Muffler assembly for engine

Abstract: A muffler assembly for an engine comprises an outer cylinder (2) constituting a muffler body, an inner cylinder (4) coaxially disposed in the outer cylinder (2), a connection cylinder (5) disposed inside the inner cylinder (4) having one end on an upstrem side and another end on a downstream side, a partition plate (7) disposed inside the inner cylinder (4) at a downstream side end of the connection cylinder (5), first (a) and second (10) silencer chambers formed on an upstream side of the one end of the connection cylinder (5) and on a downstream side of the another end of the connection cylinder (5), an inlet pipe (12) through which an engine exhaust gas is introduced into the muffler body, and an outlet pipe (18) having an upstream end disposed inside the inner cylinder (4) and a downstream end opened outward of the muffler assembly. The connection cylinder (5) has an upstream end portion to which a plurality of holes (15) are circumferentially formed. The inlet pipe (12) has a downstream side end portion to which a plurality of holes (14) are circumferentially formed so as to flow the exhaust gas passing through the inlet pipe (12) is introduced into the first silencer chamber (9). The upstream end of the outlet pipe (18) is plugged (20) and coaxially inserted into the downstream end of the connection cylinder (5), the outlet pipe (18) having an upstream end portion to which a plurality of holes (21) are formed. An resonance chamber (24) is formed so as to surround the outlet pipe (18) at the downstream portion thereof.

Description: The present invention relates to a muffler assembly according to the pre-characterizing part of claim 1, e.g.. In general, an engine unit mounted to a motorcycle, for example, is provided with an engine exhaust gas port connected to an exhaust pipe, which is then connected at its rear end to a muffler for discharging the exhaust gas after silencing noise or the exhaust gas in the muffler. Generally, a muffler device is classified into three types, i.e. expansion type, resonance type and reverse type on the basis of the flow of the exhaust gas in the muffler device. In actual, the muffler device is constructed in combination of these types as occasion demands. In order to achieve an improved silencing effect, reduce a back pressure and reduce an output loss, it is necessary for the muffler to have an increased inner volume and an elongated length. However, for a motorcycle, a cylindrical muffler is disposed at a side of a rear portion of the motorcycle body, and in this meaning, the volume and the length of the muffler are inevitably limited due to the length or size of the motorcycle body, the layout thereof and the location of other equipments for the motorcycle. On the contrary, in order to construct a muffler device having an excellent silencing effect with small volume, the structure of the muffler device is inevitably made complicated. Particularly, with respect to the motorcycles, verious requirements in operations or performances including the silencing performance of the muffler device are different in accordance with running places, using countries and so on of the motorcycle. In order to satisfy these different requirements, in a prior art technology, the muffler devices are manufactured by changing sizes, lengths and the like of connection pipes, outlet pipes and other elements for the muffler devices, resulting in complicated and increased manufacturing processes as well as increasing manufacturing cost. A muffler assembly in accordance with the pre-characterizing part of claim 1 is shown in the report 1192 of National Advisory Committee for Aeronautics 1954, page 41, wherein the connection cylinder member is formed as pipe having a downstream and an upstream open end. The exhaust gases flow from the inlet pipe into the chamber formed between the upstream end of the connecting cylinder member and the inner cylinder member. Then, the exhaust gas flows through the connection cylinder member which has said open upstream end. The exhaust gas emerges from the connection cylinder member through said downstream end thereof. Having passed the second silencer chamber, the exhaust gas enters the output pipe. The object of the present invention is to provide a muffler assembly for a motorcycle having a reduced volume and length and capable of achieving a highly improved silencing performance, reduced back pressure and a reduced output loss. This object can be achieved according to the characterizing feature of claim 1. According to the present invention, the connection cylinder member has a plurality of holes at the upstream end thereof, and so has the upstream end portion of the outlet pipe, the end portion of which being plugged. All exhaust gases leaving the connection cylinder member through the downstream end thereof enter the second silencer chamber. The upstream end of the outlet pipe may be disposed within the downstream end of the connection cylinder member. In preferred embodiments, a first punched plate to which a plurality of punched holes are formed is disposed in the muffler body between the one end