JP4258200B2 - 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]
2. Description of the Related Art Conventionally, an exhaust gas purification apparatus for an internal combustion engine in which an annular passage that branches off from the exhaust passage of the internal combustion engine and returns to the branching portion is provided, and a particulate filter that collects particulates in the exhaust gas flowing into the annular passage is disposed. It has been known. In such an exhaust purification device, a switching valve is further arranged at the branch portion, and the switching valve has a filter inflow position where most of the exhaust gas flows into the annular passage, and most of the exhaust gas does not flow into the annular passage. It is switched between a bypass position that flows in the exhaust passage downstream of the branch portion.
[0003]
Further, in such an exhaust purification device, there are two filter inflow positions of the switching valve. At one filter inflow position, the exhaust gas flows in one direction (forward direction) through the annular passage, and at the other filter position, the exhaust gas flows. The annular passage flows in the opposite direction (reverse direction) to the one direction. As a result, the particulate filter can be used efficiently.
[0004]
By the way, in such an exhaust purification device, if there is an abnormality such as a failure in the switching valve, the switching valve will not operate. When the switching valve does not operate, when exhaust gas should flow into the particulate filter, the exhaust gas does not flow into the particulate filter, and the exhaust gas is released into the atmosphere without removing fine particles, When exhaust gas should bypass the particulate filter, the exhaust gas flows into the particulate filter and the particulate filter becomes clogged. For this reason, it is necessary to monitor the abnormality of the switching valve. An exhaust emission control device that monitors the abnormality of the switching valve in this way is conventionally known (see, for example, Patent Document 1).
[0005]
[Patent Document 1]
JP 2002-38920 A
[0006]
[Problems to be solved by the invention]
In the exhaust emission control device described in Patent Document 1, the abnormality of the switching valve is determined based on the differential pressure detected by the pressure loss detecting means between when the particulate filter is in an unused state and when it is used. However, in the above exhaust purification apparatus, the differential pressure detected by the pressure loss detection means does not only indicate pressure loss due to the particulate filter, but is also affected by pressure loss due to various other factors. Therefore, even though the switching valve is abnormal, the differential pressure detected by the pressure loss detecting means may be relatively high, and it may be determined that the switching valve is normal.
[0007]
Accordingly, an object of the present invention is to provide an exhaust purification device that can accurately detect an abnormality of a switching valve.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, in the first invention, the particulate filter that collects particulates in the exhaust gas flowing in the exhaust passage of the internal combustion engine into two branch exhaust passages is provided in the first branch exhaust passage. The switching valve is disposed at a branch portion of the branch exhaust passage, and the switch valve has a filter inflow position where at least most of the exhaust gas flows into the first branch exhaust passage and at least a large portion at the second branch exhaust passage. In an exhaust gas purification apparatus for an internal combustion engine that is switched between a bypass position where exhaust gas flows in part, when the operating position of the switching valve is at the filter inflow position, pressure loss caused by the first branch exhaust passage and the particulate filter is estimated And a pressure loss estimating means for estimating a pressure loss caused by the second branch exhaust passage when the operating position of the switching valve is in the bypass position. Pressure loss value estimated by the pressure loss estimation means when commanding the switching valve to the filter inflow position and pressure loss estimation when commanding the switching valve to set the operation position of the switching valve to the bypass position When the difference from the pressure loss value estimated by the means is equal to or less than a predetermined value, it is determined that the switching valve is abnormal.
[0009]
In general, if the switching valve is commanded to change the operating position of the switching valve when there is no abnormality in the switching valve, the pressure loss value estimated by the pressure loss estimating means changes greatly. Even if the switching valve is commanded to change the operating position, the position of the switching valve is not changed, so that the pressure loss value estimated by the pressure loss estimating means does not change greatly. Therefore, according to the first aspect of the invention, when the switching valve is instructed to change the operating position of the switching valve, the switching valve is abnormal when the difference in pressure loss values estimated by the pressure loss estimating means is small. It is determined. In addition, by comparing the pressure loss value when the switching valve operating position is set to the filter inflow position with the pressure loss value when the switching valve operating position is set to the bypass position, it is possible to more accurately determine the switching valve abnormality. Can be done.
[0010]
In the second invention, an annular passage that branches off from the exhaust passage of the internal combustion engine and returns to the branch portion is provided, a particulate filter that collects particulates in the exhaust gas flowing into the annular passage is disposed, A switching valve is disposed at the branching portion, and the switching valve is located at a filter inflow position where at least most of the exhaust gas flows into the annular passage and downstream of the branching portion without flowing at least most of the exhaust gas into the annular passage. In an exhaust gas purification apparatus for an internal combustion engine that is switched between a bypass position that flows in the exhaust passage, when the operating position of the switching valve is at the filter inflow position, pressure loss caused by the annular passage and the particulate filter is estimated, and the switching valve Pressure loss estimating means for estimating pressure loss caused by the exhaust passage between the exhaust upstream and downstream of the branch when the operating position is in the bypass position; The pressure loss value estimated by the pressure loss estimation means when the switching valve is commanded to the filter inflow position and the switching valve so that the switching valve operating position is set to the bypass position. If the difference from the pressure loss value estimated by the pressure loss estimating means when commanded is less than or equal to a predetermined value, it is determined that there is an abnormality in the switching valve.
[0011]
According to a third aspect, in the first or second aspect, the pressure loss estimating means estimates the pressure loss based on either the amount of intake air taken into the internal combustion engine or the pressure upstream of the exhaust at the branch portion.
When the pressure loss estimation means estimates the pressure loss based on the intake air amount, the vehicle on which the internal combustion engine is mounted is decelerated (that is, the internal combustion engine is operated at a low load and low rotation) and the internal combustion engine The throttle valve for restricting the amount of air flowing into the engine and the EGR valve for restricting the flow rate of EGR gas are fully opened.
[0012]
According to a fourth invention, in the first invention, the branch exhaust passage is merged downstream of the particulate filter exhaust, and the pressure loss estimating means is configured to detect the pressure in the exhaust passage upstream of the branch exhaust and the exhaust of the merge portion. The pressure loss is estimated based on the differential pressure with the pressure in the exhaust passage downstream.
[0013]
In a fifth aspect based on the second aspect, the pressure loss estimation means estimates the pressure loss based on a differential pressure between the pressure in the exhaust passage upstream of the branch portion and the pressure in the exhaust passage downstream of the branch portion. To do.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an exhaust emission control device of the present invention will be described with reference to the drawings. FIG. 1 shows an in-cylinder injection self-ignition type diesel internal combustion engine equipped with an exhaust emission control device of the present invention. The exhaust purification device used in the present invention can also be mounted on a spark ignition internal combustion engine.
[0015]
1 and 2, 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, and 8 is intake air. Port, 9 is an exhaust valve, and 10 is an exhaust port. 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.
[0016]
A throttle valve 17 driven by a throttle valve driving step motor 16 is arranged in the intake duct 13, and a cooling device 18 for cooling intake air flowing in the intake duct 13 is arranged around the intake duct 13. The In the internal combustion engine shown in FIG. 1, engine cooling water is guided into the cooling device 18 and the intake air is cooled by the engine cooling water. On the other hand, the exhaust port 10 is connected to an exhaust turbine 21 of an exhaust turbocharger 14 via an exhaust manifold 19 and an exhaust pipe 20, and an outlet of the exhaust turbine 21 is connected to an exhaust purification device 23 described in detail below via an exhaust pipe 22. Connected.
