SR Motor Starter Positioning for Engine Starting Reliability
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Solution Overview
Problem
Conventional engine starter systems using electric motors face issues with torque ripples, where the motor's torque ripples are not adequately addressed, leading to potential engine starting failures due to interference with engine torque ripples, especially in SR motors which have larger ripples than magnet motors.
Innovation Solution
The engine starter system mechanically sets the positional relationship between the piston and rotor to maximize motor output at peak engine friction torque positions, allowing the motor to overcome maximum friction torque with minimal output, and switches coil phases to optimize torque delivery during engine start and stop cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the motor torque is increased to overcome the peak engine friction torque, then the engine can be started reliably, but the motor size increases
Solution Approach 1:
The system performs preliminary action by stopping the engine at a predetermined position (top dead center or slightly beyond) where the friction torque is minimized, before attempting to restart. This preliminary positioning ensures that when the restart command is given, the motor does not need to overcome maximum friction torque, thus allowing a smaller motor to reliably start the engine.
Solution Approach 2:
The system changes the operating parameter of engine position by controlling the piston to be at top dead center or slightly beyond during stoppage. This parameter change (positioning) transforms the friction torque characteristic, making it lower than at other positions, thereby reducing the motor size requirement while maintaining reliable starting.
2Ease of manufacture
If the SR motor is used to avoid rare earth materials, then the cost is reduced and structure is simplified, but the torque ripples increase
Solution Approach 1:
The system converts the harmful effect of torque ripples in SR motors into a beneficial outcome by controlling the engine stop position. By stopping at top dead center where friction torque is minimal, the system ensures that even with SR motor torque ripples, the net torque remains sufficient to reliably restart the engine, thus allowing use of cost-effective SR motors without permanent magnets.
Solution Approach 2:
The preliminary positioning of the engine at top dead center before restart compensates for the torque ripple characteristics of SR motors, allowing them to be used effectively despite their larger torque ripples compared to magnet motors.
3Reliability
If the motor operates with surplus output power to address engine friction ripples, then the engine can be started, but the motor size must be larger than minimum required
Solution Approach 1:
The system changes the friction torque parameter by controlling engine position to top dead center during stoppage. This parameter change reduces the peak friction torque that the motor must overcome, allowing the motor to operate at minimum required power without needing surplus output, thus optimizing motor size and power consumption.
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 enables reliable engine starting with a minimum-output motor, reduces starter size, and improves system reliability by synchronizing motor and engine torque ripples, preventing failures and optimizing engine start operations.
Implementation Method 1
an engine starter using an electric motor has heretofore been used
Implementation Method 2
SR motors whose structure is simple and solid has gained attention. Particularly, the use of SR motors is expanding
Data Source
AI summary
A rotor of a starter that employs an SR motor is directly connected to a crank shaft of an engine. The rotor and the crank shaft are set in such a way that when a piston is positioned at a top dead center or the like, salient poles and of the rotor face U-phase poles, so that an output torque of the starter comes to its maximum at a maximum pass-over torque position of the engine. When the engine is stopped, electricity is supplied through U-phase coils, thereby making the salient poles and the U-phase poles stop so as to face each other. In this manner, the piston is stopped at the maximum pass-over torque position. When the engine is started, electricity is supplied to W-phase coils which are adjacent to the U-phase coils, thereby making it possible to overcome a maximum friction torque with maximum outputs.