The present invention relates generally to engine exhaust systems, and more particularly to mufflers that attenuate engine exhaust acoustics.
Exhaust systems typically muffle noise produced by combustion processes within engines. At a minimum, a typical exhaust system usually includes an exhaust pipe to carry engine exhaust gases and sound away from the engine, and a muffler to attenuate the sound propagated through the exhaust pipe. Mufflers include two general types according to the mode by which noise is attenuated. Mufflers that attenuate noise by reflection of sound waves are called reactive or reflection mufflers. Mufflers that attenuate noise by absorption of sound waves are known as dissipative or absorption mufflers.
Reflection mufflers are particularly useful for low-frequency applications and for high-temperature applications that restrict or preclude use of absorption mufflers. Reflection may be provided by resonators or changes in exhaust flow direction by labyrinth-like baffling in the muffler. Reflection mufflers usually include a hollow steel housing defining an expansion chamber and one or more baffles and/or resonator chambers in communication with the expansion chamber, a steel inlet pipe extending into the expansion chamber, and a steel outlet pipe extending from the expansion chamber to the outside. Sound waves enter the main chamber through the inlet pipe, and reflect off various baffles or other surfaces in the chambers to cancel each other out and thereby reduce noise. Reflection mufflers may produce undesirable backpressure.
Current absorption mufflers may be used in applications where low pressure drop and high attenuation at predominantly middle and high frequencies are required. Absorption mufflers typically include a steel housing defining one chamber, a perforated pipe extending completely through the chamber of the housing, and absorption material disposed in the chamber between the pipe and the housing. Sound waves enter the chamber through the perforated pipe, and become absorbed by the absorption material. Until now, absorption mufflers generally produced less sound control than reflective mufflers.
An implementation of a presently preferred muffler includes an exhaust pipe having a plurality of perforations and at least one pipe sealing flange extending generally radially outwardly. The muffler also includes a housing carried by the exhaust pipe and enclosing the plurality of perforations and including at least one housing sealing flange extending generally radially inwardly and spaced radially from the exhaust pipe and spaced axially from the at least one pipe sealing flange carried by the exhaust pipe. The muffler further includes thermal insulation disposed axially between the at least one pipe sealing flange and the at least one housing sealing flange, and radially between the at least one housing sealing flange and the exhaust pipe, and radially between the at least one pipe sealing flange and the housing.
Another implementation of a presently preferred absorption muffler includes a metallic exhaust pipe including a plurality of perforations, and a polymeric housing carried by the exhaust pipe and enclosing the plurality of perforations, and including axially opposed ends. The muffler also includes thermal insulation carried radially between the exhaust pipe and the polymeric housing and axially between the axially opposed ends inclusive thereof. The muffler further includes acoustic insulation separate from the thermal insulation and carried between the thermal insulation and the polymeric housing.
An implementation of a presently preferred polymeric housing for a muffler carryable on an exhaust pipe includes an outer shell. A plurality of walls extends generally radially inwardly from the outer shell and is radially spaceable from an outer surface of the exhaust pipe. The housing also includes a sealing end including a generally radially inwardly extending sealing wall radially spaceable from the outer surface of the exhaust pipe and axially spaceable from at least one sealing flange of the exhaust pipe.
