JP2016080309A - Oil level detection device of compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly detect whether an oil level is in a proper position, without performing valve opening/closing control for each oil level detection position, in an oil level detection device of a compressor.SOLUTION: In an oil level detection device of a compressor, an upper limit pipeline 31 and a lower limit pipeline 32 are connected to above and below a proper position M of an oil level of a sealed container 8 of a compressor 7; the upper limit pipeline 31 and the lower limit pipeline 32 are made confluent and connected to a refrigerant pipeline 6 of the compressor 7; a capillary tube 35 is connected to a confluent pipeline 34; and an upstream side temperature sensor 37 and a downstream side temperature sensor 38 are arranged on the upstream and downstream sides of the capillary tube 35, respectively.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an oil level detection device for a compressor.

  Conventionally, in a compressor oil level detection device, a capillary tube is connected to a suction pipe through which refrigerant and oil sucked from a predetermined height position of a hermetic container of a compressor pass, and a temperature difference between upstream and downstream of the capillary tube Is known that detects the oil level based on the above (for example, see Patent Document 1). Specifically, in Patent Document 1, the oil level is detected by comparing the temperature difference when only the oil passes through the capillary tube and the temperature difference when only the refrigerant passes through the capillary tube.

JP 2014-89021 A

By the way, in the conventional oil level detection device, a suction pipe provided with an opening / closing valve is installed at each position for monitoring the oil level such as the upper limit oil level position, the lower limit oil level position, etc., and corresponds to the position where the oil level is detected. Only the on-off valve was opened and the temperature difference before and after passing through the capillary tube was detected. For this reason, in order to detect the oil level, it is necessary to perform opening / closing control of the opening / closing valve provided in each suction pipe.
Further, in the hermetically sealed container of the compressor, the oil level fluctuates due to undulation or foaming of the oil level. Since the suction pipe of the conventional oil level detection device opens directly into the sealed container, the suction state is affected by fluctuations in the liquid level due to undulations, etc., and the fluid in a state where oil and refrigerant are mixed May flow through the capillary tube and a significant temperature difference cannot be obtained.
The present invention has been made in view of the above-described circumstances, and in an oil level detection device for a compressor, whether or not the oil level is in an appropriate position without performing on-off valve control for each oil level detection position is appropriately determined. The purpose is to enable detection.

In order to achieve the above object, the present invention connects a plurality of oil take-off pipes above and below the proper oil level position of the compressor hermetic container, and joins the oil take-out pipes to the suction pipe of the compressor. In addition to being connected, a decompressor is connected to the junction pipe, and temperature sensors are arranged upstream and downstream of the decompressor.
Further, the present invention is characterized in that the merging pipe is piped according to the height of the appropriate position of the oil level.

Further, the present invention includes a control unit that determines the oil level based on a detection value of the temperature sensor, and the oil take-out pipe is connected to an upper limit position of the oil level of the sealed container; A lower limit pipe connected to the lower limit position of the oil level, the upper limit pipe and the lower limit pipe merge at the appropriate position, and the upper limit pipe opens and closes a flow path of the upper limit pipe The control unit closes the upper limit on-off valve when it is determined that the oil level is insufficient from the appropriate position.
Further, in the present invention, the lower limit pipe includes a lower limit side on-off valve that opens and closes a flow path of the lower limit pipe, and the control unit determines that the oil level is excessive from the appropriate position. The lower limit on-off valve is closed and the upper limit on-off valve is opened.

In addition, the present invention is characterized in that an oil supply valve for adjusting the amount of oil supplied to the sealed container is provided, and the oil supply valve is controlled based on a detection value of the temperature sensor.
Moreover, the present invention is characterized in that the compressor is a two-stage compressor, and the merging pipe is connected to a first-stage suction pipe.
Further, the present invention is characterized in that an on-off valve is connected to the junction pipe.

  ADVANTAGE OF THE INVENTION According to this invention, in the oil level detection apparatus of a compressor, the influence of the ripple etc. of the oil level can be suppressed and an oil level can be detected appropriately.

1 is a refrigeration circuit diagram of a refrigeration apparatus according to an embodiment of the present invention. It is a figure which shows an oil level detection apparatus. It is a figure which shows an oil level. It is a figure which shows an oil level. It is a flowchart of control of the detection of the oil level by a control part.

