Rack Shaft Position Sensing Coil Layout for Inclination Errors
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Solution Overview
Problem
Conventional position detection devices for rack shafts in steering systems face accuracy issues due to shaft inclination caused by vehicle vibrations, leading to errors in position detection.
Innovation Solution
A position detection device utilizing an excitation coil generating an alternating magnetic field, with a target fixed to the shaft and detection coils that induce voltages based on the magnetic flux interlinked, where the detection coils have aligned portions and a connecting path perpendicular to the axial direction, allowing for accurate position detection regardless of shaft inclination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional magnetoresistive elements are used to detect rack shaft position, then the position detection device can be implemented, but detection accuracy deteriorates when the shaft is inclined due to vibrations
Solution Approach 1:
The detection coil is divided into multiple independent coils (first detection coil, second detection coil, third detection coil, fourth detection coil) arranged at different positions. Each coil independently detects magnetic flux changes, and their outputs are combined to calculate the rack shaft position. This segmentation allows the system to compensate for inclination effects by comparing signals from multiple coils.
Solution Approach 2:
The patent combines the outputs of multiple detection coils through a calculation unit that processes the collective signals. By merging the information from four different coil positions, the system achieves accurate position detection even when the rack shaft is inclined, as the combined signal compensates for individual coil deviations.
2Measurement precision
If the detection coil is positioned close to the rack shaft to improve sensitivity, then detection sensitivity improves, but the system becomes more sensitive to inclination errors
Solution Approach 1:
Instead of using a single detection coil close to the rack shaft, the patent segments the detection function across four coils positioned at different locations. This distribution reduces the impact of inclination on any single coil while maintaining overall detection sensitivity through the combined signal from all coils.
Solution Approach 2:
The patent transitions from a single-point detection approach to a multi-point spatial distribution of detection coils. By arranging coils in a two-dimensional pattern around the rack shaft, the system detects position information from multiple spatial dimensions, enabling compensation for inclination effects through geometric relationships between coil positions.
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 solution enables precise detection of the rack shaft's position with reduced errors due to shaft inclination, enhancing the accuracy and reliability of the position detection system.
Implementation Method 1
an excitation coil that generates an alternating magnetic field; a target which is fixed to the shaft and in which a magnetic flux of the alternating magnetic field is interlinked; and 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 which is fixed to the shaft and in which a magnetic flux of the alternating magnetic field is interlinked; and a detection coil in which the magnetic flux of the alternating magnetic field is interlinked, wherein the detection coil has a first portion and a second portion, where an induced voltage is generated by the magnetic flux of the alternating magnetic field being interlinked, and a connecting path connecting the first portion and the second portion. The first portion and the second portion respectively extend along the axial direction and the coil longitudinal direction parallel to the axial direction and at least a portion of each is aligned in an alignment direction perpendicular to the axial direction. The target includes a first target portion facing the first portion, and a second target portion facing the second portion. The induced voltage generated in the first portion changes according to a position of the first target portion relative to the first portion. The induced voltage generated in the second portion changes according to a position of the second target portion relative to the second portion.