JPS6123368B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a monolithic catalytic converter that is installed in the exhaust system of an engine and performs an exhaust gas purifying action, and particularly relates to a monolithic catalytic converter that is installed in the exhaust system of an engine and performs an exhaust gas purification function. The invention relates to monolithic catalytic converters arranged in series.

(Prior art) Generally, in a catalytic converter in which multiple catalysts are arranged in series in a casing as described above, it is necessary to supply secondary air between the catalysts to ensure the oxidation reaction in the oxidation monolith catalyst. is being carried out. As an example, a plurality of monolithic catalysts are arranged in series in the axial direction of the casing via spacers that maintain a predetermined interval in a cylindrical casing equipped with an exhaust gas inlet and an exhaust gas outlet at the front and rear. A device that supplies secondary air has been proposed (see Japanese Patent Application Laid-Open No. 1983-9915).

In addition, when the first stage is a reduction monolith catalyst and the second stage is an oxidation monolith catalyst as in the above-mentioned publication, the secondary air is supplied immediately before the second stage monolith catalyst as described above, that is, at the interval mentioned above, and in addition to being supplied to the first stage monolith catalyst, Secondary air is also supplied upstream of the catalyst, both of which are used for the oxidation reaction in the subsequent oxidation monolith catalyst. Further, when the first stage is an oxidation monolith catalyst and the second stage is a reduction monolith catalyst, secondary air is supplied upstream of the first stage monolith catalyst.

(Problem to be Solved by the Invention) However, in this conventional monolithic catalytic converter, the inner circumferential surface of the spacer that maintains a predetermined distance between the monolithic catalysts has a bench lily shape that gently slopes in the axial direction. Coupled with the fact that the gas flow passing through the catalyst tends to be laminar,
The exhaust gas flow from the monolith catalyst in the front stage flows smoothly to the monolith catalyst in the rear stage, but the exhaust gas is not guided throughout the entire area of the monolith catalyst in the rear stage, and as a result, the purification performance of the monolith catalyst in the rear stage cannot be fully demonstrated. There was a problem.

The present invention has been made in view of the above, and its object is to utilize a spacer that maintains a predetermined distance between the monolithic catalysts, and to create a screen-like structure in which a turbulent flow of exhaust gas is caused in a part of the spacer. By integrally forming the baffle, even with a simple structure, turbulence is generated in the exhaust gas flow from the monolithic catalyst in the previous stage, guiding the exhaust gas to the entire area of the monolithic catalyst in the latter stage, and improving the purification performance of the monolithic catalyst in the latter stage. The goal is to enable people to fully demonstrate their abilities.

(Means for Solving the Problems) In order to achieve the above object, the solving means of the present invention includes a plurality of monolithic catalysts arranged in a cylindrical casing provided with exhaust gas inlets and outlets at the front and rear. In a monolithic catalytic converter, the spacer is arranged in series in the axial direction of the casing via a spacer that maintains an interval of and a holding portion, and a screen-like buttful extending vertically from the abutting portion of both spacing holding portions toward the inner side in the radial direction and integrally formed with the spacing holding portion. .

(Function) With the above configuration, in the present invention, the exhaust gas that has passed through the monolithic catalyst in the front stage and is purified flows into the space between the monolithic catalysts in the front stage held by the spacer in a substantially laminar flow state. , at this interval, the flow is immediately disturbed by a screen-like buffle provided on the inner circumferential surface of the spacer that extends vertically inward in the radial direction, resulting in a turbulent flow, which allows the exhaust gas to be uniformly distributed over the entire area of the monolithic catalyst in the subsequent stage. was introduced,
The exhaust gas purification function of the monolithic catalyst in the latter stage is maximized.

Further, the screen-like buttful is formed using a spacer, that is, extends vertically inward in the radial direction from the abutting portion of the upper and downstream side spacing portions forming the spacer, and is formed integrally with the spacing portion. Therefore, it is easy to form a battleship.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings.

In FIGS. 1 to 3, 1 is a cylindrical casing, and the casing 1 has a pair of press-formed shells 2, 2 divided vertically in the axial direction. The casing 1 is attached to each other at flanges 2a, 2a formed on the outer periphery, and has a catalyst storage section 1a in the center of the casing 1 with an elliptical cross section that is flat in the vertical direction. At both front and rear ends, there are inlet and outlet exhaust pipe connection parts 1b and 1c with circular cross-sections.
have. An exhaust pipe connection inlet flange 4 having an exhaust gas inlet 4a in the center is fixed to the tip of the inlet side exhaust pipe connection part 1b via a connecting ring 3 by welding. An exhaust pipe connection outlet flange 6 having an exhaust gas outlet 6a in the center is fixed to the rear side of the portion 1c via a connecting ring 5 by welding. Stud bolts 7 and 8 for connection are implanted.

