JPH10311214A - Exhaust system having catalyst - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent reduction in engine output by flow resistance of exhaust gas, and prevent the thermal degradation of a catalyst by arranging a first passage to flow exhaust gas in an exhaust pipe through a catalyst member and a second passage to flow exhaust gas by bypassing the catalyst member. SOLUTION: An exhaust system 10 having a catalyst provided in a motorcycle is composed of an exhaust tube 11, an expanded pipe 13, a cylindrical member 15 having a catalyst, a catalyst member 20 and a silencer 30. The inside of the catalyst member 20 is formed as a passage 33, and a clearance between the catalyst member 20 and the expanded pipe 13 is formed as a passage 34. Exhaust gas flowing in the expanded pipe 13 contacts with a catalyst carried on an inner peripheral surface and an outer peripheral surface of the cylindrical member 15 having a catalyst, and an unburnt component is burnt. The exhaust gas becoming a high temperature separates into currents passing through the passages 33 and 34, and in the current passing through the passage 33, to make the exhaust gas harmless is promoted by a metallic catalyst part 27. On the other hand, the exhaust gas passing through the passage 34 is blown off from the silencer 30 by passing through air vents 25a... of a partition wall 25.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an exhaust device with a catalyst for purifying exhaust gas.

[0002]

2. Description of the Related Art As a catalyst-equipped exhaust device for a motorcycle, there is known, for example, a device disclosed in Japanese Patent Application Laid-Open No. 4-287821, "Exhaust Purification Device for Motorcycles and the Like". As shown in FIG. 4 of the publication,
The catalyst tube 23 is mounted in the expansion chamber 21 of the exhaust pipe (the reference numeral is the one described in the official gazette; the same applies hereinafter) via an outer flange 34 having a vent hole 36.
The conduit 24 is connected to the expansion chamber 21 via a blind outer flange 38.

In this exhaust device with a catalyst, the exhaust gas flowing into the expansion chamber 21 is divided into an exhaust gas flowing inside the catalyst tube 23 and an exhaust gas flowing outside the catalyst tube 23. The exhaust gas flowing into the catalyst tube 23 passes through the conduit 24, converts unburned components into harmless components by a catalytic reaction, and discharges them to the atmosphere. On the other hand, the exhaust gas flowing outside the catalyst tube 23 reaches the downstream outer flange 38 through the vent hole 36 of the outer flange 34, but hits the outer flange 38 because the outer flange 38 has no vent hole. It flows backward to the upstream side. The exhaust gas that has flowed back passes through the catalyst tube 23 and the conduit 24, converts unburned components into harmless components by a catalytic reaction, and flows out to the atmosphere.

[0004]

However, since the exhaust gas flowing outside the catalyst tube 23 hits the rear outer flange 38 and flows backward to the upstream side, especially when the motorcycle is rapidly accelerated, the exhaust gas is not ventilated. The resistance increases excessively and the engine output decreases. Also, when the engine output decreases, the output characteristics of the engine change, so that drivability may deteriorate. Further, due to an increase in the exhaust gas ventilation resistance, harmful components in the exhaust gas may cause an excessive catalytic reaction with the catalyst, and the catalyst may be overheated and may be thermally degraded.

Accordingly, an object of the present invention is to provide a technique for preventing a decrease in engine output due to exhaust gas ventilation resistance, securing drivability, and preventing thermal deterioration of a catalyst.

[0006]

According to a first aspect of the present invention, there is provided an exhaust system with a catalyst having a catalyst member mounted in an exhaust pipe connected to an engine. And a second flow path for exhaust gas bypassing the catalyst member.

Since the exhaust gas is divided into the first flow path and the second flow path, a large amount of exhaust gas can be satisfactorily flowed particularly when the engine has a high output. Further, since a decrease in engine output due to exhaust gas ventilation resistance can be prevented, there is no possibility that the output characteristics of the engine will change, and good drivability can be maintained. Furthermore, since the exhaust gas ventilation resistance can be prevented from being excessive, it is possible to prevent harmful components in the exhaust gas from excessively reacting with the catalyst. As a result, there is no possibility that the catalyst will be overheated by the reaction heat.

