JP2003328817A - Control system for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stably operate an internal combustion engine in an idling state after start. <P>SOLUTION: Engine speed control is executed to increase an intake quantity at a predetermined intake increase rate if an engine speed N is lower than a target engine speed TN after a start of the internal combustion engine, whose engine operation state is an idling state, and to reduce an intake quantity at a predetermined intake reduction rate if the engine speed is higher than the target engine speed after a start of the internal combustion engine, whose engine operation state is an idling state. During execution of the engine speed control, when a fluctuation width ΔN of the engine speed exceeds an allowable fluctuation width ΔNth as the intake quantity is increased, the intake increase rate is reduced and the intake quantity is increased at the reduced intake increase rate. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an internal combustion engine.

[0002]

2. Description of the Related Art As one of internal combustion engines, a throttle valve for controlling the amount of air (intake air) sucked into a combustion chamber is provided, and fuel is supplied in accordance with the intake air amount so that the air-fuel ratio becomes a target air-fuel ratio. There is known an internal combustion engine in which fuel is injected from an injection valve into intake air. Immediately after such an internal combustion engine is started, the temperature of the internal combustion engine is low, and thus it is difficult for the fuel to burn in the combustion chamber. In such a situation, immediately after the internal combustion engine is started (engine startup), the operating state of the internal combustion engine (engine operating state) is in a so-called idling operating state in which the load required for the internal combustion engine (engine required load) is extremely small. Since the amount of fuel injected from the fuel injection valve into the intake air (fuel injection amount) is also extremely small,
The fuel is very difficult to burn in the combustion chamber, and as a result, the operation of the internal combustion engine is not stable.

Therefore, in order to avoid the instability of the operation of the internal combustion engine immediately after the engine is started, when the engine operating state is in the idling operating state (hereinafter referred to as the idling operating state after starting) immediately after the engine starting. In advance, the minimum required engine speed to stabilize the operation of the internal combustion engine is preset as a target engine speed (hereinafter, referred to as a target idle speed), and after starting, in an idling operation state,
When the engine speed is lower than the target idle speed, a technique of gradually increasing the opening degree of the throttle valve and thus gradually increasing the intake air amount is disclosed in Japanese Unexamined Patent Publication
It is disclosed in Japanese Patent Publication No. 001-9081.

According to the technique described in the publication, when the engine speed is lower than the target idle speed under the idling operation state after starting, the intake air amount is gradually increased, so that the fuel injection amount is gradually increased. Much, and thus,
The output load of the internal combustion engine (engine output load) gradually increases, and as a result, the engine speed increases toward the target idle speed. Of course, in the publication, when the engine speed becomes higher than the target idle speed, the opening of the throttle valve is gradually decreased, and thus the intake air amount is gradually decreased. By repeatedly executing the opening control of the throttle valve, the engine speed converges to the target idle speed and is maintained at the target idle speed under the idling operation state after the start.

[0005]

In the idling operation state after starting, it is required that the engine speed converges to the target idle speed as quickly as possible. In general, if the degree of opening of the throttle valve is gradually increased or gradually decreased, it is possible to converge the engine speed to the target idle speed more quickly if it is as large as possible within an appropriate range. Therefore, in order to converge the engine speed to the target idle speed as quickly as possible, the degree of gradually increasing or gradually decreasing the opening of the throttle valve is appropriate. The range tends to be set as large as possible.

However, in reality, even if the opening degree of the throttle valve is increased, the engine speed does not immediately increase uniformly as expected. That is, even if the opening degree of the throttle valve is increased, the intake amount is increased, and the fuel injection amount is increased, it is still difficult to burn the fuel in the combustion chamber, and if the fuel injection amount is increased,
Some of the fuel will not be vaporized and dispersed during intake air, and will be attached to the wall surface of the intake passage, etc., and as a result, the engine speed will increase uniformly as expected. However, it may fluctuate significantly up and down. In this case, the operation of the internal combustion engine is not stable. Therefore, an object of the present invention is to stably operate the internal combustion engine under the idling operation state after starting.

[0007]

In order to solve the above-mentioned problems, in the first invention, an intake air amount control means capable of controlling the intake air amount sucked into a combustion chamber of an internal combustion engine and an air-fuel ratio are set in advance. A fuel injection means for injecting an amount of fuel corresponding to the amount of intake air into the intake air that is taken into the combustion chamber so that the target air-fuel ratio is set to a predetermined target, and the engine operating state after the internal combustion engine is started When the engine speed is smaller than the predetermined target engine speed in the idling operation state, the intake amount is increased by the predetermined intake increase rate by the intake amount control means, while the internal combustion engine If the engine speed is higher than the target engine speed when the engine operating condition is in the idling operating condition after the start, the intake amount is reduced by the intake reduction ratio set in advance by the intake amount control means. In an internal combustion engine control device adapted to execute engine speed control, the engine speed control is performed while the intake air amount is increased by the intake air amount control means during execution of the engine speed control. When the increase / decrease range becomes larger than the predetermined allowable increase / decrease range,
The predetermined intake air increase rate is reduced, and the intake air amount control means increases the intake air amount with the reduced intake air increase rate. Here, the intake air amount control means, the fuel injection means, a predetermined target engine speed, and
The engine speed control corresponds to the throttle valve, the fuel injection valve, the target idle speed, and the IS control in the embodiments described later, respectively.

According to a second aspect of the invention, in the first aspect of the present invention, during the execution of the engine speed control, the increase / decrease range of the engine speed is increased while the intake air amount is increased by the intake air amount control means. When it becomes smaller than the permissible increase / decrease range, the predetermined intake increase rate is increased, and the intake quantity is increased by the increased intake increase rate, and thus the predetermined intake increase rate is increased. The ratio of increasing the intake air intake increase ratio is limited to a predetermined upper limit value.

[0009] Here, if the intake air increase rate is suddenly increased, the intake air amount is increased suddenly, so that there is a high possibility that the engine speed fluctuates significantly up and down. However, in the second aspect of the invention, the rate at which the intake air increase rate is increased is limited to a certain upper limit value, so even if the intake air increase rate is increased, the engine speed may fluctuate significantly up and down. Will be lower.

In a third aspect based on the first aspect, the fuel injection amount injected from the fuel injection means is increased while the intake air amount control means is increasing the intake air quantity during execution of the engine speed control. The fuel injection amount is reduced at a predetermined fuel increase rate, while the fuel injection amount is increased at a predetermined fuel increase rate while the intake air amount control means is reducing the intake air amount during execution of the engine speed control. The predetermined fuel decrease rate is increased when the predetermined intake increase rate is decreased during execution of the engine speed control.

According to this, the fuel injection amount is increased by the reduction amount of the intake air amount, and the increase ratio of the fuel injection amount is increased by the reduction amount of the intake air amount. It When the fuel injection amount increases, the engine speed increases, and when the fuel injection amount increases at a high rate, the engine speed increase rate also increases. Therefore,
According to the third aspect of the invention, the engine speed quickly reaches the target engine speed when the engine operating state is in the idling operating state after the internal combustion engine is started, even if the increase rate of the intake air amount is reduced. It will be.

