JP5721413B2 - Exhaust gas purification device for internal combustion engine - Google Patents
Exhaust gas purification device for internal combustion engine Download PDFInfo
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Description
本発明は、還元剤を用いて排気中の窒素酸化物（ＮＯｘ）を還元浄化するエンジンの排気浄化装置において、特に、排気中に噴射供給された液体還元剤又はその前駆体を拡散する拡散板に堆積した析出物を除去する技術に関する。 The present invention relates to an engine exhaust gas purification apparatus that reduces and purifies nitrogen oxides (NOx) in exhaust gas using a reducing agent, and in particular, a diffusion plate that diffuses a liquid reducing agent injected into the exhaust gas or a precursor thereof. The present invention relates to a technique for removing deposits deposited on the substrate.
エンジン排気中のＮＯｘを除去する触媒浄化システムとして、特許文献１に記載された排気浄化装置が提案されている。かかる排気浄化装置は、排気管に配設されたＮＯｘ還元触媒の排気上流に、エンジン運転状態に応じた液体還元剤又はその前駆体（以下液体還元剤で代表する）を噴射供給することで、ＮＯｘ還元触媒において排気中のＮＯｘと還元剤とを触媒還元反応させて、ＮＯｘを無害成分に浄化処理する。また、ＮＯｘ還元触媒上流の排気管内に噴射供給された液体還元剤又はその前駆体を拡散する拡散板を備えている。 As a catalyst purification system for removing NOx in engine exhaust, an exhaust purification device described in Patent Document 1 has been proposed. Such an exhaust purification device is configured to inject and supply a liquid reducing agent or a precursor thereof (hereinafter represented by a liquid reducing agent) according to the engine operating state to the upstream side of the NOx reduction catalyst disposed in the exhaust pipe. In the NOx reduction catalyst, NOx in the exhaust and a reducing agent are subjected to a catalytic reduction reaction to purify NOx into harmless components. Further, a diffusion plate is provided for diffusing the liquid reducing agent or its precursor injected and supplied into the exhaust pipe upstream of the NOx reduction catalyst.
この種の排気浄化装置においては、市街地走行等、エンジンの負荷が低いところでの走行では、排気温度が低く、尿素水等の液体還元剤に由来する物質が排気管内に析出することがある。
このように、液体還元剤由来の物質が析出される走行が繰り返されると、析出物が前記拡散板に堆積して排気通路開口面積を狭めてしまい、エンジン出力低下に至る惧れもあった。
In this type of exhaust emission control device, when the engine is traveling at a low load, such as in urban areas, the exhaust temperature is low, and substances derived from a liquid reducing agent such as urea water may be deposited in the exhaust pipe.
As described above, when the traveling in which the substance derived from the liquid reducing agent is deposited is repeated, the deposit accumulates on the diffusion plate and narrows the exhaust passage opening area, which may lead to a decrease in engine output.
本発明は、このような従来の課題に着目してなされたもので、拡散板に堆積した析出物を除去し、もって良好な運転性を維持できるようにした内燃機関の排気浄化装置を提供することを目的とする。 The present invention has been made paying attention to such conventional problems, and provides an exhaust purification device for an internal combustion engine that can remove deposits deposited on a diffusion plate and maintain good operability. For the purpose.
このため本発明に係る内燃機関の排気浄化装置は、
内燃機関の排気管に配設され、還元剤を用いて窒素酸化物を還元浄化する還元触媒と、
前記還元触媒の排気上流に液体還元剤又はその前駆体を噴射供給する還元剤噴射ノズルと、
前記還元剤噴射ノズルと前記還元触媒との間に位置する排気管に配設されて、還元剤噴射ノズルから噴射された液体還元剤又はその前駆体を拡散する拡散装置と、
を含んで構成され、
前記拡散装置を、互いに平行な支軸周りに回動自由な複数の拡散板と、これら複数の拡散板を連動して回動させるように複数の拡散板に連結されたリンク機構と、を含んで構成すると共に、
前記複数の拡散板を、前記液体還元剤又はその前駆体を拡散させる通常位置から前記リンク機構を介して相異なる回動方向にそれぞれ回動させ、該拡散板同士の表裏面相互を接触させて各拡散板の表裏両面に堆積した析出物を除去する析出物除去機構と、
を含んで構成されたことを特徴とする。
For this reason, the exhaust gas purification apparatus for an internal combustion engine according to the present invention is:
A reduction catalyst disposed in an exhaust pipe of an internal combustion engine for reducing and purifying nitrogen oxides using a reducing agent;
A reducing agent injection nozzle that injects and supplies a liquid reducing agent or a precursor thereof upstream of the exhaust of the reduction catalyst;
A diffusion device that is disposed in an exhaust pipe positioned between the reducing agent injection nozzle and the reduction catalyst, and diffuses the liquid reducing agent injected from the reducing agent injection nozzle or a precursor thereof;
Comprising
The diffusion device includes a plurality of diffusion plates that are freely rotatable around mutually parallel support shafts, and a link mechanism that is coupled to the plurality of diffusion plates so as to rotate the plurality of diffusion plates in conjunction with each other. And consisting of
The plurality of diffusion plates are respectively rotated in different rotation directions via the link mechanism from a normal position where the liquid reducing agent or its precursor is diffused, and the front and back surfaces of the diffusion plates are brought into contact with each other. A deposit removal mechanism for removing deposits deposited on the front and back surfaces of each diffusion plate;
It is characterized by including.
