JP2012007570A - System for regenerating particulate filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To carry out forced regeneration of a particulate filter efficiently in a short time for regenerating the particulate filter in an idling state of a vehicle, even when an oxidation catalyst or a fuel addition means is in a deteriorating state with time.SOLUTION: The system for regenerating a particulate filter 6 in an idling state of a vehicle includes a control device 9 to carry out forced regeneration of the particulate filter 6 by directing a fuel injection device 10 to do post injection while controlling to raise an exhaust temperature by performing a higher rotating speed of a diesel engine 1 than in normal idling. The control device 9 is designed to further increase the rotating speed of the diesel engine 1 when an increase of exhaust temperature per unit time becomes lower than a predetermined threshold value before the exhaust temperature reaches a target temperature required for the forced regeneration in carrying out the forced regeneration.

Description

  The present invention relates to a particulate filter regeneration device.

  Particulate matter (particulate matter) discharged from a diesel engine is mainly composed of soot made of carbonaceous matter and SOF content (Soluble Organic Fraction) made of high-boiling hydrocarbon components. The composition contains a small amount of sulfate (mist-like sulfuric acid component). As a measure to reduce this type of particulates, a particulate filter is installed in the middle of the exhaust pipe through which the 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 each flow path partitioned in a lattice pattern 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. Although it is necessary to regenerate, in an ordinary diesel engine operation state, there are few opportunities to obtain an exhaust temperature high enough for the particulates to self-combust.

  For this reason, for example, an oxidation catalyst obtained by adding an appropriate amount of a rare earth element such as cerium to a material in which platinum is supported on alumina is integrally supported on a particulate filter and collected in the particulate filter. The oxidation reaction of the particulates is promoted by the oxidation catalyst to lower the ignition temperature, so that the particulates can be burned and removed even at an exhaust temperature lower than that of the prior art.

  However, even in such a case, in the operation region where the exhaust temperature is low, the trapped amount exceeds the processing amount of the particulate, so if the operation state at the low exhaust temperature continues, the particulates There is a possibility that the particulate filter will fall into an over-collected state without regenerating the filter well, and the particulate filter is forcibly heated when the accumulated amount of particulates has increased. It is necessary to incinerate the curate.

  More specifically, a flow-through type oxidation catalyst is provided in front of the particulate filter, and fuel is added upstream from the oxidation catalyst, and the added fuel is oxidized by the oxidation catalyst in front of the particulate filter. The exhaust gas heated by the reaction heat is introduced into the particulate filter, the catalyst bed temperature is raised to burn out the particulate, and the particulate filter is regenerated.

  In addition, as a specific means for executing this kind of fuel addition, post injection is added at a non-ignition timing later than the compression top dead center following the main injection of fuel performed near the compression top dead center. The fuel can be added to the exhaust gas.

  Conventionally, when the amount of accumulated particulates in the particulate filter exceeds the allowable amount and forced regeneration is necessary, forced regeneration is automatically performed during traveling. For buses, trucks, etc. that operate on congested routes, etc., even if the particulate filter is automatically regenerated during driving, it may stop before the regeneration is completed. Proposal to enable the forced regeneration of the particulate filter arbitrarily by the driver's manual operation in the idling state when the vehicle is stopped for a vehicle in a driving form in which the driving conditions for executing the forced regeneration are not easily established Has been.

  However, if the vehicle is in an idling state where the vehicle is stopped, the exhaust temperature will be significantly lower than when traveling, and the progress of regeneration of the particulate filter will be delayed. It is considered that forced regeneration is performed while idling up to increase the engine speed from idling as temperature increase control to increase the exhaust temperature, so that regeneration of the particulate filter proceeds well.

  The method for forcibly regenerating this type of particulate filter is also described in the following Patent Document 1 and Patent Document 2 by the same applicant as the present invention.

JP 2003-83139 A JP 2003-155913 A

  However, the oxidizing power of the oxidation catalyst decreases due to deterioration over time, or the operation of the mechanical system of the means for adding fuel stops working as indicated by the control system due to deterioration over time, indicating the actual amount of fuel added The exhaust temperature may reach the target temperature required for forced regeneration even when forced regeneration of the particulate filter is started, especially when idling when the exhaust temperature is low as described above. Before that, the temperature rise per unit time of the exhaust temperature becomes slow, and there is a problem that it takes time to complete regeneration of the particulate filter because the exhaust temperature does not reach the target temperature.

