JP2009174386A - Exhaust emission control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust emission control device quickly raising temperature of an exhaust emission control catalyst in exhaust emission control devices for internal combustion engines having a HC adsorption catalyst disposed in an exhaust gas passage on an upstream side of the emission control catalyst. <P>SOLUTION: This exhaust emission control device executes an adsorption process for adsorbing hydrocarbon in exhaust gas to the HC adsorption catalyst at first in an engine cold start, executes a bypass process for making the exhaust gas bypass the HC adsorption catalyst and flow in the exhaust emission control catalyst, and next executes a temperature raise process for raising temperature of the exhaust emission control catalyst by making hydrocarbon adsorbed to the HC adsorption catalyst discharged and supplying the same to the exhaust emission control catalyst. Hydrocarbon of first target quantity is adsorbed to the HC adsorption catalyst before executing the temperature raise process in the present engine cold start. The process is changed over from the bypass process to the temperature raise process after temperature of the exhaust emission control catalyst exceeds the temperature at which hydrocarbon starts oxidation during the bypass process. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

本発明は、内燃機関の排気浄化装置に関する。   The present invention relates to an exhaust emission control device for an internal combustion engine.

内燃機関の排気通路に配置した排気浄化触媒を用いて、排気中のＨＣ（炭化水素）、ＣＯ（一酸化炭素）、ＮＯ_X （窒素酸化物）等の有害成分を浄化する排気浄化装置が一般に知られている。排気浄化触媒は、一般に所定の活性化温度以上にならないと、排気浄化能力を発揮しないため、触媒温度が低いときには排気ガス中の有害成分が触媒を通過して大気に放出されるおそれがある。そこで、排気通路の排気浄化触媒の上流側に、低温で排気ガス中のＨＣ成分を吸着し、高温で吸着したＨＣ成分を放出するＨＣ吸着触媒を配置して低温時のＨＣ成分の大気放出を防止するようにした排気浄化装置が知られている。 Generally, an exhaust gas purification device that purifies harmful components such as HC (hydrocarbon), CO (carbon monoxide), NO _x (nitrogen oxide) in exhaust gas using an exhaust gas purification catalyst disposed in an exhaust passage of an internal combustion engine Are known. Since the exhaust purification catalyst generally does not exhibit exhaust purification ability unless the activation temperature is higher than a predetermined activation temperature, harmful components in the exhaust gas may pass through the catalyst and be released to the atmosphere when the catalyst temperature is low. Therefore, an HC adsorption catalyst that adsorbs the HC component in the exhaust gas at a low temperature and releases the HC component adsorbed at a high temperature is arranged upstream of the exhaust purification catalyst in the exhaust passage to release the HC component to the atmosphere at a low temperature. There is known an exhaust emission control device designed to prevent this.

これらの装置では、機関冷間始動時等、排気ガス温度が低く排気浄化触媒が活性化温度に到達していない場合には排気浄化触媒上流側のＨＣ吸着触媒で排気ガス中のＨＣ成分を吸着し、低温時のＨＣの大気放出を防止するとともに、排気ガス温度が上昇して排気浄化触媒が活性化温度に到達した後は排気ガス中のＨＣ成分とＨＣ吸着触媒から放出されるＨＣ成分との両方を下流側の排気浄化触媒で浄化するようにしている。   In these devices, when the exhaust gas temperature is low and the exhaust purification catalyst does not reach the activation temperature, such as when the engine is cold started, the HC component in the exhaust gas is adsorbed by the HC adsorption catalyst upstream of the exhaust purification catalyst. The HC component in the exhaust gas and the HC component released from the HC adsorption catalyst after the exhaust gas temperature rises and the exhaust purification catalyst reaches the activation temperature are prevented. Both of these are purified by a downstream exhaust purification catalyst.

特開平６−１７３６６４号公報JP-A-6-173664

ところが、上記の排気浄化装置のように排気浄化触媒の上流側にＨＣ吸着触媒を配置し、ＨＣ吸着触媒を通過した排気ガスを排気浄化触媒に流入させるようにした場合には、排気浄化触媒の温度上昇が遅くなり機関始動後排気浄化触媒が活性化温度に到達するのに時間を要する問題がある。   However, when the HC adsorption catalyst is arranged upstream of the exhaust purification catalyst as in the above exhaust purification device and the exhaust gas that has passed through the HC adsorption catalyst is allowed to flow into the exhaust purification catalyst, There is a problem that the temperature rise becomes slow and it takes time for the exhaust purification catalyst to reach the activation temperature after the engine is started.

例えば、排気浄化触媒は機関冷間始動時には低温になっており、機関始動後に通過する排気ガスにより加熱されて触媒活性化温度に到達するが、上記のように機関からの排気ガスがまずＨＣ吸着触媒を通過した後に排気浄化触媒に流入するようにすると、上流側のＨＣ吸着触媒を通過する際に排気ガスの熱がＨＣ吸着触媒に奪われてしまい、排気浄化触媒に流入する排気ガスの温度が低くなってしまう。従って、下流側の排気浄化触媒の温度上昇が遅くなり、機関始動後に活性化温度に到達するのが遅れ、機関始動後排気浄化作用が開始されるまでに時間を要するようになる。   For example, the exhaust purification catalyst is at a low temperature when the engine is cold-started and is heated by the exhaust gas that passes after the engine is started to reach the catalyst activation temperature. However, as described above, the exhaust gas from the engine first absorbs HC. If the exhaust gas flows into the exhaust purification catalyst after passing through the catalyst, the heat of the exhaust gas is lost to the HC adsorption catalyst when passing through the upstream HC adsorption catalyst, and the temperature of the exhaust gas flowing into the exhaust purification catalyst Will be lower. Therefore, the temperature increase of the exhaust purification catalyst on the downstream side is delayed, the time for reaching the activation temperature after engine startup is delayed, and it takes time until the exhaust gas purification action is started after engine startup.

本発明は上記課題に鑑み、排気浄化触媒の上流側の排気通路にＨＣ吸着触媒が配設された内燃機関の排気浄化装置において、機関冷間始動時に排気ガスがＨＣ吸着触媒を通過させるが故にもたらされる排気浄化触媒の活性化温度への到達遅れを、ＨＣ吸着触媒に吸着されている炭化水素を有効に利用して抑制し、排気浄化触媒の迅速な昇温を図ることが可能な排気浄化装置を提供することを目的とする。   In view of the above problems, the present invention is an internal combustion engine exhaust gas purification apparatus in which an HC adsorption catalyst is disposed in the exhaust passage upstream of the exhaust gas purification catalyst, because exhaust gas passes through the HC adsorption catalyst during engine cold start. Exhaust gas purification that can suppress the arrival delay of the resulting exhaust gas purification catalyst to the activation temperature by effectively using hydrocarbons adsorbed on the HC adsorption catalyst, and can quickly raise the temperature of the exhaust gas purification catalyst An object is to provide an apparatus.

請求項１に記載の発明によれば、内燃機関の排気通路に配設され排気ガス中の少なくとも炭化水素を酸化する酸化能を有する排気浄化触媒と、該排気浄化触媒よりも上流側の排気通路に配設され炭化水素を吸着するＨＣ吸着触媒と、該ＨＣ吸着触媒をバイパスさせて前記排気浄化触媒に排気ガスを流入させるバイパス通路と、前記ＨＣ吸着触媒に流入する排気ガスの流量と前記バイパス通路に流入する排気ガスの流量とを調整する流量調整弁とを備える内燃機関の排気浄化装置であって、機関冷間始動時には、まず、排気ガスを前記ＨＣ吸着触媒に流通させた後に前記排気浄化触媒に流入させて排気ガス中の炭化水素を前記ＨＣ吸着触媒に吸着させる吸着処理を行い、次に、前記ＨＣ吸着触媒をバイパスさせて前記排気浄化触媒に排気ガスを流入させるバイパス処理を行い、次に再び、排気ガスを前記ＨＣ吸着触媒に流通させた後に前記排気浄化触媒に流入させることにより前記ＨＣ吸着触媒に吸着させていた炭化水素を放出させて前記排気浄化触媒に供給し、それにより前記排気浄化触媒を昇温させる昇温処理を行う、内燃機関の排気浄化装置において、今回の機関冷間始動時において前記昇温処理を行う前までに第１の目標量の炭化水素を前記ＨＣ吸着触媒に吸着させておき、前記バイパス処理中に前記排気浄化触媒の温度が炭化水素を酸化し始める温度を越えたときに、前記バイパス処理から前記昇温処理に切り換えるようにした、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, an exhaust purification catalyst that is disposed in the exhaust passage of the internal combustion engine and has an oxidizing ability to oxidize at least hydrocarbons in the exhaust gas, and an exhaust passage upstream of the exhaust purification catalyst. An HC adsorption catalyst that adsorbs hydrocarbons, a bypass passage that bypasses the HC adsorption catalyst and allows exhaust gas to flow into the exhaust purification catalyst, a flow rate of exhaust gas that flows into the HC adsorption catalyst, and the bypass An exhaust gas purification apparatus for an internal combustion engine comprising a flow rate adjusting valve for adjusting a flow rate of exhaust gas flowing into a passage, and at the time of engine cold start, first, after exhaust gas is circulated through the HC adsorption catalyst, the exhaust gas An adsorption process is performed in which the hydrocarbons in the exhaust gas are caused to flow into the purification catalyst and adsorbed by the HC adsorption catalyst. Next, the HC adsorption catalyst is bypassed and exhaust gas is supplied to the exhaust purification catalyst. And then, again, the exhaust gas is allowed to flow through the HC adsorption catalyst and then flow into the exhaust purification catalyst to release the hydrocarbons adsorbed on the HC adsorption catalyst, thereby purifying the exhaust gas. In the exhaust gas purification apparatus for an internal combustion engine, which performs a temperature raising process for raising the temperature of the exhaust purification catalyst by supplying to the catalyst, the first target before the temperature raising process at the time of the engine cold start When an amount of hydrocarbon is adsorbed on the HC adsorption catalyst and the temperature of the exhaust purification catalyst exceeds the temperature at which the hydrocarbon starts to be oxidized during the bypass process, the bypass process is switched to the temperature increase process. An exhaust emission control device for an internal combustion engine is provided.

