Purge Pump Rotor Dynamics Subjected to Ball Bearing Inner and Outer Race Wear Defects 2020-01-0403

The purge pump is used to pull evaporative gases from canister and send to engine for combustion in Turbocharged engines. The purge pump with impeller at one end and electric motor at the other end is supported by the ball bearing assembly. A bearing kinematic model to predict forcing function due to defect in ball bearing arrangement, coupled with bearing dynamic model of rotor because of rotating component, is proposed in this paper to get accumulated effect on transmitted force to the purge pump housing. Rotor dynamic of purge pump rotor components only produces certain order forcing responses which can be simulated into the multibody software environment, knowing the ball bearing geometry parameters hence providing stiffness parameter for rotor system.

Wear defects in the ball bearings, such as defects in the inner and outer races, cage, and balls generate different noise types that have asynchronous high-frequency orders and as well as sidebands frequencies due to frequency modulations. These wear noise frequencies are called the bearing defect-related frequencies. A defect in the ball bearing system tends to produce different order forces with amplitude depending on size of the defect because of the defect interaction with its mating moving parts (Inner Race, Outer Race, Ball Cage and Bearing Balls). These orders vary depending on the component on which defect is present.

Therefore, based on currently proposed method, all circumstances can be simulated by including BPFI (Ball Passing Frequency for Inner Race), BPFO (Ball Passing Frequency for Outer Race) and BSF (Ball Spinning Frequency) forcing function into the model which can resonate with Rotor rigid body modes (Conical and Cylindrical) and flexible modes (Bending) predicting the near actual scenario. In this paper, emphasis is made to find out the root cause and design solutions to fix the wear noise issue of Purge Pump are presented.