JPS603445A - Method of controlling air-fuel ratio of internal- combustion engine - Google Patents

Abstract

PURPOSE:To improve drivability and emission performance by controlling an air-fuel ratio to bring it to the approximation of a theoretical air-fuel ratio when the deviation between engine speeds measured for certain intervals each is greater than the specified value and controlling it to be lean when the deviation is less than the value. CONSTITUTION:A controller 44 constituted of a microcomputer takes in the newest engine speed. Ne from a revolution angle sensor 42 for every one turn of a crankshaft, reads out an engine speed Ne' preceeding thereto by one turn from RAM 52 and has Ne stored in RAM 52 as Ne'. The controller finds the deviation DELTANe between Ne and Ne' and calculates the level DELTANe' of discriminating any transient condition by multiplying Ne by the standard constant of the transient condition. In case of DELTANe<DELTANe', mixture is controlled to have a lean air-fuel ratio so as to adversely affect the exhaust gas purifying performance and improve fuel consumption. In other case of DELTANe>DELTANe', exhibiting the transient period of variation in car speed, the fuel ratio is placed under feedback control to approach the theoretical value so that a car is driven with exhaust gas purified. Since the transient condition is discriminated definitely, drivability and emission performance may be improved.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to an air-fuel ratio control device for an internal combustion engine, and in particular, to a device for controlling the air-fuel ratio of a vehicle engine to near the stoichiometric air-fuel ratio during a transient period when the vehicle speed rapidly changes. The present invention also relates to an air-fuel ratio control device for an internal combustion engine that is suitable for controlling the air-fuel ratio to a lean air-fuel ratio during steady changes in vehicle speed.

[Background of the invention]

In vehicles such as automobiles, in order to improve fuel efficiency and exhaust gas purification performance, the air-fuel ratio is controlled according to the operating state of the engine. For example, during a transient period when the vehicle speed changes rapidly, the air-fuel ratio is feedback-controlled to near the stoichiometric air-fuel ratio based on the detection output of an oxygen concentration sensor that detects the oxygen concentration in exhaust gas.
I'i, open-loose control of the air-fuel ratio to a lean air-fuel ratio is performed regardless of the detection output of the oxygen concentration sensor. By feedback controlling the air-fuel ratio to near the stoichiometric air-fuel ratio during transient conditions, the harmful gases such as carbon monoxide, hydrocarbons, and nitrogen oxides contained in the exhaust gas can be purified into harmless carbon dioxide, water vapor, and nitrogen using a three-way catalyst. can be converted into On the other hand, when the air-fuel ratio is controlled to be open-loose to a lean air-fuel ratio during steady state, the engine can be operated without impairing the exhaust gas purification performance, thereby improving fuel efficiency.

By the way, in an engine system to which the above-described air-fuel ratio control method is applied, it is determined whether or not it is in a transient state based on the engine speed detected by the rotation angle sensor built into the distributor, and the A method of controlling the air-fuel ratio to near the stoichiometric air-fuel ratio or a lean air-fuel ratio has been used. However, in conventional systems, the determination of whether or not a transient is occurring is made by comparing the amount of change in the engine speed over a certain period of time with a constant value. When a backlash occurs, the engine speed fluctuates, and there is a risk that a change in vehicle speed may be mistakenly judged as a transient state even though it is in a steady state, or conversely, that it may be mistakenly judged as a steady state even though it is a transient state. Ta. In addition, the fluctuation range becomes larger in the region where the engine speed is high, so
There is a risk that false judgments will be made more frequently. Therefore, in engine systems to which conventional air-fuel ratio control methods are applied, there is a risk that the air-fuel ratio may be controlled due to erroneous determination, which may cause the vehicle to start moving against the driver's will, and drivability may be affected. There was a risk that emission performance would deteriorate.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to provide a system for controlling the air-fuel ratio to near the stoichiometric air-fuel ratio or to a lean air-fuel ratio during transient and steady periods of changes in vehicle conditions. An object of the present invention is to provide an air-fuel ratio control device for an internal combustion engine, which can reliably determine whether a change in vehicle state is in a transient state or a steady state, and can improve drivability and emission performance.

[Summary of the invention]

In order to achieve the above object, the present invention provides feedback control of the air-fuel ratio to near the stoichiometric air-fuel ratio based on the detection output of an oxygen concentration sensor that detects the oxygen concentration in exhaust gas during transient times when vehicle conditions rapidly change. , an air-fuel ratio control device for an internal combustion engine that controls the air-fuel ratio to a leaner air-fuel ratio than the stoichiometric air-fuel ratio when the vehicle condition is steady; 2nd part
and a third means for comparing the deviation with a value set according to the internal combustion engine rotation speed; when the deviation is larger than the set value, the air-fuel ratio is moved to the vicinity of the stoichiometric air-fuel ratio, and when the deviation is smaller than the set value, the air-fuel ratio is moved to the vicinity of the stoichiometric air-fuel ratio. It is characterized by having a fourth means for controlling the air-fuel ratio to be thinner than the fuel ratio.

