Custom Drive System Helps Mercedes-Benz Reduce Draft in Convertibles

The AIRCAP® automatic draft stop, offered in the Mercedes-Benz E-Class convertibles, is distinctively different from conventional angular wind deflectors. It is entirely embedded into the car body and completely concealed into the windshield frame when deactivated. In its activated state, an aerodynamically shaped wind deflector extends on top of the windshield without disfiguring the automobile’s aesthetic side line.

The AIRCAP comprises two main components: an electrically operated wind deflector built into the windshield frame, and a wind blocker located between the rear head cushions. Its activation increases the free flow of air over the car interior, which results in dramatically reduced air pressure and reverse airflow. It can be activated while driving (up to speeds of 160 km/h, or 100 mph), and can be used all the way up to the car’s top speed. The result is increased driving comfort and clearly reduced wind noise. And, as weather conditions and temperatures call for — or just to give free rein to a boundless convertible feeling — the AIRCAP can again be deactivated at the push of a button.

The Drive System

A drive system, designed by maxon motor GmbH in Sexau, Germany, takes care of moving the AIRCAP. Its core piece is a motor/gear combination specially designed for the application based on a maxon A-max 22 DC motor and a customized gearbox with three separate reduction stages. Prominent characteristics are compact, robust design; high-capacity, silent, highly dynamic ganging; self-locking output in both end positions; and handling-optimized, screwless assembly into the wind shield frame.

The Mercedes-Benz E-Class Cabriolet with exten d - ed AIRCAP. (© Daimler AG)

Behind the concept are extraordinarily stringent requirements related to comfort, small installation space, and screwless assembly technique suitable for high-volume production. The result is a drive system that claims just 22 mm of installation height and drives the three outputs for bracing, adjustment of the lamella module, and latching of the AIRCAP in a fixed, coordinated, and synchronized ratio.

In the retracted position, the lamella module is braced and interlocked flush to the car body’s surface, and in the extended end position, it is mechanically interlocked. While being deployed, the drive overcomes wind ram pressures well beyond 250 km/h (155 mph) by torques of up to 7 Nm.

The maxon motor AIRCAP drive. (© maxon motor ag)

As for acoustics and ganging, the drive fulfills the same strict requirements that Mercedes-Benz imposes for interior passenger compartment instruments. Besides the high-end demands on power density, dependability, and comfort, the drive also complies to the rigid constraints on optimized serial production. Thus, the entire drive assembly can be mounted into the windshield frame without the use of screws. Similarly, the individual components such as the anti-vibration motor receptacle, motor, gear pinion, bipartite hull, etc., are assembled within a specially designed procedure.

This article was contributed by maxon precision motors, Fall River, MA. For more information, Click Here