JP2005113909A - Improved filter regenerating treatment technology for trapping particulate matter in engine exhaust gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device using a filter supporting an oxidation catalyst for trapping exhaust particulates, solving the problem that a computation result of a filter bed temperature produces an error with the reaction of unburnt components including HC, CO and others to possibly cause the deterioration of the filter due to overheat. <P>SOLUTION: In accordance with presumption from a temperature measurement result at the front and rear of the filter or the amount of unburnt components presumed from the operated condition of an engine, the bed temperature is corrected. An accurate bed temperature can be found by correcting the increment of the bed temperature due to the burning heat of the unburnt components which therefore avoids the deterioration of the filter due to overheat and improves the accuracy and efficiency of regenerating control. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  As shown in Patent Document 1, a filter is provided in an engine exhaust system to purify particulate matter discharged from a diesel engine or the like (hereinafter referred to as “exhaust particulates”), and trapped exhaust particulates are collected at a predetermined interval. An apparatus is known in which the filter is regenerated by oxidation or incineration.

The regeneration of the filter is performed by increasing the exhaust temperature by engine control such as retarding the fuel injection timing or secondary injection. At this time, the surface temperature (hereinafter referred to as “bed temperature”) of the filter in contact with the fine particles is calculated based on the exhaust temperatures on the filter inlet side and the outlet side, and engine control is performed so that the bed temperature becomes a target value. By doing so, the exhaust particulates are burned efficiently.
JP-A-5-106427

  In a CSF type filter carrying a catalyst for oxidizing HC and CO (hereinafter referred to as “unburned components”) in engine exhaust, not only the combustion heat of exhaust particulates but also the unburned components are oxidized during regeneration. The heat of reaction is also generated. Since the reaction heat due to the unburned component is not taken into consideration in the calculation of the bed temperature described above, it cannot always be controlled to an appropriate bed temperature in the regeneration control. For this reason, the bed temperature after regeneration control becomes too high with respect to the target temperature, or depending on the discharge amount of unburned components, a local high temperature portion may be generated in the filter, which may deteriorate the filter.

  In the present invention, the temperature measurement result before and after the filter is premised on the exhaust purification device of the engine that collects the exhaust particulates with the filter carrying the oxidation catalyst and regenerates the filter by raising the bed temperature of the filter and burning it. The bed temperature is corrected based on the unburned component amount estimated from the above or from the engine operating state.

  According to the present invention, it is possible to know the exact bed temperature by correcting the increase in the bed temperature due to the combustion heat of the unburned components, so that the deterioration of the filter due to overheating can be avoided, and the accuracy and efficiency of the regeneration control can be improved. Can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an example of an engine system to which the present invention can be applied. In the figure, reference numeral 1 denotes an engine body, 2 denotes an intake passage, and 3 denotes an exhaust passage. A fuel injection valve 4 and a fuel injection pump 5 are attached to the engine body 1. An air cleaner 6, an air flow meter 7, a compressor 9 of an exhaust turbocharger 8, an intercooler 10, and a throttle valve 11 are interposed in the intake passage 2 from the upstream side. A turbine 12 of an exhaust turbocharger 8 and a filter (DPF) 13 for collecting exhaust particulates are interposed in the exhaust passage 3 from the upstream side. Reference numerals 14 and 15 are temperature sensors which are temperature measuring means for detecting the inlet temperature and the outlet temperature of the filter 13, respectively, and 16 is a pressure sensor for detecting the pressure difference between the front and rear of the filter 12. Reference numeral 17 denotes an EGR passage that communicates the intake passage 2 and the exhaust passage 3, and an EGR valve 18 and an EGR cooler 19 are interposed in the middle thereof. The exhaust turbocharger 8 includes a variable nozzle 20 that can adjust the flow rate of the exhaust gas flowing into the turbine 12. A crank angle sensor 21 detects the engine speed and the crank position. Reference numeral 23 denotes an outside air temperature sensor as means for detecting the outside air temperature, and reference numeral 24 denotes a pressure sensor as means for detecting the pressure of the outside air.

  Reference numeral 22 denotes a control unit, which is composed of a microcomputer comprising a CPU and its peripheral devices. The control unit 22 controls the fuel injection timing, the fuel injection amount, the throttle valve opening, the EGR amount, the variable nozzle opening, and the like based on the signals from the various sensors, and the regeneration control for increasing the exhaust temperature by engine control. It functions as a means, each calculating means, and each correcting means.

