JP5573817B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust emission control device for an internal combustion engine.

  For example, as described in Patent Document 1, a selective reduction type NOx catalyst that is one of NOx purification catalysts that purifies nitrogen oxides (NOx) in exhaust gas, and NOx purification using this selective reduction type NOx catalyst. 2. Description of the Related Art An exhaust gas purification apparatus for an internal combustion engine is known that includes a reducing agent supply mechanism that supplies a reducing agent to be used into an exhaust passage and a dispersion plate that is provided in the exhaust passage and disperses the reducing agent.

  In this exhaust purification device, urea water is injected from the reducing agent supply mechanism toward the exhaust passage. The injected urea water is atomized by the dispersion plate and becomes ammonia by hydrolysis by exhaust heat. This ammonia is supplied as a reducing agent to the selective reduction type NOx catalyst.

JP 2001-516635 A

  By the way, when abnormality such as deformation occurs in the dispersion plate, the state of atomization of urea water changes. Therefore, the amount of ammonia supplied to the selective reduction type NOx catalyst changes, and as a result, the amount of NOx to be purified, that is, the NOx purification rate is lowered.

  Here, the reduction of the NOx purification rate is caused not only by the abnormality of the dispersion plate but also by the deterioration of the NOx purification catalyst and the abnormality of the reducing agent supply mechanism (for example, the abnormality of the injection valve for injecting the reducing agent). For this reason, when the NOx purification rate decreases, there is a possibility that erroneous parts such as the NOx purification catalyst and the reducing agent supply mechanism may be replaced despite the abnormality in the dispersion plate. It is desirable to specify.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an exhaust purification device for an internal combustion engine that can identify an abnormality of a dispersion plate, which is one of the causes of a decrease in the NOx purification rate. There is.

  In the following, means for achieving the above object and its effects are described. Note that “upstream” and “downstream” described in the present specification and claims are based on the flow direction of the exhaust gas in the exhaust system.

The invention described in claims 1 to 3 is provided with a NOx purification catalyst for purifying NOx by supplying a reducing agent, a reducing agent supply mechanism for supplying the reducing agent into the exhaust passage, and the NOx purification provided in the exhaust passage. An exhaust gas purification apparatus for an internal combustion engine comprising a dispersion plate that disperses a reducing agent upstream of a catalyst, and a pressure sensor that detects an exhaust pressure upstream of the dispersion plate, wherein the NOx purification rate of the NOx purification catalyst is If the exhaust pressure is lower than a predetermined value and is not a value between a predetermined upper limit pressure value and a lower limit pressure value, the gist is to perform an abnormality determination that determines that the dispersion plate is abnormal.

  When an abnormality occurs in the dispersion plate, the pressure loss of the dispersion plate changes. For this reason, the exhaust pressure upstream of the dispersion plate has an abnormal value different from the normal value. Here, the abnormal value of the exhaust pressure also occurs when pressure loss in other members constituting the exhaust system changes. However, since there is a high correlation between an abnormality in the dispersion plate and a decrease in the NOx purification rate, an abnormality may have occurred in the dispersion plate when both a decrease in the NOx purification rate and the abnormal value of the exhaust pressure occur. The nature is very high.

Therefore, in the same configuration, when the NOx purification rate is lower than a predetermined value and the exhaust pressure is an abnormal value that is not a value between a predetermined upper limit pressure value and a lower limit pressure value, the dispersion plate is abnormal. Judgment is made. Therefore, it is possible to specify the abnormality of the dispersion plate.

  As the upper limit pressure value, it is possible to set a pressure value when the exhaust pressure increases with an increase in pressure loss due to deformation of the dispersion plate, adhesion of foreign matter to the dispersion plate, or the like. In addition, as the lower limit pressure value, a pressure value when the exhaust pressure becomes lower with a decrease in pressure loss due to deformation of the dispersion plate, breakage of the dispersion plate, or the like can be set.

The invention according to claim 1 to 3, on the upstream of the pre-Symbol pressure sensor, regeneration process with trapping particulate in the exhaust gas filter is provided to be carried out, immediately after the regeneration process has been completed The gist is to perform the abnormality determination based on the exhaust pressure.

  When a filter that collects particulates in the exhaust is provided upstream of the pressure sensor, the amount of particulates accumulated in the filter affects the exhaust pressure detected by the pressure sensor. Therefore, when the abnormality determination of the dispersion plate based on the exhaust pressure is performed, there is a possibility that the change in the exhaust pressure due to the influence of the amount of accumulated particulates is erroneously determined as the change in the exhaust pressure due to the abnormality of the dispersion plate. In this regard, in the same configuration, abnormality determination of the dispersion plate is performed immediately after the filter regeneration process is completed, that is, based on the exhaust pressure when the amount of particulate accumulation is very small. Therefore, when determining the abnormality of the dispersion plate, it is possible to suppress the influence of the accumulation amount of the fine particles as much as possible, thereby improving the accuracy of the abnormality determination of the dispersion plate.

The invention as claimed in claims 1 to 3 has a differential pressure sensor for detecting a pressure difference between the upstream and downstream exhaust pressure prior Symbol filter, the pressure difference immediately after the regeneration process has been completed The gist is to prohibit the abnormality determination when the value is not between a predetermined upper limit differential pressure value and a lower limit differential pressure value.

  When the amount of particulates accumulated in the filter is excessively large, when the amount of particulates discharged from the internal combustion engine is excessively large, or when the regeneration process is not sufficiently performed, the pressure loss of the filter becomes excessively high. The pressure difference becomes large. On the other hand, if the pressure loss of the filter becomes excessively low due to the occurrence of melting damage, the pressure difference becomes small.

  Such a change in the pressure loss of the filter affects the detection value of the pressure sensor downstream of the filter. Therefore, there is a risk that an excessive increase or an excessive decrease in the exhaust pressure due to an abnormality in the filter pressure loss may be erroneously determined as an abnormality in the dispersion plate. In this regard, in the same configuration, the pressure difference immediately after the regeneration process is finished is not a value between a predetermined upper limit differential pressure value and a lower limit differential pressure value, that is, the pressure loss of the filter changes excessively. When there is a cage abnormality, the dispersion plate abnormality determination based on the exhaust pressure is prohibited. Therefore, when the abnormality determination of the dispersion plate is performed, an adverse effect due to the abnormality of the pressure loss of the filter can be suppressed as much as possible, thereby improving the accuracy of the determination of the abnormality of the dispersion plate.

