Hybrid Electric Vehicle Mode Control Method

Abstract

The present invention discloses a hybrid vehicle mode control method. Targeted at a P2.5+P4 hybrid vehicle architecture with a four-speed gearbox, the method makes targeted designs for the control of engine starting scenarios and hybrid mode operating conditions. The method mainly includes: presetting a mandatory power generation zone and a priority power generation zone of a battery; if the power level is in the mandatory power generation zone, the engine is started to conserve power; if the power level is in the priority power generation zone and the vehicle is traveling at a predetermined speed, the engine is started to generate power; and when the vehicle is traveling normally in pure electric mode, if the battery or motor is under heavy workload for a long time, the engine is started accordingly to enter a series mode or a parallel mode respectively; in addition, based on the above architecture, the present invention further proposes executing different mode judgment mechanisms according to the driver's operating intentions, so that the vehicle can reliably and accurately respond to the driver's needs, thereby providing a more ideal solution for the mode control of hybrid vehicles with the above architecture.

Description

Technical Field

[0001] The present invention relates to the technical field of hybrid vehicles, and in particular to hybrid mode management and control of a P2.5+P4 hybrid architecture, specifically a hybrid vehicle mode management and control method. Background Art

[0002] The P2.5 is a parallel hybrid vehicle approach in the industry. The P2.5 motor enables engine start-stop and parallel power assist (power assist or power generation when the engine is directly driven). Paired with a P4 motor (a wheel-direct drive motor layout), it can achieve series operation. However, the industry currently lacks a relatively ideal solution for achieving reliable and stable mode control within this P2.5+P4 architecture, particularly for engine starting and related mode switching. Summary of the Invention

[0003] In view of the above, the present invention aims to provide a hybrid electric vehicle mode control method to solve the above-mentioned technical problems.

[0004] The technical solution adopted in the present invention is as follows:

[0005] The present invention provides a hybrid vehicle mode control method. The hybrid vehicle architecture includes: a vehicle controller, a rear motor controller, a transmission controller, a front motor controller, and an engine controller. The hybrid vehicle is equipped with a four-speed transmission with four clutches. The control method includes:

[0006] Pre-configuring battery power zones, wherein the battery power zones include at least: a mandatory power generation zone and a priority power generation zone;

[0007] If it is detected that the SOC is in the mandatory power generation zone, the engine is started to maintain power until the power is replenished to the priority power generation zone; if it is detected that the SOC is in the priority power generation zone and the vehicle is traveling at a predetermined speed, the engine is started to generate power;

[0008] When the vehicle is running normally in pure electric mode, if it is detected that the battery discharge condition lasts longer than a first predetermined time, the engine is started to enter the series mode; or if it is detected that the motor operation condition lasts longer than a second predetermined time, the engine is started to enter the parallel mode;

[0009] Different mode judgment mechanisms are executed according to the driver's operating intention: when the vehicle is driving normally in pure electric mode, if full throttle acceleration is detected, the engine is started and the vehicle enters parallel mode; if the vehicle is detected to be in P gear parked and the accelerator pedal is pressed, or if the user triggers the on-the-spot charging function, the engine is started and the vehicle enters series mode; if the vehicle is in D gear and the brake pedal is detected to be pressed and then switched to the accelerator pedal, the engine is started, and after the brake pedal is released, the vehicle switches from series mode to parallel mode.

[0010] In at least one possible implementation, starting the engine to enter the series mode includes:

[0011] After starting the engine in pure electric rear-wheel drive mode, the vehicle controller sends the series mode request to the transmission controller;

[0012] The transmission controller controls the closing of the first clutch, and the front motor controller switches to the torque mode and applies a pre-calibrated torque to make the output speed of the engine controller reach a predetermined speed;

[0013] The engine controller triggers the fuel injection and ignition, and after the engine outputs positive torque, the front motor controller switches to the speed mode to adjust the engine's economic operating point, and at the same time applies negative torque to switch the vehicle from pure electric rear-wheel drive mode to series mode.

