JP2001012239A - Engine exhaust purifier - Google Patents

Abstract

(57) Abstract: A casing including a tapered portion connected to a small-diameter end of a connecting pipe connected to an exhaust pipe for guiding exhaust gas from an engine, and a cylindrical portion connected to a large-diameter end of the tapered portion. A catalyst carrier having a circular outer surface having a diameter larger than the outer diameter of the connection pipe and carrying a catalyst, wherein the upstream end of the catalyst support is disposed so as to face the downstream end of the connection pipe; In the purifier, it is possible to quickly raise the temperature of the catalyst while avoiding a decrease in output torque in a low-speed rotation range of the engine, and to prevent deterioration of ventilation resistance in the catalyst carrier during high-load operation of the engine. A connecting pipe is connected to a position where a downstream end of the connecting pipe is opposed to an upstream end of a catalyst carrier at an interval.
The small diameter end of the tapered portion 26 protrudes into the casing 24.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a tapered portion connected to a small-diameter end of a connecting pipe connected to an exhaust pipe for guiding exhaust gas from an engine, and a cylindrical portion connected to a large-diameter end of the tapered portion. An engine in which a catalyst carrier having a circular outer surface having a diameter larger than the outer diameter of the connection pipe and supporting a catalyst is disposed in a casing, with an upstream end of the catalyst support facing a downstream end of the connection pipe. Exhaust purifier.

[0002]

2. Description of the Related Art Conventionally, such an exhaust gas purifier is already known, for example, from Japanese Utility Model Application Laid-Open No. 55-135118, in which a downstream end of a connecting pipe connected to an exhaust pipe is provided.
It is connected to the small diameter end of the tapered portion in the casing.

[0003]

In a small-displacement engine mounted on a motorcycle or the like, the temperature of the catalyst carried on the catalyst carrier must be raised from the engine to the catalyst carrier in order to quickly raise the temperature to the activation temperature. It is preferable that the distance between the exhaust pipe and the connecting pipe is short when the exhaust gas purifier is arranged as described above.
However, when the axial distance between the exhaust pipe and the connecting pipe is reduced in the low-speed rotation range of the engine, the output torque of the engine is reduced. Therefore, it is desirable that the axial distance between the exhaust pipe and the connecting pipe be long. Therefore, it is conceivable to set the opening angle of the tapered portion in the casing to be large to extend the axial distance between the exhaust pipe and the connection pipe.
As the downstream end of the exhaust pipe approaches the upstream end of the catalyst carrier, the volume occupied by the tapered portion decreases, resulting in deterioration of airflow resistance in the catalyst carrier during high-load operation of the engine.

The present invention has been made in view of the above circumstances, and enables early temperature rise of a catalyst while avoiding reduction of output torque in a low-speed rotation range of an engine. It is an object of the present invention to provide an exhaust gas purifier for an engine capable of preventing deterioration of ventilation resistance in a carrier.

[0005]

In order to achieve the above object, according to the first aspect of the present invention, a connecting pipe connected to an exhaust pipe for guiding exhaust gas from an engine is connected to a small-diameter end; In a casing having a cylindrical portion connected to the large-diameter end of the tapered portion, a catalyst carrier having a circular outer surface having a larger diameter than the outer diameter of the connection pipe and supporting the catalyst is provided at the upstream end of the catalyst carrier. In an exhaust gas purifier of an engine arranged to face a downstream end of the connection pipe, the connection pipe may be tapered until the downstream end of the connection pipe faces the upstream end of the catalyst carrier at an interval. The casing is inserted into the casing from a small-diameter end of the section.

According to such a configuration, even if the distance from the engine to the catalyst carrier is set as short as possible to quickly raise the temperature of the catalyst to the activation temperature, the opening angle of the tapered portion is not set large, It is possible to prevent the axial distance between the exhaust pipe and the connection pipe from becoming short. Therefore, it is possible to prevent the output torque from being reduced in the low-speed rotation range of the engine, and to make the volume occupied by the tapered portion relatively large, so that the catalyst carrier can be used as a buffer chamber at the time of high-load operation of the engine. Can be prevented from being deteriorated.

