JP5912240B2 - Exhaust gas recirculation device - Google Patents

Exhaust gas recirculation device Download PDF

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JP5912240B2
JP5912240B2 JP2010239645A JP2010239645A JP5912240B2 JP 5912240 B2 JP5912240 B2 JP 5912240B2 JP 2010239645 A JP2010239645 A JP 2010239645A JP 2010239645 A JP2010239645 A JP 2010239645A JP 5912240 B2 JP5912240 B2 JP 5912240B2
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intake
passage
exhaust
egr
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JP2012092702A (en
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義幸 阿部
義幸 阿部
知宏 菅野
知宏 菅野
治世 木村
治世 木村
飯島 章
章 飯島
功 橘川
功 橘川
直樹 石橋
直樹 石橋
翔吾 坂下
翔吾 坂下
由加利 水島
由加利 水島
朝幸 伊藤
朝幸 伊藤
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いすゞ自動車株式会社
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    • YGENERAL 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
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02TCLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
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    • Y02T10/10Internal combustion engine [ICE] based vehicles
    • Y02T10/12Improving ICE efficiencies

Description

本発明は、エンジンの排気通路内の排気ガスの一部を吸気通路内に還流させる排気ガス還流装置に関する。   The present invention relates to an exhaust gas recirculation device that recirculates a part of exhaust gas in an exhaust passage of an engine into an intake passage.

EGR(排気ガス再循環)は、エンジンの排気通路内の排気ガスの一部をEGR通路を介して吸気通路内に再循環(還流)させることで、内燃機関の燃焼状態を制御して排気ガスのNOx発生量を抑える技術である。排気ガスを吸気通路内に還流させる際は、EGR通路の排気側圧力と吸気側圧力との圧力差をEGR通路に設けたEGRバルブの開度により制御することで、所定のEGRガス量(排気ガスの還流量)の排気ガスを吸気通路内に導入させている。   In EGR (exhaust gas recirculation), a part of the exhaust gas in the exhaust passage of the engine is recirculated (recirculated) into the intake passage through the EGR passage, thereby controlling the combustion state of the internal combustion engine and exhaust gas. This is a technique for reducing the amount of NOx generated. When the exhaust gas is recirculated into the intake passage, the pressure difference between the exhaust side pressure and the intake side pressure in the EGR passage is controlled by the opening degree of the EGR valve provided in the EGR passage, so that a predetermined EGR gas amount (exhaust gas) Exhaust gas (gas recirculation amount) is introduced into the intake passage.

特開2007−85248号公報JP 2007-85248 A

ターボ付エンジンにおいては、ターボのコンプレッサ側圧力(コンプレッサよりも下流の吸気通路内の圧力)が高くなるに従い、タービン側圧力(タービンよりも上流の排気通路内の圧力)に対するコンプレッサ側圧力の圧力差が小さくなる為、多量のEGRガス量の排気ガスを確保することが困難になってくる。このような運転条件(エンジンの高負荷高回転運転領域)では、吸気通路に設けた吸入空気絞り弁の開度を絞ることで、EGR通路の吸気側圧力が排気側圧力よりも低くなるように制御を行って、所定のEGRガス量を確保している。その際、吸入空気絞り弁の開度を絞る為、吸入空気量(新気量)が少なくなり、エンジン出力が低くなってしまう。   In a turbo engine, the pressure difference between the compressor side pressure and the turbine side pressure (pressure in the exhaust passage upstream from the turbine) as the turbo compressor side pressure (pressure in the intake passage downstream from the compressor) increases. Therefore, it becomes difficult to secure a large amount of exhaust gas of EGR gas. Under such operating conditions (engine high-load high-speed operation region), the intake-side pressure in the EGR passage is made lower than the exhaust-side pressure by restricting the opening of the intake air throttle valve provided in the intake passage. Control is performed to secure a predetermined amount of EGR gas. At that time, since the opening degree of the intake air throttle valve is reduced, the intake air amount (fresh air amount) is reduced and the engine output is reduced.

そこで、本発明の目的は、エンジンの高負荷高回転運転領域において、所望の吸入空気量を確保しつつ所望のEGRガス量も確保することにある。   Accordingly, an object of the present invention is to secure a desired EGR gas amount while securing a desired intake air amount in a high-load high-rotation operation region of the engine.

前記目的を達成する為に、本発明は、エンジンに直列に装着された高圧段ターボ及び低圧段ターボと、前記高圧段ターボの高圧段タービンと高圧段コンプレッサとを連結する回転軸に装着された電動機と、前記高圧段タービンよりも上流の前記エンジンの排気通路と前記高圧段コンプレッサよりも下流の前記エンジンの吸気通路とを連通するEGR通路と、該EGR通路に配設されたEGRバルブと、前記排気通路に接続され前記高圧段タービンをバイパスする排気バイパス通路と、該排気バイパス通路に配設された排気バイパスバルブと、前記吸気通路に接続され前記高圧段コンプレッサをバイパスする吸気バイパス通路と、該吸気バイパス通路に配設された吸気バイパスバルブと、前記エンジンの運転状態を検出する運転状態検出手段と、前記電動機、前記EGRバルブ、前記排気バイパスバルブ及び前記吸気バイパスバルブを制御する制御手段とを備え、該制御手段は、前記運転状態検出手段により前記エンジンの高負荷高回転運転状態を検出したときに、前記EGRバルブ及び前記吸気バイパスバルブを開とすると共に、前記排気バイパスバルブの開度を絞り、且つ、前記高圧段ターボが逆回転するように前記電動機を駆動することで、前記高圧段タービンよりも上流の前記排気通路内の圧力を、前記高圧段コンプレッサよりも下流の前記吸気通路内の圧力よりも高くするものである。   In order to achieve the above object, the present invention is mounted on a rotary shaft that connects a high-pressure stage turbo and a low-pressure stage turbo installed in series with an engine, and a high-pressure stage turbine and a high-pressure stage compressor of the high-pressure stage turbo. An EGR passage that communicates an electric motor, an exhaust passage of the engine upstream of the high-pressure turbine, and an intake passage of the engine downstream of the high-pressure compressor; an EGR valve disposed in the EGR passage; An exhaust bypass passage connected to the exhaust passage and bypassing the high-pressure turbine; an exhaust bypass valve disposed in the exhaust bypass passage; an intake bypass passage connected to the intake passage and bypassing the high-pressure compressor; An intake bypass valve disposed in the intake bypass passage, and an operating state detecting means for detecting an operating state of the engine; Control means for controlling the electric motor, the EGR valve, the exhaust bypass valve, and the intake bypass valve, and the control means detects a high load high rotation operation state of the engine by the operation state detection means. The EGR valve and the intake bypass valve are opened, the opening degree of the exhaust bypass valve is reduced, and the electric motor is driven so that the high-pressure turbo is reversely rotated. The pressure in the exhaust passage upstream is higher than the pressure in the intake passage downstream of the high-pressure compressor.

前記制御手段は、前記EGRバルブ及び前記吸気バイパスバルブの開度を一定に維持にした状態で、前記排気バイパスバルブの開度を変化させることで、吸入空気量及びEGRガス量を調節するものであっても良い。   The control means adjusts the intake air amount and the EGR gas amount by changing the opening degree of the exhaust bypass valve while maintaining the opening degree of the EGR valve and the intake bypass valve constant. There may be.

本発明によれば、エンジンの高負荷高回転運転領域において、所望の吸入空気量を確保しつつ所望のEGRガス量も確保することが出来るという優れた効果を奏する。   According to the present invention, there is an excellent effect that it is possible to secure a desired EGR gas amount while securing a desired intake air amount in a high-load, high-speed operation region of the engine.

本発明の一実施形態に係る排気ガス還流装置の概略図である。It is the schematic of the exhaust-gas recirculation apparatus which concerns on one Embodiment of this invention. 高圧段ターボ及び低圧段ターボの作動領域のイメージを示す図である。It is a figure which shows the image of the operation area | region of a high pressure stage turbo and a low pressure stage turbo.

以下、本発明の好適な実施形態を添付図面に基づいて詳述する。   DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

図1中、1はエンジン(本実施形態では、ディーゼルエンジン)、2は電動機付き高圧段ターボ(以下、高圧段ターボともいう)、3は低圧段ターボ、4はエンジン1の吸気ポートに連通する吸気ダクト(吸気通路)、5はエンジン1の排気ポートに連通する排気ダクト(排気通路)、6は制御手段としてのエンジン制御ユニット(以下、ECUという)、7はエンジンのシリンダ内(燃焼室内)に燃料を噴射する燃料噴射装置(インジェクタ)、8はエンジン回転数を検出するエンジン回転センサ(図示例では、クランク角センサ)、9はアクセル開度(アクセルペダルの踏み込み量)を検出するアクセル開度センサである。   In FIG. 1, 1 is an engine (in this embodiment, a diesel engine), 2 is a high-pressure turbo with electric motor (hereinafter also referred to as a high-pressure turbo), 3 is a low-pressure turbo, and 4 is connected to an intake port of the engine 1. An intake duct (intake passage), 5 is an exhaust duct (exhaust passage) communicating with an exhaust port of the engine 1, 6 is an engine control unit (hereinafter referred to as ECU) as a control means, and 7 is in an engine cylinder (combustion chamber). A fuel injection device (injector) for injecting fuel into the engine, 8 an engine rotation sensor for detecting the engine speed (crank angle sensor in the illustrated example), and 9 for an accelerator opening for detecting the accelerator opening (depressing amount of the accelerator pedal) It is a degree sensor.

吸気ダクト4には上流側から順に、吸入空気を清浄化するエアクリーナ10、吸入空気量(新気量)を検出する吸入空気量センサ(MAFセンサ)11、低圧段ターボ3の低圧段コンプレッサ3C、高圧段ターボ2の高圧段コンプレッサ2C、低圧段コンプレッサ3C或いは高圧段コンプレッサ2Cで昇圧された吸入空気を冷却するインタークーラ12、インタークーラ12通過後の吸入空気圧力を検出する吸入空気圧力センサ(MAPセンサ)13、吸気ダクト4の通路面積を変更する吸入空気絞り弁(インテークスロットル)14(図示例では、電磁弁)、吸気ダクト4内の吸気温度を検出する吸気温度センサ15が配設されている。   The intake duct 4 includes, in order from the upstream side, an air cleaner 10 that cleans the intake air, an intake air amount sensor (MAF sensor) 11 that detects an intake air amount (fresh air amount), a low pressure stage compressor 3C of the low pressure stage turbo 3, Intercooler 12 that cools the intake air boosted by the high-pressure compressor 2C, the low-pressure compressor 3C, or the high-pressure compressor 2C of the high-pressure turbo 2, the intake air pressure sensor (MAP) that detects the intake air pressure after passing the intercooler 12 Sensors) 13, an intake air throttle valve (intake throttle) 14 (in the illustrated example, an electromagnetic valve) that changes the passage area of the intake duct 4, and an intake air temperature sensor 15 that detects the intake air temperature in the intake duct 4. Yes.

また、排気ダクト5には上流側から順に、排気ダクト5内の排気温度を検出する排気温度センサ16、高圧段ターボ2の高圧段タービン2T、低圧段ターボ3の低圧段タービン3T、排気を消音する排気サイレンサ17が配設されている。   Further, in the exhaust duct 5, in order from the upstream side, an exhaust temperature sensor 16 that detects the exhaust temperature in the exhaust duct 5, the high-pressure turbine 2T of the high-pressure turbo 2 and the low-pressure turbine 3T of the low-pressure turbo 3 are silenced. An exhaust silencer 17 is disposed.

電動機付き高圧段ターボ2は、可変容量型のターボ(VGT)であって、低圧段ターボ3よりも過給容量が小さいものである。電動機付き高圧段ターボ2は、排気ダクト5に配設された高圧段タービン2Tと、吸気ダクト4に配設され、高圧段タービン2Tによって駆動される高圧段コンプレッサ2Cと、高圧段タービン2Tと高圧段コンプレッサ2Cとを連結する回転軸に装着された電動機(電動モータ)2Mとを有している。   The high-pressure turbo 2 with an electric motor is a variable capacity turbo (VGT) and has a supercharging capacity smaller than that of the low-pressure turbo 3. The high-pressure turbo 2 with an electric motor includes a high-pressure turbine 2T disposed in the exhaust duct 5, a high-pressure compressor 2C disposed in the intake duct 4 and driven by the high-pressure turbine 2T, a high-pressure turbine 2T, and a high-pressure turbine 2T. And an electric motor (electric motor) 2M attached to a rotary shaft that connects the stage compressor 2C.

一方、低圧段ターボ3は、高圧段ターボ2よりも過給容量が大きいものである。低圧段ターボ3は、高圧段タービン2Tよりも下流の排気ダクト5に配設された低圧段タービン3Tと、高圧段コンプレッサ2Cよりも上流の吸気ダクト4に配設され、低圧段タービン3Tによって駆動される低圧段コンプレッサ3Cとを有している。   On the other hand, the low pressure turbo 3 has a larger supercharging capacity than the high pressure turbo 2. The low-pressure stage turbo 3 is arranged in the low-pressure stage turbine 3T disposed in the exhaust duct 5 downstream of the high-pressure stage turbine 2T and the intake duct 4 upstream of the high-pressure stage compressor 2C, and is driven by the low-pressure stage turbine 3T. And a low-pressure compressor 3C.

即ち、本実施形態では、高圧段ターボ2と低圧段ターボ3とを直列に組み合わせた2段過給構成(シリーズ・2ステージターボ)とし、これら高圧段ターボ2及び低圧段ターボ3の内、高圧段ターボ2に電動機2Mを組み込んだ仕様としている。   In other words, in the present embodiment, a high-pressure turbo 2 and a low-pressure turbo 3 are combined in series to form a two-stage turbocharging configuration (series / two-stage turbo). The specification is that the motor 2M is incorporated in the stage turbo 2.

また、高圧段タービン2Tよりも上流(図示例では、排気温度センサ16と高圧段タービン2Tとの間)の排気ダクト5と、高圧段コンプレサッサ2Cよりも下流(図示例では、吸入空気絞り弁14と吸気温度センサ15との間)の吸気ダクト4とはEGRダクト(EGR通路)18で連通されており、EGRダクト18には上流側(排気ダクト5側)から順に、吸気ダクト4に還流させる排気再循環ガス(EGRガス)を冷却するEGRクーラ19、EGRダクト18を開閉し或いはEGRダクト18の通路面積を変更するEGRバルブ20(図示例では、電磁弁)が配設されている。   Further, the exhaust duct 5 upstream (in the illustrated example, between the exhaust temperature sensor 16 and the high pressure turbine 2T) and the downstream of the high pressure compressor 2C (in the illustrated example, the intake air throttle valve). 14 and the intake air temperature sensor 15) are communicated with an intake air duct 4 through an EGR duct (EGR passage) 18. The EGR duct 18 returns to the intake air duct 4 in order from the upstream side (exhaust duct 5 side). An EGR cooler 19 that cools the exhaust gas recirculation gas (EGR gas) to be generated, and an EGR valve 20 (in the illustrated example, an electromagnetic valve) that opens and closes the EGR duct 18 or changes the passage area of the EGR duct 18 are disposed.

また、排気ダクト5には、高圧段タービン2Tをバイパスする排気バイパスダクト(排気バイパス通路)21が接続されており、排気バイパスダクト21には、排気バイパスダクト21を開閉し或いは排気バイパスダクト21の通路面積を変更する排気バイパスバルブ(ターボバイパスバルブ)22が配設されている。   The exhaust duct 5 is connected to an exhaust bypass duct (exhaust bypass passage) 21 that bypasses the high-pressure turbine 2T. The exhaust bypass duct 21 is opened or closed or connected to the exhaust bypass duct 21. An exhaust bypass valve (turbo bypass valve) 22 for changing the passage area is provided.

一方、吸気ダクト4には、高圧段コンプレッサ2Cをバイパスする吸気バイパスダクト(吸気バイパス通路)23が接続されており、吸気バイパスダクト23には、吸気バイパスダクト23を開閉し或いは吸気バイパスダクト23の通路面積を変更する吸気バイパスバルブ24(図示例では、電磁弁)が配設されている。   On the other hand, an intake bypass duct (intake bypass passage) 23 that bypasses the high-pressure compressor 2C is connected to the intake duct 4, and the intake bypass duct 23 is opened or closed or connected to the intake bypass duct 23. An intake bypass valve 24 (in the illustrated example, an electromagnetic valve) that changes the passage area is provided.

ECU6には、エンジン回転センサ8、アクセル開度センサ9、吸入空気量センサ11、吸入空気圧力センサ13、吸気温度センサ15及び排気温度センサ16等の各種センサ類が接続されており、ECU6は、各種センサ類の検出値に基づいて、燃料噴射装置7、吸入空気絞り弁14、EGRバルブ20、電動機2M、排気バイパスバルブ22及び吸気バイパスバルブ24等の各種アクチュエータ類を制御するようになっている。   Various sensors such as an engine rotation sensor 8, an accelerator opening sensor 9, an intake air amount sensor 11, an intake air pressure sensor 13, an intake air temperature sensor 15, and an exhaust gas temperature sensor 16 are connected to the ECU 6. Various actuators such as the fuel injection device 7, the intake air throttle valve 14, the EGR valve 20, the electric motor 2M, the exhaust bypass valve 22, and the intake bypass valve 24 are controlled based on the detection values of the various sensors. .

本実施形態では、ECU6は、運転状態検出手段(本実施形態では、エンジン回転センサ8、アクセル開度センサ9)の検出値(つまり、エンジン回転数、アクセル開度)に基づいて目標燃料噴射量及び目標燃料噴射時期を求め、求めた目標燃料噴射量及び目標燃料噴射時期に応じて燃料噴射装置7を制御するようになっている。例えば、ECU6は、エンジン回転センサ8の検出値(エンジン回転数)及びアクセル開度センサ9の検出値(アクセル開度)に対応する目標燃料噴射量及び目標燃料噴射時期を各々、目標燃料噴射量マップ及び目標燃料噴射時期マップ(図示せず)から読み取り、読み取った目標燃料噴射量及び目標燃料噴射時期に応じて燃料噴射装置7を制御するようになっている。   In the present embodiment, the ECU 6 sets the target fuel injection amount based on the detection values (that is, the engine speed and the accelerator opening) of the driving state detection means (in this embodiment, the engine rotation sensor 8 and the accelerator opening sensor 9). The target fuel injection timing is obtained, and the fuel injection device 7 is controlled in accordance with the obtained target fuel injection amount and the target fuel injection timing. For example, the ECU 6 sets the target fuel injection amount and the target fuel injection timing corresponding to the detection value (engine speed) of the engine rotation sensor 8 and the detection value (accelerator opening) of the accelerator opening sensor 9 respectively. The fuel injection device 7 is controlled according to the read target fuel injection amount and the target fuel injection timing, which are read from the map and the target fuel injection timing map (not shown).

次に、本実施形態に係る排気ガス還流装置の作動を説明する。   Next, the operation of the exhaust gas recirculation device according to this embodiment will be described.

先ず、ECU6は、運転状態検出手段(エンジン回転センサ8、アクセル開度センサ9)の検出値(エンジン回転数、アクセル開度)に基づいてエンジン1の運転状態を認識するようになっている。例えば、ECU6は、エンジン回転センサ8の検出値(エンジン回転数)及びアクセル開度センサ9の検出値(アクセル開度)に対応するエンジン1の運転状態(低負荷低回転運転状態、中負荷中回転運転状態、高負荷高回転運転状態)を、エンジン運転状態マップ(図示せず)から読み取ることで、エンジン1の運転状態を認識するようになっている。   First, the ECU 6 recognizes the operating state of the engine 1 based on the detected values (engine speed, accelerator opening) of the operating state detection means (engine rotation sensor 8, accelerator opening sensor 9). For example, the ECU 6 operates the engine 1 corresponding to the detection value (engine speed) of the engine rotation sensor 8 and the detection value (accelerator opening) of the accelerator opening sensor 9 (low load low rotation operation state, medium load). The operation state of the engine 1 is recognized by reading a rotation operation state and a high load high rotation operation state) from an engine operation state map (not shown).

次いで、ECU6は、運転状態検出手段(エンジン回転センサ8、アクセル開度センサ9)によりエンジン1の低負荷低回転運転状態を検出したとき、つまり、エンジン運転状態マップから読み取ったエンジン1の運転状態が低負荷低回転運転状態であったときは、排気バイパスバルブ22及び吸気バイパスバルブ24を全閉(開度0%)とすることで、吸気を主に高圧段コンプレッサ2Cで昇圧するようになっている(高圧段ターボ2による過給;図2参照)。   Next, the ECU 6 detects the low load low rotation operation state of the engine 1 by the operation state detection means (engine rotation sensor 8, accelerator opening sensor 9), that is, the operation state of the engine 1 read from the engine operation state map. When the engine is in a low load and low speed operation state, the exhaust bypass valve 22 and the intake bypass valve 24 are fully closed (opening degree 0%), so that the intake air is mainly boosted by the high-pressure compressor 2C. (Supercharging by the high-pressure turbo 2; see FIG. 2).

エンジン1の低負荷低回転運転領域においては、ECU6は、吸入空気量センサ11の検出値(吸入空気量)に基づいてEGRバルブ20を制御することで、吸入空気量及びEGRガス量を調節するようになっている。例えば、ECU6は、目標吸入空気量マップ(図示せず)から読み取った目標吸入空気量に吸入空気量センサ11の検出値(吸入空気量)が一致するように、EGRバルブ20の開度をEGRバルブ制御マップ(図示せず)に従って変化させることで、吸入空気量及びEGRガス量を調節するようになっている。   In the low load low rotation operation region of the engine 1, the ECU 6 controls the EGR valve 20 based on the detection value (intake air amount) of the intake air amount sensor 11 to adjust the intake air amount and the EGR gas amount. It is like that. For example, the ECU 6 sets the opening degree of the EGR valve 20 to EGR so that the detected value (intake air amount) of the intake air amount sensor 11 matches the target intake air amount read from the target intake air amount map (not shown). By changing according to a valve control map (not shown), the intake air amount and the EGR gas amount are adjusted.

また、ECU6は、運転状態検出手段(エンジン回転センサ8、アクセル開度センサ9)によりエンジン1の中負荷中回転運転状態を検出したとき、つまり、エンジン運転状態マップから読み取ったエンジン1の運転状態が中負荷中回転運転状態であったときは、吸気バイパスバルブ24を全閉(開度0%)とすると共に、排気バイパスバルブ22の開度を全閉を除く開度に調節することで、吸気を低圧段コンプレッサ3Cで昇圧すると共に、低圧段コンプレッサ3Cで昇圧した吸気を高圧段コンプレッサ2Cでさらに昇圧するようになっている(高圧段ターボ2及び低圧段ターボ3による2段過給;図2参照)。   Further, the ECU 6 detects the medium-medium-load rotation operation state of the engine 1 by the operation state detection means (the engine rotation sensor 8 and the accelerator opening sensor 9), that is, the operation state of the engine 1 read from the engine operation state map. When the engine is in a mid-load rotation operation state, the intake bypass valve 24 is fully closed (opening degree 0%), and the opening degree of the exhaust bypass valve 22 is adjusted to an opening degree other than full closing, The intake air is boosted by the low-pressure compressor 3C and the intake air boosted by the low-pressure compressor 3C is further boosted by the high-pressure compressor 2C (two-stage supercharging by the high-pressure turbo 2 and the low-pressure turbo 3; 2).

エンジン1の中負荷中回転運転領域においては、ECU6は、低負荷低回転運転領域と同様に、吸入空気量センサ11の検出値(吸入空気量)に基づいてEGRバルブ20を制御することで、吸入空気量及びEGRガス量を調節するようになっている。例えば、ECU6は、低負荷低回転運転領域と同様に、目標吸入空気量マップから読み取った目標吸入空気量に吸入空気量センサ11の検出値(吸入空気量)が一致するように、EGRバルブ20の開度をEGRバルブ制御マップに従って変化させることで、吸入空気量及びEGRガス量を調節するようになっている。   In the medium load / medium rotational operation region of the engine 1, the ECU 6 controls the EGR valve 20 based on the detected value (intake air amount) of the intake air amount sensor 11 as in the low load / low rotational operation region. The intake air amount and the EGR gas amount are adjusted. For example, the ECU 6 controls the EGR valve 20 so that the detected value (intake air amount) of the intake air amount sensor 11 coincides with the target intake air amount read from the target intake air amount map, similarly to the low load low rotation operation region. The amount of intake air and the amount of EGR gas are adjusted by changing the degree of opening according to the EGR valve control map.

また、ECU6は、運転状態検出手段(エンジン回転センサ8、アクセル開度センサ9)によりエンジン1の高負荷高回転運転状態を検出したとき、つまり、エンジン運転状態マップから読み取ったエンジン1の運転状態が高負荷高回転運転状態であったときには、EGRバルブ20及び吸気バイパスバルブ24を開とすると共に、排気バイパスバルブ22の開度を絞り、且つ、高圧段ターボ2が逆回転するように電動機2Mを駆動することで、吸気を低圧段コンプレッサ3Cのみで昇圧するようになっている(低圧段ターボ3による過給;図2参照)。   Further, the ECU 6 detects the high load high rotation operation state of the engine 1 by the operation state detection means (the engine rotation sensor 8 and the accelerator opening sensor 9), that is, the operation state of the engine 1 read from the engine operation state map. Is in a high-load high-speed operation state, the EGR valve 20 and the intake bypass valve 24 are opened, the opening degree of the exhaust bypass valve 22 is reduced, and the high-pressure turbo turbo 2 rotates in the reverse direction. , The intake air is boosted only by the low-pressure compressor 3C (supercharging by the low-pressure turbo 3; see FIG. 2).

具体的には、ECU6は、EGRダクト18の排気側圧力(つまり、高圧段タービン2Tよりも上流の排気ダクト5内の圧力)が吸気側圧力(つまり、高圧段コンプレッサ2Cよりも下流の吸気ダクト4内の圧力)よりも高くなり(排気側圧力>吸気側圧力)且つEGRダクト18の排気側圧力と吸気側圧力との圧力差が所定の圧力差となるように、排気バイパスバルブ22の開度を所定開度(例えば、85〜95%程度)とすると共に、逆回転する高圧段ターボ2の回転数を所定回転数(例えば、数〜数十rpm程度)に制御するようになっている。   Specifically, the ECU 6 determines that the exhaust side pressure of the EGR duct 18 (that is, the pressure in the exhaust duct 5 upstream of the high pressure turbine 2T) is the intake side pressure (that is, the intake duct downstream of the high pressure stage compressor 2C). 4) (exhaust side pressure> intake side pressure) and the exhaust bypass valve 22 is opened so that the pressure difference between the exhaust side pressure and the intake side pressure of the EGR duct 18 becomes a predetermined pressure difference. The degree of rotation is set to a predetermined opening (for example, about 85 to 95%), and the rotation speed of the high-pressure turbo turbo 2 that rotates in reverse is controlled to a predetermined rotation speed (for example, about several to several tens of rpm). .

即ち、本実施形態では、エンジン1の高負荷高回転運転領域において、電動機2Mによって高圧段ターボ2を逆回転させ、排気バイパスバルブ22の開度を絞ることで、これら高圧段ターボ2(高圧段タービン2T)及び排気バイパスバルブ22によって排気ダクト5の通路抵抗を一時的に高めて、EGRダクト18の排気側圧力を高めている。これにより、EGRダクト18の排気側圧力を高める為に吸入空気絞り弁14の開度を絞る必要が無くなる。   That is, in the present embodiment, in the high load high rotation operation region of the engine 1, the high pressure turbo 2 is reversely rotated by the electric motor 2M, and the opening degree of the exhaust bypass valve 22 is reduced, so that these high pressure turbo 2 (high pressure stage 2 The passage resistance of the exhaust duct 5 is temporarily increased by the turbine 2T) and the exhaust bypass valve 22 to increase the exhaust side pressure of the EGR duct 18. This eliminates the need to throttle the intake air throttle valve 14 in order to increase the exhaust side pressure of the EGR duct 18.

エンジンの高負荷高回転運転領域においては、ECU6は、吸入空気量センサ11の検出値(吸入空気量)に基づいて排気バイパスバルブ22を制御することで、吸入空気量及びEGRガス量を調節するようになっている。例えば、ECU6は、EGRバルブ20及び吸気バイパスバルブ24の開度を一定(本実施形態では、全開(開度100%))に維持した状態で、目標吸入空気量マップから読み取った目標吸入空気量に吸入空気量センサ11の検出値(吸入空気量)が一致するように、排気バイパスバルブ22の開度を排気バイパスバルブ制御マップ(図示せず)に従って変化させることで、吸入空気量及びEGRガス量を調節するようになっている。なお、エンジンの高負荷高回転運転領域においては、ECU6は、吸入空気絞り弁14を常時全開とするようになっている。従って、エンジンの高負荷高回転運転領域においては、吸入空気絞り弁14による吸気絞りがなされない。   In the high load high rotation operation region of the engine, the ECU 6 controls the exhaust bypass valve 22 based on the detection value (intake air amount) of the intake air amount sensor 11 to adjust the intake air amount and the EGR gas amount. It is like that. For example, the ECU 6 maintains the target intake air amount read from the target intake air amount map in a state in which the openings of the EGR valve 20 and the intake bypass valve 24 are kept constant (in the present embodiment, fully open (open degree 100%)). By changing the opening degree of the exhaust bypass valve 22 in accordance with an exhaust bypass valve control map (not shown) so that the detected value (intake air amount) of the intake air amount sensor 11 coincides with the intake air amount sensor 11. The amount is adjusted. Note that, in the high-load high-rotation operation region of the engine, the ECU 6 always opens the intake air throttle valve 14 fully. Therefore, the intake air throttle valve 14 does not throttle the intake air in the high-load and high-speed operation region of the engine.

要するに、本実施形態では、EGRダクト18の排気側圧力が吸気側圧力よりも高い場合(つまり、エンジン1の低負荷低回転運転領域及び中負荷中回転運転領域)は、EGRバルブ20を開とすることで、EGRガスを吸気ダクト4に還流させる。一方、EGRダクト18の吸気側圧力が高いが、多量のEGRガス量を確保したい場合(つまり、エンジン1の高負荷高回転運転領域)には、EGRバルブ20及び吸気バイパスバルブ24を開とし、電動機2Mで高圧段ターボ2を逆回転させ、且つ、排気バイパスバルブ22の開度を調節することで、EGRダクト18の排気側圧力を高めることが出来、多量のEGRガスを吸気ダクト4に還流させつつ、吸入空気絞りなしで吸入空気をエンジン1のシリンダ内に導入することが可能となる。   In short, in the present embodiment, when the exhaust side pressure of the EGR duct 18 is higher than the intake side pressure (that is, the low load low rotation operation region and the medium load medium rotation operation region of the engine 1), the EGR valve 20 is opened. As a result, the EGR gas is recirculated to the intake duct 4. On the other hand, when the intake side pressure of the EGR duct 18 is high, but a large amount of EGR gas is desired to be secured (that is, in the high load high rotation operation region of the engine 1), the EGR valve 20 and the intake bypass valve 24 are opened, The exhaust side pressure of the EGR duct 18 can be increased by reversing the high-pressure stage turbo 2 with the electric motor 2M and adjusting the opening degree of the exhaust bypass valve 22, and a large amount of EGR gas is returned to the intake duct 4. It is possible to introduce the intake air into the cylinder of the engine 1 without restricting the intake air.

また、本実施形態によれば、エンジン1の高負荷高回転運転領域においてEGRダクト18の排気側圧力を高められることで、吸入空気絞りを行わなくとも多量のEGRガス量を確保出来る為、エンジン出力の低下を招くこと無く、所望のEGRガス量の確保が可能となる。従来、エンジン1の高負荷高回転運転領域での多量のEGRガス量確保は吸入空気絞りを行わないと困難であったが、本実施形態により同運転領域での多量のEGRガス量の確保が吸入空気絞りを行わなくとも可能となり、より広い運転領域での排出ガス低減が可能となる。   Further, according to the present embodiment, since the exhaust side pressure of the EGR duct 18 can be increased in the high load high rotation operation region of the engine 1, a large amount of EGR gas can be secured without performing the intake air throttling. A desired amount of EGR gas can be secured without causing a decrease in output. Conventionally, it has been difficult to secure a large amount of EGR gas in the high-load high-rotation operation region of the engine 1 unless intake air throttling is performed, but it is possible to secure a large amount of EGR gas in the same operation region by this embodiment. This is possible without reducing the intake air, and exhaust gas can be reduced in a wider operating range.

以上、本発明の好適な実施形態について説明したが、本発明は上記実施形態には限定されず他の様々な実施形態を採ることが可能である。   The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments, and various other embodiments can be adopted.

例えば、エンジン1の高負荷高回転運転領域において、EGRバルブ20及び吸気バイパスバルブ24の開度を全開に維持するとしたがこれには限定はされず、EGRバルブ20及び吸気バイパスバルブ24の開度を全閉及び全開を除く所定の開度に維持するようにしても良い。   For example, the opening degree of the EGR valve 20 and the intake bypass valve 24 is maintained fully open in the high load high rotation operation region of the engine 1, but the opening degree of the EGR valve 20 and the intake bypass valve 24 is not limited to this. May be maintained at a predetermined opening degree other than full closing and full opening.

1 エンジン
2 高圧段ターボ(電動機付き高圧段ターボ)
3 低圧段ターボ
4 吸気ダクト(吸気通路)
5 排気ダクト(排気通路)
6 ECU(制御手段)
8 エンジン回転センサ(運転状態検出手段)
9 アクセル開度センサ(運転状態検出手段)
18 EGRダクト(EGR通路)
20 EGRバルブ
21 排気バイバスダクト(排気バイパス通路)
22 排気バイパスバルブ
23 吸気バイパスダクト(吸気バイパス通路)
24 吸気バイパスバルブ
1 Engine 2 High-pressure turbo (high-pressure turbo with electric motor)
3 Low-pressure stage turbo 4 Intake duct (intake passage)
5 Exhaust duct (exhaust passage)
6 ECU (control means)
8 Engine rotation sensor (Operating state detection means)
9 Accelerator opening sensor (operating state detection means)
18 EGR duct (EGR passage)
20 EGR valve 21 Exhaust bypass duct (exhaust bypass passage)
22 Exhaust bypass valve 23 Intake bypass duct (intake bypass passage)
24 Intake bypass valve

Claims (2)

エンジンに直列に装着された高圧段ターボ及びウェストゲート弁を有しない低圧段ターボと、前記高圧段ターボの高圧段タービンと高圧段コンプレッサとを連結する回転軸に装着された電動機と、前記高圧段タービンよりも上流の前記エンジンの排気通路と前記高圧段コンプレッサよりも下流の前記エンジンの吸気通路とを連通するEGR通路と、該EGR通路に配設されたEGRバルブと、前記高圧段コンプレッサよりも下流かつ前記EGR通路と前記吸気通路の接続部よりも上流の前記吸気通路に配設された吸入空気絞り弁と、前記排気通路に接続され前記高圧段タービンをバイパスする排気バイパス通路と、該排気バイパス通路に配設された排気バイパスバルブと、前記吸気通路に接続され前記高圧段コンプレッサをバイパスする吸気バイパス通路と、該吸気バイパス通路に配設された吸気バイパスバルブと、前記エンジンの運転状態を検出する運転状態検出手段と、前記電動機、前記EGRバルブ、前記排気バイパスバルブ及び前記吸気バイパスバルブを制御する制御手段とを備え、該制御手段は、前記運転状態検出手段により前記エンジンの高負荷高回転運転状態を検出したときに、前記EGRバルブ及び前記吸気バイパスバルブを全開とすると共に、前記高圧段ターボが逆回転するように前記電動機を駆動し、且つ、前記高圧段ターボが逆回転するように前記電動機を駆動しているときには前記排気バイパスバルブの開度を全閉とすることなく絞ることで、前記吸入空気絞り弁を絞ることなく、吸入空気量が目標吸入空気量になるように、前記高圧段タービンよりも上流の前記排気通路内の圧力を、前記高圧段コンプレッサよりも下流の前記吸気通路内の圧力よりも高くすることを特徴とする排気ガス還流装置。 A high-pressure stage turbo mounted in series with the engine and a low-pressure stage turbo having no wastegate valve; an electric motor mounted on a rotary shaft connecting a high-pressure stage turbine of the high-pressure stage turbo and a high-pressure stage compressor; and the high-pressure stage An EGR passage communicating the exhaust passage of the engine upstream of the turbine and the intake passage of the engine downstream of the high pressure compressor, an EGR valve disposed in the EGR passage, and more than the high pressure compressor An intake air throttle valve disposed in the intake passage downstream and upstream of a connection portion between the EGR passage and the intake passage, an exhaust bypass passage connected to the exhaust passage and bypassing the high-pressure turbine, and the exhaust An exhaust bypass valve disposed in the bypass passage, and an intake air that is connected to the intake passage and bypasses the high-pressure compressor An ipass passage, an intake bypass valve disposed in the intake bypass passage, an operating state detecting means for detecting an operating state of the engine, and controlling the electric motor, the EGR valve, the exhaust bypass valve, and the intake bypass valve And a control means that opens the EGR valve and the intake bypass valve fully when the operating state detecting means detects a high-load high-rotation operating state of the engine, and the high-pressure stage When the electric motor is driven so that the turbo rotates reversely, and when the electric motor is driven so that the high-pressure stage turbo rotates reversely, the opening degree of the exhaust bypass valve is reduced without being fully closed. without throttling the intake air throttle valve, so that the amount of intake air becomes the target intake air amount, above the said high pressure turbine The exhaust pressure in the passage, an exhaust gas recirculation apparatus characterized by higher than the pressure downstream of the intake passage than the high pressure stage compressor. 前記制御手段は、前記EGRバルブ及び前記吸気バイパスバルブの開度を一定に維持にした状態で、前記排気バイパスバルブの開度を変化させることで、吸入空気量及びEGRガス量を調節する請求項1に記載の排気ガス還流装置。   The control means adjusts the intake air amount and the EGR gas amount by changing the opening degree of the exhaust bypass valve while maintaining the opening degree of the EGR valve and the intake bypass valve constant. 2. The exhaust gas recirculation device according to 1.
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