DE102005004674A1 - Sound proofing device for pulsating gas streams, has gas inflow tube along with perforated tubular section projecting into housing whereby valve body is designed as tubular body which forms narrow passage with tubular section - Google Patents

Abstract

The sound proofing device has a gas inflow tube (3) along with a perforated tubular section (5) projecting into the housing. The valve body is designed as a tubular body (6) and forms a narrow passage (9), in particular an annular gap with the tubular section. The tubular body is movable in the tubular section.

Description

The invention relates to a device for sound attenuation of pulsating gas streams, in particular in intake or exhaust systems of internal combustion engines in motor vehicles according to the preamble of claim 1 - known by the DE 101 31 475 B4 the applicant.

For the sound attenuation of pulsating gas streams, such as occur in particular in intake and exhaust systems of internal combustion engines, the following are used individually or in combination measures: reflection mufflers, longitudinal and shunt resonators (Helmholtz resonators), bypass or interference tubes and absorption mufflers. Since the noise emitted by internal combustion engines, in particular, is not constant but depends on the speed of the engine, silencers with a fixed geometry are inadequate because they cover predominantly only certain frequency ranges. It has therefore already proposed mufflers with variable geometry, in which individual parameters the different frequencies and amplitudes of the noise are adaptable, so that these mufflers cover a wider range of noise. By the DE 197 43 446 C2 an exhaust system with a gas outlet side optionally closable second muffler was known, which acts as a Helmholtz resonator with closed gas outlet and thus leads to an additional noise reduction, especially in the lower speed range. Other proposals provide that the geometry of a Helmholtz resonator during operation of the internal combustion engine is variable and thus adaptable to the different sound frequencies. The sound-absorbing function of the Helmholtz resonator is essentially determined by three parameters, its volume and the length and cross-section of the connecting tube (neck) to the sound-conducting channel. In the DE 43 05 333 C1 These parameters are changed depending on the speed of an internal combustion engine by appropriate design measures by means of a servomotor. This achieves a stepless adaptation of the noise damping to the engine speed. Similar solutions, eg. B. Change of the throat cross section of the Helmholtz resonator go from the DE 100 04 991 A1 as well as the DE 197 54 840 C2 out. This achieves a stepwise adaptation of the resonant frequency of the Helmholtz resonator. By the EP 1 017 936 B1 was also a Helmholtz or shunt resonator with adjustable parameters known, in each case the length and the cross section of the connecting pipe and the resonance volume in three stages by means of a servomotor can be changed.

Even with interference or bypass pipes an adaptation to different sound components is known. In the DE 198 49 698 A1 the length of a U-shaped bypass tube is changed by a telescopic arrangement of the U-legs. A similar solution according to the principle of interference was by the EP 1 067 511 A2 known for two bypass tubes whose acoustically effective lengths are infinitely variable - in the manner of a trumpet - changeable.

By the EP 1 445 437 A1 a muffler with a gas inlet tube has been known, which has a perforated wall, the passage cross-section is continuously variable by means of a sleeve axially displaceable on the perforated tube. Thus, a control of the inlet cross-section of the gas stream is achieved in a resonance chamber of the muffler, wherein the adjustment of the sleeve takes place by means of a servomotor.

By the aforementioned DE 101 31 475 B4 , from which the invention proceeds, an exhaust muffler with a valve assembly has been known, which is controlled by the pressure of the incoming gas flow and a gas spring counteracting valve spring (return spring). In this case, a designed for a flow deflection valve body is provided, which is displaceable in a perforated tube and thus changes the inlet cross-section for the gas flow in the housing of the muffler proportional to the displacement. The displacement of the valve body is either automatically, that is, depending on the gas flow pressure or by an actuator which engages the valve body.

It Object of the present invention, a device for soundproofing of to simplify the aforementioned type with regard to their structure and to improve their function, in particular a frequency-dependent sound attenuation to reach.

