JPH0762457B2 - Fuel supply control method for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel supply control method for an internal combustion engine, and more particularly, to a fuel injection valve provided at least one upstream and downstream of a throttle valve in the middle of an intake pipe. The present invention relates to a control method when fuel is supplied to a plurality of cylinders.

(Technical Background of the Invention and Problems Thereof) Supplying fuel to a plurality of cylinders from a fuel injection valve common to a plurality of cylinders, which is installed upstream of a throttle valve provided upstream of a branch portion of an intake pipe. In this type of internal combustion engine, the control pressure of the pressure regulator that adjusts the pressure (fuel pressure) of the fuel delivered to the fuel injection valve is the pressure in the intake pipe facing the injection hole of the fuel injection valve on the upstream side, that is, the upstream of the throttle valve. In general, the pressure regulator always sets the adjusted fuel pressure higher than the intake pipe internal pressure upstream of the throttle valve by a constant pressure so that the discharge pressure of the upstream fuel injection valve is always constant. Further, in the above-mentioned case, although accurate measurement by the injection time of the fuel injection valve is possible, it is difficult to secure a wide flow rate range of the supplied fuel amount. On the other hand, a technology that secures a wide flow range by adjusting the control pressure of the pressure regulator that adjusts the fuel pressure delivered to the fuel injection valve upstream of the throttle valve based on the negative pressure in the intake pipe on the throttle downstream side It is proposed in Kosho 61-2775.

However, during low load operation such as engine idle operation, in order to increase the stability of the idle speed, the intake air amount increase / decrease control is performed by changing the engine speed and the external load such as the air conditioner or power steering. The negative pressure in the intake pipe on the downstream side of the throttle valve also fluctuates, and it becomes difficult to accurately measure the required fuel amount. As a result, at the time of low load operation such as idle operation, such control becomes difficult, and the combustion state of the fuel is not stable, although high-precision control of the supply air-fuel mixture is required. Along with this, there is a problem that exhaust gas characteristics are likely to deteriorate.

On the other hand, the control accuracy of the fuel supply amount of the fuel injection valve does not need to be so high when the engine is operating under a medium or high load other than a low load, but rather the operation is performed by controlling the supply of a wide range of fuel. It was necessary to improve the performance.

(Object of the invention) The present invention has been made in view of the above circumstances, and enables highly accurate control of the air-fuel ratio of the supply air-fuel mixture during low-load operation of the engine, thereby stabilizing the combustion state of fuel and exhaust gas characteristics. It is an object of the present invention to provide a fuel supply control method for an internal combustion engine, which is capable of controlling the supply of fuel in a wide range during operation other than low load, and thereby improving operating performance.

(Structure of the Invention) In order to achieve the above object, according to the present invention, a plurality of cylinders are installed on the upstream side and the downstream side of a throttle valve upstream of an intake pipe collecting portion of an internal combustion engine having a plurality of cylinders. In the fuel supply control method for an internal combustion engine, in which fuel is supplied from the fuel injection valve according to the operating state of the engine, the fuel pressure supplied to the plurality of fuel injection valves is adjusted according to the intake pipe internal pressure downstream of the throttle valve. Fuel is controlled by the fuel injection valve on the downstream side of the throttle valve during low load operation after the engine is started, and at least on the upstream side of the throttle valve during operation other than low load of the engine. It is characterized in that the supply of fuel is controlled by a valve.

Preferably, the fuel pressures supplied to the plurality of fuel injection valves installed on the upstream side and the downstream side of the throttle valve are the same.

