JP3741030B2 - Internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an internal combustion engine, and more particularly to an internal combustion engine that is required to operate while controlling the amount of air taken into a combustion chamber.
[0002]
[Prior art]
In a lean combustion internal combustion engine represented by a diesel engine, various measures are taken in order to reduce the emission amount of nitrogen oxides (NOx) and smoke. As one of the countermeasures, conventionally, a part of exhaust gas (inert gas) is introduced into the combustion chamber as EGR gas, and the so-called “NOx” is reduced by lowering the combustion temperature. "EGR control" has generally been performed.
[0003]
In recent years, in addition to EGR control, exhaust gas purification technology has been widely adopted in which an exhaust gas purification catalyst is installed in the exhaust system, and the exhaust gas purification catalyst promotes the purification of nitrogen oxides (NOx) and soot in the exhaust gas. It is going on.
[0004]
As described above, in recent exhaust purification systems, nitrogen oxides contained in exhaust gas as much as possible are obtained by combining exhaust purification by EGR control as pretreatment and exhaust purification by exhaust purification catalyst as post-treatment. Comprehensive exhaust purification systems that reduce (NOx) and soot emissions are becoming mainstream.
[0005]
Incidentally, the EGR control may be used as one control for achieving the target air amount. That is, the amount of air taken into the combustion chamber is estimated from the output of the air flow meter, and the difference (error) between the estimated air amount and the target air amount is corrected by feedback control of the EGR valve, and taken into the combustion chamber. It may be used as air amount control for converging the air amount to the target air amount.
[0006]
Here, the target air amount is calculated from, for example, a control map having parameters such as engine demand load and combustion injection amount as parameters, and is required to ensure an optimal combustion state required at that time. Corresponds to air volume.
The reason why an error occurs between the amount of air taken into the combustion chamber and the target amount of air is, for example, a tolerance (manufacturing error) of the EGR valve or the engine body.
[0007]
Further, the exhaust purification catalyst will be described. In recent years, instead of a three-way catalyst or a lean NOx catalyst for the purpose of purifying nitrogen oxide (NOx) or the like, so-called so-called exhaust purification target is also newly adopted for particulates such as soot. Adoption of “particulate filter” is becoming mainstream.
[0008]
In this particulate filter, an activated oxygen release agent that also serves as a NOx absorbent is supported on a wall flow type filter, and the particulates collected on the filter are oxidized by the oxidizing power of the activated oxygen. By forcibly oxidizing and burning, it has an exhaust purification ability to purify without emitting a luminous flame.
[0009]
[Problems to be solved by the invention]
By the way, the present inventors have found various points to be improved regarding the combination of the EGR control and the particulate filter described above.
That is, the present inventors focused on the change in the back pressure accompanying the installation of the exhaust purification catalyst, and tried to improve the feedback control malfunction caused by the change in the back pressure.
[0010]
First, considering the relationship between the particulate filter and the back pressure, the back pressure in the exhaust passage changes according to the degree of particulate collection with respect to the particulate filter. That is, if the amount of collected fine particles is large, the ventilation resistance of the particulate filter increases, and the back pressure increases. Further, if the amount of collected particulates decreases, the ventilation resistance of the particulate filter decreases and the back pressure also decreases.
[0011]
On the other hand, in the feedback control of the EGR valve processed during EGR control, the amount of EGR valve opening correction per unit time is limited to an optimum value in consideration of the influence on the engine output. As the change of becomes larger, the follow-up performance of the feedback control decreases.
[0012]
That is, as shown in FIG. 7, if the difference between the current air amount Gn and the target air amount Gn.t is defined as the required gain ΔG.t, when the back pressure is adapted so that the change in the back pressure is within the allowable range. The air amount Gn can be converged to the target air amount Gn.t by feedback control several times with respect to the current EGR valve opening degree. However, as shown in FIG. 8, when the back pressure is incompatible with the back pressure change exceeding the allowable range, feedback control is required a considerable number of times.
[0013]
That is, when the back pressure is not suitable, the follow-up performance of the feedback control is reduced, so that the target air amount itself set at the beginning of the feedback control may have already changed to another value.
[0014]
In addition, during steady operation, the time required for feedback control can be sufficiently secured, but the opening degree of the EGR valve after the processing of the feedback control greatly deviates from the original EGR valve opening degree. That is, there is a possibility that the amount of EGR gas introduced will change significantly and the combustion state itself will change greatly.
[0015]
As described above, in the combination of the EGR control and the particulate filter, various problems due to the change in the back pressure occur. Therefore, it is necessary to control the air amount by the EGR control while sufficiently considering the mutual influence.
[0016]
Of course, the various problems described above are not limited to changes in the back pressure caused by the installation of the particulate filter, but are caused by, for example, changes in the back pressure caused by the exhaust throttle valve operation or the deterioration of the silencer. Sometimes it happens. That is, the various problems described above can be said to be phenomena caused by changes in the back pressure.
[0017]
Therefore, an object of the present invention is to provide a feedback control technique capable of avoiding a malfunction of EGR control associated with a change in back pressure. It is another object of the present invention to provide a feedback control technique that enables optimum EGR control even in combination with a particulate filter.
[0018]
[Means for Solving the Problems]
In order to solve the above technical problem, the present invention employs the following means.
That is, the present invention
EGR introduction means for introducing a part of the exhaust gas flowing through the exhaust passage of the internal combustion engine into the combustion chamber as EGR gas;
Target air amount setting means for setting a target air amount that is set according to the required combustion state and needs to be taken into the combustion chamber to achieve the combustion state;
An air amount calculating means for calculating the amount of air taken into the combustion chamber in the combustion state;
Request gain calculation means for comparing the target air amount set by the target air amount setting means with the air amount calculated by the air amount calculation means, and calculating the difference as a request gain;
Correction gain calculating means for calculating an air amount to be corrected per unit time as a correction gain based on the required gain;
A guard value setting means for setting a guard value to the correction gain calculated by the correction gain calculating means, and for limiting the correction of the air amount per unit time;
Air amount correction for controlling the EGR introduction means according to the correction gain set within the guard value and adjusting the amount of EGR gas introduced into the combustion chamber so that the amount of air taken into the combustion chamber converges to the target air amount Means,
Air flow rate adjusting means for adjusting the flow rate of air flowing into the combustion chamber through the intake passage;
Requested gain correction means for controlling the air flow rate adjusting means so as to reduce the required gain when there is a request for calculating the correction gain exceeding the guard value;
It is characterized by providing.
[0019]
According to the present invention configured as described above, the EGR gas is taken into the combustion chamber via the EGR introduction means. Further, the target air amount setting means sets the target air amount required for the current combustion state. The air amount calculating means calculates the amount of air taken into the combustion chamber, and the required gain calculating means calculates the difference between the air amount and the target air amount as the required gain.
