JP2013160208A - Exhaust emission control apparatus and exhaust emission control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exhaust emission control apparatus in which particulates in a particulate filter (PF) can be removed appropriately by determining whether the inside of the PF is in a frozen state or a water containing state, and to provide an exhaust emission control method.SOLUTION: An exhaust emission control apparatus including a PF for capturing particulates includes: a differential pressure sensor for measuring a differential pressure value at front and rear of the PF; a temperature sensor for measuring a PF exhaust gas temperature; and a control section electrically connected to the differential pressure sensor and the temperature sensor, respectively. When starting an internal combustion engine, the control section performs PF internal state determination processing for determining whether the inside of the PF is in a frozen state or a water containing state on the basis of the differential pressure value and the PF exhaust gas temperature. While it is determined by the PF internal state determination processing that the inside of the PF is in the frozen state or the water containing state, the control section controls not to perform processing for forcibly oxidizing particulates in the PF.

Description

  The present invention relates to an exhaust gas purification device and an exhaust gas purification method for purifying exhaust gas discharged from an internal combustion engine.

  In general, exhaust gas discharged from an internal combustion engine (typically, a diesel engine) includes particulate matter mainly composed of carbon (hereinafter also referred to as “PM”) and ash ( ASH) and the like, which are known to cause air pollution. For this reason, the amount of particulate matter discharged is stricter year by year along with harmful components such as hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) contained in the exhaust gas. Therefore, techniques for collecting and removing these particulate substances from exhaust gas have been conventionally performed.

  For example, a particulate filter (hereinafter also referred to as “PF”) for collecting the particulate matter. When a diesel engine is used as the internal combustion engine, PF is referred to as a diesel particulate filter (DPF: Also referred to as a diesel particulate filter)) is provided in the exhaust passage of the engine. The PF includes, for example, a honeycomb-shaped porous substrate, and collects particulate matter on the surface of the porous substrate. However, there is a limit to the amount of particulate matter that can be collected on the porous substrate. If an amount of particulate matter exceeding this amount is deposited on the PF, the PF becomes 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, at a stage where a certain amount of particulate matter is collected in the PF, as a regeneration process of the PF, the PF on which the particulate matter is deposited to some extent is set at a predetermined temperature (for example, 550 ° C. to 650 ° C. To the extent that the particulate matter is forcibly oxidized / decomposed.

  The PM forced oxidation process for PF regeneration is performed by, for example, fuel injection into an exhaust system of an internal combustion engine. The above-mentioned PM forced oxidation treatment may cause deterioration of the fuel consumption rate and PF melting damage when the treatment time becomes long. Therefore, it is desirable to monitor the clogged state due to the particulate matter in the PF and perform the PM forced oxidation process when the clogged state exceeds a predetermined determination criterion.

  This clogging detection method due to particulate matter of PF measures the upstream exhaust gas pressure and downstream exhaust gas pressure of PF, and when the differential pressure (PF differential pressure) exceeds a certain value, PM forced oxidation There is a method of performing processing. Since the PF differential pressure has a correlation with the accumulation amount of PM accumulated in the PF, the start timing of the PM forced oxidation treatment is determined based on the PF differential pressure, so that the PF differential pressure is determined according to the accumulation amount of the particulate matter. The PM forced oxidation process can be started at an appropriate timing.

  In relation to this clogging detection method using the PF differential pressure, the cited document 1 detects the differential pressure across the DPF (PF) in the diesel engine, the DPF internal exhaust temperature, the DPF inlet exhaust pressure, and the exhaust flow rate. By calculating the pressure loss coefficient of the DPF and the Reynolds number of the exhaust gas passing through the DPF, and comparing the calculated pressure loss coefficient of the DPF with the determination value calculated from the DPF internal exhaust temperature and the Reynolds number. A method of detecting a clogged state of a DPF is disclosed.

JP 2005-023884 A

  By the way, in an area where the temperature is low, such as a very cold region, it is conceivable that the inside of the PF is frozen or water-containing after the internal combustion engine is stopped. As described above, when the inside of the PF is frozen or in a water-containing state, the PF differential pressure increases. Therefore, in the above-described clogging detection method using the PF differential pressure, when the inside of the PF is frozen or in a water-containing state, the PF differential pressure increases, so that particulate matter (PM) is accumulated in the PF. May be erroneously recognized and the PM forced oxidation process may start. As a result, due to the blockage of the exhaust gas passage in the PF with ice or water, a predetermined amount of air due to fuel injection from the internal combustion engine performed by the PM forced oxidation treatment does not enter the PF. Or white smoke may be emitted, resulting in malfunction.

  The present invention was created to solve the above-described problems, and determines whether or not the inside of the PF is frozen or water-containing, and the determination determines that the inside of the PF is frozen or water-containing. If determined, the object is to control the exhaust gas purification process so as not to perform the PM forced oxidation process, and to provide an exhaust gas purification device and an exhaust gas purification method capable of realizing such an object.

  In order to achieve the above object, the present invention provides an exhaust gas purification apparatus having the following configuration. That is, the exhaust gas purification apparatus according to the present invention is an exhaust gas purification apparatus provided in an exhaust system of an internal combustion engine. The exhaust gas purifying apparatus disclosed herein includes a particulate filter (PF) that collects particulate matter (PM) in exhaust gas flowing in an exhaust passage provided in the internal combustion engine, and the exhaust gas more than the PF. A differential pressure sensor for measuring the pressure difference between the pressure upstream of the passage and the pressure downstream of the exhaust passage relative to the PF; and the temperature of the exhaust gas downstream of the exhaust passage downstream of the PF (hereinafter referred to as “PF”). A temperature sensor that measures the temperature of the outgas.) And a controller that is electrically connected to the differential pressure sensor and the temperature sensor. Here, when the internal combustion engine is started, the control unit measures the differential pressure value before and after the PF with the differential pressure sensor and measures the exhaust gas temperature downstream of the PF with the temperature sensor. Based on the differential pressure value and the exhaust gas temperature, a PF internal state determination process is performed to determine whether or not the inside of the PF is frozen or water-containing.

  When the moisture in the PF is frozen, that is, when the inside of the PF is blocked by ice, the differential pressure value before and after the PF increases. Then, when the inside of the PF is not frozen, that is, when there is no blockage by the ice in the PF and the exhaust gas starts to flow through the PF, the differential pressure value in the PF becomes small. Then, as the differential pressure value decreases, the PF outgas temperature increases. At this time, when the inside of the PF is in a water-containing state, the PF outgas temperature is a predetermined value or less (for example, 100 ° C. or less). When the inside of the PF is not in a water-containing state, that is, when the inside of the PF is in a dry state, the PF outgas temperature becomes a predetermined value or higher (for example, 100 ° C. or higher). As described above, by using the differential pressure value and the PF outgas temperature, it can be determined whether or not the inside of the PF is frozen or water-containing. This determination can be one of the determination materials for determining whether or not to perform a process such as forced oxidation of the particulate matter in the PF.