The invention according to claim 1 to 3, before Symbol limit pressure value and the lower limit pressure value is its gist to be variably set in accordance with the ash deposition amount of the filter.

  Ash that is a component derived from the lubricating oil and difficult to burn by the above-described regeneration process accumulates on the filter. In addition, as this ash, the component (metal components, such as Zn, Ca, Mg, Na, etc.) contained in the additive etc. of lubricating oil, etc. are mentioned, for example. And the said pressure difference immediately after completion | finish of a reproduction | regeneration process changes also with the accumulation amount of ash. Therefore, in this configuration, the upper limit differential pressure value and the lower limit differential pressure value for determining whether or not the pressure difference is a value outside a predetermined range are variably set according to the ash accumulation amount of the filter. I am doing so. Accordingly, it is possible to increase the accuracy of determining whether or not to perform abnormality determination of the dispersion plate.

  Since the pressure difference increases as the ash deposition amount increases, in this configuration, it is desirable to increase the upper limit pressure difference value and the lower limit differential pressure value as the ash deposition amount increases.

The amount of ash accumulation increases as the total travel distance of the vehicle increases. Therefore, when the upper limit differential pressure value and the lower limit differential pressure value are variably set according to the ash accumulation amount of the filter, the total travel distance of the vehicle on which the internal combustion engine is mounted is set as in the invention according to claim 1. It is possible to adopt a configuration in which the upper limit differential pressure value and the lower limit differential pressure value are variably set so as to increase as the length increases.

In addition, since ash is the remaining unburned fine particles in the regeneration process, the amount of ash deposition increases as the number of regeneration processes is increased. Therefore, when variably sets the upper limit pressure value and the lower limit pressure value depending on the ash accumulation amount of the filter, such as by the invention of claim 2, as the number of times the execution of the regeneration process, the upper limit It is also possible to adopt a configuration in which the differential pressure value and the lower limit differential pressure value are variably set so as to increase.

In addition, as described above, ash is also the remaining unburned fine particles in the regeneration process, so that the amount of accumulated ash increases as the integrated amount of fine particles collected by the filter increases. Therefore, when the upper limit differential pressure value and the lower limit differential pressure value are variably set in accordance with the ash accumulation amount of the filter, according to the invention of claim 3 , the total integrated amount of the fine particles collected in the filter It is also possible to adopt a configuration in which the upper limit differential pressure value and the lower limit differential pressure value are variably set so as to increase as the number increases.

According to a fourth aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to any one of the first to third aspects, the pressure difference immediately after the regeneration process is completed is determined by the upper limit differential pressure value and the lower limit. The gist is to determine that the filter is abnormal when the NOx purification rate is not a value between the differential pressure values and lower than the predetermined value.

When the pressure difference immediately after completion of the regeneration process is larger than the upper limit differential pressure value, the amount of exhaust gas passing through the filter is reduced, so the flow rate of exhaust gas flowing into the NOx purification catalyst is reduced. There is a risk that the amount of reducing agent per unit time supplied to the NOx purification catalyst will be insufficient and the NOx purification rate will decrease. Further, when the pressure difference immediately after the regeneration process is less than the lower limit differential pressure value, the amount of exhaust gas passing through the filter is increased, so the flow rate of exhaust gas flowing into the NOx purification catalyst increases, As a result, the amount of reducing agent stored in the NOx purification catalyst may be insufficient, and the NOx purification rate may be reduced. That is, when the NOx purification rate is lower than the predetermined value and the pressure difference is not a value between the upper limit differential pressure value and the lower limit differential pressure value, it is determined that an abnormality has occurred in the filter. it can. Therefore, in the same configuration, when the pressure difference immediately after the regeneration process is not a value between the upper limit differential pressure value and the lower limit differential pressure value, and the NOx purification rate is lower than the predetermined value, The filter is configured to determine that there is an abnormality. Accordingly, not only the abnormality of the dispersion plate but also the abnormality of the filter can be determined.

BRIEF DESCRIPTION OF THE DRAWINGS Schematic which shows the internal combustion engine to which this is applied, and its periphery structure about 1st Embodiment of the exhaust gas purification device of the internal combustion engine concerning this invention. The flowchart which shows the procedure of the abnormality determination process performed in the same embodiment. The flowchart which shows the procedure of the abnormality determination process performed in 2nd Embodiment. The flowchart which shows the procedure of the abnormality determination process performed in 3rd Embodiment. The graph which shows the relationship between an upper limit differential pressure value and a lower limit differential pressure value, and travel distance in the same embodiment.

(First embodiment)
A first embodiment of an internal combustion engine exhaust gas purification apparatus according to the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 is a schematic configuration diagram showing a diesel engine (hereinafter simply referred to as “engine”) to which the exhaust emission control device according to the present embodiment is applied, and a peripheral configuration thereof.
The engine 1 is provided with a plurality of cylinders # 1 to # 4. A plurality of fuel injection valves 4 a to 4 d are attached to the cylinder head 2. These fuel injection valves 4a to 4d inject fuel into the combustion chambers of the cylinders # 1 to # 4. Also, the cylinder head 2 is provided with intake ports for introducing fresh air into the cylinders and exhaust ports 6a to 6d for discharging combustion gas to the outside of the cylinders corresponding to the respective cylinders # 1 to # 4. It has been.

  The fuel injection valves 4a to 4d are connected to a common rail 9 that accumulates high-pressure fuel. The common rail 9 is connected to the supply pump 10. The supply pump 10 sucks fuel in the fuel tank and supplies high-pressure fuel to the common rail 9. The high-pressure fuel supplied to the common rail 9 is injected into the cylinder from the fuel injection valves 4a to 4d when the fuel injection valves 4a to 4d are opened.

  An intake manifold 7 is connected to the intake port. The intake manifold 7 is connected to the intake passage 3. An intake throttle valve 16 for adjusting the intake air amount is provided in the intake passage 3.

An exhaust manifold 8 is connected to the exhaust ports 6a to 6d. The exhaust manifold 8 is connected to the exhaust passage 26.
In the middle of the exhaust passage 26, there is provided a turbocharger 11 that supercharges intake air introduced into the cylinder using exhaust pressure. An intercooler 18 is provided in the intake passage 3 between the intake side compressor of the turbocharger 11 and the intake throttle valve 16. The intercooler 18 cools the intake air whose temperature has risen due to supercharging of the turbocharger 11.