[0020]
The correction gain setting means calculates an air amount to be corrected per unit time based on the required gain as a correction gain. Further, the guard value setting means sets a guard value for the calculated correction gain, and limits the correction of the air amount per unit time. Further, the air amount correcting means controls the EGR introducing means according to the correction gain set within the range of the guard value, and performs so-called EGR control for converging the air amount taken into the combustion chamber to the target air amount.
[0021]
Here, the guard value is determined in consideration of, for example, a change in the engine output accompanying the correction of the air amount and a change in the combustion state accompanying the change in the introduction amount of the EGR gas, and the feedback control is processed within the guard value. By doing so, it is possible to suppress a large change in engine output (torque shock), a large change in combustion state, and the like.
[0022]
The air flow rate adjusting means is a means for adjusting the flow rate of air flowing into the combustion chamber through the intake passage. That is, in the air amount correcting means described above, the air amount is indirectly controlled by changing the ratio of the air taken into the combustion chamber and the EGR gas. However, the air flow rate adjusting means flows into the combustion chamber. It is means for controlling the amount of air taken into the combustion chamber by directly adjusting the amount of air. Specifically, an intake throttle valve, a variable displacement supercharger, and the like can be exemplified as preferred examples of the air flow rate adjusting means.
[0023]
Further, in this configuration, when there is a request for calculating the correction gain exceeding the guard value, the required gain correction unit controls the air flow rate adjusting unit to correct the required gain. That is, when correction (feedback) exceeding the guard value is required, various problems described in the prior art occur. Therefore, the required gain is reduced by adjusting the amount of air flowing into the combustion chamber in advance. Optimize feedback control.
[0024]
Regarding the required gain correction means,
The required gain correction means has a request for calculating a correction gain exceeding the guard value, and when the amount of air taken into the combustion chamber in that state is smaller than the target air amount, the air in the intake passage The air flow rate adjusting means may be controlled to increase the flow rate. Further, when there is a request for calculating a correction gain exceeding the guard value and the amount of air taken into the combustion chamber in that state is larger than the target air amount, the air flow rate in the intake passage is reduced so as to reduce the air flow rate. It is good also as a structure which controls an air flow rate adjustment means.
[0025]
That is, when the current air amount is smaller than the target air amount, the required flow rate is reduced by increasing the air flow rate in the intake passage in advance. Conversely, when the current air amount is larger than the target air amount, the required flow rate is reduced by reducing the air flow rate in the intake passage in advance.
[0026]
In addition, regarding the EGR introduction means,
The EGR introduction means includes an EGR passage that interconnects the exhaust passage and the intake passage, and an EGR valve that adjusts the flow rate of the EGR gas flowing in the EGR passage,
The air amount correction means controls the valve opening amount of the EGR valve so that the ratio of EGR gas and air flowing into the combustion chamber varies, and the air amount taken into the combustion chamber together with the EGR gas is determined as the target air amount. It is good also as a structure converged on.
In other words, in this configuration, the EGR introduction means is configured by an EGR device including an EGR passage (exhaust gas recirculation passage) and an EGR valve.
[0027]
In addition, regarding the structure of the internal combustion engine,
A filter for collecting particulates contained in the exhaust gas may be provided in the exhaust passage of the internal combustion engine.
[0028]
In order to solve the above technical problem, the present invention employs the following means. That is, the present invention
EGR introduction means for introducing a part of the exhaust gas flowing through the exhaust passage of the internal combustion engine into the combustion chamber as EGR gas;
Target air amount setting means for setting a target air amount that is set according to the required combustion state and needs to be taken into the combustion chamber to achieve the combustion state;
An air amount calculating means for calculating the amount of air taken into the combustion chamber in the combustion state;
Request gain calculation means for comparing the target air amount set by the target air amount setting means with the air amount calculated by the air amount calculation means, and calculating the difference as a request gain;
Correction gain calculating means for calculating an air amount to be corrected per unit time as a correction gain based on the required gain;
A guard value setting means for setting a guard value to the correction gain calculated by the correction gain calculating means, and for limiting the correction of the air amount per unit time;
Guard value correction means for enlarging the guard value according to the width of the required gain when there is a request for calculating the correction gain exceeding the guard value;
An air amount correcting means for controlling the EGR introducing means according to the guard value correcting means and adjusting the amount of EGR gas introduced into the combustion chamber to converge the amount of air taken into the combustion chamber to the target air amount;
It is characterized by providing.
[0029]
According to the present invention configured as described above, when there is a request for calculating a correction gain exceeding the guard value, the guard value itself is expanded according to the required gain. That is, as the guard value increases, the correction gain also increases, so that the processing time for feedback control can be shortened.
[0030]
The various configurations described above can be combined without departing from the scope of the present invention, such as increasing the guard value with the guard value correction means while reducing the required gain with the required gain correction means. Various configurations (means) described above can be combined without departing from the scope of the present invention.
[0031]
Further, the various controls described above are not technologies that can be applied only to an internal combustion engine equipped with an EGR device as an EGR introduction means. For example, the EGR rate in the combustion chamber, that is, the air amount by changing the valve timing of the intake and exhaust valves. It is also useful in an internal combustion engine or the like having a device configuration for controlling the ratio of the EGR gas and the EGR gas. In other words, the EGR introduction means in the present invention is not limited to an EGR device provided with an EGR valve or an EGR passage.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
Next, preferred embodiments of the internal combustion engine according to the present invention will be described. The structure of the internal combustion engine described below is merely an embodiment of the present invention, and details thereof can be changed without departing from the scope of the claims.
[0033]
The internal combustion engine 1 shown in the present embodiment is a vehicular diesel engine that is a kind of lean combustion internal combustion engine. As shown in FIG. 1, in addition to four combustion chambers 2 (cylinders), a fuel supply system, an intake air System, exhaust system, control system, etc. are provided as its main components.
[0034]
The fuel supply system includes a fuel injection valve 3, a common rail (accumulation chamber) 4, a fuel supply pipe 5, a fuel pump 6, and the like, and supplies fuel to each cylinder 2. The fuel injection valve 3 is an electromagnetically driven on-off valve provided for each cylinder 2, and each fuel injection valve 3 is connected to a common rail 4 serving as a fuel distribution pipe. The common rail 4 is connected to a fuel pump 6 via a fuel supply pipe 5. The fuel pump 6 is rotationally driven using the rotation of the crankshaft 1a, which is the output shaft of the internal combustion engine 1, as a drive source.
[0035]
In the fuel supply system configured as described above, first, fuel in a fuel tank (not shown) is pumped up by the fuel pump 6. The pumped fuel is supplied to the common rail 4 through the fuel supply pipe 5. The fuel supplied to the common rail 4 is increased to a predetermined fuel pressure in the common rail 4 and is distributed to each fuel injection valve 3. When a drive voltage is applied to the fuel injection valve 3 and the fuel injection valve 3 is opened, the fuel is injected into each combustion chamber 2 via the fuel injection valve 3.
