JP3028717B2 - Fuel supply control device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply control device for an internal combustion engine, and more particularly to a technique for controlling an air-fuel ratio, which is a mixture ratio of intake air and fuel, according to an engine operating state.

[0002]

2. Description of the Related Art Conventionally, in an internal combustion engine, when an air-fuel ratio is controlled to a stoichiometric air-fuel ratio by feedback control, a feedback correction coefficient at this time is learned, and operation is performed at a predetermined air-fuel ratio leaner than the stoichiometric air-fuel ratio. The air-fuel ratio during lean burn is accurately controlled to a target value by correcting the basic fuel amount based on this learning value, obtaining a fuel amount that can accurately obtain the stoichiometric air-fuel ratio, and performing open control. One is known (see JP-A-57-105530).

[0003]

The operation by the lean burn and the recirculation of the exhaust gas, that is, the exhaust gas recirculation (hereinafter, referred to as the exhaust gas recirculation) will be described.
An engine that performs EGR according to the operation range has a problem in that it is not possible to correctly calculate a learning value of an air-fuel ratio used when performing operation by lean combustion. That is, in the region where the EGR region and the lean burn region overlap each other, when various conditions for performing the lean burn operation are not satisfied, feedback control to the stoichiometric air-fuel ratio is performed while causing a part of the exhaust gas to EGR to the intake system. However, the learned value of the air-fuel ratio obtained at this time is affected by the EGR-exhaust gas. For this reason, even if an attempt is made to obtain a predetermined lean air-fuel ratio by using the learned value during the lean burn operation, the EGR of the exhaust gas is not performed during the lean burn operation, so the basic fuel amount is corrected by the learned value. The fuel amount obtained does not correspond to the stoichiometric air-fuel ratio, and the fuel amount obtained by performing the open control (reduction correction by a predetermined coefficient) on the fuel amount as described above corresponds to the target predetermined lean air-fuel ratio. Not a value.

In view of the above problems, the present invention accurately controls the air-fuel ratio to the stoichiometric air-fuel ratio during normal operation and accurately adjusts the air-fuel ratio during lean-burn operation to a predetermined air-fuel ratio. The purpose is to control.

[0005]

Therefore, as shown in FIG. 1, the present invention relates to an intake air amount detecting means for detecting an intake air amount of an engine, and a rotational speed detecting means for detecting a rotational speed of the engine. A basic fuel supply amount calculating means for calculating a basic fuel amount to be supplied to the engine based on the detected intake air amount and the rotation speed, and an air-fuel ratio detection detecting an air-fuel ratio from an oxygen concentration in the exhaust gas. Means, a feedback correction coefficient calculating means for calculating a feedback correction coefficient for the basic fuel supply amount based on the detected air-fuel ratio, and a learning correction coefficient for the basic fuel supply amount based on the calculated feedback correction coefficient. A learning correction coefficient calculating means for calculating, and a feedback control for feedback-controlling the air-fuel ratio to near the stoichiometric air-fuel ratio using the feedback correction coefficient and the learning correction coefficient. Control means, first and second storage means for storing the calculated learning correction coefficient in association with the intake air amount and the rotation speed at that time, respectively, Exhaust gas recirculation rate setting means for setting the exhaust gas recirculation rate based on the current intake air amount and the rotation speed when in the recirculation area, and recirculating a part of the exhaust gas to the intake system based on the set exhaust gas recirculation rate Exhaust gas recirculation control means, operating state detecting means for detecting an operating state of the engine including at least the acceleration / deceleration state of the engine and the engine temperature, a detected lean air amount and a rotation speed in a predetermined lean burn region and the exhaust gas. When the recirculation region is in an overlapping region and the detected operating state satisfies a predetermined lean burn operating condition, and learning of the learning correction coefficient stored in the first storage means is not completed. In addition, Exhaust gas recirculation rate limiting means for restricting the recirculation rate to zero or a predetermined minute value; a detected intake air amount and a rotational speed in a predetermined lean combustion region, and a detected operating state in a predetermined lean combustion operating condition Is satisfied, and when learning of the learning correction coefficient stored in the first storage means is not completed, feedback control of the air-fuel ratio by the feedback control means is performed, and the feedback control is performed by the learning correction coefficient calculation means. A first learning means for storing the learned correction coefficient in the first storage means, wherein the detected intake air amount and the rotation speed are in a predetermined lean burn region, and the detected operating state is a predetermined lean burn condition. When the operating condition is satisfied and the learning of the learning correction coefficient stored in the first storage means has been completed, the exhaust gas recirculation rate is set to zero and the first storage means is stored in the storage means. The basic fuel supply amount is corrected by the stored learning correction coefficient and the target air-fuel ratio setting coefficient calculated based on the current intake air amount and the rotation speed, and the air-fuel ratio is reduced to a predetermined air-fuel ratio leaner than the stoichiometric air-fuel ratio. Lean-burn control means for controlling the feedback control when the detected intake air amount and rotation speed are outside a predetermined lean-burn region or the detected operating state does not satisfy a predetermined lean-burn operating condition. And a second learning means for performing feedback control of the air-fuel ratio by the control means and storing the learning correction coefficient calculated by the learning correction coefficient calculation means in the second storage means.

