EP1722088A2

EP1722088A2 - Exhaust gas treatment system for internal combustion engine

Info

Publication number: EP1722088A2
Application number: EP06009584A
Authority: EP
Inventors: Isao Chiba; Junko Oba
Original assignee: Honda Motor Co Ltd
Current assignee: Honda Motor Co Ltd
Priority date: 2005-05-13
Filing date: 2006-05-09
Publication date: 2006-11-15
Anticipated expiration: 2026-05-09
Also published as: EP1722088A8; JP2006316744A; EP1722088A3; EP1722088B1

Abstract

In an exhaust gas treatment system for an internal combustion engine, a basic (post-injection) fuel injection quantity is calculated at block 62a based on an operating condition of the engine, a corrected fuel injection quantity is calculated at blocks 62b1, 62b2 to correct the basic supply quantity based on an exhaust gas temperature TEX1 at a location upstream of the oxidation catalytic converter, and a final (post-injection) fuel injection quantity is calculated in blocks 62c to 62f based on the calculated quantities and injected into the engine 10. Thus the detected exhaust gas temperature TEX1 is not affected by the combustion in the DPF or the mass thereof, nor is it affected by the combustion in the converter or the mass thereof, so that the fuel supply for regeneration can be achieved with good accuracy, thereby improving the DPF regeneration efficiency.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

This invention relates to an exhaust gas treatment system for an internal combustion engine, particularly to an exhaust gas treatment system for use in an internal combustion engine equipped with an oxidation catalytic converter and a diesel particulate filter (DPF) positioned downstream thereof to capture particulates or particulate matter, and more particularly to an exhaust gas treatment system that enables regeneration of the filter by supplying unburned fuel.

Description of the Related Art

The exhaust system of a diesel engine is equipped with a DPF that removes fine particulate matter from the exhaust gas by capturing them in microporous trap. As the buildup of captured fine particulate matter increases, the filter progressively clogs. Therefore, as taught by Japanese Laid-Open Patent Application Nos. Hei 4(1992) -019315 and Hei 5(1993)-044434 , the practice is to regenerate the DPF by burning the fine particulate matter using fuel supplied through a fuel injector installed in the exhaust system.
The teaching of the first reference is to detect the exhaust gas temperature immediately downstream of the DPF and control the fuel supply quantity to increase as the air intake quantity increases and decrease as the detected exhaust gas temperature rises. The teaching of the second reference is to calculate the fuel supply quantity based on the air intake quantity and the exhaust gas temperature upstream of the DPF, and conduct control for downwardly correcting the calculated fuel supply quantity using the exhaust gas temperature on the downstream side of the DPF.
As explained, the prior art teachings of the first and second references calculate the fuel supply quantity using as one factor the exhaust gas temperature(s) downstream of or before and after the DPF, i.e., exhaust gas temperatures near the DPF. This makes it difficult to achieve the fuel supply quantity required for regeneration with good accuracy.
This is because the exhaust gas temperature changes rapidly with change in the fuel injection quantity when the internal combustion engine is in transient operation. In the prior art, the detected temperature is that near, e.g., immediately downstream of, the DPF, so that the detected value is a value skewed by the combustion in the DPF or the mass of the DPF. Moreover, when the exhaust gas temperature is high, the temperature of the exhaust manifold becomes high, so that when unburned fuel is supplied during post-injection, the unburned fuel self-ignites and bums to increase the exhaust gas temperature still further.
Moreover, when an oxidation catalytic converter for oxidizing unburned exhaust gas components is installed upstream of the DPF, the detected temperature similarly becomes a value skewed by the combustion in the catalytic converter or the mass of the catalytic converter.

