JP2011241690A - Dpf regeneration device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a DPF regeneration device capable of precluding oil dilution and also emission of white smoke.SOLUTION: The DPF regeneration device is equipped with a changeover apparatus 9 that, at forced regeneration of a DPF, makes only post injection executed when the load of an internal combustion engine 2 is below the prescribed value, and makes an exhaust pipe injection executed when the load of the engine 2 is at or over the prescribed value. The configuration includes a selective catalyst reducing member 12 installed downstream of the DPF, and an injection restrictor to reduce the injecting amount or prohibit injection at post injection and/or exhaust pipe injection when the exhaust gas temperature is at or over the prescribed value.

Description

  The present invention relates to a DPF regenerator that collects PM in exhaust gas of an internal combustion engine in a DPF and burns and removes the accumulated PM with high-temperature exhaust gas, preventing oil dilution and preventing white smoke emission. The present invention relates to a DPF regeneration device.

  In order to purify exhaust gas by removing particulate matter (hereinafter referred to as PM) from exhaust gas of an internal combustion engine such as a diesel engine, a continuously regenerating diesel particulate filter (hereinafter referred to as DPF) ) Has been developed.

  The DPF collects PM in a honeycomb structure made of porous ceramic. PM is removed from the DPF by incinerating the PM accumulated in the DPF with the heat of the exhaust gas. In an operating region where the exhaust gas temperature is low, such as when the vehicle speed is low and the internal combustion engine is lightly loaded, PM continues to accumulate in the DPF without being incinerated, causing problems such as an increase in exhaust pressure. Therefore, conventionally, when a predetermined amount of PM accumulates in the DPF, the exhaust gas temperature is forcibly raised to regenerate the DPF.

  As a forced regeneration method that raises the exhaust gas temperature, an oxidation catalyst member (Diesel Oxidation Catalyst; hereinafter referred to as DOC) is installed upstream of the DPF, and additional fuel is added to the internal combustion engine at an appropriate crank angle after the main injection. This is a post-injection method in which hydrocarbon (HC) as fuel is supplied to the oxidation catalyst member, the exhaust gas temperature is increased by the oxidation heat, and PM is incinerated. There is a system in which exhaust pipe injection for injecting fuel into the pipe is performed to supply HC to the oxidation catalyst member, and the exhaust gas temperature is increased by the oxidation heat to incinerate PM.

JP 2009-36177 A JP 2009-144578 A

  When post-injection is performed, an oil dilution may occur in which the injected fuel is mixed with the lubricating oil and the lubricating oil is diluted.

  On the other hand, when exhaust pipe injection is performed, when the exhaust gas temperature is relatively low, combustion becomes inactive, and unburned HC may be emitted into the atmosphere as white smoke.

  In addition, when the exhaust gas temperature in the selective catalyst reduction member (Selective Catalytic Reduction; SCR) downstream of the DPF becomes excessively high as the exhaust gas temperature in the DPF increases during forced regeneration of the DPF, the SCR The nitrogen oxide (NOx) purification efficiency will be reduced.

  Accordingly, an object of the present invention is to provide a DPF regeneration device that solves the above problems, prevents oil dilution, and prevents white smoke discharge.

  In order to achieve the above object, the present invention provides a diesel particulate filter (hereinafter referred to as DPF) that is installed in an exhaust gas flow path from an internal combustion engine and collects particulate matter (hereinafter referred to as PM), and is captured by the DPF. Post-injection means for performing post-injection in the internal combustion engine in order to remove the collected PM, and a diesel oxidation catalyst member installed upstream of the DPF and promoting oxidation of fuel in the exhaust gas passage ( DOC), an exhaust pipe injector installed upstream of the DOC and injecting fuel into the exhaust gas passage, load determination means for determining the magnitude of the load of the internal combustion engine, and DPF forced regeneration And switching to execute only post-injection when the load of the internal combustion engine is less than a predetermined value, and to perform exhaust pipe injection when the load of the internal combustion engine is greater than or equal to a predetermined value. It is that a stage.

