JP2011252459A - Device for detection of failure in particulate filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel technique using an electric resistance type exhaust particulate sensor for determining the presence of failure of a particulate filter.SOLUTION: Particulate matter PM passing through a particulate filter DPF provided at an exhaust tube 2 of a diesel engine during failure is detected by an electric resistance type PM sensor 1. A flow rate/pressure detector for detecting a flow rate or a pressure of exhaust gas upstream of the particulate filter DPF is provided. An electronic control unit ECU compares output value variations of a detection unit 100 of the PM sensor 1 in two operation states having different flow rates or pressures of the exhaust gas, and determines the failure of the particulate filter when a difference value or a ratio value exceeds a prescribed value.

Description

  The present invention relates to a particulate filter abnormality detection device that collects particulate matter present in exhaust gas from an internal combustion engine for a vehicle, and more particularly, particulates that pass through a particulate filter using an electrical resistance type exhaust particulate sensor. The present invention relates to an apparatus for detecting an abnormality such as breakage by detecting the amount of a particulate material.

  In automobile diesel engines, etc., environmental pollutants contained in exhaust gas, especially particulate matter (Particulate Matter; hereinafter referred to as PM as appropriate), mainly composed of particulate carbon (Soot) and soluble organic components (SOF), are captured. In order to collect, a diesel particulate filter (hereinafter referred to as DPF as appropriate) is installed in the exhaust passage. The DPF is generally made of porous ceramics having excellent heat resistance, and traps PM by passing exhaust gas through a partition wall having a large number of pores. Further, when the amount of collected PM exceeds a specified amount, high-temperature combustion exhaust gas is introduced into the DPF by heater heating or post injection, and PM is burned and removed to regenerate the DPF.

  For example, the regeneration time can be determined by using the fact that the differential pressure increases due to an increase in the amount of collected PM, and the amount of collected PM is detected based on the detection result of the differential pressure sensor. In addition, if an abnormality occurs in the flow of exhaust gas due to damage to the DPF or the like, the differential pressure across the front and rear changes as compared to the normal case, and this can be used to detect an abnormality in the DPF. Generally, when the differential pressure across the DPF falls below a predetermined value, it is determined that the exhaust gas is leaking due to breakage. Further, Patent Document 1 compares the PM accumulation amount calculated based on the front-rear differential pressure with the PM accumulation amount calculated by integrating the PM emission amount known from the engine operating state, and there is a large mismatch between the two. An apparatus is described that determines that the DPF 4 is abnormal if the error occurs.

  On the other hand, an electrical resistance type sensor for directly detecting PM in exhaust gas has been proposed, and this sensor is installed upstream of the DPF to measure the amount of PM flowing into the DPF, or installed downstream of the DPF. Therefore, a system for measuring the amount of PM that passes through the DPF has been studied. The former is used for determining the regeneration time instead of the differential pressure sensor, and the latter is used for monitoring the operating state of the DPF and determining deterioration, breakage, and the like. In recent years, in order to prevent environmental pollution, the installation of an onboard diagnosis (OBD) is obligatory, and the importance of the latter is increasing.

  The electrical resistance type sensor utilizes the conductive property of particulate carbon. Patent Documents 2 and 3 disclose a basic configuration in which a pair of conductive electrodes are formed on the surface of an insulating substrate having heat resistance. Is disclosed. When this sensor is disposed in the exhaust gas passage containing PM, PM can be detected from a change in resistance value caused by the adhesion of particulate carbon between the electrodes serving as the detection units. In addition, as a technique for detecting PM, there are a sensor for detecting heat generated by oxidation reaction of PM using a catalyst and a thermocouple, and a method for monitoring chemical species and temperature of exhaust gas using a wavelength tunable diode laser. As is known, the electric resistance type sensor has an advantage that a relatively stable output can be obtained with a simple configuration.

  Regarding failure diagnosis, Patent Document 4 exemplifies a system for detecting a damaged state of a DPF using an electric resistance type sensor. In the apparatus of Patent Document 4, an electrical insulating layer to which PM adheres, a plurality of electrodes provided apart from each other in the electrical insulating layer, and a sensor having a heater layer are disposed in the exhaust passage downstream of the DPF. There is disclosed a failure determination device including an ECU that measures an index correlating with an electrical resistance value between the electrodes and determines that a DPF failure occurs when the measured value becomes smaller than a predetermined reference.

JP-A-2005-344619 Japanese Examined Patent Publication No. 2-44386 JP 59-196453 A JP 2009-1444577 A

  When the particulate carbon is deposited, the electrodes are electrically connected to each other, and the resistance value is lowered from the initial insulation state. Therefore, in Patent Document 4, a failure determination threshold (predetermined standard) is obtained from this relationship and compared with the monitored interelectrode resistance value. To do. The threshold is set, for example, based on the OBD regulation value. In contrast to the method based on the differential pressure between the front and rear as in Patent Document 1, the device of Patent Document 4 directly detects the amount of PM that passes through the DPF, so that even minor failures such as cracks can be accurately determined. Be expected.

  However, even if there is no abnormality in the DPF, if there is a slight amount of PM that passes through the DPF, the amount of PM adhering to the electrical insulating layer gradually increases. For this reason, it is necessary not only to investigate the relationship between the PM deposition amount and the electrical resistance value (or change amount) by conducting an experiment or the like in advance, but also to investigate and specify the detection amount in a normal state in advance. Then, by comparing with the calculated amount of PM, it is determined whether or not the collection by the DPF is normally performed.

  However, the amount of PM contained in the exhaust gas from the engine varies greatly depending on the operating state (load and rotation speed). The tendency for the PM to increase is that, as the load becomes higher, for example, the amount of PM increases in the entire region from a low rotation speed to a high rotation speed as when the engine is started. Further, the PM amount tends to increase as the rotational speed increases to the output region. Furthermore, when the properties and particle distribution of the discharged PM vary depending on the operating state, the amount of PM that passes through the DPF also varies. Therefore, in order to determine the presence or absence of performance degradation or damage of the DPF, the current PM amount is compared with the PM amount map obtained in advance with respect to the operating state. Is not easy. Further, since the amount of passing PM varies depending on the PM accumulation state on the DPF, it is necessary to map the relationship with the PM accumulation amount, and the map amount to be stored is increased, and the failure determination process is complicated. There is a problem to become.

  Therefore, the present invention provides a novel method using an electric resistance type exhaust particle sensor for determining the presence or absence of an abnormality in a DPF that processes exhaust gas of an internal combustion engine, and has a simple configuration and a large number of maps and It is an object of the present invention to realize an abnormality detection device with high responsiveness and accuracy without requiring complicated correction processing.

