JP2004132201A - Clogging detection device for particulate filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a clogging detection device with good loadability capable of easily and surely determining clogging occurring in a particulate filter with a simple mechanism. <P>SOLUTION: The clogging detection device for a particulate filter 12 equipped in the middle of an exhaust pipe 11 through which exhaust gas 9 flows, is equipped with an air flow meter 17 for measuring a suction air amount in the middle of a suction pipe 5, and a determination device 18 for determining clogging of the particulate filter 12 when an abnormal reduction of the suction air amount is confirmed based on an actually measured value by the air flow meter 17. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a device for detecting clogging of a particulate filter.
[0002]
[Prior art]
Particulate matter (particulate matter) discharged from the diesel engine is mainly composed of soot composed of carbonaceous material and SOF component (Soluble Organic Fraction: soluble organic component) composed of a high-boiling hydrocarbon component. Although it has a composition containing a small amount of sulfate (mist-like sulfuric acid component), as a measure to reduce this kind of particulates, it is necessary to equip a particulate filter in the middle of the exhaust pipe through which exhaust gas flows. This has been done conventionally.
[0003]
This kind of particulate filter has a porous honeycomb structure made of ceramic such as cordierite, and the inlets of the respective flow paths partitioned in a lattice are alternately plugged, and the inlets are not plugged. The outlets of the flow passages are sealed so that only the exhaust gas that has passed through the thin porous wall that defines each flow passage is discharged to the downstream side.
[0004]
Since the particulates in the exhaust gas are collected and deposited on the inner surface of the porous thin wall, the particulates are appropriately burned and removed before the exhaust resistance increases due to clogging, and the particulate filter is removed. It is necessary to regenerate, but in the normal diesel engine operating state, there is little chance of obtaining a high exhaust temperature enough for the particulates to self-burn, so for example, an appropriate amount of platinum supported on alumina A catalyst regeneration type particulate filter integrally supporting an oxidation catalyst formed by adding a rare earth element such as cerium has been put into practical use.
[0005]
That is, if such a catalyst regeneration type particulate filter is employed, the oxidation reaction of the collected particulates is promoted, the ignition temperature is lowered, and the particulates can be burned and removed even at a lower exhaust temperature than before. It is possible.
[0006]
However, even when such a catalyst regeneration type particulate filter is employed, the oxidation catalyst carried on the particulate filter has an active temperature range, and the exhaust temperature is lower than the active lower limit temperature. If the operating state of the above is continued, a problem may occur that the particulates are not satisfactorily burnt and removed because the oxidation catalyst is not activated.
[0007]
For this reason, a fuel adding means for adding fuel to the exhaust gas on the upstream side of the particulate filter is provided, and the fuel added by the fuel adding means is oxidized on the oxidation catalyst, and the heat of the reaction reduces the catalyst bed temperature. It is considered to perform regeneration control to raise and actively combust and remove the collected particulates.However, if regeneration control is not performed at appropriate intervals due to some problem, If the particulate filter is left with insufficient regeneration, the particulate filter will be clogged and the engine performance will be adversely affected by an increase in exhaust pressure, or a large amount of accumulated particulates will burn rapidly and become particulates. There is a concern that the filter may be damaged.
[0008]
Therefore, the applicant of the present invention has already filed a patent document 1 below as a device for detecting clogging of a particulate filter. In this prior application, as shown in FIG. A differential pressure sensor e is connected to the inlet side and the outlet side of the filter case b via pressure extracting pipes c and d, and the differential pressure sensor e measures the differential pressure before and after the particulate filter a. A technique is disclosed in which clogging of the particulate filter a is determined based on the actually measured differential pressure.
[0009]
[Patent Document 1]
Japanese Patent Application No. 2001-355066 [0010]
[Problems to be solved by the invention]
However, the detection method employing the differential pressure sensor e for measuring the differential pressure before and after the particulate filter a is susceptible to exhaust pulsation (exhaust pressure fluctuation caused by an intermittent exhaust cycle). There is a problem that it is difficult to determine the true value due to the need for variation correction. Also, a differential pressure sensor e to be attached to the outer peripheral portion of the filter case b and a relatively long pipe c for extracting pressure are used. , D are likely to cause interference with peripheral structures, so that there is a problem that the mountability to a vehicle is deteriorated.
[0011]
The present invention has been made in view of the above-described circumstances, and provides a clogging detection device with good mountability, which can easily and reliably determine clogging generated in a particulate filter by a simple mechanism. The purpose is.
