JP4276525B2 - Exhaust purification equipment - Google Patents

Description

  The present invention relates to an exhaust gas purification apparatus equipped with a catalyst regeneration type particulate filter in the middle of an exhaust pipe.

  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 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 alumina loaded with platinum 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, in this type of particulate filter, when the idling state where the exhaust temperature is low continues for a long time, the catalyst bed temperature is lowered and the activity is lowered, and the hydrocarbon of unburned fuel contained in the exhaust gas is removed. As the exhaust gas temperature rises after the vehicle has started running after a long period of idling, hydrocarbons accumulated in the particulate filter suddenly accumulate. There is a concern that white smoke may be generated due to an oxidation reaction.

  Incidentally, the situation where the idling state continues for a long time is, for example, when a long-distance transport truck is resting (nap) with the engine running in a parking lot such as an expressway (air conditioning such as cooling) If you want to keep operating

  And as a countermeasure against exhaust gas whitening at the start of running after the idling state as described above continues for a long time, when it is confirmed that the idling state continues for a predetermined time or longer, the exhaust gas is exhausted upstream from the particulate filter. The exhaust temperature raising means that raises the gas to a predetermined temperature or more is activated, and the temperature rise control is used so that the hydrocarbon is oxidized before the idling state continues for a long time and a large amount of hydrocarbon accumulates in the particulate filter. (See, for example, prior application 1 “Japanese Patent Application No. 2002-88508”, prior application 2 “Japanese Patent Application 2002-296173”).

  However, if it is assumed that the exhaust temperature raising means is activated when it is confirmed that the idling state continues for a predetermined time or longer, the engine is stopped at a stage where the exhaust temperature raising means is activated when the idling state continues for a while. If this is done, the duration of the idling state is reset at the next engine restart, and the time is restarted from zero. Therefore, the engine stop immediately before the exhaust temperature raising means operates is repeated. In such a case, there has been a problem that a large amount of hydrocarbons may accumulate in the particulate filter before the exhaust gas temperature raising means does not operate.

  The present invention has been made in view of the above-described circumstances so that even if the engine is repeatedly stopped in an idling state, an amount of hydrocarbons that may generate white smoke at the start of traveling is not accumulated. An object of the present invention is to provide an exhaust emission control device capable of executing temperature rise control at an appropriate timing.

The present invention relates to a catalyst regeneration type particulate filter installed in the middle of an exhaust pipe, an exhaust temperature raising means for raising the exhaust gas temperature to a predetermined temperature or more upstream of the particulate filter, and a continuation of an idling state. An exhaust purification device comprising a control device that activates the exhaust gas temperature raising means when it continues for a predetermined waiting time, and when the idling state is interrupted by stopping the engine before the waiting time is exceeded, the engine is stopped. The control device is configured to store the idling state continuation time of the engine and to measure the standby time continuously from the stored continuation time when the engine is restarted, and when an abnormality occurs in the storage area of the control device. continuing from the temporary duration constitute the control device to count the wait time when the continued set the time and the engine restart It is characterized in.

  Thus, in this way, even if the idling state is interrupted by stopping the engine before the standby time is exceeded, the duration of the idling state until the engine is stopped is stored in the control device, and the next time Since the waiting time is counted from the continuation time stored in the control device when the engine is restarted, the exhaust temperature raising means is operated by the control device when the accumulated time reaches a predetermined waiting time. Thus, the temperature increase control is executed at an appropriate timing so that a quantity of hydrocarbons that may generate white smoke does not accumulate at the start of traveling.

Further, even if the event abnormality in the storage area of the control apparatus had occurred, the duration of provisional set in the control system, the waiting time is timed to continue from the temporary duration at the next engine restart Therefore, when the total time from the temporary duration reaches a predetermined standby time, the exhaust temperature raising means is activated by the control device, and the standby time is counted from zero each time the engine is restarted. It is possible to avoid the generation of white smoke at the start of traveling more reliably than when correcting.

  Furthermore, when the present invention is implemented more specifically, for example, a fuel injection device that injects fuel into each cylinder of the engine is adopted as an exhaust temperature raising means, and the fuel injection device rotates from the normal idling time. A fuel injection command for increasing the injection amount per main injection to increase the number and adding after injection at a combustible timing immediately after the main injection is output from the control device as a temperature increase control command Is possible.

