US4750328A — Double air-fuel ratio sensor system having improv…

Claim 1

Independent Claim 189 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 ratio 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: determining whether or not said engine is in an air-fuel ratio feedback control mode for said downstream-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 when said engine is in said air-fuel ratio feedback control mode; storing said air-fuel ratio feedback control parameter; increasing an allowable range of said air-fuel ratio feedback control parameter when said engine is in said air-fuel ratio feedback control mode to an allowable range larger than when said engine is not in said air-fuel ratio feedback control mode; imposing said allowable range on said stored air-fuel ratio feedback control parameter; and adjusting an actual air-fuel ratio in accordance with the output of said upstream-side air-fuel ratio sensor and said imposed air-fuel ratio feedback control parameter.

Claim 2

Independent Claim 189 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 ratio 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: determining whether or not said engine is in an air-fuel ratio feedback control mode for said downstream-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 when said engine is in said air-fuel ratio feedback control mode; storing said air-fuel ratio feedback control parameter; increasing an allowable range of said air-fuel ratio feedback control parameter when said engine is in said air-fuel ratio feedback control mode to an allowable range larger than when said engine is not in said air-fuel ratio feedback control mode; imposing said allowable range on said stored air-fuel ratio feedback control parameter; and adjusting an actual air-fuel ratio in accordance with the output of said upstream-side air-fuel ratio sensor and said imposed air-fuel ratio feedback control parameter.

Claim 3

Dependent Claim 77 words

A method as set forth in claim 1, wherein said allowable range increasing step comprises the steps of: setting a first predetermined allowable range in said allowable range when said engine is in said air-fuel ratio feedback control mode; and setting a second predetermined allowable range in said allowable range by reducing said first predetermined allowable range by a predetermined ratio to the center thereof when said engine is not in said air-fuel ratio feedback control mode.

Claim 4

Dependent Claim 23 words

A method as set forth in claim 2, wherein said predetermined ratio is variable in accordance with a driving parameter of said engine.

Claim 5

Dependent Claim 129 words

A method as set forth in claim 1, wherein said allowable range increasing step comprises the steps of: setting a first predetermined allowable range in said allowable range when said engine is in said air-fuel ratio feedback control mode; determining whether or not said engine is in a warming-up mode; setting a second predetermined allowable range in said allowable range by reducing said first predetermined allowable range by a predetermined ratio to the center thereof, when said engine is not in said air-fuel ratio feedback control mode and is in said warming-up mode; and setting a third predetermined allowable range smaller than said first predetermined allowable range in said allowable range when said engine is in said air-fuel ratio feedback control mode and is not in said warming-up mode.

Claim 6

Dependent Claim 23 words

A method as set forth in claim 4, wherein said predetermined ratio is variable in accordance with a driving parameter of said engine.

Claim 7

Dependent Claim 120 words

A method as set forth in claim 1, wherein said allowable range increasing step comprises the steps of: setting a first predetermined allowable range in said allowable range when said engine is in said air-fuel ratio feedback control mode; determining whether or not said engine is in a warming-up mode; setting a second predetermined allowable range in said allowable range by reducing said first predetermined allowable range by a predetermined ratio to the center thereof, when said engine is not in said air-fuel ratio feedback control mode and is in said warming-up mode; and setting a fixed value in said allowable range when said engine is in said air-fuel ratio feedback control mode and is not in said warming-up mode.

Claim 8

Dependent Claim 85 words

A method as set forth in claim 1, 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 9

Dependent Claim 75 words

A method as set forth in claim 1, 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 10

Dependent Claim 67 words

A method as set forth in claim 1, 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 11

Dependent Claim 49 words

A method as set forth in claim 1, 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 12

Independent Claim 198 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 determining whether or not said engine is in an air-fuel ratio feedback control mode for said downstream-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 when said engine is in said air-fuel ratio feedback control mode; means for storing said air-fuel ratio feedback control parameter; means for increasing an allowable range of said air-fuel ratio feedback control parameter when said engine is in said air-fuel ratio feedback control mode to an allowable range larger than when said engine is not in said air-fuel ratio feedback control mode; means for imposing said allowable range on said stored air-fuel ratio feedback control parameter; and means for adjusting an actual air-fuel ratio in accordance with the output of said upstream-side air-fuel ratio sensor and said imposed air-fuel ratio feedback control parameter.

Claim 13

Independent Claim 198 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 determining whether or not said engine is in an air-fuel ratio feedback control mode for said downstream-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 when said engine is in said air-fuel ratio feedback control mode; means for storing said air-fuel ratio feedback control parameter; means for increasing an allowable range of said air-fuel ratio feedback control parameter when said engine is in said air-fuel ratio feedback control mode to an allowable range larger than when said engine is not in said air-fuel ratio feedback control mode; means for imposing said allowable range on said stored air-fuel ratio feedback control parameter; and means for adjusting an actual air-fuel ratio in accordance with the output of said upstream-side air-fuel ratio sensor and said imposed air-fuel ratio feedback control parameter.

Claim 14

Dependent Claim 78 words

An apparatus as set forth in claim 11, wherein said allowable range increasing means comprises: means for setting a first predetermined allowable range in said allowable range when said engine is in said air-fuel ratio feedback control mode; and means for setting a second predetermined allowable range in said allowable range by reducing said first predetermined allowable range by a predetermined ratio to the center thereof when said engine is not in said air-fuel ratio feedback control mode.

Claim 15

Dependent Claim 23 words

An apparatus as set forth in claim 12, wherein said predetermined ratio is variable in accordance with a driving parameter of said engine.

Claim 16

Dependent Claim 134 words

An apparatus as set forth in claim 11, wherein said allowable range increasing means comprises: means for setting a first predetermined allowable range in said allowable range when said engine is in said air-fuel ratio feedback control mode; means for determining whether or not said engine is in a warming-up mode; means for setting a second predetermined allowable range in said allowable range by reducing said first predetermined allowable range by a predetermined ratio to the center thereof, when said engine is not in said air-fuel ratio feedback control mode and is in said warming-up mode; and means for setting a third predetermined allowable range smaller than said first predetermined allowable range in said allowable range when said engine is in said air-fuel ratio feedback control mode and is not in said warming-up mode.

Claim 17

Dependent Claim 23 words

An apparatus as set forth in claim 14, wherein said predetermined ratio is variable in accordance with a driving parameter of said engine.

Claim 18

Dependent Claim 125 words

An apparatus as set forth in claim 11, wherein said allowable range increasing means comprises: means for setting a first predetermined allowable range in said allowable range when said engine is in said air-fuel ratio feedback control mode; means for determining whether or not said engine is in a warming-up mode; means for setting a second predetermined allowable range in said allowable range by reducing said first predetermined allowable range by a predetermined ratio to the center thereof, when said engine is not in said air-fuel ratio feedback control mode and is in said warming-up mode; and means for setting a fixed value in said allowable range when said engine is in said air-fuel ratio feedback control mode and is not in said warming-up mode.

Claim 19

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 20

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 21

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 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 22

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.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1991-06-14	1991-12-14	1992-06-14	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1995-06-14	1995-12-14	1996-06-14	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1999-06-14	1999-12-14	2000-06-14	$7700.00	Window Closed / Lapsed

Double air-fuel ratio sensor system having improved exhaust emission characteristics

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