JPS61112758A - Method of controlling air-fuel ratio of internal combustion engine of electronically controlled fuel injection type - Google Patents

Abstract

PURPOSE:To stabilize the rotation of an engine when the load thereon is low, by increasing the skipped quantity of a feedback compensation coefficient depending on a deposited quantity on an intake valve when the ratio of fuel to air ischanged from a low value to a high value and vice versa. CONSTITUTION:When it is judgediin a step 101 that the ratio of fuel to air is low, a step 102 is taken so that a skipped quantity RS1 and a skip compensation quantity RS2 are added to a feedback compensation coefficient FAF. If it is judged in a step 105 that the ratio of fuel to air is not low, a step 107 is taken so that the skip compensation quantity RS2 is added to the feedback compensation coefficient FAF. The skip compensation quantity RS2 is altered depending on a deposited quantity W to prevent the fluctuation in the rotation of an engine from becoming large in idling. The rotation of the engine under low load is thusstbilized.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to an air-fuel ratio control method for an electronically controlled fuel injection internal combustion engine, and in particular detects the amount of deposits accumulated on intake pulp, etc. The present invention relates to an air-fuel ratio control method for an internal combustion engine, which stabilizes the rotational speed at low loads by correcting.

[Conventional technology]

This type of electronically controlled fuel injection internal combustion engine
An oxygen concentration sensor (0, sensor) is installed in the exhaust system of the engine (hereinafter referred to as engine) to detect the oxygen concentration in the exhaust gas, and an air flow meter is installed in the intake system as a sensor to detect the amount of intake air taken into the engine. , a fuel injection valve is provided in the intake system, and a senna is provided to detect the engine rotation speed, and detection signals from these senna are received.
It is common to have an electronic control section that executes predetermined processing to control the fuel injection valve.

According to the engine having such a configuration, the basic injection charge is determined based on the engine speed, intake air amount, and water temperature, and then 0. Feedback control was performed in which the fuel injection valve was controlled after correcting the basic injection amount based on the detection signal from the Senna.

In such engines, no consideration has been given to changes in air-fuel ratio characteristics due to fuel adhering to deposits that accumulate on the intake system, particularly on the intake valve.

Therefore, an air-fuel ratio control device has already been provided that measures the amount of accumulated deposit when the deposit is accumulated, and corrects the fuel increase value during acceleration according to the amount of deposit (% application). 1973-3288).

According to such an air-fuel ratio control device, even if there are changes over time or variations in parts, the air-fuel ratio is always removed due to the influence of deposits, so the advantage is that it is possible to constantly improve prevention of deterioration of emissions during acceleration. There is.

[Problem that the invention seeks to solve].

However, the above-mentioned air-fuel ratio control device eliminates the influence of deposits during acceleration, and the influence of deposits during feedback control during steady operation! #
It wasn't even considered. In other words, if a large amount of deposit is accumulated on the intake pulp, 0. When feedback control is performed by the sensor, if there is no deposit, the feedback waveform will not be as shown in Fig. 13 (1), but the fluctuation in engine speed ft (NE) will be small, whereas (It) As shown in K, there is a problem in that the feedback waveform period is long and the engine speed fluctuates accordingly. The reason why this rotational fluctuation occurs is, firstly, that fuel is absorbed into the deposit, and secondly, the feedback integral constant and skip cannot be set large to prevent engine rotational fluctuations. Can be mentioned.

For this reason, when the deposit is deposited on the intake pulp, it is 0. Even if the fuel amount is changed by feedback control IK based on the signal from the sensor, the change will be smoothed out by the deposit, and if the feedback cycle is several times the normal feedback cycle, the cycle will be This is because large rotational fluctuations occur depending on the speed.

The present invention solves the above-mentioned problems.

An object of the present invention is to provide an air-fuel ratio control method for an electronically controlled fuel injection engine that can maintain a normal feedback cycle even when deposits accumulate on intake pulp, thereby stabilizing the rotation under low load.

[Means for solving problems]

The present invention calculates the basic fuel injection amount from the intake air amount, engine speed, and water temperature, and further corrects the basic injection amount using the nine tweedback correction coefficients obtained from the oxygen concentration sensor to control the air-fuel ratio (during acceleration). In the air-fuel ratio control method for an electronically controlled fuel injection internal combustion engine, which estimates the amount of deposits accumulated in the intake pulp based on the air-fuel ratio deviation from the optimum air-fuel ratio at
The present invention is characterized in that the amount of deviation of the feedback correction coefficient is increased at the time of rich inversion.

