JP2021188606A - Exhaust system with catalyst - Google Patents

Abstract

The present invention provides an exhaust system capable of early activation of a catalyst and improvement of purification performance. An exhaust device 38 for purifying exhaust gas G of an engine E includes a catalyst body 46 on one side and a catalyst body 48 on the other side. Each catalyst body 46, 48 is provided in an exhaust path EP connected to the exhaust port 20a of the engine E. One catalyst body 46 is arranged at a position where it first purifies unpurified exhaust gas discharged from the exhaust port 20a. The other catalyst body 48 is arranged downstream of one catalyst body 46, and is set to have a larger heat capacity than one catalyst body 46. [Selection diagram] Figure 1

Description

The present invention relates to an exhaust device that purifies and silences engine exhaust.

In an exhaust device that purifies and silences the exhaust gas of an engine, there is a collecting pipe downstream of the exhaust pipe provided with a catalyst for purifying the exhaust gas (for example, Patent Document 1). In the exhaust device described in Patent Document 1, two catalysts are arranged along the flow direction of the exhaust to promote activation of the catalysts and improve purification performance.

Japanese Patent No. 5969328

However, due to the growing awareness of the environment in recent years, further early activation of catalysts is required.

An object of the present invention is to provide an exhaust device capable of early activation of a catalyst and a saddle-type vehicle equipped with the exhaust device.

In order to achieve the above object, the exhaust device of the present invention is an exhaust device for purifying the exhaust gas of an engine, comprising one catalyst body and the other catalyst body, and each catalyst body is connected to an exhaust port of the engine. The one catalyst body is provided in the exhaust passage, and the one catalyst body is arranged at a position where the unpurified exhaust gas discharged from the exhaust port is first purified, and the other catalyst body is on the downstream side of the one catalyst body. The heat capacity is set to be larger than that of the one catalyst body. Here, "upstream" and "downstream" mean "upstream" and "downstream" in the exhaust flow direction.

According to this configuration, the other catalyst body on the downstream side has a larger heat capacity than the one catalyst body on the upstream side. Therefore, since one catalyst body is rapidly heated to a high temperature and activated by touching the exhaust gas, the temperature of the exhaust gas is raised at an early stage, and the heated exhaust gas flows into the other catalyst body. As a result, the other catalyst is also activated early. Therefore, the purification performance of the catalyst can be improved.

In the present invention, the one catalyst body is formed in a flat plate or curved plate shape in which a plurality of through holes penetrating in the flow direction of the exhaust are formed and extends so as to intersect the flow direction, and the exhaust gas is more exhausted than the other catalyst body. The length in the flow direction may be small.

In the present invention, a first exhaust gas sensor provided on the upstream side of the one catalyst body in the exhaust passage and detecting a component in the exhaust gas, and a first exhaust gas sensor provided on the downstream side of the other catalyst body in the exhaust passage. It may be provided with a second exhaust gas sensor that detects a component in the exhaust gas. According to this configuration, the deterioration of the catalyst can be detected by the second exhaust gas sensor on the downstream side of the other catalyst body. This improves the reliability of the exhaust device containing the catalyst.

In the present invention, an upstream small-diameter portion having a smaller passage area than the exhaust passage immediately before and immediately after the upstream side of the one catalyst body in the exhaust passage is formed, and the component in the exhaust is formed in the upstream small-diameter portion. An upstream exhaust gas sensor for detecting the above may be provided. According to this configuration, it is possible to suppress the bias of the exhaust gas in the exhaust path and effectively detect the components of the exhaust gas.

In the present invention, a downstream small-diameter portion having a smaller passage area than immediately before and immediately after is formed on the downstream side of the other catalyst body in the exhaust passage, and a component in the exhaust is detected in the downstream small-diameter portion. A downstream exhaust gas sensor for this purpose may be provided. According to this configuration, the exhaust gas component can be effectively detected by suppressing the bias of the exhaust gas by the downstream side small diameter portion.

In the present invention, the engine is a multi-cylinder engine, and the exhaust passage has a plurality of pre-merging regions connected to each exhaust port, a merging region where the plurality of pre-merging regions merge, and a downstream portion of the merging region. It has a post-merging region extending to the side, and the one catalyst body may be provided in a single post-merging region or in each of a plurality of post-merging regions.

The one catalyst body may be made of a sintered body formed in the shape of a flat plate or a curved plate in which a plurality of through holes penetrating in the flow direction of the exhaust gas are formed and extend in the flow direction.

