JPH084568A - Fuel feeding device for internal combustion engine and fuel feeding method for internal combustion engine - Google Patents

Abstract

PURPOSE:To perform rapid transfer to operation of a combustion limit when the operation state of an engine enters lean burn operation region again. CONSTITUTION:A fuel feeding device for an internal combustion engine having a fuel feed means 9 regulatable of a fuel feed amount and a fuel feed control means 25 comprises a combustion fluctuation detecting means 50 to detect a combustion fluctuation state during lean combustion operation; a correction factor calculating means 51 o calculate the correction factor of a fuel feed amount based on detecting data from the combustion fluctuation detecting means 50; a correction means 52 to correct a fuel feed amount; and a correction factor holding means 53 to hold a correction factor before release when an internal combustion engine 1 is released from lean combustion operation. The correction means 52 is provided with a means 54 to effect correction during return which is operated to correct a fuel feed amount by a correction factor held at the correction factor holding means 53 when the internal combustion engine 1 returns to lean combustion operation again.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply system for an internal combustion engine, which is suitable for use in a lean-burn internal combustion engine that performs lean-burn operation at a leaner side air-fuel ratio than the air-fuel ratio under required operating conditions. And a fuel supply method for an internal combustion engine.

[0002]

2. Description of the Related Art In recent years, a lean burn internal combustion engine (so-called lean burn engine) has been provided which performs a lean burn operation at a leaner air-fuel ratio (lean) than a stoichiometric air-fuel ratio (stoichio) under required operating conditions. There is. In such a lean burn engine, during lean burn operation (lean burn operation), the air-fuel ratio is set as large as possible (that is, the air-fuel mixture becomes lean as much as possible) in order to reduce the NOx emission amount. The value of the fuel ratio is set near a limit (lean limit) at which the air-fuel mixture can perform stable combustion.

By performing such lean burn operation, NOx emission can be suppressed and fuel consumption can be greatly improved. By the way, in order to perform the lean burn operation, the control device controls the combustion state, and in this control, it is announced in a paper or the like that the engine torque is estimated from the angular acceleration of the crankshaft.

Further, for example, in Japanese Unexamined Patent Publication (Kokai) No. 58-217732, it is considered that the combustion state is stable when the engine speed fluctuation is small, and the air-fuel ratio is lean toward the lean side. A technique for controlling the fuel ratio to the rich side is disclosed.

[0005]

However, in the above-mentioned technique for estimating the engine torque from the angular velocity of the crankshaft, the state of the engine is estimated and controlled instantaneously using a changing instantaneous value. It has not been considered to carry out stable and reliable control every predetermined period in consideration of the probability and statistical properties of the torque Pi.

Further, in the case of controlling so as to perform leaner combustion while detecting the stability and instability of combustion as in the technique of Japanese Patent Laid-Open No. 58-217732, there are the following problems. In recent years, when the engine is switched to one of so-called lean burn operation and stoichiometric operation and engine output is not required, lean burn operation is performed to save fuel, and when engine output is required, stoichiometric operation is performed. An engine has been developed which is designed to obtain maximum output by driving.

In this case, it is conceivable to apply the technique described in JP-A-58-217732 in the lean burn operation range. When such an application is considered, learning of the combustion state will be performed in the lean burn operating region, but when the engine operating state leaves the lean burn operating region and then enters the lean burn operating region again, However, when trying to learn the variation between the cylinders from the beginning, there is a problem that the lean burn operation at the combustion limit cannot be realized until this learning is completed.

The present invention was devised in view of the above problems, and when the operating state of the engine enters the lean burn operating region, it is possible to quickly realize lean burn operation at the combustion limit. An object of the present invention is to provide a fuel supply device for an internal combustion engine and a fuel supply method for an internal combustion engine.

[0009]

Therefore, the fuel supply device for an internal combustion engine according to the present invention as defined in claim 1 is a fuel supply means capable of adjusting the fuel supply amount, and the fuel according to a target air-fuel ratio. The fuel supply control means for determining the fuel supply amount from the supply means and controlling the fuel supply means on the basis of this determined value, and lean combustion with an air-fuel ratio leaner than the stoichiometric air-fuel ratio in a specific operating region. In a fuel supply device for an internal combustion engine capable of operating, a combustion fluctuation detecting means for detecting a combustion fluctuation state of the internal combustion engine during the lean combustion operation, and a plurality of detection data obtained by the combustion fluctuation detecting means, A correction coefficient calculation means for calculating a correction coefficient of the fuel supply amount for bringing the combustion state close to the lean limit during lean combustion operation, and the lean combustion operation with the correction coefficient calculated by the correction coefficient calculation means. When the internal combustion engine leaves the lean combustion operation, it holds the correction coefficient calculated by the correction coefficient calculation means during the lean combustion operation before the departure. Correction coefficient holding means is provided, and when the internal combustion engine returns to the lean combustion operation after leaving the lean combustion operation, the lean combustion operation is performed by the correction coefficient held in the correction coefficient holding means. It is characterized in that a recovery correction means for correcting the fuel supply amount at the time is provided.

According to the fuel supply system for an internal combustion engine of a second aspect of the present invention, in addition to the structure of the first aspect, when the internal combustion engine is stopped, the lean combustion operation is performed before the engine is stopped. It is characterized in that an engine stop correction coefficient holding means for holding the correction coefficient calculated by the correction coefficient calculation means is provided. According to a third aspect of the present invention, in addition to the structure of the first or second aspect, the internal combustion engine has a plurality of cylinders, and the combustion fluctuation detecting means and the correction coefficient are provided. The calculation means, the correction coefficient holding means, and the correction means are provided for each cylinder.

Further, in the fuel supply system for an internal combustion engine according to the present invention as defined in claim 4, in addition to the structure according to any one of claims 1 to 3, the combustion fluctuation detecting means comprises a combustion of the internal combustion engine. Angular acceleration fluctuation detecting means for detecting a fluctuation value of the angular acceleration of the rotating shaft driven by the internal combustion engine as fluctuation data, and normalizing the fluctuation value according to the operating state of the internal combustion engine to obtain a normalized fluctuation value. And a combustion deterioration determination value calculation means for obtaining a combustion deterioration determination value by comparing the normalized variation value obtained by the normalized variation value detection means with a predetermined threshold value. The correction coefficient calculation means
It is characterized in that the correction coefficient is calculated so that the combustion deterioration determination value approaches a predetermined reference value.

According to a fifth aspect of the present invention, there is provided a fuel supply method for an internal combustion engine, the fuel supply means having an adjustable fuel supply amount, and the fuel supply amount from the fuel supply means according to a target air-fuel ratio. And a fuel supply control means for controlling the fuel supply means based on this set value, for an internal combustion engine capable of performing lean combustion operation at an air-fuel ratio leaner than the stoichiometric air-fuel ratio in a specific operating region. In a fuel supply method, a combustion fluctuation detection step for detecting a combustion fluctuation state of the internal combustion engine during the lean combustion operation, and a combustion status during the lean combustion operation based on a plurality of detection data detected in the combustion fluctuation detection step. A correction coefficient calculation step for calculating a correction coefficient for the fuel supply amount in order to approach the lean limit,
A correction step of correcting the fuel supply amount during the lean combustion operation with the correction coefficient calculated in the correction coefficient calculation step, and when the internal combustion engine leaves the lean combustion operation, during the lean combustion operation before the departure. A correction coefficient holding step of holding the correction coefficient calculated in the correction coefficient calculation step, and a step of holding the correction coefficient holding step when the internal combustion engine returns to the lean combustion operation after leaving the lean combustion operation And a correction step at the time of return for correcting the fuel supply amount during the lean combustion operation by the correction coefficient.

