JPH06102999B2 - 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 plurality of fuel injection valves provided one upstream and one 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 the cylinder.

(Technical background of the invention and its problems) As a conventional fuel supply control device of a type in which fuel is distributed and supplied from a single fuel injection valve common to a plurality of cylinders of an internal combustion engine, a conventional fuel supply control device is used when the engine is in medium or high load. While the fuel is supplied by a normal or large flow rate fuel injection valve provided on the upstream side of the throttle valve upstream of the intake pipe collecting portion, the auxiliary fuel injection valve provided on the downstream side of the throttle valve when the engine load is low. There is a type in which fuel is supplied by
No. 5422). The auxiliary fuel injection valve having excellent atomization characteristics is used to ensure the distribution of a small amount of fuel to each cylinder when the engine load is low.

By the way, in such a method, when the internal combustion engine shifts from a low load operating state to a medium / high load operating state,
In the opposite case, the auxiliary fuel injection valve (hereinafter referred to as "downstream valve") and the normal fuel injection valve (hereinafter referred to as "upstream valve") are switched, but the downstream valve is upstream. When switching to the valve, due to the difference in the positions where the downstream valve and the upstream valve are arranged, immediately after the switching, a phenomenon occurs in which it is difficult to supply the appropriate amount of fuel that actually contributes to combustion to the engine. That is, the fuel supplied from the downstream valve is immediately supplied to each cylinder of the internal combustion engine via only the downstream side portion of the intake pipe, while the fuel supplied from the upstream valve is partially partly formed on the inner wall surface of the throttle body and the throttle. Once attached to the surface of the valve, it is supplied to each cylinder of the internal combustion engine through the downstream side portion of the intake pipe. As a result, when the downstream valve interrupts fuel supply and the upstream valve supplies the same amount of fuel as the downstream valve has supplied, the fuel at the start of supply of the upstream valve is Once attached to the throttle valve, the amount of fuel contributing to combustion is temporarily insufficient,
There is a problem that the driving performance of the engine is deteriorated.

(Object of the invention) The present invention has been made in view of the above circumstances, and in the case of switching a fuel injection valve that supplies fuel according to a load state of an internal combustion engine to an upstream valve or a downstream valve for a throttle valve, a downstream valve It is an object of the present invention to provide a fuel supply control method for an internal combustion engine, which secures the accuracy of fuel supply when switching from the engine to the upstream valve and improves the operating performance of the engine.

(Structure of the Invention) In order to achieve the above object, in the present invention, a fuel injection valve is provided on each of an upstream side and a downstream side of a throttle valve upstream from a collecting portion of an intake branch pipe of an internal combustion engine including a plurality of cylinders. A fuel supply control method for an internal combustion engine, wherein at least one fuel supply valve is provided, and a quantity of fuel determined according to an operating state of the internal combustion engine is controlled by the fuel injection valve to be supplied to the internal combustion engine. Is in the idle region, and when it is in the idle region, fuel is supplied by the fuel injection valve downstream of the throttle valve, while the fuel injection valve upstream of the throttle valve is in the idle state, When it is outside the region, the fuel injection valve downstream of the throttle valve supplies a smaller amount of fuel than when it is inside the idle region, and at the same time, it is slow. A fuel injection valve upstream of the throttle valve supplies a quantity of fuel that is determined according to the operating state of the internal combustion engine, and when the idle region is shifted to the outside of the idle region, the fuel injection valve downstream of the throttle valve supplies fuel. There is provided a fuel supply control method for an internal combustion engine, characterized in that the amount is gradually reduced toward the predetermined amount.

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, a 4-cylinder 4-cycle internal combustion engine, and the engine 1 is provided with an intake pipe collecting portion (intake manifold). The intake pipe 2 is connected. A throttle body 3 is provided upstream of the collecting portion of the intake pipe 2, and a throttle valve 3'is provided inside. The throttle valve 3'has a throttle valve opening (θ _TH ) sensor 4
Are connected in series to convert the valve opening of the throttle valve 3 ′ into an electric signal and send it to an electronic control unit (hereinafter referred to as “ECU”) 5.

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 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 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 connected to a fuel pump (not shown) and electrically connected to the ECU 5, and each of the fuel injection valve 6 and the auxiliary fuel injection valve 6a is connected to the ECU 5 by a signal from the ECU 5. The valve opening time of is controlled. As the auxiliary fuel injection valve, one having an excellent atomization characteristic is used in order to ensure the distribution of a small amount of fuel to each cylinder when the engine load is low.

