Exhaust gas composition control with after-burner for use with internal combustion engines

Claim 2

Exhaust gas composition control system to reduce the emission of noxious gases, for use with an internal combustion engine comprising the combination of a thermo reactor (19, 18'') forming an after-burner to burn carbon monoxide and unburned hydrocarbons, connected to directly receive the exhaust from the engine and a single catalyst catalytic reactor (20) of the reducing catalyst type connected downstream from the thermo reactor to receive the exhaust which has passed through the after-burner to reduce nitrogen oxides; said system further comprising an oxygen sensor (22) located between the after-burner and the catalytic reactor and to be exposed to the exhaust gas stream after having passed the after-burner, the sensor (22) providing an output signal exhibiting a sharp transition jump when the sensed gases change from oxydizing to reducing state, to provide a signal representative of presence, or absence of oxygen in the exhaust stream to which the sensor is exposed; means (25, 16, 72, 75, 76) controlling the application of at least one component of the fuel-air mixture to the engine, connected to and controlled by the output signal from the sensor (22) and regulating the relative proportions of mass of air and fuel of the mixture applied to the engine such that the proportion is just slightly below the stoichiometric ratio of air and fuel; and an integrating control amplifier (24, 74) having its input connected to the sensor (22) and its output connected to the control means (25, 16, 72, 75, 76), said control amplifier including an operational amplifier (FIG. 7: 77) connected as an integrating amplifier, and having its input connected to the sensor, circuit means (87, 88, 91; 89, 90, 92) forming a reference, and connection means connecting the reference to the input of the operational amplifier to clamp the maximum integrating level of the operational amplifier to the level of the reference.

Claim 3

System according to claim 1, wherein the oxygen sensor (22) comprises a solid body (34) which conducts oxygen ions and which has two opposite faces, one face being exposed to the exhaust gases and the other to ambient air.

Claim 4

System according to claim 1, wherein the thermo reactor comprises at least a portion of the exhaust manifold (18), which portion is thermally insulated (18'') with respect to ambient air to raise the temperature of the exhaust gases therein and provide for oxidation of CO and unburned hydrocarbons therein.

Claim 5

System according to claim 1, wherein the operational amplifier has feedback capacitor means (50, 85) in the feedback path between the input and output circuit thereof.

Claim 6

System according to claim 4, wherein the reference circuit means (FIG. 7) comprises a voltage divider (87, 88; 89, 90) having one terminal connected to the output of the operational amplifier and another to a reference source (52); and a diode (91; 92) interconnecting the tap point of the voltage divider and the control input of the operational amplifier to clamp the maximum input of the operational amplifier to the voltage level of the tap point.

Claim 7

System according to claim 1, wherein the control amplifier is connected to the sensor (22) and wherein the fuel-air mixture control means comprises a carburetor nozzle (71) and controllable fuel supply means (72) connected to the carburetor nozzle and applying fuel to the nozzle, said controllable fuel supply means being controlled by the control amplifier (74).

Claim 8

System according To claim 1, wherein the fuel-air mixture control means comprises an air inlet duct (13) and a controllable valve means (15) therein; an air duct (75) applying air to the inlet of the engine downstream of the controllable valve (15); and means controlling air flow through the air duct under control of the output signal from said control amplifier.

Claim 9

System according to claim 7, wherein the air flow control means in the duct comprises an electrically operable throttle valve connected to the output of the control amplifier.

Claim 10

System according to claim 1, wherein the control means (25, 16, 72, 75, 76) is set to regulate the fuel-air mixture to provide an air number of about 0.98.

Claim 11

Exhaust emission control system for an internal combustion engine having means admitting air and fuel, respectively, comprising two serially connected reactors, one reactor being a thermo reactor (19, 18'') connected directly to the exhaust of the engine to oxidize unburned hydrocarbons and carbon monoxide and the other reactor being a single catalyst catalytic reactor (20) of the reducing catalyst type to reduce nitrogen-oxygen compounds, the catalytic reactor (20), connected to the thermo reactor (18'', 19) downstream therefrom; duct means connecting the thermo reactor (18, 19'') and, downstream, the catalytic reactor (20); an oxygen ion sensitive oxygen gauge (22) located in said interconnecting duct means to be exposed on one side thereof to the exhaust gases which have passed through the thermo reactor (19, 18'') and before being applied to the catalytic reactor (20), and the other side thereof being exposed to ambient air, said gauge providing an output signal exhibiting a sharp transition jump upon change of exhaust composition containing oxygen, or not containing oxygen; and means controlling the fuel-air ratio of the fuelair mixture being applied to the engine under control of said oxygen gauge including a control loop from said gauge to the means admitting air and fuel, respectively, said loop being pre-set to control the fuel-air mixture to provide an air number of about 0.98 so as to be just under the stoichiometric ratio to permit after-burning of exhaust gases in the thermo reactor (19, 18'') to remove oxygen from the exhaust and permit the catalytic reactor to operate under reducing conditions and to thereby remove nitrogen-oxygen compounds from the exhaust gases so that the gases exhausted from the catalytic reactor will be essentially free of unburned hydrocarbons, carbon monoxide, and nitrogen-oxygen compounds; wherein the fuel-air mixture control means comprises an electronically controlled fuel injection system which includes a controllable switching circuit having control inputs (A, B), at least one fuel injection valve (16) supplied with fuel and opening for predetermined time periods under control of the switching circuit; one control input (B) to the switching circuit having a signal applied thereto representative of air supply to the engine, and the other control input (A) having a signal applied thereto representative of the output of the oxygen gauge; the switching circuit (25) comprises a monostable flip-flop stage (55) triggered in synchronism with the rotation of the engine and having a pulse duration controlled by the control input (B) representative of air being supplied to the engine; and wherein the switching circuit (25) further comprises a pulse extending stage connected to the monostable flipflop stage (55), and providing an extension pulse; an OR-gate (56) having the outputs of the monostable flip-flop stage (55) and the pulse extending stage applied thereto to obtain a composite output pulse; and a switching amplifier (69) controlled by the output of the OR-gate (56) connected to at least one injection valve (16) to energize the injection valve.

