JP2007278246A - Exhaust emission control device for internal combustion engine - Google Patents

Exhaust emission control device for internal combustion engine Download PDF

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JP2007278246A
JP2007278246A JP2006108548A JP2006108548A JP2007278246A JP 2007278246 A JP2007278246 A JP 2007278246A JP 2006108548 A JP2006108548 A JP 2006108548A JP 2006108548 A JP2006108548 A JP 2006108548A JP 2007278246 A JP2007278246 A JP 2007278246A
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fuel ratio
sulfur component
air
exhaust
atmosphere
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Arisuke Kawamura
有輔 川村
Keizo Heiko
恵三 平工
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Toyota Motor 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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    • Y02T10/40—Engine management systems

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  • Exhaust Gas After Treatment (AREA)
  • Electrical Control Of Air Or Fuel Supplied To Internal-Combustion Engine (AREA)
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Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device for an internal combustion engine, suppressing to the minimum a hydrogen sulfide generation amount during execution of a sulfur component discharging process and also certainly discharging a sulfur component from an exhaust gas purifying catalyst, in the exhaust emission control device for the internal combustion engine in which the temperature of the exhaust gas purifying catalyst is increased to a predetermined temperature, the atmosphere of the exhaust gas purifying catalyst is controlled to a rich air-fuel ratio state, and the sulfur component discharging process to discharge the sulfur component from the exhaust gas purifying catalyst is executed. <P>SOLUTION: In this exhaust emission control device for the internal combustion engine, when executing the sulfur component discharging process, control is executed that the atmosphere of the exhaust gas purifying catalyst is made in the rich air-fuel ratio state after executing a preliminary control that the atmosphere of the exhaust gas purifying catalyst is made in a lean air-fuel ratio state in the case that the atmosphere of the exhaust gas purifying catalyst is not in the lean air-fuel ratio state, that is, the atmosphere of the exhaust gas purifying catalyst is in the rich air-fuel ratio state or a stoichiometric air-fuel ratio. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

本発明は、内燃機関の排気浄化装置、特に、排気浄化性能を維持すべく硫黄成分を排気浄化触媒から放出する処理が必要となる排気浄化触媒を備えた内燃機関の排気浄化装置に関する。   The present invention relates to an exhaust gas purification apparatus for an internal combustion engine, and more particularly to an exhaust gas purification apparatus for an internal combustion engine provided with an exhaust gas purification catalyst that requires a process for releasing a sulfur component from the exhaust gas purification catalyst in order to maintain the exhaust gas purification performance.

従来より、自動車用内燃機関においては、排気中に含まれるＨＣ（炭化水素）、ＣＯ（一酸化炭素）、ＮＯｘ（窒素酸化物）などの有害成分を浄化するために内燃機関の排気系に排気浄化触媒が配置された排気浄化装置が知られている。   2. Description of the Related Art Conventionally, in an internal combustion engine for automobiles, an exhaust gas is exhausted into an exhaust system of the internal combustion engine in order to purify harmful components such as HC (hydrocarbon), CO (carbon monoxide), and NOx (nitrogen oxide) contained in the exhaust gas. An exhaust emission control device in which a purification catalyst is arranged is known.

このような排気浄化装置に使用される排気浄化触媒としては、例えば、三元触媒が広く知られている。該三元触媒は、不完全燃焼成分であるＨＣ及びＣＯの酸化反応と、空気中の窒素と燃え残りの酸素とが反応して生成されるＮＯｘの還元反応とを同時に促進し、ＨＣ、ＣＯおよびＮＯｘの外部への排出を低減させる機能を有する。   As an exhaust purification catalyst used in such an exhaust purification device, for example, a three-way catalyst is widely known. The three-way catalyst simultaneously promotes an oxidation reaction of HC and CO, which are incomplete combustion components, and a reduction reaction of NOx produced by a reaction between nitrogen in the air and unburned oxygen, and HC, CO And a function of reducing NOx emission to the outside.

ところで、内燃機関の燃料、例えばガソリンや軽油などの燃料には、硫黄成分が含有している場合が多く、この場合、燃焼後の排気中には、ＳＯ2やＳＯ3などのＳＯｘ（硫黄酸化物）が含まれることになる。排気ガス中に硫黄成分が含まれていると、この硫黄成分が硫酸塩などの形態で排気浄化触媒に蓄積し、触媒の活性点などを覆い、触媒浄化性能が低下する場合があることが知られている。 By the way, the fuel of an internal combustion engine, for example, fuel such as gasoline or light oil often contains a sulfur component. In this case, SOx (sulfur oxidation) such as SO 2 and SO 3 is contained in the exhaust gas after combustion. Things) will be included. If the exhaust gas contains a sulfur component, this sulfur component accumulates in the exhaust purification catalyst in the form of sulfate, etc., covering the active points of the catalyst, etc., and the catalyst purification performance may be reduced. It has been.

一方で、排気浄化触媒温度を所定温度に昇温させ且つ排気浄化触媒雰囲気をリッチ空燃比状態にすることで、排気浄化触媒に蓄積された硫黄成分を放出させることができることが明らかにされている。   On the other hand, it has been clarified that the sulfur component accumulated in the exhaust purification catalyst can be released by raising the exhaust purification catalyst temperature to a predetermined temperature and setting the exhaust purification catalyst atmosphere to a rich air-fuel ratio state. .

そこで、排気浄化性能を維持すべく硫黄成分を放出する必要がある排気浄化触媒を備える排気浄化装置においては、排気浄化触媒の硫黄成分を放出する一つの方策として、排気浄化触媒温度を所定温度に昇温させ且つ排気浄化触媒に流入する排気ガスの空燃比をリッチ空燃比にして排気浄化触媒雰囲気の空燃比状態をリッチ空燃比状態にする、硫黄成分放出処理が適用されている。該硫黄成分放出処理により、排気浄化触媒に蓄積された硫黄成分を排気浄化触媒から放出させることが可能となる。   Therefore, in an exhaust purification device equipped with an exhaust purification catalyst that needs to release a sulfur component in order to maintain the exhaust purification performance, as one measure for releasing the sulfur component of the exhaust purification catalyst, the exhaust purification catalyst temperature is set to a predetermined temperature. A sulfur component release process is applied in which the air-fuel ratio of the exhaust gas that is raised in temperature and the exhaust gas flowing into the exhaust purification catalyst is set to a rich air-fuel ratio to change the air-fuel ratio state of the exhaust purification catalyst atmosphere to a rich air-fuel ratio state. By the sulfur component releasing process, the sulfur component accumulated in the exhaust purification catalyst can be released from the exhaust purification catalyst.

特開２００４−１０８１７６号公報JP 2004-108176 A

ところで、硫黄成分が蓄積された排気浄化触媒に対して上記硫黄成分放出処理が実行される際には、ＳＯｘとともに硫化水素（Ｈ2Ｓ）が一時的に発生する。このような硫化水素は強い臭気を発生させる性質があり、大気中に放出されると車輌の周囲で異臭を放つため、好ましいものではない。 By the way, when the above sulfur component release process is performed on the exhaust purification catalyst in which the sulfur component is accumulated, hydrogen sulfide (H 2 S) is temporarily generated together with SOx. Such hydrogen sulfide has a property of generating a strong odor, and if released into the atmosphere, an unpleasant odor is emitted around the vehicle, which is not preferable.

排気浄化触媒が硫黄成分脱離温度域にあるとき、排気浄化触媒雰囲気の空燃比がリッチであるほど硫黄成分が多く放出される。また、排気浄化触媒の硫黄成分蓄積量が多いほど硫黄成分は大量に放出される。そして、硫黄成分の放出量が増えると結果的に多量の硫化水素が生成され、異臭が放たれるという問題がある。   When the exhaust purification catalyst is in the sulfur component desorption temperature range, the richer the air / fuel ratio of the exhaust purification catalyst atmosphere, the more sulfur component is released. In addition, the larger the amount of sulfur component accumulated in the exhaust purification catalyst, the more sulfur component is released. And if the discharge | release amount of a sulfur component increases, a lot of hydrogen sulfide will be produced | generated as a result, and there exists a problem that a strange odor is emitted.

