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JP2011241766A - Two-stages supercharging system - Google Patents

Two-stages supercharging system Download PDF

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JP2011241766A
JP2011241766A JP2010114926A JP2010114926A JP2011241766A JP 2011241766 A JP2011241766 A JP 2011241766A JP 2010114926 A JP2010114926 A JP 2010114926A JP 2010114926 A JP2010114926 A JP 2010114926A JP 2011241766 A JP2011241766 A JP 2011241766A
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turbine
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pressure stage
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exhaust
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Koichi Hamaguchi
孝一 濱口
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Hino Motors Ltd
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Abstract

PROBLEM TO BE SOLVED: To prevent damaging caused by excessive revolutions of a high-pressure turbine and a low-pressure turbine by suppressing an increase in number of turbo revolutions at the stop time of exhaust gas recirculation.SOLUTION: The two-stages supercharging system configured to pull out a part of exhaust gas G from an exhaust system on the upstream side of a high-pressure turbine 2 to recirculate it to an intake system on the downstream side of a high-pressure compressor 3, and appropriately stop the recirculation, a high-pressure turbocharger 4 including a variable nozzle turbo, includes: a bypass flow path 11 for bypassing the exhaust gas G from the high-pressure turbine 2 around the low-pressure turbine 5 to guide it downstream of the low-pressure turbine 5; a bypass valve 12 located in the midway of the bypass flow path 11 to open/close the flow path; and a controller 13 for opening nozzle opening of the high-pressure turbine 2 by a necessary amount at the recirculation stop time of the exhaust gas G to reduce exhaust energy of the high-pressure stage, and opening an opening of the bypass valve 12 by a necessary amount to reduce a turbine gas amount of the low-pressure side.

Description

本発明は、二段過給システムに関するものである。   The present invention relates to a two-stage supercharging system.

近年、低中速域での燃費向上、トルクアップや高EGR率の実現のために、小径の高圧段ターボチャージャを採用した二段過給システムが検討されており、この種の二段過給システムにおいては、図3に示す如く、エンジン1から送出される排気Gにより高圧段タービン2を作動させ且つ高圧段コンプレッサ3で圧縮した吸気Aをエンジン1へ送給する高圧段ターボチャージャ4と、該高圧段ターボチャージャ4の高圧段タービン2から送出される排気Gにより低圧段タービン5を作動させ且つ低圧段コンプレッサ6で圧縮した吸気Aを前記高圧段コンプレッサ3へ送給する低圧段ターボチャージャ7とが備えられている。   In recent years, a two-stage turbocharging system that uses a small-diameter high-pressure turbocharger has been studied in order to improve fuel efficiency, increase torque, and achieve a high EGR rate at low and medium speeds. In the system, as shown in FIG. 3, a high-pressure stage turbocharger 4 that operates the high-pressure stage turbine 2 with exhaust G delivered from the engine 1 and supplies the intake air A compressed by the high-pressure stage compressor 3 to the engine 1; The low-pressure stage turbocharger 7 operates the low-pressure stage turbine 5 by the exhaust G sent from the high-pressure stage turbine 2 of the high-pressure stage turbocharger 4 and supplies the intake air A compressed by the low-pressure stage compressor 6 to the high-pressure stage compressor 3. And are provided.

また、高圧段タービン2より上流の排気系(具体的には排気マニホールド)から排気Gの一部を抜き出して高圧段コンプレッサ3より下流の吸気系(具体的には吸気マニホールド)に再循環するEGRライン8が設けられ、該EGRライン8には、排気系から分流した排気Gを冷却するEGRクーラ9と、吸気系へ還流すべき排気Gの流量を調整するEGRバルブ10とが設けられている。   In addition, EGR is extracted from an exhaust system (specifically, an exhaust manifold) upstream from the high-pressure stage turbine 2 and recirculated to an intake system (specifically, an intake manifold) downstream from the high-pressure stage compressor 3. A line 8 is provided, and the EGR line 8 is provided with an EGR cooler 9 that cools the exhaust gas G that has been diverted from the exhaust system, and an EGR valve 10 that adjusts the flow rate of the exhaust gas G to be recirculated to the intake system. .

而して、斯かる二段過給システムにおいては、エンジン1から送出される排気Gが、高圧段タービン2へ流入して高圧段コンプレッサ3を駆動した後、低圧段タービン5へ流入して低圧段コンプレッサ6を駆動し、該低圧段コンプレッサ6に流入して圧縮された吸気Aは、更に次の高圧段コンプレッサ3に送給されて再び圧縮されてからエンジン1へ送給されるので、該エンジン1におけるシリンダへの吸気Aの送給量が増加し、1サイクル当たりの燃料噴射量を多くすることでエンジン1の出力を高めることができる。   Thus, in such a two-stage supercharging system, the exhaust G delivered from the engine 1 flows into the high-pressure turbine 2 and drives the high-pressure compressor 3, and then flows into the low-pressure turbine 5 and low pressure. The intake air A which has driven the stage compressor 6 and has flowed into the low pressure stage compressor 6 and compressed is sent to the next high pressure stage compressor 3 and compressed again, and then sent to the engine 1. The supply amount of the intake air A to the cylinder in the engine 1 increases, and the output of the engine 1 can be increased by increasing the fuel injection amount per cycle.

