Oil return control system of air conditioning system

Abstract

The invention discloses an oil return control system of an air conditioning system. A first stop valve is arranged on a pipeline between an air conditioning box evaporator and a plate exchange heat regenerator; a branch is further arranged on a pipeline between the air conditioning box evaporator and the first stop valve, and the branch is connected to an evaporative condenser through a second stop valve; the control system responds to a vehicle power-off request signal and judges whether a compressor oil return control triggering condition is met or not according to the operation working condition of the thermal management system within a period of time, and if yes, the control system responds to a vehicle fortification request signal and starts compressor oil return control, namely, the first stop valve is controlled to be closed and the second stop valve is controlled to be opened; and the compressor and the evaporator are controlled to start and continuously work for set duration. The oil return control loop penetrating through the whole refrigerant loop is obtained by controlling the stop valve, the oil return control loop is matched with continuous evaporation of the evaporator, the oil return effect is improved, and long-time stable operation of the air conditioner is guaranteed.

Description

Technical Field

[0001] The invention belongs to the technical field of vehicle air-conditioning systems, and in particular relates to an oil return control system of an air-conditioning system. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] When the compressor is working, it not only needs lubricating oil for lubrication, but also needs lubricating oil to seal the leaking parts. Therefore, in order to ensure the normal operation of the compressor, a certain amount of lubricating oil is added to the compressor at the beginning of the design to protect the compressor. At the same time, during the long-term operation of the air conditioner, the amount of lubricating oil in the compressor must also meet the minimum content requirements.

[0004] In the air conditioning system, the high-temperature and high-pressure refrigerant gas from the compressor enters the condenser through the compressor-condenser pipeline. In this process, part of the lubricating oil is taken out of the compressor and enters the refrigeration system. In the condenser, the refrigerant gas is cooled and condensed from the high-temperature and high-pressure refrigerant gas into a medium-temperature and high-pressure liquid. At this time, the lubricating oil and the refrigerant are mutually dissolved. The refrigerant and lubricating oil mixture enters the evaporator through the throttling of the electronic expansion valve. In the evaporator, the refrigerant liquid evaporates into a low-temperature and low-pressure gas and enters the compressor, while the lubricating oil does not evaporate. A small part of it is returned to the compressor in the form of droplets and mist with the gaseous refrigerant, and most of it is still stored in the evaporator core in the form of liquid. In addition, due to the complex circulation path of the heat pump air conditioning system, there are some branches that do not participate in the refrigerant circulation, which brings the risk of oil return. In addition, in the heat pump mode, the evaporation temperature of the system is low, the refrigerant flow is small, and the structure of the outdoor evaporative condenser is lower than the indoor evaporator in the Z direction, and the flow resistance along the way is large, which makes it more difficult for the lubricating oil to return to the compressor when the air conditioning system is running in the heat pump mode.

[0005] When running for a long time, as the refrigerant in the evaporator continues to evaporate, the residual lubricating oil increases, which will affect the heat exchange efficiency of the evaporator, thereby causing the refrigeration performance of the air conditioning system to weaken. In addition, as the residual amount of lubricating oil in the evaporator increases, the lubricating oil in the compressor will gradually decrease. When the lubricating oil is insufficient, the mechanical wear of the compressor increases, affecting the reliability of the compressor and also affecting the refrigeration performance. Therefore, the air conditioning system must control the system oil circulation rate and the residual oil index of the compressor.

[0006] At present, the measures to solve the oil return problem of compressors are divided into system design optimization and control strategy optimization. System design optimization often adopts the installation of oil separators in the air-conditioning system, and control strategy optimization often adopts the oil return circulation mode. However, the installation of oil separators is likely to increase costs, and the use of the oil return circulation mode will temporarily lose the refrigeration effect of the system and increase power consumption. Summary of the invention

[0007] In order to overcome the deficiencies of the above-mentioned prior art, the present invention provides an oil return control system for an air-conditioning system. On the basis of the existing air-conditioning system, an oil return control circuit that runs through the entire refrigerant circuit is obtained by controlling the stop valve, electronic expansion valve, electric compressor, cooling fan, electric air intake grille, three-way water valve, and electronic water pump. The oil return effect is improved by cooperating with the evaporator for continuous evaporation.

