JPS63113145A - Air-fuel ratio controlling method for internal combustion engine - Google Patents

Abstract

PURPOSE:To make early learning control attainable, by renewing a reference correction value, compensating an error in the air-fuel ratio control reference value conformed to a running area, in making it correspond to this running area, when oxygen sensor output is reversed as well as when its nonreversion is continued as long as the specified time. CONSTITUTION:Each detected value of a suction absolute pressure sensor 10, a crank angle sensor 11, a cooling water temperature sensor 12, a suction temperature sensor 13, an oxygen sensor 14 or the like is inputted into a control circuit 20, and this control circuit reads both air-fuel ratio control reference and reference correction values conformed to suction absolute pressure and engine speed, calculating an air-fuel ratio correction factor on the basis of the detected value of the oxygen sensor 14, and determines control output to a linear type solenoid valve 9. And, when the output of the oxygen sensor 14 is reversed as well as when its nonreversion is continued for more than the specified time, a reference correction value for compensating an error of the reference value is renewed on the basis of the ratio of the last time control output to the reference value and the last time reference correction value.

Description

[Detailed description of the invention] Five Emperors of Skin 1 The present invention relates to an air-fuel ratio control method for an internal combustion engine.

1. To purify the exhaust gas of internal combustion engines, improve fuel efficiency, etc., the oxygen concentration in the exhaust gas is detected by the Fl element concentration sensor,
An air-fuel ratio control device is known that performs feedback control of the air-fuel ratio of an air-fuel mixture supplied to an engine in accordance with the output level of this oxygen concentration sensor.

As this air-fuel ratio control device, a solenoid valve is provided in the intake secondary air supply passage communicating downstream of the carburetor throttle valve, and the opening degree of the solenoid valve, that is, the intake secondary air supply m is controlled according to the output level of the oxygen concentration sensor. There are air-fuel ratio control devices using intake secondary air supply force for feedback control (for example, the
-3533).

In such a conventional air-fuel ratio control device, an air-fuel ratio reference value of 11Jtll representing the intake secondary air supply m is set according to a plurality of operating parameters related to the engine load,
It is determined whether the air-fuel ratio of the supplied air-fuel mixture is lean or rich with respect to the target air-fuel ratio from the output level of the oxygen concentration sensor, and the air-fuel ratio correction value is adjusted by a proportional amount or PI (proportional integral) that increases or decreases by the integral amount and corrects the air-fuel ratio control reference value according to the air-fuel ratio correction value.
Control is normally in place.

By the way, it is common for the base air-fuel ratio of the carburetor to deviate from a predetermined value due to aging or deterioration of the carburetor, causing the set reference value to no longer correspond to the target air-fuel ratio and resulting in an error. It is. Therefore, Mt! for correcting the error in the reference value for each operating region! There is a system that performs learning control in which the l=correction value is read out and a new reference correction value is stored to improve the accuracy of air-fuel ratio control.

However, depending on the settings of the fuel supply system of the internal combustion engine, the already set reference value may no longer correspond to the target air-fuel ratio even immediately after the production of an e-vehicle equipped with such an air-fuel ratio control device. , since one reference correction value is initialized when the air-fuel ratio control device starts to be used, for a while after initialization, the reference value may not be corrected because sufficient learning control results cannot be obtained, especially in operating areas that are infrequently used. This may result in poor air-fuel ratio control accuracy.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an air-fuel ratio control method for an internal combustion engine that can obtain good air-fuel ratio u1wJ accuracy even if an error occurs in the reference value immediately after the start of use of the device. It is.

The air-fuel ratio control method for an internal combustion engine of the present invention includes air-fuel ratio control when a reversal of the output value of an exhaust component concentration sensor such as an oxygen concentration sensor with respect to a target value is detected, and when a predetermined RF period has elapsed without detection of reversal. A reference correction value for correcting errors in the reference value is calculated and stored in correspondence with the operating range determined by multiple engine operating parameters, and the air-fuel ratio control reference value at that time is used as the air-fuel ratio correction value and the reference correction value. It is characterized in that the air-fuel ratio control output value for the target air-fuel ratio is determined by correcting the air-fuel ratio accordingly.

Tomo-Yutaka-1 Embodiments of the present invention will be described below with reference to the drawings.

In the air-fuel ratio control device of the intake secondary air supply system for an on-vehicle internal combustion engine that utilizes the air-fuel ratio control method of the present invention shown in FIG. The vicinity of the air outlet is the intake 2
The air supply passages 8 communicate with each other. A linear solenoid valve 9 is provided in the intake secondary air supply passage 8 . The opening degree of the solenoid valve 9 changes in proportion to the current value supplied to the solenoid 9a.

