CN115143555A

CN115143555A - Air conditioner System

Info

Publication number: CN115143555A
Application number: CN202210761040.2A
Authority: CN
Inventors: 李庆辉; 杨伟茂; 宁明辉; 王振
Original assignee: Qingdao Hisense Hitachi Air Conditioning System Co Ltd
Current assignee: Qingdao Hisense Hitachi Air Conditioning System Co Ltd
Priority date: 2022-06-30
Filing date: 2022-06-30
Publication date: 2022-10-04
Anticipated expiration: 2042-06-30
Also published as: CN115143555B

Abstract

The invention discloses an air conditioning system, which comprises a compressor, an oil separator, a gas-liquid separator, a first electronic expansion valve, an oil level detection loop and a processing unit, wherein the oil level detection loop comprises a first oil level detection unit and a second oil level detection unit; the compressor comprises a refrigerant input port, a refrigerant output port and a connecting port, an oil level detection loop is arranged between the refrigerant input port and the connecting port, a first throttling element and a temperature detection unit are arranged on the oil level detection loop, and the end part, extending into the connecting port, of a pipeline of the oil level detection loop is positioned above the safe oil level of the compressor; the oil separator is provided with an oil inlet and an oil return outlet, and the oil inlet is communicated with the refrigerant outlet; the gas-liquid separator is provided with a gas-liquid separation inlet and a first oil return port, the gas-liquid separation inlet is communicated with the oil-liquid separation oil return outlet, and a first electronic expansion valve is arranged on a pipeline between the first oil return port and the refrigerant input port; the processing unit is configured to: and controlling the opening degree of the first electronic expansion valve according to the temperature of the medium flowing through the oil level detection circuit and the exhaust temperature of the compressor. The variable oil return device can realize variable oil return of the compressor.

Description

Air conditioning system

Technical Field

The invention relates to the technical field of air conditioners, in particular to an air conditioning system.

Background

Reliable system oil return is an important factor for stable operation of an air conditioning system, particularly a multi-split air conditioning system. Once the oil return problem of the system occurs, the compressor is directly damaged, and the air conditioning system cannot operate.

When an existing air conditioning system operates, after refrigerant oil is discharged from a compressor along with a refrigerant, the refrigerant oil is separated in an oil separator and then enters a gas-liquid separator through an oil return capillary tube, the refrigerant of the system also enters the gas-liquid separator after circulation, and returns to the compressor through an oil return hole with the fixed diameter at the bottom of a U-shaped tube in the gas-liquid separator, or the oil return of the compressor is realized through the cooperation of the gas-liquid separator and an electromagnetic valve.

The oil return mode returns oil through the U-shaped pipe in the gas-liquid separator, the oil return hole on the U-shaped pipe returns the mixed liquid of the oil and the refrigerant stored in the gas-liquid separator to the compressor all the time, the liquid return risk of the compressor is increased, the reliability of the compressor is influenced, the compressor is continuously and quantitatively controlled in oil return, and the variable oil quantity control cannot be realized in the oil return control according to requirements.

Disclosure of Invention

In order to solve the technical problem, an embodiment of the present invention provides an air conditioning system for achieving oil quantity changing and oil returning of a compressor.

In order to realize the purpose of the invention, the invention is realized by adopting the following technical scheme:

the application relates to an air conditioning system, which comprises a compressor, an oil separator, a gas-liquid separator, a first electronic expansion valve, an oil level detection loop and a processing unit.

By introducing the oil level detection loop for monitoring the oil level of the compressor in real time, when the oil level is in a low-level state, the opening degree of the first electronic expansion valve is controlled, oil quantity changing and returning are achieved, the oil returning quantity of the compressor is ensured, and the operation reliability of the compressor is improved.

In some embodiments of the present application, the compressor includes a refrigerant input port, a refrigerant output port, and a connection port, and the oil level detection circuit is disposed between the refrigerant input port and the connection port;

the oil level detection loop is provided with a first throttling element and a temperature detection unit, and the end part of the oil level detection loop, which extends into the connecting port, of the pipeline is positioned above the safe oil level of the compressor.