[0008] A second aspect of the present invention is characterized in that the catalyst member is attached to the exhaust pipe through a partition wall having a vent, and the vent is formed as a part of the second flow path.

Since the second flow path can be formed in the exhaust pipe only by opening the ventilation hole in the partition wall, the second flow path for exhausting the exhaust gas by bypassing the catalyst member is easily provided in the exhaust pipe. be able to.

[0010]

Embodiments of the present invention will be described below with reference to the accompanying drawings. The drawings should be viewed in the direction of reference numerals. FIG. 1 is a side view of a motorcycle provided with an exhaust device with a catalyst according to the present invention (first embodiment). The motorcycle 1 includes a head pipe 3 attached to a front portion of a main frame 2, a front fork 4 attached to the head pipe 3, a handle 5 attached to an upper end of the front fork 4, and a lower end of the front fork 4. , A two-stroke engine 7 mounted below the main frame 2, an exhaust device 10 with a catalyst mounted on the two-stroke engine 7, and a pivot 36 at the rear end of the main frame 2. Swing arm 37
And a rear wheel 38 attached to the swing arm 37. The exhaust device with catalyst 10 will be described in detail with reference to FIG. 39a is a front fender, 39b is a headlight, 39c is a seat, 39d is a drive chain, and 39e is a rear suspension.

FIG. 2 is a sectional view of an exhaust device with a catalyst (first embodiment) according to the present invention. The exhaust device with catalyst 10
An exhaust tube 11 attached to the two-cycle engine 7 (see FIG. 1), an expansion tube 13 connected to the rear end of the exhaust tube 11, a cylindrical member 15 with a catalyst at the previous stage attached inside the expansion tube 13, It comprises a rear catalyst member 20 attached behind the catalyst-added cylindrical member 15 and a silencer 30 attached to the rear end of the expansion tube 13 (see also FIG. 1). A combination of the exhaust tube 11 and the expansion tube 13 is combined with the exhaust tube 31.
I say. Here, the inside of the catalyst member 20 is referred to as a first flow path 33, and the gap between the catalyst member 20 and the expansion pipe 13 is referred to as a second flow path 34. Reference numeral 32 denotes a mounting bracket for mounting the expansion tube 13 to the vehicle body.

The catalyst-equipped cylindrical member 15 in the first stage is formed by punching metal supporting a catalyst into a cylindrical shape, and is formed by a front support member 16 and a rear support member 17 with an expansion tube 13.
It is a member attached inside. The latter catalyst member 20 includes a catalytic converter 21 described later and a cylindrical body 23 attached to the rear end of the catalytic converter 21. Reference numeral 24 denotes a support fitting 25 for stopping the catalytic converter 21 on the expansion tube 13, and a partition wall 25 for stopping the cylindrical body 23 to the expansion tube 13.

The above-described catalytic converter 21 includes an outer cylinder 26
And a metal catalyst part 27 mounted in the outer cylinder 26. The metal catalyst part 27 is separated from the outer cylinder 26 by L (20 to 40 m).
m). By adjusting the flow of the exhaust gas during this L, it is possible to prevent the ventilation resistance of the exhaust gas from excessively increasing. The metal catalyst unit 27 will be described in detail with reference to FIG.

FIG. 3 is a sectional view taken along line 3-3 of FIG. The metal catalyst portion 27 is a member in which a corrugated plate 28a carrying a catalyst and a flat plate 28b carrying a catalyst are alternately wound.
8a and a plurality of small air holes (hereinafter, referred to as “core”) 29 formed by the flat plate 28b. The cores 29 are ventilation holes through which the exhaust gas passes, and constitute a part of the first flow path 33 shown in FIG. This metal catalyst part 27
Has the advantage of being less likely to break as compared to ceramic catalysts.

