JP2010031725A - Abnormality detection system of particulate filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect an abnormality of a particulate filter with a high degree of accuracy even in an engine operating condition of a small intake air flow in the engine. <P>SOLUTION: The abnormality detection system includes a predicted pressure difference calculating means for calculating a predicted pressure difference between upstream and downstream sides of an exhaust gas in the particulate filter based on the intake air flow rate in the engine and an area of a part through which the exhaust gas can pass in an exhaust gas passing surface of the particulate filter, and a blocking means for blocking off a part of the exhaust gas passing surface of the particulate filter based on the predicted pressure difference calculated by the predicted pressure difference calculating means. When the predicted pressure difference calculated by the predicted pressure difference calculating means is not more than a given value, the part of the exhaust gas passing surface of the particulate filter is blocked off. Then, based on a predicted pressure difference after the part of the exhaust gas passing surface has been blocked off and an actual pressure difference between the upstream and downstream sides of the exhaust gas in the particulate filter, the presence or absence of the abnormality of the particulate filter is determined. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an abnormality detection device for a particulate filter that detects an abnormality of a particulate filter, particularly a breakage such as a crack or a tear.

  The exhaust gas from an internal combustion engine, particularly the exhaust gas from a diesel engine, contains particulate matter (hereinafter also referred to as PM) containing carbon as a main component. A technique for providing a particulate filter (hereinafter also referred to as a DPF) for collecting PM in an engine exhaust system is known in order to prevent these PMs from being diffused into the atmosphere. The DPF usually includes a filter element such as a metal mesh or a porous ceramic, and collects PM in the exhaust gas in the filter element.

  However, the DPF is subject to vibrations such as engine operation and high exhaust heat, as well as thermal cycle stress due to engine stop and repeated operation, which may cause breakage and breakage. When the DPF is damaged, the PM in the exhaust gas is not collected by the DPF and is released to the atmosphere as it is, which causes a problem of deteriorating the surrounding environment. Further, even if the DPF is damaged, there is no adverse effect on the engine operation itself. For this reason, the driver often keeps driving as it is without noticing even if the DPF is damaged, which may further deteriorate the environment.

  For this reason, an anomaly detection device that detects anomalies such as DPF breakage during engine operation has been proposed. An example of this type of DPF abnormality detection apparatus is disclosed in Patent Document 1, for example. The apparatus discloses a first accumulation amount calculation means for calculating a PM accumulation amount from a differential pressure before and after the DPF, that is, a differential pressure between the exhaust upstream and downstream of the DPF, and calculates the PM emission amount from the engine operating state. Second accumulation amount calculation means for calculating the PM accumulation amount by integrating the PM discharge amount, and utilizing that the PM accumulation amount immediately before and after the accumulation calculation means is switched is substantially the same. Thus, the presence / absence of abnormality of the DPF is determined based on the consistency between the two types of calculation results of the deposition amount immediately before and after the deposition calculation means is switched.

JP-A-2005-344619

  However, in an apparatus such as Patent Document 1, the amount of engine intake air immediately before and after the switching of the deposition calculation means for determining whether there is an abnormality in the DPF is small, and the differential pressure between the exhaust upstream of the DPF and the exhaust downstream is small. In some cases, accurate diagnosis may not be possible in consideration of variations (errors) in the differential pressure.

  By the way, if a breakage such as a crack or a tear occurs in the DPF, the differential pressure between the exhaust upstream of the DPF and the exhaust downstream changes as compared with the normal case of the DPF. Detection can be performed. For example, it is determined that the DPF is damaged when the differential pressure between the exhaust upstream of the DPF and the exhaust downstream becomes equal to or less than a predetermined value. However, even in such an abnormality detection method, when the engine intake air amount is small, the range of change in the differential pressure between the exhaust upstream of the DPF and the downstream of the exhaust when the DPF is normal and damaged Cannot be obtained sufficiently, and there are cases where accurate diagnosis cannot be performed in consideration of the variation in the differential pressure.

