JP2012047722A - Particulate matter detection sensor and method for determining abnormality of the sensor - Google Patents

Particulate matter detection sensor and method for determining abnormality of the sensor Download PDF

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JP2012047722A
JP2012047722A JP2011094668A JP2011094668A JP2012047722A JP 2012047722 A JP2012047722 A JP 2012047722A JP 2011094668 A JP2011094668 A JP 2011094668A JP 2011094668 A JP2011094668 A JP 2011094668A JP 2012047722 A JP2012047722 A JP 2012047722A
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detection
particulate matter
detection unit
abnormality
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Yuzo Matsumoto
雄三 松本
Mikiyasu Matsuoka
幹泰 松岡
Yuki Sakamoto
雄紀 坂本
満 ▲さき▼本
Mitsuru Sakimoto
Takehito Kimata
岳人 木全
Takashi Sawada
高志 澤田
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Denso Corp
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Denso Corp
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
    • F02D41/1444—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases
    • F02D41/1466—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor characterised by the characteristics of the combustion gases the characteristics being a soot concentration or content
    • 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
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/02—Circuit arrangements for generating control signals
    • F02D41/14—Introducing closed-loop corrections
    • F02D41/1438—Introducing closed-loop corrections using means for determining characteristics of the combustion gases; Sensors therefor
    • F02D41/1493—Details
    • F02D41/1494—Control of sensor heater
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02D—CONTROLLING COMBUSTION ENGINES
    • F02D41/00—Electrical control of supply of combustible mixture or its constituents
    • F02D41/22—Safety or indicating devices for abnormal conditions
    • F02D41/222—Safety or indicating devices for abnormal conditions relating to the failure of sensors or parameter detection devices
    • 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
    • F01N2560/00—Exhaust systems with means for detecting or measuring exhaust gas components or characteristics
    • F01N2560/20—Sensor having heating means
    • 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
    • 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

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
  • Processes For Solid Components From Exhaust (AREA)
  • Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
  • Testing Of Short-Circuits, Discontinuities, Leakage, Or Incorrect Line Connections (AREA)

Abstract

PROBLEM TO BE SOLVED: To provide an electric resistance type particulate matter detection sensor, which is used for detection of a PM (particulate matter) in exhaust gas of an internal combustion engine, having a simple configuration to reduce the number of production processes and to suppress the production cost; having a good heat transfer property and easy temperature control; and further allowing an abnormality to be detected.SOLUTION: A gas sensor element 10 of a PM sensor 1 to be mounted on an exhaust pipe EX of an engine E/G comprises a detecting unit 100 having measurement electrodes 11, 12, and a heater unit 300, both structured on the same surface of an insulating substrate 13. A control unit 2 detects a particulate matter PM at a temperature lower than 600°C and detects a disconnection abnormality based on a leaking current at 600°C or higher.

Description

本発明は、例えば、車両用内燃機関の排気浄化システムに好適に利用されて、排出ガス中に存在する粒子状物質の量を検出する、電気抵抗式の粒子状物質検出センサとその異常判定方法に関する。   The present invention is suitably used in, for example, an exhaust purification system of an internal combustion engine for a vehicle, and detects an amount of particulate matter present in exhaust gas, and an electric resistance type particulate matter detection sensor and an abnormality determination method thereof About.

自動車用ディーゼルエンジン等において、排気ガスに含まれる環境汚染物質、特に煤粒子（Ｓｏｏｔ）及び可溶性有機成分（ＳＯＦ）を主体とする粒子状物質（Ｐａｒｔｉｃｕｌａｔｅ Ｍａｔｔｅｒ；以下、適宜ＰＭと称する）を捕集するために、排気通路にディーゼルパティキュレートフィルタ（以下、適宜ＤＰＦと称する）を設置することが行われている。ＤＰＦは、耐熱性に優れる多孔質セラミックスからなり、多数の細孔を有する隔壁に排気ガスを通過させてＰＭを捕捉する。   Collects environmental pollutants contained in exhaust gas, especially particulate matter (Particulate Matter; hereinafter referred to as PM as appropriate) mainly composed of soot particles and soluble organic components (SOF) in automobile diesel engines, etc. In order to do this, a diesel particulate filter (hereinafter referred to as DPF as appropriate) is installed in the exhaust passage. The DPF is made of porous ceramics having excellent heat resistance, and traps PM by passing exhaust gas through a partition wall having a large number of pores.

ＤＰＦは、ＰＭ捕集量が許容量を超えると、目詰まりが生じて負圧が増大したり、ＰＭのすり抜けが増加したりするおそれがあり、定期的に再生処理を行って捕集能力を回復させている。再生時期は、一般的には、ＰＭ捕集量の増加により前後差圧が増大することを利用しており、このため、ＤＰＦの上流及び下流の圧力差を検出する差圧センサが設置される。再生処理は、ヒータ加熱あるいはポスト噴射等により高温の燃焼排気ガスをＤＰＦ内に導入し、ＰＭを燃焼除去する。   If the amount of collected PM exceeds the allowable amount, DPF may cause clogging and increase the negative pressure or increase the slipping of PM. It is recovering. The regeneration period generally uses the fact that the differential pressure increases with the increase in the amount of PM collected. For this reason, a differential pressure sensor is installed to detect the pressure difference upstream and downstream of the DPF. . In the regeneration process, high-temperature combustion exhaust gas is introduced into the DPF by heater heating or post injection, and PM is burned and removed.

一方、排気ガス中のＰＭを直接検出可能な粒子状物質検出センサ（以下、適宜ＰＭセンサと称する。）について種々提案されている（特許文献１、２、３等）。このＰＭセンサを、例えばＤＰＦの下流に設置して、ＤＰＦをすり抜けるＰＭ量を測定し、車載式故障診断装置（ＯＢＤ；Ｏｎ Ｂｏａｒｄ Ｄｉａｇｎｏｓｉｓ）において、ＤＰＦの作動状態の監視、例えば亀裂や破損といった異常の検出に利用することができる。あるいはＤＰＦの上流に設置して、ＤＰＦに流入するＰＭ量を測定し、差圧センサに代わる再生時期の判断に利用することも検討されている。   On the other hand, various types of particulate matter detection sensors (hereinafter referred to as PM sensors as appropriate) that can directly detect PM in exhaust gas have been proposed (Patent Documents 1, 2, 3, etc.). This PM sensor is installed downstream of the DPF, for example, and the amount of PM passing through the DPF is measured. In an on-board diagnosis (OBD), monitoring of the operating state of the DPF, for example, abnormalities such as cracks and breakage It can be used for detection. Alternatively, it is also considered to install upstream of the DPF, measure the amount of PM flowing into the DPF, and use it to determine the regeneration time instead of the differential pressure sensor.

ＰＭセンサとして、例えば、特許文献１には、絶縁性を有する基板の表面に、一対の導電性電極を形成し、基板の裏面又は内部に発熱体を形成した電気抵抗式のスモークセンサが開示されている。
この種のＰＭセンサは、スモーク（微粒炭素）等のＰＭが導電性を有することを利用したもので、検出部となる電極間に、スモークが堆積することで生じる電気抵抗値の変化を検出する。このため、検出電極間に一定量以上のＰＭが堆積するまでは、検出電極間の電気抵抗値が極めて高く、検出が困難となる不感期間が存在する。 As a PM sensor, for example, Patent Document 1 discloses an electric resistance type smoke sensor in which a pair of conductive electrodes are formed on the surface of an insulating substrate and a heating element is formed on the back surface or inside of the substrate. ing.
This type of PM sensor utilizes the fact that PM such as smoke (fine carbon) has electrical conductivity, and detects changes in the electrical resistance value caused by the deposition of smoke between the electrodes that serve as the detection unit. . Therefore, until a certain amount or more of PM is deposited between the detection electrodes, there is a dead period in which the electrical resistance value between the detection electrodes is extremely high and detection is difficult.

また、上記基本素子構成に加えて、異常検出機能を持たせたものがある。特許文献２に開示されるＰＭセンサは、発熱体となる加熱電極を２枚の電気絶縁体で挟持し、その一方の電気絶縁体側に検出用の一対の導電性電極を、他方の電気絶縁体側に参照用の一対の導電性電極を形成した積層構造を有する。このＰＭセンサは、発熱体を挟んで計測電極と対照な位置に参照用電極を有するので、これら電極からの信号を比較することで、ＰＭセンサが正常に機能しているか、又は何らかの異常があるかどうかを検出可能となっている。   In addition to the above basic element configuration, there is a device provided with an abnormality detection function. In the PM sensor disclosed in Patent Document 2, a heating electrode serving as a heating element is sandwiched between two electrical insulators, a pair of conductive electrodes for detection is provided on one electrical insulator side, and the other electrical insulator side is provided. Has a laminated structure in which a pair of reference conductive electrodes is formed. Since this PM sensor has a reference electrode at a position opposite to the measurement electrode across the heating element, the PM sensor is functioning normally or has some abnormality by comparing signals from these electrodes. It is possible to detect whether or not.

さらに、特許文献３には、絶縁性基板の表面に一定の間隙を隔てて対向する一対の検出電極を形成すると共に、該検出電極を覆うように、所定の導電率を有する導電層を形成し、不感期間の解消と、検出電極間の断線を検出可能とするＰＭセンサが開示されている。   Further, in Patent Document 3, a pair of detection electrodes facing each other with a certain gap is formed on the surface of an insulating substrate, and a conductive layer having a predetermined conductivity is formed so as to cover the detection electrodes. In addition, a PM sensor that can eliminate dead periods and detect disconnection between detection electrodes is disclosed.

一般に、特許文献１〜３にあるような、従来の電気抵抗式のＰＭセンサでは、検出電極間に一定量以上のＰＭが堆積すると、飽和状態となり、抵抗値変化の検出が困難となるため、通電により発熱する発熱体が内蔵されている。
この発熱体は、検出部を所望の温度（例えば、４００℃〜６００℃）に加熱し、電極間抵抗を測定した後に、付着したＰＭを焼き切って検出能力を回復させることができる。 Generally, in the conventional electric resistance type PM sensor as described in Patent Documents 1 to 3, when a certain amount or more of PM is deposited between the detection electrodes, a saturation state occurs, and it becomes difficult to detect a change in resistance value. A heating element that generates heat when energized is incorporated.
The heating element can recover the detection capability by heating the detection unit to a desired temperature (for example, 400 ° C. to 600 ° C.) and measuring the interelectrode resistance, and then burning off the adhered PM.

特開昭５９−１９７８４７号公報JP 59-197847 A 欧州特許出願公開第１９２５９２６号明細書European Patent Application No. 1925926 国際公開２００８−１３８６６１号International Publication No. 2008-138661

ところが、再生時にＰＭの除去が不十分で検出電極間に残留していると、その後の検出結果に影響を与える虞がある。そこで、発熱体の温度を高くして確実なＰＭの除去を図ることが考えられるが、発熱体の温度を一定以上高くすると、その後のＰＭ検出において、発熱体への通電パルスに応じた発振ノイズが検出されることがある。
これは、本発明者等の鋭意試験により、発熱体の温度上昇に伴い、電気絶縁体として用いられているアルミナの絶縁抵抗が大きく低下し、検出電極間に導通経路が形成されるためであることが判明した。 特許文献１にあるような従来のＰＭセンサにおいては、加熱による絶縁抵抗の低下により、検出電極間に形成された導通経路に発熱体に流れる電流が漏れ、リーク電流として重畳的に検出されるため、検出電極間に断線異常等が発生していても、その異常を検知することが困難となる虞がある。 However, if the PM is not sufficiently removed during the regeneration and remains between the detection electrodes, the subsequent detection result may be affected. Therefore, it is conceivable that the temperature of the heating element is raised to surely remove PM. However, if the temperature of the heating element is raised above a certain level, oscillation noise corresponding to the energization pulse to the heating element is detected in the subsequent PM detection. May be detected.
This is because, as a result of diligent tests by the present inventors, the insulation resistance of alumina used as an electrical insulator is greatly reduced as the temperature of the heating element rises, and a conduction path is formed between the detection electrodes. It has been found. In the conventional PM sensor as disclosed in Patent Document 1, current flowing in the heating element leaks to the conduction path formed between the detection electrodes due to a decrease in insulation resistance due to heating, and is detected in a superimposed manner as a leakage current. Even if a disconnection abnormality or the like occurs between the detection electrodes, it may be difficult to detect the abnormality.

