JP5833864B2 - Exhaust gas treatment method and exhaust gas treatment control system for internal combustion engine - Google Patents

Description

  The present invention relates to an exhaust gas treatment method and an exhaust gas treatment control system for an internal combustion engine, and more particularly to an exhaust gas treatment method and an exhaust gas treatment control system for a diesel engine using a diesel engine as the internal combustion engine.

  Exhaust gas discharged from an internal combustion engine (for example, diesel engine) contains exhaust gas components such as particulate matter (hereinafter also referred to as “PM”) and ash (ASH) made of non-combustible components. If these exhaust gas components are discharged to the atmosphere, it causes air pollution, which is not preferable. In order to remove such exhaust gas components from the exhaust gas, for example, a particulate filter (hereinafter also referred to as “PF”) for collecting the PM is provided in the exhaust passage of the engine.

  This PF includes, for example, a honeycomb-shaped porous substrate, and collects PM on the surface of the porous substrate. However, there is a limit to the amount of PM that can be collected on the porous substrate, and when PM exceeding this amount is deposited on the PF, the PF is clogged and the exhaust resistance increases. This may cause adverse effects such as deterioration of the fuel consumption rate (g / KWh) and PF melting. For this reason, generally, when a certain amount of PM is collected in the PF, as a PF regeneration process, the PF on which the PM is accumulated to some extent is heated to a predetermined temperature (for example, about 550 ° C. to 650 ° C.). By doing so, the PM forced oxidation process which forcibly oxidizes and decomposes PM is performed.

  The PM forced oxidation process for PF regeneration is performed by, for example, fuel injection into an exhaust system of an internal combustion engine. Since this PM forced oxidation process may cause deterioration of the fuel consumption rate or PF melting due to the increase of the processing time, it is desirable that the PM forced oxidation process be performed at an appropriate timing according to the amount of PM deposited in the PF. As an example of a method for performing PM forced oxidation treatment at an appropriate timing, when the exhaust gas pressure on the upstream side and the exhaust gas pressure on the downstream side of PF are measured and the differential pressure (PF differential pressure) exceeds a certain value, PM For example, a method of performing forced oxidation treatment can be given. Since the PF differential pressure has a correlation with the accumulation amount of PM accumulated in the PF, by determining the start timing of the PM forced oxidation process based on the PF differential pressure, an appropriate value corresponding to the PM accumulation amount is obtained. The PM forced oxidation process can be started at the timing.

  However, as described above, the exhaust gas contains ash and the like in addition to PM, and ash is also collected in the PF. Since this ash is composed of an incombustible inorganic component, it is not decomposed by the above-mentioned PM forced oxidation treatment, and continues to accumulate in the PF according to the period of use of the internal combustion engine. Therefore, even if PM is suitably removed by the PM forced oxidation treatment, the exhaust gas pressure on the downstream side decreases with time due to the accumulation of ash. Therefore, if the start timing of the PM forced oxidation process is determined only by the PF differential pressure, the PM forced oxidation process starts before the PM deposition amount reaches an appropriate amount due to the downstream exhaust gas pressure drop due to the ash deposition.

  In relation to this, the cited document 1 discloses an invention related to a PM emission amount estimation device provided with an ash accumulation amount calculation means. In the present invention, the ash accumulation amount is calculated by the ash accumulation amount calculation means. Then, an ash accumulation amount correction coefficient is calculated based on the ash accumulation amount, and the start time of the PM forced oxidation process is corrected based on the correction coefficient. As a result, even when the ash deposition amount in the PF increases, the start time of the PM forced oxidation process can be determined based on the accurate PM deposition amount.

JP 2010-196498 A

  By the way, some conventional PFs carry a PM oxidation catalyst composed of noble metal particles that catalyze PM oxidation and combustion reactions on the surface of a porous substrate. Since the PM oxidation catalyst is present on the surface of the porous substrate, PM can be efficiently oxidized and decomposed from a relatively low temperature range.

However, regardless of whether or not the PM oxidation catalyst is present, the conventional exhaust gas treatment method assumes the state in which the PM oxidation catalyst is not carried and assumes the end time of the PM forced oxidation treatment (in other words, the PM forced oxidation treatment). It has been usual to set the time to continue. However, when the PM oxidation catalyst is exerted in a high oxidation catalyst capacity, the time for the PM forced oxidation treatment tends to be set longer than necessary. In such a situation, an excessive PM forced oxidation process that is not originally required is performed, which may cause deterioration of PF and fuel consumption rate.
Therefore, in a PF with a PM oxidation catalyst, it is originally desirable to set the end time of the PM forced oxidation treatment (PM forced oxidation treatment duration) in consideration of the oxidation catalyst ability of the PM oxidation catalyst. The oxidation catalytic ability of the catalyst depends on the amount of ash deposited in the PF. For this reason, it has been difficult to set the end time (continuation time) of the PM forced oxidation treatment while correctly reflecting the PM oxidation catalyst ability that changes with time according to the accumulation of ash.

  The present invention has been made in view of the above problems, and its purpose is to determine the PM forced oxidation treatment time while appropriately reflecting the oxidation catalyst ability of the PM oxidation catalyst that changes with time according to the amount of ash deposition. An exhaust gas treatment method that can be performed and an exhaust gas treatment control system for appropriately carrying out the method are provided.