[0006]

In this configuration, during normal operation of the engine,
A learning correction coefficient calculated including the effect of the recirculated exhaust gas (a learning correction coefficient stored in the second storage means)
Is used to correct the basic fuel supply amount, and the feedback control is performed, so that the air-fuel ratio can be accurately controlled to the stoichiometric air-fuel ratio.

[0007] The learning correction coefficient used in the lean combustion operation (the learning correction coefficient stored in the first storage means) is stored separately from the learning correction coefficient used in the normal operation, and the learning correction coefficient for the lean combustion operation is used. The lean burn operation is not performed before the learning of the learning correction coefficient is completed, and when the lean correction operation learning learning coefficient is learned, the lean overlap operation overlaps with the exhaust gas recirculation region (the exhaust gas recirculation rate is set based on the originally set exhaust gas recirculation rate). Even under the operating conditions, the exhaust gas recirculation rate is limited to zero or a small value that does not affect the calculation of the learning correction coefficient, so that the lean combustion operation learning correction coefficient is appropriately learned. By using this, the air-fuel ratio during the lean burn operation can be accurately controlled to the predetermined air-fuel ratio.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the accompanying drawings. FIG. 2 shows a basic configuration of an internal combustion engine (hereinafter, referred to as an engine) that performs fuel supply control according to the present invention.
That is, the throttle valve 12 is provided in the intake passage 20 of the engine A.
Is interposed. An EGR passage 23 is provided, which communicates a downstream side of the throttle valve 12 of the intake passage 20 with a downstream side of an oxygen concentration sensor 16 described later of the exhaust passage 21 and recirculates a part of exhaust gas to an intake system. An EGR control valve 22 as EGR control means for controlling the EGR amount based on the set EGR rate is interposed in 23.

On the other hand, means for detecting the operating state of the engine A include a crank angle sensor 11 as a rotational speed detecting means for outputting a signal for each unit angle of the crankshaft and a signal for each reference position, and a throttle valve opening. Valve opening degree sensor 24 which detects the pressure by the output voltage of the potentiometer
And a vehicle speed sensor 13 for detecting the current traveling speed of the vehicle.
And an air flow meter 14 as an intake air amount detecting means for detecting an intake air amount of the engine A, and a water temperature sensor 15 for detecting an engine water temperature as the engine temperature.

