JP2524392B2 - Fuel correction method for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a fuel correction method for an internal combustion engine equipped with an electronically controlled fuel injection device, an exhaust gas recirculation device, and the like used in automobiles and the like.

[Prior Art] Usually, an engine of an automobile or the like is provided with an exhaust gas recirculation device having an EGR valve or the like. Then, at a suitable time except when the engine is cold or under high load, the EGR
By opening the valve and returning part of the exhaust gas to the intake system, the production of NO _X is reduced.

Further, in an engine equipped with an electronically controlled fuel injection device,
When determining the fuel injection amount to be supplied from the fuel injection valve, there is one in which the required injection amount at the time of exhaust gas recirculation is used as the basic injection amount. However, the EGR valve configured to operate by the differential pressure between the atmospheric pressure and the intake pressure is used when the intake pressure is near the atmospheric pressure and a sufficient differential pressure exceeding the operating pressure does not occur between the intake pressure and the atmospheric pressure. Therefore, the fuel injection amount needs to be corrected in this region. Therefore, as a prior art of the present invention, for example, as shown in JP-A-60-173343, when the exhaust gas is not recirculated, the fuel injection amount supplied from the fuel injection valve is increased more than when the exhaust gas is recirculated. There is an example. As a specific method for increasing or decreasing the fuel injection amount, as shown in FIG. 4, the correction coefficient is increased or decreased depending on whether the difference between the atmospheric pressure and the intake pressure exceeds the operating pressure (eg, 100 mmHg) of the EGR valve. By doing so, there is a measure to increase or decrease the fuel injection amount.

[Problems to be Solved by the Invention] However, the EGR valve is not fully closed or fully opened with a specific pressure as a boundary, but is fully closed or fully opened with a certain width and characteristic. Specifically, as shown in FIG. 5, the EGR valve changes gently with respect to a change in intake pressure when the state changes from a fully open state to a fully closed state or from a fully closed state to a fully open state. However, the EGR valve operating pressure is usually in the middle of the time from when the EGR valve starts to be closed to when the EGR valve is in a fully closed state, or from when the EGR valve starts to be opened to a fully opened state. Therefore, according to the conventional method of increasing / decreasing the fuel injection amount in a skip manner using this operating pressure as a guide, the recirculation amount of exhaust gas is throttled from the time the EGR valve starts to close until it reaches the intermediate position. A / F becomes lean. On the other hand, even if the exhaust gas is recirculated to the intake system even after passing the intermediate position, the fuel injection amount is suddenly increased at this intermediate position, so that the air-fuel ratio A / F is increased in this region. Become rich. Since such a problem is repeated each time the EGR valve is opened and closed, the air-fuel ratio becomes unstable, which causes emission and the like to deteriorate.

The present invention aims to solve such a problem.

[Means for Solving the Problems] In order to achieve the above object, the present invention employs the following configurations. That is, a fuel correction method for an internal combustion engine according to the present invention includes a fuel injection valve that supplies fuel to an intake system, a negative pressure chamber and an atmospheric pressure chamber that are divided by a diaphragm, and the negative pressure chamber has a negative pressure. The fuel injection valve includes an EGR valve which is operated by a pressure difference between atmospheric pressure and intake pressure when intake pressure is introduced via a regulating valve, and when exhaust gas recirculating to the intake system via this EGR valve is not recirculated. Is a fuel correction method for an internal combustion engine in which the fuel injection amount from the EGR is increased in an exhaust gas recirculation execution region.
Before and after the operating pressure of the valve is reached, the fuel injection amount from the fuel injection valve is gradually increased or decreased by using a coefficient set corresponding to the differential pressure.

[Operation] When the EGR valve is opened or closed, the negative pressure control valve makes the operating pressure of the EGR valve approximately the middle and changes gently with respect to the intake pressure. Utilizing the characteristics enables effective fuel correction. That is, according to the configuration as described above, when the EGR valve starts to close from the fully open state, the fuel injection amount is correspondingly set using the coefficient set corresponding to the differential pressure between the atmospheric pressure and the intake pressure at that time. Is gradually increased, and when the EGR valve is fully closed, the increase in fuel injection amount is stopped.

On the other hand, when the EGR valve starts to open, the fuel injection amount is gradually reduced by using a coefficient according to the differential pressure, similarly to the case where the EGR valve starts to close from the fully open state, and when the EGR valve becomes fully open, The reduction of the fuel injection amount will be stopped.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 to 3.

