Patent Publication Number: US-2017370317-A1

Title: Abnormality diagnosis device for pm sensor

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is based on Japanese Patent Application No. 2015-8401 filed on Jan. 20, 2015, the disclosure of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to an abnormality diagnosis device for a PM sensor that detects a particulate matter (PM) in exhaust gas of an internal combustion engine. 
     BACKGROUND ART 
     In the internal combustion engine mounted to a vehicle, it is expected that increment in demand of a direct injection gasoline engine in accordance with tightening a fuel regulation. However, in the direct injection gasoline engine, an exhaust amount of the particulate matter (PM) is larger than that of the port injection gasoline engine. As a countermeasure, a configuration in which a filter that collects the PM exhausted from the engine is arranged in an exhaust passage in the engine has been known. 
     In such a system including the filter for collecting the PM, a configuration in which a PM sensor that detects an amount of the PM in the exhaust gas is arranged downstream of the filter for collecting the PM, and occurrence of failure of the filter is determined based on the amount of the PM detected by the PM sensor has been known. 
     Further, as a technique of an abnormality diagnosis of the PM sensor, a configuration disclosed in, for example, Patent Literature 1 (JP 2012-013058 A) is known. In a system in which the PM sensor is arranged downstream of the filter for collecting the PM, it is determined by the technique of an abnormality diagnosis of the PM sensor that the failure of the PM sensor is occurred when an output value of the PM sensor is always “0” while a recovery control to burn and eliminate the PM collected by the filter is suspending. 
     Further, in a conventional filter for collecting the PM, a configuration in which an inlet side of a part of cells arranged in the filter is blocked and an outlet side of the remaining cells (namely, cells with inlet side opened) is blocked is known. 
     In the conventional filter described above, since a collection rate of the PM is kept at substantially 100% (see  FIG. 5 ) and the PM hardly flows out from the filter after a PM accumulation amount is increased, the output of the PM sensor is kept at around “0” (see  FIG. 6 ) even if the PM sensor downstream of the filter is normal. Thus, in a system in which the PM sensor is arranged downstream of the conventional filter, it is difficult to determine whether the output of the PM sensor is normal, and therefore it is difficult to detect output abnormality of the PM sensor. 
     PRIOR ART LITERATURES 
     Patent Literature 
     Patent Literature 1: JP 2012-013058 A 
     SUMMARY OF INVENTION 
     It is an object of the present disclosure to provide an abnormality diagnosis device for a PM sensor capable of detecting output abnormality of the PM sensor easily. 
     According to one aspect of the present disclosure, an abnormality diagnosis device for a PM sensor includes: a one-side blocked filter that collects a particulate matter (hereinafter, referred to as “PM”) in exhaust gas of an internal combustion engine, the filter having a structure in which an inlet side of a part of cells arranged in the filter is blocked and an outlet side of at least of one cell among the remaining cells is opened, or a structure in which the outlet side of a part of the cells is blocked and the inlet side of at least one cell among the remaining cells is opened; a PM sensor that detects an amount of the PM in the exhaust gas passed through the one-side blocked filter; and an abnormality diagnosis part that executes a sensor abnormality diagnosis that determines occurrence of output abnormality of the PM sensor based on output of the PM sensor. 
     In the one-side blocked filter, since a PM collection rate is kept to have a lower collection rate (collection rate lower than 100%) than that of a conventional filter (see  FIG. 5 ) and the PM flows out from the one-side blocked filter, when the PM sensor downstream of the one-side blocked filter is normal, the output of the PM sensor indicates a value larger than “0” (a value corresponding to the amount of the PM flowing out from the one-side blocked filter) (see  FIG. 6 ). Accordingly, in the system in which the PM sensor is arranged downstream of the one-side blocked filter, it is possible to determine the occurrence of the output abnormality of the PM sensor by monitoring the output of the PM sensor, and therefore the output abnormality of the PM sensor can be detected easily. 
     In this case, it is preferable that an outflow PM amount estimation part that estimates the amount of the PM flowing out from the one-side blocked filter (hereinafter, referred to as “filter-outflow PM amount”) based on a working condition of the internal combustion engine and the PM collection rate of the one-side blocked filter is arranged and the abnormality diagnosis part executes the sensor abnormality diagnosis by comparing an amount of the PM detected based on the output of the PM sensor (hereinafter, referred to as “sensor-detection PM amount”) with the filter-outflow PM amount estimated by the outflow PM amount estimation part. 