  In a preferred aspect of the exhaust gas purifying apparatus disclosed herein, the control unit is configured to store a differential pressure value before and after the PF measured by the differential pressure sensor immediately before the internal combustion engine is stopped. ing. Here, in the PF internal state determination process, the differential pressure value measured at the start is 1.3 times or more (preferably 1.5 times or more, more preferably 2 times) the differential pressure value measured immediately before the stop. When the exhaust gas temperature (PF outgas temperature) measured at the time of starting is determined to be 70 ° C. or lower (preferably 50 ° C. or lower, more preferably 30 ° C. or lower). In addition, the inside of the PF is determined to be frozen or water-containing.

  As described above, the differential pressure value measured at the time of starting is 1.3 times or more (preferably 1.5 times or more, more preferably twice or more) of the differential pressure value measured immediately before the stop and the starting. When the measured PF outgas temperature is 70 ° C. or lower (preferably 50 ° C. or lower, more preferably 30 ° C. or lower), it is more preferable to determine whether the inside of the PF is frozen or water-containing. Can do.

  In another preferable aspect of the exhaust gas purifying apparatus disclosed herein, the control unit performs a process of forcibly oxidizing the particulate matter when the particulate matter deposited in the PF exceeds a predetermined amount. Is configured to do. The control unit is configured not to perform the process of forcibly oxidizing the particulate matter while the PF internal state determination process determines that the inside of the PF is frozen or water-containing. ing.

  When the particulate matter is forcibly oxidized when the inside of the PF is frozen or water-containing, the particulate matter is forcibly oxidized by blocking the exhaust gas passage in the PF with ice or water. Since a predetermined amount of air by fuel injection from the internal combustion engine to be performed does not enter the PF, HC gas or white smoke may be discharged, which may cause a malfunction. Therefore, with the exhaust gas purifying apparatus having such a configuration, the functional failure can be prevented by not performing the process of forcibly oxidizing the particulate matter while the inside of the PF is frozen or in a water-containing state.

  Further, according to such a configuration, the internal combustion engine is stopped during the process of forcibly oxidizing the particulate matter, and the inside of the PF is frozen or water-containing during the stop, and the internal combustion engine is started after this state. In the PF internal state determination process, it is determined that the inside of the PF is frozen or in a water-containing state, and the forced oxidation process is not performed during the determination result. can do.

  Moreover, in another preferable aspect of the exhaust gas purification apparatus disclosed herein, the control unit is configured to continuously perform the PF internal state determination process after the internal combustion engine is started. And the said control part is comprised so that the process which forcibly oxidizes the said particulate matter may be performed after determining with the said PF internal state determination process that the inside of the said PF is not freezing or a water-containing state. By the exhaust gas purifying apparatus having such a configuration, it is possible to perform the process of forcibly oxidizing the particulate matter more suitably. In addition, the above-described malfunction is prevented, and the fuel consumption rate is improved by appropriately performing the forced oxidation treatment of the particulate matter.

  Moreover, this invention provides the following exhaust gas purification methods as another side surface for implement | achieving the objective mentioned above. That is, it is a method for purifying exhaust gas discharged from an internal combustion engine in which a particulate filter (PF) for collecting particulate matter in the exhaust gas is provided in the exhaust passage. The method measures a differential pressure value between a pressure on the upstream side of the exhaust passage from the PF and a pressure on the downstream side of the exhaust passage from the PF, and the differential pressure value exceeds a predetermined differential pressure value. Sometimes it includes a forced oxidation treatment for forcibly oxidizing the particulate matter in the PF. At the time of starting the internal combustion engine, the measurement of the differential pressure value between the pressure upstream of the exhaust passage from the PF and the pressure downstream of the exhaust passage from the PF, and the exhaust passage from the PF PF internal state determination processing is performed to determine whether or not the inside of the PF is frozen or water-containing based on the differential pressure value and the exhaust gas temperature. The forced oxidation treatment is not performed while it is determined that the inside of the PF is frozen or water-containing by processing.

  When the particulate matter is forcibly oxidized when the inside of the PF is frozen or water-containing, the particulate matter is forcibly oxidized by blocking the exhaust gas passage in the PF with ice or water. Since a predetermined amount of air by fuel injection from the internal combustion engine to be performed does not enter the PF, HC gas or white smoke may be discharged, which may cause a malfunction. Therefore, according to the exhaust gas purification method having such a configuration, the PF internal state determination process prevents the malfunction in advance because the forced oxidation process is not performed while the PF is frozen or in a water-containing state. Can do.

  Further, in a preferable aspect of the exhaust gas purification method disclosed herein, when the internal combustion engine is stopped during the forced oxidation process, the PF internal state determination process is continuously performed along with the restart of the internal combustion engine after the stop. The forced oxidation treatment is restarted after determining that the inside of the PF is not frozen or containing water.

  According to the exhaust gas purification method having such a configuration, the forced oxidation treatment is performed after the PF internal state determination process determines that the inside of the PF is not frozen or in a water-containing state. Can be oxidized. In addition, the above-described malfunction is prevented, and the fuel consumption rate is improved by appropriately performing the forced oxidation treatment of the particulate matter.

  Moreover, in another preferable aspect of the exhaust gas purification method disclosed herein, the PF internal state determination process is performed by performing a difference between a differential pressure value measured at the time of starting and a differential pressure value of 1. It is determined that it is 3 times or more (preferably 1.5 times or more, more preferably 2 times or more), and the exhaust gas temperature measured at the start is 70 ° C. or lower (preferably 50 ° C. or lower, more preferably 30 It is determined that the inside of the PF is frozen or hydrated when it is determined that the temperature is equal to or lower than [° C.].

  As described above, the differential pressure value measured at the time of starting is 1.3 times or more (preferably 1.5 times or more, more preferably twice or more) of the differential pressure value measured immediately before the stop and the starting. When the PF outgas temperature measured sometimes is 70 ° C. or lower (preferably 50 ° C. or lower, more preferably 30 ° C. or lower), it is more suitably determined whether or not the inside of the PF is frozen or water-containing. be able to.

