JP2014098363A - Abnormality determination device for filter - Google Patents

Abstract

An object of the present invention is to improve the accuracy of filter abnormality determination.
A filter provided in an exhaust passage of an internal combustion engine for collecting particulate matter in the exhaust, a deposit amount estimating means for estimating the amount of particulate matter deposited on the filter, and a filter deposited on the filter. A sensor whose detection value changes according to the amount of particulate matter that is present, an amount of particulate matter estimated by the deposition amount estimation means, and a determination means that determines filter abnormality based on the detection value of the sensor; When the amount of condensed water estimated by the condensed water inflow amount estimating means for estimating the amount of condensed water flowing into the filter and the amount of condensed water inflow estimating means is equal to or greater than a threshold value And a deposit amount changing means for reducing the amount of the particulate matter estimated by the deposit amount estimating means.
[Selection] Figure 4

Description

  The present invention relates to a filter abnormality determination device.

  A differential pressure for detecting a pressure difference between the upstream side and the downstream side of the filter (hereinafter also referred to as a differential pressure across the filter), which is an abnormality of the filter that collects particulate matter (hereinafter also referred to as PM) in the exhaust gas. It can be determined using a sensor. For example, a plurality of relationships between the flow rate of the exhaust gas of the internal combustion engine and the differential pressure across the filter are obtained, and from this relationship, the ratio (slope) of the change amount of the differential pressure across the filter with respect to the change amount of the exhaust flow rate is calculated. A technique for performing filter abnormality determination based on an inclination is known (see, for example, Patent Document 1).

  By the way, when the temperature of the exhaust pipe is low, such as immediately after the internal combustion engine is started, water may condense in the exhaust pipe. When this condensed water reaches the filter, PM accumulated on the filter may be peeled off. Then, since the differential pressure across the filter decreases, the inclination changes. As a result, the accuracy of the filter abnormality determination may be reduced.

JP 2009-216077 A Japanese Patent Application Laid-Open No. 08-260942 Japanese Patent Laid-Open No. 11-153020 JP 2009-097410 A

  The present invention has been made in view of the above-described problems, and an object thereof is to further improve the abnormality determination accuracy of a filter.

In order to achieve the above object, the present invention provides:
A filter provided in an exhaust passage of the internal combustion engine for collecting particulate matter in the exhaust;
A deposition amount estimating means for estimating the amount of particulate matter deposited on the filter;
A sensor whose detection value changes according to the amount of particulate matter deposited on the filter;
Determination means for determining an abnormality of the filter based on the amount of particulate matter estimated by the accumulation amount estimation means, and a detection value of the sensor;
In the abnormality determination device for the filter provided with
A condensed water inflow amount estimating means for estimating an amount of condensed water flowing into the filter;
A deposition amount changing means for reducing the amount of particulate matter estimated by the deposition amount estimating means when the amount of condensed water estimated by the condensed water inflow amount estimating means is equal to or greater than a threshold;
Is provided.

The accumulation amount estimation means can estimate the amount of particulate matter accumulated on the filter without using the detection value of the sensor. For example, the amount of particulate matter discharged from the internal combustion engine is estimated from the operating state of the internal combustion engine (for example, engine speed and engine load), and based on this value, the amount of particulate matter deposited on the filter An estimated value (hereinafter also referred to as an estimated PM deposition amount) of the amount (hereinafter also referred to as a PM deposition amount) may be obtained. Further, the estimated PM accumulation amount may be the PM accumulation amount when the filter is assumed to be normal, or may be the PM accumulation amount when the filter is assumed to be abnormal. It may be the amount of accumulated PM when it is assumed that the boundary is between normal and abnormal. The amount of condensed water flowing into the filter estimated by the condensed water inflow amount estimating means may be an amount per unit time, an amount in a predetermined period, or an integrated value.

  Here, when a lot of condensed water flows into the filter, the condensed water may cause the PM to peel off from the filter. In this case, the detection value of the sensor changes greatly. On the other hand, if the amount of condensed water flowing into the filter is small, PM may not be separated from the filter. Therefore, the accumulation amount changing means decreases the estimated PM accumulation amount when the estimated amount of condensed water is equal to or greater than the threshold value. The amount to be decreased may be a constant amount or a total amount. Moreover, you may reduce according to the quantity of condensed water. The threshold here is the amount of condensed water flowing into the filter, and is the amount of condensed water from which the PM is separated from the filter.

  Even if the PM is peeled off from the filter, if the operation of the internal combustion engine continues thereafter, PM newly discharged from the internal combustion engine accumulates on the filter. When the operation of the internal combustion engine is continued, the temperature of the exhaust pipe rises, so that condensed water is not generated. Therefore, PM accumulates on the filter if a sufficient time has elapsed since the start of the internal combustion engine. If the filter abnormality determination is performed after such a state, the influence of the condensed water can be reduced. That is, even if the PM is separated from the filter by the condensed water, the accuracy of the filter abnormality determination is increased after the PM necessary for the filter abnormality determination is discharged from the internal combustion engine. As described above, by performing the abnormality determination after a sufficient amount of PM is discharged from the internal combustion engine, it is possible to suppress a decrease in accuracy.

  Then, if the determination means sets the filter abnormality determination time and the threshold value used at the time of filter abnormality determination based on the estimated PM accumulation amount, the filter can be filtered at an appropriate time even if the PM is separated from the filter. It is possible to carry out the abnormality determination or to set an appropriate threshold value. That is, the determination unit may set a condition for determining whether or not the filter abnormality determination can be performed based on the estimated PM accumulation amount, or a condition for determining whether or not the filter is abnormal. it can.

  The sensor is not limited to the differential pressure sensor, and may be a sensor (hereinafter referred to as a PM sensor) that detects a PM amount downstream from the filter. In addition, the determination unit may perform the abnormality determination by comparing the detection value of the sensor with a threshold value, for example, when the estimated PM accumulation amount reaches an amount necessary for performing the abnormality determination of the filter. . It should be noted that the abnormality of the filter may include a case where the filter is broken or the filter is melted or the filter is removed.

