JP2005163652A - Emission control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an emission control device for properly detecting excessive injection of fuel and a large quantity of leakage. <P>SOLUTION: The device comprises a flow-through type oxidation catalyst 14 installed in the middle of an exhaust pipe 11 for passage of exhaust gas 9, a catalyst-regeneration type particulate filter 13, a temperature sensor 15 installed between the oxidation catalyst 14 and the particulate filter 13 for detecting exhaust gas temperature, a fuel addition means 18 for adding fuel into the exhaust gas 9 at the upstream side of the oxidation catalyst 14 and the particulate filter 13, and a controller 20 for activating the fuel addition means 18 based on the detected temperature so that the particulate filter 13 can be regenerated. The controller 20 is constructed to judge whether or not the particulate filter 13 is under regeneration and to compare the temperature of the temperature sensor 15 with a first threshold and judge whether or not it is in an abnormal overheat condition when the particulate filter 13 is under regeneration. <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 as an internal combustion engine is mainly composed of carbonaceous soot and SOF (Soluble Organic Fraction) composed of high-boiling hydrocarbon components. As a component, it is composed of a small amount of sulfate (sulfate component), but as a measure to reduce this type of particulates, a particulate filter is installed in the middle of the exhaust pipe through which 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 employed, the oxidation catalyst supported by the particulate filter has an active temperature region, and the exhaust temperature is below the lower limit of activation temperature. In the low operating range, the particulates are not burned and removed well, and the trapped amount exceeds the processing amount of the particulates, so if the operating state at such a low exhaust temperature continues, the oxidation catalyst becomes active. Since the particulate filter does not progress well and the particulate filter may fall into an excessive collection state, the fuel injection device is used at the stage where the amount of particulate accumulation has increased. It is considered to regenerate the particulate filter by adding fuel to the exhaust gas upstream of the particulate filter. .

  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, the particulate filter is reproduced.

Here, some examples of such exhaust purification devices that are general examples have already been disclosed as patent publications (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 2003-222040

  However, when the fuel injection device is provided so as to add fuel upstream from the particulate filter, there is a possibility that excessive injection or a large amount of leakage may occur from the fuel injection device due to some cause, resulting in an abnormally high temperature. Therefore, it has been demanded to suitably detect excessive fuel injection and a large amount of leakage. In addition, when excessive injection or a large amount of leakage occurs and the temperature becomes abnormally high, there is a problem that a catalyst such as a particulate filter deteriorates.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an exhaust purification device that suitably detects excessive fuel injection and a large amount of leakage.

According to a first aspect of the present invention, a flow-through type oxidation catalyst and a catalyst regeneration type particulate filter installed in the middle of an exhaust pipe through which exhaust gas flows are disposed between the oxidation catalyst and the particulate filter. A temperature sensor for detecting the exhaust temperature, a fuel addition means for adding fuel into the exhaust gas upstream of the oxidation catalyst and the particulate filter, and a temperature sensor detected temperature so that the particulate filter can be regenerated. And a control device for operating the fuel addition means based on
The control device determines whether or not the particulate filter is being regenerated, and if the particulate filter is being regenerated, compares the temperature of the temperature sensor with a first threshold value to determine whether or not it is in an abnormal overheat state. The present invention relates to an exhaust emission control device that is configured to determine the above.

  According to a second aspect of the present invention, when the particulate filter is not being regenerated, the control device compares the temperature of the temperature sensor with a second threshold value, and determines whether or not it is in an abnormal overheat state. The exhaust emission control device according to claim 1.

  Claim 3 of the present invention relates to the exhaust emission control device according to claim 2, wherein the first threshold value is set to a value higher than the second threshold value.

  Thus, according to the present invention, the control device determines whether or not the particulate filter is being regenerated, and compares the temperature of the temperature sensor with the first threshold when the particulate filter is being regenerated. Therefore, even when the particulate filter is being regenerated, even if excessive injection or a large amount of leakage occurs from the fuel addition means due to some cause, the abnormal temperature is detected due to the temperature detected by the temperature sensor and the first threshold value. It is determined whether or not it is in an overheated state, and as a result, excessive injection and a large amount of leakage can be suitably detected. In addition, since appropriate measures can be taken by detecting excessive injection and a large amount of leakage, abnormal high temperatures can be suppressed, and deterioration of the catalyst such as the particulate filter can be prevented.