The invention described in claim 1 of the present invention
An exhaust particulate sensor installed in the exhaust passage of the internal combustion engine downstream of the particulate filter that collects particulate matter in the exhaust gas and detects the amount of particulate matter in the exhaust gas;
A flow rate / pressure detection means for detecting a flow rate or pressure of exhaust gas in an exhaust passage upstream of the particulate filter;
An abnormality detection unit for detecting an abnormality of the particulate filter based on the detection results of the flow rate / pressure detection means and the discharged particulate sensor;
The discharged particulate sensor has a detection part in which a pair of detection electrodes are formed on the surface of an insulating substrate, and the electrical resistance value changes according to the amount of particulate matter adhering between the pair of detection electrodes. Yes,
The abnormality detection unit compares changes in the output value of the exhaust particulate sensor in two operating states with different flow rates or pressures of the exhaust gas, and when the difference value or the ratio value exceeds a predetermined value, the particulates A determination unit that determines that the filter is abnormal is provided.

  In the invention according to claim 2 of the present invention, the abnormality detection unit uses the flow rate or pressure of the exhaust gas in the operation state at the start of abnormality detection as a first flow rate / pressure condition as a predetermined flow rate of the exhaust particulate sensor. For example, the flow rate is larger than the first flow rate / pressure condition or the pressure is changed so that the difference between the output value and the first flow rate / pressure condition is a preset flow rate or pressure. A high second flow rate / pressure condition is set, and an output value change of the discharged particulate sensor in the second flow rate / pressure condition in a predetermined period is measured. In addition, when the first flow rate / pressure condition is large or high, the second flow rate / pressure condition is set to a condition where the flow rate is lower or lower than the first condition, and the second condition is The output value change of the discharged particulate sensor during a predetermined period is measured.

  In the invention according to claim 3 of the present invention, the abnormality detecting unit measures the first output value change in the predetermined period of the discharged particulate sensor under the first flow rate / pressure condition, and then the flow rate / Wait until the detection result of the pressure detection means reaches the second flow rate / pressure condition, and measure the second output value change in the discharge particulate sensor for a predetermined period when the second flow rate / pressure condition is reached. Then, abnormality is determined based on these first and second output value changes.

The invention according to claim 4 of the present invention is
A flow rate / pressure adjusting means for adjusting the flow rate or pressure of the exhaust gas in the exhaust passage upstream of the particulate filter;
The abnormality detection unit monitors a detection result of the flow rate / pressure detection unit after measuring a first output value change in the discharge particulate sensor for a predetermined period under the first flow rate / pressure condition, When the second flow rate / pressure condition is not satisfied, the flow rate / pressure adjustment means is used to forcibly adjust the second flow rate / pressure condition, and the discharge particulate matter sensor has a first period in a predetermined period. 2 is measured, and abnormality is determined based on the first and second output value changes.

  In the invention according to claim 5 of the present invention, the abnormality detection unit presets a difference between the flow rate or pressure under the first flow rate / pressure condition and the flow rate or pressure under the second flow rate / pressure condition. To a predetermined value.

  In the invention according to claim 6 of the present invention, the abnormality detection unit calculates a difference between a flow rate or pressure under the first flow rate / pressure condition and a flow rate or pressure under the second flow rate / pressure condition as an operating state. Set according to.

  In the invention according to claim 7 of the present invention, the exhaust particulate sensor is formed by forming the pair of comb-like detection electrodes and the lead portion on the surface of the distal end portion of the insulating base located in the exhaust passage. As the detection unit, a heater electrode and a lead part are formed on the back surface of the front end of the insulating substrate, and the detection unit is heated to a predetermined temperature.

  The invention according to claim 1 of the present invention detects an abnormality of a particulate filter by a novel method using an electric resistance type discharged particulate sensor. When the exhaust gas flows into the particulate filter, the particulate matter is collected and accumulated in the pores of the porous ceramics constituting the particulate filter. When an abnormality such as breakage occurs in the particulate filter, the amount of particulate matter that passes through the particulate filter from the damaged portion and flows into the exhaust particulate sensor downstream increases, so the abnormality detection unit detects the flow rate or pressure of the exhaust gas. Sensor output values are obtained in two operating states with different values. This is because, when an abnormality occurs, the particulate matter that slips through in comparison with the normal state has more coarse particles, and the amount of particulate matter that slips through in response to changes in flow rate or pressure, and the rate of adhesion to the detection part of the discharged particulate sensor. It is focused on the fact that the output changes suddenly.

  For this reason, the sensor output value detected at these two levels of flow rate or pressure is larger when the particulate filter is abnormal than when the difference value or ratio value is normal. Therefore, by comparing these output values, it is possible to easily determine whether the particulate filter is functioning normally. Therefore, a simple configuration and a large amount of maps and complicated correction processing are unnecessary, and a highly responsive and accurate abnormality detection apparatus can be realized.

  Specifically, as in the second aspect of the present invention, specifically, the detection result of the flow rate / pressure detection means at the start of abnormality detection is set as the first flow rate / pressure condition, and the first flow rate / pressure condition is set. It is preferable to set the second flow rate / pressure condition in which the difference between the flow rate and the pressure becomes a preset flow rate or pressure. The increase in flow rate or pressure makes it easier for particulate matter to pass through the particulate filter, and the output changes greatly due to the increase in the amount of slip and the ratio of coarse particles, so compare with the change in output during normal operation. Thus, the abnormality can be detected effectively.

  Since the flow rate or the pressure fluctuates due to the change in the operating state as in the third aspect of the present invention, the first output value change is measured under the first flow rate / pressure condition, and is set in advance. Abnormality determination can be easily performed by waiting until the second flow rate / pressure condition is satisfied.

  As in the fourth aspect of the present invention, or the flow rate / pressure adjusting means can be used to force the second flow rate / pressure condition. At this time, it waits for a predetermined period before operating the flow rate / pressure adjusting means, and when the second flow rate / pressure condition is changed during standby, the second output value is not operated without operating the flow rate / pressure adjusting means. Measure changes. As a result, it is possible to determine the abnormality efficiently while minimizing the influence on the operation state.

  As in the fifth aspect of the present invention, a predetermined value for determining the second flow rate / pressure condition can be set in advance for the first flow rate / pressure condition. For example, if the flow rate / pressure increases by 20% or more during normal driving, abnormal output changes can be detected. Therefore, it is possible to easily and effectively determine abnormality by setting this value appropriately. Can do.

  As in the sixth aspect of the present invention, the predetermined value for determining the second flow rate / pressure condition may be set or corrected according to the operating state. For example, during a low load operation, the hydrocarbon (HC) component in the discharged particulates increases and tends to adhere to the particulate filter. In other words, since the particulate matter is difficult to slip through, the abnormality can be accurately determined by increasing the difference between the first flow rate / pressure condition and the second flow rate / pressure condition.