[Embodiments of the invention]

Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

FIG. 1 shows the configuration of an engine system to which the present invention is applied.

In FIG. 1, the intake system of an engine 1o is provided with an air flow meter 12, a throttle valve 14, etc., and air taken in via the air flow meter 12 is supplied to an intake manifold 1G via the throttle valve 14. , and mixes with the fuel injected from the fuel injection valve 18. This air-fuel mixture is supplied to a combustion chamber 22 through an intake valve 20, is combusted by a spark plug 26 provided in a cylinder head 24, and is discharged to an exhaust system through an exhaust valve 18.

The exhaust system includes an oxygen 'a' which detects the oxygen concentration in the exhaust gas.
An air-fuel ratio sensor (hereinafter referred to as an O2 sensor) 30 is provided, and when the air-fuel ratio of the air-fuel mixture is feedback-controlled to near the stoichiometric air-fuel ratio by a control device to be described later based on the detection output of this O2 sensor, the exhaust system A three-way catalytic converter (not shown) provided in the exhaust gas purifies and exhausts harmful residue contained in the exhaust gas.

The cylinder block 32 is provided with a water temperature sensor 34 that detects engine water temperature.

Further, a sensor 40 for each cylinder 1J and a rotation angle sensor 42 are built into the distributor 38 that distributes the ignition signal from the igniter 36 to each cylinder.

Detection outputs of sensors such as the 02 sensor 30 that detect various operating states of the engine are supplied to the control device 44.

FIG. 2 shows a configuration in which a microcomputer is used as the control device 44.

The control device 44 includes a CPU 50 as shown in FIG.
．． RAM52, R, 0M54, crowd capo) 56.58
, output port 0, 62, A/D converter 64, multiplexer 66.1 drive circuit 68°70, waveform shaping circuit FNJ
72, an input circuit 74, and a CPU 50.
11 (, AM52, ROM54, input/output capo) 56,5
8 and output ports 0°62 are connected to each other by a pass line 76.

The detection outputs of the air flow meter 12 and water temperature sensor 14 are supplied to the input/output boat 56 via a multiplexer 66 and an A/D converter 64. The detection outputs of the cylinder discrimination sensor 40 and the rotation angle sensor 42 are supplied to the input/output boat 58 via the waveform shaping circuit 72. Further, the detection output of the 0□ sensor 30 is supplied to the input/output port 58 via the input circuit 74.

The igniter 36 is connected to the distributor 38 by a control signal supplied via the output port 0 and the drive circuit 68.
The ignition signal can be supplied to the The fuel injection valve 18 can control the fuel injection time by a control signal supplied via the output port 2 and the drive circuit 70.

Further, 11,0M54 contains an arithmetic processing program for the control device 44, numerical data of a determination level for determining whether or not a change in vehicle speed is in a transient state, numerical data indicating a reference value for a transient state of a change in vehicle speed, and Various data such as numerical data of fuel injection time for the fuel injection valve 18 for controlling the air-fuel ratio to near the stoichiometric air-fuel ratio or a lean air-fuel ratio are stored.

The present embodiment has the above configuration, and its operation will be explained next.

FIG. 3 shows an example of a processing routine performed by the control device 44 when the present invention is applied to the engine system shown in FIG.

The processing routine in this embodiment is a routine that is performed every time the engine crankshaft makes one revolution. First, in step 100, every time the engine crankshaft makes one revolution, the latest engine rotation based on the detection output of the rotation angle sensor 42 is detected. The number Ne is taken in and the process moves to step 102. In step 102 '%ζ, the engine rotational speed Ne' one revolution before the crankshaft is read out from the RAM 52 and the process moves to step 104. In step 104, the engine rotation speed Ne detected in step 100 is stored as Ne' in RA, M52, and the process moves to step 106. In step 106, the engine speed Ne detected in step 100 is compared with the engine speed Ne' read out from the RAM 52 in step 102, and the deviation ΔNe is determined, and the process moves to step 108. In step 108, a process is performed to update the reference value for the transient state of vehicle speed change according to the current engine rotational speed and calculate an appropriate determination level for the transient state. That is, the reference value (constant) of the transient state of vehicle speed change and the latest engine speed Ne
The determination level ΔNe' of the transient state is calculated by multiplying by , and the process moves to step 110K. In step IIO, the deviation ΔNe calculated in steps 106 and 108 is compared with the determination level ΔNe'. In this step, if it is determined that △Ne (△Ne') and the change in vehicle speed is in a steady state, step 112
The air-fuel ratio is controlled to a lean air-fuel ratio, and the engine is operated without impairing exhaust gas purification performance.
Fuel efficiency will be improved.