[0008] To achieve the above objectives, one or more embodiments of the present invention provide the following technical solutions:

[0009] An oil return control system for an air conditioning system, comprising: a refrigerant circuit, the refrigerant circuit comprising a water-cooled condenser, a plate heat exchanger and an air conditioning box evaporator connected in sequence from an output end of a compressor, the output end of the air conditioning box evaporator is also connected to an input end of the compressor via the plate heat exchanger, a first stop valve is provided on a pipeline between the air conditioning box evaporator and the plate heat exchanger; a branch is also provided on a pipeline between the air conditioning box evaporator and the first stop valve, the branch is connected to an evaporative condenser via a second stop valve, and the output end of the evaporative condenser is connected to the plate heat exchanger;

[0010] The control system responds to the vehicle power-off request signal and determines whether the compressor oil return control triggering condition is met according to the operating conditions of the thermal management system over a period of time. If so, the control system responds to the vehicle defense request signal and starts the compressor oil return control:

[0011] Controlling the first stop valve to close and the second stop valve to open;

[0012] Control the compressor and evaporator to start and continue working for a set time.

[0013] In some embodiments, a second electronic expansion valve is further provided on the pipeline connecting the plate heat exchanger to the air-conditioning box evaporator, and when the compressor oil return control is started, the second electronic expansion valve is also controlled to open a set number of steps.

[0014] In some embodiments, the compressor oil return control trigger condition is the accumulated running time of the compressor working condition.

[0015] In some embodiments, if during a continuous timing process, the air conditioner is set to a condition where the compressor is not working, if the operating time of the condition where the compressor is not working is less than a set threshold, the operating time is recorded in the cumulative duration; if not, the timing is reset and restarted.

[0016] In some embodiments, the operating conditions where the compressor is not operating include a dehumidification operating condition and a passenger compartment heating operating condition.

[0017] In some embodiments, after the control system completes the oil return control of the compressor, the oil return control record is stored, the timer is reset, and the vehicle is powered off.

[0018] In some embodiments, when the compressor and the evaporator are in continuous operation, if a vehicle release signal is detected or the vehicle is under high pressure, the execution is exited, the timer is reset, and the air conditioning mode is reset to the mode before the oil return control is executed.

[0019] In some embodiments, a low-temperature water circuit, a battery water circuit and a warm air water circuit are also included; a third three-way valve is provided on the low-temperature water circuit, and the third end of the third three-way valve is connected to the battery water circuit; a second three-way valve is provided on the battery water circuit, and the third ends of the second three-way valve are respectively connected to the low-temperature water circuit and the warm air water circuit; a first three-way valve is provided on the warm air water circuit, and the third section of the first three-way valve is connected to the low-temperature water circuit; when the return oil control is started, the low-temperature water circuit is connected by controlling the first three-way valve, the second three-way valve and the third three-way valve, the pipelines connecting the battery water circuit, the warm air water circuit and the low-temperature water circuit are connected, and the pipelines connecting the battery water circuit and the warm air water circuit are connected.

[0020] In some embodiments, a first electronic water pump is provided on the warm air water circuit, and a third electronic water pump is provided on the low-temperature water circuit; when the oil return control is started, the first electronic water pump is also controlled to operate according to a set duty cycle, and the third electronic water pump does not operate.

[0021] In some embodiments, when the oil return control is activated, the cooling fan is also controlled to run and the electric air intake grille is also controlled to open.

[0022] In one or more of the above technical solutions, the shut-off valve in the existing refrigerant circuit is controlled, and the oil return control circuit includes each section of the pipeline in the refrigerant circuit, so that when the oil return control is performed, the refrigerant and lubricating oil mixture can flow in the entire refrigerant circuit, and then in the process of rapid flow of the high-pressure refrigerant and lubricating oil mixture, it can drive the lubricating oil stored in various places in the pipeline to flow together, and cooperate with the continuous evaporation of the evaporator, so that the refrigerant and lubricating oil mixture is vaporized and returned to the compressor, ensuring that the oil content in the compressor is within a controllable range, increasing the lubrication effect of the compressor, and thus ensuring the long-term operation of the air-conditioning system. At the same time, by controlling the three-way water valve of the coolant circuit, the electronic water pump and the cooling fan, and the electric air intake grille, the heat generated by the compressor is dissipated. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0024] Figure 1This is a schematic diagram of an air conditioning system in an embodiment of the present invention;

