EP0518501A1 Expired / Lapsed EP ⏱️ 0.0 years remaining

Reconfigurable air bag firing circuit

Assignee: Automotive Systems Laboratory Inc

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Filing: 1992-05-19

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Granted: —

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Expires: 2012-05-19

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Abstract

Abstract An air bag firing circuit (10) comprises a firing path which includes in series a safing sensor (16), a squib (20), and a FET (22) operated under microprocessor control (24) in response to the output of an electronic crash sensor (26). A power supply (28) maintains a known voltage (Vc) across the firing path (12) sufficient to explode the squib (20) upon simultaneous "closure" of both the safing sensor (16) and the FET (22) operated by the microprocessor (24) in response to crash sensor output (26). Normally, upon detection of a failure in the electronic crash sensor (26), its supporting electronics, or the FET (22) actuated in response thereto, the microprocessor (24) reconfigures the firing threshold of the safing sensor (16), as by applying a current to its integral test coil (38) to increasingly bias the sensor's inertial mass away from its switch contacts (14). However, if a failure of the safing sensor (16) is detected, reconfiguration of its threshold is inhibited notwithstanding the failure of other circuit components to prevent inadvertent deployment of the air bag. Once the safing sensor (16) is reconfigured, the microprocessor (24) turns on another FET (46) to pull one side of the squib to ground, thereby removing the inoperable FET from the firing path and ensuring continued protection of the vehicle passengers until the sensor is serviced or replaced.

Inventors

👤 Craig W. White
👤 James R. Paye
👤 Kevin E. Musser

Bibliographic Details

Application Number —

Jurisdiction EP

Data Source google_patents

Last Synchronized 2026-11-09 04:26

CPC Classifications

B; B60; B60R; B60R21/00; B60R21/02; B60R21/16; B60R21/01; B60R21/017; B60R21/0173

Claims Analysis

Total Claims: 5

Claim 1

Independent Claim 180 words

In a control circuit for a vehicle passenger safety restraint, said control circuit having: a firing path which includes, in series, current-responsive trigger means for actuating said restraint; and a first and a second normally-open switch means, said first and second switch means closing in response to an acceleration input exceeding a first and second threshold, respectively, said second threshold being nominally greater than said first threshold; means for applying a voltage across said firing path; first failure detecting means for detecting a failure of said second switch means; and shunt means responsive to said first failure detecting means for shunting said second switch means upon detection of a failure of said second switch means; and threshold-adjusting means responsive to said first failure detecting means, said threshold-adjusting means being operative to increase said first threshold above its nominal value, the improvement comprising: second failure-detecting means for detecting a failure of said first switch means, and said threshold-adjusting means being responsive to said second failure-detecting to inhibit operation of said threshold-adjusting means upon detecting a failure of said first switch means.

Claim 2

Dependent Claim 23 words

The control circuit of claim 1 wherein said threshold-adjusting means includes means for increasingly biasing said first switch means in said normally-open position.

Claim 3

Dependent Claim 205 words

A control circuit for a vehicle passenger restraint comprising: a firing path including in series: a first, normally-open, acceleration-responsive switch which closes in response to an acceleration input exceeding a first threshold, said first switch being shunted by a first shunting resistor; trigger means for actuating said restraint, said trigger means having internal electrical resistance substantially less than said resistance of said first shunting resistor; and a second and third normally-open, electrically-operated switch, said second switch being shunted by a second shunting resistor having a resistance substantially greater than the internal resistance of said trigger means; means for applying a voltage across said firing path; an electronic sensor for sensing an acceleration exceeding a second threshold, said second threshold being nominally greater than said first threshold; a microprocessor responsive to said electronic sensor for operating said controlling said second switch, said microprocessor closing said second switch when said electronic sensor senses an acceleration exceeding said second threshold; failure-detecting means for detecting a failure of first switch, said electronic sensor, said microprocessor, or said second switch; first means responsive to said failure-detecting means for increasingly biasing said first switch in said normally-open position; and second means responsive to said failure-detecting means for operating said third switch.

Claim 4

Dependent Claim 28 words

The circuit of claim 3 wherein said first means responsive to said failure-detecting means includes a constant current source; and a coil connected to said constant current source.

Claim 5

Dependent Claim 109 words

A method of operating the circuit of claim 3, said operating method including the steps of: detecting a failure of at least one of said group consisting of said electronic sensor, said microprocessor, and said second switch; confirming the continued operability of said first sensor by not detecting a failure thereof with said failure-detecting means; operating said first means responsive to said failure-detecting means to increasingly bias said first switch in said normally-open position after confirming the continued operability of said first sensor; and operating said second means responsive to said failure-detecting means to close said third switch after said first switch is increasingly biased in said normally-open position.

References Cited (Backward Citations)

EP0305656A2 Cited

US4958851A Cited

US5083276A Cited

US5085464A Cited

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