[0014] In at least one possible implementation method, the control method also includes: if the front motor controller switches from the speed mode to the torque mode, the torque is distributed to the engine, front motor and rear motor according to the current vehicle speed, SOC, throttle opening and vehicle status.

[0015] In at least one possible implementation, the control method further includes a target mode demand decision mechanism:

[0016] After the rear motor controller, transmission controller, front motor controller, and engine controller all report a fault-free state, the current series mode and parallel mode capabilities are calculated based on the current available power of the battery, front motor, engine, and rear motor, respectively. The formula is as follows:

[0017] Series mode capability = {[battery available power + (engine available power, front motor available power) min ], available power of rear motor} min ;

[0018] Parallel mode capability = engine available power + [battery available power, (front motor available power + rear motor available power)] min ;

[0019] The vehicle controller determines the target mode requirement based on the calculated series mode capability, parallel mode capability and wheel-end required torque: if the current parallel mode capability is greater than the series mode capability, and the wheel-end required torque is greater than the series mode capability, then the target mode requirement is to enter the parallel mode; if the current series mode capability is greater than the parallel mode capability, and the wheel-end required torque is greater than the parallel mode capability, then the target mode requirement is to enter the series mode.

[0020] In at least one possible implementation, the control method further includes:

[0021] Before switching to the parallel mode, determine whether the current vehicle speed is greater than the preset switching speed threshold;

[0022] If so, the minimum torque value in parallel mode is calculated based on the current vehicle speed, the available power of the battery, the current SOC, and the speed ratio of the preselected gear;

[0023] If the wheel-end demand torque is greater than the minimum torque value, entering the parallel mode is allowed.

[0024] In at least one possible implementation, the switching vehicle speed threshold is obtained according to the engine speed or based on the gear shift line of the transmission; and if the vehicle is currently in a rapid acceleration condition, the switching vehicle speed threshold is lowered.

[0025] In at least one possible implementation, the control method further includes:

[0026] When the vehicle is in series drive, the transmission controller calculates the current relatively optimal pre-selected gear in real time based on the current vehicle speed, throttle opening and engine speed;

[0027] Before the vehicle controller sends a parallel mode switching request to the transmission controller, the front motor is speed-regulated according to the speed ratio of the preselected gear, the current vehicle speed, and the rotational speed of the front axle output shaft of the vehicle;

[0028] After receiving the instruction to trigger the parallel mode start, the transmission controller controls the clutch corresponding to the preselected gear to close;

[0029] After confirming that the clutch is closed, the transmission controller updates the current actual gear position to the corresponding parallel gear position;

[0030] The vehicle controller completes the switch from series mode to parallel mode.

[0031] In at least one possible implementation, if the preselected gear changes, the vehicle controller readjusts the speed according to the changed preselected gear.

[0032] In at least one possible implementation, regulating the speed of the front motor includes:

[0033] During the speed regulation process, the vehicle controller sends a pre-fill oil instruction to the transmission controller;

[0034] The transmission controller, in combination with the current preselected gear, fills the corresponding clutch with oil until the clutch reaches a preset half-engagement point.

[0035] The main design concept of the present invention lies in the targeted design of engine starting scenarios and hybrid mode operating conditions for a P2.5+P4 hybrid vehicle architecture equipped with a four-speed transmission. This design primarily includes: presetting the battery's mandatory and priority power generation zones; starting the engine to maintain power if the SOC is in the mandatory power generation zone; starting the engine to generate power if the SOC is in the priority power generation zone and the vehicle is traveling at a predetermined speed; and, when the vehicle is operating normally in pure electric mode, if the battery or motor is under heavy load due to prolonged operation, starting the engine to enter series mode or parallel mode, respectively. Furthermore, based on the aforementioned architecture, the present invention proposes implementing different mode determination mechanisms based on the driver's operational intent, enabling the vehicle to reliably and accurately respond to the driver's needs by entering parallel or series mode, or switching between series and parallel modes. Furthermore, the present invention provides a detailed implementation reference for the processes and details involved in mode switching, offering a relatively ideal solution for mode control in P2.5+P4 hybrid vehicles. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described below with reference to the accompanying drawings, in which:

[0037] Figure 1 A schematic diagram of a hybrid vehicle mode control method provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0038] The following describes embodiments of the present invention in detail. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended only to explain the present invention and are not to be construed as limiting the present invention.

