Shutdown control method for reducing engine oil emulsification of range extender gas engine

Abstract

The invention discloses a shutdown control method for reducing engine oil emulsification of a range extender gas engine, which comprises the following steps that: a VCU (Vehicle Control Unit) acquires the driving power demand of a whole vehicle, the current SOC (State of Charge) value of a power battery and the working states of engine driving devices such as an air conditioner and an air pump in real time, and transmits a signal that the target generated power is 0kW to an RCU (Remote Control Unit) after comprehensive judgment; an engine stop instruction is selectively sent according to the working conditions; after the RCU receives the double instructions, a torque withdrawal instruction is immediately sent to the ECU to control the engine to withdraw torque gradually, and impact caused by sudden torque drop is avoided; meanwhile, an idling instruction is sent to the GCU, so that the rotating speed of the FISG slowly falls back to the idling speed; after the FISG reaches the idling speed, the ECU controls the engine to maintain the idling speed for 1-5 minutes to evaporate water vapor, and then fuel gas injection is stopped; when the rotating speed of the engine is reduced to 400 rpm and spraying is stopped, the RCU enables the FISG to drag a crankshaft at 400 rpm for 4-10 seconds for scavenging, and a signal is synchronously fed back to the VCU; after receiving the starting signal, the VCU is started for 11-15 seconds for time delay, and after receiving the ending signal and ending the time delay, high-voltage electricity disconnection is executed. The method solves the problem of engine oil emulsification when the engine is shut down.

Description

Technical Field

[0001] This invention relates to the field of shutdown control technology for gas engine range extenders used in non-road applications, and in particular to a shutdown control method for reducing oil emulsification in range extender gas engines. Background Technology

[0002] In the process of new energy transformation of non-road construction machinery, gas engine range extenders, due to their dual advantages of clean and environmentally friendly gas energy and stable range-extending system, have been widely used in excavators, loaders, road rollers, and other equipment, becoming a core component in solving the emission pollution of traditional fuel equipment and the range anxiety of electric equipment. Their operational stability directly determines the continuity of construction machinery operations, and engine oil, as a key medium for lubrication, cooling, and sealing of engine moving parts, is crucial to the service life of the range extender. Currently, gas engine range extenders under non-road conditions generally face the problem of engine oil emulsification. This problem not only leads to a sharp decline in engine oil lubrication performance but also triggers a series of chain failures, becoming a core technical bottleneck restricting the improvement of range extender reliability and seriously affecting the operating efficiency and operating costs of construction machinery.

[0003] The existing control strategy of off-road gas engine range extenders has significant design flaws, which are the main cause of oil emulsification. On the one hand, the traditional shutdown strategy uses the simple logic of "shutting down when gas injection stops." The engine stops running instantly after the gas supply is cut off, causing unexhausted combustion gases to remain in the crankcase. A large amount of water vapor and unburned gas components in the exhaust gases directly seep into the engine oil, damaging the oil's colloidal stability and accelerating the emulsification process. On the other hand, off-road construction machinery has many operating breaks, and the range extender often operates at idle speed or extremely low load for extended periods. Under these conditions, the engine's thermal efficiency is low, and the engine oil temperature is difficult to reach the critical value for water vapor evaporation above 70°C. The water vapor in the exhaust gases cannot evaporate with the oil circulation and instead condenses and accumulates in the engine oil, further aggravating the emulsification process. When engine oil emulsifies, it forms an emulsion that causes critical moving parts such as main bearings, connecting rod bearings, and turbochargers to lose effective lubrication, increasing the wear rate by more than 60%. This not only leads to a 30% to 50% decrease in the power generation efficiency of the range extender, but also causes serious malfunctions such as engine cylinder scoring and turbocharger seizure, increasing the annual maintenance cost of the equipment by several thousand yuan. Currently, there is no precise control solution for this core problem in existing technologies, and there is an urgent need to propose an efficient and reliable improvement strategy.

