Hybrid Engine Start Control During Transmission Downshift
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Solution Overview
Problem
Hybrid vehicles experience driveline torque disturbances during engine starting, especially when transmission gear downshifting occurs simultaneously, which can affect vehicle smoothness and drivability.
Innovation Solution
A method is implemented where the engine starting device is selected based on the boosting phase of the driveline disconnect clutch and the torque converter impeller speed for a target transmission gear, switching between the flywheel starter and the driveline disconnect clutch to minimize torque disturbances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the engine is started via the driveline disconnect clutch, then the engine power can be delivered quickly to the hybrid vehicle's wheels, but a driveline torque disturbance may be felt by occupants during transmission downshift
Solution Approach 1:
The system dynamically selects between two engine starting methods based on real-time transmission state. When the transmission is in a stable gear (not downshifting), the driveline disconnect clutch method is used for quick power delivery. When downshifting is detected, the system switches to the flywheel starter method to avoid torque disturbances, thus adapting the starting method to current operating conditions
Solution Approach 2:
The control system monitors transmission parameters (gear position, downshift state) and changes the engine starting parameter (selected starting method) based on these conditions. The system transitions between discrete starting modes (clutch-based vs. flywheel-based) depending on whether the transmission is in a stable state or undergoing downshift
2Object-affected harmful factors
If the engine is started via the flywheel starter, then driveline torque disturbances are reduced, but it takes longer before engine power may be delivered to the hybrid vehicle's wheels
Solution Approach 1:
The system dynamically adjusts the engine starting approach based on transmission state. During stable gear operation, it uses the faster driveline disconnect clutch method. During downshift events, it switches to the smoother flywheel starter method, creating a dynamic response that optimizes both comfort and performance based on real-time conditions
Solution Approach 2:
The control system continuously monitors transmission state (gear position, downshift occurrence) and uses this feedback to determine the appropriate engine starting method. The system receives feedback about transmission stability and adjusts the starting strategy accordingly, selecting the flywheel starter when downshift feedback is detected and the driveline disconnect clutch when stable operation is confirmed
Data Source
AI summary
Systems and methods for managing starting of an internal combustion engine during shifting of a transmission of a hybrid vehicle are presented. In one example, torque converter impeller speed or a torque multiplication ratio may be indicative of an unintended transmission downshift during engine starting so that an engine starting device may be switched to improve vehicle operation.