WO2011001825A1 - Pm sensor - Google Patents

Pm sensor Download PDF

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WO2011001825A1
WO2011001825A1 PCT/JP2010/060177 JP2010060177W WO2011001825A1 WO 2011001825 A1 WO2011001825 A1 WO 2011001825A1 JP 2010060177 W JP2010060177 W JP 2010060177W WO 2011001825 A1 WO2011001825 A1 WO 2011001825A1
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dpf
electrodes
amount
sensor
capacitance
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PCT/JP2010/060177
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French (fr)
Japanese (ja)
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正 内山
充宏 阿曽
哲史 塙
正文 野田
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いすゞ自動車株式会社
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N9/00—Electrical control of exhaust gas treating apparatus
    • F01N9/002—Electrical control of exhaust gas treating apparatus of filter regeneration, e.g. detection of clogging
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
    • G01N15/06—Investigating concentration of particle suspensions
    • G01N15/0656—Investigating concentration of particle suspensions using electric, e.g. electrostatic methods or magnetic methods
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2560/00—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics
    • F01N2560/05—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics the means being a particulate sensor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
    • F01N2900/06—Parameters used for exhaust control or diagnosing
    • F01N2900/0601—Parameters used for exhaust control or diagnosing being estimated
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N2900/00—Details of electrical control or of the monitoring of the exhaust gas treating apparatus
    • F01N2900/06—Parameters used for exhaust control or diagnosing
    • F01N2900/16—Parameters used for exhaust control or diagnosing said parameters being related to the exhaust apparatus, e.g. particulate filter or catalyst
    • F01N2900/1606—Particle filter loading or soot amount
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/22—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating capacitance
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/10—Internal combustion engine [ICE] based vehicles
    • Y02T10/40—Engine management systems

Definitions

  • the present invention relates to a PM sensor that can accurately detect the amount of PM accumulated in a DPF with a simple configuration.
  • a diesel particulate filter (hereinafter referred to as DPF) is installed in the exhaust gas exhaust passage from the internal combustion engine to the atmosphere, and the SOF contained in the exhaust gas, Particulate matter (Matter) such as SOOT is collected (hereinafter collectively referred to as PM).
  • the DPF is a member that temporarily collects PM in a filter having a honeycomb pore shape (including a square one) mainly made of ceramic.
  • DPF regeneration When PM collected in DPF accumulates, back pressure rises and engine characteristics deteriorate, so the accumulated PM is burned. This operation is called DPF regeneration. During DPF regeneration, the exhaust temperature is raised by fuel injection for raising the exhaust temperature, and the DPF is combusted by raising the temperature of the DPF.
  • DPF regeneration is performed every time the travel distance of the vehicle reaches a predetermined value because it is difficult to detect the amount of PM accumulated in the DPF (PM load; indicating the degree of filter clogging).
  • PM load indicating the degree of filter clogging
  • the amount of PM is detected from the pressure difference between exhaust gas upstream and downstream of the DPF.
  • the flow rate / temperature of the exhaust gas is constantly changing with the state change of the internal combustion engine, the amount of PM detected from the pressure difference is not accurate.
  • Patent Document 1 for the purpose of detecting the amount of PM, an air-fuel ratio change which is not necessary for vehicle travel is given, which is not preferable.
  • an object of the present invention is to provide a PM sensor that can solve the above-described problems and can accurately detect the amount of PM accumulated in the DPF with a simple configuration.
  • the present invention provides two electrodes for forming a capacitor by sandwiching one or more of the partition walls in a diesel particulate filter (DPF) having a porous filter body partitioned by a number of partition walls.
  • DPF diesel particulate filter
  • the at least one electrode is formed and installed with a wire, and the amount of PM collected in the DPF is detected from the capacitance of the capacitor.
  • One of the two electrodes may be provided on the outer periphery of the filter body, and the other electrode may be provided inside the filter body.
