JPS6125890B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a catalytic converter structure containing two catalyst beds within a single casing.

Traditionally, engine exhaust systems have been equipped with two types: a reduction or three-way catalyst (hereinafter simply referred to as a ring catalyst) that primarily functions in a reducing atmosphere, and an oxidation or three-way catalyst (hereinafter simply referred to as a ring catalyst) that primarily functions in an oxidizing atmosphere. ,
It is simply called an oxidation catalyst. ), a catalytic exhaust gas purification system is well known in which nitrogen oxides (NOx) are reduced and purified using a reduction catalyst, and then unburned components HC and CO are oxidized and purified using an oxidation catalyst. (Refer to Japanese Patent Application Laid-Open No. 47-43714).

However, in a conventional catalytic exhaust gas purification device that is equipped with two catalyst beds arranged in series with respect to the flow of exhaust gas, each filled with two types of catalysts or the same type of catalyst, the number of parts is small. Because many of the structures were complex, assembly was extremely difficult and time-consuming.

The present invention aims to completely simplify the structure of a catalytic exhaust gas purification device that is equipped with two catalyst beds arranged in series with respect to the flow of exhaust gas, and to make the structure simpler and more compact. The purpose is to achieve this goal.

In order to achieve the above object, the present invention basically consists of a single casing consisting of an upper shell and a lower shell, and a first casing in which a catalyst is filled in a container formed by an upper holding plate and a lower holding plate, respectively. The present invention provides a catalytic converter having a structure in which a second catalytic container is arranged with a space maintained between the front and rear, and in detail,
A casing consisting of an upper shell and a lower shell that have flanges around the entire circumference and are oppositely formed in a dish shape, and an upper holding plate and a lower holding plate arranged in the front and back inside the casing, each having a catalyst holding space inside. The first and second catalyst containers each have a flange made of at least one of an upper holding plate and a lower holding plate, and each of the first and second catalyst containers has a flange made of at least one of an upper holding plate and a lower holding plate, and The side flanges of the first and second catalyst containers are laterally sandwiched between the flanges of the upper and lower shells from above and below, and the front end flange of the first catalyst container is supported by the lower shell at the front end of the casing.
An inlet is connected to the front space formed by the upper holding plate and the upper shell of the catalyst container and introduces exhaust gas from outside the casing, and is connected to the rear end flange of the second catalyst container and the upper shell at the rear end of the casing. An outlet is formed to support the second catalyst container and to communicate with the rear space formed by the lower holding plate and the lower shell to discharge exhaust gas to the outside of the casing, and to connect the rear flange of the first catalyst container to the upper shell inside the casing. and the front end flange of the second catalyst container is fixed to the lower shell, and a central space is formed by the lower holding plate of the first catalyst container, the upper holding plate of the second catalyst container, and the upper and lower shells, and the first Exhaust gas introduced into the upper and lower holding plates of the second catalyst container from the inlet passes through the front space, the first catalyst holding space, the central space, the second catalyst holding space, and the rear space in sequence, and is discharged from the outlet. It is characterized by having ventilation holes.

Hereinafter, embodiments of the catalytic converter according to the present invention will be described in more detail.

1 to 5, reference numerals 1 and 2 denote a pair of plane-symmetric plate-shaped upper parts that form a relatively flat and elongated casing 3 in the direction of the central axis when stacked facing each other in the vertical direction. shell and lower shell, 4, 5 are upper shell 1 and lower shell 2,
A pair of substantially plane-symmetrical upper and lower covers cover a heat insulating material filling space 6 from the outside, respectively; 10 is a first catalyst container formed by overlapping an upper holding plate 11 and a lower holding plate 12 disposed in the rear part of the casing 3; 13 is a first catalyst container 7; A secondary air nozzle protrudes from the horizontal direction perpendicular to the center line of the casing 3 between the second catalyst container 10, and a pipe 1
3a is provided with an appropriate number of small holes 13b, 13b, and secondary air supplied from a secondary air supply source (not shown) is blown out from each small hole 13b.

