Shaft Position Detection Device with Segmented Coils for Inclination Error Compensation
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Solution Overview
Problem
Conventional position detection devices for shafts that move forward and backward in the axial direction, such as those used in vehicle steering systems, face accuracy issues due to shaft inclination caused by vibrations, leading to errors in position detection.
Innovation Solution
A position detection device comprising an excitation coil generating an alternating magnetic field, a target fixed to the shaft with interlinked magnetic flux, and detection coils with specific configurations to induce voltages varying with the target's position, ensuring accurate detection even under inclination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional magnetoresistive elements are used to detect shaft position, then the detection structure is simple, but detection accuracy deteriorates when the shaft is inclined due to vibrations
Solution Approach 1:
The detection coil is divided into multiple independent coil units arranged along the axial direction. Each coil unit detects the position of a corresponding target portion, and the overall shaft position is determined by synthesizing signals from multiple coil units. This segmentation allows the system to maintain accurate position detection even when the shaft is inclined, as the multi-point detection compensates for angular deviations.
Solution Approach 2:
The patent transitions from a single-point detection approach to a multi-dimensional detection array. By arranging coil units and target portions in both axial and radial dimensions, the system creates a two-dimensional detection matrix that can accurately determine shaft position regardless of inclination angle, effectively adding a spatial dimension to the detection capability.
2Measurement precision
If the distance between magnetoresistive elements and shaft is reduced to improve sensitivity, then detection sensitivity improves, but the system becomes more sensitive to inclination errors
Solution Approach 1:
The detection system is segmented into multiple coil units distributed along the axial direction, with each unit having its own target portion. This segmentation allows the system to maintain optimal detection sensitivity at each local position while the overall multi-unit configuration provides robustness against inclination through spatial distribution of detection points.
Solution Approach 2:
The patent optimizes the axial spacing between coil units and target portions to create a detection pattern that is insensitive to inclination. By carefully selecting the distance parameters and arrangement geometry, the system achieves a balance where each individual detection point maintains high sensitivity while the collective pattern remains stable under inclined conditions.
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 high-accuracy detection of the shaft's position by minimizing the impact of shaft inclination on magnetic flux density, maintaining consistent induced voltages and enhancing detection precision across the axial movement range.
Implementation Method 1
an excitation coil that generates an alternating magnetic field
Implementation Method 2
a detection coil in which the magnetic flux of the alternating magnetic field is interlinked
Data Source
AI summary
A position detection device, configured to detect a position of a shaft that moves forward and backward in an axial direction, is provided with an excitation coil that generates an alternating magnetic field; a target fixed to the shaft and interlinked with a magnetic flux of the alternating magnetic field; and a detection coil in which the magnetic flux of the alternating magnetic field is interlinked. The detection coil has a first portion and a second portion in which an induced voltage is generated when the magnetic flux of the alternating magnetic field is interlinked, and a connection portion connecting the first portion and the second portion. The first portion and the second portion respectively extend along a coil longitudinal direction parallel to the axial direction, and at least a portion of each is aligned perpendicular to the coil longitudinal direction. The target has at least one first target portion facing the first portion and at least two second target portions facing the second portion, with the at least two second target portions being spaced apart in the axial direction. An induced voltage generated in the first portion varies with a position of the first target portion with respect to the first portion, and an induced voltage generated in the second portion varies with a position of the second target portion with respect to the second portion. The first target portion is located between the at least two second target portions in the axial direction, and when the shaft is in a central position between one axial moving end and an other axial moving end, the first target portion faces a central part in the coil longitudinal direction of the first portion.