  • One of the two electrodes may be provided on the outer periphery of the filter body, and one or more of the other electrodes may be provided in the one or more holes.
  • FIG. 1A is a block diagram of a PM sensor according to an embodiment of the present invention.
  • FIG. 1A illustrates a case where the amount of PM is small
  • FIG. 1B illustrates a case where the amount of PM is large.
  • FIG. 2A is a model (equivalent circuit) diagram of the PM sensor in FIG. 1,
  • FIG. 2A shows a time when the amount of PM is small
  • FIG. 2B shows a time when the amount of PM is large.
  • It is a graph of the rate of change of the amount of PM versus capacitance in the PM sensor of the present invention.
  • 4A is a perspective view of a PM sensor showing an embodiment of the present invention
  • FIG. 4B is a conceptual diagram showing a half of the PM sensor of FIG. 4A.
  • one PM sensor 1 is provided in a diesel particulate filter (DPF) 3 having a porous filter body 2 partitioned by a number of ceramic partition walls.
  • DPF diesel particulate filter
  • Two electrodes 4a and 4b forming a capacitor with the above partition interposed therebetween are installed with at least one electrode 4b formed of a wire, and the amount of PM collected in the DPF 3 from the capacitance of the capacitor is It is intended to be detected.
  • a detection unit for detecting the capacitance of the capacitor formed by the electrodes 4a and 4b and a calculation unit for converting the capacitance to the amount of PM are provided inside the electronic control unit (ECU) 5. It shall be.
  • the PM sensor 1 shown in FIG. 1A is modeled as shown in FIG. That is, the capacitance detection unit 22 is connected to a capacitor 21 in which two flat electrodes having the same size are opposed to each other with a predetermined distance between the electrodes.
  • FIG. 1B shows that the amount of PM is large by making the hatching of the DPF 3 darker than that in FIG.
  • PM model of the sensor 1 the value the capacitance of the capacitor 21 is large as shown in FIG. 2 (b) from the state is a value C 0 low capacitance of the capacitor 21 as shown in FIG. 2 (a) changes to the state is a C 1 (C 1> C 0 ).
  • Detecting unit 22 detects the capacitance of capacitor 21. At this time, if the capacitance is C, the dielectric constant of the medium between the electrodes is ⁇ , the area of the electrodes is S, and the distance between the electrodes is d,
  • the capacitance C increases as the dielectric constant ⁇ increases or the inter-electrode distance d decreases.
  • the present inventors investigated through experiments how the capacitance C of the capacitor formed by the two electrodes 4a and 4b installed in the PM sensor 1 changes depending on the amount of collected PM. It was. That is, by sucking from the downstream of the PM sensor 1, air was flown from the upstream to the downstream, and PM was gradually added into the air upstream of the PM sensor 1, and the change in the capacitance C was recorded. As a result, as shown in FIG. 3, it was found that the capacitance C increased almost linearly with respect to the amount of PM input. That is, the capacitance C accurately indicates the amount of PM collected by the PM sensor 1.
  • the reason why the capacitance C increases in proportion to the amount of collected PM is that the conductor carbon is inserted between the electrodes 4a and 4b, so that the inter-electrode distance d is apparently reduced and the capacitance is increased. It is conceivable that C increases or PM increases in the medium between the electrodes 4a and 4b and the dielectric constant ⁇ increases and the capacitance C increases.
  • the amount of PM collected can be accurately detected. Since the PM sensor 1 of the present invention has a simple configuration in which only the electrodes 4a and 4b are arranged, there are advantages that manufacturing is easy and cost is low.
  • the PM sensor 1 detects the amount of PM trapped in the partition wall from the capacitance even if two electrodes 4a and 4b are installed with only one partition wall sandwiched from the operating principle described above. Is done. However, in practice, it is desirable to install the electrodes 4a and 4b so as to sandwich a plurality of partition walls.
  • At least one of the two electrodes 4a and 4b is formed of a wire, so that the electrode 4b made of the wire is inserted into the hole of the filter body 2 and disposed. Can do.
