EP2075432A1 - Exhaust collector and associated manufacturing method - Google Patents

Abstract

The method involves stucking individual gas-carrying components of inner shell bodies (4,5) into one another in the area of the sliding fits (13,14). A calibration procedure is carried out in the area of the sliding fit with components extending into one another. A reduction of cross-section is effected at the outside of the components.

Description

The present invention relates to a method for producing an air gap-insulated exhaust gas collector for an exhaust system of an internal combustion engine, in particular in a motor vehicle. The invention also relates to an air gap insulated exhaust collector made by the method.

An exhaust manifold or exhaust manifold combines the exhaust gases of several cylinders of an internal combustion engine. In the case of an air gap-insulated exhaust gas collector, at least one inner shell body provided for the exhaust gas guide is enveloped by an outer shell body to form a thermally insulating air gap. The use of air gap-insulated exhaust gas collector, the thermal load of an engine block or a cylinder head to which the exhaust manifold is flanged, can be reduced.

To increase the performance of an internal combustion engine, it is generally known to charge the combustion chambers supplied fresh gas with the aid of an exhaust gas turbocharger. For this purpose, the respective exhaust gas turbocharger exhaust side directly to the exhaust manifold be connected. The exhaust gas has at this point its highest temperature and its highest pressure, which is for the exhaust gas turbocharger, a very high enthalpy available. Modern turbochargers can work on the twin-scroll principle. On the one hand, such a twin-scroll exhaust-gas turbocharger has two separate inlet paths which lead from the common exhaust-side inlet to the common turbine of the turbocharger. On the other hand, the cylinders of the internal combustion engine which supply the turbocharger with exhaust gas are subdivided into two groups in order to supply their exhaust gases separately to one of the inlet paths of the twin-scroll turbocharger. In this way, a more uniform exhaust gas to the turbine can be realized even at lower speeds of the internal combustion engine, which improves the response of the turbocharger, in particular shifts towards smaller speeds. The separate exhaust system of the individual cylinder groups can be done via separate exhaust manifold. In the case of an air gap-insulated exhaust gas collector, this can also be achieved by arranging two separate inner shell bodies in the common outer shell body, which are each assigned to a cylinder group.

In particular, in the case of air gap-insulated exhaust gas collectors, it is customary to assemble the respective inner shell body from a plurality of individual gas-conducting components. For this purpose, the individual gas-conducting components are inserted into one another in the region of at least one sliding seat. The design with sliding seats reduces thermally induced tensions within the exhaust collector.

In the production of the individual components of the inner shell body manufacturing tolerances must be considered. As a result, the respective components within the respective sliding seat necessarily interlock with a more or less large radial clearance. However, such radial clearance leads to leakage during operation of the exhaust manifold. Since the outer shell body encloses the respective inner shell body gas-tight, such leaks are usually not critical. For the use of the exhaust manifold in conjunction with a twin-scroll turbocharger, however, there is a need to reduce the leakage in the region of the sliding seat, in particular when two inner shell body are arranged in a common outer shell body.

The present invention is concerned with the problem of providing an improved embodiment for an exhaust gas collector or for an associated production method, which is distinguished in particular by the fact that the exhaust gas collector is particularly suitable for operation with a twin-scroll turbocharger. In particular, leakages in the area of the sliding seats should be reduced.

This problem is solved according to the invention by the subject matters of the independent claims. Advantageous embodiments are the subject of the dependent claims.

The invention is based on the general idea to carry out a calibration at the respective sliding seat. As a result, at least the outer component in the respective sliding seat by forming a predetermined geometry. In particular, a predetermined, comparatively narrow radial clearance can thereby be set in the respective sliding seat. Likewise, the calibration can be performed so that the two components in the sliding seat rest against each other without play. For this purpose, it may be provided to reduce at least the respective outer component by targeted reshaping in terms of its cross-section to the extent that it comes to rest in the sliding seat on the respective inner component. In other words, in the interposed in the respective sliding fit components of the outer component is reduced by forming on the inner component. The cross-section reduction is carried out so that still the sliding seat function is guaranteed. It does not depend on a smooth running of the sliding seat, since the thermally induced relative movements between the individual parts mounted in the sliding seat by relatively large stresses or forces are generated, so that in principle a comparatively stiff sliding fit sufficient to unacceptable high voltages in the structure to avoid the exhaust collector.

The calibration can in particular be carried out so that within the respective sliding seat of the respective outer component after the cross-section reduction the respective inner member in the circumferential direction at at least three spaced apart locations. This means that a radial fixation of the two components is realized together. For example, the three circumferentially spaced contact locations may be formed by three discrete points of contact spaced apart in the circumferential direction. Likewise, at least one discrete contact point can be combined with at least one segment-shaped contact point, which enables contacting along a circumferential segment. Likewise, two or more such segmental contact points may suffice. Likewise, a circumferentially closed, so uninterrupted contact is conceivable. The individual contact points can be punctiform or linear or flat.

