JP4259068B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust emission control 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 diesel engine exhaust, has become an important issue. For this reason, a technique of providing a particulate filter (hereinafter simply referred to as “filter”) for collecting PM in an exhaust system so that PM is not released into the atmosphere is known.
[0003]
This filter can prevent PM in the exhaust gas from being collected once and released into the atmosphere. However, when PM collected by the filter accumulates on the filter, the filter may be clogged. If this clogging occurs, the pressure of the exhaust gas upstream of the filter may increase, leading to a decrease in the output of the internal combustion engine and damage to the filter. In such a case, the PM deposited on the filter can be removed by igniting and burning. The removal of PM deposited on the filter in this way is called filter regeneration.
[0004]
For example, Japanese Patent Laid-Open No. 9-94434 discloses a wall flow type filter in which a catalyst is thinly and uniformly supported in pores formed inside the partition walls between cells, and PM can be burned and removed inside the pores inside the partition walls. ing.
[0005]
[Problems to be solved by the invention]
By the way, the PM collected by the filter itself serves as a filter, and the collection rate of PM in the exhaust gas increases as the amount of collected PM increases. Accordingly, when the amount of PM accumulated on the filter is reduced by regenerating the filter, the PM collection rate may decrease.
[0006]
This invention is made | formed in view of the above problems, and it aims at providing the technique which can regenerate | regenerate a filter, maintaining the collection rate of PM by a filter.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the exhaust gas purification apparatus for an internal combustion engine of the present invention employs the following means. That is, the first invention is
A particulate filter carrying a catalyst having oxidizing ability and capable of temporarily collecting particulate matter contained in exhaust from an internal combustion engine;
Filter temperature detecting means for detecting the temperature of the particulate filter;
An 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 providing.
[0008]
The greatest 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 kept appropriate.
[0009]
Particulate matter collected in the filter can be removed by oxidation, but the oxidation rate at this time depends on the temperature of the filter (bed temperature), and the higher the temperature, the faster the oxidation rate. . Therefore, when the internal combustion engine is operated at a high rotation and high load, the oxidation rate of the particulate matter in the filter is faster than the amount of 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 requires a certain amount of time. Therefore, the filter temperature may be low even when the engine load is large, while the filter temperature may be high even when the engine load is small. Here, when the temperature of the filter is high, since the oxidation rate of the particulate matter is high, the particulate matter can be oxidized even if the amount of the particulate matter discharged from the engine is large. Therefore, if the engine operation is controlled based on the temperature of the filter and the amount of particulate matter discharged is controlled, the amount of particulate matter that accumulates on the filter can be controlled. It is possible to suppress a decrease in rate.
[0010]
In the present invention, the operating state detection means detects the engine load state and the engine speed,
A control map for controlling the operation of the internal combustion engine based on the engine load state and the engine speed may further include a plurality of control maps having different control values with respect to the filter temperature.
[0011]
By providing a plurality of control maps that differ depending on the filter temperature, it is possible to control the operation of the internal combustion engine based on the filter temperature.
[0012]
  In the present invention, the engine control means controls the operation of the engine so that the lower the temperature detected by the filter temperature detection means, the smaller the amount of particulate matter discharged.The
[0013]
When the temperature of the filter is low, the particulate matter is oxidized at a low rate. Therefore, the filter can be prevented from being clogged by setting the operation state so that the amount of particulate matter discharged is reduced.
[0014]
In the present invention, the filter detects 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. Residual amount estimation means for obtaining the amount of residual particulate matter is further provided, and the engine control means is discharged from the engine so that the amount of particulate matter estimated by the residual amount estimation means falls within a predetermined range. The amount of particulate matter can be controlled.
[0015]
When 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 particulate matter discharged from the internal combustion engine, it becomes possible to keep the increase or decrease in the amount of particulate matter deposited on the filter within a predetermined range, thereby increasing the particulate matter collection rate. 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 amount of particulate matter discharged decreases as the amount of accumulation detected by the accumulation amount detection means increases;
Can be further provided.