In order to achieve the above object, the present invention provides an exhaust gas treatment method having the following configuration.
That is, an exhaust gas treatment method according to the present invention includes a porous base material capable of collecting particulate matter (PM) contained in exhaust gas of an internal combustion engine, and a PM oxidation catalyst supported on at least a part of the base material. Is an exhaust gas treatment method for an internal combustion engine in which an exhaust system is provided with a particulate filter (PF).
The exhaust gas treatment method disclosed herein includes measuring a PF differential pressure obtained by a difference between an upstream exhaust gas pressure and a downstream exhaust gas pressure of a PF during operation of the internal combustion engine, and
Based on the measured PF differential pressure value, the PM deposition amount in the PF is estimated, and when the estimated PM deposition amount exceeds a predetermined threshold, the process of forcibly oxidizing the PM in the PF is started. Include.
In the exhaust gas treatment method disclosed herein, the estimation of the PM deposition amount based on the PF differential pressure value is performed as shown in (A) below.
(A) First, from the PF differential pressure value measured for the estimation, the PF differential pressure value measured at the start of use of the internal combustion engine or the PF measured immediately after the last PM forced oxidation process is completed. Subtract the differential pressure value. As a result, a PF differential pressure value resulting from PM deposition is calculated. Then, the estimation of the PM deposition amount is made by calculating a PF differential pressure value resulting from the calculated PM deposition, and a calibration curve (approximate expression) indicating a correlation between a preset standard PF differential pressure and the PM deposition amount. To be determined.
Further, in the exhaust gas treatment method disclosed herein, (B) the process for determining the end time of the PM forced oxidation treatment includes the following steps (1) to (3). That is,
(1) When the PM forced oxidation process is performed before the PM forced oxidation process, the PF differential pressure value measured immediately after the PM forced oxidation process immediately before the PM forced oxidation process is completed Alternatively, when the PM forced oxidation process is not performed before the PM forced oxidation process, the PF differential pressure value measured at the start of use of the internal combustion engine, the preset standard PF differential pressure, and the standard ash Estimating the ash deposition thickness in the PF based on a calibration curve (approximate equation) showing a correlation with the deposition thickness;
(2) The PM deposited on the ash deposited on the substrate by the estimated ash deposition thickness, the ash deposition thickness on the substrate set in advance, and the PM oxidation catalyst supported on the substrate Determining a PM reduction rate in the estimated ash deposition thickness based on a calibration curve (approximate equation) showing a correlation with a decrease rate of the ash;
(3) Calculate the time required for the PM forced oxidation process from the determined PM reduction rate and the estimated PM accumulation amount, and determine the end time of the PM forced oxidation process;
Moreover, in one preferable aspect of the exhaust gas treatment method disclosed herein, the calibration curve indicating the correlation between the ash deposition thickness and the PM reduction rate is at any temperature condition within a range of 550 to 650 ° C. The PM forced oxidation treatment is performed by heating the inside of the PF to 550 to 650 ° C. As the PM oxidation catalyst, cerium oxide, zirconium oxide, aluminum oxide, or a composite oxide composed of two or three of these is preferably used. For example, as the PM oxidation catalyst, an aggregate of cerium oxide and / or aluminum oxide and a noble metal is preferably used.

In the exhaust gas treatment method disclosed herein, PM deposition is performed based on the PF differential pressure value (PF differential pressure value caused by the PM deposition amount) obtained by subtracting the PF differential pressure caused by the ash deposition amount in the above (A). The amount of PM deposition is estimated by estimating the amount. Then, in step (1) of (B), the ash thickness accumulated in the PF is estimated based on the PF differential pressure resulting from the ash accumulation amount. Then, in step (2), the PM decrease in the estimated ash deposition thickness based on the estimated ash deposition amount and a calibration curve (approximate expression) indicating the correlation between the ash deposition thickness and the PM decrease rate. Determine the speed. In step (3), the PM forced oxidation treatment end timing is determined based on the PM deposition amount estimated in (A) and the PM reduction rate determined in step (2).
According to the exhaust gas treatment method disclosed herein, the PM reduction rate in the PM forced oxidation treatment is determined by reflecting the oxidation catalyst ability of the PM oxidation catalyst that changes with time due to ash deposition. The end time of the PM forced oxidation process (that is, the duration of the PM forced oxidation process) based on the PM reduction rate reflecting the decrease in the oxidation catalyst capacity and the PM deposition amount estimated from the PF differential pressure value caused by the PM deposition amount ) Is determined, the PM forced oxidation treatment time can be appropriately adjusted according to the oxidation catalyst ability of the PM oxidation catalyst. Therefore, according to the exhaust gas treatment method disclosed herein, deterioration of the fuel consumption rate and damage to the PF caused by setting the treatment time of the PM forced oxidation treatment to be longer than necessary can be suitably prevented, and PM Clogging of PF due to insufficient time for forced oxidation treatment can also be suitably prevented.

The present invention also provides a particulate material comprising a porous substrate capable of collecting particulate matter (PM) contained in exhaust gas from an internal combustion engine and a PM oxidation catalyst supported on at least a part of the substrate. A control system for treating exhaust gas of an internal combustion engine in which a filter (PF) is provided in the exhaust system is also provided. The control system is configured to measure a PF differential pressure obtained by a difference between an upstream exhaust gas pressure and a downstream exhaust gas pressure of the PF during operation of the internal combustion engine, and based on the measured PF differential pressure value. A control unit configured to estimate a PM deposition amount in the PF and to start a process of forcibly oxidizing the PM in the PF when the estimated PM deposition amount exceeds a predetermined threshold value.
Here, the control unit (A) estimates the PM accumulation amount from the PF differential pressure value measured to perform the estimation, or the PF differential pressure value measured at the start of use of the internal combustion engine or By subtracting the PF differential pressure value measured immediately after the end of the previous PM forced oxidation treatment, the PF differential pressure value resulting from PM deposition is calculated, and the calculated PF differential pressure value resulting from PM deposition; It is determined based on a calibration curve (approximate expression) indicating a correlation between a preset standard PF differential pressure and the PM deposition amount.
The control unit (B) determines the end time of the PM forced oxidation process according to the following steps:
(1) When the PM forced oxidation process is performed before the PM forced oxidation process, the PF differential pressure value measured immediately after the PM forced oxidation process immediately before the PM forced oxidation process is completed Alternatively, when the PM forced oxidation process is not performed before the PM forced oxidation process, the PF differential pressure value measured at the start of use of the internal combustion engine, the preset standard PF differential pressure, and the standard ash Estimating the ash deposition thickness in the PF based on a calibration curve (approximate equation) showing a correlation with the deposition thickness;
(2) The PM deposited on the ash deposited on the substrate by the estimated ash deposition thickness, the ash deposition thickness on the substrate set in advance, and the PM oxidation catalyst supported on the substrate Determining a PM reduction rate in the estimated ash deposition thickness based on a calibration curve (approximate equation) showing a correlation with a decrease rate of the ash;
(3) Calculate the time required for the PM forced oxidation process from the determined PM reduction rate and the estimated PM accumulation amount, and determine the end time of the PM forced oxidation process;
It is comprised based on.

  The exhaust gas treatment control system disclosed herein includes a control unit that can perform the above-mentioned “(1) Estimation of ash deposition thickness” and “(2) Determination of PM reduction rate”. The control unit can determine the end time of the PM forced oxidation process based on the PM decrease rate determined in (2) and the PM deposition amount estimated in (A). That is, according to the exhaust gas treatment control system including the control unit, the above-described exhaust gas treatment method can be suitably implemented.

  In addition, according to the present invention, it is possible to provide a vehicle including the exhaust gas treatment control system disclosed herein. As described above, the exhaust gas treatment control system can implement the exhaust gas treatment method of appropriately adjusting the treatment time of the PM forced oxidation treatment according to the oxidation catalyst ability of the PM oxidation catalyst, so that the fuel consumption rate of the vehicle Can be improved, and clogging of the PF can be suitably prevented.

The schematic diagram which shows the exhaust gas treatment control system which concerns on one Embodiment of this invention. The figure which showed typically the particulate filter (PF) in the exhaust gas treatment control system which concerns on one Embodiment of this invention. The graph which shows an example of the calibration curve which shows the correlation with a standard PF differential pressure | voltage and PM deposition amount. The graph which shows an example of the calibration curve which shows the correlation with standard PF differential pressure and standard ash deposition thickness. The graph which shows an example of the calibration curve which shows the correlation with ash deposition thickness and PM reduction | decrease rate. The figure which shows an example of the calibration curve (approximation formula) which shows a correlation with the decreasing rate of PM deposited on the ash deposited on the base material. The flowchart which shows an example of control in the control part of the exhaust gas treatment control system which concerns on one Embodiment of this invention.