[0039] The present invention proposes an embodiment of a hybrid vehicle mode control method. Specifically, the present invention mentions that the hybrid vehicle adopts a P2.5+P4 architecture. The control units involved in this architecture can be referred to as follows: VCU vehicle controller, MCU rear motor controller (i.e., P4 motor controller), TCU transmission controller, GCU front motor controller (i.e., P2.5 motor controller), SOC battery power, BMS battery management system and ECU engine controller.

[0040] In some preferred embodiments, the present invention also considers deploying a multi-speed gearbox, specifically a four-speed AT gearbox, so that the vehicle can achieve both power economy and a rich driving mode.

[0041] To elaborate, through the coordinated control of the four clutches A, B, C, and D of the aforementioned four-speed gearbox, two-speed motor and four-speed engine control can be achieved, thereby enabling the vehicle to have pure electric rear-wheel drive, pure electric front-wheel drive, pure electric four-wheel drive, series, parallel power generation, and parallel power assistance. Specifically, by closing clutch C or D, the GCU can perform the driving function on the front axle to achieve pure electric four-wheel drive or pure electric front-wheel drive; by closing clutch A, the GCU can drag the engine to generate electricity and adjust the engine's economy and power point, thereby achieving vehicle series connection; and after entering the series connection, while keeping clutch A closed, close the front axle drive clutch B or C or D to achieve engine direct drive, and enter the following parallel state (AC-1 gear, AD-2 gear, AB-3 gear, CD-4 gear); when all four clutches are disengaged, it is pure electric rear-wheel drive.

[0042] For the mode control method proposed in this example, Figure 1 As shown, the following implementation reference is given here:

[0043] Step S1: pre-configure battery power zones, wherein the battery power zones include at least a mandatory power generation zone and a priority power generation zone;

[0044] In actual operation, the battery power partition can be pre-configured: Based on the aforementioned architecture, the VCU divides the battery power SOC into zones according to the battery power sent by the BMS and the current ambient temperature and altitude information. Specifically, it can be divided into: forced power generation zone, priority power generation zone, etc. Of course, in other embodiments, it may also involve a balance zone, a priority power zone, and a forced power zone, which is not limited in the present invention. The forced power generation zone means that when the battery power is too low, the engine is forced to start to replenish the battery; and the priority power generation zone means that in this SOC range, the engine is easier to start and can be used to replenish the battery or be used for motor drive.

[0045] It can be further expanded that several energy modes can be pre-set for the control method proposed in the present invention, for example:

[0046] Pure electric priority mode: To ensure the user's driving experience, the engine is generally difficult to start. This mode will only be activated when the battery discharge power or motor capacity cannot meet the current wheel-end power demand, or the battery power drops below the aforementioned priority power generation area, or when certain vehicle components require the engine to be started. In this mode, the power conservation SOC cannot be modified.

[0047] Fuel priority mode: Prioritizes battery conservation and balancing SOC, and the wheel-end demand torque is greater than the minimum torque required to start the engine (this torque is smaller in this mode). The engine will only start when the above adjustments are met. Similarly, the battery conservation SOC cannot be modified in this mode.

[0048] Forced pure electric mode: The engine is prohibited from starting until the vehicle's battery level drops to an extremely low level (determined based on a pre-calibrated lower threshold), at which point it automatically switches to pure electric priority and the engine is forced to start for charging.

[0049] Smart mode: can receive the power conservation SOC point set by the user to solve the power consumption anxiety based on the user's perspective.