According to a fourth aspect of the present invention, in the third aspect of the present invention, during the execution of the engine speed control, while the intake air amount is being increased by the intake air amount control means, the increase / decrease range of the engine speed is allowed. When it becomes smaller than the increase / decrease range, the predetermined intake increase rate is increased,
The intake amount is increased by the intake amount control means with the increased intake increasing ratio, and at the same time, the predetermined fuel decrease ratio is decreased, and the fuel injection amount is decreased with the decreased fuel decrease ratio. As a result, the rate at which the predetermined increase rate of intake air is increased is limited to a predetermined upper limit value, and the rate at which the predetermined fuel decrease rate is reduced is predetermined. Is limited to the upper limit.

Here, if the intake air increase ratio is increased at once, the intake air amount increases at once, so the possibility that the engine speed will fluctuate significantly up and down increases. However, in the fourth aspect of the invention, the rate at which the intake air increase rate is increased is limited to a certain upper limit value. Therefore, even if the intake air increase rate is increased, the engine rotational speed may fluctuate significantly up and down. Will be lower.

In order to solve the above problems, in the fifth aspect of the invention, an intake air amount control means capable of controlling the intake air amount taken into the combustion chamber of the internal combustion engine, and a target air-fuel ratio having a predetermined air-fuel ratio. A fuel injection means for injecting an amount of fuel corresponding to the intake air amount into the intake air sucked into the combustion chamber, and an ignition means for igniting the fuel sucked into the combustion chamber, If the engine speed is smaller than the predetermined target engine speed when the engine operating state is in the idling operating state after starting the internal combustion engine, the intake amount is increased by the intake amount control means, while the internal combustion engine If the engine speed is higher than the target engine speed when the engine operating condition is in the idling operating condition after the engine is started, the intake amount is reduced by a predetermined intake reduction rate by the intake amount control means. In an internal combustion engine control device adapted to execute engine speed control, the engine speed control is performed while the intake air amount is increased by the intake air amount control means during execution of the engine speed control. When the increase / decrease range becomes larger than the predetermined allowable increase / decrease range,
The increase of the intake air amount by the intake air amount control means is stopped, and at the same time, the fuel ignition timing by the ignition means is changed so as to promote the combustion of fuel. Here, in the present invention, the intake air amount control means, the fuel injection means, the ignition means, the predetermined target engine speed, and the engine speed control are respectively the throttle valve, the fuel injection valve, and the ignition in the embodiments described later. It corresponds to the plug, the target idle speed, and the IS control.

In a sixth aspect based on the fifth aspect, the increase / decrease range of the engine speed is the allowable increase / decrease range while the intake amount is being increased by the intake amount control means during execution of the engine speed control. When the engine speed is smaller than the predetermined determination value when the engine speed becomes larger than the predetermined value, the increase of the intake quantity by the intake quantity control means is stopped and the intake quantity is maintained at the current intake quantity. During the execution of the engine speed control, the engine speed increases when the intake air amount is increased by the intake air amount control means when the increase / decrease range of the engine speed becomes larger than the allowable increase / decrease range. If it is larger than the above value, the increase of the intake air amount by the intake air amount control means is stopped and the intake air amount is reduced. According to this, it is possible to quickly reach the target engine speed while suppressing the engine speed from fluctuating up and down during execution of the engine speed control.

[0016]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below with reference to the drawings. FIG. 1 shows an overall view of an internal combustion engine including a control device according to a first embodiment of the present invention. In FIG. 1, 1 is an engine body, 2 is a cylinder block, 3 is a cylinder head, 4 is a combustion chamber, 5 is a piston, 6 is an intake port, 7 is an intake valve, 8 is an exhaust port, 9 is an exhaust valve, and 10 is The spark plug is shown. A cooling water passage 11 for cooling the internal combustion engine is formed in the cylinder block 2. Further, a water temperature sensor 12 for detecting the temperature of the cooling water in the cooling water passage 11 is attached to the cylinder block 2.

A fuel injection valve 13 is attached to the intake port 6. Further, the intake port 6 has an intake passage 1
4 is connected. A surge tank 15 is formed in the intake passage 14. A throttle valve 16 is arranged in the intake passage 14 upstream of the surge tank 15. A step motor 17 is connected to the throttle valve 16. An air cleaner 18 is arranged in the intake passage 14 upstream of the throttle valve 16. Further, an air flow meter 19 is attached to the intake passage 14 upstream of the throttle valve 16 and downstream of the air cleaner 18.

Outputs of the water temperature sensor 12 and the air flow meter 19 are input to an electronic control circuit (ECU) 20. The ECU 20 can estimate the temperature of the internal combustion engine based on the output of the water temperature sensor 12, and can calculate the amount of air (intake air) taken into the combustion chamber 4 based on the output of the air flow meter 19. On the other hand, the spark plug 10,
The fuel injection valve 13 and the step motor 17 for driving the throttle valve 16 are connected to the ECU 20, and their operations are controlled by the ECU 20. Further, the internal combustion engine has a crank angle sensor 2 for detecting a crank angle.
1, the output of this crank angle sensor 21 is ECU
It is input to 20. The ECU 20 can calculate the engine speed based on the output of the crank angle sensor 21. Further, the internal combustion engine is equipped with a load sensor 23 for detecting the load (engine required load) required of the internal combustion engine by detecting the depression amount of the accelerator pedal 22, and the output of the load sensor 23 is also output to the ECU 20. Is entered.

An exhaust passage 24 is connected to the exhaust port 8, and an oxygen sensor 25 for detecting the oxygen concentration in the exhaust gas discharged from the combustion chamber 4 is attached to the exhaust passage 24. Has been. This oxygen sensor 25
Is output to the ECU 20. The ECU 20 can calculate the air-fuel ratio in the combustion chamber 4 based on the output of the oxygen sensor 25.

In the internal combustion engine of the first embodiment, the amount of air (intake air) taken into the combustion chamber 4 is determined as the target intake air amount so that the required output can be output from the internal combustion engine. It Specifically, the target intake amount increases as the engine speed increases, and the target intake amount increases as the engine required load increases. In the first embodiment, the target intake air amount TGa is prestored in the ECU 20 in the form of a map as a function of the engine speed N and the required engine load L as shown in FIG. During operation, the target intake air amount TGa is read from the map of FIG. 2 based on the engine speed N and the engine required load L, and the amount of air taken into the combustion chamber 4 (intake air amount) is the target intake air amount. TGa
The opening degree of the throttle valve 16 (throttle opening degree) is controlled by the step motor 17 so that If the target intake air amount TGa is set large, the opening degree of the throttle valve 16 is increased. At this time, the intake air amount increases, and conversely, if the target intake air amount TGa is set small,
Since the opening degree of the throttle valve 16 is reduced, the intake amount is reduced at this time.

