An air conditioning system oil return control system

Abstract

The application 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 heat exchanger, a branch is further arranged on a pipeline between the air conditioning box evaporator and the first stop valve, the branch is connected to an evaporative condenser through a second stop valve, the control system is responsive to a vehicle power-off request signal, judges whether a compressor oil return control trigger condition is met according to an operation condition of a thermal management system in a period of time, if the condition is met, the compressor oil return control is started in response to a vehicle security request signal, the first stop valve is controlled to be closed and the second stop valve is controlled to be opened, the compressor and the evaporator are controlled to be started and work continuously for a set time length. The oil return control system of the application realizes the oil return control circuit through the control of the stop valves, and the evaporator continuously evaporates, so that the oil return effect is improved, and the long-time stable operation of the air conditioner is ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of vehicle air-conditioning systems, and in particular relates to an oil return control system for 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] Compressors require not only lubrication but also sealing of leaks. Therefore, to ensure proper operation, a certain amount of lubricant is added to the compressor during initial design to protect it. Furthermore, during long-term operation, the minimum amount of lubricant in the compressor must be maintained.

[0004] In an air conditioning system, high-temperature, high-pressure refrigerant gas from the compressor passes through the compressor-condenser pipeline and enters the condenser. During this process, some lubricating oil is carried out of the compressor and into the refrigeration system. In the condenser, the refrigerant gas is cooled, condensing from high-temperature, high-pressure refrigerant gas into a medium-temperature, high-pressure liquid. At this point, the lubricating oil and refrigerant become mutually soluble. The refrigerant and lubricating oil mixture is throttled by an electronic expansion valve and enters the evaporator. In the evaporator, the refrigerant liquid evaporates into a low-temperature, low-pressure gas and enters the compressor. The lubricating oil does not evaporate. A small amount is returned to the compressor as droplets and mist with the gaseous refrigerant, while the majority remains in liquid form in the evaporator core. Furthermore, due to the complex circulation path of heat pump air conditioning systems, some branches do not participate in the refrigerant circulation, which poses a risk of oil return problems. Furthermore, in heat pump mode, the system's evaporation temperature is low and the refrigerant flow rate is low. Furthermore, the outdoor evaporative condenser is lower in the Z direction than the indoor evaporator, resulting in greater flow resistance along the way. This makes it even more difficult for the lubricating oil to return to the compressor when the air conditioning system is operating in heat pump mode.

[0005] During extended operation, as the refrigerant in the evaporator evaporates, residual lubricant accumulates, affecting the evaporator's heat exchange efficiency and weakening the air conditioning system's cooling performance. Furthermore, as the amount of residual lubricant in the evaporator increases, the amount of lubricant in the compressor gradually decreases. Insufficient lubricant increases mechanical wear on the compressor, impacting compressor reliability and cooling performance. Therefore, air conditioning systems must carefully control the system's oil circulation rate and the amount of residual oil in the compressor.

[0006] Currently, the measures to solve the compressor oil return problem 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, installing an oil separator is likely to increase costs, and using the oil return circulation mode will temporarily lose the cooling 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. In conjunction with the continuous evaporation of the evaporator, the oil return effect is improved.

[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 further being connected to an input end of the compressor via the plate heat exchanger, a first stop valve being provided on a pipeline between the air conditioning box evaporator and the plate heat exchanger; a branch being further provided on a pipeline between the air conditioning box evaporator and the first stop valve, the branch being connected to an evaporative condenser via a second stop valve, the output end of the evaporative condenser being 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 based on the operating conditions of the thermal management system over a period of time. If so, the control system responds to the vehicle arming 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 start of the compressor and evaporator, and keep them working for the 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. 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 triggering condition is the cumulative operating time of the compressor working condition.

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

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

[0017] In some embodiments, after the control system completes the compressor oil return control, it stores the oil return control record, resets the timer, and powers off the vehicle.

