JP2005023884A - Dpf clogging detection method and exhaust emission control system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a diesel particulate filter (DPF) clogging detection method using relatively less sensors and computation for precisely detecting the clogged condition of the DPF to determine a regeneration starting time for the DPF, and to provide an exhaust emission control system. <P>SOLUTION: The exhaust emission control system 1 has the DPF 40. A pressure loss coefficient ζc of the DPF and a Reynolds number Re of exhaust gas passing through the DPF 40 are calculated from a measured differential pressure ΔPm between the front and rear of the DPF, an exhaust temperature Tim in the DPF, exhaust pressure Pi at the inlet of the DPF and an exhaust flow rate Mexh detected by an exhaust flow rate detecting means. By comparing the calculated pressure loss coefficient ζc of the DPF with determined values ζsc, ζec calculated from data of pressure loss coefficients ζs, ζe for determination value previously created on the basis of the exhaust temperature Ti in the DPF and the Reynolds number Re, the clogged condition of the DPF 40 is detected. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a DPF clogging detection method and an exhaust gas purification system for detecting a clogged state of a DPF (diesel particulate filter) that collects particulate matter discharged from a diesel engine.
[0002]
[Prior art]
Emissions of particulate matter (PM: particulate matter: hereinafter referred to as PM) emitted from diesel engines have been strengthened year by year along with NOx, CO and HC. Improvement alone has made it impossible to respond. Therefore, a technology has been developed that collects PM discharged from the engine with a filter called a diesel particulate filter (DPF) and reduces the amount of PM discharged to the outside. Yes.
[0003]
The DPF that directly collects PM includes ceramic monolith honeycomb wall flow type filters and fiber type filters made of ceramic or metal fibers. Exhaust gas purification using these DPFs Similar to other exhaust gas purification systems, the system is installed in the middle of the exhaust passage of the engine and purifies exhaust gas generated by the engine.
[0004]
When the filter collects PM, the exhaust pressure rises in proportion to the amount collected, so it is necessary to regenerate the DPF by removing the collected PM by burning or the like. Various methods have been proposed for this regeneration method, including an electric heater heating type, a burner heating type, and a backwash type.
[0005]
However, when these regeneration methods are used, PM is burned by receiving energy supply from the outside, which leads to deterioration of fuel consumption, and control during regeneration is difficult, and PM collection, PM combustion (DPF) There is a problem that the system becomes large and complicated, such as requiring a two-system DPF system that alternately performs (regeneration).
[0006]
In order to solve this problem, a technique has been proposed in which the oxidation temperature of PM is lowered using an oxidation catalyst, and PM is oxidized by exhaust heat from the engine to regenerate DPF without receiving energy from the outside. In this case, since DPF regeneration is basically continuous, it is called a continuous regeneration type DPF system. However, these systems become a simpler one-system DPF system, and regeneration control is also simplified. There is an advantage that
[0007]
The NO ₂ regeneration type DPF system, which is one of the continuous regeneration type DPF systems, is a system for regenerating DPF by oxidizing PM with NO ₂ (nitrogen dioxide), and an oxidation catalyst upstream of a normal wall flow filter. A converter is arranged to oxidize NO (nitrogen monoxide) in the exhaust gas. Therefore, NOx in the exhaust gas of stream after the oxidation catalytic converter is mostly becomes NO _2. With this NO ₂ , the PM collected by the downstream filter 3Ab is oxidized to CO ₂ (carbon dioxide), and the PM is removed. Since NO ₂ has a smaller energy barrier than O _2, it lowers the PM oxidation temperature (DPF regeneration temperature), and therefore PM combustion occurs continuously with thermal energy in the exhaust gas without supplying energy from the outside.
[0008]
In this improved NO ₂ regeneration type DPF system, a porous catalyst coat layer of an oxidation catalyst is applied to the porous wall surface of the wall flow filter, and oxidation of NO and oxidation of PM by NO ₂ generated thereby are performed in the wall flow. It is configured to be performed on the wall surface of the filter, and the system is simplified by omitting the oxidation catalytic converter.
