US4964271A — Air-fuel ratio feedback control system including …

Claim 1

Independent Claim 235 words

A method for controlling an air-fuel ratio in an internal combustion engine having a catalyst converter for removing pollutants in the exhaust gas thereof, and upstream-side and downstream-side air-fuel ration sensors disposed upstream and downstream, respectively, of said catalyst converter, for detecting a concentration of a specific component in the exhaust gas, comprising the steps of: sensing air-fuel ration feedback control conditions for said downstream-side air-fuel ration sensor; determining whether or not all the air-fuel ratio feedback control conditions for said downstream-side air-fuel ratio sensor are satisfied; controlling the air-fuel ration of said engine by an open loop control so that it is brought close to an air-fuel ratio, when at least one of the air-fuel ratio feedback control conditions for said downstream-side air-fuel ratio sensor is not satisfied; controlling the air-fuel ratio of said engine in accordance with the output of said upstream-side air-fuel ratio sensor so that it is brought close to the stoichiometric air-fuel ratio while prohibiting control of said air-fuel ratio of said engine in accordance with the output of said downstream-side air-fuel ratio sensor for a period after all the air-fuel ratio feedback control condition for said downstream-side air-fuel ratio sensor are satisfied; and controlling the air-fuel ratio of said engine in accordance with the outputs of said upstream-side and downstream-side air-fuel ratio sensors so that it is brought close to the stoichiometric air-fuel ratio after said period has passed.

Claim 2

Independent Claim 235 words

A method for controlling an air-fuel ratio in an internal combustion engine having a catalyst converter for removing pollutants in the exhaust gas thereof, and upstream-side and downstream-side air-fuel ration sensors disposed upstream and downstream, respectively, of said catalyst converter, for detecting a concentration of a specific component in the exhaust gas, comprising the steps of: sensing air-fuel ration feedback control conditions for said downstream-side air-fuel ration sensor; determining whether or not all the air-fuel ratio feedback control conditions for said downstream-side air-fuel ratio sensor are satisfied; controlling the air-fuel ration of said engine by an open loop control so that it is brought close to an air-fuel ratio, when at least one of the air-fuel ratio feedback control conditions for said downstream-side air-fuel ratio sensor is not satisfied; controlling the air-fuel ratio of said engine in accordance with the output of said upstream-side air-fuel ratio sensor so that it is brought close to the stoichiometric air-fuel ratio while prohibiting control of said air-fuel ratio of said engine in accordance with the output of said downstream-side air-fuel ratio sensor for a period after all the air-fuel ratio feedback control condition for said downstream-side air-fuel ratio sensor are satisfied; and controlling the air-fuel ratio of said engine in accordance with the outputs of said upstream-side and downstream-side air-fuel ratio sensors so that it is brought close to the stoichiometric air-fuel ratio after said period has passed.

Claim 3

Dependent Claim 103 words

A method as set forth in claim 1, further comprising the steps of: calculating a time period from a time when all the air-fuel ratio feedback control conditions for said downstream-side air-fuel ratio sensor are satisfied to a time when at least one of the air-fuel ratio feedback control conditions for said downstream-side air-fuel ratio sensor is not satisfied; determining whether or not said time period is smaller than a definite period; prohibiting the control of the air-fuel ratio of said engine in accordance with the output of said downstream-side air-fuel ratio sensor when said time period is smaller than said definite period.

Claim 4

Dependent Claim 48 words

A method as set forth in claim 1, wherein the air-fuel ratio feedback control conditions for said downstream-side air-fuel ratio sensor include all the air fuel ratio feedback control conditions for said upstream-side air-fuel ratio sensor, which include a condition of a fuel cut-off state of said engine.

Claim 5

Dependent Claim 31 words

A method as set forth in claim 1, wherein the air-fuel ratio feedback control conditions for said downstream-side air-fuel ratio sensor include a condition of a coolant temperature of said engine.

Claim 6

Dependent Claim 31 words

A method as set forth in claim 1, wherein the air-fuel ratio feedback control conditions for said downstream-side air-fuel ratio sensor include a condition of an idling state of said engine.

