JP5365550B2 - Particulate filter failure diagnosis device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a failure diagnostic device for a particular filter, which performs failure diagnosis of the particulate filter at higher accuracy. <P>SOLUTION: The failure diagnostic device compares a value detected by a PM sensor provided on the downstream side of the particulate filter with an estimated sensor PM accumulation amount to discriminate the presence or absence of a failure in the particulate filter (S112-S115). At this time, it executes the discrimination of the presence or absence of the failure in the particulate filter on condition that the ratio of a significant estimated sensor PM accumulation amount which is estimated in accordance with an integrated value for only flow-out PM amounts integrated when there is a great difference between the flow-out PM amounts in the normal state of the particulate filter and during a failure thereof, to the estimated sensor PM accumulation amount is a reference ratio or higher (S111). <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a failure diagnosis device for a particulate filter that is provided in an exhaust passage of an internal combustion engine and collects particulate matter in the exhaust gas.

2. Description of the Related Art Conventionally, there has been known a technique in which a particulate filter that collects particulate matter (hereinafter referred to as PM) in exhaust gas is provided as an exhaust purification device in an exhaust passage of an internal combustion engine. In the particulate filter, failures such as melting and breakage may occur. When such a particulate filter failure occurs, the amount of PM that is not collected by the particulate filter and flows out into the exhaust passage on the downstream side (hereinafter referred to as PM flowing out from the particulate filter per unit time). The amount is referred to as the outflow PM amount).

  Patent Document 1 discloses a technique in which a particulate amount detection sensor that detects the amount of PM in exhaust gas is provided in an exhaust passage on the downstream side of a particulate filter. Further, in this Patent Document 1, in the condition where the particulate filter failure is determined based on the PM amount detected by the particulate amount detection sensor, and the collection efficiency of the particulate filter is lower than a predetermined value. A technique for prohibiting particulate filter failure determination is disclosed.

  Patent Document 2 discloses a technique in which a PM sensor that detects the amount of PM deposited on an electrode is provided in an exhaust passage on the upstream side of a particulate filter. Patent Document 2 discloses a technique for heating and heating a PM sensor to burn and remove the deposited PM.

JP 2007-315275 A JP 2008-190502 A JP 2005-325812 A JP 2008-190470 A

  As described above, when the particulate filter malfunctions, the outflow PM amount increases. Therefore, the failure diagnosis of the particulate filter can be performed based on the outflow PM amount. However, depending on the operating state of the internal combustion engine, such as when the engine load of the internal combustion engine is low, the difference in the amount of outflow PM between when the particulate filter is normal and when it fails may be very small. If a failure diagnosis of the particulate filter is performed based on the outflow PM amount in such a case, there is a risk of performing an erroneous diagnosis.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a technique capable of performing failure diagnosis of a particulate filter with higher accuracy.

In the present invention, a PM sensor that detects the amount of PM deposited on the exhaust passage is provided downstream of the particulate filter. Further, the PM accumulation amount in the PM sensor is estimated based on the integrated value obtained by integrating the estimated value of the outflow PM amount (hereinafter, P estimated in this way).
The PM accumulation amount in the M sensor is referred to as an estimated sensor PM accumulation amount). And the presence or absence of the failure of a particulate filter is discriminate | determined by comparing the detection value of PM sensor, and the estimated sensor PM deposit amount. At this time, the PM accumulation amount in the PM sensor is further estimated based on an integrated value obtained by integrating only the outflow PM amount when the difference between the outflow PM amount between the normal time and the failure of the particulate filter is large (hereinafter, referred to as the PM sensor). The PM accumulation amount in the PM sensor thus estimated is referred to as a significant estimation sensor PM accumulation amount). Then, it is determined that the ratio of the significant estimated sensor PM accumulated amount to the estimated sensor PM accumulated amount is equal to or larger than the reference ratio, or that the difference between the estimated sensor PM accumulated amount and the significant estimated sensor PM accumulated amount is equal to or smaller than the reference amount. This is an execution condition for determining whether there is a failure in the curate filter.

