CN115711503A - Screw unit oil return device and control method thereof - Google Patents

Abstract

The application relates to an oil return device of a screw unit and a control method thereof, relating to the technical field of screw units. The screw unit oil return device comprises a compressor and an oil return pipeline at the air suction end of the compressor; the suction end of the compressor is connected with the input end of the oil return pipeline of the suction end of the compressor, and the output end of the oil return pipeline of the suction end of the compressor is connected with the first oil return port of the compressor. The method is used for solving the problem that the compressor is frequently started and stopped due to oil shortage caused by oil accumulation at the air suction end under the condition of low load of the compressor.

Description

Screw unit oil return device and control method thereof

Technical Field

The application relates to the technical field of screw units, in particular to an oil return device of a screw unit and a control method of the oil return device.

Background

The refrigeration oil plays roles of cooling, lubrication, sealing, energy regulation and the like in the running process of the water-cooled screw machine, and plays an important role in ensuring the running reliability and stability of the compressor and prolonging the service life. In the system circulation of the screw machine, the refrigeration oil enters from the oil return port of the compressor, and lubricates all parts of the compressor along with the rotation of the bearing, when the load of the compressor is large, the rotating speed of a rotor is high, and the refrigeration oil can be directly taken away to enter the system circulation; when the load of the compressor is small, the rotating speed of the rotor is low, and part of the refrigeration oil can directly drop to the bottom end of the suction end cover of the compressor, so that the refrigeration oil cannot circulate, and the fault shutdown is caused.

At present, previous people have made many researches on an oil return structure of a compressor, for example, an auxiliary oil return assembly is added on a main oil return pipeline to ensure that lubricating oil of an air conditioning system under an ultralow temperature working condition can flow back to the compressor through the auxiliary oil return assembly, so that the problem of insufficient oil return of the compressor caused by the fact that the lubricating oil blocks a capillary under the ultralow temperature working condition is effectively solved; and an oil separation structure is arranged outside the low-temperature water-cooling screw, so that the compressor oil brought out from the compressor can be separated in time, and the compressor is prevented from being not returned to the compressor in time after entering the system, so that the compressor is prevented from being damaged due to oil shortage.

However, the existing scheme can not solve the problem that the compressor is frequently started and stopped due to oil shortage because the oil is accumulated at the air suction end under low load of the compressor.

Disclosure of Invention

The application provides an oil return device of a screw unit and a control method thereof, which are used for solving the problem that the compressor is frequently started and stopped due to oil shortage caused by oil accumulation at an air suction end under low load of the compressor.

In a first aspect, an embodiment of the present application provides an oil return device for a screw unit, including a compressor and an oil return pipeline at a suction end of the compressor;

the air suction end of the compressor is connected with the input end of the oil return pipeline at the air suction end of the compressor, and the output end of the oil return pipeline at the air suction end of the compressor is connected with the first oil return port of the compressor.

Optionally, the screw unit oil return device further comprises an oil separator; the oil return pipeline at the air suction end of the compressor comprises a first electromagnetic valve and a first ejector;

the air suction end of the compressor is connected with the first input end of the first ejector, the output end of the oil separator is connected with the first end of the first electromagnetic valve, the second end of the first electromagnetic valve is connected with the second input end of the first ejector, and the output end of the first ejector is connected with the first oil return opening of the compressor.

Optionally, the compressor suction end oil return pipeline further comprises a second solenoid valve and an oil pump;

the air suction end of the compressor is connected with the first end of the second electromagnetic valve, the second end of the second electromagnetic valve is connected with the first end of the oil pump, and the second end of the oil pump is connected with the first oil return opening of the compressor.

Optionally, the screw unit oil return device further comprises a liquid level sensor;

the measuring end of the liquid level sensor is connected with the air suction end of the compressor, the first control end of the liquid level sensor is connected with the controlled end of the first electromagnetic valve, and the second control end of the liquid level sensor is connected with the controlled end of the second electromagnetic valve.

Optionally, the screw unit oil return device further comprises a main oil return pipeline; the main oil return pipeline comprises a third electromagnetic valve, a ball valve, a liquid viewing mirror and a first oil filter;

the output end of the oil separator is connected with the first end of the third electromagnetic valve, the second end of the third electromagnetic valve is connected with the first end of the ball valve, the second end of the ball valve is connected with the first end of the liquid sight glass, the second end of the liquid sight glass is connected with the input end of the first oil filter, and the output end of the first oil filter is connected with the first oil return port of the compressor.

