JP2010032488A - Particulate matter detecting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a particulate matter detecting device that easily detects particulate matter, is low cost, and has high accuracy of measurement. <P>SOLUTION: This particulate matter detecting device 100 includes: a first plate-like electrode 1, whose one surface is covered with an inter-electrode dielectric material 4; a second electrode 2, disposed on the side of the one surface of the first electrode 1 via space where gas containing the particulate matter 11 flows, to perform the discharge of electricity by a voltage applied between the first electrode 1 and the second electrode; a power supply 9 for dust collection for applying voltage; a pair of measurement electrodes 5 and 15, disposed on the surface of the inter-electrode dielectric material 4 so as to face each other; a characteristic measuring means 3 for measuring the electrical characteristics between the pair of measurement electrodes 5 and 15; and a particulate matter amount calculating means 13 for obtaining the amount of the particulate matter 11, collected by the surface of the inter-electrode dielectric material 4, based on the change amount of the electrical characteristics measured by the characteristics measuring means 3. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an apparatus for detecting particulate matter contained in exhaust gas or the like of a diesel engine.

  Diesel engine exhaust gas, etc. contains particulate matter (Particulate Matter (PM), organic solvent soluble components, and soot and sulfate detected as three components), which causes air pollution. ing. In particular, if a problem occurs in a particulate matter generation source such as a diesel engine, the particulate matter in the exhaust gas released to the atmosphere increases, which has a great adverse effect on the environment. In order to prevent this, it is important to detect particulate matter in the exhaust gas and recognize problems such as diesel engines.

  Recently, in order to prevent pollution and improve the environment, a diesel particulate filter (DPF) has been incorporated into an exhaust system or the like for exhaust gas treatment. ing. This DPF is generally made of ceramic and can be used for a long period of time with high reliability. However, it cannot be said that there is no possibility that defects such as cracks are generated due to thermal degradation, and if so, particulate matter will leak even though the amount is small. In order to prevent this, it is important to detect particulate matter in the exhaust gas treated with DPF and immediately detect the occurrence of defects.

  As a prior document, for example, Patent Document 1 can be cited. Patent Document 1 discloses a particulate matter detection device that measures the amount of particulate matter by charging the particulate matter by corona discharge and measuring its ionic current.

JP 60-123761 A

  However, in the method described in Patent Document 1, since the ion current charged in the particulate matter is weak, a large-scale detection circuit for detecting the weak ion current is necessary, and the apparatus becomes expensive. End up. In addition, if the exhaust gas flow rate is high, the particulate matter cannot be effectively charged, and the measured value will be smaller than the amount of particulate matter actually contained in the exhaust gas. There is room for improvement.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a particulate matter detection device that can easily detect particulate matter, is inexpensive, and has high measurement accuracy. As a result of repeated research, it was found that this problem can be solved by the following means.

  That is, according to the present invention, one electrode having a plate-like shape in which one surface is coated with a dielectric (referred to as an interelectrode dielectric), Formation and discharge of an electric field by a voltage applied between one electrode and a space arranged through a space in which a gas containing particulate matter flows on one side (covered with a dielectric between electrodes) A pair of measurement electrodes disposed opposite to the surface of the dielectric (interelectrode dielectric), a pair of measurement electrodes, and a pair of measurement electrodes. Measuring means for measuring the electrical characteristics between the measuring electrodes, and collecting the dust on the surface of the dielectric (dielectric between electrodes) based on the amount of change in the electrical characteristics measured by the characteristic measuring means. There is provided a particulate matter detection device comprising a particulate matter amount calculating means for obtaining the amount of the particulate matter thus obtained. That.

  The particulate matter detection device according to the present invention includes a flow meter for measuring or estimating the flow rate of the gas flowing through the space, and the gas flow rate and the amount of the particulate matter measured or estimated by the flow meter. It is preferable to provide a particulate matter concentration calculating means for calculating the concentration of the particulate matter in the gas flowing through the space based on the above.

  In the particulate matter detection device according to the present invention, the electrical characteristics are preferably one or more electrical characteristics selected from an electrical characteristics group consisting of resistance, inductance, capacitance, and impedance.

  In the particulate matter detection device according to the present invention, the pair of measurement electrodes have a linear shape, and are opposed to each other in a direction perpendicular to the direction in which the gas containing the particulate matter flows. It is preferable to be disposed on the surface. In this case, it is preferable that each of the pair of measurement electrodes exhibiting the linear shape has a plurality of facing portions, each of which forms a pair and branches into a plurality. Furthermore, in this case, it is preferable that the pair of measurement electrodes having the plurality of facing portions is disposed over the entire surface of the dielectric (interelectrode dielectric).

  In the particulate matter detection device according to the present invention, it is preferable that the two electrodes have a plate shape. In this case, it is preferable that the two electrodes are formed of a tube wall surface.

  In the particulate matter detection device according to the present invention, it is preferable that the two electrodes have a needle shape or a rod shape.

  In the particulate matter detection device according to the present invention, a dielectric (referred to as an external dielectric) that covers the other surface of the electrode having the plate shape, and a surface of the dielectric (external dielectric) And a heater disposed in the.

  In the particulate matter detection device according to the present invention, a removal power source for applying a voltage is provided between the one electrode and the pair of measurement electrodes, and one surface of the one electrode is covered by the application of the voltage. It is preferable to cause creeping discharge on the surface of the formed dielectric (interelectrode dielectric).

  In the particulate matter detection device according to the present invention, the measurement electrode is preferably covered with a film-like dielectric.

  In the particulate matter detection device according to the present invention, a detection device main body made of a dielectric long in one direction is provided with a through-hole, which is a space through which gas containing particulate matter flows, at one end. The one electrode and the second electrode are embedded in the detection device body so that one surface of the one electrode faces the through hole and sandwiches the through hole, and the pair of measurement It is preferable that the electrode is disposed on the wall surface on the side where the one electrode in the through hole is embedded.

  In the particulate matter detection device according to the present invention, an extraction terminal of at least one of the one electrode and the second electrode may be disposed at the other end of the detection device body. preferable.

  In the particulate matter detection device according to the present invention, at least one of the one electrode and the second electrode is at a position opposite to the side where the through hole is formed. It is preferable that the heater is embedded.

  The particulate matter detection device according to the present invention is a device that is installed in a flow path through which gas (exhaust gas) containing particulate matter passes and detects particulate matter contained in the gas. In the particulate matter detection device according to the present invention, a voltage is applied by a dust collecting power source to cause the two electrodes to discharge, and a space between the interelectrode dielectric side of one electrode and the two electrodes is formed. The particulate matter contained in the flowing gas is charged, or the precharged particulate matter is collected on the surface of the interelectrode dielectric covering one electrode. As a result, the particulate matter is deposited on the interelectrode dielectric, and the electrical characteristics between the pair of measurement electrodes arranged on the surface of the interelectrode dielectric are related to the amount of the deposited particulate matter. It changes with a certain relationship between them. Therefore, in the particulate matter detection device according to the present invention, the amount of particulate matter collected on the surface of the interelectrode dielectric is obtained by knowing the amount of change in electrical characteristics. Since it can be quantified, it is naturally possible to determine the presence or absence of particulate matter in the gas flowing through the space (whether the amount is 0 (zero)). Therefore, the particulate matter detection device according to the present invention is referred to as a detection device. In the particulate matter detection device according to the present invention, the amount of particulate matter contained in the gas flowing through the space is determined based on the amount of the particulate matter, and the gas is determined from the relationship with the flow rate of the gas flowing through the space. It is possible to calculate the concentration of particulate matter in

  As an electrical characteristic, for example, in order to detect an amount of change in impedance, it is only necessary to measure a change in current of 10 nA (nanoampere) level, although it varies depending on the measurement frequency and the magnitude of the measurement voltage. Therefore, the particulate matter detection device according to the present invention is not expensive, can easily detect particulate matter, measure the amount, and measure the concentration, and has a small measurement error. . In addition, detection of particulate matter, measurement of amount, measurement of concentration makes it possible to immediately detect the malfunction of diesel engines and the like, and the occurrence of DPF defects. Through these, the particles according to the present invention can be detected. The particulate matter detection device contributes to the reduction of particulate matter emission and contributes to the prevention of air pollution.

  In the particulate matter detection device according to the present invention, since measurement electrodes for measuring electrical characteristics are present on the same dielectric surface, the degree of freedom in setting the distance between the measurement electrodes is high, and high sensitivity is easy. In addition, it is possible to obtain an arbitrary sensitivity depending on the application.

  In the particulate matter detection device according to the present invention, the particulate matter deposited on the interelectrode dielectric, one electrode for collecting particulate matter by charging the particulate matter, the second electrode, and the power source for dust collection A system of a pair of measurement electrodes, a characteristic measurement unit, and a particulate matter amount calculation unit for measuring an electrical characteristic that changes depending on the amount of the gas flow meter and the flow meter are independent of each other. Therefore, it is possible to detect the particulate matter in a dynamic state in which air is flowing in the space by providing an input / output means for electric signals to and from these systems and controlling it as a whole. The amount of particulate matter that can be measured and the concentration can be measured in real time.

