Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – With indicator or control of power plant
Reexamination Certificate
1999-05-06
2003-09-16
Dolinar, Andrew M. (Department: 3747)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
With indicator or control of power plant
C060S277000
Reexamination Certificate
active
06622081
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to an apparatus for detecting deterioration of a catalytic converter of an internal combustion engine while avoiding error by performing the decision as to deterioration of the catalytic converter in the state where the temperature thereof rises. More particularly, the invention is concerned with the catalyst deterioration detecting apparatus for an internal combustion engine which can detect deterioration of the catalytic converter with enhanced reliability and accuracy by detecting accurately the temperature-rise state of the catalyst and increasing the frequency of the chance for the catalyst deterioration decision.
2. Description of Related Art
Heretofore, in an internal combustion engine (hereinafter also referred to simply as the engine) of a motor vehicle, a catalytic converter has been employed for the purpose of eliminating harmful components such as HC (hydrocarbon), CO (carbon monoxide) and NO
x
(nitrogen oxides) from the exhaust gas of the engine for purification thereof.
On the other hand, since the combustion efficiency of the engine changes in dependence on the air-fuel ratio of a mixture gas charged into the engine, a feedback control of the air-fuel ratio (A/F) has been adopted in order to control the air-fuel ratio so that it can assume a stoichiometrically optimal value (e.g. 14.7) which conforms to the operation state of the engine. To this end, an air-fuel ratio sensor such as an O
2
-sensor or the like is mounted in an exhaust pipe of the engine at a position upstream of the catalytic converter for realizing the air-fuel ratio feedback control.
In this conjunction, there has also been proposed such a dual-sensor type air-fuel ratio control system in which an additional air-fuel ratio sensor is additionally provided at a position downstream of the catalytic converter in order to protect the control performance of the system against degradation which may be brought about due to variance in the output characteristics among the air-fuel ratio sensors. A typical one of such dual-sensor type air-fuel ratio control systems is disclosed, for example, in U.S. Pat. No. 3,939,654.
In general, in the region of the exhaust pipe located downstream of the catalytic converter, the temperature of the exhaust gas is low and undergoes less change. Besides, the harmful components such as mentioned previously have been eliminated from the exhaust gas by the catalytic converter. Thus, the air-fuel ratio sensor mounted downstream of the catalytic converter is well protected against adverse influences. Additionally,it is noted that in the exhaust pipe region mentioned above, the exhaust gas has been mixed sufficiently, and thus the oxygen concentration is uniform.
Thus, the dual-sensor type air-fuel ratio control system such as mentioned above can realize the air-fuel ratio feedback control with high stability and accuracy, because the air-fuel ratio sensor disposed at the downstream side of the catalytic converter is stable in respect with the output characteristic thereof.
It is further noted that when the catalytic converter undergoes deterioration in the course of time lapse under the unfavorable conditions such as use of different fuels, exposure to unburned gas and the like, harmful exhaust gas will be discharged without being purified. Under the circumstances, such arrangement has also been adopted in which the states of the catalytic converter are detected on the basis of the output signals of the dual or paired air-fuel ratio sensors mentioned above, to thereby generate an alarm signal when deterioration of the catalytic converter is detected.
For better understanding of the present invention, the background techniques thereof will be reviewed below in some detail.
FIG. 9
is a functional block diagram showing schematically a basic arrangement of a hitherto known or conventional catalyst deterioration detecting apparatus for an internal combustion engine known heretofore which is disclosed, for example, in Japanese Unexamined Patent Application Publication No. 225203/1995 (JP-A-7-225203).
Referring to
FIG. 9
, an internal combustion engine (hereinafter referred to simply as the engine)
1
is provided with an exhaust pipe
15
for discharging an exhaust gas G from the engine
1
to the atmosphere. A catalytic converter
10
is installed in the exhaust pipe
15
for purifying on the whole the harmful components such as HC, CO and NO
x
contained in the exhaust gas G.
A first air-fuel ratio sensor
11
is mounted in the exhaust pipe at a position upstream of the catalytic converter
10
with a second air-fuel ratio sensor
12
being disposed downstream of the catalytic converter (hereinafter also referred to simply as the catalyst)
10
, wherein the first and second air-fuel ratio sensors
11
and
12
output air-fuel ratio signals V
1
and V
2
, respectively, which indicate the oxygen concentrations of the exhaust gas G prevailing at the locations of these sensors.
In
FIG. 9
, a catalyst activation decision means
101
makes decision on the basis of the engine operation state as to whether or not the catalyst
10
is activated (i.e., whether or not the temperature of the catalyst is sufficiently high). When it is decided that the catalyst
10
is activated, the catalyst activation decision means
101
issues an activation signal C.
Further provided is a catalyst deterioration decision means
102
which is designed to operate in response to the activation signal C for deciding on the basis of the air-fuel ratio signals V
1
and V
2
whether or not the catalyst
10
suffers deterioration.
Connected to the catalyst deterioration decision means
102
is an alarm means
19
which is actuated when deterioration of the catalyst is determined.
An air-fuel ratio control means
103
is adapted to perform the air-fuel ratio control for the engine
1
on the basis of the air-fuel ratio signals V
1
and V
2
.
Next, description will be directed to the operation of the conventional air-fuel ratio control system shown in FIG.
9
.
In the operating state of the engine
1
, the harmful components such as mentioned previously are eliminated from the exhaust gas G discharged from the engine
1
by means of the catalytic converter
10
. The air-flow ratio sensors
11
and
12
detect the oxygen concentrations of the exhaust gas G to output the air-fuel ratio signals V
1
and V
2
, respectively, which assume different values in dependence on whether the air-fuel ratio of the exhaust gas G is lean or rich relative to the theoretical or stoichiometric air-fuel ratio.
The air-fuel ratio control means
103
performs the air-fuel ratio control for the engine
1
on the basis of the air-fuel ratio signals V
1
and V
2
. On the other hand, the catalyst activation decision means
101
issues the activation signal C to the catalyst deterioration decision means
102
when it is decided that the catalyst
10
is in the activated state.
The catalyst deterioration decision means
102
operates only when the activation signal C is inputted, to thereby make decision as to the deterioration of the catalyst
10
on the basis of the air-fuel ratio signals V
1
and V
2
. When deterioration of the catalyst is determined, the catalyst deterioration decision means
102
drives the alarm means
19
to issue an alarm signal.
FIG. 10
is a schematic block diagram showing a hardware arrangement of a conventional catalyst deterioration detecting apparatus for an internal combustion engine. In the figure, like parts or components as those described above by reference to
FIG. 9
are denoted by like reference symbols, and repeated description thereof is omitted.
The engine
1
is equipped with an intake pipe
2
for supplying a mixture gas to the engine
1
, wherein an air, cleaner
3
is disposed at a position close to an inlet port of the intake pipe
2
for the adsorbing and eliminating dusts and other particles carried by the air taken in. Further, an intake manifold
4
is formed at an interface portion between the engi
Dolinar Andrew M.
Mitsubishi Denki & Kabushiki Kaisha
Sughrue & Mion, PLLC
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