  A first purification member 30 that purifies the exhaust gas is provided in the middle of the exhaust passage 26 and downstream of the exhaust side turbine of the turbocharger 11. Inside the first purification member 30, an oxidation catalyst 31 and a filter 32 are arranged in series with respect to the flow direction of the exhaust gas.

  The oxidation catalyst 31 carries a catalyst for oxidizing HC in the exhaust. The filter 32 is a member that collects PM (particulate matter) in the exhaust gas, and is made of porous ceramic. The filter 32 carries a catalyst for promoting the oxidation of PM, and the PM in the exhaust gas is collected when passing through the porous wall of the filter 32.

  Further, a fuel addition valve 5 for supplying fuel as an additive to the oxidation catalyst 31 and the filter 32 is provided in the vicinity of the collecting portion of the exhaust manifold 8. The fuel addition valve 5 is connected to the supply pump 10 through a fuel supply pipe 27. The position of the fuel addition valve 5 can be changed as appropriate as long as it is in the exhaust system and upstream of the first purification member 30.

  When the amount of PM trapped in the filter 32 (hereinafter referred to as PM accumulation amount PMsm) exceeds a predetermined value, regeneration processing of the filter 32 is started and fuel is supplied from the fuel addition valve 5 into the exhaust manifold 8. Be injected. The fuel injected from the fuel addition valve 5 is combusted when it reaches the oxidation catalyst 31, thereby increasing the exhaust temperature. The exhaust gas whose temperature has been raised by the oxidation catalyst 31 flows into the filter 32, whereby the temperature of the filter 32 is raised, whereby the PM deposited on the filter 32 is oxidized and the filter 32 is regenerated. Then, when the PM accumulation amount PMsm decreases to a predetermined regeneration end value PMe or less, the fuel injection from the fuel addition valve 5 is terminated and the regeneration process is terminated.

  A second purification member 40 that purifies the exhaust gas is provided in the middle of the exhaust passage 26 and downstream of the first purification member 30. A selective reduction type NOx catalyst (hereinafter referred to as SCR catalyst) 41 is disposed inside the second purification member 40 as a NOX purification catalyst that purifies NOx in the exhaust gas using a reducing agent.

  Further, a third purification member 50 for purifying exhaust gas is provided in the middle of the exhaust passage 26 and downstream of the second purification member 40. Inside the third purification member 50, an ammonia oxidation catalyst 51 for purifying ammonia in the exhaust is disposed.

  The engine 1 is provided with a urea water supply mechanism 200 as a reducing agent supply mechanism that supplies a reducing agent to the SCR catalyst 41. The urea water supply mechanism 200 includes a tank 210 that stores urea water, a urea addition valve 230 that injects urea water into the exhaust passage 26, a supply passage 240 that connects the urea addition valve 230 and the tank 210, and a supply passage 240. The pump 220 is provided in the middle.

  The urea addition valve 230 is provided in the exhaust passage 26 between the first purification member 30 and the second purification member 40, and its injection hole is directed to the SCR catalyst 41. When the urea addition valve 230 is opened, urea water is injected and supplied into the exhaust passage 26 via the supply passage 240.

  The pump 220 is an electric pump, and at the time of forward rotation, the urea water is fed from the tank 210 toward the urea addition valve 230. On the other hand, during reverse rotation, urea water is sent from the urea addition valve 230 toward the tank 210. In other words, during the reverse rotation of the pump 220, urea water is recovered from the urea addition valve 230 and the supply passage 240 and returned to the tank 210.

  Further, in the exhaust passage 26 between the urea addition valve 230 and the SCR catalyst 41, the urea water injected from the urea addition valve 230 is dispersed upstream of the SCR catalyst 41 to promote atomization of the urea water. A dispersion plate 60 is provided.

  The urea water injected from the urea addition valve 230 is hydrolyzed by the heat of the exhaust to become ammonia. The ammonia is supplied to the SCR catalyst 41 as a NOx reducing agent. Ammonia supplied to the SCR catalyst 41 is occluded by the SCR catalyst 41 and used for NOx reduction. A part of the hydrolyzed ammonia is directly used for NOx reduction before being occluded by the SCR catalyst 41.

  In addition, the engine 1 is provided with an exhaust gas recirculation device (hereinafter referred to as an EGR device). This EGR device is a device that reduces the combustion temperature in the cylinder by introducing a part of the exhaust gas into the intake air, thereby reducing the amount of NOx generated. This exhaust gas recirculation device includes an EGR passage 13 that communicates the intake passage 3 and the exhaust manifold 8, an EGR valve 15 provided in the EGR passage 13, an EGR cooler 14, and the like. By adjusting the opening degree of the EGR valve 15, the exhaust gas recirculation amount introduced into the intake passage 3 from the exhaust passage 26, that is, the EGR amount is adjusted. Further, the temperature of the exhaust gas flowing through the EGR passage 13 is lowered by the EGR cooler 14.

  Various sensors for detecting the engine operation state are attached to the engine 1. For example, the air flow meter 19 detects the intake air amount GA in the intake passage 3. The throttle valve opening sensor 20 detects the opening of the intake throttle valve 16. The engine rotation speed sensor 21 detects the rotation speed of the crankshaft, that is, the engine rotation speed NE. The accelerator sensor 22 detects an accelerator pedal depression amount, that is, an accelerator operation amount ACCP. The outside air temperature sensor 23 detects the outside air temperature THout. The vehicle speed sensor 24 detects the vehicle speed SPD of the vehicle on which the engine 1 is mounted. The ignition switch 25 detects a start operation and a stop operation of the engine 1 by a vehicle driver.

  The first exhaust temperature sensor 100 provided upstream of the oxidation catalyst 31 detects the first exhaust temperature TH1 that is the exhaust temperature before flowing into the oxidation catalyst 31. The differential pressure sensor 110 detects a differential pressure ΔP that is a pressure difference between the exhaust pressure upstream and downstream of the filter 32. A second exhaust temperature sensor 120, a first NOx sensor 130, and a pressure sensor 150 are provided in the exhaust passage 26 between the first purification member 30 and the second purification member 40 and upstream of the urea addition valve 230. ing. The second exhaust temperature sensor 120 detects a second exhaust temperature TH2, which is the exhaust temperature before flowing into the SCR catalyst 41. The first NOx sensor 130 detects a first NOx concentration N1, which is the NOx concentration in the exhaust before flowing into the SCR catalyst 41. The pressure sensor 150 detects a back pressure P that is an exhaust pressure upstream of the dispersion plate 60. The exhaust passage 26 downstream of the third purification member 50 is provided with a second NOx sensor 140 that detects a second NOx concentration N2 that is the NOx concentration of the exhaust purified by the SCR catalyst 41.