  Hereinafter, preferred embodiments of the present invention will be described. Note that matters other than matters specifically mentioned in the present specification and necessary for the implementation of the present invention can be grasped as design matters of those skilled in the art based on the prior art in this field. The present invention can be carried out based on the contents disclosed in this specification and common technical knowledge in the field.

<Exhaust gas treatment control system>
Here, first, an exhaust gas treatment control system 100 according to an embodiment of the present invention will be described with reference to FIG. As shown in FIG. 1, the exhaust gas treatment control system 100 includes an internal combustion engine (engine) 1, a control unit (ECU: Engine Control Unit) 30, and an exhaust gas purification unit 40.

A. In the exhaust gas treatment control system 100 having the configuration shown in FIG. 1, the internal combustion engine 1 is mainly composed of a diesel engine (the internal combustion engine 1 includes an accelerator for driving the engine and other operation systems. .) Hereinafter, the configuration of the diesel engine 1 will be briefly described. The diesel engine 1 described below is only an example of the internal combustion engine 1. The exhaust gas treatment control system 100 according to the present invention can use an engine other than a diesel engine (for example, a gasoline engine) as the internal combustion engine 1.

  The internal combustion engine 1 includes a plurality of combustion chambers 2 and a fuel injection valve 3 that injects fuel into each combustion chamber 2. Each combustion chamber 2 communicates with an intake manifold 4 and an exhaust manifold 5. The intake manifold 4 is connected to the outlet of the compressor 7 a of the exhaust turbocharger 7 via the intake duct 6. An inlet of the compressor 7 a is connected to an air cleaner 9 via an intake air amount detector 8. A throttle valve (EGR valve) 10 is disposed in the intake duct 6. Around the intake duct 6, a cooling device (intercooler) 11 for cooling the air flowing through the intake duct 6 is arranged. The exhaust manifold 5 is connected to the inlet of the exhaust turbine 7 b of the exhaust turbocharger 7. The outlet of the exhaust turbine 7b is connected to an exhaust passage (exhaust pipe) 12 through which exhaust gas flows. The exhaust manifold 5 is provided with an exhaust system fuel injection valve 13. As will be described in detail later, the exhaust system fuel injection valve 13 increases the temperature in the PF 80 by injecting fuel F into the exhaust system including the PF 80 when performing the PM forced oxidation process.

  The exhaust manifold 5 and the intake manifold 4 are connected to each other via an exhaust gas recirculation passage (hereinafter referred to as “EGR passage”) 18. An electronically controlled control valve 19 is disposed in the EGR passage 18. An EGR cooling device 20 for cooling the EGR gas flowing in the EGR passage 18 is disposed around the EGR passage 18.

  Each fuel injection valve 3 is connected to a common rail 22 via a fuel supply pipe 21. The common rail 22 is connected to the fuel tank 24 via the fuel pump 23. Here, the fuel pump 23 is an electronically controlled fuel pump with variable discharge amount. However, the configuration of the fuel pump 23 is not particularly limited.

B. Exhaust gas purification unit The exhaust gas purification unit 40 is provided in an exhaust system (here, the exhaust passage 12) communicating with the internal combustion engine 1. In the exhaust gas purification unit 40 having the configuration shown in FIG. 1, a PF 80 is provided on the downstream side of the exhaust passage 12. The exhaust gas purification unit 40 only needs to be provided with the PF 80, and the present invention is not particularly limited with respect to other exhaust gas purification members. For example, an exhaust gas purifying catalyst in which noble metal catalyst particles such as platinum (Pt) and palladium (Pd) are supported on a honeycomb substrate may be provided on the upstream side or downstream side of PF80.

  Here, the particulate filter (PF) 80 will be described with reference to FIG. FIG. 2 is a diagram schematically showing the structure of PF80. The particulate filter 80 collects PM composed of combustible components such as carbon fine particles contained in the exhaust gas and ash composed of incombustible components. When a diesel engine is used as the internal combustion engine 1, a diesel particulate filter (DPF) may be used as the PF.

B-1. The porous base material PF80 has a porous base material 82 formed in a honeycomb structure, and a plurality of flow paths 84 are provided along the direction in which the exhaust gas flows. The plurality of flow paths 84 provided in the PF 80 are sealed either upstream or downstream in the direction in which the exhaust gas flows. The porous substrate 82 is preferably made of a heat resistant material having a porous structure. Examples of such a heat-resistant material include cordierite, silicon carbide (silicon carbide: SiC), aluminum titanate, silicon nitride, heat-resistant metal such as stainless steel, and alloys thereof.
The exhaust gas supplied to the PF 80 first flows into the flow path 84 whose downstream side is sealed. Since the downstream side of the flow path 84 is sealed, it passes through the porous base material 82, enters the flow path 84 with the upstream side sealed, and from the downstream side of the flow path 84 with the upstream side sealed. Discharged. PM and ash contained in the exhaust gas are captured by the porous substrate 82 when the exhaust gas passes through the porous substrate 82.

B-2. PM oxidation catalyst A PM oxidation catalyst is supported on at least a part of the porous substrate 82 of the PF 80. The PM oxidation catalyst is composed of metal catalyst particles having an oxidation catalyst ability for an oxidation reaction of PM trapped by the porous substrate 82. As such metal catalyst particles, for example, noble metal particles such as silver (Ag), platinum (Pt), palladium (Pd), rhodium (Rh), and composite particles containing the noble metal particles can be preferably used. Since the PM oxidation catalyst composed of these metal catalyst particles is supported on the porous base material 82, the oxidation and decomposition of the PM trapped on the porous base material 82 becomes easy. Further, the PM oxidation catalyst is more preferably configured by supporting the catalyst metal particles on a carrier made of a metal oxide. As the PM oxidation catalyst, cerium oxide, zirconium oxide, aluminum oxide, or a composite oxide composed of two or three of these is preferably used. For example, as the PM oxidation catalyst, an aggregate of cerium oxide and / or aluminum oxide and a noble metal is preferably used. Since such a PM oxidation catalyst has a higher oxidation catalyst ability than a PM oxidation catalyst composed only of the above-described metal catalyst particles, it is easier to oxidize and decompose PM.

