EP0192995B1 - Exhaust manifold - Google Patents

Abstract

1. Exhaust manifold for a least four cylinder combustion engines with internal combustion comprising outlet pipes (1 to 6) each associated with one cylinder which are brought together groupwise into associated further exhaust pipes (7, 8), which in turn open into a common exhaut pipe (9) leading to an exhaut silencer (10 to 12), wherein all outlet pipes (1 to 6) and likewise the further exhaust pipes (7, 8) respectively each have the same length, characterized in that the total cross-sectional area of the outlet pipes (1 to 6) is larger than the total cross-sectional area of the further exhaust pipes (7, 8), the total cross-sectional area of which is in turn larger than that of the common exhaust pipe (9) ; and in that the outlet pipes (1 to 6) are brought together with nozzle-like narrowed openings into the further exhaust pipes (7, 8) which in turn open with nozzle -like narrowed openings into the common exhaust pipe (9).

Description

The invention relates to an exhaust pipe elbow for at least four-cylinder internal combustion engines with internal combustion, each with a cylinder assigned exhaust pipes, which are grouped together in associated additional exhaust pipes, which in turn lead to a common exhaust pipe leading to an exhaust muffler, with all exhaust pipes as well as the further exhaust pipes each one below the other have the same length.

From US-A-35 45 414 a corresponding exhaust manifold for a four-cylinder boxer engine is known. However, this publication does not contain any measures for how such an exhaust pipe elbow should be optimized in terms of flow with regard to a - meanwhile - desired combination with a catalytic converter arrangement for exhaust gas purification.

DE-A-33 14 839 shows an exhaust pipe elbow for four-cylinder in-line engines with exhaust pipes of approximately the same length, each of which is brought together in pairs in further exhaust pipes. One of the exhaust pipes opens laterally into the other exhaust pipe, which accordingly forms a common exhaust pipe downstream of the mouth of the one exhaust pipe. Thus, the pipe lengths of the further exhaust pipes between the merging of the exhaust pipes and the mouth of one exhaust pipe into the other exhaust pipe are of unequal length.

In addition, it is provided that the diameter of each further exhaust pipe is approximately 80% of the sum of the diameters of the outlet pipes which are brought together in the respective further exhaust pipe. If it is assumed that the outlet pipes have the same diameter d in the usual way, then the diameter D of a further exhaust pipe is

Accordingly, the further exhaust pipes each have a cross-sectional area F, where applies

The cross-sectional area of a further exhaust pipe is therefore significantly larger than the total cross-sectional area of the exhaust pipes which are respectively merged into a further exhaust pipe, since the total cross-sectional area of two exhaust pipes is 2π d ² .

This known exhaust pipe manifold, when combined with a catalytic converter, may result in a considerable loss in engine performance.

The object of the invention is now to provide an exhaust pipe elbow which, even when combined with a conventional catalytic converter arrangement, enables approximately the same power yield as is possible in previous exhaust pipe elbows only without the arrangement of a catalytic converter arrangement.

This object is achieved in an exhaust pipe elbow of the type specified above in that the total cross-sectional area of the exhaust pipes is larger than the total cross-sectional area of the outgoing exhaust pipes, the total cross-sectional area in turn is larger than that of the common exhaust pipe, and in that the exhaust pipes with nozzle-like openings in the outgoing exhaust pipes are brought together, which in turn open into the common exhaust pipe with nozzle-like narrowed orifices.

Due to the gradual narrowing of the flow cross-section available to the total amount of exhaust gas, a gradual acceleration of the exhaust gas flow is achieved within the exhaust pipe elbow according to the invention with a corresponding gradual pressure reduction. This pressure drop acts in the sense of a reduction in the flow resistance or pressure opposite the exhaust gas flow, in such a way that the inevitable loss of power caused by the catalytic converter is compensated for. Due to the nozzle-like constricted mouths of the exhaust pipes and the further exhaust pipes, the exhaust gas flows coming from the exhaust pipes in the respective further exhaust pipe or the exhaust gas flows flowing from the further exhaust pipes into the common exhaust pipe are combined at an increased speed, which already corresponds to the mean flow velocity in the further exhaust pipes or corresponds in the common exhaust pipe or is approximated. This prevents the formation of an increased dynamic pressure in the area of the pipe junctions. In addition, particularly good mixing of the individual merged exhaust gas flows is achieved with one another.