  Outputs from these various sensors are input to the control device 80. The control device 80 includes a central processing control device (CPU), a read-only memory (ROM) that stores various programs and maps in advance, a random access memory (RAM) that temporarily stores CPU calculation results, a timer counter, an input The microcomputer is mainly configured with an interface, an output interface, and the like.

  Then, by this control device 80, for example, fuel injection amount control / fuel injection timing control of the fuel injection valves 4a to 4d and the fuel addition valve 5, discharge pressure control of the supply pump 10, and driving of the actuator 17 for opening and closing the intake throttle valve 16 Various controls of the engine 1 such as quantity control and opening control of the EGR valve 15 are performed. The exhaust gas purification control such as the regeneration process for burning the PM collected by the filter 32 is also performed by the controller 80.

  Further, the control device 80 performs urea water addition control by the urea addition valve 230 as one of exhaust purification control. In this addition control, a urea addition amount without excess or deficiency is calculated based on the engine operating state or the like in order to reduce the NOx discharged from the engine 1, and the calculated urea addition amount is injected from the urea addition valve 230. Thus, the valve opening state of the urea addition valve 230 is controlled. The urea water addition for NOx reduction is continuously performed during engine operation, and is stopped when the engine operation is stopped.

  By the way, as described above, when abnormality such as deformation occurs in the dispersion plate 60, the atomization state of the urea water changes. Therefore, the amount of ammonia supplied to the SCR catalyst 41 changes, and as a result, the amount of NOx to be purified, that is, the NOx purification rate is reduced.

Therefore, the control device 80 performs the abnormality determination process shown in FIG. 2 at predetermined intervals to identify an abnormality of the dispersion plate 60 that is one of the causes of the NOx purification rate decreasing.
When this process is started, first, the NOx purification rate R is calculated from the first NOx concentration N1 and the second NOx concentration N2 (S100). Here, the NOx purification rate R is calculated from the following equation (1). In the present embodiment, the first NOx concentration N1 and the second NOx concentration N2 may be detected by a sensor, but may be estimated based on the engine operating state or the like.

R = (N1-N2) / N1 (1)
R: NOx purification rate N1: First NOx concentration N2: Second NOx concentration

Next, it is determined whether or not the NOx purification rate R is smaller than the purification rate determination value α (S110). When the NOx purification rate R is equal to or greater than the purification rate determination value α (S110: NO), it is determined that NOx purification is normally performed, and this process is temporarily terminated.

  On the other hand, when the NOx purification rate R is smaller than the purification rate determination value α (S110: YES), the back pressure P that is the exhaust pressure upstream of the dispersion plate 60 is equal to the upper limit back pressure value Pmax and the lower limit back pressure value Pmin. It is determined whether the value is between (S120). This upper limit back pressure value Pmax is a predetermined upper limit pressure value. More specifically, a pressure value when the back pressure P becomes abnormally high with an increase in pressure loss due to deformation of the dispersion plate 60 or adhesion of foreign matter to the dispersion plate 60 is set.

  The lower limit back pressure value Pmin is also a predetermined lower limit pressure value. More specifically, a pressure value is set when the back pressure P becomes abnormally low as pressure loss decreases due to deformation of the dispersion plate 60, breakage of the dispersion plate 60, or the like.

  When the back pressure P is a value between the upper limit back pressure value Pmax and the lower limit back pressure value Pmin, that is, when “Pmin <P <Pmax” is satisfied (S120: YES), the dispersion plate 60 Is determined to be normal, the process is temporarily terminated.

  On the other hand, when the back pressure P is not between the upper limit back pressure value Pmax and the lower limit back pressure value Pmin, that is, when “Pmin ≧ P” or “P ≧ Pmax” is satisfied (S120: NO). Then, it is determined that there is an abnormality in the dispersion plate 60 (S130), and this process is temporarily terminated. If it is determined in step S130 that there is an abnormality in the dispersion plate 60, the vehicle driver is notified of the occurrence of the abnormality by turning on a warning lamp or the like.

Next, the operation of this embodiment will be described.
When an abnormality occurs in the dispersion plate 60, the pressure loss of the dispersion plate 60 changes. Therefore, the back pressure P, which is the exhaust pressure upstream of the dispersion plate 60, has an abnormal value different from that in the normal state. Here, the abnormal value of the back pressure P also occurs when pressure loss in other members constituting the exhaust system changes. For example, the pressure loss also changes due to a change in the PM accumulation amount PMsm of the filter 32 or adhesion of foreign matter to the inner wall of the exhaust passage 26. However, since there is a high correlation between the abnormality of the dispersion plate 60 and the decrease in the NOx purification rate R, when both the decrease in the NOx purification rate R and the abnormal value of the back pressure P occur, the abnormality is present in the dispersion plate 60. It is very likely that it has occurred.

  Therefore, in the abnormality determination process, the NOx purification rate R is lower than the purification rate determination value α (affirmative determination in step S110), and the back pressure P is a predetermined upper limit back pressure value Pmax and lower limit back pressure value Pmin. When the abnormal value is not a value between (a negative determination in step S120), it is determined that the dispersion plate 60 is abnormal. Therefore, it is possible to identify the abnormality of the dispersion plate 60, which is one of the causes that the NOx purification rate R decreases.

As described above, according to the present embodiment, the following effects can be obtained.
(1) When the NOx purification rate R is lower than the purification rate determination value α and the back pressure P is an abnormal value that is not a value between the predetermined upper limit back pressure value Pmax and the lower limit back pressure value Pmin, dispersion The plate 60 is determined to be abnormal. Therefore, it is possible to identify the abnormality of the dispersion plate 60, which is one of the causes that the NOx purification rate R is reduced.
(Second Embodiment)
Next, a second embodiment of the internal combustion engine exhaust gas purification apparatus according to the present invention will be described with reference to FIG.

