The Analysis of the Contribution Factor on EPB Actuating Noise by Using OPAX 2020-01-1608
As eco-friendly cars such as electric and hybrid vehicles increases and the quietness of vehicles is getting better, the importance of reducing noise heard by passengers that has been masked otherwise is increasing. At the same time, with the vehicle's electrification and needs of advanced technology, EPB (Electric Parking Brake) has been expanding which was mainly introduced to luxury vehicles. EPB system consists of an electronic control unit (ECU) and actuators with simple switch operation instead of a hand or foot control to apply the parking brake. Because EPB is normally driven by motors and gear sets, actuation of EPB results in noise. It is difficult problem to reduce EPB noise in the development stage and much research has been carried out. Generally EPB noise consists of airborne noise which sounds from the EPB itself and is transmitted to the driver through air and structure borne noise which is transmitted through vibration of the rigid-body such as calipers, knuckles, cross member and floor body etc. Meanwhile reducing EPB noise has been focused on mainly noise source itself like improving gear roughness, grease materials, dimension accuracy in a view of airborne noise. But it is important also to identify the exact source-path relations of noise through a transfer path analysis (TPA) in a view of structure borne noise and to find an appropriate countermeasure to the path besides the source. Despite its importance and usefulness, the classical TPA has the disadvantage to take a long time because the experimental procedures are complex. So, we used OPAX method (Operational Path Analysis with Exogenous Inputs) which uses minimally-parameterized or reduced parametric load models describing the operational forces and acoustic loads in function of measured path references such as mount accelerations and acoustic pressures. OPAX is a fast method providing reliable path contribution results. In this study, we intend to identify the main noise sources of EPB efficiently and to find appropriate improvement measurements.