Further, in the fuel supply method for an internal combustion engine according to a sixth aspect of the present invention, in addition to the structure of the fifth aspect, the correction coefficient holding step is performed even when the internal combustion engine is stopped. It is characterized in that the correction coefficient calculated by the correction coefficient calculation means is held during the lean combustion operation before the stop. A fuel supply method for an internal combustion engine according to a seventh aspect of the present invention is, in addition to the configuration according to the fifth or sixth aspect, the internal combustion engine has a plurality of cylinders, and the above steps are performed for each cylinder. It is characterized by being performed in.

Further, in the fuel supply method for an internal combustion engine according to the present invention as defined in claim 8, in addition to the structure according to any one of claims 5 through 7, the combustion fluctuation detecting step comprises the combustion of the internal combustion engine. An angular acceleration fluctuation detecting step of detecting a fluctuation value of the angular acceleration of a rotating shaft driven by the internal combustion engine as fluctuation data, and normalizing the fluctuation value according to an operating state of the internal combustion engine to obtain a normalized fluctuation value. The normalization fluctuation value detection step and the combustion deterioration information amount detection step of detecting the combustion deterioration information amount from the data of the set number of detection cycles, the correction coefficient calculation step, the combustion deterioration information amount is predetermined. It is characterized in that the correction coefficient is calculated so as to approach the reference value of.

[0015]

In the combustion state control system for an internal combustion engine according to the first aspect of the present invention, the fuel supply control means determines the fuel supply amount from the fuel supply means in accordance with the target air-fuel ratio, and the determined value is set to this determined value. Based on this, the fuel supply means is controlled and the fuel supply amount is adjusted. Then, in a specific operation region, lean combustion operation is performed at an air-fuel ratio that is leaner than the stoichiometric air-fuel ratio.

In the lean combustion operation, the combustion fluctuation detecting means detects the combustion fluctuation state of the internal combustion engine, and the correction coefficient calculating means calculates the lean combustion operation based on a plurality of detection data obtained by the combustion fluctuation detecting means. At times, a correction coefficient of the fuel supply amount for bringing the combustion state close to the lean limit is calculated. Further, the correction means corrects the fuel supply amount during the lean combustion operation with the correction coefficient calculated by the correction coefficient calculation means, and the correction coefficient holding means causes the internal combustion engine to leave the lean combustion operation, and the lean combustion before the departure. The correction coefficient calculated by the correction coefficient calculation means is held during operation.

When the internal combustion engine returns from the lean combustion operation to the lean combustion operation again by the recovery correction means provided in the correction means, the correction coefficient held in the correction coefficient holding means causes the lean combustion operation to be performed. The fuel supply amount is corrected. In the combustion state control apparatus for an internal combustion engine according to the second aspect of the present invention, the correction coefficient holding means for the engine stop calculates the correction coefficient calculation means during the lean combustion operation before the engine stop when the internal combustion engine is stopped. The corrected correction coefficient is retained.

In the combustion state control apparatus for an internal combustion engine according to the third aspect of the present invention, the combustion fluctuation detecting means, the correction coefficient calculating means, the correction coefficient holding means, and the correcting means are used for the internal combustion engine having a plurality of cylinders. The fuel supply amount is corrected for each cylinder. In the combustion state control device for an internal combustion engine according to the fourth aspect of the present invention, the angular acceleration fluctuation detecting means detects the fluctuation value of the angular acceleration of the rotating shaft driven by the internal combustion engine as the combustion fluctuation data of the internal combustion engine. The normalized variation value detecting means normalizes the variation value according to the operating state of the internal combustion engine to calculate the normalized variation value.

Further, the combustion deterioration determination value calculation means compares the normalized variation value obtained by the normalized variation value detection means with a predetermined threshold value to obtain a combustion deterioration determination value, and the correction coefficient calculation means calculates the combustion degradation determination value. The correction coefficient is calculated so that the deterioration determination value approaches the predetermined reference value. In the combustion state control method for an internal combustion engine according to the present invention as set forth in claim 5, when the combustion variation state of the internal combustion engine is detected during lean combustion operation in the combustion variation detection step, the combustion variation relating to this combustion variation is detected in the correction coefficient calculation step. A correction coefficient of the fuel supply amount for making the combustion state close to the lean limit during lean combustion operation is calculated based on the plurality of detection data.

Further, in the correction step, the fuel supply amount during lean combustion operation is corrected using the correction coefficient calculated in the correction coefficient calculation step, and in the correction coefficient holding step, when the internal combustion engine leaves lean combustion operation, The correction coefficient calculated in the correction coefficient calculation step during the lean combustion operation before the departure is held. Then, when the internal combustion engine returns from the lean combustion operation to the lean combustion operation again, in the return correction step, the fuel supply amount during the lean combustion operation is corrected by the correction coefficient held in the correction coefficient holding step.

In the combustion state control method for an internal combustion engine according to the sixth aspect of the present invention, the correction coefficient holding step allows
When the internal combustion engine is stopped, the correction coefficient calculated by the correction coefficient calculation means during the lean combustion operation before the engine stop is held. In the combustion state control method for an internal combustion engine according to the seventh aspect of the present invention, each step is performed for each cylinder in the internal combustion engine having a plurality of cylinders.

Further, in the combustion state control method for an internal combustion engine according to the present invention as set forth in claim 8, the combustion fluctuation detecting step includes an angular acceleration fluctuation detecting step, a normalized fluctuation value detecting step, and a combustion deterioration information amount detecting step. In the angular acceleration fluctuation detecting step, the fluctuation value of the angular acceleration of the rotating shaft driven by the internal combustion engine is detected as the combustion fluctuation data of the internal combustion engine, and the fluctuation value is detected in the normalized fluctuation value detecting step. Normalized according to the operating state of the internal combustion engine,
The normalized variation value is obtained. Further, in the combustion deterioration information amount detection step, the combustion deterioration information amount is detected from the data of the set number of detection cycles.

Then, in the correction coefficient calculation step, the correction coefficient is calculated so that the combustion deterioration information amount approaches the predetermined reference value.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An internal combustion engine fuel supply apparatus and an internal combustion engine fuel supply method according to an embodiment of the present invention will now be described with reference to the drawings. FIG. 1 is a schematic control block diagram showing the configuration of the apparatus. 2 is an overall configuration diagram of an engine system having this device, FIG. 3 is a hardware block diagram showing a control system of an engine system having this device, and FIGS. 4 and 5 are for explaining the operating characteristics of this device. FIG. 4 is a map showing a detected data valid operating area, FIG. 5 is a map showing an example of switching the detected data valid operating area, and FIG. 6 is a graph showing its operating characteristics.
7 (c) is a graph showing the relationship between the drive time and the deviation of each injector provided in a multi-cylinder engine, FIG.
2 is a flow chart for explaining the operation of this device.

An engine for an automobile equipped with the present device has a theoretical air-fuel ratio (Stoichio) under required operating conditions.
It is configured as a lean burn engine that performs lean burn operation (lean burn operation) at a leaner air-fuel ratio (lean) than this, and this engine system is as shown in FIG. That is, in FIG. 2, an engine (internal combustion engine) 1 has an intake passage 3 and an exhaust passage 4 communicating with a combustion chamber 2 thereof, and the intake passage 3 and the combustion chamber 2 are controlled to communicate with each other by an intake valve 5. In addition, the exhaust passage 4 and the combustion chamber 2 are controlled to communicate with each other by an exhaust valve 6.

