Method and apparatus for diagnosing shorts in a SIR system
First Claim
1. In a supplemental inflatable restraint system for an automotive vehicle having one or more air bags, firing circuits each containing a squib for effecting inflation of the bags, and a deployment circuit for determining when air bag inflation should occur and for controlling the firing circuits, the circuits being supplied by vehicle ignition voltage, a diagnostic circuit for detecting shorting of the firing circuit to ground and shorting of the firing circuit to ignition voltage comprising:
- a current source connected to a first end of each firing circuit for supplying thereto a predetermined diagnostic current insufficient to fire a squib;
a voltage regulator connected to a second end of each firing circuit for conducting said diagnostic current to ground and for maintaining a regulated voltage at said firing circuits which, in the absence of firing circuit shorting, is independent of the current conducted thereby; and
means coupled to said firing circuits for detecting a departure from the regulated voltage indicative of said firing circuit shorting to ignition voltage and said firing circuit shorting to ground.
2 Assignments
0 Petitions
Accused Products
Abstract
Air bags are deployed by firing circuits each containing a squib in series with a common control switch, and a control containing an accelerometer and a microprocessor for operating the switch to deploy the air bags. To diagnose shorts, a current source feeds a trickle current through each squib and a current limited voltage regulator across the switch passes the combined trickle currents to ground. The microprocessor senses the voltage across the switch via an A/D converter. That voltage goes low for a short to ground and high for a short to battery voltage.
29 Citations
9 Claims
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1. In a supplemental inflatable restraint system for an automotive vehicle having one or more air bags, firing circuits each containing a squib for effecting inflation of the bags, and a deployment circuit for determining when air bag inflation should occur and for controlling the firing circuits, the circuits being supplied by vehicle ignition voltage, a diagnostic circuit for detecting shorting of the firing circuit to ground and shorting of the firing circuit to ignition voltage comprising:
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a current source connected to a first end of each firing circuit for supplying thereto a predetermined diagnostic current insufficient to fire a squib; a voltage regulator connected to a second end of each firing circuit for conducting said diagnostic current to ground and for maintaining a regulated voltage at said firing circuits which, in the absence of firing circuit shorting, is independent of the current conducted thereby; and means coupled to said firing circuits for detecting a departure from the regulated voltage indicative of said firing circuit shorting to ignition voltage and said firing circuit shorting to ground. - View Dependent Claims (2, 3, 4, 5)
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6. In a SIR system having one or more firing circuits for inflating air bags and a deployment circuit for activating the firing circuits, a method of detecting shorts of the firing circuit to ground and shorts of a firing circuit to a supply voltage comprising the steps of:
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passing diagnostic current through each firing circuit at a level insufficient to cause air bag inflation; conducting the diagnostic current to ground while developing a test voltage on the firing circuits, the test voltage being maintained at a substantially constant value independent of the magnitude of the diagnostic current in the absence of shorting of the firing circuits but varying from said constant value in the event of said shorting; and monitoring the test voltage to detect test voltages indicative of shorting to ground and shorting to the supply voltage. - View Dependent Claims (7, 8, 9)
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Specification