Starter Motor In-Rush Current Control via Dynamic Resistance
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Solution Overview
Problem
In motor vehicles with automatic stop-start systems, high in-rush currents during engine restarts can cause undesirable voltage drops, degrading systems like anti-lock braking and electronically controlled steering, while setting lower currents for dynamic restarts may result in slower start-up performance.
Innovation Solution
Implementing a method with at least two levels of in-rush current restriction for the starter motor, applied based on the vehicle's operating speed, using resistors in series with the starter motor and controlled by an electronic controller to manage voltage drops and maintain system operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high in-rush current is applied to the starter motor for rapid engine starting, then start-up performance is improved, but voltage drop increases causing degradation of vehicle electrical systems
Solution Approach 1:
The patent applies a dynamic approach by switching between different resistance levels based on vehicle operating conditions. The in-rush current resistance is dynamically adjusted: lower resistance during stationary starts to enable rapid starting, and higher resistance during moving restarts to prevent voltage drop and maintain electrical system operation. This dynamic adaptation resolves the contradiction between start-up performance and system reliability.
Solution Approach 2:
The patent changes the electrical resistance parameter of the in-rush current limiter based on vehicle speed and operating mode. By varying the resistance value (lower for stationary, higher for moving), the system optimizes both starting performance and voltage stability for different conditions, resolving the trade-off between rapid starting and electrical system protection.
2Reliability
If high in-rush current resistance is used during dynamic restart to prevent voltage drop, then vehicle electrical system operation is maintained, but start-up performance becomes slower
Solution Approach 1:
The system dynamically adjusts resistance based on real-time vehicle conditions. During moving restarts, higher resistance is applied to maintain voltage for electrical systems like anti-lock braking and steering. During stationary starts, lower resistance is applied to maximize starting torque and speed. This dynamic switching resolves the contradiction between system reliability and start-up performance.
Solution Approach 2:
The resistance parameter is changed according to vehicle operating mode: higher resistance values are used during dynamic restarts to limit voltage drop, while lower resistance values are used during stationary starts to enable rapid cranking. This parameter adaptation resolves the trade-off between electrical system stability and starting performance.
3Device complexity
If a single level of in-rush current restriction is used, then device complexity is reduced, but the system cannot adapt to different vehicle operating conditions
Solution Approach 1:
The in-rush current control system is segmented into multiple resistance levels (first level and second level) that can be selectively applied. This segmentation allows the system to handle different operating conditions (stationary vs. moving restarts) with appropriate resistance values, improving adaptability while maintaining relatively simple control logic through a controller that selects between predefined resistance levels.
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 allows continued operation of vehicle electrical consumers during engine cranking, provides optimal starter current levels for different speeds, and ensures higher current during cold starts, balancing restart performance and system voltage stability.
Implementation Method 1
controlling the in-rush current to the starter motor by providing a resistance arranged in series with the starter motor
Data Source
AI summary
A system and method for limiting engine starting current of a starter motor of an engine is described. In one example, starter motor current is controlled according to vehicle speed. The method may allow vehicle system voltage to remain at a higher level during automatically initiated engine starts.