JP3159554U - Exhaust gas purification system for internal combustion engine and vehicle equipped with the same - Google Patents

Abstract

An exhaust gas purification system capable of increasing the supply amount of secondary air necessary for purifying exhaust gas and performing combustion on the rich side inside the engine, and a vehicle equipped with the exhaust gas purification system I will provide a. An exhaust gas purification system includes an exhaust pipe, a first catalyst, a second catalyst, and a secondary air introduction path. The first catalyst 8 and the second catalyst 9 purify the exhaust gas by a reduction action or an oxidation action, and are arranged at a distance from each other in the flow direction of the exhaust gas. The secondary air introduction path 10 has one end connected to the intake path and the other end connected to a portion of the exhaust pipe 6 between the first catalyst 8 and the second catalyst 9. [Selection] Figure 1

Description

  The present invention relates to an exhaust gas purification system for an internal combustion engine and a vehicle including the same.

  Regarding the exhaust gas purification system, an exhaust gas purification system described in Patent Document 1 below has been known. The exhaust gas purification system described in Patent Document 1 below includes a first catalyst disposed on the upstream side and a second catalyst disposed on the downstream side in an exhaust pipe from which exhaust gas of an engine composed of an internal combustion engine is exhausted. And a catalyst. The first catalyst has a function of reducing exhaust gas. The second catalyst has a function of oxidizing exhaust gas. The exhaust gas purification system adjusts the air-fuel mixture (= fuel and air) during combustion of fuel in the engine to the stoichiometric air-fuel ratio or the rich side (= air ratio in the air-fuel mixture is lower than the stoichiometric air-fuel ratio). Thus, the first catalyst can reliably reduce NOx in the exhaust gas. In addition, the exhaust gas purification system can reliably oxidize CO and THC in the exhaust gas by supplying secondary air to the second catalyst. As a result, the exhaust gas is reliably purified.

JP 2004-036440 A

  In the exhaust gas purification system, when the amount of secondary air supplied to the second catalyst does not satisfy the amount necessary for exhaust gas purification, the rich side of the air-fuel mixture is used to reliably oxidize CO and THC. There is a problem that the combustion in is regulated. In other words, in order to maintain the exhaust gas purification performance and prevent the engine from being restricted by the combustion on the rich side, it is always required to supply the secondary air amount necessary for exhaust gas purification. The That is, after the exhaust gas is purified by the reducing action in the first catalyst, if the amount of secondary air supplied to the second catalyst does not satisfy the amount necessary for purifying the exhaust gas, the exhaust gas is surely discharged. In order to purify, combustion on the rich side is suppressed, and combustion of the air-fuel mixture in a range close to the theoretical air-fuel ratio is required. As a result, there is a problem that the setting range of the engine is narrowed and the specification is not flexible.

  The present invention has been made in view of the above points, and the object of the present invention is to increase the supply amount of secondary air necessary for purifying exhaust gas, and to increase the richness inside the engine. It is an object of the present invention to provide an exhaust gas purification system capable of performing combustion of the above, and a vehicle equipped with the same.

  The exhaust gas purification system according to the present invention is provided for an engine that generates driving force by sucking air from an intake passage and burning fuel, and purifies exhaust gas discharged from the engine. The exhaust gas purification system is disposed in an exhaust pipe through which exhaust gas exhausted from the engine flows and spaced from each other in the flow direction inside the exhaust pipe, and purifies the exhaust gas by a reducing action or an oxidizing action. One end of the first and second catalysts is connected to the intake path, and the other end is connected to a portion of the exhaust pipe between the first catalyst and the second catalyst, and the intake path A plurality of secondary air introduction passages for introducing air into the exhaust pipe.

  According to the present invention, the first catalyst and the second catalyst are spaced apart from each other in the flow direction. The first catalyst can reduce NOx in the exhaust gas more reliably when the fuel-air mixture is adjusted to the rich side than when the fuel is burned at the stoichiometric air-fuel ratio. it can. Further, a plurality of secondary air introduction paths are provided. One end side of the plurality of secondary air introduction paths is connected to the intake path, and the other end side is connected to the exhaust pipe. The plurality of secondary air introduction paths are connected to a portion of the exhaust pipe between the first catalyst and the second catalyst. By adopting such a configuration, the exhaust gas purification system supplies a larger amount of secondary air necessary for purification of exhaust gas to the inside of the exhaust pipe than in the case where there is one secondary air introduction path. be able to. Therefore, the exhaust gas purification system can reliably purify the exhaust gas even when the air-fuel mixture at the time of fuel combustion is on the rich side.

  Therefore, an exhaust gas purification system capable of increasing the supply amount of secondary air necessary for purifying exhaust gas and performing combustion on the rich side inside the engine, and a vehicle equipped with the exhaust gas purification system Can be provided.

