JP3646635B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an exhaust gas purification apparatus for an internal combustion engine, and more particularly to an exhaust gas purification apparatus for an internal combustion engine in which a filter is disposed in an engine exhaust passage in order to remove particulates such as soot contained in exhaust gas.
[0002]
[Prior art]
Conventionally, in a diesel engine, in order to remove particulates such as soot contained in the exhaust gas, a particulate filter capable of capturing the particulates in the exhaust gas is arranged in the engine exhaust passage, and this particulate filter allows the exhaust gas to be contained in the exhaust gas. The particulate filter is once collected and the particulate filter collected by the particulate filter is ignited and burned and removed to regenerate the particulate filter.
[0003]
However, the collected particulate matter will not ignite unless it reaches a high temperature of about 600 ° C or higher. On the other hand, the exhaust gas temperature of a diesel engine is usually much lower than 600 ° C, even when operating at high loads. The exhaust gas temperature is only 350 ° C to 400 ° C. Therefore, it is difficult to ignite the fine particles with only the exhaust gas heat.
[0004]
Therefore, there is a technology in which the catalyst is supported on the particulate filter to lower the ignition temperature of the particulates and the particulates are ignited only by the exhaust gas heat (in addition, the filter supporting the catalyst on the particulate filter is Hereinafter referred to as “particulate filter with catalyst or simply filter”). For example, the technique described in Japanese Patent Publication No. 7-106290 addresses the above problem by supporting a catalyst made of a mixture of a platinum group metal and an alkaline earth metal oxide on a particulate filter.
[0005]
[Problems to be solved by the invention]
However, even a particulate filter with a catalyst as described above may ignite only a part of the fine particles, so that the fine particles may remain unburned.
[0006]
Specifically, there is no problem if the amount of particulates contained in the exhaust gas is small, but a large amount of particulates may be generated depending on the operating state of the internal combustion engine, in which case the particulates adhering to the particulate filter are completely removed. Prior to burning, other fine particles are deposited on the fine particles to form a laminated state. Then, even if, for example, the upper layer fine particles in a place where it is easy to come into contact with oxygen burns, for example, the lower layer fine particles in a place where it is difficult to come into contact with oxygen do not burn, thus inducing a phenomenon that the fine particles remain unburned.
[0007]
This is probably because the carbon in the fine particles changes into graphite or the like that is difficult to burn while the fine particles are deposited. In that case, it is necessary to keep the accumulated fine particles at a high temperature of 600 ° C. or higher. However, as described above, in a diesel engine, the exhaust gas temperature does not reach a high temperature of 600 ° C. or higher, so if there are more fine particles (hereinafter referred to as “deposited fine particles”) than fine particles removed by ignition combustion. However, no matter how much the particulate filter with a catalyst is used, the exhaust gas heat alone is insufficient, and it becomes difficult to ignite the deposited fine particles.
[0008]
Therefore, fuel supply means is provided upstream of the installation location of the particulate filter with catalyst in the exhaust pipe to supply the fuel into the exhaust, and the deposited fine particles are burned by using the reaction heat generated by the oxidation reaction of the fuel. The technique of doing is well-known conventionally.
[0009]
However, in such a technique, the amount of fuel supplied is set based on the exhaust temperature at the start of regeneration of the filter. Therefore, for example, the engine speed increases during combustion of the deposited particulates, and the exhaust temperature rises. Then, the amount of fuel supplied becomes excessive with respect to the raised exhaust temperature, oxidation proceeds rapidly, and the filter temperature may become higher than the combustion temperature of the fine particles, and the filter may be thermally deteriorated.
[0010]
Therefore, oxygen concentration detection means for detecting the oxygen concentration in the exhaust gas is provided downstream of the filter installation location in the exhaust pipe, and whether the filter is thermally deteriorated based on the oxygen concentration detected by the oxygen concentration detection means. A technique for detecting whether or not is disclosed in, for example, Japanese Patent No. 2998321.
