JP2006112310A - Exhaust circulation device of internal combustion engine - Google Patents

Exhaust circulation device of internal combustion engine Download PDF

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JP2006112310A
JP2006112310A JP2004300300A JP2004300300A JP2006112310A JP 2006112310 A JP2006112310 A JP 2006112310A JP 2004300300 A JP2004300300 A JP 2004300300A JP 2004300300 A JP2004300300 A JP 2004300300A JP 2006112310 A JP2006112310 A JP 2006112310A
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egr
passage
internal combustion
combustion engine
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Koichiro Nakatani
好一郎 中谷
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Toyota Motor Corp
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    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02MSUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M31/00Apparatus for thermally treating combustion-air, fuel, or fuel-air mixture
    • F02M31/02Apparatus for thermally treating combustion-air, fuel, or fuel-air mixture for heating
    • F02M31/04Apparatus for thermally treating combustion-air, fuel, or fuel-air mixture for heating combustion-air or fuel-air mixture
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02BINTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B29/00Engines characterised by provision for charging or scavenging not provided for in groups F02B25/00, F02B27/00 or F02B33/00 - F02B39/00; Details thereof
    • F02B29/04Cooling of air intake supply
    • F02B29/0406Layout of the intake air cooling or coolant circuit
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02MSUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M26/00Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
    • F02M26/13Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories
    • F02M26/22Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories with coolers in the recirculation passage
    • F02M26/23Layout, e.g. schematics
    • F02M26/24Layout, e.g. schematics with two or more coolers
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02MSUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M26/00Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
    • F02M26/13Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories
    • F02M26/22Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories with coolers in the recirculation passage
    • F02M26/23Layout, e.g. schematics
    • F02M26/25Layout, e.g. schematics with coolers having bypasses
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02MSUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M26/00Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
    • F02M26/02EGR systems specially adapted for supercharged engines
    • F02M26/04EGR systems specially adapted for supercharged engines with a single turbocharger
    • F02M26/05High pressure loops, i.e. wherein recirculated exhaust gas is taken out from the exhaust system upstream of the turbine and reintroduced into the intake system downstream of the compressor
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02MSUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M26/00Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
    • F02M26/13Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories
    • F02M26/22Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories with coolers in the recirculation passage
    • F02M26/23Layout, e.g. schematics
    • F02M26/27Layout, e.g. schematics with air-cooled heat exchangers
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02MSUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
    • F02M26/00Engine-pertinent apparatus for adding exhaust gases to combustion-air, main fuel or fuel-air mixture, e.g. by exhaust gas recirculation [EGR] systems
    • F02M26/13Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories
    • F02M26/22Arrangement or layout of EGR passages, e.g. in relation to specific engine parts or for incorporation of accessories with coolers in the recirculation passage
    • F02M26/23Layout, e.g. schematics
    • F02M26/28Layout, e.g. schematics with liquid-cooled heat exchangers
    • 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
    • Y02T10/00Road transport of goods or passengers
    • Y02T10/10Internal combustion engine [ICE] based vehicles
    • Y02T10/12Improving ICE efficiencies

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Exhaust-Gas Circulating Devices (AREA)
  • Control Of Throttle Valves Provided In The Intake System Or In The Exhaust System (AREA)

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology capable of supplying more EGR gas in a cylinder, while restraining the deterioration in fuel economy, in an exhaust circulation device of an internal combustion engine. <P>SOLUTION: This exhaust circulation device has an EGR passage 21 for connecting an exhaust passage 7 and an intake passage 3 of the internal combustion engine, an EGR cooler 23 for reducing the temperature of the EGR gas flowing in the EGR passage 21, a bypass passage 22 for bypassing the EGR cooler 23, a switching valve 24 for adjusting quantity of EGR gas flowing to the EGR cooler 23 and the bypass passage 22, and a heat exchanger 26 for exchanging heat between the EGR gas flowing in the bypass passage 22 and air flowing in the intake passage 3. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は、内燃機関の排気循環装置に関する。   The present invention relates to an exhaust gas circulation device for an internal combustion engine.

EGR通路の途中にEGRクーラを備え、該EGRクーラによりEGRガスを冷却してEGRガスの体積を縮小させることにより、内燃機関の気筒内により多くのEGRガスを入れることができる。しかし、軽負荷時においてEGRガスを冷却すると、気筒内の吸気(EGRガスおよび新気)の温度が低くなりすぎて燃焼状態が不安定となり、HCを排出するおそれがある。そのため、EGRクーラを迂回させるバイパス通路が備えられ、軽負荷時にはEGRガスを該バイパス通路に流してEGRガス温度の低下を抑制していた。   By providing an EGR cooler in the middle of the EGR passage and cooling the EGR gas by the EGR cooler to reduce the volume of the EGR gas, a larger amount of EGR gas can be put into the cylinder of the internal combustion engine. However, if the EGR gas is cooled at a light load, the temperature of the intake air (EGR gas and fresh air) in the cylinder becomes too low, and the combustion state becomes unstable, and HC may be discharged. For this reason, a bypass passage that bypasses the EGR cooler is provided, and when the load is light, EGR gas is caused to flow through the bypass passage to suppress a decrease in EGR gas temperature.

