JPH11324816A - Engine control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect an exhaust gas return flow rate with a good accuracy so as to correct control of exhaust gas return flow by calculating the exhaust gas return flow rate by a detected value of a real air-fuel ratio by an operation condition detecting means, and correcting a driving rate of a control valve on the basis of the exhaust gas return flow rate. SOLUTION: By an exhaust gas return flow(EGR) calculating means 309, a rate QEGR of the EGR which return-flows by an EGR valve is calculated from a real air-fuel ratio RAF of exhaust gas, intake pipe inner pressure PIM, a fuel injection rate QF, an engine intake temperature T, and the like. A valve driving correcting rate as a correction exhaust return flow gas rate is calculated on the basis of the EGR rate QEGR by an EGR control valve driving correction rate calculating means 312, and the EGR control valve driving rate is corrected. A real EGR rate QEGR at the time of operation is calculated on the basis of the real air-fuel ratio RAF and the like by an EGR calculating means 109, and a driving rate of the EGR control valve is corrected and controlled. It is thus possible to perform EGR control accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an exhaust gas recirculation (E
The present invention relates to an engine control device that controls the amount of exhaust gas recirculation (GR), and more particularly to an engine control device that controls the amount of exhaust gas recirculation (EGR) according to the air-fuel ratio of an engine.

[0002]

2. Description of the Related Art An exhaust gas recirculation (EGR) system for recirculating exhaust gas from an engine to an intake system has been known, and the exhaust gas recirculation system is an exhaust gas recirculation passage for communicating the intake system and the exhaust system. An EGR control valve is disposed in the refrigeration system, and the opening and closing of the EGR control valve is changed to change the opening area of the exhaust gas recirculation path and adjust the amount of exhaust gas recirculated. The exhaust gas recirculation system is configured to obtain the exhaust gas recirculation rate according to the operating state of the engine.
The R control valve is driven by a stepping motor or a duty solenoid to control the opening.

[0003] Exhaust gas recirculation (EG) in an engine control apparatus having the exhaust gas recirculation system as described above.
R) The control of the amount is mainly performed by harmful components (CO, H
For the purpose of reducing C, NOx), only a specific operating region of the engine is performed. That is, the exhaust gas is recirculated to the intake system, thereby suppressing a rise in the combustion temperature in the cylinder, and in particular, reducing the amount of NOx emitted. A method of keeping the pressure difference before and after the orifice in the exhaust recirculation passage constant. And a method of controlling the EGR amount in an open loop according to the engine operating state. In recent years, there has been an increasing demand for expanding the EGR region and using a large-capacity EGR amount in order to meet the increasingly stricter exhaust gas regulations and to reduce the pumping loss of the engine and improve the fuel efficiency. I have.

[0004]

However, a large amount of EG
When the R amount is applied, even if the same EGR control is performed due to variations in individual components of the engine or the like, the actual EGR amount differs, and combustion may become unstable or the exhaust state may deteriorate. . Thus, by accurately detecting the EGR amount and correcting the EGR control, it is possible to prevent the deterioration of the exhaust state and the operability due to the combustion failure due to the excessive EGR amount and the deterioration of the exhaust state due to the shortage of the EGR amount. That is a challenge. The present invention has been made in view of the above-described problems, and has as its object to eliminate combustion instability of an engine equipped with an exhaust gas recirculation system and improve the exhaust state, and An object of the present invention is to provide an engine control device capable of coping with variations in individual components of the engine and performing more accurate EGR control.

[0005]

In order to achieve the above object,
The engine control device according to the present invention includes: an operating state detecting unit;
A GR amount calculating means; and an EGR control valve driving amount calculating means. The EGR amount calculating means calculates an EGR amount based on a detection value of the operating state detecting means, and calculates the calculated EG value.
The driving amount of the EGR control valve driving amount calculating means is corrected based on the R amount, and the detection value of the operating state detecting means is an actual air-fuel ratio of the engine.