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 sensor 8 converts the absolute pressure (P _BA ) sensor into an electric signal. The pressure signal is sent to the ECU 5.

The engine cooling water temperature sensor (hereinafter “T _W
The sensor 9) is provided, and the T _W 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 each 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 a fuel injection valve (upstream valve) 6 on the upstream side of the throttle valve and an auxiliary fuel injection valve (downstream valve) on the downstream side of the throttle valve, based on engine parameter signals from the above-mentioned various sensors supplied via the input circuit 5a. Calculate each fuel injection time of 6a,
A valve opening drive signal based on these injection times is sent to both injection valves 6
And 6a.

The upstream valve 6 and the downstream valve 6a are the methods shown in the following table according to the respective operating states during the idle operation region (low load region), outside the idle operation region (medium / high load region), and at high load and high rotation. Is controlled to perform fuel injection.

The equations in the table are used in the execution of the program shown in FIG. 2, and the details will be described later.

Hereinafter, the processing procedure of the fuel supply control program of FIG. 2 will be described in detail. This program starts processing every time the TDC signal is generated.

First, in step 1, the engine water temperature Tw is the predetermined temperature Tw.
It is determined whether or not higher than _MA (e.g. 20 ° C.), when the answer is negative (No), i.e. if the engine temperature is lower than the predetermined temperature, tentatively the valve opening time T _OUTM a downstream valve 6a Set to 0 (step 10). Then, the procedure proceeds to step 17 and subsequent steps, which will be described later, to search the basic valve opening time Ti _M from the upstream valve P _B -Ne map, and calculate the valve opening time T _OUTM of the upstream valve 6 based on the Ti _M value (step 19), the T _{OUTM is added} to the upstream valve 6 in step 8.
A valve opening drive signal corresponding to the value is output. As a result, since the first idle auxiliary air is supplied from the throttle bypass passage (not shown) when the engine is cold, a large amount of fuel flow is required accordingly, so fuel is supplied from the upstream valve. . When the fuel flow rate is comparatively high, the fuel distributability to the plurality of cylinders is secured by increasing the distance from the fuel injection valve to the intake pipe collecting portion.

When the determination result of step 1 is affirmative (Yes), it is determined in the next steps 2, 3 and 4 whether or not the operating state of the engine is in the idle operating region. That is, in step 2, it is determined whether or not the throttle valve opening θ _TH is smaller than a predetermined idle opening Zθ _IDL (for example, 0.39 °), and in step 3, the intake pipe absolute pressure P _B is the predetermined idle pressure Z _PBIDL ( For example 35
It is determined whether the engine speed Ne is lower than 0 mmHg), and the engine speed Ne is a predetermined idle speed Z _NIDL (for example, 1100r in step 4).
pm). When the affirmative these answers are all (Yes), retrieves the basic valve opening time Ti _M a from P _B -Ne map for downstream valve, the downstream valve by the following equation based on the Ti _M a value (1) The valve opening time T _OUTM a is calculated (step 5).

_{T OUTM a = Ti M a ×} K 1 + K 2 ...... (1) Here, K ₁ and K ₂ is a correction factor or correction variables are calculated according to the engine parameter signals from various sensors mentioned above engine It is calculated based on a predetermined calculation formula so that various characteristics such as the starting characteristic, the exhaust gas characteristic, the fuel consumption characteristic, the engine acceleration characteristic, etc. are optimized according to the operating state.

Next, the η _TDCAM value used in step 11 described later is preset to the initial value η _TDCAM (for example, 3} (step 6), and the upstream valve opening time T _OUTM value is set to 0 (step 7). _Therefore , the valve-opening drive signal is not output to the upstream valve at the time of executing the next step 8. Further, in step 9, next, the valve-opening drive signal corresponding to the T _OUTM a value calculated in step 5 is output. As a result, fuel is directly supplied to the cylinder from the injection valve on the downstream side of the throttle valve 3 ', and the distance between the injection valve and each cylinder becomes short, so that the cylinder The responsiveness of the fuel supply to the engine is improved.

The judgment result of either step 2, 3 or 4 is negative (No)
When the engine operating condition is outside the idle range, it is determined whether or not the η _TDCAM value is 0 (step 1
1), if the answer is negative (No), the step 5 searches the basic valve opening time Ti _M a from P _B -Ne map for the downstream valve in the same manner as the formula based on the Ti _M a value The valve opening time T _OUTM a of the downstream valve is calculated by (1) (step 12). Then η
Subtract 1 from the _TDCAM value (step 13), and proceed to step 17 and below.

