JPH04272439A - Idling control device of internal combustion engine - Google Patents

Abstract

PURPOSE:To provide the possibility of complying with different fuel properties by measuring the heaviness of the fuel to serve for correction of the target idling speed. CONSTITUTION:An idling control device of an internal combustion engine is equipped with a means 100 to sense the engine operating conditions, a means 101 to calculate the target idling speed on the basis of the operating conditions, and a means 103 which is to control an idle suction gas introducing mechanism 102 for obtainment of the target idling speed. Further this is equipped with a means 104 to measure the heaviness of the fuel and a means 105 to correct the target idling speed in accordance with the measurement.

Description

[Detailed description of the invention]

0001

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

0002

[Prior Art] The target rotation speed of the engine in the idle range is determined based on the engine cooling water temperature, the elapsed time after starting, the battery voltage, the ON status of the air conditioner, the gear position of the transmission, etc. The target engine speed is controlled by controlling the intake air through an air regulator, idle control valve, etc. installed in the air passage that bypasses the valve.

[0003] At the same time, the fuel injection amount in the idle region is
It is controlled based on the intake air amount, engine speed, cooling water temperature, etc. of the engine (see Japanese Patent Laid-Open No. 58-27844, etc.).

0004

However, even if the idle rotation is controlled in this way, if the properties of the fuel used in the engine differ from standard fuel, it becomes difficult to obtain stable idle rotation.

That is, compared to standard fuel (light fuel), when using heavy fuel with low volatility, there is a large amount of fuel that adheres to the intake port walls and flows along the intake port walls, making it difficult to start the engine. Sometimes, the response of the fuel is delayed and the air-fuel ratio of the air-fuel mixture tends to become lean. For this reason, as shown in FIG. 19, the rotation does not rise smoothly immediately after starting, and a large drop in rotation occurs due to lack of fuel.

[0006] Furthermore, heavy fuel has poor vaporization, and especially when the engine is cold, it causes a delay in ignition of the air-fuel mixture and a decrease in the combustion speed, which tends to make combustion unstable. For this reason, it is inevitable that the idle speed will fluctuate when the engine is not warmed up.

The present invention aims to solve these problems.

[0008]

[Means for Solving the Problems] As shown in FIG. 1, the present invention includes means 100 for detecting operating conditions of an engine, and means 101 for calculating a target idle rotation speed based on the operating conditions.
and a means 103 for controlling the idle intake intake mechanism 102 to obtain a target idle rotation speed. means 105 for correcting the target idle rotation speed.

[0009]Furthermore, the fuel weight measuring means 104 calculates the error between the actual air-fuel ratio of the engine and the target air-fuel ratio, and learns the maximum value, minimum value, and error area of the air-fuel ratio error when determining the transient condition of the engine. Then, the fuel weight may be calculated based on this learned value.

0010

[Effect] Therefore, in the case of heavy fuel, the target idle speed is set high and the idle speed is increased, which means that the amount of intake air is increased, so the rotation starts smoothly immediately after starting, and stable idle speed is maintained. can be secured.

[0011]

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings.

As shown in FIG. 2, 1 is each cylinder of the engine, 2 is an intake pipe that guides intake air from an air cleaner 3 to each cylinder 1, 4 is a throttle valve, and fuel is supplied to each cylinder through an injector (fuel It is injected from the injection device) 5.

Air regulators 7 for introducing auxiliary air are provided in the air passages 6 that bypass the throttle valve 4, respectively.
, an idle control valve 8 and an FICD valve 9 as an idle intake intake mechanism are interposed.

[0014] The air regulator 7 opens when the coolant temperature is low when starting the engine, and closes in accordance with a signal from the control unit 20 when the coolant temperature exceeds a predetermined value.

The idle control valve 8 is a proportional solenoid valve, and its opening degree is controlled by a duty signal from the control unit 20. The FICD valve 9 is a solenoid valve for an air conditioner, and is opened and closed by a signal from the control unit 20.

On the other hand, as operating condition detection means, an air flow sensor 11 detects the intake air amount Qa of the engine, a crank angle sensor 12 detects the engine rotation speed Ne,
A water temperature sensor 13 that detects the engine cooling water temperature Tw, a throttle opening sensor 14 that detects the opening TVO of the throttle valve 4, a vehicle speed sensor that detects the vehicle speed (not shown), and a gear position sensor (not shown) that detects the gear position of the transmission. switch) is provided.