  In a preferred embodiment of the particulate matter detection device according to the present invention, the pair of measurement electrodes are linear, and are opposed to each other long in the direction perpendicular to the direction in which the gas containing the particulate matter flows. Furthermore, the pair of measurement electrodes that are arranged on the surface of the electrode have a plurality of opposing portions, each of the pair of measuring electrodes branching into a plurality, and in addition, have a plurality of opposing portions. A pair of measurement electrodes are disposed over the entire surface of the interelectrode dielectric. According to the particulate matter detection device of the present invention having such an aspect, it is possible to improve the measurement sensitivity of the electrical characteristics and to detect the particulate matter deposited on the interelectrode dielectric without missing it. The measurement accuracy of the amount and concentration of the particulate matter is excellent.

  In the particulate matter detection device according to the present invention, as a preferred embodiment, when the two electrodes have a plate shape, in particular, it is possible to adopt an embodiment in which the two electrodes are constituted by a tube wall surface. Can be accommodated in a compact exhaust pipe.

  In a preferred embodiment, the particulate matter detection device according to the present invention includes a heater disposed on the surface of the outer electrode dielectric, so that the electrical characteristics measured by the measurement electrode are stabilized. In addition, since the particulate matter can be oxidized and removed by the heat of the heater, the particulate matter can be repeatedly and accurately detected.

  In a preferred embodiment of the particulate matter detection device according to the present invention, the particulate matter detection device includes a power supply for removal that applies a voltage between one electrode and the pair of measurement electrodes. Since creeping discharge can be caused on the surface of the interelectrode dielectric coated on the surface, particulate matter collected by the creeping discharge can be removed by oxidation. By this oxidation removal, the particulate matter can be detected repeatedly with high accuracy.

  In a preferred embodiment of the particulate matter detection device according to the present invention, since the measurement electrode is covered with a film-like dielectric, deterioration due to discharge or exhaust gas hardly occurs.

  In a preferred embodiment of the particulate matter detection device according to the present invention, a detection device made of a dielectric material that is long in one direction and has a through-hole that is a space through which gas containing particulate matter flows is formed at one end. A main body, wherein the one electrode and the two electrodes are embedded in the detection device main body so that the one surface of the one electrode faces the through hole and sandwiches the through hole, The pair of measurement electrodes are disposed on a wall surface on the side where the one electrode in the through hole is embedded. According to the particulate matter detection device of the present invention having such an aspect, only the through hole, the first electrode, and the second electrode are inserted into the pipe through which the high-temperature exhaust gas flows, and the other end side is inserted. It is possible to put the pipe out of the pipe. As a result, it is possible to place the parts that are preferably not exposed to high temperatures, such as one electrode, the second electrode, and a pair of measurement electrode takeout terminals, out of the piping, and have high accuracy and stability. Particulate matter can be detected.

  In a preferred embodiment of the particulate matter detection device according to the present invention, an extraction terminal of at least one of the one electrode and the second electrode is disposed at the other end of the detection device body. ing. According to the particulate matter detection device of the present invention having such an aspect, it is possible to bring the takeout terminal disposed at the other end of the detection device main body out of the pipe, which is highly accurate. Thus, it becomes possible to detect stable particulate matter.

  In a preferred embodiment of the particulate matter detection device according to the present invention, a position of at least one of the one electrode and the second electrode on the side opposite to the side on which the through hole is formed. In addition, at least one heater is embedded. According to the particulate matter detection device of the present invention having such an aspect, the electrical characteristics measured by the measurement electrode are stabilized. In addition, since the particulate matter can be oxidized and removed by the heat of the heater, the particulate matter can be repeatedly and accurately detected.

1 is a cross-sectional view schematically showing one embodiment of a particulate matter detection device according to the present invention. It is sectional drawing which shows typically other embodiment of the particulate matter detection apparatus which concerns on this invention. It is sectional drawing which shows typically other embodiment of the particulate matter detection apparatus which concerns on this invention. It is a figure showing typically one embodiment of the particulate matter detection device concerning the present invention, and is a perspective view showing dielectric outside an electrode and one electrode. It is a figure which shows typically one Embodiment of the particulate-material detection apparatus which concerns on this invention, and is a perspective view showing the other aspect of a measurement electrode. It is a figure which shows typically one Embodiment of the particulate-material detection apparatus which concerns on this invention, and is a perspective view showing the other aspect of a measurement electrode. It is a figure showing typically one embodiment of the particulate matter detection device concerning the present invention, and is a lineblock diagram showing an electric control system. It is a graph for demonstrating the function of the particulate matter amount calculation apparatus in the particulate matter detection device according to the present invention. It is a graph for demonstrating the function of the particulate matter concentration calculation apparatus in the particulate matter detection device according to the present invention. It is a front view which shows typically other embodiment of the particulate-material detection apparatus of this invention typically. It is a side view which shows typically other embodiment of the particulate matter detection apparatus of this invention. It is a schematic diagram which shows the A-A 'cross section of FIG. 10B. It is a schematic diagram which shows the B-B 'cross section of FIG. It is a schematic diagram which shows the C-C 'cross section of FIG. It is a schematic diagram which shows the D-D 'cross section of FIG. It is a schematic diagram which shows the E-E 'cross section of FIG. It is a schematic diagram which shows the F-F 'cross section of FIG. FIG. 15 is a schematic view showing still another embodiment of the particulate matter detection device of the present invention and corresponding to a schematic view showing a cross section of still another embodiment of the particulate matter detection device of the present invention shown in FIG. 14. It is a schematic diagram which shows the cross section which orthogonally crosses to a central axis and contains a through-hole which shows other embodiment of the particulate matter detection apparatus of this invention. It is a schematic diagram which shows the cross section which does not contain a through-hole orthogonal to a center axis | shaft which shows other embodiment of the particulate matter detection apparatus of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings as appropriate, but the present invention should not be construed as being limited thereto. Various changes, modifications, improvements, and substitutions can be added based on the knowledge of those skilled in the art without departing from the scope of the present invention. For example, the drawings show preferred embodiments of the present invention, but the present invention is not limited by the modes shown in the drawings or the information shown in the drawings. In practicing or verifying the present invention, the same means as described in this specification or equivalent means can be applied, but preferred means are those described below.

  [Particulate matter detection device] First, the particulate matter detection device according to the present invention will be described focusing on the configuration, function, action and the like.

  1 and 7 are diagrams schematically showing an embodiment of a particulate matter detection device according to the present invention. FIG. 1 is a sectional view, and FIG. 7 is a configuration diagram showing an electric control system. The particulate matter detection device 100 shown in FIGS. 1 and 7 includes an electrode 1 having a plate shape, two electrodes 2 having a plate shape, and an upper surface (one surface) of the one electrode 1 (in FIG. 1). Inter-electrode dielectric 4 covering the electrode, dust collecting power source 9 for applying a voltage between the first electrode 1 and the second electrode 2, and a linear shape arranged facing the surface of the inter-electrode dielectric 4 The measurement electrodes 5 and 15 exhibiting the above, the electrode outer dielectric 6 covering the lower surface (other surface) of the one electrode 1 (in FIG. 1), and the surface of the electrode outer dielectric 6 (lower surface in FIG. 1) Heater 7, heater power supply 10 for supplying electricity to the heater 7, sheet-like heat insulating material 8 that covers and protects the heater 7, keeps it insulated from the surroundings, a characteristic measuring device (means) 3, and particulate matter 11 Particulate matter amount calculation device (means) 13 for calculating the amount of particulate matter, and the particulate matter concentration for calculating the concentration of particulate matter 11 Detection device (means) 16, and a flow meter 14, and the controller 12. In addition, the part comprised by the one electrode 1 shown in FIG. 1, the two electrodes 2, the interelectrode dielectric 4, the measurement electrodes 5 and 15, the outer electrode dielectric 6, the heater 7, and the heat insulating material 8 is a particle. It is installed in the flow path through which the exhaust gas containing the particulate material 11 passes. These are sometimes referred to as sensor units.

  In the particulate matter detection device 100, the exhaust gas containing the particulate matter 11 from the left to the right in FIG. 1 (as indicated by arrows) covers the interelectrode dielectric 4 that covers one electrode 1 that has a plate shape. And a space between the two electrodes 2 having a plate shape. The flow rate of the exhaust gas is measured by a flow meter 14 not shown in FIG. In this state, when the dust collecting power source 9 applies a DC high voltage, for example, to the second electrode 2, discharge occurs, and the exhaust gas (molecules) around the second electrode 2 is separated into positive ions and negative ions. Then, negative ions move toward one electrode 1 to which a positive DC high voltage is applied. At this time, the particulate matter 11 contained in the exhaust gas collides with the negative ions and is negatively charged. The charged particulate matter 11 is collected and accumulated by electrostatic force on the surface of the interelectrode dielectric 4 covering the plus one electrode 1. Then, the electrical characteristics between the pair of measurement electrodes 5 and 15 change depending on the degree of deposition of the particulate matter 11, so if the amount of change in the electrical characteristics is known, dust collection collects the distance between the electrodes. The amount of particulate matter (PM) deposited on the surface of the dielectric 4 is determined. Then, the PM concentration of the exhaust gas is obtained from the amount of accumulated PM.