本出願人は、硫黄成分放出処理を実行する際の排気浄化触媒雰囲気の空燃比状態、すなわち硫黄成分放出処理における排気浄化触媒雰囲気をリッチ空燃比状態にする制御が実行される直前の排気浄化触媒雰囲気の空燃比状態が、硫黄成分放出処理実行中の排気浄化触媒からの硫黄成分の放出量および硫化水素の発生量に関与していることを突き止めた。   The present applicant has stated that the exhaust gas purification catalyst atmosphere immediately before execution of the control to make the exhaust gas purification catalyst atmosphere in the rich air fuel ratio state in the sulfur component emission process, that is, the air fuel ratio state of the exhaust gas purification catalyst atmosphere in performing the sulfur component release process. It has been found that the air-fuel ratio state of the atmosphere is involved in the amount of sulfur component released from the exhaust purification catalyst and the amount of hydrogen sulfide generated during the sulfur component release process.

特許文献１においては、このような硫化水素による異臭を防止するために、硫黄成分が蓄積された排気浄化触媒に対して硫黄成分放出処理が実行される際におけるＳＯｘの発生時期に対する硫化水素の発生時期の遅れに着眼して、硫黄成分放出処理実行中の硫化水素の発生量を最小限に抑えるともに、排気浄化触媒から硫黄成分を確実に放出させる排気浄化装置が提案されている。   In Patent Document 1, in order to prevent such an unpleasant odor caused by hydrogen sulfide, generation of hydrogen sulfide with respect to the generation timing of SOx when the sulfur component release process is performed on the exhaust purification catalyst in which the sulfur component is accumulated. In view of the timing delay, there has been proposed an exhaust purification device that minimizes the amount of hydrogen sulfide generated during execution of the sulfur component release process and reliably releases the sulfur component from the exhaust purification catalyst.

しかしながら、特許文献１においては、硫黄成分放出処理における排気浄化触媒雰囲気をリッチ空燃比状態にする制御が実行される直前の排気浄化触媒雰囲気の空燃比状態に着眼して、硫黄成分放出処理実行中の硫化水素の発生量を最小限に抑えるともに、排気浄化触媒から硫黄成分を確実に放出させることは記載されていない。   However, in Patent Document 1, the sulfur component release process is being executed focusing on the air-fuel ratio state of the exhaust purification catalyst atmosphere immediately before the control to make the exhaust purification catalyst atmosphere in the rich air-fuel ratio state in the sulfur component release process is executed. It does not describe that the generation amount of hydrogen sulfide is minimized and that the sulfur component is reliably released from the exhaust purification catalyst.

本発明は上記課題に鑑み、硫黄成分放出処理を実行する際の排気浄化触媒雰囲気の空燃比状態に着眼して、すなわち硫黄成分放出処理における排気浄化触媒雰囲気をリッチ空燃比状態にする制御が実行される直前の排気浄化触媒雰囲気の空燃比状態に着眼して、硫黄成分放出処理実行中の硫化水素の発生量を最小限に抑えるともに、排気浄化触媒から硫黄成分を確実に放出させる内燃機関の排気浄化装置を提供することを目的とする。   In view of the above-described problems, the present invention focuses on the air-fuel ratio state of the exhaust purification catalyst atmosphere when executing the sulfur component release process, that is, performs control to make the exhaust purification catalyst atmosphere in the sulfur component release process rich in the air-fuel ratio state. Focusing on the air-fuel ratio state of the exhaust purification catalyst atmosphere immediately before being performed, the generation amount of hydrogen sulfide during execution of the sulfur component release process is minimized, and the internal combustion engine that reliably releases the sulfur component from the exhaust purification catalyst An object is to provide an exhaust emission control device.

請求項１に記載の発明によれば、内燃機関本体から排出された排気ガス中の有害成分を浄化する排気浄化触媒が排気系に配置された内燃機関の排気浄化装置であって、前記排気浄化触媒の硫黄成分の蓄積量を検出する硫黄成分蓄積量検出手段を有し、前記硫黄成分蓄積量検出手段からの検出情報に基づいて、前記排気浄化触媒の温度を所定温度に昇温し且つ前記排気浄化触媒の雰囲気をリッチ空燃比状態に制御し、前記排気浄化触媒から蓄積された硫黄成分を放出する硫黄成分放出処理が実行される内燃機関の排気浄化装置において、前記硫黄成分放出処理を実行する際に、前記排気浄化触媒の雰囲気がリッチ空燃比状態あるいは理論空燃比状態にある場合には、前記排気浄化触媒の雰囲気をリーン空燃比状態にする予備制御が実行された後に、前記排気浄化触媒の雰囲気をリッチ空燃比状態にする制御が実行される、ことを特徴とする内燃機関の排気浄化装置が提供される。   According to the first aspect of the present invention, there is provided an exhaust gas purification apparatus for an internal combustion engine in which an exhaust gas purification catalyst for purifying harmful components in exhaust gas discharged from an internal combustion engine body is disposed in an exhaust system, the exhaust gas purification device. A sulfur component accumulation amount detection means for detecting an accumulation amount of the sulfur component of the catalyst, and based on detection information from the sulfur component accumulation amount detection means, raises the temperature of the exhaust purification catalyst to a predetermined temperature, and The sulfur component release process is performed in an exhaust gas purification apparatus for an internal combustion engine in which the atmosphere of the exhaust purification catalyst is controlled to a rich air-fuel ratio state and the sulfur component release process for releasing the sulfur component accumulated from the exhaust purification catalyst is executed. When the atmosphere of the exhaust purification catalyst is in a rich air-fuel ratio state or a stoichiometric air-fuel ratio state, after the preliminary control is performed to make the atmosphere of the exhaust purification catalyst a lean air-fuel ratio state Control of the atmosphere of the exhaust gas purifying catalyst to a rich air-fuel ratio condition is executed, the exhaust purification system of an internal combustion engine, wherein is provided that.

本出願人は、硫黄成分放出処理を実行する際の排気浄化触媒雰囲気の空燃比状態がリーン空燃比状態にある場合、すなわち硫黄成分放出処理における排気浄化触媒雰囲気をリッチ空燃比状態にする制御が実行される直前の排気浄化触媒雰囲気がリーン空燃比状態にある場合には、その排気浄化触媒雰囲気がリーン空燃比状態にない場合すなわちリッチ空燃比状態あるいは理論空燃比状態にある場合と比較して、硫黄成分放出処理実行中の硫化水素の発生量を低く抑えることでき、且つ、より多くの硫黄成分を排気浄化触媒から放出することができることを突き止めた。   The present applicant controls the exhaust purification catalyst atmosphere in the lean air-fuel ratio state when performing the sulfur component release process, that is, the control for making the exhaust purification catalyst atmosphere in the sulfur component release process the rich air-fuel ratio state. When the exhaust purification catalyst atmosphere immediately before execution is in the lean air-fuel ratio state, compared to the case where the exhaust purification catalyst atmosphere is not in the lean air-fuel ratio state, that is, in the rich air-fuel ratio state or the stoichiometric air-fuel ratio state. The present inventors have found that the amount of hydrogen sulfide generated during execution of the sulfur component release process can be kept low, and that more sulfur components can be released from the exhaust purification catalyst.

このことに基づいて、請求項１の発明では、硫黄成分放出処理を実行する際に、排気浄化触媒の雰囲気がリッチ空燃比状態あるいは理論空燃比状態にある場合すなわち排気浄化触媒の雰囲気がリーン空燃比状態にない場合には、排気浄化触媒の雰囲気をリーン空燃比状態にする予備制御が実行された後に、排気浄化触媒の雰囲気をリッチ空燃比状態にする制御が実行される。これにより、硫黄成分放出処理実行中の硫化水素の発生量を最小限に抑えるともに、排気浄化触媒から硫黄成分を確実に放出させることを可能とする。   Based on this, in the first aspect of the invention, when the sulfur component release process is executed, the atmosphere of the exhaust purification catalyst is in the rich air-fuel ratio state or the stoichiometric air-fuel ratio state, that is, the atmosphere of the exhaust purification catalyst is lean empty. When not in the fuel ratio state, after performing preliminary control to make the atmosphere of the exhaust purification catalyst a lean air-fuel ratio state, control is performed to make the atmosphere of the exhaust purification catalyst a rich air-fuel ratio state. As a result, the generation amount of hydrogen sulfide during execution of the sulfur component release process is minimized, and the sulfur component can be reliably released from the exhaust purification catalyst.