[0017]
The exhaust manifold 19 and the surge tank 12 are connected to each other via an exhaust gas recirculation (hereinafter referred to as EGR) passage 31, and an electrically controlled EGR control valve 32 is disposed in the EGR passage 31. A cooling device 33 for cooling the EGR gas flowing in the EGR passage 31 is disposed around the EGR passage 31. In the internal combustion engine shown in FIG. 1, engine cooling water is guided into the cooling device 33, and the EGR gas is cooled by the engine cooling water.
[0018]
On the other hand, each fuel injection valve 6 is connected to a fuel reservoir, so-called common rail 34, through a fuel supply pipe 6a. Fuel is supplied into the common rail 34 from an electrically controlled fuel pump 35 with variable discharge amount, and the fuel supplied into the common rail 34 is supplied to the fuel injection valve 6 via each fuel supply pipe 6a. A fuel pressure sensor 36 for detecting the fuel pressure in the common rail 34 is attached to the common rail 34, and a fuel pump 35 is set so that the fuel pressure in the common rail 34 becomes the target fuel pressure based on the output signal of the fuel pressure sensor 36. The discharge amount is controlled.
[0019]
The electronic control unit (ECU) 40 is a digital computer and includes a ROM (read only memory) 42, a RAM (random access memory) 43, a CPU (microprocessor) 44, an input port 45, and An output port 46 is provided. The output signal of the fuel pressure sensor 36 is input to the input port 45 via the corresponding AD converter 47.
[0020]
A load sensor 52 that generates an output voltage proportional to the amount of depression of the accelerator pedal 51 is connected to the accelerator pedal 51, and the output voltage of the load sensor 52 is input to the input port 45 via the corresponding AD converter 47. Further, the input port 45 is connected to a crank angle sensor 53 that generates an output pulse every time the crankshaft rotates, for example, 30 °. On the other hand, the output port 46 is connected to the fuel injection valve 6, the throttle valve driving step motor 16, the EGR control valve 32, and the fuel pump 35 through corresponding drive circuits 48.
[0021]
Next, the configuration of the exhaust emission control device 23 of the present invention will be described. The exhaust purification device 23 of the present invention includes a particulate filter (hereinafter referred to as a filter) 24 that collects particulates in the inflowing exhaust gas, and an exhaust pipe 25. The exhaust pipe 25 includes an upstream exhaust pipe (exhaust passage) 25a, a branch portion 25b, a filter side branch pipe (branch exhaust passage) 25c, a bypass side branch pipe (branch exhaust passage) 25d, a merging portion 25e, and a downstream portion. Side exhaust pipe 25f, and the filter 24 is built in a casing 26 disposed on the filter side branch pipe 25c.
[0022]
The exhaust pipe 25 will be described in more detail. The upstream exhaust pipe 25a is connected to the exhaust pipe 22 disposed upstream of the exhaust pipe 25. The upstream exhaust pipe 25a branches into a filter side branch pipe 25c in which the filter 24 is disposed and a bypass side branch pipe 25d for bypassing the filter 24 at the branch portion 25b. These branch pipes 25c and 25d join at a joining section 25e downstream of the filter 24 and continue to the downstream exhaust pipe 25f. And the flow control valve 27 is provided in the branch part 25b. The flow rate adjustment valve 27 is controlled by a flow rate adjustment valve step motor 28 connected to the output port 46 of the ECU 40 via a corresponding drive circuit 48.
[0023]
The flow rate adjustment valve 27 can adjust the flow rate of the exhaust gas flowing into the bypass side branch pipe 25d. In particular, the flow rate adjusting valve 27 can adjust the ratio between the flow rate of the exhaust gas flowing into the filter side branch pipe 25c and the flow rate of the exhaust gas flowing into the bypass side branch pipe 25d according to the operating position. For example, the flow rate adjusting valve 27 has a filter inflow position (a position indicated by a solid line in FIG. 1) for closing the bypass side branch pipe 25d and a bypass position (a position indicated by a broken line in FIG. 1) for closing the filter side branch pipe 25c. The flow rate of the exhaust gas flowing into each branch pipe 25c, 25d is determined according to the angle θ from the position where the filter side branch pipe 25c is closed. When the operation position of the flow rate adjusting valve 27 is at the filter inflow position, most or all of the exhaust gas flows into the filter side branch pipe 25c out of the exhaust gas flowing into the branch portion 25b from the upstream side exhaust pipe 25a. On the other hand, when the operating position of the flow rate adjusting valve 27 is in the bypass position, most or all of the exhaust gas flows into the bypass side branch pipe 25d out of the exhaust gas flowing into the branch portion 25b from the upstream side exhaust pipe 25a. . The flow rate adjusting valve 27 can also be used as a switching valve that can be switched between the filter inflow position and the bypass position.
[0024]
Furthermore, pressure sensors 29 and 30 are provided in the upstream side exhaust pipe 25a and the downstream side exhaust pipe 25f, respectively. That is, an upstream pressure sensor 29 is provided on the exhaust upstream side of the branch portion 25b where the upstream exhaust pipe 25a branches into the filter side branch pipe 25c and the bypass side branch pipe 25d, and the filter side branch pipe 25c and the bypass side branch pipe A downstream pressure sensor 30 is provided on the exhaust downstream side of the merging portion 25e where 25d merges. The pressure sensors 29 and 30 can detect the pressure of the exhaust gas flowing through the upstream exhaust pipe 25a and the pressure of the exhaust gas flowing through the downstream exhaust pipe 25f, respectively. Therefore, these pressure sensors 29 and 30 can detect the differential pressure between the pressure upstream of the branch portion 25b and the pressure downstream of the merge portion 25e. In other words, the pressure sensors 29 and 30 are pressure loss caused by the filter side branch pipe 25c and the filter 24 (hereinafter referred to as pressure loss), that is, the filter 24 is clogged when the operation position of the flow rate adjusting valve 27 is at the filter inflow position. The degree of pressure can be detected, and when the operating position of the flow rate adjusting valve 27 is in the bypass position, the pressure loss caused by the bypass side branch pipe 25d can be detected. For this reason, these pressure sensors 29 and 30 are used as pressure loss estimation means for estimating the pressure loss caused by the filter side branch pipe 25c and the filter 24 and the bypass side branch pipe 25d.
[0025]
By the way, the flow rate adjusting valve 27 described above is disposed on the flow path of the high-temperature exhaust gas, and is used under severe conditions. If it is used for a long time under such severe conditions, the flow rate adjusting valve 27 may not operate normally. For example, even if a signal is sent from the ECU 40 to the flow rate adjusting valve 27 so as to change the operating position of the flow rate adjusting valve 27, the flow rate adjusting valve 27 does not operate and the operating position is not changed.
[0026]
When the flow regulating valve 27 does not operate in this manner, the exhaust gas does not flow into the filter 24 when the exhaust gas should flow into the filter 24, such as when the exhaust gas contains a large amount of particulates. Unpurified exhaust gas is released into the atmosphere. On the other hand, the exhaust gas flows into the filter 24 when the exhaust gas should not flow into the filter 24, such as when the temperature of the filter 24 becomes too high due to oxidation of particulates in the filter 24, Furthermore, the temperature of the filter 24 becomes high and the filter 24 is melted. Therefore, in such a case, it is necessary to repair or replace the flow rate adjustment valve 27 as soon as possible. For that purpose, the flow rate adjustment valve 27 is diagnosed so that the abnormality of the flow rate adjustment valve 27 can be diagnosed. There is a need.