Due to the described fluidic optimization of the exhaust pipe elbow according to the invention, the same performance can easily be achieved in engines whose exhaust gases are catalytically broken down to reduce pollutants as in engines without a catalytic converter in the exhaust line. Due to the good mixing of the combined exhaust gas flows, a largely homogeneous exhaust gas mixture is created, the composition of which can be easily monitored with a single measuring probe (lambda probe) in front of the catalytic converter arrangement.

The exhaust pipes of the engine or one row of cylinders of the same are expediently combined into two groups, the two associated further exhaust pipes being brought together into the common exhaust pipe assigned to the engine or the row of cylinders.

With regard to the cross-sectional areas of the pipes, it is advantageous if the total cross-sectional areas of a group of exhaust pipes are approximately 1.5 to 2.5 times the cross-sectional area of the further exhaust pipe assigned to this group and the cross-sectional area of the common exhaust pipe is approximately one third to three-quarters of the total cross-sectional area of the further exhaust pipes opening therein corresponds.

In the case of six outlet pipes, which are in two Groups are brought together in two further exhaust pipes, an arrangement is particularly preferred in which the exhaust pipes have a total of approximately 1.6 times the total cross-sectional area of the further exhaust pipes and the latter together have approximately twice the cross-sectional area of the common exhaust pipe. A favorable torque curve of the engine can thus be achieved, in particular even at low speeds.

The outlet pipes should preferably have approximately twice the length of the exhaust gas pipes. The length of the common exhaust pipe can correspond approximately to the length of the exhaust gas pipes. If necessary, however, the common exhaust pipe can also be longer. A shorter dimension of the common exhaust pipe is in principle also possible, but in some circumstances a relatively small mixture of the exhaust gas flows coming from the further exhaust pipes has to be accepted.

In the case of six outlet pipes which are brought together in two groups in two further exhaust pipes, the ratio of the length of an outlet pipe to the length of a further exhaust pipe is particularly preferably approximately 6: 2.5.

The ratio of the lengths of the outgoing exhaust pipes and the common exhaust pipe can be approximately 5: 4.

A particular advantage of the invention is that the common exhaust pipe can accommodate a lambda probe, as is customary for controlling the engine in exhaust gas cleaning by means of catalysts. In this way, the lambda probe is arranged in an area of the exhaust system with a small cross-section and is acted upon by the entire exhaust gases of the engine or a row of cylinders. It is therefore reliably prevented that part of the exhaust gas flow or the exhaust gases of individual cylinders can bypass the lambda probe.

In this context, an arrangement is particularly expedient in which the lambda probe is arranged in the region of the mouth of the common exhaust pipe in a catalyst chamber. Because here the exhaust gases have reached a particularly good degree of mixing. In addition, the high flow velocity of the exhaust gases means that there is a constant gas exchange in the vicinity of the lambda probe.

In addition, the arrangement of the lambda probe in front of the catalyst chamber takes into account the fact that higher exhaust gas temperatures are advantageous for the lambda probe than those prevailing in the downstream chamber.

In view of the high stability of the exhaust pipe elbow, it is expedient if it is designed as a sheet metal part or is composed of sheet metal parts. Compared to a basically possible design as a casting, a higher resistance to mechanical vibrations is achieved. In addition, the dimensions of sheet metal parts can be changed comparatively easily, so that, if necessary, the exhaust system can be adjusted without excessive costs if the respective engine is changed.

The merging of two exhaust pipes into one exhaust pipe is preferably carried out in such a way that one exhaust pipe passes continuously through the pipe junction into the downstream exhaust pipe and the other exhaust pipe is connected laterally at an angle by arranging an opening which is drawn around half the circumference and on the first pipe the pipe wall adjoining the pipe in the axial direction on one side - upstream - of the opening is pressed in to form a surface which is oblique to the pipe axis, the layout of which resembles an ellipse half, and by the other pipe being blunt on one circumferential half and the other circumferential half End cut obliquely to the tube axis is welded to the first tube, the obliquely cut edge welding on the elliptical oblique surface edge and on the opening edges extending this edge and the bluntly cut edge on the opening edge opposite the inclined surface t is.

