JP2017078345A - Control device for reducing agent injection device - Google Patents

Control device for reducing agent injection device Download PDF

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JP2017078345A
JP2017078345A JP2015205954A JP2015205954A JP2017078345A JP 2017078345 A JP2017078345 A JP 2017078345A JP 2015205954 A JP2015205954 A JP 2015205954A JP 2015205954 A JP2015205954 A JP 2015205954A JP 2017078345 A JP2017078345 A JP 2017078345A
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injection
injection valve
reducing agent
control
aqueous solution
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JP6663680B2 (en
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修三 関根
Shuzo Sekine
修三 関根
翔吾 田代
Shogo Tashiro
翔吾 田代
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Bosch Corp
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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
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
    • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
    • F01N3/2066—Selective catalytic reduction [SCR]
    • F01N3/208—Control of selective catalytic reduction [SCR], e.g. dosing of reducing agent
    • 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
    • F01N11/00—Monitoring or diagnostic devices for exhaust-gas treatment apparatus, e.g. for catalytic activity
    • 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
    • F01N2610/00—Adding substances to exhaust gases
    • F01N2610/14—Arrangements for the supply of substances, e.g. conduits
    • F01N2610/1453—Sprayers or atomisers; Arrangement thereof in the exhaust apparatus
    • F01N2610/146—Control thereof, e.g. control of injectors or injection valves
    • 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
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
    • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
    • 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
    • Y02T10/12—Improving ICE efficiencies
    • 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)
  • Chemical Kinetics & Catalysis (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Exhaust Gas After Treatment (AREA)
  • Exhaust Gas Treatment By Means Of Catalyst (AREA)

Abstract

PROBLEM TO BE SOLVED: To determine whether an abnormality that has occurred in an injection valve is opening fixation or closing fixation during injection control of a reducing agent.SOLUTION: A control device for controlling a reducing agent injection device that injects a reducing agent for eliminating NOin exhaust gas of an internal combustion engine to an upstream side of a reduction catalyst disposed in an exhaust passage by using an injection valve mounted to an exhaust pipe of the internal combustion engine includes: an injection control section for controlling a valve opening operation of the injection valve while controlling output of a pump for pressure-feeding the reducing agent so that the pressure of the reducing agent supplied to the injection valve reaches a predetermined target value; and an abnormality determination section for determining an abnormality of the injection valve while discriminating opening fixation and closing fixation of the injection valve from each other on the basis of current waveforms carried to the injection valve and the output of the pump during execution of the injection control of the reducing agent.SELECTED DRAWING: Figure 7

Description

本発明は、内燃機関の排気通路に還元剤を供給する還元剤噴射装置を制御するための還元剤噴射装置の制御装置に関する。   The present invention relates to a control device for a reducing agent injection device for controlling a reducing agent injection device that supplies a reducing agent to an exhaust passage of an internal combustion engine.

車両に搭載されるディーゼルエンジン等の内燃機関の排気中にはＮＯX（窒素酸化物）が含まれている。かかるＮＯXを還元して窒素や水等に分解することにより排気を浄化するための装置として、尿素ＳＣＲ（Ｓｅｌｅｃｔｉｖｅ Ｃａｔａｌｙｓｔｉｃ Ｒｅｄｕｃｔｉｏｎ）システムが実用化されている。尿素ＳＣＲシステムは、還元剤として尿素水溶液を使用して、排気中のＮＯXをアンモニアと反応させることにより、ＮＯXを分解するシステムである。 NO x (nitrogen oxide) is contained in the exhaust gas of an internal combustion engine such as a diesel engine mounted on a vehicle. As an apparatus for purifying exhaust by decomposing the reduced to nitrogen and water or the like such NO X, urea SCR (Selective Catalystic Reduction) system has been put into practical use. The urea SCR system is a system that decomposes NO x by reacting NO x in exhaust with ammonia using an aqueous urea solution as a reducing agent.

かかる尿素ＳＣＲシステムは、排気通路に配置された選択還元触媒と、選択還元触媒よりも上流側の排気通路に尿素水溶液を供給するための還元剤噴射装置とを備える。選択還元触媒は、尿素水溶液が分解して生成されるアンモニアを吸着し、流入する排気中のＮＯXとアンモニアとの還元反応を促進する機能を有する。また、還元剤噴射装置は、貯蔵タンク内に収容された尿素水溶液を圧送するポンプと、ポンプにより圧送される尿素水溶液を噴射する噴射弁と、ポンプ及び噴射弁の制御を行う制御装置とを備える。 Such a urea SCR system includes a selective reduction catalyst disposed in an exhaust passage and a reducing agent injection device for supplying a urea aqueous solution to an exhaust passage upstream of the selective reduction catalyst. The selective reduction catalyst has a function of adsorbing ammonia generated by decomposition of an aqueous urea solution and promoting a reduction reaction between NO x and ammonia in the inflowing exhaust gas. The reducing agent injection device includes a pump that pumps the urea aqueous solution stored in the storage tank, an injection valve that injects the urea aqueous solution pumped by the pump, and a control device that controls the pump and the injection valve. .

尿素ＳＣＲシステムで使用される尿素水溶液は、濃度によって凍結温度が異なる。最も低い凍結温度でも、その温度はマイナス１１℃程度である。そのため、停車中に尿素水溶液が凍結し、体積が膨張することによって、ポンプや噴射弁、尿素水溶液を流通させる配管等が破損しないように、内燃機関の停止時には尿素水溶液が還元剤噴射装置内から貯蔵タンクに回収される。回収された尿素水溶液は、還元剤噴射装置の起動時に還元剤噴射装置内に再充填される。   The urea aqueous solution used in the urea SCR system has different freezing temperatures depending on its concentration. Even at the lowest freezing temperature, the temperature is about minus 11 ° C. Therefore, when the internal combustion engine is stopped, the urea aqueous solution is released from the reducing agent injection device so that the urea aqueous solution is frozen while the vehicle is stopped and the volume is expanded, so that the pump, the injection valve, the piping for circulating the urea aqueous solution, etc. are not damaged. Collected in storage tank. The recovered urea aqueous solution is refilled into the reducing agent injection device when the reducing agent injection device is started.

他方、噴射弁が高温に晒されると、噴射弁に付着している尿素水溶液の溶媒が蒸発して濃度が上昇し、凍結温度が上昇することによって、尿素水溶液が結晶化する場合がある。例えば、内燃機関の停止時に、噴射弁の冷却手段の機能が停止すると、残留する排気熱の影響を受けて噴射弁に付着している尿素水溶液が加熱され、結晶化するおそれがある。また、内燃機関の運転中であっても、尿素水溶液の噴射が長期間行われない場合には、噴射弁に付着している尿素水溶液が排気熱により加熱され、結晶化するおそれがある。尿素水溶液が結晶化すると、噴射弁の弁体が固着し、噴孔が開いたまま閉じられなくなる開固着や、噴孔が閉じられたままとなる閉固着を生じさせるおそれがある。   On the other hand, when the injection valve is exposed to a high temperature, the urea aqueous solution adhering to the injection valve evaporates to increase the concentration, and the freezing temperature rises, whereby the urea aqueous solution may crystallize. For example, when the function of the cooling means of the injection valve stops when the internal combustion engine is stopped, the urea aqueous solution adhering to the injection valve may be heated and crystallized due to the influence of residual exhaust heat. Further, even when the internal combustion engine is in operation, if the urea aqueous solution is not injected for a long time, the urea aqueous solution adhering to the injection valve may be heated by the exhaust heat and crystallized. When the urea aqueous solution is crystallized, the valve body of the injection valve is fixed, and there is a risk of causing open fixation that cannot be closed while the nozzle hole is open, or closed adhesion that the nozzle hole remains closed.

さらに、排気に含まれる煤等の微粒子が噴孔を介して噴射弁内に侵入し、弁体の摺動部分や着座部分等に付着することによって、上述した開固着や閉固着を生じるおそれもある。   Furthermore, fine particles such as soot contained in the exhaust may enter the injection valve through the nozzle hole and adhere to the sliding portion or seating portion of the valve body, which may cause the above-described open adhesion or closed adhesion. is there.

ここで、噴射弁の固着が生じた場合、その固着が開固着であるか閉固着であるかによって、取るべき処置が異なってくる。例えば、噴射弁が閉固着状態である場合、ポンプの駆動を維持したままであっても尿素水溶液が排気管内に漏れ出ることはないが、噴射弁が開固着状態となっている場合、ポンプの駆動を維持したままでは尿素水溶液が垂れ流し状態になるため、ポンプの駆動を停止させる必要がある。   Here, when sticking of the injection valve occurs, the action to be taken differs depending on whether the sticking is open sticking or closed sticking. For example, when the injection valve is closed and fixed, the urea aqueous solution does not leak into the exhaust pipe even if the pump is kept driven, but when the injection valve is open and fixed, If the drive is maintained, the urea aqueous solution will spill, and the drive of the pump needs to be stopped.

特許文献１には、噴射弁の弁体の動作不良が生じている場合に、噴射弁の開固着状態又は閉固着状態を精度よく判別することができる還元剤噴射弁の異常判定装置が提案されている。具体的には、噴射弁に対して尿素水溶液を供給する還元剤通路内を減圧したときの還元剤通路内の圧力変化に基づいて、弁体の動作不良が開固着によるものか又は閉固着によるものかを判別する異常判定装置が開示されている。   Patent Document 1 proposes an abnormality determination device for a reducing agent injection valve that can accurately determine whether the injection valve is stuck open or closed when a malfunction of the valve body of the injection valve occurs. ing. Specifically, based on the pressure change in the reducing agent passage when the inside of the reducing agent passage for supplying the urea aqueous solution to the injection valve is depressurized, the malfunction of the valve element is due to open sticking or due to closed sticking. An abnormality determination device for determining whether an object is present is disclosed.

特開２０１２−１０２６３７号公報JP 2012-102737 A

特許文献１に開示された異常判定装置は、内燃機関の停止時等、還元剤噴射装置による尿素水溶液の噴射制御を停止している間にのみ、開固着又は閉固着の判別を実行することができる。すなわち、特許文献１に開示された異常判定装置は、尿素水溶液の噴射制御中に開固着又は閉固着の判別を実行することができないため、尿素水溶液の噴射制御の開始後に噴射弁に何らかの異常が見られた場合には、噴射制御を禁止せざるを得ない。尿素水溶液の噴射制御中においても噴射弁の開固着状態又は閉固着状態を判別することができれば、噴射弁による尿素水溶液の噴射制御に支障がない場合には、噴射制御を継続させることが可能になると考えられる。   The abnormality determination device disclosed in Patent Document 1 can determine whether the sticking is open or closed only while the urea aqueous solution injection control by the reducing agent injection device is stopped, such as when the internal combustion engine is stopped. it can. That is, since the abnormality determination device disclosed in Patent Document 1 cannot perform the determination of open fixation or closed fixation during the injection control of the urea aqueous solution, there is some abnormality in the injection valve after the start of the injection control of the urea aqueous solution. If it is seen, injection control must be prohibited. If it is possible to determine whether the injection valve is open or closed, even during the urea aqueous solution injection control, the injection control can be continued if there is no problem with the urea aqueous solution injection control by the injection valve. It is considered to be.