In the internal combustion engine of the first embodiment, the fuel injection valve 13 is injected into the intake air in accordance with the intake air amount and the target air-fuel ratio so that the air-fuel ratio in the combustion chamber 4 becomes the target air-fuel ratio. A target amount of fuel (target fuel injection amount) is determined. Specifically, the target fuel injection amount is increased as the intake air amount is increased, and the target fuel injection amount is decreased as the target air-fuel ratio increases, that is, as the lean degree of the target air-fuel ratio increases. In the first embodiment, the target fuel injection amount TGi
Is the intake air amount Ga and the air-fuel ratio A as shown in FIG.
Is stored in the ECU 20 in the form of a map in advance as a function of / F, and the target fuel injection amount TGi is calculated from the map of FIG. 3 based on the intake air amount Ga and the air-fuel ratio A / F during operation of the internal combustion engine. The fuel injection valve 13 is read so that the fuel of the target fuel injection amount TGi is injected from the fuel injection valve 13.
Is controlled.

In the first embodiment, basically, the target intake air amount TGa is set as described above, and the operation of the step motor 17 for driving the throttle valve 16 is performed so that the intake air amount becomes the target intake air amount TGa. Is controlled. However,
In the first embodiment, the operating state of the internal combustion engine (engine operating state) is the depression amount of the accelerator pedal 22 until the predetermined period elapses (engine starting) from the start of the internal combustion engine (engine startup). When the engine is in a so-called idling operation state in which the required engine load is extremely small, the target intake air amount is set in a different form. Hereinafter, a method of setting the target intake air amount when the engine is started and the engine operating state is in the idling operating state (hereinafter, referred to as the post-start idling operating state) will be described.

In the idling operation state after starting, there is a minimum engine speed necessary for operating the internal combustion engine stably. However, when the engine is started, the temperature of the internal combustion engine (engine temperature) is often low,
When the engine temperature is low as described above, it is difficult for the fuel to burn in the combustion chamber 4, and the engine speed may be lower than the minimum engine speed required to stably operate the internal combustion engine. There is.

Therefore, in the first embodiment, the minimum engine speed required for operating the internal combustion engine stably in the idling operation state after starting is predetermined as the target engine speed (target idle speed). It has been done. And, under the idling operation state after starting,
The control described below (hereinafter referred to as IS control) is executed. That is, in the IS control of the first embodiment, first, the target intake air amount TGa is read from the map of FIG. 2 based on the engine speed N and the engine load demand L, but the current engine speed is the target idle speed. When it is less than the number, the target intake air amount TGa is gradually corrected to the increasing amount side. In the first embodiment, when the target intake air amount TGa is gradually corrected to the increase side, the intake amount gradually increases, and therefore the fuel injection amount also gradually increases, so the engine speed gradually increases.

On the other hand, in the IS control of the first embodiment, the target intake air amount TGa is corrected to the decrease amount side when the current engine speed exceeds the target idle speed under the idling operation state after starting. It In the first embodiment, when the target intake air amount TGa is gradually corrected to the decrease amount side,
The intake air amount gradually decreases, and therefore, the fuel injection amount also gradually decreases, so that the engine speed gradually decreases.

By repeating such correction of the target intake air amount, the engine speed is maintained at the target idle speed under the idling operation state after the start.

During execution of the IS control, the intake air amount is gradually increased while the engine speed is lower than the target idle speed. However, if the rate of increase of the intake air amount at this time is too large, the engine speed may fluctuate significantly up and down for the following reasons. That is,
When the intake air amount is increased, the fuel injection amount is also increased accordingly. However, if the temperature of the internal combustion engine (engine temperature) is low, the fuel is difficult to burn in the combustion chamber, so the fuel injection Even if the amount is increased, not all fuel will burn. Further, since the opening degree of the throttle valve 16 is increased when the intake amount is increased, the degree of negative pressure in the intake passage 14 downstream of the throttle valve 16 is small, and therefore, the fuel injection valve 13 injects into the intake air. The fuel is not easily vaporized, and a part of the fuel remains attached to the wall surface of the intake passage 14. For this reason, the air-fuel ratio is not maintained in the vicinity of the target air-fuel ratio, and therefore the output load of the internal combustion engine is not stable, so the engine speed fluctuates significantly up and down.

Therefore, in the first embodiment, during execution of the IS control, the increase / decrease range of the engine speed (hereinafter referred to as the rotation speed increase / decrease range) is monitored while the target intake air amount is gradually increased. The rate at which the target intake air amount is increased (hereinafter referred to as the intake air increase rate) is controlled in accordance with the rotation speed increase / decrease range. Specifically, a reference ratio for increasing the target intake air amount (hereinafter referred to as a reference intake air correction gain) is set in advance, and a value for correcting the reference intake air correction gain (hereinafter, an intake gain correction coefficient). Is calculated according to the increase / decrease range of engine speed (rotation speed increase / decrease range), and the value obtained by multiplying the reference intake correction gain by this intake gain correction coefficient is referred to as the intake correction gain I will call it).

In the first embodiment, as shown in FIG.
Intake gain correction coefficient ΔK as a function of rotation speed increase / decrease range ΔN
ga is predetermined. In the relationship shown in FIG. 4, the intake gain correction coefficient ΔKga remains 1.0 until the rotation speed increase / decrease range ΔN increases from zero to reach the first value ΔN1. The value gradually decreases from the point where it exceeds the value ΔN1 of 1, and further becomes constant at the smallest value from when the rotation speed increase / decrease range ΔN exceeds the second value ΔN2 (> ΔN1).

Therefore, according to the first embodiment, when the rotation speed increase / decrease range ΔN exceeds a certain value ΔN1, the intake gain correction coefficient ΔKga is made smaller than 1.0, resulting in the target intake air amount. Since the rate of increase in the engine speed is reduced, the fluctuation in the engine speed gradually subsides. Further, in this way, as the increase / decrease in the engine speed gradually subsides, the intake gain correction coefficient ΔKga increases toward 1.0, and as a result, the intake increase rate increases, so that the engine speed as a whole is increased. Will quickly reach the target idle speed.

By the way, in the first embodiment, during execution of the IS control, the intake gain correction coefficient ΔKga is gradually increased toward 1.0 as the rotational speed increase / decrease range ΔN is gradually decreased to increase the intake air. Although the ratio is increased, the rotation speed increase / decrease range ΔN becomes large again even if the ratio by which the intake air increase ratio is increased is too large.

Therefore, in the first embodiment, during execution of the IS control, the rate at which the intake gain correction coefficient ΔKga is increased exceeds a predetermined upper limit value, and as a result,
If the rate at which the increase rate of the intake air amount is increased exceeds the allowable upper limit value, the intake gain correction coefficient ΔKga
Is limited to the upper limit value, and as a result, the rate at which the increase rate of the target intake air amount is increased is limited to the allowable upper limit value. According to this, during execution of the IS control, it is possible to prevent the rotation speed increase / decrease range ΔN from increasing while the increase rate of the target intake air amount is increased.

In the first embodiment, while the engine speed N is higher than the target idle speed TN, the target intake air amount TGa is gradually reduced at a predetermined intake air reduction rate. Of course, when the increase / decrease width ΔN of the engine speed N becomes larger than the predetermined increase / decrease width ΔNth while the target intake air amount TGa is gradually decreased at the predetermined intake air reduction rate, the rotation speed is increased. Increase / decrease range Δ
Based on N, the intake correction gain ΔKga is read from the relationship of FIG. 4, the predetermined intake reduction ratio is multiplied by this intake correction gain ΔKga to reduce the intake reduction ratio, and the target intake reduction is performed with this reduced intake reduction ratio. The amount TGa may be gradually reduced.

