JP4204953B2 - 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.

  By the way, as a situation where the idling state continues for a long time as described above, for example, when a route bus running in the city center is caught in a heavy traffic jam, or a route bus that arrives at the end point turns back to the next If you are waiting with the engine running in preparation (when passengers are seated and waiting, it is necessary to continue operating air conditioning such as cooling), or long-distance transportation trucks are on highways, etc. It is assumed that there is a break (nap) with the engine running in the parking (when it is desired to continue operating an air conditioner such as cooling).

  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”).

  As explained in these prior applications 1 and 2, when operating the exhaust temperature raising means, a temperature sensor for measuring the intake air temperature (outside air temperature) is provided, and the exhaust temperature raising means is operated based on the detected temperature. Determine the standby time to wait for the operation (the time when it is estimated that the amount of hydrocarbons that may generate white smoke due to the continuation of the idling state is accumulated in the particulate filter), or the catalyst of the particulate filter Equipped with a temperature sensor that measures the exhaust temperature as a substitute for the bed temperature, and based on the detected temperature, the operating time of the exhaust temperature raising means (the time required to oxidize the hydrocarbon accumulated in the particulate filter) ) (Determining the end of operation in the prior application 1) is considered necessary.

  In other words, if the intake air temperature (outside air temperature) is high, the exhaust gas temperature in the idling state can be reduced relatively little, so that the generation of white smoke can be avoided even if the standby time for operating the exhaust gas temperature raising means is slightly longer. Also, if the catalyst bed temperature of the particulate filter is sufficiently high, it can be considered that the oxidation of hydrocarbons in the particulate filter will proceed efficiently, and even if the operating time of the exhaust gas heating means is shortened slightly, it will be white. Smoke generation can be avoided, so if the standby time and operating time of the exhaust temperature raising means are optimized based on the intake air temperature (outside air temperature) and the catalyst bed temperature of the particulate filter, the fuel efficiency can be improved by applying the temperature rise control during idling. Deterioration can be minimized.

  However, when the standby time and operating time of the exhaust temperature raising means are optimized in this way, the exhaust temperature is measured as a substitute value for the temperature sensor that measures the intake air temperature (outside air temperature) and the catalyst bed temperature of the particulate filter. In the unlikely event that the temperature sensor to be broken breaks down, there is a problem that the subsequent temperature rise control cannot be continued.

  The present invention has been made in view of the above-described circumstances, and even if a temperature sensor necessary for optimizing the standby time and operating time of the exhaust gas temperature raising means fails, the temperature rise during idling is reduced. An object of the present invention is to provide an exhaust emission control device capable of continuing without trouble without stopping control.

  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 from the particulate filter, an outside air temperature or an engine water temperature. A first temperature sensor that measures the exhaust temperature, a second temperature sensor that measures the exhaust gas temperature as a substitute value for the catalyst bed temperature of the particulate filter, a standby time is determined based on the detected temperature of the first temperature sensor, and An exhaust emission control device comprising: a control device for determining a working time based on a temperature detected by the second temperature sensor and executing a temperature raising control for intermittently operating the exhaust temperature raising means; When the temperature sensor fails, the shortest standby time is selected from the control range of the standby time, and when the second temperature sensor fails, the longest operation time is selected from the control range of the operation time. The sensor failure modes to continue the heating control by selecting the time and is characterized in that set in the control device.

  Thus, in this way, even if the first temperature sensor breaks down, the control device switches to the sensor fail mode, and within the control range of the standby time related to the operation of the exhaust gas temperature raising means. Since the temperature rise control is continued by selecting the shortest standby time, if the first temperature sensor fails, the minimum conditions of the assumed outside air temperature or engine water temperature (the hydrocarbons are not related to the outside air temperature or the engine water temperature). Even if the temperature condition is the most likely to accumulate), the exhaust gas temperature raising means is operated frequently before the large amount of hydrocarbon is accumulated in the particulate filter, and the hydrocarbon oxidation process is executed. As a result, the exhaust gas is prevented from becoming white smoke at the start of traveling after a long period of time.