また、前記排気Gの一部は、高圧段タービン2より上流の排気系からEGRライン8へ流入し、EGRクーラ9で冷却され且つEGRバルブ10で流量調整された後に吸気Aと一緒にエンジン1へ送給され、これによりシリンダ内の燃焼温度の低下が図られ、NOxの発生が低減される。   Further, a part of the exhaust G flows into the EGR line 8 from the exhaust system upstream of the high-pressure turbine 2, is cooled by the EGR cooler 9, and the flow rate is adjusted by the EGR valve 10, and then the engine 1 is combined with the intake A. Thus, the combustion temperature in the cylinder is lowered, and the generation of NOx is reduced.

この際、小径の高圧段ターボチャージャ4を採用した二段過給システムとしたことでターボ効率が既存の単段過給よりも向上されているので、従来通りの新気量を確保しながらも排気Gの再循環量をより多くすることができて高EGR率を実現することができる。   At this time, since the turbo efficiency is improved over the existing single-stage turbocharging by adopting a two-stage turbocharging system that employs a small-diameter high-pressure turbocharger 4, while maintaining the same amount of fresh air as before The recirculation amount of the exhaust G can be increased, and a high EGR rate can be realized.

尚、前述の如き二段過給システムと関連する一般的技術水準を示すものとしては、例えば、下記の特許文献1、2等が既に存在している。   For example, Patent Documents 1 and 2 listed below already exist as the general technical level related to the two-stage supercharging system as described above.

特開2005−147030号公報JP 2005-147030 A 特開平5−180089号公報JP-A-5-180089

しかしながら、斯かる従来の二段過給システムにおいては、寒冷地でのコールドスタート時等のように低水温条件下で暖機を行いたい場合や、パティキュレートフィルタに昇温した排気Gを導入して強制再生を行いたい場合、或いは、NOx低減触媒に昇温した排気Gを導入して触媒活性を上げたい場合等に、EGRクーラ9を迂回させることによる排気Gの温度低下を避けるべく排気再循環を停止すると、排気Gの一部が再循環しなくなる分だけタービンガス量が増加し、これら高圧段タービン2及び低圧段タービン5のターボ回転数が大幅に上昇してしまうので、運転条件によっては、これら高圧段タービン2及び低圧段タービン5が過回転により損傷する虞れがあった。   However, in such a conventional two-stage turbocharging system, when warming up under a low water temperature condition, such as at a cold start in a cold region, or by introducing a heated exhaust gas G to the particulate filter. When it is desired to perform forced regeneration, or when it is desired to increase the catalytic activity by introducing exhaust gas G that has been heated to the NOx reduction catalyst, the exhaust gas must be recirculated to avoid a decrease in the temperature of the exhaust gas G by bypassing the EGR cooler 9. When the circulation is stopped, the amount of turbine gas increases by the amount that a part of the exhaust G is not recirculated, and the turbo rotation speed of the high-pressure turbine 2 and the low-pressure turbine 5 is significantly increased. The high-pressure stage turbine 2 and the low-pressure stage turbine 5 may be damaged by excessive rotation.

即ち、通常の単段過給では、ターボ過回転が問題となり易い高速高負荷域でのEGR率が少ないため、排気再循環の停止時におけるタービンガス量の増加によるターボ回転数の上昇を、可変ノズルターボの採用によりベーン開度の変更で許容回転域に収めて対応することができるが、高EGR率を狙った二段過給システムにおいては、ターボマッチング上、通常の単段過給よりも小径のタービンやコンプレッサが使用されているため、排気再循環の停止時のターボ回転上昇が非常に厳しくなるという事情があった。   That is, in normal single-stage supercharging, turbo overspeed is likely to be a problem. Since the EGR rate in a high-speed and high-load region is small, the increase in turbo rotation speed due to the increase in the amount of turbine gas when exhaust recirculation is stopped can be varied. By adopting a nozzle turbo, the vane opening can be changed and accommodated within the allowable rotation range. However, in a two-stage turbocharging system aiming at a high EGR rate, the turbo matching is more efficient than a normal single-stage turbocharging. Since small-diameter turbines and compressors are used, the increase in turbo rotation when exhaust gas recirculation is stopped becomes extremely severe.