As is clear from FIGS. 1 and 5, the upper and lower shells 1, 2 include an inlet member 14 consisting of a thick-walled annular ring disposed coaxially with the center line at the front and rear ends of the casing 3; They are each narrowed into a semicircular shape toward the member 15, and then fixed to the outer peripheries of the inlet member 14 and the outlet member 15 by welding. Note that the inlet member 14 and the outlet member 15 each have a flange (not shown) on the exhaust pipe side.
so that it is joined to. For this purpose, it is preferable to fix mounting bolts (not shown) to the inlet member 14 and the outlet member 15. In this embodiment, thick rings are used as the inlet and outlet members 14 and 15, but they may also be constructed of pipes having flanges for attaching exhaust pipes to the outside of the casing.

On the other hand, as shown in FIGS. 1 and 5, the first
The upper holding plate 8 and the lower holding plate 9 that form the catalyst container 7 have almost the same shape in the axial vertical cross section. Extends backwards on an incline;
There are many ventilation holes a, ……………, a on almost the entire surface.
It consists of an upper wall 8B which is punched out, and side walls 8C, 8C which fall continuously on both sides of the upper wall 8B.

The upper holding plate 8 and the lower holding plate 9 are the front wall 8
A and the rear wall 9A, and the upper wall 8B and the lower wall 9B are overlapped with each other so as to face each other, and a catalyst holding space A having a substantially parallelogram cross section is formed inside. Fill it with. Then, the semicircular front end flanges 8a and 9a formed on the upper holding plate 8 and the lower holding plate 9 are inserted between the lower outer periphery of the inlet member 14 and the front edge 2a of the lower shell 2, and are held in place. , these are fixed to each other by welding, while the flat rear end flanges 8b and 9b are fixed to the center of the inner wall surface of the upper shell 1 by welding or the like, so that the flat rear end flanges 8b and 9b are slightly inclined upward from the front toward the rear. supported by the state. In addition, two studs 16 and 17, front and rear, are interposed in the center of the first catalyst container 7 to support an upper holding plate 8 and a lower holding plate 9. The upper and lower ends thereof protrude from the upper shell 1 and the lower shell 2, respectively, and are fixed by welding, and between the upper shell 1 and the upper holding plate 8, and between the lower shell 2 and the lower holding plate. Between the studs 9 are spacers 18 surrounding the shafts of the studs 16, 17, . . .
. . . , 18 are interposed to hold the upper holding plate 8 and the lower holding plate 9 in place. In addition, 8c, 9
c is a flange in which the side walls of the upper holding plate 8 and the lower holding plate 9 are extended along the inner surface of the side wall of the casing 3; Reinforces the support strength at the rear.

On the other hand, as shown in FIGS. 3 and 5, side flanges 8e and 9e that can be overlapped with each other are provided on both sides of the upper holding plate 8 and the lower holding plate 9. 9e is stacked and sandwiched between the side flanges 1b and 2b of the upper shell 1 and lower shell 2, and then
b, 8e, 9e, and 2b are fixed to each other by welding. In this case, each side flange 1b, 8e, 9
The flange widths of e and 2b are preferably set to a width sufficient to effectively seal exhaust gas flowing inside.

As mentioned above, each side flange 1b, 8e, 9
e and 2b are welded together, and then attached to the upper cover 4.
The side wall 4a of the lower cover 5 is wrapped around the outward bent edge 5b formed at the upper edge of the side wall 5a, and caulked to form four stacked side flanges 1b, 8e, 9e,
Hold 2b in a pinched state.

On the other hand, the second catalyst container 10 formed by the upper holding plate 11 and the lower holding plate 12 has a secondary air nozzle 13
The arrangement and support structure are rotationally symmetrical to the first catalyst container 7 with the center of rotation being the center of rotation. Therefore, the ten upper holding plates 11 and ten lower holding plates 12 of the second catalyst container correspond to the lower holding plate 9 and the upper holding plate 8 of the first catalyst container 7, respectively, and these upper holding plates 11
The catalyst holding space B formed inside by the lower holding plate 12 is filled with an oxidation catalyst.

