Internal-combustion engines – Poppet valve operating mechanism – Electrical system
Reexamination Certificate
1999-11-16
2001-05-22
Lo, Weilun (Department: 3747)
Internal-combustion engines
Poppet valve operating mechanism
Electrical system
C251S129010, C251S129100, C251S129160
Reexamination Certificate
active
06234122
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims the rights of priority of German Patent Application No. 19852655.5-33 filed Nov. 16, 1998, the subject matter of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a method for driving an electromagnetic actuator for operating a gas change valve in which the actuator has at least one electromagnet and acts via an armature on the gas change valve against the force of at least one valve spring and operates the gas change valve by movement of the armature.
Electromagnetic actuators are usually used in internal combustion engines for operating gas change valves with which the inflow and outflow of a working fluid is controlled respectively into and out of the combustion chambers of the internal combustion engine.
Such an actuator is known, for example, from DE 196 31 909 A1. This previously known actuator has two electromagnets—a closing magnet and an opening magnet—with pole surfaces situated opposite to one another and an armature that can move axially between the pole surfaces of the electromagnets and which acts on the gas change valve to be operated in opposition to the force provided by two valve springs. In non-energized electromagnets, the armature is held securely in a position of equilibrium approximately mid-way between the pole surfaces of the electromagnets due to the oppositely acting valve springs.
By alternately energizing, i.e. switching on and off, the two electromagnets, the armature and hence also the gas change valve is attracted away from the position of equilibrium by the electromagnet being energized and held securely at the pole surface of this electromagnet for the period over which current is being applied. The gas change valve is than in a closed position when the armature is located against the pole surface of the electromagnet functioning as closing magnet, and in an open position when the armature is located against the pole surface of the electromagnet functioning as opening magnet.
In the previously known actuator, the position of equilibrium of the armature is determined by measuring the inductances of the two electromagnets and by a comparison of the two measured Inductance values, and in the event of a deviation from the desired value the position of equilibrium is readjusted.
Furthermore, from U.S. Pat. No. 4,823,825 it is known that in an actuator of the type named at the outset the impact of the armature on the energized electromagnet is detected by a brief drop followed by a renewed rise in an excitation current flowing through this electromagnet. The absence of this brief drop in the excitation current indicates that a faulty function has already occurred although this cannot be avoided, it is detected immediately and therefore allows measures to be initiated To rectify the fault.
The problem is unsolved, however, of eliminating in the control the influence of operational system parameters, especially fluctuations in friction, temperature and pressure in the combustion chambers as well as changes in the viscosity of the lubricant and wear or dirtying of the actuator or gas change valve. This can result in incorrect functioning of the actuator and in particular to increased wear of the actuator, undesired noise development end increased power consumption. Reliable continuous duty of the actuator is therefore not assured.
SUMMARY OF THE INVENTION
The object of the invention is to provide a method for driving an electromagnetic actuator for operating a gas change valve in which the actuator with at least one electromagnet acts via an armature and counter to the force of at least one valve spring upon the gas change valve and operates the gas change valve by movement of the armature that makes reliable continuous duty possible.
In accordance with the invention, the object is solved by a method for driving an electromagnetic actuator for operating a gas change valve in which the actuator with at least one electromagnet acts via an armature on the gas discharge valve against the force of at least one valve spring and operates the gas change valve by movement of the armature, wherein a controlled variable (V
IST
) that depends on a change in inductance of the electromagnet is created as a measure of the impact velocity of the armature on the electromagnet, and wherein the controlled variable is adjusted to a setpoint value (V
SOLL
), which corresponds to a predetermined value of the impact velocity of the armature on the electromagnet, by controlling the supply of energy to the electromagnet. Advantageous variants and developments are disclosed and discussed.
The invention is based on the fact that the movement of the armature causes a change in the inductance of the electromagnet. The change in inductance of the electromagnet is therefore a measure of the armature velocity and consequently it is also a measure of the impact velocity of the armature on the electromagnet or the impact velocity of the gas change valve in a valve seat.
In accordance with the Invention, a controlled variable that depends on the change in inductance of the electromagnet is created as a measure of the impact velocity of the armature on the electromagnet. This controlled variable is varied by controlling the supply of energy to the electromagnet in such a way that the impact velocity of the armature on the electromagnet assumes a predetermined, i.e. demanded, value and is thus limited. This ensures that the armature is supplied with sufficient energy in order to move it to the electromagnet and hold it there, even if the system parameters change; furthermore the supply of energy is reduced to a necessary extent. This leads to fault-free operation and to a Iowa consumption of electrical power, less wear, lower noise development and to avoidance of rebounding of the armature or gas change valve from the electromagnet or valve seat.
In an advantageous development of the method, the controlled variable is created by measuring the rate of current decrease of an excitation current flowing through the electromagnet while the armature is moving. In a further advantageous development of the method, the variation of the inductance of the electromagnet is measured over a period of time and the velocity of the armature at the point of time when it impacts the electromagnet is derived as controlled variable from this inductance curve.
The inductance curve is obtained by measuring the inductance of the electromagnet over successive intervals of time. Advantageously, the inductance of the electromagnet is determined from the variations over time of an excitation voltage supplied to the electromagnet and of an excitation current flowing through the electromagnet. It is also advantageous to measure the resonant frequency of a LC oscillating circuit formed from the electromagnet and a capacitance or to measure the complex impedance of the electromagnet by means of a high-frequency measuring signal supplied to the electromagnet and the determination of the inductance of the electromagnet from the resonant frequency or from the complex inductance.
Preferably, the controlled variable is compared with a given setpoint value and a next closing time point of the electromagnet is specified in accordance with the result of the comparison. Consequently, the energy that must be supplied to the armature during the next operation of the gas change valve is controlled in such a way that the impact velocity of the armature on the electromagnet is adjusted to the given value.
The setpoint value of the controlled variable is equivalent to the specified value of the impact velocity of the armature on the electromagnet. It is advantageously specified as a function of system parameters, in particular as a function of the friction, the temperature, and the pressure prevailing in the combustion chamber when the gas change valve is opened. Preferably, also the closing time points of the electromagnet are specified as a function of system parameters. It has been found to be particularly advantage
Kirschbaum Frank
Maute Kurt
Pandit Madhukar
Virnich Michael
Daimler-Chrysler AG
Kunitz Norman N.
Lo Weilun
Spencer George H.
Venable
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