Control apparatus for internal combustion engine

Patent metadata

Field	Value
Publication number	US-10174696-B2
Application number	US-201715846690-A
Country	US
Kind code	B2
Filing date	Dec 19, 2017
Priority date	Dec 27, 2016
Publication date	Jan 8, 2019
Grant date	Jan 8, 2019

Abstract

A control apparatus for an internal combustion engine is provided. The control apparatus is equipped with an electronic control unit. A CPU with which this electronic control unit is equipped performs dither control for setting a first cylinder as a rich-burn cylinder whose air-fuel ratio is richer than a theoretical air-fuel ratio and setting each of second to fourth cylinders as a lean-burn cylinder whose air-fuel ratio is leaner than the theoretical air-fuel ratio, when a request to raise the temperature of a three-way catalyst is made. Then, the CPU reduces the degree of richness of the rich-burn cylinder and the degree of leanness of each of the lean-burn cylinders while continuing dither control, on the condition that fluctuations at a level equal to or higher than a predetermined value are caused in time-series data on the rotational speed resulting from the combustion in each of the cylinders.

First claim

What is claimed is:

1. A control apparatus for an internal combustion engine, comprising:
an electronic control unit configured to:
(i) execute a dither control process, the dither control process being a process that is designed to control the internal combustion engine, which is equipped with a catalyst designed to purify exhaust gas discharged from a plurality of cylinders, and that operates fuel injection valves corresponding to the plurality of the cylinders respectively so as to control an air-fuel ratio in a lean-burn cylinder as one of the plurality of the cylinders or each of some of the plurality of the cylinders to an air-fuel ratio leaner than a target value for an average of air-fuel ratios in the plurality of the cylinders, and so as to control an air-fuel ratio in a rich-burn cylinder as the other cylinder or each of the other cylinders to an air-fuel ratio richer than the target value; and
(ii) execute a reduction process, the reduction process being a process for reducing a first difference between the air-fuel ratio in the lean-burn cylinder and the target value and a second difference between the air-fuel ratio in the rich-burn cylinder and the target value, while, on a condition that a level of rotational fluctuations of a crankshaft becomes equal to or higher than a predetermined value when the dither control process is executed, holding the average of the air-fuel ratios in the plurality of the cylinders equal to the target value by making the air-fuel ratio in the lean-burn cylinder leaner than the target value and making the air-fuel ratio in the rich-burn cylinder richer than the target value.

2. The control apparatus according to claim 1 , wherein
the electronic control unit is configured to execute the dither control process and the reduction process when a request to raise a temperature of the catalyst is made.

3. The control apparatus according to claim 1 , wherein
the electronic control unit is configured to execute the dither control process and the reduction process when a temperature of the catalyst is equal to or higher than a predetermined temperature and equal to or lower than a prescribed temperature.

4. The control apparatus according to claim 1 , wherein
the electronic control unit is configured to execute the dither control process and the reduction process as soon as the internal combustion engine is started in a cold state.

5. The control apparatus according to claim 1 , wherein
the electronic control unit is configured to execute the reduction process again after executing the reduction process on the condition that the level of the rotational fluctuations becomes equal to or higher than the predetermined value.

6. The control apparatus according to claim 1 , wherein
the electronic control unit is configured to, in the reduction process, make amounts of reduction larger when a frequency with which the level of the rotational fluctuations becomes equal to or higher than the predetermined value is higher than a predetermined frequency than when the frequency with which the level of the rotational fluctuations becomes equal to or higher than the predetermined value is equal to or lower than the predetermined frequency, the amounts of reduction being amounts by which the first difference and the second difference are respectively reduced on the condition that the level of the rotational fluctuations becomes equal to or higher than the predetermined value.

7. The control apparatus according to claim 1 , wherein
the electronic control unit is configured to:
(i) hold the average of the air-fuel ratios in the plurality of the cylinders equal to the target value on a condition that the rotational fluctuations at the level equal to or higher than the predetermined value are not detected within a predetermined period, after executing the reduction process, and
(ii) execute an increase process for increasing the first difference between the air-fuel ratio in the lean-burn cylinder and the target value and the second difference between the air-fuel ratio in the rich-burn cylinder and the target value, while holding the average of the air-fuel ratios in the plurality of the cylinders equal to the target value after executing the reduction process.

8. The control apparatus according to claim 7 , wherein
the electronic control unit is configured to execute the increase process again after executing the increase process on the condition that the rotational fluctuations at the level equal to or higher than the predetermined value are not detected within the predetermined period.

9. The control apparatus according to claim 7 , wherein
the electronic control unit is configured to, in the increase process, make amounts of increase larger when the frequency with which the level of the rotational fluctuations becomes equal to or higher than the predetermined value is equal to or lower than a predetermined frequency than when the frequency with which the level of the rotational fluctuations becomes equal to or higher than the predetermined value is higher than the predetermined frequency, the amounts of increase being amounts by which the first difference and the second difference are respectively increased on the condition that the rotational fluctuations at the level equal to or higher than the predetermined value are not detected within the predetermined period.

10. The control apparatus according to claim 7 , wherein
the electronic control unit is configured to:
(i) execute a request value setting process for variably setting a base request value as a base value of a request value of the first difference between the air-fuel ratio in the lean-burn cylinder and the target value and the second difference between the air-fuel ratio in the rich-burn cylinder and the target value, in accordance with an operating state of the internal combustion engine,
(ii) execute a guard process for inputting the base request value and limiting the request value to a value equal to or smaller than a guard value,
(iii) control the first difference between the air-fuel ratio in the lean-burn cylinder and the target value and the second difference between the air-fuel ratio in the rich-burn cylinder and the target value to the request value in the dither control process,
(iv) reduce the guard value in the reduction process, and
(v) increase the guard value toward the base request value in the increase process.

Assignees

• Toyota Motor Co Ltd

Inventors

• Kido Eiichiro
• Idogawa Masanao

Classifications

• F01N2250/04

  afterburning and catalytic conversion · CPC title

• F02D41/1475

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

• F02D41/0082 Primary

  per groups or banks (F02D41/0087 takes precedence) · CPC title

• F01N2900/1626

  Catalyst activation temperature · CPC title

• F01N2430/06

  by varying fuel-air ratio, e.g. by enriching fuel-air mixture · CPC title