  When the control device is configured to compare the temperature of the temperature sensor with the second threshold when the particulate filter is not being regenerated and determine whether or not the particulate filter is in an abnormal overheat state, Even in the case where excessive injection or a large amount of leakage occurs and the temperature becomes abnormally high, it is determined whether or not an abnormal overheating state is detected by the temperature detected by the temperature sensor and the second threshold value. Injection and a large amount of leakage can be suitably detected. In addition, when excessive injection or a large amount of leakage occurs, the temperature is abnormally high in different temperature ranges when the particulate filter is being regenerated and when the particulate filter is not being regenerated. Since the first threshold value corresponding to the inside or the second threshold value corresponding to the non-regeneration is provided, the particulate filter is being regenerated when excessive injection or a large amount of leakage occurs, or is not being regenerated. In some cases, it is possible to cope with individual cases, and to detect excessive injection and a large amount of leakage, respectively.

  Furthermore, when excessive injection or a large amount of leakage occurs, the temperature is higher when the particulate filter is being regenerated and when the particulate filter is not being regenerated. When the first threshold value is set to a value higher than the second threshold value, the abnormal overheating state is suitably determined based on the detected temperature of the temperature sensor and the first threshold value or the second threshold value, Excessive injection and a large amount of leakage can be detected appropriately.

  According to the above-described exhaust gas purification apparatus of the present invention, even if there is excessive injection or a large amount of leakage from the fuel injection apparatus due to some cause, resulting in an abnormally high temperature, the detected temperature of the temperature sensor and the first threshold value Therefore, it is possible to determine an abnormal overheating state and to effectively detect excessive injection and a large amount of leakage.

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

  1 to 4 show an example of an embodiment of the present invention, FIG. 1 is a schematic view showing an example of an embodiment of the present invention, and FIG. 2 is a sectional view showing details of the particulate filter of FIG. FIG. 3 is a perspective view in which a part of the details of the oxidation catalyst of FIG. 1 is cut away, and FIG. 4 is a flowchart showing an example of determining whether or not an abnormal overheat state is present.

  In the exhaust purification system of this embodiment, reference numeral 1 in FIG. 1 denotes a diesel engine equipped with a turbocharger 2, and intake air 4 guided from an air cleaner 3 passes through an intake pipe 5 to the compressor 2 a of the turbocharger 2. 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 guided from the intercooler 6 to the intake manifold 7 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.

  A filter case 12 is interposed in the middle of the exhaust pipe 11, and a catalyst regeneration type particulate filter 13 that integrally carries an oxidation catalyst is provided in the rear stage in the filter case 12. As shown in an enlarged view in FIG. 2, the particulate filter 13 has a porous honeycomb structure made of ceramic. For the flow path 13a that is sealed and whose inlet is not sealed, the outlet is sealed, and only the exhaust gas 9 that has permeated through the porous thin wall 13b that defines each flow path 13a is downstream. It is designed to be discharged to the side.

  Further, a flow-through type oxidation catalyst 14 having a honeycomb structure as shown in an enlarged view in FIG. 3 is accommodated in a position immediately upstream of the particulate filter 13 in the filter case 12.

  A temperature sensor 15 is provided between the oxidation catalyst 14 and the particulate filter 13 in the filter case 12 for measuring the temperature of the exhaust gas 9 as a substitute value for the catalyst bed temperature. Fifteen temperature signals 15a are input to a control device 20 constituting an engine control computer (ECU: Electronic Control Unit).

  Since this control device 20 also serves as an engine control computer, it is also responsible for control related to fuel injection. More specifically, the control device 20 detects an accelerator opening as a load of the diesel engine 1 ( Fuel addition means for injecting fuel into each cylinder 8 of the diesel engine 1 based on the accelerator opening signal 16a from the load sensor) and the rotation speed signal 17a from the rotation sensor 17 for detecting the engine speed of the diesel engine 1 A fuel injection signal 18 a is output to the fuel injection device 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.

  On the other hand, in the control device 20, the fuel injection signal 18a in the normal mode is determined based on the accelerator opening signal 16a and the rotation speed signal 17a. On the other hand, it is necessary to perform regeneration control of the particulate filter 13. In this case, the mode is switched from the normal mode to the regeneration mode, and the non-ignition timing (start timing is 90 ° crank angle) after the main injection of fuel performed near the compression top dead center (crank angle 0 °). The fuel injection signal 18a is determined so as to perform the post-injection in the range of .degree.

  That is, when post-injection is performed at the non-ignition timing later than the compression top dead center following the main injection, unburned fuel (mainly HC: hydrocarbon) is oxidized in the exhaust gas 9 by this post-injection. The catalyst 14 and the particulate filter 13 are added upstream, and this unburned fuel undergoes an oxidation reaction on the oxidation catalyst on the surface of the particulate filter 13, and the heat of the reaction raises the catalyst bed temperature to increase the particulates. The particulates in the curate filter 13 are burned and removed.

