JP2012077719A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an internal combustion engine from stalling and overspeeding properly during idling, caused by a difference of a follow-up speed to a target between an idling speed control and an air-fuel ratio feedback control, concerning a control device of the internal combustion engine.SOLUTION: When a deviation (NE-NEtag) between an actual engine speed NE and a target engine speed NEtag in idling is a predetermined value DNEH or higher, if a first condition that the target engine speed NEtag is lower than the actual engine speed NE and an actual air-fuel ratio AF is leaner than a target air-fuel ratio AFtag as well as a second condition that the target engine speed NEtag is higher than the actual engine speed NE and the actual air-fuel ratio AF is richer than the target air-fuel ratio AFtag are satisfied, the air-fuel ratio feedback control is inhibited so that the idling speed control is given priority for performing, comparing to the air-fuel ratio feedback control.

Description

  The present invention relates to an internal combustion engine control apparatus, and more particularly to an internal combustion engine control apparatus suitable for controlling an internal combustion engine that performs idle speed control and air-fuel ratio feedback control.

  Conventionally, for example, Patent Document 1 discloses an electronic control device for an internal combustion engine that performs idle speed control and air-fuel ratio feedback control. In this conventional electronic control device, at least one of the control amounts of idle speed control and air-fuel ratio feedback control is corrected according to the changing direction of the other control amount.

  More specifically, in the above-described conventional electronic control unit, the bypass air amount is controlled via the ISC valve so that the engine speed during idling becomes the target speed, and is detected by the oxygen sensor during idling. The amount of fuel supplied from the fuel injection valve is controlled so that the air-fuel ratio becomes a preset target air-fuel ratio, and the above-mentioned bypass is set according to the deviation between the target air-fuel ratio and the actual air-fuel ratio at idle. The amount of air is corrected, and the fuel supply amount is corrected in accordance with the deviation between the target rotational speed and the actual rotational speed. In the above-described conventional electronic control device, by performing such control, hunting caused by the interaction between both control systems is prevented, and the idling speed and the air-fuel ratio are controlled with high accuracy.

JP-A 62-203952

  Incidentally, the follow-up speed of the engine speed with respect to the target (target engine speed) in the idle speed control is different from the follow-up speed of the air-fuel ratio with respect to the target (target air-fuel ratio) in the air-fuel ratio feedback control. More specifically, the follow-up speed of the air-fuel ratio with respect to the target is much higher than the follow-up speed of the engine speed with respect to the target. If control based on such a difference in follow-up speed is not performed, a stall or overspeed may occur in the internal combustion engine during idling.

  The present invention has been made to solve the above-described problems. Due to the difference in the tracking speed to the target in the idle speed control and the air-fuel ratio feedback control, the internal combustion engine is stalled or over-rotated during idling. It is an object of the present invention to provide a control device for an internal combustion engine that can suitably prevent the occurrence of this.

A first invention is a control device for an internal combustion engine,
Engine speed acquisition means for acquiring the actual engine speed of the internal combustion engine;
Air-fuel ratio acquisition means for acquiring an actual air-fuel ratio of the internal combustion engine;
Idle speed control means for performing idle speed control for adjusting the intake air amount so that the actual engine speed becomes the target engine speed during idling;
Air-fuel ratio feedback control means for performing air-fuel ratio feedback control for adjusting the fuel injection amount so that the actual air-fuel ratio becomes the target air-fuel ratio;
When the deviation between the actual engine speed and the target engine speed at the time of idling is a predetermined value or more, the target engine speed is lower than the actual engine speed, and the actual air-fuel ratio is equal to the target A first condition that is leaner than the air-fuel ratio or a second condition that the target engine speed is higher than the actual engine speed and the actual air-fuel ratio is richer than the target air-fuel ratio is satisfied A control for adjusting at least one of the idle speed control means and the air-fuel ratio feedback control means so that the idle speed control is executed with priority over the air-fuel ratio feedback control. Adjusting means;
It is characterized by providing.