More specifically, the particulate filter failure diagnosis apparatus according to the first invention is:
A particulate filter failure diagnosis device that is provided in an exhaust passage of an internal combustion engine and collects particulate matter in exhaust gas,
A PM sensor that is provided in the exhaust passage downstream of the particulate filter and detects the amount of particulate matter deposited on itself;
An outflow PM amount estimating means for estimating an outflow PM amount that is an outflow amount of particulate matter from the particulate filter when the particulate filter is assumed to be in a predetermined state;
Sensor PM accumulation amount estimation means for integrating the outflow PM amount estimated by the outflow PM amount estimation means, and estimating the amount of particulate matter deposited on the PM sensor based on the accumulated value;
And a determining unit that determines whether or not the particulate filter has failed by comparing a detection value of the PM sensor with an estimated sensor PM accumulation amount that is an estimated value of the sensor PM accumulation amount estimating unit. In the filter fault diagnosis device,
Accumulating the outflow PM amount estimated by the outflow PM amount estimation means when a significant condition is established that the difference between the outflow PM amount between the normal time and the failure of the particulate filter is greater than or equal to a predetermined amount, and the integrated value Further comprising a significant sensor PM deposition amount estimation means for estimating the amount of particulate matter deposited on the PM sensor based on
The ratio of the significant estimated sensor PM accumulated amount, which is the estimated value of the significant sensor PM accumulated amount estimating means to the estimated sensor PM accumulated amount, is greater than or equal to a reference ratio, and the presence / absence of failure of the particulate filter by the determining means. It is characterized by making it an execution condition of discrimination.

  When the significant condition is satisfied, there is a large difference in the outflow PM amount between when the particulate filter is normal and when it is out of order. Therefore, the difference in the significant estimated sensor PM accumulation amount becomes large between when the particulate filter is normal and when it is out of order.

  Note that the predetermined amount, which is a threshold value for establishing a significant condition, is a threshold value with which the presence / absence of a failure of the particulate filter can be determined with high accuracy. In the present invention, for example, when the outflow PM amount estimated by the outflow PM amount estimation means or the engine load of the internal combustion engine is equal to or greater than a predetermined threshold value, it can be determined that the significant condition is satisfied.

  In the present invention, when the ratio of the significant estimated sensor PM accumulation amount to the estimated sensor PM accumulation amount is high, the presence / absence of the particulate filter failure is determined by the determination means. Thereby, the failure diagnosis of the particulate filter can be performed with higher accuracy.

The particulate filter failure diagnosis apparatus according to the second invention is:
A particulate filter failure diagnosis device that is provided in an exhaust passage of an internal combustion engine and collects particulate matter in exhaust gas,
A PM sensor that is provided in the exhaust passage downstream of the particulate filter and detects the amount of particulate matter deposited on itself;
An outflow PM amount estimating means for estimating an outflow PM amount that is an outflow amount of particulate matter from the particulate filter when the particulate filter is assumed to be in a predetermined state;
Sensor PM accumulation amount estimation means for integrating the outflow PM amount estimated by the outflow PM amount estimation means, and estimating the amount of particulate matter deposited on the PM sensor based on the accumulated value;
And a determining unit that determines whether or not the particulate filter has failed by comparing a detection value of the PM sensor with an estimated sensor PM accumulation amount that is an estimated value of the sensor PM accumulation amount estimating unit. In the filter fault diagnosis device,
Accumulating the outflow PM amount estimated by the outflow PM amount estimation means when a significant condition is established that the difference between the outflow PM amount between the normal time and the failure of the particulate filter is greater than or equal to a predetermined amount, and the integrated value Further comprising a significant sensor PM deposition amount estimation means for estimating the amount of particulate matter deposited on the PM sensor based on
The presence or absence of failure of the particulate filter by the determination means indicates that the difference between the estimated sensor PM accumulation amount and the significant estimated sensor PM accumulation amount, which is an estimated value of the significant sensor PM accumulation amount estimation means, is equal to or less than a reference amount. It is characterized in that it is an execution condition of the discrimination.

  According to the present invention, when the difference between the estimated sensor PM accumulation amount and the significant estimated sensor PM accumulation amount is small, the determination of the presence or absence of the particulate filter failure by the determination means is executed. Thereby, the failure diagnosis of the particulate filter can be performed with higher accuracy.

  In the particulate filter failure diagnosis apparatus according to the first and second aspects of the present invention, when the execution condition is satisfied when the estimated sensor PM accumulation amount reaches a predetermined failure diagnosis execution amount, It may be one that determines whether there is a failure of the curate filter. In addition, the fault diagnosis execution amount at this time is the actual PM sensor accumulation amount when the estimated sensor PM accumulation amount reaches the fault diagnosis execution amount regardless of whether the particulate filter is in a normal state or a failure state. The PM accumulation amount may be set to a value that falls within a predetermined high accuracy detection range.

