JP2005114557A - Soot measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a soot measuring apparatus suited for continuous monitoring of the amount of soot in a vehicle in service. <P>SOLUTION: The apparatus for measuring soot contained in gas discharged from an internal combustion engine is provided. The apparatus 6 comprises a flat-plate shaped cathode 3B a flat-plate shaped anode 3A provided opposite to the cathode 3B, a voltage application means 5 for generating an electric field at space 4 between the cathode 3B and the anode 3A, and a heating means 1 for heating the cathode 3B and the anode 3A. Soot is measured from a change in the current value between the cathode and the anode when voltage is applied between the cathode 3B and the anode 3A. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an apparatus for measuring soot contained in gas discharged from an internal combustion engine such as a diesel engine.

For example, particulate matter (PM) discharged from diesel engines is soluble in organic solvents (Soluble organic
It can be separated into a fraction (SOF) and a substance insoluble in organic solvents (dry soot). Soot is a chain aggregate of spherical particles having a crystal structure, and turns black when discharged. SOF is a product obtained by discharging aggregated hydrocarbon droplets and lubricating oil, which are metastable intermediate products in the soot generation process. The discharge characteristics of SOF and soot vary significantly depending on operating conditions such as load and rotational speed.

  PM in exhaust gas is defined as follows by the filter weight method. The engine exhaust gas was diluted to 52 ° C or lower with air using a dilution tunnel, cooled, and collected on the filter by a fluorocarbon coated glass fiber filter or membrane filter that can collect 95% or more of 0.3 µm standard particles. The sum of solid or liquid particles is called PM. Then, after collection, the weight after standing for 8 hours or more in an atmosphere having an air temperature of 25 ° C. and a humidity of 60% is defined as the weight of PM.

Here, as a method for continuously measuring soot, the methods described in Patent Literature 1 and Non-Patent Literature 1 can be exemplified. In Patent Document 1, Soot contained in gas discharged from an internal combustion engine is measured by a hydrogen flame ionization detector.
Japanese Patent No. 3195725

In Non-Patent Document 1, soot is measured by a so-called EDM method. That is, the conductivity of soot is significantly higher than that of SOF or air. Therefore, as shown in FIG. 6, the anode 22 is formed inside the cylindrical insulator 21 of the device 20, and the elongated cathode 23 is fixed at the center of the in-cylinder space 24. A voltage is applied between the anode 22 and the cathode 23 by a DC power supply 25. When the exhaust gas of the diesel engine flows in the space 24, the change in the conductivity of the diesel exhaust gas is determined by the soot, and the influence of air (burned gas) and SOF can be ignored. This change in the conductivity of the exhaust gas is detected as a change in the weak current between the anode 22 and the cathode 23. Specifically, the soot particles collide with the anode 22 and are charged. The charged soot particles collide with other soot particles, the electric charge is diffused, and the charged soot particles increase. Eventually, the charged soot particles collide with the cathode 23 and a weak current flows. The magnitude of the weak current is proportional to the power of the soot number.
"Continuous measurement of black smoke in diesel exhaust particles" (Automotive Engineering Society Proceedings, No. 27, pp. 42-47, 1983, Kiichiro Takeuchi, Kozo Ishida, Fukuzen Yoshihara)

  Recently, the regulation of diesel particulate regulations has been studied, and a sensor for measuring exhaust soot from a diesel engine in a vehicle in real time is desired. However, a sensor suitable for continuously monitoring the amount of soot in a running vehicle is not yet known.

  An object of the present invention is to provide a soot measuring device suitable for continuously monitoring a soot amount in a running vehicle.

  The present invention is an apparatus for measuring soot contained in a gas exhausted from an internal combustion engine, comprising a flat cathode, a flat anode provided facing the cathode, and between the cathode and the anode. A voltage applying means for generating an electric field in the space of the cathode and a heating means for heating the cathode and the anode, and a current value between the cathode and the anode when a voltage is applied between the cathode and the anode. It is characterized by measuring soot based on the change.