  The present invention has been made in view of the above circumstances, and when regenerating a particulate filter under the condition that the vehicle is stopped in an idling state, even if the oxidation catalyst and the fuel addition means have deteriorated over time, the It is an object to enable the forced regeneration of the curate filter to be completed efficiently in a short time.

  The present invention is an apparatus for regenerating a particulate filter under the condition that the vehicle is stopped in an idling state, comprising a catalyst regeneration type particulate filter provided in the middle of an exhaust pipe with an oxidation catalyst in the preceding stage, and the oxidation filter Fuel addition means for adding fuel into the exhaust gas upstream from the catalyst, a temperature sensor for detecting the exhaust temperature between the oxidation catalyst and the particulate filter, and the engine speed increased from that during normal idling And a controller for forcibly regenerating the particulate filter by instructing the fuel addition means to perform fuel temperature increase control while increasing the temperature, and the exhaust temperature detected by the temperature sensor during forced regeneration is forcibly regenerated. The temperature increase rate per unit time of the exhaust temperature has become lower than the predetermined threshold before reaching the target temperature required for It is characterized in that constitute the control apparatus to obtain achieving a further increase of the rotational speed of the engine.

  Thus, in this way, when the particulate filter is regenerated under the condition that the vehicle is stopped in the idling state, the control device increases the engine speed from that during normal idling to increase the exhaust temperature. In accordance with an instruction from the control device, fuel is added by the fuel addition means and the particulate filter is forcibly regenerated. However, the exhaust temperature detected by the temperature sensor is necessary for forced regeneration. If the exhaust gas temperature rises slowly per unit time before reaching the target temperature, and the controller determines that the exhaust gas temperature rise rate per unit time has become lower than a predetermined threshold, the control The device instructs the engine speed to increase further, and the injection amount per main injection in the engine is further increased to increase the energy. Amount charged increases, the exhaust gas temperature will reach the target temperature required for forced regeneration earlier thereby temperature increase rate per unit of exhaust temperature time is increased greatly.

  As a result, the oxidizing power of the oxidation catalyst decreases due to deterioration over time, or the operation of the mechanical system of the means for adding fuel does not move according to the indicated value of the control system due to deterioration over time. Even if it falls below the indicated value, it is possible to take measures to further increase the engine speed when the exhaust temperature rises per unit time is slow. It becomes possible to complete the forced regeneration of the curate filter efficiently and in a short time.

  Further, in the present invention, control is performed so that the fuel addition amount can be increased by the fuel addition means when the rate of temperature increase per unit time of the exhaust temperature detected by the temperature sensor during forced regeneration is lower than a predetermined threshold. It is also possible to configure the device.

  In this way, the engine speed is further increased to promote an increase in the exhaust gas temperature, while the reaction heat is increased by increasing the amount of fuel added to the oxidation catalyst whose activity has increased with the increase in the exhaust gas temperature. More can be generated.

  According to the particulate filter regeneration device of the present invention described above, the following various excellent effects can be obtained.

  (I) According to the invention described in claim 1 of the present invention, when the particulate filter is regenerated under the condition that the vehicle is stopped in the idling state, the oxidation catalyst and the fuel addition means are deteriorated with time. However, since the engine speed can be further increased when the exhaust gas temperature rise rate per unit time becomes lower than a predetermined threshold, the forced regeneration of the particulate filter can be performed efficiently and in a short time. Can be completed.

  (II) According to the invention described in claim 2 of the present invention, an increase in the exhaust temperature is promoted by further increasing the number of revolutions of the engine. By increasing the amount of addition, more reaction heat can be generated, so that the exhaust temperature can be increased efficiently without excessively increasing the engine speed.

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. FIG. 2 is a perspective view showing a part of the oxidation catalyst of FIG. It is a graph which shows the change of the exhaust temperature with respect to time. It is a graph which shows the change of the rotation speed of the diesel engine with respect to time. It is a graph which shows the change of the fuel addition amount with respect to time.

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

  FIG. 1 shows an example of an embodiment for carrying out the present invention. An oxidation catalyst 5 is placed in the middle of an exhaust pipe 4 through which exhaust gas 3 discharged from a diesel engine 1 through an exhaust manifold 2 flows. The provided catalyst regeneration type particulate filter 6 is held by a filter case 7 and interposed.

