JP2013019389A - Failure diagnosis device for particulate filter - Google Patents

Abstract

In a particulate filter failure diagnostic apparatus for diagnosing whether a particulate filter failure has occurred using a PM sensor provided downstream of a particulate filter in an exhaust passage of an internal combustion engine, the diagnostic accuracy thereof It aims at improving.
The present invention assumes that the integrated value of the PM amount passing through the filter calculated based on the amount of change in the output value of the PM sensor during a predetermined period and the filter is in a predetermined state. By comparing the estimated PM passing filter amount with the integrated value during the predetermined period, it is diagnosed whether or not a filter failure has occurred. When the condition that the difference between the amount of PM discharged to the internal combustion engine and the reference value of the PM emission amount according to the operating state of the internal combustion engine is greater than a predetermined amount is satisfied, the amount of PM actually discharged from the internal combustion engine is Control to increase or decrease the reference value side is executed.
[Selection] Figure 5

Description

  The present invention relates to a failure diagnosis device for a particulate filter that diagnoses whether or not a failure occurs in a particulate filter provided in an exhaust passage of an internal combustion engine.

  In some cases, a particulate filter (hereinafter simply referred to as a filter) that collects particulate matter (hereinafter referred to as PM) in the exhaust gas is provided in the exhaust passage of the internal combustion engine. In the filter, a part of the PM in the exhaust gas is collected, and the collected PM gradually accumulates.

  In Patent Document 1, the amount of PM inflow into the filter is calculated based on the amount of PM discharged from the internal combustion engine and the amount of PM oxidized by the oxidation catalyst provided on the upstream side of the filter. A technique for calculating the amount of PM accumulated in the filter based on the amount of PM inflow and the amount of PM burned is described.

  Patent Document 2 describes a technique for calculating a PM accumulation amount in a filter by integrating a value obtained by multiplying the amount of PM discharged from an internal combustion engine per unit time by the collection efficiency of the filter. ing.

  Patent Document 3 describes a technique for reducing the PM emission amount from an internal combustion engine by reducing the EGR rate during a transient operation in which a control delay of the fuel injection timing in the internal combustion engine occurs.

JP 2004-044457 A Japanese Patent Application Laid-Open No. 2003-15592 Japanese Patent Laid-Open No. 09-042016

  When a failure such as breakage or melting occurs in the filter, the amount of PM that passes through the filter without being collected by the filter (hereinafter referred to as filter-passed PM amount) increases. Therefore, in order to diagnose whether or not such a filter failure has occurred, a PM sensor that outputs a signal corresponding to the amount of PM accumulated therein may be provided in the exhaust passage downstream of the filter.

  When such a PM sensor is provided, an integrated value of the PM amount passing through the filter during a predetermined period calculated based on the amount of change in the output value of the PM sensor, and a filter when the filter is assumed to be in a predetermined state By comparing the estimated value of the passing PM amount with the integrated value during the predetermined period, it is possible to diagnose whether or not a filter failure has occurred. However, the PM amount actually discharged from the internal combustion engine due to a sudden change in the operating state of the internal combustion engine during a predetermined period during which the filter-passed PM amount is integrated to perform the failure diagnosis, In some cases, the difference from the reference value of the PM emission amount according to the operating state of the internal combustion engine becomes large. In this case, the estimation accuracy of the filter passing PM amount decreases. If the estimation accuracy of the PM amount passing through the filter is lowered, there is a risk of erroneous diagnosis as to whether or not a filter failure has occurred.

The present invention has been made in view of the above problems, and diagnoses whether or not a filter failure has occurred using a PM sensor provided downstream of the filter in the exhaust passage of the internal combustion engine. An object of the present invention is to improve the diagnostic accuracy of a filter fault diagnosis apparatus.

  The present invention relates to an integrated value of the PM amount passing through the filter during the predetermined period calculated based on the amount of change in the output value of the PM sensor during the predetermined period, and a filter estimated on the assumption that the filter is in a predetermined state. By comparing the accumulated PM amount with the integrated value during the predetermined period, it is diagnosed whether a filter failure has occurred or not, and is actually discharged from the internal combustion engine during the predetermined period. When the condition that the difference between the amount of PM and the reference value of the PM emission amount according to the operating state of the internal combustion engine is larger than a predetermined amount is satisfied, the amount of PM actually discharged from the internal combustion engine is set to the reference value side. Control to increase or decrease is executed.

More specifically, the particulate filter failure diagnosis apparatus according to the present invention is:
A PM sensor provided downstream of the particulate filter in the exhaust passage of the internal combustion engine and outputting a signal corresponding to the amount of particulate matter deposited on the PM sensor;
A filter passing PM amount estimating means for estimating a filter passing PM amount that is an amount of particulate matter passing through the particulate filter, assuming that the particulate filter is in a predetermined state;
The integrated value of the filter passing PM amount during the predetermined period calculated based on the amount of change in the output value of the PM sensor during the predetermined period, and the predetermined value of the filter passing PM amount estimated by the filter passing PM amount estimating means. A particulate filter failure diagnosis device for diagnosing whether or not a particulate filter failure has occurred by comparing the integrated value during the period,
During the predetermined period, there is a predetermined condition that a difference between the amount of particulate matter actually discharged from the internal combustion engine and a reference value of the particulate matter discharge amount according to the operating state of the internal combustion engine is larger than a predetermined amount. When established, the system further comprises an actual PM emission amount control means for executing control for increasing or decreasing the amount of particulate matter actually discharged from the internal combustion engine toward the reference value side.