C. Differential pressure measuring means The exhaust gas treatment control system disclosed herein measures the exhaust gas pressure on the upstream side and the exhaust gas pressure on the downstream side of the PF during the operation of the internal combustion engine, and measures the PF differential pressure value obtained from the difference. Means (differential pressure measuring means). In the exhaust gas treatment control system having the configuration shown in FIG. 1, a differential pressure sensor 50 is provided as the differential pressure measuring means. The differential pressure sensor 50 includes a pair of pressure sensors 52 and 54 and is electrically connected to a control unit 30 described later. One of the pair of pressure sensors 52 is attached to the upstream side of the PF 80, and the other pressure sensor 54 is attached to the downstream side of the PF 80. The pressure sensors 52 and 54 measure the exhaust gas pressure upstream and downstream of the PF 80, convert the exhaust gas pressure into a signal, and send the signal to the differential pressure sensor 50. The differential pressure sensor 50 measures the PF differential pressure obtained from the difference between the upstream exhaust gas pressure and the downstream exhaust gas pressure, and sends the PF differential pressure to the control unit 30 described later.
The differential pressure measuring means only needs to be able to measure the differential pressure of the PF, and the configuration thereof does not limit the present invention. For example, in addition to the differential pressure sensor 50 as described above, a pair of pressure sensors May be directly connected to the control unit. In this case, the pressure sensor measures the exhaust gas pressure on the upstream side and the exhaust gas pressure on the downstream side of the PF, and transmits the electrical signal to the control unit. The control unit can determine the PF differential pressure from the difference between the upstream exhaust gas pressure and the downstream exhaust gas pressure.

D. Control unit (ECU)
The control unit (ECU) 30 is mainly composed of a digital computer, and functions as a control device in operation of the exhaust gas treatment control system 100. The control unit 30 includes, for example, a ROM that is a read-only storage device, a RAM that is a readable / writable storage device, and a CPU that performs arbitrary calculations and determinations. Further, the control unit 30 is provided with an input port, and is electrically connected to sensors (for example, temperature sensors 15a and 15b and an intake air amount sensor 8) installed in each part of the internal combustion engine 1 and the exhaust gas purification unit 40. Connected. As a result, information detected by a sensor or the like is transmitted to the ROM, RAM, and CPU as an electrical signal through the input port. The control unit 30 is also provided with an output port. The control unit 30 is connected to the internal combustion engine 1 and the throttle valve (EGR valve) 10 through the output port, and controls the operation of each member by transmitting a control signal to these members. Yes.

In addition, the control unit of the exhaust gas treatment control system disclosed herein estimates the PM accumulation amount in the PF based on the measured PF differential pressure value. Then, the PM forced oxidation process is started when the estimated PM deposition amount exceeds a predetermined threshold. This PM forced oxidation treatment heats the PF to such an extent that the PM deposited in the PF can be suitably oxidized, and the specific mode thereof does not limit the present invention.
For example, in the exhaust gas treatment control system 100 configured as shown in FIG. 1, the control unit 30 is connected to the differential pressure sensor 50 via an input port, and is connected to the exhaust system fuel injection valve 13 via an output port. ing. In the exhaust gas treatment control system 100, the PF differential pressure value measured by the differential pressure sensor 50 is transmitted to the control unit 30. The control unit 30 estimates the PM accumulation amount in the PF based on the PF differential pressure value from the differential pressure sensor 50 (details will be described later). When the estimated PM accumulation amount exceeds a predetermined threshold, the control unit 30 creates a fuel injection signal and transmits it to the exhaust system fuel injection valve 13. The exhaust system fuel injection valve 13 that has received the fuel injection signal injects the fuel F into the exhaust manifold 5. As a result, the exhaust gas temperature supplied to the exhaust system rises and the PM forced oxidation process is started.

  Here, in order to more appropriately determine the start time and end time of the PM forced oxidation process, the control unit 30 sets “(A) PM deposition amount estimation” and “(B) PM forced oxidation process end time. The exhaust gas treatment method including “determination” is implemented. Hereinafter, the exhaust gas treatment method performed by the control unit 30 will be described.

(A) Estimation of PM deposition amount Here, the control unit 30 estimates the PM deposition amount in the PF 80 based on the PF differential pressure value resulting from the amount of PM deposited on the PF 80 (PM deposition amount). Specifically, the PF differential pressure value (P _n-1 ) measured immediately after the end of the previous PM forced oxidation process is subtracted from the PF differential pressure value (P _n ) measured to estimate the PM deposition amount. . Since almost all PM is removed in the PF 80 immediately after the end of the PM forced oxidation process, the PF differential pressure value (P _n-1 ) immediately after the end of the PM forced oxidation process is caused by the amount of ash deposition in the PF 80. . That is, the PM deposition is obtained by subtracting the PF differential pressure value (P _n-1 ) immediately after the end of the previous PM forced oxidation process from the PF differential pressure value (P _n ) measured to estimate the PM deposition amount. The PF differential pressure value (P _PM ) resulting from the quantity can be obtained. When the immediately preceding PM forced oxidation process does not exist (when the PM forced oxidation process is performed for the first time), the use of the internal combustion engine 1 is started from the PF differential pressure value (P _n ) measured for estimating the PM deposition amount. By subtracting the PF differential pressure value (P ₀ ) sometimes measured, the PF differential pressure value (P _PM ) resulting from the PM deposition amount can be calculated.

The control unit 30 is preset with a calibration curve (approximate equation) indicating the correlation between the standard PF differential pressure and the PM deposition amount. The calibration curve (approximate equation) and the PM deposition amount are caused by the calibration curve. Based on the PF differential pressure value (P _PM ), the PM deposition amount in the PF 80 can be estimated.
This “calibration curve (approximate expression) indicating the correlation between the standard PF differential pressure and the PM deposition amount” may be determined in advance by a preliminary test or the like. For example, after preparing a plurality of PFs having different PM deposition amounts and calculating the PF differential pressure value (P _PM ) resulting from the PM deposition amount in each PF, the PF is decomposed to obtain the actual measured value of the PM deposition amount. taking measurement. Then, by examining the correlation between the calculated PF differential pressure value (P _PM ) and the measured value of the PM accumulation amount, a “calibration curve (approximate expression) indicating the correlation between the standard PF differential pressure and the PM accumulation amount” is obtained. can get. An example of the “calibration curve showing the correlation between the standard PF differential pressure and the PM deposition amount” thus obtained is shown in FIG. The calibration curve shown in FIG. 3 shows a positive correlation between the PF differential pressure and the PM deposition amount. If the PF differential pressure value (P _PM ) resulting from the PM deposition amount increases, the PM deposition in the PF 80 is performed. The amount also increases.

As described above, the PM deposition amount estimated on the basis of the PF differential pressure value (P _PM ) resulting from the PM deposition amount and a preset calibration curve is an accurate representation of the actual PM deposition amount in the PF 80. reflect. Therefore, by determining the start time of the PM forced oxidation process based on the estimated PM deposition amount, the PM forced oxidation process can be started at an appropriate timing.

