JPH029054Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a multi-stage monolithic catalytic converter for exhaust purification of a vehicle engine.

A multi-stage catalytic converter for a vehicle is composed of a plurality of monolithic carriers housed and supported in tandem in a catalyst case inserted in the middle of an engine's exhaust system.
The monolith carrier on the upstream side filters and removes solid harmful components such as lead compounds in the exhaust gas, or the monolith carrier on the downstream side filters and removes harmful exhaust gas components such as HC, CO and NOx. Mainly, the exhaust gas is purified by removing harmful gaseous components such as HC, CO, and NOx from the exhaust gas.

By the way, in this type of conventional catalytic converter,
As schematically shown in FIG. 3, the exhaust gas flowing into the catalyst case C' is connected to the upper and downstream monolithic catalyst carriers M' ₁ ,
In order to prevent leakage through the gap between the carriers M' ₁ and M' ₂ and the catalyst case C' without passing through M' ₂ , the inner circumferential surface of the catalyst case C' Annular elastic seal members 21 _{' 1 ,}
21' ₂ is inserted to improve purification performance. By the way, the exhaust pulsating pressure that acts inside the catalyst case C'
It is greatest on the upstream side of M' ₁ and gradually decreases from there toward the downstream side. In other words, in _{FIG .} , P ₃ satisfy P ₁ > P ₂ > P ₃ , so the annular elastic seal member 21' ₁ on the upstream side has the following properties:
When a relatively large exhaust pulsating pressure acts on the elastic seal member 21'1, there is a possibility that the scattered particles of the inorganic material forming the elastic seal member _21'1 may be pulled into the combustion chamber of the engine and enter the combustion chamber in a reverse flow. This has the disadvantage of increasing the number of units used and increasing costs.

The present invention has been made in view of the above-mentioned circumstances, and it is an object of the present invention to provide a multi-stage catalytic converter for vehicles that has a simple structure and eliminates all of the conventional disadvantages.

In order to achieve this object, the present invention includes a catalyst case and a plurality of monolithic supports housed and supported in tandem in the catalyst case, and in the longitudinal middle part of the catalyst case, adjacent monolithic supports are provided. In a multi-stage catalytic converter for vehicles, in which an annular recess is integrally formed to maintain a predetermined distance between monolithic carriers, the downstream end of the outer peripheral surface of the most downstream monolithic carrier and the catalyst case. A ring-shaped elastic sealing member is interposed only between the inner circumferential surfaces.

An embodiment of the present invention will be described below with reference to the drawings.

The multistage monolithic catalytic converter of this example has two monolithic catalyst carriers M ₁ on the upper and downstream sides,
It is composed of M ₂ and a catalyst case C that accommodates and supports them in tandem, and is used by being connected to the exhaust system of a vehicle engine.

The monolithic catalyst carrier on the upstream side is formed of a ceramic material into a cylindrical or elliptical cylindrical shape, and is configured to primarily react and remove harmful exhaust components such as HC, CO, and NOx contained in the exhaust gas. Furthermore, the monolithic catalyst carrier on the downstream side is also formed of ceramic material into a cylindrical or elliptical cylindrical shape, and is configured to mainly oxidize harmful exhaust components such as HC, CO, and NOx in the exhaust gas and remove ring elements.

The catalyst case C is constructed by welding joint flanges 8 and 9 of a pair of upper and lower case halves Ch and Ch made of heat-resistant metal such as stainless steel together along the longitudinal axis L-L. Cage, hollow cylindrical body 1
A tapered cylindrical front connection tube 2 is integrally extended at the front end of the , and a tapered cylindrical rear connection tube 4 is provided at the rear end.
are fixed, and front and rear mounting flanges 3 and 5 are integrally connected to the front and rear end surfaces of the front and rear connecting tubes 2 and 4, respectively, and each of the mounting flanges 3 and 5 has a plurality of mounting flanges attached thereto. Bolts 6 and 7 are fixed.

An annular concave portion 10 is integrally formed in the longitudinally intermediate portion of the body portion 1 of the catalyst case C over the entire circumference thereof. As a result, two locking step portions 11 and 12 are formed on the inner circumferential surface of the body portion 1, and these locking step portions 1
1 and 12 are the trailing edge of the upstream monolithic catalyst carrier M ₁ and the downstream monolithic catalyst carrier M ₂ as described later.
lock the leading edge of the

Body part 1 of catalyst case C configured as described above
The upstream monolithic catalyst carrier M ₁ is housed in the front half through an annular elastic holding member 13 , and the front and rear parts are supported by the front wall 14 of the body 1 and the annular recess 10 . The upstream monolithic catalyst carrier M ₁ is supported by the formed locking step portion 11 through the cushion rings 15 and 16 so that it does not move freely in the radial and axial directions. Similarly, the downstream side monolithic catalyst carrier _M2 is housed in the rear half of the body 1 of the catalyst case C via an annular elastic holding member 17, and the front and rear portions thereof are connected to the rear wall 18 of the body 1, The downstream catalyst carrier M 2 is locked with another locking step 12 formed by the annular recess 10 , and the downstream catalyst carrier M ₂ is locked with the cushion rings 19 , 20 .
It is supported in a fixed manner in the radial and axial directions via the radially and axially.

An annular gap between the inner peripheral surface of the catalyst case C and the downstream monolithic catalyst carrier M ₂ is sealed by an annular elastic seal member 21 . That is, between the downstream end of the outer circumferential surface of the downstream monolithic catalyst carrier M ₂ and the inner circumferential surface of the body 1, there is asbestos, Interam (registered trademark name).
The elastic seal member 21 is made of a heat-resistant material such as
is interposed, and the annular gap is sealed only by this elastic seal member 21.

Next, the operation of the embodiment of the present invention will be explained.

