Internal-combustion engines – Spark ignition timing control – Electronic control
Reexamination Certificate
1999-12-08
2001-08-28
Dolinar, Andrew M. (Department: 3747)
Internal-combustion engines
Spark ignition timing control
Electronic control
C701S105000, C701S108000, C701S109000
Reexamination Certificate
active
06279537
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an air fuel ratio control apparatus for an internal combustion engine with a use of a NOx catalyst.
2. Description of the Prior Art
FIG. 8
is a schematic diagram showing a conventional air fuel ratio control apparatus for an internal combustion engine and the combustion chamber
15
as well as the air intake system and the ignition system are designed to allow the lean combustion. The air intake port
2
of an internal combustion engine
1
is connected, through a manifold
4
with a fuel injection valve
3
attached to each cylinder, with an air intake pipe which comprises an air cleaner
5
, an air flow sensor
6
for detecting air intake quantity Qa, throttle valve
7
and ISC valve
8
. The air flow sensor, which is of a type such as the Karman's vortex, is preferably used. The exhaust pipe
14
, to which the air fuel ratio sensor
12
such as a linear fuel ratio sensor
12
such as a linear air fuel ratio sensor
12
as a means for detecting the excess air ratio &lgr; (air fuel ratio information) is disposed, is connected to the exhaust port of the internal combustion engine
1
through the exhaust manifold
11
.
The exhaust gas purification catalyst device
13
comprises two catalyst of a ternary catalyst
13
and a occlusion catalyst
13
b
, and the ternary catalyst
13
a
is disposed on the more upstream side of the occlusion catalyst
13
b
. The ternary catalyst
13
a
has a function of oxidization of HC (hydrocarbon) and CO (carbon monoxide) as well as of reduction of NOx. Reduction of the NOx by means of the ternary catalyst
13
is promoted utmost with the theoretical air fuel ratio being in the vicinity of 14.7. The NOx occlusion catalyst
13
b
has a function of occluding the NOx at an excessively rich Oxygen atmosphere (lean air fuel ratio) and of reducing the NOx at the oxygen deficient atmosphere (rich air fuel ratio) with existence of HC and CO. As the NOx occlusion catalyst
13
b
, a catalyst consisting of the alkali earth metals such as Ca (calcium) and Ba (barium) and Pt (platinum) is used. A catalyst, which performs reduction of NOx exhausted to the atmosphere by utilizing a characteristics of adsorbing the NOx exhausted from the internal combustion engine
1
at an excessively rich oxygen state (oxidation atmosphere) and of reducing the adsorbed NOx at an excessive hydrocarbon (HC) state (reduction atmosphere), is already known.
In the internal combustion engine
1
, an ignition plug is provided for igniting the mixture gas of air and fuel supplied to the combustion chamber
15
from the air intake port
2
.
18
is a crank angle sensor for detecting the crank angle synchronization signal &thgr; CR from the encoder being interlocked with the camshaft,
19
is a throttle sensor for detecting the throttle valve opening degree,
20
is a water temperature sensor for detecting the cooling water temperature TW,
21
is an atmospheric pressure sensor for sensing the atmospheric pressure Pa, and
22
is an intake air temperature sensor Ta. The rotation number Ne of the internal combustion engine is calculated from the time interval of generation of the crank angle synchronization signal &thgr; CR detected by the crank angle sensor
18
. Within the car room an ECU (Electronic Control Unit) which comprises unshown input output device, memory devices (such as ROM, RAM, non-volatile RAM) storing a number of control programs, central processing unit (CPU) and timer counter, is installed and it performs a synthetic control of the air fuel ratio control device including the internal combustion engine
1
. Next, description on the operation of the aforementioned apparatus will be given. The NOx occlusion catalyst
13
b
is to occlude the NOx during the lean air fuel ratio control, but because of limitations imposed on the quantity to be occluded by the catalyst for a continuous lean combustion operation, when the quantity to be occluded comes out saturated, most of the NOx (nitrogen oxide) exhausted from the internal combustion engine
1
is exhausted to the atmosphere. Then, the timing of shifting to the rich operation from the lean operation gives rise to a problem because, before the occlusion quantity of the NOx occlusion catalyst
13
b
reaches a saturated quantity, the air fuel ratio control must be shifted to the one being operated at an ideal air fuel ratio or in the vicinity of that ratio and reduction of NOx at the rich air fuel ratio or at the theoretical air fuel ratio must be started.
