JPH01244133A - Fuel injection control device for alcohol-contained fuel internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent worsening of emission of exhaust gas, by a method wherein according to alcohol concentration, an air-fuel ratio feedback control constant is changed in a manner that with the increase in alcohol concentration, a target fuel injection amount is increased. CONSTITUTION:According to an engine load, a fundamental fuel injection amount is corrected by means of an air-fuel ratio correction factor responding to an oxygen sensor output value to decide a target injection amount, and feedback control is made so that an air-fuel ratio is adjusted to a value approximately similar to a theoretical value. In which case, in an internal combustion engine using alcohol-contained fuel, the air-fuel ratio feedback control constant of an air-fuel ratio correction factor is computed so that, with the increase in alcohol concentration detected by a detecting means, a target fuel injection amount is increased. An air-fuel ratio correction factor is determined by the computing result in cooperation with an oxygen sensor output to decide a fuel injection amount. This constitution compensates for the thinning tendency of an air-fuel ratio by an oxygen sensor to detect an O2 amount lower than an actual amount according to alcohol concentration, and enables prevention of worsening of emission of exhaust gas.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel injection control device for an internal combustion engine that uses gasoline mixed with alcohol as fuel.

[Prior art]

In general, fuel injection control in an internal combustion engine refers to the amount of intake air Q.
/Target fuel injection by integrating the air-fuel ratio correction coefficient FAF with the basic fuel injection amount (time) determined according to the engine load represented by engine speed Ne and intake pipe internal pressure PM!
(time), and in air-fuel ratio feedback control, the air-fuel ratio is determined from the oxygen concentration in the exhaust gas to determine whether the air-fuel ratio is smaller (over-rich side) or larger (on the rich side) than the stoichiometric air-fuel ratio (for example, 14.7).
The oxygen sensor (0□ sensor) and comparator determine whether the signal is on the lean side (rich side), and when the signal is on the rich side (rich), the FAF
decrease. By the way, the air-fuel ratio correction coefficient FAF is the skip amount during increase/decrease reversal and the slope in the increase/decrease direction (integral processing).
Its characteristics can be changed by various feedback control constants such as , delay time at the time of reversal, etc. Therefore, for example, if the output characteristics change due to deterioration of the O sensor, etc., the FAF
A control device has been proposed in which the feedback control constant of is changed (Japanese Patent Application No. 61-169932).

[Problem to be solved by the invention]

The 02 sensor described above is equipped with a zirconia element inside, and utilizes the inherent property of the zirconia element to generate electromotive force when oxygen ions pass through it. When the oxygen concentration in the exhaust gas passing outside is high, that is, when the actual air-fuel ratio is larger than the stoichiometric air-fuel ratio (lean state), the electromotive force increases due to the small oxygen concentration difference. When the oxygen concentration in the exhaust gas is low (rich), the electromotive force becomes large due to the concentration difference.

By the way, when alcohol is mixed in the fuel used in an internal combustion engine, the amount of hydrogen (H2) contained in the alcohol combustion gas is greater than the amount of H2 contained in normal gasoline combustion gas. H2, which has a smaller molecular weight than Ot, is more likely to diffuse into the zirconia element of the 02 sensor, and the detected O2 concentration tends to be determined to be lower than the actual O2 concentration. Therefore, as shown in Fig. 2, the 02 sensor output will be a rich output even though the actual air-fuel ratio is the stoichiometric air-fuel ratio, and as a result, the control air-fuel ratio will deviate from the stoichiometric air-fuel ratio to the lean side, and NOx etc. Exhaust emissions will deteriorate. This tendency becomes more pronounced as the ratio of alcohol contained in the fuel increases.

The present invention has been made in view of this problem, and detects a lower O8 concentration than actually exists in an internal combustion engine that uses alcohol-containing twist material. Air-fuel ratio control using two sensors,
The present invention provides a fuel injection control device that approaches the original air-fuel ratio feedback control centered on stoichiometric air-fuel ratio, thereby improving exhaust emissions.

[Means to solve the problem]

Referring to FIG. 1, a fuel injection control device according to the present invention will be explained.

