Exhaust cleaning apparatus for internal combustion engines

Claim 2

An exhaust cleaning apparatus for an internal combustion engine comprising reducing catalyst means disposed in an exhaust system of the engine for reducing nitrogen oxide in exhaust gases passed to the exhaust system from the engine, oxidizing catalyst means disposed in the exhaust system and located downstream of said reducing catalyst for oxidizing carbon monoxide and unburned hydrocarbons in the exhaust gases passed from said reducing catalyst means, additional fuel supplying means for admixing additional hydrocarbons to the exhaust gases entering said reducing catalyst means, and control means for controlling said additional fuel supplying means for interrupting the supply of the additional hydrocarbons to the exhaust gases in response to engine operating conditions producing enrichment of an air-fuel mixture to be supplied to the engine, in which said control means comprises a sensor which is responsive to the concentration of oxygen in the exhaust gases entering said reducing catalyst means for producing an electrical signal in response to a concentration of the oxygen lower than a predetermined level and a switching arrangement comprising first, second and third switch means electrically connected in series to said additional fuel supplying means for controlling the fuel supplying means to interrupt the supply of said additional hydrocarbons to the exhaust gases when at least one of said first to third switch means is open, said first switch means being operative to close in response to said electrical signal from said sensor, said second switch means being responsive to the load on the engine and operative to open in response to an engine load smaller than a first predetermined value larger than said first predetermined value, said third switch means being responsive to a starting condition of the engine and operative to open when the engine is being started.

Claim 3

An exhaust cleaning apparatus for an internal combustion engine comprising reducing catalyst means disposed in an exhaust system of the engine for reducing nitrogen oxide in exhaust gases passed to the exhaust system from the engine, oxidizing catalyst means disposed in the exhaust system and located downstream of said reducing catalyst for oxidizing carbon monoxide and unburned hydrocarbons in the exhaust gases passed from said reducing catalyst means, additional fuel supplying means for admixing additional hydrocarbons to the exhaust gases entering said reducing catalyst means, and control means for controlling said additional fuel supplying means for interrupting the supply of the additional hydrocarbons to the exhaust gases in response to engine operating conditions producing enrichment of an air-fuel mixture to be supplied to the engine, in which said control means comprises a sensor which is responsive to the concentration of oxygen in the exhaust gases entering said reducing catalyst means for producing an electrical signal in response to a concentration of the oxygen lower than a predetermined level and a switching arrangement comprising first to fourth switch means which are electrically connected in series to said additional fuel supplying means for controlling the fuel supplying means to interrupt the supply of said additional hydrocarbons to the exhaust gases when at least one of said first to fourth switch means being operative to close in response to said electrical signal from said sensor, the second switch means being responsive to the load on the engine and operative to open in response to an engine load smaller than a first predetermined value or greater than second predetermined value larger than said first predetermined value, the third switch means being responsive to a starting condition of the engine and operative to open when the engine is being started, the fourth switch means being responsive to the temperatures of said reducing and oXidizing catalyst means and operative to close when said temperatures are within predetermined ranges in which said catalyst means are maintained active.

Claim 4

An exhaust cleaning apparatus for an internal combustion engine comprising reducing catalyst means disposed in an exhaust system of the engine for reducing nitrogen oxide in exhaust gases passed to the exhaust system from the engine, oxidizing catalyst means disposed in the exhaust system and located downstream of said reducing catalyst for oxidizing carbon monoxide and unburned hydrocarbons in the exhaust gases passed from said reducing catalyst means, additional fuel supplying means for admixing additional hydrocarbons to the exhaust gases entering said reducing catalyst means, and control means for controlling said additional fuel supplying means for interrupting the supply of the additional hydrocarbons to the exhaust gases in response to engine operating conditions producing enrichment of an air-fuel mixture to be supplied to the engine, in which said control means comprises a sensor which is responsive to the concentration of oxygen in the exhaust gases entering said reducing catalyst means for producing an electrical signal in response to a concentration of the oxygen lower than a predetermined level and a switching arrangement comprising first to fourth switch means which are electrically connected in series to said additional fuel supplying means for controlling the fuel supplying means to interrupt the supply of said additional hydrocarbons to the exhaust gases when at least one of said first to fourth switch means being operative to close in response to said electrical signal from said sensor, the second switch means being responsive to the load on the engine and operative to open in response to an engine load smaller than a first predetermined value or greater than second predetermined value larger than said first predetermined value, the third switch means being responsive to a starting condition of the engine and operative to open when the engine is being started, the fourth switch means being responsive to the temperatures of said reducing and oXidizing catalyst means and operative to close when said temperatures are within predetermined ranges in which said catalyst means are maintained active.