[0027]
By the way, in general, the filter 24 becomes resistant to the flow of the exhaust gas even if it does not collect any particulates or the like. Therefore, when the exhaust gas passes through the filter 24, a pressure loss due to the filter 24 occurs. . Therefore, when the exhaust gas is allowed to flow into the filter side branch pipe 25c with the operating position of the flow rate adjusting valve 27 set to the filter inflow position, a relatively large pressure loss is detected by the pressure loss estimating means. On the other hand, since there is nothing in the bypass side branch pipe 25d that causes a large pressure loss, the operating position of the flow rate adjustment valve 27 is set to the bypass position during operation of the internal combustion engine, and the exhaust gas is supplied to the bypass side branch pipe 25d. If it is made to flow, the pressure loss value estimated by the pressure loss estimation means is very small. Therefore, the pressure loss value caused by the filter side branch pipe 25c and the filter 24 estimated by the pressure loss estimating means when the operating position of the flow rate adjusting valve 27 is at the filter inflow position is set to the bypass position. In this case, the pressure loss value is larger than the pressure loss value caused by the bypass side branch pipe 25d estimated by the pressure loss estimating means, and the difference between the pressure loss values is relatively large.
[0028]
On the other hand, when the flow rate adjustment valve 27 is abnormal and the flow rate adjustment valve 27 does not move between the filter inflow position and the bypass position, or when the operation position of the flow rate adjustment valve 27 cannot be changed, the flow rate adjustment valve 27 The pressure loss value estimated by the pressure loss estimating means when the flow rate adjusting valve 27 is commanded to be the filter inflow position, and the flow rate adjusting valve 27 so that the operating position of the flow rate adjusting valve 27 is the bypass position. The difference from the pressure loss value estimated by the pressure loss estimation means when commanded is relatively small or almost zero. Therefore, when the flow adjustment valve 27 is instructed to set the operation position of the flow adjustment valve 27 to the filter inflow position and when the flow adjustment valve 27 is instructed to set the operation position of the flow adjustment valve 27 to the bypass position. The difference in pressure loss values estimated by the pressure loss estimation means (hereinafter simply referred to as the difference in pressure loss values estimated by the pressure loss estimation means) is greater in the flow rate adjustment valve than in the case where the flow rate adjustment valve 27 is operating normally. Smaller when there is an abnormality.
[0029]
Therefore, in the exhaust purification device 23 of the first embodiment of the present invention, when the difference in pressure loss values estimated by the pressure loss estimation means is equal to or less than a predetermined value, it is determined that the flow rate adjustment valve 27 is abnormal. Yes.
[0030]
Here, the predetermined value is the smallest value that can be taken by the difference in pressure loss values estimated by the pressure loss estimation means when the flow rate adjusting valve 27 is operating normally. In general, when the flow rate adjustment valve 27 is operating normally, the difference between the pressure loss values estimated by the pressure loss estimating means is the smallest when no particulates are collected in the filter 24 or when the filter 24 is When the flow rate adjustment valve 27 is operating normally, the smallest value that can be taken by the difference in pressure loss estimated by the pressure loss estimation means when the flow rate adjusting valve 27 is operating normally is that the filter 24 does not trap particulates at all. This is the difference in pressure loss when not collected or when the filter 24 is unused.
[0031]
As described above, it is possible to diagnose the abnormality of the flow rate adjustment valve 27 by determining whether or not the difference between the pressure loss values estimated by the pressure loss estimation means is equal to or less than a predetermined value. Release of fine particles into the atmosphere, pressure loss of the filter 24, and the like due to inactivity are prevented.
[0032]
In the exhaust purification device 23 according to the first embodiment of the present invention, as described above, the two pressure sensors 29 and 30 provided respectively on the exhaust upstream of the branching portion 25b and the exhaust downstream of the merging portion 25e are used as pressure loss estimating means. The pressure loss between the two pressure sensors 29, 30 is estimated from the differential pressure between the two pressure sensors 29, 30. Therefore, when the operation position of the flow rate adjusting valve 27 is at the filter inflow position, the pressure sensors 29 and 30 detect the differential pressure generated between the exhaust upstream side and the exhaust downstream side of the filter side branch pipe 25c. When the operating position of the flow rate adjusting valve 27 is in the bypass position, the pressure sensors 29 and 30 detect the differential pressure generated between the exhaust upstream side and the exhaust downstream side of the bypass side branch pipe 25d. Can do. Since the pressure loss due to the filter 24 is large as described above, the differential pressure generated between the upstream and downstream of the filter side branch pipe 25c is larger than the differential pressure generated between the upstream and downstream of the bypass side branch pipe 25d.
[0033]
Regarding the determination of the abnormality of the flow rate adjustment valve 27, when the flow rate adjustment valve 27 is commanded to set the operation position of the flow rate adjustment valve 27 to the filter inflow position, and the operation position of the flow rate adjustment valve 27 is set to the bypass position. When the difference in pressure detected from the two pressure sensors 29 and 30 (hereinafter simply referred to as the difference in pressure detected from the pressure sensor) is less than or equal to a predetermined value when the flow control valve is commanded to It is determined that the flow rate adjustment valve 27 is abnormal. More specifically, the differential pressure detected by the pressure sensors 29 and 30 when a signal is transmitted from the ECU 40 to the flow rate adjustment valve 27 so that the operation position of the flow rate adjustment valve 27 is set to the filter inflow position, and the flow rate adjustment valve If the difference from the differential pressure detected by the pressure sensors 29 and 30 when a signal is transmitted from the ECU 40 to the flow rate adjusting valve 27 so that the operating position of the engine 27 is set to the bypass position, the flow rate is adjusted. It is determined that the valve 27 is abnormal. The predetermined value is equal to the difference between the differential pressures detected by the pressure sensors 29 and 30 when nothing is collected in the filter 24 or when the filter 24 is not used.
[0034]
In the exhaust purification device 23 of the first embodiment of the present invention, the pressure in the upstream exhaust pipe 25a on the exhaust upstream side of the branching portion 25b and the confluence 25e from the pressure detected by the two pressure sensors 29 and 30. The pressure difference between the pressure in the downstream side exhaust pipe 25f on the downstream side of the exhaust gas is detected, but the pressure on the upstream side of the branch portion 25b and the exhaust gas in the merging portion 25e are detected not by the pressure sensor but by the differential pressure sensor. You may detect the differential pressure | voltage between downstream pressures.