  Here, the predetermined period is a period during which it can be determined that the amount of accumulated PM in the PM sensor increases to such an extent that a filter failure diagnosis is possible. The predetermined period is determined in advance based on experiments or the like. The predetermined state may be a state in which the degree of breakage or melting of the filter has reached a certain level that should be determined as a failure, or may be a normal state. When it is assumed that the filter is in a predetermined state, the amount of PM that has passed through the filter can be estimated based on the amount of PM discharged from the internal combustion engine, the amount of accumulated PM in the filter, and the like (hereinafter, the estimated value is referred to as estimated passage PM). Called volume). The PM emission amount from the internal combustion engine can be calculated from the operating state of the internal combustion engine. That is, the PM emission amount from the internal combustion engine used for calculation of the estimated passing PM amount is a reference value of the PM emission amount according to the operating state of the internal combustion engine. Further, the PM accumulation amount in the filter can be calculated based on the PM discharge amount from the internal combustion engine, the PM oxidation amount in the filter, and the like.

  When a filter failure such as breakage or melting occurs, an actual filter passing PM amount (hereinafter referred to as an actual passing PM amount) increases. Therefore, the integrated value of the actual passing PM amount during the predetermined period calculated based on the amount of change in the output value of the PM sensor during the predetermined period is greater than when the filter is in a normal state. Therefore, it is possible to diagnose whether or not a filter failure has occurred by comparing the accumulated value of the estimated passing PM amount and the accumulated value of the actual passing PM amount during the predetermined period.

In the present invention, a predetermined condition is established in which the difference between the actual PM emission amount from the internal combustion engine and the reference value of the PM emission amount according to the operating state of the internal combustion engine is larger than the predetermined amount during the predetermined period. In this case, control for increasing or decreasing the actual PM emission amount from the internal combustion engine to the reference value side is executed by the actual PM emission amount control means.

  Here, the predetermined amount may be a threshold value that can maintain the accuracy of the failure diagnosis of the filter within an allowable range. Further, as control for increasing or decreasing the actual PM emission amount from the internal combustion engine, control for advancing or retarding the fuel injection timing, and when the sub fuel injection is executed before the main fuel injection, the sub fuel Examples include control for increasing or decreasing the injection amount, and control for increasing or decreasing the amount of EGR gas when EGR gas is introduced into the intake system of the internal combustion engine.

  By executing the above control, it is possible to suppress an increase in the difference between the actual PM emission amount from the internal combustion engine and the reference value of the PM emission amount according to the operating state of the internal combustion engine during the predetermined period. it can. Therefore, it is possible to maintain high estimation accuracy of the estimated PM passage amount. Therefore, according to the present invention, whether or not a filter failure has occurred even when the PM emission amount from the internal combustion engine deviates from the reference value due to a change in the operating state of the internal combustion engine during the predetermined period. Can be diagnosed with high accuracy.

  Further, if the execution of the filter failure diagnosis is stopped every time a predetermined condition is satisfied during the predetermined period, the frequency of execution of the failure diagnosis is lowered. According to the present invention, filter failure diagnosis can be continued even when a predetermined condition is satisfied during a predetermined period. Therefore, it is possible to suppress a decrease in the execution frequency of the filter failure diagnosis.

  When the temperature or pressure in the cylinder changes, the PM emission amount from the internal combustion engine changes. Further, when the temperature or pressure in the cylinder changes, the temperature or pressure of the exhaust discharged from the internal combustion engine also changes. Therefore, the predetermined condition according to the present invention is that the difference between the detected value of the temperature or pressure of the exhaust discharged from the internal combustion engine and the reference value of the exhaust temperature or pressure determined according to the operating state of the internal combustion engine. It may be larger than a predetermined amount.

  Further, when EGR gas is introduced into the intake system of the internal combustion engine by the EGR device, the PM emission amount from the internal combustion engine changes when the EGR gas amount changes. Therefore, the predetermined condition according to the present invention is that the difference between the estimated value of the actual EGR gas amount and the reference value of the EGR gas amount determined according to the operation state of the internal combustion engine is larger than the predetermined amount. Good.

  When the amount of EGR gas changes, the temperature of the intake air into which the EGR gas is introduced, that is, the temperature of the intake air supplied to the internal combustion engine also changes. Therefore, the predetermined condition according to the present invention is that the detected value of the temperature of the intake air supplied to the internal combustion engine, and the reference value of the temperature of the intake air supplied to the internal combustion engine, which is determined according to the operating state of the internal combustion engine, The difference may be greater than a predetermined amount.

  According to the present invention, in a particulate filter failure diagnosis device that diagnoses whether a filter failure has occurred using a PM sensor provided downstream of a filter in an exhaust passage of an internal combustion engine, the diagnosis accuracy is improved. Can be made.

It is a figure which shows schematic structure of the intake / exhaust system of the internal combustion engine which concerns on an Example. It is a figure which shows schematic structure of the PM sensor which concerns on an Example. It is a graph which shows the relationship of the PM deposition amount in PM sensor, the electrical resistance between electrodes of PM sensor, and the output value of PM sensor. It is a flowchart which shows the flow of the failure diagnosis of the filter which concerns on an Example. It is a flowchart which shows the flow of the 1st real PM discharge amount control which concerns on an Example. It is a flowchart which shows the flow of the 2nd actual PM discharge amount control which concerns on an Example. It is a flowchart which shows the flow of the 3rd actual PM discharge amount control which concerns on an Example.

