Exhaust purification system and catalyst regeneration method

Patent metadata

Field	Value
Publication number	US-10570798-B2
Application number	US-201615544849-A
Country	US
Kind code	B2
Filing date	Jan 18, 2016
Priority date	Jan 19, 2015
Publication date	Feb 25, 2020
Grant date	Feb 25, 2020

Abstract

There is provided: a NOx occlusion reduction-type catalyst that is provided in an exhaust passage of an internal combustion engine, occludes NOx in exhaust when the exhaust is in a lean state, and reduces and purifies the occluded NOx when the exhaust is in a rich state; an exhaust injector that is provided in the exhaust passage and is positioned further upstream than the NOx occlusion reduction-type catalyst; a NOx-purging control unit that performs NOx purging of reducing and purifying the NOx occluded in the NOx occlusion reduction-type catalyst by lowering the exhaust to a prescribed target lambda by fuel injection by the exhaust injector; and a NOx-purging-prohibition processing unit that inhibits performance of the NOx purging in a case where the exhaust cannot be lowered to the target lambda even if the fuel injection is performed at a maximum limit injection amount of the exhaust injector.

First claim

The invention claimed is:

1. An exhaust purification system comprising:
a NOx-occlusion-reduction-type catalyst that is provided in an exhaust passage of an internal combustion engine, occludes NOx in exhaust when the exhaust is in a lean state, and reduces and purifies the occluded NOx when the exhaust is in a rich state;
an exhaust injector that is provided to the exhaust passage, is positioned further upstream than the NOx-occlusion-reduction-type catalyst, and injects fuel into the exhaust passage; and
an electronic control unit (ECU), wherein the ECU:
performs catalyst regeneration processing of reducing and purifying the NOx occluded in the NOx-occlusion-reduction-type catalyst by lowering a lambda value of the exhaust to a predetermined target lambda at least by fuel injection by the exhaust injector;
inhibits performance of the catalyst regeneration processing in a case where the lambda value of the exhaust cannot be lowered to the target lambda even if the fuel injection is performed at a maximum limit injection amount of the exhaust injector; and
estimates a reachable exhaust lambda based on the maximum limit injection amount of the exhaust injector and inhibits the catalyst regeneration processing by the ECU in a case where the estimated reachable exhaust lambda is greater than the target lambda.

2. An exhaust purification system comprising:
a NOx-occlusion-reduction-type catalyst that is provided in an exhaust passage of an internal combustion engine, occludes NOx in exhaust when the exhaust is in a lean state, and reduces and purifies the occluded NOx when the exhaust is in a rich state;
an exhaust injector that is provided to the exhaust passage, is positioned further upstream than the NOx-occlusion-reduction-type catalyst, and injects fuel into the exhaust passage, and
a control unit,
wherein the control unit operates so as to execute the following processing:
reducing and purifying the NOx occluded in the NOx-occlusion-reduction-type catalyst by lowering a lambda value of the exhaust to a predetermined target lambda at least by fuel injection by the exhaust injector;
inhibiting performance of the catalyst regeneration processing by the control unit in a case where the lambda value of the exhaust cannot be lowered to the target lambda even if the fuel injection is performed at a maximum limit injection amount of the exhaust injector; and
estimating a reachable exhaust lambda based on the maximum limit injection amount of the exhaust injector and inhibits the catalyst regeneration processing by the ECU in a case where the estimated reachable exhaust lambda is greater than the target lambda.

3. A catalyst regeneration method in an exhaust purification system including: an internal combustion engine; a NOx-occlusion-reduction-type catalyst that is provided in an exhaust passage of the internal combustion engine and occludes NOx in exhaust when the exhaust is in a lean state, and reduces and purifies the occluded NOx when the exhaust is in a rich state; and an exhaust injector that is provided to the exhaust passage, is positioned further upstream than the NOx-occlusion-reduction-type catalyst, and injects fuel into the exhaust passage, the method comprising:
reducing and purifying the NOx occluded in the NOx-occlusion-reduction-type catalyst by lowering a lambda value of the exhaust to a predetermined target lambda at least by fuel injection by the exhaust injector;
inhibiting performance of the catalyst regeneration processing by the control unit in a case where the lambda value of the exhaust cannot be lowered to the target lambda even if the fuel injection is performed at a maximum limit injection amount of the exhaust injector; and
estimating a reachable exhaust lambda based on the maximum limit injection amount of the exhaust injector and inhibits the catalyst regeneration processing by the ECU in a case where the estimated reachable exhaust lambda is greater than the target lambda.

Assignees

• Isuzu Motors Ltd

Inventors

• Nakada Teruo
• Sakamoto Takayuki
• Nagaoka Daiji
• Yuza Hiroyuki

Classifications

• F01N2430/06

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

• F02D41/1463

  of the exhaust gases downstream of exhaust gas treatment apparatus · CPC title

• F01N2610/03

  the substance being hydrocarbons, e.g. engine fuel · CPC title

• F01N2610/146

  Control thereof, e.g. control of injectors or injection valves · CPC title

• F02D41/0275

  the exhaust gas treating apparatus being a NOx trap or adsorbent · CPC title