Claim 5

An exhaust cleaning apparatus for an internal combustion engine comprising reducing catalyst means disposed in an exhaust system of the engine for reducing nitrogen oxide in exhaust gases passed to the exhaust system from the engine, oxidizing catalyst means disposed in the exhaust system and located downstream of said reducing catalyst for oxidizing carbon monoxide and unburned hydrocarbons in the exhaust gases passed from said reducing catalyst means, additional fuel supplying means for admixing additional hydrocarbons to the exhaust gases entering said reducing catalyst means, and control means for controlling said additional fuel supplying means for interrupting the supply of the additional hydrocarbons to the exhaust gases in response to engine operating conditions producing enrichment of an air-fuel mixture to be supplied to the engine, in which said control means comprises first and second switch means which are serially connected to said additional fuel supplying means for controlling the additional fuel supplying means to interrupt the supply of said additional hydrocarbons to the exhaust gases when at least either of said first and second switch means is open, said first switch means being responsive to the load on the engine and operative to open in response to an engine load smaller than a first predetermined value or greater than a second predetermined value larger than said first predetermined value, said second switch means being responsive to an acceleration condition of the engine and operative to open in response to the acceleration condition.

Claim 6

An exhaust cleaning apparatus for an internal combustion engine comprising reducing catalyst means disposed in an exhaust system of the engine for reducing nitrogen oxide in exhaust gases passed to the exhaust system from the engine, oxidizing catalyst means disposed in the exhaust system and located downstream of said reducing catalyst for oxidizing carbon monoxide and unburned hydrocarbons in the exhaust gases passed from said reducing catalyst means, additional fuel supplying means for admixing additional hydrocarbons to the exhaust gases entering said reducing catalyst means, and control means for controlling said additional fuel supplying means for interrupting the supply of the additional hydrocarbons to the exhaust gases in response to engine operating conditions producing enrichment of an air-fuel mixture to be supplied to the engine, in which said control means comprises first and second switch means which are serially connected to said additional fuel supplying means for controlling the additional fuel supplying means to interrupt the supply of said additional hydrocarbons to the exhaust gases when at least either of said first and second switch means is open, said first switch means being responsive to the load on the engine and operative to open in response to an engine load smaller than a first predetermined value or greater than a second predetermined value larger than said first predetermined value, said second switch means being responsive to an acceleration condition of the engine and operative to open in response to the acceleration condition.

Claim 7

An exhaust cleaning apparatus as claimed in claim 3, in which said first switch means comprises movable and stationary contacts and a cam rotatable with a throttle valve of the engine and having a cam lobe which is formed with angularly spaced protrusions located to be representative of closed-throttle and full-throttle positions of the throttle valve and engageable with said movable contact for moving the movable contact away from said stationary contact when the throttle valve is in the closed-throttle or full-throttle position.

Claim 8

An exhaust cleaning apparatus as claimed in claim 3, in which said first switch means comprise a vacuum-responsive switch and a speed-responsive switch which are connected in series to each other, said vacuum-responsive switch being responsive to the vacuum in an intake manifold of the engine and operative to open in response to a vacuum lower than a predetermined level or higher than another predetermined level which is higher than the former.

Claim 9

An exhaust cleaning apparatus as claimed in claim 3, in which said second switch means comprises a movable member rotatable with a throttle valve of the engine and responsive to an angular velocity of the throttle valve when the throttle valve is turned for acceleration, said second switch means opening in response to an angular velocity of the throttle valve greater than a predetermined level.