請求項１に記載の発明によれば、内燃機関本体から排出された排気ガス中の有害成分を浄化する排気浄化触媒が排気系に配置された内燃機関の排気浄化装置であって、排気浄化触媒の硫黄成分の蓄積量を検出する硫黄成分蓄積量検出手段を有し、該硫黄成分蓄積量検出手段からの検出情報に基づいて、排気浄化触媒の温度を所定温度に昇温し且つ排気浄化触媒の雰囲気をリッチ空燃比状態に制御し、排気浄化触媒から蓄積された硫黄成分を放出する硫黄成分放出処理が実行される内燃機関の排気浄化装置において、硫黄成分放出処理実行中の硫化水素の発生を最小限に抑えるともに、排気浄化触媒から硫黄成分を確実に放出させることが可能となる効果を奏する。   According to the first aspect of the present invention, there is provided an exhaust purification device for an internal combustion engine in which an exhaust purification catalyst for purifying harmful components in exhaust gas discharged from an internal combustion engine body is disposed in an exhaust system, the exhaust purification catalyst. And a sulfur component accumulation amount detection means for detecting the accumulation amount of the sulfur component, and based on detection information from the sulfur component accumulation amount detection means, the temperature of the exhaust purification catalyst is raised to a predetermined temperature and the exhaust purification catalyst Of sulfur sulfide during execution of sulfur component release processing in an exhaust purification device of an internal combustion engine in which the sulfur component release processing is performed to release the sulfur component accumulated from the exhaust purification catalyst by controlling the atmosphere of the engine to a rich air-fuel ratio state As a result, the sulfur component can be reliably released from the exhaust purification catalyst.

以下、添付図面を用いて本発明の実施形態について説明する。なお以下の説明において機関空燃比とは燃焼室に供給された燃料の量に対する同様に燃焼室に供給された空気の量の比を意味する。また、排気浄化触媒雰囲気がリーン空燃比状態にあるとは、排気浄化触媒が酸化雰囲気にあることを意味し、排気浄化触媒雰囲気がリッチ空燃比状態にあるとは、排気浄化触媒が還元雰囲気にあることを意味する。   Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the engine air-fuel ratio means the ratio of the amount of air supplied to the combustion chamber to the amount of fuel supplied to the combustion chamber. Further, the exhaust purification catalyst atmosphere being in a lean air-fuel ratio state means that the exhaust purification catalyst is in an oxidizing atmosphere, and the exhaust purification catalyst atmosphere being in a rich air-fuel ratio state is that the exhaust purification catalyst is in a reducing atmosphere. It means that there is.

図１は、本発明の排気浄化装置を４サイクルガソリンエンジンに適用した場合の一実施形態を示す模式図である。但し、本発明の排気浄化装置は、これに限定されることはなく、例えばディーゼルエンジン等の他の内燃機関に適用されてもよい。図１において１は機関本体、２は吸気ポート、３は吸気弁、４は排気ポート、５は排気弁、６は燃焼室、７は点火栓である。燃焼室６内にはピストン８が配置される。吸気ポート２は吸気マニホルド９に接続される。吸気マニホルド９はサージタンク１０を介して吸気通路１１に接続される。吸気通路１１には機関本体１へ吸入せしめられる吸入空気量を検出する吸入空気量検出手段１２が配置される。吸入空気量検出手段１２の上流側の吸気通路１１にはエアクリーナ１３が接続される。一方、吸入空気量検出手段１２の下流側の吸気通路１１には吸入空気量を調整するスロットル弁１５が配置される。スロットル弁１５の下流側であって吸気ポート２近傍の吸気マニホルド９には燃料噴射弁１６が取り付けられる。燃料噴射弁１６は燃料供給通路１７を介して燃料タンク１８に接続される。燃料供給通路１７には吐出量可変の燃料ポンプ１９が配置される。排気ポート４は排気マニホルド２０に接続される。排気マニホルド２０は排気通路２１に接続される。   FIG. 1 is a schematic diagram showing an embodiment in which the exhaust emission control device of the present invention is applied to a four-cycle gasoline engine. However, the exhaust emission control device of the present invention is not limited to this, and may be applied to other internal combustion engines such as a diesel engine. In FIG. 1, 1 is an engine body, 2 is an intake port, 3 is an intake valve, 4 is an exhaust port, 5 is an exhaust valve, 6 is a combustion chamber, and 7 is a spark plug. A piston 8 is disposed in the combustion chamber 6. The intake port 2 is connected to the intake manifold 9. The intake manifold 9 is connected to an intake passage 11 via a surge tank 10. An intake air amount detecting means 12 for detecting the amount of intake air sucked into the engine body 1 is disposed in the intake passage 11. An air cleaner 13 is connected to the intake passage 11 upstream of the intake air amount detection means 12. On the other hand, a throttle valve 15 for adjusting the intake air amount is disposed in the intake passage 11 on the downstream side of the intake air amount detection means 12. A fuel injection valve 16 is attached to the intake manifold 9 on the downstream side of the throttle valve 15 and in the vicinity of the intake port 2. The fuel injection valve 16 is connected to a fuel tank 18 via a fuel supply passage 17. A fuel pump 19 having a variable discharge amount is disposed in the fuel supply passage 17. The exhaust port 4 is connected to the exhaust manifold 20. The exhaust manifold 20 is connected to the exhaust passage 21.

排気通路２１には排気ガス中の有害成分を浄化するための排気浄化触媒として三元触媒２２が配置される。本実施形態においては排気浄化触媒を三元触媒２２としたが、硫黄成分放出処理が必要となる他の排気浄化触媒が適用されてもよい。三元触媒２２は、該三元触媒２２に流入する排気ガスの空燃比が理論空燃比近傍内にあるときに排気ガス中の炭化水素（ＨＣ）、一酸化炭素（ＣＯ）、および窒素酸化物（ＮＯｘ）を同時に高い浄化率にて浄化することができる。   A three-way catalyst 22 is disposed in the exhaust passage 21 as an exhaust purification catalyst for purifying harmful components in the exhaust gas. In the present embodiment, the exhaust purification catalyst is the three-way catalyst 22, but other exhaust purification catalysts that require a sulfur component release process may be applied. The three-way catalyst 22 includes hydrocarbon (HC), carbon monoxide (CO), and nitrogen oxide in the exhaust gas when the air-fuel ratio of the exhaust gas flowing into the three-way catalyst 22 is in the vicinity of the theoretical air-fuel ratio. (NOx) can be simultaneously purified at a high purification rate.

三元触媒２２の上流側の排気通路２１には排気ガスの空燃比を検出するためのセンサ（以下、上流側空燃比センサ）２３が配置される。一方、三元触媒２２下流側の排気通路２１には排気ガスの空燃比を検出するためのセンサ（以下、下流側空燃比センサ）２４が配置される。   A sensor (hereinafter, upstream air-fuel ratio sensor) 23 for detecting the air-fuel ratio of the exhaust gas is disposed in the exhaust passage 21 upstream of the three-way catalyst 22. On the other hand, a sensor (hereinafter, downstream air-fuel ratio sensor) 24 for detecting the air-fuel ratio of the exhaust gas is disposed in the exhaust passage 21 downstream of the three-way catalyst 22.

図１において、３０は触媒温度検出手段を示す。該触媒温度検出手段３０は三元触媒２２の温度を検出あるいは推定する機能を有する。三元触媒温度は、例えば、三元触媒２２の機関本体１に近い上流側あるいは下流側に配置された排気温度センサにより検出された温度情報に基づいて推定される。この場合、触媒温度検出手段３０は、排気温度センサを主要素として構成されることになる。ただし、この場合には、三元触媒２２と排気温度センサとの間には多少の隔たりがあり、この隔たりにおける温度勾配等を推定すべく、回転負荷、空燃比、熱伝達係数、触媒反応速度等のパラメータを用いて補正が行われることになり、これらの各情報を検出する各要素もまた、当該触媒温度検出手段３０の構成要素となる。   In FIG. 1, reference numeral 30 denotes a catalyst temperature detecting means. The catalyst temperature detecting means 30 has a function of detecting or estimating the temperature of the three-way catalyst 22. The three-way catalyst temperature is estimated based on, for example, temperature information detected by an exhaust temperature sensor disposed upstream or downstream of the three-way catalyst 22 near the engine body 1. In this case, the catalyst temperature detecting means 30 is configured with an exhaust temperature sensor as a main element. However, in this case, there is a slight gap between the three-way catalyst 22 and the exhaust gas temperature sensor. In order to estimate a temperature gradient or the like at this gap, the rotational load, air-fuel ratio, heat transfer coefficient, catalyst reaction rate Correction is performed using parameters such as these, and each element for detecting each piece of information is also a constituent element of the catalyst temperature detecting means 30.

