Component Functional Description-Power Transfer Unit (PTU)
An H-Bridge inside the DTCM is used to rotate the bidirectional actuator motor on the PTU assembly to engage and disengage the locking cam with the fixed cam. The teeth on the actuator motor rotate an intermediate gear which is permanently meshed with the locking cam. To engage the cams, the motor rotates the locking cam allowing the spring to force the locking cam into the fixed cam connected to the ring gear inside the PTU. To disengage the cams, the motor rotates the locking cam and a ramp acting on the moving dog ring forces the cams apart as it rotates. A brake ramp on the dog ring helps to brake the ring gear and front propeller shaft when disengaging the PTU. If the DTCM detects an overheat condition in the actuator motor, the motor will be commanded off and the PTU is disengaged until the internal temperature returns to a normal threshold.
- The actuator motor has two internal hall effect position sensors that count the rotations of the PTU actuator motor.
- The actuator motor has an internal temperature sensor to monitor the motor winding temperature.
The common position sensor supply voltage circuit feeds the two internal position sensors in the actuator. The position sensors also share a common sensor return circuit. the hall effect position sensor signals are monitored by the DTCM during operation of the actuator to determine the amount of travel of the actuator motor. The internal temperature sensor operates like a typical two wire temperature sensor with a 5.0v signal and sensor ground circuit.
The DTCM monitors the signal voltage for the temperature sensor and two position sensors inside the actuator motor. The sensor signals are monitored for circuit faults. If no circuit faults are present, the DTCM monitors the position sensors to determine that the PTU is in the correct position that is being commanded (engaged/disengaged).