Optionally, the screw unit oil return device further comprises an evaporator and an evaporator injection oil return pipeline; the evaporator injection oil return pipeline comprises a second oil filter and a second injector;

the output end of the evaporator is connected with the input end of the second oil filter, the output end of the second oil filter is connected with the first input end of the second ejector, the second end of the ball valve is connected with the second input end of the second ejector, and the output end of the second ejector is connected with the second oil return opening of the compressor.

Optionally, the liquid level sensor is configured to detect a refrigerant oil level at a suction end of the compressor, and when the refrigerant oil level is greater than or equal to a first preset level value, control the first solenoid valve to open and control the second solenoid valve to close.

Optionally, the liquid level sensor is further configured to continue to detect a level of the refrigeration oil at a suction end of the compressor after controlling the first solenoid valve to be opened and the second solenoid valve to be closed, and control the first solenoid valve to be closed when the level of the refrigeration oil is less than or equal to a second preset level value, where the second preset level value is less than the first preset level value.

Optionally, the liquid level sensor is further configured to obtain an opening duration of the first electromagnetic valve after controlling the first electromagnetic valve to be opened and controlling the second electromagnetic valve to be closed, and control the first electromagnetic valve to be closed and control the second electromagnetic valve to be opened when the opening duration is greater than or equal to a preset opening duration.

Optionally, the liquid level sensor is further configured to continue to detect a level of the refrigeration oil at a suction end of the compressor after controlling the first electromagnetic valve to be closed and controlling the second electromagnetic valve to be opened, and control the second electromagnetic valve to be closed when the level of the refrigeration oil is less than or equal to a second preset level value, where the second preset level value is less than the first preset level value.

In a second aspect, an embodiment of the present application provides a method for controlling an oil return device of a screw unit, where the method is applied to a liquid level sensor in the oil return device of the screw unit, and the method includes:

detecting the level of the refrigeration oil at the air suction end of the compressor;

and when the liquid level of the refrigeration oil is greater than or equal to a first preset liquid level value, controlling the first electromagnetic valve to be opened and controlling the second electromagnetic valve to be closed.

Optionally, after the controlling the first solenoid valve to be opened and the controlling the second solenoid valve to be closed, the method further includes:

continuously detecting the level of the refrigeration oil at the air suction end of the compressor;

and when the liquid level of the refrigeration oil is less than or equal to a second preset level value, controlling the first electromagnetic valve to be closed, wherein the second preset level value is less than the first preset level value.

Optionally, after the controlling the first solenoid valve to open and the controlling the second solenoid valve to close, the method further comprises:

acquiring the opening duration of the first electromagnetic valve;

and when the opening time is greater than or equal to the preset opening time, controlling the first electromagnetic valve to be closed and controlling the second electromagnetic valve to be opened.

Optionally, after the controlling the first solenoid valve to be closed and the controlling the second solenoid valve to be opened, the method further includes:

continuously detecting the level of the refrigeration oil at the air suction end of the compressor;

and when the liquid level of the refrigeration oil is less than or equal to a second preset level value, controlling the second electromagnetic valve to be closed, wherein the second preset level value is less than the first preset level value.

Compared with the prior art, the technical scheme provided by the embodiment of the application has the following advantages: the embodiment of the application provides a screw unit oil returning device, including compressor and compressor suction end oil return pipeline, the compressor suction end of compressor is connected the compressor and is breathed in the input that the oil return pipeline was returned to the end, the compressor suction end oil return pipeline's output is connected the first oil return mouth of compressor, the compressor suction end oil return pipeline is used for the refrigerant oil that stores up with the end of breathing in of compressor backward flow to the first oil return mouth of compressor, can improve the oil return efficiency of compressor, prevent that the refrigerant oil from storing up the end of breathing in at the compressor, guarantee compressor normal operating under the low-load, the suction end oil accumulation under the compressor low-load has been solved, lead to the compressor because the problem of the oil shortage frequently stops.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and together with the description, serve to explain the principles of the application.

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious for those skilled in the art to obtain other drawings without inventive labor.