Another exhaust device of the present invention is an exhaust device that purifies the exhaust of a multi-cylinder engine, and is provided with an exhaust passage connected to the exhaust port of the engine to purify the exhaust, and the exhaust. The other catalyst body provided on the downstream side of the one catalyst body in the road to purify the exhaust gas, and the second catalyst body provided on the upstream side of the one catalyst body in the exhaust gas path to detect the components in the exhaust gas. The exhaust gas sensor of 1 and the second exhaust gas sensor provided on the downstream side of the other catalyst body in the exhaust passage to detect the components in the exhaust gas are provided, and the one exhaust gas body is in the flow direction of the exhaust gas. A plurality of through holes penetrating the exhaust gas are formed to form a flat plate or a curved plate extending so as to intersect the flow direction, and the length of the exhaust gas in the flow direction is smaller than that of the other catalyst body. The first exhaust gas sensor has a plurality of pre-merging regions connected to each exhaust port, a merging region in which the plurality of pre-merging regions merge, and a post-merging region extending downstream from the merging region. , It is provided on the downstream side of the confluence area.

The saddle-type vehicle of the present invention is provided with the exhaust device of the present invention. According to this configuration, early activation of the catalyst and improvement of purification performance can be achieved, and the reliability of the exhaust device including the catalyst is improved.

According to the exhaust device and the saddle-mounted vehicle of the present invention, the catalyst can be activated at an early stage, the purification performance can be improved, and the reliability of the exhaust device including the catalyst is improved.

It is a side view which shows the rear part of the motorcycle which is a kind of saddle-riding type vehicle equipped with the multi-cylinder engine equipped with the exhaust device which concerns on 1st Embodiment of this invention. It is a side view which shows the exhaust device and an engine. It is a bottom view of the exhaust system and the engine as seen from below. It is a side view which shows the modification of the exhaust device. It is a system diagram which shows the exhaust system in a simplified manner. It is a system diagram which shows the exhaust apparatus which concerns on 2nd Embodiment of this invention simplified. It is a system diagram which shows the exhaust apparatus which concerns on 3rd Embodiment of this invention simplified. It is an outline drawing which shows the catalyst body on the upstream side of the exhaust apparatus which concerns on 1st to 3rd Embodiment. It is a partial vertical sectional view which shows the installation state of the catalyst body on the upstream side.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a side view showing the rear part of a motorcycle which is a kind of saddle-mounted vehicle equipped with a multi-cylinder engine equipped with an exhaust device according to the first embodiment of the present invention. In the present specification, "right" and "left" mean "right" and "left" as seen by the driver in the vehicle. Further, "upstream" and "downstream" mean "upstream" and "downstream" in the exhaust flow direction.

FIG. 1 is a side view of a motorcycle which is a kind of saddle-mounted vehicle provided with an engine exhaust device according to the first embodiment of the present invention. The body frame FR of the motorcycle of the present embodiment has a main frame 1 constituting the front half portion and a rear frame 2 constituting the rear half portion. The rear frame 2 is connected to the rear portion of the main frame 1.

A front fork 6 is rotatably supported by a head pipe 4 at the front end of the main frame 1 via a steering shaft (not shown). A front wheel 8 is attached to the lower end of the front fork 6. A handle 10 is attached to the upper end of the front fork 6.

A swing arm bracket 12 is provided at the rear end of the main frame 1. The front end portion of the swing arm 13 is supported on the swing arm bracket 12 so as to be vertically swingable around the pivot shaft 14. A rear wheel 15 is attached to the rear end of the swing arm 13.

An engine E, which is a drive source, is attached below the main frame 1 and in front of the swing arm bracket 12. The engine E drives the rear wheels 15 via a power transmission member (not shown) such as a chain.

The engine E of the present embodiment is a parallel 4-cylinder engine. The engine E is not limited to a 4-cylinder engine, and may be a multi-cylinder engine such as a 2-cylinder, 3-cylinder, 6-cylinder, or V-type 8-cylinder engine, or may be a single-cylinder engine. The engine E has a crankcase 16 that rotatably supports a crank shaft (not shown), a cylinder 18 that projects upward from the crankcase 16, and a cylinder head 20 that is attached to the upper part of the cylinder 18. There is. Further, an oil pan 22 is provided at the lower part of the crankcase 16.

The fuel tank 24 is arranged on the upper part of the main frame 1, and the seat 26 on which the operator sits is mounted on the rear frame 2.

An exhaust port 20a is formed on the front surface of the cylinder head 20, and an intake port 20b is formed on the rear surface. The exhaust port 20a and the intake port 20b are provided one for each cylinder, for a total of four. An intake system device 27 is connected to each intake port 20b. The intake system device 27 supplies the mixture of external air and fuel to the engine E as intake air.

One exhaust pipe 28 is connected to each exhaust port 20a. That is, in this embodiment, the number of exhaust pipes 28 is four. Each exhaust pipe 28 extends downward in front of the engine E and then is assembled at the lower gathering portion 30 of the engine E. At the gathering portion 30, the four exhaust pipes 28 (passages) merge to form a single passage.

