JP3715127B2 - Catalytic converter - Google Patents

Description

【００２０】
【発明の効果】
請求項１記載の発明によれば前記のように構成することにより、フレッシュ状態の触媒コンバータの使用開始時において、バーミキュライトの加熱による収縮に起因した保持マットおよびモノリス担体の、そのモノリス担体軸線方向への位置ずれを抑制し得る触媒コンバータを提供することができる。
【００２１】
請求項２記載の発明によれば、前記効果に加え、合成樹脂フィルムの過熱による早期焼失を確実に防止し、またバーミキュライトの熱劣化も防止することが可能な触媒コンバータを提供することができる。
【図面の簡単な説明】
【図１】 触媒コンバータの一例の正面図である。
【図２】 図１の２−２矢視図である。
【図３】 保持マットの斜視図である。
【図４】 加熱温度とモノリス担体に対する面圧保持率との関係を示すグラフである。
【図５】 触媒コンバータの他例の要部端面図で、図２に対応する。
【符号の説明】
１ 触媒コンバータ
５ モノリス担体
６ 保持マット
７ アウタシェル
１２ 断熱層（アルミナ繊維マット）
Ｆ 合成樹脂フィルム（ポリエチレンフィルム）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a catalytic converter applied to an exhaust system of an automobile, in particular, a columnar monolith carrier carrying a catalyst, a holding mat wound around the outer peripheral surface of the monolith carrier and containing vermiculite, and the holding mat The present invention relates to an improvement of a catalytic converter having an outer shell for covering.
[0002]
[Prior art]
Conventionally, in this type of catalytic converter, a holding mat is compressed by an outer shell to give a predetermined surface pressure to the monolith carrier, and the monolith carrier is held stationary in the outer shell by a holding force by the outer shell and the holding mat. is there.
[0003]
[Problems to be solved by the invention]
Vermiculite is expanded at a high temperature to increase the bulk of the holding mat, and thereby suppresses a decrease in holding power to the monolith carrier due to an increase in the distance between the expanded outer shell and the monolith carrier.
[0004]
However, at the start of use of the fresh catalytic converter, when the vermiculite is heated, it contracts before expansion, and accordingly the bulk of the holding mat decreases and the holding power against the monolith support decreases. There was a problem that the holding mat and the monolith carrier were likely to be displaced in the axial direction of the monolith carrier.
[0005]
[Means for Solving the Problems]
An object of the present invention is to provide the catalytic converter capable of suppressing the displacement of the holding mat and the monolithic carrier caused by the contraction due to heating of the vermiculite at the start of use of the fresh catalytic converter. .
[0006]
According to the present invention for achieving the above object, it covers a circular columnar monolithic carrier carrying a catalyst, a cylindrical retaining mat including the entire wound 且 one vermiculite on the outer peripheral surface of the monolithic carrier, the holding mat In the catalytic converter having an outer shell, an outer peripheral surface of the holding mat in order to suppress axial displacement between the holding mat and the monolith carrier due to contraction due to heating of the vermiculite at the start of use of the fresh catalytic converter Further, there is provided a catalytic converter in which a synthetic resin film that melts under heating and exhibits an adhesive force is interposed only between inner peripheral surfaces of the outer shell.
[0007]
With the above configuration, even when vermiculite contracts due to heating when the fresh catalytic converter is used , the outer peripheral surface side of the holding mat is stopped on the inner peripheral surface of the outer shell by the adhesive force of the synthetic resin film melt. In addition, since the friction coefficient between the outer peripheral surface of the monolith carrier and the inner peripheral surface of the holding mat is relatively large, the relative movement between them can be ignored, thereby suppressing the axial displacement between the holding mat and the monolith carrier. can do.
[0008]
It should be noted that vermiculite that once caused shrinkage under heating does not shrink due to subsequent heating.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
1 to 3, an automotive catalytic converter 1 is in a fresh state after production, and includes a cylindrical main body 2, an inlet cone 3 joined to an end of the exhaust gas introduction side, and an exhaust thereof. The outlet cone 4 is joined to the end portion on the gas discharge side. The cylindrical main body 2 includes a columnar monolithic carrier 5 supporting a catalyst, in the illustrated example, a columnar shape, a cylindrical holding mat 6 wound around the outer peripheral surface of the monolithic carrier 5, and the holding mat 6. A synthetic resin film F wound around the outer peripheral surface of the outer shell 7 and an outer shell 7 that covers the film F and compresses the holding mat 6. In this way, a predetermined surface pressure is applied to the monolith carrier 5 by the compression of the holding mat 6 by the outer shell 7, and the monolith carrier is held in the outer shell 7 by the holding force by the outer shell 7 and the holding mat 6. The outer shell 7 is wound around the outer peripheral surface of the holding mat 6 and the other end edge portion 8b is overlapped on one end edge portion 8a of the metal plate 8 that compresses the holding mat 6 so as to be between the end edge portions 8a and 8b. Are joined by the weld 9.
[0010]
The monolith carrier 5 is a honeycomb composed of cordierite which is ceramic. The holding mat 6 is made of a mixture of alumina fiber, silica fiber, binder and vermiculite, and therefore the entire holding mat 6 contains vermiculite. Then, the concave and convex portions 10 and 11 formed at both ends of the holding mat 6 are fitted and wound around the outer peripheral surface of the monolith carrier 5. As the binder, acrylic acid ester, NBR, or the like is used. The synthetic resin film F melts under heating and exhibits an adhesive force. For example, a polyethylene film is used, and both ends are welded. The outer shell 7, the inlet cone 3, and the outlet cone 4 are formed using a ferritic stainless steel plate (for example, JIS SUS409 or JIS SUS410).
[0011]
FIG. 4 shows the relationship between the heating temperature and the surface pressure retention ratio with respect to the monolith support 5 at the start of use of the fresh catalytic converter 1. From FIG. 4, it can be seen that the surface pressure retention decreases as the heating temperature rises and becomes the lowest at about 350 ° C., and the surface pressure retention increases in the temperature range exceeding that. This is because vermiculite contracts at a heating temperature of about 350 ° C. or lower, while vermiculite starts to expand when the heating temperature exceeds about 350 ° C. In this case, the holding mat 6 and the monolith carrier 5 are likely to be displaced in the monolith carrier axial direction a at a heating temperature of 250 to 350 ° C.
[0012]
In order to respond to this, a synthetic resin film F is used, and a polyethylene film is selected as the film F. That is, the polyethylene film F generally starts to soften at about 200 ° C. and burns down to 400 ° C. or less in an atmosphere where oxygen is sufficiently present, but burns down to about 500 ° C. in an oxygen-deficient atmosphere such as an exhaust gas atmosphere. Without demonstrating adhesive strength in the molten state. That is, the polyethylene film F functions as an adhesive in a temperature range of about 200 to about 500 ° C. including a temperature range of 250 to 350 ° C. where the positional deviation is likely to occur.
[0013]
If comprised as mentioned above, even if vermiculite shrinks by heating, the outer peripheral surface side of the holding mat 6 is stopped on the inner peripheral surface of the outer shell 7 by the adhesive force of the melt of the polyethylene film F, and the monolith carrier 5 is Since it is made of ceramics, the coefficient of friction between the outer peripheral surface and the inner peripheral surface of the holding mat 6 is relatively large so that the relative movement between them can be neglected, whereby the holding mat 6 and the monolith carrier 5 The displacement can be suppressed.
[0014]
When the polyethylene film F is wound around the outer peripheral surface of the holding mat 6 on the monolith carrier 5 and the holding mat 6 is compressed in advance, the holding mat 6 is not compressed by the metal plate 8 in forming the outer shell 7. Therefore, the workability of forming the outer shell 7 can be improved, and the sound of the catalytic converter 1 can be manufactured by preventing the holding mat 6 from being offset and the outer shell 7 being bitten by the holding mat 6. In addition, since the polyethylene film F is slippery, it is not dragged by the wound metal plate 8 in the process of forming the outer shell 7.
[0015]
Instead of the polyethylene film F, a heat-shrinkable tube made of polyethylene can be used.
[0016]
FIG. 5 shows a heat insulating layer 12 interposed between the outer peripheral surface of the monolith carrier 5 and the inner peripheral surface of the holding mat 6. The heat insulating layer 12 is made of, for example, an alumina fiber mat.
[0017]
If comprised in this way, the premature burning by the overheating of the polyethylene film F can be prevented reliably, and the thermal deterioration of vermiculite can also be prevented. Further, although the alumina fiber mat 12 is bulky, it can be pre-compressed with the polyethylene film F via the holding mat 6, so problems due to the bulk, such as deterioration of workability of forming the outer shell 7, etc. Does not occur. In this case, since the friction coefficient between the inner peripheral surface of the holding mat 6 and the outer peripheral surface of the alumina fiber mat 12 and between the inner peripheral surface of the alumina fiber mat 12 and the outer peripheral surface of the monolith carrier 5 is relatively large, relative movement between them is ignored. can do.
[0018]
The basis weight of the alumina fiber mat 12 varies depending on the temperature of the outer peripheral surface of the monolith carrier 5. For example, Table 1 shows the case where the catalytic converter 1 is applied to an exhaust system of a gasoline engine.
[0019]
[Table 1]

