Bus Bar Current Detection With Anchored Sensor Alignment
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Solution Overview
Problem
Current detecting devices face issues with measurement precision due to deviations in the positional relationship between bus bars, magnetic sensors, and shields caused by resin flow during molding, exposure of shield surfaces leading to corrosion, and thermal expansion differences resulting in stress and weld line cracks.
Innovation Solution
The device integrates bus bars and shields with a chassis, using anchor portions to maintain positional accuracy, covers shield ends with resin to prevent corrosion, and modifies shield design to reduce weld line stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the bus bar is fastened to the chassis with an overhang portion to prevent lift, then measurement precision is improved, but resin may flow onto the fastening surface during molding causing electrical connection loss
Solution Approach 1:
The bus bar is divided into two distinct portions: the fastening surface portion that protrudes from the chassis for electrical connection, and the overhang portion that is embedded in the chassis to prevent lift. This segmentation allows each portion to fulfill its specific function independently, resolving the contradiction between measurement precision and electrical connection reliability.
2Manufacturing precision
If positioning pins are used to fix the shield during insert-molding, then positioning accuracy is improved, but positioning pin marks expose the shield to corrosion
Solution Approach 1:
A resin layer is introduced as an intermediary substance that fills the positioning pin marks and covers the exposed shield surfaces. This resin intermediary protects the shield from direct contact with corrosive environments while maintaining the precise positioning achieved during molding, thus resolving the contradiction between positioning accuracy and corrosion resistance.
3Measurement precision
If the shield is made large to improve shielding effect, then measurement precision is improved, but thermal expansion difference causes stress and weld line cracks
Solution Approach 1:
Instead of uniformly increasing the entire shield size, the invention strategically positions the shield and optimizes its local dimensions to achieve effective shielding while minimizing the area subject to thermal expansion stress. The shield is designed with specific dimensional characteristics at critical locations to balance shielding effectiveness with structural integrity.
4Productivity
If the bus bar is molded integrally with the chassis to improve productivity, then manufacturing efficiency is improved, but the bus bar may deviate from design position due to resin flow
Solution Approach 1:
The bus bar is pre-positioned and fixed to the chassis before the resin molding process begins. This preliminary action ensures that the bus bar maintains its design position throughout the molding process, preventing deviation caused by resin flow while still achieving integral molding for high productivity.
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
Enhances measurement precision by stabilizing electrical connections and reducing corrosion and crack risks, ensuring accurate and reliable current detection.
Implementation Method 1
a magnetic sensor placed so as to face the bus bar, the magnetic sensor being capable of detecting a magnetic field generated when the current under measurement flows through the bus bar
Implementation Method 2
during the molding of the chassis, the bus bar may deviate from a design position due to the effect of a flowing resin
Implementation Method 3
a bent bus bar may be deformed due to a spring back effect
Implementation Method 4
there has been the fear that if the side face of the shield is exposed to the interior of the hole, corrosion occurs from the side face
Implementation Method 5
when heat is applied, the shield is likely to more greatly expand. Therefore, due to the large expansion of the shield, a portion (molded resin portion), made of a molding resin material, of the chassis, the portion being in contact with the shield, is tensioned
Data Source
AI summary
A current detecting device has: a bus bar through which a current under measurement flows; a fastening member for fastening an external member to the bus bar; a chassis formed integrally with the bus bar and a shield, the chassis holding the bus bar and fastening member in a mutual contact state; and a magnetic sensor placed so as to face the bus bar, the magnetic sensor being capable of detecting a magnetic field generated when the current under measurement flows through the bus bar. The bus bar has a fastening terminal portion on the same side as an end of the bus bar, the fastening terminal portion being in contact with the external member. A connection surface is provided so as to be exposed from the chassis, the connection surface being a surface through which the fastening terminal portion is brought into contact with the external member.