Minimizing the Fan Imbalance Excitation of an Automotive Blower System

This paper investigates an approach to minimize the mass imbalance excitation of an automotive HVAC blower system through the control of the blower fan dynamic imbalance. The total mass imbalance of a blower fan, known as the fan static imbalance, is resolved into two plane dynamic imbalances. A theoretical analysis relates the magnitude of each plane imbalance and the phase angle between the two plane imbalances, is included. The vibration spectra of the imbalance design of experiment DOE runs, in the radial and axial directions, with respect to the blower motor shaft, are recorded. The data are analyzed by linear and second order statistic models, the results and contour plots of peak vibration levels versus the two plane imbalance are described. The interaction between the resultant imbalance of a blower fan and the that of its driving motor is studied to reveal a noise factor in the DOE. The conclusions aid in defining the parameters for a second order or continuous body modal analysis.