JP2004076684A - Exhaust gas purification device for internal combustion engine - Google Patents

Abstract

An object of the present invention is to provide a technique capable of regenerating a filter while maintaining a PM collection rate of the filter.
A particulate filter supporting a catalyst having an oxidizing ability and capable of temporarily collecting particulate matter contained in exhaust gas from an internal combustion engine, filter temperature detecting means for detecting the temperature of the particulate filter, An operating state detecting means for detecting the operating state of the engine, and an engine controlling means for controlling the operation of the internal combustion engine based on the detected value of the filter temperature detecting means and the detected value of the operating state detecting means are provided. This makes it possible to control the deposition amount of the particulate matter so as to be within a predetermined range and maintain the PM collection rate.
[Selection diagram] FIG.

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an exhaust gas purification device for an internal combustion engine.
[0002]
[Prior art]
In recent years, removal of particulate matter (hereinafter, referred to as “PM”) represented by soot, which is a suspended particulate matter contained in exhaust gas of diesel engines, has become an important issue. For this reason, a technique of providing a particulate filter (hereinafter, simply referred to as “filter”) for trapping PM in an exhaust system so that PM is not released into the atmosphere is known.
[0003]
This filter can prevent PM in exhaust gas from being once collected and released into the atmosphere. However, when the PM collected by the filter accumulates on the filter, the filter may be clogged. When the clogging occurs, the pressure of the exhaust gas upstream of the filter increases, which may cause a decrease in the output of the internal combustion engine or damage to the filter. In such a case, the PM deposited on the filter can be ignited and burned to remove the PM. Removing PM accumulated on the filter in this way is called filter regeneration.
[0004]
For example, Japanese Patent Application Laid-Open No. 9-94434 discloses a wall flow type filter in which a catalyst is thinly and uniformly supported in pores formed inside partitions between cells and PM can be burned and removed inside pores inside the partitions. ing.
[0005]
[Problems to be solved by the invention]
Incidentally, the PM trapped by the filter itself functions as a filter, and the trapping rate of PM in the exhaust gas increases as the amount of trapped PM increases. Therefore, when the filter is regenerated and the amount of PM deposited on the filter decreases, the PM collection rate may decrease.
[0006]
The present invention has been made in view of the above-described problems, and has as its object to provide a technique capable of regenerating a filter while maintaining the PM collection rate of the filter.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, an exhaust gas purification apparatus for an internal combustion engine according to the present invention employs the following means. That is, the first invention is:
A particulate filter carrying a catalyst having an oxidizing ability and capable of temporarily collecting particulate matter contained in exhaust gas from an internal combustion engine;
Filter temperature detecting means for detecting the temperature of the particulate filter,
Operating state detecting means for detecting an engine operating state;
Engine control means for controlling the operation of the internal combustion engine based on the detection value of the filter temperature detection means and the detection value of the operating state detection means,
It is characterized by having.
[0008]
The most important feature of the present invention is that the amount of particulate matter discharged from the engine is adjusted based on the temperature of the filter, and the amount of particulate matter deposited on the filter is appropriately maintained.
[0009]
The particulate matter collected by the filter can be removed by oxidation, but the oxidation rate at this time depends on the temperature (bed temperature) of the filter, and the higher the temperature, the faster the oxidation rate . Therefore, when the internal combustion engine is operated at a high speed and a high load, the oxidation rate of the particulate matter in the filter becomes faster than the amount of the particulate matter discharged from the engine, and the particulate matter deposited on the filter is removed. Is done. However, even if the rotational speed or load of the internal combustion engine changes, the temperature of the filter does not change immediately, and it takes some time. Therefore, the temperature of the filter may be low even when the engine load is large, while the temperature of the filter may be high even when the engine load is small. Here, when the temperature of the filter is high, the particulate matter can be oxidized even if the amount of the particulate matter discharged from the engine is large because the oxidation rate of the particulate matter is high. Therefore, if the operation of the engine is controlled based on the temperature of the filter and the amount of particulate matter discharged is controlled, the amount of particulate matter deposited on the filter can be controlled, and clogging and collection of the filter can be controlled. It is possible to suppress a decrease in the rate.
[0010]
In the present invention, the operating state detecting means detects the load state of the engine and the number of revolutions of the engine,
It is possible to further include a plurality of control maps for controlling the operation of the internal combustion engine based on the load state of the engine and the rotation speed of the engine, the control maps having different control values with respect to the temperature of the filter.
[0011]
By providing a plurality of control maps that are different depending on the temperature of the filter, it becomes possible to control the operation of the internal combustion engine based on the temperature of the filter.
[0012]
In the present invention, the engine control means can control the operation of the engine such that the lower the temperature detected by the filter temperature detection means, the smaller the amount of particulate matter emitted.
[0013]
When the temperature of the filter is low, the rate of oxidation of the particulate matter is low. Therefore, it is possible to suppress the clogging of the filter by setting the operation state such that the emission amount of the particulate matter is reduced.
[0014]
In the present invention, the filter is determined based on the temperature detected by the filter temperature detecting means, the oxidation rate of the particulate matter collected by the filter at the temperature, and the amount of the particulate matter discharged from the internal combustion engine. The engine control unit further includes a residual amount estimating unit for obtaining an amount of the remaining particulate matter, and the engine control unit discharges the particulate matter from the engine such that the amount of the particulate matter estimated by the residual amount estimating unit falls within a predetermined range. The amount of particulate matter can be controlled.
