Apparatus and method for starting an engine using a hydraulic hybrid drivetrain

A series hydraulic hybrid driveline for a vehicle, comprising:

• a hydraulic circuit comprising a first hydraulic displacement unit in fluid communication with a second hydraulic displacement unit, the first hydraulic displacement unit having a variable hydraulic displacement and the first hydraulic displacement unit being drivingly engaged with an internal combustion engine;
• a hydraulic accumulator assembly selectively fluidly connected to the hydraulic circuit, the hydraulic accumulator assembly comprising a high pressure hydraulic accumulator and a low pressure hydraulic accumulator;
• and
• a hydraulic actuator adapted to control the hydraulic displacement of the first hydraulic displacement unit, the hydraulic actuator being in fluid communication with the hydraulic accumulator assembly and with the hydraulic circuit;
• wherein the hydraulic actuator is in fluid communication with the hydraulic accumulator assembly and with the hydraulic circuit through a pilot pressure portion, the pilot pressure portion comprising shuttle valves adapted to select a greatest hydraulic pressure between a greatest hydraulic pressure in the hydraulic circuit and a greatest hydraulic pressure in the hydraulic accumulator assembly.