Hybrid electric vehicle off-road mode control method

Abstract

The invention discloses a hybrid electric vehicle off-road mode control method, which has the main design conception that aiming at a P2.5 + P4 hybrid electric vehicle framework with a four-gear gearbox, when the hybrid electric vehicle framework enters an off-road mode for the first time, if the SOC is lower than a predefined off-road balance point, an engine is dragged by a front motor, and the hybrid electric vehicle framework enters a series rear drive; if the vehicle speed meets the parallel connection entering condition, switching to parallel connection four-wheel drive; if the vehicle speed does not meet the entering condition, a pure electric rear-drive intermediate mode is entered, and then a pure electric four-drive intermediate mode is entered; if the vehicle speed meets the condition again, the vehicle enters the parallel four-wheel drive mode through idling and speed regulation of the engine, and then the vehicle is switched between the pure electric four-wheel drive intermediate mode and the parallel four-wheel drive mode back and forth according to the comparison result of the real-time vehicle speed and the set running speed threshold value. Based on the four-wheel-drive control scheme for the specific hybrid architecture and configuration, four-wheel-drive escape can be achieved under most of working conditions, and long-time cross-country is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of hybrid electric vehicles, and particularly to a control method for the off-road mode of a hybrid electric vehicle. Background Art

[0002] In the industry, P2.5 generally refers to the parallel hybrid vehicle route. The P2.5 motor can start or stop the engine when the engine starts or stops, or participate in driving together with the engine (engine direct drive); if a P4 motor is configured, when the P4 motor drives, the P2.5 motor can adjust the engine speed to do negative torque work for power generation, realizing the series function, and the P4 motor only participates in driving and energy recovery. If a multi-gear transmission is configured (in the embodiments of the present invention, a four-speed AT transmission can be selected for the P2.5+P4 architecture, and will not be repeated hereinafter), it can take into account power economy and has rich driving modes.

[0003] Through the coordinated control of the four clutches A, B, C, and D of the transmission, two-speed control of the motor and four-speed control of the engine can be achieved. For example, when clutch C or D is closed, the front motor controller GCU drives the front motor (P2.5 motor) to participate in driving to output torque, and there is a pure electric four-wheel drive mode or a pure electric front-wheel drive mode; when clutch A is closed, the GCU starts the engine and adjusts the economic and power points of the engine, and the vehicle enters the series mode; after entering the series mode, keep clutch A closed, and close the front axle drive clutch B or C or D (specifically, when the pure electric front-wheel drive or four-wheel drive closes clutch C or D, and the parallel closes AC or AD, both close C or D, so the front axle pure electric front-wheel drive or pure electric four-wheel drive has the same front axle speed ratio as the parallel at this time), at this time the engine is in direct drive, and the parallel mode can be entered (AC - 1st gear, AD - 2nd gear, AB - 3rd gear, CD - 4th gear); when all clutches are defaultly disengaged, it is the pure electric rear-wheel drive mode.

[0004] It should be noted that, under the above architecture, the vehicle is configured with a four-wheel drive mode, that is, it has a certain off-road ability. For example, if clutch C or D is closed, at this time the vehicle is in pure electric four-wheel drive, the power is transmitted from the battery, and the GCU participates in driving, but it is difficult to start the engine for power generation (it causes too much damage to the clutch). At this time, the power output is limited by the battery capacity and the motor capacity, and the battery power cannot be replenished. If the battery power drops too low, the vehicle will have to exit the four-wheel drive and start the engine for power generation instead. Therefore, the above architecture cannot be in pure electric four-wheel drive for a long time;

[0005] In addition, if the vehicle speed is relatively high, the engine can be started at this time, and the P2.5 motor generates electricity, and the engine is in direct drive, which can take into account both vehicle power conservation and four-wheel drive. However, in the parallel mode at low speeds, limited by the minimum speed of the engine and the large speed ratio of the low gears in parallel, the engine is easily stalled. Therefore, the above architecture cannot enter the parallel mode at low speeds either. Summary of the invention

[0006] In view of the above, the present invention aims to provide a hybrid electric vehicle off-road mode control method to solve the limitation of the P2.5+P4 architecture and the inability to take into account the battery charging problem under low-speed four-wheel drive conditions to achieve long-term off-road escape.