SUMMARY OF THE INVENTION

An object of this invention is therefore to overcome the aforesaid problems by providing an exhaust gas treatment system for an internal combustion engine which, in a configuration equipped with an oxidation catalytic converter upstream of the filter (DPF), detects the exhaust gas temperature and corrects the unburned fuel supply quantity unaffected by the filter (DPF) or the oxidation catalytic converter upstream thereof and conducts regeneration treatment using the corrected unburned fuel supply quantity, thereby achieving accurate supply of the unburned fuel quantity required for regeneration and improving the regeneration efficiency of the filter (DPF).
In order to achieve the object, this invention provides a system for treating exhaust gas produced by an internal combustion engine having an oxidation catalytic converter installed in an exhaust system for oxidizing and removing unburned hydrocarbons in the exhaust gas and a filter installed downstream of the oxidation catalytic converter for capturing particulates entrained by the exhaust gas, characterized by: basic supply quantity calculating means for calculating a basic supply quantity of unburned fuel based on an operating condition of the engine; corrected supply quantity calculating means for calculating a corrected supply quantity of the unburned fuel to correct the basic supply quantity based on an exhaust gas temperature at a location upstream of the oxidation catalytic converter; and fuel supply executing means for calculating a final supply quantity of the unburned fuel based on the calculated basic supply quantity and corrected supply quantity and for executing supply of the unburned fuel based on the calculated final supply quantity of the unburned fuel to the engine such that the filter is generated.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects and advantages of the invention will be more apparent from the following description and drawings in which:

FIG. 1 is a schematic drawing showing the overall configuration of an exhaust gas treatment system for an internal combustion engine according to an embodiment of the invention;
FIG. 2 is a block diagram illustrating the operation of the system shown in FIG. 1;
FIG. 3 is a graph for explaining the tabulated characteristic of an injection quantity correction factor with respect to an exhaust gas temperature TEX1, which is used in the processing of FIG. 2; and
FIG. 4 is a graph for explaining the mapped characteristic of an exhaust gas temperature correction weight (injection quantity correction factor correction value) with respect to engine speed NE and a fuel injection quantity Q (exhaust gas flow rate), which is used in the processing of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An exhaust gas treatment system for an internal combustion engine according to an embodiment of the present invention will now be explained with reference to the attached drawings.
FIG. 1 is a schematic drawing showing the overall configuration of the exhaust gas treatment system for an internal combustion engine according to this embodiment of the invention.
The reference numeral 10 in FIG. 1 designates a four-cylinder internal combustion engine, more specifically diesel engine (compression-ignition engine) and the reference numeral 10a designates the main unit of the engine 10. Intake air sucked in through an air cleaner 12 of the engine 10 flows through an air intake pipe (air intake passage) 14.
An intake shutter or intake air throttle 16 is installed at a suitable point in the intake pipe 14. The intake shutter 16 includes a valve 16a and an electric motor or other actuator 16b connected to the valve 16a. When the actuator 16b of the intake shutter 16 is driven by a drive circuit (not shown) to rotate the valve 16a in the closing direction, the opening of the intake pipe 14 is reduced to reduce the flow rate of intake air through the intake pipe 14.
The air flowing through the intake pipe 14 passes through an intake manifold 20 installed downstream of the intake shutter 16 and arrives at the individual cylinders to be drawn into their combustion chambers (not shown) when the associated intake valve (not shown) opens and the associated piston (not shown) descends. The inspired air is compressed and reaches a high temperature when the piston ascends.
Fuel (kerosene) stored in a fuel tank (not shown) is supplied through a pump and a common rail (neither shown) to fuel injectors 22 (only one shown) directed into the combustion chambers of the individual cylinders. When each fuel injector 22 is driven through a drive circuit (not shown), it injects fuel into the associated combustion chamber and the injected fuel spontaneously ignites and burns upon coming in contact with the compressed, high-temperature intake air. As a result, the piston is first driven downward and thereafter ascends to discharge the exhaust gas into an exhaust manifold 24 (of the exhaust system) upon opening of an associated exhaust valve (not shown). The exhaust gas then flows into a downstream exhaust pipe 26 (of the exhaust system).
An EGR pipe (Exhaust Gas Recirculation passage) 30 connected to the intake pipe 14 at one end is connected to the exhaust pipe 26 at the other end. The EGR pipe 30 is equipped with an EGR valve 30a. When the EGR valve 30a is operated through a drive circuit (not shown), the EGR pipe 30 is opened to return part of the exhaust gas to the air intake system.
The turbine (not shown) of a turbocharger (illustrated as "T/C") 32 is installed in the exhaust pipe 26 at a location downstream of the point at which the EGR pipe 30 is connected. The turbine is rotated by the exhaust gas to drive a compressor 32a through a mechanical interconnection, thereby supercharging the engine 10 with intake air from the air cleaner 12.
An oxidation catalytic converter (illustrated as "CAT") 34 utilizing platinum or the like as catalyst is installed in the exhaust pipe 26 downstream of the turbocharger 32. The oxidation catalytic converter 34 oxidizes and removes unburned hydrocarbons in the exhaust gas. The oxidization conducted in the oxidation catalytic converter 34 increases the exhaust gas temperature. This will be discussed in more detail later.
A DPF (Diesel Particulate Filter) 36 is installed downstream of the oxidation catalytic converter 34 for capturing particulates entrained by the exhaust gas. The DPF 36 comprises a ceramic honeycomb filter internally provided with exhaust gas passages whose upstream ends are closed and downstream ends are opened arranged alternately with exhaust gas passages whose upstream ends are opened and downstream ends are closed. Microporous walls formed with numerous holes of around 10 µm diameter are provided between adjacent passages. Particulates contained in the exhaust gas are captured in these holes.
The DPF 36 experiences clogging owing to gradual buildup of the so-captured particulates. In this embodiment, the DPF 36 is a catalyzed soot filter (CSF) in which the temperature at which the particulates can be burned is reduced by the action of a catalyst carried on the filter and the particulates captured from the exhaust gas are burned at the reduced temperature.
After passing through the DPF 36, the exhaust gas passes through a silencer, tailpipe and the like (none of which are shown) to be discharged to outside the engine 10.
A crank angle sensor 40 including multiple sets of magnetic pickups is installed near the crankshaft (not shown) of the engine 10. The crank angle sensor 40 produces outputs indicative of a cylinder identification signal, a TDC signal at or near the TDC of each of the four cylinders, and a crank angle signal every prescribed crank angle.
A coolant temperature sensor 42 installed near a coolant passage (not shown) of the engine 10 produces an output or signal indicative of the engine coolant temperature TW. An intake air temperature sensor 44 is installed in the intake pipe 14 at a point near the air cleaner 12. The intake air temperature sensor 44 outputs a signal indicative of the temperature of intake air sucked into the engine 10 (the intake air temperature or outside air temperature).
An accelerator position sensor 50 is installed near an accelerator pedal 46 located on the floor near the driver's seat (not shown) of the vehicle in which the engine 10 is installed. The accelerator position sensor 50 produces an output or signal indicative of the accelerator position or opening θAP, which is indicative of the engine load. A wheel speed sensor 52 installed at a suitable part of a wheel (not shown) produces an output or signal every predetermined angle of rotation of the wheel indicative of a travel speed of the vehicle.
A first exhaust gas temperature sensor 54 is installed in the exhaust system of the engine 10 at a suitable location downstream of the turbocharger 32 and upstream of the oxidation catalytic converter 34. The first exhaust gas temperature sensor 54 produces an output indicative of the exhaust gas temperature TEX1 on the upstream side of the oxidation catalytic converter 34 (temperature of the exhaust gas flowing into the oxidation catalytic converter 34). A second exhaust gas temperature sensor 56 is installed downstream of the oxidation catalytic converter 34 and upstream of the DPF 36 (immediately before the DPF 36). The second exhaust gas temperature sensor 56 produces an output indicative of the exhaust gas temperature TEX2 on the upstream side of the DPF 36 (temperature of the exhaust gas flowing into the DPF 36).