そして、EGRクーラおよびバイパス通路を備えた内燃機関の排気循環装置において、吸気温度の基準値と現在値との差に基づいてEGRクーラおよびバイパス通路に流すEGRガスの分配率を変更することにより、EGRクーラでの熱交換量を制御して、吸気温度を基準値に近づける技術が知られている(例えば、特許文献1参照。)。
特開2004−44484号公報 特開平11−117815号公報 特開平7−166973号公報 特開平10−281018号公報 特開平8−82256号公報
And in the exhaust gas circulation device of the internal combustion engine provided with the EGR cooler and the bypass passage, by changing the distribution ratio of the EGR gas flowing through the EGR cooler and the bypass passage based on the difference between the reference value of the intake air temperature and the current value, A technique for controlling the amount of heat exchange in the EGR cooler to bring the intake air temperature close to a reference value is known (for example, see Patent Document 1).
JP 2004-44484 A JP-A-11-117815 Japanese Patent Laid-Open No. 7-166773 Japanese Patent Laid-Open No. 10-281018 JP-A-8-82256

しかし、バイパス通路に多くのEGRガスを流す軽負荷時においては、吸気通路に循環されるEGRガスの密度が小さいため、気筒内にEGRガスを多く入れることが困難となる。そのため、吸気絞り弁を絞って吸気通路内の圧力(以下、吸気圧という。)を低下させたり、若しくは可変容量型ターボチャージャにおいてノズルベーンを閉じる等により背圧を上昇させたりして、背圧と吸気圧との差を大きくさせて、EGRガスの循環量を増加させていた。その結果、ポンプ損失が増大し、燃費を悪化させていた。   However, at a light load in which a large amount of EGR gas flows through the bypass passage, the density of the EGR gas circulated through the intake passage is small, so that it is difficult to put a large amount of EGR gas into the cylinder. Therefore, the back pressure can be reduced by reducing the pressure in the intake passage by reducing the intake throttle valve (hereinafter referred to as intake pressure) or by increasing the back pressure by closing the nozzle vanes in the variable capacity turbocharger. The amount of EGR gas circulation was increased by increasing the difference from the intake pressure. As a result, pump loss has increased and fuel consumption has been worsened.

本発明は、上記したような問題点に鑑みてなされたものであり、内燃機関の排気循環装置において、燃費の悪化を抑制しつつ気筒内により多くのEGRガスを供給することができる技術を提供することを目的とする。   The present invention has been made in view of the above-described problems, and provides a technique capable of supplying more EGR gas into a cylinder while suppressing deterioration of fuel consumption in an exhaust gas circulation device for an internal combustion engine. The purpose is to do.

上記課題を達成するために本発明による内燃機関の排気循環装置は、
内燃機関の排気通路と吸気通路とを接続し排気の一部を排気通路から吸気通路へ導入するEGR通路と、
前記EGR通路を流れるEGRガスの温度を低下させるEGRクーラと、
前記EGRクーラを迂回するバイパス通路と、
前記EGRクーラおよび前記バイパス通路に流れるEGRガスの量を調整する切替弁と、
前記バイパス通路を流れるEGRガスと前記吸気通路を流れる空気との間で熱交換を行う熱交換手段と、
を具備することを特徴とする。
In order to achieve the above object, an exhaust gas circulation device for an internal combustion engine according to the present invention comprises:
An EGR passage that connects an exhaust passage and an intake passage of the internal combustion engine and introduces part of the exhaust from the exhaust passage to the intake passage;
An EGR cooler for lowering the temperature of the EGR gas flowing through the EGR passage;
A bypass passage that bypasses the EGR cooler;
A switching valve for adjusting the amount of EGR gas flowing through the EGR cooler and the bypass passage;
Heat exchange means for exchanging heat between the EGR gas flowing through the bypass passage and the air flowing through the intake passage;
It is characterized by comprising.

ここで、EGRクーラは、例えばEGRガスと、内燃機関外部の空気若しくは内燃機関
の冷却水と、で熱交換をしてEGRガスの温度を低下させる。また、バイパス通路は、例えばEGRクーラの上流側のEGR通路と下流側のEGR通路とを接続する通路により構成される。切替弁は、例えば、EGRクーラが備わるEGR通路とバイパス通路との通路面積を変更することにより、EGRクーラおよびバイパス通路に流れるEGRガスの量を調整する。この切替弁は、EGRガスの流量割合を変更する弁としてもよい。
Here, the EGR cooler lowers the temperature of the EGR gas by exchanging heat with, for example, EGR gas and air outside the internal combustion engine or cooling water of the internal combustion engine. Further, the bypass passage is constituted by a passage connecting, for example, an upstream EGR passage and a downstream EGR passage of the EGR cooler. For example, the switching valve adjusts the amount of EGR gas flowing through the EGR cooler and the bypass passage by changing the passage area between the EGR passage and the bypass passage provided with the EGR cooler. This switching valve is good also as a valve which changes the flow rate ratio of EGR gas.

EGRガスがEGRクーラを通過すると、該EGRガスの温度が低下する。これによりEGRガスの体積が縮小し密度が大きくなるので、気筒内へより多くのEGRガスを入れることができる。   When the EGR gas passes through the EGR cooler, the temperature of the EGR gas decreases. As a result, the volume of the EGR gas is reduced and the density is increased, so that more EGR gas can be put into the cylinder.