According to the present invention, the target fuel injection amount is determined and obtained by correcting the basic fuel injection amount calculated according to the engine load with an air-fuel ratio correction coefficient according to the oxygen sensor output value. A fuel injection control device for an internal combustion engine using alcohol-containing yarn, which performs air-fuel ratio feedback control to bring the air-fuel ratio close to the stoichiometric air-fuel ratio. an oxygen sensor that detects the concentration of alcohol; an alcohol concentration detection means that detects the concentration of alcohol contained in the fuel; and an oxygen sensor that detects the concentration of alcohol contained in the fuel; an air-fuel ratio feedback control constant calculation means for calculating an air-fuel ratio feedback control constant; an air-fuel ratio correction coefficient calculation means for calculating an air-fuel ratio correction coefficient according to the oxygen sensor output and the air-fuel ratio feedback control constant; A fuel injection control device for an alcohol-containing twisted internal combustion engine is provided, comprising fuel injection amount calculation means for calculating a fuel injection amount using an air-fuel ratio correction coefficient determined by the coefficient calculation means.

[For production]

According to the above configuration, the deviation between the actual air-fuel ratio and the air-fuel ratio detected by the oxygen sensor, which is caused by hydrogen (H2) in alcohol, is determined by detecting the alcohol concentration. By changing the feedback control constants, such as rich and lean delay times, in the direction of fuel increase, deviations in the control air-fuel ratio toward the lean side are compensated for, and feedback control centered on the stoichiometric air-fuel ratio is achieved.

[Embodiment] FIG. 3 is an overall schematic diagram showing an embodiment of a fuel injection control device for an internal combustion engine according to the present invention. In FIG. 3, an air flow meter 3 is provided in the intake passage 2 of the engine body 1. As shown in FIG. The air flow meter 3 directly measures the intake air amount Q, has a built-in potentiometer, and generates an analog voltage output signal proportional to the intake air amount Q.

This output signal is the control circuit 10's multiplexer built-in A/
The signal is supplied to the D converter 101. In addition, the distributor 4 has a shaft that is, for example, 7 in terms of crank angle.
A crank angle sensor 4a that generates a reference position detection pulse signal every 20 degrees and a crank angle sensor 4b that generates an angular position detection pulse signal every 30 degrees in terms of crank angle are provided.

The pulse signals of these crank angle sensors 4a and 4b are supplied to the input/output interface 102 of the control circuit 10, and the output of the crank angle sensor 4b is sent to the CPU 1.
03 interrupt terminal.

Further, the intake passage 2 is provided with a fuel injection valve 5 for supplying pressurized fuel from a fuel supply system to the intake boat for each cylinder.

Further, a fuel filter 7 and an alcohol concentration sensor 8 for detecting the alcohol concentration in the fuel are provided between the fuel tank 6 and the fuel injection valve 5. The alcohol concentration sensor 8 generates an analog voltage electrical signal corresponding to the alcohol concentration DA contained in the fuel.

Furthermore, an O2 sensor 9 is provided in the exhaust manifold, that is, on the upstream side of the catalytic converter (not shown), and this O2 sensor 9 sends an electrical signal according to the concentration of oxygen components in the exhaust gas. Occur. That is, the 0□ sensor 9 generates different output voltages to the A/D converter 101 of the control circuit 10 depending on whether the air-fuel ratio is lean or rich with respect to the stoichiometric air-fuel ratio.

The control circuit 10 is configured as a microcomputer, for example, and includes an A/D converter 101, an input/output interface 102, a CPU 103, and a ROM 104, an R
An AM 105, a backup RAM 106, a clock generation circuit 107, and the like are provided. Note that the backup RAM 106 is a backup battery (not shown).
Therefore, even if the ignition switch is turned off or the vehicle battery is removed, the contents of the backup RAM 106 will not be erased.

Further, in the control circuit 10, a down counter 108,
Flip-flop 109 and drive circuit 110 are for controlling fuel injection valve 5. That is, in the routine described later, when the fuel injection amount TAll is calculated, the fuel injection amount TAU is preset to the down counter 10 days, and the flip-flop 109 is also set. As a result, the drive circuit 110 starts energizing the fuel injection valve 5. On the other hand, when the down counter 108 counts the clock signal (not shown) and its carrier terminal finally reaches the "1" level, the flip-flop 109
is reset 7), and the drive circuit 110 stops energizing the fuel injection valve 5. That is, the fuel injection valve 5 is energized by the above-mentioned fuel injection amount TAU, so that an amount of fuel corresponding to the fuel injection amount TAU is sent into the combustion chamber of the engine body 1. The interrupt generation of the CPU 103 is caused by the A/D converter 1.
When the A/D conversion of 01 is completed, the input/output interface 10
2 receives the pulse signal of the crank angle sensor 4b,
etc.

