Engine ignition system with variable spark internal duration

US4176644A · kind A · utility

Assignee

• Robert Bosch GmbH · DE

Inventors

• Rainer Hellberg · Dormagen, DE
• Leo Steinke · Waiblingen, DE
• Adolf Fritz · Stuttgart, DE

Key dates

• Filing date: Oct 26, 1977
• Grant date: Dec 4, 1979
• Expiry date: Oct 26, 1997

Classification

• Technology area (CPC F): Mechanical Engineering; Lighting; Heating
• CPC primary: F02P3/0453
• WIPO field: Engines, pumps, turbines
• WIPO sector: Mechanical engineering

Abstract

An RC circuit branch determines the duration of the period for which the primary circuit of a spark coil remains interrupted after the main peak of the spark discharge in the secondary circuit that includes a spark plug. Engine speed and engine temperature are used to shorten the period during which the secondary circuit is allowed to entertain a spark discharge. As engine speed increases the spark discharge period is reduced until a certain speed is reached after which the spark discharge period remains constant with further increase of engine speed. Engine temperature is also used to shorten the spark discharge period by the use of a temperature sensitive resistor. The charging and discharging of the storage capacitor of the RC circuit branch are separately controlled by the shunt circuits in which diodes are interposed and in one embodiment an additional capacitor can be switched into parallel into the RC circuit branch when the engine is starting up. The degree of intake manifold vacuum can also be used to modify the operation of the circuit.