  The outline of the reproduction control executed by the control unit 22 is as follows. First, the trapped amount of exhaust particulates (the amount deposited on the filter) is calculated using the load Q constantly detected in the background as the engine operating state and the rotational speed Ne. The load Q uses the fuel injection amount command value as a representative value, and the rotation speed Ne reads the signal of the crank angle sensor 21. Various methods for calculating the amount of collected particulate matter are known.For example, a table in which the amount of particulate matter discharged from the engine within a certain period of time is assigned according to the load Q and the rotational speed Ne is experimentally created in advance. Then, it is obtained by integrating the reading values at regular intervals or by calculating based on the operation state signal and the signal from the differential pressure sensor 16.

  Next, when the exhaust particulate accumulation amount is equal to or greater than a reference value at which regeneration is to be started, the operating state is determined, and regeneration is started when the engine is operating in a recyclable region. In the reproducible region, an operating region where the exhaust temperature necessary for regeneration can be efficiently obtained is set according to the characteristics of the engine. In the engine system shown in FIG. 1, for example, regeneration is performed by any one of intake throttle by the throttle valve 11, retardation of the fuel injection timing, secondary injection, EGR amount reduction, and opening control of the variable nozzle 20. Then, an exhaust temperature of 300 ° C. or higher necessary for fine particle regeneration is ensured.

  During the regeneration control, the bed temperature of the filter 13 is calculated, and the engine control described above is performed so that the regeneration is performed efficiently and the predetermined bed temperature does not cause overheating.

  FIG. 2 shows a flow according to the first embodiment regarding the bed temperature calculation executed by the control unit 22. This flow is executed periodically at regular intervals. In the following description and the flow, the numbers indicated with the symbol S are processing step numbers.

  In the figure, first, the exhaust temperature Tdpf_in_mea on the filter inlet side is measured based on the signal from the temperature sensor 14 in S101. Next, in S102, the exhaust temperature Tdpf_out_cal on the filter outlet side is calculated using the measured inlet temperature Tdpf_in_mea. Since the outlet temperature Tdpf_out_cal can be estimated from the engine operating state and the inlet temperature Tdpf_in_mea, for example, the outlet temperature Tdpf_out_cal is set in advance so that the fuel injection amount Q representing the engine operating state, the engine speed Ne, and the inlet temperature Tdpf_in_mea are used as parameters. The search is made by searching the set map.

  In S103, the filter bed temperature Tbed_cal is calculated using the calculation outlet temperature Tdpf_out_cal. The calculated bed temperature Tbed_cal can also be obtained by searching a map set in advance from the engine operating state and the calculated outlet temperature Tdpf_out_cal.

  In S104, the actual exhaust temperature Tdpf_out_mea on the filter outlet side is obtained based on the signal from the temperature sensor 15, and then in S105, the calculated outlet temperature Tdpf_out_cal in S103 is subtracted from the measured outlet temperature Tdpf_out_mea, and the temperature due to the reaction of the unburned components. Calculate the increase ΔThc1.

  In S106, the corrected bed temperature Tbed_cor is calculated by adding the above-mentioned temperature rise Thc1 to the calculated bed temperature Tbed_cal in S103.

  FIG. 3 shows the relationship between the estimated temperature of each part and the actual temperature calculated by the filter regeneration. As shown in the figure, the actual outlet temperature and bed temperature have a difference of ΔT1 and ΔT2 by the amount of heat generated by the reaction of the unburned components with respect to the calculated outlet temperature and bed temperature. According to this embodiment, as the corrected bed temperature Tbed_cor, a value close to the actual bed temperature including the increase in the bed temperature due to the unburned component is obtained. Thus, by performing the above-described filter regeneration control using Tbed_cor, it is possible to efficiently perform filter regeneration and to prevent overheating of the filter and to protect it.

  FIG. 5 is a flow according to the second embodiment regarding the bed temperature calculation. The processes in S101 to S102 are the same as those in FIG. 2, and the processes in S404 to S407 are the same as those in S103 to S106 in FIG.

  This embodiment is different from FIG. 2 in that when calculating the DPF bed temperature Tbed_cal based on the DPF outlet temperature Tdpf_out_cal, the DPF outlet temperature Tdpf_out_cal is corrected according to the outside air temperature and pressure in S401 to S403.

  In S401, the detected values of the outside air temperature sensor 23 and the pressure sensor 24 are read.