It is the figure which showed typically the exhaust gas purification apparatus concerning one Embodiment of this invention. It is the figure which showed typically the particulate filter (PF) in the exhaust gas purification apparatus concerning one Embodiment of this invention. It is a flowchart explaining the determination method of PF internal state determination processing concerning one Embodiment of this invention. It is a flowchart explaining the control at the time of the internal combustion engine stop of the exhaust gas purification apparatus concerning one Embodiment of this invention. It is a flowchart explaining the control at the time of the internal combustion engine start-up of the exhaust gas purification apparatus concerning one Embodiment of this invention. It is a flowchart explaining the control at the time of the internal combustion engine start-up of the exhaust gas purification apparatus concerning 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 the field. The present invention can be carried out based on the contents disclosed in the present specification and common general technical knowledge in the field.

<Exhaust gas purification device>
Here, first, an exhaust gas purification apparatus according to an embodiment of the present invention will be described. Such an exhaust gas purification device is provided in an exhaust system of an internal combustion engine. Hereinafter, an internal combustion engine and an exhaust gas purification apparatus will be described with reference to FIG.

A. In the exhaust gas purification apparatus 100 having the configuration shown in FIG. 1, the internal combustion engine 1 is configured mainly with 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 purifying apparatus 100 according to the present invention can also use an engine other than a diesel engine (for example, a gasoline engine) as the internal combustion engine 1.

  The internal combustion engine 1 having the configuration shown in FIG. 1 includes a plurality of combustion chambers 2 and a fuel injection valve 3 that injects fuel into each of the combustion chambers 2. 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. The fuel pump 23 supplies the fuel in the fuel tank 24 to the combustion chamber 2 via the common rail 22, the fuel supply pipe 21, and the fuel injection valve 3.

  The combustion chamber 2 communicates with an intake manifold 4 and an exhaust manifold 5 respectively. Hereinafter, a system that is provided upstream of the intake manifold 4 and supplies air (oxygen) to the internal combustion engine 1 is referred to as an “intake system”. A system that is provided on the downstream side of the exhaust manifold 5 and exhausts exhaust gas generated in the internal combustion engine 1 to the outside is referred to as an “exhaust system”. The intake system and the exhaust system are in communication with each other via an exhaust gas recirculation passage 18. Further, an electronically controlled control valve 19 is disposed in the exhaust gas recirculation passage 18, and the exhaust gas to be recirculated can be adjusted by opening and closing the control valve 19. The exhaust gas recirculation passage 18 is provided with a cooling device (EGR cooling device) 20 for cooling the gas flowing in the exhaust gas recirculation passage 18.

A-1. Intake System Next, the intake system of the internal combustion engine 1 will be described. An intake duct 6 is connected to an intake manifold 4 that communicates the internal combustion engine 1 with an intake system. The intake duct 6 is connected to a compressor 7a of an exhaust turbocharger 7, and an air cleaner 9 is connected to the compressor 7a. An air flow meter 8 is disposed downstream of the air cleaner 9 (internal combustion engine 1 side). The air flow meter 8 is a sensor that detects the amount of intake air supplied to the intake duct 6. A throttle valve 10 is provided further downstream of the air flow meter 8 in the intake duct 6. The amount of air supplied to the internal combustion engine 1 can be adjusted by opening and closing the throttle valve 10. Further, a throttle sensor (not shown) for detecting the opening degree of the throttle valve 10 may be disposed in the vicinity of the throttle valve 10. A cooling device 11 for cooling the air flowing through the intake duct 6 is disposed around the intake duct 6.

A-2. Exhaust System Next, the exhaust system of the internal combustion engine 1 will be described. An exhaust manifold 5 that allows the internal combustion engine 1 to communicate with an exhaust system is connected to an exhaust turbine 7 b of an exhaust turbocharger 7. An exhaust passage 12 through which exhaust gas flows is connected to the exhaust turbine 7b. The exhaust manifold 5 is provided with an exhaust system fuel injection valve 13 for injecting fuel F into the exhaust gas. As will be described in detail later, the exhaust system fuel injection valve 13 increases the temperature in the PF 80 by injecting the fuel F into the exhaust system including the particulate filter (PF) 80 when performing the PM forced oxidation process. Let

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. Typically, although not shown, noble metal catalyst particles such as platinum (Pt) and palladium (Pd) are supported on a base material (for example, a honeycomb base material) on the upstream side or the downstream side of PF80. An exhaust gas purifying catalyst is provided.

  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 PF 80 collects particulate matter (PM) made of combustible components such as carbon fine particles contained in the exhaust gas. In the case where a diesel engine is used as the internal combustion engine 1, a diesel particulate filter (DPF) may be used as the PF80.

B-1. 2. Porous base material As shown in FIG. 2, the PF 80 has a porous base material 82 formed in a honeycomb structure, and a plurality of flow paths 84 are provided along the flow direction of exhaust gas. The plurality of flow paths 84 provided in the PF 80 are sealed either upstream or downstream in the flow direction of the exhaust gas. The porous base material 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 heat-resistant metal such as aluminum titanate, silicon nitride or 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. And 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. Particulate matter contained in the exhaust gas is 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 PF80. The PM oxidation catalyst is composed of metal catalyst particles having an oxidation catalyst ability for an oxidation reaction of particulate matter (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 particulate matter captured by the porous base material 82 can be easily oxidized and decomposed. 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, oxidation / decomposition of particulate matter becomes easier.

C. Oil temperature sensor The exhaust gas purification apparatus disclosed herein includes an oil temperature sensor in an internal combustion engine. In the exhaust gas purification apparatus 100 shown in FIG. 1, an oil temperature sensor 57 is electrically connected to a control unit 30 described later. The oil temperature sensor 57 only needs to be able to detect the temperature (oil temperature) of the lubricating oil of the internal combustion engine 1, and its specific configuration does not particularly limit the present invention. For example, the oil temperature sensor 57 is composed of a semiconductor element, and an oil temperature sensor whose resistance changes with the oil temperature can be used. Further, the arrangement position of the oil temperature sensor 57 is not particularly limited as long as the oil temperature of the internal combustion engine 1 can be measured.

D. Water temperature sensor The exhaust gas purification apparatus disclosed herein includes a water temperature sensor in an internal combustion engine. In the exhaust gas purification apparatus 100 shown in FIG. 1, a water temperature sensor 58 is electrically connected to a control unit 30 described later. The water temperature sensor 58 only needs to be able to detect the water temperature in the internal combustion engine 1, and its specific configuration does not particularly limit the present invention. For example, the water temperature sensor 58 is composed of a semiconductor element like the oil temperature sensor 57, and a sensor whose resistance changes with the water temperature can be used. Further, the arrangement position of the water temperature sensor 58 is not limited as long as the water temperature of the internal combustion engine 1 can be measured.