  As in the seventh aspect of the present invention, the detection part of the discharged particulate sensor is easily formed by a pair of comb-shaped detection electrodes provided on the insulating substrate. Preferably, when a heater portion is formed on the back surface of the insulating base and the detection portion is heated to a predetermined temperature range, the resistance value change amount can be increased and the detectable time ratio can be increased, thereby improving the detection accuracy.

In 1st Embodiment of this invention, it is a flowchart which shows the content of the determination means with which the electronic control unit used as an abnormality detection part is provided. 1 is an overall system diagram of a diesel engine to which an abnormality detection device of the present invention is applied. It is a figure which shows PM detection element structure which is the principal part of PM sensor. It is a figure which shows the state which attached PM sensor to the exhaust pipe of the diesel engine. It is a figure which shows the relationship between PM deposition amount and inter-electrode resistance value. It is a figure which shows the relationship between the exhaust pressure P in the exhaust pipe of the diesel particulate filter DPF upstream, and the output of PM sensor. In 2nd Embodiment of this invention, it is a flowchart which shows the content of the determination means with which the electronic control unit used as an abnormality detection part is provided. In 3rd Embodiment of this invention, it is a flowchart which shows the content of the determination means with which the electronic control unit used as an abnormality detection part is provided. It is an example of an output of the abnormality detection device of the present invention, and is a diagram showing the relationship between the temperature rise and the resistance change rate of the detection part of the PM sensor of the present invention in comparison between normal and abnormal.

  A first embodiment in which the particulate filter abnormality detection device of the present invention is applied to an exhaust gas purification system for an automobile diesel engine, which is an internal combustion engine, will be described with reference to the drawings. FIG. 2 is a schematic diagram of the entire system of a diesel engine E / G with a supercharger. A common rail that accumulates high-pressure fuel boosted by a high-pressure pump PMP to a common rail R common to each cylinder so as to have a predetermined injection pressure. The fuel injection system is adopted, and the engine is configured as a direct injection engine that directly injects into the combustion chamber by an injector INJ. The exhaust pipe 2 having the inside as an exhaust passage is provided with a diesel particulate filter DPF that is a particulate filter and a PM sensor 1 that is an exhaust particulate sensor, and together with an electronic control unit ECU serving as an abnormality detection unit, This constitutes an abnormality detection device for the particulate filter. FIG. 1 is a flowchart of abnormality detection processing by the electronic control unit ECU, which will be described in detail later.

In Figure 2, the exhaust manifold _{MH EX} of the diesel engine E / G, the turbine TRB _T of the turbo supercharger TRB is provided, when in conjunction with the turbine TRB _T compressor TRB _C rotates, compressed air, It passes through the intake throttle V _TH and the intercooler CL _INT and is sent to the intake manifold MH _IN . A part of the combustion exhaust discharged from the exhaust manifold MH _EX returns to the intake manifold MH _IN via the EGR valve V _EGR and the EGR cooler CL _EGR . The electronic control unit ECU, by adjusting the nozzle vanes (VN) opening provided in the turbine TRB _T, and controls the supercharging pressure, by adjusting the opening degree of the EGR valve _{V EGR,} controls the EGR recirculation amount . The intake amount is increased by supercharging to increase combustion efficiency, and the combustion is moderated by EGR to suppress the emission of NOx and the like. The intake pipe 3 upstream of the compressor CPR is provided with an air flow meter AFM that measures the flow rate of fresh air to be sucked.

The intake throttle V _TH , the EGR valve V _EGR , and the supercharging device TRB are flow rate / pressure adjusting means for adjusting the flow rate or pressure of exhaust gas upstream of the diesel particulate filter DPF in the particulate filter abnormality detection device of the present invention. Function as.

The exhaust pipe 2 connected to the exhaust manifold MH _EX is provided with a diesel oxidation catalyst DOC and a diesel particulate filter DPF, and processes combustion exhaust gas. That is, while the combustion exhaust gas discharged to the exhaust pipe 2 passes through the upstream diesel oxidation catalyst DOC, unburned hydrocarbons HC, carbon monoxide CO, and nitrogen monoxide NO are oxidized, and the downstream side While passing through the diesel particulate filter DPF, the particulate matter PM is collected. For NOx removal, for example, a selective catalyst reduction SCR (not shown) or the like is provided after the diesel particulate filter DPF, and NOx is reduced to N ₂ and H ₂ O and removed.

The diesel oxidation catalyst DOC is formed by supporting an oxidation catalyst on a known monolithic carrier, for example, a carrier surface made of a ceramic honeycomb structure such as cordierite. The diesel oxidation catalyst DOC raises the exhaust temperature by oxidative combustion of the supplied fuel or oxidizes and removes the SOF component in the particulate matter PM during forced regeneration of the diesel particulate filter DPF. Further, NO ₂ generated by oxidation of NO is used as an oxidant for the particulate matter PM deposited on the diesel particulate filter DPF at the subsequent stage, and enables continuous oxidation.

  The diesel particulate filter DPF has a known wall flow type filter structure. For example, a porous ceramic honeycomb structure made of heat-resistant ceramics such as cordierite is formed, and either the inlet side or the outlet side of a large number of cells serving as gas flow paths are staggered in adjacent cells. Seal the filter to make a filter. At this time, a large number of pores are formed through the cell walls defining the gas flow path, and the particulate matter PM in the exhaust gas introduced into the diesel particulate filter DPF is captured. Here, although the diesel oxidation catalyst DOC and the diesel particulate filter DPF are provided separately, they can be configured as a continuous regenerative diesel particulate filter in which these are integrated.

  In the present embodiment, a differential pressure sensor SP is provided in order to know the amount of particulate matter PM deposited on the diesel particulate filter DPF (PM trapping amount). The differential pressure sensor SP is connected to the upstream side and the downstream side of the diesel particulate filter DPF via a pressure introduction pipe, and outputs a signal corresponding to the differential pressure before and after to the electronic control unit ECU. Instead of the differential pressure sensor SP, pressure sensors may be installed on the upstream side and the downstream side of the diesel particulate filter DPF, respectively. Further, temperature sensors ST1, ST2, and ST3 are disposed upstream of the diesel oxidation catalyst DOC and upstream and downstream of the diesel particulate filter DPF to monitor the exhaust temperature of each part. The electronic control unit ECU monitors the catalytic activation state of the diesel oxidation catalyst DOC and the PM collection state of the diesel particulate filter DPF based on these outputs, and performs forced regeneration when the PM collection amount exceeds the allowable amount. Regeneration control for burning and removing the particulate matter PM is performed.