[0017]
When the amount of the particulate matter collected by the filter increases, the filter may be clogged. In addition, the filter may be deteriorated by heat generated when the accumulated particulate matter is oxidized. Therefore, it is possible to suppress clogging and deterioration of the filter by controlling the engine so that the discharge amount of the particulate matter decreases as the amount of the particulate matter collected by the filter increases.
[0018]
In order to achieve the above object, the exhaust gas purification apparatus for an internal combustion engine of the present invention employs the following means. That is, the second invention is
A particulate filter carrying a catalyst having oxidizing ability and capable of temporarily collecting particulate matter contained in exhaust from an internal combustion engine;
A deposition amount detecting means for detecting the amount of particulate matter deposited on the particulate filter;
A collection rate estimating 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 estimating means;
It is characterized by providing.
[0019]
The greatest feature of the present invention is to adjust the amount of particulate matter discharged from the engine based on the collection rate of the particulate matter filter, and to keep the amount of particulate matter deposited on the filter appropriate. .
[0020]
Of particulate matter in the exhaust gas, the rate of particulate matter that can be collected by the filter (collection rate) varies depending on the amount of particulate matter deposited on the filter. The collection 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 or deterioration of the filter is induced. Therefore, if the operation of the engine is controlled based on the particulate matter collection rate in the filter and the amount of particulate matter discharged is controlled, the amount of particulate matter deposited on the filter can be controlled. It is possible to suppress the clogging and the decrease in the collection rate.
[0021]
In the present invention, the engine control means can control the operation of the engine so that the collection rate of the particulate matter estimated by the collection rate estimation 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, it becomes possible to suppress clogging and deterioration of the filter by reducing the discharge amount of the particulate matter. On the other hand, when the collection 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 discharged from the engine, and to maintain the collection rate within a predetermined range. It becomes possible.
[0023]
In the first and second inventions, the particulate filter carries an NOx storage reduction catalyst,
NOx occlusion amount estimation means for estimating the NOx amount occluded in the NOx storage reduction catalyst;
Means for correcting the control value of the engine control means so that the larger the NOx occlusion amount estimated by the NOx occlusion amount estimation means, the smaller the NOx emission amount;
Can further be provided.
[0024]
There is a limit to the amount of NOx that can be stored in the NOx storage reduction catalyst. Therefore, when the stored amount of NOx increases, it becomes possible to suppress the release of NOx into the atmosphere by reducing the amount of NOx discharged from the engine.
[0025]
DETAILED DESCRIPTION OF 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, the case where the internal combustion engine according to the present invention is applied to a diesel engine for driving a vehicle will be described as an example.
[0026]
FIG. 1 is a diagram showing a schematic configuration of an engine and its intake / exhaust system according to the present embodiment.
[0027]
An 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 that injects fuel directly into the combustion chamber of each cylinder 2. Each fuel injection valve 3 is connected to a pressure accumulation chamber (common rail) 4 that accumulates fuel to a predetermined pressure.
[0029]
The common rail 4 communicates with a fuel pump 6 through a fuel supply pipe 5. This fuel pump 6 is a pump that operates using the rotational torque of the output shaft (crankshaft) of the engine 1 as a drive source, and a pump pulley 6 a attached to the input shaft of the fuel pump 6 is connected to the output shaft (crankshaft) of the engine 1. ) And the belt pulley 7 are connected to each other.
[0030]
In the fuel injection system configured as described above, when the rotational torque of the crankshaft is transmitted to the input shaft of the fuel pump 6, the fuel pump 6 transmits the rotational torque transmitted from the crankshaft to the input shaft of the fuel pump 6. The fuel is discharged at a pressure according to the pressure.
[0031]
The fuel discharged from the fuel pump 6 is supplied to the common rail 4 via the fuel supply pipe 5, accumulated in the common rail 4 up 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 through 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 the heat energy of the exhaust as a drive source is provided in the middle of the intake pipe 9. An intake throttle valve 10 for adjusting the flow rate of the 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 that is configured by a step motor or the like and that opens and closes the intake throttle valve 10. An air flow meter 12 that outputs an electrical signal corresponding to the mass of the 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 15 a via the intake pipe 9.