[0025] Figure 2 Schematic diagram of an air-conditioning oil return control circuit in an embodiment of the present invention;

[0026] Figure 3 This is an overall flow chart of the air-conditioning oil return control method in an embodiment of the present invention;

[0027] Figure 4 This is a start-stop control logic diagram of the air conditioning oil return control method in an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The embodiments of the present application will be described in more detail below with reference to the accompanying drawings. Although certain embodiments of the present application are shown in the accompanying drawings, it should be understood that the present application can be implemented in various forms and should not be construed as being limited to the embodiments described herein. Instead, these embodiments are provided to provide a more thorough and complete understanding of the present application. It should be understood that the drawings and embodiments of the present application are only for exemplary purposes and are not intended to limit the scope of protection of the present application.

[0029] In the description of the embodiments of the present application, the term “including” and similar terms should be understood as open inclusion, that is, “including but not limited to.” The term “based on” should be understood as “based at least in part on.”

[0030] Figure 1 The air conditioning system in one or more embodiments of the present invention is shown in the following figure. The air conditioning system includes a refrigerant circuit, a warm air water circuit, a low temperature water circuit and a battery water circuit.

[0031] like Figure 1 As shown by the blue line, the refrigerant circuit includes an electric compressor, a water-cooled condenser, a liquid storage tank, a plate heat exchanger, an air conditioner evaporator core and an evaporative condenser, wherein the output end of the electric compressor is connected to the water-cooled condenser, the liquid storage tank, the plate heat exchanger and the air conditioner evaporator core in sequence, and the output end of the air conditioner evaporator core is connected to the plate heat exchanger and the electric compressor in sequence, forming a circuit, i.e., the first circuit of the refrigerant circuit. In addition, a second electronic expansion valve (2# electronic expansion valve in the figure) is provided on the pipeline between the plate heat exchanger and the air conditioner evaporator core, and a first stop valve (16 stop valve in the figure) is provided on the pipeline between the air conditioner evaporator core and the plate heat exchanger. A branch is also provided on the pipeline between the air conditioner evaporator core and the first stop valve, and the branch is connected to the evaporative condenser via the second stop valve, and the output end of the evaporative condenser is connected to the plate heat exchanger. A branch is also provided on the pipeline between the plate heat exchanger and the evaporator core of the air conditioner, and the branch is connected to the pipeline between the first stop valve and the plate heat exchanger via the first electronic expansion valve.

[0032] like Figure 1 As shown by the purple line in the middle, the battery water circuit includes a battery cooler connected to both ends of the battery, a second electronic water pump and a second three-way valve are provided on the connecting pipeline, two ends of the second three-way valve are used to connect the pipeline, and the third end is divided into two paths and respectively connected to the low-temperature water circuit and the warm air water circuit.

[0033] like Figure 1 As shown by the green line in the middle, the low-temperature water circuit includes a low-temperature radiator respectively connected to the two ends of the drive motor, and a third electronic water pump and a third three-way valve are provided on the connecting pipeline. Two ends of the third three-way valve are used to connect the pipeline, and the third end is connected to the battery water circuit.

[0034] like Figure 1 As shown by the red line in the middle, the warm air water circuit includes an air conditioning box warm air heating core, and a water-cooled condenser connected to both ends of the air conditioning box warm air heating core respectively, and a first electronic water pump and a first three-way valve are provided on the connecting pipeline, two ends of the first three-way valve are used to connect the pipeline, and the third end is connected to the low-temperature water circuit.

[0035] During normal use of the in-car air conditioner, in the cooling mode, the refrigerant circuit: the first stop valve (16 stop valve) is open, and the second stop valve (10 stop valve) is closed. The low-pressure vapor refrigerant is sucked into the compressor and compressed into a high-pressure vapor refrigerant, and then passes through the water-cooled condenser to take away the heat of the refrigerant, so that the high-pressure vapor refrigerant condenses into a high-pressure liquid refrigerant. After being filtered through the liquid storage drying tank, it is heat-exchanged with the low-pressure side through the plate heat exchanger to increase the degree of supercooling. Then, the high-pressure liquid refrigerant is throttled by the second electronic expansion valve (2# electronic expansion valve), passes through the evaporator, evaporates at the evaporator, absorbs the surrounding heat, forms a low-pressure vapor refrigerant, and enters the compressor again for the next cycle. Cooling liquid circuit: the first three-way water valve (1# three-way water valve) 2-3 way, the second three-way water valve (2# three-way water valve) 1-3 way, the third three-way water valve (3# three-way water valve) 1-2 way, the first electronic water pump (1# electronic water pump) drives the water flow so that the heat of the water-cooled condenser is finally dissipated and cooled through the low-temperature radiator and air convection heat exchange.

