JP4440823B2 - Exhaust gas purification device for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust emission control device for an internal combustion engine, and more particularly to a device having a filter (DPF: Diesel Particulate Filter) for collecting particulates (particulate matter) in exhaust gas from an internal combustion engine.

  2. Description of the Related Art Conventionally, a technique for reducing a particulate discharge amount by providing a DPF for collecting particulates in exhaust gas in an exhaust system of a diesel internal combustion engine has been widely used. When a failure such as a crack or a hole occurs in the filter element constituting the DPF, the filter function of the DPF is lowered, and the particulate discharge amount is increased. Therefore, such a failure needs to be detected quickly.

In Patent Document 1, a pressure sensor is provided on the downstream side of the DPF, and the difference between the maximum value and the minimum value of the detected pressure during engine operation, that is, the pulsation amplitude is obtained. A technique for determining occurrence has been shown.
JP 2004-308454 A

  With the technique disclosed in Patent Document 1, the amount of particulate leakage due to a failure cannot be detected. For this reason, it is difficult to satisfy the requirement of “detecting a failure before the amount of particulate leakage exceeds a predetermined amount due to a decrease in the particulate collection ability of the DPF”. Further, the technique disclosed in Patent Document 1 requires complicated calculation in order to monitor and analyze the pulsation amplitude of the exhaust pressure.

  The present invention has been made in consideration of the above-described points, and an object of the present invention is to provide an exhaust purification device capable of accurately detecting a DPF failure state with a relatively simple configuration.

  In order to achieve the above object, an invention according to claim 1 is directed to an exhaust gas purification apparatus for an internal combustion engine comprising filter means (12) for collecting particulates in the exhaust gas of the internal combustion engine (1). According to the state, a first collection amount calculating means for calculating a first particulate amount (GDPF1) indicating a particulate amount to be collected by the filter means (12), and a filter means (12) A second amount indicating the amount of particulates collected by the filter means (12) in accordance with the temperature (TDPF) of the filter means (12) when the filter regeneration for incinerating the collected particulates is performed. The second collection amount calculation means for calculating the particulate amount (GDPF2) is compared with the first and second particulate amounts (GDPF1, GDPF2). According to the comparison result, characterized in that it comprises a failure determining means for performing a failure determination of the filter means (12).

  According to a second aspect of the present invention, in the exhaust gas purification apparatus for an internal combustion engine according to the first aspect, the failure determination means is responsive to a ratio of the first and second particulate amounts (GDPF2 / GDPF1). When the particulate collection rate (PMCE) of the filter means (12) is calculated and the particulate collection rate (PMCE) is equal to or less than a predetermined threshold value (CETH), the filter means (12) is out of order. It is characterized by determining.

  According to the first aspect of the present invention, the first particulate amount indicating the particulate amount to be collected by the filter means is calculated according to the operating state of the engine, and the collected particulate is incinerated. The second particulate quantity indicating the particulate quantity collected by the filter means is calculated according to the temperature of the filter means when the filter regeneration is performed, and the comparison result of the first and second particulate quantities is calculated. Accordingly, the failure determination of the filter means is performed. Since the amount of change in the temperature of the filter means when the filter regeneration is performed is substantially proportional to the amount of the collected particulates, it indicates the amount of particulates actually collected by the filter means according to the temperature of the filter means. The second particulate amount can be calculated. On the other hand, the first particulate amount calculated according to the engine operating state indicates the particulate amount discharged from the engine. When the difference between the two is large, the filter means has cracks or perforations. Conceivable. Accordingly, the failure of the filter means can be accurately determined by comparing the first and second particulate amounts.

  According to the second aspect of the present invention, the particulate collection rate of the filter means is calculated according to the ratio between the first and second particulate amounts, and the particulate collection rate is equal to or less than a predetermined threshold value. When it is determined that the filter means is out of order. As described above, the first particulate amount indicates the particulate amount discharged from the engine, and the second particulate amount indicates the particulate amount actually collected by the filter means. The ratio of the second particulate amount to the curate amount corresponds to the particulate collection rate of the filter means. Therefore, when the particulate collection rate is equal to or less than the predetermined threshold, it indicates that the particulate filter is not normally collected by the filter means, and therefore it can be determined that there is a failure. By calculating the particulate collection rate, it is possible to determine the degree of failure (critical or minor) of the filter means.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a diagram showing a configuration of an internal combustion engine including an exhaust purification device according to an embodiment of the present invention and a control device thereof. An internal combustion engine (hereinafter simply referred to as “engine”) 1 is a diesel engine that directly injects fuel into a cylinder, and a fuel injection valve 16 is provided in each cylinder. The fuel injection valve 16 is electrically connected to an electronic control unit (hereinafter referred to as “ECU”) 20, and the valve opening time and valve opening timing of the fuel injection valve 16 are controlled by the ECU 20.