  In this way, the injection amount per injection of the main injection is increased and the rotational speed is increased, so that the amount of energy input is increased and the exhaust temperature is increased, and the fuel by the after injection is converted into the output. By burning at a difficult timing, the thermal efficiency of the engine is lowered, and the amount of heat not used for power among the calorific value of the fuel is increased, so that the exhaust temperature is raised.

  Further, when such a fuel injection device is employed as the exhaust gas temperature raising means, it is preferable to use an exhaust throttle means for appropriately reducing the exhaust flow rate as the exhaust gas temperature raising means. As a result of the exhaust flow rate being throttled by the exhaust throttling means in conjunction with the increase in the rotation speed and the addition of after injection, the exhaust gas temperature is raised by raising the temperature of the exhaust gas upstream, and the exhaust resistance is increased. This makes it difficult for the intake air having a relatively low temperature to flow into the cylinder, and the residual amount of the exhaust gas having a relatively high temperature increases. The exhaust gas temperature can be further increased by being compressed at the end of the explosion stroke.

  According to the above-described exhaust purification device of the present invention, even when the engine is repeatedly stopped in the idling state, at an appropriate timing so as not to accumulate a quantity of hydrocarbons that may generate white smoke at the start of traveling. Since the temperature rise control can be executed, it is possible to achieve an excellent effect that the exhaust gas can be reliably prevented from becoming white smoke at the start of traveling after the idling state continues for a long time.

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

  1 to 5 show an example of an embodiment for carrying out the present invention. In FIG. 1, reference numeral 1 denotes a diesel engine equipped with a turbocharger 2, and intake air 4 guided from an air cleaner 3 is an intake pipe 5. And the intake air 4 pressurized by the compressor 2a is sent to the intercooler 6 to be cooled, and the intake air 4 is further supplied from the intercooler 6 to the intake manifold 7. It is guided and distributed to each cylinder 8 of the diesel engine 1 (the case of in-line 6 cylinders is illustrated in FIG. 1).

  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 passes through the exhaust pipe 11. It is designed to be discharged outside the vehicle.

  Further, in the middle of the exhaust pipe 11, a catalyst regeneration type particulate filter 12 that integrally carries an oxidation catalyst is equipped. As shown in an enlarged view in FIG. In addition, the porous honeycomb structure made of ceramic is used, and the inlets of the flow paths 12a partitioned in a lattice pattern are alternately sealed, and the outlets of the flow paths 12a that are not sealed are closed. Only the exhaust gas 9 that has passed through the porous thin wall 12b that partitions each flow path 12a is discharged to the downstream side.

  Further, a flow-through type oxidation catalyst 13 for assisting combustion removal of the particulates collected by the particulate filter 12 is disposed immediately before the particulate filter 12, which is enlarged in FIG. As shown, the oxidation catalyst 13 has a honeycomb structure in which a large number of flow paths 13a (cells) opened in the front-rear direction are defined by cell walls 13b.

  Between the upstream oxidation catalyst 13 and the particulate filter 12, a temperature at which the temperature of the exhaust gas 9 passing through the upstream oxidation catalyst 13 and entering the particulate filter 12 is measured as a substitute value of the catalyst bed temperature. A sensor 14 is provided, and a temperature signal 14a of the temperature sensor 14 is input to a control device 15 constituting an engine control computer (ECU: Electronic Control Unit).

  Since this control device 15 also serves as an engine control computer, it is also responsible for control related to fuel injection. More specifically, the control device 15 detects an accelerator opening as a load of the diesel engine 1 ( A fuel injection device that injects fuel into each cylinder 8 of the diesel engine 1 based on an accelerator opening signal 16a from the load sensor) and a rotation speed signal 17a from the rotation sensor 17 that detects the engine rotation speed of the diesel engine 1. A fuel injection signal 18 a is output to the engine 18.

  Here, the fuel injection device 18 is composed of a plurality of injectors 19 provided for each cylinder 8, and the electromagnetic valves of these injectors 19 are appropriately controlled to open by the fuel injection signal 18a. The injection timing and the injection amount are appropriately controlled.

  Further, a temperature sensor 20 for measuring the temperature of the intake air 4 as an outside air temperature is provided between the air cleaner 3 and the compressor 2a in the intake pipe 5, and a detection signal 20a of the temperature sensor 20 is also sent to the control device 15. In contrast, it is input.