  In the present invention, the accumulation amount changing means can set the amount of particulate matter estimated by the accumulation amount estimation means to zero.

  That is, the PM deposition amount may be set to 0 on the assumption that all the PM deposited on the filter has been peeled off.

  In the present invention, the determination unit can set a threshold value for determining abnormality of the filter based on the amount of particulate matter estimated by the accumulation amount estimation unit.

Here, since there is a correlation between the estimated PM accumulation amount and the detection value of the sensor, if the filter is normal, the detection value of the sensor becomes a value corresponding to the estimated PM accumulation amount. Therefore, when the detection value of the sensor is not a value corresponding to the estimated PM accumulation amount, it can be determined that the filter is abnormal. For this reason, a threshold value can be set as a boundary as to whether or not the detection value of the sensor is a value corresponding to the estimated PM accumulation amount. The threshold value may be compared with the detection value of the sensor. For example, a value using the detection value of the sensor, such as a ratio of the change amount of the detection value of the sensor to the change amount of the volume flow rate of the exhaust gas. May be compared. That is, a threshold value for performing filter abnormality determination by some method using the detection value of the sensor may be set.

  In the present invention, the determination unit can perform the filter abnormality determination only when the amount of the particulate matter estimated by the accumulation amount estimation unit is within a predetermined range.

  Here, if the amount of accumulated PM is too small, it is difficult to determine abnormality because the differential pressure across the front and rear is small even with a normal filter. Also, if the amount of accumulated PM is too large, even if the filter is abnormal, the differential pressure across the front and rear becomes large, making it difficult to determine abnormality. Therefore, the accuracy of determination can be improved by carrying out a filter abnormality determination with a predetermined range in a range where the pressure difference between the front and rear is small if it is a normal filter and a range where the pressure difference across the front is small if it is an abnormal filter. . That is, the range of the estimated PM accumulation amount in which there is a difference in the front-back differential pressure between the normal filter and the abnormal filter may be set as the predetermined range.

Moreover, in order to achieve the above-mentioned problem, the present invention
A filter provided in an exhaust passage of the internal combustion engine for collecting particulate matter in the exhaust;
A deposition amount estimating means for estimating the amount of particulate matter deposited on the filter;
A sensor whose detection value changes according to the amount of particulate matter deposited on the filter;
Determination means for determining abnormality of the filter based on the amount of particulate matter estimated by the accumulation amount estimation means and the detection value of the sensor;
In the abnormality determination device for the filter provided with
A condensed water inflow amount estimating means for estimating an amount of condensed water flowing into the filter;
Prohibiting means for prohibiting determination by the determining means when the amount of condensed water estimated by the condensed water inflow amount estimating means is greater than or equal to a threshold;
Is provided.

  That is, instead of decreasing the estimated PM accumulation amount, filter abnormality determination may be prohibited. Then, when the differential pressure across the filter changes due to the separation of PM from the filter, the filter abnormality determination is prohibited, so that erroneous determination can be suppressed. Thereby, the accuracy of the filter abnormality determination can be improved.

  According to the present invention, the filter abnormality determination accuracy can be further increased.

It is a figure which shows schematic structure of the internal combustion engine which concerns on Example 1, 2, and 3 and its exhaust system. It is the figure which showed the relationship between the integrated value (filter inflow PM amount) of PM amount which flows in into a filter, and the differential pressure before and behind a filter. It is the time chart which showed transition of the condensed water inflow amount and estimated PM deposit amount. 3 is a flowchart illustrating a flow of filter abnormality determination according to the first embodiment. 6 is a flowchart showing another flow of filter abnormality determination according to the first embodiment. 10 is a flowchart illustrating a flow of filter abnormality determination according to the second embodiment. It is the figure which showed the relationship between estimated PM deposition amount and the differential pressure before and behind a filter. 10 is a flowchart illustrating a flow of filter abnormality determination according to the third embodiment. FIG. 6 is a diagram illustrating a schematic configuration of an internal combustion engine and an exhaust system thereof according to a fourth embodiment. 10 is a flowchart illustrating a flow of filter abnormality determination according to the fourth embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be exemplarily described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention only to those unless otherwise specified.

Example 1
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine and its exhaust system according to the present embodiment. An internal combustion engine 1 shown in FIG. 1 is a diesel engine having four cylinders. Note that this embodiment can also be applied to a gasoline engine.

  An exhaust passage 2 is connected to the internal combustion engine 1. A filter 3 for collecting particulate matter (hereinafter referred to as PM) in the exhaust is provided in the middle of the exhaust passage 2. The filter 3 includes, for example, a plurality of passages extending in parallel with each other. These passages include a passage whose upstream end is closed by a plug and a passage whose downstream end is closed by a plug. The filter 3 can also be a non-woven fabric or the like.

  Further, a differential pressure sensor 4 for detecting a pressure difference between the exhaust passage 2 upstream of the filter 3 and the exhaust passage 2 downstream is attached. The differential pressure sensor 4 detects the differential pressure across the filter 3.

  Further, the internal combustion engine 1 is provided with a fuel injection valve 5 for injecting fuel into the cylinder.

  The internal combustion engine 1 configured as described above is provided with an ECU 10 that is an electronic control unit for controlling the internal combustion engine 1. The ECU 10 controls the internal combustion engine 1 in accordance with the operating conditions of the internal combustion engine 1 and the driver's request.

  In addition to the differential pressure sensor 4, the ECU 10 outputs an electric signal corresponding to the amount of depression of the accelerator pedal 11 by the driver to detect the engine load, and a crank that detects the engine speed. A position sensor 13 is connected via electrical wiring, and output signals of these various sensors are input to the ECU 10.

  Further, the ECU 10 controls the operating state of the internal combustion engine 1 based on the detection values obtained by these sensors. For example, the ECU 10 controls the fuel injection amount from the fuel injection valve 5.