     When the output of the PM sensor is normal, the sensor-detection PM amount and the filter-outflow PM amount are roughly matched with each other. Accordingly, by comparing the sensor-detection PM amount with the filter-outflow PM amount, the occurrence of the output abnormality (abnormality of the output value) of the PM sensor can be precisely determined. 
     Further, it is preferable that a discharging PM amount estimation part that estimates an amount of the PM discharged from the internal combustion engine (hereinafter, referred to as “internal combustion engine discharging PM amount”) based on a working condition of the internal combustion engine is arranged and the abnormality diagnosis part executes the sensor abnormality diagnosis by comparing a change rate of the output of the PM sensor with a change rate of the internal combustion engine discharging PM amount estimated by the discharging PM amount estimation part. 
     As the amount of the PM discharged from the internal combustion engine is changed, the amount of the PM flowing out from the one-side blocked filter is changed, and the output of the PM sensor is changed, and therefore when the output of the PM sensor is normal, the change rate of the output of the PM sensor and the change rate of the internal combustion engine discharging PM amount are roughly matched with each other. Accordingly, by comparing the change rate of the output of the PM sensor with the change rate of the internal combustion engine discharging PM amount, the output abnormality (linearity abnormality of the output) of the PM sensor can be precisely determined. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The above and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description made with reference to the accompanying drawings. 
         FIG. 1  is a diagram illustrating a schematic configuration of an engine control system according to one embodiment of the present disclosure. 
         FIG. 2  is a cross-sectional view of a one-side blocked filter along an exhaust gas flow direction. 
         FIG. 3  is a cross-sectional view of an inlet side of the one-side blocked filter along a direction orthogonal to the exhaust gas flow direction. 
         FIG. 4  is a cross-sectional view of an outlet side of the one-side blocked filter along the direction orthogonal to the exhaust gas flow direction. 
         FIG. 5  is a diagram illustrating a relationship between a PM accumulation amount and a PM collection rate. 
         FIG. 6  is a time chart illustrating behavior of an output of a PM sensor. 
         FIG. 7  is a diagram illustrating an estimation method of an engine discharging PM amount. 
         FIG. 8  is a diagram illustrating a first sensor abnormality diagnosis. 
         FIG. 9  is a diagram illustrating a second sensor abnormality diagnosis. 
         FIG. 10  is a flowchart illustrating processing of a first sensor abnormality diagnosis routine. 
         FIG. 11  is a flowchart illustrating processing of a second sensor abnormality diagnosis routine. 
     
    
    
     EMBODIMENT FOR CARRYING OUT INVENTION 
     Hereinafter, one embodiment that embodies a configuration carrying out the present disclosure is described. 
     At first, a schematic configuration of an engine control system is described with reference to  FIG. 1 . 
     An engine  11  as a direct injection internal combustion engine is formed as a direct injection gasoline engine that directly injects gasoline as fuel into a cylinder. An air cleaner  13  is arranged at the most upstream part of an inlet pipe  12  of the engine  11 , and an air flow meter  14  that detects an intake air amount is arranged at a downstream side of the air cleaner  13 . A throttle valve  16  having an opening to be adjusted by a motor  15 , and a throttle opening sensor  17  that detects the opening (throttle opening degree) of the throttle valve  16  are arranged downstream of the air flow meter  14 . 
     Further, a serge tank  18  is arranged downstream of the throttle valve  16 , and an inlet pipe pressure sensor  19  that detects an inlet pipe pressure is arranged in the serge tank  18 . Further, an inlet manifold  20  that introduces air into each cylinder of the engine  11  is arranged in the serge tank  18 . A fuel injection valve  21  that directly injects fuel (gasoline) into each cylinder is mounted to each cylinder of the engine  11 . Further, an ignition plug  22  is mounted to a cylinder head of the engine  11  so as to correspond to each cylinder, and air-fuel mixture in each cylinder is ignited by spark discharge generated by the ignition plug  22  of each cylinder. 
     Further, an exhaust gas sensor  24  (air/fuel ratio sensor, oxygen sensor or the like) that detects an air fuel ratio or rich/lean burn of the exhaust gas is arranged in an exhaust pipe  23  of the engine  11 , and a catalyst  25  such as three way catalyst that purifies CO, HC, NO x , or the like in the exhaust gas is arranged downstream of the exhaust gas sensor  24 . 
     Further, a one-side blocked filter  31  that collects a particulate matter (PM) in the exhaust gas of the engine  11  is arranged downstream of the catalyst  25  in the exhaust pipe  23  of the engine  11 . The catalyst  25  and the one-side blocked filter  31  may be housed in a single case, or alternatively may be housed in respective cases. Further, a PM sensor  32  that detects an amount of the PM in the exhaust gas passed through the one-side blocked filter  31  is arranged downstream of the one-side blocked filter  31 . 