Further, the exhaust pipe 15 is provided with an air-fuel ratio sensor (not shown) as an actual air-fuel ratio detecting means, which has a characteristic of being able to detect air-fuel ratios over a wide range from the rich side to the lean side.

Detection signals from these sensors are input to the control unit 20 together with a signal from an ignition switch (not shown), an ON signal from an air conditioner switch, and a battery voltage signal.

The control unit 20 as target idle rotation speed calculation means, idle intake intake mechanism control means, and target idle rotation speed correction means includes a CPU, RAM, R
It is composed of a microcomputer consisting of an OM, an I/O device, etc., and controls idle rotation based on the above-mentioned signals, as well as controls the amount of fuel injected from the injector 5.

Next, the control details of the control unit 20 will be explained.

First, to explain the fuel injection amount control, the fuel injection amount (injection pulse width) Te from the injector 5 is:
As shown in the following equations (1) and (2), the engine intake air amount Qa
It is obtained by multiplying the basic injection amount Tp (base air-fuel ratio), which is determined according to
It is controlled by outputting the injection pulse signal to the injector 5. This is done every cylinder and every cycle.

Tp=K (constant)×Qa/Ne
‥‥(1) Te=
Tp×Coef×α
Coef in equation (2) is the sum of the air-fuel ratio correction coefficient in the operating range, the water temperature increase correction coefficient, the starting and post-starting increase correction coefficient, etc., and is read from a predetermined table based on the operating conditions.

The air-fuel ratio feedback correction coefficient α is determined based on the difference between the actual air-fuel ratio and the target air-fuel ratio in a predetermined feedback control range and the operating conditions at that time.

Note that instead of formula (2), the correction amount Kathos based on the fuel wall flow in the intake pipe is expressed as in the following formula (3).
The fuel injection amount Te may also be determined by determining the learning term αm of the air-fuel ratio.

Te=(AVTP+Kathos)×TMR×
(α+αm) ‥‥(3) AVTP is the basic injection amount Tp
and the cylinder air amount equivalent pulse width determined from the weighted average of increases and decreases, and Kathos is the wall flow correction amount determined from the fuel adhesion amount in the intake pipe, the equilibrium adhesion amount, and the wall flow change amount for each injection. Both are calculated based on operating conditions and data read from a predetermined map table.

TMR is a target air-fuel ratio determined from operating conditions, and corresponds to Coef in equation (2) above. αm is a learning correction coefficient that corrects subtle changes in the base air-fuel ratio through learning.

On the other hand, in the idle rotation control, the target idle rotation speed is calculated based on the engine cooling water temperature Tw, the elapsed time after the engine is started, the battery voltage, the ON state of the air conditioner switch, and the gear position of the transmission.
This is corrected according to the weight of the fuel, so that the engine speed Ne becomes the corrected target idle speed.
Opening degree of idle control valve 8 and FICD
The opening and closing of the valve 9 is controlled.

The calculation of the target idle rotation speed is shown in FIGS. 3 to 5.
First, check whether the engine starts or not, and check the idle range (
It is determined whether the throttle valve 4 is in the closed position, etc.) and whether each sensor is normal. If OK, the basic idle rotation speed ISCN is read from the table determined as shown in FIG. 6 based on the water temperature Tw ( Steps 101, 102)
.

At this time, when the air conditioner switch is ON, the air conditioner load control portion FICD of the rotation speed is calculated, the gear position correction portion ISCAT is calculated depending on whether the gear position is neutral, and the voltage correction portion IS according to the battery voltage is calculated.
CV is calculated (steps 103, 104).

For the air conditioner load control FICD and the gear position correction ISCAT, in the subroutine shown in FIG. is not in neutral, the correction value #IS
A CD is set (step 121).

However, when the engine speed Ne is sufficiently larger than the maximum idle speed #FICUT, FI
CD, ISCAT is set to 0 (step 122
, 123).

Further, in the subroutine shown in FIG. 5, the battery voltage correction ISCV is set to data that sets the lower limit of the idling speed for 5 minutes to 800 rpm when the battery voltage remains below 12 V for 1.28 seconds. (steps 141, 142).

