JP3095555B2 - Engine fuel injection control system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a fuel cell system in which fuel injected from an injector adheres to a wall surface of an intake pipe and fuel already adhered to the wall surface of the intake pipe is removed into a combustion chamber during an intake stroke. The present invention relates to a fuel injection amount control device for an engine that corrects a fuel injection amount (in-mani-wet correction) in response to a part or the like.

[0002]

2. Description of the Related Art In general, fuel injected from an injector (basic injection amount) is divided into a portion adhering to a wall surface of an intake pipe and a portion directly admitted to a combustion chamber. Since some of the fuel adhering to the fuel chamber is removed into the combustion chamber, the amount of fuel flowing into the combustion chamber during the intake stroke is the sum of the above-described direct input and the removed fuel.

In view of the above, the above basic injection amount, the amount of wall adhesion,
A device has already been invented which calculates the injection amount after wet correction from the direct entry and the carry-in portion and accurately executes the adaptation to the required fuel amount (see Japanese Patent Application Laid-Open No. 58-8238).

That is, when the direct injection rate is α, the carry-off rate is β, the basic injection amount is Ta, and the fuel amount adhering to the wall surface (in-maniwet amount) is Tm, the fuel amount TcyL entering the combustion chamber is expressed by the following equation ].

[0005]

(Equation 1)

The fuel amount Tm (i) adhering to the wall this time is expressed by the following [Equation 2].

[0007]

(Equation 2)

[0008] Here, Te (i-1) is the injection amount Tm (i-1) after the previous wet correction, the previous wall-adhered fuel amount, and the injection amount Te (i) after the current wet correction is the following [ Equation 3].

[0009]

(Equation 3)

[0010] The above [Equation 3] is the current basic injection amount Ta.
By dividing the value obtained by subtracting the current removal amount βTm (i) from (i) from the direct injection rate, the injection amount Te after the current wet correction is obtained.
(i). By injecting fuel from the injector using the injection amount Te (i) after the above-described wet correction, it is possible to relatively accurately adapt to the required fuel amount.

However, such a conventional apparatus has the following problems. In other words, the above-mentioned direct entry rate α and carry-out rate β do not fluctuate significantly in a steady state in which the fluctuation of the intake air amount is small, so that no problem occurs. In this case, the direct entry rate α and the carry-out rate β greatly fluctuate, and it is difficult to accurately obtain the true values of α and β.

For example, as shown in FIG. 6 showing the relationship between the direct entry rate α and the carry-out rate β, when α = β, the control system gradually converges,
When it is in the region between α = β and 2α = β, the control system vibrates and converges, and when 2α = β, the control system diverges (the control amount is periodically changed because the control system is unstable. No condition, also referred to as upset or hunting).

In particular, during rapid acceleration / deceleration in which the change in fuel injection amount is large, the injection amount (control amount) after the wet correction greatly fluctuates in each engine cycle, and the control system does not converge. There was a problem that the operability of the engine deteriorated.

[0014]

According to the first aspect of the present invention, during a transient in which the change in the fuel injection amount is large, the injection amount after the wet correction for each engine cycle converges to the basic injection amount. It is an object of the present invention to provide an engine fuel injection amount control device capable of correcting an injection amount after a wet correction, preventing a control system from vibrating, and reliably preventing combustion fluctuation and deterioration in engine operability.

According to a second aspect of the present invention, in addition to the object of the first aspect of the present invention, by suppressing the vibration of the control system within the rich limit and the lean limit of the air-fuel ratio, an over-rich condition is achieved. It is another object of the present invention to provide an engine fuel injection amount control device capable of preventing engine misfire due to overlean.

[0016]

