JP5049951B2 - Exhaust aftertreatment device - Google Patents

Description

  The present invention relates to an exhaust aftertreatment device that incinerates and removes particulates accumulated on a filter by oxidation reaction heat of fuel injected and supplied to an exhaust passage of an engine.

  Particulates (also referred to as PM, particulate matter) contained in exhaust gas from diesel engines, etc. are collected by a filter (particulate filter), and the filter is heated at a predetermined timing to eliminate accumulated particulates. Playing the filter has been done.

  Patent Document 1 includes an injector for injecting and supplying fuel (light oil) into an exhaust passage of an engine. The fuel injected from the injector is oxidized by an oxidation catalyst, and the particulates accumulated on the filter are incinerated by the heat of oxidation reaction. It is described to be removed.

As an exhaust aftertreatment device of this type, there has heretofore been one in which pressurized fuel and pressurized air are respectively guided to a nozzle facing an exhaust passage, and fuel and air are mixed and supplied from the nozzle.
JP 2005-98184 A

  However, in such a conventional exhaust aftertreatment device, there is a possibility that an abnormality occurs in the air supply system that supplies pressurized air or an abnormality such as clogging of the nozzles.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an exhaust aftertreatment device that diagnoses an abnormality in an air supply system with respect to a nozzle.

  In the present invention, a filter interposed in the exhaust passage of the engine, a nozzle facing the upstream side of the filter of the exhaust passage, a fuel supply passage that guides pressurized fuel to the nozzle, and an air supply passage that guides pressurized air to the nozzle And an exhaust aftertreatment device that injects fuel and air upstream of the filter in the exhaust passage and burns and removes particulates deposited on the filter by oxidation reaction heat of the fuel injected from the nozzle. A pressure sensor for detecting the fuel pressure guided to the passage; an upstream fuel shut-off valve for shutting off the fuel supply passage upstream of the pressure sensor; and a downstream fuel shut-off valve for shutting off the fuel supply passage downstream of the pressure sensor And an air shut-off valve that shuts off the air supply passage, and closes the upstream fuel shut-off valve and opens the downstream fuel shut-off valve and the air shut-off valve. And configured to diagnose an abnormality in the air supply system according to the air supply pressure detected Te.

  According to the present invention, the air supply pressure led from the air supply passage to the fuel supply passage is detected by the pressure sensor interposed in the fuel supply passage, and the abnormality of the air supply system is accurately determined according to the detected air supply pressure. Can be diagnosed.

  Embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a block diagram showing a schematic configuration of an exhaust aftertreatment device. In the exhaust aftertreatment device, an oxidation catalyst (DOC) 3, a filter (DPF) 4, and a urea SCR catalyst 5 are sequentially disposed in the exhaust passage 2 of the diesel engine 10.

  In the oxidation catalyst 3, for example, activated alumina or the like is coated on the surface of a honeycomb cordierite or heat-resistant steel support, and a catalytic active component of a noble metal such as platinum, palladium or rhodium is included in the coating layer. The oxidation catalyst 3 oxidizes NO, HC, and CO in the exhaust gas and converts them into NO2, H2, and CO2.

  The filter 4 is a filter that collects particulates (PM) in the exhaust gas, and includes a heat-resistant porous filter wall such as ceramic.

  Under active conditions of the catalyst having a high temperature of the oxidation catalyst 3, continuous regeneration is performed in which the particulates captured by the filter 4 are oxidized and removed.

  Under the inactive state of the catalyst having a low temperature of the oxidation catalyst 3, the particulates may not be sufficiently processed and the deposition amount may increase. In response to this, when the particulates captured by the filter 4 reach a predetermined amount, forced regeneration is performed to forcibly remove the particulates.

  A nozzle 6 for injecting fuel and air is provided upstream of the oxidation catalyst 3 in the exhaust passage 2. At the time of forced regeneration, the fuel injected from the nozzle 6 is oxidized by the oxidation catalyst 3, and forced regeneration is performed in which particulates accumulated on the filter 4 are incinerated and removed by the oxidation reaction heat.

  FIG. 2 is a circuit diagram showing a configuration of a forced regeneration device 20 that injects fuel and air from the nozzle 6.

  The forced regeneration device 20 includes a fuel supply passage 21 that guides pressurized fuel, an air supply passage 22 that guides pressurized air, and a fuel-air mixing passage 23 that mixes pressurized fuel and pressurized air and leads them to the nozzle 6. With.

