Cylinder-by-cylinder air-fuel ratio-estimating system for internal combustion engines

• US 5,947,095 A
• Filed: 07/25/1997
• Issued: 09/07/1999
• Est. Priority Date: 08/01/1996
• Status: Expired due to Fees

• Current Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company)
• Original Assignee: Honda Giken Kogyo Kabushiki Kaisha (Honda Motor Company)
• Inventors: Kato, Akira
• Primary Examiner(s): Solis, Erick R.
• Application Number:
  US08/900,876
• Time in Patent Office: 774 Days
• Field of Search: 123/673, 123/481, 123/679
• US Class Current: 123/673
• CPC Class Codes: F02D 2041/1409 using at least a proportional, integral or derivative controller
• CPC Class Codes: F02D 2041/1415 using a state feedback or a state space representation
• CPC Class Codes: F02D 2041/1416 Observer
• CPC Class Codes: F02D 2041/1417 Kalman filter
• CPC Class Codes: F02D 2041/1418 Several control loops, either as alternatives or simultaneous
• CPC Class Codes: F02D 2041/1431 the system including an input-output delay
• CPC Class Codes: F02D 2041/1433 using a model or simulation of the system
• CPC Class Codes: F02D 2200/0406 Intake manifold pressure
• CPC Class Codes: F02D 2200/0414 Air temperature
• CPC Class Codes: F02D 2200/703 Atmospheric pressure
• CPC Class Codes: F02D 41/008 Controlling each cylinder individually
• CPC Class Codes: F02D 41/1401 characterised by the control or regulation method F02D41/1473, F02D41/1477 take precedence
• CPC Class Codes: F02D 41/1441 Plural sensors
• CPC Class Codes: F02D 41/1456 with sensor output signal being linear or quasi-linear with the concentration of oxygen
• CPC Class Codes: F02D 41/1458 with determination means using an estimation

Abstract

A cylinder-by-cylinder air-fuel ratio-estimating system for an internal combustion engine includes an air-fuel ratio sensor arranged in the exhaust system of the engine. The air-fuel ratio of a mixture supplied to each of the cylinders of the engine is estimated based on an output from the air-fuel ratio sensor, by using an observer for observing the internal operative state of the exhaust system based on a model representative of the behavior of the exhaust system. The estimated air-fuel ratio of the mixture supplied to each of the cylinders is initialized to a value corresponding to the output from the air-fuel ratio sensor, depending upon operating conditions of the engine.

Claims

1. In a cylinder-by-cylinder air-fuel ratio-estimating system for an internal combustion engine having a plurality of cylinders, and an exhaust system, the cylinder-by-cylinder air-fuel ratio-estimating system including air-fuel ratio-detecting means arranged in said exhaust system, and cylinder-by-cylinder air-fuel ratio-estimating means for estimating an air-fuel ratio of a mixture supplied to each of said cylinders, based on an output from said air-fuel ratio-detecting means, by using an observer for observing an internal operative state of said exhaust system based on a model representative of a behavior of said exhaust system, the improvement wherein:

said cylinder-by-cylinder air-fuel ratio-estimating means includes first initializing means for initializing said air-fuel ratio of said mixture supplied to said each of said cylinders estimated by said cylinder-by-cylinder air-fuel ratio-estimating means to a value corresponding to said output from said air-fuel ratio-detecting means, depending upon operating conditions of said engine.

2. A cylinder-by-cylinder air-fuel ratio-estimating system as claimed in claim 1, wherein said exhaust system includes at least one confluent portion, said air-fuel ratio-detecting means being arranged at said confluent portion of said exhaust system.

3. A cylinder-by-cylinder air-fuel ratio-estimating system as claimed in claim 2, wherein said cylinder-by-cylinder air-fuel ratio-estimating means includes confluent portion air-fuel ratio-estimating means for estimating an air-fuel ratio at said confluent portion of said exhaust system by using a delay parameter representative of a response delay of said air-fuel ratio-detecting means, said confluent portion air-fuel ratio-estimating means including second initializing means for initializing said air-fuel ratio at said confluent portion estimated by said confluent portion air-fuel ratio-estimating means to a value corresponding to said output from said air-fuel ratio-detecting means, depending upon said operating conditions of said engine.

4. A cylinder-by-cylinder air-fuel ratio-estimating system as claimed in any of claims 1 to 3, wherein said first and second initializing means are operable when said engine is in a predetermined transient operating condition.

5. A cylinder-by-cylinder air-fuel ratio-estimating system as claimed in claim 4, wherein said predetermined transient condition of said engine is an operating condition in which cylinder-by-cylinder air-fuel ratio feedback control is started, said cylinder-by-cylinder air-fuel ratio feedback control feedback-controlling said air-fuel ratio of said mixture supplied to said each of said cylinders to a desired air-fuel ratio, based on said air-fuel ratio of said mixture supplied to said each of said cylinders estimated by said cylinder-by-cylinder air-fuel ratio-estimating means and said air-fuel ratio at said confluent portion estimated by said confluent portion air-fuel ratio-estimating means.

6. A cylinder-by-cylinder air-fuel ratio-estimating system as claimed in claim 4, wherein said predetermined transient operating condition of said engine is an operating condition in which said engine has shifted to a fuel-cut state or has returned from said fuel-cut state.

7. A cylinder-by-cylinder air-fuel ratio-estimating system as claimed in claim 4, wherein said predetermined transient operating condition of said engine is an operating condition in which said engine has shifted to an idling condition or has shifted from said idling condition to a condition other than said idling condition.