また図１において、３１は硫黄成分蓄積量検出手段を示す。該硫黄成分蓄積量検出手段３１は、流入する排気ガスにより三元触媒２２に蓄積された硫黄成分量を検出あるいは推定する機能を有する。例えば、硫黄成分蓄積量は、機関空燃比、触媒温度等をパラメータとして硫黄成分蓄積量を算出するマップであって評価試験や解析評価などから得られたデータに基づいて予め作成されたマップを使用して算出される。この場合、該マップは、後述する電子制御装置５０のメモリーに記憶され格納される。また、硫黄成分蓄積量は、燃料中の硫黄成分の濃度および消費燃料から推定されてもよい。この場合、硫黄成分蓄積量検出手段３１は、燃料中の硫黄成分の濃度および消費燃料量のそれぞれを検出する構成要素を有して構成されることになる。いずれにしても、硫黄成分蓄積量検出手段３１は、三元触媒２２に蓄積された硫黄成分量を検出あるいは推定できる手段であれば、どのような形態のものが適用されてもよい。   Moreover, in FIG. 1, 31 shows a sulfur component accumulation | storage amount detection means. The sulfur component accumulation amount detection means 31 has a function of detecting or estimating the amount of sulfur component accumulated in the three-way catalyst 22 by the inflowing exhaust gas. For example, the sulfur component accumulation amount is a map that calculates the sulfur component accumulation amount using engine air-fuel ratio, catalyst temperature, etc. as parameters, and uses a map created in advance based on data obtained from evaluation tests and analytical evaluations. Is calculated. In this case, the map is stored and stored in the memory of the electronic control unit 50 described later. Further, the sulfur component accumulation amount may be estimated from the concentration of the sulfur component in the fuel and the consumed fuel. In this case, the sulfur component accumulation amount detection means 31 is configured to include components for detecting the concentration of the sulfur component in the fuel and the amount of consumed fuel. In any case, the sulfur component accumulation amount detection means 31 may be applied in any form as long as it can detect or estimate the sulfur component amount accumulated in the three-way catalyst 22.

機関本体１には点火デストリビュータ２５が取り付けられる。点火デストリビュータ２５には二つのクランク角センサ２６および２７が取り付けられる。これらクランク角センサ２６および２７から出力されるパルス信号に基づいて機関回転数が算出される。   An ignition distributor 25 is attached to the engine body 1. Two crank angle sensors 26 and 27 are attached to the ignition distributor 25. Based on the pulse signals output from the crank angle sensors 26 and 27, the engine speed is calculated.

内燃機関は電子制御装置（以下、ＥＣＵと称する）５０を具備する。ＥＣＵ５０はデジタルコンピュータからなり、双方向性バス５１により互いに接続されたＲＯＭ（リードオンリメモリ）５２、ＲＡＭ（ランダムアクセスメモリ）５３、ＣＰＵ（マイクロプロセッサ）５４、入力ポート５５、および出力ポート５６を具備する。吸入空気量検出手段１２、上流側空燃比センサ２３、および下流側空燃比センサ２４などは対応するＡＤ変換器５７を介して入力ポート５５に接続される。クランク角センサ２６および２７などは入力ポート５５に直接接続される。点火栓７、燃料噴射弁１６、および燃料ポンプ１９などは対応する駆動回路５８を介して出力ポート５６に接続される。アクセルペダル１４には負荷センサ２８が接続される。負荷センサ２８は内燃機関に対する要求機関負荷を検出する。負荷センサ２８は対応するＡＤ変換器５７を介して入力ポート５５に接続される。   The internal combustion engine includes an electronic control unit (hereinafter referred to as ECU) 50. The ECU 50 comprises a digital computer, and includes a ROM (Read Only Memory) 52, a RAM (Random Access Memory) 53, a CPU (Microprocessor) 54, an input port 55, and an output port 56 connected to each other by a bidirectional bus 51. To do. The intake air amount detection means 12, the upstream air-fuel ratio sensor 23, the downstream air-fuel ratio sensor 24, and the like are connected to the input port 55 via the corresponding AD converter 57. The crank angle sensors 26 and 27 and the like are directly connected to the input port 55. The spark plug 7, the fuel injection valve 16, the fuel pump 19, and the like are connected to the output port 56 via a corresponding drive circuit 58. A load sensor 28 is connected to the accelerator pedal 14. The load sensor 28 detects a required engine load for the internal combustion engine. The load sensor 28 is connected to the input port 55 via a corresponding AD converter 57.

ところで、上述したように、排気ガス中に硫黄成分が含まれている場合、この硫黄成分が排気浄化触媒に蓄積され、排気浄化触媒の排気浄化性能が低下するおそれがある。すなわち排気浄化触媒が硫黄成分により被毒される場合がある。そして、排気浄化性能を維持すべく排気浄化触媒から硫黄成分を放出する一つの方策として、排気浄化触媒温度を所定温度に昇温させ且つ排気浄化触媒に流入する排気ガスの空燃比をリッチ空燃比にして排気浄化触媒雰囲気の空燃比状態をリッチ空燃比状態にする、硫黄成分放出処理が適用されることが知られている。このような硫黄成分放出処理によれば、排気浄化触媒に蓄積された硫黄成分を排気浄化触媒から放出することが可能となる。   Incidentally, as described above, when the exhaust gas contains a sulfur component, the sulfur component is accumulated in the exhaust purification catalyst, and the exhaust purification performance of the exhaust purification catalyst may be deteriorated. That is, the exhaust purification catalyst may be poisoned by the sulfur component. As one measure for releasing the sulfur component from the exhaust purification catalyst in order to maintain the exhaust purification performance, the exhaust purification catalyst temperature is raised to a predetermined temperature and the air-fuel ratio of the exhaust gas flowing into the exhaust purification catalyst is set to the rich air-fuel ratio. Thus, it is known that a sulfur component release process is applied in which the air-fuel ratio state of the exhaust purification catalyst atmosphere is changed to a rich air-fuel ratio state. According to such a sulfur component releasing process, the sulfur component accumulated in the exhaust purification catalyst can be released from the exhaust purification catalyst.

しかしながら、硫黄成分が蓄積された排気浄化触媒に対して上記硫黄成分放出処理が実行される際には、ＳＯｘとともに硫化水素（Ｈ2Ｓ）が一時的に発生する。このような硫化水素は強い臭気を発生させる性質があり、多量の硫化水素が大気中に放出されることは好ましいものではない。従って、硫黄成分放出処理を実行するに当たっては、硫黄成分放出処理実行中の硫化水素の発生量を最小限に抑えるともに、排気浄化触媒から硫黄成分を確実に放出させることが望ましい。 However, when the sulfur component release process is performed on the exhaust purification catalyst in which the sulfur component is accumulated, hydrogen sulfide (H 2 S) is temporarily generated together with SOx. Such hydrogen sulfide has a property of generating a strong odor, and it is not preferable that a large amount of hydrogen sulfide is released into the atmosphere. Therefore, when performing the sulfur component releasing process, it is desirable to minimize the amount of hydrogen sulfide generated during the execution of the sulfur component releasing process and to reliably release the sulfur component from the exhaust purification catalyst.