Then, the ECU 10 determines the abnormality of the filter 3 based on the detection value of the differential pressure sensor 4. Here, the volume flow rate of the exhaust gas and the differential pressure across the filter 3 are considered to be proportional. In this embodiment, the relationship of the differential pressure across the filter 3 with respect to the volume flow rate of the exhaust gas passing through the filter 3 is detected in each of a plurality of operating states with different volume flow rates of the exhaust gas. An approximate expression showing the relationship with the front-rear differential pressure is obtained. Then, the horizontal axis is the volume flow rate of the exhaust gas, and the vertical axis is the differential pressure across the filter 3, and the slope of the approximate equation when the approximate equation is illustrated (that is, the amount of change in the volume flow rate of the exhaust gas passing through the filter 3). Is smaller than the threshold value, the filter 3 is determined to be abnormal. If the slope is equal to or greater than the threshold, it is determined that the filter 3 is normal. This threshold value is obtained in advance by experiment or simulation as the lower limit value of the slope when the filter 3 is normal.

  Further, the ECU 10 estimates the amount of PM discharged from the internal combustion engine 1 based on the operating state of the internal combustion engine 1 (hereinafter referred to as PM discharge amount), and based on the integrated value of this PM discharge amount, the filter 3. The amount of PM deposited on the surface (hereinafter referred to as PM deposition amount) is estimated.

  In the present embodiment, it may be considered that all PM discharged from the internal combustion engine 1 accumulates on the filter 3, but it may be considered that PM discharged from the internal combustion engine 1 accumulates on the filter 3 at a predetermined rate. . In this case, the estimated PM accumulation amount may be calculated by multiplying the integrated value of the PM discharge amount by a predetermined value. As this predetermined value, an optimum value is obtained in advance by experiment or simulation.

  Further, since the PM emission amount has a correlation with the operation state (engine speed and engine load) of the internal combustion engine 1, the relationship between the PM emission amount and the operation state of the internal combustion engine 1 is obtained in advance by experiment or simulation. If stored in the ECU 10, the PM emission amount can be calculated based on the operating state of the internal combustion engine 1. The engine load at this time may be the accelerator opening or the fuel injection amount. Further, the estimated PM accumulation amount may be calculated from the operating state (engine speed and engine load) of the internal combustion engine 1.

  In the present embodiment, the abnormality determination of the filter 3 is performed based on the slope of the approximate expression only when the estimated PM accumulation amount is within a predetermined range. That is, when the PM accumulation amount is too small, the difference in front-to-back differential pressure is small between the case where the filter 3 is normal and the case where it is abnormal, so that the determination accuracy decreases. Further, if the amount of accumulated PM is too large, the differential pressure across the filter 3 increases even if the filter 3 is abnormal, and the difference between the differential pressure across the filter 3 is small when the filter 3 is normal and abnormal. Therefore, the determination accuracy is lowered. When the determination accuracy decreases, the abnormality determination of the filter 3 is not performed.

  By the way, when liquid water flows into the filter 3 or when water is condensed in the filter 3, PM accumulated in the filter 3 may be separated from the filter 3. Thus, when PM peels from the filter 3, the amount of PM deposition decreases and the differential pressure across the filter 3 decreases.

  Here, FIG. 2 is a diagram showing the relationship between the integrated value of the PM amount flowing into the filter 3 (filter inflow PM amount) and the differential pressure across the filter 3. The filter inflow PM amount may be considered to be equal to the integrated value of the PM discharge amount. A, B, and C in FIG. 2 are values when the internal combustion engine 1 is stopped for one day.

  When the internal combustion engine 1 is stopped, the temperature of the wall surface of the exhaust passage 2 decreases, and moisture in the exhaust is condensed at the next engine start. For this reason, condensed water flows into the filter 3. Before the internal combustion engine 1 is stopped, the differential pressure across the filter 3 increases in accordance with the amount of PM flowing into the filter 3, but each time the internal combustion engine 1 is stopped at A, B, and C in FIG. In addition, the differential pressure across the filter 3 is reduced. This is because PM is separated from the filter 3 by the condensed water flowing into the filter 3. And if the abnormality of the filter 3 is determined when the differential pressure across the filter 3 is reduced by the condensed water, an erroneous determination is caused.

  Therefore, in this embodiment, the abnormality determination of the filter 3 is performed in consideration of separation of PM from the filter 3 due to condensed water.

Here, FIG. 3 is a time chart showing the transition of the condensed water inflow amount and the estimated PM accumulation amount. The condensed water inflow amount is an estimated value of the amount of condensed water flowing into the filter 3. The amount of condensed water inflow may be an amount per unit time or may be an amount for a predetermined period. The amount of condensed water inflow is calculated by calculating the amount of condensed water generated from the fuel injection amount and the wall surface temperature of the exhaust passage 2, and further multiplying by a coefficient determined from the flow rate of the exhaust. That is, the fuel injection amount is correlated with the amount of water vapor contained in the exhaust gas, and the wall surface temperature of the exhaust passage 2 is correlated with the proportion of water condensed in the water vapor contained in the exhaust gas. Therefore, the amount of condensed water generated in the exhaust passage 2 can be calculated from these values. Of the condensed water generated in the exhaust passage 2, the amount of condensed water flowing into the filter 3 has a correlation with the flow rate of the exhaust gas. Therefore, the amount of condensed water flowing into the filter 3 can be calculated from these values. Note that the amount of condensed water flowing into the filter 3 may be calculated using a known technique. Further, the estimated PM accumulation amount is estimated based on the operation state of the internal combustion engine 1.

  In FIG. 3, the amount of condensed water inflow reaches the threshold at the time indicated by T1. This threshold is the amount of condensed water from which the PM adhering to the filter 3 is peeled off. This threshold value is obtained in advance by experiment or simulation and stored in the ECU 10. Then, at the time T1 when the amount of condensed water inflow reaches a threshold value, the estimated amount of accumulated PM is reset. That is, the estimated PM accumulation amount is set to zero. Then, the accumulation of the estimated PM accumulation amount is newly started from this time point T1. Note that when the amount of condensed water inflow reaches a threshold value, the estimated amount of accumulated PM may be decreased by a predetermined value or may be decreased by a predetermined ratio. That is, the estimated PM accumulation amount may be decreased at the time indicated by T1.