[0007] The technical solution adopted by the present invention is as follows:

[0008] The present invention provides a hybrid electric vehicle off-road mode control method, wherein the hybrid electric vehicle architecture at least includes: a rear motor controller, a gearbox controller, a front motor controller and an engine controller, and the hybrid electric vehicle is equipped with a four-speed gearbox with four clutches, wherein the control method includes:

[0009] Predefine off-road balance point based on battery SOC;

[0010] When the vehicle enters the off-road mode for the first time, if the battery SOC is lower than the off-road balance point, the front motor is controlled to pull the engine, and the vehicle enters the series rear-wheel drive mode from the pure electric rear-wheel drive mode;

[0011] After entering the series rear-wheel drive mode, if the current vehicle speed is greater than the preset parallel entry speed threshold, it switches to the parallel four-wheel drive mode; if the current vehicle speed is lower than the parallel entry speed threshold, the transmission controller controls the first clutch of the four-speed transmission to disengage, so that the vehicle enters the preset pure electric rear-wheel drive intermediate mode, and then closes the third clutch or the fourth clutch of the four-speed transmission to make the vehicle enter the preset pure electric four-wheel drive intermediate mode;

[0012] After entering the pure electric four-wheel drive intermediate mode, if the vehicle speed is higher than the parallel entry speed threshold, the engine controller controls the engine speed regulation and enters the parallel four-wheel drive mode, and the front motor controller controls the front motor to perform the power generation task;

[0013] In parallel four-wheel drive mode, if the vehicle speed is lower than the preset parallel exit speed threshold, the engine controller will control the engine torque reduction to disengage, allowing the vehicle to enter the pure electric four-wheel drive intermediate mode; thereafter, based on the comparison result between the real-time vehicle speed and the established driving speed threshold, the vehicle will switch back and forth between the pure electric four-wheel drive intermediate mode and the parallel four-wheel drive mode.

[0014] In at least one possible implementation, after the engine controller controls the engine torque reduction to disengage and the vehicle enters the pure electric four-wheel drive intermediate mode, if the vehicle is unable to switch to the parallel four-wheel drive mode for recharging due to vehicle speed factors, and the battery SOC drops below the preset SOC lower limit threshold, the vehicle will first enter the pure electric rear-wheel drive intermediate mode s, and then enter the series rear-wheel drive mode to force power generation.

[0015] In at least one possible implementation, the pure electric rear-wheel drive intermediate mode only controls the rear motor by the rear motor controller to perform the driving task, and controls the engine by the engine controller to perform idling.

[0016] In at least one possible implementation, the pure electric four-wheel drive intermediate mode jointly drives the front motor and the rear motor by the front motor controller and the rear motor controller to perform the driving task, and controls the engine by the engine controller to perform idling.

[0017] In at least one possible implementation, the control method further includes:

[0018] When the vehicle first enters the off-road mode, if the battery SOC is higher than the off-road balance point, the vehicle directly enters the pure electric four-wheel drive mode from the pure electric rear-wheel drive mode and continuously remains in the pure electric four-wheel drive mode until the battery SOC is lower than a preset first power threshold, and the vehicle exits the pure electric four-wheel drive mode and starts the engine.

[0019] In at least one possible implementation, the control method further includes:

[0020] After the vehicle enters the off-road mode, if it is detected that the gear is in the P gear and the battery SOC is lower than the off-road balance point, the vehicle enters the series power generation mode until the battery SOC is greater than a preset second power threshold, and returns to the pure electric rear-wheel drive mode;

[0021] After the vehicle enters the off-road mode, if it is detected that the gear is in the P gear and the battery SOC is higher than the off-road balance point, the vehicle enters the pure electric rear-wheel drive mode.