According to a first aspect of the present invention, there is provided a calculating means for calculating a fuel injection amount injected from an injector, wherein the calculating means comprises a fuel injection amount for the fuel injected from the injector. The amount of fuel adhering to the wall of the intake pipe and the part of the fuel injected from the injector that enters directly into the combustion chamber, and the amount of fuel that has already adhered to the wall of the intake pipe is removed into the combustion chamber. A fuel injection amount control device for an engine, comprising: a wet correction unit that corrects a fuel injection amount from; and a post-correction calculation unit that calculates an injection amount corrected by the wet correction unit. The ratio of the carry-off ratio, which is the ratio of the amount of the wall adhering to the wall surface already adhering to the intake pipe wall, to the carry-in ratio, which is the ratio of the fuel amount injected from the injector, to the carry-in ratio is larger than the set value. A first determining means for determining whether or not the fuel injection amount is largely changed; and a second determining means for determining whether or not rapid acceleration / deceleration is large. Based on the determination results of the first and second determining means, direct entry is performed. Predicting means for predicting and calculating the next injection amount after the wet correction in the same cylinder from the injection amount after the current wet correction in the same cylinder when the ratio of the carry-out ratio to the ratio is larger than the correction value and the acceleration / deceleration is rapid. And an correcting means for correcting the injection amount after the current wet correction so that the injection amount after the wet correction for each engine cycle converges to the basic injection amount based on the calculation result of the prediction calculating means. It is a fuel injection amount control device.

According to a second aspect of the present invention, in addition to the configuration of the first aspect, the injection amount after the current wet correction by the correction means is predicted and calculated by the prediction calculation means. A third determining means for determining whether or not the next air-fuel ratio exceeds the rich limit with respect to the next air-fuel ratio based on the injection amount after the next wet correction, and the next air-fuel ratio is determined based on the determination result of the third determining means. First setting means for setting the injection amount after the current wet correction so that the air-fuel ratio becomes an air-fuel ratio richer than the lean limit when exceeding the rich limit;
When the next air-fuel ratio is within the rich limit based on the result of the determination by the third determining means, a second setting means is provided for setting the injection amount after the current wet correction so that the air-fuel ratio becomes the lean limit. A fuel injection amount control device for an engine.

[0018]

According to the first aspect of the present invention, as shown in the claim correspondence diagram of FIG.
The (calculation means) calculates the fuel injection amount Ta injected from the injector P1, and the calculation unit P2 calculates the amount (1-α) of the fuel Ta injected from the injector P1 that adheres to the intake pipe wall surface. Ta, of the fuel Ta injected from the injector P1, a directly-injected portion αTa directly drawn into the combustion chamber, and the fuel Tm already adhering to the intake pipe wall surface.
Has wet correction means for correcting the fuel injection amount based on the amount βTm carried away in the combustion chamber, and post-correction calculation means for calculating the subsequent injection amount Te by the wet correction means.

Further, the first determination means P3 determines whether or not the amount of the fuel injected from the injector P1 with respect to the direct entry αTa is the ratio of the direct injection ratio α to the removed portion βTm and the wall surface already attached to the intake pipe wall. It is determined whether or not the ratio of the removal rate β, which is the ratio of the attached components Tm, is greater than a set value,
The above-mentioned second determination means P4 determines whether or not the change in fuel injection amount is abrupt acceleration / deceleration, and the above-mentioned prediction calculation means P5 is based on the determination results of the above-mentioned first and second determination means P3, P4. When the ratio of the carry-out rate β to the direct entry rate α is larger than the set value and the vehicle is rapidly accelerated or decelerated, the injection amount Te <1> after the current wet correction in the same cylinder is used after the next wet correction. The injection amount Te <2> is predicted and calculated.

The above-mentioned correction means P6 performs the present wet correction so that the injection amount after the wet correction for each engine cycle converges on the basic injection amount Ta based on the calculation result Te << 2 >> of the prediction calculation means P5. The subsequent injection amount Te << 1 >> is corrected.

In the transient state where the change in the fuel injection amount is large, the injection amount after the wet correction for each engine cycle converges to the basic injection amount Ta in anticipation of the next injection amount. Since the corrected injection amount is corrected by the correction means P6, there is an effect that vibration of the control system can be prevented, and combustion fluctuation and deterioration in engine operability can be reliably prevented.

According to the second aspect of the present invention,
In addition to the effect of the first aspect of the present invention, the third determining means determines that the injection amount (corrected value of Te << 1 >>) after the current wet correction by the correcting means P6 is calculated by the prediction calculation. It is determined whether or not the next air-fuel ratio based on the next wet-corrected injection amount Te <2> calculated by the means P5 exceeds the rich limit, and based on the determination result of the third determining means. When the next air-fuel ratio exceeds the rich limit, the first setting means sets the injection amount T after the current wet correction.
e << 1 >> is set so that the air-fuel ratio is an air-fuel ratio richer than the lean limit, and control is performed so that the next air-fuel ratio does not exceed the rich limit.