  The fuel supply passage 21 communicates with a fuel tank via a fuel pump (not shown) and is supplied with pressurized fuel discharged from the fuel pump. The pressure of the fuel supplied to the fuel supply passage 21 is adjusted to about 100 kPa, for example.

  In the fuel supply passage 21, an upstream side fuel cutoff valve (SOV) 31, a check valve 32, a pressure sensor 33, and a downstream side fuel cutoff valve (AHI) 34 are interposed in this order.

  The upstream side fuel cutoff valve 31 and the downstream side fuel cutoff valve 34 are respectively constituted by electromagnetic valves, and are opened and closed by a drive current sent from a controller (not shown).

  The check valve 32 is interposed between the upstream fuel cutoff valve 31 and the pressure sensor 33, and stops the back flow of fuel in the fuel supply passage 21.

  The pressure sensor 33 provided as a pressure detection means detects the fuel pressure generated between the check valve 32 and the downstream side fuel cutoff valve 34 in the fuel supply passage 21, and outputs a detection signal to the controller.

  The air supply passage 22 takes in outside air via an air pump (not shown) and is supplied with pressurized air discharged from the air pump. The pressure of the air supplied to the air supply passage 22 is adjusted to about 200 kPa, for example.

  In the air supply passage 22, an orifice 26, an air shut-off valve (AIR) 27, and a check valve 28 are interposed in this order.

  The air shut-off valve 27 is constituted by an electromagnetic valve and opens and closes by a drive current sent from the controller.

  The check valve 28 stops the backflow of air in the air supply passage 22.

  The nozzle 6 has an injection hole (throttle) that reduces the passage cross-sectional area at the downstream end of the fuel-air mixing passage 23. The nozzle 6 faces the inside of the exhaust pipe defining the exhaust passage 2, and injects fuel into the exhaust gas flowing through the exhaust passage 2 in a sprayed state.

  The controller determines the forced regeneration timing of the filter 4 according to the operation state detection signal of the engine 10, and opens the upstream side fuel cutoff valve 31, the downstream side fuel cutoff valve 34, and the air cutoff valve 27 at the time of forced regeneration. Let As a result, the pressurized fuel guided from the fuel supply passage 21 and the pressurized air guided from the air supply passage 22 are mixed, and this is guided to the nozzle 6 through the fuel-air mixing passage 23 and exhausted from the nozzle 6. The fuel is sprayed into the exhaust gas flowing through the passage 2 and injected. The injected fuel is oxidized by the oxidation catalyst 3, and forced regeneration is performed by burning and removing the particulates accumulated on the filter 4 by the oxidation reaction heat.

  By the way, the forced regeneration device 20 may cause an abnormality in the fuel supply system, an abnormality in the air supply system, clogging of the nozzle 6, and the like.

  In response to this, in the present invention, the controller opens and closes the upstream side fuel cutoff valve 31, the downstream side fuel cutoff valve 34, and the air cutoff valve 27 in a predetermined procedure, and the detection signal of the pressure sensor 33 in the process. Accordingly, abnormality of the fuel supply system, abnormality of the air supply system, and clogging of the nozzle 6 are respectively diagnosed.

  Next, this control operation executed by the controller will be described with reference to the flowchart of FIG.

  Here, the forced regeneration device 20 is configured such that when the fuel supply system operates normally, 100 kPa of pressurized fuel is guided to the fuel supply passage 21, and when the air supply system operates normally, It is set so that pressurized air of 200 kPa is guided.

  In an operating state of the engine 10 in which a predetermined diagnosis condition (an operating state in which the upstream fuel cutoff valve 31 is opened and the downstream fuel cutoff valve 34 is closed) is established, first, in steps S1 to S5, air Diagnose supply system abnormalities.

  In step S1, the upstream side fuel cutoff valve 31, the downstream side fuel cutoff valve 34, and the air cutoff valve 27 are all closed.

In step S2, the fuel supply pressure P ₀ detected by the pressure sensor 33 is read. When the fuel supply system operates normally, the read fuel supply pressure P ₀ has a value of 100 kPa.

  Subsequently, in step S3, with the upstream side fuel cutoff valve 31 kept closed, the downstream side fuel cutoff valve 34 and the air cutoff valve 27 are opened, and the air supply pressure led from the air supply passage 22 is opened. Is guided to the pressure sensor 33 through the fuel supply passage 21.

  At this time, the pressurized air supplied from the air supply passage 22 is guided to the nozzle 6 from the fuel air mixing passage 23, and only air is injected from the nozzle 6. As a result, the contaminants and the like adhering to the inside of the nozzle 6 are blown off by the air flow, and a purge process for eliminating the clogging of the nozzle 6 is performed.

