Magnetic Encoder Shield Notch for Noise Reduction
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Solution Overview
Problem
Existing magnetic encoders face accuracy issues in detecting rotational angles due to external magnetic fields interfering with the magnetic flux generated by permanent magnets, leading to increased noise components in detection results.
Innovation Solution
A magnetic sensor with directional detection sensitivity is mounted on an encoder substrate, paired with a magnetic shield that includes a side portion covering the sides and a top-side portion covering the top of the sensor, featuring a notch or hole for connector insertion, which reduces external magnetic field interference by directing magnetic flux away from the sensor's detection direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a magnetic shield is used to shield the magnetic sensor from external magnetic fields, then the magnetic sensor is protected from interference, but the connector insertion portion may allow external magnetic fields to enter and increase noise in detection results
Solution Approach 1:
The patent extracts the connector insertion portion (notch or hole) from the magnetic shield structure and positions it strategically so that it does not overlap with the extended area of the magnetic sensor in the reading direction. This allows the magnetic shield to maintain its protective function while creating a specific geometric configuration that prevents external magnetic fields from entering through the connector portion and reaching the sensor.
Solution Approach 2:
The patent addresses the contradiction by transitioning from a two-dimensional shielding problem to a three-dimensional spatial arrangement. By positioning the connector insertion portion in a specific location relative to the magnetic sensor's extended area in the reading direction, the patent creates a spatial configuration where external magnetic fields cannot simultaneously pass through the connector portion and reach the sensor, thus resolving the contradiction between shielding and noise prevention.
2Reliability
If a magnetic shield completely covers the magnetic sensor, then external magnetic field interference is minimized, but thermal transmission from the shaft to the sensor increases
Solution Approach 1:
The magnetic shield is segmented into different portions: a side portion covering the sides of the magnetic sensor and a top-side portion covering the top. The connector insertion portion is provided in the side portion at a location that does not overlap the magnetic sensor's extended area. This segmentation allows the shield to provide magnetic protection while creating thermal management pathways.
Solution Approach 2:
The patent applies local quality by providing different structural characteristics in different regions of the magnetic shield. The side portion contains the connector insertion portion with specific positioning to prevent magnetic field entry, while the top-side portion provides comprehensive coverage. This localized structural differentiation allows the shield to simultaneously achieve magnetic shielding effectiveness and thermal management by preventing direct thermal conduction paths from the shaft to the sensor through strategic positioning of the connector portion.
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 configuration effectively reduces noise components in the detection results, enhancing the accuracy of rotational angle detection while maintaining a compact design and preventing thermal transmission from the shaft during motor operation.
Implementation Method 1
a magnetic shield to shield against a magnetic field
Implementation Method 2
a permanent magnet is located on a shaft about its axial center, and generates a magnetic flux to operate the magnetic sensor
Data Source
AI summary
An encoder includes a magnetic sensor having higher detection sensitivity to a magnetic field applied in a reading direction, while having lower detection sensitivity to a magnetic field applied in a direction forming a greater angle with respect to the reading direction, an encoder substrate having the magnetic sensor mounted thereon, a magnetic shield to shield against a magnetic field including a side portion covering sides of the magnetic sensor and a top-side portion covering a top of the magnetic sensor, a permanent magnet located to face the encoder substrate, a shaft having the permanent magnet attached to a tip end of the shaft, and a bracket to support the shaft in a rotatable manner, wherein on the side portion of the magnetic shield, a notch as a connector insertion portion is located not to overlap an extended area of the magnetic sensor in the reading direction.