  According to the present invention, an electric field is generated in a space between a parallel plate type cathode and an anode, and based on a change in current value between the cathode and the anode when a voltage is applied between the cathode and the anode. Measure the soot. At the same time, by providing a heating means for heating the cathode and the anode, the soot adhering to the surfaces of the cathode and the anode can be cleaned. At this time, unlike the cylindrical device used in the conventional EDM method, it is easy to uniformly heat and clean the entire cathode and anode. As a result, it is possible to clean the cathode and anode surfaces at regular intervals or at the completion of measurement while measuring the soot while the vehicle is in operation. It becomes possible to do.

  In the present invention, the weight of the soot can be measured by measuring a weak current between the cathode and the anode and providing a calibration curve that associates the weak current with the weight of the soot. However, it is not necessary to accurately measure the weight of the soot. For example, if the diesel particulate filter is broken or the particulate collection efficiency is significantly reduced, the proportion of soot in the exhaust gas increases and the weak current rises. As a result, it is possible to detect filter breakage and efficiency reduction.

Hereinafter, the present invention will be described in more detail with reference to the drawings.
FIG. 1 is a front view schematically showing a soot measuring device 6 according to an embodiment of the present invention, and FIG. 2 is a perspective view schematically showing the device 6 of FIG. The apparatus 6 of this example is provided on the surface of the flat sheet heater 1, the pair of substrates 2A and 2B mounted on the sheet heater 1, the cathode 3B provided on the surface of the substrate 2A, and the surface of the substrate 2B. The anode 3A is provided. Each of the bases 2A and 2B extends long and narrow as shown in FIG. The cathode 3B and the anode 3A are opposed to each other so as to sandwich the elongated space 4. A power source 10 is connected to the sheet heater 1.

  In the soot detection mode, a predetermined DC voltage is applied from the power source 5 between the cathode 3B and the anode 3A. In this state, as shown in FIG. 2, exhaust gas is caused to flow in the space 4 as indicated by the arrow F and is discharged as indicated by the arrow G. When exhaust gas flows in the space 4, the change in the conductivity of the exhaust gas is determined by soot, and the influence of air (burned gas) and SOF can be ignored. The change in the conductivity of the exhaust gas is detected as a change in the weak current between the anode 3A and the cathode 3B. That is, as shown in FIG. 3, when the soot particles collide with the cathode 3B, the electrons 7 in the cathode 3B are coupled as shown by the arrow A, and the particles 8A are charged. In the process in which the charged soot particles 8A move toward the anode 3A as indicated by an arrow B, they collide with other uncharged soot particles 8 as indicated by an arrow C, and the charge 7 is diffused and charged. The number of soot particles 8A increases. Eventually, the charged soot particles 8A collide with the anode 3A as indicated by arrow D, and electrons 7 are emitted into the anode 3A as indicated by arrow E. As a result, a weak current flows between the cathode and the anode. The magnitude of the weak current is proportional to the power of the soot number.

  Next, once the soot measurement is completed, the power supply 10 is turned on, the sheet heater 1 generates heat, and the substrates 2A, 2B, the anode 3A, and the cathode 3B are heated. As a result, the soot adhering to the surfaces of the anode 3A and the cathode 3B is burned and scattered. This allows a quick transition to the next soot measurement.

  Here, in the case of the conventional soot measuring device of the form shown in FIG. 6 based on the EDM principle, particulate matter such as soot adhering to each surface of the electrodes 22 and 23 is real-time while continuing soot measurement. There is no mechanism for removing and cleaning with, and in particular, it is difficult to clean the surface of the center electrode 23. In the present invention, since parallel plate electrodes are used, it is easy to clean the surfaces of the electrodes 3A and 3B by heating, which is excellent for in-vehicle use.

