JP4293891B2 - 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”).

  In addition, when the temperature increase control is automatically performed in the idling state to prevent the generation of white smoke at the time of resuming the travel, conventionally, the exhaust temperature is measured as a substitute value for the catalyst bed temperature of the particulate filter. Equipped with a temperature sensor, when a certain period of time has passed since the detected temperature has exceeded the target temperature, it is considered that all the hydrocarbons in the particulate filter have been oxidized and the exhaust temperature raising means is operated. Considered to be completed.

  However, even under conditions where the temperature detected by the temperature sensor does not reach the target temperature, the hydrocarbon oxidation process proceeds slowly in the particulate filter, so the exhaust temperature changes due to disturbances such as changes in the outside air temperature. If the time required to reach the target temperature varies, the remaining amount of hydrocarbons at the time the target temperature is reached is different.In winter, where it takes a long time to reach the target temperature, Despite the fact that the remaining amount of hydrocarbons has decreased considerably when the target temperature is reached, over a certain period of time that is more than necessary (in the case of a set time that ensures that hydrocarbons can be completely oxidized even in summer). There is a possibility that the exhaust gas temperature raising means is activated and the fuel consumption is deteriorated.

  Even under conditions where the temperature detected by the temperature sensor has reached the target temperature, the higher the temperature, the higher the reaction rate by the oxidation catalyst. By simply oxidizing the hydrocarbons, the temperature rise control corresponding to the actual hydrocarbon processing state is not executed, but the exhaust gas is exhausted even though the hydrocarbons have already been oxidized. In some cases, the operation of the temperature means continued and the fuel consumption deteriorated.

  The present invention has been made in view of the above-described circumstances. An exhaust gas in which an accurate hydrocarbon processing amount close to an actual state is grasped and an operation completion timing of the exhaust gas temperature raising means can be appropriately determined. It aims to provide a purification device.

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 for operating the exhaust temperature raising means for a required operating time when it lasts for a required standby time, and a temperature sensor for detecting the outside air temperature, and a catalyst bed temperature of the particulate filter and a temperature estimation means for estimating, and determines the waiting time on the basis of the detected temperature of the temperature sensor, are set for each temperature zone on the basis of the estimated temperature of the temperature estimation means after actuation of said exhaust gas Atsushi Nobori means created momentarily cumulated and the integrated value of hydrocarbon processing amount per unit time to determine the operation completion of the exhaust gas temperature increasing means when a higher target value It is characterized in that constitute the controller to determine the time.

Thus, in this manner, the one of the exhaust Atsushi Nobori means is actuated when the continuation of the idling state than standby time determined based on the temperature detected by the temperature sensor is confirmed by the control device, the exhaust gas temperature The exhaust gas temperature raising means when the hydrocarbon treatment amount per unit time in the temperature zone to which the estimated temperature of the temperature estimation means detected after the temperature means is operated is accumulated every moment, and the accumulated value exceeds a target value. Therefore, even if the exhaust temperature changes due to a disturbance such as a change in the outside air temperature, an accurate hydrocarbon treatment amount close to the actual state can be grasped and the timing of completion of the operation of the exhaust temperature raising means can be determined. The useless operation of the exhaust gas temperature raising means in the situation where the determination is appropriately made and all the hydrocarbons have already been oxidized is avoided.

  Furthermore, when more specifically implementing the present invention, for example, a temperature sensor that measures the exhaust gas temperature as a substitute value for the catalyst bed temperature of the particulate filter may be employed as the temperature estimating means.

  In addition, 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 set to the fuel injection device in order to increase the rotational speed from the normal idling. A fuel injection command that increases and adds after injection at a combustible timing immediately after the main injection can be output from the control device as a temperature increase control command.

  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 exhaust purification apparatus of the present invention described above, an accurate hydrocarbon processing amount close to the actual state can be grasped, and the operation completion timing of the exhaust gas temperature raising means can be appropriately determined. The temperature raising control by the exhaust temperature raising means can be completed only by the operation time, and it is possible to obtain an excellent effect that the deterioration of fuel consumption due to the temperature raising control during idling can be suppressed to the necessary minimum.

  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 (temperature estimation means for estimating the catalyst bed temperature of the particulate filter 12) is provided, and a temperature signal 14a of the temperature sensor 14 is supplied to a control device 15 constituting an engine control computer (ECU: Electronic Control Unit). It is supposed to be entered.