FIG. 1 is a schematic structural diagram of an oil return device of a screw unit in an embodiment of the present application;

FIG. 2 is a schematic structural diagram of an oil return device of a screw unit according to an embodiment of the present application;

FIG. 3 is a schematic structural view of an oil return device of the screw unit according to an embodiment of the present application;

FIG. 4 is a schematic structural diagram of an oil return device of a screw unit according to an embodiment of the present application;

FIG. 5 is a schematic structural diagram of an oil return device of a screw unit according to an embodiment of the present application;

FIG. 6 is a schematic structural diagram of an oil return device of a screw unit according to an embodiment of the present application;

FIG. 7 is a schematic flow chart of a method for controlling an oil return device of a screw unit in the embodiment of the present application;

FIG. 8 is a schematic flow chart of a method for controlling an oil return device of a screw unit according to an embodiment of the present application;

the reference numbers are as follows: 10-compressor, 20-compressor suction end oil return pipeline, 21-first electromagnetic valve, 22-first ejector, 23-second electromagnetic valve, 24-oil pump, 30-oil separator, 40-liquid level sensor, 50-main oil return pipeline, 51-third electromagnetic valve, 52-ball valve, 53-liquid viewing mirror, 54-first oil filter, 60-evaporator, 70-evaporator oil return injection pipeline, 71-second oil filter and 72-second ejector.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

In the embodiment of the present application, an oil return device for a screw machine set is provided, as shown in fig. 1, the oil return device for a screw machine set includes a compressor 10 and a compressor suction end oil return pipeline 20;

the air suction end of the compressor 10 is connected to the input end of the compressor air suction end oil return pipeline 20, and the output end of the compressor air suction end oil return pipeline 20 is connected to the first oil return port of the compressor 10.

The oil return pipeline at the air suction end of the compressor is used for returning the refrigeration oil accumulated at the air suction end of the compressor to the first oil return port of the compressor. The oil return efficiency of the compressor can be improved, the frozen oil is prevented from being accumulated at the air suction end of the compressor, the normal operation of the compressor under low load is ensured, and the problem that the compressor is started and stopped frequently due to oil shortage caused by the accumulated oil at the air suction end under the low load of the compressor is solved.

In one embodiment, as shown in fig. 2, the screw unit oil return device includes a compressor 10, a compressor suction end oil return line 20 and an oil separator 30; the compressor suction end oil return pipeline 20 comprises a first electromagnetic valve 21 and a first ejector 22;

the suction end of the compressor 10 is connected with the first input end of the first ejector 22, the output end of the oil separator 30 is connected with the first end of the first electromagnetic valve 21, the second end of the first electromagnetic valve 21 is connected with the second input end of the first ejector 22, and the output end of the first ejector 22 is connected with the first oil return port of the compressor 10.

In fig. 2, the direction of the arrow indicates the flow direction of the refrigerant oil. The frozen oil flowing out from the bottom of the suction end of the compressor and the main path oil flowing through the first electromagnetic valve from the oil separator are converged into a first oil return port of the compressor through the first ejector.

The refrigeration oil stored in the air suction end of the compressor can be returned to the first oil return opening of the compressor.

In one embodiment, as shown in fig. 3, the compressor suction-side oil return line 20 includes a first solenoid valve 21, a first ejector 22, a second solenoid valve 23, and an oil pump 24;

the air suction end of the compressor 10 is connected to the first end of the second solenoid valve 23, the second end of the second solenoid valve 23 is connected to the first end of the oil pump 24, and the second end of the oil pump 24 is connected to the first oil return port of the compressor 10.

In fig. 3, the direction of the arrow indicates the flow direction of the refrigerant oil. In fig. 3, there are two types of flow patterns of the refrigeration oil, and the first type is: the frozen oil flowing out of the bottom of the air suction end of the compressor and the oil flowing from the oil separator through the main path of the first electromagnetic valve are converged into a first oil return port of the compressor through the first ejector; the second mode is as follows: the frozen oil flowing out from the bottom of the air suction end of the compressor flows through the second electromagnetic valve and is directly pumped to the first oil return port of the compressor through the oil pump.

When can't draw through the first mode and penetrate the oil return or draw and penetrate the oil return effect not good, can adopt the second mode, directly extract the first oil return mouth to the compressor with the refrigeration oil that the suction end of compressor was deposited through the oil pump, prevent that the refrigeration oil from depositing in the suction end of compressor.

