EP2497916B1 - Assembly of a muffler on a combustion engine with improved coupling to the cylinder - Google Patents

Description

The present invention relates to an arrangement of a muffler to an internal combustion engine according to the preamble of claim 1, wherein the muffler is formed with a connection piece which is adjacent to an outlet in the cylinder of the internal combustion engine and a flow connection between a combustion chamber of the internal combustion engine and the muffler forms.

STATE OF THE ART

From the DE 195 81 467 T1 For example, a muffler for an internal combustion engine is known, and the muffler is formed with a fitting in the form of a sheet steel bushing, and the fitting abuts with an end portion to an outlet in the cylinder of the internal combustion engine, to a flow connection between a combustion chamber of the internal combustion engine and the muffler to build. The sheet metal bushing is designed as a single part and adjoins in the region of the inlet of the muffler to the housing of the muffler. In this case, in the flow connection protruding body edges of the sheet metal components can interfere with the flow of the exhaust gas and lead to a vortex formation, which can lead to unwanted disturbances in a special embodiment of the muffler.

From the DE 24 23 507 A1 a connector between the outlet of a cylinder and an exhaust pipe is shown and forms a flow connection between the combustion chamber of the internal combustion engine and the exhaust pipe, and the exhaust pipe may open into a muffler. The fitting is adapted in shape and shape to the outlet in the cylinder, and an exact mounting of the exhaust pipe to the cylinder is required to provide a fitting with the fitting arrangement of the exhaust pipe to the cylinder. Furthermore, the connection piece has an open tube end pointing in the direction of the exhaust pipe, at which turbulences in the exhaust gas mass flow can likewise be created, which are to be avoided.

The US 2011/017336 A1 discloses an arrangement of a muffler on an internal combustion engine wherein the muffler is formed with a connection piece which adjoins an outlet in the cylinder of the internal combustion engine and forms a flow connection between a combustion chamber of the internal combustion engine and the muffler, wherein the inner diameter of the end portion is formed larger as the inside diameter of the outlet.

The EP 0 717 176 A1 shows an arrangement with an internal combustion engine and disposed thereon a muffler, wherein a fitting of a muffler is provided, which has a correspondingly shaped end region with an increasing diameter to form a venturi nozzle. In this case, the end portion of the connecting piece is not directly adjacent to the outlet in the cylinder of the internal combustion engine, but it is formed between the connecting piece and the outlet an annular gap through which a secondary air flow is drawn into the muffler.

FIG. 2 shows a further prior art, and a muffler 100 is shown indicated by a housing portion. The muffler 100 is used for the arrangement of an internal combustion engine, which is represented by the partial representation of a cylinder 18 and in which a combustion chamber 13 is formed. At the muffler 100, a connecting piece 25 is arranged with an inner diameter D _AN , which adjoins with an end portion 27 to an outlet 26 with an inner diameter D _AU in the cylinder 18 of the internal combustion engine to form a flow connection between the combustion chamber 13 and the muffler 100.

Such a fitting 25 is also known as the "port liner" and projects partially into the outlet 26, and the outlet 26 is widened in the region in which the fitting 25 projects with the end region 27. The inner diameter D _{AN of} the connecting piece 25 and the inner diameter D _{AU of} the outlet 26 are of identical design, and a continuous flow connection is formed between the combustion chamber 13 and the muffler 100. However, between the end region 27 of the connecting piece 25 and the outlet 26 forms a transition region, which can lead to vortex formation in the exhaust gas mass flow. In particular, a very accurate positioning of the muffler 100 in the outlet 26 of the cylinder 18 is required, and a slightly eccentric arrangement or tilting of the muffler 100 on the cylinder 18 can result in increased edges in the flow connection causing greater vortex formation. The connection piece 25 is shown with a Zentrieranformung 30, however, in a tilting of the muffler 100 through the end portion 27 of the fitting 25 despite the Zentrieranformung 30 edge formation occur that causes a vortex formation in the exhaust gas mass flow through the fitting 25 and the outlet 26.