  It is desirable that the abnormality detection of the DPF can be accurately detected in various engine operating states in which various engine intake air amounts are different. For this purpose, it is possible to detect the DPF abnormality accurately even when the engine intake air amount is small. Necessary.

  In view of the above problems, an object of the present invention is to provide a DPF abnormality detection device capable of accurately detecting abnormality such as breakage of the DPF even in an engine operation state in which the engine intake air amount is small.

  According to the first aspect of the present invention, there is provided a particulate filter abnormality detecting device for detecting whether or not the particulate filter disposed in the exhaust passage of the internal combustion engine is damaged, wherein the exhaust upstream and the exhaust of the particulate filter are detected. Based on the actual differential pressure detecting means for detecting the actual differential pressure between the downstream, the engine intake air amount, and the area of the exhaust gas passage surface of the particulate filter through which the exhaust gas can pass, A predicted differential pressure calculating means for calculating a predicted differential pressure between the exhaust upstream of the particulate filter and the exhaust downstream; and a predicted differential pressure disposed on the exhaust gas passage surface and calculated by the predicted differential pressure calculating means. Shielding means for shielding a part of the exhaust gas passage surface, and when the predicted differential pressure calculated by the predicted differential pressure calculating means is less than a predetermined value, A part of the exhaust gas passage surface is shielded by the means, and a predicted differential pressure calculated by the predicted differential pressure calculation means after the part of the exhaust gas passage surface is shielded and detected by the actual differential pressure detection means A particulate filter abnormality detection device is provided that determines whether or not the particulate filter is abnormal based on the actual pressure difference.

  That is, in the first aspect of the invention, the exhaust gas passage surface of the particulate filter calculated based on the engine intake air amount and the area of the exhaust gas passage surface of the particulate filter through which the exhaust gas can pass is shielded. If the estimated differential pressure between the exhaust upstream of the particulate filter and the exhaust downstream of the particulate filter is not more than a predetermined value, a part of the exhaust gas passage surface of the particulate filter is shielded. Before and after such shielding, the pressure on the exhaust gas downstream side of the particulate filter is substantially atmospheric pressure and does not change, but the pressure on the exhaust gas upstream side of the particulate filter is a part of the exhaust gas passage surface of the particulate filter. When the is shielded, the area through which the exhaust gas can pass on the exhaust gas passage surface of the particulate filter is reduced, which increases. Therefore, by blocking a part of the exhaust gas passage surface of the particulate filter, the differential pressure between the exhaust upstream of the particulate filter and the exhaust downstream can be increased even when the engine intake air amount is small. And determining whether there is an abnormality in the particulate filter based on an enlarged differential pressure between the exhaust upstream and downstream of the particulate filter after a part of the exhaust gas passage surface of the particulate filter is shielded. As a result, even when the engine intake air amount is small, an abnormality such as a DPF breakage can be accurately detected.

  According to a second aspect of the present invention, the shielding means shields a part of the exhaust gas passage surface based on the predicted differential pressure calculated by the predicted differential pressure calculation means, and the exhaust gas passage. 2. The particulate filter abnormality detection according to claim 1, wherein the shielding portion of the exhaust gas passage surface is changed based on the predicted differential pressure calculated by the predicted differential pressure calculating means after a part of the surface is shielded. An apparatus is provided.

  According to a third aspect of the present invention, the shielding means adjusts the shielding area of the exhaust gas passage surface based on the predicted differential pressure calculated by the predicted differential pressure calculation means. The particulate filter abnormality detection device according to claim 1, wherein a part of the particulate filter is shielded.

  According to the description of each claim, the particulate filter abnormality detection device detects whether or not the particulate filter disposed in the exhaust passage of the internal combustion engine is broken or broken, and the engine intake air amount is small. There is a common effect that the abnormality of the particulate filter can be accurately detected even in the engine operating state.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is an overall configuration diagram showing an entire system of an internal combustion engine (diesel engine) to which an abnormality detection device for a particulate filter (hereinafter referred to as DFP) of the present invention is applied. Reference numeral 1 denotes an internal combustion engine, in which high-pressure fuel is injected from the injector 2 into the combustion chamber 3. 4 is an intake passage, and 5 is an exhaust passage. An air flow meter 7 for detecting the engine intake air amount is disposed upstream of the intake passage 4, a throttle 8 is disposed in the intake passage 4, and an intake pressure or intake temperature in the intake passage 4 is disposed downstream thereof. An intake air pressure sensor 9 and an intake air temperature sensor 10 are provided. A DPF 6 is disposed in the exhaust passage 5.

