Air-fuel ratio feedback type fuel injection system

• US 3,895,611 A
• Filed: 10/12/1973
• Issued: 07/22/1975
• Est. Priority Date: 10/17/1972
• Status: Expired due to Term

• Current Assignee: Hideaki Norimatsu, Junji Kawarada, Kunio Endo, Motoharu Sueishi, Susumu Harada
• Original Assignee: Hideaki Norimatsu, Junji Kawarada, Kunio Endo, Motoharu Sueishi, Susumu Harada
• Inventors: Endo, Kunio, Sueishi, Motoharu, Harada, Susumu, Norimatsu, Hideaki, Kawarada, Junji
• Primary Examiner(s): Antonakas, Manuel A.
• Assistant Examiner(s): Cranson, Jr., James W.
• Application Number:
  US05/406,109
• Time in Patent Office: 648 Days
• Field of Search: 123/32EA 235/150.21
• US Class Current: 123/694
• CPC Class Codes: F02D 41/1456 with sensor output signal being linear or quasi-linear with the concentration of oxygen
• CPC Class Codes: F02D 41/1482 Integrator, i.e. variable slope
• CPC Class Codes: F02D 41/28 Interface circuits
• CPC Class Codes: F02M 51/02 specially for low-pressure fuel-injection F02M51/005 takes precedence; pumpsper se F02M51/04; injectors per se F02M51/08
• CPC Class Codes: G04F 5/00 Apparatus for producing preselected time intervals for use as timing standards generating clock signals for electric digital computers G06F1/04

Abstract

There is provided an air-fuel ratio feedback type fuel injection system of the type in which the fuel quantity is controlled to suit various operating conditions of an engine by a computing unit for generating injection pulses which determine the duration of the opening of electromagnetic valves connected to a fuel line in which the pressure is maintained at a constant value. The system further comprises an oxygen concentration detector for detecting the concentration of oxygen contained in the exhaust gases, an air-fuel ratio discriminating circuit for comparing the detected signal from the oxygen concentration detector with a preset value to make a discrimination, a samplying signal generating circuit for generating a samplying signal having a predetermined frequency to sample the discrimination signals from the air-fuel ratio discriminating circuit, and a feedback system for providing negative feedback to the computing unit to reverse the discrimination signal.

Claims

1. An air-fuel ratio feedback type fuel injection system having electromagnetic valve means connected to a constant pressure fuel line to inject the fuel into an internal combustion engine mounting the fuel injection system and a computing unit connected through an electromagnetic valve actuating circuit to the electromagnetic valve means for generating an injection pulse signal to determine the opening duration of the electromagnetic valve means thereby to control the quantity of said fuel to suitable various operating conditions of the internal combustion engine, comprising:

an oxygen concentration detector mounted in an exhaust pipe of said engine for detecting the concentration of oxygen contained in the exhaust gases of said engine, an air-fuel ratio discriminating circuit means connected to said oxygen concentration detector for comparing an output signal of said detector with a predetermined value to generate an output signal, a sampling signal generating circuit means for generating a sampling signal having a predetermined frequency, an addition and subtraction command circuit means connected to said sampling signal generating circuit means and said air-fuel ratio discriminating circuit means for generating an output command signal in accordance with the output signal of said air-fuel ratio discriminating circuit each time said sampling signal is applied thereto, a reversible counter connected to said addition and subtraction command circuit means to perform the operation of addition or subtraction on the count thereof in accordance with said output command signal of said addition and subtraction command circuit means for generating a correction signal, and valve opening duration correcting means connected to said reversible counter and further to said computer unit for controlling the opening duration of said electromagnetic valve means in accordance with said correction signal of said reversible counter in cooperation with said computing unit to reverse the output signal of said air-fuel ratio discrimination circuit means by changing the quantity of said fuel through said valve means.

2. A fuel injection system according to claim 1, wherein said valve opening duration correction means comprises a D-A converter.

3. A fuel injection system according to claim 1, wherein said valve opening duration correcting means comprises a correction value setting circuit means connected to said reversible counter and to said computing unit for generating a correction pulse signal corresponding to the correction signal of said reversible counter to extend the duration of the opening of said electromagnetic valve means.

4. A fuel injection system according to claim 1 further comprising a power range detector means connected to said valve opening duration correcting means for detecting a power range requiring a large torque in said engine and stopping the operation of said valve opening duration correcting means when said power range is detected.

5. A fuel injection system according to claim 1 further comprising a holding circuit means connected to said reversible counter for maintaining the count of said reversible counter at the maximum or minimum value thereof when the count of said reversible counter exceeds the maximum or minimum capacity of said reversible counter.

6. A fuel injection system according To claim 1 further comprising means connected to said sampling signal generating means for varying the frequency of the sampling signals from said sampling signal generating means in accordance with the response time of said oxygen concentration detector.

7. A fuel injection system according to claim 1 further comprising superposing means connected to said sampling signal generating circuit, to said valve opening duration correcting means and to said computing unit for superposing an additional correction signal corresponding to the number of the sampling of said sampling signals effected in a time interval up to the reversal of the output signal of said air-fuel ratio discriminating circuit means on the output signal of said valve opening duration correcting means.

8. A fuel injection system according to claim 1 further comprising dead zone detecting means connected to said oxygen concentration detector and to said sampling signal generating circuit means for preventing the generation of the output signal of said addition and subtraction command circuit when the output of said oxygen concentration detector reaches the level of an intermediate zone.

9. A fuel injection system according to claim 1, wherein said sampling signal generating circuit means generates said sampling signals in synchronism with the rotation of said engine.