Composite Magnetic Encoder Ring for Crack-Resistant Wheel Sensing
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Solution Overview
Problem
Existing magnetic encoders used for detecting the rotational number of wheels face challenges due to low magnetic flux density per pole, susceptibility to temperature extremes, and potential for crack formation when exposed to high and low temperatures.
Innovation Solution
A magnetic encoder with a magnet portion formed by integrating a large amount of magnetic powder with a binder containing a thermoplastic resin and an impact resistance-improving agent, such as vulcanized rubber particles or modified polyamide resin, to enhance magnetic properties, fatigue resistance, and heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of poles of a magnetic encoder is increased to detect rotational number more accurately, then measurement precision is improved, but magnetic flux density per pole becomes too small
Solution Approach 1:
The patent uses a composite magnetic material consisting of magnetic powder dispersed in an elastic material matrix. This composite structure allows concentration of magnetic flux while maintaining the ability to form multiple poles, resolving the contradiction between increasing pole number and maintaining magnetic flux density per pole.
Solution Approach 2:
The patent changes the magnetic properties of the material by adjusting the magnetic powder content, particle size, and distribution within the elastic material. This allows optimization of magnetic flux density while accommodating increased pole numbers for better rotational detection accuracy.
2Quantity of substance
If a rare earth magnetic powder is used to improve magnetic property, then magnetic flux density is increased, but oxidation resistance decreases and magnetic property deteriorates in high temperature environments
Solution Approach 1:
The patent introduces an elastic material matrix as an intermediary between the magnetic powder particles and the external environment. This matrix protects the magnetic powder from oxidation while allowing the magnetic properties to be effectively utilized, solving the contradiction between high magnetic flux density and oxidation resistance.
Solution Approach 2:
The patent selects magnetic powder with appropriate particle size and controls its distribution within the elastic material to optimize both magnetic flux density and resistance to thermal degradation, balancing performance and reliability in high temperature environments.
3Quantity of substance
If a plastic magnet consisting of ferritic magnetic powder and plastic is used to improve magnetic property, then magnetic flux density is increased, but elongation and bending properties decrease making the magnet portion brittle
Solution Approach 1:
The patent employs a composite material system where magnetic powder is dispersed in an elastic material rather than using a rigid plastic matrix. This composite approach maintains high magnetic flux density while the elastic matrix provides flexibility, preventing brittleness and improving elongation and bending properties.
Solution Approach 2:
The patent changes the binder material from rigid plastic to elastic material, fundamentally altering the mechanical properties of the magnet portion while maintaining adequate magnetic flux density through proper magnetic powder selection and distribution.
4Measurement precision
If the gap between sensor and magnetic encoder is reduced to improve rotational number detection accuracy, then measurement precision is improved, but reliability decreases due to susceptibility to temperature extremes and physical damage
Solution Approach 1:
The patent optimizes the magnetic flux density through material composition and pole design, allowing for adequate detection accuracy with a larger gap. This resolves the contradiction by achieving sufficient measurement precision while maintaining reliability through increased physical separation and protection.
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 proposed magnetic encoder achieves high magnetic property retention, improved crack resistance, and enhanced reliability even under severe temperature conditions, ensuring accurate rotational number detection.
Implementation Method 1
a magnet portion formed of an elastic magnetic material obtained by mixing a magnetic powder with an elastic material such as rubber or a resin
Implementation Method 2
the magnetic powder is in a mechanically oriented state, which is achieved by kneading the powder with a roll
Data Source
AI summary
The magnetic encoder is constituted by integrally bonding a magnet portion obtainable by forming a magnetic material containing a magnetic powder and a binder for the magnetic powder in a circular ring shape to a slinger. The binder contains at least a thermoplastic resin and an impact resistance-improving agent.