Further, the intake passage 3 is provided with an air cleaner 7, a throttle valve 8 and an electromagnetic fuel injection valve (injector) 9 as fuel supply means in this order from the upstream side, and the exhaust passage 4 is provided with A three-way catalyst 10 and a muffler (silencer) (not shown) are provided in this order from the upstream side. The injector 9 is provided for each cylinder of the engine 1. Further, the intake passage 3 is provided with a surge tank 3a.

The three-way catalyst 10 purifies CO, HC, and NOx under stoichiometric operation, and is a known one. Further, the throttle valve 8 is connected to an accelerator pedal (not shown) via a wire cable, and its opening degree is adjusted according to the depression amount of the accelerator pedal.

A first bypass passage 11A for bypassing the throttle valve 8 is provided in the intake passage 3, and a stepper motor valve (hereinafter referred to as an STM valve) which functions as an ISC valve is provided in the first bypass passage 11A. 12 are installed. In addition, in the first bypass passage 11A,
A wax-type fast idle air valve 13 whose opening is adjusted according to the engine cooling water temperature is also provided, and is attached to the STM valve 12.

Here, the STM valve 12 is a valve body 12a which can abut against a valve seat portion formed in the first bypass passage 11A.
And a stepper motor (I
(SC actuator) 12b, and a spring 12c that urges the valve body in a direction that presses the valve body against the valve seat portion (a direction that closes the first bypass passage 11A). The stepper motor 12b performs stepwise adjustment of the position of the valve body 12a with respect to the valve seat portion (adjustment by the number of steps) to open the valve seat portion and the valve body 12a, that is, the STM valve 12
The opening degree of is adjusted.

Therefore, the opening degree of the STM valve 12 is an electronic control unit (ECU) 2 as a controller which will be described later.
By controlling with 5, the intake air can be supplied to the engine 1 through the first bypass passage 11A regardless of the driver's operation of the accelerator pedal, and the throttle bypass intake amount is adjusted by changing the opening degree. You can do it.

As an ISC actuator,
A DC motor may be used instead of the stepper motor 12b. Further, the intake passage 3 is provided with a second bypass passage 11B that bypasses the throttle valve 8, and an air bypass valve 14 is interposed in the second bypass passage 11B.

Here, the air bypass valve 14 has a second
It is composed of a valve body 14a capable of contacting a valve seat portion formed in the bypass passage 11B, and a diaphragm type actuator 14b for adjusting the position of the valve body, and a diaphragm chamber of the diaphragm type actuator 14b is provided with: A pilot passage 141 communicating with the intake passage on the downstream side of the throttle valve is provided.
An air bypass valve control solenoid valve 142 is provided at 41.

Therefore, by controlling the opening degree of the air bypass valve controlling solenoid valve 142 by the ECU 25, which will be described later, in this case as well, regardless of the operation of the accelerator pedal by the driver, the second bypass passage 11B is used. The intake air can be supplied to the engine 1, and the throttle bypass intake air amount can be adjusted by changing the opening thereof. The air bypass valve controlling solenoid valve 142 is opened during lean burn operation,
Other than that, the basic operation is to be closed.

An exhaust gas recirculation passage (EGR passage) for returning exhaust gas to the intake system is provided between the exhaust passage 4 and the intake passage 3.
The EGR passage 80 is provided with an EG
The R valve 81 is interposed. Here, this EGR valve 81
Is composed of a valve body 81a capable of contacting a valve seat portion formed in the EGR passage 80, and a diaphragm type actuator 81b for adjusting the position of the valve body, and is provided in a diaphragm chamber of the diaphragm type actuator 81b. Is provided with a pilot passage 82 communicating with the intake passage downstream of the throttle valve.
An ERG valve control solenoid valve 83 is interposed in the.

Therefore, by controlling the opening degree of the EGR valve controlling solenoid valve 83 by the ECU 25, which will be described later, E
The exhaust gas can be returned to the intake system through the GR passage 80. In FIG. 2, reference numeral 15 denotes a fuel pressure regulator, which operates by receiving a negative pressure in the intake passage 3 and regulates the amount of fuel returned from a fuel pump (not shown) to the fuel tank. Thus, the pressure of fuel injected from the injector 9 is adjusted.

Various sensors are provided to control the engine system. First, as shown in FIG. 2, the intake air that has passed through the air cleaner 7 is introduced into the intake passage 3
An air flow sensor (intake air amount sensor) 17 for detecting the intake air amount from the Karman vortex information and an intake air temperature sensor 1 as an intake air humidity parameter detecting means are provided in a portion flowing into the inside.
8. An atmospheric pressure sensor 19 is provided.

The intake air temperature sensor 18 detects the temperature of intake air of the engine 1. In addition, the intake passage 3
In addition to the potentiometer-type throttle position sensor 20 that detects the opening of the throttle valve 8, an idle switch 21 is provided in the portion where the throttle valve 8 is arranged.

Further, the exhaust passage 4 side is provided with an oxygen concentration sensor (hereinafter, simply referred to as “O ₂ sensor”) 22 for detecting the oxygen concentration (O ₂ concentration) in the exhaust gas, and as other sensors. , A water temperature sensor 23 for detecting the temperature of the cooling water for the engine 1 and a crank angle sensor 24 for detecting the crank angle shown in FIG. 3 (the crank angle sensor 24 functions as a rotation speed sensor for detecting the engine rotation speed Ne). Also serves as a vehicle speed sensor 30 and the like.

Detection signals from these sensors and switches are input to the ECU 25 as shown in FIG. Here, the hardware configuration of the ECU 25 is as shown in FIG.
Is configured as a computer having a CPU (arithmetic unit) 26 as its main part. The CPU 26 includes an intake air temperature sensor 18, an atmospheric pressure sensor 19, a throttle position sensor 20, an O ₂ sensor 22, and a water temperature sensor 2.
The detection signals from 3 and the like are input through the input interface 28 and the analog / digital converter 29.

The CPU 26 has an air flow sensor 17, an idle switch 21, a crank angle sensor 24,
A detection signal from the vehicle speed sensor 30 or the like is directly input through the input interface 35. Further, the CPU 26 is a ROM that stores various data in addition to program data and fixed value data via a bus line.
(Memory unit) 36 or RAM that can be updated and sequentially rewritten
Data is exchanged with 37.

Further, as a result of the calculation by the CPU 26, EC
From U25, a signal for controlling the operating state of the engine 1, such as a fuel injection control signal, an ignition timing control signal,
Various control signals such as an ISC control signal, a bypass air control signal and an EGR control signal are output. Here, the fuel injection control (air-fuel ratio control) signal is sent to the CPU 26.
Is output to the injector solenoid 9a for driving the injector 9 (accurately, the transistor for the injector solenoid 9a) via the injection driver 39, and the ignition timing control signal is output from the CPU 2
6 is output to a power transistor 41 via an ignition driver 40, and a spark is sequentially generated from the power transistor 41 to an ignition plug 42 by a distributor 43 via an ignition coil 42.

The ISC control signal is output from the CPU 26 to the stepper motor 12b via the ISC driver 44, and the bypass air control signal is output from the CPU 26 via the bypass air driver 45 to the air bypass valve controlling solenoid valve. It is adapted to be output to the solenoid 142a of 142. Further, the EGR control signal is sent to the CPU2.
6 through the EGR driver 46 to the solenoid 83a of the ERG valve control solenoid valve 83.