[0007] The invention according to claim 2 provides the above-described claim 1.
In addition to the configuration of the invention described in the above, the inner diameter of at least the downstream end of the connection pipe is set to be smaller than the inner diameter of the exhaust pipe. Exhaust gas will flow toward the part,
When the engine is started, the temperature of the catalyst supported on the center of the catalyst carrier can be quickly raised to the activation temperature.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described based on one embodiment of the present invention shown in the attached drawings.

1 to 5 show one embodiment of the present invention. FIG. 1 is a right side view of a motorcycle, FIG. 2 is a longitudinal sectional view of an exhaust gas purifier and a muffler, and FIG. 3 is FIG. Main part enlarged view of
FIG. 4 is a sectional view taken along line 4-4 in FIG. 3, and FIG. 5 is a view showing a change in the catalyst center temperature depending on the throttle ratio in the connecting pipe.

First, in FIG. 1, a body frame F of this backbone type motorcycle includes a backbone 5 made of a steel pipe inclined backward and downward, and a rear frame 6 made of a steel plate welded to the rear end of the backbone 5. Things,
A front fork 8 for pivotally supporting the front wheel WF is pivotably supported by a head pipe 7 provided at a front end of the backbone 5 so as to be steerable. A steering handle 9 is connected to an upper end of the front fork 8. A rear fork 10 for pivotally supporting the rear wheel WR is pivotally supported on the rear frame 6.
And a rear cushion 11 is provided between the rear frames 6. Further, a saddle 12 is mounted on the upper surface of the rear frame 6.
The fuel tank 13 is stored and held therein. Further, a crankcase 14 of the engine E is mounted below the joint with the backbone 5 at the front end of the rear frame 6.

An air cleaner 15 is attached to the front end of the backbone 5. Engine E cylinder head 16
The air cleaner 15 is connected to an intake port (not shown) provided through a horn pipe 17, a throttle body 18 and an intake pipe 19, and an intermediate portion of the intake pipe 19 is provided with fuel toward the intake port. Is mounted.

An exhaust port (not shown) provided below the cylinder head 16 is connected to an upstream end of an exhaust pipe 21 for guiding exhaust gas from the engine E.
The downstream end of 1 is connected to a casing 24 that is common to the exhaust gas purifier 22 and the muffler 23 disposed on the rear right side of the body frame F.

2 and 3, the casing 24
A cylindrical portion 25, a tapered portion 26 in which one end of the cylindrical portion 25 is coaxially connected to a large diameter end, for example, coaxially;
And a terminal wall 27 fixed to the other end of the
The exhaust purifier 22 includes a catalyst carrier 28 disposed coaxially with the cylindrical portion 25 in a portion near one end of a casing 24.

With further reference to FIG.
Reference numeral 8 denotes a honeycomb cylindrical shape having a circular outer surface and extending coaxially with the casing 24 by superposing a flat plate 29 and a corrugated plate 30 made of, for example, stainless steel and spirally winding the same, not shown. The catalyst is the catalyst carrier 2
8 carried.

The catalyst carrier 28 is accommodated and held in a catalyst case 31 made of the same material as the catalyst carrier 28, for example, stainless steel. That is, the catalyst case 31 is formed in a cylindrical shape longer than the catalyst carrier 28, and the catalyst carrier 28
Are fitted into the catalyst case 31 such that both ends thereof are located inside the both ends of the catalyst case 31, and the catalyst carrier 28 is welded to the catalyst case 31 in the fitted state. The catalyst case 31 is disposed, for example, concentrically in the cylindrical portion 25 such that one end in the longitudinal direction protrudes into the tapered portion 26, and is supported by the cylindrical portion 25 by a support member 32.