[0035]
Next, abnormality diagnosis control of the flow rate adjustment valve 27 in the exhaust purification device 23 of the first embodiment of the present invention will be described. In the abnormality diagnosis control, the differential pressure Pdb is detected from the two pressure sensors 29 and 30 when a signal is transmitted from the ECU 40 to the flow rate adjustment valve 27 so that the operation position of the flow rate adjustment valve 27 is set to the bypass position. When a signal is transmitted from the ECU 40 to the flow rate adjusting valve 27 so that the operating position of the flow rate adjusting valve 27 is set to the filter inflow position, the differential pressure Pdf is detected from the two pressure sensors. Then, from the two detected differential pressures, a differential pressure difference ΔPd is calculated as Pdf−Pdb. When the differential pressure difference ΔPd is equal to or greater than the predetermined value ΔPdp, it is determined that the flow rate adjustment valve 27 is not broken or abnormal. When the detected differential pressure difference ΔPd is smaller than the predetermined value ΔPdp, the flow rate adjustment is performed. It is determined that the valve 27 has a failure or abnormality. Note that the predetermined value ΔPdp may be a differential pressure difference ΔPd when the filter 24 is used for the first time and the flow rate adjustment valve 27 is operating normally, or from the time of manufacture of the filter 24 and the ECU 40 in advance. It may be determined.
[0036]
Next, a control routine for abnormality diagnosis control of the flow rate adjustment valve 27 in the exhaust emission control device according to the first embodiment of the present invention will be described with reference to FIG. First, in step 101, it is determined whether it is time to perform an abnormality diagnosis of the flow rate adjustment valve 27. This execution time refers to when a predetermined time has elapsed since the previous abnormality diagnosis was executed, or when the internal combustion engine is mounted on the vehicle, the vehicle has traveled a predetermined travel distance after the previous abnormality diagnosis was executed. When it was done. If it is determined in step 101 that it is not the implementation time, the control routine is terminated. If it is determined in step 101 that it is the implementation time, the process proceeds to step 102. In step 102, a signal is transmitted from the ECU 40 to the flow rate adjusting valve 27 so that the operating position of the flow rate adjusting valve 27 is set to the bypass position. Next, in step 103, the differential pressure Pdb between the two pressure sensors 29, 30 is calculated from the outputs of the two pressure sensors 29, 30, and the process proceeds to step 104.
[0037]
In step 104, a signal is transmitted from the ECU 40 to the flow rate adjusting valve 27 so that the operating position of the flow rate adjusting valve 27 is set to the filter inflow position. Next, in step 105, the differential pressure Pdf between the two pressure sensors 29, 30 is calculated from the outputs of the two pressure sensors 29, 30, and the process proceeds to step 106. In step 106, it is determined whether or not the differential pressure difference ΔPd calculated from the two differential pressures Pdf and Pdb is smaller than a predetermined value ΔPdp. When it is determined that the differential pressure difference ΔPd is equal to or greater than the predetermined value ΔPdp, the control routine is terminated. On the other hand, if it is determined that the differential pressure difference ΔPd is smaller than the predetermined value ΔPdp, the routine proceeds to step 107. In step 107, it is determined that the flow rate adjustment valve 27 has a failure or abnormality, a warning is given to the user, and the control routine is terminated.
[0038]
By the way, although it has been described that the abnormality of the flow rate adjustment valve 27 is determined by comparing the pressure loss value estimated by the pressure loss estimation means with a certain predetermined value, in the present invention, actually, the exhaust gas flowing into the filter 24 and the like An abnormality determination of the flow rate adjustment valve 27 is performed while correcting a predetermined value according to the flow rate. In general, the pressure loss caused by the filter side branch pipe 25c and the filter 24 or the bypass side branch pipe 25d, for example, the differential pressure between the upstream side and the downstream side of these branch pipes 25c and 25d is not only the degree of clogging of these filters 24 and the like. It changes according to the flow rate of the exhaust gas flowing into the branch pipes 25c and 25d, for example, the rotational speed of the internal combustion engine. This is shown in FIG. FIG. 3 shows the relationship between the flow rate of the exhaust gas flowing into the filter 24 in a state where particulates and the like are not collected, and the differential pressure between the exhaust upstream side and the exhaust downstream side of the filter 24.
[0039]
As can be seen from FIG. 3, when the flow rate of the exhaust gas flowing into the filter 24 is small, the differential pressure between the upstream and downstream of the filter 24 is small, so the pressure loss due to the filter 24 is small, and the exhaust gas flowing into the filter 24 When the flow rate of the filter 24 is large, the differential pressure between the upstream and downstream of the filter 24 is large, and thus the pressure loss due to the filter 24 is large. Therefore, for example, if the flow rate of the exhaust gas flowing into the filter 24 is large, the pressure loss due to the filter 24 becomes large even if the particulate matter is hardly collected in the filter 24, and conversely the exhaust gas flowing into the filter 24. When the flow rate is small, the pressure loss due to the filter 24 is reduced even if a large amount of fine particles are collected in the filter 24. For this reason, it may be determined that there is an abnormality in the flow rate adjustment valve 27 even though the pressure loss caused by the branch pipes 25c and 25d is reduced by reducing the flow rate of the inflowing exhaust gas. There is sex.
[0040]
Therefore, in the embodiment of the present invention, the influence of the flow rate of the exhaust gas flowing into the filter 24 or the like in the abnormality determination of the flow rate adjustment valve 27 is eliminated. More specifically, in the exhaust purification device 23 of the first embodiment of the present invention, the flow rate of the exhaust gas flowing into the filter-side branch pipe 25c and the filter-side branch in a state where almost no particulates or the like are collected in the filter 24. The differential pressure between the upstream and downstream of the pipe 25c is experimentally obtained in advance, and stored in the ROM 42 of the ECU 40 as a map as shown in FIG. In use, the predetermined value ΔPdp is calculated based on the flow rate of the exhaust gas discharged from the internal combustion engine. By comparing the thus calculated predetermined value ΔPdp with the above-described differential pressure difference ΔPd, it is determined whether or not the flow regulating valve 27 has a failure or abnormality. The flow rate of the exhaust gas discharged from the internal combustion engine may be detected by a flow sensor (not shown) disposed upstream of the exhaust of the branch portion 25b, or the rotational speed of the internal combustion engine or the intake amount of the internal combustion engine. Or the like.
[0041]
In particular, in the exhaust emission control device 23 of the first embodiment of the present invention, it is preferable to estimate the pressure loss by the pressure loss estimation means during deceleration. As described above, in the embodiment of the present invention, the predetermined value ΔPd is corrected based on the flow rate of the exhaust gas. However, even if such a correction is performed, the flow rate is changed if the flow rate of the exhaust gas changes frequently. The influence of the exhaust gas flow rate on the abnormality determination of the regulating valve 27 cannot be removed satisfactorily. Here, during operation of the internal combustion engine other than during deceleration, the load on the internal combustion engine frequently fluctuates, and accordingly, fuel is injected and the rotation speed of the internal combustion engine also fluctuates frequently, so that the flow rate of the exhaust gas Also fluctuate frequently. On the other hand, almost no fuel is injected into the combustion chamber 5 of the internal combustion engine at the time of deceleration, so that the rotational speed of the internal combustion engine does not fluctuate frequently and the flow rate of the exhaust gas fluctuates frequently. Absent. Therefore, in the first embodiment of the present invention, the pressure loss is estimated by the pressure loss estimating means at the time of deceleration, so that the influence of the exhaust gas flow rate on the abnormality determination of the flow rate adjustment valve 27 can be satisfactorily removed.
