MUFFLER

Abstract: A muffler for an internal combustion engine comprises: a communicating passage constituting member 18 allowing a plurality of chambers 11, 12, 13 formed by partitioning walls 9, 10 inside an outer shell 8 to be communicated with each other; and a butterfly-type valve 20 provided in the communicating passage 19. The communicating passage constituting member 18 is formed into the shape of a gutter so as to face either an inner surface of the other shell 8 at an open side of the constituting member 18 or an outer surface of the outer shell 8 at an open side of the constituting member 18. Alternatively, the communicating passage constituting member 18 is constituted by a pipe and is provided in the outer shell 8. The arrangement makes it possible to improve the engine output, reduce the back pressure, and enhance the sound-damping effect.

Description: The present invention relates to a muffler comprising: (a) an outer shell enclosing an interior space, and walls therein partitioning said interior space into at least three chambers; (b) an inlet pipe passing through at least one wall and terminating in one of said chambers; (c) a communicating passage constituting member connecting that chamber which is remotest from the inlet side, with another chamber; (d) a butterfly-type valve provided in said communicating passage; (e) an inner pipe between a first one and a second one of said chambers; and (f) an outlet pipe which terminates within said second one of said chambers and which has no direct communication with said remotest chamber. The muffler according to the present invention is preferably suited for an internal combustion engine. A muffler for an internal combustion engine is disclosed in, for instance, Japanese Patent Unexamined Publication No. 60-27719. This muffler is arranged such that the interior of the muffler is partitioned into a plurality of chambers communicating with each other through an inner pipe, and this inner pipe is provided with an opening and closing valve which opens and closes in correspondence with the engine rotational speed. Thus, the opening and closing of the valve is controlled in accordance with given objectives. For instance, when the engine rotational speed is normal, the opening and closing valve is opened to reduce the internal pressure of the muffler, thereby reducing fuel consumption. When the engine rotational speed is low, emphasis is placed on the sound-damping effect rather than on back pressure, so that the opening and closing valve is closed. On the other hand, when the engine rotational speed is high, emphasis is placed on a high output through reduced back pressure rather than on the sound-damping effect, so that the opening and closing valve is opened. In addition, the aforementioned publication also discloses a muffler in which, as shown in Fig. 6, a plate valve 3 is provided slidably in an inlet pipe 2 disposed in an outer shell 1, and the plate valve 3 is urged by a spring 4. In a medium-speed region, the plate valve 3 is closed by the urging force of the spring 4, while, in a high-speed region, the plate valve 3 is closed by the flow of an exhaust gas against the urging force of the spring 4. Furthermore, the same publication discloses another muffler which is arranged such that, as shown in Fig. 7, an opening and closing valve 6 is provided on the exhaust port side of an inner pipe 5 within an outer shell 1 in a face-to-face relationship, and this opening and closing valve 6 is moved forward and backward by a moving member 7 so as to open and close the inner pipe 5. With the above-described structures, however, there is a problem in that when the opening and closing valve 3 or 6 opening the flow of the exhaust gas is restricted by coming into contact with the entire opposing surface of the opening and closing valve 3 or 6, and the back pressure therefore becomes high. Furthermore, a muffler of the type mentioned in the beginning is disclosed in EP-A-0 077 230. This known muffler is designed such that the inlet pipe terminates within one of the "middle" chambers of the muffler. Although there is provided a connection pipe in a prolongational position to the inlet pipe, which connection pipe connects that "middle" chamber with the remotest chamber, the cross sectional area of the flow path between the inlet pipe and the return pipe directly through the "middle" chamber is by far greater than the cross sectional ares of the flow path from the "middle" chamber through the connection pipe, the remotest chamber, which is a resonance chamber, the communicating passage, another pipe and another resonance chamber to the "middle" chamber. Therefore, this bypassing flow path containing the butterfly valve does not significantly augment the flow rate of the exhaust gases through the muffler of EP-A-0 077 230 when the butterfly valve is opened. Thus the remotest chamber in this known muffler always functions as a resonance chamber independently of whether the butterfly valve is closed or open. The butterfly valve only modifies gradually the acoustique attenuation of the resonator in dependency of the rotational speed of the internal combustion engine, however, does not significantly change the flow resistance through the muffler so that the back pressure against the internal combustion engine is essentially not reduced at higher rotational speeds of the internal combustion engine. Finally, US-A-3 620 330 discloses a muffler comprising an outer shell enclosing an interior space, and walls therein partitioning said interior space into at least three chambers; an inlet pipe passing through at least one wall and terminating in