[Effect]

First, an additional skip amount corresponding to the deposit '17kK is determined. Next, each time O and Senna are reversed during feedback control, an additional skip amount is added to the original skip amount to increase the skip amount. Of course, the larger the deposit amount, the larger the additional skip amount, and the smaller the deposit amount, the smaller the additional skip amount.

If the engine speed is further increased, the feedback cycle becomes constant even if a large amount of deposit is accumulated, so that the engine speed becomes stable.

〔Example〕

Hereinafter, five embodiments of the present invention will be explained based on embodiments shown in the drawings.

First, I will briefly explain the relationship between the drawings.

FIGS. 1 to 8 show a first example of the air-fuel ratio control method according to the present invention.
FIG. 9 is a diagram showing an embodiment, and FIGS. 9 and 10 are diagrams showing a second embodiment of the present invention. Also.

FIG. 11 and FIG. 12 are diagrams showing the configuration of an electronically controlled fuel injection engine to which each embodiment of the present invention is applied.

Now, the configuration of the electronically controlled fuel injection engine will be explained.

tjlfJl1 is a system diagram of a Hiroko control fuel injection internal combustion engine to which the present invention is applied. The electricity sucked from the air cleaner 1 is sent to the air flow meter 2, the throttle valve 3. 'y''
- It is sent to the combustion chamber 8 of the engine body 7 via the intake passage 12 including the intake tank 4, the intake boat 5, and the intake valve 6. The throttle valve 3 is linked to an accelerator pedal 13 in the driver's cab. The combustion chamber 8 has a cylinder head 9 and a cylinder block 1.
0. and the piston 11, and the exhaust gas generated by the combustion of the air-fuel mixture is passed through the exhaust pulp 1.
5. Exhaust boat 16, exhaust manifold 17, exhaust pipe 1
8. Released to the atmosphere through the tank. The bypass passage 21 connects the upstream side of the throttle valve 3 and the surge tank 4, and the bypass flow rate control valve 22 controls the flow cross-sectional area of the bypass passage 21 to maintain a constant engine rotational speed during idle link. Exhaust gas recirculation (EGR1 passage 23 is connected to the exhaust manifold 1
7 and the surge tank 4, and an on-off valve type exhaust gas recirculation (EGR) control valve 24 opens and closes the EGR passage 23 in response to electric pulses.

The intake temperature sensor 28 is provided in the air flow meter 2 to detect the intake temperature, and the throttle position sensor 29 detects the opening degree of the throttle valve 3. The water temperature sensor 30 is attached to the cylinder block 10 to detect the cooling water temperature, that is, the engine temperature, and the oxygen concentration sensor 31 is attached to the collecting part of the exhaust manifold 17 to detect the oxygen concentration in the collecting part.
The crank/angle sensor 32 detects the crank angle of the crankshaft from the rotation of the shaft 34 of the power distributor 33 coupled to the crankshaft (not shown) of the engine body 7, and the vehicle speed sensor 35 detects the crank angle of the crankshaft from the rotation of the shaft 34 of the power distributor 33 coupled to the crankshaft (not shown) of the engine body 7. Detects the rotation speed of.

These sensors 2, 28, 29, 30, 31, 32°3
5 and the voltage of the storage battery 37 are sent to the electronic control section 40. A fuel injection valve 41 is provided near each intake boat 5 in correspondence with each cylinder, and a fuel pump 42 is connected to the fuel injection valve 4 via a fuel passage 44 from a fuel tank 43.
Send to 1. The electronic control unit 40 calculates the fuel injection amount using the input signal from each sensor as a parameter, and sends an electric pulse having a pulse width corresponding to the calculated fuel injection amount to the fuel injection valve 4.
Send to 1. The electronic control unit 40 also controls the bypass flow control valve 22 . It controls the EGRIIJ control valve 24, the solenoid valve 45 (Fig. 12) of the hydraulic control circuit of the 24 own valves, and the ignition coil 46. The secondary side of the ignition coil 46 is the power distributor 3
Connected to 3. The charcoal canister 48 accommodates activated carbon 49 as an adsorbent, and the inlet side boat is connected to the upper coulometric capacity of the fuel tank 43 via a passage 50.
The outlet side boat is connected to a purge boat 52 via a passage 51. The purge boat 52 is located upstream of the throttle valve 3 when the throttle valve 3 is at an opening smaller than a predetermined opening, and on the other hand, the purge boat 52 is located upstream of the throttle valve 3 when the throttle valve 3 is at a predetermined opening or more. It is located downstream of No. 3 and receives negative pressure in the intake pipe. Open/close valve 5
3 has a bimetal disc and the engine is in a low temperature state lower than the predetermined temperature.

