US4956631A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Fault detector for vehicle safety system
Assignee: Mitsubishi Electric Corp
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Filing: 1989-09-22
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Granted: 1990-09-11
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Expires: 2009-09-22
Abstract
Abstract An improved fault detector for a vehicle air bag safety system including a balanced wheatstone bridge having a squib resistor at one arm thereof and a G sensor at another arm thereof. Wherein, outputs of the wheatstone bridge are fed alternatively to a single DC amplifier circuit by utilizing switching circuits and a voltage difference of the alternative outputs derived from the DC amplifier circuit is measured for detecting any transition or a fault of the squib resistor without any influence of the input offset voltage for the DC amplifier circuit and of dispersions in circuit constant as well as components of a measuring system, thereby eliminating the precise adjustments which are required in the prior art system during the production stage for providing an inexpensive and highly reliable fault detector.
Inventors
- 👤 Hisatsugu Itoh
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 12:18
CPC Classifications
G; G01; G01R; G01R31/00; B; B60; B60R; B60R21/00; B60R21/01; B60R21/017; B60R21/0173; B60R21/0176
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
149 words
A fault detector for a vehicle safety system, comprising: a first series circuit having a squib resistor and a resistor connected thereto at a junction A; a second series circuit having a pair of resistors connected to each other at a junction B having the same resistance ratio as that of the first series circuit for providing a balanced wheatstone bridge with said first series circuit in parallel connection thereto; a DC power source for supplying electric power to the wheatstone bridge; a pair of switching circuits connected separately to the junctions A and B for alternative switching; a DC amplifier circuit connected to a common output of said switching circuits; and a judging circuit for determining existence of a fault in the squib resistor based on a difference of the output voltages of the DC amplifier circuit being switched synchronously with the alternative switching of said switching circuits.
Claim 2
Dependent Claim
149 words
A fault detector for a vehicle safety system, comprising: a first series circuit having a squib resistor and a resistor connected thereto at a junction A; a second series circuit having a pair of resistors connected to each other at a junction B having the same resistance ratio as that of the first series circuit for providing a balanced wheatstone bridge with said first series circuit in parallel connection thereto; a DC power source for supplying electric power to the wheatstone bridge; a pair of switching circuits connected separately to the junctions A and B for alternative switching; a DC amplifier circuit connected to a common output of said switching circuits; and a judging circuit for determining existence of a fault in the squib resistor based on a difference of the output voltages of the DC amplifier circuit being switched synchronously with the alternative switching of said switching circuits.
Claim 3
Dependent Claim
25 words
A fault detector as defined in claim 1, wherein said first series circuit further includes a normally open switch connected in parallel to the resistor.
Claim 4
Dependent Claim
23 words
A fault detector as defined in claim 1, wherein said pair of switching circuits are switched by signals produced by the judging circuit.
Claim 5
Dependent Claim
19 words
A fault detector as defined in claim 1, wherein said DC amplifier includes an adder and an operational amplifier.
Claim 6
Dependent Claim
24 words
A fault detector as defined in claim 1, further including a standard voltage source to provide a standard voltage to said DC amplifier circuit.
Claim 7
Dependent Claim
28 words
A fault detector as defined in claim 1, further including a resistor connected in series to the lower potential end of the wheatstone bridge at a junction C.
Claim 8
Dependent Claim
33 words
A fault detected as defined in claim 6, further including a normally open switch connected in parallel to the resistor which is connected in series to the wheatstone bridge at the junction C.
Claim 9
Dependent Claim
21 words
A fault detector as defined in claim 6, wherein the DC amplifier circuit has a plurality of operational amplifiers and resistors.
Claim 10
Dependent Claim
17 words
A fault detector as defined in claim 8, wherein the DC amplifier circuit contains two operational amplifiers.
Claim 11
Dependent Claim
28 words
A fault detector as defined in claim 6, further including an amplifier interposed between the junction C and the DC amplifier circuit for providing a bias voltage thereto.
Claim 12
Dependent Claim
23 words
A fault detector as defined in claim 10, wherein the bias voltage is fed to the first stage of the DC amplifier circuit.
Claim 13
Dependent Claim
23 words
A fault detector as defined in claim 6, wherein the standard voltage is fed to the second stage of the DC amplifier circuit.
Claim 14
Dependent Claim
19 words
A fault detector as defined in claim 1 or claim 6, further including a lamp to indicate a fault.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-09-10 | 1994-03-12 | 1994-09-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-09-10 | 1998-03-12 | 1998-09-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-09-10 | 2002-03-12 | 2002-09-11 | $7700.00 | Window Closed / Lapsed |