  In addition, the present invention provides a diesel particulate filter (hereinafter referred to as DPF) that is installed in an exhaust gas flow path from an internal combustion engine and collects particulate matter (hereinafter referred to as PM), and PM collected in the DPF. Post-injection means for performing post-injection in the internal combustion engine for removal, and a diesel oxidation catalyst member (hereinafter referred to as DOC) installed upstream of the DPF to promote oxidation of fuel in the exhaust gas passage; An exhaust pipe injector that is installed upstream of the DOC and injects fuel into the exhaust gas passage, a DPF inlet exhaust gas temperature sensor that detects an exhaust gas temperature at the inlet of the DPF, and at the time of DPF forced regeneration, When the exhaust gas temperature at the DPF inlet is less than a predetermined value, only post injection is executed, and when the exhaust gas temperature at the DPF inlet is higher than the predetermined value, the exhaust gas is exhausted. Is obtained by a switching means for executing the tube injection.

  A selective catalytic reduction member (hereinafter referred to as SCR) installed downstream of the DPF to purify nitrogen oxides, an SCR exhaust gas temperature sensor for detecting the exhaust gas temperature in the SCR, and the downstream exhaust gas temperature sensor When the exhaust gas temperature is equal to or higher than a predetermined value, an injection limiting means for reducing an injection amount in post injection and / or exhaust pipe injection or prohibiting injection may be provided.

  The present invention exhibits the following excellent effects.

  (1) Oil dilution can be prevented.

  (2) White smoke emission can be prevented.

It is a block diagram of the DPF reproduction | regeneration apparatus which shows one Embodiment of this invention. It is a control flowchart in the DPF regeneration device of the present invention. It is a graph which shows the temperature characteristic of the NOx purification efficiency in SCR. It is a graph which shows the map for referring a forced regeneration system from an engine speed and load or exhaust gas temperature.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  As shown in FIG. 1, a DPF regeneration device 1 according to the present invention is installed in an exhaust gas flow path 3 from an internal combustion engine 2 and collects particulate matter (hereinafter referred to as PM), which is a diesel particulate filter (hereinafter referred to as PM). , DPF) 4, post-injection means 5 that performs post-injection in the internal combustion engine 2 in order to remove PM trapped in the DPF 4, and fuel installed in the exhaust gas passage 3 that is installed upstream of the DPF 4 A diesel oxidation catalyst member (hereinafter referred to as DOC) 6 that promotes oxidation, an exhaust pipe injector 7 that is installed upstream of the DOC 6 and injects fuel into the exhaust gas passage 3, and determines the magnitude of the load on the internal combustion engine When the load determination means 8 and the DPF forced regeneration, the load of the internal combustion engine 2 is less than a predetermined value, only post-injection is executed, and when the load of the internal combustion engine 2 is greater than the predetermined value, the exhaust pipe Perform injection And a switching means 9 for.

  The DPF regeneration device 1 may include a DPF inlet exhaust gas temperature sensor 10 that detects an exhaust gas temperature at the inlet of the DPF 4.

  The DPF regeneration device 1 includes a differential pressure sensor 11 that detects a differential pressure between the inlet and the outlet of the DPF 4 that is a determination factor as to whether to perform forced regeneration. Further, in the present embodiment, the DPF regeneration device 1 includes a selective catalyst reduction member (hereinafter referred to as SCR) 12 that is disposed downstream of the DPF 4 and purifies nitrogen oxides, and an SCR exhaust gas that detects an exhaust gas temperature in the SCR 12. When the exhaust gas temperature detected by the SCR exhaust gas temperature sensor 13 is equal to or higher than a predetermined value, the temperature sensor 13 is provided with an injection restriction means 14 that reduces the injection amount in the post injection and the exhaust pipe injection or prohibits the injection.

  Hereinafter, each part will be described in detail.

  The internal combustion engine 2 is, for example, a diesel engine.

  The exhaust gas passage 3 guides the exhaust gas from the internal combustion engine 2 to the atmosphere.

  The DPF 4 collects PM in a honeycomb structure made of porous ceramic.

  The post injection means 5 is incorporated as a program in an electronic control unit (ECU) 15 that controls each part of the vehicle including fuel injection in the internal combustion engine 2. The ECU 15 performs multi-injection control in which fuel is injected a plurality of times at an appropriate crank angle before and after main injection within one combustion cycle. The post injection means 5 performs post injection after the main injection during the multi injection control for the purpose of forcibly regenerating the DPF 4 by raising the exhaust gas temperature.

  The DOC 6 uses an oxidation catalyst such as platinum, and can promote the oxidation of fuel, that is, HC in the exhaust gas passage 3.