[0011]
However, when it is determined that there is a risk of causing heat damage to the filter from the oxygen concentration of the exhaust gas discharged from the filter, the filter may already be thermally deteriorated. This is because there is a time delay between the actual filter temperature and the filter temperature when it is determined that there is a risk of causing heat damage to the filter.
[0012]
The present invention has been made in view of the above points, and the problem to be solved is an installation place of a particulate filter with a catalyst in an exhaust gas purification apparatus for an internal combustion engine in which a particulate filter with a catalyst is installed in an exhaust pipe. The oxygen concentration on the upstream and downstream sides of the exhaust pipe at the boundary is detected, the oxygen concentration change rate in the filter is calculated from these oxygen concentrations, the temperature rise state of the filter is determined from this oxygen concentration change rate, An object of the present invention is to provide an exhaust emission control device for an internal combustion engine that can prevent thermal damage such as thermal degradation from occurring in a filter by adjusting the amount of oxygen flowing into the internal combustion engine in accordance with the determination state.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, the exhaust temperature raising apparatus for an internal combustion engine of the present invention employs the following means.
[0014]
(1) An exhaust gas purification apparatus for an internal combustion engine according to the present invention is installed in an exhaust passage and is capable of capturing a catalyst and capturing particulates in exhaust gas, and an oxygen concentration in exhaust gas entering the filter in the exhaust passage. Based on the values detected by the oxygen concentration detecting means, the outlet oxygen concentration detecting means for detecting the oxygen concentration in the exhaust gas discharged from the filter, and the values detected by both the oxygen concentration detecting means. The oxygen concentration change rate calculating means for calculating the oxygen concentration change rate per unit time at the temperature, and the temperature rise for detecting the temperature rising state of the filter based on the oxygen concentration change rate calculated by the oxygen concentration change rate calculating means A state detecting means, and an inflowing oxygen amount adjusting means for adjusting the inflowing oxygen amount to the internal combustion engine in accordance with the temperature rising state of the filter detected by the temperature rising state detecting means. .
[0015]
Here, the ECU that controls the entire internal combustion engine will be briefly described, and the components of the present invention will be described.
[0016]
The ECU comprises a digital computer as is well known, and includes a central processing control unit CPU, a read-only memory ROM, a random access memory RAM, a backup RAM, an input interface circuit, an output interface circuit and the like connected to each other by a bidirectional bus. Composed.
[0017]
The input interface circuit is electrically connected to various sensors attached to the internal combustion engine and the vehicle. When output signals of these various sensors enter the ECU from the input interface circuit, these parameters are temporarily stored in the random access memory RAM. Remembered.
[0018]
Based on these parameters, the CPU performs necessary arithmetic processing. In executing the arithmetic processing, the CPU stores the parameters stored in the random access memory RAM through the bidirectional bus as necessary. call.
[0019]
Examples of the “fine particles” include carbon suit, unburned fuel, oil and the like when the internal combustion engine is a diesel engine.
[0020]
When the internal combustion engine is a diesel engine, the “filter” may be a filter that collects particulates discharged from the diesel engine, so-called Diesel Particulate Filter (DPF).
[0021]
(2) As the inlet side oxygen concentration detecting means and the outlet side oxygen concentration detecting means, an oxygen sensor or an air-fuel ratio sensor is suitable. Since both the oxygen sensor and the air-fuel ratio sensor are well known, detailed description is omitted.
[0022]
(3) Instead of using an oxygen sensor or an air-fuel ratio sensor for the inlet side oxygen concentration detecting means, for example, an engine speed-engine fuel injection amount line in which the engine speed is taken on the vertical axis and the engine fuel injection quantity is taken on the horizontal axis. The oxygen concentration on the inlet side may be estimated from the figure. This diagram may be referred to as an inlet side oxygen concentration estimation map, and the map may be stored in the ROM and the inlet side oxygen concentration estimated from the map may be obtained as necessary.