本発明は、斯かる実情に鑑みてなしたもので、排気再循環の停止時におけるターボ回転数の上昇を抑制して高圧段タービン及び低圧段タービンの過回転による損傷を防止することを目的としている。   The present invention has been made in view of such circumstances, and it is an object of the present invention to prevent damage caused by excessive rotation of a high-pressure turbine and a low-pressure turbine by suppressing an increase in turbo rotation speed when exhaust gas recirculation is stopped. Yes.

本発明は、エンジンから送出される排気によって高圧段タービンを作動させ且つ高圧段コンプレッサで圧縮した吸気をエンジンへ送給する高圧段ターボチャージャと、該高圧段ターボチャージャの高圧段タービンから送出される排気によって低圧段タービンを作動させ且つ低圧段コンプレッサで圧縮した吸気を前記高圧段コンプレッサへ送給する低圧段ターボチャージャとを備え、高圧段タービンより上流の排気系から排気の一部を抜き出して高圧段コンプレッサより下流の吸気系に再循環し且つその循環を適宜に停止し得るように構成した二段過給システムにおいて、高圧段ターボチャージャを可変ノズルターボで構成すると共に、高圧段タービンからの排気を低圧段タービンを迂回させて該低圧段タービンの下流へ導くバイパス流路と、該バイパス流路の途中に装備されて流路を開閉するバイパスバルブと、排気の再循環停止時に高圧段タービンのノズル開度を必要量開いて高圧段の排気エネルギーを下げ且つバイパスバルブの開度を必要量開いて低圧段のタービンガス量を下げる制御装置とを備えたことを特徴とするものである。   The present invention relates to a high-pressure stage turbocharger that operates a high-pressure stage turbine by exhaust gas delivered from an engine and supplies intake air compressed by a high-pressure stage compressor to the engine, and the high-pressure stage turbine of the high-pressure stage turbocharger. A low-pressure stage turbocharger that operates the low-pressure stage turbine by exhaust gas and feeds the intake air compressed by the low-pressure stage compressor to the high-pressure stage compressor, and extracts a part of the exhaust gas from the exhaust system upstream from the high-pressure stage turbine. In the two-stage turbocharging system configured to recirculate to the intake system downstream from the stage compressor and stop the circulation appropriately, the high-pressure stage turbocharger is configured with a variable nozzle turbo and the exhaust from the high-pressure stage turbine. A bypass flow path that bypasses the low-pressure turbine and leads downstream of the low-pressure turbine; A bypass valve that is installed in the middle of the bypass flow path and opens and closes the flow path, and when the exhaust gas recirculation is stopped, the nozzle opening of the high pressure stage turbine is opened by a necessary amount to reduce the exhaust energy of the high pressure stage and the opening of the bypass valve. And a control device that opens the necessary amount to lower the turbine gas amount in the low-pressure stage.

而して、このようにすれば、排気の再循環停止時に排気の一部が再循環しなくなることでタービンガス量が増加しても、制御装置により高圧段タービンのノズル開度が必要量開けられて高圧段の排気エネルギーが下がり、バイパスバルブの開度も必要量開けられて低圧段のタービンガス量が下がるので、高圧段タービン及び低圧段タービンの夫々におけるターボ回転数の上昇が抑制されて過回転が防止される。   Thus, in this way, even if the amount of turbine gas increases because a part of the exhaust gas is not recirculated when the exhaust gas recirculation is stopped, the control device opens the required amount of nozzle opening of the high-pressure turbine. As a result, the exhaust energy of the high-pressure stage is reduced, the opening amount of the bypass valve is opened, and the amount of turbine gas in the low-pressure stage is reduced, so that an increase in turbo rotation speed in each of the high-pressure stage turbine and the low-pressure stage turbine is suppressed. Over-rotation is prevented.

また、低圧段タービンの下流にパティキュレートフィルタやNOx低減触媒が装備されていて、これらを昇温したいがために排気の再循環が停止されているような場合には、高圧段タービンからの排気を低圧段タービンを迂回させることで該低圧段タービンにおける膨張仕事がなくなって排気温度がより高い温度に維持されるという付帯的な効果も得られる。特に低圧段タービンの下流にNOx低減触媒が装備されている場合には、該NOx低減触媒が昇温されて触媒活性が高められることでNOx還元反応が促進され、排気の再循環停止時におけるNOxの増加が抑制されることになる。   In addition, if a particulate filter or NOx reduction catalyst is installed downstream of the low-pressure stage turbine and the exhaust gas recirculation is stopped because it is desired to raise the temperature, the exhaust gas from the high-pressure stage turbine By bypassing the low-pressure turbine, an additional effect that expansion work in the low-pressure turbine is eliminated and the exhaust temperature is maintained at a higher temperature can be obtained. In particular, when a NOx reduction catalyst is equipped downstream of the low-pressure turbine, the NOx reduction catalyst is heated to increase the catalytic activity, thereby promoting the NOx reduction reaction, and NOx when exhaust gas recirculation is stopped. The increase of is suppressed.