  Various air system internal combustion engine operating condition information detected by the air flow meter 7, the intake pressure sensor 9, and the intake air temperature sensor 10 is always sent to an electronic control unit 16 (hereinafter referred to as an ECU) that controls the entire internal combustion engine system. It is output. In addition to the above sensors, the rotation angle sensor 11 that outputs a signal in synchronization with the rotation angle of the internal combustion engine 1, the water temperature sensor 13 that detects the coolant temperature of the internal combustion engine 1, and the accelerator pedal 15 based on the depression amount of the accelerator pedal 15 An accelerator opening sensor 14 for detecting the opening is provided, and internal combustion engine operating condition information detected from each sensor is output to the ECU 16. The ECU 16 outputs fuel injection amount information calculated based on various internal combustion engine operating condition information to the internal combustion engine 1, and fuel is injected from the injector 2 into the combustion chamber 3 based on this information. The fuel injection amount information constitutes one of important elements of the internal combustion engine operating condition information.

  Further, a differential pressure sensor 17 serving as an actual differential pressure detecting means for detecting an actual differential pressure between the exhaust upstream of the DPF 6 and the exhaust downstream is provided on the exhaust upstream side and the exhaust downstream side of the DPF 6. Is provided with a temperature sensor 18 for detecting the temperature of the DPF 6. The differential pressure sensor 17 and the temperature sensor 18 are connected to the ECU 16.

  In the present invention, the predicted differential pressure for calculating the predicted differential pressure between the exhaust upstream of the DPF 6 and the exhaust downstream based on the amount of engine intake air and the area of the exhaust gas passage surface of the DPF 6 through which the exhaust gas can pass. The calculating means 19 and the shielding means 20 disposed on the exhaust gas passage surface of the DPF 6 to shield a part of the exhaust gas passage surface of the DPF 6 based on the predicted differential pressure calculated by the predicted differential pressure calculation means 19. Have.

  FIG. 2 is a view showing an embodiment of the shielding means arranged on the exhaust gas passage surface of the DPF 6. The shielding means 20 shown in FIG. 2 shields a part of the exhaust gas passage surface 22 of the DPF 6 based on the predicted differential pressure calculated by the predicted differential pressure calculation means 19, and is a part of the exhaust gas passage surface 22 of the DPF 6. The shielding portion of the exhaust gas passage surface 22 of the DPF 6 is changed based on the predicted differential pressure calculated by the predicted differential pressure calculation means 19 after the portion is shielded. Specifically, the shielding unit 20 shown in FIG. 2 has a single semicircular lid 21, and the lid 21 is based on the predicted differential pressure calculated by the predicted differential pressure calculating unit 19. A part of the exhaust gas passage surface 22 is configured to be shielded. When it is not necessary to shield part of the exhaust gas passage surface of the DPF 6, as shown in FIGS. 2 (a) and 2 (b), the cover body 21 has an exhaust gas so as not to obstruct the flow of the exhaust gas. It is arranged in parallel with the flow direction. On the other hand, when it is necessary to shield a part of the exhaust gas passage surface of the DPF 6, as shown in FIG. 2 (c), the lid 21 prevents the exhaust gas from flowing so as to hinder the flow of the exhaust gas. It is arranged at right angles to the flow direction, and is configured to be capable of rotating around the rotation center 23 in the exhaust gas passage surface of the DPF 6. The lid 21 of the shielding means 20 shown in FIG. 2 is configured to be disposed on the exhaust gas passage surface on the upstream side of the DPF 6, but is disposed on the exhaust gas passage surface on the downstream side of the DPF 6. May be.

