Internal-combustion engines – Charge forming device – Including exhaust gas condition responsive means
Reexamination Certificate
2000-11-17
2003-02-04
Kwon, John (Department: 3747)
Internal-combustion engines
Charge forming device
Including exhaust gas condition responsive means
C701S109000
Reexamination Certificate
active
06513509
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device for controlling the air-fuel ratio of an internal combustion engine, which feeds, to the internal combustion engine, the fuel in an amount that meets the operation condition of the engine by using a signal detected by an air-fuel ratio sensor. More specifically, the invention relates to a device for controlling the air-fuel ratio of an internal combustion engine, which is capable of highly precisely finding learning correction values in an open-loop operation region without executing the air-fuel ratio feedback control operation, by using an air-fuel ratio sensor constituted by an ordinary oxygen sensor.
2. Prior Art
In a device for controlling the air-fuel ratio of an internal combustion engine, in general, a target air-fuel ratio is set depending upon operation condition data from various sensors (air-flow sensor that measures the amount of the air taken in, etc.), and the amount of fuel injection is so corrected that the practical air-fuel ratio comes into agreement with the target air-fuel ratio (usually, stoichiometric air-fuel ratio &lgr;=14.7).
In the device for controlling the air-fuel ratio of an internal combustion engine, further, an air-fuel ratio sensor (also called “oxygen sensor”) is usually disposed in the exhaust pipe to detect the stoichiometric air-fuel ratio while learning and correcting the air-fuel ratio feedback control quantity in order to compensate for a change caused by aging and dispersion of various parts constituting the sensors and the fuel-feeding system.
FIG. 5
is a diagram schematically illustrating the constitution of a conventional device for controlling the air-fuel ratio of an internal combustion engine.
In
FIG. 5
, an intake pipe
2
of an engine
1
constituting the main body of the internal combustion engine is provided with a throttle valve
3
for adjusting the amount of the air taken in, and a throttle opening-degree sensor
4
for measuring the opening degree &thgr; of the throttle valve
3
is coupled to the throttle valve
3
.
An air-flow sensor
5
is provided on the upstream side of the throttle valve
3
in the intake pipe
2
, and an injector
6
is provided in the intake pipe
2
on the downstream side of the throttle valve
3
to inject fuel in a required amount.
The air-flow sensor
5
measures the flow rate of the air in the intake pipe
2
as the intake air amount Qa taken in by the engine
1
.
A combustion chamber
7
in each cylinder of the engine
1
is constituted by a cylinder block
8
and a piston
9
that reciprocates in the cylinder block.
The combustion chamber
7
is provided with a spark plug
10
, an intake valve and an exhaust valve
12
.
The combustion chamber
7
is connected to an exhaust pipe
13
. An air-fuel-ratio sensor
14
which is an oxygen sensor is disposed in the exhaust pipe
13
.
The air-fuel-ratio sensor
14
produces an air-fuel ratio corresponding to the stoichiometric air-fuel ratio &lgr;.
Data (throttle opening degree &thgr;, intake air amount Qa, air-fuel ratio signal AF) detected by the sensors
4
,
5
and
14
and representing the operation conditions of the engine
1
are input to a control circuit
20
which is a microcomputer.
Though not diagramed, the control circuit
20
includes a well-known CPU, RAM and ROM connected to the CPU through a bidirectional bus, as well as input ports and output ports.
The control circuit
20
includes air-fuel ratio correction means for correcting the air-fuel ratio so as to accomplish a target air-fuel ratio depending upon the operation conditions, feedback control condition-determining means for determining the conditions for controlling the feedback of air-fuel ratio to the engine
1
depending upon the operation conditions, feedback control means for bringing the air-fuel ratio of the engine
1
into agreement with the target air-fuel ratio when the control conditions are permitted, and air-fuel ratio learning means for learning and correcting the air-fuel ratio feedback control quantity. The control circuit
20
controls the amount of fuel injected through the injector
6
based upon the operation conditions and the air-fuel ratio signal AF.
To the input ports of the control circuit
20
are connected the throttle opening-degree sensor
4
, air-flow sensor
5
, air-fuel ratio sensor
14
, as well as various other sensors (rotation sensor for detecting the rotational speed of the engine, cooling water temperature sensor, etc.) that are not shown.
The control circuit
20
processes various input data (operation conditions) to obtain control data of the engine
1
, and produces, through the output ports thereof, injection signals J for the injectors
6
, ignition signals G for the spark plugs
10
, as well as drive signals for various other actuators that are not shown.
Next, the operation of the conventional device for controlling the air-fuel ratio of an internal combustion engine shown in
FIG. 5
will be concretely described with reference to FIG.
6
.
FIG. 6
is a diagram schematically illustrating learning correction values obtained by using a conventional device for controlling the air-fuel ratio of an internal combustion engine disclosed in Japanese Examined Patent Publication (Kokoku) No. 56340/1987.
FIG. 6
illustrates learning correction values ZC
0
to ZC
9
in plural operation regions to where the air-fuel ratio feedback control is applied, and in which the abscissa represents the engine rotational speed Ne [r/min], the ordinate represents filling efficiency EC [%] corresponding to the intake air amount Qa, i.e., represents the engine load.
The feedback operation regions are sectionalized by the engine rotational speeds NC
0
to NC
2
and the engine loads EC
0
to EC
2
.
The learning correction values ZC
0
to ZC
9
in the operation regions of
FIG. 6
are obtained by sampling the air-fuel ratio feedback control quantities among the predetermined ignition cycles, and are periodically updated at every update timing when the sampling is finished.
In
FIG. 5
, first, the control circuit
20
operates the target air-fuel ratio and the target ignition timing based on the operation condition data from various sensors, and produces injection signals J for the injectors
6
and ignition signals G for the spark plugs
10
.
Therefore, the injector
6
is driven just before the intake stroke of the engine
1
to inject fuel, whereby the mixture gas containing fuel is taken into the combustion chamber
7
when the throttle valve
3
is opened, so that the interior of the combustion chamber is uniformly filled with the mixture gas.
The spark plug
10
is energized near the compression stroke of the engine
1
to ignite the mixture gas in the combustion chamber
7
, whereby the engine
1
produces a drive torque as a result of combustion.
On the other hand, feedback control means in the control circuit
20
executes the air-fuel feedback control operation when the condition for controlling the air-fuel ratio feedback is established depending upon the operation conditions of the engine
1
.
At this moment, the feedback control means operates the control quantity based upon the operation conditions and the air-fuel ratio signal AF from the air-fuel ratio sensor
14
, and so controls the feedback that the practical air-fuel ratio is brought into agreement with the target air-fuel ratio.
Thus, the air-fuel ratio of the engine
1
is controlled to accomplish a target value, whereby the catalytic converter (not shown) for purifying the exhaust gases disposed in the exhaust pipe
13
purifies the exhaust gases to a sufficient degree preventing the emission of non-purified gases.
Further, the amount of controlling the fuel (air-fuel ratio) is corrected not only by the air-fuel ratio signals AF but also by the learning correction values ZC
0
to ZC
9
in the operation regions of
FIG. 6
depending upon the operation regions, whereby the air-fuel ratio of the engine
1
is highly precisely controlled to acquire a target air-fuel ratio
Kwon John
Sughrue & Mion, PLLC
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