Claim 10

An exhaust cleaning apparatus for an internal combustion engine comprising reducing catalyst means disposed in an exhaust system of the engine for reducing nitrogen oxide in exhaust gases passed to the exhaust system from the engine, oxidizing catalyst means disposed in the exhaust system and located downstream of said reducing catalyst for oxidizing carbon monoxide and unburned hydrocarbons in the exhaust gases passed from said reducing catalyst means, additional fuel supplying means for admixing additional hydrocarbons to the exhaust gases entering said reducing catalyst means, and control means for controlling said additional fuel supplying means for interrupting the supply of the additional hydrocarbons to the exhaust gases in response to engine operating conditions producing enrichment of an air-fuel mixture to be supplied to the engine, in which said control means comprises first to third switch means which are serially connected to said additional fuel supplying means for controlling the additional fuel supplying means to interrupt the supply of said additional hydrocarbons to the exhaust gases when one of said first to third switch means is open, the first switch means being responsive to the load on the engine and operative to open in response to an engine load smaller than a first predetermined value or greater than a second predetermined value larger than the first predetermined value, the second switch means being responsive to an acceleration condition of the engine and operative to open in response to the acceleration condition, and the third switch means being responsive to a starting condition of the engine and operative to open when the engine is being started.

Claim 11

An exhaust cleaning apparatus for an internal combustion engine comprising reducing catalyst means disposed in an exhaust system of the engine for reducing nitrogen oxide in exhaust gases passed to the exhaust system from the engine, oxidizing catalyst means disposed in the exhaust system and located downstream of said reducing catalyst for oxidizing carbon monoxide and unburned hydrocarbons in the exhaust gases passed from said reducing catalyst means, additional fuel supplying means for admixing additional hydrocarbons to the exhaust gases entering said reducing catalyst means, and control means for controlling said additional fuel supplying means for interrupting the supply of the additional hydrocarbons to the exhaust gases in response to engine operating conditions producing enrichment of an air-fuel mixture to be supplied to the engine, in which said control means comprises first to third switch means which are serially connected to said additional fuel supplying means for controlling the additional fuel supplying means to interrupt the supply of said additional hydrocarbons to the exhaust gases when one of said first to third switch means is open, the first switch means being responsive to the load on the engine and operative to open in response to an engine load smaller than a first predetermined value or greater than a second predetermined value larger than the first predetermined value, the second switch means being responsive to an acceleration condition of the engine and operative to open in response to the acceleration condition, and the third switch means being responsive to a starting condition of the engine and operative to open when the engine is being started.

Claim 12

An exhaust cleaning apparatus for an internal combustion engine comprising reducing catalyst means disposed in an exhaust system of the engine for reducing nitrogen oxide in exhaust gases passed to the exhaust system from the engine, oxidizing catalyst means disposed in the exhaust system and located downstream of said reducing catalyst for oxidizing carbon monoxide and unburned hydrocarbons in the exhaust gases passed from said reducing catalyst means, additional fuel supplying means for admixing additional hydrocarbons to the exhaust gases entering said reducing catalyst means, and control means for controlling said additional fuel supplying means for interrupting the supply of the additional hydrocarbons to the exhaust gases in response to engine operating conditions producing enrichment of an air-fuel mixture to be supplied to the engine, in which said control means comprises first to fifth switch means which are serially connected to said additional fuel supplying means for controlling the additional fuel supplying means to interrupt the supply of said additional hydrocarbons to the exhaust gases when at least one of said first to fifth switch means is open, the first switch means being responsive to the load on the engine and operative to open in response to an engine load smaller than a first predetermined value or greater than a second predetermined value which is larger than said first predetermined value, the second switch means being responsive to an acceleration condition of the engine and operative to open in response to the acceleration condition, the third switch means being responsive to a starting condition of the engine and operative to open when the engine is being started, the fourth and fifth switch means being responsive to the temperatures of said reducing and oxidizing catalyst means, respectively, and operative to open in response to the temperatures of the catalyst means lower than predetermined levels or higher than other predetermined levels which are higher than the former.