Therefore, the temperature of the internal pipeline of the compressor is detected through the oil level detection circuit, and the oil level of the compressor is determined to be in a high state or a low state by combining the exhaust temperature of the compressor, so that the opening degree of the first electronic expansion valve is controlled, and the oil return amount to the compressor is controlled.

In the application, in order to realize oil return of the compressor in a matching way, an oil separator and a gas-liquid separator are also arranged;

the oil separator is provided with an oil inlet and an oil return outlet, and the oil inlet is communicated with the refrigerant outlet;

the gas-liquid separator is provided with a gas separation inlet and a first oil return port, the gas separation inlet is communicated with the oil separation oil return outlet, and a first electronic expansion valve is arranged on a pipeline between the first oil return port and the refrigerant input port.

In some embodiments of the present application, at intervals after the compressor is operated, if the oil level detection circuit detects that the oil level is in a low state, an opening degree of the first electronic expansion valve is increased, so that an amount of oil returned to the compressor is increased.

And if the oil level detection circuit detects that the oil level is in a high state, keeping the opening degree of the first electronic expansion valve at present.

The oil level detection loop can detect in real time at intervals after the compressor operates, so that the variable oil quantity control of the compressor in the whole operation process is realized, and the oil level position of an oil pool of the compressor is ensured to be above the safe oil level of the compressor, so that the compressor can operate reliably and safely.

In some embodiments of this application, when the compressor was shut down, there was not the oil return problem, and for the convenience of the variable oil volume oil return control of compressor when the operation starts next time the compressor is shut down, first electronic expansion valve is in the closed condition for the aperture to first electronic expansion valve is controlled when the operation starts next time at the compressor.

In some embodiments of the present application, an oil return capillary tube is provided on a pipeline communicating between the oil return outlet and the air distribution inlet, or an oil return capillary tube and a first filter are provided in series on a pipeline communicating between the oil return outlet and the air distribution inlet.

Therefore, when the refrigerant is discharged to the oil separator by the compressor, the lubricating oil in the refrigerant can be separated, and the refrigerant is conveniently throttled to the gas-liquid separator through the oil return capillary tube.

In some embodiments of the present application, a U-shaped pipe is present in the existing gas-liquid separator, and during gas-liquid separation, both pressure loss and oil return resistance of such a pipeline are relatively large, so that the gas-liquid separator in the air conditioning system of the present application adopts a short straight pipe, thereby effectively reducing pressure loss.

In some embodiments of the present application, the gas-liquid separator comprises:

the air inlet pipe extends out of the end part of the cylinder of the gas-liquid separator to form the gas separation inlet;

and the air outlet straight pipe extends out of the end part of the cylinder body to form the air distribution outlet.

In some embodiments of the present application, in order to reduce the amount of liquid refrigerant in the gas-liquid separator and further reduce the occurrence of excessive refrigerant return during oil return of the compressor, the air conditioning system further includes:

and a refrigerant branch flow path provided in a pipe between the oil separation port and the gas separation port of the oil separator, the refrigerant branch flow path being controlled to be disconnected or connected by a processing unit and being capable of throttling the refrigerant passing therethrough.

In some embodiments of the present application, the processing unit opens the refrigerant branch flow path after a certain time before controlling the opening size of the first electronic expansion valve.

Therefore, before the opening degree of the first electronic expansion valve is controlled, the high-temperature and high-pressure refrigerant part passing through the oil separator is divided to the gas-liquid separator, so that the content of the liquid refrigerant in the gas-liquid separator is reduced.

In some embodiments of the present application, the processing unit is configured to:

judging whether the temperature difference between the exhaust temperature of the compressor and the temperature of a medium flowing through the oil level detection loop reaches the upper limit value of a first preset value or not at intervals after the compressor is operated;

if yes, the refrigerant branch flow path is disconnected after the refrigerant branch flow path is communicated for a plurality of times, and then the first electronic expansion valve is increased in opening degree;

and if not, keeping the opening degrees of the refrigerant branch flow path and the first electronic expansion valve off.

In some embodiments of the present application, an electronic expansion valve is disposed on the refrigerant branch flow path; or alternatively

An electromagnetic valve and a second throttling element are arranged on the refrigerant branch flow path in series; or alternatively

An electronic expansion valve and a second filter are arranged in series on the refrigerant branch flow path; or

And the refrigerant branch flow path is provided with an electromagnetic valve, a second throttling element and a second filter in series.

