JP2023091199A - Exhaust emission control device - Google Patents

Abstract

To provide an exhaust emission control device capable of suppressing a wrong determination by preventing a DPF clogging determination from being made in a situation where an opening of a valve controlling exhaust gas recirculation amount in an EGR system is a predetermined value or lower.SOLUTION: An exhaust emission control device 50 for purifying exhaust gas of an engine 10 provided in a vehicle 1 includes: a DPF 52 trapping particulate matters; an ECU 60 (clogging determination section) for making a clogging determination on the basis of a pressure difference between the upstream side and downstream side of the DPF 52; and an EGR system 40 for returning part of exhaust gas to an intake side of the engine 10 via an EGR valve 41 (flow control valve). When an opening of the EGR valve 41 is a predetermined opening or smaller, the ECU 60 prohibits the clogging determination.SELECTED DRAWING: Figure 1

Description

The present invention relates to an exhaust gas purifier.

A vehicle equipped with an engine is equipped with an exhaust gas purification device for purifying exhaust gas. Some exhaust gas purifiers have a diesel particulate filter (DPF) that collects particulate matter (PM). The DPF determines clogging based on the differential pressure between the upstream side and the downstream side, as disclosed in Patent Document 1, for example.

Japanese Patent Application Laid-Open No. 2007-247596

By the way, in a vehicle equipped with an Exhaust gas recirculation system (EGR system), which suppresses the generation of NOx by returning (recirculating) part of the exhaust gas to the intake side of the engine, the flow rate of the exhaust gas flowing to the DPF affects the operation of the EGR system. affected by circumstances.

If the engine operating conditions are constant, when the EGR valve that controls the amount of exhaust gas recirculated in the EGR system is closed, there is no exhaust gas returning to the engine, or the amount of exhaust gas recirculated is small compared to the open side, so as a result, the DPF The flow rate of exhaust gas increases.

In this way, when the EGR valve is closed, the flow rate of exhaust gas flowing to the DPF increases, and the pressure difference between the upstream side and the downstream side of the DPF increases. There is a risk of erroneous determination.

In Patent Document 1, the amount of exhaust gas recirculated in the EGR system is kept constant when determining DPF clogging, thereby suppressing erroneous determinations. The above problem cannot be solved fundamentally.

Therefore, the present invention provides an exhaust gas purifying apparatus that can suppress erroneous determination by not performing DPF clogging determination under the condition that the opening degree of the valve that controls the exhaust gas recirculation amount of the EGR system is less than a predetermined value. be.

The present invention has been made to solve at least part of the above problems, and can be implemented as the following aspects or application examples.

An exhaust gas purifying device according to this application example is an exhaust gas purifying device for purifying exhaust gas from an internal combustion engine provided in a vehicle, and includes a diesel particulate filter that captures particulate matter, and an upstream side of the diesel particulate filter. and an EGR system that returns part of the exhaust gas to the intake side of the internal combustion engine via a flow control valve, and the clogging determination is based on the flow rate The clogging determination is prohibited when the degree of opening of the control valve is equal to or less than a predetermined degree of opening.

In this manner, the exhaust gas purifying apparatus prohibits determination of DPF clogging when the opening degree of the flow control valve (EGR valve) of the EGR system is in a closed state with a predetermined opening degree or less. In other words, when the exhaust gas recirculation amount is reduced by the EGR system and the exhaust gas flow rate toward the DPF is increased to increase the pressure, the DPF clogging determination is not performed. As a result, it is possible to suppress erroneous determination of DPF clogging while maintaining NOx suppression without interfering with the operation of the EGR system.

Therefore, the exhaust gas purification apparatus according to this application example can suppress erroneous determination by not determining clogging of the DPF under a condition where the opening degree of the valve that controls the exhaust gas recirculation amount of the EGR system is equal to or less than a predetermined opening degree. can.

1 is a schematic configuration diagram of a vehicle equipped with an exhaust gas purifying device according to an embodiment of the present invention; FIG.

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic configuration diagram of a vehicle equipped with an exhaust gas purifier according to one embodiment of the present invention. An engine 10 (internal combustion engine) that is a driving source of the vehicle 1 is, for example, a diesel engine. Each cylinder of the engine 10 is provided with a fuel injection valve 11. Each fuel injection valve 11 is supplied with pressurized fuel from a common rail, and opens at a timing according to the operating state of the engine 10 to open each cylinder. Inject fuel into

An intake passage 20 is connected to the intake side of the engine 10 via an intake manifold. The intake passage 20 is provided with an air filter 21 at the intake upstream end. The intake passage 20 is provided downstream of the air filter 21 with a compressor 22a of the turbocharger 22, an intercooler 23 for cooling the intake air, and an intake throttle valve 24 for adjusting the amount of intake air.

