JP2014098361A - Particulate filter PM amount calculation device - Google Patents

Abstract

An object of the present invention is to suppress a decrease in calculation accuracy due to the influence of condensed water in a PM accumulation amount calculation device for calculating the PM accumulation amount of a particulate filter disposed in an exhaust passage of an internal combustion engine. .
In order to solve the above-described problems, the present invention provides a PM accumulation amount calculation device for calculating the PM accumulation amount of a particulate filter from the amount of PM discharged from an internal combustion engine (PM emission amount). Using the amount of condensed water flowing into the curative filter as a parameter, the amount of PM that is separated or desorbed from the particulate filter (PM separation amount) is obtained, and the calculated value of the PM deposition amount is corrected according to the PM separation amount. I made it.
[Selection] Figure 3

Description

  The present invention relates to a technique for obtaining a PM (Particulate Matter) accumulation amount of a particulate filter disposed in an exhaust passage of an internal combustion engine.

  As a technique for obtaining the PM accumulation amount of the particulate filter arranged in the exhaust passage of the internal combustion engine, the PM accumulation amount is calculated using the amount of PM discharged from the internal combustion engine and the amount of PM oxidized in the particulate filter as parameters. The technique to do is known (for example, refer patent document 1).

Japanese Patent Laid-Open No. 2005-054632 Japanese Patent Application Laid-Open No. 08-260942 Japanese Patent Laid-Open No. 11-153020 JP 2009-097410 A

  By the way, according to the knowledge of the present inventor, it was found that when condensed water is present in the particulate filter, the PM collected in the particulate filter is peeled off. When separation of PM due to condensed water occurs, an error between the calculated PM deposition amount and the actual PM deposition amount increases. Therefore, if the particulate filter regeneration time is determined using the calculated value of the PM accumulation amount, or if the particulate filter failure is diagnosed, the regeneration time becomes inappropriate or the accuracy of failure diagnosis is improved. It may decrease.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to determine the effect of condensed water in a PM accumulation amount calculation device that calculates the PM accumulation amount of a particulate filter disposed in an exhaust passage of an internal combustion engine. This is to suppress a decrease in the calculation accuracy due to.

  In order to solve the above-described problems, the present invention provides a PM accumulation amount calculation device that calculates the PM accumulation amount of a particulate filter from the amount of PM discharged from an internal combustion engine (PM emission amount). With the amount of condensed water to be used as a parameter, the amount of PM peeled off or desorbed from the particulate filter (PM peel amount) was obtained, and the calculated value of the PM deposition amount was corrected according to the PM peel amount.

Specifically, the particulate filter calculating device for particulate filter according to the present invention includes:
First calculating means for calculating a PM emission amount which is an amount of PM discharged from the internal combustion engine;
Second calculating means for calculating a PM peeling amount, which is the amount of PM peeled off from the particulate filter, with the amount of condensed water flowing into the particulate filter disposed in the exhaust passage of the internal combustion engine as a parameter;
Third calculation means for calculating a PM deposition amount that is the amount of PM collected or deposited on the particulate filter, using the PM discharge amount and the PM peeling amount as parameters,
I was prepared to.

When the atmospheric temperature of the exhaust passage is low, such as when the internal combustion engine is cold started, condensed water may be generated in the exhaust passage. When such condensed water flows into the particulate filter, a part of the PM collected or deposited on the particulate filter is separated or detached. As a result, the amount of PM deposited on the particulate filter decreases.

  Therefore, according to the method in which the PM accumulation amount of the particulate filter is calculated (estimated) based on the amount of PM discharged from the internal combustion engine (PM emission amount), separation or desorption of PM due to the influence of condensed water occurs. In this case, there is a possibility that an error between the estimated value of the PM deposition amount (hereinafter referred to as “estimated PM deposition amount”) and the actual PM deposition amount (hereinafter referred to as “actual PM deposition amount”) may increase. .