This object is solved by the features of claim 1. According to the invention it is provided that within a housing-fixed, gas inlet side, perforated pipe section a tubular body is slidably disposed to form a passage gap. The tubular body is displaced by the flow pressure in the pipe section against the force of a return spring and releases with increasing displacement an increasing passage cross-section for the inflowing gas flow. With decreasing gas flow of the tubular body is returned by the return spring in an initial position in which the passage cross section through the gap between the displaceable tubular body and housing-fixed pipe section is determined. The advantage of the valve arrangement according to the invention is a high sound attenuation at low flow rates, ie at idling of the internal combustion engine, at part load and low speeds. In addition, there is the advantage of a low back pressure at full load, ie the silencer according to the invention shows a need for backpressure and noise damping adapted, variable behavior. A further advantage is that no external control elements are required because the control of the tubular body is induced by the gas flow. A further advantage is that no leakage problems occur because the valve assembly according to the invention is located within the housing. The production is simple and therefore inexpensive because comparatively large tolerances are possible. The silencer according to the invention can be used both for intake and exhaust systems of internal combustion engines and for ducts of ventilation systems as well as supply and discharge lines of compressors.

To An advantageous embodiment of the invention is the displaceable pipe body a leadership facility assigned to the housing attached and inside or outside of the housing can be arranged. Advantageously, the guide means from a pipe section fixed to the housing which the displaceable tubular body is slidably disposed. pipe body and pipe section are thus telescoped into each other. advantageously, is inside the sliding tube body and the housing fixed Pipe piece one Return spring arranged, which is designed as a compression spring. The tolerances between the slidable tubular body and the housing-fixed pipe section can so be tuned that due to an enclosed gas volume and viscous wall friction a damping effect results, which has the advantage that no tilting and also no rattling occurs.

To a further advantageous embodiment of the invention is casing divided by a partition into two chambers, and the entrance side Pipe section is through the partition through to the outlet side Chamber led. By one on either side of the partition in the pipe section arranged perforation and a perforation in the displaceable tubular body results at high flow rates, i. H. high flow pressure a short circuit or bypass flow directly from the inlet side to exit side chamber. advantageously, is additional in the partition arranged a bypass pipe with a relatively high flow resistance. Advantageous in this solution are also a relatively high back pressure at low flow rates and a good soundproofing as well as higher by rivers a low back pressure due to the opening of the bypass. The short circuit flow can also by equivalent Means, e.g. B. a local Cross-section reduction of the displaceable tubular body achieved become.

In Another advantageous embodiment of the invention can be achieved by a Combination of the aforementioned inventive measures a fine adjustment to the speed or flow conditions, especially in three stages. In a first stage, at low flow gives the sliding tube body only a minimal passage cross-section free, with a maximum attenuation achieved becomes. In a second stage at a medium flow rate becomes a larger passage area released as a result of further displacement of the tubular body, wherein a mean damping is achieved. In a third stage at a maximum flow the first and another passage cross section due to opening of a Bypass path released; thus, a reduced back pressure achieved at a relatively low attenuation. advantageously, is the lead institution, which also receives the return spring, outside of the housing arranged and over a linkage with the sliding tube body connected. This has the advantage that the guide means including spring less temperature is charged.

To a further advantageous embodiment of the invention, the mentioned above automatic, flow-induced Adjustment of the tubular body by a forced adjustment by means of an external actuator replaced or supported become. This allows an even more accurate adaptation.

In Another advantageous embodiment of the invention are the cross sections of the displaceable tubular body and of the housing Pipe section not on circular Cross sections limited, rather are not circular either Cross sections, z. As polygons possible.

embodiments The invention are illustrated in the drawing and are explained in more detail below. It demonstrate

1 a schematic representation of a muffler with inventive valve arrangement in a nearly closed state (first embodiment),

2 the silencer according to 1 in open condition,

3 a schematic view of a muffler with partition and according to the invention ßer valve arrangement in almost closed state (second embodiment),

4 the silencer according to 3 in open condition,

5 a schematic view of a muffler with partition and modified valve assembly in almost closed state (third embodiment),

6 the silencer according to 5 with about half open valve and

7 the silencer according to 5 with fully open valve.