本発明によれば、析出物除去機構によって拡散板同士が接触し、拡散板に堆積した析出物を粉砕しつつ除去して、析出物堆積量の増大を抑制することができ、もって、排気通路開口面積の減少を抑制して良好な運転性能を維持することができる。特に、相異なる方向に回動させることで、各拡散板の表裏両面の析出物を接触させて除去することができる。
また、析出物が細かく粉砕されることにより、拡散板から除去した析出物が昇華されやすくなり、排気温度を上昇させて析出物を昇華させる運転の頻度、あるいは析出物昇華用のヒーターの駆動の頻度を減少させることができ、燃費を向上できる。
According to the present invention, the diffusion plates are brought into contact with each other by the precipitate removal mechanism, and the deposits deposited on the diffusion plate are removed while being crushed, so that the increase in the amount of deposits can be suppressed, and the exhaust passage A reduction in the opening area can be suppressed and good driving performance can be maintained. In particular, by rotating in different directions, precipitates on both the front and back surfaces of each diffusion plate can be brought into contact and removed.
In addition, finely pulverized precipitates facilitate sublimation of the precipitates removed from the diffusion plate, and increase the exhaust temperature to sublimate the precipitates, or drive the precipitate sublimation heater. The frequency can be reduced and fuel consumption can be improved.
以下、本発明の実施の形態について、詳細に説明する。
図１は本発明の実施形態を示すエンジン排気系のシステム図である。
ディーゼルエンジン（エンジン本体）１の排気マニホールド２下流側の排気通路（排気管）３には、排気浄化装置を装備させるため、上流側の第１ケーシング４と、下流側の第２ケーシング５と、これらのケーシング４、５間の連通路６とが設けられる。
Hereinafter, embodiments of the present invention will be described in detail.
FIG. 1 is a system diagram of an engine exhaust system showing an embodiment of the present invention.
In order to equip the exhaust passage (exhaust pipe) 3 on the downstream side of the exhaust manifold 2 of the diesel engine (engine body) 1 with an exhaust purification device, the first casing 4 on the upstream side, the second casing 5 on the downstream side, A communication path 6 between the casings 4 and 5 is provided.
第１ケーシング４内には、前段にディーゼル酸化触媒（ＤＯＣ；Diesel Oxidation Catalyst ）７が収納され、後段にディーゼルパティキュレートフィルタ（以下「ＤＰＦ」という）８が収納されている。
ＤＰＦ８は、排気中の粒子状物質であるＰＭ（Particulate Matter）を捕集するフィルタであり、例えば、多孔質セラミックのハニカム構造の担体からなり、上流側と下流側とを連通する通路が多数並設されると共に、隣接する通路同士において上流側と下流側とが交互に封止されたウォールフロータイプのフィルタである。従って、排気は、上流端が開口し下流端が封止された通路から流入し、通路壁（その気孔）を通って、上流端が封止され下流端が開口する通路へ流出し、この際に、排気中のＰＭが通路壁に捕集される。このようなＤＰＦ８では、捕集したＰＭの堆積によって、次第に排気抵抗が増大するため、後述するように、連続的に、また強制的に、ＤＰＦ８を再生する必要がある。
In the first casing 4, a diesel oxidation catalyst (DOC; Diesel Oxidation Catalyst) 7 is accommodated in the front stage, and a diesel particulate filter (hereinafter referred to as “DPF”) 8 is accommodated in the rear stage.
The DPF 8 is a filter that collects PM (Particulate Matter) that is particulate matter in the exhaust gas. For example, the DPF 8 is made of a porous ceramic honeycomb structure carrier, and has many passages that connect the upstream side and the downstream side. And a wall flow type filter in which the upstream side and the downstream side are alternately sealed in adjacent passages. Therefore, the exhaust gas flows from the passage where the upstream end is open and the downstream end is sealed, passes through the passage wall (its pore), and flows out to the passage where the upstream end is sealed and the downstream end is open. In addition, PM in the exhaust is collected on the passage wall. In such a DPF 8, the exhaust resistance gradually increases due to the accumulation of the collected PM. Therefore, as described later, it is necessary to regenerate the DPF 8 continuously and forcibly.
