JPH02146238A - Fuel feeding control device of internal combustion engine - Google Patents

Abstract

PURPOSE:To carry out the correction to the adequate control efficiently by converting to decrease or increase the density detecting value in the direction to turn over the air-fuel ratio by the injection control responding to a specific control constant, and setting the control constant variable depending on the engine operation condition. CONSTITUTION:The engine operation condition is detected by a device (a) and the standard fuel feeding amount is set by a device (b) depending on the engine operation condition. And the standard fuel density is detected by a device (c), and the density correcting value to correct the standard fuel feeding amount depending on the standard fuel density is set by a device (d). Furthermore, the fuel feeding amount is set by a device (e) by correcting the standard fuel feeding amount depending on the temperature correcting value, and a fuel feeding device (g) is driven and controlled by a device (f) depending on the fuel feeding amount. On the other hand, the air-fuel ratio of the mixture gas and an abnormal condition of the device (c) are detected by a device (h) and a device (i) respectively, and when there is an abnormal condition, the standard fuel density is converted to a specific condition by a device (j). And the increase or the decrease of the standard fuel density is set variable by a device (k) responding to the engine operation condition.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a fuel supply control device for an internal combustion engine, and more specifically, a fuel supply control device for an internal combustion engine that can be used by switching or mixing different types of fuel, such as gasoline and alcohol. The present invention relates to a fuel supply control device for an internal combustion engine.

<Prior Art> As this type of fuel supply control device for an internal combustion engine, there is one disclosed, for example, in Japanese Patent Application Laid-Open No. 56-98540.

This device is designed to allow gasoline and alcohol to be used by switching or mixing them, and is equipped with an alcohol sensor that detects the standard fuel alcohol concentration in the fuel. Based on the detected value of the alcohol sensor, the fuel In addition to correcting and controlling the supply amount, an oxygen sensor is provided to detect the oxygen concentration in the exhaust gas, and the rich/lean ratio of the actual air-fuel ratio to the target air-fuel ratio is determined through the oxygen concentration in the exhaust gas detected by the oxygen sensor. Based on this detection result, feedback correction control of the fuel supply amount is performed so that the actual air-fuel ratio approaches the target air-fuel ratio in a predetermined operating state.

<Problems to be Solved by the Invention> By the way, in the conventional fuel supply control device for an engine that supports the use of different types of fuel as described above, when the alcohol sensor becomes abnormal and outputs a false detection value,
Since incorrect fuel supply amount correction control is performed based on this incorrect alcohol concentration detection value, when air-fuel ratio feedback control is not performed, the air-fuel ratio deviates significantly from the target air-fuel ratio, and air-fuel ratio feedback control is Even if this is done, the feedback correction will not be able to correct it completely, resulting in a large air-fuel ratio deviation.

As a result, when the alcohol sensor is abnormal, there is a problem in that the engine operating performance and exhaust characteristics deteriorate.In order to solve this problem, the applicant has developed a method for detecting the concentration of the alcohol sensor when the alcohol sensor is abnormal. When the value is changed at a constant rate and the air-fuel ratio detected through the oxygen concentration in the exhaust gas detected by the O sensor installed in the exhaust passage is reversed, that is, the air-fuel ratio detected by the 0□ sensor is approximately We previously proposed a control device configured to fix the detected concentration value when the target air-fuel ratio is reached (Japanese Patent Application No. 1983).
-242273).

However, when changing the detection value of the alcohol sensor as described above, if the rate of change is constant regardless of the engine operating condition, the rate of change actually varies depending on the engine operating condition such as engine speed and engine load. Since the optimum values are different, there is a problem that good air-fuel ratio controllability during fail-safe cannot be maintained.

In other words, if the constant rate of change is larger than the optimal value, 0
□Since there is a response delay time in detecting the air-fuel ratio by the sensor, as shown in Figure 7, the detected value of the alcohol sensor may change too much (overshoot) and actually fall short of the target air-fuel ratio (true The detected value will be fixed at a value that deviates from the alcohol concentration (alcohol concentration), and a large change in the detected value of the alcohol sensor will result in sudden air-fuel ratio fluctuations. On the other hand, if the rate of change of the detected concentration value is smaller than the optimum value, as shown in Figure 8, the air-fuel ratio will not reverse easily, and during this time it will not be possible to eliminate the deviation in the air-fuel ratio due to the false detection value of the alcohol sensor. First, fail-safe control could no longer function effectively.

