JPS6059411B2 - monolith catalytic converter - 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. This article concerns monolithic catalytic converters arranged in series.

(Prior art) Generally, in a catalytic converter in which a plurality of contacts are arranged in series at intervals in the casing as described above, secondary air is aired between the catalysts to ensure the oxidation reaction in the subsequent catalyst. This secondary air must be sufficiently mixed with the exhaust gas from the front catalyst in order to fully demonstrate the purification function of the rear catalyst, and must be uniformly distributed to the rear catalyst. need to flow into the

Therefore, conventionally, such a monolithic catalytic converter is constructed by placing multiple monolithic catalysts in a cylindrical casing with exhaust gas inlets and outlets at the front and back, and arranging the monolithic catalysts in the axial direction of the casing through spacers that maintain a predetermined interval. In addition to arranging them in series, a secondary air supply pipe constituting a secondary air supply passage is arranged in a direction crossing the above-mentioned interval, and the secondary air is supplied across the exhaust gas flow from the monolithic catalyst in the preceding stage. A method has been proposed in which exhaust gas and secondary air are mixed well and uniformly supplied to the monolithic catalyst in the subsequent stage by causing turbulence (Japanese Patent Laid-Open No. 55-1
(See Publication No. 39918).

(Problem to be Solved by the Invention) However, in this conventional monolithic catalytic converter, due to manufacturing errors in the monolithic catalyst itself and the elastic body that holds the catalyst, the spacer may shift back and forth from its normal position with respect to the casing. If this happens, there is a problem that the insertion holes of the secondary air supply pipes provided in the casing and the spacer do not match.

Therefore, it is necessary to provide an insertion hole through which the secondary air supply pipe is inserted at a position that corresponds to the casing and the spacer, respectively, and high precision is required in manufacturing. In addition, a spacer is required to maintain a predetermined distance between the monolith catalysts, and a secondary air supply pipe is required to supply secondary air to the space between the monolith catalysts, so the number of parts is increased. The problem is that there are too many. The present invention has been made in view of these points, and its object is to provide a secondary air supply passage for supplying secondary air to the spacer itself for maintaining a predetermined distance between the monolithic catalysts. The objective is to provide a monolithic catalytic converter that is integrally formed to ensure good purification performance in the subsequent monolithic catalyst while reducing the number of parts and simplifying manufacturing process. be. (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 placed in a cylindrical casing provided with exhaust gas inlets and outlets at the front and rear. A monolithic catalytic converter is assumed, which is arranged in series in the axial direction of the casing via a spacer that maintains an interval of , and a secondary air supply passage is provided in a direction that crosses the interval.

The spacer is constructed by bonding two substantially symmetrical press-molded members together, and the secondary air supply passage is integrally formed with the spacer. (Function) With the above configuration, in the present invention, at a predetermined interval maintained by a spacer between the monolithic catalysts arranged in series in the axial direction of the casing, the presence of a secondary air supply passage that crosses the interval; The ejection of secondary air from the secondary air supply passage creates a turbulent flow of exhaust gas, and after the exhaust gas and secondary air are stirred and mixed sufficiently and uniformly, they flow uniformly into the monolithic catalyst in the subsequent stage. Therefore, the purification performance of the catalyst is improved by good mixing of this exhaust gas and secondary air and uniform flow into the downstream monolithic catalyst.゜Move up.

In this case, there are two spacers: a spacer for maintaining a predetermined distance between the monolithic catalysts in the first stage, and a secondary air supply passage that crosses the space.
Since it is integrally formed with two approximately symmetrical press-molded members, the number of parts can be reduced to three, and the insertion hole between the casing and the spacer allows the insertion of the conventional secondary air supply pipe. Drilling and alignment of both insertion holes are not required, making manufacturing easy. (Example) 4 Hereinafter, an example of the present invention will be described in detail based on the drawings.

1 and 2, reference numeral 1 denotes a cylindrical casing, and the casing 1 includes a pair of press-molded shells 2, 2 which are vertically divided in the axial direction.
, 2 are joined to each other by flange portions 2a, 2a formed on the outer peripheral edges of the casing 1, and the central portion of the casing 1 has a catalyst storage portion 1a with an elliptical cross section that is flat in the vertical direction. The front and rear ends of the portion 1a have inlet and outlet exhaust pipe connecting portions 1b and 1c each having a circular cross section.

