JPS61108846A - Method for controlling fuel supply of internal-combustion engine - Google Patents

Abstract

PURPOSE:To improve drivability under the condition where an absolute pressure detecting value in an intake passage is larger than an absolute pressure discriminating value in the intake passage by comparing the discriminating value determined according to an atmospheric pressure detecting value with the detecting value and by correcting the increase of fuel and stopping exhaust reflux. CONSTITUTION:In engine operation, an engine running condition is discriminated by an ECU5 according to various running parameters and opening of an exhaust reflux valve 19 is adjusted by controlling a solenoid valve 22 controlling exhaust reflux amount. And fuel injection time corresponding to an engine operating condition is calculated to drive to control a fuel injection valve 6. In this case, an absolute pressure discriminating value in an intake passage is determined according to the atmospheric pressure value detected by an atmospheric pressure sensor 14. And an absolute pressure in an intake passage 2 is detected by an absolute pressure sensor 8. The discriminating value and the detecting value of the absolute pressure are compared by the ECU5, and when the detecting value is larger than the discriminating value, fuel amount supplied to an engine 1 is increased and reflux of exhaust is controlled to be stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a fuel supply control method during high load operation of an internal combustion engine equipped with an exhaust gas recirculation control device, and particularly relates to a fuel supply control method during high load operation of an internal combustion engine equipped with an exhaust gas recirculation control device. This invention relates to a fuel supply control method that optimizes performance.

(Technical background of the invention and its problems) A fuel supply control method that increases the amount of fuel supplied to the engine to obtain high output during high-load operation when the absolute pressure in the intake pipe of the engine exceeds a predetermined determination value. is known, for example, from JP-A-57-137633.

In such a fuel supply control method, when the engine is operated under low atmospheric pressure conditions such as at high altitudes, the absolute pressure in the intake pipe during high-load operation when the throttle valve is fully opened due to the decrease in atmospheric pressure also decreases. Therefore, if the above-mentioned discrimination value is set under standard atmospheric pressure conditions and applied to determine high-load operating conditions when the engine is operated under low atmospheric pressure conditions, it will be necessary to increase the amount of fuel supplied to the engine. Even in a high-load operating state, the intake pipe absolute pressure value does not exceed the discrimination value, so the increase is not performed, resulting in a problem that the engine output is insufficient. Therefore, it is desirable that the above-mentioned discrimination value be set according to the atmospheric pressure.

On the other hand, while an internal combustion engine is operating, a portion of its exhaust gas is returned to the intake passage via the exhaust gas recirculation path to suppress the excessive rise in the combustion temperature of the air-fuel mixture, thereby reducing the amount of nitrogen oxides (which are one of the causes of air pollution).
A method for preventing the generation of NOx (hereinafter referred to as rEGRJ)
) is already widely known. As a method of controlling the amount of exhaust gas recirculation, the target amount of valve lift of the exhaust recirculation valve disposed in the middle of the exhaust recirculation path is set according to the absolute pressure in the intake pipe and the engine speed, and this target amount of valve lift and A method of controlling the exhaust gas recirculation amount by reducing the difference in actual valve lift amount to zero is known, for example, from Japanese Patent Laid-Open No. 82057/1983.

In such an exhaust gas recirculation control method, when operating under low atmospheric pressure conditions such as at high altitudes, there may be an inconvenience that exhaust gas recirculation is executed even though the exhaust gas recirculation is not required. In particular, when the amount of fuel supplied to the engine is increased, such as during high-load operation, the combustion temperature is lowered by enriching the air-fuel mixture, and the amount of NOx generated is reduced. Therefore, when the amount of fuel is increased, there is no need to perform exhaust gas recirculation, and rather, by performing exhaust gas recirculation, a disadvantage arises in that high output cannot be obtained.

(Object of the Invention) The present invention has been made to solve such inconveniences, and provides a fuel supply control method that optimizes engine operating performance during high-load operation under low atmospheric pressure conditions such as at high altitudes. The purpose is to

(Structure of the invention) According to the present invention, to achieve such an objective.