[0009]
There is also a system in which a porous catalyst coat layer of an oxidation catalyst and a PM oxidation catalyst such as an oxide is applied to the porous wall surface of the wall flow filter, PM accumulated in the filter is burned at a low temperature, and continuously regenerated.
[0010]
Each of these DPF systems with a catalyst is a system that realizes continuous regeneration of PM by lowering the PM oxidation start temperature than a normal filter by an oxidation reaction of PM with a catalyst and NO ₂ .
[0011]
However, even if the PM oxidation start temperature is lowered, an exhaust temperature of about 350 ° C. is still necessary, so in low load operation and idle operation, the exhaust temperature is low, so PM oxidation and DPF self-regeneration occur. Absent. Therefore, if the engine operation state where the exhaust temperature is low, such as idling or low load, continues, PM will not be oxidized even if PM accumulates, resulting in increased exhaust pressure, worsening fuel consumption, and engine stop Troubles such as this may occur.
[0012]
Therefore, in these continuous regeneration type DPF systems, the clogged state of the DPF is monitored, and when the clogged state exceeds a predetermined criterion, the exhaust temperature is forcibly increased to forcibly accumulate the PM. DPF regeneration control is performed to burn and remove.
[0013]
One method of detecting this clogging state is to obtain an exhaust flow rate and a filter pressure loss (differential pressure before and after DPF) from an intake flow rate sensor, an exhaust temperature sensor, and an exhaust pressure sensor. A method has been proposed in which regeneration is started when the measured filter pressure loss is larger than the regeneration start pressure loss compared to the regeneration start pressure loss (determination value pressure loss value) (see, for example, Patent Document 1).
[0014]
Also, the filter pressure loss is calculated from the pressure sensor that measures the DPF inlet pressure and the atmospheric pressure sensor, and the filter pressure loss is calculated based on the engine speed or the engine speed and boost pressure. Compared to the above, there has been proposed a method of starting regeneration when the measured filter pressure loss is larger than this pressure loss threshold (see, for example, Patent Document 2).
[0015]
Furthermore, the coefficient related to the filter pressure loss is calculated from the pressure loss and the atmospheric pressure upstream of the DPF, and the pressure loss of the exhaust flow rate measuring unit provided upstream of the DPF, and the pressure upstream of the DPF and the engine intake pressure A method has also been proposed in which a coefficient related to the filter pressure loss is calculated from the engine speed, the coefficient related to the filter pressure loss is compared with a threshold value, and regeneration is started if the coefficient is larger than the threshold value. (For example, refer to Patent Document 3).
[0016]
[Patent Document 1]
JP-A-9-13951 [0017]
[Patent Document 2]
Japanese Patent Laid-Open No. 2002-364342
[Patent Document 3]
Japanese Patent Laid-Open No. 2002-371829
[Problems to be solved by the invention]
As described above, in order to determine the start of regeneration of the DPF, an attempt is made to detect the clogged state of the DPF with various parameters. The pressure loss of the DPF is the actual operating state of the engine, that is, the engine load, the engine speed. Because of the influence of exhaust gas flow velocity, pressure, flow rate, temperature, etc., filter pressure loss based on exhaust flow rate, filter pressure loss based on engine speed, or factors related to filter pressure loss, etc. Comparing with the corresponding threshold values alone, problems such as insufficient clogging detection accuracy in determining the DPF regeneration timing, and problems such as an increase in the number of sensors and complicated control. There is.
[0020]
On the other hand, in the flow in the flow path, the pressure loss ΔP in the circular pipe is determined by the Nikraze experiment or the like, the fluid density is ρ, the average flow velocity is U, the pipe shaft length is L, the pipe diameter is d, and the pipe friction coefficient is when the λ, ΔP = λ * (ρ * U 2/2) * can be represented by the formula (L / d), the pipe friction coefficient lambda, especially in rough the circular pipe flow, in the case of turbulent flow When the fluid kinematic viscosity coefficient is μ, a function λ = Fλ (Re, Reynolds number Re = U * d / (μ / ρ) and relative roughness of the wall surface (standard roughness / tube diameter = ε / d) It is known that ε / d).