また、尿素水溶液の噴射制御を停止している間、噴射弁の固着を生じていても、当該固着が尿素水溶液の結晶化によるものである場合、結晶化した尿素水溶液が液体の尿素水溶液に浸されることによって再び液化し、弁体の動作不良が改善される場合がある。すなわち、噴射制御開始前に噴射弁が固着している場合において、結晶化した尿素水溶液の融解を試みることができる場合がある。しかしながら、結晶化した尿素水溶液の融解を試みた場合であっても、融解が十分でない場合には、尿素水溶液の噴射制御の開始後に、噴射弁が異常と判別される場合がある。この場合、噴射弁が閉固着状態である場合には、ポンプの駆動を維持しても尿素水溶液が垂れ流し状態にならないため、噴射制御を禁止させる前に、結晶化した尿素水溶液の融解を再び試みることができる。したがって、結晶化した尿素水溶液の融解が不十分な状態を改善するためにも、尿素水溶液の噴射制御中において噴射弁の開固着状態又は閉固着状態を判別することができることが望ましい。   Even if the injection valve is stuck while the injection control of the urea aqueous solution is stopped, if the sticking is caused by crystallization of the urea aqueous solution, the crystallized urea aqueous solution is immersed in the liquid urea aqueous solution. By doing so, it may liquefy again, and the malfunction of the valve body may be improved. That is, when the injection valve is fixed before the start of injection control, it may be possible to try to melt the crystallized urea aqueous solution. However, even when attempting to melt the crystallized urea aqueous solution, if the melting is not sufficient, the injection valve may be determined to be abnormal after the start of the urea aqueous solution injection control. In this case, when the injection valve is closed and fixed, the urea aqueous solution does not spill even if the pump is driven. Therefore, before the injection control is prohibited, the crystallized urea aqueous solution is tried again. be able to. Therefore, in order to improve the state in which the crystallized urea aqueous solution is insufficiently melted, it is desirable to be able to determine whether the injection valve is in an open or closed state during injection control of the urea aqueous solution.

本発明は、上記問題に鑑みてなされたものであり、本発明の目的とするところは、還元剤の噴射制御中において、噴射弁に生じた異常が開固着であるか又は閉固着であるかを判別可能な、還元剤噴射装置の制御装置を提供することにある。   The present invention has been made in view of the above problems, and an object of the present invention is to determine whether an abnormality that has occurred in the injection valve during the injection control of the reducing agent is open fixation or closed fixation. It is an object of the present invention to provide a control device for a reducing agent injection device capable of discriminating the above.

上記課題を解決するために、本発明のある観点によれば、内燃機関の排気管に取り付けられた噴射弁により、排気通路に配設された還元触媒の上流側に、内燃機関の排気中のＮＯXを浄化するための還元剤を噴射する還元剤噴射装置を制御するための制御装置において、噴射弁に供給される還元剤の圧力が所定の目標値となるように還元剤を圧送するポンプの出力を制御しつつ、噴射弁の開弁動作を制御する噴射制御部と、還元剤の噴射制御の実行中における、噴射弁に通電される電流波形及びポンプの出力に基づいて、噴射弁の開固着又は閉固着を区別しつつ噴射弁の異常を判定する異常判定部と、を備える、還元剤噴射装置の制御装置が提供される。 In order to solve the above-described problem, according to an aspect of the present invention, an injection valve attached to an exhaust pipe of an internal combustion engine causes an upstream side of a reduction catalyst disposed in an exhaust passage to be in the exhaust of the internal combustion engine. In a control device for controlling a reducing agent injection device that injects a reducing agent for purifying NO x , a pump that pumps the reducing agent so that the pressure of the reducing agent supplied to the injection valve becomes a predetermined target value. The injection control unit that controls the valve opening operation of the injection valve while controlling the output of the injection valve, and the current of the current supplied to the injection valve and the output of the pump during execution of the injection control of the reducing agent, There is provided a control device for a reducing agent injection device, comprising: an abnormality determination unit that determines an abnormality of an injection valve while distinguishing between open fixation and closed fixation.

異常判定部は、電流波形に変化点が発現せず、かつ、ポンプの出力が第１の範囲内で維持されている場合、噴射弁が開固着状態にあると判定し、電流波形に変化点が発現せず、かつ、ポンプの出力が第１の範囲よりも小さい値の第２の範囲内で維持されている場合、噴射弁が閉固着状態にあると判定してもよい。   The abnormality determination unit determines that the injection valve is in the open fixed state when the change point does not appear in the current waveform and the output of the pump is maintained within the first range, and the change point in the current waveform May not be expressed and the output of the pump is maintained within the second range of a value smaller than the first range, it may be determined that the injection valve is in the closed stuck state.

異常判定部は、噴射弁が開固着状態にあると判定した場合に、還元剤の噴射制御を中止させてもよい。   The abnormality determination unit may stop the injection control of the reducing agent when it is determined that the injection valve is in the open fixed state.

異常判定部により噴射弁が閉固着状態にあると判定された場合に、噴射弁に供給される還元剤を一旦回収した後、噴射弁に再供給する復帰制御部を備えてもよい。   When the abnormality determination unit determines that the injection valve is in the closed and fixed state, a return control unit may be provided that once collects the reducing agent supplied to the injection valve and then re-supplyes the same to the injection valve.

異常判定部は、噴射弁が閉固着状態にあると判定した回数が所定の閾値以上になった場合に、噴射弁の噴射制御の実行を禁止してもよい。   The abnormality determination unit may prohibit the execution of the injection control of the injection valve when the number of times that the injection valve is determined to be in the closed and fixed state is equal to or greater than a predetermined threshold.

還元剤噴射装置の起動時及び復帰制御部による還元剤の再供給時に、噴射弁に供給される還元剤の圧力を高めた状態で還元剤を圧送するポンプの出力を一定にするとともに噴射弁を開弁状態で維持したときの還元剤の圧力に基づいて、噴射弁の詰まりの有無を判定する圧力判定部を備え、圧力判定部により異常なしと判定された場合に、噴射制御部が還元剤の噴射制御を開始し、異常判定部が噴射弁の異常を判定してもよい。   When the reducing agent injection device is started up and when the reducing agent is resupplied by the return control unit, the output of the pump that pumps the reducing agent is kept constant while the pressure of the reducing agent supplied to the injection valve is increased, and the injection valve is A pressure determination unit that determines whether or not the injection valve is clogged based on the pressure of the reducing agent when maintained in a valve-open state, and when the pressure determination unit determines that there is no abnormality, the injection control unit The injection control may be started, and the abnormality determination unit may determine the abnormality of the injection valve.

圧力判定部により異常ありと判定された場合に、噴射弁に供給される還元剤を一旦回収した後、噴射弁に再供給する復帰制御部を備えてもよい。   If the pressure determination unit determines that there is an abnormality, a return control unit may be provided that once collects the reducing agent supplied to the injection valve and then re-supply the injection valve.

圧力判定部は、異常ありと判定した回数が所定の閾値以上になった場合に、噴射弁の噴射制御の実行を禁止してもよい。   The pressure determination unit may prohibit the execution of the injection control of the injection valve when the number of times determined to be abnormal is equal to or greater than a predetermined threshold.

以上説明したように本発明によれば、還元剤の噴射制御中において、噴射弁に生じた異常が開固着であるか又は閉固着であるかを判別することができる。   As described above, according to the present invention, during the injection control of the reducing agent, it is possible to determine whether the abnormality that has occurred in the injection valve is open sticking or closed sticking.

本発明の実施の形態にかかる還元剤噴射装置を備えた尿素ＳＣＲシステムを示す概略図である。It is the schematic which shows the urea SCR system provided with the reducing agent injection apparatus concerning embodiment of this invention. 同実施形態にかかる還元剤噴射装置の制御装置の構成例を示すブロック図である。It is a block diagram which shows the structural example of the control apparatus of the reducing agent injection apparatus concerning the embodiment. 同実施形態にかかる還元剤噴射装置の各制御モードでの状態を示す説明図である。It is explanatory drawing which shows the state in each control mode of the reducing agent injection apparatus concerning the embodiment. 圧力に基づく噴射弁の詰まり判定を説明するための図である。It is a figure for demonstrating the clogging determination of the injection valve based on a pressure. 電流波形に基づく噴射弁の異常判定を説明するための図である。It is a figure for demonstrating the abnormality determination of the injection valve based on an electric current waveform. ポンプ出力に基づく噴射弁の異常判定を説明するための図である。It is a figure for demonstrating abnormality determination of the injection valve based on a pump output. 同実施形態にかかる還元剤噴射装置の制御装置による処理を示すフローチャートである。It is a flowchart which shows the process by the control apparatus of the reducing agent injection apparatus concerning the embodiment.

以下に添付図面を参照しながら、本発明の好適な実施の形態について詳細に説明する。なお、本明細書及び図面において、実質的に同一の機能構成を有する構成要素については、同一の符号を付することにより重複説明を省略する。   Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

＜１．尿素ＳＣＲシステムの全体構成＞
まず、還元剤噴射装置２０を備えた尿素ＳＣＲシステム１０の全体構成の一例について説明する。図１は、尿素ＳＣＲシステム１０の概略構成を示す説明図である。尿素ＳＣＲシステム１０は、ディーゼルエンジン等に代表される内燃機関５の排気系に接続された排気管１１の途中に配設された還元触媒１３と、還元触媒１３よりも上流側で排気通路内に還元剤を噴射する還元剤噴射装置２０とを備える。尿素ＳＣＲシステム１０は、車両や建設機械、農機等に搭載され、還元剤として尿素水溶液を用いて、内燃機関５から排出される排気中のＮＯXを還元して分解することで、排気を浄化するシステムである。 <1. Overall Configuration of Urea SCR System>
First, an example of the entire configuration of the urea SCR system 10 including the reducing agent injection device 20 will be described. FIG. 1 is an explanatory diagram showing a schematic configuration of the urea SCR system 10. A urea SCR system 10 includes a reduction catalyst 13 disposed in the middle of an exhaust pipe 11 connected to an exhaust system of an internal combustion engine 5 typified by a diesel engine and the like, and an upstream side of the reduction catalyst 13 in an exhaust passage. And a reducing agent injection device 20 for injecting the reducing agent. The urea SCR system 10 is mounted on vehicles, construction machines, agricultural machines, etc., and purifies exhaust gas by reducing and decomposing NO x in exhaust gas discharged from the internal combustion engine 5 using urea aqueous solution as a reducing agent. System.

尿素水溶液は、例えば凍結温度が最も低い、約３２．５％濃度の尿素水溶液とすることができる。この場合の凍結温度は、約−１１℃である。かかる尿素水溶液は、濃度が上昇するにつれて凍結温度が上昇する特性を有しており、溶媒としての水分が蒸発することによって、結晶化しやすくなる。   The urea aqueous solution can be, for example, an aqueous urea solution having a lowest freezing temperature and a concentration of about 32.5%. In this case, the freezing temperature is about -11 ° C. Such an aqueous urea solution has a characteristic that the freezing temperature increases as the concentration increases, and is easily crystallized by evaporating water as a solvent.