Generally speaking, a method of performing the rich combustion operation after performing the lean combustion operation for a predetermined interval is employed. This method is exemplified such that the ECU
23
estimates quantity of NOx exhausted from the internal combustion engine
1
, and the rich operation is performed when the quantity of the exhausted NOx reaches a predetermined valve. An example of estimation of the quantity of the exhausted NOx is disclosed by the Japanese Laid-Open Patent Application No. H7-305644 such that by obtaining an estimation value DN of exhausted NOx concentration as the air fuel ratio map and obtaining a compensation coefficient KIg as the ignition timing map and also likewise obtaining K
1
depending on the EGR quantity and temperature as other compensation coefficient map, quantity of the exhausted NOx QNO was obtained from the intake air quantity Qa according to the following equation (1):
QNO=K
1
·
KIg·Qa·DN
(1)
According to the Japanese Laid-Open Patent Application NO. H7-305644, though the NOx exhaust quantity QNO is estimated from the equation (1) as above, because of a fluctuation of ignition timing the relation between the air fuel ratio A/F and the NOx exhaust concentration estimation value DN and also the relation between the EGR quantity and the exhaust concentration estimation value DN heavily change. As a consequence the estimation accuracy can not be improved without obtaining the NOx exhaust concentration estimation value DN depending on the ignition timing. Also a number of maps are required resulting in having the memory capacity increased.
SUMMARY OF THE INVENTION
In order to solve the foregoing problems, the object of the present invention is to provide an air fuel ratio control apparatus for an internal combustion engine which is adapted to improve the estimation accuracy of the NOx exhaust concentration estimation value.
An air fuel ratio control apparatus for an internal combustion engine according to the invention comprises a NOx catalyst disposed in a exhaust gas passage of an internal combustion engine, a NOx exhaust quantity estimation means for estimating quantity of NOx exhausted from the internal combustion engine, an air fuel ratio control means for controlling the air fuel ratio based on the estimated NOx exhaust quantity estimated by the NOx exhaust quantity estimation means, and a NOx exhaust concentration estimation means for estimating the concentration of the exhausted NOx from at least either one of a value corresponding to said air fuel ratio or a value corresponding to recirculation quantity of an exhaust gas and a value corresponding to a ignition timing.
The NOx exhaust concentration estimation means calculates the estimated value of NOx exhaust concentration by means of the four fundamental rules of arithmetic based on at least either one of the air fuel ratio and the quantity of recirculation exhaust gas and the value corresponding to the ignition timing.
The estimated value of NOx exhaust concentration is calculated by the formula of:
DN=K
1
A/F+K
2
EGR,
wherein DN denotes the estimated value of NOx exhaust concentration, A/F denotes the air fuel ratio, EGR denotes the quantity of exhaust gas recirculation, and K
1
and K
2
are coefficients corresponding to the ignition timing.
The air fuel ratio control apparatus comprises a NOx exhaust quantity estimation means for estimating quantity of exhausted NOx based on the estimated value of NOx exhaust concentration and a quanti
Katashiba Hideaki
Ohuchi Hirofumi
Wachi Satoshi
Yonekura Tosiaki
Dolinar Andrew M.
Mitsubishi Denki & Kabushiki Kaisha
Sughrue Mion Zinn Macpeak & Seas, PLLC
LandOfFree
Air fuel ratio control apparatus for an internal combustion... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Air fuel ratio control apparatus for an internal combustion..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Air fuel ratio control apparatus for an internal combustion... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2454125