1. Field of The invention
The present invention relates generally to a catalytic converter for an automotive exhaust manifold. Specifically, the invention relates a manifold type catalytic converter arrangement for an internal combustion engine in which shaking and/or oscillation of the converter vessel is reduced.
2. Description of the Prior Art
Catalytic converters for automotive engines which are arranged on an engine manifold are well known. For example, one such conventional catalytic converter arrangement is disclosed in Japanese Utility Model Application (First Publication) 59-34012, explanatory diagrams of which are shown in FIGS. 7 to 9. Referring to FIGS. 7 and 8, it can be seen that such a conventional manifold type catalytic converter 24 (hereinbelow `converter 24`) includes a vessel 27 which is connected to a cylinder head 22 of an engine 21 via a flange 25 and plurality of branch tubes 26.
The flange 25 has installation openings 25A formed therein at positions opposing exhaust ports 23 of the engine 21 and a first end 26A of each of the branch tubes 26 is respectively attached to one of the installation openings 25A of the flange 25.
As may be seen in FIG. 9, the vessel 27, which is rounded in cross-section, has a curved deflection surface portion 27B oriented on a side facing the engine 21. Although not shown in the drawings, the vessel 27 accommodates a catalytic carrier for effecting conversion of exhaust gases. Second ends 26B of each of the branch tubes 26 are connected to the vessel 27.
According to the above described conventional arrangement, vibration of the converter 24 in directions transverse to the axial direction of the engine is transmitted to the converter 24, the directions of vibration, or resonance, are shown in FIGS. 7 and 9 by arrows. Further, such vibration is amplified by transmission and thus results in a `resonance peak` of relatively severe vibration being applied to the vessel 27. It will be noted that, engine vibration, due to piston motion and the like, no matter the direction of the vibration, tends to be transmitted to the converter 24 principally as side to side (i.e. directions transverse to the axial direction of the engine) oscillation. If the lower side of the vessel 27 is anchored to the engine 21 with a suitable stay (not shown), transmission of engine vibration to the converter 24 can be reduced, however, in such a case there is apprehension that engine heating during operation, may lead to deformation and/or cracking of the stay or of the branch tubes 26 of the converter 24. Thus, it has been required that such manifold type catalytic converter arrangements be provided with attachment means which provided secure anchoring of the converter while allowing appropriate movement of the converter 24 for suitably responding to engine vibration.
According to the above described conventional converter, arrangement as may be seen in FIG. 9, since the second ends 26B of the branch tubes 26 are attached to the vessel 27 along an installation line 28 which is straight and parallel to the axial direction of the engine 21, side to side rigidity of the vessel is undermined and it becomes difficult to suppress vibrations transmitted from the engine 21 to the vessel 27, and the amplifying or resonating tendency of such transmission especially when the vehicle operates at higher engine speeds, may damage the converter or converter vessel.
Thus, it has been required to provide a manifold catalytic converter arrangement for an internal combustion engine in which such resonance is effectively suppressed.