TW200936870A - Exhaust gas purifying system for an internal-combustion - Google Patents

Abstract

To provide an exhaust gas purifying system for an internal-combustion engine, in which both reduction of NOx and oxidization of CO and THC contained in exhaust gas can be effectively made by use of three catalyzers. A first catalyzer 30 is disposed in a part more upstream than a second catalyzer 40. Thereby, secondary air flowing upstream from a secondary air introducing conduit 60 in an exhaust conduit 20 can be blocked at the second catalyzer 40. As a result, NOx can be sufficiently reduced at the first catalyzer 30 in addition to reduction of NOx at the second catalyzer 40. Further, a third catalyzer 50 is disposed in a part more downstream than the second catalyzer 40. CO and THC are oxidized at the third catalyzer 50.

Description

200936870 IX. INSTRUCTIONS: TECHNICAL FIELD OF THE INVENTION The present invention relates to an exhaust gas purification system for an internal combustion engine such as that installed in a locomotive. [Prior Art] Exhaust from the engine (internal combustion engine installed in a locomotive, etc.) is discharged into the air. However, it is better to purify the exhaust gas before exhausting the exhaust gas.

good. Therefore, it has been conventionally provided that the catalyst is disposed in the middle of the exhaust duct so that the exhaust gas from the engine is discharged through the catalyst, thereby promoting purification by the catalyst. The system described in the surface is an exhaust gas purification system of v W ^ ^ m ^ ^ (for example, see the patent document). In other words, in the conventional exhaust gas purification system, the first, second, and tincture The parts of the exhaust duct are successively arranged from the upstream side of the exhaust duct to the downstream. Meanwhile, the __# 3 丨 弟 一 - 人 人 人 引入 引入 引入 — — 部分 部分 部分 部分 部分 部分 部分 部分 部分 部分 部分_The position between the catalysts. From:: The secondary air introduced into the middle of the conduit is partially branched by the second secondary air. "The position between the second and the catalyst in the middle of the conduit. Le is also the first - two The secondary air deflector output to the switch H η conduit is purified by the self-control agent (promoting oxidation) (3) and the second and the second venting 钛 钛 第 第 空气 空气 空气 空气 空气 空气 空气 空气 空气 空气 空气 空气 空气 空气 空气 空气 空气When the signal of N〇x is connected to the first-n main switch valve is connected, the first and second catalysts are reduced, and the THC is oxidized at the third 129078.doc 200936870. [Patent Document 1] JP-A -Hei 5-321653 In the conventional technology, when the second secondary air is introduced into the duct and exhaust When the conduit is connected by a signal output from the controller to the switching valve, the NOx contained in the exhaust gas is reduced at the first and second catalysts, and c〇 and THC contained in the exhaust gas are at the third catalyst. Oxidized.