[0015]
If the amount of particulate matter discharged from the internal combustion engine is larger than the amount of particulate matter oxidized by the filter, the amount of particulate matter deposited on the filter increases. On the other hand, when the amount of particulate matter discharged from the internal combustion engine is smaller than the amount of particulate matter oxidized by the filter, the amount of particulate matter deposited on the filter decreases. Therefore, by controlling the amount of the particulate matter discharged from the internal combustion engine, it is possible to keep the increase or decrease in the amount of the particulate matter deposited on the filter within a predetermined range, and to reduce the collection rate of the particulate matter. It can be maintained.
[0016]
In the present invention, a deposition amount detection means for detecting the amount of particulate matter deposited on the particulate filter,
Means for correcting the control value of the engine control means so that the emission amount of the particulate matter decreases as the amount of accumulation detected by the accumulation amount detection means increases,
May be further provided.
[0017]
If the amount of the particulate matter collected by the filter increases, the filter may be clogged. Further, the filter may be deteriorated by heat generated when the deposited particulate matter is oxidized. Therefore, by controlling the engine so that the emission amount of the particulate matter decreases as the amount of the particulate matter collected by the filter increases, clogging and deterioration of the filter can be suppressed.
[0018]
In order to achieve the above object, an exhaust gas purification apparatus for an internal combustion engine according to the present invention employs the following means. That is, the second invention is
A particulate filter carrying a catalyst having an oxidizing ability and capable of temporarily collecting particulate matter contained in exhaust gas from an internal combustion engine;
Accumulation amount detection means for detecting the amount of particulate matter accumulated in the particulate filter,
Collection rate estimation means for estimating the collection rate of particulate matter at that time from the detection value of the accumulation amount detection means,
Engine control means for controlling the operation of the internal combustion engine based on the estimated value by the collection rate estimation means,
It is characterized by having.
[0019]
The most important feature of the present invention is that the amount of particulate matter discharged from the engine is adjusted based on the trapping rate of the particulate matter in the filter, and the amount of particulate matter deposited on the filter is appropriately maintained. .
[0020]
The percentage of particulate matter (collection rate) that can be collected by the filter among the particulate matter in the exhaust gas varies depending on the amount of particulate matter deposited on the filter. This trapping rate increases as the amount of particulate matter deposited on the filter increases. On the other hand, when the amount of particulate matter deposited on the filter increases, clogging and deterioration of the filter are induced. Therefore, if the operation of the engine is controlled based on the trapping rate of the particulate matter in the filter and the emission amount of the particulate matter is controlled, it is possible to control the amount of the particulate matter deposited on the filter. Clogging and a reduction in the collection rate can be suppressed.
[0021]
In the present invention, the engine control means can control the operation of the engine such that the trapping rate of the particulate matter estimated by the trapping rate estimating means is within a predetermined range.
[0022]
When the collection rate of particulate matter is high, the amount of particulate matter deposited on the filter is large. In such a case, clogging and deterioration of the filter can be suppressed by reducing the emission amount of the particulate matter. On the other hand, if the trapping rate of the particulate matter is lower than the predetermined range, the amount of the particulate matter released into the atmosphere increases. In such a case, it is possible to optimize the amount of particulate matter deposited on the filter by increasing the amount of particulate matter emitted from the engine, and maintain the collection rate within a predetermined range. It becomes possible.
[0023]
In the first and second inventions, the particulate filter supports a storage-reduction NOx catalyst,
NOx storage amount estimation means for estimating the amount of NOx stored in the storage reduction type NOx catalyst;
Means for correcting the control value of the engine control means such that the larger the NOx storage amount estimated by the NOx storage amount estimation means, the smaller the NOx emission amount;
May be further provided.
[0024]
The amount of NOx that can be stored in the NOx storage reduction catalyst is limited. Thus, when the amount of stored NOx increases, the amount of NOx discharged from the engine is reduced, thereby making it possible to suppress the release of NOx into the atmosphere.
[0025]
BEST MODE FOR CARRYING OUT THE INVENTION
<First embodiment>
Hereinafter, specific embodiments of the internal combustion engine according to the present invention will be described with reference to the drawings. Here, an example in which the internal combustion engine according to the present invention is applied to a diesel engine for driving a vehicle will be described.
[0026]
FIG. 1 is a diagram showing a schematic configuration of an engine according to the present embodiment and an intake and exhaust system thereof.
[0027]
The engine 1 shown in FIG. 1 is a water-cooled four-cycle diesel engine having four cylinders 2.
[0028]
The engine 1 includes a fuel injection valve 3 for directly injecting fuel into a combustion chamber of each cylinder 2. Each fuel injection valve 3 is connected to a pressure accumulation chamber (common rail) 4 for accumulating fuel up to a predetermined pressure.
[0029]
The common rail 4 communicates with a fuel pump 6 via a fuel supply pipe 5. The fuel pump 6 is a pump that operates by using a rotational torque of an output shaft (crankshaft) of the engine 1 as a driving source. A pump pulley 6a attached to an input shaft of the fuel pump 6 has an output shaft (crankshaft) of the engine 1. ) Are connected via a belt 7 to a crank pulley 1a attached to the crank pulley 1).
[0030]
In the fuel injection system configured as described above, when the rotation torque of the crankshaft is transmitted to the input shaft of the fuel pump 6, the fuel pump 6 rotates the rotation torque transmitted from the crankshaft to the input shaft of the fuel pump 6. The fuel is discharged at a pressure according to.