of of the connection cylinder member and the upstream end of the inlet pipe, and a second punched plate to which a plurality of punched holes are formed is disposed in another end portion of the connection cylinder member. A cylinder member is further arranged coaxially so as to surround a downstream side portion of the outlet pipe with a space as a resonance chamber between the cylinder member and the outer peripheral surface or the outlet pipe and wherein a plurality of perforations are formed to the outer peripheral surface of the outlet pipe at portions corresponding to a location or said resonance chamber and a sound absorption material fills the resonance chamber. A support plate is further disposed inside the inner cylindrer member at a portion directly in front of one end of the connection cylinder member, the support plate having an outer peripheral portion to which a plurality of holes are formed and a central solid portion having a size sufficient for closing the one end of the connection cylinder member. According to the present invention or the characters described above, the engine exhaust gas is introduced circumferentially into the first silencer chamber from the downstream end of the inlet pipe, the back pressure of the exhaust gas can be reduced even if the downstream end of the inlet pipe is disposed near the connection cylinder, thus reducing the whole length of themuffler assembly, and the exhaust gas can be effectively diffused, thus enhancing the silencing effect. The upstream end of the outlet pipe is inserted into the downstream end of the connection cylinder, so that the relatively long outlet pipe can be arranged without extending the muffler assembly, thus effectively attenuating pressure pulsation of the exhaust gas. The location of the resonance chamber improves the silencing efficiency. In the embodiment in which the connection cylinder is provided with a plurality of holes, the exhaust gas once expanded in the first silencer chamber is throttled when passing the holes and then expanded in the second silencer chamber. The exhaust gas is again throttled when passing the holes formed to the outlet pipe. The sizes of these holes can be selectively easily changed by the drilling working, thus being adapted for various requirement for the muffler performance. BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the present invention and to show how the same is carried out, reference is first made, by way of preferred embodiments, to the accompanying drawings, in which: Fig. 1 is a general outer appearance of a muffler assembly according to the present invention; Fig. 2 is a longitudinal sectional view of the muffler assembly of Fig. 1; and Figs. 3 to 6 show sectional views taken along the line III-III, IV-IV, V-V and VI-VI shown in Fig. 2 for showing inside arrangements of various sections of the muffler assembly of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS Fig. 1 shows an outer appearance of a muffler assembly according to the present invention and Fig. 2 is a longitudinal sectional view thereof. Referring to Fig. 2, the muffler assembly 1 comprises an outer cylinder 2 as a muffler body and an inner cylinder 4 disposed substantially coaxially inside the outer cylinder 2 with a space therebetween. The location of the space is for the purpose of reducing outward radiation of impact or shock noise due to pressure pulsation caused by an exhaust gas from the engine through an exhaust pipe. End plates 3a and 3b are disposed front and rear ends of the outer cylinder 2. In the interior of the inner cylinder 4, is coaxially disposed a connection cylinder 5 at substantially the central portion therein, which is supported by a support plate 6 at its front end and a partition plate 7 at its rear end. These support plate 6 and the partition plate 7 are secured to the inner surface of the inner cylinder 4 by a suitable manner such as welding means. As shown in Fig. 3, the support plate 6 has generally a circular configuration and a plurality of windows 8, four in the illustration, are formed to the outer peripheral portion of the support plate 6 and a central portion is positioned to close the front end of the connection cylinder 5. The support plate 6 has a shape as shown in Fig. 2 as a side sectional view suitable for closing and supporting the front end of the connection cylinder 5. The partition plate 7 has also a circular configuration as shown in cross section in Fig. 2 and has a central hole through which the rear end of the connection cylinder 5 extends in a supported manner. Thus the partition plate 7 also sopports the connection cylinder 5. The interior of the muffler body is sectioned into first and second silencer chambers 9 and 10 by the support plate 6 and the partition plate 7, the first silencer chamber 9 being in the front, upstream, side of the support plate 6 and the second silencer chamber 10 being in the rear, downstream, side of the partition plate 7. As shown in Figs. 2 and 3, a punched plate 11 is disposed in the first silencer chamber 9 directly in front of the support plate 6 and the punched plate 11 is provided with a plurality of holes 