The second invention is the first invention, wherein
The control adjustment means is configured to control the air-fuel ratio so that the idle speed control is preferentially executed over the air-fuel ratio feedback control when the first condition or the second condition is satisfied. It is a means for prohibiting the use of the feedback control means.

The third invention is the first or second invention, wherein
The control adjusting means, when the deviation between the actual engine speed at the idling and the target engine speed is equal to or greater than the predetermined value, the target engine speed is lower than the actual engine speed, and When the condition that the actual air-fuel ratio is richer than the target air-fuel ratio is satisfied, the use of the air-fuel ratio feedback control is permitted.

According to a fourth invention, in any one of the first to third inventions,
The control adjusting means, when the deviation between the actual engine speed at the idling and the target engine speed is equal to or greater than the predetermined value, the target engine speed is higher than the actual engine speed, and When the condition that the actual air-fuel ratio is leaner than the target air-fuel ratio is satisfied, use of the air-fuel ratio feedback control is permitted.

The fifth invention is the second invention, wherein
Further comprising misfire detection means for detecting misfire of the internal combustion engine,
The control adjusting means permits the use of the air-fuel ratio feedback control when the misfire is detected even when the first condition is satisfied.

  According to the first invention, when the first or second condition is satisfied, the idle speed control is prioritized over the air-fuel ratio feedback control in which the follow-up speed to the target is relatively high. By performing this, it is possible to suitably prevent the internal combustion engine from stalling or over-rotating during idling.

  According to the second invention, when the first or second condition is satisfied, the idle speed control is prioritized over the air-fuel ratio feedback control in which the follow-up speed to the target is relatively high. The air-fuel ratio feedback control is prohibited to be executed. As a result, it is possible to suitably prevent the internal combustion engine from stalling or over-rotating during idling.

  According to the third or fourth aspect of the present invention, the actual engine speed and the actual air-fuel ratio can be obtained by using the idling engine speed control and the air-fuel ratio feedback control under the condition that the internal combustion engine is less likely to be stalled or over-rotated during idling. Can sufficiently follow each target value.

  According to the fifth invention, even if the first condition is satisfied, if misfire is detected, the prohibition of the air-fuel ratio feedback control is canceled and its use is permitted. For this reason, even when the first condition is satisfied, when misfire is detected, the misfire is prioritized by converging the actual air-fuel ratio to the target air-fuel ratio rather than preventing over-rotation of the internal combustion engine. This makes it possible to reliably prevent the deterioration of exhaust emissions caused by the engine and the occurrence of engine stall.

It is a figure for demonstrating the system configuration | structure of the internal combustion engine in Embodiment 1 of this invention. It is a flowchart of the routine performed in Embodiment 1 of the present invention.

Embodiment 1 FIG.
[System configuration of internal combustion engine]
FIG. 1 is a diagram for explaining a system configuration of an internal combustion engine 10 according to Embodiment 1 of the present invention. The system shown in FIG. 1 includes an internal combustion engine 10. A piston 12 is provided in the cylinder of the internal combustion engine 10. A combustion chamber 14 is formed on the top side of the piston 12 in the cylinder. An intake passage 16 and an exhaust passage 18 communicate with the combustion chamber 14.

  An air flow meter 20 that outputs a signal corresponding to the flow rate of air sucked into the intake passage 16 is provided in the vicinity of the inlet of the intake passage 16. A throttle valve 22 is provided downstream of the air flow meter 20. The throttle valve 22 is an electronically controlled throttle valve that can control the throttle opening independently of the accelerator opening.

  A fuel injection valve 24 for injecting fuel into the intake port of the internal combustion engine 10 is disposed downstream of the throttle valve 22. An ignition plug 26 is attached to the cylinder head provided in the internal combustion engine 10 so as to protrude from the top of the combustion chamber 14 into the combustion chamber 14. The intake port and the exhaust port are respectively provided with an intake valve 28 and an exhaust valve 30 for bringing the combustion chamber 14 and the intake passage 16 or the combustion chamber 14 and the exhaust passage 18 into a conduction state or a cutoff state.