本出願人は、硫黄成分放出処理における排気浄化触媒雰囲気をリッチ空燃比状態にする制御が実行される直前の排気浄化触媒雰囲気の空燃比状態が、硫黄成分放出処理実行中の排気浄化触媒からの硫黄成分の放出量および硫化水素の発生量に関与していることを突き止めた。   The present applicant has determined that the air-fuel ratio state of the exhaust purification catalyst atmosphere immediately before execution of the control for setting the exhaust purification catalyst atmosphere in the sulfur component release processing to the rich air-fuel ratio state is the It was found that it was involved in the amount of sulfur component released and the amount of hydrogen sulfide generated.

図２は、評価試験などの結果データに基づいた硫黄成分放出処理実行時におけるＳＯｘ濃度および硫化水素濃度の一例を示す図であって、硫黄成分放出処理における排気浄化触媒雰囲気をリッチ空燃比状態にする制御が実行される直前の排気浄化触媒雰囲気がリーン空燃比状態にある場合と、リーン空燃比状態にない場合すなわちリッチ空燃比あるいは理論空燃比にある場合とのそれぞれの場合における、硫黄成分放出処理実行時のＳＯｘ濃度および硫化水素濃度の相違を示す図である。   FIG. 2 is a diagram showing an example of the SOx concentration and the hydrogen sulfide concentration at the time of execution of the sulfur component release process based on result data such as an evaluation test, and the exhaust purification catalyst atmosphere in the sulfur component release process is set to a rich air-fuel ratio state. Sulfur component release when the exhaust purification catalyst atmosphere just before the control to be performed is in the lean air-fuel ratio state and when it is not in the lean air-fuel ratio state, that is, when it is in the rich air-fuel ratio or the stoichiometric air-fuel ratio It is a figure which shows the difference of SOx density | concentration at the time of processing execution, and hydrogen sulfide density | concentration.

図２から理解されるごとく、硫黄成分放出処理における排気浄化触媒雰囲気をリッチ空燃比状態にする制御が実行される直前の排気浄化触媒雰囲気がリーン空燃比状態にある場合には、その排気浄化触媒雰囲気がリーン空燃比状態にない場合と比較して、硫黄成分放出処理実行中の硫化水素濃度は低くなり、ＳＯｘ濃度は高くなることが確認された。また、この比較において、硫黄成分放出処理実行中のＳＯｘ濃度が高くなる量（ａ）は、硫化水素濃度が低くなる量（ｂ）よりも大きいことが確認された。すなわち、硫黄成分放出処理における排気浄化触媒雰囲気をリッチ空燃比状態にする制御が実行される直前の排気浄化触媒雰囲気がリーン空燃比状態にある場合には、その排気浄化触媒雰囲気がリーン空燃比状態にない場合と比較して、硫黄成分放出処理実行中の硫化水素の発生量を低く抑えることでき、且つ、より多くの硫黄成分を排気浄化触媒から放出することができることが判明した。   As understood from FIG. 2, when the exhaust purification catalyst atmosphere immediately before the control to make the exhaust purification catalyst atmosphere in the rich air-fuel ratio state in the sulfur component release process is in the lean air-fuel ratio state, the exhaust purification catalyst It was confirmed that the concentration of hydrogen sulfide during the execution of the sulfur component release process was lower and the SOx concentration was higher than when the atmosphere was not in a lean air-fuel ratio state. Further, in this comparison, it was confirmed that the amount (a) in which the SOx concentration during the sulfur component releasing process is increased is larger than the amount (b) in which the hydrogen sulfide concentration is decreased. That is, when the exhaust purification catalyst atmosphere immediately before the control for setting the exhaust purification catalyst atmosphere in the sulfur component release process to the rich air-fuel ratio state is in the lean air-fuel ratio state, the exhaust purification catalyst atmosphere is in the lean air-fuel ratio state. It was found that the amount of hydrogen sulfide generated during the execution of the sulfur component release process can be kept low, and more sulfur components can be released from the exhaust purification catalyst than in the case where the sulfur component release process is performed.

このことに基づいて、本発明の内燃機関の排気浄化装置においては、硫黄成分放出処理を実行する際に、排気浄化触媒の雰囲気がリーン空燃比状態にない場合すなわちリッチ空燃比状態あるいは理論空燃比状態にある場合には、排気浄化触媒の雰囲気をリーン空燃比状態にする予備制御を実行した後に、排気浄化触媒の雰囲気をリッチ空燃比状態にする制御を実行することで、硫黄成分放出処理実行中の硫化水素の発生量を最小限に抑えるともに、排気浄化触媒から硫黄成分を確実に放出させることを可能とする。   Based on this, in the exhaust gas purification apparatus for an internal combustion engine of the present invention, when the sulfur component release process is executed, when the atmosphere of the exhaust gas purification catalyst is not in the lean air-fuel ratio state, that is, the rich air-fuel ratio state or the stoichiometric air-fuel ratio. If so, after performing preliminary control to make the exhaust purification catalyst atmosphere a lean air-fuel ratio state, execute control to bring the exhaust purification catalyst atmosphere to a rich air-fuel ratio state, thereby executing sulfur component release processing In addition to minimizing the amount of hydrogen sulfide contained therein, it is possible to reliably release the sulfur component from the exhaust purification catalyst.

以下に、本発明の内燃機関の排気浄化装置が適用された図１に示す内燃機関で実行される硫黄成分放出処理の制御について説明する。図３は、本発明の内燃機関の排気浄化装置が適用された図１に示す内燃機関で実行される硫黄成分放出処理の制御ルーチンの一実施形態を示すフローチャート図である。   The control of the sulfur component releasing process executed in the internal combustion engine shown in FIG. 1 to which the exhaust gas purification apparatus for an internal combustion engine of the present invention is applied will be described below. FIG. 3 is a flowchart showing one embodiment of a control routine for sulfur component release processing executed in the internal combustion engine shown in FIG. 1 to which the exhaust gas purification apparatus for an internal combustion engine of the present invention is applied.

図３に示す制御ルーチンでは、まず、排気浄化触媒の硫黄成分の蓄積量に基づいて硫黄成分放出処理の実行の必要の有無の判定がなされる。硫黄成分放出処理の実行が必要と判定されると、排気浄化触媒温度が所定温度以上にあるか否かの判定がなされ、所定温度以上にないと判定された場合には排気浄化触媒の昇温制御が実行される。排気浄化触媒温度が所定温度以上にあると判定されると、次に、排気浄化触媒雰囲気の空燃比状態がリーン空燃比状態にあるか否かが判定される。ここで、排気浄化触媒雰囲気がリーン空燃比状態にないと判定されると、排気浄化触媒雰囲気をリーン空燃比状態にする予備制御が実行される。排気浄化触媒雰囲気がリーン空燃比状態になったと判定されると、次に、排気浄化触媒雰囲気をリッチ空燃比状態にする制御が実行され、排気浄化触媒から硫黄成分が放出される。そして、排気浄化触媒の硫黄成分の蓄積量が所定量以下になったことが確認されると本制御ルーチンは終了する。
以下に本制御ルーチンの各ステップの詳細について述べる。 In the control routine shown in FIG. 3, it is first determined whether or not the sulfur component release process needs to be executed based on the amount of sulfur component accumulated in the exhaust purification catalyst. When it is determined that the sulfur component release process needs to be performed, it is determined whether or not the exhaust purification catalyst temperature is equal to or higher than a predetermined temperature. Control is executed. If it is determined that the exhaust purification catalyst temperature is equal to or higher than the predetermined temperature, it is next determined whether or not the air-fuel ratio state of the exhaust purification catalyst atmosphere is a lean air-fuel ratio state. Here, if it is determined that the exhaust purification catalyst atmosphere is not in the lean air-fuel ratio state, preliminary control for changing the exhaust purification catalyst atmosphere to the lean air-fuel ratio state is executed. If it is determined that the exhaust purification catalyst atmosphere has become a lean air-fuel ratio state, then control for making the exhaust purification catalyst atmosphere a rich air-fuel ratio state is executed, and sulfur components are released from the exhaust purification catalyst. Then, when it is confirmed that the accumulated amount of the sulfur component of the exhaust purification catalyst has become equal to or less than the predetermined amount, this control routine ends.
Details of each step of this control routine will be described below.