11a for fasilitating the diffusion of the exhaust gas from the exhaust pipe in the muffler body. An inlet pipe 12 connected to the exhaust pipe is inserted into the front end of the muffler body so that the inserted end of the inlet pipe 12 is disposed in the first silencer chamber 9 near the punched plate 11. The inserted open end of the inlet pipe 12 is closed by a plugging plate 13 and a plurality of holes 14 each in shape of longitudinal slit are circumferentially formed to the outer peripheral surface, near the inserted end, of the inlet pipe 12, through which the exhaust gas flows circumferentially as shown by arrows in an expanded manner. A plurality of holes each in shape of longitudinal slit, for example, are formed to the outer peripheral surface, near the support plate 6, of the connection cylinder 5. The opened rear end of the connection cylinder 5 is closed by a punched plate 16 provided with a plurality of small holes 16a. As shown in Fig. 2, the punched plate 16 is inserted into the opened rear end of the connection cylinder 5 and secured thereto in an arrangement shown in Fig. 5. In the second silencer chamber 10, is located an outlet pipe 18 which is supported therein by a support plate 17 and the end plate 3b. As shown in Fig. 6, the support plate 17 is provided with a plurality of, three in the illustration, large windows 19 so as not to block the flowing of the exhaust gas in the second silencer chamber 10 and also provided with a central hole through which the outlet pile 18 extends in a supported manner. The front end of the outlet pipe 18 extends coaxially in the rear end of the connection cylinder 5 near the punched plate 16 and closed by a plugging plate 20. A plurality of holes 21 are formed to the front end portion of the outlet pipe 18. A number of small holes, perforations, 22 are formed to the outer peripheral surface of the outlet pipe 18. In the illustrated embodiment, a cylindrical member 25 is coaxially disposed around the outer peripheral surface of the rear side portion of the outlet pipe 18 so as to form a space between the cylindrical member 25 and the outlet pipe 18 as a resonance chamber 24 which is filled with a sound absorption material such as glass wool 23. The location of the perforations 22 may substantially correspond to the location of the resonance chamber 24. The rear end of the outlet pipe 18 is tightly supported by the end plate 3b so that the extreme end of the outlet pipe 18 extends outward of the muffler assembly 1. The respective holes of the cnnection cylinder 5 and the outlet pipe 18 are easily formed by a drilling working and the holes of the punched plates 11 and 16 are also formed easily by a punching working. According to the muffler assembly of the structure described above, the exhaust gas introduced into the inlet pipe 12 through the exhaust pipe connected to the engine exhaust port is discharged into the first silencer chamber 9 through the holes 14 formed to the rear end portion of the inlet pipe and then expanded and silenced therein. The exhaust gas then flows downwardly and is diffused through the holes 11a of the punched plate 11 as shown by arrows. The exhaust gas is thereafter introduced into the connection cylinder 5 through the holes 15 formed to the front end portion thereof and then further diffused into the second silencer chamber 10 through the holes 16a of the punched plate 16 at the rear end portion of the connection cylinder 5, thus being expanded and silenced in the second silencer chamber 10. The expanded exhaust gas is introduced into the outlet pipe 18 through the holes 21 formed to the front end portion thereof and exhausted outward of the muffler assembly 1 through the rear end of the outlet pipe 18 while being subjected to the resonance sound absorption in the resonance chamber 24. As can be understood from the foregoings, according to the muffler assembly of the present invention, various types of flows of the exhaust gas can be accomplished as shown by arrows in Fig. 2. According to the present invention, as described above, the muffler assembly has a small volume and a short longitudinal length while maintaining the improved silencing efficiency, and the throttling efficiency for the exhaust gas can be optimumly changed by changing diameters and numbers of the holes of the connection cylinder and the outlet pipe, for example, and the muffler performance can thus be easily adapted for the requirement in various places or countries at which a motorcycle is utilized. Since the rear end of the outlet pipe is inserted into the rear end portion of the connection cylinder, the whole longitudinal length of the outlet pipe can be made long in spite of the relatively short length of the muffler assembly. In this arrangement, the resonance chamber is also formed to thereby effectively attain the silencing effect and to reduce the back pressure and the output loss. Since the exhaust gas can be diffused circumferentially into the first silencer chamber through the holes formed to the rear end portion of the inlet pipe, the back pressure can be effectively reduced, thus attaining the improved silencing effect.