すなわち、請求項１の発明では、今回の機関冷間始動時においてＨＣ吸着触媒に吸着させていた炭化水素を放出させて排気浄化触媒に供給し排気浄化触媒を昇温させる昇温処理を行う前までに、第１の目標量の炭化水素をＨＣ吸着触媒に吸着させておき、ＨＣ吸着触媒をバイパスさせて排気浄化触媒に排気ガスを流入させるバイパス処理中に排気浄化触媒の温度が炭化水素を酸化し始める温度を越えたときに、バイパス処理から昇温処理に切り換えるようにすることにより、今回の機関冷間始動時において上記昇温処理を行う前までにＨＣ吸着触媒に目標量の炭化水素を確実に吸着させておくことができ、また、排気浄化触媒の炭化水素を酸化し始める温度時に目標量の大量の炭化水素を排気浄化触媒に供給することができ、これにより、炭化水素の酸化の際に発生する熱による排気浄化触媒の急速な活性化温度以上への昇温が可能となる。尚、排気浄化触媒が炭化水素を酸化し始める温度は、排気浄化触媒の活性化温度すなわち排気浄化率が目標値以上となる温度よりも低い温度である。   That is, according to the first aspect of the present invention, before the temperature increasing process for releasing the hydrocarbon adsorbed by the HC adsorption catalyst at the time of the engine cold start and supplying the hydrocarbon to the exhaust purification catalyst to raise the temperature of the exhaust purification catalyst. By the time, the first target amount of hydrocarbon is adsorbed on the HC adsorption catalyst, and the temperature of the exhaust purification catalyst is reduced during the bypass process of bypassing the HC adsorption catalyst and flowing exhaust gas into the exhaust purification catalyst. By switching from the bypass process to the temperature increase process when the temperature at which the oxidation starts is exceeded, the target amount of hydrocarbons is added to the HC adsorption catalyst before the temperature increase process at the time of the engine cold start. Can be reliably adsorbed, and a target amount of hydrocarbons can be supplied to the exhaust purification catalyst at a temperature at which the hydrocarbons of the exhaust purification catalyst start to be oxidized. Heating to more rapid activation temperature of the exhaust gas purification catalyst by the heat generated in the oxidation of hydrogen is possible. The temperature at which the exhaust purification catalyst begins to oxidize hydrocarbons is lower than the activation temperature of the exhaust purification catalyst, that is, the temperature at which the exhaust purification rate is equal to or higher than the target value.

請求項２に記載の発明によれば、前記ＨＣ吸着触媒に前記第１の目標量の炭化水素が吸着されたときに、前記吸着処理から前記バイパス処理に切り換えるようにした、ことを特徴とする請求項１に記載の内燃機関の排気浄化装置が提供される。   According to a second aspect of the present invention, when the first target amount of hydrocarbon is adsorbed to the HC adsorption catalyst, the adsorption process is switched to the bypass process. An exhaust emission control device for an internal combustion engine according to claim 1 is provided.

請求項３に記載の発明によれば、今回の機関運転の前記吸着処理の開始時に前記第１の目標量よりも少ない第２の目標量だけ前記ＨＣ吸着触媒に炭化水素が吸着されているように、前回の機関運転中に前記ＨＣ吸着触媒に炭化水素を吸着させておき、今回の機関運転の前記吸着処理中に前記第１の目標量まで炭化水素を前記ＨＣ吸着触媒に吸着させる、ことを特徴とする請求項１に記載の内燃機関の排気浄化装置が提供される。   According to the third aspect of the present invention, the hydrocarbon is adsorbed on the HC adsorption catalyst by a second target amount smaller than the first target amount at the start of the adsorption process of the current engine operation. In addition, hydrocarbons are adsorbed to the HC adsorption catalyst during the previous engine operation, and hydrocarbons are adsorbed to the HC adsorption catalyst up to the first target amount during the adsorption process of the current engine operation. An exhaust emission control device for an internal combustion engine according to claim 1 is provided.

請求項４に記載の発明によれば、前記排気浄化装置は、前記ＨＣ吸着触媒よりも上流側の排気ガス中に炭化水素を供給するＨＣ増量手段を有し、前記ＨＣ吸着触媒に炭化水素を吸着させるべきときに前記ＨＣ増量手段から炭化水素を供給する、ことを特徴とする請求項１または請求項３に記載の内燃機関の排気浄化装置が提供される。   According to the invention of claim 4, the exhaust purification device has HC increasing means for supplying hydrocarbons into the exhaust gas upstream of the HC adsorption catalyst, and hydrocarbons are supplied to the HC adsorption catalyst. The exhaust gas purification apparatus for an internal combustion engine according to claim 1 or 3, wherein hydrocarbons are supplied from the HC increasing means when they should be adsorbed.

請求項５に記載の発明によれば、前記排気浄化触媒は、尿素によりＮＯｘを選択的に還元可能な選択還元触媒であって排気ガスが流入する側に酸化触媒を備えた選択還元触媒である、ことを特徴とする請求項１に記載の内燃機関の排気浄化装置が提供される。   According to the invention described in claim 5, the exhaust purification catalyst is a selective reduction catalyst capable of selectively reducing NOx with urea, and is a selective reduction catalyst provided with an oxidation catalyst on the exhaust gas inflow side. An exhaust emission control device for an internal combustion engine according to claim 1 is provided.

各請求項に記載の発明によれば、排気浄化触媒の上流側の排気通路にＨＣ吸着触媒が配設された内燃機関の排気浄化装置において、機関冷間始動時に排気ガスがＨＣ吸着触媒を通過させるが故にもたらされる排気浄化触媒の活性化温度への到達遅れを、ＨＣ吸着触媒に吸着されている炭化水素を有効に利用して抑制し、排気浄化触媒の迅速な昇温を図ることが可能となる共通の効果を奏する。   According to the invention described in each claim, in the exhaust gas purification apparatus for an internal combustion engine in which the HC adsorption catalyst is disposed in the exhaust passage upstream of the exhaust purification catalyst, the exhaust gas passes through the HC adsorption catalyst when the engine is cold start. Therefore, the delay in reaching the activation temperature of the exhaust purification catalyst, which is caused by this, can be effectively suppressed by using the hydrocarbons adsorbed on the HC adsorption catalyst, and the exhaust purification catalyst can be quickly raised in temperature. There is a common effect.

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。
図１は本発明を圧縮自着火式内燃機関に適用した場合を示している。なお、本発明は火花点火式内燃機関にも適用することもできる。 Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 shows a case where the present invention is applied to a compression self-ignition internal combustion engine. The present invention can also be applied to a spark ignition type internal combustion engine.

図１を参照すると、１は機関本体、２は各気筒の燃焼室、３は各燃焼室２内にそれぞれ燃料を噴射するための電子制御式燃料噴射弁、４は吸気マニホルド、５は排気マニホルドをそれぞれ示す。吸気マニホルド４は吸気ダクト６を介して排気ターボチャージャ７のコンプレッサ７ａの出口に連結され、コンプレッサ７ａの入口はエアクリーナ８に連結される。吸気ダクト６内にはステップモータにより駆動されるスロットル弁９が配置され、更に吸気ダクト６周りには吸気ダクト６内を流れる吸入空気を冷却するための冷却装置１０が配置される。図１に示した実施形態では機関冷却水が冷却装置１０内に導かれ、機関冷却水によって吸入空気が冷却される。   Referring to FIG. 1, 1 is an engine body, 2 is a combustion chamber of each cylinder, 3 is an electronically controlled fuel injection valve for injecting fuel into each combustion chamber 2, 4 is an intake manifold, and 5 is an exhaust manifold. Respectively. The intake manifold 4 is connected to the outlet of the compressor 7 a of the exhaust turbocharger 7 through the intake duct 6, and the inlet of the compressor 7 a is connected to the air cleaner 8. A throttle valve 9 driven by a step motor is arranged in the intake duct 6, and a cooling device 10 for cooling intake air flowing in the intake duct 6 is arranged around the intake duct 6. In the embodiment shown in FIG. 1, the engine cooling water is guided into the cooling device 10 and the intake air is cooled by the engine cooling water.