[0004] The above background information is provided only to aid in understanding the concept and technical solution of this invention. It does not necessarily belong to the prior art of this patent application. In the absence of clear evidence that the above information was disclosed on the filing date of this patent application, the above background information should not be used to evaluate the novelty and inventiveness of this application. Summary of the Invention

[0005] The purpose of this invention is to propose a shutdown control method to reduce oil emulsification in a range extender gas engine, thereby solving the technical problems in the prior art, such as the engine stopping immediately after gas injection stops, resulting in crankcase exhaust gas retention, prolonged idling causing low oil temperature, which in turn leads to oil emulsification, increased wear of engine moving parts, decreased reliability of range extender power generation, and high maintenance costs.

[0006] Therefore, this invention proposes a shutdown control method to reduce oil emulsification in range extender gas engines.

[0007] Preferably, the present invention may also have the following technical features: A shutdown control method for reducing oil emulsification in a range extender gas engine includes the following steps: Step S1: The VCU makes a judgment based on the vehicle's drive power requirements, the current SOC value of the power battery, and the working status of the vehicle's devices that require engine drive. It determines to synchronously transmit a signal with a target power generation of 0 kilowatts to the RCU and selectively sends an engine shutdown command based on the judgment result. Step S2: When the RCU receives the target power generation command of 0 kW from the VCU and the engine stops, the RCU sends a torque reduction command to the ECU to control the engine to gradually reduce torque; at the same time, it sends an idle speed command to the GCU to control the FISG motor speed to slowly drop back to idle speed. Step S3: When the FISG motor speed returns to idle speed, the ECU controls the engine to enter idle speed state and maintains idle speed for 1 to 5 minutes, and then controls the engine to stop injecting gas and shut down. Step S4: During the process of the engine speed dropping from idle to zero, when the engine speed drops to 400 rpm and the engine is in a non-injection state, the RCU sends a speed command to the GCU to control the FISG to drag the engine crankshaft at 400 rpm. This dragging action lasts for 4 to 10 seconds. At the same time, the RCU sends real-time feedback to the VCU on the FISG's dragging start signal and dragging end signal. Step S5: When the VCU receives the "FISG towing start signal" sent by the RCU, it immediately starts the vehicle high-voltage power disconnection delay timer, with the delay duration set to 11 to 15 seconds; when the following two conditions are met simultaneously, the VCU performs the vehicle high-voltage power disconnection operation: Condition 1, receiving the "FISG towing end signal" sent by the RCU; Condition 2, the VCU's own high-voltage power disconnection delay timer has ended.

[0008] Preferably, in step S1, the judgment and output logic of the VCU is as follows: when the VCU recognizes that the vehicle speed is not zero, the vehicle drive power demand is 0 kilowatts for more than 10 consecutive seconds, the current SOC value of the vehicle power battery is ≥70%, and the vehicle's engine-driven devices do not require engine power output, the VCU synchronously transmits a signal that the target power generation is 0 kilowatts and an engine shutdown command to the RCU.

[0009] Preferably, in step S1, the judgment and output logic of the VCU is as follows: when the VCU recognizes that the vehicle speed is zero, the vehicle drive power demand is 0 kilowatts for more than 10 consecutive minutes, the current SOC value of the vehicle power battery is ≥70%, and the vehicle's engine-driven devices do not require engine power output, the VCU synchronously transmits a signal that the target power generation is 0 kilowatts and an engine shutdown command to the RCU.

[0010] Preferably, in step S1, the judgment and output logic of the VCU is as follows: when the VCU receives the driver's key stop operation signal, the VCU synchronously transmits a signal that the target power generation is 0 kilowatts and the stop command to the RCU.

[0011] Preferably, in step S1, when the VCU determines that "no shutdown command is sent" but a signal indicating a target power generation of 0 kW needs to be transmitted, the RCU, upon receiving the 0 kW power signal, sends a torque reduction command to the ECU to control the engine to gradually reduce torque, and simultaneously sends an idle speed command to the GCU to control the FISG motor speed to slowly drop back to idle speed; once the FISG motor speed returns to idle speed, the ECU controls the engine to idle.

[0012] Preferably, in step S1, the devices in the vehicle that require engine drive include an air conditioner and an air pump.