  FIG. 8 is a graph for explaining the function of the particulate matter amount calculating device 13, and FIG. 9 is a graph for explaining the function of the particulate matter concentration calculating device 16. The change amount E1 of the electrical characteristics between the measurement electrodes 5 and 15 is in a fixed relationship with the PM deposition amount W1 (see FIG. 8), and if the change amount E1 of the electrical characteristics is known by the characteristic measurement device 3, The PM deposition amount W1 is obtained by the particulate matter amount calculation device 13 having a calculation function based on FIG. If the flow rate of the exhaust gas is constant, the PM deposition amount W1 has a constant relationship with the PM concentration C1 (see FIG. 9), and if the PM deposition amount W1 is known, it has a calculation function based on FIG. The PM concentration C1 is obtained by the particulate matter concentration calculation device 16. When the flow rate of the exhaust gas changes, the particulate matter concentration calculation device 16 corrects based on the flow rate obtained by the flow meter 14, and obtains the PM concentration C1 from the PM deposition amount W1.

  In the particulate matter detection device 100, the particulate matter concentration calculation device 16 is incorporated in the control device 12. The control device 12 includes, for example, a sequencer having an electric signal input / output function, and has a function of inputting an electric signal of a flow rate measured by the flow meter 14 in addition to the particulate matter concentration calculation device 16. The entire apparatus is controlled including control of the heater power supply 10 and the dust collection power supply 9 and switching of the measurement mode.

  As an electrical characteristic between the measurement electrodes 5 and 15, for example, when impedance is obtained, an AC power source can be used to measure resistance, capacitance, and inductance, respectively. Alternatively, a change in impedance may be measured by measuring a change in voltage between the measurement electrodes 5 and 15 using a constant current source, and between the measurement electrodes 5 and 15 using a constant voltage source. A change in impedance between the measurement electrodes 5 and 15 may be measured by measuring a change in flowing current and a change in charge accumulated between the measurement electrodes 5 and 15. The characteristic measuring device 3 can have an appropriate configuration depending on such electrical characteristics and how to obtain the change.

  For example, the characteristic measuring device 3 can be composed of an AC power source for applying a voltage to the measuring electrodes 5 and 15 and a measuring device. A preferred measuring instrument is an LCR meter.

  As described above, the particulate matter detection device according to the present invention can detect particulate matter, measure the amount, and measure the concentration in a static state where no air flows in the space. In a dynamic state where air is flowing in space, it is possible to detect particulate matter, measure the amount of particulate matter that can change momentarily, and measure the concentration in real time. The dust collection efficiency with the flow velocity is different. Therefore, the basis for obtaining the PM deposition amount W1 from the change amount E1 of the electrical characteristics in the particulate matter amount calculation device 13 (corresponding to the data shown in FIG. 8), and the PM deposition amount in the particulate matter concentration calculation device 16 The basis for obtaining the PM concentration C1 from W1 (corresponding to the data shown in FIG. 9) needs to use different grounds (data) as different measurement modes in the former and the latter.

  A preferable distance between the interelectrode dielectric 4 and the second electrode 2 forming a space through which exhaust gas flows is 0.5 to 50 mm, and a more preferable distance is 0.6 to 40 mm. By setting such an interval, it is possible to discharge more efficiently and collect particulate matter. If the distance between the interelectrode dielectric 4 and the second electrode 2 is shorter than 0.5 mm, the dust collection rate may decrease and the measurement accuracy may decrease. If it is longer than 50 mm, a higher voltage is required. And wasteful energy may be required.

  The dust collection power source 9 supplies a stable DC voltage or AC voltage that can generate a discharge between the first electrode 1 and the second electrode 2. As the dust collection power source 9, for example, a power source using a flyback power source circuit or the like can be employed. In this case, energy is stored in the transformer from the power supply on the input side, and the stored energy is discharged to the output side, whereby a high-voltage DC voltage can be supplied. In a flyback power supply circuit, the accumulation and release of energy to and from the transformer are controlled by a transistor or the like, and the current on the output side is rectified by a diode.

  FIG. 4 is a perspective view showing the outer electrode dielectric 6 and one electrode 1. In FIG. 4, the arrows indicate the flow direction of the exhaust gas. The one electrode 1 serves as a member for sucking and collecting the charged particulate matter 11 while discharging as a counter electrode of the second electrode 2. As shown in FIG. 4, the plate-like electrode 1 in the particulate matter detection device 100 has a generally rectangular shape, but in addition, a polygon such as a pentagon, a circle, an ellipse, a track shape, etc. A shape, a shape in which irregularities are formed on the outer periphery, a shape in which one or a plurality of slits are formed, and the like can be adopted.

  Although the plate-like two electrodes 2 do not show a perspective view, like the one electrode 1, they are generally rectangular. Similarly to the one electrode 1, a polygon such as a pentagon, a circle, an ellipse, a track shape, a shape in which irregularities are formed on the outer periphery, or a shape in which one or a plurality of slits are formed may be employed.

  The linear measurement electrodes 5 and 15 are long in the direction perpendicular to the direction in which the exhaust gas flows (arrow in FIG. 1), and the measurement electrodes 5 and 15 are arranged to face each other. Measure changes in electrical properties. The distance between the measurement electrode 5 and the measurement electrode 15 is to clearly measure the change in electrical characteristics between the measurement electrodes 5 and 15 caused by the collection of the particulate matter 11 by one electrode 1. Is set in a range where For example, it is about 0.2 to 10 mm.

  5 and 6 are perspective views showing other modes of a pair of measurement electrodes having a linear shape. 5 and 6, arrows indicate the flow direction of the exhaust gas. The measurement electrodes 105 and 115 shown in FIG. 5 are divided into a plurality of the measurement electrodes 105 and the measurement electrodes 115, and face each other after branching, and there are a plurality of facing portions. In addition, a plurality of portions where the measurement electrode 105 and the measurement electrode 115 branch and face each other are arranged over the entire surface of the interelectrode dielectric 4. In the particulate matter detection device according to the present invention, from the viewpoint of improving the measurement sensitivity and measurement accuracy of the electrical characteristics, it is not preferable that the distance between the pair of opposed measurement electrodes is long, while the pair of opposed measurement is performed. It is preferable that the electrode is disposed at a position corresponding to the entire space through which the exhaust gas flows. The measurement electrodes 105 and 115 shown in FIG. 5 embody such a preferred embodiment. The measurement electrodes 205 and 215 shown in FIG. 6 are the same and have different branching modes. However, the measurement electrodes 205 and 215 are branched into a plurality of parts and face each other after the branching. A plurality of portions where the measurement electrode 205 and the measurement electrode 215 branch and face each other are arranged over the entire surface of the interelectrode dielectric 4.

  Returning to the description of the particulate matter detection device 100. The shape and size of the heater 7 may be determined so that the entire particulate matter 11 collected on the surface of the interelectrode dielectric 4 can be combusted.

  The heater 7 is not affected by moisture such as dew condensation when measuring the change in electrical characteristics between the measurement electrodes 5 and 15 as well as when oxidizing and removing the particulate matter 11. Used for. For example, it is possible to prevent moisture from adhering to the measurement electrodes 5 and 15 by appropriately heating at the time of detecting an impedance change or discharging. The preferable heating temperature at this time is 200-300 degreeC.

  As a preferable heater power source 10, a step-down chopper type power source can be cited from the viewpoint of enabling efficient temperature control. Particularly preferred is a step-down chopper type switching power supply using a self-extinguishing type semiconductor switch. In this case, a preferable switching frequency is 20 kHz or more which is higher than the audible frequency. In order to directly affect the fuel consumption, it is desirable to make the current and power of the heater power supply smaller. A preferred heater power source 10 has a temperature control function by calculating the temperature of the heater 7 from the voltage and current.

  The heat insulating material 8 suppresses heat radiation generated by the heater 7 and enables the heat of the heater 7 to be efficiently used for combustion of the particulate matter 11. A preferable thickness of the heat insulating material 8 is, for example, about 100 to 1000 μm as a thickness capable of suppressing heat dissipation.

  In the particulate matter detection device 100, a voltage is applied between one electrode 1 and the pair of measurement electrodes 5, 15 instead of or in combination with the heater 7 and the heater power supply 10. A mode in which a power supply for removal for causing creeping discharge on the surface of the interelectrode dielectric 4 can be employed. In this case, the measuring electrodes 5 and 15 and the characteristic measuring device 3, the one electrode 1 and the dust collecting power source 9 are disconnected, the measuring electrode 5 and the measuring electrode 15 are electrically connected, and the one electrode 1 is removed. It is necessary to construct a switching circuit that connects to the power supply. An AC power source or a pulse power source can be used as the power source for removal.

  In the above, one embodiment of the particulate matter detection device according to the present invention has been described. However, as another embodiment, an embodiment in which the two electrodes are formed of a tube wall surface, or two electrodes having a needle shape or a rod shape are employed. Can be mentioned. FIG. 2 is a cross-sectional view showing a particulate matter detection device 200 corresponding to the former. In FIG. 2, the direction in which the exhaust gas flows is represented as a direction from the near side to the far side. FIG. 3 is a cross-sectional view showing a particulate matter detection device 300 corresponding to the latter. In the particulate matter detection device 300, the discharge is a corona discharge. The particulate matter detection devices 200 and 300 are the same in principle and action as the device configuration except for the second electrode, and the description thereof is omitted.