[0036]
On the other hand, the intake system includes an intake pipe 9, an intake throttle valve 13, an intake branch pipe 8, an air cleaner box 10, an intercooler 16, and the like, and forms an intake passage for supplying air to each cylinder 2.
[0037]
The intake pipe 9 forms a passage that guides air sucked through the air cleaner box 10 to the intake branch pipe 8. The intake branch pipe 8 forms a passage for distributing the air flowing in via the intake pipe 9 to each cylinder 2. An intake air temperature sensor 12 for measuring the temperature of intake air is provided in the vicinity of the connection portion between the intake pipe 9 and the air cleaner box 10.
[0038]
The intake pipe 9 extending from the air cleaner box 10 to the intake throttle valve 13 includes a compressor housing 15a of a turbocharger 15 that compresses the intake air, and an intercooler 16 that cools the air compressed in the compressor housing 15a. Furthermore, an air flow meter 11 for measuring the flow rate of air flowing into the combustion chamber 2 through the intake pipe 9 is provided upstream of the compressor housing 15 a of the turbocharger 15.
[0039]
Further, an intake throttle valve 13 (air flow rate adjusting means) is provided immediately upstream of the intake branch pipe 8 to adjust the amount of air flowing into each cylinder 2 through the intake pipe 9. The actuator 14 is configured by a stepper motor or the like. An intake air temperature sensor 7 that measures the temperature in the intake branch pipe 8 and an intake pressure sensor 17 that measures the pressure in the intake branch pipe 8 are provided immediately downstream of the intake throttle valve 13.
[0040]
In the intake system configured as described above, first, air to be supplied to each combustion chamber 2 flows into the air cleaner box 10 due to generation of negative pressure accompanying engine operation. The air flowing into the air cleaner box 10 is removed of dust and dirt in the air cleaner box 10, and then flows into the compressor housing 15 a of the turbocharger 15 through the intake pipe 9. The air flowing into the compressor housing 15a is compressed by a compressor wheel (not shown) and then cooled by the intercooler 16. Then, after the flow rate is adjusted by the intake throttle valve 13 as necessary, it flows into the intake branch pipe 8. The air that has flowed into the intake branch pipe 8 is distributed to each cylinder 2 via each branch pipe, and is burned together with the fuel injected and supplied from the fuel injection valve 3. Note that outputs from the air flow meter 11 and the intake pressure sensor 17 are input to an electronic control unit 30 described later, and are used, for example, for feedback control of the EGR valve 26 processed by the electronic control unit 30.
[0041]
Next, the control system will be described.
The control system includes a ROM (Read Only Memory) 32, a RAM (Random Access Memory) 33, a CPU (Central Control Device) 34, an input port 35, and an output port 36 connected to each other by a bidirectional bus 31. An electronic control unit 30 (ECU).
[0042]
In addition to the output signals of the various sensors described above, the input port 35 includes a load sensor 41 that detects the amount of depression of the accelerator pedal 40, a crank angle sensor 42 that detects the rotational speed of the crankshaft 1a, and a vehicle speed sensor 43 that measures the vehicle speed. Are input via the corresponding A / D converter 37 or directly. On the other hand, the fuel injection valve 3, the reducing agent addition valve 61, the intake throttle valve driving actuator 14, the EGR valve 26, and the like are connected to the output port 36 through corresponding drive circuits 38.
[0043]
The ROM 32 stores control programs for various devices and a control map that is referred to when the programs are processed. In the RAM 33, the output signals of various sensors input to the input port 35, the control signals output to the output port 36, and the like are recorded as the operation history of the internal combustion engine. In the CPU 34, the output signals of the various sensors recorded on the RAM 33 and the control map developed on the ROM 32 are compared on a desired program, and the various control signals output in the process are sent to the output port 36. To the corresponding device, and centrally manage various devices.
[0044]
The exhaust system includes an exhaust branch pipe 18 and an exhaust pipe 19, and forms an exhaust passage for exhausting exhaust gas discharged from each cylinder 2 to the outside of the engine body. Further, it has a catalytic converter 52, a reducing agent addition device 60, an EGR device 20, and the like, and has a function as an exhaust purification device that purifies nitrogen oxides (NOx) and fine particles (for example, soot) contained in the exhaust gas. is doing.
[0045]
First, the exhaust branch pipe 18 is connected to an exhaust port 18 a provided for each cylinder 2 and forms a passage for collecting exhaust gas discharged from the exhaust port 18 a and leading it to the turbine housing 15 b of the turbocharger 15. ing. Further, the exhaust pipe 19 forms a passage from the turbine housing 15b to a silencer (not shown). In the figure, 59 is a known oxidation catalytic converter.
[0046]
The catalytic converter 52 includes a casing 53 and various exhaust purification catalysts 52a and 52b provided in the casing 53, and has an exhaust purification action of purifying harmful substances in the exhaust gas discharged from the engine body 1.
[0047]
More specifically, a casing 53 is disposed downstream of the turbine housing 15b, and an exhaust purification catalyst is provided in the casing 53 from the upstream side in the order of the NOx storage reduction catalyst 52a and the particulate filter 52b. Has been. In the following description, the NOx storage reduction catalyst 52a may be simply referred to as a lean NOx catalyst 52a.
[0048]
The lean NOx catalyst 52a, which is one of the exhaust purification catalysts, has an exhaust purification action that mainly purifies nitrogen oxides (NOx) in the exhaust gas. More specifically, when the oxygen concentration of the exhaust gas flowing into the lean NOx catalyst 52a is high, nitrogen oxide (NOx) in the exhaust gas is absorbed, and when the oxygen concentration in the exhaust gas is low, that is, in the lean NOx catalyst 52a. The nitrogen oxide (NOx) absorbed when the air-fuel ratio of the exhaust gas flowing in is low is converted to nitrogen dioxide (NO ₂ ) And nitrogen monoxide (NO) in the form of reduction and release into the exhaust gas, and at the same time the nitrogen dioxide (NO) ₂ ) And nitrogen monoxide (NO) are allowed to undergo an oxidation reaction with unburned fuel components (CO, HC) contained in the exhaust gas. ₂ O) and carbon dioxide (CO ₂ ) Has an exhaust purification ability to purify.
[0049]
The composition is, for example, alumina (Al ₂ O _Three ) As a carrier, an alkali metal such as potassium (K), sodium (Na), lithium (Li), cesium (Cs), or an alkaline earth such as barium (Ba), calcium (Ca), or the like on the carrier, or At least one selected from rare earths such as lanthanum (La) and yttrium (Y) and a noble metal such as platinum (Pt) are supported.
