EP-4180640-B1 - MULTI-CYLINDER INTERNAL COMBUSTION ENGINE, WITH CYLINDERS EQUIPPED WITH INTAKE VALVE VARIABLE ACTUATION SYSTEMS HAVING HYDRAULIC CIRCUITS WHICH CROSS EACH OTHER

EP4180640B1EP 4180640 B1EP4180640 B1EP 4180640B1EP-4180640-B1

Inventors

RICCO, RAFFAELE
STUCCHI, SERGIO
GARGANO, MARCELLO
DE MICHELE, ONOFRIO
ALTAMURA, CHIARA

Dates

Publication Date: 20260506
Application Date: 20211116

Claims (4)

A four-stroke internal-combustion engine with four cylinders in line, or a two-cylinder two-stroke internal combustion engine, comprising: - a plurality of cylinders (CYL 1, CYL 2, CYL 3, CYL 4) and a plurality of pistons movable in the cylinders operatively associated to a crankshaft, where the engine cylinders have respective operating cycles distributed in sequence along the time; - a first intake valve (V1) and a second intake valve (V2) associated to each engine cylinder, for controlling a flow of intake air from a first intake duct (5) and from a second intake duct (6), respectively, during an intake stage of the cylinder in each operating cycle of the cylinder; and - a camshaft (11) driven by the crankshaft, with a plurality of cams (CAM 1, CAM 2, CAM 3, CAM 4) associated, respectively, to the cylinders (CYL 1, CYL 2, CYL 3, CYL 4) of the engine and configured for driving the intake valves of the engine by means of respective tappets (15), - wherein the intake valves (V1, V2) are governed by said tappets (15) against the action of respective return springs (9), by interposition of a plurality of hydraulic circuits associated to respective engine cylinders, and - wherein the hydraulic circuit associated to each engine cylinder includes: - a pumping piston (16), which is driven by the tappet (15) associated to the respective engine cylinder and is configured for transferring pressurized fluid, through a pressure chamber (C), towards two hydraulic actuators (21) associated to respective intake valves (V1, V2) of the engine; and - an electrically actuated control valve (24) able to set in communication said pressurized-fluid chamber (C) with a low-pressure exhaust channel (23) which communicates with a pressurized-fluid accumulator (270) in such a way that, when said control valve (24) is open, pressurized fluid is discharged from the pressure chamber (C) into said low-pressure channel and the intake valves (V1, V2) controlled by said hydraulic circuit close due to the action of the respective return springs (9), independently of the action of the respective cam, - said engine further comprising an electronic controller (25) controlling said electrically actuated control valves (24) as a function of a plurality of operating parameters of the engine, amongst which engine load and engine r.p.m., wherein: - the hydraulic circuit associated to each pumping piston (16) and to the respective cam (CAM 1, CAM 2, CAM 3, CAM 4) has its pressure chamber (C) communicating with the hydraulic actuators (21) of two intake valves (V1, V2) associated to two different engine cylinders so that the two intake valves (V1, V2) of each engine cylinder are controlled, via two different hydraulic circuits, by tappets (15), and by cams associated to two different cylinders, in such a way that the two intake valves (V1, V2) of each engine cylinder have, during the intake stage in each operating cycle of the cylinder, respective opening and closing cycles in different angular ranges of the rotation of the crankshaft, said electronic controller (25) being configured to control said electrically actuated control valves (24) in such a way that the two intake valves (V1, V2) of each cylinder are governed: - according to a full-lift mode, where each intake valve has a lift profile corresponding to the profile of the cam that controls it; or else - according to an early-closing mode, where the lift profile is reduced with respect to the lift profile corresponding to the profile of the controlling cam; or else - according to a mode of exclusion of one of the two intake valves of each cylinder, so that in each operating cycle of the cylinder, during the intake stage, only one of the two intake valves is opened, and wherein: - the cam of said camshaft (11) that is associated to the pumping piston (16) of a given engine cylinder controls, by means of the respective hydraulic circuit, a first intake valve (V1) associated to said given engine cylinder and a second intake valve (V2) associated to the cylinder that immediately precedes said given engine cylinder in the sequence of the operating cycles of the engine cylinders, and - each cam (CAM 1, CAM 2, CAM 3, CAM 4) is configured in such a way as to give rise to a cycle of opening and closing of each of the engine intake valves controlled thereby in an angular range of rotation of the crankshaft considerably less than 180° in such a way that in each engine cylinder, in the angular range of rotation of the crankshaft corresponding to a conventional intake stage in each operating cycle of the cylinder, only one first intake valve (V1) initially opens and closes while the second intake valve (V2) remains closed, and then the second intake valve (V2) opens and closes while the first intake valve (V1) remains closed.