  In the regeneration control by the electronic control unit ECU, for example, post injection is performed to increase the amount of HC in the exhaust, the temperature of the diesel particulate filter DPF is changed by the heat of HC reaction in the diesel oxidation catalyst DOC, and the combustion temperature of the particulate matter PM. Raise more. At this time, the temperature of the diesel particulate filter DPF is monitored by the temperature sensors ST2 and ST3, and the diesel particulate filter DPF is controlled to be in a predetermined temperature range. Under the operating conditions in which the particulate matter PM can spontaneously burn, the fuel consumption can be suppressed by setting the regeneration control not to be performed. The electronic control unit ECU further receives detection signals from various sensors (not shown), calculates the optimum fuel injection amount, injection timing, injection pressure, and the like based on these signals, and controls fuel injection.

  A PM sensor 1 is disposed in the exhaust pipe 2 downstream of the diesel particulate filter DPF to detect particulate matter PM that passes through the diesel particulate filter DPF. FIG. 3 is a diagram showing the PM detection element 10 which is a main part of the PM sensor 1, and FIG. 4 is a diagram showing a state where the PM sensor 1 including the PM detection element unit 10 is attached to the exhaust pipe 2. In FIG. 3, the PM detection element 10 includes a detection unit 100 in which a pair of detection electrodes 11 and 12 are formed on the surface of an insulating substrate 13 that is an insulating base, a pair of detection electrodes 11 and 12, and an external resistance measurement unit. Lead portions 111 and 121 to be conducted and a heater portion 300 that is stacked on the back side of the detection portion 100 and heats the lead portions to a predetermined temperature (for example, about 400 ° C. to 600 ° C.).

  The detection unit 100 is formed on a flat insulating substrate 13 using a known method such as a doctor blade method or a press molding method with a ceramic material excellent in electrical insulation and heat resistance, such as alumina, and is formed on the surface of the tip portion. A pair of comb-shaped detection electrodes 11 and 12 are arranged to face each other at a predetermined inter-electrode distance. The detection electrodes 11 and 12 are formed by printing a conductive paste containing a noble metal such as platinum in a predetermined pattern. The heater unit 300 includes a flat insulating substrate 33 formed in the same manner and a heater electrode 30 formed in a predetermined pattern on the surface of the front end portion, and is connected to external energizing means by lead portions 31 and 32.

  In FIG. 4, the PM sensor 1 has a cylindrical housing 50 that is screwed to the tube wall 20 of the exhaust pipe 2, and the upper half of the PM detection element 10 that is inserted into and fixed to the cylindrical insulator 60 is disposed therein. keeping. The lower half of the PM detection element 10 is positioned in a hollow cover body 40 that is fixed to the lower end of the cylindrical housing 50 and protrudes into the exhaust pipe 2. Holes 410 and 411 through which exhaust gas containing particulate matter PM that has passed through the diesel particulate filter DPF flows are formed in the bottom and side portions of the cover body 40.

  At this time, in order to surely capture the particulate matter PM, it is preferable to arrange the PM detection element 10 so that the detection unit 100 faces the upstream side of the exhaust pipe 2 as illustrated. Further, when the insulating protective layer 14 is formed on the surface of the insulating substrate 13 excluding the detection unit 100 so as to cover the lead units 111 and 121, erroneous detection due to accumulation of particulate matter PM between the lead units 111 and 121 is detected. Can be prevented.

Next, the basic operation of the PM sensor 1 will be described. In FIG. 4, the exhaust gas that is the gas to be measured is led out through the holes 410 and 411 of the cover body 40 of the PM sensor 1. More specifically, it is introduced into the inside through a hole 411 at a position facing the exhaust gas flow, discharged from a hole 411 located at the downstream side or a hole 410 located at the bottom, and reaches the detection unit 100 of the PM detection element 10. In FIG. 3, comb-shaped detection electrodes 11 and 12 are formed on the surface of the detection unit 100 with a predetermined gap, so that conductive fine carbon particles are formed by contact with exhaust gas. When the contained particulate matter PM adheres and gradually accumulates, the detection electrodes 11 and 12 become conductive at a certain point. FIG. 5 shows changes in the electrical resistance value between the detection electrodes 11 and 12 when the PM deposition amount is increased at a constant rate. In the initial state, which is a substantially insulated state, the interelectrode resistance is 1 ×. When it is 10 ⁷ Ω or more and the detection electrodes 11 and 12 are conductive, the resistance between the electrodes rapidly decreases with the increase in the PM deposition amount, and becomes about 1 × 10 ³ Ω. The interelectrode resistance or the resistance change rate changes according to the temperature of the detection unit 100.

  For this reason, usually, the output of the PM sensor 1 is monitored in a state where the temperature of the detection unit 100 is kept substantially constant in the range of 400 to 600 ° C. by the heater unit 300 of the PM sensor 1. In this temperature range, the rate of change in resistance is large, the detectable state can be maintained for a long time, and accurate detection is possible. More specifically, when the temperature is low, the amount of PM adhering is large, so that the sensor output is saturated in a short time, the number of regeneration processes is increased, and the detectable state is shortened. Further, when the temperature is high, a part of the adhered PM is burned, so that the apparently adhered PM is reduced and the rate of resistance change is small, so that accurate detection is difficult.

  Here, if any problem such as breakage or melting of the cell wall or plugging portion occurs in the diesel particulate filter DPF, and normal collection becomes difficult, the particulate matter PM released together with the exhaust gas increases. . Therefore, conventionally, based on the relationship between the PM deposition amount and the electrical resistance value, the resistance value between the detection electrodes 11 and 12 of the PM sensor 1 is compared with a preset threshold value, and failure determination is performed. For example, if the particulate matter PM that passes through the diesel particulate filter DPF during a predetermined period is clearly more than normal, it can be determined as abnormal.

  However, as described above, since the amount and properties of the particulate matter PM discharged from the engine E / G vary depending on the operating state, the amount of the particulate matter PM that passes through the diesel particulate filter DPF also increases or decreases. Conventionally, the determination is performed based on the amount of the particulate matter PM without considering this, and there is a risk of erroneous determination if the determination threshold is set to a constant value. Alternatively, it is possible to perform correction or change the determination threshold based on a map corresponding to the driving state, but the map amount increases.

