Absolute Encoder Gear Base Magnetic Flux Shielding
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Solution Overview
Problem
Existing absolute encoders face reduced detection accuracy due to the influence of leakage magnetic flux from external permanent magnets on magnetic sensors.
Innovation Solution
An absolute encoder design featuring a gear base made of an annealed magnetic body, with a specific configuration of driving and driven gears and permanent magnets, and angle sensors to minimize the impact of leakage magnetic flux, utilizing a machining and annealing process for the gear base to enhance magnetic flux shielding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magnetic sensor is used to detect magnetic flux from a permanent magnet, then detection capability is achieved, but detection accuracy deteriorates due to leakage magnetic flux from external permanent magnets
Solution Approach 1:
A gear base made of annealed magnetic body is introduced as an intermediary element between external permanent magnets and the magnetic sensor. This gear base serves as a magnetic flux shield that redirects leakage magnetic flux away from the sensor, allowing the sensor to accurately detect only the intended magnetic flux while blocking harmful external interference
Solution Approach 2:
The magnetic properties of the gear base are changed through annealing treatment, which modifies the material's magnetic permeability and coercivity. This parameter change enables the gear base to effectively shield magnetic flux, transforming it from a ordinary structural component to an active magnetic flux management element that protects the sensor
2Reliability
If ferritic stainless steel is used for the gear base, then corrosion resistance is achieved, but magnetic shielding capability deteriorates due to work hardening from machining
Solution Approach 1:
The gear base undergoes annealing treatment that changes the material's microstructure and magnetic properties. This thermal parameter change relieves work hardening effects from machining, restores the material's magnetic permeability, and enables effective magnetic flux shielding while maintaining the inherent corrosion resistance of ferritic stainless steel
Solution Approach 2:
The solution creates a composite functional structure where ferritic stainless steel provides both mechanical strength and corrosion resistance, while the annealing process imparts magnetic shielding capabilities. The material effectively combines multiple functions: structural support, corrosion protection, and magnetic flux management
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 effectively reduces the influence of leakage magnetic flux on the magnetic sensors, improving detection accuracy and reliability of the absolute encoder.
Implementation Method 1
a gear base configured to surround at least a part of a periphery of the first angle sensor and the second angle sensor. The gear base is formed of an annealed magnetic body
Implementation Method 2
a machining process of performing machining on a plate-shaped member formed of ferritic stainless steel and an annealing process of annealing the machined plate-shaped member in a vacuum or hydrogen atmosphere at an annealing temperature of 800° C. to 900° C.
Data Source
AI summary
The influence of a leakage magnetic flux from a magnet on a magnetic sensor configured to detect a magnetic flux from the permanent magnet is reduced. An absolute encoder includes a first magnet provided at a leading end side of a first worm gear part, a first angle sensor configured to detect a rotation angle of the first worm gear part corresponding to a change in a magnetic flux generated from the first magnet, a second magnet provided at a leading end side of a second worm wheel part, a second angle sensor configured to detect a rotation angle of the second worm wheel part corresponding to a change in a magnetic flux generated from the second magnet, and a gear base part configured to surround at least a part of a periphery of the first angle sensor and the second angle sensor.