Releasing circuit and checking circuit for a motor vehicle safety device
First Claim
1. Releasing circuit for a safety device in motor vehicles, of the type wherein an acceleration sensor provides a signal which corresponds to the deceleration of the motor vehicle when it collides with an obstacle, wherein an evaluating circuit evaluates the output signal of said acceleration sensor, and wherein a switch which, starting from a certain release value of an output signal of said evaluating circuit releases said safety device through an ignition element, and a checking circuit for said releasing circuit with a check pulse generator for providing of check pulses for said evaluating circuit, and an error indicating device connected to said checking circuit, the improvement wherein said checking circuit comprises a reference pulse generator means for providing reference pulses which assume characteristic values corresponding to the check pulses, and a comparator means connected to said error indicating device for comparing the check pulses passing through said evaluating circuit and the reference pulses and wherein means for supplying clock pulses is provided, said check pulse generator comprising a controllable switch operating under control of said clock pulses.
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Abstract
The invention relates to a releasing circuit for a motor vehicle safety device having a piezoelectric acceleration sensor for delivering a signal which corresponds to the sudden deceleration of a motor vehicle when it collides with an obstacle. An evaluating circuit evaluates the output signal of the acceleration sensors. A switch releases the safety device through an ignition element starting from a predetermined release value of the output signal of the evaluating circuit. A checking circuit for the releasing circuit has a check pulse generator for delivering check pulses which are fed to the releasing circuit. The checking circuit, in addition to the check pulse generator 11, is connected to a reference pulse generator 12 that provides reference pulses which assume characteristic values in accordance with the check pulses which are evaluated in the releasing circuit. A comparator 17 connected to the error indication 22 compares the evaluated check pulses and the reference pulses.
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Citations
12 Claims
- 1. Releasing circuit for a safety device in motor vehicles, of the type wherein an acceleration sensor provides a signal which corresponds to the deceleration of the motor vehicle when it collides with an obstacle, wherein an evaluating circuit evaluates the output signal of said acceleration sensor, and wherein a switch which, starting from a certain release value of an output signal of said evaluating circuit releases said safety device through an ignition element, and a checking circuit for said releasing circuit with a check pulse generator for providing of check pulses for said evaluating circuit, and an error indicating device connected to said checking circuit, the improvement wherein said checking circuit comprises a reference pulse generator means for providing reference pulses which assume characteristic values corresponding to the check pulses, and a comparator means connected to said error indicating device for comparing the check pulses passing through said evaluating circuit and the reference pulses and wherein means for supplying clock pulses is provided, said check pulse generator comprising a controllable switch operating under control of said clock pulses.
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2. Releasing circuit for a safety device in motor vehicles, of the type wherein an acceleration sensor provides a signal which corresponds to the deceleration of the motor vehicle when it collides with an obstacle, wherein an evaluating circuit evaluates the output signal of said acceleration sensor, and wherein a switch which, starting from a certain release value of an output signal of said evaluating circuit releases said safety device through an ignition element, and a checking circuit for said releasing circuit with a check pulse generator for providing of check pulses for said evaluating circuit, and an error indicating device connected to said checking circuit, the improvement wherein said checking circuit comprises a reference pulse generator means for providing reference pulses which assume characteristic values corresponding to the check pulses, and a comparator means connected to said error indicating device for comparing the check pulses passing through said evaluating circuit and the reference pulses and wherein said reference pulse generator means has two outputs connected to said comparator means for simultaneously delivering two reference pulses which are each assigned to a single check pulse and assume values above and below the characteristic values of the check pulses evaluated in said evaluating circuit for determining a permissible tolerance range for the evaluated check pulses.
- 3. Circuit according to claim 3, wherein said comparator means comprises first and second differential amplifiers each having first and second inputs and an output, one output of said reference pulse generator being connected to one of said inputs of said first differential amplifier and the other output of said reference pulse generator being connected to an input of said second differential amplifier of opposite sense to said one input of said first differential amplifier, the check pulses evaluated in said evaluating circuit being connected to the second inputs of said differential amplifiers.
- 9. Releasing circuit for a safety device in motor vehicles, of the type wherein an acceleration sensor provides a signal which corresponds to the deceleration of the motor vehicle when it collides with an obstacle, wherein an evaluating circuit evaluates the output signal of said acceleration sensor, and wherein a switch which, starting from a certain release value of an output signal of said evaluating circuit releases said safety device through an ignition element, and a checking circuit for said releasing circuit with a check pulse generator for providing of check pulses for said evaluating circuit, and an error indicating device connected to said checking circuit, the improvement wherein said checking circuit comprises a reference pulse generator means for providing reference pulses which assume characteristic values corresponding to the check pulses, and a comparator means connected to said error indicating device for comparing the check pulses passing through said evaluating circuit and the reference pulses and further comprising a priority circuit means responsive to a controlled check pulse in said releasing circuit exceeding a value above a permissible limit for disabling said checking circuit at least for the next check pulse to be delivered and for releasing the releasing circuit.
Specification