In a specific embodiment of the engine control device according to the present invention, the EGR amount calculating means calculates the EGR amount by: Q _EGR = {η × (PIM × V) / (R × T)} − QF × R
AF where Q _EGR is the amount of exhaust gas recirculated from the exhaust system (E
(GR amount) QF: injected fuel amount RAF: actual air-fuel ratio η: engine intake efficiency PIM: intake pipe pressure V: engine displacement R: gas constant of air-fuel mixture in the intake pipe T: average temperature in the intake pipe (absolute temperature) ) Is calculated.

In another aspect of the engine control device of the present invention, the engine control device includes EGR diagnosis means, and the EGR diagnosis means calculates an EGR calculated based on a detection value of the operating state detection means. It is characterized in that it is diagnosed whether or not the EGR amount is appropriate by comparing the EGR amount of the amount calculating means with the drive amount of the EGR control valve.

Further, as another specific mode of the present invention, the engine control device changes the drive amount of the EGR control valve drive amount calculating means or sets the drive amount to zero. And a driving state determining means, and based on the determination of the driving state determining means,
It is characterized in that the drive correction amount of the GR control valve drive amount calculation means is adjusted.

In the engine control apparatus according to the present invention, the EGR amount calculating means includes an actual air-fuel ratio detected by the operating state detecting means, an engine intake efficiency, an intake pipe pressure, and an intake pipe average. Since the actual EGR amount during the operation is calculated based on the temperature and the like, and the drive amount of the EGR control valve is corrected and controlled based on the calculated actual EGR amount, more accurate EGR control is possible. is there.

An EGR diagnostic means is provided, and the diagnostic means compares and diagnoses the actual EGR amount calculated by the EGR amount calculating means with the number of driving steps of the EGR control valve to detect an abnormality in the EGR system. can do. Also,
The engine control device of the present invention is provided with an operating state determining means, and the determining means determines that the engine is in an excessive state or a low temperature state of the engine, that is, the engine speed,
Determine the engine load, engine cooling water temperature, etc.,
Based on the determination, the valve drive correction amount calculated based on the actual EGR amount can be corrected and appropriate EGR control can be performed. Furthermore, the engine control device of the present invention is provided with a drive amount changing means, and the drive amount change means forcibly changes a preset drive amount of the EGR control valve to change the actual EGR amount. Thus, the calculation accuracy of the EGR amount can be increased.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of an engine control device according to the present invention will be described in detail with reference to the drawings. FIG.
1 shows the overall configuration of an engine system including the engine control device of the present embodiment. In FIG. 1, an engine 100 includes a cylinder 108a and a piston 108b.
And an intake pipe 10 is provided above the cylinder 108a.
6 and the exhaust pipe 107 are connected, and the intake valve 1
18, an exhaust valve 119, an injector 101, and a spark plug 102 are provided.

In the intake pipe 106, an air cleaner 109 is arranged at the most upstream position, and a throttle valve 104, an ISC valve 105, a throttle sensor 11
3. Intake pipe pressure sensor 114 and intake air flow meter 11
5 are arranged. The exhaust pipe 107 has an air-fuel ratio sensor 116, an EGR control valve 117, and a catalyst 12
1 is attached.

The engine control unit (CPU) 120 includes:
The detection signals of the intake pipe pressure sensor 114, the intake air flow meter 115, the throttle sensor 113, and the air-fuel ratio sensor 116 are input, and the detection signals of the water temperature sensor 110, the crank angle sensor 111, and the cam angle sensor 112 are also input. ing. On the other hand, the output signal from the engine control device 120 is a throttle valve 104, an ISC valve 105, an injector 101, and an EGR control valve 1
17 and an output signal is also transmitted to the ignition plug 102 via the ignition coil 103.

FIG. 2 shows an engine control unit (CPU) 12.
0 shows the main structure of the engine control device 12.
Numerals 0 include a microcomputer 401, a ROM 402 storing programs and data, a RAM 403 used for temporary storage of data, an input circuit 404 for receiving signals from a sensor attached to the engine, the microcomputer 401 and a predetermined time interval. A clock circuit 405 used for a timer capable of generating an interrupt, a compare match circuit (output circuit) 406 that can be turned on / off by the clock signal and a command from the microcomputer 401, and the like.