[0018] In some embodiments, while the compressor and 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 further 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 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 refrigerant circuit. Therefore, when the oil return control is performed, the refrigerant and lubricating oil mixture can flow throughout the entire refrigerant circuit. Furthermore, during the rapid flow of the high-pressure refrigerant and lubricating oil mixture, the lubricating oil accumulated in various parts of the pipeline can be driven to flow together. In conjunction with the continuous evaporation of the evaporator, 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 coolant circuit three-way water valve, electronic water pump, cooling fan, and electric air intake grille, the heat generated by the compressor is dissipated. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, 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 structural 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 following describes embodiments of the present application in more detail 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 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 for illustrative purposes only 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 “at least partially based on.”

[0030] Figure 1 The diagram shows the architecture of an air conditioning system in one or more embodiments of the present invention. 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 middle 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. The output of the electric compressor is sequentially connected to the water-cooled condenser, the liquid storage tank, the plate heat exchanger, and the air conditioner evaporator core. The output of the air conditioner evaporator core is sequentially connected to the plate heat exchanger and the electric compressor, forming a circuit, namely the first loop of the refrigerant circuit. Furthermore, a second electronic expansion valve (electronic expansion valve #2 in the figure) is provided on the pipeline between the plate heat exchanger and the air conditioner evaporator core, and a first shut-off valve (shut-off valve #16 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 shut-off valve. This branch is connected to the evaporative condenser via the second shut-off valve, and the output 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 air conditioner evaporator core, 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 ways and connected to the low-temperature water circuit and the warm air water circuit respectively.

[0033] like Figure 1 As shown by the green line in the middle, the low-temperature water circuit includes a low-temperature radiator connected to both ends of the drive motor respectively, 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. 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 vehicle's air conditioning system, in cooling mode, the refrigerant circuit is: the first stop valve (16 stop valve) is open, and the second stop valve (10 stop valve) is closed. Low-pressure vapor refrigerant is sucked into the compressor and compressed to high-pressure vapor refrigerant. It then passes through a water-cooled condenser, which removes the refrigerant's heat, condensing the high-pressure vapor into a high-pressure liquid refrigerant. After being filtered through a liquid storage tank, it passes through a plate heat exchanger and exchanges heat with the low-pressure side to increase subcooling. The high-pressure liquid refrigerant then passes through the second electronic expansion valve (2# electronic expansion valve), throttling it, and passes through the evaporator, where it evaporates, absorbing the surrounding heat and forming a low-pressure vapor refrigerant. It then re-enters the compressor for the next cycle. Cooling liquid circuit: the first three-way water valve (1# three-way water valve) is 2-3 connected, the second three-way water valve (2# three-way water valve) is 1-3 connected, the third three-way water valve (3# three-way water valve) is 1-2 connected, and 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 convection heat exchange between the low-temperature radiator and the air.

[0036] In dehumidification mode, the first shut-off valve (16) is opened or closed based on the comfort performance temperature, and the second shut-off valve (10) is opened. The low-pressure vapor refrigerant is sucked into the compressor and compressed into a high-pressure vapor refrigerant. The refrigerant is then heated by the water-cooled condenser, causing the high-pressure vapor refrigerant to condense into a high-pressure liquid refrigerant. After being filtered by the liquid storage tank, it is transferred to the plate heat exchanger for heat exchange with the low-pressure side to increase the degree of subcooling. The high-pressure liquid refrigerant is then throttled by the second electronic expansion valve (2# electronic expansion valve), passes through the evaporator, evaporates at the evaporator, absorbs the surrounding heat, and forms a low-pressure vapor refrigerant. The 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) is 1-2 connected, the second three-way water valve (2# three-way water valve) is 1-2 connected, the third three-way water valve (3# three-way water valve) is 1-2 connected, and 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 through the convection heat exchange between the air conditioning box heater core and the air inside the vehicle.

[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, the system determines whether the compressor oil return control triggering conditions are met based on the operating conditions of the thermal management system over a period of time. If so, the system delays power-off and proceeds to step S2; if not, the system executes 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 start of the compressor and evaporator, and keep them working for the set time.