The exhaust chamber 32 is connected to the downstream side of the collecting portion 30, and the exhaust muffler 36 is connected to the downstream side of the exhaust chamber 32 via the connecting pipe 34. The exhaust G is repeatedly expanded and contracted in the exhaust chamber 32 and the exhaust muffler 36 to muffle the sound, and then is discharged to the outside. The exhaust device 38 of the engine E is composed of the exhaust pipe 28, the collecting portion 30, the exhaust chamber 32, the connecting pipe 34, and the exhaust muffler 36. Further, the exhaust pipe 28, the collecting portion 30, the exhaust chamber 32, the connection pipe 34, and the exhaust muffler 36 form an exhaust passage EP connected to the exhaust port 20a of the engine E. The exhaust chamber 32 may not be present.

In the present embodiment, the exhaust pipe 28, the collecting portion 30, the exhaust chamber 32 and the connecting pipe 34 shown in FIG. 2 are connected by welding, and one of the connecting pipe 34 and the exhaust muffler 36 is fitted to the other and the connecting pipe 34 and the exhaust muffler 36 are fitted to the other. The outer circumference is fixed by a gripping member 35 such as a clamp. However, the method of connecting each component is not limited to this.

In the present embodiment, the collecting portion 30 has two first merging portions 40 where two of the four exhaust pipes 28 merge, and a second merging portion 42 where the two first merging portions 40 merge. Have. That is, in the present embodiment, the four exhaust pipes 28 in the collecting portion 30 merge into two and then into one.

As shown in FIG. 5, the exhaust passage EP has four pre-merging regions 62 connected to each exhaust port 20a, a merging region 64 where the four pre-merging regions 62 merge, and a merging region extending downstream from the merging region 64. It has a rear region 66.

In the present embodiment, the exhaust passage EP composed of the four exhaust pipes 28 constitutes the pre-merging region 62. Further, the upstream portion of the first merging portion 40, that is, the region where the four exhaust passages EP shift to the two exhaust passages EP constitutes the merging region 64. Further, a downstream portion of the first merging portion 40, that is, a region downstream from the region where the two exhaust passages EP are formed constitutes the post-merging region 66. In the present embodiment, the downstream portion of the first confluence portion 40, that is, the region where the two exhaust passage EPs are formed constitutes the first post-merging region 66a having a plurality of regions (two in the present embodiment), and the second The merging portion 42 and the exhaust passage EP on the downstream side thereof constitute a singular second post-merging region 66b.

The collecting portion 30 shown in FIG. 2 is provided with a first exhaust gas sensor 44, an upstream side catalyst body 46, a downstream side catalyst body 48, and a second exhaust gas sensor 50 in order from the upstream side. In the present embodiment, the first and second exhaust gas sensors 44, 50 and the upstream and downstream catalyst bodies 46, 48 are provided in the second merging portion 42 of the collecting portion 30. In the present embodiment, the first exhaust gas sensor 44, the upstream catalyst body 46 (one catalyst body), the downstream side catalyst body 48 (the other catalyst body), and the second exhaust gas sensor 50 are singular second. It is provided in the post-merging region 66b.

In other words, in the present embodiment, the first exhaust gas sensor 44 constitutes an upstream exhaust gas sensor arranged on the upstream side of the catalyst body 46 on the upstream side in the exhaust passage EP. Further, the second exhaust gas sensor 50 constitutes a downstream exhaust gas sensor arranged on the downstream side of the catalyst body 48 on the downstream side in the exhaust passage EP. Further, the catalyst body 46 on the upstream side constitutes one of the catalysts arranged at a position where the unpurified exhaust gas discharged from the exhaust port 20a is first purified. Further, the catalyst body 48 on the downstream side constitutes the other catalyst arranged on the downstream side of one catalyst body 46.

Specifically, the second merging section 42 includes an upstream collecting pipe 52 provided with a first exhaust gas sensor 44, a catalyst pipe 54 provided with catalysts 46 and 48 on the upstream and downstream sides, and a second exhaust gas. It has a downstream collecting pipe 56 in which the sensor 50 is provided. As shown in the bottom view of FIG. 3, the entire upstream collecting pipe 52 and the upstream portion of the catalyst pipe 54 are arranged below the upwardly raised portion 22a forming the right half of the bottom surface of the oil pan 22. ing.

The upstream collecting pipe 52 shown in FIG. 2 is connected to the downstream end of the first confluence 40 at its upstream end. The upstream collecting pipe 52 is provided with an upstream small diameter portion 58 having a passage area smaller than that of the upstream end opening 52a. Specifically, the upstream side small diameter portion 58 is formed on the upstream side of the upstream side catalyst body 46 (one catalyst body) in the exhaust passage EP, and the passage area is formed smaller than immediately before and immediately after that.

