JPS59188053A - Air-fuel ratio compensation control for internal- combustion engine - Google Patents

Abstract

PURPOSE:To improve operation performance by renewing the learned value in accordance with the engine operation state when lean control is performed with the lean air-fuel ratio obtained on the basis of the learned value in a feedback and controlling the air-fuel ratio with the fundamental air-fuel ratio corrected by said learned value renewed. CONSTITUTION:A controller 48 feedback-controls an injector 30 in accordance with the output of an O2 sensor 40 so that the air-fuel ratio of the mixed gas becomes equal to a theoretical air-fuel ratio. Further, learning control is performed so that the fundamental air-fuel ratio is corrected to the vicinity of the theoretical air-fuel ratio from the feedback correction value, and when the engine operation state fulfills a certain condition, for example when the temp. of cooling water rises over 70 deg.C, the air-fuel ratio is feed forward controlled (lean control) on the basis of the fundamental air-fuel ratio learned. When the operation state where feedback control is performed is temporarily formed in lean control, the learned value due to the feedback control in the previous time can be renewed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an air-fuel ratio compensation control method for an internal combustion engine, and in particular, to
The present invention relates to an air-fuel ratio compensation control method for an internal combustion engine suitable for controlling the air-fuel ratio of an air-fuel mixture according to the operating state of an automobile engine.

[Prior art]

In an automobile engine, the air-fuel ratio (A/F) of the air-fuel mixture is adjusted to the stoichiometric air-fuel ratio (A/F = 14) according to the detection output of an oxygen concentration sensor (hereinafter referred to as 02 Senna) that detects the oxygen concentration in exhaust gas. .7) It has been conventionally practiced to perform feedback control in the vicinity and purify the exhaust gas using a ternary melting medium installed in the exhaust system. Furthermore, when the engine operating condition reaches a certain condition, for example, when the engine cooling water temperature reaches 70 degrees Celsius or higher, during feedback control, learning is performed from the feedback correction value in order to approximate the basic air-fuel ratio to the stoichiometric air-fuel ratio. Lean control that feedforward controls the air-fuel ratio of the mixture to a lean air-fuel ratio based on the basic air-fuel ratio determined (e.g. control as A/F-16)
Conventionally, efforts have been made to reduce fuel consumption by doing this.

However, in conventional lean control, the air-fuel ratio of the mixture is controlled at a lean air-fuel ratio based on the learned value during feedback.
Updating the lean air-fuel ratio based on the learned air-fuel ratio was not performed until feedback control was started. Therefore, in an engine to which conventional lean control is applied, when IJ-on control is continued for a long time,
Even if the operating state of the engine changes due to changes in engine water temperature or atmospheric pressure, feedback control is not performed, so the basic air-fuel ratio by learning is operated at a lean air-fuel ratio without being corrected, and the engine does not respond to changes in the operating state. control could not be performed.

Even if the operating state of the engine changes, if lean control is continued with a lean air-fuel ratio that is corrected, the combustion state will deteriorate and drivability will deteriorate. In particular, there is a problem that the engine stalls when the engine is idling.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned conventional problems, and its purpose is to change the operating state of the engine even when lean control is performed at a lean air-fuel ratio based on the learned value at the time of feedback. The learned value is updated accordingly, and the basic A/F corrected based on the updated learned value controls the air-fuel ratio of the air-fuel mixture to a lean air-fuel ratio, improving engine performance during lean control. An object of the present invention is to provide an air-fuel ratio compensation control method for an engine.

[Summary of the invention]

In order to achieve the above object, the present invention provides feedback control that feedback-controls the air-fuel ratio of the air-fuel mixture to near the stoichiometric air-fuel ratio according to the detection output of an oxygen degree sensor that detects the oxygen concentration in exhaust gas; At the time of control, in order to approximate the basic air-fuel ratio to the stoichiometric air-fuel ratio, lean control is used to feed forward the air-fuel ratio of the mixture to a lean air-fuel ratio based on the basic air-fuel ratio learned from the feedback correction value. In an air-fuel ratio compensation control method for an internal combustion engine that performs switching according to the state, an operating state of the engine to which temporary feedback control is performed during lean control is determined in advance, and when the operating state of the engine is detected during lean control, temporary feedback control is performed. The present invention is characterized in that the air-fuel ratio control is performed to update the learned value from the previous feedback control, and the next lean control is performed at a lean air-fuel ratio based on the updated learned value.