(B) Determination of end time of PM forced oxidation process Next, determination of the end time of the PM forced oxidation process by the control unit 30 will be described. In order to determine the end time of the PM forced oxidation process, the control unit 30 performs “(B-2) PM decrease rate determination” through the following “(B-1) Estimation of ash deposition thickness”. . Based on the PM reduction rate obtained in “(B-2) Determination of PM reduction rate” and the PM deposition amount obtained in “(A) Estimation of PM deposition amount”, “(B-3 ) Determine the end time. In addition, “(B-1) Estimation of ash deposition thickness” and “(B-2) Determination of PM reduction rate” are performed before “(A) Estimation of PM deposition amount” is performed. May be.

(B-1) Estimation of Ash Deposit Thickness Here, the control unit 30 estimates the ash deposit thickness in the PF 80. Specifically, when the PM forced oxidation process is performed before the current PM forced oxidation process, the PM forced oxidation process immediately before the PM forced oxidation process (the previous PM forced oxidation process) ), The PF differential pressure value (P _n-1 ) measured immediately after the measurement is finished is measured. Then, the ash in the PF 80 is based on the measured PF differential pressure value (P _n-1 ) and a calibration curve (approximate expression) indicating a correlation between a preset standard PF differential pressure and a standard ash deposition thickness. Estimate the deposition thickness. As described above, the PF differential pressure value (P _n-1 ) immediately after the end of the PM forced oxidation process is a PF differential pressure value (P _ASH ) due to the ash deposition thickness in the PF 80, and thus is set in advance. By comparing the calibration curve (approximate equation) with the PF differential pressure value (P _n-1 ) (PF differential pressure value (P _ASH ) resulting from the ash deposition thickness) immediately after the end of the PM forced oxidation treatment, The ash deposition thickness of can be accurately estimated. In addition, when the PM forced oxidation process is not performed before the current PM forced oxidation process (when the PM forced oxidation process is performed for the first time), the control unit 30 measures the PF measured at the start of use of the internal combustion engine. The differential pressure value (P ₀ ) is used as the PF differential pressure value (P _ASH ) resulting from the ash deposition thickness, and the calibration curve is compared.

The above-mentioned “calibration curve indicating the correlation between the standard PF differential pressure and the standard ash deposition thickness (approximate equation)” can be determined by various preliminary tests. For example, a plurality of PFs in which only ash is deposited (for example, after PM forced oxidation treatment) are prepared, and a PF differential pressure value (P _ASH ) resulting from the ash deposition thickness of each PF is measured. Then, by examining the correlation between the PF differential pressure value (P _ASH ) resulting from the ash deposition thickness and the ash deposition amount, a “calibration curve indicating the correlation between the standard PF differential pressure and the standard ash deposition thickness” is obtained. Can be obtained. An example of the “calibration curve showing the correlation between the standard PF differential pressure and the standard ash deposition thickness” thus obtained is shown in FIG. In the calibration curve shown in FIG. 4, the PF differential pressure value (P _ASH ) caused by the ash deposition thickness and the ash deposition thickness show a positive correlation, and the PF differential pressure value caused by the ash deposition thickness. As (P _ASH ) increases, the ash deposition thickness increases.

(B-2) Determination of PM Decrease Rate Next, the control unit 30 determines the ash deposition thickness obtained in the above “(B-1) Estimation of ash deposition thickness” and a preset base material. PM reduction rate based on comparison of calibration curve (approximate equation) showing correlation between ash deposition thickness and reduction rate of PM deposited on ash deposited on substrate by PM oxidation catalyst supported on substrate To decide. The PM reduction rate indicates a rate at which PM deposited in the PF 80 (deposited on the ash deposited on the base material) decreases during the PM forced oxidation process. This PM decrease rate changes reflecting the oxidation catalyst ability of the PM oxidation catalyst supported on the porous substrate 82 of PF80. Specifically, when the ash is not deposited in the PF 80, the surface of the PM oxidation catalyst is easy to come into contact with the PM, so that the high oxidation catalyst ability is exhibited and the PM reduction rate is increased. On the other hand, when the ash deposition thickness in the PF 80 is increased, the surface of the PM oxidation catalyst is covered with ash, so that the oxidation catalyst ability of the PM oxidation catalyst is reduced and the PM reduction rate is reduced. In the control unit 30, this “calibration curve (approximate expression) indicating the correlation between the ash deposition thickness and the PM decrease rate” is set in advance.

  The above “calibration curve (approximate expression) indicating correlation between ash deposition thickness and PM reduction rate” can be obtained by various preliminary tests. For example, a plurality of PFs having different ash deposition amounts are prepared, and PM is deposited further on the ash deposited on the PF substrate. Then, the PM deposition thickness (PM reduction rate) reduced by performing the PM forced oxidation process at a predetermined temperature for a predetermined time (for example, 1 minute) is measured for these PFs. Then, by examining the correlation between the ash deposition thickness and the PM reduction rate, a calibration curve (approximate expression) for determining the PM reduction rate can be obtained. An example of a calibration curve for determining the PM reduction rate obtained in this way is shown in FIG. The calibration curve shown in FIG. 5 shows a negative correlation between the PM decrease rate and the ash deposition thickness. According to this calibration curve, the PM reduction rate decreases as the ash deposition thickness increases. This is because the surface of the PM oxidation catalyst is covered with ash, and the oxidation catalyst ability is reduced. Further, the PM reduction rate does not decrease when the ash deposition thickness exceeds a certain value. This is because when the ash deposition thickness on the PM oxidation catalyst exceeds a certain value, the oxidation catalyst function by the PM oxidation catalyst does not reach the PM deposited on the ash at all, and the PM reduction rate causes the PM oxidation due to the oxidation ability of the ash. This is because it converges to speed.

  Further, the PM reduction rate varies depending not only on the oxidation catalyst ability of the PM oxidation catalyst but also on the heating temperature in the PM forced oxidation treatment. Therefore, the “calibration curve indicating the correlation between the ash deposition thickness and the PM reduction rate” is preferably created based on the PM reduction rate under the same temperature condition as the heating temperature in the PM forced oxidation treatment. For example, when the PM forced oxidation treatment is performed by heating the inside of the PF to 550 to 650 ° C., the temperature condition of the “calibration curve indicating the correlation between the ash deposition thickness and the PM decrease rate” is 550 to 650 ° C. It is good to be created on the basis of any temperature condition within the range. Thereby, the PM reduction rate in the PM forced oxidation process can be estimated more accurately.

  Further, as shown in FIG. 6, a correlation consisting of three parameters obtained by adding “heating temperature” in addition to “PM oxidation rate” and “ash deposition thickness” is examined, and a plurality of calibrations satisfying the correlation are obtained. More preferably, the line is preset in the control unit 30. FIG. 6 is a three-dimensional graph in which “ash deposition thickness (μm)” is set on the x-axis, “PM reduction rate (μm / min)” is set on the y-axis, and “heating temperature (° C.)” is set on the z-axis. In this case, the control unit 30 is preset with a plurality of calibration curves constituting the shaded portion in FIG. At this time, the control unit 30 employs an appropriate calibration curve from among a plurality of calibration curves based on the temperature information of the PF 80 obtained from the temperature sensors 15a and 15b attached to the PF 80. A more accurate PM reduction rate can be determined based on a comparison between the calibration curve adopted in consideration of the temperature information of the PF 80 and the ash deposition thickness.