     Further, a coolant temperature sensor  26  that detects a temperature of coolant, and a knock sensor  27  that detects a knocking are mounted to a cylinder block of the engine  11 . Further, a crank angle sensor  29  that outputs a pulse signal at a predetermined crank angle of a crank shaft  28  is mounted to an outer peripheral part of the crank shaft  28 , and a crank angle and an engine speed are detected based on the output signal of the crank angle sensor  29 . 
     Outputs of these various sensors are input to an electronic control unit  30  (hereinafter, referred to as “ECU”). The ECU  30  is mainly provided with a microcomputer. The ECU  30  controls a fuel injection amount, an ignition timing, a throttle opening (inlet air amount) and the like in accordance with a driving state of the engine by executing various programs for controlling the engine stored in an embedded ROM (storage medium). 
     As shown in  FIG. 2  to  FIG. 4 , the one-side blocked filter  31  has a structure in which cells  33  extended in an exhaust gas flow direction (direction from an inlet side toward an outlet side) are partitioned by a porous partition wall  34  (partition wall) and an end part of the inlet side of a part of cells  33  is blocked by a blocking member  35  and the outlet side of all of the cells  33  is opened. In the present embodiment, a cell  33 A in which the inlet side is blocked and the outlet side is opened (hereinafter, referred to as “inlet-side blocked cell”) and a cell  33 B in which both of the inlet side and the outlet side are opened (hereinafter, referred to as “both-sides open cell”) are arranged alternately so as to be adjacent to each other. 
     In the one-side blocked filter  31 , when the exhaust gas flows into the cell  33 B through the inlet side of the both-sides open cell  33 B, the pressure inside the both-sides open cell  33 B is increased and the pressure inside the inlet-side blocked cell  33 A becomes relatively low compared to the pressure inside the both-sides open cell  33 B. Thus, a part of the exhaust gas from the both-sides open cell  33 B passes through the porous partition wall  34  and flows into the inlet-side blocked cell  33 A to flow to an outside of the cell  33 A from the outlet side of the inlet-side blocked cell  33 A. At this time, the PM (for example, SOOT particle having a diameter of 20 nm to 100 nm) in the exhaust gas adheres inside a pore (inner surface of pore) or adheres to a wall surface of the partition wall  34  to be collected. Further, ash as a nonflammable substance (for example, ash content caused by oil of the engine  11 ) in the exhaust gas also adheres inside the pore or adheres to the wall surface of the partition wall  34  to be collected. 
     In a system including the one-side blocked filter  31  for collecting the PM, when a PM accumulation amount of the blocked filter  31  (an amount of the PM accumulated in the one-side blocked filter  31 ) becomes excessively large, the pressure loss of the exhaust becomes larger. Thus, the ECU  30  executes a recovery control in which the PM collected in the one-side blocked filter  31  is burned and eliminated so as to recover the one-side blocked filter  31  (to reduce the PM accumulation amount in the one-side blocked filter  31 ). As the recovery control, a fuel cut control to be executed when a predetermined fuel cut execution condition is satisfied (for example, during deceleration) may be adopted as an example. Further, when the PM accumulation amount in the one-side blocked filter  31  exceeds a predetermined upper limit, for example, a control in which the air fuel ratio is switched to a lean side or a control in which an exhaust temperature is increased is executed as the recovery control. 
     As shown in  FIG. 5 , in the one-side blocked filter  31 , after the PM is eliminated by means of the recovery control (after the PM accumulation amount is substantially equal to “0”), the PM is accumulated inside the pore of the partition wall  34  and thereafter the PM is accumulated on the wall surface of the partition wall  34 . In an accumulation region in the pore in which the PM is accumulated in the pore of the partition wall  34  (a region in which the PM accumulation amount is relatively small), the PM collection rate is once increased and then decreased in accordance with increment of the PM accumulation amount. After that, in an accumulation region of the wall surface in which the PM is accumulated on the wall surface of the partition wall  34 , the PM collection rate becomes substantially constant. 
     Further, the ECU  30  executes respective routines for sensor abnormality diagnoses shown in  FIG. 10  and  FIG. 11  described below so as to execute the sensor abnormality diagnosis that determines occurrence of output abnormality of the PM sensor  32  based on output of the PM sensor  32 . 
