Experimental Analysis of the Vibroacoustic Response of an Electric Window-Lift Gear Motor Generated by the Contact Between Carbon Brushes and Commutator

Abstract

This paper deals with the vibroacoustic behavior of an electric window-lift gear motor for automotive vehicle which consists of a direct current (DC) motor and a worm gear. After describing the overall vibroacoustic behavior of this system and identifying the various excitation sources involved, this study focuses on the excitation sources associated to the contacts between brushes and commutator. To that end, a specific test bench is designed. It makes use of a modified gear motor for which various specific rotors are driven with an external brushless motor. It allows the discrimination of some excitation sources associated to the contact between brushes and commutator by removing them one after the other. The respective weight of friction, mechanical shocks, electrical current flow, and commutation arcs occurring jointly at the brush/commutator interface are dissociated and evaluated. The friction and the mechanical shocks between brushes and commutator blades increase the vibroacoustic response of the window-lift gear motor. The flowing of electrical current in brushes/commutator contacts tends to moderate the frictional component of excitation sources, while commutation arcs induce their rising, leading to a global additive contribution to the dynamic response.