The input circuit 404 converts the voltages of the various sensor signals into digital data by A / D conversion. The crank angle signal and the cam angle signal cause the microcomputer to generate an interrupt through the waveform shaping input circuit. By the interruption, the cylinder of the engine 100 is determined,
By measuring the pulse time interval, the reciprocal is calculated to calculate the engine speed Ne. In addition, the communication circuit 407
Thus, the control parameters in the microcomputer 401 can be monitored.

FIG. 3 shows an engine control device 1 according to this embodiment.
FIG. 20 shows a control block diagram of No. 20; The engine control device 120 includes an operating state detecting means 301 for detecting various operating states of the engine, and an intake air amount calculating means 30 for calculating respective values based on the detection by the operating state detecting means 301.
6. Target air-fuel ratio calculating means 307, fuel correction amount calculating means 3
08, an EGR amount calculation means 309, an intake air amount calculation means 315 per cylinder, and a fuel injection amount calculation means 316, and an EGR control valve drive amount control means 311, an EGR control valve drive correction amount calculation means 312,
A fuel injection unit 318 and an ignition output unit 319 are provided. Further, the engine control device 120 includes an operating state determining unit 302, a valve driving amount changing unit 314, and E
GR diagnosis means 310 is provided.

The operating state detecting means 301 calculates an engine speed Ne, an intake pipe pressure PIM, an actual air-fuel ratio RAF, an intake air temperature T, and the like based on detection signals of the respective detectors provided in the engine 100. Things. The intake air amount calculating means 306 calculates an intake air amount QA per unit time from the engine speed Ne and the intake pipe internal pressure PIM, and the target air-fuel ratio calculating means 307 calculates the engine speed Ne.
Then, the target air-fuel ratio TABF in the engine operating state is calculated from the intake pipe internal pressure PIM. The intake air amount per cylinder calculating means 315 calculates an intake air amount QAcyl per cylinder from the number of cylinders of the engine, the intake air amount QA per unit time, and the engine speed Ne.

The fuel injection amount calculation means 316 calculates a fuel amount QF to be supplied to the engine 100 from the intake air amount QAcyl per cylinder and the target air-fuel ratio TABF. The fuel injection amount correction means 308 calculates the actual air-fuel ratio RA
Based on F, a correction amount ΔQF of the fuel injection amount QF is calculated to correct the fuel injection amount QA. Further, the ignition timing correction means 317 corrects the ignition timing corresponding to the operating state of the engine 100. The supplied fuel amount QF and the ignition timing signal calculated by the fuel correction amount calculation means 316 and the ignition timing correction means 317 are calculated by the fuel injection means 318 and the ignition output means 3.
19 is output by the injector 1 of the engine 100.
01 and is ignited by a spark plug 102.

EGR control valve drive amount calculating means 311
Is obtained from the engine speed Ne and the intake pipe internal pressure PIM.
A GR valve drive amount is calculated, and the EGR control valve 117 is driven based on the EGR valve drive amount. The EG
Since a differential pressure (PEM-PIM) between the exhaust gas pressure PEM and the intake pipe internal pressure PIM is applied to both sides of the exhaust gas flow passage of the R control valve 117, when the EGR control valve 117 is opened, the differential pressure The exhaust gas amount corresponding to the passage cross-sectional area of the control valve 117 is returned from the exhaust pipe 107 to the intake pipe 106.

The EGR amount calculating means 309 calculates the intake pipe internal pressure P
An exhaust gas amount (EGR amount) Q _EGR recirculated by the EGR control valve 117 is calculated from the IM, the actual air-fuel ratio RAF of the exhaust gas, the fuel injection amount QF, the engine intake air temperature T, and the like. E
The GR control valve drive correction amount calculating means 312 corrects the EGR control valve drive amount by calculating a valve drive correction amount that is a corrected exhaust gas recirculation gas amount based on the calculated exhaust gas recirculation gas amount (EGR amount) Q _EGR. I do.