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

<Example>
Here, the case where the present invention is applied to failure diagnosis of a filter provided in an exhaust passage of a diesel engine for driving a vehicle will be described as an example. However, the internal combustion engine which concerns on this invention is not restricted to a diesel engine, For example, a gasoline engine etc. may be sufficient.

[Schematic configuration of intake and exhaust system of internal combustion engine]
FIG. 1 is a diagram showing a schematic configuration of an intake / exhaust system of an internal combustion engine according to the present embodiment. The internal combustion engine 1 is a diesel engine for driving a vehicle. An intake passage 2 and an exhaust passage 3 are connected to the internal combustion engine 1.

  An air flow meter 4 and a throttle valve 5 are provided in the intake passage 2. The air flow meter 4 detects the intake air amount of the internal combustion engine 1. The throttle valve 5 adjusts the flow rate of the intake air supplied to the internal combustion engine 1 by changing the cross-sectional area of the intake passage 2.

  An oxidation catalyst 6 is provided in the exhaust passage 3. A filter 7 that collects PM in the exhaust is provided in the exhaust passage 3 on the downstream side of the oxidation catalyst 6. In place of the oxidation catalyst 6, a catalyst having another oxidation function (for example, a storage reduction type NOx catalyst, a selective reduction type NOx catalyst, etc.) may be provided. The filter 7 may carry a catalyst having an oxidation function. A fuel addition valve 8 is provided in the exhaust passage 3 upstream of the oxidation catalyst 6 to add fuel into the exhaust.

  One end of the EGR passage 17 is connected upstream of the fuel addition valve 8 in the exhaust passage 3, and the other end of the EGR passage 17 is connected downstream of the throttle valve 5 in the intake passage 2. Part of the exhaust discharged from the internal combustion engine 1 is introduced into the intake passage 2 through the EGR passage 17 as EGR gas. The EGR gas introduced into the intake passage 2 is supplied to the internal combustion engine 1 together with the intake air.

  An EGR valve 18 is provided in the EGR passage 17. The EGR valve 18 adjusts the flow rate of the EGR gas introduced into the intake passage 2, that is, the amount of EGR gas supplied to the internal combustion engine 1 by changing the flow passage cross-sectional area in the EGR passage 17.

  An intake air temperature sensor 19 and an air-fuel ratio sensor 12 are provided on the downstream side of the connection portion of the EGR passage 17 in the intake passage 2. The intake air temperature sensor 19 detects the temperature of intake air supplied to the internal combustion engine 1. The air-fuel ratio sensor 12 detects the air-fuel ratio of the intake air supplied to the internal combustion engine 1.

  A first exhaust temperature sensor 13 and an exhaust pressure sensor 14 are provided downstream of the connection portion of the EGR passage 17 in the exhaust passage 3 and upstream of the fuel addition valve 8. The first exhaust temperature sensor 13 detects the temperature of the exhaust discharged from the internal combustion engine 1. The exhaust pressure sensor 14 detects the pressure of the exhaust discharged from the internal combustion engine 1.

  A second exhaust temperature sensor 15 is provided in the exhaust passage 3 between the oxidation catalyst 6 and the filter 7. A PM sensor 16 is provided in the exhaust passage 3 downstream of the filter 7. The second exhaust temperature sensor 15 detects the temperature of the exhaust flowing into the filter 7. Details of the PM sensor 16 will be described later.

  The internal combustion engine 1 is also provided with an electronic control unit (ECU) 10 for controlling the internal combustion engine 1. An air flow meter 4, an intake air temperature sensor 19, an air-fuel ratio sensor 12, a first exhaust temperature sensor 13, an exhaust pressure sensor 14, a second exhaust temperature sensor 15, and a PM sensor 16 are electrically connected to the ECU 10. Further, a crank position sensor 11 of the internal combustion engine 1 is electrically connected to the ECU 10. These output signals are input to the ECU 10. The ECU 10 derives the engine speed of the internal combustion engine 1 based on the output signal of the crank position sensor 11.

  The ECU 10 is electrically connected to the throttle valve 5, the fuel addition valve 8, the EGR valve 18, and the fuel injection valve (not shown) of the internal combustion engine 1. The operation of these devices is controlled by the ECU 10.

  For example, the ECU 10 performs filter regeneration processing by adding fuel from the fuel addition valve 8 in order to remove PM accumulated on the filter 7. The fuel added from the fuel addition valve 8 is supplied to the oxidation catalyst 6. The temperature of the exhaust gas flowing into the filter 7 rises as the fuel is oxidized in the oxidation catalyst 6. As a result, the temperature of the filter 7 rises, and the PM deposited on the filter 7 is oxidized and removed. In the case where a catalyst having an oxidation function is supported on the filter 7, the fuel is also oxidized in the catalyst, so that the temperature of the filter 7 is more likely to rise during the filter regeneration process. Therefore, it becomes easy to promote the oxidation of PM.

[PM sensor]
The PM sensor 16 is a sensor that outputs an electrical signal corresponding to the amount of PM deposited on itself. FIG. 2 is a diagram showing a schematic configuration of the sensor element of the PM sensor 16. FIG. 3 is a graph showing the relationship between the PM accumulation amount in the PM sensor 16, the electrical resistance between the electrodes 16 a and 16 b of the PM sensor 16, and the output value of the PM sensor 16. In FIG. 3, the horizontal axis represents the PM accumulation amount in the PM sensor 16, the lower vertical axis represents the electrical resistance between the electrodes 16 a and 16 b of the PM sensor 16, and the upper vertical axis represents the output value of the PM sensor 16. Represents.

