Electricity: electrical systems and devices – Control circuits for electromagnetic devices – Systems for magnetizing – demagnetizing – or controlling the...
Patent
1991-06-26
1993-09-14
Gaffin, Jeffrey A.
Electricity: electrical systems and devices
Control circuits for electromagnetic devices
Systems for magnetizing, demagnetizing, or controlling the...
361152, 361194, 361195, 324381, H01H 4700
Patent
active
052455017
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND INFORMATION
The invention proceeds from a process for measuring the movement of an armature of an electromagnetic switching member.
Such a process is known from German Patent 2,251,472. According to said patent, the mechanical movement of a solenoid valve armature is controlled by the measurement of the current flowing through the magnet winding, in particular by measuring the temporal variations in the current rise.
This process has the disadvantage that disturbances in the voltage supply, which lead to temporal variations in the current flowing through the magnet winding or excitation winding, are misinterpreted as an indication of the movement of the magnet armature. Thus, a reliable monitoring of the movement of a solenoid valve armature is ruled out in this way.
The invention also relates to a device in particular for carrying out a process of the type mentioned above.
In the case of a device of this type known from German Patent 2,251,472, measurement of the temporal variations in the current applied to the excitation winding is carried out during a period that stretches from the start of the driving of the armature to beyond the termination of the movement thereof. Consequently, it must be ensured that during this monitoring phase no temporal variations take place in the current characteristic that are caused by external influences and from which conclusions could be drawn concerning a movement of the armature. The possibilities of driving the associated solenoid valve are thereby restricted.
ADVANTAGES OF THE INVENTION
By contrast, the process according to the invention has the advantage that the movement of the armature of an electromagnetic switching member can be reliably recognized independently of fluctuations in the energy supply. It is particularly advantageous that the energy required to produce the movement of the armature can be very high for a short time at the start of a switching operation, in order to accelerate the movement of the armature. As soon as the armature moves, the energy is reduced to the extent that the armature remains in its actuated position, in the closed position.
Correspondingly, in the case of the opening of the electromagnetic switching member, the energy which holds the armature in its actuated position, the closed position, is reduced very rapidly to zero, or even to a negative value. As a result, strong accelerative forces act on the armature. As soon as the latter moves, the energy is once again raised to a value which is below the holding energy that is required in order to hold the armature in its actuated position. As a result, the armature moves very rapidly into the open position. The raising of the energy to a defined value below the holding energy induces a magnetic field whose variation, which is based upon the movement of the armature or upon the termination of the movement of the armature, can be measured.
There is particular preference for a process in which the rapid raising of the energy to a high level during the closing operation, or the rapid reduction of the energy to a low level during the opening operation is maintained only for so long as a movement of the armature takes place. Since the direct measurement of the armature movement is very complicated, the defined value of the energy is set after a time T.sub.0 after which a movement of the armature certainly takes place. However, the time is chosen to be shorter than the time that elapses up to the point when the closed-circuit condition or the open-circuit condition is reached. A strong acceleration of the armature is achieved in this way.
In a preferred process, the defined value of the energy is held approximately constant at least up to the termination of the armature movement. The movement of the armature can thereby be monitored particularly simply.
Finally, in a particularly preferred process the variation in the current or in the voltage at the excitation winding is measured in a time interval that starts before the termination of the movement and ends after the termi
REFERENCES:
patent: 4680667 (1987-07-01), Petric
patent: 4729056 (1988-03-01), Edwards et al.
patent: 4856482 (1989-08-01), Linder et al.
Buisson Dominique
Graf Herbert
Hehn Lucien
Karle Anton
Lauvin Pierre
Gaffin Jeffrey A.
Robert & Bosch GmbH
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