1 shows a schematic view of a muffler 1 , which is used for a not shown exhaust system of a motor vehicle with a combus tion engine. The silencer 1 has a housing 2 on, which is a exhaust gas permeable chamber 2a forms. In the chamber 2a open coming from an unillustrated internal combustion engine gas inlet tube 3 and a leading to a tail pipe of the exhaust system leading gas outlet pipe 4 , The gas inlet pipe 3 protrudes with a perforated pipe section 5 in the chamber 2a into it, with the pipe section 5 a displaceable in the direction of arrow E (gas inlet flow) tubular body 6 absorbs. At the housing 2 is a tubular guide device 7 attached, on which the tubular body 6 is slidably disposed. Inside the sliding tube body 6 and the housing-fixed guide device 7 is a compression spring 8th arranged, which on the one hand on the housing 2 and on the other hand on the tubular body 6 supported. The pipe body 6 , which acts as a valve body is thus guided in the direction of arrow E and forms with the pipe section 5 an annular gap 9 , The inflow area of the valve body 6 has an approximately hemispherical shaped cap 10 on. The longitudinal guide between the guide device 7 and the tubular body 6 is relatively tight tolerated, so that there is a viscous wall friction due to an enclosed gas volume, which has a damping effect in the longitudinal movement of the valve body 6 entails. This avoids rattling.

The illustrated position of the tubular body 6 in 1 corresponds to a low flow of exhaust gas, represented by the arrow E. The by the compression spring 8th on the tubular body 6 applied spring force is equal to that of the exhaust gas flow on the cap 10 applied force. The pipe body 6 is in a forward position and only gives the annular gap 9 free, so that the exhaust gas - as indicated by a dashed line - with relatively strong pressure drop through the perforated pipe section 5 in the gas outlet pipe 4 flows. This results in low exhaust gas flow, a relatively high back pressure and good sound attenuation. The annular gap 9 has a cross-sectional area that is substantially smaller than the cross-sectional area of the gas inlet tube 3 is.

2 shows the muffler 1 according to 1 with an open valve position. The valve body 6 is shifted due to an increased flow pressure through the exhaust according to arrow E by the amount x in the direction of flow E, wherein the compression spring 8th was compressed. The passage cross section of the perforated pipe section 5 is now fully released so that the exhaust gas corresponding to the dot-dash line with relatively low pressure drop from the gas inlet pipe 3 to the gas outlet pipe 4 flows. The displacement x of the tubular body 6 (Difference of positions according to 1 and 2 ) is preferably larger than the diameter D of the exhaust gas inlet pipe 3 or the perforated pipe section 5 ,

3 shows a further embodiment of the invention, a silencer 11 with a housing 12 which through a partition wall 13 (also called separation floor) in two chambers, an entrance chamber 14 and an exit chamber 15 is divided. In the entrance chamber 14 opens an exhaust gas inlet pipe 16 , which deals with a pipe section 17 to the partition 13 extends and this into the exit chamber 15 penetrated into it. To the exit chamber 15 closes an outlet pipe 18 at. In the partition 13 is a bypass tube 19 arranged over which the inlet chamber 14 with the exit bracket 15 communicates, but has a relatively high flow resistance. The pipe section 17 has two perforated wall areas 20 . 21 on both sides of the partition 13 on, wherein in the partition area a smooth, non-perforated section 17a is arranged. In the pipe section 17 is a tubular body 22 displaceable leaving an annular gap 23 arranged and via a compression spring 24 opposite the housing 12 supported. The pipe body 22 is a housing-fixed, preferably tubular guide device 25 in the longitudinal direction of the inlet pipe 16 (Arrow E) out. The pipe body 22 has - deviating from the embodiment according to 1 - In the front area a perforated pipe wall section 26 on, which allows a radial flow through this section - from outside to inside and from inside to outside.

In the 3 shown position of the tubular body 22 corresponds to a low exhaust gas flow according to arrow E. The compression spring 24 holds the pipe body 22 in its forward position, leaving only the annular gap 23 is released, which from the inlet pipe 16 into the exit chamber 15 enough.

