JP2001241348A - Fuel injection control device for internal combustion engine - Google Patents

Abstract

(57) [Problem] To provide a fuel injection control device that appropriately corrects a variation in injector injection amount between cylinders and realizes highly accurate air-fuel ratio control. SOLUTION: A cylinder-specific rich / lean air-fuel ratio control means A6 for intentionally controlling a target air-fuel ratio to be a rich air-fuel ratio or a lean air-fuel ratio for each cylinder or each bank, and cylinder-specific rich / lean air-fuel ratio control Within the cylinder-specific rich / lean air-fuel ratio control period by means A6, the actual fuel injection amount for each cylinder or each bank is estimated from the difference between the actual air-fuel ratio of each cylinder and the target air-fuel ratio. Cylinder correction amount calculating means A for calculating the fuel correction amount for each bank
The fuel injection amount for each cylinder or each bank is corrected by the fuel correction amount calculated by the cylinder-specific correction amount calculating means A4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control apparatus for an internal combustion engine, and more particularly to a fuel injection control apparatus for an in-cylinder fuel injection type multi-cylinder internal combustion engine or the like which uses an air-fuel ratio sensor to measure a fuel injection amount injected from a fuel injector. The present invention relates to a fuel injection control device that performs feedback correction.

[0002]

2. Description of the Related Art There is known an in-cylinder fuel injection type internal combustion engine in which fuel is injected in a cylinder by a fuel injector provided for each cylinder to realize lean combustion by forming a stratified mixture. In the engine, it is an important issue to control the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber with high accuracy to ensure combustion stability. For this reason, a fuel injection amount feedback correction technique using an air-fuel ratio sensor has been conventionally known.

The fuel injector detects an air-fuel ratio of a combustion gas with an air-fuel ratio sensor such as an O ₂ sensor attached to an exhaust pipe of an internal combustion engine, and obtains a target air-fuel ratio from an output value thereof. This is to perform fine air-fuel ratio control by feedback-correcting the fuel injection amount injected from the engine.

In addition, the above-described feedback control is applied to intentionally release the catalyst poisoning of the catalytic converter for purifying exhaust gas by the sulfur component contained in the gasoline fuel by increasing the exhaust temperature. There is known cylinder-specific rich / lean air-fuel ratio control that forms a rich / lean air-fuel ratio for each cylinder or for each bank (cylinder row). this is,
Since the combustion gas having a lean-rich air-fuel ratio undergoes post-burning reaction in the exhaust pipe and the catalytic converter, it also plays a role as an early activation technology of the catalyst of the catalytic converter.

Further, as a prior art of a fuel injection control device for an internal combustion engine, an amount of air taken into each cylinder is estimated from engine operation parameters, and a fuel injection amount to be injected by a fuel injector is calculated based on the estimated amount of air. A method of calculating a fuel amount actually supplied into a cylinder from an output value of an air-fuel ratio sensor and an estimated value of an amount of air taken into the cylinder, and correcting a fuel injection amount injected by a fuel injector (Japanese Patent Laid-Open No. Japanese Patent Application Laid-Open No. H8-338292, which discloses selecting the optimal fuel injection correction amount for each cylinder, learning the optimal fuel injection correction amount, and controlling the subsequent fuel injection in each cylinder. Is known.

Further, as a prior art of a fuel injection control device for an internal combustion engine, a variation in air-fuel ratio between cylinders is detected by utilizing rotation fluctuation during lean burn operation, and a stoichiometric air-fuel ratio (stoichiometric) operation is performed based on this. For correcting the fuel injection amount by the fuel injector of each cylinder at the time (Japanese Patent Application Laid-Open No. 7-279732), and a value correlated with the air-fuel ratio of the air-fuel mixture supplied to the in-cylinder combustion is obtained for each cylinder. The fuel injection amount by the fuel injector for each cylinder is corrected for each cylinder based on the value to make the air-fuel ratio of the air-fuel mixture supplied to each cylinder uniform (Japanese Patent Application Laid-Open No. 5-54444). I have.

[0007]

Actually, in a fuel injector that injects fuel into each cylinder in response to an air-fuel ratio request, there is an injection amount variation due to initial and aging, and the individual variation is present. Is combustion between cylinders (air-fuel ratio)
, Which deteriorates engine operation performance, fuel economy, and exhaust performance.

[0008] Also, due to the characteristics of the air-fuel ratio sensor, the more the air-fuel ratio deviates from the stoichiometric air-fuel ratio, the more easily the sensor element temperature is affected. There is a concern that it may be difficult to perform high-precision air-fuel ratio control due to the dependence, so that an appropriate lean burn operation cannot be performed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a fuel injection type multi-cylinder internal combustion engine of a feedback control type equipped with an air-fuel ratio sensor. An object of the present invention is to provide a fuel injection control device that appropriately corrects a variation in injection amount and realizes highly accurate air-fuel ratio control.

