Hybrid Powertrain Torque Control for Gear Shift Reduction
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Solution Overview
Problem
Conventional powertrain systems in hybrid electric vehicles experience excessive gear shifting when cornering or turning on winding roads due to calibration designed for straight road conditions, leading to driver dissatisfaction and fuel economy penalties.
Innovation Solution
The powertrain system uses an electric motor, such as an electric rear axle drive or crankshaft-integrated starter/generator, to provide additional torque during cornering, allowing the vehicle to maintain higher gears and reduce shift frequency by supplementing the existing torque, thereby preventing unnecessary gear changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the transmission downshifts to maintain vehicle speed during cornering, then vehicle speed control is improved, but gear shift frequency increases and fuel economy deteriorates
Solution Approach 1:
The system dynamically adjusts the available torque distribution between the internal combustion engine and electric motor based on driving conditions. During cornering, the controller increases electric motor torque contribution to prevent unnecessary downshifts, optimizing both speed control and fuel economy by adapting torque allocation to the specific driving scenario
Solution Approach 2:
The controller modifies the torque demand parameters by increasing the electric motor's torque contribution during cornering events. This parameter change allows the transmission to maintain higher gears longer, reducing shift frequency while preserving vehicle speed control capability through the combined torque output
2Productivity
If the transmission stays in higher gear during cornering, then fuel economy is improved, but available torque for acceleration decreases
Solution Approach 1:
The system merges the torque output of the internal combustion engine with the electric motor's torque contribution. During cornering in higher gears, the electric motor supplements the engine torque, ensuring that the combined available torque meets driver demands while allowing the transmission to remain in fuel-efficient higher gears
Solution Approach 2:
The electric motor acts as an intermediary torque source between the engine and wheels. It bridges the torque gap that would otherwise require downshifting, providing additional torque exactly when and where needed during cornering to maintain both fuel economy and acceleration capability
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces gear shift frequency, enhances driver control over vehicle acceleration, and improves fuel efficiency by minimizing the need for lower gear engagement during turns.
Implementation Method 1
an electric machine able to operate as an electric motor for transmitting power to at least some of the vehicle wheels
Data Source
AI summary
In a powertrain for a motor vehicle that includes a power source, a transmission driveably connected to the power source and wheels of the vehicle, an electric machine able to operate as an electric motor for transmitting power to at least some of the vehicle wheels, a method for controlling the powertrain includes operating the power source and the transmission in a desired gear to produce a first wheel torque in response to a demanded wheel torque, increasing the demanded wheel torque while turning the vehicle along a curved path, and using the electric motor to provide a second wheel torque, such that a combined magnitude of the first wheel torque produced in the desired gear and the second wheel torque is equal to or greater than the increased demanded wheel torque.