Hereinafter, a refrigeration apparatus according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a refrigeration circuit diagram of a refrigeration apparatus according to an embodiment of the present invention. In FIG. 1, the flow of the refrigerant is indicated by arrows.
The refrigeration apparatus 1 includes a refrigeration unit 2, a cooler 3, and a control unit 4 that controls operations of the refrigeration unit 2 and the cooler 3. The refrigeration cycle is configured by connecting the refrigerator unit 2 and the cooler 3 in a ring shape with a refrigerant pipe 5 and a refrigerant pipe 6 (first-stage suction pipe).

The refrigerator unit 2 includes a compressor 7 of a two-stage compression type compressor having two refrigerant compression steps. The compressor 7 includes a substantially cylindrical sealed container 8, an electric drive unit 9 housed in the upper part of the sealed container 8, a first compression part 11 housed in the lower part of the sealed container 8, and the sealed container 8 and a second compression unit 12 housed above the first compression unit 11. The 1st compression part 11 and the 2nd compression part 12 are connected with one rotating shaft of the drive part 9, and are rotationally driven.
The closed container 8 of the compressor 7 includes a low-stage suction port 8 a and a low-stage discharge port 8 b that communicate with the first compression unit 11, and a high-stage suction port 8 c and a high stage that communicate with the second compression unit 12. A side discharge port 8d is provided.

  Specifically, the refrigerator unit 2 includes the compressor 7, an intercooler 13 that cools the refrigerant that has been compressed in the first stage, an oil separator 14 that separates the oil in the refrigerant that has been compressed in the second stage, and an oil separator. 14 includes a gas cooler 15 that cools the refrigerant that has passed through 14, an economizer 16 that further cools the refrigerant that has passed through the gas cooler 15, and an oil cooler 17 that cools the oil separated from the refrigerant by the oil separator 14. The refrigerator unit 2 includes a fan 10 that blows air to the gas cooler 15, the intercooler 13, and the oil cooler 17.

The cooler 3 is a showcase installed in, for example, a convenience store or a supermarket. The cooler 3 includes an expansion valve 18 and an evaporator 19.
One end of the refrigerant pipe 5 is connected to the low-stage discharge port 8 b of the compressor 7, and the other end of the refrigerant pipe 5 is connected to the inlet of the evaporator 19. One end of the refrigerant pipe 6 is connected to the outlet of the evaporator 19, and the other end of the refrigerant pipe 6 is connected to the low-stage suction port 8 a of the compressor 7.

  The refrigerant pipe 5 includes an intermediate pressure discharge pipe 20 that connects the low-stage discharge port 8b and the inlet of the intercooler 13, and an intermediate pressure that connects the outlet of the intercooler 13 and the high-stage suction port 8c of the compressor 7. A suction pipe 21, and a high-pressure discharge pipe 22 that connects the high-stage discharge port 8 d of the compressor 7 and the inlet of the evaporator 19 are provided. In the middle of the high-pressure discharge pipe 22, an oil separator 14, a gas cooler 15, and an economizer 16 are provided in order from the compressor 7 side. The refrigerant pipe 5 includes an economizer passage pipe 23 that branches from between the economizer 16 and the cooler 3 and passes through the economizer 16 and is connected to the intermediate pressure suction pipe 21. The economizer passage pipe 23 includes an expansion valve 25 upstream of the economizer 16.

  The refrigerator unit 2 also includes an oil return pipe 26 that connects the oil outlet of the oil separator 14 and the oil inlet of the sealed container 8. The oil cooler 17 is provided in the middle of the oil return pipe 26. An oil supply valve 27 that adjusts the flow rate of the oil flowing through the oil return pipe 26 is provided downstream of the oil cooler 17 in the oil return pipe 26.

The refrigerator unit 2 includes an oil level detection device 30 that detects the oil level of the oil stored in the sealed container 8 of the compressor 7.
The oil level detection device 30 includes a pair of upper limit piping 31 (oil extraction piping) and lower limit piping 32 (oil extraction piping) drawn from the sealed container 8, an upper limit side opening / closing valve 31a for opening and closing the flow path of the upper limit piping 31, A lower limit side opening / closing valve 32 a that opens and closes the flow path of the lower limit pipe 32 and a merge pipe 34 that extends from the merge section 33 of the upper limit pipe 31 and the lower limit pipe 32 are provided. The oil level detection device 30 includes a capillary tube 35 (decompressor) provided in the middle of the merging pipe 34, a connection pipe 36 that connects the merging pipe 34 to the refrigerant pipe 6, and an upstream of the capillary tube 35 in the merging pipe 34. And an upstream temperature sensor 37 and a downstream temperature sensor 38 provided on the downstream side, and an on-off valve 39 provided on the connection pipe 36, respectively.

