JP5604956B2 - Exhaust gas purification device - Google Patents

Exhaust gas purification device Download PDF

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JP5604956B2
JP5604956B2 JP2010098172A JP2010098172A JP5604956B2 JP 5604956 B2 JP5604956 B2 JP 5604956B2 JP 2010098172 A JP2010098172 A JP 2010098172A JP 2010098172 A JP2010098172 A JP 2010098172A JP 5604956 B2 JP5604956 B2 JP 5604956B2
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貴久 長尾
哲也 渡邊
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Mitsubishi Motors Corp
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Description

本発明は、例えば自動車に設けられて触媒を備える排ガス浄化装置に関する。   The present invention relates to an exhaust gas purification apparatus that is provided, for example, in an automobile and includes a catalyst.

従来、エンジン（内燃機関）を備える自動車は、エンジンより排出される排ガスが流動する排ガス流路中に、排ガス浄化装置が設けられている。排ガス浄化装置は、排ガス中の未燃燃料、一酸化炭素や窒素酸化物（ＮＯｘ）を浄化するために、触媒を備えている。また、２つの触媒を直列に配置するタンデム構造の排ガス浄化装置も提案されている（例えば、特許文献１参照。）。   2. Description of the Related Art Conventionally, an automobile equipped with an engine (internal combustion engine) is provided with an exhaust gas purification device in an exhaust gas passage through which exhaust gas discharged from the engine flows. The exhaust gas purifying apparatus includes a catalyst for purifying unburned fuel, carbon monoxide, and nitrogen oxide (NOx) in the exhaust gas. An exhaust gas purification device having a tandem structure in which two catalysts are arranged in series has also been proposed (see, for example, Patent Document 1).

前段に配置される触媒と後段に配置される触媒とを備える構造の排ガス浄化装置では、排ガスの浄化性能を向上する観点から、前段の触媒と後段の触媒との構造とにさらに工夫が施すことが提案されている
上記工夫の一例として、前段の触媒は、自動車の発進直後の排ガスの浄化性能を向上するために、活性温度まで後段の触媒に対して早期に昇温できるように形成されている。具体的には、前段の触媒の担体の壁部を薄くしたり、容量を小さくすることで熱容量を小さくし，また担体のセル数を多くし表面積を増やす事で熱を受けやすくする事が行われている。後段の触媒は、低セル密度であって大容量の担体が用いられており、前段の触媒で処理できなかった排ガスを浄化するように形成されている。 In the exhaust gas purification device having a structure including the catalyst arranged in the front stage and the catalyst arranged in the rear stage, further improvements should be made to the structure of the catalyst in the front stage and the catalyst in the rear stage from the viewpoint of improving exhaust gas purification performance. As an example of the above device, the catalyst in the front stage is formed so that it can be heated up to the activation temperature at an early stage with respect to the catalyst in the rear stage in order to improve the purification performance of exhaust gas immediately after the start of the automobile. Yes. Specifically, the heat capacity can be reduced by thinning the wall of the catalyst carrier in the previous stage or by reducing the capacity, and by increasing the surface area by increasing the number of cells of the carrier, it is easy to receive heat. It has been broken. The latter catalyst has a low cell density and uses a large capacity carrier, and is formed so as to purify exhaust gas that could not be treated with the former catalyst.

特開２００７−２６３０５５号公報JP 2007-263055 A

前段の触媒の熱容量を小さくするために、容量を小さくすると、触媒による排ガスの浄化性能が低下するおそれがある。担体の壁部を薄くすると、耐久性が低下するおそれがある。セル密度を高くすると（高セル密度化）、圧力損失の上昇や、熱容量が増加するおそれがある。   If the capacity is reduced in order to reduce the heat capacity of the catalyst in the preceding stage, the exhaust gas purification performance by the catalyst may be reduced. When the wall portion of the carrier is thinned, the durability may be reduced. If the cell density is increased (high cell density), the pressure loss may increase and the heat capacity may increase.

このため、本発明は、耐久性の低下、圧力損失の上昇、熱容量の増加を抑制しつつ、排ガスの浄化性能を向上できる排ガス浄化装置を提供することにある。   For this reason, this invention is providing the exhaust gas purification apparatus which can improve the purification performance of exhaust gas, suppressing the fall of durability, the raise of pressure loss, and the increase in heat capacity.