  As shown in FIG. 2, the sensor element of the PM sensor 16 has a pair of comb-shaped electrodes 16a and 16b. PM in the exhaust gas adheres to the PM sensor 16, and the adhered PM gradually accumulates. As the amount of accumulated PM in the PM sensor 16 increases, the amount of PM existing between the electrodes 16a and 16b increases.

  Therefore, as shown in FIG. 3, the larger the amount of PM deposited on the PM sensor 16, the lower the electrical resistance between the electrodes 16a and 16b. And the output value of PM sensor 16 increases, so that the electrical resistance between electrodes 16a and 16b falls. Therefore, the output value of the PM sensor 16 is a value corresponding to the PM accumulation amount in the PM sensor 16.

  The PM sensor 16 is provided on the downstream side of the filter 7. Therefore, PM that has passed through the filter 7 is collected by the PM sensor 16 without being collected by the filter 7. Accordingly, the PM accumulation amount in the PM sensor 16 is an amount corresponding to the integrated value of the actual filter passing PM amount (actual passing PM amount).

If the amount of PM existing between the electrodes 16a and 16b changes, the electrical characteristic values other than the electrical resistance such as current flowing between the electrodes 6a and 6b also change. Therefore, the PM sensor 16 may output a signal corresponding to the amount of PM deposited on itself based on an electrical characteristic value other than electrical resistance.

[Filter failure diagnosis]
As described above, in this embodiment, the filter regeneration process is executed to remove the PM accumulated on the filter 7. In the filter regeneration process, the temperature of the filter 7 rises to a temperature at which PM can be oxidized, so that there is a possibility that a failure of the filter 7 such as a breakage or a melting damage may occur. When such a failure of the filter 7 occurs, the amount of PM passing through the filter increases. As a result, there arises a problem that the PM released to the outside increases.

  Therefore, in this embodiment, failure diagnosis of the filter 7 is performed by the ECU 10. The failure diagnosis of the filter is based on the integrated value of the actual passing PM amount during a predetermined period calculated based on the output value of the PM sensor 16 and the estimated passing PM amount when the filter 7 is assumed to be in a predetermined state. This is done by comparing the integrated value during the predetermined period.

  Details of the filter failure diagnosis according to this embodiment will be described with reference to the flowchart shown in FIG. FIG. 4 is a flowchart showing a flow of filter failure diagnosis according to the present embodiment. This flow is stored in advance in the ECU 10 and is repeatedly executed by the ECU 10.

  In this flow, first, in step S101, it is determined whether or not an execution condition for failure diagnosis of the filter 7 is satisfied. The execution condition of the failure diagnosis here may be, for example, that the estimated value of the PM accumulation amount in the filter 7 has reached a predetermined accumulation amount after completion of the execution of the filter regeneration process. In this case, the predetermined accumulation amount is a value determined in advance based on experiments or the like as a threshold value with which it is possible to determine that failure diagnosis of the filter 7 is possible. The amount of accumulated PM in the filter 7 can be calculated based on the amount of PM discharged from the internal combustion engine 1, the amount of PM oxidation in the filter 7 (the amount of PM oxidized once collected by the filter 7), and the like. . The PM emission amount from the internal combustion engine 1 can be calculated based on the operating state of the internal combustion engine 1 (in this embodiment, the engine speed of the internal combustion engine 1 and the fuel injection amount in the internal combustion engine 1). The amount of PM oxidation in the filter 7 can be calculated based on the flow rate and temperature of the exhaust gas flowing into the filter 7. Further, when the elapsed time, the vehicle travel distance, or the integrated value of the fuel injection amount in the internal combustion engine 1 has reached a predetermined value after the completion of the filter regeneration process, it is determined that the failure diagnosis execution condition is satisfied. May be.

  If a negative determination is made in step S101, the execution of this flow is temporarily terminated. On the other hand, if an affirmative determination is made in step S101, then in step S102, an estimated passing PM amount Qpmout is calculated when it is assumed that the filter 7 is in a predetermined state.

  Here, the predetermined state is a state in which the degree of breakage or melting of the filter 7 has reached a certain level that should be determined as a failure. That is, when the state of the filter 7 is the predetermined state, it is assumed that the amount of PM passing through the filter is increased to a certain degree as compared to when the filter 7 is in a normal state. If the state of the filter 7 is specified to be a predetermined state, the estimated passing PM amount Qpmout can be calculated based on the PM discharge amount from the internal combustion engine 1 and the PM accumulation amount in the filter 7.

As described above, the PM emission amount from the internal combustion engine 1 can be calculated based on the operating state of the internal combustion engine 1. That is, the PM discharge amount from the internal combustion engine 1 used for calculating the estimated passing PM amount Qpmout is a reference value of the PM discharge amount according to the operating state of the internal combustion engine 1. The relationship between the operating state of the internal combustion engine 1 and the PM emission amount is obtained in advance based on experiments or the like, and is stored in the ECU 10 as a map or a function. The ECU 10 calculates the PM emission amount from the internal combustion engine 1 using the map or function.

  As the PM emission amount from the internal combustion engine 1 increases, the estimated passing PM amount Qpmout increases. Moreover, the PM collection rate of the filter 7 (the ratio of the amount of PM collected by the filter 7 to the amount of PM flowing into the filter 7) increases as the PM accumulation amount in the filter 7 increases. For this reason, the larger the amount of accumulated PM in the filter 7, the smaller the estimated passing PM amount Qpmout. The relationship between the estimated passing PM amount Qpmout when the state of the filter 7 is the predetermined state, the PM discharge amount from the internal combustion engine 1 and the PM accumulation amount in the filter 7 is obtained in advance based on experiments or the like. , Stored as a map or a function in the ECU 10. In step S102, the estimated passing PM amount Qpmout is calculated using the map or function. In this embodiment, the ECU 10 that executes the process of step S102 corresponds to the filter passing PM amount estimating means according to the present invention.

