Exhaust emission control system for internal combustion engines

• US 3,903,853 A
• Filed: 12/13/1973
• Issued: 09/09/1975
• Est. Priority Date: 01/12/1973
• Status: Expired due to Term

• Current Assignee: Harald Kizler, Peter Jurgen Schmidt
• Original Assignee: Harald Kizler, Peter Jurgen Schmidt
• Inventors: Kizler, Harald, Schmidt, Peter Jurgen
• Primary Examiner(s): Burns, Wendell E.
• Assistant Examiner(s): Reynolds, David D.
• Application Number:
  US05/424,621
• Time in Patent Office: 635 Days
• Field of Search: 60/276,285 323/40 123/32EA,119R
• US Class Current: 123/688
• CPC Class Codes: F02D 41/1482 Integrator, i.e. variable slope

Abstract

To render operation of an electronic control system connected to a sensing gauge essentially independent of fluctuations in supply voltage, and to provide an operator indication of malfunction of the system, the output from an oxygen sensor, located in the exhaust stream of the engine is applied as one leg of a bridge circuit, the other leg being supplied with a source of reference potential; the other branch is formed of a pair of resistors, an operational amplifier, connected as a comparator-threshold switch is connected across the diagonals of the bridge to provide an output signal when the sensing signal deviates from the reference; a high-resistance (with respect to the sensing element) connection is made from the supply source to the sensor so that, in case of failure of the sensor, a voltage will be applied to the bridge simulating a sensing signal and resulting in an output from the control system which commands the air-fuel composition to be very lean.

Claims

1. In an internal combustion engine exhaust emission control system, having means (1) sensing the composition of exhaust gases and providing a sensed electrical signal representative of the composition of the exhaust gases, an integrating control amplifier (29, 30) providing an output signal (29'"'"''"'"') which is available to command the relative mass ratio ( lambda ) of air and fuel being applied to the engine, and a connection circuit connecting the sensing means and the integrating control amplifier, the improvement wherein the connecting circuit comprises a bridge circuit (5), said sensing means (1) being connected to one branch of the bridge circuit to provide the sensing signal thereto;

a reference source (6, 7, 8, 9,

     11) connected into another branch of the bridge circuit and providing a reference signal, with respect to said sensing signal, the other branches of the bridge circuit being formed by balanced impedances (13,

     14); and

an operational amplifier (15) having its respective inverting and direct inputs connected across the diagonal junctions (J1, J2) of the bridge circuit to provide an output signal representative of deviation of the sensed signal from the reference signal.

2. System according to claim 1, wherein the branch of the bridge circuit to which the sensing means (1) is connected includes a transistor (2) connected as an emitter-follower, the sensing means (1) being connected to and controlling conduction of the emitter-follower transistor (2).

3. System according to claim 1, wherein the integrating control amplifier (28, 29) is connected to the output of the operational amplifier (15).

4. System according to claim 1, further comprising connection means (40) having a variable transfer function and connected between the output of the operational amplifier (15) and the integrating control amplifier (28, 29).

5. System according to claim 4, wherein the connection means (40) comprises a balanced transistor network (21, 22) having its emitter-collector paths connected between the source of voltage (3, 10;

23, 24;

25,

     26) and its output to the integrating control amplifier (29,

     30), and connected to be controlled by the output of the operational amplifier (15).

6. System according to claim 1, wherein the reference source (6, 7, 8, 9, 11) providing the reference signal includes a Zener diode (11) and a transistor (6) is provided, connected in the branch of the bridge circuit to which the reference source is connected, said transistor (6) being connected to be controlled by said Zener diode (11).

7. System according to claim 6, wherein the branch of the bridge circuit to which the sensing means (1) is connected includes a transistor (2) connected in emitter-follower circuit;

and wherein both said transistors (2,

     6) are of relatively opposite conductivity type.

8. System according to claim 1, further comprising switch means (27) connected to the input of the integrating amplifier (29, 30) and selectively switching the integrating amplifier to have different integrating time constants.

9. System according to claim 1, comprising a connecting circuit (35) between the sensing means (1) and the supply circuit for the system, said connecting circuit supplying the bridge, upon failure of said sensing means, with a signal which results in an output signal there from commanding a lean air-fuel mixture.

10. System according to claim 9, wherein the connecting circuit comprises a coupling resistor (35) connecting the terminal of the sensing means which is also connected to the bridge circuit with the supply circuit for the system.

11. System according to claim 10, wherein said coupling resistor (35) has a value which is high with respect to the internal resistance of the sensing means (1) when the sensing means is at operating temperature so as to avoid noticeably loading the sensing means.

12. An internal combustion engine'"'"''"'"'s exhaust emission control system comprising means (1) sensing the composition of exhaust gases and providing a sensed electrical signal representative of the composition of exhaust gases;

an integrating control amplifier (29,

     30) providing an output signal (29) which is available to command the relative mass ratio ( lambda ) of air and fuel being applied to the engine; and

a connecting circuit connecting the sensing means and the integrating control amplifier, said connecting circuit including a bridge circuit (5), one branch of said bridge circuit having a transistor (2) connected as an emitter-follower, the sensing means, (1) being connected to, and controlling the conduction of said emitter-follower transistor (2);

a reference source (6, 7, 8, 9,

     11) connected into another branch of the bridge circuit and providing reference signal, the other branches of the bridge circuit being formed by balanced impedences (13,

     14); and

an operational amplifier (15) having its respective inverting and direct in-puts connected across the diagonal junctions (J1, J2) of the bridge circuit, said operational amplifier (15) having its out-put connected to the in-put of the integrating control amplifier (29,

     30).

13. System according to claim 12, further comprising connection means (40) having a variable transfer function and connected between the output of the operational amplifier (15) and the integrating control amplifier (28, 29).

14. System according to claim 12, wherein the reference source (6, 7, 8, 9, 11) providing the reference signal includes a Zener diode (11) and a transistor (6) is provided, connected in the branch of the bridge circuit to which the reference source is connected, said transistor (6) being connected to be controlled by said Zener diode (11);

and wherein said transistor (6) and the transistor (2) connected in emitter-follower circuit are of relatively opposite conductivity type.

15. System according to claim 12, further comprising a coupling resistor (35) which has a value which is high with respect to the internal resistance of the sensing means (1) when the sensing means is at an operating temperature, so as to avoid noticeably loading the sensing means during normal operation, said coupling resistor being connected to the supply circuit for the system and to the control electrode of the transistor (2) in the emitter-follower'"'"''"'"'s circuit to provide a signal, upon failure of said sensing means, which results in an output from the bridge, and hence from the operational amplifier commanding the integrating amplifier to provide an output signal representative of a lean air-fuel mixture.