Electrical transmission or interconnection systems – Vehicle mounted systems – Automobile
Patent
1990-04-25
1992-09-08
Pellinen, A. D.
Electrical transmission or interconnection systems
Vehicle mounted systems
Automobile
361251, 280735, B60R 2132, F23Q 700
Patent
active
051461048
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention is directed to an electronic device used to trigger a safety device such as an inflatable retention device for use in a motor vehicle.
A device of the above-described type is known from 1141 Ingenieurs de l'Automobile (1982) No. 6, pp 69 to 77. It is of significant importance for electronic devices of this type that all structural elements, which are critical for the functioning of the device, be able to be tested. Only in this way can one ensure a high degree of operational reliability, which is necessary for safety devices of this type. From DE-A 22 22 038, it is known, in testing the firing element of such a device, to connect a constant-current source to the firing element and to provide a differential connection for measuring the voltage drop across the firing element. This approach requires additional switching devices, which are provided for testing purposes, apart from the triggering means of the firing elements. Furthermore, a disadvantage of the known devices is that the firing elements are connected in a two-pole fashion, with power output stages applied to them, so that the danger of unintentionally activating the firing elements as, for example, during testing or assembly work cannot be completely ruled out. Finally, it is only possible to test the output stages controlling the firing elements with the use of an additional mechanical switch, which disconnects the power outputs from the electric power supply under normal operating conditions, as, for example, when there is no imminent danger. The ON state of this mechanical switch, however, cannot be easily checked.
SUMMARY OF THE INVENTION
The device according to the present invention includes a firing element and a capacitor coupled in series to the firing element. The series coupled capacitor provides numerous advantages over known electronic devices. For example, the capacitor can have a capacitance value that is of a relatively small value such that the electric charge that can be stored in the series coupled capacitor is not adequate to provide an amount of energy sufficient to trigger the firing device. Thus, the direct application of a direct voltage, for example the supply voltage of the vehicle, to the firing lines leading to the firing element cannot lead to an unintentional triggering of the firing element. This cannot be ruled out in the case of previous devices. Since either the firing element itself or the capacitor connected in series to the firing element is connected on one side to the ground connection, a firing of the firing element is brought about via only one single firing line. This reduces the costs for cable connections as well as the contact resistances in the firing circuit, decreases the number of required electrical connections to the evaluation circuit and on the whole increases the operational reliability, since the number of lines that could be damaged is reduced. The device according to the present invention is also distinguished by the fact that push-pull operated current sources are used to control the firing element. They can be set to specific, predetermined current values by means of an evaluation circuit. The push-pull operation increases the functioning security of the device to prevent any false tripping of the firing element in case of a malfunction of the electronic device, since a one-sided or asymmetrical control by only one current source in the long run cannot lead to an unintentional triggering of the firing element. An intentional firing of the firing element is only possible by means of a repeated, consecutive triggering of the current source in the push-pull operation.
Now if the triggering rhythm of the current sources should also be disturbed as the result of a very improbable type of malfunction, in the case of the device according to the present invention, an erroneously initiated firing operation can still be stopped before the triggering of the firing element. On the other hand, in the case of the prior art, an activation of the firin
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Crispin Norbert
Mattes Bernhard
Schumacher Hartmut
Fleming Fritz M.
Pellinen A. D.
Robert & Bosch GmbH
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