1 is a schematic configuration diagram of an exhaust gas purification system according to Embodiment 1. FIG. It is a schematic block diagram of the exhaust gas purification system which concerns on the modification 1. FIG. It is a schematic block diagram of the exhaust gas purification system which concerns on the modification 2. FIG. It is a schematic block diagram of the exhaust gas purification system which concerns on Embodiment 2. FIG. It is a schematic block diagram of the exhaust gas purification system which concerns on the modification 3. FIG. It is a schematic block diagram of the exhaust gas purification system which concerns on the modification 4. 6 is a front view of a reed valve according to Embodiment 3. FIG. It is a figure which shows the exhaust gas characteristic in the conventional exhaust gas purification system. It is a figure which shows the exhaust gas characteristic in the exhaust gas purification system of this invention.

Embodiment 1
The exhaust gas purification system 1 according to the present embodiment will be described in detail below with reference to the drawings. FIG. 1 is a schematic configuration diagram of an exhaust gas purification system 1 according to the present embodiment. The exhaust gas purification system 1 includes an engine 2, a fuel supply device 3, an air cleaner 4, a reed valve 51, a reed valve 52, an exhaust pipe 6, catalysts 8 and 9, a silencer 7, and a secondary air introduction path 10. ing.

<engine>
The engine 2 according to the present embodiment is a gasoline engine composed of an internal combustion engine. The engine 2 takes in an air-fuel mixture based on gasoline, burns the air-fuel mixture inside, and generates driving force. However, the engine 2 may be a hybrid engine that combines a gasoline engine and an electric motor. Further, the type of engine 2 and the number of cylinders are not limited.

<Fuel supply device>
The fuel supply device 3 is a device that sends fuel to the engine 2. The fuel supply device 3 takes in the fuel F from the fuel tank 20 and supplies the fuel F to the engine 2. The air and the fuel F taken from the outside of the exhaust gas purification system 1 are mixed at a predetermined ratio so that appropriate combustion is performed in the engine 2.

  The air-fuel mixture may be produced in the form of a mist by a vaporizer (not shown). The air-fuel mixture may be produced by fuel injection (not shown) and fuel F injected into an intake passage (not shown) inside the engine 2 by electronic control. In the present embodiment, the fuel F is gasoline.

<Air cleaner>
The air cleaner 4 is a device that takes in air (oxygen) necessary for the combustion of the fuel F from the outside air of the exhaust gas purification system 1 and filters dust and the like contained in the outside air. Further, as will be described later, the air cleaner 4 takes in secondary air necessary for purifying exhaust gas generated in the engine 2. However, in the exhaust gas purification system 1, the device for taking in the secondary air is not limited to the air cleaner 4. The secondary air necessary for purifying the exhaust gas may be taken from another supply path. For example, an air pump that forcibly feeds secondary air into the intake path may be provided. The air taken in by the air cleaner 4 flows into the fuel supply device 3 through the intake passage 3a. Further, the air taken in by the air cleaner 4 flows into the exhaust pipe 6 through the secondary air introduction path 10.

<Exhaust pipe>
On the other hand, the exhaust gas of the air-fuel mixture combusted by the engine 2 is discharged to the outside of the exhaust gas purification system 1 through the exhaust pipe 6. With respect to the flow direction in which the exhaust gas is discharged, the engine 2 side is the upstream side, and the first catalyst 8 and the second catalyst 9 side is the downstream side. A part of the exhaust pipe 6 is covered with a cylindrical silencer 7. The silencer 7 has a role of absorbing the explosion sound generated in the exhaust gas purification system 1 and quieting the sound. In FIG. 1, the inside of the exhaust pipe 6 has a uniform shape. However, the exhaust pipe 6 may have a different cross-sectional area in the pipe. Moreover, the location where the exhaust pipe 6 and the engine 2 are joined may be plural.

<catalyst>
In the present embodiment, a plurality of catalysts are provided inside the exhaust pipe 6. By the plurality of catalysts, the exhaust gas generated in the engine 2 is purified into a substance that does not pollute the atmosphere. Specifically, the exhaust gas generated in the engine 2 includes carbon monoxide (CO), hydrocarbons (THC), and nitrogen oxides (NOx). Among the plurality of catalysts, the first catalyst 8 is provided upstream of the second catalyst 9 in the exhaust pipe 6. In FIG. 1, the first catalyst 8 and the second catalyst 9 are provided inside the silencer 7.

  In the following embodiments, the first catalyst 8 purifies the exhaust gas mainly by a reducing action. The second catalyst 9 purifies the exhaust gas mainly by an oxidizing action.