The present invention has been made in view of the above problems, and when changing the detected value of the alcohol sensor when the alcohol sensor is abnormal, it is possible to quickly control the air-fuel ratio to around the target air-fuel ratio while avoiding overshoot of the detected value. An object of the present invention is to provide a control device (which can correct a detected concentration value to near the true value).

Means for Solving the Problems> Therefore, in the present invention, as shown in FIG. A basic fuel supply amount setting means for setting a basic fuel supply amount, a reference fuel concentration detection means for detecting the standard fuel concentration in the fuel supplied to the engine, and a reference detected by the reference fuel concentration detection means. a concentration correction value setting means for setting a concentration correction value for correcting the basic fuel supply amount based on the concentration of fuel; and a concentration correction value setting means for setting the basic fuel supply amount set by the basic fuel supply amount setting means. a fuel supply amount setting means for correcting and setting the fuel supply amount based on the concentration correction value set by the means; and a fuel supply amount setting means for driving and controlling the fuel supply means based on the fuel supply amount set by the fuel supply amount setting means. a fuel supply control means; an air-fuel ratio detection means for detecting whether the air-fuel ratio of the engine intake air-fuel mixture is rich or lean with respect to a target air-fuel ratio via engine exhaust components; and an abnormality detection means for detecting an abnormality in the reference fuel concentration detection means. and, when an abnormality is detected by the abnormality detection means, the concentration detected by the reference fuel concentration detection means is forcibly increased or decreased by integral control according to a predetermined control constant in a direction that reverses the air-fuel ratio detected by the air-fuel ratio detection means; an abnormality fuel concentration changing means that fixes the concentration detected when the air-fuel ratio is reversed; and a right integral control that variably sets a predetermined control constant of the right integral control according to the engine operating state by the abnormal fuel concentration changing means. A fuel supply control device for an internal combustion engine that can be used by switching or mixing different types of fuel is configured, including a constant variable setting means and the like.

Effect> In this configuration, the engine operating state detection means detects the engine operating state, and the basic fuel supply amount setting means sets the basic fuel supply amount based on this engine operating state.

The reference fuel concentration detection means detects the reference fuel concentration in the fuel supplied to the engine, and the concentration correction value setting means performs concentration correction for correcting the basic fuel supply amount based on this reference fuel concentration. Set the value.

The fuel supply amount setting means sets the fuel supply amount by correcting the basic fuel supply amount based on the concentration correction value, and the fuel supply control means drives and controls the fuel supply means based on this fuel supply amount. do.

The above is the function of fuel control when the reference fuel concentration detection means is normal.For fail-safe control when the reference fuel concentration detection means is abnormal, the abnormality detection means detects an abnormality in the reference fuel concentration detection means, and The air-fuel ratio detecting means detects whether the air-fuel ratio of the engine intake air-fuel mixture is rich or lean with respect to the target air-fuel ratio through the engine exhaust component, so that the direction of error in the detected value of the reference fuel concentration detecting means can be specified.

When the abnormality detection means detects an abnormality in the reference fuel concentration detection means, the abnormality fuel concentration changing means
The concentration detected by the reference fuel concentration detection means is forcibly increased or decreased in the direction of reversing the air-fuel ratio detected by the air-fuel ratio detection means from rich to lean or from lean to rich by integral control according to a predetermined control constant, and the air-fuel ratio is increased or decreased. It is fixed at the density detection value when it is reversed.

That is, when an abnormality in the reference fuel concentration detection means is detected, the detected value is forcibly changed in the direction of inverting the air-fuel ratio from the rich/lean state at that time (in the direction of approaching the true concentration detection value), and the air-fuel ratio is When the fuel ratio reverses, it is assumed that the true concentration detected value has been crossed, and the detected value at that time is fixed, and concentration correction control of the basic fuel supply amount is performed based on the detected value immediately after the air-fuel ratio reverses. It is.

Here, the predetermined control constant used to increase or decrease the detected value by integral control when the reference fuel concentration detection means is abnormal is determined by the integral control constant variable setting means according to engine operating conditions such as engine speed and engine load. It can be set variably.

That is, when the detected value of the reference fuel concentration detecting means is forcibly increased or decreased by the abnormal fuel concentration changing means, instead of changing it at a constant rate, for example, the concentration correction result is detected immediately by the air-fuel ratio detecting means. The control constant of the integral control is changed according to the engine operating state so that the detected concentration value changes quickly when the engine speed is high and conversely changes slowly when the engine speed is low, and the optimum rate of change is achieved under all operating conditions. It is now possible to change the detected concentration value.