  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.

  Here, in the control device 15, in determining the operation time B based on the temperature detected by the temperature sensor 14, after switching from the normal mode to the temperature raising mode, each temperature zone is determined based on the temperature detected by the temperature sensor 14. The amount of hydrocarbon treatment per unit time set in is accumulated every moment, and when the accumulated value exceeds the target value, the end of the temperature raising mode (completion of exhaust temperature raising means operation) is judged and the operation time The decision of B is made.

  That is, as shown in the graph of FIG. 5, the reaction rate of the hydrocarbon oxidation treatment with respect to the catalyst bed temperature of the particulate filter 12 can be grasped in advance by a preliminary experiment or the like. If the reaction rate of the hydrocarbon oxidation treatment is read out from the control map or the like according to the above, the hydrocarbon treatment amount within the calculation cycle is calculated by multiplying the reaction rate by the calculation cycle, and this is controlled. By integrating the previous value every time the calculation is performed in the apparatus 15, an integrated value of the hydrocarbon treatment amount can be obtained.

  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. However, in this embodiment, when the temperature raising mode is selected by the control device 15, the exhaust brake 21 is initially operated. The exhaust brake 21 can be used as an exhaust throttle means for instructing another independent operation and 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) having an injection pattern that increases the injection amount per time and adds after injection at a combustible timing immediately after the main injection is output.

  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.

  Then, after switching from the normal mode to the temperature raising mode, the hydrocarbon treatment amount per unit time set for each temperature zone based on the temperature detected by the temperature sensor 14 is accumulated from moment to moment. When the value exceeds the target value, the end of the temperature raising mode (completion of the operation of the exhaust temperature raising means) will be determined, and even if the exhaust temperature changes due to a disturbance such as a change in the outside air temperature, Without being affected, the exact amount of hydrocarbon treatment close to the actual state is grasped, the timing of termination of the heating mode is properly judged, and all hydrocarbons have already been oxidized. Continuation of the useless temperature increase mode is avoided.

  Therefore, according to the above embodiment, the accurate hydrocarbon processing amount close to the actual state can be grasped, and the end timing of the temperature raising mode can be appropriately determined. Temperature increase control by increasing the number of revolutions or adding after-injection can be completed, and deterioration of fuel consumption due to temperature increase control during idling can be suppressed to a necessary minimum.

  The exhaust emission control device of the present invention is not limited to the above-described embodiment, and the exhaust gas temperature raising means may adopt a configuration other than the example shown in the figure, and the temperature estimation means may be a catalyst. In addition to adopting a temperature sensor that measures the exhaust temperature as a substitute value for the bed temperature, the catalyst bed temperature of the particulate filter in the current operating state is calculated and estimated based on the intake air temperature, engine speed, load, etc. Of course, the exhaust throttling means may be provided separately from the exhaust brake, and various modifications may 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. 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 which shows the relationship between a catalyst bed temperature and reaction rate.

Explanation of symbols

1 Diesel engine (engine)
9 exhaust gas 11 exhaust pipe 12 particulate filter 14 temperature sensor (temperature estimation means)
14a Temperature signal 15 Control device 18 Fuel injection device (exhaust temperature raising means)
21 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, an exhaust temperature raising means for raising the exhaust gas temperature to a predetermined temperature or more upstream from the particulate filter, and a standby time required to continue idling An exhaust purification device comprising a control device that operates the exhaust temperature raising means for a required operating time when it continues as described above, a temperature sensor that detects the outside air temperature, and a temperature that estimates the catalyst bed temperature of the particulate filter And a standby time is determined based on the temperature detected by the temperature sensor, and after the operation of the exhaust gas temperature raising means, per unit time set for each temperature zone based on the estimated temperature of the temperature estimation means determine the operating time momentarily cumulated and the integrated value of hydrocarbon processing amount to determine the operation completion of the exhaust gas temperature increasing means when a higher target value The controller exhaust gas purification apparatus characterized by being configured to to.   The exhaust emission control device according to claim 1, wherein a temperature sensor that measures the exhaust gas temperature as a substitute value for the catalyst bed temperature of the particulate filter is employed as the temperature estimating means.   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 gas purification command according to claim 1 or 2, 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. apparatus.   The exhaust emission control device according to claim 3, wherein an exhaust throttle means for appropriately reducing an exhaust flow rate is used in combination as an exhaust temperature raising means.

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