  When the filter 32 is provided upstream of the pressure sensor 150, the amount of PM accumulated on the filter 32 affects the back pressure P detected by the pressure sensor 150. Therefore, when the abnormality determination of the dispersion plate 60 based on the back pressure P is performed, there is a possibility that the change of the back pressure P due to the influence of the PM accumulation amount is erroneously determined as the change of the back pressure P due to the abnormality of the dispersion plate 60. is there.

  Therefore, in the present embodiment, the effect of the PM accumulation amount on the abnormality determination of the dispersion plate 60 is suppressed, and a new one as shown in FIG. 3 is provided for the abnormality determination process described in the first embodiment. Steps S200 and S210 are added.

Therefore, hereinafter, the abnormality determination process in the present embodiment will be described focusing on the differences from the first embodiment.
The abnormality determination process of this embodiment shown in FIG. 3 is also executed by the control device 80 at predetermined intervals. In FIG. 3, the same processing steps as those described in FIG.

When this process is started, first, the NOx purification rate R is calculated from the first NOx concentration N1 and the second NOx concentration N2 (S100).
Next, it is determined immediately after the end of the regeneration process of the filter 32 and whether the PM accumulation amount PMsm is smaller than the determination value A (S200). Normally, the PM deposition amount PMsm immediately after the regeneration process is completed is sufficiently small. However, when the end of the regeneration process is due to the interruption of the regeneration process or the like, the PM deposition amount PMsm immediately after the regeneration process ends is not sufficiently reduced, and the PM deposition amount PMsm decreases. There may be an incomplete state. Therefore, as the determination value A, a value that can determine that the PM accumulation amount PMsm is sufficiently small is set. For example, in the present embodiment, the same value as the regeneration end value PMe is set. Note that comparison of the determination value A and the PM accumulation amount PMsm is not necessary to perform always, or may be omitted as appropriate.

Then, when not immediately after the end of the regeneration process of the filter 32, or when the PM accumulation amount PMsm is greater than or equal to the determination value A (S200: NO), this process is temporarily ended.
On the other hand, immediately after the regeneration processing of the filter 32 is completed and the PM accumulation amount PMsm is smaller than the determination value A (S200: YES), the pressure difference between the upstream and downstream exhaust pressures of the filter 32 is obtained. It is determined whether or not the differential pressure ΔP immediately after the end of the regeneration process is a value between the upper limit differential pressure value ΔPmax and the lower limit differential pressure value ΔPmin (S210).

  The upper limit differential pressure value ΔPmax is a value determined through a prior experiment or the like. More specifically, when the PM deposition amount PMsm of the filter 32 is excessively large, when the particulate discharge amount from the engine 1 is excessively large, or when the regeneration process is not sufficiently performed, the pressure of the filter 32 is increased. Since the loss becomes excessively high, the differential pressure ΔP becomes excessively large. Thus, the value when the differential pressure ΔP is excessively large is set as the upper limit differential pressure value ΔPmax.

  The lower limit differential pressure value ΔPmin is also a value determined through a prior experiment or the like. More specifically, if the pressure loss of the filter 32 becomes excessively low due to the occurrence of melting damage or the like, the differential pressure ΔP becomes excessively small. Thus, the value when the differential pressure ΔP is excessively small is set as the lower limit differential pressure value ΔPmin.

  When the differential pressure ΔP is not a value between the upper limit differential pressure value ΔPmax and the lower limit differential pressure value ΔPmin, that is, when “ΔPmin ≧ ΔP” or “ΔP ≧ ΔPmax” is satisfied (S210: NO). The present process is temporarily terminated without determining the abnormality of the dispersion plate 60 based on the NOx purification rate R and the back pressure P. That is, when a negative determination is made in step S210, abnormality determination of the dispersion plate 60 is prohibited.

  On the other hand, when the differential pressure ΔP is a value between the upper limit differential pressure value ΔPmax and the lower limit differential pressure value ΔPmin, that is, when “ΔPmin <ΔP <ΔPmax” is satisfied (S210: YES), the NOx purification rate. It is determined whether or not R is smaller than the purification rate determination value α (S110). When the NOx purification rate R is equal to or greater than the purification rate determination value α (S110: NO), it is determined that NOx purification is normally performed, and this process is temporarily terminated.

  On the other hand, when the NOx purification rate R is smaller than the purification rate determination value α (S110: YES), the back pressure P that is the exhaust pressure upstream of the dispersion plate 60 is equal to the upper limit back pressure value Pmax and the lower limit back pressure value Pmin. It is determined whether the value is between (S120). Note that the back pressure P at this time is determined to be affirmative in step S <b> 200, and thus is the back pressure P immediately after the end of the regeneration process of the filter 32.

  When the back pressure P is a value between the upper limit back pressure value Pmax and the lower limit back pressure value Pmin, that is, when “Pmin <P <Pmax” is satisfied (S120: YES), the dispersion plate 60 Is determined to be normal, the process is temporarily terminated.

  On the other hand, when the back pressure P is not between the upper limit back pressure value Pmax and the lower limit back pressure value Pmin, that is, when “Pmin ≧ P” or “P ≧ Pmax” is satisfied (S120: NO). Then, it is determined that there is an abnormality in the dispersion plate 60 (S130), and this process is temporarily terminated. If it is determined in step S130 that there is an abnormality in the dispersion plate 60, the vehicle driver is notified of the occurrence of the abnormality by turning on a warning lamp or the like.

Next, operations unique to the present embodiment will be described.
In the abnormality determination process of this embodiment, it is determined whether or not it is immediately after the end of the regeneration process of the filter 32 in step S200. When the back pressure P is compared and determined in step S120, the comparison determination is performed using the back pressure P immediately after the regeneration processing of the filter 32 is completed, that is, when the PM accumulation amount PMsm is very small. . Therefore, when determining the abnormality of the dispersion plate 60, it is possible to suppress the influence of the PM accumulation amount as much as possible, thereby increasing the accuracy of the abnormality determination of the dispersion plate 60.

  Further, when the amount of accumulated PM in the filter 32 is excessively large, when the amount of PM discharged from the engine 1 is excessively large, or when the regeneration process is not sufficiently performed, the pressure loss of the filter 32 is excessively large. Therefore, the differential pressure ΔP increases. On the other hand, when the pressure loss of the filter 32 becomes excessively low due to the occurrence of melting damage or the like, the differential pressure ΔP becomes small.

