Powertrain Accessory Load Control for Engine Stall Prevention
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Solution Overview
Problem
Known powertrain systems employing electric motor/generators experience frequent load shedding events due to engine speed sags during vehicle deceleration, leading to rapid engine speed increases and driveline torque surges, which can cause engine stalling and inefficient energy management.
Innovation Solution
A powertrain system with an electric machine mechanically coupled to an internal combustion engine, where the engine stall threshold rate is determined during low load conditions, and the electric machine controls the time-rate change in accessory load to prevent engine stalling by generating electric power and managing energy transfer between high-voltage and low-voltage systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If load shedding scheme is executed when engine speed drops below trigger point, then engine stalling is avoided, but rapid engine speed increase occurs causing driveline torque surge
Solution Approach 1:
The control system applies preliminary anti-action by detecting the engine speed drop trend and executing load shedding before the engine actually stalls. The system anticipates the stalling condition by monitoring engine speed against a trigger point threshold, and preemptively reduces accessory load to prevent the harmful effect of engine stall while controlling the rate of speed recovery to minimize torque surge.
Solution Approach 2:
The system implements dynamics by continuously adjusting the accessory load based on real-time engine speed conditions. Rather than using a fixed load shedding strategy, the control system dynamically modulates the accessory load reduction magnitude and timing according to the current engine speed and its rate of change, allowing optimal balance between preventing stall and minimizing torque surge.
2Device complexity
If auxiliary DC/DC power module operates at constant electric power output with fixed voltage setpoint, then low-voltage electric power generation is simplified, but engine speed sags during vehicle deceleration triggering frequent load shedding
Solution Approach 1:
The system employs feedback control by continuously monitoring engine speed and using this information to adjust auxiliary DC/DC power module operation. The control system receives feedback on actual engine speed conditions and modifies the electric power generation strategy accordingly, increasing power generation during deceleration to support engine speed and reduce the frequency of load shedding events.
3Loss of energy
If electric machine generates electric power during low load conditions, then energy management efficiency improves, but engine stall risk increases due to accessory load
Solution Approach 1:
The system applies parameter changes by dynamically adjusting the accessory load parameters based on engine operating conditions. During low load conditions, the control system modifies the accessory load parameter to optimize energy management while maintaining engine stability. This involves changing the operational parameters of accessories connected to the alternator to match the available engine power reserve, ensuring energy efficiency without crossing into stall territory.
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
The system effectively prevents engine stalling by controlling the accessory load, maintaining stable engine speed and reducing driveline torque surges, thereby enhancing energy efficiency and operational reliability.
Implementation Method 1
the electric machine operating in an electric power generating mode
Implementation Method 2
a serpentine belt to transfer torque between the engine and the electric motor/generator
Data Source
AI summary
A powertrain system includes an electric machine mechanically coupled to an internal combustion engine mechanically coupled to a transmission. A method for operating the powertrain system includes determining an engine stall threshold rate during engine operation in a low load condition. A time-rate change in an accessory load is controlled by the electric machine operating in an electric power generating mode in response to the engine stall threshold rate during the engine operation in the low load condition.