[0036] In dehumidification mode, the first stop valve (16 stop valve) is opened or closed according to the comfort performance temperature, and the second stop valve (10 stop valve) is opened. The low-pressure vapor refrigerant is sucked into the compressor and compressed into a high-pressure vapor refrigerant, and then the coolant is heated by the water-cooled condenser, so that the high-pressure vapor refrigerant condenses into a high-pressure liquid refrigerant. After being filtered by the liquid storage drying tank, the plate heat exchanger and the low-pressure side heat exchange are used to increase the degree of supercooling. Then, the high-pressure liquid refrigerant is throttled by the second electronic expansion valve (2# electronic expansion valve), passes through the evaporator, evaporates at the evaporator, absorbs the surrounding heat, forms a low-pressure vapor refrigerant, enters the external evaporative condenser to evaporate and absorb the external environment heat, and finally enters the compressor for the next cycle. Coolant circuit: the first three-way water valve (1# three-way water valve) 1-2 way, the second three-way water valve (2# three-way water valve) 1-2 way, the third three-way water valve (3# three-way water valve) 1-2 way, the first electronic water pump (1# electronic water pump) drives the water flow so that the heat of the water-cooled condenser is finally heated by convection heat exchange between the air conditioning box heater core and the air in the car.

[0037] The control system further comprises a controller for starting and stopping the thermal management system and switching the mode according to a user request. In order to control the return of lubricating oil in the entire refrigerant circuit, the entire refrigerant circuit is connected as an oil return control circuit through the control of the first stop valve (16 stop valve) and the second stop valve (10 stop valve). By increasing the flow rate of the refrigerant and lubricating oil mixture and controlling the evaporator to continue evaporating, the accumulated lubricating oil is returned to the compressor. Specifically, Figure 3 As shown, the controller is configured to perform the following steps:

[0038] S1: In response to the vehicle power-off request signal, judging whether the compressor oil return control triggering condition is met according to the operating conditions of the thermal management system over a period of time, if so, delaying power-off and entering step S2; if not, executing power-off;

[0039] S2: In response to the vehicle arming request signal, start the compressor oil return control:

[0040] Control the first stop valve (16 stop valve) to close and the second stop valve (10 stop valve) to open, and the second electronic expansion valve to open a set number of steps.

[0041] Control the compressor and evaporator to start and continue working for a set time.

[0042] In step S1, in order to ensure that the execution of the oil return control strategy does not affect the user's normal use of the vehicle air conditioner, it is executed when the user is not using the vehicle. To achieve this purpose, the user's power-off operation on the vehicle is used as an opportunity to determine whether oil return control is required. If oil return is required, power-off is delayed. When the vehicle defense request signal is received in step S2, that is, after the user gets off the vehicle, the oil return control strategy is started. The entire process is carried out without the user's perception and without the need for user intervention.

[0043] In step S1, since the longer the automobile thermal management system operates, the more lubricating oil is stored in the system, this application mainly uses the working time of the compressor as the trigger judgment condition. Specifically, the operating conditions of the thermal management system include a single operating mode and a composite mode, which are distinguished according to whether the compressor is working. Only the air-conditioning operating mode in which the compressor is working is accumulated and timed, with 0.1s as the response time. When the accumulated time exceeds the set time threshold, it is considered that the oil return control trigger condition is met. As an example, the set time threshold is 8h.

[0044] That is, the start timing of the oil return control strategy is: the accumulated time exceeds the set time threshold, the vehicle is in the anti-theft state, the vehicle is locked, there is no one in the vehicle, and the vehicle is powered on.

[0045] It should be noted that if during a continuous timing process (the timing has not reached the set time threshold), the thermal management system is set to a condition where the compressor is not working, and if the operating time of the condition where the compressor is not working is less than the set threshold, the operating time is recorded in the cumulative time; if not, the timer is reset and the timing is restarted. As an example, the operating conditions where the compressor is not working include: 1. Dehumidification and battery temperature equalization; 2. Dehumidification and battery cooling; 3. Dehumidification and battery heating; 4. Passenger compartment heating; 5. Passenger compartment heating and battery cooling; 6. Passenger compartment heating and motor cooling; 7. Passenger compartment heating (battery, motor no request), if any of the preset conditions is met and the operating time is ≥1min, the timer is reset and the timing is restarted; if the operating time is <1min, the accumulated timing is added to the software timer.