Since the gas-carrying components in the sliding seat after the respective cross-sectional reduction of the outer component quasi abut each other, an increased sealing effect can be achieved in the sliding seat. It is clear that the contact does not necessarily have to be flat, as this is only possible in the ideal case. A radial definition of the nested components is also already achieved when in the circumferential direction at least three spaced contact points, a radial support takes place. Remaining radial gaps are small compared to their axial length in the sliding seat, creating a throttle effect, which acts like a seal acts, so-called throttle sealing gap. If now two inner shell body are arranged in a common outer shell body, the sliding seats have been calibrated according to the proposal according to the invention, only a small amount of gas can escape from one of the inner shell body in the outer shell body and get out of this in the other inner shell body. Due to the greatly reduced or strongly damped leakage in the region of the sliding seats, in particular a pressure equalization between the separate gas paths within the inner shell body can be avoided, which increases the efficiency of the twin-scroll turbocharger.

Other important features and advantages of the invention will become apparent from the dependent claims, from the drawing and from the associated description of the figures with reference to the drawing.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination given, but also in other combinations or in isolation, without departing from the scope of the present invention.

Fig. 1

einen Längsschnitt durch einen Abgassammler,

Fig. 2

einen Längsschnitt durch den Abgassammler im Bereich eines Schiebesitzes bei unterschiedlichen Herstellungsphasen a, b und c.

Preferred embodiments of the invention are illustrated in the drawing and are explained in more detail in the following description, wherein the same or similar or functionally identical components are provided with the same reference numerals. Show, in each case schematically,

Fig. 1

a longitudinal section through an exhaust manifold,

Fig. 2

a longitudinal section through the exhaust manifold in the region of a sliding seat at different stages of production a, b and c.

Corresponding Fig. 1 For example, an air gap-insulated exhaust collector 1 has a flange 2, an outer shell body 3 and at least one inner shell body 4, 5. In the example, the exhaust manifold 1 has two inner shell bodies 4, 5. The exhaust manifold 1 forms a total of an input area of an otherwise not shown exhaust system of an internal combustion engine, which may be arranged in particular in a motor vehicle. Preferably, in a supercharged internal combustion engine, an exhaust gas turbocharger 6 indicated here with a broken line is connected directly to the exhaust gas collector 1. This is in particular a twin-scroll turbocharger 6, which is characterized by two separate inlet paths leading from an exhaust gas inlet of the turbocharger 6 to a turbine or to a turbine wheel of the turbocharger 6.

The outer shell body 3 encloses the two inner shell body 4, 5 spaced such that a thermally insulating air gap between the skin of the outer shell body 3 and the respective skin of the respective inner shell body 4, 5 is formed.

The two inner shell bodies 4, 5 are each assembled from a plurality of individual gas-conducting components. In the example shown, each inner shell body 4, 5 has three inlet pipes 7, a connecting pipe 8, a coupling pipe 9 and an outlet pipe 10. The inlet pipes 7 each have an inlet opening 11, which are each assigned to a cylinder of the internal combustion engine in the assembled state of the exhaust manifold 1. The connecting pipe 8 connects the two first inlet pipes 11 via the coupling pipe 9 with the outlet pipe 10. The outlet pipe 10 then connects the connecting pipe 8 and the third inlet pipe 11 with an outlet opening 12 of the respective inner shell body 4, 5. The respective outlet opening 12 can now in mounted state directly to one of the two inlet paths of the twin-scroll turbocharger 6 lead.

In the example shown, the respective inner shell body 4, 5 each have two sliding seats 13 and 14. The first sliding seat 13 is formed between the first inlet pipe 11 and the connecting pipe 8, while the second sliding seat 14 between the connecting pipe 8 and the coupling pipe 9 is formed is. The respective sliding seat 13, 14 allows an axial displacement between the nested components. The axial direction is defined by the axial direction of the respective sliding seat 13, 14 and thus by the insertion direction, in which in the respective sliding seat 13, 14, the two components are inserted into one another. In the first sliding seat 13, the connecting pipe 8 is the outer component, while the first Inlet pipe 7 is the inner part. In contrast, in the second sliding seat 14, the coupling pipe 9 is the outer component, while the connecting pipe 8 forms the inner part.

