Air/fuel ratio control system for engine
First Claim
1. An air fuel ratio control system for an engine, comprising:
- an oxygen sensor for producing an oxygen sensor signal representing an air fuel ratio of exhaust gases of said engine;
a feedback correcting means for determining a feedback correction quantity in accordance with said oxygen sensor signal and performing a feedback correcting operation to maintain an air fuel ratio near a theoretical air fuel ratio;
a first memory section for storing a value of a first learning variable;
a second memory section for storing a value of a second learning variable which is distinct from said first learning variable;
a fuel injection quantity determining means for determining a fuel injection quantity by modifying a basic injection quantity corresponding to an engine operating condition, in accordance with said feedback correction quantity and said first and second learning variables;
a fuel supplying means for supplying said fuel injection quantity of fuel to an intake passage of said engine;
a first updating means for updating said first learning variable stored in said first memory section at a fast learning rate in accordance with said feedback correction quantity; and
a second updating means for updating said second learning variable stored in said second memory section at a slow learning rate which is lower than said fast learning rate in accordance with at least one of said first and second learning variables,wherein said first memory section comprises a means for storing a value of said first learning variable for each of a plurality of first learning regions which are different portions of an engine operating region, said second memory section comprises a means for storing the value of said second learning variable for a second learning region which is different from any one of said first learning regions, and said control system further comprises a reading means for reading the value of said first learning variable in the first learning region corresponding to a current engine operating condition, from said first memory section and the value of said second learning variable from said second memory section when the current engine operating condition falls in said second learning region; and
said fuel injection quantity determining means includes a means for determining said basic injection quantity in accordance with said feedback correction quantity and the values of said first and second learning variables determined by said reading means.
1 Assignment
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Accused Products
Abstract
A learning control system for controlling an air fuel ratio an engine employs a slowly updated second learning control variable in addition to a normally updated first learning control variable in order to utilize the learning function sufficiently even when a deviation of the air fuel ratio exceeds the learning range of the first variable. The control system according to an illustrated embodiment of the invention identifies a current engine operating area among a plurality of such areas, in accordance with a sensed engine operating condition, obtains a value of the first learning variable corresponding to the identified operating area, and a value of the second learning variable, determines a learning quantity which is a sum of the first and second learning variables by using the obtained values, and uses this learning quantity for determining a desired fuel supply quantity. The second learning variable is updated slowly whereas the first learning variable is updated in a sensitive and speedy manner.
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Citations
25 Claims
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1. An air fuel ratio control system for an engine, comprising:
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an oxygen sensor for producing an oxygen sensor signal representing an air fuel ratio of exhaust gases of said engine; a feedback correcting means for determining a feedback correction quantity in accordance with said oxygen sensor signal and performing a feedback correcting operation to maintain an air fuel ratio near a theoretical air fuel ratio; a first memory section for storing a value of a first learning variable; a second memory section for storing a value of a second learning variable which is distinct from said first learning variable; a fuel injection quantity determining means for determining a fuel injection quantity by modifying a basic injection quantity corresponding to an engine operating condition, in accordance with said feedback correction quantity and said first and second learning variables; a fuel supplying means for supplying said fuel injection quantity of fuel to an intake passage of said engine; a first updating means for updating said first learning variable stored in said first memory section at a fast learning rate in accordance with said feedback correction quantity; and a second updating means for updating said second learning variable stored in said second memory section at a slow learning rate which is lower than said fast learning rate in accordance with at least one of said first and second learning variables, wherein said first memory section comprises a means for storing a value of said first learning variable for each of a plurality of first learning regions which are different portions of an engine operating region, said second memory section comprises a means for storing the value of said second learning variable for a second learning region which is different from any one of said first learning regions, and said control system further comprises a reading means for reading the value of said first learning variable in the first learning region corresponding to a current engine operating condition, from said first memory section and the value of said second learning variable from said second memory section when the current engine operating condition falls in said second learning region; and
said fuel injection quantity determining means includes a means for determining said basic injection quantity in accordance with said feedback correction quantity and the values of said first and second learning variables determined by said reading means.
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2. An air fuel ratio control system for an engine, comprising:
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an oxygen sensor for producing an oxygen sensor signal representing an air fuel ratio of exhaust gases of said engine; a feedback correcting means for determining a feedback correction quantity in accordance with said oxygen sensor signal and performing a feedback correcting operation to maintain an air fuel ratio near a theoretical air fuel ratio; a first memory section for storing a value of a first learning variable; a second memory section for storing a value of a second learning variable which is distinct from said first learning variable; a fuel injection quantity determining means for determining a fuel injection quantity by modifying a basic injection quantity corresponding to an engine operating condition, in accordance with said feedback correction quantity and said first and second learning variables; a fuel supplying means for supplying said fuel injection quantity of fuel to an intake passage of said engine; a first updating means for updating said first learning variable stored in said first memory section at a fast learning rate in accordance with said feedback correction quantity; and a second updating means for updating said second learning variable stored in said second memory section at a slow learning rate which is lower than said fast learning rate in accordance with at least one of said first and second learning variables, wherein said first memory section includes a means for storing the value of said first learning variable for a first learning region which is a portion of an engine operating region, said second memory section includes a means for storing the value of said second learning variable for a second learning region which is another portion of the engine operating region and which is different from said first learning region, and said control system further comprises a reading means for reading the value of said first learning variable for the first learning region from said first memory section when the first learning region corresponds to a current engine operating condition, and the value of said second learning variable for the second learning region from said second memory section when the second learning region corresponds to the current engine operating condition; and
said fuel injection quantity determining means includes a means for determining said basic injection quantity in accordance with said feedback correction quantity and the values of said first and second learning variables determined by said reading means.
