JPH0510170A - Engine fuel injection controller - Google Patents

Abstract

PURPOSE:To compensate any stroke delay at the time of setting a fuel injection quantity as well as to improve the extent of controllability. CONSTITUTION:In an alpha-N system of fuel injection control, throttle opening after a stroke delay is predicted by a predicting means M1 from a variation in the throttle opening detected by a throttle opening sensor 6 at the time of presuming an intake air quantity available when calculating a fuel injection quantity, and on the basis of this predicted throttle opening, a throttle valve passing air quantity to be calculated by a throttle valve passing air quantity calculating means M2 and a cylinder intake air quantity to be calculated by a cylinder intake air quantity calculating means M3 are determined. In consequence, the fuel injection quantity comes to a value that compensates the stroke delay, thus controllability at the time of transition is well improved.

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 device for an engine which calculates a fuel injection amount from an intake air amount calculated based on a throttle opening and an engine speed.

[0002]

2. Description of the Related Art Generally, in this type of fuel injection control device, a basic injection amount (Tp) is calculated using the intake air amount and the engine speed as parameters, and the basic injection amount (Tp) is corrected by various correction terms. It is known that the fuel injection amount (Ti) is determined by the above.

The intake air amount is estimated from what is measured by an intake air amount sensor provided immediately downstream of the air cleaner, and from the throttle opening (α) and the engine speed (N).
There is a so-called α-N system, but the latter is adopted in various engines because of its advantages such as simplification of structure, excellent cost, and few failures. Note that this α
As a fuel injection control device by the -N method, there is, for example, Japanese Patent Laid-Open No. 1-216053.

[0004]

In the α-N system, the throttle opening plays an important role as a factor in determining the intake air amount, and the intake air amount is a throttle valve opening (or closing) operation. If it does not fluctuate in accordance with, the difference between the intake air amount estimated by the α-N method and the actual intake air amount occurs, and the air-fuel ratio controllability deteriorates.

For example, if the chamber volume from the throttle valve downstream to the intake valve is relatively large,
There is a certain time delay until the intake air that has passed through the throttle valve (hereinafter referred to as “throttle valve passing air”) is supplied into the cylinder.

[0006] In steady running, the load fluctuation is small and the air flow rate passing through the throttle valve is almost constant, so the above-mentioned time delay is relatively insignificant, but during transients, especially during acceleration operation, the throttle valve opening changes. Even if the flow rate of the air passing through the throttle valve changes in accordance with, the air-fuel ratio controllability deteriorates if the amount of intake air actually supplied into the cylinder is delayed.

Further, as shown in FIG. 7, the fuel injection time is set before the start of the intake stroke when the intake valve is opened, and during acceleration operation in which the intake amount gradually increases, the intake time when the fuel injection amount is determined. There is a phase difference (so-called stroke delay) between the quantity Q1 and the quantity Q2 of air actually sucked into the cylinder (assuming an intermediate value of the intake stroke). Therefore, even if the intake air amount flowing into the cylinder (actual cylinder intake air amount) is accurately calculated, an air-fuel ratio error will occur due to the stroke delay.

The present invention has been made in view of the above circumstances, and provides a fuel injection control device for an engine capable of improving the air-fuel ratio controllability during a transition, improving exhaust emission, and reducing the load on the catalyst. The purpose is to

[0009]

A fuel injection control device for an engine according to the present invention comprises a prediction means for calculating a predicted throttle opening after a stroke delay time based on a current throttle opening and a previously detected throttle opening. Throttle valve passing air amount calculating means for calculating the amount of air passing through the throttle valve based on the predicted throttle opening, the engine speed, and the intake manifold internal pressure calculated last time; the predicted throttle opening, the engine speed, and the intake manifold. In-cylinder intake air amount calculation means for calculating the amount of air taken into the cylinder based on the internal temperature and the previously calculated intake manifold internal pressure, the intake manifold internal temperature, the throttle valve passing air amount, and the in-cylinder intake amount Intake manifold internal pressure calculating means for calculating the intake manifold internal pressure based on And the fuel injection amount calculating means for calculating the fuel injection amount based on a ratio, in which and a fuel supply means for supplying fuel to a corresponding cylinder based on an output of the fuel injection amount calculating means.

[0010]

In the present invention, the predicted throttle opening after the stroke delay time is calculated based on the current throttle opening and the previously detected throttle opening, and then the predicted throttle opening, the engine speed and the intake air calculated last time are calculated. The amount of air passing through the throttle valve is calculated based on the manifold internal pressure.

Further, the amount of air taken into the cylinder is calculated based on the predicted throttle opening, the engine speed, the intake air temperature and the previously set intake manifold internal pressure.