In the catalyst storage portion 1a of the casing 1, a reduction monolith catalyst 9 is arranged in the upstream front stage and an oxidation monolith catalyst 10 is arranged in the downstream stage in series in the axial direction of the casing 1. are held via a spacer 11 so as to maintain a predetermined distance S between them as a mixing area. The monolithic catalysts 9 and 10 are both formed by coating a catalyst such as platinum on an elliptical columnar carrier made of ceramic material, and have a large number of ventilation holes penetrating in the axial direction in a honeycomb shape.

The spacer 11 has holding flange portions 12a and 13a each having an L-shaped cross section and protruding outward from the outer peripheral edge at one end.
Two approximately symmetrical elliptical cylindrical press-formed members 12 and 13 are used as upstream and downstream spacing parts, which have bonding flange parts 12b and 13b that protrude radially inward at the inner peripheral edge of the other end. , are formed by bonding each other at the bonding flange portions 12b, 13b in the front and back, and each of the press-formed members 12,1
The outer circumferential surfaces of the holding flange portions 12a and 13a of No. 3 are brought into contact with the inner circumferential surface of the casing 1 and fixed to the casing 1 by, for example, plug welding. It comes into contact with the rear end surface of the reduction monolith catalyst 9 in the axial direction via the body 14 to elastically hold it, and
The holding flange portion 13a is configured to abut and press against the front end surface of the oxidation monolith catalyst 10 in the axial direction, thereby maintaining a predetermined distance S between the two monolith catalysts 9 and 10.

In addition, the inner peripheral surface of the spacer 11, that is, the bonding portion of the press-formed members 12 and 13 serving as the abutment portion of the upstream and downstream side spacing portions has a radial inner surface formed by the bonding flange portions 12b and 13b. A screen-like buttful 15 extending vertically in both directions is integrally formed.

On the other hand, 16 is from the flange parts 2a, 2a bonded part of the shells 2, 2 in the casing 1,
Press-formed members 12 and 13 in spacer 11
Bonded portion (bonded flange portions 12b, 13b)
By inserting the insertion hole 17 formed on the long axis of the ellipse,
The secondary air supply pipe 16 is a secondary air supply pipe disposed at the predetermined interval S in a direction transverse to the long axis direction of the ellipse, and the secondary air supply pipe 16 is connected to the flange portion 2a of the shell 2, 2,
2a is fixed by welding or the like and cantilevered at the bonded part 2a, and its front end 16a is closed, and its rear end 16b is attached to the casing 1.
It is led out and connected to an air pump (not shown) via a connecting flange 18, thereby forming a secondary air supply passage 19. Further, in the rear half of the outer circumferential surface of the secondary air supply pipe 16, a large number of secondary air jetting holes 20, 20, . , so that the secondary air from the air pump is ejected and supplied rearward within the interval S from the secondary air ejection holes 20, 20, . . . through the secondary air supply passage 19 (secondary air supply pipe 16). has been done.

Reference numeral 21 denotes a cone-shaped pressure member, which includes a support portion 21a that presses and holds the front end surface of the reduction monolith catalyst 9 in the axial direction, and a support portion 21a that presses and holds the front end surface of the reduction monolith catalyst 9 in the axial direction.
The baffle portion 21b is formed integrally with a baffle portion 21b made of a perforated plate located a predetermined distance forward from the axial front end face of the exhaust gas for rectifying the flow of exhaust gas, and is fixed to the casing 1 by, for example, plug welding. Also, 22
and 23 are connected to the outer circumferential surfaces of both the monolithic catalysts 9 and 10 and the casing 1 so as to elastically hold the outer circumferential surfaces of the reduction monolithic catalyst 9 and the oxidation monolithic catalyst 10, respectively.
24 is an elastic material such as a steel mesh interposed between the inner circumferential surface of the catalyst storage portion 1a of the casing 1;
The axial rear end surface of the oxidation monolith catalyst 10 is covered with an elastic body 25 such as a steel mesh.
This is a support member that elastically holds the material through the support member.

Therefore, in the above embodiment, the exhaust gas flowing into the casing 1 from the exhaust gas inlet 4a of the exhaust pipe connection inlet flange 4 first passes through the buff-full portion 21b of the pressure member 21, and then passes through the reduction monolith. It flows into the catalyst 9 and is reduced and purified by the catalyst 9. At this time, the exhaust gas is rectified by the buffing portion 21b and uniformly flows into the reduction monolith catalyst 9, so that the reduction purification performance is improved.

Next, the exhaust gas that has passed through the reduction monolith catalyst 9 and has been reduced and purified flows in a substantially laminar flow state into a gap S, which is a mixing area held by a spacer 11. The secondary air supply pipe 16 is immediately disturbed by a screen-like buffle 15 provided on the inner circumferential surface of the air supply pipe 11 and extends vertically inward in the radial direction, resulting in a turbulent flow.
The presence of the (secondary air supply passage 19) and the ejection of secondary air from the secondary air ejection holes 20, 20, . . . of the secondary air supply pipe 16 further promote turbulence, and as a result, The exhaust gas and the secondary air are vigorously agitated to be sufficiently and uniformly mixed, and then uniformly flow into the entire area of the oxidation monolith catalyst 10.