Immediately after starting the engine, a post-start timer TIMST (set at the time of starting) is started, and a correction coefficient ISCGAS based on the fuel weight is started.
(described later), and the post-start timer TIM as shown in Figure 7.
The post-start time correction coefficient ISCTIM is read from the table determined based on the ST count (steps 106 to 10).
8).

When each correction amount and correction coefficient are determined, the idle basic rotation speed ISCN is determined by the air conditioner load control amount FICD, the gear position correction amount ISCAT, and the battery voltage correction amount ISCV.
The fuel weight correction coefficient ISCG is added to the result.
AS, the target idle rotation speed NSET is determined by multiplying by the post-start time correction coefficient ISCTIM+1 (step 1
10).

[0035] This calculation is performed at a predetermined period, and
When the timer TIMST becomes 0 after starting, step 105
109, the fuel weight correction coefficient ISCGAS and the post-start time correction coefficient ISCTIM are canceled.

Note that a limiter (upper limit) is set for the target idle rotation speed NSET (step 111).

[0037] Target idle speed NS obtained in this way
Based on ET, the opening degree of the idle control valve 8 and the opening/closing of the FICD valve are set, and the idle rotation is controlled.

In this case, the fuel weight can be determined from the specific gravity or capacitance of the fuel, and therefore a sensor for detecting the specific gravity or capacitance of the fuel may be provided as a measuring means. In this example, the fuel weight is learned based on actual fuel injection amount control (air-fuel ratio control), and the fuel weight correction coefficient ISCGAS is determined based on the learned value.

Next, learning of fuel weight will be explained based on FIGS. 9 to 17.

FIGS. 9 and 10 show the control air-fuel ratio measurement routine, in which the air-fuel ratio sensor output AB is determined in steps 201 to 203.
Convert YF to an actual air-fuel ratio MR using an air-fuel ratio table. Enter the actual air-fuel ratio found this time into MR0 in memory,
The actual air-fuel ratio obtained last time and the previous time were MR1, respectively.
Shift to MR2.

On the other hand, for the target air-fuel ratio TMR (determined based on operating conditions), the current value is stored in TMR0 of the memory, and the values from the previous six times are stored in TMR1 to TM, respectively.
Shift to R6 (step 204).

Once the target air-fuel ratio and the actual air-fuel ratio are determined, the air-fuel ratio error EMR is the difference between them (step 205). Here, the target air-fuel ratio TMR3 three times before is used for the current actual air-fuel ratio MR0 because the fuel injected into the intake port is set at the air-fuel ratio in the exhaust system so that the target air-fuel ratio is obtained. Since there is a time delay before reaching the sensor, this is adjusted. Based on this EMR, a feedback correction coefficient α is calculated in step 222.

Note that during acceleration, this air-fuel ratio error EMR is not used, but the air-fuel ratio error E for acceleration, which is calculated separately, is used.
Use MRA (described below).

In step 206, a target air-fuel ratio damper value (corresponding to the target air-fuel ratio during acceleration) TMRD is obtained from the product of the target air-fuel ratio TMR and the feedback correction coefficient α using the following equation (4).

TMRD=TMR3×α3×TCMR#
+Old TMRD×(1-TCMR#)
(4) Here, the reason why the target air-fuel ratio and the feedback correction coefficient are both set to the values three times before is to take fuel delay, exhaust gas response, sensor response, etc. into consideration. In addition, TCMR# is a damping coefficient (constant value) for monitoring the fuel wall flow in the intake pipe and the sensor response, and this coefficient allows the TM
The change in R3×α3 is smoothed out.

Next, the difference between the current actual air-fuel ratio MR0 and the target air-fuel ratio damper value TMRD is set as the air-fuel ratio error EMRA used for transient learning (step 207).

From this air-fuel ratio error EMRA, the following equation (5
), the average value AVEMA is obtained (step 208).

AVEMA=EMRA×KAVEMA#
+ Old AVEMA × (1-KAVEM
A#) ‥‥(5) Here, KAVEMA
# is an averaging coefficient (constant value). The reason why the average value is used is to eliminate the influence of the actual air-fuel ratio MR, which fluctuates under the influence of exhaust pulsation, HC, etc.

