Method for estimating a top dead centre for a high-pressure pump of a fuel injection system in an automotive vehicle engine

A method for estimating an angular position of top dead center (25) for a high-pressure fuel injection pump (4) that forms part of an injection system (1) for injecting fuel into a motor vehicle internal combustion engine (12),

• the pump (4) having at least one piston (19) that moves in a chamber of the pump (4) between the top dead center (25) at which a volume of the chamber is smallest and a bottom dead center at which the volume of the chamber is greatest, the pump (4) being equipped with a digital control valve (13) for controlling a quantity of fuel delivery, said digital control valve (13) configured to be commanded electrically to be actuated between an open position in which a high-pressure part of the injection system is not supplied with fuel and a closed position in which the high-pressure part of the injection system is supplied with fuel with the digital control valve (13) then being in a fully closed position, an electrical current applied to the digital control valve (13) as the digital control valve (13) closes then being removed in order to open the digital control valve (13), a movement of the digital control valve (13) toward the open position creating an induced current which, when a profile over time is monitored, facilitates a detection of a position of a start-of-opening (23) of the digital valve (13) and an instant at which said start-of-opening (23) occurs, the method comprising:
• estimating an angular position at an instant at which the piston (19) of the pump (4) passes through the top dead center (25) as a function of an angular position of the pump (4) at the instant at which said start-of-opening (23) of the digital control valve (13) occurs,
• the estimated angular position at the instant of the pump (4) passing through the top dead center (25) further taking account of at least one of the following parameters:
• pressures upstream and downstream of the pump (4),
• an elastic modulus of the fuel, being dependent on temperature and pressure of the fuel, and
• technical characteristics of the pump (4).