還元触媒１３は、内燃機関５の排気中に含まれるＮＯXを、尿素水溶液を用いて選択的に還元する。本実施形態では、還元剤噴射装置２０により噴射される尿素水溶液が分解して生成されるアンモニアが還元触媒１３に吸着され、還元触媒１３に流入する排気中のＮＯXがアンモニアと反応することにより還元される。かかる還元触媒１３は、触媒温度が高いほどアンモニアの吸着可能量が減少する特性を有する。また、還元触媒１３は、吸着可能量に対する実際のアンモニアの吸着率が高いほど、ＮＯXの還元効率が高くなる特性を有する。 The reduction catalyst 13 selectively reduces NO x contained in the exhaust gas of the internal combustion engine 5 using an aqueous urea solution. In the present embodiment, ammonia generated by decomposition of the urea aqueous solution injected by the reducing agent injection device 20 is adsorbed by the reduction catalyst 13, and NO x in the exhaust gas flowing into the reduction catalyst 13 reacts with ammonia. Reduced. The reduction catalyst 13 has a characteristic that the amount of ammonia that can be adsorbed decreases as the catalyst temperature increases. Further, the reduction catalyst 13 has a characteristic that the reduction efficiency of NO x increases as the actual ammonia adsorption rate with respect to the adsorbable amount increases.

還元剤噴射装置２０は、還元触媒１３よりも上流側の排気通路内に、還元剤としての尿素水溶液を噴射する。尿素水溶液の噴射量は、排気中に含まれるＮＯXの濃度や、還元触媒１３におけるアンモニアの吸着可能量、還元触媒１３の温度等に基づいて、還元触媒１３の下流側にＮＯXあるいはアンモニアが流出しないように制御される。 The reducing agent injection device 20 injects a urea aqueous solution as a reducing agent into the exhaust passage upstream of the reduction catalyst 13. Injection amount of the urea aqueous solution, and the concentration of NO X contained in the exhaust, the ammonia adsorption capacity of the reduction catalyst 13, based on the temperature of the reduction catalyst 13, is NO X or ammonia to the downstream side of the reduction catalyst 13 It is controlled so that it does not flow out.

還元触媒１３よりも上流側の排気管１１には、排気温度Ｔｇａｓを検出するための温度センサ１５が取り付けられている。温度センサ１５によって検出される排気温度Ｔｇａｓは、還元触媒１３の温度推定にも用いられる。これ以外に、排気管１１には、図示しないＮＯX濃度センサやアンモニアセンサ等が設けられていてもよい。 A temperature sensor 15 for detecting the exhaust temperature Tgas is attached to the exhaust pipe 11 upstream of the reduction catalyst 13. The exhaust gas temperature Tgas detected by the temperature sensor 15 is also used for estimating the temperature of the reduction catalyst 13. In addition to this, the exhaust pipe 11 may be provided with a NO x concentration sensor, an ammonia sensor, or the like (not shown).

＜２．還元剤噴射装置＞
次に、還元剤噴射装置２０の構成の一例について詳細に説明する。図１に示すように、還元剤噴射装置２０は、還元触媒１３よりも上流側の排気管１１に固定された噴射弁３１と、尿素水溶液を圧送するポンプ４１を有するポンプユニット４０とを備える。ポンプ４１及び噴射弁３１は、制御装置１００によって駆動制御される。制御装置１００は、内燃機関５の制御装置７０から、内燃機関５の燃料噴射量や噴射タイミング、エンジン回転数等の運転状態に関する情報を取得可能になっている。 <2. Reducing agent injection device>
Next, an example of the configuration of the reducing agent injection device 20 will be described in detail. As shown in FIG. 1, the reducing agent injection device 20 includes an injection valve 31 fixed to the exhaust pipe 11 upstream of the reduction catalyst 13 and a pump unit 40 having a pump 41 that pumps an aqueous urea solution. The pump 41 and the injection valve 31 are driven and controlled by the control device 100. The control device 100 can acquire information on the operating state such as the fuel injection amount, injection timing, and engine speed of the internal combustion engine 5 from the control device 70 of the internal combustion engine 5.

貯蔵タンク５０とポンプ４１とは第１の還元剤通路５８で接続され、ポンプ４１と噴射弁３１とは第２の還元剤通路５７で接続されている。第２の還元剤通路５７には、他端が貯蔵タンク５０に接続されたリターン通路５９が接続されており、リターン通路５９にはオリフィス４５が備えられている。オリフィス４５は、第２の還元剤通路５７内の圧力が保持されやすくなるように設けられている。また、第２の還元剤通路５７には、噴射弁３１に供給される尿素水溶液の圧力Ｐｕを示す、第２の還元剤通路５７内の圧力を検出するための圧力センサ４３が備えられている。   The storage tank 50 and the pump 41 are connected by a first reducing agent passage 58, and the pump 41 and the injection valve 31 are connected by a second reducing agent passage 57. A return passage 59 having the other end connected to the storage tank 50 is connected to the second reducing agent passage 57, and the return passage 59 is provided with an orifice 45. The orifice 45 is provided so that the pressure in the second reducing agent passage 57 can be easily maintained. Further, the second reducing agent passage 57 is provided with a pressure sensor 43 for detecting the pressure in the second reducing agent passage 57 that indicates the pressure Pu of the urea aqueous solution supplied to the injection valve 31. .

噴射弁３１は、例えば、通電制御により開弁及び閉弁が切り替えられる電磁式噴射弁が用いられる。かかる噴射弁３１はコイルを備え、当該コイルへの通電により発生する磁力によって弁体が移動して開弁する構造を有している。本実施形態では、噴射弁３１に供給される尿素水溶液の圧力Ｐｕが所定の目標値Ｐｔｇｔとなるように制御されるため、制御装置１００は、尿素水溶液の目標噴射量に応じて開弁時間を調節する。この噴射弁３１は、排気管１１内に直接的に尿素水溶液を噴射するものであり、噴孔が排気管１１内に臨むようにして排気管１１に取り付けられている。   As the injection valve 31, for example, an electromagnetic injection valve that can be switched between opening and closing by energization control is used. The injection valve 31 includes a coil, and has a structure in which the valve body is moved and opened by a magnetic force generated by energizing the coil. In the present embodiment, since the pressure Pu of the urea aqueous solution supplied to the injection valve 31 is controlled to be a predetermined target value Ptgt, the control device 100 sets the valve opening time according to the target injection amount of the urea aqueous solution. Adjust. The injection valve 31 directly injects the urea aqueous solution into the exhaust pipe 11, and is attached to the exhaust pipe 11 so that the injection hole faces the exhaust pipe 11.

噴射弁３１は、冷却カバー内に保持され、当該冷却カバーには、内燃機関５の冷却水が流通可能になっている。冷却カバー内の冷却水の通路は、冷却水循環通路８７の一部を構成する。冷却水循環通路８７は、内燃機関５に設けられた冷却装置６０の冷却通路８６から分岐し、噴射弁３１の冷却カバーを経由して、再び内燃機関５の冷却通路８６に合流する。内燃機関５の始動後、冷却水循環通路８７には、常時冷却水が流れる。したがって、内燃機関５の運転中、高温の排気熱等により噴射弁３１が加熱され得る状況において、冷却水循環通路８７に冷却水が流れ、噴射弁３１の過熱が抑制される。   The injection valve 31 is held in a cooling cover, and the cooling water of the internal combustion engine 5 can flow through the cooling cover. The cooling water passage in the cooling cover constitutes a part of the cooling water circulation passage 87. The cooling water circulation passage 87 branches from the cooling passage 86 of the cooling device 60 provided in the internal combustion engine 5, and joins the cooling passage 86 of the internal combustion engine 5 again via the cooling cover of the injection valve 31. After the internal combustion engine 5 is started, cooling water always flows through the cooling water circulation passage 87. Therefore, during the operation of the internal combustion engine 5, in a situation where the injection valve 31 can be heated by high-temperature exhaust heat or the like, the cooling water flows through the cooling water circulation passage 87, and overheating of the injection valve 31 is suppressed.

ポンプ４１は、例えば電動式のダイヤフラムポンプやモータポンプからなる。ポンプ４１の出力は、制御装置１００から出力される制御信号に基づいて制御される。本実施形態では、制御装置１００は、噴射弁３１に供給される圧力Ｐｕが所定の目標値Ｐｔｇｔに維持されるように、圧力センサ４３により検出される圧力Ｐｕと目標値Ｐｔｇｔとの偏差ΔＰに基づいて、ポンプ４１の出力をフィードバック制御する。   The pump 41 is composed of, for example, an electric diaphragm pump or a motor pump. The output of the pump 41 is controlled based on a control signal output from the control device 100. In the present embodiment, the control device 100 sets the deviation ΔP between the pressure Pu detected by the pressure sensor 43 and the target value Ptgt so that the pressure Pu supplied to the injection valve 31 is maintained at the predetermined target value Ptgt. Based on this, the output of the pump 41 is feedback controlled.

ポンプユニット４０には、ポンプ４１によって圧送される尿素水溶液の流れる方向を切り替えるための流路切替弁７１が備えられている。流路切替弁７１は、例えば電磁切替弁により構成され、制御装置１００によって駆動される。本実施形態では、流路切替弁７１は、ポンプ４１の吸入側と第１の還元剤通路５８、及び、ポンプ４１の吐出側と第２の還元剤通路５７をそれぞれ接続する第１の状態と、ポンプ４１の吐出側と第１の還元剤通路５８、及び、ポンプ４１の吸入側と第２の還元剤通路５７をそれぞれ接続する第２の状態とを切り替える。   The pump unit 40 is provided with a flow path switching valve 71 for switching the flow direction of the urea aqueous solution pumped by the pump 41. The flow path switching valve 71 is configured by, for example, an electromagnetic switching valve and is driven by the control device 100. In the present embodiment, the flow path switching valve 71 has a first state in which the suction side of the pump 41 and the first reducing agent passage 58 and the discharge side of the pump 41 and the second reducing agent passage 57 are respectively connected. The discharge side of the pump 41 and the first reducing agent passage 58 and the second state in which the suction side of the pump 41 and the second reducing agent passage 57 are connected are switched.

排気管１１内への尿素水溶液の噴射制御を行う場合には、尿素水溶液が貯蔵タンク５０側から噴射弁３１側へ流れるように、流路切替弁７１が作動される。また、還元剤噴射装置２０内の尿素水溶液を貯蔵タンク５０に回収する場合には、尿素水溶液が噴射弁３１側から貯蔵タンク５０側へ流れるように、流路切替弁７１が作動される。なお、流路切替弁７１を用いる代わりに、逆回転可能なポンプを用いることによって、尿素水溶液が回収可能になっていてもよい。   When controlling the injection of the aqueous urea solution into the exhaust pipe 11, the flow path switching valve 71 is operated so that the aqueous urea solution flows from the storage tank 50 side to the injection valve 31 side. Further, when the urea aqueous solution in the reducing agent injection device 20 is collected in the storage tank 50, the flow path switching valve 71 is operated so that the urea aqueous solution flows from the injection valve 31 side to the storage tank 50 side. Instead of using the flow path switching valve 71, the urea aqueous solution may be recovered by using a reverse-rotatable pump.