  When the PM accumulation amount in the PM sensor is smaller than a certain level and larger than a certain level, the detection accuracy of the PM accumulation amount by the PM sensor decreases. Here, the high-accuracy detection range is a range between the lower limit value and the upper limit value of the PM deposition amount that can maintain the detection accuracy of the PM sensor with high accuracy. The failure state is a state where the degree of deterioration of the particulate filter exceeds an allowable range, that is, a state where the PM collection capability of the particulate filter is reduced beyond the allowable range.

  By setting the failure diagnosis execution amount to the above value, the particulate filter failure diagnosis can be executed with high detection accuracy of the PM sensor.

  According to the present invention, failure diagnosis of a particulate filter can be performed with higher accuracy.

It is a figure which shows schematic structure of the exhaust system of the internal combustion engine which concerns on an Example. It is a figure which shows schematic structure of the PM sensor which concerns on an Example. It is a graph which shows the relationship of the PM deposition amount in PM sensor, the electrical resistance between electrodes of PM sensor, and the output value of PM sensor. It is a figure which shows transition of the output value of a downstream PM sensor, and the estimation sensor PM deposit amount. It is a figure which shows the relationship between the presence or absence of establishment of significant conditions, and transition of estimated sensor PM deposit amount and significant estimated sensor PM deposit amount. It is a graph which shows the relationship between PM accumulation amount in a downstream PM sensor, and the electrical resistance between the electrodes of a downstream PM sensor. It is a flowchart which shows the failure diagnosis flow of the particulate filter which concerns on an Example. It is a flowchart which shows the failure diagnosis flow of the particulate filter which concerns on the modification of an Example.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. The dimensions, materials, shapes, relative arrangements, and the like of the components described in the present embodiment are not intended to limit the technical scope of the invention to those unless otherwise specified.

<Example>
An embodiment of the present invention will be described with reference to FIGS.

(Schematic configuration of exhaust system of internal combustion engine)
FIG. 1 is a diagram showing a schematic configuration of an exhaust system of an internal combustion engine according to the present embodiment. The internal combustion engine 1 is a diesel engine for driving a vehicle. An exhaust passage 2 is connected to the internal combustion engine 1.

  The exhaust passage 2 is provided with a particulate filter 3 that collects PM in the exhaust. An oxidation catalyst 4 is provided as a pre-stage catalyst upstream of the particulate filter 3 in the exhaust passage 2.

  An upstream PM sensor 5 is provided in the exhaust passage 2 downstream of the oxidation catalyst 4 and upstream of the particulate filter 3, and the downstream PM sensor is disposed in the exhaust passage 2 downstream of the particulate filter 3. 6 and a temperature sensor 13 for detecting the temperature of the exhaust. Each of the PM sensors 5 and 6 is a sensor that outputs an electrical signal corresponding to the amount of accumulated PM.

  FIG. 2 is a diagram showing a schematic configuration of the PM sensors 5 and 6. As shown in FIG. 2, the PM sensors 5, 6 include a pair of electrodes 9a, 9b. FIG. 3 is a graph showing the relationship between the PM deposition amount in the PM sensors 5 and 6, the electrical resistance between the electrodes 9 a and 9 b of the PM sensors 5 and 6, and the output value of the PM sensors 5 and 6. In FIG. 3, the horizontal axis represents the amount of PM deposited on the PM sensors 5 and 6, the lower vertical axis represents the electrical resistance between the electrodes 9a and 9b of the PM sensors 5 and 6, and the upper vertical axis represents the PM sensor. The output values of 5 and 6 are represented.

  PM in the exhaust gas adheres and accumulates on the PM sensors 5 and 6. As the PM deposition amount in the PM sensors 5 and 6 increases, the electrical resistance between the electrodes 9a and 9b decreases. As the electrical resistance between the electrodes 9a and 9b decreases, the output values of the PM sensors 5 and 6 increase.

  Each PM sensor 5, 6 is provided with electric heaters 7, 8. By heating the PM sensors 5 and 6 by the electric heaters 7 and 8, the PM deposited on the PM sensors 5 and 6 can be oxidized and removed. In the present embodiment, the downstream PM sensor 6 corresponds to the PM sensor according to the present invention.

The internal combustion engine 1 is provided with an electronic control unit (ECU) 10. The ECU 10 is a unit that controls the operating state and the like of the internal combustion engine 1. In addition to the PM sensors 5 and 6 and the temperature sensor 13, an air flow meter (not shown), a crank position sensor 11 and an accelerator opening sensor 12 are electrically connected to the ECU 10. The crank position sensor 11 detects the crank angle of the internal combustion engine 1. The accelerator opening sensor 12 detects the accelerator opening of a vehicle on which the internal combustion engine 1 is mounted. Output signals from the sensors are input to the ECU 10. The ECU 10 derives the temperature of the particulate filter 3 based on the detection value of the temperature sensor 13. The ECU 10 derives the engine rotation speed of the internal combustion engine 1 based on the detection value of the crank position sensor 11 and derives the engine load of the internal combustion engine 1 based on the detection value of the accelerator opening sensor 12.

