Power plants – Internal combustion engine with treatment or handling of... – By means producing a chemical reaction of a component of the...
Reexamination Certificate
2000-10-06
2001-12-11
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...
C060S274000, C123S692000
Reexamination Certificate
active
06327850
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus for controlling the air-fuel ratio of a multicylinder internal combustion engine.
2. Description of the Related Art
Internal combustion engines having a multiplicity of cylinders, such as V-type 6-cylinder engines, V-type 8-cylinder engines, or in-line 6-cylinder engines, suffer structural limitations that make it difficult to combine exhaust gases generated by the combustion of an air-fuel mixture in the cylinders in a region close to the cylinders. Therefore, such multicylinder internal combustion engines generally have an exhaust system including relatively long auxiliary exhaust passages that extend separately from respective cylinder groups into which the cylinders are grouped. The auxiliary exhaust passages have downstream ends joined to a main exhaust passage which is shared by all the cylinders. In the exhaust system, exhaust gases from the cylinders of the cylinder groups are combined and discharged into the auxiliary exhaust passages near the cylinder groups, and then introduced from the auxiliary exhaust passages as combined exhaust gases into the main exhaust passage.
FIGS. 14 through 16
of the accompanying drawings schematically show respective V-type engines
1
each having two cylinder groups
3
,
4
disposed one on each side of an output shaft, i.e., crankshaft,
2
. Each of the cylinder groups
3
,
4
comprises a plurality of cylinders
5
juxtaposed closely to each other in the axial direction of the output shaft
2
. If the V-type engine
1
is a V-type 6-cylinder engine, then each of the cylinder groups
3
,
4
comprises three cylinders. If the V-type engine
1
is a V-type 8-cylinder engine, then each of the cylinder groups
3
,
4
comprises four cylinders.
The V-type engine
1
has an exhaust system including an auxiliary exhaust pipe, i.e., an auxiliary exhaust passage,
6
extending from the cylinder group
3
for receiving exhaust gases produced in the cylinders
5
of the cylinder group
3
and combined by an exhaust manifold near the cylinder group
3
, and an auxiliary exhaust pipe, i.e., an auxiliary exhaust passage,
7
extending from the cylinder group
4
for receiving exhaust gases produced in the cylinders
5
of the cylinder group
4
and combined by an exhaust manifold near the cylinder group
4
. The auxiliary exhaust pipes
6
,
7
have downstream ends connected to a main exhaust pipe, i.e., a main exhaust passage,
8
.
FIG. 17
of the accompanying drawings schematically shows an in-line 6-cylinder engine
101
having six cylinders
103
Juxtaposed in the axial direction of an output shaft, i.e., a crankshaft,
102
. The cylinders
103
are grouped into a right cylinder group
104
of three closely positioned cylinders
103
and a left cylinder group
105
of three closely positioned cylinders
103
. The in-line 6-cylinder engine
101
has an exhaust system including auxiliary exhaust pipes, or auxiliary exhaust passages,
106
,
107
extending respectively from the cylinder groups
103
,
104
. The auxiliary exhaust pipes
106
,
107
have downstream ends connected to a main exhaust pipe, i.e., a main exhaust passage,
108
.
In the above multicylinder internal combustion engines whose exhaust system includes the auxiliary exhaust passages associated with the respective cylinder groups and the main exhaust passage to which the auxiliary exhaust passages are connected in common, catalytic converters, such as three-way catalytic converters, for purifying exhaust gases are generally arranged in the following layouts:
In
FIG. 14
, catalytic converters
9
,
10
are connected to the respective auxiliary exhaust pipes
6
,
7
. In
FIG. 15
, catalytic converters
9
,
10
,
11
are connected respectively to the auxiliary exhaust pipes
6
,
7
and the main exhaust pipe
8
. In
FIG. 16
, a catalytic converter
11
is connected to the main exhaust pipe
8
only.