The intake air amount data Q of the air flow meter 3 and the concentration data DA of the alcohol concentration sensor 8 are taken in by an A/D conversion routine executed at predetermined intervals and stored in the RAM.
105 in a predetermined area.

That is, data Q and DA in RAM 105 are updated at predetermined time intervals. Also, rotation speed data Ne
is calculated by an interrupt of the crank angle sensor 4b every 30'' CA and stored in a predetermined area of the I?AM 105.

The operation of the control circuit shown in FIG. 3 will be explained below.

FIG. 4 shows an air-fuel ratio feedback control routine for calculating an air-fuel ratio correction coefficient PAP based on the output of the 08 sensor 9, and is executed every predetermined time, for example, every 4 strokes.

In step 401, it is determined whether a closed loop (feedback) condition for the air-fuel ratio by the Ot sensor 9 is satisfied. The closed loop condition is not satisfied during engine starting, during fuel increase operation after engine start, during warm-up increase operation, during power increase operation, during lean control, inactive state of Ot sensor 9, etc.; in other cases, closed loop condition is not met. The condition is satisfied. If the closed-loop condition is not met, the process proceeds to step 423, where the air-fuel ratio correction coefficient FAF is set to the average value of FAF immediately before the closed-loop control is stopped. On the other hand, if the closed loop condition is satisfied, the process proceeds to step 402.

In step 402, 0. The output V of the sensor 9 is A/D converted and taken in, and in step 403 it is determined whether or not V is less than the comparison voltage Vl (for example, 0.45V) as shown in FIG. or lean. If lean (V≦Vm), it is determined in step 404 whether the delay counter CDLY is positive or not, and CDL
If Y>0, set CDLY to O in step 405 and proceed to step 406. In step 406, delay counter CDLY is decremented by 1, and then in step 407
Then, it is determined whether CDLY<TDL. In addition, T
DL is a lean delay time for maintaining the determination that the vehicle is in a rich state even if the output of the 0□ sensor 9 changes from rich to lean, and is defined as a negative value.

Therefore, only when CDIJ<TDL, step 40
At step 8, CDLY is set to TDL, and at step 409, the air-fuel ratio flag F is set to "0" (lean).
V>VR), it is determined in step 410 whether the delay counter CDIJ is negative or not, and if CDLY<0, in step 411 CDLY is set to 0 and the process proceeds to step 412. In step 412, the delay counter CDLY is incremented by 1, and then in step 413, C
Determine whether DLY<TDR. In addition, TDR is 02
This is a rich delay time for maintaining the determination that the lean state is present even if the output of the sensor 9 changes from lean to rich, and is defined as a positive value.

Therefore, only when CDLY > TDR, step 4
In step 14, CDLY is set to TDR, and in step 415, the air-fuel ratio flag F is set to "l" (rich).

In step 416, it is determined whether the sign of the air-fuel ratio flag F has been reversed, that is, it is determined whether the air-fuel ratio after the delay processing has been reversed. If the air-fuel ratio is reversed, it is determined in step 417 whether the reversal is from rich to lean or from lean to rich. If it is a reversal from rich to lean (F=10'), P is set in step 418.
AP -FAF+R5R, which is a skip increase, and conversely, if it is reversed from lean to rich (F-“1”),
In step 419, it is decreased in a skip manner to FAF4-PAP+R5L. In other words, skip processing is performed.

If the sign of the air-fuel ratio flag F is not inverted in step 416, integration processing is performed in steps 420, 421, and 422, that is, in step 420, F-“0” (
lean), in step 421 FAF4-FAF
On the other hand, if F=“1′” (rich), then in step 422, FAP←FAP− is set to IL. Here, the integral constants KIR and IL are skip constants R5R and R
It is set smaller than 5L. Therefore, step 4
21 gradually increases the fuel injection amount in a lean state (F="0"), and step 422 gradually increases the fuel injection amount in a rich state CF="1")
to gradually reduce the fuel injection amount.