The catalytic converter configured as described above has its front mounting flange 3 connected to an upstream exhaust pipe connected to an engine, and its rear mounting flange 5 connected to a downstream exhaust pipe connected to an exhaust muffler.

Exhaust gas discharged from the engine and containing harmful components first flows into the upstream monolithic catalyst carrier _M1 . And within the catalyst carrier M ₁ , mainly
HC, CO and NOx are primarily removed by reaction.

The exhaust gas discharged from the upstream monolithic catalyst carrier M ₁ flows into the gaps formed by the annular recess 10 at predetermined intervals, where it becomes turbulent.
It flows into the downstream monolithic catalyst carrier _M2 , which is a three-way catalyst, where harmful exhaust components such as CO, HC, and NOx are secondarily oxidized and reduced, and the purified exhaust gas is released into the atmosphere through the exhaust muffler. released to.

By the way, the pulsating pressure of the exhaust gas flowing into the catalytic converter is firstly attenuated by passing through the upstream monolithic catalyst carrier _M1 , and then secondarily attenuated by passing through the downstream monolithic catalyst carrier _M2 . So,
Relatively strong exhaust pulsating pressure acts on the outer periphery of the upstream monolithic catalyst carrier M ₁ , and if there is an elastic seal between the outer periphery of the upstream monolithic catalyst carrier and the inner periphery of the catalyst case as in a conventional catalytic converter. If a member is interposed, this elastic seal member will be subjected to strong exhaust pulsation pressure, and the scattered particles of inorganic substances that make up the elastic seal member will be pulled, creating the possibility that they will flow back into the combustion chamber. In the invention, an annular elastic seal member 21 is interposed only between the downstream end of the outer peripheral surface of the downstream monolithic catalyst carrier M ₂ and the inner peripheral surface of the catalyst case C, so that the exhaust pulsation acting on this seal member 21 is prevented. The pressure is relatively low, so that the flying particles of the inorganic material constituting the elastic seal member 21 are not pulled by the exhaust pulsation pressure and do not enter the combustion chamber.

Furthermore, according to the experimental results, even if only a single elastic sealing member is used to seal between the catalyst case C and the downstream monolithic catalyst carrier _M2 , the exhaust purification performance of the catalytic converter will not deteriorate to a non-negligible extent. do not have. Figure 2 shows the change in exhaust purification rate with respect to the number of elastic seal members. According to this graph, the exhaust purification rate only slightly decreases by Δη when the number of seal members is one or two. Therefore, there is no need to provide two or more seal members.

In the above embodiment, the case where two monolithic catalyst carriers were housed and supported in the catalyst case was explained.
There may be three or more of them, in which case an annular elastic seal member is provided only on the outer periphery of the catalyst carrier on the most downstream side. Also, the upstream monolith carrier
M ₁ may be replaced with a monolith filter carrier capable of filtering and removing solid harmful components such as lead compounds in exhaust gas, and furthermore, the upstream monolith catalyst carrier M ₁
One or more monolithic filter carriers may be provided upstream of the filter.

As described above, according to the present invention, the catalyst case,
A plurality of monolithic carriers are housed and supported in tandem in the catalyst case, and an annular shaped carrier is provided in the longitudinally intermediate portion of the catalyst case to maintain a predetermined distance between adjacent monolithic carriers. In a multi-stage catalytic converter for vehicles in which a concave portion is integrally formed, an annular elastic sealing member is interposed only between the downstream end of the outer peripheral surface of the most downstream monolithic carrier and the inner peripheral surface of the catalyst case. Therefore, the only annular elastic seal member located near the downstream end of the catalyst case effectively prevents the exhaust gas from passing through the catalyst case, and reduces the exhaust pulsating pressure acting on the annular elastic seal member. Therefore, since the annular elastic seal member is unevenly distributed in the part farthest from the fuel chamber in the catalyst case, the influence of inorganic particles scattered from the annular elastic seal member can be minimized. It is possible to effectively prevent the fuel from entering the combustion chamber due to being pulled by the exhaust pulsating pressure. Furthermore, on the upstream side of the annular elastic seal member, the annular gap between the outer peripheral surface of each monolith carrier and the inner peripheral surface of the catalyst case is divided in the longitudinal direction of the catalyst case by the side wall of the recessed part of the catalyst case. It is possible to more effectively prevent inorganic particles from passing through each of the annular gaps and scattering toward the combustion chamber.

In addition, even if there are multiple monolithic carriers, only one relatively expensive annular elastic sealing member is required.
This can greatly contribute to reducing the cost of catalytic converters.

[Brief explanation of the drawing]

Figure 1 is a longitudinal side view of the catalytic converter of the present invention.
FIG. 2 is a graph showing the exhaust gas purification rate versus the number of annular seal members, and FIG. 3 is a schematic diagram of a conventional catalytic converter. M ₁ , M ₂ ... Upper and downstream monolithic catalyst carriers, C
... Catalyst case, 10 ... Annular recess, 21 ...
Elastic sealing member.

Claims (1)

[Scope of utility model registration request] It is equipped with a catalyst case C and a plurality of monolith carriers M ₁ and M ₂ that are housed and supported in tandem in the catalyst case C, and adjacent monolith carriers M are arranged in a longitudinally intermediate portion of the catalyst case C. In a multi-stage catalytic converter for a vehicle, which is integrally formed with an annular recessed portion 10 for maintaining a predetermined distance between M ₁ and M 2 _, the downstream end of the outer circumferential surface of the monolithic carrier M ₂ on the most downstream side. A multi-stage catalytic converter for a vehicle, characterized in that an annular elastic seal member 21 is interposed only between the inner peripheral surface of the catalyst case C and the inner peripheral surface of the catalyst case C.