[0031]
The fuel discharged from the fuel pump 6 is supplied to a common rail 4 via a fuel supply pipe 5, accumulated in the common rail 4 to a predetermined pressure, and distributed to the fuel injection valves 3 of each cylinder 2. When a drive current is applied to the fuel injection valve 3, the fuel injection valve 3 opens, and as a result, fuel is injected from the fuel injection valve 3 into the cylinder 2.
[0032]
An intake branch pipe 8 is connected to the engine 1, and each branch pipe of the intake branch pipe 8 communicates with a combustion chamber of each cylinder 2 via an intake port (not shown).
[0033]
The intake branch pipe 8 is connected to an intake pipe 9, and a compressor housing 15 a of a turbocharger 15 that operates using heat energy of exhaust gas as a drive source is provided in the intake pipe 9. An intake throttle valve 10 that adjusts a flow rate of intake air flowing through the intake pipe 9 is provided at a portion of the intake pipe 9 located immediately upstream of the intake branch pipe 8. The intake throttle valve 10 is provided with an intake throttle actuator 11 which is constituted by a step motor or the like and drives the intake throttle valve 10 to open and close. An air flow meter 12 that outputs an electric signal corresponding to the mass of intake air flowing through the intake pipe 9 is attached to the intake pipe 9 upstream of the turbocharger.
[0034]
In the intake system configured as described above, the intake air flows into the compressor housing 15a via the intake pipe 9.
[0035]
The intake air flowing into the compressor housing 15a is compressed by rotation of a compressor wheel provided in the compressor housing 15a, and then flows into the intake branch pipe 8. The intake air flowing into the intake branch pipe 8 is distributed to the combustion chamber of each cylinder 2 via each branch pipe, and is burned using the fuel injected from the fuel injection valve 3 of each cylinder 2 as an ignition source.
[0036]
On the other hand, an exhaust branch pipe 13 is connected to the engine 1, and each branch pipe of the exhaust branch pipe 13 communicates with a combustion chamber of each cylinder 2 via an exhaust port 1 b.
[0037]
The exhaust branch pipe 13 is connected to a turbine housing 15b of the turbocharger 15. The turbine housing 15b is connected to an exhaust pipe 14, and the exhaust pipe 14 is connected downstream to a muffler (not shown).
[0038]
In the middle of the exhaust pipe 14, there is provided a particulate filter (hereinafter simply referred to as a filter) 16 for carrying a storage-reduction type NOx catalyst and for trapping PM in the exhaust gas.
[0039]
Here, the filter 16 according to the present embodiment will be described.
[0040]
FIG. 2 is a sectional view of the filter 16. FIG. 2A is a diagram illustrating a cross section of the filter 16 in the lateral direction. FIG. 2B is a diagram illustrating a vertical cross section of the filter 16.
[0041]
As shown in FIGS. 2A and 2B, the filter 16 is a so-called wall flow type having a plurality of exhaust passages 50 and 51 extending in parallel with each other. These exhaust passages are constituted by an exhaust inflow passage 50 whose downstream end is closed by a plug 52 and an exhaust outflow passage 51 whose upstream end is closed by a plug 53. In FIG. 2A, hatched portions indicate plugs 53. Therefore, the exhaust inflow passages 50 and the exhaust outflow passages 51 are alternately arranged via the thin partition walls 54. In other words, the exhaust inflow passage 50 and the exhaust outflow passage 51 are arranged such that each exhaust inflow passage 50 is surrounded by the four exhaust outflow passages 51 and each exhaust outflow passage 51 is surrounded by the four exhaust inflow passages 50.
[0042]
The filter 16 is formed of a porous material such as cordierite, so that the exhaust gas flowing into the exhaust inflow passage 50 passes through the surrounding partition wall 54 as shown by an arrow in FIG. Out of the exhaust passage 51.
[0043]
In the present embodiment, a carrier layer made of, for example, alumina is formed on the peripheral wall surface of each exhaust inflow passage 50 and each exhaust outflow passage 51, that is, on both side surfaces of each partition wall 54 and on the inner wall surface of the pores in the partition wall 54. A NOx storage reduction catalyst is supported on the carrier.
[0044]
The filter 16 has, for example, alumina as a carrier, and an alkali metal such as potassium (K), sodium (Na), lithium (Li), or cesium (Cs) and barium (Ba) or calcium (Ca) on the carrier. ) And at least one selected from rare earths such as lanthanum (La) or yttrium (Y) and a noble metal such as platinum (Pt). In the present embodiment, an NOx storage reduction catalyst (hereinafter, simply referred to as a NOx catalyst) constituted by supporting barium (Ba) and platinum (Pt) on a carrier made of alumina is employed. Furthermore, O ₂ Ceria with storage capacity (Ce ₂ O ₃ ) May be added.
[0045]
When the oxygen concentration of the exhaust gas flowing into the NOx catalyst is high, the NOx catalyst configured as described above stores nitrogen oxides (NOx) in the exhaust gas.
[0046]
On the other hand, the NOx catalyst releases the stored nitrogen oxides (NOx) when the oxygen concentration of the exhaust gas flowing into the NOx catalyst decreases. At this time, if reducing components such as hydrocarbons (HC) and carbon monoxide (CO) are present in the exhaust gas, the NOx catalyst converts the nitrogen oxides (NOx) released from the NOx catalyst into nitrogen (N ₂ ).
[0047]
An exhaust temperature sensor 17 that outputs an electric signal corresponding to the temperature of exhaust flowing through the exhaust pipe 14 is attached to the exhaust pipe 14 downstream of the turbocharger 15 and upstream of the filter 16. The temperature of the exhaust gas flowing into the filter 16 is detected by the exhaust temperature sensor 17, and the bed temperature of the filter 16 can be estimated from the detected temperature.