Further, the EGR diagnosing means 310 calculates the EG based on the calculated exhaust gas recirculation gas amount (EGR amount) Q _EGR .
It is determined whether the operation of the R system is normal or not, and
If it is determined that the GR system has failed, the EG
R control valve drive amount calculation means 311 outputs
The R control valve 117 is operated so as to be fully closed to ensure the operability of the engine (vehicle). In the event of an abnormality, the alarm is output to the alarm drive means 320 to turn on the alarm lamp 321 to notify the driver of the EGR system abnormality. The operating state determining means 302 corrects the valve driving amount of the EGR control valve driving calculating means 311 by determining the output values such as the engine speed, the engine load and the coolant temperature detected by the operating state detecting means 301.

Further, the valve driving amount changing means 314
Is arranged on the output side of the EGR control valve driving amount calculating means 311 and is calculated by the EGR amount calculating means 309.
In order to increase the calculation accuracy of the GR amount, the calculated EG
Change the R control valve drive amount or make it zero. As described above, the engine control device 120 of the present embodiment receives the detection signal of the intake pipe pressure sensor 114 or the air flow meter 115 and performs an operation such as a predetermined table conversion, thereby obtaining the engine per unit time. Intake air volume QA
, And at the same time, the pulse signal of the crank angle sensor 111 is input, and the number of pulses within a predetermined time or the predetermined number of pulses can be used to calculate the engine speed Ne according to the engine rotation time. .

The engine control unit 120 determines the intake air amount QA per unit time by the engine speed Ne.
Divided by the number of cylinders.
The intake air amount QAcyl for each time can be calculated.
Then, a target air-fuel ratio (TABF) is realized for each intake air QAcyl of each cylinder by multiplying the intake air amount QAcyl for each cylinder by a predetermined air-fuel ratio correction coefficient COEF. The amount of fuel is obtained, and by controlling the valve opening time of the injector 101, the required amount of fuel QF is injected to form an air-fuel mixture for each combustion,
The fuel amount QF can be corrected according to the output values of the water temperature sensor 110 and the throttle sensor 113.

Further, the engine control unit 120 retrieves an ignition timing from an ignition timing map set in advance so as to obtain the maximum torque from the relationship between the intake pipe pressure PIM or the intake air amount QA and the engine speed Ne. The target ignition timing is determined, the power is supplied to the ignition plug 102 for a predetermined time, and the power supply is cut off at the ignition timing.
02 can generate sparks and ignite the mixture in the cylinder 108a. The coefficient KT obtained from the flow rate characteristic of the injector 101 is added to the basic intake air amount QAcyl.
By multiplying by I, the basic fuel injection amount TP is obtained. Further, the required fuel amount is calculated by multiplying by a predetermined multiplier (1 + COEF),
The calculated value is added to the current time in the compare match circuit 406 to cause a compare match, and the injector 101 can be opened for a time corresponding to the required fuel amount.

Further, the exhaust gas is supplied to the air-fuel ratio sensor 11.
6, a signal corresponding to the air-fuel ratio is input to the engine control device 120 and the actual air-fuel ratio RA
F, the actual air-fuel ratio RAF and a predetermined target air-fuel ratio TAB
F and the air-fuel ratio correction coefficient CO
This is for correcting EF. Engine 10 of the present embodiment
Although the exhaust gas of 0 is purified by passing through the catalyst 121, if the operation is continued with the air-fuel ratio kept constant, the catalyst effect is gradually reduced, so that the air-fuel ratio may be changed to some extent. is necessary. For this reason, the engine control device 120 of this embodiment also needs control to increase the deviation of the air-fuel ratio.

FIG. 4 shows the characteristics of the air-fuel ratio sensor 116 used in this embodiment.
No. 16 has a characteristic that the voltage is low when the air-fuel ratio is rich and increases as the air-fuel ratio becomes lean. FIG.
3 shows a calculation control means of an air-fuel ratio correction coefficient COEF. The air-fuel ratio correction coefficient COEF is calculated as in the following equation (1).