Claim 7

Dependent Claim 34 words

A method as set forth in claim 1, wherein the air-fuel ratio feedback control conditions for said downstream-side air-fuel ratio sensor include a condition of an activation state of said downstreamside air-fuel ratio sensor.

Claim 8

Dependent Claim 30 words

A method as set forth in claim 1, wherein the air-fuel ratio feedback control conditions for said downstream-side air-fuel ratio sensor include a condition of a load of said engine.

Claim 9

Dependent Claim 16 words

A method as set forth in claim 1, wherein said period is a definite time period.

Claim 10

Dependent Claim 42 words

A method as set forth in claim 1, wherein said period is defined by a definite number of reversions of the output of said upstream-side air-fuel ratio sensor which is switched from the rich side to the lean side and vice versa.

Claim 11

Dependent Claim 139 words

A method as set forth in claim 1, wherein said air-fuel ratio controlling step in accordance with the output of said upstream-side air-fuel ratio sensor comprises the steps of: calculating a first air-fuel ratio correction amount in accordance with the output of said upstream-side air-fuel ratio sensor; and adjusting an actual air-fuel ratio in accordance with said first air-fuel ratio correction amount, and wherein said air-fuel ratio controlling step in accordance with the output of said upstream-side and downstream-side air-fuel ratio sensors comprises the steps of: calculating said first air-fuel ratio correction amount in accordance with the output of said upstream-side air-fuel ratio sensor; calculating a second air-fuel ratio correction amount in accordance with the output of said downstream-side air-fuel ratio sensor; and adjusting said actual air-fuel ratio in accordance with said first and second air-fuel ratio correction amounts.

Claim 12

Dependent Claim 142 words

A method as set forth in claim 1, wherein said air-fuel ratio controlling step in accordance with the output of said upstream-side air-fuel ratio sensor comprises the steps of: calculating an air-fuel ratio correction amount in accordance with the output of said upstream-side air-fuel ratio sensor; and adjusting an actual air-fuel ratio in accordance with said air-fuel ratio correction amount; wherein said air-fuel ratio controlling step in accordance with the output of said upstream-side and downstream-side air-fuel ratio sensors comprises the steps of: calculating said air-fuel ratio correction amount in accordance with the output of said upstream-side air-fuel ratio sensor; calculating an air-fuel ratio feedback control parameter in accordance with the output of said downstream-side air-fuel ratio sensor; and adjusting said actual air-fuel ratio in accordance with the output of said upstream-side air-fuel ratio sensor and said air-fuel ratio feedback control parameter.

Claim 13

Dependent Claim 85 words

A method as set forth in claim 11, wherein said air-fuel ratio feedback control parameter is defined by a lean skip amount by which said air-fuel ratio correction amount is skipped down when the output of said upstream-side air-fuel ratio sensor is switched from the lean side to the rich side and a rich skip amount by which said air-fuel ratio correction amount is skipped up when the output of said downstream-side air-fuel ratio sensor is switched from the rich side to the lean side.

Claim 14

Dependent Claim 75 words

A method as set forth in claim 11, wherein said air-fuel ratio feedback control parameter is defined by a lean integration amount by which said air-fuel ratio correction amount is gradually decreased when the output of said upstream-side air-fuel ratio sensor is on the rich side and a rich integration amount by which said air-fuel ratio correction amount is gradually increased when the output of said upstream-side air-fuel ratio sensor is on the lean side.

Claim 15

Dependent Claim 67 words

A method as set forth in claim 11, wherein said air-fuel ratio feedback control parameter is determined by a rich delay time period for delaying the output of said upstream-side air-fuel ration sensor switched from the lean side to the rich side and a lean delay time period for delaying the output of said upstream-side air-fuel ratio sensor switched from the rich side to the lean side.

Claim 16

Dependent Claim 49 words

A method as set forth in claim 11, wherein said air-fuel ratio feedback control parameter is determined by a reference voltage with which the output of said upstream-side air-fuel ratio sensor is compared, thereby determining whether the air-fuel ratio is on the rich side or on the lean side.