The internal combustion engine may be configured as a two-stroke engine, and the muffler may allow exhaust backflow toward the combustion chamber to prevent unburned fuel-air mixture from entering the muffler. The silencer may have a specially designed chamber and a corresponding flow connection between the silencer inlet and the chamber, so that when opening the outlet of the Cylinder, the exhaust gas from the combustion chamber can first flow into the chamber via a flow channel, and after filling the chamber, a majority of the exhaust gas can flow back toward the muffler inlet. In this case, the exhaust gas flowing back forms a gas barrier against the opening of the combustion chamber, and unburned fuel-air mixture, which has passed from the combustion chamber into the muffler inlet during the charge exchange, can be pushed back into the combustion chamber by the backflowing exhaust gas. This principle requires a special design of the flow channel between the combustion chamber and the first chamber in the muffler, and the flow of exhaust gas should be possible vortex free, in particular, the fitting and the outlet from both directions with exhaust gas flows through, and the Rückströmprinzip the exhaust gas in the muffler can be used particularly effectively with a trouble-free flow in the connection piece and in the outlet.

DISCLOSURE OF THE INVENTION

It is therefore an object of the present invention to improve the arrangement of a muffler at the outlet of a cylinder of an internal combustion engine so that a trouble-free flow connection between a combustion chamber in the cylinder and the muffler is possible. In particular, it is the object of the present invention to facilitate the installation of a muffler on the cylinder of an internal combustion engine.

This object is achieved on the basis of an arrangement of a muffler on an internal combustion engine according to the preamble of claim 1 in conjunction with the characterizing features. Advantageous developments of the invention are specified in the dependent claims.

The invention includes the technical teaching that the inner diameter of the end portion of the connecting piece is formed larger than the inner diameter of the outlet in the cylinder of the internal combustion engine.

Thus, the connector according to the invention forms an end portion having an inner diameter which deviates at least from the inner diameter of the connecting piece and the inner diameter of the end portion of the connecting piece should be at least greater than the inner diameter of the outlet. Thus, the advantage is achieved that the abutting portion of the end portion the connecting piece is led out to the outlet on the cylinder at least a little radially from the main flow of the exhaust gas. By increasing the inner diameter of the end portion, the abutting portion of the end portion at the outlet is not directly in fluid communication, and vortex formation, which may continue as wake turbulence in the exhaust gas mass flow, can be largely avoided. It was found that even by the enlargement of the inner diameter of the end portion of the connecting piece a vortex formation of the exhaust gas could be largely avoided both from the direction of the combustion chamber in the muffler and in the reverse direction. Furthermore, the advantage is achieved that a slightly off-center mounting of the connection piece in the outlet on the cylinder of the internal combustion engine has no negative influence on the flow behavior of the exhaust gas, since even with a misaligned arrangement of the connection piece at the outlet no edge is formed in a transition region, which in the flow area would protrude.

According to an advantageous embodiment, the connecting piece may have an inner diameter, which is formed in the end region continuously and in particular free from diameter jumps to the inner diameter of the end region growing. The connecting piece and in particular the end region of the connecting piece can be rotationally symmetrical about a channel flow direction, and the end region can be formed by a funnel-shaped widening of the connecting piece. For example, the fitting may be made of a sheet metal sleeve, and the end portion may have been expanded by a mandrel. As the inner diameter of the fitting progressively increases toward the end region, a smooth contour with no edges and no diameter jumps is created, and the outer edge of the end portion may be brought into abutment with the outlet, with the end portion expanded to a diameter greater than the major diameter of the flow connection through which the exhaust gas flows.

According to a further advantageous embodiment, the inner diameter of the connecting piece and the inner diameter of the outlet may have the same value. Consequently, the diameter of the increases Flow connection only in the end portion of the fitting, and the inner diameter of the fitting, which is not expanded, may correspond to the inner diameter of the outlet. Due to the constant inner diameter of the outlet in the transition into the connecting piece, a flow of the exhaust gas with a constant flow velocity, without the flow accelerated by a flow constriction.

