JP2004183581A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device for an internal combustion engine capable of realizing a decrease in the discharge of toxic substance and early activity of a catalyst by efficiently and appropriately carrying out fuel increase correction at the low temperature of the internal combustion engine. <P>SOLUTION: This exhaust emission control device for the internal combustion engine is provided with a fuel increase correction means for making an increase correction of a fuel injection quantity according to the low temperature degree of the internal combustion engine (S24); an exhaust flow control means for suppressing exhaust flow in an exhaust system (S12); an internal EGR quantity correlation value detecting means for detecting the internal EGR quantity correlation value of the internal combustion engine varied by suppressing exhaust flow by the exhaust flow control means (S14); and a fuel increase quantity reducing means for reducing the increase correction quantity of the fuel injection quantity by the fuel increase correction means, in proportion to the increase degree of the internal EGR quantity correlation value detected by the internal EGR quantity correlation value. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an exhaust gas purifying apparatus for an internal combustion engine, and more particularly to a technique for efficiently and appropriately performing fuel increase correction at a low temperature of the internal combustion engine to achieve reduction of harmful substance emissions and early catalyst activation.
[0002]
[Related background art]
By suppressing the exhaust flow in the exhaust system (from the combustion chamber to the exhaust pipe) (exhaust pressure increase, exhaust density increase, exhaust residence time extension, backflow into the cylinder, etc.), unburned matter (HC) , CO, etc.) and oxygen are promoted, and it is known that the emission of harmful substances and the early activation of the catalyst at the time of cold start can be realized (for example, see Patent Document 1).
[0003]
On the other hand, in the intake pipe injection type internal combustion engine, at the time of a cold start or the like, fuel attached to the intake port wall surface is unlikely to evaporate due to the low temperature of the intake port wall surface, and the fuel supplied to the cylinder decreases. Therefore, it is generally known to perform low-temperature increase correction for increasing the amount of fuel in accordance with the intake port wall surface temperature and, in turn, the degree of low temperature of the internal combustion engine.
[0004]
[Patent Document 1]
JP 2001-27145 A [0005]
[Problems to be solved by the invention]
By the way, when the exhaust gas flow is suppressed as described above, the exhaust pressure rises and the pressure difference between the exhaust pressure and the intake pressure increases. Therefore, when the internal EGR increases and the intake valve opens, high-temperature EGR gas Is strongly returned to the intake port.
As described above, when a large amount of high-temperature EGR gas is blown back to the intake port, vaporization of fuel attached to the intake port wall is promoted even during a cold start or the like, and the low-temperature increase correction is performed as described above. In such a case, the excess fuel is supplied by the amount of the vaporized fuel to enrich the air-fuel ratio, and the combustion air-fuel ratio and the exhaust air-fuel ratio become over-rich. There is a problem that the exhaust gas deteriorates.
[0006]
Therefore, in order to prevent such over-rich, it is conceivable to limit the low-temperature fuel increase correction and reduce the fuel increase correction amount during the suppression of the exhaust flow.
However, for example, when any failure such as sticking occurs in the exhaust flow control valve for suppressing the exhaust flow, the exhaust flow control valve does not actually suppress the exhaust flow even if the exhaust flow control command is issued. In this situation, if it is determined that the exhaust gas flow is being suppressed in such a situation and the increase correction amount is reduced, the amount of the EGR gas blown back to the intake port is small, and the vaporization of the fuel adhering to the intake port wall surface is reduced. On the contrary, there is a problem that the fuel is insufficient, the air-fuel ratio becomes over lean, and the combustion deteriorates. If the combustion deteriorates in this way, the engine may be stalled, which is not preferable.
[0007]
The present invention has been made to solve such a problem, and an object of the present invention is to efficiently and appropriately perform fuel increase correction at a low temperature of an internal combustion engine to reduce the emission of harmful substances and An object of the present invention is to provide an exhaust gas purification device for an internal combustion engine that can realize early catalyst activation.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, a fuel increase correction means for increasing and correcting a fuel injection amount in accordance with a degree of low temperature of an internal combustion engine is provided in an exhaust system of the internal combustion engine. Exhaust flow control means for suppressing exhaust flow in the system; internal EGR amount correlation value detection means for detecting an internal EGR amount correlation value of the internal combustion engine that changes as exhaust flow is suppressed by the exhaust flow control means; The fuel injection system further comprises a fuel increase decreasing means for decreasing the fuel injection amount increase correction amount by the fuel increase correction means as the internal EGR amount correlation value detected by the internal EGR amount correlation value detection means increases.