[0042]
Further, as described above, it is preferable that the flow rate of the exhaust gas flowing into the branch pipes 25c and 25d is larger as long as the influence of the flow rate of the exhaust gas on the abnormality determination of the flow rate adjustment valve 27 is removed. That is, if the flow rate of the exhaust gas is large, the actual pressure loss value estimated by the pressure loss estimating means increases accordingly. In general, the larger the pressure loss value, the smaller the relative error between the estimated pressure loss value and the actual pressure loss value. Therefore, the greater the flow rate of the exhaust gas flowing into the branch pipes 25c, 25d, The relative error between the estimated pressure loss value and the actual pressure loss value becomes small. Therefore, in the first embodiment, when the pressure loss is estimated by the pressure loss estimating means, the throttle valve 17 is fully opened and the EGR valve 32 is fully opened in order to increase the flow rate of the exhaust gas flowing into the branch pipes 25c and 25d. Closed. That is, when the throttle valve 17 is fully opened, the intake air amount itself increases, and when the EGR valve 32 is fully closed, the exhaust gas is prevented from returning to the intake passages 8 and 11 again. As a result, the flow rate of the exhaust gas flowing into the branch pipes 25c and 25d increases, and the pressure loss detection accuracy can be increased.
[0043]
Furthermore, in the exhaust purification device 23 of the first embodiment, the detected differential pressure or pressure is also affected by temperature. That is, even if the degree of clogging of the filter 24 is the same, the differential pressure or pressure detected when the temperature of the exhaust gas or the filter 24 is high is large, and the differential pressure or pressure detected when the temperature of the exhaust gas or the filter 24 is low. small. Therefore, in the present invention, the temperature of the exhaust gas or the filter 24 is detected, and the differential pressure or pressure detected by the differential pressure sensor or pressure sensor 29, 30 is corrected based on the detected temperature. More specifically, when the operating position of the flow rate adjusting valve 27 is in the bypass position, the exhaust temperature is detected, the differential pressure or pressure is corrected based on the detected exhaust temperature, and the operating position of the flow rate adjusting valve 27 is determined. When in the filter inflow position, it is preferable to detect the filter temperature and correct the differential pressure or pressure based on the detected filter temperature.
[0044]
Next, the exhaust emission control device 60 of the second embodiment of the present invention will be described. The configuration of the exhaust purification device 60 of the second embodiment of the present invention is basically the same as the configuration of the exhaust purification device 23 of the first embodiment, but in the first embodiment, the exhaust purification device 60 is disposed downstream of the merging portion 25e. The existing pressure sensor 30 is not arranged in the second embodiment.
[0045]
Generally, the exhaust gas downstream of the exhaust gas purification apparatus of the present invention is open to the atmosphere, or a further exhaust gas purifier is provided. Since the atmospheric pressure basically does not fluctuate greatly, the pressure on the exhaust downstream side of the merging portion 25e is substantially constant when the exhaust downstream of the exhaust purification device is open to the atmosphere. Further, even if an additional exhaust purifier is provided downstream of the exhaust section 25e, the exhaust purifier is provided with a bypass passage or the like so long as the exhaust gas flow path is switched. The pressure on the exhaust downstream side of the portion 25e does not vary greatly. In this way, when the pressure on the exhaust downstream side of the merging portion 25e does not vary greatly and is substantially constant, if only the pressure on the exhaust upstream side of the branching portion 25b is measured, the pressure on the exhaust upstream side of the branching portion 25b The differential pressure from the pressure on the exhaust downstream side of the merging portion 25e can be estimated, and the pressure loss caused by the filter side exhaust pipe 25c and the filter 24 and the pressure loss caused by the bypass side exhaust pipe 25d can be calculated. Therefore, in the exhaust purification device 60 of the second embodiment of the present invention, a single pressure sensor 29 can detect a failure or abnormality of the flow rate adjustment valve.
[0046]
More specifically, in the exhaust gas purification device 60 of the second embodiment of the present invention, as described above, one pressure sensor 29 provided upstream of the exhaust of the branch portion 25b is used as the pressure loss estimating means. The pressure loss between the exhaust upstream side of the branch portion 25b and the exhaust downstream side of the merge portion 25e is estimated from the pressure on the exhaust upstream side of the branch portion 25b detected by the sensor 29. Therefore, when the operating position of the flow rate adjusting valve 27 is at the filter inflow position, the pressure loss caused between the exhaust upstream side and the exhaust downstream side of the filter side branch pipe 25c can be estimated by the pressure sensor 29. When the operation position of the regulating valve 27 is in the bypass position, the pressure sensor 29 can estimate the pressure loss generated between the exhaust upstream side and the exhaust downstream side of the bypass side branch pipe 25d.
[0047]
Regarding the determination of the abnormality of the flow rate adjustment valve 27, when the flow rate adjustment valve 27 is commanded to set the operation position of the flow rate adjustment valve 27 to the filter inflow position, the operation position of the flow rate adjustment valve 27 is set to the bypass position. As described above, when the difference between the pressure detected from the pressure sensor 29 when the flow rate adjusting valve 27 is commanded is equal to or less than a predetermined value, it is determined that the flow rate adjusting valve 27 is abnormal. More specifically, the pressure detected by the pressure sensor 29 when a signal is transmitted from the ECU 40 to the flow rate adjusting valve 27 so that the operating position of the flow rate adjusting valve 27 is set to the filter inflow position, and the operation of the flow rate adjusting valve 27 If the difference from the pressure detected by the pressure sensor 29 when a signal is transmitted from the ECU 40 to the flow rate adjusting valve 27 so that the position is set to the bypass position is equal to or less than a predetermined value, the flow rate adjusting valve is abnormal. judge. The predetermined value is equal to the pressure difference detected by the pressure sensor when nothing is collected by the filter 24 or when the filter 24 is not used.
[0048]
Next, abnormality diagnosis control of the flow rate adjustment valve 27 in the exhaust purification device 60 of the second embodiment of the present invention will be described. In the abnormality diagnosis control, the pressure sensor 29 detects the pressure Pb when a signal is transmitted from the ECU 40 to the flow rate adjustment valve 27 so that the operation position of the flow rate adjustment valve 27 is set to the bypass position. The pressure Pf is detected from the pressure sensor 29 when a signal is transmitted from the ECU 40 to the flow rate adjusting valve 27 so that the operating position is the filter inflow position. Then, a pressure difference ΔP is calculated as Pf−Pb from the two detected pressures. If the pressure difference ΔP is greater than or equal to the predetermined value ΔPp, it is determined that there is no failure or abnormality in the flow rate adjustment valve. If the detected differential pressure difference ΔP is smaller than the predetermined value ΔPp, the flow rate adjustment valve 27 Is determined to have a fault or abnormality. The predetermined value ΔPp may be a differential pressure difference ΔP when the filter 24 is used for the first time and the flow rate adjustment valve 27 is operating normally. It may be determined.
[0049]
In the exhaust purification device 60 of the second embodiment, since one pressure sensor can be reduced compared to the exhaust purification device 23 of the first embodiment, the manufacturing cost of the exhaust purification device can be reduced. .
[0050]
Next, the exhaust emission control device 65 of the third embodiment of the present invention will be described. The configuration of the exhaust gas purification device 65 of the third embodiment of the present invention is basically the same as the configuration of the exhaust gas purification device 23 of the first embodiment, but in the first embodiment, the exhaust upstream side of the branch portion 25b and the merging In the third embodiment, the pressure sensors 29 and 30 respectively disposed on the exhaust downstream side of the portion 25e are not disposed. Further, in the exhaust purification device 65 of the third embodiment, an air flow meter 66 is disposed in the intake duct on the intake upstream side of the compressor 15 of the exhaust turbocharger 14 and is sucked from the atmosphere into the combustion chamber 5 of the internal combustion engine. The amount of air (hereinafter referred to as intake air amount) can be measured.