  On the other hand, the particulate filter PM calculation device of the particulate filter according to the present invention estimates (calculates) the PM deposition amount of the particulate filter using the PM discharge amount and the PM separation amount as parameters. It is possible to suppress an error from the actual PM deposition amount. Therefore, according to the PM accumulation amount calculating device of the particulate filter according to the present invention, it is possible to suppress a decrease in estimation accuracy (calculation accuracy) due to the influence of condensed water.

  Here, the third calculation means according to the present invention may calculate the estimated PM accumulation amount by integrating the value obtained by subtracting the PM removal amount from the PM discharge amount, or alternatively, the PM separation amount may be calculated from the integrated value of the PM discharge amount. The estimated PM deposition amount may be calculated by subtracting the amount.

In addition, this invention can also be grasped | ascertained as a failure diagnosis apparatus provided with the above-mentioned PM accumulation amount calculating apparatus. In that case, the particulate filter failure diagnosis apparatus according to the present invention is:
The above-mentioned PM accumulation amount calculation device;
A sensor whose detection value changes according to the amount of PM deposited on the particulate filter;
A diagnostic means for performing failure diagnosis of the particulate filter based on the detection value of the sensor;
Correction means for correcting a judgment criterion for failure diagnosis according to the PM accumulation amount calculated by the third calculation means;
You may make it provide.

  When the condensed water flows into the particulate filter, a part of the PM is separated or detached from the particulate filter, so that the actual PM deposition amount decreases. Accordingly, the detection value of the sensor decreases. Therefore, there is a possibility that the detection value of the sensor or the value obtained from the detection value falls below the determination criterion. When such a situation occurs, there is a possibility that the particulate filter may be erroneously diagnosed as having failed even though the particulate filter has not failed.

  On the other hand, when the determination criterion is corrected according to the PM accumulation amount calculated by the third calculation means, it is possible to suppress the occurrence of the erroneous diagnosis as described above. Therefore, it is possible to suppress a decrease in diagnostic accuracy due to the influence of condensed water.

In addition, the particulate filter failure diagnosis apparatus according to the present invention includes:
The above-mentioned PM accumulation amount calculation device;
A sensor whose detection value changes according to the amount of PM deposited on the particulate filter;
A diagnostic means for performing failure diagnosis of the particulate filter based on the detection value of the sensor;
Permission means for permitting failure diagnosis by the diagnosis means, provided that the amount of accumulated PM calculated by the third calculation means is equal to or greater than a threshold value;
You may make it provide.

As described above, when the ambient temperature of the exhaust passage is low, PM may be separated or detached from the particulate filter due to the influence of condensed water. In this case, the detection value of the sensor changes greatly. However, even if the PM is peeled off from the filter, if the operation of the internal combustion engine is continued thereafter, PM newly discharged from the internal combustion engine accumulates on the filter. Furthermore, since the atmospheric temperature in the exhaust passage rises as the operation of the internal combustion engine continues, almost no condensed water is generated.

  Therefore, when the operating time of the internal combustion engine becomes longer, a relatively large amount of PM accumulates on the particulate filter. When failure diagnosis is performed after such a state is reached, it is possible to suppress a decrease in diagnosis accuracy due to the influence of condensed water. That is, even when PM is separated or detached from the particulate filter due to the influence of the condensed water, the failure diagnosis is performed after exhausting PM from the internal combustion engine to such an extent that the particulate filter can be properly diagnosed. If implemented, a decrease in diagnostic accuracy can be suppressed.

  The sensor used in the failure diagnosis device for the particulate filter includes a differential pressure sensor for detecting the differential pressure across the particulate filter, or a PM sensor for detecting the amount of PM contained in the exhaust gas flowing out from the particulate filter. Can be used.

  ADVANTAGE OF THE INVENTION According to this invention, the fall of the calculation precision by the influence of condensed water can be suppressed in PM deposit amount calculating apparatus which calculates PM deposit amount of the particulate filter arrange | positioned in the exhaust passage of an internal combustion engine.