An oxygen concentration sensor (hereinafter, referred to as an air-fuel ratio detecting means) for detecting an air-fuel ratio from an oxygen concentration in exhaust gas.
O ₂ referred to sensor) 16 is provided. A control unit B includes a CPU 17 and a ROM 19. The CPU 17 includes the crank angle sensor 11, the throttle valve opening sensor 24, the vehicle speed sensor 13, the air flow meter 14, the water temperature sensor 15, and the oxygen concentration sensor 16
The detection signal output from the controller A is input, and the operation shown in the flowchart described later is performed to adjust the basic fuel injection pulse width as the basic fuel supply amount and various corrections so that the air-fuel ratio becomes in accordance with the operation state of the engine A. The actual fuel injection pulse width as the actual fuel supply amount is calculated, and a control signal is output to the fuel injection valves 18a to 18d provided for each cylinder.
Further, the CPU 17 outputs a control signal of the EGR control valve 22.

The ROM 19 stores various data (for example, a fuel feedback correction coefficient table or EGR according to the engine operating state) necessary for the operation of the CPU 17.
Table storing the rate, etc.). The operation of one embodiment of the fuel supply control device according to the present invention will be described with reference to FIGS.

FIG. 3 is a flowchart showing the control operation performed by the CPU.
msec). In this flowchart,
In step 1 (abbreviated as S1 in the figure; the same applies hereinafter),
The engine intake air amount Qa and the rotation speed Ne are read.
In this case, the intake air amount Qa is read from the output value of the air flow meter 14. Further, it reads an output signal from the crank angle sensor 11 and converts this output into an engine speed.

In step 2, an engine operating state such as an acceleration / deceleration state of the engine A is read based on input of output signals of various sensors such as the throttle valve opening sensor 24 and the water temperature sensor 15. In step 3, based on the intake air amount Qa and the rotation speed Ne read in step 1, a basic fuel amount (basic fuel injection pulse width T
p) and various correction coefficients Coef for the basic fuel injection pulse width Tp based on the engine operating state.
Is calculated.

[0014] In step 4, reads the output value of the O ₂ sensor 16. In step 5, with reference to the map of FIG. 7, it is determined whether or not the current operating point is in the EGR region based on the intake air amount Qa and the rotation speed Ne. If it is in the EGR range, the process proceeds to step 6, and the EGR rate is set from the intake air amount Qa and the rotation speed Ne with reference to the map of FIG.
Proceed to step 7 and proceed directly to step 7 if it is not in the EGR area. In step 7, it is determined based on the intake air amount Qa and the rotation speed Ne whether or not the current operating point is in the lean burn region. If it is the lean burn region, the process proceeds to step 8 to determine whether or not the condition is the lean burn operating condition based on the operating state. If not, the process proceeds to step 9. If it is determined in step 7 that the region is not the lean burn region, the process directly proceeds to step 9.

In step 9, normal control is executed. This normal control will be described later based on the flowchart of FIG. If it is determined in step 8 that the condition is the lean burn operation condition, the process proceeds to step 10 in which a learning correction coefficient for lean burn operation (based on the basic fuel injection pulse width Tp based on the feedback correction coefficient) is calculated. It is determined whether or not learning is completed. If the learning is completed, the process proceeds to step 11, and if the learning is not completed,
Proceed to step 12.

Then, in step 11, lean burn control is executed, and in step 12, learning control is executed. The lean burn control and the learning control will be described later based on the flowcharts in the drawings. FIG. 4 is a flowchart showing a routine of the normal control in step 9 of the flowchart in FIG. 3. In step 21, a feedback correction coefficient α for the basic fuel injection pulse width Tp is calculated based on the detected air-fuel ratio.

In step 22, a learning correction coefficient Lalpha during the EGR operation corresponding to the intake air amount Qa and the rotation speed Ne is calculated from the map of FIG. 9 (based on the basic fuel injection pulse width Tp based on the feedback correction coefficient). Read). In step 23, the fuel injection pulse width Ti actually output to the fuel injection valve is calculated based on the following equation. In the following equation, Ts is a known invalid injection pulse width Ts.

