Acoustics – Sound-modifying means – Muffler – fluid conducting type
Reexamination Certificate
2000-02-09
2001-10-23
Dang, Khanh (Department: 2837)
Acoustics
Sound-modifying means
Muffler, fluid conducting type
C181S264000, C060S299000
Reexamination Certificate
active
06305493
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an exhaust system for internal combustion engines, in particular two-cycle internal combustion engines, with a resonance-type exhaust part which includes at least one diffuser-cone unit with a diffuser and a countercone, with a connecting part having a preferably constant cross section arranged between the diffuser outlet cross section and cone inlet cross section.
DESCRIPTION OF THE PRIOR ART
In an exhaust system of the kind mentioned above, an exhaust pipe with an initially constant progress of cross section is led away from the port via an outlet conduit. To produce a returning suction wave, a diffuser is connected thereto which opens into a countercone or baffle plate after a short transition element. A pressure wave running from the cylinder is produced in said constriction of cross section, which wave supplies the cylinder chamber with fresh air which reaches the exhaust system during the scavenging phase from the inlet slot through the cylinder chamber.
U.S. Pat. No. 4,424,882 A shows an arrangement for an exhaust system. This arrangement describes exhaust mufflers in which the exhaust gas from the engine flows into a large volume and from there further into a second chamber through at least two similarly long nozzles, such as diffuser-type tubes, situated adjacent to one another. Systems of this type aim at obliterating the gas-dynamic activity, as a result of which they cannot be used for reducing the scavenging losses and for the improvement of the torque characteristics.
AT 399 914 B describes an exhaust system for two-cycle internal combustion engines with a muffler pipe, with the initial region thereof being bordered by conical regions formed by diffusers, which regions are connected on the one hand via piping of different length with the initial region of the muffler pipe and open on the other hand into a common collecting vessel to which the tail pipe, comprising a catalyst and/or a muffler, is connected. This system ensures that a pressure wave coming from the cylinder is reflected twice as a suction wave and reaches the still open exhaust port in a time staggered manner as a result of the different run length. In this way the duration of action of the suction wave in comparison with other exhaust systems which utilize the exhaust reflection wave is extended with a single resonance chamber in order to convey back the fresh gases to the cylinder which have entered the exhaust towards the end of the scavenging phase.
Exhaust systems with resonator-type exhaust parts which are provided with at least one diffuser-cone unit require a relatively large amount of space due to the relatively high length of the diffuser and the conical part.
From DE 614 775 C a sound absorber is known with several chambers which are arranged behind one another in the direction of flow of the exhaust gases, with a deflection arc being provided after each chamber. Embodiments of exhaust systems with deflection arcs before each diffuser are shown in the already mentioned AT 399 914 B in order to arrange the diffusers mutually parallel on a common collecting vessel.
SUMMARY OF THE INVENTION
It is the object of the present invention to provide a compact exhaust system with a resonator-type exhaust part which is easy to produce.
This is achieved in accordance with the invention in such a way that the connecting part is arranged as a first deflection arc, preferably with an angle of deflection of about 180° ± 30°. The resonator-type exhaust part can thus be provided with a very compact arrangement. A particularly compact solution is obtained when a second deflection art is provided in the initial zone of the diffuser whose angle of deflection is preferably 180°±30°. It is particularly advantageous if the center line of the second deflection arc is substantially arranged in a second plane which is disposed inclined to a first plane which is defined by the center line of the first deflection arc, with the second plane preferably being arranged approximately normal to the first plane.
It is preferably further provided that in the end zone of the countercone a third deflection arc is arranged whose angle of deflection is preferably 180° ± 30°. The third deflection arc can be arranged in a third plane which is inclined to the first plane, with the third plane preferably enclosing an angle of approx. 90° to the first plane and being arranged particularly preferably approximately parallel to the second plane. This leads to an arrangement in which the central line of the resonance-type exhaust part is connected in at least three planes and the exhaust gas flows through the resonance-type exhaust part in at least four passes, with the first and fourth pass being formed by the inlet part and the end part, the second pass comprising the diffuser and the third pass the countercone. The resonance-type exhaust part can thus be provided with a particularly compact design.
An embodiment that is particularly easy to produce provides that the diffuser and preferably also the inlet part and/or the second deflection arc and/or at least partly the first deflection arc are formed by a diffuser insert which is preferably arranged as a deep-drawing part. The countercone, as preferably also the end piece and/or the third deflection arc and/or at least partly the first deflection arc, can be formed by a cone insert which is preferably arranged as a deep-drawing part. Diffuser insert and cone insert are joined with screws for example, with a separating plate being arranged between the diffuser insert and the cone insert.
In order to avoid burbling and turbulence in the zone of the strongly bent deflection arcs, it can further be provided that in the zone of the first, second and/or third deflection arcs baffle plates are arranged, with the baffle plates preferably being fastened to the separating plate.
In a further development of the invention it is also possible that the diffuser is arranged as a double diffuser, with a secondary diffuser, preferably with the same inlet/outlet cross-sectional ratio as the diffuser, being arranged within the diffuser, with the secondary diffuser preferably being fastened to the separating plate.
In a particularly preferred embodiment it is provided that the resonance-type exhaust part is provided with at least two diffuser-cone units which are switched in parallel in respect of flow and are preferably arranged symmetrically with respect to a central plane and branch off from a common inlet piece and open into a common end piece, with the branches and/or the opening being arranged in the zone of the central plane. In this manner two or more diffuser-cone units can be arranged in a common housing in a particularly compact manner. The diffusers and countercones can also be formed in this case by separate inserts which are arranged as deep-drawing parts for example, thus allowing a particularly simple and inexpensive production.
In order to improve the exhaust gas quality it can be further provided that the separating plate, the diffuser insert, the cone insert, the baffle plates and/or the secondary diffuser are catalytically coated.
It is naturally also possible that the resonance-type exhaust part consists of ceramic at least in sections.
The tail pipe is preferably disposed in the zone of the central plane and in a central section of the resonance-type exhaust part, so that a heat discharge occurs according to the principle of reverse flow.
REFERENCES:
patent: 1280386 (1918-10-01), Buehner
patent: 1821688 (1931-09-01), Bourne
patent: 3665712 (1972-05-01), Tenney
patent: 3842599 (1974-10-01), Ehlen
patent: 4165798 (1979-08-01), Martimez
patent: 4418790 (1983-12-01), Agnew
patent: 4424882 (1984-01-01), Moller
patent: 5736690 (1998-04-01), Karlsson
patent: 399914 (1995-08-01), None
patent: 614775 (1935-05-01), None
patent: 2643240 (1978-04-01), None
patent: 2828006 (1979-01-01), None
patent: 219052 (1985-02-01), None
AVL List GmbH
Dang Khanh
Dykema Gossett PLLC
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