JPS63268951A - Fuel supply control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To enable the unbalance of the output and the air-fuel ratio at every cylinder to be decreased by controlling to correct the fuel supply quantity in such a manner that the calorific values during the combustion stroke, which are calculated according to pressure signals from within-cylinder pressure sensors, are in the same level. CONSTITUTION:A control unit 10 calculates the calorific values during the combustion stroke at every cylinder according to pressure signals from within-cylinder pressure sensors 14 which are placed in every cylinder for an engine 1 respectively. In addition, at every cylinder, it compares the average calorific value at each cylinder with the average calorific value in the whole engine, and then corrects the fuel injection quantity from a fuel injection valve 5 according to the comparison as above. That is, the fuel injection quantity at a cylinder having a large average calorific value is decreased by a prescribed quantity, while, the fuel injection quantity at a cylinder having a small average calorific value is increased by a prescribed quantity. Thereby, the unbalance of the fuel injection quantity at every cylinder is decreased, and the calorific value at every cylinder can be equalized, and consequently, the operability, such as stability in idling, can be improved remarkably.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a fuel supply control device for an internal combustion engine that has an in-cylinder pressure sensor for each cylinder of the engine and controls the amount of fuel supplied to each cylinder.

<Prior art> As a conventional fuel supply control device for an internal combustion engine,
As described in Publication No. 51135, each cylinder of the engine has an in-cylinder pressure sensor, and the indicated average effective pressure of each cylinder detected and calculated by each in-cylinder pressure sensor is used as the indicated average effective pressure of all cylinders. It is known that the fuel injection amount to each cylinder is controlled so as to approach the arithmetic mean value of the pressure.

According to this, there are variations in fuel injection valves for each cylinder.

Even when there is variation in the intake amount of fresh air between cylinders, such as during idling, it is possible to avoid unbalanced output between cylinders and improve engine drivability such as idling stability.

<Problems to be solved by the invention> However, the in-cylinder pressure or indicated mean effective pressure Pi is influenced by various factors such as fresh air charging amount, air-fuel ratio 9 ignition timing, combustion period, condition of Pi fluctuation 1 ignition quality If we try to correct the difference in Pi due to the deviations of these various elements with the fuel injection amount, the fuel injection amount will be forced to the rich side for cylinders with small Pi, and to the lean side for cylinders with large Pi. Even if the overall air-fuel ratio can be brought close to the stoichiometric air-fuel ratio, the air-fuel ratio of each cylinder will be unbalanced, and rich cylinders will have high HC and Co emissions, while thin cylinders will have low NOx emissions. There was a problem in that the amount of emissions increased significantly.

SUMMARY OF THE INVENTION In view of these conventional problems, it is an object of the present invention to make it possible to avoid an imbalance in output without causing an imbalance in the air-fuel ratio of each cylinder.

<Means for Solving the Problem> Therefore, as shown in FIG. A calorific value calculation means calculates the calorific value during the combustion stroke for each cylinder, and a fuel supply device supplies fuel to each cylinder so that the calorific value of each cylinder is at the same level based on the calculation result of the calorific value calculation means. This configuration includes fuel supply amount correction control means for correcting and controlling the supply amount.

<Operation> In this way, instead of controlling directly using cylinder pressure or indicated mean effective pressure, by calculating the calorific value of each cylinder and controlling it so that they are at the same level, the output of each cylinder can be unbalanced. This eliminates the occurrence of balance and air-fuel ratio assist balance, improves engine drivability such as idle stability, and improves emissions.

<Example> An embodiment of the present invention will be described below.

In Fig. 2, the engine 1 is a ■-type multi-cylinder engine, and air taken in from an air cleaner 2 passes through a throttle valve 3 and then branches at an intake manifold 4, and a fuel injection valve is installed for each cylinder in the branch. The fuel is supplied to each cylinder together with the fuel injected from No. 5. An ignition plug 6 is provided in each cylinder of the engine 1, and the air-fuel mixture is ignited and combusted by spark ignition. Exhaust gas from each cylinder of the engine 1 joins together at an exhaust manifold 7, passes through a catalyst 8 and a muffler 9, and is discharged.

The fuel injection valve 5 is an electromagnetic fuel injection valve that opens when the solenoid is energized, and closes when the energization is stopped. Fuel is injected and supplied under pressure from the pump and adjusted to a predetermined pressure by a pressure regulator.

The control unit 10 includes a CPU and a ROM.

It is equipped with a microcomputer including a RAM and an input/output ink face, receives input signals from various sensors, performs arithmetic processing as described later, and controls the operation of the fuel injection valve 5.

As the various sensors mentioned above, an air flow meter 11 is provided downstream of the air cleaner 2, and the air flow meter 11 is installed downstream of the air cleaner 2.
Outputs a signal according to the

Further, a crank angle sensor I2 is provided, and outputs a position signal for each unit crank angle and a reference signal for each reference crank angle. Here, the engine rotation speed N can be calculated by measuring the number of position signals generated per unit time or the period of the reference signal.

Further, an 02 sensor 13 is provided at the built-in portion of the exhaust manifold 7. The 02 sensor 13 is a known sensor whose electromotive force suddenly changes when the air-fuel mixture is combusted near the stoichiometric air-fuel ratio.