In one embodiment, as shown in fig. 4, the screw unit oil return device includes a compressor 10, a compressor suction end oil return line 20, an oil separator 30 and a liquid level sensor 40;

the measuring end of the liquid level sensor 40 is connected with the suction end of the compressor 10, the first control end of the liquid level sensor 40 is connected with the controlled end of the first electromagnetic valve 21, and the second control end of the liquid level sensor 40 is connected with the controlled end of the second electromagnetic valve 23.

In fig. 4, the direction of the arrow indicates the flow direction of the refrigerant oil.

Install level sensor at the end of breathing in of compressor, level sensor can detect the refrigeration oil liquid level of the end of breathing in of compressor to according to the refrigeration oil liquid level of the end of breathing in of compressor, control opening or closing of first solenoid valve, control opening or closing of second solenoid valve, realize that the refrigeration oil that the end of breathing in of automatic control compressor stores up flows in the first oil return mouth of compressor through first ejector, perhaps flows in the first oil return mouth of compressor through the oil pump.

In one embodiment, as shown in fig. 5, the screw unit oil return device includes a compressor 10, a compressor suction side oil return line 20, an oil separator 30, a liquid level sensor 40, and a main oil return line 50; the main return line 50 comprises a third solenoid valve 51, a ball valve 52, a sight glass 53 and a first oil filter 54;

the output end of the oil separator 30 is connected with the first end of a third electromagnetic valve 51, the second end of the third electromagnetic valve 51 is connected with the first end of a ball valve 52, the second end of the ball valve 52 is connected with the first end of a liquid observation mirror 53, the second end of the liquid observation mirror 53 is connected with the input end of a first oil filter 54, and the output end of the first oil filter 54 is connected with the first oil return port of the compressor 10.

In fig. 5, the direction of the arrow indicates the flow direction of the refrigerant oil. The flow direction of the refrigeration oil in the main oil return pipeline is as follows: the refrigeration oil passes through the third electromagnetic valve, the ball valve, the liquid viewing mirror and the first oil filter from the oil separator and directly enters the first oil return port of the compressor. Most of the return oil to the compressor comes from the main return line.

In one embodiment, as shown in fig. 6, the screw unit oil return device includes a compressor 10, a compressor suction end oil return line 20, an oil separator 30, a liquid level sensor 40, a main oil return line 50, an evaporator 60, and an evaporator injection oil return line 70; the evaporator injection oil return pipeline 70 comprises a second oil filter 71 and a second injector 72;

the output end of the evaporator 60 is connected with the input end of the second oil filter 71, the output end of the second oil filter 71 is connected with the first input end of the second ejector 72, the second end of the ball valve 52 is connected with the second input end of the second ejector 72, and the output end of the second ejector 72 is connected with the second oil return port of the compressor 10.

In fig. 6, the direction of the arrow indicates the flow direction of the refrigerant oil. The flow direction of the refrigerant oil in the evaporator injection oil return pipeline is as follows: the frozen oil flowing out from the bottom of the evaporator passes through the second oil filter, and then flows into a second oil return port of the compressor together with the oil coming out of the oil separator through the third electromagnetic valve and the main path of the ball valve through the second ejector.

In one specific embodiment, the liquid level sensor is used for detecting the level of the refrigeration oil at the air suction end of the compressor, and controlling the first electromagnetic valve to be opened and the second electromagnetic valve to be closed when the level of the refrigeration oil is greater than or equal to a first preset level value.

The first preset level value may be an empirical value or a numerical value obtained through multiple tests, and is used for judging whether to control the first solenoid to be opened. The liquid level of the refrigeration oil is greater than or equal to the first preset liquid level value, which indicates that more refrigeration oil is stored in the air suction end of the compressor, and the refrigeration oil stored in the air suction end of the compressor needs to be returned to the first oil return opening of the compressor, so that the refrigeration oil is prevented from being stored in the air suction end of the compressor, and the normal operation of the compressor under low load is ensured. By controlling the opening of the first electromagnetic valve, the frozen oil flowing out of the bottom of the air suction end of the compressor and the oil flowing from the oil separator through the main path of the first electromagnetic valve are converged into the first oil return port of the compressor through the first ejector. The second electromagnetic valve is controlled to be closed, so that the refrigeration oil flowing out of the bottom of the air suction end of the compressor is prevented from flowing through the second electromagnetic valve, and the first oil return port of the compressor is directly extracted through the oil pump.