還元剤噴射装置２０には内燃機関５の冷却水が循環する。内燃機関５の冷却装置６０から分岐した冷却水循環通路８５は、途中で、噴射弁３１の冷却カバーを通過する冷却水循環通路８７と、貯蔵タンク５０やポンプユニット４０を通過する冷却水循環通路８９とに分岐する。このうち、冷却水循環通路８９には制御装置１００によって駆動される開閉弁８１が設けられ、冷却水の流通及び遮断が切り替え可能になっている。内燃機関５の運転中、冷却水循環通路８７には常時冷却水が流れ、噴射弁３１を冷却する。一方、冷却水循環通路８９を流れる冷却水は、昇温媒体として用いられ、貯蔵タンク５０やポンプユニット４０の加熱が必要なときに開閉弁８１が開かれ、冷却水が流される。   Coolant for the internal combustion engine 5 circulates in the reducing agent injection device 20. The cooling water circulation passage 85 branched from the cooling device 60 of the internal combustion engine 5 includes a cooling water circulation passage 87 that passes through the cooling cover of the injection valve 31 and a cooling water circulation passage 89 that passes through the storage tank 50 and the pump unit 40 on the way. Branch. Among these, the cooling water circulation passage 89 is provided with an on-off valve 81 driven by the control device 100 so that the circulation and blocking of the cooling water can be switched. During operation of the internal combustion engine 5, cooling water always flows through the cooling water circulation passage 87 to cool the injection valve 31. On the other hand, the cooling water flowing through the cooling water circulation passage 89 is used as a temperature raising medium, and when the storage tank 50 and the pump unit 40 need to be heated, the on-off valve 81 is opened and the cooling water is allowed to flow.

＜３．制御装置＞
次に、本実施形態にかかる還元剤噴射装置２０の制御に用いられる制御装置１００の構成例について説明する。制御装置１００は、公知のマイクロコンピュータやポンプ４１及び噴射弁３１、流路切替弁７１の駆動回路等を備えて構成される。図２は、制御装置１００の構成を機能的に示すブロック図である。また、図３は、圧力判定部１０５による詰まり判定実行時、噴射制御部１０１による尿素水溶液の噴射制御実行時、及び復帰制御部１０７による復帰制御実行時のそれぞれにおける、ポンプ４１、尿素水溶液の流れ、及び噴射弁３１の制御状態を示す。 <3. Control device>
Next, the structural example of the control apparatus 100 used for control of the reducing agent injection apparatus 20 concerning this embodiment is demonstrated. The control device 100 includes a known microcomputer, a pump 41, an injection valve 31, a drive circuit for the flow path switching valve 71, and the like. FIG. 2 is a block diagram functionally showing the configuration of the control device 100. 3 shows the flow of the pump 41 and the urea aqueous solution at the time of executing the clogging determination by the pressure determination unit 105, at the time of executing the injection control of the urea aqueous solution by the injection control unit 101, and at the time of executing the return control by the return control unit 107, respectively. And the control state of the injection valve 31 is shown.

制御装置１００は、噴射制御部１０１と、異常判定部１０３と、圧力判定部１０５と、復帰制御部１０７とを備える。これらの各部は、具体的には、マイクロコンピュータによるプログラムの実行により実現されるものであってよい。制御装置１００には、直接、あるいは、ＣＡＮ等のバス配線を介して、圧力センサ４３や温度センサ１５の検出信号、及び、内燃機関５の運転状態に関連する情報等が入力される。また、制御装置１００は、ＲＡＭ（Ｒａｎｄｏｍ Ａｃｃｅｓｓ Ｍｅｍｏｒｙ）やＲＯＭ（Ｒｅａｄ Ｏｎｌｙ Ｍｅｍｏｒｙ）等の図示しない記憶素子を備える。これらの記憶素子は、マイクロコンピュータにより実行されるプログラムや、演算処理に用いられる各種パラメータ、演算結果、検出結果等を記憶する。   The control device 100 includes an injection control unit 101, an abnormality determination unit 103, a pressure determination unit 105, and a return control unit 107. Specifically, each of these units may be realized by executing a program by a microcomputer. The control device 100 receives detection signals from the pressure sensor 43 and the temperature sensor 15 and information related to the operating state of the internal combustion engine 5 directly or via a bus wiring such as CAN. The control device 100 includes a storage element (not shown) such as a RAM (Random Access Memory) and a ROM (Read Only Memory). These storage elements store programs executed by the microcomputer, various parameters used for arithmetic processing, calculation results, detection results, and the like.

（３−１．噴射制御部）
噴射制御部１０１は、内燃機関５の排気中に含まれるＮＯXを浄化するために、尿素水溶液を排気管１１内に噴射する噴射制御を実行する。本実施形態では、噴射制御部１０１は、後述する圧力判定部１０５により噴射弁３１に異常がないと判定された場合に、尿素水溶液の噴射制御を開始する。噴射制御部１０１は、ポンプ４１の出力制御、及び、噴射弁３１の通電制御を実行する。噴射制御部１０１は、圧力センサ４３の検出信号を読み込み、噴射弁３１に供給される尿素水溶液の圧力Ｐｕが、所定の目標値Ｐｔｇｔとなるように、ポンプ４１の出力をフィードバック制御する。また、噴射制御部１０１は、尿素水溶液の目標噴射量を算出するとともに、算出された目標噴射量に基づいて噴射弁３１の開弁時間を制御する。 (3-1. Injection control unit)
The injection control unit 101 executes injection control for injecting an aqueous urea solution into the exhaust pipe 11 in order to purify NO X contained in the exhaust gas of the internal combustion engine 5. In the present embodiment, the injection control unit 101 starts the urea aqueous solution injection control when it is determined by the pressure determination unit 105 described later that the injection valve 31 is normal. The injection control unit 101 executes output control of the pump 41 and energization control of the injection valve 31. The injection control unit 101 reads the detection signal of the pressure sensor 43, and feedback-controls the output of the pump 41 so that the pressure Pu of the urea aqueous solution supplied to the injection valve 31 becomes a predetermined target value Ptgt. The injection control unit 101 calculates the target injection amount of the urea aqueous solution and controls the valve opening time of the injection valve 31 based on the calculated target injection amount.

図３に示したように、噴射制御実行時には、ポンプ４１の出力は、尿素水溶液の圧力Ｐｕに基づいてフィードバック制御される。また、尿素水溶液が貯蔵タンク５０側から噴射弁３１側に向かって（順方向）に流れるように流路切替弁７１が保持される。また、噴射弁３１は、目標噴射量に基づいて開弁時間が調節されるように、噴射弁３１への通電時間が制御される。本実施形態では、噴射制御部１０１は、目標噴射量に基づいて、所定の噴射サイクル中の開弁時間の比であるデューティ比を制御する。   As shown in FIG. 3, when the injection control is executed, the output of the pump 41 is feedback-controlled based on the pressure Pu of the aqueous urea solution. Further, the flow path switching valve 71 is held so that the urea aqueous solution flows from the storage tank 50 side toward the injection valve 31 side (forward direction). In addition, the energization time of the injection valve 31 is controlled so that the valve opening time of the injection valve 31 is adjusted based on the target injection amount. In the present embodiment, the injection control unit 101 controls a duty ratio that is a ratio of the valve opening time during a predetermined injection cycle based on the target injection amount.

例えば、噴射制御部１０１は、内燃機関５の排気中のＮＯX量に基づき、当該ＮＯXを還元するために必要なアンモニア量を求めるとともに、還元触媒１３におけるアンモニアの目標吸着量に対して過不足のアンモニア量を求め、これらの総和に対応する尿素水溶液の量を目標噴射量とし得る。排気中のＮＯX量としては、内燃機関５の運転状態に基づき推定されるＮＯX濃度、あるいは、ＮＯXセンサにより検出されるＮＯX濃度に、排気流量を乗じて求められるＮＯX量を用いることができる。そして、噴射制御部１０１は、算出されたＮＯX量に対応するアンモニア量を求める。 For example, the injection control unit 101 obtains the ammonia amount necessary for reducing the NO x based on the NO x amount in the exhaust gas of the internal combustion engine 5 and exceeds the target adsorption amount of ammonia in the reduction catalyst 13. An insufficient ammonia amount is obtained, and the amount of urea aqueous solution corresponding to the sum of these amounts can be set as the target injection amount. The amount of NO X in the exhaust gas, NO X concentrations are estimated based on the operating state of the internal combustion engine 5 or, the NO X concentration detected by the NO X sensor, using the amount of NO X obtained by multiplying the exhaust gas flow rate be able to. The injection control unit 101 obtains an ammonia amount corresponding to the calculated NO x amount.

また、還元触媒１３におけるアンモニアの目標吸着量としては、排気温度Ｔｇａｓに基づき推定される触媒温度に応じた吸着可能量に対して目標吸着率を乗じた値を用いることができる。目標吸着率は、例えば、７０〜８０％とし得る。目標吸着率を７０〜８０％とすることにより、吸着率が比較的高く維持されて、ＮＯXの還元効率が高くなる一方、触媒温度が急激に上昇した場合であっても、アンモニアの吸着可能量が、現在のアンモニアの吸着量を下回らないようにすることができる。そして、噴射制御部１０１は、積算により求められる現在のアンモニア吸着量と、目標吸着量との差分から、過不足のアンモニア量を求める。 Further, as the target adsorption amount of ammonia in the reduction catalyst 13, a value obtained by multiplying the adsorbable amount according to the catalyst temperature estimated based on the exhaust gas temperature Tgas by the target adsorption rate can be used. The target adsorption rate can be, for example, 70 to 80%. By setting the target adsorption rate to 70 to 80%, the adsorption rate is maintained relatively high, and the NO x reduction efficiency is increased, while ammonia can be adsorbed even when the catalyst temperature rises rapidly. The amount can be kept below the current ammonia adsorption. And the injection control part 101 calculates | requires the ammonia amount of excess and deficiency from the difference of the present ammonia adsorption amount calculated | required by integration, and a target adsorption amount.

そして、噴射制御部１０１は、還元触媒１３の目標吸着量に対する過不足のアンモニア量と、先に求めたアンモニア量とを加算し、算出されたアンモニア量に対応する尿素水溶液の量を目標噴射量として、噴射弁３１を駆動制御する。上述のとおり、噴射弁３１に供給される尿素水溶液の圧力は一定に保たれるように制御されるため、噴射制御部１０１は、目標噴射量に応じて、噴射時間を調節する。このように尿素水溶液の噴射制御を実行することにより、還元触媒１３の下流側へのアンモニアの流出が抑制されつつ、還元触媒１３におけるアンモニアの吸着率が高く維持され、ＮＯXの還元効率を向上させることができる。 Then, the injection control unit 101 adds the excess / deficient ammonia amount with respect to the target adsorption amount of the reduction catalyst 13 and the previously obtained ammonia amount, and calculates the amount of urea aqueous solution corresponding to the calculated ammonia amount as the target injection amount. Then, the injection valve 31 is driven and controlled. As described above, since the pressure of the urea aqueous solution supplied to the injection valve 31 is controlled to be kept constant, the injection control unit 101 adjusts the injection time according to the target injection amount. By executing the injection control of the urea aqueous solution in this way, the ammonia outflow rate to the downstream side of the reduction catalyst 13 is suppressed, while the ammonia adsorption rate at the reduction catalyst 13 is maintained high, and the NO x reduction efficiency is improved. Can be made.

（３−２．復帰制御部）
復帰制御部１０７は、噴射弁３１に供給される尿素水溶液を一旦貯蔵タンク５０に回収した後、再び噴射弁３１側に尿素水溶液を供給する制御（以下、かかる制御を「復帰制御」ともいう。）を行う。本実施形態では、後述する異常判定部１０３によって噴射弁３１が閉固着状態にあると判定された場合、及び、後述する圧力判定部１０５によって噴射弁３１に異常ありと判定された場合に、復帰制御を実行する。 (3-2. Return control unit)
The return control unit 107 once collects the urea aqueous solution supplied to the injection valve 31 in the storage tank 50 and then supplies the urea aqueous solution to the injection valve 31 again (hereinafter, such control is also referred to as “return control”). )I do. In the present embodiment, when the abnormality determination unit 103 described later determines that the injection valve 31 is in the closed fixed state and when the pressure determination unit 105 described later determines that the injection valve 31 is abnormal, the return is performed. Execute control.