  Next, in step S103, the estimated passing PM amount Qpmout calculated in step S102 is added to calculate the estimated passing PM amount integrated value ΣQpmoute. Next, in step S104, it is determined whether or not a predetermined period Δta has elapsed since the execution condition for failure diagnosis of the filter 7 was established. Here, the predetermined period Δta is a period during which it can be determined that the PM accumulation amount in the PM sensor 16 increases to the extent that the failure diagnosis of the filter 7 can be performed, and is a predetermined period determined based on experiments or the like. .

  If a negative determination is made in step S104, the processes in steps S102 and S103 are repeated. That is, the estimated passing PM amount Qpmout is accumulated from when the execution condition for failure diagnosis of the filter 7 is satisfied until the predetermined period Δta elapses. If the determination in step S104 is affirmative, then in step S105, based on the amount of change in the output value of the PM sensor 16 during the predetermined period Δta, the integrated value ΣQpmoutr of the actual passing PM amount during the predetermined period Δta. Is calculated.

  The PM sensor 16 is provided with an electric heater for heating the PM sensor 16, and when the failure diagnosis execution condition for the filter 7 is satisfied, the PM sensor 16 is heated by the electric heater to be deposited on the PM sensor 16. The PM that has been deposited may be oxidized so that the amount of PM deposited on the PM sensor 16 once becomes substantially zero. In this case, the integrated value ΣQpmoutr of the actual passing PM amount during the predetermined period Δta can be calculated based on the output value of the PM sensor 16 when the predetermined period Δta has elapsed.

  Next, in step S106, it is determined whether or not the integrated value ΣQpmoutr of the actual passing PM amount during the predetermined period Δta is equal to or greater than the integrated value ΣQpmout of the estimated passing PM amount during the predetermined period Δta. When the integrated value ΣQpmoutr of the actual passing PM amount during the predetermined period Δta is equal to or larger than the integrated value ΣQpmout of the estimated passing PM amount during the predetermined period Δta, the estimated passing PM amount when the filter 7 is assumed to be in a predetermined state. It can be determined that the above PM passes through the filter 7. That is, in this case, it can be determined that the failure level of the filter 7 is equal to or higher than the failure level in the predetermined state.

  Therefore, if an affirmative determination is made in step S106, it is then determined in step S107 that a failure of the filter 7 has occurred. On the other hand, if a negative determination is made in step S106, it is then determined in step S108 that the filter 7 is in a normal state.

In the filter failure diagnosis as described above, the estimated passing PM amount Qpmout may be calculated on the assumption that the filter 7 is in a normal state. That is, the “predetermined state” may be a normal state. In this case, when the difference between the integrated value of the actual passing PM amount during the predetermined period Δta and the integrated value of the estimated passing PM amount during the predetermined period Δta is equal to or greater than a threshold value at which it can be determined that the filter 7 is malfunctioning. It is determined that the filter 7 has failed.

[Real PM emission control]
As described above, when performing the failure diagnosis of the filter according to the present embodiment, the estimated passing PM amount Qpmout from the time when the execution condition of the failure diagnosis of the filter 7 is satisfied until the predetermined period Δta elapses and It is necessary to calculate an integrated value of the actual passing PM amount Qpmoutr and compare the integrated values. However, due to a sudden change in the operation state of the internal combustion engine 1 such as when the steady operation is changed to the transient operation during the predetermined period Δta, the actual PM emission amount from the internal combustion engine 1 (hereinafter, actual There is a case where the difference between the PM emission amount) and a reference value of PM emission amount according to the operating state of the internal combustion engine 1 (hereinafter referred to as reference PM emission amount) becomes large.

  As described above, the estimated passing PM amount Qpmout is calculated based on the reference PM discharge amount. Therefore, when the difference between the actual PM discharge amount and the reference PM discharge amount increases, the estimation accuracy of the estimated passing PM amount Qpmout decreases. When the estimation accuracy of the estimated passing PM amount Qpmout is lowered, there is a possibility that an erroneous diagnosis occurs in the failure diagnosis of the filter 7 performed based on the integrated value of the estimated passing PM amount.

  Further, in order to suppress such a misdiagnosis, a difference between the actual PM discharge amount and the reference PM discharge amount during a predetermined period Δta is a threshold value that can maintain the accuracy of failure diagnosis of the filter 7 within an allowable range. When a condition that can be determined to be larger is satisfied, if the failure diagnosis of the filter 7 is stopped, there is a problem that the frequency of execution of the failure diagnosis decreases.

  Therefore, in this embodiment, when the above condition is satisfied during the predetermined period Δta, actual PM emission amount control is executed, which is control for increasing or reducing the actual PM emission amount toward the reference PM emission amount side. By executing the actual PM emission amount control, the difference between the actual PM emission amount and the reference PM emission amount can be reduced. Therefore, it is possible to maintain high estimation accuracy of the estimated PM passage amount. As a result, even when the above-described conditions are satisfied during the predetermined period Δta, it is possible to accurately diagnose whether or not the filter 7 has failed. Further, even if the above condition is satisfied during the predetermined period Δta, the failure diagnosis of the filter 7 can be continued, so that a decrease in the frequency of execution of the failure diagnosis can be suppressed.

