JPH02283835A - Fuel feed control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent the increase of production of NOX because of an air-fuel ratio being brought into a lean state and the increase of production of CO because of the air-fuel ratio being brought into a rich state by a method wherein based on a deviation between pulsating amplitude of an average exhaust pressure and pulsating amplitude responding to each cylinder, a fuel feed amount is regulated classified by a cylinder. CONSTITUTION:An internal combustion engine is provided at each cylinder with a fuel feed means A. In this case, the running state of the internal combustion engine is detected by a running state detecting means B. According to a detected running state, a fuel teed amount responding to a target air-fuel ratio is set by a fuel feed amount set means C. Meanwhile, the exhaust pressure of the internal combustion engine is detected by an exhaust pressure detecting means D. Further, pulsating amplitude of a detected exhaust pressure is averaged by an averaging means E. Based on a deviation between averaged pulsating amplitude and pulsating amplitude responding to each cylinder, an amount of fuel fed classified by a cylinder is regulated by a means F for regulating an amount of fuel fed classified by a cylinder. This constitution prevents the occurrence of seizure and the increase of an NOX discharge amount due to failure in ignition of a specified cylinder and because of an air-fuel ratio being brought into an excessive lean state or the increase of CO and HC because of the air-fuel ratio being brought into an excessive rich state.

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to a fuel supply control device for an internal combustion engine.

<Prior Art> In an electronically controlled fuel injection type internal combustion engine, fuel supply is generally controlled by a method as described below. First, the intake air flow rate and intake pressure are detected as state quantities related to the intake air, and the basic fuel supply amount TP is calculated based on these and the detected value of the engine speed. Then, the basic fuel supply amount T is adjusted to various correction coefficients C0EF set based on operating conditions such as engine temperature, and a feed buff ratio set based on the air-fuel ratio determined through detection of the oxygen concentration in the exhaust gas. Calculate the final fuel supply amount T by correcting it using the correction coefficient α, the correction numerator 3 based on the battery voltage, etc. TI=TP
・C0EF・LAMBDA+T5), and the calculated amount of fuel is supplied to the engine by a fuel injection valve or the like (see Japanese Patent Laid-Open No. 60-240840, etc.).

In addition, as an exhaust purification measure, COHC and NO are added to the exhaust system.
Many are equipped with a three-way catalyst that comprehensively purifies x by burning it near the stoichiometric air-fuel ratio.

<Problem to be Solved by the Invention> Incidentally, in the case of an internal combustion engine in which each cylinder is equipped with a fuel supply means such as a fuel injection valve, the air-fuel ratio of a particular cylinder may be lower than the target air-fuel ratio ( It may be controlled to be richer or richer than the stoichiometric air-fuel ratio.

In this case, with conventional air-fuel ratio control, even when feedback control is performed to the target air-fuel ratio based on the gas components in the exhaust, the air-fuel ratio of all cylinders is controlled uniformly so that the air-fuel ratio of all cylinders approaches the target air-fuel ratio on average. Therefore, it was not possible to prevent deviations in the air-fuel ratio of only specific cylinders.

Therefore, if the difference in air-fuel ratio in a particular cylinder becomes too large, there is a risk of misfire or excessive lean, resulting in seizure. In addition, in the case of an engine equipped with a three-way catalyst,
In cylinders shifted to the lean side, NOx increases, and in cylinders shifted to the rich side, CO and HC increase.

The present invention was made in view of these conventional problems, and an object of the present invention is to provide a fuel supply control device for an internal combustion engine that solves the above problems by adjusting the air-fuel ratio for each cylinder based on the exhaust pressure. shall be.

<Means for Solving the Problems> Therefore, as shown in FIG. 1, the present invention provides an internal combustion engine having a fuel supply means for each cylinder. A fuel supply amount setting means for setting a fuel supply amount corresponding to a target air-fuel ratio according to the operating state, an exhaust pressure detection means for detecting the exhaust pressure of the engine, and an average for averaging the pulsation amplitude of the detected exhaust pressure. and cylinder-by-cylinder fuel supply amount adjusting means for adjusting the fuel supply amount for each cylinder based on the deviation between the averaged pulsation amplitude and the pulsation amplitude corresponding to each cylinder.