一方、排気マニホルド５は排気ターボチャージャ７の排気タービン７ｂの入口に連結され、排気タービン７ｂの出口は排気管１１を介してＨＣ吸着触媒１２を内蔵したケーシング１３に連結され、さらに、ケーシング１３の出口は排気管１１を介して酸化能を有する排気浄化触媒１４を内蔵したケーシング１５に連結される。また、ＨＣ吸着触媒１２の上流側の排気管１１上に位置する分岐部１６からＨＣ吸着触媒１２をバイパスさせるためのバイパス通路１７が分岐し、バイパス通路１７はＨＣ吸着触媒１２と排気浄化触媒１４との間の排気管１１に連結される。分岐部１６には、ＨＣ吸着触媒１２に流入する排気ガスの流量とバイパス通路１７に流入する排気ガスの流量とを調整する流量調整弁１８が設けられる。排気マニホルド５の集合部出口にはＨＣ吸着触媒によりも上流側の排気ガス中に炭化水素を供給するためのＨＣ増量手段１９が配置される。尚、ＨＣ増量手段１９は、流量調節弁１８とＨＣ吸着触媒１２との間の排気管部に配置されてもよい。   On the other hand, the exhaust manifold 5 is connected to the inlet of the exhaust turbine 7 b of the exhaust turbocharger 7, and the outlet of the exhaust turbine 7 b is connected to the casing 13 containing the HC adsorption catalyst 12 via the exhaust pipe 11. The outlet is connected through an exhaust pipe 11 to a casing 15 containing an exhaust purification catalyst 14 having oxidation ability. Further, a bypass passage 17 for bypassing the HC adsorption catalyst 12 is branched from a branch portion 16 located on the exhaust pipe 11 on the upstream side of the HC adsorption catalyst 12, and the bypass passage 17 includes the HC adsorption catalyst 12 and the exhaust purification catalyst 14. It connects with the exhaust pipe 11 between. The branch portion 16 is provided with a flow rate adjusting valve 18 that adjusts the flow rate of the exhaust gas flowing into the HC adsorption catalyst 12 and the flow rate of the exhaust gas flowing into the bypass passage 17. An HC increasing means 19 for supplying hydrocarbons into the exhaust gas upstream of the HC adsorption catalyst is disposed at the outlet of the collecting portion of the exhaust manifold 5. The HC increasing means 19 may be disposed in the exhaust pipe portion between the flow rate control valve 18 and the HC adsorption catalyst 12.

排気マニホルド５と吸気マニホルド４とは排気ガス再循環（以下、ＥＧＲと称す）通路２０を介して互いに連結され、ＥＧＲ通路２０内には電子制御式ＥＧＲ制御弁２１が配置される。また、ＥＧＲ通路２０周りにはＥＧＲ通路２０内を流れるＥＧＲガスを冷却するためのＥＧＲ冷却装置２２が配置される。図１に示した実施形態では機関冷却水がＥＧＲ冷却装置２２内に導かれ、機関冷却水によってＥＧＲガスが冷却される。一方、各燃料噴射弁３は燃料供給管２３を介して燃料リザーバ、いわゆるコモンレール２４に連結される。このコモンレール２４内へは電子制御式の吐出量可変な燃料ポンプ２５から燃料が供給され、コモンレール２４内に供給された燃料は各燃料供給管２３を介して燃料噴射弁３に供給される。   The exhaust manifold 5 and the intake manifold 4 are connected to each other via an exhaust gas recirculation (hereinafter referred to as EGR) passage 20, and an electronically controlled EGR control valve 21 is disposed in the EGR passage 20. Further, an EGR cooling device 22 for cooling the EGR gas flowing through the EGR passage 20 is disposed around the EGR passage 20. In the embodiment shown in FIG. 1, the engine cooling water is guided into the EGR cooling device 22, and the EGR gas is cooled by the engine cooling water. On the other hand, each fuel injection valve 3 is connected to a fuel reservoir, so-called common rail 24, via a fuel supply pipe 23. Fuel is supplied into the common rail 24 from an electronically controlled fuel pump 25 with variable discharge amount, and the fuel supplied into the common rail 24 is supplied to the fuel injection valve 3 through each fuel supply pipe 23.

電子制御ユニット３０はデジタルコンピュータからなり、双方向性バス３１によって互いに接続されたＲＯＭ（リードオンリメモリ）３２、ＲＡＭ（ランダムアクセスメモリ）３３、ＣＰＵ（マイクロプロセッサ）３４、入力ポート３５および出力ポート３６を具備する。流量調整弁１８よりも上流側の排気通路及びＨＣ吸着触媒１２の出口部には、流量調整弁１８よりも上流側の排気ガスの温度およびＨＣ吸着触媒１２の温度をそれぞれ検出するための温度センサ２６、２７が取付けられ、これら温度センサ２６、２７の出力信号は対応するＡＤ変換器３７を介して入力ポート３５に入力される。また、アクセルペダル４０にはアクセルペダル４０の踏込み量に比例した出力電圧を発生する負荷センサ４１が接続され、負荷センサ４１の出力電圧は対応するＡＤ変換器３７を介して入力ポート３５に入力される。更に入力ポート３５にはクランクシャフトが例えば１５°回転する毎に出力パルスを発生するクランク角センサ４２が接続される。一方、出力ポート３６は対応する駆動回路３８を介して燃料噴射弁３、スロットル弁９駆動用ステップモータ、ＨＣ増量手段１９、ＥＧＲ制御弁２１、燃料ポンプ２５、および、後述する尿素供給弁５０などに接続される。   The electronic control unit 30 is composed of a digital computer, and is connected to each other by a bidirectional bus 31. A ROM (read only memory) 32, a RAM (random access memory) 33, a CPU (microprocessor) 34, an input port 35 and an output port 36. It comprises. Temperature sensors for detecting the temperature of the exhaust gas upstream of the flow rate adjustment valve 18 and the temperature of the HC adsorption catalyst 12 at the exhaust passage upstream of the flow rate adjustment valve 18 and the outlet portion of the HC adsorption catalyst 12, respectively. 26 and 27 are attached, and the output signals of these temperature sensors 26 and 27 are input to the input port 35 via the corresponding AD converters 37. A load sensor 41 that generates an output voltage proportional to the amount of depression of the accelerator pedal 40 is connected to the accelerator pedal 40, and the output voltage of the load sensor 41 is input to the input port 35 via the corresponding AD converter 37. The Further, the input port 35 is connected to a crank angle sensor 42 that generates an output pulse every time the crankshaft rotates, for example, 15 °. On the other hand, the output port 36 is connected to the fuel injection valve 3, the throttle valve 9 driving step motor, the HC increasing means 19, the EGR control valve 21, the fuel pump 25, and a urea supply valve 50, which will be described later, via a corresponding drive circuit 38. Connected to.

図１に示す実施形態における酸化能を有する排気浄化触媒１４は、尿素によりＮＯｘを選択的に還元可能な選択還元触媒であって排気ガスが流入する側に酸化触媒を備えた選択還元触媒である。ＨＣ吸着触媒１２と選択還元触媒１４との間の排気管１１には選択還元触媒１４に尿素を供給するための尿素供給弁５０が配置される。選択還元触媒１４は例えば遷移金属を含有するゼオドライトからなる。尿素供給弁５０から尿素水溶液が供給されると尿素水溶液中の大部分の尿素は選択還元触媒１４に吸着され吸着された尿素は形態変化をしつつ、即ち中間生成物に変化しつつアンモニアＮＨ₃を生成する。排気ガス中に含まれるＮＯｘは選択還元触媒１４上においてこれら生成されたアンモニアと反応して還元せしめられる。本発明の実施形態では選択還元触媒１４に吸着されている尿素吸着量がＮＯｘを還元するのに十分な量となるように尿素供給弁５０から尿素水溶液が供給される。しかしながら、本発明に適用可能な排気浄化触媒はこのような選択還元触媒に限られることはなく、排気ガス中の少なくとも炭化水素を酸化する酸化能を有する排気浄化触媒であればよい。例えば、流入する排気ガスの空燃比がリーンのときに排気ガス中のＮＯｘを吸蔵し、流入する排気中の酸素濃度が低下すると吸蔵しているＮＯｘを放出して還元するＮＯｘ吸蔵還元触媒であって排気ガスが流入する側に酸化触媒を備えたＮＯｘ吸蔵還元触媒が適用されてもよい。 The exhaust purification catalyst 14 having oxidation ability in the embodiment shown in FIG. 1 is a selective reduction catalyst that can selectively reduce NOx with urea and is provided with an oxidation catalyst on the exhaust gas inflow side. . A urea supply valve 50 for supplying urea to the selective reduction catalyst 14 is disposed in the exhaust pipe 11 between the HC adsorption catalyst 12 and the selective reduction catalyst 14. The selective reduction catalyst 14 is made of, for example, a zeolite containing a transition metal. When an aqueous urea solution is supplied from the urea supply valve 50, most of the urea in the aqueous urea solution is adsorbed by the selective reduction catalyst 14, and the adsorbed urea undergoes a change in form, that is, ammonia NH ₃ while changing to an intermediate product. Is generated. NOx contained in the exhaust gas reacts with the generated ammonia on the selective reduction catalyst 14 and is reduced. In the embodiment of the present invention, the urea aqueous solution is supplied from the urea supply valve 50 so that the amount of urea adsorbed on the selective reduction catalyst 14 is sufficient to reduce NOx. However, the exhaust purification catalyst applicable to the present invention is not limited to such a selective reduction catalyst, and any exhaust purification catalyst having an oxidizing ability to oxidize at least hydrocarbons in the exhaust gas may be used. For example, it is a NOx occlusion reduction catalyst that stores NOx in exhaust gas when the air-fuel ratio of inflowing exhaust gas is lean, and releases and reduces the stored NOx when the oxygen concentration in the inflowing exhaust gas decreases. Thus, a NOx occlusion reduction catalyst having an oxidation catalyst on the side into which the exhaust gas flows may be applied.