The engine 1 includes an intake pipe 2, an exhaust pipe 4, and a supercharger 8. The supercharger 8 includes a turbine 10 that is driven by exhaust kinetic energy, and a compressor 9 that is rotationally driven by the turbine 10 and compresses intake air.
The turbine 10 includes a plurality of variable vanes (not shown), and is configured to change the turbine rotational speed (rotational speed) by changing the opening degree of the variable vanes. The vane opening degree of the turbine 10 is electromagnetically controlled by the ECU 20.

  An intercooler 5 for cooling the pressurized air and an intake shutter (throttle valve) 3 for controlling the intake air amount are provided in the intake pipe 2 downstream of the compressor 9. The intake shutter 3 is controlled to be opened and closed by the ECU 20 via an actuator (not shown).

  Between the upstream side of the turbine 10 in the exhaust pipe 4 and the downstream side of the intake shutter 5 in the intake pipe 2, an exhaust gas recirculation passage 6 for returning the exhaust gas to the intake pipe 2 is provided. The exhaust gas recirculation passage 6 is provided with an exhaust gas recirculation control valve (hereinafter referred to as “EGR valve”) 7 for controlling the exhaust gas recirculation amount. The EGR valve 7 is an electromagnetic valve having a solenoid, and the valve opening degree is controlled by the ECU 20.

On the downstream side of the turbine 10 in the exhaust pipe 4, a catalytic converter 11 for purifying exhaust and a DPF 12 are provided in this order from the upstream side.
The catalytic converter 11 contains a NOx absorbent that absorbs NOx and a catalyst for promoting oxidation and reduction. The NOx absorbent absorbs NOx in an exhaust lean state in which the air-fuel ratio of the air-fuel mixture in the combustion chamber of the engine 1 is set to be leaner than the stoichiometric air-fuel ratio and the oxygen concentration in the exhaust is relatively high (NOx is high). On the other hand, when the air-fuel ratio of the air-fuel mixture is set near the stoichiometric air-fuel ratio or richer than the stoichiometric air-fuel ratio, the exhaust gas has a characteristic of releasing the absorbed NOx in an exhaust rich state where the oxygen concentration in the exhaust gas is relatively low. .

  In the catalytic converter 11, in the exhaust rich state, NOx released from the NOx absorbent is reduced by HC and CO and discharged as nitrogen gas, and HC and CO are oxidized and discharged as water vapor and carbon dioxide. It is configured.

  When the exhaust gas passes through the fine holes in the filter wall, the DPF 12 deposits soot, which is a particulate material mainly composed of carbon (C) in the exhaust gas, on the surface of the filter wall and the holes in the filter wall. Collect by letting. As a constituent material of the filter wall, for example, ceramics such as silicon carbide (SiC) or a porous metal body is used.

  If soot is collected up to the limit of the soot collecting ability of the DPF 12, that is, the accumulation limit, the exhaust pressure rises, so it is necessary to perform a regeneration process for burning the soot in a timely manner. In this regeneration process, post-injection control is executed in order to raise the exhaust temperature to the soot combustion temperature. In the post injection control, the fuel injection valve 16 performs not only normal injection in the compression stroke, but also post injection (post injection) in the subsequent explosion stroke and exhaust stroke. The fuel injected by the post injection may be burned in the combustion chamber of the engine 1 or may be burned in the catalytic converter 11 depending on the injection timing.

The DPF 12 is provided with a DPF temperature sensor 23 for detecting the temperature (hereinafter referred to as “DPF temperature”). The detection signal of the temperature sensor 23 is supplied to the ECU 20.
Further, a crank angle position sensor 22 that detects the rotation angle of the crankshaft of the engine 1, an intake air flow rate sensor 21 that detects the intake air flow rate GA of the engine 1, and a cooling water temperature sensor (not shown) that detects the cooling water temperature of the engine 1. The detection signals of these sensors are supplied to the ECU 20. The engine speed NE of the engine 1 is calculated from the output of the crank angle position sensor.