更に、本発明をより具体的に実施するに際しては、高圧段タービンのノズル開度とバイパスバルブの開度を制御する制御装置が、エンジンの回転数と燃料噴射量とに基づき排気の再循環停止時専用の制御マップから高圧段タービンのノズル開度とバイパスバルブの開度を読み出して制御を行うように構成されていることが好ましい。   Furthermore, when carrying out the present invention more specifically, the control device for controlling the nozzle opening of the high-pressure turbine and the opening of the bypass valve is configured to stop the recirculation of exhaust gas based on the engine speed and the fuel injection amount. It is preferable that the control is performed by reading the nozzle opening of the high-pressure turbine and the opening of the bypass valve from the control map dedicated to the hour.

また、排気の再循環停止時専用の制御マップから読み出した高圧段タービンのノズル開度とバイパスバルブの開度をエンジンの冷却水温度、吸気温度、気圧に基づき補正してから制御を行うようにすると更に良い。   In addition, control is performed after correcting the nozzle opening of the high-pressure turbine and the opening of the bypass valve read from the control map dedicated to when exhaust gas recirculation is stopped based on the engine coolant temperature, intake air temperature, and air pressure. Then better.

本発明の二段過給システムによれば、下記の如き種々の優れた効果を奏し得る。   According to the two-stage supercharging system of the present invention, various excellent effects as described below can be obtained.

(I)排気の再循環停止時に排気の一部が再循環しなくなることでタービンガス量が増加しても、制御装置により高圧段タービンのノズル開度を必要量開けて高圧段の排気エネルギーを下げ、バイパスバルブの開度も必要量開けて低圧段のタービンガス量を下げることができ、これにより高圧段タービン及び低圧段タービンの夫々におけるターボ回転数の上昇を抑制することができるので、高圧段タービン及び低圧段タービンの過回転による損傷を未然に防止することができる。   (I) Even if the amount of turbine gas increases because a part of the exhaust gas is not recirculated when the exhaust gas recirculation is stopped, the controller opens the required amount of nozzle pressure of the high pressure stage turbine to increase the exhaust energy of the high pressure stage. Lowering the opening of the bypass valve and opening the required amount to lower the turbine gas amount in the low-pressure stage, which can suppress the increase in the turbo rotation speed in each of the high-pressure turbine and the low-pressure turbine. Damage due to excessive rotation of the stage turbine and the low-pressure stage turbine can be prevented in advance.

(II)高圧段タービンからの排気を低圧段タービンを迂回させることで該低圧段タービンにおける膨張仕事をなくし、排気温度をより高い温度に維持することができるので、低圧段タービンの下流にパティキュレートフィルタやNOx低減触媒が装備されていて、これらを昇温したいがために排気の再循環を停止するような場合には、排気温度を相乗的に高めてパティキュレートフィルタやNOx低減触媒の良好な昇温を図ることができ、特に低圧段タービンの下流にNOx低減触媒が装備されている場合には、NOx低減触媒を昇温して触媒活性を高めることでNOx還元反応を促進し、排気の再循環停止時におけるNOxの増加を抑制することができる。   (II) By bypassing the exhaust from the high-pressure stage turbine to the low-pressure stage turbine, the expansion work in the low-pressure stage turbine can be eliminated, and the exhaust temperature can be maintained at a higher temperature. If a filter or NOx reduction catalyst is installed and the exhaust gas recirculation is stopped because it is desired to raise the temperature, the exhaust gas temperature must be increased synergistically to improve the performance of the particulate filter or NOx reduction catalyst. In particular, when a NOx reduction catalyst is equipped downstream of the low-pressure stage turbine, the NOx reduction catalyst is heated to increase the catalytic activity to promote the NOx reduction reaction, and An increase in NOx at the time of recirculation stop can be suppressed.

本発明を実施する形態の一例を示す概略図である。It is the schematic which shows an example of the form which implements this invention. 制御装置による具体的な制御手順を示すフローチャートである。It is a flowchart which shows the specific control procedure by a control apparatus. 従来例を示す概略図である。It is the schematic which shows a prior art example.

以下、本発明の実施の形態を添付図面を参照して説明する。   Embodiments of the present invention will be described below with reference to the accompanying drawings.

図1及び図2は本発明を実施する形態の一例を示すもので、図3と同一の符号を付した部分は同一物を表わしている。   1 and 2 show an example of an embodiment for carrying out the present invention, and portions denoted by the same reference numerals as those in FIG. 3 represent the same items.