また、特許文献２にあるように計測電極とは別に参照用電極を形成することにより、計測電極の異常を検出することは可能であるが、構造は複雑で、製造コストの増大を招く虞がある。さらに、特許文献２にあるような構成とした場合にも、加熱時に電気絶縁体の絶縁抵抗が低下しリーク電流が発生すると、検出電極間に発生した異常の検出が困難となる虞がある。   In addition, as disclosed in Patent Document 2, it is possible to detect an abnormality of the measurement electrode by forming a reference electrode separately from the measurement electrode, but the structure is complicated and there is a risk of increasing the manufacturing cost. is there. Further, even in the configuration as disclosed in Patent Document 2, if the insulation resistance of the electrical insulator is reduced and a leakage current is generated during heating, it may be difficult to detect an abnormality occurring between the detection electrodes.

一方、特許文献３のように、検出電極間に所定の導電率を有する導電層を形成した場合に、ＰＭを精度良く検出するためには、導電層の導電率を極めて高い精度に調整する必要があり、そもそもの製造が困難であり、製造コストの増大を招く虞がある。また、このような導電層を形成した場合であっても、発熱体により絶縁体の絶縁抵抗が低下した場合に、異常の検出が困難となったり、ＰＭ検出精度の低下を招いたりする虞があることは、他のＰＭセンサと同様である。   On the other hand, as in Patent Document 3, when a conductive layer having a predetermined conductivity is formed between the detection electrodes, in order to accurately detect PM, it is necessary to adjust the conductivity of the conductive layer with extremely high accuracy. In the first place, it is difficult to manufacture, and there is a risk of increasing the manufacturing cost. Further, even when such a conductive layer is formed, there is a risk that abnormality detection may be difficult or PM detection accuracy may be reduced when the insulation resistance of the insulator is reduced by the heating element. It is the same as other PM sensors.

そこで、本発明はかかる実情に鑑みなされたものであり、従来と同様の構成あるいは、より簡易な構成において、通電により発熱する発熱体の温度を所定のリーク電流発生温度以上の高温として意図的にリーク電流を発生させ、このリーク電流利用して、異常の有無を検出可能とする異常検出手段を備えたＰＭセンサとその異常判定方法の提供を目的とするものである。   Therefore, the present invention has been made in view of such circumstances, and in a configuration similar to the conventional one or a simpler configuration, the temperature of the heating element that generates heat by energization is intentionally set to be higher than a predetermined leakage current generation temperature. An object of the present invention is to provide a PM sensor provided with an abnormality detecting means that generates a leakage current and uses the leakage current to detect the presence or absence of an abnormality, and an abnormality determination method thereof.

本発明の請求項１に記載の発明は、内燃機関の排気通路に配設されて、排出ガス中の粒子状物質を検出すべく、絶縁性基体の表面に一対の計測電極を対向形成した検知部と、該検知部を所定温度に加熱する加熱電極を含むヒータ部とを具備するセンサ素子と、上記ヒータ部への通電を制御すると共に上記検知部に堆積する粒子状物質の量に応じて変化する電気的特性を計測する制御部を有する粒子状物質検出センサであって、上記制御部は、上記ヒータ部に通電して、上記検知部を一定温度以上に加熱したときに、上記絶縁性基体の絶縁抵抗の低下により上記ヒータ部から上記検知部に漏れるリーク電流に基づく上記検知部出力の変化を正常時と比較して、上記検知部の異常を検出する異常検出手段を有する。   According to a first aspect of the present invention, there is provided a detection in which a pair of measurement electrodes are formed on the surface of an insulating substrate so as to detect particulate matter in exhaust gas, which is disposed in an exhaust passage of an internal combustion engine. And a sensor element comprising a heating part including a heating electrode for heating the detection part to a predetermined temperature, and controlling the energization to the heater part and depending on the amount of particulate matter deposited on the detection part A particulate matter detection sensor having a control unit for measuring a changing electrical characteristic, wherein the control unit energizes the heater unit and heats the detection unit to a predetermined temperature or more, so that the insulating property is detected. It has an abnormality detection means for detecting an abnormality of the detection unit by comparing a change in the detection unit output based on a leakage current leaking from the heater unit to the detection unit due to a decrease in the insulation resistance of the base body with a normal time.

例えば、所定の温度においてリーク電流によって発生する出力が所定値となるように設計したセンサ素子の所定の温度における出力を予め測定し、これを正常時出力として記憶し、所定の温度において検出した結果とを閾値判定することによって異常を検出できる。   For example, the output at a predetermined temperature of the sensor element designed so that the output generated by the leakage current at the predetermined temperature becomes a predetermined value is measured in advance, stored as normal output, and detected at the predetermined temperature. An abnormality can be detected by determining the threshold values.

本発明の請求項２に記載の発明において、上記異常検出手段は、上記検知部の出力が正常時と比較して所定の閾値以上高くなるときには電源側断線異常と判定し、上記検知部の出力が正常時と比較して所定の閾値より低くなるときには劣化異常と判定し、上記検知部出力が検出されないときには接地側断線異常と判定する。   In the invention according to claim 2 of the present invention, the abnormality detection means determines that the power supply side disconnection abnormality is present when the output of the detection unit is higher than a normal value by a predetermined threshold or more, and the output of the detection unit. Is lower than a predetermined threshold as compared with the normal state, it is determined that the deterioration is abnormal, and when the detection unit output is not detected, it is determined that the ground side disconnection is abnormal.

本発明の請求項３に記載の発明において、上記制御部は、上記ヒータ部に通電して、上記検知部に堆積する粒子状物質が燃焼を開始する温度より低い温度に上記検知部を加熱し、上記一対の計測電極間の電気抵抗値に基づく上記検知部の出力から粒子状物質を検出する。   In the invention according to claim 3 of the present invention, the control unit energizes the heater unit to heat the detection unit to a temperature lower than a temperature at which particulate matter deposited on the detection unit starts combustion. The particulate matter is detected from the output of the detection unit based on the electrical resistance value between the pair of measurement electrodes.

本発明の請求項４に記載の発明において、上記一対の計測電極と上記加熱電極とを上記絶縁性基体の同一表面に近接配置し、上記一対の計測電極間の電気抵抗値を検出する。   In the invention according to claim 4 of the present invention, the pair of measurement electrodes and the heating electrode are arranged close to each other on the same surface of the insulating substrate, and an electric resistance value between the pair of measurement electrodes is detected.

本発明の請求項５に記載の発明において、上記ヒータ部は、上記加熱電極を上記計測電極に近接配置すると共に、上記加熱電極と外部とを接続するヒータリード部を有する。   In the invention according to claim 5 of the present invention, the heater portion includes a heater lead portion that places the heating electrode close to the measurement electrode and connects the heating electrode to the outside.

本発明の請求項６に記載の発明において、上記計測電極と上記加熱電極の距離は、１００μｍ〜１３６０μｍの範囲とする。   In the invention according to claim 6 of the present invention, the distance between the measurement electrode and the heating electrode is in the range of 100 μm to 1360 μm.

本発明の請求項７に記載の発明において、上記計測電極は、電極リード部に接続される基部と複数の補助電極からなる櫛状電極である。   In the invention according to claim 7 of the present invention, the measurement electrode is a comb-like electrode comprising a base connected to the electrode lead portion and a plurality of auxiliary electrodes.

本発明の請求項８の記載の発明は、内燃機関の排気通路に配設されて、排出ガス中の粒子状物質を検出すべく、絶縁性基体の表面に一対の計測電極を対向形成した検知部と、該検知部を所定温度に加熱する加熱電極を含むヒータ部とを具備するセンサ素子と、上記ヒータ部への通電を制御する制御部を有する粒子状物質検出センサの異常判定方法であって、上記加熱電極への通電により所定のリーク電流発生温度以上に上記検知部を加熱し、上記絶縁性基体の絶縁抵抗を意図的に低下させたときに検出されるリーク電流と、予め測定した正常時におけるリーク電流と、を比較して、上記検知部出力が正常時と比較して所定の閾値を超えて高くなるときには電源側断線異常と判定し、上記検知部出力が正常時と比較して所定の閾値より低くなるときには劣化異常と判定し、上記検知部出力が検出されないときには接地側断線異常と判定する。   The invention according to claim 8 of the present invention is a detection in which a pair of measurement electrodes are formed on the surface of an insulating substrate so as to be detected in the exhaust passage of the internal combustion engine so as to detect particulate matter in the exhaust gas. A particulate matter detection sensor abnormality determination method comprising: a sensor element comprising: a heater part including a heating part for heating the detection part to a predetermined temperature; and a control part for controlling energization to the heater part. Then, the leakage current detected when the detection part is heated to a predetermined leak current generation temperature or more by energizing the heating electrode and the insulation resistance of the insulating substrate is intentionally reduced is measured in advance. Compared with the leakage current at normal time, when the detection unit output is higher than a normal value by exceeding a predetermined threshold, it is determined that the power supply side disconnection is abnormal, and the detection unit output is compared with normal time. Lower than a predetermined threshold The can was determined to degrade abnormal, when said detection unit output is not detected is judged to ground disconnection abnormality.

上記制御部により検知部を粒子状物質が燃焼を開始する温度以上に加熱することで、上記検知部に堆積した粒子状物質が焼失し、上記一対の計測電極間の電気抵抗が上昇し、一対の計測電極間には電流が流れ難くなるが、本発明の請求項１に記載の発明によれば、温度上昇に伴い上記絶縁性基体の絶縁抵抗が低下し、上記加熱電極に流れる電流が漏れて上記検知部に重畳され、リーク電流の変化が検出されるので、これを正常時と比較し閾値判定することで、上記検知部の異常を容易に検出することができる。   By heating the detection unit above the temperature at which the particulate matter starts to burn by the control unit, the particulate matter deposited on the detection unit is burned out, and the electrical resistance between the pair of measurement electrodes is increased. However, according to the first aspect of the present invention, the insulation resistance of the insulating base decreases as the temperature rises, and the current flowing through the heating electrode leaks. Since the change of the leakage current is detected by being superimposed on the detection unit, the abnormality of the detection unit can be easily detected by determining the threshold value by comparing this with the normal state.

また、本発明によれば、従来からある粒子状物質検出センサの基本的な構造を大きく変えることなく、検出部の故障診断が可能となる。   Further, according to the present invention, it is possible to diagnose a failure of the detection unit without greatly changing the basic structure of a conventional particulate matter detection sensor.

本発明者等の鋭意試験により、上記一対の計測電極の内、電源側に断線異常が生じた場合には、正常時に比べ温度上昇に伴うリーク電流に基づく検出出力が高くなり、上記検知部に計測電極の剥離、マイグレーション、灰分（Ａｓｈ）の堆積等により劣化が生じた場合には、劣化度合いに応じて上記検知部出力が低下し、上記一対の計測電極の内、接地側に断線異常が生じた場合には、リーク電流が検出されないことが判明した。
したがって、本発明の請求項２に記載の発明によれば、粒子状物質検出センサに発生した異常の原因を特定することが可能となり、異常発生時に速やかな対応をすることが可能となり、センサの信頼性が向上する。 When a disconnection abnormality occurs on the power source side of the pair of measurement electrodes, the detection output based on the leakage current accompanying the temperature rise is higher than in the normal state, and the detection unit When degradation occurs due to separation, migration, accumulation of ash (Ash), etc., the detection unit output decreases according to the degree of degradation, and there is a disconnection abnormality on the ground side of the pair of measurement electrodes. When it occurred, it was found that no leakage current was detected.
Therefore, according to the invention described in claim 2 of the present invention, it is possible to specify the cause of the abnormality that has occurred in the particulate matter detection sensor, and it is possible to promptly respond to the occurrence of the abnormality, Reliability is improved.

本発明の請求項３に記載の発明によれば、上記制御部は、通常時には粒子状物質の燃焼開始温度（例えば、６００℃）より低い温度とすることで、リーク電流の影響なく粒子状物質を検出することができる。   According to the invention described in claim 3 of the present invention, the control unit normally sets the temperature lower than the combustion start temperature of the particulate matter (for example, 600 ° C.), so that the particulate matter is not affected by the leakage current. Can be detected.

本発明の請求項４に記載の粒子状物質検出センサは、検知部とヒータ部とが絶縁性基体の同一表面に近接配置されるので、熱伝導率が向上し温度制御性に優れる。
また、コンパクトで薄型であり、従来よりも検知部の構造の簡素化が図られ、生産工程数を減らすことができるので、生産コストが低減できる。
さらに、検出温度より高い、所定のリーク電流発生温度以上に加熱することにより、リーク電流を意図的に流して、正常時と比較して断線異常を検出する際に、リーク電流が上記絶縁性基体の表面を流れるため、検知部とヒータ部とが絶縁性基体を挟んで対向する従来の構造と比べリーク電流が発生し易く、異常検出時の加熱温度を低くすることが可能となり、検出結果を利用して異常の種類を特定することも可能となる。加えて、異常検出のための加熱温度を低くすることにより、電極の耐久性の向上を図ることも可能となり、実用性、信頼性が高いセンサを実現できる。 In the particulate matter detection sensor according to claim 4 of the present invention, since the detection part and the heater part are disposed close to the same surface of the insulating substrate, the thermal conductivity is improved and the temperature controllability is excellent.
Further, the structure is compact and thin, and the structure of the detection unit is simplified as compared with the conventional one, and the number of production steps can be reduced, so that the production cost can be reduced.
Furthermore, when the leakage current is intentionally flowed by heating to a temperature higher than the detection temperature, which is higher than the detection temperature, and the disconnection abnormality is detected as compared with the normal time, the leakage current is Therefore, it is easy to generate a leakage current compared to the conventional structure where the detection unit and the heater unit are opposed to each other with the insulating substrate interposed therebetween, and the heating temperature at the time of detecting an abnormality can be lowered. It is also possible to specify the type of abnormality by using it. In addition, by lowering the heating temperature for abnormality detection, it is possible to improve the durability of the electrode, and a sensor with high practicality and reliability can be realized.

