Method and apparatus for controlling the air-fuel ratio of the operating mixture of an internal combustion engine

US4528957A · kind A · utility

Assignee

• Robert Bosch GmbH · DE

Inventors

• Werner Jundt · Ludwigsburg, DE
• Rolf Reischl · Stuttgart, DE

Key dates

• Filing date: May 14, 1984
• Grant date: Jul 16, 1985
• Expiry date: May 14, 2004

Classification

• Technology area (CPC F): Mechanical Engineering; Lighting; Heating
• CPC primary: F02D41/148
• WIPO field: Engines, pumps, turbines
• WIPO sector: Mechanical engineering

Abstract

The invention is directed to a method and an apparatus for controlling the air-fuel ratio of the operating mixture supplied to an internal combustion engine. The apparatus includes an oxygen sensor that is responsive to the oxygen content of the burnt operating mixture. The operating state of the sensor is detected by superposing a constant reference quantity on the oxygen sensor output quantity. The resultant of these quantities is fed to at least two comparators having different thresholds. The comparator outputs are processed to detect the operational readiness of the sensor. In this arrangement, the air-fuel ratio of the operating mixture is adjustable in dependence on the output quantity of the comparator to which the higher threshold is applied. This upper threshold and the special course of the Lambda sensor output voltage coact to compensate for the lean shift of the Lambda control during the warm-up phase of the internal combustion engine. In addition, this method largely avoids the transient response behavior of the control apparatus referred to as "idle hunting" without necessitating additional circuit configurations. The use of the higher one of the two thresholds as th…