The support member 32 has a support cylindrical portion 32a which is slidably fitted from one end in the longitudinal direction of the catalyst case 31 to an intermediate portion in the longitudinal direction, and extends radially outward from the other end of the support cylindrical portion 32a. An overhanging flange portion 32b and a mounting cylindrical portion 32c which is connected to the outer peripheral edge of the flange portion 32b and fitted to the inner surface of the cylindrical portion 25 are integrally formed, and are the same as the catalyst carrier 28 and the catalyst case 31. It is formed of a material such as stainless steel.

One end of the support cylindrical portion 32a is connected to the catalyst case 31.
Is welded and fixed to one end. At this time, one end of the catalyst case 31 projecting from one end of the catalyst carrier 28 is attached to the support cylindrical portion 3.
By welding one end of 2a, it is possible to avoid as much as possible the influence of heat during welding on the catalyst carried on the catalyst carrier 28. The outer peripheral edge of the mounting cylindrical portion 32c, that is, the flange portion 32b is a cylindrical portion 2 of the casing 24.
5 is welded and fixed to the inner surface.

When the temperature of the exhaust gas is relatively high, the support cylindrical portion 32a and one end of the catalyst case 31, which are welded and fixed to each other, are set at the upstream end as in this embodiment. However, if the temperature of the exhaust gas is relatively low, which is slightly higher than the activation temperature of the catalyst, it is preferable to set the temperature at the downstream end. That is, when the exhaust gas discharged from the engine E along with the start of the engine E flows from the upstream side to the downstream side through the catalyst carrier 28, the temperature of the catalyst carrier 28 is reduced by the catalytic reaction when the catalyst reaches the activation temperature. The temperature gradually increases from the upstream end, and the temperature of the catalyst case 31 also increases sequentially from the upstream end. At this time, the support member 3
Since one end of the second support cylindrical portion 32a is welded and fixed to the upstream end of the catalyst case 31, it is possible to prevent an excessive stress due to a difference in thermal expansion from acting on the welded and fixed portion. Therefore, when the temperature of the exhaust gas is relatively high, one end of the support cylindrical portion 32a is welded and fixed to the upstream end of the catalyst case 31. On the other hand, since the heat transfer effect from the catalyst case 31 to the casing 24 is generated by the support member 32, one end of the support cylindrical portion 32a may be turned off when the temperature of the exhaust gas is only relatively low, slightly exceeding the activation temperature. If the catalyst is welded and fixed to the upstream end of the catalyst case 31, the heat transfer to the casing 24 by the support member 32 delays the temperature rise of the catalyst and delays the start of the catalytic reaction. Is desirably welded and fixed to the downstream end of the catalyst case 31.

A small diameter end of the tapered portion 26 of the casing 24 is provided with a cap 33, and a connection pipe 34 is coaxially connected to the small diameter end of the tapered portion 26 via the cap 33. Thus, the downstream end of the exhaust pipe 21 is coaxially connected to the connection pipe 34.

The cap 33 has a small-diameter cylindrical portion 33a and is formed in a stepped cylindrical shape. The small-diameter cylindrical portion 33a protrudes outward from the tapered portion 26 so as to be coaxial with the small-diameter end of the tapered portion 26. Is welded and fixed.

The connecting pipe 34 is formed by welding and fixing an outer pipe 35 and an inner pipe 36 inserted into the outer pipe 35 so that both ends protrude outward from both ends of the outer pipe 35. Things.
Thus, the downstream end of the connection pipe 34, that is, the inner pipe 3
6 is inserted into the casing 24 from the small-diameter end of the tapered portion 26 to a position where the downstream end faces the upstream end of the catalyst carrier 28 at an interval L, and the connection pipe 34 is connected to the small-diameter cylinder of the cap 33. Through the part 33 and the outer pipe 35
Is welded and fixed to the cap 33.

Further, the outer diameter of the inner pipe 36 is set so as to fit into the exhaust pipe 21, and the downstream end of the exhaust pipe 21 is fitted with the upstream end of the inner pipe 36. Downstream end of exhaust pipe 21 and outer pipe 3
5 are welded and fixed to each other.