  On the other hand, even if the second temperature sensor breaks down, the control device switches to the sensor fail mode and selects the longest operating time within the control range of the operating time of the exhaust gas temperature raising means to raise the temperature. Since the control continues, the worst condition that takes the longest time to raise the catalyst bed temperature of the particulate filter, such as idling state from engine start in cold region (winter), etc. if the second temperature sensor fails Even as a result, the exhaust temperature raising means continues to operate until all the hydrocarbons accumulated in the particulate filter are oxidized, and as a result, the exhaust gas at the start of traveling after the idling state continues for a long time. White smoke is surely prevented.

  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 if the temperature sensor necessary for optimizing the standby time and the operation time of the exhaust gas temperature raising means fails, the control device switches to the sensor failure mode, While the shortest standby time is selected in the control range of the standby time related to the operation of the exhaust temperature raising means, the longest operation time is selected in the control range of the exhaust temperature raising means. Therefore, it is possible to continue the temperature increase control without idling during idling, and to reliably prevent the exhaust gas from becoming white smoke at the start of running after the idling state has continued for a long time. The effects can be achieved.

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

  1 to 6 show an example of an embodiment for carrying out the present invention. Reference numeral 1 in FIG. 1 denotes a diesel engine equipped with a turbocharger 2, and an 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 further flows 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 (second temperature sensor) 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 (valve opening timing) and the injection amount (valve opening time) are appropriately controlled.

  Further, a temperature sensor 20 (first temperature sensor) that measures 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 of the temperature sensor 20 is provided. 20 a is also input to the control device 15.

  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 30 minutes to 4 hours) is determined based on the temperature detected by the temperature sensor 20 and the operating time B (FIG. 4 is determined based on the temperature detected by the temperature sensor 14. When the mode is switched from the normal mode to the temperature raising mode intermittently, and the temperature raising mode is switched to this temperature raising mode, as shown in FIG. 4, the rotational speed is from the normal idling time (about 450 rpm). Of main injection that was performed near the compression top dead center (crank angle 0 °) in order to execute the control to increase the engine speed (about 450-1500 rpm) With increasing injection amount or the 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, the control device 15 is further provided with a sensor fail mode in preparation for the failure of the temperature sensors 14 and 20, and when the signal input from the temperature sensors 14 and 20 disappears under idling conditions. The mode is switched to the sensor fail mode, and the temperature increase control is continued in the sensor fail mode.

That is, when the temperature sensor 20 fails, the shortest standby time A _min is selected from the control range of the standby time A as shown in FIG. 5, while when the temperature sensor 14 fails, the operation time B as shown in FIG. In this control range, the longest operation time B _max is selected and the temperature increase control is continued.

  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.

  When the temperature of the exhaust gas 9 is raised on the upstream side of the particulate filter 12 in this way, the catalyst bed temperature of the particulate filter 12 is raised and the oxidation catalyst is activated, and the idling state is achieved. However, hydrocarbons are oxidized and released before a large amount of hydrocarbons are accumulated in the particulate filter 12 for a long time.

At this time, even if the temperature sensor 20 breaks down, the control device 15 switches to the sensor fail mode and selects the shortest standby time A _min in the control range of the standby time A to control the temperature increase. Therefore, even if the temperature sensor 20 malfunctions under the assumed minimum temperature of the outside air temperature (temperature condition in which hydrocarbons are most likely to accumulate), a large amount of hydrocarbons are present in the particulate filter 12. As a result of the exhaust gas temperature raising means being operated frequently and the hydrocarbon oxidation process being executed before the gas is accumulated, the exhaust gas is surely prevented from becoming white smoke at the start of traveling after the idling state continues for a long time. It will be.

  In this embodiment, the standby time A is determined based on the intake air temperature (outside air temperature) measured by the temperature sensor 20, but instead of the intake air temperature (outside air temperature), the engine water temperature is adopted, and this engine water temperature is used. It is also possible to determine the waiting time A based on this.