酸化触媒７は、排気中のＮＯを酸化させてＮＯ２を生成し、このＮＯ２を酸化剤としてＤＰＦ８に供給すると共に、酸化熱を発生させて、下流側のＤＰＦ８を昇温させる。このようにＤＰＦ８の前段に酸化触媒７を配置することにより、ＤＰＦ８に捕集されているＰＭは、酸化触媒７から供給されたＮＯ２と反応して酸化し、ＤＰＦ８の連続再生が行われるようになる。 The oxidation catalyst 7 is NO in the exhaust is oxidized to generate NO 2, it is supplied to the DPF8 the NO 2 as an oxidizing agent, to generate oxidation heat, raising the temperature of the DPF8 downstream. By arranging the oxidation catalyst 7 in the preceding stage of the DPF 8 in this way, the PM collected in the DPF 8 reacts with the NO 2 supplied from the oxidation catalyst 7 and is oxidized, so that the continuous regeneration of the DPF 8 is performed. become.
第２ケーシング５内には、前段にアンモニアを還元剤としてＮＯｘを還元する機能を有するＳＣＲ触媒９が収納され、後段にＳＣＲ触媒９から流出したアンモニアを酸化してＮ２とする酸化触媒としての機能を有するアンモニア酸化触媒１０が収納されている。尚、「ＳＣＲ」は、Selective Catalytic Reduction の略語である。
そして、第２ケーシング５上流の連通路６には、ＳＣＲ触媒９へ向けて、還元剤（アンモニア）の前駆体としての尿素水溶液（以下「尿素水」という）を加圧空気と共に噴射する尿素水噴射ノズル１１が設けられている。尚、尿素水は、図示しない尿素水タンクから噴射量制御用の制御モジュール１２を介してノズル１１へ供給され、制御モジュール１２は電子制御ユニット（ＥＣＵ）５０により制御される。
In the second casing 5, an SCR catalyst 9 having a function of reducing NOx using ammonia as a reducing agent is housed in the first stage, and a function as an oxidation catalyst that oxidizes ammonia flowing out of the SCR catalyst 9 to N2 in the rear stage. The ammonia oxidation catalyst 10 having “SCR” is an abbreviation for Selective Catalytic Reduction.
A urea aqueous solution (hereinafter referred to as “urea water”) as a reducing agent (ammonia) precursor is injected into the communication passage 6 upstream of the second casing 5 together with the pressurized air toward the SCR catalyst 9. An injection nozzle 11 is provided. The urea water is supplied from a urea water tank (not shown) to the nozzle 11 via the control module 12 for controlling the injection amount, and the control module 12 is controlled by an electronic control unit (ECU) 50.
尿素水噴射ノズル１１から噴射された尿素水は、排気の熱により加水分解してアンモニアとなる。ＳＣＲ触媒９は、このようにして生成されたアンモニアを吸着し、吸着したアンモニアを還元剤として、ＮＯｘとアンモニア（ＮＨ３）とを選択的に還元反応させ、ＮＯｘを無害な水（Ｈ２Ｏ）と窒素（Ｎ２）へ浄化する。ここにおいて、ＳＣＲ触媒９と尿素水噴射ノズル１１とでＮＯｘ還元装置を構成している。 The urea water injected from the urea water injection nozzle 11 is hydrolyzed by the heat of the exhaust to become ammonia. The SCR catalyst 9 adsorbs the ammonia generated in this manner, selectively reduces NOx and ammonia (NH 3 ) using the adsorbed ammonia as a reducing agent, and converts NOx into harmless water (H 2 O). ) And nitrogen (N 2 ). Here, the SCR catalyst 9 and the urea water injection nozzle 11 constitute a NOx reduction device.
また、連通路６の尿素水噴射ノズル１１とＳＣＲ触媒９との間の部分には、還元剤としてのアンモニアを含んだ排気を拡散する複数枚の拡散板２３が配設される。後述するように、通常運転中は、複数枚の拡散板２３が排気流通方向と平行ないし若干傾斜して配設されている。
かかる拡散板２３を通過することにより、アンモニアを含んだ排気は均一に拡散されるため、ＳＣＲ触媒９に供給されるアンモニア濃度のむらを抑制し、ＳＣＲ触媒９によるＮＯｘ浄化効率を向上させることができる。
Further, a plurality of diffusion plates 23 for diffusing exhaust gas containing ammonia as a reducing agent are disposed in a portion of the communication path 6 between the urea water injection nozzle 11 and the SCR catalyst 9. As will be described later, during normal operation, a plurality of diffusion plates 23 are arranged parallel to or slightly inclined from the exhaust flow direction.