Here, the flow of the refrigerant and oil in the refrigeration apparatus 1 will be described.
The low-pressure refrigerant sucked from the low-stage suction port 8a of the compressor 7 is increased to the intermediate pressure by the first compression unit 11 and then discharged into the sealed container 8. Thereby, the pressure inside the airtight container 8 becomes an intermediate pressure. The refrigerant having the intermediate pressure is discharged from the low stage discharge port 8b to the intermediate pressure discharge pipe 20, cooled through the intercooler 13, and sucked into the high stage suction port 8c through the intermediate pressure suction pipe 21. . This refrigerant flows into the second compression section 12 and is pressurized to a high pressure, discharged from the high-stage discharge port 8d to the high-pressure discharge pipe 22, oil is separated by the oil separator 14, and passes through the gas cooler 15 and the economizer 16. And further cooled.

The refrigerant that has passed through the economizer 16 reaches the cooler 3, is decompressed by the expansion valve 18, and then flows to the evaporator 19. The refrigerant that has passed through the evaporator 19 returns to the low-stage suction port 8a of the compressor 7 through the refrigerant pipe 6.
Further, a part of the refrigerant that has flowed to the economizer 16 through the high pressure discharge pipe 22 branches to the economizer passage pipe 23 and is decompressed by the expansion valve 25, and then flows to the economizer 16 from the reverse direction. The refrigerant flowing through the economizer 16 is cooled. The refrigerant used for cooling the refrigerant in the economizer 16 joins the intermediate pressure suction pipe 21 through the economizer passage pipe 23.

A part of the intermediate-pressure refrigerant discharged from the first compression unit 11 into the sealed container 8 and a part of the oil in the sealed container 8 flow through the upper limit pipe 31 and the lower limit pipe 32 and join the merge pipe 34. It merges in the middle of the refrigerant pipe 6 through the capillary tube 35 and returns to the low-stage suction port 8a.
The oil separated from the refrigerant by the oil separator 14 is cooled by the oil cooler 17 through the oil return pipe 26 and returned to the sealed container 8 at a flow rate adjusted by the oil supply valve 27.

Next, the oil level detection device 30 will be described in detail.
FIG. 2 is a diagram illustrating the oil level detection device 30.
In the sealed container 8, an appropriate position M of the oil level (liquid level height) of the oil stored in the sealed container 8, an upper limit position H of the oil level, and a lower limit position L of the oil level are set. Yes.
The upper limit position H is an upper limit of the allowable oil level, and is set to a height at which oil does not affect the drive unit 9, for example. The lower limit position L is a lower limit of the allowable oil level, and is set, for example, corresponding to the position of the oil intake port of the oil that lubricates the inside of the compressor 7. The appropriate position M is set at an upper and lower intermediate position between the upper limit position H and the lower limit position L.

The airtight container 8 has an upper outlet 41 to which the upper limit pipe 31 is connected at an upper limit position H on its side wall, and a lower outlet 42 to which the lower limit pipe 32 is connected at a lower limit position L on its side wall. .
The upper limit pipe 31 includes an upper horizontal portion 43 that is drawn from the upper outlet 41 and extends substantially horizontally, and an upper vertical portion 44 that is bent downward at the end of the upper horizontal portion 43 and extends substantially vertically.
The lower limit pipe 32 includes a lower horizontal portion 45 that is pulled out from the lower outlet 42 and extends substantially horizontally, and a lower vertical portion 46 that is bent upward at the end of the lower horizontal portion 45 and extends substantially vertically. .
By connecting the lower end of the upper vertical portion 44 and the upper end of the lower vertical portion 46, one vertical pipe portion 47 extending substantially vertically between the upper horizontal portion 43 and the lower horizontal portion 45 is formed. The

The merge portion 33 is provided at an upper and lower intermediate position between the upper outlet 41 and the lower outlet 42, that is, at the same height as the appropriate position M.
The merge pipe 34 extends substantially horizontally from the merge section 33. That is, the merging pipe 34 extends substantially horizontally at the same height position as the appropriate position M, and the inlet of the merging pipe 34 coincides with the merging portion 33.
The connection pipe 36 connects the end of the merging pipe 34 in the middle of the refrigerant pipe 6.