  FIG. 3 is a flowchart for determining whether there is an abnormality in the DPF 6 using the shielding means 20 shown in FIG. Based on FIG. 3, the flow of determination of the presence or absence of abnormality of the DPF 6 will be described.

  First, in step 101, it is confirmed whether there is an abnormality detection request for the DPF 6. When it is confirmed that the abnormality detection request is present, in step 102, the predicted differential pressure calculation means 19 determines that the exhaust gas passage surface of the DPF 6 is not shielded by the lid 21 and the exhaust upstream of the DPF 6 The predicted differential pressure ΔP ′ between the exhaust downstream and the exhaust downstream is calculated based on the engine intake air amount and the area of the portion of the DPF 6 through which the exhaust gas can pass. Since the movement of the particulate matter (PM) in the DPF 6 depends on the temperature of the DPF 6, and the movement of the particulate matter affects the differential pressure between the exhaust upstream of the DPF 6 and the exhaust downstream, the exhaust upstream of the DPF 6 The differential pressure difference ΔP ′ between the exhaust gas and the downstream side of the exhaust gas may be calculated based on the amount of engine intake air, the area of the exhaust gas passage surface of the DPF 6 through which the exhaust gas can pass, and the DPF temperature. When it is confirmed in step 101 that there is no abnormality detection request for the DPF 6, a time counter tw described later is set to zero in step 117, and the flowchart shown in FIG.

  In step 103 subsequent to step 102, the exhaust gas passage surface of the DPF 6 needs to be shielded by the lid 21 in order to detect the abnormality of the DPF 6 with high accuracy based on the predicted differential pressure ΔP ′ calculated in step 102. A determination is made whether or not there is. Specifically, it is determined whether or not the predicted differential pressure ΔP ′ calculated in step 102 exceeds a predetermined value (R1) that is a threshold value for determining whether or not the cover 21 needs to be shielded. .

  If the predicted differential pressure ΔP ′ calculated in step 102 exceeds a predetermined value (R1), it is determined that shielding by the lid body 21 is unnecessary, and is calculated in step 102 in subsequent step 104. The difference dΔP between the predicted differential pressure ΔP ′ and the actual differential pressure ΔPs between the exhaust upstream and downstream of the DPF 6 detected by the differential pressure sensor 17 is calculated. Is judged. Specifically, it is determined whether or not the difference dΔP calculated in step 104 exceeds a predetermined value (R2) that is a threshold for determining whether there is an abnormality in the DPF 6. If the difference dΔP calculated in step 104 exceeds the predetermined value (R2), it is determined that there is an abnormality in the DPF 6 and the process proceeds to step 106, and if the difference dΔP does not exceed the predetermined value (R2) Therefore, it is determined that there is no abnormality in the DPF 6, and the process proceeds to Step 107.

  On the other hand, if the predicted differential pressure ΔP ′ calculated in step 102 does not exceed the predetermined value (R1), it is determined that the cover 21 needs to be shielded, and the process proceeds from step 108 to step 110. In steps 108 and 109, when the predicted differential pressure ΔP ′ exceeding the predetermined value (R1) is not obtained for a certain period after the DPF abnormality detection request is confirmed, shielding by the lid 21 is executed. Thus, steps 102 and 103 are executed until the standby counter tw exceeds a predetermined value (R3). Then, when the predetermined differential pressure ΔP ′ calculated in step 102 does not exceed the predetermined value (R1) even if the predetermined period has elapsed, that is, even if the standby counter tw exceeds the predetermined value (R3), the step At 110, a part of the exhaust gas passage surface of the DPF 6 is shielded by the lid 21. When the shielding is executed, the pressure on the downstream side of the DPF 6 is substantially atmospheric pressure and does not change. However, the pressure on the upstream side of the DPF 6 is such that when a part of the exhaust gas passage surface of the DPF 6 is shielded, the DPF 6 This increases because the area through which the exhaust gas can pass on the exhaust gas passage surface is reduced. Therefore, the differential pressure between the exhaust upstream of the DPF 6 and the exhaust downstream can be increased, and the differential pressure between the exhaust upstream of the DPF 6 and the exhaust downstream is sufficient when the DPF is normal and damaged. Even when the engine differential air pressure is small and the estimated differential pressure ΔP ′ calculated in step 102 does not exceed the predetermined value (R1), the DPF is cracked or broken. It is possible to accurately detect an abnormality caused by damage such as.

