Turn-off protected ignition system for internal combustion engines

US4167170A · kind A · utility

Assignee

• Robert Bosch GmbH · DE

Inventors

• Gerhard Sohner · Schorndorf, DE
• Helmut Roth · Stuttgart, DE

Key dates

• Filing date: Nov 30, 1977
• Grant date: Sep 11, 1979
• Expiry date: Nov 30, 1997

Classification

• Technology area (CPC F): Mechanical Engineering; Lighting; Heating
• CPC primary: F02P3/0435
• WIPO field: Engines, pumps, turbines
• WIPO sector: Mechanical engineering

Abstract

A transistorized ignition system is protected against interruption of power supply by, for example, turn-off of the main or ignition switch while the transistor is in conductive condition so that, upon sudden interruption, an ignition event could be triggered at a time unsuitable for the remainder of the engine. A turn-off protection circuit is provided which includes a coupling resistor connected to the junction of the primary of the ignition coil and the main ignition current supply transistor thereto. The coupling resistor is connected in a circuit which holds the main current supply transistor in conductive condition, supplied from the energy stored in the ignition coil even after the main, ignition switch has been opened. A closed circuit for current flow due to this stored energy is provided within the overall ignition circuit. Preferably, the system includes a coupling transistor, connected across the power supply, which is blocked when the main transistor is conductive, so that the main transistor is controlled by power supply voltage appearing at the collector of the coupling transistor; the coupling resistor of the turn-off protected circuit then applies the inductive vol…