[0035]
The intake air flowing into the compressor housing 15a is compressed by the rotation of the compressor wheel built in the compressor housing 15a, and then flows into the intake branch pipe 8. The intake air that has flowed into the intake branch pipe 8 is distributed to the combustion chambers of the respective cylinders 2 through the respective branch pipes, and is burned using the fuel injected from the fuel injection valves 3 of the respective cylinders 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 1b.
[0037]
The exhaust branch pipe 13 is connected to a turbine housing 15 b 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]
A particulate filter (hereinafter simply referred to as a filter) 16 is provided in the middle of the exhaust pipe 14 for supporting the NOx storage reduction catalyst and collecting PM in the exhaust.
[0039]
Here, the filter 16 according to the present embodiment will be described.
[0040]
FIG. 2 is a cross-sectional view of the filter 16. FIG. 2A is a diagram illustrating a cross section in the horizontal direction of the filter 16. FIG. 2B is a view showing a longitudinal 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 flow passages 50 and 51 extending in parallel with each other. These exhaust flow passages include 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 four exhaust outflow passages 51 and each exhaust outflow passage 51 is surrounded by four exhaust inflow passages 50.
[0042]
The filter 16 is made of a porous material such as cordierite, so that the exhaust gas flowing into the exhaust inflow passage 50 is adjacent to the surrounding partition wall 54 as indicated by an arrow in FIG. To the exhaust outlet passage 51.
[0043]
In this embodiment, a carrier layer made of alumina, for example, is formed on the peripheral wall surfaces of the exhaust inflow passages 50 and the exhaust outflow passages 51, that is, on both side surfaces of the partition walls 54 and on the inner wall surfaces of the pores in the partition walls 54. The NOx storage reduction catalyst is supported on the carrier.
[0044]
The filter 16 uses, 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). ), An alkaline earth such as lanthanum (La) or yttrium (Y), and a noble metal such as platinum (Pt). In the present embodiment, an occlusion reduction type NOx catalyst (hereinafter simply referred to as NOx catalyst) configured by supporting barium (Ba) and platinum (Pt) on a support made of alumina is employed. In addition, O₂Ceria with storage capability (Ce₂O_Three) May be added.
[0045]
The thus configured NOx catalyst occludes nitrogen oxide (NOx) in the exhaust when the oxygen concentration of the exhaust flowing into the NOx catalyst is high.
[0046]
On the other hand, the NOx catalyst releases the stored nitrogen oxide (NOx) when the oxygen concentration of the exhaust gas flowing into the NOx catalyst decreases. At that time, if a reducing component such as hydrocarbon (HC) or carbon monoxide (CO) is present in the exhaust, the NOx catalyst converts nitrogen oxide (NOx) released from the NOx catalyst to nitrogen (N₂).
[0047]
An exhaust temperature sensor 17 that outputs an electrical signal corresponding to the temperature of the exhaust gas 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 this temperature.
[0048]
The exhaust pipe 14 downstream of the filter 16 is provided with an exhaust throttle valve 18 that adjusts the flow rate of the exhaust gas flowing through the exhaust pipe 14. The exhaust throttle valve 18 is provided with an exhaust throttle actuator 19 that is configured by a step motor or the like and that drives the exhaust throttle valve 18 to open and close.
[0049]
In the exhaust system configured as described above, the air-fuel mixture (burned gas) combusted 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 flows into the turbine housing 15b. The exhaust gas flowing into the turbine housing 15b rotates the turbine wheel rotatably supported in the turbine housing 15b using the energy of the exhaust gas. At that time, the rotational torque of the turbine wheel is transmitted to the compressor wheel of the compressor housing 15a described above.
[0050]
Exhaust gas discharged from the turbine housing 15b flows into the filter 16 through the exhaust pipe 14, PM in the exhaust gas is collected, and harmful gas components are removed or purified, and then released into the atmosphere through the muffler. Is done.
[0051]
Further, the exhaust branch pipe 13 and the intake branch pipe 8 serve as an exhaust gas recirculation passage (hereinafter referred to as an EGR passage) 20 for recirculating a part of the exhaust gas flowing through the exhaust branch pipe 13 to the intake branch pipe 8. It is communicated through. In the middle of the EGR passage 20, a flow rate adjusting valve that 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 applied power. (Hereinafter referred to as 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 becomes conductive, and a part of the exhaust gas flowing through the exhaust branch pipe 13 is sucked through the EGR passage 20. It is guided 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 side of the intake branch pipe 8.
