Magnetic Encoder Main Track Positioning for Pitch Accuracy
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Solution Overview
Problem
Magnetic encoders face challenges in maintaining high magnetization accuracy due to deformation caused by press-fitting, which affects the pitch accuracy of magnetic tracks, making it difficult to produce encoders that meet required detection accuracy for absolute angles.
Innovation Solution
The magnetic encoder design features a main track with a larger number of magnetic poles, located away from the press-fitting portion, and a sub track with fewer poles, where the main track is magnetized last to minimize accuracy degradation, allowing for high-accuracy absolute angle detection despite potential core member deformation during press-fitting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the main track is located close to the press-fitting portion for compact design, then the device complexity is reduced, but the manufacturing precision of the main track deteriorates due to deformation during press-fitting
Solution Approach 1:
The patent applies local quality by differentiating the positions of main track and sub track relative to the press-fitting portion. The main track is deliberately positioned away from the press-fitting portion where deformation is minimal, while the sub track is positioned closer where deformation occurs. This spatial differentiation of functional elements based on local deformation characteristics resolves the contradiction between compact design and manufacturing precision.
Solution Approach 2:
The patent applies preliminary action by performing magnetization of the main track before the press-fitting operation. The main track is magnetized with high-precision pole patterns prior to any deformation occurring during press-fitting of the rotary shaft. This ensures that the critical main track maintains its pitch accuracy despite subsequent mechanical deformation of the core member.
2Measurement precision
If the number of magnetic poles is increased to improve angle detection resolution, then the measurement precision of angle detection is improved, but the magnetization accuracy requirement becomes more stringent and difficult to achieve
Solution Approach 1:
The patent applies segmentation by dividing the angle detection function across two separate tracks: the main track with N pole pairs for coarse angle detection and the sub track with (N-1) pole pairs for fine resolution enhancement. This segmentation allows the system to achieve high angle detection resolution without requiring extremely high magnetization accuracy on a single track, as the combined information from both tracks provides the enhanced resolution.
Solution Approach 2:
The patent applies parameter changes by varying the number of pole pairs between the main track and sub track. The main track has N pole pairs while the sub track has (N-1) pole pairs, creating a deliberate parameter difference that enables high-resolution angle detection through comparative analysis of the two tracks' magnetic field patterns, thereby reducing the stringent accuracy requirements on individual tracks.
3Productivity
If the sub track is magnetized first and then the main track, then the productivity of magnetization process is improved, but the measurement precision of the main track deteriorates due to magnetic flux interference
Solution Approach 1:
The patent applies the taking out principle by extracting the magnetization process of the main track from the sequence and performing it first, before the sub track magnetization. This separation of the magnetization steps ensures that the critical main track is magnetized without any magnetic flux interference from subsequent sub track magnetization, thereby maintaining high pitch accuracy while still achieving efficient production through optimized process sequencing.
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 enables the magnetic encoder to detect absolute angles with improved accuracy and reduced pitch errors, even under conditions of core member deformation, simplifying production and maintaining high angular precision.
Implementation Method 1
two or more rows of magnetic tracks arranged adjacent to each other on a magnetic member provided on the track formation surface of the core member, each track having N poles and S poles alternately magnetized thereon
Data Source
AI summary
The magnetic encoder includes: a core member of annular shape having a press-fitting portion which bends and extends from an edge of a track formation surface, and to which a rotary shaft is press-fitted and fixed; and two or more rows of magnetic tracks arranged adjacent to each other on a magnetic member provided on the track formation surface, each track having N poles and S poles alternately magnetized thereon. The two or more rows of magnetic tracks include a main track that has a largest number of magnetic poles and is used for calculating an angle of rotation, and a sub track used for calculating a phase difference from the main track. The main track is located on a side more distant from the press-fitting portion than the sub track.