     In the one-side blocked filter  31 , the PM collection rate is kept to have a lower collection rate (collection rate less than 100%) than that of the conventional filter (see  FIG. 5 ), and the PM flows out from the one-side blocked filter  31 . Thus, when the PM sensor  32  downstream of the one-side blocked filter  31  is normal, the output of the PM sensor  32  indicates a value larger than “0” (a value corresponding to the amount of the PM flowing out from the one-side blocked filter  31 ) (see  FIG. 6 ). Accordingly, in the system in which the PM sensor  32  is arranged downstream of the one-side blocked filter  31 , it is possible to determine the occurrence of the output abnormality of the PM sensor  32  by monitoring the output of the PM sensor  32 , and therefore the output abnormality of the PM sensor  32  can be detected easily. 
     In the present embodiment, after the PM accumulation amount in the one-side blocked filter  31  exceeds a predetermined value “A” (the PM accumulation amount necessary for stabilizing the PM collection rate), a first sensor abnormality diagnosis is executed by the ECU  30  by executing a first sensor abnormality diagnosis routine shown in  FIG. 10  described below. In the first sensor abnormality diagnosis, the filter-outflow PM amount (an amount of the PM flowing out from the one-side blocked filter  31 ) is estimated based on the working condition of the engine  11  and the PM collection rate of the one-side blocked filter  31 , and then the occurrence of the output abnormality of the PM sensor  32  is determined by comparing the sensor-detection PM amount (an amount of the PM detected based on the output of the PM sensor  32 ) with the filter-outflow PM amount. 
     When the output of the PM sensor  32  is normal, the sensor-detection PM amount and the filter-outflow PM amount are roughly matched with each other. Accordingly, by comparing the sensor-detection PM amount with the filter-outflow PM amount, the occurrence of the output abnormality (abnormality of the output value) of the PM sensor  32  can be precisely determined. 
     Specifically, in the first sensor abnormality diagnosis, as shown in  FIG. 7 , based on an engine speed, an engine load (for example, inlet pipe pressure, inlet air amount, or the like), a coolant temperature, a working history or the like, an engine discharging PM amount PME (an amount of the PM discharged from the engine  11 ) is calculated by a map, a formula, or the like. The map, the formula, or the like of the engine discharging PM amount PME is made based on experimental data, design data, or the like in advance and stored in a ROM of the ECU  30 . 
     Further, based on the working condition of the engine  11 , the sensor-detection PM amount, or the like, the PM accumulation amount is calculated by the map, the formula, or the like, and then the PM collection rate is calculated by the map, the formula, or the like in accordance with the PM accumulation amount. Here, in a system having a differential pressure sensor that detects a difference (before and after differential pressure) between an upstream exhaust pressure and a downstream exhaust pressure of the one-side blocked filter  31 , the PM accumulation amount may be calculated by a map, a formula, or the like in accordance with output of the differential pressure sensor. The map, the formula, or the like of the PM accumulation amount and the PM collection rate is made by experimental data, design data, or the like in advance and stored in the ROM of the ECU  30 . 
     After that, by using the engine discharging PM amount PME and the PM collection rate, the filter-outflow PM amount PMF is calculated by the following formula. 
       Filter-outflow  PM  amount  PMF =Engine discharging  PM  amount  PME ×(1− PM  collection rate)
 
     In this way, after the filter-outflow PM amount PMF is estimated (calculated), based on whether an absolute value |PMS−PMF| of difference between the sensor-detection PM amount PMS and the filter-outflow PM amount PMF is equal to or less than a predetermined value α, it is determined whether the sensor-detection PM amount PMS is within a normal range (range of PMF±α). 
     As a result, as shown in (a) in  FIG. 8 , in a case in which the absolute value |PMS−PMF| of the difference between the sensor-detection PM amount PMS and the filter-outflow PM amount PMF is equal to or less than the predetermined value α, namely the sensor-detection PM amount PMS is within the normal range (range of PMF±α), it is determined that the PM sensor  32  is normal (output abnormality of the PM sensor  32  is not occurred). 
     Contrary to this, as shown in (b), (c) in  FIG. 8 , in a case in which the absolute value |PMS−PMF| of the difference between the sensor-detection PM amount PMS and the filter-outflow PM amount PMF exceeds the predetermined value α, namely the sensor-detection PM amount PMS is out of the normal range (range of PMF±α), it is determined that the output abnormality (the abnormality of the output value) of the PM sensor  32  is occurred. At this time, as shown in (b) in  FIG. 8 , in a case in which the sensor-detection PM amount PMS is smaller than a lower limit (PMF−α) of the normal range, it is determined that the output of the PM sensor  32  is excessively small and the output abnormality of the PM sensor  32  is occurred. On the other hand, as shown in (c) in  FIG. 8 , in a case in which the sensor-detection PM amount PMS is larger than an upper limit (PMF+α) of the normal range, it is determined that the output of the PM sensor  32  is excessively large and the output abnormality of the PM sensor  32  is occurred. 
