DE7307335U - EXHAUST SILENCER FOR TWO-STROKE ENGINES - Google Patents

Description

Donaldson Company, Inc., 14oo West 94th Street, Minneapolis, Minnesota (V.St.A.)

/ Exhaust silencer

for two-stroke engines

The innovation relates to exhaust silencers, especially for two-stroke engines, with a cylindrical housing Surrounded exhaust pipe, the wall of which has an opening to form a control chamber between the exhaust pipe and the housing, the opening being partially covered by a hood attached to the outside of the exhaust pipe.

It has long been known that the horsepower output of a two-stroke engine is significantly influenced by the design of the exhaust system and by a properly designed exhaust system compared to a silencerless engine up to

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35% can be increased. Compared to an engine with a poorly built exhaust system, the increase in performance is even higher. A well-known method of increasing the performance of two-stroke engines is to use one known as a "megaphone" Exhaust device, which is an exhaust pipe, the end of which is flared and funnel-shaped is designed so that the open exhaust port to the appropriate Time a negative pressure wave is applied to improve the flushing. Length and cross section of this Megaphones or horns are held in such a way that negative maximum pressure flows into the exhaust opening at the bottom dead center of the piston.

Such a horn improves engine performance, but does not dampen the exhaust noise. So for this you have to have a Damping device can be installed behind the horn in the direction of flow. With regard to such systems it has also been recognized that the size of the chamber attached to the horn is important and in order to achieve this must be precisely calculated for maximum performance.

The simple row arrangement of a bell with the one behind Chamber and damper have at least two basic disadvantages. It is difficult to do that To make the system so physically compact that it can be used as an in

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self-contained unit can be used on small vehicles such as motorcycles and snowmobiles. Second and perhaps a more significant disadvantage is that the bell itself produces a sound that is reflected in the In the course of the exhaust gas flow through the damper propagates. The sound made by a bell is louder than that from an unexpanded tube with the same inlet and outlet diameter. For systems according to the state of the art was thus the damping element through the horn imposed an abnormally heavy damping work.

One of the first steps that led to the present innovation was the consideration that in the event that the noise generated by the horn can be prevented from flowing through the damper, a considerable part of the Damping work could be turned off. The same Damper would then be without undesired, additional gas flow resistance reduce exhaust noise to lower levels. This usually involves changes to the damper, such as the installation of additional baffles, which increases gas flow resistance and adversely affects engine performance will.

The next step was the realization that the noise due to the arrangement of the control chamber for the sound

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funnel outside of the gas flow path are reduced can, but at the same time it was recognized that the arrangement of the Regelkairaner outside of the gas flow path with the simultaneous installation of a horn would lead to great difficulties in construction and construction.

Further considerations and attempts led to the present one Embodiment. The Regelkairaner is outside of the gas flow path and is thus available through a single opening in the exhaust pipe that extends through the control duct extends, in communication, over the hole in the control chamber a funnel-shaped hood is attached as a replica of a megaphone. The exhaust pipe runs through the Control chamber in a damper arranged behind it. The success of this combination has been very satisfactory. Control chamber and cover act as a horn to increase the engine output. Additional generated in the control chamber Noises are reflected back in the direction of the motor, but the funnel-shaped cover prevents them from to be reflected in the direction of flow towards the damper. By reducing the noise fed to the muffler, sufficient sound attenuation could be achieved with one below the Normal measure lying gas flow resistance can be achieved.

It was also found that the torque at low

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Engine speeds through a second control chamber at the end of the Main exhaust pipe can be improved significantly. This second chamber throws a corresponding one at low engine speeds Blast wave back. Because the overall system in the end of the main exhaust pipe is longer than the first standard length, the torque in the low speed range is reduced increasing, modified pressure wave is formed and thus the overall performance is also increased, because a horn is typically used is less effective at low engine speeds.

An exemplary embodiment of the innovation will be explained below. The drawings show in

Fig. 1 is a side view of a silencer according to the innovation with partially interrupted walls and sectional views, in

FIG. 2 shows a section in the plane 2-2 according to FIG. 1 and in FIG. 3 a section in the plane 3-3 according to FIG. 1.

Fig. 1 shows a muffler for a two-stroke engine with a substantially cylindrical, at the ends with the head walls 11 and 12 closed housing 1o. The head wall 12 is provided with an axial inlet opening formed by the outwardly bent flange 12a. In the longitudinal axis of the Housing 1o is an exhaust pipe 13, which extends from the

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Opening in the head wall 12 within the housing Io up to a point extends from the head wall 11 by about 1/4 the length between the head walls 12 and 11 is removed. In the preferred embodiment, the exhaust pipe 13 a round cross-section over its entire length. For reasons of gas tightness, the tube 13 is on its inlet side welded into the flange 12a or fastened in a similar form therein.