Ti = Tp * Coef * α * Lalpha + Ts In step 24, a learning correction coefficient Lalpha during the EGR operation is calculated based on the feedback correction coefficient α, and the calculated learning correction coefficient Lalpha is used as the intake air amount at that time. Qa and the rotation speed Ne are stored in association with each other. FIG. 5 is a flowchart showing a lean burn control routine in step 11 of the flowchart in FIG.
In step 31, the EGR rate is set to zero. In step 32, a target air-fuel ratio setting coefficient Dml (a coefficient for setting a target air-fuel ratio suitable for the current operating condition) corresponding to the intake air amount Qa and the rotation speed Ne is read from the map of FIG.

In step 33, a learning correction coefficient LLalpha for lean burn operation corresponding to the intake air amount Qa and the rotation speed Ne stored in the map of FIG. 11 is read. In step 34, the fuel injection pulse width Ti actually output to the fuel injection valve is calculated based on the following equation. Ti = Tp * Coef * Dml * LLalpha + Ts FIG. 6 is a flowchart showing a learning control routine of step 12 in the flowchart of FIG.
In step 1, based on the intake air amount Qa and the rotation speed Ne, it is determined whether or not the region is an overlap region between the lean burn region and the EGR region. This step 41 is unnecessary when the lean burn region is included in the EGR region as in the present embodiment, that is, when the lean burn region is entirely the overlap region.

If it is determined in step 41 that the area is the overlap area, the routine proceeds to step 42, where the EGR rate is set to 0.
Alternatively, the process proceeds to step 43 after being set to a minute value. If it is determined in step 41 that the area is not the overlap area, the process proceeds directly to step 43. In step 43, a feedback correction coefficient α for the basic fuel injection pulse width Tp is calculated based on the detected air-fuel ratio.

In step 44, a learning correction coefficient LLalpha for lean burn operation corresponding to the intake air amount Qa and the rotational speed Ne stored in the map of FIG. 11 is read. In step 45, the fuel injection pulse width Ti actually output to the fuel injection valve is calculated based on the following equation.

Ti = Tp * Coef * α * LLalpha + Ts In step 46, the learning correction coefficient LLalpha at the time of lean burn operation is determined based on the feedback correction coefficient α.
Is calculated, and the calculated learning correction coefficient LLalpha is stored in association with the intake air amount Qa and the rotation speed Ne at that time. In the above flowchart, step 3 is based on the detected intake air amount and the rotation speed.
It corresponds to a basic fuel supply amount calculating means for calculating a basic fuel amount to be supplied to the engine. Steps 21 and 43 correspond to feedback correction coefficient calculating means for calculating a feedback correction coefficient for the basic fuel supply amount based on the detected air-fuel ratio. Steps 24 and 34 correspond to a learning correction coefficient calculating unit that calculates a learning correction coefficient for the basic fuel supply amount based on the calculated feedback correction coefficient.

