JPS63147952A - Method of controlling supply of fuel for internal combustion engine - Google Patents

Abstract

PURPOSE:To make it possible to satisfactorily distribute fuel among a plurality of engine cylinders, by supplying fuel from only a fuel injection valve upstream of a throttle valve when the temperature of an engine is below a predetermined temperature. CONSTITUTION:In an internal combustion engine 1 comprising a plurality of engine cylinders, an fuel injection valve 6 and an auxiliary fuel injection 6a are disposed respectively upstream and downstream of a throttle valve 3', and an ECU 5 control the supply of fuel. In this arrangement, when the temperature of an engine detected by an engine cooling water temperature sensor 9 is below a predetermined value, fuel is fed from the fuel injection valve 6. Meanwhile, when the temperature of the engine exceeds the predetermined value and the opening degree of the throttle valve detected by a throttle valve opening degree sensor 4 is below a predetermined opening degree, fuel is fed from the auxiliary fuel injection valve 6a. With this arrangement, even though the temperature of the engine is low, it is possible to satisfactorily distributes fuel among engine cylinders, and further, it is possible to a eliminate the necessity of changeover from the auxiliary fuel injection valve 6a to the fuel injection valve 6, thereby it is possible to prevent variations in the supply amount of fuel which are liable to occur upon changeover between the values 6, 6a.

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, the present invention relates to a fuel supply control method for an internal combustion engine. The present invention relates to a control method when supplying fuel to cylinders.

(Technical background of the invention and its problems) A conventional fuel supply control device that distributes and supplies fuel from a common fuel injection valve to a plurality of cylinders of an internal combustion engine has been designed to distribute and supply fuel from a common fuel injection valve to multiple cylinders of an internal combustion engine. While fuel is supplied by a fuel injection valve installed upstream of the upstream throttle valve, there is also a type in which fuel is supplied by an auxiliary fuel injection valve installed downstream of the throttle valve when the engine is under low load. 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.

According to this method, even during low load operation when the throttle valve is fully open or close to this, the supply of fuel to the cylinders is not obstructed by the throttle valve.
In other words, the responsiveness of fuel supply is improved.

When the engine temperature is high, fuel atomization in the intake pipe is good, so in order to improve the responsiveness of fuel supply to the cylinders and ensure precision in controlling minute flow rates, the amount of fuel discharged from the fuel injection valve upstream of the throttle remains the same as before. It is desirable to inject fuel from an auxiliary fuel injection valve with a small diameter.

However, when the engine temperature is low, the injection time of the auxiliary fuel injection valve becomes longer because the amount of fuel is increased during cold operation, and the temperature of the intake pipe is also low. Fuel atomization deteriorates. In order to avoid this worsening of fuel atomization, if fuel is injected from an auxiliary fuel injection valve installed downstream of the throttle valve, which is close to the gathering part of the intake pipe, the distribution of fuel to multiple cylinders will be poor. There was a problem.

Furthermore, in the conventional fuel supply control method described above, when the engine temperature is low, such as when the engine is cold, the fuel injection valve that supplies fuel when transitioning from a low-load operating state to a high-load operating state is injected with auxiliary fuel downstream of the throttle valve. When changing from an injector to a conventional fuel injector upstream of the throttle valve, there is a problem in that there is variation in the fuel paper actually delivered to the engine. That is,
In such a case, if the auxiliary fuel injection valve downstream of the throttle valve was injecting the maximum amount of fuel, it will immediately interrupt this fuel injection, and the fuel injection valve upstream of the throttle valve will suddenly inject a large amount of fuel. It will start. At this time, the throttle valve and the inner wall of the intake pipe near the throttle valve go from a dry state to a wet state with fuel rapidly adhering to it.The lower the temperature of the intake pipe wall, the more this adhering fuel paper becomes. The amount of fuel actually supplied to the engine varies greatly over time. As a result, a problem arises in that the accuracy of fuel supply control decreases when switching from the auxiliary fuel injection valve to the normal fuel injection valve.

