JP4261325B2 - Exhaust purification equipment - Google Patents

Description

  The present invention relates to an exhaust emission control device.

  Particulate matter (particulate matter) discharged from a diesel engine as an internal combustion engine is mainly composed of carbonaceous soot and SOF (Soluble Organic Fraction) composed of high-boiling hydrocarbon components. As a component, it is composed of a small amount of sulfate (sulfate component), but as a measure to reduce this type of particulates, a particulate filter is installed in the middle of the exhaust pipe through which exhaust gas flows. It has been done conventionally.

  This type of particulate filter has a porous honeycomb structure made of ceramics such as cordierite, and the inlets of the respective flow paths partitioned in a lattice shape are alternately sealed, and the inlets are not sealed. About the flow path, the exit is sealed, and only the exhaust gas which permeate | transmitted the porous thin wall which divides each flow path is discharged | emitted downstream.

  Then, the particulates in the exhaust gas are collected and deposited on the inner surface of the porous thin wall, so that the particulates are appropriately burned and removed before the exhaust resistance increases due to clogging. It is necessary to regenerate, but in normal diesel engine operating conditions, there are few opportunities to obtain exhaust temperatures that are high enough for the particulates to self-combust. For example, an appropriate amount for platinum-supported alumina A catalyst regeneration type particulate filter in which an oxidation catalyst formed by adding a rare earth element such as cerium is integrally supported is being put to practical use.

  That is, if such a catalyst regeneration type particulate filter is employed, the oxidation reaction of the collected particulates is promoted to lower the ignition temperature, and the particulates can be burned and removed even at an exhaust temperature lower than the conventional one. It becomes possible.

  However, even when such a catalyst regeneration type particulate filter is employed, the oxidation catalyst supported by the particulate filter has an active temperature region, and the exhaust temperature is below the lower limit of activation temperature. In the low operating range, the particulates are not burned and removed well, and the trapped amount exceeds the processing amount of the particulates, so if the operating state at such a low exhaust temperature continues, the oxidation catalyst becomes active. Since the particulate filter does not progress well and the particulate filter may fall into an excessive collection state, the fuel injection device is used at the stage where the amount of particulate accumulation has increased. It is considered to regenerate the particulate filter by adding fuel to the exhaust gas upstream of the particulate filter. .

  In other words, if fuel is added upstream from the particulate filter, the added fuel undergoes an oxidation reaction on the oxidation catalyst of the particulate filter, and the heat of the reaction raises the catalyst bed temperature to burn out the particulate. Thus, the particulate filter is reproduced.

  In addition, the engine is provided with EGR means such as an EGR pipe and an EGR valve so that a part of the exhaust gas is extracted from the exhaust manifold and recirculated to the intake manifold side of the engine. When adding fuel by adding means and closing the EGR valve to stop the exhaust gas recirculation and not regenerating the particulate filter, stop the fuel adding means and open the EGR valve to recirculate the exhaust gas. It is considered.

Here, some examples of such exhaust purification devices that are general examples have already been disclosed as patent publications (see, for example, Patent Document 1).
JP 2003-155915 A

  However, when shifting from the regeneration of the particulate filter to the case where the particulate filter is not regenerated, the fuel is added by the fuel injection device of the fuel addition means and the recirculation by the EGR means is stopped. Since the fuel injection device of the fuel adding means is stopped and the exhaust gas is immediately recirculated by the EGR means, the unburned fuel adhering to the exhaust manifold and the like flows into the EGR means and the intake manifold. There has been a problem that the performance of the EGR means is lowered by being repeated many times.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide an exhaust purification device that prevents unburned fuel adhering to an exhaust manifold or the like from flowing into the EGR means or the intake manifold.

According to the first aspect of the present invention, a particulate filter provided in the middle of an exhaust pipe through which exhaust gas from the engine circulates, and a part of the exhaust gas is extracted from the exhaust manifold of the engine and then recirculated to the intake manifold side of the engine. An EGR means for circulation, and a fuel addition means for adding fuel arranged upstream of the particulate filter and the EGR means,
When shifting from the state where the fuel is added by the fuel addition means and the EGR means is stopped to the state where the fuel addition means is stopped and the exhaust gas is recirculated by the EGR means, the fuel addition means is stopped and the EGR is stopped. For a while to stop the means ,
The present invention relates to an exhaust emission control device configured to stop the fuel addition means and stop the EGR means based on the engine speed and the engine load .