Embodiments 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, an internal combustion engine of four cylinders, and an intake pipe 2 is connected to the engine 1 via an intake manifold. There is. A throttle body 3 is provided upstream of the collecting portion of the intake pipe 2, and a throttle valve 3'is provided inside. A throttle valve opening (θ _TH ) sensor 4 is connected to the throttle valve 3 ′ so that the valve opening of the throttle valve 3 ′ is converted into an electric signal and sent to an electronic control unit (hereinafter referred to as “ECU”) 5. Has been

A fuel injection valve 6 is provided slightly upstream of the throttle body 3 of the intake pipe 2 so that fuel is supplied to all cylinders of the internal combustion engine 1 when the engine 1 is operating at medium and high loads. 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 collecting portion so that the internal combustion engine 1 is fully warmed during low load operation. Fuel is supplied to the cylinders. The fuel injection valve 6 and the auxiliary fuel injection valve 6a are EC
The valve opening time T of each of the fuel injection valve 6 and the auxiliary fuel injection valve 6a is electrically connected to U5 and is controlled by a signal from the ECU5.
_OUTM and T _OUTMa are controlled.

An absolute pressure (P _BA ) sensor 8 is provided downstream of the throttle valve 3 ′ of the throttle body 3 via a pipe 7. The absolute pressure signal converted into an electric signal by the absolute pressure sensor 8 is provided. Is sent to the ECU 5.

The fuel injection valve 6 and the auxiliary fuel injection valve 6a are connected to a fuel pump 17 in a fuel tank 16 via a pipe line 21, a strainer 15, and pipe lines 22, 23 and 24. The fuel pump 17 is EC
It is controlled by U5. Also, pipelines 22,2
3 and 24 are pipeline 25, pressure regulator 18 and pipeline 2
It is connected to the fuel tank 16 via 6. The pressure regulator 18 is for adjusting the fuel pressure in the pipe lines 22 to 25 in accordance with the negative pressure (absolute pressure P _BA ) in the intake pipe downstream of the throttle valve 3 ′, and the negative pressure chamber 18 a has a pipe line. It is connected via 31 to the intake pipe 2 downstream of the throttle valve 3 ′. That is, the valve opening pressure of the valve body 18b that opens and closes the opening end 26a of the pipe line 26 is determined by the combined force of the biasing force of the coil spring 18c and the negative pressure in the intake pipe downstream of the throttle valve 3 '.
The difference between the fuel pressure (absolute pressure) within .about.25 and the intake pipe absolute pressure P _BA downstream of the throttle valve _3'is always constant. Therefore,
The discharge pressure of the auxiliary fuel injection valve 6a is constant regardless of the magnitude of the intake pipe absolute pressure P _BA , and the fuel injection amount of the auxiliary fuel injection valve 6a is determined only by the valve opening time T _OUTMa of the auxiliary fuel injection valve 6a. Therefore, 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 the absolute pressure P _{BA in} the intake pipe downstream of the throttle valve 3 '. It changes according to the size. That is, the delivery pressure of the fuel injection valve 6
When the engine has a low load, P _D is connected to the pipes 22 to 25 as the absolute pressure P _{BA in} the intake pipe downstream of the throttle valve 3'becomes lower.
Since the fuel pressure inside is low, it becomes low, and when the engine is under high load, the absolute pressure in the intake pipe downstream of the throttle valve 3 '
The higher the P _BA , the higher the fuel pressure in pipes 22 to 25, and hence the higher. Therefore, when the engine has a low load, the fuel injection valve 6 has a lower fuel pressure for the same fuel supply amount.
Since the valve opening time T _OUTM of the fuel injection valve 6 becomes longer, it becomes possible to control the fuel amount with a small flow rate, and when the engine has a high load, the valve opening time T _OUTM of the fuel injection valve 6 is short for the same fuel supply amount. As a result, a large flow rate of fuel can be secured and high output can be easily obtained.