[0054]
The engine 1 configured as described above is provided with an electronic control unit (ECU) 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 the driver's request.
[0055]
Various sensors are connected to the ECU 22 via electrical 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, the reducing agent injection valve 23, which will be described later, and the like, and these can be controlled. It is possible. The ECU 22 stores various application programs and various control maps.
[0056]
In the present embodiment, 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 from the filter 16 is provided, 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 decreased and the concentration of the reducing agent is increased.
[0057]
As shown in FIG. 1, the reducing agent supply mechanism is mounted so that its injection hole faces the exhaust port 1b or the exhaust branch pipe 13, and is opened by a signal from the ECU 22 to inject fuel. A valve 23 and a reducing agent supply path 24 that guides the fuel discharged from the fuel pump 6 to the reducing agent injection valve 23 are provided.
[0058]
In such a reducing agent supply mechanism, 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 1b or the exhaust branch pipe 13 reduces the oxygen concentration of the exhaust gas flowing from the upstream side of the exhaust branch pipe 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]
As a result of supplying the reducing agent to the filter 16 in this way, the oxygen concentration of the exhaust gas flowing into the filter 16 changes in a relatively short cycle. Then, the active oxygen is released by the fuel that has flowed into the filter 16, so that the PM is easily oxidized and the oxidizable removal amount per unit time is improved. Further, the addition of fuel removes oxygen poisoning of the catalyst and increases the activity of the catalyst, so that active oxygen is easily released. Furthermore, the temperature of the filter 16 rises due to the oxidation reaction of the fuel. Then, PM is oxidized and burned by active oxygen and removed. The exhaust gas having a low oxygen concentration flowing into the filter 16 reduces nitrogen oxide (NOx) stored in the filter 16.
[0062]
Here, when the amount of collected PM increases, the filter 16 serves as a filter and the collection rate is improved. Therefore, if the regeneration of the filter 16 is performed to remove all the PM collected by the filter 16, the PM collection rate may decrease.
[0063]
By the way, when the operating state of the engine changes, the temperature of the exhaust gas changes, and the temperature of the filter 16 changes in accordance with the change in the exhaust gas temperature. At this time, since the temperature of the filter 16 gradually changes, a certain amount of time is required until the temperature of the filter 16 corresponds to the engine operating state. If the engine operation control is performed based only on the engine operation state while the temperature is changing as described above, PM may be accumulated on the filter 16 more than necessary or PM may be removed more than necessary. It was.
[0064]
For example, in a conventional engine, the filter 16 is at a low temperature during low-load operation, so that the PM oxidation rate is slowed down, and operation control is performed to reduce the PM emission amount to suppress clogging of the filter 16. It was. However, when shifting to low load operation after high load operation continues, the temperature of the filter 16 is still high, so the PM oxidation rate is fast. Therefore, it is not necessary to perform operation control that reduces the amount of PM emission as described above. Further, since the PM emission amount and the NOx emission amount are in an inversely proportional relationship, the operation control for reducing the NOx emission amount is performed without performing the operation control for reducing the PM emission amount. Further, the addition of fuel for reducing NOx stored in the NOx storage reduction catalyst can be reduced, and fuel consumption can be reduced.
[0065]
On the other hand, when shifting to the high load operation state after the low load operation continues, the temperature of the filter 16 is still low, so the PM oxidation rate is slow. Therefore, when the PM emission amount is large, the filter 16 is clogged. For this reason, the clogging of the filter 16 can be suppressed by performing the operation control that promptly increases the temperature of the filter 16.
[0066]
FIG. 3 is a map for determining engine operating conditions from the rotational speed and torque (load) for each temperature of the filter 16. For example, when the bed temperature of the filter 16 is lower than 200 ° C., the map 1 is used, for example, when the temperature is 200 ° C. or higher and lower than 300 ° C., the map 2 is used, and when the bed temperature is 300 ° C. or higher and lower than 400 ° C. For example, when the temperature is 400 ° C. or higher, map 4 is used.