先ず、ステップ１０１においては、三元触媒２２の硫黄成分の蓄積量に基づいて、硫黄成分放出処理の実行の必要性の有無の判定がなされる。該判定は、三元触媒２２の硫黄成分の蓄積量が硫黄成分蓄積量検出手段３１から検出され、該検出情報がＥＣＵ５０に取り込まれ、三元触媒２２の硫黄成分の蓄積量が、三元触媒２２の浄化性能や内燃機関の設計仕様などに基づいて予め設定された所定量を越えたか否かの判定がＥＣＵ５０によりなされることで行われる。三元触媒２２の硫黄成分の蓄積量が所定量を越えたことが確認されると、硫黄成分放出処理の実行が必要であるとＥＣＵ５０により判定され、続くステップ１０２に進む。   First, in step 101, based on the amount of sulfur component accumulated in the three-way catalyst 22, it is determined whether or not it is necessary to perform sulfur component release processing. In this determination, the accumulated amount of the sulfur component of the three-way catalyst 22 is detected from the sulfur component accumulated amount detecting means 31, the detected information is taken into the ECU 50, and the accumulated amount of the sulfur component of the three-way catalyst 22 is determined by the three-way catalyst. The ECU 50 determines whether a predetermined amount that has been set in advance is exceeded based on the purification performance of the engine 22 or the design specifications of the internal combustion engine. When it is confirmed that the accumulated amount of the sulfur component of the three-way catalyst 22 exceeds the predetermined amount, the ECU 50 determines that the sulfur component releasing process needs to be executed, and the process proceeds to the subsequent step 102.

ステップ１０２においては、硫黄成分放出処理の実行が必要であるとの判定を受けて、三元触媒２２の温度が所定温度以上にあるか否かの判定がなされる。該判定は、三元触媒２２の温度が触媒温度検出手段３０から検出され、該検出情報がＥＣＵ５０に取り込まれ、三元触媒２２の温度が、三元触媒２２の浄化性能や内燃機関の設計仕様などに基づいて予め設定された所定温度以上にあるか否かの判定がＥＣＵ５０によりなされることで行われる。三元触媒２２の温度が所定温度以上にないことがＥＣＵ５０により確認されると、続くステップ１０３に進む。   In step 102, in response to the determination that the sulfur component releasing process needs to be executed, it is determined whether or not the temperature of the three-way catalyst 22 is equal to or higher than a predetermined temperature. In this determination, the temperature of the three-way catalyst 22 is detected from the catalyst temperature detecting means 30, and the detected information is taken into the ECU 50. The temperature of the three-way catalyst 22 is determined based on the purification performance of the three-way catalyst 22 and the design specifications of the internal combustion engine. The ECU 50 determines whether or not the temperature is equal to or higher than a predetermined temperature set in advance based on the above. When the ECU 50 confirms that the temperature of the three-way catalyst 22 is not equal to or higher than the predetermined temperature, the process proceeds to the subsequent step 103.

ステップ１０３においては、三元触媒２２の温度が所定温度以上にないとの判定を受けて、三元触媒２２の昇温制御が実行される。三元触媒２２の温度を所定温度以上に昇温する手段としては種々の手段が考えられるが、例えば、点火時期を遅角制御することによりなされてもよい。また、三元触媒２２にヒータが備えられ、該ヒータにより三元触媒２２の昇温がなされてもよい。この場合、該ヒータが本発明の内燃機関の排気浄化装置の一構成要素として加えられることになる。   In step 103, in response to the determination that the temperature of the three-way catalyst 22 is not equal to or higher than a predetermined temperature, the temperature increase control of the three-way catalyst 22 is executed. Various means are conceivable as means for raising the temperature of the three-way catalyst 22 to a predetermined temperature or higher. For example, the ignition timing may be controlled by retarding the ignition timing. The three-way catalyst 22 may be provided with a heater, and the temperature of the three-way catalyst 22 may be increased by the heater. In this case, the heater is added as a component of the exhaust gas purification apparatus for an internal combustion engine of the present invention.

ステップ１０３において三元触媒２２の昇温制御が実行されると、ステップ１０２に戻り、再び、三元触媒２２の温度が所定温度以上にあるか否かの判定がなされる。ステップ１０３における三元触媒２２の昇温制御は、三元触媒２２の温度が所定温度以上になったと判定されるまで実行され、ステップ１０２において三元触媒２２の温度が所定温度以上にあると判定されるとステップ１０４に進む。   When the temperature increase control of the three-way catalyst 22 is executed in step 103, the process returns to step 102, and it is determined again whether or not the temperature of the three-way catalyst 22 is equal to or higher than a predetermined temperature. The temperature increase control of the three-way catalyst 22 in step 103 is executed until it is determined that the temperature of the three-way catalyst 22 has become equal to or higher than the predetermined temperature, and in step 102, it is determined that the temperature of the three-way catalyst 22 is higher than the predetermined temperature. Then, the process proceeds to step 104.

ステップ１０４においては、三元触媒雰囲気がリーン空燃比状態にあるか否かの判定がなされる。該判定は、三元触媒２２の下流側の排気通路２１に配設された下流側空燃比センサ２４からの検出情報に基づいてＥＣＵ５０によりなされる。三元触媒雰囲気がリーン空燃比状態にない、すなわち、三元触媒雰囲気がリッチ空燃比状態あるいは理論空燃比状態にあると判定されると、続くステップ１０５に進む。   In step 104, it is determined whether or not the three-way catalyst atmosphere is in a lean air-fuel ratio state. This determination is made by the ECU 50 based on detection information from the downstream air-fuel ratio sensor 24 disposed in the exhaust passage 21 on the downstream side of the three-way catalyst 22. If it is determined that the three-way catalyst atmosphere is not in the lean air-fuel ratio state, that is, the three-way catalyst atmosphere is in the rich air-fuel ratio state or the stoichiometric air-fuel ratio state, the routine proceeds to the subsequent step 105.

ステップ１０５においては、三元触媒雰囲気がリーン空燃比状態にないとの判定を受けて、三元触媒雰囲気をリーン空燃比状態にする予備制御が実行される。本実施形態においては、三元触媒雰囲気をリーン空燃比状態にする制御は、機関空燃比をリーン空燃比に制御し、三元触媒２２に流入する排気ガスの空燃比をリーン空燃比にすることでなされる。   In step 105, in response to the determination that the three-way catalyst atmosphere is not in the lean air-fuel ratio state, preliminary control for changing the three-way catalyst atmosphere to the lean air-fuel ratio state is executed. In the present embodiment, the control to bring the three-way catalyst atmosphere to the lean air-fuel ratio state is to control the engine air-fuel ratio to the lean air-fuel ratio and to make the air-fuel ratio of the exhaust gas flowing into the three-way catalyst 22 the lean air-fuel ratio. Made in

尚、機関空燃比をリーン空燃比にする制御は、三元触媒２２の下流側の排気通路２１に配設された下流側空燃比センサ２４からの検出情報に基づいて目標機関空燃比がフィードバック制御され、該目標機関空燃比を達成すべく、三元触媒２２の上流側の排気通路２１に配設された上流側空燃比センサ２３の検出情報に基づいて、燃料噴射弁１６からの燃料噴射量などがＥＣＵ５０により制御されることによりなされる。   In order to control the engine air-fuel ratio to be a lean air-fuel ratio, the target engine air-fuel ratio is feedback controlled based on detection information from the downstream air-fuel ratio sensor 24 disposed in the exhaust passage 21 downstream of the three-way catalyst 22. In order to achieve the target engine air-fuel ratio, the fuel injection amount from the fuel injection valve 16 is based on the detection information of the upstream air-fuel ratio sensor 23 disposed in the exhaust passage 21 upstream of the three-way catalyst 22. And the like are performed by being controlled by the ECU 50.

また、三元触媒雰囲気をリーン空燃比状態にする予備制御は、他の手段で実行されてもよく、例えば、機関本体１から排出された排気ガス中に直接二次空気を供給し、三元触媒２２に流入する排気ガスの空燃比をリーン空燃比にすることでなされてもよい。この場合には、二次空気供給手段が本発明の内燃機関の排気浄化装置の一構成要素として加えられることになる。   Further, the preliminary control for making the three-way catalyst atmosphere a lean air-fuel ratio state may be executed by other means, for example, by supplying secondary air directly into the exhaust gas discharged from the engine body 1, and This may be done by setting the air-fuel ratio of the exhaust gas flowing into the catalyst 22 to a lean air-fuel ratio. In this case, the secondary air supply means is added as a component of the exhaust gas purification apparatus for the internal combustion engine of the present invention.