  The ECU 20 shapes input signal waveforms from various sensors, corrects the voltage level to a predetermined level, converts an analog signal value into a digital signal value, a central processing unit (hereinafter referred to as “CPU”). A storage circuit that stores various calculation programs executed by the CPU, calculation results, and the like, and an output circuit that supplies control signals to the fuel injection valve 16, the EGR valve 7, and the like.

FIG. 2 is a flowchart showing a processing procedure for determining a failure of the DPF 12, specifically, a deterioration of the filter function due to cracking or perforation of the filter wall. This failure determination process is executed by the CPU of the ECU 20.
In step S101, the amount of particulates (hereinafter referred to as “first DPF accumulation amount”) GDPF1 to be collected in the DPF 12 according to the operating state of the engine 1 is calculated. The first DPF accumulation amount GDPF1 is calculated according to the operation state of the engine 1 (for example, the engine speed NE and the intake air flow rate GA) based on an algorithm and a map stored in advance, and the accumulation amount is calculated at regular intervals. This is done by calculating. This first DPF accumulation amount GDPF1 accurately indicates the accumulation amount when all the particulates discharged from the engine 1 are collected in the DPF 12. Therefore, when there is a crack or the like on the filter wall of the DPF 12, the actual deposition amount is smaller than the first particulate amount GDPF1.

  If the first DPF accumulation amount GDPF1 calculated in step S101 does not exceed the predetermined regeneration control threshold GPTH, the answer to step S102 is negative (NO), and the failure determination is not executed. When the first DPF accumulation amount GDPF1 exceeds a predetermined regeneration control threshold value GPTH, regeneration control for burning the deposited soot is performed, and the processing after step S103 is performed. The regeneration control is performed by raising the exhaust gas temperature by post injection as described above.

  In step S103, the DPF temperature sensor 23 measures the DPF temperature TDPF. This DPF temperature TDPF is the maximum value of the detected temperature during regeneration control. In step S104, the GDPF2 table shown in FIG. 3 is searched according to the DPF temperature TDPF, and the particulate amount (hereinafter referred to as “second DPF accumulation amount”) GDPF2 collected in the DPF 12 is calculated. The GDPF2 table is set so that the second DPF accumulation amount GDPF2 increases as the DPF temperature TDPF increases. Focusing on the fact that the DPF temperature TDPF increases as the amount of particulates burned during regeneration control increases, the GDPF2 table measures the DPF temperature in advance by changing the amount of accumulated particulates, and stores it in a storage circuit in the ECU 20. I remembered it.

In step S105, the first DPF accumulation amount GDPF1 and the second DPF accumulation amount GDPF2 are applied to the following equation (1), and the particulate collection rate PMCE by the DPF 12 is calculated.
PMCE = GDPF2 / GDPF1 (1)
In step S106, it is determined whether or not the collection rate PMCE is equal to or less than a determination threshold value CETH (for example, 0.8). As a result, when the collection rate PMCE is equal to or less than the determination threshold CETH, it is determined that the DPF 12 has failed, that is, the filter function has been degraded due to cracking or perforation (step S107), and the collection rate PMCE is When it is larger than the determination threshold value CETH, it is determined that the DPF 12 is normal (step S108).

  As described above, in the present embodiment, when the first DPF accumulation amount GDPF1 indicating the particulate amount to be collected in the DPF 12 is calculated and the regeneration control of the DPF 12 is performed according to the operating state of the engine 1. In accordance with the measured DPF temperature TDPF, the second DPF accumulation amount GDPF2 indicating the particulate amount actually collected in the DPF 12 is calculated, and the comparison result between the first and second DPF accumulation amounts GDPF1, GDPF2 Accordingly, the failure determination of the DFP 12 is performed. The first DPF accumulation amount GDPF1 calculated according to the engine operating state indicates the amount of particulates discharged from the engine 1, and when the difference from the second DPF accumulation amount GDPF2 is large, the DPF 12 is cracked. Or it is thought that perforation has occurred. Therefore, the failure of the DPF 12 can be accurately determined by comparing the first and second DPF accumulation amounts GDPF1, GDPF2.

  More specifically, the collection rate PMCE is calculated as a ratio of the second DPF accumulation amount GDPF2 to the first DPF accumulation amount GDPF1, and when the collection rate PMCE is equal to or less than the determination threshold CETH, the DPF 12 fails. It is determined that By calculating the collection rate PMCE, it is possible to determine the degree of failure (critical or minor) of the DPF 12.

