JP2705298B2 - Fuel supply control device for internal combustion engine - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to a fuel supply control device for an internal combustion engine, and more particularly to a control of a required supply fuel amount based on a fuel property detection result and a fuel behavior model of an intake system. The present invention relates to a model reference type fuel supply control device.

(Prior Art) As a device for controlling the fuel supply amount of an internal combustion engine according to operating conditions, a basic fuel injection amount determined based on an intake air amount and a rotation speed is corrected by a cooling water temperature or an acceleration state, or 2. Description of the Related Art There is known an electronically controlled fuel injection device that obtains a target air-fuel ratio by correcting the oxygen concentration in exhaust gas by feedback. According to this type of fuel injection device, it is possible to accurately achieve the target value during steady operation, but during transients such as during acceleration, the air-fuel ratio is mainly reduced due to the adhesion and evaporation of fuel in the intake pipe. An error may occur, and if optimization is attempted to prevent such an error, there is no other way than to determine the correction amount experimentally according to the operating conditions, so that a large number of steps are required for matching. was there.

On the other hand, a fuel behavior model that describes the behavior of fuel flowing into the engine cylinder as a state variable with the amount of fuel attached to the intake pipe wall and the amount of fuel evaporation in the intake pipe is set,
By estimating the state variables based on the fuel properties and operating conditions represented by the octane number of the fuel, and then executing an arithmetic expression based on the fuel behavior model, the fuel according to the operating conditions can be operated by operating only a small number of parameters. A fuel injection amount control device capable of obtaining an injection amount has been proposed (see JP-A-1-271623).

However, according to this fuel injection amount control device, the fuel behavior model uses only the amount of fuel adhesion and the amount of fuel evaporation on the wall surface of the intake pipe as state variables. There is a problem that the air-fuel ratio cannot always be accurately controlled because the state is not considered.

The present invention has been made in view of such a problem. The fuel state quantity in the intake pipe is represented by a spray model representing the state quantity of the fuel spray, and the attached fuel quantity is represented by the intake pipe wall portion and the intake valve surface portion. It is intended to improve the control accuracy of the fuel injection amount by calculating based on a wall flow model provided according to the above.

(Means for Solving the Problems) In order to achieve the above object, according to the present invention, as shown in FIG. 1, a means 101 for detecting an engine operating condition and a target air-fuel ratio based on the detected operating condition are determined. Means for calculating 102
Means for detecting a predetermined physical property value representative of the fuel property
3, a spray model having at least the ratio (a2, a3) of the fuel spray attached to the intake pipe wall surface and the intake valve surface as variables representing the state quantity of the fuel spray, and a variable representing the fuel state quantity in the intake pipe According to the intake pipe wall portion and the intake valve surface portion, at least a ratio (a5, a6) directly flowing into the cylinder as a wall flow from each surface and a vaporization ratio (a7, a8) from each surface are provided. Means 104 for calculating a total fuel state quantity in the intake pipe based on the wall flow model and operating conditions, and means 105 for calculating the required fuel quantity in the cylinder from the output from each of the means and the target air-fuel ratio When,
Means 10 for calculating fuel supply amount based on each calculation result
6 is provided.

(Operation) In the above configuration, while the fuel property, which is a characteristic factor of the fuel behavior, is detected by the detecting means 103, the calculating means 104 calculates the state quantity model representing the fuel spray state and the adhesion to the intake system. A fuel state quantity is calculated from a fuel state model representing the fuel amount and the vaporized fuel amount for both the intake pipe wall surface part and the intake valve surface part, and the required fuel amount in the cylinder is calculated by the calculating means 105 based on the above calculation results. Is calculated.