In one embodiment, the liquid level sensor is further configured to control the first electromagnetic valve to close and the second electromagnetic valve to close when the frozen oil level is less than a first preset level value.

The liquid level of the refrigeration oil is smaller than a first preset liquid level value, which indicates that the refrigeration oil stored in the air suction end of the compressor is not too much, the oil return of the compressor is not affected, and the refrigeration oil stored in the air suction end of the compressor does not need to flow back to the first oil return opening of the compressor, so that the opening of the first electromagnetic valve does not need to be controlled, and the opening of the second electromagnetic valve does not need to be controlled. At the moment, the compressor performs oil return through the main oil return pipeline and the evaporator injection oil return pipeline. The first electromagnetic valve is controlled to be closed, main oil return can be achieved only through one path of oil return, if the first electromagnetic valve is opened, the main oil return is changed into two paths of oil return, the oil return flow rate of the path of the third electromagnetic valve can be influenced, and therefore injection oil return at the bottom of the evaporator is influenced.

In a specific embodiment, the liquid level sensor is further configured to continue to detect the refrigerant oil level at the suction end of the compressor after controlling the first solenoid valve to be opened and the second solenoid valve to be closed, and control the first solenoid valve to be closed when the refrigerant oil level is less than or equal to a second preset level value, where the second preset level value is less than the first preset level value.

The second preset level value may be an empirical value or a numerical value obtained through multiple tests, and is used for judging whether to control the first electromagnetic valve to be closed. The liquid level of the refrigeration oil is less than or equal to the second preset liquid level value, which shows that the oil return effect of the refrigeration oil at the air suction end of the compressor is good, the refrigeration oil stored at the air suction end of the compressor is little, and the first electromagnetic valve does not need to be opened. The first electromagnetic valve does not need to be opened all the time, and the first electromagnetic valve is controlled to be closed when the amount of the refrigerant oil accumulated at the air suction end of the compressor is large. When the liquid level of the refrigeration oil is less than or equal to the second preset liquid level value, the first electromagnetic valve is controlled to be closed, the first electromagnetic valve can be prevented from being opened all the time, and the oil return flow rate of the main oil return pipeline and the evaporator injection oil return pipeline is further influenced.

In a specific embodiment, the liquid level sensor is further configured to obtain an opening duration of the first electromagnetic valve after controlling the first electromagnetic valve to open and controlling the second electromagnetic valve to close, and control the first electromagnetic valve to close and control the second electromagnetic valve to open when the opening duration is greater than or equal to a preset opening duration.

The preset starting time length can be an empirical value or a numerical value obtained by a plurality of tests. When opening for a long time more than or equal to predetermine when opening for a long time, control first solenoid valve is closed, control second solenoid valve is opened, can avoid first solenoid valve to open always, control first solenoid valve is closed, control second solenoid valve is opened, can be with the refrigeration oil that flows from the suction end bottom of compressor, the second solenoid valve flows through, directly take out the first oil return mouth of compressor through the oil pump, the oil return effect of the refrigeration oil that deposits in the suction end bottom of compressor is better, and can not influence the main oil return pipeline and the oil return velocity of flow that the evaporimeter draws back the oil pipe way.

In a specific embodiment, the liquid level sensor is further configured to continue to detect the level of the refrigeration oil at the suction end of the compressor after controlling the first solenoid valve to be closed and controlling the second solenoid valve to be opened, and control the second solenoid valve to be closed when the level of the refrigeration oil is less than or equal to a second preset level value, where the second preset level value is less than the first preset level value.

When the liquid level of the refrigeration oil is less than or equal to the second preset liquid level value, the refrigeration oil return effect of the air suction end of the compressor is good, the refrigeration oil stored in the air suction end of the compressor is small, the second electromagnetic valve does not need to be opened all the time, and at the moment, the second electromagnetic valve can be controlled to be closed.

To sum up, the screw unit oil returning device that provides in the embodiment of the application, including compressor and compressor suction end oil return pipeline, the suction end of compressor is connected the input that the compressor suction end oil return pipeline, the first oil return mouth of compressor is connected to the output that the compressor suction end oil return pipeline, the compressor suction end oil return pipeline is used for the refrigeration oil that stores up the suction end of compressor to flow back to the first oil return mouth of compressor, can improve the oil return efficiency of compressor, prevent that the refrigeration oil from storing up the suction end at the compressor, guarantee the compressor normal operating under the low-load, the suction end oil accumulation under the compressor low-load has been solved, lead to the compressor because the problem of the frequent start-stop of oil shortage.