     Further, in the present embodiment, after the PM accumulation amount in the one-side blocked filter  31  exceeds the predetermined value “A” (the PM accumulation amount necessary for stabilizing the PM collection rate), a second sensor abnormality diagnosis is executed by the ECU  30  by executing a second sensor abnormality diagnosis routine shown in  FIG. 11  described below. In the second sensor abnormality diagnosis, the engine discharging PM amount (an amount of the PM discharged from the engine  11 ) is estimated based on the working condition of the engine  11 , and then the occurrence of the output abnormality of the PM sensor  32  is determined by comparing a change rate (for example, increasing rate) of the output of the PM sensor  32  with a change rate (for example, increasing rate) of the engine discharging PM amount. 
     When the PM amount discharged from the engine  11  is changed, the amount of the PM flowing out from the one-side blocked filter  31  is changed and the output of the PM sensor  32  is changed, and therefore when the output of the PM sensor  32  is normal, the change rate of the output of the PM sensor  32  and the change rate of the engine discharging PM amount are roughly matched with each other. Accordingly, by comparing the change rate of the output of the PM sensor  32  with the change rate of the engine discharging PM amount, the occurrence of the output abnormality (linearity abnormality of the output) of the PM sensor  32  can be precisely determined. 
     Specifically, in the second sensor abnormality diagnosis, as shown in  FIG. 9 , before fuel injection timing of the engine  11  is compulsorily changed, output S 1  of the PM sensor  32  is read, and based on the working condition of the engine  11  (engine speed, engine load, coolant temperature, working history or the like), an engine discharging PM amount PME 1  is calculated by a map, a formula, or the like (see  FIG. 7 ). 
     And then, after the fuel injection timing of the engine  11  is compulsorily changed (advanced) and the amount of the PM discharged from the engine  11  is compulsorily changed (increased), output S 2  of the PM sensor  32  is read, and based on the working condition of the engine  11 , an engine discharging PM amount PME 2  is calculated by a map, a formula or the like. 
     After that, an increasing rate ΔS=S 2 /S 1  of the output of the PM sensor  32  is calculated and an increasing rate ΔPME=PME 2 /PME 1  of the engine discharging PM amount is calculated. Further, based on whether an absolute value |ΔS−ΔPME| of difference between the increasing rate ΔS of the output of the PM sensor  32  and the increasing rate ΔPME of the engine discharging PM amount is equal to or less than a predetermined value β, it is determined whether the increasing rate ΔS of the output of the PM sensor  32  is within a normal range (range of ΔPME±β). 
     As a result, in a case in which the absolute value |ΔS−ΔPME| of the difference between the increasing rate ΔS of the output of the PM sensor  32  and the increasing rate ΔPME of the engine discharging PM amount is equal to or less than the predetermined value β, namely the increasing rate ΔS of the output of the PM sensor  32  is within the normal range (range of ΔPME±β), it is determined that the PM sensor  32  is normal (the output abnormality of the PM sensor  32  is not occurred). 
     Contrary to this, in a case in which the absolute value |ΔS−ΔPME| of the difference between the increasing rate ΔS of the output of the PM sensor  32  and the increasing rate ΔPME of the engine discharging PM amount exceeds the predetermined value β, namely the increasing rate ΔS of the output of the PM sensor  32  is out of the normal range (range of ΔPME±β), it is determined that the output abnormality (linearity abnormality of the output) of the PM sensor  32  is occurred. At this time, in a case in which the increasing rate ΔS of the output of the PM sensor  32  is smaller than an lower limit (ΔPME−β) of the normal range, it is determined that the increasing rate ΔS of the output of the PM sensor  32  is excessively small and the output abnormality of the PM sensor  32  is occurred. On the other hand, in a case in which the increasing rate ΔS of the output of the PM sensor  32  is larger than an upper limit (ΔPME+β) of the normal range, it is determined that the increasing rate ΔS of the output of the PM sensor  32  is excessively large and the output abnormality of the PM sensor  32  is occurred. 
     The sensor abnormality diagnosis according to the present embodiment described above is executed by the ECU  30  in accordance with each routine for the sensor abnormality diagnosis shown in  FIG. 10  and  FIG. 11 . Hereinafter, processing in each routine is described. 
     The first sensor abnormality diagnosis routine shown in  FIG. 10  is repeated at a predetermined frequency during a period of power ON of the ECU  30 , and the first sensor abnormality diagnosis routine is served as an abnormality diagnosis part. 