本発明の請求項５に記載の発明のように、上記計測電極と上記加熱電極とを近接配置することにより、リーク電流を流れ易くして、異常検出時の加熱温度を低くして上記効果を発揮する粒子状物質検出センサを容易に実現することができる。   As in the invention according to claim 5 of the present invention, the measurement electrode and the heating electrode are arranged close to each other, thereby facilitating the flow of a leakage current and lowering the heating temperature at the time of detecting an abnormality, thereby achieving the above effect. It is possible to easily realize the particulate matter detection sensor to be exhibited.

本発明の請求項６に記載の発明のように、上記計測電極と上記加熱電極の距離は、１００μｍ〜１３６０μｍの範囲とするのが望ましく、検出時のリーク電流による検知部出力への影響を抑制しながら、上記効果が得られる。   As in the sixth aspect of the present invention, the distance between the measurement electrode and the heating electrode is preferably in the range of 100 μm to 1360 μm, and the influence of the leakage current upon detection on the detection unit output is suppressed. However, the above effect can be obtained.

本発明の請求項７に記載の発明によれば、上記計測電極として櫛状電極が好適に用いられ、リーク電流の検出によって検知部の異常を検出可能な粒子状物質検出センサが実現できる。   According to the seventh aspect of the present invention, a comb-like electrode is preferably used as the measurement electrode, and a particulate matter detection sensor capable of detecting an abnormality of the detection unit by detecting a leakage current can be realized.

本発明の請求項８に記載の発明によれば、上記粒子状物質検出センサに発生する異常の種類を特定して検出することができる。   According to the eighth aspect of the present invention, it is possible to identify and detect the type of abnormality occurring in the particulate matter detection sensor.

（ａ）は、アルミナの絶縁抵抗値の温度特性を示す図、（ｂ）は、本発明の第１の実施形態におけるＰＭセンサ素子のリーク電流の流れを示す概略図である。(A) is a figure which shows the temperature characteristic of the insulation resistance value of an alumina, (b) is the schematic which shows the flow of the leakage current of PM sensor element in the 1st Embodiment of this invention. （ａ）は、ＰＭセンサの要部拡大断面図であり、排気管に取り付けた状態を示す図、（ｂ）は、本発明が適用される自動車用ディーゼルエンジンの排ガス浄化システムの全体構成を示す概略図である。(A) is a principal part expanded sectional view of PM sensor, and is a figure which shows the state attached to the exhaust pipe, (b) shows the whole structure of the exhaust gas purification system of the diesel engine for motor vehicles to which this invention is applied. FIG. 本発明の第１の実施形態におけるＰＭセンサの温度特性と、断線時の出力変化を正常時と比較するための評価条件及び回路構成を示す図である。It is a figure which shows the evaluation conditions and circuit structure for comparing the temperature characteristic of PM sensor in the 1st Embodiment of this invention, and the output change at the time of a disconnection with the time of normal. 本発明の第１の実施形態におけるＰＭセンサに用いられる異常検出方法を示すフローチャートである。It is a flowchart which shows the abnormality detection method used for PM sensor in the 1st Embodiment of this invention. 本発明の第１の実施形態におけるＰＭセンサの異常検出原理を示す特性図である。It is a characteristic view which shows the abnormality detection principle of PM sensor in the 1st Embodiment of this invention. 本発明の第２実施形態であり、（ａ）は、ＰＭセンサの主要部であるセンサ素子構成を説明するための分解斜視図、（ｂ）は、ＰＭセンサの主要部の概略構成を示す斜視図である。FIG. 4 is a second embodiment of the present invention, in which (a) is an exploded perspective view for explaining a sensor element configuration that is a main part of the PM sensor, and (b) is a perspective view showing a schematic configuration of the main part of the PM sensor. FIG. 本発明の第２の実施形態における異常検出方法を示すフローチャート。The flowchart which shows the abnormality detection method in the 2nd Embodiment of this invention. 本発明の第２の実施形態におけるＰＭセンサ構成による異常検出時の温度特性から異常原因を特定する方法を示す特性図である。It is a characteristic view which shows the method of specifying the cause of abnormality from the temperature characteristic at the time of abnormality detection by PM sensor structure in the 2nd Embodiment of this invention. （ａ）は、本発明の第３実施形態であり、ＰＭセンサの主要部であるセンサ素子構成を説明するための分解斜視図、（ｂ）は、本発明の第３実施形態であり、ＰＭセンサの主要部であるセンサ素子構成を説明するための上面視図である。(A) is 3rd Embodiment of this invention, an exploded perspective view for demonstrating the sensor element structure which is the principal part of PM sensor, (b) is 3rd Embodiment of this invention, and is PM. It is a top view for demonstrating the sensor element structure which is the principal part of a sensor.

以下、本発明の粒子状物質検出センサ（以下、適宜、ＰＭセンサと称す。）１を、内燃機関の排ガス浄化システムへ適用した第１実施形態について、図面を参照しながら説明する。   Hereinafter, a first embodiment in which a particulate matter detection sensor (hereinafter, appropriately referred to as a PM sensor) 1 of the present invention is applied to an exhaust gas purification system of an internal combustion engine will be described with reference to the drawings.

図１を参照して本発明の第１の実施形態におけるＰＭセンサ１の概要について説明する。本発明のＰＭセンサ１は、内燃機関の燃焼排気流路に設けられ、燃焼排気を被測定ガスとして、被測定ガス中の粒子状物質の量を検出するものであり、その検出結果は、内燃機関の燃焼制御、排気浄化装置の再生、異常診断等に利用される。   An outline of the PM sensor 1 according to the first embodiment of the present invention will be described with reference to FIG. The PM sensor 1 according to the present invention is provided in a combustion exhaust passage of an internal combustion engine, and detects the amount of particulate matter in the measurement gas using the combustion exhaust as the measurement gas. It is used for engine combustion control, regeneration of exhaust purification devices, abnormality diagnosis, and the like.

図１（ａ）は、本発明の要部であるＰＭセンサ１に絶縁基板１３として用いられるアルミナの絶縁抵抗の温度変化を示す特性図である。   FIG. 1A is a characteristic diagram showing the temperature change of the insulation resistance of alumina used as the insulating substrate 13 in the PM sensor 1 which is the main part of the present invention.

図１（ｂ）に示すように、本実施形態におけるＰＭセンサ１は、絶縁基板１３の表面に一対の測定電極１１、１２を形成した検知部１００と、絶縁基板１３の内部に設けられ、通電により発熱する加熱電極３１を含むヒータ部３００とからなるセンサ素子１０の検知部１００を被測定ガス中に載置し、測定電極１１、１２間に堆積する粒子状物質ＰＭの量によって変化する電気的特性として、測定電極間の電気抵抗を計測することによって、被測定ガス中のＰＭ量を検出すると共に、ヒータ部３００への通電により、絶縁基板１３の絶縁抵抗が低下したときに発生するリーク電流を検出し、正常時との比較により、断線や劣化等の異常を検出するものである。   As shown in FIG. 1B, the PM sensor 1 in the present embodiment is provided in the inside of the insulating substrate 13 and the detection unit 100 in which the pair of measurement electrodes 11 and 12 are formed on the surface of the insulating substrate 13. The detection unit 100 of the sensor element 10 including the heating unit 31 including the heating electrode 31 that generates heat is placed in the gas to be measured, and the electricity varies depending on the amount of the particulate matter PM deposited between the measurement electrodes 11 and 12. As a characteristic, a leak that occurs when the insulation resistance of the insulating substrate 13 is lowered by detecting the amount of PM in the gas to be measured by measuring the electrical resistance between the measurement electrodes and energizing the heater unit 300. Current is detected, and abnormalities such as disconnection and deterioration are detected by comparison with the normal state.

なお、本実施形態においては、絶縁基板１３にアルミナを用いた例を示したが、アルミナに限定するものではなく、スピネル、チタニアなどの耐熱性の絶縁体を適宜用いることができる。但し、絶縁基板１３を他の材料とした場合には、例えば、数百℃から１０００℃程度の高温時において絶縁抵抗が低下し、リーク電流が発生するものであり、その抵抗値の変化についての温度特性を予め計測しておく必要がある。
また、本実施形態においては、測定電極１１、１２は、電極リード部に接続される基部と複数の補助電極からなる、いわゆる櫛状電極を構成している。
本発明においては、センサ素子１０の構造を、特に限定するものではなく、従来からある公知の電気抵抗式のＰＭセンサの構成に、ヒータ部３００への通電により発熱する温度を所定の通常の検出温度以上に高くし、意図的にリーク電流を発生させ、このリーク電流の値を予め特定した正常時におけるリーク電流と比較して、異常の有無を検出する異常検出手段を設けたことを特徴とするものである。 In this embodiment, an example in which alumina is used for the insulating substrate 13 has been described. However, the insulating substrate 13 is not limited to alumina, and a heat-resistant insulator such as spinel or titania can be used as appropriate. However, when the insulating substrate 13 is made of another material, for example, the insulation resistance decreases at a high temperature of about several hundred to 1000 ° C., and a leak current is generated. It is necessary to measure temperature characteristics in advance.
In the present embodiment, the measurement electrodes 11 and 12 constitute so-called comb-like electrodes each including a base connected to the electrode lead portion and a plurality of auxiliary electrodes.
In the present invention, the structure of the sensor element 10 is not particularly limited, and the temperature of the heat generated by energization of the heater unit 300 is detected in a predetermined normal manner in the configuration of a conventionally known electric resistance PM sensor. It is characterized by having an abnormality detection means for detecting the presence or absence of an abnormality by making the leakage current intentionally higher than the temperature and comparing the value of this leakage current with a normal leakage current specified in advance. To do.

図２（ｂ）は、内燃機関である自動車用ディーゼルエンジンＥ／Ｇのシステム概略図であり、図２（ａ）は、図２（ｂ）の要部を拡大した図で、エンジンＥ／Ｇの排気管ＥＸに、ＰＭセンサ１を取り付けた状態を示す。   FIG. 2B is a system schematic diagram of an automotive diesel engine E / G which is an internal combustion engine, and FIG. 2A is an enlarged view of the main part of FIG. A state in which the PM sensor 1 is attached to the exhaust pipe EX is shown.

図２（ｂ）のエンジンＥ／Ｇは、各気筒に共通のコモンレールＲに、高圧ポンプにて昇圧した高圧燃料を所定の噴射圧となるように蓄圧するコモンレール燃料噴射システムを採用し、インジェクタＩＮＪによって燃焼室内に直接噴射する直噴エンジンとして構成されている。ＰＭセンサ１は、エンジンＥ／Ｇの排気通路である排気管ＥＸにおいて、ディーゼルパティキュレートフィルタＤＰＦの下流に設けられ、エンジンＥ／Ｇ各部とともに制御部２によって制御される。制御部２は、ＰＭセンサ１の出力に基づき粒子状物質ＰＭを検出する一方、ＰＭセンサ１の異常検出機能を備えており、この詳細については後述する。   The engine E / G in FIG. 2B employs a common rail fuel injection system that accumulates high-pressure fuel boosted by a high-pressure pump in a common rail R common to each cylinder so that a predetermined injection pressure is obtained. Thus, the engine is configured as a direct injection engine that directly injects the fuel into the combustion chamber. The PM sensor 1 is provided downstream of the diesel particulate filter DPF in the exhaust pipe EX that is an exhaust passage of the engine E / G, and is controlled by the control unit 2 together with each part of the engine E / G. The control unit 2 detects the particulate matter PM based on the output of the PM sensor 1 and has an abnormality detection function of the PM sensor 1, which will be described in detail later.