<Secondary air introduction path>
The air taken in by the air cleaner 4 is guided to the exhaust pipe 6 by two secondary air introduction paths 10 including a secondary air introduction pipe 10a and a secondary air introduction pipe 10b. By using the air guided to the exhaust pipe 6, the first catalyst 8 and the second catalyst 9 purify the exhaust gas and the like flowing through the exhaust pipe 6. The joint 10a3 of the secondary air introduction pipe 10a and the joint 10b3 of the secondary air introduction pipe 10b are joined at different positions in the exhaust gas flow direction of the exhaust pipe 6. In FIG. 1, the secondary air introduction pipe 10a is joined to the exhaust pipe 6 on the upstream side of the secondary air introduction pipe 10b. The secondary air introduction pipe 10b is joined to the exhaust pipe 6 on the downstream side of the secondary air introduction pipe 10a. The first hose 10 a 1 is provided between the air cleaner 4 and the reed valve 51. The second hose 10 a 2 is provided between the reed valve 52 and the exhaust pipe 6. Further, the first hose 10 b 1 is provided between the air cleaner 4 and the reed valve 52. The second hose 10b2 is provided between the reed valve 52 and the exhaust pipe 6.

  In the following embodiments, the secondary air introduction tube 10a and the secondary air introduction tube 10b may have the same tube length or different tube lengths. Moreover, the tube outline of the secondary air introduction pipe | tube 10a and the secondary air introduction pipe | tube 10b, ie, the cross-sectional shape of a tube, may respectively be the same, and may differ. Further, the sizes of the tube outer shells of the secondary air introduction pipe 10a and the secondary air introduction pipe 10b, that is, the cross-sectional areas of the tubes may be the same or different. Furthermore, the tube outline of the secondary air introduction pipe 10 a does not have to be a constant size in the pipe line between the air cleaner 4 and the exhaust pipe 6. Similarly, the tube outline of the secondary air introduction pipe 10 b does not have to be a fixed size in the pipe line between the air cleaner 4 and the exhaust pipe 6.

  On the other hand, in the following embodiment, the distance in the length direction of the exhaust pipe 6 between the joint port 10a3 and the lower end side in the flow direction of the first catalyst 8 is L1. Further, the distance in the length direction of the exhaust pipe 6 between the joint port 10b3 and the upper end side in the flow direction of the second catalyst 9 is L2. At this time, the relationship between the sizes of L1 and L2 is always L1 <L2.

<Reed valve>
As described above, the air taken in by the air cleaner 4 is guided to the exhaust pipe 6 by the secondary air introduction pipe 10a and the secondary air introduction pipe 10b. At this time, the inflow direction of the secondary air into the exhaust pipe 6 is restricted only in one direction by the reed valve 51 and the reed valve 52. The inflow direction of the secondary air is only the flow from the air cleaner 4 to the exhaust pipe 6. In other words, the reed valve 51 and the reed valve 52 allow the flow of secondary air from the air cleaner 4 to the exhaust pipe 6 by opening and closing the valves 51a and 52a, respectively, and the inflow of gas from the exhaust pipe 6 to the air cleaner 4 Is configured to block. Specifically, negative pressure is generated in the exhaust pipe 6 due to exhaust pulsation due to opening and closing of the intake valve and the exhaust valve of the engine 2. At this time, the reed valve 51 and the reed valve 52 open the valve 51a and the valve 52a, respectively, and suck the air inside the air cleaner 4. The sucked air flows into the exhaust pipe 6. When the inside of the exhaust pipe 6 is at a positive pressure, the reed valve 51 and the reed valve 52 close the valve 51a and the valve 52a, respectively. Thereby, the reed valves 51 and 52 prevent the gas inside the exhaust pipe 6 from flowing into the air cleaner 4 from the exhaust pipe 6. In FIG. 1, the valve 51a and the valve 52a are shown in an opened state.

  In the following embodiments, the shape of the case outside the reed valve of the reed valve 51 and the reed valve 52 is not shown, but the inner diameter on the inlet side of the secondary air is smaller than the inner diameter on the outlet side. Note that the inlet side refers to the inlet side of the first hose 10 a 1 with respect to the reed valve 51 when the secondary air introduction pipe 10 a is taken as an example in the secondary air introduction path 10. Similarly, with respect to the reed valve 51, the second hose 10a2 side is the outlet side. In the following description, what is described as a valve represents the valve 51a and the valve 52a in the following embodiments. Further, what is described as a reed valve represents a reed valve 51, a reed valve 52, and a reed valve 50 described later.