In some embodiments of the present application, when a second throttling element is provided on the refrigeration branch flow path, the second throttling element is a capillary tube.

Other features and advantages of the present invention will become more apparent from the following detailed description of the invention when taken in conjunction with the accompanying drawings.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.

FIG. 1 is a first block diagram of an embodiment of an air conditioning system according to the present invention;

FIG. 2 is a second block diagram of an embodiment of an air conditioning system according to the present invention;

FIG. 3 is a third block diagram of an embodiment of an air conditioning system according to the present invention;

FIG. 4 is a fourth block diagram of an embodiment of an air conditioning system according to the present invention;

fig. 5 is a first flowchart illustrating a method for controlling an opening degree of a first electronic expansion valve according to an embodiment of the air conditioning system of the present invention;

FIG. 6 is a schematic diagram of a partial structure of a gas-liquid separator in an embodiment of an air conditioning system according to the present invention;

FIG. 7 is a fifth block diagram of an embodiment of an air conditioning system according to the present invention;

FIG. 8 is a second flowchart illustrating a method of controlling an opening of a first electronic expansion valve according to an embodiment of the present invention;

FIG. 9 is a sixth block diagram of an embodiment of an air conditioning system according to the present invention;

fig. 10 is a seventh structural diagram of an embodiment of an air conditioning system according to the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the 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 invention. In the description of the present invention, it is to be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate orientations or positional relationships based on those shown in the drawings, and are merely for convenience of description and simplicity of description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, are not to be construed as limiting the present invention.

In the description of the present invention, it should be noted that the terms "mounted," "connected," and "connected" are to be construed broadly and may be, for example, fixedly connected, detachably connected, or integrally connected unless otherwise explicitly stated or limited. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art. In the foregoing description of embodiments, the particular features, structures, materials, or characteristics may be combined in any suitable manner in any one or more embodiments or examples.

The terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified.

[ basic operation principle of air conditioner ]

The air conditioner performs a cooling and heating cycle of the air conditioner by using a compressor, a condenser, an expansion valve, and an evaporator. The cooling and heating cycle includes a series of processes involving compression, condensation, expansion, and evaporation to cool or heat an indoor space.

The low-temperature and low-pressure refrigerant enters the compressor, the compressor compresses the refrigerant gas in a high-temperature and high-pressure state, and the compressed refrigerant gas is discharged. The discharged refrigerant gas flows into the condenser. The condenser condenses the compressed refrigerant into a liquid phase, and heat is released to the surrounding environment through the condensation process.

The expansion valve expands the high-temperature and high-pressure liquid-phase refrigerant condensed in the condenser into a low-pressure liquid-phase refrigerant. The evaporator evaporates the refrigerant expanded in the expansion valve and returns the refrigerant gas in a low-temperature and low-pressure state to the compressor. The evaporator can achieve a refrigerating effect by heat exchange with a material to be cooled using latent heat of evaporation of a refrigerant. The air conditioner can adjust the temperature of the indoor space throughout the cycle.

The outdoor unit of the air conditioner refers to a portion of a refrigeration cycle including a compressor, an outdoor heat exchanger, and an outdoor fan, the indoor unit of the air conditioner includes a portion of an indoor heat exchanger and an indoor fan, and a throttling device (e.g., a capillary tube or an electronic expansion valve) may be provided in the indoor unit or the outdoor unit.

The indoor heat exchanger and the outdoor heat exchanger serve as a condenser or an evaporator. The air conditioner performs a heating mode when the indoor heat exchanger serves as a condenser, and performs a cooling mode when the indoor heat exchanger serves as an evaporator.

The indoor heat exchanger and the outdoor heat exchanger are switched to be used as a condenser or an evaporator, a four-way valve is generally adopted, and specific reference is made to the arrangement of a conventional air conditioner, which is not described herein again.