An exhaust passage 30 is connected to the exhaust side of the engine 10 via an exhaust manifold. The exhaust passage 30 is provided with a turbine 22b of the turbocharger 22 coaxially connected to the compressor 22a.

An EGR system 40 is provided between the intake passage 20 and the exhaust passage 30 to return (recirculate) part of the exhaust gas as EGR gas to the intake passage 20 via an EGR valve 41 (flow control valve). there is Specifically, the EGR system 40 has an EGR passage 42 that communicates the intake passage 20 and the exhaust passage 30 . The EGR passage 42 of the present embodiment connects the exhaust gas upstream side of the turbine 22 b in the exhaust passage 30 and the intake downstream side of the intake throttle valve 24 in the intake passage 20 . The EGR passage 42 is provided with an EGR cooler 43 for cooling the EGR gas.

The EGR valve 41 is provided downstream of the EGR cooler 43 in the EGR passage 42 in the EGR gas flow. The EGR valve 41 can be opened and closed by an actuator (not shown) to adjust the amount of recirculated EGR gas. Specifically, the EGR valve 41 increases the recirculation amount of EGR gas when it is opened, decreases the recirculation amount of EGR gas when it is closed, and stops the recirculation of EGR gas when it is fully closed.

During the operation of the engine 10, the intake air introduced into the intake passage 20 is pressurized by the compressor 22a of the turbocharger 22 and then distributed to each cylinder through the intercooler 23 and the intake throttle valve 24. sucked inside. In the cylinder, fuel is injected from the fuel injection valve 11 at a predetermined timing, ignited and burned near the compression top dead center, and exhaust gas after combustion is discharged to the exhaust passage 30 . When the EGR valve 41 is open, part of the exhaust gas is recirculated to the intake passage 20 through the EGR passage 42 as EGR gas. The remaining exhaust gas passes through the exhaust passage 30 and is discharged to the exhaust gas purification device 50 after rotating the turbine 22b.

The exhaust gas purification device 50 includes, in order from the exhaust upstream side, a front oxidation catalyst (DOC: Diesel Oxidation Catalyst) 51, a DPF (diesel particulate filter) 52, a SCR (Selective Catalytic Reduction) 53, a rear oxidation catalyst (CUC: Clean-up Catalyst) 54. The front oxidation catalyst 51 and the DPF 52 are housed in the upstream casing 50a, and the SCR 53 and the rear oxidation catalyst 54 are housed in the downstream casing 50b. Further, the upstream casing 50a and the downstream casing 50b are connected by an intermediate passage 50c.

The pre-oxidation catalyst 51 has a function of oxidizing components in the exhaust gas. The pre-oxidation catalyst 51 oxidizes, for example, hydrocarbons (HC) and carbon monoxide (CO) in unburned fuel, and produces nitrogen dioxide (NO ₂ ) from nitrogen monoxide (NO) in exhaust gas.

The DPF 52 is a porous filter having a function of collecting particulate matter (PM) in exhaust gas. Particulate matter captured by the DPF 52 is incinerated and removed by reacting with nitrogen dioxide (NO ₂ ) produced by the pre-oxidation catalyst 51 when the exhaust gas temperature is relatively high, thereby regenerating the DPF 52 .

The SCR 53 has a function of adsorbing NOx in the exhaust gas and selectively reducing NOx to nitrogen (N ₂ ) using ammonia (NH ₃ ) as a reducing agent to purify the exhaust gas. A urea injection valve 55 is provided in the intermediate passage 50c, and urea water is supplied from the urea injection valve 55 and becomes ammonia (NH ₃ ) as a reducing agent at the SCR 53 .

The post-oxidation catalyst 54 mainly has a function of oxidizing and removing ammonia (NH ₃ ) left over from the SCR 53 .

Further, the DPF 52 is provided with a differential pressure sensor 56 that detects a pressure difference (differential pressure) between the exhaust gas upstream side and the exhaust gas downstream side of the DPF 52 . Specifically, the differential pressure sensor 56 has an upstream pipe 56a connected between the front stage oxidation catalyst 51 of the upstream casing 50a and the DPF 52, and the other end of the differential pressure sensor 56 connected to the intermediate passage 50c on the exhaust gas downstream side. It has a side conduit 56b. The differential pressure sensor 56 can detect the degree of clogging of the DPF 52, that is, the amount of particulate matter collected, by detecting the pressure difference (differential pressure) between the two points to which this pipe line is connected.