Further, when a transient operation is detected by the operating state detecting means, a function may be provided to stop the adjustment by the cylinder-specific fuel supply amount adjusting means.

Further, a configuration may be adopted in which a limit value is set for the cumulative value of the adjustment amount by the cylinder-specific fuel supply amount adjustment means.

Function> The fuel supply amount setting means adjusts the fuel supply corresponding to the target air-fuel ratio according to the operating state detected by the operating state detecting means (for example, detected from the engine rotation speed and the engine load such as the intake air flow rate). Set the amount.

The exhaust pressure detection means detects the exhaust pressure, and the averaging means averages the amplitude of the detected exhaust pressure pulsations.

The fuel supply amount adjusting means for each cylinder adjusts the fuel supply amount for each cylinder based on the deviation between the averaged pulsation amplitude and the pulsation amplitude corresponding to each cylinder.

This makes it possible to adjust the air-fuel ratio to an appropriate level so that the exhaust pressure remains constant for each cylinder, thereby preventing misfires.

It is possible to prevent burn-in and improve exhaust emission and emission characteristics.

Furthermore, during transient operation, since the reliability of detecting a deviation in air-fuel ratio by exhaust pressure detection is low, transient performance can be ensured by stopping the adjustment of the fuel supply amount for each cylinder.

Further, by setting a limit value to the cumulative value of the adjustment amount by the cylinder-specific fuel supply amount adjustment means, the deviation in the air-fuel ratio does not become too large.

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

In FIG. 2 showing the configuration of one embodiment, an air flow meter 13 for detecting the intake air flow rate Q and a throttle valve 14 for controlling the intake air flow IQ in conjunction with the accelerator pedal are provided in the intake passage 12 of the engine 11. An electromagnetic fuel injection valve 15 serving as a fuel supply means is provided for each cylinder in the downstream manifold portion.

The fuel injection valve 15 is driven to open by an injection pulse signal from a control unit 16 containing a microcomputer, and injects fuel that is pressure-fed from a fuel pump (not shown) and controlled to a predetermined pressure by a pressure regulator. Furthermore, a water temperature sensor 17 that detects the temperature TW of the cooling water in the cooling jacket of the engine 11 is provided, and an oxygen sensor that detects the air-fuel ratio of the intake air-fuel mixture by detecting the oxygen concentration in the exhaust gas of the air passage 18. 19
is further provided with a three-way catalyst 20 that oxidizes Co and HC in exhaust gas on the downstream side and reduces NO3 for purification. An exhaust pressure sensor 21 is provided.

22 is a spark plug.

Further, the distributor (not shown in FIG. 2) has a built-in crank angle sensor 23, and a crank angle signal outputted from the crank angle sensor 23 in synchronization with the engine rotation is counted for a certain period of time, or The engine rotation speed N is detected by measuring the period of the crank reference angle signal. Furthermore, a throttle sensor 24 detects the opening degree of the throttle valve 14.
is provided.

The control unit 16 manually inputs these various signals and uses the intake air flow rate Q detected by the air flow meter 13 and the engine rotational speed N detected by the crank angle sensor 23 to generate an amount corresponding to the cylinder intake air amount. The basic fuel injection amount TP (= -Q/N) is set, and this is corrected by the cooling water temperature Tw, etc. During feedback control, correction is made based on the air-fuel ratio detected by the oxygen sensor 19, and each A fuel injection amount T1 to be injected from a fuel injection valve I5 of a cylinder is set, and an injection signal having a pulse width commensurate with this is output to perform fuel injection control.

Furthermore, in the fuel injection control, the air-fuel ratio for each cylinder is adjusted by detecting exhaust pressure.

3 to 5 show various routines related to the operation of the control unit 16. Each routine will be explained below.

FIG. 3 shows a routine for determining transient conditions and setting the fuel injection amount corresponding to the target air-fuel ratio. This routine corresponds to fuel supply amount setting means. This is a minute unit time, for example, 10m5
Start every time.

In step 11, it is determined whether the rate of change ΔTVO of the throttle valve opening detected by the throttle sensor 24 is greater than or equal to a predetermined value ΔT■0°.

If the predetermined value ΔTV00 or more, the process advances to step 12 and the transient determination flag Ftr is set to 1.