The refrigeration working principle of the air conditioner is as follows: the compressor works to enable the interior of the indoor heat exchanger (in the indoor unit, the evaporator at the moment) to be in an ultralow pressure state, liquid refrigerant in the indoor heat exchanger is rapidly evaporated to absorb heat, air blown out by the indoor fan is cooled by the coil pipe of the indoor heat exchanger to become cold air which is blown into a room, the evaporated and vaporized refrigerant is compressed by the compressor, is condensed into liquid in a high-pressure environment in the outdoor heat exchanger (in the outdoor unit, the condenser at the moment) to release heat, and the heat is dissipated into the atmosphere through the outdoor fan, so that the refrigeration effect is achieved by circulation.

The heating working principle of the air conditioner is as follows: the gaseous refrigerant is pressurized by the compressor to become high-temperature and high-pressure gas, and the high-temperature and high-pressure gas enters the indoor heat exchanger (the condenser at the moment), is condensed, liquefied and released heat to become liquid, and simultaneously heats indoor air, so that the aim of increasing the indoor temperature is fulfilled. The liquid refrigerant is decompressed by the throttling device, enters the outdoor heat exchanger (an evaporator at the moment), is evaporated, gasified and absorbs heat to form gas, absorbs heat of outdoor air (the outdoor air becomes cooler) to form gaseous refrigerant, and enters the compressor again to start the next cycle.

The present application relates to compressor reliable variable oil return in air conditioning systems, and thus, compressor related components in air conditioning systems are described as follows.

[ air-conditioning System ]

As shown in fig. 1 to 4 and 7, the air conditioning system of the present application includes a compressor 10, an oil separator 20, a gas-liquid separator 30, a first electronic expansion valve 40, an oil level detection circuit 50, and a processing unit (not shown), wherein: the compressor 10 communicates with the oil separator 20 and the gas-liquid separator 30, respectively, and the oil separator 20 and the gas-liquid separator 30 communicate with the indoor side.

In the air conditioning system, the refrigerant oil is used to lubricate and cool the cylinders of the compressor 10 because the compressor 10 is a device requiring high sealing performance, and thus the lubrication and cooling of the cylinders of the compressor 10 are accomplished by the circulation of the refrigerant in the system by mixing the refrigerant oil in the refrigerant.

The compressor 10 is provided with a refrigerant outlet 11, a refrigerant inlet 12, and a connection port 13, which are respectively communicated with the compressor cylinder.

The compressor 10 is configured to suck a gaseous refrigerant from a refrigerant inlet 12, compress and liquefy the gaseous refrigerant, output a liquid refrigerant to an indoor unit side (not shown) through a pipeline via a refrigerant outlet 11, vaporize the liquid refrigerant in a coil pipe of the indoor unit side to absorb heat, and finally return to the compressor 10 to complete the whole cycle process.

The oil level detection circuit 50 is disposed between the connection port 13 and the refrigerant input port 12, and includes a first throttling element 51 (e.g., a capillary tube, an electronic expansion valve, etc.).

When the air conditioning system is circulated, the refrigerant gas of high temperature and high pressure compressed in the compressor 10 can press the refrigerant oil in the compressor 10 to the refrigerant input port 12 through the oil level detection circuit 50, and thus, the temperature of the medium flowing through the oil level detection circuit 50 can be detected by the temperature detection unit 52 provided in the oil level detection circuit 50, thereby determining the oil level in the oil tank of the compressor 10.

When the oil level is high, the medium in the oil level detection circuit 50 is the frozen oil, and therefore, the temperature Toi detected by the temperature detection unit 52 is substantially equal to the compressor discharge temperature Td.

When the oil level is low, the medium in the oil level detection circuit 50 is a refrigerant, and the temperature Toi detected by the temperature detection unit 52 decreases after the refrigerant is throttled by the first throttling element 51.

Therefore, the oil level can be accurately detected by the external oil level detection circuit 50, a reliable basis is provided for oil return of the compressor 10, and the external oil level detection circuit 50 is simple in structure and easy to install and maintain in a later period.

The end of the pipe through which the oil level detection circuit 50 extends into the connection port 13 is located above the safe oil level of the compressor, and therefore, when the oil level of the compressor 10 is lower than the safe oil level of the compressor, the medium to be pressed into the oil level detection circuit 50 is a refrigerant, and when the oil level of the compressor 10 is higher than the safe oil level of the compressor, the medium to be pressed into the oil level detection circuit 50 is a refrigerant oil.

