JPS63147954A - Method of controlling supply of fuel for internal combustion engine - Google Patents

Abstract

PURPOSE:To make it possible to precisely control the metering of fuel during an engine operates at a high rotational speed with a high load, by providing such an arrangement, when the time of fuel injection exceeds a time corresponding to the intervals of generation of crank angle signals, fuel in an amount relating to the value by which the time of fuel injection exceeds the time corresponding to the intervals of generation of the crank angle signals, is fed from a predetermined fuel injection valve. CONSTITUTION:In an internal combustion engine 1 comprising a plurality of engine cylinders, a fuel injection valve 6 and an auxiliary fuel injection valve 6a are disposed respectively upstream and downstream of a throttle valve 3', and an ECU 5 controls the supply of fuel. During an engine operating condition other than a predetermined low load condition, in which fuel is fed from the fuel injection valve 6, the intervals of crank angle signals generated from an engine rotational speed sensor 10 are measured, and the time corresponding to thus measured intervals is compared with the time of fuel injection. When the time of fuel injection exceeds the time corresponding to the intervals of the signals, fuel in an amount relating to the value by which the former time exceeds the latter time is fed from the fuel injection valve 6a. With this arrangement, it is possible to make the atomization of fuel satisfactory during low load operation of the engine 1, and to precisely control the metering of fuel during the engine operates at a high rotational speed with a high load.

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to a fuel supply control method for an internal combustion engine, and in particular, to a method for controlling fuel supply to an internal combustion engine, and in particular, to a method for controlling fuel supply to an internal combustion engine. The present invention relates to a control method when supplying fuel to multiple cylinders.

(Technical background of the invention and its problems) A conventional fuel supply control device that distributes and supplies fuel from a single fuel injection valve common to multiple cylinders of an internal combustion engine has been designed to , fuel is supplied by a normal, high-flow fuel injection valve installed upstream of the throttle valve upstream of the intake pipe assembly, while an auxiliary fuel injection valve installed downstream of the throttle valve is used when the engine is under low load. There is a type that uses a valve to supply fuel (Japanese Patent Laid-Open No. 47
-35422). As the auxiliary fuel injection valve, one having excellent atomization characteristics is used to ensure distribution of a small amount of fuel to each cylinder when the engine is under low load.

By the way, the amount of fuel supplied to a fuel injection valve or an auxiliary fuel injection valve is determined by the valve opening time.

Therefore, when the engine is under high load, the amount of fuel supplied increases and the valve opening time increases. However, when the engine is running at high speeds, the intake stroke time of the engine is shortened, so when the engine is under high load and high speeds, the opening time of the fuel injection valve may be longer than the intake stroke time. In this case, if a fuel injection valve is installed upstream of the intake pipe gathering portion and the fuel is injected and supplied in synchronization with the intake stroke, the fuel injected outside the intake stroke time will be sucked into other cylinders. Therefore, the opening time of the fuel injection valve cannot exceed the intake stroke time. Due to this situation, for example, the fuel injection valve should be used with a large flow rate (large diameter).
If a large amount of fuel is injected within a short valve opening time, conversely, fuel atomization and control accuracy will deteriorate when a small amount of fuel is injected under low load. On the other hand, if a small-diameter fuel injection valve is used to obtain good fuel atomization at low loads, the problem arises that the maximum fuel flow rate that allows accurate fuel metering control is limited. be.

(Object of the Invention) The present invention has been made in view of the above-mentioned circumstances, and is aimed at improving fuel mist during low engine load when fuel is supplied from a fuel injection valve provided upstream of the intake pipe assembly. It is an object of the present invention to provide a fuel supply control method for an internal combustion engine, which enables accurate fuel metering control during high-load, high-speed rotation while ensuring a high engine speed.

(Structure of the Invention) In order to achieve the above object, in the present invention, at least two or more fuel injection valves are provided upstream of a collection point of intake branch pipes of an internal combustion engine equipped with a plurality of cylinders, and the internal combustion engine determines the fuel injection time of the fuel injection valve according to the operating state of the internal combustion engine in synchronization with a crank angle signal of the at least two or more fuel injection valves when the internal combustion engine is at least in a predetermined low-load operating state. When the engine is in an operating state other than the predetermined low-load operating state, a predetermined fuel injection valve among the predetermined fuel injection valves is used to adjust the amount of fuel according to the fuel injection time, respectively, by using a fuel injection valve other than the predetermined fuel injection valve. In a fuel supply control method for an internal combustion engine, the interval between occurrences of the crank angle signal is measured during an operating state of the internal combustion engine other than the predetermined low-load operating state, and the fuel injection is performed at a time corresponding to the occurrence interval. Fuel supply control for an internal combustion engine, characterized in that when the fuel injection time exceeds the time corresponding to the occurrence interval, the predetermined fuel injection valve supplies fuel corresponding to the exceeded time. A method is provided.

