JPS635131A - Air-fuel ratio control method for multi-fuel engine - Google Patents

Abstract

PURPOSE:To optimize an air-fuel ratio, by a method wherein a reference value for regulating an air-fuel ratio responding to an engine load is corrected by means of a correction factor depending upon an output from an O2 sensor, based on the correction factor, an alcohol content is detected, and a target value of air-fuel ratio, on which feedback control is applied, is corrected. CONSTITUTION:An electronic control device 1 computes a fundamental injection time, based on detecting valves from an intake air absolute pressure sensor 12 and a crank angle sensor. 14. The electronic control device multiplies a correction factor responding to a deviation between a detecting value from an O2 sensor 15 and a target air-fuel ratio to control the opening time of an injector 5. Further, when an average learning of the correction factors is fluctuated and exceeds a given range, a target air-fuel ratio, on which feedback control is applied, is corrected by means of the correction factor.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention allows operation at the optimum air-fuel ratio even when Gun IJ 7 or alcohol-mixed gasoline of any mixed specific gravity is supplied as fuel. Related to internal combustion and engine air-fuel ratio control methods.

(Prior art) In order to operate an internal combustion engine, the total oxygen concentration in exhaust gas is detected by an oxygen sensor consisting of a solid electrolyte, a solid oxygen pump, and an oxygen concentration battery, and the detected value is used to determine the upper air-fuel ratio. This is disclosed in Japanese Unexamined Patent Publication No. 192955/1983.

(Problems to be Solved by the Invention) The above-mentioned conventional technology can be used to operate the engine at a stoichiometric air-fuel ratio, but it is difficult to control the engine's trough mode depending on the mixing ratio of alcohol mixed in gasoline. However, it is not possible to control the parameters directly in the city.

(Means for Solving the Problems) The present invention provides engine operation 'd: j! fil '$1
This invention was invented by focusing on the fact that the magnitude of the feedback correction coefficient in a microcomputer that uses alcohol is proportional to the alcohol mixing ratio. Oxygen mW in the exhaust gas for the exhaust system of multi-fuel engines including
Equipped with an oxygen concentration sensor that generates an output proportional to the engine load, the air-fuel ratio adjustment standard AT stage is set according to multiple operating parameters related to the engine load.
determining an output value for the target air-fuel ratio by correcting it with a correction coefficient according to the difference between the output of the sensor and the target air-fuel ratio;
The air-fuel ratio control method for an internal combustion engine that adjusts the air-fuel ratio according to the output value is characterized in that the alcohol mixture ratio gt is detected from the magnitude of the correction coefficient, and the target air-fuel ratio is corrected according to the detected value. shall be.

(Embodiment) Fig. 1 shows an engine control device implementing the present invention, and the engine 11'l includes an intake pipe (2), an air cleaner (3), a throttle valve (4), an injector (5), an advance angle device t (6),
Equipped with an exhaust pipe (7) and a three-way catalyst (8), the microcomputer QG for engine control includes a throttle valve opening sensor 0.
υ, intake pipe absolute pressure sensor port, water temperature sensor U, crank angle sensor α, oxygen 11 [sensor (02 sensor) (2) output side is connected, injector (5) and advance angle device fk (61 The input side of is connected.

As the 0□ sensor sensor, an appropriate sensor such as the sensor described in the above-mentioned publication or an oxygen m degree proportional sensor can be used. 0□
The output WFNote of the sensor is as shown in Fig. 3, and 11
! Lines (g) and (16a) are custom-made curves for the wide range air-fuel ratio detection sensor described in the above-mentioned publication, and dotted lines α7 and (17a) are custom-made curves for the oxygen sensitivity degree proportional sensor. When the fuel is Gafflin 100 and the stoichiometric air-fuel ratio is 14.7, the output of the zero sensor is a! ＠、Indicated by the mark, when gasoline was 15 and methanol was 85, the stoichiometric air-fuel ratio was 7.6.
6a), move to position (17a) and add methanol 100
When you feel regret, move to 6.7.

FIG. 2 shows the control circuit for the control device it B CU m in which the oxygen-degree proportional sensor system is used as the 0□ sensor (to). This 02 sensor U9 is formed of a sintered body of zirconium ZrO2, which is a solid electrolyte for acid accumulation ion conduction. There will be an atmospheric standard chamber (1) that will communicate with the atmosphere. Electrode pairs are provided on both side walls of the gas retention chamber by electroplating.
1a), (21b) and the solid electrolyte body form an oxygen pump element 2υ, and the electric current fE(22a), (22b)
A battery element @ is formed by the solid electrolyte body.