  As described above, according to the present invention, when the fuel addition means is added and the EGR means is stopped, the fuel addition means is stopped and the exhaust gas is recirculated by the EGR means. In addition, since the fuel addition means is stopped and the EGR means is stopped for a while, the unburned fuel adhering to the exhaust manifold and the like is removed, and the unburned fuel flows into the EGR means and the intake manifold. As a result, the performance of the EGR means can be suitably maintained.

  When the fuel addition unit is stopped and the EGR unit is stopped based on the engine speed and the engine load, the fuel addition unit is stopped and the EGR unit is stopped properly. Therefore, unburned fuel adhering to the exhaust manifold or the like can be removed, and the flow of unburned fuel into the EGR means or the intake manifold can be suitably prevented.

  According to the exhaust purification apparatus of the present invention described above, since the fuel addition means is stopped and the EGR means is stopped for a while, unburned fuel adhering to the exhaust manifold and the like is removed, and the EGR means is removed. The outstanding effect that the inflow of unburned fuel can be prevented can be produced.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  1 to 4 show an example of an embodiment of the present invention, FIG. 1 is a schematic view showing an example of an embodiment of the present invention, and FIG. 2 is a sectional view showing details of the particulate filter of FIG. FIG. 3 is a perspective view showing a detail of the oxidation catalyst of FIG. 1 with a part cut away, and FIG. 4 is a flowchart showing an example of processing when shifting from regeneration control to normal control.

  In FIG. 1, reference numeral 1 denotes a diesel engine equipped with a turbocharger 2. The intake air 4 guided from the air cleaner 3 is sent to the compressor 2a of the turbocharger 2 through the intake pipe 5 and added by the compressor 2a. The compressed intake air 4 is sent to the intercooler 6 to be cooled, and the intake air 4 is further guided from the intercooler 6 to the intake manifold 7 to each cylinder 8 of the diesel engine 1 (in the case of inline 6 cylinders in FIG. 1). Is distributed).

  Further, the exhaust gas 9 discharged from each cylinder 8 of the diesel engine 1 is sent to the turbine 2b of the turbocharger 2 through the exhaust manifold 10, and the exhaust gas 9 that has driven the turbine 2b is discharged to the exhaust pipe 11 (exhaust gas). It is designed to be discharged out of the vehicle through the flow path).

  A filter case 12 is interposed in the middle of the exhaust pipe 11, and a catalyst regeneration type particulate filter 13 that integrally carries an oxidation catalyst is provided in the rear stage in the filter case 12. As shown in an enlarged view in FIG. 2, the particulate filter 13 has a porous honeycomb structure made of ceramic, and the inlets of the respective flow paths 13a partitioned in a lattice pattern are alternately arranged. For the flow path 13a that is sealed and whose inlet is not sealed, the outlet is sealed, and only the exhaust gas 9 that has permeated through the porous thin wall 13b that defines each flow path 13a is downstream. It is designed to be discharged to the side.

  In addition, a flow-through type oxidation catalyst 14 having a honeycomb structure as shown in an enlarged view in FIG. 3 is accommodated at a position immediately upstream of the particulate filter 13 in the filter case 12.

  Further, in the example shown in FIG. 1, the EGR pipe 15 of the EGR means extends between one end of the exhaust manifold 10 in the direction in which the cylinders 8 are arranged and one end of the intake pipe 5 connected to the intake manifold 7. And a part of the exhaust gas 9 extracted from the exhaust manifold 10 is recirculated to the intake pipe 5 via the EGR cooler 16 and the EGR valve 17 of the EGR means in a water-cooled manner. The exhaust gas 9 recirculated to the side suppresses the combustion of fuel in each cylinder 8 and lowers the combustion temperature so that the generation of NOx can be reduced.

  A temperature sensor 18 for measuring the temperature of the exhaust gas 9 as a substitute value of the catalyst bed temperature is provided between the oxidation catalyst 14 and the particulate filter 13 in the filter case 12, and the temperature sensor 18 temperature signals 18a are input to a control device 19 constituting an engine control computer (ECU: Electronic Control Unit).