  The exhaust pipe injector 7 is configured such that a fuel injector (nozzle) is attached to the exhaust gas passage 3 and fuel is injected into the exhaust gas passage 3. Exhaust pipe injection using the exhaust pipe injector 7 is controlled by the ECU 15. The exhaust pipe injection may be controlled independently of the multi-injection control in each cylinder, or may be controlled in conjunction with or in synchronization with the multi-injection control.

  The load determination means 8 is incorporated in the ECU 15 as a program. The load determination means 8 determines whether the load torque applied to the internal combustion engine 2 is less than a predetermined value or greater than a predetermined value. The ECU 15 grasps the load torque by a conventionally known technique. That is, the ECU 15 constantly detects load torque, engine speed, accelerator opening, air amount, and the like as engine parameters representing the engine state and uses them for fuel injection control and the like.

  The switching means 9 is incorporated in the ECU 15 as a program. The switching means 9 switches between post injection and exhaust pipe injection, which are forced regeneration methods during DPF forced regeneration. In the present embodiment, the switching means 9 switches between a system that executes only post injection and a system that executes post injection in addition to exhaust pipe injection.

  The DPF inlet exhaust gas temperature sensor 10 detects the exhaust gas temperature at the inlet of the DPF 4 and is provided between the DOC 6 and the DPF 4.

  The differential pressure sensor 11 detects a differential pressure that is a pressure difference of exhaust gas between the inlet and the outlet of the DPF 4. When PM accumulates in the DPF 4, the differential pressure increases as the accumulation amount increases, so that the forced regeneration timing can be determined based on the differential pressure.

  The SCR 12 decomposes NOx in the exhaust gas into nitrogen gas.

  The SCR exhaust gas temperature sensor 13 detects the exhaust gas temperature in the SCR 12. The SCR exhaust gas temperature sensor 13 may be installed at the outlet of the DPF 4, but here it is installed at the inlet of the SCR 12.

  The injection restriction means 14 is incorporated in the ECU 15 as a program. The injection limiting unit 14 limits the injection amount in the post injection and the exhaust pipe injection based on the exhaust gas temperature in the SCR 12.

  Hereinafter, the operation of the DPF regeneration device 1 will be described with reference to FIG.

  The ECU 15 determines whether to perform forced regeneration based on the differential pressure between the inlet and the outlet of the DPF 4 detected by the differential pressure sensor 11. That is, if the differential pressure is greater than or equal to a predetermined value, it is determined that a predetermined amount or more of PM has accumulated in the DPF 4, and the forced regeneration mode is entered. The forced regeneration mode may be entered when the vehicle is driven for a predetermined distance or for a predetermined time without being limited to the determination based on the differential pressure.

  Step S1: The DPF regeneration device 1 determines whether or not the forced regeneration mode is in effect. If it is not the forced regeneration mode, the control flow of FIG. 2 is terminated. If it is the forced regeneration mode, the process proceeds to step S2.

  Step S2: The load determining means 8 determines whether or not the magnitude of the load on the internal combustion engine 2 is greater than or equal to a predetermined value. If the magnitude of the load is less than the predetermined value, the process proceeds to step S3, and if it is equal to or greater than the predetermined value, the process proceeds to step S4.

  Step S3: The switching means 9 executes only post injection. As a result, the exhaust gas temperature is raised only by post injection.

  Step S4: The switching means 9 performs exhaust pipe injection (in this embodiment, post injection in addition to exhaust pipe injection). As a result, the exhaust gas temperature rise using both the exhaust pipe injection and the post injection is performed.

  Step S5: The injection limiting means 14 determines whether the exhaust gas temperature (SCR inlet temperature) at the inlet of the SCR 12 detected by the SCR exhaust gas temperature sensor 13 is equal to or higher than a predetermined value. If the SCR inlet temperature is lower than the predetermined value, the process proceeds to step S6, and if it is equal to or higher than the predetermined value, the process proceeds to step S7.

  Step S6: Since the injection limiting means 14 does not need to lower the exhaust gas temperature in the SCR 12, it maintains the same injection amount as before in the post injection or the exhaust pipe injection being executed.

  Step S7: Since the injection limiting means 14 needs to lower the exhaust gas temperature in the SCR 12, the injection amount in the post-injection or exhaust pipe injection that is being executed is reduced more than before. Note that the amount of one injection in post injection or exhaust pipe injection is set in advance by experiments. Further, the amount by which the injection amount is reduced is also set in advance by experiments. If necessary, the injection amount may be reduced, that is, the injection may be prohibited.