When the next air-fuel ratio is within the rich limit based on the result of the determination by the third determining means, the second setting means determines the injection amount Te << 1 >> after the current wet correction by the air-fuel ratio at the lean limit. Set to be.

As described above, since the vibration of the control system is suppressed within the rich limit and the lean limit of the air-fuel ratio, it is possible to prevent the engine from misfiring due to over-rich and over-lean.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings. The drawing shows the fuel injection amount control device for the engine,
In FIG. 1, an air flow sensor 2 is connected to the rear of an air cleaner 1 for purifying intake air, and the air flow sensor 2 detects the intake air amount Q.

A throttle body 3 is connected to the rear of the above-mentioned airflow sensor 2, and a throttle valve 5 for controlling the amount of intake air is provided in a throttle chamber 4 in the throttle body 3. And this throttle valve 5
A surge tank 6 as an expansion chamber having a predetermined capacity is connected to the downstream intake passage, an intake manifold 8 communicating with an intake port 7 is connected downstream of the surge tank 6, and an injector 9 is connected to the intake manifold 8. Is arranged.

On the other hand, the above-described intake port 7 and exhaust port 11 which are appropriately communicated with the combustion chamber 23 of the engine 10 have:
Intake valve 12 that is opened and closed by a valve operating mechanism (not shown)
And an exhaust valve 13 respectively, and a spark plug 14 having a spark gap facing the above-described combustion chamber 23 is mounted on the cylinder head 24.

An O2 sensor 16 is provided in an exhaust passage 15 communicating with the above-described exhaust port 11, and a catalytic converter, a so-called catalyst, for detoxifying harmful gas is connected to the rear of the exhaust passage 15.

Further, a bypass passage 17 for bypassing the above-mentioned throttle valve 5 is provided, and an ISC valve 18 as an ISC (idle speed control) mechanism is provided in the bypass passage 17 while a downstream side of the element 19 of the air cleaner 1 is provided. , An intake air temperature sensor 20, a throttle sensor 21 in the throttle body 3, and a water temperature sensor 22 in the water jacket.

FIG. 2 is an explanatory view showing the state of the fuel injected from the injector 9 and the fuel flowing into the combustion chamber 23. The basic injection amount Ta injected from the injector 9 adheres to the intake pipe wall surface. Wall adhesion (1-α)
Ta and a direct entry αTa directly drawn into the combustion chamber 23. Further, the fuel (in-mani-wet amount) Tm attached to the intake pipe wall surface is vaporized and the removed amount βTm sucked into the combustion chamber 23, remains as it is without vaporizing, and is vaporized and sucked during the next injection. And remaining fuel. Here, α is the direct injection rate as a ratio of the fuel injected from the injector 9 to the direct injection αTa, and β is the ratio of the wall adhesion Tm already adhering to the intake pipe wall to the carry-over βTm. The leaving rate.

FIG. 3 shows a control circuit of the fuel injection amount control device for the engine. The CPU 30 controls the intake air amount Q from the air flow sensor 2, the engine speed Ne from the distributor 25, and the throttle opening TVO from the throttle sensor 21. The injector 9 is driven in accordance with a program stored in the ROM 26 based on various necessary signal inputs such as the engine water temperature tw from the water temperature sensor 22, and the RAM 27 stores various signals of [Equation 4] to [Equation 9] to be described later. Necessary data, such as the arithmetic expression (1), lean limit air-fuel ratio data, and rich limit air-fuel ratio data, are stored.