[0048]
An exhaust throttle valve 18 that adjusts the flow rate of exhaust flowing through the exhaust pipe 14 is provided in the exhaust pipe 14 downstream of the filter 16. The exhaust throttle valve 18 is provided with an exhaust throttle actuator 19 configured by a step motor or the like and driving the exhaust throttle valve 18 to open and close.
[0049]
In the exhaust system configured as described above, the air-fuel mixture (burned gas) burned in each cylinder 2 of the engine 1 is discharged to the exhaust branch pipe 13 through the exhaust port 1b, and then from the exhaust branch pipe 13 to the turbocharger. 15 into the turbine housing 15b. The exhaust gas flowing into the turbine housing 15b rotates a turbine wheel rotatably supported in the turbine housing 15b by using energy of the exhaust gas. At this time, the rotational torque of the turbine wheel is transmitted to the compressor wheel of the compressor housing 15a described above.
[0050]
The exhaust gas discharged from the turbine housing 15b flows into a filter 16 through an exhaust pipe 14, where PM in the exhaust gas is collected and harmful gas components are removed or purified, and then discharged to the atmosphere via a muffler. Is done.
[0051]
Further, the exhaust branch pipe 13 and the intake branch pipe 8 form an exhaust recirculation passage (hereinafter, referred to as an EGR passage) 20 for recirculating a part of the exhaust flowing through the exhaust branch pipe 13 to the intake branch pipe 8. Are communicated through. In the middle of the EGR passage 20, a flow regulating valve which is constituted by an electromagnetic valve or the like and changes the flow rate of exhaust gas (hereinafter referred to as EGR gas) flowing through the EGR passage 20 according to the magnitude of the applied power. (Hereinafter, referred to as an EGR valve.) 21 is provided.
[0052]
In the exhaust gas recirculation mechanism configured as described above, when the EGR valve 21 is opened, the EGR passage 20 is brought into a conductive state, and a part of the exhaust flowing through the exhaust branch pipe 13 passes through the EGR passage 20 and enters the intake passage. It is led to the branch pipe 8.
[0053]
The EGR gas recirculated from the exhaust branch pipe 13 to the intake branch pipe 8 through the EGR passage 20 is guided to the combustion chamber of each cylinder 2 while being mixed with fresh air flowing from the upstream of the intake branch pipe 8.
[0054]
The engine 1 configured as described above is provided with an electronic control unit (ECU: Electronic Control Unit) 22 for controlling the engine 1. The ECU 22 is a unit that controls the operating state of the engine 1 in accordance with the operating conditions of the engine 1 and a driver's request.
[0055]
Various sensors are connected to the ECU 22 via electric wiring, and output signals of the various sensors described above are input to the ECU 22. On the other hand, the ECU 22 is connected to the fuel injection valve 3, the intake throttle actuator 11, the exhaust throttle actuator 19, the EGR valve 21, a reducing agent injection valve 23 described later, and the like through electric wiring, and controls these. It is possible. The ECU 22 stores various application programs and various control maps.
[0056]
In the present embodiment, there is provided a reducing agent supply mechanism for adding fuel (light oil) as a reducing agent to the exhaust gas flowing through the exhaust pipe 14 upstream of the filter 16, and the fuel is supplied from the reducing agent supply mechanism into the exhaust gas. By adding, the oxygen concentration of the exhaust gas flowing into the filter 16 is reduced and the concentration of the reducing agent is increased.
[0057]
As shown in FIG. 1, the reducing agent supply mechanism is mounted such that its injection hole faces the exhaust port 1 b or the exhaust branch pipe 13, and the valve is opened by a signal from the ECU 22 to inject fuel. There is provided a valve 23 and a reducing agent supply passage 24 for guiding the fuel discharged from the fuel pump 6 to the reducing agent injection valve 23.
[0058]
In such a reducing agent supply mechanism, the high-pressure fuel discharged from the fuel pump 6 is applied to the reducing agent injection valve 23 via the reducing agent supply path 24. Then, the reducing agent injection valve 23 is opened by a signal from the ECU 22, and fuel as a reducing agent is injected into the exhaust branch pipe 13.
[0059]
The reducing agent injected from the reducing agent injection valve 23 into the exhaust port 1 b or the exhaust branch 13 reduces the oxygen concentration of the exhaust flowing from the upstream of the exhaust branch 13.
[0060]
Thereafter, the reducing agent injection valve 23 is closed by a signal from the ECU 22, and the addition of the reducing agent into the exhaust branch pipe 13 is stopped.
[0061]
In this way, as a result of the supply of the reducing agent to the filter 16, the exhaust gas flowing into the filter 16 changes in oxygen concentration in a relatively short cycle. Then, the active oxygen is released by the fuel flowing into the filter 16, so that the PM is transformed into a substance easily oxidized, and the oxidizable amount per unit time is improved. In addition, the addition of fuel removes oxygen poisoning of the catalyst and increases the activity of the catalyst, so that active oxygen is easily released. Further, the temperature of the filter 16 rises due to the oxidation reaction of the fuel. Then, the PM is oxidized and combusted and removed by the active oxygen. The exhaust gas having a low oxygen concentration flowing into the filter 16 reduces nitrogen oxides (NOx) stored in the filter 16.
[0062]
Here, in the filter 16, when the amount of trapped PM increases, the PM itself functions as a filter and the trapping rate is improved. Therefore, if the filter 16 is regenerated and all the PM trapped by the filter 16 is removed, the PM trapping rate may decrease.