  According to the present invention, according to the above control flow, only the post-injection is executed if the load of the internal combustion engine 2 is less than a predetermined value. In the engine state where the load is small, the exhaust gas temperature is low, and if exhaust pipe injection is performed, white smoke may be generated and discharged to the atmosphere. However, in the present invention, if the magnitude of the load is less than a predetermined value, Since only the post injection is performed and the exhaust pipe injection is not performed, generation of white smoke is prevented in advance. On the other hand, if the load of the internal combustion engine 2 is greater than or equal to a predetermined value, post injection is executed in addition to exhaust pipe injection. When the engine is heavily loaded, the exhaust gas temperature is high, and white smoke is not generated even when exhaust pipe injection is performed. Compared with the prior art in which only post injection is performed regardless of load, in the present invention, which may be used in combination with exhaust pipe injection, the total injection amount by post injection is reduced, so the amount of fuel mixed in the lubricating oil is reduced, and the oil Dilution can be prevented.

  The generation of white smoke depends on the exhaust gas temperature. Therefore, in the control flow described above, the exhaust gas temperature may be used instead of the load as the switching condition. In this case, the DPF inlet exhaust gas temperature sensor 10 is required. When the exhaust gas temperature at the inlet of the DPF 4 detected by the DPF inlet exhaust gas temperature sensor 10 is less than a predetermined value during the forced regeneration of the DPF, the switching means 9 executes only post injection, and the exhaust gas temperature at the inlet of the DPF 4 is predetermined. When the value is greater than or equal to the value, exhaust pipe injection (in this embodiment, post injection in addition to exhaust pipe injection) is executed.

  Further, as a condition for switching, only the load of the internal combustion engine 2 is used, or only the exhaust gas temperature at the inlet of the DPF 4 is used as a condition, and the combination of the exhaust gas temperature or the load of the internal combustion engine 2 and the engine speed As a condition. Both conditions are set in order to avoid exhaust pipe injection in an engine state where white smoke is generated, while reducing the injection amount in post injection. The switching means 9 switches the forced regeneration method by referring to the map with the engine parameter as a condition.

  According to the present invention, according to the control flow of FIG. 2, the injection amount is maintained if the exhaust gas temperature at the inlet of the SCR 12 is less than a predetermined value, and the injection amount is reduced or injected if the exhaust gas temperature exceeds a predetermined value. As a result, the exhaust gas temperature is adjusted to be lower than the predetermined value.

  Here, as shown in FIG. 3, the NOx purification efficiency in the SCR 12 depends on the SCR inlet temperature. That is, in the region B1 where the SCR inlet temperature is the highest, the NOx purification efficiency is moderate. In the region B2 where the SCR inlet temperature is medium, the NOx purification efficiency is the highest. In the region B3 where the SCR inlet temperature is the lowest, the NOx purification efficiency is the lowest. Accordingly, the injection amount is maintained as it is in the state of the region B2 where the SCR inlet temperature is increased by the post injection or the exhaust pipe injection and the SCR inlet temperature becomes medium. However, the SCR inlet temperature further increases and exceeds the predetermined value. In the state of the region B1, the SCR inlet temperature is lowered by reducing the injection amount or prohibiting the injection, thereby preventing the NOx purification efficiency from being lowered.

  Next, a map referred to by the switching means 9 for switching the forced regeneration method will be described. The map shown in FIG. 4 is a two-dimensional map with the engine speed on the horizontal axis and the load or exhaust gas temperature on the vertical axis.

  When the vertical axis is a load, a region where the load is higher than a predetermined value T (hatched hatching) A1 is a region where exhaust pipe injection and post injection are used together. A region where the load is less than the predetermined value T (vertical hatching) A2 is a region where only post injection is performed.

  Even when the vertical axis represents the exhaust gas temperature, the region (shaded hatching) A1 where the exhaust gas temperature is higher than the predetermined value T is a region where exhaust pipe injection and post injection are used together, and the exhaust gas temperature is less than the predetermined value T. Area (vertical hatching) A2 is an area only for post injection.

  According to this two-dimensional map, when the engine parameter is in the region A1, exhaust pipe injection and post injection are used together, and when the engine parameter is in the region A2, only post injection is executed. Thereby, oil dilution can be prevented and white smoke emission can be prevented.