Furthermore, an in-cylinder pressure sensor 14 made of a piezoelectric element formed as a mounting washer is provided on the spark plug 6 of each cylinder,
A signal corresponding to the cylinder pressure P is output via an amplifier (not shown).

Here, the CPU of the microcomputer built in the control unit 1o performs arithmetic processing according to the program on the ROM, and determines the fuel injection amount as ft+IJ? Wholesale.

That is, the intake air flow ff1Q detected based on the signal from the air flow meter 11 and the crank angle sensor
Calculate the basic fuel injection amount Tp = -Q/NCK is a constant) from the engine speed N calculated based on the signal from
Various correction coefficients C0EF, including acceleration correction coefficients, etc.
The actual air-fuel ratio detected based on the signal from the 02 sensor 13 is compared with the stoichiometric air-fuel ratio, and the air-fuel ratio feedback correction coefficient α is set by proportional/integral control. Furthermore, the voltage correction numerator s based on the battery voltage is The fuel injection lTi is calculated by correcting as shown in the following equation.

T 1 = Tp - COEF / α + Ts Then, the fuel injection l'r'i set to all cylinders in this way is shown in Fig. 3 as flowchart 1. Calorific value calculation, cylinder-specific injection ■ control Correction control is performed for each cylinder according to a routine, and the drive pulse signal of the corrected fuel injection (pulse l corresponding to JTi) is applied to the fuel injection valve 5 of the corresponding cylinder to perform fuel injection.

The calorific value calculation and cylinder-specific injection amount control routine shown in FIG. 3 are executed for each unit crank angle.

In step 11 (indicated by Sll in the figure; the same applies hereinafter), the cylinder pressure P=PJ=P (θj) at the crank angle θ=θJ (j=1...) is read. Further, in step 12, the combustion chamber volume at that time is V=V.

−V(θJ) is calculated.

Next, in step 13, a polytropic index PN is calculated.

VI = VST (stroke volume) Next step 1
In step 5, it is determined whether j=720 or not, and when j≠720, this routine is ended. Therefore, until j=720, only steps 11 to 14 are repeatedly executed for each unit crank angle.

When j=720, that is, every cycle (two revolutions of the engine), the process proceeds to step 16 and subsequent steps.

In step 16, the calorific value Q8 is calculated for each cylinder (#i cylinder) according to the following equation.

Qr=fQidθ=ΣQ,Δθ Therefore, steps 11 to 14 and 16 correspond to the calorific value calculation means.

Next, in step 17, the latest n is updated for each cylinder (#i cylinder).
The average heat generation l summer in the cycle is calculated according to the following formula.

Next, in step 18, the average calorific value of the entire engine -q-
Calculate according to the following formula (for 4 cylinders).

Page 1□ΣQ.

Next, in step 19, the average calorific value page for each cylinder (#i cylinder) is compared with the average calorific value page of the entire engine, and the U
When i>-Q-, the process proceeds to step 20, where the fuel injection amount Ti of the #i cylinder is decreased by ΔT, and the process proceeds to step 20.

If it is the page, the process proceeds to step 21 and the fuel injection amount Ti of the #i cylinder is increased by ΔT.

Therefore, steps 17 to 21 correspond to the fuel supply amount correction control means.

By doing so, it is possible to reduce the imbalance in the amount of fuel supplied to each cylinder, to make the amount of heat generated in each cylinder uniform, and to significantly improve drivability such as idling stability.

In this example, a multi-point injection system is shown in which a fuel injection valve is provided for each cylinder in the intake manifold knob or intake port, but a single fuel injection valve is installed in common for all cylinders in the gathering part of the intake passage. For single point injection systems with
Injection may be performed a number of times in accordance with the number of cylinders per cycle in synchronization with engine rotation, and each injection pulse 1] may be individually controlled in accordance with the calorific value of each cylinder to which fuel is supplied.

<Effects of the Invention> As explained above, according to the present invention, the amount of heat generated during the combustion stroke of each cylinder is calculated based on the pressure signal from the in-cylinder pressure sensor provided for each cylinder, and the amount of heat generated in each cylinder is calculated. Since the amount of fuel supplied to each cylinder is corrected and controlled so that the amount is at the same level, it is possible to reduce imbalances in the output of each cylinder and imbalances in the air-fuel ratio, improving engine operability such as idle stability. It is possible to achieve the effect of improving emissions as well as improving emissions.

[Brief explanation of the drawing]

FIG. 1 is a functional block diagram showing the configuration of the present invention, FIG. 2 is a system diagram showing an embodiment of the invention, and FIG. 3 is a flowchart 1 showing control contents. 1... Engine 5... Fuel injection valve 6... Spark plug 10... Control unit 11... Air flow meter 12... Crank angle sensor 13.
...02 sensor 14...Cylinder pressure sensor

Claims (1)

[Claims] A cylinder pressure sensor provided for each cylinder of the engine, a calorific value calculating means for calculating the calorific value during the combustion stroke for each cylinder based on the pressure signal from each cylinder pressure sensor, and a calorific value calculating means for calculating the calorific value during the combustion stroke for each cylinder. A fuel supply control device for an internal combustion engine, comprising: fuel supply amount correction control means for correcting and controlling the amount of fuel supplied to each cylinder by a fuel supply device so that the calorific value of each cylinder is at the same level based on a calculation result.