In step S4, the air supply pressure P ₁ detected by the pressure sensor 33 is read.

Here, when the air supply system operates normally, the read air supply pressure P ₁ has a value of 200 kPa.

Subsequent step S5, it is determined whether or not higher than the fuel supply pressure P ₀ of the air supply pressure P ₁ is read to read.

When it is determined that the air supply pressure P ₁ is higher than the fuel supply pressure P _0, it is determined that the air supply system is operating normally, and the process proceeds to step S6.

On the other hand, when it is determined that the air supply pressure P ₁ is equal to or lower than the fuel supply pressure P _0, it is determined that an abnormality has occurred in the air supply system, and the process proceeds to step S6.

  In step S6, an air supply system abnormality flag indicating that an abnormality has occurred in the air supply system is set. When it is determined in another routine (not shown) that the air supply system abnormality flag is set, an abnormality display of the air supply system is output to a display (not shown), and the abnormality of the air supply system occurs to the driver. Let them know.

  If it is determined in steps S1 to S5 that the air supply system is operating normally, an abnormality of the nozzle 6 is diagnosed in steps S6 to S9.

  First, in step S6, the air cutoff valve 27 is closed with the upstream side fuel cutoff valve 31 being continuously closed and the downstream side fuel cutoff valve 34 being continuously opened. As a result, the air supply pressure introduced from the air supply passage 22 is shut off to the pressure sensor 33, and the residual air pressure generated in the fuel-air mixing passage 23 upstream of the nozzle 6 is introduced.

Followed at step S7, read air residual pressure P ₂ detected by the pressure sensor 33.

Here, when the nozzle 6 is not clogged, the read air residual pressure P ₂ is reduced to approximately 0 kPa to the exhaust pressure in the exhaust passage 2. When the nozzle 6 is clogged, the read air residual pressure P ₂ hardly decreases, and the air pressure equivalent to 200 kPa led from the air supply passage 22 remains.

Subsequent step S8, the air supply pressure P ₁ read is equal to or higher than or air residual pressure P _2.

When it is determined that the air supply pressure P ₁ is higher than the residual air pressure P _2, it is determined that the nozzle 6 is operating normally without clogging, and the process proceeds to step S9.

On the other hand, when it is determined that the air supply pressure P ₁ is equal to or lower than the residual air pressure P _2, it is determined that the nozzle 6 is clogged and the residual air pressure P ₂ is high in the fuel / air mixing passage 23, and the abnormal time is determined. Proceed to step S11.

  In step S11, a nozzle abnormality flag indicating that an abnormality has occurred in the nozzle 6 is set. When it is determined in another routine (not shown) that the nozzle abnormality flag is set, a nozzle abnormality display is output to a display (not shown) to notify the driver that a nozzle abnormality has occurred.

  Further, in another routine (not shown), whether or not an abnormality has occurred in the fuel system is determined according to the detection signal of the pressure sensor 33. Description of this control content is omitted.

In the present embodiment, a filter 4 interposed in the exhaust passage 2 of the engine 10, a nozzle 6 facing the upstream side of the filter 4 of the exhaust passage 2, a fuel supply passage 21 that guides pressurized fuel to the nozzle 6, An air supply passage 22 for introducing pressurized air to the nozzle 6 is provided. Fuel and air are injected upstream of the filter 4 in the exhaust passage 2 and deposited on the filter 4 by the oxidation reaction heat of the fuel injected from the nozzle 6. An exhaust aftertreatment device for removing particulates by incineration,
A pressure sensor 33 that detects the fuel pressure guided to the fuel supply passage 21, an upstream fuel cutoff valve 31 that shuts off the fuel supply passage 21 upstream of the pressure sensor 33, and a fuel supply passage downstream of the pressure sensor 33 21, a downstream fuel cutoff valve 34 that shuts off the air supply passage 22, and an air cutoff valve 27 that shuts off the air supply passage 22. The upstream fuel cutoff valve 31 is closed and the downstream fuel cutoff valve 34 and the air cutoff valve 27 are respectively connected. An abnormality of the air supply system is diagnosed according to the air supply pressure P ₁ detected by the pressure sensor 33 in the opened state.

Based on the above configuration, the pressure sensor 33 interposed in the fuel supply passage 21 to detect an air supply pressure P ₁ derived from the air supply passage 22 to the fuel supply passage 21, depending on the air supply pressure P ₁ detected Abnormalities in the air supply system can be accurately diagnosed.