E. Temperature Sensor The exhaust gas purification device disclosed herein includes a temperature sensor in an internal combustion engine. In the exhaust gas purification apparatus 100 shown in FIG. 1, the temperature sensor 56 is disposed downstream of the PF 80 in the exhaust passage 12. The temperature sensor 56 is electrically connected to the control unit 30 described later. By this temperature sensor 56, the temperature of the exhaust gas flowing to the downstream side of the exhaust passage 12 from the PF 80 (PF outgas temperature) is measured.

F. Differential pressure measuring means The exhaust gas purifying apparatus disclosed by the present invention measures the exhaust gas pressure upstream of the PF and the exhaust gas pressure downstream of the PF during operation of the internal combustion engine, and obtains the PF obtained by the pressure difference. Means for measuring a differential pressure value (differential pressure measuring means) are provided. In the exhaust gas purification apparatus 100 having the configuration shown in FIG. 1, a differential pressure sensor 50 is provided as the differential pressure measuring means. Further, the differential pressure sensor 50 is electrically connected to a control unit 30 described later. The differential pressure sensor 50 includes a pair of an upstream pressure sensor 52 and a downstream pressure sensor 54. The upstream pressure sensor 52 is attached to the upstream side of the PF 80, and the downstream pressure sensor 54 is attached to the downstream side of the PF 80. The upstream pressure sensor 52 and the downstream pressure sensor 54 are electrically connected to the control unit 30 described later. The upstream pressure sensor 52 and the downstream pressure sensor 54 measure the pressure of the exhaust gas flowing on the upstream side and the downstream side of the PF 80, respectively. Each pressure is converted into a signal and sent to the differential pressure sensor 50. The differential pressure sensor 50 measures the PF differential pressure value obtained from the difference between the exhaust gas pressure on the upstream side of the PF 80 and the exhaust gas pressure on the downstream side, and sends the PF differential pressure value to the control unit 30 described later.

  In addition, the said differential pressure measurement means should just be able to measure the differential pressure of PF80, and the structure does not limit this invention. For example, in addition to the differential pressure sensor 50 as described above, the upstream pressure sensor 52 and the downstream pressure sensor 54 may be directly connected to the control unit 30 described later. In this case, the upstream pressure sensor 52 measures the exhaust gas pressure on the upstream side of the PF 80, and the downstream pressure sensor 54 measures the exhaust gas pressure on the downstream side of the PF 80. Then, the electrical signals obtained by the exhaust gas pressure on the upstream side and the exhaust gas pressure on the downstream side are transmitted to the control unit 30. Then, the control unit 30 can obtain the PF differential pressure value based on the difference between the upstream side exhaust gas pressure and the downstream side exhaust gas pressure.

G. Control unit (ECU)
Next, the control unit (ECU) 30 of the exhaust gas purification apparatus 100 disclosed here will be described. The control unit 30 is mainly composed of a digital computer and functions as a control device in the operation of the internal combustion engine 1 and the exhaust gas purification device 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, a CPU that performs arbitrary calculations and determinations, and the like.

  The control unit 30 having the configuration shown in FIG. 1 is provided with an input port, and sensors (for example, an oil temperature sensor 57, a water temperature sensor 58, a temperature sensor) installed in each part of the internal combustion engine 1 and the exhaust gas purification unit 40. 56, differential pressure sensor 50, etc.). As a result, information detected by each sensor is transmitted as electrical signals to the ROM, RAM, and CPU via 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 purification device disclosed herein, like the control unit provided in this type of device, deposits particulate matter (PM) in the PF based on the measured PF differential pressure value. Estimate the amount. Then, processing for forcibly oxidizing the particulate matter (PM forced oxidation processing) is started when the estimated amount of PM deposition exceeds a predetermined threshold. In addition, this PM forced oxidation process heats PF to such an extent that the particulate matter deposited in the PF can be suitably oxidized, and its specific mode does not limit the present invention. . The control unit 30 can also perform a PF internal state determination process characterizing the present invention. Details will be described later.

<Method of estimating PM deposition amount>
First, the estimation method of the particulate matter (PM) accumulation amount in the PF 80 described above performed by the control unit 30 according to the present embodiment will be described in detail. Note that the method for estimating the PM deposition amount in the PF 80 disclosed herein is not intended to limit the present invention. For example, the PM deposition amount in the PF 80 can be estimated by the following method. The control unit 30 is connected to the differential pressure sensor 50 via an input port, and the PF differential pressure value (ΔP _n ) 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 80 based on the PF differential pressure value (ΔP _n ) measured from the differential pressure sensor 50. Specifically, the PF differential pressure value (ΔP _n-1 ) measured immediately after the end of the previous PM forced oxidation process is subtracted from the PF differential pressure value (ΔP _n ) measured to estimate the PM deposition amount. . It can be said that the PF differential pressure value (ΔP _n-1 ) immediately after the end of the immediately preceding PM forced oxidation treatment is in a state in which almost all of the particulate matter in the PF 80 has been removed. Therefore, by subtracting the PF differential pressure value (ΔP _n-1 ) immediately after the end of the previous PM forced oxidation process from the PF differential pressure value (ΔP _n ) measured to estimate the PM deposition amount, PM A PF differential pressure value (ΔP) resulting from the accumulation amount 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.

<PM forced oxidation treatment>
Next, the above-described PM forced oxidation process performed by the control unit 30 according to the present embodiment will be described in detail. This PM forced oxidation process is a process performed when the PF differential pressure value (ΔP) resulting from the PM deposition amount obtained by the above-described PM deposition amount estimation method exceeds a predetermined threshold. The control unit 30 is connected to the exhaust system fuel injection valve 13 via an output port. When the PF differential pressure value (ΔP) resulting from the 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.

<PF internal state determination processing>
Next, the PF internal state determination process performed by the control unit 30 according to the present embodiment will be described in detail. The PF internal state determination process is a process for determining whether or not the inside of the PF is frozen or wet. When the moisture in the PF is frozen, that is, when the inside of the PF is blocked by ice, the differential pressure value before and after the PF increases. Then, when the inside of the PF is not frozen, that is, when there is no blockage by the ice in the PF and the exhaust gas starts to flow through the PF, the differential pressure value in the PF becomes small. As the differential pressure value decreases, the exhaust gas temperature on the downstream side of the exhaust passage from PF (hereinafter also referred to as “PF outgas temperature”) increases. At this time, when the inside of the PF is in a water-containing state, the PF outgas temperature is a predetermined value or less (for example, 100 ° C. or less). When the inside of the PF is not in a water-containing state, that is, when the inside of the PF is in a dry state, the PF outgas temperature becomes a predetermined value or higher (for example, 100 ° C. or higher). Thus, by using the differential pressure value and the PF outgas temperature, it can be determined that the inside of the PF is in an icing state or a water-containing state.