If the determination result in step 11 is affirmative (Yes), the value T _OUTM a calculated in step 12 is decreased by the decrease degree according to the engine speed Ne in the next steps 14 and 15 or steps 14 and 16. That is, in step 14, the engine speed Ne is a predetermined value.
It is determined whether or not Z _N e or _AM (e.g. 900 rpm) higher than, by subtracting a predetermined value [Delta] T _OUTM a ₁ from the last T _OUTM a value first when the answer is negative (No) (e.g., 0.4 msec) , If this answer is affirmative (Yes), from the previous T _OUTM a value to the second predetermined value ΔT _OUTM
Subtract a ₂ (for example, 0.2 msec), and then proceed to step 17 onward.

In step 17, T calculated in step 12, 15 or 16 is calculated.
_OUTM a value to determine whether T _OUTM smaller lower limit than the minimum value of a T _OUTM a _LMT (eg 3.0 msec) is smaller than that calculated in step 5 or 12, when the answer to this question is affirmative (Yes) lower limit Ti _M a value in step 18 Ti _M a _LMT as T _OUTM a the value T
_OUTM a = Ti _M a × K ₁ + K ₂ formula (Formula (1) above), that is, T _OUTM a = Ti _M a _LMT × K ₁ + K ₂ and then step 1
Proceed to step 9, and if this answer is negative (No), proceed directly to step 19. As a result, even after the _engine operating state shifts from the idle range to the outside of the idle range, a substantially constant amount T _OUTM a
Fuel of _LMT or more is supplied from the downstream valve 6a. Where Ti _M
a The _LMT value is the minimum flow rate value at which the fuel supplied from the downstream valve can be accurately metered (for example, 1.8 msec). Therefore, even while the fuel is being injected from the upstream valve 6 and adhering to the inner wall surface of the throttle body 3 and the throttle valve 3 ′ immediately after the fuel injection of the upstream valve 6 due to the transition to the outside of the idle region, the downstream valve 6 a Since the fuel is supplied from the above, the required fuel supply amount at the time of switching from the downstream valve 6a to the upstream valve 6 is secured, and the fluctuation of the air-fuel ratio is suppressed, so that the deterioration of drivability is prevented. Further, in this embodiment, by executing the steps 11, 12, 13 and 14, 15 or steps 14, 16 at the time of switching from the downstream valve 6a to the upstream valve 6, the fuel supply amount of the downstream valve 6a is gradually increased. By reducing the amount, the change 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 Ti _M is searched from the upstream valve P _B -Ne map, and the Ti _M
Based on the value, the valve opening time T _OUTM of the upstream valve is _calculated by the following equation (2).
To calculate.

T _OUTM = Ti _M × K ₁ + K ₂ (2) Here, K ₁ and K ₂ are the same as those in the above formula (1).

In the next step 20, it is judged whether or not the T _OUTM value calculated in step 19 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 in the case of a 4-cylinder cycle engine. Further, T _OUTLMT is the time required for the upstream valve 6 to be completely opened from the opened state. Step 20
If the determination result of is positive (Yes), the valve opening time of the downstream valve is calculated by the following equation (3) (step 21).

T _OUTM a ＝ {T _OUTM − (Me−T _OUTLMT )} × K _AUX + T _V a ……
(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. By calculating the valve opening time T _OUTM a of the downstream valve by the above equation (3), the valve opening time T calculated by the upstream valve in step 19 when the valve opening time becomes long at the time of high load and high engine rotation.
_The fuel that cannot be supplied in _OUTM is supplied from the downstream valve 6a. As a result, the required amount of fuel is secured even under high load and high rotation. Further, the upstream valve 6 does not need to use a valve with such a large flow rate (large diameter), and the atomization of a small amount of fuel can be made good even at a low load.

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

T _OUTM = Me-T _OUTLMT (4) Here, Me and T _OUTLMT are the same as those in the above equation (3). Therefore, the upper limit of the opening time of the upstream valve 6 is Me-T
_It becomes _OUTLMT , and the upstream valve 6 is completely closed each time fuel is supplied to each cylinder, and is not continuously opened. As a result, there is a characteristic region in which the fuel amount Qf is not proportional to the valve opening time T _OUTM as shown in FIG. 4 during the continuous injection from the large flow rate region of the fuel injection valve, so use that region. Is prevented.

After performing step 22, proceed to step 8. Again step
If the determination result of 20 is negative (No), all the required fuel can be supplied only by the upstream valve 6, so steps 21 and 22 are skipped and the process directly proceeds to step 8.