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

FIG. 1 is an overall configuration diagram of a fuel supply control device to which the method of the present invention is applied. Reference numeral 1 indicates, for example, a 4-cylinder, 4-stroke internal combustion engine. The intake pipe 2 is connected to the intake pipe 2. A throttle body 3 is provided upstream of the gathering portion of the intake pipe 2, and a throttle valve 3' is provided inside. A throttle valve opening (OTH) sensor 4 is connected to the throttle valve 3' and converts the valve opening of the throttle valve 3' into an electrical signal and controls an electronic control unit (hereinafter referred to as rI!).
CU J) 5.

A fuel injection valve 6 is provided in the intake pipe 2 slightly upstream of the throttle body 3, and is configured to supply fuel to the cylinder of the internal combustion engine 1 when the engine 1 is operated under high load.

On the other hand, an auxiliary fuel injection valve 6a is provided slightly downstream of the throttle body 3 of the intake pipe 2 and upstream of the intake pipe gathering part.
Fuel is supplied to the cylinders of the internal combustion engine 1 during low load operation in a sufficiently warmed state. The fuel injection valve 6 and the auxiliary fuel injection valve 6a are connected to a fuel pump (not shown) and electrically connected to the ECU 3, and each of the fuel injection valve 6 and the auxiliary fuel injection valve 6a is activated by a signal from the ECU 3. The opening time of the valve is controlled. As the auxiliary fuel injection valve, one with excellent atomization characteristics is used to ensure distribution of a small amount of fuel to each cylinder when the engine is under low load.

Further, an absolute pressure (Pe^) sensor 8 is provided downstream of the throttle valve 3' of the throttle body 3 via a pipe 7, and an absolute pressure signal converted into an electrical signal by the absolute pressure sensor 8 is provided. is sent to the ECU 3.

The engine cooling water temperature sensor (rT) is installed on the engine 1 body.
A Tw sensor (referred to as "w sensor") 9 is provided, and the Tw sensor 9 is made of a thermistor or the like, and is inserted into the circumferential wall of the engine cylinder filled with cooling water, and supplies its detected water temperature signal to the ECU 3. An engine rotation speed sensor (hereinafter referred to as "rN e sensor") 10 is attached around the camshaft or crankshaft (not shown) of the engine, and the Ne sensor 10 rotates at a predetermined crank angle position every 1800 revolutions of the engine crankshaft. , that is, the top dead center (T
DC), a crank angle position signal (hereinafter referred to as rTDC signal) is output at a crank angle position before a predetermined crank angle, and this TDC signal is
Sent to 5.

A three-way catalyst 12 is disposed in the exhaust pipe 11 of the engine 1 to purify HC, CO, and NOx components in the exhaust gas. An 02 sensor 13 is inserted into the exhaust pipe 11 upstream of the three-way catalyst 12, and this sensor 13 detects the oxygen concentration in the exhaust gas and supplies an 02'a degree signal to the E CtJ 5.

Furthermore, other parameter sensors 14 such as an atmospheric pressure sensor are connected to the ECU 3, and the other parameter sensors 14 supply their detected value signals to the ECU 3.

The ECU 3 includes an input circuit 5a having functions such as shaping input signal waveforms from various sensors, correcting voltage levels to predetermined levels, and converting analog signal values into digital signal values.
Central processing circuit (hereinafter referred to as "rcpu") 5b, C)
) It is composed of a storage means 5c for storing various calculation programs and calculation results executed by U5b, and an output circuit 5d for supplying drive signals to the fuel injection valve 6 and the auxiliary fuel injection valve 6a, respectively.

The CPU 5b executes the fuel supply control program shown in FIG. 2 every time the TDC signal is input manually.

The program is based on engine parameter signals from the aforementioned various sensors supplied via the input circuit 5a.
The fuel injection time of each of the fuel injection valve (upstream valve) 6 upstream of the throttle valve and the auxiliary fuel injection valve (downstream valve) 6a downstream of the throttle valve is calculated, and a valve opening drive signal based on these injection times is used to control both injections. Output to valves 6 and 6a.