[0021]
Then, when the pressure loss coefficient ζ ζ = ΔP / (ρU 2 /2), ζ = λ * (L / d) , and the the pressure loss coefficient zeta, as with the pipe friction factor lambda, the Reynolds number Re and the wall of the Colebrook's equation that gives a function of relative friction (ε / d) ζ = Fζ (Re, ε / d) and gives a pipe friction coefficient of a practical pipe approximately, and a Moody diagram that summarizes this equation in a diagram As can be seen from the above, when the Reynolds number Re is fixed, the pressure loss coefficient ζ is monotonous with respect to the relative roughness (ε / d) in a turbulent region where the Reynolds number Re and the relative roughness (ε / d) are relatively large. Increase function.
[0022]
In the PM collection process of the DPF, the PM adheres to the wall surface of the exhaust gas passage of the DPF, and the increase in the adhered PM increases the relative roughness (ε / d) of the wall surface. The flow in the DPF is similar to the flow in the pipe. Based on the Reynolds number Re, it is considered that the accumulated state of PM, that is, the clogged state of the DPF can be detected from the pressure loss coefficient ζ.
[0023]
The present invention has been made in order to solve the above-mentioned problems by obtaining these findings. The purpose of the present invention is to detect DPF clogging in order to determine the DPF regeneration start time and regeneration end time. Using the fact that the pressure loss coefficient becomes a monotone function of the wall roughness when the exhaust temperature and the Reynolds number are constant, it is possible to accurately detect the clogged state of the DPF with relatively few sensors and calculations. An object of the present invention is to provide a DPF clogging detection method and an exhaust gas purification system.
[0024]
[Means for Solving the Problems]
A method for detecting clogging of a DPF for achieving the above object includes a DPF that collects particulate matter in an exhaust passage of an internal combustion engine, a differential pressure sensor that detects a differential pressure across the DPF, and the DPF In the exhaust gas purification system comprising an exhaust temperature sensor for detecting the exhaust temperature inside the exhaust gas, an inlet exhaust pressure sensor for detecting the exhaust pressure at the inlet of the DPF, and an exhaust flow rate detecting means for detecting the exhaust flow rate, DPF differential pressure measured by the pressure sensor, DPF internal exhaust temperature measured by the exhaust temperature sensor, DPF inlet exhaust pressure measured by the inlet exhaust pressure sensor, and detected by the exhaust flow rate detecting means From the exhaust flow rate, the pressure loss coefficient of the DPF and the Reynolds number of the exhaust gas passing through the DPF are calculated, and the calculated pressure loss coefficient of the DPF is calculated using the DPF internal exhaust temperature and the Reynolds number. By comparing the determined value calculated from the data of the previously prepared determined values for pressure loss coefficient number based, and detecting the clogging of the DPF.
[0025]
In the DPF clogging detection method described above, whether the pressure loss coefficient data for the determination value is data for determining whether to start the regeneration control of the DPF, or whether the regeneration control of the DPF is to be terminated. It is characterized in that it is at least one of data for judging whether or not reproduction is complete.
[0026]
Here, the pressure loss coefficient zeta, [Delta] P the DPF differential pressure, the density of the exhaust gas [rho, the average flow rate through the DPF when a U, the value represented by ^{ζ = ΔP / (ρU 2/} 2) is there.
[0027]
According to the DPF clogging detection method of the present invention, the clogged state of the DPF that progresses as PM is collected in the exhaust gas is simulated by the pressure loss in the rough pipe flow, and the exhaust gas temperature and Reynolds. Since the pressure loss coefficient based on the number is adopted as the criterion, the clogging state can be estimated with high accuracy.
