US 5,293,153 A · Method and apparatus for testing an airbag restraint system with parallel sensors

Abstract

A method and apparatus are disclosed for testing an airbag restraint system of the type having at least two parallel connected inertia sensors connected in series with a squib across a source of electrical energy, each inertia sensor having a normally open switch and an associated parallel connected resistor. Each parallel connected inertia sensor has a series connected diode for isolating its associated inertia sensor circuit from other circuit components in the firing circuit. A microcontroller monitors at least one voltage value at a component connection while at least one parallel connected inertia sensor is isolated. The microcontroller determines a value functionally related to the resistance of at least one circuit component in the firing circuit while at least one parallel connected inertia sensor is isolated. The microcontroller compares the determined value against predetermined limits. If the determined value is not within the predetermined limits, an error indication is provided.

Drawings

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Drawings

Claims9

Dependent claims

An apparatus for testing an airbag restraint system of the type having a firing circuit including at least two parallel connected inertia sensors connected in series with a squib across a source of electrical energy, each of said at least two parallel connected inertia sensors having a normally open switch and an associated parallel connected resistor, said apparatus comprising:

means for isolating at least one of the parallel connected inertia sensors of the firing circuit from the other inertia sensor of the firing circuit;
means for monitoring, in said firing circuit, at least one voltage value at a component connection while said at least one of the parallel connected inertia sensors is isolated;
means for determining from the monitored voltage value a value functionally related to the resistance of at least one circuit component of said firing circuit while said at least one of the parallel connected inertia sensors is isolated;
means for comparing the determined value against a predetermined limit;
and
means for providing an error indication in response to said means for comparing.

3 more elements

An apparatus for testing an airbag restraint system of the type having a firing circuit including a safing inertia sensor having a normally open safing inertia switch and a safing resistor connected in parallel with the safing inertia switch, one terminal f the safing inertia switch connected to a source of electrical energy, a second terminal of said safing inertia switch connected to a first terminal of a squib, a first diode and a second diode each having their anode connected to a second terminal of said squib, the cathode of the first diode connected to a first parallel inertia sensor having a first normally open parallel inertia switch and a resistor connected in parallel with the first parallel inertia switch, the second terminal of said first parallel inertia switch being connected to electrical ground, a second parallel inertia sensor having a second normally open parallel inertia switch and a resistor connected in parallel with the second parallel inertia switch, one terminal of said second parallel inertia switch connected to the cathode of said second diode, the second terminal of said second parallel inertia switch being connected to electrical ground, said apparatus comprising:

a first switching network connected between said source of electrical energy and the cathode of the first diode, said first switching network including a first actuatable solid state switch connected in series with a first test resistor having a known resistance value;
a second switching network connected between the source of electrical energy and the cathode of the second diode, said second switch network including a second actuatable solid state switch connected in series with a second test resistor having a known resistance value;
a third switching network connected between the anodes of the first and second diodes and electrical ground, said third switching network including a third actuatable solid state switch connected in series with a third test resistor having a known resistance value;
means for controlling said first, second, and third solid state switches so as to selectively reverse bias said first and second diodes, and establish known test currents selectively though said parallel connected resistors of said safing sensor and the parallel connected resistors of the first and second parallel inertia sensors;
means for monitoring the voltage values of the source of electrical energy and the voltage value present at selected circuit junctions;
means for determining the resistance values of selected sensors based upon said monitored voltage values;
and
means to warn the vehicle operator if the determined resistance values are not within predetermined limits.

5 more elements

Dependencies are inferred from the claim text.

Description4,142 words

Summary997 words

#The present invention relates to diagnostic testing of an airbag restraint system and is particularly directed to a method and apparatus for testing an airbag restraint system having parallel sensors.

#Airbag-restraint systems for passenger vehicles are known. These systems typically include a firing circuit having a squib and at least two normally open inertia switches, all connected in series across a source of electrical energy. The two inertia switches are known in the art as the safing sensor and the front sensor. The safing sensor is located in the passenger compartment and the front sensor is located near the front of the vehicle. Upon closure of the two inertia switches, as occurs during a vehicle crash, electrical current of sufficient magnitude and duration passes through the squib so as to ignite the squib. The squib, when ignited, ignites a combustible gas generating composition or pierces a container of pressurized gas which results in inflation of the airbag.

#If the firing circuit in an airbag restraint system is non-operative, the airbag would not be deployed upon the occurrence of a crash condition. Such non-operative conditions, for example, include (i) an open circuit in the series connection of the squib and the two inertia switches, or (ii) a short circuited squib. Also, a nonoperative condition exists if excessive impedance exists in connections between firing circuit components so that upon closure of the inertia switches, the squib does not draw enough current to fire the squib.

Brief description of the drawings58 words

#Further features and advantages of the present invention will become apparent to those skilled in the art to which the present invention relates from reading the following detailed description with reference to the accompanying drawing, FIG. 1, which is a schematic illustration of an apparatus for testing an airbag restraint system made in accordance with the present invention.

Detailed description3,087 words

#Referring to the drawing, an airbag restraint system 20, made in accordance with the present invention,, is shown. The airbag system 20 includes a firing circuit 22. A diagnostic circuit 26 monitors the operativeness of the firing circuit 22. An indicator 28, such as a light or buzzer, located in the passenger compartment of the vehicle, is energized by the diagnostic circuit 26 if an unacceptable condition is detected in the firing circuit 22.

#The firing circuit 22 includes a squib 30 connected in a first series path of a safing inertia sensor 32, a diode 34, and parallel connected front inertia sensors 36, 38. The squib 30 is connected in a second series path of the safing inertia sensor 32, a diode 39, and a tunnel inertia sensor 40. The diode 34 with sensors 36, 38 are operatively connected in parallel with diode 39 and sensor 40.

#The safing sensor 32 includes a normally open inertia switch 42 and a parallel connected resistor 44. The front sensor 36 includes a normally open inertia switch 46 and a parallel connected resistor 48. The front sensor 38 includes a normally open inertia switch 50 and a parallel connected resistor 52. The tunnel sensor 40 includes a normally open inertia switch 54 and a parallel connected resistor 56.

Facts

Application

07/682,566Filed 9 Apr 1991

Granted

8 Mar 1994

Term ended

9 Apr 2011

Estimated · how

Pre-1995 term; greater of 17 years from grant or 20 years from filing when eligible. Maintenance-fee lapses, terminal disclaimers and statutory extensions have not been checked. The continuity chain may be incomplete; this is not an enforceability determination.

Classification4 codes

B60R 21/0176
Diagnostic or recording means therefor: for firing circuits using only mechanical switches as collision detecting means, in series with…
G01R 31/007
On road vehicles, e.g. automobiles or trucks: using microprocessors or computers
B60R
Vehicle fittings and parts
G01R
Measuring electric variables

Method and apparatus for testing an airbag restraint system with parallel sensors

Life of this patent

Method and apparatus for testing an airbag restraint system with parallel sensors

Life of this patent

Life of this patent

Abstract

Drawings

Drawings

Claims9

Description4,142 words

Drawings

Classification4 codes

Life of this patent

Description4,142 words