[0012]
[Means for Solving the Problems]
The present invention is a device for detecting clogging of a particulate filter provided in the middle of an exhaust pipe through which exhaust gas flows, and an air flow meter that is mounted in the middle of an intake pipe and measures an intake air flow rate. A determination device that determines that the particulate filter is clogged when an abnormal decrease in the intake air flow rate is confirmed based on the actually measured value.
[0013]
Thus, when the particulate filter is clogged in this way, the exhaust pressure increases due to a large increase in exhaust resistance, and the same state as before the clogging occurs even in the same operation state. Since the intake air flow is significantly reduced in comparison, the determination device determines that the particulate filter is clogged when an abnormal decrease in the intake air flow is confirmed based on the actual measurement value measured by the air flow meter. Will be dropped.
[0014]
Further, in practicing the present invention more specifically, the determination device for determining clogging of the particulate filter is configured such that the particulate matter is measured at the same measurement point as an actual measurement value measured at a predetermined measurement point in a steady state of the internal combustion engine. Determines the deviation from the reference value measured when the filter is not clogged, and determines that the particulate filter is clogged if this deviation exceeds the allowable deviation for clogging determination. It is preferred that
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0016]
1 and 2 show an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a diesel engine equipped with a turbocharger 2, and intake air 4 guided from an air cleaner 3 is used as an intake pipe 5 To the compressor 2a of the turbocharger 2, the intake air 4 pressurized by the compressor 2a is sent to the intercooler 6 where it is cooled, and the intake air 4 further flows from the intercooler 6 to the intake manifold 7. It is guided and distributed to each cylinder 8 of the diesel engine 1 (FIG. 1 illustrates the case of in-line six cylinders).
[0017]
Further, the exhaust gas 9 discharged from each cylinder 8 of the diesel engine 1 is sent to the turbine 2b of the turbocharger 2 via the exhaust manifold 10, and the exhaust gas 9 that drives the turbine 2b is exhausted by the exhaust pipe 11 (exhaust gas). Through the flow path).
[0018]
In the middle of the exhaust pipe 11, a catalyst regeneration type particulate filter 12 integrally supporting an oxidation catalyst is mounted and held in a filter case 13, and is shown in an enlarged scale in FIG. As described above, the particulate filter 12 has a porous honeycomb structure made of ceramic, and the inlets of the respective flow paths 12a partitioned in a lattice are alternately plugged, and the inlets are not plugged. As for 12a, the outlet thereof is plugged, and only the exhaust gas 9 that has passed through the porous thin wall 12b that defines each flow path 12a is discharged to the downstream side.
[0019]
Further, in the example shown in FIG. 1, one end of the exhaust manifold 10 in the direction in which the cylinders 8 are arranged and one end of the intake pipe 5 connected to the intake manifold 7 are connected by an EGR pipe 14. A part of the exhaust gas 9 extracted from the exhaust manifold 10 is recirculated to the intake pipe 5 via a water-cooled EGR cooler 15 and an EGR valve 16, and is recirculated from the exhaust side to the intake side. The generation of NOx can be reduced by suppressing the combustion of fuel in each cylinder 8 with the exhaust gas 9 and lowering the combustion temperature.
[0020]
An air flow meter 17 for measuring an intake flow rate is provided between the air cleaner 3 and the compressor 2a in the intake pipe 5, and a detection signal 17a of the air flow meter 17 forms an engine control computer (ECU: Electronic Control Unit). This is input to the determination device 18. In the determination device 18, the particulate filter 12 is checked at the same measurement point as the actual measurement value measured at a predetermined measurement point in the steady state of the diesel engine 1. A deviation from a reference value measured without clogging is determined, and if this deviation exceeds an allowable deviation for clogging determination, it is determined that the particulate filter 12 is clogged. .
[0021]
Further, since the determination device 18 in the present embodiment also serves as an engine control computer, it also controls fuel injection, and more specifically, detects the accelerator opening as the load of the diesel engine 1. Fuel is supplied to each cylinder 8 of the diesel engine 1 on the basis of an accelerator opening signal 19a from an accelerator sensor 19 (load sensor) and a rotation speed signal 21a from a rotation sensor 21 for detecting the engine rotation speed of the diesel engine 1. A fuel injection signal 20a for instructing a fuel injection timing and an injection amount to the fuel injection device 20 to be injected is output. When the fuel injection signal 20a is output, the operation state of the diesel engine 1 is determined. 18 so that they can always be grasped.
[0022]
Further, a warning lamp 22 is provided on an instrument panel or the like in the driver's seat to turn on upon receiving a warning signal 22a when the determination device 18 determines that the particulate filter 12 is clogged.