  A catalyst (three-way catalyst) 32 for purifying exhaust gas is disposed in the exhaust passage 18. Further, an air-fuel ratio sensor 34 for detecting the air-fuel ratio of the exhaust gas is attached to the exhaust passage 18 upstream of the catalyst 32 at that position. The air-fuel ratio sensor 34 is a sensor that emits a substantially linear output with respect to the air-fuel ratio of the exhaust gas. Further, an oxygen sensor 36 that generates a signal corresponding to whether the air-fuel ratio at that position is rich or lean is disposed downstream of the catalyst 32.

  The system of this embodiment includes an ECU (Electronic Control Unit) 40. In addition to the sensors described above, the ECU 40 is connected with a crank angle sensor 42 for detecting the engine speed and an in-cylinder pressure sensor 44 for detecting the pressure in the combustion chamber 14 (in-cylinder pressure). . The ECU 40 is connected to the various actuators described above. The ECU 40 can control the operating state of the internal combustion engine 10 based on the sensor outputs.

[Idle speed control]
In the system of the present embodiment configured as described above, the engine speed detected using the crank angle sensor 42 during idling (hereinafter referred to as “actual engine speed NE”) is a predetermined target engine speed. Idle speed control (ISC: Idle Speed Control) is performed to adjust the intake air amount so as to be NEtag. More specifically, this idle speed control can be executed by feedback control of the opening degree of the throttle valve 22 so that the actual engine speed NE becomes the target engine speed NEtag, for example. In addition, the ECU 40 stores the throttle opening and the intake air amount for setting the actual engine speed NE during idling to the target engine speed NEtag as ISC learning values. The idle speed control is performed by adjusting the intake air amount by using the opening adjustment of the ISC valve provided in the bypass passage that bypasses the throttle valve 22 instead of or in addition to the opening adjustment of the throttle valve 22. It may be performed by.

[Air-fuel ratio feedback control]
Further, in the system of the present embodiment, during the operation of the internal combustion engine 10, the air injection amount that adjusts the fuel injection amount so that the actual air-fuel ratio AF of the internal combustion engine 10 becomes a predetermined target air-fuel ratio AFtag (for example, the theoretical air-fuel ratio). Fuel ratio feedback control is performed. As the actual air-fuel ratio AF used in the air-fuel ratio feedback control, a value calculated using the above-described in-cylinder pressure sensor 44 or a value detected using the air-fuel ratio sensor 34 and / or the oxygen sensor 36 is used. . When the in-cylinder pressure sensor 44 is used, the amount of heat generated by the combustion of the fuel supplied into the combustion chamber 14 according to a predetermined relational expression based on the in-cylinder pressure (combustion pressure) detected by the in-cylinder pressure sensor 44. Then, the actual air-fuel ratio AF can be calculated according to a predetermined relational expression based on the calorific value.

[Control of Embodiment 1]
(Issues in idle speed control)
The follow-up speed with respect to the target (target engine speed NEtag) in the idle speed control is different from the follow-up speed with respect to the target (target air-fuel ratio AFtag) in the air-fuel ratio feedback control. More specifically, the follow-up speed of the air-fuel ratio with respect to the target is much higher than the follow-up speed of the engine speed with respect to the target. Such a difference in the follow-up speed occurs for the following reason. That is, the air-fuel ratio feedback control is required to be effective immediately from a request for reducing exhaust emissions, a request for drivability of the internal combustion engine 10 and a request for suppressing misfire. On the other hand, regarding the feedback control of the idling engine speed, since the response of the intake air amount is slow, there is a concern that if the feedback is performed quickly, the feedback diverges and induces hunting of the engine speed. Therefore, it is necessary to adjust the idle speed more slowly than the adjustment of the air-fuel ratio.

