Electronic shift or clutch actuator for a vehicle transmission

Abstract

The present invention is directed to an electronic actuator for use in a vehicle transmission such as a four wheel drive transfer case. In one preferred embodiment, the transfer case includes two separate electronic actuators, a range shift actuator which is utilized to effect shifting of the transfer case between high range, neutral, and low range drive positions, and a clutch actuator which is utilized to control engagement of a clutch between two wheel drive, automatic ('on demand' four wheel drive), and 'part time' four wheel drive operating modes. The range shift actuator includes a rotary electric motor coaxially mounted relative to a rear output shaft of the transfer case, and a linear screw for translating the rotational movement of the motor shaft to selective axial movement of a range shift sleeve. The clutch actuator is similar to the range shift actuator except that, since the torque requirements necessary to bias the clutch are substantially greater than that necessary to effect the range shift, the clutch actuator includes additional gear reduction to enable the actuator to generate a sufficient axial force to fully engage the clutch. The actuators do not draw any current load after they have moved to their controlled positions and, because the linear screws can not be back driven, their previously set positions are maintained in the event of motor failure or power loss.