図１に示す実施形態におけるＨＣ吸着触媒１２はゼオライトからなる。このゼオライトは機関冷間始動時におけるようにゼオライトの温度が低いときでも未燃ＨＣを吸着する機能を有する。そして、ＨＣ吸着触媒１２の温度が上昇するとＨＣ吸着触媒１２からのＨＣ脱離作用が開始される。   The HC adsorption catalyst 12 in the embodiment shown in FIG. 1 is made of zeolite. This zeolite has a function of adsorbing unburned HC even when the temperature of the zeolite is low as in the cold start of the engine. When the temperature of the HC adsorption catalyst 12 rises, the HC desorption action from the HC adsorption catalyst 12 is started.

上記のように、本発明の排気浄化装置は、内燃機関の排気通路に配設され排気ガス中の少なくとも炭化水素を酸化する酸化能を有する排気浄化触媒１４と、該排気浄化触媒１４よりも上流側の排気通路に配設され炭化水素を吸着するＨＣ吸着触媒１２と、該ＨＣ吸着触媒１２をバイパスさせて排気浄化触媒１４に排気ガスを流入させるバイパス通路１７と、ＨＣ吸着触媒１２に流入する排気ガスの流量とバイパス通路１７に流入する排気ガスの流量とを調整する流量調整弁１８とを備える。   As described above, the exhaust purification apparatus of the present invention is provided in the exhaust passage of the internal combustion engine and has an oxidation purification catalyst 14 having an oxidizing ability to oxidize at least hydrocarbons in the exhaust gas, and upstream of the exhaust purification catalyst 14. HC adsorption catalyst 12 which is disposed in the exhaust passage on the side and adsorbs hydrocarbons, bypass passage 17 which bypasses the HC adsorption catalyst 12 and allows exhaust gas to flow into the exhaust purification catalyst 14, and flows into the HC adsorption catalyst 12 A flow rate adjusting valve 18 for adjusting the flow rate of the exhaust gas and the flow rate of the exhaust gas flowing into the bypass passage 17 is provided.

本発明の排気浄化装置は、機関冷間始動時には、まず、排気ガスをＨＣ吸着触媒１２に流通させた後に排気浄化触媒１４に流入させて排気ガス中の炭化水素をＨＣ吸着触媒１２に吸着させる吸着処理を行い、次に、ＨＣ吸着触媒１２をバイパスさせて排気浄化触媒１４に排気ガスを流入させるバイパス処理を行い、次に再び、排気ガスをＨＣ吸着触媒１２に流通させた後に排気浄化触媒１４に流入させることによりＨＣ吸着触媒１２に吸着させていた炭化水素を放出させて排気浄化触媒１４に供給し、それにより排気浄化触媒１４を昇温させる昇温処理を行う。   In the exhaust purification apparatus of the present invention, when the engine is cold start, first, exhaust gas is circulated through the HC adsorption catalyst 12 and then flows into the exhaust purification catalyst 14 to adsorb hydrocarbons in the exhaust gas to the HC adsorption catalyst 12. An adsorption process is performed, and then a bypass process is performed in which the HC adsorption catalyst 12 is bypassed and exhaust gas is allowed to flow into the exhaust purification catalyst 14, and then the exhaust gas is again circulated through the HC adsorption catalyst 12 and then the exhaust purification catalyst. The hydrocarbons adsorbed on the HC adsorption catalyst 12 are discharged by being introduced into the exhaust gas 14 and supplied to the exhaust purification catalyst 14, thereby performing a temperature raising process for raising the temperature of the exhaust purification catalyst 14.

ところで、排気浄化触媒１４は機関冷間始動時には低温になっており、機関始動後に通過する排気ガスにより加熱されて触媒活性化温度に到達するが、機関本体１からの排気ガスがまずＨＣ吸着触媒１２を通過した後に排気浄化触媒１４に流入するようにすると、上流側のＨＣ吸着触媒１２を通過する際に排気ガスの熱がＨＣ吸着触媒１２に奪われてしまい、排気浄化触媒１４に流入する排気の温度が低くなってしまう。従って、下流側の排気浄化触媒１４の温度上昇が遅くなり、機関始動後に排気浄化触媒１４が活性化温度に到達するのが遅れ、機関始動後排気浄化作用が開始されるまでに時間を要するようになる。   By the way, the exhaust purification catalyst 14 is at a low temperature when the engine is cold-started, and is heated by the exhaust gas that passes after the engine is started to reach the catalyst activation temperature. If the exhaust gas flows into the exhaust purification catalyst 14 after passing through 12, the heat of the exhaust gas is taken away by the HC adsorption catalyst 12 when passing through the upstream HC adsorption catalyst 12, and flows into the exhaust purification catalyst 14. Exhaust temperature will be lowered. Therefore, the temperature rise of the exhaust purification catalyst 14 on the downstream side is delayed, the exhaust purification catalyst 14 is delayed from reaching the activation temperature after the engine is started, and it takes time until the exhaust purification action is started after the engine is started. become.

このことに基づき、本発明の排気浄化装置においては、今回の機関冷間始動時において昇温処理を行う前までに第１の目標量の炭化水素をＨＣ吸着触媒１２に吸着させておき、バイパス処理中に排気浄化触媒１４の温度が炭化水素を酸化し始める温度を越えたときに、バイパス処理から前記昇温処理に切り換えるようにする。尚、排気浄化触媒１４が炭化水素を酸化し始める温度は、排気浄化触媒１４の活性化温度すなわち排気浄化率が目標値以上となる温度よりも低い温度である。   Based on this, in the exhaust gas purification apparatus of the present invention, the first target amount of hydrocarbon is adsorbed to the HC adsorption catalyst 12 before the temperature raising process at the time of the engine cold start, and the bypass is performed. When the temperature of the exhaust purification catalyst 14 exceeds the temperature at which the hydrocarbon starts to be oxidized during the process, the process is switched from the bypass process to the temperature increasing process. The temperature at which the exhaust purification catalyst 14 begins to oxidize hydrocarbons is lower than the activation temperature of the exhaust purification catalyst 14, that is, the temperature at which the exhaust purification rate is equal to or higher than the target value.

このような本発明の排気浄化装置によれば、今回の機関冷間始動時においてＨＣ吸着触媒１２に吸着させていた炭化水素を放出させて排気浄化触媒１４に供給し排気浄化触媒１４を昇温させる昇温処理を行う前までに、第１の目標量の炭化水素をＨＣ吸着触媒１２に吸着させておき、ＨＣ吸着触媒１２をバイパスさせて排気浄化触媒１４に排気ガスを流入させるバイパス処理中に排気浄化触媒１４の温度が炭化水素を酸化し始める温度を越えたときに、バイパス処理から昇温処理に切り換えるようにすることにより、今回の機関冷間始動時において上記昇温処理を行う前までにＨＣ吸着触媒１２に目標量の炭化水素を確実に吸着させておくことができ、また、排気浄化触媒１４の炭化水素を酸化し始める温度時に目標量の大量の炭化水素を排気浄化触媒１４に供給することができ、これにより、炭化水素の酸化の際に発生する熱による排気浄化触媒１４の急速な活性化温度以上への昇温が可能となる。また、このような排気浄化触媒１４の急速な昇温を可能とする本発明の排気浄化装置によれば、排気浄化触媒１４に吸着されていた炭化水素を除去することができ、例えば尿素によりＮＯｘを選択的に還元可能な選択還元触媒１４のＨＣ被毒を防止することが可能となる。   According to such an exhaust purification device of the present invention, hydrocarbons adsorbed by the HC adsorption catalyst 12 at the time of the engine cold start this time are released and supplied to the exhaust purification catalyst 14 to raise the temperature of the exhaust purification catalyst 14. During the bypass process in which the first target amount of hydrocarbon is adsorbed to the HC adsorption catalyst 12 and the HC adsorption catalyst 12 is bypassed and the exhaust gas is allowed to flow into the exhaust purification catalyst 14 before performing the temperature raising process. When the temperature of the exhaust purification catalyst 14 exceeds the temperature at which the hydrocarbons start to be oxidized, switching from the bypass process to the temperature raising process is performed before performing the temperature raising process at the time of the engine cold start. The target amount of hydrocarbons can be reliably adsorbed by the HC adsorption catalyst 12 by the time, and the target amount of hydrocarbons is exhausted at a temperature at which the exhaust purification catalyst 14 begins to oxidize. It can be supplied to the purifying catalyst 14, thereby, Atsushi Nobori becomes possible to by heat generated in the oxidation of hydrocarbons or rapid activation temperature of the exhaust purification catalyst 14. Further, according to the exhaust gas purification apparatus of the present invention that enables the temperature of the exhaust gas purification catalyst 14 to be rapidly raised, hydrocarbons adsorbed on the exhaust gas purification catalyst 14 can be removed. It is possible to prevent HC poisoning of the selective reduction catalyst 14 that can selectively reduce the HC.