  • one polarity electrode (outer electrode) 42a is provided on the outer periphery of the filter body 43, and one or more of the other polarity electrodes (inner electrode) 42b are provided. Each is provided in one or more holes 44.
  • the filter body 43 has a large number of square holes 44 formed by partition walls 45 arranged in a honeycomb shape, and the holes 44 closed on the upstream side and opened on the downstream side and the holes 44 closed on the downstream side and opened on the upstream side are alternately adjacent to each other. Yes.
  • the exhaust gas from the internal combustion engine enters the hole 44 opened on the upstream side, and the exhaust gas passes through the hole 44 opened on the downstream side over the entire surface of the partition wall. At this time, PM accumulates in the partition wall, and the purified exhaust gas flows downstream.
  • the inner electrode 42 b is a wire, for example, and may be disposed in the plurality of holes 44.
  • a plurality of wire rods are arranged around a virtual elliptic cylinder, and these wire rods are collectively connected to the detection unit 22 in FIG.
  • the surface area of the outer electrode 42a is large, the surface area of the inner electrode 42b can be increased by increasing the number of wires, and the capacitance C is large because the inter-electrode distance d is small. For this reason, it is easy to detect the capacitance C in the detection unit 22.

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  • Life Sciences & Earth Sciences (AREA)
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  • Combustion & Propulsion (AREA)
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  • Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
  • Processes For Solid Components From Exhaust (AREA)
  • Exhaust Gas After Treatment (AREA)

Abstract

A PM sensor is provided which is simple in structure but capable of precisely detecting an amount of PM accumulated in a DPF. In a diesel particulate filter (DPF) (3) having multi-aperture filter body (2) partitioned by many division walls, two electrodes (4a, 4b) form a capacitor with one or more division walls therebetween, and at least one (4b) of the two electrodes (4a, 4b) is formed by a wire rod, and the amount of PM collected in the DPF (3) is detected from the electrostatic capacity of the capacitor.

Description

ＰＭセンサPM sensor
　本発明は、簡素な構成で正確にＤＰＦに溜まったＰＭの量を検出することができるＰＭセンサに関する。 The present invention relates to a PM sensor that can accurately detect the amount of PM accumulated in a DPF with a simple configuration.
　ディーゼルエンジンなどの内燃機関を搭載した車両では、内燃機関から大気までの排気ガスの排出流路にディーゼルパティキュレートフィルタ（Diesel Particulate Filter；以下、ＤＰＦという）を設置し、排気ガスに含まれるＳＯＦ、ＳＯＯＴなどの粒子状物質（Particurate Matter）を捕集している（以下、これらをＰＭと総称する）。ＤＰＦは、主としてセラミックからなるハニカム細孔状（四角いものを含む）のフィルタにＰＭを一時的に捕集する部材である。 In a vehicle equipped with an internal combustion engine such as a diesel engine, a diesel particulate filter (hereinafter referred to as DPF) is installed in the exhaust gas exhaust passage from the internal combustion engine to the atmosphere, and the SOF contained in the exhaust gas, Particulate matter (Matter) such as SOOT is collected (hereinafter collectively referred to as PM). The DPF is a member that temporarily collects PM in a filter having a honeycomb pore shape (including a square one) mainly made of ceramic.
　ＤＰＦに捕集されたＰＭが溜まると背圧が上昇しエンジン特性の低下をきたすため、堆積したＰＭを燃焼させる。この動作をＤＰＦ再生という。ＤＰＦ再生時には、排気温度を上昇させるための燃料噴射によって排気温度を上昇させ、ＤＰＦを昇温することで、ＤＰＦに捕集されているＰＭを燃焼させる。 ∙ When PM collected in DPF accumulates, back pressure rises and engine characteristics deteriorate, so the accumulated PM is burned. This operation is called DPF regeneration. During DPF regeneration, the exhaust temperature is raised by fuel injection for raising the exhaust temperature, and the DPF is combusted by raising the temperature of the DPF.
