Rotary Symmetry Lead Wire Layout for EPS Motor Drive
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Solution Overview
Problem
Conventional driving devices for electric power steering systems face challenges in accurately controlling assist torque and reducing detection errors in rotation angle sensors due to magnetic field interference from lead wire energization, leading to inefficiencies in torque output and increased noise and vibration.
Innovation Solution
A driving device with a rotary electric machine, a substrate, magnetic detection elements, switching elements, lead wire sets, power supply terminals, ground terminals, and a control circuit unit, where the lead wire sets are arranged in rotational symmetry to cancel magnetic fields and improve detection accuracy, and the motor windings are optimized with phase-shifted current supply to reduce torque ripple and heat generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If lead wire sets are arranged in conventional configurations, then device complexity is reduced, but magnetic field interference causes detection errors in rotation angle sensors
Solution Approach 1:
The patent applies asymmetry by arranging lead wire sets in specific asymmetric patterns around the rotary electric machine. Instead of uniform symmetric distribution, the lead wires are positioned at specific angular intervals (e.g., 120 degrees for three-phase systems) to create magnetic field cancellation effects that reduce interference with the rotation angle sensor while maintaining electrical functionality.
Solution Approach 2:
The patent converts the harmful magnetic field generated by lead wire energization into a beneficial effect by strategically positioning lead wires so that their magnetic fields cancel each other out. The magnetic fields that would normally interfere with the rotation angle sensor are instead arranged to oppose and neutralize each other, transforming the harmful interference into a net-zero or reduced magnetic environment.
2Stability of the object's composition
If motor windings are energized with phase-shifted currents, then torque ripple is reduced, but device complexity increases due to optimized current supply requirements
Solution Approach 1:
The patent implements periodic action through phase-shifted current supply to the motor windings. Currents are supplied in periodic cycles with specific phase differences (e.g., 120 degrees for three-phase motors), creating a rotating magnetic field that produces smooth, continuous torque. This periodic energization pattern eliminates torque ripple while maintaining simple control logic through standard inverter circuitry.
3Power
If multiple systems of motor windings are used, then power output is increased, but heat generation increases leading to temperature-dependent errors
Solution Approach 1:
The patent applies segmentation by dividing the motor windings into multiple independent systems (e.g., three-phase windings). Each phase winding is energized separately with phase-shifted currents, allowing the total power output to be distributed across multiple channels. This segmentation reduces the heat concentration in any single winding while maintaining high overall power output through the combined effect of all phases.
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 solution enhances the accuracy of rotation angle detection, reduces torque ripple and noise, and improves the efficiency of assist torque control by canceling magnetic fields and averaging current supply, resulting in improved motor performance and reduced temperature-dependent errors.
Implementation Method 1
the lead wire sets are arranged in rotational symmetry to cancel magnetic fields
Implementation Method 2
a rotary electric machine, a substrate, a magnetic detection element, switching elements
Data Source
AI summary
Switching elements are mounted on a substrate and switch energization of motor windings. A lead wire set connects phase coils of the motor windings to the substrate. The switching elements, the lead wire set, a power terminal which is a power supply terminal and a ground terminal, and a control circuit unit are provided for each system. The switching elements, the lead wire set and the power terminal are collectively arranged in a power region for each system, and the lead wire sets are arranged in rotational symmetry.