Internal-combustion engines – Poppet valve operating mechanism – Hydraulic system
Patent
1996-05-06
1998-10-27
Lo, Weilun
Internal-combustion engines
Poppet valve operating mechanism
Hydraulic system
123 9015, 123 9016, F01L 902, F01L 1300
Patent
active
058265511
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for controlling the lift of a valve of an internal combustion engine cylinder, and more specifically, to a process of this type which makes it possible to vary the opening time of such a valve by controlling the triggering of "events" related to this valve. 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 thus the "events" 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 exhaust gas retained in this cylinder, as described, for example, in French patent 2 133 288.
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 represented in FIG. 1 of 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, 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 its seat by a spring 10 which is powerful enough so that the oil pressure in the chamber 9 alone cannot 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 represented 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 event triggering device constituted by the solenoid valve 11, it is possible to vary the instants at which the valve 2 opens or closes, since the mechanism described has a short response time which is consistent 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 and delivers, to another computer 14 for controlling the lift of the valve, a set-point val
REFERENCES:
patent: 4133332 (1979-01-01), Benson
patent: 4615306 (1986-10-01), Wakeman et al.
patent: 4724810 (1988-02-01), Poirier et al.
patent: 4796573 (1989-01-01), Wakeman et al.
patent: 5193494 (1993-03-01), Sono et al.
patent: 5363817 (1994-11-01), Ikeda et al.
patent: 5503120 (1996-04-01), Shirey et al.
Greenberg Laurence A.
Lerner Herbert L.
Lo Weilun
Siemens Automotive S.A.
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