請求項１に記載の発明の排ガス浄化装置は、第１の担体と、前記第１の担体に担持される第１の触媒活性物質とを具備する第１の触媒と、前記第１の触媒に対して直列に配置される第２の触媒であって、第２の担体と、前記第２の担体に担持される第２の触媒活性物質とを具備する第２の触媒とを備える。前記第１の担体は、当該第１の担体を形成する壁部に、当該壁部を貫通し４つの縁面により規定される貫通孔が形成される。前記縁面を含む前記第１の担体の表面に担持される前記第１の触媒活性物質の担持量は、前記第２の触媒活性物質の担持量以上とされる。前記貫通孔は、前記第１の担体の熱容量が前記第２の担体の熱容量よりも小さくなるように形成される。前記第１の担体の質量と前記第１の触媒活性物質の質量の合計である前記第１の触媒の質量は、前記第２の担体の質量と前記第２の触媒活性物質の質量の合計である前記第２の触媒の質量よりも小さくされる。前記貫通孔の前記壁部に占める割合は、前記第１の担体において単位面積当たりに担持できる前記第１の触媒活性物質の最大質量である担持限界質量に基づいて設定される。 An exhaust gas purification apparatus according to a first aspect of the present invention is directed to a first catalyst comprising a first carrier, a first catalytically active substance supported on the first carrier, and the first catalyst. On the other hand, the second catalyst is arranged in series, and includes a second carrier comprising a second carrier and a second catalytically active substance carried on the second carrier. The first carrier, the wall forming the first carrier, the through hole penetrating the wall Ru is defined by four edge surfaces is formed. The amount of the first catalytically active material supported on the surface of the first carrier including the edge surface is set to be equal to or greater than the amount of the second catalytically active material supported. The through hole is formed such that the heat capacity of the first carrier is smaller than the heat capacity of the second carrier. The first is the mass to the total mass of the first catalytically active substance carrier wherein the first mass of the catalyst, of the second carrier of the mass and the second mass of the catalytically active substance The total mass of the second catalyst is made smaller. The ratio of the through hole to the wall is set based on a loading limit mass that is the maximum mass of the first catalytically active substance that can be supported per unit area in the first carrier.

請求項２に記載の発明の排ガス浄化装置は、請求項１の記載において、前記第１の触媒の熱容量が前記第２の触媒の熱容量より小さくなるように、前記壁部に占める前記貫通孔の割合と前記第１の触媒活性物質の担持量を設定する。
請求項３に記載の発明の排ガス浄化装置は、請求項１又は２の記載において、前記縁面を含む前記第１の担体の表面積は、前記第１の触媒活性物質の担持量を前記担持限界質量で除した値と等しい。 An exhaust gas purifying apparatus according to a second aspect of the present invention is the exhaust gas purifying apparatus according to the first aspect, wherein the through hole occupying the wall portion is configured such that the heat capacity of the first catalyst is smaller than the heat capacity of the second catalyst. The ratio and the loading amount of the first catalytically active substance are set.
According to a third aspect of the present invention, there is provided the exhaust gas purifying apparatus according to the first or second aspect, wherein the surface area of the first carrier including the edge surface is the amount of the first catalytically active substance supported. Equal to the value divided by mass.

本発明によれば、耐久性の低下、圧力損失の上昇、熱容量の増加を抑制しつつ、排ガスの浄化性能を向上できる排ガス浄化装置を提供できる。   ADVANTAGE OF THE INVENTION According to this invention, the exhaust gas purification apparatus which can improve the purification performance of exhaust gas can be provided, suppressing the fall of durability, the raise of pressure loss, and the increase in heat capacity.

本発明の一実施形態の排ガス浄化装置を備えるエンジンシステムを示す概略図。Schematic which shows an engine system provided with the exhaust gas purification apparatus of one Embodiment of this invention. 図１に示された前段触媒装置と後段触媒装置とを分解した状態を示す概略図。Schematic which shows the state which decomposed | disassembled the front | former stage catalyst apparatus and back | latter stage catalyst apparatus which were shown by FIG. 図２に示された前段用触媒の一部を拡大して示す斜視図。The perspective view which expands and shows a part of catalyst for the front | former stage shown by FIG. 図２に示された前段用担体の作成手順の一例を示す概略図。Schematic which shows an example of the preparation procedure of the front | former stage carrier shown by FIG. 図２に示された前段用触媒において、第１，２のシート部材の開口率を変化させた場合の、前段用触媒の浄化性能を示すグラフ。The graph which shows the purification | cleaning performance of the catalyst for a front | former stage in the case of changing the aperture ratio of the 1st, 2nd sheet member in the catalyst for a front | former stage shown by FIG.

本発明の一実施形態に係る排ガス浄化装置を、図１〜５を用いて説明する。図１は、本実施形態の排ガス浄化装置２０を備えるエンジンシステム１０を示す概略図である。エンジンシステム１０は、一例として自動車に用いられる。図１に示すように、エンジンシステム１０は、エンジン１１と、吸気系１２と、排ガス系１３とを備えている。   An exhaust gas purification apparatus according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic diagram showing an engine system 10 including an exhaust gas purification device 20 of the present embodiment. The engine system 10 is used for an automobile as an example. As shown in FIG. 1, the engine system 10 includes an engine 11, an intake system 12, and an exhaust gas system 13.

エンジン１１は、シリンダ１４とピストン１５とを備える、燃料としてガソリンを用いるレシプロ式内燃機関である。吸気系１２は、吸気通路１６を備えている。吸気通路１６は、エンジン１１の燃焼室１７に吸気する。   The engine 11 includes a cylinder 14 and a piston 15 and is a reciprocating internal combustion engine that uses gasoline as fuel. The intake system 12 includes an intake passage 16. The intake passage 16 takes air into the combustion chamber 17 of the engine 11.

