Electricity: electrical systems and devices – Control circuits for electromagnetic devices – Systems for magnetizing – demagnetizing – or controlling the...
Reexamination Certificate
1998-09-18
2001-02-13
Fleming, Fritz (Department: 2836)
Electricity: electrical systems and devices
Control circuits for electromagnetic devices
Systems for magnetizing, demagnetizing, or controlling the...
C361S160000, C361S170000
Reexamination Certificate
active
06188562
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process and apparatus for the recognition of the state of a magnetically operated device.
More specifically, the present invention relates to a sensing technique for armature drop off in a device such as a solenoid valve.
BACKGROUND OF THE INVENTION
It is well known in the solenoid valve art that solenoid coil power is supplied by either a longitudinal regulator or a switching regulator. In either case, the function of the regulator is to adjust and control the supply voltage at an appropriate level for the magnetizing solenoid coil.
Since a switching regulator is generally more efficient than a longitudinal regulator, it is usually preferred in solenoid valve applications. A switching regulator alternately switches the supply voltage on and off to the solenoid coil. When the supply is switched on, the resultant current flow in the solenoid coil rises exponentially. When the current level reaches an upper limit value, the regulator shuts the supply off. As a result, the current then drops exponentially. When the current reaches a lower limit value, the supply voltage is again switched on by the action of the regulator. Thus, a mean supply voltage is established, which is regulated at a suitable value for a particular magnetizing solenoid coil. This type of process is disclosed in the German patent application DE 38 17 770.
To be able to switch on a solenoid valve rapidly and reliably, a relatively strong current is initially required for the magnetizing coil. The resulting magnetic force causes the armature of the solenoid to be moved against the force of a return spring. When the armature has reached its switch on position, the magnetizing current is lowered to a holding value, which is sufficient to hold the armature in place. This holding current is preferably adjusted to the lowest possible value, in order to save energy during continuous operation. There is, of course, a nominal holding current limit for reliably preventing the armature from dropping off. This nominal current limit must be set conservatively, i.e., at a higher than minimal level, if the solenoid valve is located in an area exposed to mechanical shock and vibration. This is generally the case, for example, if the solenoid valve is installed in a motor vehicle, especially in the proximity of the engine. This type of environment may cause a holding armature to drop off accidentally, causing the solenoid valve to shut off (or on) a pressure medium. Such an erroneous actuation should be avoided in any situation, but especially when the solenoid valve is used in an application that is relevant for safety, e.g., in the anti-lock braking system of a vehicle.
In the prior art, as disclosed in German patent applications DE 27 28 666 and DE 38 17 770, there are known techniques for recognizing the type of solenoid failure caused by a jammed armature. In these configurations, the switch on current waveform is monitored to detect a sudden deflection, which typically occurs at the time of armature movement.
However, the present invention has a different objective; namely, to detect armature drop off from a holding position as a result of a mechanical disturbance, and to take immediate corrective actions, including automatic restart and transmittal of an error message.
It is a further object of the present invention to detect armature drop off without the addition of special sensors.
It is yet a further object of the present invention to enable a significant reduction in the holding current safety margin, to such an extent that the power loss of a solenoid valve in continuous operation can be reduced by half. As a result, the structural volume of the solenoid valve can also be reduced.
SUMMARY OF THE INVENTION
In accordance with an illustrative embodiment of the present invention, a method for the recognition of an armature drop off within a solenoid valve is as follows:
a) supplying a large magnitude regulated switching current to the solenoid valve coil to achieve switch on of the solenoid valve armature,
b) reducing the switching current magnitude to a lower level which is sufficient to hold the armature in the switch on position,
c) monitoring the period of the lower level switching current with a time period measuring device,
d) comparing the measured lower level switching current period with a predetermined threshold value, which represents a transitory expanded lower level switching current period attributable to a drop off of the armature,
e) generating an error signal when the measured lower level switching current period exceeds the predetermined threshold value, and
f) restarting the initial turn on cycle in order to return the armature to its switch on position.
An alternative embodiment of the present invention monitors the amplitude of the coil current, in order to detect a sudden increase in the lower level switching current, which is also indicative of an armature drop off.
The aforementioned illustrative embodiments of the present invention are more fully described below in conjunction with the following drawings.
REFERENCES:
patent: 4608620 (1986-08-01), Hines
patent: 4631629 (1986-12-01), Mallick, Jr.
patent: 4797779 (1989-01-01), Richards et al.
patent: 4970622 (1990-11-01), Buechl
patent: 5053911 (1991-10-01), Kopec et al.
patent: 5196983 (1993-03-01), Stumpf
patent: 5428496 (1995-06-01), Buchta
patent: 5539608 (1996-07-01), Hurley et al.
patent: 5668693 (1997-09-01), Tennies et al.
patent: 5784245 (1998-07-01), Moraghan et al.
patent: 2728666 (1978-11-01), None
patent: 3611220 (1987-01-01), None
patent: 3817770 (1989-11-01), None
patent: 3922900 (1991-01-01), None
patent: 3928651 (1991-03-01), None
patent: 4013393 (1991-10-01), None
patent: 4403156 (1994-04-01), None
patent: 4237706 (1994-11-01), None
patent: 4433209 (1996-03-01), None
Lutz Danne
Thies Holger
Fleming Fritz
ProskauerRose LLP
WABCO GmbH
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