[0028]
When PM accumulation in the DPF is considered as an increase in the relative roughness (ε / d) of the wall surface, and the flow of the DPF is considered to be a flow in a rough pipe, the pressure loss coefficient ζ of the DPF is the flow of the flow in the rough pipe. As with the pipe friction coefficient λ, the function ζ = Fζ (Re, ε / d) of the Reynolds number Re and the relative roughness (ε / d) of the wall surface, and the exhaust temperature T only has an effect on the Reynolds number Re. In practice, however, the exhaust temperature affects the viscosity of the exhaust gas, and thus affects ε / d through the state of the laminar flow near the inner wall surface of the exhaust passage. Further, since there is a change in the size of the exhaust passage (cell, etc.) due to the thermal expansion of the DPF itself, it has been experimentally found that the pressure loss coefficient ζ of the DPF also differs if the exhaust temperature T is different even if the Reynolds number Re is the same. Yes. Therefore, when the PM accumulation state, that is, the clogged state of the DPF is detected from the pressure loss coefficient ζ, it is necessary to consider not only the Reynolds number Re but also the exhaust temperature T. Therefore, in the present invention, the Reynolds number Re At the same time, the exhaust temperature T is used as a base.
[0029]
An exhaust gas purification system for realizing the DPF clogging detection method includes a DPF that collects particulate matter in an exhaust passage of an internal combustion engine, and a regeneration control means for regenerating the DPF. In the exhaust gas purification system provided, a differential pressure sensor that detects a differential pressure across the DPF, an exhaust temperature sensor that detects an exhaust temperature inside the DPF, and an inlet exhaust pressure that detects an exhaust pressure at the inlet of the DPF A sensor and an exhaust flow rate detecting means for detecting an exhaust flow rate, wherein the regeneration control means includes a differential pressure across the DPF measured by the differential pressure sensor, and an internal exhaust temperature of the DPF measured by the exhaust temperature sensor. From the DPF inlet exhaust pressure measured by the inlet exhaust pressure sensor and the exhaust flow rate detected by the exhaust flow rate detecting means, the DPF pressure loss coefficient and the D The Reynolds number of the exhaust gas passing through F is calculated, and the calculated pressure loss coefficient of the DPF is a judgment value calculated from the pressure loss coefficient data for the judgment value prepared in advance based on the DPF internal exhaust temperature and the Reynolds number. By comparing, it is characterized by detecting the clogged state of the DPF.
[0030]
Further, the exhaust gas purification system uses the DPF front-rear differential pressure measured instead of the pressure loss coefficient, and compares it with the determination value for the DPF front-rear differential pressure calculated from the data of the determination value pressure-loss coefficient. Thus, the clogged state of the DPF is detected.
[0031]
That is, when comparing, without calculating the pressure loss coefficient from the measured differential pressure across the DPF, the density and average flow velocity are used based on the pressure loss coefficient for the judgment value obtained from the data of the pressure loss coefficient for the judgment value. A determination value for differential pressure across the DPF is calculated and compared to detect a clogged state of the DPF.
[0032]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a DPF clogging detection method and an exhaust gas purification system according to an embodiment of the present invention will be described with reference to the drawings, taking as an example a continuous regeneration DPF including an oxidation catalytic converter and a filter with a catalyst.
[0033]
FIG. 1 shows a configuration of an exhaust gas purification system 1 according to this embodiment. In the exhaust gas purification system 1, a continuous regeneration type DPF (hereinafter referred to as DPF) 40 that collects PM (particulate matter) in exhaust gas and removes it by combustion is disposed in an exhaust pipe 30 of the diesel engine 10. The DPF 40 includes an oxidation catalytic converter 40a on the upstream side and a filter 40b with a catalyst on the downstream side.
[0034]
The oxidation catalyst converter 40a is formed by supporting an oxidation catalyst such as platinum (Pt) on a support such as a porous ceramic honeycomb structure, and the catalyst-equipped filter 40b is formed of a porous ceramic honeycomb channel. It is formed by a monolith honeycomb wall flow type filter in which the inlet and the outlet are alternately sealed. An oxidation catalyst such as platinum or a PM oxidation catalyst such as cerium oxide is supported on the filter portion. In the filter with catalyst 40b, PM in the exhaust gas G is collected (trapped) by a porous ceramic wall.