  In step 111 following step 110, the exhaust upstream and downstream of exhaust of the DPF 6 are determined based on the area of the exhaust gas passing surface of the DPF 6 that is shielded by the lid 21 and the amount of engine intake air. The predicted differential pressure ΔP′h is calculated by the predicted differential pressure calculating means 19.

  In the present embodiment, in order to detect an abnormality of the DPF 6 with higher accuracy, the predicted differential pressure ΔP′h calculated in step 111 does not exceed a predetermined value (R4) set in advance by design specifications or the like. The high-precision abnormality detection described later is executed.

  Based on this, in step 112 following step 111, the predicted differential pressure ΔP′h calculated in step 111 is high so as to determine whether or not it is necessary to perform high-precision abnormality detection. It is determined whether or not a predetermined value (R4) that is a threshold value for determining whether or not accuracy abnormality detection is necessary is exceeded.

  If the predicted differential pressure ΔP′h calculated in step 111 exceeds a predetermined value (R4), it is determined that it is not necessary to perform high-accuracy abnormality detection. A difference dΔPh between the calculated predicted differential pressure ΔP′h and the actual differential pressure ΔPsh between the exhaust upstream and downstream of the DPF 6 detected by the differential pressure sensor 17 is calculated. The presence or absence of abnormality is determined. Specifically, it is determined whether or not the difference dΔPh calculated in step 113 exceeds a predetermined value (R5) that is a threshold for determining whether there is an abnormality in the DPF 6. If the difference dΔPh calculated in step 113 exceeds the predetermined value (R5), it is determined that there is an abnormality in the DPF 6 and the process proceeds to step 106, and if the difference dΔPh does not exceed the predetermined value (R5) Therefore, it is determined that there is no abnormality in the DPF 6, and the process proceeds to Step 107.

  On the other hand, if the predicted differential pressure ΔP′h calculated in step 111 does not exceed the predetermined value (R4), it is determined that high-precision abnormality detection is necessary, and the process proceeds to subsequent steps 115 and 116. In step 115, it is determined whether the DPF 6 is clearly abnormal before executing the high-precision abnormality detection in step 116. If it is determined that there is an obvious abnormality, the process proceeds to step 106. Specifically, the divergence ratio of the actual differential pressure ΔPsh between the exhaust upstream and the exhaust downstream of the DPF 6 detected by the differential pressure sensor 17 with respect to the predicted differential pressure ΔP′h calculated in step 111 (ΔPsh / If ΔP′h) does not exceed the predetermined value (R6), which is a threshold value that clearly indicates that the DPF 6 is abnormal, it is determined that the DPF 6 is clearly abnormal and the routine proceeds to step 106, and the predetermined value (R6) is reached. ), The process proceeds to step 116 where high-precision abnormality detection is executed.

  FIG. 4 is a flowchart of DPF high-precision abnormality detection. When the portion of the exhaust gas passage surface of the DPF 6 through which the exhaust gas can pass is changed in the shielding by the lid 21, the differential pressure between the exhaust upstream and the exhaust downstream of the DPF 6 is broken or broken. Unlike the case where the exhaust gas passes through the portion and the case where the exhaust gas does not pass through, the pressure difference between the exhaust upstream of the DPF 6 and the exhaust downstream is lower when the exhaust gas passes through the damaged portion. This high-precision abnormality detection is utilized, and if there is an abnormality in the DPF 6 when the differential pressure between the exhaust upstream of the DPF 6 and the exhaust downstream changes before and after the passage of the exhaust gas is changed. to decide. The flow of determining whether there is an abnormality in the DPF 6 based on such high-precision abnormality detection will be described with reference to FIG.