[0051]
By the way, in the exhaust purification device 65 configured as in the third embodiment, the pressure in the exhaust manifold 19 can be estimated from the intake air amount measured by the air flow meter 66. More specifically, when the pressure in the exhaust manifold 19 becomes high, the exhaust gas hardly flows out from the combustion chamber 5 of the internal combustion engine, so that the intake gas (intake air and EGR gas) does not easily flow into the combustion chamber 5. Therefore, when the amount of intake air measured by the air flow meter 66 decreases and, conversely, when the pressure in the exhaust manifold 19 decreases, the exhaust gas easily flows out from the combustion chamber 5 of the internal combustion engine. Intake gas easily flows in, and the amount of intake air measured by the air flow meter 66 increases. As described above, the pressure loss caused by the filter 24 and the like can be estimated by detecting the pressure on the exhaust upstream side of the branch portion 25b. Therefore, according to the exhaust purification device 65 of the third embodiment, the flow rate adjustment When the operating position of the valve 27 is in the filter inflow position, the pressure loss generated between the exhaust upstream side and the exhaust downstream side of the filter side branch pipe 25c can be estimated by the air flow meter 66. When the operating position is in the bypass position, the air flow meter 66 can estimate the pressure loss generated between the exhaust upstream side and the exhaust downstream side of the bypass side branch pipe 25d.
[0052]
Further, when the EGR valve 32 is fully open, when the pressure of the exhaust gas in the exhaust manifold 19 changes, the amount of EGR gas that is the amount of exhaust gas flowing into the combustion chamber 5 from the exhaust manifold 19 via the EGR passage 31 is increased. Change. In general, when the pressure of the exhaust gas in the exhaust manifold 19 increases, the amount of EGR gas increases, and when the pressure of the exhaust gas in the exhaust manifold 19 decreases, the amount of EGR gas decreases. Then, the intake air amount changes according to the EGR gas amount. Generally, when the amount of EGR gas increases, the amount of intake air decreases. Conversely, when the amount of EGR gas decreases, the amount of intake air increases. Therefore, even when the EGR valve 32 is fully opened, the amount of intake air decreases when the pressure of the exhaust gas in the exhaust manifold 19 increases, and the amount of intake air increases when the pressure of the exhaust gas in the exhaust manifold 19 decreases. Therefore, by fully opening the EGR valve 32, the pressure loss caused by the filter 24 and the like can be more accurately measured from the intake air amount measured by the air flow meter 66.
[0053]
Further, as described in the first embodiment, the pressure loss due to the filter 24 and the like changes according to the flow rate of the exhaust gas flowing into the filter 24 and the like, for example, the rotational speed of the internal combustion engine. Similar to the embodiment, the pressure loss value estimated from the air flow meter 66 is corrected based on the flow rate of the exhaust gas flowing into the filter 24 and the like. Similarly to the first embodiment, the influence of the exhaust gas flow rate can be satisfactorily removed from the pressure loss value by measuring the intake air amount by the air flow meter 66 during deceleration and estimating the pressure loss value. I am doing so. Further, as in the first embodiment, the pressure loss detection accuracy is improved by fully opening the throttle valve 17 when the pressure loss is estimated.
[0054]
Therefore, in the exhaust emission control device 65 of the third embodiment of the present invention, the air flow meter 66 is used as the pressure loss estimating means. When the vehicle is decelerated and the throttle valve 17 and the EGR valve 32 are fully opened, the air flow meter 66 The pressure loss between the exhaust upstream side of the branch portion 25b and the exhaust downstream side of the merging portion 25e is estimated from the detected intake air amount.
[0055]
Regarding the determination of the abnormality of the flow rate adjustment valve 27, when the vehicle is decelerated and the throttle valve 17 and the EGR valve 32 are fully opened, the flow rate is set so that the operation position of the flow rate adjustment valve 27 is set to the filter inflow position. The difference in the intake air amount detected from the air flow meter 66 is less than or equal to a predetermined value when the control valve 27 is commanded and when the flow control valve 27 is commanded to set the operating position of the flow control valve 27 to the bypass position. In this case, it is determined that the flow rate adjustment valve 27 is abnormal. More specifically, when the vehicle is decelerated and the throttle valve 17 and the EGR valve 32 are fully opened, a signal is sent from the ECU 40 to the flow rate adjustment valve 27 so that the operation position of the flow rate adjustment valve 27 is set to the filter inflow position. Detected by the air flow meter 66 when a signal is transmitted from the ECU 40 to the flow rate adjusting valve 27 so that the intake air amount detected by the air flow meter 66 and the operating position of the flow rate adjusting valve 27 are set to the bypass position. When the difference from the intake air amount to be performed is equal to or less than a predetermined value, it is determined that the flow rate adjustment valve 27 is abnormal. The predetermined value is equal to the difference in the intake air amount detected by the air flow meter 27 when nothing is collected in the filter 24 or when the filter 24 is not used.
[0056]
Next, abnormality diagnosis control of the flow rate adjustment valve 27 in the exhaust purification device 65 of the third embodiment of the present invention will be described. In the abnormality diagnosis control, when the vehicle is decelerated and the throttle valve 17 and the EGR valve 32 are fully opened, a signal is transmitted from the ECU 40 to the flow rate adjustment valve 27 so that the operation position of the flow rate adjustment valve 27 is set to the bypass position. When the intake air amount Qaf is detected from the air flow meter 66 and a signal is transmitted from the ECU 40 to the flow rate adjusting valve 27 so that the operating position of the flow rate adjusting valve 27 is set to the filter inflow position, the air flow meter 66 The intake air amount Qab is detected. Then, a difference ΔQa between the two intake air amounts detected is calculated as Qaf−Qab. When the difference ΔQa in the intake air amount is equal to or larger than the predetermined value ΔQap, it is determined that there is no failure or abnormality in the flow rate adjustment valve 27. It is determined that the flow rate adjustment valve 27 has a failure or abnormality. The predetermined value ΔQap may be the difference ΔQa in the intake air amount when the filter 24 is used for the first time and the flow rate adjustment valve 27 is operating normally, or from the time of manufacture of the filter 24 and the ECU 40. It may be determined in advance.
[0057]
Next, an exhaust emission control device 70 according to a fourth embodiment of the present invention will be described with reference to FIG. The exhaust purification device 70 of the fourth embodiment has the same configuration as the exhaust purification device 23 of the first embodiment, but the configuration of the exhaust pipe 75 is different from the configuration of the exhaust pipe 25 of the first embodiment. 6A is when the flow rate adjusting valve 77 is in the first operating position, FIG. 6B is when the flow rate adjusting valve 77 is in the second operating position, and FIG. Respectively, when in the neutral operating position. In addition, the arrows in these drawings indicate the flow of exhaust gas.
[0058]
As shown in FIG. 6, in the fourth embodiment, the exhaust pipe 75 includes main exhaust pipes 75a and 75e, and annular branch pipes (annular passages) 75c and 75d connected to the main exhaust pipes 75a and 75e. A casing 76 containing the filter 24 is disposed on the annular branch pipes 75c and 75d. A branch portion 75b is disposed at a connection portion between the main exhaust pipes 75a and 75e and the annular branch pipes 75c and 75d. That is, the annular branch pipe 75c branches from the branch portions 75b of the main exhaust pipes 75a and 75e and returns to the branch portion 75b again.