Now, focusing on the function for controlling the fuel injection of the engine 1, as shown in FIG. 1, in order to perform this fuel injection control (injector drive time control), the ECU 25 is Combustion fluctuation detecting means 50
A correction coefficient calculation means 51 and a correction means 52 are provided. The combustion variation detecting means 50 is a means for detecting combustion variation of the engine 1, and the correction coefficient calculating means 51
A correction coefficient for correcting the fuel injection time is set based on the engine operation information from the combustion fluctuation detecting means 50. Then, the correction unit 52 is configured to correct the fuel injection time using the correction value calculated by the correction coefficient calculation unit 51.

The combustion fluctuation detecting means 50, the correction coefficient calculating means 51, and the correcting means 52 will be described in detail below. The combustion fluctuation detecting means 50 detects the combustion fluctuation state of the engine 1 during lean combustion operation. Angular acceleration fluctuation detecting means 50A for detecting the fluctuation value of the angular acceleration of the crankshaft as the combustion fluctuation data of No. 1, and the normalized fluctuation value for normalizing this fluctuation value according to the operating state of the internal combustion engine to obtain the normalized fluctuation value. The detecting means 50B.

In the angular acceleration variation detecting means 50A, the crank angle sensor 24 detects the angular velocity Acc. The smoothed value AccAV obtained by smoothing (averaging) the angular velocity Acc and the crank angle sensor 24 outputting the angular velocity Acc. The combustion fluctuation state of the engine 1 is detected by obtaining the difference ΔAcc from the calculated angular acceleration Acc. That is, in the combustion fluctuation detecting means 50, the acceleration fluctuation value ΔAcc (n) is calculated by the following equation.

ΔAcc (n) = Acc (n) −AccAV (n) Note that the subscript n in (n) above indicates that the cycle is the nth (current) ignition operation in the identified cylinder. . Further, AccAV (n) is calculated by performing the primary filter processing according to the following equation.

AccAV (n) = α · AccAV (n-1)
+ (1-α) · Acc (n) Here, α is the update gain in the primary filter processing. Then, in the combustion variation detecting means 50, the variation value ΔAcc (n) is normalized by the normalized variation value detecting means 50B according to the operating state of the engine, and the normalized variation value IAC (n) is It is calculated by the following formula.

IAC (n) = ΔAcc (n) · Kte (Ev, Ne) Here, Kte (Ev, Ne) is calculated from the volume efficiency Ev of the intake air and the detection signal of the crank angle sensor 24 or the like. The output correction coefficient is set based on the engine speed Ne that is set, and is set using an output correction coefficient characteristic map (not shown) provided in the ECU 25.

Thus, the combustion fluctuation detecting means 50 detects the combustion fluctuation state of the engine 1. Further, the correction coefficient calculation means 51 is configured to perform combustion of the engine 1 during lean combustion operation based on a plurality of detection data (for example, data such as ΔAcc (n) and IAC (n) described above) obtained by the combustion variation detection means 50. A correction coefficient Kac for bringing the state closer to the lean limit is calculated.

The correction coefficient calculation means 51 first compares the normalized fluctuation value IAC (n) with a predetermined threshold value IACTH to determine the combustion deterioration determination value Vac (j) and the combustion deterioration cycle number Ndet.
(j) is requested. The normalization fluctuation value IAC (n) is a predetermined threshold value for the combustion deterioration determination value Vac (j).
Cumulative amount of deterioration below IACTH is calculated. That is, the combustion deterioration determination value Vac (j) is calculated by the following equation.

Vac (j) = Σ {IAC (j) <IACTH}
{{IACTH-IAC (j)} where {IAC (j) <IACTH} in the above equation is IAC
(J) is a function that takes “1” when <IACTH holds, and takes “0” when not holds, and when the normalized fluctuation value IAC (n) is below a predetermined threshold value IACTH,
It is configured such that the lower amount is accumulated as the worsening amount.

Therefore, the combustion deterioration determination value Vac (j)
Is obtained by accumulating the deterioration amount with the difference between the threshold IACTH and the normalized fluctuation value IAC (j) as the weight, and the influence of the numerical value near the threshold can be reduced to accurately reflect the deterioration state. Is configured. In addition, j indicates a cylinder of the engine, and for example, the value with j corresponds to the cylinder number or the like.

Further, the combustion deterioration cycle number Ndet (j) is
The number of cycles when it is determined that the combustion fluctuation state of each cylinder is deteriorated based on the detection information by the combustion fluctuation detection means 50, and is a set control cycle, for example, 128.
(Or 256) is the number of combustion deterioration cycles in the cycle, and is represented by the following equation. Ndet (j) = Σ {IAC (j) <IACTH} Next, the calculation of the correction coefficient Kac will be described in detail. The correction coefficient Kac is calculated for each cylinder based on the number of deterioration cycles Ndet (j) for each cylinder. By comparing the magnitude of the cylinder-specific deterioration cycle number Ndet (j) with two threshold values (lean determination deterioration cycle number N1 and rich determination determination deterioration cycle number N2), the following It is calculated in three cases. When Ndet ≥ N2 In this case, the correction coefficient Kac for correcting the air-fuel ratio to be rich is set by the following equation.

Kac (j) = Kac (j−1) + Kar (Vac−Vaco) Note that Kac (j) on the right side is the correction coefficient calculated in the previous calculation cycle (n−1) for the number j cylinder. Shows. When N1 ≤ Ndet <N2 In this case, the correction coefficient Kac for maintaining (holding) the air-fuel ratio is set by the following equation.

When Kac (j) = Kac (j-1) Ndet <N1 In this case, the correction coefficient Kac for correcting the air-fuel ratio to lean is set by the following equation. Kac (j) = Kac (j-1) + Kal (Vaco-Vac) Note that, in the above-mentioned items (1) to (4), Kar is the enrichment gain,
Kal is a lean gain, and Vaco is an acceleration deterioration accumulated amount allowable variation value. This acceleration deterioration integrated amount allowable fluctuation value Vaco
Is the target value of COV (Coefficient of variance) (10%
It is a value corresponding to the combustion fluctuation target value Vaco. By not correcting the fuel in the range of ΔVac on both sides of the combustion fluctuation target value Vaco, the rotation fluctuation can be evaluated for a finite period (128 cycles), The limit cycle due to the error caused by the calculation is prevented.

Further, the combustion deterioration determination value Vac is updated every set number of combustions, for example, 128 (or 256) cycles, and the control is performed by grasping the combustion state for a relatively long period. By performing, stable and reliable control that reflects statistical characteristics is performed. In addition, (V
ac-Vaco) and (Vaco-Vac) at the time of leaning correction, the lower limit value is clipped by 0 at the time of calculation.

The above-mentioned correction coefficient Kac (j) is configured to be clipped by the upper and lower limit values so that it falls within the range of 0.9 <Kac (j) <1.1, for example. It is configured such that a shock or the like is prevented and stable control is performed by performing a gradual correction without setting a rapid correction. In this way, when the correction coefficient calculation means 51 calculates the correction coefficient Kac for making the combustion state of the engine 1 closer to the lean limit during lean combustion operation, the correction means 52 then sets the fuel injection time Tinj. It is like this.

That is, the fuel injection time Tinj is Tinj = TB * Kac * Ketc ± Kacc / dec + TD. Here, TB is the basic drive time (basic pulse injection width) of the injector 9 set from the intake air amount information detected by the air flow sensor 17 and the engine speed Ne information from the crank angle sensor 24, and TD
Is a correction drive time for correcting the drive time according to the battery voltage from the battery (not shown).