<Example> The present invention will be explained in detail below.

In FIG. 2 showing one embodiment, an engine 1 is configured to be able to use alcohol mixed fuel by switching between gasoline and alcohol as fuel, or by mixing these. Duct 3
．． Air is taken in via the throttle valve 4 and the intake manifold 5.

A branch portion of the intake manifold 5 is provided with a fuel injection valve 6 as a fuel supply means for each cylinder.

The fuel injection valve 6 opens when a solenoid is energized,
It is an electromagnetic fuel injection valve that closes when energized, and opens when energized by a drive pulse signal from a control unit 12, which will be described later, and is fed under pressure from a fuel pump (not shown) and adjusted to a predetermined pressure by a pressure regulator. The fuel is injected and supplied. Although this example is a multi-point injection system, it may also be a single-point injection system in which a single fuel injection valve is provided in common to all cylinders, such as upstream of the throttle valve 4.

An ignition plug 7 is provided in the fuel chamber of the engine 1, which ignites a spark to ignite and burn the air-fuel mixture.

From the engine 1, an exhaust manifold 8 exhaust duct 9. Exhaust gas is discharged via a three-way catalyst 10 and a muffler 11. The three-way catalyst 10 is an exhaust purification device that oxidizes Co and HC in the exhaust components, and also reduces NOx and converts it into other harmless substances, and converts the air-fuel mixture to the stoichiometric air-fuel ratio (target air-fuel ratio). Both conversion efficiencies are the best when burned at

The control unit 12 includes a CPU and a ROM.

It is equipped with a microcomputer that includes a RAM, an A/D converter, an input/output interface, etc., and receives input signals from various sensors and processes them as described below.
Controls the operation of the fuel injection valve 6.

As the various sensors, an air flow meter 13 of a hot wire type or a flap type is provided in the intake duct 3, and outputs a voltage signal according to the intake air flow rate Q.

Further, a crank angle sensor 14 is provided, and in the case of a four-cylinder engine, outputs a reference signal for every 180 degrees of crank angle and a unit signal for every 1 degree or 2 degrees of crank angle. Here, the engine rotational speed N can be calculated by measuring the cycle of the reference signal or the number of unit signals generated within a predetermined time.

Further, a water temperature sensor 15 and the like for detecting the cooling water temperature Tw of the water jacket of the engine 1 are provided.

Furthermore, an 0□ sensor 16 as an air-fuel ratio detection means is provided at the gathering part of the exhaust manifold 8, and the oxygen o, v in the exhaust gas is
The air-fuel ratio of the air-fuel mixture taken into the engine 1 via the A degree is detected. The 0□ sensor 16 is a known sensor whose output changes suddenly near the stoichiometric air-fuel ratio, and detects whether the actual air-fuel ratio is rich or lean with respect to the stoichiometric air-fuel ratio based on the output.

Further, an alcohol sensor 17 serving as a reference fuel concentration detection means for detecting the concentration ALC of alcohol, which is the reference fuel in the fuel supplied to the fuel injection valve 6, is installed in the fuel supply pipe or fuel tank on the upstream side of the fuel injection valve 6. It is provided.

Here, the CPU of the microcomputer built in the control unit 12 performs arithmetic processing according to the program on the ROM shown as flowcharts in FIGS. Perform fail-safe control.

In this embodiment, basic fuel supply amount setting means, fuel supply amount setting means, fuel supply control means, concentration correction value setting means, abnormality detection means, abnormal fuel concentration changing means, and integral control constant variable setting means are used. The functions are provided in the form of software as shown in the flowcharts of FIGS. 3 to 6, and the engine operating state detection means includes the air flow make 13. This corresponds to the crank angle sensor 14 and the like.

The routine shown in the flowchart of FIG. 3 is executed every predetermined minute time (for example, Ioms), and first,
Step 1 (indicated as Sl in the figure).

(Similarly below), basic fuel injection 1! (Supply amount) Tp (←KXQ/N; is a constant) is calculated.

In step 2, various correction coefficients C0EF are set, mainly based on the cooling water temperature Tw detected by the water temperature sensor 15, including an amount increase at startup, an amount increase when the engine is cold, and the like.