The cutting plane of the oblique cut and the axis of the other tube should form approximately the same angle as the oblique surface and the axis of the one tube, so that the tube axes form a V that is approximately symmetrical to the oblique surface.

The design described enables a particularly high stability due to the one-piece tube arranged continuously. At the same time, the design of the inclined surface together with the connection shown of the other tube ensures the formation of the nozzle-shaped constrictions for the exhaust gas flows which merge into one another in a structurally particularly simple manner.

When the ends of three pipes are brought together into a further pipe, a funnel part is preferably arranged, one end of which has a cross section corresponding to the further pipe and the other end of which has a cloverleaf-like cross section. The ends of the three tubes arranged in bundles next to one another are cut off obliquely on the circumferential side facing away from the other two pipes, and inserted with the obliquely cut off areas in the funnel in such a way that the funnel covers the obliquely cut off circumferential sides, i.e. the funnel replaces the cut-off wall part of the pipe ends. Again, the nozzle-shaped constriction is formed because the wall parts of the pipe ends that extend into the funnel form conical pipe elements together with the opposite wall part of the funnel.

• Fig. 1 in schematisierter Form einen erfindungsgemäßen Abgasrohrkrümmer für einen Sechszylinder-Reihenmotor,
• Fig. 2 einen entsprechenden Abgasrohrkrümmer für einen Vierzylinder-Reihenmotor,
• Fig. 3 eine Draufsicht auf die Zusammenführung zweier Abgasrohre,
• Fig. 4 eine Draufsicht auf das in Fig. 3 untere Abgasrohr entsprechend dem Pfeil IV in Fig. 3,
• Fig. 5 eine Zusammenführung dreier Rohre und
• Fig. 6 eine Ansicht des zur Zusammenführung der drei Rohre dienenden Trichters entsprechend dem Pfeil VI in Fig. 5.

Otherwise, with regard to preferred features of the invention, reference is made to the subclaims and the following description of the invention with reference to the drawing, in which particularly preferred embodiments are shown. Show

• 1 in schematic form an exhaust pipe elbow according to the invention for a six-cylinder in-line engine,
• 2 shows a corresponding exhaust pipe elbow for a four-cylinder in-line engine,
• 3 is a plan view of the merging of two exhaust pipes,
• 4 is a plan view of the lower exhaust pipe in FIG. 3 according to arrow IV in FIG. 3,
• Fig. 5 is a merge of three pipes and
• 6 is a view of the funnel used to bring the three tubes together according to arrow VI in FIG. 5.

1, a total of six exhaust pipes 1 to 6 are arranged on the exhaust side of a six-cylinder in-line engine, not shown, each of which is assigned to a cylinder. These outlet pipes 1 to 6 have the same length as possible and are combined into two groups, such that the outlet pipes 1 to 3 are brought together in a further exhaust pipe 7 and the outlet pipes 4 to 6 are brought together in a further exhaust pipe 8. The total cross-sectional area of the exhaust pipes 1 to 3 or 4 to 6 of each group is approximately twice as large as the cross-sectional area of the respectively assigned exhaust pipe 7 or 8.

The further exhaust pipes 7 and 8 are in turn brought together in a common exhaust pipe 9, the cross-sectional area of which corresponds approximately to the cross-sectional area of each of the further exhaust pipes 7 and 8, i.e. the total cross-sectional area of the secondary exhaust pipes 7 and 8 is approximately twice as large as the cross-sectional area of the common exhaust pipe 9.

In Fig. 1, various options are now shown for the elements of the exhaust line connected to the common exhaust pipe 9.

Thus, the common exhaust pipe 9 can bifurcate in its further course and open into a front silencer 10, which is followed by a rear silencer 11, front silencer 10 and rear silencer 11 being connected to one another via double pipes and the rear silencer being opened to the atmosphere via a double pipe. This embodiment is shown in the upper right section of FIG. 1.

Instead, the common exhaust pipe 9 can also open into the front silencer 10 ', which in turn is connected via a simple pipe to the rear silencer 11', which in this case is connected to the atmosphere via a simple exhaust pipe.