Steps 23, 34, and 45 correspond to feedback control means for performing feedback control of the air-fuel ratio near the stoichiometric air-fuel ratio using the feedback correction coefficient and the learning correction coefficient. Steps 24 and 46 correspond to first and second storage means for storing the calculated learning correction coefficients in association with the intake air amount and the rotational speed at that time, respectively.
Step 6 corresponds to an exhaust gas recirculation rate setting unit that sets the exhaust gas recirculation rate based on the current intake air amount and the current rotational speed when the detected intake air amount and rotational speed are in the predetermined exhaust gas recirculation region. Step 42, the detected intake air amount and the rotation speed are in a region where the predetermined lean combustion region and the exhaust gas recirculation region overlap with each other, and the detected operation state satisfies the predetermined lean combustion operation condition; Further, when the learning of the learning correction coefficient stored in the first storage means has not been completed, it corresponds to an exhaust gas recirculation rate limiting means for limiting the exhaust gas recirculation rate to zero or a predetermined minute value. Step 4
5 and 46, the detected intake air amount and the rotation speed are in a predetermined lean burn region, and the detected operating state satisfies a predetermined lean burn operation condition, and are further stored in the first storage means. When the learning of the learning correction coefficient is not completed, the feedback control means performs the air-fuel ratio feedback control, and stores the learning correction coefficient calculated by the learning correction coefficient calculation means in the first storage means. It corresponds to a first learning means. Steps 31-34
Means that the detected intake air amount and rotation speed are in a predetermined lean burn region, the detected operating state satisfies a predetermined lean burn operating condition, and the learning correction stored in the first storage means. When the learning of the coefficient is completed, the exhaust gas recirculation rate is set to zero, and the calculation is performed based on the learning correction coefficient stored in the first storage means, the current intake air amount, and the rotation speed. This corresponds to a lean combustion control unit that corrects the basic fuel supply amount with the target air-fuel ratio setting coefficient and controls the air-fuel ratio to a predetermined air-fuel ratio leaner than the stoichiometric air-fuel ratio. Steps 23 and 24 are performed by the feedback control means when the detected intake air amount and rotation speed are outside the predetermined lean burn region, or when the detected operating state does not satisfy the predetermined lean burn operation condition. This corresponds to a second learning unit that performs feedback control of the air-fuel ratio and stores the learning correction coefficient calculated by the learning correction coefficient calculation unit in the second storage unit.

According to this embodiment, as is apparent from the description of the flowcharts in FIGS. 3 to 6, during the normal operation of the engine A, the learning correction coefficient (including the influence of the recirculated exhaust gas) is calculated. Since the basic fuel injection pulse width Tp is corrected using the learning correction coefficient (Lalpha) stored in the second storage unit and feedback control is performed, the air-fuel ratio can be accurately controlled to the stoichiometric air-fuel ratio. .

A learning correction coefficient (learning correction coefficient stored in the first storage means) LLal used in the lean burn operation.
pha is stored separately from the learning correction coefficient used during the normal operation, and lean learning operation is not performed before learning of the learning correction coefficient for lean combustion operation is completed, and the learning correction coefficient for lean combustion operation is learned. When this is done, the EGR region overlaps with the EGR region (EGR based on the originally set EGR rate).
Even under operating conditions, the EGR rate is limited to zero or a small value that does not affect the calculation of the learning correction coefficient, so that the air-fuel ratio during lean-burn operation can be accurately adjusted to a predetermined air-fuel ratio. Can be controlled.

As described above, the present invention has been described with reference to the specific embodiments. However, the present invention is not limited to these embodiments, and is attached to the present invention by a person skilled in the art. Without departing from the scope of the appended claims.
It should be noted that various changes and modifications are possible.

[0027]

As described above, according to the present invention,
During normal operation of the engine, the basic fuel supply amount is corrected using the learning correction coefficient calculated including the effect of the recirculated exhaust gas, and the feedback control is performed. Can be controlled to the stoichiometric air-fuel ratio,
The learning correction coefficient used for the lean burn operation is stored separately from the learning correction coefficient used during the normal operation, and the lean burn operation is not performed before the lean correction operation learning is completed. When learning the learning correction coefficient for operation, the exhaust gas recirculation rate should be limited to zero or a small value that does not affect the calculation of the learning correction coefficient, even under operating conditions that overlap with the exhaust gas recirculation region. Therefore, the usefulness of accurately controlling the air-fuel ratio at the time of the lean burn operation to the predetermined air-fuel ratio is great.

[Brief description of the drawings]

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

FIG. 2 is a basic configuration diagram of an internal combustion engine to which the present invention is applied;

FIG. 3 is a flowchart illustrating control contents according to an embodiment of the present invention.

FIG. 4 is a flowchart illustrating a normal control routine of the flowchart of FIG. 3;

FIG. 5 is a flowchart illustrating a lean burn control routine of the flowchart of FIG. 3;

FIG. 6 is a flowchart illustrating a learning control routine of the flowchart in FIG. 3;

FIG. 7 is a map for determining an EGR region.