In step 3, when in a predetermined feedback control operating region, the actual air-fuel ratio is set to the target air-fuel ratio (theoretical air-fuel ratio).
Air-fuel ratio feedback correction coefficient LAN to bring it closer to
BDA is set by proportional-integral control. Specifically, O
Based on the rich/lean ratio of the actual air-fuel ratio detected by the t-sensor 16 with respect to the target air-fuel ratio, when rich (lean), the air-fuel ratio feedback correction coefficient LAMBDA is decreased (increased) by a predetermined integral;
When the lean is reversed, the bone P is increased or decreased by a predetermined proportional bone P. Here, the air-fuel ratio feedback correction coefficient LAN0DA
The control constants of the integral I and the proportional bone P used in the proportional-integral control are set in advance to optimal values for each operating state that is divided into multiple categories depending on the engine rotational speed N and the basic fuel injection amount Tp representing the engine load. It is obtained by searching from a map stored in ROM.

In the next step 4, an alcohol concentration correction coefficient KMET is set based on the alcohol concentration ALC in the supplied fuel detected by the alcohol sensor 17.

In step 5, a voltage correction numerator s is set to correct changes in the effective valve opening time of the electromagnetic fuel injection valve 6 due to battery voltage.

Then, in the next step 6, the basic fuel injection 1tTp is corrected according to the following formula to set the final fuel injection amount (supply amount) Ti.

T i 4-T P XCO [lPXLAMBDAXK
MET+T sIn the next step 7, the fuel injection amount T
Set i to the output register. As a result, when the predetermined fuel injection timing is reached, this output register is set.
The latest fuel injection amount Ti is read out, and a drive pulse signal in the pulse corresponding to this fuel injection amount Ti is applied to the fuel injection valve 6, thereby injecting fuel to the engine 1.

By the way, since the alcohol concentration correction coefficient KMET used to calculate the fuel injection amount Ti is set based on the detected value of the alcohol sensor 17 as described above, it is possible that the alcohol concentration correction coefficient KMET is set based on the detected value of the alcohol sensor 17. If a detected value different from the actual concentration is output, the air-fuel ratio controllability will deteriorate and drivability will be affected. An undercarriage is provided as shown in FIGS. 4 to 6.

The routine shown in the flowchart of FIG. 4 is an abnormality determination routine for the alcohol sensor 17 that is executed at predetermined intervals. First, in step 11, the detected value ALC from the alcohol sensor 17 is read.

Then, in the next step 12, the deviation ΔALC between the detected value ALC read in step 11 during the previous execution and the detected value ALC read this time is calculated, and this deviation Δ
Determine whether ALC is within a set value. here,
If the deviation ΔALC is within the set value, the detected value ALC
may be an abnormal value, but it is not immediately recognized that the alcohol sensor 17 is abnormal because it is in a stable state, but the deviation ΔALC is greater than the set value and the detected value ALC is large. If the ratio is changing, this is a phenomenon that cannot be recognized when the alcohol sensor 17 is normal, so step 18 is hesitation and the alcohol sensor 17 is changed.
Determine whether there is an abnormality.

If it is determined in step 12 that the deviation ΔALC is within the set value, the process proceeds to step 13, where air-fuel ratio feedback control is performed to bring the actual air-fuel ratio closer to the stoichiometric air-fuel ratio, which is the target air-fuel ratio. In other words, it is determined whether the operating range is in which air-fuel ratio feedback control is to be performed.

If the air-fuel ratio feedback control is in progress, the process advances to step 14 to check whether the feedback control is in a normal state, repeating the 2-chip lean correction, or conversely, whether the air-fuel ratio feedback correction coefficient LAMBDA is at its upper and lower limits. Determine whether the system is stuck for a long time and is virtually uncontrollable.

Here, if it is determined that the air-fuel ratio feedback correction coefficient LAMBDA is inconsistent and good feedback correction control is not being performed, then step 1
Proceed to step 5 to set the idle rotation speed feedback control m (T
It is determined whether or not SC control is not being performed (clamping).

The feedback control of the idle rotation speed is the second
Although not shown in the figure, by controlling the amount of air supplied through an auxiliary air passage provided to bypass the throttle valve 4, the rotational speed during idling operation can be brought closer to the target rotational speed. When such idle rotation feedback control is performed, the air-fuel ratio may also vary as the engine rotation speed N fluctuates around the target idle rotation speed.

Therefore, when performing idle rotation feedback control, the air-fuel ratio feedback correction coefficient LAMBD
Since there is a possibility that the stiffness is caused by the idle rotation control, the routine is ended without making an abnormality determination in step 16. On the other hand, when the idle rotation feedback control is not performed in a clamp state, the air-fuel ratio feedback correction coefficient LAMBDA
It is estimated that the deviation from the upper and lower limit values is due to incorrect concentration correction based on the abnormality detection value of the alcohol sensor 17, and the process proceeds to step 16 to determine whether the alcohol sensor 17 is abnormal.