[0022] In at least one possible implementation, the control method further includes:

[0023] In the pure electric four-wheel drive mode, if the vehicle speed is higher than a predetermined first vehicle speed threshold and the engine has been started, the transmission controller controls the second clutch or the third clutch or the fourth clutch in the four-speed transmission, and directly makes the vehicle enter the parallel four-wheel drive mode, and the front motor controller changes from the driving working mode to the power generation working mode; thereafter, if in the parallel four-wheel drive mode, the vehicle speed is lower than a predetermined second vehicle speed threshold, the transmission controller controls to directly disconnect the first clutch combined with the engine, and makes the vehicle enter the pure electric four-wheel drive mode.

[0024] Compared with the prior art, the main design concept of the present invention is that for the hybrid vehicle architecture of P2.5+P4 with a four-speed gearbox, when entering the off-road mode for the first time, if the SOC is lower than the predefined off-road balance point, the front motor will pull up the engine and enter the series rear-wheel drive; if the vehicle speed meets the conditions for entering the parallel connection, it will switch to the parallel four-wheel drive; if the vehicle speed does not meet the entry conditions, it will enter the pure electric rear-wheel drive intermediate mode, and then enter the pure electric four-wheel drive intermediate mode; if the vehicle speed meets the conditions again, the engine will idle and the speed will be adjusted to enter the parallel four-wheel drive mode. After that, according to the comparison result between the real-time vehicle speed and the established driving speed threshold, the vehicle will switch back and forth between the pure electric four-wheel drive intermediate mode and the parallel four-wheel drive mode. Based on the above-mentioned four-wheel drive control scheme for a specific hybrid architecture and configuration of the present invention, it can meet the four-wheel drive escape under most working conditions and achieve long-term off-roading. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] 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:

[0026] Figure 1 A schematic diagram of an off-road mode control method for a hybrid vehicle provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0027] Embodiments of the present invention are described in detail below, and 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 only used to explain the present invention, and cannot be interpreted as limiting the present invention.

[0028] The present invention proposes an embodiment of a hybrid electric vehicle off-road mode control method. Specifically, Figure 1 shown, including:

[0029] Step S1: Different SOC values ​​may be predefined as off-road balance points in different off-road scenarios.

[0030] Step S2: When the vehicle enters the off-road mode for the first time, if the battery SOC is lower than a preset off-road balance point (SOC1, representing the SOC threshold for starting the engine when entering the off-road mode for the first time), the front motor controller GCU controls the front motor to start the engine, and the vehicle enters the series rear-wheel drive mode from the pure electric rear-wheel drive mode.

[0031] Step S3. After entering the series rear-wheel drive mode, if the current vehicle speed is greater than the preset parallel entry vehicle speed threshold (V1, representing the vehicle speed threshold for the pure electric four-wheel drive standby to enter the parallel four-wheel drive), switch to the parallel four-wheel drive mode; if the current vehicle speed is lower than the parallel entry vehicle speed threshold, disengage the first clutch A and enter the preset pure electric rear-wheel drive intermediate mode (pure electric rear-wheel drive standby. Specifically, the rear motor is controlled by the P4 rear motor controller MCU to perform the driving task, and the engine idles in the speed mode). Subsequently, engage the drive clutch C or D to enter the pure electric four-wheel drive intermediate mode (pure electric four-wheel drive standby. Specifically, it can be jointly driven by the GCU + MCU. Similarly, the engine preferably idles in the speed mode).

[0032] Step S4. After entering the pure electric four-wheel drive intermediate mode, if the vehicle speed is higher than the parallel entry vehicle speed threshold (V1), control the engine to adjust its speed to enter the parallel four-wheel drive mode, and the front motor is used for power generation;

[0033] Step S5. In the parallel four-wheel drive mode, if the vehicle speed is lower than the preset parallel exit vehicle speed threshold (V2, representing the vehicle speed threshold for the parallel four-wheel drive to exit and enter the pure electric four-wheel drive standby), the engine controller ECU controls the engine to reduce torque and disengage, and the vehicle enters the pure electric four-wheel drive standby. Thereafter, according to the comparison result between the real-time vehicle speed and the established driving speed threshold, the vehicle switches back and forth between the pure electric four-wheel drive standby and the parallel four-wheel drive.

