INTERNAL-COMBUSTION ENGINE WITH AN ELECTRONICALLY CONTROLLED HYDRAULIC SYSTEM FOR VARIABLE ACTUATION OF THE INTAKE VALVES, PROVIDED WITH A DEVICE FOR REFILLING THE SYSTEM WITH FLUID

摘要

In an engine having an electronically controlled hydraulic system for variable actuation of intake valves, an operating step of refilling, prior to ignition of the engine, is activated to refill a pressure chamber of the system with fluid when, after prolonged engine inactivity, the chamber has been emptied. In this refilling step, fuel supply to the engine is inhibited, and a camshaft is rotationally driven following upon activation of an engine-starting electrical machine. In this way, a pumping member associated to a tappet for actuating an intake valve is used as a pump for drawing fluid into the pressure chamber from an auxiliary fluid tank. During this step, a control valve is opened and closed in synchronism with movement of the pumping member so as to be open when the pumping member advances towards the pressure chamber and closed when the pumping member moves away from the pressure chamber.

主权项

1. An internal-combustion engine, comprising:
an engine shaft and at least one cylinder that defines a combustion chamber; at least one intake duct and at least one exhaust duct, which give out into said combustion chamber; at least one intake valve and at least one exhaust valve, which are associated to said intake and exhaust ducts and are provided with respective return springs that push the valves towards a closed position; a camshaft for actuating said at least one intake valve by a respective tappet, said camshaft being driven in rotation by the engine shaft, wherein said at least one intake valve is controlled by the respective tappet, against action of the return spring, by interposition of an hydraulic arrangement that includes a pressure chamber facing which is a pumping plunger, connected to the tappet, said pressure chamber being adapted to communicate with a chamber of a hydraulic actuator associated to said at least one intake valve; an electrically actuated control valve associated to said at least one intake valve of each cylinder and adapted to set in communication said pressure chamber with an exhaust volume in order to decouple said at least one intake valve from the respective tappet and cause fast closing of said at least one intake valve as a result of the respective return spring; an electronic control arrangement, for controlling said electrically actuated valve in order to vary an instant of opening and/or an instant of closing and lift of said at least one intake valve as a function of one or more operating parameters of the engine; and electrically actuated fuel-injectors, controlled by said electronic control arrangement for supplying fuel into said combustion chamber, there being associated to said engine an electrical machine for starting the engine to activate rotation of the engine shaft in a step of engine cranking, said engine being characterized in that: said pressure chamber is in communication with an auxiliary fluid tank via a non-return valve that enables passage of fluid only from said auxiliary tank in a direction of the pressure chamber, said auxiliary tank not having any direct communication with said exhaust volume; and said electronic control are arrangement is programmed for activating an operating step prior to ignition of the engine for refilling the pressure chamber, wherein the following operations are carried out: a) a supply of fuel to said combustion chamber is inhibited; b) said electrical machine is activated for setting in rotation the engine shaft and consequently said camshaft so that a reciprocating motion of said pumping plunger is activated; c) said electrically actuated control valve is cyclically opened and closed, in synchronism with movement of said pumping plunger, in such a way that said control valve is open in a step where the pumping plunger advances towards the pressure chamber and is closed in a step where the pumping plunger moves away from said pressure chamber so that the pumping plunger functions as a suction pump for recalling fluid from said auxiliary tank to the pressure chamber; and d) after a time interval, the supply of fuel to said combustion chamber is enabled and the electrically actuated control valve is kept closed to obtain actuation of the intake valves and ignition of the engine.