However, the first and second catalysts according to the conventional art are not formed in consideration of a suitable material for reducing ruthenium. The third catalyst is also not formed in consideration of suitable materials for oxidizing CO and THC. Therefore, there is a problem that the three catalysts cannot necessarily sufficiently purify NOx, CO or THC. Further, when the first secondary air introduction duct and the exhaust duct are connected by a signal output from the controller to the switching valve, the three catalysts (first, second, and third catalysts) are used for oxidation to be included in the row Cc^〇thc in the gas. Therefore, there is a problem that the flaw contained in the exhaust gas cannot be sufficiently performed. The above considerations take into consideration the above problems, and at the same time, the internal combustion engine is used for the purpose of "reducing the inclusion of three catalysts simultaneously with the reduction of N〇x and the oxidation of CO and THC." According to the conventional technology, according to the exhaust gas purification filature, 4 into. The single-use platoon: 3 . - exhaust duct 'for discharging from the internal combustion cited f-catalyst, which is provided in the exhaust (four) - reducing N0x contained in at least the exhaust gas; a second catalyst, which provides 129078.doc 200936870 for the middle portion of the exhaust conduit downstream of the first catalyst 'to reduce at least the flow from the first catalyst N 〇 x of the exhaust component in the gas; - the third catalyst 'provided that the intermediate portion of the exhaust conduit is downstream of the first catalyst, and the third catalyst is formed of a material different from the first and second catalysts' a CO and a THC for oxidizing at least a venting component contained in the exhaust gas flowing from the second catalyst; and a secondary air enthalpy conduit for supplying the second and third catalysts in the exhaust conduit Position between, used to put two Air is introduced into the exhaust duct. In the invention having the above structure, secondary air is introduced into a position between the second catalyst and the third catalyst in the exhaust duct, and the second catalyst is used for reduction in the exhaust gas The third catalyst is also used to reduce helium in the exhaust gas component. Therefore, it is necessary to reduce the internal combustion engine by using two catalysts (first and second catalysts). It is contained in the exhaust gas, and C 〇 and thc are oxidized by the secondary air at the third catalyst formed by the materials different from the first and second catalysts. In one aspect of the present invention The exhaust duct may include another secondary air introduction guide provided at a position between the first and second catalysts for introducing primary air into the exhaust duct. In the invention having the above structure, More efficiently oxidizing c〇 and THC by introducing a secondary air introduced into the exhaust duct at the second and third catalysts. In one aspect of the invention, the other two Secondary air introduction catheter There is a flow control valve 'which is used to control the flow of the two-person two gas introduced into the exhaust duct from the introduction duct. In the invention having the above structure, from the other two 129078.doc 200936870 air bow i into the duct The flow of the secondary air a introduced into the exhaust duct is controlled by the control valve so that the oxidation amount of CO and THC by the secondary air at the second and third catalysts can be appropriately adjusted.

An exhaust gas purification system for an internal combustion engine according to the present invention comprises: an exhaust duct for discharging exhaust gas from an internal combustion engine; and a first catalyst provided in a middle portion of the exhaust duct for purifying exhaust gas; a second catalyst provided in the middle of the exhaust conduit downstream of the first catalyst for purifying the exhaust gas flowing from the first catalyst; and a third catalyst provided in the middle of the exhaust conduit is second The catalyst is further downstream for purifying the exhaust gas flowing from the first catalyst; a first secondary air introduction conduit is provided at a position between the first and second catalysts in the exhaust conduit for the secondary air Introduced into the exhaust conduit; and a second secondary air introduction conduit provided at a location between the second and third catalysts within the exhaust conduit for introducing secondary air into the exhaust conduit. The medium primary air is passed through the first and second catalysts in the first secondary air, and the NOx contained in the exhaust gas is introduced into the exhaust gas guide at the gas introduction conduit of the present invention having the above structure. Therefore, an exhaust material such as from the inside must be reduced to the first catalyst, and an exhaust material such as CO and THC contained in the exhaust gas must be passed through (iv) two catalysts (second and third catalysts). Reduction with secondary air. At the same time, secondary air is introduced into the position between the second and third catalysts in the exhaust conduit through the second secondary air introduction conduit. Therefore, the exhaust materials of wC0*THC can be more surely oxidized by the secondary air at the third catalyst. In one aspect of the invention, the first secondary space

The inlet tube has a state-of-the-art 129078.doc 200936870 volume control valve that is used to control the flow of the secondary air. In the invention having the above structure introduced into the exhaust duct, the second air from the first two-air introduction duct is inserted into the #^ θ + ^ ^ 梆虱 pilot. Traffic is subject to

The flow control valve is controlled, and the π A is further 5 J so that the oxidation amount of CO and THC by the secondary air at the second and third agents can be appropriately adjusted.