  Such a change in the pressure loss of the filter 32 affects the detection value of the pressure sensor 150 downstream of the filter 32. Therefore, there is a possibility that an excessive increase or an excessive decrease in the back pressure P due to an abnormality in the pressure loss of the filter 32 may be erroneously determined as an abnormality in the dispersion plate 60. In this regard, in the abnormality determination process of the present embodiment, the differential pressure ΔP immediately after the regeneration process is finished is not a value between the upper limit differential pressure value ΔPmax and the lower limit differential pressure value ΔPmin, that is, the pressure loss of the filter 32 is excessive. When there is an abnormality, the abnormality determination of the dispersion plate 60 based on the back pressure P or the like is prohibited. Therefore, when the abnormality determination of the dispersion plate 60 is performed, the adverse effect due to the pressure loss abnormality of the filter 32 is suppressed as much as possible, and the accuracy of the abnormality determination of the dispersion plate 60 is increased.

As described above, according to the present embodiment, in addition to the effects of the first embodiment, the following effects can be further obtained.
(2) The abnormality determination of the dispersion plate 60 is performed based on the back pressure P immediately after the regeneration processing of the filter 32 is completed. Therefore, when the abnormality determination of the dispersion plate 60 is performed, the influence of the PM accumulation amount of the filter 32 can be suppressed as much as possible, thereby improving the accuracy of the abnormality determination of the dispersion plate 60.

(3) When the differential pressure ΔP immediately after the regeneration processing of the filter 32 is not a value between the upper limit differential pressure value ΔPmax and the lower limit differential pressure value ΔPmin, the abnormality determination of the dispersion plate 60 is prohibited. Therefore, when the abnormality determination of the dispersion plate 60 is performed, an adverse effect due to the abnormality of the pressure loss of the filter 32 can be suppressed as much as possible, thereby improving the accuracy of the abnormality determination of the dispersion plate 60.
(Third embodiment)
Next, a third embodiment in which the exhaust gas purification apparatus for an internal combustion engine according to the present invention is embodied will be described with reference to FIGS.

In the second embodiment, the upper limit differential pressure value ΔPmax and the lower limit differential pressure value ΔPmin are set in order to determine whether or not the differential pressure ΔP is outside the predetermined range.
Here, it is known that ash that is a component derived from lubricating oil and difficult to burn by the above-described regeneration process accumulates on the filter 32. In addition, as this ash, the component (metal components, such as Zn, Ca, Mg, Na, etc.) contained in the additive etc. of lubricating oil, etc. are mentioned, for example. The differential pressure ΔP immediately after the regeneration process is finished also changes depending on the amount of ash accumulated. Therefore, it is desirable to set the upper limit differential pressure value ΔPmax and the lower limit differential pressure value ΔPmin in consideration of such a change in the differential pressure ΔP due to the ash deposition amount. Therefore, in the present embodiment, the upper limit differential pressure value ΔPmax and the lower limit differential pressure value ΔPmin are variably set according to the ash accumulation amount of the filter 32.

Hereinafter, the abnormality determination process in the present embodiment will be described focusing on the differences from the third embodiment.
The abnormality determination process of this embodiment shown in FIG. 4 is also executed by the control device 80 at predetermined intervals. In FIG. 4, the same step numbers are assigned to the same processing steps as those described in FIG. 2 and FIG.

When this process is started, first, the NOx purification rate R is calculated from the first NOx concentration N1 and the second NOx concentration N2 (S100).
Next, it is determined immediately after the end of the regeneration process of the filter 32 and whether the PM accumulation amount PMsm is smaller than the determination value A (S200).

Then, when not immediately after the end of the regeneration process of the filter 32, or when the PM accumulation amount PMsm is greater than or equal to the determination value A (S200: NO), this process is temporarily ended.
On the other hand, when the regeneration process of the filter 32 is completed and the PM accumulation amount PMsm is smaller than the determination value A (S200: YES), the upper limit differential pressure value is based on the total travel distance TR of the vehicle on which the engine 1 is mounted. ΔPmax and the lower limit differential pressure value ΔPmin are calculated (S300). The upper limit differential pressure value ΔPmax and the lower limit differential pressure value ΔPmin here are based on the upper limit differential pressure value ΔPmax and the lower limit differential pressure value ΔPmin described in the second embodiment. However, in the present embodiment, the upper limit differential pressure value ΔPmax and the lower limit differential pressure value ΔPmin are variably set in consideration of a change in the differential pressure ΔP due to the ash accumulation amount of the filter 32.

  Here, since the differential pressure ΔP increases as the ash deposition amount increases, it is desirable to increase the upper limit differential pressure value ΔPmax and the lower limit differential pressure value ΔPmin as the ash deposition amount increases. The ash accumulation amount increases as the total travel distance TR of the vehicle increases. Therefore, as shown in FIG. 5, the upper limit differential pressure value ΔPmax and the lower limit differential pressure value ΔPmin are variably set based on the total travel distance TR as the total travel distance TR is longer.

  When the upper limit differential pressure value ΔPmax and the lower limit differential pressure value ΔPmin are thus set, the differential pressure ΔP immediately after the end of the regeneration process of the filter 32 becomes a value between the upper limit differential pressure value ΔPmax and the lower limit differential pressure value ΔPmin. It is determined whether or not (S210).

  When the differential pressure ΔP is a value between the upper limit differential pressure value ΔPmax and the lower limit differential pressure value ΔPmin, that is, when “ΔPmin <ΔP <ΔPmax” is satisfied (S210: YES), the NOx purification rate. It is determined whether or not R is smaller than the purification rate determination value α (S110). When the NOx purification rate R is equal to or greater than the purification rate determination value α (S110: NO), it is determined that NOx purification is normally performed, and this process is temporarily terminated.

  On the other hand, when the NOx purification rate R is smaller than the purification rate determination value α (S110: YES), the back pressure P that is the exhaust pressure upstream of the dispersion plate 60 is equal to the upper limit back pressure value Pmax and the lower limit back pressure value Pmin. It is determined whether the value is between (S120). Note that the back pressure P at this time is determined to be affirmative in step S <b> 200, and thus is the back pressure P immediately after the end of the regeneration process of the filter 32.

