JPH05195763A - Integrated tandem metal catalyst bearer - Google Patents

Abstract

PURPOSE:To provide a single body type tandem metal catalyst bearer, in which the purifying efficiency of a downstream side honeycomb body is enhanced through enhancement of the air warm-up performance of the downstream honeycomb body. CONSTITUTION:A single body type tandem metal catalyst bearer is composed of an outer cylinder 1 and an upstream and a downstream metal honeycomb body 2, 3, which are installed apart in the axial direction within the outer cylinder 1 and joined therewith in one place over the axial direction. The joining position of the outer cylinder 1 with the downstream metal honeycomb body 3 is located the end on inlet side of the downstream metal honeycomb body 3. The heat of the exhaust gas stagnating in the space 4 between the honeycomb bodies 2, 3 is conducted first to the outer cylinder to be immediately conducted further to the downstream honeycomb body 3 via the brazing part 3a, which enables enhancing the air warm-up performance of the downstream honeycomb body 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an integrated tandem metal catalyst carrier used as an exhaust gas purifying catalyst for an internal combustion engine.

[0002]

2. Description of the Related Art An exhaust gas purifying catalyst for an internal combustion engine is arranged in an exhaust passage to purify HC, CO, NO _x, etc. in the exhaust gas. As a metal catalyst carrier used for this exhaust gas purification catalyst, a metal flat plate and a corrugated plate are stacked and wound in a roll to form a honeycomb body, and the honeycomb body is generally housed in a metal outer cylinder. Is known to be. In this metal carrier, the flat plate and the corrugated plate of the honeycomb body, and the outer cylinder and the honeycomb body are integrally joined by brazing or the like. Then, a precious metal catalyst is supported on the surface of the honeycomb passage of the honeycomb body to form an exhaust gas purification catalyst.

Exhaust gas passing through the honeycomb body has a larger flow rate toward the central portion of the honeycomb body. Therefore, in the metal catalyst carrier, due to the effects of contact with high-temperature exhaust gas, heat generation due to catalytic reaction, heat release from the outer cylinder to the outside air, etc. A temperature distribution of Due to this, distortion due to a large thermal stress occurs, and the honeycomb body and the outer cylinder are separated from each other, the flat plate and the corrugated plate that form the honeycomb body are separated from each other, and each component is cracked or damaged.

As a metal catalyst carrier for preventing such a problem, in Japanese Utility Model Laid-Open No. 2-83320, a pair of upstream and downstream metal honeycomb bodies are axially spaced from each other in a metal outer cylinder. There is disclosed an integrated tandem metal catalyst carrier in which an upstream honeycomb body is joined to an outer cylinder at an inlet end portion thereof, and a downstream honeycomb body is joined to an outer casing thereof at an outlet end portion thereof.

In this metal catalyst carrier, a turbulent flow of exhaust gas is generated in the space between the pair of honeycomb bodies, and the temperature distribution of the downstream side honeycomb body is made more uniform. Further, due to the existence of the non-bonded portion between each honeycomb body and the outer cylinder, the thermal stress strain in the axial direction of the honeycomb body is absorbed. Therefore, the problems due to the thermal stress can be improved.

[0006]

However, in the integrated tandem metal catalyst carrier as described above, in the space portion between the pair of honeycomb bodies, the turbulent flow of the exhaust gas generated in the space portion causes exhaust gas The amount of heat released from the outer cylinder to the outside air increases, resulting in heat loss. For this reason, it becomes difficult to effectively transfer the heat generated in the upstream honeycomb body to the downstream honeycomb body, and the warm-up performance of the downstream honeycomb body deteriorates and the purification efficiency of the downstream honeycomb body deteriorates. There is.

The present invention has been made in view of the above circumstances, and the warm-up performance of the downstream honeycomb body is improved by making the heat conducting portion between the downstream honeycomb body and the outer cylinder upstream of the downstream honeycomb body. It is an object of the present invention to improve the purification efficiency of the downstream honeycomb body.

[0008]

Means for Solving the Problems The inventors of the present invention have studied the cause of the decrease in the warm-up performance of the honeycomb body in the integrated tandem metal catalyst carrier. It was found that the joining position at the time of joining by brazing affects the warm-up performance of the honeycomb body. As described above, the warm air performance varies depending on the joining position because a minute gap is formed between the honeycomb body and the outer cylinder in the non-joint portion, and the presence of this gap causes the exhaust gas to be transmitted to the outer cylinder. It is considered that this is because heat is easily released to the outside air.

The present invention was made based on the above findings, and the integrated tandem metal catalyst carrier of the present invention comprises:
An integrated tandem metal comprising an outer cylinder and a pair of upstream and downstream metal honeycomb bodies which are axially separated from each other in the outer cylinder and are joined to the outer cylinder at one axial position. In the catalyst carrier, the joining position between the outer cylinder and the downstream side metal honeycomb body is an end portion on the inlet side of the downstream side metal honeycomb body.

[0010]

In the integrated tandem metal catalyst carrier, the axial length of the upstream metal honeycomb body is shortened and the heat capacity is correspondingly reduced, so that the temperature rise characteristic of the upstream honeycomb body is improved. In the integrated tandem metal catalyst carrier, the heat of the exhaust gas staying in the space between the pair of upstream and downstream metal honeycomb bodies is transferred to the outer cylinder. Since the body is joined to the outer cylinder at the end portion on the inlet side, the heat transferred from the space portion to the outer cylinder is immediately transmitted to the honeycomb body on the downstream side via the joint portion. Therefore, the heat of the exhaust gas staying in the space can be efficiently transmitted to the downstream honeycomb body without escaping the heat to the outside as much as possible, and the warming performance of the downstream honeycomb body can be improved.