At the same time there is a flow connection for the incoming exhaust gas from the annular gap 23 radially outward through the perforated section 20 into the entrance chamber 14 from where via the bypass tube 19 a connection in the outlet chamber 15 consists. In this position, therefore, results for the exhaust gas flow, a relatively high flow resistance, which has a corresponding back pressure result. The damping effect in this position is relatively high. The flow path of the exhaust gas is indicated by dash-dotted lines.

4 shows the exhaust silencer 11 according to 3 with an open valve position, ie the tubular body 22 is shifted in the direction of arrow E due to an increased gas flow pressure. In this open position is the perforated wall section 26 of the tubular body 22 in the area of the partition 13 and the two perforated wall sections 20 . 21 of the pipe section 17 , This results in a bypass or short circuit from the inlet pipe for the gas flow 16 in the exit chamber 15 or to the outlet pipe 18 , The flow - represented by a dot-dash line - thus initially passes from radially outward through the perforation into the interior of the wall section 26 and then exits downstream radially outward from the wall section 26 out. This results in a lower back pressure for the exhaust gas flow at increased flow.

5 shows a further embodiment of the invention, a silencer 30 with a housing 31 which through a partition wall 32 in two chambers 33 . 34 is divided. Via a gas inlet pipe 35 , According to the arrow E, the exhaust gas flow enters the housing 31 and leaves this via an outlet pipe 36 , according to the arrow A. The inlet pipe 35 is through a pipe section 37 with two perforated wall areas 38 . 39 into the area of the partition 32 extended. The gas outlet pipe 36 protrudes into the exit chamber 34 in and points in the area of the partition wall 32 a perforated section 40 on. The partition 32 points in the area of the perforated section 40 an opening 41 and one in the entry chamber 33 projecting partial load pipe 42 on. In the pipe section 37 is a tubular body 43 with a perforated wall section 44 slidably arranged and via a linkage 45 with a guide device 46 verbun the, which is also a return spring 47 , in this case a Schraubenzugfeder accommodates. The outside of the case 31 arranged guide device 46 with return spring 47 is therefore not exposed to the high exhaust gas temperatures.

In the 5 shown position of the tubular body 43 corresponds to a low exhaust gas flow. The passage from the inlet pipe 35 to the outlet pipe 36 is almost closed. The exhaust gas flow enters, according to the arrow E, enters the annular gap outside of the tubular body 43 and passes through the perforated wall section 38 over the inlet chamber 33 , the part load pipe 42 and the opening 41 in the outlet pipe 36 , The flow path is indicated by a dot-dash line between arrow E and A; it is characterized by a relatively high flow resistance. The damping is maximum in this valve position.

6 shows the muffler 30 with a second valve position, which corresponds to a mean flow, according to the arrow E. The valve body 43 is in a middle position, ie the first upstream perforated wall area 38 is now released so that the flow through this area over the partial load pipe 42 in the outlet pipe 36 can get. The flow path is again indicated by a dot-dash line between the arrows E and A. In this valve position with a mean exhaust gas flow results in a mean damping.

7 shows the muffler 30 with a third valve position at maximum flow, ie the valve body 43 is moved to its extreme end position in the direction of arrow E. The perforated wall area 44 of the displaceable tubular body 43 is now in the perforated area 39 of the pipe section 37 , This is an additional flow path through the bypass of the wall section for the incoming gas flow 44 free. Thus, there are two flow paths, which are shown by dotted lines. The back pressure is therefore relatively low, as is the damping effect.

The embodiment according to the 5 . 6 . 7 thus provides a combination of the embodiments according to 1 and 3 with a graduated adaptation of the damping to the flow conditions or the engine speed of an internal combustion engine.