In fuel supply control that recirculates part of the exhaust gas into the intake passage and supplies the required amount of fuel to the engine depending on the operating state of the internal combustion engine, atmospheric pressure is detected and the intake air is recirculated according to the detected atmospheric pressure value. Determine the absolute pressure discrimination value in the passage,
The absolute pressure in the intake passage is detected, the detected absolute pressure value in the intake passage is compared with the absolute pressure discrimination value in the intake passage, and the absolute pressure value in the intake pipe is greater than the discrimination value in the intake passage. There is provided a fuel supply control method for an internal combustion engine, characterized in that the amount of fuel supplied to the internal combustion engine is increased and the recirculation of the exhaust gas is stopped.

(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 showing an internal combustion engine equipped with an exhaust gas recirculation control device to which the method of the present invention is applied, and the reference numeral 1 is
shows, for example, a four-cylinder internal combustion engine, an intake pipe (intake passage) 2 is connected to the engine 1, and a throttle valve 3 is provided in the middle of the intake pipe 2. A throttle valve opening (θTH) sensor 4 is connected to the throttle valve 3 to convert the valve opening of the throttle valve 3 into an electrical signal and send it to an electronic control unit (hereinafter referred to as rECUJ) 5.

A fuel injection valve 6 is provided in the intake pipe 2 between the engine 1 and the throttle valve 3. This fuel injection valve 6 is provided for each cylinder slightly upstream of an intake valve (not shown) in the intake pipe 2, and each injection valve 6 is connected to a fuel pump (not shown) and electrically connected to the ECU 3. Well, ECU3
The valve opening time of the fuel injection is controlled by the signal from the.

On the other hand, the absolute pressure (
PBA) sensor 8 is provided, and the absolute pressure signal converted into an electrical signal by this absolute pressure sensor 8 is
Sent to CU3.

The engine main body 1 is provided with an engine water temperature (Tw) sensor 9, which is made of a thermistor, etc., and is installed in the circumferential wall of the engine cylinder filled with engine cooling water, and supplies its detected water temperature signal to the ECU 3. .

Engine speed sensor (hereinafter referred to as rNe sensor) 1
0 is attached around the camshaft or crankshaft (not shown) of the engine, and outputs an engine rotational speed signal, that is, a pulse signal that occurs at a predetermined crank angle position every 180 rotations of the engine crankshaft. , this pulse signal is sent to the ECU 3.

A three-way catalyst 12 is provided in the exhaust pipe (exhaust passage) 11 of the engine 1.
is arranged to purify HC, Go 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 02 sensor 13 detects the oxygen concentration in the exhaust gas and supplies the detected value signal to the ECU 3.

Furthermore, an atmospheric pressure sensor 14 is connected to the ECU 3, and this atmospheric pressure sensor 14 detects the atmospheric pressure and sends the detected value signal to the EC.
Supply to U3.

The exhaust recirculation passage 1 connects the exhaust pipe 11 to the intake pipe 2.
8 is provided, and an exhaust gas recirculation valve 19 is provided in the middle of this passage 18.
is provided. The exhaust gas recirculation valve 19 is a negative pressure responsive valve, and is mainly operated by the negative pressure introduced by a valve body 19a arranged to be able to open and close the passage 18 and a solenoid valve 22, which is connected to the valve body and will be described later. diaphragm 19b;
It consists of a spring 19c that biases the diaphragm 19b in the valve closing direction. A communication passage 20 is connected to the negative pressure chamber 19b defined by the diaphragm 19b, and the negative pressure in the intake pipe 2- is controlled by a normally closed solenoid valve 22 provided in the middle of the communication passage 20.
Been introduced through.

The atmospheric chamber 11e communicates with the atmosphere. Furthermore, the communication path 20
An atmospheric communication passage 23 is connected downstream of the solenoid valve 22, and atmospheric pressure is introduced into the communication passage 20 and then into the negative pressure chamber through an orifice 21 provided in the middle of the communication passage 23. It is like that.