Alternatively, the inner diameter of the fitting may have a value smaller than the value of the inner diameter of the outlet. Thereby, the advantage is achieved that the edge, which is formed by the end of the outlet in the wall of the cylinder, has a smaller influence on the flow behavior of the exhaust gas in the flow connection. In this case, the diameter of the outlet between the inner diameter of the connecting piece and the inner diameter of the end portion of the connecting piece are. Consequently, the end portion overhangs the diameter of the outlet in the radial direction, and the edge of the outlet is attenuated by the smaller diameter of the fitting in the influence on the flow behavior of the exhaust gas.

According to the invention, the cylinder has a flat running surface and extending around the outlet, wherein the connecting piece is held by holding means with the end region arranged adjacent to the connection surface. The holding means may for example be brackets which have a certain spring action and the muffler may be slightly eccentrically arranged with the connector to the outlet on the cylinder, without jamming or distortion of the connector takes place in the outlet of the cylinder. Thus, the channel flow direction along which the fitting and the outlet extend in the cylinder forms a surface normal to the mating surface on the outside of the cylinder.
Advantageously, the outer surface may have a transition region that extends from a planar region of the connection surface in the outlet forming a rounding. The formation of a curve avoids an edge between the outlet and the connection surface, which in particular can influence the flow of exhaust gas when the exhaust gas from the exhaust gas flows Silencer flows back towards the combustion chamber of the cylinder. If the transition region is rounded, for example by forming a radius between the connection surface and the inner wall of the outlet, a further edge is avoided, which can protrude into the flow region of the exhaust gas.

The fitting of the muffler may form with its end portion a muffler inlet which merges into a flow channel, the flow channel extending into the muffler and opening at the muffler inlet opposite channel end into a first chamber, the flow channel between the muffler inlet and the first chamber so streamlined is formed, that the exhaust gas flowing into the muffler inlet due to its inertia predominantly flows into the first chamber and flows back after filling the first chamber, and thereby forms a back pressure in the direction of the combustion chamber. Thus, a gas barrier is formed, through which the escape of unburned fuel-air mixture from the combustion chamber is prevented or fuel-air mixture that has entered the muffler inlet, can be transported back into the combustion chamber by the backflowing exhaust gas.

Furthermore, the muffler may have a second chamber into which exhaust gas flows through a main outlet branched off from the flow channel and from which the exhaust gas flows out through an outlet, and wherein, for example, the first chamber may be formed enclosed by the second chamber.

Brief description of the drawings

• Figur 1 ein Ausführungsbeispiel eines Schalldämpfers in Anordnung an einem Verbrennungsmotor mit einer verbesserten Ankopplung an den Zylinder des Verbrennungsmotors,
• Figur 2 eine Anordnung eines Anschlussstückes eines Schalldämpfers am Auslass eines Zylinders gemäß dem Stand der Technik,
• Figur 3 ein erstes Ausführungsbeispiel der erfindungsgemäßen Anordnung des Anschlussstückes am Auslass eines Zylinders,
• Figur 4 ein zweites Ausführungsbeispiel der Anordnung eines Anschlussstückes am Auslass eines Zylinders und
• Figur 5 ein drittes Ausführungsbeispiel der Anordnung eines Anschlussstückes am Auslass eines Zylinders.

Further, measures improving the invention will be described in more detail below together with the description of preferred embodiments of the invention with reference to FIGS. It shows:

• FIG. 1 An embodiment of a muffler in an arrangement on an internal combustion engine with an improved coupling to the cylinder of the internal combustion engine,
• FIG. 2 an arrangement of a fitting of a silencer at the outlet of a cylinder according to the prior art,
• FIG. 3 A first embodiment of the inventive arrangement of the connector at the outlet of a cylinder,
• FIG. 4 A second embodiment of the arrangement of a connector at the outlet of a cylinder and
• FIG. 5 A third embodiment of the arrangement of a connector at the outlet of a cylinder.

