Control system for normalizing the air/fuel ratio in a fuel injection system

• US 3,990,411 A
• Filed: 07/14/1975
• Issued: 11/09/1976
• Est. Priority Date: 07/14/1975
• Status: Expired due to Term

• Current Assignee: Siemens-Bendix Automotive Electronics LP
• Original Assignee: Gene Y. Wen, The Bendix Corporation (Honeywell International Inc.)
• Inventors: Wen, Gene Y., Toelle, Alvin Dan, Oberstadt, Allan Lee
• Primary Examiner(s): Myhre, Charles J.
• Assistant Examiner(s): Cox, Ronald B.
• Application Number:
  US05/595,455
• Time in Patent Office: 484 Days
• Field of Search: 123/32 EA, 60/276
• US Class Current: 123/683
• CPC Class Codes: F02D 41/068 for warming-up
• CPC Class Codes: F02D 41/1489 Replacing of the control value by a constant
• CPC Class Codes: F02D 41/149 Replacing of the control value by an other parameter

Abstract

In a closed loop fuel injection system for an internal combustion engine, a control system responding to several engine operating conditions and to rich fuel power demands operates to normalize the air/fuel ratio to a fixed air/fuel ratio. In the preferred embodiment the system responds to the operating temperature of a gas sensor to effectively remove the influence of the sensor control signals at nonoperational temperature upon the air/fuel ratio developed by the electronic control unit. In addition transducers responding to engine speed, wide open throttle, and coolant temperatures generate control signals to the control system indicating a requirement for engine operation of normalized air/fuel ratio.

Claims

1. In a closed loop fuel injection system for an internal combustion engine, a control system for normalizing the fuel injection system to a fixed air/fuel ratio during predetermined operating conditions, said control system comprising:

an electrochemical gas sensor positioned in the combustion system of the engine and operable at a high sensor temperature to generate a first voltage signal in response to the presence of a predetermined constituent gas and to generate a second voltage signal in response to the absence of a predetermined constituent gas, said sensor having an internal impedance varying inversely with the temperature of said sensor from a very high internal impedance at its low nonoperable temperature to a very low internal impedance at its high operating temperature;

a gas sensor amplifier circuit means electrically connected to said sensor, said circuit means normally having a high voltage level output signal when said sensor'"'"'s internal impedance is very high corresponding to the low temperature of said sensor and adapted to switch said output signal between said high voltage level and a low voltage level in response to said first and second voltage signals from said sensor;

delay means responsive to said high voltage level output signal from said gas sensor amplifier circuit means for generating an output voltage signal and operative in response to the switching of said output signal from said amplifier circuit means from said high to said low voltage level for maintaining said output voltage level output signal for an extended predetermined period of time;

fuel delivery control means for providing the control authority for operation of the fuel injectors, said means including primary and secondary integrators, said primary integrator normally generating an electrical signal for controlling the air/fuel ratio within a first control authority range for normal engine operation in response to said first and second voltage signals from said sensor and operative to generate an electrical signal for controlling the air/fuel ratio to a fixed air/fuel ratio and said secondary integrator normally responsive to said primary integrator for increasing said first control authority range during engine demand operation outside of normal engine operation;

a first switch means electrically connected in shunt with the integrating capacitor of said primary integrator and responsive to said high voltage level output signal from said sensor amplifier circuit means to maintain said fixed air/fuel ratio; and

a second switch means electrically connected in shunt with the integrating capacitor of said secondary integrator and responsive to said output signal from said delay means for maintaining said primary integrator within said first control authority range.

2. In the control system according to Claim 1 additionally including a speed transducer responsive to the speed of the engine and operable to generate a pulsed electrical signal having a frequency proportional to the speed of the engine;

and

speed transducer circuit means responsive to said pulsed electrical signal for generating an output signal having a high voltage level below a first speed and a low voltage level above a second speed, said high output signal operable for activating said delay means and said first and second switch means.

3. In the control system according to claim 2 wherein said first speed is below the idle speed of the engine and said second speed is greater than the idle speed of the engine.

4. In the control system according to claim 3 wherein said speed transducer circuit means includes a feedback means for maintaining said output signal at a said high voltage as the speed is increased from said first to said second speed and for maintaining said output signal at said low voltage level as the speed is decreased below said second speed.

5. In the control system according to claim 1 additionally including

an engine coolant transducer responsive to the coolant temperature of the engine for generating an electrical signal proportional thereto, and

coolant transducer circuit means responsive to said electrical signal for generating an output signal having a high voltage level when the coolant is below a predetermined temperature and switching to a low voltage above said predetermined temperature, said high output voltage signal operable for activating said first and second switch means.

6. In the control system according to claim 1 additionally including wide open throttle transducer means responsive to the wide open position of the throttle of the engine for generating an output signal having a high voltage level, said high voltage level operable for activating said first and second switch means.

7. In the control system according to claim 1 wherein said first control authority range operates to maintain the air/fuel ratio substantially at stoichiometric air/fuel ratio conditions and said secondary integrator operates to increase said first control authority range by at least a factor of three.

8. In the control system according to claim 7 wherein said first control authority range is five percent and said second integrator increases said first control authority range by eighteen percent thereby allowing the engine to operate with air/fuel ratios having values from substantially 12 to substantially 18.

9. In a closed loop fuel injection system for an internal combustion engine, control system for normalizing the fuel injection system to a fixed air/fuel ratio during predetermined operating conditions, said control system comprising:

an electrochemical exhaust gas sensor positioned in the exhaust system of the engine, said sensor having an internal impedance varying inversely with the temperature of said sensor from a very high internal impedance at its low, nonoperable temperature to a very low internal impedance at its high, operating temperature;

a gas sensor amplifier circuit means electrically connected to said sensor, said circuit means responsive to the change in internal impedance thereof for generating an output signal having a high voltage level in response to said very high internal impedance;

speed transducer means responsive to speed of the engine and operable to generate a pulse electrical signal having a frequency proportional to the speed of the engine;

speed transducer circuit means responsive to said pulse electrical signal for generating an output signal having a high voltage level below a first speed;

a delay means receiving as its input signal said high voltage output signal from said gas sensor amplifier circuit means and said speed transducer circuit means for generating a high voltage level output signal in response thereto and for maintaining said high voltage level output signal for an extended predetermined period of time after said signals are removed from the input of said delay means;

an engine coolant transducer responsive to the coolant temperature of the engine for generating an electrical signal having a high voltage level below a predetermined operating temperature;

wide open throttle transducer means responsive to the wide open position of the throttle of the engine for generating a high voltage output signal;

fuel delivery control means including primary and secondary integrators each respectively having an integrating capacitor, said primary integrator normally maintaining a first air/fuel ratio and operative to maintain a second fixed air/fuel ratio and said secondary integrator normally responsive to said primary integrator for modifying said first air/fuel ratio;

a first switch means electrically connected in shunt with said integrating capacitor of said primary integrator and responsive to one of said high voltage level output signals from said sensor amplifier circuit means, said speed transducer means, said wide open throttle transducer means, and said engine coolant transducer means; and

a second switch means electrically connected in shunt with said integrating capacitor of said secondary integrator and responsive to said high voltage output signal from said delay means for maintaining the output of said primary integrator unmodified.