Wheel Speed Sensor with Segmented Magnetic Targets
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Solution Overview
Problem
Conventional wheel speed sensors have limitations in increasing the number of magnetic pole pairs, which hinders accurate measurement of rotational speed and direction, essential for advanced vehicle control functions like autonomous driving and automatic parking.
Innovation Solution
A wheel speed detecting device with a frame surrounding the inner ring of a wheel bearing, featuring multiple targets and sensors with varying magnetic field detection resolutions, including a first target made of rubber magnet and a second target with neodymium material, to provide enhanced rotational information for precise wheel control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of magnetic pole pairs is increased to improve measurement accuracy, then rotational speed and direction measurement accuracy is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The measurement function is segmented into two independent target structures: a first target with multiple magnetic pole pairs for rotational speed measurement, and a second target with fewer magnetic pole pairs for rotational direction measurement. This segmentation allows each target to be optimized for its specific function, achieving high measurement accuracy without requiring an excessive number of magnetic pole pairs in both targets.
Solution Approach 2:
Different regions of the target structure are assigned different qualities: the first target uses multiple magnetic pole pairs for high-speed rotation detection, while the second target uses fewer magnetic pole pairs for direction detection. This local differentiation optimizes the overall measurement system without uniformly increasing complexity across the entire device.
2Measurement precision
If the number of magnetic pole pairs is increased to improve measurement accuracy, then rotational speed and direction measurement accuracy is improved, but manufacturing precision requirements increase
Solution Approach 1:
The manufacturing process is segmented into two separate target fabrication processes. The first target requires high precision for multiple magnetic pole pairs, while the second target requires lower precision for fewer magnetic pole pairs. This segmentation reduces the overall manufacturing precision burden compared to creating a single target with an extremely high number of magnetic pole pairs for both measurement functions.
Solution Approach 2:
The second target uses fewer magnetic pole pairs than would be needed for high-precision rotational speed measurement, but this partial action is sufficient for rotational direction detection. This approach avoids the excessive manufacturing precision requirements that would result from using a high number of magnetic pole pairs for both measurement functions simultaneously.
3Device complexity
If a single target structure is used to measure both rotational speed and direction, then device complexity is reduced, but measurement accuracy is insufficient for advanced vehicle control functions
Solution Approach 1:
The single target structure is segmented into two separate targets: a first target optimized for rotational speed measurement and a second target optimized for rotational direction measurement. This segmentation resolves the contradiction by achieving high measurement accuracy for both parameters while maintaining reasonable device complexity through functional separation rather than using an overly complex single target structure.
Solution Approach 2:
The wheel speed detecting device achieves multi-functionality by using two targets with different numbers of magnetic pole pairs to simultaneously measure both rotational speed and rotational direction. This multi-functional approach provides the comprehensive measurement accuracy needed for advanced vehicle control functions without requiring an excessively complex single target structure.
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 device enables accurate control of the wheel by providing multiple rotational information with different resolutions, improving the installation and detection of speed information, and ensuring firm fixation of targets and sensors, thus enhancing the accuracy of wheel speed measurements.
Implementation Method 1
sensor configured to detect magnetic fields induced from each of the first target and the second target
Implementation Method 2
the first target may be formed of a rubber magnet in which rubber and magnetic material are mixed, and the magnetic material may include at least one among ferrite, neodymium (NdFeB) and samarium cobalt (Sm—Co)
Data Source
AI summary
One aspect of the present disclosure provides a wheel speed detecting device installable in a wheel bearing comprising an outer ring and an inner ring rotatable relative to the outer ring by rolling elements. The wheel speed detecting device may comprise a frame fixed on the inner ring so as to surround an outer circumference of the inner ring, a first target disposed along an outer circumference of the frame, a second target disposed at a central portion of the frame, and sensor configured to detect signals generated from each of the first target and the second target to measure rotational information of the inner ring.