As a gearbox supplier for EV’s, Valeo has defined an innovative methodology to design internal devices that brings additional functionalities. Passenger cars are often equipped with a park lock system as a back up to the parking brake (hand brake) to face regulations or to enhance safety and anti-theft needs. For a long time, park locks were present only on automatic transmissions and were mechanically controlled from the gear lever with a cable. With the electrification revolution, it is now common to have a "by wire" control of the park lock. Electrical control allows new concepts of actuation: When the usual cable driven park lock of an automatic transmission would only deliver a few degrees of angle (typically around 20°), it is now possible with an electric rotational actuator to do much more. Advantages like stability, tolerances and actuation time have led to a 180° actuation angle park lock. It will be described and compared with the historical 20°. One of the main items to be addressed on a park lock system is the dynamical behavior (ratcheting). Ratcheting being the behavior of the park pawl bouncing from tooth to tooth on the park wheel when the vehicle speed is too high to allow the locking. The transition of vehicles to electric drivetrains has induced a migration of the park lock position from the gearbox output to the input. This drift has changed a lot the ratcheting of the park pawl as the rotation speed has been multiplied by the gear ratio (typically 10 to 15) and the torque divided by the same value. This study applies to electric drive vehicles, but could be also applied to fuel cell vehicles. An innovative design has been proposed thanks to this predictive simulation methodology. This innovative design can be easily implemented on any EV gearboxes for OEMs

Dipl.-Ing. Christophe Mollier, Product Design leader, Valeo