By passing through the diffusion plate 23, the exhaust gas containing ammonia is uniformly diffused. Therefore, unevenness of the ammonia concentration supplied to the SCR catalyst 9 can be suppressed, and the NOx purification efficiency by the SCR catalyst 9 can be improved. .
ここで、既述したように、特に、低負荷走行運転時等で排気温度が低下すると、尿素水が拡散板２３の表面に液状で付着しやすく、付着した尿素水の水分が蒸発することにより、還元剤に由来する物質などが析出し、拡散板２３表面に堆積する。かかる現象の繰り返しにより、拡散板２３表面の析出物堆積量が増大すると、排気通路面積が減少して排気流通抵抗の増大によりエンジン出力が低下する惧れがある。 Here, as described above, when the exhaust gas temperature is lowered particularly during low-load running operation, the urea water tends to adhere to the surface of the diffusion plate 23 in a liquid state, and the moisture of the attached urea water evaporates. A substance derived from the reducing agent is deposited and deposited on the surface of the diffusion plate 23. If the amount of deposits deposited on the surface of the diffusion plate 23 increases due to the repetition of such a phenomenon, the exhaust passage area may decrease and the engine output may decrease due to an increase in exhaust flow resistance.
そこで、本実施形態では、拡散板に堆積した析出物を除去する析出物除去機構２１を、以下のように配設する。
図２，図３は、析出物除去機構２１の構成を示す。
上流側及び下流側の連通路６壁に円筒状リング部材２２が連結され、該円筒状リング部材２２の内側に複数枚の拡散板２３が互いに平行に配設される。これら拡散板２３の長手方向両側には支軸２４が連結され、各支軸２４の端部は円筒状リング部材２２壁に形成した係合部に係合して支持される。これにより、各拡散板２３が支軸２４周り回動自由に支持される。
Therefore, in the present embodiment, the precipitate removing mechanism 21 that removes the deposit accumulated on the diffusion plate is arranged as follows.
2 and 3 show the configuration of the precipitate removing mechanism 21. FIG.
A cylindrical ring member 22 is connected to the walls of the upstream and downstream communication passages 6, and a plurality of diffusion plates 23 are arranged inside the cylindrical ring member 22 in parallel to each other. Support shafts 24 are connected to both sides in the longitudinal direction of the diffusion plates 23, and the end portions of the support shafts 24 are engaged and supported by engaging portions formed on the wall of the cylindrical ring member 22. Thereby, each diffusion plate 23 is supported around the support shaft 24 so as to freely rotate.
前記各拡散板２３を、これらの並び方向（排気流通方向に垂直な方向）に貫通するロッド２５が配設される。該ロッド２５は、例えば、弾性変形する鋼製ワイヤ等で形成され、膨大形成した係合部２５ａ間に、各拡散板２３を相互の平行状態を維持しつつ挟持する。ロッド２５の一端（図では下端）部は、円筒状リング部材２２をスライド自由に貫通して、アクチュエータ２６の駆動軸２６ａに連結される。アクチュエータ２６は、支持部材２７を介して、円筒状リング部材２２に支持される。 A rod 25 that passes through each of the diffusion plates 23 in the arrangement direction thereof (direction perpendicular to the exhaust flow direction) is disposed. The rod 25 is formed of, for example, an elastically deformed steel wire or the like, and sandwiches the diffusion plates 23 between the enormously formed engaging portions 25a while maintaining the mutual parallel state. One end (lower end in the figure) of the rod 25 passes through the cylindrical ring member 22 so as to slide freely, and is connected to a drive shaft 26 a of the actuator 26. The actuator 26 is supported by the cylindrical ring member 22 via the support member 27.
アクチュエータ２６は、駆動軸２６ａが伸縮駆動され、例えば、電動式として、通電ＯＦＦでは、内蔵スプリングに付勢されて駆動軸２６ａが中立位置にあって、拡散板２３を排気流通方向と平行ないし若干傾斜させて維持する。また、一方向に通電すると駆動軸２６ａが中立位置から伸張し、逆方向に通電すると中立位置から引き込まれるように動作する。 The actuator 26 is driven to extend and contract by the drive shaft 26a. For example, when the power is off, the actuator 26 is urged by a built-in spring so that the drive shaft 26a is in a neutral position, and the diffusion plate 23 is parallel to the exhaust flow direction or slightly. Keep tilted. Further, when energized in one direction, the drive shaft 26a extends from the neutral position, and when energized in the opposite direction, the drive shaft 26a operates so as to be drawn from the neutral position.