  In S402, a map search is performed for the DPF outlet temperature correction coefficient based on the outside air temperature and pressure read in S401. Specifically, for example, a map in which a correction coefficient is set for each outside air temperature and a map in which a correction coefficient is set for each pressure are set in advance, and the correction coefficient based on the outside air temperature and the correction based on the pressure are searched. Each coefficient is obtained.

  In S403, the DPF outlet temperature Tdpf_out_cal is corrected using the correction coefficient obtained in S402.

  According to the present embodiment, the DPF outlet temperature Tdpf_out_cal is corrected according to changes in environmental factors such as outside air temperature and pressure. For example, when the outside air temperature is extremely low, the ignition delay time during DPF regeneration is increased. The unburned component is excessively supplied, and it is possible to protect the DPF by preventing the excessive temperature rise of the DPF due to the oxidation reaction of the unburned component.

  FIG. 4 is a flow according to the third embodiment regarding bed temperature calculation. The processing of S101 to S103 is the same as that in FIG. 2, and the outlet temperature Tdpf_out_cal and the bed temperature Tbed_cal are calculated based on the measured inlet temperature Tdpf_in_mea. This embodiment differs from the process of FIG. 2 in that the temperature increase ΔTch2 due to the reaction of the unburned components is calculated from the amount of unburned components.

  First, in S204, the map is searched for the emission amounts of HC and CO which are unburned components. Since the unburned component emission amount is determined by the engine characteristics, a map that gives the unburned component emission amount in advance using the engine operating state, for example, the fuel injection amount Q and the rotational speed Ne described above as parameters, is searched. To ask for it.

  Next, in S205, the bed temperature increase ΔTch2 due to the reaction of the unburned component is calculated from the amount of the unburned component, the calorific value at the time of reaction, the conversion efficiency, and the heat capacity of the filter.

  In S206, the corrected bed temperature Tbed_cor is calculated by adding the bed temperature increase ΔTch2 calculated as described above to the bed temperature Tbed_cal calculated in S103.

  According to this embodiment, since the corrected bed temperature Tbed_cor is calculated based on the actual discharge amount of unburned components, higher accuracy can be expected.

  FIG. 6 is a flow according to the fourth embodiment regarding the bed temperature calculation. The processing of S101 to S103 and S204 is the same as that in FIG. 4, and the outlet temperature Tdpf_out_cal and the bed temperature Tbed_cal are calculated based on the measured inlet temperature Tdpf_in_mea. This embodiment differs from FIG. 4 in that when calculating the temperature increase ΔTch3 due to the reaction of the unburned components, the unburned component discharge amount is corrected according to the intake air temperature and pressure.

  In S301, the detected values of the outside air temperature sensor 23 and the pressure sensor 24 are read.

  In S302, the map is searched for the discharge amount correction coefficient based on the outside air temperature and pressure read in S301. Specifically, for example, a map that gives a correction coefficient using the outside air temperature as a parameter and a map that gives a correction coefficient using the pressure as a parameter are set in advance, and these are searched and the correction coefficient based on the outside air temperature and the correction based on the pressure Each coefficient is obtained.

  In S303, the unburned component discharge amount is corrected by multiplying the unburned component discharge amount obtained in S204 by the correction coefficient based on the outside air temperature and pressure obtained in S302. The ignition delay time during DPF regeneration changes depending on the outside air temperature and pressure, and the unburned component discharge amount also changes accordingly. With this correction, the unburned component discharge amount can be calculated with high accuracy.

  In S304 and S305, processing similar to S205 and S206 in FIG. 4 is performed using the corrected unburned component discharge amount obtained in S303, and a bed temperature increase ΔTch3 due to the reaction of unburned components is calculated. In addition to the bed temperature Tbed_cal calculated in S103, a corrected bed temperature Tbed_cor is calculated.

  According to the present embodiment, the emission amount of the unburned component is corrected by the change in the ignition delay time based on the outside air temperature and pressure, so that the corrected bed temperature Tbed_cor is calculated with high accuracy according to the environmental requirements. As a result, the ignition delay time is expanded and the unburned component is excessively supplied, thereby preventing the excessive temperature rise of the DPF caused by the oxidation reaction and protecting it.

  In S304, a map that provides the bed temperature increase ΔTch3 due to the reaction of the unburned component using the discharge amount of the unburned component and the DPF inlet temperature Tdpf_in_mea as parameters may be prepared and searched.

  Instead of performing corrections in S301 to S303, a map to be searched in S204 may be prepared for each outside temperature and pressure, and the search may be performed after reading the outside temperature and pressure in S301.

  The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims.

  The present invention is applicable to a filter regeneration processing control device that collects particulate matter in engine exhaust.