一方、EGRガスがバイパス通路を通過すると、該バイパス通路を流れるEGRガスと吸気通路を流れる新気とで熱交換が行われるので、EGRガスの体積は縮小して密度は大きくなり、且つ新気の体積は膨張して密度は小さくなる。この場合、EGRガスが持っていた熱が新気に移動するので、EGRガスがEGRクーラにより冷却される場合と異なり、EGRガスが持っていた熱が外部に放出されることはほとんどない。   On the other hand, when the EGR gas passes through the bypass passage, heat exchange is performed between the EGR gas flowing through the bypass passage and the fresh air flowing through the intake passage, so that the volume of the EGR gas is reduced and the density is increased. The volume of swells and the density decreases. In this case, since the heat of the EGR gas moves to fresh air, unlike the case where the EGR gas is cooled by the EGR cooler, the heat of the EGR gas is hardly released to the outside.

そして、EGRガスは体積が縮小しているので、背圧と吸気圧との差を大きくすることなく、気筒内へ多くのEGRガスを入れることができる。また、EGRガスの持っていた熱が新気に移動し、この新気が気筒内に流入するので、気筒内の吸気の温度が低下することもない。   Since the volume of the EGR gas is reduced, a large amount of EGR gas can be put into the cylinder without increasing the difference between the back pressure and the intake pressure. Further, since the heat of the EGR gas moves to fresh air and this fresh air flows into the cylinder, the temperature of the intake air in the cylinder does not decrease.

このようにして、燃費の低下を抑制しつつ、また吸気の温度が低下することを抑制しつつ、気筒内の吸気におけるEGRガスの割合(以下、EGR率という。)を大きくすることができる。   In this way, it is possible to increase the ratio of EGR gas in the intake air in the cylinder (hereinafter referred to as the EGR rate) while suppressing a decrease in fuel consumption and a decrease in intake air temperature.

なお、本発明においては、前記切替弁は、内燃機関が所定の負荷以下で運転されているときに前記バイパス通路へEGRガスを流すことができる。
ここで、EGRクーラへEGRガスを流すと、EGRガスが冷却される。しかし、内燃機関が軽負荷で運転されている場合には、EGRガスの温度がもともと低いので、さらにEGRクーラにてEGRガスの温度を低下させてしまうと、吸気の温度が下がりすぎてその後の燃焼状態が悪化するおそれがある。その点、内燃機関が軽負荷で運転されている場合にバイパス通路へEGRガスを流すようにすれば、吸気の温度が下がりすぎるのを抑制できる。すなわち、前記所定の負荷とは、軽負荷とすることができ、EGRクーラへEGRガスを流した場合に気筒内の温度が下がりすぎて燃焼状態が悪くなる負荷状態とすることもできる。また、内燃機関が発生し得る最高トルクの3分の1以下のトルクが発生される負荷状態を「軽負荷」としてもよい。
In the present invention, the switching valve can flow EGR gas into the bypass passage when the internal combustion engine is operated at a predetermined load or less.
Here, when the EGR gas is caused to flow to the EGR cooler, the EGR gas is cooled. However, when the internal combustion engine is operated at a light load, the temperature of the EGR gas is originally low, and if the temperature of the EGR gas is further lowered by the EGR cooler, the temperature of the intake air is lowered too much and the subsequent Combustion state may be deteriorated. In that respect, if the EGR gas is allowed to flow through the bypass passage when the internal combustion engine is operated at a light load, it is possible to suppress the intake air temperature from being excessively lowered. That is, the predetermined load can be a light load, and can also be a load state where the temperature in the cylinder is too low and the combustion state becomes worse when EGR gas is flowed to the EGR cooler. Further, a load state in which a torque equal to or less than one third of the maximum torque that can be generated by the internal combustion engine may be set as “light load”.

また、本発明においては、前記吸気通路において前記熱交換手段により熱交換が行われる箇所よりも上流側に、該吸気通路を流れる空気の量を調整する吸気絞り弁をさらに備えることができる。   In the present invention, an intake throttle valve that adjusts the amount of air flowing through the intake passage may further be provided upstream of the portion of the intake passage where heat is exchanged by the heat exchange means.

吸気絞り弁は、例えば、吸気通路の通路面積を変更することにより吸気通路を流れる空気の量を調整する。
EGRガスがバイパス通路および熱交換手段へ流され、該熱交換手段においてEGRガスと新気とで熱交換が行われることにより、該新気の温度が上昇されたとしても、熱交換手段よりも上流の新気の温度は上昇しない。したがって、吸気絞り弁を熱交換手段の上流側に備えれば、温度の低い箇所に吸気絞り弁を設置することができる。また、吸気絞り弁の開度が小さい場合には、吸気絞り弁の上流と下流とで圧力差が生じ、新気が吸気絞り弁を通過する際に該新気の温度が低下する。そのため、下流の熱交換手段においてEGRガスからより多くの熱を奪うことが可能となる。これにより、EGRガスの温度はより低下
されるので、該EGRガスの密度はより大きくなり、気筒内により多くのEGRガスを入れることができる。
For example, the intake throttle valve adjusts the amount of air flowing through the intake passage by changing the passage area of the intake passage.
Even if the temperature of the fresh air rises due to the EGR gas flowing into the bypass passage and the heat exchange means, and heat exchange between the EGR gas and fresh air in the heat exchange means, the heat exchange means The temperature of fresh air upstream does not rise. Therefore, if the intake throttle valve is provided on the upstream side of the heat exchanging means, the intake throttle valve can be installed at a location where the temperature is low. Further, when the opening degree of the intake throttle valve is small, a pressure difference is generated between the upstream and downstream sides of the intake throttle valve, and the temperature of the fresh air decreases when the fresh air passes through the intake throttle valve. Therefore, it becomes possible to take more heat from the EGR gas in the downstream heat exchange means. Thereby, since the temperature of the EGR gas is further lowered, the density of the EGR gas becomes larger, and more EGR gas can be put into the cylinder.

