Air/fuel ratio control system for internal combustion engines, having exhaust gas recirculation control function

• US 4,380,988 A
• Filed: 08/24/1981
• Issued: 04/26/1983
• Est. Priority Date: 08/28/1980
• Status: Expired due to Term

• Current Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company)
• Original Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company)
• Inventors: Otsuka, Kazuo, Hasegawa, Shumpei, Narasaka, Shin
• Primary Examiner(s): Burns, Wendell E.
• Application Number:
  US06/295,750
• Time in Patent Office: 610 Days
• Field of Search: 123/571
• US Class Current: 123/698
• CPC Class Codes: F02D 41/0002 Controlling intake air
• CPC Class Codes: F02D 41/005 according to engine operating conditions
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

An air/fuel ratio control system for performing feedback control of the air/fuel ratio of an air/fuel mixture being supplied to an internal combustion engine. The air/fuel ratio control system is provided with an exhaust gas recirculation system which is adapted to use a pressure sensor and a temperature sensor for detection of conditions of interruption of the exhaust gas recirculation at low engine load and at low engine temperature. At the same time, the above sensors are used for detection of various engine operating conditions for control of the air/fuel ratio of the mixture, and are adapted to produce outputs continuously variable with wide ranges of changes in the absolute pressure in the intake system of the engine and in the engine temperature. The exhaust gas recirculation system thus precludes the use of special sensors and therefore has a simple exhaust gas recirculation control section.

Claims

1. An air/fuel ratio control system for performing feedback control of the air/fuel ratio of an air/fuel mixture being supplied to an internal combustion engine having an intake system, an exhaust system and a throttle valve arranged within said intake system, said air/fuel ratio control system comprising in combination:

means for detecting the concentration of an exhaust gas ingredient emitted from said engine;

fuel quantity adjusting means for producing said mixture being supplied to said engine; and

an electrical circuit operatively connecting said concentration detecting means with said fuel quantity adjusting means in a manner effecting feedback control operation to control the air/fuel ratio of said mixture to a predetermined value in response to an output signal produced by said concentration detecting means;

an exhaust gas recirculation passage communicating said intake system with said exhaust system;

an exhaust gas recirculation valve arranged across said exhaust gas recirculation passage and having means actuatable by negative pressure to open said valve;

a port opening in said intake system at a location slightly upstream of said throttle valve in idle position thereof;

a negative pressure passage communicating said port with said exhaust gas recirculation valve;

a solenoid valve arranged to close said negative pressure passage;

an absolute pressure sensor adapted to produce an output signal continuously variable with a change in absolute pressure present in said intake system;

an engine temperature sensor adapted to produce an output signal continuously variable with a change in engine coolant temperature; and

a circuit provided within said electrical circuit for detecting an operating condition of said engine and electrically connected to said solenoid valve;

said electrical circuit being operable on output signals produced by said absolute pressure sensor and said engine temperature sensor to carry out control of the air/fuel ratio of said mixture, said output signals of said absolute pressure sensor and said engine temperature sensors being supplied to said engine operating condition detecting circuit;

said electrical circuit being also operable on said output signals of said two last-mentioned sensors to cause said solenoid valve to close said negative pressure passage and simultaneously allow atmospheric air to be introduced into said negative pressure-actuatable means of said exhaust gas recirculation valve when said output signal of said absolute pressure sensor has a value lower than a first predetermined value or when said output signal of said engine temperature sensor has a value lower than a second predetermined value.

2. The air/fuel ratio control system as claimed in claim 1, wherein said electrical circuit includes:

a first comparator adapted to produce a high level output when said output signal of said absolute pressure sensor has a value lower than said first predetermined value;

a second comparator adapted to produce a high level output when said output signal of said engine temperature has a value lower than said second predetermined value;

an AND circuit arranged to be supplied with outputs from said first and second comparators; and

a transistor arranged to be supplied with an output from said AND circuit and operable on the same output to drive said solenoid valve.