Engine air/fuel ratio control system with both normal idling and idle up idling capability
An engine includes a three way catalytic converter in its exhaust system, and a carburetor whose throttle valve has a normal and an idle up idling position, selected between by an idle up device. A device for weakening the air/fuel ratio of the mixture in the engine intake system only functions when no oxygen is detected in the engine exhaust system by an oxygen sensor. A means for supplying enough secondary air into the exhaust system upstream of the oxygen sensor to make the exhaust gases leaner than stoichiometric functions according to supply of a controlling vacuum. A first vacuum take out port is provided in the throat of the carburetor at a position downstream of the throttle valve when it is in the normal idling position and upstream of it when it is opened a little from the normal idling position. A second vacuum take out port is provided in the throat at a position downstream of the throttle valve when it is in the idle up idling position and upstream of it when it is opened a little from the idle up idling position. A vacuum switching system supplies vacuum from either the first or second take out port to the secondary air supplying means as controlling vacuum, according as idle up is being not performed, or is being performed, respectively.
- Assignee:
- Toyota Jidosha Kogyo K K (Japan)
- Patent Number(s):
- US 4376427
- OSTI ID:
- 6455379
- Resource Relation:
- Patent Priority Date: Priority date 20 Nov 1980, Japan; Other Information: PAT-APPL-321191
- Country of Publication:
- United States
- Language:
- English
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