[0009]
Therefore, by controlling the exhaust gas flow by the exhaust gas flow control means, the emission of harmful substances and the early activation of the catalyst can be realized. However, the internal EGR amount correlation is reduced according to the low temperature of the internal combustion engine. The larger the value, that is, the higher the amount of high-temperature EGR gas blown back to the intake port due to the suppression of the exhaust flow, and the more the vaporization of the fuel attached to the intake port wall surface is promoted, the more the fuel increase correction amount is reduced. The air-fuel ratio and the exhaust air-fuel ratio do not become overrich, and deterioration of the exhaust gas is prevented. Further, when there is a failure such as sticking in the exhaust flow control means, for example, the exhaust flow control valve, and the exhaust flow is not actually suppressed in response to the exhaust flow suppression command and the internal EGR amount correlation value is small, In a situation in which the amount of high-temperature EGR gas blown back to the port is small and the vaporization of the fuel attached to the intake port wall surface is not promoted, the fuel increase correction amount is determined as an appropriate amount corresponding to the internal EGR amount correlation value. Since the decrease is suppressed, the combustion air-fuel ratio and the exhaust air-fuel ratio do not become excessively lean, and the deterioration of the combustion and the engine stall are prevented.
[0010]
In the invention according to claim 2, the internal EGR amount correlation value is an exhaust pressure in the exhaust system, and the internal EGR amount correlation value detecting means detects an exhaust pressure in the exhaust system. It is characterized by comprising means.
In other words, when the exhaust gas flow is suppressed, the correlation between the internal EGR and the exhaust pressure is high. Therefore, the exhaust pressure in the exhaust system is detected as the internal EGR amount correlation value, so that the internal EGR amount and, consequently, the exhaust gas adhering to the intake port wall surface are detected. It is possible to easily understand the amount of fuel vaporized easily and accurately. As a result, the combustion air-fuel ratio and the exhaust air-fuel ratio are prevented from becoming over-rich or over-lean, and deterioration of exhaust gas and combustion are accurately prevented.
[0011]
Further, in the invention according to claim 3, the internal EGR amount correlation value is a difference between the exhaust pressure in the exhaust system and the intake pressure in the intake system, and the internal EGR amount correlation value detecting means is provided in the exhaust system. Exhaust pressure detecting means for detecting the exhaust pressure of the exhaust system and intake pressure detecting means for detecting the intake pressure in the intake system for detecting a difference between the exhaust pressure in the exhaust system and the intake pressure in the intake system. It is characterized by doing.
[0012]
That is, when the exhaust flow is suppressed, the correlation between the internal EGR and the pressure difference between the exhaust pressure and the intake pressure is extremely high, and therefore, the pressure difference between the exhaust pressure and the intake pressure is detected as the internal EGR amount correlation value. In addition, the amount of internal EGR, that is, the amount of fuel adhering to the wall surface of the intake port, can be easily determined, and the amount can be more accurately grasped. As a result, the combustion air-fuel ratio and the exhaust air-fuel ratio are prevented from becoming over-rich or over-lean more satisfactorily, and the deterioration of exhaust gas and the deterioration of combustion are properly prevented.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
Referring to FIG. 1, there is shown a schematic configuration diagram of an exhaust gas purification device for an internal combustion engine according to the present invention mounted on a vehicle, and the configuration of the exhaust gas purification device will be described below.
As shown in FIG. 1, an intake pipe injection (Multi Port Injection: MPI) gasoline engine is used as an engine body (hereinafter simply referred to as an engine) 1 which is an internal combustion engine.
[0014]
The cylinder head 2 of the engine 1 is provided with an ignition plug 4 for each cylinder, and the ignition plug 4 is connected to an ignition coil 8 for outputting a high voltage.