  First, in step 201, as in step 111 of FIG. 3, the DPF 6 is based on the area of the portion through which the exhaust gas can pass on the exhaust gas passage surface of the DPF 6 that is shielded by the lid 21, the amount of engine intake air, and the like. A predicted differential pressure ΔP′h between the exhaust upstream and the exhaust downstream is calculated by the predicted differential pressure calculating means 19. In the subsequent step 202, the actual differential pressure ΔP1 between the exhaust upstream of the DPF 6 and the exhaust downstream when the shielding portion of the exhaust gas passage surface of the DPF 6 by the lid 21 is in the first state is the differential pressure sensor 17. Is detected. In the subsequent step 203, the deviation ratio (KΔP1 = ΔP1 / ΔP′h) of the actual differential pressure ΔP1 with respect to the predicted differential pressure ΔP′h in the first state is calculated.

  When the steps 201 to 203 are completed, the lid body 21 is rotated by 90 °, 180 ° and 270 ° around the rotation center 23 on the exhaust passage surface of the DPF 6 in the following steps 204 and 205. The shielding part of the exhaust gas passage surface of the DPF 6 by 21 is changed to the second, third and fourth states. Then, in each of the second, third, and fourth states, as in step 203, the exhaust of the DPF 6 detected by the differential pressure sensor 17 with respect to the predicted differential pressure ΔP′h calculated in step 201. The respective deviation ratios (KΔP2, KΔP3, KΔP4) of the actual differential pressures ΔP2, ΔP3, ΔP4 between the upstream and the exhaust downstream are calculated.

  In steps 206 to 208 following step 205, the divergence ratios of the actual differential pressures ΔP1, ΔP2, ΔP3, and ΔP4 with respect to the predicted differential pressure ΔP′h in the first to fourth states calculated in steps 203 to 205, respectively. Among (KΔP1, KΔP2, KΔP3, KΔP4), a maximum deviation ratio (KΔPmax) and a minimum deviation ratio (KΔPmin) are determined, and a difference between the maximum deviation ratio (KΔPmax) and the minimum deviation ratio (KΔPmin) is calculated. Then, a relative differential pressure index (KΔP = KΔPmax−KΔPmin) is calculated.

  In step 209 following step 208, it is determined whether or not the relative differential pressure index (KΔP) calculated in step 208 exceeds a predetermined value (R7) serving as a threshold for determining whether or not there is an abnormality in the DPF 6. Done. When the relative differential pressure index (KΔP) calculated in step 208 exceeds the predetermined value (R7), it is determined that there is an abnormality in the DPF 6 and the process proceeds to step 210, and the relative differential pressure index (KΔP) ) Does not exceed the predetermined value (R7), it is determined that there is no abnormality in the DPF 6 and the process proceeds to step 211.

  By the way, the shielding means shown in FIG. 2 is configured so as to shield a part of the exhaust gas passage surface of the DPF 6 by the single lid body 21 and the shielding area is constant. A part of the exhaust gas passage surface of the DPF 6 may be shielded by the single lid. According to the shielding means having a plurality of lids, the shielding area can be adjusted, and the differential pressure between the exhaust upstream of the DPF 6 and the exhaust downstream is determined as the minimum differential pressure required for detecting the abnormality of the DPF 6. It is possible to control the deterioration of fuel consumption accompanying the increase in the differential pressure to a minimum. Furthermore, every time the abnormality of the DPF 6 is detected, it is possible to change the selection of the lid that shields a part of the exhaust gas passage surface of the DPF 6, and it is possible to always prevent the abnormal part from being covered by the lid, Therefore, it is possible to prevent an error in detecting the abnormality of the DPF 6.