  Next, a method for determining whether or not the inside of the PF 80 is in an icing state or a water-containing state by the exhaust gas purifying apparatus 100 having the configuration shown in FIG. 1 will be described with reference to the flowchart of FIG. As shown in FIG. 3, the PF internal state determination processing includes “differential pressure value measurement before and after PF (S10)”, “PF outgas temperature measurement (S20)”, “PF outgas temperature determination (S30)”, “ Each step includes “Differential pressure value determination before and after PF (S40)”, “PF inside: frozen or hydrated state (S50)”, and “PF inside: dried state (S60)”. Hereinafter, each step will be described.

In the “PF internal state determination process” shown in FIG. 3, when the internal combustion engine (engine) 1 is stopped, the control unit 30 uses the differential pressure sensor 50 to detect the differential pressure value ΔP before and after the PF 80 immediately before the engine 1 is stopped. It is assumed that the _STOP is measured and the engine 1 is stopped after the measurement. Then, it is assumed that the engine is started next time after the stop.

1-A. Differential pressure measurement before and after PF (S10)
After starting the PF internal state determination process, first, in step S10, the differential pressure value ΔP in the PF 80 is measured. Specifically, the control unit 30 uses the differential pressure sensor 50 to measure a differential pressure value ΔP between the pressure upstream of the exhaust passage 12 relative to the PF 80 and the pressure downstream of the PF 80 downstream of the exhaust passage 12.

1-B. PF outgas temperature measurement (S20)
In step S20, the outgas temperature T of the PF 80 is measured. The control unit 30 measures the temperature of the exhaust gas flowing on the downstream side of the exhaust passage 12 from the PF 80, that is, the PF outgas temperature T by the temperature sensor 56. In this embodiment, the PF outgas temperature measurement (S20) is performed after the differential pressure value measurement before and after the PF (S10). However, this order does not particularly limit the present invention. After the temperature measurement (S20), the differential pressure value measurement before and after the PF (S10) may be performed.

1-C. PF outgas temperature judgment (S30)
After measuring the PF outgas temperature T, in step S30, the PF outgas temperature T is determined. Specifically, the control unit 30 sets in advance a predetermined temperature value whether or not the inside of the PF 80 is frozen or in a water-containing state, and whether or not the PF outlet gas temperature T is equal to or lower than the predetermined temperature value. Determine. When the outgas temperature T is equal to or lower than the predetermined temperature, it is determined that the inside of the PF 80 is frozen or water-containing, and the determination result is YES and step S50 is then performed. On the other hand, if the outlet gas temperature T is higher than the predetermined temperature value, the determination result is NO and then step S40 is performed. The predetermined temperature value is 70 ° C., preferably 50 ° C., and more preferably 30 ° C.

1-D. Differential pressure value judgment before and after PF (S40)
In step S40, using the differential pressure value ΔP measured in step S10, it is determined whether or not the inside of the PF is frozen or water-containing. Specifically, the control unit 30 is preset with a differential pressure determination predetermined value as to whether or not the inside of the PF 80 is frozen or wet with the differential pressure value ΔP, and the differential pressure value ΔP is determined as the differential pressure determination. It is determined whether or not it is equal to or greater than a predetermined value. If the differential pressure value ΔP is greater than or equal to the predetermined value, it is determined that the inside of the PF 80 is frozen or water-containing, and then step S50 is performed. On the other hand, when the differential pressure value ΔP is smaller than the predetermined value, it is determined that the inside of the PF 80 is in a dry state (not in an icing state and not in a water-containing state), and then Step S60 is performed. The predetermined value for determining the differential pressure is the engine stop differential pressure value ΔP _STOP × 1.3 (that is, the rate of increase with the engine stop differential pressure value ΔP _STOP is 30%). Pressure value ΔP _STOP × 1.5 (that is, the rate of increase with the engine stop differential pressure value ΔP _STOP is 50%), more preferably the differential pressure value before engine stop ΔP _STOP × 2 (that is, engine stop differential pressure value ΔP _STOP And the rate of increase is 10%).
In FIG. 3, the differential pressure value measurement before and after the PF is first performed (S10), but step S10 may be performed immediately before step S40.

1-E. Inside of PF: Freezing or water content (S50)
When it is determined in step S30 or step S40 that the inside of the PF 80 is frozen or water-containing, the control unit 30 determines that the internal state of the PF 80 is frozen or water-containing, and ends the PF internal state determination process. To do.

1-F. Inside of PF: dry state (S60)
When it is determined in step S50 that the inside of the PF is not frozen or wet, the control unit 30 determines that the internal state of the PF 80 is not frozen and is not wet, that is, a dry state. Then, the PF internal state determination process ends. Thus, when it determines with the inside of PF80 being a dry state, the process which forcedly oxidizes the particulate matter mentioned above can be performed.

  The procedure for performing the determination process (PF internal state determination process) on whether or not the inside of the PF 80 is in an icing state or a water-containing state has been described above by the exhaust gas purification apparatus 100 according to the present invention. In this way, by measuring the differential pressure before and after the PF and the exhaust gas temperature, and comparing each with a predetermined value, it can be determined whether or not the inside of the PF 80 is frozen or water-containing.

  Next, an embodiment of the exhaust gas purification method executed in the above-described exhaust gas purification apparatus 100 will be described with reference to the flowcharts of FIGS. FIG. 4 is a flowchart illustrating the control when the internal combustion engine (engine) 1 is stopped in the embodiment according to the present invention. 5 and 6 are flowcharts for explaining the control at the time of starting the internal combustion engine 1 in the embodiment according to the present invention.

  In describing the present embodiment, an operation mode is defined, and the operation mode includes “stop”, “normal”, “PM forced oxidation”, and “PM forced oxidation prohibited”. “Stop” is an operation mode in which the internal combustion engine is stopped. “Normal” is a normal operation mode in which the PM forced oxidation treatment is not performed. “PM forced oxidation” is an operation mode in which particulate matter (PM) in the PF is removed by the above-described PM forced oxidation treatment. “PM forced oxidation prohibition” is an operation mode in which the PM forced oxidation treatment is prohibited because the inside of the PF is frozen or water-containing.