In the exhaust gas purifying system for an internal combustion engine according to the present invention, the gas is introduced into the position between the second and third catalysts in the exhaust duct. Therefore, by using two catalysts (the first and the The second catalyst) must reduce the exhaust material such as N 〇 x contained in the exhaust gas from the internal combustion stylus and by being different from the first _ JC ^ - / ώ - / L = & The secondary air at the third catalyst formed by the material of the first catalyst must oxidize CO and THC. Therefore, the exhaust material such as THC contained in the exhaust gas can be sufficiently purified by using three catalysts. [Embodiment] An exhaust gas purifying system for an internal combustion engine according to the embodiment of the present invention will be described below with reference to Figs. For example, an exhaust gas purification system for an internal combustion engine according to an embodiment of the present invention is installed in a locomotive, and includes an engine 10, an exhaust duct 2G, a first catalyst, and a catalyst. The second catalyst 40, the third catalyst 5, and the secondary air introduction conduit 60, for example, the engine 10 is mounted in the locomotive. In the engine unit 1, air from an air cleaner 11 and fuel from a fuel supply unit i 4 are mixed and supplied (injected) to a cylinder (not shown) in the engine 10. The fuel is burned in the engine, and therefore the piston (not shown) in the engine 10 is driven (to move 129078.doc -10- 200936870). In addition, an oxygen sensor (not shown) is attached to a portion of the exhaust conduit 20 that is downstream of the opening of the secondary air introduction conduit 6〇 and upstream of the third catalyst 50, or close to the muffler 12 (described below) on a portion of the stream below. An output signal from one of the oxygen sensors is input to the controller (not shown). In the fuel supply device 14, the amount of fuel supplied to the engine 10 is controlled via a controller based on an output signal from the oxygen sensor so that the exhaust gas discharged from the exhaust conduit 20 conforms to stoichiometric air - Fuel ratio. One of the upstream ends of the exhaust duct 20 is connected to the engine 1A. The exhaust duct 2 exhausts the exhaust of the combustion mixture (fuel and air) in the engine 10. The exhaust gas contains exhaust materials such as helium, CO and THC. The muffler 12 attached to the downstream end of the exhaust duct 2 is for reducing the exhaust sound of the exhaust gas discharged outward. The first catalyst 30 is a reduction catalyst which contains a noble metal portion having money as its main component. The first catalyst 30 is disposed in the upstream portion of the exhaust conduit 20. For example, the first catalyst 3 is disposed in an upstream portion of an exhaust pipe. Further, the first catalyst 3 〇 mainly promotes the reduction of NOx contained in the exhaust gas flowing in the exhaust duct 20. The second catalyst 40 is a reduction catalyst comprising a noble metal portion having ruthenium as its main component similar to the first catalyst 30. The second catalyst 40 is disposed in the exhaust duct 2〇 at a position further downstream than the first catalyst 30 located in the muffler 12. In addition, the second catalyst 4 〇 primarily promotes the reduction of NOx contained in the exhaust gas flowing in the exhaust conduit 20. The third catalyst 50 is an oxidation catalyst which comprises a noble metal portion having palladium as its main component, and the third catalyst 5 is different from the first catalyst 129078.doc • 11 - 200936870 chemical agent 30 and second catalyst 40 Material. The third catalyst 5 is disposed in the exhaust conduit 20 at a position further downstream than the second catalyst 4A located in the muffler 12. The third catalyst 50 primarily promotes oxidation of CO and THE contained in the exhaust gas flowing through the exhaust conduit 2A. The upstream end of the secondary air introduction guide 60 is connected to the air cleaner 丨丨. The downstream end of the secondary air introduction duct 60 is connected to a position between the second catalyst 40 and the third catalyst 5A in the muffler 12 of the exhaust duct 2. The secondary air introduction duct 60 continuously supplies the air from the outer boundary of the air cleaner to the position between the second catalyst 4A and the third catalyst 50 in the exhaust duct 20 via the reed valve 13. Thereby, the oxidation of C0 and THC at the third catalyst 5〇 is promoted. In this embodiment, since the secondary air introduction duct 6 is connected to the position between the second catalyst 40 and the third catalyst 50 of the exhaust duct 20, it is supplied from the secondary air introduction duct 60 into the exhaust duct 20. Air is supplied to the third catalyst 50. However, a portion of the air flows countercurrently to the exhaust duct 2〇 and is also supplied to the second catalyst 40. Therefore, although the reduction