The electromagnetic valve 22 is connected to the ECU 3 and is operated by a drive signal from the ECU 3 whose on-off time ratio changes, thereby controlling the lift operation and speed of the valve body of the exhaust recirculation valve 19.

The exhaust gas recirculation valve 19 is provided with a valve lift sensor 24 that detects the operating position of the valve body of the valve 19 and sends a detected value signal to the ECU 3.

The ECU 3 determines the engine operating state according to the engine parameter signals from the various sensors described above, and when the determined operating state is an operating state in which exhaust gas should be recirculated, the ECU 3 changes the intake pipe absolute pressure detection value PBA and the engine rotation value Ne. The valve opening target value LQMD of the exhaust gas recirculation valve 19 is set accordingly. Second
The figure shows a lift map given by the intake pipe absolute pressure PBA and the engine speed Ne, and the ECU 3 reads the above-mentioned valve opening target value LCMD from this map. Then, this valve opening target value LQMD is compared with the actual valve opening value LAC detected by the valve lift sensor 24, and a drive signal is generated to operate the solenoid valve 22 so that the absolute pressure of the deviation becomes zero. It is supplied to the solenoid valve 22.

When the solenoid valve 22 is energized and the communication passage 20 is opened, the negative pressure Ps in the intake pipe downstream of the throttle valve 3 is introduced into the negative pressure chamber 19d of the exhaust recirculation valve 19, and the differential pressure acting on both sides of the diaphragm 19b becomes large. The diaphragm 19b is the spring 19
c, and the valve opening of the valve body 19a increases. Conversely, when the solenoid valve 22 is deenergized, only atmospheric pressure is introduced into the negative pressure chamber 19d via the atmospheric communication passage 23, and the valve body 1
9a is deflected to the closed side. In this way, the lift amount of the exhaust gas recirculation valve 19 is controlled, and a required amount of exhaust gas is recirculated to the intake pipe 2.

Furthermore, the ECU 3 determines the engine operating state based on the engine parameter signals from the various sensors mentioned above, and determines the fuel injection time T of the fuel injection valve 6 given by the formula shown below.
Calculate o g T.

Togt=TiXKwotXKo, XK1+K.

Here, Ti indicates the basic fuel injection time, and this basic fuel injection time Ti is determined by the intake pipe absolute pressure PBA and the engine rotation speed N.
It is set according to e. KWOT is the enrichment coefficient during high-load operation according to the present invention, and its value is set by a control program described later. Ko, is set according to the oxygen concentration in the exhaust gas detected by the 02 sensor 13 when the engine is in the closed loop operating region,
This is a correction coefficient that is set to a value of 1.0, for example, when the engine is in an open-loop operation region such as a high-load operation region. K and 2 are the various sensors mentioned above, namely, the throttle valve opening sensor 4, the absolute pressure sensor 8, and the engine water temperature sensor 9. A correction coefficient and a correction variable that are calculated according to the engine parameter signals from the Ne Sesan 10°02 Sesan 13 and the atmospheric pressure sensor 14, and according to the engine operating state.

Various characteristics such as starting characteristics, exhaust gas characteristics, fuel consumption characteristics, engine acceleration characteristics, etc. are calculated based on a predetermined calculation formula so as to be optimal.

The ECU 3 calculates the fuel injection time TO obtained as described above.
A drive signal for opening the fuel injection valve 6 is supplied to the fuel injection valve 6 based on the UT.

FIG. 3 is a diagram showing the circuit configuration inside the ECU 3 of FIG.
After the engine rotation speed signal from the Ne sensor 10 is waveform-shaped by a waveform shaping circuit 501, it is sent to the central processing unit C and below rC.
PUJ) 503 as an interrupt signal to start a program described in the flowcharts of FIGS. 4 and 7, which will be described later, and is also supplied to the Me counter 502. The Me counter 502 counts the time interval from the input of the previous predetermined crank angle position signal from the Ne sensor 10 to the input of the current predetermined crank angle position signal, and the counted value Me is the reciprocal of the engine rotation speed Ne. is proportional to. Me counter 502 supplies this coefficient value Me to CPU 503 via data bus 510.