Then, in step 209, the cylinder air change amount AVTP-AVTP3 is compared with the transient learning judgment level (constant value) LTL#, and AVTP-AVTP3≧LTL
If #, it is determined that acceleration (transient state) has entered and step 2
Proceed to step 10. After entering acceleration, or if not in acceleration, the process proceeds to step 212. Note that AVTP3 is the value from three times ago.

In step 210, the air-fuel ratio error EMRA at that time is stored in the memory EMRAS, and the air-fuel ratio error average value AVEMA is also stored in the memory AVEST.

In step 212, a counter value CTES for the number of data samples is incremented.

That is, when acceleration is determined, the immediately preceding air-fuel ratio error EMRA and air-fuel ratio error average value AVEMA are stored, and at step 213, the counter value CTES is compared with the sampling delay (constant value) SMPDLY#, and CTES> When it comes to SMPDLY#, step 215
Proceed to subsequent data sampling.

[0053] This sampling delay SMPDLY#
defines the data capture delay from AVTP change.

Data sampling is performed from step 215 to
At step 218, the air-fuel ratio error EMRA being sampled is compared with the values stored in EMRMX and EMRMN in the memory, and if EMRA≧EMRMX, the air-fuel ratio error is stored in EMRMX, and if EMRA<EMRMN, the air-fuel ratio error is stored in EMRMN. put in. In other words, EMRMX
The maximum air-fuel ratio error value is held in EMRMN, and the minimum air-fuel ratio error value is held in EMRMN.

On the other hand, in step 219, the air-fuel ratio errors EMRA are integrated to obtain the air-fuel ratio error area SEMRA.

Note that when the counter value CTES exceeds the number of data samples NS, data sampling is terminated. TRST and FTLS are flags.

[0057] Also, in steps 221 and 222, the AVT
Perform data shift of P and α.

In this way, the air-fuel ratio error state during acceleration is measured.

FIGS. 11 to 13 show routines for learning and calculating the fuel weight from the error state of the air-fuel ratio during acceleration (transient state). At steps 301 and 340, various sensors related to learning (for example, intake Check whether the air amount sensor, water temperature sensor, crank angle sensor, etc.) are abnormal (NG), and if abnormal, check the TLT (fuel weight learned value) table (with water temperature Tw as a parameter) in the memory. clear. This table is also cleared when the learned value is not normal (OK) in the initialization routine (Figure 1
4).

Steps 302 to 310 are a part for determining conditions for performing learning, and if all of the following six conditions are satisfied, the flow advances to step 311 and subsequent steps.

<1> FTLS=1, that is, the acceleration state is entered (step 302).

<2> Water temperature Tw falls within a predetermined temperature range (TLT
WL#≦Tw<TLTWU#) (Step 3
03). For example, set the learning water temperature lower limit value TLTWL# to 20.
℃, and the water temperature upper limit value TLTWU# is set to 85℃.

<3> Engine speed Ne is within a predetermined range (TLNL#≦Ne<TLNU#) (steps 304, 307). For example, the learning rotation lower limit value TLN
L# is 1000 rpm, rotation upper limit value TLNU# is 300
Set to 0 rpm.

<4> Engine load is above a predetermined value (Qa>
LTLQ#) (step 308). here,
LTLQ# is the learning load lower limit value, and is for stopping learning when the accelerator pedal is released, for example.

<5> All data sampling has been completed (step 309). In addition, the number of samples is NS
is set by the water temperature Tw.

<6> Even after the sample period has elapsed, the engine rotational speed Ne does not exceed the rotational upper limit value TLNU# (step 310).

Note that in step 311, AVEMA is the value immediately after the sample period has elapsed, that is, the value immediately after acceleration;
Difference in the average air-fuel ratio error value before and after acceleration | AVEMA-A
If VEST| exceeds the predetermined value KGKSAE#, learning is not performed. This is because if the difference before and after acceleration is large, the air-fuel ratio error during steady state is likely to be large, so if learning is performed in this case, the accuracy will decrease.

Then, in steps 312 to 317, the air-fuel ratio error area SEMRA obtained in the air-fuel ratio measurement routine is corrected based on the air-fuel ratio error average value AVEMA immediately after the sample period has elapsed (immediately after acceleration).

In this case, the air-fuel ratio error EMRA before acceleration
When S is larger than the air-fuel ratio error average value AVEMA,
The difference multiplied by EMRSG# is corrected from SEMRA.