In view of existing or future environmental protection regulations, it is desirable to remove the pollutants in the exhaust gases by catalytic decomposition. In this case, instead of the front silencer 10 or 10 ', a catalytic converter chamber 12 is arranged, in which the exhaust gases flow through a catalytic converter and, at least in part, are broken down into their elementary components. The catalyst chamber 12 is then in turn followed by a rear silencer 11 ″, which in turn is connected to the atmosphere via an end pipe.

In principle, instead of the arrangement shown at the bottom right in FIG. 1, in which the common exhaust pipe 9 opens into the catalyst chamber 12 without being forked, it is also possible to provide a fork of the common exhaust pipe 9, so that the fork pipe sections are divided into separate catalyst chambers, which in one common housing can be arranged, open. In the latter case, the two catalyst chambers connected in parallel are expediently connected via a double tube to a common rear silencer or to separate rear silencers, which in turn can be accommodated in a common housing.

For catalytic converter operation, it is expedient for the engine to be controlled by means of a lambda probe 13, in particular with regard to the mixing ratio of the supplied fuel with air and the ignition times. In the arrangement according to the invention, the lambda probe 13 is arranged on a corresponding bore in the common exhaust pipe 9. This ensures that the lambda probe 13 is acted upon by the exhaust gases of all cylinders. This is all the more so as a corresponding acceleration of the exhaust gas flow occurs due to the overall cross section of the exhaust line decreasing from the exhaust pipes 1 to 6 via the further exhaust pipes 7 and 8 and the common exhaust pipe 9, and the increased flow rates thus promote intensive mixing of the exhaust gases.

In addition, it is advantageous that the lambda probe 13 is only a relatively short distance from the engine along the flow path of the exhaust gases and is accordingly acted upon by exhaust gases of relatively high temperature, as is favorable for optimal functioning of the lambda probe 13.

In contrast, the catalytic converter or the catalytic converter chamber 12 accommodating it can be arranged at a greater distance from the engine in order to avoid the catalytic converter being overheated when the engine is operating at full load, in particular when operating at full load and at low speed.

The invention thus enables optimal placement of both the lambda probe 13 and the catalyst. In addition, the back pressure generated by the catalytic converter due to its throttling effect in the exhaust line is largely compensated by the fact that - as already mentioned - the pressure of the exhaust gases corresponding to the narrowing of the cross-section of the exhaust line from the exhaust pipes 1 to 6 via the exhaust pipes 7 and 8 and the common exhaust pipe 9 gradually decreases, with a corresponding increase in flow velocity.

The embodiments shown in FIG. 2 correspond to the embodiments according to FIG. 1 in all essential points. In Fig. 2 only the case of a four-cylinder in-line engine is shown, in which according to the number of cylinders only four exhaust pipes 1 to 4 are to be arranged. It is spatially easily possible to take into account the firing order of the cylinders of the engine, for example by exhaust pipes 1 and 4 or exhaust pipes 2 and 3 each opening into one of the exhaust pipes 7 and 8, for example if the first, fourth, second and third cylinders are fired in succession. Otherwise, the explanations and explanations for FIG. 1 apply analogously to FIG. 2.

In Figures 1 and 2 is shown by dashed lines, arranged within the tubes wall parts 14 that the mouth areas of the exhaust pipes 1 to 6 or the mouth areas of the further exhaust pipes 7 and 8 according to a preferred embodiment of the invention in the exhaust gas flow direction like a nozzle can or should be narrowed.

In the following FIGS. 3 to 6, structurally preferred possibilities are now shown to implement the corresponding nozzle-shaped mouth areas in the area of the pipe junctions by means of sheet metal parts.

3 shows the merging of two exhaust pipes 107 and 108. The exhaust pipe 107 corresponds, for example, to a section of the outgoing exhaust pipe 7 in FIGS. 1 or 2, while the exhaust pipe 108 with its area 108 'is a section of the outgoing exhaust pipe 8 in FIGS. 1 and 2 and with its area 108 "is a section of the common area Exhaust pipe 9 forms in Figures 1 and 2.