If the control based on the difference in the follow-up speed as described above is not performed, there is a possibility that the internal combustion engine may stall or over-rotate during idling.
Specifically, at the time of idling, in the case where the actual engine speed NE is lower than the target value and the actual air-fuel ratio AF is richer than the target value, the air-fuel ratio is set to the theoretical air-fuel ratio that is the target value. When the lean correction of the target is performed, the speed of following the target is relatively increased before the actual engine speed NE is increased by the idle speed control (increase of the intake air amount) by the gentle speed of the speed following the target. There is a possibility that the actual engine speed NE is further lowered due to the lean correction of the air-fuel ratio by the high air-fuel ratio feedback control, and the internal combustion engine 10 is stalled. Such a case is likely to occur when the amount of intake air suddenly decreases due to factors other than adjustment of the throttle valve 22, such as malfunction of the intake valve 28, for example.
In idling, when the actual engine speed NE is higher than the target value and the actual air-fuel ratio AF is leaner than the target value, the air-fuel ratio rich correction is performed so that the theoretical air-fuel ratio is the target value. Is executed, the air-fuel ratio with a relatively high tracking speed to the target is lowered before the actual engine speed NE is lowered by the idle speed control (the reduction of the intake air amount) due to the gentle tracking speed to the target. There is a possibility that the actual engine speed NE increases (overspeed) due to rich correction of the air-fuel ratio by feedback control. Such a case is likely to occur when the ISC learning value is canceled immediately after battery replacement, for example. In addition, the initial value of the ISC learning value is generally set to be large in consideration of a decrease in the opening area of the throttle valve 22 due to deposit adhesion over time, and as a result, immediately after the cancellation of the ISC learning value. Tends to increase the idling speed.

(Outline of control of Embodiment 1)
Therefore, in the present embodiment, in order to suitably prevent the internal combustion engine 10 from being stalled or over-rotated during idling due to the difference in the tracking speed to the target in the idle speed control and the air-fuel ratio feedback control. The following control was performed. That is, when the absolute value of the rotational speed deviation (NE-NEtag) between the actual engine speed NE at idling and the target engine speed NEtag is greater than or equal to the upper predetermined value DNEH (for example, 300 rpm), the target engine speed NEtag. Is smaller than the actual engine speed NE and the first condition that the actual air-fuel ratio AF is leaner than the target air-fuel ratio AFtag is satisfied, the absolute value of the engine speed deviation (NE-NEtag) is lower Until the predetermined value DNEL (for example, 100 rpm) or less, the idle speed control is preferentially executed over the air-fuel ratio feedback control. Specifically, the air-fuel ratio feedback control is prohibited when the first condition is satisfied. However, even if the first condition is satisfied, if a misfire is detected, the execution of the air-fuel ratio feedback control is permitted.

  Further, in the present embodiment, when the absolute value of the rotational speed deviation (NE−NEtag) is equal to or larger than the upper predetermined value DNEH, the target engine rotational speed NEtag is higher than the actual engine rotational speed NE and the actual air-fuel ratio AF. Even when the second condition in which the engine speed is richer than the target air-fuel ratio AFtag is satisfied, it is compared with the air-fuel ratio feedback control until the absolute value of the rotational speed deviation (NE-NEtag) becomes equal to or lower than the lower predetermined value DNEL. Thus, in order to preferentially execute the idle speed control, the air-fuel ratio feedback control is prohibited.

  Further, in the present embodiment, when the absolute value of the rotational speed deviation (NE-NEtag) is equal to or larger than the upper predetermined value DNEH, the target engine rotational speed NEtag is lower than the actual engine rotational speed NE and the actual air-fuel ratio AF When the third condition that is richer than the target air-fuel ratio AFtag is satisfied, the use of both the idling engine speed (feedback) control and the air-fuel ratio feedback control is permitted. Similarly, when the absolute value of the rotational speed deviation (NE−NEtag) is equal to or greater than the upper predetermined value DNEH, the target engine speed NEtag is higher than the actual engine speed NE and the actual air-fuel ratio AF is the target. Even when the fourth condition that is leaner than the air-fuel ratio AFtag is satisfied, the use of both the idling engine speed (feedback) control and the air-fuel ratio feedback control is permitted.