  Here, specific actual PM emission amount control according to the present embodiment will be described with reference to FIGS. FIG. 5 is a flowchart showing a flow of the first actual PM emission amount control according to the present embodiment. This flow is stored in advance in the ECU 10 and is repeatedly executed by the ECU 10.

  When the temperature or pressure in the cylinder in the internal combustion engine 1 changes, the actual PM emission amount changes. That is, when the temperature or pressure in the cylinder becomes high, the ignition delay period is shortened, so that the actual PM emission amount increases. On the contrary, when the temperature or pressure in the cylinder becomes low, the ignition delay period is extended, so that the actual PM emission amount decreases.

Further, when the temperature or pressure in the cylinder in the internal combustion engine 1 changes, the temperature or pressure of the exhaust discharged from the internal combustion engine 1 also changes. Therefore, in the first actual PM emission amount control flow, the detected value of the temperature or pressure of the exhaust discharged from the internal combustion engine 1 and the reference of the exhaust temperature or pressure determined according to the operating state of the internal combustion engine 1 When the difference between the value (that is, the temperature or pressure of the exhaust gas when the operating state of the internal combustion engine 1 is stable and steady) is larger than a predetermined amount, the difference between the actual PM emission amount and the reference PM emission amount is Then, it is determined that a condition that is greater than a threshold value that can maintain the accuracy of failure diagnosis of the filter 7 within an allowable range is established.

  In the first actual PM emission amount control flow, first, in step S201, it is determined whether or not a predetermined period Δta in the above-described filter failure diagnosis flow is in progress. That is, it is determined whether or not the estimated passing PM amount Qpmout is being accumulated in order to diagnose the failure of the filter 7. If a negative determination is made in step S201, the execution of this flow is temporarily terminated.

  On the other hand, if an affirmative determination is made in step S201, then in step S202, a reference value Toutgbase for the exhaust gas temperature is calculated based on the operating state of the internal combustion engine 1. Next, in step S203, an exhaust pressure reference value Poutgbase is calculated based on the operating state of the internal combustion engine 1. The relationship between the operating state of the internal combustion engine 1 and the reference values Toutgbase, Poutgbase of the exhaust gas temperature or pressure is obtained in advance based on experiments or the like, and is stored in the ECU 10 as a map or a function. In steps S202 and S203, exhaust gas temperature or pressure reference values Toutgbase and Poutgbase are calculated using the map or function.

  Next, in step S204, a difference ΔToutg between the actual exhaust gas temperature Toutg detected by the first exhaust gas temperature sensor 13 and the exhaust gas temperature reference value Toutgbase calculated in step S202 is calculated. Next, in step S205, a difference ΔPoutg between the actual exhaust pressure Poutg detected by the exhaust pressure sensor 14 and the exhaust pressure reference value Poutgbase calculated in step S203 is calculated.

  Next, in step S206, it is determined whether the exhaust gas temperature difference ΔToutg calculated in step S204 is greater than a predetermined amount ΔToutg0 or the exhaust gas pressure difference ΔPoutg calculated in step S205 is greater than a predetermined amount ΔPoutg0. Determined. Each predetermined amount ΔToutg0, ΔPoutg0 is predetermined based on experiments or the like.

  If an affirmative determination is made in step S206, then, in step S207, the actual exhaust temperature Toutg is higher than the exhaust temperature reference value Toutgbase, or the actual exhaust pressure Poutg is the exhaust pressure reference value Poutgbase. It is determined whether or not it is higher.

  When an affirmative determination is made in step S207, it can be determined that the actual PM discharge amount is larger than the reference PM discharge amount. In this case, next, in step S208, as the actual PM emission amount control for reducing the actual PM emission amount, the fuel injection timing in the internal combustion engine 1 is set to a reference timing (compression stroke top dead center) determined according to the operation state. The control is executed so as to be retarded from the later time and the time near the top dead center of the compression stroke. If the fuel injection timing is retarded from the reference timing, the fuel injection timing becomes later than the compression stroke top dead center, so the ignition delay period is extended. As a result, the actual PM emission amount decreases.

  On the other hand, if a negative determination is made in step S207, that is, the actual exhaust temperature Toutg is lower than the exhaust temperature reference value Toutgbase, or the actual exhaust pressure Poutg is lower than the exhaust pressure reference value Poutgbase. In this case, it can be determined that the actual PM emission amount is smaller than the reference PM emission amount. In this case, next, in step S209, as the actual PM emission amount control for increasing the actual PM emission amount, the fuel injection timing in the internal combustion engine 1 is advanced from the reference timing determined according to the operating state. Is executed. If the fuel injection timing is advanced from the reference timing, the fuel injection timing approaches the top dead center of the compression stroke, so the ignition delay period is shortened. As a result, the actual PM emission amount increases.

  Here, when the fuel injection timing is retarded or advanced as the actual PM emission amount control, the fuel injection timing may be retarded or advanced by a predetermined amount from the reference timing. Further, depending on the difference between the exhaust temperature difference ΔToutg calculated in step S204 and the predetermined amount ΔToutg0, or the difference between the exhaust pressure difference ΔPoutg calculated in step S205 and the predetermined amount ΔPoutg0, the fuel injection timing is determined. The amount of retardation or amount of advance may be determined. In this case, the larger the difference, the larger the retard amount or advance amount of the fuel injection timing.

  If a negative determination is made in step S206, then in step S210, the fuel injection timing in the internal combustion engine 1 is controlled to a reference time determined according to the operating state.