[0013] Preferably, in step S3, the idling time is specifically 3 minutes.

[0014] Preferably, in step S4, the time for which the FISG drags the engine crankshaft to maintain a speed of 400 rpm is specifically 6 seconds.

[0015] Preferably, in step S5, the time for delaying the high voltage under the VCU is specifically 13 seconds.

[0016] Preferably, the hardware foundation of the range extender system used in this method includes: VCU, RCU, ECU, FISG, and GCU; wherein, the gas engine crankshaft is rigidly connected to the FISG rotor, and the VCU, RCU, and ECU communicate with each other via a CAN communication bus.

[0017] The beneficial effects of this invention compared to the prior art include:

[0018] 1. This application addresses the oil emulsification problem during the shutdown phase of a gas turbine engine through a dual anti-emulsification design of "idle-speed water removal + towing scavenging." During the shutdown process, the engine idles for 1 to 5 minutes, utilizing residual heat from the cylinder block to fully evaporate water vapor in the crankcase. Once the engine speed drops to 400 rpm and combustion gas injection ceases, the flywheel integrated generator (FISG) immediately drives the crankshaft to maintain this speed for 4 to 10 seconds, forcibly expelling residual exhaust gas and water vapor through fresh air circulation. This continuous control logic reduces the water vapor content in the crankcase by more than 65%, lowering the oil emulsification rate from 85% in traditional models to below 5%, effectively preventing lubrication failure caused by emulsified oil, reducing wear on engine moving parts, and extending the service life of core components.

[0019] 2. This application eliminates mechanical and electrical shocks during shutdown by employing a gradient control strategy with multiple controllers working together. After receiving the shutdown command, the range extender controller (RCU) synchronously controls the engine to gradually reduce torque (torque smoothly drops from the rated value to zero) and the FISG to slowly return to idle speed, with the speed change rate controlled within 500 rpm / s to avoid mechanical stress caused by sudden torque drop and speed change. The vehicle controller (VCU) is set with a high-voltage disconnection delay of 11 to 15 seconds to ensure that the high-voltage circuit is disconnected step by step after the FISG completes scavenging, preventing the motor from generating back electromotive force that could damage circuit components. Tests show that the voltage fluctuation of the generator system during shutdown is ≤ ±2V, the wear of the engine main bearing is reduced by 60%, and the failure rate of the system during continuous operation is reduced by 70%.

[0020] 3. The control logic of this application can accurately match the complex working conditions of off-road construction machinery, achieving the dual goals of "differentiated shutdown + function priority". The vehicle controller (VCU) makes a comprehensive judgment based on vehicle speed, drive power, battery charge, and auxiliary device status: when the vehicle is coasting (vehicle speed is not zero and there is no drive power for 10 seconds), when it is stationary in standby (vehicle speed is zero and there is no drive power for 10 minutes), or when the driver actively operates, it can trigger a targeted shutdown process; when the battery does not need to be charged but devices such as air conditioning and air pumps need power, the system only stops generating electricity and maintains the engine idling speed to ensure continuous operation of auxiliary functions. This adaptable design enables the equipment to respond efficiently in different scenarios such as relocation, standby, and operation, increasing continuous operation time by 40% and significantly enhancing operational flexibility.

[0021] 4. This application achieves energy saving and consumption reduction while ensuring anti-emulsification effect through precise time and operating condition control. The engine idling time is set to 1 to 5 minutes (preferably 3 minutes), which ensures sufficient evaporation of water vapor and avoids fuel waste caused by excessive idling. The FISG traction power is controlled within 2kW, and the energy consumption of the scavenging process is only 0.017kWh / cycle, which is far lower than the traditional idling water removal mode. At the same time, the solution to the oil emulsification problem extends the engine oil change cycle by 30% and reduces the annual maintenance cost of the range extender system, achieving a balance between "anti-emulsification protection" and "economy". Attached Figure Description

[0022] Figure 1 This is a hardware architecture model diagram of a specific embodiment of the present invention.

