Exhaust discharge control device for internal combustion engine

Details Exhaust discharge control device for internal combustion engine Exhaust discharge control device for internal combustion engine

1999-08-05

2001-05-22

Denion, Thomas (Department: 3748)

Power plants

Internal combustion engine with treatment or handling of...

By means producing a chemical reaction of a component of the...

C060S286000, C060S287000, C060S292000, C060S297000, C060S324000

Reexamination Certificate

active

06233925

ABSTRACT:

INCORPORATION BY REFERENCE
The disclosure of Japanese Patent Applications No. HEI 10-243391 filed on Aug. 28, 1998 and No. HEI 10-257277 filed on Sep. 10, 1998, including the specification, drawings and abstract, is incorporated herein by reference in their entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an exhaust discharge control device for an internal combustion engine.
2. Description of the Related Art
It is assumed that the ratio of the entire air amount to the entire amounts of fuel and a reducing agent supplied into an exhaust passage, a combustion chamber and an intake passage upstream of a certain position within the exhaust passage is referred to as an air-fuel ratio of an exhaust gas flowing at that position. Here, there is a known exhaust discharge control device for an internal combustion engine that allows burning of a lean air-fuel mixture gas, in which an NO
x
absorbent that absorbs NO
x
if the air-fuel ratio of the inflowing exhaust gas is lean and discharges the absorbed NO
x
if the oxygen concentration of the inflowing exhaust gas is low, is disposed in the exhaust passage of the internal combustion engine such that the air-fuel ratio of the exhaust gas flowing into the NO
x
absorbent is made rich or a stoichiometric air fuel ratio temporarily to discharge and reduce the absorbed NO
x
from the NO
x
absorbent (see Japanese Patent Publication No. 2600492).
If the oxygen concentration of the exhaust gas flowing into the NO
x
absorbent is reduced, NO
x
or SO
x
is discharged and removed. Based on this, it is considered that as the oxygen concentration of the exhaust gas flowing into the NO
x
absorbent becomes lower, NO
x
or SO
x
is purified more excellently, and if oxygen is hardly contained in the exhaust gas flowing into the NO
x
absorbent, NO
x
or SO
x
is can be purified further excellently.
SUMMARY OF THE INVENTION
The inventor of the present invention confirmed, however, that NO
x
or SO
x
in the NO
x
absorbent can be better purified in a state where a certain amount of oxygen exists in the NO
x
absorbent. It is, therefore, necessary to keep oxygen in the NO
x
absorbent when discharging NO
x
or SO
x
from the NO
x
absorbent so as to purify NO
x
or SO
x
in the NO
x
absorber more excellently. The above-cited reference discloses no description with respect to the aforementioned point.
It is an object of the present invention to provide an exhaust discharge control device for an internal combustion engine capable of well purifying NO
x
or SO
x
in an NO
x
absorbent.
To attain the above object, in the present invention, an exhaust discharge control device for an internal combustion engine has an NO
x
absorbent that is disposed in an engine exhaust passage, absorbs NO
x
if the air-fuel ratio of an inflowing exhaust gas is lean, and discharges the absorbed NO
x
if the oxygen concentration of the inflowing exhaust gas decreases, and includes oxygen concentration control means for leaving oxygen in the exhaust gas flowing into the NO
x
absorbent if NO
x
or SO
x
is to be discharged from the NO
x
absorbent and for maintaining the oxygen concentration of the exhaust gas within a predetermined range. That is, since oxygen is contained in the exhaust gas flowing into the NO
x
absorbent when discharging NO
x
or SO
x
from the NO
x
absorbent, oxygen can be kept within the NO
x
absorbent.
In addition, the amount of hydrocarbon adhered onto the NO
x
absorbent may be obtained, and the oxygen concentration of the exhaust gas flowing into the NO
x
absorbent may be increased so as to discharge more amount of NO
x
or SO
x
from the NO
x
absorbent as the hydrocarbon amount becomes larger. Thus, if oxygen exists in the NO
x
absorbent, NO
x
or SO
x
is well purified in the NO
x
absorbent.
Further, the temperature of the NO
x
absorbent may be detected such that the oxygen concentration of the exhaust gas flowing into the NO
x
absorbent is increased for discharging more amount of NO
x
or SO
x
from the NO
x
absorbent as the temperature becomes higher. That is, the hydrocarbon adhered to the NO
x
absorbent reacts with oxygen more actively as the temperature of the NO
x
absorbent becomes higher. Also, an oxygen occluding material that stores oxygen if the oxygen concentration of the inflowing exhaust gas increases and discharges the stored oxygen if the oxygen concentration of the inflowing exhaust gas decreases, may be provided in the NO
x
absorbent. That is, if the oxygen concentration of the exhaust gas which flows into the NO
x
absorbent so as to discharge NO
x
or SO
x
from the NO
x
absorbent decreases, oxygen is discharged from the oxygen occluding material, thus supplying oxygen to the NO
x
absorbent.
Moreover, a hydrocarbon absorbent may be provided in the NO
x
absorbent. The hydrocarbon absorbent absorbs hydrocarbon when the temperature of the hydrocarbon absorbent becomes low and releases the absorbed hydrocarbon when the temperature of the hydrocarbon absorbent becomes high. That is, if the oxygen concentration of the exhaust gas flowing into the NO
x
absorbent is decreased so as to discharge NO
x
or SO
x
from the NO
x
absorbent, the temperature of the inflowing exhaust gas increases. Therefore, hydrocarbon is released from the hydrocarbon absorbent. The hydrocarbon then reacts with oxygen in the NO
x
absorbent and is reformed into the reducing agent effective for NO
x
and SO
x
. As a result, excellent purification of NO
x
or SO
x
is realized.


REFERENCES:
patent: 5472673 (1995-12-01), Goto et al.
patent: 5657625 (1997-08-01), Koga et al.
patent: 5758493 (1998-06-01), Asik et al.
patent: 5778666 (1998-07-01), Cullen et al.
patent: 5974788 (1999-11-01), Hepburn et al.
patent: 6014859 (2000-01-01), Yoshizaki et al.
patent: 6023929 (2000-02-01), Ma
patent: 6122910 (2000-09-01), Hoshi et al.
patent: 6-88518 (1994-03-01), None
patent: 6-129239 (1994-05-01), None
patent: 2600492 (1997-01-01), None

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