[0042] In the step S1, in order to make the execution of the oil return control strategy not affect the normal use of the vehicle air conditioner by the user, the oil return control strategy is executed when the user does not use the vehicle, in order to achieve this purpose, the user's power-off operation on the vehicle is taken as the timing of determining whether the oil return control is needed, if the oil return is needed, the power-off is delayed, and the oil return control strategy is started again when the vehicle security request signal is received in the step S2, that is, after the user gets off the vehicle, the whole process is carried out without the user's awareness, and the user does not need to intervene.

[0043] In the step S1, the longer the automobile thermal management system runs, the more lubricating oil accumulates in the system, therefore, the working time of the compressor is mainly taken as the trigger judgment condition. Specifically, the thermal management system running conditions include a single running mode and a composite mode, which are distinguished according to whether the compressor works, only the air conditioner running mode in which the compressor works is counted, and the response time is 0.1 s, 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 8 h.

[0044] That is, the starting timing of the oil return control strategy is that 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 whole vehicle is in the power-on state.

[0045] It should be noted that if the thermal management system is set to the compressor non-working condition in a continuous timing process (the timing does not reach the set time threshold), if the running time of the compressor non-working condition is less than the set threshold, the running time is recorded in the accumulated time, if not, the timing is cleared and the timing is restarted. As an example, the compressor non-working conditions include: 1, dehumidification, battery temperature equalization; 2, dehumidification, battery cooling; 3, dehumidification, battery heating; 4, passenger compartment heating; 5, passenger compartment heating, battery cooling; 6, passenger compartment heating, motor cooling; 7, passenger compartment heating (no request for battery and motor), any preset condition is met, the running time is greater than or equal to 1 min, the timer is cleared and the timing is restarted; if the running time is less than 1 min, the accumulated time is recorded in the software timer.

[0046] The method further includes S3: after the compressor oil return control process is completed, the oil return control record of this time is stored, the timing is cleared, and the vehicle is powered off.

[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. 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 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 mix the lubricating oil gas with the refrigerant gas into 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 entire vehicle is detected to be under high pressure, the oil return control will be terminated.

[0050] Specifically, when the execution conditions meet 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 heater water circuit and the low-temperature water circuit, and the pipes connecting the battery water circuit and the heater 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 controlled to open. 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 by the refrigerant side of the compressor through the water-cooled condenser and the low-temperature radiator.

[0052] As an example, the following operating 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 remains 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 address the issue of low compressor oil return, which can permanently damage the compressor and affect normal system operation. These solutions have been verified in real vehicles and can effectively save costs and power consumption, with a wide range of use cases and applications.

[0054] In addition, although adopting specific order to describe each operation, this should be understood as requiring such operation to be carried out with shown specific order or with sequential order, or requiring all illustrated operations to be carried out to obtain desired result.Under certain environment, multitasking and parallel processing may be advantageous.Similarly, although comprising some specific implementation details in the above discussion, these should not be interpreted as limiting the scope of the application.Some features described in the context of independent embodiment can also be implemented in a single implementation in combination.On the contrary, the various features described in the context of independent implementation also can be implemented in a plurality of implementations individually or in the mode of any suitable subcombination.

[0055] Although the subject matter has been described in language specific to structural features and / or methodological logical acts, it should be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts 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: The refrigerant circuit includes a water-cooled condenser, a plate heat exchanger, and an air-conditioning box evaporator connected in sequence from the output end of the compressor, the output end of the air-conditioning box evaporator is further 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 further 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 based on the operating conditions of the thermal management system over a period of time. If so, the control system responds to the vehicle arming 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 start-up of the compressor and evaporator, and keep them working for a set period of time; 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 pipeline connecting the battery water circuit and the warm air water circuit is connected.

2. The oil return control system for an air conditioning 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 oil return control system for an air conditioning 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 according to claim 3, characterized in that: If during a continuous timing process, the air conditioner is set to the compressor non-working condition, if the operating time of the compressor non-working condition 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 according to claim 4, characterized in that: The operating conditions in which the compressor does not operate include a dehumidification operating condition and a passenger compartment heating operating condition.

6. The oil return control system for an air conditioning system according to claim 1, characterized in that: 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.

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 is released from the defense signal 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 oil return control system for an air conditioning system according to claim 1, 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 is not operated.

9. The oil return control system for an air conditioning system according to claim 1, 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.

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