JP2005155530A - Exhaust emission control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device capable of increasing the safety of hot exhaust emission produced by the regenerative control of a particulate filter. <P>SOLUTION: This exhaust emission control device comprises the catalyst regenerative particulate filter 6 installed in an exhaust pipe 4, a fuel adding means (fuel injection device 10) for adding a fuel in the exhaust emission 3 on the upstream side of the particulate filter 6, and a control device 9 making the fuel adding means add the fuel when the particulate filter 6 must be regenerated by burning out collected particulates and performing a regenerative control to increase an idling speed higher than usual only when the fuel is added in the idling. The control device 9 is formed in such a way that even if the particulate filter 6 must be regenerated while a vehicle is stopped at idling, the performance of the regenerative control is retained temporarily and permitted after the traveling of the vehicle is started. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an exhaust emission control device.

  Particulate matter (particulate matter) discharged from a diesel engine is mainly composed of soot composed of carbonaceous matter and SOF content (Soluble Organic Fraction) composed 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 a ceramic such as cordierite, and the inlets of the flow paths 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. 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 used, the trapped amount exceeds the particulate processing amount in the operation region where the exhaust temperature is low, so such a low exhaust gas. If the operation state at the temperature continues, the particulate filter may not be regenerated well, and the particulate filter may fall into an excessive collection state, and the particulate filter is in a stage where the amount of accumulated particulates has increased. It has been studied to forcibly regenerate the particulate filter by adding fuel to the exhaust gas further upstream.

  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, regeneration of the particulate filter is achieved.

Incidentally, methods for forcibly regenerating this type of particulate filter are also described in Patent Document 1 and Patent Document 2 below.
JP 2003-155914 A JP 2003-193824 A

  However, when performing the regeneration control as described above, if the fuel addition by the fuel addition means is automatically executed in a situation where the driver is away from the vehicle in the idling state, the driver remains absent. There is a risk that hot exhaust gas may be discharged outside the vehicle.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an exhaust emission control device with improved safety for high-temperature exhaust gas generated by regeneration control of a particulate filter.

  The present invention relates to a catalyst regeneration type particulate filter installed in the middle of an exhaust pipe, a fuel addition means for adding fuel to exhaust gas upstream of the particulate filter, and combustion removal of the collected particulate A control device for performing regeneration control for adding fuel to the fuel addition means when the particulate filter needs to be regenerated and for increasing the idling rotational speed only when fuel is added in the idling state. In the exhaust gas purification apparatus provided, the control device is configured to temporarily reserve the execution of the regeneration control and permit the regeneration control to be executed after the start of traveling even when the particulate filter needs to be regenerated during idling stop. It is characterized by this.

  Thus, in this way, even if it is necessary to regenerate the particulate filter while the vehicle is idling, the regeneration control is not performed immediately and the regeneration control is performed after the start of traveling. Therefore, the regeneration control is surely executed under the situation where the driver is present in the vehicle.

  In other words, the regeneration control is not executed in the situation where the driver cannot leave the vehicle in the idling state and cannot confirm the surrounding safety. Therefore, the regeneration control is automatically performed on the vehicle that is idling stopped without the driver. This prevents the situation where hot exhaust gas is discharged outside the vehicle.

  Furthermore, in carrying out the present invention more specifically, an engine fuel injection device is employed as a fuel addition means, and fuel injection into the cylinder is controlled to leave a large amount of unburned fuel in the exhaust gas. It is possible to configure so that fuel can be added.

  Further, it may be configured such that after-injection is added at a combustible timing immediately after main injection to each cylinder when fuel is added in an idling state, and in this way, fuel from after-injection is converted to output. By burning at a timing that is difficult to be performed, the thermal efficiency of the engine decreases, and the amount of heat that is not used for power out of the calorific value of the power fuel increases, thereby increasing the exhaust temperature.

  Furthermore, it is also possible to provide an exhaust throttle means for appropriately reducing the exhaust flow rate from the engine and to close the exhaust throttle means when adding fuel in the idling state.

  In this way, the exhaust flow rate is throttled by the exhaust throttling means in conjunction with the increase in idling speed on the engine side and the addition of after-injection as described above. When the exhaust resistance increases, the intake of the relatively low temperature exhaust gas becomes difficult to flow into the cylinder, and the residual amount of the relatively high temperature exhaust gas increases. Even if the air in the cylinder containing a large amount is compressed in the next compression stroke and reaches the explosion stroke, the exhaust temperature can be further raised.