  Next, still another embodiment of the particulate matter detection device according to the present invention will be described. As shown in FIG. 10A to FIG. 16, the particulate matter detection device 400 of the present embodiment has a one-way direction in which a through-hole 22 that is a space through which a gas containing particulate matter flows is formed at one end 21 a. The detection device body 21 made of a long dielectric is provided, and one electrode 31 and two electrodes 32 are detected so as to sandwich the through hole 22 with one surface of the one electrode 31 facing the through hole 22 side. A pair of measurement electrodes 41, 42 is embedded in the wall surface on the side where one electrode 31 in the through hole 22 is embedded. Here, FIG. 10A is a front view schematically showing still another embodiment of the particulate matter detection device of the present invention. FIG. 10B is a side view schematically showing still another embodiment of the particulate matter detection device of the present invention. FIG. 11 is a schematic diagram showing the A-A ′ cross section of FIG. 10B. FIG. 12 is a schematic diagram showing a B-B ′ cross section of FIG. 11. FIG. 13 is a schematic diagram showing a C-C ′ cross section of FIG. 11. FIG. 14 is a schematic diagram showing a D-D ′ cross section of FIG. 11. FIG. 15 is a schematic diagram illustrating a cross section taken along line E-E ′ of FIG. 11. FIG. 16 is a schematic diagram illustrating a cross section taken along the line F-F ′ of FIG. 11.

  In the particulate matter detection device 400 of the present embodiment, the first electrode 31 and the second electrode 32 are embedded in the detection device main body 21, and the detection device main body 21 is formed of a dielectric. The first electrode 31 and the second electrode 32 are each covered with a dielectric. That is, the dielectric covering one surface of one electrode 31 is constituted by a part of the detection device main body 21 made of a dielectric.

  Thereby, it becomes possible to measure the mass of the particulate matter only for the exhaust gas flowing into the through hole in the exhaust gas flowing downstream of the DPF, and all the particles contained in the exhaust gas flowing downstream of the DPF. It is possible to estimate the amount of particulate matter in the entire exhaust gas by measuring only the particulate matter that has flowed into the through-holes instead of directly measuring the particulate matter. Accordingly, it can be installed in a narrow space, and can be manufactured at a lower cost. In addition, even when the total flow rate of the exhaust gas flowing downstream of the DPF is high, only a part of the exhaust gas (particulate matter) is introduced into the through hole. When the particulate matter is charged, all the particulate matter in the through hole can be effectively charged, and a measurement value with less error can be obtained. In addition, since the detection device main body is formed long in one direction and a through hole is formed at one end thereof, and at least a pair of electrodes is disposed (embedded), the through hole and the pair of electrodes are arranged. Only the portion to be provided can be inserted into a pipe through which high-temperature exhaust gas flows, and the other end can be brought out of the pipe. As a result, it is possible to place portions that are preferably not exposed to high temperatures, such as the extraction terminals of the pair of electrodes, out of the piping, and to perform highly accurate and stable detection of particulate matter. It becomes possible.

  In the particulate matter detection device 400 of the present embodiment, an extraction terminal for at least one of the one electrode 31 and the second electrode 32 is disposed at the other end 21 b of the detection device body 21. It is preferable. The take-out terminal is a portion that is electrically connected to an electrode disposed in the detection device main body 21 of the particulate matter detection device 400 and connects a wiring from a power source or the like for applying a voltage to the electrode from the outside. . The particulate matter detection device 400 includes a plurality of extraction terminals (extraction terminals 31a, 32a, 33a, 41a) independently connected to the first electrode 31, the second electrode 32, the heater 33, the measurement electrodes 41, 42, and the like. 42a). In the particulate matter detection device 400 of this embodiment shown in FIG. 10B, the takeout terminal 32 a of the second electrode 32 is disposed at the other end 21 b of the detection device main body 21. In this way, by arranging the extraction terminal of at least one of the one electrode 31 and the second electrode 32 at the other end 21 b of the detection device main body 21, the through hole 22 and the one electrode 31 are arranged. In addition, since the distance between the portion (one end portion 21a) where the second electrode 32 and the pair of measurement electrodes 41, 42 are disposed and the takeout terminal can be increased, the through hole 22 or the like is disposed. It is possible to insert only the end portion 21a into the pipe through which the high-temperature exhaust gas circulates and to bring the other end portion 21b side where the takeout terminal 32a is disposed out of the pipe. If the extraction terminal 32a is heated to a high temperature, the detection accuracy of the particulate matter is lowered, and it may be difficult to perform stable detection, or a contact failure between the electrical terminal and the harness for connecting to the outside when used for a long period of time. Therefore, it is possible to detect the particulate matter with high accuracy by taking out the extraction terminal 32a out of the pipe and not exposing it to a high temperature. .

  As shown in FIG. 10B, the takeout terminal 32a disposed at the other end 21b of the detection device main body 21 is disposed on the side surface of the other end 21b of the detection device main body 21 so as to extend in the longitudinal direction. Preferably it is. The surface on which the takeout terminal 32a is disposed need not be the side surface of the other end portion 21b of the detection device main body 21, and may be any surface. In FIG. 10B, the other end 21b of the detection device main body 21 is formed to have a narrow width. However, the width of the other end 21b may be narrowed as described above. It does not have to be. The shape and size of the takeout terminal 32a are not particularly limited. For example, a strip shape having a width of 0.1 to 2 mm and a length of 0.5 to 20 mm is preferable. Examples of the material of the takeout terminal 32a include Ni, Pt, Cr, W, Mo, Al, Au, Ag, Cu, stainless steel, and Kovar.

  The extraction terminals of both the first electrode 31 and the second electrode 32 may be arranged at the other end 21 b of the detection device main body 21, but the extraction terminal 32 a of the second electrode 32 is arranged at the other end of the detection device main body 21. It is preferable that the take-out terminal 31a of one electrode 31 is arranged at a position between one end 21a and the other end 21b of the detection device main body 21. As a result, the takeout terminal 32a of the second electrode 32 and the takeout terminal 31a of the first electrode 31 are arranged at an interval, whereby the gap between the first electrode 31 and the second electrode 32 is set. When a voltage is applied between the takeout terminal 31a and the takeout terminal 32a in order to apply a voltage, it is possible to prevent a short circuit from occurring due to creeping discharge on the surface of the detection device main body 21. Here, in the present embodiment, “one end portion of the detection device main body” refers to a position corresponding to 30% of the total length of the detection device main body 21 from one tip portion 21c of the detection device main body. The range. The term “the other end of the detection device main body” refers to a range from the other tip portion 21d of the detection device main body to a position corresponding to 30% of the total length of the detection device main body 21. Accordingly, the position between the one end 21a and the other end 21b of the detection device main body 21 is a portion obtained by removing the range of the one end 21a and the other end 21b from the detection device main body 1. It turns out that. In the particulate matter detection device 400 of the present embodiment, the distance between the takeout terminal 31a and the takeout terminal 32a is preferably 5 to 100 mm, and more preferably 10 to 70 mm. If it is shorter than 5 mm, it may be easy to cause a short circuit due to creeping discharge. If it is longer than 100 mm, the detection device main body 21 of the particulate matter detection device 400 is attached to the piping or the like so that the extraction terminal 31a is located outside the piping. When it does, the part which protrudes outside the piping of the detection apparatus main body 21 becomes long too much, and it may become difficult to attach the detection apparatus main body 21 to a narrow space.

  Further, the distance between the extraction terminal 31a disposed at a position between the one end 21a and the other end 21b of the detection device main body 21 and the through hole 22 is preferably longer than 10 mm, and 20 mm. More preferably, it is longer. When it is shorter than 10 mm, when the particulate matter detection device 400 is attached to the pipe so that the portion of the through hole 22 is inserted into the pipe, the heat of the hot exhaust gas flowing through the pipe is taken out to the extraction terminal 31a. May be easily affected.

  The shape and size of the extraction terminal 31a are not particularly limited. For example, it is preferably a polygonal shape such as a square having a width of 0.5 to 3 mm and a length of 0.5 to 3 mm, but may be a circle, an ellipse, a racetrack shape, or other shapes. Examples of the material of the takeout terminal 31a include Ni, Pt, Cr, W, Mo, Al, Au, Ag, Cu, stainless steel, and Kovar.

  In the particulate matter detection device 400 of the present embodiment, the detection device main body 21 is formed long in one direction, and the length in the longitudinal direction is not particularly limited, but the particulate matter in the exhaust gas when inserted into the exhaust gas pipe. It is preferable that the length be such that sampling can be efficiently performed. For example, about 50 to 200 mm is preferable. In the particulate matter detection device 400 of the present embodiment, the through hole 22 is formed in one end portion 21a in the longitudinal direction. The thickness of the detection device main body 21 (the length in the direction (thickness direction) perpendicular to both the “longitudinal direction of the detection device main body” and the “gas flow direction”) is not particularly limited. About 5 to 3 mm is preferable. Here, the “thickness of the detection device main body 21” refers to the thickness of the thickest portion in the thickness direction. Further, the length of the detection device main body 21 in the flow direction when the gas flows through the through hole 22 is not particularly limited, but is preferably about 2 to 20 mm, for example. As shown in FIGS. 10A and 10B, the shape of the detection device main body 1 may be a plate having a rectangular cross-section perpendicular to the longitudinal direction, or the cross-sectional shape may be a rod shape such as a circle or an ellipse. Other shapes may be used as long as the shape is long in one direction. As a preferable material of the detection apparatus main body 21, the material mentioned as a preferable material of the interelectrode dielectric 4 and the outer electrode dielectric 6 in one Embodiment of the particulate matter detection apparatus of the said invention can be mentioned. . And since it is excellent in thermal shock resistance, cordierite is more preferable. Since these materials are both dielectrics, the first electrode 31 and the second electrode 32 covered with the dielectric are formed by embedding the first electrode 31 and the second electrode 32 inside the detection device main body 21. It becomes possible to form. The particulate matter detection device 400 has excellent heat resistance, dielectric breakdown resistance, and the like. Here, in the present embodiment, the “dielectric” refers to a substance that has a dielectric property superior to conductivity, and that behaves as an insulator against a DC voltage.