reaction of NOx occurs at the second catalyst 40, the oxidation reaction of CO and THC also occurs. Therefore, NOx cannot be sufficiently reduced by only the second catalyst 40. Therefore, in this embodiment, the first catalyst 30 is disposed at a portion further upstream than the second catalyst 40. Therefore, the air flowing from the secondary air introduction duct 6 〇 upstream (countercurrently) in the exhaust duct 20 is blocked at the second catalyst 4〇, so that the crucible can be reduced at the second catalyst 4〇, and ν Niobium may also be sufficiently reduced at the first catalyst 30. Further, I29078.doc -12·200936870 CO and THC contained in the exhaust gas can be sufficiently oxidized at the third catalyst 50 by the secondary air from the secondary air introduction conduit 6〇. Therefore, in this embodiment, NOx and oxidized CO and THC can be simultaneously and efficiently reduced by using three kinds of catalysts 3, 40, and 50. Thereby, the performance, reliability, and the like of the exhaust purification system 1 can be improved. In this embodiment, since the reduction catalyst is divided into two catalysts 3〇 and 40', the first catalyst 3〇 is rapidly activated when the engine 1 is started and still cold. Thus, the other two catalysts 4〇 and 5〇 are also rapidly activated by the activation of the catalyst 3〇. In other words, the first catalyst 30 can be used as a "preheating" in addition to the reduction catalyst for hydrazine to rapidly activate the other two catalysts 40 and 50. Thus, immediately after starting the engine, Ν〇χ The reduction and (: oxidation of yttrium and THC. Therefore, the purification of the three components of the exhaust gas can be improved. Further, since the reduction catalyst is divided into two catalysts 30 and 40, each of the catalysts 30 and 40 is Therefore, such a structure can easily achieve a configuration requirement such as a tilt angle and a vehicle appearance in the case where the first catalyst 30 is disposed in the exhaust pipe. Preferably, the catalyst 3() should be non- A necessary volume is obtained by expanding it in the radial direction and expanding the length direction. Such a structure can achieve the above-mentioned configuration requirements, daily meeting, and can also effectively enhance the flow into the second and third catalysts. 4 0 and 5 〇 排 排 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 、 In the example The reference numerals of the cage members are the same as those of the first embodiment, 129078.doc 200936870 and will not be described. The exhaust gas purification system for internal combustion engines according to this embodiment includes An engine (not showing the exhaust duct 20; the first catalyst 3〇; the second catalyst 70; the third catalyst 50 and a secondary air introduction duct 8〇. The second catalyst 70 mainly promotes the flow in the exhaust duct 20 The reduction of NOx contained in the exhaust gas is similar to the second catalyst 40 described in the first embodiment. However, the second catalyst is different from the second catalyst in the first embodiment in the following aspects: catalyst 70 installation A portion of the exhaust duct 2 that is further upstream than the muffler 12. The secondary air introduction duct 8 is connected to a position between the second catalyst 7A of the exhaust duct 20 and the third catalyst 5? In this embodiment of the above structure, in addition to C 〇 and THC, ΝΟχ can be sufficiently purified by the use of three catalysts 30, 70 and 50, and thus can achieve almost the same operation and effect as the first embodiment. 'Figure 4 shows a third embodiment according to the present invention. In this embodiment, the reference numerals given to the structural elements are the same as those of the first embodiment, and are not described. The exhaust gas purification for the internal combustion engine according to this embodiment System 9A includes: an engine (not shown); an exhaust conduit 20; a first catalyst 30; a second catalyst 100; a third catalyst 50 and a secondary air introduction conduit 110. The second catalyst 1 00 is primarily promoted The reduction of the ruthenium contained in the exhaust gas flowing in the exhaust gas conduit 20 is similar to the second catalyst 40 described in the first embodiment. However, the second catalyst ι00 is different from the first embodiment in the following respects. The second catalyst: the catalyst 1〇〇 is installed in the portion of the exhaust duct 20 that is further upstream than the muffler 12. 