[0023] Figure 2 This is a block diagram of a specific embodiment of the method of the present invention. Detailed Implementation

[0024] The present invention will now be described in further detail with reference to specific embodiments and the accompanying drawings. It should be emphasized that the following description is merely exemplary and is not intended to limit the scope or application of the present invention.

[0025] Non-limiting and non-exclusive embodiments will be described with reference to the following figures, wherein the same reference numerals denote the same parts unless otherwise specifically stated.

[0026] This embodiment discloses a shutdown control method for reducing oil emulsification in a range extender gas engine, such as... Figure 1 and 2 As shown, this is mainly applied to range extender systems used in non-road construction machinery (such as excavators and loaders). These types of equipment often operate under conditions of frequent start-stop cycles, high loads, and alternating idling. During the shutdown phase of the gas engine, exhaust gas and water vapor can easily remain in the crankcase, leading to oil emulsification. This method effectively solves the above problems by precisely controlling the shutdown process. The following is a detailed explanation of the specific hardware and control logic.

[0027] The range extender system upon which this method relies includes: Vehicle Control Unit (VCU), Range Extender Control Unit (RCU), Gas Engine Control Unit (ECU), Flywheel Integrated Generator (FISG) and its controller (GCU). The hardware connections are as follows: the gas engine crankshaft and FISG rotor are rigidly connected via flanges; the VCU, RCU, and ECU exchange signals via a CAN communication bus.

[0028] Specifically, a shutdown control method for reducing oil emulsification in a range extender gas engine includes the following steps:

[0029] Step S1: The VCU makes a judgment based on the vehicle's drive power requirements, the current SOC value of the power battery, and the working status of the vehicle's devices that require engine drive. It determines to synchronously transmit a signal with a target power generation of 0 kilowatts to the RCU and selectively sends an engine shutdown command based on the judgment result.

[0030] Step S2: When the RCU receives the target power generation command of 0 kW from the VCU and the engine stops, the RCU sends a torque reduction command to the ECU to control the engine to gradually reduce torque; at the same time, it sends an idle speed command to the GCU to control the FISG motor speed to slowly drop back to idle speed.

[0031] Step S3: When the FISG motor speed returns to idle speed, the ECU controls the engine to enter idle speed state and maintains idle speed for 1 to 5 minutes, and then controls the engine to stop injecting gas and shut down.

[0032] Step S4: During the process of the engine speed dropping from idle to zero, when the engine speed drops to 400 rpm and the engine is in a non-injection state, the RCU sends a speed command to the GCU to control the FISG to drag the engine crankshaft at 400 rpm. This dragging action lasts for 4 to 10 seconds. At the same time, the RCU sends real-time feedback to the VCU on the FISG's dragging start signal and dragging end signal.

[0033] Step S5: When the VCU receives the "FISG towing start signal" sent by the RCU, it immediately starts the vehicle high-voltage power disconnection delay timer, with the delay duration set to 11 to 15 seconds; when the following two conditions are met simultaneously, the VCU performs the vehicle high-voltage power disconnection operation: Condition 1, receiving the "FISG towing end signal" sent by the RCU; Condition 2, the VCU's own high-voltage power disconnection delay timer has ended.

[0034] Specifically, the VCU, as the control core, collects three key signals in real time: the vehicle's drive power demand (feedback from the motor controller), the current SOC value of the power battery, and the working status of the vehicle's devices that require engine drive (including the start / stop signal of the air conditioning compressor and the air pump pressure switch signal). Based on the above signals, it determines whether to trigger the shutdown process and executes the signal transmission action simultaneously. The VCU's judgment logic is divided into two scenarios: "triggering shutdown" and "only stopping power generation".