Throttle valve opening sensor 4. The respective output signals from various sensors such as the absolute pressure sensor 8, the engine water temperature sensor 9, 02 sensor 13, and the atmospheric pressure sensor 14 are sent to the level correction circuit 50.
After being corrected to the predetermined voltage level at 4, multiplexer 5
05 are sequentially supplied to the A/D converter 506.

The A/D converter 506 sequentially converts the output signals from the aforementioned sensors into digital signals and supplies the digital signals to the CPU 503 via the data bus 510.

The CPU 503 further connects a read-only memory (ROM) 507, a random access memory (RAM) 50B, and a drive circuit 509, ! via a data bus 510. 511, the RAM 508 temporarily stores the calculation results etc. of the CPU 503, and the ROM 507 is connected to the CPU 503.
The control program, which will be described later, is stored therein.

In accordance with this control program as described later, the CPU 503 determines the operating state of the engine according to various engine parameters, supplies a control signal for the electromagnetic valve 22 that controls the amount of exhaust gas recirculation to the drive circuit 511, and controls the operation of the engine. The fuel injection time TOuT of the fuel injection valve 6 is calculated according to the state, and this calculated value is supplied to the drive circuit 509 via the data bus 510. The drive circuit 509 supplies the fuel injection valve 6 with a drive signal that opens the fuel injection valve 6 according to the calculated value, and the drive circuit 511 supplies the solenoid valve 22 with a drive signal that turns the solenoid valve 22 on and off. .

FIG. 4 shows how the Ne sensor 10 is operated by the CPU 503 in FIG.
6 is a flowchart illustrating a procedure for setting the enrichment coefficient value KWOT, which is executed every time an interrupt signal is generated from the engine and is applied when the engine is in the high-load operating region shown by diagonal lines in FIG. 5.

First, in step 401, it is determined whether the engine speed Ne is larger than a predetermined rotational speed value N)IOP (for example, 3000 rpm), and if the result of the first determination is negative (No),
That is, if the engine speed value Ne is less than or equal to the predetermined speed value NHOP, the process proceeds to step 402.

In step 402, an intake pipe absolute pressure discrimination value PBAWOTa, which will be described later, is stored in the ROM of FIG.
Read from 507. Figure 6 shows the discriminant value PBAWOTll
In the table diagram showing the relationship between the detected atmospheric pressure value PA and the atmospheric pressure PA, the detected atmospheric pressure value PA is the value P AW Q T 1 (for example, 600 II
liHg) or less, the value P F3A'W OT,.

(for example, 520 mmHg) is from the value PAWOTl to the value P
When the value P BAWQTal (e.g. 600 mm Hg) is between AWOTe (e.g. 700 mm Hg)
g) is greater than or equal to the value PAWOT, the value P8AwO
Tan (for example, 700 mrnHg) is read out respectively.

In step 403, the intake pipe absolute pressure PEA of the intake pipe 2 is determined as the discrimination value PBAWOT read out in step 402 described above.
, determine whether it is larger than or not, and 1 determination result is negative (No)
In the case of , that is, the intake pipe absolute pressure value PaA is equal to the predetermined pressure value po
If it is smaller than AwoT, it is determined that the engine load state is not high enough to enrich the air-fuel mixture, and the enrichment coefficient Kwov is set to a value of 1°0 (step 41
1).

If the determination result in step 403 is affirmative (Yes),
That is, the intake pipe absolute pressure value PeA is equal to the predetermined pressure value PBAWOT.
, the engine is determined to be in a high load state and the process proceeds to step 404. In step 404, the engine water temperature value Tw is set to a predetermined water temperature value TKWOT (for example, 100°C).
If the engine water temperature value Tw is larger than the predetermined water temperature value TKwoT (if the determination result in step 404 is affirmative (Yes)), the enrichment coefficient KWOT is determined.
is set to the value XWOT (for example, 1.25) (step 409), and if the Tw value is smaller than the TKWOT value (if the determination result in step 404 is negative), the enrichment coefficient KWOT is set to the value XWOT.