If the determination is less than the predetermined value ΔTVO0, step 1
3, the rate of change ΔN of the engine rotational speed N is set to the predetermined value Δ
If it is greater than or equal to a predetermined value ΔN0, proceed to step 12 and set the transient determination flag Fr to 1. If it is less than the predetermined value ΔN0, proceed to step 14 and set the transient determination flag. Reset Ftr to 0.

In step 15, the basic fuel injection amount T is calculated based on the intake air flow rate Q detected by the air flow meter 13 and the engine rotational speed X obtained from the detection signal from the crank angle sensor 23 using the following formula. .

T, = -Q/N (K is a constant) In step 16, the fuel injection amount T1 after various corrections is calculated using the following equation.

TI = 27F - LA? IBOA-COEF+T.

Here, LAMBDA is an air-fuel ratio feedback correction coefficient set based on the oxygen concentration in the exhaust gas detected by the oxygen sensor 19, C0EF is various correction coefficients set based on water temperature, etc., and T is correction based on battery voltage. It's a minute.

FIG. 4 shows a routine for setting the amount of correction of the fuel supply amount for each cylinder based on the detection result of the exhaust pressure.

This routine is performed every predetermined period (for example, 1 m5).

In step 21, the exhaust pressure BP@ detected by the exhaust pressure sensor 21 is read.

In step 22, the detected exhaust pressure BP is compared with the currently stored maximum value BPnax of exhaust pressure.

If BPNAX≦BP・, proceed to step 23, update BP as BPMAX, and then step 24
If BPMAX>BP, proceed directly to step 24.
Proceed to.

In step 24, the detected exhaust pressure BP is compared with the currently stored minimum value BPx+N, and B P ,4,≧B
In the case of P, BP is updated as BPMIN in step 25, and if BPMIN<BP, the process directly proceeds to step 26.

In step 26, it is determined whether a transient state exists or not based on whether a transient determination flag Ftr set in a routine to be described later is 1 or not.

During a transient period when the flag Ftr is set to 1, no misfire determination is performed, so this routine is immediately terminated.

In addition, in the steady state when the flag Ftr is O, step 27
Proceed to and check the cylinder discrimination flag F.

Flag F is 1, the most recently input crank reference angle signal R
When EF is for the #1 cylinder, the process advances to step 28, and a flag FOLD is checked to determine whether or not the flag F has just been switched.

Then, while the corresponding flag F is 1 when the flag FOLD is 1, this routine is ended. As a result, during steady state, by repeating steps 1 to 7 and 25, the maximum value BPMAX and BP of the exhaust pressure during this period are
MI- is required.

On the other hand, when the flag FOLD is not 1, that is, immediately after the flag F is switched to 1, the process advances to step 29 and subsequent steps.

In step 29, the flag FOLD is set for the next determination.
to 1 cent.

In step 30, a variation width ΔBP4 expressed as a deviation between the currently stored maximum value B P MAX and minimum value BPMIH of the exhaust pressure is calculated. The maximum value BPNAX and the minimum value (I!!BPs+n) used here are values obtained during a predetermined period in the same state before the flag F is switched to 1.Specifically, the ignition cylinder If the order is #1 → #3 → #4 → #2 → #1, the period from inputting the crank angle M''S signal REF of the #2 cylinder to manually inputting the crank angle reference signal REF of the #1 cylinder. The exhaust pressure during this period is mainly #
Since this is the pressure of the combustion exhaust of four cylinders, the variation range ΔBP4 indicates the amplitude of the pulsation of the exhaust pressure of the #4 cylinder.

Next, in step 31, in order to determine the air-fuel ratio deviation of the next cylinder, the latest detected value BP is set as the initial value of the six maximum values BPM and the minimum value BPMIN.

In step 32, the deviation between the latest weighted average value ΔBPAV of the variation width ΔBPi (i=1 to 4) of each cylinder, which is determined as described later, and the variation width ΔBP4 of the #4 cylinder is calculated as BPm(-ΔBPAV- ΔBP4) is calculated.

