Magnetic Wire Motion Sensing with Alternating Pole Layout
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Solution Overview
Problem
Existing motion detection devices using magnetic wires with a large Barkhausen effect face issues such as phase differences in pulse generation positions, increased magnet costs, and large device sizes due to specific magnet requirements, which limit their applicability to hollow shafts and increase assembly complexity.
Innovation Solution
A motion detection device design featuring a magnetic wire with a coil and symmetrical magnetic flux conducting pieces, paired with a magnetic field source of individual magnets, where the magnetic poles alternate and intersect perpendicularly to the wire, ensuring steep magnetic flux changes and reduced magnet usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If specific magnet requirements are used to ensure steep magnetic flux changes, then measurement precision is improved, but device complexity and magnet costs increase
Solution Approach 1:
The magnetic field source is segmented into multiple individual magnets (first magnetic pole and second magnetic pole) with alternating polarities, allowing independent positioning and optimization of each magnet to achieve steep magnetic flux changes while simplifying the overall arrangement
Solution Approach 2:
The magnetic wire is positioned in a specific local region between the alternating magnetic poles where the magnetic flux density changes most steeply, optimizing the measurement precision at the critical detection point without requiring complex overall magnet arrangement
2Reliability
If larger magnets are used to cover the magnetic wire length, then reliability of pulse generation is improved, but device size increases
Solution Approach 1:
Instead of using one large magnet, the magnetic field source is divided into multiple smaller magnets (first magnetic pole and second magnetic pole) with alternating polarities, each covering a portion of the magnetic wire length, achieving reliable pulse generation while reducing overall device volume
Solution Approach 2:
The magnetic poles are arranged in an alternating polarity pattern along the magnetic wire length, creating a multi-dimensional magnetic flux distribution that ensures consistent pulse generation without requiring increased magnet size in any single dimension
3Productivity
If magnetic poles are arranged closer together, then productivity of pulse generation is improved, but phase difference in pulse generation position increases
Solution Approach 1:
The magnetic wire is divided into multiple segments, each experiencing magnetic flux changes from alternating poles, allowing high-frequency pulse generation while maintaining position accuracy through the symmetrical arrangement of magnetic poles around the magnetic wire center
4Ease of manufacture
If general-purpose magnets are used instead of specialized magnets, then manufacturing cost is reduced, but magnetic flux density change may become less steep
Solution Approach 1:
The magnetic field source is segmented into multiple individual magnets with alternating polarities, allowing the use of standard general-purpose magnets while achieving steep magnetic flux changes through the cumulative effect of multiple poles positioned at optimized intervals
Solution Approach 2:
The arrangement interval and positioning of multiple magnetic poles are optimized to create steep magnetic flux density changes, allowing general-purpose magnets to achieve performance previously requiring specialized magnets
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 design minimizes phase differences in pulse generation, reduces magnet costs, and allows for compact device sizes, suitable for various applications including hollow shafts, by utilizing general-purpose magnets and simplified assembly.
Implementation Method 1
Magnetic wires having a large Barkhausen effect (large Barkhausen jump) are known in the name of Wiegand wire or pulse wire... When the hard layer and the soft layer are magnetized in the same direction axially of the wire and the strength of an external magnetic field applied in a direction opposite to that magnetization direction is increased to a certain magnetic field strength, the magnetization direction of the soft layer is reversed. The reversal of the magnetization direction starts at a certain position of the magnetic wire to propagate to the entire wire, whereby the magnetization direction of the soft layer is totally reversed. At this time, the large Barkhausen effect is exhibited to induce a pulse signal in the coil wound around the magnetic wire.
Implementation Method 2
A power generation sensor is produced by winding a coil around the magnetic wire... When the external magnetic field strength is further increased to another certain magnetic field strength, the magnetization direction of the hard layer is reversed... A voltage output from the coil is characteristically constant irrespective of the change rate of an input magnetic field (external magnetic field), and is free from chattering because of the hysteresis with respect to the input magnetic field.
Data Source
Figure 1A~1B
Figure 1C
Figure 2A~2B
AI summary
A motion detection device (5) includes a first supporting body (51), a second supporting body (52) that moves relative thereto, a power generation sensor (100) disposed on the first supporting body, and a magnetic field source (400) supported by the second supporting body. The power generation sensor includes a magnetic wire (110), a coil (120), and magnetic flux conducting pieces (130, 131). The magnetic flux conducting pieces include axially-orthogonal portions and axially-parallel portions and have wire placement portions to which the axially-orthogonal portions and both end portions of the magnetic wire are fixed. The power generation sensor is configured such that a region located on a side of the axially-parallel portions opposite from the magnetic wire serves as a detection region (140). The magnetic field source has a plurality of magnetic poles. The magnetic poles having different polarities sequentially enter the detection region along a track (30) parallel to an axial direction of the magnetic wire and oppose the power generation sensor. The direction of the magnetic flux of each magnetic pole is a direction perpendicular to the moving direction thereof and intersecting with the magnetic wire.