It is a figure which shows schematic structure of the internal combustion engine and its exhaust system in a 1st Example. It is a figure which shows the relationship between the integrated value of PM discharge | emission amount, and filter differential pressure before and after. It is a flowchart which shows the calculation processing routine of PM deposition amount. It is a flowchart which shows the failure diagnosis processing routine in a 2nd Example. It is a flowchart which shows the other example of the failure diagnosis processing routine in 2nd Example. It is a figure which shows schematic structure of the internal combustion engine and its exhaust system in a 3rd Example. It is a flowchart which shows the other example of the failure diagnosis processing routine in a 3rd 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 1>
First, an embodiment of a particulate filter PM amount calculation apparatus according to the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine to which the present invention is applied and its exhaust system. The internal combustion engine 1 shown in FIG. 1 is a compression ignition type internal combustion engine (diesel engine) having four cylinders, but may be a spark ignition type internal combustion engine (gasoline engine).

  The internal combustion engine 1 includes a fuel injection valve 5 that injects fuel into the cylinder. The internal combustion engine 1 is connected to an exhaust passage 2 through which gas (exhaust gas) combusted in the cylinder flows. A particulate filter 3 that collects particulate matter (PM) in the exhaust is provided in the middle of the exhaust passage 2. The particulate filter 3 is, for example, a wall flow type filter in which a passage whose upstream end is closed by a plug and a passage whose downstream end is closed by a plug are alternately arranged.

The internal combustion engine 1 configured as described above is provided with an ECU 10. The ECU 10 is an electronic control unit that includes a CPU, a ROM, a RAM, a backup RAM, and the like.
The ECU 10 is electrically connected to various sensors such as the differential pressure sensor 4, the accelerator opening sensor 12, and the crank position sensor 13.

  The differential pressure sensor 4 is attached to the exhaust passage 2 and detects a difference between the exhaust pressure upstream of the particulate filter 3 and the exhaust pressure downstream of the particulate filter 3 (hereinafter referred to as “filter differential pressure before and after”). It is a sensor. This differential pressure sensor 4 is an embodiment of the sensor according to the present invention. The accelerator opening sensor 12 is a sensor that outputs an electrical signal correlated with the operation amount (accelerator opening) of the accelerator pedal 11. The crank position sensor 13 is a sensor that outputs an electrical signal correlated with the rotational position of the output shaft (crankshaft) of the internal combustion engine 1, and the crankshaft rotational speed (engine speed) is determined from the output signal of the crank position sensor 13. Is calculated.

  The ECU 10 controls the operation state of the internal combustion engine 1 (for example, the valve opening timing (fuel injection timing) and the valve opening time (fuel injection amount) of the fuel injection valve 5) based on the output signals of the various sensors described above. The ECU 10 executes a process of calculating (estimating) the amount of PM (PM deposition amount) collected or deposited on the particulate filter 3 based on the output signals of the various sensors described above.

  Hereinafter, a method for calculating the PM deposition amount in this embodiment will be described. First, the ECU 10 calculates the amount of PM discharged from the internal combustion engine 1 per unit time (PM discharge amount) using the fuel injection amount, the intake air amount, the engine speed, etc. as parameters, and integrates the PM discharge amount. To do. Since the integrated value of the PM emission amount is substantially equal to the amount of PM collected or deposited on the particulate filter 3 (PM accumulation amount), the integrated value of the PM emission amount is an estimated value of the PM accumulation amount (estimated PM accumulation amount). ).

  Further, it may be considered that the PM discharge amount is collected by the particulate filter 3 at a predetermined rate. In that case, the PM emission amount may be multiplied by a coefficient corresponding to the predetermined ratio, and the integrated value of the calculation result may be used as the PM deposition amount. The predetermined ratio may be a fixed value, but may be a variable value that is changed according to the flow rate (flow rate) of the exhaust gas. Since the flow rate of the exhaust gas is equal to the intake air amount of the internal combustion engine 1, the relationship between the intake air amount and a predetermined ratio (coefficient) may be experimentally obtained in advance.

  The calculation process of the estimated PM accumulation amount by the above method is repeated as long as the operation of the internal combustion engine 1 is continued. However, when the process (regeneration process) for oxidizing and removing the PM collected or deposited on the particulate filter 3 is executed, the estimated PM deposition amount is reset.