The DPF 36 is provided with a differential pressure sensor 60 that produces an output indicative of the differential pressure PDIF between the pressure of the exhaust gas flowing into the DPF 36 and the pressure of the exhaust gas flowing out of the DPF 36, i.e., the differential pressure PDIF between the inlet side and outlet side pressures of the DPF 36.
The outputs of the foregoing sensors are sent to an ECU (Electronic Control Unit) 62. The ECU 62 is constituted as a microcomputer comprising a CPU, ROM, RAM and input/output circuit. The ECU 62 detects or calculates the engine speed NE of the engine 10 by using a counter to count the crank angle signals outputted by the crank angle sensor 40 and detects or calculates the vehicle speed by using a counter to count the signals outputted by the wheel speed sensor 52.
The ECU 62 is housed in a case (not shown) and installed at an appropriate location near the driver's seat of the vehicle. An atmospheric pressure sensor 64 accommodated in the case sends the ECU 62 an output indicative of the atmospheric pressure at the current location of the engine 10.
The operation of the exhaust gas treatment system shown in FIG. 1 will now be explained.
FIG. 2 is a block diagram illustrating the operation. The diagram comprises functional blocks representing the processing operations of the ECU 62. The operation of the system will be explained with reference to these blocks.
First, in block 62a, the basic (post-injection) fuel injection quantity (basic supply quantity of unburned fuel) required for regenerating the DPF 36 is determined or calculated based on the engine speed NE and the ordinary, i.e., not post-injection fuel injection quantity Q. The fuel injection quantity Q is determined in another processing step (not shown) by using the accelerator position θAP to retrieve a value from an appropriate characteristic and correcting the retrieved value based on other operating parameters.
The fuel injection quantity Q is determined as the valve open time of the injector 22. Every time each cylinder of the engine 10 is about to shift from the intake stroke to the compression stroke, the associated injector 22 injects fuel into the combustion chamber of the cylinder in a quantity equal to the determined fuel injection quantity Q.
As pointed out above, the fuel injected into the combustion chamber spontaneously ignites and bums to drive down the piston upon coming into contact with the intake air raised to a high temperature by compression. The exhaust gas produced by the combustion is discharged into the exhaust system, i.e., exhaust manifold 24 and exhaust pipe 26 when the exhaust valve opens during the exhaust stroke.
Post-injection is performed after the combustion of the fuel injected by ordinary combustion at about the time power stroke is shifting from the expansion stroke to the exhaust stroke during low or medium load operation of the engine 10 by injecting fuel through the injector 22 based on the post-injection quantity. Most of the fuel injected by the post-injection does not burn because no compressed air is present. It is therefore discharged into the exhaust system as unburned fuel. Almost all of the unburned fuel components are hydrocarbons (HC). The block 62a thus functions as basic supply quantity calculating means for calculating the basic supply quantity of unburned fuel based on an operating condition of the engine 10.
In block 62b, the engine speed NE and fuel injection quantity Q are used to determine or calculate a corrected fuel injection quantity (corrected supply quantity of the unburned fuel) for correcting the calculated basic (post-injection) fuel injection quantity. A correction factor for correcting the calculated corrected fuel injection quantity is also determined or calculated in block 62b.
Specifically, the exhaust gas temperature TEX1 (exhaust gas temperature on the upstream side of the oxidation catalytic converter 34) is read in block 62b1 and then, in block 62b2, the read exhaust gas temperature TEX1 is used to determine or calculate the corrected fuel injection quantity by retrieval from a tabulated characteristic determined beforehand and stored in ROM.
FIG. 3 is a graph for explaining the tabulated characteristic. As shown, the corrected fuel injection quantity is determined or defined to decrease with increasing exhaust gas temperature TEX1. This is because the required (post-injection) fuel injection quantity decreases with increasing exhaust gas temperature TEX1.
Thus, the blocks 62b1 and 62b2 function as corrected supply quantity calculating means for calculating the corrected supply quantity of the unburned fuel to correct the basic supply quantity based on the exhaust gas temperature TEX1 at a location upstream of the oxidation catalytic converter 34.
Next, in block 62b3, the engine speed NE and (ordinary) fuel injection quantity Q are used to determine or calculate an exhaust gas temperature correction weight (correction value of the corrected supply quantity of the unburned fuel) by retrieval from a mapped characteristic determined and stored in ROM beforehand.
FIG. 4 is a graph for explaining the mapped characteristic. The exhaust gas flow rate or exhaust gas volume depends on the engine speed NE and fuel injection quantity Q, namely, it increases as they increase. The foregoing therefore means that the exhaust gas temperature correction weight is calculated based on the exhaust gas flow rate in accordance with the mapped characteristic.
The exhaust gas flow rate affects the fuel supply quantity (i.e., the exhaust gas temperature) required for regeneration of the DPF 36, and the amount of heat needed to heat the DPF 36 to the temperature required for regeneration increases (or decreases) as the exhaust gas flow rate increases (or decreases). Therefore, as shown in FIG. 4, the exhaust gas temperature correction weight is determined or defined to increase with increasing engine speed NE and fuel injection quantity Q and decrease with decreasing engine speed NE and fuel injection quantity Q, i.e., so as to increase and decrease as the exhaust gas flow rate increases and decreases.
The exhaust gas temperature correction weight is calculated as a multiplier coefficient such as 1.1 or 1.2. The corrected injection quantity is multiplied by the exhaust gas temperature correction weight in block 62b4, thereby correcting the corrected fuel injection quantity. Thus, the blocks 62b3, 62b4 function as corrected supply quantity correction value calculating means for calculating the correction value of the corrected supply quantity based on a flow rate of the exhaust gas produced by the engine 10 such that the correction value increases with increasing flow rate of the exhaust gas.