     In Step  101 , it is determined whether the PM accumulation amount in the one-side blocked filter  31  exceeds the predetermined value “A” (see  FIG. 5 ). The predetermined value “A” corresponds to the PM accumulation amount necessary for stabilizing the PM collection rate of the one-side blocked filter  31 , and for example, the predetermined value “A” is set to a PM accumulation amount when the pore accumulation region is transited to the wall surface accumulation region or an amount slightly larger than the PM accumulation amount. 
     In Step  101 , in a case in which the PM accumulation amount does not exceed the predetermined value “A”, it is determined that the PM collection rate is not stable and this routine is ended without executing processing after Step  102  in the first sensor abnormality diagnosis. 
     On the other hand, in Step  101 , in a case in which the PM accumulation amount exceeds the predetermined value “A”, it is determined that the PM collection rate is stable and the processing after Step  102  in the first sensor abnormality diagnosis is executed in the following way. 
     In Step  102 , the amount of the PM detected based on the output of the PM sensor  32  is acquired as the sensor-detection PM amount. 
     After that, the processing proceeds to Step  103 , and based on the working condition of the engine  11  (engine speed, engine load, coolant temperature, working history, or the like), the engine discharging PM amount PME is calculated by the map, the formula, or the like, and then the filter-outflow PM amount PMF is calculated by the following formula by using the engine discharging PM amount PME and the PM collection rate. 
       Filter-outflow  PM  amount  PMF =Engine discharging  PM  amount  PME ×(1− PM  collection rate)
 
     The processing of Step  103  is served as an outflow PM amount estimation part. 
     After that, the processing proceeds to Step  104 , and based on whether the absolute value |PMS−PMF| of the difference between the sensor-detection PM amount PMS and the filter-outflow PM amount PMF is equal to or less than the predetermined value α, it is determined whether the sensor-detection PM amount PMS is within the normal range (range of PMF±α). 
     In Step  104 , in a case in which the absolute value |PMS−PMF| of the difference is equal to or less than the predetermined value α, namely the sensor-detection PM amount PMS is within the normal range (range of PMF±α), the processing proceeds to Step  105 , and it is determined that the PM sensor  32  is normal (the output abnormality of the PM sensor  32  is not occurred). 
     Contrary to this, in Step  104 , in a case in which the absolute value |PMS−PMF| of the difference exceeds the predetermined value α, namely the sensor-detection PM amount PMS is out of the normal range (range of PMF±α), the processing proceeds to Step  106 , and it is determined that the output abnormality (the abnormality of the output value) of the PM sensor  32  is occurred. At this time, in a case in which the sensor-detection PM amount PMS is smaller than the lower limit (PMF−α) of the normal range, it is determined that the output of the PM sensor  32  is excessively small and the output abnormality of the PM sensor  32  is occurred. On the other hand, in a case in which the sensor-detection PM amount PMS is larger than the upper limit (PMF+α) of the normal range, it is determined that the output of the PM sensor  32  is excessively large and the output abnormality of the PM sensor  32  is occurred. 
     Further, the second sensor abnormality diagnosis routine shown in  FIG. 11  is repeated at a predetermined frequency during the period of the power ON of the ECU  30 , and the second sensor abnormality diagnosis routine is served as an abnormality diagnosis part. 
     When this routine is started, at first in Step  201 , it is determined whether a predetermined execution condition is satisfied based on, for example, whether an engine working state is in a normal state or the like. 
     In Step  201 , in a case in which the execution condition is not satisfied, this routine is ended without executing processing after Step  202 . 
     On the other hand, in Step  201 , in a case in which the execution condition is satisfied, the processing proceeds to Step  202 , and it is determined whether the PM accumulation amount in the one-side blocked filter  31  exceeds the predetermined value “A” (see  FIG. 5 ). 
     In Step  202 , in a case in which the PM accumulation amount does not exceed the predetermined value “A”, it is determined that the PM collection rate is not stable and this routine is ended without executing processing after Step  203  in the second sensor abnormality diagnosis. 
     On the other hand, in Step  202 , in a case in which the PM accumulation amount exceeds the predetermined value “A”, it is determined that the PM collection rate is stable and the processing after Step  203  in the second sensor abnormality diagnosis is executed in the following way. 
     At first, in Step  203 , after output S 1  of the PM sensor  32  is acquired, the processing proceeds to Step  204 , and based on the working condition of the engine  11  (engine speed, engine load, coolant temperature, working history, or the like), the engine discharging PM amount PME 1  is calculated by a map, a formula, or the like. The processing of Step  204  is served as a discharging PM amount estimation part. 