まず、図２（ｂ）において、エンジンＥ／Ｇのシステム構成について説明する。エンジンＥ／Ｇの排気マニホールドＭＨＥＸには、タービンＴＲＢが設けられ、タービンＴＲＢに連動して過給器ＴＲＢＣＧＲが回転すると、圧縮された空気がインタクーラＣＬＲＩＮＴを通過して吸気マニホールドＭＨＩＮに送られる。排気マニホールドＭＨＥＸから排出される燃焼排気の一部はＥＧＲバルブＶＥＧＲ及びＥＧＲクーラＣＬＲＥＧＲを介して吸気マニホールドＭＨＩＮに還流する。過給により吸気量を増大して燃焼効率を高め、ＥＧＲにより燃焼を緩やかにしてＮＯｘ等の排出を抑制する。 First, referring to FIG. 2B, the system configuration of the engine E / G will be described. The exhaust manifold MH EX of the engine E / G is provided with a turbine TRB. When the turbocharger TRB CGR rotates in conjunction with the turbine TRB, the compressed air passes through the intercooler CLR INT and enters the intake manifold MH IN . Sent. A part of the combustion exhaust discharged from the exhaust manifold MH EX returns to the intake manifold MH IN via the EGR valve V EGR and the EGR cooler CLR EGR . The intake amount is increased by supercharging to increase combustion efficiency, and the combustion is moderated by EGR to suppress the emission of NOx and the like.

排気マニホールドＭＨＥＸに接続する排気管ＥＸには、ディーゼル酸化触媒ＤＯＣ及びディーゼルパティキュレートフィルタＤＰＦが設けられ、燃焼排気ガスを処理する。すなわち、排気管ＥＸに排出された燃焼排気ガスは、上流側のディーゼル酸化触媒ＤＯＣを通過する間に、未燃焼の炭化水素ＨＣ、一酸化炭素ＣＯ及び一酸化窒素ＮＯが酸化され、下流側のディーゼルパティキュレートフィルタＤＰＦを通過する間に、煤粒子（Ｓｏｏｔ）、可溶性有機成分（ＳＯＦ）及び無機成分からなる粒子状物質ＰＭが捕集される。 The exhaust pipe EX connected to the exhaust manifold MH EX is provided with a diesel oxidation catalyst DOC and a diesel particulate filter DPF, and processes the combustion exhaust gas. That is, while the combustion exhaust gas discharged to the exhaust pipe EX passes through the upstream diesel oxidation catalyst DOC, unburned hydrocarbons HC, carbon monoxide CO, and nitrogen monoxide NO are oxidized, and the downstream side While passing through the diesel particulate filter DPF, particulate matter PM composed of soot particles (Soot), soluble organic components (SOF) and inorganic components is collected.

ディーゼル酸化触媒ＤＯＣは公知のモノリス担体、例えばコーディエライト等のセラミックスハニカム構造体よりなる担体表面に、酸化触媒を担持してなる。ディーゼル酸化触媒ＤＯＣは、ディーゼルパティキュレートフィルタＤＰＦの強制再生時に、供給される燃料の酸化燃焼により排気温度を上昇させ、あるいは粒子状物質ＰＭ中のＳＯＦ成分を酸化除去する。また、ＮＯの酸化により生成するＮＯ２は、後段のディーゼルパティキュレートフィルタＤＰＦに堆積した粒子状物質ＰＭの酸化剤として使用され、連続的な酸化を可能にする。 The diesel oxidation catalyst DOC is formed by supporting an oxidation catalyst on a known monolithic carrier, for example, a carrier surface made of a ceramic honeycomb structure such as cordierite. The diesel oxidation catalyst DOC raises the exhaust temperature by oxidative combustion of the supplied fuel or oxidizes and removes the SOF component in the particulate matter PM when the diesel particulate filter DPF is forcibly regenerated. Further, NO 2 produced by oxidation of NO is used as an oxidant for particulate matter PM deposited on the diesel particulate filter DPF at the subsequent stage, and enables continuous oxidation.

ディーゼルパティキュレートフィルタＤＰＦは、公知のウォールフロータイプのフィルタ構造を有する。例えば、コーディエライト等の耐熱性セラミックスよりなる多孔質セラミックスハニカム構造体を成形し、ガス流路となる多数のセルの入口側又は出口側のいずれか一方を、隣接するセルで互い違いになるように目封じしてフィルタとする。この時、ガス流路を区画するセル壁を貫通して多数の細孔が形成され、ディーゼルパティキュレートフィルタＤＰＦに導入される排出ガス中の粒子状物質ＰＭを捕獲する。ディーゼル酸化触媒ＤＯＣとディーゼルパティキュレートフィルタＤＰＦを一体化した連続再生式ディーゼルパティキュレートフィルタとして構成することもできる。   The diesel particulate filter DPF has a known wall flow type filter structure. For example, a porous ceramic honeycomb structure made of heat-resistant ceramics such as cordierite is formed, and either one of the inlet side or the outlet side of a number of cells serving as gas flow paths is staggered between adjacent cells. Seal the filter to make a filter. At this time, a large number of pores are formed through the cell walls that define the gas flow path, and the particulate matter PM in the exhaust gas introduced into the diesel particulate filter DPF is captured. It can also be configured as a continuously regenerating diesel particulate filter in which the diesel oxidation catalyst DOC and the diesel particulate filter DPF are integrated.

排気管ＥＸには、ディーゼルパティキュレートフィルタＤＰＦに堆積した粒子状物質ＰＭの量を監視するために、差圧センサＳＰが設けられる。差圧センサＳＰは、圧力導入管を介してディーゼルパティキュレートフィルタＤＰＦの上流側及び下流側と接続されており、その前後差圧に応じた信号を出力する。また、ディーゼル酸化触媒ＤＯＣの上流及び、ディーゼルパティキュレートフィルタＤＰＦの上下流には、温度センサＳ１、Ｓ２、Ｓ３が配設されて、各部の排気温度を監視している。   The exhaust pipe EX is provided with a differential pressure sensor SP in order to monitor the amount of particulate matter PM deposited on the diesel particulate filter DPF. The differential pressure sensor SP is connected to the upstream side and the downstream side of the diesel particulate filter DPF via a pressure introduction pipe, and outputs a signal corresponding to the differential pressure before and after. Further, temperature sensors S1, S2, and S3 are disposed upstream of the diesel oxidation catalyst DOC and upstream and downstream of the diesel particulate filter DPF to monitor the exhaust temperature of each part.

制御部２は、これら出力に基づいてディーゼル酸化触媒ＤＯＣの触媒活性状態やディーゼルパティキュレートフィルタＤＰＦのＰＭ捕集状態を監視し、ＰＭ捕集量が許容量を超えると、強制再生を行って粒子状物質ＰＭを燃焼除去する再生制御を実施する。さらに制御部２には、エンジンＥ／Ｇの運転状態を知るための各種センサ信号、例えばエアフロメータＡＦＭからの吸気量や吸気温度、エンジン潤滑油や冷却水の温度、エンジン回転数、スロットル開度等が入力している。制御部２は、これら信号に基づいて燃料噴射量、噴射時期等を算出し、燃料噴射を制御する。
本発明において、制御部２は、上記機能に加えて、ヒータ部３００に通電して、検知部１００を一定温度以上に加熱したときに、ヒータ部３００から検知部１００に漏れるリーク電流に基づく検知部出力Ｖ−ＯＵＴＰＵＴの変化を正常時と比較して、検知部１００の異常を検出する異常検出手段を有すること最大の特徴とするものである。 Based on these outputs, the control unit 2 monitors the catalytic activation state of the diesel oxidation catalyst DOC and the PM trapping state of the diesel particulate filter DPF. If the PM trapping amount exceeds an allowable amount, the controller 2 performs forced regeneration to generate particles. The regeneration control for burning and removing the particulate matter PM is performed. Further, the control unit 2 has various sensor signals for knowing the operating state of the engine E / G, for example, the intake air amount and intake air temperature from the air flow meter AFM, the temperature of engine lubricating oil and cooling water, the engine speed, and the throttle opening degree. Etc. are entered. The control unit 2 calculates the fuel injection amount, the injection timing, and the like based on these signals, and controls the fuel injection.
In the present invention, in addition to the above function, the control unit 2 energizes the heater unit 300 to detect the leakage current that leaks from the heater unit 300 to the detection unit 100 when the detection unit 100 is heated to a certain temperature or higher. Compared with the normal state, the change in the partial output V-OUTPUT has an abnormality detecting means for detecting an abnormality of the detection unit 100.

次に、本発明のＰＭセンサ１の基本作動について説明する。図２（ａ）、（ｂ）において、被被測定ガスとなるエンジンＥ／Ｇの排出ガスは、ＰＭセンサ１のカバー体４０の上流側の通孔４１１から内部に導入され、ＰＭセンサ素子１０と接触した後、底面の通孔４１０又は下流側の通孔４１１から排出される。ＤＰＦで捕集されずに下流側へすり抜けてきた粒子状物質ＰＭは、ＰＭセンサ素子１０の検知部１００に到達すると、一対の計測電極１１、１２表面及び両電極間の絶縁基板１３表面に付着し、堆積していく。   Next, the basic operation of the PM sensor 1 of the present invention will be described. 2 (a) and 2 (b), the exhaust gas of the engine E / G, which is the gas to be measured, is introduced into the inside from the upstream through hole 411 of the cover body 40 of the PM sensor 1, and the PM sensor element 10 After being in contact with the gas, it is discharged from the bottom through-hole 410 or the downstream through-hole 411. When particulate matter PM that has passed through downstream without being collected by the DPF reaches the detection unit 100 of the PM sensor element 10, it adheres to the surface of the pair of measurement electrodes 11, 12 and the insulating substrate 13 between the electrodes. Then, it accumulates.

検知部１００の櫛歯形状の計測電極１１、１２は、所定の間隙を有して形成されているので、初期状態では非導通状態である。   Since the comb-shaped measurement electrodes 11 and 12 of the detection unit 100 are formed with a predetermined gap, they are in a non-conductive state in the initial state.

粒子状物質ＰＭは導電性の煤粒子を含むために、排出ガスとの接触により粒子状物質ＰＭが徐々に堆積すると、ある時点で計測電極１１、１２間が導通する。そして、ＰＭ堆積量の増加に伴い電極間抵抗は大きく低下する。計測電極間の電気抵抗値は粒子状物質ＰＭの堆積量に依存して変化するので、この関係に基づいて、ディーゼルパティキュレートフィルタＤＰＦ下流の粒子状物質ＰＭを検出し、例えばディーゼルパティキュレートフィルタＤＰＦの故障判定に利用することができる。   Since the particulate matter PM contains conductive soot particles, when the particulate matter PM is gradually deposited by contact with the exhaust gas, the measurement electrodes 11 and 12 are electrically connected at a certain point. And the inter-electrode resistance greatly decreases as the PM deposition amount increases. Since the electrical resistance value between the measurement electrodes varies depending on the amount of the particulate matter PM deposited, based on this relationship, the particulate matter PM downstream of the diesel particulate filter DPF is detected. For example, the diesel particulate filter DPF It can be used for the failure determination of

なお、粒子状物質ＰＭを確実に捕捉するため、図示するように、ＰＭセンサ素子１０の検知部１００が排気管ＥＸの上流側を向くように配置するとよい。検知部１００を除く絶縁基板１３の表面を覆って絶縁保護層１４が形成されているので、リード部１１１、１１２やヒータ部３００の形成部位を粒子状物質ＰＭの堆積から保護することができる。端子部１２１、１２２、３２１、３２２が形成されるＰＭセンサ素子１００の基端側は、排気管ＥＸの外部へ取り出され、ワイヤハーネスにより制御部２へ接続される。   In order to reliably capture the particulate matter PM, as shown in the figure, the PM sensor element 10 may be arranged so that the detection unit 100 faces the upstream side of the exhaust pipe EX. Since the insulating protective layer 14 is formed so as to cover the surface of the insulating substrate 13 excluding the detection unit 100, the formation site of the lead units 111 and 112 and the heater unit 300 can be protected from the deposition of the particulate matter PM. The proximal end side of the PM sensor element 100 in which the terminal portions 121, 122, 321, 322 are formed is taken out of the exhaust pipe EX and connected to the control unit 2 by a wire harness.

ＰＭ検出時には、ヒータ部３００により検知部１００を検知部１００に堆積したＰＭが燃焼を開始しない一定温度以下、例えば、６００℃より低い温度範囲、好適には２００℃〜４００℃の温度範囲に制御するのがよい。図１（ａ）に示すように、温度が上昇すると、絶縁基板１３を構成するアルミナの絶縁抵抗値は低下する。   At the time of PM detection, the heater unit 300 controls the detection unit 100 so that the PM deposited on the detection unit 100 does not start combustion at a certain temperature or lower, for example, a temperature range lower than 600 ° C., preferably a temperature range of 200 ° C. to 400 ° C. It is good to do. As shown in FIG. 1A, when the temperature rises, the insulation resistance value of alumina constituting the insulating substrate 13 decreases.