An intake port 9 is formed for each cylinder in the cylinder head 2, and an opening / closing operation is performed on the combustion chamber 5 side of each intake port 9 in accordance with a cam of a camshaft 12 that rotates according to engine rotation. An intake valve 11 is provided for communicating and shutting off each intake port 9 with the combustion chamber 5. One end of an intake manifold 10 is connected to each intake port 9. An electromagnetic fuel injection valve 6 is attached to the intake manifold 10, and a fuel supply device (not shown) having a fuel tank is connected to the fuel injection valve 6 via a fuel pipe 7. .
[0015]
An electromagnetic throttle valve 17 for adjusting the amount of intake air is provided upstream of the fuel injection valve 6 of the intake manifold 10, and a throttle position sensor (TPS) for detecting the valve opening of the throttle valve 17. ) 18 are provided. An intake pressure sensor 19 for detecting the pressure of intake air in the intake manifold 10, that is, the intake pressure, is provided downstream of the throttle valve 17 of the intake manifold 10, that is, on the intake port side.
[0016]
An exhaust port 13 is formed in the cylinder head 2 in a substantially horizontal direction for each cylinder, and a cam of a camshaft 16 that rotates according to engine rotation is provided on the combustion chamber 5 side of each exhaust port 13. Exhaust valves 15 which open and close in accordance with each other and perform communication and cutoff between each exhaust port 13 and the combustion chamber 5 are provided. One end of an exhaust manifold 14 is connected to each exhaust port 13.
[0017]
Since the MPI engine is a publicly known one, a detailed description of its configuration will be omitted.
An exhaust pipe 20 is connected to the other end of the exhaust manifold 14, and a three-way catalytic converter 30 is interposed in the exhaust pipe 20 as an exhaust purification catalyst device. An O ₂ sensor 22 and an exhaust pressure sensor 24 for detecting the pressure of exhaust gas in the exhaust pipe 20, that is, an exhaust pressure, are disposed upstream of the three-way catalytic converter 30 in the exhaust pipe 20.
[0018]
Further, an exhaust flow control device (exhaust flow control means) 40 is provided downstream of the three-way catalytic converter 30 in the exhaust pipe 20.
Exhaust flow control device 40 is a device intended primarily harmful substances in exhaust gas (HC, other unburned substances such as CO, NOx, smoke, containing H ₂ or the like) that promote the reduction of exhaust At least one of the atmospheric pressure, the exhaust density, and the exhaust flow speed can be changed. Specifically, the exhaust flow control device 40 is configured by a closed-type on-off valve 42 capable of adjusting the flow area of the exhaust pipe 20.
[0019]
Various methods are conceivable as the closed-type on-off valve 42. Here, for example, a butterfly valve is employed. The butterfly valve is provided with an actuator 44, and the butterfly valve is opened and closed by the actuator 44.
The ECU 50 includes an input / output device, a storage device (ROM, RAM, nonvolatile RAM, and the like), a central processing unit (CPU), a timer counter, and the like. Control is performed.
[0020]
The input side of the ECU 50, TPS18 described above, the intake pressure sensor 19, _{O 2} sensor 22, other exhaust pressure sensor 24, a crank angle sensor 52 for detecting the crank angle of the engine 1, detects the cooling water temperature Tw of the engine 1 Various sensors such as a water temperature sensor 54 are connected, and detection information from these sensors is input. The engine speed Ne is detected based on the crank angle information from the crank angle sensor 52.
[0021]
On the other hand, various output devices such as the above-described fuel injection valve 6, ignition coil 8, throttle valve 17, and actuator 44 are connected to the output side of the ECU 50. These various output devices are connected to detection information from various sensors. The fuel injection amount, the fuel injection timing, the ignition timing, the exhaust flow control amount, and the like calculated based on the above are output, whereby the air-fuel ratio is controlled to an appropriate target air-fuel ratio, and the appropriate amount of fuel is supplied from the fuel injection valve 6. Is injected at an appropriate timing, spark ignition is performed at an appropriate timing by the spark plug 4, and the on-off valve 42 is opened and closed at an appropriate timing so as to attain a desired exhaust flow control amount (for example, a target exhaust pressure). .
[0022]
Specifically, in the exhaust gas purifying apparatus according to the present invention, when the engine 1 is in a cold state, the exhaust gas flow control is performed so as to activate the three-way catalytic converter 30 at an early stage, and the on-off valve 42 is closed to operate the exhaust gas. The flow is controlled. As a result, the exhaust pressure or exhaust density in the exhaust system increases, and the relationship between unburned substances such as HC and CO and oxygen or NOx in the exhaust system is strengthened, the reaction is promoted, and emission of harmful substances is improved. And the exhaust gas temperature rises to activate the three-way catalytic converter 30 early.
