Shaft Axial Position Detection via Hardness-Induced Magnetic Strips
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Solution Overview
Problem
Existing cylinder position sensing devices are limited by the need for strong magnetic materials, are costly, and impractical for certain shafts due to machining requirements, making them unreliable and expensive for determining shaft position effectively.
Innovation Solution
A shaft with a hardened outer metallic layer featuring strips of different hardness levels, which induce distinct magnetic fields sensed by a sensor assembly, allowing a data processor to determine the axial position based on the angular difference between these fields, eliminating the need for strong magnets and complex machining.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If Hall effect sensors with strong magnets are used to sense cylinder position, then measurement precision is improved, but device complexity and cost increase due to expensive magnetic materials and limited stroke requirements
Solution Approach 1:
The patent extracts the magnetic sensing function from complex Hall effect sensor assemblies and transfers it to a simpler shaft-mounted magnet. The sensor assembly is eliminated entirely, with only a single magnet embedded in the shaft performing the positioning function, thereby reducing device complexity while maintaining measurement precision
Solution Approach 2:
The patent uses a simple magnet embedded in the shaft to create a magnetic field signature that serves as a positional reference. This magnetic signature is detected by external sensors, creating a simplified copying mechanism that replaces complex direct sensing assemblies while maintaining accurate position detection capability
2Measurement precision
If magnetostrictive sensors with multiple magnets are used, then measurement precision is improved, but ease of manufacture deteriorates due to machining and labor requirements for mounting magnets
Solution Approach 1:
The patent removes the requirement for multiple magnets and complex mounting procedures. A single magnet is embedded directly in the shaft during manufacturing, eliminating the need for separate machining operations and labor-intensive mounting processes required by magnetostrictive sensor systems
Solution Approach 2:
The shaft itself serves the dual function of mechanical operation and positional sensing reference. The embedded magnet in the shaft creates a magnetic field that is naturally detected by external sensors, making the shaft self-sufficient for positioning without requiring additional sensor mounting hardware or complex preparation
3Measurement precision
If traditional cylinder position sensors are used, then measurement precision is improved, but device complexity increases due to sealing and moving parts requirements
Solution Approach 1:
The patent replaces mechanical sensing systems with magnetic field-based sensing. A magnet embedded in the shaft creates a magnetic field that is detected by external magnetic sensors, eliminating the need for mechanical connections, seals, and moving parts while maintaining accurate position detection capability
Solution Approach 2:
The patent introduces a magnetic field as an intermediary between the shaft position and the detection system. The embedded magnet generates a magnetic field that serves as a non-contact signal carrier, allowing external sensors to detect shaft position without physical contact or sealing requirements
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 method provides a reliable and economical means to detect shaft position without the need for expensive magnets, reducing costs and complexity, while maintaining accuracy through the use of external sensors that do not require sealing or moving parts.
Implementation Method 1
A first strip extends in a generally longitudinal direction in the outer metallic layer. The first strip has a second hardness level different from the first hardness level. A second strip in the outer metallic layer has the second hardness level. A sensor assembly senses an angular difference between a first magnetic field associated with the first strip and a second magnetic field associated with the second strip.
Data Source
AI summary
A shaft comprises a hardened outer metallic layer having a first hardness level with a generally uniform radial depth. A first strip extends in a generally longitudinal direction in the outer metallic layer. The first strip has a second hardness level different from the first hardness level. A second strip in the outer metallic layer has the second hardness level. The first strip and the second strip are spaced apart from each other over at least a longitudinal region. A sensor senses an angular difference between a first magnetic field associated with the first strip and a second magnetic field associated with the second strip. A data processor references an established relationship between a position of the shaft and the angular difference between magnetic fields associated with the first strip and the second strip to detect a Position of the shaft with respect to a reference point.