(Object of the Invention) The present invention was made in view of the above circumstances, and it is possible that when the temperature of the engine is low, the distribution of fuel to multiple cylinders becomes poor, or the distribution of fuel from the auxiliary fuel injection valve to the normal fuel injection valve becomes poor. An object of the present invention is to provide a fuel supply control method for an internal combustion engine that prevents problems such as fluctuations in the amount of fuel supplied due to switching.

(Structure of the Invention) In order to achieve the above object, the present invention provides fuel injection valves installed on the upstream side and the downstream side of a throttle valve upstream of an intake pipe gathering part of an internal combustion engine having a plurality of cylinders. and a fuel supply control method for an internal combustion engine in which fuel is supplied from an auxiliary fuel injection valve according to the operating state of the engine, wherein when the engine temperature is lower than a predetermined temperature, the fuel injection valve on the upstream side of the throttle valve supplies fuel. An internal combustion engine characterized in that when the engine temperature is higher than the predetermined temperature and the throttle valve opening is below the predetermined opening, fuel is supplied by an auxiliary fuel injection valve downstream of the throttle valve. A fuel supply control 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 diagram of a fuel supply control device to which the method of the present invention is applied. Reference numeral 1 indicates, for example, a four-cylinder internal combustion engine, and an intake pipe 2 is connected to the engine 1 via an intake manifold. ing. Intake/P? A throttle body 3 is provided upstream of the convergence part 2, and a throttle valve 3' is provided inside. A throttle valve opening (CITM+) sensor 4 is connected to the throttle valve 3' and converts the valve opening of the throttle valve 3' into an electrical signal and sends it to an electronic control unit (rECUJ) 5. It is like that.

A fuel injection valve 6 is provided slightly upstream of the throttle body 3 in the intake pipe 2, and is configured to supply fuel to all cylinders of the internal combustion engine 1 when the internal combustion engine 1 is operated under a medium to high load. On the other hand, a little downstream of the throttle body 3 of the air pipe 2, R
An auxiliary fuel injection valve 6a is provided upstream of the intake pipe gathering portion to supply fuel to all 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 E
It is electrically connected to CU3, and the valve opening times TOυTM and TouTva of each of the fuel injection valve 6 and the auxiliary fuel injection valve 6a are controlled by a signal from EC:U5.

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

The fuel injection valve 6 and the auxiliary fuel injection valve 6a are connected to a pipe line 21,
The strainer 15 is connected to a fuel pump 17 in a fuel tank 16 via lines 22, 23 and 24. still,
The fuel pump 17 is controlled by the ECU 3. Further, the pipes 22, 23, and 24 are connected to the fuel tank 16 via a pipe 25, a pressure regulator 18, and a pipe 26. pressure regulator 1
8 is for adjusting the fuel pressure in the pipes 22 to 25 according to the negative pressure (absolute pressure Pa^) in the intake pipe downstream of the throttle valve 3', and the negative pressure chamber 18a is connected to the pipe 31. It is connected to the intake pipe 2 downstream of the throttle valve 3' through the throttle valve 3'. That is, the valve opening pressure of the valve body 18b that opens and closes the open end 26a of the pipe line 26 is determined by the biasing force of the coil spring 18c and the throttle valve 3.
The difference between the fuel pressure (absolute pressure) in the pipes 22 to 25 and the absolute pressure Pa in the intake pipe downstream of the throttle valve 3' is always constant. becomes. Therefore, the discharge pressure of the auxiliary fuel injection valve 6a remains constant regardless of the magnitude of the intake pipe absolute pressure Pal^, and the fuel injection amount of the auxiliary fuel injection valve 6a is determined only by the opening time TouTMa of the auxiliary fuel injection valve 6a. can,
Accurate fuel metering can be performed.

On the other hand, since the pressure in the intake pipe 2 upstream of the throttle valve 3' is always close to atmospheric pressure, the discharge pressure of the fuel injection valve 6 is equal to the absolute pressure Po^ in the intake pipe downstream of the throttle valve 3'.
It changes depending on the size of.

