Air-fuel ratio imbalance detection device for internal combustion engine

Patent metadata

Field	Value
Publication number	US-9518523-B2
Application number	US-201114117489-A
Country	US
Kind code	B2
Filing date	May 16, 2011
Priority date	May 16, 2011
Publication date	Dec 13, 2016
Grant date	Dec 13, 2016

Abstract

A plurality of cylinders are provided. An in-cylinder pressure sensor is mounted on each of the plurality of cylinders. A combustion parameter (e.g., the amount of generated heat) is calculated from the output of the in-cylinder pressure sensor. The air-fuel ratio for a cylinder is enleaned by reducing a fuel injection amount until the combustion parameter coincides with a predetermined value. Each cylinder is subjected to fuel injection amount reduction control so that the combustion parameter coincides with the predetermined value. The air-fuel ratio for each cylinder is then calculated in accordance with the reduction amount of fuel injection amount. The calculated air-fuel ratios are compared to detect an air-fuel ratio imbalance between the cylinders.

First claim

The invention claimed is:

1. An air-fuel ratio imbalance detection device for an internal combustion engine, comprising a controller configured to perform a method including:
acquiring an output from an in-cylinder pressure sensor mounted on each of a plurality of cylinders of the internal combustion engine;
calculating a combustion parameter including an amount of generated heat within the plurality of cylinders based on an output of the in-cylinder pressure sensor;
providing control to enlean an air-fuel ratio for each of the plurality of cylinders by reducing a fuel injection amount so that the amount of generated heat coincides with a predetermined amount of generated heat;
responsive to determining that the amount of generated heat coincides with the predetermined amount of generated heat, detecting an air-fuel ratio imbalance between the plurality of cylinders based on a reduction amount of fuel injection amount, the reduction amount being provided by control that is exercised for each of the plurality of cylinders;
receiving output of an air-fuel ratio sensor disposed in an exhaust path into which exhaust gas from the plurality of cylinders is introduced; and
calculating the predetermined amount of generated heat with which the amount of generated heat should coincide under the control based on a ratio and an average value, the ratio being between an air-fuel ratio value that is obtained based on the output of the air-fuel ratio sensor and a predetermined lean air-fuel ratio value, the average value being an average of the amount of generated heat for the plurality of cylinders.

2. The air-fuel ratio imbalance detection device for an internal combustion engine, according to claim 1 ,
wherein the method further includes:
reducing the fuel injection amount for each of the plurality of cylinders;
comparing the amount of generated heat against the predetermined amount of generated heat after a start of reduction by the reducer; and
terminating the reduction by the reducer based on a result of the comparison.

3. The air-fuel ratio imbalance detection device for an internal combustion engine according to claim 2 ,
wherein the method further includes:
calculating an air-fuel ratio for a cylinder subjected to fuel injection amount reduction, based on the reduction amount of fuel injection amount from a start of the fuel injection amount reduction to an end of the fuel injection amount reduction.

4. The air-fuel ratio imbalance detection device for an internal combustion engine according to claim 2 ,
wherein the method further includes:
reducing the fuel injection amount by a predetermined amount at a beginning of fuel injection amount reduction; and
increasing an amount of the reduction when the result of comparison made indicates that the amount of generated heat is greater than the predetermined amount of generated heat.

5. The air-fuel ratio imbalance detection device for an internal combustion engine, according to claim 1 ,
wherein the method further includes:
reducing the fuel injection amounts for the plurality of cylinders so that the amount of generated heat for a target cylinder coincides with a predetermined amount of generated heat, the target cylinder being selected from the plurality of cylinders; and
selecting a target cylinder from the plurality of cylinders such that each of the plurality of cylinders is selected as the target cylinder at least once during a period of operation;
calculating the reduction amount of fuel injection amount for the target cylinder applied to the control;
acquiring a calculated value of an air-fuel ratio for the target cylinder based on the reduction amount of fuel injection amount, the calculated value of the air fuel ratio being an air fuel ratio of the target cylinder before the target cylinder is controlled; and
detecting an air-fuel ratio imbalance between the plurality of cylinders based on a comparison of the calculated values of the air-fuel ratios between the plurality of cylinders.

6. The air-fuel ratio imbalance detection device for an internal combustion engine according to claim 1 , wherein
the combustion parameter further includes at least one of quantities selected from a group of an in-cylinder pressure, internal energy, indicated torque, indicated work, and a burning velocity, or a physical quantity correlated with at least one of the quantities selected from the group.

7. A non-transitory computer-readable medium storing instructions that, when executed by a controller, cause the controller to perform a method comprising:
acquiring an output from an in-cylinder pressure sensor mounted on each of a plurality of cylinders of an internal combustion engine;
calculating a combustion parameter including an amount of generated heat within the plurality of cylinders based on an output of the in-cylinder pressure sensor;
providing control to enlean an air-fuel ratio for each of the plurality of cylinders by reducing a fuel injection amount so that the amount of generated heat calculated coincides with a predetermined amount of generated heat; and
responsive to determining that the amount of generated heat coincides with the predetermined amount of generated heat, detecting an air-fuel ratio imbalance between the plurality of cylinders based on a reduction amount of fuel injection amount, the reduction amount being provided by control that is exercised for each of the plurality of cylinders by the injection amount controller;
receiving output of an air-fuel ratio sensor disposed in an exhaust path into which exhaust gas from the plurality of cylinders is introduced; and
calculating the predetermined amount of generated heat with which the amount of generated heat should coincide under the control based on a ratio and an average value, the ratio being between an air-fuel ratio value that is obtained based on the output of the air-fuel ratio sensor and a predetermined lean air-fuel ratio value, the average value being an average of the amount of generated heat for the plurality of cylinders.

Assignees

• Ikeda Shinji
• Sano Takeshi
• Shimode Kazumasa
• Toyota Motor Co Ltd

Inventors

• Ikeda Shinji
• Sano Takeshi
• Shimode Kazumasa

Classifications

• F02D41/0085 Primary

  Balancing of cylinder outputs, e.g. speed, torque or air-fuel ratio · CPC title

• F02D41/30 Primary

  Controlling fuel injection {(F02D41/182, F02D41/24 take precedence)} · CPC title

• F02D41/1475

  Regulating the air fuel ratio at a value other than stoichiometry · CPC title

• F02D35/023

  by determining the cylinder pressure · CPC title

• F02D41/1454

  the characteristics being an oxygen content or concentration or the air-fuel ratio · CPC title