排ガス系１３は、エンジン１１から排出される排ガスＧを外部へ導く排ガス通路１８と、排ガス通路１８中を流れる排ガスＧを浄化する排ガス浄化装置２０とを備えている。排ガス浄化装置２０は、排ガス通路１８中に組み込まれている。排ガスＧは、排ガス浄化装置２０を通過する。排ガスＧは、排ガス浄化装置２０を通過することによって、浄化される。   The exhaust gas system 13 includes an exhaust gas passage 18 that guides the exhaust gas G discharged from the engine 11 to the outside, and an exhaust gas purification device 20 that purifies the exhaust gas G flowing through the exhaust gas passage 18. The exhaust gas purification device 20 is incorporated in the exhaust gas passage 18. The exhaust gas G passes through the exhaust gas purification device 20. The exhaust gas G is purified by passing through the exhaust gas purification device 20.

排ガス浄化装置２０は、本発明で言う排ガス浄化装置の一例である。排ガス浄化装置２０は、上流側に配置される前段触媒装置３０と、前段触媒装置３０に対して下流に配置される後段触媒装置４０と、前段触媒装置３０と後段触媒装置４０とを収容するハウジング６０とを備えている。   The exhaust gas purification device 20 is an example of the exhaust gas purification device referred to in the present invention. The exhaust gas purification device 20 includes a front-stage catalyst device 30 disposed upstream, a rear-stage catalyst device 40 disposed downstream of the front-stage catalyst device 30, and a housing that houses the front-stage catalyst device 30 and the rear-stage catalyst device 40. 60.

ハウジング６０は、排ガス通路１８の一部を構成している。なお、上流、下流は、排ガスＧの流れる方向に沿って定義される。本実施形態では、図中に矢印で示すように、排ガスＧは、一方向に流れる。前段触媒装置３０と後段触媒装置４０とは、排ガスＧが流れる方向にそって、直列に並んで配置される。   The housing 60 constitutes a part of the exhaust gas passage 18. The upstream and downstream are defined along the direction in which the exhaust gas G flows. In the present embodiment, the exhaust gas G flows in one direction as indicated by arrows in the drawing. The front-stage catalyst device 30 and the rear-stage catalyst device 40 are arranged in series along the direction in which the exhaust gas G flows.

図２は、前段触媒装置３０と後段触媒装置４０とを分解した状態を示す概略図である。図２に示すように、前段触媒装置３０は、前段用ハウジング３１と、前段用触媒３２とを備えている。前段用触媒３２は、本発明で言う第１の触媒の一例である。図２中、分解された前段用触媒３２を２点鎖線で示す。前段用ハウジング３１は、筒状であって、両端開口が排ガスＧの流れる方向に並んでいる。   FIG. 2 is a schematic view showing a state where the front-stage catalyst device 30 and the rear-stage catalyst device 40 are disassembled. As shown in FIG. 2, the front-stage catalyst device 30 includes a front-stage housing 31 and a front-stage catalyst 32. The pre-stage catalyst 32 is an example of the first catalyst referred to in the present invention. In FIG. 2, the decomposed upstream catalyst 32 is indicated by a two-dot chain line. The front-stage housing 31 has a cylindrical shape, and both end openings are arranged in the direction in which the exhaust gas G flows.

前段用触媒３２は、前段用担体３３と、前段用担体３３に担持される前段用触媒活性物質３４とを備えている。図２中、前段用触媒３２の一部を拡大して示している。図２中に拡大して示すように、前段用担体３３は、前段用ハウジング３１内に収容された状態において前段用ハウジング３１の一端の開口３１ａから他端の開口３１ｂまで連通する複数の通路３５を備えるハニカム構造である。前段用担体３３は、本発明で言う第１の担体の一例である。排ガスＧは、前段用触媒３２を一端の開口３１ａから他端の開口３１ｂまで通過することができる。前段用触媒３２は、本発明で言う第１の触媒の一例である。   The front-stage catalyst 32 includes a front-stage carrier 33 and a front-stage catalyst active material 34 supported on the front-stage carrier 33. In FIG. 2, a part of the pre-stage catalyst 32 is shown enlarged. As shown in an enlarged view in FIG. 2, the front carrier 33 has a plurality of passages 35 communicating from the opening 31 a at one end to the opening 31 b at the other end of the front housing 31 in a state of being accommodated in the front housing 31. Is a honeycomb structure. The front carrier 33 is an example of the first carrier referred to in the present invention. The exhaust gas G can pass through the upstream catalyst 32 from the opening 31a at one end to the opening 31b at the other end. The pre-stage catalyst 32 is an example of the first catalyst referred to in the present invention.