The control unit 4 detects the temperature of the joining pipe 34 upstream of the capillary tube 35 with the upstream temperature sensor 37, and detects the temperature of the joining pipe 34 downstream of the capillary tube 35 with the downstream temperature sensor 38.
The upper limit side opening / closing valve 31a, the lower limit side opening / closing valve 32a, and the opening / closing valve 39 are electromagnetic valves. The control unit 4 opens and closes the upper limit side opening / closing valve 31a and the lower limit side opening / closing valve 32a based on the detection results of the upstream temperature sensor 37 and the downstream temperature sensor 38.

  3A and 3B are diagrams showing the oil level, where FIG. 3A shows a state where the oil level is at a level P1 between the appropriate position M and the lower limit position L, and FIG. 3B shows that the oil level is lower than the lower limit position L. The state at the lower level P3 is shown. 4A and 4B are diagrams illustrating the oil level. FIG. 4A illustrates a state where the oil level is at a level P2 between the appropriate position M and the upper limit position H, and FIG. 4B illustrates that the oil level is higher than the upper limit position H. The state at the upper level P4 is shown.

As shown in FIGS. 3 (a) and 4 (a), in the normal state where the oil level is between the upper limit position H and the lower limit position L, except when detecting the upper limit and the lower limit of the oil level described later. The control unit 4 opens the upper limit side opening / closing valve 31a and the lower limit side opening / closing valve 32a.
Since the pressure in the sealed container 8 is an intermediate pressure and higher than the pressure in the refrigerant pipe 6, the refrigerant in the sealed container 8 is opened when the upper limit side on-off valve 31 a, the lower limit side on-off valve 32 a and the on-off valve 39 are opened. A part of the oil is sucked out from the upper limit pipe 31 and the lower limit pipe 32 and flows to the refrigerant pipe 6 side.
Here, the liquid level position F in the vertical pipe portion 47 of the oil flowing through the upper limit pipe 31 and the lower limit pipe 32 to the vertical pipe portion 47 coincides with the oil level in the sealed container 8 in the normal state.

  As shown in FIG. 3A, in the state where the oil level is level P1, the liquid level position F coincides with the level P1 in the hermetic container 8, and is located below the inlet of the merge pipe 34. In this state, the oil does not flow through the merge pipe 34, and the refrigerant in the sealed container 8 flows through the upper limit pipe 31 to the merge pipe 34 and the capillary tube 35, and then flows through the connection pipe 36 to the refrigerant pipe 6. Here, the gaseous refrigerant passing through the capillary tube 35 is decompressed and expanded in the capillary tube 35. For this reason, the temperature of the refrigerant downstream of the capillary tube 35 is significantly lower than the temperature of the refrigerant upstream of the capillary tube 35, and the temperature difference Td (the temperature difference detected by the upstream temperature sensor 37 and the downstream temperature sensor 38). (Not shown, the same applies hereinafter) becomes larger.

  As shown in FIG. 4A, in the state where the oil level is level P2, the liquid level position F coincides with the level P2 in the sealed container 8, and is located above the inlet of the merge pipe 34. In this state, the refrigerant in the sealed container 8 does not flow into the merge pipe 34, and the oil in the sealed container 8 flows through the lower limit pipe 32 to the merge pipe 34 and the capillary tube 35 and through the connection pipe 36. It flows into the pipe 6. Here, the oil remains liquid even after passing through the capillary tube 35, and the state does not change before and after the capillary tube 35. For this reason, the temperature of the oil downstream of the capillary tube 35 is substantially the same as the temperature of the oil upstream of the capillary tube 35, and the temperature difference Td detected by the upstream temperature sensor 37 and the downstream temperature sensor 38 is , Almost zero.

  As shown in FIG. 3B, when the oil level is level P3, when the upper limit side opening / closing valve 31a is closed and the lower limit side opening / closing valve 32a is opened, the oil does not flow into the lower limit piping 32, but the gas state The refrigerant flows through the lower limit pipe 32 to the merge pipe 34, passes through the capillary tube 35, and flows into the refrigerant pipe 6. In this state, since the refrigerant expands in the capillary tube 35, the temperature difference Td based on the upstream temperature sensor 37 and the downstream temperature sensor 38 becomes large.

