Engine Idle-Stop Restart Torque Control via Transmission Shifting
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Solution Overview
Problem
Existing engine idle-stop systems often result in reduced driveline torque during restart, leading to sluggish vehicle performance and NVH issues due to torque mitigation approaches that fail to maintain desirable launch characteristics.
Innovation Solution
A method that reduces engine torque conveyed to wheels during restart by upshifting the transmission and applying alternator loads, while decreasing torque reduction when operator demand increases, allowing for immediate restoration of driveline torque through downshifting and adjusting engine and transmission torque reductions based on demand.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If torque mitigation approaches are applied during engine restart (such as engaging transmission gears, applying alternator load, shifting transmission gears), then the restart torque spike is reduced and NVH issues are minimized, but driveline torque is reduced leading to sluggish vehicle performance and degraded launch characteristics
Solution Approach 1:
The system dynamically adjusts the torque mitigation strategy based on real-time detection of operator torque demand. When high torque demand is detected (accelerator pedal tip-in), the system immediately decreases torque reduction by downshifting transmission gears and reducing alternator load, thereby restoring driveline torque for fast launch. When low torque demand is detected, the system maintains torque reduction to minimize NVH issues. This dynamic adaptation resolves the contradiction between comfort and performance.
Solution Approach 2:
The system continuously monitors operator torque demand and uses this feedback to adjust torque mitigation in real-time. The controller detects accelerator pedal position and torque demand signals, and automatically modifies transmission gear selection and alternator load application accordingly. This closed-loop feedback mechanism enables the system to optimize the trade-off between NVH performance and launch characteristics based on actual driver intent.
2Reliability
If transmission gears are engaged or shifted to reduce torque during restart, then restart quality is improved by reducing torque spikes, but the time required to restore driveline torque is increased
Solution Approach 1:
The system prepares the transmission for potential torque restoration by pre-positioning gears and pre-loading clutch elements during the idle-stop period. When high torque demand is detected, the transmission can immediately downshift and engage torque transmission paths without delay. This preliminary preparation eliminates the time penalty that would otherwise be required to engage transmission components during active acceleration.
Solution Approach 2:
The transmission system dynamically switches between torque-mitigation mode and torque-transmission mode based on operator demand. When high torque demand is detected, the system immediately decreases torque reduction by downshifting gears and adjusting clutch engagement, thereby rapidly restoring driveline torque. This dynamic response minimizes the time loss while maintaining restart quality under normal conditions.
3Object-affected harmful factors
If engine shaft output torque is reduced via alternator load or combustion event skipping during restart, then vehicle lurch is reduced, but driveline torque is insufficient to achieve desirable fast launch when operator demands high torque
Solution Approach 1:
The system dynamically adjusts engine shaft output torque based on real-time detection of operator torque demand. When high torque demand is detected (accelerator pedal tip-in), the system immediately decreases torque reduction by reducing alternator load and resuming combustion events, thereby restoring full driveline torque for fast launch. When low torque demand is detected, the system maintains torque reduction to minimize vehicle lurch and improve restart comfort.
Solution Approach 2:
The system continuously monitors operator torque demand signals and uses this feedback to adjust engine shaft output torque in real-time. The controller detects accelerator pedal position and immediately modifies combustion event scheduling and alternator load application accordingly. This closed-loop feedback enables the system to optimize the trade-off between reducing vehicle lurch and maintaining sufficient driveline torque based on actual driver intent.
Data Source
AI summary
Systems and methods are provided for restarting an engine that can be selectively deactivated during idle-stop conditions. In one embodiment, the engine is restarted with torque reduction over an interval of the restart, for example, by upshifting the transmission. In response to a vehicle launch request, the torque reduction is decreased, for example, by downshifting the transmission, to expedite return of driveline torque.