[0023]
However, when the engine 1 is cold started, the temperature of the intake port wall surface is low, and the fuel adhering to the intake port wall surface is unlikely to evaporate. Therefore, the amount is increased immediately after the start (from the start to immediately after the engine 1 starts its own operation). Fuel increase) or warm-up increase (meaning fuel increase from the time immediately after start-up until the coolant temperature of the engine 1 reaches a predetermined temperature), that is, low temperature fuel increase correction is performed to prevent deterioration of combustion. When the exhaust flow is suppressed, the exhaust pressure rises and the internal EGR increases. Therefore, if the low-temperature increase correction of the fuel is performed simultaneously with the suppression of the exhaust flow, the exhaust pressure and the suction pressure are reduced. Due to a large pressure difference from the atmospheric pressure, the high-temperature EGR gas is strongly returned to the intake port, and the vaporization of the fuel attached to the intake port wall surface is promoted, so that the combustion air-fuel ratio and the exhaust air-fuel ratio are over-rich. Phenomenon of becoming occurs.
[0024]
Therefore, the exhaust gas purifying apparatus according to the present invention further limits the low-temperature fuel increase correction in accordance with a value (internal EGR correlation value) having a high correlation with the internal EGR that changes due to suppression of the exhaust flow. explain.
First, a first embodiment will be described.
Referring to FIG. 2, a control routine of the low-temperature increase correction control according to the first embodiment of the present invention is shown in a flowchart, and will be described below with reference to the flowchart.
[0025]
In step S10, it is determined whether the operating condition of the exhaust flow control is satisfied.
Specifically, whether the engine is in a cold start state, that is, the cooling water temperature Tw of the engine 1 is within a predetermined temperature range (for example, 50 ° C.>Tw> −10 ° C.), and after the engine 1 starts It is determined whether or not it is within a predetermined time range (for example, starting to 100 seconds). For example, when the cooling water temperature Tw is −7 ° C., it is determined whether the temperature is within a range of 30 seconds to 90 seconds after the start. When the cooling water temperature Tw is 25 ° C., it is within a range of immediately after the startup to 90 seconds. It is determined whether it is within.
[0026]
If the result of the determination in step S10 is false (No) and it is determined that the above condition is not satisfied, the process proceeds to step S22, and the exhaust flow control, that is, the suppression of the exhaust flow is not performed. An increase correction amount of the low temperature increase correction is set according to the temperature of 1, that is, the cooling water temperature Tw. Although the increase correction amount of the low temperature increase correction is set here according to the cooling water temperature Tw, the increase correction amount may be set according to the lubricating oil temperature of the engine 1 or the intake air temperature. Alternatively, if possible, the fuel adhesion ratio to the intake port wall surface may be detected and set according to the fuel adhesion ratio.
[0027]
Then, in step S18, the fuel injection amount is set based on the increase correction amount, and the fuel injection is performed in step S20 based on the set fuel injection amount. On the other hand, if the result of the determination in step S10 is true (Yes) and it is determined that the above condition is satisfied, then the flow proceeds to step S12.
In step S12, the exhaust flow control is activated to suppress the exhaust flow. As a result, the emission of harmful substances in the exhaust gas is properly prevented, and the exhaust gas temperature rises, whereby early activation of the three-way catalytic converter 30 is achieved.
[0028]
In step S14, the exhaust pressure sensor 24 detects an exhaust pressure Pex (internal EGR correlation value) having a high correlation with the internal EGR (internal EGR amount correlation value detecting means). That is, there is a correlation between the internal EGR amount and the amount of fuel vaporized on the intake port wall surface. If the internal EGR amount can be detected, the fuel vaporization amount can be directly known. Since it is difficult to detect, the exhaust pressure Pex having a high correlation with the internal EGR is detected as the internal EGR correlation value, and the internal EGR amount, and hence the amount of fuel vaporized on the intake port wall surface, are estimated. As a result, the amount of internal EGR, and hence the amount of fuel vaporized on the intake port wall surface, can be easily and accurately grasped.