[0046] The method further comprises S3: after the compressor oil return control process is completed, storing the oil return control record, resetting the timer, and powering off the vehicle.

[0047] In step S2, in order to fully return the accumulated lubricating oil in the refrigeration circuit, the present application controls the shut-off valve in the existing refrigerant circuit to obtain an oil return control circuit, and the oil return control circuit includes each section of the pipeline in the refrigerant circuit, so that when the oil return control is performed, the refrigerant and lubricating oil mixture can flow in the entire refrigerant circuit, and then in the process of rapid flow of the high-pressure refrigerant and lubricating oil mixture, it can drive the lubricating oil accumulated in various places in the pipeline to flow together, and cooperate with the continuous evaporation of the evaporator, so that the refrigerant and lubricating oil mixture is vaporized and returned to the compressor.

[0048] Specifically, the first stop valve is controlled to close and the second stop valve is controlled to open to obtain an oil return control circuit; the compressor and the evaporator are controlled to start. Based on this, the high-temperature and high-pressure gas compressed by the compressor is condensed by the water-cooled condenser and the evaporative condenser to obtain a high-pressure liquid, which is throttled through the first throttle valve and enters the external evaporator. Since the lubricating oil is easy to remain in the evaporator and the low-temperature and low-pressure pipeline, it continues to evaporate and mixes the lubricating oil gas with the refrigerant gas and enters the compressor, and circulates periodically. The continuous working time is set (for example, 55s). When the time requirement is met, the oil return control ends. The oil return control circuit is as follows: Figure 2 Shown by black lines.

[0049] While the compressor and evaporator are working continuously, if the vehicle release signal is detected, the oil return control will be terminated, the timer will be reset, and the air conditioning mode will be reset to the mode before the oil return control was executed; if the whole vehicle is detected to be under high pressure, the oil return control will be terminated.

[0050] Specifically, when the execution condition reaches any of the following preset conditions, the execution is exited, the timer is reset, and the previous system operation mode is maintained: 1. The system runs in heat pump dehumidification mode for 55 seconds; 2. The vehicle's anti-theft system is disabled; 3. The entire vehicle is under high pressure.

[0051] As the compressor works, the refrigerant side will continue to generate heat. In order to achieve heat dissipation, in some embodiments, the first three-way valve, the second three-way valve and the third three-way valve are controlled to connect the low-temperature water circuit, the battery water circuit, the pipes connecting the warm air water circuit and the low-temperature water circuit, and the pipes connecting the battery water circuit and the warm air water circuit; at the same time, the first electronic water pump is controlled to operate based on the set motion duty cycle, and the cooling fan is controlled to operate and the electric air intake grille is opened. Figure 2 As shown by the yellow line in the middle, the water in the pipeline enters the low-temperature water pipeline through part of the pipeline in the warm air water circuit. While flowing in the low-temperature water pipeline, it enters the warm air water pipeline through part of the pipeline in the battery water circuit, and then releases the heat generated on the refrigerant side by the work of the compressor through the water-cooled condenser and the low-temperature radiator.

[0052] As an example, the following working parameters are set: 1. The compressor operating speed is 2000rpm; 2. The maximum duty cycle of the cooling fan is 20%; 3. The electric air intake grille is open and the air conditioning state is maintained off; 4. 1# three-way water valve 2-3 way, 2# three-way water valve 1-3 way, 3# three-way water valve 1-2 way; 5. 10 stop valve is open, 16 stop valve is closed, 2# electronic expansion valve step number 315Step; 6. 1# electronic water pump operating duty cycle is 75%, 2# and 3# electronic water pumps are stopped.

[0053] One or more of the above embodiments can effectively solve the problem of low oil return volume of the compressor, permanent damage to the compressor, and affecting the normal operation of the system. It has been verified in real vehicles and can effectively save costs and power consumption, and has a wide range of usage scenarios and application scenarios.