  FIG. 5 is a view showing another embodiment of the shielding means arranged on the exhaust gas passage surface of the DPF 6. The shielding means shown in FIG. 5 is configured to shield a part of the exhaust gas passage surface so as to adjust the shielding area of the exhaust gas passage surface based on the predicted differential pressure calculated by the predicted differential pressure calculation means 19. Is done. Specifically, the shielding means 30 shown in FIG. 5 includes four quadrant-shaped first lid bodies 31, second lid bodies 32, third lid bodies 33, and fourth lid bodies 34. And each lid body is configured to be able to shield a part of the exhaust gas passage surface of the DPF 6 based on the predicted differential pressure calculated by the predicted differential pressure calculating means 19. When it is not necessary to shield a part of the exhaust gas passage surface of the DPF 6, as shown in FIG. 5 (a), each cover body has an exhaust gas flow direction so as not to hinder the exhaust gas flow. Arranged in parallel. On the other hand, when it is necessary to shield a part of the exhaust gas passage surface of the DPF 6, it was selected to shield a part of the exhaust gas passage surface of the DPF 6, as shown in FIG. The lid is disposed at right angles to the flow direction of the exhaust gas so as to hinder the flow of exhaust gas. 5 is configured to be disposed on the exhaust gas passage surface on the upstream side of the DPF 6, but is disposed on the exhaust gas passage surface on the downstream side of the DPF 6. May be. Further, the number of lids is not limited to four, and is appropriately determined according to design specifications.

  FIG. 6 is a flowchart for determining whether there is an abnormality in the DPF 6 using the shielding means 30 shown in FIG. Based on FIG. 6, the flow of determination of the presence or absence of abnormality of the DPF 6 will be described.

  The flowchart shown in FIG. 6 is based on the predicted differential pressure between the exhaust upstream of the DPF 6 and the exhaust downstream calculated by the predicted differential pressure calculating means 19 when the exhaust gas passage surface of the DPF 6 is not shielded by each lid. Thus, it is assumed that the process is started when it is determined that a part of the exhaust gas passage surface of the DPF 6 needs to be shielded by the lid 21 in order to accurately detect the abnormality of the DPF 6.

  First, in step 301, a differential pressure ΔPrq is set for enabling the abnormality of the DPF 6 to be detected stably. The differential pressure ΔPrq is set in advance based on design specifications and the like. In the subsequent step 302, the predicted differential pressure calculation means 19 calculates the predicted differential pressure ΔP ′ between the exhaust upstream of the DPF 6 and the exhaust downstream when the exhaust gas passage surface of the DPF 6 is not shielded by the lids. It is calculated based on the intake air amount and the area of the portion through which the exhaust gas can pass on the exhaust gas passage surface of the DPF 6. Since the movement of the particulate matter (PM) in the DPF 6 depends on the temperature of the DPF 6 and the movement of the particulate matter affects the differential pressure between the exhaust upstream of the DPF and the exhaust downstream, the exhaust upstream of the DPF 6 The differential pressure difference ΔP ′ between the exhaust gas and the downstream side of the exhaust gas may be calculated based on the amount of engine intake air, the area of the exhaust gas passage surface of the DPF 6 through which the exhaust gas can pass, and the DPF temperature.

  When the predicted differential pressure ΔP ′ between the exhaust upstream of the DPF 6 and the exhaust downstream when the exhaust gas passage surface of the DPF 6 is not shielded by the respective lids is calculated in the subsequent step 303 at step 301. By calculating the difference between the calculated differential pressure ΔPrq and the predicted differential pressure ΔP ′ calculated in step 302, the differential pressure dΔPrq desired to be corrected in order to detect the abnormality of the DPF 6 with high accuracy is calculated.

  In the subsequent step 304, the number of lids that need to be closed to shield a part of the exhaust gas passage surface of the DPF 6 based on the differential pressure dΔPrq to be corrected calculated in step 303, the engine intake air amount, and the like. Ncl is determined. When the number Ncl of lids that need to be closed is determined, in subsequent steps 305 and 306, a part of the exhaust gas passage surface of the DPF 6 is shielded by the Ncl lids that need to be closed. In order to determine the lid that is initially closed when the abnormality of the DPF 6 is detected, the lid that is closed last is stored in order to shield a part of the exhaust gas passage surface of the DPF 6 this time. Specifically, the lid that is first closed when the next abnormality of the DPF 6 is detected is different from the lid that was closed last when the abnormality of the DPF 6 was detected this time. Thereby, it is possible to always prevent the abnormal part from being covered with the lid, and it is possible to prevent an error in detecting the abnormality of the DPF 6. The closing order of the Ncl lids that need to be closed to shield a part of the exhaust gas passage surface of the DPF 6 may be sequentially closed clockwise or counterclockwise, or may be randomly closed. May be.