The opening time T _OUTM of the fuel injection valve 6 and the auxiliary fuel injection valve 6
The reference values Ti _M and Ti _Ma of the valve opening time T _OUTMa of a are E described later.
The basic valve opening times Ti _M and Ti _Ma are retrieved from the two parameters of the intake pipe absolute pressure P _BA and the engine speed Ne, which are stored in a map stored in the storage means 5c of the CU 5. Regarding the reference value Ti _Ma of the valve opening time T _OUTMa of the auxiliary fuel injection valve 6a, the reference value corresponding to the required air-fuel ratio A / F is a value proportional to the required fuel supply amount Qf as in the normal case. Therefore, accurate measurement is possible even at a minute flow rate.
However, the valve opening time T _OUTM reference value Ti _{M of} the fuel injection valve 6
For, the reference value corresponding to the required air-fuel ratio A / F is a value calculated in advance by the following procedure. Fuel injection valve 6
Since the discharge pressure P _D of the fuel injection valve 6 changes depending on the intake pipe absolute pressure P _BA downstream of the throttle valve 3 ′ as described above, first, the fuel injection valves 6 corresponding to a plurality of predetermined values of the intake pipe absolute pressure P _BA are provided. Of the discharge pressure values P _D are determined, and then the engine speed
A plurality of required fuel supply amount values Qf corresponding to a plurality of predetermined values of Ne and the intake pipe absolute pressure P _BA are respectively determined, and a plurality of combinations of the discharge pressure value P _D and the required fuel supply amount value Qf are determined. The corresponding basic valve opening times Ti _M and Ti _Ma are obtained and stored in the map (P _BA- Ne map).

That is, the discharge pressure P _D changes in response to the intake pipe absolute pressure P _BA , and the engine load parameter for determining the basic valve opening times Ti _M and Ti _Ma is also the intake pipe absolute pressure P _BA.
Since the two phenomena of charging efficiency for the discharge pressure P _D and the cylinders on the _BA -Ne map can be expressed on the same map, the 2
The basic valve opening times Ti _M and Ti _Ma determined from the phenomenon may be set. In other words, the map values Ti _M and Ti _Ma of the P _BA -Ne map are set by considering the discharge pressure P _D corresponding to P _BA in addition to the filling efficiency according to the conventional P _BA -Ne. .

The engine cooling water temperature sensor (hereinafter “Tw
The sensor 9) is provided, and the Tw sensor 9 is composed of a thermistor or the like, is inserted into the engine cylinder peripheral wall filled with cooling water, and supplies the detected water temperature signal to the ECU 5. An engine speed sensor (hereinafter referred to as "Ne sensor") 10 is mounted around a cam shaft or a crank shaft (not shown) of the engine.
A crank angle position signal (hereinafter referred to as a "TDC signal") at a predetermined crank angle position for every 0 ° rotation, that is, at a crank angle position that is a predetermined crank angle before the top dead center (TDC) at the start of the intake stroke of each cylinder. Is output),
This TDC signal is sent to ECU5.

A three-way catalyst 12 is arranged in the exhaust pipe 11 of the engine 1 to purify HC, CO and NOx components in the exhaust gas. An O ₂ sensor 13 is attached to the exhaust pipe 11 on the upstream side of the three-way catalyst 12, and the sensor 13 detects the oxygen concentration in the exhaust gas and outputs an O ₂ concentration signal.
Supply to ECU5.

Further, another parameter sensor 14 such as an atmospheric pressure sensor is connected to the ECU 5, and the other parameter sensor 14 supplies the detection value signal to the ECU 5.

The ECU 5 shapes the input signal waveforms from various sensors, corrects the voltage level to a predetermined level, converts an analog signal value into a digital signal value, and the like, an input circuit 5a, a central processing circuit (hereinafter, "CPU"). 5b, a storage means 5c for storing various calculation programs executed by the CPU 5b and calculation results, and an output circuit 5d for supplying drive signals to the fuel injection valve 6 and the auxiliary fuel injection valve 6a. It

The CPU 5b executes the fuel supply control program shown in FIG.
It is executed every time a signal is input. The program is based on engine parameter signals from the above-mentioned various sensors supplied via the input circuit 5a, and a fuel injection valve (hereinafter referred to as an upstream valve) 6 upstream of the throttle valve and an auxiliary fuel injection valve downstream of the throttle valve ( Hereinafter, each fuel injection time of the downstream valve 6a is calculated, and a valve opening drive signal based on these injection times is output to both the injection valves 6 and 6a.