That is, the discharge pressure 1'D of the fuel injection valve 6 is equal to the absolute pressure P in the intake pipe downstream of the throttle valve 3' when the engine is under low load.
As a^ becomes lower, the fuel pressure in the pipes 22 to 25 becomes lower, so the fuel pressure in the pipes 22 to 25 becomes lower, and when the engine is under high load, as the absolute pressure Pa^ in the intake pipe downstream of the throttle valve 3' increases, the pressure in the pipes 22 to 25 decreases. It becomes high because the fuel pressure in ~25 becomes high. Therefore, when the engine is under low load, the valve opening time TOLITM of the fuel injection valve 6 becomes longer when the fuel pressure is lower for the same fuel supply amount, making it possible to control the fuel metering at a minute flow rate. When the engine is under load, the opening time ToυTV of the fuel injection valve 6 becomes shorter for the same amount of fuel supplied, so a large amount of fuel can be supplied, making it easy to obtain high output.

Note that the respective reference values Ti of the valve opening time TOLITM of the fuel injection valve 6 and the valve opening time TOυTMa of the auxiliary fuel injection valve 6a are
M, TiMa are stored in a map stored in the storage means 5c of the ECU 3, which will be described later, and the intake pipe absolute pressure Pa
The basic valve opening times TiM and TiMa are retrieved from two parameters: ^ and engine speed Ne. Reference value T i M of valve opening time TouTMa of auxiliary fuel injection valve 6a
As for a, since the reference value corresponding to the required air-fuel ratio A/F is a value proportional to the required fuel supply ff1Qf as in the normal case, accurate metering is possible even at a minute flow rate. However, the opening time T of the fuel injection valve 6
Regarding the reference value TiM of OUTM, the reference value corresponding to the required air-fuel ratio A/F is a value calculated in advance according to the following procedure. As mentioned above, the discharge pressure PD of the fuel injection valve 6 changes according to the intake pipe absolute pressure PB^ downstream of the throttle valve 3', so first, the fuel corresponding to a plurality of predetermined values of the intake pipe absolute pressure P8^ is Multiple discharge pressure values P of the injection valve 6
o is determined, then a plurality of required fuel supply amount values Qf corresponding to the combinations of a plurality of predetermined values of the engine speed Ne and the intake pipe absolute pressure PB^ are determined, and the discharge pressure value Pe+
The actual valve opening times TjM and TiMa corresponding to a plurality of combinations of the required fuel supply amount value Qf are calculated and stored in a map (Pe type-Ne map).

That is, the discharge pressure Pa changes in response to the intake pipe absolute pressure Pa^, and the engine load parameters for determining the basic valve opening times 'riM and TiMa also change depending on the intake pipe absolute pressure PH.
^, so the two phenomena of discharge pressure Po and charging efficiency for each cylinder can be expressed on the same map on the Pa equation-Ne map, so set the basic valve opening times TiM and TiMa determined from these two phenomena. do it. In other words,
Map values Tiv and T i M of PB8-Ne map
a is PB in addition to the filling efficiency according to the conventional Pa^-Ne
It is set in consideration of the discharge pressure P according to ^.

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 ECtJ5. An engine rotation speed sensor (hereinafter referred to as "rNe sensor") 10 is attached around the camshaft or crankshaft (not shown) of the engine, and the Ne sensor 10 is mounted at a predetermined crank angle position every time the engine crankshaft 180a rotates. , Top dead center (TD) at the start of the intake stroke of each cylinder
Regarding C), a crank angle position signal (hereinafter referred to as "rTDC signal") is output at a crank angle position before a predetermined crank angle.

This TDC signal is sent to ECU3.

A three-way catalyst 12 is disposed in the exhaust pipe 11 of the engine 1 to purify HC and CO1NOx 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 N1 element concentration in the exhaust gas and supplies an 02 concentration signal to the ECU 3.

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.

EC1J5 shapes input signal waveforms from various sensors,
An input circuit 5a having functions such as correcting the voltage level to a predetermined level and converting analog signal values into digital signal values.
, central processing circuit (hereinafter referred to as rCPUJ) 5b, C
It is comprised of a storage means 5c for storing various calculation programs and calculation results executed by the PU 5b, 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.