  Further, the “PM reduction rate (μm / min)” can be influenced by the oxygen concentration of the exhaust gas. For this reason, a correlation consisting of three parameters including “PM oxidation rate” and “ash deposition thickness” plus “oxygen concentration of exhaust gas” is examined, and a plurality of calibration curves satisfying the correlation are included in the control unit. 30 may be set in advance. In this case, a sensor capable of detecting the oxygen concentration is provided in the exhaust system, and an appropriate calibration curve is adopted based on the detected oxygen concentration. A more accurate PM reduction rate can be determined based on a comparison between the calibration curve adopted in consideration of the oxygen concentration of the exhaust gas and the ash deposition thickness.

(B-3) Determination of End Time Then, the control unit 30 estimates the PM decrease rate determined in the above “(B-2) Determination of PM decrease rate” and “(A) Estimation of PM deposition amount”. The end time of the PM forced oxidation process is calculated from the amount of PM deposited. Specifically, by appropriately dividing the PM deposition amount estimated from the PF differential pressure value (P _PM ) caused by the PM deposition amount by the PM decrease rate reflecting the current oxidation catalyst ability, the PM is appropriately adjusted from the PF 80. The processing time that can be removed can be calculated. Then, the end time of the PM forced oxidation process is determined based on the appropriate processing time. At this time, the end time of the PM forced oxidation process can be corrected with parameters other than the “PM reduction rate” and the “PM deposition amount”. Parameters for correcting the end time include, for example, temperature information and PF differential pressure value of PF 80 measured during the PM forced oxidation process, the amount of fuel actually injected into the exhaust system, oxygen concentration of exhaust gas, exhaust gas Examples include flow rate.

  In the exhaust gas treatment method disclosed herein, (A) PM that can be removed by PM forced oxidation treatment by estimating the PM deposition amount based on the PF differential pressure value obtained by subtracting the PF differential pressure due to the ash deposition amount. Estimate the amount of deposits. Next, (B-1) the ash deposition thickness is estimated, and (B-2) the PM reduction rate is determined based on the estimated ash deposition thickness and a preset calibration curve (approximate equation). Then, based on the PM decrease rate obtained in (B-2) and the PM accumulation amount obtained in (A), (B-3) the end time is determined. According to the exhaust gas treatment method disclosed herein, the PM reduction rate is determined in consideration of the oxidation catalyst ability of the PM oxidation catalyst that decreases due to ash deposition, and the processing time of the PM forced oxidation treatment is based on the PM reduction rate. Is determined. Therefore, it is possible to suitably prevent deterioration of the fuel consumption rate (g / KWh) and damage to the PF due to setting the processing time of the PM forced oxidation process to be longer than necessary. Moreover, clogging of PF due to insufficient processing time of the PM forced oxidation treatment can be suitably prevented.

The exhaust gas control system 100 and the exhaust gas treatment method disclosed herein have been described above. Next, an example of the exhaust gas treatment method will be described with reference to the flowchart shown in FIG. The control shown in FIG. 7 includes “a. Initial correction (S1)”, “b. Initial IG-ON (S2)”, “c. Initial differential pressure value (P ₀ ) measurement (S3)”, “d. "IG-ON (S4)", "e. Engine operation (S5)", "f. Total oil consumption estimation (S6)", "g. Ash accumulation thickness estimation 1 (S7)", "Ash “Estimation of PF differential pressure estimated value (P ₄ ) due to accumulated thickness (S 7 ′)”, “h. Determination of PM decrease rate (S 8)”, “Current PF differential pressure value (P ₂ ) measurement (S 8) ')', 'I. PM deposition amount estimation (S9)', 'j. PM forced oxidation treatment start determination (S10)', 'k.PM forced oxidation treatment start (S11)', 'l.PM “Estimation of Completion Time of Forced Oxidation Process (S12)”, “M.PM Regeneration Completion Determination (S13)”, “N.PM Forced Oxidation Process Time Determination (S14) "," O.PF pressure value _{(P 1)} measured (S15) "," p. Ash deposition thickness estimated 2 (S16) "," q.IG-OFF (S17) "," the r.PF state The step of “memory (S18)” is included. Hereinafter, each step will be described.

a. Initial correction (S1)
In the flowchart shown in FIG. 7, first, the ash deposition thickness in the PF 80 and the PM deposition amount are corrected to zero (S1). This makes it possible to accurately measure the ash deposition thickness and PM deposition amount described below.

b. First time IG-ON (S2)
Next, the control unit 30 starts the exhaust gas treatment control in response to the first ignition (IG) being turned on.

c. Initial differential pressure (P ₀ ) measurement (S3)
The control unit 30 measures the initial differential pressure value (P ₀ ) of the PF 80 after the start of control. The initial differential pressure value (P ₀ ) reflects the PF differential pressure (PF differential pressure derived from the structure of the porous substrate 82) in a state where neither PM nor ash is deposited on the PF 80.

d. IG-ON determination (S4)
Then, when the “measurement of the initial differential pressure value (P ₀ )” is completed, it is determined whether or not the ignition is continued. When the determination result here is NO, the control unit 30 continues monitoring until the ignition is turned on.

e. Investigation of engine operating condition (S5)
When the determination result of “IG-ON determination (S4)” is YES, the control unit 30 investigates the operating state of the operating engine (internal combustion engine) (S5). Here, the investigation items by the control unit 30 include, for example, the engine speed, the accelerator opening, the amount of fuel supplied to the engine, the exhaust gas temperature, the traveling speed of the vehicle, the oil temperature, the water temperature, and the like. These parameters can be used as correction values in the following control.

f. Estimation of total oil consumption (S6)
Next, the control unit 30 estimates the total consumption of oil supplied to the internal combustion engine 1 based on the operating state of the internal combustion engine (engine) 1 (S6). For example, assuming that the time for performing the control disclosed here once is one cycle, the internal combustion engine in the one cycle is based on the engine speed, the traveling speed of the vehicle, the amount of fuel supplied to the engine, and the like. Estimate the amount of oil that will be supplied to the (engine) 1. Generally, the ash that accumulates on the PF 80 is generated by combustion of engine oil. Therefore, the “estimated value of total oil consumption” obtained here can be used to correct the value of the ash deposition thickness in “Ash deposition thickness estimation 1 (S7)” described later.