[0029]
In step S16, the larger the detected exhaust pressure Pex is, the lower the increase correction amount of the low-temperature increase correction is set to be on the lower side than the above-described normal increase correction amount set according to the cooling water temperature Tw (fuel increase decrease). means). That is, FIG. 3 shows an example of the relationship between the exhaust pressure Pex and the increase correction amount. In this way, the increase correction amount of the low-temperature increase correction decreases as the exhaust pressure Pex increases. As shown in the figure, the increase correction amount changes according to the cooling water temperature Tw of the engine 1, but the decreasing tendency of the increase correction amount is the same regardless of the cooling water temperature Tw.
[0030]
After the increase correction amount of the low-temperature increase correction is set in accordance with the exhaust pressure Pex, in the same manner as described above, in step S18, the fuel injection amount is set based on the increase correction amount, and based on the set fuel injection amount, In S20, fuel injection is performed.
As a result, the exhaust pressure rises due to the suppression of the exhaust flow and the internal EGR increases, and the high temperature EGR gas is strongly returned to the intake port due to a large pressure difference between the exhaust pressure and the intake pressure, and the fuel adhered to the intake port wall surface Even if the gasification of the fuel gas is promoted, the increased air-fuel ratio and the air-fuel ratio of the exhaust gas are increased because the increase correction amount is set to be reduced in accordance with the internal EGR and the exhaust pressure Pex which is highly correlated with the vaporized amount of the fuel attached to the intake port wall surface. Enrichment is prevented well, and deterioration of exhaust gas is prevented.
[0031]
If the increase correction amount is set in accordance with the exhaust pressure Pex in this manner, the exhaust flow control device 40 will fail due to, for example, the sticking of the closed-type on-off valve 42, and the exhaust flow control command will be issued in response to the exhaust flow control command. When the flow control device 40 does not operate normally and the exhaust pressure Pex does not actually increase, that is, when the amount of the high-temperature EGR gas blown back to the intake port is small and the vaporization of the fuel attached to the intake port wall surface is not promoted. Even in this case, the fuel increase correction amount is set to an appropriate amount according to the exhaust pressure Pex, and the decrease in the fuel increase correction amount is suppressed, so that the combustion air-fuel ratio and the exhaust air-fuel ratio may also be overlean. This prevents deterioration of combustion and, consequently, engine stall.
[0032]
Next, a second embodiment will be described.
Referring to FIG. 3, a control routine of the low-temperature increase correction control according to the second embodiment of the present invention is shown in a flowchart, and will be described below with reference to the flowchart.
In FIG. 3, the same steps as those in FIG. 2 are denoted by the same reference numerals, and the description thereof will be omitted. Here, only the portions different from the first embodiment will be described.
[0033]
In the second embodiment, after the exhaust flow control is activated in step S12 after step S10 to suppress the exhaust flow, in step S14 ', the exhaust pressure Pex detected by the exhaust pressure sensor 24 and the intake pressure sensor 19 are used. A pressure difference ΔP (internal EGR correlation value) between the exhaust pressure Pex and the intake pressure Pin is detected based on the detected intake pressure Pin (internal EGR amount correlation value detecting means). That is, although only the exhaust pressure Pex has a high correlation with the internal EGR and thus the amount of fuel adhering to the intake port wall surface, the EGR gas is blown back to the intake port by the pressure difference ΔP between the exhaust pressure Pex and the intake pressure Pin. Therefore, the pressure difference ΔP has a very high correlation with the internal EGR, particularly the amount of fuel vaporized on the intake port wall surface. In this case, the pressure difference ΔP is detected as the internal EGR correlation value instead of the exhaust pressure Pex, and the internal EGR is detected. Estimate the amount and thus the amount of fuel vaporized on the intake port wall. As a result, the amount of internal EGR, and thus the amount of fuel adhering to the intake port wall surface, can be easily and more accurately grasped.
[0034]
Then, in step S16 ', the larger the detected pressure difference .DELTA.P, the smaller the amount of increase in the low-temperature increase correction is set to a side smaller than the normal amount of increase correction (fuel increase decrease means), and in step S18, the increase correction is performed. The fuel injection amount is set based on the amount, and the fuel injection is performed in step S20 based on the set fuel injection amount. Note that the relationship between the pressure difference ΔP and the increase correction amount is the same as the relationship between the exhaust pressure Pex and the increase correction amount in FIG.