[0027]

COEF = KMR + KTW + KAS + LALPAM + KREV (1) where, KMR: engine speed Ne and suction pipe internal pressure PI
LALPHAM: Correction value for controlling the target air-fuel ratio KTW: Value corresponding to the value of the water temperature sensor KAS: Correction amount after engine start KREV: Correction amount according to rotation fluctuation

In addition to this, there is a correction for taking in the electric load signal and suppressing the decrease of the engine speed Ne, but the description is omitted because it is not directly involved in the present embodiment. When the engine is started, the cooling water temperature is low and the fuel is not sufficiently vaporized. This correction value is referred to as KT
W. The correction value KTW decreases as the water temperature rises, and becomes zero when the water temperature is 80 ° C. or higher, which is a normal operation state. Immediately after the start, it is necessary to fill the intake pipe 106 with fuel, and a large amount of fuel is injected. This correction value is defined as KAS. Immediately after the engine starts, it has a maximum value and then gradually decreases, and after a predetermined time, the correction value K
AS becomes zero.

Exhaust gas components are classified into hydrocarbon HC, carbon monoxide CO, and nitrogen oxide NOx, and change according to the mixing ratio of fuel and air. When the amount of fuel is larger than the air-fuel ratio of 14.7, a large amount of HC is emitted. When fuel is low, CO is high. In the vicinity of 14.7, NOx increases. in this case,
HC, CO, and NOx can be purified by passing exhaust gas through a catalyst. When the mixing ratio becomes about 30, the engine 1
NOx and CO emitted from 00 decrease. However, there is a problem that combustion is likely to be unstable and rotation fluctuations occur. Therefore, a target value (target air-fuel ratio TABF) is set so as to reduce the mixture ratio while suppressing rotation fluctuation.

The correction value for controlling the mixture ratio is LALP
It is a HAM, and when the mixture ratio is reduced, the correction value is set low, and when it is increased, the correction value is set high. The correction value LALPHAM
Is compared with a value indicated by the air-fuel ratio sensor 116 provided in the exhaust pipe 107, and a deviation from the correction value LALPHAM is calculated every fixed time or every certain number of reference interruptions. Voltage LAFV of air-fuel ratio sensor 116
Is calculated by a table conversion or a function conversion.
Converted to F.

The microcomputer obtains a target air-fuel ratio TABF determined by the rotational speed Ne and the intake pipe internal pressure PIM, is compared with the actual air-fuel ratio RAF, and corrects the correction value LALPAM according to the air-fuel ratio difference Δλ. Correction value LPA
LPHA is the term (λP) proportional to the difference Δλ, the difference Δλ
(ΛI) and a term (λD) proportional to the derivative of the actual air-fuel ratio RAF. Let the proportional coefficients be k
Assuming that P, kI and kD, LALPHA = λP + λI + λD λP = kP × Δλ λI = kI × Σ (Δλ) λD = kD × (RAF-RAF [i-1]).

Here, Σ (Δλ) is calculated for each operating region using the rotation speed Ne and the intake pipe internal pressure PIM.
Even when the operation state changes suddenly, the response delay of the integral can be reduced. In addition, responsiveness can be improved by switching the integral depending on the presence or absence of EGR control described later. By returning the exhaust gas to the combustion chamber of the cylinder 108a, the gas not involved in combustion stays in the combustion chamber, so that the pressure in the combustion chamber can be maintained at a certain value or more. Therefore, torque loss can be reduced.

As means for returning exhaust gas to the combustion chamber, EG
An R device 117 is provided, and the recirculated exhaust gas amount (EGR amount) Q _EGR is determined according to the difference between the exhaust gas pressure and the intake pipe pressure and the passage area of the EGR control valve 117. FIG. 6 shows the EGR
This shows a control state when calculating the passage area of the control valve 117. The recirculated exhaust gas amount (EGR amount)
Q _EGR can be controlled by opening and closing the EGR passage area as shown in FIG. 6. At this time, the recirculated exhaust gas amount (EGR amount) Q _EGR and the intake air amount QA are calculated by the following equation (2). ).