FIG. 5 is a time chart showing an example of changes in engine speed and the like when the IS control is executed according to the first embodiment. In FIG. 5, (A) shows the transition of the engine speed N, and (B) shows the target intake air amount TGa.
, (C) shows the change of the intake correction gain Kga, and (D) shows the change of the intake gain correction coefficient ΔKga.

When the internal combustion engine is started at time t0, the engine speed N once exceeds the target idle speed TN and reaches a peak, and then at time t6, falls below the target idle speed TN. Substantially, the correction of the target intake air amount TGa is started from here. That is, time t6
In the above, since the engine speed N is lower than the target idle speed TN, the intake correction gain Kga is increased from 0. At this time, however, the vertical fluctuation of the engine speed N (the speed increase / decrease range ΔN) is relatively small. , Intake gain correction coefficient ΔKg
a is maintained at 1.0, and as a result, the intake correction gain Kga is set to the reference intake correction gain value RKga. Here, the target intake air amount TGa is calculated by adding this intake air correction gain Kga to the target intake air amount TGa read from the map of FIG. 2. Therefore, when the intake air correction gain Kga is increased, the target intake air amount TGa is gradually increased. Be increased.

At time t9, when the engine speed N starts to fluctuate relatively upward and downward, the intake gain correction coefficient ΔK
ga decreases from 1.0 at once. Since the intake correction gain Kga is calculated by multiplying the reference intake correction gain RKga by this intake gain correction coefficient ΔKga, the intake correction gain Kga also decreases at once. After the time t9, while the increase / decrease range ΔN of the engine speed is relatively large, the target intake air amount TGa is gradually increased, but the increase rate is smaller than the increase rate from the time t6 to the time t9.

After the time t9, the increase / decrease width ΔN of the engine speed gradually decreases, so that the intake gain correction coefficient Δ
Kga is gradually increased toward 1.0. Therefore, the intake correction gain Kga is also set to the reference intake correction gain RKg.
It gradually increases toward a. Of course, during this period, the target intake air amount TGa also gradually increases, and the engine speed N also gradually increases toward the target idle speed TN.

At time t13, when the engine speed N reaches the target idle speed TN, no more
Since it is not necessary to increase the target intake air amount TGa, the intake air correction gain Kga is set to zero. Since the increase / decrease width ΔN of the engine speed is small after time t13, the intake gain correction coefficient ΔKga becomes 1.0.

FIG. 6 shows a flowchart of a routine executed to set a target intake air amount in the IS control according to the first embodiment. In the routine of FIG. 6,
First, at step 10, it is judged if the flag Fn indicating that the engine operating state is the idling operating state after starting is set (Fn = 1). When it is determined in step 10 that Fn = 1, the routine proceeds to step 11.

In step 11, the target intake air amount TGa is read from the map of FIG. 2 when the routine first proceeds to step 11 in the IS control once, while the routine proceeds to step 11 in the IS control once. Is the second time or more, the target intake air amount TGa set in the previous routine is read.

Next, at step 12, the engine speed N is smaller than the target idle speed TN (N <T
N) or not. In step 12, N <
If it is determined to be TN, the routine proceeds to step 13 and the engine speed increase / decrease range (rotation speed increase / decrease range) Δ
N is larger than a predetermined increase / decrease width ΔNth (ΔN
> ΔNth) is determined.

When it is judged at step 13 that ΔN> ΔNth, the routine proceeds to step 14, where the intake correction gain Kga is calculated according to the flowchart of FIG. 7, and then at step 15, it is read at step 11. A value obtained by adding the intake correction gain Kga calculated in step 14 to the target intake air amount TGa is set as the current target intake air amount TGa. On the other hand, if it is determined in step 13 that ΔN ≦ ΔNth, the routine proceeds to step 17, where step 1
A value obtained by adding the reference intake air correction gain RKga to the target intake air amount TGa read in 1 is set as the current target intake air amount TGa.

On the other hand, when it is judged at step 12 that N ≧ TN, the routine proceeds to step 16, where the target intake air amount TGa read at step 11 is obtained.
A value obtained by subtracting the reference intake air correction gain RKga from is set as the current target intake air amount. Note that step 10
In, when it is determined that Fn = 0, the routine ends.

The predetermined increase / decrease width ΔNth in the flowchart of FIG. 6 substantially corresponds to the first value ΔN1 in FIG.

FIG. 7 shows a flow chart of a routine executed to calculate the intake correction gain according to the first embodiment. The routine of FIG. 7 is a routine executed as step 14 of FIG. In the routine of FIG. 7, first, at step 20, the intake correction gain ΔKga is calculated according to the flowchart of FIG. 8, and then at step 21, the reference intake correction gain RK is calculated.
Ga is the intake gain correction coefficient Δ calculated in step 21.
A value obtained by multiplying Kga is set as the current intake correction gain Kga.

FIG. 8 shows the intake gain according to the first embodiment.
Flow of routine executed to calculate the correction coefficient
The chart is shown. The routine shown in FIG.
This is a routine executed as step 20. Figure 8
In Chin, first, in step 30, shown in FIG.
The intake gain correction coefficient ΔKga is read from the relationship
Then, in step 31, read in step 30
The included intake gain correction coefficient ΔKga is in the previous routine.
Intake gain correction coefficient ΔKga set in advance _n-1Than
Is greater than a predetermined value (upper limit value) X (ΔKga−ΔKg
au_n-1> X). In step 31
And ΔKga-ΔKgau_n-1> X
If so, the routine proceeds to step 32, where the previous
Intake gain correction coefficient ΔKga set in the routine
_n-1The value obtained by adding a predetermined value (upper limit) X to
Correction coefficient ΔKga_nIs set as.

On the other hand, in step 31, ΔKga-
When it is determined that ΔKgau _n-1 ≦ X, the routine proceeds to step 33, the intake gain correction coefficient DerutaKga read in step 30 is set as it is as the current intake gain correction coefficient ΔKga _n.

In the first embodiment, the temperature of the internal combustion engine may also be used when determining that the engine operating state is the idling operating state after starting. That is, in addition to the condition for determining that the engine operating condition is the post-start idling operating condition in the first embodiment, a condition that the temperature of the internal combustion engine is lower than a predetermined temperature may be added.

Incidentally, there is a demand for the IS control to converge the engine speed to the target idle speed as quickly as possible. Therefore, in the second embodiment, the first
Similar to the embodiment, when the engine speed is increased toward the target idle speed while the IS control is being executed, the target intake air amount T
Although the intake correction gain Kga corresponding to the increase rate of Ga is reduced, the target fuel injection amount TGi is increased according to the degree to which the intake correction gain Kga is reduced. Specifically, a ratio (hereinafter referred to as a reference fuel correction gain) serving as a reference for increasing the target fuel injection amount is set in advance, and a value for correcting the reference fuel correction gain (hereinafter referred to as fuel gain correction). (Hereinafter referred to as a coefficient) according to the rotation speed increase / decrease range ΔN, and a value obtained by multiplying the reference fuel correction gain by this fuel gain correction coefficient is used as a fuel correction gain (hereinafter, referred to as a target fuel injection amount increase rate). I have to.