[0050]
In addition, when supplementary explanation of the exhaust gas purification action is given here, in the lean combustion internal combustion engine shown in the present embodiment, combustion is usually performed in an oxygen-excess atmosphere. For this reason, the oxygen concentration in the exhaust gas discharged with combustion hardly decreases until the above reduction / release action is promoted, and unburned combustion components (CO, HC) contained in the exhaust gas. The amount of is also negligible.
[0051]
For this reason, in this embodiment, engine fuel (HC), which is a reducing agent, is injected and supplied into the exhaust gas, thereby promoting reduction in oxygen concentration and supplementing hydrocarbon (HC), which is an unburned combustion component, and exhaust gas. Promotes the cleansing action. The supply of the reducing agent is performed by a reducing agent adding device 60 described later. Details thereof will be described later.
[0052]
One particulate filter 52b has an exhaust purification action of oxidizing and burning particulates such as soot contained in the exhaust gas. More specifically, it has a filter 58 carrying an activated oxygen release agent, and has an exhaust purification action of removing (purifying) particulates collected on the filter 58 by oxidizing and burning them with activated oxygen.
[0053]
As shown in FIG. 2, the filter 58 alone has a honeycomb shape formed of a porous material such as cordierite, and includes a plurality of flow paths 55 and 56 extending in parallel to each other. More specifically, an exhaust gas inflow passage 55 whose downstream end is closed by a plug 55a and an exhaust gas outflow passage 56 whose upstream end is closed by a plug 56a are provided, and each exhaust gas inflow passage 55 and exhaust gas are provided. The outflow passages 56 are arranged side by side in the vertical and horizontal directions of the filter 58 through thin partition walls 57.
[0054]
Further, alumina (Al ₂ O _Three ), Etc., and a noble metal catalyst such as platinum (Pt) on the support, and if there is excess oxygen in the surroundings, the excess oxygen is occluded, and conversely the oxygen concentration When the oxygen content decreases, an active oxygen release agent that releases the stored oxygen in the form of active oxygen is supported.
[0055]
In addition, as active oxygen release agents, potassium (K), sodium (Na), lithium (Li), cesium (Cs), alkali metals such as rubidium (Rb), barium (Ba), calcium (Ca), strontium Use at least one selected from alkaline earth metals such as (Sr), rare earths such as lanthanum (La) and yttrium (Y), and transition metals such as cerium (Ce) and tin (Sn) Can do.
[0056]
Preferably, the alkali metal or alkaline earth metal has a higher ionization tendency than calcium (Ca), that is, potassium (K), lithium (Li), cesium (Cs), rubidium (Rb), barium (Ba), strontium. (Sr) or the like may be used.
[0057]
In the particulate filter 52b configured in this way, first, exhaust gas flows in the order of the exhaust gas inflow passage 55 → the partition wall 57 → the exhaust gas outflow passage 56 (arrow a in FIG. 2), and so on. The fine particles are collected on the surface and inside of the partition wall 57 in the process of passing through the partition wall 57. The fine particles collected in the partition wall 57 are oxidized by the activated oxygen that is increased by changing the oxygen concentration of the exhaust gas flowing into the partition wall 57 (filter) a plurality of times, and finally emits a luminous flame. It burns out without being removed from the filter 58.
[0058]
Thus, in the present embodiment, the NOx storage reduction catalyst 52a and the particulate filter 52b are disposed in the exhaust passage to purify the NOx and soot particles contained in the exhaust gas.
[0059]
In the present embodiment, as described above, the NOx storage reduction catalyst 52a and the particulate filter 52b are arranged in series. The reason for this is that the temperature of the particulate filter 52b is raised by using the heat of reaction accompanying the oxidation / reduction reaction in the NOx storage reduction catalyst 52a, and the oxidation / reduction reaction in the NOx storage reduction catalyst 52a. This is based on the reason that the activated oxygen from the released NOx storage reduction catalyst 52a is used for the exhaust gas purifying action of the particulate filter 52b. The occlusion reduction type NOx catalyst 52a carries a substance substantially the same as the activated oxygen release agent, as is apparent from the above. Therefore, it can be said that the NOx storage reduction catalyst 52a has a function as an activated oxygen release agent.
[0060]
The reducing agent addition device 60 includes a reducing agent addition valve 61, a reducing agent supply path 62, a fuel pressure control valve 64, a fuel pressure sensor 63, an emergency shutoff valve 66, and the like, and an appropriate amount of reducing agent (engine fuel) as required. Is added into the exhaust passage upstream of the catalytic converter 52.
[0061]
The reducing agent addition valve 61 is an electrical on-off valve that is provided at the collecting portion of the exhaust branch pipe 18 and opens when a predetermined voltage is applied. The reducing agent supply passage 62 forms a passage for guiding a part of the fuel pumped up by the fuel pump 6 to the reducing agent addition valve 61. The fuel pressure control valve 64 is arranged in the middle of the reducing agent supply path 62 and maintains the fuel pressure in the reducing agent supply path 62 at a predetermined fuel pressure. The fuel pressure sensor 63 detects the fuel pressure in the reducing agent supply path 62. The emergency shutoff valve 66 stops the fuel supply into the reducing agent supply path 62 when an abnormality occurs in the pressure in the reducing agent supply path 62.
[0062]
In the reducing agent addition device 60 configured as described above, the fuel discharged from the fuel pump 6 is maintained at a predetermined fuel pressure by the fuel pressure control valve 64 and then supplied to the reducing agent addition valve 61 through the reducing agent supply path 62. The When a predetermined voltage is applied to the reducing agent addition valve 61 and the valve is opened, the fuel in the reducing agent supply path 62 is injected and supplied into the exhaust branch pipe 18 through the reducing agent addition valve 61. The fuel (reducing agent) supplied to the exhaust branch pipe 18 is stirred in the turbine housing 15 b and then flows into the catalytic converter 52 through the exhaust pipe 19. Therefore, the exhaust gas with a low oxygen concentration and mixed with hydrocarbon (HC), which is an unburned combustion component, flows into the catalytic converter 52. As a result, the above-described exhaust purification action is promoted.
[0063]
Next, the EGR device 20 will be described.
The EGR device 20 corresponds to the EGR introduction means referred to in the present invention, and includes an EGR passage 25, an EGR valve 26, an oxidation catalyst 28 for the EGR device 20, an EGR cooler 27, and the like.
[0064]
The EGR passage 25 forms a passage connecting the exhaust branch pipe 18 and the intake branch pipe 8. The EGR valve 26 is an electrical on-off valve provided at a connection portion between the EGR passage 25 and the intake branch pipe 8. The EGR valve 26 passes through the EGR passage 25 based on EGR control or the like processed in the electronic control unit 30. The amount of flowing exhaust gas (EGR gas) is adjusted. The oxidation catalyst 28 for the EGR device 20 is disposed in an EGR passage 25 that connects the exhaust branch pipe 18 and the EGR cooler 27, and purifies unburned fuel components in the exhaust gas that is EGR gas that circulates from the exhaust branch pipe 18. To do. The EGR cooler 27 cools the exhaust gas flowing in the EGR passage 25 using the engine coolant as a heat medium. In the following description, the exhaust gas flowing through the EGR passage 25 may be referred to as EGR gas.