[0034]

## EQU2 ## EGR amount Q _EGR + QA = η × (PIM × V) / (R × T) (2) Q _EGR : Exhaust gas amount recirculated from the exhaust system (EGR)
QA: New air volume drawn into the engine η: Engine intake efficiency PIM: Pressure in the intake pipe V: Engine displacement R: Gas constant of air-fuel mixture in the intake pipe T: Average temperature in the intake pipe (absolute temperature)

Further, the exhaust air-fuel ratio (actual air-fuel ratio) RAF
Is expressed by the following equation (3) using the supplied fuel amount QF and the fresh air amount QA sucked into the engine.

[0036]

RAF = QA / QF (3) From the formulas (2) and (3), the following recirculated exhaust gas amount (EGR amount) Q
Equation (4) of _EGR can be derived.

[0037]

Q _EGR = {η × (PIM × V) / (R × T)} − QF × RAF (4)

The intake efficiency η, the engine displacement V, and the gas constant R of the air-fuel mixture in the intake pipe are values that can be measured in advance, and the fuel amount QF is a value calculated by the engine control device 120 by itself. The exhaust air-fuel ratio (actual air-fuel ratio) RAF is measured by an air-fuel ratio sensor 116 installed in the exhaust system. Therefore, if the temperature T in the intake pipe 106 is detected by any method, the recirculated exhaust gas amount (EGR amount) Q _EGR can be obtained. In the present embodiment, the output of the intake air temperature sensor is used to eliminate the influence of the temperature T in the intake pipe.

An opening set value of the EGR control valve 117 is obtained according to the recirculated exhaust gas amount (EGR amount) Q _EGR , and the EGR control valve 117 is opened until the set value is reached.
The EGR control valve 117 varies the passage area using a duty valve or a stepping motor. Further, as another embodiment, there is no EGR recirculation passage,
The same applies to the case of self EGR based on the opening / closing timing of the intake / exhaust valve.

In the present embodiment, the number of steps of the EGR control valve (stepping motor) 117 is mapped using the intake pipe pressure PIM and the engine speed Ne as search axes, and the EGR control valve 117 is determined by the number of steps searched from the map. Is driven to realize a predetermined EGR amount or EGR rate. By correcting the map of the number of driving steps of the EGR control valve 117 by comparing the EGR amount Q _EGR obtained by the formula (4) with the target EGR amount, the EGR amount is not affected by the engine individual difference. The amount can be kept constant. Of course, the same effect can be obtained not by correcting the map itself but also by outputting the searched number of steps with correction.

It is also possible to feedback-control the driving steps of the EGR control valve 117 by comparing the target EGR amount map and the EGR amount Q _EGR without mapping the number of driving steps of the EGR control valve 117. EGR
As a method for _improving the calculation accuracy of the amount Q _EGR , the EGR amount Q
Forcibly changing the _EGR, it is effective for calculating the EGR amount Q _EGR from the change and the change in air-fuel ratio of the intake pipe pressure at that time. Further, as a target for forcibly changing the EGR amount, EGR amount Q _EGR is set to be substantially zero.
It is also effective means to forcibly drive the GR control valve 117 and calculate the EGR amount from the change in the intake pipe pressure and the change in the air-fuel ratio at that time.

For example, in an operating state where the EGR rate is high, the EGR
If the amount Q _EGR is forcibly changed, drivability may be deteriorated. In the transient state, the error included in the calculation result of the EGR amount Q _EGR increases. By performing the operation while avoiding such an operating condition, the calculation _accuracy of the EGR amount Q _EGR can be improved. Further, based on the driving step of the EGR control valve 117 corrected in this way, even in a region where the execution of the engine control is difficult,
By correcting the number of driving steps, the EGR amount Q _EGR
Controllability can be improved.

It is also possible to detect an abnormality in the EGR control system from the relationship between the EGR amount Q _EGR obtained as described above and the number of drive steps. That is, the EGR control valve 11
7 for the number of drive steps and the engine operating state,
The upper limit Q _EGR MAX and the lower limit Q _EGR MIN of the normal value of the R amount are calculated and compared with the actual EGR amount Q _EGR . As a result, Q _EGR <Q _EGR MIN or Q _EGR > Q _EGR MAX
If so, the EGR system has some abnormality (the EGR control valve 117 sticks and does not operate, the EGR control valve control system is disconnected, etc.), and the EGR amount is too large or too small. Can be detected.