The program is based on engine parameter signals from the various sensors mentioned above supplied via the input circuit 5a.
Fuel injection valve upstream of the throttle valve (hereinafter referred to as upstream valve)
6 and the auxiliary fuel injection valve (hereinafter referred to as downstream valve) 6a downstream of the throttle valve, and outputs a valve opening drive signal based on these injection times to both injection valves 6 and 6a.

Hereinafter, the processing procedure of the fuel supply control program shown in FIG. 2 will be explained in detail.

This program is executed every time the TDC signal is generated.

First, in step 1, the engine water temperature Tw is set to a predetermined temperature T.
If the answer is negative (NO), that is, if the engine temperature is lower than a predetermined temperature, the opening time TOυ〒Ma of the downstream valve 6a is determined.
is set to O (step 8).

Then, the process proceeds to step 15 to be described later, and the upstream valve P
Search the basic valve opening time TiM from the B^-Na map, and calculate the valve opening time TOυTM of the upstream valve 6 based on the T'iM value according to the following equation (1). A valve opening drive signal corresponding to the TOUTM value is output.

TouTM=TiMXKIM+2M-(1) where K8 and Ill are correction coefficients and correction constants determined based on the various engine parameter signals described above.

As a result, when the engine is cold, fuel is supplied from the upstream valve, so that the distribution of fuel to a plurality of cylinders is ensured.

When the determination result of step 1 is the front chamber (Yes).

In the next step 2, it is determined whether the throttle valve opening OT I+ is smaller than a predetermined low throttle opening Z 01DL (for example, 0.39'), and the answer is affirmative (Yes).
When the engine temperature is higher than the predetermined temperature and the throttle valve opening is below the predetermined opening, the downstream valve Pa^
-Search the basic valve opening time TiMa from the Ne map and
1' i Based on the Ma value, the opening time of the downstream valve "I'
Calculate oυd Ma according to the following formula (2) (Step 3
).

TOUT Ma=TiMaXK, 2a − to a+
(2) Here, Kla and 2a are correction coefficients and correction constants determined based on the various engine parameter signals described above.

Next, the nTpCAM value used in step 9 described later is reset to the initial value nTDCAM (for example, 3) (step 4), and the valve opening time TOIJTM value of the upstream valve is set to 0 (step 5). Therefore, when the next step 6 is executed, no valve opening drive signal is output to the upstream valve. Furthermore, in the next step 7, T calculated in step 3 is
Outputs a valve opening drive signal according to the ou〒Ma value, and ends this program.

As a result, the responsiveness of fuel supply to the cylinders is improved.

If the determination result in step 2 is negative (NO),
Step 9) Determine whether the 17e+cA+w value is O or not.
, if this answer is negative (NO), the basic valve opening time Tiv is calculated from the downstream valve Pa-Ne map as in step 3 above.
a is searched, and the valve opening time TouTMa of the downstream valve is calculated based on the TiMa value (step 10).

Next, subtract 1 from the nTDCAM value (Step 11)
, proceed to step 15 and subsequent steps.

If the determination result in step 9 is affirmative (Yes), in the next step 12.13 or step 12.14, the TOLI and T y'a values calculated in step 10 are calculated with the degree of decrease according to the engine speed Ne. reduce That is, in step 12, it is determined whether the engine speed Ne is higher than a predetermined value zNeAM (for example, 900 rpm), and if the answer is affirmative (Yes), the subtracted value Δ from the previous TouTMa value is determined.
1'OUTM a2 (for example, 1.0m5ec) is subtracted, and if the answer is negative (NO), the previous ToutM
Subtract value ΔTouTMa from a value, (for example, 1.0m5e
c), and then proceed to step 15 and subsequent steps.

In step 15, the TOUTMa value calculated in step 10.13 or 14 is set to the lower limit TOLIT psaLM.
It is determined whether or not it is smaller than T (for example, 3,0 m5ec), and if the answer is affirmative (Yes), the process proceeds to step 17 while setting the TouTMa value as the lower limit value TouTMaLMT in step 16, and if this answer is negative (No). If so, proceed directly to step 17. In step 17, the basic valve opening time TiM is searched from the Pa-Ne map for upstream valves, and the valve opening time TOIJTM of the upstream valve is determined based on the TiM value.
is calculated according to the above formula (1).