A negative pressure detection boat 6 is provided on the inner wall surface of the carburetor 1 near the throttle valve 3. The negative pressure detection boat 6 is located upstream of the throttle valve 3 when the opening of the throttle valve 3 is less than a predetermined opening, and is located downstream of the throttle valve 3 when the opening of the throttle valve 3 is greater than the predetermined opening. The negative pressure in the negative pressure detection boat 6 is supplied to the negative pressure switch 7 via the negative pressure passage 6a. The negative pressure switch 7 is provided to detect the closed state of the throttle valve 3, and is turned on when the negative pressure in the negative pressure detection boat 6 is, for example, 301IIIHg or less.

On the other hand, 10 is an absolute pressure sensor installed in the intake manifold 4 and generates an output at a level corresponding to the absolute pressure inside the intake manifold 4, and 11 generates a pulse in accordance with the rotation of the crankshaft (not shown) of the engine 5. 12 is a cooling water temperature sensor that generates an output at a level corresponding to the cooling water temperature of the engine 5; 13 is an intake temperature sensor that detects the intake air temperature; 14 is an exhaust manifold 1 of the engine 5;
5 is an oxygen concentration sensor that generates an output voltage according to the oxygen concentration in exhaust gas. A catalytic converter 33 is provided in the exhaust manifold 15 downstream of the oxygen Q degree sensor 14 in order to promote reduction of harmful components in the exhaust gas.

The negative pressure switch 7 , solenoid valve 9 , absolute pressure sensor 101 , crank angle sensor 11 , water temperature sensor 12 , intake temperature sensor 13 , and oxygen concentration sensor 14 are connected to a control circuit 20 . The negative pressure switch 7 generates a low level output when turned off, and generates a high level output when turned on.

The control circuit 20 includes an absolute pressure sensor 101 as shown in FIG.
Water temperature sensor 12, intake temperature sensor 13, oxygen concentration sensor 1
4, a multiplexer 22 that selectively outputs one of the sensor outputs that have passed through the level conversion circuit 21;
A/2 converts the signal output from 2 into a digital signal.
A D converter 23, a waveform shaping circuit 24 that shapes the output signal of the crank angle sensor 11, and a clock pulse generation circuit (not shown) that outputs the generation interval of the TDC signal output as a pulse from the waveform shaping circuit 24. A counter 25 that measures the number of clock pulses, a level conversion circuit 26 that converts the output level of the negative pressure switch 7, a digital input camosulator 27 that converts the converted output into digital data, and a solenoid valve 9 that is driven to open. Drive circuit 2
8 and cp, which performs digital operations according to the program.
u <central processing circuit) 29, ROM 30 in which various processing programs and data are written in advance, and RAM 31
It consists of The solenoid 9a of the electromagnetic valve 9 is connected in series with a drive transistor and a current detection resistor (both not shown) of a drive circuit 28, and a power supply voltage is supplied across the series circuit. Multiplexer 22, A/D converter 23, counter 25, digital input camosulator 2
7. Drive circuit 28, CPU 29, ROM 30 and RAM
31 are connected to each other by an input/output bus 32.

In such a configuration, information on the absolute pressure in the intake manifold 4, cooling water temperature, intake air temperature, and oxygen concentration in exhaust gas is alternatively sent from the A/D converter 23, and information representing the engine rotation speed is sent from the counter 25. However, the on/off of the negative pressure switch 7 is controlled by the digital input camosulator 27 from the CPU 2.
9 via the input/output bus 32. CPU2
9 is a predetermined period T+ (for example, 5QISe
C) By running the processing program every time ff1l
An air-fuel ratio control output value DOLIT representing the value of current supplied to the solenoid 9a of the a-valve 9 is calculated as data, and the calculated output value DOUT is supplied to the drive circuit 28.

The drive circuit 28 performs closed loop control on the current value flowing through the solenoid 9a so that the current value flowing through the solenoid 9a becomes the output value DOUT.

Next, the steps of the air-fuel ratio control method according to the present invention will be described in the third step.
A detailed explanation will be given according to the operation flow diagram of the CPU 29 shown in the figure.

As shown in FIG. 3, CPtJ29 first calculates the intake absolute pressure P.
BA % Cooling water temperature TW1 Intake temperature T^, engine speed Ne and oxygen concentration 02 are each read (step 51)
, it is determined whether the intake air ITA is higher than a predetermined temperature T+ (for example, 25° C.) (step 52). TA>T
If I, it is determined whether the cooling water) IWTW is higher than a predetermined temperature T2 (for example, 80° C.) (step 53). If TA≦T+ or TW≦T2, the air-fuel ratio feedback control conditions are not satisfied, so the output value is the same.