[0023]
The “oxygen concentration change rate calculating means” is set to calculate the oxygen concentration change rate in the filter from the values detected by the inlet side oxygen concentration detecting means and the outlet side oxygen concentration detecting means, and stored in the ROM. Examples include stored application programs. The application program is executed by the CPU, and the attribute of the CPU is in the ECU. Therefore, the ECU can be referred to as oxygen concentration change rate calculation means.
[0024]
The “temperature rise state detection means” is set to detect the temperature rise state of the filter from the oxygen concentration change rate calculated by the oxygen concentration change rate calculation means (hereinafter referred to as “oxygen concentration change rate”). And application programs stored in the ROM. The application program is executed by the CPU, and the attribute of the CPU is in the ECU. Therefore, the ECU can be referred to as a temperature rise state detection means.
[0025]
(4) Also, if the oxygen concentration change rate calculated by the oxygen concentration change rate calculating means is equal to or greater than a predetermined oxygen concentration change rate and the state continues for a predetermined time or more, the temperature rise state of the filter is abnormal. It is also conceivable to have a temperature rise abnormality determination means for determining that there is a certain temperature.
[0026]
Examples of such “temperature rise abnormality determining means” include application programs stored in the ROM. The application program is executed by the CPU, and the CPU attribute is in the ECU. Therefore, the ECU can be referred to as a temperature rise abnormality determination means.
[0027]
Therefore, if the oxygen concentration change rate is equal to or higher than the predetermined oxygen concentration change rate and the state continues for a predetermined time or longer, the oxidation reaction in the filter is accelerated, the filter temperature is increased, and the filter is eventually deteriorated by heat. It means that it is in a state where it ends up. Therefore, the predetermined oxygen concentration change rate and the predetermined time indicate that the oxidation reaction in the filter proceeds rapidly, and that the filter is likely to be thermally deteriorated if the state is kept as it is. It means a critical point. Therefore, if the change rate of the oxygen concentration becomes equal to or higher than the predetermined change rate of oxygen concentration and the state continues for a predetermined time or more, the oxidation reaction in the filter proceeds rapidly, which may cause a thermal deterioration phenomenon of the filter. Means a sufficient condition to be high.
[0028]
As the “inflowing oxygen amount adjustment means”, the intake throttle valve is used to perform the intake throttle or the air-fuel ratio is enriched so that the amount of oxygen flowing into the internal combustion engine can be adjusted according to the temperature rise state by the temperature rise state detection means. Application programs that are set so that The application program is executed by the CPU, and the attribute of the CPU is in the ECU. Therefore, the ECU can be referred to as inflowing oxygen amount adjusting means.
[0029]
Note that enrichment of the air-fuel ratio can be performed by increasing the amount of engine fuel injected from a fuel injection device such as an injector of an internal combustion engine. And oxygen sensor (O ₂ Sensor) or an air-fuel ratio sensor (A / F sensor), the amount of increase in the fuel injection amount is determined.
[0030]
In the exhaust gas purification apparatus for an internal combustion engine having such a configuration, the oxygen concentration on the inlet side and the outlet side of the exhaust gas with respect to the filter is detected in the flow direction of the exhaust gas in the exhaust passage, and the oxygen concentration on the outlet side of the exhaust gas is By looking at how it changes compared to the oxygen concentration on the inlet side of the exhaust gas, that is, by looking at the rate of change per unit time of the oxygen concentration before and after the filter in the exhaust passage, Feedback control can be performed so that the internal temperature of the filter does not rise excessively.
[0031]
Then, the temporal change rate of the oxygen concentration difference before and after the filter, which is correlated with the heat generation rate (oxidation reaction rate) inside the filter, that is, the oxygen concentration before the exhaust gas entering the filter is exhausted from the filter. A predetermined oxygen concentration that is one of the critical points at which the rate of change per unit time of how much has changed (how much concentration difference has occurred) causes thermal degradation of the filter Rate of change When the temperature rise state detecting means determines that the state has exceeded the predetermined time, which is another one of the critical points, which is more than that and causes the filter to be thermally deteriorated. Predicts that the filter is currently in a critical state where the filter temperature is excessively increased by the temperature increase abnormality determination means and may eventually deteriorate due to heat, that is, the filter is abnormally heated. In that case, the temperature of the filter is prevented from excessively rising due to the oxidation reaction by reducing the amount of oxygen in the exhaust gas by enriching the intake air throttle or the air-fuel ratio. Therefore, the thermal deterioration of the filter can be effectively prevented.
