Air fuel ratio control device

Abstract

Abstract PURPOSE: To premit compensation for fluctuations of O 2 sensors by providing the O 2 sensors on the upstream and downstream sides of a tertiary catalyst of an exhaust system and effecting feedback control according to detection signals from the individual sensors at the time of a predetermined engine operating condition. CONSTITUTION: When the intake air quantity is below a predetermined quantity (i.g., at the time of low intake), the output of a comparator 104 of a discriminating circuit 10 is at a low level, and a transistor (tr) 203 in a switching circuit 20 is non-conductive, so that no current flows through a relay coil 211. Thus, in this state contacts 210c and 210a are connected, and a detection signal from an O 2 sensor 8 provided on the upstaream side of a tertiary catalyst 7a is supplied to a comparator circuit 30 for feedback control through an intergrating circuit 40 and a control unit 6 to provide for a predetermined air-to-fuel ratio. When the intake air quantity exceeds a predetermined quantity (i.e., at the time of high intake), the output of the comparator 10 is inverted to a high level to trigger the transistor 203, thus energizing the coil 211 to connect contacts 210c and 210b. At this time, a detection signal from an O 2 sensor 9 provided on the downstream side of the catalyst 7a is supplied to the circuit 30 for feed-back control to provide for a predetermined air- to-fuel ratio. COPYRIGHT: (C)1980,JPO&Japio

Inventors

• 👤 Hideaki Norimatsu
• 👤 Shigehiko Tajima

Bibliographic Details