On the other hand, in step 110, it is determined that ΔNe)ΔNe', and the process moves to step 114 when the change in vehicle speed is transient.

In step 114, the air-fuel ratio is feedback-controlled to near the stoichiometric air-fuel ratio based on the detection output of the 02 sensor 30, and the engine is operated with the exhaust gas purified.

With the above processing, the processing routine for one revolution of the engine crankshaft is completed.

In this way, in this embodiment, when determining whether the change in vehicle speed is in a transient period, the current engine speed Ne
and the engine speed Ne′ before one revolution of the engine crankshaft.
In addition, the reference value for the transient state of vehicle speed change is updated with the current engine rotation speed Ne to determine the determination level ΔNe' for the transient state, and this determination level ΔNe' and the deviation ΔNe is compared, so even if a crash occurs in the gear that drives the crankshaft, it is possible to reliably determine whether or not a transient is occurring, and this determination result can be used to Accordingly, the air-fuel ratio can be controlled to be near the stoichiometric air-fuel ratio or to a lean air-fuel ratio.Therefore, drivability and emission performance can be improved.

In addition, in the above embodiment, it was described that the engine speed is detected, but the current intake pipe pressure and the intake pipe pressure a predetermined time ago are detected, the deviation is calculated, and the reference value for the transient state of the load is determined. A determination level for a transient state is calculated by updating it based on the current intake pipe pressure, and this determination level is compared with the deviation, and if the deviation is less than the determination level, it is determined that the change in load is in a steady state. It is also possible to determine that the load change is in a transient state when the deviation exceeds a determination level, and to control the air-fuel ratio in accordance with this determination result.

In the above embodiment, L-JEFI (electronically controlled fuel injection device) was described, but D-J EFI and D
-J SPI (SinglePoint Inje)
It is also possible to apply the above embodiment to D-JEFT.

L-J EFI detects the amount of intake air with an air flow meter, D・', -J EFI detects the intake pipe negative pressure as an absolute pressure with a negative pressure sensor, and performs basic injection according to the intake pipe negative pressure from the map. It is the type that you can measure. Father, D-J
SPI has an injector installed at the capretor position,
This type performs fuel injection with a single injector, and this type has better controllability than one using a carburetor, and is also advantageous in terms of cost.

〔Effect of the invention〕

As explained above, according to the present invention, the reference value for the transient state of vehicle speed change is updated by the current engine N rotation speed to calculate the determination level of the transient state. It is possible to prevent misjudgment as to whether or not the
It has the excellent effect of being able to reliably control the air-fuel ratio to near the stoichiometric air-fuel ratio during transient periods and to a lean air-fuel ratio during steady-state conditions (4: Lean air-fuel ratio), improving drivability and emission performance. .

[Brief explanation of the drawing]

FIG. 1 is a system configuration diagram of an engine to which the present invention is applied;
FIG. 2 is a block diagram for explaining the configuration of the apparatus shown in FIG. 1, and FIG. 3 is a flow chart for explaining the operation of the present invention. 10... Engine 12... Air flow meter 18.
...Fuel injection valve 30...02 sensor 34...Water temperature sensor 42...Rotation angle sensor 44...Control device. Agent Tatsuyuki Unuma (and 1 other person) Figure 2 4, 4 Figure 3

Claims (1)

[Claims] (1) The air-fuel ratio is feedback-controlled to near the stoichiometric air-fuel ratio based on the detection output of the oxygen concentration sensor that detects the oxygen concentration in exhaust gas during transient periods when vehicle conditions change rapidly, and when the vehicle condition is steady, the air-fuel ratio is controlled to be close to the stoichiometric air-fuel ratio. In an air-fuel ratio control device for an internal combustion engine that controls the air-fuel ratio to a highly lean air-fuel ratio, a first means for detecting the internal combustion engine rotation speed, a second means for calculating a deviation in the internal combustion engine rotation speed at regular intervals, third means for comparing the deviation with a value set according to the internal combustion engine rotation speed;
Air-fuel ratio control for an internal combustion engine, characterized in that it has a fourth means for controlling the air-fuel ratio to near the stoichiometric air-fuel ratio when the deviation is larger than the set value, and to control the air-fuel ratio to a thinner air-fuel ratio than the stoichiometric air-fuel ratio when it is small. Device.