  Since this control device 19 also serves as an engine control computer, it is also responsible for control relating to fuel injection. More specifically, the control device 19 detects an accelerator opening as a load of the diesel engine 1 ( Fuel addition means for injecting fuel into each cylinder 8 of the diesel engine 1 based on the accelerator opening signal 20a from the load sensor) and the rotation speed signal 21a from the rotation sensor 21 that detects the engine speed of the diesel engine 1 A fuel injection signal 22 a is output to the fuel injection device 22.

  Here, the fuel injection device 22 is composed of a plurality of injectors 23 provided for each cylinder 8, and the electromagnetic valves of these injectors 23 are appropriately controlled to open by the fuel injection signal 22a. The injection timing (valve opening timing) and the injection amount (valve opening time) are appropriately controlled.

  Further, in the control device 19, the intake throttle 24 provided in the intake pipe 5 downstream of the intercooler 6, the exhaust brake 25 provided in the exhaust pipe 11 upstream of the particulate filter 13, and the EGR pipe 15 Opening command signals 24a, 25a and 17a for commanding the respective opening to the EGR valve 17 are output.

  Here, the intake throttle 24 may be functionally used as an intake shutter used in combination with an idling stop device, a noise suppressor used in combination with an auxiliary brake, or the like. In the present embodiment, such an intake throttle 24 is used. By instructing the EGR valve 17 to perform another operation independent of the original operation, the EGR valve 17 is utilized as an intake throttle means (temperature raising means) for raising the catalyst bed temperature as will be described later. The exhaust brake 25 may be configured in substantially the same manner as the intake throttle 24.

  The idling stop device refers to a device that reduces the amount of exhaust gas by stopping the engine 1 while the vehicle is stopped for the purpose of low pollution. In such an idling stop device, the intake air is used to smoothly stop the engine 1. In general, an intake shutter is provided so as to shut off the intake air, and the auxiliary brake such as the exhaust brake 25 and the engine retarder is provided with an intake air in order to prevent the noise during the operation from leaking to the outside as much as possible. A noise suppressor is usually provided in the tube 5.

  In the control device 19, the fuel injection signal 22a in the normal mode is determined based on the accelerator opening signal 20a and the rotation speed signal 21a. On the other hand, the particulate filter 13 needs to be forcibly regenerated. In this case, the normal mode is switched to the forced regeneration mode, and the post-injection is performed at the non-ignition timing later than the compression top dead center following the main injection of the fuel near the compression top dead center (crank angle 0 °). The correct fuel injection signal 22a is determined.

  That is, when post-injection is performed at the non-ignition timing later than the compression top dead center following main injection, unburned fuel (mainly HC: hydrocarbon) is oxidized in the exhaust gas 9 by this post-injection. The catalyst and the particulate filter 13 are added upstream, and this unburned fuel undergoes an oxidation reaction on the oxidation catalyst on the surface of the particulate filter 13, and the heat of the reaction raises the catalyst bed temperature, causing the particulates. The particulates in the filter 13 are burned and removed.

  Here, in the regeneration control for regenerating the particulate filter 13 by burning and removing the particulates, the fuel is added by the fuel injection device 22 of the fuel addition means, and the EGR valve 17 of the EGR means is closed to close the EGR pipe. On the other hand, in the normal control in which the particulate filter 13 is not regenerated, the fuel addition by the fuel injection device 22 of the fuel addition means is stopped and the EGR of the EGR means is stopped. The valve 17 is opened and recirculated through the EGR pipe 15 and the like, and the control device 19 appropriately controls the fuel injection device 22, the intake throttle 24, the exhaust brake 25, and the EGR valve 17.

  Further, the control device 19 is provided with a flow process as shown in FIG. 4 described in the following operation when switching from regeneration control to normal control.

  The operation of the embodiment of the present invention will be described below.

  That is, when switching from regeneration control of the particulate filter 13 to normal control, the control device 19 first determines in step S1 whether regeneration control of the particulate filter 13 is requested in step S1, as shown in FIG. If there is a request for regeneration control of the particulate filter 13, the process proceeds to step 2, where regeneration control is performed and the process ends. On the other hand, if there is no request for regeneration control of the particulate filter 13, the process proceeds to step 3. In step 3, it is determined whether or not the regeneration control has been performed immediately before. It progresses to step S4, transfers to scavenging control at step 4, and complete | finishes.

  Here, in the scavenging control, the addition of fuel by the fuel injection device 22 of the fuel addition means is stopped, and the EGR valve 17 of the EGR means is closed to stop the recirculation process by the EGR pipe 15 and the like for a while. Subsequently, unburned fuel adhering to the exhaust manifold 10 or the like is removed to a level that does not cause any problem.