g. Ash deposition thickness estimate 1 (S7)
Next, the control unit 30 performs estimation of the ash thickness deposited on the first PF 80 (S7). Specifically, the "c. Measurement of the initial pressure value _{(P 0)} (S3)" and the initial differential pressure of PF80 obtained in _{(P 0),} and the standard PF differential pressure that is set in advance The ash deposition thickness in the PF 80 is estimated based on a calibration curve showing a correlation with the standard ash deposition thickness. Further, immediately after step S7, the control unit 30 estimates a PF differential pressure value (P ₄ ) due to ash estimated from the ash deposition thickness based on the estimated ash deposition thickness. To implement.

h. Determination of PM decrease rate (S8)
Next, in step S8, the control unit 30 calculates the ash deposition thickness obtained in the “first ash deposition thickness estimation (S7)” and a calibration curve indicating the correlation between the ash deposition thickness and the PM decrease rate. Based on (approximate expression), the PM reduction rate when the current PF 80 is subjected to PM forced oxidation is determined. Further, immediately after Step S8, the control unit 30 performs Step S8 ′ for measuring the PF differential pressure value (P ₂ ) in the current PF 80.

i. Estimation of PM deposition amount (S9)
Next, the control unit 30 estimates the PM accumulation amount in the PF 80 (S9). Here, the PF differential pressure value (P ₄ ) caused by ash estimated in step S7 ′ is subtracted from the current PF differential pressure value (P ₂ ) measured in step S8 ′. As a result, the PF differential pressure value (P _PM ) due to the PM accumulated in the PF 80 is calculated. Then, the PM deposition amount in the PF 80 is estimated based on the “calibration curve (approximate expression) indicating the correlation between the standard PF differential pressure and the PM deposition amount” and the PF differential pressure value (P _PM ) caused by the PM. . In step S9, the initial differential pressure obtained in step S3 instead of the current PF differential pressure value (P ₂ ) when step S13 (described later) is not passed (when the initial control is performed). When the value (P ₀ ) is adopted (that is, P ₂ = P ₀ ) and control other than P ₂ = P ₀ is performed, the above-described processing is performed.

j. PM forced oxidation start time determination (S10)
The control unit 30 determines the start time of the PM forced oxidation process based on the PM deposition amount in the PF 80 estimated in the “PM deposition amount estimation (S9)” (S10). Specifically, a threshold value for the PM accumulation amount is preset in the control unit 30, and it is determined whether or not the estimated PM accumulation amount exceeds the threshold value. If the determination result here is NO, the process returns to step S5 and the investigation of the engine operating state is resumed.

k. Start of PM forced oxidation treatment (S11)
When the “PM forced oxidation process start determination (S10)” is YES, the control unit 30 starts the PM forced oxidation process (S11). In the case of the exhaust gas treatment system 100 having the configuration shown in FIG. 1, first, the control unit 30 creates a fuel injection signal and transmits it to the exhaust system fuel injection valve 13. Thus, the exhaust system fuel injection valve 13 injects fuel into the exhaust system (here, in the exhaust manifold 5). The injected fuel is burned in the exhaust system, and the temperature of the exhaust gas is raised to a temperature at which PM is decomposed by oxidation (for example, 500 ° C. to 700 ° C.).

l. Estimating the end time of PM forced oxidation treatment (S12)
Here, with the start of the PM forced oxidation process, the control unit 30 obtains the PM reduction rate obtained in the “determination of PM reduction rate (S8)” and “PM deposition amount estimation (S9)”. Based on the amount of accumulated PM, the end time of the PM forced oxidation process is estimated (S12). Specifically, the predicted value of the time until the PM deposited on the PF 80 is suitably removed is calculated by dividing the PM deposition amount by the PM reduction rate. The control unit 30 determines the end time of the PM forced oxidation process based on the predicted value.

m. PM regeneration completion determination (S13)
While the PM forced oxidation process is being performed, the control unit 30 continues to compare the current PF differential pressure value with the reference value set in the control unit 30. At this time, the current PF differential pressure value is obtained by adding the ash-induced PF differential pressure value (P ₄ ) estimated in step S7 ′ and the initial differential pressure value (P ₀ ) measured in step S3 (P _3). ) (Or lower than a preset allowable value), it is determined that the PM deposited on the PF 80 has been appropriately removed (YES), the PM forced oxidation process is terminated, and the PF 80 PF Proceed to the differential pressure (P ₁ ) measurement (S15).

n. PM forced oxidation treatment time elapsed determination (S14)
On the other hand, even when the PM removal completion determination (S13) is NO, when the end time determined in the “determination of the end time of the PM forced oxidation process (S12)” elapses (YES), the control unit 30 causes the PM to The forced oxidation process is terminated. The PM forced oxidation process is continued while the determination results of “PM removal completion determination (S13)” and “PM forced oxidation process time elapse determination (S14)” are NO.

o. PF differential pressure value (P ₁ ) measurement immediately after forced oxidation treatment (S15)
When the PM forced oxidation process ends, the control unit 30 measures the PF differential pressure value (P ₁ ) of the PF 80 immediately after the PM forced oxidation process ends. The PF differential pressure value (P ₁ ) of the PF 80 immediately after the end of the PM forced oxidation treatment reflects the ash deposition thickness deposited on the porous base material 82, and the “q. This is used for “estimation of the thickness” and “i. PM deposition amount estimation (S9)” in the next control.

p. Ash deposition thickness estimate 2 (S16)
Next, the control unit 30 estimates the ash deposition thickness after the PM forced oxidation process based on the PF differential pressure (P ₂ ) of the PF 80 immediately after the end of the PM forced oxidation process (S16). Here, in the PF 80 based on the PF differential pressure value (P ₁ ) of the PF 80 immediately after the end of the PM forced oxidation process, and the calibration curve used in the “ash deposition thickness estimation 1 (S7)” and the same type of calibration curve. Estimate the ash deposition thickness.

q. IG-OFF (S17)
Then, the control unit 30 determines whether or not the ignition is turned off. If the determination result is NO, the process returns to the “e. Investigation of engine operating state (S5)” and the control is repeated.

r. Storing PF status (S18)
On the other hand, when the “IG-OFF (S17)” is YES, the control unit 30 stores the PF state measured after the PM forced oxidation process, and then ends the control. The information stored at this time includes, for example, the PF differential pressure value (P ₁ ) obtained in step S15 and the ash deposition thickness obtained in step S16. In addition, the current PF differential pressure value is measured, and the current PM deposition amount is calculated by subtracting the PF differential pressure value (P ₁ ) obtained in step S15 from the current PF differential pressure value. The amount of accumulated PM may be stored.

  According to the exhaust gas treatment method and the exhaust gas treatment system disclosed here, the treatment time of the PM forced oxidation treatment is determined in consideration of the oxidation catalyst ability of the PM oxidation catalyst that is reduced by the accumulation of ash. Therefore, it is possible to suitably prevent deterioration of the fuel consumption rate (g / KWh) and damage to the PF due to setting the processing time of the PM forced oxidation process to be longer than necessary. Moreover, clogging of PF due to insufficient processing time of the PM forced oxidation treatment can be suitably prevented. For this reason, since clogging of PF can be prevented at lower cost, the fuel consumption of the vehicle can be improved more suitably.