When producing the respective inner shell body 4, 5, first the individual components 7, 8, 9, 10 are inserted into one another in the region of the sliding seats 13, 14. Subsequently, at least in one of the sliding seats 13, 14, preferably in both sliding seats 13, 14 carried out a calibration, in which at least at the respective outer component is a cross-sectional reduction. This calibration process can be carried out in a targeted manner so that then there is a predetermined, comparatively narrow radial gap between the two nested components in the sliding seat. The gap width of this radial gap may in particular be smaller than the wall thickness of the respective inner component and / or the respective outer component in the respective sliding seat 13, 14. Preferred is an embodiment in which the gap width is less than 50% or even less than 20% of the wall thickness of the outer and / or inner component. In any case, the gap width after the calibration process is significantly smaller than in the case of conventional construction, when the separately produced components are inserted into one another in the respective sliding seat 13, 14 due to comparatively large manufacturing tolerances. Likewise, the calibration can be carried out in such a way that subsequently the respective outer component comes into contact with the respective inner component.

The cross-sectional reduction required for this purpose can be carried out such that subsequently the outer component contacts the respective inner component in the region of the respective sliding seat 13, 14 at at least three points which are spaced from each other in the circumferential direction. Ideal is an interruption in the circumferential direction, in particular flat, touch, between the nested components within the respective sliding seat 13, 14. It is important that the cross-section reduction is carried out in einstecksteckenden components, so that it is possible, the respective outer component to calibrate on the cross section of each inner component.

The calibration can in particular be carried out so that the two components are then inserted into each other in the sliding seat 13, 14 without play. Additionally or optionally, the calibration can also be carried out in such a way that a radial interference fit is produced in the respective sliding seat 13, 14. The radial compression is specifically realized so that the press fit thermally induced relative axial movements that may be required between the by the sliding seat 13, 14 abutted components.

The calibration with cross-section reduction can be carried out, for example, with the aid of a forming tool which has two half-shells which are lowered onto one another. This transformation can be realized particularly inexpensive. In particular, the respective inner shell body 4, 5 can be inserted after the mating of the individual components in one of the half-shells of the forming tool. The other half-shell is then lowered, thereby realizing the transformation for calibration. Particularly advantageous in this case is an embodiment in which two or more sliding seats 13, 14 can be deformed within the same inner shell body 4, 5 with respect to a cross-sectional reduction in the same forming tool simultaneously. Accordingly, then only one operation is required to calibrate all sliding seats 13, 14 according to the invention. In a further development may also be provided to arrange the two inner shell body 4, 5 of the exhaust manifold 1 in the same forming tool to simultaneously calibrate the respective sliding seats 13, 14 of the two inner shell body 4, 5 in a forming step.

The cross-sectional reductions of the respective outer components in the respective sliding seat 13, 14 can in principle be carried out in such a way that, in principle, a reduction in cross-section of the respective inner component is also accepted. In this case, however, it must be ensured that subsequently the resulting interference fit or the sliding seat 13, 14 present thereafter can still fulfill its functionality as a sliding seat 13, 14 during the thermal loads occurring during operation of the exhaust manifold 1. As already explained above, while a sluggish sliding seat 13, 14 is relatively uncritical, since sufficiently large forces occur during operation.

According to the Fig. 2a to 2c can be provided in a particular embodiment, when assembling the inner shell body 4, 5 in the then to be calibrated sliding seat 13, 14 a spacer sleeve 19 radially between the respective inner component 7 and 8 and the outer component 8 and 9 to arrange, see. Fig. 2a , This spacer sleeve 19 ensures during the calibration process that the two nested components 7 and 8 or 8 and 9 do not come into contact with each other due to the forming process. During reshaping, the outer component 8 or 9 is thus supported via the spacer sleeve 19 on the inner component 7 or 8, at the same time also forming on the inner component 7 or 8 being basically feasible. By using such a spacer sleeve 19, a defined radial gap can be formed in the respective sliding seat 13 or 14 by the calibration, which can initially be tightly closed by the spacer sleeve 19, cf. Fig. 2b , Appropriately, the spacer sleeve 19 is now made of a material, for. B. of a plastic which is volatile at the usual temperatures during operation of the exhaust collector 1. In particular, the spacer sleeve 19 is fully incinerable. After volatilization of the spacer sleeve 19, the respective sliding seat 13 or 14 has the desired defined, ie calibrated radial clearance, which - as explained above - can be significantly smaller than in the conventional design without calibration, cf. Fig. 2c. Fig. 2a shows the components 7 and 8 or 8 and 9 with inserted spacer sleeve 19 before calibration. Fig. 2b shows the ingredients 7 and 8 and 8 and 9 with the spacer sleeve 19 after calibration and Fig. 2c shows the calibrated sliding seat 13 and 14 after removing the spacer sleeve 19th