  As shown in FIG. 4 (b), when the oil level is level P4, when the upper limit side on / off valve 31a is opened and the lower limit side on / off valve 32a is closed, the refrigerant does not flow into the upper limit pipe 31 and the oil is not supplied. , Flows through the upper limit pipe 31 to the merge pipe 34, passes through the capillary tube 35, and flows into the refrigerant pipe 6. In this state, since oil passes through the capillary tube 35, the temperature difference Td based on detection by the upstream temperature sensor 37 and the downstream temperature sensor 38 is almost zero.

FIG. 5 is a flowchart of oil level detection control by the control unit 4. The control unit 4 executes the processing of this flowchart at a predetermined sampling interval.
The control unit 4 detects the oil level based on the temperature difference Td between the upstream and downstream of the capillary tube 35. Hereinafter, the process of detecting the oil level by the control unit 4 will be described with reference to FIGS.
First, in the state where the upper limit side opening / closing valve 31a and the lower limit side opening / closing valve 32a are opened, the control unit 4 has a predetermined temperature difference in the temperature difference Td obtained from the detection values of the upstream temperature sensor 37 and the downstream temperature sensor 38. It is determined whether there is, that is, whether the temperature difference Td is 5 ° C. or more (step S1). Here, the predetermined temperature difference is not limited to 5 ° C. as long as it is a significant value capable of determining that the refrigerant is flowing through the capillary tube 35.

Next, when the temperature difference Td is 5 ° C. or more (step S1: Yes), the controller 4 is in a state where the oil level is level P1 (FIG. 3A), that is, the oil is insufficient from the appropriate position M. It is determined that the oil supply valve 27 is present (step S2), and the opening of the oil supply valve 27 is increased to increase the amount of oil supplied to the sealed container 8 (step S3). As a result, the oil level usually shifts in a direction exceeding the appropriate position M.
Subsequently, the control unit 4 closes the upper limit side on-off valve 31a after a predetermined time has elapsed after opening the oil supply valve 27 (step S4), and determines whether or not the temperature difference Td is 5 ° C. or more (step). S5).
Here, the temperature difference Td becomes 5 ° C. or more in step S5 is an abnormal state in which the oil level becomes a level P3 below the lower intake port 42 as shown in FIG. . In step S5, the temperature difference Td is less than 5 ° C. when oil flows through the capillary tube 35 and the oil level is above the lower limit position L.

  When the temperature difference Td is 5 ° C. or more (step S5: Yes), the control unit 4 issues an oil shortage alarm on the display or the like and stops the operation of the compressor 7 (step S6). When the temperature difference Td is less than 5 ° C. (step S5: No), the controller 4 switches the upper limit side on / off valve 31a and the lower limit side on / off valve 32a to open (step S7), and the process of step S1. Return to.

  Further, when the temperature difference Td is less than 5 ° C. in Step S1 (Step S1: No), the control unit 4 is in a state where the oil level is level P2 (FIG. 4A), that is, the oil is more than the proper position M. It is determined that the state is excessive (step S8), the opening of the oil supply valve 27 is decreased, and the amount of oil supplied to the sealed container 8 is decreased (step S9). As a result, the oil level usually shifts below the appropriate position M.

Subsequently, the control unit 4 closes the lower limit side on-off valve 32a after a predetermined time has elapsed since the oil supply valve 27 was closed (Step S10), and determines whether or not the temperature difference Td is 5 ° C. or more (Step S10). S11).
Here, the temperature difference Td is less than 5 ° C. in step S11 is an abnormal state where the oil level is above the upper limit position H as shown in FIG. Further, the temperature difference Td becomes 5 ° C. or more in step S11 when the refrigerant flows through the capillary tube 35 and the oil level is below the upper limit position H.

  When the temperature difference Td is less than 5 ° C. (step S11: No), the control unit 4 issues an oil excess alarm on the display or the like and stops the operation of the compressor 7 (step S12). When the temperature difference Td is 5 ° C. or more (step S11: Yes), the control unit 4 switches the upper limit side on / off valve 31a and the lower limit side on / off valve 32a to open (step S7), and the process of step S1. Return to.