[0067]
With this map, 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 are controlled, and the engine 1 is operated. Here, when the EGR valve 21 is opened, the EGR amount sucked into the engine 1 increases, and when the EGR valve 21 is closed, the EGR amount sucked into the engine 1 decreases. Since the EGR gas lowers the combustion temperature in the cylinder 2, it can reduce the NOx emission amount, but the combustion state becomes unstable, which may increase the PM emission amount. Further, when the intake throttle valve 10 is opened, the amount of fresh air sucked into the engine 1 is increased, and a stable combustion state is obtained, so that the combustion temperature rises and the NOx emission amount increases, but PM Emissions will decrease. On the other hand, closing the intake throttle valve 10 reduces the amount of fresh air taken into the engine 1 and makes the combustion state unstable, so that the combustion temperature decreases. Therefore, although the NOx emission amount decreases, the PM emission amount increases. Further, by retarding the fuel injection timing, the air-fuel mixture discharged without increasing the engine output increases, so that the temperature of the exhaust gas rises, and the heat generated by the oxidation of unburned gas in the NOx storage reduction catalyst As a result, the temperature of the filter 16 can be increased. Further, since the atomization of the fuel is promoted by increasing the fuel injection pressure, the combustion temperature can be increased and the PM emission amount can be decreased. In addition, the opening degree of the exhaust throttle valve 18 or the opening degree of the nozzle vane when a variable displacement turbocharger is used as the turbocharger 15 may be controlled. Here, when the opening degree of the exhaust throttle valve 18 or the nozzle vane is controlled to the closed side, the recirculation amount of the EGR gas increases, so that the PM discharge amount increases and the NOx discharge amount decreases.
[0068]
The opening degree of the EGR valve 21, the opening degree of the intake throttle valve 10, the injection timing and injection 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 and the filter temperature, The relationship between the engine speed and the engine load is obtained in advance by experiments or the like and mapped 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 range of (1) and (2) in the figure is a region where operation control different from conventional engine operation control is performed. In FIG. 4, the vehicle is first operated in a steady state or an idle state with a low load. In this case, since the temperature of the exhaust discharged from the engine 1 is low, the floor temperature of the filter 16 is low, and the map 1 in FIG. 3 is applied. Next, although the speed of the vehicle gradually increases as the vehicle accelerates, the bed temperature of the filter 16 does not rise immediately. Therefore, the map is not changed immediately after the vehicle starts accelerating, and is changed to the map 2 in FIG. 3 when the bed temperature of the filter 16 becomes 200 ° C., for example. Next, when the bed temperature of the filter 16 becomes 300 ° C., for example, the map 16 in FIG. 3 is changed. Here, although the vehicle speed is constant, the floor temperature of the filter 16 continues to rise. Then, when the floor temperature of the filter 16 becomes 400 ° C., for example, the map 16 in FIG. 3 is changed. Thereafter, the vehicle is decelerated, but the floor temperature of the filter 16 does not decrease immediately, so the map 4 is continuously applied. When the vehicle is operated in a low-load steady state or in an idle state and the floor temperature of the filter 16 is lowered to, for example, 400 ° C., the map 3 is displayed. 1 is changed.
[0070]
In this way, it is possible to control the operation of the engine 1 based on the filter 16 bed temperature.
[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 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 NOx emission amount, and to reduce the amount of fuel added for NOx reduction, thereby suppressing deterioration of fuel consumption. Further, when the floor temperature of the filter is low, the temperature of the filter can be raised by retarding 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 purification apparatus for an internal combustion engine according to the present embodiment is different from the first embodiment in that the engine control is performed so that the amount of PM deposited on the filter 16 is within a predetermined range. Note that the basic configuration of the engine 1 and other hardware to be applied is the same as that of the first embodiment, and thus description thereof is omitted.
[0073]
When PM accumulates on the filter 16, the PM itself serves as a filter. Therefore, if the amount of PM deposited on the filter 16 is small, PM may pass through the filter 16 and the PM collection rate may be lowered.
[0074]
FIG. 5 is a diagram showing the relationship between the amount of PM deposited and the collection rate.