  In FIG. 3, the estimated PM deposition amount reaches the threshold at the time indicated by T2. This threshold value is a lower limit value of the PM accumulation amount at which the filter 3 can be determined to be abnormal. Note that the estimated PM accumulation amount is set to 0 when the filter 3 is regenerated.

  FIG. 4 is a flowchart showing a flow of abnormality determination of the filter 3 according to the present embodiment. This routine is repeatedly executed by the ECU 10 every predetermined time.

  In step S101, the amount of condensed water generation is calculated. The amount of condensed water generated is the amount of condensed water generated in the exhaust passage 2 and is calculated based on the fuel injection amount and the wall surface temperature of the exhaust passage 2. The fuel injection amount is calculated based on the accelerator opening, the intake air amount, and the engine speed. The wall surface temperature of the exhaust passage 2 may be measured with a sensor attached, or may be estimated from the operating state of the internal combustion engine 1. The relationship between the fuel injection amount and the wall surface temperature of the exhaust passage 2 and the amount of condensed water generation is obtained in advance through experiments or simulations and stored in the ECU 10.

  In step S102, a condensed water inflow rate, which is a ratio of condensed water flowing into the filter 3 among the generated condensed water, is calculated. This condensed water inflow rate is correlated with the flow rate of the exhaust gas. Further, the exhaust flow rate is calculated based on the intake air amount and the fuel injection amount. The relationship between the intake air amount and the fuel injection amount and the exhaust gas flow rate is obtained in advance through experiments or the like and stored in the ECU 10. Further, the relationship between the exhaust gas flow rate and the condensed water inflow rate is also obtained in advance by experiments or the like and stored in the ECU 10.

  In step S103, the amount of condensed water inflow that is the amount of condensed water flowing into the filter 3 is calculated. The condensed water inflow amount is calculated by multiplying the condensed water generation amount calculated in step S101 by the condensed water inflow rate calculated in step S102. Note that the amount of condensed water inflow may be calculated using a known technique. Further, the amount of condensed water generated may be a value obtained by integrating the amount of condensed water flowing into the filter 3. In the present embodiment, the ECU 10 that processes step S103 corresponds to the condensed water inflow amount estimating means in the present invention.

In step S104, it is determined whether or not the amount of condensed water inflow is greater than or equal to a threshold value. The threshold value is a lower limit value of the inflow amount of condensed water from which the PM accumulated on the filter 3 peels from the filter 3.
It is obtained in advance by experiment or simulation and stored in the ECU 10.

  If an affirmative determination is made in step S104, the process proceeds to step S105, whereas if a negative determination is made, the process proceeds to step S106.

  In step S105, the estimated PM accumulation amount MPM is reset. Note that a predetermined amount may be subtracted from the estimated PM accumulation amount MPM, or the estimated PM accumulation amount MPM may be multiplied by a predetermined value that is a value greater than 0 and less than 1. In this embodiment, the ECU 10 that processes step S105 corresponds to the accumulation amount changing means in the present invention.

  In step S106, the volume flow rate DVOL is calculated. Since the volume flow rate DVOL is correlated with the intake air amount and the fuel injection amount, these relationships are obtained in advance through experiments or simulations and stored in the ECU 10.

  In step S107, the differential pressure ΔP across the filter 3 is detected. This front-rear differential pressure ΔP is detected by the differential pressure sensor 4.

  In step S108, an approximate expression of the front-rear differential pressure ΔP with respect to the volume flow rate DVOL is calculated. A plurality of relationships between the volume flow rate DVOL and the front-rear differential pressure ΔP are obtained, and an approximate expression is obtained by a known technique.

  In step S109, the estimated PM accumulation amount MPM is calculated. The estimated PM accumulation amount MPM may be an integrated value of the PM discharge amount, or may be calculated by multiplying the integrated value by a predetermined value. Since the PM emission amount has a correlation with the operation state (engine speed and engine load) of the internal combustion engine 1, the relationship between the PM emission amount and the operation state of the internal combustion engine 1 is obtained in advance through experiments or simulations and is sent to the ECU 10. Remember. In this embodiment, the ECU 10 that processes step S109 corresponds to the accumulation amount estimation means in the present invention.

  In step S110, it is determined whether or not the estimated PM accumulation amount MPM is not less than the lower limit threshold MPML and not more than the upper limit threshold MPMH.

  In this step, it is determined whether or not the estimated PM accumulation amount MPM is within a range where the accuracy of abnormality determination is within an allowable range. That is, when the PM accumulation amount is too small, the difference in front-to-back differential pressure is small between the case where the filter 3 is normal and the case where it is abnormal, so that the determination accuracy decreases. Further, if the amount of accumulated PM is too large, the differential pressure across the filter 3 increases even if the filter 3 is abnormal, and the difference between the differential pressure across the filter 3 is small when the filter 3 is normal and abnormal. Therefore, the determination accuracy is lowered.

  For the lower limit threshold MPML and the upper limit threshold MPMH, optimum values are obtained in advance by experiments or simulations and stored in the ECU 10. The lower limit threshold MPML may be the maximum value of the estimated PM accumulation amount when the differential pressure across the filter 3 reaches the threshold at which the abnormality determination of the filter 3 can be performed in the normal filter 3. That is, assuming that the filter 3 is normal and the time until the differential pressure across the filter 3 reaches the threshold is the longest, the estimated PM when the differential pressure across the filter 3 reaches the threshold in this case Let the accumulation amount be the lower limit threshold MPML. Thereby, when the filter 3 is normal, it can suppress misjudging that it is abnormal.

Further, the upper limit threshold MPMH may be the minimum value of the estimated PM accumulation amount when the differential pressure across the filter 3 reaches the threshold at which the abnormality determination of the filter 3 can be performed in the abnormal filter 3. That is, assuming that the filter 3 is abnormal and the time until the differential pressure across the filter 3 reaches the threshold is the shortest, the estimated PM when the differential pressure across the filter 3 in this case reaches the threshold Let the accumulation amount be the upper threshold MPMH. Thereby, when the filter 3 is abnormal, it can suppress misjudging that it is normal.