In this case, the amount of fuel adhering to the intake system, the amount of vaporization, and the amount actually sucked into the cylinder are affected not only by the fuel state quantity on the intake pipe wall portion, but also by the fuel spray properties and the intake valve that affect them. Therefore, the final fuel supply amount calculated by the calculating means 106 becomes a value more consistent with the actual requirement.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 2 is a diagram schematically showing a mechanical configuration of the embodiment, in which 1 is an internal combustion engine main body, 2 is a crankshaft, 3 is a piston, 4 is a cylinder, 5 is an intake valve, and 6 is an exhaust valve. , 7 are an intake port, 8 an intake pipe, 9 is a throttle valve, and 10 is a fuel tank. Numeral 11 denotes an electromagnetic opening / closing type fuel injection valve provided at the inlet of the intake port 7 toward the head of the intake valve 5, and is provided for each cylinder in the case of a multi-cylinder engine. This fuel injection valve 11
Injects fuel in response to a control pulse signal from the control circuit 12 having a function of calculating the fuel injection amount. Fuel whose pressure has been adjusted so that the pressure difference from the intake pipe internal pressure is constant is supplied to the fuel injection valve 11 via a fuel pumping device (not shown), and the fuel injection amount is determined by the valve opening time, that is, the control pulse. It is controlled by adjusting the pulse width of the signal.

On the other hand, 13 is an intake air amount sensor that detects an intake air amount Ga, 14 is a pressure sensor that detects an intake pipe internal pressure Po, 15 is a water temperature sensor that detects a cooling water temperature Tw, and 16 is an engine speed Ne.
And a crank angle sensor for detecting the operating condition in the present embodiment.

Numeral 17 denotes a fuel property detecting device which is a means for detecting a physical property value corresponding to the fuel property.
It can be constituted by various means as shown in FIG. FIG. 3A shows the pressure (saturated vapor pressure) Pfv of the fuel vapor layer in the fuel tank 10 detected by the pressure sensor 17a, and FIG. 3B detects the specific gravity ρl of the fuel in the fuel tank 10 by the hydrometer 17b. FIG. 3C shows a configuration in which the permittivity ε of the fuel in the fuel tank is detected by the permittivity meter 17c. When the properties of the fuel to be used are known in advance, information on the properties of the fuel can be obtained by means shown in FIGS. 4A to 4C.
FIG. 4A is a diagram in which information on the fuel property is selectively inputted by manually switching the changeover switch 18, for example, a high level for heavy fuel or winter, and a low level for light fuel or summer. It is configured so that the output can be set in terms of level. FIG. 4B shows a case where a gas station prepares an IC card or a magnetic card 19 in which fuel property information is stored in advance, and a card reader is used at the time of refueling.
The fuel property information is transferred to a control circuit on the vehicle side via the control unit 20. FIG. 4C shows the refueling nozzle 21.
A bar code 22 indicating the fuel property is recorded on the vehicle, and the fuel property is input to a control circuit on the vehicle side via a bar code reader 24 provided at a fuel filler port 23 of the vehicle at the time of refueling.

In the present invention, the control circuit 12 is based on a spray model representing the state quantity of the fuel spray and a wall flow model that gives the amount of fuel adhesion in the intake pipe according to the intake pipe wall and the intake valve surface. Means 104 for calculating a fuel state in the intake pipe
Means 105 for calculating the required amount of fuel in the cylinder from the outputs from the fuel property detecting means 103 and the fuel state calculating means 104 and the target air-fuel ratio determined according to the engine operating conditions; The functions of the means 106 for calculating the values are realized on a microcomputer, and the predetermined values are calculated based on the signals from the input ports 12a and the input ports 12a to which the detected values from the above sensors and the fuel properties are input. CPU 12b for processing, ROM 12c for storing calculation programs and constants, RAM 12d for temporarily storing calculation results, transient calculation values, and the like, and calculation results by CPU 12b, that is, the fuel supply amount is output to the fuel injection valve as a pulse signal. Output port 12
e.

Next, an outline of the arithmetic processing in the control circuit 12 will be described based on a flowchart (FIG. 5) and a block diagram (FIG. 6) showing the input / output relationship of each signal. In this control, the processing of each step shown in FIG. 5 is repeated every cycle of one cylinder.

At the beginning of the control, first, signals indicating operating conditions are input from various sensors in block A of FIG. 6 (step 501), and based on this, a predetermined physical property value Pv representative of the fuel property in block D, for example, saturation. Calculate the vapor pressure (Step 50
2).

