Electricity: electrical systems and devices – Control circuits for electromagnetic devices – For relays or solenoids
Reexamination Certificate
1999-12-06
2001-10-02
Jackson, Stephen W. (Department: 2836)
Electricity: electrical systems and devices
Control circuits for electromagnetic devices
For relays or solenoids
C361S170000, C361S187000
Reexamination Certificate
active
06297941
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The invention relates to a device for controlling an electromechanical actuator which has an actuating element and an actuating drive. The actuating drive has a moveable armature plate and an electromagnet with a core and a coil. A controller is provided. The control variable of the controller is the current through the coil and its actuating variable is a voltage which is applied to the coil. The invention relates, in particular, to an actuator for controlling an internal combustion engine.
A prior art actuator of this type with an actuating element and an actuating drive is described, for instance, in U.S. Pat. No. 5,053,911 (European publication EP 0 400 389 A2). There, the actuating drive comprises an electromagnet with a core and with a coil. The electromagnet is disposed in a housing. An armature plate is arranged moveably relative to the first electromagnet and is prestressed into a predetermined position of rest by a spring. In order to bring the armature plate out of its position of rest into bearing contact with the first electromagnet, the coil is energized with a pickup current (attraction current). The pickup current generates an electromagnetic force which pulls the armature plate onto the electromagnet counter to a force generated by the spring. The actuator is assigned a two-state controller with hysteresis, the control variable of which is the current through the coil and the actuating variable of which is a pulse-shaped voltage signal which is applied to the coil.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a device for controlling an electromechanical actuator, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which device is simple and ensures accurate, in particular accurately timed, control of the actuator.
With the foregoing and other objects in view there is provided, in accordance with the invention, a device for controlling an electromechanical actuator having an actuating element and an actuating drive with a moveable armature plate and with an electromagnet having a core and a coil. The control device comprises:
a controller having a current through the coil as a control variable, and having a voltage applied to the coil as an actuating variable;
a voltage source connected to the controller for generating a supply voltage; and
the controller having a pulse width modulator adapted to modulate the actuating variable, starting from a jump in a desired value of the controller at least until an actual value of the controller reaches the desired value, in dependence on the supply voltage.
The invention is equally applicable to an actuating element with a second electromagnet that has a further core and a further coil and that is disposed at a predetermined distance from the first electromagnet. In that case there is provided a second controller having the current through the further coil as a control variable and the voltage applied to the further coil as an actuating variable; and a second pulse width modulator modulates the actuating variable of the second controller in dependence on the supply voltage.
In other words, the objects of the invention are satisfied with the pulse width modulator that modulates the actuating variable as a function of the supply voltage. Thus, a constant switching time, irrespective of fluctuations in the supply voltage, is ensured. The switching time is defined as the time required to bring the armature plate from a predetermined position of rest into bearing contact with the electromagnet counter to a spring force generated by the spring. The constant switching time is an important advantage, since, particularly in the case of a motor vehicle, the supply voltage is subject to pronounced fluctuations. Another advantage is that a costly and complicated voltage regulator can be dispensed with, since the current profile in the circuit-closing phase of the regulator, that is to say before the regulating range of the regulator is reached, is, on average over time, always the same, irrespective of the supply voltage, even though only control by the regulator takes place.
In accordance with an advantageous implementation of the invention, the actuating element is a gas exchange valve and the actuator is arranged in an internal combustion engine. Thus, constant switching times of the gas exchange valve, irrespective of the supply voltage, and, consequently, low-consumption and low-emission operation of the internal combustion engine are ensured.
In accordance with a concomitant feature of the invention, the controller is a two-state controller with hysteresis.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a device for controlling an electromechanical actuator, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
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Hoffmann Christian
Koch Achim
Wimmer Richard
Greenberg Laurence A.
Jackson Stephen W.
Lerner Herbert L.
Siemens Aktiengesellschaft
Stemer Werner H.
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