  If an affirmative determination is made in step S110, the process proceeds to step S111. On the other hand, if a negative determination is made, the abnormality determination of the filter 3 cannot be performed, and thus this routine is ended.

  In step S111, it is determined whether the slope of the approximate expression calculated in step S108 is greater than or equal to a threshold value TH. The threshold value TH is obtained in advance by experiment or simulation as a lower limit value of the slope when the filter 3 is normal, and is stored in the ECU 10.

  When an affirmative determination is made in step S111, the process proceeds to step S112 and it is determined that the filter 3 is normal. On the other hand, if a negative determination is made in step S111, the process proceeds to step S113, where it is determined that the filter 3 is abnormal. In the present embodiment, the ECU 10 that processes step S110 and subsequent steps corresponds to the determination means in the present invention.

  In the present embodiment, the abnormality determination of the filter 3 is performed based on the inclination. However, if the abnormality determination of the filter 3 using the differential pressure across the filter 3 and the estimated PM accumulation amount is used, other than the inclination The present invention can also be applied to abnormality determination based on the above. For example, in step S110, it is determined whether the abnormality determination of the filter 3 can be performed according to the estimated PM accumulation amount MPM. Instead, the threshold value in step S111 is determined according to the estimated PM accumulation amount MPM. TH may be changed.

  FIG. 5 is a flowchart showing another flow of the abnormality determination of the filter 3 according to the present embodiment. This routine is repeatedly executed by the ECU 10 every predetermined time. Also, steps that are the same as the steps shown in FIG. 4 are denoted by the same reference numerals and description thereof is omitted.

  In the flow shown in FIG. 5, the process proceeds to step S201 after the process of step S109 is completed. In step S201, the threshold TH used in step S111 is calculated based on the estimated PM accumulation amount MPM. Here, assuming that the volume flow rate is the same, the differential pressure across the filter 3 becomes larger when the filter 3 is normal than when it is abnormal. For this reason, when the filter 3 is normal, the inclination is larger than when the filter 3 is abnormal. Therefore, by increasing the threshold value TH according to the estimated PM accumulation amount MPM, the accuracy of the abnormality determination of the filter 3 can be improved.

  The relationship between the estimated PM accumulation amount MPM and the threshold value TH is obtained in advance through experiments or simulations and stored in the ECU 10.

  As described above, according to the present embodiment, it is estimated that separation of PM has occurred due to condensed water when performing abnormality determination of the filter 3 based on the estimated amount of accumulated PM and the differential pressure across the filter 3. Therefore, it is possible to determine the abnormality of the filter 3 with higher accuracy because the estimated amount of accumulated PM is reduced.

(Example 2)
In the present embodiment, it is determined whether or not the abnormality determination of the filter 3 is to be performed based on the amount of condensed water inflow. Since other devices are the same as those in the embodiment, description thereof is omitted.

  Here, in Example 1, the inclination is obtained from the approximate expression indicating the relationship between the volume flow rate and the differential pressure across the filter 3, and whether or not the abnormality determination of the filter 3 is performed based on the estimated PM accumulation amount MPM. Judgment. Alternatively, the inclination threshold is set based on the estimated PM accumulation amount. On the other hand, in this embodiment, the ratio (inclination) of the change amount of the differential pressure across the filter 3 with respect to the change amount of the estimated PM accumulation amount MPM is obtained, and if this ratio is equal to or greater than the threshold value, the filter 3 is normal. judge. Further, it is determined whether or not to perform abnormality determination of the filter 3 based on the amount of condensed water inflow.

  That is, when the filter 3 is normal, the differential pressure across the filter 3 increases as the estimated PM accumulation amount MPM increases. However, when the filter 3 is abnormal, the estimated PM accumulation amount MPM increases. However, the increase in the differential pressure across the filter 3 is slow. That is, when the filter 3 is abnormal, the ratio (inclination) of the amount of change in the differential pressure across the filter 3 to the amount of change in the estimated PM accumulation amount MPM is small. By comparing the inclination with a threshold value, An abnormality determination of the filter 3 can be performed.

  FIG. 6 is a flowchart showing a flow of abnormality determination of the filter 3 according to the present embodiment. This routine is repeatedly executed by the ECU 10 every predetermined time. Also, steps that are the same as the steps shown in FIG. 4 are denoted by the same reference numerals and description thereof is omitted.

  In the flow shown in FIG. 6, when the process of step S103 is completed, the process proceeds to step S301. In step S301, it is determined whether the amount of condensed water inflow is equal to or greater than a threshold value. The threshold value is obtained in advance through experiments or simulations and stored in the ECU 10 as a lower limit value of the inflow amount of condensed water from which the PM accumulated on the filter 3 separates from the filter 3.

  If an affirmative determination is made in step S301, this routine is terminated. That is, in this routine, when PM is separated from the filter 3, the abnormality determination of the filter 3 is prohibited. On the other hand, if a negative determination is made in step S301, the process proceeds to step S302. In this embodiment, the ECU 10 that processes step S301 corresponds to the prohibiting means in the present invention.

  In step S302, the differential pressure ΔP1 across the filter 3 is detected. The differential pressure ΔP1 across the filter 3 is detected by the differential pressure sensor 4.

  In step S303, the estimated PM accumulation amount MPM1 is calculated.

  In step S304, the differential pressure ΔP2 across the filter 3 is detected. The differential pressure ΔP2 across the filter 3 is detected by the differential pressure sensor 4.

  In step S305, the estimated PM accumulation amount MPM2 is calculated.