また、本発明では、制御部２により検知部１００を検知部１００に堆積したＰＭが燃焼を開始する一定温度以上、例えば、６００℃以上に加熱したときの検知部出力から、ＰＭセンサ１の異常、特にＰＭセンサ素子１０内における異常を検出することができる。上述したように、温度が上昇するとアルミナの絶縁抵抗値は急低下するため、図１（ｂ）のように、加熱電極３１から絶縁基板１３を介して計測電極へリーク電流が発生する。   Moreover, in this invention, abnormality of PM sensor 1 is detected from the detection part output when PM which accumulated the detection part 100 on the detection part 100 by the control part 2 heats more than the fixed temperature which starts combustion, for example, 600 degreeC or more. In particular, an abnormality in the PM sensor element 10 can be detected. As described above, since the insulation resistance value of alumina rapidly decreases as the temperature rises, a leak current is generated from the heating electrode 31 to the measurement electrode via the insulating substrate 13 as shown in FIG.

本発明では、この現象を利用し、異常検出手段として、素子温度を上昇させて、意図的にリーク電流を流し、正常時と電極に劣化や断線等の異常が発生したときとの出力差から、断線や劣化等の異常を検知する。   In the present invention, by utilizing this phenomenon, as an abnormality detection means, an element temperature is raised, a leak current is intentionally passed, and from an output difference between when it is normal and when an abnormality such as deterioration or disconnection occurs in the electrode. Detect abnormalities such as disconnection and deterioration.

図３は、本発明のＰＭセンサ１に用いられる回路構成の一例を示す図で、検知部１００の計測電極１１、１２（図中櫛歯電極）間の抵抗Ｒには、電極側電源ＶＣＣ（５Ｖ）が接続され、ＧＮＤ側に直列接続した分圧抵抗Ｒ２の両端間の電圧を検知部出力とするようになっている。ヒータ部３００の加熱電極３１（ヒータ抵抗ＲＨ）には、ヒータ側電源ＶＢ（１４Ｖ）、ＭＯＳ−ＦＥＴ、シャント抵抗Ｒ１が直列接続され、シャント抵抗Ｒ１の両端間電圧ＶＡから算出されるヒータ電流と、ヒータ電圧ＶＲＨに基づいて、ヒータ温度を制御する。また、抵抗Ｒとヒータ抵抗ＲＨの間には、アルミナ絶縁抵抗ＲＡＬが介在している。   FIG. 3 is a diagram showing an example of a circuit configuration used in the PM sensor 1 of the present invention. The resistance R between the measurement electrodes 11 and 12 (comb electrode in the figure) of the detection unit 100 is connected to the electrode side power supply VCC ( 5V) is connected, and the voltage across the voltage dividing resistor R2 connected in series to the GND side is used as the output of the detection unit. A heater-side power source VB (14V), a MOS-FET, and a shunt resistor R1 are connected in series to the heating electrode 31 (heater resistor RH) of the heater unit 300, and the heater current calculated from the voltage VA across the shunt resistor R1 The heater temperature is controlled based on the heater voltage VRH. An alumina insulation resistance RAL is interposed between the resistance R and the heater resistance RH.

検知部出力Ｖ−ＯＵＴＰＵＴは、ヒータ部３００への通電をしていない状態では、検知部に堆積したＰＭ量に応じた検出電極間Ｒの変化を検出し、異常判定時には、ヒータ部３００への通電により、所定の温度以上に加熱して、意図的に絶縁基体１３を構成するアルミナの絶縁抵抗ＲＡＬを低くし、発生したリーク電流に基づく変化を検出する。   The detection unit output V-OUTPUT detects a change in the detection electrode R according to the amount of PM accumulated on the detection unit in a state where the heater unit 300 is not energized. The current is heated to a predetermined temperature or higher by energization to intentionally lower the insulation resistance RAL of alumina constituting the insulating base 13, and a change based on the generated leakage current is detected.

ここで、本発明に以上検出手段として用いられるリーク電流を利用した異常判定方法の具体例について、図４を参照して説明する。
図４は、本発明に用いられる異常判定方法の一例を示すフローチャートである。 Here, a specific example of the abnormality determination method using the leakage current used as the detection means in the present invention will be described with reference to FIG.
FIG. 4 is a flowchart showing an example of the abnormality determination method used in the present invention.

ステップＳ１００の異常検出要否判定行程では、検出素子１０の加熱再生時期か否かが判定され、検出素子１０の再生を要し、ヒータ部３００への通電により、ＰＭ燃焼時期である場合には、判定Ｙｅｓとなり、ステップＳ１１０のＰＭ燃焼制御行程に進み、検出素子１０の再生を必要とせず、ＰＭ燃焼時期でない場合には、判定Ｎｏとなり、異常判定行程を終了する。   In the abnormality detection necessity determination process in step S100, it is determined whether or not it is the heating regeneration timing of the detection element 10, and the regeneration of the detection element 10 is required. If the determination is Yes, the process proceeds to the PM combustion control process in step S110, the regeneration of the detection element 10 is not required, and the PM combustion time is not reached, the determination is No and the abnormality determination process is terminated.

次いで、ステップＳ１１０のＰＭ燃焼制御工程では、発熱体３００へ、ＰＭ燃焼をするための通電が開始され、リーク電流が発生することなく、ＰＭが燃焼する所定のＰＭ燃焼温度（例えば、６００℃）に昇温される。   Next, in the PM combustion control step of step S110, energization for PM combustion is started to the heating element 300, and a predetermined PM combustion temperature (for example, 600 ° C.) at which PM burns without generating a leakage current. The temperature is increased.

ステップＳ１２０のＰＭ燃焼完了判定行程では、ＰＭ燃焼が完了したか否かが判定される。具体的には、検知部出力Ｖ−ＯＵＴＰＵＴから算出した検出間抵抗Ｒが所定の閾値以上となっているか、又は、ＰＭ燃焼のために発熱体３００への通電時間が所定の時間を経過したか等によってＰＭ燃焼が完了したか否かを判定することができる。   In the PM combustion completion determination process in step S120, it is determined whether PM combustion is completed. Specifically, whether the detection resistance R calculated from the detection unit output V-OUTPUT is equal to or greater than a predetermined threshold, or whether the energization time to the heating element 300 has passed a predetermined time due to PM combustion It can be determined whether or not PM combustion is completed.

ＰＭ燃焼完了と判定されれば、判定Ｙｅｓとなり、ステップＳ１３０のリーク電流検出温度昇温行程に進む。   If it is determined that PM combustion is completed, the determination becomes Yes, and the process proceeds to the leakage current detection temperature heating step in step S130.

ＰＭ燃焼未完了と判定されれば、判定Ｎｏとなり、ステップ１１０に戻り、発熱体３００への通電を維持する。   If it is determined that PM combustion is not completed, the determination is No, the process returns to step 110, and energization of the heating element 300 is maintained.

ステップＳ１３０のリーク電流検出温度昇温行程では、リーク電流を意図的に発生させるべく、発熱体３００の温度を所定のリーク電流発生温度（例えば８００〜１０００℃）に昇温する。   In the leakage current detection temperature raising step in step S130, the temperature of the heating element 300 is raised to a predetermined leakage current generation temperature (for example, 800 to 1000 ° C.) in order to intentionally generate a leakage current.

次いで、ステップＳ１４０のリーク電流検出行程では、検知部を所定のリーク電流発生温度に昇温した状態で、リーク電流の検出を検出する。
このとき、検知部１００には、ＰＭが堆積しておらず、リーク電流発生温度以下では検出電極１１、１２間がほぼ絶縁状態であるので、検知部出力は、ほぼ０となるが、リーク電流検出行程では、リーク電流発生温度以上に昇温されているので、絶縁性基体１３の絶縁抵抗ＲＡＬが低下し、ヒータ部３００から検知部１００にリーク電流が流れ、これが検知部出力Ｖ−ＯＵＴＰＵＴとして検出される。 Next, in the leakage current detection process of step S140, detection of leakage current is detected in a state where the temperature of the detection unit is raised to a predetermined leakage current generation temperature.
At this time, since PM is not deposited on the detection unit 100 and the detection electrodes 11 and 12 are substantially insulated below the leakage current generation temperature, the detection unit output is almost zero. In the detection process, since the temperature is raised above the leak current generation temperature, the insulation resistance RAL of the insulating base 13 is reduced, and a leak current flows from the heater unit 300 to the detection unit 100, and this is detected as the detection unit output V-OUTPUT. Detected.

次いで、ステップＳ１５０のリーク電流閾値判定行程では、検出されたリーク電流量と予め計測した正常時におけるリーク電流量とを比較し、正常範囲内か否かを判定する。
正常時におけるリーク電流量との差が一定の範囲内となるときには、判定Ｙｅｓとなり、ステップＳ１６０の正常判定行程に進み、正常時におけるリーク電流量との差が一定の範囲を超えるときには、判定Ｎｏとなり、ステップＳ１７０の異常判定行程に進む。 Next, in the leakage current threshold determination process in step S150, the detected leakage current amount is compared with the leakage current amount measured in advance in the normal state to determine whether or not it is within the normal range.
When the difference from the normal leakage current amount is within a certain range, the determination is Yes, and the process proceeds to the normal determination process in step S160. When the difference from the normal leakage current amount exceeds a certain range, the determination No. Thus, the process proceeds to the abnormality determination step in step S170.

ステップＳ１６０で正常判定された場合には、異常判定を終了し、通常のＰＭ検出に移行する。
ステップＳ１６０でセンサ異常判定された場合には、異常診断信号を発振したり、異常警告をしたりする等必要な処置をし、異常判定を終了する。 If the normal determination is made in step S160, the abnormality determination is terminated and the routine proceeds to normal PM detection.
If the sensor abnormality is determined in step S160, necessary measures such as oscillating an abnormality diagnosis signal or giving an abnormality warning are taken, and the abnormality determination is terminated.

ここで、本発明の第１の実施形態におけるＰＭセンサの異常検出原理について説明する。
設定温度を４００℃〜１２００℃の範囲として、正常時、即ち、櫛歯電極部分に断線や劣化を生じていない状態における出力電圧の温度特性を予め検出し、それを基準として、閾値判定することにより、電源側の櫛歯電極（図３中Ａ点）断線時と、ＧＮＤ側の櫛歯電極（図３中Ｂ点）断線時とについて、異常の検出を行うことができる。その結果を、図５に示す。 Here, the abnormality detection principle of the PM sensor in the first embodiment of the present invention will be described.
Set the temperature in the range of 400 ° C to 1200 ° C, detect the temperature characteristics of the output voltage in the normal state, that is, in the state where no breakage or deterioration has occurred in the comb electrode portion, and determine the threshold value based on that. Accordingly, it is possible to detect an abnormality when the comb electrode on the power source side (point A in FIG. 3) is disconnected and when the comb electrode on the GND side (point B in FIG. 3) is disconnected. The result is shown in FIG.

本発明者等の鋭意試験により、一対の計測電極１１、１２の内、電源側に断線異常が生じた場合には、正常時に比べ温度上昇に伴うリーク電流の上昇速度が速くなり、接地側に断線異常が生じた場合には、リーク電流が検出されず、検知部１００に計測電極１１、１２の剥離、マイグレーション、灰分（Ａｓｈ）の堆積等により劣化が生じた場合には、劣化度合いに応じて検知部出力が低下し、一対の計測電極１１、１２の内、接地側に断線異常が生じた場合には、リーク電流が検出されないことが判明した。   When a disconnection abnormality occurs on the power source side of the pair of measurement electrodes 11 and 12 by the intensive studies of the present inventors, the rate of increase of the leakage current accompanying the temperature rise is faster than in the normal state, and the ground side is When a disconnection abnormality occurs, a leak current is not detected, and if the detection unit 100 is deteriorated due to separation of the measurement electrodes 11 and 12, migration, accumulation of ash (Ash), or the like, depending on the degree of deterioration As a result, it was found that when the output of the detection unit decreases and a disconnection abnormality occurs on the ground side of the pair of measurement electrodes 11 and 12, no leakage current is detected.

