Torque Sensor Magnetic Flux Leakage Reduction
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Solution Overview
Problem
Existing torque sensor apparatuses suffer from significant magnetic flux leakage due to the design of magnetic flux collecting portions, which reduces the effective magnetic flux sensed by magnetic sensors, particularly in electric power steering systems.
Innovation Solution
The torque sensor apparatus incorporates a multipolar magnet, magnetic yokes, and magnetic flux collecting bodies with a unique configuration where the magnetic sensors are placed between the magnetic flux collecting portions, and the connecting section is designed with a smaller width than the mounting section to minimize leakage, forming a magnetic circuit that reduces flux loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the magnetic flux collecting portion is designed with a wide connecting section to join the main body portion and mounting section, then the structural integrity and ease of manufacture are improved, but the magnetic flux leakage into the surrounding space is increased
Solution Approach 1:
The connecting section is designed with a narrower width specifically at the region where magnetic flux leakage occurs, while maintaining adequate width for structural integrity. This localized modification reduces magnetic flux leakage into the surrounding space without compromising the overall structural strength or manufacturability of the magnetic flux collecting portion.
2Measurement precision
If the magnetic sensors are placed between two separate magnetic flux collecting portions, then the magnetic flux concentration at the sensing location is improved, but the magnetic flux leakage into the space between the portions is increased
Solution Approach 1:
The space between the two magnetic flux collecting portions, which was previously a source of magnetic flux leakage, is utilized as the mounting location for the magnetic sensor. The magnetic flux that would have leaked into this space is now directed through the sensor, converting the harmful leakage into a beneficial sensing mechanism that improves measurement precision.
3Strength
If the magnetic flux collecting portion is formed integrally into the magnetic flux collecting ring, then the structural strength and stability are improved, but the formation of the ring into a circular form becomes difficult
Solution Approach 1:
The magnetic flux collecting portion is divided into a main body portion and a mounting section that can be formed separately. The main body portion maintains the circular form for ease of ring formation, while the mounting section is added subsequently to provide sensor mounting capabilities. This segmentation allows the ring to be formed easily while still achieving the required structural strength and sensor integration.
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 enhances the sensitivity of the magnetic sensors by minimizing magnetic flux leakage, allowing for more accurate torque sensing and improved performance in electric power steering systems.
Implementation Method 1
The main body portion is placed adjacent to a corresponding one of the first and second magnetic yokes. The magnetic flux collecting portion radially outwardly projects from the main body portion and is magnetically coupled with a corresponding one of the first and second magnetic yokes through the main body portion to conduct a magnetic flux between the corresponding one of the first and second magnetic yokes and the magnetic flux collecting portion.
Implementation Method 2
The magnetic sensor is held between the magnetic flux collecting portions of the first and second magnetic flux collecting bodies and includes a magnetic sensing device, which senses a strength of a magnetic field generated between the magnetic flux collecting portions of the first and second magnetic flux collecting bodies.
Data Source
AI summary
A torsion bar has first and second end portions that are fixed to input and output shafts, respectively, to coaxially connect between the input and output shafts. A multipolar magnet is fixed to the input shaft. First and second magnetic yokes are fixed to the output shaft. Magnetic sensors are held between magnetic flux collecting portions of first and second magnetic flux collecting rings, which are magnetically coupled to the first and second magnetic yokes, respectively. In each of the magnetic flux collecting portion, a connecting section and a mounting section are configured such that a width of the connecting section is smaller than a width of the mounting section.