As shown in FIG. 3, the BOU (IGK) includes a sensor control unit (c) and a control circuit of a microcomputer.The sensor control unit (c) includes a differential amplifier circuit (7),
Reference voltage (7), current detection resistor (b) and switch (
7), the electrode (22a) of the battery element (2) is connected to the inverting input terminal of the differential amplifier circuit (2), and the current detection resistor (22a) is connected to the inverting input terminal of the differential amplifier circuit.
The electrode (21a) of the oxygen pump element is connected to
The other electrodes (22b) and (21b) are grounded. The differential amplifier circuit (7) includes an electrode (22a) in the battery element @,
(22b) and the output voltage of the reference voltage source (7), the next voltage is output.

The output voltage of the reference voltage source (to) is a voltage (for example, 0.4 V) corresponding to the stoichiometric air/fuel ratio.

The output end of the differential amplifier circuit (A) is connected to the switch (2), and the oxygen pump element Yuno1 is connected to the pole (21a) through the flow detection resistor.
Both ends of the current detection resistor wire serve as output ends of the 02 sensor and are connected to the control circuit (1) of the microcomputer.

The control circuit ■ includes a throttle valve opening sensor l that generates nine output voltages depending on the opening degree of the throttle valve (4), an absolute pressure sensor recess that generates nine output voltages depending on the absolute pressure in the intake pipe, and an engine cooling water temperature sensor. A crank angle sensor α4, which generates a pulse signal in synchronization with the rotation of the engine (1), and an ignition switch 6η are connected, and the battery voltage is controlled by the ignition switch Gυ to the control circuit ( 7). Further, an injector (5) of the intake pipe (2) and an advance angle device (6) of the engine (1) are connected to the drive circuit within this control circuit.

The control circuit (7) includes a differential input h/DK filter (b) that converts both vIAt pressures of the current detection resistor @ into digital signals, a throttle valve opening sensor 0υ, an absolute pressure sensor D, and a water temperature sensor ω. A 4-channel conversion circuit that converts each output level, a multiplexer that selectively outputs one of the sensor outputs that have passed through the level conversion circuit (7), and a signal output from this multiplexer. An A/D converter ■ that converts the signal into a digital signal, a waveform shaping circuit (to) that shapes the output signal of the crank angle sensor (to) and outputs it as a TDO signal, and a TDO from the waveform shaping circuit (to). A counter that measures the signal generation interval by the number of clock pulses output from a clock pulse generation circuit (not shown).
, a level conversion circuit (to) that converts the output level of the ignition switch (to), and a level conversion circuit.
A digital input modulator port that converts the switch output into digital data, a drive circuit (40a'') that drives the injector (5), a drive circuit (40b) that turns on the switch (to), and a lead angle bag ft (61). A drive circuit (40c') to drive and a CPU (central processing circuit') that performs digital calculations according to the program (7'tR with AD and various processing programs and data written in advance)
OM), AM (!13), A/D converter (to), (b), multiplexer (to), counter, digital input camosulator, and drive circuit (40a).
, (40b), (40c), 0PUQI), ROMi
and RAM[ are connected to each other by input/output paths.

A TDO signal is supplied to the OPU (41) from the waveform shaping circuit (to).

In such a configuration, the A/D converter c! 14 The pump current value Ip flowing through the oxygen pump element (to) is.

- Information on the throttle valve opening uth, intake pipe absolute pressure PBA, and cooling water temperature TW is alternatively sent from the A/D converter On/off information of the ignition switch Gl) is supplied from the camosulator (to) to the OPU@ via the input/output bus. 0PU (b) is ROM (
The above-mentioned information is read according to the calculation program stored in the engine (11), and based on that information, the fuel supply routine is executed in synchronization with the TDO signal and the amount of fuel supplied to the engine (11) is calculated from a predetermined calculation formula. Injector (5)
The fuel injection time TOUT is calculated. Then, the fuel injection is performed in synchronization with the crank angle sensor signal, and the calculation is also performed in synchronization with the crank angle signal, and the drive circuit (40a) drives the injector (5) for the fuel injection time ToUT, and the engine (1) It supplies fuel to the

The fuel injection time I'OUT is calculated, for example, from the following equation.

TOUT = Ti X Ko2 X KWOT X K
TW ”・”・11) Here, Ti is the engine rotation f
The basic injection time ti minus the basic supply amount determined from iNe and the intake pipe absolute pressure PB input, Ko2 is the air-fuel ratio feedback correction coefficient set according to the output level of the oxygen all sensor, and KWOT is the air-fuel ratio feedback correction coefficient at high load. Correction factor for fuel increase,
KTW is the cooling water temperature coefficient. These Ti, Ko2, K
WOT and KTW are set in the subroutine of the fuel supply routine.