The above catalytic converter layouts are applicable to not only the exhaust systems of the V-type engines
1
shown in
FIGS. 14 through 16
, but also the exhaust system of the in-line 6-cylinder engine
101
shown in FIG.
17
.
It is more important than ever for exhaust gas purifying systems for use with not only the above multi-cylinder internal combustion engines, but also other internal combustion engines, to have catalytic converters with a reliable exhaust gas purifying capability for effective environmental protection.
In order to achieve a desired exhaust gas purifying capability of a catalytic converter irrespective of deterioration of the catalytic converter, the applicant of the present application has proposed a system having an O
2
sensor disposed downstream of the catalytic converter for detecting the concentration of a certain component, e.g., the concentration of oxygen, in exhaust gases that have passed through the catalytic converter. The proposed system controls the air-fuel ratio of a mixture of air and fuel combusted by an internal combustion engine for converging the output of the O
2
sensor, i.e., the detected oxygen concentration, to a predetermined target value, i.e., a constant value. See, for example, Japanese laid-open patent publication No. 11-93741 or U.S. Pat. No. 6,082,099, for details.
According to the disclosed arrangement, the O
2
sensor is disposed downstream of the catalytic converter in an exhaust system, such as for an in-line 4-cylinder engine, wherein exhaust gases from all the cylinders are combined and introduced into a single exhaust pipe near the engine and the catalytic converter is connected to the single exhaust pipe only. A target air-fuel ratio, more precisely a target value for the air-fuel ratio represented by the oxygen concentration in the exhaust gases in a region where the exhaust gases from all the cylinders are combined, is determined for an air-fuel mixture combusted by the engine in order to converge the output of the O
2
sensor to the predetermined target value, and the air-fuel ratio of the air-fuel mixture combusted in the cylinders of the engine is controlled depending on the target air-fuel ratio.
In view of the above technical background, there have been proposed exhaust systems for use with multi-cylinder internal combustion engines having auxiliary exhaust passages associated with respective cylinder groups. Each of the proposed exhaust systems controls the air-fuel ratio of the internal combustion engine in order to achieve a desired purifying capability of catalytic converters connected to the auxiliary exhaust passages and the main exhaust passage. Those proposed exhaust systems will be described below.
If the catalytic converters
9
,
10
are connected to the respective auxiliary exhaust pipes
6
,
7
as shown in
FIG. 14
, then in order to achieve a total purifying capability of the catalytic converters
9
,
10
, an O
2
sensor
12
is mounted on the main exhaust pipe
8
near an upstream end thereof where the auxiliary exhaust pipes
6
,
7
are joined, and the air-fuel ratios of the air-fuel mixtures combusted in the cylinder groups
3
,
4
of the engine
1
are controlled in order to converge the output of the O
2
sensor
12
to the predetermined target value.
If the catalytic converters
9
,
10
,
11
are connected respectively to the auxiliary exhaust pipes
6
,
7
and the main exhaust pipe
8
, as shown in
FIG. 15
, then in order to achieve a total purifying capability of the catalytic converters
9
,
10
,
11
, an O
2
sensor
12
is mounted on the main exhaust pipe
8
downstream of the catalytic converter
11
, and the air-fuel ratio of the air-fuel mixture combusted in the cylinder groups
3
,
4
of the engine
1
is controlled in order to converge the output of the O
2
sensor
12
to the predetermined target value.
If the catalytic converter
11
is connected to the main exhaust pipe
8
only, as shown in
FIG. 16
, then in order to achieve a purifying capability of the catalytic converter
11
, an O
2
sensor
12
is mounted on the main exhaust pipe
8
downstream of the catalytic con
Akazaki Shusuke
Iwaki Yoshihisa
Yasui Yuji
Arent Fox Kintner & Plotkin & Kahn, PLLC
Denion Thomas
Honda Giken Kogyo Kabushiki Kaisha
Tran Diem
LandOfFree
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