  First, control of the exhaust gas purification apparatus 100 according to the present invention when the engine 1 is stopped will be described. In this control, the engine 1 is stopped during the PM forced oxidation process when the temperature in the extremely cold region is low. As shown in FIG. 4, the exhaust gas purifying apparatus 100 includes “an engine stop request during PM forced oxidation process (S100)”, “differential pressure value measurement before and after PF when the engine is stopped (S110)”, “engine stop ( S120) ”. Hereinafter, each step will be described.

2-A. Engine stop request during PM forced oxidation (S100)
First, in step S100, the control unit 30 receives an engine stop request signal during the PM forced oxidation process. Then, after receiving the signal, step S110 is performed.

2-B. Differential pressure value measurement before and after PF when engine is stopped (S110)
Next, in step S110, a differential pressure value before and after the PF when the engine is stopped is measured. Specifically, the control unit 30 measures the engine stop differential pressure value ΔP _STOP between the pressure upstream of the exhaust passage 12 relative to the PF 80 and the pressure downstream of the exhaust passage 12 relative to the PF 80 by the differential pressure sensor 50. .

2-C. Engine stop (S120)
After measuring the engine stop differential pressure value ΔP _STOP in step S110, the control unit 30 sets the operation mode to “stop” and stops the engine.

  Next, the control of the exhaust gas purifying apparatus 100 according to the present invention when the engine 1 is started will be described. This control is performed on the premise that the steps described with reference to FIG. 4 are performed and the engine 1 is stopped. As shown in FIGS. 5 and 6, the exhaust gas purifying apparatus 100 includes “engine start (S200)”, “oil temperature and water temperature measurement in the engine (S210)”, “pressure difference measurement before and after PF (S220, S300, S340) ”,“ PF outgas temperature measurement (S230) ”,“ Oil temperature determination (S240) ”,“ Water temperature determination (S250) ”,“ PF outgas temperature determination (S260) ”,“ Difference before and after PF ” "Pressure value determination (S270)", "Operation mode: normal (S280, S370)", "Operation mode: PM forced oxidation prohibition (S290)", "PM forced oxidation treatment start determination (S310)", "Operation mode: PM Each step includes “forced oxidation (S320)”, “PM forced oxidation process start (S330)”, “PM forced oxidation process end determination (S350)”, and “PM forced oxidation process stop (S360)”. Hereinafter, each step will be described.

3-A. Engine start (S200)
First, in step S200, the engine is started. The control unit 30 transmits an engine start signal for starting the engine to a cell motor (not shown) to start the engine. Further, the operation mode at the time of starting the engine is “normal”.

3-B. Oil temperature and water temperature measurement in the engine (S210)
After engine start, at step S210, for measuring the oil temperature _{T O,} and the water temperature _{T W} of the engine 1. Specifically, the control unit 30, by the oil temperature sensor 57 measures the oil temperature T _O of the engine 1, for measuring the water temperature T _W of the engine 1 by the water temperature sensor 58.

3-C. Differential pressure measurement before and after PF (S220)
In step S220, a differential pressure value ΔP before and after the PF 80 is measured in order to determine whether or not the inside of the PF 80 is frozen or wet. The control unit 30 uses the differential pressure sensor 50 to measure a differential pressure value ΔP between the pressure upstream of the exhaust passage 12 relative to the PF 80 and the pressure downstream of the exhaust passage 12 relative to the PF 80.

3-D. PF outgas temperature measurement (S230)
In step S230, the outlet gas temperature T from the PF 80 is measured in order to determine whether or not the inside of the PF 80 is frozen or water-containing. The control unit 30 measures the temperature of the exhaust gas flowing on the downstream side of the exhaust passage 12 from the PF 80, that is, the PF outgas temperature T by the temperature sensor 56.
In this embodiment, each value is measured in the order of step S210, step S220, and step S230. However, this order of measurement does not limit the present invention. For example, the measurement may be performed in the order of step S230, step S220, and step S210, or may be performed in the order of step S220, step S210, and step S230.

3-E. Oil temperature judgment (S240)
In step S240, based on the oil temperature _{T O} of the engine 1 measured by the step S210, a determination is oil temperature. The oil temperature determination is one of the conditions for determining whether or not the PM forced oxidation process can be performed. Control unit 30, a predetermined value oil temperature for determining whether to execute the PM forced oxidation treatment by the oil temperature T _O is set in advance, the oil temperature T _O is in the oil temperature greater than a predetermined value It is determined whether or not. When the oil temperature _TO is equal to or higher than the oil temperature predetermined value, it is determined that the PM forced oxidation process can be performed (YES), and then step S250 is performed. On the other hand, when the oil temperature _TO is smaller than the oil temperature predetermined value, it is determined that the PM forced oxidation process cannot be performed (NO), and step S210 is performed again. In addition, although the said oil temperature predetermined value is not specifically limited, For example, it is 40 degreeC, Preferably it is 70 degreeC, More preferably, it is 80 degreeC.
Further, in the present embodiment, to measure the oil temperature T _O of the engine 1 in step S210, the oil temperature T _O may be measured immediately before the step S240.

3-F. Water temperature judgment (S250)
Next, in step S250, based on the water temperature _{T W} of the engine 1 measured by the step S210, it performs the temperature determination. The water temperature determination is one of the conditions for determining whether or not the PM forced oxidation process can be performed, similarly to the oil temperature determination described above. Control unit 30 is set water temperature a predetermined value for determining whether to execute the PM forced oxidation treatment by the water temperature T _W is beforehand, the water temperature T _W is whether a said water temperature above a predetermined value judge. The water temperature T _W is equal to or larger than the water temperature a predetermined value, determines that it is possible to carry out the PM forced oxidation treatment (YES), then performs step S260. On the other hand, if the water temperature T _W is lower than the temperature predetermined value, it determines that it is impossible to carry out the PM forced oxidation treatment (NO), performs step S210 again. In addition, although the said water temperature predetermined value is not specifically limited, For example, it is 40 degreeC, Preferably it is 70 degreeC, More preferably, it is 80 degreeC.
Further, in the present embodiment, to measure the water temperature T _W of the engine 1 in step S210, the temperature T _W may be measured immediately before the step S250.