[0035]
A mass airflow (MAF) sensor 11 that detects an intake mass flow rate Mm in the intake pipe 20 of the engine 10 is a differential pressure sensor 41 that detects a differential pressure ΔPm across the DPF 40 in a conduction pipe connected to the front and rear of the DPF 40. Further, the DPF 40 is provided with an exhaust temperature sensor 42 for detecting the exhaust temperature Tim inside, and an inlet exhaust pressure sensor 43 for detecting the exhaust pressure Pim at the DPF inlet. The output values of these sensors are input to a control device (electronic control box: ECU: engine control unit) 50 that performs overall control of the operation of the engine 10 and also controls regeneration of the DPF 40.
[0036]
In this control device, the clogged state of the DPF 40 is detected from the measured values from the sensors 11, 41, 42, and 43 and various data inputted in advance, and the clogged state exceeds a predetermined regeneration start reference. The regeneration control is performed for regeneration of the DPF 40, and when the clogged state of the DPF 40 becomes a predetermined regeneration termination reference, the regeneration control is terminated. Note that this predetermined reproduction start reference is set according to the necessity of the reproduction control, and is not necessarily set so that the reproduction is started not only in a full clogged state but also in a half clogged state. Also good.
[0037]
The regeneration control differs depending on the type of the DPF 40. For example, the fuel injection valve, the exhaust throttle valve, the intake air intake valve, and the like of the engine 10 are controlled by the control signal output from the control device 50 to flow into the DPF 40. The temperature of the exhaust gas G to be raised is raised to a temperature equal to or higher than the combustion start temperature of the PM collected by the DPF 40, and the collected PM is burned and removed to regenerate the DPF 40.
[0038]
In the regeneration control of the exhaust gas purification system 1, the detection of the clogged state of the DPF 40 and the determination of the start of the regeneration control and the end of the regeneration control are performed. This determination is illustrated in FIGS. 2 and 3. Such a clogging state determination control flow is performed. The control flow illustrated in FIG. 2 and FIG. 3 is shown as a control flow that is repeatedly called from the main control flow and executed.
[0039]
That is, when the main control program for controlling the entire engine starts with the start of the engine, it is repeatedly called as necessary from the main control flow or the DPF regeneration control flow that is a sub-flow of the main control flow, and the clogging in FIG. The state determination control flow starts, executes this control flow, and returns to the main control flow or the like. Then, the control flow of FIG. 2 is repeatedly executed until the main control flow ends.
[0040]
When the clogging state determination control flow of FIG. 2 starts, calculation data and a determination value data map are input in step S11.
[0041]
The calculation data includes the cross-sectional area A of the exhaust gas G for obtaining the average exhaust gas flow velocity U, the Reynolds number dimension d, and the relationship between the exhaust gas temperature T and the viscosity μ, which is exhaust gas viscosity calculation data. Data (μ = fμ (T)), the density ρ0 of the exhaust gas in the reference state (reference pressure P0, reference temperature T0), and the like. The passage cross-sectional area A is a value such as the sum of the cross-sectional area of the flow path and the cell in the DPF, and the dimension d for the Reynolds number is a value for calculating the Reynolds number Re. Is a fixed value representative of the dimension of the portion through which, for example, the pipe diameter of the DPF, the inner diameter of the cell of the DPF, and the like.
[0042]
Further, the determination value data map includes a regeneration start determination value ζs = Fζs (Re, T) for determining whether or not to start the regeneration control of the DPF 40, and whether or not to terminate the regeneration control of the DPF 40. There is a reproduction end determination value ζe = Fζe (Re, T) for determination. In this determination value data map, when the exhaust gas temperature T is constant, based on the Reynolds number Re, the determined regeneration start determination value ζs and regeneration end determination value ζe are converted into map-like data. Is. When the exhaust temperature T is constant, the horizontal axis is the base of the Reynolds number Re, and the regeneration start determination value ζs is plotted on the vertical axis, the result is as shown in FIG.