The passage 49 is closed to stop releasing fuel evaporative gas into the intake system.

FIG. 12 shows details of the electronic control section 40.

CPU (Central Processing Unit) 5 consisting of a microprocessor
6. ROM (read only memory) 57, RAM (random access memory) 58, and another RAM 59 as a non-volatile memory element that can be supplied with power from the auxiliary power source and retain memory even when the engine is stopped. A/D (analog/digital) converter with multiplexer 60. and buffer work 1
0 (input/output) devices 61 are connected to each other via a bus 62. Air 70-meter 2, intake temperature sensor 28,
Water temperature sensor 30. Air-fuel ratio sensor 31 and storage battery 37
The output of is sent to the A/D converter 60.

Further, the outputs of the throttle position sensor 29 and the crank angle sensor 82 are sent to the I10 device 61, and the bypass flow control valve 22. EGRf! rlJ control valve 24, fuel injection valve 41
．． The solenoid valve 45 and the ignition coil 46 receive input from the CPU 56 via the I10 device 61.

When the engine is in a steady state, the amount of fuel supplied to the engine is determined by the electronic control unit 40 as a basic fuel amount from the detection signals of the air 70-meter 2, crank angle sensor 32, and water temperature sensor 30, and then ．． The valve opening time of the fuel injection valve 41 is determined by correcting it using the feedback correction amount FAF determined from the signal of the sensor 31.

Next, an air-fuel ratio control method for the engine configured as described above will be explained based on FIGS. 1 to 8, but before that, the contents of each figure will be explained.

FIG. 1 is a flowchart shown to explain the characteristic part of the air-fuel ratio control method of the present invention, FIG. 2 is a characteristic diagram showing the relationship between the correction amount R820 and the deposit amount W (DEP) used in the method, and FIG. 3 4 is a characteristic diagram showing the relationship between the feedback waveform and engine speed NB obtained by the same method, and FIG.
Figure 5 shows 0 during acceleration. A characteristic diagram showing the relationship between the behavior of Senna and the air-fuel ratio behavior during acceleration. Figure 6 is a diagram shown to explain the deposition status. Figure 7 shows the air-fuel ratio behavior during acceleration and the amount of deposits attached to the intake system. Characteristic diagram 1 showing the relationship between
FIG. 8 is a flowchart showing the deposit amount detection process.

In short, the feature of this embodiment is that when the load is light (special K, idle link) K As shown in Fig. 3, by adding a skip when switching between LE/Rich and removing the skip correction amount R82 during feedback,
This is intended to shorten the feedback cycle.

Now, this embodiment will be explained in more detail.

This routine is entered when the feedback control conditions are established.

First, in step 100, it is determined whether the detection signal from the O sensor 31 has been inverted. In step 100, 0. When the detection signal from the sensor IF" 31 is not inverted, the process proceeds to step 104. When it is inverted, the process proceeds to step 101 because it is the timing to perform skipping.Step 1
01 is 0. It is determined whether the signal from the sensor 31 is ON or not. If it is determined that -/ in step '101,
Proceeding to step 102, the skip amount R8x and the skip correction amount R,82 are added to the feedback correction coefficient FAF to obtain the feedback correction coefficient FAF, and this routine ends.

On the other hand, if it is determined in step 101 that it is not lean and that the toe is tight, the process proceeds to step 103, and this step 1
03 is the feedback correction coefficient FAP and the amount R
81 and the sum of the skip correction amount R820 is subtracted to obtain the feedback correction coefficient FAF, and this routine ends. In this way, in one step 102, as shown in FIG. , 1.
, . . . time point skip control is performed, and step 10
In step 3, skip control is performed at the point "11"?+... in the figure.

On the other hand, in step 104, after the detection signal from the O2 sensor 31 is inverted, it is determined whether the engine has rotated exactly twice. If the result of step 104 is negative, it is not the timing to execute the skip, so the routine ends.