[0034] In this regard, it should be further supplemented that if the vehicle has been in a low vehicle speed condition and cannot enter the parallel four-wheel drive mode for charging, and the vehicle's SOC drops to an extremely low level (which can be compared with the preset SOC lower limit threshold SOC2, and SOC2 represents the SOC threshold for exiting the pure electric four-wheel drive standby and entering the pure electric rear-wheel drive standby), and it does not meet the requirement for continuing pure electric four-wheel drive, the vehicle first enters the pure electric rear-wheel drive standby and then enters the series rear-wheel drive mode to forcibly generate electricity. Thereafter, when the power generation reaches the preset power value, it enters the parallel four-wheel drive mode or the pure electric four-wheel drive standby mode again.

[0035] For the initial entry into the off-road mode, the following operating conditions can also be supplemented: If entering the off-road mode for the first time and the vehicle's SOC is relatively high, greater than SOC1, it directly enters the pure-electric four-wheel drive mode from the pure-electric rear-wheel drive mode, and then remains in the pure-electric four-wheel drive mode until the SOC is lower than the preset first power threshold (which can be expressed as SOC3, representing the SOC threshold for starting the engine in the pure-electric four-wheel drive mode), at which point the vehicle exits the pure-electric four-wheel drive mode and starts the engine; after this operating condition, the vehicle enters the pure-electric four-wheel drive standby mode. As described above, thereafter, it switches back and forth between the pure-electric four-wheel drive standby and the parallel four-wheel drive. The condition is the aforementioned driving speed threshold. When this threshold represents the current high vehicle speed, it switches from the pure-electric four-wheel drive standby to the parallel four-wheel drive, and vice versa, when the current vehicle speed is low, the parallel four-wheel drive switches to the pure-electric four-wheel drive standby.

[0036] It should also be particularly noted that during the process of the pure-electric rear-wheel drive standby and the pure-electric four-wheel drive standby mentioned in the foregoing embodiments switching back and forth with the series-parallel combination, the present invention also includes the relevant implementation details of engine speed regulation and torque unloading. Expanding on this:

[0037] (1) In the series rear-wheel drive mode, disconnect the engine from the first clutch A, and the engine idles into the rear-wheel drive standby. The engine unloads the torque to about 0 Nm to prevent the engine from spinning at a disengaged speed.

[0038] (2) When entering the pure-electric four-wheel drive standby from the pure-electric rear-wheel drive standby (similarly, when entering the pure-electric rear-wheel drive from the series rear-wheel drive), the GCU needs to regulate the engine speed according to the current vehicle speed and the gear ratio.

[0039] (3) When entering the parallel four-wheel drive from the pure-electric four-wheel drive standby, the engine needs to be regulated according to the current gear ratio and vehicle speed.

[0040] (4) When entering the pure-electric four-wheel drive standby from the parallel four-wheel drive, the engine torque needs to be unloaded to around 0 Nm to prevent the engine from spinning and improve drivability.

[0041] (6) Similarly, it also includes the mode switching conditions such as from the rear-wheel drive standby to the series, and from the series to the parallel, etc., all of which may involve the above details. The present invention will not elaborate on this.

[0042] Finally, for the scenarios involved in the present invention, the following additional special operating conditions are provided for implementation reference:

[0043] Working condition 1: If the vehicle is in P gear after entering the off-road mode, if the vehicle SOC is lower than SOC1, the vehicle enters series power generation until the SOC is greater than the preset second SOC threshold (which can be expressed as SOC4, which represents the P gear power generation SOC threshold, that is, the hysteresis threshold set for power generation), and returns to the pure electric rear-wheel drive mode; if the P gear vehicle SOC is greater than SOC1, the vehicle enters the pure electric rear-wheel drive mode.