  As shown in FIG. 11, in the particulate matter detection device 400 of the present embodiment, one electrode 31 and two electrodes 32 are embedded in the wall forming the through hole 22, and the through hole 22 is sandwiched between them. One electrode 31 and two electrodes 32 covered with a dielectric are arranged. Thereby, by applying a predetermined voltage between the first electrode 31 and the second electrode 32, it is possible to cause a discharge in the through hole 22. Note that it is necessary that at least a pair of electrodes be provided. Further, the electrode is only required to be embedded in the wall forming the through hole 22 and is preferably disposed so as to sandwich the through hole 22 as shown in FIG. If a discharge can be caused in the through hole 22, a pair of electrodes may be disposed at any position on the wall surrounding the through hole 22. The type of discharge is preferably one selected from the group consisting of silent discharge, streamer discharge, and corona discharge. In order to generate such a discharge, the particulate matter detection device 400 of the present embodiment further includes a dust collection power source connected to the extraction terminals 31a and 32a. As the dust collection power source, a high voltage AC power source, a DC power source, or the like is preferable. Moreover, as a voltage applied in order to discharge, alternating voltage, such as a pulse voltage and a rectangular wave, is preferable. Further, the condition of the voltage to be applied varies depending on the gap and the gas temperature, but is preferably 200 kV / cm or less. Moreover, 0.1-10 W is preferable for the electric power when a voltage is applied.

  The particulate matter detection device 400 according to the present embodiment generates a particulate matter by causing a discharge in the through hole 22 when the particulate matter contained in the fluid flowing into the through hole 22 is not charged. The charged particulate matter is electrically adsorbed on the wall surface of the through hole 22 by being charged. If the particulate matter contained in the fluid flowing into the through-hole 22 is already charged before flowing into the through-hole 22, there is no need to recharge by the discharge in the through-hole 22. Therefore, the charged particulate matter is electrically adsorbed on the wall surface of the through hole 22 without causing a discharge in the through hole 22. When the particulate matter is charged by causing a discharge in the through hole 22, the charged particulate matter is electrically connected to the electrode side having a polarity opposite to the polarity of the charged particulate matter during the discharge. Are attracted and adsorbed to the wall surface. On the other hand, when the particulate matter is charged before flowing into the through hole 22, a voltage under a predetermined condition is applied between the one electrode 31 and the second electrode 32 to charge the particulate matter. The electrode is electrically attracted to the side of the electrode having the opposite polarity to the polarity of the particulate matter. Here, when the particulate matter is charged before flowing into the through hole 22, the voltage condition applied between the first electrode 31 and the second electrode 32 is 4 kV / cm to 40 kV / cm. It is preferable that

  The shape and size of the first electrode 31 and the second electrode 32 are not particularly limited as long as the discharge can be caused in the through hole 2. For example, examples of the shape include a rectangle, a circle, and an oval. The size of the first electrode 31 and the second electrode 32 is preferably, for example, 70% or more of the area of the through hole 22 when viewed from the side surface.

  The thickness of each of the first electrode 31 and the second electrode 32 is not particularly limited as long as it can cause discharge in the through hole 22. For example, it is preferable that it is 5-30 micrometers. Preferred materials for the first electrode 31 and the second electrode 32 include the materials listed as preferred materials for the first electrode 31 and the second electrode 32 in one embodiment of the particulate matter detection device of the present invention. be able to.

  The distance between the first electrode 31 and the through hole 22 and the distance between the second electrode 32 and the through hole 22 are preferably 50 to 500 μm, and more preferably 100 to 300 μm. By setting it as such a range, an electric discharge can be effectively produced in a through-hole. The distance between each of the first electrode 31 and the second electrode 32 and the through hole 22 is the distance between the dielectric covering the first electrode 31 and the dielectric covering the second electrode 32 of the portion facing the through hole 22. That is the thickness.

  In the particulate matter detection device 400 of the present embodiment, as shown in FIG. 12, a wire 31b extending in the longitudinal direction of the detection device main body 21 is connected to one electrode 31, and the wire 31b is connected to the tip of the wire 31b. At the (tip on the side not connected to one electrode 31) portion, interlayer connection (via connection) is made to the extraction terminal 31a shown in FIG. 10B. Further, as shown in FIG. 13, each of the measurement electrodes 41 and 42 is connected to each of wirings 41 b and 42 b extending in the longitudinal direction of the detection device main body 21, and each of the wirings 41 b and 42 b is connected to the tip thereof. At the (tip on the side not connected to each of the measurement electrodes 41 and 42) portion, interlayer connection is made to each of the extraction terminals 41a and 42a shown in FIG. 10B. The characteristic measuring device 3 (see FIG. 7) is connected to the extraction terminals 41a and 42a of the measurement electrodes 41 and 42. A particulate matter amount calculating device 13 (see FIG. 7) is connected to the characteristic measuring device 3 (see FIG. 7). As shown in FIG. 14, a through hole 22 is formed in one end portion 21 a of the detection device main body 21. Here, FIG. 12 is a schematic diagram showing the BB ′ cross section of FIG. 11, FIG. 13 is a schematic diagram showing the BB ′ cross section of FIG. 11, and FIG. It is a schematic diagram which shows D 'cross section.

  Further, as shown in FIG. 15, the second electrode 32 is connected to a wiring 32b extending in the longitudinal direction of the detection device main body 21, and the wiring 32b is interlayer-connected to an extraction terminal 32a shown in FIG. 10B. Here, FIG. 15 is a schematic diagram showing a cross section taken along line E-E ′ of FIG. 11.

  The widths of the wiring 31b, the wiring 32b, the wiring 41b, and the wiring 42b are not particularly limited, and are preferably about 0.2 to 1 mm, for example. Moreover, the thickness of the wiring 31b, the wiring 32b, the wiring 41b, and the wiring 42b is not specifically limited, For example, about 5-30 micrometers is preferable. Examples of the material of the wiring 31b, the wiring 32b, the wiring 41b, and the wiring 42b include platinum, molybdenum, tungsten, and the like.

  As shown in FIGS. 11 and 16, the particulate matter detection device 400 of the present embodiment is arranged inside the detection device main body 21 along the wall surface of the through hole 22 (a wall surface parallel to the side surface of the detection device main body 21). It is preferable to further include a heater 33 disposed (embedded). The particulate matter adsorbed on the electrode can be heated and oxidized by the heater 33, and the internal space of the through hole 22 is adjusted to a desired temperature and the through hole is formed at the time of mass measurement of the particulate matter. The temperature can be adjusted to stably measure the change in the electrical characteristics of the wall. The heater 33 may be in the form of a wide film, but as shown in FIG. 16, a linear metal material is arranged in a wave shape and arranged so as to make a U-turn at the tip portion. preferable. By adopting such a shape, the inside of the through hole can be uniformly heated. Examples of the material of the heater 33 include platinum, molybdenum, tungsten, and the like. The heater 33 is preferably embedded in the detection device main body 21 along the wall surface of the through hole 22, but only at the position where the through hole 2 is disposed as shown in FIGS. 14 and 16. Alternatively, it may be formed so as to extend toward the other end 21b of the detection device main body 21. Thereby, the temperature difference between the inside of the through hole and the vicinity of the through hole can be reduced, and there is an advantage that the element is not easily damaged even when rapidly heated. It is preferable that the temperature of the internal space of the through hole 22 can be raised to 650 ° C. by the heater 33.

  In the particulate matter detection device 400 of the present embodiment, at least one of the first electrode 31 and the second electrode 32 is at least at a position opposite to the side where the through hole 22 is formed. One heater 33 is preferably provided. In the particulate matter detection device 400 of this embodiment shown in FIG. 11, the heater 33 is disposed at a position opposite to the side where the through hole 22 of the second electrode 32 is formed. Thus, the heater 33 is disposed at a position opposite to the side where the through hole 22 is formed, of at least one of the one electrode 31 and the second electrode 32. A discharge can be caused between the first electrode 31 and the second electrode 32 without being affected by the electrical effects of the conductors constituting the heater 33. In FIG. 11, the number of heaters 33 is one, but a plurality of heaters 33 may be provided at positions opposite to the side where the through holes 22 of the two electrodes 32 are provided. In FIG. 11, the heater 33 is disposed at a position on the opposite side of the second electrode 32 with respect to the side where the through hole 22 is disposed, but the one electrode 31 and the second electrode 32 are disposed. It is also preferable that at least one heater 33 is disposed at a position on the opposite side of each (both) side where the through hole 22 is formed. The arrangement and the number of the heaters 33 can be the arrangement and the number necessary for achieving the purpose of adjusting the temperature and oxidizing and removing the collected particulate matter.