The internal-combustion engine according to Claim 1, characterized in that each of said electrically actuated control valves (24) is a two-way, two-position solenoid valve.
The internal-combustion engine according to Claim 1, characterized in that each of said electrically actuated control valves (24) is a three-way, three-position solenoid valve.
A method for controlling operation of a four-stroke internal-combustion engine with four cylinders in line, or a two-cylinder two-stroke internal-combustion engine, wherein said engine comprises: - a plurality of cylinders and a plurality of pistons movable in the cylinders operatively associated to a crankshaft, where said cylinders have operating cycles distributed in sequence along the time; - a first intake valve (V1) and a second intake valve (V2) associated to each engine cylinder for controlling a flow of intake air from a first intake duct (5) and from a second intake duct (6), respectively, associated to the cylinder, during an intake stage of the cylinder in each operating cycle of the cylinder; - a camshaft (11) driven by the crankshaft, with a plurality of cams (CAM 1, CAM 2, CAM 3, CAM 4) associated to respective engine cylinders (CYL 1, CYL 2, CYL 3, CYL 4) and configured for driving the intake valves (V1, V2) of the engine by means of respective tappets (15); - wherein the intake valves (V1, V2) are governed by said tappets (15) against the action of respective return springs (9) by interposition of a plurality of hydraulic cylinders associated to respective engine cylinders, and - wherein the hydraulic circuit associated to each engine cylinder includes: - a pumping piston (16), which is driven by the tappet (15) associated to the respective engine cylinder and is configured for transferring pressurized fluid through a pressure chamber (C) towards two hydraulic actuators (21) associated to respective intake valves (V1, V2) of the engine; and - an electrically actuated control valve (24) designed to set in communication said pressurized-fluid chamber (C) with a low-pressure exhaust channel (23), which communicates with a pressurized-fluid accumulator (270), in such a way that, when said control valve (24) is open, pressurized fluid is discharged from the pressure chamber into said low-pressure channel, and the intake valves controlled by said hydraulic circuit close due to the action of the respective return springs (9) independently of the action of the respective cam, said method comprising controlling, by means of an electronic controller (25), said electrically actuated control valves (24) as a function of a plurality of operating parameters of the engine, amongst which engine load and engine r.p.m., wherein: - the hydraulic circuit associated to each pumping piston (16) and to the respective cam has its pressure chamber (C) communicating with the hydraulic actuators of two intake valves associated to two different engine cylinders so that the two intake valves (V1, V2) of each engine cylinder are controlled, via two different hydraulic cylinders, by tappets and cams associated to two different cylinders, in such a way that the two intake valves (V1, V2) of each engine cylinder have respective opening and closing cycles in different angular ranges of the rotation of the crankshaft during the intake stage in each operating cycle of the cylinder, said engine comprising the operation of controlling, by means of said electronic controller (25) said electrically actuated control valves (24) in such a way that the two intake valves (V1, V2) of each cylinder are governed: - according to a full-lift mode, where each intake valve has a lift profile corresponding to the profile of the cam that controls it; or else - according to an early-closing mode, where the lift profile is reduced with respect to the lift profile corresponding to the profile of the controlling cam; or else - according to a mode of exclusion of one of the two intake valves of each cylinder, so that in each operating cycle of the cylinder, during the intake stage, only one of the two intake valves is opened, and wherein: - the cam of said camshaft (11) that is associated to the pumping piston (16) of a given engine cylinder controls, by means of the respective hydraulic circuit, a first intake valve (V1) associated to said given engine cylinder and a second intake valve (V2) associated to the cylinder that immediately precedes said given engine cylinder in the sequence of the operating cycles of the engine cylinders, and - each cam (CAM 1, CAM 2, CAM 3, CAM 4) is configured in such a way as to give rise to a cycle of opening and closing of each of the engine intake valves controlled thereby in an angular range of rotation of the crankshaft considerably less than 180° in such a way that in each engine cylinder, in the angular range of rotation of the crankshaft corresponding to a conventional intake stage in each operating cycle of the cylinder, only one first intake valve (V1) initially opens and closes while the second intake valve (V2) remains closed, and then the second intake valve (V2) opens and closes while the first intake valve (V1) remains closed.