Based on the same concept, the embodiment of the present application provides a method for controlling an oil return device of a screw unit, which is applied to a liquid level sensor in the oil return device of the screw unit provided in the present application, and the specific implementation of the method for controlling the oil return device of the screw unit can refer to the description of the method embodiment section, and the repeated points are not repeated, as shown in fig. 7, the method for controlling the oil return device of the screw unit mainly includes:

and step 701, detecting the liquid level of the refrigeration oil at the air suction end of the compressor.

And 702, controlling the first electromagnetic valve to be opened and controlling the second electromagnetic valve to be closed when the liquid level of the refrigeration oil is greater than or equal to a first preset liquid level value.

The liquid level of the refrigeration oil is greater than or equal to the first preset liquid level value, which indicates that more refrigeration oil is stored in the air suction end of the compressor, and the refrigeration oil stored in the air suction end of the compressor needs to be returned to the first oil return opening of the compressor, so that the refrigeration oil is prevented from being stored in the air suction end of the compressor, and the normal operation of the compressor under low load is ensured. By controlling the opening of the first electromagnetic valve, the refrigeration oil flowing out from the bottom of the air suction end of the compressor and the main oil flowing from the oil separator through the first electromagnetic valve are gathered into the first oil return port of the compressor through the first ejector. The second electromagnetic valve is controlled to be closed, so that the refrigeration oil flowing out of the bottom of the air suction end of the compressor is prevented from flowing through the second electromagnetic valve, and the first oil return port of the compressor is directly extracted through the oil pump.

In one embodiment, after detecting the level of the refrigeration oil at the suction end of the compressor, the method for controlling the oil return device of the screw unit further comprises the following steps: and when the frozen oil liquid level is smaller than a first preset liquid level value, controlling the first electromagnetic valve to be closed and controlling the second electromagnetic valve to be closed.

The liquid level of the refrigeration oil is smaller than the first preset liquid level value, which indicates that the refrigeration oil accumulated at the air suction end of the compressor is not too much, the oil return of the compressor is not affected, and the refrigeration oil accumulated at the air suction end of the compressor does not need to flow back to the first oil return opening of the compressor, so that the first electromagnetic valve does not need to be controlled to be opened, and the second electromagnetic valve does not need to be controlled to be opened. At the moment, the compressor performs oil return through the main oil return pipeline and the evaporator injection oil return pipeline. The first electromagnetic valve is controlled to be closed, main oil return can be achieved through one path of oil return, if the first electromagnetic valve is opened, the main oil return is changed into two paths of oil return, the oil return flow rate of the path of the third electromagnetic valve can be influenced, and therefore injection oil return at the bottom of the evaporator is influenced.

In one embodiment, after the first electromagnetic valve is controlled to be opened and the second electromagnetic valve is controlled to be closed, the method for controlling the oil return device of the screw unit further comprises the following steps: continuously detecting the level of the refrigeration oil at the air suction end of the compressor; and when the liquid level of the refrigeration oil is less than or equal to a second preset liquid level value, controlling the first electromagnetic valve to be closed, wherein the second preset liquid level value is less than the first preset liquid level value.

The liquid level of the refrigeration oil is less than or equal to the second preset liquid level value, which shows that the oil return effect of the refrigeration oil at the air suction end of the compressor is good, the refrigeration oil stored at the air suction end of the compressor is little, and the first electromagnetic valve does not need to be opened. The first electromagnetic valve does not need to be opened all the time, and the first electromagnetic valve is controlled to be closed only when the amount of the refrigerant oil accumulated at the air suction end of the compressor is large. When the liquid level of the refrigeration oil is less than or equal to the second preset liquid level value, the first electromagnetic valve is controlled to be closed, the first electromagnetic valve can be prevented from being opened all the time, and the oil return flow rate of the main oil return pipeline and the evaporator injection oil return pipeline is further influenced.