The vehicle 1 is equipped with an ECU (electronic control unit) 60 including an input/output device (not shown), a storage device (ROM, RAM, etc.) in which control programs, control maps, etc. are stored, a central processing unit (CPU), and the like. It is Various signals are input to and output from the ECU 60, some of which include a detection signal (differential pressure information) from the differential pressure sensor 56 and an opening degree signal (opening degree information) of the EGR valve 41 .

The ECU 60 has a function of a clogging determination section that determines clogging of the DPF 52 based on the differential pressure detected by the differential pressure sensor 56 . Specifically, the ECU 60 determines whether or not the differential pressure detected by the differential pressure sensor 56 is equal to or greater than a predetermined threshold value when a clogging determination execution condition such as the engine 10 being in a predetermined operating state is satisfied. judge. If the differential pressure is greater than or equal to a predetermined threshold value, it is determined that the DPF 52 is abnormally clogged, and if it is less than the predetermined threshold value, it is determined that the DPF 52 is normal. It should be noted that when it is determined that clogging abnormality has occurred, the ECU 60 carries out warning processing to the driver or the mechanic.

On the other hand, the ECU 60 prohibits clogging determination when the opening degree of the EGR valve 41 is less than or equal to the predetermined opening degree even when the clogging determination implementation condition is satisfied. The predetermined degree of opening of the EGR valve 41 for prohibiting this clogging determination is set according to the degree of influence of the pressure rise on the exhaust upstream side of the DPF 52, and may be a constant value, or may vary according to the operating state of the engine 10. can be a value. After prohibiting the clogging determination, the ECU 60 performs the clogging determination if the clogging determination implementation condition is satisfied when the opening degree of the EGR valve 41 opens from the predetermined opening degree.

In this manner, the exhaust gas purification device 50 prohibits clogging determination of the DPF 52 when the opening degree of the EGR valve 41 of the EGR system 40 is in a closed state with a predetermined opening degree or less. In other words, in a situation where the EGR system 40 reduces the amount of exhaust gas recirculated and the flow rate of the exhaust gas toward the DPF 52 increases and the pressure rises, the clogging determination of the DPF 52 is not performed. As a result, it is possible to suppress erroneous determination of clogging of the DPF 52 while maintaining NOx suppression without interfering with the operation of the EGR system 40 .

As described above, the exhaust gas purifying device 50 according to the present embodiment does not determine clogging of the DPF 52 when the opening degree of the EGR valve 41 that controls the exhaust gas recirculation amount of the EGR system 40 is equal to or less than a predetermined opening degree. Misjudgment can be suppressed.

This completes the description of the embodiment of the exhaust purification device according to the present invention, but the aspect of the present invention is not limited to this embodiment.

Although only one EGR valve 41 is provided in the above embodiment, the EGR passage may be branched and an EGR valve may be provided in each branched passage.

In the above embodiment, the differential pressure sensor 56 detects the differential pressure between the exhaust gas upstream side and the exhaust gas downstream side of the DPF 52, but the means for detecting the differential pressure is not limited to this. For example, a pressure sensor may be provided on each of the exhaust gas upstream side and the exhaust gas downstream side of the DPF, and the differential pressure may be calculated by calculating the difference in pressure detected by each pressure sensor.

1: Vehicle 10: Engine 11: Fuel injection valve 20: Intake passage 21: Air filter 22: Turbocharger 22a: Compressor 22b: Turbine 23: Intercooler 24: Intake throttle valve 30: Exhaust passage 40: EGR system 41: EGR valve ( flow control valve)
42: EGR passage 43: EGR cooler 50: Exhaust gas purification device 50a: Upstream casing 50b: Downstream casing 50c: Intermediate passage 51: Pre-stage oxidation catalyst 52: DPF (diesel particulate filter)
53: SCR
54: post-oxidation catalyst 55: urea injection valve 56: differential pressure sensor 56a: upstream pipeline 56b: downstream pipeline 60: ECU (clogging determination unit)

Claims (1)

An exhaust gas purification device for purifying exhaust gas from an internal combustion engine provided in a vehicle,
a diesel particulate filter that traps particulate matter;
A clogging determination unit that determines clogging based on the differential pressure between the upstream side and the downstream side of the diesel particulate filter,
an EGR system that returns a portion of the exhaust gas to the intake side of the internal combustion engine via a flow control valve;
with
The exhaust gas purifier according to claim 1, wherein the clogging determination unit prohibits the clogging determination when the degree of opening of the flow control valve is less than or equal to a predetermined degree of opening.

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