     After that, the processing proceeds to Step  205 , and the fuel injection timing of the engine  11  is compulsorily advanced, and thereby the amount of the PM discharged from the engine  11  is compulsorily increased. After that, the processing proceeds to Step  206 , and after output S 2  of the PM sensor  32  is acquired, the processing proceeds to Step  207 , and based on the working condition of the engine  11 , an engine discharging PM amount PME 2  is calculated by a map, a formula, or the like. The processing of Step  207  is also served as the discharging PM amount estimation part. 
     After that, the processing proceeds to Step  208 , and after the increasing rate ΔS=S 2 /S 1  of the output of the PM sensor  32  is calculated, the processing proceeds to Step  209 , and the increasing rate ΔPME=PME 2 /PME 1  of the engine discharging PM amount is calculated. 
     After that, the processing proceeds to Step  210 , and based on whether the absolute value |ΔS−ΔPME| of the difference between the increasing rate ΔS of the output of the PM sensor  32  and the increasing rate ΔPME of the engine discharging PM amount is equal to or less than the predetermined value β, it is determined whether the increasing rate ΔS of the output of the PM sensor  32  is within the normal range (range of ΔPME±β). 
     In Step  210 , in a case in which the absolute value |ΔS−ΔPME| of the difference is equal to or less than the predetermined value β, namely the increasing rate ΔS of the output of the PM sensor  32  is within the normal range (range of ΔPME±β), the processing proceeds to Step  211 , and it is determined that the PM sensor  32  is normal (the output abnormality of the PM sensor  32  is not occurred). 
     Contrary to this, in Step  210 , in a case in which the absolute value |ΔS−ΔPME| of the difference exceeds the predetermined value β, namely the increasing rate ΔS of the output of the PM sensor  32  is out of the normal range (range of ΔPME±β), the processing proceeds to Step  212 , and it is determined that the output abnormality (the linearity abnormality of the output) of the PM sensor  32  is occurred. At this time, in a case in which the increasing rate ΔS of the output of the PM sensor  32  is less than the lower limit (ΔPME−β) of the normal range, it is determined that the increasing rate ΔS of the output of the PM sensor  32  is excessively small and the output abnormality of the PM sensor  32  is occurred. On the other hand, in a case in which the increasing rate ΔS of the output of the PM sensor  32  is more than the upper limit (ΔPME+β) of the normal range, it is determined that the increasing rate ΔS of the output of the PM sensor  32  is excessively large and the output abnormality of the PM sensor  32  is occurred. 
     In the present embodiment described above, by focusing on that the value of the output of the PM sensor  32  downstream of the one-side blocked filter  31  is larger than “0” (the value corresponding to the amount of the PM flowing out from the one-side blocked filter  31 ), the first and the second sensor abnormality diagnoses that determine the occurrence of the output abnormality of the PM sensor  32  based on the output of the PM sensor  32  are executed. With this, the occurrence of the output abnormality of the PM sensor  32  can be determined and the output abnormality of the PM sensor  32  can be detected easily. 
     In the first sensor abnormality diagnosis, the filter-outflow PM amount PMF is estimated based on the working condition of the engine  11  and the PM collection rate of the one-side blocked filter  31 , and by comparing the sensor-detection PM amount PMS with the filter-outflow PM amount PMF, the occurrence of the output abnormality of the PM sensor  32  is determined. With this, the occurrence of the output abnormality (the abnormality of the output value) of the PM sensor  32  can be precisely determined. 
     In the second sensor abnormality diagnosis, the engine discharging PM amount is estimated based on the working condition of the engine  11 , and by comparing the increasing rate of the output of the PM sensor  32  with the increasing rate of the engine discharging PM amount, the occurrence of the output abnormality of the PM sensor  32  is determined. With this, the occurrence of the output abnormality (the linearity abnormality of the output) of the PM sensor  32  can be precisely determined. 
     Further, in the present embodiment, the fuel injection timing of the engine  11  is compulsorily advanced and then the change rate of the output of the PM sensor  32  and the change rate of the engine discharging PM amount are calculated. With such a configuration, when the fuel injection timing of the engine  11  is compulsorily advanced and the amount of the PM discharged from the engine  11  is compulsorily changed, the change rate of the output of the PM sensor  32  and the change rate of the engine discharging PM amount can be calculated. With this, the second sensor abnormality diagnosis can be executed by calculating the change rate of the output of the PM sensor  32  and the change rate of the engine discharging PM amount in a short period of time. 