  Since the inner diameter of the case outside the reed valve is different between the inlet side and the outlet side of the case, the following effects can be obtained. The reed valve opens and closes due to the pulsation of positive pressure and negative pressure generated in the secondary air introduction path 10. When the rotational speed of the engine 2 increases, the phase difference between the opening and closing of the valve and the pressure pulsation inside the secondary air introduction path 10 increases. That is, the valve opening / closing operation time becomes longer than the time when the positive pressure and the negative pressure inside the secondary air introduction path 10 are switched. Therefore, when the phase difference between the opening and closing of the valve and the pressure pulsation inside the secondary air introduction path 10 becomes large, the time during which the valve is still open when the inside of the secondary air introduction path 10 is positive becomes longer. . At this time, the secondary air that should flow to the exhaust pipe 6 is pushed back from the outlet side of the valve to the inlet side. By reducing the secondary air that is pushed back, the reed valve can send a lot of secondary air to the exhaust pipe 6. In principle, in the valve, since the inner diameter on the inlet side is smaller than the inner diameter on the outlet side, the secondary air pushed back by the positive pressure is hardly returned. As described above, this is because the rotational speed of the engine 2 increases, the phase difference between the opening and closing of the valve and the pressure pulsation inside the secondary air introduction path 10 becomes large, and the inside of the secondary air introduction path 10 becomes normal. This is effective when the valve is open for a long time under pressure. On the other hand, when increasing the amount of secondary air introduced in the region where the engine 2 has a low rotational speed, it is effective to increase the inner diameter of the inlet side of the valve.

  Below, the relationship between the amount of secondary air introduced, the amount of exhaust gas discharged, and the air-fuel ratio of the engine 2 and the catalyst will be described.

  FIG. 8 shows exhaust gas characteristics in a conventional exhaust gas purification system or the like. In the description of FIG. 8, the same reference numerals are given to the same elements as those in the present embodiment. The vertical axis represents the exhaust gas emission amount behind the second catalyst 9. The upper horizontal axis indicates the air-fuel ratio in the engine 2. The lower horizontal axis indicates the air-fuel ratio behind the second catalyst 9. The term “rear” refers to the rear as viewed from the flow direction of the exhaust gas in the exhaust pipe 6. As shown in FIG. 8, NOx always decreases in the emission amount when a state richer than the stoichiometric air-fuel ratio (= the air ratio is lower than the stoichiometric air-fuel ratio) is created behind the second catalyst 9. On the other hand, when CO and THC are richer than the stoichiometric air-fuel ratio in the combustion of the fuel F in the engine 2, the emission amount tends to increase.

  As described above, when CO and THC are richer than the stoichiometric air-fuel ratio behind the second catalyst 9, the amount of discharge always increases. In other words, a large amount of secondary air is required to fully exhibit the function of the second catalyst 9.

  A range A between the theoretical air-fuel ratio of the upper horizontal axis and the theoretical air-fuel ratio of the lower horizontal axis shown in FIG. The conforming range A is a setting range of the engine 2 that can achieve a clean exhaust gas. In order for the engine 2 to have a high degree of freedom in setting, it is necessary to expand the adaptation range A. In other words, the engine 2 can increase the degree of freedom of setting by expanding the matching range A. The degree of freedom of setting refers to a range in which the exhaust gas is reliably purified even when the engine 2 burns the fuel F on the richer side than the stoichiometric air-fuel ratio. By widening the range, the engine 2 can have a setting with a high degree of freedom. When the amount of secondary air introduced is increased in a state where the second catalyst 9 reacts with the exhaust gas, the theoretical air-fuel ratio of the lower horizontal axis shown in FIG. 8 moves to the left side of the figure. That is, the adaptation range A is expanded by increasing the amount of secondary air introduced.

  FIG. 9 shows the exhaust gas characteristics when the amount of secondary air introduced is increased. In FIG. 9, the matching range A ′ is enlarged to the left on the horizontal axis below the matching range A. Further, when the CO and THC emissions shown in FIG. 9 are richer than the stoichiometric air-fuel ratio, the emissions tend to increase as in FIG. However, in the state of FIG. 9 where the amount of secondary air introduced is increasing, the rate of increase in CO and THC (the slope in FIG. 9) is suppressed as compared to FIG.

  8 and 9, the vertex of the NOx emission amount in the matching ranges A and A ′ is shown as C on the vertical axis. This vertex C is a value affected by the engine 2, the first catalyst 8, and the second catalyst 9, and does not affect the amount of secondary air introduced. Therefore, in FIG. 8 and FIG. 9, the value of the vertex C is assumed to be equal.

(Function and effect)
In the present embodiment, the secondary air introduction path 10 includes a secondary air introduction pipe 10a and a secondary air introduction pipe 10b. Thereby, compared with the case where there is one secondary air introduction path, the amount of secondary air introduced can be increased. By increasing the amount of secondary air introduced, the exhaust gas can be reliably purified even when the engine 2 burns on the richer side than the stoichiometric air-fuel ratio. That is, the exhaust gas purification system 1 can be set to have a higher degree of freedom for the combustion on the rich side in the engine 2.

  Moreover, in this embodiment, the junction part with the exhaust pipe 6 differs between the secondary air introduction pipe | tube 10a and the secondary air introduction pipe | tube 10b, respectively. That is, the joint between the secondary air introduction pipe 10a and the exhaust pipe 6 is the joint 10a3. Further, the joint between the secondary air introduction pipe 10b and the exhaust pipe 6 is a joint 10b3. Therefore, the secondary air introduction path 10 can obtain the introduction amount and introduction timing of the secondary air according to the position at the joint port 10a3 and the joint port 10b3. Thereby, the exhaust gas purification system 1 can introduce secondary air with high accuracy. Therefore, even when the engine 2 burns on the richer side than the stoichiometric air-fuel ratio, the exhaust gas can be reliably purified. That is, the exhaust gas purification system 1 can be set to have a higher degree of freedom for the combustion on the rich side in the engine 2.