Incidentally, at least the downstream end of the connecting pipe 34, in this embodiment, the inner diameter D1 over the entire length of the connecting pipe 34
That is, the inner diameter D1 of the inner pipe 36 is
The exhaust gas from the exhaust pipe 21 is throttled by the connection pipe 34 and introduced into the casing 24.

By narrowing at least the downstream end of the connecting pipe 34, exhaust gas flows from the connecting pipe 34 toward the center of the catalyst carrier 28. The temperature of the catalyst supported on the portion can be quickly raised. At this time, (D
The catalyst temperature at the center of the catalyst carrier 28 when (1 / D2) is changed is as shown in FIG.
If it is less than 5, the effect of intensively directing the flow of the exhaust gas to the center of the catalyst carrier 28 cannot be obtained, and the temperature rise of the catalyst center is insufficient. If D1 / D2 exceeds 0.40, the exhaust gas , The exhaust gas amount is reduced and the temperature of the catalyst center is not sufficiently increased. Therefore 0.05 ≦
It is desirable to set D1 / D2 ≦ 0.40.

Further, if the distance L between the downstream end of the connecting pipe 34 and the upstream end of the catalyst carrier 28 is too small, it causes the local deterioration of the catalyst to be accelerated.
When starting, the effect of rapidly increasing the temperature of the catalyst supported on the center of the catalyst carrier 28 cannot be obtained, so that in practice, 0.5 × D1 to 5 × D1, more preferably 0.5 × D1 to 5 × D1 It is desirable to set the interval L at × D1 to × D1.

Referring again to FIG. 2, the muffler 23 includes a first expansion chamber 37, a second expansion chamber 38, and a fourth expansion chamber 40 in the casing 24 in order from the upstream side along the axial direction.
And a third expansion chamber 39. The first expansion chamber 37 has a casing between the tapered portion 26 and the flange portion 32b of the support member 32 so as to face the upstream end of the catalyst carrier 28. 24.

A cylindrical body 41 is inserted into the casing 24 in the rear half of the cylindrical part 25 on the downstream side so as to form a slight gap with the inner surface of the cylindrical part 25. , 41b... Protruding from the upstream end and the downstream end of the cylindrical portion 25 are welded and fixed to the inner surface of the cylindrical portion 25.

The second expansion chamber 38 includes a partition wall 42 having an outer periphery fixed to a substantially central inner surface of the cylindrical body 41 so as to partition the inside of the cylindrical body 41 into an upstream half and a downstream half. It is formed in the casing 24 between the support member 32 and the downstream end of the catalyst carrier 28 faces the second expansion chamber 38.
The flange portion 32b of the support member 32 also functions as a partition separating the first and second expansion chambers 37 and 38.

The third expansion chamber 39 is formed in the casing 24 between the partition wall 43 whose outer periphery is fixed to the inner surface near the downstream end of the cylindrical body 41 and the terminal wall 27, and the fourth expansion chamber 40 is formed of the partition wall. It is formed in the cylindrical body 41 between 42 and 43.

Between the second and third expansion chambers 38, 39, a pair of communicating pipes 44, both ends of which are supported by partition walls 42, 43, are provided.
The third and fourth expansion chambers 39 and 40 are communicated by a pair of communication pipes 45 supported by a partition 43. In addition, a single discharge pipe 46 whose upstream end is opened to the fourth expansion chamber 40 and whose downstream end is opened to the outside penetrates the center of the partition 43 and the terminal wall 27, and is connected to the partition 43 and the terminal wall 27. The exhaust gas is fixed and supported, and is finally discharged from the discharge pipe 46.

