Magnetic Disk Torque Structure for High Shear Stress
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Solution Overview
Problem
Existing torque generating devices using magnetic viscous fluids struggle to achieve large shear stress while maintaining miniaturization, as the magnetic field is primarily applied near the outer peripheral portion of the rotor, limiting braking force and shear stress generation.
Innovation Solution
A torque generating device configuration featuring a magnetic disk with a magnetic gap between yokes, allowing magnetic flux to cross in a wide range except at the outer peripheral edge, generating resistance force without increasing device size, utilizing a magnetic disk, yokes, and a coil to create a magnetic field with a magnetic viscous fluid in between.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the magnetic field is applied only near the outer peripheral portion of the rotor, then the device structure is simplified, but the braking force and shear stress generation are insufficient
Solution Approach 1:
The patent introduces a third yoke that extends in the radial direction beyond the outer peripheral edge of the magnetic disk, creating a magnetic path in the radial dimension. This allows magnetic flux to pass through a wider area including regions that overlap with the magnetic disk, thereby increasing the effective area for shear stress generation without significantly increasing device complexity
Solution Approach 2:
The third yoke serves multiple functions: it provides a magnetic path for flux generation, defines the magnetic gap region, and extends the magnetic field coverage to areas that overlap with the magnetic disk. This multi-functional design enables broader magnetic field application while maintaining structural efficiency
2Force
If the device size is increased to apply magnetic field in a wider range, then the shear stress increases, but the device miniaturization goal is compromised
Solution Approach 1:
Instead of increasing the axial thickness of yokes to expand magnetic field coverage, the patent extends the third yoke in the radial direction. This dimensional change allows the magnetic field to cover a wider area without increasing the axial height of the device, thus maintaining miniaturization while increasing shear stress generation area
Solution Approach 2:
The magnetic gap is specifically positioned to overlap with the outer peripheral edge of the magnetic disk, concentrating the magnetic field application where it is most effective for shear stress generation. This localized optimization increases shear stress without requiring uniform magnetic field expansion throughout the entire device volume
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 enables the generation of large shear stress without increasing device size, effectively addressing the limitations of existing technologies by ensuring a wide range of magnetic flux passage and resistance force application.
Implementation Method 1
a coil disposed so as to overlap the magnetic disk when viewed in a direction along a direction in which the rotation axis extends
Implementation Method 2
a magnetic viscous fluid filled between the magnetic disk and each of the first yoke and the second yoke
Data Source
AI summary
A torque generating device includes a magnetic disk configured to rotate around a rotation axis, first and second yokes located on opposite sides across the magnetic disk, a coil disposed to overlap the magnetic disk along a direction of the rotation axis, a third yoke of which at least a region proximity to the magnetic disk is located outside the magnetic disk and the coil and that makes up a magnetic path of a magnetic field generated by the coil with the first and second yokes, and a magnetic viscous fluid filled between the magnetic disk and the first and second yokes. The third yoke has a magnetic gap between the third and first yokes. The magnetic gap is formed at a position outside an outer peripheral edge of the magnetic disk or overlapping the outer peripheral edge of the magnetic disk along the direction of the rotation axis.