[0011]

EXAMPLES The present invention will be specifically described below with reference to examples. (Embodiment 1) The integrated tandem metal catalyst carrier of this embodiment comprises a metal outer cylinder 1 and a pair of upstream and downstream metal honeycomb bodies 2 and 3 which are axially separated from each other in the outer cylinder 1. It consists of and.

The outer cylinder 1 is a cylindrical member made of a ferrite alloy and having a plate thickness of 1.5 mm and a diameter of 90 mm. The upstream metal honeycomb body 2 is composed of a flat plate 21 made of Al-containing ferrite alloy and having a plate thickness of 50 μm, and a corrugated plate 22 obtained by processing the flat plate 21 into a corrugated shape. It is formed by winding. The flat plate 21 and the corrugated plate 22 are integrally joined by brazing. The length of the metal honeycomb body 2 is 50 mm.

The metal honeycomb body 3 on the downstream side has the same structure as the metal honeycomb body 2 on the upstream side. And
The metal honeycomb body 2 on the upstream side is joined to the outer cylinder 1 at the end portion on the outlet side. This joining is performed by inserting the metal honeycomb body 2 into the outer cylinder 1 and then performing brazing in which high-temperature high-vacuum processing is performed using a Ni-based brazing material. The range of the brazing part 2a is 15 mm from the outlet side end.

The metal honeycomb body 3 on the downstream side is joined to the outer cylinder 1 at the end portion on the inlet side by brazing similar to the above. The range of the brazing portion 3a is 15 mm from the inlet end. A space 4 having a length of 20 mm is formed in the axial direction between the metal honeycomb bodies 2 and 3. In addition, the outer cylinder 1 and the metal honeycomb bodies 2 and 3
A minute gap A of about 30 μm is formed between the and. (Example 2) The length of the upstream metal honeycomb body 2 was set to 40.
mm, the range of the brazing part 2a is 10 mm from the end on the outlet side
And the length of the metal honeycomb body 3 on the downstream side is 60
mm, the range of the brazing part 3a is 15 mm from the inlet end
In the same manner as in Example 1 except that the length of the space 4 between the two was 30 mm to obtain an integrated tandem metal catalyst carrier of Example 2. (Example 3) The length of the upstream metal honeycomb body 2 was set to 20.
mm, the range of the brazing part 2a is 10 mm from the end on the outlet side
And the length of the metal honeycomb body 3 on the downstream side is 80
mm, the range of the brazing part 3a is 20 mm from the end on the inlet side
In the same manner as in Example 1 except that the length of the space 4 between the two was set to 10 mm to obtain an integrated tandem metal catalyst carrier of Example 3. (Example 4) An integrated tandem metal catalyst carrier of Example 4 was obtained in the same manner as in Example 1 except that the upstream side metal honeycomb body 2 was joined to the outer cylinder 1 at its inlet end. It was (Comparative Example) Except that the upstream side metal honeycomb body 2 is joined to the outer cylinder 1 at its inlet end and the downstream metal honeycomb body 3 is joined to the outer cylinder 1 at its outlet side. In the same manner as in Example 1, an integrated tandem metal catalyst carrier of Comparative Example was obtained. (Evaluation) The integrated tandem metal catalyst carriers of Examples 1 to 4 and Comparative Example described above were catalyzed and mounted on the exhaust system of an actual engine, and the warm-up performance of the catalyst at engine start was evaluated. This was done by measuring the temperature of the downstream metal honeycomb body 3 15 seconds after the engine was started. The results are shown in Table 1.

[0015]

[Table 1] As is clear from Table 1, it is understood that the warm-up performance of the downstream metal honeycomb body 3 is improved by setting the joining site in the downstream metal honeycomb body 3 as the inlet end. This is because the heat of the exhaust gas accumulated in the space 4 between the metal honeycomb bodies 2 and 3 is transferred to the outer cylinder 1, and immediately after that, the brazing portion 3a formed at the inlet end of the metal honeycomb body 3 on the downstream side. It is considered that this is due to returning to the downstream side metal honeycomb body 3 via the. From this, the metal honeycomb body 2,
As a brazing material for joining 3 and the outer cylinder 1, it is preferable to use one having excellent thermal conductivity.

[0016]

As described in detail above, in the integrated tandem metal catalyst carrier of the present invention, the heat transferred to the outer cylinder from the space between the pair of metal honeycomb bodies is not released to the outside air as much as possible, and the joint is formed. It can be efficiently transmitted to the downstream side metal honeycomb body. Therefore, it becomes possible to improve the downstream side warming performance and the purification efficiency of the downstream side honeycomb body.

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing an integrated tandem metal catalyst carrier according to this embodiment.

FIG. 2 is a partially cutaway perspective view of the integrated tandem metal catalyst carrier according to the present embodiment.

[Explanation of symbols]

1 is an outer cylinder, 2 is an upstream side metal honeycomb body, 3 is a downstream side metal honeycomb body, 2a, 3a are brazing parts, and 4 is a space part.

Claims (1)

[Claims] 1. An outer cylinder, and a pair of upstream and downstream metal honeycomb bodies which are axially separated from each other in the outer cylinder and are joined to the outer cylinder at one axial position. In the integral tandem metal catalyst carrier, the joining position between the outer cylinder and the downstream side metal honeycomb body is an inlet side end of the downstream side metal honeycomb body. Catalyst carrier.