By the way, when the internal combustion engine 1 is cold-started and the atmosphere temperature in the exhaust passage 2 is low, water vapor (H ₂ O) contained in the exhaust is condensed and condensed water is generated. In addition, when the internal combustion engine 1 has been stopped for a relatively long time, condensed water is generated in the exhaust passage 2. When the condensed water generated in this way flows into the particulate filter 3, a part of the PM collected or deposited on the particulate filter 3 is peeled off or detached.

Here, the relationship between the integrated value of the PM emission amount and the differential pressure before and after the filter is shown in FIG. A, B, and C in FIG. 2 are values when the operation stop state of the internal combustion engine 1 continues for one day. When the operation stop state of the internal combustion engine 1 becomes longer, the wall surface temperature of the exhaust pipe decreases, and moisture in the exhaust is condensed at the next engine start. For this reason, condensed water flows into the particulate filter 3. Therefore, before the operation of the internal combustion engine 1 is stopped, the differential pressure across the filter increases approximately in proportion to the integrated value of the PM emission amount, but the internal combustion engine 1 is restarted at A, B, and C in FIG. Each time it is applied, the differential pressure across the filter decreases. This is presumably because the condensed water flowing into the particulate filter 3 peels or desorbs the PM collected or deposited on the particulate filter 3. Therefore, according to the method of using the integrated value of the PM emission amount as the estimated PM accumulation amount or the method of using the integrated value of the value obtained by multiplying the PM emission amount and the coefficient as the estimated PM accumulation amount, the condensed water flows into the particulate filter 3. When this is done, the error between the estimated PM accumulation amount and the actual PM accumulation amount may increase.

  Therefore, in this embodiment, the estimated PM deposition amount is corrected based on the amount of PM that is separated or desorbed from the particulate filter 3 due to the influence of condensed water (PM separation amount).

  The amount of PM separation correlates with the amount of condensed water flowing into the particulate filter 3 (hereinafter referred to as “condensed water inflow amount”). For example, the amount of PM separation increases when the amount of condensed water inflow is large compared to when the amount of condensed water inflow is small. Therefore, if the correlation between the condensed water inflow amount and the PM separation amount is experimentally obtained in advance, the PM separation amount can be specified (estimated) using the condensed water inflow amount as a parameter.

  The amount of condensed water inflow is the ratio of the amount of condensed water generated in the exhaust passage 2 upstream of the particulate filter 3 (hereinafter referred to as “condensed water generation amount”) and the ratio of the amount of condensed water inflow to the amount of condensed water generated. (Inflow rate) can be calculated as parameters.

The amount of condensed water generated (in other words, the amount of saturated water vapor generated in the exhaust passage 2 upstream from the particulate filter 3) is determined by the wall surface temperature of the exhaust pipe that defines the exhaust passage 2 upstream from the particulate filter 3 and the exhaust gas. can be calculated from the amount of water vapor (H 2 _O), included. The wall surface temperature of the exhaust pipe can be calculated using the heat capacity of the exhaust pipe upstream of the particulate filter 3, the flow rate of the exhaust, and the temperature of the exhaust as parameters. The exhaust temperature may be measured by an exhaust temperature sensor or may be calculated by a calculation model. On the other hand, the amount of water vapor (H ₂ O) contained in the exhaust can be calculated from the fuel injection amount.

  Further, the inflow rate can be calculated using the flow rate (flow rate) of the exhaust gas as a parameter. Since the flow rate (flow rate) of the exhaust gas correlates with the intake air amount of the internal combustion engine 1, the inflow rate can be calculated using the detection value of a sensor (for example, an air flow meter) that detects the intake air amount as a parameter.

  Next, as a method of correcting the estimated PM accumulation amount based on the condensate inflow amount, a method of subtracting the PM separation amount from the integrated value of the PM discharge amount, and a value obtained by subtracting the PM separation amount from the PM discharge amount are integrated. The method can be used. According to these methods, even when PM is separated or desorbed from the particulate filter 3 due to the influence of condensed water, an error between the estimated PM accumulation amount and the actual PM accumulation amount can be suppressed to be small. That is, the estimation accuracy (calculation accuracy) of the estimated PM accumulation amount can be increased.