FIG. 4 is a sectional view taken along line 4-4 of FIG. The partition wall 25 is a donut-shaped flat plate attached between the expansion tube 13 and the cylindrical body 23, and has, for example, eight air holes 25a. The ventilation holes 25a are connected to the second flow path 34 shown in FIG.
A part of. The diameter and the number of holes of these ventilation holes 25a are set so that the opening ratio of the partition wall 25 is 2 to 3%. 10 to 10 of the exhaust gas flowing through the exhaust pipe 31
This is to allow 20% of the exhaust gas to flow backward through the ventilation holes 25a.

The operation of the above-described exhaust device with catalyst according to the present invention (first embodiment) will be described below. FIG. 5 is an operation explanatory view of the exhaust device with catalyst (first embodiment) according to the present invention. Exhaust gas flowing from the exhaust tube 11 into the expansion tube 13 as shown by the arrow flows through the expansion tube 13 from left to right in the figure, during which the exhaust gas contacts the catalyst supported on the inner and outer peripheral surfaces of the cylindrical member 15 with catalyst. Then, unburned components burn.
This combustion makes the exhaust gas harmless, and the combustion heat makes it possible to raise the temperature of the exhaust gas.

The exhaust gas which has become high temperature is next indicated by arrows,
, And so on. That is, the arrow points to the first flow path 3
3, the second-stage catalytic reaction occurs in the metal catalyst section 27, and the detoxification of exhaust gas can be promoted. The reaction in the metal catalyst section 27 is favorable because the exhaust gas has a high temperature. Thereafter, the exhaust gas reaches the silencer 30 as shown by the arrow.

On the other hand, the exhaust gas passing through the second flow path 34 passes through the outside of the catalyst member 20 as indicated by an arrow, and further passes through the ventilation holes 25a of the partition wall 25 as indicated by an arrow, from the silencer 30 to the atmosphere. discharge.

As described above, since the exhaust gas in the expansion pipe 13 is made to flow separately to the first flow path 33 and the second flow path 34, a large amount of exhaust gas can be satisfactorily flowed even at a high engine output. be able to. Since the engine output can be prevented from lowering due to exhaust gas ventilation resistance, there is no possibility that the output characteristics of the engine will change, and good drivability can be maintained. Further, since the ventilation resistance of the exhaust gas does not become excessive, there is no danger that the harmful components in the exhaust gas will excessively react with the catalyst and the catalyst will overheat due to the heat of reaction.

A second embodiment will be described. FIG. 6 is a cross-sectional view of an exhaust device with a catalyst (second embodiment) according to the present invention. Catalyst member 41 of exhaust device 40 with catalyst
The reduced diameter portion 42 is attached to the rear end of the cylindrical body 42 attached to the outer cylinder 26.
a is provided.

The operation of the exhaust device with a catalyst (second embodiment) will be described below. FIG. 7 is an operation explanatory view of the exhaust device with a catalyst (second embodiment) according to the present invention. Since the flow of the exhaust gas is the same as that of the first embodiment up to the arrows,,,, the description thereof is omitted, and the flow of the arrows,, is described.

A part of the exhaust gas flowing backward from the ventilation holes 25a of the second flow path 34 merges with the exhaust gas indicated by the arrows as indicated by arrows and is discharged from the silencer 30 to the atmosphere. Then, the remaining exhaust gas returns to the upstream side along the reduced diameter portion 42a as shown by the arrow. At this time,
Since the exhaust gas can be maintained in a rectified state by the reduced diameter portion 42a, the flow of the exhaust gas is not disturbed.