[0050] Continuing with the above, in step S2, if it is detected that the SOC is in the mandatory power generation zone, the engine is started to maintain power until the power is replenished to the priority power generation zone; if it is detected that the SOC is in the priority power generation zone and the vehicle is traveling at a predetermined speed (the vehicle can be controlled to travel at a preset low speed to maintain pure electric power, and the purpose of this predetermined speed is to ensure the user's driving experience), the engine is started to generate power;

[0051] Step S3: When the vehicle is running normally in pure electric mode, if it is detected that the battery discharge condition lasts longer than a first predetermined time, the engine is started to enter the series mode; or if it is detected that the motor operation condition lasts longer than a second predetermined time, the engine is started to enter the parallel mode;

[0052] Specifically, when the vehicle is driving normally in pure electric mode (mainly in pure electric rear-wheel drive mode), if it is detected that the battery is in a high-load discharge state for a long time, that is, the available discharge power of the battery may jump, then the available power generation of the battery cannot meet the wheel-end drive power when the driver is driving at a constant speed at the current vehicle speed, so the engine needs to start and enter the series connection to supplement the power for the wheel-end drive. This can be expanded upon. When the engine is started in pure electric rear-wheel drive mode, the VCU sends the target mode in series to the TCU, and the TCU closes clutch A. At this time, the GCU is rigidly connected to the ECU, and the GCU switches to the torque mode. After applying a certain torque (calibrated amount) to make the ECU speed reach the specified speed, the ECU injects fuel and ignites. After the engine outputs positive torque, the GCU switches to the speed mode to adjust the engine's economic point and applies negative torque. The actual mode of the vehicle switches from pure electric rear-wheel drive to the series mode to power the battery.

[0053] Accordingly, when the vehicle is running normally in pure electric mode, if it is detected that the motor is in a high-load working state for a long time, that is, the motor power may decrease due to problems such as overheating, and cannot meet the wheel-end drive power for the current vehicle to continue to travel at a constant speed, the engine needs to start and enter parallel mode, the engine participates in the drive, and the vehicle switches to engine direct drive or parallel four-wheel drive (the engine and P4 motor drive at the same time); Regarding the four-wheel drive mode: Since this mode is based on the aforementioned P2.5+P4 hybrid architecture, it provides reliable four-wheel drive capabilities and can therefore be used for light off-road driving. For example, when the user selects the off-road mode, the vehicle can enter the pure electric four-wheel drive mode from the pure electric rear-wheel drive, or enter the low-speed parallel four-wheel drive mode.

[0054] Next, in step S4, the following mode determination mechanism is executed according to the driver's operation intention:

[0055] When the vehicle is running normally on pure electric power, if it detects that the driver is accelerating at full throttle to overtake, the vehicle starts the engine and enters parallel operation, and the vehicle switches to parallel four-wheel drive to improve the vehicle's power;

[0056] If the vehicle is detected to be in P gear, the driver steps on the accelerator, or the user triggers the on-site charging function after receiving MP4 feedback, the engine starts and enters the series connection to charge the vehicle;

[0057] If the vehicle is in the established vehicle "launch" mode, that is, pressing the brake pedal in D gear and switching to pressing the accelerator pedal to enter the launch mode, the engine will start at this time. After the user releases the brake pedal, the vehicle will quickly switch from series to parallel, giving the entire vehicle maximum acceleration capability.

[0058] Furthermore, engine startup also includes the following: if the vehicle is in a low-temperature environment and the air conditioning is turned on after the vehicle is started, the engine will activate the heating thermal management water pump to heat the passenger compartment. This is not detailed or limited in the present invention, but it can be specifically explained that the decision to enter series mode or parallel mode can also include the following process:

[0059] First, based on the fault status of the GCU, MCU, TCU, and engine, it is determined whether series or parallel operation is currently permitted. Second, due to the characteristics of the P2.5+P4 architecture described above in this embodiment, when in parallel operation, if the vehicle speed is too low, the engine speed may be dragged down to a very low level due to wheel-end resistance, causing the engine to stall. Therefore, the condition for entering parallel operation requires that the current vehicle speed at least meet the preset speed value.