　このとき、ＤＰＦにＰＭが溜まりすぎていると、ＤＰＦ再生時の熱でＤＰＦが損傷してしまう。ＤＰＦにＰＭが溜まりすぎないうちにＤＰＦ再生するために、従来は、正確に堆積量を計測できないので、一般的に安全係数を比較的多く取りＤＰＦを再生している。 At this time, if PM accumulates too much in the DPF, the DPF will be damaged by the heat during the DPF regeneration. In order to regenerate the DPF before PM accumulates too much in the DPF, conventionally, since the amount of deposition cannot be measured accurately, the DPF is generally regenerated with a relatively large safety factor.
　しかし、必要以上に短い間隔でＤＰＦ再生を実行すると燃料が余分に消費されることになり、燃費が悪化する。したがって、ＰＭの量を正確に検出し、最も適切な時期にＤＰＦ再生を行うようにするのが望ましい。 However, if DPF regeneration is performed at intervals shorter than necessary, extra fuel will be consumed and fuel consumption will deteriorate. Therefore, it is desirable to accurately detect the amount of PM and perform DPF regeneration at the most appropriate time.
特開２００８－２６１２８７号公報JP 2008-261287 A 特開２００５－２１４０８４号公報JP 2005-214084 A
　従来、車両の走行距離が所定値に達するごとにＤＰＦ再生するようにしたのは、ＤＰＦに溜まったＰＭの量（ＰＭロード；フィルタの詰まり具合を表す）を検出するのが困難であるからである。例えば、特許文献２の技術では、ＤＰＦの上流側と下流側の排気ガスの圧力差からＰＭの量を検出している。しかし、排気の流量・温度は、内燃機関の状態変化に伴ってたえず変化しているため、圧力差から検出するＰＭの量は正確でない。また、特許文献１では、ＰＭの量を検出するという目的のために、車両走行上に必要のない空燃比変化を与えることになり、好ましくない。 Conventionally, DPF regeneration is performed every time the travel distance of the vehicle reaches a predetermined value because it is difficult to detect the amount of PM accumulated in the DPF (PM load; indicating the degree of filter clogging). is there. For example, in the technique of Patent Document 2, the amount of PM is detected from the pressure difference between exhaust gas upstream and downstream of the DPF. However, since the flow rate / temperature of the exhaust gas is constantly changing with the state change of the internal combustion engine, the amount of PM detected from the pressure difference is not accurate. Further, in Patent Document 1, for the purpose of detecting the amount of PM, an air-fuel ratio change which is not necessary for vehicle travel is given, which is not preferable.
　また、実験室において、ＤＰＦに溜まったＰＭの量を検出する分析装置が知られているが、このような分析装置は大規模であり、車両には搭載できない。 Also, in the laboratory, an analyzer that detects the amount of PM accumulated in the DPF is known, but such an analyzer is large and cannot be mounted on a vehicle.
　そこで、本発明の目的は、上記課題を解決し、簡素な構成で正確にＤＰＦに溜まったＰＭの量を検出することができるＰＭセンサを提供することにある。 Therefore, an object of the present invention is to provide a PM sensor that can solve the above-described problems and can accurately detect the amount of PM accumulated in the DPF with a simple configuration.
　上記目的を達成するために本発明は、多数の隔壁で仕切られた多孔状のフィルタ本体を有するディーゼルパティキュレートフィルタ（ＤＰＦ）に、１個以上の上記隔壁を挟んでコンデンサを形成する２つの電極を、少なくとも一方の電極は線材により形成して設置し、上記コンデンサの静電容量から上記ＤＰＦに捕集されているＰＭの量が検出されるようにしたものである。 In order to achieve the above object, the present invention provides two electrodes for forming a capacitor by sandwiching one or more of the partition walls in a diesel particulate filter (DPF) having a porous filter body partitioned by a number of partition walls. The at least one electrode is formed and installed with a wire, and the amount of PM collected in the DPF is detected from the capacitance of the capacitor.
