JPS63159646A - Fuel supply controller for internal combustion engine - Google Patents

Abstract

PURPOSE:To stabilize rotational speed by correctively increase or decrease fuel supply to cylinders causing changes in the rotational frequency of an engine in every predetermined stroke of each cylinder and correcting in the reverse direction the other cylinders reversely to make total fuel supply for all cylinders constant. CONSTITUTION:A calculating means B calculates a variation in the rotational speed of an engine judged by a cylinder judging means A in every predetermined stroke of each cylinder, and when the variation exceeds a predetermined one, the basic fuel supply is corrected by a first correcting means C to eliminate the variation for the cylinder causing the variation. Also, the fuel supply to the other cylinders is corrected by a second correcting means D in the opposite direction to the correcting direction of the first correcting means C with the corrected amount in the corrected cylinder being delivered and set divided by the number of the other cylinders and set. And fuel supply means for respec tive cylinders are controlled through output means F according to the basic fuel supply set by a setting means E according to the running condition or corrected fuel supply.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fuel supply control device for an internal combustion engine, which is equipped with a fuel supply means such as a fuel injection valve for each cylinder. This invention relates to a system in which the fuel supply amount is corrected for each cylinder so as to control fluctuations in engine rotational speed caused by the engine speed.

<Prior Art> In a conventional electronically controlled fuel injection type internal combustion engine, the fuel injection amount Tt is determined, for example, by the following formula.

Tt=TpXCOBFXα+Ts Here, Tp is the basic injection amount and is given by the following formula.

Tp=KXQ/N is a constant, Q is the intake air flow rate, and N is the engine rotation speed. Further, C0EF is various increase correction coefficients, and is given by a formula such as C0EF-1+Ktw+Kas+Kacc+Kmr. Ktw is water temperature increase correction coefficient r
Kas is a starting and post-start increase correction coefficient, Kacc is an acceleration increase correction coefficient, and Krar is a mixture ratio correction coefficient. α
is an air-fuel ratio feedback correction coefficient for performing air-fuel ratio feedback control (λ control) to be described later. Ts is a voltage correction element, which is used to correct variations in the injection amount due to fluctuations in the power supply voltage.

Air-fuel ratio feedback control involves installing an 02 sensor in the engine's exhaust system to detect the actual air-fuel ratio, and determining whether the actual air-fuel ratio is richer or leaner than the stoichiometric air-fuel ratio using a slice level. The fuel injection amount is controlled so as to approach the stoichiometric air-fuel ratio, and for this purpose, it is controlled by changing the air-fuel ratio feedback correction coefficient α.

<Problems to be Solved by the Invention> However, such conventional electronically controlled fuel injection multi-cylinder internal combustion engines, particularly so-called multi-point injection internal combustion engines in which each cylinder has a fuel injection valve, have structural problems. Alternatively, if a difference occurs in the fuel injection amount of each fuel injection valve due to changes over time, etc., the distribution of fuel between the cylinders may not be uniform. As a result, if a specific cylinder misfires or, conversely, strong combustion (combustion pressure is too high) occurs, the engine speed will fluctuate greatly, and engine stability, especially idle stability, will deteriorate, leading to surging. Problems include problems such as a deterioration of the engine's output and fuel efficiency as well as a deterioration of the engine's output and fuel efficiency, or extremely deterioration of the exhaust characteristics from a specific cylinder when the engine is fully opened, leading to burnout of the three-way catalyst, etc. that functions as an exhaust treatment means. This results in a point.

The present invention was made in view of the above circumstances, and it appropriately corrects the deterioration of the fuel distribution characteristics, thereby improving the stability of the engine, improving the output and fuel efficiency, and improving the ternary performance. The purpose is to prevent catalyst burnout.