  In addition, electric heaters 7 and 8 are electrically connected to the ECU 10. These are controlled by the ECU 10.

(Particulate filter failure diagnosis)
Next, the particulate filter failure diagnosis method according to the present embodiment will be described with reference to FIGS. In the present embodiment, the outflow PM amount when the particulate filter 3 is assumed to be in a normal state is estimated, and the PM accumulation amount in the downstream PM sensor 6 is calculated based on the integrated value obtained by integrating the outflow PM amount. presume. Hereinafter, the PM accumulation amount in the downstream PM sensor 6 estimated in this way is referred to as an estimated sensor PM accumulation amount. And the presence or absence of the failure of the particulate filter 3 is discriminate | determined by comparing the output value of the downstream PM sensor 6, and the estimated sensor PM accumulation amount.

  FIG. 4 is a diagram showing the transition of the output value of the downstream PM sensor 6 and the estimated sensor PM accumulation amount. FIG. 4A shows a case where the particulate filter 3 is in a normal state, and FIG. 4B shows a case where a failure occurs in the particulate filter 3. 4A and 4B, the horizontal axis represents time t. 4A and 4B, the solid line L1 represents the output value of the downstream PM sensor 6, and the broken line L2 represents the estimated sensor PM accumulation amount.

  In this embodiment, when the estimated sensor PM accumulation amount reaches the failure diagnosis execution amount Gtrg, it is determined whether or not there is a failure in the particulate filter 3. When the estimated sensor PM accumulation amount reaches the failure diagnosis execution amount Gtrg, the electric heater 8 is operated to remove the PM accumulated on the downstream PM sensor 6. As a result, the output value of the downstream PM sensor 6 and the estimated sensor PM accumulation amount are temporarily reduced to zero. Thereafter, the output value of the downstream PM sensor 6 and the estimated sensor PM accumulation amount increase again.

  As shown in FIG. 4A, when the particulate filter 3 is in a normal state, the difference between the output value of the downstream PM sensor 6 and the estimated sensor PM accumulation amount is very small. On the other hand, when a failure occurs in the particulate filter 3, the actual outflow PM amount is larger than that in the normal state. Therefore, as shown in FIG. 4B, the difference between the output value of the downstream PM sensor 6 and the estimated sensor PM accumulation amount is larger than that in the normal state. Therefore, when the estimated sensor PM accumulation amount reaches the failure diagnosis execution amount Gtrg, the presence or absence of a failure of the particulate filter 3 is determined by comparing the output value of the downstream PM sensor 6 with the estimated sensor PM accumulation amount. Can do.

  However, when the engine load of the internal combustion engine 1 is low or when the amount of accumulated PM in the particulate filter 3 is relatively large, such as when the original outflow PM amount is smaller than a certain level, the particulate filter 3 is normal. There is a case where there is almost no difference between the amount of outflow PM between the time and the time of failure. Until the estimated sensor PM accumulation amount reaches the failure diagnosis execution amount Gtrg, if the period in such a state is long, the estimated sensor PM accumulation amount is executed even if the particulate filter 3 has a failure. When the amount Gtrg is reached, the difference between the output value of the downstream PM sensor 6 and the estimated sensor PM accumulation amount becomes relatively small. In this case, if the failure diagnosis of the particulate filter 3 as described above is executed, there is a risk of erroneous diagnosis.

Therefore, in this embodiment, in addition to the estimated sensor PM accumulation amount, only the outflow PM amount when the significant condition is satisfied is integrated, and the PM accumulation amount in the downstream PM sensor 6 is estimated based on the integrated value. Hereinafter, the PM accumulation amount in the downstream side PM sensor 6 estimated in this way is referred to as a significant estimation sensor PM accumulation amount.

  Here, the significant condition is a condition in which the difference between the amount of outflow PM between the normal time and the failure time of the particulate filter is equal to or greater than a predetermined amount. Here, the predetermined amount is a threshold value with which the presence or absence of failure of the particulate filter 3 can be determined with high accuracy. In the present embodiment, it is determined that the significant condition is satisfied when the estimated value of the outflow PM amount when the particulate filter 3 is assumed to be in a normal state is equal to or greater than a predetermined outflow amount. Note that it can be determined that the significant condition is satisfied when the engine load of the internal combustion engine 1 is equal to or greater than a predetermined load. The predetermined flow rate and the predetermined load, which are threshold values for establishing a significant condition, can be set in advance based on experiments or the like.

