JPH08100643A - Holding structure for catalyst - Google Patents

Abstract

PURPOSE: To prevent damage of catalyst by avoiding direct contact to external air, providing satisfactory moisture keeping performance, improving exhaust emission control performance, and eliminating thermal expansion difference between a catalyst and a catalyst case. CONSTITUTION: A catalyst 28 held by a catalyst case 30 is arranged inside an exhaust pipe composed of an upstream side exhaust pipe 24-1 and a downstream side exhaust pipe 24-2. A holding flange 32 is provided on the catalyst case 30, and is arranged between an upstream side connection flange 36 of the upstream side exhaust pipe 24-1 and a downstream side connection flange 44 of the downstream side exhaust pipe 24-2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalyst holding structure, and more particularly to a catalyst holding structure which can improve exhaust purification performance and prevent damage to the catalyst.

[0002]

2. Description of the Related Art In a vehicle engine, a catalyst device is provided in the middle of an exhaust pipe in order to convert harmful exhaust gas from a combustion chamber into harmless exhaust gas by the action of a catalytic substance under a predetermined gas composition and temperature conditions. ing. In this catalytic device,
In general, a catalyst in which a catalyst substance that reacts with exhaust gas is held on a metal carrier is held by a catalyst case (outer cylinder).

Examples of this catalyst holding structure are shown in FIGS. 8, 9, and 10, respectively.

In FIG. 8, 102 is an exhaust pipe and 104 is a catalyst. The catalyst 104 is held by the catalyst case 106. A holding flange 108 is fixed to the upstream end portion of the catalyst case 106 by welding. The holding flange 108 is connected to the upstream exhaust pipe 102 via the gasket 10 that serves as a seal at the connecting portion.
-1 for connecting bolts 114 to the upstream connecting flange 112
Are linked by. Further, the downstream exhaust pipe 102-2 is connected to the downstream end portion of the catalyst case 106 by welding. Therefore, the catalyst 104 held by the catalyst case 106 is retained by the holding flange 108 and the downstream exhaust pipe 102-2 in the upstream exhaust pipe 102-.
1 and the downstream exhaust pipe 102-2. At this time, the outer surface of the catalyst case 106 is in direct contact with the outside air.

Further, in FIG. 9, 202 is an exhaust pipe, 2
Reference numeral 04 is a catalyst. The catalyst 204 is used in the catalyst case 2.
Hugged by 06. This catalyst case 206
The upstream exhaust pipe 202-1 is directly connected to the upstream end portion of the by welding or the like. In addition, the catalyst case 20
A downstream side exhaust pipe 202-2 is directly connected to the downstream side end portion of 6 by welding or the like. Therefore, the catalyst 204 held by the catalyst case 206 is held by the upstream side exhaust pipe 202-1 and the downstream side exhaust pipe 202-2.
At this time, the outer surface of the catalyst case 206 is in direct contact with the outside air.

Further, in FIG. 10, 302 is an exhaust pipe,
304 is a catalyst. In this catalyst 304, one end side of an upstream bracket 308 is fixed by welding to an upstream end portion of a catalyst case 306. Further, the downstream bracket 31 is provided at the downstream end portion of the catalyst case 306.
One end side of 0 is fixed by welding. The catalyst 304 held in the catalyst case 306 is the exhaust pipe 3
02, and the other end side of the upstream bracket 308 and the other end side of the downstream bracket 310 are respectively fixed to the exhaust pipe 302 by welding so that they are held in the exhaust pipe 302.

As such a catalyst device, for example, Japanese Utility Model Laid-Open No. 4-69619 and Japanese Utility Model Laid-Open No. 4-8732 are available.
No. 3 and Japanese Utility Model Laid-Open No. 4-132425. The one described in Japanese Utility Model Laid-Open No. 4-69619 has a cross section L consisting of a tubular portion and an inner flange portion in front of and behind the outer tube.
The tubular portion of the character-shaped multi-action regulating member is fitted, and the tubular portion of the movement regulating member is fitted to the end surface of the one end opening of the throttle tube, the end surface of the tubular portion of the movement regulating member, and the tubular shape of the movement regulating member. The end faces of the parts are simultaneously welded to the outer circumference of the outer cylinder. The one disclosed in Japanese Utility Model Laid-Open No. 4-87323 has a heat insulating layer formed between an outer case provided with one end and the other end in communication with an exhaust passage, and between the outer case and the inner surface of the case. In addition, the inner case accommodated therein and the catalyst provided inside the inner case are provided. Actual Kaihei 4-132425
The one described in Japanese Patent Laid-Open Publication No. 2003-242242 is such that the catalyst carrier is press-fitted into the outlet side case, one end of the catalyst carrier is brought into contact with the inside of the outlet side case, and the other end of the catalyst carrier is projected from the end of the outlet side case. A gasket that abuts on the other protruding end and elastically presses the catalyst carrier is interposed between the outlet side case and the inlet side case.