[0010]

In order to achieve the above object,
The fuel injection control device for an internal combustion engine according to the present invention measures or estimates the amount of intake air entering a cylinder of the internal combustion engine, and supplies a fuel having a fuel injection amount corresponding to the amount of intake air from a fuel injector provided for each cylinder. A fuel injection control device for an internal combustion engine that injects fuel for each cylinder and performs feedback control on the fuel injection amount using the actual air-fuel ratio of the combustion gas detected by the air-fuel ratio detection means so that the actual air-fuel ratio matches the target air-fuel ratio. Cylinder-specific rich / lean air-fuel ratio control means for intentionally controlling the target air-fuel ratio to be a rich air-fuel ratio or a lean air-fuel ratio for each or each bank; and cylinder-specific rich / lean air-fuel ratio control means for controlling the cylinder-specific rich / lean air-fuel ratio. During the lean air-fuel ratio control period, the actual fuel injection amount for each cylinder or each bank is estimated from the deviation of the actual air-fuel ratio of each cylinder from the target air-fuel ratio. Cylinder-specific correction amount calculating means for calculating a fuel correction amount for each cylinder or each bank, and correcting the fuel injection amount for each cylinder or each bank with the fuel correction amount calculated by the cylinder-specific correction amount calculating means. It is characterized by doing.

As a result, the fuel injection amount between the cylinders can be made uniform, the combustion stability can be improved, and the high-precision air-fuel ratio control can be realized, so that the lean fuel-air mixture can be burned more efficiently. Performance can be improved. The fuel injection control device for an internal combustion engine according to the present invention can be applied to an in-cylinder injection system in which the fuel injector provided for each cylinder injects fuel in a cylinder.

In a specific embodiment of the fuel injection control device for an internal combustion engine according to the present invention, the cylinder-specific rich / lean air-fuel ratio control means controls the cylinder-specific rich / lean air-fuel ratio control to perform a rich air-fuel ratio control in an exhaust system. It is characterized in that it is carried out for the purpose of reducing the exhaust gas by the afterburning reaction based on the fuel ratio and lean air-fuel ratio, and for the early warm-up of the catalyst by the heat generated by the afterburning in the catalytic converter for purifying exhaust gas.

In a specific embodiment of the fuel injection control device for an internal combustion engine according to the present invention, the cylinder-specific rich / lean air-fuel ratio control means does not fix the rich air-fuel ratio or the lean air-fuel ratio for each cylinder. The cylinders of the rich air-fuel ratio and the lean air-fuel ratio are switched and set by the pattern cycle of (1).

In a specific aspect of the fuel injection control apparatus for an internal combustion engine according to the present invention, a plurality of types of patterns are provided as pattern cycles in the cylinder-specific rich / lean air-fuel ratio control means in accordance with the operating state of the internal combustion engine. It is characterized in that the pattern cycle is switched according to the control parameters of the internal combustion engine.

In a specific embodiment of the fuel injection control device for an internal combustion engine according to the present invention, the rich / lean air-fuel ratio control means shifts the pattern by a predetermined cylinder in accordance with the order of the ignition cylinder every time one pattern cycle elapses. Each cylinder is controlled so as to receive both a rich air-fuel ratio and a lean air-fuel ratio request.

In a specific embodiment of the fuel injection control device for an internal combustion engine according to the present invention, the rich / lean air-fuel ratio control means detects a change in air-fuel ratio for each cylinder in accordance with the detection response of the air-fuel ratio sensor. It is characterized by manipulating the inversion cycle of the rich / lean air-fuel ratio so that it can be performed.

Further, in a specific embodiment of the fuel injection control device for an internal combustion engine according to the present invention, the cylinder-specific correction amount calculating means calculates a target air-fuel ratio between the target cylinder air-fuel ratio during the rich control and the target air-fuel ratio during the lean control of the corresponding cylinder. It is characterized in that the correction amount is calculated in consideration of the deviation.

Further, in a specific embodiment of the fuel injection control device for an internal combustion engine according to the present invention, the output value of the air-fuel ratio sensor used in the cylinder-by-cylinder correction amount calculating means is such that the output value of the fuel in response to the rich and lean air-fuel ratio demands In consideration of a transportation delay, a combustion time, a sensor response, and the like, a sensor output value is sampled after a lapse of a predetermined time or a predetermined crank angle with reference to an angle signal of a fuel injection timing or an ignition timing.

In a specific embodiment of the fuel injection control device for an internal combustion engine according to the present invention, the sampling of the output value of the air-fuel ratio sensor is performed for each cylinder in accordance with a rich / lean pattern cycle. Is determined. In a specific aspect of the fuel injection control device for an internal combustion engine according to the present invention, the correction amount calculated by the cylinder-by-cylinder correction amount calculating means is stored in a nonvolatile storage means for each cylinder. .

Further, in a specific embodiment of the fuel injection control device for an internal combustion engine according to the present invention, the calculation of the correction amount by the cylinder-specific correction amount calculating means is performed by using a coefficient for a deviation from a target air-fuel ratio of the corresponding cylinder. Is calculated by adding. In a specific aspect of the fuel injection control device for an internal combustion engine according to the present invention, the calculation of the correction amount by the cylinder-by-cylinder correction amount calculating means has experienced the rich air-fuel ratio and the lean air-fuel ratio in the corresponding cylinder at least a predetermined number of times. On the basis of this, the calculation is performed from the deviation from the target air-fuel ratio in each case.