  In the present embodiment, whether or not the oil level is above or below the appropriate position M, which is an arbitrary reference position, is determined by determining whether or not the temperature difference Td is 5 ° C. or more in step S1. Can be detected. In the present embodiment, the merging pipe 34 is communicated with the sealed container 8 via the upper limit pipe 31 and the lower limit pipe 32 that open into the sealed container 8 at positions above and below the merging pipe 34 provided with the capillary tube 35. The height position of the merging pipe 34 matches the appropriate position M. Here, the liquid surface position F of the vertical pipe portion 47 changes in conjunction with the oil level in the sealed container 8, but the upper outlet 41 and the lower outlet 42 are located at positions away from the oil level. Therefore, fluctuations such as the undulation of the liquid level of the oil in the sealed container 8 hardly affect the liquid level position F. For this reason, it can suppress that the fluid of the state with which the refrigerant | coolant and oil were mixed to the capillary tube 35 can be suppressed, the big temperature difference Td can be obtained, and determination of an oil level can be performed correctly.

  On the other hand, for example, when the upper end pipe 31 and the lower limit pipe 32 are not provided and the merging pipe 34 is straightly extended and connected to the sealed container 8, fluctuations such as the undulation of the oil level of the oil Directly affects the entrance. For this reason, the fluid in which the refrigerant and oil are mixed flows into the capillary tube 35, the temperature difference Td becomes small, and it is difficult to accurately determine the oil level.

  As described above, according to the embodiment to which the present invention is applied, the upper limit pipe 31 and the lower limit pipe 32 are connected above and below the oil level appropriate position M of the hermetic container 8 of the compressor 7, and the upper limit pipe 31 and The lower limit pipe 32 is joined and connected to the refrigerant pipe 6 on the suction side of the compressor 7, and the capillary tube 35 is connected to the junction pipe 34, and the upstream temperature sensor 37 and the downstream temperature are upstream and downstream of the capillary tube 35. A sensor 38 was arranged. For this reason, based on the temperature difference Td detected by the upstream temperature sensor 37 and the downstream temperature sensor 38, it can be detected whether the oil level is above or below the junction pipe 34, with a simple configuration. Oil level can be detected. At this time, the upper limit pipe 31 and the lower limit pipe 32 do not need to be configured so that the flow paths of the upper limit pipe 31 and the lower limit pipe 32 are closed, and in the case of detecting only the oil level with respect to the merge pipe 34. It is not necessary to provide the upper limit side on / off valve 31a and the lower limit side on / off valve 32a, and the control of the upper limit side on / off valve 31a and the lower limit side on / off valve 32a becomes unnecessary. Further, the oil level F in the portion where the upper and lower upper limit pipes 31 and the lower limit pipe 32 above and below the proper oil level position M substantially coincides with the oil level in the hermetic container 8, and the liquid level F is hermetically sealed. The container 8 is hardly affected by the oil level ripples and the like, and is stable. For this reason, it is possible to suppress the fluid in a state where the oil and the refrigerant are mixed from flowing into the merge pipe 34, and to appropriately detect the oil level based on the temperature difference Td between the upstream and downstream of the capillary tube 35.

Further, since the merging pipe 34 is piped in accordance with the height of the appropriate position M of the oil level, it can be appropriately detected based on the temperature difference Td whether the oil level is above or below the proper position M.
Moreover, the control part 4 which determines an oil level based on the detected value of the upstream temperature sensor 37 and the downstream temperature sensor 38 is provided, and an oil extraction piping is the upper limit connected to the upper limit position H of the oil level of the airtight container 8. A pipe 31 and a lower limit pipe 32 connected to the lower limit position L of the oil level are provided. The upper limit pipe 31 and the lower limit pipe 32 merge at an appropriate position M, and the upper limit pipe 31 opens and closes the flow path of the upper limit pipe 31. When the control unit 4 determines that the oil level is lower than the appropriate position M, the upper limit side opening / closing valve 31a is closed. Thereby, when the oil level is below the lower limit position L, the refrigerant flows through the lower limit pipe 32 without flowing through the upper limit pipe 31, and the temperature difference Td upstream and downstream of the capillary tube 35 of the refrigerant is detected. By doing so, it can be easily detected that the oil level is below the lower limit position L.

Further, the lower limit pipe 32 includes a lower limit side open / close valve 32a that opens and closes the flow path of the lower limit pipe 32. When the control unit 4 determines that the oil level is excessive from the appropriate position M, the lower limit side open / close valve 32a. Is closed and the upper limit side on-off valve 31a is opened. Accordingly, when the oil level is above the upper limit position H, the refrigerant flows through the upper limit pipe 31 without flowing through the lower limit pipe 32, and the temperature difference between the upstream and downstream of the capillary tube 35 of the refrigerant is detected. Thus, it can be easily detected that the oil level is above the upper limit position H.
Further, the amount of oil supplied to the sealed container 8 can be adjusted by the oil supply valve 27 in accordance with the detected oil level, and the oil level can be positioned in the vicinity of the appropriate position M.