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3. An air fuel ratio control system for an engine, comprising:
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an oxygen sensor for producing an oxygen sensor signal representing an air fuel ratio of exhaust gases of said engine; a feedback correcting means for determining a feedback correction quantity in accordance with said oxygen sensor signal and performing a feedback correcting operation to maintain an air fuel ratio near a theoretical air fuel ratio; a first memory section for storing a value of a first learning variable; a second memory section for storing a value of a second learning variable which is distinct from said first learning variable; a fuel injection quantity determining means for determining a fuel injection quantity by modifying a basic injection quantity corresponding to an engine operating condition, in accordance with said feedback correction quantity and said first and second learning variables; a fuel supplying means for supplying said fuel injection quantity of fuel to an intake passage of said engine; a first updating means for updating said first learning variable stored in said first memory section at a fast learning rate in accordance with said feedback correction quantity; and a second updating means for updating said second learning variable stored in said second memory section at a slow learning rate which is lower than said fast learning rate in accordance with at least one of said first and second learning variables, wherein said first memory section includes a means for storing a value of said first learning variable for each of a plurality of first learning regions which are different portions of an engine operating region determined by an engine load and an engine speed of the engine, said second memory section includes a means for storing the value of said second learning variable for a second learning region which is a portion of the engine operating region and which encompasses at least a portion of a first one of said first learning regions and a portion of a second one of said first learning regions, and said control system further comprises a calculating means for reading the value of said first learning variable in the first learning region corresponding to a current engine operating condition determined by the engine load and the engine speed, from said first memory section and the value of said second learning variable from said second memory section when the current engine operating condition falls into said second learning region, and calculating a learning quantity which is a sum of said first and second learning variables; and
said fuel injection quantity determining means includes a means for determining said basic injection quantity in accordance with said feedback correction quantity and said learning quantity determined by said calculating means. - View Dependent Claims (4)
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5. An air, fuel ratio control system for an engine, said control system comprising:
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an oxygen sensor for producing an oxygen sensor signal representing an air fuel ratio of exhaust gases of said engine; a feedback correcting means for determining a feedback correction quantity in accordance with said oxygen sensor signal and performing a feedback correcting operation to maintain an air fuel ratio near a theoretical air fuel ratio; a first memory section for storing a value of a first learning variable for each of a plurality of first learning regions which are different subregions of an engine operating region; a second memory section for storing a value of a second learning variable for a second learning region which contains all of said first learning regions; a fuel injection quantity determining means for determining a fuel injection quantity by modifying a basic injection quantity corresponding to an engine operating condition, in accordance with said feedback correction quantity and said first and second learning variables; a fuel supplying means for supplying said fuel injection quantity of fuel to an intake passage of said engine; a first updating means for updating said first learning variable stored in said first memory section at a fast learning rate in accordance with said feedback correction quantity; and a second updating means for updating said second learning variable stored in said second memory section at a slow learning rate which is lower than said fast learning rate in accordance with at least one of said first and second learning variables. - View Dependent Claims (6, 7)
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8. An air fuel ratio control system for an engine, comprising:
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a sensor group comprising an oxygen sensor for sensing an actual air fuel ratio of an exhaust gas mixture from said engine, a first parameter sensor for sensing a first engine operating parameter distinct from an engine temperature, and a second parameter sensor for sensing a second engine operating parameter distinct from the engine temperature; an actuator for varying a fuel quantity supplied to said engine in accordance with a control signal, said actuator comprising a fuel injector; and a control unit for producing said control signal in accordance with signals sent from said sensor group, said control unit comprising; a first memory section for storing a table of values of a first learning variable each value of which is identified by a set of a value of a first argument determined by said first engine operating parameter and a value of a second argument determined by said second engine operating parameter; a second memory section for storing a value of a second learning variable; and a processing section for determining a basic fuel supply quantity in accordance with said first and second engine operating parameters independently of the engine temperature, determining a feedback correction quantity in accordance with the signal supplied from said oxygen sensor, determining a learning quantity which is determined in accordance with said first learning variable and said second learning variable by obtaining one of the values of said first learning variable in accordance with said first and second operating parameters from said table stored in said first memory section and obtaining the value of said second learning variable stored in said second memory section, determining a desired fuel supply quantity represented by said control signal by modifying said basic fuel supply quantity with said feedback correction quantity and said learning quantity, updating each value of said first learning variable at a first rate, and updating the value of said second learning variable gradually at a second rate lower than said first rate. - View Dependent Claims (9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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Specification