1 Internal combustion engine
2 Combustion chamber 3 Fuel injection valve 4 Intake manifold 5 Exhaust manifold 6 Intake duct 7 Exhaust turbocharger 7a Compressor 8 Intake air amount detector (intake air amount sensor)
9 Air cleaner 10 Throttle valve (EGR valve)
11 Cooling device (intercooler)
12 Exhaust passage (exhaust pipe)
13 Exhaust fuel injection valves 15a, 15b Temperature sensor 18, exhaust gas recirculation passage "EGR passage"
20 EGR Cooling Device 21 Fuel Supply Pipe 22 Common Rail 23 Fuel Pump 24 Fuel Tank 30 Control Unit (ECU: Engine Control Unit)
40 Exhaust Gas Purification Unit 50 Differential Pressure Sensor 52 Upstream Pressure Sensor 54 Downstream Pressure Sensor 80 Particulate Filter (PF)
82 porous substrate 84 flow path 100 exhaust gas treatment control system

Claims (6)

A particulate filter (PF) including a porous base material capable of collecting particulate matter (PM) contained in exhaust gas of an internal combustion engine and a PM oxidation catalyst supported on at least a part of the base material is exhausted. An exhaust gas treatment method for an internal combustion engine provided in a system,
Measuring a PF differential pressure value determined by a difference between an upstream exhaust gas pressure and a downstream exhaust gas pressure of the PF during operation of the internal combustion engine; and
Estimating a PM deposition amount in the PF based on the measured PF differential pressure value, and starting a process for forcibly oxidizing the PM in the PF when the estimated PM deposition amount exceeds a predetermined threshold;
Where
(A) The estimation of the PM deposition amount is as follows:
The PF differential pressure value measured at the start of use of the internal combustion engine or the PF differential pressure value measured immediately after the end of the previous PM forced oxidation process is subtracted from the PF differential pressure value measured for the estimation. Thus, a PF differential pressure value resulting from PM deposition is calculated, and a calibration indicating a correlation between the calculated PF differential pressure value resulting from PM deposition and a preset standard PF differential pressure and PM deposition amount. Line (approximate equation) and
(B) The determination of the end time of the PM forced oxidation treatment is performed by the following steps:
(1) When the PM forced oxidation process is performed before the PM forced oxidation process, the PF differential pressure value measured immediately after the PM forced oxidation process immediately before the PM forced oxidation process is completed Alternatively, when the PM forced oxidation process is not performed before the PM forced oxidation process, the PF differential pressure value measured at the start of use of the internal combustion engine, the preset standard PF differential pressure and the standard ash Estimating the ash deposition thickness in the PF based on a calibration curve (approximate equation) showing a correlation with the deposition thickness;
(2) The PM deposited on the ash deposited on the substrate by the estimated ash deposition thickness, the ash deposition thickness on the substrate set in advance, and the PM oxidation catalyst supported on the substrate Determining a PM reduction rate in the estimated ash deposition thickness based on a calibration curve (approximate equation) showing a correlation with a decrease rate of the ash;
(3) A time required for the PM forced oxidation process is calculated from the determined PM decrease rate and the estimated PM accumulation amount, and an end time of the PM forced oxidation process is determined;
An exhaust gas treatment method comprising:   The calibration curve indicating the correlation between the ash deposition thickness and the PM decrease rate is created based on the PM decrease rate under any temperature condition in the range of 550 to 650 ° C., and the PM forced oxidation The exhaust gas treatment method according to claim 1, wherein the treatment is performed by heating the inside of the PF to 550 to 650 ° C.   The exhaust gas treatment method according to claim 1 or 2, wherein the PM oxidation catalyst is a cerium oxide, zirconium oxide, aluminum oxide, or a composite oxide comprising two or three of these, with a noble metal supported thereon. A particulate filter (PF) including a porous base material capable of collecting particulate matter (PM) contained in exhaust gas of an internal combustion engine and a PM oxidation catalyst supported on at least a part of the base material is exhausted. A control system for treating exhaust gas of an internal combustion engine provided in the system,
Means for measuring a PF differential pressure determined by a difference between an upstream exhaust gas pressure and a downstream exhaust gas pressure of the PF during operation of the internal combustion engine;
Based on the measured PF differential pressure value, a PM deposition amount in the PF is estimated, and when the estimated PM deposition amount exceeds a predetermined threshold, a process for forcibly oxidizing the PM in the PF is started. A configured control unit; and
Where the control unit comprises:
(A) Estimating the amount of accumulated PM.
The PF differential pressure value measured at the start of use of the internal combustion engine or the PF differential pressure value measured immediately after the end of the previous PM forced oxidation process is subtracted from the PF differential pressure value measured for the estimation. Thus, a PF differential pressure value resulting from PM deposition is calculated, and a calibration indicating a correlation between the calculated PF differential pressure value resulting from PM deposition and a preset standard PF differential pressure and PM deposition amount. Based on the line (approximation),
(B) Determining the end time of the PM forced oxidation treatment, the following steps:
(1) When the PM forced oxidation process is performed before the PM forced oxidation process, the PF differential pressure value measured immediately after the PM forced oxidation process immediately before the PM forced oxidation process is completed Alternatively, when the PM forced oxidation process is not performed before the PM forced oxidation process, the PF differential pressure value measured at the start of use of the internal combustion engine, the preset standard PF differential pressure and the standard ash Estimating the ash deposition thickness in the PF based on a calibration curve (approximate equation) showing a correlation with the deposition thickness;
(2) The PM deposited on the ash deposited on the substrate by the estimated ash deposition thickness, the ash deposition thickness on the substrate set in advance, and the PM oxidation catalyst supported on the substrate Determining a PM reduction rate in the estimated ash deposition thickness based on a calibration curve (approximate equation) showing a correlation with a decrease rate of the ash;
(3) A time required for the PM forced oxidation process is calculated from the determined PM decrease rate and the estimated PM accumulation amount, and an end time of the PM forced oxidation process is determined;
An exhaust gas treatment control system, characterized in that it is configured based on   The calibration curve indicating the correlation between the ash deposition thickness and the PM decrease rate is created based on the PM decrease rate under any temperature condition in the range of 550 to 650 ° C., and the PM forced oxidation The exhaust gas treatment control system according to claim 4, wherein the treatment includes heating the inside of the PF to 550 to 650 ° C. 6. The exhaust gas treatment control system according to claim 4, wherein the PM oxidation catalyst is a cerium oxide, zirconium oxide, aluminum oxide, or a composite oxide comprising two or three of these, and a noble metal supported thereon. .

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