Set to a smaller value XWOTO (for example, 1.13) (step 408). The reason why the KWOT value is set in accordance with the engine water temperature value Tw in this way is to prevent engine knock, which tends to occur when the engine water temperature is high and in a high load operating state.

If the determination result in step 401 is positive (Yes), that is, the engine rotation value Ne is equal to the predetermined rotation value NHO.
If it is larger than P, the process proceeds to step 405, where the intake pipe absolute pressure PBA is set to a predetermined pressure value PBAWOT1 (for example, 700
It is determined whether it is larger than mIll(g). If the determination result in step 405 is affirmative (Yes), that is, if the intake pipe absolute pressure value PBA is greater than the predetermined pressure value PBAWOT, it is determined that the engine is in a high load state, and the process proceeds to step 406.

On the other hand, if the determination result in step 405 is negative (No), the process proceeds to step 407, and the valve opening θ of the throttle valve 3 is
It is determined whether TH is larger than a predetermined opening degree value θll0T (for example, 45°). If the determination result in step 407 is negative (No), that is, the valve opening value θTH is the predetermined opening value θ
If it is less than WOT, it is determined that the engine is not in a high load state, and the process proceeds to step 411 described above, where the enrichment coefficient KW is determined.
Set OT to the value 1.0. If the determination result in step 407 is affirmative (Yes), it is determined that the engine is in a high load state, and the process proceeds to step 406.

In step 406, it is determined whether or not the engine water temperature value Tw is greater than a predetermined water temperature value T (woT) in the same manner as in step 404 described above.If the first determination result is affirmative (Yes), that is, T
If the w value is greater than T(wor value, the above step 40
Proceed to step 9 and set the enrichment coefficient KWOT to the value XWOT2(1
゜25), and if negative (NO), step 41
0 and sets the enrichment coefficient KWOT to the value XWOT, (for example, 1.18).

Next, the enrichment coefficient value KWO set as described above
Apply T to the above equation to determine the fuel injection time TOUT (step 412), and end the program.

7 shows the solenoid valve 22 of FIG. 1 which is executed by the CPU 503 of FIG. 3 every time an interrupt signal from the Ne sensor 10 is generated.
3 is a flowchart showing a control procedure.

First, it is determined whether or not the engine is in a fuel cut operation region during deceleration, that is, whether or not fuel supply to the engine should be stopped (step 7o1). In the fuel cut operation range, no fuel is supplied to the engine, so the engine does not emit NOx. Therefore, when the engine is in the fuel cut operation region, that is, step 701
If the determination result is affirmative (Yes), the solenoid valve 22 is deenergized (step 702), and the recirculation of exhaust gas is stopped.

If the determination result in step 701 is negative (NO), that is, if the engine is not in the fuel cut operation region, the process proceeds to step 703, where it is determined whether the aforementioned enrichment coefficient value KWOT is larger than the value 1.0. If the determination result in step 703 is affirmative (Yes), that is, when the engine is in a high-load operating region, the process proceeds to step 702 described above in order to prevent a decrease in engine output due to exhaust gas recirculation;
Stop the recirculation of exhaust gas.

If the determination result in step 703 is negative (NO), that is, if the engine is not in the high load operating region, step 704
Then, the intake pipe absolute pressure value PBA becomes the predetermined judgment value PBAI.
:C (for example, 650 mmHg), and if the PB'A value is larger than a predetermined judgment value PBAEC (the judgment result is positive (Yes)), it is judged that the engine is in a state close to a high-load operating state. Then, exhaust gas recirculation is stopped (step 702).