[0020]
【The invention's effect】
According to the first aspect of the present invention, when the fresh catalytic converter is used, the holding mat and the monolith carrier due to the shrinkage caused by heating of the vermiculite in the axial direction of the monolith carrier are obtained. Thus, it is possible to provide a catalytic converter that can suppress the positional deviation.
[0021]
According to invention of Claim 2, in addition to the said effect, the catalytic converter which can prevent the premature burning by the overheating of a synthetic resin film reliably, and can also prevent the thermal deterioration of a vermiculite can be provided.
[Brief description of the drawings]
FIG. 1 is a front view of an example of a catalytic converter.
FIG. 2 is a view taken along arrow 2-2 in FIG.
FIG. 3 is a perspective view of a holding mat.
FIG. 4 is a graph showing the relationship between the heating temperature and the surface pressure retention rate with respect to the monolith carrier.
FIG. 5 is an end view of a main part of another example of the catalytic converter and corresponds to FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Catalytic converter 5 Monolith carrier 6 Holding mat 7 Outer shell 12 Heat insulation layer (alumina fiber mat)
F Synthetic resin film (polyethylene film)

Claims (2)

Covering the catalyst circularly columnar monolithic carrier carrying (5), a cylindrical retaining mat including the whole 且 one vermiculite wound around the outer peripheral surface of the monolithic carrier (5) (6), the retaining mat (6) In a catalytic converter having an outer shell (7),
In order to suppress the axial displacement between the holding mat (6) and the monolithic carrier (5) due to the shrinkage caused by heating of the vermiculite at the start of use of the fresh catalytic converter, the outer periphery of the holding mat (6) A catalytic converter characterized in that a synthetic resin film (F) that melts under heating and exhibits adhesive force is interposed only between the surface and the inner peripheral surface of the outer shell (7).   The catalytic converter according to claim 1, wherein a heat insulating layer (12) is interposed between the outer peripheral surface of the monolith support (5) and the inner peripheral surface of the holding mat (6).

Images