[0023]
Thus, when the particulate filter 12 is clogged, the exhaust pressure increases due to a large increase in the exhaust resistance, and the state before the clogging occurs even in the same operation state. Since the intake air flow rate is significantly reduced as compared to the actual measurement value measured by the air flow meter 17 at a predetermined measurement point in the steady state of the diesel engine 1, the particulate filter 12 is not clogged at the same measurement point. When the deviation from the reference value measured in the state exceeds the allowable deviation for clogging determination, the determination device 18 determines that the particulate filter 12 is clogged, and a warning is issued from the determination device 18. The signal 22a is output, and the warning lamp 22 on the instrument panel or the like in the driver's seat is turned on.
[0024]
Therefore, according to the above-described embodiment, the variation corresponding to the operating state of the diesel engine 1 is small without targeting the differential pressure across the particulate filter 12 under the influence of the exhaust pulsation as in the conventional differential pressure sensor. Since the clogging of the particulate filter 12 is determined based on the intake flow rate at which an actually measured value is obtained, the particulate matter can be easily and reliably determined by an extremely simple mechanism in which the air flow meter 17 is disposed in the middle of the intake pipe 5. Clogging of the curated filter 12 can be determined.
[0025]
In addition, the air flow meter 17 is employed as compared with the case where a differential pressure sensor and each pipe for extracting pressure (see FIG. 3) are additionally provided on the outer peripheral portion of the filter case 13 on the exhaust pipe 11 side where layout conditions are severe. In this case, since a small space is required only for installation in the middle of the intake pipe 5, interference with peripheral structures is less likely to occur, and mountability to a vehicle can be greatly improved.
[0026]
Particularly, in the present embodiment, an EGR pipe 14 for recirculating a part of the exhaust gas 9 extracted from the exhaust manifold 10 to the intake pipe 5 via a water-cooled EGR cooler 15 and an EGR valve 16 is provided. Although illustrated, in the diesel engine 1 having such an exhaust gas 9 recirculation device, the intake flow rate is used for correcting the recirculation amount of the exhaust gas 9 by the EGR valve 16. Since it is general, an existing air flow meter for measuring the intake flow rate used for correcting the recirculation amount of the exhaust gas 9 is also used as the air flow meter 17 for determining the clogging of the particulate filter 12. In this case, it is not necessary to newly equip the air flow meter 17, so that the cost can be largely reduced.
[0027]
The device for detecting clogging of a particulate filter according to the present invention is not limited to the above-described embodiment, and it goes without saying that various changes can be made without departing from the spirit of the present invention.
[0028]
【The invention's effect】
According to the particulate filter clogging detection device of the present invention described above, the operation state of the diesel engine is not determined without targeting the differential pressure across the particulate filter under the influence of exhaust pulsation as in the conventional differential pressure sensor. Since the clogging of the particulate filter is determined based on the intake flow rate at which an actual measured value with a small variation corresponding to the above is obtained, it can be easily and easily realized by an extremely simple mechanism in which an air flow meter is arranged in the middle of the intake pipe. Clogging of the particulate filter can be determined with certainty, and compared with the case where a differential pressure sensor and pressure extraction pipes are attached to the outer peripheral part of the filter case on the exhaust pipe side where layout conditions are severe. When using an air flow meter, it is necessary to install Since suffices Do arrangement space, an excellent effect equal variety that can be easily occur interference with peripheral structure greatly improves the mountability on a vehicle.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an example of an embodiment for carrying out the present invention.
FIG. 2 is a sectional view showing details of the particulate filter of FIG. 1;
FIG. 3 is a schematic view showing a conventional example.
[Explanation of symbols]
1 diesel engine (internal combustion engine)
4 Intake 5 Intake pipe 8 Cylinder 9 Exhaust gas 11 Exhaust pipe 12 Particulate filter 17 Air flow meter 17a Detection signal 18 Judgment device

Claims (2)

A clogging detection device for a particulate filter mounted in the middle of an exhaust pipe through which exhaust gas flows, based on an air flow meter mounted in the middle of the intake pipe and measuring the intake flow rate, based on a value measured by the air flow meter. A determination device for determining that the particulate filter is clogged when an abnormal decrease in the intake air flow rate is confirmed. The determination device that determines clogging of the particulate filter is an actual measurement value measured at a predetermined measurement point in a steady state of the internal combustion engine, and a reference value measured at the same measurement point without clogging the particulate filter. 2. The method according to claim 1, wherein a deviation from the particulate filter is determined, and when the deviation exceeds an allowable deviation for clogging determination, it is determined that the particulate filter is clogged. For detecting clogging of particulate filters.

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