Also, in step 104, 0. If it is determined that the engine rotational speed has increased by two revolutions after the detection signal from the 7/S 31 is inverted, it is time to return the additional skip amount R82, so the process proceeds to step 105.

In this step 105, 0. Signal from sensor 31
Determine whether or not the If it is determined in step 105 that the engine is lean, the process proceeds to step 106, where control is performed to reduce the feedback correction coefficient FAF by the skip correction amount R82. This step 106 corresponds to 't' in FIG.
* “@...It is a point-in-time control. Also, step 10
If it is determined no in step 6, the process proceeds to step 107, and in step 101, control is performed to add the skip correction amount R82 to the feedback correction coefficient FAF. This step 107
is the control at time t4+'8... in FIG.

Here, the skip correction amount R8, is the deposit amount W(DE
The skip correction amount is changed according to P) so that engine rotational fluctuations during idle link do not become large. As shown in Fig. 2, when there is no deposit amount W (DEP), the skip correction amount S2 is also set to zero, and the skip correction amount R82 is proportional to the deposit amount W (DEP). It is something.

Next, a method for determining the deposit amount W (DEP) will be explained with reference to FIGS. 4 to 8.

FIG. 4 is a diagram illustrating how the air-fuel ratio fluctuates when drivability deteriorates during acceleration, particularly when deposits form on the back surface of the intake valve. In Figure 4, A/F(A) represents the change situation before the deposit is deposited.
F (B) shows the state of change in the air-fuel ratio after the deposit is attached. In addition, ACC is the acceleration point, A/F (
OPT) respectively indicate the optimum air-fuel ratio.

As can be understood from this figure, the deposit amount W(DE
P) is attached, the air-fuel ratio A/F is ACC at the time of acceleration.
This results in a significant shift to the lean side.

FIGS. 5(1) and (II) are plots of the relationship between the air-fuel ratio behavior during acceleration and the behavior of the 0° sensor during acceleration as parameters.

Here, the air-fuel ratio behavior during acceleration refers to the maximum deviation value D (A/F) from the optimal air-fuel ratio A/F (OPT) to the lean side of the air-fuel ratio during acceleration, and is the behavior of the OtScene during acceleration. is 0 during acceleration. The time during which the senna output detects the lean state of the mixed gas, means the lean continuation time TL during acceleration.

Figure 5 (1) VC, ACC are acceleration points, S'(
6J indicates 0, a lean signal from the sensor 31.

Figure 7 shows an example of air-fuel ratio deviation from the optimum air-fuel ratio.
Deposits attached to the intake system (DEP) as shown in Figure 6
Figures 4 to 7 show the relationship between the amount W (DEP) and the maximum air-fuel ratio deviation value D (A/F) during acceleration.
It can be understood from the figure that the value corresponding to the deposit amount can be detected by measuring the lean duration time TL during acceleration.

FIG. 8 is a flowchart shown to explain the air-fuel ratio deviation detection process in detail.

FIG. 8 shows that, as shown in step 201, (for example, s3
2. (Every Tms) Processing is executed at regular intervals.

As a method of detecting the air-fuel ratio deviation, 0. A method is adopted in which the output signal of the sensor 31 is compared with a constant voltage level, two values of the mixed gas ratio state and rich state are detected, and the ratio duration time TL and rich duration time T)L during acceleration are measured. are doing. For example, the influence of deposits is
Steps 202 and 203 occur only when the cooling water temperature is low, and in order to facilitate estimation of the deposit amount.
．． In step 204, for example, the cooling water temperature is less than 80°C, the acceleration flk is within 5 seconds, and the rotation speed is 90 Orpm ~ 2
The lean duration time TL and rich duration time T in the case of 000 rpm are measured. Further, in step 205, the feedback sub-section is limited so that rich and lean appear alternately. In step 206, a rich or lean judgment is made. In the case of lean, in step 207, the lean time counter is incremented by 1,
The lean duration time TL is counted in units of 32.7 (ms). In step 208, it is determined whether the value of the rich time counter exceeds a certain value (rich time limit),
If it exceeds the rich correction counter in step 209,
Do 1. Next, in step 210, the rich time counter is set to 0.

If it is determined in step 206 that it is rich, the rich time counter is incremented by 1 and lean time is determined in steps 211 to 214 in the same manner as described above. Deposit adhesion and peeling can be estimated from the values of the lean correction counter and rich correction counter obtained in steps 206 to 214 described above.

