The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Feb. 19, 1985
Filed:
Mar. 31, 1983
Osamu Sangu, Toyota, JP;
Seiko Hotta, Oobu, JP;
Nippondenso Co., Ltd., Kariya, JP;
Abstract
In a method and apparatus for detecting an open circuit in a glow plug group for combination with a heating control circuit of the glow plug group mounted on an internal combustion engine, an output signal generated from a detecting element connected in series with the glow-plug group while electric power is supplied to the glow plug group is applied to a first comparator to detect a change of the composite resistance of the glow plug group due to a temperature rise caused by its heating. At this time, if an open circuit failure has occurred in the glow plug group, the state of the resistance change of the glow plug group varies greatly. The first comparator produces a time measurement signal indicating a time when the composite resistance of the glow plug group has reached a predetermined value and supplies the time measurement signal to a glow plug open circuit detecting circuit. In a glow plug open circuit detecting circuit, a second comparator produces a time limit signal which continues for a preset time-length from the time of application of a power supply voltage, and a gate circuit gates the time measurement signal with the time limit signal and generates a glow plug open circuit detection signal for actuating an open circuit indicator only when the time indicated by the time measurement signal is shorter than the preset time-length.