図３は、前段用触媒３２の一部を拡大して示す斜視図である。前段用触媒３２は、上記したように、前段用ハウジング３１の一端の開口３１ａから他端の開口３１ｂまで連通して排ガスＧが通過可能な通路３５を複数備えるハニカム構造である。図３に示すように、前段用担体３３において、通路３５を規定する壁部３６には、複数の貫通孔３７が形成されている。貫通孔３７は、隣り合う通路３５を互いに連通している。貫通孔３７は、本発明でいう貫通孔の一例である。   FIG. 3 is an enlarged perspective view showing a part of the pre-stage catalyst 32. As described above, the front-stage catalyst 32 has a honeycomb structure including a plurality of passages 35 that allow the exhaust gas G to pass from the opening 31a at one end of the front-stage housing 31 to the opening 31b at the other end. As shown in FIG. 3, in the front carrier 33, a plurality of through holes 37 are formed in the wall portion 36 that defines the passage 35. The through holes 37 communicate adjacent passages 35 with each other. The through hole 37 is an example of a through hole as referred to in the present invention.

前段用担体３３の作成手順の一例を説明する。図４は、前段用担体３３の作成手順の一例を示す概略図である。図４に示すように、前段用担体３３は、第１のシート部材５０と、第２のシート部材５１とを組み合わせるとともに、第１，２のシート部材５０，５１が組み合わさった状態で、これをロール状に丸めることによって形成される。   An example of the preparation procedure of the upstream carrier 33 will be described. FIG. 4 is a schematic diagram showing an example of a procedure for creating the upstream carrier 33. As shown in FIG. 4, the front carrier 33 is a combination of the first sheet member 50 and the second sheet member 51 and the first and second sheet members 50 and 51 combined. It is formed by rounding into a roll shape.

第１のシート部材５０は、図に示すように、薄いシート状であって、当該第１のシート部材５０を貫通する複数の貫通孔３７が形成されている。第２のシート部材５１は、第１のシート部材５０と同様のシート部材をひだ折りすることによって形成される。第１，２のシート部材５０，５１に形成される貫通孔３７が、前段用担体３３に形成される貫通孔３７となる。   As shown in the figure, the first sheet member 50 has a thin sheet shape, and a plurality of through holes 37 penetrating the first sheet member 50 are formed. The second sheet member 51 is formed by folding a sheet member similar to the first sheet member 50. The through holes 37 formed in the first and second sheet members 50 and 51 become the through holes 37 formed in the front carrier 33.

ここで言う開口率とは、第１，２のシート部材５０，５１の上面５２，５３において周縁５４，５６内に規定される範囲の面積に対する、貫通孔３７の面積の割合である。 The term aperture ratio is to the area of the range defined in the peripheral 54,5 6 in the upper surface 52, 53 of the first and second sheet members 50 and 51, the ratio of the area of the through-hole 37.

上記のように構成される前段用担体３３に、前段用触媒活性物質３４が担持される。前段用触媒活性物質３４は、本発明で言う第１の触媒活性物質の一例である。なお、前段用触媒活性物質３４は、担持されている様子を図２に示している。前段用触媒活性物質３４は、前段用担体３３の表面に担持されており、それゆえ、他の図面においては符号３４は前段用担体３３の表面を示している。実際には、前段用担体３３の表面には、図２に示すように、前段用触媒活性物質３４が担持されている。   The front-stage catalyst active material 34 is supported on the front-stage carrier 33 configured as described above. The upstream catalytically active material 34 is an example of the first catalytically active material referred to in the present invention. FIG. 2 shows a state where the pre-stage catalytic active material 34 is supported. The front-stage catalytically active material 34 is carried on the surface of the front-stage carrier 33. Therefore, in other drawings, the reference numeral 34 indicates the surface of the front-stage carrier 33. Actually, as shown in FIG. 2, the front-stage catalyst active material 34 is supported on the surface of the front-stage carrier 33.

触媒活性物質としては、例えば、プラチナＰｔ、パラジウムＰｄ、ロジウムＲｈなどがある。本実施形態では、前段用触媒活性物質として、一例として、プラチナＰｔと、パラジウムＰｄと、ロジウムＲｈとが用いられている。これら３種の物質は、所定の割合で混合されている。   Examples of the catalytically active substance include platinum Pt, palladium Pd, and rhodium Rh. In the present embodiment, platinum Pt, palladium Pd, and rhodium Rh are used as an example of the pre-stage catalytic active material. These three substances are mixed at a predetermined ratio.

図２中、分解された後段触媒装置４０を２点鎖線で示す。図２に示すように、後段触媒装置４０は、後段用ハウジング４１と、後段用触媒４２とを備えている。後段用ハウジング４１は、筒状であって、両端が排ガスＧの流れる方向に並んでいる。図２中、後段用触媒４２の一部を拡大して示す。   In FIG. 2, the decomposed rear-stage catalyst device 40 is indicated by a two-dot chain line. As shown in FIG. 2, the rear catalyst device 40 includes a rear housing 41 and a rear catalyst 42. The rear housing 41 has a cylindrical shape, and both ends thereof are arranged in the direction in which the exhaust gas G flows. In FIG. 2, a part of the rear catalyst 42 is shown in an enlarged manner.