また、本発明においては、前記吸気通路において前記熱交換手段により熱交換が行われる箇所よりも上流側に、該吸気通路を流れる空気の温度を低下させるインタークーラをさらに備えることができる。   In the present invention, an intercooler that lowers the temperature of the air flowing through the intake passage may be further provided upstream of the portion of the intake passage where heat exchange is performed by the heat exchange means.

すなわち、インタークーラにおいて新気の温度が低下されるので、該インタークーラを通過した新気を熱交換手段に流入させることにより、熱交換手段においてEGRガスからより多くの熱を奪うことができる。また、熱交換手段において温度が上昇した新気がインタークーラを流れて温度が低下してしまうことがなく、新気の温度を高く保つことができる。   That is, since the temperature of fresh air is lowered in the intercooler, more heat can be taken from the EGR gas in the heat exchange means by flowing the fresh air that has passed through the intercooler into the heat exchange means. Further, the fresh air whose temperature has increased in the heat exchange means does not flow through the intercooler and the temperature does not decrease, and the temperature of the fresh air can be kept high.

本発明においては、前記吸気絞り弁は、前記インタークーラよりも下流に備えることができる。これにより、より温度の低い所に吸気絞り弁を設置することができ、熱による影響を低減することができる。   In the present invention, the intake throttle valve can be provided downstream of the intercooler. Thereby, the intake throttle valve can be installed at a lower temperature, and the influence of heat can be reduced.

本発明に係る内燃機関の排気循環装置では、新気とEGRガスとで熱交換をすることにより、EGRガスの密度を大きくすることができ気筒内により多くのEGRガスを供給することができる。しかも、新気の温度が上昇されるので、気筒内での温度が低くなることを抑制することができる。さらに、ポンプ損失を増加させることもないので、燃費の悪化を抑制することができる。   In the exhaust gas recirculation apparatus for an internal combustion engine according to the present invention, the density of EGR gas can be increased by exchanging heat between fresh air and EGR gas, and more EGR gas can be supplied into the cylinder. In addition, since the temperature of the fresh air is raised, it is possible to suppress the temperature in the cylinder from being lowered. Furthermore, since the pump loss is not increased, deterioration of fuel consumption can be suppressed.

以下、本発明に係る内燃機関の排気循環装置の具体的な実施態様について図面に基づいて説明する。   Hereinafter, a specific embodiment of an exhaust gas circulation device for an internal combustion engine according to the present invention will be described with reference to the drawings.

図1は、本実施例に係る内燃機関の排気循環装置を適用する内燃機関1とその吸・排気系の概略構成を示す図である。
図1に示す内燃機関1は、4つの気筒2を有する水冷式の4サイクル・ディーゼルエンジンである。
FIG. 1 is a diagram showing a schematic configuration of an internal combustion engine 1 to which the exhaust gas circulation device for an internal combustion engine according to the present embodiment is applied and its intake / exhaust system.
An internal combustion engine 1 shown in FIG. 1 is a water-cooled four-cycle diesel engine having four cylinders 2.

内燃機関1には、吸気通路3が接続されている。吸気通路3の途中には、排気のエネルギを駆動源として作動するターボチャージャ4のコンプレッサハウジング4aが設けられている。ターボチャージャ4よりも下流の吸気通路3には、該吸気通路3内を流通する吸気の流量を調節する吸気絞り弁5が設けられている。また、ターボチャージャ4よりも上流の吸気通路3の途中には、該吸気通路3を通過する空気の流量に応じた信号を出力するエアフローメータ6が取り付けられている。このエアフローメータ6の出力信号により内燃機関1に吸入される新気の量を得ることができる。   An intake passage 3 is connected to the internal combustion engine 1. A compressor housing 4 a of a turbocharger 4 that operates using exhaust energy as a drive source is provided in the intake passage 3. An intake throttle valve 5 that adjusts the flow rate of the intake air flowing through the intake passage 3 is provided in the intake passage 3 downstream of the turbocharger 4. An air flow meter 6 that outputs a signal corresponding to the flow rate of air passing through the intake passage 3 is attached in the middle of the intake passage 3 upstream of the turbocharger 4. The amount of fresh air taken into the internal combustion engine 1 can be obtained from the output signal of the air flow meter 6.

一方、内燃機関1には、排気通路7が接続されている。排気通路7の途中には、前記ターボチャージャ4のタービンハウジング4bが設けられている。
また、内燃機関1には、排気通路7内を流通する排気の一部(以下、EGRガスという。)を吸気通路3へ再循環させるEGR装置20が備えられている。このEGR装置20は、EGR通路21、バイパス通路22、EGRクーラ23、切替弁24、EGR弁25を備えて構成されている。EGR通路21は、ターボチャージャ4よりも上流の排気通路7と、吸気絞り弁5よりも下流の吸気通路3と、を接続している。このEGR通路21を通って、EGRガスが再循環される。
On the other hand, an exhaust passage 7 is connected to the internal combustion engine 1. In the middle of the exhaust passage 7, a turbine housing 4 b of the turbocharger 4 is provided.
Further, the internal combustion engine 1 is provided with an EGR device 20 that recirculates a part of the exhaust gas (hereinafter referred to as EGR gas) flowing through the exhaust passage 7 to the intake passage 3. The EGR device 20 includes an EGR passage 21, a bypass passage 22, an EGR cooler 23, a switching valve 24, and an EGR valve 25. The EGR passage 21 connects the exhaust passage 7 upstream of the turbocharger 4 and the intake passage 3 downstream of the intake throttle valve 5. The EGR gas is recirculated through the EGR passage 21.

