Exhaust purification system of internal combustion engine

Patent metadata

Field	Value
Publication number	US-10072545-B2
Application number	US-201615200136-A
Country	US
Kind code	B2
Filing date	Jul 1, 2016
Priority date	Jul 6, 2015
Publication date	Sep 11, 2018
Grant date	Sep 11, 2018

Abstract

An exhaust purification system of an internal combustion engine having an upstream side catalyst a downstream side catalyst, a downstream side air-fuel ratio sensor provided between the upstream side catalyst and the downstream side catalyst, and a control device able to control an air-fuel ratio of exhaust gas flowing into the upstream side catalyst as air-fuel ratio control.

First claim

The invention claimed is:

1. An exhaust purification system of an internal combustion engine comprising:
an upstream side catalyst provided in an exhaust passage of the internal combustion engine;
a downstream side catalyst provided at a downstream side from the upstream side catalyst in a direction of exhaust flow in the exhaust passage;
a downstream side air-fuel ratio sensor provided between the upstream side catalyst and the downstream side catalyst in the exhaust passage; and
a control device configured to control an air-fuel ratio of an exhaust gas flowing into the upstream side catalyst as air-fuel ratio control,
wherein the control device is further configured to:
switch the air-fuel ratio of the exhaust gas flowing into the upstream side catalyst to a lean air-fuel ratio leaner than a stoichiometric air-fuel ratio when an output air-fuel ratio of the downstream side air-fuel ratio sensor becomes equal to or less than a constant rich judged air-fuel ratio richer than the stoichiometric air-fuel ratio and
switch the air-fuel ratio of the exhaust gas flowing into the upstream side catalyst to a rich air-fuel ratio richer than the stoichiometric air-fuel ratio when an oxygen storage amount of the upstream side catalyst becomes a switching reference storage amount smaller than a maximum storable amount of oxygen; and
make the concentration of NO X in the exhaust gas flowing into the upstream side catalyst increase without making the concentration of oxygen in the exhaust gas flowing into from the upstream side catalyst increase as control for increasing NO X when the oxygen storage amount of the downstream side catalyst becomes a predetermined limit storage amount smaller than the maximum storable amount of oxygen.

2. The exhaust purification system of an internal combustion engine according to claim 1 ,
wherein the control device is further configured so as not to execute the control for increasing NO X even when the oxygen storage amount of the downstream side catalyst becomes the limit storage amount or less if a temperature of the downstream side catalyst is less than a predetermined temperature.

3. The exhaust purification system of an internal combustion engine according to claim 1 ,
wherein the control device is further configured so as not to execute the control for increasing NO X even when the oxygen storage amount of the downstream side catalyst becomes the limit storage amount or less when the oxygen storage amount of the downstream side catalyst becomes the limit storage amount or less.

4. The exhaust purification system of an internal combustion engine according to claim 1 ,
wherein the control device is further configured to control the air-fuel ratio of the exhaust gas flowing into the upstream side catalyst in the air-fuel ratio control so that the air-fuel ratio of the exhaust gas flowing out from the upstream side catalyst does not become a constant lean judged air-fuel ratio or more leaner than the stoichiometric air-fuel ratio, and
wherein the lean judged air-fuel ratio is a lean air-fuel ratio with a difference from the stoichiometric air-fuel ratio equal to the difference between the rich judged air-fuel ratio and the stoichiometric air-fuel ratio.

5. The exhaust purification system of an internal combustion engine according to claim 1 further comprising a spark plug igniting an air-fuel mixture in a combustion chamber of the internal combustion engine,
wherein the control device is further configured to make the timing of ignition of the air-fuel mixture by the spark plug advance and thereby make the concentration of NO x in the exhaust gas flowing into the upstream side catalyst increase in the control for increasing NO X .

6. The exhaust purification system of an internal combustion engine according to claim 1 further comprising an EGR mechanism feeding part of the exhaust gas discharged from a combustion chamber of the internal combustion engine to the combustion chamber again,
wherein the control device is further configured to use the EGR mechanism to make the amount of exhaust gas again fed to the combustion chamber decrease and thereby make the concentration of NO X in exhaust gas flowing into the upstream side catalyst increase in the control for increasing NO X .

7. The exhaust purification system of an internal combustion engine according to claim 1 further comprising:
a cylinder fuel injector directly injecting fuel into a combustion chamber; and
an intake passage fuel injector injecting fuel into an intake passage of the internal combustion engine,
wherein the control device is further configured to:
be able to change a ratio of an amount of feed of fuel from the intake passage fuel injector to an amount of feed of fuel from the cylinder fuel injector, defined as an intake passage injection ratio; and
make the intake passage injection ratio increase and thereby make a concentration of NO X flowing into the upstream side catalyst increase in the control for increasing NO X .

8. An exhaust purification system of an internal combustion engine comprising:
an upstream side catalyst provided in an exhaust passage of the internal combustion engine;
a downstream side catalyst provided at a downstream side from the upstream side catalyst in a direction of exhaust flow in the exhaust passage;
a downstream side air-fuel ratio sensor provided between the upstream side catalyst and the downstream side catalyst in the exhaust passage; and
a control device configured to control an air-fuel ratio of an exhaust gas flowing into the upstream side catalyst as air-fuel ratio control,
wherein the control device is further configured to:
switch the air-fuel ratio of the exhaust gas flowing into the upstream side catalyst to a lean air-fuel ratio leaner than a stoichiometric air-fuel ratio when an output air-fuel ratio of the downstream side air-fuel ratio sensor becomes equal to or less than a constant rich judged air-fuel ratio richer than the stoichiometric air-fuel ratio and
switch the air-fuel ratio of the exhaust gas flowing into the upstream side catalyst to a rich air-fuel ratio richer than the stoichiometric air-fuel ratio when an oxygen storage amount of the upstream side catalyst becomes a switching reference storage amount smaller than a maximum storable amount of oxygen;
make the concentration of NO X in the exhaust gas flowing into the upstream side catalyst increase without making the concentration of oxygen in the exhaust gas flowing out the upstream side catalyst increase as control for increasing NO X when the oxygen storage amount of the downstream side catalyst becomes a predetermined limit storage amount smaller than the maximum storable amount of oxygen; and
not execute the control for increasing NO X even when the oxygen storage amount of the downstream side catalyst becomes the limit storage amount or less if a temperature of the downstream side catalyst is less than a predetermined temperature.

9. An exhaust purification system of an internal combustion engine comprising:
an upstream side catalyst provided in an exhaust passage of the internal combustion engine;
a downstream side catalyst provided at a downstream side from the upstream side catalyst in a direction of exhaust flow in the exhaust passage;
a downstream side air-fuel ratio sensor provided between the upstream side catalyst and the downstream side catalyst in the exhaust passage; and
a control device configured to control an air-fuel ratio of an exhaust gas flowing into the upstream side catalyst as air-fuel ratio control,
wherein the control device is further configured to:
switch the air-fuel ratio of the exhaust gas flowing into the upstream side catalyst to a lean air-fuel ratio

Assignees

• Toyota Motor Co Ltd

Inventors

• Hirooka Shigemasa

Classifications

• F02D2200/0814

  Oxygen storage amount · CPC title

• F01N3/20 Primary

  specially adapted for catalytic conversion (F01N3/22 takes precedence) · CPC title

• F02D41/1454

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

• F01N3/0885

  Regeneration of deteriorated absorbents or adsorbents, e.g. desulfurization of NOx traps · CPC title

• F02D41/146

  the characteristics being an NOx content or concentration · CPC title