The first parameter a ₁ ~a ₉ is calculated in each Block E~H fuel behavior model (step 50
3). In detail, in block E, when the particles are sucked into the cylinder in the state of particles, a ₁ , the ratio a ₂ of adhering to the port wall surface, the ratio a ₃ of adhering to the intake valve surface, and the vaporization ratio a _{4 of} particles are calculated. . In block F, the moving distance during one cycle is calculated from the moving speed of the wall flow fuel on each of the port wall surface and the intake valve surface portion, and the fuel ratios a ₅ and a ₆ directly flowing into the cylinder from each are calculated. You. In block G, the vaporization ratios a ₇ and a ₈ from the wall fuel are calculated for each of the port wall surface and the intake valve surface portion. In block H, the proportion of the fuel a ₉ drawn from the vaporized fuel in the intake pipe into the cylinder
Is calculated.

Further, based on these parameters a _{1 to} a ₉ , the second parameter b _{1 to} b ₈ , the third parameter c _{1 to} c
₄ is calculated (step 504). The details of the second and third parameters will be described later.

On the other hand, in block B, the target air-fuel ratio A / F is calculated based on the input value of the operating condition in block A (step 5).
05) Then, on the basis of the target air-fuel ratio A / F and the intake air amount Ga, the required fuel amount Ga / (A / F) in the cylinder is calculated in the block C.
Is calculated (step 506). Further, in the next block J, the final fuel injection amount Gfi is calculated based on each state quantity of the fuel in the intake pipe calculated in the previous cycle, the required fuel amount, and each parameter calculated in blocks E to I. Is calculated. The calculation result in block J is output to the fuel injection valve as fuel injection signal Ti in block M (steps 507, 509). In the block K, the fuel state quantity of the next cycle is calculated from the fuel state quantity and the fuel injection quantity of the current cycle in accordance with the fuel behavior model represented by the above parameters (step 508). It is memorized. The stored value of block L is block J
Is used in the calculation of the fuel injection amount Gfi in the above.

Next, an example of a method of calculating each of the above parameters in the fuel behavior model in the intake pipe will be described.

(1) Fuel Model In the present invention, the wall flow in the intake pipe is divided into the wall flow Gwf on the suction port wall and the wall flow Gvf on the intake valve surface, and changes in the respective amounts per time are detected. Some of the fuel injection amount _{dGfi, a 2 · dGfi, a} 3 · dGfi are respectively attached, the amount of fuel sucked into the cylinder by movement of the wall flow is a ₅ ·
GWF, fuel quantity by vaporization from a ₆ · Gvf next, also wall flow a ₇ · GWF, represented by a ₈ · Gvf. From these, the change in the wall flow rate is expressed as follows.

_{dGwf / dt = a 2 · dGfi} / dt-a 5 · Gwf-a 7 · Gwf ... (1) dGvf / dt = a 3 · dGfi / dt-a 6 · Gvf-a 8 · Gwf ... (2) Also, The change in the vaporized fuel amount Gvp in the intake pipe is caused by the vaporized component a ₄ · dGfi from the injected fuel and the vaporized component a ₇ · Gwf, a ₈ ·
The amount of fuel a ₉ increased by Gvf and drawn into the cylinder
-Since it decreases by Gvp, it is expressed as follows.

_{dGvp / dt = a 4 · dGfi} / dt + a 7 · Gwf + a 8 · Gvf-a 9 · Gvp ... (3) Next, change of the fuel amount Gcyl to be sucked into the cylinder,
Min a ₁ · Gfi sucked directly particle state of the injected fuel
If, min a ₅ · GWF sucked by the movement of the wall flow, a ₆ · Gvf
And the amount a ₉ · Gvp inhaled from the vaporized fuel in the intake pipe, so that it is expressed as follows.

_{dGcyl / dt = a 1 · dGfi} / dt + a 5 · Gwf + a 6 · Gvf + a 9 · Gvp ... (4) In addition, (1) to (4) the parameters of a ₁ ~a ₉ in formula engine specifications, operating It is a value determined by conditions and fuel properties.

Now, assuming that each equation is integrated for one cycle and the change from the (i) cycle to the (i + 1) cycle is obtained, first, the equation (1) becomes as follows.

Here, assuming that the wall flow rate Gwf of the port wall portion changes linearly from the (i) cycle to the (i + 1) cycle, the following equation is derived from the equation (5).

Gwf (i + 1) = Gwf (i) + a 2 · Gfi (i) - (a 5 + a 7) (Gwf (i + 1) + Gwf (i)) /
2 ... (6) Gwf (i + 1) = b 1 · Gwf (i) + b 2 · Gfi (i) ... (7) _{However, b 1 = (1-a} 5/2-a 7/2) / (1 + a 5 _{/ 2 + a 7/2)} b 2 = a 2 / (1 + a 5/2 + a 7/2) ... (8) varies linearly from even (i) cycle to the (i + 1) cycles for wall flow Gvf intake valve surface portion Then, the following equation is derived from the equation (2).