EGR通路21には、排気通路7側から順に、EGRクーラ23、切替弁24、EGR弁25が配設されている。そして、バイパス通路22の一端は、EGRクーラ23よりも排気通路7側のEGR通路21に接続され、他端は、切替弁24に接続されている。   In the EGR passage 21, an EGR cooler 23, a switching valve 24, and an EGR valve 25 are arranged in this order from the exhaust passage 7 side. One end of the bypass passage 22 is connected to the EGR passage 21 closer to the exhaust passage 7 than the EGR cooler 23, and the other end is connected to the switching valve 24.

EGRクーラ23には、内燃機関1の冷却水が循環しており、該EGRクーラ23においてEGRガスと内燃機関の冷却水とで熱交換が行われ、EGRガスが冷却される。切替弁24は、後述するECU10からの信号により作動し、EGRガスの全体量に対して、EGRクーラ23とバイパス通路22とを通過するEGRガスの割合を変更する弁である。EGR弁25は、後述するECU10からの信号により開閉し、該EGR通路21から吸気通路3へ流出するEGRガスの量を調整する。   Cooling water for the internal combustion engine 1 circulates in the EGR cooler 23, and heat exchange is performed between the EGR gas and the cooling water for the internal combustion engine in the EGR cooler 23, thereby cooling the EGR gas. The switching valve 24 is a valve that operates in response to a signal from the ECU 10 described later, and changes the ratio of EGR gas that passes through the EGR cooler 23 and the bypass passage 22 with respect to the total amount of EGR gas. The EGR valve 25 is opened and closed by a signal from the ECU 10 described later, and adjusts the amount of EGR gas flowing out from the EGR passage 21 to the intake passage 3.

バイパス通路22の途中には、熱交換器26が備えられている。この熱交換器26は2つの通路が設けられており、一方の通路はバイパス通路22の一部となり、他方の通路は吸気絞り弁5よりも下流の吸気通路3の一部となっている。そして、熱交換器26内の一方の通路を流れるEGRガスと、他方の通路を流れる新気と、の間で熱交換が行われる。なお、本実施例においては、熱交換器26が、本発明における熱交換手段に相当する。   A heat exchanger 26 is provided in the middle of the bypass passage 22. The heat exchanger 26 is provided with two passages, one passage being a part of the bypass passage 22 and the other passage being a part of the intake passage 3 downstream of the intake throttle valve 5. And heat exchange is performed between EGR gas which flows through one channel | path in the heat exchanger 26, and the fresh air which flows through the other channel | path. In this embodiment, the heat exchanger 26 corresponds to the heat exchange means in the present invention.

また、内燃機関1には該内燃機関1を制御するための電子制御ユニットであるECU10が併設されている。このECU10は、内燃機関1の運転条件や運転者の要求に応じて内燃機関1の運転状態を制御するユニットである。   The internal combustion engine 1 is also provided with an ECU 10 that is an electronic control unit for controlling the internal combustion engine 1. The ECU 10 is a unit that controls the operation state of the internal combustion engine 1 in accordance with the operation conditions of the internal combustion engine 1 and the request of the driver.

ECU10には、エアフローメータ6の他、アクセル開度に応じた信号を出力するアクセル開度センサ11が電気配線を介して接続され、該センサ等の出力信号が入力されるようになっている。このアクセル開度センサ11により内燃機関1の負荷を得ることができる。   In addition to the air flow meter 6, an accelerator opening sensor 11 that outputs a signal corresponding to the accelerator opening is connected to the ECU 10 via an electrical wiring, and an output signal from the sensor or the like is input thereto. The load of the internal combustion engine 1 can be obtained by the accelerator opening sensor 11.

一方、ECU10には吸気絞り弁5、切替弁24、およびEGR弁25が電気配線を介して接続され、ECU10によりこれらが制御される。
なお、本実施例においては、内燃機関1に流入するEGRガスの流量をそのときの内燃機関1の運転状態に応じて適正な量となるように、エアフローメータ6の出力値に基づいて吸入空気量のフィードバック制御(以下、吸入空気量フィードバック制御という。)を行う。この吸入空気量フィードバック制御では、内燃機関1の運転状態に対して予め設定された目標新気量と、エアフローメータ6から得られる吸入空気量とが等しくなるように吸気絞り弁5やEGR弁25の開度を調整する。
On the other hand, the intake throttle valve 5, the switching valve 24, and the EGR valve 25 are connected to the ECU 10 through electric wiring, and these are controlled by the ECU 10.
In the present embodiment, the intake air is based on the output value of the air flow meter 6 so that the flow rate of the EGR gas flowing into the internal combustion engine 1 becomes an appropriate amount according to the operating state of the internal combustion engine 1 at that time. Perform feedback control of the amount (hereinafter referred to as intake air amount feedback control). In this intake air amount feedback control, the intake throttle valve 5 and the EGR valve 25 are set so that the target fresh air amount preset for the operating state of the internal combustion engine 1 is equal to the intake air amount obtained from the air flow meter 6. Adjust the opening.