Further, Ketc is a correction coefficient including elements other than the correction coefficient Kac, Kacc / dec is a correction coefficient according to acceleration / deceleration of the engine, and the correction coefficient K during acceleration.
Acc is added, and the correction coefficient Kdec is subtracted during deceleration. By the way, the above-mentioned correction coefficient calculation means 51
The correction coefficient Kac calculated by the above is updated only when all the following conditions are satisfied.

A. The operation control state of the engine 1 is in the lean operation state. B. The idle switch 21 is off. C. The operating state of the engine 1 is staying in the detection data effective operating area (hereinafter, referred to as X zone) shown in FIG. Here, the X zone is a region defined by the volumetric efficiency of the intake air amount of the engine 1 and the rotation speed (that is, the rotation speed of the engine), and when all of the following conditions 1 to 3 are satisfied: It is determined that the operating state of the engine is in the X zone.

1. The engine speed Ne is within the range of two thresholds (XXZONNEL, XXZONNEH), that is, XXZO
NNEL ≦ Ne ≦ XXZONNEH. 2. The volumetric efficiency Ev of the intake air amount has two threshold values (Ev-
L, Ev-H), that is, Ev-L≤Ev≤
Must be Ev-H. 3. The shift position of the transmission is in the D range (A / T
(In the case of a car), or the shift position of the transmission is at the third speed or higher (in the case of an M / T car). Then, when all of these conditions are satisfied, the correction coefficient K
ac is supposed to be updated.

The setting of such an X zone will be described below. For example, in FIG. 6, (a)
6A to 6C are graphs showing the relationship between the drive time of each injector 9 provided in a 6-cylinder engine and the deviation of the flow rate gradient, and FIGS. 9A to 9C are different sample examples. As shown in these graphs, the linearity of the injector operation deteriorates in a region where the fuel injection amount is small or a region where the fuel injection amount is large. The combustion limit control of lean operation, that is, the combustion limit control (lean control) based on this while learning the combustion fluctuation requires high accuracy, so if the linearity of the injector operation is poor, perform appropriate control. Is difficult. Therefore, except for such a region, lean control is performed in a region in which the linearity of the injector is ensured such that the deviation of each injector 9 is within ± 1%, whereby accurate variation correction (that is, The fuel limit control for each cylinder) is appropriately performed. The X zone defined by the volumetric efficiency Ev and the engine speed Ne corresponds to the lean control range in which the linearity of the injector is ensured, that is, the lean operation itself is a region larger than the X zone. The learning area for performing lean limit operation is limited to the X zone.

The volumetric efficiency Ev corresponds to the load of the engine 1, but this engine load may change depending on the usage state of the electric system. Specifically, the engine load (that is,
The vertical fluctuation of the volumetric efficiency Ev) is relatively significant. Therefore, in this device, as shown in FIG.
The range of the X zone is switched according to the off state. For example, in FIG. 5, both the upper limit threshold Ev-H and the lower limit threshold Ev-L of the volumetric efficiency Ev of the intake air amount are changed depending on whether the air conditioner is on or off.

In this case, the threshold value of the engine speed Ne is not changed, but instead of the threshold value of the volumetric efficiency Ev, the engine speed Ne is turned on or off depending on whether the air conditioner is turned on or off.
The threshold value may be changed. Also, the volumetric efficiency E
Both the threshold value of v and the engine speed Ne may be changed. In this way, the upper limit threshold value Ev-H and the lower limit threshold value Ev of the volumetric efficiency Ev of the intake air amount are changed depending on whether the air conditioner is on or off.
By setting -L to switch the range of the X zone, it is possible to perform more detailed combustion limit control.

As shown in FIG. 1, the ECU 25 is provided with a correction coefficient holding means 53. When the correction coefficient holding means 53 causes the operating region of the engine 1 to depart from the X zone, the pre-disengagement The correction coefficient Kac during X zone operation is stored (stored). In cases other than this X zone, the case where the operating state of the engine 1 is the lean combustion operating state and is outside the X zone shown in FIG. 4 is also included, and in this case, the correction means 5
2, the correction coefficient Kac held in the correction coefficient holding means 54 is used to correct the fuel supply amount during lean combustion operation.

Further, the correction means 52 is provided with a return time correction means 54. When the engine 1 returns from the lean combustion operation to the lean combustion operation again, the correction coefficient holding means 53 holds the correction. The coefficient Kac is adapted to correct the fuel supply amount during lean combustion operation.
As a result, when the lean combustion operation returns to the normal air-fuel ratio operation state and then the lean combustion operation is resumed, the fuel injection drive time is reset using the correction coefficient learned during the lean combustion operation immediately before that. Therefore, it is not necessary to learn the variation between the cylinders from the beginning again, and it becomes possible to immediately shift to the lean limit combustion limit control state.

The ECU 25 is also provided with an engine stop correction coefficient holding means 55. The engine stop correction coefficient holding means 55 holds the correction coefficient at the time of lean combustion operation when the engine 1 is stopped. As a result, when the engine 1 is restarted to enter the lean combustion operation state, the correction coefficient Kac held in the engine stop time correction coefficient holding means 55 is used to promptly correct the fuel supply amount during the lean combustion operation. Has become.

In practice, the engine stop correction coefficient holding means 5
5 is not provided separately from the correction coefficient holding means 53, but the correction coefficient holding means 53 is also used as the engine stop correction coefficient holding means 55. That is, the correction coefficient holding means 53 is configured to keep the correction coefficient Kac in memory even when the engine is stopped, by the battery backup.

Therefore, even when the engine 1 is restarted,
Since the fuel injection driving time is set using the correction coefficient learned during the lean combustion operation immediately before that, the combustion limit control state of the lean operation can be promptly changed. When using the correction coefficient Kac held in the correction coefficient holding means 53, the correction coefficient held in the correction coefficient holding means 54 is used for control so as to realize stable lean operation. It is designed to be clipped to 1.0) or higher.

Since the fuel supply system for an internal combustion engine according to an embodiment of the present invention is configured as described above, the internal combustion engine according to an embodiment of the present invention can be executed by the procedure shown in the flowchart of FIG. 7, for example. The fuel supply amount (that is, the fuel injection drive time) related to the fuel supply method for use is corrected. First, in step S1, it is determined whether the engine 1 is in the lean operation range. Then, if the engine 1 is in the lean operation region, the process proceeds to step S2, and if it is not in the lean operation region, the process is returned.

At step S2, it is judged whether the operating condition of the engine 1 is within the X zone shown in FIG.
If it is determined that the operating state of the engine 1 is in the X zone, then the process proceeds to step S3. Also, Engine 1
If the operating state is outside the X zone, the process proceeds to step S9 and the counter value is set to N = 0. Then, in step S10, the correction coefficient Kac (j) = Kac (j-
After setting 1), in step S11, Kac
(J) is clipped to a predetermined value (here, 1) or more.
Next, in step S12, the fuel injection time is set by the following equation using the clipped correction coefficient Kac (j) (correction step).

Tinj = TB.multidot.Kac.multidot.Ketc. ± .Kacc / dec + TD Then, the process proceeds to step S13 where the previous correction coefficient storage value Kac (j-1) is the current correction coefficient storage value Kac.
The value of this correction coefficient Kac (j-1) is stored as a battery backup. If the process proceeds from step S2 to step S3, the control cycle is 12
It is determined whether the number of cycles has become eight, that is, whether the learning of the combustion fluctuation is completed. That is, here, it is determined whether or not the counter value N = 128.

