Patent ID: 6808052
Filing Date: 2004-10-26
Classification: B60K,F16D,Y10T

Abstract:
A transfer case for use in a four-wheel drive vehicle having a powertrain and first and second drivelines comprising:a first shaft driven by the powertrain and adapted for connection to the first driveline; a second shaft adapted for connection to the second driveline; a friction clutch assembly operably disposed between said first and second shafts; a ball screw operator rotatably driven by one of said first and second shafts and having a first component in threaded engagement with a second component, and a third component in threaded engagement with said second component, said first component being axially moveable relative to said second component in response to relative rotation between said second and third components, said first component is adapted to exert a clutch engagement force on said friction clutch assembly the magnitude of which corresponds to the axial position of said first component relative to said second component; an electric motor having a rotor fixed for rotation with said second component of said ball screw operator, said motor is operable in a motor mode wherein said rotor is driven to cause relative rotation between said second and third components, and said motor is operable in a brake mode wherein said rotor is braked to cause relative rotation between said second and third components; and a controller for actuating said motor so as to control the direction and amount of rotation of said rotor which, in turn, controls the direction and amount of axial travel of said first component of said ball screw operator for varying the clutch engagement force exerted on said friction clutch assembly, said controller further operable for switching from said motor mode to said brake mode when the rotary speed of one of said first and second shafts exceeds a predetermined threshold value.