RECONFIGURABLE AIR BAG FIRING CIRCUIT

• Main Authors: KEVIN E. MUSSER, JAMES R. PAYE, CRAIG W. WHITE
• Format: Patent
• Language: English
• Published: 24.12.1992
• Subjects: INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT; MEASURING; MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION,OR SHOCK; PERFORMING OPERATIONS; PHYSICS; TESTING; TRANSPORTING; VEHICLES IN GENERAL; VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISEPROVIDED FOR

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.