In this embodiment, the upstream side fuel cutoff valve 31, the downstream side fuel cutoff valve 34, and the air cutoff valve 27 are all closed to detect the pressure sensor 33 in a state where both the fuel supply pressure and the air supply pressure are shut off. The fuel supply pressure P ₀ is read, the upstream fuel cutoff valve 31 is subsequently closed, the fuel supply pressure introduced from the fuel supply passage 21 is shut off, and the downstream fuel cutoff valve 34 and the air cutoff valve 27 are opened. Load the air supply pressure P ₁ of the air supply pressure by valve derived from the air supply passage 22 is detected by the pressure sensor 33 in a state to be guided respectively to the pressure sensor 33 and the nozzle 6, the detected air supply pressure P ₁ There is determined that the air supply system in the case of more than the fuel supply pressure P ₀ is operating normally, when the air supply pressure P ₁ detected is lower than the fuel supply pressure P ₀ in the air supply system Always has that a determined configuration occurs.

Based on the above configuration, the read air supply pressure P ₁ and the fuel supply pressure P ₀ can be compared to accurately diagnose an abnormality in the air supply system.

In this embodiment, after it is determined that the air supply system is operating normally, the upstream side fuel cutoff valve 31 is continuously closed and the downstream side fuel cutoff valve 34 is continuously opened to open the air cutoff valve 27. When the air residual pressure P ₂ detected by the pressure sensor 33 is detected with the valve closed, and the detected air supply pressure P ₁ is equal to or lower than the air residual pressure P ₂ , an abnormality has occurred in the nozzle 6. Based on the above configuration, the air supply pressure P ₁ and the air residual pressure P ₂ are compared, and when the nozzle 6 is clogged and the air-air pressure P ₂ is high in the fuel / air mixing passage 23, Diagnose accurately.

  The present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

The block diagram which shows schematic structure of the exhaust gas aftertreatment apparatus which shows embodiment of this invention. The circuit diagram which similarly shows the structure of a forced regeneration apparatus. The flowchart which shows this control content performed with a controller.

Explanation of symbols

3 Oxidation catalyst 4 Filter 6 Nozzle 10 Engine 20 Forced regeneration device 21 Fuel supply passage 22 Air supply passage 23 Fuel / air mixing passage 26 Orifice 27 Air shut-off valve 28 Check valve 31 Upstream fuel shut-off valve 32 Check valve 33 Pressure sensor 34 Downstream side Fuel shut-off valve

Claims (3)

  A filter disposed in an exhaust passage of the engine, a nozzle facing the upstream side of the filter in the exhaust passage, a fuel supply passage for guiding pressurized fuel to the nozzle, and an air supply passage for guiding pressurized air to the nozzle And an exhaust aftertreatment device that injects fuel and air upstream of the filter in the exhaust passage and burns and removes particulates deposited on the filter by oxidation reaction heat of the fuel injected from the nozzle. A pressure sensor for detecting a fuel pressure guided to the fuel supply passage, an upstream fuel cutoff valve for shutting off the fuel supply passage upstream of the pressure sensor, and the fuel supply passage downstream of the pressure sensor. A downstream fuel shut-off valve that shuts off the air supply passage, and an air shut-off valve that shuts off the air supply passage. Exhaust post-treatment device, characterized in that for diagnosing an abnormality in the air supply system in accordance with the air supply pressure detected by the pressure sensor air shutoff valve in a state of being opened, respectively.   The fuel supply pressure detected by the pressure sensor is detected in a state where the upstream side fuel cutoff valve, the downstream side fuel cutoff valve, and the air cutoff valve are all closed, and the upstream side fuel cutoff valve is continued. The fuel supply pressure guided from the fuel supply passage is shut off, the downstream fuel cutoff valve and the air cutoff valve are opened, and the air supply pressure guided from the air supply passage is connected to the pressure sensor. When the air supply pressure detected by the pressure sensor is detected in a state of being led to the nozzles, and the detected air supply pressure is equal to or higher than the fuel supply pressure, the air supply system is operating normally. 2. After exhausting according to claim 1, wherein it is determined that an abnormality has occurred in the air supply system when the detected air supply pressure is lower than the fuel supply pressure. Management apparatus.   After it is determined that the air supply system is operating normally, the upstream fuel cutoff valve is continuously closed, the downstream fuel cutoff valve is continuously opened, and the air cutoff valve is closed. An air residual pressure detected by the pressure sensor in a state is detected, and it is determined that an abnormality has occurred in the nozzle when the read air supply pressure is equal to or lower than the air residual pressure. Item 3. The exhaust aftertreatment device according to Item 2.

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