An exhaust pipe connection inlet flange 4 having an exhaust gas inlet port 4a at the center is fixed to the tip of the inlet side exhaust pipe connection part 1b via a connecting ring 3 by welding, and an outlet side exhaust pipe connection part 1c An exhaust pipe connection outlet flange 6 having an exhaust gas outlet 6a in the center is fixed to the rear end by welding via the connecting ring 5, and each of the flanges 4 and 6 has an exhaust pipe connected thereto. Stud bolt 7 for connection
, 8 have been planted. In the catalyst storage portion 1a of the casing 1, a reduction monolith catalyst 9 is arranged in the upstream front stage, an oxidation monolith catalyst 10 is arranged in the downstream downstream stage in series in the axial direction of the casing 1, and both monolith catalysts 9,
10 is 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 made of an elliptical columnar carrier made of a ceramic material coated with a catalyst such as platinum, and have a large number of ventilation holes penetrating in the axial direction in a honeycomb shape. The spacer 11 consists of two approximately symmetrical elliptical dish-shaped press molded members 12, each having an L-shaped cross-sectional flange portion 12a, 13a protruding outward on the outer periphery of the tip.
13 are arranged in the front and back and are bonded to each other at their bottoms, and the outer circumferential surfaces of the flange portions 12a, 13a of each of the press molded members 12, 13 are brought into contact with the inner circumferential surface of the casing 1. It is fixed to the casing 1 by plug welding, and the axial rear end surface of the reduction monolith catalyst 9 is brought into contact with the flange portion 12a via an elastic body 14 such as a steel mesh to elastically hold it, and the flange portion 12a is The front end surface of the oxidation monolith catalyst 10 in the axial direction is brought into contact with the portion 13a and held under pressure, so that both the monolith catalysts 9 and 1
0 to the predetermined interval S described above.

Further, an annular secondary air chamber 15 is formed between the spacer 11 and the inner peripheral surface of the casing 1, and the secondary air chamber 15 includes a flange portion 2a of the shells 2, 2 in the casing 1. , 2a, one end of the secondary air supply pipe 16 arranged and fixed on the bonding surface is open, and the other end of the secondary air supply pipe 16 is led out of the casing 1 and connected to the air pump via the connection flange 17. (not shown).

On the bottom bonding surfaces of each of the press molded members 12 and 13 constituting the spacer 11, there is formed a concave groove portion having a semicircular cross section and extending in the long axis direction of the ellipse and recessed in the opposite front and rear directions. 12b and 13b are formed,
A secondary air supply passage 1 whose one end communicates with the secondary air chamber 15 and which crosses the interval S in the direction of the long axis of the ellipse of the casing 1
8 are integrally formed with the spacer 11, and a large number of secondary air ejection holes are provided on the outer circumferential surface of the downstream side concave groove portion 13b to communicate the secondary air supply passage 18 with the space within the space S. 19, 19... are bored, and the secondary air flowing into the secondary air chamber 15 is transferred to the secondary air supply passage 18.
The configuration is such that the secondary air jets 5 are supplied from the secondary air jet holes 19, 19, . . . toward the rear within the interval S. Incidentally, reference numeral 20 denotes a communication port formed by drilling the bottom bonding surface of each of the press molding members 12 and 13 constituting the spacer 11, excluding the concave groove portions 12b and 13b. Reference numeral 21 denotes a cone-shaped pressure member, which includes a support portion 21a that presses and holds the axial front end surface of the reduction monolith catalyst 9 in the axial direction, and a support portion 21a located a predetermined distance forward from the axial front end surface of the reduction monolith catalyst 9. It is integrally formed with a baffle portion 21b for rectifying the flow of exhaust gas, and is fixed to the casing 1 by, for example, plug welding.

Further, 22 and 23 are steel meshes interposed between the outer circumferential surfaces of the monolithic catalysts 9 and 10 and the inner circumferential surface of the casing 1 so as to elastically hold the outer circumferential surfaces of the monolithic catalysts 9 and 10. The elastic body 24 is a support member that elastically holds the axial rear end surface of the oxidation monolith catalyst 10 at the axial rear end of the catalyst storage portion 1a of the casing 1 via an elastic body 25 such as a steel mesh.
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 baffle portion 2 of the pressure member 21.
After passing through 1b, it flows into the reduction monolith catalyst 9 and is reduced and purified by the catalyst 9.