On the other hand, based on the temperature in the intake manifold, the amount of air passing through the throttle valve, and the amount of intake air in the cylinder,
Calculate the intake manifold internal pressure to be used next time.

Then, the fuel injection amount is set based on the in-cylinder intake air amount and the target air-fuel ratio, and the fuel is supplied to the corresponding cylinder by the fuel supply means.

As a result, the stroke delay during the transient operation is compensated and the deviation from the target air-fuel ratio is reduced.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

1 to 6 show an embodiment of the present invention, FIG. 1 is a control block diagram of a fuel injection control device, FIG. 2 is a flowchart showing a procedure for setting a fuel injection amount, and FIG. 3 shows an intake state. A conceptual diagram, FIG. 4 is a conceptual diagram showing a setting state of a throttle opening degree, FIG. 5 is a time chart of a throttle opening degree, an intake air amount, an excess air ratio, and FIG. 6 is a conceptual diagram of an engine control system.

(Structure) Reference numeral 1 in FIG. 6 is an engine body, and a throttle valve 3 is interposed in the middle of an intake pipe 2 communicating with an intake port 1a of the engine body 1. And the intake port 1a form a volume of the intake manifold 2a. An air cleaner 4 is attached upstream of the intake pipe 2, and an intake temperature sensor 5 is installed in an expansion chamber of the air cleaner 4.
Is attached, and a throttle opening sensor 6 is connected to the throttle valve 3. Further, an injector (fuel supply means) 7 is attached to the intake port 1a downstream of the intake pipe 2.

Further, the exhaust port 1 of the engine body 1
An air-fuel ratio sensor 9 is attached to the exhaust pipe 8 communicating with b,
The catalyst 10 is interposed downstream thereof.

On the other hand, a crank rotor 11 integrally formed with a crank pulley or the like (not shown) is axially attached to the crank shaft 1c of the engine body 1, and a crank angle sensor 12 is provided on the outer periphery of the crank rotor 11 so as to face it. ..

Reference numeral 20 is a control device comprising a microcomputer, etc., and the CPU (central processing unit) 21, ROM 22, RAM 23, and I / O interface 24 of this control device 20 are mutually connected via a bus line 25. The sensors 5, 6, 9 and 12 are connected to the input port of the I / O interface 24, and the injector 7 is connected to the output port via the drive circuit 26.

The ROM 22 stores a control program, fixed data and the like. The fixed data includes an air passage area map 1, a flow rate function map 2, a flow rate coefficient map 3, a coefficient map 4, a coefficient map 5, and
There is a volumetric efficiency map 6.

Further, the RAM 23 stores data after processing the output signals of the respective sensors, data processed by the CPU 21, and the like.

Further, the CPU 21 follows the RAM 23 according to the control program stored in the ROM 22.
The fuel injection amount and the like are calculated based on various data stored in.

[0024]

An intake manifold internal pressure calculation for calculating an intake manifold internal pressure P (k + 1) to be used next time based on the intake temperature T, the throttle valve passage air amount Mat (k) and the cylinder intake amount Map (k). Means M4, basic fuel injection amount calculation means M5 for calculating the basic fuel injection amount Tp based on the in-cylinder intake air amount and preset target air-fuel ratio (A / F), and air detected by the air-fuel ratio sensor 9. Feedback correction amount calculation means M6 for calculating the feedback correction amount KFB based on the fuel ratio λ, and fuel injection amount calculation means M7 for correcting the basic fuel injection amount Tp with the feedback correction amount KFB to set the fuel injection amount Ti. It is composed of.

(Operation) Next, the fuel injection control procedure in the controller 20 will be described with reference to the flow chart of FIG.

[0027]

[0028]

Pa: Atmospheric pressure ρa: Atmospheric pressure density However, the above flow rate function Ψ is P / Pa> {2 / (K + 1)}
^{When 1 / (K-1)} ,

[0030]

When P / Pa <{2 / (K + 1)} ^{1 / (K-1)} ,

[0032]

K: Specific heat ratio g: Gravity acceleration can be obtained, but in the flow rate function map 2 in the figure, the atmospheric pressure Pa is considered to be normal pressure, and only the pressure P in the intake manifold 2a is used as a parameter.

[0034]

[0035]

D: Exhaust Volume The volumetric efficiency is determined by the equation (3) by performing steady operation, measuring the manifold internal pressure, the rotation speed, the intake air temperature, and the suction amount under each operating condition, and creating a map.

By the way, FIG. 3 shows an intake system model, in which the air amount d in the intake manifold 2a per unit time is d.
M / dt is the difference between the inflowing air amount (air amount passing through the throttle valve 3) Mat and the inflowing air amount into the cylinder (cylinder intake air amount) Map, that is, dM / dt = Mat-Map ... … (4) can be represented.