  As shown in FIG. 16, the heater 33 is connected to the wirings 33b and 33b, and the wirings 33b and 33b are interlayer connected to the extraction terminals 33a and 33a shown in FIG. 10B, respectively. Similarly to the extraction terminals 31a and 32a of the first electrode 31 and the second electrode 32, the extraction terminal 33a of the heater 33 avoids the influence of heat when the one end 21a side of the detection device body 21 is heated. In order to achieve this, it is preferable that the other end portion 21b of the detection device main body 21 is disposed. In FIG. 10B, the extraction terminals 41 a and 42 a are arranged at both end edges in the width direction on the side surface of the detection device main body 21, and the extraction terminals 33 a and 33 a are arranged at the center in the width direction on the side surface of the detection device main body 21. The two terminals are arranged side by side, and the extraction terminal 32a is disposed between the extraction terminal 41a and the extraction terminal 33a. Although it is one of the preferable aspects that the arrangement of these extraction terminals is such an arrangement, the arrangement is not limited to such an arrangement.

  When the heater 33 is linear, the width of the line is not particularly limited, and is preferably about 0.05 to 1 mm, for example. Moreover, the thickness of the heater 33 is not specifically limited, For example, about 5-30 micrometers is preferable. The width of the wiring 33b is not particularly limited, and is preferably about 0.7 to 4 mm, for example. Moreover, the thickness of the wiring 33b is not specifically limited, For example, about 5-30 micrometers is preferable. The width of the takeout terminal 33a corresponding to the heater 33 is not particularly limited, and is preferably about 0.1 to 2 mm, for example. The thickness of the takeout terminal 33a is not particularly limited, and is preferably about 5 to 1000 μm, for example. Examples of the material of the wiring 33b and the extraction terminal 33a include nickel, platinum, chromium, tungsten, molybdenum, aluminum, gold, silver, copper, stainless steel, and kovar.

  In addition, the particulate matter detection device 400 of the present embodiment applies a voltage between one electrode 31 and the pair of measurement electrodes 41 and 42 to cause a discharge in the through hole 2 and is adsorbed by the electrodes. It is preferable that the particulate matter can be removed by oxidation. The discharge generated in the through hole is preferably a creeping discharge generated on the surface of the dielectric coated on one surface of the one electrode 31. As conditions for causing discharge when oxidizing and removing particulate matter, the electric field strength is 10 to 200 kV / cm, and the energy input amount is 0.05 to 10 J / μg with respect to the material to be treated. preferable. In order to cause such discharge, it is preferable to further include a power supply for removal.

  The particulate matter detection device 400 of the present embodiment preferably further includes a heating power source connected to the take-out terminal 33a of the heater 33. Examples of the heating power source include a constant current power source.

  In the particulate matter detection device 400 of the present embodiment, the shape and size of the through hole 22 are not particularly limited as long as the exhaust gas can be passed through and the amount of particulate matter can be measured. For example, the length of the through hole 22 in the longitudinal direction of the detection device main body is preferably about 2 to 20 mm, and the width of the portion of the through hole 22 sandwiched between the first electrode 31 and the second electrode 32 (detection device main body). The length in the direction perpendicular to both the longitudinal direction and the gas flow direction is preferably about 3 to 30 mm. By setting it as such a range, the exhaust gas containing a particulate matter can be fully distribute | circulated in the through-hole 22, and also in order to charge a particulate matter in the through-hole 22, an effective discharge is caused. It becomes possible. Moreover, as a shape of the through-hole 22, it is preferable that at least one of the inlet part into which the fluid flows in, and the outlet part from which the fluid flows out of the through-hole 22 are expanded. Since at least one of the inlet portion into which the fluid flows and the outlet portion from which the fluid flows out of the through hole 22 is expanded, the particulate matter detection device penetrates the exhaust gas flowing through the pipe more efficiently. It is possible to flow into the hole (when the inlet portion is expanded) and / or outflow (when the outlet portion is expanded). In another embodiment of the particulate matter detection device of the present invention shown in FIG. 17 (particulate matter detection device 500), only the inlet portion 22a into which the fluid flows in the through hole 22 is expanded, and the expanded portion 22b. Is formed. In the particulate matter detection device 500 shown in FIG. 17, the through hole 22 is expanded so as to extend in the longitudinal direction of the detection device main body 21, but extends so as to extend in the thickness direction of the detection device main body 21. It may be expanded. FIG. 17 shows still another embodiment of the particulate matter detection device of the present invention, and a cross section of still another embodiment (particulate matter detection device 400) of the particulate matter detection device of the present invention shown in FIG. It is a schematic diagram corresponded to the schematic diagram shown.

  The expanded width of the expanded portion 22b (the width of the most distal portion of the through hole 22 in the gas flow direction) T1 is preferably 2 to 200% with respect to the width T2 of the unexpanded portion of the through hole 22. . Further, the depth L1 of the expanded portion 22b in the gas flow direction of the through hole 22 (depth of the expanded portion) L1 is 5 to 30% of the length L2 of the through hole 22 in the gas flow direction of the detection device main body 21. preferable.

  As shown in FIGS. 18A and 18B, another embodiment of the particulate matter detection device (particulate matter detection device 600) of the present invention has a cross-sectional shape perpendicular to the central axis of the detection device main body 21 with the through-hole 22. In the penetrating direction, it is preferable that the shape gradually becomes thicker from one end side toward the central part, is thickest at the central part, and gradually becomes thinner toward the other end side. By making the shape of the detector main body in this way, the flow of exhaust gas in the pipe is good when the gas flow direction of the through hole is matched (parallel) to the flow direction of the exhaust gas in the pipe. Can be. The “center portion” of the particulate matter detection device (detection device main body) in the penetration direction of the through hole is the center of the particulate matter detection device when the length in the penetration direction of the through hole is divided into three equal parts. Means a “one-third range” located. Therefore, when the phrase “thickest in the central part in the penetration direction of the through-hole of the particulate matter detection device” is used, the thickest part is located in the “one-third range located in the central part”. means. Here, FIG. 18A is a schematic view showing a cross-section perpendicular to the central axis and including a through hole, showing still another embodiment of the particulate matter detection device of the present invention, and FIG. 18B is a particle of the present invention. It is a schematic diagram which shows the cross section which is orthogonal to the central axis and does not contain a through-hole which shows other embodiment of a particulate matter detection apparatus.

  In the particulate matter detection device 400 of the present embodiment, the detection device body 21 is preferably formed by laminating a plurality of tape-shaped ceramics (ceramic sheets). Thereby, since the particulate matter detection device 400 can be produced by laminating a plurality of tape-shaped ceramics with each electrode, wiring, etc. being sandwiched between them, the particulate matter detection device 400 of the present embodiment is reduced. It becomes possible to manufacture efficiently.

  The particulate matter detection device 400 of the present embodiment can exert its effect particularly when the particulate matter passing through the through hole 22 is to be discharged from the diesel engine.

  Still another embodiment (particulate matter detection device 400) of the particulate matter detection device of the present embodiment described above is one of the particulate matter detection devices of the present invention described above, except for the contents of the elements described above. The same as in the case of the embodiment is preferable.

  [Materials of Particulate Matter Detection Device] Next, materials forming the constituent elements of the particulate matter detection device according to the present invention will be described by taking the case of the particulate matter detection device 100 as an example.

  Preferred materials for forming the first electrode 1, the second electrode 2, and the measurement electrodes 5 and 15 and the wiring used for connecting them are gold, silver, copper, platinum, palladium, nickel, titanium, manganese, molybdenum, and tungsten. And those containing at least one selected from the group consisting of: A preferable content of these components is 20% by volume or more, and a more preferable content is 60% by volume or more. Stainless steel can be used as a material for forming the first electrode 1, the second electrode 2, the measurement electrodes 5 and 15, and the wiring used for connecting them.

  Preferred materials for forming the interelectrode dielectric 4, the outer electrode dielectric 6, and the heat insulating material 8 are alumina, magnesium oxide, silicon oxide, silicon nitride, aluminum nitride, zirconia, cordierite, mullite, spinel, and aluminum-titanium. Examples thereof include a ceramic containing at least one selected from the group consisting of a series oxide, a magnesium-calcium-titanium series oxide, a barium-titanium-zinc series oxide, and a barium-titanium series oxide. A ceramic-glass composite material that can be fired at a low temperature in which a glass component is mixed with the ceramics can also be used. Such a ceramic interelectrode dielectric 4 and an outer electrode dielectric 6 are not easily destroyed even when a temperature change occurs, and are excellent in thermal shock resistance. In the case of the heat insulating material 8, alumina, magnesium oxide, silicon oxide, silicon nitride, aluminum nitride, zirconia, cordierite, mullite, spinel, aluminum-titanium oxide, magnesium-calcium-titanium oxide, barium-titanium. -Ceramics containing at least one selected from the group consisting of zinc-based oxides and barium-titanium-based oxides can be mentioned. A ceramic-glass composite material that can be fired at a low temperature in which a glass component is mixed with the ceramics can also be used. These can also be made porous or fiber-like.