In block 62c, the corrected fuel injection quantity is added to the basic (post-injection) fuel injection quantity. As a result, the basic (post-injection) fuel injection quantity is corrected by the exhaust gas temperature TEX1 on the upstream side of the oxidation catalytic converter 34 and, in addition, the corrected fuel injection quantity is corrected by the flow rate of the exhaust gas discharged from the engine 10 so as to increase with increasing exhaust gas flow rate.
Next, in block 62d, a correction amount for the temperature feedback correction by the temperature sensor at the inlet of the DPF (the second exhaust gas temperature sensor 56) is calculated. Specifically, the amount of change (increase or decrease) in the manipulated variable (injection quantity) that will make the exhaust gas temperature TEX2 detected by the second exhaust gas temperature sensor 56 equal to a desired temperature, e.g., 600 °C, is calculated in response to the error or deviation between exhaust gas temperature TEX2 and the desired temperature using a PI control term (or PID control term). The calculated change is added to the sum of the basic (post-injection) fuel injection quantity and the corrected fuel injection quantity in block 62e.
Next, in block 62f, the final (post-injection) fuel injection quantity (unburned fuel supply quantity) is determined or calculated in terms of the valve opening time of the injector 22 based on the basic (post-injection) fuel injection quantity, corrected fuel injection quantity and temperature feedback correction amount, and the aforesaid post-injection (unburned fuel supply) is executed based on the calculated final (post-injection) fuel injection quantity.
Thus, the blocks 62c to 62f function as fuel supply executing means for calculating the final supply quantity of the unburned fuel based on the calculated basic supply quantity and corrected supply quantity and for executing supply of the unburned fuel based on the calculated final supply quantity of the unburned fuel to the engine 10 such that the filter (DPF 36) is regenerated.
The injected fuel flows through the exhaust system to the oxidation catalytic converter 34 to give rise to an oxidization reaction (i.e., combustion). The exhaust gas heated by the combustion flows into the DPF 36 located downstream to burn the accumulated particulates captured by the DPF 36. As a result, the DPF 36 is unclogged and regenerated.
This embodiment is thus configured to have a system for treating exhaust gas produced by an internal combustion engine (10) having an oxidation catalytic converter (34) installed in an exhaust system (exhaust manifold 24, exhaust pipe 26) for oxidizing and removing unburned hydrocarbons in the exhaust gas and a filter (DPF 36) installed downstream of the oxidation catalytic converter for capturing particulates entrained by the exhaust gas, characterized by: basic supply quantity calculating means (ECU 62, block 62a) for calculating a basic supply quantity of unburned fuel (basic (post-injection) fuel injection quantity) based on an operating condition of the engine, more specifically based on the engine speed NE and fuel injection quantity Q; corrected supply quantity calculating means (ECU 62, blocks 62b1, 62b2) for calculating a corrected supply quantity of the unburned fuel (corrected fuel injection quantity) to correct the basic supply quantity based on an exhaust gas temperature at a location upstream of the oxidation catalytic converter; and fuel supply executing means (ECU 62, blocks 62c, 62f) for calculating a final supply quantity of the unburned fuel (final (post-injection) fuel injection quantity) based on the calculated basic supply quantity and corrected supply quantity and for executing supply of the unburned fuel based on the calculated final supply quantity of the unburned fuel to the engine such that the filter is generated.
Thus the detected exhaust gas temperature TEX1 is not affected by the combustion in the DPF 36 or the mass of the DPF 36, nor is it affected by the combustion in the oxidation catalytic converter 34 or the mass thereof, so that the fuel supply quantity required for regeneration can be achieved with good accuracy, thereby improving the regeneration efficiency of the DPF 36.
In addition, the system further includes: corrected supply quantity correction value calculating means (ECU 62, blocks 62b3, 62b4) for calculating a correction value of the corrected supply quantity (exhaust gas temperature correction weight) based on a flow rate of the exhaust gas produced by the engine. Therefore, by calculating and injecting the post-injection quantity also taking into account the exhaust gas flow rate which has an effect on the unburned fuel supply quantity (exhaust gas temperature) required for regenerating the DPF 36, it becomes possible to achieve the fuel supply quantity required for regenerating the DPF 36 without excess or deficiency, thereby further enhancing the regeneration efficiency of the DPF 36.
Further, the corrected supply quantity correction value calculating means calculates the correction value such that the correction value increases with increasing flow rate of the exhaust gas, more specifically, with increasing engine speed NE and fuel injection quantity Q. Therefore, when the fuel supply quantity required for regeneration increases (or decreases) with increasing (or decreasing) exhaust gas flow rate, i.e., with increase (or decrease) in the amount of heat needed to heat the DPF 36 to the required temperature, the required heat can be supplied accordingly without excess or deficiency, thereby further enhancing the regeneration efficiency of the DPF 36.
In the foregoing, it is explained that the injection quantity correction factor (supply quantity correction factor) is calculated as an addition value (addition term) and the injection quantity correction factor correction value is calculated as a multiplier coefficient (multiplier term). However, it is instead possible to calculate both as addition terms or both as multiplier terms.
In the foregoing embodiment, the unburned fuel is supplied by conducting post-injection through the injectors 22, but is possible instead to supply the unburned fuel through an exhaust injector provided in the exhaust system.
Although the foregoing explanation is made taking application of the invention to a vehicle engine as an example, the invention can also be applied to an engine for a boat propulsion system such as an outboard motor having a vertically oriented crankshaft.
In an exhaust gas treatment system for an internal combustion engine, a basic (post-injection) fuel injection quantity is calculated at block 62a based on an operating condition of the engine, a corrected fuel injection quantity is calculated at blocks 62b1, 62b2 to correct the basic supply quantity based on an exhaust gas temperature TEX1 at a location upstream of the oxidation catalytic converter, and a final (post-injection) fuel injection quantity is calculated in blocks 62c to 62f based on the calculated quantities and injected into the engine 10. Thus the detected exhaust gas temperature TEX1 is not affected by the combustion in the DPF or the mass thereof, nor is it affected by the combustion in the converter or the mass thereof, so that the fuel supply for regeneration can be achieved with good accuracy, thereby improving the DPF regeneration efficiency.