[0032]
In addition, if an inlet side oxygen concentration estimation map is used for the inlet side oxygen concentration detection means without using an oxygen sensor or an air / fuel ratio sensor, the inlet side oxygen concentration estimation map may be inaccurate even if it is inferior in accuracy compared with the case of direct detection by an oxygen sensor or air / fuel ratio sensor. Since it is not necessary to use an oxygen sensor or an air-fuel ratio sensor as the side oxygen concentration detection means, the number of parts can be reduced accordingly.
[0033]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of an exhaust emission control device for an internal combustion engine according to the present invention will be described below with reference to the accompanying drawings.
[0034]
FIG. 1 shows a case where an exhaust emission control device for an internal combustion engine of the present invention is applied to a diesel engine which is a compression ignition type internal combustion engine.
[0035]
Referring to FIG. 1, 1 is an engine body, 2 is a cylinder block, 3 is a cylinder head, 4 is a piston, 5 is a combustion chamber, 6 is an electrically controlled fuel injection valve, 7 is an intake valve, 8 is an intake port, 9 Is an exhaust valve, and 10 is an exhaust port.
[0036]
The intake port 8 is connected to a surge tank 12 via a corresponding intake branch pipe 11, and the surge tank 12 is connected to a compressor 15 of an exhaust turbocharger 14 via an intake duct 13. The intake pipe 90 to which the compressor 15 is attached is provided with an air cleaner and an air flow meter (not shown).
[0037]
A throttle valve 17 driven by a step motor 16 is disposed in the intake duct 13, and a cooling device 18 for cooling intake air flowing in the intake duct 13 is disposed around the intake duct 13. In the embodiment shown in FIG. 1, the engine cooling water is guided into the cooling device 18 and the intake air is cooled by the engine cooling water.
[0038]
On the other hand, the exhaust port 10 is connected to a turbine 21 of a turbocharger 14 via an exhaust manifold 19 and an exhaust pipe 20, and an outlet of the turbine 21 is connected to an exhaust purification device A provided in an exhaust pipe 70 that is an exhaust passage. . The exhaust port 10 is provided with a fuel addition nozzle (not shown) as fuel supply means. Therefore, the fuel addition nozzle is located upstream of the exhaust purification device A in the exhaust pipe 70.
[0039]
The exhaust gas purification apparatus A is formed by enclosing a particulate filter 22 with a catalyst, which is a filter that supports an oxidation catalyst in a DPF and can capture particulates in exhaust gas, in a case body 23. In order to remove particulates such as soot in the exhaust gas using this exhaust purification device A, the particulates are once collected by a filter, and the collected particulates are ignited and burned. In order to ignite and burn fine particles, in addition to using exhaust gas heat, fuel is supplied from the fuel addition nozzle into the exhaust gas, and reaction heat generated by the oxidation reaction of the fuel is used. Thus, the particulates are removed from the filter by burning and removing the particulates, thereby regenerating the filter. Instead of the oxidation catalyst, a NOx catalyst having a fuel oxidation function may be supported on the DPF.
[0040]
Further, the exhaust manifold 19 and the surge tank 12 are connected to each other via an EGR passage 24 that is a constituent member of an exhaust gas recirculation device (hereinafter referred to as “EGR”). Further, the EGR passage 24 has an electric control type EGR control valve 25. In addition, the EGR passage 24 is provided with a cooling device 26 for cooling the EGR gas flowing therethrough. In the embodiment shown in FIG. 1, engine cooling water is guided into the cooling device 26, and the EGR gas is cooled by the engine cooling water.
[0041]
On the other hand, the fuel injection valve 6 is connected to a common rail 27 as a fuel reservoir via a fuel supply pipe 6a.
