Air-fuel ratio control device for an internal combustion engine

• US 4,240,389 A
• Filed: 05/18/1978
• Issued: 12/23/1980
• Est. Priority Date: 02/15/1978
• Status: Expired due to Term

• Current Assignee: Toyota Jidosha Kogyo Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Toyota Jidosha Kogyo Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Shimazaki, Ruji
• Primary Examiner(s): Myhre, Charles J.
• Assistant Examiner(s): Nelli, Raymond A.
• Application Number:
  US05/907,339
• Time in Patent Office: 950 Days
• Field of Search: 123/32 EH, 123/119 EC, 123/32 EE
• US Class Current: 123/492
• CPC Class Codes: F02D 41/045 Detection of accelerating or decelerating state detection thereof in general G01P
• CPC Class Codes: F02D 41/1479 Using a comparator with variable reference

Abstract

Disclosed is an air-fuel control device for an internal combustion engine which includes: an O₂ sensor for detecting the oxygen concentration of exhaust gas; a control circuit having a comparator for comparing the output voltage from the O₂ sensor with a reference voltage (V_R), so that the air-fuel ratio of the mixture discriminated as rich or lean with respect to a stoichiometric air-fuel ratio, and; an installation for supplying fuel into an intake passage, so that when the air-fuel ratio of the mixture is leaner than the stoichiometric value the amount of fuel is increased and when the air-fuel ratio of the mixture is richer than the stoichiometric value the amount of fuel is decreased. This device further includes a sensor for detecting the accelerating operating conditions of the engine, and a mechanism for changing the reference voltage (V_R) to a value (V_R2) different from a predetermined value (V_R1) so that the air-fuel ratio of the mixture is changed so as to be richer only when the engine is in the accelerating operating conditions.

Claims

1. An air-fuel ratio control device for an internal combustion engine comprising:

a first sensor provided in an exhaust passage for detecting the oxygen concentration of exhaust gas;

a control circuit having means for comparing the output voltage from said first sensor with a reference voltage so that an air-fuel ratio of the mixture being introduced into the internal combustion engine is discriminated as rich or lean with respect to stoichiometric air-fuel ratio during all operating conditions of the engine;

means for supplying fuel into an intake passage of the internal combustion engine, so that when the air-fuel ratio of the mixture is leaner than the stoichimetric air-fuel ratio the amount of fuel is increased and when the air-fuel ratio of the mixture is richer than the stoichiometric air-fuel ratio the amount of fuel is decreased;

a second sensor for detecting the accelerating operating conditions of the internal combustion engine, said second sensor having an output signal indicating engine acceleration and comprising a diaphragm-type switch having a diaphragm which is actuated by vacuum pressure drawn from the intake passage downstream of a throttle valve, said diaphragm-type switch sends an accelerating signal to the control circuit when the absolute value of intake pressure is abruptly increased; and

means, responsive to said output signal, for changing said reference voltage to a value different from a predetermined value so that the air-fuel ratio of the mixture being controlled is changed so as to be richer only when the internal combustion engine is in the accelerating operating conditions.

2. An air-fuel ratio control device as set forth in claim 1, wherein said first sensor for detecting the oxygen concentration of exhaust gas is an O₂ sensor.

3. An air-fuel ratio control device as set forth in claim 1, wherein said comparing means of the control circuit comprises:

a comparator to which the output voltage of the first sensor and the reference voltage are input, and;

a variable resistance for changing said reference voltage being input into said comparator, the resistance value of said variable resistance being changed by said reference voltage changing means.

4. An air-fuel ratio control device as set forth in claim 1, wherein said comparing means of the control circuit comprises a first comparator to which a reference voltage (V_R1) for ordinary conditions is input and a second comparator to which a reference voltage (V_R2) for accelerating conditions different from V_R1 is input, and said reference voltage changing means selects one of said first and second comparators.