PREFERRED EMBODIMENTS OF THE INVENTION

FIG. 1 shows a muffler 100 in the arrangement on an internal combustion engine 10, which is designed as a two-stroke engine. The internal combustion engine 10 has a cylinder 18 in which a combustion chamber 13 is formed. The combustion chamber 13 is movably limited by the piston 21, which is guided in a liftable manner in the cylinder 18 and is connected via a connecting rod 23 to a crankshaft 22 to form a crank mechanism. The cylinder 18 is arranged in a known manner on a crankcase 24 in which the crankshaft 22 is mounted.

In the wall of the cylinder 18, an outlet is arranged, on which the muffler 100 is flanged via a connecting piece 25. Thus, the outlet and the connection piece 25 form a silencer inlet 11, which releases a flow connection between the combustion chamber 13 in the cylinder 18 and the silencer 100 in the region of the bottom dead center of the piston 21, and exhaust gas can pass from the combustion chamber 13 through the silencer inlet 11 into the silencer 100 reach.

The silencer inlet 11 is adjoined by a flow channel 12, which opens into a first chamber 15 with a channel end 14 opposite the silencer inlet 11. Further, the muffler 100 has a second chamber 16, which is exemplified larger than the first chamber 15 and the first chamber 15 completely encloses and a part of the flow channel 12. The exhaust gas entering the muffler inlet 11 may first at least partially enter the first chamber 15, wherein a main outlet 17 is arranged on the flow channel 12, and the exhaust gas may pass from the flow channel 12 through the main outlet 17 into the second chamber 16. Furthermore, the first chamber 15 has a secondary outlet 20, so that exhaust gas from the first chamber 15 directly into the second chamber 16 can flow. The exhaust gas can leave the muffler 100 through an outlet 19, which is introduced in the wall of the second chamber 16 and reach the outside.

The flow channel 12 is designed so as to flow together with the connection piece 25 in such a way that the exhaust gas flowing into the muffler inlet 11 through the outlet of the cylinder 18 predominantly flows into the first chamber 15 and, after filling the first chamber 15, again in the direction of the muffler inlet 11 flows back to form against the outlet of the combustion chamber 13 a back pressure. This ensures that unburned fuel-air mixture does not enter the flow channel 12 in an uncontrolled manner, while the piston 21 of the internal combustion engine 10 is at the bottom dead center shown, and a charge change takes place in the combustion chamber 13. Due to the streamlined design of the flow channel 12, the exhaust gas first passes through the muffler inlet 11 into the first chamber 15, and fills it. Subsequently, the exhaust gas flows back in the direction of the muffler inlet 11 due to the overpressure in the first chamber 15, so that the flow channel 12 and the connecting piece 25 are alternately flowed through with exhaust gas.

FIG. 2 shows a detailed view of the arrangement of the fitting 25 at the outlet 26 of the cylinder 18 according to the prior art. The fitting 25 extends concentrically around a channel flow direction 12 'and merges into the flow channel 12. In this case, the connecting piece 25 is aligned with the outlet 26 in the cylinder 18, so that the outlet 26 is arranged concentrically around the channel flow direction 12 '.

The muffler 100 is shown as part of the housing by way of example, and the fitting 25 has a centering projection 30 for centering the fitting 25 concentric with the channel flow direction 12 'at the outlet 26 of the cylinder 18. The connecting piece 25 is formed in one piece with the flow channel 12, however, so-called "port liners" are known, which form an intermediate piece between the muffler 100 and the cylinder 18 of the internal combustion engine 10. In particular, this intermediate piece serves to ensure that the hot exhaust gases leaving the combustion chamber 13 and entering the muffler 100 do not act directly on the material of the cylinder 18. These port liners are preferably made of a steel sheet and form the connecting piece 25 between the outlet 26 of the combustion chamber 13 in the cylinder 18 and the muffler 100. As already described in the introduction, edges and shoulders in the flow connection between the combustion chamber 13 and the muffler 100 to a Disturbing the exhaust gas mass flow lead, which are to be avoided so as not to adversely affect the effect of the advantageous exhaust gas flow of the type described above.