<Means for Solving the Problems> Therefore, in the present invention, as shown in FIG. 1, in a fuel supply control device for an internal combustion engine having a fuel supply means for each cylinder, a rotation speed detection method for detecting the engine rotation speed is provided. basic fuel supply amount setting means for setting a basic fuel supply amount according to engine operating conditions including engine rotational speed; cylinder discrimination means for determining a cylinder in a predetermined stroke; and a predetermined stroke for each cylinder. a rotational speed change amount calculation means for calculating the amount of change in the engine rotational speed for each period; a first fuel supply amount correction means for increasing or decreasing the basic fuel supply amount, and a correction amount set by distributing the correction amount of the cylinder corrected by the first fuel supply amount correction means among the number of other cylinders; a second fuel supply amount correction means for increasing or decreasing the fuel supply amount of the other cylinder in a direction opposite to the increase or decrease direction by the first fuel supply amount correction means; and a second fuel supply amount correction means corresponding to the basic fuel supply amount or the corrected fuel supply amount. The fuel supply signal output means outputs the fuel supply signal to the fuel supply means of the cylinder at the fuel supply time determined by the cylinder determination means.

In this configuration, the basic fuel supply amount setting means:
A basic fuel supply amount that is substantially common to all cylinders is set depending on the engine operating state.

On the other hand, the rotational speed detection means detects the engine rotational speed at each predetermined stroke period of each cylinder, and the rotational speed change amount calculation means calculates the amount of change in the engine rotational speed each time.

Then, the basic fuel supply amount of the cylinder that affected the rotational speed change is corrected by the first fuel supply amount correction means based on the amount of change in the rotational speed, and the second fuel supply amount correction means The amount of fuel supplied to all cylinders is increased or decreased in the opposite direction so that the total amount of fuel supplied to all cylinders becomes constant.

A fuel supply signal corresponding to the fuel supply timing corrected and set for each cylinder in this way is output from the fuel supply signal output means to the fuel supply means of the cylinder discriminated by the cylinder discrimination means, and from the fuel supply means. It is supplied to the corresponding cylinder.

Therefore, while suppressing deterioration of fuel and exhaust emissions,
Fluctuations in engine speed due to misfires and strong twisting can be prevented.

<Example> Embodiments of the present invention will be described below based on the drawings.

In FIG. 2 showing the configuration of an embodiment, an air flow meter 3 for detecting the flow rate of intake air is installed in an intake passage 2 of an internal combustion engine 1 from the upstream side. Throttle valve 4. A throttle opening sensor 5 including an idle switch for detecting the opening of the throttle valve 4 and a fuel injection valve 6 as fuel supply means are provided for each cylinder. In addition, a crank angle sensor 7 as an engine rotation speed detection means
A water temperature sensor 8 for detecting the temperature of the cooling water and a 0□ sensor 10 for detecting the oxygen concentration in the exhaust gas are provided in the exhaust passage 9.

The intake air flow rate signal Q from the air flow meter 3, the reference signal output from the crank angle sensor 7 at each predetermined stroke period of each cylinder (among them, the signal corresponding to a specific cylinder, for example, cylinder #1 is distinguished from the others) unit angle signal output for each tiny unit crank angle, throttle valve opening signal from throttle opening sensor 5, cooling water temperature signal from water temperature sensor 8, and cooling water temperature signal from 02 sensor 10. The oxygen concentration signal of
The control unit 11 sets the fuel injection (jt (fuel supply amount)) according to the engine operating state detected based on these signals.
Fuel injection control is performed by outputting an injection pulse (fuel supply signal) having a pulse width corresponding to the injection amount to the fuel injection valve 6.

Here, the fuel injection amount is set by setting the basic fuel injection amount according to the engine operating state, and then setting the fuel injection amount for each cylinder according to the change in the engine speed detected at each combustion stroke timing of each cylinder. The injection amount is adjusted to increase or decrease.

Hereinafter, the fuel injection amount control routine will be explained according to the flowcharts shown in FIGS. 3 to 5.

FIG. 3 shows a routine that is performed every time a reference signal is input from the crank angle sensor 7 and determines which cylinder is to be subjected to fuel increase/decrease correction.

In step (denoted as S in the figure) 1, the engine rotational speed N is detected as the reciprocal of the time (period) from inputting the reference signal from the previous crank angle sensor 7 to inputting the reference signal this time, and temporarily stores it.