[0008]

However, in the conventional catalyst holding structure shown in FIGS. 8 and 9, since the catalyst case comes into contact with the outside air, the temperature of the catalyst is lowered and the exhaust purification performance is lowered. There was an inconvenience. Also, FIGS.
As shown in FIG. 2, there is a disadvantage that the difference between the temperature of the catalyst case and the temperature of the catalyst is large and the catalyst is damaged due to the difference in thermal expansion.

Further, in the catalyst holding structure shown in FIGS. 9 and 10, it is necessary to manufacture the exhaust pipe for each difference in the specifications of the catalyst, which is disadvantageous in terms of management cost.

Further, in the catalyst holding structure shown in FIGS. 8, 9 and 10, when the catalyst is damaged and needs to be replaced, the replacement portion is large and the replacement cost is high. .

[0011]

In order to eliminate the above-mentioned inconvenience, the present invention provides a catalyst in which a catalytic substance is carried on a metal carrier, and provides a catalyst case for holding the catalyst. The catalyst held in the catalyst case is arranged in an exhaust pipe composed of an upstream exhaust pipe and a downstream exhaust pipe,
A holding flange is provided on the catalyst case, and the holding flange is provided between the upstream coupling flange of the upstream exhaust pipe and the downstream coupling flange of the downstream exhaust pipe.

[0012]

According to the structure of the present invention, since the catalyst does not come into direct contact with the outside air, the heat retaining property of the catalyst is improved, so that the exhaust purification performance can be improved and the catalyst case is restrained. Since the catalyst case expands to the same degree of thermal expansion as the catalyst by keeping the temperature, there is no difference in thermal expansion between the catalyst and the catalyst case, and it is possible to prevent damage to the catalyst. Even if the catalyst should be damaged, the replacement cost is low because there are few replacement parts.

[0013]

Embodiments of the present invention will be described in detail and specifically with reference to the drawings. 1 to 5 show a first embodiment of the present invention. In FIG. 5, 2 is an engine,
4 is an air cleaner, 6 is a carburetor, 8 is an intake manifold,
Reference numeral 10 is an intake passage, 12 is an exhaust manifold, and 14 is an exhaust passage. The intake passage 10 includes an intake port 1 of the engine 2.
It communicates with 6. This intake port 16 has an intake valve 18
And communicates with the combustion chamber 20 via. This combustion chamber 20
Communicate with the exhaust passage 14 via the exhaust valve 22.

A catalyst device 26 for purifying the exhaust gas is provided in the middle of the exhaust pipe 24 connected to the exhaust passage 14. The catalyst device 26 is provided between the upstream exhaust pipe 24-1 and the downstream exhaust pipe 24-2.

The catalyst device 26 includes a catalyst 28 and the catalyst 2
8 and a catalyst case (outer cylinder) 30 that holds 8 in FIG.

The catalyst 28 is constituted, for example, by combining a flat plate made of heat-resistant steel and a corrugated plate and spirally winding a metal carrier to carry a catalyst substance (not shown).

The outer peripheral portion of the catalyst case 30 is shown in FIG.
As shown in 2, the base portion of the holding flange 32 is fixed by welding. The holding flange 32 is made of, for example, a stainless steel material. A plurality of holding flange side bolt holes 34 are formed in the outer edge portion of the holding flange 32.

An upstream coupling flange 36 is formed on the upstream exhaust pipe 24-1. An upstream gasket accommodation groove 38 and an upstream flange bolt hole 40 are formed outside the upstream gasket accommodation groove 38 in the upstream coupling flange 36. The upstream gasket 42 is housed in the upstream gasket housing groove 38.

