Exhaust gas composition control system for internal combustion engines, and control method

• US 3,875,907 A
• Filed: 09/20/1973
• Issued: 04/08/1975
• Est. Priority Date: 10/19/1972
• Status: Expired due to Term

• Current Assignee: Johannes Brettschneider, Wolf Wessel
• Original Assignee: Johannes Brettschneider, Wolf Wessel
• Inventors: Wessel, Wolf, Brettschneider, Johannes
• Primary Examiner(s): Antonakas, Manuel A.
• Assistant Examiner(s): Cranson, James W.
• Application Number:
  US05/399,261
• Time in Patent Office: 565 Days
• Field of Search: 123/32EA,148E,119R 60/276
• US Class Current: 123/687
• CPC Class Codes: F02D 35/00 Controlling engines, dependent on conditions exterior or interior to engines, not otherwise provided for
• 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

Abstract

The exhaust gas composition is sensed by a sensor which provides an electrical output signal which is appliied to an integral controller which controls the mixing device (fuel injection system or carburetor) which mixes air and fuel to provide the air-fuel mixture for the engine, in proper proportion for minimum noxious exhaust emission. In accordance with the invention, the integral controller integrates at a rate which is controlled by the speed of the engine. A speed-dependent pulse signal is derived, applied to a monostable multivibrator (MMV) which samples the signal applied to the integral controller, so that the integral controller will integrate only when it receives the sample signal, and hold the then obtained integrated signal until the next sampled signal is applied thereto.

Claims

1. Exhaust gas composition control system for internal combustion engines (10) having sensing means (12) sensing the composition of exhaust gases from the engine;

an integral controller (30,

     16) integrating the sensed signal with respect to time and providing an output control signal;

means (11), mixing and proportioning the air and fuel being applied to the engine, said output control signal from the integral controller (13,

     16) being connected and applied to said proportioning means and controlling said mixing and proportioning means to mix the air-fuel mass ratio which results in a predetermined exhaust gas composition as sensed by said sensor when the mixture is burned in the engine;

the improvement wherein the integral controller integrates in steps, or recurring pulses, or cycles; and

means (S) are provided deriving a pulsed signal representative of engine speed (n), said pulsed speed signal being applied to said integral controller (13,

     16) to control the rate of cyclical recurrence of integration steps thereof in dependence on engine speed to effect integration at a time-average rate determined by said speed signal.

2. System according to claim 1, wherein said integral controller has a fixed integration rate.

3. System according to claim 1 wherein said integral controller has a predetermined integration rate;

said pulsed speed signal is a pulsed on-off signal having an on-off ratio which is dependent on speed; and

said integral controller is controlled by the ON pulses of said speed signal to effect integration at its predetermined rate during the ON-pulses only.

4. System according to claim 1 further comprising a threshold switch (14) connected to the output of the exhaust gas sensing means (12) and providing on-off sensing output signals when the sensed exhaust gas signal passes a pre-set limit;

and a switching circuit (15) controlled by said engine speed signal (n), the on-off sensing signal being connected to said integral controller (16) through said switching circuit and being further modified by said switching circuit in accordance with the speed of the engine.

5. System according to claim 4 further comprising a monostable multivibrator (36) controlled by said engine speed signal (n) and providing output pulses at a rate representative of engine speed to form said pulsed speed signal;

said output pulses being connected to said switching circuit (15) to interrupt the on-off sensing signal being applied to said integral controller (16) and command the integral controller to integrate the sensing signal only during occurrence of the output pulses from the monostable multivibrator (36).

6. System according to claim 5 wherein the integration rate of the integral controller (16) is fixed and the duration of integration per unit time is controlled by the number of output pulses per unit time.

7. System according to claim 5 wherein the mixing and proportioning means comprises a fuel injection system, said system including said means (S) deriving the engine speed representative signal to control the integration time of the integral controller (16) in accordance with the repetition rate of fuel injection events of the fuel injection system.

8. System according to claim 5 wherein said switching circuit (15) comprises a switching transistor (26) controlled by said monostable multivibrator (36);

a pair of transistors (24,

     25) connected to receive the on-off sensing output signal and respectively conductive during the ON, or OFF time, said switching transistor (26) being connected to said transistors (24,

     25) of the pair to additionally control their conduction and inhibit conduction theref during the OFF time of the MMV (36).

9. System according to claim 8 wherein a voltage divider is provided having three resistors (29, 30, 31), and having two tap points formed between the junction of two respective resistors (29, 30;

30,

     31), one terminal electrode of the transistors, each, of the pair being connected to a respective tap point of the voltage divider; and

conduction of the transistors is controlled by a connection to the bases thereof, said connection including a first connection to the on-off sensing output signal and a second connection to said switching transistor (26).

10. Method of controlling the composition of the exhaust gases of an internal combustion engine which comprises the steps of mixing air and fuel to prepare an air-fuel mixture for application to the engine;

sensing engine speed;

sensing exhaust gas composition and deriving a sensing signal representative of said composition;

controlling the relative proportion of air and fuel being mixed as a function of (a) exhaust gas composition, (b) time, (c) engine speed;

wherein said controlling step comprises integrating the sensed signal in cyclically repetitive steps; and

controlling the recurrence rate of said repetitive steps, and hence the integration rate as a function of engine speed.

11. Method according to claim 10 wherein the step of integrating the sensed signal in cyclically repetitive steps comprises periodically integrating said sensed signal at a fixed integration rate.

12. Method according to claim 10 wherein the step of controlling the recurrence rate of said repetitive steps includes controlling the duration of interruption of integration, between steps, as a function of engine speed.

13. Method according to claim 10, wherein the step of controlling the recurrence rate of said repetitive steps comprises pulsing the sensing signal as a function of engine speed, and the integration step comprises integrating the pulsed signal.

14. Method according to claim 13 wherein the step of pulsing the sensing signal comprises periodically sampling the sensing signal at a rate representative of engine speed, and the integrating step comprises integrating the sampled signal, with respect to time, at a fixed rate, during said sampling periods.