In the present embodiment, the upstream side small diameter portion 58 is formed to have a smaller passage inner diameter than the upstream side and the downstream side. That is, the upstream collecting pipe 52 is gradually reduced in diameter from the upstream end opening 52a toward the downstream to become the minimum inner diameter in the upstream small diameter portion 58, and gradually decreases from the upstream small diameter portion 58 toward the downstream end opening 52b. The diameter has been expanded. As a result, the catalyst tube 54 on the downstream side can be formed with a large diameter.

A first exhaust gas sensor 44 (upstream exhaust gas sensor) is provided in the upstream side small diameter portion 58. The first exhaust gas sensor 44 detects a specific component in the exhaust gas. The first exhaust gas sensor 44 is, for example, an oxygen concentration sensor. In this embodiment, the first exhaust gas sensor 44 is used to adjust the fuel concentration.

The upstream end of the catalyst pipe 54 is connected to the downstream end of the upstream collecting pipe 52. Specifically, the downstream end of the upstream collecting pipe 52 is fitted to the opening of the upstream end of the catalyst pipe 54, and the outer periphery of the fitting portion is gripped by a fixing member 55 such as a clamp. The method of connecting the upstream collecting pipe 52 and the catalyst pipe 54 is not limited to this.

The catalyst tube 54 is made of a cylindrical pipe, and constitutes a storage portion in which the catalyst bodies 46 and 48 on the upstream side and the downstream side are housed. Further, the catalyst tube 54 is formed to have a larger diameter than the upstream small diameter portion 58. That is, the catalyst tube 54 constitutes a large-diameter portion having a larger passage area than the upstream small-diameter portion 58 in the gathering portion 30. When the diameter of the catalyst tube 54 is large, the flow path resistance becomes small and the exhaust performance is improved. When passing through the catalyst pipe 54, the exhaust G is purified by the catalyst bodies 46 and 48 on the upstream side and the downstream side.

The catalyst body 46 on the upstream side is provided on the downstream side of the first exhaust gas sensor 44 in the collecting portion 30. The downstream side catalyst body 48 is provided on the downstream side of the upstream side catalyst body 46 in the gathering portion 30. The upstream side catalyst body 46 is formed to have a smaller length in the flow direction of the exhaust G than the downstream side catalyst body 48.

Specifically, the catalyst body 46 on the upstream side is a so-called metal mesh catalyst, and a wire mesh is fixed to the inside of the catalyst tube 54 by welding, and a precious metal catalyst is supported on the wire mesh. More specifically, the catalyst body 46 on the upstream side is configured such that the catalyst is supported on a carrier obtained by sintering a plurality of wire meshes. The catalyst body 46 (one of the catalyst bodies) on the upstream side is formed in a flat plate shape in which a plurality of through holes penetrating in the flow direction of the exhaust gas are formed and extend so as to intersect the flow direction. The catalyst body 46 (one of the catalyst bodies) on the upstream side may be formed in a curved plate shape instead of a flat plate shape. The catalyst body 46 on the upstream side is formed, for example, by stacking a plurality of plate members having through holes formed in the flow direction. Instead of this, the plate members may be stacked in the flow direction to form a gap serving as an exhaust passage between the plate members and the pipe wall.

The upstream catalyst 46 is supported with platinum, for example, with an emphasis on temperature rise, and the upstream catalyst 46 is supported with rhodium, palladium, for example, with an emphasis on purification. .. The upstream side catalyst body 46 (one catalyst body) is formed to have a smaller length in the exhaust flow direction than the downstream side catalyst body 48 (the other catalyst body). However, the material of the catalyst body 46 on the upstream side is not limited to this. For example, the material of the catalyst body 46 on the upstream side may be a noble metal other than platinum and copper.

In the present embodiment, two catalyst bodies 46 on the upstream side are provided along the flow direction of the exhaust gas G. However, the number and material of the catalyst body 46 on the upstream side are not limited to this. That is, the number of catalyst bodies 46 on the upstream side may be one or three or more. When there are a plurality of catalyst bodies 46 on the upstream side, the catalyst body 46 on the most upstream side constitutes one catalyst arranged at a position where the unpurified exhaust gas discharged from the exhaust port 20a is first purified. When a plurality of upstream catalyst bodies 46 are provided, the lengths of the respective catalyst bodies 46 in the flow direction may be the same or different. In that case, the length of the total exhaust gas of the catalyst body 46 on the upstream side in the flow direction may be smaller than that of the catalyst body 48 on the downstream side. Further, when a plurality of upstream catalyst bodies 46 are provided, the same noble metal may be supported on all the upstream catalyst bodies 46, or different noble metals may be supported.