Therefore, the deposit amount W (DEP) can be determined by calculating the air-fuel ratio maximum deviation value D (man/F) from the engine duration time TL and the rotational speed NE using Fig. 5(n). , this D(A
/F) using FIG. 6. This requested deposit! The additional skip iR, 82 is calculated from kW (DEP) with reference to FIG.

The adhesion of awards and deposits can also be detected in the following manner. That is, values representative of the rotation speed behavior under each acceleration condition when acceleration is performed without a deposit (for example, rotation speed change per unit time) are stored in memory in advance, and the values are detected by the rotation speed sensor during acceleration. and the rotation speed behavior during acceleration stored in the memory under acceleration conditions detected by a sensor that detects acceleration conditions (e.g., throttle position sensor, absorption air amount sensor?). Deposit adhesion can also be detected by comparing with a representative value.

In the above explanation, values representing the rotational speed behavior under each acceleration condition are stored in the memory, but an arithmetic expression for calculating a value representing the rotational speed behavior from the acceleration conditions is stored in the memory and compared with the calculated value. Deposit can also be detected by doing this.

9 and 10 show a second embodiment of the air-fuel ratio control method related to misfire aAK, FIG. 9 is a flowchart showing the characteristics of this embodiment, and FIG. 10 is an operation waveform diagram.

In addition, how to detect the deposit amount.

This second embodiment also uses the chart 70 in FIG. 8.

The air-fuel ratio control method shown in FIG. 9 does not subtract the skip correction amount R82 after two rotations, but instead keeps the feedback correction coefficient FAF (integral term) constant or decreases over time. Such an operation can be realized using the following flowchart.

That is, the difference between the second embodiment and the first embodiment is as follows.
Step 104 of the first embodiment is eliminated, and the process of step 106 is changed to the process of step 300, and the process of step 107 is changed to the process of step 301.

In steps 300 and 301, the feedback correction coefficient FAF decreases by a constant value α every time this routine is passed.
When it is increased, it becomes K. Of course, the processing of the integral term of FAF is executed in a separate routine, so if the slope of the integral is subtracted by a larger value α or added, the slope of the integral term will be constant or the opposite slope. become.

Even in this case, the same effects as in the first embodiment can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, the feedback period can be maintained constant even when deposits are accumulated, so that rotation at low loads can be stabilized.

[Brief explanation of drawings]

FIGS. 1 to 8 are rounded diagrams for explaining the first embodiment of the present invention, and FIG.
- chart, Figure 2 is a diagram showing the relationship between deposit amount and additional step, Figure 3 is an operation waveform diagram of the same example, Figure 4 is a waveform diagram showing changes in air-fuel ratio during acceleration before and after deposit deposition, Figure 5 The figure is a characteristic diagram showing the relationship between OtSessen behavior during acceleration and the air-fuel ratio behavior during acceleration, Figure 6 is a diagram showing the deposit adhesion situation, and Figure 7 is the relationship between the air-fuel ratio behavior during acceleration and the amount of deposits attached to the intake system. FIG. 8 is a characteristic diagram showing the deposit amount detection process, FIG. 9 and FIG. 1O are for explaining the second embodiment of the present invention,
' Fig. 9 is a 70-chart showing the characteristic parts of the same embodiment, Fig. 1θ is an operation waveform diagram according to the same embodiment, Fig. 11 and Fig. 1
FIG. 2 is a configuration diagram showing an engine to which the above embodiment is applied;
FIG. 13 is a diagram showing conventional feedback and engine speed. -6...Intake pulp, 31...0. sensor,
40... Electronic control section, 41... Fuel injection section.

Claims (1)

[Claims] The basic fuel injection amount is determined from the intake air amount, internal combustion engine speed, and water temperature, and the basic injection amount is corrected using the feedback correction coefficient determined from the oxygen concentration sensor output to control the air-fuel ratio. In an air-fuel ratio control method for an electronically controlled fuel injection internal combustion engine that estimates the amount of deposit accumulated on an intake valve based on the air-fuel ratio deviation from the fuel ratio, the skip amount of the feedback correction coefficient is set at the time of lean-rich reversal according to the amount of deposit. An air-fuel ratio control method for an electronically controlled fuel injection internal combustion engine, characterized in that the air-fuel ratio is increased.