  According to the above-described exhaust purification device of the present invention, even if the vehicle needs to regenerate the particulate filter while idling is stopped, the execution of the regeneration control is temporarily reserved by the control device, and the travel start after idling stops Since the regeneration control is executed after that, the regeneration control is surely executed in a situation where the driver exists in the vehicle, and the regeneration control is performed on the vehicle that is idling stopped without the driver. It is possible to avoid the situation where the hot exhaust gas is automatically started and exhausted outside the vehicle, and the safety of the hot exhaust gas generated by the particulate filter regeneration control can be greatly improved. An excellent effect can be achieved.

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

  1 to 3 show an example of an embodiment for carrying out the present invention. In the exhaust emission control device of this embodiment, as shown in FIG. 1, an automobile diesel engine 1 (engine) is passed through an exhaust manifold 2. When a catalyst regeneration type particulate filter 6 integrally carrying an oxidation catalyst is accommodated in the muffler 5 of the exhaust pipe 4 through which the exhaust gas 3 that has been exhausted flows (the front stage of the particulate filter 6) The filter case 7 that holds the particulate filter 6 forms an outer cylinder of the muffler 5.

  That is, a particulate filter 6 as shown in an enlarged view in FIG. 2 is accommodated inside the filter case 7, and this particulate filter 6 has a porous honeycomb structure made of ceramic, and has a lattice structure. The inlets of the respective flow paths 6a partitioned in a shape are alternately sealed, and the outlets of the flow paths 6a whose inlets are not sealed are sealed. Only the exhaust gas 3 that has permeated through the porous thin wall 6b is discharged to the downstream side.

  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 (pressure loss on the outlet side is preset in advance) is within the normal range. When the pressure difference exceeds the normal range, it is determined that the particulate filter 6 has fallen into an overcollected state.

  Further, since the control device 9 also serves as an engine control computer, it is also responsible for control relating to fuel injection. More specifically, the control device 9 detects an accelerator opening as a load of the diesel engine 1. Fuel injection for injecting fuel into each cylinder of the diesel engine 1 based on an accelerator opening signal 11a from the engine 11 (load sensor) and a rotation speed signal 12a from the rotation sensor 12 that detects the engine rotation speed of the diesel engine 1 A fuel injection signal 10 a is output to the device 10.

  Here, the fuel injection device 10 is composed of a plurality of injectors provided for each cylinder, and the solenoid valve of each injector is appropriately controlled to be opened by the fuel injection signal 10a, and the fuel injection timing. In addition, the injection amount is appropriately controlled.

  On the other hand, 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, it is necessary to perform regeneration control of the particulate filter 6. In this case, the normal mode is switched to the 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 fuel performed near the compression top dead center (crank angle 0 °). The fuel injection signal 10a of the injection pattern is determined.

  That is, when post-injection is performed at a non-ignition timing later than the compression top dead center following main injection, unburned fuel (mainly HC: hydrocarbon) is added to the exhaust gas 3 by this post-injection. As a result, the unburned fuel undergoes an oxidation reaction on the oxidation catalyst on the surface of the particulate filter 6, and the catalyst bed temperature rises due to the reaction heat, and the particulates in the particulate filter 6 are burned and removed. It will be.

  However, when the regeneration control is executed when the vehicle is in an idling state, the main injection is performed once near the compression top dead center (crank angle 0 °) in order to increase the rotational speed compared with the normal idling. The amount of per shot is also increased.

  In other words, when the regeneration control of the particulate filter 6 is performed when the idling is stopped, the temperature and flow rate of the exhaust gas 3 are too low and it is difficult to perform the combustion removal of the particulates satisfactorily. By increasing the injection amount, the rotational speed is increased from that during normal idling, thereby increasing the amount of energy input and raising the temperature and flow rate of the exhaust gas 3 to a level suitable for regeneration control.

  Further, in addition to the control for increasing the rotational speed of the diesel engine 1, after-injection may be performed at a combustible timing immediately after the main injection if necessary. Thus, the combustion immediately after the main injection is performed. If after-injection is performed at a possible timing, the fuel of the after-injection is burned at a timing that is difficult to be converted to output, thereby lowering the thermal efficiency of the diesel engine 1 and increasing the amount of heat that is not used for power out of the calorific value of fuel This makes it possible to further increase the exhaust temperature.