Next, a description will be given of this embodiment. A connecting pipe 34 connected to an exhaust pipe 21 for guiding exhaust gas from the engine E has a downstream end opposed to an upstream end of the catalyst carrier 28 at an interval. Up to a position where the catalyst 24 enters the casing 24 from the small-diameter end of the tapered portion 26 of the casing 24, so that the distance from the engine E to the catalyst carrier is set as short as possible in order to quickly raise the temperature of the catalyst to the activation temperature. Also, it is possible to prevent the axial distance between the exhaust pipe 21 and the connection pipe 34 from becoming short without setting the opening angle of the tapered portion 26 large. Therefore engine E
Can be prevented from decreasing in the low-speed rotation region of the engine E, and the volume occupied by the tapered portion 26, that is, the volume of the first expansion chamber 37, is made relatively large to serve as a buffer chamber during high-load operation of the engine E. By using the catalyst carrier, it is possible to prevent the deterioration of the ventilation resistance in the catalyst carrier 28.

Further, since the inner diameter D1 of at least the downstream end of the connecting pipe 34 is set smaller than the inner diameter D2 of the exhaust pipe 21, exhaust gas flows from the connecting pipe 34 toward the center of the catalyst carrier 28. That is, when the engine E is started, the temperature of the catalyst supported on the center of the catalyst carrier 28 can be quickly raised to the activation temperature.

Further, the cylindrical portion 25 provided in the casing 24
Inside, a cylindrical catalyst case 31 for holding a catalyst carrier 28 supporting a catalyst is arranged, for example, concentrically, and a support member 32 for supporting the catalyst case 31 on the cylindrical portion 25 extends longitudinally from one end in the longitudinal direction of the catalyst case 31. A support cylindrical portion 32a having an intermediate portion in the direction relative to each other and slidably fitted thereto, and one end of which is fixed to one end of the catalyst case 31;
Flange 32b extending radially outward from the other end of 2a
The outer peripheral edge of the flange portion 32b (the mounting cylindrical portion 32c in this embodiment) is fixed to the inner surface of the cylindrical portion 25. Therefore, the single supporting member 32 allows the catalyst case 31 to be deformed by thermal expansion of the catalyst case 31.
Can be supported by the cylindrical portion 25 of the casing 24,
Moreover, since the support member 32 has a simple shape, the number of components for supporting the catalyst case 31 can be reduced, and the cost can be reduced.

The outer peripheral edge of the flange portion 32b extending radially outward from the other end of the support cylindrical portion 32a is fixed to the cylindrical portion 25 of the casing 24 at a position corresponding to the longitudinal middle portion of the catalyst case 31. The support member 32 is fixed to the cylindrical portion 25 at a position near the position of the center of gravity of the catalyst carrier 28 and the catalyst case 31. It can be minimized.

Further, since the heat transfer area of the heat transfer path between the cylindrical portion 25 of the casing 24 and the catalyst case 31 is smaller than that of the conventional one using a plurality of supporting members, the catalyst is less affected by the external temperature. In particular, the catalyst case 31
Among them, the influence of the external temperature on the catalyst carried on the catalyst carrier 28 in the portion of the support member 32 that is not fitted to the support cylindrical portion 32a becomes smaller, and the catalyst temperature can be further stabilized.

Moreover, the silencer 23 is formed by partitioning the inside of the casing 24 into a plurality of expansion chambers 37 to 40 in the axial direction thereof.
The first expansion chamber 37 facing the upstream end of the catalyst carrier 28
And the second expansion chamber 38 facing the downstream end of the catalyst carrier 28, so that the exhaust gas purifier 22 constitutes a part of the muffler 23 with the casing 24 in common. The number of parts can be reduced, and the size and weight can be reduced.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various design changes can be made without departing from the present invention described in the appended claims. It is possible to do.

For example, in the above embodiment, the exhaust purifier 22
Although the muffler 23 and the muffler 23 are configured in the common casing 24, the present invention can be applied to an exhaust gas purifier configured independently of the muffler 23.

