Latest Technologies Applied to Automatic Transmission Maji-Band™

Various products with paper-based wet-friction material have been developed for smoother shifting of automatic transmissions. Band brakes have been featured as friction engagement elements for planetary gears, which provide higher holding-torque capacity than same-size multiple friction-disk brakes caused by a self-energizing mechanism. The advantages that should be focused on are better shift quality for the release element during up shifting because of the different torque capacity in the drum rotating direction. In 1988, BorgWarner developed the Maji-Band for band brakes (coiled-steel straps joined into bands), which is lightweight and compact, and provides approximately 3.5 times higher torque capacity than single wrapped band brakes and lower drag torque than multiple friction-disk brakes. However, it is difficult to control shift quality as the engaging element for upshifting is caused by instability in attaining the required torque to dynamically follow the servo-applied force. This article describes a more robust Maji-Band that is controlled mainly by servo-applied force in comparison with multiple friction-disk brakes.