At this time, the exhaust gas is rectified by the baffle portion 21b and uniformly flows into the reduction monolith catalyst 9, so that the reduction purification performance is improved. Thereafter, the exhaust gas that has passed through the reduction monolith catalyst 9 and has been reduced and purified is transferred to the spacer 11.
The presence of a secondary air supply passage 18 that crosses the interval S in the direction of the long axis of the ellipse, and the secondary air injection holes 19, 19, of the secondary air supply passage 18, in the interval S as a mixing area maintained by the The ejection of secondary air from ... creates a turbulent flow, and after the exhaust gas and secondary air are stirred and mixed sufficiently and uniformly, they flow uniformly into the oxidation monolith catalyst 10, and the oxidation monolith catalyst It is oxidized and purified at 10.

At this time, the purification performance of the oxidation monolith catalyst 10 is improved by good mixing of the exhaust gas and secondary air and uniform flow into the oxidation monolith catalyst 10. 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. In that case, in the monolithic catalytic converter of the above embodiment, a spacer 11 is provided between the reduction monolithic catalyst 9 and the oxidation monolithic catalyst 10 to maintain a spacing S as a mixing area, and the spacing S is arranged in the direction of the long axis of the ellipse. The secondary air supply passage 18 that traverses two approximately symmetrical press molded members 12.
, 13, the number of parts can be reduced, and it is also possible to drill the insertion hole between the casing and the spacer for inserting the secondary air supply pipe as in the conventional case, and to make it easier to drill the insertion hole in both the holes. This eliminates the need for alignment, making manufacturing easier.

Further, the concave groove portions 12b and 13b of the press molded members 12 and 13 forming the secondary air supply passage 18 are connected to the casing 1.
Since it is disposed across the central part (catalyst storage part 1a), especially in the direction of the long axis of the ellipse, which has weak rigidity, the rigidity of the casing 1 and the spacer 11 itself increases.
Membrane vibration of the casing 1 due to engine vibration and exhaust pulsation is suppressed, and as a result, it is possible to prevent cracks from occurring in the casing 1 and the frames 2, 13 of the breath molded member 1 itself, and also to prevent the monolith from forming cracks. The fixing force of the catalysts 9, 10 is increased, and damage to the monolithic catalysts 9, 10 can be further prevented. Note that the present invention is not limited to the above-mentioned embodiment, and includes various other modifications. For example, in the above-mentioned embodiment, the casing 1
Although a case has been described in which two reduction monolith catalysts 9 are placed in the front stage and two oxidation monolith catalysts 10 are placed in the rear stage, the present invention is also applicable to cases in which three or more monolith catalysts are arranged in series with a predetermined distance from each other. Of course, the same can be applied to.

Further, in the above embodiment, the casing 1 is composed of a pair of shells 2, 2 that are vertically divided in the axial direction, but it goes without saying that it may be composed of a shell that is integrally formed into a cylindrical shape.

Furthermore, as a means for fixing the press molded members 12, 13 and other members, in addition to welding as described above, various fixing means can be employed. (Effects of the Invention) As explained above, according to the monolithic catalytic converter of the present invention, two spacers are provided to maintain a predetermined distance between the monolithic catalysts arranged in series in the axial direction of the cylindrical casing. The spacer is constructed by bonding approximately symmetrical press molded members, and the spacer is integrally formed with a secondary air supply passage in a direction that crosses the above-mentioned interval, thereby improving the purification performance of the monolithic catalyst. As the number of parts is reduced, manufacturing and processing become easier, and costs can be reduced.

Furthermore, it has excellent practical effects, such as increasing the rigidity of the casing and improving durability.

[Brief explanation of the drawing]

The drawings illustrate an embodiment of the invention, with FIG. 1 being a cross-sectional view and FIG. 2 being a longitudinal sectional view. DESCRIPTION OF SYMBOLS 1...Casing, 4...Inlet flange for exhaust pipe connection, 4a...Exhaust gas inlet, 6...Outlet flange for exhaust pipe connection, 6a...Exhaust gas outlet, 9... Reduction monolith catalyst, 10... Oxidation monolith catalyst, 11.
... Spacer, 12, 13 ... Breath molding member, 12
b, 13b...Concave groove portion, 18...Secondary air supply passage, 19...Secondary air jet hole, S...Spacing.

Claims (1)

[Claims] 1 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 outlet at the front and rear, and monolithic catalysts are arranged in series in the axial direction of the casing through spacers that maintain a predetermined interval. In a monolithic catalytic converter equipped with a secondary air supply passage, the spacer is
A monolithic catalytic converter characterized in that it is constructed by bonding two substantially symmetrical press-formed members together, and that the secondary air supply passage is integrally formed with the spacer.