[0035]
As a result, the exhaust pressure rises due to the suppression of the exhaust flow and the internal EGR increases, and the high temperature EGR gas is strongly returned to the intake port due to a large pressure difference between the exhaust pressure and the intake pressure, and the fuel adhered to the intake port wall surface Even if the vaporization is promoted, the increase correction amount is set to be reduced according to the internal EGR, particularly the pressure difference ΔP between the exhaust pressure Pex and the intake pressure Pin, which is highly correlated with the vaporization amount of the fuel attached to the intake port wall surface. Thus, the combustion air-fuel ratio and the exhaust air-fuel ratio are prevented from becoming over-rich, whereby the deterioration of exhaust gas is prevented.
[0036]
Further, if the increase correction amount is set in accordance with the pressure difference ΔP between the exhaust pressure Pex and the intake pressure Pin in this way, a failure occurs in the exhaust flow control device 40 due to, for example, sticking of the closed-type on-off valve 42 and the like, Actually, even when the exhaust pressure Pex does not increase, that is, when the amount of the high-temperature EGR gas blown back to the intake port is small and the vaporization of the fuel attached to the intake port wall surface is not promoted, the increase correction amount of the fuel is not increased. Since the reduction amount of the increase correction amount is suppressed by setting the appropriate amount in accordance with the pressure difference ΔP, the combustion air-fuel ratio and the exhaust air-fuel ratio are prevented from becoming overlean more conversely. Engine stall is prevented.
[0037]
As described above, the description of the embodiment is finished. As described above, in the exhaust gas purifying apparatus for an internal combustion engine according to the present invention, the exhaust pressure Pex or the exhaust pressure Pex having a high correlation with the internal EGR and, consequently, the vaporization amount of the fuel attached to the intake port wall surface. Is set in accordance with the pressure difference ΔP (internal EGR amount correlation value) between the intake pressure Pin and the intake pressure Pin, and the larger the exhaust pressure Pex or the pressure difference ΔP is, that is, the more the exhaust gas flow is reduced, the more the exhaust flow is suppressed. The correction amount for increasing the fuel is decreased as the amount of the hot EGR gas blown back increases and the vaporization of the fuel attached to the intake port wall surface is promoted.
[0038]
Therefore, it is possible to prevent the combustion air-fuel ratio and the exhaust air-fuel ratio from becoming over-rich, thereby preventing deterioration of the exhaust gas, and causing a failure in the exhaust flow control device 40, so that the exhaust pressure Pex does not actually increase. Even in this case, it is possible to prevent the combustion air-fuel ratio and the exhaust air-fuel ratio from becoming overlean well, and to prevent deterioration of combustion and eventually engine stall.
[0039]
In the above embodiment, the low-temperature fuel increase correction is set in accordance with the exhaust pressure Pex or the pressure difference ΔP between the exhaust pressure Pex and the intake pressure Pin (correlation value of the internal EGR amount). When the exhaust pressure Pex or the pressure difference ΔP reaches the set threshold, the increase correction amount may be uniformly reduced by a fixed amount.
Further, instead of the pressure difference ΔP between the exhaust pressure Pex and the intake pressure Pin, a pressure wave that is blown back within a predetermined period from the opening timing of the intake valve 11 of the engine 1 is detected based on the intake pressure information, and the pressure due to the pressure wave is detected. The rising amount may be used as the pressure difference ΔP.
In this case, a single sensor is required, that is, the exhaust pressure sensor 24 which requires heat resistance and is expensive is not used, and only the intake pressure sensor 19 which does not require heat and is lower in cost may be used. Cost increase can be suppressed.