Further, in a specific embodiment of the fuel injection control device for an internal combustion engine according to the present invention, the calculation of the cylinder-specific correction amount by the cylinder-specific correction amount calculating means is not performed during the lean combustion composed of the stratified mixture. During the calculation of the correction amount, the air-fuel ratio feedback control that operates to match the target air-fuel ratio is stopped.

In a specific embodiment of the fuel injection control device for an internal combustion engine according to the present invention, the cylinder-by-cylinder correction amount calculation by the cylinder-by-cylinder correction amount calculation means is performed in accordance with a fuel injection amount that changes in an operating state. One or more correction amounts are calculated for each time, and after the calculation is completed, the correction amounts are switched according to the operation state.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A fuel injection control apparatus for a direct injection internal combustion engine according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram of a direct injection internal combustion engine system which is a feature of the present embodiment.

Intake port 1A of the internal combustion engine (engine) 1
Includes an air cleaner 5, an air flow sensor 7, an electronically controlled throttle valve (ETC) 4, a collector 8, and an intake pipe 10.
Are connected in order. The air taken into the internal combustion engine 1 is taken in from the inlet 6 of the air cleaner 5, passes through an air flow meter 7, which is a means for measuring the amount of intake air Q, and enters the collector 8 at a controlled flow rate by the ETC 4. The air taken into the collector 8 is distributed to each intake pipe 10 connected to each cylinder (cylinder) 9 of the internal combustion engine 1, and is guided into the cylinder (combustion chamber) 9.

A fuel such as gasoline is sucked and pressurized from a fuel tank 11 by a fuel pump 12 and supplied to a fuel system provided with a fuel injector 13. The pressurized fuel is regulated to a constant pressure (for example, 5 MPa) by a fuel pressure regulator 14, and is supplied from a fuel injector 13 provided for each cylinder 9 to the inside of the cylinder 9, that is,
It is injected directly into the cylinder. The injected fuel is ignited by the spark of the ignition plug 16 due to the discharge voltage raised by the ignition coil 15.

An exhaust pipe 20 and a catalytic converter 21 for purifying exhaust gas are connected to an exhaust port 1B of the internal combustion engine 1. An A / F for detecting the actual air-fuel ratio of the combustion gas upstream of the catalytic converter 21 is provided. A sensor (air-fuel ratio sensor) 22 is provided. Further, a crank angle sensor 18 for detecting a rotation angle of a crank shaft 19 is provided in a crank chamber portion of the engine 1.

A control unit 17 for controlling fuel injection and ignition timing is provided. The control unit 17 inputs a signal indicating the intake air flow rate from the air flow meter 7, an angle signal POS of the crankshaft 19 from the crank angle sensor 18, and an exhaust gas detection signal from the exhaust A / F sensor 22.

The intake air amount signal output from the air flow meter 7 is subjected to processing such as filter processing means in the control unit 17 and is converted into an intake air amount Q. The intake air amount Q is divided by the engine speed. By multiplying the coefficient k so that the air-fuel ratio becomes stoichiometric (A / F = 14.7), the basic fuel injection pulse width per cylinder, that is,
A basic fuel injection amount is determined. Note that the intake air amount Q can also be estimated by calculation from various operating parameters of the internal combustion engine 1.

The control unit 17 obtains a fuel injection amount by performing various fuel amount corrections according to the operating state of the internal combustion engine based on the basic fuel injection amount, and drives the fuel injector 13 to control each cylinder. Control to supply fuel.
Since the actual air-fuel ratio (actual air-fuel ratio) of the exhaust gas can be known from the output of the A / F sensor 22 provided in the exhaust pipe 20, when it is desired to obtain a desired air-fuel ratio, the air-fuel ratio of the A / F sensor 22 is determined. A desired air-fuel ratio state can be obtained by performing air-fuel ratio feedback control in which the control unit 17 adjusts the supplied fuel amount based on the signal. That is, A /
The fuel injection amount can be feedback-controlled using the actual air-fuel ratio of the combustion gas detected by the F sensor 22 so that the actual air-fuel ratio matches the target air-fuel ratio.

FIG. 2 is a control block diagram of a fuel injection control device for an internal combustion engine according to one embodiment of the present invention. The intake air amount Q measured and detected by the air flow meter 7 is multiplied by a coefficient k (process A7) to calculate a basic fuel injection pulse width Tp per cylinder, that is, a basic fuel injection amount. Fuel based on the calculated basic fuel injection amount is supplied to the internal combustion engine (engine) A1 by the existing fuel injectors INJ # 1 to INJ # n (A9) for the number of cylinders. In order to know the actual burned air-fuel ratio, the actual air-fuel ratio is detected by A / F output detecting means A2 comprising an air-fuel ratio sensor or the like attached to the exhaust pipe of the internal combustion engine. Based on the detected air-fuel ratio, the air-fuel ratio feedback control means A5 calculates the feedback coefficient Y so as to match the target air-fuel ratio in the current operation range, and corrects the above-described basic injection pulse width Tp, Operate the engine near the target air-fuel ratio.