  When the estimated sensor PM accumulation amount reaches the failure diagnosis execution amount Gtrg, the output of the downstream PM sensor 6 is output only when the ratio of the significant estimated sensor PM accumulation amount to the estimated sensor PM accumulation amount is equal to or greater than the reference ratio. It is determined whether or not there is a failure in the particulate filter 3 by comparing the value with the estimated sensor PM accumulation amount. Here, the reference ratio is a threshold value with which the presence / absence of a failure of the particulate filter 3 can be determined with high accuracy. The reference ratio can also be determined in advance based on experiments or the like.

  FIG. 5 is a diagram illustrating the relationship between the presence / absence of a significant condition and the transition of the estimated sensor PM accumulation amount Gpme and the significant estimation sensor PM accumulation amount Gpme_sig. In FIG. 5, the horizontal axis represents time t. In FIG. 5, the upper part represents whether or not a significant condition is satisfied, the middle part represents the transition of the estimated sensor PM deposition amount Gpme, and the lower stage represents the transition of the significant estimated sensor PM deposition amount Gpme_sig.

  As shown in FIG. 5, the significant estimated sensor PM accumulation amount Gpme_sig increases only when the significant condition is satisfied. Therefore, at the timing t1 when the estimated sensor PM accumulation amount Gpme reaches the failure diagnosis execution amount Gtrg, the value of the significant estimated sensor PM accumulation amount Gpme_sig is smaller than the value of the estimated sensor PM accumulation amount Gpme. However, at t1, the ratio to the estimated sensor PM accumulation amount Gpme is equal to or higher than the reference ratio. Therefore, at t1, it is determined whether or not the particulate filter 3 has failed.

  On the other hand, after t1, PM accumulated on the downstream PM sensor 6 is removed (after the estimated sensor PM accumulation amount Gpme and the significant estimated sensor PM accumulation amount Gpme_sig become zero), and then the estimated sensor PM accumulation amount The significant condition is not satisfied until the timing t2 when Gpme reaches the failure diagnosis execution amount Gtrg. Therefore, the significant estimated sensor PM accumulation amount Gpme_sig at time t2 is zero. In this case, the ratio of the significant estimated sensor PM accumulation amount Gpme_sig to the estimated sensor PM accumulation amount Gpme is naturally smaller than the reference ratio. Therefore, at t2, it is not determined whether or not the particulate filter 3 has failed.

(Setting method of fault diagnosis execution amount)
Here, a method for setting the fault diagnosis execution amount Gtrg in the particulate filter fault diagnosis method will be described with reference to FIG. FIG. 6 is a graph showing the relationship between the PM accumulation amount in the downstream PM sensor 6 and the electrical resistance between the electrodes 9a and 9b of the downstream PM sensor 6. In FIG. 6, the horizontal axis represents the PM accumulation amount in the downstream PM sensor 6, and the vertical axis represents the electrical resistance between the electrodes 9 a and 9 b of the downstream PM sensor 6.

As shown in FIG. 6, when the PM accumulation amount in the downstream PM sensor 6 is smaller than a certain level and larger than a certain level, the change in electrical resistance between the electrodes 9a and 9b with respect to the change in the PM accumulation amount becomes very small. . In such a case, the detection accuracy of the PM accumulation amount by the downstream PM sensor 6 is lowered. If a failure diagnosis of the particulate filter is performed in a state where the detection accuracy of the downstream PM sensor 6 is lowered, there is a risk of erroneous diagnosis.

  Therefore, in the present embodiment, as shown in FIG. 6, a range in which the change in electrical resistance between the electrodes 9a and 9b with respect to the change in the PM deposition amount in the downstream PM sensor 6 is sufficiently large is set as a high-precision detection range. That is, the high-accuracy detection range is a range between the lower limit value PMmn and the upper limit value PMmax of the PM accumulation amount that can maintain the detection accuracy of the PM sensor with high accuracy.

  The downstream side PM sensor 6 when the estimated sensor PM accumulation amount reaches the failure diagnosis execution amount Gtrg, regardless of whether the failure diagnosis execution amount Gtrg is in the normal state or the failure state of the particulate filter 3. The actual PM accumulation amount at is set to a value that falls within the high accuracy detection range. Such a failure diagnosis execution amount Gtrg can be set in advance based on experiments or the like.

