Internal-combustion engines – Poppet valve operating mechanism – With means for varying timing
Reexamination Certificate
1998-07-28
2001-02-06
Lo, Weilun (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
With means for varying timing
C123S090110, C123S306000, C123S346000
Reexamination Certificate
active
06182621
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application claims the priority of German Application No. 197 33 139.4 filed Jul. 31, 1997, which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
For influencing the formation of mixture and the motion of a charge in cylinders of externally ignited piston-type internal-combustion engines, published International Application WO 91/14858 describes means in the region of the intake valves for a controllable flow deflection as the intake gas passes from the intake opening into the cylinder. An insufficient mixture formation is caused by an insufficient or missing vacuum in the intake pipe due to a poor fuel vaporization and cannot be improved at a fully open cross-sectional flow passage area of the valve because of the low intake velocity. Slides, gates, pivotal nozzles and the like are proposed as means for deflecting the flow. Such elements are arranged in the channel-like intake port immediately in the region of the intake opening and are operated by suitable setting means as a function of the operational condition of the engine. The setting means are actuated by a control device to so deflect the inflowing air/fuel mixture (hereafter designated as gas flow) under certain operational conditions that during the suction stroke within the cylinder chamber a turbulence (vortex) is generated whose rotary axis extends essentially transversely to the cylinder axis. It is a disadvantage of such an arrangement that the flow deflecting elements are disposed and supported in the intake port immediately upstream of the intake opening, that is, in a region in which only little room is available for additional structural components.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an improved method of the above-outlined type which affects the mixture formation and the charge motion in engine cylinders without the need of encumbering structural components.
This object and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the method of affecting a mixture formation and motion of a charge in a cylinder of an externally ignited internal-combustion engine during a suction cycle of a gas intake valve of the cylinder is performed such that during a beginning (leading) and/or terminal (trailing) portion of the suction cycle the valve is opened and maintained open only partially at a valve stroke which is less than one half of its full stroke and for the remainder of the suction cycle the gas intake valve is fully open at a full valve stroke.
By changing the cross-sectional area of the valve flow passage as outlined above, the mixture preparation and charge motion may be advantageously affected. By initially providing only a small cross-sectional flow passage area, the mixture preparation is improved and subsequently, by opening the valve to the full cross-sectional flow passage area, the combustion chamber is filled with the fresh mixture. In the first phase of the piston stroke the fuel/air mixture flows into the combustion chamber at a high velocity through the only slightly opened cylinder valve, positively supporting the mixture preparation and mixture homogenization. The charge quantity required for obtaining a desired load point may, however, not be obtained with a constantly small cross-sectional area of the flow passage so that during the same opening phase (suction cycle) the cylinder valve is fully opened by a suitable control system to thus ensure an optimal filling of the combustion chamber with a fresh mixture.
The method according to the invention may be performed in several ways. Thus, according to a preferred embodiment of the invention, in the beginning the open period of the gas intake valve during a full “closed-open-closed” suction cycle, the valve is maintained only partially open and only for a short period, at the end of which the valve is closed and shortly thereafter re-opened to the full flow passage area. In this manner with a first, partial mixture charge a motion is initiated in the cylinder chamber at an increasing vacuum, so that subsequently, at full valve opening, the full charge quantity may flow in with high speed by virtue of the increased vacuum.
According to another preferred embodiment of the method of the invention, the gas intake valve is first opened to the full cross section, thereafter maintained at a partially open state and then fully closed. With such a method too, it is possible to introduce a residual quantity of fresh gas at high velocity into the cylinder towards the end of the suction cycle and to thus favorably affect the charge motion in the cylinder. As a variant, the valve may be fully closed after the initial full opening and thereafter opened and maintained briefly in a partially open state.
The above-outlined different modes of operation may be combined with one another dependent upon the load conditions, and it is also feasible to control, in engines having a plurality of gas intake valves for each cylinder, all or only a single valve of the cylinder with the method according to the invention.
While it is in principle feasible to obtain the inventive suction cycle characteristics of the cylinder valve by mechanical drives, the method according to the invention finds particularly advantageous application in piston-type internal-combustion engines whose cylinder valves are operated by electromagnetic actuators in which the control periods are freely variable. Thus, by different opening and closing moments for the individual suction cycle stages (partially open or fully open cross-sectional flow passage area), different open periods for the suction cycle stages can be obtained.
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patent: 5860399 (1999-01-01), Speil et al.
patent: 91/14858 (1991-10-01), None
Esch Thomas
Salber Wolfgang
FEV Motorentechnik GmbH & Co. KG
Kelemen Gabor J.
Lo Weilun
Venable
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