UT is set to O (step 54), and the air-fuel ratio feedback coefficient KO2 is set equal to 1 (step 55). T
If W > T 2, it is assumed that the air-fuel ratio feedback control conditions are satisfied and a reference value DBASE representing the reference current value to be supplied to the solenoid valve 9 is searched (step 56).
. As shown in Fig. 4, the reference value DBASε determined from the absolute pressure PBA and the engine speed Ne is stored in the ROM 30.
Since it is written in advance as an ASε data map,
The CPU 29 searches the DBASE data map for a reference value D8ASE corresponding to the read absolute pressure PEA and engine speed Ne. After searching for the reference value DOA S E,
Determine whether the oxygen concentration is leaner than the reference concentration corresponding to the target air-fuel ratio, that is, determine whether the output voltage VO2 of the oxygen concentration sensor 14 is smaller than the reference value vrer (0,5 (V)). (step 57). ■02〈■re“
If so, since the air-fuel ratio is leaner than the target air-fuel ratio, the air-fuel ratio flag FAF representing the determination result of the previous step 57 is set.
is 1 (step 58).

If FA F = O, the previous air-fuel ratio was determined to be rich and reversed from rich to lean, so the proportional control portion PL is subtracted from the air-fuel ratio correction coefficient 02 (air-fuel ratio correction value) and the calculated value is used this time. correction coefficient K.

2 (step 59), and the air-fuel ratio flag FAF is set equal to 1 (step 60). If FA F -1, it was determined that the air-fuel ratio was lean last time as well, so the integral control portion I is subtracted from the air-fuel ratio correction coefficient KO2, and the resulting value is set as the current correction coefficient KO2 (step 61). on the other hand,
If VO2≧Vref in step 57, the air-fuel ratio is richer than the target air-fuel ratio, so the air-fuel ratio flag FAF
It is determined whether or not is O (step 62). F.A.
If t: = 1, the previous air-fuel ratio was determined to be lean and was reversed from lean to rich, so the air-fuel ratio correction coefficient K
Add the proportional control amount PR to O2 and set the calculated value as the current correction coefficient KO2 (Step 63), and set the air-fuel ratio flag FAF.
is set equal to O (step 64). FA F-0
If so, since it was determined that the air-fuel ratio was rich last time, the integral control amount IR is added to the air-fuel ratio correction coefficient Ko2, and the calculated value is set as the current correction coefficient KO2 (step 65). After execution of step 60 or 64, timer A (not shown)
A predetermined time (for example, 0.3 sec) is set to start down measurement (step 66). Timer A consists of a down counter that measures time by counting clock pulses. When timer 8 starts measuring the predetermined time, the intake manifold absolute pressure PEA and engine speed N
The correction coefficient Kref (reference correction value) corresponding to
Search from ef data map (step 67), K
The ref data map is formed in the RAM 31, and as shown in FIG. Correction coefficient K
ref is initialized when power is turned on to the control circuit 20,
The initial value is 1.0. Once the correction coefficient K ref is retrieved, the correction coefficient K ref is calculated using the following equation (step 68).

Here, Cref is a constant, and 10000H is 1 in hexadecimal.
0000, and Dourn-+ is the control output value DOLJT calculated last time in step 73.

On the other hand, if integral control is performed in step 61.65, timer A measures a predetermined time and determines whether the measured value T+n has reached O (step 69) oT+n
If =o, steps 66°67.68 are executed to calculate the correction coefficient K ref.

When the correction coefficient K ref has been calculated, the calculated correction coefficient Krer is written in the area of the K ref data map corresponding to the absolute pressure PEA and the engine speed Ne (step 7o), and it is determined whether or not the engine is in the idle operating range. (Step 71). If T+n>O, correction coefficient K according to intake manifold absolute pressure PEA and engine speed Ne
Step 7: Search ref from Krer data map
2) In step 71, it is determined whether or not the engine is in the idle operating range. If it is not in the idle operating range, the reference value D
8ASE, correction coefficient K ref and air-fuel ratio correction coefficient K.