　上記２つの電極のうち一方の電極を上記フィルタ本体の外周に設け、他方の電極を上記フィルタ本体内部に設けてもよい。 One of the two electrodes may be provided on the outer periphery of the filter body, and the other electrode may be provided inside the filter body.
　上記２つの電極のうち一方の電極を上記フィルタ本体の外周に設け、他方の電極１個以上を１個以上の上記孔内にそれぞれ設けてもよい。 One of the two electrodes may be provided on the outer periphery of the filter body, and one or more of the other electrodes may be provided in the one or more holes.
　本発明によれば、簡素な構成で正確にＤＰＦに溜まったＰＭの量を検出することができる。 According to the present invention, it is possible to accurately detect the amount of PM accumulated in the DPF with a simple configuration.
本発明の一実施形態を示すＰＭセンサのブロック構成図であり、図１（ａ）はＰＭの量が少ない時、図１（ｂ）はＰＭの量が多い時を表す。FIG. 1A is a block diagram of a PM sensor according to an embodiment of the present invention. FIG. 1A illustrates a case where the amount of PM is small, and FIG. 1B illustrates a case where the amount of PM is large. 図１のＰＭセンサのモデル（等価回路）図であり、図２（ａ）はＰＭの量が少ない時、図２（ｂ）はＰＭの量が多い時を表す。FIG. 2A is a model (equivalent circuit) diagram of the PM sensor in FIG. 1, FIG. 2A shows a time when the amount of PM is small, and FIG. 2B shows a time when the amount of PM is large. 本発明のＰＭセンサにおけるＰＭの量対静電容量の変化率のグラフである。It is a graph of the rate of change of the amount of PM versus capacitance in the PM sensor of the present invention. 図４（ａ）は、本発明の一実施形態を示すＰＭセンサの斜視図、図４（ｂ）は、図４（ａ）のＰＭセンサの半分を示した概念図である。4A is a perspective view of a PM sensor showing an embodiment of the present invention, and FIG. 4B is a conceptual diagram showing a half of the PM sensor of FIG. 4A.
　以下、本発明の一実施形態を添付図面に基づいて詳述する。 Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.
　図１（ａ）に示されるように、本発明に係るＰＭセンサ１は、セラミックからなる多数の隔壁で仕切られた多孔状のフィルタ本体２を有するディーゼルパティキュレートフィルタ（ＤＰＦ）３に、１個以上の隔壁を挟んでコンデンサを形成する２つの電極４ａ，４ｂを、少なくとも一方の電極４ｂは線材により形成して設置し、そのコンデンサの静電容量からＤＰＦ３に捕集されているＰＭの量が検出されるようにしたものである。 As shown in FIG. 1 (a), one PM sensor 1 according to the present invention is provided in a diesel particulate filter (DPF) 3 having a porous filter body 2 partitioned by a number of ceramic partition walls. Two electrodes 4a and 4b forming a capacitor with the above partition interposed therebetween are installed with at least one electrode 4b formed of a wire, and the amount of PM collected in the DPF 3 from the capacitance of the capacitor is It is intended to be detected.
　この実施形態では、電子制御装置（ＥＣＵ）５の内部に電極４ａ，４ｂが形成するコンデンサの静電容量を検出する検出部と、静電容量をＰＭの量に変換する演算部が設けられているものとする。 In this embodiment, a detection unit for detecting the capacitance of the capacitor formed by the electrodes 4a and 4b and a calculation unit for converting the capacitance to the amount of PM are provided inside the electronic control unit (ECU) 5. It shall be.
　図１（ａ）のＰＭセンサ１は、図２（ａ）のようにモデル化して示される。すなわち、２つの同寸法平板状の電極を所定の電極間距離を隔てて対向させたコンデンサ２１に対し静電容量の検出部２２が接続されている。 The PM sensor 1 shown in FIG. 1A is modeled as shown in FIG. That is, the capacitance detection unit 22 is connected to a capacitor 21 in which two flat electrodes having the same size are opposed to each other with a predetermined distance between the electrodes.