図1に全体図を示す如く、本形態例の二段過給システムにおいては、先に図3で説明した従来の二段過給システムと基本的な構成は同様であるが、従来の二段過給システムに用いられていた高圧段ターボチャージャ4を可変ノズルターボで構成しており、しかも、高圧段タービン2からの排気Gを低圧段タービン5を迂回させて該低圧段タービン5の下流へ導くバイパス流路11と、該バイパス流路11の途中に装備されて流路を開閉するバイパスバルブ12と、排気Gの再循環停止時に高圧段タービン2のノズル開度を必要量開いて高圧段の排気エネルギーを下げ且つバイパスバルブ12の開度を必要量開いて低圧段のタービンガス量を下げる制御装置13とを備えている。   As shown in FIG. 1, the basic configuration of the two-stage turbocharging system of this embodiment is the same as that of the conventional two-stage turbocharging system described above with reference to FIG. The high-pressure stage turbocharger 4 used in the supercharging system is composed of a variable nozzle turbo, and the exhaust G from the high-pressure stage turbine 2 bypasses the low-pressure stage turbine 5 and goes downstream of the low-pressure stage turbine 5. A bypass flow path 11 to be guided, a bypass valve 12 that is provided in the middle of the bypass flow path 11 to open and close the flow path, and opens the nozzle opening degree of the high pressure turbine 2 when a recirculation stop of the exhaust gas G is opened. And a control device 13 for lowering the amount of turbine gas in the low-pressure stage by lowering the exhaust energy of the engine and opening the necessary opening of the bypass valve 12.

前記高圧段ターボチャージャ4は、既存の可変ノズルターボと同等の構造を有するもので良く、例えば、高圧段ターボチャージャ4のタービンスクロール内におけるノズル部に角度調整可能な多数のノズルベーンを環状に備え、該各ノズルベーンをリングプレート等を介しアクチュエータ14により連動して傾動操作し得るようにすれば良い。   The high-pressure stage turbocharger 4 may have a structure equivalent to an existing variable nozzle turbo. For example, the nozzle section in the turbine scroll of the high-pressure stage turbocharger 4 is annularly provided with a number of nozzle vanes that can be adjusted in angle. The nozzle vanes may be tilted in conjunction with the actuator 14 via a ring plate or the like.

また、前記制御装置13にあっては、エンジン1の別の制御系から導いたエンジン1の回転数を示す検出信号15、エンジン1の燃料噴射量を示す検出信号16、排気Gの再循環の停止(EGRバルブ10の閉止)を指示するEGRカット信号17、エンジン1の冷却水の温度を示す検出信号18、吸気Aの温度を示す検出信号19、気圧を示す検出信号20が入力されるようになっており、これらの各種信号に基づき以下に詳述する制御手順により制御値を決定して前記高圧段タービン2のアクチュエータ14及びバイパスバルブ12に向け制御信号21,22を出力し得るようにしてある。   In the control device 13, a detection signal 15 indicating the number of revolutions of the engine 1 derived from another control system of the engine 1, a detection signal 16 indicating the fuel injection amount of the engine 1, and a recirculation of the exhaust G An EGR cut signal 17 for instructing the stop (closing of the EGR valve 10), a detection signal 18 indicating the temperature of the cooling water of the engine 1, a detection signal 19 indicating the temperature of the intake air A, and a detection signal 20 indicating the atmospheric pressure are input. Based on these various signals, control values are determined by a control procedure described in detail below so that control signals 21 and 22 can be output to the actuator 14 and the bypass valve 12 of the high-pressure turbine 2. It is.

即ち、前記制御装置13においては、図2にフローチャートで示す如き制御手順で高圧段タービン2のアクチュエータ14及びバイパスバルブ12の制御が行われるようになっており、先ずステップS1で排気Gの再循環の停止(EGRバルブ10の閉止)を指示するEGRカット信号17がオンであるか否かが判定されるようになっている。   That is, in the control device 13, the actuator 14 and the bypass valve 12 of the high-pressure turbine 2 are controlled according to the control procedure shown in the flowchart of FIG. 2, and first, the exhaust gas G is recirculated in step S1. It is determined whether or not the EGR cut signal 17 for instructing the stop (closing of the EGR valve 10) is ON.

そして、ステップS1でEGRカット信号17がオンであるとの判定が成された場合には、次のステップS2へと進んで、検出信号15,16から判るエンジン1の回転数と燃料噴射量とに基づきEGRカットモード用(排気Gの再循環停止時専用)の制御マップから高圧段タービン2のノズル開度とバイパスバルブ12の開度が読み出され、次いで、次のステップS3にて前記制御マップから読み出された高圧段タービン2のノズル開度とバイパスバルブ12の開度が、エンジン1の冷却水温度、吸気温度、気圧に基づき補正されてから制御信号21,22として出力されるようになっている。   If it is determined in step S1 that the EGR cut signal 17 is ON, the process proceeds to the next step S2, and the engine speed and fuel injection amount determined from the detection signals 15 and 16 are determined. Based on the control map for the EGR cut mode (exclusive when the exhaust gas G is recirculated and stopped), the nozzle opening degree of the high-pressure turbine 2 and the opening degree of the bypass valve 12 are read out, and then the control is performed in the next step S3. The nozzle opening degree of the high-pressure turbine 2 and the opening degree of the bypass valve 12 read from the map are corrected based on the cooling water temperature, the intake air temperature, and the atmospheric pressure of the engine 1 so as to be output as the control signals 21 and 22. It has become.