In this way, when the detection value ALC of the alcohol sensor 17 is changing at a rate higher than a predetermined rate, and when the air-fuel ratio feedback correction coefficient LAMBDA is stuck to the upper and lower limits during idle rotation control clamping, This is to determine that the alcohol sensor 17 is abnormal.

Based on this abnormality determination, a fail-safe control routine shown in the flowchart of FIG. 5 is executed.

This routine is executed in synchronization with the engine rotation, and first, in step 21, it is determined whether or not there is an abnormality determination of the alcohol sensor 17, which is made according to the routine shown in the flowchart of FIG. If an abnormality determination has not been made, this routine is ended as is, but if an abnormality determination has been made, the process advances to step 22 and subsequent steps to execute predetermined fail-safe control.

In step 22, it is determined whether this is the first execution of this routine after the alcohol sensor 17 was determined to be abnormal.

If it is determined that it is the first time, the process proceeds to step 23, and based on the detection of the 02 sensor 16, the alcohol sensor 1
The direction in which the air-fuel ratio deviates, rich or lean, at the time of abnormality No. 7 is memorized.

In the next step 26, it is determined whether the target air-fuel ratio is rich or lean based on the current detection value of the 0□ sensor 16, and if it is rich, the process proceeds to step 27 and the detection value ALC (previous value) of the alcohol sensor 17 is used. Predetermined integral C
The detected concentration is forcibly corrected to increase by adding 1, and the alcohol concentration correction coefficient KMET is set based on the alcohol concentration ALC that has been corrected to increase. That is, as the alcohol concentration increases, the amount of fuel to be supplied for the same amount of air decreases accordingly, so if the air-fuel ratio is rich, the detected value ALC of the alcohol sensor 17 will be lower than the actual concentration. Therefore, it is estimated that the fuel amount is excessive, so the fuel injection amount Ti should be decreased (correction is made to increase the concentration).On the other hand, if the air-fuel ratio is lean in step 26, When it is determined, the process proceeds to step 28, where the predetermined integral C2 is subtracted from the detection value ALC (previous value) of the alcohol sensor 17, and the detected concentration is forcibly corrected to decrease.Such decrease correction control is performed by:
This is due to the opposite reason to the one used when determining richness.

If it is determined in step 22 that it is not the first time, the process proceeds to step 24. In step 24, the step 2
It is determined whether or not the air-fuel ratio has been reversed from the initial air-fuel ratio state stored in step 23 by the forced increase/decrease correction of the alcohol concentration ALC in step 7 or 28. Then, if the air-fuel ratio has not reversed from the state at the time when the abnormality of the alcohol sensor 17 was detected, step 2
Proceed to step 6 and check the alcohol concentration ALC according to the current air-fuel ratio.
Perform the increase/decrease correction again. If it is determined that the air-fuel ratio has been reversed, the process proceeds to step 25, where the alcohol concentration ALC resulting from the previous increase/decrease correction is clamped.
The subsequent alcohol concentration correction coefficient KMET is set based on the alcohol concentration ALC immediately after the air-fuel ratio is reversed.

For example, if the alcohol sensor 17 outputs a value lower than the actual alcohol concentration due to an abnormality and the air-fuel ratio becomes rich, the alcohol concentration ALC is gradually increased and the air-fuel ratio is reversed from rich to lean. By estimating that the alcohol concentration has crossed the true alcohol concentration and clamping the alcohol concentration ALC at that time, fuel correction control can be performed based on the alcohol concentration ALC that is close to the true value even when the alcohol sensor 17 is abnormal. It was designed to be carried out.

By the way, the predetermined integrals (control constants) C8 and C! used in steps 27 and 28 to correct the increase/decrease in alcohol concentration ALC! are variably set according to the engine operating state according to the routine shown in the flowchart of FIG.

The routine shown in the flowchart of FIG. 6 is executed at the same timing as the routine shown in the flowchart of FIG. 5 in synchronization with engine rotation.

First, in step 31, values corresponding to the current engine rotational speed N and basic fuel injection amount Tp are retrieved and read from the map of the integral I used for integral control of the air-fuel ratio feedback correction coefficient LAMBDA. The integral I read in step 31 is a control constant that increases or decreases the air-fuel ratio feedback correction coefficient LAMBDA in the air-fuel ratio feedback control operation region.