Furthermore, when the air-fuel ratio error EMRAS before acceleration is smaller than the air-fuel ratio error average value AVEMA, the difference (absolute difference) multiplied by EMRSG# is calculated as SEMR.
Add + correction to A.

EMRSG# is area correction gain (constant value)
It is. Note that the difference between the air-fuel ratio error EMRAS before acceleration and the air-fuel ratio error average value AVEMA is the predetermined value KGEMRS.
If the value is # or above, no correction is performed.

Next, this air-fuel ratio error area SEMRA is divided by the number of data samples NS to obtain the height of the error area, and this height is compared with the air-fuel ratio error average value AVEMA (steps 318, 319).

When height-AVEMA≧0, a learning rewrite amount regarding the air-fuel ratio error area is retrieved from a predetermined TDTA table according to the difference, and this is stored in TINDEX of the work memory (step 320).

Furthermore, when height - AVEMA < 0, the learning rewrite amount regarding the air-fuel ratio error area is similarly searched from the TDTA table according to the difference (absolute difference), and this is stored in TINDEX+1 of the work memory (step 321, 322).

An example of the TDTA table is shown in FIG. Note that the reason why a separate work memory is provided is that the direction of correction is different. In addition, 0 is written to unnecessary work memory.

On the other hand, in steps 323 to 328, the maximum value EMRMX and the minimum value EMR of the air-fuel ratio error during the sample period are determined based on the air-fuel ratio error average value AVEMA.
Perform MN correction.

In this case, the air-fuel ratio error EMRA before acceleration
When S is greater than AVEMA, the difference is EMASG
The product multiplied by # is corrected from EMRMX.

Furthermore, when the air-fuel ratio error EMRAS before acceleration is smaller than AVEMA, the difference (absolute difference) is
The product multiplied by ASG# is +corrected to EMRMN.

EMASG# is the maximum and minimum correction gain (constant value). Note that when the difference between EMRAS and AVEMA is greater than or equal to the predetermined value KGEMAS#, no correction is performed.

[0080] When the maximum value EMRMX≧AVEMA,
According to the difference, the learning rewrite amount regarding the maximum air-fuel ratio error value is searched from the TDTR table and stored in TINDEX+2 of the work memory (steps 329 and 33).
0).

Furthermore, when the minimum value EMRMN≦AVEMA, the learning rewrite amount regarding the minimum air-fuel ratio error value is searched from the TDTL table according to the difference (absolute difference),
This is stored in TINDEX+3 of the work memory (steps 332, 333).

FIG. 16 shows an example of the TDTR and TDTL tables.
, shown in FIG. Note that in the case of EMRMX<AVEMA or EMRMN>AVEMA, the difference is set to 0.

[0083] Air-fuel ratio error area, air-fuel ratio error maximum value,
Once the learning rewrite amount regarding the minimum air-fuel ratio error value is determined, these are summed (step 335).

Next, using this total rewriting amount TINDEX, the fuel weight learning value T is calculated using the water temperature Tw as a parameter.
Update LT (value of TLT table) (step 33
6). This learning value update is the total rewriting amount TINDEX
For example, 4-point learning or 2-point learning is performed based on the water temperature Tw and water temperature Tw.

Then, in step 338, the value of the TLT table, that is, the fuel weight learning value T is determined based on the water temperature Tw.
Search for LT. In this case, the wall temperature TWF of the suction port etc.
TWF, which is obtained by adding TLT to O (determined from the operating conditions), may be used as the fuel weight learning value.

[0086] The fuel weight learning value TLT obtained in this way
Based on the above figure 3, the fuel weight correction coefficient ISCGAS
Determine. This is done by reading the table values determined as shown in Figure 8 based on the fuel weight learning value TLT.
When the fuel weight is large, a large correction coefficient ISCGAS is taken corresponding to the fuel weight.

Because of this configuration, the engine idle range has a target idle speed determined based on the engine cooling water temperature, battery voltage, air conditioner load, gear position, and fuel weight. so that it becomes a number,
Opening degree of idle control valve 8 and FICD
The opening and closing of the valve 9 is controlled.

That is, in the case of heavy fuel, there is a large amount of wall flow on the intake port wall, etc., so the response of the fuel is delayed when starting the engine, but in this case, the target idle speed is set higher based on the degree of heavy fuel. Accordingly, the opening degree of the idle control valve 8 is widened.