[0060] Based on the current battery capacity (available power), GCU capacity, engine capacity, and MCU capacity, calculate the current series mode and parallel mode capacity (that is, the available drive power in series / parallel) using the following formula:

[0061] Series capacity = {[battery capacity + (engine capacity, GCU capacity) min ]、MCU capabilities} min

[0062] Parallel capability = engine capability + [battery capability, (GCU capability + MCU capability)] min

[0063] The VCU determines the actual series or parallel demand based on the current series and parallel capabilities and the wheel-end torque demand. If the current parallel capability is greater than the series capability, and the wheel-end torque demand is greater than the series capability, the VCU demands parallel operation. The same applies to series operation, which is not detailed here. If both series and parallel capabilities are relatively large (i.e., the difference between the two is not significant), the above determination method only takes effect when the wheel-end torque demand is high. In this case, for dynamic considerations, the series or parallel mode is determined based on the current series and parallel capabilities when the wheel-end torque demand is high.

[0064] In conjunction with the aforementioned influence of vehicle speed, entering parallel mode, particularly during normal driving, can be further explained. Generally, in parallel front-wheel drive mode, the vehicle speed required to maintain the lowest engine speed in the lowest gear (maximum speed ratio) cannot be zero. Therefore, vehicle speed is a prerequisite for entering parallel mode, and parallel mode is permitted only when the vehicle speed exceeds a certain value. Furthermore, for economic reasons, series mode is preferred at lower speeds, and parallel mode is permitted only when the vehicle speed exceeds a certain value. Furthermore, for NVH considerations, the engine speed of the series generator should not be too high, so the series and parallel mode switching speeds can be determined based on the engine speed. Furthermore, the series and parallel mode switching speeds can also be determined based on the transmission's shift line. Furthermore, in conjunction with the aforementioned embodiment based on driver intent, it can be further explained that during rapid acceleration (full throttle), the driver demands high torque, so a low gear with a large speed ratio can be selected. Furthermore, because the series-parallel mode switching speed can be lowered during rapid acceleration, the vehicle can enter parallel mode more quickly.

[0065] After the vehicle speed conditions meet the switching requirements, the minimum torque value in parallel mode can be calculated based on the current vehicle speed, battery capacity, current power and the speed ratio of the pre-selected gear. From this calculation result, once the demand enters parallel, the required torque at the wheel end should be greater than the minimum torque value.

[0066] In combination with the above-mentioned embodiment of the structure including a 4-speed gearbox, since the parallel 4th gear uses clutches C and D, the whole vehicle cannot directly switch from series (A clutch) to parallel 4th gear, and can only switch to parallel 1 / 2 / 3 gears.

[0067] Therefore, during the series drive process, the TCU calculates the ideal pre-selected gear in real time based on vehicle speed, throttle, engine speed, etc.; the ideal gear here refers to the relatively optimal gear currently calculated.

[0068] Before the VCU sends a parallel mode switch request to the TCU, the GCU must adjust its speed based on the preselected gear ratio, current vehicle speed, and front axle output shaft speed sent by the TCU. Specifically, during this speed adjustment process, the VCU sends a pre-fill command to the TCU. The TCU searches for the corresponding clutch based on the current preselected gear and fills it with oil until it reaches the kisspoint (partial engagement point). It should be noted that this pre-fill prevents the TCU from changing the preselected gear due to changes in vehicle speed or other factors.

[0069] The TCU then waits for the VCU to initiate parallel mode, at which point it executes the clutch engagement. If the preselected gear changes during this process due to network latency, the VCU re-enacts the aforementioned speed control using the changed preselected gear. After the clutch engages, the TCU updates the current gear to parallel 1 / 2 / 3, and the VCU changes the current mode to parallel.