In this oxidation monolith catalyst 10, the oxidation purification performance is significantly improved due to good mixing of the exhaust gas and secondary air and uniform inflow into the entire area of the oxidation monolith catalyst 10, and the exhaust gas is oxidized well. be purified. Thereafter, the exhaust gas thus reduced and oxidized and purified is discharged from the exhaust gas outlet 6a of the exhaust pipe connection outlet flange 6.

Further, the screen-like buttful 15 has a spacer 1
1, that is, 2 forming the spacer 11.
Since it is integrally formed by extending vertically inward in the radial direction from the bonded part of the press-formed members 12 and 13 (upstream/downstream spacing holding parts), the buttful 15 can be easily formed. This prevents an increase in the number of parts and a deterioration in ease of assembly.

Note that the present invention is not limited to the above-mentioned embodiment, but also includes various other modifications. For example, in the above-mentioned embodiment, the spacer 11 is formed of two press-formed members 12 and 13. It was made into a split mold, but as shown in Figures 4 and 5 (the same parts as in Figures 1 to 3 are given the same reference numerals and their explanations are omitted), they were made by press molding. The spacer 11' is an integrally molded spacer 11', and the spacer 11' has a spacer 11' in the center of its inner circumferential surface near the insertion opening 17' for inserting the secondary air supply pipe 16 and in the direction of the long axis of the ellipse with the insertion opening 17. A screen-like buffle 15' extending vertically inward in the radial direction may be integrally formed in the portions other than the opposing portions, and the same effect as described above can be obtained.

Furthermore, in the above embodiment, two reduction monolith catalysts 9 are arranged in series in the front stage and two oxidation monolith catalysts 10 are arranged in the rear stage in the casing 1, but in the present invention, conversely, the oxidation monolith catalyst 9 is arranged in the front stage,
In addition to the case where two reduction monolith catalysts are arranged in series at the rear stage, the present invention can be similarly applied to cases where three or more monolith catalysts are arranged in series with a predetermined interval between them. Further, the secondary air supply position may be any position upstream of the oxidation monolith catalyst. In short, any method may be used as long as the baffle 15, 15' makes the exhaust gas turbulent, thereby improving the reaction of the oxidation or reduction monolith catalyst behind the baffle.

Furthermore, in the above embodiment, the casing 1 is a bonded type consisting of a pair of upper and lower shells 2, 2 divided in the axial direction, but it may also be a rolled type in which the casing 1 is integrally formed into a cylindrical shape. Needless to say.
In addition to welding as described above, various types of fixing means can be used to fix the spacer 11 and other members.

(Effects of the Invention) As explained above, according to the monolithic catalytic converter of the present invention, the spacer is arranged to maintain a predetermined distance between the monolithic catalysts arranged in series in the axial direction of the cylindrical casing. Since the spacer has a screen-like baffle integrally formed on its inner circumferential surface that extends vertically inward in the radial direction, it is possible to prevent turbulence in the exhaust gas flow from the monolithic catalyst on the front stage side even though the structure is simple. This has the remarkable effect of generating a flow and uniformly introducing exhaust gas into the entire area of the monolithic catalyst on the downstream side, thereby improving the purification performance of the monolithic catalyst on the downstream side.

[Brief explanation of the drawing]

The drawings illustrate an embodiment of the present invention, and FIG. 1 is a cross-sectional view showing one embodiment, FIG. 2 is a sectional view taken along the line -- in FIG. 1, and FIG. be. 4 and 5 are a view corresponding to FIG. 3 and a longitudinal cross-sectional view of a main part, respectively, showing a modified example. 1...Casing, 4a...Exhaust gas inlet,
6a... Exhaust gas outlet, 9... Reduction monolith catalyst, 10... Oxidation monolith catalyst, 11, 11'...
...Spacer, 12, 13...Press molded member, 1
5, 15'...Bassful, 19...Secondary air supply passage, S...Spacing.

Claims (1)

[Claims] 1. In a monolithic catalytic converter in which a plurality of monolithic catalysts are arranged in series in the axial direction of the casing via spacers that maintain predetermined intervals in a cylindrical casing provided with an exhaust gas inlet and an exhaust gas outlet at the front and rear, the above-mentioned The spacer consists of an upstream spacing section on the upstream side and a downstream spacing section on the downstream side with respect to the flow direction of exhaust gas, and the spacer extends vertically inward in the radial direction from the abutting part of both spacing sections. A monolithic catalytic converter characterized by comprising a screen-like buffle extending from the spacer and integrally formed with the spacer.