Electricity: electrical systems and devices – Control circuits for electromagnetic devices – Systems for magnetizing – demagnetizing – or controlling the...
Reexamination Certificate
1998-08-13
2001-02-20
Fleming, Fritz (Department: 2836)
Electricity: electrical systems and devices
Control circuits for electromagnetic devices
Systems for magnetizing, demagnetizing, or controlling the...
C361S154000
Reexamination Certificate
active
06191929
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a control device for an internal combustion engine. The control device has a magnetic actuator with a coil and an armature, a final control element connected to the armature, a regulating unit for regulating a current in the coil and a measuring device for generating test signals which act on the coil.
A control device including an actuator having a coil, a core and an armature, a final control element and a regulating unit are described in Published European Patent Application EP 0 400 389 A2. To attract the armature to the core, the coil is supplied with an attraction current which has an amplitude that is large enough that the force required to accelerate and move the armature is available through the magnetic flux. When the armature abuts against the core, the current through the coil is limited to a holding current. An amplitude of the holding current is provided so that at least a holding force required to hold the armature on the core is applied through the magnetic flux.
The current through the coil is reset by an on-off controller to the respective theoretical value of the attraction current or of the holding current. In this case, the pulse/pause ratio of the actuation signal is dependent upon the attainment of an upper and a lower threshold value of the current.
The recognition of an instant of impact of the armature on the core has extremely great importance, since in the event of a delayed switch over to the holding current very high losses occur in the coil, which may lead to the thermal destruction thereof.
In the above-mentioned control device, the temporal duration of the pulses of the actuation signal is determined by the regulating unit and is used as an indirect measure of the inductance of the coil, which increases as the spacing between the core and the armature decreases. On this basis, the holding current is predetermined as a theoretical value when the determined time duration is above a limiting value. In this connection, it is a significant disadvantage that the instant of impact of the armature cannot be determined precisely. If the armature impinges on the core shortly before the current reaches its lower threshold value, then the impact cannot be detected until after the following pulse of the actuation signal. Accordingly, high losses arise in the coil, since the current is limited to the holding current too late. The losses can be reduced only in circumstances in which the attraction current has an appropriately low magnitude. However, this brings about an increase in the time which the armature requires to pass from a neutral position to abutment against the core. Accordingly, the final control element can no longer be driven as rapidly. This is a disadvantage, in particular in the case of injection valves or in the case of inlet/exhaust valves of an internal combustion engine.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a control device for an internal combustion engine which overcomes the above-mentioned disadvantages of the prior art devices of this general type, in which the response time and the losses of the control device are reduced.
With the foregoing and other objects in view there is provided, in accordance with the invention, a control device for an internal combustion engine, including: a magnetic actuator having a coil and an armature; a regulating unit connected to the magnetic actuator for regulating a current through the coil to a setpoint value if a pulse signal is present at the regulating unit; and a measuring device connected to magnetic actuator, the measuring device including: a signal generator for generating and supplying a test signal to the coil, the coil generating an output signal in dependence on the test signal; a measuring system receiving the output signal generated by the coil; and an evaluating device receiving the test signal and the output signal for determining an inductance value of the coil in dependence on the test signal and the output signal, the evaluating unit generating a first control signal in dependence on the inductance value, the first control signal changing the setpoint value to a holding value.
The invention is based on the finding that during the movement of the armature the inductance of the coil changes, and that when the armature resides on the core the inductance remains constant until the armature is released from the core. As a result of the determination of a change in the inductance, it is accordingly possible to determine a precise instant of impact of the armature on the core. To this end, the control device has a measuring device by which the inductance of the coil is determined and by which, as a function of the inductance, a first control signal is generated, by which the theoretical value is set to a holding value. The measuring device includes a signal generator, which generates a test signal which acts on the coil. Advantageously, the test signal has a small amplitude. Furthermore, a narrow-band test signal, the frequency of which is substantially higher than that of the current through the coil, is advantageous.
Preferably, the first control signal is generated when the inductance alters or changes by less than a lower threshold value in a predetermined time interval. The time interval can be selected to be so small that the instant of impact can be determined sufficiently precisely. It is extremely advantageous that the instant of impact can be determined independently of temperature and aging effects.
Preferably, a second control signal is generated when the inductance alters or changes by more than a predetermined upper threshold value in the time interval. As a result of this, it is also possible to precisely determine an instant of release of the armature from the core.
In accordance with an added feature of the invention, a magnitude of the current through the coil is determined in the measuring device, a position of the armature is read out from a performance graph as a function of the magnitude of the current through the coil and the inductance value.
In accordance with a concomitant feature of the invention, there is a final control element connected to the magnetic actuator.
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 control device for an internal combustion engine, 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
Fleming Fritz
Greenberg Laurence A.
Lerner Herbert L.
Siemens Aktiengesellschaft
Stemer Werner H.
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