  The measurement electrodes 5 and 15 can be covered with a film-like dielectric. In this case, the dielectric can be made of alumina, magnesium oxide, silicon oxide, silicon nitride, aluminum nitride, zirconia, cordierite. A ceramic containing at least one selected from the group consisting of mullite, spinel, aluminum-titanium oxide, magnesium-calcium-titanium oxide, barium-titanium-zinc oxide, and barium-titanium oxide. I can list them. A ceramic-glass composite material that can be fired at a low temperature in which a glass component is mixed with the ceramics can also be used.

  Preferred materials for forming the heater 7 are platinum, copper, nickel, titanium, manganese, tungsten, molybdenum, tungsten carbide, and the like. In particular, platinum exhibits high accuracy in the relationship between the resistance value and the temperature. By using this as the material of the heater 7, temperature control with high accuracy becomes possible.

  [Method for Producing Particulate Matter Detection Device] Next, a method for producing a particulate matter detection device according to the present invention will be described by taking as an example the case where the particulate matter detection device 100 is produced.

  First, a binder, a plasticizer, a dispersant, a solvent such as water or an organic solvent, etc., are mixed with the ceramic raw material preferable as the above-described interelectrode dielectric 4, outer electrode dielectric 6, and heat insulating material 8 as necessary. Then, a slurry-like raw material for molding is prepared. In mixing, an alumina pot and alumina cobblestone, or a monoball (ball mill) can be used. The raw materials for the interelectrode dielectric 4, the outer electrode dielectric 6, and the heat insulating material 8 may have the same composition or different compositions. It is preferable to add a foaming agent to the raw material for molding the heat insulating material 8.

  As the binder, methyl cellulose, polyvinyl alcohol, polyethylene oxide or the like can be suitably used as the aqueous binder, and polyvinyl butyral, acrylic resin, polyethylene, polypropylene or the like can be suitably used as the non-aqueous binder. . Examples of acrylic resins include (meth) acrylic resins, (meth) acrylic acid ester copolymers, acrylic acid ester-methacrylic acid ester copolymers, and the like. From the viewpoint of suppressing the occurrence of cracks during the subsequent forming, drying, and firing of the green sheet, the preferred addition amount of the binder is 3 to 20 parts by mass, particularly preferably 100 parts by mass of the ceramic raw material. The addition amount is 6 to 17 parts by mass.

  Preferred plasticizers are glycerin, polyethylene glycol, dibutyl phthalate, di-2-ethylhexyl phthalate, diisononyl phthalate and the like. A preferable addition amount of the plasticizer is 30 to 70 parts by mass with respect to 100 parts by mass of the binder, and a particularly preferable addition amount is 45 to 55 parts by mass. When the amount is more than 70 parts by mass, the green sheet becomes too soft and may be easily deformed in the process of processing the sheet. When the amount is less than 30 parts by mass, the green sheet becomes too hard and cracks are generated only by bending. , Handling may be worse.

  Preferred dispersing agents are anionic surfactants, wax emulsions, pyridine and the like in aqueous systems, and fatty acids, phosphate esters, synthetic surfactants and the like in non-aqueous systems. The preferable addition amount of a dispersing agent is 0.5-3 mass parts with respect to 100 mass parts of ceramic raw materials, and especially preferable addition amount is 1-2 mass parts. When the amount is less than 0.5 parts by mass, the dispersibility of the ceramic raw material may be lowered, and a crack or the like may occur in the green sheet. If the amount is more than 3 parts by mass, the dispersibility of the ceramic raw material remains unchanged, and impurities during firing increase.

  Preferred organic solvents (solvents) are xylene, butanol and the like. An organic solvent may be used individually by 1 type, and may mix and use multiple. A preferable amount of the solvent added is 50 to 200 parts by mass with respect to 100 parts by mass of the ceramic raw material, and a particularly preferable amount of addition is 75 to 150 parts by mass.

  Then, the slurry-like forming raw material is stirred and defoamed under reduced pressure, and further prepared to have a predetermined viscosity. From the viewpoint of facilitating molding into a sheet shape, the preferable viscosity is 2.0 to 6.0 Pa · s as a value measured with a B-type viscometer, and the more preferable viscosity is 3.0 to 5.0 Pa · s. The particularly preferred viscosity is 3.5 to 4.5 Pa · s. A slurry is preferred.

  Next, the obtained forming raw material is formed into a sheet shape, and a green sheet to be the interelectrode dielectric 4, the outer electrode dielectric 6, and the heat insulating material 8 is formed later. A preferable forming method is a doctor blade method, a press forming method, a rolling method, a calendar roll method, or the like. A preferable green sheet has a thickness of 50 to 800 μm.

  Then, on the surface of the obtained green sheet, one electrode 1, a pair of measurement electrodes 5, 15, a heater 7, and a conductor paste that becomes necessary wiring are disposed, and the green sheets are laminated to form a green sheet. A laminate is obtained. For the conductive paste, a solvent such as binder and terpineol is added to a powder made of a material suitable for the electrode 1 described above, the pair of measurement electrodes 5 and 15, the heater 7, and necessary wiring, and a triroll mill or the like is used. And kneaded thoroughly. A suitable arrangement means for the conductive paste is a screen printing method. Specifically, the conductor paste is arranged by printing one electrode 1 and a conductor paste to be necessary wiring on one surface of the green sheet to be the outer electrode dielectric 6, and further interelectrode dielectric 4. And the measurement electrodes 5, 15 and necessary wirings in a desired pattern (see FIGS. 5 and 6 for the measurement electrodes 5, 15) on the surface of the green sheet to be the interelectrode dielectric 4. (Refer to) Print. On the other hand, on the other surface of the green sheet that will be the dielectric 6 outside the electrode, a heater 7 and a conductive paste that will be necessary wiring are printed, and a green sheet that will be the heat insulating material 8 is further laminated (see FIG. 1). The green sheets are preferably laminated while being pressurized.

  Next, the obtained green laminated body is dried at 60 to 150 ° C., and if it contains an organic binder, it is degreased at 400 to 800 ° C., and then fired at 1200 to 1600 ° C. In this way, the fired laminate including the one electrode 1, the interelectrode dielectric 4, the measurement electrodes 5 and 15, the outer electrode dielectric 6, the heater 7, and the heat insulating material 8 constituting the particulate matter detection device 100. Is obtained.

  For the second electrode 2, a commercially available thin plate made of the above-described suitable material is purchased and used and integrated with the fired laminate through a support member. As the second electrode, a laminate of ceramic and conductor paste may be used. As the support member, a sintered body made of a material suitable for the above-described interelectrode dielectric 4, outer electrode dielectric 6, and heat insulating material 8 can be used.

  Further, the fired laminate and the support member for the second electrode 2 may be integrated so as to form a cavity (space) through which exhaust gas containing the particulate matter 11 flows. In this case, before obtaining the fired laminate, a green sheet that forms a cavity on the interelectrode dielectric 4 (measurement electrodes 5 and 15) side of the green laminate, a green sheet that serves as a top plate, Are further laminated, and on the inner surface (surface facing the cavity) of the green sheet serving as the top plate, the second electrode 2 and the conductor paste serving as necessary wiring are disposed later, Obtaining, drying, necessary degreasing, and firing may be performed.

  As the dust collection power source 9, the characteristic measuring device 3, and the heater power source 10, commercially available products that meet the above-described preferable specifications are purchased. A commercially available product can also be used for the flow meter 14. The dust collecting power source 9 is connected to one electrode 1 and the second electrode 2, the characteristic measuring device 3 is connected to the measuring electrodes 5 and 15, and the heater power source 10 is connected to the heater 7. The particulate matter amount calculating device 13 and the particulate matter concentration calculating device 16 can be constructed by software in a computer such as a sequencer. The control device 12 can be constructed by software and a control circuit (hardware) in a computer such as a sequencer so as to realize the operation of the particulate matter detection device 100 described above or later. As described above, the particulate matter detection device 100 can be manufactured.

  10A and 10B, when the particulate matter detection device according to another embodiment of the present invention (particulate matter detection device 400) is manufactured, the forming raw material is processed into a sheet shape to obtain a green sheet. When forming the green sheet, the shape of the green sheet is long in one direction as shown in FIGS. 12 to 16, and when stacked, the particulate matter detection device as shown in FIGS. 10A, 10B, and 11 is used. Make the shape of Then, a plurality of green sheets are formed, and a conductor paste that will later become one electrode 31 or the like is disposed at a predetermined position on the surface of the predetermined green sheet, and each green sheet is laminated to form a green laminate. obtain. At this time, the second electrode 32 is also formed by disposing a conductive paste that will later become the second electrode 32 on the green sheet.

  [Method of Using Particulate Matter Detection Device] Next, a method of using the particulate matter detection device according to the present invention will be described by taking the case of using the particulate matter detection device 100 as an example.

  (Dust collection step) First, the sensor part of the particulate matter detection device 100 is installed in, for example, an exhaust system (exhaust gas pipe) of a diesel engine, and power supply, control line connection, etc. are performed to make it usable. Then, for example, a high DC voltage is applied between the second electrode 2 and the first electrode 1 by the dust collecting power source 9 to charge the particulate matter 11 and deposit it on the surface of the interelectrode dielectric 4. When the particulate matter detection device 400 shown in FIGS. 10A and 10B is used, one end 21a of the particulate matter detection device 400 is inserted into the exhaust gas pipe, and the through hole 22 is formed in the exhaust gas pipe. It is preferable to arrange the particulate matter detection device so that the other end 21b is located outside the exhaust gas pipe. At this time, it is preferable that the take-out end portion 31a of one electrode 31 is taken out from the exhaust gas pipe.