以下に、本発明の排気浄化装置における機関冷間始動時の制御について説明する。図２は本発明の排気浄化装置における機関冷間始動時の制御の一実施形態を示す図である。   Below, the control at the time of engine cold start in the exhaust emission control device of the present invention will be described. FIG. 2 is a diagram showing an embodiment of the control at the time of engine cold start in the exhaust gas purification apparatus of the present invention.

図２に示される実施形態においては、今回の機関運転の吸着処理の開始時に第１の目標量よりも少ない第２の目標量だけＨＣ吸着触媒１２に炭化水素が吸着されているように、前回の機関運転中にＨＣ吸着触媒１２に炭化水素を吸着させておき、今回の機関運転の吸着処理中に第１の目標量まで炭化水素をＨＣ吸着触媒１２に吸着させる。そのために、ＨＣ吸着触媒１２に第１の目標量の炭化水素が吸着されるまで、まず、排気ガスをＨＣ吸着触媒１２に流通させた後に排気浄化触媒１４に流入させて排気中の炭化水素をＨＣ吸着触媒１２に吸着させる吸着処理を行う。これにより、今回の機関冷間始動時においてＨＣ吸着触媒１２から炭化水素が放出されるのに先立って、すなわち昇温処理を行う前までにＨＣ吸着触媒１２に第１の目標量の炭化水素を吸着させておくことができるとともに、機関冷間始動時における炭化水素の排出を抑制することが可能となる。尚、機関冷間始動時の炭化水素の排出量が極めて少ないような機関の場合には、前回の機関運転中に第１の目標量の炭化水素をＨＣ吸着触媒１２に吸着させておき、今回の機関冷間始動時のＨＣ吸着触媒１２への炭化水素の吸着処理を省くような制御が機関冷間始動時になされてもよい。   In the embodiment shown in FIG. 2, the hydrocarbon is adsorbed on the HC adsorption catalyst 12 by the second target amount that is smaller than the first target amount at the start of the adsorption process of the current engine operation so that the previous time. During the engine operation, hydrocarbons are adsorbed to the HC adsorption catalyst 12, and the hydrocarbons are adsorbed to the HC adsorption catalyst 12 up to the first target amount during the adsorption process of the current engine operation. Therefore, until the first target amount of hydrocarbons is adsorbed by the HC adsorption catalyst 12, first, the exhaust gas is circulated through the HC adsorption catalyst 12 and then flows into the exhaust purification catalyst 14 to remove hydrocarbons in the exhaust. An adsorption process for adsorbing to the HC adsorption catalyst 12 is performed. As a result, prior to the release of hydrocarbons from the HC adsorption catalyst 12 at the time of the engine cold start this time, that is, before the temperature raising process is performed, the first target amount of hydrocarbons is supplied to the HC adsorption catalyst 12. It can be adsorbed, and it is possible to suppress hydrocarbon emissions during engine cold start. In the case of an engine in which the amount of hydrocarbons discharged at the cold start of the engine is extremely small, the first target amount of hydrocarbons is adsorbed to the HC adsorption catalyst 12 during the previous engine operation, and this time A control may be performed at the time of engine cold start so that the hydrocarbon adsorption process to the HC adsorption catalyst 12 at the time of engine cold start is omitted.

また、排気ガスをＨＣ吸着触媒１２に流通させた後に排気浄化触媒１４に流入させて排気中の炭化水素をＨＣ吸着触媒１２に吸着させる吸着処理が、ＨＣ吸着触媒１２に流入する排気ガスの温度が第１の目標量の炭化水素をＨＣ吸着触媒１２に吸着保持しておくことが可能な温度を越えてしまうまでの間、行なわれるように制御されてもよい。このように制御される場合には、今回の機関冷間始動時においてＨＣ吸着触媒１２から炭化水素が放出されるのに先立ってＨＣ吸着触媒１２に少なくとも第２の目標量以上の炭化水素を吸着させておくことができるとともに、機関冷間始動時における炭化水素の排出を抑制することが可能となる。   Further, an adsorption process in which the exhaust gas is allowed to flow through the HC adsorption catalyst 12 and then flowed into the exhaust purification catalyst 14 to adsorb hydrocarbons in the exhaust gas to the HC adsorption catalyst 12, is the temperature of the exhaust gas flowing into the HC adsorption catalyst 12. May be controlled until the temperature exceeds the temperature at which the first target amount of hydrocarbons can be adsorbed and held on the HC adsorption catalyst 12. When controlled in this way, at least the second target amount or more of hydrocarbons are adsorbed to the HC adsorption catalyst 12 prior to the release of hydrocarbons from the HC adsorption catalyst 12 at the time of the engine cold start. In addition, it is possible to suppress hydrocarbon emissions during engine cold start.

そして、このような吸着処理の次に、ＨＣ吸着触媒１２をバイパスさせて排気浄化触媒１４に排気ガスを流入させるバイパス処理を行い、バイパス処理中に排気浄化触媒１４の温度が、炭化水素を酸化し始める温度を越えたときに、再び、排気ガスをＨＣ吸着触媒１２に流通させた後に排気浄化触媒１４に流入させることによりＨＣ吸着触媒１２に吸着させていた目標量の大量の炭化水素を放出させて排気浄化触媒１４に供給し、排気浄化触媒１４の急速な昇温を可能とする。以下に図２に示された各ステップについて説明する。   Then, after such an adsorption process, a bypass process is performed in which the HC adsorption catalyst 12 is bypassed and exhaust gas is allowed to flow into the exhaust purification catalyst 14, and the temperature of the exhaust purification catalyst 14 oxidizes hydrocarbons during the bypass process. When the temperature at which the HC adsorption catalyst 12 starts is exceeded, the exhaust gas is again circulated through the HC adsorption catalyst 12 and then flows into the exhaust purification catalyst 14 to release a large amount of hydrocarbons adsorbed on the HC adsorption catalyst 12. Thus, the exhaust gas is supplied to the exhaust purification catalyst 14 so that the exhaust purification catalyst 14 can be rapidly heated. The steps shown in FIG. 2 will be described below.

図２に示される実施形態においては、機関冷間始動時、まずステップ１０１において内燃機関が始動され、続くステップ１０２にて、流量調整弁１８による排気ガスのＨＣ吸着触媒側への制御、すなわち排気ガスをＨＣ吸着触媒１２に流通させた後に排気浄化触媒１４に流入させるように流量調整弁１８が制御され、排気ガス中の炭化水素をＨＣ吸着触媒１２に吸着させる吸着処理を行う。ステップ１０２に続くステップ１０３からステップ１０５においては、内燃機関本体１から排出される排気ガス量と前回の機関運転中にＨＣ吸着触媒１２に吸着された炭化水素量とに基づいてＨＣ吸着触媒１２に吸着されている炭化水素量を算出し、該算出された炭化水素量が第１の目標量に達したか否かが判定される。そして、ステップ１０５にて、ＨＣ吸着触媒１２に吸着されている炭化水素量が第１の目標量に達したと判定されると、続くステップ１０６に進む。尚、ＨＣ吸着触媒１２への炭化水素の吸着は、ＨＣ増量手段１９により行われてもよい。   In the embodiment shown in FIG. 2, when the engine is cold start, first, the internal combustion engine is started in step 101, and then in step 102, control of the exhaust gas to the HC adsorption catalyst side by the flow rate adjusting valve 18, that is, exhaust gas is performed. The flow rate adjusting valve 18 is controlled so that the gas flows through the HC adsorption catalyst 12 and then flows into the exhaust purification catalyst 14, and an adsorption process for adsorbing hydrocarbons in the exhaust gas to the HC adsorption catalyst 12 is performed. In Step 103 to Step 105 following Step 102, the HC adsorption catalyst 12 is changed based on the amount of exhaust gas discharged from the internal combustion engine body 1 and the amount of hydrocarbon adsorbed on the HC adsorption catalyst 12 during the previous engine operation. The amount of adsorbed hydrocarbon is calculated, and it is determined whether or not the calculated amount of hydrocarbon has reached the first target amount. If it is determined in step 105 that the amount of hydrocarbons adsorbed on the HC adsorption catalyst 12 has reached the first target amount, the process proceeds to the subsequent step 106. The adsorption of hydrocarbons to the HC adsorption catalyst 12 may be performed by the HC increasing means 19.