  In addition, the control device 20 extracts the rotational speed of the diesel engine 1 based on the rotational speed signal 17a from the rotational sensor 17, and at the time of determining the fuel injection signal 18a based on the accelerator opening signal 16a from the accelerator sensor 16. The known fuel injection amount is extracted, and the basic generation amount of the particulates based on the current operation state of the diesel engine 1 is estimated from the particulate generation map based on the rotation speed and the injection amount. Multiply the basic generation amount by a correction coefficient considering various conditions related to the generation of particulates, and subtract the particulate processing amount in the current operating state to obtain the final generation amount. The amount of particulates accumulated is estimated from time to time to estimate the amount of particulates deposited.

  There are various ways of estimating the amount of accumulated particulates, and the particulates can be determined by methods other than the estimation method exemplified here, for example, opening / closing of an exhaust brake (not shown) and other conditions. It is of course possible to presume the estimated values of these and integrate them to estimate the amount of particulate deposition.

  Further, after it is estimated by the control device 20 that the particulate accumulation amount has reached a predetermined target value, the exhaust temperature on the inlet side of the particulate filter 13 is set to a predetermined temperature based on the temperature signal 15a from the temperature sensor 15. The fuel injection control is switched from the normal mode to the regeneration mode after waiting for the above conditions, and fuel is added to the exhaust gas 9 on the upstream side of the particulate filter 13, whereby various control processes are performed. The regeneration of the particulate filter 13 is executed.

  Here, in addition to the regeneration control of the particulate filter 13, the control device 20 detects the particulate filter so as to detect whether there is excessive injection or a large amount of leakage in the fuel injection device 18 of the fuel addition means. The first threshold value corresponding to the case where 13 is being reproduced and the second threshold value corresponding to the case where the particulate filter 13 is not being reproduced are input. A flow process as shown in FIG. 4 is provided.

  The first threshold value is set to a value higher than the second threshold value, and the first threshold value is a predetermined time (n seconds in FIG. 4) during the regeneration of the particulate filter 13, and the oxidation catalyst. 14 and the catalyst of the particulate filter 13 are not exposed to a temperature at which the catalyst deteriorates. Specifically, the catalyst is set at a temperature about 100 to 200 ° C. higher than the regeneration temperature of the particulate filter 13 (about 600 ° C.). Yes. Further, the second threshold value is such that the oxidation catalyst and the catalyst of the particulate filter 13 are not exposed to a temperature at which the catalyst of the oxidation filter and the particulate filter 13 deteriorates for a predetermined long time (m seconds in FIG. 4) while the particulate filter 13 is not regenerated. Specifically, the temperature is set at a temperature that is about 100 to 200 ° C. higher than the non-regeneration temperature of the particulate filter 13 (about 200 to 500 ° C. in a normal state).

  The operation of the embodiment of the present invention will be described below.

  When checking the temperature state between the oxidation catalyst 14 and the particulate filter 13, the controller 20 first regenerates the particulate filter 13 from the state of the fuel injection device 18 and the like in step S1, as shown in FIG. If the particulate filter 13 is being regenerated, the process proceeds to step 2. In step 2, the temperature of the particulate filter 13 measured by the temperature sensor 15 (oxidation catalyst and particulate filter is measured). 13) and the first threshold value. When the temperature of the particulate filter 13 is equal to or higher than the first threshold value and n seconds have elapsed, the process proceeds to step 3, It is determined that there is an abnormal overheating state, and it is determined that the fuel injection device 18 has excessive injection or a large amount of leakage. On the other hand, if the temperature of the particulate filter 13 is not equal to or higher than the first threshold value in step 2, or if the temperature of the particulate filter 13 is equal to or higher than the first threshold value and is less than n seconds, the step 4, it is determined in step 4 that there is no abnormal overheating, and it is determined that there is no excessive injection or a large amount of leakage in the fuel injection device 18.

  If the particulate filter 13 is not regenerated in step S1, the process proceeds to step 5. In step 5, the temperature of the particulate filter 13 measured by the temperature sensor 15 (between the oxidation catalyst and the particulate filter 13). ) And the second threshold value, and when the temperature of the particulate filter 13 is equal to or higher than the second threshold value and m seconds have elapsed, the process proceeds to step 3 and an abnormal overheat state is detected in step 3 It is determined that the fuel injection device 18 has excessive injection or a large amount of leakage. On the other hand, in step 5, when the temperature of the particulate filter 13 is not the second threshold value or higher, or when the temperature of the particulate filter 13 is the second threshold value or lower and is less than m seconds, Proceeding to step 4, it is determined in step 4 that there is no abnormal overheating, and it is determined that there is no excessive injection or a large amount of leakage in the fuel injection device 18.

