Torque Sensor Hall IC Mounting for EPS Accuracy
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Solution Overview
Problem
Existing torque sensors in electric power steering systems face reduced detection accuracy due to increased distance between magnetic collecting portions, which decreases magnetic flux density and permeability, making it difficult to achieve high detection accuracy.
Innovation Solution
A torque sensor design incorporating a cylindrical multipolar magnet, magnetic yokes, and magnetic collecting elements with a Hall IC mounted on a circuit board with cutouts, allowing for increased magnetic flux density and reduced distance between magnetic collecting portions, enhancing detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the Hall IC is mounted on the printed circuit board with the device portion parallel to the board, then the sensor unit thickness is reduced, but the distance between magnetic collecting portions increases, reducing magnetic flux density and detection accuracy
Solution Approach 1:
The Hall IC is rotated 90 degrees relative to the conventional mounting orientation. Instead of having the device portion parallel to the circuit board, the Hall IC is mounted with its sensitive surface facing the magnetic collecting portions, effectively changing the spatial dimension of the magnetic flux path to maintain short distance while accommodating the parallel mounting configuration.
Solution Approach 2:
A non-magnetic spacer or magnetic shield is introduced between the Hall IC and the magnetic collecting portions to optimize the magnetic flux distribution. This intermediary element guides the magnetic flux directly to the Hall IC's sensitive surface, compensating for the increased distance caused by the parallel mounting arrangement.
2Ease of manufacture
If the distance between magnetic collecting portions is increased, then the Hall IC can be mounted parallel to the circuit board, but the magnetic flux density decreases due to the inverse square relationship with distance
Solution Approach 1:
The magnetic flux density is enhanced by changing the geometric parameters of the magnetic collecting portions, such as increasing their cross-sectional area or adjusting their positioning relative to the Hall IC. This compensates for the reduced magnetic field strength caused by the increased distance in the parallel mounting configuration.
Solution Approach 2:
Magnetic shielding materials with high permeability are used in the magnetic collecting portions to concentrate and guide the magnetic flux. This composite approach combines the structural benefits of parallel mounting with enhanced magnetic flux density through optimized magnetic material selection and configuration.
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 high magnetic flux density and improved detection accuracy, enabling precise torque measurement while allowing for a downsized sensor unit, effectively addressing the limitations of previous technologies.
Implementation Method 1
a Hall IC that includes a Hall element arranged between the magnetic collecting portions, the Hall IC mounted parallel to the circuit board so as to extend over the cutout, the magnetic flux detecting element detecting a magnetic flux between the magnetic collecting portions
Implementation Method 2
a cylindrical multipolar magnet that rotates integrally with one of a first shaft and a second shaft coaxially arranged
Implementation Method 3
a pair of magnetic collecting elements each including at least one magnetic collecting portion, the magnetic collecting elements provided with at least a set of the magnetic collection portions that is formed of a pair of the magnetic collecting portions facing each other, and the magnetic collecting elements each magnetically coupled to corresponding one of the pair of magnetic yokes
Data Source
AI summary
A torque sensor includes a pair of magnetic yokes arranged in a magnetic field from a multipolar magnet that rotates integrally with, for example, a first shaft, and the magnetic yokes rotate integrally with, for example, a second shaft. The torque sensor includes magnetic collecting elements magnetically coupled to the respective magnetic yokes and a magnetic flux detecting element. The magnetic collecting elements have a pair of magnetic collecting portions (magnetic collecting protrusions) facing each other. The magnetic flux detecting element includes a circuit board with a cutout formed therein and a Hall IC having a Hall element arranged between the magnetic collecting portions, and the Hall IC is mounted parallel to the circuit board so as to extend over the cutout. At least a part of one of the magnetic collecting portions is arranged in the cutout.