Then, until the counter value N reaches 128, the counter value is incremented to N = N + 1 in step S14. Then, in step S15, Kac
(J) = Kac (j-1), and then step S7
Proceed to. When the counter value N reaches 128, step S4
Then, the number of cylinder deterioration cycles Ndet, the combustion deterioration determination value Vac, and the 128 cycle counter value N are reset.

Then, the process proceeds to step S5 (combustion fluctuation detection step), in which the number of cylinder deterioration cycles Ndet and the combustion deterioration determination value V are determined based on the rotation fluctuation data for 128 cycles.
ac is calculated. The combustion fluctuation detecting step includes an angular acceleration fluctuation detecting step, a normalized fluctuation value detecting step, and a combustion deterioration information amount detecting step. In the angular acceleration variation detection step, the crank angle sensor 24 detects the angular acceleration A.
cc is detected, and this angular acceleration Acc is a smoothed value A
By calculating the difference ΔAcc between ccAV and the angular acceleration Acc output from the crank angle sensor 24, the angular acceleration fluctuation value ΔAcc (n) corresponding to the combustion fluctuation state of the engine 1 is detected. The acceleration fluctuation value ΔAcc (n) is calculated by the following equation.

ΔAcc (n) = Acc (n) −AccAV (n) AccAV (n) is calculated by performing the primary filter processing according to the following equation. AccAV (n) = α ・ AccAV (n-1) + (1-α)
Acc (n) (α: update gain in primary filter processing) Then, in the normalized fluctuation value detection step, fluctuation value ΔAcc
(N) is normalized according to the operating state of the engine 1.
That is, the normalized variation value IAC (n) is calculated by the following equation.

IAC (n) = ΔAcc (n) · Kte (E
v, Ne) As described above, in the combustion fluctuation detecting step, the combustion fluctuation state of the engine 1 is detected. Next, in the combustion deterioration information amount detection step, a correction coefficient Kac for making the combustion state of the engine 1 close to the lean limit during lean combustion operation is calculated based on a plurality of detection data obtained in the combustion variation detection step.

In the correction coefficient calculation step, the normalized variation value IAC (n) is compared with a predetermined threshold value IACTH to determine the combustion deterioration information value Vac (j) and the combustion deterioration cycle number Ndet (j). Is calculated by the following equation. Vac (j) = Σ {IAC (j) <IACTH} · {IACTH −
IAC (j)} Ndet (j) = Σ {IAC (j) <IACTH} The combustion deterioration determination value Vac (j) is the deterioration amount with the difference between the threshold IACTH and the normalized fluctuation value IAC (j) as the weight. Accumulated values are obtained, and the influence of numerical values near the threshold value is reduced to accurately reflect the state of deterioration.

Then, the number N of deterioration cycles for each cylinder is
The correction coefficient Kac (j) is calculated in step S6 based on det and the combustion deterioration determination value Vac (correction coefficient calculation step). That is, the magnitude of the number of deteriorating cycles for each cylinder Ndet is compared with two threshold values (N1, N2), and the case is classified into the following three cases. Ndet ≧ N2 ... Kac (j) = Kac (j-1) +
Kar (Vac-Vaco) N1≤Ndet <N2 ... Kac (j) = Kac (j-
1) Ndet <N1 ... Kac (j) = Kac (j-1) +
Kal (Vaco-Vac) Further, in step S7, the fuel injection time is set by the following equation (correction step).

Tinj = TB · Kac · Ketc ± Kacc / dec
+ TD Next, in step S8 (correction coefficient holding step), the updated value Kac (j) is set as the current correction coefficient storage value Kac (j-1), and this correction coefficient Kac (j-
The value of 1) is stored by battery backup. This step S8 is continued even when the engine is stopped, and in this case, step S8 corresponds to the engine stop correction coefficient holding step.

After that, the process returns to step S1 to repeat this routine again. In this way, the combustion deterioration determination value Vac (j) and the combustion deterioration cycle number Ndet (j) are set to the set number of times of combustion, for example, 128.
(Or 256) It is updated for each cylinder every cycle. Then, by performing control by grasping the combustion state for a relatively long period, stable and reliable correction reflecting statistical characteristics is performed.

Further, (Vac-Vaco) at the time of enrichment correction
The lower limit of (Vaco-Vac) during lean correction is clipped at 0 during calculation. Then, the above-mentioned correction coefficient Kac
(J) is configured to be clipped at the upper and lower limits, and is set to fall within the range of 0.9 <Kac (j) <1.1, for example, without performing rapid correction, Prevents shocks by gradually correcting,
Stable correction is performed.

The correction coefficient Kac calculated in the above-mentioned correction coefficient calculation step is updated only when all of the three conditions A to C are satisfied, and in particular, the condition C, that is, the operating state of the engine 1 is The linearity of the injector is maintained under the condition of being in the X zone shown in FIG. 4, and the correction coefficient Kac is updated from the combustion fluctuation data under conditions of good detection accuracy and control accuracy, so that appropriate control is performed. become.

Further, in the present invention, as shown in FIG. 5, the range setting of the X zone is set according to the on / off state of the air conditioner, that is, the volumetric efficiency E of the intake air amount according to the on / off state of the air conditioner.
By switching the upper threshold Ev-H and the lower threshold Ev-L of v,
Since it is set so as to switch the range of the X zone, more detailed combustion limit control can be performed. Further, when the operating region of the engine 1 is separated from the X zone by the correction coefficient holding step, the correction coefficient K before the separation is set.
ac is retained (stored). Of course, even if the operating region of the engine deviates from the lean combustion operating region, the correction coefficient Kac (j) obtained before this desorption is similarly held.

Therefore, when the operating state of the engine 1 is the lean combustion operating state and is outside the X zone shown in FIG. 4, the correction coefficient Kac held in the correction coefficient holding step is used in the correction step. The fuel supply amount during lean burn operation is corrected. As a result, the lean operation can be more accurately limit-controlled. When the engine 1 returns from the lean burn operation to the lean burn operation again, the fuel supply amount during the lean burn operation is corrected based on the correction coefficient Kac held in the correction coefficient holding step.

As a result, when the lean combustion operation is temporarily exited from the operating state with the normal air-fuel ratio, and then the lean combustion operation is resumed, the fuel injection drive is performed using the correction coefficient learned during the lean combustion operation immediately before that. Since the time is reset, it is not necessary to learn the variation between the cylinders from the beginning, and it is possible to immediately shift to the lean limit combustion limit control state.

When the engine is stopped, this correction coefficient holding step functions as an engine stop correction coefficient holding step, and the correction coefficient during lean combustion operation is held even when the engine 1 is stopped. As a result, when the engine 1 is restarted to enter the lean combustion operation state, the fuel supply amount during the lean combustion operation is corrected by the correction coefficient Kac held in the engine stop time correction coefficient holding step.

Therefore, even when the engine 1 is restarted,
Since the fuel injection drive time is set by using the correction coefficient learned during the lean combustion operation immediately before that, the combustion limit control state of the lean operation can be promptly changed. Further, when performing correction by holding such a correction coefficient, the correction coefficient held in the correction coefficient holding step is clipped to a predetermined value (for example, 1.0) or more, so that stable lean operation is realized.