  In the present embodiment, the joint 10a3 of the secondary air introduction pipe 10a and the joint 10b3 of the secondary air introduction pipe 10b are provided at different positions in the exhaust pipe 6. Further, the secondary air introduction pipe 10a and the secondary air introduction pipe 10b can have different cross sectional shapes and cross sectional areas. Therefore, the secondary air introduction path 10 can obtain the introduction amount and introduction timing of the secondary air according to the position at the joint port 10a3 and the joint port 10b3. Thereby, the exhaust gas purification system 1 can introduce secondary air with high accuracy. Therefore, even when the engine 2 burns on the richer side than the stoichiometric air-fuel ratio, the exhaust gas can be reliably purified. That is, the exhaust gas purification system 1 can be set to have a higher degree of freedom for the combustion on the rich side in the engine 2.

  The secondary air introduction pipe 10 a is provided in the vicinity of the first catalyst 8. Specifically, the distance L1 in the length direction of the exhaust pipe 6 between the joint port 10a3 and the lower end side in the flow direction of the first catalyst 8, and the exhaust between the joint port 10b3 and the upper end side in the flow direction of the second catalyst 9. L1 <L2 is always established with respect to the size relationship with the interval L2 in the length direction of the tube 6. Thus, if L1 is a comparatively short space | interval, in addition to the reduction | restoration effect | action, about the 1st catalyst 8, the function which purifies exhaust gas by an oxidation effect | action can be provided in a part of 1st catalyst 8. In this case, the first catalyst 8 can effectively utilize the backflow of exhaust gas caused by pressure pulsation inside the exhaust pipe 6. That is, the flow of exhaust gas in the exhaust pipe 6 is not always in a fixed direction, and there is a scene in which exhaust gas flows backward in the exhaust pipe 6 due to pulsation inside the exhaust pipe 6. At this time, when the first catalyst 8 has a function resulting from the oxidation reaction, the exhaust gas can purify CO and THC in the first catalyst 8 by an oxidizing action. Therefore, the exhaust gas purification system 1 can expect more purification of the exhaust gas by the first catalyst 8.

  The secondary air introduction path 10 is provided with a reed valve 51 and a reed valve 52. The reed valve 51 and the reed valve 52 are configured to allow the flow of secondary air only in the flow direction from the air cleaner 4 to the exhaust pipe 6 using exhaust pulsation in the exhaust pipe 6. Therefore, the exhaust gas purification system 1 can introduce the secondary air with high accuracy. Therefore, even when the engine 2 burns on the richer side than the stoichiometric air-fuel ratio, the exhaust gas can be reliably purified. That is, the exhaust gas purification system 1 can be set to have a higher degree of freedom for the combustion on the rich side in the engine 2.

  In the present embodiment, the exhaust gas purification system 1 can reliably purify the exhaust gas by the above-described operation even when the engine 2 burns on the richer side than the stoichiometric air-fuel ratio. Therefore, the vehicle including the exhaust gas purification system 1 is a vehicle in which the exhaust gas is purified with relatively high accuracy even when the engine 2 is operated at a high speed.

  Further, the exhaust gas purification system 1 can be used for a motorcycle. In the motorcycle, the accelerator operation is complicated, and the engine 2 is required to burn on the richer side. The exhaust gas purification system 1 according to the present embodiment can reliably purify exhaust gas even when the engine 2 burns on the richer side than the stoichiometric air-fuel ratio. Therefore, the motorcycle including the exhaust gas purification system 1 is a motorcycle that can purify the exhaust gas with relatively high accuracy even when the engine 2 is operated at a high speed.

<< Modification 1 >>
In the embodiment, the joint 10a3 of the secondary air introduction pipe 10a and the joint 10b3 of the secondary air introduction pipe 10b are joined at different positions in the exhaust gas flow direction in the exhaust pipe 6. However, the joint 10a3 of the secondary air introduction pipe 10a and the joint 10b3 of the secondary air introduction pipe 10b may be joined at the same position in the exhaust gas flow direction in the exhaust pipe 6. FIG. 2 is a schematic configuration diagram of the exhaust gas purification system 1 according to the first modification. The same reference numerals in FIG. 2 and FIG. 1 represent common components, and description thereof is omitted.