[Embodiments of the invention]

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

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

In FIG. 1, an intake pipe 12 of an engine 1o is provided with an air cleaner 14 for taking in outside air, a throttle valve 18 that rotates in conjunction with an accelerator pedal, and controls the flow rate of intake air. There is.

The air cleaner 14 has a built-in intake temperature sensor 22 that detects the temperature of intake air. Also, the throttle valve 18
A throttle sensor 24 for detecting opening of the idle switch throttle valve 18 is disposed. The intake manifold 26 is provided with a pressure sensor 28 that detects intake pipe pressure and an injector 30 that injects fuel toward the intake boat of the engine 10. Further, the main body of the engine 10 is provided with a rotational speed sensor 32 that outputs a pulse signal of a frequency corresponding to the rotational speed of the crankshaft of the engine 10, and a water temperature sensor 34 that detects the engine cooling water temperature.

On the other hand, on the exhaust manifold 38 outlet side of the exhaust pipe 36, an oxygen sensor 40 is arranged to detect the oxygen concentration in the exhaust gas. A three-way catalytic converter 42 is disposed downstream of the exhaust pipe 36.

The transmission 44 is also provided with a vehicle speed sensor 46 that detects the running speed of the vehicle from the rotational speed of the output shaft of the transmission 44.

Intake air temperature sensor 22, intake air amount sensor 20. Detection outputs of sensors such as the throttle sensor 24 that detect various operating states of the engine 10 are supplied to an engine control device 48, respectively.

As shown in FIG.
It consists of a microcomputer with PU50 as the core, timer 52, interrupt control section 54, rotational speed counter 56, digital input port 58, analog input port 0, power supply circuit 62, R, AM64, I(, OM 66
, a counter 68, a power amplifying section 70, and an output circuit 72 are provided, and the respective sections of p1 are connected by a pass line 74.

The rotational speed counter 56 receives the detection output of the rotational speed sensor 32, counts the engine rotational speed once per engine rotation, and outputs an interrupt command signal to the interrupt control unit 54 at the end of this counting. be able to. Interrupt control unit 5
4 generates an interrupt signal according to the interrupt command signal, and
50 can be caused to execute an interrupt processing routine for calculating the fuel injection time.

A throttle full M signal from the throttle sensor 24, a vehicle speed signal from the vehicle speed sensor 46, and a starter signal from the starter switch 76 are supplied to the digital human-powered boat 58. Further, an intake air amount sensor 20, an intake air temperature sensor 22, a pressure sensor 28,
Water temperature sensor 34, O.

Each detection output of the sensor 40 is supplied to an analog input port 0 and converted into a digital signal.

Further, the counter 68 inputs a digital signal representing the calculated valve opening time of the injector 30, that is, the fuel injection amount, to the CPU 50 from a down counter including a register, and sends the calculated valve opening time of the injector 30, that is, a digital signal representing the fuel injection amount, to the CPU 50. The pulse signal can be supplied to the power amplification section 70. The power amplifying section 70 amplifies the power of the pulse signal from the counter 68 and supplies it to the injector 30.

Furthermore, when it is detected that the engine water temperature exceeds the set temperature based on the detection output of the water temperature sensor 34, the output circuit 72 supplies a control signal to the drive circuit 78 to turn on the electric fan 80 that cools the engine cooling water. can operate.

The RAM 64 stores data calculated by the CPU 50, and the ROM 56 stores control programs and various numerical data. Numerical data stored in the ROM 66 includes, for example, throttle opening, engine water temperature, intake pipe pressure, rate of change in engine speed, rate of change in traveling speed, etc. in order to determine whether to perform lean control. There are numerical data of setting values for and numerical data of feedback correction coefficients.