  Further, an exhaust brake 13 capable of adjusting the opening degree is provided at an appropriate position upstream of the particulate filter 6 so as to narrow down the flow path of the exhaust pipe 4 to an appropriate opening degree. However, in this embodiment, when the regeneration mode is selected by the control device 9, the exhaust brake 13 is independent from the original operation. The exhaust brake 13 can be used as an exhaust throttle means for instructing another operation and increasing the exhaust temperature as will be described later.

  Further, in addition to the accelerator sensor 11 and the rotation sensor 12 described above, a vehicle speed signal 14a from a vehicle speed sensor 14 for detecting the vehicle speed is inputted to the control device 9, and particularly in FIG. Although not shown, detection signals from the neutral switch for detecting that the gear position is in the neutral position and the side brake switch for detecting that the side brake is being pulled are also input to the control device 9. The controller 9 determines whether or not the vehicle is idling based on these detection signals.

  That is, in the control device 9, it is confirmed by the rotation sensor 12 that the rotation speed is within a relatively low predetermined rotational speed range, the accelerator sensor 11 confirms that the accelerator is off (load is zero), and the neutral position is set by the neutral switch. When it is confirmed that the vehicle is in the position, it is confirmed that the side brake is being pulled by the side brake switch, and the vehicle speed sensor 14 confirms that the vehicle speed is zero, it is determined that the current driving state is in the idling state. It is supposed to be.

  In determining the idling state, not all signals from these sensors and switches are necessarily required. At least the rotation sensor 12, the accelerator sensor 11, the neutral switch, the side brake switch, and the vehicle speed sensor 14 It is possible to configure the idling determination means by combining with any of them, and further another signal such as a clutch signal may be considered for the purpose of more reliable determination.

  Then, regarding the exhaust gas purification apparatus that can execute the regeneration control of the particulate filter 6 as described above, in this embodiment, even if it is necessary to regenerate the particulate filter 6 during idling stop, the regeneration control is performed. The control device 9 incorporates an interlock that temporarily reserves the execution of the operation and permits the execution of the regeneration control after the start of traveling.

  That is, even if the control device 9 switches from the normal mode to the regeneration mode under the condition that the current operating state is determined to be in the idling state by the idling determination means described above, fuel addition, increase in idling rotational speed, after injection The regeneration control such as the addition of the exhaust brake 13 and the closing operation of the exhaust brake 13 is not immediately executed. The vehicle speed sensor 14 confirms the vehicle speed higher than a predetermined value and the accelerator sensor 11 confirms the accelerator input. The regeneration control is executed after the determination.

  Thus, when the vehicle is stopped in the idling state, it is determined by the control device 9 that the particulate filter 6 has fallen into the excessive collection state based on the pressure signal 8a from the pressure sensor 8, and the fuel injection by the control device 9 is performed. Even if the control of the device 10 is switched from the normal mode to the regeneration mode, the regeneration control such as fuel addition, increase in idling rotational speed, addition of after injection, and closing operation of the exhaust brake 13 is temporarily retained by the control device 9.

  Next, when the vehicle starts traveling after idling stops, the traveling start is detected by the control device 9 based on the vehicle speed signal 14a and the accelerator opening signal 11a from the vehicle speed sensor 14 and the accelerator sensor 11, and thereafter the regeneration control is executed. The fuel injection signal 10a in the regeneration mode is output from the control device 9 during the travel, and the fuel injection device 10 that has received this signal performs non-ignition later than the compression top dead center following the main injection. As a result of the post injection at the timing, unburned fuel (mainly HC: hydrocarbon) is added to the exhaust gas 3 by this post injection, and this unburned fuel is oxidized on the oxidation catalyst on the surface of the particulate filter 6. The catalyst heats up due to the reaction heat, and the particulates in the particulate filter 6 are burned and removed. That.

  As shown in the graph of FIG. 3, when the vehicle stops again and enters the idling state before the regeneration control of the particulate filter 6 is completed, the regeneration mode corresponding to the idling state from the control device 9 is set. The fuel injection signal 10a is output, and the fuel injection device 10 receiving the fuel injection signal 10 increases the injection amount per main injection and increases the rotational speed, thereby increasing the amount of energy input to each cylinder and increasing the exhaust temperature. In addition, when after-injection is added, the thermal efficiency of the diesel engine 1 is reduced by burning at a timing when the fuel by the after-injection is difficult to be converted into output, and the amount of heat generated by the fuel The amount of heat that is not used for the power of the engine increases and the exhaust temperature is further increased.

