Internal-combustion engines – Poppet valve operating mechanism – Electrical system
Reexamination Certificate
2000-02-22
2001-09-18
Lo, Weilun (Department: 3748)
Internal-combustion engines
Poppet valve operating mechanism
Electrical system
C123S090650, C251S129150, C251S129190, C335S277000
Reexamination Certificate
active
06289858
ABSTRACT:
This application claims the priority of German Application Nos. 198 49 690.7 filed Oct. 28, 1998 and 199 22 972.4 filed May 19, 1999, which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
German Offenlegungsschrift (application published without examination) No. 33 07 070 discloses an electromagnetic actuator for operating a component, particularly a cylinder valve of an internal-combustion engine. The actuator has an armature which may be reciprocated back and forth between two electromagnets by magnetic forces against oppositely oriented resetting springs. The actuator system is designed in such a manner that in case the electromagnets are in a de-energized state, the armature, urged by the oppositely acting resetting springs, assumes a position between the two pole faces. In such a known system it is assumed that the two resetting springs are identical in their geometry, especially as concerns their length in a relaxed state and their spring curve. The purpose of such an identical arrangement is to ensure that essentially identical magnetic forces are needed for attracting and holding the armature at the respective pole faces and that essentially identical spring forces are present first, for accelerating the armature when its leaves the respective pole face and second, for braking the armature when it approaches the respective opposite pole face. Such springs are conventionally compression coil springs. In a mass manufacture of such coil springs, however, it is not feasible to make identical springs in sufficient quantities at an acceptable cost.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an improved actuator of the above-outlined type which permits greater tolerances for the geometry and characteristics of the resetting springs.
This object and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the electromagnetic actuator for operating a driven component includes first and second electromagnets having respective first and second pole faces oriented toward one another and defining a space therebetween; an armature disposed in the space and movable back and forth between the first and second pole faces; a driving component attached to the armature for moving therewith as a unit; and a resetting spring assembly coupled to the armature and exerting forces opposing movements of the armature caused by electromagnetic forces generated by the electromagnets. The resetting spring assembly is in a relaxed state when the armature is in a mid position between the first and second pole faces. A coupling device connects the driving component with the driven component for effecting a transmission of moving forces from the driving component to the driven component to cause displacements of the driven component as a function of displacements of the armature and the driving component. The coupling device includes a length-compensating arrangement between the driving and driven components.
An actuator according to the invention as summarized above has the advantage that the resetting spring arrangement may be composed of compression springs or tension springs or bending springs and, in particular, may be composed of a sole spring. When the armature moves out of its mid position between the two pole faces, the spring arrangement is armed to exert a resetting force on the armature against the magnetic force, and in either direction of motion the spring behavior is practically identical. The coupling device provides for the required form-fit between the driving component (such as a guide bar affixed to the armature) and the driven component (such as an engine valve of an internal combustion engine). In this manner the armature and the driven component are reciprocated as a unit in response to pushing and pulling forces. Further, by the slack adjusting means incorporated in the coupling device a reliable end position of the armature and the driven component are ensured.
Thus, if the electromagnetic actuator is used for operating an engine valve, in the de-energized state of the electromagnets the engine valve is maintained by the resetting spring arrangement in a halfway open stroke so that upon energization of one of the electromagnets, the engine valve is moved into the closed position and upon energizing the other electromagnet, the engine valve is moved into the fully open position. To counteract external interferences which disturb the operation of the engine valves, such as the fluctuating temperatures which result in alternating lengths of the driving and the driven components, and also to compensate for component wear which may likewise lead to length changes, the coupling element provides for an automatic length compensation. In particular, in case the actuator is used for driving an engine valve, it is of importance that in the closed position of the engine valve the valve head lies tightly against the valve seat and at the same time the armature engages the pole face of the closing magnet. Only these simultaneous occurrences ensure that the closed position of the valve may be maintained with a minimum holding current and thus with a small energy input. Upon an increase of the operating temperature, the driving component (that is, the guide bar affixed to the armature) as well as the driven component (that is, the valve stem of the engine valve) lengthen. Consequently, in case of a rigid coupling between the two components the valve head would no longer engage its valve seat when the armature lies against the pole face of the closing magnet. Therefore, the coupling device according to the invention is so designed that an overall length change of the two components (lengthening or contracting) is compensated for. Thus, in the cold condition when the total length of the components is reduced, the armature may arrive into contact with the pole face of the closing magnet when the valve head has reached the valve seat, and likewise, in case of a lengthening due to a heat-up of the valve seat, the valve head may be firmly seated when the armature has reached the pole face of the closing magnet. In this manner an automatic compensation is achieved so that in the closed position the valve head as well as the armature reliably assume at all times their contacting position with the valve seat and the pole face of the closing magnet, respectively.
According to the invention, the coupling device is resiliently yielding at least in the direction of motion of the driving and driven components. In an internal-combustion engine environment the structure of the coupling device is such that even in case of the maximum feasible overall length change of the driving and driven components, the coupling device is still at least slightly armed (tensioned) when the valve body engages the valve seat and the armature engages the pole face of the closing magnet to ensure a reliable closed position of the valve.
Further according to the invention, the coupling device has a closed housing, serving as a basis for a number of various structural variants.
Thus, according to a first embodiment, the housing has elastic walls. Such a housing may be composed of a sleeve made, for example, of an elastomer having reinforcing fiber or metal inserts. The resilient sleeve is fixedly attached at its opposite ends to the driving and driven components, respectively, and its inner space is sealed outwardly. The required elasticity for bridging the clearance between the driving and driven components is ensured by the resilient housing material and possibly also by the particular shape of the housing. When the housing is exposed to pulling forces, the clearance between the two components increases, while in case of compressing forces the two components arrive in a direct, end-to-end contact with one another.
The sealed inner housing chamber is filled with a liquid for obtaining a dampening effect. If, during displacement of the system the coupling device is exposed to compression, the driving and the driven c
Altdorf Joachim
Hartmann Ernst-Siegfried
Schebitz Michael
Schwaderlapp Thomas
Wahnschaffe Jurgen
FEV Motorentechnik GmbH
Kelemen Gabor J.
Lo Weilun
Venable
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