  In the control device 15, the fuel injection signal 18a in the normal mode is determined based on the accelerator opening signal 16a and the rotation speed signal 17a, while the idling state is confirmed by the idling determination means described later. The standby time A (see FIG. 4: about 1 to 2 hours) is determined based on the temperature detected by the temperature sensor 20 and the operating time B (see FIG. 4) based on the temperature detected by the temperature sensor 14. ) Is intermittently switched from the normal mode to the temperature raising mode, and when switching to this temperature raising mode, as shown in FIG. 4, the rotational speed is increased from the normal idling time (about 450 rpm). Injection per main injection that was performed near the compression top dead center (crank angle 0 °) in order to execute the control to increase (approximately 1000 rpm) With increasing fuel injection signal 18a of the injection pattern to add after injection with combustible timing just after the main injection (fuel injection command) are outputted.

  However, in this control device 15, when the driver stops the engine by operating the key (ignition OFF) before the standby time A is exceeded, and the idling state is interrupted by this, the duration of the idling state until the engine stops. Is stored, and when the engine is restarted (ignition is ON), the standby time is counted continuously from the stored duration.

  Moreover, in the unlikely event that an abnormality occurs in the storage area of the control device 15, a temporary duration is set, and when the engine is restarted, the standby time is counted continuously from the temporary duration. It is also.

  Furthermore, an exhaust brake 21 whose opening degree can be adjusted to restrict the flow path of the exhaust pipe 11 to an appropriate opening degree is provided at an appropriate position upstream of the particulate filter 12, and the exhaust brake 21 is provided with a control device. 15, the opening degree is controlled by an opening degree command signal 21 a from 15, but in this embodiment, when the temperature raising mode is selected by the control device 15, the original operation with respect to the exhaust brake 21 is performed. The exhaust brake 21 can be used as an exhaust throttle means for raising the exhaust temperature as will be described later.

  Here, in addition to the temperature sensors 14 and 20, the accelerator sensor 16, and the rotation sensor 17 described above, the control device 15 described above includes a neutral switch 22 that detects that the gear position is in the neutral position, and a side brake. Detection signals 22a and 23a and a vehicle speed signal 24a are input from the side brake switch 23 for detecting the pulling and the vehicle speed sensor 24 for detecting the vehicle speed, and the vehicle is operated based on these signals. It is determined whether or not the vehicle is in the idling state, and when it is confirmed that the idling state has exceeded the waiting time A, the switching from the normal mode to the temperature raising mode is executed intermittently.

  More specifically, the rotation sensor 17 confirms that the engine speed is within a relatively low predetermined rotational speed range, the accelerator sensor 16 confirms that the accelerator is off (load is zero), and the neutral switch 22 changes the gear position to the neutral position. If it is confirmed that there is a side brake applied by the side brake switch 23 and the vehicle speed sensor 24 confirms that the vehicle speed is zero, the control device determines that the current driving state is in the idling state. 15 is determined.

  Here, the determination of the idling state does not necessarily require all signals from these sensors and switches, but at least the rotation sensor 17, the accelerator sensor 16, the neutral switch 22, the side brake switch 23, the vehicle speed. It is possible to configure the idling determination means by combining with any one or more of the sensors 24.

  Thus, when the operation control of this embodiment is performed by such a control device 15, the idling state is determined by the idling determination means comprising the rotation sensor 17, the accelerator sensor 16, the neutral switch 22, the side brake switch 23, and the vehicle speed sensor 24. Under the confirmed conditions, the control device 15 switches from the normal mode to the temperature raising mode at the standby time A determined based on the temperature detected by the temperature sensor 20, and main injection from the control device 15 to the fuel injection device 18 is performed. A fuel injection signal 18a (fuel injection command) of an injection pattern that increases the injection amount per time and adds after injection at a combustible timing immediately after the main injection becomes the detected temperature of the temperature sensor 14. The output continues for the operation time B determined on the basis thereof.

  As a result, by increasing the injection amount per main injection, the amount of energy input increases, the exhaust temperature rises, and the fuel from after injection burns at a timing that is difficult to convert to output. The thermal efficiency of the diesel engine 1 decreases, the amount of heat not used for power out of the calorific value of the fuel increases, and the exhaust temperature increases.