In step S306, it is determined whether the increase amount ΔMPM of the estimated PM accumulation amount is equal to or greater than a threshold value. The increase amount ΔMPM of the estimated PM accumulation amount is a value obtained by subtracting the estimated PM accumulation amount MPM1 calculated in step S303 from the estimated PM accumulation amount MPM2 calculated in step S305. This value is an estimated PM deposition amount that has increased from the processing of step S303 to the processing of step S305. Further, the threshold value here can be an increase amount at which the accuracy of the inclination calculated in step S307 is within an allowable range. That is, if the increase amount ΔMPM of the estimated PM accumulation amount is too small, the change amount of the differential pressure across the filter 3 is small, so the ratio of the change amount of the differential pressure across the filter 3 to the increase amount ΔMPM of the estimated PM accumulation amount. Even if (slope) is calculated, the error increases. For this reason, there exists a possibility that the precision of abnormality determination may fall. Therefore, after the estimated PM accumulation amount has increased sufficiently, the abnormality determination of the filter 3 is performed. The threshold value is obtained in advance by experiments or the like and stored in the ECU 10. If an affirmative determination is made in step S306, the process proceeds to step S307. On the other hand, if a negative determination is made, the process returns to step S304.

  In step S307, the ratio of the change amount (ΔP2−ΔP1) of the differential pressure across the filter 3 to the increase amount ΔMPM of the estimated PM accumulation amount is calculated as a slope. Then, the process proceeds to step S111.

  As described above, when the estimated amount of accumulated PM is used as a parameter for determining the abnormality of the filter 3, the estimated amount of accumulated PM is not reset when the inflow of condensed water is equal to or greater than the threshold value, but the abnormality determination of the filter 3 is performed. It may be prohibited. That is, erroneous determination can be suppressed by prohibiting abnormality determination when PM is separated from the filter 3 by condensed water.

(Example 3)
In the present embodiment, the abnormality determination of the filter 3 is performed based on the integrated value of the PM amount discharged from the internal combustion engine 1 (hereinafter referred to as PM discharge amount) and the estimated PM accumulation amount. The integrated value of the PM emission amount is reset every time the internal combustion engine 1 is stopped. Here, since the condensed water is generated when the internal combustion engine 1 is started, separation of PM from the filter 3 due to the condensed water does not occur if a sufficient time has elapsed from the starting time of the internal combustion engine 1. Therefore, erroneous determination can be suppressed by determining abnormality of the filter 3 at a time when PM is estimated to be accumulated on the filter 3. Further, in this embodiment, there is no need to calculate the condensed water inflow amount.

  Here, FIG. 7 is a diagram showing the relationship between the estimated amount of accumulated PM and the differential pressure across the filter 3. FIG. 7 is a diagram abstracted for explanation. In FIG. 7, the solid line indicates the case where the filter 3 is normal, and the alternate long and short dash line indicates the case where the filter 3 is abnormal. In this embodiment, it is assumed that all PM discharged from the internal combustion engine 1 accumulates on the filter 3. That is, it is considered that the increase amount of the estimated PM deposition amount per unit time is equal to the increase amount of the integrated value of the PM discharge amount per unit time.

  The integrated value of the PM emission amount from when the engine is started is reset every time the internal combustion engine 1 is started. Then, the integrated value of the PM emission amount increases according to the operating state from the start of the internal combustion engine 1. The estimated PM accumulation amount is not reset even when the internal combustion engine 1 is started, and increases according to the operating state of the internal combustion engine 1. The degree of increase is higher when the filter 3 is normal than when the filter 3 is abnormal. That is, compared with the case where the filter 3 is abnormal, when the filter 3 is normal, the increase amount of the differential pressure across the filter 3 with respect to the increase amount of the estimated PM accumulation amount becomes large. For this reason, the inclination in FIG. 7 becomes larger when the filter 3 is normal.

  In this embodiment, when the estimated PM accumulation amount is equal to or higher than the lower limit threshold MPMDPFIL and equal to or lower than the upper limit threshold MPMH, the abnormality determination of the filter 3 is permitted. That is, when the estimated PM accumulation amount is less than the lower limit threshold value MPMDPFIL and more than the upper limit threshold value MPMH, abnormality determination of the filter 3 is prohibited.

  The lower limit threshold value MPMDPFIL may be the maximum value of the estimated PM accumulation amount when the differential pressure across the filter 3 reaches the threshold value H at which the abnormality determination of the filter 3 can be performed in the normal filter 3. Here, the increase in the differential pressure across the filter 3 is slowest when PM is separated from the filter 3 every time the internal combustion engine 1 is started. Therefore, when the filter 3 is normal and the integrated value of the PM emission amount is the estimated PM accumulation amount, the estimated PM accumulation amount is reset every time the internal combustion engine 1 is started. The slowest rise is the slowest.

  As described above, assuming that the filter 3 is normal and the time until the differential pressure across the filter 3 reaches the threshold value H is the longest, the differential pressure across the filter 3 in this case reaches the threshold value H. The estimated PM accumulation amount at the time is defined as a lower limit threshold value MPMDPFIL. Thereby, when the filter 3 is normal, it can suppress misjudging that it is abnormal. Note that the lower limit threshold value MPMDPFIL can be said to be an estimated PM accumulation amount in which the differential pressure across the filter 3 rises to the threshold value H if the filter 3 is normal even when PM is peeled off from the filter 3.

  If the estimated PM accumulation amount is less than the lower limit threshold value MPMDPFIL, the PM accumulation amount is too small. That is, even when the filter 3 is normal, since PM is not deposited on the filter 3, the differential pressure across the filter 3 may be small and may be less than the threshold value H. However, when the filter 3 is normal, the time until the differential pressure across the filter 3 becomes equal to or higher than the threshold value H is shorter than when the filter 3 is abnormal. Therefore, when the filter 3 is normal, the lower limit threshold value MPMDPFIL is set as the beginning of a period in which the differential pressure across the filter 3 is equal to or higher than the threshold value H. The solid line in FIG. 7 shows the transition when the filter 3 is normal in a situation where the differential pressure across the filter 3 is difficult to increase. Note that the lower limit threshold value MPMDPFIL according to the present embodiment may be equal to the lower limit threshold value MPML according to the above embodiment.

