Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
1999-09-09
2001-12-11
Lieu, Julie (Department: 2736)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S602000, C318S450000, C318S483000, C015S250001, C015S250120
Reexamination Certificate
active
06329923
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention is based on an apparatus and a method for operating a rain sensor.
From German published, nonexamined Patent Application DE-OS 41 12 847, an apparatus for operating a rain sensor is already known having a transmitter which is triggered by a preceding control arrangement, a receiver which outputs a sensor signal to a signal processor, and an evaluator, which outputs a switching signal for turning a windshield wiper on as a function of the sensor signal.
A regulator is also provided that regulates the sensor signal, which corresponds to a clean window, to a predetermined resting level. To that end, the controller outputs a control signal to the control arrangement of the transmitter for the sake of slowly regulating the transmission power to a predetermined resting level. Alternatively, the controller outputs a control signal to the signal processor for slowly regulating the gain of the sensor signal to be amplified. With the regulator, production variations among individual components of the rain sensor as well as tolerances in rain sensor installation can be compensated for over a wide range.
A disadvantage is that the controller regulates the sensor signal corresponding to a clean, dry window to the resting level, preferably at the outset, and that over the further course of sensor operation the control signal of the controller is allowed to vary in comparison with the sensor signal only extremely slowly, so that changes in the sensor signal will not be cancelled out. That is, the regulator essentially performs a (one-time) calibration of the rain sensor.
This then means that the evaluation of the sensor signal takes place essentially in the working range that has been set. This has the disadvantage that at small sensor signals, any change in the sensor signal has poorer resolution than an equally major relative change in large sensor signals.
In accordance with the present invention, the control signal outputted by a controller as a function of the sensor signal is also delivered to an evaluation arrangement for treating switching events of the device.
SUMMARY OF THE INVENTION
The apparatus according to the invention has the advantage that a controller regulates a rain sensor as a function of the degree of wetting of a window, and that the sensor signal and in addition the control signal of the controller are delivered to an evaluation arrangement for evaluation. In this way, the control signal and the working range can be tracked directly and quickly as a function of the sensor signal, without the sensor signal being cancelled out. The working range of the sensor signal can therefore be selected to be smaller, so that for a suitable gain the resolution becomes greater.
With the provisions recited in the dependent claims, advantageous refinements of and improvements to the characteristics recited in the main claim are obtained. One particular advantage is the spatial separation of the evaluation arrangement from the control circuit for the rain sensor, which is made possible by the fact that the regulation is performed by an electronic regulator, so that a microcontroller is used only for the evaluation.
As a further advantage, the evaluation arrangement or microcontroller is there for part of a central electronic system of a motor vehicle.
It is also advantageous that the microcontroller requires only low power and a low clock speed, because as a “listener”, it merely evaluates signals.
Another advantage is that the controller regulates the working range of the transmitter continuously or in stages and is embodied in a space-saving way as an ASIC (application-specific IC).
The separate transmission of the sensor signal and the control signal to the microcontroller is especially advantageous. As a result, a wide dynamic scope of the microcontroller input and high resolution are obtained. A further advantage is the use of a differential amplifier to evaluate the sensor signal. This sets a differential working range, so that slight signal changes can be evaluated with high resolution in the evaluation arrangement.
REFERENCES:
patent: 4916374 (1990-04-01), Schierbeek et al.
patent: 5059877 (1991-10-01), Teder
patent: 6040669 (2000-03-01), Hog
Lieu Julie
Robert Bosch GmbH GmbH
Striker Michael J.
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