  Hereinafter, the calculation procedure of the estimated PM deposition amount will be described with reference to FIG. FIG. 3 is a flowchart showing a routine for calculating the PM accumulation amount. This arithmetic processing routine is stored in advance in the ROM or the like of the ECU 10 and is periodically executed by the ECU 10 (CPU).

In the arithmetic processing routine of FIG. 3, the ECU 10 first reads various data in S101. For example, the ECU 10 reads data such as an exhaust flow rate (intake air amount), an exhaust temperature, and a fuel injection amount.

  In the process of S102, the ECU 10 calculates the wall surface temperature of the exhaust pipe upstream from the particulate filter 3. Specifically, the ECU 10 calculates the wall surface temperature using the heat capacity of the exhaust pipe, the exhaust gas flow rate, and the exhaust gas temperature as parameters. In addition, since the heat capacity of the exhaust pipe is constant, a map or a function expression for deriving the wall surface temperature using the exhaust flow rate and the exhaust temperature as arguments may be created in advance.

In the process of S103, the ECU 10 calculates the amount of water vapor (H ₂ O) contained in the exhaust gas using the fuel injection amount as a parameter.

In the process of S104, the ECU 10 calculates the amount of condensed water generated using the wall surface temperature obtained in the process of S102 and the amount of water vapor (H ₂ O) obtained in the process of S103 as parameters. At this time, the correlation between the wall surface temperature, the amount of water vapor (H ₂ O), and the amount of condensed water generated may be stored in advance in the ROM of the ECU 10 in a map or functional form.

  In the process of S105, the ECU 10 calculates the inflow rate of the condensed water. Specifically, the ECU 10 calculates the inflow rate using a map or a function expression for deriving the inflow rate using the exhaust gas flow rate as an argument.

  In the process of S106, the ECU 10 calculates the amount of condensed water flowing into the particulate filter 3 (condensed water inflow amount). Specifically, the ECU 10 calculates the amount of condensed water inflow by multiplying the amount of condensed water generated in S104 by the inflow rate determined in S105.

  In S107, the ECU 10 calculates the PM separation amount using the condensed water inflow amount obtained in S106 as a parameter. At that time, a map or a function expression for deriving the PM separation amount using the amount of condensed water inflow as an argument may be obtained in advance. Here, the ECU 10 executes the processing of S102 to S107, thereby realizing the second calculation means according to the present invention.

  In the processing of S108, the ECU 10 calculates the PM emission amount from the operating state (fuel injection amount, intake air amount, engine speed, etc.) of the internal combustion engine 1. When a PM sensor is attached to the exhaust passage upstream from the particulate filter 3, the detected value of the PM sensor may be used as the PM discharge amount. Here, the ECU 10 executes the process of S108, thereby realizing the first calculation means according to the present invention.

  In the process of S109, the ECU 10 calculates the estimated PM accumulation amount. Specifically, the ECU 10 calculates the estimated PM accumulation amount by integrating the value obtained by subtracting the PM peeling amount obtained in S107 from the PM discharge amount obtained in S108. In addition, the ECU 10 may calculate the estimated PM accumulation amount by subtracting the PM separation amount obtained in S107 from the integrated value of the PM discharge amount obtained in S108. As described above, the ECU 10 executes the process of S109, thereby realizing the third calculation means according to the present invention.

  As described above, when the estimated PM accumulation amount is obtained in accordance with the arithmetic processing routine of FIG. 3, even if condensed water is generated in the exhaust passage upstream of the particulate filter 3, the estimated PM accumulation amount and the actual PM accumulation are determined. The error from the amount can be kept small. As a result, the estimation accuracy (calculation accuracy) of the estimated PM accumulation amount can be increased.