     Further, in the present embodiment, the first sensor abnormality diagnosis or the second sensor abnormality diagnosis is executed after the PM accumulation amount in the one-side blocked filter  31  exceeds the predetermined value “A”. With such a configuration, since the sensor abnormality diagnosis can be executed in a state in which the PM collection rate is stable after the PM accumulation amount in the one-side blocked filter  31  exceeds the predetermined value “A”, the sensor abnormality diagnosis can be executed in a state in which the change of the output of the PM sensor  32  caused by the change of the PM collection rate is substantially eliminated, and therefore accuracy in the abnormality diagnosis of the PM sensor  32  can be improved. 
     Further, in the embodiment described above, in the first sensor abnormality diagnosis, based on whether the absolute value of the difference between the sensor-detection PM amount and the filter-outflow PM amount is equal to or less than the predetermined value, it is determined whether the sensor-detection PM amount is within the normal range. However, it is not limited to this, and for example, based on whether a ratio of the sensor-detection PM amount and the filter-outflow PM amount is within a predetermined range, it may be determined whether the sensor-detection PM amount is within the normal range. 
     Further, in the embodiment described above, in the second sensor abnormality diagnosis, based on whether the absolute value of the difference between the increasing rate of the output of the PM sensor  32  and the increasing rate of the engine discharging PM amount is equal to or less than the predetermined value, it is determined whether the increasing rate of the output of the PM sensor  32  is within the normal range. However, it is not limited to this, and for example, based on whether a ratio of the increasing rate of the output of the PM sensor  32  and the increasing rate of the engine discharging PM amount is within a predetermined range, it may be determined that the increasing rate of the output of the PM sensor  32  is within the normal range. 
     Further, in the embodiment described above, in the second sensor abnormality diagnosis, the increasing rate of the output of the PM sensor  32  and the increasing rate of the engine discharging PM amount are compared with each other, however it is not limited to this, and a decreasing rate of the output of the PM sensor  32  and a decreasing rate of the engine discharging PM amount may be compared with each other. 
     Further, in the embodiment described above, in the second sensor abnormality diagnosis, the fuel injection timing is compulsorily changed and then the change rate of the output of the PM sensor  32  and the change rate of the engine discharging PM amount are calculated. However, it is not limited to this, and for example, a number of divided injections of fuel or fuel pressure may be compulsorily changed, or alternatively two or three elements among the fuel injection timing and the number of the divided injections of fuel and the fuel pressure may be compulsorily changed. 
     Further, in the second sensor abnormality diagnosis, the change rate of the output of the PM sensor  32  and the change rate of the engine discharging PM amount may be calculated when a working state of the engine is changed according to request or the like of a driver (when the amount of the PM discharged from the engine  11  is changed) instead of compulsorily changing the fuel injection timing, the number of the divided injections of fuel, or the fuel pressure. 
     Further, in the embodiment described above, the first sensor abnormality diagnosis or the second sensor abnormality diagnosis is executed after the PM accumulation amount in the one-side blocked filter  31  exceeds the predetermined value “A”, however it is not limited to this, and the first sensor abnormality diagnosis or the second sensor abnormality diagnosis may be executed before the PM accumulation amount exceeds the predetermined value “A”. 
     Further, in the embodiment described above, the system including the one-side blocked filter having the structure in which the inlet side of a part of the cells is blocked and the outlet side of all of the cells is opened is adopted in the present disclosure, however it is not limited to this. A system including a one-side blocked filter having a structure in which the inlet side of a part of the cells is blocked and the outlet side of a part of the remaining cells (cells with the inlet side opened) is blocked may be adopted in the present disclosure. Alternatively, a system including a one-side blocked filter having a structure in which the outlet side of a part of the cells is blocked and the inlet side of all of the cells is opened, or a one-side blocked filter having a structure in which the outlet side of a part of the cells is blocked and the inlet side of a part of the remaining cells (cells with the outlet side opened) is blocked may be adopted in the present disclosure. In other words, a system including a one-side blocked filter having a structure in which both of the inlet side of a part of the cells and the outlet side of a part of the cells are opened can be adopted in the present disclosure. 
     Further, in the embodiment described above, the system including the direct injection gasoline engine is adopted in the present disclosure, however it is not limited to this. A system including a diesel engine or an intake port injection gasoline engine may be adopted in the present disclosure as long as the system has the one-side blocked filter. 
     The present disclosure is described based on the embodiment, however the present disclosure is not limited to the embodiment or the structure. The present disclosure includes various modified embodiments or modifications in the equivalent range. In addition, while the various combinations and configurations, other combinations and configurations, including more, less or only a single element, are also within the scope of the present disclosure.