Electrical transmission or interconnection systems – Vehicle mounted systems – Automobile
Patent
1988-10-25
1990-08-21
Pellinen, A. D.
Electrical transmission or interconnection systems
Vehicle mounted systems
Automobile
340436, 340515, 340669, 280735, 180282, 73 1B, B60R 2100
Patent
active
049509152
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to an impact sensor with a testing circuit for a vehicle.
BACKGROUND OF THE INVENTION
Such an impact sensor is known from German Patent Publication DE-OS 2,207,831. The impact sensor is arranged in a sensor housing and serves for triggering a passive safety device when the vehicle impacts on an obstacle. The triggering of the safety device involves, for example, inflating an air cushion or the pulling tight of a safety belt. In the sensor housing there are arranged an acceleration sensor, an evaluating circuit for the electrical output signals thereof, a trigger circuit for triggering the passive safety device and a testing circuit for testing the ability of the impact sensor to function. The testing circuit produces an impulse train, whereby the impulse amplitudes are so dimensioned that in the evaluating and triggering circuit given threshold values can be checked. The testing impulses are caused to pass through the entire circuit and they are evaluated in the testing circuit. During the testing of the impact sensor to see whether it is able to function, the trigger circuit is separated from the passive safety device.
In the known sensor the acceleration system is a piezoelectric crystal, the signal of which are integrated once or twice depending on whether the triggering criterium is selected as a certain critical speed or a certain critical distance. The mentioned testing impulses are thereby directly applied to the electrodes of the piezoelectric crystal. The testing circuit is switched on at least prior to the beginning of a trip and preferably also at regular time intervals during the trip. The ability to function can be indicated, for example optically. For example, a light emitting diode could blink for a certain time after starting during the operation of the ignition of the vehicle. The diode could extinguish when the sensor is functional. If, during a testing it is ascertained that the sensor is not functioning properly, then, for example, a continuous blinking could be triggered.
In the known testing circuit only the electrical and electronic components of the impact sensor are tested. A further testing, for example, of a mechanical type is not provided.
OBJECT OF THE INVENTION
The invention has for its object to simplify the testing of the impact sensor and to provide a simple indication of the ability to function properly or of the disablement.
SUMMARY OF THE INVENTION
According to the invention an electro-acoustic transducer is provided in the sensor housing. The transducer is coupled with the acceleration sensor acoustically. Preferably, the coupling takes place through the sensor housing. The testing of the trigger circuit can be called an acoustical testing. The disclosed acoustical testing has several advantages. Prior to beginning a trip with the vehicle, the electro-acoustic transducer is switched-on with switching-on the ignition, whereby the transducer operates intermittently, for example, in synchronism with the above mentioned light emitting diode, to emit a characteristic testing signal. The vibrations of the testing signal of the electro-acoustic transducer are transmitted either directly or through the sensor housing to the piezoelectric acceleration sensor. This sensor provides, in response to the testing signal, a signal which is passed through the evaluation and trigger circuit and the processing of which is tested by the testing circuit. Additionally, the frequency characteristic of the testing signal emitted by the electro-acoustic transducer can be tested in the testing circuit. Based on such a testing, a conclusion can be made, for example, whether the sensor housing is mechanically rigidly connected to the supporting structure of the motor vehicle.
The electro-acoustical transducer preferably radiates the testing signal oscillations in the audible range so that the ability of the impact sensor to function can be signalled acoustically in addition to an optical indication. In case the impace sensor is disabled, it is
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Proceedings of the 27th Annual ISA Conference, New York, Oct. 9-12, 1972, Instrument Society of America.
Laucht Horst
Spies Hans
Woehrl Alfons
Fasse W. G.
Kane, Jr. D. H.
Messerschmitt-Boelkow-Blohm GmbH
Osborn David
Pellinen A. D.
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