  This particulate filter 6 has a porous honeycomb structure made of ceramic as shown in an enlarged view in FIG. 2, and the inlets of the respective flow paths 6a partitioned in a lattice pattern are alternately sealed, and the inlets are sealed. The outlet of the flow path 6a that is not made is sealed so that only the exhaust gas 3 that has permeated through the porous thin wall 6b that defines each flow path 6a is discharged downstream. It has become. Incidentally, the oxidation catalyst 5 provided in the preceding stage of the particulate filter 6 has a flow-through structure as shown in FIG.

  A pressure sensor 8 is provided on the inlet side of the filter case 7, and a pressure signal 8a of the pressure sensor 8 is input to a control device 9 constituting an engine control computer (ECU: Electronic Control Unit). In this control device 9, based on the pressure signal 8a from the pressure sensor 8, the pressure difference between the inlet side and the outlet side of the particulate filter 6 (the pressure loss corresponding to the operating region on the outlet side is initialized in advance. ) Is calculated, and the accumulated amount of particulates in the particulate filter 6 is estimated based on the pressure difference.

  That is, in the example shown here, the accumulation amount estimation means for estimating the accumulation amount of the particulates in the particulate filter 6 is constituted by the pressure sensor 8 and the control device 9. There are various methods for estimating the amount of accumulated particulates. For example, the basic generation amount of particulates based on the current operating state of the diesel engine 1 is estimated, and this basic generation amount is calculated. Multiply the correction factors considering various conditions related to the generation of particulates and subtract the particulate processing amount in the current operation state to obtain the final generation amount, and accumulate this final generation amount every moment It is also possible to estimate the amount of particulate deposition.

  Further, since the control device 9 shown here also serves as an engine control computer, it is also responsible for control relating to fuel injection. More specifically, the accelerator opening is determined by the load of the diesel engine 1. As shown in FIG. 2, fuel is supplied to each cylinder of the diesel engine 1 on the basis of the accelerator opening signal 11a from the accelerator sensor 11 (load sensor) detected as follows and the rotational speed signal 12a from the rotational sensor 12 that detects the engine rotational speed of the diesel engine 1. The fuel injection signal 10a is output to the fuel injection device 10 that injects fuel.

  The fuel injection device 10 is composed of a plurality of injectors provided for each cylinder, and the solenoid valves of these injectors are appropriately controlled to open by the fuel injection signal 10a, so that the fuel injection timing ( The valve opening timing) and the injection amount (valve opening time) are appropriately controlled.

  Moreover, in the control device 9, the fuel injection signal 10a in the normal mode is determined based on the accelerator opening signal 11a and the rotation speed signal 12a. On the other hand, when the forced regeneration of the particulate filter 6 is to be performed, Mode is switched to the regeneration mode, and fuel injection with an injection pattern in which post-injection is performed at a non-ignition timing later than the compression top dead center following the main injection of fuel performed near the compression top dead center (crank angle 0 °). The signal 10a is also determined.

  That is, in this embodiment, the fuel injection device 10 functions as a fuel addition means for forced regeneration of the particulate filter 6, and as described above, the compression top dead center following the main injection. When post-injection is performed at a later timing of non-ignition, unburned fuel (mainly HC: hydrocarbon) is added to the exhaust gas 3 by this post-injection, and this unburned fuel becomes particulate. The oxidation reaction is performed on the oxidation catalyst 5 in the preceding stage of the filter 6, and the catalyst bed temperature rises due to the reaction heat, so that the particulates in the particulate filter 6 are burned and removed.

  Further, the instrument panel in the cab 13 has a warning lamp 14 for notifying the driver that the particulate filter 6 needs to be forcibly regenerated, and the fuel injection under the condition that the diesel engine 1 is idling. A regeneration button 15 that constitutes an operating means for arbitrarily executing fuel addition by the device 10 by manual operation of the driver is provided.

  Then, the control device 9 determines whether or not the accumulated amount of particulates estimated based on the pressure signal 8a from the pressure sensor 8 exceeds the allowable amount. The warning signal 14a is output from 9 and the warning lamp 14 of the instrument panel is lit, so that the driver is informed of the necessity of forced regeneration of the particulate filter 6 by manual operation.