具体的に、復帰制御部１０７は、流路切替弁７１に通電することによって、尿素水溶液が噴射弁３１側から貯蔵タンク５０側に流れるように流路を切り替え、あらかじめ設定された所定時間、ポンプ４１を駆動させる。このとき、復帰制御部１０７は、噴射弁３１に通電し、噴射弁３１に開弁指示を出力してもよい。これにより、還元剤噴射装置２０内の尿素水溶液がポンプ４１によって吸い戻され、貯蔵タンク５０内に回収される。その後、復帰制御部１０７は、流路切替弁７１への通電を停止して、尿素水溶液が貯蔵タンク５０側から噴射弁３１側に流れるように流路を切り替え、ポンプ４１を駆動させる。これにより、還元剤噴射装置２０内に尿素水溶液が再充填される。   Specifically, the return control unit 107 switches the flow path so that the urea aqueous solution flows from the injection valve 31 side to the storage tank 50 side by energizing the flow path switching valve 71, and the pump is operated for a predetermined time. 41 is driven. At this time, the return control unit 107 may energize the injection valve 31 and output a valve opening instruction to the injection valve 31. Accordingly, the urea aqueous solution in the reducing agent injection device 20 is sucked back by the pump 41 and collected in the storage tank 50. Thereafter, the return control unit 107 stops energization of the flow path switching valve 71, switches the flow path so that the urea aqueous solution flows from the storage tank 50 side to the injection valve 31 side, and drives the pump 41. Thereby, the reducing agent injection device 20 is refilled with the urea aqueous solution.

図３に示したように、復帰制御実行時には、ポンプ４１の出力は一定にされる。また、尿素水溶液を回収する際には、尿素水溶液が噴射弁３１側から貯蔵タンク５０側に向かって（逆方向）に流れるように流路切替弁７１が切り替えられる。その後、尿素水溶液を再充填する際には、尿素水溶液が貯蔵タンク５０側から噴射弁３１側に向かって（順方向）に流れるように流路切替弁７１が切り替えられる。また、尿素水溶液を回収する際には、噴射弁３１には開弁指示が出力され、尿素水溶液を再充填する際には、噴射弁３１は閉弁状態で保持される。   As shown in FIG. 3, when the return control is executed, the output of the pump 41 is kept constant. Further, when recovering the urea aqueous solution, the flow path switching valve 71 is switched so that the urea aqueous solution flows from the injection valve 31 side toward the storage tank 50 side (reverse direction). Thereafter, when the urea aqueous solution is refilled, the flow path switching valve 71 is switched so that the urea aqueous solution flows from the storage tank 50 side toward the injection valve 31 side (forward direction). Further, when recovering the urea aqueous solution, a valve opening instruction is output to the injection valve 31, and when refilling the urea aqueous solution, the injection valve 31 is held in a closed state.

復帰制御部１０７により、尿素水溶液の回収及び再充填が行われることで、例えば、噴射弁３１内で尿素水溶液が結晶化している場合に、液体の尿素水溶液が噴射弁３１に到達して、結晶化している尿素水溶液が融解する可能性が生じる。例えば、尿素水溶液を回収した際に第２の還元剤通路５７のうちの噴射弁３１に近い領域に付着して尿素水溶液を残留させることができる場合がある。かかる場合には、次に尿素水溶液が再充填される際に、残留した尿素水溶液が噴射弁３１側に押し込まれて、噴射弁３１内で結晶化した尿素水溶液に到達し得る。これにより、結晶化した尿素水溶液が融解し、尿素水溶液の噴射制御を禁止せずに、尿素水溶液の噴射制御を実行可能な状態に復帰させることができる。   By the recovery and refilling of the urea aqueous solution by the return control unit 107, for example, when the urea aqueous solution is crystallized in the injection valve 31, the liquid urea aqueous solution reaches the injection valve 31 and is crystallized. There is a possibility that the urea aqueous solution is melted. For example, when the urea aqueous solution is recovered, the urea aqueous solution may be allowed to remain on the region near the injection valve 31 in the second reducing agent passage 57. In such a case, when the urea aqueous solution is refilled next time, the remaining urea aqueous solution is pushed into the injection valve 31 side and can reach the urea aqueous solution crystallized in the injection valve 31. Thereby, the crystallized urea aqueous solution is melted, and the injection control of the urea aqueous solution can be returned to a state where the injection control of the urea aqueous solution can be performed without prohibiting the injection control of the urea aqueous solution.

（３−３．圧力判定部）
圧力判定部１０５は、還元剤噴射装置２０の起動時、及び、復帰制御部１０７による尿素水溶液の再充填時に、圧力センサ４３により検出される尿素水溶液の圧力に基づいて、噴射弁３１の詰まりの有無を判定する。具体的に、圧力判定部１０５は、噴射弁３１に供給される尿素水溶液の圧力Ｐｕが所定値以上に高められた状態で、ポンプ４１の出力を一定とし、噴射弁３１を開弁状態で維持する。図３に示したように、詰まり判定実行時には、ポンプ４１の出力は一定にされる。また、尿素水溶液が貯蔵タンク５０側から噴射弁３１側に向かって（順方向）に流れるように流路切替弁７１が保持される。また、噴射弁３１には、全開指示が出力される。 (3-3. Pressure determination unit)
The pressure determination unit 105 detects the clogging of the injection valve 31 based on the pressure of the urea aqueous solution detected by the pressure sensor 43 when the reducing agent injection device 20 is started up and when the urea solution is refilled by the return control unit 107. Determine presence or absence. Specifically, the pressure determination unit 105 maintains the injection valve 31 in an open state while keeping the output of the pump 41 constant while the pressure Pu of the urea aqueous solution supplied to the injection valve 31 is increased to a predetermined value or more. To do. As shown in FIG. 3, the output of the pump 41 is kept constant when the clogging determination is executed. Further, the flow path switching valve 71 is held so that the urea aqueous solution flows from the storage tank 50 side toward the injection valve 31 side (forward direction). Further, a full open instruction is output to the injection valve 31.

このとき、噴射弁３１が正常に開弁している場合と、噴射弁３１に詰まりが生じている場合とでは、尿素水溶液の圧力変化に差が生じ得る。図４は、ポンプ４１の出力を一定にした状態で噴射弁３１を開弁状態で維持した場合の尿素水溶液の圧力変化を示す説明図である。図４は、３つの噴孔を有する噴射弁３１を用いた場合の例を示している。噴射弁３１が正常に開弁している場合、すなわち、３つの噴孔すべてから尿素水溶液が噴出している場合には、尿素水溶液の圧力Ｐｕは所定の速度で低下する（線Ａ）。一方、噴射弁３１が開弁しない場合、すなわち、３つの噴孔すべてから尿素水溶液が噴出しない場合には、尿素水溶液の圧力Ｐｕは変化しない（線Ｄ）。噴孔が詰まっているのではなく、噴射弁３１が閉固着状態になっている場合においても、尿素水溶液の圧力Ｐｕは変化しない（線Ｄ）。   At this time, there may be a difference in the pressure change of the urea aqueous solution between the case where the injection valve 31 is normally opened and the case where the injection valve 31 is clogged. FIG. 4 is an explanatory diagram showing the pressure change of the urea aqueous solution when the injection valve 31 is maintained in the open state with the output of the pump 41 being constant. FIG. 4 shows an example in which an injection valve 31 having three injection holes is used. When the injection valve 31 is normally opened, that is, when the urea aqueous solution is ejected from all three nozzle holes, the pressure Pu of the urea aqueous solution decreases at a predetermined speed (line A). On the other hand, when the injection valve 31 is not opened, that is, when the urea aqueous solution is not ejected from all three nozzle holes, the pressure Pu of the urea aqueous solution does not change (line D). Even when the injection hole is not clogged and the injection valve 31 is in the closed and fixed state, the pressure Pu of the urea aqueous solution does not change (line D).

また、噴射弁３１が開弁する場合であっても、噴孔の一部が詰まっている場合には、尿素水溶液の圧力Ｐｕの低下速度は正常な状態に比べて小さくなる。例えば、１つの噴孔が詰まっており、２つの噴孔から尿素水溶液が噴出している場合には、尿素水溶液の圧力Ｐｕの低下速度は、正常な場合に比べてやや小さくなり（線Ｂ）、２つの噴孔が詰まっており、１つの噴孔から尿素水溶液が噴出している場合には、尿素水溶液の圧力Ｐｕの低下速度は、さらに小さくなる（線Ｃ）。   Even when the injection valve 31 is opened, if the injection hole is partially clogged, the rate of decrease in the pressure Pu of the urea aqueous solution is smaller than in a normal state. For example, when one nozzle hole is clogged and urea aqueous solution is ejected from the two nozzle holes, the rate of decrease in the pressure Pu of the urea aqueous solution is slightly smaller than that in a normal case (line B). When two nozzle holes are clogged and the urea aqueous solution is ejected from one nozzle hole, the rate of decrease in the pressure Pu of the urea aqueous solution is further reduced (line C).

したがって、例えば、噴射弁３１を開弁状態にしてから所定時間経過後の圧力の閾値として、各圧力変化の態様を区別し得る複数の閾値を、固定するポンプ４１の出力に応じて設定しておくことにより、噴射弁３１の詰まりの有無を判定することができる。このとき、閾値を複数設定して、噴孔の詰まり度合いまで区別できるようにしてもよいし、１つの閾値を設定して、噴孔の詰まりの有無のみを区別できるようにしてもよい。   Therefore, for example, as a pressure threshold value after a predetermined time has elapsed since the injection valve 31 is opened, a plurality of threshold values that can distinguish the mode of each pressure change are set according to the output of the pump 41 to be fixed. Thus, it is possible to determine whether or not the injection valve 31 is clogged. At this time, a plurality of threshold values may be set so that the degree of clogging of the nozzle holes can be distinguished, or one threshold value can be set so that only the presence or absence of clogging of the nozzle holes can be distinguished.

本実施形態では、圧力判定部１０５は、噴射弁３１に異常ありと判定された場合に、復帰制御部１０７に復帰制御を実行させる。このとき、圧力判定部１０５は、第１カウンタ値をカウントアップし、第１カウンタ値が所定の閾値Ｔｈ１に到達した場合に、噴射弁３１の異常が解消されないものとみなして、尿素水溶液の噴射制御を禁止する。   In the present embodiment, the pressure determination unit 105 causes the return control unit 107 to perform return control when it is determined that there is an abnormality in the injection valve 31. At this time, the pressure determination unit 105 counts up the first counter value, and when the first counter value reaches a predetermined threshold value Th1, it is considered that the abnormality of the injection valve 31 is not eliminated, and the injection of the urea aqueous solution Prohibit control.