The catalyst body 46 on the upstream side is formed by, for example, plastic working. Specifically, as shown in FIG. 8, in the upstream catalyst body 46, the wire mesh 45 is formed into a curved plate shape by plastic working such as press drawing. In the present embodiment, the catalyst body 46 on the upstream side has a bowl shape curved in the exhaust flow direction D1. Specifically, the upstream end 46a of the exhaust flow direction D1 in the upstream catalyst body 46 is open, and the bottom portion 46b on the downstream side is curved in a hemispherical shape so as to project toward the exhaust flow direction D1. ing.

By forming the curved shape in this way, the supported area of the catalyst can be increased as compared with the one having a disk (circular flat plate) shape having the same diameter. This improves the purification performance. Further, the thermal stress can be released not in the radial direction but in the axial direction (exhaust flow direction D1), that is, it expands and contracts in the axial direction. This improves durability against thermal stress. Further, the curved shape makes it easy to avoid interference with a sensor or the like, and the degree of freedom of arrangement is improved.

Further, in the present embodiment, a part of the bowl-shaped bottom portion 46b of the catalyst body 46 on the upstream side is deformed to increase the area of the catalyst supported on the wire mesh. Specifically, a step portion 46c is formed on the inner peripheral surface of the bottom portion 46b. The step portion 46c may be one or a plurality. This increases the area of the catalyst and improves the purification performance.

Further, in the present embodiment, a tubular portion 46d having a uniform outer diameter is formed in the upstream portion of the exhaust gas flow direction D1 in the upstream catalyst body 46. The tubular portion 46d is partially crushed by plastic working to form a region with few voids. As shown in FIG. 9, the catalyst body 46 on the upstream side is welded to the catalyst tube 54 in the tubular portion 46d having few voids. This improves weldability.

Further, since it is formed in a curved shape, the direction of the holes in the wire mesh is not constant (parallel). That is, the exhaust G is discharged from the catalyst body 46 on the upstream side so as to intersect with each other when viewed from the exhaust flow direction D1. This makes it possible to improve the diffusion effect of the exhaust gas. By improving the diffusion effect of the exhaust gas, the exhaust gas hits the upstream end surface of the catalyst body 48 on the downstream side in a wide range, so that the purification efficiency of the catalyst body 48 on the downstream side can be improved. Further, by improving the diffusion effect of the exhaust gas, the exhaust energy can be attenuated, which can be expected to contribute to the muffling of the exhaust gas.

The catalyst body 48 on the downstream side is composed of, for example, a metal honeycomb structure. Specifically, in the downstream catalyst body 48, a noble metal is supported on a cylindrical carrier having a large number of cells. The catalyst body 48 on the downstream side has a higher purification performance than the catalyst body 46 on the upstream side, and functions as a main catalyst. In other words, the downstream side catalyst body 48 (the other catalyst body) has a larger heat capacity than the most upstream side catalyst body 46 (the other catalyst body).

The upstream end of the downstream collecting pipe 56 is connected to the downstream end of the catalyst pipe 54. The catalyst pipe 54 and the downstream collecting pipe 56 are joined by welding, for example. The second exhaust gas sensor 50 shown in FIG. 3 is provided on the downstream collecting pipe 56. That is, the second exhaust gas sensor 50 is provided on the downstream side of the catalyst body 48 on the downstream side in the collecting portion 30. The second exhaust gas sensor 50 detects a specific component in the exhaust gas. The second exhaust gas sensor 50 is, for example, an oxygen concentration sensor. In the present embodiment, the second exhaust gas sensor 50 is used to detect deterioration of the catalyst bodies 46 and 48. The exhaust chamber 32 is connected to the downstream end of the downstream collecting pipe 56.

As shown in the modified example of FIG. 4, a downstream small-diameter portion 60 having a passage area smaller than that of the catalyst tube 54 is provided on the downstream side of the catalyst tube 54 (catalyst accommodating portion) in the collecting portion 30, and the downstream small-diameter portion is provided. A second exhaust gas sensor 50 may be provided in 60. Specifically, in the downstream collecting pipe 56, the inner diameter of the passage gradually decreases from the upstream end toward the downstream side, and the downstream side small diameter portion 60 is formed. In other words, the downstream side small diameter portion 60 is formed on the downstream side of the downstream side catalyst body 48 (the other catalyst body) in the exhaust passage EP, and the passage area is formed smaller than immediately before and immediately after that. ..

In this modification, the downstream end of the catalyst pipe 54 is connected to the large diameter portion of the upstream end of the downstream small diameter portion 60, and the inlet pipe 32a of the exhaust chamber 32 is connected to the downstream small diameter portion of the downstream small diameter portion 60. ing. That is, after passing through the catalyst pipe 54, in the exhaust passage EP, the inner diameter of the passage gradually becomes smaller in the downstream side small diameter portion 60, and the second exhaust gas sensor 50 is attached to the portion where the inner diameter is smaller than that of the catalyst pipe 54. There is. Further, on the downstream side of the second exhaust gas sensor 50, the downstream collecting pipe 56 is connected to the exhaust chamber 32. As a result, the inlet pipe 32a of the exhaust chamber 32 can be formed with a small diameter.