In step 2, it is determined whether the reference signal is a cylinder discrimination signal for a specific cylinder (#1 cylinder), and if YES, the process proceeds to step 3, where data cylD indicating the specific cylinder is set to 0.

After that, when the reference signal is input, proceed to step 4 and input the data. , ID is counted up by 1, for example #2. #3
, 94 cylinders each have cylD set to 3.1°2,
When the cylinder discrimination signal for the #1 cylinder is input again, cyID is reset to O, thereby making it possible to discriminate each cylinder.

That is, the crank angle sensor 7 and the functions of steps 2 to 4 constitute cylinder discrimination means.

Next, in step 5, the cylinder to which the fuel increase/decrease correction is to be performed is determined based on the data cylD (0 to 3) of the determined cylinder stored in step 3 or step 4. When the ignition order is #1 → #3 → #4-#2, a change in rotational speed due to misfire or strong twist firing is detected when the reference signal is input twice after the change, and based on this, the cy
When j2D=o, in step 6, the cylinder data n is set to 4.
cyj! When D=1, n=2 in step 7. cyj2
When D=2, n=1 in step 8. If it is cyj2D-3, set it to n-3 in step 9.

In step 10, the value obtained by adding a predetermined rotation Nl (for example, 6 rpm) to the engine rotation speed N calculated in step 1 is compared with the engine rotation speed N calculated last time, and if the former exceeds the latter, that is, the rotation speed If it is determined that the decrease is large, the process proceeds to step 12, where the fuel increase correction coefficient Kn for the cylinder n is increased by a predetermined amount in order to increase the fuel supply amount of the cylinder n determined in steps 6 to 9 that caused the decrease. For example, in this embodiment, 1% is added.

The function of step E2 corresponds to first fuel supply amount correction means.

Next, proceed to step 13 and add Kn added in step 12.
It is determined whether or not exceeds the upper limit value, for example, 5%. If not, the process proceeds to step 14 and the fuel correction coefficient K of each other cylinder is determined.
i is subtracted from the correction bone set by dividing 1% of the correction bone of cylinder n by the number of other cylinders, that is, 1/3%, contrary to the addition of cylinder n.

Therefore, the sum of the correction coefficients Kn and Ki of the gold cylinder remains constant as before correction.

That is, the function of step 13 corresponds to second fuel supply amount correction means.

In addition, when it is determined in step 13 that the fuel increase correction means Kn of cylinder n exceeds the upper limit value 5%, the process proceeds to step 15, and the correction value obtained by dividing the value obtained by subtracting the upper limit value from Kn by the number of other cylinders is determined. Find A.

In step 16, Kn is reset to the upper limit value, and the correction coefficients Ki for the other cylinders are subtracted by the value obtained by dividing the increase in Kn by the number of cylinders 3, that is, by 1/3-A.

This function corresponds to the first fuel supply amount correction means and the second fuel supply amount correction means.

In this case as well, the sum of the correction coefficients Kn and Ki for all cylinders remains constant, unchanged from the value before correction.

After step 14 or step 16, the process proceeds to step 17, in which it is determined whether there is a correction coefficient Ki for cylinders other than misfires that is less than the lower limit value -5% as a result of subtraction, and if there is a cylinder that is less than the lower limit value, step Proceeding to step 18, the correction coefficient Kt for that cylinder is fixed at the lower limit value -5%.

In this case, the correction coefficients for the other cylinders are not corrected, so the sum of the correction coefficients for the gold cylinder increases slightly, but it is a very small amount. Next, the previous value and the value obtained by subtracting N from the current value are compared.

As a result of the comparison, if it is determined that the former is greater than or equal to the latter, it is determined that the rotation speed is normal because the rotation speed is within the predetermined rotation N1 during fluctuation, and the correction coefficients Kn and Ki of the gold cylinder are maintained at the current state in step 19. .

In addition, if it is determined in step 11 that the former is lower than the latter, that is, if it is determined that the increase in rotational speed is large, strong combustion is determined (combustion pressure is too large), and step 2
0, the correction coefficient Kn of cylinder n, which is the cause, is set to 1% by a predetermined amount.
Subtract.

