Protective circuit for the ignition system of an internal combustion engine

US4077377A · kind A · utility

Assignee

• Robert Bosch GmbH · DE

Inventors

• Werner Jundt · Ludwigsburg, DE
• Bernd Bodig · Leinfelden, DE
• Helmut Roth · Stuttgart, DE
• Gerhard Sohner · Schorndorf, DE
• Peter Werner · Wiernsheim, DE

Key dates

• Filing date: Sep 21, 1976
• Grant date: Mar 7, 1978
• Expiry date: Sep 21, 1996

Classification

• Technology area (CPC F): Mechanical Engineering; Lighting; Heating
• CPC primary: F02P9/002
• WIPO field: Engines, pumps, turbines
• WIPO sector: Mechanical engineering

Abstract

To prevent a spurious inductive spark when the master ignition switch of the vehicle is opened with the breaker terminals closed, so that current stored in the ignition coil might cause a spurious inductive voltage pulse, a protective circuit branch is connected in parallel across the primary of the ignition coil and includes an auxiliary semiconductor short-circuiting switch, preferably a thyristor, the conduction of which is controlled to close by an auxiliary control circuit which senses opening of the master ignition switch and permits application of a portion of the inductive current flow to the gate of the thyristor to render it conductive, thus short-circuiting the primary of the ignition coil and preventing an inductive voltage kick which might cause a spurious spark.