Magnetic Position Sensor With Segmented Stator Air Gaps
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Solution Overview
Problem
Existing magnetic position sensors face challenges with high sensitivity to mechanical tolerances, significant signal shifts due to temperature variations, and the need for a large form factor to achieve sufficient signal variation, making them unsuitable for small, precise applications.
Innovation Solution
A magnetic linear or rotary position sensor design featuring a stator assembly with a first permanent magnet integral to a first ferromagnetic part, defining two air gaps with a movable ferromagnetic element and a third air gap for a magnetosensitive element, which reduces sensitivity to geometric tolerances and temperature variations, allowing for compact and precise measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the magnetosensitive probe is integrated in a cavity in the permanent magnet (prior art structure), then the sensor can detect position continuously, but the sensor exhibits high sensitivity to mechanical tolerances and significant signal shift with temperature
Solution Approach 1:
The sensor is divided into functionally independent parts: the permanent magnet assembly (with first ferromagnetic part and permanent magnet) and the magnetosensitive element assembly (in the third air gap), allowing independent optimization and compensation of each part's characteristics
Solution Approach 2:
The second ferromagnetic part acts as an intermediary element that mediates the magnetic field between the permanent magnet and the magnetosensitive element, enabling field shaping that reduces sensitivity to tolerances and temperature while maintaining measurement precision
2Measurement precision
If the sensor uses a structure with sufficient signal variation (prior art), then position can be detected continuously, but the form factor becomes large
Solution Approach 1:
The magnetic field is optimized locally in the third air gap where the magnetosensitive element is positioned, creating concentrated field variations that provide sufficient signal for precise measurement within a compact sensor footprint
Solution Approach 2:
The magnetic circuit utilizes three-dimensional flux paths through multiple air gaps (first, second, and third) and ferromagnetic parts, enabling compact arrangement of components while maintaining adequate magnetic field variation for measurement
3Device complexity
If the ferromagnetic parts are coupled by the permanent magnet (prior art), then the structure is simplified, but severe geometrical constraints are imposed preventing use in small footprint applications
Solution Approach 1:
The ferromagnetic parts are segmented into separate components (first ferromagnetic part coupled to permanent magnet, second ferromagnetic part defining third air gap) that can be independently sized and positioned, enabling compact overall form factor while maintaining structural functionality
Solution Approach 2:
The magnetic circuit components are nested within each other with the magnetosensitive element positioned in the third air gap between the two ferromagnetic parts, achieving compact integration of all necessary elements in a small footprint configuration
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 significantly reduces sensitivity to geometric tolerances and temperature variations, enabling precise and compact position sensing with minimal added components, suitable for small displacements and stable temperature performance.
Implementation Method 1
the magnetosensitive element is subjected to a magnetic field whose amplitude depends on the position of the mobile ferromagnetic element
Implementation Method 2
the magnetosensitive element comprises a Hall probe sensitive to the amplitude of at least one of the components of the magnetic field
Data Source
Figure 1~2
Figure 3
Figure 4a~4b
AI summary
This invention relates to a contactless magnetic sensor for detecting a linear or angular position, comprising a moveable ferromagnetic element (1) the position of which is detected, and a stator assembly (2) itself comprising two ferromagnetic parts (3, 4), defining with the moveable ferromagnetic element (1) two respective air gaps (7, 8), a permanent magnet (5) and a magnetosensitive element (6) subjected to a magnetic field that depends on the position of the moveable ferromagnetic element (1) and designed to deliver a measurement signal that depends on the magnetic field to which it is subjected. According to the invention, the two ferromagnetic parts (3, 4) define there between a third air gap (9), the permanent magnet (5) being rigidly connected only to the first ferromagnetic part (3) and the magnetosensitive element (6) being placed in the third air gap (9).