[0065]
According to the EGR device 20 configured as described above, a part of the exhaust gas flowing in the exhaust branch pipe 18 flows into the EGR passage 25 at a flow rate corresponding to the opening amount of the EGR valve 26. Further, the EGR gas (exhaust gas) flowing into the EGR passage 25 flows into the EGR cooler 27 through the oxidation catalyst 28 for the EGR device 20. The EGR gas flowing into the EGR cooler 27 is cooled when passing through the EGR cooler 27 and flows into the intake branch pipe 8. Then, the EGR gas that has flowed into the intake branch pipe 8 flows into each combustion chamber 2 while being mixed with the air flowing from the upstream side of the intake branch pipe 8, and is burned together with the engine fuel injected from the fuel injection valve 3.
[0066]
In the exhaust gas that becomes EGR gas, water vapor (H ₂ O) and carbon dioxide (CO ₂ ) And other inert gases. For this reason, when the exhaust gas which is the inert gas flows into the combustion chamber 2, the combustion temperature is lowered due to the mixing of the exhaust gas, and the generation of nitrogen oxides (NOx) is suppressed. In addition, since the amount of oxygen in the combustion chamber 2 decreases with the introduction of EGR gas, nitrogen oxide (NOx) and oxygen (O ₂ ) And the nitrogen oxide (NOx) emission control.
[0067]
By the way, in the above-described internal combustion engine 1, the target air amount is set in order to satisfy the engine required output and to achieve the combustion state required at that time, such as ensuring a stable combustion state.
The target air amount is calculated from, for example, a control map using engine demand load, fuel injection amount, and the like as parameters. In this example, an air amount (intake amount) corresponding to the target air amount and an appropriate amount of combustion injection are calculated. Thus, a combustion state satisfying the engine required load is established. The setting of the target air amount described here is merely an example. For example, the target air amount is set even during so-called “low temperature combustion” in which the temperature of the catalytic converter 52 is rapidly increased.
[0068]
Further, in connection with the description of the EGR device 20 described above, the amount of EGR gas introduced and the amount of air taken into the combustion chamber 2 flow into the combustion chamber 2 in a state where they are mixed with each other, and thus have a correlation. is there. In other words, the amount of air flowing into the combustion chamber 2 can be controlled by adjusting the amount of EGR gas introduced. Further, since the amount of EGR gas introduced is substantially proportional to the opening degree of the EGR valve 26, the amount of air flowing into the combustion chamber 2 can be controlled by controlling the opening degree of the EGR valve 26 by EGR control.
[0069]
Therefore, in the present embodiment, an air amount control map using the opening degree of the EGR valve 26 and the target air amount as parameters is prepared, and the EGR valve 26 is controlled according to the EGR valve opening degree read from the air amount control map. Air corresponding to the amount of air is taken into each combustion chamber 2.
[0070]
However, since it is actually affected by tolerances (machine differences), the current situation is that it cannot be handled only by the air amount control map. Here, the tolerance means a manufacturing error caused by a difference in manufacturing time or manufacturing factory of the engine body 1, the turbocharger 15, and the EGR valve 26.
[0071]
Therefore, in the present embodiment, by performing feedback control of the EGR valve 26 based on the difference between the air amount taken into the combustion chamber 2 and the target air amount, efforts are made to absorb the error (difference) in the air amount. Yes. That is, the EGR control is performed as an air amount control that corrects the opening degree of the EGR valve 26 and converges the air amount taken into the combustion chamber 2 to the target air amount.
[0072]
FIG. 3 is a Gn-EGR valve opening characteristic diagram in which the vertical axis represents the air amount (Gn) and the horizontal axis represents the EGR valve opening. Curves I, II, and III in the figure are Gn-EGR valve opening curves showing the air amount Gn corresponding to the opening of the EGR valve 26 from time to time. From the top, I: theoretical Gn− EGR valve opening curve, II: Gn-EGR valve opening curve when tolerance is affected, III: Gn-EGR valve opening curve when back pressure is increased. The Gn-EGR valve opening curve when the back pressure increases as shown in III will be described in detail later.
[0073]
Further, a method of using the Gn-EGR valve opening curve will be described. A target air amount Gn.t is set on the vertical axis, and an intersection of the target air amount Gn.t and the Gn-EGR valve opening curve is set. By tracing, the EGR valve opening required for ensuring the target air amount Gn.t can be calculated. In other words, if the opening degree of the EGR valve 26 is determined and the intersection of the EGR valve opening degree and the Gn-EGR valve opening curve is traced, the current air amount corresponding to the opening degree of the EGR valve 26 is obtained. Can be estimated. The Gn-EGR valve opening curve can be grasped by various preliminary experiments.
[0074]
In the following description, the theoretical Gn-EGR valve opening curve is curve I, the Gn-EGR valve opening curve when tolerance is affected is curve II, and the Gn-EGR valve opening curve when back pressure is increased is curved. Sometimes called III.
[0075]
First, the curve I will be described.
A curve I is a state in which an air amount corresponding to the target air amount Gn.t can be secured only by changing the setting of the EGR valve opening. In this state, the target air amount is not performed without performing feedback control of the EGR valve 26. An amount of air corresponding to Gn.t is obtained.
[0076]
For more details, Gn in the figure ₁ If the target air amount Gn.t is set in the EGR valve opening E ₁ The air amount Gn corresponding to the target air amount Gn.t ₁ Is obtained. In terms of the relationship with the curve I, the EGR valve opening E ₁ Air amount Gn corresponding to the target air amount Gn.t from the intersection point a with the curve I ₁ Is guided.
[0077]
However, since it is actually affected by the tolerance as described above, the Gn-EGR valve opening curve is actually established on the curve II.
That is, when affected by the tolerance, the air amount Gn is equal to the EGR valve opening E. ₁ Becomes a small value or a large value with respect to the target air amount Gn.t.
[0078]
3 assumes a case where the air amount Gn is small with respect to the target air amount Gn.t and an influence of tolerance occurs in the direction, and the EGR valve opening degree E ₁ As shown in FIG. 3, the air amount at is the air amount Gn. ₂ (Gn.t> Gn ₂ ). Speaking of curve II, EGR valve opening E ₁ And air amount Gn from intersection b of curve II ₂ Is guided.
[0079]
Therefore, in the present embodiment, feedback control of the EGR valve 26 is performed on the curve II, and the air amount Gn ₂ Is converged to the target air amount Gn.t. That is, the EGR valve opening E ₁ EGR valve opening E ₂ (Arrow F in the figure) and air amount Gn ₂ Is raised to the target air amount Gn.t. In terms of correspondence with FIG. 3, point C in the figure corresponds to the air amount Gn after feedback control.