  The particulate filter abnormality detection device of the present invention is a flow rate / pressure detection means for detecting the flow rate or pressure of exhaust gas in the exhaust pipe 2 upstream of the diesel particulate filter DPF in order to eliminate such a conventional problem. An abnormality detection unit that detects an abnormality of the diesel particulate filter DPF based on the detection result and the detection result of the PM sensor 1 is provided. The abnormality detection unit detects the particulate matter PM by the PM sensor 1 in two operating states with different exhaust gas flow rates or pressures. At this time, the first flow rate / pressure condition is the flow rate or pressure at the start of abnormality detection, and the second flow rate / pressure condition is set with a higher flow rate or higher pressure. Then, the presence or absence of abnormality is determined by comparing the sensor output values under the first and second flow rate / pressure conditions. Here, when the first flow rate / pressure condition is large or high, the magnitude relationship between the first and second flow rate / pressure conditions can be reversed.

  FIG. 6 shows the relationship between the exhaust pressure P in the exhaust pipe 2 upstream of the diesel particulate filter DPF and the output of the PM sensor 1, that is, the slipping amount of the particulate matter PM. Here, a normal diesel particulate filter DPF (when normal) that is not damaged and a diesel particulate filter DPF (when the DPF is damaged) with internal cell walls being damaged are prepared, and the exhaust pressure P is set to a predetermined value. Changes in the output value of the PM sensor 1 when the range was changed were examined. As is apparent from the figure, as the collection characteristics of the diesel particulate filter DPF, the PM slip-through amount does not change greatly even when the DPF upstream pressure increases from P1 to P2 in the normal state. The higher the is, the more slipping through.

  When the collection of the diesel particulate filter DPF is normally performed, the amount of particulate matter PM that passes through without being collected in the pores is very small, and the amount of slipping through even if the exhaust pressure increases due to the fine particles. There is no significant increase. On the other hand, when the DPF breaks, the apparent amount of filter pores increases due to cracks in the cell walls and plugged breakage points, the amount of PM passing through increases, and coarse particles due to the increase in the filter pore diameter (A collection of small particles) also slips through. For this reason, the influence of the exhaust pressure becomes larger than that in the normal state, and when the exhaust pressure increases, a larger amount of coarse particles escapes, so that the PM slipping amount increases rapidly. When the exhaust flow rate is changed instead of the exhaust pressure, the same relationship is obtained for the exhaust flow rate V1 and the exhaust flow rate V2 upstream of the DPF.

  The present invention pays attention to the difference in the PM slip-through amount depending on the flow rate or pressure of the exhaust gas in FIG. 6, and in the first pressure condition P1 where the exhaust pressure is low and the second pressure condition P2 where the exhaust pressure is high. Each of the PM sensors 1 detects a resistance change rate in a predetermined period, and compares the detected resistance change rate with a normal time. The difference in the detected resistance change rate may be compared between the first flow rate condition V1 with a small exhaust flow rate and the second flow rate condition V2 with a large exhaust flow rate. A predetermined value (determination threshold) based on a difference ΔP (or ΔV) between the first pressure condition P1 (or flow rate condition V1) and the second pressure condition P2 (or flow rate condition V2) and the resistance change rate at normal time. ) Is set in advance, it is possible to easily determine abnormality.

  The flow rate / pressure detection means for detecting the flow rate or pressure of the exhaust gas is not limited as long as it can directly or indirectly detect the flow rate or pressure of the exhaust gas. For example, an exhaust flow meter or a pressure sensor is installed upstream of the diesel particulate filter DPF, and is used as a flow rate / pressure detection means for directly detecting the flow rate or pressure, and in general, fresh air sucked into the engine E / G Since the amount has a correlation with the exhaust flow rate, the air flow meter AFM can be used as the exhaust flow rate detection means. Further, if the pressure sensor is provided on the upstream side and the downstream side of the diesel particulate filter DPF in place of the differential pressure sensor SP, the upstream pressure sensor can be used as the exhaust pressure detection means.

  Next, an example of determination means provided in the electronic control unit ECU serving as the abnormality detection unit will be described based on the flowchart of FIG. In the present embodiment, the output value change of the PM sensor 1 is compared in the first flow rate condition V1 and the second flow rate condition V2 in which the flow rate of the exhaust gas is different. In FIG. 1, when abnormality detection is started, in step S100, data is first taken in from various sensors, and the temperature sensor ST2 output upstream of the diesel particulate filter DPF is taken in as exhaust gas temperature T1. Further, the cooling water temperature Tw of the diesel engine E / G is taken from a water temperature sensor (not shown), the rotational speed NE of the diesel engine E / G is taken from the engine speed sensor, and the fuel injection amount Q is obtained based on the output of the accelerator opening sensor or the like. . Further, the air flow meter AFM output is taken in as the exhaust flow rate upstream of the diesel particulate filter DPF (pre-DPF flow rate V0).

  In the present embodiment, the first flow rate condition V1 is an exhaust flow rate at the start of abnormality detection, and is determined by consequence. Here, the intake air amount (mass flow rate) by the air flow meter AFM taken in step S100 is defined as a pre-DPF flow rate V0 (execution). In step S110, this pre-DPF flow V0 is set to the pre-detection DPF flow V1, which is the first flow condition.

  In step S120, the resistance change rate ΔR1 (first output value change) between the detection electrodes 11 and 12 of the PM sensor 1 at the pre-detection DPF flow rate V1 (first flow rate condition) is measured. At this time, the resistance change rate of the detection unit 100 after a lapse of a certain time is proportional to the change rate (attachment area and adhesion thickness) of the particulate matter PM adhering between the detection electrodes 11 and 12, and the diesel particulates. When there is some abnormality in the filter DPF, as shown in FIG. 6 described above, the detected resistance change rate ΔR1 becomes larger than that in the normal state.

  Next, in step S130, a change flow rate difference ΔV for setting the second flow rate condition V2 is determined. The change flow rate difference ΔV determined here is a flow rate difference that can detect a clear difference from the normal state when there is an abnormality such as DPF breakage. Specifically, the target flow rate is determined in advance from the relationship shown in FIG. 6 so as to increase the flow rate by at least 20%, preferably by 50% or more with respect to the pre-detected DPF flow rate V1. The change flow rate difference ΔV can be set in advance. If the flow rate increases by at least 20%, it is possible to determine abnormality by comparison with the normal state. The larger the change flow rate difference ΔV, the easier the abnormality determination, but the second flow rate that can be measured by the flow rate change due to the event. The probability of reaching the condition is low. The change flow rate difference ΔV can be set according to the operation state known from the various data captured in step S110.

  In step S140, the process waits until the second flow rate condition is met. First, the pre-execution DPF flow V2 is calculated again from the air flow meter AFM output, and it is determined whether or not the absolute value of [pre-DPF flow V2−pre-DPF pre-flow V1] is greater than or equal to a predetermined change flow rate difference ΔV. . If a positive determination is made, the process proceeds to step S150. If a negative determination is made, this step is repeated until a positive determination is made. Since the exhaust flow rate changes relatively easily due to a change in operating conditions, for example, acceleration or deceleration operation, the second flow rate condition (the flow rate before pre-DPF) is set by setting the change flow rate difference ΔV to an appropriate value beforehand. V2 = flow rate before the running DPF V1 ± ΔV).