An engine 1, which is an internal combustion engine shown in the drawings, is used in an automobile and has a fuel injection valve 2 for injecting fuel into an intake system.
And an exhaust gas recirculation device 3 for returning a part of the exhaust gas to the intake system.

The fuel injection valve 2 is attached to the intake pipe 4 and has an electromagnetic coil inside. Then, when the fuel injection signal a is applied to the electromagnetic coil from the electronic control unit 5, the amount of fuel corresponding to the fuel injection signal a is injected near the intake port.

In the exhaust gas recirculation device 3, an EGR valve 9 is provided in an exhaust gas recirculation passage 8 that connects the exhaust passage 6 and the intake passage 7.
The EGR valve 9 is controlled to be opened and closed by the electronic control unit 5 via the first negative pressure switching valve 10 and the like.

The EGR valve 9 is a diaphragm whose internal space is divided into a negative pressure chamber and an atmospheric pressure chamber, and intake pressure is introduced into the negative pressure chamber via an EGR modulator 11 (negative pressure adjusting valve). Therefore, the atmospheric pressure is always introduced into the atmospheric pressure chamber. The exhaust gas recirculation passage 8 is opened and closed before and after the differential pressure between the atmospheric pressure and the intake pressure reaches the operating pressure (for example, 100 mmHg) of the EGR valve 9.

The first negative pressure switching valve 10 is a vacuum switching type three-way switching valve. The first port 10a communicates with the EGR port 13 opened upstream of the throttle valve 12, and the second port 10b communicates with the air cleaner 14. It is in communication. This EGR
The opening position of the port 13 is similar to the structure in the exhaust pressure control type exhaust gas recirculation device widely known in the art,
EGR at appropriate times except when the engine is cold or under heavy load
In order to operate the valve 9, the throttle valve 12 is located upstream of the tip of the throttle valve 12 at the time of idling, that is, on the air cleaner 14 side, and is located downstream of the tip of the throttle valve 12 during medium to high speed operation corresponding to the exhaust gas recirculation execution region. Is set to. Therefore, the intake pressure in the EGR port 13, that is, the intake pressure reaching the negative pressure chamber of the EGR valve 9 substantially linearly corresponds to the intake pressure PMTP in the surge tank 18 during the medium to high speed operation. Also,
The third port 10c is connected to the EGR via the EGR modulator 11.
It communicates with the negative pressure chamber of the valve 9. When the electric input terminal is not energized, the first port 10a and the third port 10c are held on the intake pressure side to conduct electricity, and when the electric input terminal is energized, The second port 10b and the third port 10c are maintained so that they are held at the atmospheric pressure side.

Further, the intake system of the engine 1 is provided with a pressure sensor 16 via a second negative pressure switching valve 15. The second negative pressure switching valve 15 is a vacuum switching type three-way switching valve similar to the first negative pressure switching valve 10, and has a first port.
15a communicates with the surge tank 18 via the gas filter 17, and the second port 15b communicates with the air cleaner 14. The third port 15c communicates with the pressure sensor 16. When the electric input terminal is not energized, it is held on the intake pressure side and the first port 15
When a and the third port 15c communicate with each other and the electric input terminal is energized, the second port is held at the atmospheric pressure side.
15b and the third port 15c communicate with each other.

The electronic control unit 5 includes a central processing unit 19 and a memory.
The input unit 21 includes at least an intake pressure signal b and an atmospheric pressure signal c from the pressure sensor 16, which is composed of a microcomputer unit having an input interface 21, an input interface 21, and an output interface 22.
Alternatively, an engine rotation signal or the like from a crank angle sensor (not shown) is input. On the other hand, from the output interface 22, a control signal d to the first negative pressure switching valve 10, a control signal e to the second negative pressure switching valve 15, a fuel injection signal a to the fuel injection valve 2 and the like. Each is output.

Further, the electronic control unit 5 contains a program as schematically shown in FIG. 2, and the program is repeatedly executed every predetermined engine rotation. First, at step 51, the second negative pressure switching valve 15 is energized to take in the atmospheric pressure PA value from the pressure sensor 16, and the routine proceeds to step 52. At step 52, the energization of the second negative pressure switching valve 15 is stopped, the intake pressure PMTP value is taken from the pressure sensor 16, and the routine proceeds to step 53. In step 53, the intake pressure signal b
After calculating the basic injection amount TPBSE according to the intake air amount calculated from the engine rotation signal, etc., the routine proceeds to step 54. In step 54, the correction coefficient FTPEGRO determined by the load is retrieved from Table-1. That is, depending on the load, there are a region where exhaust gas recirculation is easily performed and a region where it is difficult to perform recirculation (low negative pressure). Therefore, by changing this correction coefficient FTPEGRO in accordance with the intake pressure PMTP value, such region I am trying to make corrections.

