Air-fuel ratio control apparatus for internal combustion engine and method for controlling air-fuel ratio

Patent metadata

Field	Value
Publication number	US-9523318-B2
Application number	US-201213557221-A
Country	US
Kind code	B2
Filing date	Jul 25, 2012
Priority date	Oct 11, 2011
Publication date	Dec 20, 2016
Grant date	Dec 20, 2016

Abstract

An air-fuel ratio control apparatus includes an air-fuel ratio detector, an oscillation signal generator, an air-fuel ratio oscillation device, a sum/difference frequency component intensity calculator, a decision parameter calculator, and an imbalance failure determination device. The sum/difference frequency component intensity calculator is configured to calculate, while the air-fuel ratio oscillation device is in operation, at least one of a component intensity of a difference frequency and a component intensity of a sum frequency. The decision parameter calculator is configured to calculate, according to at least one of the component intensity of the difference frequency and the component intensity of the sum frequency, a decision parameter to determine a degree of imbalance of an air-fuel ratio. The imbalance failure determination device is configured to determine an imbalance failure in which the degree of imbalance of the air-fuel ratio exceeds an allowable limit using the decision parameter.

First claim

What is claimed is:

1. An air-fuel ratio control apparatus for an internal combustion engine, comprising:
an air-fuel ratio detector configured to detect an air-fuel ratio in an exhaust passage provided in the internal combustion engine including a plurality of cylinders;
an oscillation signal generator configured to generate an oscillation signal to oscillate the air-fuel ratio at an oscillation frequency different from a 0.5th-order frequency which is a half of a frequency corresponding to a rotational speed of the internal combustion engine;
an air-fuel ratio oscillation device configured to oscillate the air-fuel ratio according to the oscillation signal;
a sum/difference frequency component intensity calculator configured to calculate, while the air-fuel ratio oscillation device is in operation, at least one of a component intensity of a difference frequency and a component intensity of a sum frequency, the difference frequency representing a difference between the 0.5th-order frequency and the oscillation frequency which are included in an output signal of the air-fuel ratio detector, the sum frequency representing a sum of the 0.5th-order frequency and the oscillation frequency which are included in the output signal of the air-fuel ratio detector;
a decision parameter calculator configured to calculate, according to at least one of the component intensity of the difference frequency and the component intensity of the sum frequency, a decision parameter to determine a degree of imbalance of the air-fuel ratio corresponding to each of the plurality of cylinders;
an imbalance failure determination device configured to determine an imbalance failure in which the degree of imbalance of the air-fuel ratio exceeds an allowable limit using the decision parameter; and
an oscillation frequency component intensity calculator configured to calculate, while the air-fuel ratio oscillation device is in operation, a component intensity of the oscillation frequency included in the output signal of the air-fuel ratio detector, wherein
the sum/difference frequency component intensity calculator is configured to calculate both of the component intensity of the difference frequency and the component intensity of the sum frequency,
the decision parameter calculator includes a difference frequency component ratio calculator and a correction ratio calculator,
the difference frequency component ratio calculator is configured to calculate a difference frequency component ratio by dividing the component intensity of the difference frequency by the component intensity of the oscillation frequency, and
the correction ratio calculator is configured to calculate a correction ratio by dividing the component intensity of the sum frequency by the component intensity of the difference frequency and configured to calculate the decision parameter by multiplying the difference frequency component ratio by the correction ratio and thereby correct for a variation of the output signal to the air-fuel ratio detector.

