Influence of Working Gap on Magnetic Field and Transmission Torque of Magneto-Rheological Coupler

This paper studies the influence of the working gap on the magnitude and distribution of the magnetic flux density and the shear stress of a magneto-rheological coupler. The results of the Finite Element Analysis (FEA) and experiments indicate that the magnitude of the magnetic flux density decreases with the increase of the working gap, while the distribution of the magnetic flux density and the shear stress becomes more uniform along the axial length direction. Because of the magnetic saturation and the existence of the stress yield of the Magneto-Rheological Fluid (MRF), the working gap, for the range of 0.6mm to 2.0mm, has limited influence on the magnetic flux density and stress. The experimental results show that the transmission torque only decreases 25% during this range. Based on these findings, the working gap should be chosen properly to obtain a sufficient magnetic field and transmission torque for a given device with consideration of machining and assembling costs associated with a smaller working gap.