Releasing circuit and checking circuit for a motor vehicle safety device

• US 4,410,875 A
• Filed: 02/03/1982
• Issued: 10/18/1983
• Est. Priority Date: 03/02/1978
• Status: Expired due to Fees

• Current Assignee: Alfons Wohrl, Johann Spies
• Original Assignee: Alfons Wohrl, Johann Spies
• Inventors: Wohrl, Alfons, Spies, Johann
• Primary Examiner(s): TRAFTON, DAVID
• Assistant Examiner(s): Nowicki, Joseph
• Application Number:
  US06/345,363
• Time in Patent Office: 622 Days
• Field of Search: 340/52 R, 340/52 H, 340/669, 307/10 R, 280/735, 180/274
• US Class Current: 180/274
• CPC Class Codes: B60R 2021/01184 Fault detection or diagnostic circuits in power circuits B60R2021/01129
• CPC Class Codes: B60R 21/0132 responsive to vehicle motion parameters , e.g. to vehicle longitudinal or transversal deceleration or speed value

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.

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.

4. Circuit according to claim 1, wherein said checking circuit comprises an addressable selecting circuit, means for connecting the selecting circuit to various switching points in said releasing circuit, and means operating in dependence on the check pulses for connecting each of said switching points separately to said comparator means through said selecting circuit.

5. Circuit according to claim 4, wherein said selecting circuit comprises a counter and a switching matrix addressed by said counter, parallel inputs of said switching matrix being connected through check lines to said various switching points in said releasing circuit.

6. Circuit according to claim 1, wherein said clock pulse supplying means of said checking circuit is switched on during the entire operating period of said releasing circuit and controls the delivery of the check and reference pulses and the operability of said comparator means, said means for supplying clock pulses being connected to clock pulse inputs of said check pulse generator and said reference pulse generator means and to an enabling input of said comparator.

7. Circuit according to claim 6, wherein said check pulse generator comprises a first plurality of resistors each corresponding to a different magnitude check pulse, wherein said reference pulse generator comprises a second plurality of resistors each corresponding to a different magnitude reference pulse, and wherein said checking circuit comprises a counter connected to said means for supplying clock pulses, outputs of said counter being connected through a switch means in said check pulse generator controlled by said clock pulse generator to sequentially select the resistors of said first plurality of resistors for obtaining the check pulses, said counter being connected to said reference pulse generator, said second plurality of resistors generating reference pulses, and said counter sequentially providing address inputs to an addressable switching matrix connecting said comparator to the check pulses from said evaluation circuit.

8. Circuit according to claim 1, wherein said checking circuit comprises means for providing the check pulses in certain time intervals which are significantly longer than the duration of the check pulses in other time intervals, the duration of said check pulses being significantly shorter than the output signal of said acceleration sensor which occur when said motor vehicle collides with an obstacle.

11. Circuit according to claim 1, wherein said check pulse generator is connected to said releasing circuit through said acceleration sensor.

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.

12. Circuit according to claim 3, further comprising an OR gate and an AND gate, wherein the outputs of said differential amplifiers are connected through said OR gate to an input of said AND gate, means for enabling the AND gate during the check pulses, said AND gate having an output being connected to said error indicating device, said error indicating device being enabled during a check operation.

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.

10. Circuit according to claim 9, wherein said priority circuit comprises a differential threshold value switch having one input connected to an output of said check pulse generator and having a second input connected to a switching point of said releasing circuit which determines the permissible limit, and wherein the output of said threshold value switch is connected through a timer to an interrupt input of said checking circuit.