The engine control device 48 is brought into operation by supplying power 84 to the power supply circuit 62 by operating the key switch 82, and executes various controls based on the control program and detection outputs of various sensors.

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

FIG. 3 is a flowchart of the processing routine of the present invention performed by the engine control device 48, and shows the portion for calculating the injector 300 valve opening time.

When the injection time τ calculation routine 100 is started, first in step 101 the rotational speed Ne is determined, and in 102 the intake pipe pressure Pm f
Take in. Next, in step 103, Ne.

The basic injection f) iTp corresponding to the movement is calculated from the map stored in the ROM 66. Next step 104
During this injection time Tp, air-fuel ratio correction is performed by learning control, which will be described later. In step 105, 02 sensor 4
Based on the signal from 0, the air-fuel ratio is corrected, and step 1
In step 06, the injection time τ is determined by multiplying by the lean control correction ratio FLEAN. Next, the process advances to step 107, and it is determined whether or not it is the injection time. If it is the injection time, the injection process is performed at step 108, and if not, the process directly goes to step 109, where the lean control process is executed.

Next, referring to FIG. 4, the lean control process in step 109 will be explained.

When the lean control routine 200 is started, first in step 201, the neutrality of the lean control is established based on the detection outputs of the throttle sensor 24, water temperature sensor 34, pressure sensor 28, rotational speed sensor 32, and vehicle speed sensor 40. Make a judgment as to whether or not there is one. That is, in this example, all conditions such as the accelerator opening degree being 30 degrees or less, the engine water temperature being 70 degrees Celsius or more, the intake pipe pressure being 450 mm1 (fabs or less), and the amount of change in vehicle speed in 2 seconds being 5 hours or less are met. If the condition is not satisfied in step 201, the process advances to step 205, where the feedback control routine is executed.Subsequently, in step 206, a learning control routine is started, and the present process ends.

If the condition is satisfied in step 201, step 20
Proceed to step 2 to determine whether the idle switch is ON, that is, the throttle valve is fully closed. If the idle switch is ON, proceed to step 203 and determine whether or not the electric fan is operating. If it is operating, proceed to step 205.
Execute feedback control. If it is not in operation at step 203, the process advances to step 204, and time control is performed. Here, a reduction correction coefficient FLEAN corresponding to the intake pipe pressure is determined.

Next, the feedback control routine in step 205 will be explained with reference to FIG.

First, in step 301, 02 shown in FIG.
A signal S7 from the sensor 40 is taken in. Next, in step 302, if 87>REF2 (comparison voltage), the process proceeds to step 303, and if S7≦R, 'E F 2, the process proceeds to step 307. In step 303, it is determined whether the rich flag F1% in the diagram Φ) is 11, that is, the air-fuel ratio state at the time of the previous processing was rich, and if it is 1, step 30
4, the previous correction coefficient PAF shown in the diagram (C) is reduced by a certain value αi to obtain FAF. If PR=0 in step 303, it is determined that the air-fuel ratio state has changed for the first time, and in step 305, PR is set to 1, and in the next step 306, FAF is reduced by αs(αs:)czi). , this process ends.

Similarly, in step 307, it is determined whether FR=1 or not, and if FR=0, the process proceeds to step 308, where FAF is increased by βi. If PR=1 in step 307, the process proceeds to step 309, where FR=0 and the process proceeds to step 310. In step 310, βS (βS>βi) is added to FAF, and the process ends.

Next, the learning control process in step 206 will be explained according to FIGS. 7 and 8.

Figure 7 shows F when the intake pipe pressure (operating conditions) changes.
This shows the movement of A F, but each learning area KGI
~K G 6 differs in the amount of deviation from FAF=1 before learning, as shown in FIG. 8(a), depending on the operating conditions. This amount of rubbing KG 1~KG6
is stored in RAM in correspondence with each intake pipe pressure, and the arithmetic processing shown in Fig. 3 is performed. After practicing, F'
The amount of AF deviation can be reduced to almost zero (+) as shown in the figure.