129078.doc 200936870 The secondary air introduction duct 110 is connected to a position between the second catalyst 100 of the exhaust duct 20 and the third catalyst 50, which is similar to the secondary air introduction duct 60 according to the first embodiment. However, the secondary air introduction duct 110 is different from the secondary air introduction duct in the first embodiment in that it is connected to a portion of the exhaust duct 20 that is further upstream than the silencer 12. Therefore, the cold secondary air is directly supplied to the exhaust duct 20 without being heated at the muffler 12, and the oxygen concentration of the secondary air can be made higher. Thereby, the combustion efficiency (oxidation efficiency) of CO and THC at the third catalyst 5〇 can be improved. By this embodiment having the above structure, in addition to CO and THC, NOx can be sufficiently purified by the use of three catalysts 30, 1 and 50, and thus almost the work of the first embodiment can be realized. And effects. Next, Fig. 5 shows a fourth embodiment according to the present invention. The reference numerals given to the structural elements in this embodiment are the same as those of the first embodiment and will not be described. The exhaust gas purification system 内2〇 for an internal combustion engine according to this embodiment includes a cheek like the first embodiment: an engine (not shown); an exhaust duct 2〇; a first catalyst 30; a second catalyst 40; The three catalysts 50 and the secondary air introduction conduit 60 (which is a first secondary air introduction conduit). However, the exhaust gas purifying system 120 according to this embodiment is different from the exhaust gas purifying system in the first embodiment in that the downstream end of the other secondary air introducing duct 130 is connected to the muffler 12 of the exhaust duct 2 The position between the second catalyst 40 and the third catalyst 5〇. Reed valve 1 40 ' is a flow control valve that is electronically controlled to open or close corresponding to an output signal from a controller (not shown), the reed valve 14 〇 129078.doc 15 200936870 provided in the second The secondary air is introduced into the middle of the conduit i 3 以 so that the exhaust flowing in the drain conduit 20 conforms to stoichiometric air-fueling. Therefore, in the case where it is required to increase the reduction of the helium more than the oxidation of the CO and THC, the reed valve 140 is closed and closed by the output signal from the controller and thereby blocks the flow from the secondary air introduction duct 130 to The flow of secondary air of the exhaust duct 20. Therefore, the second catalyst 40 can be mainly used for the reduction of hydrazine.簧 In the case where it is required to increase the oxidation of CO and THC more than the reduction of ΝΟχ, the reed valve 14 打开 is opened by the output signal from the controller, and thus the secondary air from the secondary air introduction duct 13 Flow into the exhaust duct 20. Therefore, the second catalyst 4〇 can be mainly used for the deuteration of c〇 and THC. Further, in this case, secondary air is introduced into the exhaust duct 2〇 by the two secondary air introduction ducts and 13〇, and thus the secondary air introduced into the exhaust duct 20 can be increased. flow. Therefore, CO and THC can be oxidized more efficiently.借 By the embodiment having the above structure, c 〇, ΤΗ ^ ^ can be sufficiently purified by using the three catalysts 30, 40, and 50, and thus the operation and effect almost equal to that of the first embodiment can be achieved. Next, Fig. 6 shows a fifth embodiment according to the present invention. In this embodiment, the reference numerals given to the structural elements are the same as those of the first embodiment, and are not described. The exhaust gas purification system 15A for an internal combustion engine includes an engine similar to the first embodiment (not shown); an exhaust duct 2; a first catalyst 30, a second catalyst 4; a third catalyst 5 and 2 The secondary air inlet 129078.doc 200936870 is an inlet duct 60 which is a first secondary air introduction duct. However, the exhaust gas purifying system 丨5〇 according to this embodiment is different from the exhaust gas in the first embodiment in the following points a purification system: a downstream end of the secondary air introduction guide g 160 (which is a second secondary air introduction conduit) is connected between the second catalyst 4A of the exhaust conduit 20 and the third catalyst 5? And more than the silencer 12 In addition, the reed valve 17 is a flow control valve that opens or closes corresponding to an output signal from a controller (not shown), the reed valve being provided in a second secondary air similar to the fourth embodiment. The middle portion of the conduit 160 is introduced. By the embodiment having the above structure, the operation and effect almost identical to that of the first embodiment can be achieved. Next, Fig. 7 shows a sixth embodiment according to the present invention. The reference numerals given to the structural elements are the same as those of the first embodiment, and are not described. The exhaust gas purification system 丨8〇 for an internal combustion engine according to this embodiment includes: an engine (not shown); an exhaust duct 20; a first catalyst 3〇; a second catalyst 40; a third catalyst 5〇; a secondary air introduction duct 19〇 which is a first secondary air introduction duct; and another secondary