[0044] Working condition two: If the vehicle speed is high in the pure electric four-wheel drive mode and the engine has been started, the transmission controller TCU closes one of three of the four clutches, the second clutch B or the third clutch C or the fourth clutch D, and directly enters the parallel four-wheel drive mode. The front motor controller GCU switches from the driving working mode to the power generation working mode; accordingly, if the vehicle speed is too low in the parallel four-wheel drive mode, the TCU can directly disconnect the first clutch A combined with the engine to enter the pure electric four-wheel drive mode and disengage the engine.

[0045] Regarding the above-mentioned working condition 2, the engine controller ECU can also control the engine to enter the speed mode mentioned above to perform idle idling, that is, the engine needs to be able to maintain the speed at a lower torque when the clutch is not engaged, or when the pure electric four-wheel drive vehicle speed is high, the engine can adjust the speed at a lower torque according to the current parallel gear ratio to facilitate the parallel four-wheel drive mode.

[0046] In summary, the main design concept of the present invention is that for the hybrid vehicle architecture of P2.5+P4 with a four-speed gearbox, when entering the off-road mode for the first time, if the SOC is lower than the predefined off-road balance point, the front motor will pull up the engine and enter the series rear-wheel drive; if the vehicle speed meets the conditions for entering the parallel connection, it will switch to the parallel four-wheel drive; if the vehicle speed does not meet the entry conditions, it will enter the pure electric rear-wheel drive intermediate mode, and then enter the pure electric four-wheel drive intermediate mode; if the vehicle speed meets the conditions again, the engine will idle and the speed will be adjusted to enter the parallel four-wheel drive mode. After that, according to the comparison result between the real-time vehicle speed and the established driving speed threshold, the vehicle will switch back and forth between the pure electric four-wheel drive intermediate mode and the parallel four-wheel drive mode. Based on the above-mentioned four-wheel drive control scheme for a specific hybrid architecture and configuration of the present invention, it can meet the four-wheel drive escape under most working conditions and achieve long-term off-roading.

[0047] In the embodiments of the present invention, if there are any expressions referring to the orientation of expression, they are based on the relative concepts of the embodiments. In addition, "at least one" means one or more, and "a plurality of" means two or more. "And / or" describes the association relationship of associated objects and indicates that there can be three relationships. For example, A and / or B can represent the cases where A exists alone, A and B exist simultaneously, and B exists alone. Wherein A and B can be singular or plural. The character " / " generally represents an "or" relationship between the associated objects before and after. "At least one of the following" and its similar expressions refer to any combination of these items, including any combination of single items 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 and b and c, where a, b, and c can be single or multiple.

[0048] The structure, features, and effects of the present invention have been described in detail based on the embodiments shown in the drawings above. However, the above are only the preferred embodiments of the present invention. It should be noted that for the technical features involved in the above embodiments and their preferred modes, those skilled in the art can reasonably combine and match them into a variety of equivalent solutions without departing from and without changing the design concept and technical effects of the present invention. Therefore, the scope of the present invention is not limited by the drawings shown. Any changes made in accordance with the concept of the present invention or modified into equivalent embodiments with equivalent changes still fall within the spirit covered by the specification and the drawings, and should be within the protection scope of the present invention.