In the second embodiment, as shown in FIG. 9A, the intake gain correction coefficient ΔKga is predetermined as a function of the rotation speed increase / decrease width ΔN, and as shown in FIG. 9B. , The fuel gain correction coefficient ΔKgi is defined as a function of the rotation speed increase / decrease width ΔN. The relationship shown in FIG. 9 (A) is the same as the relationship shown in FIG. On the other hand, FIG.
In the relationship shown in (B), the fuel gain correction coefficient ΔKgi
Means that the rotation speed increase / decrease width ΔN increases from zero and the first value ΔN1
Until 1.0, the rotation speed increase / decrease range ΔN gradually increases from the point where it exceeds the first value ΔN1,
Further, the rotation speed increase / decrease range ΔN is the second value ΔN2 (> ΔN
It becomes constant with the largest value from the point where it exceeds 1).

Therefore, according to the second embodiment, when the rotation speed increase / decrease width ΔN exceeds a certain value ΔN1, the intake gain correction coefficient ΔKga is made smaller than 1.0, and as a result, the target intake air amount is increased. The increase rate of the target intake air amount is reduced, and according to this, the time taken until the engine speed reaches the target idle speed becomes longer. However, in the second embodiment, the increase rate of the target intake air amount is decreased. In accordance with, the fuel gain correction coefficient ΔKgi is made larger than 1.0,
Then, the increase rate of the target fuel injection amount is increased, and as a result, the target fuel injection amount is increased according to the degree to which the increase rate of the target intake air amount is decreased. The rotation speed will be reached quickly.

By the way, in the second embodiment, during execution of the IS control, the intake gain correction coefficient ΔKga is gradually increased toward 1.0 as the rotational speed increase / decrease width ΔN is gradually decreased, and the target intake air is increased. As the rate of increase in the amount is increased, the fuel gain correction coefficient ΔKgi is 1.0
The target fuel injection amount increase rate is gradually decreased toward the target. However, even if the target intake air amount increase rate is increased or the target fuel injection amount decrease rate is too large, the rotation speed increases. The number increase / decrease width ΔN becomes large again.

In the second embodiment, as in the first embodiment, when the intake gain correction coefficient ΔKga is increased during execution of the IS control, it exceeds a predetermined upper limit value. Is the intake gain correction coefficient ΔKg
a is limited to the upper limit value, and as a result, the rate at which the increase rate of the target intake air amount is increased is limited to the allowable upper limit value. Further, in the second embodiment, during execution of the IS control, the rate at which the fuel gain correction coefficient ΔKgi is reduced exceeds the predetermined upper limit value, and as a result, the increase rate of the target fuel injection amount is reduced. If the percentage exceeds the allowable upper limit,
The fuel gain correction coefficient ΔKgi is limited to its upper limit value,
As a result, the rate at which the increase rate of the target fuel injection amount is reduced is limited to the allowable upper limit value.
According to this, during execution of the IS control, it is possible to prevent the rotation speed increase / decrease range ΔN from increasing while the increase rate of the target intake air amount is increased and the increase rate of the target fuel injection amount is decreased. Will be done.

FIG. 10 is a time chart showing an example of changes in the engine speed and the like when the IS control is executed according to the second embodiment. In FIG.
(A) shows the transition of the engine speed N, (B) shows the transition of the target intake air amount TGa, and (C) shows the intake correction gain Kga.
, (D) shows the transition of the intake gain correction coefficient ΔKga, (E) shows the transition of the target fuel injection amount TGi, (F) shows the transition of the fuel correction gain Kgi,
(G) shows the fuel gain correction coefficient ΔKgi.

When the internal combustion engine is started at time t0, the engine speed N once exceeds the target idle speed TN and reaches a peak, and then at time t3, falls below the target idle speed TN. Substantially, the correction of the target intake air amount TGa is started from here. That is, time t3
In the above, since the engine speed N is lower than the target idle speed TN, the intake correction gain Kga is increased from zero. At this time, however, the vertical fluctuation of the engine speed N (the speed increase / decrease range ΔN) is relatively small. , Intake gain correction coefficient ΔKg
a is maintained at 1.0, and as a result, the intake correction gain Kga is set to the reference intake correction gain RKga. Here, the target intake air amount TGa is calculated by adding this intake air correction gain Kga to the target intake air amount TGa read from the map of FIG. 2. Therefore, when the intake air correction gain Kga is increased, the target intake air amount TGa is gradually increased. Be increased.

On the other hand, after the time t3, since the target intake air amount TGa is gradually increased, the target fuel injection amount TGi read from the map of FIG. 3 is also gradually increased, but the fuel correction gain Kgi at this time is zero. Therefore, the increase rate of the target fuel injection amount TGi is a rate according to the map of FIG.

At time t6, when the engine speed N starts to fluctuate relatively large up and down, the intake gain correction coefficient ΔK
ga is reduced from 1.0 at once. Since the intake correction gain Kga is calculated by multiplying the reference intake correction gain RKga by this intake gain correction coefficient ΔKga, the intake correction gain Kga also decreases at once. Then, after the time t6, while the increase / decrease range ΔN of the engine speed is relatively large, the target intake air amount TGa is gradually increased, but its increase rate is smaller than the increase rate from the time t3 to the time t6.

On the other hand, at the time t6, the intake gain correction coefficient ΔKga is suddenly reduced from 1.0, so that the fuel gain correction coefficient ΔKgi is changed from 1.0 to match the degree to which the intake gain correction coefficient ΔKga is reduced. It is made big at once. The fuel correction gain Kgi is calculated by multiplying the reference fuel correction gain RKgi by this fuel gain correction coefficient ΔKgi.
gi also becomes bigger at a stretch. Then, after the time t6, the intake correction gain K based on the increasing rate of the target intake air amount TGa
While ga is smaller than the reference intake correction gain RKga, that is, while the increase / decrease range ΔN of the engine speed is relatively large,
The target fuel injection amount TGi is gradually increased, but its increase rate is larger than the increase rate according to the map of FIG.

After the time t6, the increase / decrease width ΔN of the engine speed gradually decreases, so the intake gain correction coefficient ΔK
ga is gradually increased toward 1.0, so that the intake correction gain Kga is also equal to the reference intake correction gain RKg.
It gradually increases toward a. Also, after time t6,
The fuel gain correction coefficient ΔKgi is gradually reduced toward 1.0, and therefore the fuel correction gain Kgi is also gradually reduced toward the reference fuel correction gain RKgi.

At time t9, when the engine speed N reaches the target idle speed TN, it is no longer necessary to increase the target intake air amount TGa anymore, so the intake correction gain Kga is made zero. On the other hand, at this time, since it is not necessary to increase the target fuel injection amount TGi read from the map of FIG. 3, the fuel correction gain Kgi is also set to zero. It should be noted that since the increase / decrease width ΔN of the engine speed is small after time t9, the intake gain correction coefficient ΔKga and the fuel gain correction coefficient ΔKgi are 1.0.

