Valves and valve actuation – Electrically actuated valve – Balanced valve
Reexamination Certificate
2002-10-28
2004-10-05
Jacyna, J-Casimer (Department: 3754)
Valves and valve actuation
Electrically actuated valve
Balanced valve
C251S129210
Reexamination Certificate
active
06799746
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to an electromagnet which can be applied in a particularly advantageous manner to a proportional magnet, which is arranged within a hydraulic system of an apparatus for varying the control times of inlet or outlet valves for an internal combustion engine, for operating a hydraulic valve.
BACKGROUND TO THE INVENTION
DE 195 04 185 A1 discloses an electromagnet of this general type for operating a hydraulic valve. It has a coil former which is fitted with at least one coil winding and has an external circumference surrounded by a magnet housing. At the end, this coil former is bounded by an upper pole shoe, which is formed by an annular pole disk with a pole tube inserted in it and on which an electrical connecting body rests. It is also bounded by a lower pole shoe, which is formed by a pole plate with an integrally formed pole core and projects into the hollow cylinder of the coil former. The hollow cylinder of the coil former is clad with a nonmagnetic metal tube, having a cavity in the form of an armature space for a cylindrical magnet armature which moves axially. The magnet armature in turn divides the armature space into a first chamber and a second chamber, which are connected to one another via a number of eccentric axial holes in the magnet armature, in order to equalize the pressure of operating fluid which enters the armature space via the hydraulic valve. Furthermore, a push rod is mounted in a central basic hole in the valve-side end face of the magnet armature, is passed through a likewise central axial hole in the lower pole shoe, and is connected to a control piston which is arranged in the interior of a valve housing of a hydraulic valve. The valve housing of the hydraulic valve case rests on the lower pole shoe of the electromagnet, forming a seal. The interior of the valve housing, which guides the control piston, is connected to the first chamber of the armature space via a further eccentric hole, which is arranged alongside the central axial hole, in the lower pole shoe for pressure equalization.
However, this known electromagnet has the disadvantage that its individual parts require precise and costly manufacture and a high level of installation complexity due to their design configuration and their arrangement with respect to one another, causing production of such an electromagnet to be expected to be very costly. For production engineering, for example, it has been found to be very costly to design the magnet armature and the push rod as an assembly in which these items are firmly connected to one another, while at the same time passing the push rod through the central axial hole in the lower pole shoe. This requires complex calibration work on all the parts to avoid axial offsets between the longitudinal axis of the magnet armature and the longitudinal axis of the push rod, and between the push rod and the longitudinal axis of the central axial hole in the lower pole shoe. Such axis offsets would cause the radial air gaps between the magnet armature and the armature guide and/or between the push rod and the axial hole to not be of equal magnitude. In consequence, the magnet armature or the push rod thus rest on the armature guide or on the axial hole at one point when a current or flow is passed through the electromagnet, causing a friction force to act on the magnet armature in the opposite sense to its movement direction. This could lead to unacceptably high hysteresis. Furthermore, however, the eccentric pressure equalizing channels arranged in the magnet armature and in the lower pole shoe have been found to be highly costly, since they normally have to be drilled, and eccentric incorporation of these holes significantly increases the manufacturing costs.
OBJECT OF THE INVENTION
The invention therefore has the object of providing an electromagnet, in particular a proportional magnet for operating a hydraulic valve, wherein its individual parts and their arrangement with respect to one another are physically simple, involve a low level of manufacturing and assembly effort, and have optimized-cost production. At the same time, it optimally guides the magnet armature and the push rod and has adequate capabilities for pressure equalization between the first chamber and the second chamber of the armature space, as well as between the first chamber and the interior of a valve housing.
SUMMARY OF THE INVENTION
According to the invention, this object is achieved for an electromagnet wherein the push rod, which is guided in the axial hole in the lower pole shoe, is in the form of a loose profiled rod which is separated from the magnet armature. The cross-sectional shape of the rod is different from that of the axial hole and its cross-sectional area is less than that of the axial hole, so that the free cross-sectional spaces within the axial hole in the lower pole shoe may also be used as pressure equalizing channels between the interior of the valve housing of the hydraulic valve and the first chamber in the armature space of the electromagnet. The separation of the push rod from the magnet armature of the electromagnet has the advantages that it is no longer possible for any axis offsets to occur between the longitudinal axis of the magnet armature and the longitudinal axis of the push rod, or between the latter and the longitudinal axis of the axial hole in the lower pole shoe, and that both the magnet armature and the push rod can thus be guided optimally, separately from one another. The axial hole in the lower pole shoe is preferably in the form of a central through-hole with a circular profile cross section, having a diameter that corresponds approximately to the largest profile width of the push rod. This makes it possible to guide the push rod exactly in the axial hole in the lower pole shoe, while at the same time saving the previously normal separate pressure equalizing channels, which were formed by complex eccentric holes in the lower pole shoe, since these are now formed by the free cross-sectional spaces which are produced alongside the profiled push rod in the axial hole.
A further feature for optimized-cost production of the electromagnet is that the magnet armature, which has an end face that rests on the push rod, has a central longitudinal hole with a diameter that is smaller than the largest profile width of the push rod and that is larger than the smallest profile width of the push rod. As a result, the end face of the push rod only partially covers the longitudinal hole in the magnet armature so that the longitudinal hole can be used as a pressure equalizing channel between the first chamber and the second chamber in the armature space of the electromagnet via the free cross-sectional areas of its opening. This configuration is possible only because of the separation of the magnet armature and push rod and by the profiled configuration of the push rod. It has the advantage that a pressure equalizing channel between the chambers in the armature space of the electromagnet is formed by a single, central through-hole in the magnet armature. The through-hole can be produced relatively easily and possibly even without cutting. As a result, it is possible to save the previously normal separate pressure equalizing channels, which were likewise formed by costly eccentric holes or by axial grooves in the magnet armature. Those profile sections of the profiled push rod which project beyond the opening of the longitudinal hole in the magnet armature and rest on the end face of the magnet armature ensure that, despite the shape and size of the push rod, which is guided centrally in the lower pole shoe and despite the longitudinal hole, which is likewise arranged in the central magnet armature, a contact surface which is sufficient to transmit the electromagnetically produced axial movements of the magnet armature to the push rod is provided between the magnet armature and the push rod. The required continuous contact between the magnet armature and the push rod is ensured, in a manner which allows force
Ina-Schaeffler KG
Jacyna J-Casimer
Ostrolenk Faber Gerb & Soffen, LLP
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