Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
1999-09-08
2001-03-06
Dougherty, Thomas M. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S317000
Reexamination Certificate
active
06198199
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a method for diagnosing a short circuit of a capacitive actuator, in particular a piezoelectrically operated fuel injection valve of an internal combustion engine of a motor vehicle.
German Patent DE 196 52 801 C1 discloses a device for driving capacitive actuators, by which the actuators, of which each is connected in series with a selector switch constructed as a low-side switch, are charged one after another from the series circuit of a charging capacitor and a recharging capacitor.
It has emerged from the operation of such circuits that shorts of the negative—but also of the positive—actuator terminal to the frame can occur with such actuators. This fault (if not all actuators are short circuited in the case of a short circuit of a positive actuator terminal) has the effect that as every other actuator is driven the actuator short circuited to the frame is also always driven. These two actuators act relative to the drive circuit like one actuator with double the capacitance.
However, since the capacitance of an actuator can likewise vary by a factor of 2 in the permissible temperature range, this fault cannot be detected with the aid of simple voltage monitoring.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method for diagnosing a short circuit at a capacitive actuator which overcomes the above-mentioned disadvantages of the prior art methods of this general type, by which it is possible unambiguously to diagnose a short circuit of the actuator to the frame.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for diagnosing in a drive circuit having a capacitive actuator and voltage source with a positive pole and a negative pole a short circuit between the negative pole and the capacitive actuator, the drive circuit including a low-side selector switch connected in series with the capacitive actuator and a first series circuit formed of a charging capacitor and a recharging capacitor for charging the capacitive actuator, the charging capacitor disposed between the positive pole and the negative pole of the voltage source, the drive circuit further having a second series circuit formed of a charging switch, the recharging capacitor, a recharging coil, the capacitive actuator and the selector switch connected in parallel with the charging capacitor, the method which includes:
calculating a charge value corresponding to a quantity of charge QL flowing off from the recharging capacitor during a charging operation;
comparing the charge value with a value ∫idt calculated from a current i flowing during the charging operation via the selector switch connected to the capacitive actuator; and
diagnosing the short circuit of the capacitive actuator to the negative pole if ∫idt<k*Q
L
where k<1.
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 method for diagnosing a short circuit at a capacitive 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.
REFERENCES:
patent: 4688536 (1987-08-01), Mitsuyasu et al.
patent: 6016040 (2000-01-01), Hoffmann et al.
patent: 19652801C1 (1998-04-01), None
Freudenberg Hellmut
Gerken Hartmut
Hecker Martin
Hoffmann Christian
Pirkl Richard
Dougherty Thomas M.
Greenberg Laurence A.
Lerner Herbert L.
Siemens Aktiengesellschaft
Stemer Werner H.
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