Start-up or disengagement method for an electro-hydraulic transmission

A process for start-up of a secondary propulsion system for a vehicle displacement component, the vehicle comprising a primary propulsion system, said primary propulsion system comprising

• a variable displacement hydraulic pump having a discharge and an admission,
• a hydraulic motor having a discharge and an admission, adapted to drive said displacement component in rotation and which can be selectively engaged or disengaged from said displacement component, the hydraulic motor being fed by the hydraulic pump via a closed-loop hydraulic circuit comprising a feed pump, the hydraulic circuit comprising an engagement valve adapted to selectively connect hydraulic motor to the hydraulic pump or isolate the hydraulic motor relative to the hydraulic pump and connect the discharge of the hydraulic pump to its admission, and connect the discharge of the hydraulic motor to its admission,
• an electric motor, adapted to drive the hydraulic pump,
• a source of electric power, adapted to feed the electric motor, said process for start-up comprising the following steps, given a configuration when the propulsion system is at a standstill, in which the electric motor, the hydraulic pump and the feed pump are at a standstill, and the hydraulic motor is disengaged:
• start-up of the feed pump
• starting up of the electric motor, so as to drive the hydraulic pump in rotation,
• adjustment of the displacement of the hydraulic pump and/or of the rotational speed of the electric motor to provide a flow rate corresponding to a setpoint applied to the hydraulic motor,
• control of the engagement valve to execute start-up of the hydraulic motor.