WO2008126877A1

WO2008126877A1 - Exhaust purification device for internal combustion engine

Info

Publication number: WO2008126877A1
Application number: PCT/JP2008/057041
Authority: WO
Inventors: Shunsuke Toshioka; Tomihisa Oda; Kazuhiro Itoh
Original assignee: Toyota Jidosha Kabushiki Kaisha
Priority date: 2007-04-05
Filing date: 2008-04-03
Publication date: 2008-10-23
Also published as: JP2008255890A

Abstract

In an internal combustion engine, a selective NOx reduction main catalyst (15)is placed in an engine exhaust path and a selective NOx reduction auxiliary catalyst (17) having smaller volume, heat capacity, and pressure loss than the selective NOx reduction main catalyst (15) is placed on the upstream of the selective NOx reduction main catalyst (15). Urea is supplied from a urea water supply valve (18) to the selective NOx reduction auxiliary catalyst (17), and selective reduction of NOx by the selective NOx reduction auxiliary catalyst (17) is started as early as possible after the engine is started.

Description

Description Exhaust gas purification device for internal combustion engine Technical field

The present invention relates to an exhaust emission control device for an internal combustion engine. Background art

Selectively reduced may N_〇 _x selective reduction catalyst the NO _x contained in the exhaust gas by ammonia in the engine exhaust passage disposed, NO contained in the upstream of the N_〇 _x election selective reduction based catalyst in the exhaust gas N_〇 capable of occluding _x _x storage catalyst or an internal combustion engine in which an oxidation catalyst is arranged is known (for example, Japanese 2 0 0 6 - see 5 1 2 5 2 9 JP).

Meanwhile _the NO _x selective reduction catalyst is not performed Atsushi Nobori due to the catalytic reaction differs from _the NO _x storage catalyst and the oxidation catalyst carrying a noble metal such as platinum, thus the engine after starting N_〇 _x selective reduction catalyst N_〇 _{x The} temperature is raised by the exhaust gas temperature flowing into the selective reduction catalyst. In this case, if the oxidation reaction starts in the NO _x storage catalyst or oxidation catalyst, the exhaust gas temperature will rise, but the N _{0 x} selective reduction catalyst is located downstream, so the N _{0 x} selective reduction catalyst will rise in temperature. takes the amount of time until the selective reduction of N_〇 _x is started, it is impossible you to ensure good cleaning action of the thus was after engine start by N_〇 _x. Disclosure of the invention

An object of the present invention is to provide an exhaust purification system of an internal combustion engine capable of ensuring a good cleaning action of N_〇 _x after engine start.

According to the present invention, arranged N_〇 _x selective reduction catalyst in the engine exhaust passage , In the exhaust purification system of an internal combustion engine so as to selectively reduce New Omicron _chi contained in the exhaust gas after the removal Monia generated from the urea to supply urea N_〇 _x selective reduction catalyst, Nyu_〇 _chi a selective reduction catalyst New 〇 _chi selective reduction main catalyst is disposed upstream of the New Omicron _chi selective reduction main catalyst and volume than Nyu_〇 _chi selective reduction main catalyst, and a small Nyu_〇 _chi selective reduction cocatalyst heat capacity and pressure loss is constituted by, Nyu_〇 _chi selective reduction cocatalyst exhaust purification system of an internal combustion engine which is adapted to start the selective reduction action of Nyu_〇 _chi early after engine start by supplying New Omicron _chi selective reduction promoter catalyze urea to Is provided.

Nyu_〇 _χ selective reduction supplemental catalyst as described above, Nyu_〇 _χ selective reduction main is located upstream of the catalyst and Nyu_〇 _χ selective reduction main catalyst activated after starting early because volume and heat capacity is smaller than the selective reduction action of Nyu_〇 _χ is is started. As a result, the purification rate of Nyu_〇 _χ is made to improve. Brief Description of Drawings

Figure 1 is an overall view of a compression ignition type internal combustion engine, FIG. 2 is NO _x enlarged perspective view of the selective reduction main catalyst and N_〇 _x selective reduction supplemental catalyst shown in FIG. 1, another 3 compression ignition internal combustion engine FIG. BEST MODE FOR CARRYING OUT THE INVENTION

Figure 1 shows an overall view of a compression ignition type internal combustion engine.

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 via the intake duct 6, and the inlet of the compressor 7 a is connected to the air cleaner 9 via the intake air amount detector 8 Is done. In the intake duct 6 A throttle valve 10 driven by the step motor is arranged, and a cooling device 11 for cooling the 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 11 and the intake air is cooled by the engine cooling water.

