DE4228187C2 - Exhaust manifold for internal combustion engines - Google Patents

Description

The invention relates to an exhaust manifold for Internal combustion engines with a cylinder side flange and one with respect to the flow direction of the exhaust gases downstream flange, between which arcuate running elbow pipes of different lengths arranged are, with at least one manifold outside the Flange opens into another manifold pipe.

Is from the heterogeneous state of the art DE-OS 35 00 568 and DE-GM 82 26 865.7 known, which each describe an exhaust manifold that, based on a manifold, four equally long, arched Has manifold tubes, the end portions of this Manifold pipes not into each other, but into the above. Manifold lead. At this state of the art tried the occurring longitudinal strains by in the To master busbar arranged expansion waves.

Furthermore, from FR-PS 26 12 252 a Exhaust manifold known, the arc-shaped, has manifold pipes of different lengths, but the four manifold pipes only in the area of the downstream Flange open into each other. Likewise, from this Documentation no discernible evidence that the pipes have been hydrostatically reshaped and that they different cross sections that are favorable for bending exhibit. Rather, those known manifold pipes point out only a circular cross-section in the confluence area on.

Finally, EP-OS 03 21 869 describes one Heterogeneous state of the art exhaust manifold that from consists of a single conventionally bent manifold pipe in which a variety of mounting holes for short Flange connecting pipes can be arranged. This one too Exhaust manifold has the basic problem that at Large heat stresses that do not occur gentle on materials within the system, d. H. between individual flange fastenings can be dismantled.

The well-known exhaust manifold after not in print verifiable genus of the claim has elbow pipes of different lengths, two of which are always on one level merged in the manner of a trouser piece and in one up receiving opening of a secondary flange are welded. For Formation of this trouser piece will be the manifold pipes in the Proximity of the secondary flange on the sides facing each other flattened end-to-end and in the area of the An position together to form a midrib welds. This results in a common end area of the two merged manifold pipes, the inside and outside is essentially circular, the  Middle rib, however, extends into the end area. In Be For this reason, the middle rib is richly divided between the secondary flange and the common wall of the Manifold pipes available.

In addition, the manifold pipes are made by bending been put. However, no bending can be done create manifold pipes, so that the manifold pipes according State of the art always certain deviations from the circle have shape.

If now those made by bending and each with a common end portion forming manifold pipes the secondary flange on the one pointing away from the elbow pipes Side of the flange are welded, then result not only in the area of the midrib, but due to the Deviations from the circular shape also in other areas Chen air gaps between the outer peripheral surface of the common same end area of the manifold pipes and the peripheral surface the receiving openings of the secondary flange. During loading The engine is now driven by the well-known exhaust manifold heated to a temperature of approx. 700 ° C. When heating the un manifold pipes of different lengths in the exhaust manifold but there is a different amount of linear expansion of the individual manifold pipes. Because the distance between the two flanges to each other, however, through the shortest manifold pipe is true, step in the longer elbow pipes increased Tensions that are not sufficient due to bending deformation of the manifold pipes can be reduced. This then often leads to cracks on the flange side Welded joints.  

In addition, there is the known exhaust manifold additional problems especially in the cooling phase. Basically, the much thinner manifolds cool pipes are much faster than the two relatively thick flanges. Because between the common end of the Elbow pipes and the peripheral surface of the receiving opening, however an "insulating" air gap is at least partially present the end area of the elbow pipes cools quickly ler than the flange receiving the end region. Thereby occurs within the welded joint additional thermal stresses which damage it and can even lead to tearing.

Ultimately, those manufactured by means of bending Elbow pipes always have different wall thicknesses, which means irregular when heating the exhaust manifold Stress curve within the individual manifold pipes results.

As a result, all of this means that the lifespan the known exhaust manifold is relatively low.

The object of the invention is therefore one To create exhaust manifolds for internal combustion engines, in which by gentle degradation of those that occur during heating Voltages the lifespan is significantly extended.

The invention solves this problem essentially through that the manifold pipes along their entire length are completely hydrostatically formed that each Elbow pipe another, constantly changing over the pipe length  has changing bend, the manifold in the area of the bends with an oval, easy to bend Cross-section are provided, the short cross-sectional axis in Bending direction is arranged.

Due to the above Features essential to the invention on the other hand, the new exhaust manifold, especially the Welded joints, a significantly longer service life.

The exhaust manifold according to the invention can also also made of manifold pipes different, seamless changing cross sections and / or circumferences are formed.

The exhaust manifold according to the invention is advantageous Suitable for use during operation due to the caused different length changes in the amount Tensile and compressive stresses, in particular to protect the flange-side welded connections of the exhaust manifold degrading material-harmless way. this happens according to the invention in that each in different Bent elbow pipe directions in each Bending direction a cross section favorable for bending has, that is provided with a cross section, which the bending is opposed by a reduced section modulus. Due to the production of this particular trained manifold pipes using the hydroforming process the pipes also have a minimum of 25% reduced wall thickness compared to the prior art. This has, in connection with the operation of a catalytic converter, the main advantage of significantly reducing the so-called "thermal mass" of the exhaust manifold, whereby the length of the warm-up phase when operating a Catalyst is significantly reduced.

In addition, due to the hydrostatic deformation of the pipes ensures that there are no deviations from the desired cross section comes and that the wall thickness in the we is approximately the same at every point. Due to the constant cross sections of the manifold pipes and through that  Merge two elbow pipes outside the end the dimensional accuracy of the in the receiving opening arranged common end area significantly improved who the. Therefore, unlike the prior art, it does not to form air gaps between the end region of a Manifold and the peripheral surface of a receiving opening, so that the heat flow is not hindered and is approximately parallel cooling of the end area and flange results.

Furthermore, the constant wall thickness leads to one uniform stress distribution within the wall of the individual manifold pipes.

Further advantages of the invention result from the following subclaims and the description of a Embodiment. It shows

Fig. 1 is schematic view of an exhaust manifold to an engine arranged,

Fig. 2 is a plan view of the exhaust manifold in accordance with the viewing arrow II in Fig. 1,

Fig. 3 is a view of the exhaust manifold according to the viewing arrow III in Fig. 2,

Fig. 4 is a side view of the exhaust manifold in accordance with the viewing arrow IV in Fig. 2,

Fig. 5 is a side view of the exhaust manifold in accordance with the viewing arrow V in Fig. 2,

Fig. 6 shows a cross section through a manifold according to section line VI-VI in Fig. 5 and

Fig. 7 shows a cross section through a manifold according to section line VII-VII in Fig. 5 and

Fig. 8 is a cross-section through a header pipe according to the section line VIII-VIII in Fig. 5.

In the drawings, the exhaust manifold is generally designated by the reference number 10 .

The exhaust manifold 10 is net angeord a primary flange 11 with an elastically suspended, ie with respect to its longitudinal axis x pendulum rotatably mounted motor 12th The exhaust manifold 10 consists of manifold tubes 13 , 14 , 15 and 16 of different lengths, each of which has circular end regions 26 on both sides (see FIG. 6). Each of the elbow pipe 13 , 14 , 15 and 16 is welded on one side in receiving openings 17 of the primary flange 11 angeord net.

In addition, the exhaust manifold 10 has a secondary flange 18 with two receiving openings 19 on the so-called "hot side". In the receiving openings 19 of the secondary flange 18 , the elbow pipes 14 and 16 with the other end region 26 are welded firmly. In contrast, the manifold pipes 13 and 15 open with their secondary-side end regions 26 , which are designated in FIG. 2 with 29 , in the area of neckings 20 , 21 into the manifold pipe 16 and the manifold pipe 14, respectively. While the end regions 26 of the elbow pipes 14 and 16 are each connected to the flanges 11 and 18 by means of a weld seam 27 (see FIG. 3), the end regions 29 of the elbow pipes 13 and 15 are connected to the flanges 20 , by means of a further weld seam 28 . 21 firmly arranged.

Primary flange 11 and secondary flange 18 have white openings 22 for bolts (not shown) with which the exhaust manifold 10 can be connected to the cooled motor 12 (cold side) and to a flange 23 of two front pipes 24 (see FIG. 1 ).

While the flanges 11 and 18 are produced in the present case by stamping processes, the special shape of the individual elbow pipes 13 to 16 is created by the hydroforming process. In this process, metal pipes made of heat-resistant, austenitic stainless steel of smaller diameter and greater wall thickness are roughly pre-shaped by mechanical shaping so that the preform of the elbow pipe can already be recognized. This intermediate product is then inserted into a die, the engraving of which can already determine the final shape of the elbow pipe, although several intermediate stages may also be necessary to produce the final elbow pipe. The intermediate tube product received by the die is then acted upon by a hydraulic hydraulic fluid with a high hydrostatic internal pressure, thereby widened and nestled against the engraving, so that the manifold tube is essentially finished. It is important that it is possible with the help of the hydroforming process to produce manifold pipes in series, which have approximately identical dimensions and are easily plug-in.

To produce the ver provided with a neck 20 or 21 manifold pipes 14 or 16 , the neck are essentially also created by widening the manifold pipe at the desired location by means of a hydraulic Druckflüs liquid. The still closed neck is then "cut open" so that there is an opening 25 in each of the elbow pipes 14 and 16 . The outer diameter of the neck 21 , 22 and the inner diameter of the opening 25 are dimensioned such that the end regions 26 of the elbow pipes 13 and 15 either up on the neck 20 , 21 or inserted into the opening 25 and can be welded there .

The manifold pipes 13 to 16 can be dimensioned with the help of the hydroforming process so that they have constantly changing radii of curvature, cross sections (see FIGS. 6, 7 and 8) and / or circumferences over the longitudinal course. For example, all elbow pipes 13 to 16 are curved in each area, the changes in curvature being smooth. In addition, the cross section of the manifold tubes 13 to 16 is at least outside the ver welded in the flanges 11 and 18 end regions 26 more or less oval. The oval, deflection-favorable cross-section (see FIGS . 7 and 8) enables each individual manifold pipe 13 to 16 to catch the different increases in length that occur when the exhaust manifold 10 is heated by bending, without causing larger tensile or compressive loads, e.g. B. could damage the weld 27 between the manifold pipes 13 to 16 and the individual flanges 11 and 18 . It is important that the oval cross-section in the coordinate system is oriented so that the short cross-sectional axis of the oval tube runs in the bending direction, so that the tube opposes the bending only a small section modulus.

Basically, the distance between the flanges 11 and 18 to each other in particular by the shortest manifold tube be true. This shortest manifold pipe naturally also has the smallest increase in length when the exhaust manifold 10 is heated. The difference in length between the shortest elbow pipe and the longer elbow pipe initially leads to a build-up of tension (compression) in the three longer elbow pipes, which, due to their flexible cross-section and the continuously curved shape, can reduce this tension by bending deformation. On the other hand, the shortest tube is basically stretched in principle, whereby the likewise curved course and favorable cross-section enables this stretching.

Claims (7)

1. Exhaust manifold for internal combustion engines with a cylinder-side flange and a downstream with respect to the flow direction of the exhaust gases, between which arc-shaped manifold pipes of different lengths are arranged, at least one manifold pipe opening outside the flange into another manifold pipe, characterized in that the Elbow pipes ( 13 , 14 , 15 , 16 ) are completely hydrostatically formed over their entire length so that each elbow pipe ( 13 , 14 , 15 , 16 ) has a different bend that changes constantly along the pipe length, the elbow pipes ( 13 , 14 , 15 , 16 ) in the area of the bends are provided with an oval cross-section which is favorable for bending, the short cross-sectional axis of which is arranged in the bending direction. 2. Exhaust manifold according to claim 1, characterized in that the manifold tubes ( 13 , 14 , 15 , 16 ) have different cross-sections and / or circumferences which change continuously. 3. Exhaust manifold according to claim 1 or 2, characterized in that a manifold pipe ( 14 , 16 ) has at least one neck ( 21 , 20 ), on which the end region ( 29 ) at least at least one opening manifold pipe ( 15 , 13 ) gas-tight is fixed. 4. Exhaust manifold according to claim 3, characterized in that the end region ( 29 ) of the outlet manifold tube ( 15 , 13 ) in the neck ( 21 , 20 ) of the other manifold tube ( 14 , 16 ) can be inserted and welded there. 5. Exhaust manifold according to claim 3, characterized in that the end region ( 29 ) of the merging elbow pipe ( 15 , 13 ) on a neck ( 21 , 20 ) of the other elbow pipe ( 14 , 16 ) can be pushed on and welded there. 6. Exhaust manifold according to one of the preceding claims, characterized in that the manifold tubes ( 13 , 14 , 15 , 16 ) have a substantially constant wall thickness. 7. Exhaust manifold according to one of the preceding claims, characterized in that two of the manifold pipes ( 13 , 14 , 15 , 16 ) open into one another via a piece of trousers.