ところで、従来、内燃機関1の軽負荷時において、EGRガスをバイパス通路22に流していたが、EGR率を高めるために、EGR通路21の入口付近の排気通路7の圧力(以下、背圧P4という。)と、EGR通路21の出口付近の吸気通路3の圧力(以下、吸気圧PBという。)と、の差を大きくする必要があった。そのために、吸気絞り弁5を閉じたり、可変容量型ターボチャージャではノズルベーンを閉じたり、排気絞り弁を閉じたりしていた。これにより、ポンプ損失が増大して燃費が悪化していた。   By the way, conventionally, when the internal combustion engine 1 is lightly loaded, EGR gas has flowed into the bypass passage 22, but in order to increase the EGR rate, the pressure in the exhaust passage 7 near the inlet of the EGR passage 21 (hereinafter referred to as back pressure P4). And the pressure in the intake passage 3 in the vicinity of the outlet of the EGR passage 21 (hereinafter referred to as intake pressure PB) must be increased. For this purpose, the intake throttle valve 5 is closed, or in the variable capacity turbocharger, the nozzle vane is closed or the exhaust throttle valve is closed. As a result, the pump loss increased and the fuel consumption deteriorated.

すなわち、気筒2内に流入するEGRガスの体積VEGRは、背圧P4と吸気圧PBとの差にEGR弁25の通路面積Sを乗じた値に比例するが、軽負荷時においてはEGR弁25の通路面積Sはほぼ最大となっているので、背圧P4を大きくするか吸気圧PBを小さくすることで、気筒2内に流入するEGRガスの体積VEGRを大きくしていた。しかし、ポンプ損失は背圧P4と吸気圧PBとの差に比例するので、EGRガスの体積VEGRを大きくすると、ポンプ損失が大きくなる。   That is, the volume VEGR of the EGR gas flowing into the cylinder 2 is proportional to a value obtained by multiplying the difference between the back pressure P4 and the intake pressure PB by the passage area S of the EGR valve 25, but at a light load, the EGR valve 25 Therefore, the volume VEGR of the EGR gas flowing into the cylinder 2 is increased by increasing the back pressure P4 or decreasing the intake pressure PB. However, since the pump loss is proportional to the difference between the back pressure P4 and the intake pressure PB, increasing the EGR gas volume VEGR increases the pump loss.

一方、本実施例においては、内燃機関1の軽負荷時にも高いEGR率を確保するために、切替弁24により主に熱交換器26へEGRガスを流通させる。なお、本実施例においては、アクセル開度センサ11により得られる開度が予め定められた開度よりも小さいときを軽負荷とする。   On the other hand, in this embodiment, in order to ensure a high EGR rate even when the internal combustion engine 1 is lightly loaded, the EGR gas is circulated mainly to the heat exchanger 26 by the switching valve 24. In the present embodiment, a light load is set when the opening obtained by the accelerator opening sensor 11 is smaller than a predetermined opening.

ここで、EGRガスが熱交換器26を通過することにより、該EGRガスの温度は低下するが、該熱交換器26を通過する新気の温度は上昇する。そのため、EGRガスの体積は縮小し、新気の体積は膨張する。このEGRガスと新気とが混ざり合って気筒2内に流入する。ここで、EGRガスの密度は大きく、新気の密度は小さいので、混ざり合った吸気ではEGRガスの割合が相対的に高くなりEGR率が高くなる。すなわち、EGRガスの体積VEGRを小さくすることにより気筒2内に流入するEGR量を多くすることができる。また、熱交換器26を通過する前にEGRガスが持っていた熱は新気に与えられているので、混ざり合った吸気の温度が下がりすぎることもない。   Here, when the EGR gas passes through the heat exchanger 26, the temperature of the EGR gas decreases, but the temperature of fresh air that passes through the heat exchanger 26 increases. Therefore, the volume of EGR gas is reduced and the volume of fresh air is expanded. The EGR gas and fresh air are mixed and flow into the cylinder 2. Here, since the density of EGR gas is large and the density of fresh air is small, the ratio of EGR gas becomes relatively high in the mixed intake air, and the EGR rate becomes high. That is, the amount of EGR flowing into the cylinder 2 can be increased by reducing the volume VEGR of the EGR gas. Further, since the heat that the EGR gas had before passing through the heat exchanger 26 is given to the fresh air, the temperature of the mixed intake air does not drop too much.

したがって、軽負荷時においては、背圧と吸気圧との差を大きくする必要はない。そのため、ポンプ損失が大きくなることがなく、燃費の悪化を抑制できる。
また、本実施例においては、内燃機関1の中負荷時若しくは高負荷時に、高いEGR率を確保するために、切替弁24により主にEGRクーラ23側へEGRガスを流通させる。EGRガスがEGRクーラ23を通過することにより、該EGRガスの温度が低下し、該EGRガスの体積が縮小する。これにより、気筒2内のEGR率を高くすることができる。
Therefore, it is not necessary to increase the difference between the back pressure and the intake pressure at light loads. Therefore, pump loss does not increase and fuel consumption can be prevented from deteriorating.
In the present embodiment, EGR gas is circulated mainly to the EGR cooler 23 side by the switching valve 24 in order to ensure a high EGR rate at the time of medium load or high load of the internal combustion engine 1. When the EGR gas passes through the EGR cooler 23, the temperature of the EGR gas is reduced, and the volume of the EGR gas is reduced. Thereby, the EGR rate in the cylinder 2 can be increased.

