Electricity: magnetically operated switches – magnets – and electr – Magnets and electromagnets – With magneto-mechanical motive device
Reexamination Certificate
2000-12-28
2001-12-04
Donovan, Lincoln (Department: 2832)
Electricity: magnetically operated switches, magnets, and electr
Magnets and electromagnets
With magneto-mechanical motive device
C335S255000, C335S257000, C251S129010, C123S090110
Reexamination Certificate
active
06326873
ABSTRACT:
DESCRIPTION
FIELD OF THE INVENTION
The invention concerns an electromagnetic valve drive that is installed in a cylinder head of an internal combustion engine and has the following features:
a) the valve drive is comprised of a gas exchange valve, an actuator rod, an armature, a closing magnet, an opening magnet, a closing spring and an opening spring, or a plurality of these;
b) the armature is preferably disc-shaped and connected to the actuator rod that acts at one end on the gas exchange valve;
c) the closing magnet is situated opposite a gas exchange valve-distal end face of the armature and the opening magnet is situated opposite a gas exchange valve-proximate end face of the armature, the closing and opening magnets being spaced from each other so that in an end position of the armature on the closing magnet, the gas exchange valve is closed and in an end position of the armature on the opening magnet, the gas exchange valve is open;
d) the closing and opening springs possess at one end a support on the cylinder head and act at another end on the gas exchange valve in opposite directions and at least indirectly through a retainer;
e) in each end position of the armature, one of the springs is pre-stressed so that on alternating energization of the closing and opening magnets, the valve drive functions as an oscillatory spring-mass system; and
f) at least one support or one retainer is adjustable in height.
BACKGROUND OF THE INVENTION
DE-PS 39 11 496 describes a generic valve drive of the pre-cited type. In this valve drive, the height of the closing spring can be varied through an eccentric. The variation of the height of the closing spring is intended to vary its resilient force so that the opening period of the gas exchange valve can be influenced.
However, a person of ordinary skill in the art finds no suggestion in the aforesaid document as to how disturbances that can have a negative influence on the oscillatory spring-mass system can be excluded in a simple manner. Such disturbances are mainly gas forces acting on the gas exchange valve and an increasing impact on the valve seat with increasing running time of the internal combustion engine. Installation tolerances can constitute additional disturbances. These can arise, for example, from differing lengths of the springs used but attention must also be paid to differing spring constants. In the most unfavorable case, these disturbances can lead to inoperatability of the oscillatory spring-mass system because the armature can no longer be excited out of its idle position to effect a complete oscillation between its end positions.
OBJECT OF THE INVENTION
The object of the invention is therefore to provide an electromagnetic valve drive of the aforesaid type in which the mentioned drawbacks are eliminated and in which, particularly, the discussed disturbances are excluded by simple measures.
SUMMARY OF THE INVENTION
The invention achieves this object by the features of the characterizing part of the main claim.
According to this claim, the valve drive comprises means for establishing an equilibrium between the closing and opening springs which is determined by symmetric energies of the closing and opening springs at a half stroke of the armature. These equilibrating means are preferably embodied in an axially displaceable support or retainer, and it is preferably the support of the closing spring that is configured for axial displacement.
Due to this equilibration, the energies of the springs are balanced which results in equal impact speeds of the armature in its end positions (on the magnets). A particular advantage of the means of the invention is that the equilibrium is permanently re-adjusted during the operation of the internal combustion engine. By raising or lowering the support of the closing spring, all the disturbances previously mentioned can be eliminated. Only very low levels of energy are required to activate and, in particular, to operate the spring-mass oscillatory system.
Although it is also conceivable to configure the support of the opening spring or the retainers with a variable height, the most appropriate solution is to vary the height of the support, i.e. the base, of the closing spring.
According to a further proposition of the invention, this support is configured as a hydraulically lifting annular piston. However, it is also conceivable to arrange a ball and ramp system or a wedge ramp adjuster in this region. Lifting can also be effected directly through mechanical, magnetic or electromagnetic means.
It is proposed that the closing and opening springs be configured to surround the valve stem and the actuator rod respectively. Advantageously, these springs extend axially outside of the magnets but if required, they can also be integrated in the magnet stack.
According to still another proposition of the invention, the duct for supplying the servo medium to the lifting the annular piston comprises closing means. These closing means permit a lift only when the armature is in abutment with the closing magnet. Further, according to the invention, an annular groove is arranged on the outer peripheral surface of the actuator rod and is aligned to a section of the duct only when the armature is in abutment with the closing magnet. Advantageously, this section of the duct extends through the closing magnet itself.
The supply of the servo medium to the duct is accomplished by an electromagnetic switching valve such as a 3/3 or 3/2 proportional valve. This switching valve can be energized by a control unit. To determine the impact speed of the armature on the closing and opening magnets, the control unit, in its turn, cooperates with measuring means known to a person skilled in the art. Due to the different impact speeds, different current flow paths result in the magnets. These are transmitted as information to the control unit. The torque or the load can optionally serve as further input quantities for the control unit. In this way, disturbances such as gas forces that have an indirect detrimental effect on the oscillatory system can be taken into account.
Advantageously, the retainers for the springs are made in the form of spring plates, known per se. At the same time, the valve drive of this application may comprise a hydraulic clearance compensation element. This reduces all clearances occurring in the valve drive to zero in a phase in which the gas exchange valve is closed. The clearance compensation element is supplied with hydraulic medium in a simple manner axially through the actuator rod.
Due to the fact that the support of the opening spring is made as a thrust bearing, the torques acting in the direction of rotation on the support upon a deflection of the opening spring are eliminated.
According to a final proposition of the invention, the annular piston is sealed relative to the annular recess radially inward and outward by at least one sealing ring. Due to this, only small losses of hydraulic medium are to be expected in this region. The sealing rings are preferably configured so that only low friction occurs between them and the annular gap and, at the same time, the sealing action is adequate.
REFERENCES:
patent: 5787858 (1998-08-01), Meneely
patent: 6067946 (2000-05-01), Bunker et al.
patent: 6076490 (2000-06-01), Esch et al.
patent: 6101992 (2000-08-01), Pischinger et al.
Bierman, Muserlian and Lucas
Donovan Lincoln
Ina Walzlager Schaeffler OHG
Nguyen Tuyen
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