The secondary air nozzle 13 has passage holes 1b' and 2b' formed by curving the respective flanges 1b and 2b into semicircular shapes, which are the joint parts of the upper shell 1 and lower shell 2 on the sides of the casing 3. It projects into the central space D and is welded and fixed to the upper and lower shells 1 and 2, respectively.

Further, the temperature sensor 19 is connected to the side of the casing 3 from the opposite direction of the secondary air nozzle 13.
Similar to the secondary air nozzle 13, it protrudes into the central space D from semicircular insertion holes 1b'' and 2b'' formed in the flanges 1b and 2b of the upper shell 1 and the lower shell 2, respectively, in opposition to the secondary air nozzle. ing. The temperature sensor 19 includes a protection tube 20 and a sensor body 21
The protection tube 20 is inserted into the insertion holes 1b'' and 2b'' formed in the flanges 1b and 2b of the upper and lower shells 1 and 2, and is welded to the upper and lower shells 1 and 2 at these portions. It is fixed and protects the sensor body 21 inside. The protective tube 20 has a flange on the outside of the casing, and a flange fixed to the sensor body 21 is fixed to the flange with bolts, so that the sensor body 21 is attached. The temperature sensor 19 is connected to the sensor body 2
The temperature inside the catalytic converter is detected by the temperature sensing part formed at the tip of the catalytic converter.
This is used to control secondary air, alarms, etc.

As a result of the above configuration, inside the casing, there are a front space C between the upper shell 1 and the upper holding plate 8 of the first catalyst container 7, a first catalyst holding space A, and a space between the casing 3 and the first catalyst container. 7 lower holding plate 9 and second
A central space D that is long in the front-rear direction and is defined by the upper holding plate 11 of the catalyst container 10, and a second catalyst holding space B.
and a rear space E between the lower shell 2 and the lower holding plate 12 of the second catalyst container 10. The exhaust gas introduced from the opening 14a of the inlet member 14 has a reducing atmosphere composition, and the exhaust gas first flows into the front space C from the inlet IP substantially defined by the opening 14a, and The exhaust gas that has flowed into the space C flows into the first catalyst holding space A through the ventilation holes a, ......, a of the upper holding plate 8 of the first catalyst container 7, and is held within the space A. The resulting reduction catalyst performs a reducing action, thereby removing NOx from the exhaust gas.

The exhaust gas from which NOx has been removed flows into the central space D from the vent holes a, ......, a of the lower holding plate 9 of the first catalyst container 7, and flows down from the front to the rear of the central space D. In the process, the entire composition is made into an oxidizing atmosphere by the secondary air supplied from the secondary air nozzle 13, and the exhaust gas made into an oxidizing atmosphere is passed through the ventilation holes a, . . . in the upper holding plate 11 of the second catalyst container 10. ……
. . . flows into the second catalyst holding space B from a.

The exhaust gas flowing into the second catalyst holding space B is oxidized by the oxidation catalyst held in the space B, and as a result, HC and CO are removed. The exhaust gas from which unburned components have been removed flows out into the rear space E from the vent holes a, . . . , a of the lower holding plate 12 of the second catalyst container 10. It is discharged to the outside from an outlet OP substantially formed by the opening 15a of.

The secondary air nozzle 13 and the temperature sensor 19 are installed in the upper shell 1 and the lower shell 2 on the sides of the casing 3.
The casing is fixed to the upper and lower shells 1, 2 from the mating parts (insertion holes 1b', 2b' and 1b'', 2b'' of the upper and lower shells 1, 2) and protrudes into the central space D. 1, it can be supported reliably without the need for machining such as drilling holes, and it is possible to reduce the number of machining steps and facilitate assembly.

In the above embodiment, since the secondary air nozzle 13 and the temperature sensor 19 are arranged in the center of the casing 1, the upper shell 1 and the lower shell 2 have the same shape, and are configured so that parts can be shared. has been done. In addition, since the first catalyst container 7 and the second catalyst container 10 have the same capacity of their respective catalyst holding spaces A and B, both containers can be replaced and parts can be shared.