The pipe 108, which is made in one piece by bringing the pipes 107 and 108 together, has between its regions 108 'and 108 "an opening 109 which extends over approximately half the circumference. Following the opening 109, the circumferential wall of the pipe is on the side facing the exhaust gas flow direction of the opening 109 is pressed inward to form an inclined surface 110, which in the example shown forms an angle of approximately 20 ° with the tube axis. In plan view, the inclined surface 110 has approximately the shape of an ellipse half.

The merged with the pipe 108 end of the pipe 107 is cut obliquely on its side facing the pipe 108, approximately at an angle of likewise 20 °, to the pipe axis, such that an edge 111 is formed, the contour of which when viewed in the direction of the arrow VI has approximately the same shape as the edge of the inclined surface 110 and the edges 109 "of the opening 109 which continue this edge. On the circumferential half opposite the edge 111, the end of the tube 107 is cut bluntly to form an edge 112 which adjoins the edge 109 ' Opening 109 fits.

To connect the pipes 107 and 108, the edges 111 and 112 of the pipe 107 are welded to the edges of the inclined surface 110 and the adjoining opening edges 109 "and 109 '. The inclined surface 110 thus narrows both of the above-mentioned in the area where pipes 107 and 108 are brought together Pipes in the same way.

In addition to being easy to manufacture, the construction shown is characterized by high stability because one of the tubes is made in one piece.

5 and 6, a funnel 100 is arranged to bring together three pipes, the downstream end of which (on the right in FIG. 5) has a cross section corresponding to the exhaust gas line, not shown below. At the other end, the funnel widens with a cloverleaf-like cross section, such that the cloverleaf cross section at the end of the funnel corresponds to the cross section of three bundled tubes, of which only tubes 101 and 102 are visible in FIG. 5. Each of these tubes is cut obliquely at its ends, similar to tube 107 in FIG. 3, on the circumferential side facing away from the other two tubes. This allows the tubes 101 and 102 to be pushed into the funnel 100 accordingly and welded to the same and to one another.

The funnel thus covers the respective obliquely cut circumferential side of the tubes 101 and 102.

At the same time, the wall regions of the tubes 101 and 102 protruding into the funnel 100 together with the associated “cloverleaf” segment of the funnel 100 each form a nozzle which narrows in the flow direction, so that the exhaust gas flow coming from each of the tubes 101 and 102 before being combined with the Exhaust gas flows of the other pipes is accelerated accordingly.

In the example in FIG. 5, a fastening flange is arranged on the funnel 100. Instead, other fastening elements can optionally also be used for connection to further exhaust pipes. If necessary, a part of the outgoing exhaust pipe can also be connected directly to the funnel 100. Otherwise, articulated connections or bellows connections can also be arranged if the exhaust parts are to be movable relative to one another.

In a six-cylinder engine with a displacement of approximately 2500 cm ³ , an exhaust pipe elbow according to the invention has the following dimensions, for example:

Claims (14)

1. Exhaust manifold for at least four cylinder combustion engines with internal combustion comprising outlet pipes (1 to 6) each associated with one cylinder which are brought together groupwise into associated further exhaust pipes (7,8), which in turn open into a common exhaust pipe (9) leading to an exhaust silencer (10 to 12), wherein all outlet pipes (1 to 6) and likewise the further exhaust pipes (7,8) respectively each have the same length, characterized in that the total cross-sectional area of the outlet pipes (1 to 6) is larger than the total cross-sectional area of the further exhaust pipes (7,8), the total cross-sectional area of which is in turn larger than that of the common exhaust pipe (9); and in that the outlet pipes (1 to 6) are brought together with nozzle-like narrowed openings into the further exhaust pipes (7,8) which in turn open with nozzle-like narrowed openings into the common exhaust pipe (9).

2. Exhaust manifold in accordance with claim 1, characterized in that the outlet pipes (1 to 6) of at least one cylinder bank of the engine are combined into two groups in each case, and the two associated further exhaust pipes (7,8) are brought together into the common exhaust pipe (9) associated with the cylinder bank.