また、アクチュエータ２６を、エアシリンダと、該エアシリンダの複数の圧力室へのエア供給経路を切り換える切換弁とで構成し、エアシリンダの駆動軸を通常の中立位置、伸張位置、引込位置に切換自由に構成してもよい。
かかる構成を備えた析出物除去機構の作用を説明する。
アクチュエータ２６を駆動して駆動軸２６ａを伸張すると、ロッド２５の伸張を介して各拡散板２３が図２で時計回りに回動する。これにより、図に点線ａで示すように、上下に隣合う拡散板２３同士において、上側の拡散板２３の中立位置において支軸２４より右側に位置する部分の下面と、下側の拡散板２３の同じく支軸２４より左側に位置する部分の上面とが重なって接触する。
The actuator 26 is composed of an air cylinder and a switching valve for switching an air supply path to a plurality of pressure chambers of the air cylinder, and the drive shaft of the air cylinder is switched to a normal neutral position, an extended position, and a retracted position. It may be configured freely.
The operation of the precipitate removing mechanism having such a configuration will be described.
When the actuator 26 is driven to extend the drive shaft 26a, each diffusion plate 23 rotates clockwise in FIG. As a result, as shown by the dotted line a in the figure, the lower diffusion plate 23 and the lower diffusion plate 23 located on the right side of the support shaft 24 at the neutral position of the upper diffusion plate 23 between the upper and lower diffusion plates 23. Similarly, the upper surface of the portion located on the left side of the support shaft 24 overlaps and comes into contact.
次いで、アクチュエータ２６を駆動して駆動軸１５ａを引き込むと、ロッド２５の引込を介して各拡散板２３が図２で反時計回りに回動する。これにより、図に一点鎖線ｂで示すように、上下に隣合う拡散板２３同士において、中立位置において支軸２４より左側に位置する部分の下面と、下側の拡散板２３の同じく支軸２４より右側に位置する部分の上面とが重なって接触する。 Next, when the actuator 26 is driven to retract the drive shaft 15a, each diffusion plate 23 rotates counterclockwise in FIG. As a result, as indicated by a one-dot chain line b in the figure, in the diffusion plates 23 adjacent to each other in the vertical direction, the lower surface of the portion located on the left side of the support shaft 24 in the neutral position, and the support shaft 24 of the lower diffusion plate 23 as well. The upper surface of the portion located on the right side overlaps and comes into contact.
このようにして、駆動軸２６ａの伸張及び引込によって、各拡散板２３の重なり合う面に堆積していた析出物同士が押し潰されて砕かれ、拡散板２３から剥がれ落ちて除去される。
なお、伸張と引込の順序を変えてもよいことは勿論である。
また、図で一番上の拡散板２３の上面と、一番下の拡散板２３の下面は、隣り合う拡散板２３と重ならないが、接触時に生じる振動によってこれらの面に堆積した析出物を振り落として除去することができる。
In this manner, the deposits deposited on the overlapping surfaces of the diffusion plates 23 are crushed and crushed by the extension and retraction of the drive shaft 26a, and are peeled off from the diffusion plates 23 and removed.
Of course, the order of extension and drawing may be changed.
In the figure, the upper surface of the uppermost diffusion plate 23 and the lower surface of the lowermost diffusion plate 23 do not overlap with the adjacent diffusion plates 23, but deposits deposited on these surfaces due to vibrations generated at the time of contact. It can be removed by shaking.
かかるアクチュエータ２６の駆動軸２６ａの伸張及び引込操作は、１回でもよいが、数回繰り返せば、より多くの析出物を除去することができる。
なお、拡散板２３への析出物の堆積は、堆積が進むほど尿素水が付着されやすくなって、さらに堆積が促進されることになるので、所定量以上堆積したときに析出物を除去しておくことが望ましい。
Such extension and retraction operation of the drive shaft 26a of the actuator 26 may be performed once, but if it is repeated several times, more precipitates can be removed.
In addition, deposition of deposits on the diffusion plate 23 becomes easier to attach urea water as deposition progresses, and further facilitates deposition. Therefore, when depositing a predetermined amount or more, deposits are removed. It is desirable to keep it.
そこで、上記析出物除去機構２１を拡散板２３に所定量以上の析出物が堆積したときに駆動するように制御するため、図１に示すように、析出物堆積量を推定するための排気温度及び排気温度を検出するための排気温度センサ３１及び排気圧力センサ３２を、尿素水噴射ノズル１１近傍の連通路６壁に配設する。
また、析出物除去機構２１によって除去され連通路６壁に落下した尿素などの析出物を加熱してガス化しアンモニアに転化させるヒーター３３を拡散板２３下流直下の連通路６底壁に配設する。
Therefore, in order to control the precipitate removing mechanism 21 to be driven when a predetermined amount or more of deposits is deposited on the diffusion plate 23, as shown in FIG. 1, the exhaust temperature for estimating the deposit accumulation amount is shown. An exhaust temperature sensor 31 and an exhaust pressure sensor 32 for detecting the exhaust temperature are disposed on the wall of the communication passage 6 near the urea water injection nozzle 11.