2. An air-fuel ratio control apparatus for an internal combustion engine, comprising:
an air-fuel ratio detector configured to detect an air-fuel ratio in an exhaust passage provided in the internal combustion engine including a plurality of cylinders;
an oscillation signal generator configured to generate an oscillation signal to oscillate the air-fuel ratio at an oscillation frequency different from a 0.5th-order frequency which is a half of a frequency corresponding to a rotational speed of the internal combustion engine;
an air-fuel ratio oscillation device configured to oscillate the air-fuel ratio according to the oscillation signal;
a sum/difference frequency component intensity calculator configured to calculate, while the air-fuel ratio oscillation device is in operation, at least one of a component intensity of a difference frequency and a component intensity of a sum frequency, the difference frequency representing a difference between the 0.5th-order frequency and the oscillation frequency which are included in an output signal of the air-fuel ratio detector, the sum frequency representing a sum of the 0.5th-order frequency and the oscillation frequency which are included in the output signal of the air-fuel ratio detector;
a decision parameter calculator configured to calculate, according to at least one of the component intensity of the difference frequency and the component intensity of the sum frequency, a decision parameter to determine a degree of imbalance of the air-fuel ratio corresponding to each of the plurality of cylinders;
an imbalance failure determination device configured to determine an imbalance failure in which the degree of imbalance of the air-fuel ratio exceeds an allowable limit using the decision parameter; and
an oscillation frequency component intensity calculator configured to calculate, while the air-fuel ratio oscillation device is in operation, a component intensity of the oscillation frequency included in the output signal of the air-fuel ratio detector, wherein
the sum/difference frequency component intensity calculator is configured to calculate both of the component intensity of the difference frequency and the component intensity of the sum frequency,
the decision parameter calculator includes a sum frequency component ratio calculator and a correction ratio calculator,
the sum frequency component ratio calculator is configured to calculate a sum frequency component ratio by dividing the component intensity of the sum frequency by the component intensity of the oscillation frequency, and
the correction ratio calculator is configured to calculate a correction ratio by dividing the component intensity of the difference frequency by the component intensity of the sum frequency and configured to calculate the decision parameter by multiplying the sum frequency component ratio by the correction ratio and thereby correct for a variation of the output signal to the air-fuel ratio detector.

3. An air-fuel ratio control apparatus for an internal combustion engine, comprising:
an air-fuel ratio detector configured to detect an air-fuel ratio in an exhaust passage provided in the internal combustion engine including a plurality of cylinders;
an oscillation signal generator configured to generate an oscillation signal to oscillate the air-fuel ratio at an oscillation frequency different from a 0.5th-order frequency which is a half of a frequency corresponding to a rotational speed of the internal combustion engine;
an air-fuel ratio oscillation device configured to oscillate the air-fuel ratio according to the oscillation signal;
a sum/difference frequency component intensity calculator configured to calculate, while the air-fuel ratio oscillation device is in operation, at least one of a component intensity of a difference frequency and a component intensity of a sum frequency, the difference frequency representing a difference between the 0.5th-order frequency and the oscillation frequency which are included in an output signal of the air-fuel ratio detector, the sum frequency representing a sum of the 0.5th-order frequency and the oscillation frequency which are included in the output signal of the air-fuel ratio detector;
a decision parameter calculator configured to calculate, according to at least one of the component intensity of the difference frequency and the component intensity of the sum frequency, a decision parameter to determine a degree of imbalance of the air-fuel ratio corresponding to each of the plurality of cylinders;
an imbalance failure determination device configured to determine an imbalance failure in which the degree of imbalance of the air-fuel ratio exceeds an allowable limit using the decision parameter;
a 0.5th-order frequency component intensity calculator configured to calculate a component

Assignees

• Miyauchi Atsuhiro
• Sekiguchi Tooru
• Tani Michinori
• Watanabe Seiji
• Honda Motor Co Ltd

Inventors

• Miyauchi Atsuhiro
• Sekiguchi Tooru
• Tani Michinori
• Watanabe Seiji

Classifications

• F02D41/1401

  characterised by the control or regulation method (F02D41/1473, F02D41/1477 take precedence) · CPC title

• F02D2041/288

  for performing a transformation into the frequency domain, e.g. Fourier transformation · CPC title

• F02D41/1456

  with sensor output signal being linear or quasi-linear with the concentration of oxygen · CPC title

• F02D41/0085 Primary

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

• F02D41/1495

  Detection of abnormalities in the air/fuel ratio feedback system · CPC title