3. Exhaust manifold in accordance with one of the claims 1 and 2, characterized in that the total cross-sectional area of a group of outlet pipes (1 to 3, 4to 6; 1 and 4, and 3) corresponds approximately to 1.5 to 2.5 times the cross-sectional area of the further exhaust pipe (7,8) associated with this group; and in that the total cross-sectional area of the common exhaust pipe (9) corresponds approximately to one third to three quarters of the total cross-sectional area of the further exhaust pipes (7,8) which open into it.

4. Exhaust manifold in accordance with one of the claims 1 to 3, characterized in that, with six outlet pipes (1 to 6) which are brought together in two groups (1 to 3, 4 to 6) into two further exhaust pipes (7,8), the outlet pipes (1 to 6) have as a whole approximately 1.6 times the total cross-sectional area of the further exhaust pipes (7,8) and the latter together have approximately twice the cross-sectional area of the common exhaust pipe (9).

5. Exhaust manifold in accordance with one of the claims 1 to 4, characterized in that the outlet pipes (1 to 6) have at least approximately twice the length of the further exhaust pipe (7,8) measured from the opening of the outlet pipes into the respective further exhaust pipe up to its opening into the common exhaust pipe (9).

6. Exhaust manifold in accordance with one of the claims 1, to 5, characterized in that the further exhaust pipes (7,8) have a comparable length to the common exhaust pipe (9).

7. Exhaust manifold in accordance with one of the claims 1 to 6, characterized in that with six outlet pipes (1 to 6) which are combined in two groups (1 to 3, 4 to 6) into two further exhaust pipes (7,8) the ratio of the length of an outlet pipe to the length of a further exhaust pipe lies approximately at 6:2.5.

8. Exhaust manifold in accordance with claim 7, characterized in that the ratio of the lengths of the further exhaust pipes (7,8) and the common exhaust pipe (9) lies at 5:4.

9. Exhaust manifold in accordance with one of the claims 1 to 8, characterized in that the common exhaust pipe (9) receives a lambda probe (13) and directs the exhaust gases into a chamber (12) with a catalyzer for catalytic breakdown of the exhaust gases.

10. Exhaust manifold in accordance with claim 9, characterized in that the lambda probe is arranged in the region of the opening of the common exhaust pipe (9) into the exhaust silencer or into a catalyzer chamber.

11. Exhaust manifold in accordance with one of the claims 1 to 10, characterized in that the common exhaust pipe (9), the further exhaust pipes (7,8) which open into it and also the outlet pipes (1 to 6) associated with the further exhaust pipes are formed as a sheet metal part or parts.

12. Exhaust manifold in accordance with claim 1, characterized in that for the bringing together of two further exhaust pipes (107, 108) the one exhaust pipe (108) passes in one piece continuously into the subsequent - common - exhaust pipe and the other - further - exhaust pipe (107) is attached obliquely to the side in that an opening drawn around approximately half the circumference is provided in the first pipe (108) and the tube wall adjoining one side of the opening in the axial direction of this pipe is depressed to form a surface inclined to the pipe axis with the outline of the inclined surface resembling one half of an ellipse; and in that the other pipe (107) is welded onto the first pipe (108) at its end which is cut off bluntly to the pipe axis at one circumferential half and obliquely to the pipe axis at the other circumferential half, with the obliquely cut-off edge being welded to the ellipse-like edge of the inclined surface and also to the edges of the opening which extend this edge, and with the bluntly cut-off edge being welded to the edge of the opening opposite to the inclined surface.

13. Exhaust manifold in accordance with claim 12, characterized in that the plane of cutting of the oblique cut and also the axis of the other pipe (107) form approximately the same angle as the inclined surface and the axis of the one pipe (108).

14. Exhaust manifold in accordance with one of the claims 11 to 13, characterized in that for the bringing together of the ends of the three pipes (101 to 103) into a - further - pipe a funnel part (100) is provided one end of which has a cross-section corresponding to the further pipe and the other end of which has a clover leaf like cross-section; and in that the ends of the three pipes (101 to 103) arranged in a bundle alongside one another are respectively cut obliquely away at the circumferential side remote from the other pipes and are inserted with their obliquely cut-off regions into the funnel (100) in such a way that the funnel (100) covers over the obliquely cut-off circumferential sides.

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