[0043]
In the next step S12, measured values of the intake flow rate (intake mass flow rate) Mm, the fuel injection amount Qf, the DPF internal exhaust temperature Tim, the DPF front-rear differential pressure ΔPm, and the DPF inlet pressure Pim are input. The intake air flow rate Mm is detected by the mass airflow sensor 11, the DPF internal exhaust temperature Tim is detected by the exhaust temperature sensor 42, the DPF differential pressure ΔPm is detected by the differential pressure sensor 41, and the DPF inlet pressure Pim is detected by the inlet exhaust pressure sensor 43. The fuel injection amount Qf is a value instructed by engine control.
[0044]
In the next step S13, the exhaust gas viscosity μc = fμ (Tim), density ρc = ρ0 * (Pim / P0) * (T0 / Tim), and average flow velocity Uc = Mexh / (ρc * A) are calculated. . Mexh is an exhaust flow rate (exhaust mass flow rate) calculated from the intake air flow rate Mm measured by the mass air flow sensor 11 and the fuel injection amount Qf, and the exhaust flow rate accompanied by the input of the mass air flow sensor 11 and the fuel injection amount Qf. Exhaust flow rate detection means is configured by calculation means for calculating Mexh.
[0045]
Then, to calculate the Reynolds number Rec = Uc * d / (μc / ρc) in step S14, to calculate the pressure loss coefficient ^{ζc = ΔPm / (ρc * Uc} 2/2) in step S15. Further, in step S16, the regeneration start determination value ζsc = Fζs (Rec, Tim) from the determination value data of the regeneration start determination value ζs = Fζs (Re, T) where the exhaust temperature T is Tim and the Reynolds number Re is Rec. Is calculated. This calculation is obtained by calculation from the function Fζs or by referring to a data map of the regeneration start determination value ζs based on the Reynolds number Re and the exhaust temperature T.
[0046]
In step S17, the pressure loss coefficient ζc calculated in step S15 is compared with the regeneration start determination value ζsc calculated in step S16 to determine the clogged state of the DPF.
[0047]
If the pressure loss coefficient ζc is smaller than the regeneration start determination value ζsc, it is determined that there is no clogging that requires regeneration control, and the process returns to step S12. If the pressure loss coefficient ζc is equal to or greater than the regeneration start determination value ζsc, it is determined that the clogged state requires regeneration control, and the DPF clogging signal Is is turned ON (Is = 1) in step S18. Then, the reproduction starts in step S19, and the reproduction control of another flow is started. When the reproduction start is finished, the flow of FIG. 2 returns, is called again, starts, and steps S11 to S19 are repeated.
[0048]
Note that, in the case of the reproduction end determination, as shown in FIG. 3, step S16 to step S19 are changed to step S16A to step S19A.
[0049]
In step S16A, instead of the regeneration start determination value ζsc, from the determination value data of regeneration end determination value ζe = Fζe (Re, T), the regeneration end determination in which the exhaust temperature T is Tim and the Reynolds number Re is Rec. The value ζec = Fζe (Rec, Tim) is calculated. This calculation is obtained by calculation from the function Fζe or by referring to a data map of the regeneration end determination value ζe based on the Reynolds number Re and the exhaust temperature T.
[0050]
In step S17A, the pressure loss coefficient ζc calculated in step S15 is compared with the regeneration end determination value ζse calculated in step S16A to determine the clogged state of the DPF. When the pressure loss coefficient ζc is larger than the regeneration end determination value ζse, it is determined that the clogging is necessary for the regeneration control, and the process returns to step S12. If the pressure loss coefficient ζc is equal to or less than the regeneration end determination value ζse, it is determined that the regeneration control may be terminated, and the DPF clogging signal Is is turned off (Is = Is = S18A). 0), the reproduction ends in step S19A, and reproduction control of another flow is started.