On the other hand, the drive circuit (40b) turns on the switch (7) in response to an on-drive command from the 0PU 141, and stops the on-drive of the switch (e) in response to an on-drive stop command. When the switch (to) is turned on, a pump current begins to flow between the electrodes (21a) and (21b) of the oxygen pump element from the output end of the differential amplifier circuit (to the differential amplifier circuit) via the switch (2) and the low resistor (2).

When the supply of pump current to the oxygen pump element (2) is started, if the air-fuel ratio of the air-fuel mixture supplied to the engine (1) at that time is in the lean region, the electrode (22
a), (22b) The voltage generated in the dark is the reference voltage source (
Since the output voltage of (e) becomes low, the output level of the differential amplifier circuit (7) becomes a positive level, and this positive level voltage is supplied to the series circuit of the resistor @ and the oxygen pump element 12υ.

The oxygen pump element C2υ is connected from the electrode (21a) to the electrode (
21b), the oxygen in the gas retention chamber is ionized at the electrode (21b) and moves throughout the oxygen pump element eυ, causing electricity! (21a) is released as oxygen gas, and the oxygen in the gas retention chamber is pumped out.

Gas retention chamber 01 is created by pumping out oxygen from the gas retention chamber pronunciation.
ci1 between the exhaust gas in the
Differences in cumulative saponification occur. A voltage Vs is generated between the electrodes (22a) and (22b) of the battery element (4) in accordance with this oxygen haze difference, and this voltage Vs is supplied to the inverting input terminal of the differential amplifier circuit 4. The output voltage of the differential amplifier circuit (7) is the voltage v
3 and the output voltage of the reference voltage source (4), the pump current value is proportional to the elementary concentration in the exhaust gas, and the pump current value is output as the voltage across the resistor. Ru.

When the air-fuel ratio is in the rich region, the voltage Vs exceeds the output voltage of the reference voltage #. Therefore, the output level of the differential amplifier circuit (c) is inverted from a positive level to a negative level. This negative level causes the oxygen pump element □□□ to
, (21b) The pump current flowing in the dark decreases and the current direction is reversed. In other words, the pump current is 1! Pole (21
a) Since it flows from the sword 1 towards the electrode (21b'), the external *
2 is 1! At f1 (21a), the ion ratio is acid g, r
Move within the i'ump yokoshi V and get 1! It is released from the electrode (21b) into the gas retention chamber α- as oxygen gas.

Oxygen is pumped into the gas retention chamber (lL field. Therefore,
Since oxygen is pumped in and out by supplying a pump current so that the oxygen me in the gas retention chamber α is always constant, W, Figure 2 aη.

As shown in (17a), the pump current value Ip is proportional to the oxygen the in the exhaust gas in the lean and rich regions, respectively. The feedback correction coefficient Ko2 described above is set according to this pump current value Ip.

The control circuit (1) includes engine speed Ne, which is an operating parameter related to engine load, and intake pipe absolute pressure F.
Air-fuel ratio l from B etc.! A reference value λBASB next to Il is set. The relationship between these parameters is shown in Figure 4, where Kref1 * Kref2 is
Feedback correction coefficient Ko2 in control circuit (7)
It is the average learned value of , and is proportional to the alcohol mixing ratio XK.

Then, this reference value λBASB is corrected by a fee two pack correction coefficient which is a first correction coefficient.

Fee 2 pack correction coefficient Ko 2 or its average learning value K
It has been found that ref has a proportional relationship of 1 with the alcohol mixing ratio α, as shown in FIG. When you have an ex-friend, Ko 2 or Kr
Air-fuel ratio reference value λBA8 E with ef as the first correction coefficient
is corrected, and further correction is performed using a second correction coefficient corresponding to the engine operating speed parameter.

During engine operation, the feedback correction coefficient Ko2 continues to change slightly due to engine fluctuations over time or external influences, as shown in Figure 6. However, when alcohol is mixed into the fuel, the average learned value of Ko2 changes from Krefl. Kre
There is a large change in f2.

From this Kref@keKo2, Krefn= #Ko2
It is determined by n+(1-β)Krefn=. Here β
Normally, the value is 1), 18, which is the averaging coefficient or the averaging coefficient. In the sixth factor, feedback correction coefficient Ko2
The value of f fluctuates greatly, and the average value changes from Krefl to Kref.
2, the darkness ΔTfa continues for a certain period of time, and the fluctuation range ΔKref
When it exceeds a certain threshold value ΔKREiF 'j-, it is judged that alcohol has been mixed in, and at this time Kre
The reference value of the air-fuel ratio is corrected using f as the first correction coefficient.