  In particular, in the present embodiment, since the exhaust brake 13 is used in combination as an exhaust throttle means for appropriately reducing the exhaust flow rate, the exhaust brake 13 is adjusted in accordance with the increase in the rotational speed on the diesel engine 1 side and the addition of after injection. The exhaust flow rate is narrowed down and the exhaust gas 3 on the upstream side is heated to raise the exhaust gas temperature, and the exhaust resistance is increased, so that the intake air having a relatively low temperature does not easily flow into the cylinder. Even if the residual amount of the exhaust gas 3 having a relatively high temperature increases and the air in the cylinder containing a large amount of the exhaust gas 3 having a relatively high temperature is compressed in the next compression stroke, the further exhaust temperature is reached. Will increase.

  When the exhaust gas 3 is heated at the upstream side of the particulate filter 6 in this way and the post-injection is performed at a timing that does not ignite later than the compression top dead center following the main injection, Unburned fuel is added to the catalyst, and the fuel undergoes an oxidation reaction on the oxidation catalyst on the surface of the particulate filter 6, and the catalyst bed temperature rises due to the reaction heat, and the particulates in the particulate filter 6 are burned and removed. The forced regeneration of the particulate filter 6 is performed.

  Therefore, according to the above-described embodiment, even if it is necessary to regenerate the particulate filter 6 while the vehicle is idling stopped, the execution of the regeneration control is temporarily reserved by the control device 9 and after the start of running after idling stops. Therefore, regeneration control is executed in a situation where there is a driver in the vehicle, and regeneration control is automatically performed on a vehicle that is idling stopped without a driver. The high temperature exhaust gas 3 can be avoided and the safety of the high temperature exhaust gas 3 generated by the regeneration control of the particulate filter 6 can be greatly improved. it can.

  The exhaust emission control device of the present invention is not limited to the above-described embodiment. In the above embodiment, the fuel injection device is used as the fuel addition means, and the fuel is performed near the compression top dead center. Fuel is added to the exhaust gas by performing post-injection at a timing of non-ignition later than the compression top dead center following the main injection of the engine, but the timing of main injection into the cylinder is delayed from normal The fuel may be added to the exhaust gas, and only the means for adding fuel by controlling the fuel injection into the cylinder and leaving a large amount of unburned fuel in the exhaust gas. In addition, an injector may be provided as a fuel addition means at an appropriate position of the exhaust pipe (or an exhaust manifold may be used), and fuel may be directly injected into the exhaust gas by this injector. The exhaust throttle means for appropriately reducing the exhaust flow rate does not necessarily use an exhaust brake, and an exhaust throttle valve may be separately provided in the middle of the exhaust pipe. Of course, various modifications can be made within the range not to be performed.

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 a graph shown about the rotation speed control by the control apparatus of FIG.

Explanation of symbols

1 Diesel engine (engine)
3 exhaust gas 4 exhaust pipe 6 particulate filter 9 control device 10 fuel injection device (exhaust temperature raising means)
13 Exhaust brake (Exhaust throttle means: Exhaust temperature raising means)

Claims (4)

  A catalyst regeneration type particulate filter installed in the middle of the exhaust pipe, a fuel addition means for adding fuel to the exhaust gas on the upstream side of the particulate filter, and particulates by burning and removing the collected particulates Exhaust gas purification comprising a control device for performing regeneration control for adding fuel to the fuel addition means when it is necessary to regenerate the filter and for increasing the idling speed only when fuel is added in an idling state In the device, the control device is configured to temporarily reserve the execution of the regeneration control and permit the execution of the regeneration control after the start of traveling even if it is necessary to regenerate the particulate filter while idling is stopped. Exhaust purification device.   The fuel injection device of the engine is adopted as a fuel addition means, and fuel injection can be performed by controlling fuel injection into the cylinder and leaving a large amount of unburned fuel in the exhaust gas. The exhaust emission control device according to claim 1.   The exhaust emission control device according to claim 1 or 2, wherein after-injection is added at a combustible timing immediately after main injection to each cylinder when fuel is added in an idling state.   The exhaust according to claim 1, 2 or 3, further comprising exhaust throttle means for appropriately reducing an exhaust flow rate from the engine, wherein the exhaust throttle means is closed when fuel is added in an idling state. Purification equipment.

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