[0063]
When the operating state of the engine changes, the temperature of the exhaust gas changes, and the temperature of the filter 16 changes with the change in the exhaust gas temperature. At this time, since the temperature of the filter 16 gradually changes, it takes some time until the temperature of the filter 16 becomes suitable for the engine operating state. If the engine operation control is performed only based on the engine operation state while the temperature is changing, PM may be unnecessarily accumulated in the filter 16 or may be unnecessarily removed. Was.
[0064]
For example, in the conventional engine, it is assumed that the filter 16 has a low temperature during low-load operation, so that the oxidation rate of PM is slowed down. I was However, when the operation shifts to the low load operation after the high load operation continues, the PM oxidation rate is high because the temperature of the filter 16 is still high. Therefore, it is not necessary to perform the operation control for reducing the PM emission amount as described above. Further, since the PM emission amount and the NOx emission amount are inversely proportional, if the operation control for reducing the NOx emission amount is performed without performing the operation control for reducing the PM emission amount, The addition of fuel for reducing the NOx stored in the NOx storage reduction catalyst can be reduced, and the fuel consumption can be reduced.
[0065]
On the other hand, when the operation shifts to the high-load operation state after the low-load operation continues, the PM oxidation speed is low because the temperature of the filter 16 is still low. Therefore, when the amount of emitted PM is large, the filter 16 is clogged. Therefore, clogging of the filter 16 can be suppressed by performing operation control for quickly increasing the temperature of the filter 16.
[0066]
FIG. 3 is a map for determining the engine operating conditions from the rotation speed and the torque (load) for each temperature of the filter 16. If the bed temperature of the filter 16 is, for example, less than 200 ° C., Map 1 is used. For example, if the bed temperature is 200 ° C. or more and less than 300 ° C., Map 2 is used. For example, when the temperature is 400 ° C. or more, the map 4 is used.
[0067]
The map controls the opening of the EGR valve 21, the opening of the intake throttle valve 10, the injection timing and amount of fuel injected from the fuel injection valve 3, and the engine 1 is operated. Here, when the EGR valve 21 opens, the amount of EGR sucked into the engine 1 increases, and when the EGR valve 21 closes, the amount of EGR sucked into the engine 1 decreases. The EGR gas lowers the combustion temperature in the cylinder 2 so that the emission amount of NOx can be reduced. However, the combustion state becomes unstable, so that the emission amount of PM may increase. In addition, when the intake throttle valve 10 is opened, the amount of fresh air sucked into the engine 1 increases, and a stable combustion state is obtained, so that the combustion temperature rises and the PM amount of NOx increases. Emissions are reduced. On the other hand, by closing the intake throttle valve 10, the amount of fresh air sucked into the engine 1 decreases, and the combustion state becomes unstable, so that the combustion temperature decreases. Therefore, the emission amount of PM increases while the emission amount of NOx decreases. Further, by retarding the fuel injection timing, the amount of air-fuel mixture discharged without increasing the engine output increases, so that the temperature of the exhaust gas is raised. Also, the heat generated by the oxidation of unburned gas in the NOx storage reduction catalyst is generated. Thus, the temperature of the filter 16 can be increased. Further, since the atomization of the fuel is promoted by increasing the injection pressure of the fuel, the combustion temperature can be increased and the emission amount of PM can be reduced. In addition, the opening degree of the exhaust throttle valve 18 or the opening degree of the nozzle vane may be controlled when a variable displacement turbocharger is used as the turbocharger 15. Here, when the opening degree of the exhaust throttle valve 18 or the nozzle vane is controlled to the closing side, the recirculation amount of the EGR gas increases, so that the emission amount of PM increases and the emission amount of NOx decreases.
[0068]
The opening degree of the EGR valve 21, the opening degree of the intake throttle valve 10, the injection timing and amount of fuel injected from the fuel injection valve 3, the opening degree of the exhaust throttle valve 18, the opening degree of the nozzle vane, the filter temperature, The relationship between the engine speed and the engine load is obtained in advance through experiments or the like and mapped and stored in the ECU 22.
[0069]
Next, FIG. 4 is a time chart showing the relationship between the temperature of the filter 16 and the usage map. The ranges of (1) and (2) in the figure are regions in which operation control different from conventional engine operation control is performed. In FIG. 4, the vehicle is initially operated in a steady state or an idle state with a low load. In this case, since the temperature of the exhaust gas discharged from the engine 1 is low, the bed temperature of the filter 16 is low, and Map 1 in FIG. 3 is applied. Next, although the speed is gradually increased as the vehicle accelerates, the bed temperature of the filter 16 does not rise immediately. Accordingly, the map is not changed immediately after the vehicle starts accelerating, but is changed to Map 2 in FIG. 3 when the bed temperature of the filter 16 becomes, for example, 200 ° C. Next, when the bed temperature of the filter 16 becomes, for example, 300 ° C., the map is changed to the map 3 in FIG. Here, although the vehicle speed becomes constant, the bed temperature of the filter 16 continues to rise. Then, when the bed temperature of the filter 16 becomes, for example, 400 ° C., the map is changed to the map 4 in FIG. Then, although the vehicle is decelerated, the map 4 is continuously applied because the bed temperature of the filter 16 does not immediately decrease. When the vehicle is operated in a low load steady state or an idle state, and the floor temperature of the filter 16 is reduced to, for example, 400 ° C., the map is displayed on the map 3, the map is reduced to 300 ° C., the map is displayed on the map 2, It is changed to 1.