  By setting the failure diagnosis execution amount Gtrg to such a value, failure diagnosis of the particulate filter 3 can be executed when the detection accuracy of the downstream PM sensor 6 is high. Therefore, the accuracy of the failure diagnosis can be further increased.

  In this embodiment, the estimated sensor PM accumulation amount may be calculated both when it is assumed that the particulate filter 3 is in a normal state and when the particulate filter 3 is assumed to be in a failure state. . Then, when both the estimated sensor PM accumulation amounts are within the high-precision detection range, a failure diagnosis of the particulate filter 3 may be executed. According to this, the failure diagnosis of the particulate filter 3 can be executed when the detection accuracy of the downstream PM sensor 6 is high as in the case where the failure diagnosis execution amount Gtrg is set to the above value. .

(Particulate filter failure diagnosis flow)
The failure diagnosis flow of the particulate filter according to the present embodiment will be described based on the flowchart shown in FIG. This flow is stored in advance in the ECU 10 and is repeatedly executed by the ECU 10.

  In this flow, first, in step S101, the amount of PM per unit time (hereinafter referred to as inflow PM amount) dGpmin flowing into the particulate filter 3 is calculated. The inflow PM amount dGpmin is calculated based on the amount of change per unit time of the output value of the upstream PM sensor 5. Further, the inflow PM amount dGpmin may be calculated based on the operating state of the internal combustion engine 1.

  Next, in step S102, the PM trap rate kTrp (outflow PM amount / inflow PM amount) in the particulate filter 3 is calculated. The PM trap rate is calculated based on the PM accumulation amount in the particulate filter 3, the inflow PM amount dGpmin, and the flow rate of the exhaust gas flowing into the particulate filter 3. The PM accumulation amount in the particulate filter 3 can be calculated based on the operating state history of the internal combustion engine 1, the temperature history of the particulate filter 3, and the like. The flow rate of the exhaust gas flowing into the particulate filter 3 can be calculated based on the detected value of the air flow meter.

  Next, in step S103, the inflow PM amount dGpmin is multiplied by the PM trap rate kTrp to calculate the outflow PM amount dGpmout when it is assumed that the particulate filter 3 is in a normal state. In this embodiment, the ECU 10 that executes the process of step S103 corresponds to the outflow PM amount estimating means according to the present invention.

  Next, in step S104, the outflow PM amount integrated value Gpmout is calculated by integrating the outflow PM amount dGpmout.

  Next, in step S105, the estimated sensor PM accumulation amount Gpme is calculated based on the integrated value Gpmout of the outflow PM amount. The relationship between the integrated value Gpmout of the outflow PM amount and the estimated sensor PM accumulation amount Gpme is obtained in advance based on experiments or the like, and these relationships are stored in the ECU 10 as a map. In this embodiment, the ECU 10 that executes the processes of steps S104 and S105 corresponds to the sensor PM accumulation amount estimating means according to the present invention.

  Next, in step S106, it is determined whether or not the outflow PM amount dGpmout is greater than or equal to a predetermined outflow amount dGpmout0, that is, whether or not a significant condition is satisfied. If the determination in step S106 is affirmative, the process of step S107 is executed next. If the determination is negative, the process of step S118 is executed next.

  In step S107, the outflow PM amount integrated value Gpmout_sig is calculated by integrating the outflow PM amount dGpmout when the outflow PM amount dGpmout is equal to or greater than the predetermined outflow amount dGpmout0.

  Next, in step S108, the significant estimated sensor PM accumulation amount Gpme_sig is calculated based on the integrated value Gpmout_sig of the outflow PM amount. The relationship between the integrated value Gpmout_sig of the outflow PM amount and the significant estimated sensor PM accumulation amount Gpme_sig is obtained in advance based on experiments or the like, and these relationships are stored in the ECU 10 as a map. In this embodiment, the ECU 10 that executes the processes of steps S107 and S108 corresponds to the significant sensor PM accumulation amount estimation means according to the present invention.

  Next, in step S109, it is determined whether or not the estimated sensor PM accumulation amount Gpme is equal to or greater than the failure diagnosis execution amount Gtrg. If an affirmative determination is made in step S109, the process of step S110 is executed next. If a negative determination is made, the process of step S101 is executed again.

  Next, in step S110, the ratio k_sig of the significant estimated sensor PM accumulation amount Gpme_sig to the estimated sensor PM accumulation amount Gpme is calculated.