Gvf (i + 1) = Gvf (i) + a 3 · Gfi (i) - (a 6 + a 8) (Gvf (i + 1) + Gvf (i)) / 2 ... (9) Gvf (i + 1) = b 3 · Gvf (i ) + b ₄ · Gfi However (i) ... (10), b 3 = (1-a 6/2-a 8/2) / (1 + a 6/2 + a 8/2) b 4 = a 3 / (1 + a 6 / _{2 + a 8/2) ...} (11) next, assuming that varies linearly intake pipe vaporized fuel Gvp from (i) cycle to the (i + 1) cycle, the following equation (3) below is derived.

Gvp (i + 1) = Gvp (i) + a 4 · Gfi (i) + a 7 (Gwf (i + 1) + Gwf (i)) / 2 + a 8 (Gvf (i + 1) + Gvf (i)) / 2 -a 9 (Gvp ( i + 1) + Gvp (i)) / 2 (12) Equation (12) can be expressed as follows using equations (7), (8), (10), and (11).

Gvp (i + 1) = b 5 · Gwf (i) + b 6 · Gvf (i) + b 7 · Gvp (i) + b 8 · Gfi (i) ... (13) _{However, b 5 = (a 7 (} b 1 +1) / 2) / (1 + a 9/2) b 6 = (a 8 (b 3 +1) / 2) / (1 + a 9/2) b 7 = (1-a 9/2) / (1 + a 9/2) b _{8 = (a 7 b 2/} 2 + a 8 b 4/2 + a 4) / (1 + a 9/2) ... (14) above (7), (10), which is as follows summarized (13).

On the other hand, the in-cylinder intake fuel amount Gcyl (i) is expressed as follows by integrating equation (4) in the same manner as described above.

Gcyl (i) = a ₁ · Gfi (i) + a ₅ (Gwf (i + 1) + Gwf (i)) / 2 + a ₆ (Gvf (i + 1) + Gvf (i)) / 2 + a ₇ (Gvp (i + 1) + Gvp (i )) / 2 ... (16) Substituting equations (7), (10) and (13) into this equation gives the following.

_{Gcyl (i) = c 1 ·} Gwf (i) + c 2 · Gvf (i) + c 3 · Gvp (i) + c 4 · Gfi (i) ... (17) _{However, c 1 = a 5 (b} 1 +1) / _{2 + a 9 b 5/2} c 2 = a 6 (b 3 +1) / 2 + a 9 b 6/2 c 3 = a 9 (b 7 +1) / 2 c 4 = a 5 b 2/2 + a 6 b 4/2 + a 9 _{b 8/2 + a1 ... (} 18) (17) When rewriting equation can be expressed as follows.

The required fuel amount in the cylinder is expressed as follows from the intake air amount Ga (i) and the target air-fuel ratio A / F obtained from the engine operating conditions.

Gcyl (i) = Ga (i) / (A / F) (20) where Equations (15) and (19) are expressed as follows.

X (i + 1) = A.X (i) + B.Z (i) (22) Y (i + 1) = C.X (i) + D.Z (i) (23) The fuel behavior in the intake pipe is described above. Formulated.

The state quantity parameters a _{1 to} a ₉ in the equations (1) to (4) are obtained by a model to be described later according to operating conditions and the like, whereby b _{1 to} b ₈ and c _{1 in the} equations (15) and (19) are obtained. The variables of ~ c ₄ are also obtained. Further, since the required fuel amount in the cylinder is also determined by the operating conditions as in equation (20), first, the fuel injection amount Gfi (i) is determined by equation (23).

_{Gfi (i) = d 1 ·} Gwf (i) + d 2 · Gvf (i) d 3 · Gvp (i) + d 4 · Ga (i) / (A / F) ... (24) However, d ₁ = c ₁ / c ₄ , d ₂ = c ₂ / c ₄ d ₃ = c ₃ / c ₄ , d ₄ = 1 / c ₄ (25) Further, the fuel injection amount Gfi (i) of the current cycle and each state amount G
From wf (i), Gvf (i), and Gvp (i), each state quantity Gwf (i + 1), Gvf (i + 1), Gv in the next cycle is calculated by equation (22).
p (i + 1) can be obtained.