[0070] Finally, it can be added that, again in conjunction with the aforementioned embodiment based on user intention, if the GCU is in a working condition where it switches from speed mode to torque mode, the VCU distributes the torque among the ECU, GCU, and MCU based on the current vehicle speed, battery level, throttle, and other vehicle states. For example, if the current vehicle speed and battery level are both relatively high, and the user drives with a large throttle, the actual vehicle mode switches from series to parallel. The original driving force of the vehicle comes entirely from the MCU. At this time, from the perspective of power and safety, part of the driving force of the MCU needs to be transferred to the front axle and distributed by the ECU and GCU. At this time, the vehicle is in parallel four-wheel drive, and the GCU assists. If the current battery level is low, the GCU may allocate some negative torque for power generation. At this time, the MCU may only perform energy recovery. The driving force of the vehicle is entirely borne by the ECU. At this time, the vehicle is in a parallel front-wheel drive power generation state.

[0071] In summary, the main design concept of the present invention is to provide targeted design for engine starting scenarios and hybrid mode operating conditions for a P2.5+P4 hybrid vehicle architecture with a four-speed transmission. This includes: presetting the battery's mandatory power generation zone and priority power generation zone; starting the engine to maintain power if the SOC is in the mandatory power generation zone; starting the engine to generate power if the SOC is in the priority power generation zone and the vehicle is traveling at a predetermined speed; and starting the engine to enter series or parallel mode, respectively, if the battery or motor is under heavy workload due to prolonged operation while the vehicle is operating normally in pure electric mode. Furthermore, based on the above architecture, the present invention proposes implementing different mode determination mechanisms based on the driver's operational intent, enabling the vehicle to reliably and accurately respond to the driver's needs to enter parallel or series mode, or to switch between series and parallel modes. Furthermore, the present invention provides a detailed implementation reference for the processes and details involved in mode switching, offering a relatively ideal solution for mode control in P2.5+P4 hybrid vehicles.

[0072] If the expressions expressing directions are mentioned in the embodiments of the present invention, they are relative concepts based on the embodiments. In addition, "at least one" refers to one or more, and "more" refers to two or more. "And / or" describes the association relationship of the associated objects, indicating that three relationships may exist. For example, A and / or B can represent the existence of A alone, the existence of A and B at the same time, and the existence of B alone. Among them, A and B can be singular or plural. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship. "At least one of the following" and similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b and c can represent: a, b, c, a and b, a and c, b and c or a, b and c, where a, b, c can be single or multiple.

[0073] The above describes in detail the structure, features and effects of the present invention based on the embodiments shown in the drawings, but the above is only a preferred embodiment of the present invention. It should be noted that the technical features involved in the above embodiments and their preferred modes can be reasonably combined and matched into a variety of equivalent schemes by those skilled in the art without departing from or changing the design ideas and technical effects of the present invention; therefore, the scope of implementation of the present invention is not limited to what is shown in the drawings. Any changes made in accordance with the concept of the present invention, or modifications to equivalent embodiments with equivalent changes, which still do not exceed the spirit covered by the description and drawings, should be within the scope of protection of the present invention.

Claims

1. A hybrid vehicle mode control method, wherein the hybrid vehicle architecture includes: The vehicle controller, rear motor controller, gearbox controller, front motor controller, and engine controller are provided, and the hybrid vehicle is equipped with a four-speed gearbox with four clutches. The control method includes: Pre-configuring battery power zones, wherein the battery power zones include at least: a mandatory power generation zone and a priority power generation zone; If it is detected that the SOC is in the mandatory power generation zone, the engine is started to maintain power until the power is replenished to the priority power generation zone; if it is detected that the SOC is in the priority power generation zone and the vehicle is traveling at a predetermined speed, the engine is started to generate power; When the vehicle is running normally in pure electric mode, if it is detected that the battery discharge condition lasts longer than a first predetermined time, the engine is started to enter the series mode; or if it is detected that the motor operation condition lasts longer than a second predetermined time, the engine is started to enter the parallel mode; Different mode determination mechanisms are implemented based on the driver's operating intention: when the vehicle is driving normally on pure electric power, if full throttle acceleration is detected, the engine is started and the vehicle enters parallel mode; if the vehicle is detected to be in P gear and the accelerator pedal is pressed, or if the user triggers the on-site charging function, the engine is started and the vehicle enters series mode; if the vehicle is in D gear and the brake pedal is detected to be pressed and then the accelerator pedal is pressed, the engine is started and the vehicle switches from series mode to parallel mode after the brake pedal is released; The vehicle controller determines the target mode requirement based on the obtained series mode capability, parallel mode capability, and wheel-end torque requirements: If the current parallel mode capability is greater than the series mode capability, and the wheel-end torque requirement is greater than the series mode capability, the target mode requirement is to enter the parallel mode; If the current series mode capability is greater than the parallel mode capability, and the wheel-end required torque is greater than the parallel mode capability, the target mode requirement is to enter the series mode; If the series capacity and parallel capacity are similar, the decision to enter the series mode or parallel mode is based on the current series capacity and parallel capacity only when the wheel-end torque demand is larger; The control method further includes: Before switching to the parallel mode, determine whether the current vehicle speed is greater than the preset switching speed threshold; If so, the minimum torque value in parallel mode is calculated based on the current vehicle speed, the available power of the battery, the current SOC, and the speed ratio of the preselected gear; If the wheel-end demand torque is greater than the minimum torque value, entering the parallel mode is allowed.

