Torque Index Sensor Magnetic Shielding for EPS Reliability
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Solution Overview
Problem
Magnetic field interference between torque sensors and index sensors in electronic power steering systems leads to measurement errors and reduced operational reliability.
Innovation Solution
A ring-shaped shielding member made of ferromagnetic material is placed between the index sensor magnet and the stator to shield magnetic field interference, effectively reducing errors by ensuring the index sensor magnet rotates with the shield and maintaining accurate measurements regardless of its position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the torque sensor and index sensor are integrated and disposed adjacent to each other, then the device complexity is reduced and manufacturing cost is lowered, but magnetic field interference occurs between the two magnetic detecting devices causing measurement errors
Solution Approach 1:
A magnetic shielding plate is introduced as an intermediary component between the torque sensor and index sensor. The shielding plate, made of ferromagnetic material, intercepts and redirects magnetic field lines, preventing direct magnetic field interference between the two sensors while allowing both sensors to function in their integrated configuration.
Solution Approach 2:
The magnetic shielding plate is divided into multiple segments: a first shielding plate positioned between the torque sensor and index sensor, and a second shielding plate positioned between the index sensor and stator. This segmentation allows targeted shielding of specific interference paths while maintaining sensor functionality.
2Reliability
If the magnetic shielding plate is positioned close to the stator collector, then magnetic field interference from the index magnet is reduced, but the shielding effectiveness depends heavily on precise positioning
Solution Approach 1:
The shielding plate is made of ferromagnetic material with high magnetic permeability, giving it specialized local quality for attracting and redirecting magnetic field lines. This material property ensures the shielding plate effectively intercepts magnetic fields regardless of minor positioning variations, reducing sensitivity to precise placement.
3Reliability
If a ring-shaped shielding member is used to shield the index sensor magnet, then magnetic field interference is reduced, but the shielding member adds device complexity and manufacturing steps
Solution Approach 1:
The magnetic shielding plate is integrated with the stator collector structure, merging two components into one. The shielding plate serves dual functions: it provides magnetic field shielding and acts as part of the stator assembly, eliminating the need for separate shielding member installation and reducing overall device complexity.
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 significantly enhances the operational reliability of torque index sensors by minimizing magnetic field interference, ensuring accurate torque and rotational measurements, and maintaining sensor performance across various rotational positions.
Implementation Method 1
A ring-shaped shielding member made of ferromagnetic material is placed between the index sensor magnet and the stator to shield magnetic field interference
Data Source
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AI summary
A torque index sensor according to an embodiment of the present invention includes a rotor rotating with the first shaft which is one of an input shaft and an output shaft having a first magnet on an outer circumferential surface thereof, a stator disposed on an outer side of the first magnet and rotating with the second shaft which is the other of the input shaft and the output shaft, a shield disposed on a lower side of the stator and rotating with the second shaft and a second magnet combined with a lower side of the shield and rotating with the second shaft. The torque index sensor shields magnetic field interference and improves operational reliability.