GB2277969A - Articulated coupling for internal combustion engine - Google Patents

Abstract

An articulated connection 1 is provided between tubular parts 2, 3 of the exhaust gas pipe. A bellows 17, and a vibration damping pad 8 of pressed metal wire located inside a housing of parts 6, 12 each having an end 4, 9 connectable to one of the tubular parts 2, 3. The outer housing part 6 is connected to the upstream inlet connection end 4. The bellows (17) is situated behind the damping pad 8. A protective pipe 19 extends radially inside a supporting pipe 11 connected with the inner housing part 12, 16. <IMAGE>

Description

EXHAUST GAS PIPE PARTICULARLY FOR MOTOR VEHICLES Exhaust gas pipe, particularly for motor vehicles, with an articulated connection of tubular parts of the exhaust pipe, with a bellows and at least one vibration damping pad of pressed metal wire inside a housing of inner and outer housing parts each connected by a tubular connection end connectable to the tubular parts.

EP-A-208128 makes known an articulated connection of tubular parts, particularly in the case of exhaust gas pipes of motor vehicles, which has a bellows and, following the latter as seen in the direction of flow, a damping device consisting of two damping pads adjacent to each other, which are internally secured by a supporting pipe which bears an internal housing part and which is constructed in one piece with a connection end on the inlet side, while the damping pads are overlapped on the outside by external housing parts which are provided on a connection end on the outlet side.

The particular drawback of this system resides in the fact that the supporting pipe and the internal housing parts are connected with that end of the connection which is on the inlet side and which in turn is connected with tubular parts connected with the combustion engine generating the exhaust gases, so that the high temperature of the combustion engine is liable to be conducted direct through the highly heat conductive tubular parts into the zone of the inner housing parts and from there direct into the metallic damping pads as a result of heat conduction.

Owing to the high exhaust gas temperatures of 950 - 1000"C the operating properties of the damping pads, of which the material at this temperature only has a limited strength, suffer deterioration. In one constructional version this drawback is aggravated by the fact that the supporting pipe and the inner housing parts are directly connected with the hot current of gas.

The chambers are subjected to vigorous turbulence from the highly turbulent current of gas, giving off considerable heat to the adjacent parts, i.e. supporting pipe and pads. Owing to the upsetting of the pads with the predominantly angular movements of the pipe ends with the Austenite steels normally used permanent deformations occur; the properties of the pads are nullified.

The avoidance of these drawbacks by the use of valuable materials such as alloys with a nickel base and by high pre-compression, necessitating considerable weight, proves costly; in addition, the greater rigidity prevents the required vibration insulating effect from being obtained.

In another constructional version the supporting pipe and the inner housing parts also contain a protective pipe which is connected to the upstream connection end and which thus likewise suffers a temperature increase from heat conduction, so that the foregoing remarks apply here as well. In the last analysis the protective pipe can, at best, postpone the additional heating of the internal housing parts. After a sufficient period of operation, however, a stable thermal state will come about in which considerable heat is caused to enter the damping pads, both as a result of the hot exhaust gases flowing through and also in particular as a result of the heat emanating from the combustion engine through heat conduction.

A further reduction in the cross section of the protective pipe combined with a considerable length is likewise involved, i.e. greater flow resistance with counter-pressure, detracting from the performance of the engine.

The purpose of the invention is therefore to avoid the aforementioned disadvantages and enable the ingress of heat into the damping pads to be reliably reduced. According to the invention this object is achieved, in an exhaust gas pipe of the type mentioned at the beginning, as a result of the fact that the outer housing part is connected with that end of the connection which is upstream and on the inlet side.

The essential principle of the invention resides in the fact that the housing part which is connected or constructed in one piece with the inlet side connection end, which in its turn is directly connected in a satisfactorily heat conductive manner with the combustion engine generating high temperatures, extends around the damping pads on the outside and is thus directly connected with the ambient air and its temperatures, with the result that the outer housing part likewise is subjected to a cooling effect which prevents excessive heating of the outer housing part and thus of the damping pads around which the latter extends.

A further version to which particular preference is given may be so designed that the protective pipe extends axially over the entire length of the damping pad or pads, while in particular with the connection end, bearing the outer housing part, a protective pipe is connected which extends radially inside a supporting pipe provided with the inner housing part and connected with the other connection end.

The protective pipe leading radially from the inlet side to inside the supporting pipe ensures that in the gap between the free end of the said pipe and the outer housing part no hot gases can flow into the damping pads and that no eddies which can cause noise will occur in this zone.

It has been found that a short protective pipe, such as is feasible in this case, if it does not exceed the length required to cover that of the pad, causes no measurable deterioration of the flow of gas but even has a favourable effect on the gas exchange in the engine, particularly in the case of a double-flow forward pipe.

The inner housing parts for the damping pads are connected with the outlet side connection end of the articulated connection or are constructed in one piece therewith, via a protective pipe borne by the bellows. The construction according to the invention ensures that the deleterious effects of the conduction of heat from the combustion engine to the inner housing parts are prevented (this being avoided in the invention) and also prevents cumulative heating of the said parts by the hot exhaust gases, as occurs in the prior art discussed farther back.

A preferred embodiment of the invention provides that the protective pipe is to be constructed in one piece with that part of the exhaust gas pipe which is connected with the inlet side connection end, if the protective pipe likewise is constructed separately from the feed. pipe of the exhaust gas pipe and can be connected, i.e. welded, to the articulated connection itself, or to be more exact, to that connection end thereof which is on the inlet side.

A version to which particular preference is given provides that the bellows is to be positioned, as viewed in the direction of flow, behind the damping pad or pads.

This makes it possible for the protective pipe, regardless of whether it only extends into the zone of the free end of the inner supporting pipe for the damping pads or extends over the entire axial length of the said pads, to be made relatively short, as it does not have to extend axially over the entire bellows, as is the case in the prior art.

This not only enables material to be saved but also provides, in the finished exhaust gas pipe or finished articulated connection, a saving of weight, which is likewise significant.

Further advantages and characteristics of the invention will emerge from the claims and from the following description, in which a preferred example of the invention is explained in detail by reference to the drawings. The latter is as follows: Figure 1: a preferred version of the exhaust gas pipe according to the invention, in longitudinal section according to the line I-I of Figure 2, only the upper zone of the circularly symmetrical pipe being shown; Figure 2: a section along the line II-II of Figure 1; Figure 3: a further preferred embodiment similar to that of Figure 1; Figure 4: a section through the version shown in Figure 3; Figures 5-7: further preferred embodiment of the invention, shown in longitudinal section.

The exhaust gas pipe according to the invention is provided with an articulated connection 1 between an inlet pipe 2 of the exhaust gas pipe and an outlet pipe 3 of the exhaust gas pipe. The arrow A indicates the direction of flow of the exhaust gas passing through the exhaust gas pipe.

The articulated connection 1 has a tubular connection end 4 which is situated upstream or on the inlet side and with which is provided an outer housing part 6 of a housing 7 for a vibration damping pad 8, while the parts 6, 7, can be interconnected in a suitable manner or alternatively constructed in one piece. A supporting pipe 11, extending radially inside the damping pad 8 is provided with the downstream or outlet side tubular connection end 9 of the articulated connection 1 and can in its turn be constructed in one piece with the said connection end 9.

The supporting pipe 11 is provided, in the zone of the damping pad 8, with a housing part 12 of the housing 7, this part extending radially inside the said pad. The feet 12a of the said part do not rest by their full surface against the supporting pad 11, air gaps 12b being formed.

This still further reduces the heat transference from the interior of the pipe 11 to the damping pads 8.

In the example illustrated the damping pad 8 or damping pads 8 are secured in the axial direction by radially directed end faces 13, 14, of the housing part 6 and a radial shaft 16 of the housing part 12. The end face 14 is welded at the point marked 10 to the outer housing part. The converse system can equally well be adopted, i.e. the shaft can be situated on the outer housing part 6, end face terminations being provided on the inner housing part 12 and on the protective pipe 11.

The housing part 12 is connected to the supporting pipe 11 by welds.

With the outer housing part 6 is connected a bellows 17 by one end, the other end of the latter being connected to the connection part 9, e.g. by means of an auxiliary ring 18 mounted thereon. With the upstream or inlet side connection end 4 is connected a protective pipe 19, which extends radially from there to inside the supporting pipe 11. The protective pipe 19, as shown in the drawings, is advantageously shaped in one piece onto the inlet part 2 of the pipe, but may also be constructed separately from this latter and provided from the outset on the articulated connection 1, by positioning it inside the interior of the inlet said connection end 4 and rigidly connecting it thereto, e.g. by welding. In this case the inlet part 2 of the pipe would extend by a certain distance into the outer zone of the protective pipe 19 and be connected at that point with this latter.