Claims

A system for treating exhaust gas produced by an internal combustion engine (10) having an oxidation catalytic converter (34) installed in an exhaust system (24, 26) for oxidizing and removing unburned hydrocarbons in the exhaust gas and a filter (36) installed downstream of the oxidation catalytic converter for capturing particulates entrained by the exhaust gas,
characterized by:
basic supply quantity calculating means (62, 62a) for calculating a basic supply quantity of unburned fuel based on an operating condition of the engine;

corrected supply quantity calculating means (62, 62b1, 62b2) for calculating a corrected supply quantity of the unburned fuel to correct the basic supply quantity based on an exhaust gas temperature at a location upstream of the oxidation catalytic converter; and

fuel supply executing means (62, 62c to 62f) for calculating a final supply quantity of the unburned fuel based on the calculated basic supply quantity and corrected supply quantity and for executing supply of the unburned fuel based on the calculated final supply quantity of the unburned fuel to the engine such that the filter is regenerated.
The system according to claim 1, further including:
corrected supply quantity correction value calculating means (62, 62b3, 62b4) for calculating a correction value of the corrected supply quantity based on a flow rate of the exhaust gas produced by the engine.
The system according to claim 2, wherein the corrected supply quantity correction value calculating means calculates the correction value such that the correction value increases with increasing flow rate of the exhaust gas.
A method of treating exhaust gas produced by an internal combustion engine (10) having an oxidation catalytic converter (34) installed in an exhaust system (24, 26) for oxidizing and removing unburned hydrocarbons in the exhaust gas and a filter (36) installed downstream of the oxidation catalytic converter for capturing particulates entrained by the exhaust gas,
characterized by the steps of:
calculating a basic supply quantity of unburned fuel based on an operating condition of the engine (62, 62a);

calculating a corrected supply quantity of the unburned fuel to correct the basic supply quantity based on an exhaust gas temperature at a location upstream of the oxidation catalytic converter(62, 62b1, 62b2); and

calculating a final supply quantity of the unburned fuel based on the calculated basic supply quantity and corrected supply quantity and for executing supply of the unburned fuel based on the calculated final supply quantity of the unburned fuel to the engine such that the filter is regenerated (62, 62c, 62f).
The method according to claim 4, further including the step of:
calculating a correction value of the corrected supply quantity based on a flow rate of the exhaust gas produced by the engine(62, 62b3, 62b4).
The method according to claim 5, wherein the step of corrected supply quantity correction value calculation calculates the correction value such that the correction value increases with increasing flow rate of the exhaust gas.