[0042]
Fuel is supplied into the common rail 27 by an electrically controlled fuel pump 28 with variable discharge amount. The fuel supplied into the common rail 27 is supplied to the fuel injection valve 6 through the fuel supply pipe 6a. A fuel pressure sensor 29 for detecting the fuel pressure in the common rail 27 is attached to the common rail 27, and a fuel pump is used so that the fuel pressure in the common rail 27 becomes the target fuel pressure based on the output signal of the fuel pressure sensor 29. 28 discharge amount is controlled.
[0043]
The amount of fuel injected from the fuel injection valve 6 is in the form of a map as a function of the amount of depression of the accelerator pedal 40 and the engine speed, and the ROM 32 of an electronic control unit (hereinafter referred to as “ECU”) 30 described below. A required torque corresponding to the amount of depression of the accelerator pedal 40 and the engine speed is obtained from a required torque calculation map (not shown) stored therein, and is calculated based on this required torque.
[0044]
The ECU 30 is a digital computer, and is connected to each other by a bidirectional bus 31. A ROM (read only memory) 32, a RAM (random access memory) 33, a CPU (microprocessor) 34, an input port 35, an output port 36, and an AD converter. 37.
[0045]
The output signal of the fuel pressure sensor 29 is input to the input port 35 via the corresponding AD converter 37.
[0046]
An exhaust temperature sensor 79 for detecting an exhaust gas temperature (outlet gas temperature) To discharged from the exhaust purification device A is attached to the exhaust pipe 70 in the vicinity of the downstream side of the exhaust purification device A. Further, an oxygen sensor (or air-fuel ratio sensor) 81 as an outlet side oxygen concentration detection means for detecting the oxygen concentration in the exhaust gas discharged from the exhaust gas purification apparatus A (filter) is attached at a location downstream of the exhaust temperature sensor 79. It is. An oxygen sensor (or air-fuel ratio sensor) 83 is also attached to the upstream side of the exhaust purification device A in the exhaust pipe 70, and the oxygen sensor 83 detects the oxygen concentration in the exhaust gas entering the exhaust purification device A. Therefore, the oxygen sensor 83 can be said to be an inlet side oxygen concentration detection means of the exhaust purification device A. Output signals from the temperature sensor 79 and the oxygen sensors 81 and 83 enter the input port 35 via the AD converter 37.
[0047]
Further, in the exhaust pipe 70, downstream of the oxygen sensor 81, a catalytic converter and an exhaust throttle valve (both not shown) for storing, for example, an NOx storage reduction catalyst are attached in the case body.
[0048]
A load sensor 41 that generates an output voltage proportional to the amount of depression of the accelerator pedal 40 is connected to the accelerator pedal 40, and the output voltage of the load sensor 41 enters the input port 35 via the corresponding AD converter 37. Further, a crank angle sensor 42 that generates an output pulse every time a crankshaft (not shown) rotates, for example, 30 ° is connected to the input port 35.
[0049]
On the other hand, the output port 36 is connected to the fuel injection valve 6, the throttle valve driving step motor 16, the EGR control valve 25, and the fuel pump 28 via a corresponding drive circuit 38.
[0050]
Next, in order to realize a filter temperature increase abnormality determination control execution routine for determining whether or not there is an abnormality in the temperature increase state of the filter included in the exhaust gas purification apparatus A according to the present embodiment, using the flowchart of FIG. Explain the program.
[0051]
This program includes steps 101 to 107 described below. Moreover, the program which consists of these steps is memorize | stored in ROM of ECU30, and is called as needed. All processes in the steps are performed by the CPU 34 of the ECU 30. For example, step 101 is abbreviated as S101 using the symbol S.
[0052]
In S101, the oxygen sensors 81 and 83 detect the oxygen concentration in the upstream exhaust gas entering the filter of the exhaust gas purification apparatus A in the exhaust pipe 70 and the oxygen concentration in the exhaust gas discharged from the filter. At the same time, the exhaust gas temperature To of the exhaust gas purification apparatus A is detected by the exhaust gas temperature sensor 79.