The upstream valve 6 and the downstream valve 6a are operated according to the methods shown in the table below according to each operating state in the idling operating range (low load range), outside the idling operating range (middle/high load range), and at high load and high rotation. It is controlled to perform fuel injection.

Each formula in the table is used in executing the program shown in FIG. 2, and details thereof will be described later.

Hereinafter, the processing procedure of the fuel supply control program shown in FIG. 2 will be explained in detail. Processing of this program is started every time the above-mentioned TDC signal is generated.

First, in step 1, it is determined whether the engine water i1JTw is higher than a predetermined temperature "1'WM^ (for example, 20°C). If the answer is negative (No), that is, if the engine temperature is lower than the predetermined temperature, , the opening time ′rOυ of the downstream valve 6a
7 M a is provisionally set to O (step 10).

Then, the process proceeds to step 17 to be described later, and the upstream valve P
Search the basic valve opening time Tix from the a-Ne map and find the corresponding T
Calculate the valve opening time TOUTM of the upstream valve 6 based on the iM value (Step 19), and in Step 8, the upstream valve 6 is
Outputs a valve opening drive signal according to the uTM value. As a result,
When the engine is cold, auxiliary air for fast idle is supplied from the throttle bypass passage (not shown), which requires a large amount of fuel flow.
Fuel is supplied from the upstream valve. In this way, when the fuel flow rate is relatively large, increasing the distance from the fuel injector to the intake pipe collection part ensures better distribution of fuel to the plurality of cylinders.

When the determination result in step 1 is affirmative (Yes), it is determined in the next steps 2.3 and 4 whether or not the engine is in the idle operating range. That is, in step 2, it is determined whether the throttle valve opening θT)4 is smaller than a predetermined idle opening 2θIDL (for example, 0.39°), and in step 3, the intake pipe absolute pressure Pa is determined to be a predetermined idle pressure Zptzb.
(for example, 350 mmHg),
In step 4, it is determined whether the engine speed Ne is lower than a predetermined idle speed ZNIDL (for example, 1100 rpm). If all of these answers are affirmative (Yes), the basic valve opening time Ti is determined from the downstream valve Pa-Ne map.
Ma is searched, and the downstream valve opening time Tot+tva is calculated based on the Tiua value using the following equation (1) (Step 5).

T 0LIT Ma=T i MaXK, +, -(1
) Here, 1 and 2 are correction coefficients or correction variables that are calculated according to engine parameter signals from the various sensors mentioned above, and depending on the engine operating condition, start characteristics, exhaust gas characteristics, fuel consumption characteristics, engine It is calculated based on a predetermined calculation formula so that the acceleration characteristics and other characteristics are optimized.

Next, 72TllCA used in step 11 described later.
Preset the M value to the initial value nTDcAM (for example, 3) (Step 6), and set the upstream valve opening time TOLJTM value to 0.
(step 7), so the next step 8
When this is executed, no valve opening drive signal is output to the upstream valve. Furthermore, in the first step 9, a valve opening drive signal is outputted according to the TouTMa value calculated in the step 5,
Exit this program. As a result, fuel is supplied to the cylinders directly from the injection valve downstream of the throttle valve 3', and the distance between the injection valve and each cylinder is shortened, improving the responsiveness of fuel supply to the cylinders. become.

Steps 2, 3. Or, any of the judgment results in 4 is negative (
No), that is, when the engine operating state is outside the idle range, it is determined whether the nTDCAM value is 0 or not (step 11). If the answer is negative (No), the same process as in step 5 is performed. The basic valve opening time TiMa is retrieved from the Pe-Ne map for downstream valves, and the valve opening time Tourhsa of the downstream valve is calculated based on the TiMa value using the above equation (1) (step 12). Next, 1 is subtracted from the QrocAM value (step 13), and the process proceeds to step 17 and subsequent steps.

When the determination result in step 11 is affirmative (Yes), the Tot+rMa value calculated in step 12 is decreased in the primary step 14.15 or step 14.16 by the degree of decrease according to the engine rotation speed Ne. That is, step 1
4, the engine speed Ne is set to a predetermined value ZNeAM (for example, 9
If the answer is negative (NO), the first predetermined value ΔTOuTMa1 (for example, 0.4m5ec) is subtracted from the previous TouTMa value (step 15), and the answer of step 14 is When it is the front foot (Yes), the second predetermined value ΔTour is calculated from the previous TouTma value.
Step 1: Subtract Ma, (for example 0.2m5ec)
6), then proceed to step 17 and subsequent steps.

