Current Sensor Magnetic Shield Cutouts for Precision Downsizing
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Solution Overview
Problem
Current sensors for multi-phase conductors face challenges in maintaining measurement precision due to insufficient fixation of magnetic shields, which can lead to positional deviations and reduced accuracy, especially when downsizing is required.
Innovation Solution
A current sensor design featuring a magnetic shield with cutouts along its circumferential edges, insert-molded in the lid portion, allows for precise positioning and reduced distance between adjacent shields, enhancing measurement precision while enabling downsizing without compromising accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the size of the magnetic shield is reduced to downsize the current sensor, then the device size is reduced, but the magnetic sensor cannot be covered with sufficient breadth and measurement precision is lowered
Solution Approach 1:
The magnetic shield is extended in the thickness direction (vertical dimension) to form a plate-like structure with sufficient magnetic shielding capability, while keeping the planar dimensions (length and width) small. This dimensional transformation allows the shield to provide adequate coverage for the magnetic sensor without increasing the overall footprint of the current sensor, thus resolving the contradiction between downsizing and maintaining measurement precision.
2Reliability
If a pressing member is brought into contact between mutual adjacent magnetic shields during insert molding to press both magnetic shields, then the magnetic shields are fixed, but the distance between adjacent magnetic shields becomes relatively large
Solution Approach 1:
The pressing member that previously needed to be inserted between adjacent magnetic shields to achieve fixation is eliminated. Instead, the plate-like magnetic shield structure itself provides stable fixation through its geometry and integration with the lid portion, allowing adjacent shields to be positioned closer together without requiring intermediate pressing members, thus reducing the distance between shields while maintaining fixation reliability.
3Ease of manufacture
If the magnetic shield is positioned by being incorporated into the case of the current sensor when the case is assembled, then the magnetic shield is fixed, but the fixing is insufficient and positional deviation is generated under vibration
Solution Approach 1:
The magnetic shield is integrated with the lid portion through insert molding, merging two previously separate components (magnetic shield and lid) into a single integrated structure. This integration ensures that the magnetic shield is firmly fixed to the lid portion, preventing positional deviation under vibration while maintaining ease of manufacture through the one-step insert molding process, thus resolving the contradiction between assembly simplicity and fixation stability.
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 achieves downsizing without lowering measurement precision by ensuring precise positioning and reduced magnetic flux disturbance, preventing burrs and maintaining high accuracy.
Implementation Method 1
a magnetic shield that shields a magnetic sensor from an external magnetic field
Implementation Method 2
a magnetic sensor that detects an induced magnetic field generated by a current flowing in each bus bar
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A current sensor 1 that can be downsized without lowering measurement precision has bus bars 2, magnetic sensors 6 that measure induced magnetic fields generated from the bus bars 2 a circuit board 7 on which the magnetic sensors 6 are mounted, a case 3 that fixes the bus bars 2 and circuit board 7, a lid portion 4 that closes the case 3, and lid-portion magnetic shields 8 provided in the lid portion 4. The lid-portion magnetic shield 8 has cutouts 8a along its circumferential edges. Hole portions 4a are formed from which the outer edges of the cutouts 8a of the lid-portion magnetic shield 8 are exposed are formed in the lid portion 4. Due to this, when the lid portion 4 is formed, the distance between adjacent lid-portion magnetic shields 8 can be shortened when the lid-portion magnetic shield 8 is positioned by pressing portions in a mold.