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 inlet of the oxidation catalyst 12. Downstream of this oxidation catalyst 1 2, a particulate filter 1 3 is arranged adjacent to the oxidation catalyst 1 2 to collect particulate matter contained in the exhaust gas, and the outlet of this particulate filter 1 3. is connected to the inlet mouth of N_〇 _x selective reduction main catalyst 1 5 through the exhaust pipe 1 4. Medium 1 6 tactile oxidation is coupled to the outlet of the N_〇 _x selective reduction main catalyst 1 5. Volume than N_〇 _x selective reduction main catalyst 1 5 to the exhaust pipe 1 in 4 of the NO _x selective reduction main catalyst 1 5 on the upstream according to the present invention, a small N_〇 _x selective reduction cocatalyst 1 7 heat capacity and pressure loss Be placed. '' As shown in Fig. 1, this N〇 _x selective reduction auxiliary catalyst 1 7 is located upstream of the exhaust pipe 1 4 with a urea water supply valve 1 8, which is connected to the supply pipe 1 9, It is connected to a urea water tank 2 1 through a supply pump 20. The urea water stored in the urea water tank 2 1 is injected into the exhaust gas flowing through the exhaust pipe 14 from the urea water supply valve 1 8 by the supply pump 2 0, and ammonia generated from the urea ((NH ₂ ) ₂ C ○ + H ₂ 0 → 2 NH ₃ + C 0 ₂ ) is reduced in NO _J ^ N ○ _x selective reduction auxiliary catalyst 17 and NO _x selective reduction main catalyst 15 contained in the exhaust gas.

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 2 2, and an electronically controlled EGR control valve 2 3 is disposed in the EGR passage 2 2. . EGR A cooling device 24 for cooling the EGR gas flowing in the EGR passage 22 is disposed around the passage 22. In the embodiment shown in FIG. 1, the engine cooling water is guided into the cooling device 24, and the EGR gas is cooled by the engine cooling water. On the other hand, each fuel injection valve 3 is connected to a common rail 26 via a fuel supply pipe 25, and this common rail 26 is connected to a fuel tank 28 via an electronically controlled variable discharge fuel pump 27. Is done. The fuel stored in the fuel tank 2 8 is supplied to the common rail 26 by the fuel pump 2 7, and the fuel supplied to the common rail 26 is supplied to the fuel injection valve via each fuel supply pipe 25. Supplied to 3. The oxidation catalyst 1 2 carries a example a noble metal catalyst such as platinum, the oxidation catalyst 1 2 oxidizes the HC contained in the exhaust gas and the working to convert NO contained in the exhaust gas to N 0 ₂ It works. On the other hand, as the particulate filter 13, a particulate filter that does not support a catalyst can be used, and a particulate filter that supports a noble metal catalyst such as platinum can also be used.

Further, either N_〇 _x selective reduction cocatalyst 1 7 and N_〇 _x selective reduction main catalyst 1 5 is composed of F e Zeorai Bok ammonia adsorption type having a high N_〇 _x purification rate at low temperatures, or adsorption of ammonia Non-functional titanium and vanadium catalyst. The oxidation catalyst 16 carries, for example, a noble metal catalyst made of platinum, and this oxidation catalyst 16 acts to oxidize ammonia leaked from the N 0 _x selective reduction main catalyst 15.

Figure 2 shows an enlarged perspective view of N_〇 _x selective reduction cocatalyst 1 7 and NO _x selection selective reduction source main catalyst 1 5 shown in FIG. As can be seen from FIG. 2, the NO _x selective reduction main catalyst 15 has a plurality of cells 3 1 extending in the axial direction separated by a plurality of thin partition walls 30 intersecting each other. _{The x} selective reduction auxiliary catalyst 1 7 also has a plurality of cells 33 extending in the axial direction separated by a plurality of thin partition walls 3 2 intersecting each other. On the other hand, the axial length is short compared to N_〇 _x selective reduction cocatalyst 1 7 The N_〇 _x selective reduction main catalyst 1 5 as shown in FIG. 2, moreover N_〇 _x selective reduction cocatalyst 1 7 has a smaller diameter than the N_〇 _x selective reduction main catalyst 1 5. Therefore, the NO _x selective reduction auxiliary catalyst 17 has a smaller volume than the NO _x selective reduction main catalyst 15 and therefore has a smaller heat capacity.