one of said chambers; a first communicating passage constituting member connecting that chamber which is remotest from the inlet side with the adjacent chamber; a second communicating passage constituting member connecting that chamber which is positioned next to said remotest chamber with one of the chambers; a valve provided between said two communicating passage constituting members for selectively closing one of them; an outlet pipe which terminates within said one of the chambers and which has a direct communiction with the remotest chamber. This muffler is further constructed such that the inlet pipe terminates within that chamber which is positioned next to the remotest chamber and includes a wall portion having holes in an area situated within other chambers. This muffler according to US-A-3 620 330 operates as follows: When the valve closes the first communicating passage constituting member, the exhaust gas passes through two high-frequency resonance chambers, two expansion chambers and a chamber which has both characters of a high-frequency resonance chamber and an expansion chamber. At the time, if pressed, the remotest chamber has the character of a middle-frequency resonance chamber due to the direct connection thereof with the outlet pipe. When, on the other hand, the valve closes the opening of the second communicating passage constituting member the exhaust gas passes through the above-mentioned two high-frequency resonance chambers and two expansion chambers, i.e. one of the above-mentioned expansion chambers and the aforementioned middle-frequency resonance chamber which now functions as an expansion chamber. That is to say, in the former position of the valve, whole of the muffler quantity is used for muffling so that the muffler has a structure possible to muffle from the low-frequency to the high-frequency, whereas in the latter position of the valve the quantity of two of the expansion chambers in the muffler is not used for muffling so that the muffling quantity as the whole is decreased. However, the exhaust resistance can be decreased by shortening the exhaust passage. Accordingly, it is an object of the present invention to provide a muffler which is capable of overcoming the above-described problem. To this end, the present invention provides a muffler of the type mentioned in the beginning which is characterized in that (1) said inlet pipe passes through the walls and terminates within said remotest chamber; (2) said inlet pipe includes a wall portion having holes in an area situated within that chamber which is positioned next to said remotest chamber; (3) said communicating passage bypasses at least said chamber which is positioned next to the remotest chamber; (4) said first one of said chambers being that chamber which is positioned next to the remotest chamber; and (5) said second one of said chambers being said other chamber. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a sectional side-elevational view illustrating an embodiment of a muffler according to the present invention; Fig. 2 is a cross-sectional side view taken along the line II - II in Fig. 1; Figs. 3 to 5 are cross-sectional views illustrating three other embodiments according to the present invention, respectively; and Figs. 6 and 7 are cross-sectional side views illustrating two examples of a conventional muffler. DESCRIPTION OF THE PREFERRED EMBODIMENTS: Referring now to the accompanying drawings, a description of the embodiments will be given according to the present invention. In an embodiment according to the present invention which is illustrated in Figs. 1 and 2, the interior of an outer shell 8 is partitioned by partition walls 9, 10 into a first chamber 11, a second chamber 12 and a third chamber 13. An end of an inlet pipe 14 is open into the first chamber 11, while an end of an outlet pipe 15 is open into the third chamber 13. An inner pipe 16 allows the second chamber 12 and the third chamber 13 to communicate with each other. Communication holes 17 which are formed on the inlet pipe 14 are open in the second chamber 12. A gutter-shaped communication passage constituting member 18 is arranged along the inner surface of the outer shell 8, facing the inner surface of the outer shell 8 at its open side, and is secured to the outer shell 8. Thus, a passage 19 by which the first chamber 11 and the third chamber 13 communicate is formed of the communicating passage constituting member 18 and the outer shell 8. A butterfly-type valve 20 for opening and closing the communicating passage 19 is rotatably provided in the communicating passage 19. The valve 20 is openably driven by a driving member 21 provided on the outside of the outer shell 8. In accordance with the above-described arrangement of the invention, with the valve 20 closed, the first chamber 11 serves as a resonance chamber, and an exhaust gas from the inlet pipe 14 flows into the second chamber 12 through the communicating holes 17, passes through the inner pipe 16 and the third chamber 13, and is discharged through the outlet pipe 15. In addition, with the valve 20 opened, the first chamber 11 serves as an expansion chamber, and a part of the exhaust gas from the inlet pipe 14 passes through the first chamber 11, the communicating passage 19 and the third chamber 13 and is discharged through the outlet pipe 15. At this time, since the valve 20 is of the butterfly type, circulation resistance of the exhaust gas flow circulated through the communicating passage 19 is small. For that reason, the back pressure produced by the circulation resistance becomes small. Fig. 3 shows a second embodiment according to