<Secondary air introduction path>
The air taken in by the air cleaner 4 is guided to the exhaust pipe 6 by two secondary air introduction paths 10 including a secondary air introduction pipe 10a and a secondary air introduction pipe 10b. By using the air guided to the exhaust pipe 6, the first catalyst 8 and the second catalyst 9 purify the exhaust gas and the like flowing through the exhaust pipe 6. The joint 10a3 of the secondary air introduction pipe 10a and the joint 10b3 of the secondary air introduction pipe 10b are provided at substantially the same position in the form of facing each other in the exhaust gas flow direction of the exhaust pipe 6. In this case, the secondary air introduction pipe 10a and the secondary air introduction pipe 10b do not necessarily face each other directly in the exhaust pipe 6. For example, when the exhaust pipe 6 has a shape having a circular cross section, the joint port 10a3 and the joint port 10b3 do not have to be located at positions 180 degrees apart on the circumference in any cross section of the exhaust pipe 6. . In this case, in any cross section of the exhaust pipe 6, the angular interval between the arrangement positions on the circumference is not particularly limited. As shown in FIG. 2, the first hose 10 a 1 is provided between the air cleaner 4 and the reed valve 51. The second hose 10 a 2 is provided between the reed valve 52 and the exhaust pipe 6. Further, the first hose 10 b 1 is provided between the air cleaner 4 and the reed valve 52. The second hose 10b2 is provided between the reed valve 52 and the exhaust pipe 6.

  The joint port 10a3 and the joint port 10b3 can be joined at the same position so as to face each other in the flow direction of the exhaust gas in the exhaust pipe 6 as in Modification 1. In this case, compared with the case where the joint port 10a3 and the joint port 10b3 are provided at different positions in the exhaust gas flow direction of the exhaust pipe 6, the amount by which the secondary air introduction path 10 interferes with the structure of the silencer 7 is reduced. Can be made. In this case, the layout design inside the silencer 7 related to the secondary air introduction path 10 can be facilitated.

<< Modification 2 >>
In the first embodiment and the first modification, the first catalyst 8 and the second catalyst 9 are provided inside the silencer 7. However, one of the first catalyst 8 and the second catalyst 9 may be provided outside the silencer 7. FIG. 3 is a schematic configuration diagram of the exhaust gas purification system 1 according to the second modification.

<catalyst>
As shown in FIG. 3, the first catalyst 8 is provided outside the silencer 7. The second catalyst 9 is provided inside the silencer 7. The first catalyst 8 is provided upstream of the second catalyst 9 in the exhaust pipe 6.

  As described above, the silencer 7 has a role of absorbing explosive sound generated in the exhaust gas purification system 1 and quieting the sound. Further, as shown in Modification 2, the first catalyst 8 can be provided outside the silencer 7. The second catalyst 9 is provided inside the silencer 7. In this case, the silencer 7 has an internal structure in which two secondary air introduction paths 10, a secondary air introduction pipe 10 a and a secondary air introduction pipe 10 b, are joined to the exhaust pipe 6 inside the silencer 7. In comparison, interference between the silencer 7 and the secondary air introduction path 10 is reduced. Although not shown, when the secondary air introduction passages 10 of both the secondary air introduction pipe 10 a and the secondary air introduction pipe 10 b are joined to the exhaust pipe 6 outside the silencer 7, Interference with the air introduction path 10 is further reduced.

<< Embodiment 2 >>
In the first embodiment, the air cleaner 4 is shared by the intake air related to the combustion of the fuel F in the engine 2 and the secondary air introduction path 10. Hereinafter, in this embodiment, the air cleaner 4 uses the air cleaner 4a and the sub air cleaner 4b, or the main air cleaner 4c and the sub air cleaner 4b. In the following embodiments, when simply referred to as an air cleaner, the air cleaner 4a and the sub air cleaner 4b or the main air cleaner 4c and the sub air cleaner 4b are combined. In this embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

<Air cleaner>
As shown in FIG. 4, the air cleaner includes an air cleaner 4a and a sub air cleaner 4b. The air cleaner 4 a performs intake of air necessary for combustion of the fuel F in the engine 2 and intake of air used for the secondary air introduction path 10. Further, the sub air cleaner 4 b performs intake of air used for the secondary air introduction path 10. The air taken in by the air cleaner 4a flows into the fuel supply device 3 through the intake passage 3a. Further, the air taken in by the air cleaner 4 a flows into the exhaust pipe 6 through the secondary air introduction path 10. The air taken in by the sub air cleaner 4 b flows into the exhaust pipe 6 through the secondary air introduction path 10.

<catalyst>
In FIG. 4, the first catalyst 8 and the second catalyst 9 are provided inside the silencer 7. However, as in the second modification, either the first catalyst 8 or the second catalyst 9 may be provided outside the silencer 7.