[0053]
In S102, the oxygen concentration difference (ΔO2) between the upstream side and the downstream side of the exhaust gas purification apparatus A obtained in S101 is calculated.
[0054]
In S103, in order to calculate the oxygen concentration change rate (hereinafter referred to as "oxygen concentration change rate") R, for example, the first oxygen concentration difference (ΔO2) at the time of execution of this routine is calculated from the second oxygen concentration difference (ΔO2). Deducted too Unit of Divide by time.
[0055]
These relationships are shown by Formula (1).
[0056]
R = ((ΔO2) n− (ΔO2) n−1) / t (1)
However,
n: Indicates the number of executions of this routine.
[0057]
n-1: Indicates the previous execution count of this routine.
[0058]
t: Unit time
S103 is referred to as oxygen concentration change rate calculating means for calculating the oxygen concentration change rate per unit time in the filter based on the values detected by the oxygen sensors 83 and 81 which are oxygen concentration detecting means. Since this program including S103 is stored in the ROM 32 and the attribute of the ROM 32 is in the ECU 30, the ECU 30 can also be referred to as oxygen concentration change rate calculating means.
[0059]
In S104, the oxygen concentration change rate R obtained in S103 is compared with a predetermined oxygen concentration change rate Rs, and the magnitude relationship is determined by equation (2) using an inequality including equal signs.
[0060]
R ≧ Rs (2)
However,
Rs: One of the indexes that means that the oxidation reaction proceeds rapidly in the filter of the exhaust gas purification apparatus A and the filter is thermally deteriorated.
If a positive determination is made in S104, the process proceeds to S105. If a negative determination is made, this program is repeated as necessary. This is because the oxidation reaction does not occur rapidly and is not the subject of the present invention.
[0061]
In S105, it is determined whether or not the relationship of R ≧ Rs, which is the state when an affirmative determination is made in S104, lasts for a predetermined time Ts or longer. Here, Ts means that when the relationship of R ≧ Rs continues for a predetermined time Ts or longer, the oxidation reaction in the filter is accelerated accordingly, the filter temperature rises abnormally, and the filter eventually deteriorates thermally. It is an index that means being in a state. The predetermined time Ts is a constant determined by the outgas temperature To obtained in S101 and by the type of filter. In order to obtain the predetermined time Ts, it is obtained from a one-dimensional map (not shown) determined based on the prepared outgas temperature To.
[0062]
Therefore, the predetermined oxygen concentration change rate Rs and the predetermined time Ts mean critical points at which the oxidation reaction in the filter proceeds rapidly and the filter eventually undergoes thermal degradation. In other words, when the oxygen concentration change rate R becomes equal to or higher than the predetermined oxygen concentration change rate Rs and the state continues for the predetermined time Ts or longer, the oxidation reaction in the filter proceeds rapidly, and the heat of the filter This is a sufficient condition for causing the deterioration phenomenon.
[0063]
These S104 and S105 can be referred to as a temperature rise state detection means for detecting the temperature rise state of the filter based on the oxygen concentration change rate calculated in S103, which is an oxygen concentration change rate calculation means. The program including S104 and S105 is stored in the ROM 32, and the attribute of the ROM 32 is in the ECU 30, so the ECU 30 can also be referred to as a temperature rise state detecting means.
[0064]
If an affirmative determination is made in S105, the process proceeds to S106. If a negative determination is made, this program is repeated as necessary. The reason for ending this program when a negative determination is made is that the filter is not in a state of causing deterioration even if an oxidation reaction occurs.
[0065]
In step S106, the process proceeds when the conditions in steps S104 and S105 are met. In step S106, it is determined that the filter is in an abnormal temperature rise state. Therefore, in S106, the specific state R ≧ Rs when the oxygen concentration change rate R calculated in the oxygen concentration change rate calculating means S104 and S105 is compared with a predetermined oxygen concentration change rate Rs continues for a predetermined time Ts or longer. In this case, it can be said that the temperature rise abnormality determination means determines that the temperature rise state of the filter is abnormal. The program including S106 is stored in the ROM 32, and the attribute of the ROM 32 is in the ECU 30, so the ECU 30 can also be referred to as a temperature rise abnormality determining means.