The ^{interior of the housing 1} Jo is divided into different chambers by the three partition plates 19, 2o and 21, which include a closed control chamber 15, a resonance chamber 16, a second closed control chamber 17 and an exhaust gas collection chamber 18. The separating plates 19 to 21 are attached to the inner wall of the housing 1o essentially as round disks with a flange bent up on the periphery in such a way that no gas can pass through. The separating plates 19 and 2o each have a central flange opening through which the tube 13 extends and is connected to it in a gas-tight manner.

The first control chamber 15 is on the inlet side of the damper housing arranged between the partition 19 and the head wall 12. In the preferred embodiment, the control chamber surrounds 15 the tube 13 as a cylindrical annular chamber. In the wall of the tube 13 is a single one, extending axially and radially

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Direction extending opening 23 as a connection between the Tube 13 and the chamber 15 introduced and is preferably approximately in the middle between the ends of the control chamber 15, wherein its cross-section is designed so that it makes up approximately 7o% of the cross-section of the tube 13. With an opening in Tests of this size have given the best results, but any other reasonable size can also be used Opening cross-section can be used with success.

A hood 24 fastened on the pipe 13 covers the opening 23 inside the control chamber 15 from a funnel shape. In the embodiment shown, the cover is through a h Flange 24a fastened on the upstream side of the opening 23 over approximately 3/4 of its circumference and at least partially widened over the opening in the downstream direction, so that the open side of the cover 24 is on the downstream side. The cover 24 is preferably made so long that that it completely covers the opening 23 and that its downstream edge runs parallel to the axis of the tube 13 Level lies. Viewed from the downstream side of the control chamber 15 in the direction of the head wall 12, according to FIG. 3 of an essentially oval opening is formed on the downstream side of the hood 24. The funnel-shaped hood 24 acts in conjunction with a two-stroke engine connected to the pipe 13 as part of a megaphone. Part of that coming from the engine

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Sound waves occurs as indicated by the arrows in Fig. 1 in the Regelkanuner 15, which the sound at a certain Reflects the frequency and reflects "negative pressure waves" towards the engine for the purpose of a better flushing effect. The hood 24 works, however as a deflection device and essentially prevents sound waves from being thrown back through the opening 23 in the direction of flow onto the head wall 11. The regulating ducts 15 therefore produce no noise and therefore does not contribute to the load on the damping elements.

The next chamber 16 in the flow direction is formed between the partition walls 19 and 2o, with one between them lying pipe section of the pipe 13 is provided with a series of holes 25 so that the gas flow and the sound energy in the chamber 16 can reach. The chamber 16 and the holes 25 act as a Helmholtz resonator for the purpose of eliminating noise within a certain frequency range.

The chamber 16 communicates with the last chamber 18 via a series of tubes 26. In the illustrated embodiment are eight tubes 26 parallel to tube 13 and evenly distributed around it, with each tube 26 approximately midway between the outer surface of the tube 13 and the inner wall surface of the housing 1c. The tubes 26 extend through corresponding openings in the partitions 2ο and 21 and

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are attached in a gastight manner. Those located in the chamber 16 Exhaust gases can therefore flow freely through the pipes 26 and thus reach the chamber 18. The one between the partition 21 and the head wall 11 lying chamber 18 is provided with a radially projecting outlet pipe 27, through which the exhaust gases leave the housing 1o.

The remaining chamber 17 is located between the partition walls 2o and 21. The pipe 13 opens with its downstream side approximately in the middle of the chamber 17, where the inlet and outlet to and from the chamber 17 are possible through the pipe 13 alone are. The chamber 17 therefore acts as an expansion chamber and provides an additional chamber through expansion and contraction Soundproofing. In addition, the chamber 17 bypassing the outlet end of the exhaust pipe 13 is particularly beneficial low engine speeds increase the engine performance.

Protection claims:

- Io -

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Claims (2)

1. Exhaust silencer, in particular for two-stroke engines, with an exhaust pipe surrounded by a cylindrical housing, the wall of which has an opening to form a control chamber between the exhaust pipe and the housing, the opening being partially covered by a hood attached to the outside of the exhaust pipe; characterized in that the opening (23) in the exhaust pipe extends in the axial and radial direction and that the hood (24) covering the opening (23) has the shape of a funnel and its open side is directed towards the downstream side. 2. Exhaust silencer according to claim 1, wherein the exhaust pipe is provided with holes and opens into a second control chamber located in the housing, characterized / that the holes (25) present in the exhaust pipe (13) become one in the housing (1o) in front of the second Control chamber (17) arranged resonance chamber (16) lead, which at least partially surrounds the exhaust pipe (13) and via a series of axially arranged pipes (26) with an exhaust gas collection chamber (18) in connection, which is located on the resonance chamber (16) facing away from the second control chamber (17) and has an outlet opening (27). ⁷ 307335 09/30/76