Fig. 1 to 4 and 7 relate to one compressor 10, and a plurality of compressors may be arranged to work in parallel according to actual needs.

For example, referring to fig. 9 and 10, reference is made to compressors 10 and 10'.

When multiple compressors 10 and 10 'are connected in parallel, each compressor 10/10' operates independently and returns oil independently.

With continued reference to fig. 1-4 and 7, the liquid refrigerant output from the refrigerant output 11 of the compressor 10 first enters the oil separator 20.

The oil separator 20 is provided with an oil inlet 21, an oil return outlet 22, and an oil outlet 23.

After the liquid refrigerant enters the oil separator 20 through the oil inlet 21, the refrigerant oil mixed in the refrigerant is separated from the refrigerant, and then is output to the gas-liquid separator 30 through the oil return outlet 22. The refrigerant enters the four-way valve 90 through the check valve Z communicating with the oil outlet 23, and is distributed by the four-way valve 90 and is output to the indoor unit side through a pipeline.

The gas-liquid separator 30 is provided with a gas-distributing inlet 31 and a gas-distributing outlet 32, the gas-distributing inlet 31 is communicated with the four-way valve 90, and the gas-distributing outlet 32 is communicated with the refrigerant input port 12.

The gaseous refrigerant returned from the indoor unit side passes through the four-way valve 90, then also enters the gas-liquid separator 30 through the gas-separation inlet 31, and then returns to the compressor 10 through the gas-separation outlet 32.

The air inlet 31 is communicated with the oil return outlet 22 through a pipeline.

Referring to fig. 1 to 3, an oil return capillary tube 60 may be provided on the pipe; referring to fig. 4, an oil return capillary 60 and a filter 702 may be connected in series to the pipeline, and the refrigerant oil output from the oil return outlet 22 enters the air inlet 31 through the oil return capillary 60 or both the oil return capillary 60 and the filter 702.

The bottom of the gas-liquid separator 30 is further provided with a first oil return port 33, the first oil return port 33 is communicated with the gas-liquid separator 30 and communicated with the refrigerant input port 12 of the compressor 10 through a pipeline, and the refrigerant oil entering the gas-liquid separator 30 returns to the compressor 10 through the pipeline communicating the first oil return port 33 and the refrigerant input port 12, thereby completing the circulation process.

The first electronic expansion valve 40 is disposed on a pipeline for communicating the first oil return port 33 with the refrigerant inlet 12.

Further, a temperature sensor (not labeled) for detecting the compressor discharge temperature Td is provided at the discharge port of the compressor 10.

The processing unit is connected to the temperature detection unit 52, the temperature detection unit detecting Td, the first electronic expansion valve 40 and the compressor 10, respectively, and the processing unit is configured to control the opening degree of the first electronic expansion valve 40 according to the detected temperature Tio and the compressor discharge temperature Td.

As described above with reference to the oil level detection circuit 50, when the oil level in the compressor 10 is high, the opening degree of the first electronic expansion valve 40 is controlled in accordance with the detected temperature Tio and the temperature Td.

From the detected temperature Tio and the temperature Td, a temperature difference between the temperature Td and the temperature Tio is calculated, which is denoted as oil level detection circuit superheat degree TdSH = Td-Tio in the present application.

In conjunction with the above, when the oil level of the compressor 10 is high, the temperature Tio and the temperature Td are substantially the same, and the degree of superheat TdSH = Td-Tio varies within a small range; when the oil level of the compressor 10 is low, the temperature Tio of the refrigerant after throttling is reduced by throttling the refrigerant by the first throttling element 51, and the superheat TdSH = Td-Tio is increased at this time.

According to the above principle, the oil return of the compressor 10 is determined when the compressor 10 is in operation, and the oil return amount is controlled by controlling the opening degree of the first electronic expansion valve 40 when the compressor 10 returns oil.

Referring to fig. 5, a flowchart for controlling the opening degree of the first electronic expansion valve 40 is shown.

S1: the temperature Tio and the temperature Td are detected.

As described above, the temperature Tio is detected by the temperature detection unit 52, and the temperature Td is detected by the temperature detection unit (not labeled).