Is the air-fuel ratio correction coefficient PAP calculated in steps 418, 419, 421, and 422 RA? 1105, and the routine ends at step 424. In addition, in order to prevent over-rich or over-lean when the FAF calculated as described above becomes too thick (or too small), guard with maximum or minimum values between steps 422 and 424. Steps may be provided.

FIG. 5 is a timing diagram supplementary explanation of the operation according to the flowchart of FIG. 4. When the air-fuel ratio signal A/F for rich and rich discrimination is obtained from the output of the Oz sensor 9 as shown in FIG. 5(^), the delay counter CDLY is
As shown in FIG. 5 (8), the count is increased in the rich state and counted down in the lean state. As a result, as shown in FIG. 5(C), a delayed air-fuel ratio signal A/F' is formed.For example, at time t, the air-fuel ratio signal ^/F changes from lean to rich. Also, the delayed air-fuel ratio signal A/F'' is held lean for the rich delay time TDR, and then changes to rich at time t2.At time t2, the air-fuel ratio signal A/F changes from rich to rich. Even if the air-fuel ratio signal A/F' changes to lean, the delayed air-fuel ratio signal A/F' is held rich for a lean delay time (-TDL) and then changes to lean at time t4.However, the air-fuel ratio signal A/F' changes to lean at time t4. When F' is reversed in a period shorter than the rich delay time TDR as at time LS+L6.L?, it takes time for the delay counter CDLY to reach the rich delay time TDH, and as a result, after the delay processing at time t, The air-fuel ratio signal A/F' is inverted.In other words, the air-fuel ratio signal A/F' after the delay process is more stable than the air-fuel ratio signal A/F before the delay process.In this way, after the delay process Based on the stable air-fuel ratio signal ^/F', the air-fuel ratio signal correction coefficient FAF shown in FIG. 5(0) is obtained.

As shown in FIG. 5, the air-fuel ratio feedback control Il constants, such as TDR, TDL, RSR, R3L, KI
By changing IL to R, the control air-fuel ratio can be changed.

For example, rich delay time TDR > lean delay time (-T
DL), the controlled air-fuel ratio can shift to the rich side, and conversely, if the lean delay time (-TDL)>rich delay time TDR is set, the controlled air-fuel ratio can shift to the rich side. Furthermore, if the rich skip amount RSR is increased, the controlled air-fuel ratio can be shifted to the rich side, and even if the lean skip amount RSL is decreased, the controlled air-fuel ratio can be shifted to the rich side. , the controlled air-fuel ratio can be shifted to the lean side, and even if the rich skip amount RSR is reduced, the controlled air-fuel ratio can be shifted to the lean side. Furthermore, if the rich integral constant KIR is increased, the controlled air-fuel ratio can be shifted to the lean side, and even if the ratio is decreased to the lean integral constant, the controlled air-fuel ratio can be shifted to the rich side. If it is increased, the controlled air-fuel ratio can be shifted to the lean side, and even if the rich integral constant KIR is made small, the controlled air-fuel ratio can be shifted to the lean side.

Therefore, in the present invention, the lean tendency of the air-fuel ratio due to alcohol is compensated for by changing the air-fuel ratio feedback control constant in accordance with the alcohol concentration DA contained in the fuel.

FIG. 6 shows a routine for making the air-fuel ratio feedback control constants, such as delay times TDR and -TDL, variable, and is executed at predetermined time intervals. That is, step 60
1, the alcohol concentration DA is detected from the alcohol concentration sensor 8.
In step 602, the delay times TDR and -TDL corresponding to the detected alcohol concentration DA are determined using a map as shown in the figure. This map is stored in a predetermined area of the ROM 104 in advance,
Each delay time TDR, -T corresponds to the alcohol concentration DA.
DL is set.

The map is set so that the higher the alcohol concentration DA, the richer delay time TDR increases and the leaner delay time (-TDL) decreases in proportion to it, as shown in Figure 5 (C). ) in lean shape B (F
= "0") for a longer time, the FAF is increased, and thus the fuel injection amount is increased, or in other words, the controlled air-fuel ratio is shifted to the rich side.