If it is detected that Q _EGR has an abnormal value such that the predetermined exhaust level cannot be maintained, it is possible to prompt the driver to repair the vehicle by issuing an alarm. At this time, in order to execute the engine control device of the present embodiment under operating conditions suitable for the control, information such as the engine speed, the engine load, and the cooling water temperature is fetched, and the conditions are determined. It is possible to carry out. For example, if the EGR amount Q _EGR is forcibly changed in an operation state where the EGR rate is high, the drivability may be deteriorated. In the transient state, the EGR amount Q _EGR
The error included in the calculation result of? By avoiding such an operation state and performing the operation in a steady state after the engine 100 has been completely warmed up, the calculation _accuracy of the EGR amount Q _EGR can be improved.

When using a stepping motor, FIG.
As shown in (1), the valve is driven by the motor in the closing direction so that the valve is at the fully closed position at the time of starting, and after the O point calibration, the valve is driven in the opening direction. Then, as shown in FIG. 7 (2), after starting the engine in the opening direction, the valve is driven at a constant pulse interval until several steps before a predetermined valve opening position, and the remaining steps are performed by the pulse Drive at a step interval longer than the interval. FIG.
This shows a diagnostic method of the GR control valve 117 itself.

One means for diagnosing the failure of the EGR control valve 117 itself is (1) to measure the current flowing through the winding when the stepping motor is driven. If the current is greater than or equal to a predetermined value during driving and the current is zero during non-driving (when the motor is stopped), the motor is assumed to be normal. Another diagnostic means is (2) monitoring the terminal voltage of the winding. When driving, the terminal voltage is grounded, and when not driving, the voltage applied to the motor is normal when it is zero.

(3) A slider capable of measuring the amount of movement of the plunger in the valve 117 is provided. If the measured amount of movement of the plunger is proportional to the driving of the motor, it is determined that the plunger is normal. Furthermore, (4) since the exhaust gas heats the recirculation pipe, if the temperature of the EGR pipe rises with an increase in the EGR ratio, it can be confirmed that the EGR is normally applied. In this case, it is necessary to attach a temperature sensor for measuring the temperature of the pipe and connect it to the A / D input of the microcomputer.

As another EGR diagnosis method, (5) EG
Since the intake pipe pressure increases in accordance with the R ratio, it can be determined that there is normal if there is a pressure change. At the same time, the intake air amount is reduced, so that it can be determined that the intake air amount is normal based on a change in the intake air amount according to the EGR ratio. Further, since the combustion becomes unstable due to the increase in the EGR ratio, the rotation fluctuation correction amount increases. Therefore, if the rotation fluctuation occurs according to the EGR ratio, it can be determined that the rotation is normal.

When the EGR is applied, the intake pipe pressure increases, so that the basic fuel injection amount increases accordingly. Therefore, as shown in FIG. 9, the pressure increase EGRDP set by the rotation speed and the EGR rate is obtained and subtracted from the basic fuel injection amount. At the same time, the target air-fuel ratio correction value LALPHAM
Is corrected in accordance with the presence or absence of EGR for each operating region, and learning is performed, whereby a good air-fuel ratio correction can be performed even when the operating region changes. As described above, one embodiment of the present invention has been described in detail. However, the present invention is not limited to the above-described embodiment, and various designs are possible without departing from the spirit of the invention described in the claims. It can be changed. For example, in the above-described embodiment, the basic fuel injection system that calculates the basic fuel by measuring the pressure in the intake pipe is used.As a means for measuring the intake air amount of the engine, a system using an air flow meter, Alternatively, a similar result can be obtained in a system using an in-cylinder pressure sensor.

[0050]

As will be understood from the above description, the engine control device of the present invention calculates the actual EGR amount during the operation based on the actual air-fuel ratio and the like by the EGR amount calculating means. Since the drive amount of the EGR control valve is corrected and controlled based on the calculated actual EGR amount, more accurate EGR control is possible, and EGR control can be performed over a wide range of air-fuel ratio. As well as reducing CO ₂ emissions.

