Circuit arrangement for measuring an ion current in a combustion chamber of an internal combustion engine

US5914604A · kind A · utility

Assignees

• Daimler-Benz AG · DE
• VOLKSWAGEN AKTIENGESELLSCHAFT · DE

Inventors

• Ulrich Bahr · Braunschweig, DE
• Michael Daetz · Wolfsburg, DE

Key dates

• Filing date: Feb 18, 1997
• Grant date: Jun 22, 1999
• Expiry date: Feb 18, 2017

Classification

• Technology area (CPC F): Mechanical Engineering; Lighting; Heating
• CPC primary: F02P2017/125
• WIPO field: Engines, pumps, turbines
• WIPO sector: Mechanical engineering

Abstract

An ion current in the combustion chamber of an internal combustion engine is measured by using the spark plug as an ion current sensor. The ignition circuit arrangement has an ignition coil or transformer with a primary winding forming a primary circuit and a secondary winding forming a secondary circuit in which the spark plug is connected. A measuring voltage is applied to the secondary circuit by circuit components forming a measuring circuit for measuring the ion current. The measuring circuit provides a measuring voltage at a value that is lower than the battery voltage of the ignition system or corresponds to the battery voltage at most. A rectifying element is connected to the secondary circuit which feeds the secondary or ignition current into the battery circuit of the ignition system while an ion current caused to flow by the measuring voltage applied to the secondary circuit is measured between sparking times when no ignition current is flowing.