Further, this correction M is corrected by a 7cg2 correction coefficient according to the engine operating parameters. The second correction coefficients include the starting correction coefficient KNe, the water temperature correction coefficient KTW, the starting increase coefficient fiKA8T, and the throttle full-open increase coefficient KWOT.
, another speed correction coefficient a, TAOO ignition advance angle, etc., and there is a certain relationship between each of these coefficients and Kref, a part of which is shown in FIGS. 7 to 9. By mixing alcohol, the octane number improves due to the anti-knock property of alcohol, and the ignition advance angle σi? As shown in Fig. 7, the ignition timing is advanced according to the octane number when it changes from Krefl to Kref2 to achieve the optimum ratio. FIG. 8 shows the relationship between the starting boost coefficient aKAsT and Kref. As the alcohol mixture ratio increases, the amount of vaporized fuel decreases, so it is necessary to increase the amount of fuel at the time of starting, and the coefficient KA 8 T increases. Figure 9 shows the relationship between the full-open throttle increase coefficient KWOT and Krer.The increase in alcohol mixture increases the amount of fuel and increases the engine cooling effect. The coefficient KWOT is reduced by the booster of Kref. Shut up.

These second correction coefficients are also corrected based on the Kref value, that is, the alcohol content.

The air-fuel ratio can be changed particularly easily when an oxygen alt proportional sensor is used as the 02 sensor. Fuel ratio, Kre
A target air-fuel ratio is set by correcting it according to the value of f, and alcohol-containing! The optimum air-fuel ratio is determined by making corrections using various coefficients, and at the same time, the ignition advance angle σi? Also change.

For example, adjusting the air-fuel ratio! Perform in the order shown in Figure 10. In the same figure, p is the output current of the sensor, Lo2 is the detected air-fuel ratio, Lref is the target air-fuel ratio, KO2 is the feedback correction coefficient, Δ is the integral force subtraction constant, and KREF is the average value of Ko2. 2 + (1-1')
Kre f −・= (2+ relationship, 1s
= KRBP is the threshold for determining alcohol content, α is the alcohol mixture Kitamoto (咄), K is a constant, KA 8 T is the starting power increase coefficient, KWOT is the throttle full-open power increase coefficient, TOt
JT is fuel injection time. In FIG. 10, the feedback correction coefficient Ko2 is calculated from the output current of the 02 sensor read in step l, and in step (5) Ko
Calculate the average value KFLRF of 2 using the above formula (2), compare it with the threshold value ΔKRBF in step (6), and if there is a variation greater than this, it is assumed that alcohol has been mixed in, and the mixing ratio is determined in step (7). α is calculated, and the target air-fuel ratio Lref is set in step (3). This Lref is KI'Lg
F Therefore, it is corrected by the first correction coefficient. Then step (9).

KA8T of the second correction coefficient according to the operating parameters in aG
, KWOT, etc., and the fuel injection time To UT is calculated and output in step αυ, C12. The blade extension of the injection time is performed using the above formula fi+. In the internal formula, TiM is a map value of the basic injection time, which is a function of engine rotational speed Ne and intake pipe absolute pressure PBO.

(Effects of the Invention) The present invention automatically sets the stoichiometric air-fuel ratio according to the alcohol mixture even if alcohol is mixed in the fuel, and further corrects this according to the operating conditions, so that the optimum air-fuel ratio can be achieved. The engine can be operated with.

[Brief explanation of the drawing]

Fig. 1 is a layout diagram of the engine control device used to implement the present invention, Fig. 2 is a control circuit diagram, and Fig. 3 is the output of the 02 sensor. Figure a, Figure 4 is a 1liI diagram showing the relationship between load conditions and feedback correction coefficient, Figure 5 is a diagram showing the relationship between alcohol mixture Kitamoto and feedback correction coefficient,
FIG. 6 is a diagram showing one example of changes in the feedback correction coefficient. FIGS. 7, 8, and 9 are diagrams showing the relationships between various operating nomura meters, and FIG. giE10 is an explanatory diagram of the control order. Fit...Engine (5)...Injector (1 (1...Microcomputer shout...02 2 people outside the sensor Fig. 1 Fig. 10 Fig. 3

Claims (1)

[Claims] The exhaust system of a multi-fuel engine containing alcohol is equipped with an oxygen concentration sensor that generates an output proportional to the oxygen concentration in the exhaust gas, and sets and sets reference values for air-fuel ratio adjustment according to multiple engine operating parameters related to engine load. An air-fuel ratio of an internal combustion engine in which an output value for a target air-fuel ratio is determined by correcting the reference value determined by a correction coefficient according to a deviation between the output of the sensor and a target air-fuel ratio, and the air-fuel ratio is adjusted according to the output value. An air-fuel ratio control method for a multi-fuel engine, characterized in that the alcohol mixture ratio is detected from the magnitude of the correction coefficient, and the target air-fuel ratio is corrected according to the detected value.