The control output value DOLJT is calculated by multiplying by 2 (step 73). If it is in the idle operating range, the air-fuel ratio correction coefficient KO2 is the upper limit value KO2) 4 (for example, 1.10
) (step 74) 6
When KO2>KO2H, set the air-fuel ratio correction coefficient Ko, + to the upper limit value equal to 02H (Step 75), KO2≦
At the end of Ko2, the air-fuel ratio correction coefficient KO2 is the lower limit ff1K
It is determined whether or not it is smaller than o2L (for example, 0.90) (step 76). When KO2<KO2L, the air-fuel ratio correction coefficient Koz is made equal to the lower limit value KozLk (step 77). In this way, in the case of the idle operating range, after setting the air-fuel ratio correction coefficient KO2 to a value between the upper limit 1irjKozH and the lower limit KO2L, step 73 is executed to calculate the control output 1mDour.

fi, I+ After calculating the output filIDo LJ T,
The output 1if7Do LI T is outputted to the drive circuit 28 (step 78).

The drive circuit 28 detects the current value flowing through the solenoid 9a of the solenoid valve 9 using a current detection resistor, compares the detected current value with the control output value DOLJT, and turns on and off the drive transistor according to the comparison result to control the solenoid. 9
Supply current to a.

Therefore, a current having a magnitude represented by the control output value DOUT flows through the solenoid 9a, and m of secondary intake air is supplied into the intake manifold 4 in proportion to the current value flowing through the solenoid 9a. In addition, the control output (iillDo U
When T is 0, the solenoid valve 9 is closed and the supply of intake secondary air is stopped.

Note that the idle operating range is determined as follows, for example.

As shown in FIG. 6, the CPU 29 first determines whether the negative pressure switch 7 is on (step 81). When the negative pressure switch 7 is on, the absolute pressure PBA in the intake manifold 4 reaches a predetermined value of 1iriPBAref (for example, 46
0 to 480 mmh) (step 82). If PaA<PaArQf, it is assumed that a large negative pressure exists in the intake manifold 4 and the throttle valve 3 is closed, and the engine speed Ne is at the predetermined value NeroL.
(for example, 900 to 1000r, p, m) (step 83). Ne＜Ne■l
: If it is IL, it is determined that the vehicle is in the idle operating range.

As described above, in the air-fuel ratio control method of the present invention, the reference correction value for correcting the error in the air-fuel ratio 11Jl reference value is frequently updated, so the reference value for the operating range that is used less frequently is used. The correction value can be updated quickly, and even if the reference value does not correspond to the target air-fuel ratio from the beginning of use of the device due to a deviation in the settings of the fuel supply system during production, it can be corrected at an early stage. Therefore, it is possible to improve the air-fuel ratio control t1M degree immediately after the start of use, and it is possible to obtain good exhaust gas purification performance.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an apparatus to which the air-fuel ratio control method of the present invention is applied, FIG. 2 is a block diagram showing a specific configuration of a control circuit in the apparatus of FIG. 1, and FIGS. 3 and 6 are FIG. 4 is a flowchart showing the operation of the CPU, FIG. 4 is a diagram showing a D8ASE data map, and FIG. 5 is a diagram showing a Kref data map. Explanation of symbols for main parts 1... Carburetor 2... Air cleaner 3... Throttle valve 4... Intake manifold 7... Negative pressure Switch 8...Intake secondary air supply passage 9...Linear type solenoid valve 10...Absolute pressure sensor 11...Crank angle sensor 12... ... Cooling water temperature sensor 14 ... Oxygen concentration sensor 15 ... Exhaust manifold 33 ... Catalytic converter Applicant Honda Motor Co., Ltd. Agent Patent attorney Motohiko Fujimura Procedural Amendment Form Showa January 27, 63

Claims (1)

[Claims] In an internal combustion engine equipped with an exhaust component concentration sensor that generates an output according to the exhaust component concentration in exhaust gas in the exhaust system, an air-fuel ratio control reference value is set in advance according to multiple engine operating parameters related to engine load, and the air-fuel ratio is When the feedback control conditions are satisfied, the output value of the exhaust component concentration sensor is compared with a target value at predetermined intervals, and an air-fuel ratio correction value is set according to the comparison result, and the output value of the exhaust component concentration sensor is When a reversal to the target value is detected,
and when a predetermined period of time has elapsed without detection of reversal, a reference correction value for correcting an error in the reference value corresponding to the detected value of the plurality of engine operating parameters at that time is calculated and determined based on the plurality of engine operating parameters. the reference value corresponding to the detected value of the plurality of engine operating parameters is corrected according to the air-fuel ratio correction value and the reference correction value to obtain an air-fuel ratio control output value for the target air-fuel ratio; An air-fuel ratio control method, characterized in that the air-fuel ratio of the air-fuel mixture determined and supplied to the engine is adjusted in accordance with the control output value.