The following detailed description of preferred embodiments and best mode will be set forth with reference to the accompanying drawings, in which:
Referring in more detail to the drawings,
Referring now to
Still referring to
The first muffler housing 18 may be generally oval and assembled from opposed semi-oval halves. The halves may be welded together along their common seam, may be integrally fastened together, and/or may be strapped together using any suitable straps such as zip ties 20 around a trunk 22 and/or band clamps 24 around one or more collars 26 that may be disposed at axially opposed sealing ends of the housing 18. The collars 26 are sown as being of reduced diameter compared to the trunk 22 but may be of any suitable size. The second muffler housing 19 may be generally cylindrical in shape and assembled from opposed semi-circular halves. The halves may be welded together along their common seam, may be integrally fastened together, and/or may be strapped together using any suitable straps such as band clamps 24 around a trunk 23 and/or one or more collars 27 at axially opposed sealing ends of the housing 19. The collars 27 are shown as being of increased diameter compared to the trunk 23 but may be of any suitable size. Finally, in
As shown in exemplary
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Also, between the ends of the muffler 14, the exhaust pipe 12 may include perforations 58 that may include a plurality of sets 60a, 60b, 60c, 60d, 60e of the perforations 58 that may be axially spaced apart. The quantity, size, spacing, and/or other parameters of the perforations 58 of any given set 60a-60e may provided in correspondence to the volume, length, diameter, and/or other parameters of the corresponding acoustic chambers. Those skilled in the art will recognize that such parameters will vary from application to application depending, for example, on exhaust pipe size, exhaust flow rates, exhaust temperatures, and the like.
Nonetheless, the relative sizes, quantities, spacing, and/or other parameters of the perforations, and the corresponding acoustic chamber volumes and/or other parameters of the acoustic chambers, may provide relatively wide frequency band attenuation from chamber to chamber with at least some overlap of frequency attenuation from one chamber to another. The parameters may be selected to achieve in-chamber acoustic attenuation ranges over, for example, a 50 Hz range up to a 600 Hz range. More particularly the parameters may be selected to provide on the order of about a 300 Hz range of acoustic attenuation in any given chamber. Also, the parameters may be selected to provide frequency band overlapping from chamber to chamber to avoid standing peaks of certain frequencies in order to obtain satisfactory acoustic performance. Non-limiting examples of muffler parameter values are provided below.
The first acoustic chamber defined between the end wall 38 and the first divider wall 40a may be of a first axial length, such as about 65 mm. The second acoustic chamber defined between the first and second divider walls 40a, 40b may be of a second length greater than the first, such as about 95 mm. The third and fourth acoustic chambers defined between the second through fourth divider walls 40b, 40c, 40d may be of an equal third length greater than the second, such as about 104 mm. The fifth acoustic chamber defined between the fourth divider wall 40d and the end wall 38 may be of a fourth length less than the third but greater than the second, such as about 100 mm.
The acoustic chambers and perforations 58 may be arranged and sized to attenuate overlapping acoustic frequency bands. For example, the first acoustic chamber and set of perforations 60a may attenuate about 450 to about 700 Hz with a target of about 600 Hz. The second acoustic chamber and set of perforations 60b may attenuate about 400 to about 500 Hz with a target of about 450 Hz. The third and fourth acoustic chambers and sets of perforations 60c, 60d may attenuate about 150 to about 350 Hz and target about 250 Hz. Finally, the fifth acoustic chamber and set of perforations 60e may attenuate about 300 to about 400 Hz with a target of about 350 Hz. The acoustic insulation 46 further assists to attenuate a broader, higher frequency band, for example, from about 600 Hz to about 3,000 Hz.
Still referring to
The housing 18 may be radially spaced from the exhaust pipe 12. As shown in
Referring finally to
The second muffler housing 19 may include the trunk 23, and the collars 27 at axially opposed ends of the housing 19. The collars 27 may include one or more generally radially extending sealing flanges, for example, axially outer end walls 33, axially inner end walls 35, and one or more divider walls 37 therebetween. The sealing flanges 54 may be disposed in alternating axial arrangement with the housing sealing flanges including the walls 33, 35, 37.
Similarly, the trunk 23 may include axially outer end walls 39, and one or more divider walls 41a, 41b therebetween. The divider walls 41a, 41b and end walls 39 define a plurality of acoustic chambers. As with the first muffler 14, the walls 39, 41a, 41b may be evenly spaced apart and/or may be unevenly spaced in any suitable manner to provide equal or unequal sized acoustic chambers. Any suitable quantities and configurations of flanges or walls may be used.