In the second embodiment, the rate of increase in the target fuel injection amount is determined by the reference fuel correction gain RKgi.
Is calculated by multiplying by the fuel gain correction coefficient ΔKgi.
A map similar to that shown in FIG. 9B is obtained in advance as a function of N,
The target fuel injection amount may be directly calculated from the variation range ΔN of the engine speed.

FIG. 11 shows a flowchart of a routine executed to set the target fuel injection amount when the IS control is executed according to the second embodiment. Figure 1
In No. 1, first, in step 40, it is determined whether or not the flag Fn indicating that the engine operating state is the idling operating state after starting is set (Fn = 1). If it is determined in step 40 that Fn = 1, the routine proceeds to step 41, where
The target fuel injection amount TGimn is read from the map of
Next, at step 42, it is judged if the engine speed N is lower than the target idle speed TN (N <TN).

When it is determined in step 42 that N <TN, the routine proceeds to step 43, where the engine speed increase / decrease range (rotation speed increase / decrease range) ΔN is larger than a predetermined increase / decrease range ΔNth. (ΔN> ΔNt
h) or not. In step 43, ΔN
When it is determined that> ΔNth, the routine proceeds to step 44, where the fuel correction gain Kgi is calculated according to the flowchart of FIG. 12, and then step 4
In 5, the value obtained by adding the fuel correction gain Kgi calculated in step 44 to the target fuel injection amount TGimn read in step 41 is the current target fuel injection amount TG.
It is set as i.

On the other hand, when it is judged in step 42 that N ≧ TN, and in step 43, ΔN ≦ Δ
If it is determined to be Nth, it is not necessary to correct the target fuel injection amount TGimn read in step 41, so the routine proceeds to step 46, and the target fuel injection amount TGimn read in step 41 is unchanged this time. Is set as the target fuel injection amount TGi.

Note that the predetermined increase / decrease width ΔNth in the flowchart of FIG. 11 is substantially equal to that of FIG. 9 (B).
Corresponds to the first value ΔN1.

FIG. 12 shows a flowchart of a routine executed to calculate the fuel correction gain according to the second embodiment. This routine is a routine executed as step 44 in FIG. In the routine of FIG. 12, first, at step 50, the fuel gain correction coefficient ΔKgi is calculated according to the flowchart of FIG. 13, and then at step 51, the fuel gain correction coefficient ΔKgi calculated at step 50 is added to the reference fuel correction gain RKgi. The value obtained by multiplying by is the fuel correction gain K this time.
It is set as gi.

FIG. 13 shows a flowchart of a routine executed to calculate the fuel gain correction coefficient according to the second embodiment. This routine is a routine executed as step 50 in FIG. In the routine of FIG. 13, first, in step 60, the routine of FIG.
The fuel gain correction coefficient ΔKgi is read from the relationship of (B), and then, in step 61, the fuel gain correction coefficient ΔKgi read in step 60 is higher than the fuel gain correction coefficient ΔKgi _{n- 1} set in the previous routine. It is smaller than a predetermined value Y (ΔKgi _n-1 -Δ
It is determined whether or not (Kgi> Y).

At step 61, ΔKgi _n-1 −Δ
When it is determined that Kgi> Y, the routine proceeds to step 62, where the value obtained by subtracting the predetermined value Y from the fuel gain correction coefficient ΔKgi _n−1 set in the previous routine is the current fuel gain correction coefficient ΔKgi. Set as _n . On the other hand, in step 61, ΔKgi _n−1 −Δ
When it is determined that Kgi ≦ Y, the routine proceeds to step 63, where the fuel gain correction coefficient ΔKgi calculated at step 60 is the current fuel gain correction coefficient ΔKgi.
It is set as a gi _n.

The engine speed can also be increased or decreased by changing the timing of igniting the fuel in the combustion chamber by the spark plug 10 (fuel ignition timing). Therefore, in the IS control of the third embodiment, in order to maintain the engine speed at the target idle speed under the idling operation state after starting, the target intake air amount is controlled and the target fuel ignition timing is also controlled. I have to.

Specifically, when the IS control is started to be executed, the target intake air amount is read from the map of FIG. 2, and the engine speed is smaller than the target idle speed and the increase / decrease range of the engine speed is increased. While the (rotational speed increase / decrease range) is relatively small, the target intake air amount is gradually increased at a predetermined increase rate. According to this, as the target intake air amount increases, the target fuel injection amount read from the map of FIG. 3 also increases, and as a result, the engine speed gradually increases toward the target idle speed. Become.

On the other hand, the target fuel ignition timing at this time is the target fuel ignition timing preset according to the engine operating state. In the third embodiment, the target fuel ignition timing TTi is prestored in the ECU 20 in the form of a map as a function of the engine speed N and the required engine load L, as shown in FIG. While the engine is operating, it is read from the map of FIG. 14 based on the engine speed N and the engine request load L.

On the other hand, when the engine speed is smaller than the target idle speed and the range of increase or decrease in the engine speed becomes relatively large, the increase of the target intake air amount is stopped and the engine speed is further increased. It suppresses the increase / decrease range from increasing. At the same time, the fuel ignition timing is changed so as to promote the combustion of the fuel in the combustion chamber, whereby the engine speed is gradually increased toward the target idle speed.

According to this, the engine speed can quickly reach the target idle speed while suppressing the increase or decrease of the speed.

Generally, the earlier the fuel ignition timing is advanced, that is, the more the fuel ignition timing is shifted to the advance side,
Since the combustion of the fuel in the combustion chamber is promoted, in the third embodiment, in order to promote the combustion of the fuel in the combustion chamber, the fuel ignition timing is shifted to the advance side.

Further, in the third embodiment, while the engine speed is higher than the target idle speed, the target intake air amount is gradually reduced at a predetermined reduction rate. According to this, as the target intake air amount decreases, the target fuel injection amount read from the map of FIG. 3 also decreases, and as a result, the engine speed gradually decreases toward the target idle speed. Become.

In the third embodiment, after the engine speed N reaches the target idle speed TN while the increase of the target intake air amount is stopped and the fuel ignition timing is changed, the engine speed N The fuel ignition timing is gradually changed so as to approach the timing read from the map of FIG. 14 so that N is maintained at the target idle speed TN, and the target intake air amount TGa is gradually increased.

By the way, as described above, when the target intake air amount is large and therefore the opening of the throttle valve is large, the degree of negative pressure in the intake passage is small and a part of the fuel injected from the fuel injection valve It remains attached to the wall of the intake passage,
The operation of the internal combustion engine becomes unstable. Therefore, during execution of the IS control, the opening degree of the throttle valve is set to the engine speed N
Even when the engine speed is close to the target idle speed TN, when the engine speed increase / decrease range (rotation speed increase / decrease range) ΔN is relatively large, such a large engine speed increase / decrease range means that the target intake air amount is too large. It is thought that the cause is.