Here, the CPU 30 includes a wet correcting means for correcting the fuel injection amount based on the basic injection amount Ta, the wall adhesion amount (1-α) Ta, the direct injection amount αTa, and the carry-off amount βTm, and the wet correction means. And a post-correction calculating means for calculating the injection amount Te after the correction (refer to the third step S3 in the flowchart of FIG. 4). Determining means (see the first step S1 in the flowchart of FIG. 4) for determining whether or not is larger than a set value, and second determining means (see FIG. 4
2nd step S2 in the flowchart of FIG.
On the basis of the determination results of the first and second determination means, when the ratio of the carry-in rate β to the straight-in rate α is larger than the set value and the vehicle is rapidly accelerated or decelerated, the current wet correction in the same cylinder is performed. Prediction calculating means for predicting and calculating the next injection amount Te <2> after wet correction from the subsequent injection amount Te << 1 >> (FIG. 4)
4th step S4 in the flowchart of FIG.
The injection amount after the current wet correction is Te << 1 >> such that the injection amount after the wet correction converges on the basic injection amount Ta for each engine cycle based on the calculation result of the prediction calculation means.
A correction means (refer to the fifth step S5 in the flowchart of FIG. 4) for correcting the injection amount TLlim after the current wet correction by the correction means to a TLlim after the next wet correction calculated by the prediction calculation means. Determination means for determining whether or not the next air-fuel ratio based on the injection amount Te << 2 >> exceeds the rich limit (rich limit A / F) (see the sixth step S6 in the flowchart of FIG. 4). And the next air-fuel ratio is set to the rich limit TRlim based on the determination result of the third determination means (FIG. 5).
), The injection amount T after the current wet correction
e << 1 >> when the air-fuel ratio is lean limit TLlim (see Fig. 5)
The first setting means (refer to the tenth step S10 in the flowchart of FIG. 4) for setting the value Te << 1 >>'(see FIG. 5) that provides a richer air-fuel ratio, and the determination result of the third determination means Next time air-fuel ratio is rich limit TR
lim (see FIG. 5), the second setting means (the flowchart of FIG. 4) for setting the injection amount Te << 1 >> after the current wet correction so that the air-fuel ratio becomes the lean limit TLlim (see FIG. 5). (See the seventh step S7).

The operation of the fuel injection amount control device for an engine configured as described above will be described in detail below with reference to the flowchart shown in FIG. The contents of various symbols used in the following description are as follows.

Α: direct injection rate β: carry-out rate Ta (i): current basic injection amount (a value in which all corrections except for the in-mani-wet correction have been completed) Tm: wall adhesion amount Tm (i): current Wall adhesion amount Te << 1 >> (i) ... injection amount after the current wet correction, where << 1 >> indicates the first cycle of the engine cycle Te << 2 >> (i + 1) ... after the next wet correction Injection amount, where << 2 >> indicates the second cycle of the engine cycle TLlim: fuel injection amount at which the air-fuel ratio reaches the lean limit (lean limit injection amount) TRlim (i + 1): the next air-fuel ratio becomes the lean limit (1−α)... Not entering directly (1-β)... Not being removed Te <1> ′ ′... The air-fuel ratio becomes an air-fuel ratio richer than the lean limit TLlim. Value, where << 1 >> indicates the first cycle of the engine cycle 14.7 In the first step S1, the CPU 30 compares whether the ratio between the direct entry rate α and the carry-out rate β is greater or smaller than a set value (1.0 in this embodiment), and when α> β, While returning, α
When ≤β, the process proceeds to the next second step S2. Note that the above-described direct entry rate α and carry-out rate β are the engine water temperature tw and CE
= Engine load CE calculated by the formula of Q / Ne
The CPU 30 retrieves from.

In this embodiment, α ≦ β, in other words, α
/ Β ≦ 1, but α / β is not necessarily 1.0
The value may not be (set value) but may be set to a value close to 1.0, such as 1.1 or 0.9.

In the above-described second step S2, the CPU 30 determines the last throttle opening TVO (i-1) and the current throttle opening TV based on the input from the throttle sensor 21.
It is determined whether or not the difference ΔTVO from O (i), that is, the amount of change in the throttle opening is greater than a predetermined determination value. If ΔTVO <determination value in a steady state, the process returns to the first step S1, while ΔTV during transients such as acceleration / deceleration
If O ≧ determination value, the process proceeds to the next third step S3.

In the third step S3, the CPU 30 calculates the current (first cycle) wet-corrected injection amount Te << 1 >> in the same cylinder based on the following [Equation 4].

[0038]

(Equation 4)

Next, in a fourth step S4, the CPU 30 predicts and calculates the next (second cycle) post-wet correction injection amount Te << 2 >> (i + 1) based on the following [Equation 5]. It is assumed that the value of the basic injection amount Ta is the same as in the first cycle.

[0040]

(Equation 5)

In the above [Equation 5], (1-β) Tm indicates the amount not taken away, and Te << 1 >> (1-α) indicates the amount not directly entered.

Next, in a fifth step S5, the CPU 30 calculates the lean limit injection amount TLlim (the injection amount after the wet correction for each engine cycle is the basic injection amount Ta) based on the following [Equation 6]. Is calculated so as to converge to.