In the first embodiment of FIGS. 1 to 3, the upstream side small diameter portion 58 is provided, and in the modified example of FIG. 4, the downstream side small diameter portion 60 is provided. However, the exhaust device 38 of the present invention may or may not include both the upstream side small diameter portion 58 and the downstream side small diameter portion 60. Further, the shapes of the upstream side and downstream side small diameter portions 58 and 60 are not limited to the illustrated example.

Next, the flow of the exhaust gas G of the present embodiment will be described with reference to FIG. When the engine E is started, the exhaust G is led out to the four exhaust pipes 28. The exhaust G is merged at the first merging section 40 and the second merging section 42, and flows into the single collecting section upstream pipe 52. In the collecting portion upstream pipe 52, a specific component (for example, oxygen concentration) in the exhaust gas is detected by the first exhaust gas sensor 44.

After passing through the collecting portion upstream pipe 52, the exhaust G flows into the catalyst pipe 54. In the catalyst pipe 54, the exhaust G passes through the catalyst body 46 on the upstream side. The catalyst body 46 on the upstream side is a metal mesh catalyst having a small flow direction dimension (length) of the exhaust gas G, and when the exhaust gas G passes through the catalyst body 46 on the upstream side, it is purified and the temperature rises at an early stage. Will be done. The heated exhaust G is introduced into the catalyst body 48 on the downstream side. The exhaust G is purified as it passes through the catalyst body 48 on the downstream side. Since the exhaust gas G is heated by the catalyst body 46 on the upstream side, the purification performance of the catalyst body 48 on the downstream side is improved.

The exhaust gas G that has passed through the catalyst pipe 54 flows into the collecting portion downstream pipe 56. In the collecting portion downstream pipe 56, a specific component (for example, oxygen concentration) in the exhaust gas is detected by the second exhaust gas sensor 50. After passing through the collecting portion downstream pipe 56, the exhaust G flows into the exhaust chamber 32 of FIG. The exhaust G is muted by the exhaust chamber 32 and the exhaust muffler 36, and then discharged to the outside.

According to the above configuration, the upstream catalyst body 46 shown in FIG. 2 is formed of a wire mesh having a small heat capacity, and the length of the exhaust gas in the flow direction is smaller than that of the downstream catalyst body 48 on the downstream side. Has been done. Since the upstream side catalyst body 46 is rapidly heated to a high temperature and activated by touching the exhaust gas, the exhaust gas G is heated at an early stage, and the heated exhaust gas G flows into the downstream side catalyst body 48. As a result, the catalyst 48 on the downstream side is also activated at an early stage. As a result, the purification performance of the catalyst body 48 on the downstream side of the main is improved. Further, the deterioration of the catalyst bodies 46 and 48 can be detected by the second exhaust gas sensor 50. This improves the reliability of the exhaust device 38 including the catalyst bodies 46 and 48.

The second merging portion 42 is provided with a first exhaust gas sensor 44, an upstream side catalyst body 46, a downstream side catalyst body 48, and a second exhaust gas sensor 50. As a result, the first exhaust gas sensor 44, the upstream side catalyst body 46, the downstream side catalyst body 48, and the second exhaust gas sensor 50 can be used as one. Therefore, the increase in the number of parts is suppressed and the structure is simplified.

Further, the first exhaust gas sensor 44 is provided in the upstream side small diameter portion 58 having a passage area smaller than that of the upstream end opening 52a in the gathering portion 30. As a result, it is possible to suppress the bias of the exhaust G of each exhaust pipe 28 and effectively detect the component of the exhaust G.

Further, the catalyst tubes (large diameter portion) 54 having a larger passage area than the upstream side small diameter portion 58 in the gathering portion 30 are provided with the catalyst bodies 46 and 48 on the upstream side and the downstream side. As a result, the area of the catalyst body 46 on the upstream side can be increased to raise the temperature of the exhaust G at an early stage, and the area of the catalyst body 48 on the downstream side can be increased to improve the purification performance.

As in the modified example of FIG. 4, the second exhaust gas sensor 50 may be provided in the downstream side small diameter portion 60 having a passage area smaller than that of the catalyst pipe 54 (catalyst accommodating portion). As a result, it is possible to suppress the bias of the exhaust G and effectively detect the component of the exhaust G.

