INTRODUCTION Global warming issues with CO 2 emission by cars and rapidly diminishing fossil fuel have forced car manufacturers to develop more environmentally friendly and fossil fuel free cars. In order to meet this demand, there has been comprehensive research on electric cars mainly in that electric vehicles have zero CO 2 emission and can enhance energy efficiency using regenerative braking in which they recover kinetic energy and charge battery during deceleration and stop [ 1, 2]. In the view of NVH, electric vehicles are known as more silent than conventional vehicles because they remove combustion engines which are the main source of the noise and vibration of vehicles. However, in practical development processes noise issues in electric vehicles are more complicated. Quieter environments in a passenger cabin using electric motors for traction of the car instead of combustion engines make unwanted noises become more prominent. This paper presents experimental research on electric vehicle cabin noise reduction. Particular concerns are on structural integrity of the traction motor. Many researchers reported that structural vibration of the stator core dominatesthe noise and vibration of the motor system [ 3, 5]. However, in this research it was shown that structural characteristics of the assembled system of stator core and frame contribute to noise radiated from the traction motor. From the experimental modal analysis results of the traction motor contributions of the structural resonances on the vehicle cabin noise was illustrated. Interfacial damping of the traction motor frame was employed in order to reduce the resonant vibration and noise emission from the traction motor. Researchers like Banks and Nada, [ 6, 9] reported that significant damping can be obtained in the frictional interfaces with fastening pressure to allow some interfacial slip on a simplified geometry such like double- layered beam, sliding joints. This paper presents a practical application of interfacial damping to an electric vehicle NVH problem. 100 kW Fuel Cell Electric Vehicle (FCEV) traction motors and 60 kW Electric Vehicle (EV) traction motors were used for the noise measurement and modal tests. 2013-01-2590 Published 10/14/2013 Copyright © 2013 SAE International and Copyright © 2013 KSAE doi:10.4271/2013-01-2590 saepcelec.saejournals.org Study on the Vehicle Cabin Noise Employing the Interfacial Friction in Double Layered Frames Used in Electric Vehicle Traction Motors Jongchan Park and Hyeoun Dong Lee Hyundai Mobis ABSTRACT Electric vehicles are considered not only eco-friendly but also quieter than vehicles with conventional internal combustion engines. However, less noisy environments in cabins make passengers feel uncomfortable to moderate noise. This paper discusses noise reduction for electric vehicles radiated from traction motors. In the analysis of the noise generation mechanisms it is demonstrated that frequency ranges of the highest level in the noise spectrum of electromagnetic harmonic orders of the induction motor coincide with structural resonances of the motor housing. Interfacial friction between the inner and outer housings of the motor is employed in reducing structural vibration of the motor. Measured noise in the cabin and vibration at the motor housing indicates that slip damping presented from interfacial friction between the inner and outer housing is effective in reducing noise from the traction motor and in the cabin. CITATION: Park, J. and Lee, H., "Study on the Vehicle Cabin Noise Employing the Interfacial Friction in Double Layered Frames Used in Electric Vehicle Traction Motors," SAE Int. J. Passeng. Cars – Electron. Electr. Syst. 7(1):2014, doi: 10.4271/2013-01-2590. ____________________________________ 28Downloaded from SAE International by Brought to you by the University of Kansas (Technical reports: 1998 to Present), Sunday, August 26, 2018INTERFACIAL CONTACT SURFACE AND FRICTIONAL DAMPING The ph