Motor Sensor Magnet Protection via Magnetic Shield
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Solution Overview
Problem
Conventional electric power steering motors lack reliability due to the lack of specific safety features protecting the permanent magnet and resolver from damage, leading to potential failures under various environmental conditions.
Innovation Solution
The motor design includes a stator and rotor with a bearing mechanism, a sensor with a yoke and annular-shaped sensor magnet covered by a nonmagnetic magnet cover, and a busbar unit with a relay to prevent electromagnetic locking, enhancing the motor's reliability and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional magnetic sensors and permanent magnets are arranged in the motor without specific safety features, then the motor structure remains simple, but the reliability is low due to potential damage from environmental conditions
Solution Approach 1:
The patent applies beforehand cushioning by providing a protective structure (housing with magnetic shield) that prevents damage to the sensor and permanent magnet before environmental conditions can cause harm. The magnetic shield is positioned to block external magnetic fields and physical impacts from reaching the sensitive components, thus cushioning them against potential damage in advance.
Solution Approach 2:
The patent uses an intermediary approach by introducing a magnetic shield as a mediator between the external environment and the sensitive components (sensor and permanent magnet). This magnetic shield intercepts harmful magnetic fields and physical impacts, transferring or blocking them before they can affect the reliability of the motor components.
2Reliability
If no specific safety features are provided for the resolver, then the motor structure remains simple, but the resolver is vulnerable to damage reducing reliability
Solution Approach 1:
The magnetic shield is positioned to protect the resolver before damage can occur. The shield structure is designed to intercept potential harmful factors (magnetic fields, physical impacts) in advance, cushioning the resolver against damage that would otherwise reduce reliability.
Solution Approach 2:
The magnetic shield serves as an intermediary protective element between the external environment and the resolver. It mediates the interaction by blocking or attenuating harmful influences before they reach the resolver, thus protecting it without requiring complex active protection systems.
3Reliability
If the sensor magnet is exposed without coverage, then the sensor structure remains simple, but the magnet is vulnerable to damage affecting motor reliability
Solution Approach 1:
The magnet cover is designed to protect the sensor magnet before damage can occur. It provides a physical barrier that cushions the magnet against impacts, contamination, and other environmental factors that would otherwise compromise motor reliability.
Solution Approach 2:
The magnet cover acts as an intermediary protective layer between the external environment and the sensor magnet. It mediates by blocking harmful factors while allowing the magnetic field to pass through, thus protecting the magnet without interfering with its function.
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 improved design enhances the motor's reliability by protecting the sensor magnet and preventing damage, ensuring consistent operation and safety under various conditions, while maintaining compact dimensions suitable for vehicle power steering applications.
Implementation Method 1
a Hall element arranged opposite from the yoke with respect to the sensor magnet and arranged opposite to the sensor magnet
Implementation Method 2
a field magnet which is arranged at the rotor core and which along with the armature generates a torque centered about the central axis
Data Source
AI summary
A motor includes a sensor which magnetically detects an angular position centered about a central axis of a rotor core with respect to an armature. The sensor preferably includes a yoke which has a substantially annular shape, is made of a magnetic material, is arranged substantially perpendicularly to the central axis and is affixed to a shaft, a sensor magnet affixed at the yoke, a magnet cover which covers a surface of the sensor magnet other than a portion in contact with the yoke, a first Hall element and a second Hall element both of which are arranged facing in an axial direction a surface of the sensor magnet opposite from a surface thereof at which the yoke is arranged. Since the sensor magnet is covered by the yoke and the magnet cover, even when the sensor magnet is damaged, the damaged sensor magnet is prevented from damaging other components of the motor. By virtue of such configuration, the reliability of the motor is improved.