FIG. 6 is a schematic view of the engine exhaust device 38A according to the second embodiment of the present invention. In the following description, only the parts different from the first embodiment will be described, and the parts common to the first embodiment will be omitted. In the second embodiment, the first exhaust gas sensor 44 and the upstream catalyst body 46 are provided in each of the two first confluence portions 40, and the downstream side catalyst body 48 and the second confluence portion 42 are provided in the second confluence portion 42. An exhaust gas sensor 50 is provided.

Specifically, in the present embodiment, the first exhaust gas sensor 44 and the upstream catalyst body 46 (one catalyst body) are provided one by one in each of a plurality of (two in the present embodiment) first post-merging region 66a. It is provided. The downstream catalyst body 48 (the other catalyst body) and the second exhaust gas sensor 50 are provided in the singular second post-merging region 66b.

In the second embodiment, when the engine E is started, the exhaust G is led out to the four exhaust pipes 28. The exhaust G is merged at the two first merging portions 40, 40. In each of the first confluence portions 40, 40, a specific component (for example, oxygen concentration) in the exhaust gas is detected by the first exhaust gas sensors 44, 44, and at the same time, it passes through the catalyst bodies 46, 46 on the upstream side. When the exhaust gas G passes through the catalyst bodies 46, 46 on the upstream side, it is purified and the temperature is raised.

After passing through the catalyst bodies 46 and 46 on the upstream side, the exhaust G is merged at the second merging portion 42 and flows into the single catalyst pipe 54. In the catalyst pipe 54, the exhaust G passes through the catalyst body 48 on the downstream side. The exhaust G is purified as it passes through the catalyst body 48 on the downstream side. Since the exhaust G is heated by the catalyst bodies 46 and 46 on the upstream side, the purification performance of the catalyst body 48 on the downstream side is improved.

The exhaust gas G that has passed through the catalyst pipe 54 flows into the collecting portion downstream pipe 56. In the collecting portion downstream pipe 56, a specific component (for example, oxygen concentration) in the exhaust gas is detected by the second exhaust gas sensor 50. After passing through the collecting portion downstream pipe 56, the exhaust G is muted by the exhaust chamber 32 (not shown) and the exhaust muffler 36 (not shown), and then discharged to the outside.

According to the second embodiment, the first exhaust gas sensor 44 and the upstream catalyst body 46 are provided in each of the two first merging portions 40, 40, and the downstream side catalyst body 48 is provided in the second merging portion 42. And a second exhaust gas sensor 50 are provided. Therefore, the length of the catalyst tube 54 can be reduced, and each of the catalyst bodies 46 on the upstream side can be made small.

FIG. 7 is a schematic view of the engine exhaust device 38B according to the third embodiment of the present invention. In the following description, only the parts different from the first and second embodiments will be described, and the parts common to the first and second embodiments will be omitted. In the third embodiment, the first exhaust gas sensor 44, the upstream side catalyst body 46 and the downstream side catalyst body 48 are provided in each of the two first confluence portions 40 and 40, and the second confluence portion 42 is provided with a second exhaust gas sensor 44. The exhaust gas sensor 50 of 2 is provided.

Specifically, in the present embodiment, the first exhaust gas sensor 44, the upstream catalyst 46 (one catalyst) and the downstream catalyst 48 (the other catalyst) are plural (2 in the present embodiment). One) is provided in each of the first post-merging regions 66a. The second exhaust gas sensor 50 is provided in the singular second post-merging region 66b.

In the third embodiment, when the engine E is started, the exhaust G is led out to the four exhaust pipes 28. The exhaust G is merged at the two first merging portions 40, 40. In each of the first confluence portions 40, 40, first, a specific component (for example, oxygen concentration) in the exhaust gas is detected by the first exhaust gas sensors 44, 44.

Subsequently, the exhaust gas G flows into the catalyst bodies 46, 46 on the upstream side. When the exhaust gas G passes through the catalyst bodies 46, 46 on the upstream side, it is purified and the temperature is raised. The exhaust G further flows into the catalyst bodies 48, 48 on the downstream side. The exhaust G is purified as it passes through the catalyst bodies 48, 48 on the downstream side. Since the exhaust G is heated by the catalyst bodies 46, 46 on the upstream side, the purification performance of the catalyst bodies 48, 48 on the downstream side is improved.

After passing through the catalyst bodies 48 and 48 on the downstream side, the exhaust G is merged at the second merging portion 42 and flows into the single collecting portion downstream pipe 56. In the collecting portion downstream pipe 56, a specific component (for example, oxygen concentration) in the exhaust gas is detected by the second exhaust gas sensor 50. After passing through the collecting portion downstream pipe 56, the exhaust G is muted by the exhaust chamber 32 (not shown) and the exhaust muffler 36 (not shown), and then discharged to the outside.