[0070]
Thus, operation control of the engine 1 based on the filter 16 bed temperature can be performed.
[0071]
As described above, according to the present embodiment, it is possible to change the operation control map based on the bed temperature of the filter 16 and perform the operation control of the engine 1 according to the PM emission amount and the NOx emission amount. Become.
[0072]
When the bed temperature of the filter is high, it is possible to perform operation control for reducing the emission amount of NOx, and to reduce the amount of fuel added for NOx reduction, thereby suppressing deterioration of fuel efficiency. When the bed temperature of the filter is low, the temperature of the filter can be raised by delaying the injection timing of the fuel injected from the fuel injection valve 3. Thereby, clogging of the filter can be suppressed.
<Second embodiment>
The exhaust gas purifying apparatus for an internal combustion engine according to the present embodiment is different from the first embodiment in that engine control is performed such that the amount of PM deposited on the filter 16 falls within a predetermined range. The basic configuration of the engine 1 and other hardware to which the present invention is applied is the same as that of the first embodiment, and a description thereof will be omitted.
[0073]
When PM accumulates on the filter 16, the PM itself functions as a filter. Therefore, if the amount of PM deposited on the filter 16 is small, the PM may pass through the filter 16 and the PM collection rate may be reduced.
[0074]
FIG. 5 is a diagram showing the relationship between the amount of accumulated PM and the trapping rate.
[0075]
In the low trapping rate region in FIG. 5, the trapping rate decreases because the amount of deposited PM is small. On the other hand, in the region where the PM oxidation rate is low, the amount of deposited PM is large, so that the oxidation rate of the PM is slowed, which may cause the filter to be clogged. There is a possibility that the filter may be deteriorated, and furthermore, the ventilation resistance of the filter 16 may increase and the engine output may decrease.
[0076]
Therefore, in the present embodiment, the engine control is performed so that the amount of deposited PM is in a range larger than the low trapping rate region in FIG.
[0077]
Next, FIG. 6 is a diagram showing a relationship between the bed temperature of the filter 16 and the amount of PM emission from the engine when performing engine control according to the present embodiment. Here, as the bed temperature of the filter 16 increases, the oxidation rate of PM increases, and the amount of PM collected by the filter 16 decreases. On the other hand, the lower the bed temperature of the filter 16 is, the slower the PM oxidation rate is. Therefore, it is necessary to reduce the amount of PM discharged from the engine 1.
[0078]
In the present embodiment, the operation control of the engine 1 is performed so that the PM emission amount falls within the PM emission amount control region in FIG. In this region, the upper limit of the PM emission amount is set so that the amount of the PM captured by the filter 16 that is oxidized and reduced is equal to the amount of the PM exhausted from the engine 1 (FIG. 6). Middle PM emission upper limit line). On the other hand, if the amount of PM discharged from the engine 1 is too small, the amount of deposited PM is reduced and the PM collection rate is reduced. (The lower limit line of PM emission in FIG. 6). Here, similarly to the first embodiment, the PM emission amount includes the opening degree of the EGR valve 21, the opening degree of the intake throttle valve 10, the injection timing and injection amount of the fuel injected from the fuel injection valve 3, It is controlled by the opening degree of the exhaust throttle valve 18, the opening degree of the nozzle vane, and the like.
[0079]
Since the oxidation rate of PM varies depending on the amount of PM deposited on the filter 16, the amount of PM deposited may be detected and the control range may be changed based on the detected value. That is, the oxidation rate of PM becomes slower as the amount of PM trapped by the filter 16 increases, and thus the control range is changed so that the amount of emitted PM decreases. The amount of PM trapped by the filter 16 is determined, for example, by attaching a differential pressure sensor (not shown) for detecting the differential pressure across the filter 16 to the exhaust pipe, and calculating the PM amount according to the detection value of the differential pressure sensor. It can be obtained by previously obtaining it by experiments or the like. Further, the PM emission amount according to the operation state may be obtained in advance through experiments or the like and mapped, and the PM emission amount obtained from the map may be integrated to obtain the PM accumulation amount. Further, the amount of accumulated PM may be estimated according to the traveling distance or traveling time of the vehicle.
[0080]
The oxidation rate of PM (or the amount of PM reduction) is obtained from the bed temperature of the filter 16, while the amount of PM discharged from the engine 1 is obtained, and the PM residual amount is calculated from these values to obtain the PM residual amount. May be controlled so as to fall within a predetermined range. The relationship between the bed temperature of the filter 16 and the PM oxidation rate (or the amount of PM reduction) can be obtained in advance by experiments or the like. The residual amount of PM can be obtained by integrating the PM reduction amount and the emission amount.
[0081]
Further, in the present embodiment, the mode in which engine control is performed in accordance with the amount of PM emitted from the engine has been described. Alternatively, the engine control in accordance with the collection rate of PM captured in filter 16 may be performed. May be performed. The PM collection rate can be determined based on the relationship in FIG. Here, the emission amount of PM is controlled so as not to enter the low trapping rate region and the oxidation rate decreasing region shown in FIG.
[0082]
As described above, according to the present embodiment, it is possible to suppress a decrease in the PM trapping rate due to a decrease in the PM deposited on the filter 16, and to suppress clogging and deterioration of the filter 16. .
<Third embodiment>
The present embodiment is different from the first and second embodiments in that engine operation control is performed according to the bed temperature of the filter 16 and the amount of PM deposited on the filter 16. The basic configuration of the engine 1 and other hardware to which the present invention is applied is the same as that of the first embodiment, and a description thereof will be omitted.