Claims

1. A control method for the off-road mode of a hybrid vehicle, wherein the architecture of the hybrid vehicle at least includes: A rear motor controller, a transmission controller, a front motor controller, and an engine controller, and the hybrid vehicle is equipped with a four-speed transmission with four clutches. The control method is characterized in that it includes: Pre-defining an off-road balance point based on the battery SOC; When the vehicle first enters the off-road mode, if the battery SOC is lower than the off-road balance point, control the front motor to tow the engine, and the vehicle enters the series rear-wheel drive mode from the pure electric rear-wheel drive mode; After entering the series rear-wheel drive mode, if the current vehicle speed is greater than the preset parallel entry vehicle speed threshold, switch to the parallel four-wheel drive mode; if the current vehicle speed is lower than the parallel entry vehicle speed threshold, the transmission controller controls the first clutch of the four-speed transmission to disengage, so that the vehicle enters a preset pure electric rear-wheel drive intermediate mode, and then closes the third clutch or the fourth clutch of the four-speed transmission, so that the vehicle enters a preset pure electric four-wheel drive intermediate mode; After entering the pure electric four-wheel drive intermediate mode, if the vehicle speed is higher than the parallel entry vehicle speed threshold, the engine controller controls the engine to adjust the speed and enters the parallel four-wheel drive mode, and the front motor controller controls the front motor to perform the power generation task; In the parallel four-wheel drive mode, if the vehicle speed is lower than the preset parallel exit vehicle speed threshold, the engine controller controls the engine to reduce the torque and disengage, so that the vehicle enters the pure electric four-wheel drive intermediate mode; thereafter, according to the comparison result of the real-time vehicle speed and the established driving speed threshold, the vehicle switches back and forth between the pure electric four-wheel drive intermediate mode and the parallel four-wheel drive mode.

2. The off-road mode control method for a hybrid vehicle according to claim 1, wherein After the engine controller controls the engine to reduce the torque and disengage, so that the vehicle enters the pure electric four-wheel drive intermediate mode, if the vehicle fails to switch back to the parallel four-wheel drive mode for charging due to the vehicle speed factor, and the battery SOC drops below the preset SOC lower limit threshold, the vehicle first enters the pure electric rear-wheel drive intermediate mode s, and then enters the series rear-wheel drive mode to force power generation.

3. The off-road mode control method for a hybrid vehicle according to claim 1, wherein, In the pure electric rear-wheel drive intermediate mode, only the rear motor controller controls the rear motor to perform the driving task, and the engine controller controls the engine to perform idling.

4. The off-road mode control method for a hybrid vehicle according to claim 1, wherein In the pure electric four-wheel drive intermediate mode, the front motor controller and the rear motor controller jointly drive the front motor and the rear motor to perform the driving task, and the engine controller controls the engine to perform idling.

5. The off-road mode control method for a hybrid vehicle according to claim 1, characterized in that The control method further includes: When the vehicle first enters the off-road mode, if the battery SOC is higher than the off-road balance point, the vehicle directly enters the pure electric four-wheel drive mode from the pure electric rear-wheel drive mode and remains in the pure electric four-wheel drive mode until the battery SOC is lower than the preset first power threshold, and the vehicle exits the pure electric four-wheel drive mode and starts the engine.

6. The off-road mode control method for a hybrid vehicle according to any one of claims 1 to 5, characterized in that, The control method further includes: After the vehicle enters the off-road mode, if it is detected that the gear is in the P gear and the battery SOC is lower than the off-road balance point, the vehicle enters the series power generation mode until the battery SOC is greater than the preset second power threshold, and returns to the pure electric rear-wheel drive mode; After the vehicle enters the off-road mode, if it is detected that the gear is in the P gear and the battery SOC is higher than the off-road balance point, the vehicle enters the pure electric rear-wheel drive mode.

7. The off-road mode control method for a hybrid vehicle according to any one of claims 1 to 5, characterized in that, The control method further includes: In the pure electric four-wheel drive mode, if the vehicle speed is higher than the established first vehicle speed threshold and the engine has been started, the transmission controller controls the second clutch or the third clutch or the fourth clutch in the four-speed transmission, and directly makes the vehicle enter the parallel four-wheel drive mode. The front motor controller changes from the driving mode to the power generation mode. After that, if in the parallel four-wheel drive mode, the vehicle speed is lower than the established second vehicle speed threshold, the transmission controller controls to directly disconnect the first clutch combined with the engine, and makes the vehicle enter the pure electric four-wheel drive mode.

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