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

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

First, in step 1, the engine water temperature Tw is the predetermined temperature Tw.
_It is determined whether the temperature is higher than _MA (for example, 60 ° C.). When the answer is negative (No), that is, when the engine temperature is lower than the predetermined temperature, the valve opening time T _OUTMa of the downstream valve 6a is set to 0. (Step 8). Then, proceed to step 15 and later described below,
Find the basic valve opening time Ti _M than P _BA -Ne map for the upstream valve,
Based on the Ti _M value, the valve opening time T _OUTM of the upstream valve 6 is calculated according to the following equation (1) (step 17), and in step 6, the upstream valve 6 outputs a valve opening drive signal corresponding to the T _OUTM value. To do.

T _OUTM = Ti _M × K _1M + K _2M (1) Here, K _1M and K _2M are correction coefficients and correction constants determined based on the various engine parameter signals described above.

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

If the determination result in step 1 is affirmative (Yes), it is determined in the next step 2 whether or not the throttle valve opening θ _TH is smaller than a predetermined low throttle opening Zθ _IDL (for example, 0.39 °). There affirmative (Yes), that is, when the engine temperature is high and the throttle valve opening than the predetermined temperature is equal to or less than a predetermined opening degree, the basic valve opening time from P _BA -Ne map for the downstream valve Ti
Search _Ma and open time T of the downstream valve based on the Ti _Ma value
_OUTMa is calculated according to the following equation (2) (step 3).

T _OUTMa = Ti _Ma × K ₁ a + K ₁ a (2) Here, K ₁ a and K ₂ a are correction coefficients and correction constants determined based on the various engine parameter signals described above.

Next, the n _TDCAM value used in step 9 described later is initialized.
n _TDCAM (for example, 3) is reset (step 4), and the valve opening time T _OUTM value of the upstream valve is set to 0 (step 5).
For this reason, the valve opening drive signal is not output to the upstream valve when the next step 6 is executed. Next step 7
Then, the valve opening drive signal corresponding to the T _OUTMa value calculated in step 3 is output, and this program ends. As a result, the responsiveness of fuel supply to the cylinder is improved.

If the determination result of step 2 is negative (No), the n
_It is determined whether the _TDCAM value is 0 (step 9), and if the answer is negative (No), it is for the downstream valve as in step 3 above.
The basic valve opening time Ti _Ma is searched from the P _B -Ne map, and the valve opening time T _OUTMa of the downstream valve is calculated based on the Ti _Ma value (step 10). Then subtract 1 from the n _TDCAM value (step 1
1) Go to step 15 and below.

If the determination result in step 9 is affirmative (Yes), the T _OUTMa value calculated in step 10 is decreased by the decrease degree according to the engine speed Ne in the next steps 12 and 13 or steps 12 and 14. That is, in step 12, the engine speed Ne is a predetermined value.
It is determined whether it is higher than Z _NeAM (eg 900 rpm), and when this answer is affirmative (Yes), subtracted value ΔT from the previous T _OUTMa value.
_OUTMa2 (for example, 1.0msec) is subtracted, and this answer is negative (N
o), the subtracted value ΔT _OUTMa1 from the previous T _OUTMa value (for example,
1.0 msec), and then proceed to step 15 and below.

In step 15, T calculated in step 10, 13 or 14 is
_It is determined whether the _OUTMa value is smaller than the lower limit value T _OUTMaLMT (for example, 3.0 msec). If the answer is affirmative (Yes), set the T _OUTMa value to the lower limit value T _{OUTMaLMT in} step 16, and then proceed to step 17. If the answer is no (No), proceed directly to step 17. In step 17, the basic valve opening time Ti _M is searched from the upstream valve P _B -Ne map, and the upstream valve opening time T _OUTM is calculated according to the above equation (1) based on the Ti _M value.