ステップ１０６においては、ＨＣ吸着触媒１２をバイパスさせて排気浄化触媒１４に排気ガスを流入させるバイパス処理を行うように流量調節弁１８が制御される。ステップ１０６に続くステップ１０７においては、バイパス処理中に排気浄化触媒１４の温度が炭化水素を酸化し始める温度（Ｔ２）を越えたか否かが判定される。本実施形態においては、流量調整弁１８よりも上流側の排気ガスの温度を検出する温度センサ２６から検出された温度が、排気浄化触媒１４の炭化水素の酸化開始温度に達したときに、排気浄化触媒１４の温度が炭化水素を酸化し始める温度に達したと判断するものとする。排気浄化触媒１４の炭化水素の酸化開始温度に達しているような高温の排気ガスによれば、該高温の排気ガスをＨＣ吸着触媒１２に流入させることにより、ＨＣ吸着触媒１２に吸着されている炭化水素を放出させることができる。   In step 106, the flow rate control valve 18 is controlled so as to perform bypass processing for bypassing the HC adsorption catalyst 12 and allowing exhaust gas to flow into the exhaust purification catalyst 14. In step 107 following step 106, it is determined whether or not the temperature of the exhaust purification catalyst 14 has exceeded a temperature (T2) at which hydrocarbons start to be oxidized during the bypass process. In the present embodiment, when the temperature detected by the temperature sensor 26 that detects the temperature of the exhaust gas upstream of the flow rate adjusting valve 18 reaches the hydrocarbon oxidation start temperature of the exhaust purification catalyst 14, the exhaust gas is exhausted. It is determined that the temperature of the purification catalyst 14 has reached a temperature at which hydrocarbons start to be oxidized. According to the high temperature exhaust gas that has reached the hydrocarbon oxidation start temperature of the exhaust purification catalyst 14, the high temperature exhaust gas is adsorbed by the HC adsorption catalyst 12 by flowing into the HC adsorption catalyst 12. Hydrocarbons can be released.

ステップ１０７にて排気浄化触媒１４の温度が炭化水素を酸化し始める温度に達したと判定されると、続くステップ１０８に進み、流量調整弁１８による排気ガスのＨＣ吸着触媒側への制御、すなわち排気ガスをＨＣ吸着触媒１２に流通させた後に排気浄化触媒１４に流入させるように流量調整弁１８が制御され、ＨＣ吸着触媒１２に吸着させていた炭化水素を放出させて排気浄化触媒１４に供給し、排気浄化触媒１４を昇温させる昇温処理を行う。今回の機関冷間始動時においてＨＣ吸着触媒１２から炭化水素が放出されるのに先立って、すなわち該昇温処理を行う前までにＨＣ吸着触媒１２には第１の目標量の炭化水素が吸着されており、排気浄化触媒１４の炭化水素の酸化開始温度時に目標量の大量の炭化水素を排気浄化触媒１４に供給することができ、これにより、炭化水素の酸化の際に発生する熱による排気浄化触媒１４の急速な活性化温度以上への昇温が可能となる。ステップ１０８に続くステップ１０９においては、ＨＣ吸着触媒１２の炭化水素の吸着量が０（ゼロ）になったか否か、すなわちＨＣ吸着触媒１２に吸着されていた炭化水素が全て放出されたか否かが判定され、ＨＣ吸着触媒１２に吸着されている炭化水素が全て放出されたと判定されると、機関冷間始動時の本制御が終了される。   If it is determined in step 107 that the temperature of the exhaust purification catalyst 14 has reached the temperature at which hydrocarbons start to be oxidized, the process proceeds to the next step 108, where control of the exhaust gas to the HC adsorption catalyst side by the flow rate adjusting valve 18, that is, The flow control valve 18 is controlled so that the exhaust gas flows through the HC adsorption catalyst 12 and then flows into the exhaust purification catalyst 14, and the hydrocarbon adsorbed by the HC adsorption catalyst 12 is released and supplied to the exhaust purification catalyst 14. Then, the temperature raising process for raising the temperature of the exhaust purification catalyst 14 is performed. The first target amount of hydrocarbon is adsorbed to the HC adsorption catalyst 12 before the hydrocarbon is released from the HC adsorption catalyst 12 at the time of the engine cold start, that is, before the temperature raising process is performed. Therefore, a large amount of a target amount of hydrocarbons can be supplied to the exhaust purification catalyst 14 at the hydrocarbon oxidation start temperature of the exhaust purification catalyst 14, thereby exhausting by heat generated during the oxidation of hydrocarbons. It is possible to raise the temperature of the purification catalyst 14 to a temperature higher than the rapid activation temperature. In step 109 following step 108, it is determined whether or not the amount of adsorption of hydrocarbons of the HC adsorption catalyst 12 has become 0 (zero), that is, whether or not all the hydrocarbons adsorbed on the HC adsorption catalyst 12 have been released. If it is determined that it is determined that all the hydrocarbons adsorbed on the HC adsorption catalyst 12 have been released, the control at the time of engine cold start is terminated.

次に、本発明の排気浄化装置おいて、今回の機関運転の吸着処理の開始時に第１の目標量よりも少ない第２の目標量だけＨＣ吸着触媒１２に炭化水素が吸着されているように、前回の機関運転中にＨＣ吸着触媒１２に炭化水素を吸着させておく制御の実施形態について説明する。   Next, in the exhaust emission control device of the present invention, at the start of the adsorption process of the current engine operation, hydrocarbons are adsorbed on the HC adsorption catalyst 12 by a second target amount that is smaller than the first target amount. An embodiment of control for adsorbing hydrocarbons to the HC adsorption catalyst 12 during the previous engine operation will be described.

図３は、前回の機関運転中にＨＣ吸着触媒１２に炭化水素を吸着させておく制御の第一の実施形態を示す図である。具体的には、前回の機関運転中におけるＨＣ捕集制御すなわち前回の機関運転中であってイグニッションスイッチがオフされるまでの間にＨＣ吸着触媒１２に第２の目標量の炭化水素を吸着させておく制御の一実施形態を示す図である。図３に示される第一の実施形態においては、前回の機関運転中に流量調整弁１８の開度を制御してＨＣ吸着触媒１２への排気ガスの流入量やＨＣ吸着触媒１２の温度を制御して、今回の機関運転の吸着処理の開始時に第１の目標量よりも少ない第２の目標量だけＨＣ吸着触媒１２に炭化水素が吸着されているように、前回の機関運転中にＨＣ吸着触媒１２に炭化水素を吸着させておく。以下に、図３に示される第一の実施形態の制御について説明する。   FIG. 3 is a diagram showing a first embodiment of control for adsorbing hydrocarbons to the HC adsorption catalyst 12 during the previous engine operation. Specifically, the second target amount of hydrocarbon is adsorbed by the HC adsorption catalyst 12 during the previous engine operation, that is, during the previous engine operation and before the ignition switch is turned off. It is a figure which shows one Embodiment of the control to keep. In the first embodiment shown in FIG. 3, the opening of the flow rate adjustment valve 18 is controlled during the previous engine operation to control the amount of exhaust gas flowing into the HC adsorption catalyst 12 and the temperature of the HC adsorption catalyst 12. Then, the HC adsorption during the previous engine operation is performed so that the hydrocarbon is adsorbed to the HC adsorption catalyst 12 by a second target amount smaller than the first target amount at the start of the adsorption process of the current engine operation. Hydrocarbon is adsorbed on the catalyst 12 in advance. Below, control of 1st embodiment shown by FIG. 3 is demonstrated.

図３に示された第一の実施形態においては、まず、ステップ２０１にて、前回の機関運転中において、ＨＣ吸着触媒１２の温度が予め設定された所定温度（Ｔ１）以下となるように流量調整弁１８の開度を制御する。例えば、ＨＣ吸着触媒１２の温度が所定温度（Ｔ１）よりも高い場合であって、温度センサ２６により検出された流量調整弁１８よりも上流の排気ガスの温度が所定温度（Ｔ１）よりも低い場合には、流量調整弁１８よりも上流側の排気ガスをＨＣ吸着触媒１２に流入させることによりＨＣ吸着触媒１２を冷却することができるので、流量調整弁１８の開度を制御して流量調整弁１８よりも上流側の排気ガスをＨＣ吸着触媒１２に流入させるようにする。これに対して、ＨＣ吸着触媒１２の温度が所定温度（Ｔ１）よりも高い場合であって、温度センサ２６により検出された流量調整弁１８よりも上流の排気ガスの温度が所定温度（Ｔ１）よりも高い場合には、流量調整弁１８よりも上流側の排気ガスをＨＣ吸着触媒１２に流入させるとＨＣ吸着触媒１２の温度を所定温度（Ｔ１）に下げることができないので、流量調整弁１８の開度を制御して流量調整弁１８よりも上流側の排気ガスをＨＣ吸着触媒１２に流入させないようにし、ＨＣ吸着触媒１２の温度を下げる。尚、本実施形態においては、ＨＣ吸着触媒１２の出口部に配設された温度センサ２７により検出された温度をＨＣ吸着触媒１２の温度とする。また、所定温度（Ｔ１）は、ＨＣ吸着触媒１２に第２の目標量の炭化水素を吸着させておくことができる温度に設定される。   In the first embodiment shown in FIG. 3, first, in step 201, the flow rate is set so that the temperature of the HC adsorption catalyst 12 is equal to or lower than a predetermined temperature (T1) set in advance during the previous engine operation. The opening degree of the regulating valve 18 is controlled. For example, when the temperature of the HC adsorption catalyst 12 is higher than a predetermined temperature (T1), the temperature of the exhaust gas upstream of the flow rate adjusting valve 18 detected by the temperature sensor 26 is lower than the predetermined temperature (T1). In this case, since the HC adsorption catalyst 12 can be cooled by causing the exhaust gas upstream of the flow rate adjustment valve 18 to flow into the HC adsorption catalyst 12, the flow rate adjustment is performed by controlling the opening degree of the flow rate adjustment valve 18. The exhaust gas upstream of the valve 18 is caused to flow into the HC adsorption catalyst 12. In contrast, the temperature of the HC adsorption catalyst 12 is higher than the predetermined temperature (T1), and the temperature of the exhaust gas upstream of the flow rate adjustment valve 18 detected by the temperature sensor 26 is the predetermined temperature (T1). Is higher than the flow rate adjustment valve 18, if the exhaust gas upstream of the flow rate adjustment valve 18 is caused to flow into the HC adsorption catalyst 12, the temperature of the HC adsorption catalyst 12 cannot be lowered to the predetermined temperature (T1). Is controlled so that the exhaust gas upstream of the flow rate adjustment valve 18 does not flow into the HC adsorption catalyst 12, and the temperature of the HC adsorption catalyst 12 is lowered. In the present embodiment, the temperature detected by the temperature sensor 27 disposed at the outlet of the HC adsorption catalyst 12 is the temperature of the HC adsorption catalyst 12. The predetermined temperature (T1) is set to a temperature at which the HC adsorption catalyst 12 can adsorb the second target amount of hydrocarbons.