S2: and calculating the superheat degree TdSH of the oil level detection circuit.

From the detected temperature Tio and the temperature Td, the oil level detection circuit superheat degree TdSH = Td-Tio is calculated.

After the compressor 10 operates for a period of time, it is determined whether the superheat TdSH reaches an upper limit value of a first preset value, if so, the opening degree of the first electronic expansion valve 40 is increased, otherwise, the current opening degree of the first electronic expansion valve 40 is maintained.

The first preset value may be a superheat interval or a superheat value.

S3: after the compressor 10 operates for a period of time, the degrees of superheat TdSH and the first value X are determined, and if the degree of superheat TdSH is greater than the first value X, S4 is performed, otherwise, S5 is performed.

The operation time of the compressor 10 can be freely set here, for example, T =5 minutes.

As fig. 5 is merely an example, when the degree of superheat TdSH reaches the upper limit value of the first preset value, that is, the degree of superheat TdSH is equal to or greater than the first value X, it also proceeds to S4.

The calculation of TdSH as described above may be performed again at the time of the compressor operation T.

S4: the first electronic expansion valve 40 is increased by one opening degree and returns to S3.

When the superheat TdSH is larger than the first value X, it indicates that the superheat TdSH is increasing, and therefore, it may indirectly indicate that the oil level in the compressor 10 is low, and at this time, it is determined that the compressor 10 should return oil.

Specifically, the oil return is realized by an opening degree of the first electronic expansion valve 40.

The first opening degree here refers to a certain opening degree, and for example, if the first electronic expansion valve 40 is fully opened, the first opening degree may be 5 pulses, 10 pulses, or the like.

S5: the current opening degree of the first electronic expansion valve 40 is maintained, and the process returns to S3.

If the superheat TdSH is less than or equal to the first value X, it indicates that the superheat TdSH is not increased and fluctuates within the defined range, and therefore, it may indirectly indicate that the oil level in the compressor 10 is high, and at this time, it is determined that variable oil return is not performed to the compressor 10, and therefore, the current opening degree of the first electronic expansion valve 40 is maintained.

As described above, the process returns to S3 to determine the magnitude of the superheat TdSH at regular intervals (for example, 5 minutes) throughout the continuous operation of the compressor 10.

The oil level of the compressor is monitored in real time by combining the oil level detection loop 50, and the oil quantity of the compressor 10 is controlled according to the requirement by adjusting the opening degree of the first electronic expansion valve 40, so that the oil of the compressor 10 is accurately returned according to the actual operation condition, and the reliable operation of the compressor 10 is ensured.

The oil level detection circuit 50 is simple in structure, is arranged outside the compressor 10, and is convenient to arrange and maintain in a later period.

Referring to fig. 2 to 4, in order to ensure the quality of the oil return, a filter 70 is disposed on a pipeline between the first oil return port 33 of the gas-liquid separator 30 and the refrigerant input port 12.

Referring to fig. 3 and 4, the refrigerant flowing through the four-way valve 90 at the indoor side passes through the filter 701 and flows toward the gas inlet 31 of the gas-liquid separator 30.

In order to reduce the pressure loss of the refrigerant passing through the gas-liquid separator 30, referring to fig. 6, the outlet pipe of the gas-liquid separator 30 is designed as a short straight pipe, so that the pressure loss of the system can be effectively reduced, and the performance of the system can be improved.

The end part of the air inlet pipe 34 extending out of the cylinder body of the gas-liquid separator 30 forms a gas distribution inlet 31; the outlet pipe is changed from an original U-shaped pipe into an outlet straight pipe 35, and the outlet straight pipe 35 extends out of the end part of the cylinder body of the gas-liquid separator 30 to form a gas distribution outlet 32.

In order to reduce the liquid return of the compressor 10, a refrigerant branch circuit 80 is provided in a pipe between the refrigerant outlet 11 and the refrigerant inlet 12 of the compressor 10.

The oil outlet 23 of the oil separator 20 is connected to the input ends of the four-way valve 90 and the refrigerant branch circuit 80 through the check valve Z, and the output end of the refrigerant branch circuit 80 is connected to the four-way valve 90, the air inlet 31, and the oil return outlet 22.