In the next step 18, the TO calculated in step 17 is
It is determined whether the IJTM value is larger than a predetermined value Me-TouTLMT. Here, Me is the generation interval of the TDC signal, which corresponds to the time of the intake stroke. Further, TOLITLM T is a value obtained by converting the opening time of the downstream valve to the opening time of the upstream valve during high load, and represents the amount of fuel injected by the downstream valve. Predetermined value M
e −T o u t L M〒 represents the amount of fuel injected by the upstream valve that is actually drawn into the cylinder;
When the value exceeds the predetermined value Me -Tou T L MT, the excess fuel first adheres to the throttle valve etc., and then evaporates from the throttle valve and adheres to the inner wall of the intake pipe downstream of the throttle valve.

However, if the amount of fuel that adheres to the inner wall of the intake pipe downstream of the throttle valve is supplied by the downstream valve, the amount of evaporation from the throttle valve will be reduced, so the change in the amount of fuel adhering to the throttle valve will be small, and the fuel will be supplied Control accuracy is further improved. Therefore, the determination result in step 18 is affirmative (
If Yes), the opening time of the downstream valve is calculated using the following equation (3) (step 19).

”110LIT Ma=(TouTM-(Me-TOL
ITLM T))XKAux+Tva... (3) Here, KAux is the flow rate ratio of the downstream valve to the upstream valve, and Tva is a correction value according to fluctuations in battery voltage. After executing step 19, proceed to step 6. Further, if the determination result in step 18 is negative (NO), it means that the amount of fuel that adheres to the throttle valve or the inner wall of the intake pipe is not needed, that is, the engine is in a deceleration state, etc.
Skip step 19 and proceed directly to step 6.

Finally, in step 6, a valve opening drive signal corresponding to the TouTM value is output to the upstream valve, and in step 7, a valve opening drive signal corresponding to the TourMa value is output to the downstream valve, and one program is completed.

(Effects of the Invention) As described in detail above, according to the fuel supply control method for an internal combustion engine of the present invention, the upstream side and the downstream side of the throttle valve upstream of the intake pipe gathering part of an internal combustion engine equipped with a plurality of cylinders In the fuel supply control method for an internal combustion engine, in which fuel is supplied according to the operating state of the engine from a fuel injection valve and an auxiliary fuel injection valve respectively installed in the engine, when the engine temperature is lower than a predetermined temperature, the upstream side of the throttle valve When the engine temperature is higher than the predetermined temperature and the throttle valve opening is below the predetermined opening, fuel is supplied by the auxiliary fuel injection valve downstream of the throttle valve. Therefore, even when the engine temperature is low, fuel can be distributed favorably to a plurality of cylinders. In addition, when the engine temperature is low, there is no need to switch from the auxiliary fuel injection valve downstream of the throttle valve to the fuel injection valve upstream of the throttle valve when transitioning from a low-load operating state to a high-load operating state. Fluctuations in the amount of fuel supplied due to switching can be prevented. Furthermore, when the engine temperature is high, the fuel injection valve is switched at the moment the throttle valve opens, that is, at the moment the intake air flow changes, so the amount of fuel supplied changes depending on the intake air condition in the intake pipe. This can be prevented.

[Brief Description of the Drawings] 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, and Fig. 2 is a flowchart of a fuel supply control program executed by the ECU shown in Fig. 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. Fuel is supplied from fuel injection valves and auxiliary fuel injection valves installed on the upstream and downstream sides of the throttle valve upstream of the intake pipe assembly of an internal combustion engine equipped with a plurality of cylinders according to the operating state of the engine. In the internal combustion engine fuel supply control method, when the engine temperature is lower than a predetermined temperature, fuel is supplied by a fuel injection valve on the upstream side of the throttle valve, and when the engine temperature is higher than the predetermined temperature and the throttle valve opening is A fuel supply control method for an internal combustion engine, characterized in that when the opening degree is below a predetermined opening degree, fuel is supplied by an auxiliary fuel injection valve downstream of the throttle valve.