[0066]
In step S107, the throttle valve 17 is closed by the step motor 16 and the intake air is throttled, that is, the amount of oxygen flowing into the diesel engine is adjusted according to the temperature rise state of the filter detected by the ECU 30 serving as the temperature rise state detection means. Can be said to be an inflowing oxygen amount adjusting means. The program including S107 is stored in the ROM 32, and the attribute of the ROM 32 is in the ECU 30, so that the ECU 30 can also be referred to as an inflowing oxygen amount adjusting means. Further, the air-fuel ratio may be made rich instead of performing intake throttling. By doing so, the amount of oxygen in the exhaust gas is reduced, thereby preventing overheating of the filter due to the oxidation reaction.
[0067]
In this embodiment, the oxygen sensor 83 is used as the inlet side oxygen concentration detection means, but instead, for example, the vertical axis represents the engine speed and the horizontal axis represents the engine fuel injection amount. The oxygen concentration on the inlet side may be estimated from an engine speed-engine fuel injection amount diagram. This diagram may be referred to as an inlet side oxygen concentration estimation map, and the map may be stored in the ROM and the inlet side oxygen concentration estimated from the map may be obtained as necessary.
[0068]
In the diesel engine having such a configuration, the oxygen concentration on the inlet side and the outlet side of the exhaust gas with respect to the filter in the exhaust gas flow direction in the exhaust pipe 70 is detected, and the oxygen concentration on the outlet side of the exhaust gas is the exhaust gas inlet. By looking at how the oxygen concentration changes in comparison with the oxygen concentration on the side, that is, by looking at the rate of change per unit time of the oxygen concentration before and after the filter in the exhaust pipe 70 as a boundary, Feedback control can be performed by an intake throttle or the like so that the temperature does not rise excessively.
[0069]
Then, the temporal change rate of the oxygen concentration difference before and after the filter, which is correlated with the heat generation rate (oxidation reaction rate) inside the filter, that is, the oxygen concentration before the exhaust gas entering the filter is exhausted from the filter. The rate of change R per unit time of how much has changed (how much concentration difference has occurred) causes a thermal deterioration of the filter, and is a predetermined oxygen concentration change rate Rs that is one of the critical points. The temperature rise state detecting means (S104) is more than the predetermined time Ts, which lasts for a predetermined time Ts, which is another one of the critical points, which causes thermal deterioration of the filter. , S105), the filter is in a critical state where the filter temperature is excessively increased by the temperature rise abnormality determining means (S106) and may eventually be deteriorated. Motor is in a state of being abnormally heated, the predicted. In that case, the temperature of the filter is prevented from excessively rising due to the oxidation reaction by reducing the amount of oxygen in the exhaust gas by enriching the intake air throttle or the air-fuel ratio. Therefore, the thermal deterioration of the filter can be effectively prevented.
[0070]
Further, if the inlet side oxygen concentration estimation map is used as the inlet side oxygen concentration detection means without using an oxygen sensor or an air fuel ratio sensor, the accuracy may be inferior to the case of direct detection by an oxygen sensor or an air fuel ratio sensor. However, since it is not necessary to use an oxygen sensor or an air-fuel ratio sensor as the inlet side oxygen concentration detection means, the number of parts can be reduced accordingly.
[0071]
In addition, even when fine particles partially burn inside the filter, the exhaust gas purification apparatus for an internal combustion engine according to the present invention can detect in real time and can grasp in advance the state where the filter is likely to overheat. .