かかる圧力判定部１０５による詰まり判定は、後述する異常判定部１０３による異常判定に比べて、比較的簡易に実施することができる。したがって、圧力判定部１０５による詰まり判定において異常ありと判定された場合には、少なくとも詰まりが解消されるまでの間、尿素水溶液の噴射制御を停止させることができる。一方、圧力判定部１０５による詰まり判定では、噴射弁３１が開固着状態になっている場合であっても、異常なしと判定されることも考えられる。このため、本実施形態にかかる制御装置１００は、圧力判定部１０５による詰まり判定とは別に、異常判定部１０３による異常判定を実行する。   Such clogging determination by the pressure determination unit 105 can be performed relatively easily as compared with abnormality determination by an abnormality determination unit 103 described later. Therefore, when it is determined that there is an abnormality in the clogging determination by the pressure determination unit 105, the injection control of the urea aqueous solution can be stopped at least until the clogging is eliminated. On the other hand, in the clogging determination by the pressure determination unit 105, it may be determined that there is no abnormality even when the injection valve 31 is in the open fixed state. For this reason, the control device 100 according to the present embodiment executes the abnormality determination by the abnormality determination unit 103 separately from the clogging determination by the pressure determination unit 105.

（３−４．異常判定部）
異常判定部１０３は、圧力判定部１０５によって噴射弁３１に異常がないと判定され、尿素水溶液の噴射制御が開始された状態で、噴射弁３１に通電される電流波形及びポンプ４１の出力に基づいて、噴射弁３１の異常を判定する。具体的に、異常判定部１０３は、尿素水溶液の噴射制御が実行されている状態で、噴射弁３１に通電される電流波形及びポンプ４１の出力を監視し、電流波形に基づいて弁体が移動しているか否かを判別することにより、弁体の固着の有無を判定する。さらに、異常判定部１０３は、弁体が固着している場合に、ポンプ４１の出力に基づいて、当該固着が開固着であるか閉固着であるかを判定する。 (3-4. Abnormality determination unit)
The abnormality determination unit 103 determines that the injection valve 31 is normal by the pressure determination unit 105 and starts the injection control of the urea aqueous solution, and based on the current waveform supplied to the injection valve 31 and the output of the pump 41. The abnormality of the injection valve 31 is determined. Specifically, the abnormality determination unit 103 monitors the current waveform supplied to the injection valve 31 and the output of the pump 41 while the urea aqueous solution injection control is being executed, and the valve body moves based on the current waveform. Whether or not the valve body is fixed is determined by determining whether or not the valve body is engaged. Furthermore, when the valve body is fixed, the abnormality determination unit 103 determines whether the fixing is open fixing or closed fixing based on the output of the pump 41.

図５は、弁体の固着の有無による、噴射弁３１に通電される電流波形の違いを示す説明図である。噴射弁３１は、電磁コイルへの通電量が増大するにつれて弁体を引き付ける磁力が増大し、弁体が移動する構成を有する。弁体が固着していない場合（実線）、通電量を徐々に大きくしていくと、弁体が移動し始めるときに一旦電流値が低下するため、電流波形に変化点が発現する。一方、弁体が固着している場合（破線）、通電量を増大させても弁体が移動しないため、電流波形に変化点は発現しない。   FIG. 5 is an explanatory diagram showing a difference in a current waveform supplied to the injection valve 31 depending on whether or not the valve body is fixed. The injection valve 31 has a configuration in which the magnetic force that attracts the valve body increases and the valve body moves as the energization amount to the electromagnetic coil increases. When the valve body is not fixed (solid line), if the energization amount is gradually increased, the current value once decreases when the valve body starts to move, so that a change point appears in the current waveform. On the other hand, when the valve body is firmly attached (broken line), the valve body does not move even if the energization amount is increased, and therefore no change point appears in the current waveform.

異常判定部１０３は、噴射制御を実行している間に噴射弁３１に通電される電流波形に、このような変化点が発現したか否かを判別することにより、弁体の固着の有無を判定し得る。電流波形に変化点が発現した場合、すなわち、弁体が固着していない場合には、すでに圧力判定部１０５によって行われた詰まり判定の異常なしの結果と併せて、噴射弁３１による尿素水溶液の噴射制御を正常に行い得ると判断し得る。このため、異常判定部１０３は、噴射弁３１に異常がないものとして、尿素水溶液の噴射制御を継続させる。   The abnormality determination unit 103 determines whether or not the valve element is fixed by determining whether or not such a change point has occurred in the current waveform supplied to the injection valve 31 while the injection control is being performed. It can be determined. When a change point appears in the current waveform, that is, when the valve element is not fixed, the result of the determination of clogging already performed by the pressure determination unit 105 is combined with the result of the urea aqueous solution generated by the injection valve 31. It can be determined that the injection control can be performed normally. Therefore, the abnormality determination unit 103 continues the injection control of the urea aqueous solution on the assumption that there is no abnormality in the injection valve 31.

一方、噴射弁３１に通電される電流波形に変化点が発現しない場合、すなわち、弁体が固着している場合、当該固着が開固着か閉固着かによって、ポンプ４１の出力に差が生じる。図６は、噴射弁３１の開固着状態及び閉固着状態でのポンプ４１の出力を示す説明図である。尿素水溶液の噴射制御中には、噴射弁３１に供給される尿素水溶液の圧力Ｐｕが目標値Ｐｔｇｔに維持されるようにポンプ４１の出力が制御されるため、弁体が固着している場合には、尿素水溶液の噴射量（ゼロも含む）は一定であり、ポンプ４１の出力は略一定になる。   On the other hand, when the change point does not appear in the current waveform supplied to the injection valve 31, that is, when the valve body is fixed, a difference occurs in the output of the pump 41 depending on whether the fixing is open fixing or closed fixing. FIG. 6 is an explanatory diagram showing the output of the pump 41 when the injection valve 31 is in the open and closed state. During the urea aqueous solution injection control, the output of the pump 41 is controlled so that the pressure Pu of the urea aqueous solution supplied to the injection valve 31 is maintained at the target value Ptgt. , The injection amount (including zero) of the urea aqueous solution is constant, and the output of the pump 41 is substantially constant.

ただし、噴射弁３１が閉固着状態の場合には、尿素水溶液は噴射されない一方、噴射弁３１が開固着状態の場合には、尿素水溶液が噴射される。そのため、尿素水溶液の圧力Ｐｕを目標値Ｐｔｇｔに維持するためのポンプ４１の出力は、噴射弁３１が開固着状態の場合の方が、閉固着状態の場合に比べて大きくなる。したがって、異常判定部１０３は、噴射弁３１の開固着状態又は閉固着状態を区別し得る閾値や範囲等と、実際のポンプ４１の出力とを比較することにより、噴射弁３１の固着状態を判別する。   However, when the injection valve 31 is closed and fixed, the urea aqueous solution is not injected, whereas when the injection valve 31 is open and fixed, the urea aqueous solution is injected. Therefore, the output of the pump 41 for maintaining the pressure Pu of the aqueous urea solution at the target value Ptgt is larger when the injection valve 31 is in the open fixed state than in the closed fixed state. Therefore, the abnormality determination unit 103 determines the fixed state of the injection valve 31 by comparing the threshold value, range, and the like that can distinguish the open fixed state or the closed fixed state of the injection valve 31 with the actual output of the pump 41. To do.

噴射弁３１が開固着状態の場合、噴射弁３１に尿素水溶液が供給される間、常に排気管１１内に尿素水溶液が噴射される状態になる。これにより、排気管１１内に尿素水溶液が付着して、加熱されることによって結晶化が進行したり、生成されるアンモニアが還元触媒１３に吸着しきれずに還元触媒１３の下流側に流出したりするおそれがある。このため、異常判定部１０３は、噴射弁３１が開固着状態の場合には、尿素水溶液の噴射制御を禁止する。これに伴って、異常判定部１０３は、還元剤噴射装置２０内の尿素水溶液を貯蔵タンク５０内に回収したり、運転者等への警告表示を行ったりしてもよい。   When the injection valve 31 is in the open fixed state, the urea aqueous solution is always injected into the exhaust pipe 11 while the urea aqueous solution is supplied to the injection valve 31. As a result, the urea aqueous solution adheres to the exhaust pipe 11 and is heated to cause crystallization, or the produced ammonia cannot be completely adsorbed by the reduction catalyst 13 and flows out downstream of the reduction catalyst 13. There is a risk. For this reason, the abnormality determination part 103 prohibits the injection control of the urea aqueous solution when the injection valve 31 is in the open fixed state. In connection with this, the abnormality determination part 103 may collect | recover the urea aqueous solution in the reducing agent injection apparatus 20 in the storage tank 50, or may perform a warning display to a driver | operator.

一方、噴射弁３１が閉固着状態の場合、噴射弁３１に尿素水溶液を供給しても、尿素水溶液が排気管１１内に漏れ出ることはない。そのため、異常判定部１０３は、噴射弁３１が閉固着状態である場合、復帰制御部１０７に復帰制御を実行させ、結晶化した尿素水溶液の融解によって、弁体の固着の解消を試みる。このとき、異常判定部１０３は、第２カウンタ値をカウントアップし、第２カウンタ値が所定の閾値Ｔｈ２に到達した場合に、噴射弁３１の閉固着状態が解消されないものとみなして、尿素水溶液の噴射制御を禁止する。   On the other hand, when the injection valve 31 is closed and fixed, even if the urea aqueous solution is supplied to the injection valve 31, the urea aqueous solution does not leak into the exhaust pipe 11. Therefore, when the injection valve 31 is in the closed and fixed state, the abnormality determination unit 103 causes the return control unit 107 to perform return control, and attempts to eliminate sticking of the valve body by melting the crystallized urea aqueous solution. At this time, the abnormality determination unit 103 counts up the second counter value, and assumes that the closed adhering state of the injection valve 31 is not resolved when the second counter value reaches a predetermined threshold Th2, and the urea aqueous solution The injection control is prohibited.

かかる異常判定部１０３による噴射弁３１の異常判定は、尿素水溶液の噴射制御を実行中に行うことができる。したがって、噴射弁３１に異常がない場合には、尿素水溶液の噴射制御に影響を与えることなく、噴射弁３１の異常判定を完了させることができる。また、かかる噴射弁３１の異常判定は、噴射弁３１の開固着状態と閉固着状態とを判別することができるために、閉固着状態の場合には、噴射制御を禁止する前に、弁体の固着の解消を試みることができる。したがって、結晶化した尿素水溶液を融解させることができた場合には、尿素水溶液の噴射制御を継続することができる。   The abnormality determination of the injection valve 31 by the abnormality determination unit 103 can be performed during the execution of the urea aqueous solution injection control. Therefore, when there is no abnormality in the injection valve 31, the abnormality determination of the injection valve 31 can be completed without affecting the injection control of the urea aqueous solution. Further, since the abnormality determination of the injection valve 31 can determine the open fixed state and the closed fixed state of the injection valve 31, in the closed fixed state, before the injection control is prohibited, the valve body is prohibited. You can try to eliminate the sticking. Therefore, when the crystallized urea aqueous solution can be melted, the injection control of the urea aqueous solution can be continued.

＜４．フローチャート＞
次に、図７を参照して、本実施形態にかかる制御装置１００により実行される還元剤噴射装置の制御方法の例について説明する。 <4. Flow chart>
Next, an example of a control method for the reducing agent injection device executed by the control device 100 according to the present embodiment will be described with reference to FIG.

まず、ステップＳ１０において、内燃機関５のイグニションスイッチがオンにされる等によって、還元剤噴射装置２０が起動すると、ステップＳ１４において、第１カウンタ及び第２カウンタの値がリセットされる。   First, in step S10, when the reducing agent injection device 20 is activated by turning on the ignition switch of the internal combustion engine 5, the values of the first counter and the second counter are reset in step S14.