A downstream side coupling flange 44 is formed on the downstream side exhaust pipe 24-2. The downstream side coupling flange 44 has a downstream side gasket accommodation groove 46 at a position corresponding to the upstream side gasket accommodation groove 38, and the upstream side flange bolt hole 40 outside the downstream side gasket accommodation groove 46. Downstream flange bolt hole 48
And are formed. The downstream gasket 50 is accommodated in the downstream gasket accommodation groove 46.

The holding flange 32 is interposed between the upstream connecting flange 36 and the downstream connecting flange 44, and holds the catalyst 28 held in the catalyst case 30 in the exhaust pipe 24. Therefore, the exhaust pipe 22 in the portion where the catalyst 28 is arranged is formed to be expanded and has an inner diameter slightly larger than the outer diameter of the catalyst case 30.

Holding flange 32 and upstream connecting flange 3
6 and the downstream side coupling flange 44 are integrally fastened together by a coupling bolt 52 inserted into the holding flange bolt hole 34, the upstream side flange bolt hole 40 and the downstream side flange bolt hole 48, and the upstream side. Side gasket 42
And is sealed by the downstream gasket 50.

Next, the operation of the first embodiment will be described.

When the engine 2 is in operation, the combustion chamber 2
The exhaust gas from 0 is purified by the catalyst device 26.

At this time, since the catalyst 28 is disposed in the exhaust pipe 24 and does not come into direct contact with the outside air, it becomes difficult for the catalyst 28 and the catalyst case 30 to be cooled, whereby the catalyst temperature is maintained high, and The heat retention improves, and as a result,
Exhaust gas purification efficiency can be improved.

Further, since the catalyst 28 and the catalyst case 30 are not exposed to the outside air, and the catalyst case 30 is not restrained and is kept warm, the catalyst case 30
Has a thermal expansion of about the same as that of the catalyst 28, and
As shown in FIG. 4, the temperatures of the catalyst 28 and the catalyst case 30 are made uniform, so that the difference in thermal expansion between the catalyst 28 and the catalyst case 30 is eliminated, thereby preventing the catalyst 28 from being damaged. You can

Further, even if the catalyst 28 is damaged due to other factors, it is possible to replace only the catalyst 28 and use other parts, thereby reducing the replacement site and replacing cost. Can be reduced.

Furthermore, it is possible to eliminate the need to manufacture an exhaust pipe for each specification of the catalyst 28, and to reduce the cost for management.

Further, since the hot exhaust gas does not directly contact the joint portion of the holding flange 32, the upstream joint flange 36, and the downstream joint flange 44, the temperatures of the upstream and downstream gaskets 42 and 50 should be kept low. As a result, the durability of the upstream and downstream gaskets 42, 50 can be improved, and thus the sealing performance can be improved.

FIG. 6 shows a second embodiment of the present invention.

In the following embodiments, parts having the same functions as those of the above-mentioned first embodiment are designated by the same reference numerals.

The features of this second embodiment are as follows. That is, the holding flange 62 of the catalyst 28 is
An upstream end portion of the catalyst case 30 is extended, and the extended portion is bent outward to be integrally formed with the catalyst case 30. The holding flange 62 is interposed between the upstream side coupling flange 36 and the downstream side coupling flange 44 and integrally fastened together by a coupling bolt (not shown).

According to the structure of the second embodiment, the catalyst 28
Is installed in the exhaust pipe 24 and does not come into direct contact with the outside air,
The catalyst 28 and the catalyst case 30 are less likely to be cooled,
As a result, the catalyst temperature can be maintained high, and thus the heat retaining property can be improved, and as a result, the exhaust gas purification efficiency can be improved.

As described above, the catalyst 28 and the catalyst case 30 are not exposed to the outside air, and the catalyst case 30 is not restrained and is kept warm.
Has a thermal expansion of about the same degree as the catalyst 28, and thus the catalyst 2
8 and the temperature of the catalyst case 30 become uniform, so that
By eliminating the difference in thermal expansion between the catalyst 28 and the catalyst case 30, it is possible to prevent the catalyst 28 from being damaged.