<Secondary air introduction path>
As shown in FIG. 4, the joint port 10a3 of the secondary air introduction pipe 10a and the joint port 10b3 of the secondary air introduction pipe 10b are joined at different positions in the exhaust gas flow direction of the exhaust pipe 6. However, in the present embodiment, the joint 10a3 and the joint 10b3 may be joined at the same position in the exhaust gas flow direction in the exhaust pipe 6, as shown in the first modification. Further, the secondary air introduction pipe 10a and the secondary air introduction pipe 10b are constituted by a portion divided into a first hose 10a1, 10b1 and a second hose 10a2, 10b2, with the reed valve 51 and the reed valve 52 being respectively separated. ing. The first hose 10 a 1 is provided between the sub air cleaner 4 b and the reed valve 51. The second hose 10 a 2 is provided between the reed valve 51 and the exhaust pipe 6. The first hose 10b1 is provided between the air cleaner 4a and the reed valve 52. The second hose 10b2 is provided between the reed valve 52 and the exhaust pipe 6. However, the secondary air introduction pipe 10a may be joined to the air cleaner 4a, and the secondary air introduction pipe 10b may be joined to the sub air cleaner 4b.

<< Modification 3 >>
In the second embodiment, the air cleaner includes an air cleaner 4a and a sub air cleaner 4b. The air cleaner 4 a performs intake of air necessary for combustion of the fuel F in the engine 2 and intake of air used for the secondary air introduction path 10. Further, the sub air cleaner 4 b performs intake of air used for the secondary air introduction path 10. However, the air cleaner is not limited to the form of the air cleaner 4a and the sub air cleaner 4b. In Modification 3, the air cleaner includes a main air cleaner 4c and a sub air cleaner 4b.

<Air cleaner>
FIG. 5 is a schematic configuration diagram of the exhaust gas purification system 1 in Modification 3. The main air cleaner 4 c is an air cleaner that performs intake of air necessary for combustion of the fuel F in the engine 2. Therefore, the air taken in by the main air cleaner 4c flows into the fuel supply device 3 through the intake passage 3a. The sub air cleaner 4 b is a dedicated air cleaner used for the secondary air introduction path 10. Therefore, the air taken in by the sub air cleaner 4 b flows into the exhaust pipe 6 through the secondary air introduction path 10.

<Secondary air introduction path>
In the third modification, the first hoses 10a1 and 10b1 are provided between the sub air cleaner 4b and the reed valves 51 and 52, respectively. The second hoses 10a2 and 10b2 are provided between the reed valves 51 and 52 and the exhaust pipe 6, respectively.

  In the present embodiment, the air cleaner is configured in any form of an air cleaner 4a and a sub air cleaner 4b, and a main air cleaner 4c and a sub air cleaner 4b. Unlike the case of the first embodiment, a sub air cleaner 4b is provided as an air cleaner dedicated to introducing secondary air. Since the sub air cleaner 4b is provided for introducing secondary air, the path from the sub air cleaner 4b to the exhaust pipe 6 is freely set depending on the position of the sub air cleaner 4b. The accuracy of the secondary air introduction can be improved by freely setting the path from the sub air cleaner 4b to the exhaust pipe 6. The accuracy of secondary air introduction depends on the amount of secondary air introduction and the timing of introduction. That is, by providing the sub air cleaner 4b, it is possible to freely set the introduction amount and introduction timing of the secondary air necessary for purifying the exhaust gas.

<< Embodiment 3 >>
In the first and second embodiments, the secondary air introduction path 10 is provided with two reed valves, a reed valve 51 and a reed valve 52. However, the reed valve is not provided for each of the plurality of introduction pipes (secondary air introduction pipe 10a and secondary air introduction pipe 10b) in the secondary air introduction path 10 as in the first and second embodiments. Alternatively, a configuration in which a plurality of introduction pipes are integrally joined as follows may be employed.

<Air cleaner>
The air cleaner shown in FIG. 6 includes a main air cleaner 4c and a sub air cleaner 4b. However, in the present embodiment, the air cleaner may be an integrated air cleaner as the air cleaner 4 as in the first embodiment.

<catalyst>
The first catalyst 8 and the second catalyst 9 are provided inside the silencer 7. However, in the present embodiment, any one of the first catalyst 8 and the second catalyst 9 may be provided outside the silencer 7 as in the second modification.

<Secondary air introduction path>
As shown in FIG. 6, the joint 10 a 3 of the secondary air introduction pipe 10 a and the joint 10 b 3 of the secondary air introduction pipe 10 b are provided at different positions in the exhaust gas flow direction of the exhaust pipe 6. However, in the present embodiment, the joint 10a3 and the joint 10b3 may be provided at the same position in the exhaust gas flow direction in the exhaust pipe 6 as shown in the first modification.

<Reed valve>
As shown in FIG. 6, the reed valve 50 joins the first hose 101, the second hose 10a2, and the second hose 10b2. The reed valve 50 has one port on the inlet side, which is the upstream side, as viewed from the flow direction of the secondary air, and has a number corresponding to the number of secondary air introduction paths 10 on the outlet side which is the downstream side. Has a mouth.

