Internal-combustion engines – Poppet valve operating mechanism – Electrical system
Patent
1993-02-26
1994-05-31
Argenbright, Tony M.
Internal-combustion engines
Poppet valve operating mechanism
Electrical system
123 9012, 123 9048, 251 57, 25112901, 137909, F01L 902, F01L 904, F01L 2502
Patent
active
053159616
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND AND SUMMARY OF THE INVENTION
This invention relates to a valve tappet for an internal-combustion engine and, more particularly, to a hydraulic valve tappet for an internal-combustion engine, having a housing which is disposed in a receiving device and having a piston which is displaceably guided in this housing. The piston is connected with a charge cycle valve.
Tappets of this type are used for the transmission of forces acting between the camshaft and the intake and the exhaust valves. In modern high-performance internal-combustion engines, cup-shaped valve tappets are frequently used which are disposed in the cylinder head to be directly displaceable between the cams and the valves. These are usually connected to the oil circulating system and cause a hydraulic valve clearance compensation which renders respective servicing operations superfluous, as known, for example, from the German Patent Document DE-37 24 655.
For improving the torque, the emission, the fuel consumption and the idling quality, it is known to design the valve stroke and/or the valve overlap to be variable. A cam-controlled valve tappet which influences the valve stroke using a hydraulic arrangement is disclosed, for example, in the German Patent Document DE-36 25 627. The tappet shown there is in an operative connection with a charge cycle valve by way of a hydraulic space. For the variation of the valve stroke, a portion of the hydraulic fluid can be discharged from the hydraulic space by a control valve.
A survey of variable valve actuating mechanisms is disclosed in SAE Paper 891674, "A Survey of Variable Valve Actuation Technology".
From the journal Automotive Engineering, Volume 91, Number 11, 1983, Pages 61-66, it is known to construct a valve, through which an electroviscous fluid (EVF) flows, of several cylinder shells which are arranged coaxially with respect to one another and which are spaced with respect to one another by radially extending struts. This valve is inserted as a piston into a hydraulic cylinder through which an EVF flows. This fluid flows axially through the cylinder shells in an unimpaired manner so that the piston remains in its position. By the feeding of an electric field, the viscosity of the EVF can be changed arbitrarily within a very short time period from liquid to solid. In this case, the flow resistance between the cylinder shells increases so that the piston is displaced by the afterflow of fluid into the hydraulic cylinder.
From the German Patent Document DE-36 09 861, it is known to utilize the two electrodes and the EVF-layer disposed in-between as a movement sensor for the control and regulation of a hydraulic EVF-system (Oppermann effect). As a function of the flow rate of the EVF between the electrodes, a flow signal is generated in the electrodes which is fed to an electronic circuit which supplies a corresponding output voltage to the electrodes and therefore, in turn, affects the viscosity. The movement sensor therefore, at the same time, represents the control element for influencing the movement.
There is therefore needed a hydraulic valve tappet for an internal-combustion engine by means of which the valve stroke can be varied during the operation of the internal-combustion engine.
This need is met by a hydraulic valve tappet for an internal-combustion engine, having a housing which is disposed in a receiving device and having a piston which is displaceably guided in this housing. The piston is connected with a charge cycle valve. A rigid hydraulic high-pressure valve is fastened in the housing. A variable operating space is formed between the high-pressure valve and the piston, which is filled with a fluid. The viscosity of the fluid can be changed by the feeding of an electric voltage.
This valve tappet permits a continuous variation of the valve stroke of a charge cycle valve by the arrangement of a rigid high-pressure valve, that is, a high-pressure valve which has no moving parts, and of an operating space which is formed between this high-pressure valve and the disp
REFERENCES:
patent: 4840112 (1989-06-01), Bhadra et al.
patent: 4930463 (1990-06-01), Hare, Sr.
patent: 5014829 (1991-05-01), Hare, Sr.
patent: 5099884 (1992-03-01), Monahan
patent: 5103779 (1992-04-01), Hare, Sr.
patent: 5158109 (1992-10-01), Hare, Sr.
patent: 5161653 (1992-11-01), Hare, Sr.
Automotive Engineering by David Scott and Jack Yamaguchi entitled "Solidifying Fluid Transforms Clutches and Flow Valves", pp. 61-66, Nov. 1983.
SAE Technical Paper Series by T. Ahmad and M. A. Theobald entitled "A Survey of Variable-Valve-Actuation Technology", Aug. 1989.
Argenbright Tony M.
Dr. Ing. h.c.F. Porsche AG
Lo Weilun
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