  Further, when the regeneration button 15 is operated by the driver and the regeneration command signal 15a is input to the control device 9 under the condition that the diesel engine 1 is stopped in the idling state, the rotational speed is increased from that during normal idling. As much as possible, increase the injection amount per main injection that was performed near the compression top dead center (crank angle 0 °), and add post injection at a timing that does not ignite later than the compression top dead center following the main injection. The fuel injection signal 10a having such an injection pattern is output.

  In other words, when the particulate filter 6 is forcibly regenerated when the idling is stopped, the temperature and flow rate of the exhaust gas 3 are too low to perform good combustion removal of the particulates. By increasing the injection amount, the number of revolutions is increased from that during normal idling, thereby increasing the amount of energy input and increasing the temperature and flow rate of the exhaust gas 3 to a level suitable for forced regeneration, and performing fuel addition by post injection. I am doing so.

  In addition, when the exhaust gas temperature detected by the temperature sensor 16 during the forced regeneration does not reach the target temperature necessary for the forced regeneration, and the temperature increase rate per unit time of the exhaust temperature becomes lower than a predetermined threshold value. The control device 9 can further increase the rotational speed of the diesel engine 1.

  That is, as an example is shown in FIG. 4, the oxidizing power of the oxidation catalyst 5 decreases due to deterioration over time, or the mechanical operation of each injector of the fuel injection device 10 constituting the fuel addition means changes over time. If the actual amount of fuel added falls below the indicated value due to the deterioration of the control system due to the deterioration, the fuel addition by post injection is started at the point A in the graph of FIG. However, before the exhaust temperature reaches the target temperature required for forced regeneration, the temperature rise per unit time of the exhaust temperature becomes slow, and from this there may occur a situation where the exhaust temperature does not reach the target temperature. In this case, the controller 9 determines that the temperature increase rate per unit time of the exhaust gas temperature (ΔTemp / ΔTime in the graph of FIG. 4) has become lower than a predetermined threshold, and FIG. As shown by the rough diagram, a measure for increasing the number of revolutions increased at time A when fuel addition is started to another level at time B (the fuel injection signal 10a for further increasing the injection amount per main injection). Output).

  In addition to the accelerator sensor 11 and the rotation sensor 12 described above, the control device 9 in the present embodiment includes a neutral switch 17 for detecting that the gear position is at the neutral position and a vehicle speed sensor 18 for detecting the vehicle speed. Detection signals 17a and 18a from the vehicle are also input to the control device 9, and based on these signals, the control device 9 determines whether or not the vehicle is idling. .

  That is, in the control device 9, the accelerator sensor 11 confirms that the accelerator is off (the load is zero), the neutral switch 17 confirms that the gear position is in the neutral position, and the vehicle speed sensor 18 indicates that the vehicle speed is zero. When is confirmed, it is determined that the current driving state is in the idling state.

  Thus, if the regenerating apparatus for the particulate filter 6 is configured as described above, when the driver who visually recognizes the lighting of the warning lamp 14 stops the vehicle in an idling state and presses the regenerating button 15, the particulates. The forced regeneration of the filter 6 is started, and more specifically, the injection amount per main injection in the fuel injection control is increased, and the rotational speed of the diesel engine 1 becomes higher than that during normal idling. At the same time, as a result of post injection being performed at a timing that does not ignite later than the compression top dead center following the main injection, the temperature and flow rate of the exhaust gas 3 are raised to a level suitable for forced regeneration, and unburned in the exhaust gas 3 Then, the fuel undergoes an oxidation reaction on the oxidation catalyst 5, and the reaction heat causes the bed temperature of the particulate filter 6 to be collected. Ikyureto been burned and removed, so that the regenerating of the particulate filter 6 can be achieved.

  At this time, before the exhaust temperature detected by the temperature sensor 16 reaches the target temperature necessary for forced regeneration, the temperature increase per unit time of the exhaust temperature becomes dull, and the control device 9 per unit time of the exhaust temperature When it is determined that the rate of temperature increase is lower than the predetermined threshold, the control device 9 instructs the further increase in the rotational speed of the diesel engine 1, and the injection amount per main injection in the diesel engine 1 is determined. The amount of energy input is further increased to increase the temperature increase rate per unit time of the exhaust temperature, and the exhaust temperature reaches the target temperature required for forced regeneration at an early stage.