This is because the air-fuel ratio is controlled at a leaner side than the stoichiometric air-fuel ratio (for example, 15) due to the bad quality of alcohol in the fuel, but by increasing FAF, the air-fuel ratio is returned to the rich direction, and control is centered around the stoichiometric air-fuel ratio. is intended to. Each delay time TDR determined in this manner.

(-TDL) is stored in RAM 105 in step 603, and the routine ends in step 604.

FIG. 7 shows a routine for calculating a target fuel injection amount from FAF that changes with the air-fuel ratio feedback control constant variably set as described above, and is executed at every predetermined crank angle, for example, 360° CA. Step 701
Then, the RAM 105 reads the intake air amount data Q and the rotational speed data Ne, and the basic injection 11TAUP is performed.
For example, TAUP←KQ/Ne (K is a constant). In step 702, the target fuel injection amount TAU
is calculated by TALI ``TAUP - FAF · ex + β. Note that α and β are correction amounts determined by other operating state parameters, such as a signal from a throttle position sensor (not shown), a signal from an intake temperature sensor,
These are correction amounts determined by battery voltage, etc., and are also stored in the RAM 105.Next, in step 703, the injection amount TAU is set by the down counter 108, and the flip-flop 109 is set to start fuel injection. Let it start. The routine then ends at step 704. Furthermore, as mentioned above, the injection amount TA
When the time corresponding to U has elapsed, the down counter 108
The flip-flop 109 is reset by the carrier signal, and the fuel injection ends.

In the above embodiment, Q/Ne is read, but instead, the intake pipe pressure PM may be detected by an intake pipe pressure sensor (not shown) and used as a load. Also, in the routine of FIG. Although the time TDR, (-TDL) is made variable, either the rich delay time TDR or the lean delay time (-TDL) may be made variable, or the delay time TDR, (-TDL) may be made variable. Instead, the skip amount R5R, RSL.

The integral constants KIR and KIL may be made variable.

〔Effect of the invention〕

As explained above, according to the present invention, the air-fuel ratio feedback control constant is changed according to the alcohol concentration, so that the higher the alcohol concentration, the more the air-fuel ratio correction coefficient increases, that is, the target fuel injection amount increases. Since the adjustment is made to 0.0, it is less than the actual value. The lean tendency of the air-fuel ratio caused by the oxygen sensor that detects the amount of alcohol is compensated for according to the alcohol concentration, and therefore helps prevent deterioration of exhaust emissions.

[Brief explanation of the drawing]

FIG. 1 is an overall block diagram for explaining the present invention in detail, and FIG. 2 is a 0. Graph for explaining the output characteristics of the sensor; FIG. 3 is an overall schematic diagram showing an embodiment of the air-fuel ratio control device for an internal combustion engine according to the present invention; FIGS. A flowchart for explaining the operation of the control circuit shown in the figure, FIG. 5 provides a supplementary explanation of the flowchart of FIG. 4. FIG. l... Engine body, 3... Air flow meter, 4... Distributor, 4a, 4b... Crank angle sensor, 8... Alcohol concentration sensor, 9... 0. Sensor, 10... control circuit.

Claims (1)

[Claims] 1. Determine the target fuel injection amount by correcting the basic fuel injection amount calculated according to the engine load with the air-fuel ratio correction coefficient according to the oxygen sensor output value, and calculate the air-fuel ratio obtained thereby. A fuel injection control device for an internal combustion engine using alcohol-containing strands, which performs air-fuel ratio feedback control to approximate the stoichiometric air-fuel ratio, and is installed in the exhaust system of the engine to detect the oxygen concentration in the exhaust gas. an oxygen sensor, an alcohol concentration detection means for detecting the concentration of alcohol contained in the fuel, and an air-fuel ratio feedback device for the air-fuel ratio correction coefficient so that the higher the detected alcohol concentration, the higher the target fuel injection amount. air-fuel ratio feedback control constant calculation means for calculating a control constant; air-fuel ratio correction coefficient calculation means for calculating an air-fuel ratio correction coefficient according to the oxygen sensor output and the air-fuel ratio feedback control constant; and the air-fuel ratio correction coefficient calculation means 1. A fuel injection control device for an alcohol-containing twisted internal combustion engine, comprising fuel injection amount calculation means for calculating a fuel injection amount using an air-fuel ratio correction coefficient determined by.