次いで、ステップＳ１８において、制御装置１００の圧力判定部１０５は、噴射弁３１に供給される尿素水溶液の圧力Ｐｕに基づいて、噴射弁３１の詰まり判定を行う。例えば、貯蔵タンク５０内の尿素水溶液がポンプ４１によって噴射弁３１に向けて圧送され、圧力センサ４３により検出される圧力Ｐｕが目標値Ｐｔｇｔになった状態で、圧力判定部１０５は、ポンプ４１の出力を一定にするとともに、噴射弁３１を開弁状態で維持する。そして、圧力判定部１０５は、噴射弁３１を開弁状態にしてから所定時間経過した時点の圧力Ｐｕの値を求め、噴射弁３１の詰まりの有無を判定する。ある時点の圧力Ｐｕの値の代わりに、噴射弁３１を開弁状態にしてからの圧力の降下速度を用いて、噴射弁３１の詰まり判定をしてもよい。   Next, in step S <b> 18, the pressure determination unit 105 of the control device 100 determines whether the injection valve 31 is clogged based on the pressure Pu of the aqueous urea solution supplied to the injection valve 31. For example, in a state where the urea aqueous solution in the storage tank 50 is pumped toward the injection valve 31 by the pump 41 and the pressure Pu detected by the pressure sensor 43 reaches the target value Ptgt, the pressure determination unit 105 While keeping the output constant, the injection valve 31 is maintained in the open state. And the pressure determination part 105 calculates | requires the value of the pressure Pu when the predetermined time passes, after making the injection valve 31 into a valve opening state, and determines the presence or absence of the injection valve 31 clogging. Instead of the value of the pressure Pu at a certain time point, the clogging of the injection valve 31 may be determined using the pressure decrease rate after the injection valve 31 is opened.

次いで、ステップＳ２２において、圧力判定部１０５は、詰まり判定の結果、噴射弁３１に異常があるか否かを判別する。噴射弁３１に異常がある場合（Ｓ２２：Ｙｅｓ）、ステップＳ２６において、圧力判定部１０５は、復帰制御部１０７による復帰制御を実行させる。例えば、復帰制御部１０７は、流路切替弁７１に通電し、ポンプ４１により圧送される尿素水溶液が、噴射弁３１側から貯蔵タンク５０側に流れるようにした後、ポンプ４１を所定時間駆動する。これにより、還元剤噴射装置２０内の尿素水溶液が貯蔵タンク５０内に吸い戻される。このとき、噴射弁３１に開弁指示を出力してもよい。噴孔の一部が詰まっている場合には、噴射弁３１が開弁していた方が、尿素水溶液を効率的に吸い戻すことができる。   Next, in step S22, the pressure determination unit 105 determines whether or not the injection valve 31 is abnormal as a result of the clogging determination. When there is an abnormality in the injection valve 31 (S22: Yes), in step S26, the pressure determination unit 105 causes the return control unit 107 to perform return control. For example, the return control unit 107 energizes the flow path switching valve 71 so that the urea aqueous solution pumped by the pump 41 flows from the injection valve 31 side to the storage tank 50 side, and then drives the pump 41 for a predetermined time. . Thereby, the urea aqueous solution in the reducing agent injection device 20 is sucked back into the storage tank 50. At this time, a valve opening instruction may be output to the injection valve 31. When a part of the nozzle hole is clogged, the urea aqueous solution can be sucked back more efficiently when the injection valve 31 is open.

また、復帰制御部１０７は、尿素水溶液の吸い戻しが終了した後には、流路切替弁７１への通電を停止し、ポンプ４１により圧送される尿素水溶液が、貯蔵タンク５０側から噴射弁３１側に流れるようにし、ポンプ４１を駆動する。これにより、尿素水溶液が還元剤噴射装置２０内に再充填される。かかる復帰制御の結果、尿素水溶液が、噴射弁３１内で結晶化した尿素水溶液に到達すれば、結晶化した尿素水溶液が融解して、噴射弁３１の異常が解消され得る。   In addition, the return control unit 107 stops energizing the flow path switching valve 71 after the urea aqueous solution sucks back, and the urea aqueous solution pumped by the pump 41 is transferred from the storage tank 50 side to the injection valve 31 side. The pump 41 is driven. Thereby, the urea aqueous solution is refilled in the reducing agent injection device 20. If the urea aqueous solution reaches the crystallized urea aqueous solution in the injection valve 31 as a result of the return control, the crystallized urea aqueous solution is melted and the abnormality of the injection valve 31 can be eliminated.

復帰制御部１０７による復帰制御が終了した後、ステップＳ３０において、圧力判定部１０５は、第１カウンタ値が、あらかじめ設定した閾値Ｔｈ１以上になっているか否かを判別する。第１カウンタ値が閾値Ｔｈ１未満である場合（Ｓ３０：Ｎｏ）、噴射弁３１の詰まりの解消の余地があるため、圧力判定部１０５は、ステップＳ３４において、第１カウンタ値をカウントアップした後、ステップＳ１８に戻って、詰まり判定を繰り返す。一方、第１カウンタ値が閾値Ｔｈ１以上である場合（Ｓ３０：Ｙｅｓ）、所定回数復帰制御を実施したにもかかわらず噴射弁３１の詰まりが解消されておらず、尿素水溶液の噴射制御を実行することが困難であるとみなすことができる。したがって、圧力判定部１０５は、ステップＳ３８に進み、エラー判定する。この場合、尿素水溶液の噴射制御は実行されない。圧力判定部１０５は、運転者等に対して噴射弁３１の異常を知らせるために、警告装置を作動させてもよい。   After the return control by the return control unit 107 ends, in step S30, the pressure determination unit 105 determines whether or not the first counter value is greater than or equal to a preset threshold value Th1. When the first counter value is less than the threshold value Th1 (S30: No), there is room for eliminating the clogging of the injection valve 31, so the pressure determination unit 105 counts up the first counter value in step S34. Returning to step S18, clogging determination is repeated. On the other hand, when the first counter value is equal to or greater than the threshold Th1 (S30: Yes), the clogging of the injection valve 31 has not been eliminated despite the return control being performed a predetermined number of times, and the urea aqueous solution injection control is executed. Can be considered difficult. Therefore, the pressure determination unit 105 proceeds to step S38 and determines an error. In this case, the urea aqueous solution injection control is not executed. The pressure determination unit 105 may activate a warning device to notify the driver or the like of an abnormality in the injection valve 31.

一方、上述のステップＳ２２において、詰まり判定の結果、噴射弁３１に異常が無い場合（Ｓ２２：Ｎｏ）、ステップＳ４２において、噴射制御部１０１は、尿素水溶液の噴射制御を開始する。例えば、噴射制御部１０１は、噴射弁３１に供給される尿素水溶液の圧力Ｐｕが目標値Ｐｔｇｔとなるようにポンプ４１の出力をフィードバック制御する。また、噴射制御部１０１は、尿素水溶液の目標噴射量に基づいて噴射弁３１の開弁時間を設定し、噴射弁３１への通電制御を行う。   On the other hand, if there is no abnormality in the injection valve 31 as a result of the clogging determination in step S22 described above (S22: No), the injection control unit 101 starts injection control of the urea aqueous solution in step S42. For example, the injection control unit 101 feedback-controls the output of the pump 41 so that the pressure Pu of the aqueous urea solution supplied to the injection valve 31 becomes the target value Ptgt. Further, the injection control unit 101 sets a valve opening time of the injection valve 31 based on the target injection amount of the urea aqueous solution, and performs energization control to the injection valve 31.

尿素水溶液の噴射制御が開始された後、ステップＳ４６において、異常判定部１０３は、噴射弁３１に通電されている電流波形及びポンプ４１の出力に基づく噴射弁３１の異常判定を実行する。具体的には、異常判定部１０３は、所定のサイクルごとに、噴射弁３１に通電されている電流値及びポンプ４１の出力を検出する。また、異常判定部１０３は、検出された噴射弁３１の電流波形における所定の変化点の有無により、弁体の固着の有無を判定する。さらに、異常判定部１０３は、弁体が固着している場合には、ポンプ４１の出力を、あらかじめ設定した閾値あるいは範囲と比較することにより、噴射弁３１の開固着状態又は閉固着状態を判定する。   After the urea aqueous solution injection control is started, in step S <b> 46, the abnormality determination unit 103 performs abnormality determination of the injection valve 31 based on the current waveform supplied to the injection valve 31 and the output of the pump 41. Specifically, the abnormality determination unit 103 detects the current value energized in the injection valve 31 and the output of the pump 41 for each predetermined cycle. Moreover, the abnormality determination part 103 determines the presence or absence of sticking of a valve body by the presence or absence of the predetermined change point in the detected current waveform of the injection valve 31. Further, when the valve body is fixed, the abnormality determination unit 103 determines the open fixed state or the closed fixed state of the injection valve 31 by comparing the output of the pump 41 with a preset threshold value or range. To do.

次いで、ステップＳ５０において、異常判定部１０３は、噴射弁３１の異常判定の結果、噴射弁３１に異常があるか否かを判別する。噴射弁３１に異常がない場合（Ｓ５０：Ｎｏ）、還元剤噴射装置２０は正常に噴射制御を実行可能であるとみなせるため、異常判定部１０３は、ステップＳ７０に進んで、噴射制御部１０１に、尿素水溶液の噴射制御を継続させる。一方、噴射弁３１に異常がある場合（Ｓ５０：Ｙｅｓ）、ステップＳ５４において、異常判定部１０３は、噴射弁３１の異常が閉固着によるものか否かを判別する。   Next, in step S50, the abnormality determination unit 103 determines whether or not the injection valve 31 has an abnormality as a result of the abnormality determination of the injection valve 31. When there is no abnormality in the injection valve 31 (S50: No), since the reducing agent injection device 20 can be considered to be able to execute the injection control normally, the abnormality determination unit 103 proceeds to step S70 and the injection control unit 101 Then, the injection control of the urea aqueous solution is continued. On the other hand, when there is an abnormality in the injection valve 31 (S50: Yes), in step S54, the abnormality determination unit 103 determines whether or not the abnormality of the injection valve 31 is due to closed adhesion.

噴射弁３１が開固着状態である場合（Ｓ５４：Ｎｏ）、ポンプ４１の駆動を継続すると、尿素水溶液が排気管１１中に垂れ流しの状態になることから、異常判定部１０３は、ステップＳ３８に進み、エラー判定した上で、尿素水溶液の噴射制御を速やかに停止する。異常判定部１０３は、運転者等に対して噴射弁３１の異常を知らせるために、警告装置を作動させてもよい。一方、噴射弁３１が閉固着状態である場合（Ｓ５４：Ｙｅｓ）、ステップＳ５８において、異常判定部１０３は、第２カウンタ値があらかじめ設定した閾値Ｔｈ２未満であるか否かを判別する。   When the injection valve 31 is in the open fixing state (S54: No), if the drive of the pump 41 is continued, the urea aqueous solution will be in a state of flowing down into the exhaust pipe 11, and the abnormality determination unit 103 proceeds to step S38. After determining the error, the urea aqueous solution injection control is immediately stopped. The abnormality determination unit 103 may activate a warning device in order to notify the driver or the like of the abnormality of the injection valve 31. On the other hand, when the injection valve 31 is in the closed adhering state (S54: Yes), in step S58, the abnormality determination unit 103 determines whether or not the second counter value is less than a preset threshold value Th2.