[0043]

(Equation 6)

Here, the above-described lean limit A / F is set to, for example, about 18 with respect to the stoichiometric air-fuel ratio of 14.7.

Next, in the sixth step S6, when the current fuel injection is executed at the lean limit injection amount TLlim, the CPU 30 sets the air-fuel ratio corresponding to the next fuel injection amount Te << 2 >> (i + 1) to the rich limit. Is determined by the following [Equation 7].

[0046]

(Equation 7)

A part of the denominator in the above [Equation 7], β
{TLlim (1-α) + (1-β) Tm} is (1
(Cycle cycle) is the amount removed from the intake pipe wall when fuel is injected at the lean limit injection amount TLlim. The rich limit A / F is, for example, about 1% with respect to the stoichiometric air-fuel ratio of 14.7.
Set to 1.

If it is determined that the control air-fuel ratio in the next (second cycle) is within the rich limit by the determination in the above-described sixth step S6, the process proceeds to the next seventh step S7, while the next (2 cycle) In the case of the NO determination that the control air-fuel ratio of the item 3) exceeds the rich limit, another eighth
Move to step S8.

In the above-described seventh switch S7, the CPU 30 sets the injection amount after the current wet correction so that the air-fuel ratio becomes the lean limit in anticipation that the next air-fuel ratio is within the rich limit. That is, the injection amount after the current wet correction is changed from the Te <1> in FIG. 5 to the lean limit injection amount TLlim.
And the injector 9 is driven with this value.

On the other hand, in the above-mentioned eighth step S8, the CPU
Numeral 30 designates a fuel injection amount (rich limit injection amount) TRlim (i + 1) at which the next air-fuel ratio becomes the rich limit based on the following [Equation 8] in order to cope with the next air-fuel ratio exceeding the rich limit. To calculate.

[0051]

(Equation 8)

Next, in a ninth step S9, the CPU 30 sets the injection amount after the current wet correction based on the following [Equation 9] to a value Te such that the air-fuel ratio becomes an air-fuel ratio richer than the lean limit TLlim. << 1 >>'is calculated.

[0053]

(Equation 9)

In the equation shown in [Equation 9], TRlim is substituted for Te << 2 >> of the above-mentioned [Equation 5], Te << 1 >>'is substituted for Te << 1 >>, and this Te << 1 >>'Is converted into an expression for obtaining'.

Next, in a tenth step S10, the CPU 30
Anticipating that the next air-fuel ratio will exceed the rich limit,
The value Te already calculated in the ninth step S9 described above
The injector 9 is driven by << 1 >>'(a value corrected so that the next air-fuel ratio does not exceed the rich limit).

In short, in the transient state in which the change in the fuel injection amount is large, the injection amount after the wet correction for each engine cycle is changed in FIG. 5 in anticipation of the injection amount Te <2> to be injected next time (second cycle). The injection amount after the current wet correction is changed from Te << 1 >> to T by the correction means (refer to the fifth step S5 in FIG. 4) so as to converge to the basic injection amount Ta in the time chart.
Since the correction is made to Llim (see FIG. 5), there is an effect that vibration (so-called turbulence) of the control system can be prevented, and combustion fluctuation and deterioration of engine operability can be reliably prevented.

Although the air-fuel ratio slightly deviates from the stoichiometric air-fuel ratio by the above-described fuel injection amount control, there is no problem because it is a very short time during the transition. That is, the above-described control is a control in which the vibration convergence of the control system is prioritized over the control in which A / F = 14.7.

In addition, the third determination means (see the sixth step S6 in FIG. 4) determines the injection amount after the current wet correction by the correction means (see the fifth step S5 in FIG. 4) (this embodiment). TLlim) with respect to the next air-fuel ratio (control A / F) based on the next wet-corrected injection amount Te << 2 >> predicted and calculated by the prediction calculation means (see the fourth step S4 in FIG. 4). It is determined whether or not the air-fuel ratio exceeds the rich limit TRlim. When the next air-fuel ratio exceeds the rich limit based on the determination result of the third determining means (see the sixth step S6 in FIG. 4), the first setting means ( In the tenth step S10 in FIG. 4), the injection amount after the current wet correction is changed to the air-fuel ratio Te whose air-fuel ratio is richer than the lean limit TLlim.
<< 1 >>'is set, and control is performed so that the next air-fuel ratio does not exceed the rich limit TRlim.