[0051]
Further, by using the DPF front-rear differential pressure ΔPm measured instead of the pressure loss coefficient, and comparing it with the DPF front-rear differential pressure determination values ΔPms, ΔPme calculated from the determination value pressure-loss coefficient data, You may comprise so that a clogged state may be detected.
[0052]
In this configuration, the pressure loss coefficient ζc is not calculated from the measured differential pressure before and after the DPF ΔPm, and the density ρc and the average flow velocity are calculated based on the determination value pressure loss coefficients ζs and ζe obtained from the determination value pressure loss coefficient data. The determination values ΔPs (= ζs * ρc * Uc * Uc / 2) and ΔPe (= ζe * ρc * Uc * Uc / 2) for the differential pressure across the DPF are calculated using Uc, and the measured differential across the DPF is calculated. The clogged state of the DPF is detected by comparing the pressure ΔPm with the determination value ΔPs (or ΔPe) for the differential pressure across the DPF.
[0053]
In other words, when the measured DPF front-rear differential pressure ΔPm is equal to or larger than the DPF front-rear differential pressure determination value ΔPs, which is the regeneration start determination value, it is determined that the clogged state requires regeneration control, and the regeneration ends. If it is equal to or less than the DPF front-rear differential pressure determination value ΔPe, it is determined that the regeneration control may be terminated.
[0054]
By these clogging state determination control, the clogging state of the DPF 40 can be estimated with high accuracy.
[0055]
Next, creation of determination value data will be described.
The determination value data is obtained by making the DPF clogged at the start of regeneration. In this state, the engine operating state is changed, the exhaust temperature Tim and the Reynolds number Rec are changed, and the DPF pressure loss coefficient ζsc is calculated. In this state, the relationship between the exhaust temperature Tim, the Reynolds number Rec, and the DPF pressure loss coefficient ζsc is obtained, the DPF pressure loss coefficient ζs is arranged based on the exhaust temperature T and the Reynolds number Re, and the DPF regeneration start determination value ζs = A function and a data map of Fζs (Re, T) are created.
[0056]
Further, the DPF is made clogged at the end of regeneration, and in this state, the engine operating state is changed, the exhaust temperature Tim and the Reynolds number Rec are changed, and the DPF pressure loss coefficient ζec is calculated. The exhaust temperature in this state The relationship between Tim, the Reynolds number Rec, and the DPF pressure loss coefficient ζec is obtained, the DPF pressure loss coefficient ζe is arranged based on the exhaust temperature T and the Reynolds number Re, and the DPF regeneration end determination value ζe = Fζe (Re, T ) Functions and data maps.
[0057]
The reproduction start determination value ζs = Fζs (Re, T) and the reproduction end determination value ζe = Fζe (Re, T) are input to the control device in advance in the form of a function, a data map, or the like. The
[0058]
In the above description, the continuous regeneration type DPF including the upstream oxidation catalyst converter and the downstream filter with catalyst has been described as an example. However, the present invention includes an oxidation catalyst converter and a filter that does not carry a catalyst. Continuous regeneration type DPF, continuous regeneration type DPF in which an oxidation catalyst and a PM oxidation catalyst are supported on a filter with a catalyst without an oxidation catalyst converter, and a DPF composed of a filter that does not carry a catalyst (a DPF that does not belong to the continuous regeneration type) ) And the like.
[0059]
【The invention's effect】
As described above, according to the DPF clogging detection method and the exhaust gas purification system of the present invention, the clogged state of the DPF that progresses with the collection of PM in the exhaust gas is imitated by a rough flow in the pipe. Thus, the pressure loss coefficient based on the temperature of the exhaust gas flowing through the DPF and the Reynolds number is adopted as a criterion for detecting the clogged state of the DPF, so that the clogged state can be estimated with high accuracy.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an exhaust gas purification system according to the present invention.
