JPH022023B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a thermally expandable seal used in a catalytic converter for exhaust gas purification and the like.

In recent years, in catalytic converters in which a monolithic catalyst is housed in a case, a thermally expandable sealing material made of ceramic fibers mixed with vermiculite powder has been adopted as a seal to close the space between the monolithic catalyst and the case in the axial direction. There is a tendency to
This thermally expandable sealing material expands when heated to a high temperature, and once it expands, it solidifies and does not contract again. It also exhibits excellent heat resistance, and in its unexpanded state, it can be used as a monolithic catalyst. When the catalytic converter is inserted between the case and exposed to high temperatures, it expands to fill the gap between the monolithic catalytic converter and the case, creating a reliable seal between the two, which is extremely useful. fragile,
When assembled into a catalytic converter, there is a risk that it will easily break if it comes into contact with a case or the like.

For this reason, in the past, a thermally expandable sealing material was compressed to a thickness that was less than the gap between the monolithic scatterer and the case, and then vacuum-packed with a synthetic resin film to prevent the sealing material from breaking during assembly. A method has been proposed to avoid this problem, but in such a method, there is a limit to the size of the product that can be packaged due to the capacity of the suction pump, etc. If the film is damaged during transportation or assembly, air can enter through the scratches, causing the sealing material to return to its pre-compression thickness with its restoring elastic force. I had a problem where it got hot.

The present invention has been completed in view of the above points, and produces a thermally expandable sealing material that can avoid crushing during assembly and fully exhibit its sealing performance. You can also
The object of the present invention is to provide a method capable of manufacturing long seals with simple equipment.

Hereinafter, an embodiment in which the method of the present invention is applied to a seal for a catalytic converter will be described with reference to the accompanying drawings.

The manufacturing process of the thermally expandable seal 1 will be explained with reference to a to d in FIG. 1. First, the manufacturing process of the thermally expandable seal 1 shown in FIG. 2, specifically, there is alumina-silica fiber mixed with vermiculite powder, which is sold by 3M of the United States under the trademark INT-ARAM, and its shape is similar to that of the monolithic carrier to be inserted. It has a strip shape with a rectangular cross section and a thickness approximately equal to the gap between the talist and the case.

Then, as shown in Figure b, a sheet-like backing material 3 made of hard vinyl chloride, hard polyethylene, paper, or the like is superimposed on both the upper and lower surfaces of the ceramic fiber 2, and a sheet-shaped backing material 3 made of hard vinyl chloride, hard polyethylene, paper, or the like is layered on the outer periphery of the material. As shown, a tube 4 made of heat-shrinkable synthetic resin is covered. Suitable materials for the tube 4 include cross-linked polyethylene sold under the trade name "Lectron" by Nitto Denko, or Teflon.
It has the property of shrinking when heated to a relatively low temperature of about 100 to 150 degrees.

Then, when heated to 100 to 150 degrees through a heating furnace, the tube 4 contracts and due to the contraction force,
The ceramic fibers 2 are compressed and held in a state where the thickness is reduced compared to the normal state, and the thermally expandable seal 1 as shown in FIG. 4D is completed.

Here, since the covering material 3 is applied to both the upper and lower surfaces of the ceramic fiber 2, it is possible to prevent the ceramic fiber 2 from curving around its axis when compressed by the contraction of the tube 4. Can be done.

Note that if the shrinkage force of the tube 4 alone is insufficient to compress the ceramic fiber 2, a method is adopted in which the ceramic fiber 2 is compression-molded by a press and then covered with the tube 4. The above-mentioned padding material 3 is placed on both the upper and lower sides of the
By applying this, it is possible to prevent the ceramic fibers 2 from being damaged.

Next, to explain the assembly procedure of the catalytic converter with reference to FIG. It is wrapped around and fixed by adhesive or the like, and a cylindrical supporter 11 made of corrugated metal mesh is fitted onto the remaining outer circumferential portion. Then, a cushion ring 13 made of a compression-molded metal mesh is attached to the outlet 12a side of the case 12, and then the monolithic catalyst 10 equipped with the thermally expandable seal 1 and the supporter 11 is inserted from the inlet 12b. At this time, the thermally expandable seal 1 is compressed to a thickness that is less than the gap between the monolithic scatterer 10 and the case 12, and its outer periphery is covered with the tube 4, so that it cannot be inserted. This is done extremely smoothly, and there is no risk of it coming into contact with the case 12 and breaking it.

Then, when the catalytic converter is put into use and exposed to a high temperature atmosphere of several hundred degrees, the padding material 3 and the tube 4 melt and disappear, and at the same time, the ceramic fibers 2 are removed from the monolithic catalytic converter 10 and the case 12. It expands to fill the gap between them, reliably sealing the space between them, and firmly fixing the monolithic catalyst 10 to the case 12.

In this embodiment, the ceramic fiber 2 is encapsulated with the heat-shrinkable synthetic resin tube 4, but instead of this, it may be similarly encapsulated with a heat-shrinkable synthetic resin film.

Furthermore, the method of the present invention is not limited to manufacturing seals for catalytic converters as shown in this example, but can also be effectively applied to manufacturing seals used in other devices. can.

That is, the method for manufacturing a thermally expandable seal of the present invention includes a thermally expandable sealing material that expands when heated above a certain temperature, and a thermally expandable synthetic resin that contracts when heated to a temperature lower than the certain temperature. The sealing material is encapsulated with a thin film of heat-shrinkable synthetic resin and heated to the low temperature to maintain the sealing material in a compressed state by contraction of the thin film, and the sealing material is heated by the contraction force of the thin film of heat-shrinkable synthetic resin. Since the expandable sealing material is held in a compressed state, it is possible to manufacture a thermally expandable seal that can reliably avoid crushing when assembling the thermally expandable sealing material, and it is also possible to manufacture a thermally expandable seal that can reliably avoid breakage during assembly. Compared to vacuum packaging, manufacturing efficiency is improved because long stickers can be manufactured, and expensive equipment such as a vacuum packaging machine is not required; all that is required is a heating furnace. It is possible to reduce the cost of equipment, and furthermore, it is possible to avoid a situation where the film is damaged and the sealing material swells before being assembled.

[Brief explanation of drawings]

1 and 2 show an embodiment of the present invention,
1A to 1D are explanatory diagrams of the manufacturing process of the thermally expandable seal, and FIG. 2 is a longitudinal sectional view of a catalytic converter incorporating the thermally expandable seal. 1: thermally expandable seal, 2: ceramic fiber,
3: Backing material, 4: Tube.

Claims (1)

[Claims] 1. A thermally expandable sealing material that expands when heated above a certain temperature is encapsulated with a thin film of a heat-shrinkable synthetic resin that contracts when heated to a temperature lower than the certain temperature, A method for manufacturing a thermally expandable seal, comprising heating the sealing material to the low temperature and maintaining the sealing material in a compressed state by the contraction force of the thin film. 2. The method of manufacturing a heat-expandable seal according to claim 1, wherein the heat-expandable seal material is covered with a thin film of the heat-shrinkable synthetic resin. 3. The method of manufacturing a heat-expandable seal according to claim 1, characterized in that the compression-molded heat-expandable sealing material is encapsulated with a thin film of the heat-shrinkable synthetic resin.