ここで、前記制御マップは、排気Gの再循環を停止した状態において、高圧段タービン2及び低圧段タービン5の過回転を効果的に回避し得る制御値を、エンジン1の回転数と燃料噴射量が異なる様々な運転状態に関し実験により検証して作成したものであり、実測のエンジン1の回転数と燃料噴射量とが判れば、前記制御マップから適切な高圧段タービン2のノズル開度とバイパスバルブ12の開度とを読み出せるようになっている。   Here, the control map shows the control value that can effectively avoid over-rotation of the high-pressure turbine 2 and the low-pressure turbine 5 in a state where the recirculation of the exhaust G is stopped, and the rotational speed of the engine 1 and the fuel injection. Various operational states with different amounts were verified by experimentation, and if the actually measured engine speed and fuel injection amount were found, the appropriate nozzle opening of the high-pressure turbine 2 and The opening degree of the bypass valve 12 can be read out.

尚、高圧段タービン2のノズル開度とバイパスバルブ12の開度は、エンジン1の冷却水温度、吸気温度、気圧によりエンジン性能やタービン流量が変化するため、前記制御マップから読み出された高圧段タービン2のノズル開度とバイパスバルブ12の開度に関し、エンジン1の冷却水温度、吸気温度、気圧に基づき適切な補正係数を乗算して補正を行うようにしているが、この補正係数も実験により検証して作成したものである。   The nozzle opening degree of the high-pressure turbine 2 and the opening degree of the bypass valve 12 change the engine performance and the turbine flow rate depending on the cooling water temperature, the intake air temperature, and the atmospheric pressure of the engine 1. The nozzle opening of the stage turbine 2 and the opening of the bypass valve 12 are corrected by multiplying an appropriate correction coefficient based on the coolant temperature, intake air temperature, and atmospheric pressure of the engine 1. It was created by verification through experiments.

また、先のステップS1でEGRカット信号17がオンであるとの判定が成されなかった場合には、ステップS4へ進んでEGRモード用(排気Gの再循環時専用)の制御マップから高圧段タービン2のノズル開度とバイパスバルブ12の開度が読み出され、次いで、次のステップS5にて前記制御マップから読み出された高圧段タービン2のノズル開度とバイパスバルブ12の開度が、エンジン1の冷却水温度、吸気温度、気圧に基づき補正されてから制御信号21,22として出力されるようになっている。   If it is not determined in step S1 that the EGR cut signal 17 is ON, the process proceeds to step S4, and the high pressure stage is determined from the control map for the EGR mode (exclusive for exhaust gas recirculation). The nozzle opening of the turbine 2 and the opening of the bypass valve 12 are read out, and then the nozzle opening of the high-pressure turbine 2 and the opening of the bypass valve 12 read from the control map in the next step S5. The control signals 21 and 22 are output after correction based on the coolant temperature, intake air temperature, and atmospheric pressure of the engine 1.

尚、排気Gの再循環時にあっては、高圧段ターボチャージャ4が可変ノズルターボで構成されているので、高圧段タービン2の排気エネルギーを重視してノズル開度を制御するようにすれば良く、また、バイパスバルブ12の開度については、基本的に全閉として良いが、必要に応じて所要の開度で開けるようにしても良い。   When the exhaust gas G is recirculated, since the high-pressure stage turbocharger 4 is composed of a variable nozzle turbo, it is only necessary to control the nozzle opening with an emphasis on the exhaust energy of the high-pressure stage turbine 2. The opening of the bypass valve 12 may be basically fully closed, but may be opened at a required opening as required.

而して、このように二段過給システムを構成すれば、排気Gの再循環停止時に排気Gの一部が再循環しなくなることでタービンガス量が増加しても、制御装置13により高圧段タービン2のノズル開度が必要量開けられて高圧段の排気エネルギーが下がり、バイパスバルブ12の開度も必要量開けられて低圧段のタービンガス量が下がるので、高圧段タービン2及び低圧段タービン5の夫々におけるターボ回転数の上昇が抑制されて過回転が防止される。   Thus, if the two-stage supercharging system is configured in this way, even if the amount of turbine gas increases because a part of the exhaust G is not recirculated when the recirculation of the exhaust G is stopped, the controller 13 increases the pressure. The required amount of nozzle opening of the stage turbine 2 is opened to lower the exhaust energy of the high pressure stage, and the opening amount of the bypass valve 12 is also opened to reduce the amount of turbine gas in the low pressure stage. An increase in the turbo rotational speed in each of the turbines 5 is suppressed and over-rotation is prevented.