In the arithmetic processing routine described above, the processes of S102 to S107 can be combined into one process. For example, a function equation or a calculation model for deriving the PM separation amount using arguments of the heat capacity of the exhaust pipe, the flow rate of the exhaust gas, the exhaust gas temperature, and the fuel injection amount are created in advance. It may be used to calculate the amount of PM peeling.

<Example 2>
Next, an embodiment of a particulate filter failure diagnosis apparatus according to the present invention will be described with reference to FIG.

  The failure diagnosing device in the present embodiment is a device that diagnoses that the particulate filter 3 is broken on the condition that the detected value of the differential pressure sensor 4 is below the criterion. The “determination criterion” here corresponds to a minimum value that can be taken by the detection value of the differential pressure sensor 4 when the particulate filter 3 is normal and condensed water does not flow into the particulate filter 3.

  By the way, when the failure diagnosis of the particulate filter 3 is performed based on the detection value of the differential pressure sensor 4 when the condensed water flows into the particulate filter 3 or immediately after the inflow, the particulate filter 3 is normal. Regardless, the detection value of the differential pressure sensor 4 may fall below the threshold value.

  Therefore, the failure diagnosis apparatus of the present embodiment corrects the determination criterion based on the estimated PM accumulation amount calculated by the above-described PM accumulation amount calculation device, and the detection value of the differential pressure sensor 4 is lower than the corrected determination criterion. On the condition, the particulate filter 3 is diagnosed as having a failure. The correction of the determination criterion is performed so that the determination criterion becomes a smaller value when the estimated PM accumulation amount is small than when it is large.

  Hereinafter, the execution procedure of the failure diagnosis process in the present embodiment will be described with reference to FIG. FIG. 4 is a flowchart showing a failure diagnosis processing routine in the present embodiment. This failure diagnosis processing routine is stored in advance in the ROM of the ECU 10 and is periodically executed by the ECU 10 (CPU).

  In the failure diagnosis processing routine, the ECU 10 first reads various data in the processing of S201. For example, the ECU 10 reads data such as the exhaust flow rate (intake air amount), the exhaust temperature, the fuel injection amount, the detection value of the differential pressure sensor 4 (differential pressure before and after the filter), and the like.

  In the process of S202, the ECU 10 calculates the estimated PM accumulation amount using the exhaust gas flow rate (intake air amount), the exhaust gas temperature, and the fuel injection amount read in S201 as parameters. The calculation procedure at this time is the same as the processing of S102 to S109 of FIG.

  In the process of S203, the ECU 10 corrects the determination criterion using the estimated PM accumulation amount obtained in the process of S202 as a parameter. In that case, ECU10 correct | amends so that a criterion may become a small value compared with the time when estimation PM accumulation amount is small. In addition, the correction amount of the determination criterion may be determined according to the amount of PM peeling used for calculating the estimated PM deposition amount. For example, the correction amount may be increased when the amount of PM peeling is large compared to the case where the amount of PM peeling is small (the determination criterion after correction may be decreased). Note that the correction means according to the present invention is realized when the ECU 10 executes the process of S203.

In the process of S204, the ECU 10 determines whether or not the differential pressure before and after the filter read in the process of S201 is greater than or equal to the determination criterion corrected in the process of S203. If an affirmative determination is made in the process of S204, the ECU 10 proceeds to the process of S205 and determines that the particulate filter 3 is normal. On the other hand, when a negative determination is made in the process of S204, the ECU 10 proceeds to the process of S206 and determines that the particulate filter 3 is out of order. It should be noted that the diagnosis means according to the present invention is realized by the ECU 10 executing the processing of S204 to S206.

  According to the embodiment described above, even when the condensed water flows into the particulate filter 3, the failure diagnosis of the particulate filter 3 can be performed accurately.