In the example shown, the inlet pipes 7 are connected to the flange 2, in particular welded. The outer shell body 3 is firmly connected in the region of the inlet pipes 7 with the inner shell bodies 4, 5, in particular welded. A connection to the flange 2 is not provided for the outer shell body 3 here, but can be realized in another embodiment. The shell body 3 encloses a receiving space 15, in which both inner shell body 3, 4 are housed. Only the inlet pipes 7 project out of the outer shell body 3. In the example, a partition wall 16 is arranged in the outer shell body 3, which divides the receiving space 15 into two subspaces 17 and 18, in each of which one of the inner shell body 4, 5 is arranged. The partition wall 16 can in particular gas-tight or approximately gas-tight, the two subspaces 17, 18 separate from each other, whereby a pressure equalization between the two subspaces 17, 18 can be hindered.

The calibrated sliding seats 13, 14 are characterized by a reduced leakage, whereby a pressure equalization between the exhaust gas flows within the two inner shell body 4, 5 is hindered. In addition, the partition wall 16 can bring about a further contribution to suppressing a pressure equalization between the two gas paths. Furthermore, the separate connection of the two inner shell body causes 4, 5 via the separate outlet openings 12 to the two separate inlet paths of the turbocharger 6, a further independent and separate gas supply to the turbocharger 6. In this way, the twin-scroll turbocharger 6 can be operated particularly effectively.

Claims (12)

Method for producing an air gap-insulated exhaust collector (1) for an exhaust system of an internal combustion engine, in particular in a motor vehicle, in which individual gas-carrying components (7, 8, 9, 10) of an inner shell body (4, 5) are inserted into one another in the region of at least one sliding seat (13, 14), - In which in the region of at least one such sliding seat (13, 14) with ineinandersteckenden components (7, 8, 9, 10), a calibration is performed, in which at least at the respective outer component (8, 9) is a cross-sectional reduction. Method according to claim 1,
characterized,
that the calibration is carried out so that the respective components (7, 8, 9, 10) subsequently in the sliding seat (13, 14) are inserted into one another without play. Method according to claim 1 or 2,
characterized,
that the calibration process is carried out in such a way that in the respective sliding seat (13, 14) a radial interference fit is created which permits thermally induced relative axial movements between the components (7, 8, 9, 10) mounted on the respective sliding seat (13, 14) , Method according to one of claims 1 to 3,
characterized,
that the calibration process is carried out so that in the respective sliding seat (13, 14) radially between the outer component and the inner component there is no gap or gap with a small gap width, in particular smaller than a wall thickness of the outer component and / or the inner Component in the region of the sliding seat (13, 14) and preferably less than 50% or less than 20% of this wall thickness may be. Method according to claim 1,
characterized,
that the calibration is carried out with the aid of a spacer sleeve (19) in the sliding seat (13, 14) radially between the inner component (7, 8) and the outer part (8, 9), said spacer sleeve (19), in particular for the temperatures occurring during operation of the exhaust collector (1) can be designed to be volatile. Method according to one of claims 1 to 5,
characterized,
that the calibration process is carried out by means of a forming tool having two half-shells. Method according to claim 6,
characterized,
that in the same forming tool at least two sliding seats (13, 14), the calibration of the respective outer component (8, 9) is carried out simultaneously. Method according to claim 6 or 7,
characterized,
that in the same forming tool at least two inner shell bodies (4, 5) in each case at least one sliding seat (13, 14), the calibration of the respective outer component (8, 9) is performed. Air gap-insulated exhaust manifold for an exhaust system of an internal combustion engine, in particular in a motor vehicle, - With an outer shell body (3), - With at least one inner shell body (4, 5) which is assembled from at least two gas-conducting components (7, 8, 9, 10), which are inserted into each other in the region of at least one sliding seat (13, 14), - Wherein at least one such sliding seat (13, 14) has been calibrated by at least the outer component (8, 9) has been carried out by forming a cross-sectional reduction. Exhaust manifold according to claim 9,
characterized,
that the respective components (7, 8, 9, 10) in the respective slide seating (13, 14) are inserted into one another without play. Exhaust manifold according to claim 9 or 10,
characterized,
that in the respective sliding seat (13, 14) there is a radial press fit, the thermally induced relative axial movements between the over the sliding seat (13, 14) mounted to each other components (7, 8, 9, 10). Exhaust manifold according to one of claims 9 to 11,
characterized,
that in the respective sliding seat (13, 14) the nested components (7, 8, 9, 10) abut each other axially gap-free or that radially between the outer component and the inner component is a gap with a small gap width, in particular smaller than a Wall thickness of the outer component and / or the inner component in the region of the sliding seat (13, 14) and preferably less than 50% or less than 20% of this wall thickness may be.

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