On the other hand, when a control request for the purpose of raising the temperature of the catalyst and reducing the exhaust is generated, the rich / lean air-fuel ratio control means A6 for each cylinder sets the rich air-fuel ratio or the lean air-fuel ratio for each cylinder. The following control amounts X1 to Xn are calculated. The calculated control amounts X1 to Xn are corrected to the basic fuel injection amount in process A8, and the fuel of the corrected fuel injection amount is supplied to the fuel injectors INJ # 1 to INJ # n (A9).
More injection is performed.

Thus, as shown in the example of the cylinder-by-cylinder air-fuel ratio requirement shown in FIG. 3, the # 1 and # 2 cylinders have a rich air-fuel ratio, the # 3 and # 4 cylinders have a lean air-fuel ratio, and the # 5 and 6 have a rich air-fuel ratio. As the fuel ratio, a rich combustion cylinder or a lean combustion cylinder is formed. Here, the set pattern cycle of the rich cylinder / lean cylinder is variable in order to respond to the demands such as the number of cylinders of the internal combustion engine, the ignition order, the cylinder arrangement, and the like.

During the period in which the rich / lean combustion cylinder intentionally formed exists, the cylinder-specific correction amount calculating means A4
Then, the actual air-fuel ratio detected by the A / F output detection means A2 is compared with a target air-fuel ratio predicted in advance when the actual air-fuel ratio is corrected to the control amounts X1 to Xn. The correction amounts Z1 to Zn are calculated as the injection flow rate variations of the injectors INJ # 1 to INJ # n (A9), and the injection amounts of the respective cylinders are corrected.

Here, the feedback correction by the air-fuel ratio feedback control means A5 is prohibited during the calculation of the correction amounts Z1 to Zn. In other words, the cylinder-by-cylinder correction amount calculation means A4 does not execute the cylinder-by-cylinder correction amount calculation during lean burn composed of a stratified mixture, and operates during the correction amount calculation to match the target air-fuel ratio. Stop the feedback control.

The calculated correction amounts Z1 to Zn are stored in the cylinder-by-cylinder correction amount storage means A3 composed of a nonvolatile memory, and are always used as each injector correction coefficient after the cylinder-specific rich / lean air-fuel ratio control request is released. It will be used for correcting the basic injection amount.

During the cylinder-specific rich / lean air-fuel ratio control, the catalyst of the catalytic converter 21 alternately receives rich and lean exhaust air-fuel ratio exhaust gas as shown in FIG. Become. The excess oxygen ratio of the exhaust gas is
When lean exhaust gas is leaner than the stoichiometric air-fuel ratio, FIG.
As shown in (b), the value becomes large when lean exhaust gas is received.

Here, the catalyst used in the catalytic converter 21 has a function of once adsorbing substances to be oxidized such as HC and CO and oxidizing them when oxygen is present in the atmosphere. Therefore, the catalytic converter 21
When receiving a rich exhaust gas, the catalyst adsorbs HC and CO contained in the exhaust gas, and when receiving a lean exhaust gas, oxidizes HC and CO using oxygen in the exhaust gas. Acts harmless. At the same time, the catalyst generates heat in a pattern as shown in FIG.

Therefore, if this operation (cylinder rich / lean air-fuel ratio control) is performed at a low temperature before activation of the catalyst,
Purification of exhaust gas and early activation of the catalyst can be achieved. Further, it is possible to prevent the sulfur component contained in the fuel from accumulating inside the catalyst and lowering the exhaust gas purification efficiency by using the heat generated by this operation.

FIGS. 5A to 5C show changes in the catalyst temperature, the HC exhaust concentration, and the cooling water temperature of the internal combustion engine when the cylinder-specific rich / lean air-fuel ratio control is performed and not performed. 5 (a) to 5 (c), by performing the rich / lean air-fuel ratio control for each cylinder, the temperature of the catalyst is quickly increased,
Further, it can be seen that HC emission can be suppressed.

FIG. 6 shows the relationship between the control amount by the cylinder-specific rich / lean air-fuel ratio control means and the output value of the air-fuel ratio sensor. In FIG. 6, the ignition order is # 1 → 2 → 3 → 4 → 5 →
In the 6-cylinder internal combustion engine of 6, the control amount from the rich / lean air-fuel ratio control means for each cylinder is such that the # 1, 3, 5 cylinders are rich air-fuel ratios, the # 2, 4, 6 cylinders are lean air-fuel ratios, The following describes an example of a pattern cycle in which lean combustion alternates.

The output value of the air-fuel ratio sensor with respect to the control amount for each cylinder changes to a waveform as shown in FIG. #
Since rich combustion is performed by the control amount X1 given to one cylinder, the actual air-fuel ratio detected by the air-fuel ratio sensor becomes the rich air-fuel ratio. Here, the air-fuel ratio predicted in advance when the control amount X1 is given is indicated by the target air-fuel ratio MR. The air-fuel ratio state of the # 1 cylinder of the air-fuel ratio sensor output value is on the rich side by s1 with respect to the target air-fuel ratio MR.

Since the control amount X2 given to the # 2 cylinder causes lean combustion, the actual air-fuel ratio detected by the air-fuel ratio sensor indicates the lean air-fuel ratio, and is predicted in advance when the control amount X2 is given. Assuming that the lean air-fuel ratio to be performed is the target air-fuel ratio ML, the air-fuel ratio state of the # 2 cylinder is richer than the target air-fuel ratio ML by s2. Similarly, also in the other cylinders, the air-fuel ratio state is richer or leaner than the target air-fuel ratios MR and ML by s3, s4, s5, and s6. These deviations from the target air-fuel ratios MR and ML are variations in the fuel injectors of each cylinder.