  Here, if it is determined in step 3 that the state is abnormally overheated, fail-safe control is performed, the output of the diesel engine 1 is limited, and a warning lamp (not shown) is turned on. On the other hand, if it is determined in step 4 that there is no abnormal overheating, normal control is continued and terminated.

  As described above, according to the present embodiment, the control device 20 determines whether or not the particulate filter 13 is being regenerated. If the particulate filter 13 is being regenerated, the control device 20 sets the temperature of the temperature sensor 15 to the first. Therefore, during regeneration of the particulate filter 13, even if excessive injection or a large amount of leakage occurs from the fuel injection device 18 of the fuel addition means for some reason, It can be determined whether or not an abnormal overheating state is detected based on the detected temperature of the sensor 15 and the first threshold value, and as a result, excessive injection and a large amount of leakage can be suitably detected. In addition, since appropriate measures can be taken by detecting excessive injection or a large amount of leakage, abnormal high temperatures can be suppressed, and deterioration of the catalyst such as the particulate filter 13 can be prevented.

  When the control device 20 is configured to compare the temperature of the temperature sensor 15 with the second threshold when the particulate filter 13 is not being regenerated and determine whether or not the particulate filter is in an abnormal overheat state, the particulate filter During non-regeneration of 13, even if excessive injection or a large amount of leakage occurs and the temperature becomes abnormally high, it is determined whether or not an abnormal overheating state is detected by the temperature detected by the temperature sensor 15 and the second threshold, As a result, excessive injection and a large amount of leakage can be suitably detected. In addition, when excessive injection or a large amount of leakage occurs, when the particulate filter 13 is being regenerated and when the particulate filter 13 is not being regenerated, the temperature becomes abnormally high in different temperature ranges. Since the first threshold corresponding to the regeneration or the second threshold corresponding to the non-regeneration is provided, the particulate filter 13 is being regenerated when excessive injection or a large amount of leakage occurs, When the reproduction is in progress, it is possible to individually detect excessive injection and a large amount of leakage.

  Furthermore, when excessive injection or a large amount of leakage occurs, the temperature when the particulate filter 13 is being regenerated and when the particulate filter 13 is not being regenerated is higher when the regeneration is being performed. However, when the first threshold value is set to a value higher than the second threshold value, an abnormal overheat state is suitably determined by the temperature detected by the temperature sensor 15 and the first threshold value or the second threshold value. Judgment can be made and excessive injection and a large amount of leakage can be detected appropriately.

  The exhaust emission control device of the present invention is not limited to the above-described embodiment. The addition of fuel by the fuel addition means is not the post injection, but the after injection that is injected at a combustible timing immediately after the main injection. Of course, other injections may be used, and various modifications 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. It is the perspective view which notched a part which shows the detail of the oxidation catalyst of FIG. It is a flowchart which shows an example which determines whether it is in an abnormal overheating state.

Explanation of symbols

9 exhaust gas 11 exhaust pipe 13 particulate filter 14 oxidation catalyst 15 temperature sensor 18 fuel injection device (fuel addition means)
20 Control device

Claims (3)

A flow-through type oxidation catalyst and a catalyst regeneration type particulate filter installed in the middle of an exhaust pipe through which exhaust gas flows, and a temperature that is disposed between the oxidation catalyst and the particulate filter and detects the exhaust temperature. A fuel addition means for adding fuel into the exhaust gas upstream of the oxidation catalyst and the particulate filter, and a fuel addition means for operating the fuel addition means based on the temperature detected by the temperature sensor so that the particulate filter can be regenerated. A control device,
The control device determines whether or not the particulate filter is being regenerated, and if the particulate filter is being regenerated, compares the temperature of the temperature sensor with a first threshold value to determine whether or not it is in an abnormal overheat state. An exhaust emission control device configured to determine the above.   2. The exhaust gas purification according to claim 1, wherein the control device compares the temperature of the temperature sensor with a second threshold value when the particulate filter is not being regenerated and determines whether or not it is in an abnormal overheat state. apparatus.   The exhaust emission control device according to claim 2, wherein the first threshold value is set to a value higher than the second threshold value.

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