Claims: A muffler assembly for an engine comprising: an outer cylinder member (2) constituting a muffler body; an inner cylinder member (4) coaxially disposed in the outer cylinder member (2) with a space therebetween; a connection cylinder member (5) disposed inside the inner cylinder member (4), the connection cylinder member having an upstream end and a downstream end; a first silencer chamber (9) formed at the upstream end of the connection cylinder member (5); a second silencer chamber (10) formed at the downstream end of the connection cylinder member (5); an inlet pipe (12) through which engine exhaust gas is introduced into the muffler body; an outlet pipe (18) having an upstream end disposed inside the inner cylinder member (4) and a downstream end opened outward of the muffler assembly, and a partition plate (7) disposed inside the inner cylinder member (4) at the downstream end of the connection cylinder (5), characterized in that a plurality of holes (15) are circumferentially formed in the connection cylinder member (5) at an upstream end portion thereof, the upstream end of the outlet pipe (18) is plugged (20), the outlet pipe (18) being supported by a support plate (17) to the inner cylinder member (4) and having an upstream end portion in which a plurality of holes (21) are formed, the support plate (17) being provided with a plurality of holes (19) and in that a cylinder member (25) is further arranged coaxially about a downstream end portion of the outlet pipe (18) with a space constituting a resonance chamber (24) between the cylinder member (25) and an outer peripheral surface of the outlet pipe (18) and a sound absorption material (23) filled in the resonance chamber (24). A muffler assembly according to claim 1, wherein said inlet pipe (12) has a downstream end plugged (13) and positioned near the upstrem end of the connection cylinder member (5), said inlet pipe (12) having a downstream end portion in which a plurality of holes (14) are formed in a circumferential arrangement to permit the flow of exhaust gas passing from the inlet pipe (12) circumferentially into the first silencer chamber (9). A muffler assembly according to claim 1 or 2, wherein a first punched plate (11), through which a plurality of punched holes (11a) are formed, is disposed in the muffler body between the upstream end of the connection cylinder member (S) and the downstream end of the inlet pipe (12). A muffler assembly according to claim 3, wherein a second punched plate (16), through which a plurality of punched holes (16a) are formed, is disposed in a downstream end portion of the connection cylinder member(5). A muffler assembly according to any of claims 1 to 4, wherein the upstream end of said outlet pipe (18) is coaxially inserted into the downstream end of the connection cylinder member (5). A muffler assembly according to any of claims 1 to 5, wherein a plurality of perforations (22) are formed through the outer peripheral surface of the outlet pipe (18) proximate said resonance chamber (24). A muffler assembly according to any of claims 1 to 6, wherein the sound absorption material is a glass wool (23). A muffler assembly according to any of claims 1 to 7, wherein said support plate (17) is disposed directly in front of the upstream end of the connection cylinder member (5), said support plate (17) having an outer peripheral portion through which a plurality of holes (19) are formed and a central solid portion having a size sufficient for closing the upstream end of the connection cylinder member (5).

Inventors: KONDO YUTAKA, TAKAHASHI KAZUTOSHI, KONDO, YUTAKA, TAKAHASHI, KAZUTOSHI
Applicants: SUZUKI CO LTD, SUZUKI KABUSHIKI KAISHA
Application year: 1991
Main classification: F01N1
IPC codes: F01N1