[0054] In addition, although each operation is described in a specific order, this should be understood as requiring such operation to be performed in the specific order shown or in a sequential order, or requiring that all illustrated operations should be performed to obtain desired results. Under certain circumstances, multitasking and parallel processing may be advantageous. Similarly, although some specific implementation details are included in the above discussion, these should not be interpreted as limiting the scope of the application. Some features described in the context of a separate embodiment can also be implemented in a single implementation in combination. On the contrary, the various features described in the context of a single implementation can also be implemented in multiple implementations individually or in any suitable sub-combination mode.

[0055] Although the subject matter has been described in language specific to structural features and / or methodological logical actions, it should be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or actions described above. On the contrary, the specific features and actions described above are merely example forms of implementing the claims.

Claims

1. An oil return control system for an air conditioning system, characterized in that: It comprises a refrigerant circuit, the refrigerant circuit comprises a water-cooled condenser, a plate heat exchanger and an air-conditioning box evaporator which are sequentially connected from the output end of the compressor, the output end of the air-conditioning box evaporator is also connected to the input end of the compressor via the plate heat exchanger, a first stop valve is provided on the pipeline between the air-conditioning box evaporator and the plate heat exchanger; a branch is also provided on the pipeline between the air-conditioning box evaporator and the first stop valve, the branch is connected to the evaporative condenser via a second stop valve, and the output end of the evaporative condenser is connected to the plate heat exchanger; The control system responds to the vehicle power-off request signal and determines whether the compressor oil return control triggering condition is met according to the operating conditions of the thermal management system over a period of time. If so, the control system responds to the vehicle defense request signal and starts the compressor oil return control: Controlling the first stop valve to close and the second stop valve to open; Control the compressor and evaporator to start and continue working for a set time.

2. The air conditioning system oil return control system according to claim 1, characterized in that: A second electronic expansion valve is also provided on the pipeline connecting the plate heat exchanger to the air-conditioning box evaporator. When the compressor oil return control is started, the second electronic expansion valve is also controlled to open a set number of steps.

3. The air conditioning system oil return control system according to claim 1, characterized in that: The compressor oil return control triggering condition is the cumulative running time of the compressor working condition.

4. The oil return control system for an air conditioning system as claimed in claim 3, characterized in that: If during a continuous timing process, the air conditioner is set to a condition where the compressor is not working, if the operating time of the condition where the compressor is not working is less than the set threshold, the operating time is recorded in the cumulative time; if not, the timing is reset and restarted.

5. The oil return control system for an air conditioning system as claimed in claim 4, characterized in that: The operating conditions where the compressor does not operate include a dehumidification operating condition and a passenger compartment heating operating condition.

6. The air conditioning system oil return control system according to claim 1, characterized in that: After the control system completes the compressor oil return control, the oil return control record is stored, the timer is reset, and the vehicle is powered off.

7. The oil return control system for an air conditioning system according to claim 1, characterized in that: While the compressor and evaporator are working continuously, if the vehicle release signal is detected or the vehicle is under high pressure, the execution will be exited, the timer will be reset, and the air conditioning mode will be reset to the mode before the oil return control was executed.

8. The air conditioning system oil return control system according to claim 1, characterized in that: It also includes a low-temperature water circuit, a battery water circuit and a warm air water circuit; a third three-way valve is provided on the low-temperature water circuit, and the third end of the third three-way valve is connected to the battery water circuit; a second three-way valve is provided on the battery water circuit, and the third ends of the second three-way valve are respectively connected to the low-temperature water circuit and the warm air water circuit; a first three-way valve is provided on the warm air water circuit, and the third section of the first three-way valve is connected to the low-temperature water circuit; when the return oil control is started, the low-temperature water circuit is connected by controlling the first three-way valve, the second three-way valve and the third three-way valve, the pipelines connecting the battery water circuit, the warm air water circuit and the low-temperature water circuit are connected, and the pipelines connecting the battery water circuit and the warm air water circuit are connected.

9. The oil return control system for an air conditioning system according to claim 8, characterized in that: The warm air water circuit is provided with a first electronic water pump, and the low temperature water circuit is provided with a third electronic water pump; when the oil return control is started, the first electronic water pump is also controlled to operate according to the set duty cycle, and the third electronic water pump does not operate.

10. The oil return control system for an air conditioning system according to claim 8, characterized in that: When the oil return control is activated, the cooling fan is also controlled to run and the electric air intake grille is opened.

Images