In the next step 18, it is determined whether or not the T _OUTM value calculated in step 17 is larger than a predetermined value Me−T _OUTLMT . Here, Me is the generation interval of the TDC signal, which corresponds to the time of the intake stroke. Further, T _OUTLMT is a value obtained by converting the valve opening time of the downstream valve under high load into the valve opening time of the upstream valve, and represents the fuel amount injected by the downstream valve. The predetermined value Me-T _OUTLMT represents the amount of fuel actually injected by the upstream valve into the cylinder, and the T _OUTM value is the predetermined value Me-T.
_When it exceeds _OUTLMT , the excess fuel first adheres to the throttle valve, etc., then evaporates from the throttle valve and adheres to the inner wall of the intake pipe downstream of the throttle valve. However, if the fuel adhering to the inner wall of the intake pipe on the downstream side of the throttle valve is supplied by the downstream valve, the amount of evaporation from the throttle valve will decrease, so the change in the amount of fuel adhering to the throttle valve will be small and the fuel supply The control accuracy is further improved. Therefore, when the determination result of step 18 is affirmative (Yes), the valve opening time of the downstream valve is calculated by the following equation (3) (step 19).

T _OUTMa = {T _OUTM − (Me−T _OUTLMT )} × K _AuX + T _Va …
(3) where K _AuX is the flow rate ratio of the downstream valve to the upstream valve,
T _Va is a correction value according to the fluctuation of the battery voltage. After performing step 19, proceed to step 6. Also, step 18
If the result of the determination is negative (No), it means that fuel adhering to the throttle valve or the inner wall of the intake wall is not needed, that is, the engine is in a deceleration state, etc. Go to 6.

Finally, in step 6, the valve opening drive signal corresponding to the T _OUTM value is output to the upstream valve, and in step 7, the valve opening drive signal corresponding to the T _OUTMa value is output to the downstream valve, and this program ends.

(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 collecting portion of the internal combustion engine having a plurality of cylinders. In a fuel supply control method for an internal combustion engine, in which fuel is supplied from a plurality of fuel injection valves installed in each of the plurality of fuel injection valves, the fuel pressure supplied to the plurality of fuel injection valves is adjusted to the downstream side of the throttle valve. Control in accordance with the intake pipe internal pressure of the engine, fuel supply is controlled by a fuel injection valve downstream of the throttle valve during low load operation after the engine is started, and at least the throttle valve is operated during operation other than low load of the engine. Since the fuel supply is controlled by the fuel injection valve on the upstream side of the engine, the air-fuel ratio of the supply air-fuel mixture can be controlled with high accuracy during low-load operation of the engine. As a result, it is possible to stabilize the combustion state of the fuel and improve the exhaust gas characteristics, and it is possible to supply and control the fuel amount in a wide range during the operation other than the low load operation, so that the operation performance can be improved.

[Brief description of 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 of 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 speed sensor.

Claims (2)

[Claims] Claim: What is claimed is: 1. An internal combustion engine having a plurality of cylinders, wherein fuel is supplied from a plurality of fuel injection valves installed upstream and downstream of a throttle valve upstream of an intake pipe collecting portion in accordance with an operating state of the engine. In a fuel supply control method for an internal combustion engine for supplying, a fuel pressure supplied to the plurality of fuel injection valves is controlled according to an intake pipe internal pressure downstream of the throttle valve, and a low load after a low load after the engine is started. The fuel injection valve downstream of the throttle valve controls fuel supply during load operation, and the fuel injection valve at least upstream of throttle valve controls fuel supply during operation of the engine other than low load. Supply control method for internal combustion engine. 2. The internal combustion engine according to claim 1, wherein the fuel pressures supplied to a plurality of fuel injection valves installed on the upstream side and the downstream side of the throttle valve are the same. Fuel supply control method.