後段用触媒４２は、本発明で言う第２の触媒の一例である。図２中に拡大して示すように、後段用触媒４２は、後段用担体４３と、後段用担体４３に担持される後段用触媒活性物質４４とを備えている。後段用担体４３は、後段用ハウジング４１に収容されたときに、後段用ハウジング４１の一端の開口４１ａから他端の開口４１ｂまで連通する複数の通路４５を備えるハニカム構造である。後段用担体４３は、前段用担体３３のように壁部に貫通孔は形成されていない。後段用担体４３は、本発明で言う第２の担体の一例である。   The post-stage catalyst 42 is an example of a second catalyst referred to in the present invention. As shown in an enlarged view in FIG. 2, the post-stage catalyst 42 includes a post-stage support 43 and a post-stage catalyst active material 44 carried on the post-stage support 43. The rear carrier 43 has a honeycomb structure including a plurality of passages 45 communicating from the opening 41 a at one end to the opening 41 b at the other end of the rear housing 41 when accommodated in the rear housing 41. The rear carrier 43 has no through-hole formed in the wall portion unlike the front carrier 33. The post-stage carrier 43 is an example of a second carrier referred to in the present invention.

後段用触媒活性物質は、本発明で言う第２の触媒活性物質の一例である。後段用触媒活性物質４４は、一例として、プラチナＰｔと、パラジウムＰｄと、ロジウムＲｈ＊とが用いられている。これら３種の物質は、所定の割合で混合されている。なお、混合の割合は、前段用触媒３２と同様であってもよいし、または、異なる割合であってもよい。また、後段用触媒活性物質４４は、前段用触媒活性物質３４と異なる物質であってもよい。後段用触媒４２は、本発明で言う第２の触媒の一例である。 The latter catalytically active material is an example of the second catalytically active material referred to in the present invention. For example, platinum Pt, palladium Pd, and rhodium Rh * are used as the post-stage catalytic active material 44. These three substances are mixed at a predetermined ratio. The mixing ratio may be the same as that of the pre-stage catalyst 32, or may be a different ratio. Further, the post-stage catalytic active material 44 may be a material different from the pre-stage catalytic active material 34. The post-stage catalyst 42 is an example of a second catalyst referred to in the present invention.

前段用触媒活性物質３４の量と、前段用担体３３に形成される貫通孔３７と、後段用触媒４２との関係について説明する。前段用触媒３２の質量をａ１とする。後段用触媒４２の質量をｂ１とする。ｂ１は、ａ１よりも大きい（ａ１＜ｂ１）。なお、前段用触媒３２の質量ａ１は、本実施形態では、前段用担体３３の質量と、前段用触媒活性物質３４の質量との合計である。後段用触媒４２の質量ｂ１は、本実施形態では、後段用担体４３の質量と、後段用触媒活性物質４４の質量の合計である。   The relationship between the amount of the front-stage catalyst active material 34, the through-hole 37 formed in the front-stage carrier 33, and the rear-stage catalyst 42 will be described. The mass of the pre-stage catalyst 32 is a1. The mass of the post-stage catalyst 42 is b1. b1 is larger than a1 (a1 <b1). In this embodiment, the mass a1 of the upstream catalyst 32 is the sum of the mass of the upstream carrier 33 and the upstream catalytically active material 34. In this embodiment, the mass b1 of the post-stage catalyst 42 is the sum of the mass of the post-stage support 43 and the mass of the post-stage catalyst active material 44.

前段用触媒活性物質３４の質量をａ２とする。後段用触媒活性物質４４の質量をｂ２とする。本実施形態では、ａ２は、ｂ２より大きい（ａ２＞ｂ２）。前段用触媒活性物質３４の質量ａ２は、前段用触媒３２に求められる排ガスＧの浄化性能に合わせて決定されている。   The mass of the pre-stage catalytic active material 34 is a2. The mass of the post-stage catalytic active substance 44 is b2. In this embodiment, a2 is larger than b2 (a2> b2). The mass a2 of the pre-stage catalyst active material 34 is determined in accordance with the purification performance of the exhaust gas G required for the pre-stage catalyst 32.

前段用担体３３の表面積をＡとする。前段用担体３３の表面積について、具体的に説明する。前段用担体３３の表面積は、前段用担体３３において流動する排ガスＧと接触する可能性がある面の面積である。表面積Ａは、図３に示すように、第１，２のシート部材５０，５１の両面に加えて、貫通孔３７を規定する４つの縁面５５も含む。   The surface area of the front carrier 33 is A. The surface area of the front carrier 33 will be specifically described. The surface area of the front carrier 33 is an area of a surface that may come into contact with the exhaust gas G flowing in the front carrier 33. As shown in FIG. 3, the surface area A includes four edge surfaces 55 that define the through holes 37 in addition to both surfaces of the first and second sheet members 50 and 51.