  When the actual PM accumulation amount of the particulate filter 3 is small, the difference between the differential pressure before and after the filter when the particulate filter 3 is normal and the differential pressure before and after the filter when the particulate filter 3 is faulty. Get smaller. Similarly, even when the actual PM accumulation amount of the particulate filter 3 is large, the difference between the differential pressure before and after the filter when the particulate filter 3 is normal and the differential pressure before and after the filter when the particulate filter 3 is malfunctioning. Becomes smaller. Therefore, in the failure diagnosis process of the particulate filter 3, the difference between the differential pressure before and after the filter when the particulate filter 3 is normal and the differential pressure before and after the filter when the particulate filter 3 is faulty becomes relatively large. It is preferable to implement in the range of the actual PM deposition amount (hereinafter referred to as “diagnosis range”).

  Therefore, the ECU 10 performs the failure diagnosis process of the particulate filter 3 on the condition that the estimated PM accumulation amount calculated by the PM accumulation amount calculation device belongs to the diagnosable range (permission to execute the failure diagnosis process is permitted). You may be allowed to do so. In this case, as shown in FIG. 5, the ECU 10 may execute the process of S301 instead of the process of S203 in FIG. 4 (or before and after the process of S203). That is, in the process of S301, the ECU 10 determines whether or not the estimated PM accumulation amount calculated in the process of S202 belongs to the diagnosis permission range. If a negative determination is made in the process of S301, the processes of S204 to S206 may be skipped, and if a positive determination is made in the process of S301, the processes of S204 to S206 may be executed.

<Example 3>
Next, another embodiment of the particulate filter failure diagnosis apparatus according to the present invention will be described with reference to FIGS. Here, a configuration different from the above-described second embodiment will be described, and description of the same configuration will be omitted.

  In the above-described second embodiment, the example in which the failure diagnosis of the particulate filter 3 is performed using the detection value (differential pressure before and after the filter) of the differential pressure sensor 4 has been described, but in this embodiment, the particulate filter 3 An example in which a failure diagnosis of the particulate filter 3 is performed using the detection value of the PM sensor arranged in the downstream exhaust passage 2 will be described.

  FIG. 6 is a diagram showing a schematic configuration of the internal combustion engine and its exhaust system in the present embodiment. In FIG. 6, a PM sensor 14 is attached to the exhaust passage 2 downstream from the particulate filter 3. The PM sensor 14 is a sensor that outputs an electrical signal correlated with the amount of PM contained in the exhaust gas flowing out from the particulate filter 3 (hereinafter referred to as “PM outflow amount”). In the example shown in FIG. 6, the differential pressure sensor is omitted, but a differential pressure sensor may be provided.

  In such a configuration, the ECU 10 determines that the particulate filter 3 is malfunctioning on the condition that the detection value of the PM sensor exceeds the upper limit value. When the particulate filter 3 is cracked or missing, the amount of PM flowing out from the particulate filter 3 (hereinafter referred to as “PM outflow amount”) is larger than when the particulate filter 3 is normal. Become. Therefore, when the particulate filter 3 is normal, the detection value of the PM sensor becomes larger than the maximum value (upper limit value) that the PM outflow amount can take.

  By the way, when PM peels or desorbs from the particulate filter 3 due to the influence of the condensed water, the actual PM deposition amount of the particulate filter 3 decreases. Here, the ratio of the amount of PM that passes through the particulate filter 3 with respect to the amount of PM that flows into the particulate filter 3 (hereinafter referred to as “PM slipping rate”) correlates with the actual PM deposition amount. For example, when the actual PM deposition amount is small, the PM slip-through rate is larger than when it is large. As a result, there is a possibility that the detection value of the PM sensor 14 exceeds the upper limit value even though the particulate filter 3 has not failed.

  Therefore, the upper limit value is corrected based on the estimated PM accumulation amount calculated by the above-described PM accumulation amount calculation device, and the corrected upper limit value is compared with the detection value of the PM sensor 14, whereby the particulate filter 3. A failure diagnosis was performed.

  Hereinafter, the execution procedure of the failure diagnosis process of the particulate filter 3 in the present embodiment will be described with reference to FIG. FIG. 7 is a flowchart showing a failure diagnosis processing routine in the present embodiment. This failure diagnosis processing routine is stored in advance in the ROM of the ECU 10 and is periodically executed by the ECU 10 (CPU).

