Hybrid EV Torque Control for EV-to-HEV Kick-Down Shifts
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Solution Overview
Problem
Hybrid electric vehicles face challenges in quickly switching to HEV mode and performing kick-down shifts due to insufficient torque control and durability issues with starter-generator motors, leading to torque mismatches and delayed gear-shifting sensations.
Innovation Solution
A method for determining available torque in target gears of motors connected to the engine, allowing for precise control of operating points to ensure torque conditions are met during mode switching and kick-down shifts, using a control unit to manage torque distribution between the first and second motors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the engine torque is increased quickly to satisfy the required torque during mode switching, then the torque demand can be met, but a torque mismatch occurs between the modeling torques and actual torque
Solution Approach 1:
The control method performs preliminary determination of available torque in target gears before the actual shift occurs. By calculating and preparing the torque distribution between the first motor and second motor in advance, the system can execute the kick-down shift without torque mismatch, resolving the contradiction between quick torque response and torque control accuracy.
2Reliability
If a limit is set to the rate of increase of torque, then torque mismatch is reduced, but the shift standby time increases and gear-shifting sensation is delayed
Solution Approach 1:
The system determines the operating points of both motors before the actual shift ends, performing preliminary torque distribution calculations. This allows the torque to be ready for immediate transmission when the shift occurs, eliminating the need to limit the rate of torque increase while avoiding delay in gear-shifting sensation.
3Power
If the starter-generator motor is used to provide additional torque, then the torque demand can be met, but the reactivity and accuracy are insufficient and belt durability problems occur
Solution Approach 1:
The patent segments the torque provision function into two separate motors: the first motor directly connected to the engine for reliable torque control, and the second motor connected to the first motor for additional torque support. This segmentation eliminates the need for the starter-generator motor while achieving both torque demand satisfaction and reliable torque control.
4Speed
If the engine torque is increased quickly during kick-down shift, then the acceleration response is improved, but gearshift difference arises due to transmission input terminal torque and hydraulic transmission mismatch
Solution Approach 1:
The control method determines available torque in target gears and establishes motor operating points before the actual shift occurs. This preliminary action ensures that the torque distribution is optimized in advance, allowing quick acceleration response while preventing gearshift difference and maintaining gear-shifting robustness.
Data Source
AI summary
Disclosed are a hybrid electric vehicle and a driving control method therefor, which are capable of switching to a driving mode and performing a kick-down shift more quickly. In particular, the method for controlling the hybrid electric vehicle includes: determining a first motor directly connected to an engine and an available torque in a target gear of each second motors connected to the first motor when a driving mode is changed from an electric vehicle (EV) mode to a hybrid electric vehicle (HEV) mode and a kick-down shift is required simultaneously; and determining operating points of the first motor and the second motor before an actual shift ends, based on the determined available torque and the type of kick-down shift.