  When the back pressure P is a value between the upper limit back pressure value Pmax and the lower limit back pressure value Pmin, that is, when “Pmin <P <Pmax” is satisfied (S120: YES), the dispersion plate 60 Is determined to be normal, the process is temporarily terminated.

  On the other hand, when the back pressure P is not between the upper limit back pressure value Pmax and the lower limit back pressure value Pmin, that is, when “Pmin ≧ P” or “P ≧ Pmax” is satisfied (S120: NO). Then, it is determined that there is an abnormality in the dispersion plate 60 (S130), and this process is temporarily terminated. If it is determined in step S130 that there is an abnormality in the dispersion plate 60, the vehicle driver is notified of the occurrence of the abnormality by turning on a warning lamp or the like.

  When it is determined in step S210 that the differential pressure ΔP is not between the upper limit differential pressure value ΔPmax and the lower limit differential pressure value ΔPmin, that is, “ΔPmin ≧ ΔP” or “ΔP ≧ ΔPmax”. Is established (S210: NO), it is determined in step S310 whether or not the NOx purification rate R is smaller than the purification rate determination value α. The process in step S310 is the same as the process in step S110. When the NOx purification rate R is equal to or greater than the purification rate determination value α (S310: NO), it is determined that NOx purification is normally performed, and this process is temporarily terminated.

On the other hand, when the NOx purification rate R is smaller than the purification rate determination value α (S310: YES), it is determined that there is an abnormality in the filter 32 (S320), and this process is temporarily terminated.
Next, operations unique to the present embodiment will be described.

  In the abnormality determination process of this embodiment, when the differential pressure ΔP of the filter 32 is not a value between the upper limit differential pressure value ΔPmax and the lower limit differential pressure value ΔPmin, the abnormality determination of the dispersion plate 60 is not performed. Here, as described above, the differential pressure ΔP immediately after completion of the regeneration process varies depending on the amount of ash deposited. Accordingly, if the upper limit differential pressure value ΔPmax and the lower limit differential pressure value ΔPmin are set without considering such a change in the differential pressure ΔP due to the amount of ash deposition, the determination accuracy for determining whether or not the dispersion plate 60 is abnormally deteriorated. It becomes like this.

  Therefore, in the abnormality determination process of the present embodiment, the upper limit differential pressure value ΔPmax and the lower limit differential pressure value ΔPmin are variably set according to the ash accumulation amount of the filter 32. Therefore, the determination accuracy for determining whether or not the dispersion plate 60 is abnormal is increased.

Further, when the differential pressure ΔP immediately after the regeneration process is greater than or equal to the upper limit differential pressure value ΔPmax, the amount of exhaust gas passing through the filter 32 is small, so the flow rate of exhaust gas flowing into the SCR catalyst 41 decreases. As a result, the amount of reducing agent supplied to the SCR catalyst 41 per unit time may be insufficient, and the NOx purification rate R may decrease. In addition, when the differential pressure ΔP immediately after the regeneration process is smaller than the lower limit differential pressure value ΔPmin, the amount of exhaust passing through the filter 32 is large, so the flow rate of exhaust flowing into the SCR catalyst 41 increases. . When the exhaust gas flow rate increases in this way, the exhaust gas containing the reducing agent quickly passes through the SCR catalyst 41, so that the amount of reducing agent stored in the SCR catalyst 41 is insufficient and the NOx purification rate R decreases. There is a risk. That is, when the NOx purification rate R is lower than the predetermined value and the differential pressure ΔP is not a value between the upper limit differential pressure value ΔPmax and the lower limit differential pressure value ΔPmin, it is assumed that an abnormality has occurred in the filter 32. Can be determined.

  Therefore, in the abnormality determination process of the present embodiment, the differential pressure ΔP immediately after the regeneration process ends is not a value between the upper limit differential pressure value ΔPmax and the lower limit differential pressure value ΔPmin (negative determination in step S210), and NOx When the purification rate R is lower than the purification rate determination value α (affirmative determination in step S310), it is determined in step S320 that the filter 32 is abnormal. Therefore, not only the abnormality of the dispersion plate 60 but also the abnormality of the filter 32 can be determined.

As described above, according to the present embodiment, the following effects can be obtained in addition to the effects of the second embodiment.
(4) When the differential pressure ΔP of the filter 32 is not a value between the upper limit differential pressure value ΔPmax and the lower limit differential pressure value ΔPmin, the abnormality determination of the dispersion plate 60 is not performed. Then, the upper limit differential pressure value ΔPmax and the lower limit differential pressure value ΔPmin are variably set according to the ash accumulation amount of the filter 32. More specifically, the upper limit differential pressure value ΔPmax and the lower limit differential pressure value ΔPmin are variably set to increase as the total travel distance TR of the vehicle that correlates with the ash accumulation amount is longer. Accordingly, it is possible to improve the accuracy of determining whether or not to perform abnormality determination of the dispersion plate 60.

  (5) When the differential pressure ΔP immediately after the regeneration process is not a value between the upper limit differential pressure value ΔPmax and the lower limit differential pressure value ΔPmin, and the NOx purification rate R is lower than the purification rate determination value α, the filter 32 is determined to be abnormal. Therefore, not only the abnormality of the dispersion plate 60 but also the abnormality of the filter 32 can be determined.

In addition, each said embodiment can also be changed and implemented as follows.
-In 2nd Embodiment, you may abbreviate | omit the process of step S210 previously shown in FIG. 3, ie, the comparison determination process of differential pressure | voltage (DELTA) P. Even in this case, the effect (2) described in the second embodiment can be obtained.

  In the third embodiment, when the upper limit differential pressure value ΔPmax and the lower limit differential pressure value ΔPmin are variably set, the correlation between the total travel distance TR of the vehicle and the ash accumulation amount is used. In addition, since ash is also the unburned fine particles in the regeneration process, the amount of ash deposition increases as the number of regeneration processes is increased. Therefore, as shown in FIG. 5, the upper limit differential pressure value ΔPmax and the lower limit differential pressure value ΔPmin may be variably set so as to increase the number of times the filter 32 is regenerated. This modification can be easily implemented by storing the number of times the regeneration process of the filter 32 is executed in the control device 80.

  Further, as described above, ash is also the unburned residue of fine particles in the regeneration process. Therefore, the greater the total amount of fine particles collected by the filter 32, in other words, the greater the total amount of fine particles processed by the regeneration process, the more the ash. The amount of deposition increases. Therefore, as shown in FIG. 5, the upper limit differential pressure value ΔPmax and the lower limit differential pressure value ΔPmin may be variably set as the integrated value of the PM accumulation amount PMsm increases.