  Further, the end of the scavenging control is determined based on the engine speed and the engine load. Specifically, the engine load and the engine speed are extracted at predetermined intervals, and based on the extracted value, the vehicle travels. The engine load corresponding to the state and the coefficient attached to the map of the engine speed are integrated, and when the value exceeds the threshold, it is judged that the vehicle has returned to the normal driving state, and the scavenging control is performed. It is set to end.

  On the other hand, in the flow when switching from regeneration control to normal control of the particulate filter 13, if the regeneration control is not performed immediately before in step 3, the process proceeds to step S5, and whether or not the scavenging control is being performed in step 5. If the scavenging control is not being performed, the process proceeds to step S7, and the process shifts to the normal control in step 7 and ends. If the scavenging control is being performed, the process proceeds to step S6. In step 6, it is determined whether the scavenging control has been completed. If the scavenging control has not been completed, the process proceeds to step S4. If the control is continued and the scavenging control is finished, the process proceeds to step S7, and the process shifts to the normal control in step 7 and is finished.

  Thus, according to the present embodiment, the fuel injection device 22 is in a state where fuel is added by the fuel injection device 22 of the fuel addition device and the recirculation process is stopped by closing the EGR valve 17 of the EGR device. The fuel addition by the fuel injection device 22 is stopped and the recirculation by the EGR valve 17 or the like is stopped when shifting to the state where the exhaust gas 9 is stopped and the exhaust gas 9 is recirculated by the EGR valve 17 or the like Since the unburned fuel adhering to the exhaust manifold 10 and the like is removed, the flow of unburned fuel to the EGR valve 17 and the intake manifold 7 is prevented, so that the performance of the EGR valve 17 and the like is favorable. Can be maintained.

  When the fuel addition by the fuel injection device 22 of the fuel addition means is stopped and the recirculation by the EGR valve 17 or the like is stopped based on the engine speed and the engine load, the fuel injection device 22 The state in which the fuel addition is stopped and the recirculation by the EGR valve 17 or the like can be appropriately terminated, so that the unburned fuel adhering to the exhaust manifold 10 or the like is removed, and the unremoved fuel to the EGR valve 17 and the intake manifold 7 is removed. The inflow of fuel can be suitably prevented.

  Further, in this embodiment, the fuel injection device 22 is illustrated as a fuel addition means for adding fuel into the exhaust gas 9 on the upstream side of the particulate filter 13, but as this kind of fuel addition means, For example, a fuel addition injector may be separately provided at any location in the exhaust passage from the exhaust port 10a to the exhaust manifold 10, and the fuel may be added into the exhaust gas 9 by this injector. It is. Furthermore, the fuel addition means can be used when only post injection as described above, after injection and post injection are used together, or after injection with a significantly increased injection amount than when used as a temperature raising means. It is effective as

  It should be noted that the exhaust emission control device of the present invention is not limited to the embodiment described above, and it is needless to say that changes can be made without departing from the scope of the present invention.

It is the schematic which shows an example of the form which implements this invention. It is sectional drawing which shows the detail of the particulate filter of FIG. It is the perspective view which notched a part which shows the detail of the oxidation catalyst of FIG. It is a flowchart which shows an example of the process at the time of transfer from reproduction | regeneration control to normal control.

Explanation of symbols

1 Diesel engine (engine)
9 Exhaust gas 11 Exhaust pipe 13 Particulate filter 15 EGR pipe (EGR means)
16 EGR cooler (EGR means)
17 EGR valve (EGR means)
22 Fuel injector (fuel addition means)

Claims (1)

A particulate filter installed in the middle of an exhaust pipe through which exhaust gas from the engine flows, EGR means for extracting a part of the exhaust gas from the exhaust manifold of the engine and recirculating it to the intake manifold side of the engine; A fuel addition means for adding fuel by being arranged upstream of the curate filter and the EGR means,
When shifting from the state where the fuel is added by the fuel addition means and the EGR means is stopped to the state where the fuel addition means is stopped and the exhaust gas is recirculated by the EGR means, the fuel addition means is stopped and the EGR is stopped. For a while to stop the means ,
An exhaust emission control device configured to stop the fuel addition means and stop the EGR means based on the engine speed and the engine load .

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