the present invention, which is arranged such that at a downstream end 18a the above-described communicating passage constituting member 18 is bent in parallel with an outer plate 8a of the outer shell 8 to form a communicating passage 19, and a butterfly-type valve 20 which is similar to the above-described one is provided in a bent portion 19a thereof. This embodiment can perform the same operation and have the same advantages as the above-described embodiment. Fig. 4 illustrates a third embodiment according to the present invention which is arranged such that the aforementioned communicating passage constituting member 18 is formed into the shape of a gutter so as to face the outer surface of the outer shell 8 at the open side of the constituting member 18. It should be noted that opposite ends of the communicating passage constituting member 18 are bent toward the outer surface of the outer shell 8, and communicating openings are formed on the outer shell 8 for communication with the first chamber 11 and the third chamber 13. Fig. 5 illustrates a fourth embodiment of the present invention, which is arranged such that the aforementioned communicating passage constituting member 18 is constituted by a pipe, and is provided in the outer shell 8 to allow the first chamber 11 and the third chamber 13 to be communicated with each other. As described above, according to the present invention, when the engine rotational speed is low and the load is light, one chamber disposed in the muffler can be used as a low-frequency resonance chamber to enhance the characteristics of damping the low-frequency sound. Meanwhile, when the engine rotational speed is high and the load is heavy, the low-frequency resonance chamber can be converted into an expansion chamber to reduce the back pressure and improve the engine output. In addition, since the opening and closing valve for converting the aforementioned chamber into either the low-frequency resonance chamber or the expansion chamber is of the butterfly type, it is possible to reduce the circulation resistance of the exhaust gas passing through the opening and closing valve when the valve is fully opened, thereby allowing the back pressure to be further reduced. In addition, since the communicating passage constituting member having the opening and closing valve is formed into the shape of a gutter, the communicating passage can be formed on the outer shell by making use of a part of the outer shell as a part of its constituent walls. As a result, the communicating passage can be provided effectively in a corner space inside the muffler. For that reason, restrictions imposed on the inner pipe are small so that the inner pipe can be provided with a wide sectional area. As a result, the flow rate under control can be increased, thereby making it possible to sufficiently perform the desired objects including a reduction in the back pressure and the sound-damping effect. In addition, if the aforementioned gutter-like communicating passage constituting member is provided on the outer surface of the outer shell, a part of the outer shell can be utilized as a part of the constituent walls so that the chambers inside the muffler can be made large. Furthermore, if the communicating passage constituting member is constituted by a pipe, the valve for using in the passage can be not in a special shape but in an ordinary circular shape.

Claims: A muffler comprising: (a) an outer shell (8) enclosing an interior space, and walls (9, 10) therein partitioning said interior space into at least three chambers (11, 12, 13); (b) an inlet pipe (14) passing through at least one wall and terminating in one of said chambers (11, 12, 13); (c) a communicating passage constituting member (18) connecting that chamber (11) which is remotest from the inlet side, with another chamber (13); (d) a butterfly-type valve (20) provided in said communicating passage (19); (e) an inner pipe (16) between a first one (12) and a second one (13) of said chambers (11, 12, 13); and (f) an outlet pipe (15) which terminates within said second one (13) of said chambers (11, 12, 13) and which has no direct communication with said remotest chamber (11); characterized in that (1) said inlet pipe (14) passes through the walls (9, 10) and terminates within said remotest chamber (11); (2) said inlet pipe (14) includes a wall portion having holes (17) in an area situated within that chamber (12) which is positioned next to said remotest chamber (11); (3) said communicating passage (19) bypasses at least said chamber (12) which is positioned next to the remotest chamber (11); (4) said first one of said chambers (11, 12, 13) being that chamber (12) which is positioned next to the remotest chamber (11); and (5) said second one of said chambers (11, 12, 13) being said other chamber (13). A muffler according to claim 1, characterized in that said communicating passage constituting member (18) is formed into a shape of a gutter so as to face an inner surface of said outer shell (8) at an open side of said communicating passage constituting member (18). A muffler according to claim 1, characterized in that said communicating passage constituting member (18) is formed into a shape of a gutter so as to face an outer surface of said outer shell (8) at an open side of said communicating passage constituting member (18). A muffler according to claim 1, characterized in that said communicating passage constituting member (18) is formed of a pipe and is provided in said outer shell (8).

Inventors: HASE, SHUICHI
Applicants: SANGO CO., LTD.
Application year: 1989
Main classification: F01N1
IPC codes: F01N1, F02D9