US5359852A — Air fuel ratio feedback control

Claim 1

Independent Claim 262 words

A method of controlling air/fuel ratio using electronic engine controls for an internal combustion engine including the steps of: providing a pair of sensor means for characterizing at least one constituent of an exhaust gas in an exhaust stream from the internal combustion engine, a first sensor means being positioned upstream of a catalyst and a second sensor means being positioned downstream of the catalyst; providing a control module having an input connected to the upstream and downstream sensors means and an output connected to the actuators controlling the engine, as to establish a first feedback loop including the first upstream sensor means and a second feedback loop including the second downstream sensor means; providing an air/fuel ratio bias table in said first feedback loops to alter the transfer function of said first feedback loop; and using an output of said second downstream sensor means to bias the output of the air/fuel bias table thereby compensating the first and second air/fuel ratio feedback loops for aging of said first upstream sensor means and providing a capability to stay within a catalyst window of operation as a function of engine speed and torque operating points, including the steps of: determining a purge flow is low; determining vehicle speed is above a predetermined low speed and has a predetermined amount of stability; determining that the engine speed, load and coolant temperature are within a predetermined window; determining that an air meter associated with the internal combustion engine is properly working; and determining that the second downstream sensor means in a non-test mode of operation.

Claim 2

Independent Claim 262 words

A method of controlling air/fuel ratio using electronic engine controls for an internal combustion engine including the steps of: providing a pair of sensor means for characterizing at least one constituent of an exhaust gas in an exhaust stream from the internal combustion engine, a first sensor means being positioned upstream of a catalyst and a second sensor means being positioned downstream of the catalyst; providing a control module having an input connected to the upstream and downstream sensors means and an output connected to the actuators controlling the engine, as to establish a first feedback loop including the first upstream sensor means and a second feedback loop including the second downstream sensor means; providing an air/fuel ratio bias table in said first feedback loops to alter the transfer function of said first feedback loop; and using an output of said second downstream sensor means to bias the output of the air/fuel bias table thereby compensating the first and second air/fuel ratio feedback loops for aging of said first upstream sensor means and providing a capability to stay within a catalyst window of operation as a function of engine speed and torque operating points, including the steps of: determining a purge flow is low; determining vehicle speed is above a predetermined low speed and has a predetermined amount of stability; determining that the engine speed, load and coolant temperature are within a predetermined window; determining that an air meter associated with the internal combustion engine is properly working; and determining that the second downstream sensor means in a non-test mode of operation.

Claim 3

Dependent Claim 46 words

A method as recited in claim 1 in which said sensor means is an exhaust gas oxygen (EGO) sensor and further comprising using a tri-state feedback in said first and/or second feedback loops in order to avoid low frequency fluctuations in the air/fuel ratio control system.

Claim 4

Dependent Claim 18 words

A method as recited in claim 2 wherein said second sensor means is an exhaust gas emission sensor.

Claim 5

Dependent Claim 231 words

A structure for controlling air/fuel ratio of an electronic engine control system including: a first upstream exhaust gas oxygen sensor positioned in front of a catalyst in the exhaust gas of the engine; a second exhaust gas oxygen sensor, downstream from the said exhaust gas oxygen sensor and catalyst, coupled to the exhaust gas stream of the engine; a post catalyst sensor feedback controller means coupled to the said second EGO sensor for providing a trim bias signal for shifting the A/F trim values; an air/fuel bias table storing an air/fuel trim amount as a function of rpm and torque; and providing a base air/fuel bias signal; a summer means coupled to said air/fuel bias table update means for receiving said air/fuel bias signal and to said post catalyst sensor feedback controller for receiving the trim bias signal; an air/fuel feedback controller coupled to the summer for receiving a combined bias signal and for generating a processed bias signal; a base fuel controller coupled to the engine for controlling the introduction of fuel into the engine and coupled to the air fuel feedback controller for receiving the processed bias signal; and said post-catalyst sensor feedback controller for generating the trim bias including: means for determining low purge flow, sufficiently high vehicle speed, a predetermined range of magnitudes for engine speed, load, and coolant temperature, an operational air meter, a non-diagnostic condition.

Claim 6

Dependent Claim 231 words

A structure for controlling air/fuel ratio of an electronic engine control system including: a first upstream exhaust gas oxygen sensor positioned in front of a catalyst in the exhaust gas of the engine; a second exhaust gas oxygen sensor, downstream from the said exhaust gas oxygen sensor and catalyst, coupled to the exhaust gas stream of the engine; a post catalyst sensor feedback controller means coupled to the said second EGO sensor for providing a trim bias signal for shifting the A/F trim values; an air/fuel bias table storing an air/fuel trim amount as a function of rpm and torque; and providing a base air/fuel bias signal; a summer means coupled to said air/fuel bias table update means for receiving said air/fuel bias signal and to said post catalyst sensor feedback controller for receiving the trim bias signal; an air/fuel feedback controller coupled to the summer for receiving a combined bias signal and for generating a processed bias signal; a base fuel controller coupled to the engine for controlling the introduction of fuel into the engine and coupled to the air fuel feedback controller for receiving the processed bias signal; and said post-catalyst sensor feedback controller for generating the trim bias including: means for determining low purge flow, sufficiently high vehicle speed, a predetermined range of magnitudes for engine speed, load, and coolant temperature, an operational air meter, a non-diagnostic condition.

Claim 7

Dependent Claim 40 words

A structure for controlling air/fuel ratio of an electronic engine as recited in claim 4 wherein said post-catalyst sensor feedback controller for generating the trim bias further includes: a transfer function means for determining a learning rate for the bias.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1997-10-31	1998-05-02	1998-11-01	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2001-10-31	2002-05-02	2002-11-01	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2005-10-31	2006-05-02	2006-11-01	$7700.00	Window Closed / Lapsed

Air fuel ratio feedback control

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