(Specific processing in Embodiment 1)
FIG. 2 is a flowchart showing a control routine executed by the ECU 40 in order to realize the above function. Note that this routine is periodically executed every predetermined time when the internal combustion engine 10 is in the idling operation state. Further, it is assumed that the idling speed (feedback) control and the air-fuel ratio feedback control described above are executed in parallel with the processing of this routine using different routines.

  In the routine shown in FIG. 2, first, the actual engine speed NE is acquired using the output of the crank angle sensor 42 (step 100). Next, the target engine speed NEtag at idling stored in the ECU 40 is acquired (step 102).

  Next, the actual air-fuel ratio AF (estimated value) is acquired using the output of the cylinder pressure sensor 44 (step 104). Next, the current target air-fuel ratio AFtag (for example, the theoretical air-fuel ratio) is acquired (step 106).

  Next, the misfire determination flag XMF is acquired (step 108). The determination of the presence or absence of misfire can be made, for example, by determining whether or not the rotational fluctuation of the internal combustion engine 10 is greater than or equal to a predetermined value or by determining based on a change in the output waveform of the in-cylinder pressure sensor 44. The misfire determination flag XMF is a flag that is turned on when a misfire is detected by such a method.

  Next, it is determined whether or not the absolute value of the rotational speed deviation (NE-NEtag) between the actual engine speed NE and the target engine speed NEtag is larger than an upper predetermined value DNEH (for example, 300 rpm) (step 110). ). As a result, when the determination in step 110 is satisfied, it is determined whether the actual engine speed NE is higher than the target engine speed NEtag (step 112).

  If it is determined in step 112 that NE> NEtag is satisfied, it is then determined whether the actual air-fuel ratio AF is greater than the target air-fuel ratio AFtag (step 114). As a result, when it is determined that AF> AFtag is satisfied, that is, when it can be determined that the actual air-fuel ratio AF is leaner than the target air-fuel ratio AFtag (when the first condition is satisfied), the air-fuel ratio is determined. The feedback prohibition flag XAFFBINH is set to ON (step 116).

  Next, it is determined whether the misfire determination flag XMF is not ON (step 118). As a result, if the misfire determination flag XMF is not ON, that is, if no misfire is detected, then, the absolute value of the rotational speed deviation (NE-NEtag) is lower than the lower predetermined value DNEL (for example, 100 rpm). It is also determined whether or not is smaller (step 120). As a result, while the absolute value of the rotational speed deviation (NE−NEtag) has not yet reached the lower predetermined value DNEL, the air-fuel ratio feedback prohibition flag XAFFBINH remains on, while the rotational speed deviation (NE− If the absolute value of NEtag) reaches the lower predetermined value DNEL, the air-fuel ratio feedback prohibition flag XAFFBINH is turned OFF (step 122). If the determination in step 118 is not established, that is, if it can be determined that misfire has been detected because the misfire determination flag XMF is ON, the routine proceeds to step 122, where the air-fuel ratio feedback prohibition flag XAFFBINH is set. It is turned off.

  On the other hand, if it is determined in step 114 that AF> AFtag is not established, that is, if it can be determined that the actual air-fuel ratio AF is richer than the target air-fuel ratio AFtag, the air-fuel ratio feedback prohibition flag XAFFBINH is set. Therefore, the use of both the idling speed (feedback) control and the air-fuel ratio feedback control is permitted.

  If it is determined in step 112 that NE> NEtag is not established, it is then determined whether the actual air-fuel ratio AF is smaller than the target air-fuel ratio AFtag (step 124). As a result, when it is determined that AF <AFtag is satisfied, that is, when it can be determined that the actual air-fuel ratio AF is richer than the target air-fuel ratio AFtag (when the second condition is satisfied), the air-fuel ratio The feedback prohibition flag XAFFBINH is set to ON (step 126). Thereafter, the processes of steps 128 and 130 similar to the processes of steps 120 and 122 are sequentially performed.