This function corresponds to first fuel supply amount correction means. Next, in step 21, it is determined whether the subtraction result (n) is less than the lower limit value -5%. If not, the process proceeds to step 22, where the correction coefficients Ki of the other cylinders are added by 173%.

This function corresponds to second fuel supply amount correction means.

As a result, as in the case of misfire, the sum of all correction coefficients remains constant.

If it is determined in step 21 that Kn is less than 15%, the process proceeds to step 23, where a corrected bone B is obtained by dividing the value obtained by subtracting the lower limit value from Kn by the other number of cylinders, 3.

In step 24, Kn is reset to the lower limit value, and the correction coefficients Ki for the other cylinders are added in increments of 1/3-B, that is, the value obtained by dividing the decrease in Kn by the number of cylinders 3.

This function corresponds to the first fuel supply amount correction means and the second fuel supply amount correction means.

After step 22 or step 24, the process proceeds to step 25, in which it is determined whether there is any correction coefficient Ki that exceeds the upper limit (I!5%) as a result of addition among the correction coefficients Ki of cylinders other than strong combustion, and the cylinder that exceeds If so, the process advances to step 26 and the correction coefficient Ki for that cylinder is fixed at the upper limit value of 5%.

In this case as well, since no correction is made for other cylinders, the sum of correction coefficients for all cylinders decreases slightly, but by a very small amount.

Note that the function of step 10.11 corresponds to rotational speed change amount calculation means.

FIG. 4 shows a fuel injection amount calculation routine performed every unit time (for example, 10 m5).

In the figure, step 31 is the intake air flow from the air flow meter 3! Q-t-read, in step 32 the third
Read the engine rotation speed N calculated in step 1 of the figure. However, the engine rotational speed N which is proportional to the number of inputs of the unit angle signal from the crank angle sensor 7 per unit time may be calculated based on the number of inputs per unit time.

In step 33, the basic injection amount of fuel injected from the fuel injection valve 6 is calculated based on the intake air flow rate Q and the engine speed N using the following formula: Tp = -Q/N (K is a constant) In step 34, , determine whether the idle switch is ON. That is, in this embodiment, the fuel supply amount correction according to the present invention is performed only when the engine is idling, but it may be performed at times other than when the engine is idling.

When the engine is not idling, the process proceeds to step 35, where the correction coefficients for all cylinders are set to O.

When the engine is idling, switches 36 to 40 are used to determine the cylinder to which the increase/decrease correction should be performed.

That is, the switch 36 selects the data cylD (0~
Regarding 3), the cylinder in which the fuel increase/decrease correction is to be performed is determined.

Based on this cyj! When D=O, in step 37, the data 2 of 4 set in the routine of FIG. 3 is set to 9.
and similarly in steps 38-40 cyff
When D=1, KI. When cyJD=2.

cyj! When D=3, the data of is set as KN.

Next, in step 41, the final fuel injection 11Ti is calculated using the following equation.

Ti −Tp−COEF・α・(1+KN) +T
5 Here, C0EF is various correction coefficients determined based on the throttle valve opening degree, cooling water temperature, etc., α is the feedback correction coefficient for the air-fuel ratio determined based on the oxygen concentration in the exhaust gas, and KM is # )l (N-1 to 4) The correction coefficient Ts for the cylinders is a correction amount based on the buffer voltage.

The thus corrected fuel injection amount is injected and supplied from the fuel injection valve 6 at a predetermined crank angle timing of each cylinder, which is set based on the engine operating state.

This injection valve operation routine will be explained with reference to FIG.

This routine is interrupted when the value counted by the counter matches the injection timing.

cyj in step 51! The cylinder is discriminated based on the value of D, and an injection pulse having a pulse width corresponding to the fuel injection 11Ti is output to the fuel injection valve 6 of the cylinder discriminated in steps 52 to 55. Here, the functions of steps 52 to 55 constitute fuel supply signal output means. Next, in steps 56 to 59, 1 to 5 are added to the correction coefficients used this time in preparation for the next calculation.
4 is stored as the previous value.

