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

Patent metadata

Field	Value
Publication number	US-9970336-B2
Application number	US-201514874720-A
Country	US
Kind code	B2
Filing date	Oct 5, 2015
Priority date	Dec 10, 2014
Publication date	May 15, 2018
Grant date	May 15, 2018

Abstract

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.

First claim

What is claimed is:

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 a discharge 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 discharge volume; and
said electronic control arrangement is programmed for activating an operating cranking step of the engine prior to ignition of the engine for the purpose of refilling the pressure chamber before the engine is started, 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.

2. The engine according to claim 1 , wherein said time interval is a pre-set time interval.

3. The engine according to claim 1 , wherein said time interval corresponds to a pre-set number of cycles of forward and backward movements of the pumping plunger.

4. The engine according to claim 1 , further comprising a pressure sensor adapted to detect pressure in the pressure chamber and to issue a signal that is received by said electronic control arrangement and in that said time interval corresponds to an amount of time necessary for said pressure sensor to warn that a pre-set value of the pressure in the pressure chamber has been exceeded.

5. The engine according to claim 1 , wherein a sensor arrangement is provided, adapted to detect movement of said at least one intake valve and in that said electronic control arrangement is programmed for activating the operating step prior to ignition of the engine for refilling the pressure chamber when, in the step of engine cranking, absence of movement of said at least one intake valve is detected.

6. The engine according to claim 5 , wherein said sensor arrangement comprises a pressure sensor for detecting pressure in an intake manifold of the engine, and is adapted to issue a signal that is received by said electronic control arrangement.

7. The engine according to claim 5 , wherein said sensor arrangement comprises an accelerometer associated to said at least one intake valve, the signal of which is received by said electronic control arrangement.

8. The engine according to claim 1 , wherein a pressure sensor is provided, adapted to detect pressure in the pressure chamber and to issue a signal that is received by said electronic control arrangement, and in that said electronic control arrangement is programmed for activating the operating step prior to ignition of the engine for refilling the pressure chamber when, in the step of engine cranking, a pressure in the pressure chamber lower than a pre-set threshold value is detected.

9. The engine according to claim 1 , wherein said auxiliary fluid tank is connected to said pressure chamber by a connection duct having a first end that communicates with the pressure chamber on a downstream side of the control valve, opposite to a side of said discharge volume, and a second end connected to said auxiliary tank in a bottom part of said tank, and in that, in a normal condition of use of the engine, said second end is situated at a level lower than a level of said first end, and also than a level of the actuators of the intake valves and than a level of the pumping plunger, said actuators and said pumping plunger being consequently at a height greater than zero with respect to an outlet of the auxiliary tank.

10. The engine according to claim 9 , wherein said auxiliary tank is also connected to a channel for supplying pressurized fluid, which communicates with said auxiliary tank in a top part of said auxiliary tank.

11. The engine according to claim 10 , wherein said auxiliary tank has at least one top opening for venting into atmosphere.

12. A method for control of an internal-combustion engine, the engine comprises:
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 associated to said intake and exhaust ducts and 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 a discharge volume in order to decouple said at least one intake valve f

Assignees

• Fiat Ricerche

Inventors

• Gentile Luca
• Vattaneo Francesco

Classifications

• F01L2001/34446

  Fluid accumulators for the feeding circuit · CPC title

• F02D2041/001

  for engines with variable valve actuation · CPC title

• F01L2800/01

  Starting · CPC title

• F01L1/3442

  using hydraulic chambers with variable volume to transmit the rotating force · CPC title

• F02D13/0261

  Controlling the valve overlap · CPC title