In the case of the # 1 cylinder, since it is on the rich side for s1, the fuel injector has a rich side variation with respect to the central characteristic of the fuel injector flow characteristic with respect to the fuel injection command value shown in FIG. That is, for the fuel injection command value calculated by the calculation, the fuel injector INJ # of the # 1 cylinder is used.
1 injects more fuel. Similarly, the fuel injector INJ # 2 of the # 2 cylinder is on the richer side than the target with respect to the lean request, indicating that the fuel is injected more than the fuel injection command value (see FIG. 6). The correction amount of each cylinder fuel injector is calculated by calculating the minute.

FIG. 8 shows the relationship between the control amount and the output value of the air-fuel ratio sensor by the cylinder-specific rich / lean air-fuel ratio control means in different pattern cycles of the cylinder-specific rich / lean air-fuel ratio control, similarly to FIG. ing. In this example, cylinders # 1, 3, and 5 have a lean air-fuel ratio, and cylinders # 2, 4, and 6 have a rich air-fuel ratio. Similar to the rich / lean pattern cycle in FIG. If there is, the actual air-fuel ratio state of each cylinder detected by the air-fuel ratio sensor deviates from the target air-fuel ratio as in s1 'to s6', and the amount is shown in FIG.
S1 to s6. In general, the variation in the injection amount of the fuel injector itself is caused by INJ # 1 in FIG.
This is because, as shown in INJ # n, the central characteristic is biased toward either the rich side (flow rate: high) or the lean side (flow rate: low).

However, considering the existence of a singular point,
In order to improve the correction accuracy, for example, to calculate the correction amount of the fuel injector of the # 1 cylinder, the deviation from the target air-fuel ratio when the # 1 cylinder is set to the rich air-fuel ratio and when the # 1 cylinder is set to the lean air-fuel ratio is calculated. It is desirable to use both. This can be realized by shifting the rich / lean pattern by a predetermined cylinder in accordance with the order of the ignition cylinders every time one cycle elapses, and controlling each cylinder to receive a request for a rich air-fuel ratio and a lean air-fuel ratio.

The deviation of the air-fuel ratio of each cylinder from the target air-fuel ratio has a gradient of the variation in the flow characteristic of the fuel injector. Since the deviation of the air-fuel ratio changes depending on the operation load, for example, Z1a shown in FIG. , Z1b, etc.
By calculating the correction amounts separately for one or more correction amount calculation areas, it becomes possible to perform highly accurate air-fuel ratio correction and fuel injector inter-cylinder variation correction.

FIG. 9 shows an example of a processing flow of cylinder-specific rich / lean air-fuel ratio control by the cylinder-specific rich / lean air-fuel ratio control means A6. First, it is determined whether or not there is a rich / lean air-fuel ratio control request from catalyst temperature rise and reduction of exhaust gas components (step 91). If there is a request, assuming a 6-cylinder internal combustion engine as an example, whether the # 1,2,3 cylinders are rich air-fuel ratios and # 4,5,6 are lean air-fuel ratios,
Or # 1,3,5 cylinders with rich air-fuel ratio, # 2,4,6
Is determined as a lean air-fuel ratio, and a pattern cycle of a control amount for each cylinder is determined (step 92).

Next, the control amount for each cylinder on the rich side and the lean side is determined (step 93), and the control amount is output to each fuel injector (INJ) (step 9).
4). FIG. 10 shows an example of determining the pattern cycle of the control amount in step 92 of FIG. In this example, the pattern cycle is determined using the internal combustion engine speed, which is an internal combustion engine control parameter.The higher the internal combustion engine speed, the shorter the cycle of the output value of the air-fuel ratio sensor by the rich / lean air-fuel ratio control. Therefore, there is a possibility that the amount of change in the air-fuel ratio for each cylinder cannot be detected accurately. Therefore, the reversal cycle of the rich / lean air-fuel ratio is controlled in consideration of the detection response of the air-fuel ratio sensor.

First, the internal combustion engine speed NE and a predetermined value NE1
Are compared (step 101), and when it is determined that the rotation is low, it is determined whether the set pattern cycle MODE1_A has been experienced for m cycles (step S) (step S10).
3). If experienced, select MODE1_B, otherwise select MODE1_A (106) (step 1)
03). MODE1_B is a rich / lean inversion cycle similar to the pattern cycle of MODE1_A, but it is assumed that the rich / lean air-fuel ratio is reversed for each cylinder.

Now, taking the # 1 cylinder as an example, MODE
The rich air-fuel ratio is experienced by m at 1_A, and the lean air-fuel ratio is experienced by m at MODE1_B, and the accuracy of the correction amount calculation can be improved. Similarly, the predetermined value NE2 is compared with the rotational speed of the internal combustion engine (step 102), the high rotational speed and the medium rotational speed are determined, and the pattern cycles MODE2_A, MODE2_B, MODE are determined according to the number of experiences (the number of cycles).
3_A and MODE3_B are selected (step 104,
Step 105, Step 106).