  At this time, as shown in the graph of FIG. 4, even if the temperature rise per unit time of the exhaust temperature becomes dull before the exhaust temperature reaches the target temperature required for forced regeneration, the control device 9 controls the exhaust temperature. It is determined that the rate of temperature increase per unit time has become lower than a predetermined threshold value, and as shown in the graph of FIG. 5, the control device 9 further increases the rotational speed of the diesel engine 1 at the time point B. Therefore, as shown in the right end of the graph of FIG. 4, the temperature increase rate per unit time of the exhaust temperature is greatly increased, and the exhaust temperature reaches the target temperature necessary for forced regeneration at an early stage. Become.

  As a result, the oxidizing power of the oxidation catalyst 5 decreases due to deterioration over time, or the operation of the mechanical system in each injector of the fuel injection device 10 does not move as indicated by the control system due to deterioration over time. Even if the addition amount falls below the indicated value, it is possible to take measures to further increase the rotational speed of the diesel engine 1 when the exhaust temperature rise per unit time is slow. Thus, the forced regeneration of the particulate filter 6 can be efficiently completed in a short time.

  In the example shown in FIG. 5, the number of revolutions of the diesel engine 1 is only increased by one step. However, by increasing the temperature increase rate repeatedly and decreasing the increase range, the speed is increased step by step. Of course, it may be.

  FIG. 6 is a graph for explaining another embodiment of the present invention. As shown in the graph of FIG. 6, the fuel addition amount at the forced regeneration is the target addition stepwise from the time point A at the start. When the temperature increase rate per unit time of the exhaust gas temperature detected by the temperature sensor 16 during forced regeneration is lower than a predetermined threshold, the control device 9 performs fuel injection at time B. You may make it perform the increase in the fuel addition amount by the apparatus 10 collectively.

  In other words, in this way, while increasing the rotational speed of the diesel engine 1 to promote an increase in the exhaust temperature, the fuel addition amount is increased with respect to the oxidation catalyst 5 whose activity has increased with the increase in the exhaust temperature. As a result, more reaction heat can be generated, and the exhaust temperature can be increased efficiently without excessively increasing the rotational speed of the diesel engine 1.

  The particulate filter regeneration device of the present invention is not limited to the above-described embodiments. In such embodiments, the fuel injection device is employed as the fuel addition means, and the vicinity of the compression top dead center. In this example, fuel is added to the exhaust gas by performing post-injection at a non-ignition timing later than the compression top dead center following the main injection of the fuel at It is possible to insert an injector as a fuel addition means into the manifold and add the fuel directly into the exhaust gas by the injector, or under the condition that the vehicle is stopped in an idling state. If the forced regeneration of the curate filter is to be performed, it is not necessarily limited to the one that performs the forced regeneration by manual operation, and there is a condition that the vehicle is stopped in an idling state. Of course, it is possible to apply to the one that automatically performs forced regeneration when necessary, and various modifications can be made without departing from the scope of the present invention. .

1 Diesel engine (engine)
Reference Signs List 3 exhaust gas 4 exhaust pipe 5 oxidation catalyst 6 particulate filter 9 control device 10 fuel injection device (fuel addition means)
16 Temperature sensor

Claims (2)

  An apparatus for regenerating a particulate filter under a condition that the vehicle is stopped in an idling state, comprising a catalyst regeneration type particulate filter provided in the middle of an exhaust pipe with an oxidation catalyst provided upstream and upstream of the oxidation catalyst The fuel addition means for adding fuel to the exhaust gas, the temperature sensor for detecting the exhaust temperature between the oxidation catalyst and the particulate filter, and the engine temperature is increased to raise the exhaust temperature by increasing the engine speed during normal idling. A control device for instructing fuel addition to the fuel addition means while performing temperature control and forcibly regenerating the particulate filter, and the exhaust temperature detected by the temperature sensor during forced regeneration is a target required for forced regeneration If the temperature rise rate per unit time of the exhaust temperature becomes lower than the predetermined threshold before reaching the temperature, the engine Particulate filter regeneration apparatus characterized by the configured the control unit to obtain achieving a further increase in speed.   The controller is configured so that the fuel addition amount can be increased by the fuel addition means when the rate of temperature increase per unit time of the exhaust temperature detected by the temperature sensor during forced regeneration is lower than a predetermined threshold. The particulate filter regeneration device according to claim 1.

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