Next, the effect when such control is performed will be explained based on FIG. 6.

Now, when cylinder #1 misfires during the combustion stroke, the combustion pressure of this cylinder decreases, resulting in a decrease in the average effective pressure Pi, and accordingly, the rotational speed decreases.

This decrease in rotational speed is detected when the reference signal for the #4 cylinder is input, and at that time, the correction coefficient for the #1 cylinder is increased by +, so the next fuel injection amount is increased, and this causes the cylinder's Combustion pressure increases and average effective pressure recovers.

Further, as shown in the figure, when strong twist firing occurs in the #2 cylinder, the average effective pressure Pi increases due to the increase in combustion pressure, and the rotational speed increases accordingly.

In this case, an increase in rotational speed is detected when the reference signal for #3 cylinder is input, and the correction coefficient for #2 cylinder is reduced by 2, thereby reducing the combustion pressure in the cylinder and reducing the average effective pressure. Control the rise.

On the other hand, for cylinders other than the cylinders whose fuel injection amount has been increased or decreased due to misfire or strong twist firing, the fuel injection amount is increased or decreased so that the total fuel injection amount of all cylinders is kept constant. Therefore, the overall air-fuel ratio can be kept constant (target air-fuel ratio), and each cylinder is adjusted proportionally according to the number of misfires or strong twist firings, so the engine is always in operating condition. Appropriate control is carried out accordingly.

Note that since the upper and lower limits of the correction amount are set, the air-fuel ratio difference between cylinders will not become too large.

As a result, it is possible to equalize the average effective pressure for each cylinder without deteriorating the exhaust emission function or fuel efficiency, thereby suppressing rotational synchronization during idling or steady driving.
Not only can surging be prevented from occurring, but also burnout of the three-way catalyst can be prevented.

<Effects of the Invention> As explained above, according to the present invention, the amount of fuel supplied to the cylinder that is the cause of the change is corrected to increase or decrease in accordance with the change in the engine rotation speed during a predetermined stroke time period of each cylinder, In addition, since the other cylinders are configured to increase or decrease in the opposite direction so that the total amount of fuel supplied to all cylinders remains constant, the rotational speed due to misfires and combustion can be reduced without deteriorating exhaust emission performance or fuel efficiency. Changes can be suppressed within a short period of time to stabilize the rotational speed during idling or steady running, preventing surging and preventing burnout of the three-way catalyst.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a diagram showing the configuration of an embodiment of the present invention, FIG. 3 is a flowchart showing the combustion state determination routine of the same embodiment, and FIG. 4 is the same. FIG. 5 is a flowchart showing the fuel injection amount calculation routine, FIG. 5 is a flowchart showing the fuel injection pulse output control routine, and FIG. 6 is a time chart showing the combustion state of each cylinder.

Claims (1)

[Claims] In a fuel supply control device for an internal combustion engine, which includes a fuel supply means for each cylinder, a rotation speed detection means detects the engine rotation speed, and a basic fuel supply amount is set according to the engine operating state including the engine rotation speed. Basic fuel supply amount setting means;
Cylinder discrimination means for discriminating a cylinder in a predetermined stroke; rotation speed change amount calculation means for calculating the amount of change in engine rotation speed for each predetermined stroke period of each cylinder; a first fuel supply amount correction means for increasing or decreasing the fuel supply amount in a direction to eliminate the change in the cylinder that affected the change; and a correction amount of the cylinder corrected by the first fuel supply amount correction means. The fuel supply amount of the other cylinders is divided by the number of other cylinders and the fuel supply amount is adjusted by the set correction amount by the number of other cylinders.
a second fuel supply amount correcting means for increasing or decreasing the increase or decrease in the direction opposite to the increase/decrease direction by the fuel supply amount correcting means; and a fuel supply signal corresponding to the basic fuel supply amount or the corrected fuel supply amount, which is determined by the cylinder determining means. 1. A fuel supply control device for an internal combustion engine, comprising a fuel supply signal output means for outputting a fuel supply signal to a fuel supply means of a cylinder at a fuel supply time.