1 is a schematic diagram of an engine system to which the present invention can be applied. The flowchart which showed the process sequence which concerns on 1st Embodiment of the bed temperature calculation of this invention. The characteristic diagram which showed the characteristic of the bed temperature at the time of reproduction | regeneration in relation to the estimated value. The flowchart which showed the process sequence which concerns on 3rd Embodiment of the bed temperature calculation of this invention. The flowchart which showed the process sequence which concerns on 2nd Embodiment of the bed temperature calculation of this invention. The flowchart which showed the process sequence which concerns on 4th Embodiment of the bed temperature calculation of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine main body 2 Intake passage 3 Exhaust passage 4 Fuel injection valve 5 Fuel injection pump 7 Air flow meter 8 Exhaust turbocharger 9 Compressor 11 Throttle valve 12 Turbine 13 Filter 17 EGR passage 18 EGR valve 20 Variable nozzle 21 of turbocharger 21 Crank angle sensor 22 control unit

Claims (10)

A particulate matter collection filter carrying a catalyst for oxidizing unburned components in the engine exhaust;
In an engine exhaust purification device comprising regeneration control means for regenerating the filter by raising the bed temperature of the filter and burning the particulate matter trapped in the filter,
Inlet temperature measuring means for detecting the exhaust temperature on the filter inlet side;
Outlet temperature calculating means for calculating the exhaust temperature on the filter outlet side based on the measured inlet temperature;
Bed temperature calculation means for calculating the bed temperature of the filter based on the measured inlet temperature and the calculated outlet temperature;
Reaction temperature calculation means for calculating a temperature rise due to the reaction of the unburned component;
Bed temperature correcting means for correcting the bed temperature based on the calculated temperature rise due to the reaction,
The exhaust emission control device for an engine, wherein the regeneration control means performs regeneration control so that the corrected bed temperature becomes a predetermined regeneration temperature. Comprising outlet temperature measuring means for detecting the exhaust temperature on the filter outlet side,
2. The engine exhaust gas purification apparatus according to claim 1, wherein the reaction temperature calculation unit calculates a temperature increase due to a reaction of the unburned component based on the measured outlet temperature and the calculated outlet temperature. Means for detecting the outside air temperature;
Means for detecting the pressure of the outside air;
An outlet temperature correcting means for correcting the calculated outlet temperature according to one or both of the outside air temperature and pressure;
3. The engine exhaust gas purification apparatus according to claim 2, wherein the reaction temperature calculation means calculates a temperature rise due to a reaction of the unburned component based on the measured outlet temperature and the corrected outlet temperature after correction. Comprising unburned component emission calculating means for calculating the amount of unburned component emission based on the engine state;
2. The exhaust emission control device for an engine according to claim 1, wherein the reaction temperature calculation means calculates a temperature increase due to a reaction of the unburned component based on the calculated unburned component emission amount. Means for detecting the outside air temperature;
Means for detecting the pressure of the outside air;
An unburned component discharge amount correcting means for correcting the calculated unburned component discharge amount according to either or both of the outside air temperature and the pressure;
The engine exhaust gas purification apparatus according to claim 4, wherein the reaction temperature calculation means calculates a temperature rise due to a reaction of the unburned component based on the corrected unburned component emission amount after correction. The outlet temperature calculating means includes
6. The outlet temperature is calculated by searching a map formed in advance so as to give the exhaust temperature on the filter outlet side based on the exhaust temperature on the filter inlet side and the engine operating state. An exhaust purification device for an engine according to any one of the above. The bed temperature calculating means includes
6. The structure according to claim 1, wherein the bed temperature is calculated by searching a map formed in advance so as to apply the bed temperature based on the exhaust gas temperature on the filter inlet side and the engine operating state. The engine exhaust gas purification apparatus as described.   The engine exhaust purification device according to any one of claims 1 to 5, wherein the engine operating state includes an engine speed and a fuel injection amount as a load representative value. The reproduction control means includes
The filter is regenerated by controlling the engine exhaust temperature so that the bed temperature becomes a predetermined regeneration temperature based on the corrected bed temperature when the filter is regenerated. Engine exhaust purification system. The reproduction control means includes
Fuel injection timing control, fuel injection amount control, nozzle opening control of variable nozzle exhaust turbocharger, EGR control, intake air amount control, auxiliary equipment load control,
The engine exhaust gas purification device according to claim 9, wherein the engine exhaust temperature is increased by applying at least one of the above.

Images