　次に、ＰＭセンサ１の動作を説明する。 Next, the operation of the PM sensor 1 will be described.
　図１（ａ）のようにＤＰＦ３に捕集されたＰＭの量が少ない状態から、徐々にＰＭの量が増加し、図１（ｂ）のようにＤＰＦ３に捕集されたＰＭの量が多い状態になったとする。図１（ｂ）はＤＰＦ３のハッチングを図１（ａ）より濃くすることでＰＭの量が多いことを表している。このとき、ＰＭセンサ１のモデルは、図２（ａ）のようにコンデンサ２１の静電容量が小さい値Ｃ0である状態から図２（ｂ）のようにコンデンサ２１の静電容量が大きい値Ｃ1である状態に変化する（Ｃ1＞Ｃ0）。 From the state where the amount of PM collected in the DPF 3 is small as shown in FIG. 1A, the amount of PM gradually increases, and as shown in FIG. 1B, the amount of PM collected in the DPF 3 is large. Suppose that it is in a state. FIG. 1B shows that the amount of PM is large by making the hatching of the DPF 3 darker than that in FIG. At this time, PM model of the sensor 1, the value the capacitance of the capacitor 21 is large as shown in FIG. 2 (b) from the state is a value C 0 low capacitance of the capacitor 21 as shown in FIG. 2 (a) changes to the state is a C 1 (C 1> C 0 ).
　検出部２２では、コンデンサ２１の静電容量を検出する。このとき、静電容量をＣ、電極間の媒体の誘電率をε、電極の面積をＳ、電極間の距離をｄとすると、 Detecting unit 22 detects the capacitance of capacitor 21. At this time, if the capacitance is C, the dielectric constant of the medium between the electrodes is ε, the area of the electrodes is S, and the distance between the electrodes is d,
Figure JPOXMLDOC01-appb-M000001
Figure JPOXMLDOC01-appb-M000001
となる。よって、誘電率εが大きくなるか電極間距離ｄが小さくなるかすれば、静電容量Ｃは大きくなる。 It becomes. Therefore, the capacitance C increases as the dielectric constant ε increases or the inter-electrode distance d decreases.
　ここで、本発明者らは、ＰＭセンサ１内に設置した２つの電極４ａ，４ｂが形成するコンデンサの静電容量Ｃが捕集されたＰＭの量によってどのように変化するかを実験により調べた。すなわち、ＰＭセンサ１の下流から吸引することによって上流から下流に空気を流し、そのＰＭセンサ１の上流において空気中にＰＭを少量ずつ投入し、静電容量Ｃの変化を記録した。その結果、図３に示されるように、ＰＭの投入量に対してほぼ直線的に静電容量Ｃが増大することが分かった。すなわち、静電容量Ｃは、ＰＭセンサ１に捕集されたＰＭの量を正確に示す。 Here, the present inventors investigated through experiments how the capacitance C of the capacitor formed by the two electrodes 4a and 4b installed in the PM sensor 1 changes depending on the amount of collected PM. It was. That is, by sucking from the downstream of the PM sensor 1, air was flown from the upstream to the downstream, and PM was gradually added into the air upstream of the PM sensor 1, and the change in the capacitance C was recorded. As a result, as shown in FIG. 3, it was found that the capacitance C increased almost linearly with respect to the amount of PM input. That is, the capacitance C accurately indicates the amount of PM collected by the PM sensor 1.
　静電容量Ｃが捕集されたＰＭの量に比例して増加する理由としては、電極４ａ，４ｂ間に導体である炭素が入ることで、見かけ上、電極間距離ｄが小さくなり静電容量Ｃが大きくなる、あるいは、電極４ａ，４ｂ間の媒体中にＰＭが増加して誘電率εが大きくなり静電容量Ｃが大きくなると考えられる。 The reason why the capacitance C increases in proportion to the amount of collected PM is that the conductor carbon is inserted between the electrodes 4a and 4b, so that the inter-electrode distance d is apparently reduced and the capacitance is increased. It is conceivable that C increases or PM increases in the medium between the electrodes 4a and 4b and the dielectric constant ε increases and the capacitance C increases.