In this example, the period of air-fuel ratio detection becomes shorter as the internal combustion engine speed becomes higher, so that the rich-lean inversion period is set longer. Further, the pattern cycle can be set using parameters other than the internal combustion engine speed.

FIG. 11 shows the response of the output value of the air-fuel ratio sensor. The actual air-fuel ratio is detected by the air-fuel ratio sensor after the fuel supply to the internal combustion engine (lag) from the fuel supply time due to a dead time until the fuel is ignited and a primary delay in combustion. Therefore, for air-fuel ratio detection,
As shown in FIG. 12, the output value of the air-fuel ratio sensor is sampled after a lapse of a predetermined time or after a lapse of a crankshaft angle, using the ignition timing of the cylinder to be detected or the like as a reference signal. The sampling delay D in FIG. 12 indicates this, and it is assumed that this is corrected by a parameter that affects the delay such as the engine speed.

That is, the output value of the air-fuel ratio sensor used in the cylinder-by-cylinder correction amount calculating means A4 is determined based on the fuel injection timing in consideration of fuel transport delay, combustion time, sensor responsiveness, etc. for rich and lean air-fuel ratio requests. Alternatively, the sensor output value is sampled for a predetermined time or after a predetermined crank angle has elapsed based on the angle signal of the ignition timing.

When performing rich / lean air-fuel ratio control for each cylinder, when the air-fuel ratio sensor detects a change in the air-fuel ratio of the corresponding cylinder, interference with the air-fuel ratio components of other cylinders is a concern in addition to the above-mentioned delay factors. Is done. FIG. 13 shows an example of sampling a specific cylinder in order to accurately detect the actual air-fuel ratio for the rich / lean request of the corresponding cylinder. The control amount is # 1,
When a few cylinders are operated with a rich air-fuel ratio and # 4, 5, and 6 are operated with a lean air-fuel ratio, the actual air-fuel ratio in the rich combustion in the # 1 cylinder is detected after the delay, and the deviation from the target air-fuel ratio is detected. Minute s1
Is calculated. Next, when sampling the # 2 cylinder, the air-fuel ratio component of the # 1 cylinder is dragged and an accurate air-fuel ratio cannot be detected, so sampling is prohibited. Similarly, on the lean side, only the air-fuel ratio component of the # 4 cylinder, which is the first cylinder in which the rich / lean is reversed, is detected, and other sampling is prohibited.

In the next cycle, sampling is performed by shifting the pattern cycle of the control amount by a predetermined number of cylinders to allocate each cylinder to the cylinder immediately after the rich / lean inversion. In this example, after three cycles, the deviation from the target air-fuel ratio on the rich and lean sides is calculated for each cylinder.

FIG. 14 shows an example of calculating the control amount for each cylinder in step 93 of FIG. The control amount X is set in advance in a map including the engine speed and the engine load, and is calculated according to the operating state during the cylinder-specific rich / lean air-fuel ratio control. The control amount X can also be obtained by calculation using other control parameters.

FIG. 15 shows an example of a processing flow of cylinder-by-cylinder correction amount calculation by the cylinder-by-cylinder correction amount calculation means A4. First,
It is determined whether or not the cylinder-specific rich / lean air-fuel ratio control, which is a prerequisite for the calculation of the correction amount, is being performed (step 51). If the control is not being performed, the correction amount is not calculated. If the rich / lean air-fuel ratio control is being performed for each cylinder, the air-fuel ratio component AF for each cylinder is sampled (step 52).

Next, target air-fuel ratios MR and ML are calculated from a control amount X for setting each cylinder to a rich / lean air-fuel ratio (step 53), and the air-fuel ratio component AF is compared with the target air-fuel ratio.
The shift x1 is calculated for each cylinder (step 54).
Assuming that the number of times of calculation of the deviation for each cylinder is m, the calculation of the deviation is repeated until the predetermined number A is reached (step 55). Here, as described above, calculation is performed for both the shift on the rich side and the shift on the lean side of the corresponding cylinder. When the predetermined number A is satisfied, a correction amount Z for each cylinder is obtained from the A values calculated so far (step 56).

Next, the correction amount Z for each cylinder is output (step 57), and this is output to the RA in the correction amount calculating means A4 for each cylinder.
It is stored in M (step 58). FIG. 16 shows the target air-fuel ratio M
An example of R and ML calculations is shown. This is obtained by setting a target air-fuel ratio in a map for the control amount X in advance. This target air-fuel ratio may be obtained by calculation using other control parameters.

In the above-described calculation of the correction amount Z for each cylinder, the average value of the detected values may be simply used as the variation of the corresponding cylinder, but the weight coefficient k is obtained from the average value to improve the accuracy of the correction amount. It is also possible. FIG. 17 shows a setting example of the weight coefficient k. The correction amount is updated by a predetermined value using the weight coefficient k. Accuracy can be improved by repeatedly updating the correction amount to the reference value of the fuel injector each time a cylinder-specific rich / lean air-fuel ratio control request is generated, instead of calculating the correction amount all at once. FIG. 18 shows the process of updating the correction amount as described above.