3-G. PF outgas temperature judgment (S260)
In step S260, the PF outlet gas temperature is determined based on the outlet gas temperature T of PF 80 measured in step S230. The PF outgas temperature determination is a condition for determining whether or not the inside of the PF 80 is frozen or water-containing. Specifically, the control unit 30 is preset with a predetermined temperature value for determining whether or not the inside of the PF 80 is frozen or containing water, and the PF outgas temperature T exceeds the predetermined temperature value. It is determined whether or not. If the outgas temperature T is higher than the predetermined temperature value, it is determined that the inside of the PF 80 is not frozen or water-containing, the determination result is YES, and step S270 is then performed. On the other hand, when the outgas temperature T is equal to or lower than the predetermined temperature, it is determined that the inside of the PF 80 is still frozen or water-containing, that is, the state where the PM forced oxidation treatment is not performed. Step S290 is performed. The predetermined temperature value is 70 ° C., preferably 50 ° C., and more preferably 30 ° C.
In the present embodiment, the PF outgas temperature T is measured in step S230. However, the PF outgas temperature T may be measured immediately before step S260.

3-H. Differential pressure value judgment before and after PF (S270)
In step S270, the differential pressure value is determined based on the differential pressure value ΔP before and after PF 80 measured in step S220. The differential pressure value determination is a condition for determining whether or not the inside of the PF 80 is frozen or wet. Specifically, the control unit 30 is preset with a predetermined differential pressure value for determining whether or not the inside of the PF 80 is frozen or in a water-containing state, and the differential pressure value ΔP is set to the predetermined differential pressure value. Determine whether it is below. When the differential pressure value ΔP is smaller than the predetermined differential pressure value, it is determined that the inside of the PF 80 is not frozen or hydrated, that is, the inside of the PF 80 is in a dry state. In other words, it is determined that the PM forced oxidation process can be performed. Therefore, the determination result is set to YES, and step S300 in FIG. 6 is performed next. On the other hand, when the differential pressure value ΔP is equal to or greater than the predetermined differential pressure value, it is determined that the inside of the PF 80 is still frozen or in a water-containing state, that is, the state where the PM forced oxidation treatment is not performed. Therefore, the determination result is NO, and step S290 is performed next. In this embodiment, the differential pressure value ΔP before and after PF80 is measured in step S220. However, the differential pressure value ΔP before and after PF may be measured immediately before step S270.

The predetermined pressure difference value is the engine stop differential pressure value ΔP _STOP (step S110 in FIG. 4) measured when the engine is stopped. The predetermined differential pressure value is the engine stop differential pressure value ΔP _STOP × 1.3 (that is, the rate of increase with the engine stop differential pressure value ΔP _STOP is 30%), and preferably the differential pressure value ΔP before engine stop. _STOP × 1.5 (that is, the rate of increase with the engine stop differential pressure value ΔP _STOP is 50%), more preferably the differential pressure value before engine stop ΔP _STOP × 2 (that is, the increase with the engine stop differential pressure value ΔP _STOP) The rate is 100%). In the case where no value to the engine stop pressure value [Delta] P _STOP is present, may be set to an initial value [Delta] P ₀ in advance the difference圧所value to the control unit 30, the differential pressure [Delta] P and the initial value [Delta] P ₀ You may determine by comparing.

3-I. Operation mode: Normal (S280)
When the determination result is NO in step S240 and step S250, that is, it is determined that the PM forced oxidation process cannot be performed, the control unit 30 sets the operation mode to “normal” and again performs step S210. To implement.

3-J. Operation mode: PM forced oxidation prohibited (S290)
If the determination result is NO in step S260 and step S270, that is, if it is determined that the inside of the PF 80 is in a frozen state or a water-containing state, the process is performed even if the PM forced oxidation process can be performed. Is prohibited. Therefore, the control unit 30 sets the operation mode to “PM forced oxidation prohibition” and executes Step S210 again.

3-K. Differential pressure measurement before and after PF (S300)
When it is determined in step S240, step S250, step S260, and step S270 described above that the PM forced oxidation process is possible and the inside of the PF 80 is not frozen or in a water-containing state (dry state), step S300 will be described later. The differential pressure value ΔP _PM-START before and after PF 80 for determining whether to start the PM forced oxidation process is measured. The control unit 30 measures a differential pressure value ΔP _PM-START between the pressure upstream of the exhaust passage 12 relative to the PF 80 and the pressure downstream of the exhaust passage 12 relative to the PF 80 by the differential pressure sensor 50.

3-L. PM forced oxidation treatment start determination (S310)
In step S310, based on the differential pressure value ΔP _PM-START measured in step S300, the start determination of the PM forced oxidation process for removing the particulate matter deposited in the PF 80 is performed. Specifically, the control unit 30 is preset with a PM forced oxidation start predetermined value (differential pressure value) for determining whether or not to start the PM forced oxidation process, and the differential pressure value ΔP _PM− It is determined whether _START is equal to or greater than the predetermined value. When the differential pressure value ΔP _PM-START is equal to or greater than the predetermined value, it is necessary to remove the accumulated particulate matter in the PF 80. Therefore, it is determined to start the PM forced oxidation process, and the determination result is set to YES. Next, step S320 is performed. On the other hand, when the differential pressure value ΔP _PM-START is smaller than the predetermined value, it is determined that the particulate matter deposition amount in the PF 80 has not yet been removed, that is, the PM forced oxidation process is not started, and the determination result Is NO, then step S370 is performed.

3-M. Operation mode: PM forced oxidation (S320)
When it is determined in step S310 that the amount of the particulate matter accumulated in the PF 80 is an amount until removal, that is, it is determined to start the PM forced oxidation process, the control unit 30 starts the PM forced oxidation process. Sets the operation mode to “PM forced oxidation”.

3-N. PM forced oxidation treatment started (S330)
In step S330, the PM forced oxidation process is started. Specifically, as described above, the control unit 30 creates a fuel injection start 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 start 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 treatment is performed.

3-O. Differential pressure measurement before and after PF (S340)
After the PM forced oxidation process is started in step S330, a differential pressure value ΔP _PM−STOP before and after PF80 is measured in order to make a PM forced oxidation process end determination (S350) described later in step S350. The control unit 30 measures the differential pressure value ΔP _PM−STOP between the pressure upstream of the exhaust passage 12 relative to the PF 80 and the pressure downstream of the exhaust passage 12 relative to the PF 80 by the differential pressure sensor 50.

3-P. PM forced oxidation treatment end determination (S350)
In step S350, the amount of particulate matter deposited in the PF 80 is estimated based on the differential pressure value ΔP _PM−STOP in step S340 during the PM forced oxidation process, and the PM forced oxidation process completion determination is made based on the estimation. To do. Specifically, the control unit 30 is preset with a PM forced oxidation end predetermined value (differential pressure value) for determining whether to end the PM forced oxidation process, and the differential pressure value ΔP _PM− It is determined whether or not _STOP is below the predetermined value. When the differential pressure value ΔP _PM−STOP is lower than the predetermined value, it is determined that the particulate matter deposited in the PF 80 has been removed, and the PM forced oxidation process is terminated, and the determination result is set to YES. Next, step S360 is performed. On the other hand, when the differential pressure value ΔP _PM−STOP is equal to or greater than the predetermined value, it is determined that the particulate matter deposited in the PF 80 has not been removed yet, that is, the PM forced oxidation process is continued, and the determination result is NO. Then, step S340 is performed again.