air introduction duct 2〇〇 The second secondary air introduction duct secondary air introduction duct 190 is connected to a position between the second catalyst 40 and the third catalyst 50 of the exhaust duct 20 and is further upstream than the muffler 12. The reed valve 210 is connected The secondary air is introduced into the middle of the conduit 190. The secondary air introduction conduit 200 is connected to the position between the first catalyst 30 and the second catalyst 40 of the exhaust conduit 20. The reed valve 220 corresponds to an I29078.doc 17 200936870 A flow control valve that opens or closes an output signal of a controller (not shown) that is provided in the middle portion of the secondary air introduction duct 2. By the embodiment having the above structure, almost equal to The operation and effect of the fourth embodiment Next, Fig. 8 shows a seventh embodiment according to the present invention. In this embodiment, the reference numerals given to the structural elements are the same as those of the first embodiment, and are not described. An exhaust gas purification system 23 for an internal combustion engine according to this embodiment includes an engine (not shown); an exhaust duct 2; a first catalyst 3; a second catalyst 240; a third catalyst 50; a secondary air introduction duct 6〇, which is a first secondary air introduction duct; and another secondary air introduction duct 250 (which is a second secondary air introduction duct, the second catalyst 240 is installed in the exhaust duct 20) A position further upstream than the muffler 12. The secondary air introduction duct 250 is connected to a position between the first catalyst 30 and the second catalyst 240 of the exhaust duct 2. The reed valve 26 is a corresponding to a controller a flow control valve 'opened or closed (not shown) output signal, which is provided in the middle portion of the secondary air introduction duct 25A. By the embodiment having the above structure, almost equal to the fourth implementation can be realized The operation and effect of the example. The description made in the first embodiment includes an example of the diameter of the exhaust duct 2〇 which is the same as the diameter of the first catalyst 3〇 and the second catalyst 40. However, the present invention does not In the above case, an exhaust duct 2a can be formed to have a diameter smaller than the diameter of the second catalyst 4a and 129078.doc -18 - 200936870 of the third catalyst 50A accommodated in the muffler 12, This is an example of variation shown in Figure 9. In the fourth embodiment, the description includes an example in which an on-off valve is used to allow the flow of secondary air or to block the flow of secondary air. The invention is not limited to the above, but a regulating valve for variably adjusting the flow rate of the secondary air can be used. This modification is also applicable to the fifth, sixth, and seventh embodiments. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic view of an exhaust gas purifying system for an internal combustion engine according to a first embodiment of the present invention. Fig. 2 is a view showing an exhaust pipe such as Fig. 1 and basic components of first, second and third catalysts. Fig. 3 is a view showing an exhaust duct, a first catalyst, a second catalyst, a third catalyst, and the like of an exhaust gas purifying system for an internal combustion engine according to a second embodiment of the present invention. One display according to this A view of an exhaust duct, a first catalyst, a second catalyst, a third catalyst, and the like of an exhaust gas purification system for an internal combustion engine according to a third embodiment of the present invention. FIG. 5 is a view showing internal combustion according to a fourth embodiment of the present invention. A view of an exhaust duct, a first catalyst, a second catalyst, a third catalyst, etc. of an exhaust gas purification system for an engine. Fig. 6 is a view showing an exhaust gas purifying system for an internal combustion engine according to a fifth embodiment of the present invention. A view of the exhaust duct, the first catalyst, the second catalyst, the second catalyst, etc. 129078.doc -19. 200936870 T, which is a row of a gas purification system for an internal combustion engine according to a sixth embodiment of the present invention View of the gas conduit, the first catalyst, the second catalyst, the third catalyst, and the like. f 8 疋 A view of the exhaust gas conduit catalyst 1 catalyst and the second catalyst, etc. of the exhaust gas purification system for the internal combustion engine according to the seventh embodiment of the present invention. Fig. 9 is a view showing an exhaust duct, a catalyst, a second catalyst, a third catalyst, and the like of the exhaust gas purification system for an internal combustion engine according to a variation example of the present invention. [Explanation of main component symbols] ❹ 60, 90, 120, 230 10 11 12 13, 210 14