Although several embodiments of the fuel injection control device for an internal combustion engine according to the present invention have been described in detail above, the present invention is not limited to the above embodiments, but is described in the claims. Various changes can be made in the design without departing from the spirit of the invention. For example,
The fuel correction is not performed for each cylinder, and in a double-row cylinder engine, it can be simply performed for each cylinder row, that is, for each bank.

[0062]

As can be understood from the above description, according to the fuel injection control apparatus for an internal combustion engine according to the present invention, in a fuel injection type internal combustion engine having an air-fuel ratio sensor, the fuel injector injection amount between cylinders Variation can be corrected, and highly accurate air-fuel ratio control can be realized.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a direct injection internal combustion engine system of an embodiment of a fuel injection control device for an internal combustion engine according to the present invention.

FIG. 2 is a control block diagram of a fuel injection control device for an internal combustion engine according to the embodiment of FIG. 1;

FIG. 3 is an explanatory diagram showing an example of a cylinder-by-cylinder air-fuel ratio request.

4 (a) to 4 (c) are graphs showing an exhaust air-fuel ratio, an oxygen excess ratio, and a calorific value of a catalyst during cylinder-specific rich / lean air-fuel ratio control.

FIGS. 5A to 5C are graphs showing changes in catalyst temperature, HC exhaust concentration, and cooling water temperature of the internal combustion engine when cylinder-specific rich / lean air-fuel ratio control is performed and not performed.

FIG. 6 is a graph showing a relationship between a control amount by cylinder-specific rich / lean air-fuel ratio control means and an air-fuel ratio sensor output value.

FIG. 7 is a graph showing a fuel injector flow rate characteristic with respect to a fuel injection command value.

FIG. 8 is a graph showing a relationship between a control amount and an air-fuel ratio sensor output value by cylinder-specific rich / lean air-fuel ratio control means in different pattern cycles of cylinder-specific rich / lean air-fuel ratio control.

9 is a processing flowchart of cylinder-by-cylinder rich / lean air-fuel ratio control in the fuel injection control device for the internal combustion engine of FIG. 1;

10 is a flowchart of a process for determining a pattern cycle of cylinder-specific rich / lean air-fuel ratio control in the fuel injection control device for an internal combustion engine in FIG. 1;

FIG. 11 is a graph showing a response characteristic of an air-fuel ratio sensor output value.

FIG. 12 is a graph showing an example of sampling the output of an air-fuel ratio sensor using a reference signal.

13 is a graph showing a specific cylinder sampling example in the internal combustion engine fuel injection control device of FIG. 1;

FIG. 14 is a graph showing an example of control amount calculation in the fuel injection control device for an internal combustion engine of FIG. 1;

FIG. 15 is a processing flowchart of cylinder-by-cylinder correction amount calculation in the fuel injection control device for an internal combustion engine of FIG. 1;

FIG. 16 is a graph showing a calculation example of target air-fuel ratios MR and ML.

FIG. 17 is a graph showing a setting example of a weight coefficient k.

FIG. 18 is a graph showing the history of correction amount update.

[Explanation of symbols]

 1. Internal combustion engine body 4. ETC5. Air cleaner 6. Inlet 7. Air flow meter 8. Collector 9. Cylinder 10. Intake pipe 11. Fuel tank 12. Fuel pump 13. Fuel injector 14. Fuel pressure regulator 15. Ignition coil 16. Spark plug 17. Control unit 18. Crank angle sensor 19. Crankshaft 20. Exhaust pipe 21. Catalytic converter 22. A / F sensor A2. A / F output detection means A3. Cylinder-based correction amount storage means A4. Correction amount calculating means for each cylinder A5. Air-fuel ratio feedback control means A6. Cylinder-specific rich / lean air-fuel ratio control means

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F01N 3/24 F02D 41/02 330A F02D 41/02 330 45/00 358H 362E 45/00 358 364N 362 B01D 53 / 36 ZABB 364 101B F-term (reference) 3G084 AA04 BA09 BA13 CA09 DA02 DA10 DA23 DA25 EA01 EA04 EA11 EB09 EB12 EB16 EB25 EC01 EC03 FA13 FA17 FA29 FA33 FA35 FA38 FA39 3G091 AA02 AA12 AA12AA12AA12AA12A13A BA19 CB02 CB06 CB07 DA01 DA02 DA08 DB02 DB06 DB07 DB08 DB09 DB10 DB13 DB15 DB16 DC01 DC02 EA01 EA03 EA05 EA16 EA30 EA31 EA34 FA02 FA04 FB10 FB12 FC02 FC07 HA11 HA18 HA36 HB05 3G301 HA04 HA06 JA02 HA02 HA02 JA02 HA02 MA11 NA01 NA08 NB02 NB03 NB07 NC04 ND02 ND15 NE14 PA01Z PB03Z P B05Z PD03A PE01Z PE03Z PE05Z PE09Z 4D048 AA06 AA13 AA18 AB01 AB02 AB05 AB07 BC01 CC53 DA01 DA03 DA08 DA13 DA20 EA04

Claims (15)