　以上説明したように、本発明のＰＭセンサ１は、ＤＰＦ３に、１個以上の隔壁を挟んでコンデンサを形成する２つの電極４ａ，４ｂを設置したので、コンデンサの静電容量ＣからＤＰＦ３に捕集されているＰＭの量を正確に検出することができる。本発明のＰＭセンサ１は、電極４ａ，４ｂを配置するだけの簡素な構成であるため、製造が容易であり、コストが安いという利点がある。 As described above, in the PM sensor 1 of the present invention, the two electrodes 4a and 4b that form a capacitor with one or more partition walls interposed in the DPF 3, the capacitance C of the capacitor is captured by the DPF 3. The amount of PM collected can be accurately detected. Since the PM sensor 1 of the present invention has a simple configuration in which only the electrodes 4a and 4b are arranged, there are advantages that manufacturing is easy and cost is low.
　なお、ＰＭセンサ１は、前述した動作原理から、ただ１個の隔壁を挟んで２つの電極４ａ，４ｂを設置しても、その隔壁に捕集されているＰＭの量が静電容量から検出される。しかし、実際には、複数の隔壁を挟むように電極４ａ，４ｂを設置するのが望ましい。 Note that the PM sensor 1 detects the amount of PM trapped in the partition wall from the capacitance even if two electrodes 4a and 4b are installed with only one partition wall sandwiched from the operating principle described above. Is done. However, in practice, it is desirable to install the electrodes 4a and 4b so as to sandwich a plurality of partition walls.
　また、本発明のＰＭセンサ１は、２つの電極４ａ，４ｂのうち、少なくとも一方の電極４ｂは線材により形成したので、線材からなる電極４ｂはフィルタ本体２の孔内に挿入して配置することができる。 In the PM sensor 1 of the present invention, at least one of the two electrodes 4a and 4b is formed of a wire, so that the electrode 4b made of the wire is inserted into the hole of the filter body 2 and disposed. Can do.
　次に、本発明のより具体的な実施形態を説明する。 Next, a more specific embodiment of the present invention will be described.
　図４に示されるように、本発明のＰＭセンサ４１は、一方の極性の電極（外側電極）４２ａをフィルタ本体４３の外周に設け、他方の極性の電極（内側電極）４２ｂの１個以上を１個以上の孔４４内にそれぞれ設けたものである。 As shown in FIG. 4, in the PM sensor 41 of the present invention, one polarity electrode (outer electrode) 42a is provided on the outer periphery of the filter body 43, and one or more of the other polarity electrodes (inner electrode) 42b are provided. Each is provided in one or more holes 44.
　フィルタ本体４３はハニカム状に並べられた隔壁４５によって形成された四角い孔４４が多数並んでおり、上流側が閉じ下流側が開いた孔４４と下流側が閉じ上流側が開いた孔４４が交互に隣接している。上流側が開いた孔４４に内燃機関からの排気ガスが入り、隔壁の全面において排気ガスが下流側が開いた孔４４に抜ける。このとき隔壁にＰＭが溜まり、浄化された排気ガスが下流に出ていく。 The filter body 43 has a large number of square holes 44 formed by partition walls 45 arranged in a honeycomb shape, and the holes 44 closed on the upstream side and opened on the downstream side and the holes 44 closed on the downstream side and opened on the upstream side are alternately adjacent to each other. Yes. The exhaust gas from the internal combustion engine enters the hole 44 opened on the upstream side, and the exhaust gas passes through the hole 44 opened on the downstream side over the entire surface of the partition wall. At this time, PM accumulates in the partition wall, and the purified exhaust gas flows downstream.