[0083]
In the first embodiment, the engine control map according to the bed temperature of the filter 16 is provided. In the present embodiment, the engine control map according to the bed temperature of the filter 16 and the amount of PM deposited on the filter 16 is used. It has a control map.
[0084]
When the amount of PM trapped in the filter 16 is small, the PM may pass through the filter 16 and the trapping rate decreases. Here, when the bed temperature of the filter 16 is high, the amount of PM trapped by the filter 16 decreases because the PM oxidation rate is high. On the other hand, when the amount of PM collected by the filter 16 increases, the filter 16 may be damaged or deteriorated by the heat generated during the oxidation reaction of the PM. In addition, when the amount of trapped PM increases, the ventilation resistance of the filter 16 increases and the engine output decreases.
[0085]
Here, in the same manner as in the first embodiment, the PM discharge amount is determined by the opening degree of the EGR valve 21, the opening degree of the intake throttle valve 10, the injection timing and the injection amount of the fuel injected from the fuel injection valve 3. , The opening degree of the exhaust throttle valve 18, the opening degree of the nozzle vane, and the like.
[0086]
Next, in the same manner as in the second embodiment, the amount of PM collected by the filter 16 is determined by attaching a differential pressure sensor (not shown) for detecting a differential pressure across the filter 16 to the exhaust pipe. The PM amount according to the detection value of the differential pressure sensor can be obtained by previously obtaining the amount of PM by an experiment or the like. Further, the PM emission amount according to the operation state may be obtained in advance through experiments or the like and mapped, and the PM emission amount obtained from the map may be integrated to obtain the PM accumulation amount. Further, the amount of accumulated PM may be estimated according to the traveling distance or traveling time of the vehicle.
[0087]
The opening degree of the EGR valve 21, the opening degree of the intake throttle valve 10, the injection timing and the injection amount of the fuel injected from the fuel injection valve 3, based on the PM accumulation amount, the bed temperature of the filter 16, the engine speed, and the engine load. A map for controlling the degree of opening of the exhaust throttle valve 18, the degree of opening of the nozzle vane, and the like is obtained in advance through experiments and the like and stored in the ECU 22. In this manner, the operation of the engine 1 is controlled based on the amount of accumulated PM, the bed temperature of the filter 16, the engine speed, and the engine load, and an optimal amount of accumulated PM can be maintained.
[0088]
Note that, in the present embodiment, similarly to the first embodiment, an engine control map corresponding to the bed temperature of the filter 16 is provided, and the map is corrected based on the amount of PM deposited on the filter 16. It is good.
[0089]
As described above, according to the present embodiment, it is possible to suppress a decrease in the PM trapping rate due to a decrease in PM deposited on the filter 16 and to suppress clogging and deterioration of the filter 16. Can be.
<Fourth embodiment>
In the present embodiment, as compared with the first embodiment, engine operation control is performed according to the bed temperature of the filter 16 and the amount of NOx stored in the storage-reduction type NOx catalyst carried on the filter 16. Different in that. The basic configuration of the engine 1 and other hardware to which the present invention is applied is the same as that of the first embodiment, and a description thereof will be omitted.
[0090]
In the first embodiment, the engine control map according to the bed temperature of the filter 16 is provided. However, in the present embodiment, the engine control map according to the bed temperature of the filter 16 is stored in the NOx storage reduction catalyst. Correction is made according to the amount of stored NOx.
[0091]
Here, the amount of NOx discharged from the engine increases as the amount of EGR gas decreases, as the amount of fresh air sucked into the engine increases, and as the fuel injection timing increases, and as the fuel injection pressure increases. Further, the air-fuel ratio in the cylinder increases near the stoichiometric air-fuel ratio. Therefore, when the amount of stored NOx increases and the amount of discharged NOx is reduced, the fuel is injected from the fuel injection valve 3 such that the opening of the EGR valve 21 is closed and the opening of the intake throttle valve 10 is opened. The engine control map controls the fuel injection timing to be advanced, the fuel injection pressure to be reduced, the injection amount to be near the stoichiometric air-fuel ratio, the exhaust throttle valve 18 to be open, and the nozzle vane to be open. Is corrected.
[0092]
The amount of NOx stored in the NOx storage reduction catalyst can be determined, for example, by attaching a NOx sensor to an exhaust pipe downstream of the filter 16 and detecting the amount of NOx detected by the NOx sensor. Further, the NOx emission amount according to the operation state may be obtained in advance through experiments or the like and mapped, and the NOx emission amount obtained from this map may be integrated to obtain the stored NOx amount. Further, the amount of stored NOx may be estimated according to the vehicle traveling distance or the traveling time.
[0093]
As described above, by correcting the engine control map, the NOx emission amount can be reduced, the amount of NOx stored in the NOx storage reduction catalyst increases, and NOx reduction cannot be performed. Even in this case, it is possible to suppress emission of NOx into the atmosphere. Further, addition of fuel for reducing NOx stored in the NOx storage reduction catalyst can be reduced, and fuel efficiency can be reduced.
[0094]
In the present embodiment, an engine control map may be provided for each bed temperature of the filter 16 and the amount of NOx stored in the NOx storage reduction catalyst.
[0095]
Further, the engine control may be performed by detecting the PM accumulation amount of the filter 16 and the NOx occlusion amount of the NOx storage reduction catalyst, and targeting either the PM or NOx emission amount. In general, the emission amount of NOx decreases as the emission amount of PM increases, and the emission amount of NOx increases as the emission amount of PM decreases. Here, depending on the state of the filter 16 or the operation state of the engine 1, the engine control may be performed by giving priority to either PM or NOx emission.