Description

Field of the invention The present invention relates to internal-combustion engines of the type comprising: a plurality of cylinders and a plurality of pistons movable in the cylinders and operatively associated to a crankshaft, wherein the engine cylinders have respective operating cycles distributed in sequence along the time;a first intake valve and a second intake valve associated to each engine cylinder, for controlling a flow of intake air respectively from a first intake duct and from a second intake duct of the cylinder during an intake stage of the cylinder in each operating cycle of the cylinder; anda camshaft driven by the crankshaft, with a plurality of cams associated to respective engine cylinders and configured for driving the intake valves of the engine by means of respective tappets,wherein the intake valves of the engine cylinders are governed by said tappets, against the action of respective return springs, by interposition of a plurality of hydraulic circuits associated to respective engine cylinders, andwherein the hydraulic circuit associated to each engine cylinder includes: a pumping piston, which is driven by the tappet associated to the respective engine cylinder and is configured for transferring pressurized-fluid, through a pressure chamber, towards two hydraulic actuators associated to respective intake valves of the engine; andan electrically actuated control valve able to set said pressurized-fluid chamber in communication with a low-pressure exhaust channel, which communicates with a pressurized-fluid accumulator, in such a way that, when said control valve is opened, pressurized fluid is discharged from the pressure chamber into said low-pressure channel and the intake valves controlled by said hydraulic circuit close due to the action of the respective return springs, independently of the action of the respective cam. Engines of this type are described, for example, in the documents EP 0 803 642 B1, EP 1 555 398, EP 1 508 676 B1, EP 1 674 673 B1, and EP 2 261 471 A1 filed in the name of the present applicant. Prior art For some time now, the present applicant has developed internal-combustion engines comprising a system for variable actuation of the intake valves of the type referred to above, marketed under the trademark "MULTIAIR". The present applicant is the holder of a large number of patents and patent applications regarding engines equipped with a system of the type specified above. Figure 1 of the annexed drawings is a cross-sectional view of an engine equipped with the MULTIAIR system, as described in the European patent EP 0 803 642 B1. With reference to Figure 1, the engine illustrated therein is a multicylinder engine, for example an engine with four cylinders in line, comprising a cylinder head 1. The cylinder head 1 includes, for each cylinder, a cavity 2 formed by the base surface 3 of the cylinder head 1 and defining the combustion chamber, giving out into which are two intake ducts 4, 5 and two exhaust ducts 6. Communication of the two intake ducts 4, 5 with the combustion chamber 2 is controlled by two intake valves 7 of the traditional mushroom type, each comprising a stem 8 slidably mounted in the body of the cylinder head 1. Each valve 7 is recalled towards the closing position by springs 9 set between an inner surface of the cylinder head 1 and an end retainer 10 of the valve. Communication of the two exhaust ducts 6 with the combustion chamber is controlled by two valves 70, which are also of a traditional type, associated to which are springs 9 for return towards the closed position. Opening of each intake valve 7 is controlled, in the way that will be described in what follows, by a camshaft 11, which is rotatably mounted about an axis 12 within supports of the cylinder head 1 and comprises a plurality of cams 14 for actuation of the intake valves 7. Each cam 14 that controls an intake valve 7 co-operates with the cap 15 of a tappet 16 mounted so that it can slide along an axis 17 that, in the case of the example illustrated in the prior document referred to, is oriented substantially at 90° with respect to the axis of the valve 7. The cap 15 is recalled against the cam 14 by a spring associated thereto. The tappet 16 constitutes a pumping piston slidably mounted within a bushing 18 carried by a body 19 of a pre-assembled unit 20, which incorporates all the electrical and hydraulic devices associated to actuation of the intake valves, according to what will be described in detail hereinafter. The pumping piston 16 is able to transmit a thrust to the stem 8 of the valve 7 so as to bring about opening of the latter against the action of the elastic means 9 via pressurized fluid (preferably oil coming from the lubricating circuit of the engine) present in a pressure chamber C, facing which is the pumping piston 16, and via a piston 21 slidably mounted in a cylindrical body constituted by a bushing 22 that is also carried by the body 19 of the subunit 2