  On the other hand, if it is determined in step 124 that AF <AFtag is not satisfied, that is, if it can be determined that the actual air-fuel ratio AF is leaner than the target air-fuel ratio AFtag, the air-fuel ratio feedback prohibition flag XAFFBINH is set. Therefore, the use of both the idling speed (feedback) control and the air-fuel ratio feedback control is permitted.

  According to the routine shown in FIG. 2 described above, when the first condition is satisfied during idling, the absolute value of the rotational speed deviation (NE-NEtag) is less than or equal to the lower predetermined value DNEL. The air-fuel ratio feedback prohibition flag XAFFBINH is set to ON. While the flag XAFFBINH is ON, the use of air-fuel ratio feedback control is prohibited. As described above, according to the above routine, when the first condition is satisfied, the idle speed control is preferentially executed as compared with the air-fuel ratio feedback control in which the follow-up speed to the target is relatively high. Therefore, the air-fuel ratio feedback control is prohibited. As a result, it is possible to prevent the rich correction of the actual air-fuel ratio AF by the air-fuel ratio feedback control prior to the reduction of the intake air amount for the convergence of the actual engine speed NE in the idling engine speed control. . Thereby, it is possible to suitably prevent over-rotation of the internal combustion engine 10 during idling.

  Further, according to the above routine, even when the second condition is satisfied during idling, the air-fuel ratio feedback is continued until the absolute value of the rotational speed deviation (NE-NEtag) becomes equal to or lower than the lower predetermined value DNEL. The prohibit flag XAFFBINH is set to ON. As described above, when the second condition is satisfied, the idling speed control is prioritized over the air-fuel ratio feedback control in which the follow-up speed to the target is relatively high by setting the flag to ON. By prohibiting the air-fuel ratio feedback control to be executed, the leanness of the actual air-fuel ratio AF is achieved by the air-fuel ratio feedback control before the increase of the intake air amount for the convergence of the actual engine speed NE in the idling engine speed control. It is possible to prevent correction. Thereby, it is possible to suitably prevent the internal combustion engine 10 from stalling during idling.

  Further, according to the routine, when the third or fourth condition is satisfied, the use of both the idle speed (feedback) control and the air-fuel ratio feedback control is permitted. Thus, unlike when the first or second condition is satisfied, the actual engine speed is reduced by using the above two feedback controls under conditions where the internal combustion engine 10 is less likely to be stalled or over-rotated during idling. The NE and the actual air-fuel ratio AF can sufficiently follow the target values NEtag and AFtag.

  Further, according to the above routine, if misfire is detected even when the first condition is satisfied, the prohibition of the air-fuel ratio feedback control is canceled and its use is permitted. According to such a process, even when the first condition is satisfied, when the misfire is detected, the actual air-fuel ratio AF is converged to the target air-fuel ratio AFtag rather than preventing the internal combustion engine 10 from over-rotating. By giving priority to this, it becomes possible to reliably prevent deterioration of exhaust emission and engine stall caused by misfire.

  By the way, in the above-described first embodiment, when the first or second condition is satisfied at the time of idling, the use of the air-fuel ratio feedback control is prohibited, so that the idling speed control is performed as compared with the air-fuel ratio feedback control. Is executed with priority. However, in the present invention, the aspect of the control adjustment performed by the control adjustment means in order to perform the idle rotation speed control with priority over the air-fuel ratio feedback control is not limited to the above. Absent. That is, when the first or second condition is satisfied at the time of idling, for example, the feedback gain of the air-fuel ratio feedback control is made smaller than normal while permitting the use of the air-fuel ratio feedback control together with the idle speed control. For example, the tracking speed to the target in the air-fuel ratio feedback control may be lowered relative to the tracking speed to the target in the idle speed control. Alternatively, if it is possible to increase the follow-up speed to the target in the idle speed control within a range where feedback divergence does not occur, the idle speed is determined when the first or second condition is satisfied at the time of idling. While allowing the use of the air-fuel ratio feedback control together with the control, the target tracking speed in the air-fuel ratio feedback control is increased to the target in the idle speed control by increasing the tracking speed to the target in the idle speed control from the normal time. It may be relatively lowered with respect to the following speed.