  The reed valve 50 has a base 50a. The reed valve 50 is joined to the first hose 101 on the back side of the sheet of FIG. Further, the reed valve 50 is joined to the second hose 10a2 and the second hose 10b2 on the front side of the drawing sheet of FIG. The reed valve 50 has a partition wall 50b in the center of the base 50a. By the partition wall 50b, the valve window 51b and the valve window 52b are separated on the left and right of the base 50a. Both the stopper A and the valve 51a are attached to the base 50a by the screw 80. Further, both the stopper B and the valve 52a are attached to the base 50a by the screw 80. The stopper A and the stopper B are components that influence the inflow characteristics of the secondary air depending on their shapes. Therefore, the shapes of the stopper A and the stopper B may be different from each other. Similarly, the valve 51a and the valve 52a contribute to the inflow characteristics of the secondary air depending on the material and the like. For this reason, the valve 51a and the valve 52a may be different in thickness, material, and the like.

  The inflow direction of the secondary air is only the flow from the air cleaner 4 to the exhaust pipe 6. The reed valve 50 is configured to cause secondary air to flow in the direction from the back surface of the paper surface to the front surface of the paper surface in FIG.

  In the present embodiment, secondary air out of the air sucked by the air cleaner is sent to the exhaust pipe 6 by the reed valve 50. The secondary air is air necessary for purifying exhaust gas generated in the engine 2. The air sucked by the air cleaner is also used when the fuel F is burned in the engine 2. Unlike the case where the reed valve 51 and the reed valve 52 are provided as in the first and second embodiments, the reed valve 50 can reduce the number of parts in the exhaust gas purification system 1. Further, the reed valve 50 is limited to one arrangement position in the exhaust gas purification system 1 by reducing the number of parts.

DESCRIPTION OF SYMBOLS 1 Exhaust gas purification system 2 Engine 3 Fuel supply device 3a Intake passage 4 Air cleaner 4a Air cleaner 4b Sub air cleaner 4c Main air cleaner 6 Exhaust pipe 7 Silencer 8 First catalyst 9 Second catalyst 10 Secondary air introduction path 10a Secondary air introduction pipe ( Secondary air introduction path)
10a1 1st hose 10a2 2nd hose 10a3 Joint 10b Secondary air introduction pipe (secondary air introduction path)
10b1 First hose 10b2 Second hose 10b3 Joint 20 Fuel tank 50 Reed valve 51 Reed valve 51a Valve 51b Valve window (secondary air inlet)
52 Reed valve 52a Valve 52b Valve window (secondary air inlet)
101 First hose

Claims (11)

An exhaust gas purification system that is provided for an engine that generates driving force by sucking air from an intake path and burning fuel, and purifies exhaust gas exhausted from the engine,
An exhaust pipe through which exhaust gas discharged from the engine flows;
A first catalyst and a second catalyst disposed in the exhaust pipe at intervals in the flow direction, and purifying the exhaust gas by a reducing action or an oxidizing action;
One end is connected to the intake passage, the other end is connected to a portion of the exhaust pipe between the first catalyst and the second catalyst, and air is introduced from the intake passage into the exhaust pipe. A plurality of secondary air introduction paths;
Exhaust gas purification system with   The exhaust gas purification system according to claim 1, wherein the plurality of secondary air introduction paths are individually connected between the intake path and the exhaust pipe, and joint ports are individually provided in the exhaust pipe. . Further equipped with a silencer made of a cylindrical shape,
A portion of the exhaust pipe is covered by the silencer;
The exhaust gas purification system according to claim 1, wherein the first catalyst or the second catalyst is disposed in a portion of the exhaust pipe covered with the silencer.   The exhaust gas purification system according to claim 2, wherein each of the plurality of secondary air introduction paths includes pipes having different diameters. The plurality of connection ports include a first connection port and a second connection port,
The distance between the first catalyst and the first connection port is shorter than the distance between the second connection port and the second catalyst with respect to the flow direction of the exhaust gas. Exhaust gas purification system. The plurality of connection ports include a first connection port and a second connection port,
The exhaust gas purification system according to claim 2, wherein the first connection port and the second connection port are provided at the same position with respect to a flow direction of the exhaust gas. The intake path includes a number of air cleaners according to the number of the secondary air introduction paths,
The exhaust gas purification system according to claim 2, wherein the plurality of secondary air introduction paths are respectively connected to the plurality of air cleaners.   Provided individually in the plurality of secondary air introduction paths, adjusts at least the amount of air sucked from the intake path and the introduction timing, and allows only the air flow from the intake path side to the exhaust pipe side. The exhaust gas purification system according to claim 1, further comprising a plurality of reed valves.   The plurality of reed valves are configured integrally, so that the number of inlets on the upstream side in the flow direction of air sucked from the intake path is one, and the number of outlets on the downstream side is The exhaust gas purification system according to claim 8, comprising a reed valve having a number corresponding to the number of secondary air introduction paths.   A vehicle comprising the exhaust gas purification system according to claim 1.   The vehicle according to claim 10 which is a motorcycle.

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