Claim 12

Exhaust emission control system for an internal combustion engine having means admitting air and fuel, respectively, comprising two serially connected reactors, one reactor being a thermo reactor (19, 18'') connected directly to the exhaust of the engine to oxidize unburned hydrocarbons and carbon monoxide and the other reactor being a single catalyst catalytic reactor (20) of the reducing catalyst type to reduce nitrogen-oxygen compounds, the catalytic reactor (20), connected to the thermo reactor (18'', 19) downstream therefrom; duct means connecting the thermo reactor (18, 19'') and, downstream, the catalytic reactor (20); an oxygen ion sensitive oxygen gauge (22) located in said interconnecting duct means to be exposed on one side thereof to the exhaust gases which have passed through the thermo reactor (19, 18'') and before being applied to the catalytic reactor (20), and the other side thereof being exposed to ambient air, said gauge providing an output signal exhibiting a sharp transition jump upon change of exhaust composition containing oxygen, or not containing oxygen; and means controlling the fuel-air ratio of the fuelair mixture being applied to the engine under control of said oxygen gauge including a control loop from said gauge to the means admitting air and fuel, respectively, said loop being pre-set to control the fuel-air mixture to provide an air number of about 0.98 so as to be just under the stoichiometric ratio to permit after-burning of exhaust gases in the thermo reactor (19, 18'') to remove oxygen from the exhaust and permit the catalytic reactor to operate under reducing conditions and to thereby remove nitrogen-oxygen compounds from the exhaust gases so that the gases exhausted from the catalytic reactor will be essentially free of unburned hydrocarbons, carbon monoxide, and nitrogen-oxygen compounds; wherein the fuel-air mixture control means comprises an electronically controlled fuel injection system which includes a controllable switching circuit having control inputs (A, B), at least one fuel injection valve (16) supplied with fuel and opening for predetermined time periods under control of the switching circuit; one control input (B) to the switching circuit having a signal applied thereto representative of air supply to the engine, and the other control input (A) having a signal applied thereto representative of the output of the oxygen gauge; the switching circuit (25) comprises a monostable flip-flop stage (55) triggered in synchronism with the rotation of the engine and having a pulse duration controlled by the control input (B) representative of air being supplied to the engine; and wherein the switching circuit (25) further comprises a pulse extending stage connected to the monostable flipflop stage (55), and providing an extension pulse; an OR-gate (56) having the outputs of the monostable flip-flop stage (55) and the pulse extending stage applied thereto to obtain a composite output pulse; and a switching amplifier (69) controlled by the output of the OR-gate (56) connected to at least one injection valve (16) to energize the injection valve.

Claim 13

System according to claim 10, wherein the thermo reactor comprises at least a portion of the exHaust manifold (18) of the engine, said portion being thermally insulated (18'') with respect to ambient air to provide a temperature range therein at which exhaust gases from the engine including CO and unburned hydrocarbons are oxidized.

Claim 14

System according to claim 10, further comprising an integrating control amplifier (24, 74) having its input connected to the sensor (22) and its output connected to the control means (25, 16, 72, 75, 76), said control amplifier including an operational amplifier (FIG. 7: 77) connected as an integrating amplifier, and having its input connected to the sensor, circuit means (87, 88, 91; 89, 90, 92) forming a reference, and connection means connecting the reference to the input of the operational amplifier to clamp the maximum integrating level of the operational amplifier to the level of the reference.

Claim 15

System according to claim 12, wherein the reference circuit means (FIG. 7) comprises a voltage divider (87, 88; 89, 90) having one terminal connected to the output of the operational amplifier and another to a reference source (52); and a diode (91; 92) interconnecting the tap point of the voltage divider and the control input of the operational amplifier to clamp the maximum input of the operational amplifier to the voltage level of the tap point.