Furthermore, _the NO _x selective reduction cocatalyst 1 7 by as shown in FIG. 2 in order to reduce the heat capacity of the NO _x selective reduction cocatalyst 1 7 co Reducing the pressure loss N_〇 _x selective reduction cocatalyst 1 7 cell 3 The flow area of 3 is larger than the flow area of the cell 3 1 of N0 _x selective reduction main catalyst 15 and the thickness of the thin partition 3 2 of the N0 _x selective reduction auxiliary catalyst 1 7 is N0. _{x The} selective reduction main catalyst 15 is formed thinner than the thin partition wall 30 of the 15.

Further, N_〇 _x selective reduction aid for N_〇 thin partition walls 3 1 _x selective reduction main catalyst 1 5 is formed ceramic Kkuka et but that further small fence the heat capacity of the NO _x selective reduction cocatalyst 1 7 The thin wall 3 2 of the catalyst 17 can be formed from a metal plate.

Meanwhile N_〇 _x selective reduction main catalyst 1 5 because not carrying a noble metal such as platinum not performed heating the catalytic reaction and hence the engine starting after _the NO _x selective reduction main catalyst 1 5 _the NO _x selective reduction main catalyst 1 The temperature rises due to the exhaust gas temperature flowing into 5. In this case, N_〇 since the exhaust gas temperature if it had contact to the oxidation catalyst 1 2 oxidation reaction begins to rise but the original main catalyst 1 5 instead N_〇 _x selected is arranged downstream _x selective reduction main catalyst 1 5 takes time until the selective reduction of the temperature rise to N_〇 _x is started, will not come in to ensure a good cleaning action of N_〇 _x after engine start and thus. However upstream of N_〇 _x selective reduction main catalyst 1 5 In the present invention, New Omicron _chi selective reduction main catalyst 1 5 smaller volume and heat capacity as compared to, vo _chi selective reduction that is activated after starting early Te従Tsu Since the auxiliary catalyst 17 is arranged, the selective reduction action of Νχ _χ starts early after the engine starts. As a result, it is possible to improve the purification rate vo _chi.

FIG. 3 shows another embodiment of the compression ignition type internal combustion engine. In this embodiment Patikyure Tofiru evening 1 3 arranged downstream of the oxidation catalyst 1 6, therefore the inlet of the outlet of the oxidation catalyst 1 2 In this embodiment the exhaust pipe 1 4 through the New Omicron _chi selective reduction main catalyst 1 5 Connected to Volume, small vo _chi selective reduction cocatalyst 1 7 heat capacity and pressure loss are arranged than Nyu_〇 _chi selective reduction main catalyst 1 5 to vo _chi selective reduction main catalyst 1 5 upstream of the exhaust pipe 1 in 4 in this embodiment .

Claims

. 1. _the NO _x selective reduction catalyst arranged in the engine exhaust passage, included are _the NO _x selective manner into exhaust gas by the ammonia generated from the urea to supply urea to the N_〇 _x selective reduction catalyst In the exhaust gas purification apparatus for an internal combustion engine that is to be reduced, the N0 _x selective reduction catalyst is the N0 _x selective reduction port.

A main catalyst, the NO _x is disposed upstream of the selective reduction main catalyst and the! ^ _{〇! (Than} selection selective reduction original main catalyst volume, is constituted by a small N_〇 _x selective reduction based cocatalyst heat capacity and pressure loss, the in N_〇 _x election. selective reduction based cocatalyst by supplying urea to said N_〇 _x selective reduction cocatalyst by the燃囲institution among which is adapted to start the selective reduction action of N_〇 _x early after engine startup exhaust gas purification apparatus.

2. have the _the NO _x selective reduction main catalyst and _the NO _x selective reduction supplemental catalyst plurality of cells extending in an axial direction which are separated by a plurality of thin partition walls which intersect the physician each other, the N_〇 _x selective reduction supplemental the flow passage area of the cell of the catalyst exhaust gas control apparatus according to claim 1, which is larger than the flow passage area of the cell of the N_〇 _x selective reduction main catalyst.

3. the N_〇 _x selective reduction main catalyst and _the NO _x selective reduction supplemental catalyst has a plurality of cells extending in an axial direction which are separated by a plurality of thin partition walls which intersect the physician each other, the N_〇 _x selective reduction 2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein a thickness of the thin partition wall of the auxiliary catalyst is formed thinner than a thickness of the thin partition wall of the NO _x selective reduction main catalyst.

4. The NO _x selective reduction auxiliary catalyst and the NO _x selective reduction auxiliary catalyst have a plurality of cells extending in the axial direction separated by a plurality of thin partition walls intersecting each other, and the NO _x selective reduction auxiliary catalyst 2. The exhaust gas purification apparatus for an internal combustion engine according to claim 1, wherein the thin partition wall is formed of a metal plate, and the thin partition wall of the NO _x selective reduction main catalyst is formed of ceramic.