  Further, the upper limit threshold MPMH in FIG. 7 may be the minimum value of the estimated PM accumulation amount when the differential pressure across the filter 3 reaches the threshold H at which the abnormality determination of the filter 3 can be performed in the abnormal filter 3. Here, the increase in the differential pressure across the filter 3 is the fastest when PM is not separated from the filter 3 even when the internal combustion engine 1 is started. Therefore, when the filter 3 is abnormal, the increase in the differential pressure across the filter 3 is the fastest when the estimated PM accumulation amount is not reset. As described above, assuming that the filter 3 is abnormal and the time until the differential pressure across the filter 3 reaches the threshold value H is the shortest, the differential pressure across the filter 3 in this case reaches the threshold value H. The estimated PM accumulation amount at that time is defined as an upper limit threshold MPMH. Thereby, when the filter 3 is abnormal, it can suppress misjudging that it is normal.

  If the estimated PM accumulation amount exceeds the upper limit threshold MPMH, the PM accumulation amount increases too much, and if the abnormality determination of the filter 3 is performed, an erroneous determination may occur. That is, even when an abnormality occurs in the filter 3, as PM is collected in the filter 3, the differential pressure across the filter 3 may increase and become greater than or equal to the threshold value H. However, when an abnormality occurs in the filter 3, it takes time until the differential pressure across the filter 3 becomes equal to or higher than the threshold value H. Therefore, when abnormality occurs in the filter 3, the upper limit threshold MPMH is set as the end of the period in which the differential pressure across the filter 3 is less than the threshold H. The dashed-dotted line in FIG. 7 has shown transition when the filter 3 is abnormal in the situation where the differential pressure before and after the filter 3 is likely to increase. The upper limit threshold MPMH according to the present embodiment may be equal to the upper limit threshold MPMH according to the above embodiment.

  When the estimated PM accumulation amount is equal to or higher than the lower limit threshold MPMDPFIL and equal to or lower than the upper limit threshold MPMH, if the differential pressure across the filter 3 is equal to or higher than the threshold H, the slope is sufficiently large and the filter 3 is determined to be normal. If it is less than the threshold value H, the slope is small and it can be determined that the filter 3 is abnormal.

  The threshold value H at which the abnormality determination of the filter 3 can be performed may be determined according to the accuracy of the abnormality determination and the frequency of performing the abnormality determination. That is, if the abnormality determination is performed when the integrated value of the PM emission amount is large, the accuracy of the abnormality determination is increased, but the frequency of performing the abnormality determination is decreased. Further, if the internal combustion engine 1 is stopped while waiting for the integrated value of the PM emission amount to increase, the opportunity to perform abnormality determination is lost. Therefore, the threshold value H may be changed depending on which is prioritized.

  FIG. 8 is a flowchart showing a flow of abnormality determination of the filter 3 according to the present embodiment. This routine is repeatedly executed by the ECU 10 every predetermined time. Also, steps that are the same as the steps shown in FIG. 4 are denoted by the same reference numerals and description thereof is omitted.

  In step S401, the PM emission amount MPMENGO is calculated. For example, the PM amount discharged from the internal combustion engine 1 is calculated based on the fuel injection amount and the like.

  In step S402, the integrated value MPMDPFI of the PM emission amount MPMENGO is calculated. The integrated value MPMDPFI of the PM emission amount MPMENGO is reset every time the internal combustion engine 1 is started.

  In step S403, it is determined whether or not the PM discharge amount integrated value MPMDPFI is greater than or equal to the lower limit threshold value MPMDPFIL. As the lower limit threshold value MPMDPFIL, an optimal value is obtained in advance through experiments or simulations and stored in the ECU 10.

  If an affirmative determination is made in step S403, the process proceeds to step S106. On the other hand, if a negative determination is made, the process returns to step S402. In steps S401 to S403, the normal filter 3 is prevented from being erroneously determined to be abnormal due to the influence of separation of PM from the filter 3 by condensed water. That is, even if the PM is separated from the filter 3, the abnormality determination of the filter 3 is not performed until the differential pressure across the filter 3 becomes equal to or higher than the threshold value H. An abnormality determination can be performed.

  In the flow shown in FIG. 8, the process proceeds to step S404 after the process of step S109. In step S404, it is determined whether or not the estimated PM accumulation amount MPM is equal to or less than the upper limit threshold MPMH. As the upper limit threshold MPMH, an optimal value is obtained in advance through experiments or simulations and stored in the ECU 10. If an affirmative determination is made in step S404, the process proceeds to step S111. On the other hand, if a negative determination is made, there is a risk of erroneous determination if the abnormality of the filter 3 is determined. In step S109 and step S404, it is suppressed that the abnormal filter 3 is erroneously determined to be normal. That is, when the differential pressure across the abnormal filter 3 is greater than or equal to the threshold value H, the abnormality determination of the filter 3 is not performed.

  As described above, by limiting the timing of performing the abnormality determination of the filter 3 based on the estimated PM accumulation amount MPM, it is possible to reduce the influence of separation of the PM from the filter 3 due to condensed water. Thereby, the accuracy of the abnormality determination of the filter 3 can be improved. Further, since it is not necessary to estimate the amount of condensed water generated, the adaptation work and the actual control can be simplified.

(Example 4)
FIG. 9 is a diagram showing a schematic configuration of the internal combustion engine and its exhaust system according to the present embodiment. In this embodiment, a PM sensor 6 is provided in the exhaust passage 2 downstream of the filter 3 instead of the differential pressure sensor 4 shown in FIG. The output signal of the PM sensor 6 is input to the ECU 10.

As this PM sensor 6, for example, a sensor in which a current flows according to the amount of PM attached to the electrode is used. By reading the magnitude of this current, the amount of PM in the exhaust can be obtained. The PM sensor 6 may be any sensor that can measure the PM amount. This PM amount may be an instantaneous value or may be the total amount of PM in a relatively long period. And filter 3
The abnormality determination of the filter 3 can be carried out based on the downstream PM amount.