  In step S150, the resistance change rate ΔR2 (second output value change) between the detection electrodes 11 and 12 of the PM sensor 1 is measured at the pre-action DPF flow rate V2 (second flow rate condition). When there is some abnormality in the DPF, not only the time change of the detection output of the PM sensor 1 is increased, but also the difference in resistance change rate under the first and second flow rate conditions is increased. Therefore, in the subsequent step 160, the measured resistance change rates ΔR1 and ΔR2 are compared to make an abnormality determination. Here, the difference value (ΔR1−ΔR2) between the resistance change rate ΔR1 and the resistance change rate ΔR2 is calculated, and whether the difference value per unit flow rate (ΔR1−ΔR2) / (ΔV1−ΔV2) exceeds a predetermined value set in advance. Determine whether or not. For example, the predetermined value is sufficiently larger than the value when the diesel particulate filter DPF is operating normally based on the relationship shown in FIG. Alternatively, a plurality of values corresponding to the types of abnormalities such as minor breakage, performance degradation or melting damage can be set in advance by experiments or the like.

  If the determination in step 160 is affirmative, it is determined that there is some abnormality in the diesel particulate filter DPF and, for example, a warning lamp is lit to notify the driver of the abnormality. When a negative determination is made in step 160, it is determined that the diesel particulate filter DPF is normal, and this process is temporarily terminated.

  As described above, in this embodiment, two flow conditions with different exhaust flow rates upstream of the diesel particulate filter DPF are set according to circumstances, and the resistance under the first flow condition and the second flow condition with the change flow rate difference ΔV is set. An abnormality of the diesel particulate filter DPF can be easily detected based on the change rates ΔR1 and ΔR2. Therefore, with a relatively simple configuration using an electrical resistance PM sensor, a large amount of maps and temperature correction are not required, and accurate determination is possible.

  Next, the determination means of the abnormality detection unit in the second embodiment of the present invention will be described based on the flowchart of FIG. In the present embodiment, the first flow rate condition V1 is determined at the start of the abnormality diagnosis, and then the second flow rate condition V2 is forcibly determined when the second flow rate condition V2 is not reached within a predetermined period. Then, the output value change of the PM sensor 1 is compared. Steps S200 to S220 in FIG. 7 are substantially the same as steps S100 to S120 in FIG. 1. First, in step S200, the electronic control unit ECU serving as the abnormality detection unit performs the cooling water temperature Tw, the exhaust gas temperature T1, the diesel engine E. Various data such as the rotational speed NE of / G and the fuel injection amount Q are taken in, and the pre-DPF flow rate V0 (execution) is calculated from the output of the air flow meter AFM. Further, the resistance R0 between the detection electrodes 11 and 12 is measured as the PM sensor 1 output.

  In step S210, the flow rate upstream of the diesel particulate filter DPF is set to the first flow rate condition. Here, the pre-execution DPF flow rate V0 captured in step S200 is set as the pre-detection DPF flow rate V1 that is the first flow rate condition (pre-detection DPF flow rate V1 = pre-execution DPF flow rate V0). In step S220, the PM sensor 1 output is captured again, and the time change ΔR1 of the detection output is calculated from the PM sensor 1 output R0 captured in step S200 and stored in the memory.

  In step S230, a change flow rate difference ΔV for setting the second flow rate condition V2 is determined. The target flow rate is at least 20% increase, preferably 50% increase. Further, the maximum waiting time timeMax for waiting until the second flow rate condition V2 is reached is set. Here, the maximum standby time timeMax is the PM sensor 1 output R0 measured in step S210 and the output when the particulate matter PM is deposited on the PM sensor 1 to the maximum allowable amount during the predetermined period determined at the start of abnormality detection. For example, a time that is expected to reach about 80% of the permissible amount, or a predetermined time during which failure diagnosis can be performed about three times in the mode running time (20 minutes).

  In step S240, the timer is started and the measured value of the timer is set as the standby time t1. In subsequent step S250, it is determined whether or not the standby time t1 measured by the timer is less than the maximum standby time timeMax. If the determination is affirmative, the process proceeds to step S260. In step S260, the flow before the DPF D2 is calculated again from the output of the air flow meter AFM, and the absolute value of the flow V1 before the DPF D2 before the DPF is equal to or greater than the predetermined change flow rate difference ΔV. It is determined whether or not. If a negative determination is made in step S260, the process returns to step S250 to continue waiting, and steps S250 and S260 are repeated until an affirmative determination is made. If a positive determination is made in step S260, the process proceeds to step S280.

  After step S260 is determined to be negative, if the returned step S250 is determined to be negative, the standby time t1 has reached the maximum standby time timeMax, so the standby is terminated and the second flow rate condition V2 is forcibly set. Therefore, the process proceeds to step S270. In step S270, an operation of increasing the exhaust gas flow upstream of the diesel particulate filter DPF by ΔV is performed in order to obtain the target flow [pre-DPF flow V1 + ΔV]. Next, a method for forcibly changing the flow rate will be described.

Here, as the flow rate adjusting means for forcibly changing the flow rate, there are an intake throttle V _TH (intake amount), an EGR valve V _EGR (EGR recirculation amount), and a turbocharger TRB (supercharge amount). The exhaust gas flow rate can be increased by adjusting at least one or more of these. At this time, if the flow rate adjusting means is selected according to the operation state known from the detected flow rate V1 before DPF or the data taken in step S210, the desired exhaust flow rate can be efficiently achieved. As an example, when the pre-detection DPF flow rate V1 is a flow rate corresponding to the idle operation region, for example, when the intake air amount is 5 g / s, it is easy to increase the intake air amount by 50% or more by the intake throttle _VTH . and 7.5g / s~10g / s as an intake example the aim flow rate (second flow rate condition), while the fuel injection amount Q constant, the more open side intake throttle V _TH opening, introducing the new air . At that time, in order to minimize the torque fluctuation, the injection timing is retarded or the EGR recirculation amount by the EGR valve V _EGR is increased so that the ignition timing is substantially the same by using a map that has been taken in advance. As a result, the exhaust flow before the DPF can be forcibly increased with a minimum torque fluctuation.