また、低圧段タービン5の下流にパティキュレートフィルタやNOx低減触媒が装備されていて、これらを昇温したいがために排気Gの再循環が停止されているような場合には、高圧段タービン2からの排気Gを低圧段タービン5を迂回させることで該低圧段タービン5における膨張仕事がなくなって排気温度がより高い温度に維持されるという付帯的な効果も得られる。特に低圧段タービン5の下流にNOx低減触媒が装備されている場合には、該NOx低減触媒が昇温されて触媒活性が高められることでNOx還元反応が促進され、排気Gの再循環停止時におけるNOxの増加が抑制されることになる。   In addition, when a particulate filter or a NOx reduction catalyst is provided downstream of the low-pressure stage turbine 5 and the recirculation of the exhaust G is stopped because it is desired to raise the temperature thereof, the high-pressure stage turbine 2 By diverting the exhaust G from the low-pressure stage turbine 5, expansion work in the low-pressure stage turbine 5 is eliminated, and an incidental effect that the exhaust temperature is maintained at a higher temperature is also obtained. In particular, when a NOx reduction catalyst is installed downstream of the low-pressure stage turbine 5, the NOx reduction catalyst is heated to increase the catalytic activity, thereby promoting the NOx reduction reaction. The increase in NOx at the point is suppressed.

従って、上記形態例によれば、排気Gの再循環停止時に排気Gの一部が再循環しなくなることでタービンガス量が増加しても、制御装置13により高圧段タービン2のノズル開度を必要量開けて高圧段の排気エネルギーを下げ、バイパスバルブ12の開度も必要量開けて低圧段のタービンガス量を下げることができ、これにより高圧段タービン2及び低圧段タービン5の夫々におけるターボ回転数の上昇を抑制することができるので、高圧段タービン2及び低圧段タービン5の過回転による損傷を未然に防止することができる。   Therefore, according to the above embodiment, even when the amount of turbine gas increases because a part of the exhaust gas G is not recirculated when the recirculation of the exhaust gas G is stopped, the control device 13 controls the nozzle opening degree of the high pressure turbine 2. The required amount can be opened to lower the exhaust energy of the high-pressure stage, and the opening degree of the bypass valve 12 can also be opened to reduce the amount of turbine gas in the low-pressure stage, whereby the turbo in each of the high-pressure turbine 2 and the low-pressure turbine 5 can be reduced. Since an increase in the rotational speed can be suppressed, damage due to excessive rotation of the high-pressure turbine 2 and the low-pressure turbine 5 can be prevented in advance.

また、高圧段タービン2からの排気Gを低圧段タービン5を迂回させることで該低圧段タービン5における膨張仕事をなくし、排気温度をより高い温度に維持することができるので、低圧段タービン5の下流にパティキュレートフィルタやNOx低減触媒が装備されていて、これらを昇温したいがために排気Gの再循環を停止するような場合には、排気温度を相乗的に高めてパティキュレートフィルタやNOx低減触媒の良好な昇温を図ることができ、特に低圧段タービン5の下流にNOx低減触媒が装備されている場合には、NOx低減触媒を昇温して触媒活性を高めることでNOx還元反応を促進し、排気Gの再循環停止時におけるNOxの増加を抑制することができる。   Further, by bypassing the exhaust G from the high-pressure stage turbine 2 through the low-pressure stage turbine 5, the expansion work in the low-pressure stage turbine 5 can be eliminated and the exhaust temperature can be maintained at a higher temperature. When a particulate filter or NOx reduction catalyst is installed downstream, and when it is desired to raise the temperature of the exhaust gas and recirculation of the exhaust G is stopped, the exhaust gas temperature is increased synergistically to increase the particulate filter or NOx. The temperature of the reduction catalyst can be increased satisfactorily. In particular, when a NOx reduction catalyst is equipped downstream of the low-pressure stage turbine 5, the NOx reduction reaction is performed by raising the temperature of the NOx reduction catalyst and increasing the catalytic activity. And the increase in NOx at the time of recirculation stop of the exhaust G can be suppressed.

尚、本発明の二段過給システムは、上述の形態例にのみ限定されるものではなく、高圧段タービンのノズル開度とバイパスバルブの開度の制御については、必ずしもエンジンの回転数と燃料噴射量との制御マップに基づいて行うことに限定されないこと、その他、本発明の要旨を逸脱しない範囲内において種々変更を加え得ることは勿論である。   Note that the two-stage turbocharging system of the present invention is not limited to the above-described embodiment. The control of the opening degree of the nozzle and the bypass valve of the high-pressure turbine is not necessarily limited to the engine speed and the fuel. Of course, the present invention is not limited to the control based on the injection amount control map, and various modifications can be made without departing from the scope of the present invention.