以下、本発明者等が行った試験結果、及び、異常の判定方法について図５を参照して説明する。図示するように、素子温度が８００℃を超えるとリーク電流が発生し、温度上昇とともに出力電圧も上昇している。また、電源側の櫛歯電極（図３中Ａ点）断線時には出力が増大し、ＧＮＤ側の櫛歯電極（図３中Ｂ点）断線時には出力電圧が０Ｖに低下する。
つまり、予め計測した正常時の出力との比較により断線時箇所を特定できることが分かる。本実施形態においては、異常検出手段として、検知部１００の出力が正常時と比較して所定の閾値以上高くなるときには電源側（図３中Ａ点）断線異常と判定し、検知部１００の出力が検出されないときには接地側（図３中Ｂ点）断線異常と判定する。 Hereinafter, the test results performed by the present inventors and the abnormality determination method will be described with reference to FIG. As shown in the figure, when the element temperature exceeds 800 ° C., a leakage current is generated, and the output voltage increases with the temperature rise. Further, the output increases when the comb electrode on the power supply side (point A in FIG. 3) is disconnected, and the output voltage decreases to 0 V when the comb electrode on the GND side (point B in FIG. 3) is disconnected.
That is, it can be seen that the disconnection point can be specified by comparison with the normal output measured in advance. In this embodiment, as an abnormality detection means, when the output of the detection unit 100 is higher than a normal threshold by a predetermined threshold or more, it is determined that the power supply side (point A in FIG. 3) is broken, and the output of the detection unit 100 If is not detected, it is determined that the grounding side (point B in FIG. 3) is broken.

図６（ａ）、（ｂ）は、本発明に第２の実施形態における粒子状物質検出センサとしてのＰＭセンサ１の概略構成図であり、その主要部であるＰＭセンサ素子１０と制御部２を示している。
本実施形態のＰＭセンサ１は、ディーゼルパティキュレートフィルタＤＰＦを通過して下流側にすり抜ける粒子状物質ＰＭを検出する。 FIGS. 6A and 6B are schematic configuration diagrams of the PM sensor 1 as the particulate matter detection sensor according to the second embodiment of the present invention, and the PM sensor element 10 and the control unit 2 which are main parts thereof. Is shown.
The PM sensor 1 of the present embodiment detects particulate matter PM that passes through the diesel particulate filter DPF and slips downstream.

図６（ａ）、（ｂ）において、ＰＭセンサ素子１０は、絶縁性基体である絶縁基板１３の先端側表面（図の右端側上面）に、検知部１００と、ヒータ部３００を有している。
検知部１００は、一対の計測電極として計測電極１１、１２と電極リード部１１１、１１２を対向形成して構成され、電極リード部１１１、１１２の端部にそれぞれ設けた端子部１２１、１２２を介して外部の制御部２に接続して、計測電極間（１１、１２）の電気抵抗が計測されるようになっている。 6 (a) and 6 (b), the PM sensor element 10 has a detection unit 100 and a heater unit 300 on the front end side surface (upper right side upper surface in the figure) of an insulating substrate 13 that is an insulating base. Yes.
The detection unit 100 is configured by forming the measurement electrodes 11 and 12 and the electrode lead portions 111 and 112 to face each other as a pair of measurement electrodes, and via terminal portions 121 and 122 provided at end portions of the electrode lead portions 111 and 112, respectively. By connecting to the external control unit 2, the electrical resistance between the measurement electrodes (11, 12) is measured.

ヒータ部３００は、検知部１００の計測電極１１、１２周りに形成される加熱電極３１とヒータリード部３１１、３１２にて構成され、ヒータリード部３１１、３１２の端部にそれぞれ設けた端子部３２１、３２２を介して接続される制御部２により、通電が制御される。ここでは、端子部１２１、１２２と端子部３２１、３２２は、基板長手方向に、端子部１２１、１２２が基端側（図の左端側）となるように配置される。   The heater unit 300 includes a heating electrode 31 and heater lead units 311 and 312 formed around the measurement electrodes 11 and 12 of the detection unit 100, and terminal units 321 provided at end portions of the heater lead units 311 and 312, respectively. 322, the energization is controlled by the control unit 2 connected through 322. Here, the terminal portions 121 and 122 and the terminal portions 321 and 322 are arranged so that the terminal portions 121 and 122 are on the base end side (left end side in the drawing) in the substrate longitudinal direction.

検知部１００は、電気絶縁性及び耐熱性に優れたセラミックス材料、例えばアルミナをドクターブレード法、プレス成形法等の公知の手法を用いて平板状の絶縁基板１３に形成し、その先端部表面に、所定の電極間距離をおいて対向する基部から対向方向に延びる複数の補助電極を設けた櫛歯形状の計測電極１１、１２を形成している。計測電極１１、１２は、例えば白金等の貴金属を含む導電性ペーストを、所定のパターンに印刷して形成され、同様にして絶縁基板１３表面に印刷形成される電極リード部１１１、１１２の一端に、それぞれ接続している。計測電極１１、１２の基部は基板長手方向に延びて、電極リード部１１１、１１２に接続し、計測電極１１、１２の補助電極は交互に位置して、電極間隔を所定間隔に保っている。   The detection unit 100 is formed on a flat insulating substrate 13 using a known technique such as a doctor blade method or a press molding method with a ceramic material excellent in electrical insulation and heat resistance, for example, alumina, and is formed on the surface of the tip portion. The comb-shaped measuring electrodes 11 and 12 are provided with a plurality of auxiliary electrodes extending in the opposing direction from the opposing bases at a predetermined inter-electrode distance. The measurement electrodes 11 and 12 are formed by printing a conductive paste containing a noble metal such as platinum in a predetermined pattern, and similarly at one end of electrode lead portions 111 and 112 that are printed on the surface of the insulating substrate 13. , Each connected. The base portions of the measurement electrodes 11 and 12 extend in the longitudinal direction of the substrate and are connected to the electrode lead portions 111 and 112. The auxiliary electrodes of the measurement electrodes 11 and 12 are alternately positioned to keep the electrode interval at a predetermined interval.

ヒータ部３００は、本発明では、検知部１００が形成される絶縁基板１３の先端部表面に、同様の手法で、所定パターンの加熱電極３１とヒータリード部３１１、３１２を印刷形成してなる。ヒータ部３００の加熱電極３１は、計測電極１１、１２の外周を囲むコ字状に形成されて、検知部１００を加熱する。加熱電極３１用材料は、Ｗ、Ｔｉ、Ｃｕ、Ａｌ、Ｎｉ、Ｃｒ、Ｐｄ、Ａｇ、Ｐｔ、Ａｕ及びこれらの合金等が挙げられ、センサ素子の小型化の観点から耐マイグレーション性に優れた高抵抗材料を用いることが好ましい。加熱電極３１の幅は、２μｍ〜１００μｍ、厚みは、０．２μｍ〜１００μｍとするのがよい。本発明では、検知部１００とヒータ部３００が同一表面に、近接位置しているため、効率よく所定温度に加熱することができる。   In the present invention, the heater unit 300 is formed by printing the heating electrode 31 and the heater leads 311 and 312 having a predetermined pattern on the surface of the front end portion of the insulating substrate 13 on which the detection unit 100 is formed by the same method. The heating electrode 31 of the heater unit 300 is formed in a U shape surrounding the outer periphery of the measurement electrodes 11 and 12, and heats the detection unit 100. Examples of the material for the heating electrode 31 include W, Ti, Cu, Al, Ni, Cr, Pd, Ag, Pt, Au, alloys thereof, and the like. It is preferable to use a resistance material. The width of the heating electrode 31 is preferably 2 μm to 100 μm, and the thickness is preferably 0.2 μm to 100 μm. In the present invention, since the detection unit 100 and the heater unit 300 are located close to each other on the same surface, they can be efficiently heated to a predetermined temperature.

本実施形態のＰＭセンサ１は、検知部１００とヒータ部３００が近接するため、比較的低い温度とすることで検知部出力への影響を抑制することができ、昇温も容易でエネルギーコストが低減できる。
また、好ましくは、検知部１００の計測電極１１、１２とヒータ部３００の加熱電極３１の間の距離を、１００μｍ〜１３６０μｍの範囲で近接配置するのがよい。 両電極間距離が１００μｍ以上あれば、上記温度範囲において、リーク電流等による検知部出力への影響なく、精度よい検出が可能である。両電極間距離が１３６０μｍより大きいと、検知部１００とヒータ部３００を同一表面に形成するメリットが得にくく、また、絶縁基板１３をコンパクトにすることが難しい。 Since the detection unit 100 and the heater unit 300 are close to each other in the PM sensor 1 of this embodiment, the influence on the output of the detection unit can be suppressed by setting the temperature to a relatively low temperature. Can be reduced.
In addition, preferably, the distance between the measurement electrodes 11 and 12 of the detection unit 100 and the heating electrode 31 of the heater unit 300 should be close to each other in the range of 100 μm to 1360 μm. If the distance between both electrodes is 100 μm or more, accurate detection is possible in the above temperature range without affecting the output of the detector due to leakage current or the like. When the distance between both electrodes is larger than 1360 μm, it is difficult to obtain the merit of forming the detection unit 100 and the heater unit 300 on the same surface, and it is difficult to make the insulating substrate 13 compact.

また、絶縁基板１３の表面には、検知部１００形成領域に開口部１４１を有する絶縁保護層１４が被覆形成される。絶縁保護層１４は、電極リード部１１１、１１２を覆って、リード部１１１、１１２間に粒子状物質ＰＭが堆積することによる誤検出を防止し、さらにヒータ部３００の加熱電極３１とヒータリード部３１１、３１２を覆って、検知部１００との間を絶縁保持することができる。絶縁保護層１４は、絶縁性、耐熱性に優れた無機質粉末又は基板と同材質の粉末のペーストを用いて形成され、例えば、絶縁基板１３と同じアルミナが好適に用いられる。   In addition, an insulating protective layer 14 having an opening 141 in the detection unit 100 formation region is formed on the surface of the insulating substrate 13. The insulating protective layer 14 covers the electrode lead portions 111 and 112 to prevent erroneous detection due to the particulate matter PM being deposited between the lead portions 111 and 112, and further, the heating electrode 31 and the heater lead portion of the heater portion 300. 311 and 312 can be covered and insulated from the detection unit 100. The insulating protective layer 14 is formed by using an inorganic powder excellent in insulating properties and heat resistance or a paste of powder of the same material as the substrate, and for example, the same alumina as the insulating substrate 13 is preferably used.

図６（ａ）において、ＰＭセンサ１は、排気管ＥＸの管壁に螺結される筒状ハウジング５０を有し、その内部に筒状インシュレータ６０に挿入固定されたＰＭセンサ素子１０の上半部を保持している。ＰＭセンサ素子１０の下半部は、筒状ハウジング５０の下端部に固定されて排気管ＥＸ内に突出する中空のカバー体４０内に位置している。カバー体４０の底部及び側部には、ディーゼルパティキュレートフィルタＤＰＦを通過した粒子状物質ＰＭを含む排出ガスが流出入するための通孔４１０、４１１が穿設されている。   6A, the PM sensor 1 has a cylindrical housing 50 that is screwed to the tube wall of the exhaust pipe EX, and the upper half of the PM sensor element 10 that is inserted and fixed to the cylindrical insulator 60 therein. Holding the department. The lower half of the PM sensor element 10 is positioned in a hollow cover body 40 that is fixed to the lower end of the cylindrical housing 50 and protrudes into the exhaust pipe EX. Through holes 410 and 411 through which exhaust gas containing particulate matter PM that has passed through the diesel particulate filter DPF flows in and out are formed in the bottom and sides of the cover body 40.

ここで、本実施形態における異常判定方法について図７を参照して説明する。
本実施形態においては、計測電極１１、１２と加熱電極３１とが絶縁基板１３の同一平面上に形成されているので、リーク電流を発生する温度が低くなり、加熱により変化するリーク電流量をより細かく検出し、閾値判定することにより、検知部１００に発生する異常の有無だけでなく、異常の種類を特定することが可能となる。 Here, the abnormality determination method in the present embodiment will be described with reference to FIG.
In the present embodiment, since the measurement electrodes 11 and 12 and the heating electrode 31 are formed on the same plane of the insulating substrate 13, the temperature at which leakage current is generated is lowered, and the amount of leakage current that changes due to heating is further increased. By finely detecting and determining the threshold value, it is possible to specify not only the presence or absence of an abnormality occurring in the detection unit 100 but also the type of abnormality.

ステップステップＳ２００の異常検出要否判定行程では、検出素子１０の加熱再生時期か否かが判定され、検出素子１０の再生を要し、ヒータ部３００への通電により、ＰＭ燃焼時期である場合には、判定Ｙｅｓとなり、ステップＳ２１０のＰＭ燃焼制御行程に進み、検出素子１０の再生を必要とせず、ＰＭ燃焼時期でない場合には、判定Ｎｏとなり、異常判定行程を終了する。   In the abnormality detection necessity determination process in step S200, it is determined whether or not it is the heating regeneration timing of the detection element 10, the regeneration of the detection element 10 is required, and when the PM combustion timing is due to energization of the heater unit 300. Is judged Yes, the process proceeds to the PM combustion control process of step S210, and the regeneration of the detection element 10 is not required, and if it is not the PM combustion time, the judgment is No and the abnormality determination process is terminated.