Thereafter, in step 8, a valve opening drive signal corresponding to the T _OUTM value is output to the upstream valve, and in step 9, a valve opening drive signal corresponding to the T _OUTM a value is output to the downstream valve, and this program ends.

Finally, the fuel supply characteristics when using the program shown in FIG. 2 will be described with reference to FIG. FIG. 3 shows the time variation of the fuel supply amount of the upstream valve and the downstream valve when the engine temperature is accelerated from the idle state when the engine temperature Tw is higher than T _WMA . First, when the engine operating state is in the idle range, fuel corresponding to the T _OUTM a value corresponding to the map value is supplied from the downstream valve. Next, when the engine operating state shifts from the idle range to the outside of the idle range,
Fuel supply quantity from the downstream valve is gradually decreased to a predetermined rate of decrease [Delta] T _OUTM a ₁ or _{ΔT OUTM a 2 T OUTM a LMT} (= Ti M a LMT × K 1
+ K ₂ ) value. The fuel injection amount from the upstream valve during this period is the amount corresponding to T _OUTM according to the map value, but since the fuel adheres to the inner wall surface of the throttle body and the throttle valve, the fuel that actually reaches the cylinder from the upstream valve Increases from 0 to the T _OUTM value. Then, when the engine operating state shifts to the high load and high speed range, the fuel supply amount from the upstream valve may become the maximum amount Me-T _OUTLMT that can be supplied during the intake stroke, and at that time, the fuel from the downstream valve is supplied. The supply amount is {T _OUT − (Me−T _OUTLMT )} × K _AUX to supplement the shortage.

(Effect 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 of the throttle valve upstream of the collecting portion of the intake branch pipe of the internal combustion engine having a plurality of cylinders, and At least one fuel injection valve is provided on each of the downstream sides, and the fuel of the internal combustion engine is supplied to the internal combustion engine after the fuel injection valve controls the amount of fuel determined by the operating state of the internal combustion engine. In the supply control method, it is determined whether or not the internal combustion engine is in an idle region, and when it is in the idle region, fuel is supplied by a fuel injection valve downstream of the throttle valve, while fuel upstream of the throttle valve is supplied. When the injection valve is in a resting state and is outside the idle region, the fuel injection valve downstream of the throttle valve causes a smaller amount of fuel than when it is inside the idle region. Fuel is supplied at the same time as the fuel is supplied by the fuel injection valve upstream of the throttle valve, and when the amount of fuel is changed from the idle region to the outside of the idle region, the fuel downstream of the throttle valve is supplied. Since the fuel supply amount of the injection valve is gradually reduced toward the predetermined amount, the actual fuel supply amount to the engine at the time of switching from the fuel injection valve downstream of the throttle valve to the fuel injection valve upstream of the throttle valve is The value can be set to an appropriate value, the fluctuation of the air-fuel ratio can be prevented, and the operating performance of the engine 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, FIG. 2 is a flow chart of a fuel supply control program executed by the ECU of FIG. 1, and FIG. FIG. 4 is a graph showing the time variation of the fuel supply amount when used, and FIG. 4 is a fuel injection characteristic diagram 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 speed sensor.

Claims (2)

[Claims] 1. At least one fuel injection valve is provided on each of an upstream side and a downstream side of a throttle valve upstream of a collecting portion of an intake branch pipe of an internal combustion engine having a plurality of cylinders, and the internal combustion engine is in an operating state. In a fuel supply control method for an internal combustion engine, which supplies the internal combustion engine with the amount of fuel determined according to the fuel injection valve, it is determined whether the internal combustion engine is in an idle region, When in the idle region, fuel is supplied by the fuel injection valve downstream of the throttle valve, while the fuel injection valve upstream of the throttle valve is in a resting state, and when outside the idle region, fuel downstream of the throttle valve The internal combustion engine is supplied by the fuel injection valve upstream of the throttle valve while supplying a predetermined amount of fuel smaller than that in the idle region by the injection valve. When an amount of fuel that is determined according to the operating state is supplied and when shifting from the idle region to the outside of the idle region, gradually decreasing the fuel supply amount of the fuel injection valve downstream of the throttle valve toward the predetermined amount. A fuel supply control method for an internal combustion engine, comprising: 2. A predetermined amount of fuel is supplied from a fuel injection valve downstream of the throttle valve for a predetermined time after the idle region is moved to the outside of the idle region, and the predetermined time has elapsed. The fuel supply control method for an internal combustion engine according to claim 1, wherein the fuel supply amount of the fuel injection valve downstream of the throttle valve is gradually reduced toward the predetermined amount.