Further, since the compressor 7 is a two-stage compressor, and the merging pipe 34 is connected to the refrigerant pipe 6 that is the first-stage suction pipe, the pressure difference between the merging pipe 34 and the refrigerant pipe 6 becomes large. The refrigerant passing through the capillary tube 35 can be greatly depressurized. For this reason, the temperature difference Td of the refrigerant passing through the capillary tube 35 can be increased, and the oil level can be correctly detected based on the temperature difference Td.
Further, since the on-off valve 39 is connected to the junction pipe 34, when the oil level detection is unnecessary, the flow of the junction pipe 34 can be stopped by closing the on-off valve 39, so that the efficiency of the compressor 7 is increased. Can be improved. For example, the control unit 4 closes the on-off valve 39 when the compressor 7 is started up or when the cooler 3 is defrosted.

In addition, the said embodiment shows the one aspect | mode which applied this invention, Comprising: This invention is not limited to the said embodiment.
In the above-described embodiment, the merging pipe 34 is described as being arranged in accordance with the height of the appropriate position M of the oil level. However, the present invention is not limited to this, and the merging pipe 34 is to be detected. It can be placed at any oil level.
In the above embodiment, the upper horizontal portion 43, the upper vertical portion 44, the lower horizontal portion 45, and the lower vertical portion 46 are described. However, the present invention is not limited to this. It is only necessary that the upper outlet 41 and the lower outlet 42 be arranged at the upper and lower positions of the merging portion 33, and the upper limit piping 31 and the lower limit piping 32 are connected to the merging portion from the upper outlet 41 and the lower outlet 42, for example. The piping may be obliquely directed toward the 33 side.

4 Control section 6 Refrigerant piping (Compressor suction piping, first stage suction piping)
7 Compressor 8 Airtight container 27 Oil supply valve 30 Oil level detection device 31 Upper limit piping (oil extraction piping)
31a Upper limit side open / close valve 32 Lower limit piping (oil extraction piping)
32a Lower limit side open / close valve 34 Junction piping 35 Capillary tube (pressure reducer)
37 Upstream temperature sensor (temperature sensor)
38 Downstream temperature sensor (temperature sensor)
39 On-off valve H Upper limit position L Lower limit position M Appropriate position

Claims (7)

  Connect multiple oil take-off pipes above and below the appropriate oil level of the compressor's sealed container, join each oil take-out pipe and connect it to the compressor suction pipe, and connect a decompressor to the merge pipe An oil level detection device for a compressor, wherein temperature sensors are arranged upstream and downstream of the decompressor.   2. The oil level detection device for a compressor according to claim 1, wherein the merging pipe is piped in accordance with a height of the appropriate position of the oil level. A control unit for determining the oil level based on a detection value of the temperature sensor;
The oil extraction pipe includes an upper limit pipe connected to the upper limit position of the oil level of the sealed container and a lower limit pipe connected to a lower limit position of the oil level, and the upper limit pipe and the lower limit pipe are The upper limit pipe is joined at an appropriate position, and the upper limit pipe includes an upper limit side on-off valve that opens and closes the flow path of the upper limit pipe.
The said control part closes the said upper limit side on-off valve, when it determines with the said oil level being insufficient from the said appropriate position, The oil level detection apparatus of the compressor of Claim 2 characterized by the above-mentioned. The lower limit pipe includes a lower limit side on-off valve that opens and closes the flow path of the lower limit pipe,
The compressor according to claim 3, wherein the control unit closes the lower limit side on-off valve and opens the upper limit side on-off valve when the oil level is determined to be excessive from the appropriate position. Oil level detector.   The oil supply valve which adjusts the quantity of the oil supplied to the said airtight container is provided, The said oil supply valve is controlled based on the detected value of the said temperature sensor, The one in any one of Claim 1 to 4 characterized by the above-mentioned. The compressor oil level detection device described.   The oil level detection device for a compressor according to claim 1 or 2, wherein the compressor is a two-stage compressor, and the merging pipe is connected to a first-stage suction pipe.   The oil level detection device for a compressor according to any one of claims 1 to 6, wherein an on-off valve is connected to the merging pipe.

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