[0039]

As described above, according to the first aspect of the present invention, even if the distance from the engine to the catalyst carrier is set as short as possible in order to quickly raise the temperature of the catalyst to the activation temperature, the opening of the tapered portion is increased. Without setting a large angle, it is possible to prevent the axial distance between the exhaust pipe and the connection pipe from becoming short,
It is possible to prevent the output torque from being reduced in the low-speed rotation range of the engine, and to make the volume occupied by the tapered portion relatively large, so that it can be used as a buffer chamber during high-load operation of the engine, and Deterioration of ventilation resistance can be prevented.

According to the second aspect of the present invention, the temperature of the catalyst supported on the central portion of the catalyst carrier can be quickly raised to the activation temperature when the engine is started.

[Brief description of the drawings]

FIG. 1 is a right side view of a motorcycle.

FIG. 2 is a vertical sectional view of an exhaust gas purifier and a silencer.

FIG. 3 is an enlarged view of a main part of FIG. 2;

FIG. 4 is a sectional view taken along line 4-4 of FIG. 3;

FIG. 5 is a diagram showing a change in catalyst center temperature depending on a throttle ratio in a connection pipe.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 21 ... Exhaust pipe 22 ... Exhaust gas purifier 24 ... Casing 25 ... Cylindrical part 26 ... Tapered part 28 ... Catalyst carrier 34 ... Connection pipe E ... Engine

[Procedure amendment]

[Submission date] May 16, 2000 (2000.5.1)
6)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0021

[Correction method] Change

[Correction contents]

The connecting pipe 34 is formed by welding and fixing an outer pipe 35 and an inner pipe 36 inserted into the outer pipe 35 so that both ends protrude outward from both ends of the outer pipe 35. Things.
Thus, the downstream end of the connection pipe 34, that is, the inner pipe 3
6 is inserted into the casing 24 from the small-diameter end of the tapered portion 26 to a position where the downstream end faces the upstream end of the catalyst carrier 28 at an interval L, and the connection pipe 34 is connected to the small-diameter cylinder of the cap 33. part 33 a pierces the outer pipe 3
5 is welded and fixed to the cap 33.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0024

[Correction method] Change

[Correction contents]

By narrowing at least the downstream end of the connecting pipe 34, exhaust gas flows from the connecting pipe 34 toward the center of the catalyst carrier 28. The temperature of the catalyst supported on the portion can be quickly raised. On this occasion,
The catalyst temperature at the center of the catalyst carrier 28 when {(D2-D1) / D2 } is changed is as shown in FIG.
If {(D2-D1) / D2 } is less than 0.05, the effect of directing the flow of exhaust gas to the center of the catalyst carrier 28 cannot be obtained, and the temperature rise of the catalyst center temperature is insufficient.
When {(D2-D1) / D2 } exceeds 0.40, the exhaust gas is excessively throttled and the amount of the exhaust gas is reduced, so that the temperature rise of the catalyst center temperature is insufficient. Therefore 0.05 ≦
It is desirable to set {(D2−D1) / D2 } ≦ 0.40.

[Procedure amendment 3]

[Document name to be amended] Drawing

[Correction target item name] Fig. 5

[Correction method] Change

[Correction contents]

FIG. 5

Claims (2)

[Claims] 1. A tapered portion (26) connected to a small-diameter end portion of a connecting pipe (34) connected to an exhaust pipe (21) for guiding exhaust gas from an engine (E), and a large-sized tapered section (26). A casing (2) having a cylindrical portion (25) connected to the radial end;
4) A catalyst carrier (28) having a circular outer surface having a diameter larger than the outer diameter of the connecting pipe (34) and supporting a catalyst is provided inside the connecting pipe (34) at the upstream end of the catalyst carrier (28). 34) In an exhaust gas purifier of an engine arranged to face the downstream end of
The connecting pipe (34) extends from the small-diameter end of the tapered portion (26) to the casing until the downstream end of the connecting pipe (34) is opposed to the upstream end of the catalyst carrier (28) at intervals. (24) An exhaust gas purifier for an engine, which is inserted into the inside. 2. The exhaust gas purifier according to claim 1, wherein an inner diameter of at least a downstream end of the connection pipe is set smaller than an inner diameter of the exhaust pipe.