  In the internal combustion engine 1, when the sub fuel injection is performed before the main fuel injection performed near the top dead center of the compression stroke, as the actual PM emission amount control performed in step S208 or S209 of the above flow, Control for decreasing or increasing the fuel injection amount may be executed. By reducing the sub fuel injection amount, the ignition delay period of the fuel injected by the main fuel injection can be extended. Moreover, the ignition delay period of the fuel injected by the main fuel injection can be shortened also by increasing the sub fuel injection amount. Therefore, the actual PM emission amount can be reduced or increased by decreasing or increasing the auxiliary fuel injection amount. Further, as the actual PM emission amount control, both control for delaying or advancing the fuel injection timing and control for decreasing or increasing the sub fuel injection amount may be executed.

  FIG. 6 is a flowchart showing a flow of second actual PM emission amount control according to the present embodiment. This flow is stored in advance in the ECU 10 and is repeatedly executed by the ECU 10.

  When the amount of EGR gas supplied to the internal combustion engine 1 changes, the actual PM emission amount changes. That is, when the amount of EGR gas supplied to the internal combustion engine 1 increases, the combustion temperature in the cylinder decreases, so the actual PM emission amount increases. Conversely, when the amount of EGR gas supplied to the internal combustion engine 1 decreases, the combustion temperature in the cylinder rises, so the actual PM emission amount decreases.

  Therefore, in the second actual PM emission amount control flow, the estimated value of the EGR gas amount actually supplied to the internal combustion engine 1 and the reference value of the EGR gas amount determined according to the operating state of the internal combustion engine 1 ( That is, when the difference from the EGR gas amount when the operation state of the internal combustion engine 1 is stable and steady operation is larger than a predetermined amount, the difference between the actual PM discharge amount and the reference PM discharge amount is It is determined that a condition that is greater than a threshold value that can maintain the accuracy of failure diagnosis within an allowable range is established.

  In the second actual PM emission amount control flow, first, in step S301, in the same manner as step S201 in the first actual PM emission amount control flow, during the elapse of the predetermined period Δta in the filter failure diagnosis flow described above. It is determined whether or not there is. If a negative determination is made in step S301, the execution of this flow is temporarily terminated.

  On the other hand, when an affirmative determination is made in step S301, next, in step S302, a reference value Regrbase for the EGR gas amount is calculated based on the operating state of the internal combustion engine 1. The relationship between the operating state of the internal combustion engine 1 and the reference value Regrbase of the EGR gas amount is obtained in advance based on experiments or the like, and is stored in the ECU 10 as a map or a function. In step S302, the EGR gas amount reference value Regrbase is calculated using the map or function.

Next, in step S303, an estimated value Regr of the actual EGR gas amount is calculated based on the intake air amount detected by the air flow meter 4 and the air-fuel ratio of the intake air detected by the air-fuel ratio sensor 12. Next, in step S304, a difference ΔRegr between the EGR gas amount reference value Regrbase calculated in step S302 and the actual EGR gas amount estimated value Regr calculated in step S303 is calculated.

  Next, in step S305, it is determined whether or not the EGR gas amount difference ΔRegr calculated in step S304 is greater than a predetermined amount ΔRegr0. The predetermined amount ΔRegr0 is determined in advance based on experiments or the like.

  If an affirmative determination is made in step S305, it is then determined in step S306 whether or not the actual EGR gas amount estimated value Regr is larger than the EGR gas amount reference amount Regrbase.

  If an affirmative determination is made in step S306, it can be determined that the actual PM emission amount is larger than the reference PM emission amount. In this case, next, in step S307, as the actual PM emission amount control for reducing the actual PM emission amount, the target EGR rate (the target value of the EGR rate that is the ratio of the EGR gas amount to the total amount of intake air) is operated. Control for reducing the reference target value determined according to the state is executed. When the target EGR rate is reduced from the reference target value, the amount of EGR gas actually supplied to the internal combustion engine 1 decreases, so that the combustion temperature in the cylinder rises. As a result, the actual PM emission amount decreases.

  On the other hand, when a negative determination is made in step S306, that is, when the estimated value Regr of the actual EGR gas amount is smaller than the reference amount Regrbase of the EGR gas amount, the actual PM emission amount is less than the reference PM emission amount. I can judge. In this case, next, in step S308, as the actual PM emission amount control for increasing the actual PM emission amount, control for increasing the target EGR rate from the reference target value determined according to the operation state is executed. . When the target EGR rate is increased from the reference target value, the amount of EGR gas actually supplied to the internal combustion engine 1 increases, so that the combustion temperature in the cylinder decreases. As a result, the actual PM emission amount increases.

  Here, when the target EGR rate is reduced or increased as the actual PM emission amount control, it may be reduced or increased by a certain amount that is determined in advance from the reference target value. Further, the reduction amount or the increase amount of the target EGR rate may be determined according to the difference between the EGR gas amount difference ΔRegr calculated in step S304 and the predetermined amount ΔRegr0. In this case, the larger the difference, the larger the amount of reduction or increase in the target EGR rate.

  If a negative determination is made in step S305, then, in step S309, the target EGR rate is set to a reference target value determined according to the operating state.

  FIG. 7 is a flowchart showing a flow of third actual PM emission amount control according to the present embodiment. This flow is stored in advance in the ECU 10 and is repeatedly executed by the ECU 10. Note that, in this flow, steps in which the same processes as those in the second actual PM emission amount control flow shown in FIG. 6 are executed are denoted by the same reference numerals and description thereof is omitted.

