Ignition circuit for a two-stroke engine

US4979477A · kind A · utility

Assignee

• Andreas Stihl · DE

Inventors

• Hans Nickel · Cottenweiler, DE
• Michael Wissmann · Markgröningen, DE

Key dates

• Filing date: Aug 3, 1989
• Grant date: Dec 25, 1990
• Expiry date: Aug 3, 2009

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y02T10/40
• WIPO field: Engines, pumps, turbines
• WIPO sector: Mechanical engineering

Abstract

The invention is directed to an ignition circuit for an internal combustion engine such as a two-stroke engine of a handheld, portable tool such as a motor-driven chain saw or the like. The engine has a cylinder and a piston conjointly defining a combustion chamber and a crankshaft connected to the piston. The ignition circuit includes a spark plug mounted in the cylinder and voltage source. A switch is actuable between an on-condition wherein the voltage source is connected to the spark plug for initiating a spark in the chamber and an off-condition wherein the voltage source is disconnected from the spark plug. An electronic control circuit actuates the switch between the two conditions in dependence upon the angular position of the crankshaft and other operating parameters of the engine such as the engine speed. The electronic control circuit includes a high-speed control circuit and an idle-speed control circuit for determining the firing time in the control range of the idle speed.