Abstract
Sunroof buffeting is generated by the resonance of the cabin cavity whose opening is aerodynamically excited by the periodic convection of vortices in the shear layer over the sunroof opening. Generation and convection of vortices in the shear layer are controlled by the resonance of the cabin cavity. A recent trend is a large sunroof opening such as a panoramic sunroof in accordance with the customer’s preference for a feeling of openness. Since the sunroof buffeting tends to become louder as the sunroof opening area becomes larger, a conventional passive deflector may not be a solution in this case, and a new effective method like an active deflector system is required to reduce the sunroof buffeting. In this study, the concept of the active deflector system suggested by Kook et.al is more practically developed for the real-car sunroof which has a retractable sunroof deflector system.
In the active deflector system, a combination of a microphone sensor mounted inside the car cabin, a controller, a power amplifier and deflector actuators is added for active buffeting control. Since the acoustic pressure inside the cavity is influenced by the shear layer modified by the active deflector, the active deflector and the acoustic response of the cavity form a closed-loop system. This mechanism is not the conventional active noise control, but a kind of new active flow control for low-frequency wind noise reduction.
A new actuator-deflector linkage design was revised for the retractable deflector. To make them smaller and lighter was the first consideration of this new design. The voice-coil actuator and the controller were also newly developed. The problems of rattle noise and weak structural rigidity were found out and solved. Final test results showed the reduction of buffeting of 15dB through this retractable active sunroof deflector system.
KEYWORDS Sunroof, buffeting, sunroof deflector, wind noise, active deflector system