According to the third embodiment, each of the two first confluence portions 40 and 40 is provided with a first exhaust gas sensor 44, an upstream side catalyst body 46 and a downstream side catalyst body 48, and the second confluence portion 42. Is provided with a second exhaust gas sensor 50. As described above, since the upstream side and the downstream side catalyst bodies 46 and 48 are provided in each of the two first confluence portions 40 and 40, the purification performance is good.

The present invention is not limited to the above embodiments, and various additions, changes, or deletions can be made without departing from the gist of the present invention. For example, in the above embodiment, the number of exhaust passages EP is reduced to four, two, and one by merging, but the exhaust passage EP may be branched and increased after merging. In that case, the catalyst body may be provided in the branched and increased portion of the exhaust passage EP.

Further, in the above embodiment, an example in which the exhaust device of the present invention is applied to a motorcycle has been described, but the exhaust device of the present invention can also be applied to a saddle-mounted vehicle such as a three-wheeled vehicle or a four-wheeled vehicle other than a motorcycle. Further, the exhaust device of the present invention can be applied to vehicles other than saddle-mounted vehicles, and can also be applied to engines other than vehicles. Therefore, such things are also included within the scope of the present invention.

20a Exhaust ports 38, 38A, 38B Exhaust device 44 First exhaust gas sensor (upstream exhaust gas sensor)
46 Upstream catalyst (one catalyst)
48 Downstream catalyst (the other catalyst)
50 Second exhaust gas sensor (downstream exhaust gas sensor)
52a Assembly part upstream end opening 54 Catalyst tube (large diameter part, catalyst housing part)
58 Upstream side small diameter part 60 Downstream side small diameter part 62 Pre-merging area 64 Confluence area 66 Post-merging area E Engine EP Exhaust channel

Claims (9)

It is an exhaust device that purifies the exhaust of the engine.
With one catalyst and the other catalyst,
Each catalyst is provided in an exhaust passage connected to the exhaust port of the engine.
The one catalyst body is arranged at a position where the unpurified exhaust gas discharged from the exhaust port is first purified.
An exhaust device in which the other catalyst body is arranged on the downstream side of the one catalyst body and has a larger heat capacity than the one catalyst body. The one catalyst body is formed in the shape of a flat plate or a curved plate having a plurality of through holes penetrating in the flow direction of the exhaust gas and extending so as to intersect the flow direction of the exhaust gas. The exhaust device according to claim 1, which is formed to have a small length. A first exhaust gas sensor provided on the upstream side of the one catalyst body in the exhaust gas passage and detecting a component in the exhaust gas, and a first exhaust gas sensor.
The exhaust device according to claim 1 or 2, further comprising a second exhaust gas sensor provided on the downstream side of the other catalyst body in the exhaust passage and detecting a component in the exhaust. On the upstream side of the one catalyst body in the exhaust passage, an upstream small diameter portion having a smaller passage area than immediately before and immediately after is formed.
The exhaust device according to any one of claims 1 to 3, wherein an upstream exhaust gas sensor for detecting a component in the exhaust is provided in the upstream small diameter portion. On the downstream side of the other catalyst body in the exhaust passage, a small diameter portion on the downstream side having a smaller passage area than immediately before and immediately after is formed.
The exhaust device according to any one of claims 1 to 4, wherein a downstream exhaust gas sensor for detecting a component in the exhaust is provided in the downstream small diameter portion. The engine is a multi-cylinder engine
The exhaust passage has a plurality of pre-merging regions connected to each exhaust port, a merging region in which the plurality of pre-merging regions merge, and a post-merging region extending downstream from the merging region.
The exhaust device according to any one of claims 1 to 5, wherein the one catalyst body is provided in a single post-merging region or in each of a plurality of post-merging regions. 1. The exhaust device according to any one of 6. An exhaust device that purifies the exhaust of a multi-cylinder engine.
One of the catalysts provided in the exhaust passage connected to the exhaust port of the engine to purify the exhaust, and
The other catalyst body provided on the downstream side of the one catalyst body in the exhaust gas passage to purify the exhaust gas, and the other catalyst body.
A first exhaust gas sensor provided on the upstream side of the one catalyst body in the exhaust gas passage and detecting a component in the exhaust gas, and a first exhaust gas sensor.
It is provided with a second exhaust gas sensor provided on the downstream side of the other catalyst body in the exhaust passage to detect components in the exhaust gas.
The one catalyst body is formed in the shape of a flat plate or a curved plate having a plurality of through holes penetrating in the flow direction of the exhaust gas and extending so as to intersect the flow direction of the exhaust gas. Formed small in length,
The exhaust passage has a plurality of pre-merging regions connected to each exhaust port, a merging region in which the plurality of pre-merging regions merge, and a post-merging region extending downstream from the merging region.
The first exhaust gas sensor is an exhaust device provided on the downstream side of the confluence region. A saddle-mounted vehicle provided with the exhaust device according to any one of claims 1 to 8.

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