On the other hand, the equation of state in the intake manifold 2a is as follows: P · V = M · R · T (4) P: Intake manifold pressure V: Intake manifold volume M: Intake manifold air amount (g) R : Gas constant T: Manifold internal temperature.

Assuming that the amount of air passing through the throttle valve 3 changes adiabatically, the above-mentioned amount of air passing through the throttle valve Mat is as in the above equation (2), while the in-cylinder intake air amount Map is above (3). The pressure dP / dt in the intake manifold 2a per unit time is expressed by the formula (2) to
From equation (5),

[0040]

Can be obtained by

[0042]

It becomes

If the gas constant R and the intake manifold volume V in the equation (6) 'are regarded as constant, (RT) / V becomes a function of the manifold internal temperature T.

After that, in S106, the coefficient RT / which is set based on the coefficient map 5 using the intake air temperature T as a parameter is set.
V, the intake manifold internal pressure P used in the next routine based on the throttle valve passing air amount Mat and the in-cylinder intake amount Map is set from the above equation (6) ', and the intake manifold internal pressure stored at the predetermined address of the RAM 23 is set. P (k
+1) is updated and the process returns to S102.

On the other hand, in S107, the basic fuel injection amount Tp is calculated from the following equation based on the in-cylinder intake air amount Map (k) calculated in S105 and the target air-fuel ratio A / F.

Tp ← {k / (A / F)} × Map (k) (7) k: constant determined by injector characteristics, etc. Then, in S108, the basic fuel injection amount Tp is set to the air-fuel ratio sensor 9 The fuel injection amount Ti (Ti ← Tp ×) is corrected by the air-fuel ratio feedback correction amount KFB set based on the output signal of
KFB) is set.

Thereafter, in S109, a drive signal corresponding to the fuel injection amount Ti is output to the injector 7 of the corresponding cylinder at a predetermined timing.

[0049]

As a result, the excess air ratio does not compensate for the stroke delay as shown by the broken line in FIG. 5 (c) (shown by the solid line).
In comparison with the above, the value is almost constant even if it is transient.

[0051]

As described above, according to the present invention, α
In the fuel injection control device that adopts the -N method, the intake air amount used when determining the fuel injection amount is calculated based on the predicted throttle opening degree that compensates for the stroke delay, so that the air-fuel ratio controllability even during the transition Controllability, exhaust emission improvement, and reduction of catalyst load without deteriorating the ignition timing control accuracy that determines the intake air amount as one parameter, which improves drivability. Excellent effects such as improvement of

[Brief description of drawings]

1 to 6 show an embodiment of the present invention, and FIG. 1 is a control block diagram of a fuel injection control device.

FIG. 2 is a flowchart showing a procedure for setting a fuel injection amount.

FIG. 3 is a conceptual diagram showing an intake state.

FIG. 4 is a conceptual diagram showing a setting state of a throttle opening.

FIG. 5 is a time chart of throttle opening, intake air amount, and excess air ratio.

FIG. 6 is a conceptual diagram of an engine control system.

FIG. 7 is a conceptual diagram showing the relationship between the intake air amount at the time of fuel injection determination and the intake air amount at the intake stroke.

[Explanation of symbols]

7 ……………… Fuel supply means α (k) ……… Current throttle opening α (k-1)… Previous throttle opening Map (k) …… Cylinder intake air amount Mat (K) …… Throttle valve passing air amount M1 ………… Predicting means M2 ………… Throttle valve passing air amount calculating means M3 ………… Cylinder intake air amount calculation Means M4 ………… Intake manifold internal pressure calculation means M7 ………… Fuel injection amount calculation means N ……………… Engine speed P (k) ……… Intake manifold internal pressure T ………… Intake manifold internal temperature Ti ………… Fuel injection amount Td ………… Stroke delay time

Claims (1)

Claims: 1. Prediction means for calculating a predicted throttle opening after a stroke delay time based on a current throttle opening and a previously detected throttle opening, said predicted throttle opening and engine speed And a throttle valve passage air amount calculating means for calculating the throttle valve passage air amount based on the previously calculated intake manifold internal pressure, the predicted throttle opening, the engine speed, the intake manifold temperature, and the previously calculated intake manifold. In-cylinder intake air amount calculating means for calculating the amount of air taken into the cylinder based on the internal pressure, and calculating the intake manifold internal pressure based on the intake manifold internal temperature, the throttle valve passing air amount, and the in-cylinder intake amount And a fuel injection amount based on the in-cylinder intake amount and the target air-fuel ratio. Fuel injection amount calculating means, the fuel injection control apparatus for an engine, characterized in that it comprises a fuel supply means for supplying fuel to a corresponding cylinder based on an output of the fuel injection amount calculating means.