[0035] The first type of scenario (triggered shutdown) includes three typical operating conditions: Condition 1: When the equipment is in a coasting state during a transfer or work break, the VCU detects that the vehicle speed is not zero (the typical measured speed range is 10~30km / h, which can be adjusted according to the equipment type, such as 8~25km / h for loaders and 10~20km / h for excavators during transfer), and detects that the vehicle's drive power demand has been 0kW for more than 10 consecutive seconds (the driver releases the accelerator pedal, and the vehicle coasts by inertia). Simultaneously, the following conditions are met: the current SOC value of the power battery is ≥70%, the air conditioner is off, and the air pump pressure is ≥0.8MPa (no engine drive required). At this time, the VCU immediately transmits a "target power generation 0kW" signal and an "engine shutdown command" to the RCU. The control advantage under this condition is that it avoids frequent start-stop of the range extender during short-term no-load driving, reducing mechanical shock, while triggering shutdown in advance. The equipment preparation process allows time for subsequent anti-emulsification operations. In condition two, when the equipment is parked (vehicle speed 0 km / h), if the VCU detects that the vehicle's drive power demand is 0 kW for more than 10 consecutive minutes, and the vehicle's current SOC is ≥70%, and the vehicle's engine-driven devices have no power demand, the VCU simultaneously sends a "target power generation 0 kW" signal and an "engine stop command" to the RCU. This setting addresses the contradiction between "idling energy consumption" and "easy emulsification with direct shutdown" in traditional control, balancing energy saving and anti-emulsification effects, especially in scenarios where the equipment is idling for extended periods. In condition three, when the VCU receives a driver's key stop operation signal (or a central control screen stop command), regardless of the current SOC and power status, it simultaneously transmits two signals to the RCU (a target power generation 0 kW signal and an engine stop command) to ensure immediate response to driver operations and improve equipment operation safety.

[0036] The second scenario involves stopping power generation only: When the VCU determines that the battery SOC is ≥75% (no power generation required), but the air conditioning is on (requiring the engine to maintain idle speed), it only sends a "target power generation 0kW" signal to the RCU, without sending a shutdown command. At this time, the RCU sends a torque reduction command to the ECU to gradually reduce engine torque, and simultaneously sends an idle speed command to the GCU to slowly reduce the FISG speed to idle. Once the FISG speed stabilizes at idle, the ECU controls the engine to maintain idle speed, thus satisfying the continuous operation of the air conditioning while avoiding fuel waste caused by the range extender's ineffective power generation. Specifically, the devices requiring engine drive include the air conditioning and air pump. The power requirements of these devices directly affect the VCU's judgment logic and are crucial for ensuring compatibility between the shutdown procedure and equipment functionality.

[0037] Specifically, in step S2, after receiving the signal from the VCU, the RCU performs differentiated control based on whether an engine shutdown command is included. This embodiment focuses on the scenario where an engine shutdown command is included: the RCU immediately sends a torque reduction command to the ECU, controlling the throttle opening of the gas engine to gradually decrease from the rated operating condition. For example, the engine output torque smoothly decreases from 120 N·m to 0 N·m. The entire torque reduction process can last for 3 seconds to avoid mechanical shock caused by a sudden drop in torque. At the same time, the RCU sends an idle speed command to the GCU, controlling the FISG motor speed to slowly decrease from the current operating speed (e.g., 2000 rpm) to 800 rpm (FISG idle speed). The decrease process adopts a linear control strategy with a speed change rate ≤ 500 rpm / s to prevent voltage fluctuations caused by sudden changes in motor speed. This step, through "torque reduction and idle speed synchronous control," allows the range extender to smoothly transition from "generator load state" to "shutdown preparation state," laying the foundation for subsequent idle water removal and exhaust gas scavenging, and avoiding the sudden change in operating conditions caused by "direct fuel cut-off shutdown" in traditional control.

[0038] Specifically, in step S3, after the GCU feedback indicates that the FISG motor speed has stabilized at idle (800 rpm), the ECU immediately controls the gas engine to enter idle mode, maintaining the idle speed at the same level as the FISG (800 rpm) for 1 to 5 minutes, preferably 3 minutes. The 3-minute idle duration was determined based on extensive experimental data: if the duration is less than 1 minute, the engine block temperature will not rise sufficiently, and water vapor in the crankcase cannot evaporate effectively; if the duration is greater than 5 minutes, it will cause unnecessary fuel consumption and increased emissions. 3 minutes achieves the optimal balance between "water removal effect" and "economy." After the idle duration ends, the ECU controls the gas engine's gas injection valve to completely close, stopping gas injection. The engine, under inertia, begins to drop from 800 rpm to zero speed. During this process, the ECU continuously monitors the engine speed and injection valve status to ensure precise execution of the injection cessation action and prevent unburned gas from entering the crankcase and exacerbating oil contamination.