When the next air-fuel ratio is within the rich limit based on the determination result of the third determining means (see the sixth step S6 in FIG. 4), the second setting means (see the seventh step S7 in FIG. 4). ) Sets the injection amount after the current wet correction so that the air-fuel ratio becomes the lean limit TLlim.

As described above, since the vibration of the control system is suppressed within the rich limit and the lean limit of the air-fuel ratio, it is possible to prevent the engine from misfiring due to over-rich and over-lean.

In correspondence between the configuration of the present invention and the above-described embodiment, the first determining means of the present invention is the CPU of the embodiment.
The second determining means corresponds to the second step S2 controlled by the CPU 30, and the prediction calculating means corresponds to the fourth step S4 controlled by the CPU 30. The means is a CPU 30
The third determining means corresponds to a fifth step S5 under the control of the CPU 30,
The first setting means corresponds to the tenth step S10 under the control of the CPU 30, and the second setting means corresponds to the seventh step S7 under the control of the CPU 30, but the present invention is limited to only the configuration of the above-described embodiment. However, for example, in the case of split injection in which two fuel injections are performed within one cycle of the engine, the correction may be performed at any of the two divided injections. It can be applied to such a split injection.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a fuel injection amount control device for an engine according to the present invention.

FIG. 2 is an explanatory diagram showing a fuel injection state and a carried amount.

FIG. 3 is a control circuit block diagram.

FIG. 4 is a flowchart showing in-maniwet correction.

FIG. 5 is a time chart showing in-maniwet correction.

FIG. 6 is an explanatory diagram showing a direct entry rate and a carry-out rate.

FIG. 7 is a diagram corresponding to claims.

[Explanation of symbols]

 9 Injector 23 Combustion chamber S1 First determining means S2 Second determining means S3 Computing means S4 Predicting computing means S5 Correcting means S6 Third determining means S7 Second setting means S10 First setting means

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-58-8238 (JP, A) JP-A-4-66740 (JP, A) JP-A-2-173334 (JP, A) JP-A-4- 292544 (JP, A) JP-A-3-213634 (JP, A) JP-A-3-130546 (JP, A) JP-A-3-121224 (JP, A) (58) Fields investigated (Int. ⁷ , DB name) F02D 41/04 330 F02D 41/10 330 F02D 41/12 330

Claims (2)

(57) [Claims] 1. An arithmetic unit for calculating an amount of fuel injected from an injector, wherein the arithmetic unit includes a portion of fuel injected from the injector that adheres to a wall surface of an intake pipe and an amount of fuel that is injected from the injector. Wet correction means for correcting the fuel injection amount based on a portion of the fuel directly entering the combustion chamber and a portion of the fuel already attached to the intake pipe wall being removed into the combustion chamber; and A fuel injection amount control device for an engine having a post-correction calculating means for calculating an injection amount corrected by the means, wherein the fuel injection amount control device is a fuel injection amount control device, the fuel injection amount control device comprising: First determining means for determining whether or not the ratio of the carry-off rate, which is the ratio of the amount of the wall surface adhering to the carry-on portion already adhered to the intake pipe wall surface, is greater than a set value;
Second to determine whether the fuel injection amount change is rapid acceleration or deceleration
When the ratio of the carry-out ratio to the direct entry ratio is larger than the set value and the vehicle is suddenly accelerated or decelerated based on the determination results of the determination unit and the first and second determination units, the current cylinder Predicting means for predicting and calculating the injection amount after the next wet correction from the injection amount after the wet correction, and the injection amount after the wet correction for each engine cycle converges to the basic injection amount based on the calculation result of the prediction calculating means. And a correction means for correcting the injection amount after the current wet correction. 2. The fuel injection amount after the current wet correction by the correction means exceeds the rich limit with respect to the next air-fuel ratio based on the next fuel injection amount after the wet correction predicted and calculated by the prediction calculation means. When the next air-fuel ratio exceeds the rich limit based on the determination result of the third determination unit that determines whether or not the air-fuel ratio is greater than the lean limit, When the next air-fuel ratio is within the rich limit based on the determination result of the first setting unit that sets the air-fuel ratio on the rich side and the determination result of the third determination unit, the injection amount after the current wet correction is set to the air-fuel ratio. 2. The fuel injection amount control device for an engine according to claim 1, further comprising second setting means for setting the fuel ratio to a lean limit.