  For example, as the amount of accumulated PM increases, PM is more easily collected by the filter 3, so that the amount of PM passing through the filter 3 decreases. On the other hand, when an abnormality such as a crack occurs in the filter 3, the amount of PM flowing out from the filter 3 increases. For this reason, for example, the abnormality of the filter 3 can be determined by comparing the PM amount flowing out from the filter 3 with a threshold value. However, when the PM peels from the filter 3, the PM easily passes through the filter 3. For this reason, the detection value of PM sensor 6 may become large. Thus, in addition to the abnormality of the filter 3, the detection value of the PM sensor 6 increases due to the separation of the PM from the filter 3, so that the accuracy of the abnormality determination of the filter 3 based on the detection value of the PM sensor 6 can be reduced. On the other hand, when it is estimated that PM has peeled from the filter 3, it is possible to suppress a decrease in determination accuracy by resetting the estimated amount of accumulated PM.

  In this embodiment and the above-described embodiment, the PM emission amount is estimated based on the operating state of the internal combustion engine 1. Instead, a PM sensor is provided in the exhaust passage 2 upstream of the filter 3. The PM discharge amount may be detected by the PM sensor.

  FIG. 10 is a flowchart showing a flow of abnormality determination of the filter 3 according to the present embodiment. This routine is repeatedly executed by the ECU 10 every predetermined time. Further, steps in which the same processing as that of the flow is performed are denoted by the same reference numerals and description thereof is omitted.

  In the flow shown in FIG. 10, step S501 is processed after step S106. In step S501, the ratio of the PM amount passing through the filter 3 to the PM amount flowing into the filter 3 is calculated as a passing rate KPM. Here, even if the filter 3 is normal, there is PM passing through the filter 3. The passage rate KPM decreases as the estimated PM deposition amount MPM increases. Further, the passing rate KPM decreases as the volume flow rate DVOL decreases. That is, since the passage rate KPM has a correlation with the estimated PM accumulation amount MPM and the volume flow rate DVOL, these relationships are obtained in advance through experiments or simulations and stored in the ECU 10. Further, the estimated PM accumulation amount MPM used in this step is reset in step S105 when the PM is separated from the filter 3 by the condensed water.

  In step S502, an integrated value of the PM amount passing through the filter 3 (passed PM amount integrated value MPMDPFO) is calculated. By integrating the PM emission amount MPMENGO calculated in step S401 by the value obtained by multiplying the passage rate KPM calculated in step S501, the passing PM amount integrated value MPMDPFO is calculated.

  In step S503, it is determined whether or not the passing PM amount integrated value MPMDPFO is equal to or greater than a threshold value. This threshold is a lower limit value of the passing PM amount integrated value MPMDPFO where the accuracy of the abnormality determination of the filter 3 is within an allowable range. This value is obtained in advance by experiment or simulation and stored in the ECU 10.

  Here, the PM sensor 6 detects the amount of PM by, for example, passing a current between a pair of electrodes and changing a resistance value due to PM deposited between the electrodes. For this reason, it is difficult to detect the amount of PM unless a certain amount of PM is deposited between the electrodes. The PM amount can be detected when the passing PM amount integrated value MPMDPFO is equal to or greater than a threshold value.

  If an affirmative determination is made in step S503, the process proceeds to step S504. On the other hand, if a negative determination is made, the process returns to step S401.

In step S504, it is determined whether or not the PM amount detected by the PM sensor 6 is equal to or less than a threshold value TH. The threshold value TH is obtained in advance through experiments or simulations and stored in the ECU 10 as an upper limit value when the filter 3 is normal. That is, if a crack or a melt loss occurs in the filter 3, the amount of PM passing through the filter 3 increases, and thus the amount of PM detected by the PM sensor 6 increases. Therefore, when the amount of PM detected by the PM sensor 6 exceeds the threshold value TH, it can be determined that the filter 3 is abnormal.

  If an affirmative determination is made in step S504, the process proceeds to step S112. On the other hand, if a negative determination is made, the process proceeds to step S113.

  As described above, according to the present embodiment, even when the PM sensor 6 is used, the influence of the separation of the PM from the filter 3 due to the condensed water can be reduced. Accuracy can be improved.

1 Internal combustion engine 2 Exhaust passage 3 Filter 4 Differential pressure sensor 5 Fuel injection valve 6 PM sensor 10 ECU
11 Accelerator pedal 12 Accelerator opening sensor 13 Crank position sensor

Claims (5)

A filter provided in an exhaust passage of the internal combustion engine for collecting particulate matter in the exhaust;
A deposition amount estimating means for estimating the amount of particulate matter deposited on the filter;
A sensor whose detection value changes according to the amount of particulate matter deposited on the filter;
Determination means for determining an abnormality of the filter based on the amount of particulate matter estimated by the accumulation amount estimation means, and a detection value of the sensor;
In the abnormality determination device for the filter provided with
A condensed water inflow amount estimating means for estimating an amount of condensed water flowing into the filter;
A deposition amount changing means for reducing the amount of particulate matter estimated by the deposition amount estimating means when the amount of condensed water estimated by the condensed water inflow amount estimating means is equal to or greater than a threshold;
An abnormality determination device for a filter comprising:   2. The filter abnormality determination device according to claim 1, wherein the accumulation amount changing unit sets the amount of particulate matter estimated by the accumulation amount estimation unit to zero.   3. The filter abnormality determination device according to claim 1, wherein the determination unit sets a threshold for determining abnormality of the filter based on the amount of particulate matter estimated by the accumulation amount estimation unit.   The said determination means performs abnormality determination of the said filter, only when the amount of the particulate matter estimated by the said deposition amount estimation means is in a predetermined range, The any one of Claim 1 to 3 Filter abnormality determination device. A filter provided in an exhaust passage of the internal combustion engine for collecting particulate matter in the exhaust;
A deposition amount estimating means for estimating the amount of particulate matter deposited on the filter;
A sensor whose detection value changes according to the amount of particulate matter deposited on the filter;
Determination means for determining abnormality of the filter based on the amount of particulate matter estimated by the accumulation amount estimation means and the detection value of the sensor;
In the abnormality determination device for the filter provided with
A condensed water inflow amount estimating means for estimating an amount of condensed water flowing into the filter;
Prohibiting means for prohibiting determination by the determining means when the amount of condensed water estimated by the condensed water inflow amount estimating means is greater than or equal to a threshold;
An abnormality determination device for a filter comprising:

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