  In particular, in the present embodiment, the exhaust brake 21 that constitutes an exhaust throttle means for appropriately reducing the exhaust flow rate is used in combination as the exhaust temperature raising means. Therefore, the increase in the rotational speed on the diesel engine 1 side and the addition of after-injection are performed. Accordingly, the exhaust gas flow rate is narrowed by the exhaust brake 21 and the exhaust gas 9 on the upstream side is heated to raise the exhaust gas temperature. And the residual amount of the exhaust gas 9 having a relatively high temperature increases, and the air in the cylinder containing a large amount of the exhaust gas 9 having a relatively high temperature is compressed in the next compression stroke to reach an explosion stroke. In this way, the exhaust gas temperature can be further increased.

  However, if the idling state is interrupted by stopping the engine before the waiting time A is exceeded, the duration of the idling state until the engine is stopped is stored in the control device 15 and the left side of the graph in FIG. As illustrated in FIG. 4, since the standby time A is counted from the continuation time stored in the control device 15 at the next engine restart, the control is performed when the accumulated time reaches the predetermined standby time A. The apparatus 15 is switched from the normal mode to the temperature raising mode, and the temperature raising control is executed at an appropriate timing so that an amount of hydrocarbons that may generate white smoke does not accumulate at the start of traveling.

  Further, in the unlikely event that an abnormality occurs in the storage area of the control device 15, a temporary duration is set, and as illustrated on the right side of the graph in FIG. Since the standby time A is counted from the temporary duration, when the total time from the temporary duration reaches the predetermined standby time A, the control device 15 switches from the normal mode to the temperature raising mode, and the engine is restarted. White smoke generation at the start of traveling can be avoided more reliably than when the standby time A is measured again from zero each time the engine is started.

  The temporary duration described here may be changed as appropriate according to the operation mode of the vehicle, and the vehicle in which hydrocarbons easily accumulate in the particulate filter 12 due to the operation mode. In this case, it is preferable to set the provisional duration time slightly longer so that the generation of white smoke at the start of traveling can be avoided more reliably.

  Therefore, according to the above embodiment, even when the engine is repeatedly stopped in the idling state, the temperature rise control is performed at an appropriate timing so that the amount of hydrocarbons that may cause white smoke does not accumulate at the start of traveling. Therefore, it is possible to reliably prevent the exhaust gas 9 from becoming white smoke at the start of traveling after the idling state continues for a long time.

  The exhaust emission control device of the present invention is not limited to the above-described embodiment. The exhaust gas temperature raising means may employ a configuration other than the illustrated example, and the exhaust throttle means may be an exhaust gas. It may be provided separately from the brake, the intake throttle means for appropriately reducing the intake flow rate may be used instead of the exhaust throttle means, or may be used in combination with the exhaust throttle means. Of course, various changes can be made without departing from the scope of the 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. FIG. 2 is a perspective view showing the details of the oxidation catalyst of FIG. It is a graph which shows the pattern of the rotation speed control by the control apparatus of FIG. It is a graph explaining time-measurement of the waiting time in the control apparatus of FIG.

Explanation of symbols

1 Diesel engine (engine)
DESCRIPTION OF SYMBOLS 9 Exhaust gas 11 Exhaust pipe 12 Particulate filter 15 Control apparatus 18 Fuel injection apparatus (exhaust temperature rising means)
21 Exhaust brake (exhaust throttle means: exhaust temperature raising means)

Claims (3)

A catalyst regeneration type particulate filter installed in the middle of the exhaust pipe, an exhaust gas temperature raising means for raising the exhaust gas temperature to a predetermined temperature or more upstream from the particulate filter, and a continuation of idling state for a predetermined standby time An exhaust emission control device comprising a control device that activates the exhaust gas temperature raising means when it continues as described above, when the idling state is interrupted by engine stop before the standby time is exceeded, The control device is configured to store a continuation time and count the standby time continuously from the stored continuation time when the engine is restarted, and to set a temporary continuation time when an abnormality occurs in the storage area of the control device. JP that constitute the controller to count the wait time continuing set and when the engine resumes from the temporary duration Exhaust gas purification device to. A fuel injection device that injects fuel into each cylinder of the engine is adopted as an exhaust temperature raising means, and the injection amount per main injection is increased with respect to the fuel injection device in order to increase the number of revolutions from the time of normal idling. The exhaust emission control device according to claim 1 , wherein a fuel injection command for adding after-injection at a combustible timing immediately after the main injection is output from the control device as a temperature increase control command. The exhaust emission control device according to claim 2 , wherein an exhaust throttle means for appropriately reducing an exhaust flow rate is used as an exhaust temperature raising means.

Images