Next, a third embodiment will be described. FIG. 8 is a cross-sectional view of an exhaust device with a catalyst (third embodiment) according to the present invention, and the same members as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted. Catalyst member 51 of exhaust device 50 with catalyst
Is characterized in that a collar 52 is attached to the rear end of the cylindrical body 23. The collar 52 is a tubular body formed so as to reduce its diameter toward the rear, and has a rear end outer periphery of the cylindrical body 23 and the partition wall 2.
5 is a member welded to FIG.

The operation of the exhaust device with a catalyst (third embodiment) will now be described. FIG. 9 is an operation explanatory view of the exhaust device with catalyst (third embodiment) according to the present invention. As in the second embodiment, the flow of the exhaust gas is indicated by arrows,,,,.
, And are the same as those in the first embodiment, and the description thereof will be omitted.

A part of the exhaust gas flowing backward from the ventilation holes 25a of the second flow path 34 merges with the exhaust gas indicated by the arrows as indicated by the arrows and is discharged from the silencer 30 into the atmosphere. Then, the remaining exhaust gas returns to the upstream side along the collar 52 as shown by arrows. At this time, since the exhaust gas can be maintained in a rectified state by the collar 52,
Exhaust gas flow is not disrupted.

[0026]

According to the present invention, the following effects are exhibited by the above configuration. Since the exhaust gas is divided into the first flow path and the second flow path, a large amount of exhaust gas can be satisfactorily flowed particularly when the engine has a high output. As a result, the ventilation resistance of the exhaust gas passing through the exhaust pipe at the time of high output of the engine does not become excessive, and there is no possibility that the engine output decreases. Further, since a decrease in engine output due to exhaust gas ventilation resistance can be prevented, there is no possibility that the output characteristics of the engine will change, and good drivability can be maintained. Furthermore, since the ventilation resistance of the exhaust gas does not become excessive, it is possible to prevent harmful components in the exhaust gas from excessively reacting with the catalyst. As a result, there is no possibility that the catalyst will be overheated due to the reaction heat, and the catalyst can be prevented from being thermally degraded.

According to the second aspect, the second flow path can be formed in the exhaust pipe only by opening the ventilation hole in the partition wall.
A second flow path for exhausting exhaust gas by bypassing the catalyst member can be easily provided in the exhaust pipe. As a result, an increase in the cost of the exhaust device with a catalyst can be suppressed.

[Brief description of the drawings]

FIG. 1 shows an exhaust device with a catalyst according to the present invention (first embodiment).
Side view of a motorcycle equipped with

FIG. 2 is an exhaust device with a catalyst according to the present invention (first embodiment).
Cross section of

FIG. 3 is a sectional view taken along line 3-3 in FIG. 1;

FIG. 4 is a sectional view taken along line 4-4 in FIG. 1;

FIG. 5 is an exhaust device with a catalyst according to the present invention (first embodiment).
Action explanation diagram

FIG. 6 is an exhaust device with a catalyst according to the present invention (second embodiment).
Cross section of

FIG. 7 is an exhaust device with a catalyst according to the present invention (second embodiment).
Action explanation diagram

FIG. 8 is an exhaust device with a catalyst according to the present invention (third embodiment).
Cross section of

FIG. 9 is an exhaust device with a catalyst according to the present invention (third embodiment).
Action explanation diagram

[Explanation of symbols]

7: engine (two-cycle engine), 10: exhaust device with catalyst, 20: catalyst member, 25: partition wall, 25a: vent hole, 31: exhaust pipe, 33: first flow path, 34: second flow path.

Claims (2)

[Claims] 1. An exhaust system with a catalyst, wherein a catalyst member is mounted in an exhaust pipe connected to an engine.
An exhaust device with a catalyst, comprising: a first flow path through which exhaust gas flows through the catalyst member; and a second flow path through which exhaust gas bypasses the catalyst member. 2. The catalyst according to claim 1, wherein the catalyst member is attached to an exhaust pipe through a partition wall having a vent hole, and the vent hole is a part of the second flow path. With exhaust device.