Electrical transmission or interconnection systems – Vehicle mounted systems – Automobile
Reexamination Certificate
1998-04-08
2001-01-30
Paladini, Albert W. (Department: 2836)
Electrical transmission or interconnection systems
Vehicle mounted systems
Automobile
C180S282000, C280S728100, C340S315000, C701S045000
Reexamination Certificate
active
06181021
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an arrangement for activating a deployment mechanism of a restraint system for vehicle occupants; specifically the deployment mechanism is connected to a secondary side of a transfer unit.
2. Background Invention
A restraint system is described in German Patent No. DE 24 33 555 A1. The restraint system described is an airbag arranged in a steering wheel. In order to bypass the complex and failure-prone slip rings or volute springs previously used to transfer signals between a control unit located on the vehicle chassis and the deployment mechanism (firing pellet) installed in the airbag, according to this existing art a rotary transfer unit is used, whose primary and secondary windings are arranged rotatably with respect to one another about the steering wheel axis. The firing pellet of the airbag is connected to the secondary winding, and the primary winding is connected via a switch to a battery of the vehicle. By means of pulses fed in on the primary side, a voltage which leads to deployment of the firing pellet is induced in the secondary winding. In order for the voltage induced in the secondary winding to be great enough to deploy the firing pellet, the magnetic coupling between the primary and secondary windings of the transfer unit must be very high. A high magnetic coupling is achieved by embedding both windings in ferromagnetic coil elements. A transfer unit of this kind is capable of receiving a great deal of energy, even if its winding terminals erroneously come into contact with the vehicle's voltage lines. In some circumstances, however, this energy is already sufficient to deploy the airbag. Improper deployment of this kind should, however, be prevented in all cases.
In German Patent No. DE 44 04 816 A1, an arrangement for activating a deployment mechanism of a restraint system is described in which the supply voltage for the deployment mechanism is transferred directly from the primary side to the secondary side of a transformer. A voltage regulator prepares the voltage transferred to the secondary side for the deployment mechanism and for other electronic circuits on the secondary side. As a result, a relatively high supply voltage must continuously be transferred via the transformer, which in turn requires a high magnetic coupling—associated with the aforementioned disadvantages—between the primary and secondary windings of the transformer.
SUMMARY OF THE INVENTION
An object of the present invention is to specify an arrangement of the kind cited initially which is capable of preventing improper deployments of a restraint system to which the deployment signal is delivered via a transfer unit.
According to the present invention, the object is achieved by the fact that upstream from the deployment mechanism is an electrical energy accumulator, for example a capacitor, which is fed by a charging current delivered via the transfer unit. This makes it possible to use a transfer unit which contains very little or even no ferromagnetic material, so that the magnetic coupling between the windings is very low, and it is therefore not capable of receiving an amount of energy that would be sufficient to deploy the restraint system with a pulse. The deployment system is thus fired solely by the energy charged in the energy accumulator. In order to deploy the restraint system, a low-power trigger signal is transferred from the transfer unit to a control circuit, connected to the secondary side, which switches the energy accumulator through to the deployment mechanism. A transfer unit of this kind, which contains little or even no ferromagnetic material, also has the advantage that it possesses little weight and requires little installation space.
According to the present invention, the control circuit connected on the secondary side to the transfer unit can also be used to monitor the charge status of the electrical accumulator, and also to check the function of the deployment mechanism by means of a resistance measurement and, if the resistance deviates from a defined value, to send an error signal back via the transfer unit to a control unit. It is advantageous to bypass the electrical accumulator with a switch which short-circuits and thereby discharges the energy accumulator if the restraint system is not built into a vehicle. To allow the control circuit to distinguish the trigger signal from the energy accumulator charging current, both of which are induced by the transfer unit on the secondary side, the trigger signal should have a frequency or duration or digital code which is recognizable by the control circuit.
REFERENCES:
patent: 5515399 (1996-05-01), Swart
patent: 5856710 (1999-01-01), Baughman et al.
patent: 24 33 555 A1 (1976-01-01), None
patent: 0283188 (1988-09-01), None
patent: 58-115945 (1983-07-01), None
Dukart Anton
Zabler Erich
Kenyon & Kenyon
Paladini Albert W.
Robert & Bosch GmbH
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