  When the amount of EGR gas changes, the temperature of the intake air into which the EGR gas is introduced, that is, the temperature of the intake air supplied to the internal combustion engine 1 also changes. That is, when the EGR gas amount increases, the temperature of the intake air supplied to the internal combustion engine 1 increases. Conversely, when the EGR gas amount decreases, the temperature of the intake air supplied to the internal combustion engine 1 decreases.

Therefore, in the third actual PM emission amount control flow, the intake air supplied to the internal combustion engine 1 determined according to the detected value of the temperature of the intake air supplied to the internal combustion engine 1 and the operating state of the internal combustion engine 1. The difference between the actual PM discharge amount and the reference PM discharge amount is the filter 7 when the difference from the reference value (that is, the intake air temperature when the EGR gas amount is the reference value) is greater than a predetermined amount. It is determined that the condition that exceeds the threshold value that can maintain the accuracy of the fault diagnosis within the allowable range is established.

  In the third actual PM emission amount control flow, when an affirmative determination is made in step S301, the process of step S402 is then executed. In step S402, based on the operating state of the internal combustion engine 1, a reference value Tinbase for the temperature of the intake air supplied to the internal combustion engine 1 is calculated. The relationship between the operating state of the internal combustion engine 1 and the reference value Tinbase of the intake air temperature is obtained in advance based on experiments or the like, and is stored in the ECU 10 as a map or a function. In step S402, the reference value Tinbase of the intake air temperature is calculated using the map or function.

  Next, in step S403, a difference ΔTing between the actual intake air temperature Ting detected by the intake air temperature sensor 19 and the intake air temperature reference value Tingbase calculated in step S402 is calculated.

  Next, in step S404, it is determined whether or not the intake air temperature difference ΔTing calculated in step S403 is greater than a predetermined amount ΔTing0. The predetermined amount ΔTing0 is determined in advance based on experiments or the like.

  If an affirmative determination is made in step S404, it is then determined in step S405 whether or not the actual intake air temperature Ting is higher than a reference amount Tingbase of the intake air temperature.

  When an affirmative determination is made in step S405, it can be determined that the actual EGR gas amount is larger than the EGR gas amount reference amount Regrbase, and therefore the actual PM discharge amount is larger than the reference PM discharge amount. In this case, the process of step S307 is performed next. On the other hand, if a negative determination is made in step S405, it can be determined that the actual EGR gas amount is smaller than the reference amount Regrbase of the EGR gas amount, and therefore the actual PM discharge amount is smaller than the reference PM discharge amount. In this case, the process of step S308 is performed next.

  If a negative determination is made in step S404, then the process of step S309 is executed.

  By executing the first, second, or third actual PM discharge amount control flow as described above, the estimated passing PM amount is being accumulated to perform the failure diagnosis of the filter 7 (predetermined period Δta). It is possible to maintain high estimation accuracy of the estimated passing PM amount during

  In this embodiment, the ECU 10 that executes step S208 or S209 in the first actual PM emission amount control flow, or step S307 or S308 in the second or third actual PM emission amount control flow is executed. The ECU 10 to be executed corresponds to the actual PM emission amount control means according to the present invention.

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Intake passage 3 ... Exhaust passage 6 ... Oxidation catalyst 7 ... Particulate filter (filter)
10. ・ ECU
11. Crank position sensor 12 Air-fuel ratio sensor 13 First exhaust temperature sensor 14 Exhaust pressure sensor 15 Second exhaust temperature sensor 16 PM sensor 17 EGR passage 18 EGR valve 19 ..Intake air temperature sensor

Claims (4)

A PM sensor provided downstream of the particulate filter in the exhaust passage of the internal combustion engine and outputting a signal corresponding to the amount of particulate matter deposited on the PM sensor;
A filter passing PM amount estimating means for estimating a filter passing PM amount that is an amount of particulate matter passing through the particulate filter, assuming that the particulate filter is in a predetermined state;
The integrated value of the filter passing PM amount during the predetermined period calculated based on the amount of change in the output value of the PM sensor during the predetermined period, and the predetermined value of the filter passing PM amount estimated by the filter passing PM amount estimating means. A particulate filter failure diagnosis device for diagnosing whether or not a particulate filter failure has occurred by comparing the integrated value during the period,
During the predetermined period, there is a predetermined condition that a difference between the amount of particulate matter actually discharged from the internal combustion engine and a reference value of the particulate matter discharge amount according to the operating state of the internal combustion engine is larger than a predetermined amount. A particulate filter failure diagnosis device further comprising actual PM emission control means for executing control to increase or decrease the amount of particulate matter actually discharged from the internal combustion engine to the reference value side when established.   The predetermined condition is that a difference between a detected value of the temperature or pressure of the exhaust discharged from the internal combustion engine and a reference value of the exhaust temperature or pressure determined according to the operating state of the internal combustion engine is larger than a predetermined amount. The particulate filter failure diagnosis apparatus according to claim 1. An EGR device for introducing a part of the exhaust gas of the internal combustion engine into the intake system as EGR gas;
2. The predetermined condition is that a difference between an estimated value of an actual EGR gas amount and a reference value of an EGR gas amount determined according to an operation state of the internal combustion engine is larger than a predetermined amount. Particulate filter failure diagnosis device. An EGR device for introducing a part of the exhaust gas of the internal combustion engine into the intake system as EGR gas;
The predetermined condition is that the difference between the detected value of the temperature of the intake air supplied to the internal combustion engine and the reference value of the temperature of the intake air supplied to the internal combustion engine, which is determined according to the operating state of the internal combustion engine, is The particulate filter failure diagnosis device according to claim 1, wherein the particulate filter failure diagnosis device is greater than a fixed amount.

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