次いで、ステップＳ２１０のＰＭ燃焼制御工程では、発熱体３００へ、ＰＭ燃焼をするための通電が開始され、リーク電流が発生することなく、ＰＭが燃焼する所定のＰＭ燃焼温度（例えば、６００℃）に昇温される。   Next, in the PM combustion control step of step S210, energization for PM combustion is started to the heating element 300, and a predetermined PM combustion temperature (for example, 600 ° C.) at which PM burns without generating a leakage current. The temperature is increased.

ステップＳ２２０のＰＭ燃焼完了判定行程では、ＰＭ燃焼が完了したか否かが判定される。具体的には、検知部出力Ｖ−ＯＵＴＰＵＴから算出した検出間抵抗Ｒが所定の閾値以上となっているか、又は、ＰＭ燃焼のために発熱体３００への通電時間が所定の時間を経過したか等によってＰＭ燃焼が完了したか否かを判定することができる。   In the PM combustion completion determination process in step S220, it is determined whether PM combustion is completed. Specifically, whether the detection resistance R calculated from the detection unit output V-OUTPUT is equal to or greater than a predetermined threshold, or whether the energization time to the heating element 300 has passed a predetermined time due to PM combustion It can be determined whether or not PM combustion is completed.

ＰＭ燃焼完了と判定されれば、判定Ｙｅｓとなり、ステップＳ２３０のリーク電流検出温度昇温行程に進む。ＰＭ燃焼未完了と判定されれば、判定Ｎｏとなり、ステップ２１０に戻り、発熱体３００への通電を維持する。   If it is determined that PM combustion is completed, the determination becomes Yes, and the process proceeds to the leakage current detection temperature heating step in step S230. If it is determined that PM combustion is not completed, the determination is No, the process returns to step 210, and energization of the heating element 300 is maintained.

ステップＳ２３０のリーク電流検出温度昇温行程では、リーク電流を意図的に発生させるべく、発熱体３００の温度を所定のリーク電流発生温度（例えば６００〜８００℃）に昇温する。
このとき、本実施形態においては、上記第１の実施形態の場合よりも低い温度からリーク電流が発生する。 In the leakage current detection temperature heating process in step S230, the temperature of the heating element 300 is raised to a predetermined leakage current generation temperature (for example, 600 to 800 ° C.) in order to intentionally generate a leakage current.
At this time, in this embodiment, a leak current is generated from a lower temperature than in the case of the first embodiment.

次いで、ステップＳ２４０のリーク電流検出行程では、検知部を所定のリーク電流発生温度に昇温した状態で、リーク電流の検出を検出する。
このとき、検知部１００には、ＰＭが堆積しておらず、リーク電流発生温度以下では検出電極１１、１２間がほぼ絶縁状態であるので、検知部出力は、ほぼ０となるが、リーク電流検出行程では、リーク電流発生温度以上に昇温されているので、絶縁性基体１３の絶縁抵抗ＲＡＬが低下し、ヒータ部３００から検知部１００にリーク電流が流れ、これが検知部出力Ｖ−ＯＵＴＰＵＴとして検出される。 Next, in the leakage current detection process in step S240, detection of leakage current is detected in a state where the detection unit is heated to a predetermined leakage current generation temperature.
At this time, since PM is not deposited on the detection unit 100 and the detection electrodes 11 and 12 are substantially insulated below the leakage current generation temperature, the detection unit output is almost zero. In the detection process, since the temperature is raised above the leak current generation temperature, the insulation resistance RAL of the insulating base 13 is reduced, and a leak current flows from the heater unit 300 to the detection unit 100, and this is detected as the detection unit output V-OUTPUT. Detected.

次いで、ステップＳ２５０の第１のリーク電流閾値判定行程では、検出されたリーク電流量と予め計測した正常時における第１のリーク電流量閾値ＶＲＥＦ１とを比較し、第１の閾値ＶＲＥＦ１以上か否かを判定する。
検知出力が正常時における第１のリーク電流量閾値を超え、Ｖ＞ＶＲＥＦ１となる場合には、判定Ｙｅｓとなり、ステップＳ２６０の電源側断線異常行程に進み、第１のリーク電流量閾値ＶＲＥＦ１以下の場合には、判定Ｎｏとなり、ステップＳ２７０の第２のリーク電流閾値判定行程に進む。 Next, in the first leakage current threshold determination process in step S250, the detected leakage current amount is compared with the first leakage current amount threshold value V REF1 measured in advance in the normal state to determine whether it is greater than or equal to the first threshold value V REF1 . Determine whether or not.
When the detected output exceeds the first leakage current amount threshold value at the normal time and V> V REF1 is satisfied, the determination is Yes, the process proceeds to the power supply side disconnection abnormality process in step S260, and the first leakage current amount threshold value V REF1 is reached. In the following cases, the determination is No, and the process proceeds to the second leakage current threshold determination process in step S270.

検知出力が正常時における第１のリーク電流量閾値ＶＲＥＦ１以下で第２のリーク電流量閾値ＶＲＥＦ２を超え、ＶＲＥＦ１≧Ｖ＞ＶＲＥＦとなる場合には、判定Ｙｅｓとなり、ステップＳ２８０の正常判定行程に進み、第２のリーク電流量閾値ＶＲＥＦ２以下の場合には、判定Ｎｏとなり、ステップＳ２９０の第３のリーク電流閾値判定行程に進む。 If the detected output is equal to or lower than the first leakage current amount threshold value V REF1 when the detection output is normal and exceeds the second leakage current amount threshold value V REF2 , and V REF1 ≧ V> V REF is satisfied, the determination becomes Yes, and the normality of step S280 Proceeding to the determination step, if it is equal to or smaller than the second leakage current amount threshold V REF2 , the determination is No, and the processing proceeds to the third leakage current threshold determination step in step S290.

検知出力が正常時における２のリーク電流量閾値ＶＲＥＦ２以下で、第３のリーク電流量閾値を超え、ＶＲＥＦ２≧Ｖ＞ＶＲＥＦ３となる場合には、判定Ｙｅｓとなり、ステップＳ３００の接地側断線行程に進み、第３のリーク電流量閾値ＶＲＥＦ３以下の場合には、判定Ｎｏとなり、ステップＳ３１０の劣化判定行程に進む。 If the detection output is less than or equal to the leakage current amount threshold value V REF2 of 2 at the normal time, exceeds the third leakage current amount threshold value, and V REF2 ≧ V> V REF3 , the determination is Yes and the ground side disconnection in step S300 When the process proceeds to step S310 and the third leak current amount threshold value VREF3 or less, the determination is No, and the process proceeds to the deterioration determination process of step S310.

このようにして、電源側断線検出判定と、正常判定と、接地側断線検出判定と、劣化判定とを分類して検出することが可能となる。
各判定結果に応じた対応を処理し、異常検出行程を終了する。
なお、各閾値ＶＲＥＦ１〜ＶＲＥＦ３は、予め正常時のリーク電流を計測し、それをマップデータとして記憶させ、加熱温度に応じた閾値を選択して判定に利用することができる。
また、実際の判定手段は、コンパレータ等を用いたアナログロジック回路によって容易に実現できる。また、検出結果をＡ／Ｄ変換して、制御部２に演算回路を設けて演算処理をすることによって異常判定するようにしても良い。 In this way, it is possible to classify and detect the power source side disconnection detection determination, the normality determination, the ground side disconnection detection determination, and the deterioration determination.
The response corresponding to each determination result is processed, and the abnormality detection process is terminated.
Each of the threshold values V REF1 to V REF3 can be used for determination by measuring a normal leakage current in advance and storing it as map data and selecting a threshold value according to the heating temperature.
The actual determination means can be easily realized by an analog logic circuit using a comparator or the like. Alternatively, the detection result may be A / D converted, and an abnormality may be determined by providing an arithmetic circuit in the control unit 2 and performing arithmetic processing.

本発明の構成による結果を、図８に示す。図示するように、電源側の櫛歯電極（Ａ点）断線時の出力が、低温側にシフトし、加熱−計測電極距離を短くして両電極を近づけることで、素子温度がＰＭの燃焼が開始される温度と同程度の６００℃から出力が立ち上がっている。   The result of the configuration of the present invention is shown in FIG. As shown in the figure, the power at the time when the comb electrode on the power source side (point A) is disconnected is shifted to the low temperature side, the heating-measurement electrode distance is shortened, and both electrodes are brought closer, so that the element temperature is burned with PM. The output rises from 600 ° C., which is about the same as the starting temperature.

さらに、図８（ａ）に示すように、本発明のＰＭセンサ１によれば、上記第１の実施形態における通常の構成のＰＭセンサ１に比べ、リーク電流の発生温度が下がり、６００℃以上でリーク電流が検出可能となる。
そこで、本図（ｂ）に示すように、正常時に対して出力電圧が所定の閾値（ＶＲＥＦ１）以上高くなっている場合には、電源側において断線が発生している電源側断線異常と判定でき、被測定ガスからの受熱や繰り返し加熱再生されることによって計測電極１１、１２の劣化や、灰分の付着、電極剥離、マイグレーション等の劣化によって、検出電極間の抵抗値が増大し、ヒータ部３００からのリーク電流が流れ難くなり、劣化の程度に応じて出力電圧が低下するため、正常時との比較によって、出力電圧が所定の閾値（ＶＲＥＦ２）以上低下した場合には、劣化の程度が進んだ劣化異常と判定することができ、さらに、第三の閾値（ＶＲＥＦ３）以下で、出力電圧が０Ｖにはりついていれば、ＧＮＤ側において断線が発生している接地側断線異常と判定でき、容易に異常原因の特定を区別して検知することができる。 Further, as shown in FIG. 8A, according to the PM sensor 1 of the present invention, the temperature at which leakage current is generated is lower than that of the PM sensor 1 having the normal configuration in the first embodiment, and is 600 ° C. or higher. Thus, the leak current can be detected.
Therefore, as shown in FIG. 5B, when the output voltage is higher than a predetermined threshold (V REF1 ) compared to the normal time, it is determined that the power supply side disconnection abnormality has occurred on the power supply side. The resistance value between the detection electrodes is increased due to deterioration of the measurement electrodes 11 and 12 due to heat reception from the gas to be measured and repeated heating and regeneration, deterioration of adhesion of ash, electrode peeling, migration, and the like. Since the leakage current from 300 becomes difficult to flow and the output voltage decreases according to the degree of deterioration, the degree of deterioration when the output voltage decreases more than a predetermined threshold (V REF2 ) by comparison with the normal state can be determined to be advanced deterioration abnormal, further, a third threshold value (V REF3) below, if the output voltage if stuck to 0V, and the ground disconnection in the GND side is generated It can be determined that a disconnection abnormality can be detected by distinguishing the specific easily abnormality cause.

図９には、ＰＭセンサ素子１０の他の構成例を示す。図９（ａ）の第３実施形態において、ヒータ部３００は、検知部１００が形成される絶縁基板１３の先端部表面に、同様の手法で形成される。また、本実施形態では、絶縁基板１３の裏面側に制御部２へ接続される端子部３３１、３３２を形成し、スルーホール３４１、３４２を介して、表面側の端子部３２１、３２２と接続している。端子部３２１、３２２と端子部３３１、３３２は、絶縁基板１３の表裏面の対向位置にあり、絶縁基板１３を貫通するスルーホール３４に充填される導電材によって両端子部が導通する。   FIG. 9 shows another configuration example of the PM sensor element 10. In the third embodiment shown in FIG. 9A, the heater unit 300 is formed on the surface of the distal end portion of the insulating substrate 13 on which the detection unit 100 is formed by the same method. Further, in the present embodiment, terminal portions 331 and 332 connected to the control unit 2 are formed on the back surface side of the insulating substrate 13 and connected to the surface side terminal portions 321 and 322 via the through holes 341 and 342. ing. The terminal portions 321 and 322 and the terminal portions 331 and 332 are located at opposite positions on the front and back surfaces of the insulating substrate 13, and both terminal portions are electrically connected by a conductive material filled in the through hole 34 that penetrates the insulating substrate 13.

このように、ヒータ部３００と検知部１００を絶縁基板１３の同一表面に形成した本実施形態の構成において、それぞれの端子部３２１、３２２、端子部３３１、３３２を、絶縁基板１３の別の面に配置することができる。この構成は、例えばスペースの制約がある場合に有利であり、出力取り出しや電源供給のためのワイヤハーネスと、検知部１００及びヒータ部３００とを容易に接続できる。
なお、本発明において必ずしも必須ではないが、絶縁保護層１４を、検知部１００と端子部１２１、１２２の形成領域を除く絶縁基板１３の表面に形成しても良い。このような構成とすることにより、検知部１００以外へのＰＭの堆積による検出異常を抑制できる。 As described above, in the configuration of the present embodiment in which the heater unit 300 and the detection unit 100 are formed on the same surface of the insulating substrate 13, the terminal units 321 and 322 and the terminal units 331 and 332 are connected to different surfaces of the insulating substrate 13. Can be arranged. This configuration is advantageous, for example, when space is limited, and can easily connect the wire harness for output extraction and power supply to the detection unit 100 and the heater unit 300.
Although not necessarily essential in the present invention, the insulating protective layer 14 may be formed on the surface of the insulating substrate 13 excluding regions where the detection unit 100 and the terminal units 121 and 122 are formed. By adopting such a configuration, it is possible to suppress detection abnormality due to PM accumulation other than the detection unit 100.