In the next step 32, the integral ■ read in step 31 is multiplied by a constant for correcting it to an optimal value for increasing integral control of alcohol concentration, and the calculation result is used to calculate the alcohol concentration when the alcohol sensor 17 is abnormal. Let ALC be the integral CI used in the increase control in step 27.

In addition, in step 33, a constant for correcting the integral I read in step 31 to an optimal value for alcohol concentration reduction integral control is multiplied by 2, and the calculation result is used to calculate the alcohol concentration when the alcohol sensor 17 is abnormal. Let ALC be the integral C8 used when performing the reduction control in step 28.

In this way, in this embodiment, the alcohol sensor 1
When increasing or decreasing the alcohol concentration detection value ALC by integral control in the direction in which the air-fuel ratio is reversed at the time of abnormality 7,
Basic fuel injection amount T representing engine rotational speed N and engine load
Integral control is performed in synchronization with engine rotation using integrals C+ and Cz that are variably set according to p. Therefore, even if the optimum rate of change in the alcohol concentration ALC varies depending on the engine operating state, it is possible to quickly respond to this and avoid overshoot while bringing the detected alcohol concentration value ALC closer to the true value when the alcohol sensor 17 is abnormal. It is something that can be done. Here, when the engine rotational speed N is high and the concentration correction result is quickly detected by the 0□ sensor 16, it is fast, and when the engine rotation speed N is high and the concentration correction result is detected quickly by the 0 It is preferable to change the alcohol concentration ALC so that it becomes smaller during load.

In particular, if the alcohol concentration ALC is changed by a value based on the integral constant of the air-fuel ratio feedback correction coefficient LANBDA, as in the case of this embodiment, the integral constant in the air-fuel ratio feedback control will cause an overshoot of the air-fuel ratio. Since it is variably set in consideration of control responsiveness, there is no need to fine-tune the integral constant for integral control of alcohol concentration AL-C, and the alcohol concentration ALC can be easily set to the optimum value according to the driving condition. It is something that can be changed.

<Effects of the Invention> As explained above, according to the present invention, when the means for detecting the reference fuel concentration is abnormal, the detected concentration value is forcibly increased or decreased in the direction of reversing the air-fuel ratio by integral control according to a predetermined control constant. The concentration detection value is fixed at the time when the air-fuel ratio is reversed, while the predetermined control constant is variably set depending on the engine operating state. This has the advantage of being able to quickly correct the detected concentration value to near the true value without overshooting when the concentration is detected, and to quickly and favorably restore engine operability in the event of an abnormality in concentration detection. be.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a system schematic diagram showing an embodiment of the present invention, FIGS. 3 to 6 are flowcharts showing control details in the above embodiment, and FIG. 8 and 8 are time charts for explaining the problems of conventional control, respectively. 1... Engine 6... Fuel injection valve 12... Control unit 13... Air flow meter
14...Crank angle sensor call sensor 16...0□ Sensor patent applicant Japan Electronics Co., Ltd. Agent Patent attorney Fujio Sasashima 17...A Figure 4 Figure 6

Claims (1)

[Scope of Claims] A fuel supply control device for an internal combustion engine that can be used by switching or mixing different types of fuel, comprising an engine operating state detecting means for detecting an engine operating state; and the engine operating state detecting means. basic fuel supply amount setting means for setting a basic fuel supply amount based on the engine operating state detected by the engine; reference fuel concentration detection means for detecting a reference fuel concentration in the fuel supplied to the engine; concentration correction value setting means for setting a concentration correction value for correcting the basic fuel supply amount based on the concentration of the reference fuel detected by the fuel concentration detection means; a fuel supply amount setting means for correcting and setting the fuel supply amount based on the concentration correction value; and a fuel supply control means for driving and controlling the fuel supply means based on the fuel supply amount set by the fuel supply amount setting means. , an air-fuel ratio detection means for detecting a rich/lean air-fuel ratio of an engine intake air-fuel mixture with respect to a target air-fuel ratio via engine exhaust components; an abnormality detection means for detecting an abnormality in the reference fuel concentration detection means; When an abnormality is detected by the means, the concentration detected by the reference fuel concentration detecting means is forcibly increased or decreased by integral control according to a predetermined control constant in a direction that reverses the air-fuel ratio detected by the air-fuel ratio detecting means, so that the air-fuel ratio is reversed. an integral control constant variable setting means for variably setting a predetermined control constant of the right integral control by the abnormal fuel concentration changing means according to the engine operating state; 1. A fuel supply control device for an internal combustion engine, comprising: