EP0860591B1 - Process for manufacturing an air-gap insulated exhaust manifold - Google Patents

Description

The invention relates to a method for producing a Air gap-insulated exhaust manifold according to the preamble of the claim 1.

A generic method is known from DE 195 11 514 C1. The exhaust manifold there is made up of three inner pipe sections, as well as a lower and an upper shell that the outer shell form, composed. The inner tube sections, which consisting of a 90 ° elbow, a T-piece and a header pipe exist in the order given in the Production line with sliding seat inserted into each other, the T-piece with one end of its crossbeam with the two other pipe sections is connected. Not with each other connected ends of the pipe sections are parallel to each other in one level and each have flanges for screwing to a cylinder head of an internal combustion engine. This in approximately Y-shaped piece of manifold beyond a second free end that is not parallel to the other ends the remaining inner tube sections is aligned, but extends in the opposite direction. The second an output flange is attached to the free end of the header piece, to which an exhaust pipe can optionally be connected with a catalyst is. For the preliminary centering of the inner tube sections during assembly within the later outer shell - Forming the desired uniform air gap - Spacers are placed on the individual before the plugging process Sections pushed. These are made of a material that is due to the heat in the later operation of the exhaust system of the exhaust gas dissolves, so that the inner tube sections the operational thermal alternating loads radially can expand freely. The inner tube sections are in plug-in position inserted into the lower shell, whereupon the upper shell these put on and by means of a machine-controlled die is pressed. Then the inner tube sections welded to the outer shell at the mouth openings, wherein the centering is retained. Then the upper shell with the lower shell welded to the edges.

The areas of overlap of the inner tube sections are in their Longitudinal extension through the dimensions of the section ends in generally short, which makes the sections in the outer shell relatively are movable and in particular the pipe bend is unhindered can detach from this. Because of the loose connection the inner tube sections together by the desired one Sliding seat in the connector, the degree of looseness significantly from the manufacturing tolerances of the inner tube sections depends in the radial direction, it can happen that due to vibration of the parts during assembly, for example when manually placing the top shell on the Lower shell and the subsequent mechanical pressing, as well by the centrifugal forces in the swiveling movement of the Rotary table during the transfer of the assembly part from the assembly occur to the welding station, the inner tube sections move, which can detach the connectors. In particular, this happens with the pipe bend piece that can virtually turn out of the connection. By the solution the plug connection becomes the continuous exhaust pipe destroyed, which later leads to significant disruptions when driving of the exhaust gas flow and by the greatly increased Flow resistance to high engine power losses leads. Likewise, the air gap insulation is removed because the hot exhaust gas can flow freely onto the outer shell. Of further it can through the loose ends of the inner tube sections ugly rattling noises occur during driving, namely whenever sections strike the outer shell. To the another is a weld of the pipe bend on the inside the outer shell is highly problematic because of its Unscrew from the connector at the fastening end is positioned tilted so that the welding robot, such Deviations in the relative position of the two weld partners from the programmed target range can't see, not hit the right spot, so that the welded joint - if any at all Should come about in a way - in no way mechanical loads can endure. In addition, the elbow can also be so far out of the connector that he with its end the correspondingly designed outlet of the outer shell covered, so that a weld fillet weld in no case is more possible and thus the joining of the pipe bend with the Outer shell is omitted. It is of course conceivable that the fitter the manufacturing tolerances regarding the inner tube sections loosening the plug connection through specific variation the insertion depth can be compensated, after which the one described above Production is complete and of perfect quality. Most, however, is due to the necessary care short process cycle times not enough time available. Furthermore, human error must always be expected the inner tube sections are too short into each other be put.

Furthermore, from DE 44 37 380 A1 is an air gap insulated Exhaust pipe known, the inner tube sections via a spacer sleeve be plugged into each other, while driving the spacer sleeve due to its heat volatile material and due to the heat development of the hot exhaust gas and dissolves sliding seat with an annular gap between the inner tube sections releases.

The invention has for its object a generic To further develop methods so that in a simple manner both a sliding fit of the nested inner tube sections as well as the formation of a uniform air gap insulation the inner tube sections after completion of the production the exhaust manifold is always guaranteed.

The task is according to the invention by the features of the claim 1 solved.

Thanks to the invention is seen - across the assembly process a rigid at first and later for driving in Framework of the game and the thermal expansion or contraction of the inner tube sections enables movable plug connection. The background of an initially rigid connector lies in the exact arrangement and alignment of the inner tube sections to each other and the inner tube sections to the outer shell. The former is necessary because it is otherwise in operation the exhaust system to a misalignment of the inserted ends of the Inner tube sections comes in their respective recordings, so that the desired sliding fit of the connectors is prevented becomes. However, this is for a compensation of the relative movement the plug-in partner caused by alternating thermal loads comes about, indispensable. The latter is for uniformity the course of the air insulation gap between the outer shell and inner tube required. Furthermore, manual assembly errors and shifts of the plug partners to each other, the resulting from mechanical swiveling movements and vibrations result when putting on and attaching the upper shell, taking a total the respective insertion depth becomes impermissibly low, avoided by the non-positive connection. The minor Insertion depth promotes misalignment of the plug partners and can in the worst case, to dissolve the plug connection by slipping out of the inserted plug partner. Farther is achieved by the slip-free connection achieved according to the invention an exact arrangement of the pipe bend end of the inner pipe allows on the outer shell, so that an optimal weld between the outer shell and the inner tube in this area is executable. The inner tube remains with this weld centered immovably in the outer shell and with respect to one perfectly functioning sliding seat between the inner tube sections permanently optimally aligned. So that a sliding seat is achieved, the rigid connector after the Welding can be loosened. This will be advantageous simply by exposure to heat, under which the Lanyard that previously ensured the rigid connection dissolves. Thus, on the one hand by the invention Ensuring a functioning sliding seat after the end of production of the exhaust manifold and the other one uniform air gap insulation guaranteed. Furthermore, the inner tube - assembled separately - as a pre-assembled unit be delivered to the production line, reducing production time is saved. The pre-assembled unit must then just inserted and welded to the outer shell become.

Fig. 1 einen erfindungsgemäßen Abgaskrümmer ohne Verbindungsmittel an den Innenrohrabschnitten in einem seitlichen Längsschnitt,

Fig. 2 in einer perspektivischen Darstellung einen erfindungsgemäßen Abgaskrümmer mit Verbindungsmittel an den Innenrohrabschnitten und mit abgenommener Oberschale.

Expedient embodiments of the invention can be found in the subclaims; otherwise the invention is explained in more detail below with reference to an embodiment shown in the drawings; shows:

1 shows an exhaust manifold according to the invention without connecting means on the inner tube sections in a lateral longitudinal section,

Fig. 2 is a perspective view of an exhaust manifold according to the invention with connecting means on the inner tube sections and with the upper shell removed.

1 shows an air-gap-insulated exhaust manifold 1, which consists of an exhaust pipe inner tube 2 and one Course of the inner tube 2 adapted outer shell 3. The Inner tube 2 in turn consists of three sections, a Y-shaped Collecting pipe section 4, a T-piece 5 and a 90 ° elbow 6. The T-bar of the T-piece 5 forms on the pipe bend side with its end 7 the sliding seat mount for the one facing it end 8 of the pipe bend 6 inserted in it. To the other Side is the end 9 of the T-beam in the sliding seat holder 10 of the header piece 4 inserted, these formed by one end of the fork of the Y-shape of the pipe section 4 is. The other end 11 of the fork, the free end 12 of the T-piece 5 and the free end 13 of the pipe bend 6 are mutually aligned parallel in one plane.

The ends 11, 12 and 13 are at their mouth openings 14 which is composed of a lower shell 15 and an upper shell Outer shell 3, only representative here the lower shell 15 is shown, forming a fillet weld welded. The orifices 14 are for this purpose adjacent outlet openings 16 of the outer shell 3 set back. Inlet flanges 17 are welded to them, with which the exhaust manifold 1 to a cylinder head an internal combustion engine is screwed. At the foot of 18 Collecting pipe piece 4, this is also with the outer shell 3 welded in the area of the mouth opening, the outer shell 3 carries an output flange 19 on which an exhaust line an exhaust system can be attached gas-tight.

On the end 8 of the pipe bend 6 and the end 9 of the T-piece 5 is a slotted spacer ring in the area of the sliding seat 20 postponed, by means of which the put together Inner tube 2 is centered in the outer shell 3, with an almost uniformly running heat insulating gap 21 between the Inner tube 2 and the outer shell 3 is formed. The spacer rings 20 align the inner tube sections 4,5,6 with each other to avoid any eventual occurrence in later driving To avoid misjudging, however, is the production of such Spacer rings 20 are also subject to tolerances, so that the probability optimal alignment is low. moreover there must be some play around the inner tube sections 4,5,6 stuck together and to form a To ensure sliding fit.

The spacer rings 20 consist of a heat-volatile material, preferably made of polyethylene, making the spacer rings 20 after the inner tube 2 has been exposed to hot exhaust gas decompose and / or burn. On the one hand, the between Inner tube 2 and outer shell 3 due to the two-sided Installation of the respective spacer 20 undesirable heat transfer prevented and on the other hand the ends 8.9 are released, after which the pipe bend 6 and the T-piece 5 there accordingly the heat load can expand freely.

To ensure the optimal alignment for the Plug connection a connecting means (in this embodiment not shown) used this by generation a frictional connection between the two plug-in partners rigid designed, creating a precisely defined arrangement of the two Plug partners to each other is made possible. The lanyard can be an adhesive strip in the respective recording 7.10 of the inner tube sections 4.5 is attached circumferentially and from a material with the same properties regarding Heat acts like the spacer rings 20. The non-positive Connection is made when the Inner tube sections 4,5,6.

It is also conceivable that the positive connection after the insertion of the inner tube sections 5,6 by wrapping the Plug connection by means of a connecting means adhesive tape is done.

Furthermore, it is conceivable that the connecting means from a elastic cuff is formed on the receiving end 7, 10 of one inner tube section 4, 5 is pushed on. The end to be inserted 8.9 of the other inner tube section 5,6 is pushed through the cuff, both pushing the sleeve onto an inner tube section 4, 5 as well as pushing the end to be inserted 8.9 of other inner tube section 5.6 by the sleeve friction he follows. This can consist of a rubber-like, Rigid and heat-volatile material exists and is present the respective plug-in partner closely. Axial movements of the Plug partners are compensated elastically, after which these always be returned to their original plug position. The spacer rings 20 are only in terms of centering supportive for the respective lanyard.

As an alternative to the exemplary embodiment from FIG. 1, FIG. 2 the ends 7, 8 and the end 9 and the sliding seat receptacle 10 rigidly with each other via a respectively pushed-on sleeve 22 connected, which consists of a heat-volatile material and after initially loosely applied under the influence of heat on the ends 7,8 or end 9 and sliding seat receptacle 10 shrunk becomes. Due to the circumferential uniform thickness of the cuff 22 is the inner tube 2 in the outer shell 3 when inserting automatically centered in these, with the Insulating gap 21 sets. In the cuff 22, which is essentially for a rigid connection between. the inner tube sections 4,5,6 is the gap-forming function of the Spacer rings 20 virtually integrated, which can be omitted. To support the centering, the spacer rings 20 however, in other areas of the inner tube 2, advantageously be arranged in the region of the knee of the pipe bend 6. The cuff 22 can also be a piece of tubing.

The inner tube 2 can be optimally centered when it is inserted into the lower shell 15 automatically, for example, by radial protruding spacer beads suitably arranged on the circumference Cuff 22 take place, the support of the cuff 22 in the lower shell 15 is minimized, causing surface unevenness the otherwise shrunken ones lying on a large surface Cuff 22 and manufacturing tolerances of the lower shell 15 for the centering of the inner tube 2 is no longer important.

The manufacturing process of Exhaust manifold shown with the sleeve 22 as a connecting means become. First, a cuff 22 is placed on the End 7 of the T-piece 5 and on the end 10 of the header piece 4 pushed. Then the inner tube sections 4,5,6 inserted into each other, the end 8 of the pipe bend 6 Recording in the end 7 of the T-piece 5 and the end 9 of the T-piece 5 inclusion in the end 10 of the header 4 under each Formation of a sliding seat takes place. The end 8 of the pipe bend 6 and the end 9 of the T-piece 5 are here through the cuff 22 pushed through. The cuff is in this position 22 by the action of heat, for example by means of a The hair dryer is shrunk onto the ends 7,8 and 9,10. Thereby becomes the plug connection of the aligned inner tube sections 4,5,6 rigidly fixed and the sliding seat loses its effect for now.

Then the inner tube 2 is inserted into the lower shell 15, positioned and the upper shell placed on the lower shell 15. A die then presses on the top shell, after which it fits snugly sits on the lower shell 15. Then the on a Round table assembly of a welding station (Welding robot) by swiveling the rotary table. In the station is at the mouth openings 14 of the inner tube 2nd this with the formation of a fillet weld on the outer shell 3 on the inside all around laser welded. In conclusion, the Input flanges 17 on the ends 11, 12, 13 of the inner tube sections 4,5,6 and the output flange 19 on the end 18 of the Collected pipe piece 4 inserted and also laser welded.

This is followed by local heat treatment at the locations of the shrunk-on cuffs 22, whereby this in the The plug-in connection dissolves without residue and thus the sliding seat is released again. After that, the making of the Exhaust manifold 1 completed. The heat treatment can be done in simpler This can also be done retrospectively by exposure to the exhaust gas heat done in engine operation.

Otherwise it is conceivable instead of a frictional connection to provide a locking connection in which the locking elements also consist of a heat-volatile material. Of Another is also a determination of the plug-in connection brief exposure to cold at the location of the plug connection is conceivable, so that by contraction of the respective recording the associated one inserted end is clamped.

Claims (9)

1. A process for the manufacture of an air-gap-insulated exhaust manifold (1) which consists of an exhaust-gas-carrying inner pipe (2) comprising individual sections (4, 5, 6) and an outer shell (3) divided into an upper and a lower shell (15) and designed to follow the course of the inner pipe (2), the inner pipe sections (4, 5, 6) - at least one of which is designed as a pipe bend (6) - being inserted one into the other with the internal diameter of the receiving end (7, 10) of each pipe section (4, 5) being greater than the external diameter of the pipe section end (8, 9) to be inserted into this receiving end (7, 10), and being centred and inserted into the lower shell (15) of the outer shell (3) as an assembled component, the upper shell then being placed upon the lower shell and pressed into it, and the upper and lower shells (15) and the inner pipe sections (4, 5, 6) then being welded to the outer shell (3) in the area of their outlet openings (16),
   characterised in that
   prior to the insertion of the inner pipe (2) into the lower shell (15), the inner pipe sections (4, 5, 6) are joined together non-positively by a means of connection (22) made of a heat-volatile material, the means of connection (22) melting due to the effect of heat following the welding of the upper and lower shells (15) to the inner pipe sections (4, 5, 6).
2. A process in accordance with claim 1,
   characterised in that
   the means of connection (22) is melted by the effect of the heat of the exhaust gas.
3. A process in accordance with claim 1,
   characterised in that
   the non-positive connection is effected as the inner pipe sections (4, 5, 6) are inserted.
4. A process in accordance with claim 1,
   characterised in that
   the non-positive connection is effected following the insertion of the inner pipe sections (4, 5, 6) by wrapping an adhesive strip forming the means of connection around the plug-in connection.
5. A process in accordance with claim 1,
   characterised in that
   an elastic sleeve (22) forming the means of connection is pushed over the receiving end (7, 10) of one inner pipe section (4, 5), following which the inner pipe sections (4, 5, 6) are inserted one into the other, during insertion the end of the inner pipe section (6) to be inserted being pushed into the receiving end (7) of the other inner pipe section (5) and the end (9) of the other inner pipe section (4) to be inserted being pushed through the sleeve. (22).
6. A process in accordance with claim 5,
   characterised in that
   both the pushing of the sleeve (22) over one inner pipe section (4, 5) and the pushing of the end (8, 9) of the other inner pipe section (5, 6) to be inserted through the sleeve (22) constitutes a frictional engagement.
7. A process in accordance with claim 5,
   characterised in that
   when the inner pipe sections (4, 5, 6) are inserted one into the other, the sleeve (22) is shrunk by the effect of heat.
8. A process in accordance with claim 1,
   characterised in that
   individually slotted spacer rings (20) made of a material which melts under the effect of heat are placed on the inner pipe sections (5, 6) in order to centre the sections (4, 5, 6).
9. A process in accordance with claim 5,
   characterised in that
   the inner pipe sections (4, 5, 6) are centred automatically by means of radially spaced spacer beads on the sleeve (22) as they are placed in the lower shell (15).

Images