[0080]
FIG. 4 shows a processing routine that is processed in the feedback control of the EGR valve 26. Further, the processing routine shown in FIG. 4 is processed in the electronic control unit 30, and includes the target air amount setting means, air amount calculating means, required gain calculating means, correction gain calculating means, and air amount correcting means in the present invention. The control system is configured. That is, the various means described above are composed of a control program for processing the processing routine shown in FIG. 4 and various hardware configurations required for processing the control program.
[0081]
Hereinafter, basic feedback control of the EGR valve 26 processed on the curve II will be described with reference to FIG.
[0082]
First, the electronic control unit 30 receives the start of the internal combustion engine (step 101), and determines whether or not it is a combustion state in which EGR gas should be introduced (step 102). An example of the determination criteria in step 102 is as follows. In the electronic control unit 30, the medium load operation region where the oxygen concentration is relatively high and the amount of smoke generated due to the introduction of EGR gas is small, or the low temperature described above. It is determined that the EGR gas is to be introduced when combustion is required. Note that the determination criterion exemplified here is an example, of course.
[0083]
Subsequently, the electronic control unit 30 sets a target air amount Gn.t to be taken into the combustion chamber 2 in order to achieve the requested combustion state (step 103), and opens the opening corresponding to the set target air amount Gn.t. At this time, the EGR valve 26 is opened (step 104). That is, at step 103, the target air amount setting means according to the present invention is configured. The opening degree of the EGR valve 26 corresponding to the target air amount Gn.t is an EGR valve opening degree calculation map that maps the correlation between the EGR valve opening degree and the target air amount Gn.t shown in FIG. Can be calculated.
[0084]
Subsequently, the electronic control unit 30 reads the output of the air flow meter 11, and calculates the air amount Gn corresponding to the current EGR valve opening from the output (step 105). Subsequently, the target air amount Gn.t set in step 103 is compared with the air amount Gn calculated in step 105, and the difference (target air amount Gn.t−air amount Gn) is calculated as the required gain. Calculated as ΔG.t (step 106). That is, the air amount calculating means according to the present invention is configured in step 105, and the required gain calculating means is configured in step 106.
[0085]
Subsequently, the electronic control unit 30 calculates a correction gain ΔG to be corrected per unit time based on the required gain ΔG.t calculated in step 106 as shown in the following equation (step 107).
[0086]
[Expression 1]
Correction gain ΔG = Required gain ΔG.t × Correction constant K ... [Formula 1]
[0087]
Here, the correction constant K is set to an appropriate value in consideration of the overshoot characteristic and the undershoot characteristic associated with the correction of the opening degree of the EGR valve 26.
[0088]
In the present embodiment, a guard value ΔG.limit is set for the correction gain ΔG in order to avoid engine output fluctuations (torque shock) due to a significant change in the air amount Gn. The guard value ΔG.limit is a numerical value obtained in various preliminary experiments, and the electronic control unit 30 determines a correction gain ΔG for the air amount Gn within the range of the guard value ΔG.limit (correction gain). ΔG <guard value ΔG.limit). Step 107 constitutes a correction gain calculation means and a guard value setting means according to the present invention.
[0089]
Subsequently, the electronic control unit 30 corrects the opening degree of the EGR valve 26 according to the correction gain ΔG calculated in step 107, and brings the air amount Gn close to the target air amount Gn.t (step 108). When it is determined that the target air amount Gn.t has not yet been reached after the processing of step 108 (step 109), the processing routine from step 105 to step 108 is repeated again, and finally the air amount Gn is set. It converges to the target air amount Gn.t. That is, feedback control of the EGR valve 26 is performed to absorb an error in the air amount Gn with respect to the target air amount Gn.t. Further, Step 108, Step 109, and the EGR valve 26 constitute the air amount correction means according to the present invention.
[0090]
By the way, the internal combustion engine shown in the present embodiment is provided with a particulate filter 52b in its exhaust system. Therefore, the back pressure in the exhaust pipe 19 (exhaust passage) varies greatly according to the amount of collected particulates (attachment amount) to the particulate filter 52b. Further, the change in the back pressure due to the installation of the particulate filter 52b has a much larger influence on the EGR control than the above-described tolerance. Therefore, in the internal combustion engine shown in the present embodiment, the Gn-EGR valve opening curve (curve III) is established at a position greatly deviated from the curve I as shown in FIG. The opening degree correction of the EGR valve 26 is necessary.
[0091]
That is, with reference to FIG. 3, when the back pressure rises, the EGR valve opening degree E is derived at the intersection d in the figure. ₁ Air amount Gn at _Three (Gn.t> Gn ₂ > Gn _Three ). Therefore, air amount Gn _Three Is corrected to the target air amount Gn.t, it is necessary to significantly reduce the opening degree of the EGR valve 26 and increase the air amount (see arrow F ′ in FIG. 3).
[0092]
However, in the feedback control of the EGR valve 26 as described above, since the correction gain ΔG is set within the range of the guard value ΔG.limit, the follow-up performance of the feedback control becomes lower as the required gain ΔG.t increases ( (See FIGS. 7 and 8). In addition, with the significant correction of the opening degree of the EGR valve 26, the ratio of EGR gas and air may change, and the combustion state (combustion mode) itself may be changed. That is, there is a limit to the correction of the air amount that can be processed by the feedback control of the EGR valve 26.
[0093]
When the target air amount Gn.t is used as a reference, the opening correction region of the EGR valve 26 in which the variation of the engine output and the change of the combustion state are allowed is a region X in FIG. Further, the width of the region X in FIG. 3 can be grasped by various preliminary experiments, and the electronic control unit 30 records the required gain corresponding to the region X as the maximum allowable required gain ΔG.max.
[0094]
Therefore, in the present embodiment, considering the change in back pressure, the following feedback control correction program (hereinafter simply referred to as a correction program) is processed together with the feedback control so as to optimize the feedback control. Yes.
[0095]
The flowchart shown in FIG. 5 is an example of a processing routine that is processed by the correction program.
[0096]
First, in the present correction program, after the processing of step 107 described above, it is determined whether or not the correction gain ΔG that should be originally calculated in step 107 is a correction gain that exceeds the guard value ΔG.limit (step). 201). That is, it is determined whether or not the correction request exceeds the guard value ΔG.limit.
[0097]
Subsequently, when the electronic control unit 30 determines that the correction request exceeds the guard value ΔG.limit, the electronic control unit 30 processes the opening degree correction within the guard value ΔG.limit according to step 108 described above. Note that the correction of the opening degree of the EGR valve 26 here is performed in the processing routine shown in FIG. 4, so in this processing routine, the time required for the processing in step 108 (predetermined time) is counted (step 202). ), The process proceeds to the next step 203. If a negative determination is made in step 201, it is determined that the air amount Gn can be corrected by basic feedback control, and this processing routine is temporarily terminated.