  Next, in step S111, it is determined whether or not the ratio k_sig calculated in step S110 is greater than or equal to the reference ratio k0. If an affirmative determination is made in step S111, the process of step S112 is executed next, and if a negative determination is made, the process of step S117 is executed next.

  In step S112, a ratio rGpm of the detection value Gpmd of the downstream PM sensor 6 with respect to the estimated sensor PM accumulation amount Gpme is calculated.

  In step S113, it is determined whether or not the ratio rGpm calculated in step S112 is equal to or greater than a predetermined determination ratio rGpm0. Here, the determination ratio rGpm0 is a threshold with which it can be determined that the particulate filter 3 is in a normal state. The determination ratio rGpm0 is set based on the inflow PM amount dGpmin and the flow rate of the exhaust gas flowing into the particulate filter 3.

If an affirmative determination is made in step S113, it is determined in step S114 that the particulate filter 3 is in a normal state. On the other hand, if a negative determination is made in step S113, it is determined in step S115 that a failure has occurred in the particulate filter 3. In the present embodiment, the ECU 10 that executes the processes of steps S112 to S115 corresponds to a determination unit according to the present invention.

  Following the processing in step S114 or step S115, in step S116, the electric heater 8 is operated, and the PM accumulated on the downstream PM sensor 6 is removed.

  Next, in step S117, the values of the estimated sensor PM accumulation amount Gpme and the significant estimation sensor PM accumulation amount Gpme_sig are reset to zero.

  In step S118, it is determined whether or not the estimated sensor PM accumulation amount Gpme is equal to or greater than the failure diagnosis execution amount Gtrg. When an affirmative determination is made in step S118, the process of step S117 is executed next, and the PM accumulated on the downstream PM sensor 6 is removed without executing failure diagnosis of the particulate filter 3. On the other hand, if a negative determination is made in step S118, then the process of step S101 is executed again.

  As described above, in this embodiment, when the ratio of the significant estimated sensor PM accumulation amount to the estimated sensor PM accumulation amount is high, the presence / absence of the failure of the particulate filter 3 is determined. Thereby, failure diagnosis of the particulate filter 3 can be performed with higher accuracy.

  In the above flow, the difference between these values is calculated by subtracting the estimated sensor PM accumulation amount Gpme from the detection value Gpmd of the downstream PM sensor 6 in step S112, and this difference is determined in step S113. It may be determined whether or not it is equal to or less than the determination value. The determination value in this case is also a threshold with which it can be determined that the particulate filter 3 is in a normal state, similar to the determination ratio rGpm0. The determination value is also set based on the inflow PM amount dGpmin and the flow rate of the exhaust gas flowing into the particulate filter 3.

  Also in this case, if an affirmative determination is made in step S113, it can be determined that the particulate filter 3 is in a normal state. If a negative determination is made in step S113, it can be determined that a failure has occurred in the particulate filter 3.

  In this way, by comparing the estimated sensor PM accumulation amount Gpme with the detection value Gpmd of the downstream PM sensor 6, it is possible to determine whether or not the particulate filter 3 has failed, and the comparison method is particularly limited. It is not a thing.

  Further, in this embodiment, instead of when the estimated sensor PM accumulation amount Gpme reaches the failure diagnosis execution amount Gtrg, the failure of the particulate filter 3 occurs when the significant estimated sensor PM accumulation amount Gpme_sig becomes a predetermined failure diagnosis execution amount. The presence or absence of may be determined.

  In the present embodiment, the outflow PM amount dGpmout is estimated on the assumption that a failure has occurred in the particulate filter 3, and the estimated sensor PM accumulation amount Gpme and the significant estimation sensor are based on the integrated value of the estimated values. The PM deposition amount Gpme_sig may be estimated. Even in this case, by comparing the estimated sensor PM accumulation amount Gpme with the detection value Gpmd of the downstream PM sensor 6, it is possible to determine whether or not the particulate filter 3 has failed. Even in this case, the accuracy of failure diagnosis can be improved by setting the ratio k_sig of the significant estimated sensor PM accumulation amount Gpme_sig to the estimated sensor PM accumulation amount Gpme as a condition for executing the failure diagnosis.

(Modification)
FIG. 8 is a flowchart showing a failure diagnosis flow of the particulate filter according to a modification of the present embodiment. This flow is obtained by replacing steps S110 and S111 in the flowchart shown in FIG. 7 with steps S210 and S211.

  In step S210, the difference q_sig between these values is calculated by subtracting the significant estimated sensor PM accumulation amount Gpme_sig from the estimated sensor PM accumulation amount Gpme.