[0075]
In the low collection rate region in FIG. 5, the collection rate decreases because the amount of PM deposited is small. On the other hand, in the PM oxidation rate lowering region, since the amount of PM deposited is large, the PM oxidation rate becomes slow and the filter may be clogged, or the filter 16 may be melted or damaged by the heat generated during the PM oxidation reaction. There is a possibility that the engine output deteriorates, or the ventilation resistance of the filter 16 increases and the engine output may decrease.
[0076]
Therefore, in the present embodiment, engine control is performed so that the amount of accumulated PM is within a range that is greater than the low collection rate region in FIG. 5 and less than the PM oxidation rate decrease region.
[0077]
Next, FIG. 6 is a diagram showing the relationship between the bed temperature of the filter 16 and the PM emission from the engine when engine control according to the present embodiment is performed. Here, as the bed temperature of the filter 16 increases, the oxidation rate of PM increases, and the amount of PM trapped in the filter 16 decreases. On the other hand, since the oxidation rate of PM becomes slower as the bed temperature of the filter 16 becomes lower, it is necessary to reduce the PM emission amount 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 PM collected by the filter 16 is reduced by oxidation and the amount of PM discharged from the engine 1 is the same amount (FIG. 6). The upper limit PM emission line). On the other hand, if the amount of PM discharged from the engine 1 becomes too small, the amount of accumulated PM will decrease and the PM collection rate will decrease. (PM lower limit line in FIG. 6). Here, the PM emission amount is the same as that in the first embodiment, 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, It is controlled by the opening degree of the exhaust throttle valve 18 and the opening degree of the nozzle vane.
[0079]
Since the PM oxidation rate varies depending on the amount of PM deposited on the filter 16, the PM deposition amount may be detected and the control range may be changed based on this detected value. That is, as the amount of PM collected by the filter 16 increases, the PM oxidation rate becomes slower, so the control range is changed so that the amount of PM emission decreases. The amount of PM collected by the filter 16 is obtained by, for example, attaching a differential pressure sensor (not shown) for detecting the differential pressure before and after the filter 16 to the exhaust pipe, and determining the PM amount according to the detected value of the differential pressure sensor. It can be obtained by obtaining in advance by experiments or the like. Further, the PM emission amount corresponding to the operation state can be obtained in advance by experiments or the like and mapped, and the PM emission amount obtained from this map can be integrated to obtain the PM accumulation amount. Furthermore, the PM accumulation amount may be estimated according to the vehicle travel distance or travel time.
[0080]
The PM oxidation rate (or PM reduction amount) is obtained from the bed temperature of the filter 16, while the PM amount discharged from the engine 1 is obtained, and the PM residual amount is calculated from these values to obtain the PM residual amount. The engine 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 PM reduction amount) can be obtained in advance by experiments or the like. The PM residual amount can be obtained by integrating the PM reduction amount and the discharge amount.
[0081]
In the present embodiment, the aspect of performing the engine control according to the PM emission amount from the engine has been described. Instead, the engine control according to the PM collection rate collected by the filter 16 is performed. May be performed. The PM collection rate can be obtained based on the relationship shown in FIG. Here, the PM emission amount is controlled so as not to enter the low collection rate region and the oxidation rate reduction region shown in FIG.
[0082]
As described above, according to the present embodiment, it is possible to suppress a decrease in the collection rate of PM due to a decrease in PM accumulated on the filter 16, and it is possible 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 accumulated on the filter 16. Note that the basic configuration of the engine 1 and other hardware to be applied is the same as that of the first embodiment, and thus description thereof is omitted.
[0083]
In the first embodiment, the engine control map corresponding to the bed temperature of the filter 16 is provided. However, in this embodiment, the engine corresponding to the bed temperature of the filter 16 and the amount of PM deposited on the filter 16 is used. Has a control map.
[0084]
When the amount of PM collected by the filter 16 is small, the PM may pass through the filter 16 and the collection rate becomes low. Here, when the bed temperature of the filter 16 is high, since the oxidation rate of PM is fast, the amount of PM collected in the filter 16 is reduced. On the other hand, when the amount of PM collected by the filter 16 increases, the filter 16 may be melted or deteriorated by heat generated during the oxidation reaction of PM. Further, when the amount of collected PM increases, the ventilation resistance of the filter 16 increases and the engine output decreases.