[0096]
As described above, according to the present embodiment, the operation control map is changed based on the bed temperature of the filter 16, and the operation control map is corrected based on the NOx storage amount, and the operation control map is changed according to the NOx storage amount. The operation control of the engine 1 can be performed.
[0097]
As a result, the amount of fuel added for NOx reduction can be reduced, and deterioration of fuel efficiency can be suppressed. Further, when the occlusion amount increases, the release of NOx into the atmosphere can be suppressed.
[0098]
【The invention's effect】
In the exhaust gas purification device for an internal combustion engine according to the present invention, the amount of particulate matter deposited on the filter can be maintained within a predetermined range, and a decrease in the trapping rate of particulate matter can be suppressed. Further, it is possible to suppress deterioration of the filter and occurrence of clogging.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of an engine according to a first embodiment and an intake / exhaust system thereof.
FIG. 2A is a diagram illustrating a cross section of a particulate filter in a lateral direction. (B) is a figure which shows the longitudinal cross section of a particulate filter.
FIG. 3 is a map for determining an engine operating condition from a rotation speed and a torque (load) for each temperature of a filter 16;
FIG. 4 is a time chart illustrating a relationship between a temperature of a filter 16 and a use map.
FIG. 5 is a diagram showing a relationship between a PM accumulation amount and a trapping rate.
FIG. 6 is a diagram illustrating a relationship between a filter bed temperature and a PM emission amount from an engine when engine control according to a second embodiment is performed.
[Explanation of symbols]
1. Engine
1a ... Crank pulley
1b ... exhaust port
2 .... cylinder
3 ... Fuel injection valve
4 .... Common rail
5. Fuel supply pipe
6. Fuel pump
6a: Pump pulley
7 ··· Belt
8. Intake branch pipe
9 ··· Intake pipe
10 ... intake throttle valve
11 Actuator for intake throttle
12 ・ ・ ・ Air flow meter
13 ・ ・ ・ Exhaust branch pipe
14 ・ ・ ・ Exhaust pipe
15 ・ ・ ・ Turbocharger
16 ... Particulate filter
17 ・ ・ ・ Exhaust gas temperature sensor
18 Exhaust throttle valve
19 ・ ・ ・ Actuator for exhaust throttle
20 EGR passage
21 ・ ・ ・ EGR valve
22 ... ECU
23 ・ ・ ・ Reducing agent injection valve
24 ... Reducing agent supply path

Claims (8)

A particulate filter carrying a catalyst having an oxidizing ability and capable of temporarily collecting particulate matter contained in exhaust gas from an internal combustion engine;
Filter temperature detecting means for detecting the temperature of the particulate filter,
Operating state detecting means for detecting an engine operating state;
Engine control means for controlling the operation of the internal combustion engine based on the detection value of the filter temperature detection means and the detection value of the operating state detection means,
An exhaust gas purifying apparatus for an internal combustion engine, comprising: The operating state detecting means detects a load state of the engine and a rotation speed of the engine,
2. The control map according to claim 1, further comprising a plurality of control maps for controlling the operation of the internal combustion engine based on a load state of the engine and a rotation speed of the engine, the control maps having different control values with respect to the temperature of the filter. Exhaust purification device for internal combustion engine. The internal combustion engine according to claim 1 or 2, wherein the engine control means controls the operation of the engine such that the lower the temperature detected by the filter temperature detection means, the smaller the amount of particulate matter emitted. Engine exhaust purification device. Particulate matter remaining in the filter from the temperature detected by the filter temperature detecting means, the oxidation rate of the particulate matter collected by the filter at that temperature, and the amount of the particulate matter discharged from the internal combustion engine The engine control means further comprises: a residual amount estimating means for obtaining the amount of the particulate matter, wherein the engine control means comprises: The exhaust gas purifying apparatus for an internal combustion engine according to any one of claims 1 to 3, wherein Accumulation amount detection means for detecting the amount of particulate matter accumulated in the particulate filter,
Means for correcting the control value of the engine control means so that the emission amount of the particulate matter decreases as the amount of accumulation detected by the accumulation amount detection means increases,
The exhaust gas purification device for an internal combustion engine according to any one of claims 1 to 4, further comprising: A particulate filter carrying a catalyst having an oxidizing ability and capable of temporarily collecting particulate matter contained in exhaust gas from an internal combustion engine;
Accumulation amount detection means for detecting the amount of particulate matter accumulated in the particulate filter,
Collection rate estimation means for estimating the collection rate of particulate matter at that time from the detection value of the accumulation amount detection means,
Engine control means for controlling the operation of the internal combustion engine based on the estimated value by the collection rate estimation means,
An exhaust gas purifying apparatus for an internal combustion engine, comprising: 7. The internal combustion engine according to claim 6, wherein the engine control means controls the operation of the engine such that the trapping rate of the particulate matter estimated by the trapping rate estimating means is within a predetermined range. Engine exhaust purification device. The particulate filter supports an NOx storage reduction catalyst,
NOx storage amount estimation means for estimating the amount of NOx stored in the storage reduction type NOx catalyst;
Means for correcting the control value of the engine control means such that the larger the NOx storage amount estimated by the NOx storage amount estimation means, the smaller the NOx emission amount;
The exhaust gas purification apparatus for an internal combustion engine according to any one of claims 1 to 7, further comprising:

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