If the determination result in step 704 is negative (No), the process proceeds to step 705, where it is determined whether the throttle valve opening value θTl (is larger than a predetermined determination value θN:c (for example, 55°)) and the oTH value is If it is larger than the predetermined determination value θ (the determination result is Yes), it is determined that the engine is in a state close to a high-load operating state, and exhaust gas recirculation is stopped (step 702).

On the other hand, if the determination results in step 704 and step 705 are both negative (NO), the process proceeds to step 706, and the engine water temperature value Tw is equal to the predetermined determination value TwI! : (for example, 70°C). The engine water temperature Tw is the predetermined determination value Tw.

If it is lower, it means that the engine is in a warm-up state, and if exhaust gas is recirculated in such a case, the operation of the engine will become unstable and may cause engine stall. Therefore, when the engine water temperature is low, that is, when the determination result in step 706 is negative (NO), the process proceeds to step 702 described above, and the exhaust gas recirculation is stopped. on the other hand,
If the determination result in step 704 is affirmative (Yes), it is determined that warm-up has been completed, and all the start conditions for exhaust gas recirculation control are satisfied, and the process proceeds to step 707.
Duty ratio control of the electromagnetic valve 22 is executed based on the deviation between the target valve opening value LcMI) and the actual valve opening value LAC〒 of the exhaust gas recirculation valve 19 described above.

Note that control can be stabilized by providing so-called hysteresis characteristics to the discrimination values such as NHOρ applied to each discrimination in the above-described embodiments.

(Effects of the Invention) As detailed above, according to the present invention, the intake pipe absolute pressure discrimination value is determined according to the atmospheric pressure value, and the intake passage absolute pressure detection value is larger than the intake passage discrimination value. Since the exhaust recirculation is stopped in synchronization with the increase in the amount of fuel supplied to the internal combustion engine, it is possible to reliably stop the exhaust recirculation even during high-load operation under low atmospheric pressure conditions such as at high altitudes. This makes it possible to ensure optimization of engine operating performance during high-load operation.

[Brief explanation of drawings]

Fig. 1 is an overall configuration diagram of a fuel supply control system for an internal combustion engine equipped with an exhaust gas recirculation control system to which the method of the present invention is applied; Figure 3 is a block diagram showing the internal configuration of the electronic control unit (ECU) in Figure 1, Figure 4 is a flowchart showing the procedure for setting the enrichment coefficient value KWOT during high load operation, and Figure 5 is a high load operation area. A graph showing,
Figure 6 shows atmospheric pressure PA and intake pipe absolute pressure discrimination value PBAIJ.
FIG. 7 is a table diagram showing the relationship with OT, and a flowchart showing the control procedure of the solenoid valve shown in FIG. 1. DESCRIPTION OF SYMBOLS 1... Internal combustion engine, 2... Intake passage, 5... Electronic control unit (ECU), 6... Fuel injection valve, 7... Absolute pressure sensor, 9... Engine water temperature sensor, 10 ...Engine speed sensor (Ne sensor),
11...Exhaust passage, 13...0□sensor, 14...
・Atmospheric pressure sensor, 18... Exhaust recirculation passage, 19...
Exhaust recirculation valve, 22... Solenoid valve, 24... Valve lift sensor.

Claims (1)

[Claims] 1. A fuel supply control method for recirculating a part of exhaust gas into an intake passage and supplying a required amount of fuel to the engine according to the operating state of an internal combustion engine, which includes: detecting atmospheric pressure; An intake passage absolute pressure discrimination value is determined according to the detected atmospheric pressure value, the absolute pressure in the intake passage is detected, and the detected intake passage absolute pressure value is compared with the intake passage absolute pressure discrimination value. and when the intake passage absolute pressure detection value is larger than the intake passage discrimination value, the amount of fuel supplied to the internal combustion engine is increased and the recirculation of the exhaust gas is stopped. Control method. 2. The fuel supply control method for an internal combustion engine according to claim 1, wherein the intake passage absolute pressure discrimination value is set to a smaller value as the detected atmospheric pressure value decreases.