[Claims] An intake air amount entering a cylinder of an internal combustion engine is measured or estimated, and a fuel of a fuel injection amount corresponding to the intake air amount is injected for each cylinder from a fuel injector provided for each cylinder, and an air-fuel ratio is calculated. A fuel injection control device for an internal combustion engine that performs feedback control of a fuel injection amount so that an actual air-fuel ratio matches a target air-fuel ratio using an actual air-fuel ratio of a combustion gas detected by a detection unit. A cylinder-specific rich / lean air-fuel ratio control means for controlling the target air-fuel ratio to be a rich air-fuel ratio and a lean air-fuel ratio, and a cylinder-specific rich / lean air-fuel ratio control period by the cylinder-specific rich / lean air-fuel ratio control means. Then, the actual fuel injection amount for each cylinder or each bank is estimated from the deviation of the actual air-fuel ratio of each cylinder from the target air-fuel ratio. A cylinder correction amount calculating means for calculating a fuel correction amount, wherein the fuel injection amount for each cylinder or each bank is corrected by the fuel correction amount calculated by the cylinder correction amount calculating means. Engine fuel injection control device. 2. The fuel injection control device for an internal combustion engine according to claim 1, wherein the fuel injector provided for each cylinder is an in-cylinder injection type that injects fuel in a cylinder. 3. The cylinder-specific rich / lean air-fuel ratio control means performs cylinder-specific rich / lean air-fuel ratio control to reduce exhaust gas by a post-burning reaction based on a rich air-fuel ratio and a lean air-fuel ratio in an exhaust system, and to purify exhaust gas. The fuel injection control device for an internal combustion engine according to claim 1, wherein the control is performed for early warm-up of the catalyst due to heat generated by afterburning in the catalytic converter. 4. The rich / lean air-fuel ratio control means for each cylinder does not fix the rich air-fuel ratio or the lean air-fuel ratio for each cylinder, but switches between the rich air-fuel ratio and the lean air-fuel ratio in a predetermined pattern cycle. The fuel injection control device for an internal combustion engine according to claim 1, wherein: 5. The cylinder-specific rich / lean air-fuel ratio control means includes a plurality of patterns as a pattern cycle according to an operation state of the internal combustion engine, and switches the pattern cycle according to a control parameter of the internal combustion engine. The fuel injection control device for an internal combustion engine according to claim 4. 6. The rich / lean air-fuel ratio control means includes:
5. The method according to claim 4, wherein the pattern is shifted by a predetermined number of cylinders in accordance with the order of the ignition cylinders every one cycle of the pattern cycle, and each cylinder is controlled so as to receive both the rich air-fuel ratio and the lean air-fuel ratio requirement. A fuel injection control device for an internal combustion engine. 7. The rich / lean air-fuel ratio control means includes:
5. The fuel injection control of an internal combustion engine according to claim 4, wherein an inversion cycle of the rich / lean air-fuel ratio is operated so that a change in air-fuel ratio for each cylinder can be detected in accordance with a detection response of the air-fuel ratio sensor. apparatus. 8. The correction amount calculating means for each cylinder calculates a correction amount in consideration of a deviation from a target air-fuel ratio in each of the rich control and the lean control of the corresponding cylinder. Item 2. A fuel injection control device for an internal combustion engine according to Item 1. 9. An output value of an air-fuel ratio sensor used in the cylinder-by-cylinder correction amount calculating means is determined by taking into account fuel transport delay, combustion time, sensor responsiveness, etc. with respect to rich and lean air-fuel ratio requests, 2. The fuel injection control device for an internal combustion engine according to claim 1, wherein the sensor output value is sampled for a predetermined time or after a predetermined crank angle has elapsed with reference to the angle signal of the ignition timing. 10. The internal combustion engine according to claim 9, wherein the sampling of the output value of the air-fuel ratio sensor determines whether or not to perform sampling for each cylinder in accordance with a rich / lean pattern cycle. Fuel injection control device. 11. The fuel injection control device for an internal combustion engine according to claim 1, wherein the correction amount calculated by the cylinder-by-cylinder correction amount calculation means is stored in a non-volatile storage means for each cylinder. 12. The method according to claim 1, wherein the correction amount calculated by the cylinder-by-cylinder correction amount calculating means is calculated by adding a coefficient to a deviation from a target air-fuel ratio of the corresponding cylinder. A fuel injection control device for an internal combustion engine. 13. The calculation of the correction amount by said cylinder-specific correction amount calculating means is performed based on a difference between a target air-fuel ratio and a target air-fuel ratio under a condition that a rich air-fuel ratio and a lean air-fuel ratio have experienced a predetermined number of times or more in a corresponding cylinder. The fuel injection control device for an internal combustion engine according to claim 1, wherein the calculation is performed. 14. The cylinder-by-cylinder correction amount calculation means by the cylinder-by-cylinder correction amount calculation means is not performed during lean burn composed of a stratified mixture, and operates during the correction amount calculation to match the target air-fuel ratio. The fuel injection control device for an internal combustion engine according to claim 1, wherein the fuel ratio feedback control is stopped. 15. The cylinder-by-cylinder correction amount calculation by the cylinder-by-cylinder correction amount calculation means includes calculating one or a plurality of correction amounts for each cylinder in accordance with a fuel injection amount that changes in an operating state. 2. The fuel injection control device for an internal combustion engine according to claim 1, wherein the correction amount is switched according to an operation state after the termination.