Therefore, in the fourth embodiment, when the engine speed is lower than the target idle speed and the engine speed is higher than a predetermined judgment value in the third embodiment, the speed increase / decrease range is increased. When it is relatively large, the target intake air amount is reduced, and the target fuel ignition timing is changed so as to promote the combustion of fuel in the combustion chamber.
As a result, the engine speed is gradually increased toward the target idle speed. According to this
The engine speed can quickly reach the target idle speed while reducing the speed increase / decrease range.

In the fourth embodiment, while the increase of the target intake air amount is stopped and the fuel ignition timing is changed, or while the target intake air amount is gradually decreased and the fuel ignition timing is changed. After the engine speed N reaches the target idle speed TN, the fuel ignition timing approaches the timing read from the map of FIG. 14 so that the engine speed N is maintained at the target idle speed TN. While being gradually changed, the target intake air amount TGa is gradually increased.

FIG. 14 is a time chart showing an example of changes in engine speed and the like when the IS control is executed according to the fourth embodiment. In FIG.
(A) shows the transition of the engine speed N, (B) shows the transition of the target intake air amount TGa, and (C) shows the intake correction gain Kga.
Of the ignition timing correction coefficient Kti.
Is shown.

When the internal combustion engine is started at time t0, the engine speed N once exceeds the target idle speed TN and reaches a peak, and then at time t3, falls below the target idle speed TN. Substantially, the correction of the target intake air amount TGa is started from here. That is, time t3
In the above, since the engine speed N is lower than the target idle speed TN, the intake correction gain Kga is increased from zero to the reference intake correction gain RKga. Therefore, time t
After 3, the target intake air amount TGa is increased by this reference intake air correction gain RKga.

At time t6, when the engine speed increase / decrease range (rotation speed increase / decrease range) ΔN becomes large, at this time,
Since the engine speed N is smaller than the predetermined determination value Nth, the intake correction gain Kga is set to zero. Therefore, after the time t6, the target intake air amount TGa is not increased and is maintained at the value at that time. On the other hand, after the time t6, even if the target intake air amount TGa cannot be increased, the engine speed N is changed to the target idle speed T
In order to increase toward N, the ignition timing correction coefficient Kti for correcting the target fuel ignition timing TTimn read from the map of FIG. 14 is gradually increased from 1.0. In the third embodiment, the final target fuel ignition timing is set by multiplying the target fuel ignition timing TTimn read from the map of FIG. 14 by the ignition timing correction coefficient Kti.

At time t8, the engine speed N is still smaller than the target idle speed TN, but becomes larger than the predetermined determination value Nth, the intake correction gain Kga is set to a value smaller than zero. As a result, after the time t8, the target intake air amount TGa is gradually decreased by the intake air correction gain Kga having this value. On the other hand, after the time t8, the ignition timing correction coefficient Kti is
The target fuel ignition timing is continuously changed and gradually increased.

At time t10, when the engine speed N reaches the target idle engine speed TN with the engine speed increasing / decreasing width ΔN becoming smaller, the intake correction gain Kga becomes larger than zero but smaller than the reference intake correction gain Kga. To be done. As a result, after time t10, the target intake air amount TGa is gradually increased with the intake air correction gain Kga having this value. On the other hand, after time t10, the ignition timing correction coefficient Kti is gradually decreased and the target fuel ignition timing is continuously changed.

FIG. 16 shows a flow chart of a routine for executing the IS control of the fourth embodiment. In the routine of FIG. 16, first, at step 70,
It is determined whether or not the flag Fn indicating that the engine operating state is in the idling operating state after starting is set (Fn = 1). When it is judged at step 70 that Fn = 1, the routine proceeds to step 71, where it is judged if the engine speed N is smaller than the target idle speed TN (N <TN).

When it is determined in step 71 that N <TN, the routine proceeds to step 72, and the engine speed increase / decrease range (rotation speed increase / decrease range) ΔN is smaller than the predetermined increase / decrease range ΔNth. (ΔN <ΔNt
h) or not. At step 72, ΔN
When it is determined that <ΔNth, the routine proceeds to step 73, where it is determined whether the engine speed N is smaller than a predetermined determination value Nth (N <Nth). When it is determined in step 73 that N <Nth, the routine proceeds to step 74, and the control I is executed. In the control I, the target intake air amount is maintained at the current target intake air amount, and the fuel ignition timing read from the map of FIG. 14 is shifted to the advance side at a predetermined rate.

On the other hand, in step 73, N ≧ Nth
If so, the routine returns to step 76.
Then, the control II is executed. In control II, the target intake air amount is gradually reduced at a predetermined reduction rate, and the fuel ignition timing read from the map of FIG. 14 is gradually shifted to the advance side at a predetermined rate. .

In step 72, ΔN ≧ ΔN
When it is determined to be th, the routine proceeds to step 77, and control III is executed. In control III, the target intake air amount is increased at a predetermined increase rate, and the fuel ignition timing is the fuel ignition timing read from the map of FIG. Further, when it is determined in step 71 that N ≧ TN, the routine proceeds to step 75, and the control IV is executed. In control IV, the target intake air amount is reduced at a predetermined reduction rate, and the fuel ignition timing is the fuel ignition timing read from the map of FIG. When it is determined in step 70 that Fn = 0, the routine ends.

[0089]

According to the first to fourth aspects of the present invention, during execution of the engine speed control, while the intake air amount is being increased by the intake air amount control means, the rotational speed increase / decrease range is larger than the predetermined allowable increase / decrease range Is also increased, the predetermined intake increase rate is decreased, and the intake amount control means increases the intake amount with the decreased intake increase rate. That is, according to the present invention, when the intake air amount is increased in order to increase the engine speed, and when the engine speed fluctuates largely up and down, the intake amount is increased at a relatively small rate. It According to this, the fluctuation of the engine speed becomes small, so that the internal combustion engine can be operated stably when the engine operating state is in the idling operating state after the internal combustion engine is started.

In the fifth and sixth aspects of the invention, during execution of the engine speed control, the rotational speed increase / decrease range is larger than a predetermined allowable increase / decrease range while the intake air amount is increased by the intake air amount control means. Then, the increase of the intake air amount by the intake air amount control means is stopped, and at the same time, the fuel ignition timing by the ignition means is changed so as to promote the combustion of the fuel. That is, according to the present invention, when the intake air amount for increasing the engine speed is increased, when the engine speed fluctuates largely up and down, the increase of the intake amount is stopped and the fuel ignition timing is increased. Is changed so that the combustion of combustion is promoted. According to this, since the fluctuation of the engine speed becomes smaller and the engine speed continuously increases toward the target engine speed, when the engine operating state is in the idling operating state after the internal combustion engine is started, The engine can be operated stably.

[Brief description of drawings]

FIG. 1 is an overall view of an internal combustion engine including a control device according to a first embodiment.

FIG. 2 is a diagram showing a map used for setting a target intake air amount TGa.

FIG. 3 is a diagram showing a map used to set a target fuel injection amount TGi.

FIG. 4 is a diagram showing a relationship used for calculating an intake air correction gain ΔKga based on a rotation speed increase / decrease range ΔN in the first embodiment.