In order to make the flow of exhaust gas uniform in the casing 3 as described above, as shown in FIG. The front wall 11A of No. 11 is moderately protruded forward in the center line direction at its axial center, while the rear walls of the lower holding plate 9 of the first catalyst container 7 and the lower holding plate 12 of the second catalyst container 10 9A and 12A are made to protrude moderately rearward in the center line direction at their central portions in the axial direction, and as shown in FIG. 3, the first and second catalyst containers 7 and 10
Each upper holding plate 8, 11 and each lower holding plate 9, 1
The upper walls 8B, 11B and the lower walls 9B, 12B of 2 are
The tapered surface is formed so that the distance between the upper shell 1 and the lower shell 2 gradually increases from the center in the width direction to both sides thereof, and the flow resistance at the centerline portion of the casing 3 is set to an appropriate value compared to the both side portions. It is preferable to increase the width so that the flow becomes uniform in the width direction.

Furthermore, in order to equalize the flow of exhaust gas within the casing 3, it is effective to consider the arrangement of the studs 16, 17 provided in each catalyst container 7, 10. That is, as in this embodiment, the studs 16, 1 provided in the first and second catalyst containers 7, 10
If the studs 7 are arranged in tandem in the center in the front-rear direction, the presence of these studs has the advantage that the flow of exhaust gas is diffused from side to side, making the flow uniform.

In addition, in order to equalize the flow of exhaust gas from the first catalyst container 7 to the second catalyst container 10 in the central space D and to promote mixing of the secondary air and exhaust gas, it is necessary to adjust the temperature of the secondary air nozzle 13. sensor 19
It is preferable that the two be located opposite each other in the central space D in a substantially straight line. This makes it possible to provide uniform flow resistance to the flow of exhaust gas over the entire width, allowing the flow to be uniformly introduced into the second catalyst container 10 without being biased, and thereby
This allows uniform mixing with the secondary air ejected from the small hole 13b of the secondary air nozzle 13.

Regarding the support structure of the first catalyst container 7,
For example, as shown in FIG. 6a, while the front end flange 8a of the upper holding plate 8 and the front edge 2a of the lower shell 2 are welded to the inlet member 14, the front end flange 9a of the lower holding plate 9 is It is held between the front end flange 8a of the holding plate 8 and the lower shell 2 in a state where the restraint is relaxed, or the sixth
As shown in Figure b, the front end flanges 8a and 9a of the upper and lower holding plates 8 and 9 may be supported to relieve restraint by being sandwiched between the inlet member 14 and the front edge 2a of the lower shell 2, which are welded together. good. Alternatively, as shown in FIG. 6c, the rear end flange 8b of the upper holding plate 8 may be sandwiched between the rear end flange 9b of the upper shell 1 and the lower holding plate 9, which are welded and fixed to each other, to relieve the restraint. good. Although not specifically illustrated, these restraint relaxation structures can also be employed for the support structure of the second catalyst container 10.

In addition, as for the side flanges 8e, 9e or 11e, 12e of the first catalyst container 7 or the second catalyst container 10, as shown in FIG. (Of course, the restraint may be relaxed on the lower holding plate 9 or 12 side.) Alternatively, as shown in FIG. 7b, the upper and lower holding plates 8 and 9 or 11 and 12 are simultaneously relaxed. It's okay.

These restraint-relaxing structures are advantageous in that they can prevent large thermal stress that may occur in the first catalyst container 7 and/or the second catalyst container 10.

As described above, in the present invention, a casing is configured by an upper shell and a lower shell, a first catalyst container and a second catalyst container are configured by two sets of an upper holding plate and a lower holding plate, and a second catalyst container is configured by two sets of an upper holding plate and a lower holding plate. A first catalyst container is arranged at the front part of the casing, and a second catalyst container is arranged at the rear part of the casing. The front end of the container is supported by the lower shell and the rear end by the upper shell, while both sides of the first and second catalyst containers are supported by the casing by being supported between the side flanges of the upper and lower shells. Inside, an inlet part, a front space, a first catalyst holding space, a central space,
A second catalyst holding space, a rear space, and an outlet are sequentially formed, and exhaust gas introduced from the outside is introduced into the first catalyst holding space from the inlet through the front space.
A catalytic converter is provided in which NOx, for example, is purified by a catalyst filled in the space, and then released into a central space, and unburned components, for example, are purified by a catalyst filled with exhaust gas from the central space into a second catalyst holding space. This is what we provide.