  In the present embodiment, the DPF 12 corresponds to a filter unit. The intake air flow rate sensor 21, the crank angle position sensor 22, and the ECU 20 constitute a first collection amount calculation means, the temperature sensor 23 and the ECU 20 constitute a second collection amount calculation means, and the ECU 20 serves as a failure determination means. Constitute. Specifically, step S101 in FIG. 2 corresponds to the first collection amount calculation means, steps S103 and S104 correspond to the second collection amount calculation means, and steps S105 to S108 correspond to the failure determination means.

(Modification)
In the embodiment described above, failure diagnosis is performed during regeneration control of the DPF 12 by post injection or the like, but failure diagnosis may be performed when natural regeneration is performed in the DPF 12. For example, when the engine 1 is in a high load operation, the exhaust temperature rises and natural regeneration in which the particulates accumulated in the DPF 12 are burned is performed. Diagnosis can be performed.

  FIG. 4 is a flowchart showing a procedure for failure determination according to this modification. The flowchart shown in FIG. 4 is obtained by replacing step S102 in FIG. 2 with step S102a. In step S102a, it is determined whether or not natural reproduction is being performed. When natural reproduction is being performed, step S103 and subsequent steps are executed. Whether or not natural regeneration is being performed is determined, for example, based on whether or not both the engine speed and the engine load exceed a predetermined threshold.

  In the above-described embodiment, the collection rate PMCE is calculated, and the failure diagnosis is performed by comparing the collection rate PMCE and the determination threshold value CETH. However, the first DPF accumulation amount GDPF1 and the second DPF accumulation When the difference from the amount GDPF2 is larger than the corresponding determination threshold value, it may be determined that the DPF 12 is out of order.

  In the above-described embodiment, the temperature of the DPF 12 is directly detected by the temperature sensor 23 during the regeneration control. However, a temperature sensor is provided on the downstream side of the DPF 12, and the temperature TDEX of the exhaust discharged from the DPF 12 is detected as the temperature of the DPF 12. You may do it. Further, the upstream temperature TDIN of the DPF 12 is also detected, and the temperature increase amount ΔTDPF is calculated by subtracting the upstream temperature TDIN from the downstream temperature TDEX, and the second DPF accumulation amount GDPF2 is calculated according to the temperature increase amount ΔTDPF. You may make it calculate.

  Further, during the regeneration control, the downstream temperature TDEX is measured and integrated at regular intervals to calculate the temperature integrated value ITDEX, and the second DPF accumulation amount GDPF2 is detected according to the temperature integrated value ITDEX. It may be.

  Further, during the regeneration control, the downstream temperature TDEX is measured at regular intervals, and the difference is taken to calculate the temperature increase rate parameter DTDEX indicating the temperature increase rate, and according to the temperature increase rate parameter DTDEX, The DPF accumulation amount GDPF2 of 2 may be detected.

  The present invention can also be applied to an exhaust purification device such as a marine vessel propulsion engine such as an outboard motor having a vertical crankshaft.

It is a figure showing composition of an internal combustion engine provided with an exhaust-air-purification device concerning one embodiment of the present invention, and its control device. It is a flowchart which shows the procedure of failure determination. It is a figure which shows the table used by the process of FIG. It is a figure which shows the modification of the process shown in FIG.

Explanation of symbols

1 Internal combustion engine 4 Exhaust pipe 12 DPF (filter means)
20 Electronic control unit (first collection amount calculation means, second collection amount calculation means, failure determination means)
21 Intake air flow rate sensor (first collected amount detection means)
22 Engine speed sensor (first collected amount detection means)

Claims (2)

In an exhaust gas purification apparatus for an internal combustion engine comprising filter means for collecting particulates in the exhaust gas of the internal combustion engine,
A first collection amount calculating means for calculating a first particulate amount indicating a particulate amount to be collected by the filter means in accordance with an operating state of the engine;
The second particulate quantity indicating the particulate quantity collected by the filter means is calculated according to the temperature of the filter means when the filter regeneration for incinerating the particulate matter collected by the filter means is performed. Second collection amount calculating means for
An exhaust emission control device for an internal combustion engine, comprising: failure determination means for comparing the first and second particulate amounts and determining failure of the filter means according to the comparison result.   The failure determination means calculates a particulate collection rate of the filter means according to a ratio of the first and second particulate amounts, and when the particulate collection rate is equal to or less than a predetermined threshold, 2. The exhaust emission control device for an internal combustion engine according to claim 1, wherein it is determined that the filter means has failed.

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