2. The hybrid vehicle mode control method according to claim 1, characterized in that: Starting the engine to enter the series mode includes: After starting the engine in pure electric rear-wheel drive mode, the vehicle controller sends the series mode request to the transmission controller; The transmission controller controls the closing of the first clutch, and the front motor controller switches to the torque mode and applies a pre-calibrated torque to make the output speed of the engine controller reach a predetermined speed; The engine controller triggers the fuel injection and ignition, and after the engine outputs positive torque, the front motor controller switches to the speed mode to adjust the engine's economic operating point, and at the same time applies negative torque to switch the vehicle from pure electric rear-wheel drive mode to series mode.

3. The hybrid vehicle mode control method according to claim 2, characterized in that: The control method also includes: if the front motor controller switches from the speed mode to the torque mode, the torque is distributed to the engine, the front motor and the rear motor according to the current vehicle speed, SOC, throttle opening and the vehicle status.

4. The hybrid vehicle mode control method according to claim 1, characterized in that: The control method also includes a target mode demand decision mechanism: After the rear motor controller, transmission controller, front motor controller, and engine controller all report a fault-free state, the current series mode and parallel mode capabilities are calculated based on the current available power of the battery, front motor, engine, and rear motor, respectively. The formula is as follows: Series mode capability = {[battery available power + (engine available power, front motor available power) min], rear motor available power} min ; Parallel mode capability = engine available power + [battery available power, (front motor available power + rear motor available power)] min .

5. The hybrid vehicle mode control method according to claim 1, characterized in that: The switching vehicle speed threshold is obtained according to the engine speed or based on the shift line of the transmission; and if the vehicle is currently in a rapid acceleration condition, the switching vehicle speed threshold is lowered.

6. The hybrid vehicle mode control method according to claim 1, characterized in that: The control method further includes: When the vehicle is in series drive, the transmission controller calculates the current relatively optimal pre-selected gear in real time based on the current vehicle speed, throttle opening and engine speed; Before the vehicle controller sends a parallel mode switching request to the transmission controller, the front motor is speed-regulated according to the speed ratio of the preselected gear, the current vehicle speed, and the rotational speed of the front axle output shaft of the vehicle; After receiving the instruction to trigger the parallel mode start, the transmission controller controls the clutch corresponding to the preselected gear to close; After confirming that the clutch is closed, the transmission controller updates the current actual gear position to the corresponding parallel gear position; The vehicle controller completes the switch from series mode to parallel mode.

7. The hybrid vehicle mode control method according to claim 6, characterized in that: If the pre-selected gear changes, the vehicle controller will readjust the speed according to the changed pre-selected gear.

8. The hybrid vehicle mode control method according to claim 6 or 7, characterized in that: The speed regulation of the front motor comprises: During the speed regulation process, the vehicle controller sends a pre-fill oil instruction to the transmission controller; The transmission controller, in combination with the current preselected gear, fills the corresponding clutch with oil until the clutch reaches a preset half-engagement point.

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