  Next, in step S211, it is determined whether or not the difference q_sig calculated in step S210 is equal to or smaller than a reference amount q0. Here, the reference amount is a threshold value with which the presence / absence of a failure of the particulate filter 3 can be determined with high accuracy. The reference amount can also be determined in advance based on experiments and the like, similarly to the reference ratio k0.

  In this modification, when the difference between the estimated sensor PM accumulation amount and the significant estimated sensor PM accumulation amount is small, the presence / absence of the failure of the particulate filter 3 is determined. Thereby, failure diagnosis of the particulate filter 3 can be performed with higher accuracy.

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Exhaust passage 3 ... Particulate filter 4 ... Oxidation catalyst 5 ... Upstream PM sensor 6 ... Downstream PM sensor 7, 8 ... Electric heater 9a , 9b ... Electrode 10 ... ECU
11 .... Crank position sensor 12 .... Accelerator opening sensor 13 .... Temperature sensor

Claims (3)

A particulate filter failure diagnosis device that is provided in an exhaust passage of an internal combustion engine and collects particulate matter in exhaust gas,
A PM sensor that is provided in the exhaust passage downstream of the particulate filter and detects the amount of particulate matter deposited on itself;
An outflow PM amount estimating means for estimating an outflow PM amount that is an outflow amount of particulate matter from the particulate filter when the particulate filter is assumed to be in a predetermined state;
Sensor PM accumulation amount estimation means for integrating the outflow PM amount estimated by the outflow PM amount estimation means, and estimating the amount of particulate matter deposited on the PM sensor based on the accumulated value;
And a determining unit that determines whether or not the particulate filter has failed by comparing a detection value of the PM sensor with an estimated sensor PM accumulation amount that is an estimated value of the sensor PM accumulation amount estimating unit. In the filter fault diagnosis device,
Accumulating the outflow PM amount estimated by the outflow PM amount estimation means when a significant condition is established that the difference between the outflow PM amount between the normal time and the failure of the particulate filter is greater than or equal to a predetermined amount, and the integrated value Further comprising a significant sensor PM deposition amount estimation means for estimating the amount of particulate matter deposited on the PM sensor based on
The ratio of the significant estimated sensor PM accumulated amount, which is the estimated value of the significant sensor PM accumulated amount estimating means to the estimated sensor PM accumulated amount, is greater than or equal to a reference ratio, and the presence / absence of failure of the particulate filter by the determining means. A particulate filter failure diagnosis apparatus, characterized in that it is used as a determination execution condition. A particulate filter failure diagnosis device that is provided in an exhaust passage of an internal combustion engine and collects particulate matter in exhaust gas,
A PM sensor that is provided in the exhaust passage downstream of the particulate filter and detects the amount of particulate matter deposited on itself;
An outflow PM amount estimating means for estimating an outflow PM amount that is an outflow amount of particulate matter from the particulate filter when the particulate filter is assumed to be in a predetermined state;
Sensor PM accumulation amount estimation means for integrating the outflow PM amount estimated by the outflow PM amount estimation means, and estimating the amount of particulate matter deposited on the PM sensor based on the accumulated value;
And a determining unit that determines whether or not the particulate filter has failed by comparing a detection value of the PM sensor with an estimated sensor PM accumulation amount that is an estimated value of the sensor PM accumulation amount estimating unit. In the filter fault diagnosis device,
Accumulating the outflow PM amount estimated by the outflow PM amount estimation means when a significant condition is established that the difference between the outflow PM amount between the normal time and the failure of the particulate filter is greater than or equal to a predetermined amount, and the integrated value Further comprising a significant sensor PM deposition amount estimation means for estimating the amount of particulate matter deposited on the PM sensor based on
The presence or absence of failure of the particulate filter by the determination means indicates that the difference between the estimated sensor PM accumulation amount and the significant estimated sensor PM accumulation amount, which is an estimated value of the significant sensor PM accumulation amount estimation means, is equal to or less than a reference amount. Particulate filter failure diagnosis apparatus, characterized in that it is used as an execution condition for the discrimination. When the execution condition is satisfied when the estimated sensor PM accumulation amount reaches a predetermined failure diagnosis execution amount, the determination unit determines whether or not there is a failure of the particulate filter,
Regardless of whether the failure diagnosis execution amount is a normal state or a failure state of the particulate filter, the actual particles in the PM sensor when the estimated sensor PM accumulation amount reaches the failure diagnosis execution amount The particulate filter failure diagnosis apparatus according to claim 1, wherein the amount of deposit of the particulate matter is set to a value that falls within a predetermined high-precision detection range.

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