Next, when the pre-detection DPF flow rate V1 is a flow rate corresponding to the normal operation region, for example, the forced flow rate increase method in the idle operation region can be applied even when the intake air amount is in the range of 10 to 30 g / s. Similarly, the intake throttle _VTH opening may be adjusted so as to increase by 50% or more. In addition, in the diesel engine E / G with a supercharger as shown in FIG. 1, the turbocharger TRB can also be used. As the fuel injection amount Q constant if, by adjusting the amount of fresh air in the turbo supercharger TRB and the intake throttle V _TH, while the torque variation to a minimum, and increased exhaust flow. Further, in a region where the detected pre-PFF flow rate V1 corresponds to high speed and high load operation, the intake throttle _VTH is normally controlled to be fully open and the EGR valve V _EGR is fully closed. For this reason, the turbocharger TRB is used as the flow rate adjusting means, and the flow rate can be forcibly changed by adjusting the nozzle vane (VN).

  In step S280, the resistance change rate ΔR2 between the detection electrodes 11 and 12 of the PM sensor 1 is measured at the pre-execution DPF flow V2 (second flow condition). In the subsequent step 290, the measured resistance change rates ΔR1 and ΔR2 are compared. Also in the present embodiment, the difference value (ΔR1−ΔR2) between the resistance change rate ΔR1 and the resistance change rate ΔR2 is calculated, and the difference value (ΔR1−ΔR2) / (ΔV1−ΔV2) per unit flow rate is set to a predetermined value. Abnormality judgment is performed depending on whether or not.

  If the determination in step 290 is affirmative, it is determined that there is some abnormality in the diesel particulate filter DPF, and for example, a warning lamp is lit to notify the driver of the abnormality. When a negative determination is made in step 290, it is determined that the diesel particulate filter DPF is normal, and this process is temporarily terminated.

  As described above, in the present embodiment, not only the first flow rate condition and the second flow rate condition (change flow rate difference ΔV), which are different from each other in the exhaust flow rate upstream of the diesel particulate filter DPF, are set, but the predetermined maximum flow rate is set. When the waiting time timeMax is exceeded, the flow rate is forcibly increased from the first flow rate condition by the change flow rate difference ΔV to obtain the second flow rate condition. Thereby, even when the flow rate change is small in the steady operation state, the output change under the two flow rate conditions can be detected, and the abnormality of the diesel particulate filter DPF can be detected easily and reliably.

  Next, the determination means of the abnormality detection unit in the third embodiment of the present invention will be described based on the flowchart of FIG. FIG. 9 is an output detection example of the PM sensor 1 at the time of abnormality diagnosis based on the present embodiment. In the first and second embodiments, the abnormality diagnosis is defined by the exhaust gas flow rate upstream of the diesel particulate filter DPF. However, in this embodiment, the abnormality diagnosis is defined by the pressure, and the first pressure condition P1 is established at the start of the abnormality diagnosis. After the determination, the degree of pressure increase ΔP is determined, and the output value change of the PM sensor 1 is compared as the second pressure condition P2 in which the pressure is higher than the first pressure condition. Further, when determining the pressure increase ΔP, the pressure increase ΔP is corrected in consideration of the properties of the particulate matter PM depending on the operating state.

  Steps S300 to S320 in FIG. 8 are substantially the same as steps S100 to S120 in FIG. 1. First, in step S300, the electronic control unit ECU serving as the abnormality detection unit performs the cooling water temperature Tw, the exhaust gas temperature T1, the diesel engine E. Various data such as the rotational speed NE of / G and the fuel injection amount Q are taken in. In addition, a pre-DPF pressure P0 (execution) is calculated from a pressure sensor installed upstream of the diesel particulate filter DPF.

  In step S310, the pressure upstream of the diesel particulate filter DPF is set to the first pressure condition. Here, the pre-execution DPF pressure P0 taken in step S300 is set as the pre-detection DPF pressure P1 that is the first pressure condition (pre-detection DPF pressure P1 = pre-execution DPF pressure P0). In step S320, the resistance change rate ΔR1 (first output value change) between the detection electrodes 11 and 12 of the PM sensor 1 at the pre-detection DPF pressure P1 (first pressure condition) is measured and stored in the memory.

  In step S330, the degree of pressure increase ΔP for setting the second pressure condition is determined. Although it is possible to wait until the pressure reaches a predetermined change pressure difference as in the first and second embodiments, in this embodiment, the pressure is forcibly increased to the second pressure condition without waiting. It is an example to change. The method of determining the pressure increase ΔP is the same as that for the flow rate, and as described above, the pressure increase ΔP is set according to the pre-detected DPF pressure P1 so that the target flow rate is increased by at least 20% or more, preferably 50% or more. To do. Further, in step S340, it is determined whether the temperature is a predetermined temperature or lower or a low load condition. If the determination is affirmative, the process proceeds to step S350 to correct the pressure increase ΔP. If a negative determination is made, the process proceeds to step S360.

  In steps S340 and S350, the amount of hydrocarbon (HC) contained in the particulate matter PM increases / decreases depending on the operating conditions. In particular, the amount of hydrocarbon (HC) increases immediately after starting the engine or during low load operation. This is because the particulate matter PM tends to adhere to the diesel particulate filter DPF. Under such operating conditions, even if an abnormality occurs in the diesel particulate filter DPF, it becomes difficult for the amount of the particulate matter PM to pass through. Therefore, the operating state is determined from the engine cooling water temperature and other data taken in step S300, and the pressure increase ΔP is set higher so that the abnormality diagnosis can be performed reliably.

  In step S360, the pressure upstream of the diesel particulate filter DPF is set to the second pressure condition. Here, the pressure upstream of the diesel particulate filter DPF is forcibly changed from the pre-detected DPF pressure P1, which is the first pressure condition, by the pressure increase ΔP determined in step S340 (or the pressure increase ΔP corrected in step S350). Let At this time, the pre-detection DPF pressure P2 that is the second pressure condition = pre-detection DPF pressure P1 + pressure increase ΔP.

Even when the pressure is forcibly changed, the intake throttle V _TH , the EGR valve V _EGR , and the turbocharger TRB can be used as the pressure adjusting means, similarly to the flow rate adjusting means described above. By adjusting at least one or a plurality of these, an operation for increasing the pressure is performed to increase the pressure corresponding to the degree of pressure increase ΔP. Preferably, the injection amount Q and the fresh air amount are constant, and the EGR amount is increased, and the pressure is preferably increased without changing the ratio of the fuel and oxygen amount.

  In step S370, the resistance change rate ΔR2 between the detection electrodes 11 and 12 of the PM sensor 1 is measured at the pre-detection DPF pressure P2 (second pressure condition). In the subsequent step 380, the measured resistance change rates ΔR1 and ΔR2 are compared. Also in the present embodiment, the difference value | ΔR2−ΔR1 | between the resistance change rate ΔR1 and the resistance change rate ΔR2 is calculated, and abnormality determination is performed based on whether or not a predetermined value is exceeded.