In a specific embodiment, after the first electromagnetic valve is controlled to be opened and the second electromagnetic valve is controlled to be closed, the method for controlling the oil return device of the screw unit further includes: acquiring the opening duration of a first electromagnetic valve; and when the opening duration is greater than or equal to the preset opening duration, controlling the first electromagnetic valve to be closed and controlling the second electromagnetic valve to be opened.

When opening for a long time more than or equal to predetermine when opening for a long time, control first solenoid valve is closed, control second solenoid valve is opened, can avoid first solenoid valve to open always, control first solenoid valve is closed, control second solenoid valve is opened, can be with the refrigeration oil that flows from the suction end bottom of compressor, the second solenoid valve flows through, directly take out the first oil return mouth of compressor through the oil pump, the oil return effect of the refrigeration oil that deposits in the suction end bottom of compressor is better, and can not influence the main oil return pipeline and the oil return velocity of flow that the evaporimeter draws back the oil pipe way.

In a specific embodiment, after the first electromagnetic valve is controlled to be closed and the second electromagnetic valve is controlled to be opened, the method for controlling the oil return device of the screw unit further comprises the following steps: continuously detecting the level of the refrigeration oil at the air suction end of the compressor; and when the liquid level of the refrigeration oil is less than or equal to a second preset liquid level value, controlling the second electromagnetic valve to be closed, wherein the second preset liquid level value is less than the first preset liquid level value.

When the liquid level of the refrigeration oil is less than or equal to the second preset liquid level value, the refrigeration oil return effect of the air suction end of the compressor is good, the refrigeration oil stored in the air suction end of the compressor is not too much, the second electromagnetic valve does not need to be opened all the time, and at the moment, the second electromagnetic valve can be controlled to be closed.

In one embodiment, as shown in fig. 8, a method flow for controlling the oil return device of the screw unit includes:

step 801, detecting the level of the refrigeration oil at the suction end of the compressor.

Step 802, determining whether the liquid level of the refrigeration oil is greater than or equal to a first preset liquid level value, if so, executing step 803, otherwise, executing step 804.

And step 803, controlling the first electromagnetic valve to be opened and controlling the second electromagnetic valve to be closed.

And step 804, controlling the first electromagnetic valve to close, and controlling the second electromagnetic valve to close.

Step 805, determining whether the opening duration of the first electromagnetic valve is greater than or equal to a preset opening duration, if so, executing step 806, otherwise, executing step 807.

And 806, controlling the first electromagnetic valve to be closed, controlling the second electromagnetic valve to be opened, and controlling the oil pump to be opened.

Step 807, judging whether the liquid level of the refrigeration oil is less than or equal to a second preset liquid level value, if so, executing step 808, otherwise, executing step 809.

And 808, controlling the first electromagnetic valve to be closed.

And step 809, controlling the first electromagnetic valve to keep an opening state.

Step 810, judging whether the liquid level of the refrigeration oil is less than or equal to a second preset liquid level value, if so, executing step 811, otherwise, executing step 812.

And step 811, controlling the second electromagnetic valve to close and the oil pump to close.

And step 812, controlling the second electromagnetic valve to keep an open state, and controlling the oil pump to keep the open state.

It is noted that, in this document, relational terms such as "first" and "second," and the like, may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrases "comprising one of 8230; \8230;" 8230; "does not exclude the presence of additional like elements in a process, method, article, or apparatus that comprises the element.

The previous description is only an example of the present application, and is provided to enable any person skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (14)

1. An oil return device of a screw unit is characterized by comprising a compressor and an oil return pipeline at a suction end of the compressor;

the air suction end of the compressor is connected with the input end of the oil return pipeline of the air suction end of the compressor, and the output end of the oil return pipeline of the air suction end of the compressor is connected with the first oil return port of the compressor.

2. The screw unit oil return device of claim 1, further comprising an oil separator; the oil return pipeline at the air suction end of the compressor comprises a first electromagnetic valve and a first ejector;

the air suction end of the compressor is connected with the first input end of the first ejector, the output end of the oil separator is connected with the first end of the first electromagnetic valve, the second end of the first electromagnetic valve is connected with the second input end of the first ejector, and the output end of the first ejector is connected with the first oil return opening of the compressor.

3. The screw unit oil return device according to claim 2, wherein the compressor suction end oil return line further comprises a second solenoid valve and an oil pump;

the air suction end of the compressor is connected with the first end of the second electromagnetic valve, the second end of the second electromagnetic valve is connected with the first end of the oil pump, and the second end of the oil pump is connected with the first oil return port of the compressor.