1

silencer

2

casing

2a

chamber

3

Gas inlet tube

4

Gas outlet pipe

5

perforated pipe section

6

pipe body

7

guide means

8th

compression spring

9

annular gap

10

cap

11

silencer

12

casing

13

partition wall

14

inlet chamber

15

exit chamber

16

Exhaust gas inlet pipe

17

pipe section

18

outlet pipe

19

bypass

20

perforated wall area

21

perforated wall area

22

pipe body

23

annular gap

24

compression spring

25

guide means

26

The tube wall section

30

silencer

31

casing

32

partition wall

33

chamber

34

chamber

35

Gas inlet tube

36

Gas outlet pipe

37

pipe section

38

perforated wall area

39

perforated wall area

40

perforated section

41

opening

42

Partial load tube

43

pipe body

44

perforated wall section

45

linkage

46

guide means

47

Return spring

Claims (15)

Device for silencing pulsating gas streams, in particular in intake or exhaust systems of internal combustion engines in motor vehicles with a housing through which a gaseous medium (gas) can flow ( 1 ), which a gas inlet and a gas outlet pipe ( 3 . 4 ) and a valve arrangement with a spring-loaded, acted upon by the gas flow, displaceable valve body ( 6 ) for the flow-dependent change of a passage cross-section for the incoming gas, characterized in that the gas inlet tube ( 3 ) a projecting into the housing, perforated pipe section ( 5 ), that the valve body as a tubular body ( 6 ) is formed and with the pipe section ( 5 ) a passage gap ( 9 ), in particular forms an annular gap and that the tubular body ( 6 ) is displaceable in the pipe section. Device according to claim 1, characterized in that on the housing ( 2 ) a management facility ( 7 ) for guiding the tubular body ( 6 ) is secured in the direction of displacement. Apparatus according to claim 2, characterized in that the guide device ( 7 ) tubular and telescopic in the tubular body ( 6 ) is arranged. Device according to claim 1, 2 or 3, characterized in that the housing ( 12 ) by a partition wall ( 13 ) in two chambers ( 14 . 15 ), that the perforated pipe section ( 17 ) the partition ( 13 ) and that the tubular body ( 22 ) a front perforated wall area ( 26 ) or has a reduced cross-sectional area. Apparatus according to claim 4, characterized in that the pipe section ( 17 ) in the region of the partition ( 13 ) a continuous, non-perforated pipe section ( 17a ) having. Apparatus according to claim 4 or 5, characterized in that in the partition ( 13 ) a connecting pipe ( 19 ) is arranged, over which the two chambers ( 14 . 15 ) are in gas flow communication. Apparatus according to claim 5 or 6, characterized in that the perforated front region ( 26 ) of the tubular body ( 22 ) - in the direction of displacement - has a length which is approximately equal to or greater than the length of the continuous piece of pipe ( 17a ). Device according to at least one of claims 1 to 7, characterized in that the tubular body ( 6 . 22 ) on the inflow side a streamlined, in particular hemispherical cap ( 10 ) having. Device according to at least one of claims 4 to 8, characterized in that the guide device ( 46 ) outside the housing ( 31 ) and via a linkage ( 45 ) with the tubular body ( 43 ) connected is. Device according to at least one of claims 4 to 9, characterized in that the pipe section ( 37 ) a first, upstream and a second, downstream in the region of the partition ( 32 ), perforated wall area ( 38 . 39 ) and that the perforated tubular body ( 43 ) between the perforated areas ( 38 . 39 ) is displaceable. Apparatus according to claim 10, characterized in that the gas outlet pipe ( 36 ) into the exit chamber ( 34 ) projecting, partially perforated channel section ( 40 ) having. Apparatus according to claim 11, characterized in that the channel section ( 40 ) over a Opening ( 41 ) and / or a partial load tube ( 42 ) with the inlet chamber ( 33 ) connected is. Device according to at least one of claims 2 to 12, characterized in that the guide means as at least a spring element, in particular as at least one compression spring is. Device according to at least one of the claims 1 to 13, characterized in that the tubular body by a pneumatic, electric or hydraulic servomotor is adjustable. Device according to at least one of the preceding claims, characterized in that the cross sections of the displaceable tubular body ( 6 . 22 . 43 ) and the housing-fixed pipe section ( 5 . 23 . 37 ) are not circular.