Valves and valve actuation – Electrically actuated valve – Solenoid having plural coils
Reexamination Certificate
2000-05-23
2001-11-27
Fox, John (Department: 3753)
Valves and valve actuation
Electrically actuated valve
Solenoid having plural coils
C251S129160, C335S281000
Reexamination Certificate
active
06322048
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
Priority is claimed under 35 U.S.C. §119 with respect to German Patent Application No. 199 24 814.1-33 filed on May 29, 1999.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an actuator for electromagnetic valve control with two electromagnets, between which a retaining plate with at least one tappet oscillates, and which in each case consists of a yoke with a coil window and an exciting coil.
2. Description of the Related Art
An actuator for electromagnetic valve control substantially consists of the opening magnet and the closing magnet, which are separated from one another by at least one component made of a nonferromagnetic material. This component can, for example, be a housing part. The retaining plate made of a ferromagnetic material is located between the electromagnets, the opening magnet and the closing magnet; it is moved in the appropriate direction by applying current to the exciting coil of the opening magnet or the exciting coil of the closing magnet. The yoke of the opening magnet has a bushing for a valve tappet which transmits forces acting upon the retaining plate to at least one intake/exhaust valve.
The actuator can, for example, be so designed that the actuator spring is arranged on the outside of the closing magnet on the side of the actuator opposite to the intakelexhaust valve. For this, a spring tappet having an actuator spring plate is arranged as an extension of the valve tappet, the spring tappet being seated by a bushing in the yoke of the closing magnet. The yoke of the closing magnet has a formed shape, in which an internal thread is tapped and which creates a wall around the bushing of the spring tappet. A screw cap is screwed into the internal thread of the wall which screw cap, together with the wall, forms a hollow space in which the actuator spring is arranged lying on the actuator spring plate. The pretensioning of the actuator spring can be changed by turning the screw cap, thus making the rest position of the retaining plate adjustable.
An actuator together with an intake/exhaust valve forms a functional unit in which the intake/exhaust valve, corresponding to a conventional cylinder head with camshafts, is pulled into the valve seat of the cylinder head by a valve spring and a valve spring plate.
If a functional unit consisting of an actuator and an intake/exhaust valve is mounted on the internal combustion engine, then the valve stem of the intake/exhaust valve, the valve tappet and the spring tappet of the actuator are pressed against each other. In the rest position of the functional unit, the retaining plate is located in the middle between the opening magnet and the closing magnet, with the valve spring and the actuator spring being pretensioned. Here, the valve plate of the intake/exhaust valve is located in the middle position between the valve seat of the cylinder head, in which the intake/exhaust valve is closed, and the position in which the intakelexhaust valve is maximally opened.
As a result of the continually changing magnetic fields of the electromagnets during the operation of an actuator for electromagnetic valve control, eddy currents arise in the yokes of the electromagnets which, in accordance with Lenz's Law, counteract the build-up and degradation of the magnetic field. During operation of the actuators this results in an increase in power consumption and an increase in undesirable heating of the actuators.
In order to prevent the formation of eddy currents, U.S. Pat. No. 4,715,331 proposes, for example, that the yokes of the electromagnets be composed of low-retentive metal sheets analogous to the iron core of a transformer.
The disadvantages of such laminated yokes lie in the low mechanical strength of the laminated core and in the high number of individual parts which have to be handled and machined during the manufacture of the electromagnets.
BRIEF SUMMARY OF THE INVENTION
The object of the invention is to specify an actuator for electromagnetic valve control with two electromagnets, each of which consists of a yoke with a coil window and an exciting coil, in which the eddy currents in the yokes of the electromagnets are effectively suppressed and in which the yokes possess the required mechanical strength.
In accordance with the invention, this task is solved by the features in patent claim
1
, according to which both yokes of the electromagnets consist of at least two solid yoke parts, and according to which the solid yoke parts, of which there are at least two, are joined to one another.
In this case, the solid yoke parts, of which there are at least two, are so formed that the surfaces of the solid yoke parts, of which there are at least two and which are joined to one another, form slots that prevent eddy currents. In this case, the slots that prevent the eddy currents do not need to be arranged parallel to one another.
In an advantageous further development of the invention, the surfaces in contact as a result of the joining of the solid yoke parts, of which there are at least two, are designed to have a surface which supports the joint.
The solid yoke parts, of which there are at least two, of the respective yoke can be welded to one another.
In this case, the welded joint is so arranged that the surfaces of the solid yoke parts that are to be joined, of which there are at least two, provide a high ohmic resistance to the current flowing in the yoke parts, of which there are at least two. For example, a welded joint can be made at one edge of the yoke parts that are to be joined, of which there are at least two, in such a manner that a small distance remains between the yoke parts, of which there are at least two.
Alternatively, the solid yoke parts, of which there are at least two, of the respective yoke can be joined to one another by adhesive.
In this case, the adhesive for bonding the yoke parts is provided to have a high ohmic resistance.
An epoxy resin, to which an electrically insulating filler is added, can be used as the adhesive.
The actuator for electromagnetic valve control in accordance with the invention effectively suppresses the formation of eddy currents in the yokes of the electromagnets, and these yokes possess the required mechanical strength.
The actuator for electromagnetic valve control with two electromagnets, each consisting of a yoke with a coil window and an exciting coil, is shown and described by means of two embodiments in the following with reference to three figures.
REFERENCES:
patent: 2498702 (1950-02-01), Nahman
patent: 2796561 (1957-06-01), Rigoulot
patent: 4715331 (1987-12-01), Kreuter
patent: 4887059 (1989-12-01), Asano et al.
patent: 5207410 (1993-05-01), Wakeman
patent: 6155503 (2000-12-01), Benson et al.
patent: 09303599 A (1997-02-01), None
patent: WO 91 06109 A (1991-05-01), None
Gramann Matthias
Maute Kurt
Muller Christoph
Nagel Michael
Thiel Wolfgang
Daimler-Chrysler AG
Fox John
Kunitz Norman N.
Venable
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