17, 18: inflator 19: oil guide tube
21 to 27: refrigerant pipe 30: judging unit
31: Mycom 35: Timer
36: Oil level sensor 40, 41, 45: Oil recovery unit
42, 46: Oil recovery pipe 43, 47: Check valve
110: shell 111: suction pipe
112: discharge pipe 130: reciprocating motor
140: cylinder 150: piston
161, 162: resonance spring

Claims (15)

A primary compressor in which a suction pipe is connected to an internal space of the shell and one end of a discharge pipe is connected to the compression unit;
A secondary compressor in which the other end of the discharge pipe of the primary compressor is connected to the inside of the shell and the other end of the discharge pipe is connected to the compression unit;
A condenser to which the other end of the discharge pipe of the secondary compressor is connected;
A refrigerant switching valve installed at an outlet side of the condenser;
A first evaporator connected to the outlet of the refrigerant switching valve and connected to the shell of the primary compressor;
A second evaporator connected to another outlet of the refrigerant switching valve and integrated with a discharge pipe of the primary compressor and connected to the shell of the secondary compressor;
A determination unit for determining whether the oil is biased by one of the primary compressor or the secondary compressor; And
And an oil recovery unit that performs an equalizing operation by a pressure difference between the primary compressor and the secondary compressor in accordance with contents detected by the determination unit,
The oil recovery unit includes:
An oil recovery pipe installed to communicate with an inner space of each of the shells of the primary compressor and the secondary compressor to discharge oil collected in a space inside the shell of the compressor; And
And a microcomputer controlling the operation of the primary compressor and the secondary compressor and controlling the opening direction of the refrigerant switching valve,
The microcomputer,
A determination unit determining whether an oil recovery operation is necessary; And
And an output unit for returning the oil to the primary compressor and the secondary compressor when the determination unit determines that the oil recovery operation is required,
The output unit includes:
The refrigerant switching valve opens both the outlet of the refrigerant switching valve toward the first evaporator and the outlet of the second evaporator toward the second evaporator for a predetermined time during the off time of the refrigeration cycle, The oil of the secondary compressor is moved to the refrigeration cycle,
The first and second evaporators are opened and the first and second evaporators are closed, respectively, so that both the compressors are operated for a predetermined period of time to allow the oil to flow into the first compressor,
The first compressor is stopped and the secondary compressor is operated for a predetermined time so that the oil of the primary compressor is introduced into the secondary compressor. delete The method according to claim 1,
Wherein one end of the oil return pipe communicates with the internal space of the compressor shell while the other end is connected to a refrigerant discharge pipe of the compressor or a pipe of a cycle connected to the refrigerant discharge pipe. The method according to claim 1,
Wherein the oil return pipe is connected to the shell inner space of the primary compressor and the shell inner space of the secondary compressor so as to communicate with each other. The method according to claim 3 or 4,
Wherein the oil return pipe is provided with a valve for opening and closing the oil return pipe. The method according to claim 1,
A plurality of oil return pipes are provided so as to communicate with the shell of the primary compressor and the shell of the secondary compressor, respectively,
Wherein the oil return pipes are inserted to correspond to the amount of oil sealed in the shell. The method according to claim 6,
Wherein the oil return pipe communicating with the shell of the primary compressor is inserted closer to the bottom of the shell than the oil return pipe communicated with the shell of the secondary compressor. The method according to any one of claims 1, 3, 4, and 6 to 7,
Wherein the determination unit comprises a timer for accumulating the operation time of either one of the primary compressor and the secondary compressor to determine the accumulated operation time. delete The method according to claim 1,
Wherein the determination unit includes an oil level sensor in at least one of the compressors to detect changes in the oil level of the compressor. Stage compressor in which a suction pipe is connected to the internal space of the shell and a discharge pipe is connected to the compression unit, respectively, and a high-stage compressor are connected in series, and a condenser is connected to the discharge side of the high- A refrigerant switching valve is connected to the outlet of the condenser, and the refrigerant switching valve has a low-stage measuring outlet and a high-stage measuring outlet so that the low-stage measuring outlet is connected to the low-stage measuring evaporator, Wherein the low stage evaporator is connected to the suction side of the low stage compressor while the high stage evaporator is connected to the suction side of the high stage compressor,
Determining whether an equalizing operation is required between the low-stage compressor and the high-stage compressor; And
If it is determined that oil equalization operation is necessary, the process proceeds to a step of transferring the oil to the oil-less compressor in the oil-rich compressor,
In the oil equalizing operation,
Opening both the low-stage measurement outlet and the high-stage measurement outlet of the refrigerant change-over valve for a predetermined time in a state where both the low-stage compressor and the high-stage compressor are stopped;
And the oil is recovered by the high-stage compressor after the operation of recovering the oil by the low-stage compressor after the oil is circulated in the cycle. 12. The method of claim 11,
In the operation of recovering the oil by the low-stage compressor, the low-stage compressor outlet and the high-stage compressor are operated for a predetermined time while the lower stage outlet of the refrigerant switching valve is opened and the high- Wherein the step of introducing the refrigerant into the compressor is performed. 13. The method of claim 12,
In the operation of recovering the oil by the high-stage compressor, the low-stage compressor is stopped while the low-stage metering outlet of the refrigerant switching valve is opened and the high-stage metering outlet is closed, To a high-stage compressor; and advancing the oil to the high-stage compressor. 14. The method of claim 13,
Wherein the machine room fan is operated to cool the condenser in the operation of allowing the low-stage compressor and the high-stage compressor to recover oil. Stage compressor is connected in series with a low-stage compressor in which a suction pipe communicates with the internal space of the shell and a discharge pipe is connected to the compression unit, respectively, and a condenser is connected to the discharge side of the high- Wherein the refrigerant switching valve has a lower stage outlet and a higher stage outlet so that the lower stage outlet is connected to the lower stage evaporator while the higher stage outlet is connected to the higher stage evaporator, Stage compressor is connected to the suction side of the compressor, while the high-stage evaporator is connected to the suction side of the high-stage compressor,
Determining whether an equalizing operation is required between the low-stage compressor and the high-stage compressor; And
If it is determined that oil equalization operation is necessary, the process proceeds to a step of transferring the oil to the oil-less compressor in the oil-rich compressor,
In the oil equalizing operation,
Opening both the low-stage measurement outlet and the high-stage measurement outlet of the refrigerant change-over valve for a predetermined time in a state in which both the low-stage compressor and the high-stage compressor are stopped; And
Stage compressor is operated for a predetermined time while the outlet of the lower end of the refrigerant switching valve is opened and the outlet of the lower end of the high-stage compressor is closed, the internal pressure of the low- Wherein the oil of the low-stage compressor is moved to the high-stage compressor by raising the internal pressure of the low-stage compressor to be higher than the internal pressure of the stage compressor.

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