In step 17, the ToutMa value calculated in step 12.15 or 16 is determined to be a lower limit value TOUTM smaller than the minimum value of ToutMa calculated in step 5 or 12.
It is determined whether or not it is smaller than aLMT (for example, 3,0 m 5ec), and if the answer is affirmative (Yes), the TiMa value is set as the lower limit value TixaLM in step 18.
urMa i direct to TOIJTya=TiMaXK1+,
.

(formula (1) above), that is, ToutMa
”TiMa and xTXK, step 19 from 2 to 10
If the answer is negative (NO), the process directly advances to step 19. As a result, even after the engine operating state shifts from the idle range to outside the idle range, a substantially constant amount of
Fuel equal to or greater than oυTMaLMT is supplied from the downstream valve 6a. Here, the value of the TiHa control T is the minimum flow rate value at which the fuel supplied from the downstream valve can be accurately measured (for example, 1.8 m5ec).

Therefore, even while fuel is injected from the upstream valve 6 and adheres to the inner wall surface of the throttle body 3 and the throttle valve 3' immediately after the start of fuel injection by the upstream valve 6 due to the transition to the outside of the idle area, the downstream valve 6a Since fuel is supplied from the downstream valve 6a to the upstream valve 6, the required fuel supply amount is ensured when switching from the downstream valve 6a to the upstream valve 6, and fluctuations in the air-fuel ratio are suppressed, thereby preventing deterioration of drivability. Furthermore, in this embodiment, by executing steps 11, 12.13 and step 14.15 or step 14.16 when switching from the downstream valve 6a to the upstream valve 6, the amount of fuel supplied to the downstream valve 6a is gradually reduced. Since the air-fuel ratio is decreased, changes in the air-fuel ratio at the time of switching the fuel supply can be suppressed as much as possible. In step 19, the basic valve opening time TiM is retrieved from the upstream valve Pa-Ne map, and based on the TiM value, the valve opening time TOUT of the upstream valve is calculated using the following equation (2).

TouTM=Ti MXK1+2− (2) Here,
K1 and K2 are the same as in the above formula (1).

In the next step 20, the TO calculated in step 19 is
It is determined whether the IJTM value is larger than a predetermined value Me-TouTLMT. Here, Me is 1' D
This is the generation interval of the C signal, which corresponds to the time of the intake stroke in the case of a 4-cylinder, 4-cycle engine. Further, TouTLMT is the time required for the flow riser 6 to change from the valve open state to the completely closed state. Step 20
When the determination result is affirmative (Yes), the valve opening time of the downstream valve is calculated using the following equation (3) (step 21).

TouTya value (TouTM - (Me-TOIJTL
%14 T)) By calculating the valve opening time TouTMa of the downstream valve using both equations (3), when the valve opening time becomes longer during high engine load and high rotation, the upstream valve is controlled within the valve opening time TOUTM calculated in step 19. The fuel that cannot be completely supplied is supplied from the downstream valve 6a. As a result, the necessary fuel paper is secured even under high load and high rotation. Furthermore, the upstream valve 6 does not have to have such a large flow rate (large diameter).

Good atomization of fuel can be achieved even under low load.

Next, the opening time of the upstream valve is calculated using the following equation (4) (step 22).

TOLIT hs = M e-T outTLMT - (
4) Here, Me and TouTLMT are the same as those in both equations (3). Therefore, the upper limit of the opening time of the upstream valve 6 is M e -T outTLMT, and the upstream valve 6 is completely closed every time fuel is supplied to each cylinder.

The valve does not open continuously. As a result, as shown in Fig. 4, there is a characteristic region where the fuel 1fQf is not proportional to the valve opening time T0IJT during continuous injection from the large flow range of the fuel injector, so it is not possible to use that region. Prevented.

After executing step 22, proceed to step 8. Further, when the determination result in step 20 is negative (No), the upstream valve 6
Skip steps 21 and 22 and go directly to step 8, since all the necessary fuel can be supplied by
Proceed to.

After that, in step 8, a valve opening drive signal corresponding to the TouTM value is output to the upstream valve, and in step 9, a valve opening drive signal corresponding to the TouTya value is output to the downstream valve, and one program is completed.