It is hardly necessary for the protective pipe 19 to coincide axially with the supporting pipe 11. The essential requirement is that the intermediate space or gap 21 between the transition from the connection end 4 and the end face 13 on the one hand and the free end of the supporting pipe 11 or of the inner housing part 16 on the other should be covered over, so that no entering hot exhaust gas will penetrate the damping pad 8 and so that in particular it will not cause eddies, by which noise could be produced.

Owing to the foregoing and also to the fact that the housing part 6, which is connected with the inlet side connection end 4, which in its turn is connected with the inlet pipe 2 and via this latter with the combustion engine generating the exhaust gas, and is thus also in thermal connection therewith and consequently becomes very hot, constitutes the outer part of the housing, and the gap 21 is covered over by the protective pipe 19, the system enables the serious thermal problems which occur when the inner housing part is connected with the inlet pipe 2, since here high temperatures are directly introduced into the damping pad and thus detract from its damping properties, to be avoided, since the outer housing parts 6 themselves are no longer connected with the flow of exhaust gas but, on the contrary, are surrounded by ambient air, which leads to rapid cooling.

A preferred embodiment may provide that the protective pipe 19 is to extend over the entire axial length of the damping pad or pads 8 within the supporting pipe 11, as is the case in the version shown in Figures 3, and 5-7.

The housing part 12 can also be made in one piece with the supporting pipe 11 by a knob-shaped beading 20 thereon, as is the case with the versions shown in Figures 3-7.

The version shown in Figure 3 corresponds, except for the aforementioned deviations, to that shown in Figure 1, while in particular the end face 14 is welded at 10 onto the outer housing part 6. Unless completely annular pads are provided, situated on both sides of the beading 20, it is possible, for the version shown in Figures 3, 5-7, as may be seen from Figure 4, for a pad 8, annular in itself, to be folded over or bent over along a diameter, so that as seen in projections it only forms a half-ring, which is then mounted, on both sides of the beading 20, onto the pipe 11, as may be seen in particular from Figure 4.

In the embodiments illustrated in Figures 5-7, the connection end is merely bent upwards, radially to the end face 13, while the housing part 6 is constructed in one piece with the end face 14 and connected to the end face 13 at the point marked 15 by welding.

In the version shown in Figure 5 the protective pipe 19 is once again, as in that shown in Figure 1, made in one piece with the inlet pipe 2 of the exhaust gas pipe, while in Figure 6 the protective pipe 19 is constructed separately from the inlet pipe 2 of the exhaust gas pipe and is welded to the connection end 4 at the point marked 22. The inlet pipe 2 is inserted into the widened end of the protective pipe 19.

The version of the articulated connection itself which is shown in Figure 7 corresponds to that shown in Figure 6, while in this case the attachment to the exhaust gas pipe or to the engine outlet is provided not via an inlet pipe 2 but via a separate radial flange part 23, the pads 8 being fixed and secured angularly by the beadings 20 and via their web zones 8.

Claims (7)

1. An exhaust gas pipe, particularly for motor vehicles, comprising an articulated connection between tubular parts of the exhaust gas pipe, a bellows, and at least one vibration damping pad of pressed metal wire inside a housing of inner and outer housing parts each having a tubular connection end connectable to the tubular parts, and in which the outer housing part is connected to the upstream inlet connection end.

2. An exhaust gas pipe in accordance with claim 1, characterised by the fact that the bellows is situated behind the damping pad or pads as seen in the direction of flow.

3. An exhaust gas pipe in accordance with claim 1 or claim 2, characterised by the fact that at the connection end carrying the outer housing part a protective pipe is connected which extends radially inside a supporting pipe connected with the other connection end and provided with the inner housing part.

4. An exhaust gas pipe in accordance with claim 3, characterised by the fact that the protective pipe is constructed in one piece with that tubular part of the exhaust gas pipe which is connected with the connection end which is on the inlet side.

5. An exhaust gas pipe in accordance with claim 3 or claim 4, characterised by the fact that the protective pipe extends axially over the entire length of the damping pad or pads.

6. An exhaust gas pipe, in accordance with any one of the foregoing claims, characterised by the fact that air gaps are formed between a supporting pipe bearing the inner housing part for damping pads and the housing part mounted on the said supporting pipe.

7. An exhaust gas pipe substantially as described herein with reference to or as illustrated in the accompanying drawings.