  In the failure diagnosis processing routine, the ECU 10 first reads various data in the processing of S401. For example, the ECU 10 reads data such as an exhaust flow rate (intake air amount), an exhaust temperature, a fuel injection amount, a detection value of the PM sensor 14 (PM outflow amount), and the like.

  In the process of S402, the ECU 10 calculates the estimated PM accumulation amount using the exhaust gas flow rate (intake air amount), the exhaust gas temperature, and the fuel injection amount read in S401 as parameters. The calculation procedure at this time is the same as the processing of S102 to S109 of FIG.

  In the process of S403, the ECU 10 calculates the PM slipping rate using the estimated PM accumulation amount obtained in the process of S402 as a parameter. Specifically, the ECU 10 calculates the PM slipping rate using the estimated PM accumulation amount and the exhaust gas flow rate as parameters. At that time, a map or a function formula for deriving the PM slip-out rate with the estimated PM accumulation amount and the exhaust gas flow rate as arguments is obtained in advance, and the PM slip-out rate is derived from the map or the function formula and the detection value of the PM sensor 14. Also good.

  In the process of S404, the ECU 10 corrects the upper limit value based on the PM slipping rate obtained in the process of S403. At that time, the ECU 10 corrects the upper limit value so that the upper limit value is larger when the PM slip-through rate is larger than when the PM slip-through rate is small.

  In the process of S405, the ECU 10 determines whether or not the PM outflow amount read in the process of S401 is equal to or less than the upper limit value corrected in the process of S404. If the determination in step S405 is affirmative, the ECU 10 proceeds to step S406 and determines that the particulate filter 3 is normal. On the other hand, when a negative determination is made in the process of S405, the ECU 10 proceeds to the process of S407 and determines that the particulate filter 3 is out of order.

  According to the embodiment described above, even when the condensed water flows into the particulate filter 3, the failure diagnosis of the particulate filter 3 can be performed accurately.

1 Internal combustion engine 2 Exhaust passage 3 Particulate filter 4 Differential pressure sensor 5 Fuel injection valve 10 ECU
11 Accelerator pedal 12 Accelerator opening sensor 13 Crank position sensor 14 PM sensor

Claims (5)

First calculating means for calculating a PM emission amount which is an amount of PM discharged from the internal combustion engine;
Second calculating means for calculating a PM peeling amount, which is the amount of PM peeled off from the particulate filter, with the amount of condensed water flowing into the particulate filter disposed in the exhaust passage of the internal combustion engine as a parameter;
Third calculation means for calculating a PM deposition amount that is the amount of PM collected or deposited on the particulate filter, using the PM discharge amount and the PM peeling amount as parameters,
Particulate filter PM deposition amount calculation device comprising:   2. The PM accumulation amount calculation of the particulate filter according to claim 1, wherein the third calculation means calculates a PM accumulation amount of the particulate filter by integrating a value obtained by subtracting the PM separation amount from the PM discharge amount. apparatus.   2. The particulate filter PM accumulation amount calculation device according to claim 1, wherein the third calculation means calculates the PM accumulation amount of the particulate filter by subtracting the PM separation amount from an integrated value of the PM discharge amount. . The PM accumulation amount calculating device for the particulate filter according to any one of claims 1 to 3,
A sensor whose detection value changes according to the amount of PM deposited on the particulate filter;
Diagnostic means for diagnosing failure of the particulate filter based on the detection value of the sensor;
Correction means for correcting the determination criteria of the failure diagnosis according to the PM accumulation amount calculated by the third calculation means;
A particulate filter failure diagnosis apparatus comprising: The PM accumulation amount calculating device for the particulate filter according to any one of claims 1 to 3,
A sensor whose detection value changes according to the amount of PM deposited on the particulate filter;
Diagnostic means for diagnosing failure of the particulate filter based on the detection value of the sensor;
Permission means for permitting failure diagnosis by the diagnosis means, provided that the amount of accumulated PM calculated by the third calculation means is equal to or greater than a threshold;
A particulate filter failure diagnosis apparatus comprising:

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