[Brief description of the drawings]

FIG. 1 shows an engine control device (CP) according to an embodiment of the present invention.
FIG. 1 is an overall configuration diagram of an engine system provided with U).

FIG. 2 is an internal configuration diagram of the engine control device of FIG. 1;

FIG. 3 is a control block diagram of the engine control device of FIG. 1;

FIG. 4 is a characteristic diagram of an air-fuel ratio sensor provided in the engine control device of FIG. 1;

FIG. 5 is a diagram showing calculation control means of an air-fuel ratio correction coefficient COEF in the engine control device of FIG. 1;

FIG. 6 is an explanatory diagram for calculating an opening area of an EGR control valve (stepping motor) of the engine control device of FIG. 1;

FIG. 7 is an explanatory diagram of driving means for a stepping motor (EGR control valve) of the engine control device of FIG. 1;

FIG. 8 is a diagram showing some diagnostic modes in an EGR abnormality diagnosing means of the engine control device of FIG. 1;

FIG. 9 is a diagram showing correction control of a basic fuel injection amount during EGR of the engine control device of FIG. 1;

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 internal combustion engine 101 injector 102 spark plug 103 ignition coil 104 throttle valve 105 ISC valve 106 intake pipe 107 exhaust pipe 108a cylinder 108b piston 109 air cleaner 110 water temperature sensor 111 crank angle sensor 112 cam angle sensor 113 throttle position sensor 114 intake pipe pressure sensor 115 Intake air flow meter 116 Air-fuel ratio sensor 117 EGR control valve 118 Intake valve 119 Exhaust valve 120 Engine control device 121 Catalyst 301 Operating state detector 302 Operating state determining means 309 EGR amount calculating means 310 EGR diagnostic means 311 EGR control valve driving amount Calculation means 312 EGR control valve drive correction amount calculation means 314 Valve drive amount change means

Claims (7)

[Claims] 1. An engine control device comprising an operating state detecting means, an EGR amount calculating means, and an EGR control valve driving amount calculating means, wherein the EGR amount calculating means comprises an actual air-fuel ratio of the operating state detecting means. An engine control device for calculating an EGR amount based on a detected value. 2. An engine control device comprising an operating state detecting means, an EGR amount calculating means, and an EGR control valve driving amount calculating means, wherein the EGR amount calculating means performs EGR based on a detection value of the operating state detecting means. An engine control device which calculates an amount of the EGR control valve and calculates a drive amount of the EGR control valve drive amount calculating means based on the calculated EGR amount. 3. The engine control device according to claim 2, wherein the detection value of the operating state detection means is an actual air-fuel ratio of the engine. 4. The EGR amount calculating means calculates the EGR amount as Q _EGR = {η × (PIM × V) / (R × T)} − QF × R
AF where Q _EGR is the amount of exhaust gas recirculated from the exhaust system (EGR
QF: Injected fuel amount RAF: Actual air-fuel ratio η: Engine intake efficiency PIM: Intake pipe pressure V: Engine displacement R: Gas constant of air-fuel mixture in intake pipe T: Average temperature in intake pipe (absolute temperature) The engine control device according to claim 2, wherein the calculation is performed by the following equation. 5. An engine control apparatus comprising: an operating state detecting means; an EGR amount calculating means; an EGR control valve driving amount calculating means; and an EGR diagnosing means. The EGR amount is calculated by comparing the EGR amount of the EGR amount calculating means calculated based on the detected value with the driving amount of the EGR control valve.
An engine control device for diagnosing whether a GR amount is appropriate. 6. A valve driving amount changing means for changing a driving amount of said EGR control valve driving amount calculating means or for setting the driving amount to zero is provided. The engine control device according to the paragraph. 7. The engine control apparatus according to claim 1, further comprising an operating state determining unit, wherein the engine control unit adjusts a drive correction amount of the EGR control valve driving amount calculating unit based on the determination by the operating state determining unit. Item 6. An engine control device according to any one of Items 1 to 5.