図７（ｂ）の第４実施形態において、ヒータ部３００は、実施形態１、２のように検知部１００の外側を囲う形状とする代わりに、内側に形成することもできる。本実施形態では、検知部１００の計測電極１１、１２と電極リード部１１１、１１２の内側に、これらに沿うようにコ字状にヒータ部３００の加熱電極３１とヒータリード部３１１、３１２を形成し、絶縁基板１３の基端部側表面に形成した端子部３２１、３２２とヒータリード部３１１、３１２を接続する。ここでは、電極リード部１１１、１１２に接続する端子部１２１、１２２が、端子部３２１、３２２より先端側（図の右端側）に位置し、この電極リード部１１１、１１２及び端子部１２１、１２２を覆って、絶縁保護層１４が形成される。   In the fourth embodiment of FIG. 7B, the heater unit 300 can be formed inside instead of the shape surrounding the outside of the detection unit 100 as in the first and second embodiments. In the present embodiment, the heating electrode 31 and the heater lead portions 311 and 312 of the heater unit 300 are formed inside the measurement electrodes 11 and 12 and the electrode lead portions 111 and 112 of the detection unit 100 in a U-shape along these. Then, the terminal portions 321 and 322 formed on the base end side surface of the insulating substrate 13 and the heater lead portions 311 and 312 are connected. Here, the terminal portions 121 and 122 connected to the electrode lead portions 111 and 112 are located on the distal end side (right end side in the drawing) from the terminal portions 321 and 322, and the electrode lead portions 111 and 112 and the terminal portions 121 and 122 are connected. Insulating protective layer 14 is formed.

この構成では、絶縁保護層１４に検知部１００を露出させるための開口部を形成する必要がなく、簡易な形状で製作が容易である。また、電極リード部１１１、１１２に接続する端子部１２１、１２２は、図示しないスルーホールを介して絶縁基板１３の裏面側の端子部に接続される。あるいは、端子部１２１、１２２上に絶縁保護層１４を形成しない構成とすることもできる。   In this configuration, it is not necessary to form an opening for exposing the detection unit 100 to the insulating protective layer 14, and the manufacturing is easy with a simple shape. The terminal portions 121 and 122 connected to the electrode lead portions 111 and 112 are connected to the terminal portion on the back surface side of the insulating substrate 13 through a through hole (not shown). Alternatively, the insulating protective layer 14 may not be formed on the terminal portions 121 and 122.

ここで、本実施形態では、ＰＭセンサ素子１０を、絶縁基板１３の表面に検知部１００とヒータ部３００の両方を有する構成としたので、熱伝導率を向上させ、温度制御しやすくなる。特に、ＰＭ検出時には、ヒータ部３００により素早く検出温度まで加熱し、応答性よく高効率で粒子状物質ＰＭを検出する。また、従来の素子構造のように、絶縁基板１３の裏面側にヒータ部となる他の絶縁基板を積層する必要がなく、構成が簡易でコンパクトにできる。したがって、生産工程数を低減でき、原料コストを削減して、生産コストを低減する効果がある。さらに、ヒータ部となる他の絶縁基板が不要となるので、ＰＭセンサ素子１０を薄型として、省スペースとすることができる。   Here, in this embodiment, since the PM sensor element 10 is configured to have both the detection unit 100 and the heater unit 300 on the surface of the insulating substrate 13, the thermal conductivity is improved and temperature control is facilitated. In particular, at the time of PM detection, the heater unit 300 quickly heats to the detection temperature, and the particulate matter PM is detected with high responsiveness and high efficiency. Further, unlike the conventional element structure, it is not necessary to stack another insulating substrate serving as a heater portion on the back side of the insulating substrate 13, and the configuration can be simplified and made compact. Therefore, it is possible to reduce the number of production steps, reduce raw material costs, and reduce production costs. Furthermore, since another insulating substrate that becomes a heater portion is not required, the PM sensor element 10 can be made thin to save space.

このようにして形成される本発明の粒子状物質検出センサは、内燃機関の排気浄化装置に適用されて、排出される粒子状物質の検出に好適に利用される。具体的には、ＤＰＦの下流に設置されて、ＤＰＦの異常検出に利用することができる。あるいは、ＤＰＦの上流に設置されて、ＤＰＦに流入する粒子状物質ＰＭを直接検出するシステムに利用することもできる。   The particulate matter detection sensor of the present invention formed in this way is applied to an exhaust gas purification device for an internal combustion engine, and is suitably used for detecting particulate matter to be discharged. Specifically, it is installed downstream of the DPF and can be used for detecting an abnormality of the DPF. Alternatively, it can be used in a system that is installed upstream of the DPF and directly detects the particulate matter PM flowing into the DPF.

ＤＰＦ ディーゼルパティキュレートフィルタ
ＥＸ 排気管（排気通路）
Ｅ／Ｇ ディーゼルエンジン（内燃機関）
１ ＰＭセンサ（粒子状物質検出センサ）
１０ ＰＭセンサ素子（センサ素子）
１００ 検知部
１１、１２ 計測電極（計測電極）
１１１、１１２ 電極リード部
１２１、１２２ 端子部
１３ 絶縁性基板（絶縁性基体）
１４ 絶縁保護層
２ 制御部
２１ ヒータ電源
３００ ヒータ部
３１ 加熱電極
３２ 絶縁性基板
３１１、３１２ ヒータリード部
３２１、３２２ 端子部
４０ カバー体
４１０、４１１ 通孔
５０ ハウジング
６０ インシュレータ DPF Diesel particulate filter EX Exhaust pipe (exhaust passage)
E / G diesel engine (internal combustion engine)
1 PM sensor (particulate matter detection sensor)
10 PM sensor element (sensor element)
100 Detection unit 11, 12 Measurement electrode (measurement electrode)
111, 112 Electrode lead part 121, 122 Terminal part 13 Insulating substrate (insulating base)
14 Insulating protective layer 2 Control unit 21 Heater power supply 300 Heater unit 31 Heating electrode 32 Insulating substrate 311, 312 Heater lead unit 321, 322 Terminal unit 40 Cover body 410, 411 Through hole 50 Housing 60 Insulator

Claims (8)

内燃機関の排気通路に配設されて、排出ガス中の粒子状物質を検出すべく、絶縁性基体の表面に一対の計測電極を対向形成した検知部と、該検知部を所定温度に加熱する加熱電極を含むヒータ部とを具備するセンサ素子と、上記ヒータ部への通電を制御すると共に上記検知部に堆積する粒子状物質の量に応じて変化する電気的特性を計測する制御部を有する粒子状物質検出センサであって、
上記制御部は、上記ヒータ部に通電して、上記検知部を一定温度以上に加熱したときに、上記絶縁性基体の絶縁抵抗の低下により上記ヒータ部から上記検知部に漏れるリーク電流に基づく上記検知部の出力の変化を正常時と比較して、上記検知部の異常を検出する異常検出手段を有することを特徴とする粒子状物質検出センサ。 A detection unit disposed in an exhaust passage of the internal combustion engine to detect particulate matter in the exhaust gas, and a pair of measurement electrodes opposed to each other on the surface of the insulating base, and the detection unit is heated to a predetermined temperature. A sensor element including a heater unit including a heating electrode; and a control unit that controls energization to the heater unit and measures electrical characteristics that change according to the amount of particulate matter deposited on the detection unit. A particulate matter detection sensor,
The control unit is based on a leakage current leaking from the heater unit to the detection unit due to a decrease in insulation resistance of the insulating base when the heater unit is energized to heat the detection unit to a certain temperature or higher. A particulate matter detection sensor comprising abnormality detection means for detecting an abnormality of the detection unit by comparing a change in output of the detection unit with a normal state. 上記異常検出手段は、上記検知部の出力が正常時と比較して所定の閾値を超えて高くなるときには電源側断線異常と判定し、上記検知部の出力が正常時と比較して所定の閾値より低くなるときには劣化異常と判定し、上記検知部出力が検出されないときには接地側断線異常と判定する請求項１に記載の粒子状物質検出センサ。   The abnormality detection means determines that the power supply side disconnection abnormality is present when the output of the detection unit exceeds a predetermined threshold value compared to when it is normal, and determines that the output of the detection unit is a predetermined threshold value compared with when the detection unit is normal. 2. The particulate matter detection sensor according to claim 1, wherein when it becomes lower, it is determined that the abnormality is deterioration, and when the detection unit output is not detected, it is determined that the ground side disconnection is abnormal. 上記制御部は、上記ヒータ部に通電して上記一対の計測電極間の電気抵抗値に基づく上記検知部の出力から粒子状物質を検出する請求項１、又は、２に記載の粒子状物質検出センサ。 The particulate matter detection according to claim 1, wherein the control unit detects the particulate matter from the output of the detection unit based on an electric resistance value between the pair of measurement electrodes by energizing the heater unit. Sensor. 上記一対の計測電極と上記加熱電極とを上記絶縁性基体の同一表面に近接配置し、上記一対の計測電極間の電気抵抗値を検出する請求項１ないし３のいずれか１項に記載の粒子状物質検出センサ。 The particle according to any one of claims 1 to 3, wherein the pair of measurement electrodes and the heating electrode are arranged in proximity to the same surface of the insulating substrate to detect an electric resistance value between the pair of measurement electrodes. A substance detection sensor. 上記ヒータ部は、上記加熱電極を上記計測電極に近接配置すると共に、上記加熱電極と外部とを接続するヒータリード部を有する請求項１ないし４のいずれか１項に記載の粒子状物質検出センサ。   The particulate matter detection sensor according to any one of claims 1 to 4, wherein the heater unit includes a heater lead unit that places the heating electrode close to the measurement electrode and connects the heating electrode to the outside. . 上記計測電極と上記加熱電極との距離は、１００μｍ〜１３６０μｍの範囲とする請求項１ないし５のいずれか１項に記載の粒子状物質検出センサ。   The particulate matter detection sensor according to any one of claims 1 to 5, wherein a distance between the measurement electrode and the heating electrode is in a range of 100 µm to 1360 µm. 上記計測電極は、電極リード部に接続される基部と複数の補助電極からなる櫛状電極である請求項１ないし６のいずれか１項に記載の粒子状物質検出センサ。   The particulate matter detection sensor according to claim 1, wherein the measurement electrode is a comb-like electrode including a base connected to the electrode lead portion and a plurality of auxiliary electrodes. 内燃機関の排気通路に配設されて、排出ガス中の粒子状物質を検出すべく、絶縁性基体の表面に一対の計測電極を対向形成した検知部と、該検知部を所定温度に加熱する加熱電極を含むヒータ部とを具備するセンサ素子と、上記ヒータ部への通電を制御すると共に上記検知部に堆積する粒子状物質の量に応じて変化する電気的特性を計測する制御部とを有する粒子状物質検出センサの異常判定方法であって、
上記加熱電極への通電により所定のリーク電流発生温度以上に上記検知部を加熱し、上記絶縁性基体の絶縁抵抗を意図的に低下させたときに検出されるリーク電流と、予め測定した正常時におけるリーク電流とを比較して、上記検知部の出力が正常時と比較して所定の閾値以上高くなるときには電源側断線異常と判定し、上記検知部の出力が正常時と比較して所定の閾値より低くなるときには劣化異常と判定し、上記検知部出力が検出されないときには接地側断線異常と判定する粒子状物質検出センサの異常判定方法。 A detection unit disposed in an exhaust passage of the internal combustion engine to detect particulate matter in the exhaust gas, and a pair of measurement electrodes opposed to each other on the surface of the insulating base, and the detection unit is heated to a predetermined temperature. A sensor element including a heater unit including a heating electrode; and a control unit that controls energization to the heater unit and measures an electrical characteristic that varies depending on the amount of particulate matter deposited on the detection unit. An abnormality determination method for a particulate matter detection sensor having,
Leakage current detected when the detection unit is heated to a predetermined leak current generation temperature or higher by energizing the heating electrode, and the insulation resistance of the insulating substrate is intentionally reduced, and normal time measured in advance When the output of the detection unit is higher than a normal threshold by a predetermined threshold or more, it is determined that the power supply side disconnection is abnormal, and the output of the detection unit is An abnormality determination method for a particulate matter detection sensor that determines a deterioration abnormality when the value is lower than a threshold and determines a ground-side disconnection abnormality when the detection unit output is not detected.
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