Claim 16

Exhaust gas composition control system to reduce the emission of noxious gases, for use with an internal combustion engine comprising the combination of a thermo reactor (19, 18'') forming an after-burner to burn carbon monoxide and unburned hydrocarbons, connected to directly receive the exhaust from the engine and a single catalyst catalytic reactor (20) of the reducing catalyst type connected downstream from the thermo reactor to receive the exhaust which has passed through the after-burner to reduce nitrogen oxides; said system further comprising an oxygen sensor (22) located between the after-burner and the catalytic reactor and to be exposed to the exhaust gas stream after having passed the afterburner, the sensor (22) providing an output signal exhibiting a sharp transition jump when the sensed gases change from oxydizing to reducing state, to provide a signal representative of presence, or absence of oxygen in the exhaust stream to which the sensor is exposed; means (25, 16, 72, 75, 76) controlling the application of at least one component of the fuel-air mixture to the engine, connected to and controlled by the output signal from the sensor (22) and regulating the relative proportions of mass of air and fuel of the mixture applied to the engine such that the proportion is just slightly below the stoichiometric ratio of air and fuel; wherein the fuel-air mixture control means comprises an electronically controlled fuel injection system which includes a controllable, transistorized switching circuit (25), having control inputs (A, B), at least one fuel injection valve (16) supplied with fuel and opening for predetermined time periods under control of the switching circuit; one control input (B) to the switching circuit having a signal applied thereto representative of air being supplied to the engine, and another control input (A) having the output of the sensor (22) applied thereto; the switching circuit (25) comprises a monostable flip-flop stage (55) triggered in synchronism with the rotation of the engine and having a pulse duration controlled by the control input (B0 representative of air being supplied to the engine; and wherein the switching circuit (25) further comprises a pulse extending stage connected to the monostable flip-flop stage (55), and providing an extension pulse; an OR-gate (56) having the outputs of the monostable flip-flop stage (55) and the pulse extending stage applied thereto to obtain a composite output pulse; and a switching amplifier (69) controlled by the output of the OR-gate (56) connected to at least one injection valve (16) to energize the injection vaLve.

Claim 17

Exhaust gas composition control system to reduce the emission of noxious gases, for use with an internal combustion engine comprising the combination of a thermo reactor (19, 18'') forming an after-burner to burn carbon monoxide and unburned hydrocarbons, connected to directly receive the exhaust from the engine and a single catalyst catalytic reactor (20) of the reducing catalyst type connected downstream from the thermo reactor to receive the exhaust which has passed through the after-burner to reduce nitrogen oxides; said system further comprising an oxygen sensor (22) located between the after-burner and the catalytic reactor and to be exposed to the exhaust gas stream after having passed the afterburner, the sensor (22) providing an output signal exhibiting a sharp transition jump when the sensed gases change from oxydizing to reducing state, to provide a signal representative of presence, or absence of oxygen in the exhaust stream to which the sensor is exposed; means (25, 16, 72, 75, 76) controlling the application of at least one component of the fuel-air mixture to the engine, connected to and controlled by the output signal from the sensor (22) and regulating the relative proportions of mass of air and fuel of the mixture applied to the engine such that the proportion is just slightly below the stoichiometric ratio of air and fuel; wherein the fuel-air mixture control means comprises an electronically controlled fuel injection system which includes a controllable, transistorized switching circuit (25), having control inputs (A, B), at least one fuel injection valve (16) supplied with fuel and opening for predetermined time periods under control of the switching circuit; one control input (B) to the switching circuit having a signal applied thereto representative of air being supplied to the engine, and another control input (A) having the output of the sensor (22) applied thereto; the switching circuit (25) comprises a monostable flip-flop stage (55) triggered in synchronism with the rotation of the engine and having a pulse duration controlled by the control input (B0 representative of air being supplied to the engine; and wherein the switching circuit (25) further comprises a pulse extending stage connected to the monostable flip-flop stage (55), and providing an extension pulse; an OR-gate (56) having the outputs of the monostable flip-flop stage (55) and the pulse extending stage applied thereto to obtain a composite output pulse; and a switching amplifier (69) controlled by the output of the OR-gate (56) connected to at least one injection valve (16) to energize the injection vaLve.

Claim 18

System according to claim 14, comprising a control amplifier connected to the sensor, and wherein the other control input (A) is connected to the pulse extending stage, the duration of the extension pulse being controllable by the output of the control amplifier (24).

Claim 19

System according to claim 14, further comprising an integrating control amplifier (24, 74) having its input connected to the sensor (22) and its output connected to the control means (25, 16, 72, 75, 76), said control amplifier including an operational amplifier (FIG. 7: 77) connected as an integrating amplifier, and having its input connected to the sensor, circuit means (87, 88, 91; 89, 90, 92) forming a reference, and connection means connecting the reference to the input of the operational amplifier to clamp the maximum integrating level of the operational amplifier to the level of the reference.

Claim 20

System according to claim 16, wherein the reference circuit means (FIG. 7) comprises a voltage divider (87, 88; 89, 90) having one terminal connected to the output of the operational amplifier and another to a reference source (52); and a diode (91; 92) interconnecting the tap point of the voltage divider and the control input of the operational amplifier to clamp the maximum input of the operational amplifier to the voltage level of the tap point.