Magnetic Encoder Heat-Treated Ferromagnetic Shielding
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Solution Overview
Problem
Magnetic linear or rotary encoders face limitations in measurement accuracy due to environmental influences, despite the use of the ratiometric difference method, which is necessary for high-precision measurements.
Innovation Solution
The solution involves stabilizing the crystalline structure of ferromagnetic components through heat treatment to maintain a homogeneous magnetic resistance across temperature fluctuations, shielding external fields, and ensuring that only non-ferromagnetic materials are used in electronic components to minimize interference, allowing the ratiometric difference method to produce flawless and highly accurate measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the ratiometric difference method is used to achieve high-precision measurements, then measurement accuracy is improved, but measurement results still fluctuate due to environmental influences
Solution Approach 1:
The patent applies parameter changes by tempering ferromagnetic components to stabilize their magnetic properties across temperature variations. This heat treatment modifies the crystalline structure of the ferromagnetic materials, making their magnetic resistance temperature-independent, thereby eliminating environmental fluctuations that cause measurement instability while maintaining the high accuracy achieved through the ratiometric difference method
2Measurement precision
If ferromagnetic components are used in the encoder, then magnetic field guidance is improved, but temperature-dependent magnetic property changes cause measurement errors
Solution Approach 1:
The patent applies preliminary action by tempering ferromagnetic components during manufacturing before the encoder is put into service. This pre-applied heat treatment stabilizes the crystalline structure and magnetic properties of the ferromagnetic materials, ensuring that magnetic resistance remains constant across the operating temperature range of -40°C to +125°C, thereby eliminating temperature-dependent measurement errors while maintaining effective magnetic field guidance
3Reliability
If external magnetic field shielding is implemented, then measurement reliability is improved, but device complexity increases
Solution Approach 1:
The patent applies multi-functionality by designing the ferromagnetic components to serve dual purposes: they provide magnetic field guidance for precise measurement while simultaneously acting as shielding elements that redirect external magnetic fields away from the sensitive measurement area. This eliminates the need for separate shielding structures, maintaining measurement reliability while avoiding increased device complexity
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 approach results in significantly improved measurement accuracy by maintaining a consistent magnetic field relationship and eliminating hysteresis effects, leading to the highest precision achievable with the ratiometric difference method.
Implementation Method 1
all ferromagnetic parts of the encoder that come into contact with the measuring field should be tempered, i.e. subjected to a heat treatment, so that their crystal structure is stabilized
Implementation Method 2
the crystalline structure of the ferromagnetic circuit remains generally homogeneous in a defined range of changing environmental parameters
Implementation Method 3
the sensor has a ferromagnetic shield in addition to the tempered return body, which does not have to be tempered. Its task is to weaken external fields
Implementation Method 4
four magnetic field sensors in order to be able to calculate two differences from four measured values
Data Source
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AI summary
The invention relates to a magnetic linear or rotary encoder (1) for monitoring the motion of a body, comprising: an exciting unit (8), which reproduces said motion and has at least one pair of primary permanent magnets (16, 17), which are arranged opposite one another and are magnetically connected to one another by means of a ferromagnetic yoke body (9) and form a measurement field space therebetween; a fine-resolution sensor unit (29; 29'), which is used to determine a fine position value, is arranged in a stationary manner and has a plurality of magnetic field sensors (25, 26, 27, 28); and processing electronics, which evaluate the signals of the fine-resolution sensor unit and have a data memory. Said magnetic linear or rotary encoder is characterised in that a ferromagnetic deflecting body (18) is provided, which deflects at least some of the magnetic field lines of the magnetic field produced by the primary permanent magnets in a direction perpendicular to the magnetisation vector of the primary permanent magnets, that the fine-resolution sensor unit is designed and arranged in such a way that the individual magnetic field sensors of the fine-resolution sensor unit are penetrated by the magnetic field lines deflected by the deflecting body by means of a perpendicular component, that at least the yoke body is made of a thermally treated, ferromagnetic material, and that the fine-resolution sensor unit does not contain a ferromagnetic component.