第２カウンタ値が閾値Ｔｈ２以上である場合（Ｓ５８：Ｎｏ）、所定回数復帰制御を実施したにもかかわらず噴射弁３１の閉固着状態が解消されておらず、尿素水溶液の噴射制御を実行することが困難であるとみなすことができる。したがって、異常判定部１０３は、ステップＳ３８に進み、エラー判定し、尿素水溶液の噴射制御を停止させる。異常判定部１０３は、運転者等に対して噴射弁３１の異常を知らせるために、警告装置を作動させてもよい。一方、第２カウンタ値が閾値Ｔｈ２未満の場合、噴射弁３１の閉固着状態の解消の余地があるため、ステップＳ６２において、異常判定部１０３は、復帰制御部１０７による復帰制御を実行させる。復帰制御は、上述したステップＳ２６の復帰制御と同様の手順に沿って実行し得る。   When the second counter value is equal to or greater than the threshold value Th2 (S58: No), the closed adhering state of the injection valve 31 is not resolved despite the execution of the return control for a predetermined number of times, and the urea aqueous solution injection control is executed. Can be considered difficult. Therefore, the abnormality determination unit 103 proceeds to step S38, determines an error, and stops the injection control of the urea aqueous solution. The abnormality determination unit 103 may activate a warning device in order to notify the driver or the like of the abnormality of the injection valve 31. On the other hand, when the second counter value is less than the threshold value Th2, there is room for cancellation of the closed adhering state of the injection valve 31, and therefore in step S62, the abnormality determination unit 103 causes the return control unit 107 to perform return control. The return control can be executed according to the same procedure as the return control in step S26 described above.

復帰制御部１０７による復帰制御が終了した後、異常判定部１０３は、ステップＳ６６において、第２カウンタ値をカウントアップした後、ステップＳ１８に戻って、再び詰まり判定から上記のフローチャートを繰り返す。   After the return control by the return control unit 107 ends, the abnormality determination unit 103 increments the second counter value in step S66, returns to step S18, and repeats the above flowchart from the clogging determination again.

以上説明したように、本実施形態にかかる還元剤噴射装置２０の制御装置１００によれば、還元剤噴射装置２０を制御することにより、比較的簡易な詰まり判定によって噴射弁３１の異常を検出しつつ、詰まり判定によって異常が見られない場合であっても、噴射制御中に実行される異常判定によって噴射弁３１の異常を検出することができる。また、噴射制御中に実行される異常判定では、噴射制御を停止させることなく、噴射弁３１の開固着状態又は閉固着状態を区別しつつ、噴射弁３１の異常の有無を判定することができる。したがって、噴射弁３１に異常がない場合には、尿素水溶液の噴射制御を継続させることができる。   As described above, according to the control device 100 of the reducing agent injection device 20 according to the present embodiment, by controlling the reducing agent injection device 20, an abnormality of the injection valve 31 is detected by a relatively simple clogging determination. On the other hand, even if no abnormality is found by the clogging determination, the abnormality of the injection valve 31 can be detected by the abnormality determination executed during the injection control. Further, in the abnormality determination executed during the injection control, it is possible to determine whether the injection valve 31 is abnormal or not while stopping the injection control and distinguishing the open fixed state or the closed fixed state of the injection valve 31. . Therefore, when there is no abnormality in the injection valve 31, the injection control of the urea aqueous solution can be continued.

また、本実施形態にかかる還元剤噴射装置２０の制御装置１００は、噴射弁３１の開固着状態又は閉固着状態を区別することができる。したがって、噴射弁３１の開固着状態では速やかに尿素水溶液の噴射制御を停止して、排気管１１内への尿素水溶液の垂れ流しを防ぐことができる。一方、噴射弁３１の閉固着状態では、尿素水溶液の噴射制御を停止させる前に、復帰制御によって噴射弁３１の閉固着状態の解消を試みることができる。これにより、噴射弁３１の異常を解消できないと判定された場合にのみ、尿素水溶液の噴射制御が禁止されることになり、必要以上に噴射制御が禁止されることがなくなる。   Moreover, the control apparatus 100 of the reducing agent injection device 20 according to the present embodiment can distinguish between the open fixed state and the closed fixed state of the injection valve 31. Therefore, when the injection valve 31 is in the open fixed state, the urea aqueous solution injection control can be quickly stopped to prevent the urea aqueous solution from flowing into the exhaust pipe 11. On the other hand, in the closed fixed state of the injection valve 31, before the injection control of the urea aqueous solution is stopped, it is possible to try to eliminate the closed fixed state of the injection valve 31 by the return control. Thereby, only when it is determined that the abnormality of the injection valve 31 cannot be resolved, the injection control of the urea aqueous solution is prohibited, and the injection control is not prohibited more than necessary.

以上、添付図面を参照しながら本発明の好適な実施形態について詳細に説明したが、本発明はかかる例に限定されない。本発明の属する技術の分野における通常の知識を有する者であれば、特許請求の範囲に記載された技術的思想の範疇内において、各種の変更例または修正例に想到し得ることは明らかであり、これらについても、当然に本発明の技術的範囲に属するものと了解される。   The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention pertains can come up with various changes or modifications within the scope of the technical idea described in the claims. Of course, it is understood that these also belong to the technical scope of the present invention.

５ 内燃機関
１０ 尿素ＳＣＲシステム
１１ 排気管
１３ 還元触媒
１５ 温度センサ
２０ 還元剤噴射装置
３１ 噴射弁
４１ ポンプ
４３ 圧力センサ
５０ 貯蔵タンク
１００ 制御装置
１０１ 噴射制御部
１０３ 異常判定部
１０５ 圧力判定部
１０７ 復帰制御部
DESCRIPTION OF SYMBOLS 5 Internal combustion engine 10 Urea SCR system 11 Exhaust pipe 13 Reduction catalyst 15 Temperature sensor 20 Reducing agent injection apparatus 31 Injection valve 41 Pump 43 Pressure sensor 50 Storage tank 100 Control apparatus 101 Injection control part 103 Abnormality determination part 105 Pressure determination part 107 Return control Part

Claims (8)

内燃機関の排気管に取り付けられた噴射弁により、排気通路に配設された還元触媒の上流側に、前記内燃機関の排気中のＮＯXを浄化するための還元剤を噴射する還元剤噴射装置を制御するための制御装置において、
前記噴射弁に供給される前記還元剤の圧力が所定の目標値となるように前記還元剤を圧送するポンプの出力を制御しつつ、前記噴射弁の開弁動作を制御する噴射制御部と、
前記還元剤の噴射制御の実行中における、前記噴射弁に通電される電流波形及び前記ポンプの出力に基づいて、前記噴射弁の開固着又は閉固着を区別しつつ前記噴射弁の異常を判定する異常判定部と、
を備える、還元剤噴射装置の制御装置。 A reducing agent injection device for injecting a reducing agent for purifying NO x in the exhaust gas of the internal combustion engine to the upstream side of the reduction catalyst disposed in the exhaust passage by an injection valve attached to an exhaust pipe of the internal combustion engine In a control device for controlling
An injection control unit that controls the valve opening operation of the injection valve while controlling the output of the pump that pumps the reducing agent so that the pressure of the reducing agent supplied to the injection valve becomes a predetermined target value;
Based on the current waveform energized to the injection valve and the output of the pump during execution of the injection control of the reducing agent, the abnormality of the injection valve is determined while distinguishing whether the injection valve is open or closed. An abnormality determination unit;
A control device for a reducing agent injection device. 前記異常判定部は、前記電流波形に変化点が発現せず、かつ、前記ポンプの出力が第１の範囲内で維持されている場合、前記噴射弁が開固着状態にあると判定し、
前記電流波形に変化点が発現せず、かつ、前記ポンプの出力が前記第１の範囲よりも小さい値の第２の範囲内で維持されている場合、前記噴射弁が閉固着状態にあると判定する、請求項１に記載の還元剤噴射装置の制御装置。 The abnormality determination unit determines that the injection valve is in an open fixing state when no change point is expressed in the current waveform and the output of the pump is maintained within the first range;
When no change point appears in the current waveform and the output of the pump is maintained within a second range that is smaller than the first range, the injection valve is closed and fixed. The control device of the reducing agent injection device according to claim 1, wherein the determination is made. 前記異常判定部は、前記噴射弁が開固着状態にあると判定した場合に、前記還元剤の噴射制御を中止させる、請求項２に記載の還元剤噴射装置の制御装置。   The control device for a reducing agent injection device according to claim 2, wherein the abnormality determination unit stops the injection control of the reducing agent when it is determined that the injection valve is in an open fixed state. 前記異常判定部により前記噴射弁が閉固着状態にあると判定された場合に、前記噴射弁に供給される前記還元剤を一旦回収した後、前記噴射弁に再供給する復帰制御部を備える、請求項２又は３に記載の還元剤噴射装置の制御装置。   When the abnormality determining unit determines that the injection valve is in a closed fixed state, a recovery control unit is provided that once collects the reducing agent supplied to the injection valve and then re-supplys the injection valve. The control apparatus of the reducing agent injection apparatus of Claim 2 or 3. 前記異常判定部は、前記噴射弁が閉固着状態にあると判定した回数が所定の閾値以上になった場合に、前記噴射弁の噴射制御の実行を禁止する、請求項４に記載の還元剤噴射装置の制御装置。   The reducing agent according to claim 4, wherein the abnormality determination unit prohibits execution of injection control of the injection valve when the number of times that the injection valve is determined to be in a closed and fixed state is equal to or greater than a predetermined threshold. Control device for injection device. 前記還元剤噴射装置の起動時及び前記復帰制御部による前記還元剤の再供給時に、前記噴射弁に供給される還元剤の圧力を高めた状態で前記還元剤を圧送するポンプの出力を一定にするとともに前記噴射弁を開弁状態で維持したときの前記還元剤の圧力に基づいて、前記噴射弁の詰まりの有無を判定する圧力判定部を備え、
前記圧力判定部により異常なしと判定された場合に、前記噴射制御部が前記還元剤の噴射制御を開始し、前記異常判定部が前記噴射弁の異常を判定する、請求項４又は５に記載の還元剤噴射装置の制御装置。 When the reducing agent injection device is started up and when the reducing agent is resupplied by the return control unit, the output of the pump that pumps the reducing agent in a state where the pressure of the reducing agent supplied to the injection valve is increased is made constant. And a pressure determination unit that determines whether or not the injection valve is clogged based on the pressure of the reducing agent when the injection valve is maintained in an open state.
The said injection control part starts the injection control of the said reducing agent, and the said abnormality determination part determines the abnormality of the said injection valve, when it determines with no abnormality by the said pressure determination part. Control device for the reducing agent injection apparatus. 前記圧力判定部により異常ありと判定された場合に、前記噴射弁に供給される還元剤を一旦回収した後、前記噴射弁に再供給する復帰制御部を備える、請求項６に記載の還元剤噴射装置の制御装置。   The reducing agent according to claim 6, further comprising a return control unit that once collects the reducing agent supplied to the injection valve and then re-supplying the same when the pressure determination unit determines that there is an abnormality. Control device for injection device. 前記圧力判定部は、異常ありと判定した回数が所定の閾値以上になった場合に、前記噴射弁の噴射制御の実行を禁止する、請求項７に記載の還元剤噴射装置の制御装置。
The control device of a reducing agent injection device according to claim 7, wherein the pressure determination unit prohibits execution of injection control of the injection valve when the number of times determined to be abnormal is equal to or greater than a predetermined threshold.
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