　内側電極４２ｂは、例えば、線材であり、複数個の孔４４内に配置するとよい。ここでは、仮想的な楕円筒の周囲に複数本の線材を配置し、これらの線材を一括して図２の検出部２２に接続する。 The inner electrode 42 b is a wire, for example, and may be disposed in the plurality of holes 44. Here, a plurality of wire rods are arranged around a virtual elliptic cylinder, and these wire rods are collectively connected to the detection unit 22 in FIG.
　ＰＭセンサ４１は、外側電極４２ａの表面積が大きく、内側電極４２ｂも線材の本数を多くすることでの表面積が大きくでき、また、電極間距離ｄが小さいので、静電容量Ｃが大きい。このため、検出部２２における静電容量Ｃの検出が容易になる。 In the PM sensor 41, the surface area of the outer electrode 42a is large, the surface area of the inner electrode 42b can be increased by increasing the number of wires, and the capacitance C is large because the inter-electrode distance d is small. For this reason, it is easy to detect the capacitance C in the detection unit 22.
　１，４１　ＰＭセンサ
　２，４３　フィルタ本体
　３　ディーゼルパティキュレートフィルタ（ＤＰＦ）
　４ａ，４ｂ　電極
　４２ａ　外側電極
　４２ｂ　内側電極
　４４　孔
　４５　隔壁
　５　ＥＣＵ 1,41 PM sensor 2,43 Filter body 3 Diesel particulate filter (DPF)
4a, 4b electrode 42a outer electrode 42b inner electrode 44 hole 45 partition 5 ECU

Claims (3)

  1. 　多数の隔壁で仕切られた多孔状のフィルタ本体を有するディーゼルパティキュレートフィルタ（ＤＰＦ）に、１個以上の上記隔壁を挟んでコンデンサを形成する２つの電極を、少なくとも一方の電極は線材により形成して設置し、上記コンデンサの静電容量から上記ＤＰＦに捕集されているＰＭの量が検出されるようにしたことを特徴とするＰＭセンサ。 In a diesel particulate filter (DPF) having a porous filter body partitioned by a large number of partition walls, two electrodes forming a capacitor with at least one partition wall interposed therebetween, at least one electrode is formed of a wire material. And a PM sensor that detects the amount of PM trapped in the DPF from the capacitance of the capacitor.
  2. 　上記２つの電極のうち一方の電極を上記フィルタ本体の外周に設け、他方の電極を上記フィルタ本体内部に設けたことを特徴とする請求項１記載のＰＭセンサ。 The PM sensor according to claim 1, wherein one of the two electrodes is provided on the outer periphery of the filter body, and the other electrode is provided inside the filter body.
  3. 　上記２つの電極のうち一方の電極を上記フィルタ本体の外周に設け、他方の電極１個以上を１個以上の上記孔内にそれぞれ設けたことを特徴とする請求項１又は２記載のＰＭセンサ。 3. The PM sensor according to claim 1, wherein one of the two electrodes is provided on an outer periphery of the filter body, and one or more of the other electrodes are provided in the one or more holes. .
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JP5874196B2 (en) * 2011-05-20 2016-03-02 いすゞ自動車株式会社 Particulate matter sensor
JP2012246778A (en) * 2011-05-25 2012-12-13 Isuzu Motors Ltd Pm sensor
JP6179378B2 (en) * 2013-12-06 2017-08-16 いすゞ自動車株式会社 Exhaust purification device

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JP2007262973A (en) * 2006-03-28 2007-10-11 Ngk Insulators Ltd Particulate quantity detection system

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WO2007066462A1 (en) * 2005-12-05 2007-06-14 Ngk Insulators, Ltd. Honeycomb structure body and method of producing the same
JP2007262973A (en) * 2006-03-28 2007-10-11 Ngk Insulators Ltd Particulate quantity detection system

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103502588A (en) * 2011-05-20 2014-01-08 五十铃自动车株式会社 Particulate matter sensor
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