In the example, secondary air is supplied between the first and second catalyst containers, the first catalyst container is filled with a reduction catalyst, the second catalyst container is filled with an oxidation catalyst, and NOx is removed on the first catalyst side. Although the second catalyst side is used to purify CO and HC, the catalytic converter of the present invention is not limited to this. For example, a three-way catalyst may be filled in both containers without supplying secondary air between the two containers, and CO, HC, and NOx may be purified simultaneously in the first and second catalyst containers, or the first catalyst container may be made smaller. The second catalyst container can be filled with an oxidation catalyst for cold startup, and the second catalyst container can be made larger and filled with a three-way or oxidation catalyst during normal operation.

According to this invention, a catalytic converter having an inlet, an outlet, first and second catalyst holding spaces, front and rear spaces, and a central space is basically formed by a combination of a total of six molded metal plates. It is possible to compactly house two catalyst beds in a single casing, and the first and second
The catalyst container is supported by the casing on its front and rear sides, as well as on its left and right sides, so that the supporting strength is sufficient. For catalytic converters equipped with this, the structure can be thoroughly simplified and made more compact.

[Brief explanation of the drawing]

FIG. 1 is an axial vertical sectional view showing an embodiment of a catalytic converter according to the present invention, and FIG. 2 is a -
3 is a sectional view in the - line direction of FIG. 2, FIG. 4 is a sectional view in the - line direction of FIG. 2,
FIG. 5 is an exploded perspective view of six metal plates that basically constitute the catalytic converter according to the present invention, and FIGS. 6 a, b, and c show support structures for the front and rear ends of the catalyst container, respectively. Main part sectional view showing an example of 7th
Figures a and b are sectional views of essential parts showing the support structure of the side portion of the catalyst container, respectively. 1, 2... Upper and lower shells, 3... Casing, 7... First catalyst container, 8, 9... Upper and lower holding plates, 10... Second catalyst container, 11, 12...
Upper and lower holding plates, 13...Secondary air nozzle, 1
4, 15... Inlet, outlet member, 19... Temperature sensor, A, B... First and second catalyst holding spaces, C...
...Front space, D...Central space, E...Rear space,
IPOP...Inlet, outlet, a...Vent hole.

Claims (1)

[Claims] 1. A casing consisting of an upper shell and a lower shell which have flanges around almost the entire circumference and are formed into opposing dish shapes, and an upper holding plate and a lower holding plate which are arranged in the front and back inside the casing, and each has a catalyst inside. first and second catalyst containers configured by overlapping both plates to form a holding space, the first and second catalyst containers each having a flange made of at least one of an upper holding plate and a lower holding plate; The side flanges of the first and second catalyst containers are sandwiched from above and below by the flanges of the upper and lower shells on the sides of the casing, and the front end flange of the first catalyst container is supported by the lower shell at the front end of the casing, and the first catalyst container An inlet is communicated with the front space formed by the upper holding plate and the upper shell to introduce exhaust gas from outside the casing, and the rear end flange of the second catalyst container is supported by the upper shell at the rear end of the casing. At the same time, an outlet is formed that communicates with the rear space formed by the lower holding plate and the lower shell of the second catalyst container and discharges exhaust gas to the outside of the casing, and the rear end flange of the first catalyst container is fixed to the upper shell inside the casing. In addition, the front end flange of the second catalyst container is fixed to the lower shell, and a central space is formed by the lower holding plate of the first catalyst container, the upper holding plate of the second catalyst container, and the upper and lower shells, and Exhaust gas introduced into the upper and lower holding plates of the second catalyst container through the inlet sequentially passes through the front space, the first catalyst holding space, the center space, the second catalyst holding space, and the rear space, and is discharged from the outlet. A catalytic converter characterized by having ventilation holes.