[0085]
Here, in the same way as in the first embodiment, the PM discharge amount is 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. It is controlled by the opening degree of the exhaust throttle valve 18 and the opening degree of the nozzle vane.
[0086]
Next, the amount of PM collected by the filter 16 is set in the same manner as in the second embodiment by attaching a differential pressure sensor (not shown) for detecting the differential pressure before and after the filter 16 to the exhaust pipe. The amount of PM corresponding to the detection value of the differential pressure sensor can be obtained in advance through experiments or the like. Further, the PM emission amount corresponding to the operation state can be obtained in advance by experiments or the like and mapped, and the PM emission amount obtained from this map can be integrated to obtain the PM accumulation amount. Furthermore, the PM accumulation amount may be estimated according to the vehicle travel distance or travel time.
[0087]
The opening amount of the EGR valve 21, the opening amount of the intake throttle valve 10, the injection timing and the injection amount of fuel injected from the fuel injection valve 3, depending on the PM accumulation amount, the bed temperature of the filter 16, the engine speed, and the engine load. A map for controlling the opening degree of the exhaust throttle valve 18 and the opening degree of the nozzle vane is obtained in advance through experiments or the like and stored in the ECU 22. In this way, it is possible to control the operation of the engine 1 from the PM accumulation amount, the bed temperature of the filter 16, the engine speed, and the engine load, and maintain the optimum PM accumulation amount.
[0088]
In the present embodiment, as in 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 accumulated in the filter 16. It is also good.
[0089]
As described above, according to the present embodiment, it is possible to suppress a decrease in the collection rate of PM due to a decrease in PM accumulated on the filter 16 and to suppress clogging and deterioration of the filter 16. Can do.
<Fourth embodiment>
In the present embodiment, compared with the first embodiment, engine operation control is performed according to the bed temperature of the filter 16 and the amount of NOx occluded in the NOx storage reduction catalyst supported on the filter 16. It is different in point. Note that the basic configuration of the engine 1 and other hardware to be applied is the same as that of the first embodiment, and thus description thereof is omitted.
[0090]
In the first embodiment, the engine control map corresponding to the bed temperature of the filter 16 is provided. However, in this embodiment, the engine control map corresponding to the bed temperature of the filter 16 is used as the NOx storage reduction catalyst. Correction is made according to the amount of NOx occluded.
[0091]
Here, the amount of NOx discharged from the engine increases as the EGR gas amount decreases, the fresh air amount sucked into the engine increases, and the fuel injection timing increases, so that the fuel injection pressure increases. Further, the air-fuel ratio in the cylinder increases near the stoichiometric air-fuel ratio. Accordingly, when the NOx occlusion amount increases and the NOx emission amount is reduced, the opening of the EGR valve 21 is injected from the fuel injection valve 3 to the closed side and the opening of the intake throttle valve 10 to the open side. Engine control map to control the fuel injection timing to the advance side, the fuel injection pressure to the pressure reduction side, the injection amount to the theoretical air-fuel ratio side, the exhaust throttle valve 18 to the open side, and the nozzle vane to the open side Correct.
[0092]
The amount of NOx occluded in the NOx storage reduction catalyst can be obtained from the amount of NOx detected by an NOx sensor attached to the exhaust pipe downstream of the filter 16, for example. Further, the NOx emission amount corresponding to the operation state can be obtained in advance by experiments or the like and mapped, and the NOx emission amount obtained from this map can be integrated to obtain the stored NOx amount. Furthermore, the amount of stored NOx may be estimated according to the vehicle travel distance or travel time.
[0093]
As described above, when the engine control map is corrected, 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 so, it is possible to suppress the release of NOx into the atmosphere. Further, the addition of fuel for reducing NOx stored in the NOx storage reduction catalyst can be reduced, and fuel consumption 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 PM accumulation amount of the filter 16 and the NOx occlusion amount of the NOx storage reduction catalyst may be detected, respectively, and engine control may be performed with either PM or NOx emission amount as a target. In general, if the PM emission amount increases, the NOx emission amount decreases, and if the PM emission amount decreases, the NOx emission amount increases. Here, depending on the state of the filter 16 or the operating state of the engine 1, either PM or NOx emission may be prioritized and engine control may be performed.