また、本実施例においては、吸気絞り弁5が熱交換器26よりも上流に設けられているため、該熱交換器26において新気の温度が上昇したとしても、該新気が吸気絞り弁5を通過することがないため、該吸気絞り弁5が受ける熱の影響が小さい。   In the present embodiment, since the intake throttle valve 5 is provided upstream of the heat exchanger 26, even if the temperature of the fresh air rises in the heat exchanger 26, the fresh air is 5 does not pass through, the influence of heat received by the intake throttle valve 5 is small.

以上説明したように、本実施例によれば、軽負荷時においても燃費の悪化を抑制しつつEGR率を高くすることができる。   As described above, according to the present embodiment, the EGR rate can be increased while suppressing deterioration of fuel consumption even at light loads.

本実施例においては、吸気絞り弁5よりも上流で且つターボチャージャ4よりも下流の吸気通路3の途中にインタークーラ27を備えている。その他のハードウェアについては、実施例1と共通なので説明を省略する。   In this embodiment, an intercooler 27 is provided in the middle of the intake passage 3 upstream of the intake throttle valve 5 and downstream of the turbocharger 4. The other hardware is the same as that of the first embodiment, so that the description thereof is omitted.

図2は、本実施例に係る内燃機関の排気循環装置を適用する内燃機関1とその吸・排気系の概略構成を示す図である。
インタークーラ27では、ターボチャージャ4により圧縮されることで温度が上昇した新気と、該インタークーラ27の外部の空気と、の間で熱交換がなされ、新気の温度が低下される。
FIG. 2 is a diagram showing a schematic configuration of the internal combustion engine 1 to which the exhaust gas circulation device for the internal combustion engine according to this embodiment is applied and its intake / exhaust system.
In the intercooler 27, heat is exchanged between the fresh air whose temperature has been increased by being compressed by the turbocharger 4 and the air outside the intercooler 27, and the temperature of the fresh air is lowered.

ここで、バイパス通路22へEGRガスが流されると、熱交換器26においてEGRガスの温度が低下されると供に、吸気通路3を流れる新気の温度が上昇される。そして、仮に熱交換器26よりも下流にインタークーラ27が備えられているとすると、熱交換器26において上昇した新気の温度がインタークーラ27により低下され、気筒2内での吸気の温度が低くなってしまう。   Here, when the EGR gas is caused to flow into the bypass passage 22, the temperature of the fresh air flowing through the intake passage 3 is increased while the temperature of the EGR gas is lowered in the heat exchanger 26. If the intercooler 27 is provided downstream of the heat exchanger 26, the temperature of fresh air that has risen in the heat exchanger 26 is lowered by the intercooler 27, and the temperature of the intake air in the cylinder 2 is reduced. It will be lower.

その点、インタークーラ27を熱交換器26よりも上流に備えることにより、熱交換器26において上昇された新気の温度がインタークーラ27において低下されることがない。そのため、新気の温度を高いまま維持することができ、気筒2内の温度を高くすることができる。   In that regard, by providing the intercooler 27 upstream of the heat exchanger 26, the temperature of the fresh air raised in the heat exchanger 26 is not lowered in the intercooler 27. Therefore, the fresh air temperature can be maintained high, and the temperature in the cylinder 2 can be increased.

また、気筒2内の吸気の温度が低いほうが好ましい高負荷時においては、EGRガスがEGRクーラ23を通過するように切替弁24が制御されるので、インタークーラ27により低下された新気の温度が、熱交換器26において上昇されることがない。そのため、新気の温度を低いまま維持することができ、且つ気筒2内へ多くのEGRガスを入れることもできる。   Further, at the time of high load when it is preferable that the temperature of the intake air in the cylinder 2 is low, the switching valve 24 is controlled so that the EGR gas passes through the EGR cooler 23. Therefore, the temperature of the fresh air lowered by the intercooler 27 is controlled. Is not raised in the heat exchanger 26. Therefore, the temperature of the fresh air can be kept low, and a large amount of EGR gas can be put into the cylinder 2.

一方、インタークーラ27を吸気絞り弁5よりも上流に備えることにより、該インタークーラ27において温度が低下された新気が吸気絞り弁5を通過することになり、該吸気絞り弁5は熱の影響を受けにくくなる。すなわち、ターボチャージャ4よりも下流を流れる新気の温度が一番低くなる場所に吸気絞り弁5を配置することができる。   On the other hand, by providing the intercooler 27 upstream of the intake throttle valve 5, fresh air whose temperature has been reduced in the intercooler 27 passes through the intake throttle valve 5, and the intake throttle valve 5 is heated. Less affected. That is, the intake throttle valve 5 can be arranged at a place where the temperature of fresh air flowing downstream from the turbocharger 4 is lowest.

また、軽負荷時においては、吸気絞り弁5の開度が閉じ側へ制御されるが、このような場合、吸気絞り弁5よりも下流側の新気の圧力が上流側よりも低くなるため、新気が該吸気絞り弁5を通過するときに該新気の温度が低下する。そのため、熱交換器26に温度の低い新気が流入し、該熱交換器26において新気とEGRガスとの間でより多くの熱交換が行われる。これにより、EGRガスの温度をより低くすることができ、EGRガスの密度がより大きくなるので、より多くのEGRガスを気筒2内に入れることができる。   Further, at the time of light load, the opening degree of the intake throttle valve 5 is controlled to the closed side. In such a case, the pressure of fresh air downstream of the intake throttle valve 5 is lower than that of the upstream side. When the fresh air passes through the intake throttle valve 5, the temperature of the fresh air decreases. Therefore, fresh air having a low temperature flows into the heat exchanger 26, and more heat exchange is performed between the fresh air and the EGR gas in the heat exchanger 26. As a result, the temperature of the EGR gas can be further lowered and the density of the EGR gas can be increased, so that more EGR gas can be put into the cylinder 2.