FIG. 5 is a diagram showing a time chart showing an example of changes in engine speed N and the like when IS control is executed according to the first embodiment.

FIG. 6 is a flowchart showing a routine for setting a target intake air amount TGa in IS control according to the first embodiment.

FIG. 7 is a flowchart showing a routine for calculating an intake air correction gain Kga according to the first embodiment.

FIG. 8 is an intake gain correction coefficient ΔK according to the first embodiment.
6 is a flowchart showing a routine for calculating ga.

FIG. 9 is an intake correction gain ΔKga and a fuel correction gain ΔK based on a rotation speed increase / decrease range ΔN in the second embodiment.
It is a figure which shows the relationship used in order to calculate gi.

FIG. 10 is a diagram showing a time chart showing an example of changes in engine speed N and the like when IS control is executed according to the second embodiment.

FIG. 11 is a flowchart showing a routine for setting a target fuel injection amount TGi in IS control according to the second embodiment.

FIG. 12 shows a fuel correction gain Kgi according to the second embodiment.
6 is a flowchart showing a routine for calculating

FIG. 13 is a fuel gain correction coefficient Δ according to the second embodiment.
It is a flowchart which shows the routine for calculating Kgi.

FIG. 14 is a diagram showing a map used for setting a target fuel ignition timing.

FIG. 15 is a diagram showing a time chart showing an example of changes in engine speed N and the like when IS control is executed according to the fourth embodiment.

FIG. 16 is a flowchart showing a routine for executing IS control of the fourth embodiment.

[Explanation of symbols]

1 ... Engine body 4 ... Combustion chamber 10 ... Spark plug 13 ... Fuel injection valve 14 ... Intake passage 16 ... Throttle valve 24 ... Exhaust passage 25 ... Oxygen sensor

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F02D 43/00 301 F02D 43/00 301B 301K 45/00 322 45/00 322C F02P 5/15 F02P 5/15 EF term (reference) 3G022 CA01 CA03 DA01 DA07 EA01 FA08 GA01 GA05 GA06 GA08 GA09 3G065 CA00 DA06 EA03 FA02 FA03 FA06 FA09 GA05 GA09 GA10 GA46 3G084 BA05 BA13 BA17 CA01 CA03 DA10 EA11 FA10 FA38 FA20 FA20 FA13 FA20 FA13 EC07 FA07 FA20 FA20 JA21 KA01 KA07 LA00 LA03 LC04 MA11 NA08 NB11 NC02 ND01 ND05 NE03 NE08 NE09 NE16 NE17 NE22 PA01Z PD02Z PE01Z PE03Z PE08Z PF03Z

Claims (6)

[Claims] 1. An intake air amount control means capable of controlling an intake air amount sucked into a combustion chamber of an internal combustion engine, and an amount of fuel corresponding to an intake air amount so that an air-fuel ratio becomes a predetermined target air-fuel ratio. And a fuel injection means for injecting into the combustion chamber during intake air, and the engine speed is a predetermined target engine speed when the engine operating state is in an idling operating state after the internal combustion engine is started. When it is smaller than the number, the intake air amount control means increases the intake air amount at a predetermined intake air increase rate, while on the other hand, when the engine operating state is in the idling operating state after the internal combustion engine is started, the engine speed is When the engine speed is higher than the target engine speed, the engine speed control is executed to reduce the intake air amount by the intake air amount control means at a predetermined intake air reduction rate. In the above, during execution of the engine speed control, while the intake air amount is increased by the intake air amount control means, when the increase / decrease range of the engine speed becomes larger than a predetermined allowable increase / decrease range, A control device for an internal combustion engine, wherein the predetermined intake air increase ratio is reduced, and the intake air amount is increased by the intake air amount control means at the reduced intake air increase ratio. 2. When the increase / decrease range of the engine speed is smaller than the allowable increase / decrease range while the intake amount is being increased by the intake amount control means during execution of the engine speed control. The predetermined intake increase rate is increased, and the intake amount is increased by the intake amount control means with the increased intake increase rate, thus increasing the predetermined increase rate. The control device for an internal combustion engine according to claim 1, wherein the control device is limited to a predetermined upper limit value. 3. The fuel injection quantity injected from the fuel injection means is reduced at a predetermined fuel reduction rate while the intake quantity is increased by the intake quantity control means during execution of the engine speed control. On the other hand, during the execution of the engine speed control, while the intake air amount is controlled by the intake air amount control means, the fuel injection amount is increased at a predetermined fuel increase rate. The control device for the internal combustion engine according to claim 1, wherein the predetermined fuel decrease rate is increased when the predetermined intake increase rate is decreased during execution of the number control. 4. A fourth aspect of the present invention is the third aspect of the invention, wherein during the execution of the engine speed control, the increase / decrease range of the engine speed is increased while the intake amount is increased by the intake amount control means. When it becomes smaller than the allowable increase / decrease range, the predetermined intake increase rate is increased,
The intake amount is increased by the intake amount control means with the increased intake increasing ratio, and at the same time, the predetermined fuel decrease ratio is decreased, and the fuel injection amount is decreased with the decreased fuel decrease ratio. As a result, the rate at which the predetermined increase rate of intake air is increased is limited to a predetermined upper limit value, and the rate at which the predetermined fuel decrease rate is reduced is predetermined. The upper limit value is limited to the upper limit value.
A control device for an internal combustion engine according to. 5. An intake air amount control means capable of controlling an intake air amount sucked into a combustion chamber of an internal combustion engine, and an amount of fuel corresponding to an intake air amount so that an air fuel ratio becomes a predetermined target air fuel ratio. Fuel injection means for injecting into the combustion chamber during intake air, and ignition means for igniting the fuel sucked into the combustion chamber, and the engine operating state after idling is the idling operating state. When the engine speed is lower than the predetermined target engine speed when the engine speed is set to 1, the intake air amount is increased by the intake air amount control means, while the engine operating state is in the idling operating state after the internal combustion engine is started. When the engine speed is higher than the target engine speed, the engine speed control is executed by the intake amount control means to reduce the intake amount at a predetermined intake reduction rate. In the control device for an internal combustion engine, during execution of the engine speed control, the increase / decrease range of the engine speed is larger than a predetermined allowable increase / decrease range while the intake amount is increased by the intake amount control means. When the increase in the intake air amount is increased, the increase of the intake air amount by the intake air amount control means is stopped, and at the same time, the fuel ignition timing by the ignition means is changed so as to promote the combustion of fuel. Control device. 6. The engine speed is increased when the increase / decrease range of the engine speed is larger than the allowable increase / decrease range while the intake amount is increased by the intake amount control means during execution of the engine speed control. Is smaller than a predetermined determination value, the increase of the intake air amount by the intake air amount control means is stopped and the intake air amount is maintained at the intake air amount at that time.
When the increase / decrease range of the engine speed becomes larger than the allowable increase / decrease range while the intake amount is being increased by the intake amount control means during the execution of the engine speed control, the engine speed exceeds the determination value. The control device for an internal combustion engine according to claim 5, wherein when the intake air amount is larger, the intake air amount control means stops increasing the intake air amount and reduces the intake air amount.