[0039] Specifically, in step S4, as the engine speed drops from 800 rpm to zero, the ECU feeds back speed and torque signals to the RCU in real time. When the engine speed is detected to have dropped to 400 rpm and the available engine torque is 0 N·m (confirming that it is in a non-injection state), the RCU immediately sends a speed command to the GCU, controlling the FISG to drag the engine crankshaft at a constant speed of 400 rpm. This dragging action lasts for 4 to 10 seconds, preferably 6 seconds. The dragging power of the FISG can be set to 2 kW, which ensures stable crankshaft rotation while avoiding excessive energy consumption. During the dragging process, the engine intake and exhaust valves operate according to normal valve timing. Fresh air enters the cylinder through the intake manifold and is then discharged through the exhaust valve, simultaneously driving the exhaust gas and water vapor in the crankcase out, achieving the purpose of "scavenging and removing water". Test data shows that this dragging scavenging step can reduce the water vapor content in the crankcase by more than 65%, providing a key guarantee for reducing oil emulsification. At the same time, the RCU feeds back two types of signals to the VCU in real time via the CAN bus: the FISG towing start signal and the towing end signal. The signal transmission period can be set to 100ms to ensure that the VCU accurately grasps the scavenging progress.

[0040] Specifically, in step S5, when the VCU receives the "FISG towing start signal" sent by the RCU, it immediately starts the high-voltage disconnection delay timer. The delay duration is set to 11 to 15 seconds, preferably 13 seconds. This duration is determined by considering two factors: first, to cover the 6-second towing scavenging time of the FISG, ensuring that the scavenging action is fully completed; second, to reserve a 7-second system buffer time for the FISG to switch from "towing state" to "free stop state," avoiding the generation of reverse electromotive force in the motor when the high-voltage power is disconnected. When the VCU simultaneously meets two conditions, it immediately performs the vehicle high-voltage disconnection operation: condition one, receiving the "FISG towing end signal" sent by the RCU; condition two, its own high-voltage disconnection delay timer has ended. If the towing scavenging is completed within 6 seconds, the VCU will wait for the delay timer to end before disconnecting the power; if the towing time is extended due to a fault (not exceeding 10 seconds), the VCU will immediately disconnect the power when it receives the end signal if the delay timer has exceeded 10 seconds, ensuring system safety. During the high-voltage disconnection process, the VCU first cuts off the high-voltage power supply circuit of the FISG, and then disconnects the power battery from the high-voltage load of the vehicle. The whole process lasts 500ms, which avoids the generation of electric arc and improves system reliability.

[0041] Those skilled in the art will recognize that numerous variations are possible with respect to the above description, and the embodiments and figures are merely for describing one or more specific implementations.

[0042] Although exemplary embodiments of the invention have been described and illustrated, those skilled in the art will understand that various changes and substitutions can be made thereto without departing from the spirit of the invention. Furthermore, many modifications can be made to adapt specific situations to the doctrine of the invention without departing from the central concepts of the invention described herein. Therefore, the invention is not limited to the specific embodiments disclosed herein, but may include all embodiments and equivalents that fall within the scope of the invention.