前段用担体３３の、担持限界質量をＬとする。担持限界質量は、前段用担体３３において、単位面積に担持可能な前段用触媒活性物質３４の最大質量である。担持限界質量Ｌは、予め決まった値である。前段用担体３３に必要な表面積、つまり、前段用担体３３において排ガスＧが接触可能な面の面積の最小値をＳｍｉｎとすると、Ｓｍｉｎ＝ａ１／Ｌとなる。このため、Ａ≧Ｓｍｉｎとなる。貫通孔３７は、前段用担体３３の表面積Ａが、Ｓｍｉｎ以上となるように、形成されている。   Let L be the carrying limit mass of the carrier 33 for the previous stage. The support limit mass is the maximum mass of the pre-stage catalytic active material 34 that can be supported on a unit area in the pre-stage carrier 33. The carrying limit mass L is a predetermined value. Smin = a1 / L, where Smin is the surface area required for the front carrier 33, that is, the minimum surface area of the front carrier 33 that can contact the exhaust gas G. For this reason, A ≧ Smin. The through hole 37 is formed such that the surface area A of the front carrier 33 is equal to or greater than Smin.

本実施形態では、一例としてＡ＝Ｓｍｉｎとなる。前段用担体３３に貫通孔３７が形成されていない点のみ異なり、他の構造（形状、大きさ）が前段用担体３３と同じである担体を仮想した場合、この仮想担体の表面積は、貫通孔３７を考慮した分Ｓｍｉｎよりも多くなる。   In this embodiment, A = Smin as an example. The only difference is that the through hole 37 is not formed in the front carrier 33, and when a carrier having the same structure (shape and size) as that of the front carrier 33 is assumed, the surface area of the virtual carrier is the through hole. It is more than Smin considering 37.

図５は、前段用触媒３２において、第１，２のシート部材５０，５１の開口率を変化させた場合の、前段用触媒３２の浄化性能を示すグラフである。ここで言う開口率とは、上記した、第１，２のシート部材５０，５１の周縁５４，５６の内側の範囲の面積に対する貫通孔３７の面積の割合である。 FIG. 5 is a graph showing the purification performance of the pre-stage catalyst 32 when the opening ratios of the first and second sheet members 50 and 51 are changed in the pre-stage catalyst 32. The opening ratio here, described above, and the ratio of the area of the through holes 37 to the area of the inner range of peripheral 54,5 6 of the first and second sheet members 50 and 51.

図５中横軸は、開口率を示し、図中右側に進むにつれて開口率が大きくなることを示す。図５中縦軸は、排ガスＧ中において浄化すべき物質の低減効果を示している。浄化すべき物質は、例えば、ＮＯｘや未燃燃料である。縦軸において目盛り１は、低減されていないことを示す。目盛りにおいて１より小さい値は（例えば、０．９や０．７など）、浄化すべき物質が低減していることを示しており、それゆえ、前段用触媒３２の浄化性能が向上していることを示している。   The horizontal axis in FIG. 5 indicates the aperture ratio, and indicates that the aperture ratio increases as it proceeds to the right side in the figure. The vertical axis in FIG. 5 indicates the effect of reducing substances to be purified in the exhaust gas G. The substance to be purified is, for example, NOx or unburned fuel. The scale 1 on the vertical axis indicates that it has not been reduced. A value smaller than 1 on the scale (for example, 0.9, 0.7, etc.) indicates that the substance to be purified is reduced, and therefore the purification performance of the pre-stage catalyst 32 is improved. It is shown that.

図５では、開口率が０（零）％である構造の排ガス中の浄化すべき物質の量（質量）を基準としている。縦軸の目盛りは、開口率が０％である構造の排ガス中の浄化すべき物質の量（質量）に対する割合を示している。   In FIG. 5, the amount (mass) of the substance to be purified in the exhaust gas having a structure with an aperture ratio of 0 (zero)% is used as a reference. The scale on the vertical axis indicates the ratio to the amount (mass) of the substance to be purified in the exhaust gas having a structure with an aperture ratio of 0%.

このため、開口率が０％の構造は、縦軸が１を示しており、つまり、浄化すべき物質が低減されていないことを示している。縦軸の０．９は、排ガス中の浄化すべき物質の量（質量）が、開口率０％（目盛りが１）の構造の排ガス中の浄化すべき物質の量（質量）に対して０．１（１割）減少したことを示す。   For this reason, in the structure with an aperture ratio of 0%, the vertical axis indicates 1, that is, the substance to be purified is not reduced. 0.9 on the vertical axis indicates that the amount (mass) of the substance to be purified in the exhaust gas is 0 with respect to the amount (mass) of the substance to be purified in the exhaust gas having an opening ratio of 0% (scale is 1). .1 (10%) decrease.

図５では、開口率がＰの位置近辺で前段用触媒３２の排ガス浄化性能が高いことが示されている。本実施形態の第１，２のシート部材５０，５１は、一例として開口率がＰである。開口率がＰである場合、前段用担体３３の表面積Ａは、Ｓｍｉｎである。   FIG. 5 shows that the exhaust gas purification performance of the pre-stage catalyst 32 is high near the position where the aperture ratio is P. The first and second sheet members 50 and 51 of this embodiment have an aperture ratio of P as an example. When the aperture ratio is P, the surface area A of the front carrier 33 is Smin.