  On the other hand, even if the temperature sensor 14 breaks down, the control device 15 switches to the sensor fail mode and selects the longest operating time in the control range of the operating time of the exhaust gas temperature raising means to control the temperature rise. Therefore, if the temperature sensor 14 fails, it is the worst condition that takes the longest time to raise the catalyst bed temperature of the particulate filter 12 such as an idling state after starting the engine in a cold region (winter). Even if, as a result of the operation of the exhaust gas temperature raising means being continued until all the hydrocarbons accumulated in the particulate filter 12 are oxidized, the operation of the exhaust gas 9 at the start of traveling after the idling state has continued for a long time. White smoke is surely prevented.

  That is, as illustrated on the right side of FIG. 6, when the temperature increase control is started from the engine start in the cold region (winter), the engine is cooled and the exhaust temperature at the start of the temperature increase is low. Although it takes extra time to increase the exhaust gas temperature above the target temperature, it is possible to prevent the generation of white smoke at the start of traveling even under such worst conditions.

Therefore, according to the above-described embodiment, the standby time A and the operation time B are optimized for the temperature rise control for preventing the exhaust gas 9 from becoming white smoke at the start of traveling after the idling state has continued for a long time. Even if the temperature sensors 14 and 20 required for conversion to malfunction, the control device 15 switches to the sensor failure mode, and the shortest standby time A _min is selected from the control range of the standby time A. Since the longest operating time B _{max in} the control range of the operating time B is selected, the temperature rise control during idling can be continued without being stopped, and the idling state is long. It is possible to reliably prevent the exhaust gas 9 from becoming white smoke at the start of running after being continued.

  The exhaust emission control device of the present invention is not limited to the above-described embodiment example, and the exhaust gas temperature raising means may adopt a configuration other than the example shown in the figure, and an oxidation catalyst is provided in the previous stage. In the case of a particulate filter that is not equipped, the exhaust temperature on the outlet side may be used as a substitute value for the catalyst bed temperature, the exhaust throttle means may be provided separately from the exhaust brake, and the intake flow rate may be set appropriately. Of course, the intake throttle means for narrowing down may be adopted instead of the exhaust throttle means, or may be used in combination with the exhaust throttle means. In addition, various changes can be made without departing from the scope of the present invention. .

It is the schematic which shows an example of the form which implements this invention. It is sectional drawing which shows the detail of the particulate filter of FIG. 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 waiting time and intake air temperature. It is a graph which shows the relationship between an operation period and exhaust temperature.

Explanation of symbols

1 Diesel engine (engine)
4 Intake 9 Exhaust gas 11 Exhaust pipe 12 Particulate filter 13 Oxidation catalyst 14 Temperature sensor (second temperature sensor)
14a Temperature signal 15 Control device 18 Fuel injection device (exhaust temperature raising means)
18a Fuel injection signal 20 Temperature sensor (first temperature sensor)
20a Detection signal 21 Exhaust brake (exhaust throttle means: exhaust temperature raising means)
21a Opening command signal

Claims (3)

  A catalyst regeneration type particulate filter installed in the middle of the exhaust pipe, an exhaust temperature raising means for raising the exhaust gas to a predetermined temperature or more upstream from the particulate filter, and a first temperature measuring the outside air temperature or engine water temperature One temperature sensor, a second temperature sensor that measures the exhaust gas temperature as a substitute value for the catalyst bed temperature of the particulate filter, a standby time is determined based on the detected temperature of the first temperature sensor, and the second temperature sensor An exhaust gas purification apparatus comprising: a control device for determining a working time based on a temperature detected by a temperature sensor and executing a temperature raising control for intermittently operating the exhaust gas temperature raising means. In the event of a failure, the shortest standby time is selected from the control range of the standby time, and in the event of a failure of the second temperature sensor, the longest operation time is selected from the control range of the operation time. Exhaust gas purification apparatus characterized by a sensor fail mode is set to the control unit to continue the temperature increase control by.   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