Further, a heater 33 for heating and gasifying the precipitates such as urea removed by the precipitate removing mechanism 21 and falling on the wall of the communication path 6 to convert it into ammonia is disposed on the bottom wall of the communication path 6 immediately below the diffusion plate 23. .
次に、電子制御ユニット（ＥＣＵ）５０による析出物除去機構２１及びヒーター３３の制御を、図４のフローチャートに基づいて説明する。
このフローは、所定時間周期で実行される。
Next, control of the deposit removing mechanism 21 and the heater 33 by the electronic control unit (ECU) 50 will be described based on the flowchart of FIG.
This flow is executed at a predetermined time period.
ステップＳ１では、排気温度ｔが、所定温度ｔ０未満であるかを判定する。所定温度ｔ０は、例えば、尿素水の析出物の融点とし、したがって、所定温度ｔ０未満では、析出が生じる。
ステップＳ１で所定温度ｔ０未満と判定されたときは、ステップＳ２へ進んで積算カウンタの値Ｃをインクリメントする（Ｃ←Ｃ＋１）。
そして、ステップＳ３で、積算カウンタの値Ｃが所定値Ｃ０以上に達したか、つまり、還元剤に由来する物質が析出している時間の積算値が所定時間以上に達して、拡散板２３への析出物の堆積量が所定値以上になったかを判定する。
In step S1, it is determined whether the exhaust temperature t is lower than a predetermined temperature t0. The predetermined temperature t0 is, for example, the melting point of the precipitate of urea water, and therefore precipitation occurs below the predetermined temperature t0.
When it is determined in step S1 that the temperature is lower than the predetermined temperature t0, the process proceeds to step S2 to increment the value C of the integration counter (C ← C + 1).
Then, in step S3, whether the value C of the integration counter has reached a predetermined value C0 or more, that is, the integrated value of the time during which the substance derived from the reducing agent is deposited has reached a predetermined time or more, and It is determined whether or not the amount of deposits of deposits exceeds a predetermined value.
また、積算カウンタの値Ｃが所定値Ｃ０に達する前は、ステップＳ４へ進み、拡散板２３上流の排気圧力Ｐが所定値Ｐ０以上であるかを判定する。排気圧力Ｐが所定値Ｐ０以上のときは、拡散板２３への析出物の堆積量が増大して拡散板２３の通路面積が減少し、その結果、排気抵抗の増大によって排気圧力Ｐが所定値Ｐ０以上に増大したと推定される。
そこで、ステップＳ３で積算カウンタの値Ｃが所定値Ｃ０に達したと判定されたとき、または、ステップＳ排気圧力Ｐが所定値Ｐ０以上に増大したと判定されたとき、ステップＳ５へ進み、拡散板２３に堆積した析出物を除去するため、前記析出物除去機構２１を駆動する。すなわち、上述したようにアクチュエータ１５を駆動して拡散板２３同士を接触させて、析出物を砕いて除去する。
Further, before the value C of the integration counter reaches the predetermined value C0, the process proceeds to step S4, and it is determined whether the exhaust pressure P upstream of the diffusion plate 23 is equal to or higher than the predetermined value P0. When the exhaust pressure P is equal to or higher than the predetermined value P0, the amount of deposits deposited on the diffusion plate 23 increases and the passage area of the diffusion plate 23 decreases. It is estimated that it increased to P0 or more.
Therefore, when it is determined in step S3 that the value C of the integration counter has reached the predetermined value C0, or when it is determined that the exhaust pressure P in step S has increased to the predetermined value P0 or more, the process proceeds to step S5 and diffusion is performed. In order to remove the deposits deposited on the plate 23, the precipitate removing mechanism 21 is driven. That is, as described above, the actuator 15 is driven to bring the diffusion plates 23 into contact with each other, and the precipitate is crushed and removed.
ステップＳ６では、上記のようにして拡散板２３から連通路６壁上に落下した析出物を加熱する。あるいは、排気温度を上昇させる運転を行う。これにより、固形の析出物がガス化され、アンモニアガスとしてＳＣＲ触媒９に供給される。
このようにすれば、拡散板２３に析出物が所定量以上堆積する毎に拡散板２３同士を接触させて析出物を砕きつつ除去することができ、排気通路面積の減少による排気抵抗の増大、ひいてはエンジン出力の低減、燃費悪化を抑制して良好なエンジン性能を維持することができる。
In step S6, the precipitate that has dropped from the diffusion plate 23 onto the wall of the communication path 6 as described above is heated. Alternatively, an operation for increasing the exhaust temperature is performed. Thereby, the solid precipitate is gasified and supplied to the SCR catalyst 9 as ammonia gas.