[0059]
More specifically, the main exhaust pipe is composed of an upstream partial exhaust pipe 75a upstream of the branch portion 75b and a downstream partial exhaust pipe 75e downstream of the branch portion 75b, and the annular branch pipe is a branch portion. 75d and a first partial annular branch pipe 75c that connects one surface of the filter 24, and a second partial annular branch pipe 75d that connects the branch portion 75b and the other surface of the filter 24 opposite to the one surface. It consists of. The upstream partial exhaust pipe 75a branches into three exhaust pipes of a first partial annular branch pipe 75c, a second partial annular branch pipe 75d, and a downstream partial exhaust pipe 75e at the branch portion 75b. Pressure sensors 79 and 80 are provided in the upstream partial exhaust pipe 75a and the downstream partial exhaust pipe 75e, respectively, and are connected to the input port 45 of the ECU 40 via the corresponding A / D converter 47.
[0060]
Further, a flow rate adjusting valve 77 is provided at the branching portion 75b. The operation of the flow rate adjusting valve 77 is controlled by a flow rate adjusting valve step motor 78 connected to the output port 37 of the ECU 40 via the corresponding drive circuit 48. The flow rate adjusting valve 77 continuously rotates around the center of the branch portion 75b, and the angle θ changes with respect to the axis line of the main exhaust pipes 75a and 75e, thereby flowing into the branch portion 75b from the upstream partial exhaust pipe 75a. The flow rate of the exhaust gas flowing into the first partial annular branch pipe 75c and the second partial annular branch pipe 75d is adjusted.
[0061]
In particular, the flow rate adjustment valve 77 of the second embodiment rotates roughly between three operating positions having different angles. These three positions are the first operating position (filter inflow position) shown in FIG. 6 (A), the second operating position (filter inflow position) shown in FIG. 6 (B), and FIG. 6 (C). And the neutral operating position shown. When the flow regulating valve 77 is in the first operating position shown in FIG. 6A, at least most of the exhaust gas flowing from the upstream partial exhaust pipe 75a into the branch portion 75b flows into the first partial annular branch pipe 75c. , Passes through the filter 24 in one direction, flows to the second partial annular branch pipe 75d, and returns to the branch portion 75b again. All exhaust gas that has returned from the second partial annular branch pipe 75d back to the branch section 75b flows out to the downstream partial exhaust pipe 75e. In the following description, the direction in which exhaust gas flows through the annular branch pipes 75c and 75d and the filter 24 in this way is assumed to be the forward direction.
[0062]
When the flow rate adjusting valve 77 is in the second operating position shown in FIG. 6B, at least most of the exhaust gas flowing from the upstream partial exhaust pipe 75a into the branch portion 75b is the second partial annular branch pipe 75d. Flows through the filter 24 in the direction opposite to the one when the flow rate adjusting valve 77 is in the first operating position, flows to the first partial annular branch pipe 75c, and returns to the branch portion 75b again. All the exhaust gas that has returned from the first partial annular branch pipe 75c back to the branch section 75b flows out to the downstream partial exhaust pipe 75e. In the following description, the direction in which the exhaust gas flows through the annular branch pipes 75c and 75d and the filter 24 in this way is described as the reverse direction.
[0063]
That is, as described above, depending on the operating position of the flow rate adjusting valve 77, the exhaust gas that has flowed into the branch portion 75b from the upstream partial exhaust pipe 75a passes through the annular branch pipes 75c and 75d in which the filter 24 is disposed in one direction. Alternatively, it can flow in the opposite direction and then flow out to the downstream partial exhaust pipe 75e via the branch portion 75b.
[0064]
Thus, in the fourth embodiment, the flow of exhaust gas passing through the filter 24 can be reversed between the forward direction and the reverse direction, so that the amount of collected particulates by the position in the filter 24 is reduced. The filter 24 can be used efficiently. Further, the clogging of the filter 24 can be prevented by reversing the flow direction of the exhaust gas.
[0065]
On the other hand, when the flow rate adjusting valve 77 is in the neutral operation position shown in FIG. 6C, at least most of the exhaust gas flowing from the upstream partial exhaust pipe 75a into the branch portion 75b flows into the annular branch pipes 75c and 75d. Without flowing into the downstream partial exhaust pipe 75e. That is, when the flow rate adjustment valve 77 is in the neutral operation position, the exhaust gas flows out to the downstream side exhaust pipe 75e without passing through the filter 24. Therefore, in the fourth embodiment, the neutral operation position of the flow rate adjusting valve 77 is a bypass position for bypassing the filter 24, similarly to the bypass position of the flow rate adjusting valve 77 in the above embodiment.
[0066]
As described above, the exhaust purification device 70 of the fourth embodiment is similar to the exhaust purification device of the first to third embodiments, with the operating position of the flow rate adjusting valve 77 being the first operating position and the second operating position. Can be allowed to flow into the filter, or the exhaust gas can bypass the filter by setting the operating position of the flow rate adjusting valve 77 to the neutral operating position. Therefore, in the exhaust purification device 70 of the fourth embodiment, the flow rate is set so that the operating position of the flow rate adjusting valve 77 is the first operating position and the second operating position, as in the exhaust purification devices of the first to third embodiments. By estimating the difference in pressure loss between when the control valve 77 is commanded and when the flow control valve is commanded to be in the neutral operating position, an abnormality in the flow control valve can be detected.
[0067]
More specifically, in the exhaust purification device 70 of the fourth embodiment of the present invention, the determination of the abnormality of the flow rate adjustment valve 77 is estimated when the flow rate adjustment valve 77 is set to the first operation position or the second operation position. This is based on the difference between the pressure loss between the upstream side exhaust pipe 75a and the downstream side exhaust pipe 75e and the pressure loss when the flow rate adjustment valve 77 is set to the neutral operating position. The pressure loss between the upstream exhaust pipe 75a and the downstream exhaust pipe 75e is detected by the pressure sensor 79 provided in the upstream exhaust pipe 75a and the pressure sensor 80 provided in the downstream exhaust pipe 75e. It is estimated from the differential pressure between the exhaust pipe 75a and the downstream exhaust pipe 75e. Alternatively, the pressure loss between the upstream side exhaust pipe 75a and the downstream side exhaust pipe 75e is detected by the pressure sensor 79 provided in the upstream side exhaust pipe 75a as in the exhaust purification device 60 of the second embodiment. It may be estimated from the pressure in the exhaust pipe 75a, or may be estimated from the intake air amount detected by the air flow meter 66 provided on the intake passage in the same manner as the exhaust purification device 65 of the third embodiment.
[0068]
The filter 24 used in the above embodiment may be a particulate filter provided with an active oxygen generator so that fine particles collected by the mechanism described below can be continuously oxidized and removed. Good.
[0069]
Hereinafter, the exhaust gas purification mechanism by the filter, particularly the particulate removal action in the exhaust gas will be described. In FIG. 7, a case where platinum (Pt) is used as a noble metal catalyst and potassium (K) is used as an active oxygen generator will be described as an example. However, other noble metals, alkali metals, alkaline earth metals, rare earths, Even if a transition metal is used, the same fine particle removing action is performed.