  A preferable time for applying the high voltage is 0.5 to 120 seconds, and more preferably 2 to 10 seconds. If the time is shorter than 0.5 seconds, the dust collection amount of the particulate matter 11 decreases, so the measurement accuracy of the particulate matter amount 11 may decrease. If it is longer than 120 seconds, the dust collection amount of the particulate matter 11 Therefore, it may be difficult to accurately grasp the amount of the particulate matter 11 from detection of the amount of change in impedance.

  A preferable voltage to be supplied to the first electrode 1 and the second electrode 2 varies depending on the distance between the electrodes, but by increasing the applied voltage, the electric field is strengthened and the dust collecting power is improved. On the other hand, the voltage is preferably 10 kV or less in practice because insulation, insulation distance, and the like become problems and the apparatus becomes large.

  A preferable current due to the discharge flowing between the first electrode 1 and the second electrode 2 is 1 mA or less, and a more preferable current is 1 to 100 μA. If it is less than 1 μA, the dust collection rate may decrease.

  Since the electric power used directly affects fuel consumption, it is desirable that the electric power used be small. Also, considering the reduction of electromagnetic noise generated and the size of the circuit that generates discharge, the preferred power consumption is 10 W or less, and the more preferred power consumption is 1 W or less.

  (Measurement step) When the deposition of the particulate matter 11 is finished, the application of the high voltage between the second electrode 2 and the first electrode 1 is stopped, and the characteristic measuring device 3 is operated, preferably about 1 to 60 seconds. , The amount of change in impedance between the measurement electrodes 5 and 15 is measured. The amount and concentration of the particulate matter 11 are determined by the amount of change in impedance. As described above, the amount of change in impedance between the measurement electrodes 5 and 15 can be measured while being deposited on the surface of the interelectrode dielectric 4 (while applying a high voltage). However, these are handled as different measurement modes.

  When the characteristic measuring device 3 is constituted by an AC power source for applying a voltage to the measurement electrodes 5 and 15 and a measuring device, a preferable voltage value applied from the AC power source is 1 to 60 V, and a more preferable voltage value. Is 2-30V. If the voltage is less than 1V, the detection signal is small and susceptible to noise. If the voltage is greater than 60V, the general-purpose IC may not be used. A preferable measurement frequency is 300 kHz or less.

  (Removal step) When the measurement of the amount of change in impedance between the measurement electrodes 5 and 15 is finished, the heater 7 is operated by the heater power source 10 to oxidize the particulate matter 11 deposited on the surface of the interelectrode dielectric 4. Remove.

  When the heater power supply 10 is a step-down chopper type switching power supply, the preferred current passed through the heater 7 is about 0.8 to 4 A, and the preferred power consumption is 48 W or less.

  A preferable time when the particulate matter 11 is removed by oxidation by the heater 7 is 1 to 600 seconds, and a particularly preferable time is 3 to 120 seconds. When the time is shorter than 1 second, the particulate matter 11 may not be oxidized and removed. When the time is longer than 600 seconds, energy may be consumed wastefully.

  A preferable temperature when the particulate matter 11 collected on the surface of the interelectrode dielectric 4 is oxidized and removed by the heater 7 is 500 to 900 ° C., and a particularly preferable temperature is 550 to 700 ° C. When the temperature is lower than 500 ° C., the particulate matter may be difficult to be removed by oxidation. When the temperature is higher than 900 ° C., the lifetime of the device may be shortened.

  As described above, a voltage is applied between one electrode 1 and the pair of measurement electrodes 5 and 15 in place of or in combination with the heater 7 and the heater power source 10, and the electrodes A removal power source for causing creeping discharge is provided on the surface of the interlevel dielectric 4, and the particulate matter 11 collected by the creeping discharge can be oxidized and removed. In this case, a preferable voltage for the creeping discharge varies depending on the thickness of the interelectrode dielectric 4, but is, for example, 2 to 15 kV. The preferred power usage is 10-30W. A preferable time for creeping discharge is 1 to 600 seconds, and a particularly preferable time is 3 to 120 seconds. When the time is shorter than 1 second, the particulate matter 11 may not be oxidized and removed. When the time is longer than 600 seconds, energy may be consumed wastefully.

  As described above, by repeating the dust collection process, the measurement process, and the removal process, it is possible to stably detect the particulate matter 11 over a long period of time. In addition, when exhaust gas from a diesel engine is targeted for particulate matter detection, discharge should be performed when conditions such as the rotational speed, torque, exhaust gas flow rate, temperature, etc. of the diesel engine reach a specific state. Is preferred. These are determined by the control device 12 (sequencer or the like) by inputting the diesel engine information as a signal to the control device 12 and providing a thermometer in the exhaust gas pipe and inputting the information to the control device 12 as a signal. It is possible to

  The particulate matter detection device according to the present invention can be suitably used as a means for detecting particulate matter contained in exhaust gas or the like of a diesel engine or a flue.

1: one electrode, 2, 202, 302: second electrode, 3: characteristic measuring device, 4: interelectrode dielectric, 5, 15, 105, 115, 205, 215: measurement electrode, 6: outer electrode dielectric 7: heater, 8: heat insulating material, 9: power supply for dust collection, 10: power supply for heater, 11: particulate matter, 12: control device, 13: particulate matter amount calculation device, 14: flow meter, 16: Particulate matter concentration calculation device, 21: detection device main body, 21a: one end, 21b: the other end, 21c: one tip portion, 21d: the other tip portion, 22: through hole, 22a: inlet portion 22b: expanded portion, 31: one electrode, 31a, 32a, 33a, 41a, 42a: extraction terminal, 31b, 32b, 33b: wiring, 32: second electrode, 33: heater, 41, 42: measurement electrode , 100, 200, 300, 400, 500, 00: particulate matter detection device, L1: depth of the expansion portion, L2: length in the gas flow portion of the through-hole, T1: expanding the width, T2: expansion that is not wide.

Claims (15)

One electrode having a plate-like shape in which one surface is coated with a dielectric, and one electrode disposed on the one surface side of the one electrode through a space through which a gas containing particulate matter flows Two electrodes that perform either or both of forming an electric field and / or discharging according to a voltage applied between the power source, a power source that applies the voltage, and
A pair of measuring electrodes disposed opposite to the surface of the dielectric, a characteristic measuring means for measuring electrical characteristics between the pair of measuring electrodes, and the electrical measured by the characteristic measuring means Particulate matter amount calculation means for obtaining the amount of particulate matter collected on the surface of the dielectric based on the amount of change in characteristics;
A particulate matter detection device comprising:   A flow meter for measuring or estimating a flow rate of the gas flowing in the space, and particles in the gas flowing in the space based on the flow rate of the gas measured or estimated by the flow meter and the amount of the particulate matter The particulate matter detection device according to claim 1, further comprising particulate matter concentration calculation means for calculating the concentration of the particulate matter.   3. The particulate matter detection device according to claim 1, wherein the electrical characteristic is one or more electrical characteristics selected from a group of electrical characteristics including resistance, inductance, capacitance, and impedance.   The pair of measurement electrodes are linear, and are arranged on the surface of the dielectric so as to face each other in a direction perpendicular to the direction in which the gas containing the particulate matter flows. The particulate matter detection device according to claim 1.   5. The particulate matter detection device according to claim 4, wherein each of the pair of measurement electrodes exhibiting a linear shape branches into a plurality of portions and has a plurality of opposed portions.   The particulate matter detection device according to claim 5, wherein the pair of measurement electrodes having the plurality of facing portions are arranged over the entire surface of the dielectric.   The particulate matter detection device according to any one of claims 1 to 6, wherein the two electrodes have a plate shape.   The particulate matter detection device according to claim 7, wherein the second electrode includes a tube wall surface.   The particulate matter detection device according to any one of claims 1 to 6, wherein the two electrodes have a needle shape or a rod shape.   The particulate matter according to any one of claims 1 to 9, further comprising: a dielectric covering the other surface of the electrode having the plate shape; and a heater disposed on the surface of the dielectric. Detection device.   A power supply for removal is provided for applying a voltage between the one electrode and the pair of measurement electrodes to oxidize and remove particulate matter by creeping discharge, and by applying the voltage, one of the one electrode is provided. The particulate matter detection device according to any one of claims 1 to 10, wherein creeping discharge is caused on the surface of the dielectric coated on the surface.   The particulate matter detection device according to any one of claims 1 to 11, wherein the measurement electrode is covered with a film-like dielectric. One end is provided with a detection device body made of a dielectric long in one direction, in which a through-hole that is a space through which a gas containing particulate matter flows is formed, and the one electrode and the second electrode, One surface of the one electrode is embedded in the detection device main body so as to sandwich the through hole in a state facing the through hole side,
The particulate matter detection device according to any one of claims 1 to 12, wherein the pair of measurement electrodes is disposed on a wall surface on the side where the one electrode in the through hole is embedded.   The particulate matter detection device according to claim 13, wherein an extraction terminal of at least one of the one electrode and the second electrode is disposed at the other end of the detection device main body.   The at least one heater is embedded in a position opposite to the side where the through hole is formed in at least one of the one electrode and the second electrode. The particulate matter detection device described.

Images