  This two-dimensional map does not depend very much on the engine speed, and the predetermined value T that becomes the boundary between the regions A1 and A2 is slightly high when the engine speed is low and slightly low when the engine speed is high. Yes. Therefore, the object of the present invention is substantially achieved even when only the load is used as in the control flow of FIG. On the other hand, when the engine speed is also included in the condition using a two-dimensional map, it is possible to perform switching according to a fine engine state, and a higher effect can be obtained.

  In the present embodiment, the switching means 9 switches between a system that executes only post injection and a system that executes post injection in addition to exhaust pipe injection, but a system that executes only post injection and an exhaust pipe. The method of performing only injection may be switched, or only exhaust pipe injection through a method of performing exhaust pipe injection (in this embodiment, post injection in addition to exhaust pipe injection) from a method of performing only post injection. You may make it transfer to the system which performs.

  In the present embodiment, the DPF 4 and the SCR 12 are installed in the exhaust gas flow path 3. However, there is a vehicle in which only the DPF 4 is installed and the SCR 12 is not installed. In this case, since it is not necessary to consider the NOx purification efficiency, the control of the injection amount adjustment after step S5 becomes unnecessary.

  Next, paying attention to FIG. 3, the NOx purification efficiency is remarkably low in the state of the region B3 where the post injection or the exhaust pipe injection is not performed and the SCR inlet temperature is low. Therefore, not only during forced regeneration of the DPF, but when the exhaust gas temperature is always low, the NOx purification efficiency in the SCR 12 can be kept high by raising the exhaust gas temperature by post injection or exhaust pipe injection.

DESCRIPTION OF SYMBOLS 1 DPF regeneration apparatus 2 Internal combustion engine 3 Exhaust gas flow path 4 DPF (diesel particulate filter)
5 Post injection means 6 DOC (diesel oxidation catalyst member)
7 Exhaust pipe injector 8 Load judging means 9 Switching means 10 DPF inlet exhaust gas temperature sensor 11 Differential pressure sensor 12 SCR (selective catalyst reducing member)
13 SCR exhaust gas temperature sensor 14 injection limiting means 15 ECU

Claims (3)

A diesel particulate filter (hereinafter referred to as DPF) that is installed in an exhaust gas flow path from the internal combustion engine and collects particulate matter (hereinafter referred to as PM);
Post-injecting means for performing post-injection in the internal combustion engine in order to remove the PM trapped in the DPF;
A diesel oxidation catalyst member (hereinafter referred to as DOC) which is installed upstream of the DPF and promotes oxidation of fuel in the exhaust gas flow path;
An exhaust pipe injector installed upstream of the DOC and injecting fuel into the exhaust gas flow path; load determining means for determining a load size of the internal combustion engine;
Switching means for executing only post-injection when the load of the internal combustion engine is less than a predetermined value during forced DPF regeneration and executing exhaust pipe injection when the load of the internal combustion engine is greater than or equal to a predetermined value A DPF regeneration device comprising: A diesel particulate filter (hereinafter referred to as DPF) that is installed in an exhaust gas flow path from the internal combustion engine and collects particulate matter (hereinafter referred to as PM);
Post-injecting means for performing post-injection in the internal combustion engine in order to remove the PM trapped in the DPF;
A diesel oxidation catalyst member (hereinafter referred to as DOC) which is installed upstream of the DPF and promotes oxidation of fuel in the exhaust gas flow path;
An exhaust pipe injector that is installed upstream of the DOC and injects fuel into the exhaust gas passage; a DPF inlet exhaust gas temperature sensor that detects an exhaust gas temperature at the inlet of the DPF; Switching means for performing only post-injection when the exhaust gas temperature at the inlet of the exhaust gas is less than a predetermined value and executing exhaust pipe injection when the exhaust gas temperature at the inlet of the DPF is equal to or higher than a predetermined value. DPF regeneration device. A selective catalytic reduction member (hereinafter referred to as SCR) installed downstream of the DPF to purify nitrogen oxides;
An SCR exhaust gas temperature sensor for detecting an exhaust gas temperature in the SCR;
And an injection limiting means for reducing an injection amount in post injection and / or exhaust pipe injection or prohibiting injection when the exhaust gas temperature detected by the downstream exhaust gas temperature sensor is equal to or higher than a predetermined value. The DPF regeneration device according to claim 1 or 2.

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