ステップ２０１にてＨＣ吸着触媒１２の温度が所定温度（Ｔ１）以下にされると、続くステップ２０２からステップ２０４に進み、機関本体１からの排出された排気ガス量から機関本体１から排出された炭化水素量（ｄＱｈｃ）を算出し、流量調整弁１８の開度などからＨＣ吸着触媒１２に流入する炭化水素量（ｄＱｈｃｉ）を算出し、ＨＣ吸着触媒１２に吸着されている炭化水素量（Ｑｈｃ）を算出する。そして、続くステップ２０５にてＨＣ吸着触媒１２に吸着されている炭化水素が第２の目標量に達したか否かが判定される。尚、ＨＣ吸着触媒１２への炭化水素の吸着は、ＨＣ増量手段１９により行われてもよい。   When the temperature of the HC adsorption catalyst 12 is made equal to or lower than the predetermined temperature (T1) in step 201, the process proceeds from step 202 to step 204, where the exhaust gas amount discharged from the engine body 1 is discharged from the engine body 1. The amount of hydrocarbons (dQhc) is calculated, the amount of hydrocarbons (dQhci) flowing into the HC adsorption catalyst 12 is calculated from the opening degree of the flow regulating valve 18 and the like, and the amount of hydrocarbons adsorbed on the HC adsorption catalyst 12 (Qhc) ) Is calculated. Then, in subsequent step 205, it is determined whether or not the hydrocarbons adsorbed on the HC adsorption catalyst 12 have reached the second target amount. The adsorption of hydrocarbons to the HC adsorption catalyst 12 may be performed by the HC increasing means 19.

ステップ２０５にて、ＨＣ吸着触媒１２に吸着されている炭化水素が第２の目標量に達したと判定されと、ステップ２０６に進み、流量調整弁１８によりＨＣ吸着触媒１２をバイパスさせて排気浄化触媒１４に排気ガスを流入させるバイパス処理が実行され、一連の作業が終了される。尚、ステップ２０５にて、ＨＣ吸着触媒１２に吸着されている炭化水素が第２の目標量に達していないと判定されるとステップ２０１に戻り、ステップ２０１からステップ２０５の一連の制御が繰り返し実行される。   If it is determined in step 205 that the hydrocarbon adsorbed on the HC adsorption catalyst 12 has reached the second target amount, the process proceeds to step 206, and the exhaust gas purification is performed by bypassing the HC adsorption catalyst 12 by the flow rate adjustment valve 18. A bypass process for causing the exhaust gas to flow into the catalyst 14 is executed, and a series of operations is completed. If it is determined in step 205 that the hydrocarbon adsorbed on the HC adsorption catalyst 12 has not reached the second target amount, the process returns to step 201 and the series of control from step 201 to step 205 is repeatedly executed. Is done.

図４は、前回の機関運転中にＨＣ吸着触媒１２に炭化水素を吸着させておく制御の第二の実施形態を示す図である。具体的には、前回の機関運転停止時のＨＣ補給制御、すなわち前回の機関運転中であってイグニッションスイッチのオフ時から機関が停止するまでの間にＨＣ吸着触媒１２に第２の目標量の炭化水素を吸着させておく制御の一実施形態を示す図である。図４に示される第二の実施形態においては、前回の機関運転中であってイグニッションスイッチのオフ時から機関が停止するまでの間に、ＨＣ増量手段１９により排気通路１１に炭化水素を供給して、今回の機関運転の吸着処理の開始時に第１の目標量よりも少ない第２の目標量だけＨＣ吸着触媒１２に炭化水素が吸着されているように、ＨＣ吸着触媒１２に炭化水素を吸着させておく。以下に、図４に示された第二の実施形態について説明する。   FIG. 4 is a diagram showing a second embodiment of control for adsorbing hydrocarbons on the HC adsorption catalyst 12 during the previous engine operation. Specifically, the HC replenishment control at the time of the previous engine operation stop, that is, during the previous engine operation, the second target amount is set in the HC adsorption catalyst 12 during the period from when the ignition switch is turned off until the engine is stopped. It is a figure which shows one Embodiment of the control which makes hydrocarbon adsorb | suck. In the second embodiment shown in FIG. 4, hydrocarbons are supplied to the exhaust passage 11 by the HC increasing means 19 during the previous engine operation and before the engine is stopped after the ignition switch is turned off. Thus, the hydrocarbon is adsorbed to the HC adsorption catalyst 12 so that the hydrocarbon is adsorbed to the HC adsorption catalyst 12 by a second target amount that is smaller than the first target amount at the start of the adsorption process of the engine operation this time. Let me. Below, 2nd embodiment shown by FIG. 4 is described.

図４に示された第二の実施形態においては、前回の機関運転において、まず、ステップ３０１にてイグニッションスイッチのオフが確認されると、続くステップ３０２にて、ＨＣ吸着触媒１２に吸着されている炭化水素量が第２の目標量に達しているか否かが判定される。ステップ３０２にて、ＨＣ吸着触媒１２に吸着されている炭化水素量が第２の目標量に達していないと判定されると、ステップ３０３に進み、イグニッションスイッチがオフされてから機関が停止するまでの間、流量調整弁１８による排気ガスのＨＣ吸着触媒側への制御、すなわち流量調整弁１８により排気ガスをＨＣ吸着触媒１２に流入させて後に排気浄化触媒１４に流入させるように制御する。そして、ステップ３０３に続くステップ３０４において、機関本体１から排出される排気ガスの温度が所定温度（Ｔ１）よりも低くなったか否かが判定される。本実施形態においては、流量調整弁１８よりも上流側の排気通路に配設された温度センサ２６により検出された温度に基づいて、機関本体１から排出される排気ガスの温度が所定温度（Ｔ１）よりも低くなったか否かが判定される。また、機関本体１から排出される排気ガスの温度が所定温度（Ｔ１）よりも低くなったときには、ＨＣ吸着触媒１２の温度も所定温度（Ｔ１）以下であるものとする。尚、所定温度（Ｔ１）は、図３に示された第一の実施形態と同様に、ＨＣ吸着触媒１２に第２の目標量の炭化水素を吸着させておくことができる温度に設定される。   In the second embodiment shown in FIG. 4, in the previous engine operation, first, when it is confirmed in step 301 that the ignition switch is turned off, in the subsequent step 302, it is adsorbed by the HC adsorption catalyst 12. It is determined whether or not the amount of hydrocarbons that has reached the second target amount. If it is determined in step 302 that the amount of hydrocarbons adsorbed on the HC adsorption catalyst 12 has not reached the second target amount, the process proceeds to step 303 until the engine is stopped after the ignition switch is turned off. During this period, the exhaust gas is controlled to the HC adsorption catalyst side by the flow rate adjusting valve 18, that is, the exhaust gas is controlled to flow into the HC adsorption catalyst 12 and then into the exhaust purification catalyst 14 by the flow rate adjusting valve 18. Then, in step 304 following step 303, it is determined whether or not the temperature of the exhaust gas discharged from the engine body 1 has become lower than a predetermined temperature (T1). In the present embodiment, the temperature of the exhaust gas discharged from the engine body 1 is set to a predetermined temperature (T1) based on the temperature detected by the temperature sensor 26 disposed in the exhaust passage upstream of the flow rate adjustment valve 18. ) Is determined. Further, when the temperature of the exhaust gas discharged from the engine body 1 becomes lower than the predetermined temperature (T1), the temperature of the HC adsorption catalyst 12 is assumed to be equal to or lower than the predetermined temperature (T1). The predetermined temperature (T1) is set to a temperature at which the second target amount of hydrocarbons can be adsorbed to the HC adsorption catalyst 12, as in the first embodiment shown in FIG. .

