Hybrid Vehicle Shift Control via Electric Machine Speed Synchronization
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Solution Overview
Problem
Conventional automatic step ratio transmissions face challenges in providing high-quality, user-commanded shifts due to unsynchronized speeds across the transmission, leading to delayed and inaccurate gear shifts that affect vehicle driveability.
Innovation Solution
A hybrid vehicle system utilizing an electric machine connected by clutches to an engine and transmission, where the controller synchronizes the electric machine speed with the transmission output speed and gear ratio to facilitate quick and precise user-commanded shifts, ensuring smooth and timely gear changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the transmission controller anticipates the shift and controls the engine speed for synchronized speeds, then the shift quality is improved, but the response time to user commanded shift is delayed
Solution Approach 1:
The controller pre-calculates and prepares the target engine speed based on the user's shift command and current transmission state, enabling immediate execution of the shift without waiting for speed synchronization calculations, thus reducing response time while maintaining shift quality
Solution Approach 2:
The patent replaces traditional engine-based speed control with electric machine speed control. The electric machine can rapidly adjust its speed to match the target speed calculated from the shift command, providing faster response time while achieving the same synchronization goal, thereby resolving the contradiction between quick response and smooth shift quality
2Adaptability or versatility
If the user commands a sequential upshift or downshift, then the gear selection flexibility is improved, but the speed synchronization across the transmission becomes challenging
Solution Approach 1:
The controller acts as an intermediary that receives user shift commands and automatically calculates the appropriate target engine/electric machine speed based on current transmission state and desired gear ratio. This intermediary calculation layer simplifies the user interface while managing the complex speed synchronization requirements in the background
Solution Approach 2:
The system dynamically changes the control parameter from engine speed control to electric machine speed control during user-commanded shifts. The electric machine's speed is adjusted to match the target speed derived from the shift command and current output speed, providing a straightforward method to achieve synchronization across different gear ratios without complex mechanical adjustments
Data Source
AI summary
A hybrid vehicle has an engine, an electric machine connected to the engine by an upstream clutch, a transmission gearbox connected to the electric machine by a downstream clutch, and a controller. The controller is configured to, in response to a user commanded shift of the transmission, control the electric machine speed to a designated speed based on gearbox output speed and the transmission gear ratio after the shift, thereby synchronizing speeds across the gearbox for the shift. A method for controlling a hybrid vehicle provides, in response to a user commanded shift of an automatic transmission gearbox, controlling an electric machine speed to a target speed based on the transmission gear ratio after the shift where the target speed is synchronized with the transmission gearbox output speed.