[0098]
In step 203, the air amount Gn ′ after the opening correction is calculated from the output of the air flow meter 11 output after the opening correction of the EGR valve 26, and the air amount Gn ′ and the target air amount Gn.t are calculated. The required gain ΔG.t ′ is calculated by comparison (step 203). In step 203, it is sufficient to determine only the magnitude of the required gain ΔG.t ′, and the required gain ΔG.t ′ is grasped by an absolute value (| target air amount Gn.t−air amount Gn ′. | = Requested gain ΔG.t ′).
[0099]
Subsequently, the electronic control unit 30 compares the above-described maximum allowable required gain ΔG.max with the required gain ΔG.t ′ calculated in step 203 (step 204), and the required gain ΔG.t ′ is the maximum allowable When it is determined that the required gain ΔG.max has been exceeded, it is determined that the feedback program needs to be optimized by this correction program, and a correction request flag is established (step 205). When it is determined that the maximum allowable required gain ΔG.max has not been reached, it is determined that the required gain ΔG.t ′ can be corrected by continuing normal feedback control, and this processing routine is temporarily terminated.
[0100]
Subsequently, the electronic control unit 30 reads the output of the crank angle sensor and the fuel injection amount per unit time, and determines whether or not the current operation state is a steady operation (step 206). When it is determined that the operation is steady, the opening control of the intake throttle valve 13 is started to optimize the feedback control. That is, feedback control correction is started.
[0101]
First, in the correction of feedback control, the electronic control unit 30 determines the control direction of the intake throttle valve 13 based on the required gain ΔG.t ′ after the process of step 206 (step 207). The determination of the control direction is to determine whether to control the intake throttle valve 13 in the opening direction or conversely in the closing direction, and determines whether the required gain ΔG.t ′ is positive or negative. By doing so, the control direction is determined.
[0102]
That is, in this step 207, it is determined from the positive / negative of the required gain ΔG.t ′ how the back pressure at the present time changes with respect to the median value (standard value) of the back pressure (required gain ΔG.t). '> 0), the control direction of the intake throttle valve 13 is determined according to the determination result.
[0103]
Subsequently, when the electronic control unit 30 determines in step 207 that the air amount Gn ′ is too small with respect to the target air amount Gn.t (required gain ΔG.t> 0), the electronic throttle unit 13 The required gain ΔG.t ′ is reduced by opening the valve and increasing the flow rate of the air flowing through the intake pipe 9 (intake passage) in advance (step 208). If it is determined in step 207 that the actual air amount Gn is too large with respect to the target air amount Gn.t (required gain ΔG.t <0), the intake throttle valve 13 is closed, and the intake pipe The required gain ΔG.t ′ is reduced by reducing in advance the flow rate of air flowing through the inside 9 (step 209). Then, the electronic control unit 30 continues the feedback control in the processing routine after step 108.
[0104]
The opening operation amount of the intake throttle valve 13 is calculated from the air change amount per unit opening operation amount learned during steady operation or the like. That is, the opening operation amount of the intake throttle valve 13 is set so that the required gain ΔG.t ′ is equal to or less than the maximum allowable required gain ΔG.max, and the opening amount of the intake throttle valve 13 is set based on the set opening operation amount. Perform the operation. That is, in the processing routine after step 207, the intake throttle valve 13 (air flow rate adjusting means) is controlled so that the required gain ΔG.t ′ is equal to or less than the maximum allowable required gain ΔG.max.
[0105]
Thus, in this correction program, the required gain ΔG.t ′ is reduced by following the feedback control by manipulating the opening of the intake throttle valve 13 and changing the absolute amount of air flowing into the combustion chamber 2 in advance. Increases sex. In addition, the required gain correction means according to the present invention is configured by the correction program and the hardware configuration necessary for processing the correction program.
[0106]
In addition, if it demonstrates with reference to FIG. 3, since the curve III will be raised entirely by valve opening of the intake throttle valve 13 after the process of this correction | amendment program, it will approach the curve II and the curve I. FIG. When the curve II is established above the curve II or the curve I, the curve III is entirely lowered by closing the intake throttle valve 13, so that the curve II or the curve I is approached.
[0107]
Therefore, since feedback control is processed within the opening correction region X of the EGR valve 26, fluctuations in engine output, changes in combustion state, and the like accompanying feedback control of the EGR valve 26 are suppressed.
[0108]
The processing routine described above is an embodiment of the present invention, and details thereof can be changed as desired. For example, one of the conditions for establishing the correction request flag is that the required gain ΔG.t ′ exceeds the maximum allowable required gain ΔG.max (see step 204). Even when ΔG is calculated and the correction gain ΔG is a request that exceeds the guard value ΔG.limit, the establishment requirement of the correction request flag can be satisfied.
[0109]
It is also possible to establish the correction request flag only on the condition that the calculation of the correction gain ΔG exceeding the guard value ΔG.limit is requested in the process of step 201. It is also possible to establish a correction request flag on condition that the required gain ΔG.t calculated in the previous step 106 exceeds the maximum allowable required gain ΔG.max.
[0110]
Further, after the processing of step 208 and step 209 of the correction program described above, it is confirmed that the required gain ΔG.t ′ is smaller than the maximum allowable required gain ΔG.max, and this processing routine is terminated. Good. In this case, when the required gain ΔG.t ′ has not yet reached the maximum allowable required gain ΔG.max, step 208 or step 209 is continued to suppress the required gain ΔG.t ′ to the maximum allowable required gain ΔG.max. To.
[0111]
In the correction program described above, the feedback control is optimized by opening the intake throttle valve 13. However, the feedback control can also be optimized in the following correction control. Hereinafter, with reference to FIG. 6, the optimization of the feedback control will be described.
[0112]
First, in the electronic control unit 30, after the correction request flag is established (step 205), the guard value ΔG.limit is expanded according to the width of the required gain ΔG.t ′ (step 301), and the expanded guard value ΔG. A correction gain ΔG ′ is calculated within limit ′ (step 302). Then, the electronic control unit 30 processes the feedback control of the EGR valve 26 after step 108 according to the correction gain ΔG ′ (step 303).
[0113]
According to this correction method, when there is a calculation request for the correction gain ΔG exceeding the guard value ΔG.limit, the guard value ΔG.limit is expanded, and the correction gain is within the expanded guard value ΔG.limit ′. Since ΔG ′ is calculated, the calculated correction gain ΔG ′ is larger than the previous correction gain ΔG (ΔG ′> ΔG). The enlargement of the guard value ΔG.limit is achieved not only by increasing the numerical value itself but also by increasing the correction constant K in Equation 1 described above.