Further, according to the present invention, there are the following effects. In other words, it becomes possible to perform combustion fluctuation estimation that considers the stochastic characteristics of engine torque and air-fuel ratio control that uses this estimation, and perform real-time engine combustion state control that considers the statistical properties of combustion fluctuation. Then, it will be possible to use the in-vehicle computer again. Also, it becomes possible to reliably correct the inter-cylinder difference of the combustion fluctuation limit due to the variation of the air-fuel ratio due to the injector, intake pipe shape, and valve timing deviation, and it becomes possible to set all of the cylinders to the combustion limit. , NOx emissions can be minimized.

Further, the rotation fluctuation of each cylinder can be detected and controlled by one crank angle sensor, and more reliable lean burn control can be performed at low cost.

[0090]

As described in detail above, according to the fuel supply device for an internal combustion engine of the present invention as set forth in claim 1, the fuel supply means capable of adjusting the fuel supply amount and the target air-fuel ratio are set. A fuel supply control means for determining the fuel supply amount from the fuel supply means and controlling the fuel supply means based on the determined value, and with an air-fuel ratio leaner than the stoichiometric air-fuel ratio in a specific operating region. In a fuel supply device for an internal combustion engine capable of performing lean combustion operation, based on a plurality of detection data obtained by the combustion fluctuation detection means for detecting a combustion fluctuation state of the internal combustion engine during the lean combustion operation, and a plurality of detection data obtained by the combustion fluctuation detection means. Correction coefficient calculation means for calculating a correction coefficient of the fuel supply amount for bringing the combustion state close to the lean limit during the lean combustion operation, and the lean combustion with the correction coefficient calculated by the correction coefficient calculation means When the internal combustion engine leaves the lean combustion operation, the correction coefficient calculated by the correction coefficient calculation means is held during the lean combustion operation before the departure when the internal combustion engine leaves the lean combustion operation. When the internal combustion engine returns to the lean combustion operation after the internal combustion engine has left the lean combustion operation, the correction coefficient retained by the correction coefficient retaining means is used for the lean combustion. With the configuration in which the return time correction means for correcting the fuel supply amount during operation is provided, when the lean combustion operation is switched back to the lean combustion operation after returning to the operation state at the normal air-fuel ratio, The fuel supply amount is reset using the correction coefficient learned during the combustion operation. Therefore, it is not necessary to learn the variation between the cylinders from the beginning again, and it becomes possible to immediately shift to the lean limit combustion limit control state.

According to the fuel supply system for an internal combustion engine of the present invention as set forth in claim 2, in addition to the structure of claim 1, when the internal combustion engine is stopped, the lean combustion operation before the engine stop is performed. Due to the configuration in which the engine stop correction coefficient holding means for holding the correction coefficient calculated by the correction coefficient calculation means is provided at times, the combustion limit control state for lean operation can be promptly entered even when the internal combustion engine is restarted. You can

According to the fuel supply system for an internal combustion engine of the present invention as defined in claim 3, in addition to the configuration of claim 1 or 2, the internal combustion engine has a plurality of cylinders, and the above combustion fluctuations occur. With the configuration in which the detection means, the correction coefficient calculation means, the correction coefficient holding means, and the correction means are provided for each cylinder, the fuel supply amount is corrected for each cylinder, and fine control of the internal combustion engine is performed. .

According to the fuel supply system for an internal combustion engine of the present invention as set forth in claim 4, in addition to the structure as set forth in any one of claims 1 to 3, the combustion fluctuation detecting means includes the internal combustion engine. Angular velocity fluctuation detecting means for detecting a fluctuation value of the angular acceleration of a rotary shaft driven by the internal combustion engine as combustion fluctuation data of the internal combustion engine, and normalizing the fluctuation value by normalizing the fluctuation value according to the operating state of the internal combustion engine. And a combustion deterioration determination value calculation means for calculating a combustion deterioration determination value by comparing the normalized variation value obtained by the normalization variation value detection means with a predetermined threshold value. The correction coefficient calculation means is configured to calculate the correction coefficient such that the combustion deterioration determination value approaches a predetermined reference value, thereby controlling the combustion state corresponding to the operating state of the internal combustion engine. I will be able to There is an advantage that it is possible to perform emission limit operating in a wider operating range.

According to the fuel supply method for an internal combustion engine of the present invention as defined in claim 5, the fuel supply means capable of adjusting the fuel supply amount and the fuel supplied from the fuel supply means according to the target air-fuel ratio An internal combustion engine that has a fuel supply control unit that sets a supply amount and controls the fuel supply unit based on this set value, and that can perform lean combustion operation at an air-fuel ratio leaner than the stoichiometric air-fuel ratio in a specific operating region. In the engine fuel supply method, a combustion fluctuation detection step of detecting a combustion fluctuation state of the internal combustion engine during the lean combustion operation, and based on a plurality of detection data detected in the combustion fluctuation detection step, during the lean combustion operation A correction coefficient calculation step for calculating a correction coefficient for the fuel supply amount for bringing the combustion state close to the lean limit, and the lean combustion operation with the correction coefficient calculated in the correction coefficient calculation step. And a correction coefficient for holding the correction coefficient calculated in the correction coefficient calculation step during the lean combustion operation before the departure when the internal combustion engine leaves the lean combustion operation. Holding step and when the internal combustion engine returns to the lean combustion operation after leaving the lean combustion operation, the correction coefficient held in the correction coefficient holding step corrects the fuel supply amount during the lean combustion operation. It consists of the correction step at the time of return, so that when the lean combustion operation returns to the normal air-fuel ratio operation state and then the lean combustion operation is switched again, the correction coefficient learned during the lean combustion operation immediately before that is used. Fuel supply is reset. Therefore, it is not necessary to learn the variation between the cylinders from the beginning again, and it becomes possible to immediately shift to the lean limit combustion limit control state.

According to the fuel supply method for an internal combustion engine of the present invention as set forth in claim 6, in addition to the structure of claim 5, the correction coefficient holding step is performed even when the internal combustion engine is stopped. The combustion limit control of the lean operation is promptly performed even when the internal combustion engine is restarted by the configuration that the correction coefficient calculated by the correction coefficient calculation means is held during the lean combustion operation before the engine is stopped. You can move to the state.

According to the fuel supply method for an internal combustion engine of the present invention as set forth in claim 7, in addition to the configuration of claim 5 or 6, the internal combustion engine has a plurality of cylinders, and each of the above steps is performed. However, due to the configuration being performed for each cylinder,
The fuel supply amount is corrected for each cylinder, and fine control of the internal combustion engine is performed. Further, in a fuel supply method for an internal combustion engine according to an eighth aspect of the present invention, in addition to the configuration according to any one of the fifth to seventh aspects, the combustion variation detecting step is performed as combustion variation data of the internal combustion engine. Angular acceleration fluctuation detection step of detecting a fluctuation value of angular acceleration of a rotary shaft driven by the internal combustion engine, and normalized fluctuation for normalizing the fluctuation value according to an operating state of the internal combustion engine to obtain a normalized fluctuation value A value detection step and a combustion deterioration information amount detection step of detecting the combustion deterioration information amount from the data of the set number of detection cycles, wherein the correction coefficient calculation step is performed by the combustion deterioration information amount having a predetermined reference value. By being configured to calculate the correction coefficient so as to approach to, it becomes possible to control the combustion state corresponding to the operating state of the internal combustion engine, and to perform lean limit operation in a wider operating range. There is an advantage that will be able Nau.

[Brief description of drawings]

FIG. 1 is a schematic control block diagram showing a configuration of a fuel supply device for an internal combustion engine of the present invention.

FIG. 2 is an overall configuration diagram of an engine system having a fuel supply device for an internal combustion engine of the present invention.