4. The screw unit oil return device of claim 3, further comprising a level sensor;

the measuring end of the liquid level sensor is connected with the air suction end of the compressor, the first control end of the liquid level sensor is connected with the controlled end of the first electromagnetic valve, and the second control end of the liquid level sensor is connected with the controlled end of the second electromagnetic valve.

5. The screw unit oil return device of claim 4, further comprising a main oil return line; the main oil return pipeline comprises a third electromagnetic valve, a ball valve, a liquid viewing mirror and a first oil filter;

the output end of the oil separator is connected with the first end of the third electromagnetic valve, the second end of the third electromagnetic valve is connected with the first end of the ball valve, the second end of the ball valve is connected with the first end of the liquid observation mirror, the second end of the liquid observation mirror is connected with the input end of the first oil filter, and the output end of the first oil filter is connected with the first oil return port of the compressor.

6. The screw unit oil return device of claim 5, further comprising an evaporator and an evaporator injection oil return line; the evaporator injection oil return pipeline comprises a second oil filter and a second injector;

the output end of the evaporator is connected with the input end of the second oil filter, the output end of the second oil filter is connected with the first input end of the second ejector, the second end of the ball valve is connected with the second input end of the second ejector, and the output end of the second ejector is connected with the second oil return port of the compressor.

7. The screw unit oil return device according to any one of claims 4 to 6, wherein the liquid level sensor is configured to detect a level of the refrigeration oil at a suction end of the compressor, and control the first solenoid valve to open and the second solenoid valve to close when the level of the refrigeration oil is greater than or equal to a first preset level value.

8. The oil return device of screw unit according to claim 7, wherein the liquid level sensor is further configured to continue to detect the refrigerant oil level at the suction end of the compressor after controlling the first solenoid valve to open and the second solenoid valve to close, and control the first solenoid valve to close when the refrigerant oil level is less than or equal to a second preset level value, where the second preset level value is less than the first preset level value.

9. The screw unit oil return device according to claim 7, wherein the liquid level sensor is further configured to obtain an opening duration of the first electromagnetic valve after controlling the first electromagnetic valve to be opened and controlling the second electromagnetic valve to be closed, and control the first electromagnetic valve to be closed and control the second electromagnetic valve to be opened when the opening duration is greater than or equal to a preset opening duration.

10. The oil return device of screw unit according to claim 9, wherein the liquid level sensor is further configured to continue to detect the refrigerant oil level at the suction end of the compressor after controlling the first solenoid valve to be closed and the second solenoid valve to be opened, and to control the second solenoid valve to be closed when the refrigerant oil level is less than or equal to a second preset level value, where the second preset level value is less than the first preset level value.

11. A control method of an oil return device of a screw unit is applied to a liquid level sensor in the oil return device of the screw unit according to claim 4, and comprises the following steps:

detecting the level of the refrigeration oil at the air suction end of the compressor;

and when the liquid level of the refrigeration oil is greater than or equal to a first preset liquid level value, controlling the first electromagnetic valve to be opened and controlling the second electromagnetic valve to be closed.

12. The screw unit oil return device control method according to claim 11, wherein after the first solenoid valve is controlled to be opened and the second solenoid valve is controlled to be closed, the method further comprises:

continuously detecting the level of the refrigeration oil at the air suction end of the compressor;

and when the liquid level of the refrigeration oil is less than or equal to a second preset level value, controlling the first electromagnetic valve to be closed, wherein the second preset level value is less than the first preset level value.

13. The screw unit oil return device control method according to claim 11, wherein after the first solenoid valve is controlled to be opened and the second solenoid valve is controlled to be closed, the method further comprises:

acquiring the opening duration of the first electromagnetic valve;

and when the opening duration is greater than or equal to the preset opening duration, controlling the first electromagnetic valve to be closed and controlling the second electromagnetic valve to be opened.

14. The method for controlling an oil return device of a screw unit according to claim 13, wherein after the first solenoid valve is controlled to be closed and the second solenoid valve is controlled to be opened, the method further comprises:

continuously detecting the level of the refrigeration oil at the air suction end of the compressor;

and when the liquid level of the refrigeration oil is less than or equal to a second preset level value, controlling the second electromagnetic valve to be closed, wherein the second preset level value is less than the first preset level value.

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