このように構成される排ガス浄化装置２０では、前段用担体３３に貫通孔３７を形成することによって前段用担体３３の質量を小さくし、前段用触媒３２の質量ａ１を後段用触媒４２の質量ｂ１よりも小さくしている。それゆえ、前段用触媒３２の熱容量を後段用触媒４２よりも小さくできる。このため、前段用触媒３２を後段用触媒４２に対して早期に昇温度できる。言い換えると、前段用触媒活性物質３４の活性温度まで早期に昇温することができる。   In the exhaust gas purification apparatus 20 configured as described above, the mass of the front stage carrier 33 is reduced by forming the through-hole 37 in the front stage carrier 33, and the mass a1 of the front stage catalyst 32 is changed to the mass b1 of the rear stage catalyst 42. Smaller than that. Therefore, the heat capacity of the front stage catalyst 32 can be made smaller than that of the rear stage catalyst 42. Therefore, the temperature of the front stage catalyst 32 can be raised earlier than that of the rear stage catalyst 42. In other words, the temperature can be raised quickly to the activation temperature of the pre-stage catalytic active material 34.

前段用触媒活性物質３４を早期に活性化できるので、自動車の走行開始直後などでも前段触媒装置３０が早く昇温することで排ガスを浄化できる。そして、後段用触媒４２は、前段用触媒３２で処理されなかった排ガスを浄化する。このように、排ガス浄化装置２０が自動車の走行開始から早期に機能するので、排ガスの浄化性能が向上する。   Since the pre-stage catalytic active material 34 can be activated at an early stage, the exhaust gas can be purified by raising the temperature of the pre-stage catalyst device 30 quickly even immediately after the start of driving of the automobile. Then, the rear stage catalyst 42 purifies the exhaust gas that has not been treated by the front stage catalyst 32. Thus, since the exhaust gas purification device 20 functions early from the start of driving of the automobile, the exhaust gas purification performance is improved.

さらに、貫通孔３７を形成する構造であるので、前段用担体３３を軽量化するために壁部３６を薄くすることがなく、それゆえ、前段用担体３３の耐久性が低下を抑制することができる。また、貫通孔３７を形成する構造であるので、前段用担体３３の容量を小さくすることがなく、それゆえ、排ガスの浄化性能が低下することがない。また、通路３５の密度を向上することがないので、圧力損失が向上することがない。   Further, since the through-hole 37 is formed, the wall portion 36 is not thinned in order to reduce the weight of the front carrier 33, and therefore the durability of the front carrier 33 can be prevented from being lowered. it can. Further, since the through hole 37 is formed, the capacity of the front carrier 33 is not reduced, and therefore the exhaust gas purification performance is not lowered. Further, since the density of the passage 35 is not improved, the pressure loss is not improved.

また、前段用触媒活性物質３４の質量ａ２が、後段用触媒活性物質４４の質量ｂ２より大きいことによって、前段触媒装置３０の浄化性能をより一層高くすることができる。なお、本実施形態では、ａ２＞ｂ２としたが、これに限定されない。例えば、ａ２＝ｂ２であってもよい。   Further, since the mass a2 of the upstream catalytically active material 34 is larger than the mass b2 of the downstream catalytically active material 44, the purification performance of the upstream catalytic device 30 can be further enhanced. In the present embodiment, although a2> b2, it is not limited to this. For example, a2 = b2.

この発明は、上述した実施の形態そのままに限定されるものではなく、実施段階ではその要旨を逸脱しない範囲で構成要素を変形して具体化できる。また、上述した実施の形態に開示されている複数の構成要素の適宜な組み合わせにより種々の発明を形成できる。例えば、上述した実施の形態に示される全構成要素から幾つかの構成要素を削除しても良い。
以下に、本願出願の当初の特許請求の範囲に記載された発明を付記する。
［１］
第１の担体と、前記第１の担体に担持される第１の触媒活性物質とを具備する第１の触媒と、
前記第１の触媒に対して直列に配置される第２の触媒であって、第２の担体と、前記第２の担体に担持される第２の触媒活性物質とを具備する第２の触媒と
を具備し、
前記第１の担体は、当該第１の担体を形成する壁部に、当該壁部を貫通する貫通孔が形成され、
前記第１の触媒活性物質の担持量は、前記第２の触媒活性物質の担持量以上とされ、
前記貫通孔は、前記第１の担体の熱容量が前記第２の担体の熱容量よりも小さくなるように形成され、
前記貫通孔の前記壁部に占める割合は、前記第１の担体において単位面積当たりに担持できる前記第１の触媒活性物質の最大質量である担持限界質量に基づいて設定される
ことを特徴とする排ガス浄化装置。
［２］
前記第１の触媒の熱容量が前記第２の触媒の熱容量より小さくなるように、前記壁部に占める前記貫通孔の割合と前記第１の触媒活性物質の担持量を設定する
ことを特徴とする［１］に記載の排ガス浄化装置。 The present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above-described embodiments. For example, you may delete some components from all the components shown by embodiment mentioned above.
Hereinafter, the invention described in the scope of claims of the present application will be appended.
[1]
A first catalyst comprising a first carrier and a first catalytically active substance carried on the first carrier;
A second catalyst disposed in series with the first catalyst, the second catalyst comprising a second carrier and a second catalytically active substance carried on the second carrier. When
Comprising
In the first carrier, a through-hole penetrating the wall is formed in the wall forming the first carrier,
The loading amount of the first catalytically active substance is not less than the loading amount of the second catalytically active substance,
The through hole is formed such that the heat capacity of the first carrier is smaller than the heat capacity of the second carrier,
The ratio of the through hole to the wall is set based on a loading limit mass that is the maximum mass of the first catalytically active substance that can be supported per unit area in the first carrier.
An exhaust gas purification apparatus characterized by that.
[2]
The ratio of the through-holes occupying the wall and the loading amount of the first catalytically active substance are set so that the heat capacity of the first catalyst is smaller than the heat capacity of the second catalyst.
The exhaust gas purifying apparatus according to [1], wherein