FIG. 3 is a hardware block diagram showing a control system of an engine system having a fuel supply device for an internal combustion engine of the present invention.

FIG. 4 is a map showing the operating characteristics of the fuel supply system for an internal combustion engine of the present invention, which is a map showing a detection data effective operation region.

FIG. 5 is a map showing operating characteristics of the fuel supply system for an internal combustion engine of the present invention, which is a map showing an example of switching the detection data effective operation area.

FIG. 6 is a graph showing the operating characteristics of the fuel supply system for an internal combustion engine of the present invention, in which (a) to (c) are all relationships between the drive time and deviation of each injector provided in a multi-cylinder engine. It is a graph which shows.

FIG. 7 is a flow chart for explaining the operation of the internal combustion engine fuel supply apparatus of the present invention.

[Explanation of symbols]

1 engine (internal combustion engine) 2 combustion chamber 3 intake passage 3a surge tank 4 exhaust passage 5 intake valve 6 exhaust valve 7 air cleaner 8 throttle valve 9 electromagnetic fuel injection valve (injector) 9a injector solenoid 10 three-way catalyst 11A first bypass passage 11B 2nd bypass passage 12 Stepper motor valve (STM valve) 12a Valve body 12b Stepper motor (ISC actuator) 12c Spring 13 First idle air valve 14 Air bypass valve 14a Valve body 14b Diaphragm type actuator 15 Fuel pressure regulator 16 Spark plug 17 an air flow sensor (intake air amount sensor) 18 intake air humidity parameter atmospheric pressure sensor intake air temperature sensor 19 as a detecting means 20 throttle position sensor 21 the idle switch 22 O ₂ sensor 23 water temperature Sensor 24 crank angle sensor (engine speed sensor) 25 ECU as air-fuel ratio control means 26 CPU (arithmetic unit) 28 input interface 29 analog / digital converter 30 vehicle speed sensor 35 input interface 36 ROM (storage means) 37 RAM 39 injection driver 40 Ignition driver 41 Power transistor 42 Ignition coil 43 Distributor 44 ISC driver 45 Bypass air driver 46 EGR driver 50 Combustion fluctuation detection means 50A Angular acceleration fluctuation detection means 50B Normalized fluctuation value detection means 51 Correction coefficient calculation means 52 Correction means 53 Correction Coefficient holding means 54 Correcting means at return 55 Correction coefficient holding means at engine stop 80 Exhaust gas recirculation passage (EGR passage) 81 EGR valve 81a Valve body 81b Diaphragm type a Chueta 82 pilot passage 83 ERG valve control solenoid valve 83a solenoid 141 pilot passage 142 solenoid valve 142a solenoid control air bypass valve

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location F02D 45/00 358 Z 362 J

Claims (8)

[Claims] 1. A fuel supply means capable of adjusting a fuel supply quantity, a fuel supply quantity from the fuel supply means is determined according to a target air-fuel ratio, and the fuel supply means is controlled based on the determined value. A fuel supply device for an internal combustion engine, which is capable of performing lean combustion operation at an air-fuel ratio leaner than the stoichiometric air-fuel ratio in a specific operating region, in a specific operating region, and a combustion fluctuation of the internal combustion engine during the lean combustion operation. A combustion variation detecting means for detecting the state, and a correction coefficient for the fuel supply amount for bringing the combustion state close to the lean limit during the lean combustion operation based on a plurality of detection data obtained by the combustion variation detecting means. The internal combustion engine is provided with a correction coefficient calculation means and a correction means for correcting the fuel supply amount during the lean combustion operation with the correction coefficient calculated by the correction coefficient calculation means. When leaving the operation, a correction coefficient holding means for holding the correction coefficient calculated by the correction coefficient calculating means during the lean combustion operation before the departure is provided, and the correction means holds the lean combustion operation of the internal combustion engine. When returning to the lean combustion operation again after the separation, the recovery correction means is provided for correcting the fuel supply amount during the lean combustion operation by the correction coefficient held in the correction coefficient holding means. A fuel supply device for an internal combustion engine. 2. An engine stop correction coefficient holding means for holding the correction coefficient calculated by the correction coefficient calculation means during the lean combustion operation before the engine stop, when the internal combustion engine is stopped. The fuel supply device for an internal combustion engine according to claim 1, wherein 3. The internal combustion engine has a plurality of cylinders, and the combustion fluctuation detection means, the correction coefficient calculation means, the correction coefficient holding means, and the correction means are provided for each cylinder. The fuel supply device for an internal combustion engine according to claim 1 or 2. 4. An angular acceleration fluctuation detecting means for detecting a fluctuation value of angular acceleration of a rotating shaft driven by the internal combustion engine as combustion fluctuation data of the internal combustion engine, and the fluctuation value for the combustion fluctuation detecting means. And a normalized variation value detecting means for obtaining a normalized variation value by normalizing according to the operating state of the internal combustion engine, and comparing the normalized variation value obtained by the normalized variation value detection means with a predetermined threshold value. Combustion deterioration determination value calculation means for obtaining a combustion deterioration determination value is provided, and the correction coefficient calculation means is configured to calculate the correction coefficient so that the combustion deterioration determination value approaches a predetermined reference value. The fuel supply device for an internal combustion engine according to any one of claims 1 to 3, characterized in that. 5. A fuel supply means capable of adjusting a fuel supply quantity, and a fuel supply quantity from the fuel supply means is set according to a target air-fuel ratio, and the fuel supply means is controlled based on the set value. A fuel supply method for an internal combustion engine, which is capable of performing lean combustion operation at an air-fuel ratio leaner than the stoichiometric air-fuel ratio in a specific operating region, and a combustion fluctuation of the internal combustion engine during the lean combustion operation. A combustion variation detection step for detecting the state, and a correction coefficient of the fuel supply amount for bringing the combustion state close to the lean limit during the lean combustion operation based on a plurality of detection data detected in the combustion variation detection step And a correction step for correcting the fuel supply amount during the lean combustion operation with the correction coefficient calculated in the correction coefficient calculation step. When leaving the lean combustion operation, a correction coefficient holding step of holding the correction coefficient calculated in the correction coefficient calculation step during the lean combustion operation before the leaving, and the internal combustion engine again after the lean combustion operation is left, When returning to the lean combustion operation, the internal combustion engine is characterized by comprising a return time correction step for correcting the fuel supply amount during the lean combustion operation by the correction coefficient held in the correction coefficient holding step. Fuel supply method. 6. The correction coefficient holding step is configured to hold the correction coefficient calculated by the correction coefficient calculation means during the lean combustion operation before the engine is stopped, even when the internal combustion engine is stopped. The fuel supply method for an internal combustion engine according to claim 5, wherein 7. The fuel supply method for an internal combustion engine according to claim 5, wherein the internal combustion engine has a plurality of cylinders, and the above steps are performed for each cylinder. 8. An angular acceleration fluctuation detecting step of detecting a fluctuation value of angular acceleration of a rotary shaft driven by the internal combustion engine as combustion fluctuation data of the internal combustion engine in the combustion fluctuation detecting step; A normalization fluctuation value detection step for obtaining a normalization fluctuation value by normalizing according to the operating state of the internal combustion engine; and a combustion deterioration information quantity detection step for detecting the combustion deterioration information quantity from the data in the set detection cycle number. The correction coefficient calculating step is configured to calculate the correction coefficient such that the combustion deterioration information amount approaches a predetermined reference value. A method for supplying fuel for an internal combustion engine according to item 1.