In step 33, for the magnitude of the deviation ΔBPm,
The injection amount correction ff1m1 for bringing the air-fuel ratio of the #4 cylinder closer to the target air-fuel ratio (stoichiometric air-fuel ratio) is searched from the membership function stored in the ROM. Here, as shown in the figure, when the deviation BPm is large with a positive value, that is, when the exhaust pressure of the cylinder in question is too low, it is determined that the air-fuel ratio of the cylinder is deviating in the rich direction, and the value of ml becomes negative. When ml is a negative value (decreasing correction amount) and is large, in other words, when the exhaust pressure of the same cylinder is too high, it is determined that there is a deviation in the return direction, and a positive value (increase correction amount) is applied. amount) is set to be large.

Next, in step 34, the variation width ΔBPi(l
Calculate BPAV to the weighted average value of −1 to 4) using the following formula.

Further, when it is determined in step 27 that the flag F is not 1, the process proceeds to step 35, and it is determined whether or not the flag F is 2. If it is 2, the process proceeds to step 36, and the flag FOLD is determined.
is 2 or not. If the value is 2, this routine is ended, and if it is not 2, the process proceeds to step 37, where the flag FOLD is set to 2, and then the process proceeds to step 38. In step 38, after calculating the corrected 11m3 in the #3 cylinder in the same way as was done in steps 30 to 34, the previously calculated 8BP3 is calculated.
The weighted average value ΔBPAV is calculated using .

Similarly, if the flag F is not 2 in step 35, the process proceeds to step 39, where it is determined whether the flag F is 3, and if it is 3, it is determined whether the flag FOLD is 3, in step 40. If not 3, proceed to step 41 and select #
After calculating the variation width ΔBP2 and the correction amount m2 for the two cylinders, the load average value ΔBPAV is calculated using eight BP2.

Further, if the flag F is not 3, it is determined in step 42 whether the flag FOLD is 4 or not, and if it is not 4, the flag FOLD is set to 4 in step 44, and then the process proceeds to step 45 to change the #l cylinder. After calculating the width ΔBPI and correction 1ml, use ΔBP1 to calculate the weighted average value ΔB.
Calculate PAV.

Figure 5 shows the correction 1m set in the routine of Figure 4 above.
A routine is shown in which the air-fuel ratio is adjusted by correcting the fuel injection amount for each cylinder using i. This routine is started every time the crank angle sensor 23 inputs the crank reference angle signal REF for ignition, which is output at a predetermined crank angle position of each cylinder (for example, 70 degrees before compression top dead center). Further, the cylinders can be identified by changing the pulse width of each of these signals REF, or by changing only the signal of a specific cylinder, and by counting the number of times the signal is manually input after inputting the specific cylinder signal for other cylinders.

In step 51, it is determined whether the signal corresponds to the #1 cylinder ignition.

If YES, the process advances to step 52 and the cylinder discrimination flag F is set to 4. This is because the cylinder to which fuel is most recently injected is the #4 cylinder.

Next, the process proceeds to step 53, where the latest correction amount m4 determined in FIG. .

In step 54, the absolute value lM4 of the cumulative value M4 is compared with a limit value, and if it exceeds the limit value, step 54
Proceed to Step 5, set the cumulative value M4 to the limit value, and proceed to Step 5.
Proceed to step 6, and if it is not exceeded, continue to step 56.
Proceed to.

In step 56, fuel injection filr for #4 cylinder, 4
is the common fuel injection amount T for all cylinders, which is determined by the routine shown in Figure 3.
, by adding the cumulative value M4 to .

If the determination in step 51 is No, step 5
Proceeding to step 7, it is determined whether the signal corresponds to the #33 cylinder fuel injection, and if YES, the flag F is set to 2 for the #2 cylinder fuel injection in the step 58, and the following steps 59 to 62
Now, the cumulative value M2 is updated in the same manner as in steps 53 to 56, and compared with the limit value, and if it exceeds the limit value, it is set to the limit value, and the fuel injection amount T, 2 for the #2 cylinder is set.

If No in step 57, proceed to step 63,
Determine whether the signal corresponds to #44 cylinder fire, and select YES.
In this case, proceed to step 64 and set flag F to 1 for #1 cylinder fuel injection, and then similarly proceed to steps 65 to 68.
Then, update the cumulative value M1, compare it with the limit value, and if it exceeds it, set it to the limit value, and set the fuel injection amount T+1 for #1 cylinder.
Set.