  As shown in FIG. 9, when the output of the PM sensor 1 increases the upstream pressure of the diesel particulate filter DPF with respect to the output change rate at the pre-detection DPF pressure P1 (first pressure condition) set according to the course, As a result, the output change rate increases. When the diesel particulate filter DPF has an abnormality such as breakage, the sensor output change during pressure increase is larger than that during normal operation. Therefore, the output change rate at the pre-detection DPF pressure P2 (second pressure condition) as the pressure increase degree ΔP. Can be easily determined by comparing the output change rate with the pre-detection DPF pressure P1 (first pressure condition).

  If the determination in step 380 is affirmative, it is determined that there is some abnormality in the diesel particulate filter DPF, and for example, a warning lamp is lit to notify the driver of the abnormality. When the determination at step 380 is negative, it is determined that the diesel particulate filter DPF is normal, and this process is temporarily terminated.

  As in this embodiment, by comparing the output changes in the first pressure condition and the second pressure condition (pressure increase ΔP) in which the exhaust pressure upstream of the diesel particulate filter DPF is different, the diesel particulate filter DPF Abnormalities can be detected easily and reliably. Further, by increasing the pressure to the second pressure condition without waiting from the first pressure condition, it is possible to quickly detect an abnormality.

  In the first and second embodiments, the flow rate is changed, and in the third embodiment, the pressure is changed. However, the first and second embodiments are limited to the flow rate and the pressure, respectively. Instead, the flowchart of each abnormality determination can be applied to any case where the flow rate or the pressure condition is changed.

  Further, the PM sensor used in the present invention is not limited to the configuration of the above-described embodiment, and the shape and arrangement of the pair of detection electrodes, the heater unit, the cover body, and other components can be changed as appropriate. Furthermore, the configuration of the particulate filter and the configuration of each part of the exhaust treatment system and the fuel injection system can be arbitrarily changed.

  The particulate filter abnormality detection device of the present invention is used for applications such as an on-board failure diagnosis device (OBD) that is required to be installed in a vehicle equipped with a diesel particulate filter, and prevents discharge of environmental pollutants. . In addition to the automobile diesel engine, it can be suitably used for any other engine having a different system configuration or a system having a particulate filter for collecting particulate matter contained in exhaust gas in the exhaust passage. it can.

AFM air flow meter (flow rate / pressure detection means)
TRB, turbocharger (flow rate / pressure control means)
TRB _C compressor TRB _T turbine V _TH throttle valve (flow rate / pressure control means)
V _EGR EGR valve (flow rate / pressure control means)
SP Differential Pressure Sensor DPF Diesel Particulate Filter (Particulate Filter)
ECU Electronic control unit (abnormality detection unit)
E / G diesel engine (internal combustion engine)
ECU Electronic control unit (abnormality detection unit)
1 PM sensor (exhaust particulate sensor)
DESCRIPTION OF SYMBOLS 10 PM detection element 100 Detection part 11, 12 Detection electrode 111, 121 Lead part 13 Insulating substrate (insulating base | substrate)
14 Insulating protective layer 2 Exhaust pipe (exhaust passage)
20 Tube wall 30 Heater electrode 31, 32 Lead part 300 Heater part 40 Cover body 410, 411 hole 50 housing 60 insulator

Claims (7)

An exhaust particulate sensor installed in the exhaust passage of the internal combustion engine downstream of the particulate filter that collects particulate matter in the exhaust gas and detects the amount of particulate matter in the exhaust gas;
A flow rate / pressure detection means for detecting a flow rate or pressure of exhaust gas in an exhaust passage upstream of the particulate filter;
An abnormality detection unit for detecting an abnormality of the particulate filter based on the detection results of the flow rate / pressure detection means and the discharged particulate sensor;
The discharged particulate sensor has a detection part in which a pair of detection electrodes are formed on the surface of an insulating substrate, and the electrical resistance value changes according to the amount of particulate matter adhering between the pair of detection electrodes. Yes,
The abnormality detection unit compares changes in the output value of the exhaust particulate sensor in two operating states with different flow rates or pressures of the exhaust gas, and when the difference value or the ratio value exceeds a predetermined value, the particulates A particulate filter abnormality detection apparatus comprising: a determination unit that determines that the filter is abnormal.   The abnormality detection unit measures the change in the output value of the exhaust particulate sensor for a predetermined period using the flow rate or pressure of the exhaust gas in the operation state at the start of abnormality detection as the first flow rate / pressure condition, The second flow rate / pressure condition is set such that the difference from the first flow rate / pressure condition is a preset flow rate or pressure, and the output value of the discharged particulate sensor in a predetermined period at the second flow rate / pressure condition. 2. The particulate filter abnormality detection device according to claim 1, wherein the change is measured.   The abnormality detection unit measures the first output value change in the predetermined period of the discharged particulate sensor under the first flow rate / pressure condition, and then the detection result of the flow rate / pressure detection means is the second flow rate. / Wait until the pressure condition is satisfied, and when the second flow rate / pressure condition is satisfied, the second output value change in the predetermined period of the discharged particulate sensor is measured, and the first and second output values are measured. The particulate filter abnormality detection device according to claim 2, wherein abnormality is determined based on the change. A flow rate / pressure adjusting means for adjusting the flow rate or pressure of the exhaust gas in the exhaust passage upstream of the particulate filter;
The abnormality detection unit monitors a detection result of the flow rate / pressure detection unit after measuring a first output value change in the discharge particulate sensor for a predetermined period under the first flow rate / pressure condition, When the second flow rate / pressure condition is not satisfied, the flow rate / pressure adjustment means is used to forcibly adjust the second flow rate / pressure condition, and the discharge particulate matter sensor has a first period in a predetermined period. 3. The particulate filter abnormality detection device according to claim 2, wherein a change in the output value of 2 is measured, and abnormality is determined based on the first and second output value changes.   5. The abnormality detection unit according to claim 1, wherein a difference between the flow rate or pressure under the first flow rate / pressure condition and the flow rate or pressure under the second flow rate / pressure condition is set to a predetermined value set in advance. The abnormality detection apparatus of the particulate filter of Claim 1.   The abnormality detection unit sets a difference between a flow rate or pressure under the first flow rate / pressure condition and a flow rate or pressure under the second flow rate / pressure condition according to an operating state. The abnormality detection apparatus of the particulate filter of Claim 1.   The exhaust particulate sensor includes a pair of comb-like detection electrodes and a lead portion formed on a surface of a tip portion of the insulating base located in the exhaust passage to form the detection portion, and the tip of the insulating base The particulate filter abnormality detection device according to any one of claims 1 to 6, wherein a heater electrode and a lead portion are formed on a back surface, and the detection portion is heated to a predetermined temperature.

Images