Motor, Park Pawl: Operation
During each key-up/wake-up cycle, the Electronic Shift Module (ESM) performs an initialization process as commanded from the Electric Vehicle Control Unit (EVCU) to identify the park-pawl location. The ESM has the 20 amps required for controlling the park-pawl motor operation. The two quadrature sensors within the park pawl read at 90 degrees phase shift and provide speed and direction of the move. To learn this position the ESM will send a request to run the motor to the park direction, when it reaches end stop and the ESM sees the current spike and no more counts, the motor operation stops.
The motor will then move away from the end stop but stay in the park position. On the next selection to take it out of park and with the brake applied, the motor will travel to the other end stop and learn the full calibration travel. The next requests will have the motor travel between software stops and faster speeds and the motor will not contact end stops.
After every 10th travel, the system will recalibrate the end stops or on a key ON it will restart the calibration process. If vehicle speed is greater then 2 mph, and the key is turned off or park is selected, the actuator will remain in the neutral position. If a second request for park is requested and the vehicle is traveling below 2 mph, the vehicle will shift to park.
How It Works:
- The park lock actuator is an electronic controlled actuator, which is able to generate a form fit which blocks the drive train to prevent an unwanted moving of the vehicle
- The form fit is achieved by moving the park pawl (9) towards the park gear (1).
- During engagement the actuator releases the spring (4) preloaded cone (3), which moves the pawl (9) in direction park wheel (1).
- As soon as the park pawl (9) finds a gap the park lock will block the drive train
- During disengagement the actuator pushes the cone (3) back. The park pawl (9) will be pushed back by the separating forces of the park gear (1) and the leg spring (7).
- In case of a malfunction, the actuator (8) can be released manually by a tool (e.g. screwdriver or the like), at the end of the E-Motor housing, which is closed by a rubber cap.
- A Belleville Spring (10) (12) and sleeve (11) are implemented to reduce the impact during calibration.