FIG. 8 is a map storing an EGR rate.

FIG. 9 is a map in which a learning correction coefficient Lalpha during EGR operation is stored.

FIG. 10 is a map in which a target air-fuel ratio setting coefficient Dml is stored.

FIG. 11 is a learning correction coefficient LLalph during lean burn operation.
Map that memorized a

[Explanation of symbols]

 A engine B control unit 11 crank angle sensor 13 vehicle speed sensor 14 air flow meter 15 water temperature sensor 16 oxygen concentration sensor 17 CPU 19 ROM 22 EGR control valve 24 throttle valve opening sensor

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-64-60746 (JP, A) JP-A-63-123543 (JP, A) JP-A-60-198346 (JP, A) JP-A-60-1983 195358 (JP, A) JP-A-62-41941 (JP, A) JP-A-60-173333 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02D 41/00-41 / 40 F02D 45/00 340 F02M 25/07 550

Claims (1)

(57) [Claims] An intake air amount detecting means for detecting an intake air amount of the engine, a rotational speed detecting means for detecting a rotational speed of the engine, and a supply to the engine based on the detected intake air amount and the rotational speed. Basic fuel supply amount calculation means for calculating a basic fuel amount to be calculated; air-fuel ratio detection means for detecting an air-fuel ratio from the oxygen concentration in exhaust gas; and, based on the detected air-fuel ratio, Feedback correction coefficient calculating means for calculating a feedback correction coefficient; learning correction coefficient calculating means for calculating a learning correction coefficient for a basic fuel supply amount based on the calculated feedback correction coefficient; the feedback correction coefficient and the learning correction coefficient Feedback control means for performing feedback control of the air-fuel ratio to near the stoichiometric air-fuel ratio by using the First and second storage means for storing the amount of intake air and the rotation speed in association with each other; and when the detected intake air amount and rotation speed are in a predetermined exhaust gas recirculation region, the current intake air amount and rotation Exhaust gas recirculation rate setting means for setting the exhaust gas recirculation rate based on the speed; exhaust gas recirculation control means for recirculating a part of the exhaust gas to the intake system based on the set exhaust gas recirculation rate; Operating state detecting means for detecting an operating state of the engine including the engine temperature and the detected intake air amount and rotational speed are in a region where a predetermined lean burn region and the exhaust gas recirculation region overlap each other,
When the detected operating condition satisfies a predetermined lean burn operating condition and the learning of the learning correction coefficient stored in the first storage means is not completed, the exhaust gas recirculation rate is set to zero or a predetermined value. Exhaust gas recirculation rate limiting means for limiting to a minute value, the detected intake air amount and the rotation speed are in a predetermined lean burn region, and the detected operating state satisfies a predetermined lean burn operating condition, and When the learning of the learning correction coefficient stored in the first storage means is not completed, feedback control of the air-fuel ratio is performed by the feedback control means, and the learning correction coefficient calculated by the learning correction coefficient calculation means is replaced with the learning correction coefficient. A first learning means stored in the first storage means, the detected intake air amount and the rotation speed are in a predetermined lean burn region, and the detected operating state is a predetermined lean burn operating condition. When satisfied, and when the learning of the learning correction coefficient stored in the first storage unit is completed, the exhaust gas recirculation rate is set to zero, and the learning stored in the first storage unit is set. Lean combustion for correcting the basic fuel supply amount with a correction coefficient and a target air-fuel ratio setting coefficient calculated based on the current intake air amount and the rotation speed, and controlling the air-fuel ratio to a predetermined air-fuel ratio leaner than the stoichiometric air-fuel ratio Control means for controlling the air-fuel ratio by the feedback control means when the detected intake air amount and the detected rotation speed are out of a predetermined lean burn region, or when the detected operating state does not satisfy the predetermined lean burn operation condition. And a second learning means for storing the learning correction coefficient calculated by the learning correction coefficient calculation means in the second storage means. Fuel supply control system of the engine.