FIG. 3 shows a first embodiment of a fitting 25 which is arranged with the outlet 26 of the cylinder 18 concentrically around the channel flow direction 12 'on the cylinder 18. The exemplary embodiment shows a connecting piece 25 with an inner diameter D _{AN of} the connecting piece 25, which is of the same design as the inner diameter D _{AU of} the outlet 26. According to the invention, the connecting piece 25 has an end region 27, with which the connecting piece 25 abuts against a connecting surface 28 on the cylinder 18 borders. The end portion 27 has an inner diameter D _E, which is formed larger than the inner diameter D _AN of the connection piece 25. This creates a funnel-like or tulip-shaped widening of the end portion 27, so that the flow connection between the combustion chamber 13 in the cylinder 18 and located on the connection piece 25 Subsequent muffler 100 no edge or no paragraph is formed by or through which could form turbulence in the exhaust gas mass flow.

FIG. 4 shows a further embodiment of the arrangement of the connecting piece 25 at the outlet 26 of the cylinder 18. The connecting piece 25 has an inner diameter D _AN , which is smaller than the inner diameter D _{AU of} the outlet 26. However, the end portion 27 of the connecting piece 25 is widened such that the inner diameter D _{E of} the end region 27 is greater than the inner diameter D _{AU of} the outlet 26. This results in a flow constriction, which, however, has no disturbing influence on the exhaust gas mass flow, in particular if the exhaust gas from the combustion chamber 13 through the outlet 26 and through the adjoining Connector 25 enters the muffler 100. In this case, both the connecting piece 25 and the outlet 26 extend rotationally symmetrical about the channel flow direction 12 '. In an eccentric arrangement of the connecting piece 25, for example can occur due to vibration, incorrect assembly or the like, the flow of exhaust gas mass flow is still not adversely affected, since only the position of the end portion 27 displaced adjacent to the connection surface 28, but without forming an exhaust flow disturbing edge.

FIG. 5 shows a further embodiment of the arrangement of a connecting piece 25 to the outlet 26 of the cylinder 18. The connector 25 in turn has an end portion 27, and the inner diameter D _{E of} the end portion 27 is greater than the inner diameter D _{AN of} the connector 25. In this embodiment corresponds the inner diameter D _aN of the connection piece 25 to the inner diameter D _AU of the outlet 26. in this case, a rounding 29 is provided which forms a rounded transition from the outlet 26 in the connection surface 28th The connection surface 28 forms a plane surface and extends radially around the outlet 26, so that the channel flow direction 12 'forms a surface normal to the connection surface 28. However, the inner diameter D _{E of} the end region 27 is dimensioned such that the end region 27 with an annular line contact adjoins the connection surface 28 already transferred to the planar extension. This results in a flow of the exhaust gas between the combustion chamber 13 and the muffler 100, which has no disturbing edges both in a first flow direction, namely from the combustion chamber 13 to the muffler 100, and the flow back from the muffler 100 into the combustion chamber 13 is also not through an edge affects negatively.

The inventive measures according to the embodiments described above ensures that the positive effect of the exhaust gas recirculation flow can be further improved. If the flow of the exhaust gas from the muffler 100 in the direction of the combustion chamber 13 of the internal combustion engine 10 does not experience any negative effects due to edges or heels, so that eddies can form, the effect can be positively utilized so that the exhaust gas flowing back towards the combustion chamber 13 becomes a gas barrier forms, wherein the flow of the exhaust gas can even reach sound velocities. Furthermore, there are advantages through a simplified assembly by mounting means, which are shown in the present unspecified, the However, allow a simple pressing of the connecting piece 25 with the end portion 27 against the connection surface 28 of the cylinder 18.

The invention is not limited in its execution to the above-given preferred embodiments. Rather, a number of variants is conceivable, which makes use of the illustrated solution even with fundamentally different types of use. Any features and / or advantages resulting from the claims, the description or the drawings, including constructive details or spatial arrangements, can be essential to the invention, both individually and in the most diverse combinations. For example, the in FIG. 5 shown rounding 29 in the embodiment according to FIG. 4 Use find that shows a fitting 25 which has a diameter which is different from the diameter of the outlet 26. Further, there is a possibility that the diameter of the fitting 25 may be made larger than the diameter of the outlet 26.