[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 storage amount of NOx, according to the NOx storage amount. It is possible to control the operation of the engine 1.
[0097]
Thereby, the fuel addition amount for NOx reduction can be reduced and deterioration of fuel consumption can be suppressed. Further, when the amount of occlusion increases, the release of NOx into the atmosphere can be suppressed.
[0098]
【The invention's effect】
In the exhaust gas purification apparatus for an internal combustion engine according to the present invention, the amount of the particulate matter deposited on the filter can be maintained within a predetermined range, and a decrease in the collection rate of the particulate matter can be suppressed. In addition, the deterioration of the filter and the occurrence of clogging can be suppressed.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of an engine and an intake / exhaust system thereof according to a first embodiment.
FIG. 2A is a diagram showing a transverse cross section of a particulate filter. (B) is a figure which shows the longitudinal direction cross section of a particulate filter.
FIG. 3 is a map for determining engine operating conditions from the rotation speed and torque (load) for each temperature of the filter 16;
FIG. 4 is a time chart showing the relationship between the temperature of the filter 16 and a usage map.
FIG. 5 is a graph showing the relationship between the amount of PM deposited and the collection rate.
FIG. 6 is a diagram showing the relationship between the filter bed temperature and the PM emission amount from the engine when engine control according to the 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 ... Intake throttle actuator
12 ... Air flow meter
13 ... Exhaust branch pipe
14 ... Exhaust pipe
15 ... Turbocharger
16 ... Particulate filter
17 ... Exhaust temperature sensor
18 ... Exhaust throttle valve
19 ... Exhaust throttle actuator
20 ... EGR passage
21 ... EGR valve
22 ... ECU
23 ... Reducing agent injection valve
24 ... Reducing agent supply path

Claims (7)

A particulate filter carrying a catalyst having oxidizing ability and capable of temporarily collecting particulate matter contained in exhaust from an internal combustion engine;
Filter temperature detecting means for detecting the temperature of the particulate filter;
An 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;
Wherein the engine control unit, an exhaust gas purification for an internal combustion engine, characterized that you control the operation of the engine as emissions decreases enough particulate matter is low the temperature detected by the filter temperature detection means apparatus. The operating state detecting means detects the load state of the engine and the engine speed,
The control map for controlling the operation of the internal combustion engine based on the engine load state and the engine speed, further comprising a plurality of control maps having different control values with respect to the temperature of the filter. An exhaust purification device for an internal combustion engine. 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 the temperature, and the amount of particulate matter discharged from the internal combustion engine A residual amount estimating means for determining the amount of particulate matter, and the engine control means is configured to reduce the amount of particulate matter discharged from the engine so that the amount of particulate matter estimated by the residual amount estimating means is within a predetermined range. The exhaust emission control device for an internal combustion engine according to claim 1 or 2 , wherein A deposition amount detecting 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 amount of particulate matter discharged decreases as the amount of accumulation detected by the accumulation amount detection means increases;
The exhaust emission control device for an internal combustion engine according to any one of claims 1 to 3 , further comprising: A particulate filter carrying a catalyst having oxidizing ability and capable of temporarily collecting particulate matter contained in exhaust from an internal combustion engine;
A deposition amount detecting means for detecting the amount of particulate matter deposited on the particulate filter;
A collection rate estimating 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 estimating means;
An exhaust emission control device for an internal combustion engine, comprising: The engine control means according to claim 5, the collection rate of particulate matter estimated by said collection rate estimation Teite stage and controls the operation of the engine to be within a predetermined range An exhaust purification device for an internal combustion engine. The particulate filter carries an NOx storage reduction catalyst,
NOx occlusion amount estimation means for estimating the NOx amount occluded in the NOx storage reduction catalyst;
Means for correcting the control value of the engine control means such that the larger the NOx occlusion amount estimated by the NOx occlusion amount estimation means, the smaller the NOx emission amount;
The exhaust emission control device for an internal combustion engine according to any one of claims 1 to 6 , further comprising:

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