For this reason, the idle intake air and fuel are quickly increased immediately after starting, so the engine speed is as shown in Figure 1.
8, the engine speed rises smoothly, so even with heavy fuel, the engine speed does not drop immediately after starting, and a good start and stable rotational state can be ensured.

In addition, in the case of heavy fuel, combustion tends to become unstable when the engine is cold, but a timer is started immediately after the engine is started, and as shown in FIG. The target idle speed is maintained at a high level based on the engine speed and the count of the timer, that is, the engine speed is maintained at a high level via the idle control valve 8 and the like.

[0091] Therefore, when the warm-up is not progressing, the rotation does not fluctuate due to insufficient torque, and stable idling rotation can be ensured. Note that since the correction amount based on the fuel weight is reduced as the timer counts, fuel efficiency is improved.

On the other hand, the fuel weight may be measured directly from the specific gravity of the fuel, but it can be measured from the error state of the air-fuel ratio in fuel injection amount control, especially during transient periods when the air-fuel ratio is likely to be affected by the fuel properties. Since the error area and the maximum and minimum error values of the air-fuel ratio are measured, and the fuel heaviness is learned based on comparison with the error average value, the fuel heaviness can be determined accurately.

[0093] Therefore, an appropriate target idle rotation speed for heavy fuel can be set, accurate idle rotation control can be obtained, and high reliability of control is ensured.

[0094]

As described above, according to the present invention, there is provided a means for detecting engine operating conditions, a means for calculating a target idle speed based on the operating conditions, and a means for calculating an idle intake speed to obtain the target idle speed. In the idle rotation control device for an internal combustion engine, the device includes means for measuring the degree of gravity of the fuel, and means for correcting the target idle rotation speed according to the measured value. Regardless of differences in fuel properties, a good and stable rotational state can be ensured from the idle range immediately after startup, improving idling performance.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of the present invention.

FIG. 2 is a configuration diagram showing a control system.

FIG. 3 is a flowchart of calculation of target idle rotation speed.

FIG. 4 is a flowchart of calculation of air conditioner load, etc.

FIG. 5 is a flowchart of calculation for battery correction.

FIG. 6 is a characteristic diagram showing table values of basic idle rotation speed.

FIG. 7 is a characteristic diagram showing table values of post-start time correction coefficients.

FIG. 8 is a characteristic diagram showing table values of gravity correction coefficients.

FIG. 9 is a flowchart of air-fuel ratio measurement.

FIG. 10 is a flowchart of air-fuel ratio measurement.

FIG. 11 is a flowchart of fuel weight learning.

FIG. 12 is a flowchart of fuel weight learning.

FIG. 13 is a flowchart of fuel weight learning.

FIG. 14 is a flowchart of fuel weight learning.

FIG. 15 is a characteristic diagram of a learning data table.

FIG. 16 is a characteristic diagram of a learning data table.

FIG. 17 is a characteristic diagram of a learning data table.

FIG. 18 is an explanatory diagram showing an idle rotation state.

FIG. 19 is an explanatory diagram showing a conventional idle rotation state.

[Explanation of symbols]

2 Intake pipe 4 Throttle valve 5 Injector 6 Air passage 7 Air regulator 8 Idle control valve 9 FICD valve 11 Air flow sensor 12 Crank angle sensor 13 Water temperature sensor 14 Throttle opening sensor 15 Exhaust pipe 20 Control unit

Claims (2)

[Claims] 1. An internal combustion engine comprising: means for detecting engine operating conditions; means for calculating a target idle speed based on the operating conditions; and means for controlling an idle intake intake mechanism to obtain the target idle speed. An idle rotation control device for an internal combustion engine, characterized in that the device is provided with means for measuring the heaviness of fuel and means for correcting the target idle rotation speed according to the measured value. . 2. The fuel weight measurement means includes means for detecting the actual air-fuel ratio of the engine, means for calculating an error from the target air-fuel ratio, means for determining the transient condition of the engine, and means for determining the transient condition. 2. The idle rotation control device for an internal combustion engine according to claim 1, comprising means for learning the maximum value, minimum value, and error area of the air-fuel ratio error, and means for calculating the fuel gravity based on these learned values.