ステップ１０５において三元触媒雰囲気をリーン空燃比状態にする予備制御が実行されると、ステップ１０４に戻り、再び、三元触媒雰囲気がリーン空燃比状態にあるか否かの判定がなされる。ステップ１０５における三元触媒雰囲気をリーン空燃比状態にする予備制御は、三元触媒雰囲気がリーン空燃比状態になったと判定されるまで実行され、ステップ１０４において、三元触媒雰囲気がリーン空燃比状態にあると判定されるとステップ１０６に進む。   When the preliminary control for setting the three-way catalyst atmosphere to the lean air-fuel ratio state is executed in step 105, the process returns to step 104, and it is determined again whether or not the three-way catalyst atmosphere is in the lean air-fuel ratio state. The preliminary control for changing the three-way catalyst atmosphere to the lean air-fuel ratio state in step 105 is executed until it is determined that the three-way catalyst atmosphere has become the lean air-fuel ratio state. In step 104, the three-way catalyst atmosphere is set to the lean air-fuel ratio state. If it is determined that there is, the process proceeds to step 106.

ステップ１０６においては、三元触媒雰囲気がリーン空燃比状態にあるとの判定を受けて、三元触媒雰囲気をリッチ空燃比状態にする制御が実行される。本実施形態においては、三元触媒雰囲気をリッチ空燃比状態にする制御は、機関空燃比をリッチ空燃比に制御し、三元触媒２２に流入する排気ガスの空燃比をリッチ空燃比にすることでなされる。   In step 106, in response to the determination that the three-way catalyst atmosphere is in the lean air-fuel ratio state, control for changing the three-way catalyst atmosphere to the rich air-fuel ratio state is executed. In the present embodiment, the control to bring the three-way catalyst atmosphere to the rich air-fuel ratio is performed by controlling the engine air-fuel ratio to the rich air-fuel ratio and setting the air-fuel ratio of the exhaust gas flowing into the three-way catalyst 22 to the rich air-fuel ratio. Made in

尚、機関空燃比をリッチ空燃比にする制御は、ステップ１０５と同様に、三元触媒２２の下流側の排気通路２１に配設された下流側空燃比センサ２４からの検出情報に基づいて目標機関空燃比がフィードバック制御され、該目標機関空燃比を達成すべく、三元触媒２２の上流側の排気通路２１に配設された上流側空燃比センサ２３の検出情報に基づいて、燃料噴射弁１６からの燃料噴射量などがＥＣＵ５０により制御されることによりなされる。   Note that the control for making the engine air-fuel ratio a rich air-fuel ratio is performed based on detection information from the downstream air-fuel ratio sensor 24 disposed in the exhaust passage 21 downstream of the three-way catalyst 22, as in step 105. The fuel injection valve is controlled based on the detection information of the upstream air-fuel ratio sensor 23 disposed in the exhaust passage 21 upstream of the three-way catalyst 22 so that the engine air-fuel ratio is feedback-controlled and the target engine air-fuel ratio is achieved. The fuel injection amount from 16 is controlled by the ECU 50.

また、三元触媒雰囲気をリッチ空燃比状態にする制御は、他の手段で実行されてもよく、例えば、機関本体１から排出された排気ガス中に直接二次燃料を供給し、三元触媒２２に流入する排気ガスの空燃比をリッチ空燃比にすることでなされてもよい。この場合には、二次燃料供給手段が本発明の内燃機関の排気浄化装置の一構成要素として加えられることになる。   Further, the control for bringing the three-way catalyst atmosphere into the rich air-fuel ratio state may be executed by other means. For example, the secondary fuel is directly supplied into the exhaust gas discharged from the engine body 1, and the three-way catalyst is supplied. Alternatively, the air-fuel ratio of the exhaust gas flowing into the engine 22 may be set to a rich air-fuel ratio. In this case, the secondary fuel supply means is added as a component of the exhaust gas purification apparatus for the internal combustion engine of the present invention.

ステップ１０６に続くステップ１０７においては、ステップ１０１からステップ１０６までの一連の硫黄成分放出処理の実行により、三元触媒２２の硫黄成分の蓄積量が所定量以下になったか否かの判定がなされる。該判定は、三元触媒２２の硫黄成分の蓄積量が硫黄成分蓄積量検出手段３１により検出され、該検出情報がＥＣＵ５０に取り込まれ、三元触媒２２の硫黄成分の蓄積量が、三元触媒２２の浄化性能や内燃機関の設計仕様などに基づいて予め設定された所定量以下になったか否かの判定がＥＣＵ５０によりなされることで行われる。   In step 107 following step 106, it is determined whether or not the accumulated amount of sulfur components in the three-way catalyst 22 has become a predetermined amount or less by executing a series of sulfur component releasing processes from step 101 to step 106. . In this determination, the sulfur component accumulation amount of the three-way catalyst 22 is detected by the sulfur component accumulation amount detection means 31, the detection information is taken into the ECU 50, and the sulfur component accumulation amount of the three-way catalyst 22 is determined by the three-way catalyst. The ECU 50 determines whether or not a predetermined amount or less is set based on the purification performance of the engine 22 or the design specifications of the internal combustion engine.

ステップ１０７において、三元触媒２２の硫黄成分の蓄積量が所定量以下になっていないと判定されると、ステップ１０６に戻り、三元触媒雰囲気をリッチ空燃比状態にする制御が実行される。ステップ１０６における三元触媒雰囲気をリッチ空燃比状態にする制御は、ステップ１０７において、三元触媒２２の硫黄成分の蓄積量が所定量以下になったと判定されるまで実行される。そして、ステップ１０７において、三元触媒２２の硫黄成分の蓄積量が所定量以下になったと判定されると一連の制御ルーチンは終了される。   If it is determined in step 107 that the amount of sulfur component accumulated in the three-way catalyst 22 is not less than or equal to the predetermined amount, the process returns to step 106, and control is performed to bring the three-way catalyst atmosphere to a rich air-fuel ratio state. The control to bring the three-way catalyst atmosphere to the rich air-fuel ratio state in step 106 is executed until it is determined in step 107 that the accumulation amount of the sulfur component of the three-way catalyst 22 has become a predetermined amount or less. When it is determined in step 107 that the amount of sulfur component accumulated in the three-way catalyst 22 has become equal to or less than a predetermined amount, the series of control routines is terminated.

以上、図３に示される硫黄成分放出処理の制御ルーチンによれば、ステップ１０４において、硫黄成分放出処理における排気浄化触媒雰囲気をリッチ空燃比状態にする制御が実行される直前の排気浄化触媒の雰囲気がリーン空燃比状態にないと判定された場合すなわちリッチ空燃比状態あるいは理論空燃比状態にあると判定された場合には、ステップ１０５において排気浄化触媒の雰囲気をリーン空燃比状態にする予備制御が実行された後に、ステップ１０６において排気浄化触媒の雰囲気をリッチ空燃比状態にする制御を実行することで、硫黄成分放出処理実行中の硫化水素の発生量を最小限に抑えるともに、排気浄化触媒から硫黄成分を確実に放出させることが可能となる。   As described above, according to the control routine for the sulfur component release process shown in FIG. 3, in step 104, the atmosphere of the exhaust purification catalyst immediately before the control for changing the exhaust purification catalyst atmosphere in the sulfur component release process to the rich air-fuel ratio state is executed. When it is determined that the air-fuel ratio is not in the lean air-fuel ratio state, that is, when it is determined that the air-fuel ratio state is in the rich air-fuel ratio state or the stoichiometric air-fuel ratio state, in step 105, preliminary control is performed to bring the atmosphere of the exhaust purification catalyst into the lean air-fuel ratio state. After being executed, in step 106, control is performed to bring the atmosphere of the exhaust purification catalyst to a rich air-fuel ratio state, thereby minimizing the amount of hydrogen sulfide generated during execution of the sulfur component release process, and from the exhaust purification catalyst. The sulfur component can be reliably released.