Further, even if the catalyst 28 is damaged due to other factors, it is possible to replace only the catalyst 28 and use other parts, thereby reducing the replacement portion and the replacement cost. Can be reduced.

Furthermore, it is possible to eliminate the need to manufacture the exhaust pipe 24 for each specification of the catalyst 28, and to reduce the cost for management.

Further, the holding flange 62 is attached to the catalyst case 3
Since it is configured with a part of 0, a separate holding flange is unnecessary, the number of parts can be reduced, the weight can be reduced, and the cost can be reduced.

FIG. 7 shows a third embodiment of the present invention.

The features of the third embodiment are as follows. That is, the holding flange 72, which is structurally substantially the same as that of the above-described first embodiment, is fixed to the outer peripheral portion of the catalyst case 30, as shown in FIG.
When the case length, which is the distance between a and the downstream end surface 30b, is set to 1, from a point moved from the upstream end surface 30a of the catalyst case 30 to the downstream end surface 30b side by about 1/4,
The position is set within the coupling range from the upstream end surface 30a of the catalyst case 30 to the point moved by about 3/4 to the downstream end surface 30b, that is, the position where the catalyst case 30 is bonded to the substantially central portion.

According to the structure of the third embodiment, the same effect as that of the first embodiment can be obtained, and when the connecting range of the holding flange 72 is set to the case length of 1, the catalyst case 30 is used.
About 1/4 from the upstream end face 30a of the downstream end face 30b of the downstream side
From the point moved to the downstream end surface 30b from the upstream end surface 30a of the catalyst case 30 to the point where the holding flange 71 is coupled, and the temperature of the holding flange 71 is high. It is possible to surely reduce the thermal influence of the exhaust gas on the joint portion.

[0040]

As is apparent from the above detailed description, according to the present invention, the catalyst held in the catalyst case is disposed in the exhaust pipe including the upstream exhaust pipe and the downstream exhaust pipe, and the catalyst is A holding flange is provided on the case, and the holding flange is interposed between the upstream connecting flange of the upstream exhaust pipe and the downstream connecting flange of the downstream exhaust pipe to prevent the catalyst from directly contacting the outside air and to exhaust the exhaust gas. Purification performance can be improved. In addition, since the catalyst case is not restrained and is kept warm, the catalyst case thermally expands to about the same degree as the catalyst. Therefore, the difference in thermal expansion between the catalyst case and the catalyst case is eliminated, and the catalyst case It can prevent damage.

Furthermore, even if the catalyst should be damaged, since there are few replacement parts, the replacement cost can be reduced.

Furthermore, it is not necessary to manufacture an exhaust pipe for each different specification of the catalyst, which can be inexpensive in terms of management.

[Brief description of drawings]

FIG. 1 is a sectional view of a catalyst device according to a first embodiment.

FIG. 2 is a perspective view showing a state where a catalyst is held by a catalyst case.

FIG. 3 is a diagram illustrating a temperature state of a catalyst and a catalyst case.

FIG. 4 is a temperature distribution diagram of line AA in FIG.

FIG. 5 is a configuration diagram of an engine.

FIG. 6 is a sectional view of a catalyst device according to a second embodiment.

FIG. 7 is a sectional view of a catalyst device according to a third embodiment.

FIG. 8 is a sectional view of a conventional catalyst device.

FIG. 9 is a cross-sectional view of a conventional catalyst device.

FIG. 10 is a sectional view of a conventional catalyst device.

FIG. 11 is a diagram for explaining temperature states of a conventional catalyst and a catalyst case.

12 is a temperature distribution diagram of line BB in FIG.

[Explanation of symbols]

 2 engine 24 exhaust pipe 26 catalyst device 28 catalyst 30 catalyst case 32 holding flange 36 upstream side coupling flange 44 downstream side coupling flange 52 coupling bolt

Claims (1)

[Claims] 1. A catalyst having a catalyst substance supported on a metal carrier is provided, a catalyst case for holding the catalyst is provided, and the catalyst held in the catalyst case is provided with an upstream exhaust pipe and a downstream side. The catalyst case is provided with a holding flange, and the holding flange is interposed between the upstream connecting flange of the upstream exhaust pipe and the downstream connecting flange of the downstream exhaust pipe. A catalyst holding structure characterized by being provided.