実施例1に係る内燃機関の排気循環装置を適用する内燃機関とその吸・排気系の概略構成を示す図である。BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram illustrating a schematic configuration of an internal combustion engine to which an exhaust gas circulation device for an internal combustion engine according to a first embodiment is applied and an intake / exhaust system thereof. 実施例2に係る内燃機関の排気循環装置を適用する内燃機関とその吸・排気系の概略構成を示す図である。It is a figure which shows schematic structure of the internal combustion engine which applies the exhaust-gas-circulation apparatus of the internal combustion engine which concerns on Example 2, and its intake / exhaust system.

符号の説明Explanation of symbols

1 内燃機関
2 気筒
3 吸気通路
4 ターボチャージャ
4a コンプレッサハウジング
4b タービンハウジング
5 吸気絞り弁
6 エアフローメータ
7 排気通路
10 ECU
11 アクセル開度センサ
20 EGR装置
21 EGR通路
22 バイパス通路
23 EGRクーラ
24 切替弁
25 EGR弁
26 熱交換器
27 インタークーラ
DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Cylinder 3 Intake passage 4 Turbocharger 4a Compressor housing 4b Turbine housing 5 Intake throttle valve 6 Air flow meter 7 Exhaust passage 10 ECU
11 Accelerator opening sensor 20 EGR device 21 EGR passage 22 Bypass passage 23 EGR cooler 24 Switching valve 25 EGR valve 26 Heat exchanger 27 Intercooler

Claims (5)

内燃機関の排気通路と吸気通路とを接続し排気の一部を排気通路から吸気通路へ導入するEGR通路と、
前記EGR通路を流れるEGRガスの温度を低下させるEGRクーラと、
前記EGRクーラを迂回するバイパス通路と、
前記EGRクーラおよび前記バイパス通路に流れるEGRガスの量を調整する切替弁と、
前記バイパス通路を流れるEGRガスと前記吸気通路を流れる空気との間で熱交換を行う熱交換手段と、
を具備することを特徴とする内燃機関の排気循環装置。
An EGR passage that connects an exhaust passage and an intake passage of the internal combustion engine and introduces part of the exhaust from the exhaust passage to the intake passage;
An EGR cooler for lowering the temperature of the EGR gas flowing through the EGR passage;
A bypass passage that bypasses the EGR cooler;
A switching valve for adjusting the amount of EGR gas flowing through the EGR cooler and the bypass passage;
Heat exchange means for exchanging heat between the EGR gas flowing through the bypass passage and the air flowing through the intake passage;
An exhaust gas circulation device for an internal combustion engine, comprising:
前記切替弁は、内燃機関が所定の負荷以下で運転されているときに前記バイパス通路へEGRガスを流すことを特徴とする請求項1に記載の内燃機関の排気循環装置。   2. The exhaust gas recirculation device for an internal combustion engine according to claim 1, wherein the switching valve causes EGR gas to flow into the bypass passage when the internal combustion engine is operated at a predetermined load or less. 前記吸気通路において前記熱交換手段により熱交換が行われる箇所よりも上流側に、該吸気通路を流れる空気の量を調整する吸気絞り弁をさらに備えることを特徴とする請求項1または2に記載の内燃機関の排気循環装置。   The intake throttle valve for adjusting the amount of air flowing through the intake passage is further provided upstream of a portion where heat is exchanged by the heat exchange means in the intake passage. An exhaust gas circulation device for an internal combustion engine. 前記吸気通路において前記熱交換手段により熱交換が行われる箇所よりも上流側に、該吸気通路を流れる空気の温度を低下させるインタークーラをさらに備えることを特徴とする請求項1から3の何れかに記載の内燃機関の排気循環装置。   4. The intercooler according to claim 1, further comprising an intercooler for lowering a temperature of air flowing through the intake passage, upstream of a portion where heat is exchanged by the heat exchange means in the intake passage. 2. An exhaust gas circulation device for an internal combustion engine according to 1. 前記吸気絞り弁は、前記インタークーラよりも下流に備えることを特徴とする請求項4に記載の内燃機関の排気循環装置。   The exhaust air circulation device for an internal combustion engine according to claim 4, wherein the intake throttle valve is provided downstream of the intercooler.
JP2004300300A 2004-10-14 2004-10-14 Exhaust circulation device of internal combustion engine Withdrawn JP2006112310A (en)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2010168955A (en) * 2009-01-21 2010-08-05 Nissan Motor Co Ltd Device and method for controlling recirculation exhaust gas temperature of internal combustion engine
CN101542099B (en) * 2006-11-27 2011-11-16 斯堪尼亚有限公司 Arrangement for recirculation of exhaust gases in a supercharged combustion engine
CN103790727A (en) * 2014-02-14 2014-05-14 吉林大学 Gasoline engine load adjusting method and device

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101542099B (en) * 2006-11-27 2011-11-16 斯堪尼亚有限公司 Arrangement for recirculation of exhaust gases in a supercharged combustion engine
JP2010168955A (en) * 2009-01-21 2010-08-05 Nissan Motor Co Ltd Device and method for controlling recirculation exhaust gas temperature of internal combustion engine
CN103790727A (en) * 2014-02-14 2014-05-14 吉林大学 Gasoline engine load adjusting method and device

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