Also, the differential pressure between the atmospheric pressure PA and the intake pressure PMTP is the EGR valve 9
Before and after reaching the operating pressure (for example, 100 mmHg), the correction coefficient KTPEGR that is gradually changed is searched from Table-2. The correction coefficient KTPEGR is changed in a region in which the EGR valve 9 is opened and closed, and is substantially inversely proportional to the opening thereof. Then, as schematically shown in FIG. 3, etc., within a certain range from the reference value (PA-125 mmHg) set near the operating pressure of the EGR valve 9, the intake pressure PMTP gradually changes in response to the change. Is done.

That is, such setting of the tables 1 and 2 is possible because the EGR port 13 is provided at a position where the intake pressure near the throttle valve 12 can be introduced into the EGR valve 9, as described above. Normally, the surge tank 18 is provided to prevent intake pulsation, and in the operating region where exhaust gas recirculation is performed except when the engine is cold or under high load, the intake pressure near the throttle valve 12 is It is propagated in the surge tank 18 while having a linear relationship. That is,
The intake pressure PMTP in the surge tank 18 is the throttle valve 12
It changes substantially linearly in accordance with the intake pressure in the vicinity. Therefore, the intake pressure PMTP in the surge tank 18
Is the first negative pressure switching valve 10 in the exhaust gas recirculation execution region.
And the intake pressure introduced into the EGR valve 9 via the EGR modulator 11 with the above relationship, and thus indirectly from the intake pressure PMTP of the surge tank 18 and the atmospheric pressure PA. The operating pressure of can be detected.

Then, 1 is added to the value FTPEGRO × KTPEGR obtained by multiplying these correction coefficients FTPEGRO and KTPEGR by EGR correction coefficient FTPE
Determine GR and proceed to step 55. In step 55, the basic injection amount TPBSE is multiplied by the EGR correction coefficient FTPEGR, and the value is corrected by various other correction coefficients determined according to the engine condition, and is actually supplied from the fuel injection valve 2 to the combustion chamber 23. Determine the fuel injection amount TAU.

According to such a configuration, when the engine 1 is in the cold state or the idling state, or in the high load range, the electronic control unit 5 energizes the first negative pressure switching valve 10,
The second port 10b and the third port 10c are electrically connected. Then, when the second port 10b and the third port 10c are brought into conduction, atmospheric pressure acts on the negative pressure chamber of the EGR valve 9, so that the EGR valve 9
The exhaust gas recirculation passage 8 is closed by the valve 9, and exhaust gas recirculation is prohibited.

On the other hand, in the exhaust gas recirculation execution region, energization of the first negative pressure switching valve 10 is stopped and the second negative pressure switching valve 10 is stopped.
The pressure sensor 16 controls the atmospheric pressure PA by the port switching control of 15.
And intake pressure PMTP are detected respectively. And atmospheric pressure PA
When the differential pressure between the intake air pressure PMTP and the intake pressure PMTP exceeds the operating pressure of the EGR valve 9, and the EGR valve 9 is in the fully open state, a part of the exhaust gas is recirculated to the intake passage 7 through the exhaust gas recirculation passage 8. It In this case, the basic injection amount T based on the EGR correction coefficient FTPEGR
PBSE will not be increased.

On the other hand, the differential pressure between the atmospheric pressure PA and the intake pressure PMTP is the EGR valve 9
When the EGR valve 9 is in the fully closed state when the operating pressure is lower than, the exhaust gas is not recirculated, so that the basic injection amount TPBTE is increased and corrected by the EGR correction coefficient FTPEGR.

Then, when the intake pressure PMTP changes from the fully open state of the EGR valve 9 to the atmospheric pressure PA side and the pressure difference between the atmospheric pressure PA and the EGR valve 9 falls below the operating pressure of the EGR valve 9, in other words, the EGR valve 9 is fully opened. When changing to the closed state, the EGR correction coefficient FTPEGR gradually increases in inverse proportion to the opening degree. That is, as the exhaust gas recirculation amount is gradually reduced, the basic injection amount TP
Since the BSE is gradually increased and corrected, the fuel injection amount TAU supplied from the fuel injection valve 2 gradually increases.
Then, this increase is stopped when the EGR valve 9 is fully closed.