ステップ３０４において、ＨＣ吸着触媒１２に流入する排気ガスの温度が所定温度（Ｔ１）よりも低くなったと判定された場合には、続くステップ３０５に進み、必要量のＨＣの供給、すなわち、第２の目標量の炭化水素をＨＣ吸着触媒１２に吸着させるために必要な量の炭化水素をＨＣ増量手段１９により排気通路に供給することにより、イグニッションスイッチがオフされてから機関が停止されるまでの間に第２の目標量の炭化水素をＨＣ吸着触媒１２に吸着させる。   In step 304, when it is determined that the temperature of the exhaust gas flowing into the HC adsorption catalyst 12 has become lower than the predetermined temperature (T1), the process proceeds to the subsequent step 305, where a required amount of HC is supplied, that is, the second The amount of hydrocarbon necessary for adsorbing the target amount of hydrocarbons to the HC adsorption catalyst 12 is supplied to the exhaust passage by the HC increasing means 19 until the engine is stopped after the ignition switch is turned off. In the meantime, the second target amount of hydrocarbon is adsorbed on the HC adsorption catalyst 12.

以上、本発明の排気浄化装置によれば、排気浄化触媒の上流側の排気通路にＨＣ吸着触媒が配設された内燃機関の排気浄化装置において、今回の機関冷間始動時において上記昇温処理を行う前までにＨＣ吸着触媒に目標量の炭化水素を確実に吸着させておくことができ、また、排気浄化触媒の炭化水素を酸化し始める温度時に目標量の大量の炭化水素を排気浄化触媒に供給することができ、これにより、炭化水素の酸化の際に発生する熱による排気浄化触媒の急速な活性化温度以上への昇温が可能となる。   As described above, according to the exhaust gas purification apparatus of the present invention, in the exhaust gas purification apparatus for an internal combustion engine in which the HC adsorption catalyst is disposed in the exhaust passage upstream of the exhaust gas purification catalyst, the temperature increasing process is performed at the time of the engine cold start. The target amount of hydrocarbons can be surely adsorbed to the HC adsorption catalyst before the start of the operation, and the target amount of hydrocarbons is exhausted at a temperature at which the exhaust purification catalyst begins to oxidize. This makes it possible to raise the temperature of the exhaust purification catalyst to a temperature higher than the rapid activation temperature by heat generated during the oxidation of hydrocarbons.

本発明の排気浄化装置が適用された内燃機関全体を示す図である。It is a figure showing the whole internal-combustion engine to which the exhaust emission control device of the present invention is applied. 本発明の排気浄化装置における機関冷間始動時の制御の一実施形態を示す図である。It is a figure which shows one Embodiment of the control at the time of engine cold start in the exhaust gas purification apparatus of this invention. 前回の機関運転中にＨＣ吸着触媒に炭化水素を吸着させておく制御の第一の実施形態を示す図である。It is a figure which shows 1st embodiment of control which makes hydrocarbon adsorb | suck to HC adsorption catalyst during the last engine operation. 前回の機関運転中にＨＣ吸着触媒に炭化水素を吸着させておく制御の第二の実施形態を示す図である。It is a figure which shows 2nd embodiment of control which makes hydrocarbon adsorb | suck to HC adsorption catalyst during the last engine operation.

符号の説明Explanation of symbols

４ 吸気マニホルド
５ 排気マニホルド
１２ ＨＣ吸着触媒
１４ 排気浄化触媒
１７ バイパス通路
１８ 流量調整弁 4 Intake manifold 5 Exhaust manifold 12 HC adsorption catalyst 14 Exhaust purification catalyst 17 Bypass passage 18 Flow control valve

Claims (5)

内燃機関の排気通路に配設され排気ガス中の少なくとも炭化水素を酸化する酸化能を有する排気浄化触媒と、該排気浄化触媒よりも上流側の排気通路に配設され炭化水素を吸着するＨＣ吸着触媒と、該ＨＣ吸着触媒をバイパスさせて前記排気浄化触媒に排気ガスを流入させるバイパス通路と、前記ＨＣ吸着触媒に流入する排気ガスの流量と前記バイパス通路に流入する排気ガスの流量とを調整する流量調整弁とを備える内燃機関の排気浄化装置であって、
機関冷間始動時には、まず、排気ガスを前記ＨＣ吸着触媒に流通させた後に前記排気浄化触媒に流入させて排気ガス中の炭化水素を前記ＨＣ吸着触媒に吸着させる吸着処理を行い、次に、前記ＨＣ吸着触媒をバイパスさせて前記排気浄化触媒に排気ガスを流入させるバイパス処理を行い、次に再び、排気ガスを前記ＨＣ吸着触媒に流通させた後に前記排気浄化触媒に流入させることにより前記ＨＣ吸着触媒に吸着させていた炭化水素を放出させて前記排気浄化触媒に供給し、それにより前記排気浄化触媒を昇温させる昇温処理を行う、内燃機関の排気浄化装置において、
今回の機関冷間始動時において前記昇温処理を行う前までに第１の目標量の炭化水素を前記ＨＣ吸着触媒に吸着させておき、前記バイパス処理中に前記排気浄化触媒の温度が炭化水素を酸化し始める温度を越えたときに、前記バイパス処理から前記昇温処理に切り換えるようにした、ことを特徴とする内燃機関の排気浄化装置。 An exhaust purification catalyst that is disposed in the exhaust passage of the internal combustion engine and has an oxidizing ability to oxidize at least hydrocarbons in the exhaust gas, and an HC adsorption that is disposed in the exhaust passage upstream of the exhaust purification catalyst and adsorbs hydrocarbons Adjusting a catalyst, a bypass passage for bypassing the HC adsorption catalyst and allowing exhaust gas to flow into the exhaust purification catalyst, a flow rate of exhaust gas flowing into the HC adsorption catalyst, and a flow rate of exhaust gas flowing into the bypass passage An exhaust purification device for an internal combustion engine comprising a flow regulating valve for performing
At the time of engine cold start, first, an exhaust gas is allowed to flow through the HC adsorption catalyst and then flowed into the exhaust purification catalyst to adsorb hydrocarbons in the exhaust gas to the HC adsorption catalyst. Bypassing the HC adsorption catalyst so as to allow exhaust gas to flow into the exhaust purification catalyst, and then again flowing the exhaust gas through the HC adsorption catalyst and then flowing into the exhaust purification catalyst, the HC In an exhaust gas purification apparatus for an internal combustion engine, a hydrocarbon that has been adsorbed by an adsorption catalyst is released and supplied to the exhaust gas purification catalyst, thereby performing a temperature raising process for raising the temperature of the exhaust gas purification catalyst.
The first target amount of hydrocarbon is adsorbed to the HC adsorption catalyst before the temperature increase process at the time of the engine cold start this time, and the temperature of the exhaust purification catalyst is changed to the hydrocarbon during the bypass process. An exhaust emission control device for an internal combustion engine, wherein when the temperature exceeds the temperature at which oxidation of the engine starts, the bypass processing is switched to the temperature raising processing. 前記ＨＣ吸着触媒に前記第１の目標量の炭化水素が吸着されたときに、前記吸着処理から前記バイパス処理に切り換えるようにした、ことを特徴とする請求項１に記載の内燃機関の排気浄化装置。   2. The exhaust gas purification of an internal combustion engine according to claim 1, wherein when the first target amount of hydrocarbon is adsorbed on the HC adsorption catalyst, the adsorption process is switched to the bypass process. apparatus. 今回の機関運転の前記吸着処理の開始時に前記第１の目標量よりも少ない第２の目標量だけ前記ＨＣ吸着触媒に炭化水素が吸着されているように、前回の機関運転中に前記ＨＣ吸着触媒に炭化水素を吸着させておき、今回の機関運転の前記吸着処理中に前記第１の目標量まで炭化水素を前記ＨＣ吸着触媒に吸着させる、ことを特徴とする請求項１に記載の内燃機関の排気浄化装置。   During the previous engine operation, the HC adsorption is performed so that hydrocarbons are adsorbed by the HC adsorption catalyst by a second target amount that is smaller than the first target amount at the start of the adsorption process of the current engine operation. The internal combustion engine according to claim 1, wherein hydrocarbons are adsorbed on a catalyst, and hydrocarbons are adsorbed on the HC adsorption catalyst up to the first target amount during the adsorption process of the current engine operation. Engine exhaust purification system. 前記排気浄化装置は、前記ＨＣ吸着触媒よりも上流側の排気ガス中に炭化水素を供給するＨＣ増量手段を有し、前記ＨＣ吸着触媒に炭化水素を吸着させるべきときに前記ＨＣ増量手段から炭化水素を供給する、ことを特徴とする請求項１または請求項３に記載の内燃機関の排気浄化装置。   The exhaust purification device has HC increasing means for supplying hydrocarbons into the exhaust gas upstream of the HC adsorption catalyst, and when the hydrocarbons are to be adsorbed by the HC adsorption catalyst, carbonization is performed from the HC increasing means. The exhaust gas purification apparatus for an internal combustion engine according to claim 1 or 3, wherein hydrogen is supplied. 前記排気浄化触媒は、尿素によりＮＯｘを選択的に還元可能な選択還元触媒であって排気ガスが流入する側に酸化触媒を備えた選択還元触媒である、ことを特徴とする請求項１に記載の内燃機関の排気浄化装置。   The exhaust purification catalyst is a selective reduction catalyst capable of selectively reducing NOx with urea, and is a selective reduction catalyst having an oxidation catalyst on a side into which exhaust gas flows. Exhaust gas purification device for internal combustion engine.

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