Also, between the ends of the muffler 15, the exhaust pipe 12 may include perforations 59 that may include a plurality of sets 61 of the perforations 59 that may be axially spaced apart. As previously disclosed in the example above with respect to the first muffler 14, the quantity, size, spacing, and other parameters of the perforations 59 may provided in correspondence to the volume, length, diameter, and other parameters of the acoustic chambers.
The thermal insulation 29 may extend over and between the flanges 54 and along the pipe 12 to hug the pipe 12 and flanges 54 and cover the perforations 59. The thermal insulation 29 may be one layer as shown, but may include multiple layers such as from multiple sleeves or from a sleeve folded or rolled back onto itself. The thermal insulation 29 may be disposed between the acoustic insulation 47 and the exhaust pipe 12.
The housing 15 may be radially spaced from the exhaust pipe 12. The radially extending end walls 33, 35, 39 and divider walls 37, 41a-41b of the housing 19 have radially inner surfaces or diameters. The internal size of the radially inner surfaces or diameters is greater than the external size of the outer surface or diameter of the exhaust pipe 12, thereby defining radial spaces therebetween. Also, the axially extending shell walls 43, 45 of the housing 19 are also greater in size than corresponding portions of the exhaust pipe 12 to define radial spaces therebetween.
One or both of the mufflers 14, 15 may provide one or more of the following benefits to one degree or another. It is estimated that the mufflers 14, 15 may weigh on the order of about 25% less than current mufflers, may cost on the order of about 20% less than current mufflers (not including downstream vehicle assembly savings), and may be on the order of about 50% smaller than current mufflers, which may lead to better packaging of exhaust systems within vehicles. Also, because of good thermal insulation performance, it is believed that the mufflers 14, 15 may reduce or eliminate the current need to provide heat shields between current mufflers and other portions of the vehicle. Because the mufflers 14, 15 are flow-through or absorption mufflers, they may yield less backpressure in the exhaust system 10, thereby possibly leading to better engine performance, fuel economy, and the like.
Moreover, the mufflers 14, 15 may provide better, or at least comparable, acoustic attenuating performance with respect to current reflection mufflers. Accordingly, the mufflers 14, 15 may provide a particularly significant advantage when used for non-automotive applications conventionally requiring absorption muffler designs.
While certain preferred embodiments have been shown and described, persons of ordinary skill in this art will readily recognize that the preceding description has been set forth in terms of description rather than limitation, and that various modifications and substitutions can be made without departing from the spirit and scope of the invention. The invention is defined by the following claims.
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/975,342, filed Sep. 26, 2007.
Number | Name | Date | Kind |
---|---|---|---|
3187837 | Beeching | Jun 1965 | A |
4045057 | Halter | Aug 1977 | A |
4239091 | Negrao | Dec 1980 | A |
4993513 | Inoue et al. | Feb 1991 | A |
5052513 | Yoshikawa et al. | Oct 1991 | A |
5321214 | Uegane et al. | Jun 1994 | A |
5468923 | Kleyn | Nov 1995 | A |
5799395 | Nording et al. | Sep 1998 | A |
5979598 | Wolf et al. | Nov 1999 | A |
6543577 | Ferreira et al. | Apr 2003 | B1 |
6855293 | Zengerle et al. | Feb 2005 | B1 |
7007720 | Chase et al. | Mar 2006 | B1 |
20050167192 | Simon | Aug 2005 | A1 |
20070157598 | Atanas et al. | Jul 2007 | A1 |
Number | Date | Country |
---|---|---|
1 171 223 | May 2003 | EP |
1 030 962 | Aug 2003 | EP |
1 900 913 | Mar 2008 | EP |
1 900 914 | Mar 2008 | EP |
1 332 071 | Sep 2008 | EP |
1.159.824 | Feb 1958 | FR |
1 309 141 | Mar 1973 | GB |
2129490 | May 1984 | GB |
Number | Date | Country | |
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20090078499 A1 | Mar 2009 | US |
Number | Date | Country | |
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60975342 | Sep 2007 | US |