The refrigerant branch circuit 80 can be disconnected or communicated, and is provided with a throttling element.

In some embodiments of the present application, the refrigerant branch circuit 80 may be provided with an electronic expansion valve, the refrigerant branch circuit 80 is disconnected by closing the electronic expansion valve, and the refrigerant branch circuit 80 is communicated and throttled by opening the electronic expansion valve at different opening degrees.

In some embodiments of the present application, referring to fig. 7, a solenoid valve 82 and a throttling element 83 may be disposed in series on the refrigerant branch circuit 80, and the throttling element 83 may be selected as a capillary tube.

The refrigerant branch circuit 80 is disconnected by closing the solenoid valve 82; by opening the solenoid valve 82, the refrigerant branch circuit 80 is communicated, wherein the capillary tube is used for throttling.

In order to improve the oil return quality of the refrigeration oil, referring to fig. 7, a filter 81 may be further provided on the refrigerant branch circuit 80.

A filter 701 is also provided in a pipe between the output end of the refrigerant branch circuit 80 and the gas-liquid separation inlet 31 of the gas-liquid separator 30.

When the refrigerant flows through the refrigerant branch loop 80, the high-temperature and high-pressure gaseous refrigerant output from the refrigerant output port 11 of the compressor 10 enters the gas-liquid separator 30 through the refrigerant branch loop 80, so that the content of the liquid refrigerant at the bottom of the gas-liquid separator 30 is reduced, and the excessive refrigerant return during oil return of the compressor 10 is reduced.

Referring to fig. 8, a flow chart for controlling oil return to the compressor 10 when the compressor 10 is in operation is shown.

S1': the temperature Tio and the temperature Td are detected.

S2': and calculating the superheat degree TdSH of the oil level detection circuit.

Based on the detected temperature Tio and the temperature Td, an oil level detection circuit superheat degree TdSH = Td-Tio is calculated.

The first preset value may be a superheat interval or a superheat value.

S3': after the compressor 10 operates for a period of time, the degrees of superheat TdSH and the first value X are determined, and if the degree of superheat TdSH is greater than the first value X, S4 is performed, otherwise, S5 is performed.

As fig. 8 is merely an example, when the degree of superheat TdSH reaches the upper limit value of the first preset value, that is, the degree of superheat TdSH is equal to or greater than the first value X, the process also proceeds to S4'.

The calculation of TdSH as described above may be performed again when compressor 10 is operating for time T.

S4': the refrigerant branch circuit 80 is connected, and after a certain period of time (for example, several seconds), the refrigerant branch circuit 80 is disconnected again, and the process proceeds to S5'.

Referring to fig. 7, the refrigerant branch circuit 80 is selected as a filter 81, a solenoid valve 82, and a capillary tube 83 connected in series.

The solenoid valve 82 is opened, i.e., communicates with the refrigerant branch circuit 80; the solenoid valve 82 is closed, i.e., the refrigerant branch circuit 80 is disconnected.

Before the opening degree of the first electronic expansion valve 40 is adjusted, the content of the liquid refrigerant in the gas-liquid separator 30 is reduced by the refrigerant branch circuit 80, so that excessive refrigerant liquid return during oil-changing oil return is avoided.

And S5': the first electronic expansion valve 40 is increased by one opening degree and returns to S3'.

Specifically, the oil return is realized by the first electronic expansion valve 40 having an opening degree.

S6': the current opening degrees of the refrigerant branch circuit 80 and the first electronic expansion valve 40 are kept off, and the process returns to S3'.

If the superheat TdSH is less than or equal to the first value X, it indicates that the superheat TdSH is not increased and fluctuates within the range, and therefore, it may indirectly indicate that the oil level in the compressor 10 is high, and at this time, it is determined that oil is not returned to the compressor variable, and therefore, the opening degree of the first electronic expansion valve 40 is currently maintained.

As described above, the process returns to S3' to determine the magnitude of the superheat TdSH at regular intervals (e.g., 5 minutes) throughout the continuous operation of the compressor 10.

Note that, the opening degree of the first electronic expansion valve 40 is adjusted to zero when the compressor 10 is stopped, and thus, the opening degree of the first electronic expansion valve 40 is adjusted from zero when the compressor 10 is started next time.

