Starter Motor Current Control via Mechanical Relay and Electronic Switch
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Solution Overview
Problem
Existing engine automatic stop-and-start systems face challenges in restarting internal combustion engines efficiently and cost-effectively, as they require high-capacity power transistors for cranking the engine, which are expensive, and mechanical relays lack the accuracy to control current supply to the starter motor.
Innovation Solution
A system that uses a combination of a mechanical relay and an electronic switching element, where the mechanical relay supplies high current for engine restart and the electronic switching element controls current with high accuracy using PWM, preventing sudden voltage drops and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a high-capacity power transistor is used to supply high current for engine cranking, then the engine restart capability is achieved, but the system cost increases significantly
Solution Approach 1:
The patent divides the switching function into two separate components: a mechanical relay for high-current supply and an electronic switching element for control. This segmentation allows each component to be optimized for its specific function, using a low-cost mechanical relay for the high-current path and a small, inexpensive electronic switch for precise control, thereby avoiding the need for an expensive high-capacity power transistor while maintaining both power delivery and control capabilities
Solution Approach 2:
The patent introduces a mechanical relay as an intermediary component between the power supply and the starter motor. This mechanical relay acts as a mediator that can handle high currents while being controlled by a low-power electronic switching element, thus bridging the gap between low-power control signals and high-power actuation without requiring expensive high-current electronic switches
2Ease of manufacture
If a mechanical relay is used to control current supply, then the system cost is reduced, but the current control accuracy deteriorates
Solution Approach 1:
The electronic switching element serves as an intermediary control device that precisely regulates the activation and deactivation timing of the mechanical relay. By using PWM control through the electronic switch, the system achieves accurate current control while the mechanical relay handles the high-current switching, combining the precision of electronic control with the cost-effectiveness of mechanical relays
Solution Approach 2:
The patent replaces the purely mechanical control mechanism with an electronically controlled switching element that uses PWM (pulse-width modulation) for precise duty cycle control. This substitution allows accurate control of the mechanical relay's activation timing, thereby achieving precise current control accuracy while maintaining the use of inexpensive mechanical relays for high-current handling
3Measurement precision
If an electronic switching element is used for precise current control, then the current control accuracy is improved, but the system cannot supply sufficient high current for engine cranking
Solution Approach 1:
The patent segments the current control function into two distinct roles: the electronic switching element handles precise timing control and PWM modulation for accuracy, while the mechanical relay handles the actual high-current supply. This functional segmentation allows each component to operate within its optimal capability range, with the electronic switch providing precise control signals and the mechanical relay delivering the necessary high current for engine cranking
4Productivity
If the starter motor is activated immediately upon engine restart request, then the engine restart speed is improved, but sudden voltage drops occur affecting other vehicle systems
Solution Approach 1:
The patent implements preliminary control actions through the electronic switching element that gradually activates the mechanical relay before full power is applied to the starter motor. By using PWM control to progressively build up current flow, the system prepares the electrical system for the high-current demand, preventing sudden voltage drops while still achieving rapid engine restart through coordinated control of the relay and motor activation
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 solution improves engine restartability while meeting low-cost requirements by accurately controlling current supply to the starter motor, preventing voltage drops, and reducing the need for expensive high-capacity transistors.
Implementation Method 1
the electronic switching element controls current with high accuracy using PWM
Implementation Method 2
a first mechanical relay electrically connected between the power supply and the motor and working to turn on and off a supply of a current based on the electrical power to the motor
Data Source
AI summary
In a system for cranking a crankshaft of an internal combustion engine, a starter is provided with a motor working to, when energized, rotatably drive an output shaft with a pinion and an actuator working to, when energized, shift the pinion toward the ring gear to be engaged with the ring gear. A power supply is electrically connected to the motor and operative to output electrical power. A first mechanical relay is electrically connected between the power supply and the motor, and works to turn on and off a supply of a current based on the electrical power to the motor for rotating the pinion. A switching element is electrically connected across the first mechanical relay, and works to turn on and off the supply of the current to the motor for rotating the pinion.