Claim 13

An exhaust cleaning apparatus for an internal combustion engine comprising reducing catalyst means disposed in an exhaust system of the engine for reducing nitrogen oxide in exhaust gases passed to the exhaust system from the engine, oxidizing catalyst means disposed in the exhaust system and located downstream of said reducing catalyst for oxidizing carbon monoxide and unburned hydrocarbons in the exhaust gases passed from said reducing catalyst means, additional fuel supplying means for admixing additional hydrocarbons to the exhaust gases entering said reducing catalyst means, and control means for controlling said additional fuel supplying means for interrupting the supply of the additional hydrocarbons to the exhaust gases in response to engine operating conditions producing enrichment of an air-fuel mixture to be supplied to the engine, in which said control means comprises first to fifth switch means which are serially connected to said additional fuel supplying means for controlling the additional fuel supplying means to interrupt the supply of said additional hydrocarbons to the exhaust gases when at least one of said first to fifth switch means is open, the first switch means being responsive to the load on the engine and operative to open in response to an engine load smaller than a first predetermined value or greater than a second predetermined value which is larger than said first predetermined value, the second switch means being responsive to an acceleration condition of the engine and operative to open in response to the acceleration condition, the third switch means being responsive to a starting condition of the engine and operative to open when the engine is being started, the fourth and fifth switch means being responsive to the temperatures of said reducing and oxidizing catalyst means, respectively, and operative to open in response to the temperatures of the catalyst means lower than predetermined levels or higher than other predetermined levels which are higher than the former.

Claim 14

An exhaust cleaning apparatus for an internal combustion engine comprising reducing catalyst means disposed in an exhaust system of the engine for reducing nitrogen oxide in exhaust gases passed to the exhaust system from the engine, oxidizing catalyst means disposed in the exhaust system and located downstream of said reducing catalyst for oxidizing carbon monoxide and unburned hydrocarbons in the exhaust gases passed from said reducing catalyst means, additional fuel supplying means for admixing additional hydrocarbons to the exhaust gases entering said reducing catalyst means, and control means for controlling said additional fuel supplying means for interrupting the supply of the additional hydrocarbons to the exhaust gases in response to engine operating conditions producing enrichment of an air-fuel mixture to be supplied to the engine, in which said control means comprises first to sixth means which are serially connected to said additional fuel supplying means for controlling the additional fuel supplying means to interrupt the supply of said additional hydrocarbons to the exhaust gases, the first switch means being responsive to the load on the engine and operative to open in reSponse to an engine load smaller than a first predetermined value or greater than a second predetermined value which is larger than the first predetermined value, the second switch means being responsive to an acceleration of the engine and operative to open in response to the acceleration condition, the third switch being responsive to a starting condition of the engine and operative to open when the engine is being started, the fourth and fifth switch means being responsive to the temperatures of said reducing and and oxidizing catalyst means, respectively, and operative to open in response to the temperatures of the catalyst means lower than predetermined levels or higher than other predetermined levels which are higher than the former, and the sixth switch means being responsive to the engine temperature and operative to open in response to an engine temperature lower than a predetermined level.

Claim 15

An exhaust cleaning apparatus for an internal combustion engine comprising reducing catalyst means disposed in an exhaust system of the engine for reducing nitrogen oxide in exhaust gases passed to the exhaust system from the engine, oxidizing catalyst means disposed in the exhaust system and located downstream of said reducing catalyst for oxidizing carbon monoxide and unburned hydrocarbons in the exhaust gases passed from said reducing catalyst means, additional fuel supplying means for admixing additional hydrocarbons to the exhaust gases entering said reducing catalyst means, and control means for controlling said additional fuel supplying means for interrupting the supply of the additional hydrocarbons to the exhaust gases in response to engine operating conditions producing enrichment of an air-fuel mixture to be supplied to the engine, in which said control means comprises first to sixth means which are serially connected to said additional fuel supplying means for controlling the additional fuel supplying means to interrupt the supply of said additional hydrocarbons to the exhaust gases, the first switch means being responsive to the load on the engine and operative to open in reSponse to an engine load smaller than a first predetermined value or greater than a second predetermined value which is larger than the first predetermined value, the second switch means being responsive to an acceleration of the engine and operative to open in response to the acceleration condition, the third switch being responsive to a starting condition of the engine and operative to open when the engine is being started, the fourth and fifth switch means being responsive to the temperatures of said reducing and and oxidizing catalyst means, respectively, and operative to open in response to the temperatures of the catalyst means lower than predetermined levels or higher than other predetermined levels which are higher than the former, and the sixth switch means being responsive to the engine temperature and operative to open in response to an engine temperature lower than a predetermined level.