Magnetic Pivoting Device Counter-Pivot Flux Concentration
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Solution Overview
Problem
Existing magnetic pivoting devices in watch movements face challenges due to inhomogeneous magnetic fields at small scales and the counter-pivot stone increasing the gap width, leading to reduced magnetic field intensity and restoring force.
Innovation Solution
A watch movement with a magnetic bearing system featuring a counter-pivot made of high magnetic permeability material with a hardness greater than 500 HV and a coefficient of friction less than or equal to 0.1, positioned between the magnet and pivot, acting as a pole piece to concentrate the magnetic flux and enhance the magnetic restoring force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a counter-pivot stone is inserted between the magnet and the pivot, then the magnetic gap is increased, but the magnetic field intensity and restoring force are considerably reduced
Solution Approach 1:
The patent changes the material parameters of the counter-pivot from conventional materials to materials with high magnetic permeability (greater than 10) and high hardness (greater than 500 HV). This parameter change allows the counter-pivot to concentrate magnetic flux while maintaining low friction, thereby increasing magnetic field intensity at the pivot surface without compromising structural stability
Solution Approach 2:
The counter-pivot acts as a magnetic intermediary element between the magnet and the pivot. By using material with high magnetic permeability, it serves as a magnetic flux concentrator that enhances the magnetic field distribution, effectively mediating the magnetic interaction while reducing the negative impact of the increased gap width
2Force
If permanent magnets with high magnetic energy density are used, then magnetic field intensity is increased, but magnetic field homogeneity decreases at the grain scale
Solution Approach 1:
The high permeability counter-pivot serves as a magnetic flux concentrator that redistributes the magnetic field lines. This intermediary element helps to homogenize the magnetic field at the pivot surface by concentrating flux through its high permeability material, compensating for the inhomogeneity introduced by the magnet's granular structure
Solution Approach 2:
The patent applies local quality by making the counter-pivot's magnetic permeability significantly higher than other components. This localized high permeability region creates a concentrated magnetic flux path that improves field homogeneity at the critical pivot interface, while allowing the magnet itself to maintain its high energy density permanent magnet material composition
3Force
If the counter-pivot dimensions are reduced to concentrate magnetic flux, then magnetic field intensity is increased, but the counter-pivot wear resistance must be maintained
Solution Approach 1:
The patent specifies composite material properties for the counter-pivot that combine high magnetic permeability (greater than 10) with high hardness (greater than 500 HV). This composite material approach allows the counter-pivot to simultaneously achieve magnetic flux concentration and wear resistance, maintaining both functional and mechanical performance despite reduced dimensions
Solution Approach 2:
The patent changes the material parameters of the counter-pivot to include high hardness (greater than 500 HV) alongside high magnetic permeability. This parameter change ensures that even with reduced dimensions for flux concentration, the counter-pivot maintains sufficient wear resistance through its enhanced material hardness
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 configuration improves the precision of magnetic field distribution, increases the magnetic field intensity and radial gradient, allowing for better centering of the pivot and reducing the risk of magnetic field disruption, while simplifying construction and reducing costs.
Implementation Method 1
a magnet (4), in the kitten, which exerts an attraction force on a pivot (2) made of magnetic material of the shaft (1)
Implementation Method 2
the counter-pivot (63) is formed of a material with high magnetic permeability and has, in cross-section at the pivot axis, dimensions smaller than those of the magnet
Data Source
Figure 1
Figure 2~4
Figure 5~9
AI summary
The device for pivoting a shaft (101) about a predetermined pivot axis in a watch movement comprises at least one magnetic bearing (205) having a magnet (206) that exerts an attractive force on a pivot (103) made of the shaft's magnetic material, and a counter-pivot (63) arranged between the magnet and the pivot. The counter-pivot is made of a material having a hardness greater than 500 HV and a coefficient of friction less than or substantially equal to 0.1 with the material of which the pivot is made. The counter-pivot (63) is made of a material with high magnetic permeability and has, in cross-section with respect to the pivot axis, dimensions smaller than those of the magnet. The counter-pivot is arranged in the watch movement so as to be centered on the pivot axis.