Cylinder-by-cylinder air-fuel-ratio controller for internal combustion engine

Patent metadata

Field	Value
Publication number	US-9644554-B2
Application number	US-201414463281-A
Country	US
Kind code	B2
Filing date	Aug 19, 2014
Priority date	Sep 9, 2013
Publication date	May 9, 2017
Grant date	May 9, 2017

Abstract

An air-fuel-ratio of each cylinder is estimated based on a detection value of an air-fuel-ratio sensor. An air-fuel-ratio detection timing determination is executed to determine whether a deviation in air-fuel-ratio detection timing exists based on the estimated air-fuel-ratio while the cylinder-by-cylinder air-fuel-ratio control is performed. An observation residual is computed based on the detection value of the air-fuel-ratio sensor and the estimated air-fuel-ratio. When the observation residual is greater than or equal to a specified threshold value, the air-fuel-ratio detection timing determination is prohibited. Therefore, when the observation residual is still large before the estimated air-fuel-ratio of each cylinder is converged, or when the observation residual is still large due to a temporal deterioration in estimating accuracy of the estimated air-fuel-ratio, the air-fuel-ratio detection timing determination can be prohibited.

First claim

What is claimed is:

1. A cylinder-by-cylinder air-fuel-ratio controller for an internal combustion engine, comprising:
an air-fuel-ratio sensor detecting an air-fuel-ratio of an exhaust gas at a confluent portion into which the exhaust gas flows from each of multiple cylinders of the internal combustion engine;
an estimation portion executing an air-fuel-ratio estimation for estimating the air-fuel-ratio of each cylinder based on a detection value which the air-fuel-ratio sensor detects at an air-fuel-ratio detection timing for each cylinder;
a control portion executing a cylinder-by-cylinder air-fuel-ratio control in which the air-fuel-ratio of each cylinder is controlled based on the estimated air-fuel-ratio of each cylinder;
a determining portion determining whether a deviation in the air-fuel-ratio detection timing exists based on the estimated air-fuel-ratio while the cylinder-by-cylinder air-fuel-ratio control is executed;
a correcting portion correcting the air-fuel-ratio detection timing when the determining portion determines that the deviation in the air-fuel-ratio detection timing exists;
a residual computing portion computing an observation residual based on the detection value of the air-fuel-ratio sensor and the estimated air-fuel-ratio; and
a determination prohibiting portion prohibiting the determining portion from determining whether the deviation in the air-fuel-ratio detection timing exists when the observation residual is greater than or equal to a specified threshold value.

2. A cylinder-by-cylinder air-fuel-ratio controller for an internal combustion engine according to claim 1 , further comprising:
a control prohibiting portion prohibiting the control portion from executing a cylinder-by-cylinder air-fuel-ratio control when the observation residual is greater than or equal to the specified threshold value.

3. A cylinder-by-cylinder air-fuel-ratio controller for an internal combustion engine according to claim 1 , wherein
the residual computing portion normalizes the observation residual by means of an amplitude of the detection value which the air-fuel-ratio sensor detects when the residual computing portion computes the observation residual.

4. A cylinder-by-cylinder air-fuel-ratio controller for an internal combustion engine according to claim 1 , further comprising:
an initial-value computing portion computing an initial estimated air-fuel-ratio based on the estimated air-fuel-ratio immediately before or after executing the cylinder-by-cylinder air-fuel-ratio control, wherein
the determining portion determines that the deviation in the air-fuel-ratio detection timing exists in a case that the estimated air-fuel-ratio becomes larger than the initial estimated air-fuel-ratio when a correction quantity for each cylinder by the cylinder-by-cylinder air-fuel-ratio control exceeds a specified value.

5. A cylinder-by-cylinder air-fuel-ratio controller for an internal combustion engine according to claim 4 , wherein
the initial-value computing portion prohibits the control portion from executing the cylinder-by-cylinder air-fuel-ratio control or restricts a variation of the correction quantity for each cylinder until a computation of the initial estimated air-fuel-ratio is completed.

6. A cylinder-by-cylinder air-fuel-ratio controller for an internal combustion engine according to claim 4 , wherein
the determining portion establishes the specified value according to the initial estimated air-fuel-ratio.

7. A cylinder-by-cylinder air-fuel-ratio controller for an internal combustion engine according to claim 4 , wherein
the determining portion restricts a variation of the correction quantity for each cylinder when executing the air-fuel-ratio detection timing determination.

8. A cylinder-by-cylinder air-fuel-ratio controller for an internal combustion engine according to claim 4 , wherein
the initial-value computing portion computes the initial estimated air-fuel-ratio when the observation residual is less than the specified threshold value.

9. A cylinder-by-cylinder air-fuel-ratio controller for an internal combustion engine according to claim 1 , further comprising:
a gain-switching portion setting a gain of the air-fuel-ratio estimation to a high gain when the observation residual is greater than or equal to the specified threshold value, the gain-switching portion setting the gain of the air-fuel-ratio estimation to a low gain when the observation residual is less than the specified threshold value.

Assignees

• Denso Corp

Inventors

• Iwase Noriaki
• Mukai Yasuo

Classifications

• F02D41/1458

  with determination means using an estimation · CPC title

• F02D41/2451

  characterised by what is learned or calibrated · CPC title

• F02D41/008 Primary

  Controlling each cylinder individually · CPC title

• F02D2250/14

  Timing of measurement, e.g. synchronisation of measurements to the engine cycle · CPC title

• F02D41/2454

  Learning of the air-fuel ratio control · CPC title