If No in step 63, proceed to step 69 and set the flag F to 3 for fuel injection in the #3 cylinder. Similarly, in steps 70 to 73, the cumulative value M3 is updated and compared with the limit value. If it exceeds, set it to the limit value and set the fuel injection amount T, 3 for #3 cylinder.

In step 74, the injection signal corresponding to the cylinder-specific fuel injection amount Tli set in steps 56, 62, 68, and 73 is output to the fuel injection valve 15 of the corresponding i cylinder.

In this way, while monitoring the exhaust pressure for each cylinder,
Since the fuel supply amount can be adjusted to correct the deviation of the air-fuel ratio from the target air-fuel ratio, it is possible to prevent a misfire in a specific cylinder due to manufacturing variations between cylinders or changes over time, seizure due to excessive lean, and NOx emissions. An increase in C09HC due to increase or excessive enrichment can be suppressed.

In addition, since the fuel supply amount for each cylinder is adjusted only during steady operation, adjustments based on erroneous detection can
The air-fuel ratio can be adjusted with high reliability without adversely affecting transient operation performance.

Furthermore, by setting the adjustment N (cumulative value Mi) so that it does not exceed the limit value, excessive adjustment can be avoided.
It is also possible to suppress carbonization and enrichment.

Note that, based on the deviation ΔBPm, it is possible to detect whether or not a misfire has occurred for each cylinder. For example, if the amplitude of the exhaust pressure is extremely low, a misfire will occur because the fuel supply to that cylinder is cut off, and if the amplitude is extremely high, a misfire will occur due to an abnormality in the ignition system or fuel supply system. This is due to the combustion of unburned HC components in a three-way catalyst. In addition, if the overall exhaust pressure is high, this may be due to air leaking into the intake manifold, causing misfires (incomplete combustion) in all cylinders and making the air-fuel ratio excessively lean.

Therefore, in these cases, a flag indicating the misfire state for each cylinder may be set, and upon detection of the flag, the fuel supply amount for the misfiring cylinder may be set to O.

<Effects of the Invention> As explained above, according to the present invention, it is possible to adjust the fuel supply amount in the direction of correcting air-fuel ratio deviations for each cylinder by the exhaust pressure, thereby preventing misfires or excessive It is possible to suppress seizure caused by lean fuel consumption, an increase in NOx emissions, or an increase in C01HC caused by excessive enrichment.

In addition, by making adjustments only in steady state, transient operation performance and reliability are improved, and by setting a limit value for the amount of adjustment, excessive leanness due to adjustment can be avoided.
Enrichment can be suppressed.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of the present invention, and FIG. 2 is a block diagram showing the configuration of the present invention.
Figures 3 to 5 are diagrams showing the configuration of an embodiment of the present invention.
1 is a flowchart 1 showing various routines for performing control according to the present invention. 11... Engine 15... Fuel injection valve 16...
Control unit 19...Oxygen sensor 21
... Crank angle sensor 22 ... Spark plug 23
...Exhaust pressure sensor 24...Throttle sensor Patent applicant Japan Electronics Co., Ltd. Representative Patent attorney Fujio Sasashima Figure 2 Figure 3

Claims (3)

[Claims] (1) In an internal combustion engine equipped with a fuel supply means for each cylinder, an operating state detection means for detecting the engine operating state and a fuel supply that sets the fuel supply amount corresponding to the target air-fuel ratio according to the detected operating state. an exhaust pressure detection means for detecting the exhaust pressure of the engine, an averaging means for averaging the pulsation amplitude of the detected exhaust pressure, and a pulsation amplitude corresponding to each cylinder with respect to the averaged pulsation amplitude. 1. A fuel supply control device for an internal combustion engine, comprising: cylinder-by-cylinder fuel supply amount adjustment means for adjusting the fuel supply amount for each cylinder based on the deviation of the fuel supply amount for each cylinder. (2) The fuel supply control device for an internal combustion engine according to claim 1, wherein the adjustment by the cylinder-specific fuel supply amount adjustment means is stopped when the transient operation is detected by the operation state detection means. (3) The fuel supply control device for an internal combustion engine according to claim 1 or 2, wherein a limit value is set for the cumulative value of the adjustment amount by the cylinder-specific fuel supply amount adjustment means.