The application provides an air conditioning system can carry out real-time supervision to compressor 10 oil level through the oil level detection return circuit 50 of peripheral hardware, according to compressor 10 actual operating conditions, when the oil level is low (for example be less than compressor safety oil level), in time carry out the variable oil volume oil return to compressor 10, reach or be higher than compressor safety oil level until the oil level, realize the reliable oil return of compressor 10, ensure that compressor 10 reliably operates.

The oil return of the compressor 10 is reliably realized, the content of the refrigeration oil in the air conditioning system is regulated and controlled, the oil injection amount of the system is reduced, and the oil amount in the heat exchanger is reduced, so that the thermal resistance in the heat exchanger is reduced, and the heat exchange performance of the heat exchanger is improved.

Referring to fig. 9 and 10, there is shown an air conditioning system with multiple compressors 10 and 10' operating in parallel.

Each compressor 10/10 'works independently and controls oil return independently, and the way of controlling oil return by each compressor 10/10' is the same as the way described above, and is not described herein.

The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made to the embodiments described in the foregoing embodiments, or equivalents may be substituted for some of the features thereof; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions.

Claims

1. An air conditioning system is characterized by comprising a compressor, an oil separator, a gas-liquid separator, a first electronic expansion valve, an oil level detection loop and a processing unit;

the compressor comprises a refrigerant input port, a refrigerant output port and a connecting port, the oil level detection loop is arranged between the refrigerant input port and the connecting port, a first throttling element is arranged on the oil level detection loop, and the end part of the oil level detection loop, which extends into the connecting port, of a pipeline is positioned above the safe oil level of the compressor;

the gas-liquid separator is provided with a gas separation inlet and a first oil return port, the gas separation inlet is communicated with the oil separation oil return outlet, and a first electronic expansion valve is arranged on a pipeline between the first oil return port and the refrigerant input port;

the processing unit is configured to:

and controlling the opening degree of the first electronic expansion valve according to the temperature of the medium flowing through the oil level detection circuit and the exhaust temperature of the compressor.

2. The air conditioning system according to claim 1, wherein the opening degree of the first electronic expansion valve is controlled in accordance with the temperature of the medium flowing through the oil level detection circuit and the compressor discharge temperature, specifically:

and judging whether the temperature difference between the exhaust temperature of the compressor and the temperature of the medium flowing through the oil level detection circuit reaches the upper limit value of a first preset value at intervals after the compressor is operated, if so, increasing the first opening degree of the first electronic expansion valve, and if not, keeping the current opening degree of the first electronic expansion valve.

3. The air conditioning system of claim 2,

when the compressor is stopped, the first electronic expansion valve is in a closed state.

4. The air conditioning system according to claim 1, wherein an oil return capillary tube is provided on a pipe communicating between the oil return outlet and the air inlet; or

An oil return capillary tube and a first filter are arranged in series on a pipeline communicated between the oil return outlet and the gas distribution inlet.

5. The air conditioning system of claim 1, wherein the gas-liquid separator comprises: the gas inlet pipe extends out of the end part of the cylinder body of the gas-liquid separator to form the gas separation inlet;

6. The air conditioning system of claim 1, further comprising:

7. The air conditioning system of claim 6, wherein the processing unit opens the refrigerant branch flow path a number of times before controlling the opening degree of the first electronic expansion valve and then closes the refrigerant branch flow path.

8. The air conditioning system of claim 7, wherein the processing unit is configured to:

judging whether the temperature difference between the exhaust temperature of the compressor and the temperature of the medium flowing through the oil level detection circuit reaches the upper limit value of a first preset value at intervals after the compressor operates;

if not, the user can not select the specific application, and keeping the current opening degrees of the refrigerant branch flow path and the first electronic expansion valve disconnected.

9. The air conditioning system as claimed in any one of claims 6 to 8, wherein an electronic expansion valve is provided on the refrigerant branch flow path; or

An electromagnetic valve and a second throttling element are arranged on the refrigerant branch flow path in series; or

10. The air conditioning system according to claim 9, wherein when a second throttling element is provided on the refrigeration branch flow path, the second throttling element is a capillary tube.