尚、本発明の排気浄化装置が適用された図１に示す内燃機関で実行される図３に示される硫黄成分放出処理の制御ルーチンにおいては、ステップ１０４における三元触媒雰囲気がリーン空燃比状態にあるか否かの判定が、三元触媒２２下流側の排気通路２１に配設された下流側空燃比センサ２４からの検出情報に基づいてなされるが、下流側空燃比センサ２４が配設されない場合も想定される。このような場合には、三元触媒雰囲気がリーン空燃比状態にあるか否かの判定は、吸入空気量、上流側空燃比センサ２３からの検出値および三元触媒２２の最大酸素吸蔵量などをパラメータとして三元触媒雰囲気の空燃比状態を特定するマップであって評価試験や解析評価などから得られたデータに基づいて予め作成されたマップを使用してなされてもよい。この場合、該マップは、ＥＣＵ５０のメモリーに記憶され格納される。   In the control routine of the sulfur component release process shown in FIG. 3 executed in the internal combustion engine shown in FIG. 1 to which the exhaust gas purification apparatus of the present invention is applied, the three-way catalyst atmosphere in step 104 is set to the lean air-fuel ratio state. Whether or not there is is determined based on detection information from the downstream air-fuel ratio sensor 24 disposed in the exhaust passage 21 downstream of the three-way catalyst 22, but the downstream air-fuel ratio sensor 24 is not disposed. Cases are also envisaged. In such a case, whether or not the three-way catalyst atmosphere is in the lean air-fuel ratio state is determined by determining the intake air amount, the detected value from the upstream air-fuel ratio sensor 23, the maximum oxygen storage amount of the three-way catalyst 22, and the like. May be made using a map that specifies the air-fuel ratio state of the three-way catalyst atmosphere using the map obtained in advance based on data obtained from an evaluation test or analysis evaluation. In this case, the map is stored and stored in the memory of the ECU 50.

また、複数の排気浄化触媒が直列にあるいは並列に排気系に配設される場合も想定される。このような場合には、硫黄成分放出処理を実行する際に、全ての排気浄化触媒の雰囲気をリーン空燃比状態にする予備制御が実行された後に、排気浄化触媒の雰囲気をリッチ空燃比状態にする制御が実行されてよい。このように制御することで、より最小限に硫黄成分放出処理実行中の硫化水素の発生量を抑えることができるとともに、より確実に排気浄化触媒から硫黄成分を放出させることが可能となる。   It is also assumed that a plurality of exhaust purification catalysts are arranged in the exhaust system in series or in parallel. In such a case, when the sulfur component release process is executed, after preliminary control is performed to make all the exhaust purification catalyst atmospheres in a lean air-fuel ratio state, the exhaust purification catalyst atmosphere is changed to a rich air-fuel ratio state. Control may be performed. By controlling in this way, the generation amount of hydrogen sulfide during execution of the sulfur component release process can be suppressed to a minimum, and the sulfur component can be more reliably released from the exhaust purification catalyst.

本発明の排気浄化装置を４サイクルガソリンエンジンに適用した場合の一実施形態を示す模式図である。It is a mimetic diagram showing one embodiment at the time of applying the exhaust-air-purification device of the present invention to a 4-cycle gasoline engine. 評価試験などの結果データに基づいた硫黄成分放出処理実行時におけるＳＯｘ濃度および硫化水素濃度の一例を示す図であって、硫黄成分放出処理における排気浄化触媒雰囲気をリッチ空燃比状態にする制御が実行される直前の排気浄化触媒雰囲気がリーン空燃比状態にある場合と、リーン空燃比状態にない場合すなわちリッチ空燃比あるいは理論空燃比にある場合とのそれぞれの場合における、硫黄成分放出処理実行時のＳＯｘ濃度および硫化水素濃度の相違を示す図である。It is a figure which shows an example of the SOx density | concentration at the time of execution of sulfur component discharge | release processing based on result data, such as an evaluation test, Comprising: The control which makes the exhaust gas purification catalyst atmosphere in a sulfur component discharge | release process a rich air-fuel ratio state is performed In the case where the exhaust purification catalyst atmosphere immediately before being performed is in the lean air-fuel ratio state and in the case where the exhaust air-fuel ratio state is not in the lean air-fuel ratio state, that is, in the case of the rich air-fuel ratio or the stoichiometric air-fuel ratio. It is a figure which shows the difference of SOx density | concentration and hydrogen sulfide density | concentration. 本発明の内燃機関の排気浄化装置が適用された図１に示す内燃機関で実行される硫黄成分放出処理の制御ルーチンの一実施形態を示すフローチャート図である。It is a flowchart figure which shows one Embodiment of the control routine of the sulfur component discharge | release process performed with the internal combustion engine shown in FIG. 1 with which the exhaust gas purification apparatus of the internal combustion engine of this invention was applied.

符号の説明Explanation of symbols

１ 機関本体
２ 吸気ポート
３ 吸気弁
４ 排気ポート
５ 排気弁
６ 燃焼室
７ 点火栓
８ ピストン
９ 吸気マニホルド
１１ 吸気通路
１２ 吸入空気量検出手段
１３ エアクリーナ
１５ スロットル弁
１６ 燃料噴射弁
２０ 排気マニホルド
２１ 排気通路
２２ 三元触媒
２３ 上流側空燃比センサ
２４ 下流側空燃比センサ
３０ 触媒温度検出手段
３１ 硫黄成分蓄積量検出手段
５０ ＥＣＵ DESCRIPTION OF SYMBOLS 1 Engine body 2 Intake port 3 Intake valve 4 Exhaust port 5 Exhaust valve 6 Combustion chamber 7 Spark plug 8 Piston 9 Intake manifold 11 Intake passage 12 Intake air amount detection means 13 Air cleaner 15 Throttle valve 16 Fuel injection valve 20 Exhaust manifold 21 Exhaust passage 22 three-way catalyst 23 upstream air-fuel ratio sensor 24 downstream air-fuel ratio sensor 30 catalyst temperature detection means 31 sulfur component accumulation amount detection means 50 ECU

Claims (1)

内燃機関本体から排出された排気ガス中の有害成分を浄化する排気浄化触媒が排気系に配置された内燃機関の排気浄化装置であって、
前記排気浄化触媒の硫黄成分の蓄積量を検出する硫黄成分蓄積量検出手段を有し、
前記硫黄成分蓄積量検出手段からの検出情報に基づいて、前記排気浄化触媒の温度を所定温度に昇温し且つ前記排気浄化触媒の雰囲気をリッチ空燃比状態に制御し、前記排気浄化触媒から蓄積された硫黄成分を放出する硫黄成分放出処理が実行される内燃機関の排気浄化装置において、
前記硫黄成分放出処理を実行する際に、前記排気浄化触媒の雰囲気がリッチ空燃比状態あるいは理論空燃比状態にある場合には、
前記排気浄化触媒の雰囲気をリーン空燃比状態にする予備制御が実行された後に、前記排気浄化触媒の雰囲気をリッチ空燃比状態にする制御が実行される、
ことを特徴とする内燃機関の排気浄化装置。 An exhaust gas purification device for an internal combustion engine in which an exhaust gas purification catalyst for purifying harmful components in exhaust gas discharged from an internal combustion engine body is disposed in an exhaust system,
A sulfur component accumulation amount detecting means for detecting the accumulation amount of the sulfur component of the exhaust purification catalyst;
Based on detection information from the sulfur component accumulation amount detection means, the temperature of the exhaust purification catalyst is raised to a predetermined temperature, and the atmosphere of the exhaust purification catalyst is controlled to a rich air-fuel ratio state, and accumulated from the exhaust purification catalyst. In the exhaust gas purification apparatus for an internal combustion engine in which the sulfur component release process for releasing the sulfur component is performed,
When executing the sulfur component release process, if the atmosphere of the exhaust purification catalyst is in a rich air-fuel ratio state or a stoichiometric air-fuel ratio state,
After the preliminary control for setting the atmosphere of the exhaust purification catalyst to a lean air-fuel ratio state is executed, the control for setting the atmosphere of the exhaust purification catalyst to a rich air-fuel ratio state is executed.
An exhaust emission control device for an internal combustion engine.
JP2006108548A 2006-04-11 2006-04-11 Exhaust emission control device for internal combustion engine Withdrawn JP2007278246A (en)

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