In the third embodiment, the differential pressure ΔP immediately after completion of the regeneration process is not a value between the upper limit differential pressure value ΔPmax and the lower limit differential pressure value ΔPmin, and the NOx purification rate R is greater than the purification rate determination value α. When it is low, it is determined that the filter 32 is abnormal, but each of these processes may be omitted. Even in this case, the effect (4) described in the third embodiment can be obtained.

Although urea water is used as the reducing agent, other liquid reducing agents may be used.
As the NOx purification catalyst, a catalyst different from the selective reduction type NOx catalyst may be used.

  DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Cylinder head, 3 ... Intake passage, 4a-4d ... Fuel injection valve, 5 ... Fuel addition valve, 6a-6d ... Exhaust port, 7 ... Intake manifold, 8 ... Exhaust manifold, 9 ... Common rail, DESCRIPTION OF SYMBOLS 10 ... Supply pump, 11 ... Turbocharger, 13 ... EGR passage, 14 ... EGR cooler, 15 ... EGR valve, 16 ... Intake throttle valve, 17 ... Actuator, 18 ... Intercooler, 19 ... Air flow meter, 20 ... Throttle valve opening Degree sensor, 21 ... Engine rotation speed sensor, 22 ... Accelerator sensor, 23 ... Outside air temperature sensor, 24 ... Vehicle speed sensor, 25 ... Ignition switch, 26 ... Exhaust passage, 27 ... Fuel supply pipe, 30 ... First purification member, 31 ... oxidation catalyst, 32 ... filter, 40 ... second purification member, 41 ... selective reduction type NOx catalyst (SCR catalyst), 50 ... first Purifying member 51 ... Ammonia oxidation catalyst 60 ... Dispersion plate 80 ... Control device 100 ... First exhaust temperature sensor 110 ... Differential pressure sensor 120 ... Second exhaust temperature sensor 130 ... First NOx sensor 140 ... First 2 ... NOx sensor, 150 ... pressure sensor, 200 ... urea water supply mechanism (reducing agent supply mechanism), 210 ... tank, 220 ... pump, 230 ... urea addition valve, 240 ... supply passage.

Claims (4)

A NOx purification catalyst that purifies NOx by supplying a reducing agent, a reducing agent supply mechanism that supplies the reducing agent into the exhaust passage, and a dispersion that is provided in the exhaust passage and disperses the reducing agent upstream of the NOx purification catalyst. In an exhaust gas purification apparatus for an internal combustion engine comprising a plate,
A pressure sensor that detects the exhaust pressure upstream of the dispersion plate, a filter that is provided upstream of the pressure sensor, collects particulates in the exhaust gas, and performs a regeneration process, and exhausts upstream and downstream of the filter. A differential pressure sensor for detecting a pressure difference between atmospheric pressures,
When the NOx purification rate at the NOx purification catalyst is lower than a predetermined value and the exhaust pressure immediately after the regeneration process is finished is not a value between a predetermined upper limit pressure value and a lower limit pressure value, the dispersion An abnormality determination is made to determine that there is an abnormality in the board,
When the pressure difference immediately after the regeneration process is not a value between a predetermined upper limit differential pressure value and a lower limit differential pressure value, the abnormality determination is prohibited,
The exhaust gas purification apparatus for an internal combustion engine, wherein the upper limit differential pressure value and the lower limit differential pressure value are variably set so as to increase the total travel distance of the vehicle on which the internal combustion engine is mounted. A NOx purification catalyst that purifies NOx by supplying a reducing agent, a reducing agent supply mechanism that supplies the reducing agent into the exhaust passage, and a dispersion that is provided in the exhaust passage and disperses the reducing agent upstream of the NOx purification catalyst. In an exhaust gas purification apparatus for an internal combustion engine comprising a plate,
A pressure sensor for detecting an exhaust pressure upstream of the dispersion plate;
A filter that is provided upstream of the pressure sensor and that collects particulates in the exhaust and performs a regeneration process;
A differential pressure sensor for detecting the pressure difference between the exhaust pressure upstream and downstream of the filter,
When the NOx purification rate at the NOx purification catalyst is lower than a predetermined value and the exhaust pressure immediately after the regeneration process is finished is not a value between a predetermined upper limit pressure value and a lower limit pressure value, the dispersion An abnormality determination is made to determine that there is an abnormality in the board,
When the pressure difference immediately after the regeneration process is not a value between a predetermined upper limit differential pressure value and a lower limit differential pressure value, the abnormality determination is prohibited,
The exhaust gas purification apparatus for an internal combustion engine, wherein the upper limit differential pressure value and the lower limit differential pressure value are variably set so as to increase the number of times the regeneration process is executed. A NOx purification catalyst that purifies NOx by supplying a reducing agent, a reducing agent supply mechanism that supplies the reducing agent into the exhaust passage, and a dispersion that is provided in the exhaust passage and disperses the reducing agent upstream of the NOx purification catalyst. In an exhaust gas purification apparatus for an internal combustion engine comprising a plate,
A pressure sensor for detecting an exhaust pressure upstream of the dispersion plate;
A filter that is provided upstream of the pressure sensor and that collects particulates in the exhaust and performs a regeneration process;
A differential pressure sensor for detecting the pressure difference between the exhaust pressure upstream and downstream of the filter,
When the NOx purification rate at the NOx purification catalyst is lower than a predetermined value and the exhaust pressure immediately after the regeneration process is finished is not a value between a predetermined upper limit pressure value and a lower limit pressure value, the dispersion An abnormality determination is made to determine that there is an abnormality in the board,
When the pressure difference immediately after the regeneration process is not a value between a predetermined upper limit differential pressure value and a lower limit differential pressure value, the abnormality determination is prohibited,
The exhaust gas purification apparatus for an internal combustion engine, wherein the upper limit differential pressure value and the lower limit differential pressure value are variably set so as to increase as the total integrated amount of particulates collected by the filter increases. When the pressure difference immediately after the regeneration process is not a value between the upper limit differential pressure value and the lower limit differential pressure value and the NOx purification rate is lower than the predetermined value, the filter is abnormal. The exhaust emission control device for an internal combustion engine according to any one of claims 1 to 3.