Automotive-type internal combustion engine exhaust gas emission control system

• US 3,916,848 A
• Filed: 12/13/1973
• Issued: 11/04/1975
• Est. Priority Date: 01/12/1973
• Status: Expired due to Term

• Current Assignee: Peter-Jurgen Schmidt
• Original Assignee: Peter-Jurgen Schmidt
• Inventors: Schmidt, Peter-Jurgen
• Primary Examiner(s): Myhre, Charles J.
• Assistant Examiner(s): Cangelosi, Joseph A.
• Application Number:
  US05/424,464
• Time in Patent Office: 691 Days
• Field of Search: 123/32EA
• US Class Current: 123/688
• CPC Class Codes: F02D 41/1495 Detection of abnormalities in the air/fuel ratio feedback system

Abstract

A timing circuit is connected between a threshold switch providing alternately voltages representative of excess, or absence of oxygen in the exhaust emission from the engine, the timing circuit measuring the time interval between change-over of the threshold switch as determined by changes in the composition of the exhaust emission; if the change-over is within a predetermined timing range, a control switch is held in one position; if the change-over rate drops, however, indicative of malfunction in the exhaust emission sensor, or associated connected equipment, the switch is placed into another state whereupon it will command a fuel-air control amplifier to provide a control ratio of a predetermined value and, if desired, additionally provide a sensed output to control an alarm or other trouble indicator. Switching change of the control switch can be overriden by other signals available within the automotive vehicle.

Claims

1. In an internal combustion engine exhaust emission control system having means (1) sensing the composition of the exhaust gases and providing a sensed electrical signal, an integrating control amplifier (29, 30) connected to said sensing means (1) and providing an output signal (29'"'"''"'"') which is available to command the relative mass ratio ( lambda ) of airfuel applied to the engine;

and a threshold switch (15), connecting the sensing means (1) to the integrating control amplifier and operative to change switching state above, and below its threshold level, said threshold switch, upon normal operation of the system, cyclically switching between its states, a timing circuit (36) connected to the threshold switch (15) and measuring the time intervals between change-over of switching state of the threshold switch (15), as determined by changing output from the sensing means (1) the timing circuit sensing the intervals between change-over of the threshold switch (15'"'"''"'"'); and

a change-over switch (46;

47,

     49) controlled by said timing circuit (36) the timing circuit controlling said change-over switch to be in a first state when the duration of the intervals between change-over of the threshold switch are below a predetermined timing interval, indicative of proper operation of the sensing means and of the threshold switch, the timing circuit controlling said change-over switch (46;

47,

     49) to be in another state when the switching interval since the last change-over of the threshold switch is above said predetermined interval, said change-over switch, when in the second state, providing an output signal (49'"'"''"'"') indicative of excess time lapse between change-over of the threshold switch (15) and representative of system malfunction.

2. System according to claim 1, further comprising a monostable flip-flop (37, 39) connected between the Threshold switch (15) and the timing circuit (36) and triggered into unstable state by change of state of the threshold switch (15);

and wherein said timing circuit comprises a capacitor (44) connected to be charged during one state of the monostable flip-flop (37,

     39) and a discharge circuit (45) permitting discharge of the capacitor during the other state of the monostable flip-flop, said discharge circuit having a time constant which prevents complete discharge of the capacitor when the switching interval of the threshold switch (15) is within said predetermined value to provide a residual charge on the capacitor (44), said residual charge holding said change-over switch (46) in said state indicative of proper operation.

3. System according to claim 2, wherein the capacitor (44) is charged during the unstable state of the monostable flip-flop (37, 39) and discharged during the stable state thereof and said discharge circuit has a high time constant and is connected to and controlling said change-over switch (46) to change state indicative of '"'"''"'"''"'"''"'"'trouble'"'"''"'"''"'"''"'"' operation upon discharge of the capacitor below a predetermined level.

4. System according to claim 1, wherein the integrating control amplifier comprises an operational amplifier (29);

and a coupling circuit (54) is provided between the output (49'"'"''"'"') of the change-over switch (46) and the inverting input of the operational amplifier (29) to modify the input signal applied thereto.

5. System according to claim 4, wherein the coupling circuit comprises a diode (54).

6. System according to claim 4, further comprising selectively variable input resistance means (28, 31, 32) connected to the coupling network and the operational amplifier (29, 30).

7. System according to claim 2, wherein the monostable flip-flop (37, 39) comprises a transistor (37) having its emitter-collector path connected in parallel to the capacitor (44) of the timing circuit;

and a coupling capacitor (39) and a diode (38) coupling network connecting the output of the threshold switch (15) to the control electrode of the transistor (37).

8. System according to claim 1, wherein the timing circuit comprises a capacitor (44);

and the change-over switch (46) comprises an emitter-follower input transistor (47) connected to the timing capacitor (44), and a switching output transistor (49) connected to and controlled by said input transistor (47).

9. System according to claim 1, further comprising alarm circuit means (53'"'"''"'"', 60, 61) connected to the output (49'"'"''"'"') of the change-over switch (46) to provide an alarm output signal upon sensing of '"'"''"'"''"'"''"'"'trouble'"'"''"'"''"'"''"'"' operation.

10. System according to claim 1, further comprising at least one override connection terminal (52, 52'"'"''"'"') connected to the change-over switch (46) to hold said switch in a position indicating proper operation of the sensing means to override control of the integrating control amplifier (29, 30) by said change-over switch (46) upon energization of at least one of said override terminals.

11. System according to claim 1, wherein the relative mass ratio ( lambda ) of the air-fuel applied to the engine is controlled to apply a lean mixture to the engine when the timing circuit has sensed a time interval from the last change-over of the threshold switch (15) which is above the time duration of the predetermined interval.