Further, when the intake pressure PMTP changes from the fully closed state of the EGR valve 9 to the vacuum side, and the differential pressure from the atmospheric pressure PA exceeds the operating pressure of the EGR valve 9, in other words, the EGR valve 9 from the fully closed state. On the contrary, when changing to the fully open state, the EGR correction coefficient FTPEGR
Gradually decreases. That is, the increase correction amount of the basic injection amount TPBSE gradually decreases as the exhaust gas recirculation amount increases, so that the fuel injection amount TAU supplied from the fuel injection valve 2 is increased.
Is gradually narrowed down. Then, this reduction is stopped when the EGR valve 9 is fully opened.

Therefore, according to such a configuration, the EGR valve 9
Is switched from the fully open state to the fully closed state, or when the fully closed state is switched to the fully open state, the fuel supply amount is gradually increased as the exhaust gas recirculation amount is reduced, and the exhaust gas recirculation amount is increased. Since the fuel supply amount is gradually reduced as the amount of fuel increases, it is possible to reliably prevent the air-fuel ratio from switching to lean / rich in the first half and the second half of the EGR valve 9 when opening / closing. . As a result, EGR valve 9
Since the disturbance of the air-fuel ratio at the time of opening and closing can be effectively reduced, the efficiency of removing harmful components in the exhaust gas in such a region can be effectively increased.

When the EGR valve 9 is in the fully open state or the fully closed state, the fuel injection amount TAU supplied from the fuel injection valve 2 is adjusted according to each situation, so that the harmful components are generated in these regions. Can be effectively suppressed.

Moreover, since the differential pressure between the atmospheric pressure PA detected by the pressure sensor 16 and the intake pressure PMTP is a relative pressure, the atmospheric pressure PA
Even if is changed, the above control is effectively performed.

If the correction coefficient for increasing / decreasing the fuel injection amount when the EGR valve is opened / closed is changed in small increments, the fuel can be corrected more accurately.

Further, in this embodiment, the correction coefficient is changed substantially linearly (proportionally) in accordance with the opening / closing characteristics of the EGR valve, but the correction coefficient is not necessarily limited to such a change. Of course. For example, if the EGR valve does not change by a constant value at approximately the same speed, or if the speed of change is different for the load, the exhaust gas recirculation amount can be changed by changing the curve in a corresponding manner. Therefore, the fuel injection amount can be finely adjusted.

[Advantages of the Invention] According to the present invention having the above-described configuration, the fuel supply amount can be finely adjusted in accordance with the exhaust gas recirculation amount when the EGE valve is opened and closed. Disturbance of the air-fuel ratio during opening / closing can be suppressed. As a result, it is possible to provide a fuel correction method for an internal combustion engine with excellent control accuracy, which can effectively improve the emission when the EGR valve is opened and closed, as well as when the exhaust gas recirculation is executed or not executed.

[Brief description of drawings]

1 to 3 show an embodiment of the present invention, FIG. 1 is a schematic overall configuration diagram, FIG. 2 is a flowchart diagram showing a control procedure, and FIG. 3 is a diagram showing control setting conditions. is there. Fourth
FIG. 5 is a diagram corresponding to FIG. 3 showing a conventional example, and FIG. 5 is a diagram showing defects in the conventional example. 1 ... Internal combustion engine (automobile engine) 2 ... Fuel injection valve 3 ... Exhaust gas recirculation device 5 ... Electronic control device 6 ... Exhaust passage 7 ... Intake passage 8 ... Exhaust gas recirculation passage 9 ... EGR valve

Claims (1)

(57) [Claims] 1. A fuel injection valve for supplying fuel to an intake system, a negative pressure chamber and an atmospheric pressure chamber divided by a diaphragm, and intake pressure is introduced into the negative pressure chamber via a negative pressure adjusting valve. And an EGR valve that operates by a pressure difference between the atmospheric pressure and the intake pressure, and increases the fuel injection amount from the fuel injection valve when the exhaust gas that recirculates to the intake system through the EGR valve is not recirculated. A method of correcting fuel for an internal combustion engine, comprising:
In the exhaust gas recirculation execution region, the fuel injection amount from the fuel injection valve is gradually increased and decreased before and after the differential pressure reaches the operating pressure of the EGR valve using a coefficient set corresponding to the differential pressure. A method for correcting fuel in an internal combustion engine, comprising: