JP6515655B2 - Internal combustion engine - Google Patents

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JP6515655B2
JP6515655B2 JP2015086564A JP2015086564A JP6515655B2 JP 6515655 B2 JP6515655 B2 JP 6515655B2 JP 2015086564 A JP2015086564 A JP 2015086564A JP 2015086564 A JP2015086564 A JP 2015086564A JP 6515655 B2 JP6515655 B2 JP 6515655B2
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valve
exhaust
exhaust gas
flow control
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JP2016205206A (en
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訓己 金山
訓己 金山
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Mitsubishi Motors Corp
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
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    • Y02T10/12—Improving ICE efficiencies

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Description

この発明は、排気ガスの一部を吸気側に導く排気再循環の機能を備えた内燃機関に関する。   The present invention relates to an internal combustion engine provided with an exhaust gas recirculation function that guides part of exhaust gas to the intake side.

排気ガスの一部を吸気側に導く排気再循環いわゆるＥＧＲ（Exhaust Gas Recirculation）により、排気ガスに含まれる窒素酸化物（NOx）等の有害物質の低減および燃費の向上を図るようにした内燃機関が知られている。   An internal combustion engine that reduces harmful substances such as nitrogen oxides (NOx) contained in exhaust gas and improves fuel efficiency by means of exhaust gas recirculation (EGR) that guides part of exhaust gas to the intake side. It has been known.

この内燃機関では、排気路と吸気路との間に排気再循環路である低圧ＥＧＲ流路が配置され、そのＥＧＲ流路にＥＧＲクーラおよびＥＧＲバルブが配置される。ＥＧＲクーラは、ＥＧＲ流路に流れる排気ガスの熱を当該内燃機関の冷却水（エンジン冷却水）に与える熱交換器である。このＥＧＲクーラを通る排気ガスは、エンジン冷却水に熱を奪われることで温度低下し、ガス密度が高まった状態で吸気路に流れる。   In this internal combustion engine, a low pressure EGR passage, which is an exhaust gas recirculation passage, is disposed between the exhaust passage and the intake passage, and an EGR cooler and an EGR valve are disposed in the EGR passage. The EGR cooler is a heat exchanger that provides the heat of the exhaust gas flowing through the EGR passage to the coolant (engine coolant) of the internal combustion engine. The exhaust gas passing through the EGR cooler is lowered in temperature by the heat taken from the engine cooling water, and flows into the intake passage in a state where the gas density is increased.

このような内燃機関では、エンジン冷却水の温度が低い冷態時、エンジン内の潤滑油の粘度が高くてフリクションが大きく、また燃焼室から逃げていく熱量も多いため、燃費が悪化してしまう。対策として、冷態時は、排気路中の全ての排気ガスをＥＧＲ流路に流入させてＥＧＲクーラに通し、ＥＧＲクーラを経た排気ガスを吸気路でなく排気路に導く流路が形成される。この流路により、全ての排気ガスの熱がエンジン冷却水を温める暖機に使用される。   In such an internal combustion engine, in the cold state where the temperature of the engine cooling water is low, the viscosity of the lubricating oil in the engine is high and friction is large, and the amount of heat which escapes from the combustion chamber is also large. . As a countermeasure, in the cold state, all the exhaust gases in the exhaust passage are made to flow into the EGR passage and pass through the EGR cooler, and a passage is formed which leads the exhaust gas passed through the EGR cooler to the exhaust passage instead of the intake passage. . With this flow path, the heat of all the exhaust gas is used to warm up the engine cooling water.

特開２００７−２４０２２号公報Japanese Patent Application Publication No. 2007-24022 特開２００９−１２７５１３号公報JP, 2009-127513, A

上記のように、全ての排気ガスをＥＧＲクーラに通して排気路に導く内燃機関では、暖機は促進されるが、暖機中はせっかくの排気再循環の機能がまったく活かされない状態となる。   As described above, in the internal combustion engine in which all the exhaust gases are led to the exhaust path through the EGR cooler, the warm-up is promoted, but during warm-up, the exhaust gas recirculation function is not fully utilized.

この発明の目的は、冷態時の暖機を促進しながら、排気再循環の機能を有効に活かすことができる内燃機関を提供することである。   An object of the present invention is to provide an internal combustion engine capable of effectively utilizing the function of exhaust gas recirculation while promoting warm-up in the cold state.

請求項１に係る発明の内燃機関は、燃焼用空気を燃焼室に導く吸気路と、前記燃焼室から流出する排気が通る排気路と、この排気路に配置された排気スロットル弁と、前記排気路における前記排気スロットル弁より上流側の位置に流れる排気ガスを前記吸気路に導く排気再循環路と、この排気再循環路に流れる排気ガスの熱と当該内燃機関の冷却水の熱とを交換する熱交換器と、前記排気再循環路における前記熱交換器より下流側の位置に配置された第１流量調整弁と、前記排気再循環路における前記熱交換器と前記第１流量調整弁との間に流れる排気ガスを前記排気路における前記排気スロットル弁より下流側の位置に導く暖機経路と、この暖機経路に配置された第２流量調整弁と、前記排気スロットル弁、前記第１流量調整弁、及び、前記第２流量調整弁のそれぞれの開度変化を制御する制御手段とを備え、前記内燃機関を流れる冷却水の温度が第１設定値未満の場合、前記第１流量調整弁および前記排気スロットル弁を全閉にして、前記第２流量調整弁を全開にし、さらに、前記冷却水の温度が前記第１設定値以上であって前記第１設定値より高い第２設定値未満の場合、前記排気スロットル弁の全閉を保った状態で、前記第１流量調整弁の開度を増していき、かつ前記第２流量調整弁の開度を徐々に絞る。 The internal combustion engine of the invention according to claim 1 comprises an intake passage for introducing combustion air to a combustion chamber, an exhaust passage through which exhaust gas flowing out from the combustion chamber passes, an exhaust throttle valve disposed in the exhaust passage, and the exhaust gas. An exhaust gas recirculation passage for guiding exhaust gas flowing to a position upstream of the exhaust throttle valve in the passage to the intake passage, and heat of the exhaust gas flowing in the exhaust gas recirculation passage and heat of cooling water of the internal combustion engine are exchanged. Heat exchanger, a first flow control valve disposed at a position downstream of the heat exchanger in the exhaust gas recirculation passage, the heat exchanger in the exhaust gas recirculation passage, and the first flow control valve And a second flow control valve disposed in the warm-up path, the first exhaust throttle valve, and the first throttle path . Flow control valve and before Control means for controlling an opening change of each of the second flow control valves, and when the temperature of the cooling water flowing through the internal combustion engine is less than a first set value, the first flow control valve and the exhaust throttle valve The exhaust throttle is fully closed, the second flow control valve is fully open, and the temperature of the cooling water is equal to or higher than the first set value and lower than a second set value higher than the first set value. With the valve fully closed, the opening degree of the first flow control valve is increased, and the opening degree of the second flow control valve is gradually narrowed.

請求項２に係る発明の内燃機関は、請求項１に係る発明の制御手段について限定している。制御手段は、前記冷却水の温度が前記第１設定値以上であって前記第１設定値より高い第２設定値未満の場合、前記第１流量調整弁の開度を所定の速さで増していき、その第１流量調整弁が全開に至った後、その第１流量調整弁が全開に至るまでの開度変化より遅い速さで前記第２流量調整弁の開度を徐々に絞る。 The internal combustion engine of the invention according to claim 2 limits the control means of the invention according to claim 1 . The control means increases the opening degree of the first flow rate adjusting valve at a predetermined speed when the temperature of the cooling water is equal to or higher than the first set value and less than a second set value higher than the first set value. After the first flow control valve is fully opened, the opening of the second flow control valve is gradually narrowed at a speed slower than the change in opening until the first flow control valve is fully open.

請求項３に係る発明の内燃機関は、請求項２に係る発明の制御手段について限定している。制御手段は、前記冷却水の温度が前記第２設定値以上となった場合、前記第１流量調整弁の全開を保った状態で、前記第２流量調整弁を全閉にしかつ前記排気路から前記吸気路への排気再循環量が目標値となるよう前記排気スロットル弁の開度を制御する。 The internal combustion engine of the invention according to claim 3 limits the control means of the invention according to claim 2 . The control means fully closes the second flow control valve while keeping the first flow control valve fully open when the temperature of the cooling water becomes equal to or higher than the second set value, and the exhaust passage The opening degree of the exhaust throttle valve is controlled so that the exhaust gas recirculation amount to the intake passage becomes a target value.

請求項４に係る発明の内燃機関は、請求項２又は３に係る発明の制御手段について限定している。制御手段は、前記冷却水の温度が前記第２設定値に達するまでの期間において、当該内燃機関の負荷が所定値以上となった場合、前記排気スロットル弁を前記冷却水の温度にかかわらず強制的に所定開度に開く。 The internal combustion engine of the invention according to claim 4 limits the control means of the invention according to claim 2 or 3 . The control means forces the exhaust throttle valve regardless of the temperature of the cooling water when the load of the internal combustion engine becomes a predetermined value or more in a period until the temperature of the cooling water reaches the second set value. Open at a predetermined opening.

この発明によれば、冷態時の暖機を促進しつつ、排気再循環の機能を有効に活かすことができる。これにより、燃費の大幅な向上が図れるとともに、窒素酸化物等の有害物質の低減効果が向上する。   According to the present invention, it is possible to effectively utilize the exhaust gas recirculation function while promoting warm-up in the cold state. As a result, the fuel efficiency can be significantly improved, and the reduction effect of harmful substances such as nitrogen oxides is improved.

この発明の一実施形態の内燃機関の構成を示す図。BRIEF DESCRIPTION OF THE DRAWINGS The figure which shows the structure of the internal combustion engine of one Embodiment of this invention. 同実施形態の制御を示すフローチャート。The flowchart which shows control of the embodiment. 同実施形態におけるエンジン冷却水温度、低圧ＥＧＲ流量、暖機経路流量を各バルブの開度変化と共に示すタイムチャート。The time chart which shows the engine cooling water temperature in the embodiment, a low pressure EGR flow rate, and a warming up path flow rate with the opening change of each valve.

以下、この発明の一実施形態を図面を参照しながら説明する。
図１において、多気筒の筒内直接噴射式内燃機関であるディーゼルエンジン１は、吸気ポート２から燃焼室１ａに取込んだ空気をピストンで圧縮し、その圧縮空気に燃料を噴射することで着火・燃焼を行い、燃焼により生じる排気ガスを排気ポート３から排出する。 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
In FIG. 1, the diesel engine 1, which is a multi-cylinder direct injection internal combustion engine, is ignited by compressing air taken into the combustion chamber 1a from the intake port 2 with a piston and injecting fuel into the compressed air. Combustion is performed, and exhaust gas generated by the combustion is discharged from the exhaust port 3.

吸気ポート２は、吸気管（吸気路）１１およびその吸気管１１に配置されたインタークーラ１２を介してターボチャージャ１３の過給側流路に連通される。ターボチャージャ１３は、吸気管（吸気路）１４およびその吸気管１４に配置された塵埃除去用のフィルタ１５を通して大気を取込み、取込んだ大気をタービン回転により圧縮し吐出する。吐出される空気は、吸気管１１およびインタークーラ１２を通って吸気ポート２に流入する。また、吸気管１１には、吸気の流れ方向においてインタークーラ１２より下流側の位置に、吸気流量調整用の吸気スロットル弁１６が配置される。   The intake port 2 is in communication with the supercharger-side flow path of the turbocharger 13 via an intake pipe (intake path) 11 and an intercooler 12 disposed in the intake pipe 11. The turbocharger 13 takes in air through an intake pipe (intake passage) 14 and a dust removal filter 15 disposed in the intake pipe 14, and compresses and discharges the taken-in air by turbine rotation. The discharged air flows into the intake port 2 through the intake pipe 11 and the intercooler 12. Further, an intake throttle valve 16 for adjusting an intake flow rate is disposed in the intake pipe 11 at a position downstream of the intercooler 12 in the flow direction of intake air.

排気ポート３から排出される排気ガスは、排気管（排気路）２１、ターボチャージャ１３のタービン側流路、排気管（排気路）２２、その排気管２２に配置された酸化触媒２３およびディーゼルパティキュレートフィルタ２４を通って大気中に放出される。ディーゼルパティキュレートフィルタ２４は、排気ガスに含まれる微粒子状物質（Particulate）を除去する。また、排気管２２には、排気の流れ方向においてディーゼルパティキュレートフィルタ２４より下流側の位置に、排気流量調整用の排気スロットル弁２５が配置される。   The exhaust gas discharged from the exhaust port 3 includes an exhaust pipe (exhaust path) 21, a turbine-side flow path of the turbocharger 13, an exhaust pipe (exhaust path) 22, an oxidation catalyst 23 disposed in the exhaust pipe 22, and a diesel It is released into the atmosphere through the curate filter 24. The diesel particulate filter 24 removes particulate matter (Particulate) contained in the exhaust gas. Further, an exhaust throttle valve 25 for adjusting the exhaust gas flow rate is disposed in the exhaust pipe 22 at a position downstream of the diesel particulate filter 24 in the flow direction of the exhaust gas.

排気管２１に排気再循環路である高圧ＥＧＲ流路（配管）１７の一端が接続され、その高圧ＥＧＲ流路１７の他端が吸気管１１における吸気スロットル弁１６より下流側の位置に接続される。そして、高圧ＥＧＲ流路１７の中途部に、高圧ＥＧＲバルブ１８が配置される。高圧ＥＧＲ流路１７は、排気管２１に流れる排気ガスの一部を吸気管１１に導く。高圧ＥＧＲバルブ１８は、全閉から全開まで開度が連続的に変化する流量調整弁であり、開度変化によって排気ガスの流量を調整する。   One end of a high pressure EGR passage (piping) 17 which is an exhaust gas recirculation passage is connected to the exhaust pipe 21, and the other end of the high pressure EGR passage 17 is connected to a position downstream of the intake throttle valve 16 in the intake pipe 11. Ru. Then, a high pressure EGR valve 18 is disposed in the middle of the high pressure EGR passage 17. The high pressure EGR passage 17 guides a part of the exhaust gas flowing to the exhaust pipe 21 to the intake pipe 11. The high pressure EGR valve 18 is a flow control valve whose opening degree changes continuously from fully closed to fully open, and adjusts the flow rate of the exhaust gas by change of the opening degree.

排気管２２におけるディーゼルパティキュレートフィルタ２４と排気スロットル弁２５との間の位置に排気再循環路である低圧ＥＧＲ流路（配管）２６の一端が接続され、その低圧ＥＧＲ流路２６の他端が吸気管１４におけるフィルタ１５とターボチャージャ１３との間の位置に接続される。そして、低圧ＥＧＲ流路２６の中途部に、低圧ＥＧＲクーラ２７および低圧ＥＧＲバルブ２８が配置される。   One end of a low pressure EGR flow path (piping) 26 which is an exhaust gas recirculation path is connected to a position between the diesel particulate filter 24 and the exhaust throttle valve 25 in the exhaust pipe 22, and the other end of the low pressure EGR flow path 26 is The intake pipe 14 is connected to a position between the filter 15 and the turbocharger 13. Then, the low pressure EGR cooler 27 and the low pressure EGR valve 28 are disposed in the middle of the low pressure EGR passage 26.

低圧ＥＧＲ流路２６は、排気管２２から流入する排気ガスを吸気管１４に導く。低圧ＥＧＲクーラ２７は、排気ガスが通る排気ガス流路、および冷却水タンクとの間で循環するエンジン冷却水が通る水流路を含み、排気ガス流路とエンジン冷却水とを熱交換を行う熱交換器である。低圧ＥＧＲバルブ２８は、全閉から全開まで開度が連続的に変化する流量調整弁（第１流量調整弁）であり、その開度変化によって排気ガスの流量を調整する。なお、低圧ＥＧＲクーラ２７と低圧ＥＧＲバルブ２８の位置関係は、排気ガスの流れ方向において、低圧ＥＧＲクーラ２７が上流側、低圧ＥＧＲバルブ２８が下流側の関係となる。   The low pressure EGR passage 26 guides the exhaust gas flowing from the exhaust pipe 22 to the intake pipe 14. The low pressure EGR cooler 27 includes an exhaust gas passage through which the exhaust gas passes, and a water passage through which the engine cooling water circulating between the cooling water tank passes, and the heat for heat exchange between the exhaust gas passage and the engine cooling water It is an exchanger. The low pressure EGR valve 28 is a flow control valve (first flow control valve) whose opening degree changes continuously from fully closed to fully open, and adjusts the flow rate of exhaust gas by the change in the opening degree. The positional relationship between the low pressure EGR cooler 27 and the low pressure EGR valve 28 is such that the low pressure EGR cooler 27 is upstream and the low pressure EGR valve 28 is downstream in the flow direction of the exhaust gas.

低圧ＥＧＲ流路２６における低圧ＥＧＲクーラ２７と低圧ＥＧＲバルブ２８との間の位置に暖機経路（配管）３１の一端が接続され、その暖機経路３１の他端が排気管２２における排気スロットル弁２５より下流側の位置に接続される。そして、暖機経路３１の中途部に、暖機経路バルブ３２が配置される。暖機経路３１は、低圧ＥＧＲ流路２６に流れる排気ガスを排気管２２における排気スロットル弁２５より下流側の位置に導く。暖機経路バルブ３２は、全閉から全開まで開度が連続的に変化する流量調整弁（第２流量調整弁）であり、その開度変化によって排気ガスの流量を調整する。   One end of a warming up path (piping) 31 is connected to a position between the low pressure EGR cooler 27 and the low pressure EGR valve 28 in the low pressure EGR flow path 26, and the other end of the warming up path 31 is an exhaust throttle valve in the exhaust pipe 22 It is connected to a position downstream of 25. Then, the warm-up path valve 32 is disposed in the middle of the warm-up path 31. The warm-up path 31 guides the exhaust gas flowing through the low pressure EGR passage 26 to a position downstream of the exhaust throttle valve 25 in the exhaust pipe 22. The warm-up path valve 32 is a flow control valve (second flow control valve) whose opening degree changes continuously from fully closed to fully open, and adjusts the flow rate of the exhaust gas by the change in the opening degree.

一方、コントロールユニット４０に、吸気スロットル弁１６、高圧ＥＧＲバルブ１８、排気スロットル弁２５、低圧ＥＧＲバルブ２８、暖機経路バルブ３２、冷却水温度センサ（温度検知手段）４１、およびアクセル開度センサ４２が接続される。冷却水温度センサ４１は、上記冷却水タンク内のエンジン冷却水の温度Ｔｗを検知する。アクセル開度センサ４２は、エンジン１の負荷の大きさに対応するアクセル開度（アクセルペダルの踏込み量）を検知する。   On the other hand, in the control unit 40, the intake throttle valve 16, the high pressure EGR valve 18, the exhaust throttle valve 25, the low pressure EGR valve 28, the warming up path valve 32, the coolant temperature sensor (temperature detecting means) 41, and the accelerator opening sensor 42. Is connected. The coolant temperature sensor 41 detects the temperature Tw of the engine coolant in the coolant tank. The accelerator opening degree sensor 42 detects an accelerator opening degree (depression amount of an accelerator pedal) corresponding to the magnitude of the load of the engine 1.

コントロールユニット４０は、冷却水タンク内のエンジン冷却水の温度Ｔｗと、排気管２２から吸気管１４への排気再循環量（低圧ＥＧＲ流量）とを、排気スロットル弁２５、低圧ＥＧＲバルブ２８、暖機経路バルブ３２のそれぞれ開度変化により制御するもので、主要な機能として次の（１）〜（４）の手段を備える。
（１）冷却水温度センサ４１の検知温度Ｔｗが設定値（第１設定値）Ｔｗ１未満の場合、低圧ＥＧＲバルブ２８および排気スロットル弁２５を全閉にして、暖機経路バルブ３２を全開にする第１制御手段。 The control unit 40 controls the temperature Tw of the engine cooling water in the cooling water tank and the exhaust recirculation amount (low pressure EGR flow rate) from the exhaust pipe 22 to the intake pipe 14 by the exhaust throttle valve 25, the low pressure EGR valve 28, and the warm The control is performed by changing the opening degree of each of the machine path valves 32, and the following means (1) to (4) are provided as main functions.
(1) When the detected temperature Tw of the coolant temperature sensor 41 is less than the set value (first set value) Tw1, the low pressure EGR valve 28 and the exhaust throttle valve 25 are fully closed, and the warm-up path valve 32 is fully opened. First control means.

（２）冷却水温度センサ４１の検知温度Ｔｗが設定値Ｔｗ１以上かつ設定値（第２設定値）Ｔｗ２未満の場合、排気スロットル弁２５の全閉を保った状態で、低圧ＥＧＲバルブ２８の開度を増していき、かつ暖機経路バルブ３２の開度を徐々に絞っていく第２制御手段。設定値Ｔｗ２は、設定値Ｔｗ１より高い完全暖機温度である。   (2) When the detected temperature Tw of the coolant temperature sensor 41 is equal to or greater than the set value Tw1 and less than the set value (second set value) Tw2, the low pressure EGR valve 28 is opened with the exhaust throttle valve 25 kept fully closed. A second control means for gradually increasing the degree and gradually reducing the opening degree of the warm-up path valve 32. The set value Tw2 is a complete warm-up temperature higher than the set value Tw1.

（３）冷却水温度センサ４１の検知温度Ｔｗが設定値Ｔｗ２以上となった場合、低圧ＥＧＲバルブ２８の全開を保った状態で、暖機経路バルブ３２を全閉しかつ低圧ＥＧＲ流量が目標値となるよう排気スロットル弁２５の開度を制御する第３制御手段。   (3) When the detected temperature Tw of the coolant temperature sensor 41 becomes equal to or higher than the set value Tw2, the warm-up path valve 32 is fully closed and the low pressure EGR flow rate is the target value while keeping the low pressure EGR valve 28 fully open. Third control means for controlling the opening degree of the exhaust throttle valve 25 so as to be

（４）冷却水温度センサ４１の検知温度Ｔｗが設定値Ｔｗ２に達するまでの期間において、アクセル開度センサ４２により検知されるアクセル開度（エンジン１の負荷）が所定値以上となった場合、排気スロットル弁２５を第１および第２制御手段の制御にかかわらず所定開度に開く第４制御手段。   (4) In the period until the detected temperature Tw of the coolant temperature sensor 41 reaches the set value Tw2, if the accelerator opening (load of the engine 1) detected by the accelerator opening sensor 42 becomes equal to or greater than a predetermined value, Fourth control means for opening the exhaust throttle valve 25 to a predetermined opening regardless of the control of the first and second control means.

なお、上記（２）の第２制御手段は、具体的には、冷却水温度センサ４１の検知温度Ｔｗが設定値Ｔｗ１以上かつ設定値（第２設定値）Ｔｗ２未満の場合、排気スロットル弁２５の全閉を保った状態で、低圧ＥＧＲバルブ２８の開度を所定の速さで増していき、その低圧ＥＧＲバルブ２８が全開に至った後、その低圧ＥＧＲバルブ２８が全開に至るまでの開度変化より遅い速さで暖機経路バルブ３２の開度を徐々に絞っていく。   Note that, specifically, the second control means of the above (2) is the exhaust throttle valve 25 when the detected temperature Tw of the coolant temperature sensor 41 is equal to or higher than the set value Tw1 and lower than the set value (second set value) Tw2. Under the condition that the low pressure EGR valve 28 is fully opened, the low pressure EGR valve 28 is fully opened, and then the low pressure EGR valve 28 is fully opened. The opening degree of the warming up path valve 32 is gradually reduced at a speed slower than the degree change.

つぎに、コントロールユニット４０が実行する制御を図２のフローチャートおよび図３のタイムチャートを参照しながら説明する。図３は、エンジン冷却水の温度Ｔｗ、低圧ＥＧＲ流量、暖機経路流量の変化を排気スロットル弁２５、低圧ＥＧＲバルブ２８、暖機経路バルブ３２の開度変化と共に示している。   Next, control executed by the control unit 40 will be described with reference to the flowchart of FIG. 2 and the time chart of FIG. FIG. 3 shows changes in engine coolant temperature Tw, low pressure EGR flow rate, and warm-up path flow rate together with changes in the opening degree of the exhaust throttle valve 25, low pressure EGR valve 28, and warm-up path valve 32.

［１］Ｔｗ＜Ｔｗ１の場合
冷却水温度センサ４１の検知温度Ｔｗが設定値Ｔｗ１未満の場合（ステップＳ１のＹＥＳ）、コントロールユニット４０は、低圧ＥＧＲバルブ２８を全閉し（ステップＳ２）、排気スロットル弁２５を全閉し（ステップＳ３）、かつ暖機経路バルブ３２を全開する（ステップＳ４）。そして、コントロールユニット４０は、ステップＳ１の温度判定処理に戻る。 [1] In the case of Tw <Tw1
If the detected temperature Tw of the coolant temperature sensor 41 is less than the set value Tw1 (YES in step S1), the control unit 40 fully closes the low pressure EGR valve 28 (step S2) and fully closes the exhaust throttle valve 25 ( Step S3) The warm-up path valve 32 is fully opened (step S4). Then, the control unit 40 returns to the temperature determination process of step S1.

低圧ＥＧＲバルブ２８および排気スロットル弁２５が全閉して暖機経路バルブ３２が全開するので、排気管２２のディーゼルパティキュレートフィルタ２４を経た排気ガスはその全てが低圧ＥＧＲ流路２６に流入する。低圧ＥＧＲ流路２６に流入した排気ガスは、低圧ＥＧＲクーラ２７を通る際に、低圧ＥＧＲクーラ２７に流れるエンジン冷却水と熱交換する。低圧ＥＧＲクーラ２７を経た排気ガスは、その全てが暖機経路３１に流入する。暖機経路３１に流入した排気ガスは、全開の暖機経路バルブ３２を通って排気管２２の末端側に流れる。   Since the low pressure EGR valve 28 and the exhaust throttle valve 25 are fully closed and the warming up path valve 32 is fully opened, the exhaust gas passing through the diesel particulate filter 24 of the exhaust pipe 22 all flows into the low pressure EGR passage 26. When passing through the low pressure EGR cooler 27, the exhaust gas flowing into the low pressure EGR passage 26 exchanges heat with the engine coolant flowing to the low pressure EGR cooler 27. The exhaust gas that has passed through the low pressure EGR cooler 27 all flows into the warming up path 31. The exhaust gas flowing into the warm-up path 31 flows to the distal side of the exhaust pipe 22 through the fully open warm-up path valve 32.

排気ガスの全てが低圧ＥＧＲクーラ２７を通って流れるので、エンジン冷却水の温度Ｔｗが効率よく迅速に上昇し、暖機が促進される。よって、燃費の大幅な向上が図れる。また、暖機経路バルブ３２が全開するので、低圧ＥＧＲクーラ２７から流出する排気ガスを排気管２２に効率よく導くことができる。   Since all of the exhaust gas flows through the low pressure EGR cooler 27, the temperature Tw of the engine cooling water efficiently and quickly rises, promoting warm-up. Therefore, the fuel consumption can be greatly improved. Further, since the warm-up path valve 32 is fully opened, the exhaust gas flowing out of the low pressure EGR cooler 27 can be efficiently introduced to the exhaust pipe 22.

なお、コントロールユニット４０は、アクセル開度センサ４２により検知されるアクセル開度（エンジン１の負荷）が所定値以上となった場合、全閉状態となっている排気スロットル弁２５を冷却水温度センサ４１の検知温度Ｔｗにかかわらず所定開度に開く。排気スロットル弁２５が開くことにより、排気の圧力損失が解消される。つまり、暖機よりも圧力損失の解消が優先される。   The control unit 40 controls the exhaust throttle valve 25 which is fully closed when the accelerator opening (load of the engine 1) detected by the accelerator opening sensor 42 becomes equal to or greater than a predetermined value. The predetermined opening degree is opened regardless of the detected temperature Tw of 41. By opening the exhaust throttle valve 25, the pressure loss of the exhaust is eliminated. That is, elimination of pressure loss is given priority over warm-up.

［２］Ｔｗ１≦Ｔｗ＜Ｔｗ２の場合
冷却水温度センサ４１の検知温度Ｔｗが上昇して設定値Ｔｗ１以上・設定値Ｔｗ２未満の領域に達した場合（ステップＳ１のＮＯ、ステップＳ５のＹＥＳ）、コントロールユニット４０は、排気スロットル弁２５の全閉を保った状態で（ステップＳ６）、低圧ＥＧＲバルブ２８の開度を所定の速さで増していくとともに（ステップＳ７）、この低圧ＥＧＲバルブ２８の開度変化より遅い速さで暖機経路バルブ３２の開度を徐々に絞っていく（ステップＳ８）。そして、コントロールユニット４０は、ステップＳ１の温度判定処理に戻る。 [2] In the case of Tw1 ≦ Tw <Tw2
When the detected temperature Tw of the coolant temperature sensor 41 rises and reaches the region of the set value Tw1 or more and less than the set value Tw2 (NO in step S1 and YES in step S5), the control unit 40 While maintaining the fully closed state (step S6), the opening degree of the low pressure EGR valve 28 is increased at a predetermined speed (step S7), and the warm-up is performed at a speed slower than the opening degree change of the low pressure EGR valve 28 The opening degree of the path valve 32 is gradually reduced (step S8). Then, the control unit 40 returns to the temperature determination process of step S1.

低圧ＥＧＲバルブ２８が開いていくので、低圧ＥＧＲクーラ２７を経て暖機経路３１に流入していた排気ガスが、少しずつ低圧ＥＧＲバルブ２８および低圧ＥＧＲ流路２６を通って吸気管１４に流入するようになる。すなわち、低圧ＥＧＲバルブ２８の開度変化に伴って低圧ＥＧＲ流量が徐々に増えていく。低圧ＥＧＲ流量は、暖機経路バルブ３２の開度変化に委ねられる。   Since the low pressure EGR valve 28 opens, the exhaust gas flowing into the warming up path 31 through the low pressure EGR cooler 27 gradually flows into the intake pipe 14 through the low pressure EGR valve 28 and the low pressure EGR flow path 26. It will be. That is, the low pressure EGR flow rate gradually increases with the change in the opening degree of the low pressure EGR valve 28. The low pressure EGR flow rate is entrusted to the opening change of the warming up path valve 32.

低圧ＥＧＲバルブ２８が全開に至っても、暖機経路バルブ３２が開いて暖機経路３１がまだ導通しているので、しかも排気管２２の末端側の内部圧力のほうが吸気管１４の内部圧力よりも低いので、低圧ＥＧＲ流路２６から吸気管１４に流れる低圧ＥＧＲ流量は急には増大しない。できるだけ多くの排気ガスが低圧ＥＧＲクーラ２７を通って暖機経路３１に流入する暖機優先の流路が保たれる。   Even if the low pressure EGR valve 28 is fully opened, the warm-up path valve 32 is open and the warm-up path 31 is still conducted, and the internal pressure at the end of the exhaust pipe 22 is more than the internal pressure of the intake pipe 14 Because the pressure is low, the low pressure EGR flow rate flowing from the low pressure EGR passage 26 to the intake pipe 14 does not increase suddenly. As a result, the warm-up priority flow path in which as much exhaust gas as possible flows into the warm-up path 31 through the low pressure EGR cooler 27 is maintained.

この場合、暖機を優先しながらも、低圧ＥＧＲバルブ２８が開き始めるのと同時に低圧ＥＧＲが導入開始となり、低圧ＥＧＲ流量が徐々に増えていく。すなわち、低圧ＥＧＲの機能を有効に活かすことができる。これにより、窒素酸化物等の有害物質の低減効果が向上する。   In this case, although the warm-up is prioritized, the low pressure EGR starts being introduced at the same time as the low pressure EGR valve 28 starts to open, and the low pressure EGR flow rate gradually increases. That is, the function of the low pressure EGR can be effectively utilized. Thereby, the reduction effect of harmful substances, such as nitrogen oxide, improves.

とくに、コントロールユニット４０は、暖機経路バルブ３２の開度を徐々に絞っていく処理を、低圧ＥＧＲバルブ２８が全開した後で開始する。これにより、コントロールユニット４０は、暖機経路バルブ３２の開度変化を低圧ＥＧＲ流量としてそのまま的確に認識することができる。   In particular, the control unit 40 starts the process of gradually reducing the opening degree of the warm-up path valve 32 after the low pressure EGR valve 28 is fully opened. Thus, the control unit 40 can accurately recognize the change in the opening degree of the warming up path valve 32 as the low pressure EGR flow rate as it is.

なお、コントロールユニット４０は、アクセル開度センサ４２により検知されるアクセル開度（エンジン１の負荷）が所定値以上となった場合、全閉状態となっている排気スロットル弁２５を冷却水温度センサ４１の検知温度Ｔｗにかかわらず所定開度に開く。排気スロットル弁２５が開くことにより、排気の圧力損失が解消される。つまり、暖機よりも圧力損失の解消が優先される。   The control unit 40 controls the exhaust throttle valve 25 which is fully closed when the accelerator opening (load of the engine 1) detected by the accelerator opening sensor 42 becomes equal to or greater than a predetermined value. The predetermined opening degree is opened regardless of the detected temperature Tw of 41. By opening the exhaust throttle valve 25, the pressure loss of the exhaust is eliminated. That is, elimination of pressure loss is given priority over warm-up.

［３］Ｔｗ２＜Ｔｗの場合
冷却水温度センサ４１の検知温度Ｔｗがさらに上昇して完全暖機温度である設定値Ｔｗ２に達した場合（ステップＳ１のＮＯ、ステップＳ５のＮＯ）、コントロールユニット４０は、低圧ＥＧＲバルブ２８の全開を保った状態で（ステップＳ９）、暖機経路バルブ３２を全閉し（ステップＳ１０）、かつ低圧ＥＧＲ流量が目標値となるよう排気スロットル弁２５の開度を制御する（ステップＳ１１）。そして、コントロールユニット４０は、ステップＳ１の温度判定処理に戻る。 [3] When Tw2 <Tw
When the detected temperature Tw of the coolant temperature sensor 41 further rises and reaches the set value Tw2 which is the complete warming up temperature (NO in step S1, NO in step S5), the control unit 40 fully opens the low pressure EGR valve 28. In step S9, the warm-up path valve 32 is fully closed (step S10), and the opening degree of the exhaust throttle valve 25 is controlled so that the low pressure EGR flow rate becomes a target value (step S11). Then, the control unit 40 returns to the temperature determination process of step S1.

暖機経路バルブ３２が全閉するので、低圧ＥＧＲクーラ２７を経た排気ガスは、低圧ＥＧＲバルブ２８および低圧ＥＧＲ流路２６を通って吸気管１４に流入する。コントロールユニット４０は、エンジン１の運転に最適な低圧ＥＧＲ流量を各種センサの検知結果を用いる演算により目標値として求め、求めた目標値に低圧ＥＧＲ流量が一致するように排気スロットル弁２５の開度を制御する。すなわち、低圧ＥＧＲの機能を最大限に活かすことができる。   Since the warm-up path valve 32 is fully closed, the exhaust gas having passed through the low pressure EGR cooler 27 flows into the intake pipe 14 through the low pressure EGR valve 28 and the low pressure EGR passage 26. The control unit 40 obtains a low pressure EGR flow rate optimal for the operation of the engine 1 as a target value by calculation using detection results of various sensors, and the opening degree of the exhaust throttle valve 25 so that the low pressure EGR flow rate matches the obtained target value. Control. That is, the low pressure EGR function can be fully utilized.

なお、コントロールユニット４０は、冷却水温度センサ４１の検知温度Ｔｗと設定値Ｔｗ１，Ｔｗ２とを比較する温度判定処理において、検知温度Ｔｗの上昇時は設定値Ｔｗ１，Ｔｗ２をそのまま用い、検知温度Ｔｗの下降時は設定値Ｔｗ１，Ｔｗ２よりヒステリシス値ΔＴだけ低い値をＴｗ１´（＝Ｔｗ１−ΔＴ），Ｔｗ２´（＝Ｔｗ２−ΔＴ）を用いる。   Note that, in the temperature determination process where the control unit 40 compares the detected temperature Tw of the cooling water temperature sensor 41 with the set values Tw1 and Tw2, when the detected temperature Tw rises, the set values Tw1 and Tw2 are used as they are, and the detected temperature Tw At the time of descent, the values Tw1 '(= Tw1-.DELTA.T) and Tw2' (= Tw2-.DELTA.T) lower than the set values Tw1 and Tw2 by the hysteresis value .DELTA.T are used.

［４］変形例
上記実施形態および変形例は、例として提示したものであり、発明の範囲を限定することは意図していない。この新規な実施形態および変形例は、その他の様々な形態で実施されることが可能であり、発明の要旨を逸脱しない範囲で、種々の省略、書き換え、変更を行うことができる。これら実施形態や変形は、発明の範囲は要旨に含まれるとともに、特許請求の範囲に記載された発明とその均等の範囲に含まれる。
以下に、本願出願の当初の特許請求の範囲に記載された発明を付記する。
（１）燃焼用空気を燃焼室に導く吸気路と、前記燃焼室から流出する排気が通る排気路と、前記排気路に配置された排気スロットル弁と、前記排気路における前記排気スロットル弁より上流側の位置に流れる排気ガスを前記吸気路に導く排気再循環路と、前記排気再循環路に流れる排気ガスの熱と当該内燃機関の冷却水の熱とを交換する熱交換器と、前記排気再循環路における前記熱交換器より下流側の位置に配置された第１流量調整弁と、前記排気再循環路における前記熱交換器と前記第１流量調整弁との間に流れる排気ガスを前記排気路における前記排気スロットル弁より下流側の位置に導く暖機経路と、前記暖機経路に配置された第２流量調整弁と、前記排気スロットル弁、前記第１流量調整弁、及び、前記第２流量調整弁のそれぞれの開度変化を制御する制御手段と、を備えることを特徴とする内燃機関。
（２）前記制御手段は、前記内燃機関を流れる冷却水の温度が第１設定値未満の場合、前記第１流量調整弁および前記排気スロットル弁を全閉にして、前記第２流量調整弁を全開にすることを特徴とする（１）に記載の内燃機関。
（３）前記制御手段は、前記冷却水の温度が前記第１設定値以上であって前記第１設定値より高い第２設定値未満の場合、前記排気スロットル弁の全閉を保った状態で、前記第１流量調整弁の開度を増していき、かつ前記第２流量調整弁の開度を徐々に絞ることを特徴とする（１）又は（２）に記載の内燃機関。
（４）前記制御手段は、前記冷却水の温度が前記第１設定値以上であって前記第１設定値より高い第２設定値未満の場合、前記第１流量調整弁の開度を所定の速さで増していき、その第１流量調整弁が全開に至った後、その第１流量調整弁が全開に至るまでの開度変化より遅い速さで前記第２流量調整弁の開度を徐々に絞ることを特徴とする（３）に記載の内燃機関。
（５）前記制御手段は、前記冷却水の温度が前記第２設定値以上となった場合、前記第１流量調整弁の全開を保った状態で、前記第２流量調整弁を全閉にしかつ前記排気路から前記吸気路への排気再循環量が目標値となるよう前記排気スロットル弁の開度を制御することを特徴とする（３）又は（４）に記載の内燃機関。
（６）前記制御手段は、前記冷却水の温度が前記第２設定値に達するまでの期間において、当該内燃機関の負荷が所定値以上となった場合、前記排気スロットル弁を前記冷却水の温度にかかわらず強制的に所定開度に開くことを特徴とする（３）から（５）のいずれかに記載の内燃機関。 [4] Modifications The above embodiments and modifications are presented as examples, and are not intended to limit the scope of the invention. This novel embodiment and modification can be implemented in other various forms, and various omissions, rewrites and changes can be made without departing from the scope of the invention. These embodiments and modifications are included in the scope of the invention in the scope, and are included in the invention described in the claims and the equivalents thereof.
In the following, the invention described in the original claims of the present application is appended.
(1) An intake passage for introducing combustion air to a combustion chamber, an exhaust passage through which exhaust gas flows out from the combustion chamber, an exhaust throttle valve disposed in the exhaust passage, and an upstream side of the exhaust throttle valve in the exhaust passage An exhaust gas recirculation passage for introducing the exhaust gas flowing to the side of the intake passage; a heat exchanger for exchanging heat of the exhaust gas flowing through the exhaust gas recirculation passage with heat of cooling water of the internal combustion engine; The first flow control valve disposed at a position downstream of the heat exchanger in the recirculation path, and the exhaust gas flowing between the heat exchanger and the first flow control valve in the exhaust recirculation path A warm-up path leading to a position downstream of the exhaust throttle valve in the exhaust path, a second flow control valve disposed in the warm-up path, the exhaust throttle valve, the first flow control valve, and Each of 2 flow control valves Internal combustion engine, characterized in that it comprises a control means for controlling the opening change, the.
(2) When the temperature of the coolant flowing through the internal combustion engine is less than a first set value, the control means fully closes the first flow control valve and the exhaust throttle valve to set the second flow control valve. The internal combustion engine according to (1), wherein the engine is fully open.
(3) When the temperature of the cooling water is equal to or higher than the first set value and less than a second set value higher than the first set value, the control means keeps the exhaust throttle valve fully closed. The internal combustion engine according to (1) or (2), wherein the opening degree of the first flow control valve is increased and the opening degree of the second flow control valve is gradually narrowed.
(4) When the temperature of the cooling water is equal to or higher than the first set value and is lower than a second set value higher than the first set value, the control means sets the opening degree of the first flow rate adjustment valve The speed increases, and after the first flow control valve is fully opened, the opening of the second flow control valve is slower than the change in opening until the first flow control valve is fully open. The internal combustion engine according to (3), characterized by gradually squeezing.
(5) When the temperature of the cooling water becomes equal to or higher than the second set value, the control means fully closes the second flow control valve while keeping the first flow control valve fully open and The internal combustion engine according to (3) or (4), wherein an opening degree of the exhaust throttle valve is controlled such that an exhaust gas recirculation amount from the exhaust path to the intake path becomes a target value.
(6) When the load of the internal combustion engine becomes equal to or greater than a predetermined value in a period until the temperature of the cooling water reaches the second set value, the control means determines the temperature of the cooling water as the temperature of the cooling water The internal combustion engine according to any one of (3) to (5), wherein the internal combustion engine forcibly opens at a predetermined opening regardless of the opening degree.

１…エンジン、１ａ…燃焼室、２…吸気ポート、３…排気ポート、１１…吸気管（吸気路）、１２…インタークーラ、１３…ターボチャージャ、１４…吸気管（吸気路）、１５…フィルタ、２１，２２…排気管（排気路）、２３…酸化触媒、２４…ディーゼルパティキュレートフィルタ、２５…排気スロットル弁、２６…低圧ＥＧＲ流路（排気再循環流路）、２７…低圧ＥＧＲクーラ、２８…低圧ＥＧＲバルブ（第１流量調整弁）、３１…暖機経路、３２…暖機経路バルブ（第２流量調整弁）、４０…コントロールユニット、４１…冷却水温度センサ、４２…アクセル開度センサ   DESCRIPTION OF SYMBOLS 1 ... engine, 1a ... combustion chamber, 2 ... intake port, 3 ... exhaust port, 11 ... intake pipe (intake path), 12 ... intercooler, 13 ... turbocharger, 14 ... intake pipe (intake path), 15 ... filter 21, 22 ... exhaust pipe (exhaust passage), 23 ... oxidation catalyst, 24 ... diesel particulate filter, 25 ... exhaust throttle valve, 26 ... low pressure EGR passage (exhaust recirculation passage), 27 ... low pressure EGR cooler, 28: low pressure EGR valve (first flow control valve), 31: warm-up path, 32: warm-up path valve (second flow control valve), 40: control unit, 41: cooling water temperature sensor, 42: accelerator opening degree Sensor

Claims (4)

燃焼用空気を燃焼室に導く吸気路と、
前記燃焼室から流出する排気が通る排気路と、
前記排気路に配置された排気スロットル弁と、
前記排気路における前記排気スロットル弁より上流側の位置に流れる排気ガスを前記吸気路に導く排気再循環路と、
前記排気再循環路に流れる排気ガスの熱と当該内燃機関の冷却水の熱とを交換する熱交換器と、
前記排気再循環路における前記熱交換器より下流側の位置に配置された第１流量調整弁と、
前記排気再循環路における前記熱交換器と前記第１流量調整弁との間に流れる排気ガスを前記排気路における前記排気スロットル弁より下流側の位置に導く暖機経路と、
前記暖機経路に配置された第２流量調整弁と、
前記排気スロットル弁、前記第１流量調整弁、及び、前記第２流量調整弁のそれぞれの開度変化を制御する制御手段と、
を備え、
前記制御手段は、前記内燃機関を流れる冷却水の温度が第１設定値未満の場合、前記第１流量調整弁および前記排気スロットル弁を全閉にして、前記第２流量調整弁を全開にし、さらに、前記冷却水の温度が前記第１設定値以上であって前記第１設定値より高い第２設定値未満の場合、前記排気スロットル弁の全閉を保った状態で、前記第１流量調整弁の開度を増していき、かつ前記第２流量調整弁の開度を徐々に絞る
ことを特徴とする内燃機関。 An intake passage for introducing combustion air to the combustion chamber;
An exhaust passage through which the exhaust gas flowing out of the combustion chamber passes;
An exhaust throttle valve disposed in the exhaust passage;
An exhaust gas recirculation passage for guiding exhaust gas flowing to a position upstream of the exhaust throttle valve in the exhaust passage to the intake passage;
A heat exchanger for exchanging heat of exhaust gas flowing into the exhaust gas recirculation passage with heat of cooling water of the internal combustion engine;
A first flow control valve disposed at a position downstream of the heat exchanger in the exhaust gas recirculation passage;
A warm-up path for leading exhaust gas flowing between the heat exchanger in the exhaust gas recirculation path and the first flow rate adjustment valve to a position downstream of the exhaust throttle valve in the exhaust path;
A second flow control valve disposed in the warm-up path;
Control means for controlling changes in the opening degree of each of the exhaust throttle valve, the first flow control valve, and the second flow control valve;
Equipped with
When the temperature of the cooling water flowing through the internal combustion engine is less than a first set value, the control means fully closes the first flow control valve and the exhaust throttle valve and fully opens the second flow control valve. Furthermore, when the temperature of the cooling water is equal to or higher than the first set value and less than a second set value higher than the first set value, the first flow rate adjustment is performed with the exhaust throttle valve kept fully closed. An internal combustion engine characterized by increasing the opening degree of the valve and gradually reducing the opening degree of the second flow rate adjusting valve . 前記制御手段は、前記冷却水の温度が前記第１設定値以上であって前記第１設定値より高い第２設定値未満の場合、前記第１流量調整弁の開度を所定の速さで増していき、その第１流量調整弁が全開に至った後、その第１流量調整弁が全開に至るまでの開度変化より遅い速さで前記第２流量調整弁の開度を徐々に絞る
ことを特徴とする請求項１記載の内燃機関。 When the temperature of the cooling water is equal to or higher than the first set value and lower than a second set value higher than the first set value, the control means sets the opening degree of the first flow rate adjustment valve at a predetermined speed. After the first flow control valve is fully opened, it gradually narrows the opening of the second flow control valve at a slower speed than the change in opening until the first flow control valve is fully opened. internal combustion engine according to claim 1, wherein a. 前記制御手段は、前記冷却水の温度が前記第２設定値以上となった場合、前記第１流量調整弁の全開を保った状態で、前記第２流量調整弁を全閉にしかつ前記排気路から前記吸気路への排気再循環量が目標値となるよう前記排気スロットル弁の開度を制御する
ことを特徴とする請求項２に記載の内燃機関。 The control means fully closes the second flow control valve while maintaining the full opening of the first flow control valve when the temperature of the cooling water becomes equal to or higher than the second set value, and the exhaust passage The internal combustion engine according to claim 2 , wherein the opening degree of the exhaust throttle valve is controlled so that the exhaust gas recirculation amount from the valve to the intake passage becomes a target value. 前記制御手段は、前記冷却水の温度が前記第２設定値に達するまでの期間において、当該内燃機関の負荷が所定値以上となった場合、前記排気スロットル弁を前記冷却水の温度にかかわらず強制的に所定開度に開く
ことを特徴とする請求項２又は請求項３に記載の内燃機関。 The control means controls the exhaust throttle valve regardless of the temperature of the cooling water when the load of the internal combustion engine becomes a predetermined value or more in a period until the temperature of the cooling water reaches the second set value. The internal combustion engine according to claim 2 or 3, wherein the internal combustion engine is forcibly opened to a predetermined opening degree.
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