1 エンジン
2 高圧段タービン
3 高圧段コンプレッサ
4 高圧段ターボチャージャ
5 低圧段タービン
6 低圧段コンプレッサ
7 低圧段ターボチャージャ
8 EGRライン
11 バイパス流路
12 バイパスバルブ
13 制御装置
21 制御信号
22 制御信号
A 吸気
G 排気
DESCRIPTION OF SYMBOLS 1 Engine 2 High pressure stage turbine 3 High pressure stage compressor 4 High pressure stage turbocharger 5 Low pressure stage turbine 6 Low pressure stage compressor 7 Low pressure stage turbocharger 8 EGR line 11 Bypass flow path 12 Bypass valve 13 Controller 21 Control signal 22 Control signal A Intake G exhaust

Claims (3)

エンジンから送出される排気によって高圧段タービンを作動させ且つ高圧段コンプレッサで圧縮した吸気をエンジンへ送給する高圧段ターボチャージャと、該高圧段ターボチャージャの高圧段タービンから送出される排気によって低圧段タービンを作動させ且つ低圧段コンプレッサで圧縮した吸気を前記高圧段コンプレッサへ送給する低圧段ターボチャージャとを備え、高圧段タービンより上流の排気系から排気の一部を抜き出して高圧段コンプレッサより下流の吸気系に再循環し且つその循環を適宜に停止し得るように構成した二段過給システムにおいて、高圧段ターボチャージャを可変ノズルターボで構成すると共に、高圧段タービンからの排気を低圧段タービンを迂回させて該低圧段タービンの下流へ導くバイパス流路と、該バイパス流路の途中に装備されて流路を開閉するバイパスバルブと、排気の再循環停止時に高圧段タービンのノズル開度を必要量開いて高圧段の排気エネルギーを下げ且つバイパスバルブの開度を必要量開いて低圧段のタービンガス量を下げる制御装置とを備えたことを特徴とする二段過給システム。   A high-pressure stage turbocharger that operates a high-pressure stage turbine by exhaust gas sent from the engine and supplies intake air compressed by a high-pressure stage compressor to the engine, and a low-pressure stage by exhaust gas sent from the high-pressure stage turbine of the high-pressure stage turbocharger A low-pressure stage turbocharger that operates the turbine and feeds the intake air compressed by the low-pressure stage compressor to the high-pressure stage compressor, and extracts a part of the exhaust gas from the exhaust system upstream from the high-pressure stage turbine and downstream from the high-pressure stage compressor. In the two-stage turbocharging system configured to recirculate to the intake system of the engine and to stop the circulation appropriately, the high-pressure stage turbocharger is composed of a variable nozzle turbo and the exhaust from the high-pressure stage turbine is discharged to the low-pressure stage turbine. A bypass flow path that bypasses the low-pressure turbine and bypasses the low-pressure turbine, and the bypass A bypass valve that is installed in the middle of the road and opens and closes the flow path, and when the exhaust recirculation is stopped, the nozzle opening of the high pressure stage turbine is opened by a necessary amount to lower the exhaust energy of the high pressure stage and the opening amount of the bypass valve is necessary. A two-stage turbocharging system comprising: a control device that opens to lower a turbine gas amount in a low-pressure stage. 高圧段タービンのノズル開度とバイパスバルブの開度を制御する制御装置が、エンジンの回転数と燃料噴射量とに基づき排気の再循環停止時専用の制御マップから高圧段タービンのノズル開度とバイパスバルブの開度を読み出して制御を行うように構成されていることを特徴とする請求項1に記載の二段過給システム。   The control device for controlling the nozzle opening of the high-pressure turbine and the opening of the bypass valve determines whether the nozzle opening of the high-pressure turbine is determined from a dedicated control map for exhaust gas recirculation stop based on the engine speed and the fuel injection amount. The two-stage turbocharging system according to claim 1, wherein the two-stage supercharging system is configured to perform control by reading an opening degree of the bypass valve. 排気の再循環停止時専用の制御マップから読み出した高圧段タービンのノズル開度とバイパスバルブの開度をエンジンの冷却水温度、吸気温度、気圧に基づき補正してから制御を行うように制御装置が構成されていることを特徴とする請求項2に記載の二段過給システム。   Control device that performs control after correcting the nozzle opening of the high-pressure turbine and the opening of the bypass valve based on the engine coolant temperature, intake air temperature, and air pressure, read from the control map dedicated for exhaust gas recirculation stop The two-stage supercharging system according to claim 2, wherein:
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JP2015108312A (en) * 2013-12-04 2015-06-11 川崎重工業株式会社 Engine system
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