Finally, the fuel supply characteristics when using the program shown in FIG. 2 described above will be explained with reference to FIG. 3. FIG. 3 shows changes over time in the amount of fuel supplied to the upstream and downstream valves when the engine is accelerated from an idling state when the engine temperature Tw is higher than TIIIM^. First, when the engine operating state is in the idle range, fuel corresponding to the TouTMa value according to the map value is supplied from the downstream valve. Next, when the engine operating state shifts from the idle region to outside the idle region, the amount of fuel supplied from the downstream valve gradually decreases by a predetermined reduction degree ΔTouTxa+ or ΔToUTMa2, and becomes TouTyaLMT(=l″1sat, MTXK
, + has a value of 2). During this period, the amount of fuel injected from the upstream valve corresponds to "1'OUTM" according to the map value, but since the fuel adheres to the inner wall surface of the throttle body and the throttle valve, it actually reaches the cylinder from the upstream valve. The fuel to be used gradually increases from O to the T'OUTM value.
When the engine operating state shifts to a high-load, high-speed range, the fuel supply I^ from the upstream valve may become the maximum amount that can be supplied during the intake stroke, and at that time, the fuel supply from the downstream valve is the amount to replenish the shortage (To
uT-(Me-TOUTLMT))XKAux.

(Effects of the Invention) As detailed above, according to the fuel supply control method for an internal combustion engine of the present invention, at least two or more intake branch pipes of an internal combustion engine including a plurality of cylinders a fuel injection valve, the fuel injection time of the fuel injection valve is determined in accordance with the operating state of the internal combustion engine in synchronization with a crank angle signal of the internal combustion engine, and at least a predetermined low-load operating state of the internal combustion engine is determined. Sometimes, a predetermined fuel injector of the at least two or more fuel injectors is used, and when the engine is in an operating state other than the predetermined low-load operating state, another fuel injector other than the predetermined fuel injector is used. A fuel supply control method for an internal combustion engine that performs fuel metering control in accordance with a fuel injection time, the method comprising: measuring the occurrence interval of the crank angle signal during an operating state other than the predetermined low load operating state of the internal combustion engine; The fuel injection time is compared with the time corresponding to the occurrence interval, and when the fuel injection time exceeds the time corresponding to the occurrence interval, the predetermined fuel injection valve supplies fuel corresponding to the exceeded time. For example, even though it is a method of supplying fuel to multiple cylinders from a single fuel injector, it is possible to achieve good fuel atomization when the engine is under low load, and it is also possible to control fuel metering when the engine is under high load and at high speeds. can be done accurately.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of a fuel supply control device for an internal combustion engine that implements the method of the present invention, FIG. 2 is a flowchart of a fuel supply control program executed by the ECU in FIG. 1, and FIG.
The figure is a graph showing the temporal change in the amount of fuel supplied according to the method of the present invention, and FIG. 4 is a graph showing the fuel injection characteristics of the fuel injection valve. 1... Internal combustion engine, 3'... Throttle valve, 4.
...Throttle valve opening sensor, 5...Electronic control unit (ECU), 5b-CPU, 5c-storage means, 6...Fuel injection valve, 6a...Auxiliary fuel injection valve. 8... Intake pipe absolute pressure sensor, 10... Engine rotation speed sensor.

Claims (1)

[Claims] 1. At least two or more fuel injection valves are provided upstream of a collection point of intake branch pipes of an internal combustion engine having a plurality of cylinders, and the fuel injection valves are responsive to the operating state of the internal combustion engine in synchronization with a crank angle signal of the internal combustion engine. the fuel injection time of the fuel injection valve is determined, and at least when the internal combustion engine is in a predetermined low load operating state, a predetermined fuel injection time of the at least two or more fuel injectors is used to inject the fuel into the predetermined low load state of the engine. In the fuel supply control method for an internal combustion engine, the fuel supply control method for an internal combustion engine performs fuel metering control according to the fuel injection time using each fuel injection valve other than the predetermined fuel injection valve in an operating state other than the load operating state. The occurrence interval of the crank angle signal is measured during an operating state other than the predetermined low-load operating state, the time corresponding to the occurrence interval is compared with the fuel injection time, and the fuel injection time is determined according to the occurrence interval. 1. A fuel supply control method for an internal combustion engine, characterized in that when the time exceeds the specified time, fuel corresponding to the exceeded amount is supplied by the predetermined fuel injection valve.