As a result, even when FAF=1.0 and feedback is discontinued, it is possible to obtain the μa view with an excess air ratio of 1.0.

As mentioned above, by canceling lean control and performing feedback control and learning control when the electric fan is operating, it is possible to always obtain the injection amount with an excess air ratio of 1.0, and based on this value, Since the injection amount during lean control is determined, control accuracy during lean control is improved.

In this way, in this embodiment, even when lean control is being performed, when the idle switch is on and the electric fan is in operation, the learned value is updated to correspond to the operating state. Feedback control is performed to perform the next level control at a lean air-fuel ratio based on the updated learning value, so even if the operating state changes while the idle state due to lean control continues. Engine stall can be prevented from occurring, and drivability can be prevented from deteriorating.

Furthermore, in the embodiment described above, when lean control is performed, the engine operating state for which temporary feedback control is performed is that the idle switch is ON and the electric fan is in operation. However, changes in atmospheric pressure and vehicle speed It is possible to apply the above-mentioned embodiments even under the following conditions.

[Effects of the Invention] As explained above, according to the present invention, the operating state of the engine for which temporary feedback control is performed during lean control is determined in advance, and when the operating state of the engine is detected during lean control, the operating state of the engine is temporarily controlled. Air-fuel ratio control is performed using feedback control to update the learned value from the previous feedback control1, and the next lean control is performed at a lean air-fuel ratio based on the updated learning value, so lean control is continued. Even if the operating state of the engine changes while the engine is running, the air-fuel ratio can be controlled in response to the change in operating state, and this has the excellent effect of preventing engine performance from deteriorating during lean control.

[Brief explanation of the drawing]

FIG. 1 is a system configuration diagram of an engine to which the present invention is applied;
2 is a block diagram for explaining the configuration of the engine control device shown in FIG. 1, FIG. 3 is a flowchart for explaining the operation of the present invention, and FIG. 4 is a flowchart for explaining the lean control routine according to the present invention. Flowchart, FIG. 5 is a flowchart of the correction coefficient calculation routine according to the present invention, and (a) to FIG.
(C) is a time chart for explaining the flowchart of FIG. 5, FIG. 7 is a diagram showing the relationship between time and intake pipe pressure, and FIGS. 8 (a) and (b) are details of the present invention. FIG. 3 is a characteristic diagram of a correction coefficient for explaining the present invention. DESCRIPTION OF SYMBOLS 10... Engine, 20... Intake air amount sensor, 22... Intake temperature sensor, 24... Throttle sensor, 28... Pressure sensor, 30... Injector, 32... Rotational speed sensor, 34...Water temperature sensor, 40...0. Sensor, -46...Vehicle speed sensor, 48...Engine control device. Agent Tatsuyuki Unuma (and 1 other person) Figure 1 4 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Time M → Haruma - Hajime Ukema

Claims (1)

[Claims] (1) Feedback control that feedback controls the air-fuel ratio of the air-fuel mixture to near the stoichiometric air-fuel ratio according to the detection output of the oxygen concentration sensor that detects the oxygen concentration in exhaust gas, and the basic air-fuel ratio that is determined from the feedback correction value during feedback control. Internal combustion control that performs learning control to correct the air-fuel ratio to near the stoichiometric air-fuel ratio and performs lean control that feedforward controls the air-fuel ratio of the air-fuel mixture to a lean air-fuel ratio based on the learned basic air-fuel ratio, depending on the engine operating state. In an engine air-fuel ratio compensation control method, an operating state of the engine for which temporary feedback control is performed during lean control is determined in advance, and when the operating state of the engine is detected during lean control, air-fuel ratio control is performed using temporary feedback control, and the operating state of the engine is determined in advance. 1. An air-fuel ratio compensation control method for an internal combustion engine, comprising updating a learned value through feedback control, and performing next lean control at a lean air-fuel ratio based on the updated learned value.