[0072]
【The invention's effect】
In the exhaust gas purification apparatus for an internal combustion engine according to the present invention, in the exhaust gas purification apparatus for an internal combustion engine in which a particulate filter with catalyst is installed in the exhaust pipe, the upstream and downstream sides of the exhaust pipe with the installation location of the particulate filter with catalyst as a boundary. The oxygen concentration is detected, the oxygen concentration change rate in the filter is calculated from these oxygen concentrations, the temperature rising state of the filter is determined from the oxygen concentration change rate, and the oxygen flowing into the internal combustion engine is determined according to the determination state By adjusting the amount, it is possible to prevent the filter from causing heat damage such as heat deterioration.
[Brief description of the drawings]
FIG. 1 is an overall view of an internal combustion engine to which an exhaust gas purification apparatus for an internal combustion engine of the present invention is applied.
FIG. 2 is a flowchart for explaining a program for realizing a filter temperature increase abnormality determination control execution routine for determining whether or not there is an abnormality in the temperature increase state of the filter according to the exhaust gas purification apparatus of the internal combustion engine of the present invention;
[Explanation of symbols]
1 Engine body
2 Cylinder block
3 Cylinder head
4 Piston
5 Combustion chamber
6 Electrically controlled fuel injection valve
6a Fuel supply pipe
7 Intake valve
8 Intake port
9 Exhaust valve
10 Exhaust port
11 Intake branch pipe
12 Surge tank
13 Air intake duct
14 Exhaust turbocharger
15 Compressor
16 step motor
17 Throttle valve
18 Cooling device
19 Exhaust manifold
20 Exhaust pipe
21 Turbine
22 Particulate filter with catalyst (filter)
23 Case body
24 EGR passage
25 Electrically controlled EGR control valve
26 Cooling device
27 Common rail
28 Fuel pump
29 Fuel pressure sensor
30 ECU (oxygen concentration change rate calculating means, temperature rising state detecting means, inflowing oxygen amount adjusting means, temperature rising abnormality determining means)
31 Bidirectional bus
32 ROM
33 RAM
34 CPU
35 input ports
36 output ports
37 AD converter
38 Drive circuit
40 accelerator pedal
41 Load sensor
42 Crank angle sensor
70 Exhaust pipe (exhaust passage)
79 Exhaust temperature sensor
81 Oxygen sensor (exit side oxygen concentration detection means)
83 Oxygen sensor (inlet oxygen concentration detection means)
A Exhaust gas purification device
ΔO2 Oxygen concentration difference
R Oxygen concentration change rate
Rs Predetermined oxygen concentration change rate
To exhaust gas temperature
Ts Predetermined time

Claims (4)

A filter installed in the exhaust passage and capable of carrying a catalyst and capturing particulates in the exhaust gas;
An inlet side oxygen concentration detection means for detecting an oxygen concentration in exhaust gas entering the filter in the exhaust passage;
Outlet side oxygen concentration detection means for detecting the oxygen concentration in the exhaust gas discharged from the filter;
Oxygen concentration change rate calculating means for calculating the oxygen concentration change rate per unit time in the filter based on the values detected by both the oxygen concentration detecting means;
A temperature rise state detecting means for detecting a temperature rise state of the filter based on the oxygen concentration change rate calculated by the oxygen concentration change rate calculating means;
An inflowing oxygen amount adjusting means for adjusting the inflowing oxygen amount to the internal combustion engine according to the temperature rising state of the filter detected by the temperature rising state detection means;
An exhaust gas purification apparatus for an internal combustion engine having   2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the inlet side oxygen concentration detecting means and the outlet side oxygen concentration detecting means are an oxygen sensor or an air-fuel ratio sensor.   The exhaust gas of an internal combustion engine according to claim 1, wherein the inlet side oxygen concentration detection means obtains an oxygen concentration in exhaust gas entering the filter in the exhaust passage from an engine speed and an engine fuel injection amount. Purification equipment.   When the specific state when the oxygen concentration change rate calculated by the oxygen concentration change rate calculating means is compared with a predetermined oxygen concentration change rate is maintained for a predetermined time or more, the temperature rising state of the filter is abnormal. The exhaust gas purification apparatus for an internal combustion engine according to any one of claims 1 to 3, further comprising a temperature rise abnormality determination means for determining.

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