  In the present invention, the internal combustion engine is not particularly limited, but a diesel engine is particularly preferable. The material of the cathode or anode is not particularly limited, but an electrode containing at least one metal selected from the group consisting of tungsten, molybdenum, titanium, manganese, chromium, zirconia, nickel, iron, silver, copper, platinum, and palladium. Can be illustrated. Also, the heating means is not particularly limited. However, when the heating means is a sheet heater, and the sheet heater is integrated with the cathode and the anode, the anode and the cathode can be quickly heated with high efficiency and soot can be removed. Although the material of a sheet-like heater is not limited, The platinum heater by a thick film printing and baking technique can be illustrated.

  In a preferred embodiment, soot can be measured by the EDM method as described above. However, the specific method is not limited as long as the change in resistance value in the space between the anode and the cathode can be measured. For example, it can be used that soot aggregates to form a bridge in the space between the anode and the cathode. When soot aggregates between the anode and the cathode to form a bridge, the resistance value between the anode and the cathode is remarkably lowered and the weak current value is increased.

FIG. 4 is a perspective view schematically showing the soot measuring device 19 according to this embodiment, and FIG. 5 is a plan view schematically showing the device 19 of FIG.
In the apparatus 19 of this example, a pair of elongated electrode supply sections 15 and 16 are provided substantially parallel to each other on a substrate 11 made of a sheet heater. A plurality of elongated anodes 13A are provided from the electrode supply unit 16 in a direction perpendicular to the electrode supply unit 16. A plurality of elongate cathodes 13B are provided from the electrode supply unit 15 in a direction perpendicular to the electrode supply unit 15. The anode 13A and the cathode 13B are alternately formed in a nested manner. The space 14 between the electrode supply portions 15 and 16 is bent as shown in FIG. 5 in particular, and a gap 14a is formed between the pair of the anode 13A and the cathode 13B facing each other.

  In the soot detection mode, a predetermined DC voltage is applied from the power source 5 between the anode 13A and the cathode 13B. In this state, as shown in FIG. 5, exhaust gas is allowed to flow in the space 4 as indicated by the arrow F and is discharged as indicated by the arrow G. When exhaust gas flows through the space 4, if there is a large amount of soot in the exhaust gas, the soot aggregates to form a bridge 18, and the resistance value between the anode and the cathode decreases. As a result, a weak current flows between the cathode and the anode. The magnitude of the weak current is proportional to the power of the soot number.

  Next, once the soot measurement is completed, the power source 10 is turned on, the sheet heater 11 generates heat, and the anode 13A and the cathode 13B are heated. As a result, the soot adhering to the surfaces of the anode 13A and the cathode 13B is burned and scattered. This allows a quick transition to the next soot measurement.

  As described above, according to the present invention, it is possible to provide a soot measuring device suitable for continuously monitoring the amount of soot in a running vehicle.

It is a front view showing roughly soot measuring device 6 concerning one embodiment of the present invention. It is a perspective view which shows schematically the soot measuring apparatus 6 of FIG. FIG. 2 is a schematic diagram for explaining a measurement principle by an EDM method in the measurement apparatus of FIG. 1. It is a perspective view which shows roughly the soot measuring apparatus 19 which concerns on other embodiment of this invention. It is a top view which shows roughly the soot measuring apparatus 19 of FIG. It is sectional drawing which shows schematically the conventional soot measuring apparatus 20 based on EDM method.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Sheet heater (heating means) 2A, 2B Substrate 3A, 13A Anode 3B, 13B Cathode 4, 14, 14a Space 5 DC power source 6, 19 Soot measuring device 7 Charge 8 Uncharged soot particle 8A Charged soot particle 10 AC power supply 15, 16 Power supply unit 18 Aggregated soot particles F, G Flow of exhaust gas

Claims (2)

An apparatus for measuring soot contained in a gas discharged from an internal combustion engine,
A flat cathode, a flat anode provided opposite to the cathode, voltage applying means for generating an electric field in a space between the cathode and the anode, and heating for heating the cathode and the anode Means for measuring the soot based on a change in a current value between the cathode and the anode when a voltage is applied between the cathode and the anode. apparatus.   The apparatus according to claim 1, wherein the soot amount is measured by an EDM method.

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