Current Sensor Magnetic Shield Segmentation for Residual Magnetization
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Solution Overview
Problem
Current sensors in hybrid electric vehicles and electric vehicles face measurement errors and reduced accuracy due to external magnetic fields and residual magnetization in magnetic shields, which also limit their thinness and design flexibility.
Innovation Solution
A current sensor design featuring a magnetic detection unit positioned between first and second magnetic shields, with the shields' configuration allowing for a magnetic field canceling position that reduces measurement errors and increases thinness, utilizing a specific correlation between the length of the shields and the conductor's placement to minimize residual magnetization effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magnetic shield is provided to control external magnetic fields, then detection accuracy under external magnetic fields is improved, but residual magnetization in the shield causes measurement errors when the conductor is not energized
Solution Approach 1:
The magnetic shield is divided into multiple sections (first shield section, second shield sections, third shield section, fourth shield sections) with different lengths and configurations. This segmentation allows each section to serve specific functions: shielding external fields while minimizing residual magnetization effects at the detection position.
Solution Approach 2:
Different sections of the magnetic shield have different lengths and positions tailored to their specific roles. The first shield section and third shield section face each other to shield external fields, while the second and fourth shield sections extend toward the opposite shield to control residual magnetization distribution, creating locally optimized magnetic field control.
2Measurement precision
If two U-shaped magnetic shields are used to shield external fields, then detection accuracy is improved, but the sensor thickness increases and design flexibility is reduced
Solution Approach 1:
The traditional U-shaped magnetic shields are segmented into multiple sections with different lengths. The first and third shield sections face each other to provide essential shielding, while the second and fourth shield sections are optimized in length to minimize overall thickness while maintaining shielding effectiveness.
Solution Approach 2:
The magnetic shield sections extend in different directions (first direction along the conductor, second direction orthogonal to first direction, third direction orthogonal to both). This multi-dimensional arrangement allows efficient space utilization, achieving effective shielding with reduced overall sensor thickness compared to conventional U-shaped shields.
3Measurement precision
If the magnetic detection element is positioned to cancel residual magnetization fields, then measurement accuracy when not energized is improved, but the design becomes more complex and manufacturing more difficult
Solution Approach 1:
The magnetic detection element is pre-positioned at a specifically designed magnetic field canceling position during manufacturing. This position is determined in advance based on the lengths and positions of the magnetic shield sections, ensuring that residual magnetization fields are canceled before the sensor enters service, simplifying both design and manufacturing.
Solution Approach 2:
The lengths of the magnetic shield sections (particularly the relationship between the first/third shield sections and second/fourth shield sections) are carefully controlled parameters that determine the magnetic field canceling position. By optimizing these dimensional parameters, the detection element position is automatically optimized for canceling residual magnetization, reducing design 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 design effectively reduces measurement errors when the conductor is not energized, enhances measurement accuracy, and achieves greater thinness by optimizing the placement of the magnetic detection unit and shields, while also absorbing external magnetic fields.
Implementation Method 1
providing a magnetic shield surrounding the periphery of the conductor and the magnetic detection element such as an MR element or Hall element has been proposed
Implementation Method 2
the magnetic field generated from the conductor due to the flowing of the current is detected by the magnetic detection element
Implementation Method 3
because a magnetic shield, which is made of a magnetic material, has a hysteresis property, even if the conductor is in a non-energized state, some magnetization remains in the magnetic shield
Data Source
AI summary
A current sensor includes a magnetic detection unit capable of detecting the magnetism, a first magnetic shield and a second magnetic shield. The first magnetic shield includes a first shield section and two second shield sections respectively connected in the vicinity of the two ends thereof. The second magnetic shield includes a third shield section and two fourth shield sections respectively connected in the vicinity of the two ends thereof. Between the first shield section and the third shield section is a conductor placement region, and the magnetic detection unit is positioned between the first shield section and the conductor placement region and is provided at a magnetic field canceling position where the magnetic field in the second direction is substantially zero at non-energized times after a prescribed current has flowed in the conductor, in relationship to the length of the two fourth shield sections along the third direction.