In this way, each time deposits of a predetermined amount or more are deposited on the diffusion plate 23, the diffusion plates 23 can be brought into contact with each other to be removed while being crushed, and the exhaust resistance is increased by reducing the exhaust passage area. As a result, it is possible to maintain good engine performance by suppressing engine output reduction and fuel consumption deterioration.
特に、拡散板２３同士の接触により砕かれた析出物は、昇華されやすくなるため、ヒーター３３の加熱温度を低くしたり、加熱時間を短くしたりすることができ、燃費を向上できる。また、排気温度上昇運転で析出物を昇華する場合は、排気温度を下げたり、運転時間を短縮したりすることができ、燃費向上、排気エミッションの改善、及び、運転性向上を図れる。なお、析出物が昇華されやすくなることにより、ヒーターの設置を省略して排気温度上昇運転でも十分に昇華させることが可能となる場合もある。 In particular, since the precipitates crushed by the contact between the diffusion plates 23 are easily sublimated, the heating temperature of the heater 33 can be lowered, the heating time can be shortened, and fuel consumption can be improved. Further, when the precipitate is sublimated in the exhaust temperature increasing operation, the exhaust temperature can be lowered or the operation time can be shortened, so that the fuel consumption can be improved, the exhaust emission can be improved, and the drivability can be improved. In addition, since the precipitate is easily sublimated, it may be possible to sufficiently sublimate the exhaust gas temperature increase operation by omitting the installation of the heater.
また、拡散板２３上の析出物を砕くことにより、より効率的に除去することができるため、除去後、所定量に堆積するまでの時間を短縮でき、ひいては、燃費を向上できる。
なお、本制御では、排気温度（が所定値以下の積算時間）と、排気圧力との双方に基づいて、析出物堆積量を推定したが、簡易的にはいずれか一方のみに基づいて析出物堆積量を推定し、析出物除去機構を作動させる構成としてもよい。より簡易的には、キースイッチのＯＦＦ時に析出物除去機構を作動させる構成としてもよく、運転性への影響を回避できる。
Moreover, since it can remove more efficiently by crushing the deposit on the diffusion plate 23, it is possible to shorten the time until it is deposited to a predetermined amount after the removal, thereby improving the fuel efficiency.
In this control, the deposit accumulation amount is estimated based on both the exhaust temperature (the accumulated time when the exhaust gas is below a predetermined value) and the exhaust pressure. It is good also as a structure which estimates the amount of deposits and operates a deposit removal mechanism. More simply, the deposit removing mechanism may be operated when the key switch is turned off, and the influence on drivability can be avoided.
また、上記実施形態では、アクチュエータ２６の駆動軸２６ａを中立位置に対して伸張及び引込操作することにより、拡散板２３同士が接触する総面積を大きくして、析出物の除去効率を高めることができる。但し、簡易的には、中立位置に対して伸張または引込操作の一方のみを行う構成としてもよく、低コストのアクチュエータを使用できる。
また、上記実施形態では、各拡散板２３を、これらを貫通するロッド２５を用いて連動させる構成としたため、ロッド２５ないし駆動軸２６ａが一箇所で円筒状リング部材２２壁（排気通路壁）を貫通させれば済み、排気シール処理が容易に行える。
Further, in the above embodiment, by extending and retracting the drive shaft 26a of the actuator 26 with respect to the neutral position, the total area where the diffusion plates 23 come into contact with each other can be increased, and the precipitate removal efficiency can be increased. it can. However, for simplicity, it may be configured to perform only one of the extending and retracting operations with respect to the neutral position, and a low-cost actuator can be used.
Moreover, in the said embodiment, since each diffusion plate 23 was set as the structure linked using the rod 25 which penetrates these, the rod 25 thru | or the drive shaft 26a are the cylindrical ring member 22 wall (exhaust passage wall) in one place. It only needs to be penetrated, and the exhaust seal process can be performed easily.
但し、この構成に限らず、例えば、図５に示すように、各拡散板２３の支軸２４を、円筒状リング部材２２壁を貫通して外側に突出させ、これら支軸２４の突出端部にそれぞれレバー４１の一端部を連結し、該レバー４１の他端部に連結した一本のリンク４２をアクチュエータ２６に連結して駆動し、各拡散板２３を連動して回動させるような構成としてもよい。 However, the present invention is not limited to this configuration. For example, as shown in FIG. 5, the support shaft 24 of each diffusion plate 23 protrudes outward through the wall of the cylindrical ring member 22, and the protruding end portions of these support shafts 24. The one end of the lever 41 is connected to each other, and one link 42 connected to the other end of the lever 41 is connected to the actuator 26 and driven to rotate each diffusion plate 23 in conjunction with each other. It is good.