[0040]
【The invention's effect】
As described above in detail, according to the exhaust gas purifying apparatus for an internal combustion engine of the first aspect of the present invention, when suppressing the exhaust flow by the exhaust flow control means, the internal EGR is controlled according to the low temperature degree of the internal combustion engine. Since the larger the amount correlation value is, that is, the higher the amount of high-temperature EGR gas blown back to the intake port due to the suppression of the exhaust flow and the more the vaporization of the fuel attached to the intake port wall surface is promoted, the more the fuel increase correction amount is reduced. It is possible to prevent the exhaust air from deteriorating by preventing the combustion air-fuel ratio and the exhaust air-fuel ratio from becoming over-rich, and the exhaust flow control means, for example, the exhaust flow control valve has a failure such as sticking. Actually, when the exhaust gas flow is not suppressed and the internal EGR amount correlation value is small, that is, the amount of high-temperature EGR gas blown back to the intake port is small, and the amount of fuel adhering to the intake port wall surface is small. Under such a situation that the fuel consumption is not promoted, the fuel increase correction amount is set to an appropriate amount according to the internal EGR amount correlation value so as to suppress the decrease of the increase correction amount, and conversely, the combustion air-fuel ratio and the exhaust air-fuel ratio become over-lean. This prevents deterioration of combustion and, consequently, engine stall. As a result, when the internal combustion engine is at a low temperature, the fuel increase correction can be efficiently and appropriately performed to reduce the emission of harmful substances and achieve early catalyst activation.
[0041]
Further, according to the exhaust gas purifying apparatus for an internal combustion engine, when the exhaust gas flow is suppressed, the correlation between the internal EGR and the exhaust pressure is high, and the exhaust pressure in the exhaust system is detected as the internal EGR amount correlation value. By doing so, it is possible to easily and accurately grasp the internal EGR amount, and hence the amount of fuel vaporized on the intake port wall surface. As a result, it is possible to prevent the combustion air-fuel ratio and the exhaust air-fuel ratio from becoming over-rich or over-lean, and it is possible to accurately prevent deterioration of exhaust gas and combustion.
[0042]
According to the exhaust gas purifying apparatus for an internal combustion engine of the third aspect, when the exhaust gas flow is suppressed, the correlation between the internal EGR and the pressure difference between the exhaust pressure and the intake pressure is extremely high, and By detecting the pressure difference as the internal EGR amount correlation value, the internal EGR amount, and hence the amount of fuel vaporized on the intake port wall surface, can be easily and more accurately grasped. As a result, the combustion air-fuel ratio and the exhaust air-fuel ratio are prevented from becoming over-rich or over-lean, and the deterioration of the exhaust gas and the deterioration of the combustion can be accurately prevented.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an exhaust gas purification device for an internal combustion engine according to the present invention.
FIG. 2 is a flowchart illustrating a control routine of low-temperature increase correction control according to the first embodiment of the present invention.
FIG. 3 is a diagram illustrating an example of a relationship between an exhaust pressure Pex and an increase correction amount.
FIG. 4 is a flowchart showing a control routine of low-temperature increase correction control according to a second embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Engine 6 Fuel injection valve 10 Intake manifold 11 Intake valve 14 Exhaust manifold 15 Exhaust valve 19 Intake pressure sensor 20 Exhaust pipe 24 Exhaust pressure sensor 30 Three-way catalytic converter 40 Exhaust flow control device (exhaust flow control means)
42 Sealed on-off valve 50 ECU (Electronic control unit)
52 Crank angle sensor 54 Water temperature sensor

Claims (3)

Fuel increase correction means for increasing the fuel injection amount in accordance with the degree of low temperature of the internal combustion engine;
Exhaust flow control means provided in an exhaust system of the internal combustion engine, for suppressing exhaust flow in the exhaust system;
An internal EGR amount correlation value detection unit that detects an internal EGR amount correlation value of the internal combustion engine that changes as the exhaust flow is suppressed by the exhaust flow control unit;
Fuel increase decreasing means for decreasing the fuel injection amount increase correction amount by the fuel increase amount correction means as the internal EGR amount correlation value detected by the internal EGR amount correlation value detection means increases;
An exhaust gas purifying apparatus for an internal combustion engine, comprising: The internal EGR amount correlation value is an exhaust pressure in the exhaust system,
2. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein said internal EGR amount correlation value detecting means comprises exhaust pressure detecting means for detecting an exhaust pressure in said exhaust system. The internal EGR amount correlation value is a difference between the exhaust pressure in the exhaust system and the intake pressure in the intake system,
The internal EGR amount correlation value detection means includes exhaust pressure detection means for detecting exhaust pressure in the exhaust system and intake pressure detection means for detecting intake pressure in the intake system. The exhaust gas purifying apparatus for an internal combustion engine according to claim 1, wherein a difference between an atmospheric pressure and an intake pressure in the intake system is detected.

Images