  When the Ncl lids that need to be closed to shield a part of the exhaust gas passage surface of the DPF 6 are closed, the exhaust gas on the exhaust gas passage surface of the DPF 6 after being shielded by the lid passes in the subsequent step 307. The predicted differential pressure ΔP′h between the exhaust upstream of the DPF 6 and the exhaust downstream of the DPF 6 is calculated by the predicted differential pressure calculating means 19 based on the area of the possible portion, the engine intake air amount, etc., and the process proceeds to the next step 308.

  In step 308, the deviation ratio (KΔP = ΔPsh) of the actual differential pressure ΔPsh between the exhaust upstream of the DPF 6 and the exhaust downstream detected by the differential pressure sensor 17 with respect to the predicted differential pressure ΔP′h calculated in step 307. / ΔP′h) is calculated, and in the subsequent step 309, it is determined whether there is an abnormality in the DPF 6. Specifically, it is determined whether or not the deviation ratio KΔP calculated in step 308 exceeds a predetermined value (R8) that is a threshold value for determining whether there is an abnormality in the DPF 6. If the deviation ratio KΔP calculated in step 308 exceeds the predetermined value (R8), it is determined that there is no abnormality in the DPF 6 and the process proceeds to step 310, and the deviation ratio KΔP exceeds the predetermined value (R8). If not, it is determined that there is an abnormality in the DPF 6 and the process proceeds to Step 311.

1 is an overall configuration diagram showing an entire system of an internal combustion engine to which a particulate filter abnormality detection device of the present invention is applied. It is a figure which shows one Embodiment of the shielding means arrange | positioned at the exhaust-gas passage surface of a particulate filter. It is a flowchart for judging the presence or absence of abnormality of the particulate filter using the shielding means shown in FIG. It is a flowchart of the highly accurate abnormality detection of a particulate filter. It is a figure which shows another one Embodiment of the shielding means arrange | positioned at the exhaust-gas passage surface of a particulate filter. It is a flowchart for judging the presence or absence of abnormality of the particulate filter using the shielding means shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 4 Intake passage 5 Exhaust passage 17 Differential pressure sensor 18 Temperature sensor 19 Predicted differential pressure calculation means 20 Shielding means

Claims (3)

A particulate filter abnormality detection device for detecting the presence or absence of damage to a particulate filter disposed in an exhaust passage of an internal combustion engine,
An actual differential pressure detection means for detecting an actual differential pressure between the exhaust upstream of the particulate filter and the exhaust downstream;
A predicted differential pressure between the exhaust upstream of the particulate filter and the exhaust downstream is calculated based on the engine intake air amount and the area of the exhaust gas passage surface of the particulate filter through which the exhaust gas can pass. A predicted differential pressure calculating means;
A shielding unit that is disposed on the exhaust gas passage surface and shields a part of the exhaust gas passage surface based on the predicted differential pressure calculated by the predicted differential pressure calculation unit;
After the predicted differential pressure calculated by the predicted differential pressure calculating means is less than or equal to a predetermined value, a part of the exhaust gas passage surface is shielded by the shielding means and a part of the exhaust gas passage surface is shielded The particulate filter abnormality is determined based on the predicted differential pressure calculated by the predicted differential pressure calculation means and the actual differential pressure detected by the actual differential pressure detection means. Detection device.   The shielding unit shields a part of the exhaust gas passage surface based on the predicted differential pressure calculated by the predicted differential pressure calculation unit, and the part after the part of the exhaust gas passage surface is shielded The particulate filter abnormality detection device according to claim 1, wherein the shielding portion of the exhaust gas passage surface is changed based on the predicted differential pressure calculated by the predicted differential pressure calculating means.   The said shielding means shields a part of said exhaust gas passage surface so as to adjust the shielding area of the exhaust gas passage surface based on the predicted differential pressure calculated by the predicted differential pressure calculation device. The particulate filter abnormality detection device described.

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