さらに、拡散板に堆積した析出物の除去操作をマニュアルで行う構成としてもよい。マニュアル操作としては、手動スイッチでアクチュエータを駆動する構成の他、アクチュエータを省略し、排気通路外側に突出させた拡散板連動機構の操作部材を手動操作する構成としてもよい。
また、アクチュエータとして駆動軸の駆動量をリニアに制御できる構成とし、排気流量に応じて拡散板の排気流通方向に対する傾斜角を可変に制御するようにしてもよい。例えば、排気流量の小さい低負荷運転時には、拡散板の排気流通方向に対する傾斜角を大きくして、拡散板通過時の絞り機能を増大させて拡散機能を高めることができる。
Furthermore, it is good also as a structure which performs the removal operation of the deposit deposited on the diffusion plate manually. As manual operation, in addition to the configuration in which the actuator is driven by a manual switch, the actuator may be omitted, and the operation member of the diffusion plate interlocking mechanism protruding outside the exhaust passage may be manually operated.
Further, the actuator may be configured such that the drive amount of the drive shaft can be linearly controlled, and the inclination angle of the diffusion plate with respect to the exhaust flow direction may be variably controlled in accordance with the exhaust flow rate. For example, at the time of low load operation with a small exhaust flow rate, the diffusion function can be enhanced by increasing the inclination angle of the diffusion plate with respect to the exhaust circulation direction and increasing the throttle function when passing through the diffusion plate.
１ ディーゼルエンジン
３ 排気通路
６ 連通路
９ ＳＣＲ触媒
１０ アンモニア酸化触媒
１１ 尿素水噴射ノズル
１２ 制御モジュール
２１ 析出物除去機構
２２ 円筒状リング部材
２３ 拡散板
２４ 支軸
２５ ロッド
２６ アクチュエータ
２６ａ 駆動軸
３１ 排気温度センサ
３２ 排気圧力センサ
５０ 電子制御ユニット（ＥＣＵ）
DESCRIPTION OF SYMBOLS 1 Diesel engine 3 Exhaust passage 6 Communication passage 9 SCR catalyst 10 Ammonia oxidation catalyst 11 Urea water injection nozzle 12 Control module 21 Precipitate removal mechanism 22 Cylindrical ring member 23 Diffusion plate 24 Support shaft 25 Rod 26 Actuator 26a Drive shaft 31 Exhaust temperature Sensor 32 Exhaust pressure sensor 50 Electronic control unit (ECU)
Claims (4)
前記還元触媒の排気上流に液体還元剤又はその前駆体を噴射供給する還元剤噴射ノズルと、
前記還元剤噴射ノズルと前記還元触媒との間に位置する排気管に配設されて、還元剤噴射ノズルから噴射された液体還元剤又はその前駆体を拡散する拡散装置と、
を含んで構成され、
前記拡散装置を、互いに平行な支軸周りに回動自由な複数の拡散板と、これら複数の拡散板を連動して回動させるように複数の拡散板に連結されたリンク機構と、を含んで構成すると共に、
前記複数の拡散板を、前記液体還元剤又はその前駆体を拡散させる通常位置から前記リンク機構を介して相異なる回動方向にそれぞれ回動させ、該拡散板同士の表裏面相互を接触させて各拡散板の表裏両面に堆積した析出物を除去する析出物除去機構と、
を含んで構成されたことを特徴とする内燃機関の排気浄化装置。 A reduction catalyst disposed in an exhaust pipe of an internal combustion engine for reducing and purifying nitrogen oxides using a reducing agent;
A reducing agent injection nozzle that injects and supplies a liquid reducing agent or a precursor thereof upstream of the exhaust of the reduction catalyst;
A diffusion device that is disposed in an exhaust pipe positioned between the reducing agent injection nozzle and the reduction catalyst, and diffuses the liquid reducing agent injected from the reducing agent injection nozzle or a precursor thereof;
Comprising
The diffusion device includes a plurality of diffusion plates that are freely rotatable around mutually parallel support shafts, and a link mechanism that is coupled to the plurality of diffusion plates so as to rotate the plurality of diffusion plates in conjunction with each other. And consisting of
The plurality of diffusion plates are respectively rotated in different rotation directions via the link mechanism from a normal position where the liquid reducing agent or its precursor is diffused, and the front and back surfaces of the diffusion plates are brought into contact with each other. A deposit removal mechanism for removing deposits deposited on the front and back surfaces of each diffusion plate;
An exhaust emission control device for an internal combustion engine, comprising:
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| KR101837559B1 (en) * | 2016-09-19 | 2018-03-12 | 융진기업 주식회사 | SCR Mixer Having Variable Vane And SCR Apparatus Including The Same |
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