Air-fuel ratio imbalance detection device for internal combustion engine

摘要

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.

主权项

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.