[0114]
If the air amount Gn is corrected according to the newly calculated correction gain ΔG ′ in this way, the air amount change per unit time becomes large, and the air amount Gn can be converged to the target air amount Gn.t at an early stage. Further, since the guard value ΔG.limit ′ is enlarged according to the width (width) of the required gain ΔG.t ′, overshoot (overresponse) in feedback control is also avoided.
[0115]
As the guard value ΔG.limit increases, the amount of change in the engine output during the feedback control period increases. For example, when the target air amount Gn, t is prioritized, such as during sudden acceleration. Then, the present control that can optimize the feedback control only by changing the numerical value in the control is useful. Therefore, both a correction program for processing the opening degree control of the intake throttle valve 13 and a correction program for expanding the guard value ΔG.limit are prepared, and the correction program according to the operating condition required at that time. Is switched, more optimal feedback control is performed, thereby improving the driver viability and the exhaust gas purification rate.
[0116]
【The invention's effect】
As described above, according to the present invention, since the above-described various feedback control correction programs are included, problems of EGR control (feedback control) due to changes in back pressure can be avoided. In addition, since EGR control problems associated with changes in back pressure can be avoided, optimum EGR control is possible even in combination with a particulate filter.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an internal combustion engine according to an embodiment.
FIG. 2 is a view showing a cross-sectional structure of a particulate filter installed in an exhaust passage.
FIG. 3 is a Gn-EGR valve opening curve diagram of the internal combustion engine shown in the present embodiment.
FIG. 4 is a flowchart for explaining basic feedback control of EGR control according to the present embodiment.
FIG. 5 is a flowchart for explaining an example of a feedback control correction program according to the present embodiment.
6 is a flowchart showing a modification example of the feedback control correction program shown in FIG.
FIG. 7 is a diagram showing a change over time in the amount of air by feedback control when back pressure is applied.
FIG. 8 is a diagram showing a change over time in the air amount by feedback control when the back pressure is incompatible.
[Explanation of symbols]
1 Internal combustion engine (engine body)
1a Crankshaft
2 Combustion chamber (cylinder)
3 Fuel injection valve
4 Common rail
5 Fuel supply pipe
6 Fuel pump
8 Intake branch pipe
7 Intake air temperature sensor
9 Intake pipe (intake passage))
10 Air cleaner box
11 Air flow meter
12 Intake air temperature sensor
13 Inlet throttle valve
14 Actuator
15 Turbocharger
15a Compressor housing
15b Turbine housing
16 Intercooler
17 Intake pressure sensor
18 Exhaust branch pipe
18a Exhaust port
19 Exhaust pipe (exhaust passage)
20 EGR equipment
25 EGR passage
26 EGR valve
27 EGR cooler
28 Oxidation catalyst for EGR equipment
30 Electronic control unit
31 Bidirectional bus
35 input ports
36 output ports
37 A / D converter
38 Drive circuit
40 accelerator pedal
41 Load sensor
42 Crank angle sensor
43 Vehicle speed sensor
52 Catalytic converter
52a NOx storage reduction catalyst
52b Particulate filter
53 Casing
55 Exhaust gas inflow passage
55a stopper
56 Exhaust gas outflow passage
56a stopper
57 Bulkhead
58 Filter
59 Oxidation Catalytic Converter
60 Reducing agent addition device
61 Reducing agent addition valve
62 Reducing agent supply path
63 Fuel pressure sensor
64 Fuel pressure control valve
66 Emergency shut-off valve

Claims (6)

EGR introduction means for introducing a part of the exhaust gas flowing through the exhaust passage of the internal combustion engine into the combustion chamber as EGR gas;
Target air amount setting means for setting a target air amount that is set according to the required combustion state and needs to be taken into the combustion chamber to achieve the combustion state;
An air amount calculating means for calculating the amount of air taken into the combustion chamber in the combustion state;
Request gain calculation means for comparing the target air amount set by the target air amount setting means with the air amount calculated by the air amount calculation means, and calculating the difference as a request gain;
Correction gain calculating means for calculating an air amount to be corrected per unit time as a correction gain based on the required gain;
A guard value setting means for setting a guard value to the correction gain calculated by the correction gain calculating means, and for limiting the correction of the air amount per unit time;
Air amount correction for controlling the EGR introduction means according to the correction gain set within the guard value and adjusting the amount of EGR gas introduced into the combustion chamber so that the amount of air taken into the combustion chamber converges to the target air amount Means,
Air flow rate adjusting means for adjusting the flow rate of air flowing into the combustion chamber through the intake passage;
Requested gain correction means for controlling the air flow rate adjusting means so as to reduce the required gain when there is a request for calculating the correction gain exceeding the guard value;
An internal combustion engine comprising: The required gain correction means has a request for calculating a correction gain exceeding the guard value, and when the amount of air taken into the combustion chamber in that state is smaller than the target air amount, the air in the intake passage 2. The internal combustion engine according to claim 1, wherein the air flow rate adjusting means is controlled to increase the flow rate. The required gain correction means has a request for calculating a correction gain exceeding the guard value, and when the amount of air taken into the combustion chamber in that state is larger than the target air amount, the air in the intake passage The internal combustion engine according to claim 1 or 2, wherein the air flow rate adjusting means is controlled so as to reduce a flow rate. The EGR introduction means includes an EGR passage that interconnects the exhaust passage and the intake passage, and an EGR valve that adjusts the flow rate of the EGR gas flowing in the EGR passage,
The air amount correction means controls the valve opening amount of the EGR valve so that the ratio of EGR gas and air flowing into the combustion chamber varies, and the air amount taken into the combustion chamber together with the EGR gas is set as the target air amount. The internal combustion engine according to any one of claims 1 to 3, wherein the internal combustion engine is converged to. 5. The internal combustion engine according to claim 1, wherein the exhaust passage of the internal combustion engine is provided with a filter for collecting particulates contained in the exhaust gas. EGR introduction means for introducing a part of the exhaust gas flowing through the exhaust passage of the internal combustion engine into the combustion chamber as EGR gas;
Target air amount setting means for setting a target air amount that is set according to the required combustion state and needs to be taken into the combustion chamber to achieve the combustion state;
An air amount calculating means for calculating the amount of air taken into the combustion chamber in the combustion state;
Request gain calculation means for comparing the target air amount set by the target air amount setting means with the air amount calculated by the air amount calculation means, and calculating the difference as a request gain;
Correction gain calculating means for calculating an air amount to be corrected per unit time as a correction gain based on the required gain;
A guard value setting means for setting a guard value to the correction gain calculated by the correction gain calculating means, and for limiting the correction of the air amount per unit time;
Guard value correction means for enlarging the guard value according to the width of the required gain when there is a request for calculating the correction gain exceeding the guard value;
An air amount correcting means for controlling the EGR introducing means according to the guard value correcting means and adjusting the amount of EGR gas introduced into the combustion chamber to converge the amount of air taken into the combustion chamber to the target air amount;
An internal combustion engine comprising:

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