In the first embodiment described above, the ECU 40 executes the process of step 100, so that the “engine speed acquisition means” in the first invention executes the process of step 104. The “air-fuel ratio acquisition means” in the first invention executes the idle speed control in parallel with the routine shown in FIG. 2, so that the “idle speed control means” in the first invention becomes the above-mentioned FIG. By executing the air-fuel ratio feedback control in parallel with the routine shown in FIG. 1, the “air-fuel ratio feedback control means” in the first invention executes the series of processes of steps 110 to 130 described above, thereby executing the first invention. The “control adjusting means” in FIG.
Further, in the first embodiment described above, the “misfire detection means” in the fifth aspect of the present invention is realized by the ECU 40 executing the processing of steps 108 and 118 described above.

10 Internal combustion engine 14 Combustion chamber 16 Intake passage 18 Exhaust passage 22 Throttle valve 24 Fuel injection valve 34 Air-fuel ratio sensor 36 Oxygen sensor 40 ECU (Electronic Control Unit)
42 Crank angle sensor 44 In-cylinder pressure sensor AF Actual air-fuel ratio AFtag Target air-fuel ratio DNEH Upper predetermined value DNEL Lower predetermined value NE Actual engine speed NEtag Target engine speed XAFFBINH Air-fuel ratio feedback prohibition flag XMF Misfire determination flag

Claims (5)

Engine speed acquisition means for acquiring the actual engine speed of the internal combustion engine;
Air-fuel ratio acquisition means for acquiring an actual air-fuel ratio of the internal combustion engine;
Idle speed control means for performing idle speed control for adjusting the intake air amount so that the actual engine speed becomes the target engine speed during idling;
Air-fuel ratio feedback control means for performing air-fuel ratio feedback control for adjusting the fuel injection amount so that the actual air-fuel ratio becomes the target air-fuel ratio;
When the deviation between the actual engine speed and the target engine speed at the time of idling is a predetermined value or more, the target engine speed is lower than the actual engine speed, and the actual air-fuel ratio is equal to the target A first condition that is leaner than the air-fuel ratio or a second condition that the target engine speed is higher than the actual engine speed and the actual air-fuel ratio is richer than the target air-fuel ratio is satisfied A control for adjusting at least one of the idle speed control means and the air-fuel ratio feedback control means so that the idle speed control is executed with priority over the air-fuel ratio feedback control. Adjusting means;
A control device for an internal combustion engine, comprising:   The control adjustment means is configured to control the air-fuel ratio so that the idle speed control is preferentially executed over the air-fuel ratio feedback control when the first condition or the second condition is satisfied. 2. The control apparatus for an internal combustion engine according to claim 1, wherein the control means is a means for prohibiting use of the feedback control means.   The control adjusting means, when the deviation between the actual engine speed at the idling and the target engine speed is equal to or greater than the predetermined value, the target engine speed is lower than the actual engine speed, and 3. The control device for an internal combustion engine according to claim 1, wherein when the condition that the actual air-fuel ratio is richer than the target air-fuel ratio is satisfied, use of the air-fuel ratio feedback control is permitted.   The control adjusting means, when the deviation between the actual engine speed at the idling and the target engine speed is equal to or greater than the predetermined value, the target engine speed is higher than the actual engine speed, and 4. The internal combustion engine according to claim 1, wherein when the condition that the actual air-fuel ratio is leaner than the target air-fuel ratio is satisfied, use of the air-fuel ratio feedback control is permitted. Engine control device. Further comprising misfire detection means for detecting misfire of the internal combustion engine,
The internal combustion engine according to claim 2, wherein the control adjustment means permits the use of the air-fuel ratio feedback control when the misfire is detected even when the first condition is satisfied. Engine control device.

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