Fuel purge control

An engine control unit for, in use, controlling delivery of fuel from a vapour collection device to at least one combustion chamber of an internal combustion engine to thereby purge fuel that has accumulated in the vapour collection device by means of a purge flow passing from the vapour collection device to the engine, the purge flow rate being varied by means of a flow control valve located between the vapour collection device and the engine, the engine control unit adapted to operate according to a method comprising the steps of determining a minimum valve signal value and a maximum valve signal value as a function of engine load and engine speed to thereby respectively define the minimum and maximum extent of valve signal values for controlling opening of the valve, said function being independent of exhaust-air/fuel ratio feedback control;

• and selecting either one of the minimum valve signal value, maximum valve signal value, and an interpolation between the maximum and minimum valve signal values in which said selecting is performed in dependence on engine operating conditions so as to optimise an amount of fuel purged from the vapour collection device,
• wherein the amount of interpolation between the respective minimum and maximum valve signal values is provided by an adaption value for obtaining an intermediate valve signal value between said minimum and maximum valve signal values the method further including determining the adaption value as a function of a coolant temperature of the engine,
• including determining an initial adaption value upon first starting up the engine, such that the initial adaption value is relatively low if the engine coolant temperature is relatively high to thereby restrict a purge air flow to the engine and such that the initial adaption value is relatively high if the engine coolant temperature is relatively low to thereby provide for a greater purge air flow to the engine.

An internal combustion engine comprising at least one combustion chamber and adapted to, in use, deliver fuel from a vapour collection device to said at least one combustion chamber to thereby purge fuel that has accumulated in the vapour collection device by means of a purge flow passing from the vapour collection device to the engine, the purge flow rate being varied by means of a flow control valve located between the vapour collection device and the engine, the engine adapted to operate according to a method comprising the steps of determining a minimum valve signal value and a maximum valve signal value as a function of engine load and engine speed to thereby respectively define the minimum and maximum extent of valve signal values for controlling opening of the valve, said function being independent of exhaust-air/fuel ratio feedback control;

• and selecting either one of the minimum valve signal valve, maximum valve signal value, and an interpolation between the maximum and minimum valve signal values in which said selecting is performed in dependence on engine operating conditions so as to optimise an amount of fuel purged from the vapour collection device,
• wherein the amount of interpolation between the respective minimum and maximum valve signal values is provided by an adaption value for obtaining an intermediate valve signal value between said minimum and maximum valve signal values, the method further including determining the adaption value as a function of a coolant temperature of the engine,
• wherein the engine is operated under closed loop speed control at idle operation of the engine and is operated under open loop control under other engine operating conditions.