Fault diagnosis apparatus for control circuit of vehicle passenger protecting device

• US 5,409,258 A
• Filed: 01/18/1994
• Issued: 04/25/1995
• Est. Priority Date: 04/27/1993
• Status: Expired due to Term

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Kawabata, Munehiro
• Primary Examiner(s): FERRITER, KARIN L
• Application Number:
  US08/182,234
• Time in Patent Office: 462 Days
• Field of Search: 280/728 R, 280/734, 280/735, 180/282, 340/436, 340/438, 307/10.1, 364/424.03, 371/25.1
• US Class Current: 280/735
• CPC Class Codes: B60R 21/0173 Diagnostic or recording means therefor
• CPC Class Codes: G01R 31/006 on road vehicles, e.g. automobiles or trucks testing of ignition installations peculiar to internal combustion engines F02P17/00
• CPC Class Codes: G01R 31/2829 Testing of circuits in sensor or actuator systems testing of apparatus for measuring electric or magnetic variables G01R35/00; testing of indicating or recording apparatus G01D; in airbag systems B60R21/0173; checking gas analysers G01N33/007; monitoring or fail-safe circuits for electromagnets H01F7/1844

Abstract

A fault diagnosis apparatus for diagnosing a control circuit comprising a squib that activates an air bag or the like, a first and a second switching element for activating the squib, and a collision judging circuit that turns on the first and the second switching elements upon detecting an impact in excess of a predetermined level. A microcomputer included in the apparatus generates a signal that turns on either of the two switching elements. The voltage between the activated switching element and the squib is then detected and compared by the microcomputer with the voltage in normal operation for fault diagnosis.

Claims

1. A fault diagnosis apparatus for diagnosing a control circuit comprising activating means for activating a vehicle passenger protecting device, first and second switching means for placing said activating means in operating state, and collision detecting means for turning on both said first and said second switching means upon detecting an impact in excess of a predetermined level, said fault diagnosis apparatus including:

diagnostic means for diagnosing said control circuit for fault by outputting signals for alternately turning on said first and said second switching means, and by comparing the output potential of the respective switching means upon output of said signals with a known output potential of the same switching means in normal operation.

2. A fault diagnosis apparatus according to claim 1, wherein said control circuit includes a power supply and ground;

said power supply, said first switching means, said activating means, said second switching means and said ground of said control circuit being connected in series;

said diagnostic means of said fault diagnosis apparatus detecting the potential of the point of connection between said first switching means and said activating means upon output of the signal for turning on said first switching means, and detecting the potential of the point of connection between said second switching means and said activating means upon output of the signal for turning on said second switching means.

3. A fault diagnosis apparatus according to claim 2, further comprising a resistance connected in parallel with a serial circuit composed of said first switching means and said activating means.

4. A fault diagnosis apparatus according to claim 3, wherein said diagnostic means judges any one of the switching means to be faulty if the detected potential is different from the potential in normal operation.

5. A fault diagnosis apparatus according to claim 4, wherein said diagnostic means comprises:

an analog-digital converter for converting the value of the detected potential to a digital value; and

a microcomputer for outputting the signal for turning on any one of the switching means and carrying out fault diagnosis by use of the detected potential value received from said analog-digital converter.