20/20A 30

40, 40A, 70, 100, 240 50, 50A 60, 80, 110, 190 130, 160, 200, 250 140, 170, 220, 260 Exhaust gas purification system engine air filter muffler reed valve fuel supply Exhaust duct first catalyst second catalyst third catalyst primary air introduction duct another secondary air introduction duct flap valve (flow control valve) I29078.doc 20-

Claims (1)

200936870 Patent application scope: 1. An exhaust gas purification system for an internal combustion engine, comprising: an exhaust duct for discharging exhaust gas from an internal combustion engine; a first catalyst provided in the middle of the exhaust duct a portion for reducing at least Ν〇χ contained in the exhaust gas; ❹ ❹ a second catalyst 'provided in a portion of the exhaust conduit, downstream of the first catalyst, for reduction from the first catalyst At least a portion of the exhaust gas component contained in the exhaust gas flowing out; a third catalyst provided in a middle portion of the exhaust gas conduit, further downstream than the first catalyst, forming a material different from the First and second catalysts for oxidizing at least c〇 and THC of the exhaust gas component contained in the exhaust gas from the second catalyst; and a primary air introduction conduit provided in the row A position between the first and second catalysts in the gas conduit for introducing secondary air into the exhaust conduit. 2. The internal combustion system according to the π-month item i: the bow; the exhaust gas purification system, wherein the venting conduit has another secondary air introduction conduit, and the secondary air introduction conduit is provided to the second enthalpy The position between the two is used to introduce secondary air into the exhaust conduit. 3. An exhaust gas purification system for use in an internal combustion engine according to claim 2, wherein the additional-secondary air introduction conduit has a flow control valve for controlling the introduction of the inlet conduit into the The flow of secondary air within the exhaust duct. An exhaust gas purification system for an internal combustion engine, comprising: 129078.doc 200936870 an exhaust duct for discharging exhaust gas from an internal combustion engine; a first catalyst provided for the exhaust duct The middle portion is for purifying the exhaust gas; a second catalyst is provided in the middle of the exhaust duct downstream of the first catalyst for purifying the exhaust gas flowing from the first catalyst; and a third catalyst Providing a portion of the exhaust conduit downstream of the second catalyst for purifying exhaust gas flowing from the second catalyst; and a first secondary air introduction conduit 'provided in the exhaust conduit first a position between the second catalyst and a second catalyst for introducing secondary air into the exhaust conduit; and a second secondary air introduction conduit provided at a position between the second and third catalysts in the exhaust conduit Used to introduce secondary air into the exhaust conduit. 5. The exhaust gas purification system for an internal combustion engine according to claim 4, wherein the first primary air introduction conduit has a flow control valve for controlling introduction of the introduction conduit into the exhaust conduit The flow of secondary air. 129078.doc