Claims

1. A shutdown control method for reducing oil emulsification in a range extender gas engine, characterized in that, Includes the following steps: Step S1: The VCU makes a judgment based on the vehicle's drive power requirements, the current SOC value of the power battery, and the working status of the vehicle's devices that require engine drive. It determines to synchronously transmit a signal with a target power generation of 0 kilowatts to the RCU and selectively sends an engine shutdown command based on the judgment result. Step S2: When the RCU receives the target power generation command of 0 kW from the VCU and the engine stops, the RCU sends a torque reduction command to the ECU to control the engine to gradually reduce torque; at the same time, it sends an idle speed command to the GCU to control the FISG motor speed to slowly drop back to idle speed. Step S3: When the FISG motor speed returns to idle speed, the ECU controls the engine to enter idle speed state and maintains idle speed for 1 to 5 minutes, and then controls the engine to stop injecting gas and shut down. Step S4: During the process of the engine speed dropping from idle to zero, when the engine speed drops to 400 rpm and the engine is in a non-injection state, the RCU sends a speed command to the GCU to control the FISG to drag the engine crankshaft at 400 rpm. This dragging action lasts for 4 to 10 seconds. At the same time, the RCU sends real-time feedback to the VCU on the FISG's dragging start signal and dragging end signal. Step S5: When the VCU receives the "FISG towing start signal" sent by the RCU, it immediately starts the vehicle high-voltage power disconnection delay timer, with the delay time set to 11 to 15 seconds; when the following two conditions are met simultaneously, the VCU performs the vehicle high-voltage power disconnection operation: Condition 1, receiving the "FISG towing end signal" sent by the RCU; Condition 2, the VCU's own high-voltage power disconnection delay timer has ended.

2. The shutdown control method for reducing oil emulsification in a range extender gas engine according to claim 1, characterized in that, In step S1, the judgment and output logic of the VCU is as follows: when the VCU recognizes that the vehicle speed is not zero, the vehicle drive power demand is 0 kilowatts for more than 10 consecutive seconds, the current SOC value of the vehicle power battery is ≥70%, and the vehicle's engine-driven devices do not require engine power output, the VCU synchronously transmits a signal that the target power generation is 0 kilowatts and an engine shutdown command to the RCU.

3. The shutdown control method for reducing oil emulsification in a range extender gas engine according to claim 1, characterized in that, In step S1, the judgment and output logic of the VCU is as follows: when the VCU recognizes that the vehicle speed is zero, the vehicle drive power demand is 0 kilowatts for more than 10 consecutive minutes, the current SOC value of the vehicle power battery is ≥70%, and the vehicle's engine-driven devices do not require engine power output, the VCU synchronously transmits a signal that the target power generation is 0 kilowatts and an engine shutdown command to the RCU.

4. The shutdown control method for reducing oil emulsification in a range extender gas engine according to claim 1, characterized in that, In step S1, the judgment and output logic of the VCU is as follows: when the VCU receives the driver's key stop operation signal, the VCU synchronously transmits a signal that the target power generation is 0 kilowatts and the stop command to the RCU.

5. The shutdown control method for reducing oil emulsification in a range extender gas engine according to claim 1, characterized in that, In step S1, when the VCU determines that "no shutdown command is sent" but a signal of 0 kW of target power generation needs to be transmitted, the RCU sends a torque reduction command to the ECU to control the engine to gradually reduce torque, and sends an idle speed command to the GCU to control the FISG motor speed to slowly drop back to idle speed; after the FISG motor speed returns to idle speed, the ECU controls the engine to idle.

6. The shutdown control method for reducing oil emulsification in a range extender gas engine according to claim 1, characterized in that, In step S1, the devices in the vehicle that require engine drive include air conditioning and air pump.

7. The shutdown control method for reducing oil emulsification in a range extender gas engine according to claim 1, characterized in that, In step S3, the idling time is specifically 3 minutes.

8. The shutdown control method for reducing oil emulsification in a range extender gas engine according to claim 1, characterized in that, In step S4, the time during which the FISG drags the engine crankshaft to maintain a speed of 400 rpm is specifically 6 seconds.

9. The shutdown control method for reducing oil emulsification in a range extender gas engine according to claim 1, characterized in that, In step S5, the VCU delay time for the high voltage is specifically 13 seconds.

10. The shutdown control method for reducing oil emulsification in a range extender gas engine according to claim 1, characterized in that, The hardware foundation of the range extender system used in this method includes: VCU, RCU, ECU, FISG, and GCU; wherein, the gas engine crankshaft is rigidly connected to the FISG rotor, and the VCU, RCU, and ECU communicate with each other via a CAN communication bus.

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