3-Q. Stop PM forced oxidation treatment (S360)
If it is determined in step S350 that the accumulated amount of particulate matter in the PF 80 has been removed, the PM forced oxidation process is stopped in step S360. Specifically, the control unit 30 creates a fuel injection stop 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 stop signal stops the injection of the fuel F into the exhaust manifold 5. Thereby, the rise of the exhaust gas temperature supplied to the exhaust system is stopped, and the PM forced oxidation process is stopped.

3-R. Operation mode: Normal (S370)
In step S370, the control unit 30 sets the operation mode to “normal”. As a result, the engine 1 enters a normal operation mode in which the PM forced oxidation process is not performed.

  According to the exhaust gas purification device and the exhaust gas purification method disclosed herein, it is determined whether or not the inside of the PF is frozen or water-containing based on the differential pressure value before and after the PF and the PF outgas temperature. Also, in an area where the temperature is low, such as in a very cold region, if the internal combustion engine is stopped during the PM forced oxidation process, the PM forced oxidation process is performed when the internal combustion engine is next started up in a frozen or wet state. In this way, due to blockage of the exhaust gas passage in the PF with ice or water, a predetermined amount of air due to fuel injection from the internal combustion engine performed by the PM forced oxidation process does not enter the PF. Gas or white smoke may be discharged, which may cause malfunction. With the exhaust gas purification apparatus and the exhaust gas purification method having such a configuration, it is determined whether or not the PF is frozen or water-containing at the next start of the internal combustion engine when the internal combustion engine is stopped during the PM forced oxidation process. When the inside of the PF is frozen or hydrated, the PM forced oxidation treatment can not be performed. As a result, it is possible to prevent malfunction due to misfire of the internal combustion engine and discharge of HC gas or white smoke. In addition, since the particulate matter in the PF can be preferably removed, the fuel consumption rate is improved.

1 Internal combustion engine
DESCRIPTION OF SYMBOLS 2 Combustion chamber 3 Fuel injection valve 4 Intake manifold 5 Exhaust manifold 6 Intake duct 7 Exhaust turbocharger 8 Air flow meter 9 Air cleaner 10 Throttle valve 11 Cooling device 12 Exhaust passage 13 Exhaust fuel injection valve 18 Exhaust gas recirculation 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 Differential Pressure Sensor 54 Downstream Differential Pressure Sensor 56 Temperature Sensor 57 Oil Temperature Sensor 58 Water Temperature Sensor 80 Particulate Filter (PF)
82 Porous substrate 84 Flow path 100 Exhaust gas purification device

Claims (7)

An exhaust gas purification device provided in an exhaust system of an internal combustion engine,
A particulate filter (PF) for collecting particulate matter in the exhaust gas flowing in the exhaust passage provided in the internal combustion engine;
A differential pressure sensor for measuring a differential pressure between a pressure upstream of the exhaust passage relative to the PF and a pressure downstream of the PF downstream of the exhaust passage;
A temperature sensor for measuring the temperature of the exhaust gas downstream of the exhaust passage from the PF;
A control unit electrically connected to the differential pressure sensor and the temperature sensor, and
With
Here, when the internal combustion engine is started, the control unit measures a differential pressure value before and after the PF by the differential pressure sensor and measures an exhaust gas temperature downstream of the PF by the temperature sensor. An exhaust gas purification apparatus configured to perform a PF internal state determination process for determining whether or not the inside of the PF is frozen or water-containing based on the differential pressure value and the exhaust gas temperature. The control unit is configured to store a differential pressure value before and after the PF measured by the differential pressure sensor immediately before stopping the internal combustion engine,
Here, in the PF internal state determination process, it is determined that the differential pressure value measured at the start is 1.3 times or more of the differential pressure value measured immediately before the stop, and is measured at the start. The exhaust gas purification device according to claim 1, wherein the exhaust gas purification device is configured to determine that the inside of the PF is frozen or water-containing when the exhaust gas temperature is determined to be 70 ° C or lower. The control unit is configured to perform a process of forcibly oxidizing the particulate matter when the particulate matter deposited in the PF exceeds a predetermined amount,
Here, the control unit is configured not to perform the process of forcibly oxidizing the particulate matter while determining that the inside of the PF is frozen or containing water by the PF internal state determination process. The exhaust gas purification apparatus according to claim 1 or 2, wherein The control unit is configured to continuously perform the PF internal state determination process after the internal combustion engine is started.
Here, the process for forcibly oxidizing the particulate matter is performed after it is determined by the PF internal state determination process that the inside of the PF is not frozen or in a water-containing state. Exhaust gas purification equipment. A method for purifying exhaust gas discharged from an internal combustion engine having a particulate filter (PF) for collecting particulate matter in exhaust gas provided in an exhaust passage,
The differential pressure value between the pressure upstream of the exhaust passage from the PF and the pressure downstream of the exhaust passage from the PF is measured, and when the differential pressure value exceeds a predetermined differential pressure value, the PF Including forced oxidation treatment to forcibly oxidize the particulate matter inside
Here, at the time of starting the internal combustion engine, the measurement of the differential pressure value between the pressure upstream of the exhaust passage from the PF and the pressure downstream of the exhaust passage from the PF, and the exhaust from the PF An exhaust gas temperature on the downstream side of the passage is measured, and a PF internal state determination process is performed to determine whether or not the inside of the PF is frozen or water-containing based on the differential pressure value and the exhaust gas temperature. The exhaust gas purification method is characterized in that the forced oxidation process is not performed while the determination process determines that the inside of the PF is frozen or water-containing.   When the internal combustion engine is stopped during the forced oxidation process, the PF internal state determination process is continuously performed together with the restart of the internal combustion engine after the stop, and the inside of the PF is not in a frozen state or a water-containing state. 6. The exhaust gas purification method according to claim 5, wherein the forced oxidation process is resumed after the determination.   In the PF internal state determination process, it is determined that the differential pressure value measured at the start is 1.3 times or more of the differential pressure value measured immediately before the internal combustion engine is stopped, and the exhaust gas measured at the start 7. The exhaust gas purification method according to claim 5, wherein when the temperature is determined to be 70 ° C. or less, it is determined that the inside of the PF is frozen or water-containing.

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