２０…排ガス浄化装置、３２…前段用触媒（第１の触媒）、３３…前段用担体（第１の担体）、３４…前段用触媒活性物質（第１の触媒活性物質）、３７…貫通孔、４２…後段用触媒（第２の触媒）、４３…後段用担体（第２の担体）、４４…後段用触媒活性物質（第２の触媒活性物質）。   DESCRIPTION OF SYMBOLS 20 ... Exhaust gas purification apparatus, 32 ... Pre-stage catalyst (first catalyst), 33 ... Pre-stage carrier (first carrier), 34 ... Pre-stage catalytic active substance (first catalytic active substance), 37 ... Through-hole , 42 ... latter stage catalyst (second catalyst), 43 ... latter stage carrier (second carrier), 44 ... latter stage catalyst active substance (second catalyst active substance).

Claims (3)

第１の担体と、前記第１の担体に担持される第１の触媒活性物質とを具備する第１の触媒と、
前記第１の触媒に対して直列に配置される第２の触媒であって、第２の担体と、前記第２の担体に担持される第２の触媒活性物質とを具備する第２の触媒と
を具備し、
前記第１の担体は、当該第１の担体を形成する壁部に、当該壁部を貫通し４つの縁面により規定される貫通孔が形成され、
前記縁面を含む前記第１の担体の表面に担持される前記第１の触媒活性物質の担持量は、前記第２の触媒活性物質の担持量以上とされ、
前記貫通孔は、前記第１の担体の熱容量が前記第２の担体の熱容量よりも小さくなるように形成され、
前記第１の担体の質量と前記第１の触媒活性物質の質量の合計である前記第１の触媒の質量は、前記第２の担体の質量と前記第２の触媒活性物質の質量の合計である前記第２の触媒の質量よりも小さくされ、
前記貫通孔の前記壁部に占める割合は、前記第１の担体において単位面積当たりに担持できる前記第１の触媒活性物質の最大質量である担持限界質量に基づいて設定される
ことを特徴とする排ガス浄化装置。 A first catalyst comprising a first carrier and a first catalytically active substance carried on the first carrier;
A second catalyst disposed in series with the first catalyst, the second catalyst comprising a second carrier and a second catalytically active substance carried on the second carrier. And
The first carrier, the wall forming the first carrier, the through hole penetrating the wall Ru is defined by four edge surfaces are formed,
The amount of the first catalytically active substance supported on the surface of the first carrier including the edge surface is not less than the amount of the second catalytically active substance supported,
The through hole is formed such that the heat capacity of the first carrier is smaller than the heat capacity of the second carrier,
The first is the mass to the total mass of the first catalytically active substance carrier wherein the first mass of the catalyst, of the second carrier of the mass and the second mass of the catalytically active substance Less than the total mass of the second catalyst,
The ratio of the through hole to the wall is set based on a loading limit mass that is a maximum mass of the first catalytically active substance that can be supported per unit area in the first carrier. Exhaust gas purification device. 前記第１の触媒の熱容量が前記第２の触媒の熱容量より小さくなるように、前記壁部に占める前記貫通孔の割合と前記第１の触媒活性物質の担持量を設定する
ことを特徴とする請求項１に記載の排ガス浄化装置。 The ratio of the through-holes occupying the wall and the loading amount of the first catalytic active substance are set so that the heat capacity of the first catalyst is smaller than the heat capacity of the second catalyst. The exhaust gas purification apparatus according to claim 1. 前記縁面を含む前記第１の担体の表面積は、前記第１の触媒活性物質の担持量を前記担持限界質量で除した値と等しい
ことを特徴とする請求項１又は２に記載の排ガス浄化装置。 3. The exhaust gas purification according to claim 1, wherein a surface area of the first carrier including the edge surface is equal to a value obtained by dividing a loading amount of the first catalytically active substance by the loading limit mass. apparatus.
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