Electricity: electrical systems and devices – Control circuits for electromagnetic devices – Systems for magnetizing – demagnetizing – or controlling the...
Reexamination Certificate
1999-12-24
2003-05-06
Huynh, Kim (Department: 2836)
Electricity: electrical systems and devices
Control circuits for electromagnetic devices
Systems for magnetizing, demagnetizing, or controlling the...
C361S139000, C251S129010
Reexamination Certificate
active
06560088
ABSTRACT:
PRIORITY CLAIM
This application is based on and claims the priority under 35 U.S.C. §119 of German Patent Application 198 60 272.3, filed on Dec. 24, 1998 the entire disclosure of which is incorporated herein by reference.
FIELD OF THE INVENTION
The invention relates to a method and a circuit arrangement for reducing the level of noise produced during actuation of an electromagnetically actuated device, whereby such noise results from excessive acceleration and deceleration of an armature of the device when an excessive actuating current has been applied to the device.
BACKGROUND INFORMATION
Various types of electromagnetically actuated or operated devices, such as electromagnetic valves and relays for example, are known in the art. Such devices typically comprise an electromagnet including a magnetic coil as well as a movable armature, which is moved or changed in position when a sufficient actuating current is applied to the magnetic coil. More particularly, the armature begins to move once the actuating current has reached a predetermined minimum threshold value as the current is increased from a minimum or zero value up to its maximum operating value. Typically, however, the maximum or full actuating current applied to the magnetic coil during the actuation exceeds the minimum threshold level that is necessary for moving and thereby actuating the armature. As a result, the armature is very strongly and excessively accelerated and driven against a mechanical end limit stop or the like.
The rapid excessive acceleration of the armature, and especially the impact of the excessively accelerated armature against its mechanical end limit stop results in the transfer and conversion of excessive amounts of energy. Most importantly, the kinetic energy of the moving armature is converted largely into sound energy and deformation or wear energy when the armature abruptly stops by impacting against the mechanical end limit stop. The greater the actuating current that is applied to the magnetic coil, the greater will be the acceleration and the ultimate velocity and energy of the armature, and thus also the greater will be the amount of noise and wear produced when the armature impacts against the end limit stop. It is therefore desirable to actuate the electromagnet with the lowest possible actuation current that will still effectively move the armature from its initial position to its actuated position.
Throughout this specification, the term “armature” will be used to refer to any component that is driven and moved by the electromagnet or especially the magnetic coil in an electromagnetically actuated device. The process in which the armature is moved, will generally be referred to as the switching process or the actuating process of the electromagnet.
German Patent Publication DE-C2 3,425,574 discloses a method of operating an electromagnetically actuated device in the manner that has generally been described above. Particularly, the disclosed method involves increasing the actuating current provided to the magnetic coil in a gradual or progressive manner, over the entire range between the minimum current (zero amps) and the maximum current that is ultimately applied to the magnetic coil. By gradually or progressively increasing or ramping-up the actuating current, it may be expected that an excessive actuating current could be avoided, because the armature will be actuated as soon as the gradually increasing current reaches the minimum threshold value necessary for driving the armature. The point at which the plunger or armature of the electromagnet begins to move always lies within the range of this gradual or progressive increase of the actuating current, because this range extends continuously from zero amps up to the maximum amperage that is ultimately applied to the magnetic coil.
A disadvantage of such a known approach is that the specific time point of actuation of the armature is not specifically controlled or defined. Thus, if the time period within which the electro-magnetic is to be switched is relatively short, then it becomes absolutely necessary to increase or ramp-up the actuation current from zero amps up to maximum amperage with a relatively steep current increase slope so as to achieve the total ramp-up of the current in the required short time period. Unfortunately, that leads to an actuation of the electromagnet at a higher current level than would be absolutely necessary, i.e. at a higher current than the abovementioned minimum threshold level, because the current keeps rapidly increasing even as the armature is being actuated. As a result, the armature is excessively accelerated, and caused to strongly impact against the mechanical stop, which leads to a higher generation of noise and also increased wear of the various mechanical components.
SUMMARY OF THE INVENTION
In view of the above, it is an object of the invention to provide a method and a circuit arrangement that makes it possible to achieve an exact switching of the electromagnet and/or the armature of an electromagnetically actuatable device, while applying the minimum possible current to the electromagnet for achieving the actuation. More particularly, it is an object of the invention to control the operation of an electromagnetically actuatable device so that the actuation current applied to the electromagnet undergoes the smallest possible rate of increase during the time in which the actuation or switching process is carried out, while achieving the quickest possible total ramp-up of the current from zero amps to maximum amperage. The invention further aims to avoid or overcome the disadvantages of the prior art, and to achieve additional advantages, as are apparent from the present specification.
The above objects have been achieved according to the invention in a method and a circuit arrangement for controlling the actuation current applied to the electromagnet of the electromagnetically actuatable device. According to the invention, the ramp-up of the actuation current is divided into at least two or preferably three portions or ranges. An actuating range or transition function represents only a central portion of the total current variation between zero amps and maximum amps for the process of switching the electromagnet. The ramp-up current variation further includes two non-actuating ranges respectively before and after the actuating range in time. Each of the non-actuating ranges involves a steeper or more rapid increase rate of the current in comparison to the current variation that exists during the actuating range or transition function.
In the first non-actuating range, the current rapidly or steeply increases from a minimum value (e.g. zero amps) up to an initial value at the start of the actuating range. In the second nonactuating range that follows the actuating range, the current rapidly or steeply increases from the final current value of the actuating range up to the maximum value of the current that is ultimately applied to the electromagnet. If only two (rather than three) distinct ranges are used, the non-actuating range may occur before the actuating range (in which case the final current value of the actuating range is equal to the maximum amperage), or after the actuating range (in which case the initial current value of the actuating range is equal to the minimum or zero current value).
The actuating range is particularly selected to cover the time span and/or the current value range in which the switching or actuation of the electromagnet takes place. In this manner, the switching or actuation of the electromagnet is carried out with a gradually increasing current or with some other gentle variation of the current value as will be described in detail herein, while also achieving a rapid or steep increase of the current between the minimum value and the maximum value during the non-actuating ranges before and after the actuating range. Particularly, the current increase during each of the non-actuating ranges may be a substantially instantaneous current jump, limited only
Beck Stefan
Ebel Martin
Poeppel Josef
Daimler-Chrysler AG
Fasse W. F.
Fasse W. G.
Huynh Kim
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