Claim 17

Independent Claim 242 words

An apparatus for controlling an air-fuel ratio in an internal combustion engine having a catalyst converter for removing pollutants in the exhaust gas thereof, and upstream-side and downstream-side air-fuel ratio sensors disposed upstream and downstream, respectively, of said catalyst converter, for detecting a concentration of a specific component in the exhaust gas, comprising: means for sensing air-fuel ratio feedback control conditions for said downstream-side air-fuel ratio sensor; means for determining whether or not all the air-fuel ratio feedback control conditions for said downstream-side air-fuel ratio sensor are satisfied; means for controlling the air-fuel ratio of said engine by an open loop control so that it is brought close to an air-fuel ratio, when at least one of the air-fuel ratio feedback control conditions for said downstream-side air-fuel ratio sensor is not satisfied; means for controlling the air-fuel ratio of said engine in accordance with the output of said upstream-side air-fuel ratio sensor so that it is brought close to the stoichiometric air-fuel ratio while prohibiting control of said air-fuel ratio of said engine in accordance with the output of said downstream-side air-fuel ratio sensor for a period after all the air-fuel ratio feedback control conditions for said downstream-side air-fuel ratio sensor are satisfied; and means for controlling the air-fuel ratio of said engine in accordance with the outputs of said upstream-side and downstream-side air-fuel ratio sensors so that it is brought close to the stoichiometric air-fuel ratio after said period has passed.

Claim 18

Independent Claim 242 words

An apparatus for controlling an air-fuel ratio in an internal combustion engine having a catalyst converter for removing pollutants in the exhaust gas thereof, and upstream-side and downstream-side air-fuel ratio sensors disposed upstream and downstream, respectively, of said catalyst converter, for detecting a concentration of a specific component in the exhaust gas, comprising: means for sensing air-fuel ratio feedback control conditions for said downstream-side air-fuel ratio sensor; means for determining whether or not all the air-fuel ratio feedback control conditions for said downstream-side air-fuel ratio sensor are satisfied; means for controlling the air-fuel ratio of said engine by an open loop control so that it is brought close to an air-fuel ratio, when at least one of the air-fuel ratio feedback control conditions for said downstream-side air-fuel ratio sensor is not satisfied; means for controlling the air-fuel ratio of said engine in accordance with the output of said upstream-side air-fuel ratio sensor so that it is brought close to the stoichiometric air-fuel ratio while prohibiting control of said air-fuel ratio of said engine in accordance with the output of said downstream-side air-fuel ratio sensor for a period after all the air-fuel ratio feedback control conditions for said downstream-side air-fuel ratio sensor are satisfied; and means for controlling the air-fuel ratio of said engine in accordance with the outputs of said upstream-side and downstream-side air-fuel ratio sensors so that it is brought close to the stoichiometric air-fuel ratio after said period has passed.

Claim 19

Dependent Claim 107 words

An apparatus as set forth in claim 16, further comprising: means for calculating a time period from a time when all the air-fuel ratio feedback control conditions for said downstream-side air-fuel ratio sensor are satisfied to a time when at least one of the air-fuel ratio feedback control conditions for said downstream-side air-fuel ratio sensor is not satisfied; means for determining whether or not said time period is smaller than a definite period; and means for prohibiting the control of the air-fuel ratio of said engine is accordance with the output of said downstream-side air-fuel ratio sensor when said time period is smaller than said definite period.

Claim 20

Dependent Claim 47 words

An apparatus as set forth in claim 16, wherein the air-fuel ratio feedback control conditions for said downstream-side air-fuel ratio sensor include all the air-fuel ratio feedback control conditions for said upstream-side air-fuel ratio sensor, which include a condition of a fuel cut-off state of said engine.

Claim 21

Dependent Claim 31 words

An apparatus as set forth in claim 16, wherein the air-fuel ratio feedback control conditions for said downstream-side air-fuel ratio sensor include a condition of a coolant temperature of said engine.

Claim 22

Dependent Claim 31 words

An apparatus as set forth in claim 16, wherein the air-fuel ratio feedback control conditions for said downstream-side air-fuel ratio sensor include a condition of an idling state of said engine.

Claim 23

Dependent Claim 34 words

An apparatus as set forth in claim 16, wherein the air-fuel ratio feedback control conditions for said downstream-side air-fuel ratio sensor include a condition of an activation state of said downstream-side air-fuel ratio sensor.