Further, from these values and the required fuel amount Ga (i + 1) / A / F in the cylinder in the next cycle, the fuel injection amount Gfi in the next cycle is calculated.
(I + 1) is obtained by equation (24).

As described above, each fuel amount in the intake pipe can be obtained by using the equations (22) and (23).

(2) parameter calculation will be described (1) to (4) for calculation of the parameters a ₁ ~a ₉ in the formula.

First, a description will be given of a ₁ ~a ₄ relates to a fuel spray,
Since a ₂ and a ₃ are the ratio of the fuel spray adhering to the suction port wall surface and the ratio of the fuel spray adhering to the intake valve surface, respectively, mechanical properties such as the shape of the intake pipe of the engine, the fuel injection direction, the spread of the fuel spray, etc. It is a value determined by the condition. a ₄ is a vaporization rate of the fuel particles, the vaporization amount dw of the particles in consideration of the diffusion of the stadium particles around the saturated vapor layer, represented for example by the following equation.

dw = K ₁ (d · Va ^1/2 / T) Po · In (Pv / (Po−Pv)) (26) where d: particle diameter, T: temperature, Va: air velocity (engine speed Ne) , Po: intake pipe pressure, Pv: saturated vapor pressure of fuel, K ₁ : constant, and Pv will be described later in a model for obtaining a fuel property value.

From the above equation (26), the vaporization ratio a ₄ is expressed as follows:
It can be seen that the value is determined by the spray particle size and the operating conditions.

a ₄ = dw / Wd = K ₂ ((Ne ^1/2 · Po) / d ² · T) × In (Pv / (Po−Pv)) (27) where K2 is a constant.

Finally, the percentage of fuel that is drawn into the cylinder in particulate form
a ₁ is, once the a ₂ ~a ₄ as described above, determined in _{a 1 = 1-a 2 -a} 3 -a 4 ... (28).

Next, since the ratios a ₅ and a ₆ that flow directly into the cylinder due to the movement of the wall flow are determined by the movement speed of the wall flow, the respective movement speeds Vwf and Vv at the port wall surface and the intake valve surface portion, respectively.
Find f.

The speed changes dVwf and dVvf during one cycle are determined by the shear force τa from the airflow and the shear force τw from the wall, and are expressed by the following equation.

_{dVwf = K 3 τa + K 4} τw = K 3 'PoVa 2 + K 4' (exp (1 / T)) 1/4 Vwf 2 ... (29) _{However, K 3, K 4, K} 3 ', K 4' is a constant .

_{dVvf = K 5 τa + K 6} τw = K 5 'PoVa 2 + K 6' (exp (1 / T)) 1/4 Vvf 2 ... (30) _{However, K 5, K 6, K} 5 ', K 6' is a constant .

 Therefore, the speed during one cycle is as follows: Vwf (i + 1) = Vwf (i) + dVwf (31) Vvf (i + 1) = Vvf (o) + dVvf (32)

Since the parameters a ₅ and a ₆ are determined by the average speed during one cycle, a ₅ = K ₇ (Vwf (i) + dVwf / 2) (33) a ₆ = K ₈ (Vvf (i) + dVvf / 2) …… (34) However, K ₇ and K ₈ are constants.

It is expressed as

Next, the vaporization ratios a ₇ and a ₈ from the wall flow are determined. First, the vaporization amounts dGwvp and dGvvp per hour from the wall flows of the port wall surface and the intake valve surface are respectively expressed by the following equations.

dGwvp = K ₉ (A ₁ Va ^0.8 / h ₁ T) Po × In (Pv ₁ / Po−Pv ₁ )… (35) dGvvp = K ₁₀ (A ₂ Va ^0.8 / h ₂ T) Po × In (Pv ₂ / Po−Pv ₂ )… (36) where: An: wall flow surface area, hn: wall flow thickness, Va: air velocity (can be replaced by engine speed Ne), T: temperature, Po: intake pipe pressure , Pv: saturated vapor pressure of fuel, K ₉ , K ₁₀ : constants.