LIST OF REFERENCE NUMBERS

100

silencer

10

internal combustion engine

11

muffler inlet

12

flow channel

12 '

Channel flow direction

13

combustion chamber

14

channel end

15

first chamber

16

second chamber

17

main outlet

18

cylinder

19

outlet

20

auxiliary outlet

21

piston

22

crankshaft

23

pleuel

24

crankcase

25

connector

26

outlet

27

end

28

Termination surface

29

curve

30

Centering shaping

D _AN

Inner diameter of the connection piece

D _AU

Inner diameter of the outlet

D _E

Inner diameter of the end region

Claims (9)

1. An arrangement with an internal combustion engine (10) and a silencer (100) arranged on the latter, wherein the silencer is formed with a connecting piece (25) which with an end region (27) adjoins an outlet (26) in the cylinder (18) of the internal combustion engine (10) for discharging exhaust gas and forms a flow connection between a combustion chamber (13) of the internal combustion engine (10) and the silencer, characterized in that the inner diameter (D_AN) of the connecting piece (25) is formed continually growing into the end region (27) up to the inner diameter (D_E) of the end region (27) and in that the inner diameter (D_E) of the end region (27) is greater than the inner diameter (D_AU) of the outlet (26), wherein the cylinder (18) comprises a connecting surface (28) which is preferentially embodied flat and extends round about the outlet (26), wherein the connecting piece (25) is held arranged with the end region (27) bearing against the connecting surface (28) through holding means.
2. The arrangement according to claim 1, characterized in that the inner diameter (D_AN) is formed growing free of diameter jumps as far as to the inner diameter (D_E) of the end region (27).
3. The arrangement according to claim 1 or 2, characterized in that the inner diameter (D_AN) of the connecting piece (25) and the inner diameter (D_AU) of the outlet (26) have a same value.
4. The arrangement according to claim 1 or 2, characterized in that the inner diameter (D_AN) of the connecting piece (25) has a value which is smaller than the value of the inner diameter (D_AU) of the outlet (26).
5. The arrangement according to any one of the aforementioned claims, characterized in that the connecting surface (28) has a transition region which merges from a region of the connecting surface (28) designed flat into the outlet (26) forming a rounding (29).
6. The arrangement according to any one of the aforementioned claims, characterized in that the connecting surface (28) radially about the outlet (26) comprises a flat extension, which is defined in such a manner that an off-centre arrangement of the connecting piece (25) on the outlet (26) is made possible while the flow connection between the combustion chamber (13) of the internal combustion engine (10) and the silencer is retained free of edges.
7. The arrangement according to any one of the aforementioned claims, characterized in that the connecting piece (25) and in particular the end region (27) of the connecting piece (25) about a channel flow direction (12') is formed rotation-symmetrically, wherein the end region (27) is formed by a funnel-shaped expansion of the connecting piece (25).
8. The arrangement according to any one of the aforementioned claims, characterized in that the connecting piece (25) with its end region (27) forms a silencer inlet (11), which merges into a flow channel (12), wherein the flow channel (12) on the channel end (14) located opposite the silencer inlet (11) opens into a first chamber (15), wherein the flow channel (12) between the silencer inlet (11) and the first chamber (15) is formed flow-favourably in such a manner that the exhaust gas flowing into the silencer inlet (11) because of its inertia predominantly flows into the first chamber (15) and after a filling of the first chamber (15) flows back again and because of this a back pressure is formed in the direction of the combustion chamber (13).
9. The arrangement according to any one of the aforementioned claims, characterized in that a second chamber (16) is provided, into which exhaust gas flows through a main outlet (17) branched off the flow channel (12) and out of which the exhaust gas flows through an outlet (19), wherein the first chamber (15) is preferentially enclosed by the second chamber (16).

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