Claim 24

Dependent Claim 30 words

An apparatus as set forth in claim 16, wherein the air-fuel ratio feedback control conditions for said downstream-side air-fuel ratio sensor include a condition of a load of said engine.

Claim 25

Dependent Claim 16 words

An apparatus as set forth in claim 16, wherein said period is a definite time period.

Claim 26

Dependent Claim 42 words

An apparatus as set forth in claim 16, wherein said period is defined by a definite number of reversions of the output of said upstream-side air-fuel ratio sensor which is switched from the rich side to the lean side and vice versa.

Claim 27

Dependent Claim 143 words

An apparatus as set forth in claim 16, wherein said air-fuel ratio controlling means in accordance with the output of said upstream-side air-fuel ratio sensor comprises: means for calculating a first air-fuel ratio correction amount in accordance with the output of said upstream-side air-fuel ratio sensor; and means for adjusting an actual air-fuel ratio in accordance with said first air-fuel ratio correction amount, and wherein said air-fuel ratio controlling means in accordance with the output of said upstream-side and downstream-side air-fuel ratio sensors comprises: means for calculating said first air-fuel ratio correction amount in accordance with the output of said upstream-side air-fuel ratio sensor; means for calculating a second air-fuel ratio correction amount in accordance with the output of said downstream-side air-fuel ratio sensor; and means for adjusting said actual air-fuel ratio in accordance with said first and second air-fuel ratio correction amounts.

Claim 28

Dependent Claim 147 words

An apparatus as set forth in claim 16, wherein said air-fuel ratio controlling means in accordance with the output of said upstream-side air-fuel ratio sensor comprises: means for calculating an air-fuel ratio correction amount in accordance with the output of said upstream-side air-fuel ratio sensor; and means for adjusting an actual air-fuel ratio in accordance with said air-fuel ratio correction amount, and wherein said air-fuel ratio controlling means in accordance with the output of said upstream-side and downstream-side air-fuel ratio sensors comprises: means for calculating said air-fuel ratio correction amount in accordance with the output of said upstream-side air-fuel ratio sensor; means for calculating an air-fuel ratio feedback control parameter in accordance with the output of said downstream-side air-fuel ratio sensor; and means for adjusting said actual air-fuel ratio in accordance with the output of said upstream-side air-fuel ratio sensor and said air-fuel ratio feedback control parameter.

Claim 29

Dependent Claim 85 words

An apparatus as set forth in claim 26, wherein said air-fuel ratio feedback control parameter is defined by a lean skip amount by which said air-fuel ratio correction amount is skipped down when the output of said upstream-side air-fuel ratio sensor is switched from the lean side to the rich side and a rich skip amount by which said air-fuel ratio correction amount is skipped up when the output of said downstream-side air-fuel ratio sensor is switched from the rich side to the lean side.

Claim 30

Dependent Claim 75 words

An apparatus as set forth in claim 26, wherein said air-fuel ratio feedback control parameter is defined by a lean integration amount by which said air-fuel ratio correction amount is gradually decreased when the output of said upstream-side air-fuel ratio sensor is on the rich side and a rich integration amount by which said air-fuel ratio correction amount is gradually increased when the output of said upstream-side air-fuel ratio sensor is on the lean side.

Claim 31

Dependent Claim 67 words

An apparatus as set forth in claim 26, wherein said air-fuel ratio feedback control parameter is determined by a rich delay time period for delaying the output of said upstream-side air-fuel ratio sensor switched from the lean side to the rich side and a lean delay time period for delaying the output of said upstream-side air-fuel ratio sensor switched from the rich side to the lean side.

Claim 32

Dependent Claim 49 words

An apparatus as set forth in claim 26, wherein said air-fuel ratio feedback control parameter is determined by a reference voltage with which the output of said upstream-side air-fuel ratio sensor is compared, thereby determining whether the air-fuel ratio is on the rich side or on the lean side.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1993-10-22	1994-04-23	1994-10-23	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1997-10-22	1998-04-23	1998-10-23	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2001-10-22	2002-04-23	2002-10-23	$7700.00	Window Closed / Lapsed

Air-fuel ratio feedback control system including at least downstream-side air-fuel ratio sensor

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