From the equations (35) and (36), the parameters a ₇ and a ₈ are expressed as follows.

_{a 7 = (dGwvp / Ne)} / Gwf = K 11 (Po / h 1 2 TNe 0.2) In (Pv 1 / Po-Pv 1) ... (37) However K ₁₁ is a constant.

_{a 8 = (dGvvp / Ne)} / Gvf = K 12 (Po / h 2 2 TNe 0.2) In (Pv 2 / Po-Pv 2) ... (38) However K ₁₂ is a constant.

Finally, the ratio a ₉ sucked from the intake pipe vaporized fuel into the cylinder, which depends pipe air velocity Va i.e. engine speed Ne, is expressed as follows.

a ₉ = K ₁₃ · Ne… (39) where K ₁₃ is a constant.

As described above, the model parameters a ₁ ~a ₉ is determined by the physical model.

(3) Detection of Fuel Physical Property Value Next, an example of a specific method for detecting a fuel physical property value will be described.

First, a volume ratio of a combination of a plurality of single component fuels can be obtained by detecting a value representing a characteristic of the fuel, for example, specific gravity, vapor pressure, or the like. That is, since gasoline is a multi-fuel, it is generally difficult to express its physical property values. However, each physical property value can be approximated as an arbitrary combination of single components.

Specifically, considering that, for example, four types of single components are represented, each composition ratio can be determined by specific gravity and vapor pressure as shown in FIG. Single component fuel, the saturated vapor pressure at a certain temperature, Pv (j) = Po · exp (K 14 (j) -K 15 (j) / T) ... (40) However, K _14, K ₁₅ is constant.

Where the composition ratio is Rx (j), the saturated vapor pressure Pv of the fuel represented by the four types can be obtained as follows.

(Effects of the Invention) As described above, according to the present invention, not only the fuel property such as the specific fuel weight is detected, but also the state quantity representing the spray state of the fuel injection valve, the amount of adhering fuel in the intake system, and the vaporized fuel. The fuel condition, which represents the amount for both the wall surface of the intake pipe and the surface of the intake valve, was modeled, and the amount of fuel supplied was calculated from the fuel condition calculated by these models and the target air-fuel ratio. The amount of fuel adhesion, the amount of evaporation, and the amount actually sucked into the cylinder can be calculated in consideration of the spray properties affecting these and the fuel state of the intake valve. The effect that air-fuel ratio control can be realized is obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of the present invention, FIG. 2 is a schematic configuration diagram showing a mechanical configuration of an embodiment of the present invention, and FIG.
4A to 4C are schematic structural diagrams showing an embodiment of a means for detecting fuel properties, FIG. 5 is a flowchart showing the processing contents of a control circuit in the embodiment, and FIG. FIG. 7 is a block diagram showing an output relationship, and FIG. 7 is an explanatory diagram showing differences in fuel properties according to the vapor pressure and specific gravity. 101 engine operating condition detecting means 102 target air-fuel calculating means 103 fuel property value detecting means 104 fuel state quantity calculating means 105 required cylinder fuel quantity calculating means 106 Fuel supply amount calculation means 1 ... internal combustion engine body, 4 ... cylinder, 5 ... intake valve,
7 ... intake port, 8 ... intake pipe, 11 ... fuel injection valve,
12 ... control circuit, 13 ... intake air amount sensor, 14 ... intake pipe pressure sensor, 15 ... water temperature sensor, 16 ... crank angle sensor, 17 ... fuel property detection means.

Claims (1)

(57) [Claims] A means for detecting an engine operating condition; a means for calculating a target air-fuel ratio based on the detected operating condition; a means for detecting a predetermined physical property value representing fuel property; At least the ratio of the fuel spray to the intake pipe wall and the intake valve surface (a
According to the spray model having (2, a3) and the variables representing the fuel state quantity in the intake pipe, the ratio of direct flow into the cylinder as a wall flow from at least the respective surfaces (wall flow and intake valve surface) as variables ( a5, a6) and a wall flow model having a vaporization ratio (a7, a8) from each surface; means for calculating a total fuel state quantity in the intake pipe based on operating conditions; Fuel supply control for an internal combustion engine, comprising: means for calculating a required fuel amount in a cylinder from an output from the ECU and a target air-fuel ratio; and means for calculating a fuel supply amount based on the calculation results. apparatus.