FIG. 2 is a diagram showing an example of a control flow for clogging determination for starting regeneration control according to the embodiment of the present invention.
FIG. 3 is a diagram showing an example of a control flow for clogging determination at the end of regeneration control according to the embodiment of the present invention.
FIG. 4 is a diagram schematically showing a data map of reproduction start determination values according to the present invention.
[Explanation of symbols]
1 Exhaust Gas Purification System 11 Mass Air Flow Sensor 20 Exhaust Passage 40 Continuous Regeneration DPF (DPF)
41 Differential pressure sensor 42 Exhaust temperature sensor 43 Inlet exhaust pressure sensor A Exhaust gas passage cross section d Reynolds number dimension Is DPF clogging signal Mm Intake mass flow rate Mexh Exhaust mass flow rate P0 Reference pressure Pim DPF inlet pressure ΔPm Differential pressure across DPF Qf Fuel injection amount Re, Rec Reynolds number T0 Reference temperature T, Ti, Tim DPF internal exhaust temperature U, Uc Average exhaust gas flow velocity μ, μc Exhaust gas viscosity ρ0 Exhaust gas reference density ρc Exhaust gas density ζ , Ζc Pressure loss coefficient ζs, ζsc Reproduction start judgment value

Claims (4)

A DPF that collects particulate matter in an exhaust passage of the internal combustion engine; a differential pressure sensor that detects a differential pressure across the DPF; an exhaust temperature sensor that detects an exhaust temperature inside the DPF; and an inlet of the DPF In an exhaust gas purification system comprising an inlet exhaust pressure sensor for detecting an exhaust pressure and an exhaust flow rate detecting means for detecting an exhaust flow rate,
Detected by the exhaust flow rate detecting means, the DPF differential pressure measured by the differential pressure sensor, the DPF internal exhaust temperature measured by the exhaust temperature sensor, the DPF inlet exhaust pressure measured by the inlet exhaust pressure sensor, and the exhaust flow rate detecting means. From the exhaust flow rate calculated, the pressure loss coefficient of the DPF and the Reynolds number of the exhaust gas passing through the DPF are calculated,
The clogged state of the DPF is detected by comparing the calculated pressure loss coefficient of the DPF with a determination value calculated from the pressure loss coefficient data for the determination value prepared in advance based on the DPF internal exhaust temperature and the Reynolds number. A method for detecting clogging of a DPF, characterized in that The determination value pressure loss coefficient data is at least one of data for determining whether or not to start regeneration control of the DPF and data for determining whether or not to end regeneration control of the DPF. The DPF clogging detection method according to claim 1, wherein: In an exhaust gas purification system provided with a DPF for collecting particulate matter in an exhaust passage of an internal combustion engine, and provided with a regeneration control means for regenerating the DPF,
A differential pressure sensor that detects a differential pressure across the DPF, an exhaust temperature sensor that detects an exhaust temperature inside the DPF, an inlet exhaust pressure sensor that detects an exhaust pressure at the inlet of the DPF, and an exhaust flow rate An exhaust flow rate detecting means,
The regeneration control means includes a differential pressure across the DPF measured by the differential pressure sensor, a DPF internal exhaust temperature measured by the exhaust temperature sensor, a DPF inlet exhaust pressure measured by the inlet exhaust pressure sensor, The DPF pressure loss coefficient and the Reynolds number of the exhaust gas passing through the DPF are calculated from the exhaust flow rate detected by the exhaust flow rate detecting means, and the calculated DPF pressure loss coefficient is based on the DPF internal exhaust temperature and the Reynolds number. An exhaust gas purification system that detects a clogged state of the DPF by comparing with a judgment value calculated from data of a judgment value pressure loss coefficient prepared in advance. The clogged state of the DPF is detected by using the differential pressure before and after the DPF measured instead of the pressure loss coefficient and comparing it with the determination value for the differential pressure before and after the DPF calculated from the pressure loss coefficient data for the determination value. The exhaust gas purification system according to claim 3.

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