[0070]
FIGS. 7A and 7B schematically show enlarged views of the surface of the support layer formed on the surface of the partition walls of the filter and on the pore surfaces of the partition walls. 7A and 7B, reference numeral 85 indicates platinum particles, and reference numeral 86 indicates a carrier layer containing an active oxygen generator such as potassium.
[0071]
First, when the ratio of air and fuel supplied into the intake passage and the combustion chamber 5 is referred to as the air-fuel ratio of the exhaust gas, when the air-fuel ratio of the exhaust gas flowing into the filter is lean,_X, Especially NO and NO₂NO is generated in the exhaust gas._xIt is included. Thus, the filter contains excess oxygen and NO_XExhaust gas containing
[0072]
When the exhaust gas flows into the filter, the oxygen in the exhaust gas becomes O as shown in FIG.₂ ^-Or O^2-It adheres to the surface of platinum in the form of On the other hand, NO in the exhaust gas is O on the surface of platinum.₂ ^-Or O^2-Reacts with NO₂(2NO + O₂→ 2NO₂). Then the generated NO₂And NO in exhaust gas₂Part of the oxygen is absorbed by the active oxygen generator 86 while being oxidized on platinum, and nitrate ions (NO) as shown in FIG._Three ^-) In the form of active oxygen generator 86 and nitrate (KNO)_Three) Is generated. That is, oxygen in the exhaust gas is held in the active oxygen generator 86 in the form of nitrate ions.
[0073]
Incidentally, fine particles mainly composed of carbon (C) are generated in the combustion chamber. Therefore, these fine particles are contained in the exhaust gas. The fine particles in the exhaust gas come into contact with and adhere to the surface of the active oxygen generating agent 86 as shown in FIG. 7B when the exhaust gas flows through the filter.
[0074]
When the fine particles 87 adhere on the active oxygen generator 86, a difference in concentration occurs between the surface of the active oxygen generator 86 and the inside thereof. The active oxygen generator 86 stores oxygen in the form of nitrate ions, and the stored oxygen tends to move toward the contact surface between the fine particles 87 and the active oxygen generator 86. As a result, nitrate (KNO) formed in the active oxygen generator 86_Three) Is decomposed into K, O, and NO, O goes to the surface of the active oxygen generator 86, while NO is released from the active oxygen generator 86 to the outside. The NO released to the outside in this manner is oxidized on the downstream platinum by the mechanism described above, and is again held in the form of nitrate ions in the active oxygen generator 86.
[0075]
By the way, O toward the contact surface between the fine particles 87 and the active oxygen generator 86 is nitrate (KNO)._ThreeSince the oxygen is decomposed from a compound such as), it is an active oxygen having unpaired electrons and extremely high reactivity. When these active oxygens come into contact with the fine particles 87, the fine particles 87 are oxidized within a short time (several seconds to several tens of minutes) without emitting a luminous flame, and the fine particles 87 disappear completely. Therefore, the particulates 87 are oxidized and removed in this way, and the particulates 87 are hardly deposited on the filter.
[0076]
【The invention's effect】
According to the present invention, when the switching valve is commanded to change the operating position of the switching valve, it is determined that there is an abnormality in the switching valve when the difference in pressure loss values estimated by the pressure loss estimating means is large. Thus, the abnormality of the switching valve can be reliably detected.
[Brief description of the drawings]
FIG. 1 is a diagram of an internal combustion engine equipped with an exhaust emission control device according to a first embodiment of the present invention.
FIG. 2 is a flowchart of abnormality diagnosis control.
FIG. 3 is a diagram showing the relationship between the flow rate of exhaust gas and the differential pressure between the upstream and downstream of the filter.
FIG. 4 is a diagram of an internal combustion engine provided with an exhaust purification device of a second embodiment of the present invention.
FIG. 5 is a diagram of an internal combustion engine provided with an exhaust purification device of a third embodiment of the present invention.
FIG. 6 is a diagram of an exhaust emission control device according to a fourth embodiment of the present invention.
FIG. 7 is a diagram relating to an explanation of the particulate removal action.
[Explanation of symbols]
23. Exhaust purification device
24 ... Particulate filter
25 ... exhaust pipe
27 ... Flow control valve
29, 30 ... Pressure sensor
40 ... ECU

Claims (5)

The exhaust passage of the internal combustion engine branches into two branch exhaust passages, a particulate filter that collects particulates in the inflowing exhaust gas is disposed in the first branch exhaust passage, and a switching valve is provided at the branch portion of the branch exhaust passage. The switching valve switches between a filter inflow position where at least most of the exhaust gas flows into the first branch exhaust passage and a bypass position where at least most of the exhaust gas flows into the second branch exhaust passage. In an exhaust gas purification device for an internal combustion engine,
When the switching valve operating position is at the filter inflow position, the pressure loss due to the first branch exhaust passage and the particulate filter is estimated, and when the switching valve operating position is at the bypass position, the pressure loss due to the second branch exhaust passage is estimated. Pressure loss estimating means for estimating, and bypassing the pressure loss value estimated by the pressure loss estimating means when the switching valve is commanded to set the operating position of the switching valve to the filter inflow position, and the operating position of the switching valve When the switch valve is instructed to be in the position, if the difference from the pressure loss value estimated by the pressure loss estimation means is equal to or less than a predetermined value, it is determined that the switch valve is abnormal. An exhaust purification device for an internal combustion engine. An annular passage that branches off from the exhaust passage of the internal combustion engine and returns to the branch portion is provided, a particulate filter that collects particulates in the exhaust gas flowing into the annular passage is disposed, and a switching valve is disposed at the branch portion. The switching valve is provided with a filter inflow position where at least most of the exhaust gas flows into the annular passage, and a bypass that flows through the exhaust passage downstream of the branch portion without flowing at least most of the exhaust gas into the annular passage. In an exhaust gas purification apparatus for an internal combustion engine that can be switched between positions,
When the operating position of the switching valve is in the filter inflow position, pressure loss caused by the annular passage and the particulate filter is estimated, and when the operating position of the switching valve is in the bypass position, the exhaust between the exhaust upstream of the branching section and the exhaust downstream Pressure loss estimating means for estimating the pressure loss caused by the passage, and switching the pressure loss value estimated by the pressure loss estimating means when commanding the switching valve to set the operation position of the switching valve to the filter inflow position When the switching valve is commanded to set the valve operating position to the bypass position, if the difference from the pressure loss estimated by the pressure loss estimating means is equal to or less than a predetermined value, it is determined that the switching valve is abnormal. An exhaust purification device for an internal combustion engine. The exhaust of the internal combustion engine according to claim 1 or 2, wherein the pressure loss estimation means estimates the pressure loss based on either an amount of intake air taken into the internal combustion engine or a pressure in the exhaust passage upstream of the exhaust at the branch portion. Purification equipment. The branch exhaust passage is merged downstream of the particulate filter exhaust, and the pressure loss estimating means calculates a pressure difference between the pressure in the exhaust passage upstream of the branch portion and the pressure in the exhaust passage downstream of the merge portion. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the pressure loss is estimated based on the pressure loss. 3. The exhaust gas purification of an internal combustion engine according to claim 2, wherein the pressure loss estimating means estimates the pressure loss based on a differential pressure between a pressure in the exhaust passage upstream of the branch portion and an exhaust passage downstream of the branch portion. apparatus.

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