Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Patent
1996-05-10
1997-11-25
Lo, Weilun
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
423 9012, 423 9015, F01L 902, F02D 1302, F02D 4114, F02D 4124
Patent
active
056900651
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The present invention relates to a process for optimizing the air filling of an internal combustion engine cylinder under a heavy load and, more specifically, to a process of this type implemented with the aid of means which make it possible to vary the instant at which an intake valve associated with this cylinder closes. The object of the present invention is also to provide a device for implementing this process.
Conventionally, the "lift" of an intake or exhaust valve is controlled by a cam which is interdependent with the crankshaft of the engine or with a camshaft which rotates in sync with the crankshaft. The mechanical link established between each valve and the associated control cam is desmodromic, and the "events" which are constituted by the opening or closing of the valve occur at predetermined, invariable moments in the operating cycle of the engine, or "engine cycle."
It is currently proposed that these events be made to occur in a controlled, variable way, in order to adjust, for example, the quantity of air or air/fuel mixture taken in by a cylinder of the engine, or even the quantity of combustion gas retained in this cylinder.
This presupposes the availability of means which make it possible to control the "lift" of the valves with the requisite flexibility, a flexibility which is absent from the conventional cam mechanisms. Electromechanical devices, for example with electromagnets, and mechanohydraulic devices such as that schematically shown in FIG. 1 in the appended drawing, have been specifically designed for this purpose.
The latter device comprises, as shown, a conventional cam 1 which acts on a valve 2 through a chamber 3 which is fixed in relation to the engine 4, which has four cylinders 4.sub.1, 4.sub.2, 4.sub.3, 4.sub.4, for example. The chamber 3 is filled with a liquid under pressure such as the lubricating oil for the engine, delivered by an oil pump 5 through a conduit 6 equipped with a nonreturn valve 7.
The chamber 3 is closed by two end pistons 8 and 9. The piston 8 is normally loaded against the cam 1 by the oil pressure established in the chamber. The valve 2 is interdependent with the piston 9, and loaded against a seat provided in the associated cylinder 4.sub.1 by a spring 10 which is powerful enough so that the oil pressure in the chamber 9 alone can not cause a "lift" of the valve. A two-way solenoid valve 11 with two positions makes it possible to control the oil pressure in the chamber, by selectively connecting it to a tank 12 out in the open. Devices of this type are well known, and further details related to them could be obtained by referring to U.S. Pat. Nos. 4,133,332; 4,615,306; and 4,796,573.
The operation of the mechanism shown in FIG. 1 is described as follows: When the solenoid valve 11 is driven to be in the position shown in the figure, the chamber 3 is disconnected from the tank 12 and the nonreturn valve 6 prevents any backflow of oil toward the conduit 6. The incompressibility of the oil contained in the chamber 3 results in the transmission of the displacements of the piston 8, under the pressure from the cam 1, to the piston 9 and to the valve 2. Therefore this valve is subject to the displacements imposed on it by the cam 1. If the solenoid valve is driven so as to connect the chamber 3 with the tank 12, the pressure in this chamber drops and the chamber empties, at least partially, into the tank when the cam 1 causes the piston 8 to descend. At this point there is no longer a transmission of the displacements of the piston 8 to the valve, which remains in its seat in the closed position.
It is understood that by controlling the excitation of the solenoid valve in the appropriate way, it is possible to vary the instants at which the valve 2 opens and closes, since the mechanism described has a short response time which is compatible with the duration of the operating cycles of the engine, even at high speed.
This control presupposes that a computer 13 associated with the engine generates
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Vehicle Electronics in the 90's: Proceedings of the International Congress on Transportation Electronics, (BEHR) pp. 325-333; Oct. 1990.
Greenberg Laurence A.
Lerner Herbert L.
Lo Weilun
Siemens Automotive S.A.
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