Patent Publication Number: US-11377996-B2

Title: Muffler with baffle defining multiple chambers

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     This application is a National Stage Application of PCT/US2018/036242, filed Jun. 6, 2018, which claims the benefit of and priority to U.S. Provisional Application No. 62/517,362, filed Jun. 9, 2017, both of which are incorporated herein by reference in their entireties. 
    
    
     BACKGROUND 
     The present application generally relates to the field of mufflers, such as those for use with internal combustion engines. 
     SUMMARY 
     One embodiment relates to an internal combustion engine. The engine includes an engine block including a cylinder, and a muffler assembly configured to receive exhaust gases from the cylinder. The muffler assembly includes a housing defining an interior volume and including an exhaust inlet and an exhaust outlet, and a baffle assembly positioned within the interior volume. The baffle assembly includes a plurality of chambers in fluid communication with each other. The plurality of chambers are in fluid communication with the exhaust inlet and the exhaust outlet so that the plurality of chambers are configured to cause exhaust gases to be directed through the muffler assembly from the exhaust inlet to the exhaust outlet through four passes in the baffle assembly before exiting through the exhaust outlet. 
     Another embodiment relates to a muffler assembly configured to dampen noise of exhaust gases flowing therethrough. The muffler assembly includes a housing defining an interior volume and including an exhaust inlet and an exhaust outlet, and a baffle assembly positioned within the interior volume. The baffle assembly includes multiple chambers in fluid communication with each other. The multiple chambers are in fluid communication with the exhaust inlet and the exhaust outlet so that the multiple chambers are configured to cause exhaust gases to be directed through the muffler assembly from the exhaust inlet to the exhaust outlet through four passes in the baffle assembly before exiting through the exhaust outlet. 
     Alternative exemplary embodiments relate to other features and combinations of features as may be generally recited in the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The disclosure will become more fully understood from the following detailed description, taken in conjunction with the accompanying figures, in which: 
         FIG. 1  is a front perspective view of an internal combustion engine, according to an exemplary embodiment. 
         FIG. 2  is a rear perspective view of the internal combustion engine of  FIG. 1 . 
         FIG. 3  is a perspective view of a muffler assembly of the engine of  FIG. 1 . 
         FIG. 4  is an exploded view of the muffler assembly of  FIG. 3 . 
         FIG. 5  is a front perspective view of a baffle assembly of the muffler assembly of  FIG. 3 . 
         FIG. 6  is a rear perspective view of the baffle assembly of  FIG. 5 . 
         FIG. 7  is a section view of the muffler assembly of  FIG. 3  along section line  7 - 7 . 
         FIG. 8  is a section view of the muffler assembly of  FIG. 3  along section line  8 - 8 . 
         FIG. 9  is a schematic diagram of a fluid flow through the muffler assembly of FIG. 
         FIG. 10  is a bottom perspective view of a cover of the muffler assembly of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION 
     Before turning to the figures, which illustrate the exemplary embodiments in detail, it should be understood that the present application is not limited to the details or methodology set forth in the description or illustrated in the figures. It should also be understood that the terminology is for the purpose of description only and should not be regarded as limiting. 
     Referring to  FIGS. 1-2 , an internal combustion engine  100  is illustrated according to an exemplary embodiment. The internal combustion engine  100  includes an engine block  101  having one or more cylinders  103 , cylinder heads  105 , and pistons, and a crankshaft  107 . Each piston reciprocates in a cylinder  103  along a cylinder axis to drive the crankshaft  107 . The crankshaft  107  rotates about a crankshaft axis  109 . The crankshaft  107  is positioned in part within a crankcase  113 . In an exemplary embodiment, the crankshaft  107  may be oriented horizontally (i.e., a horizontal engine) with the engine  100  in its normal operating position. In other embodiments, the crankshaft  107  is vertically oriented (i.e., a vertical engine) with the engine  100  in its normal operating position. The engine may include one cylinder or two or more cylinders. The engine  100  also includes an air-fuel mixing device  111  for supplying an air-fuel mixture to the cylinder (e.g., a carburetor, an electronic fuel injection system, a fuel direct injection system, etc.), a fuel tank  108 , an air filter assembly  102 , and a muffler assembly  120 . 
     The engine  100  can be used on a variety of end products, including outdoor power equipment, portable jobsite equipment, and standby or portable generators. Outdoor power equipment includes lawn mowers, riding tractors, snow throwers, pressure washers, tillers, log splitters, zero-turn radius mowers, walk-behind mowers, riding mowers, stand-on mowers, pavement surface preparation devices, industrial vehicles such as forklifts, utility vehicles, commercial turf equipment such as blowers, vacuums, debris loaders, overseeders, power rakes, aerators, sod cutters, brush mowers, etc. Outdoor power equipment may, for example, use the engine  100  to drive an implement, such as a rotary blade of a lawn mower, a pump of a pressure washer, an auger of a snow thrower, and/or a drivetrain of the outdoor power equipment. Portable jobsite equipment includes portable light towers, mobile industrial heaters, and portable light stands. 
     Referring to  FIGS. 1-10 , the engine  100  includes a muffler assembly  120  according to an exemplary embodiment. The muffler assembly  120  includes an exhaust conduit  122  that is fastened (e.g., bolted) directly to the cylinder  103  or cylinder head  105  to receive exhaust gases from the cylinder  103  of the engine  100 . The muffler assembly  120  may include support structures (e.g., brackets) bolted to the cylinder  103  or otherwise on the engine  100 . The muffler assembly  120  is configured to reduce the noise emitted from exhaust gases exiting the cylinder  103  of the engine  100  after the combustion process. With the use of a baffle assembly  140 , the muffler assembly  120  is configured to provide four passes of sound filtering to the exhaust gases exiting the engine  100  via the muffler assembly  120 , as described further herein. 
     The muffler assembly  120  includes a housing  132  formed by a cover  134  and a base  136 . The housing  132  includes a front  112 , a rear  114 , a left side  116 , a right side  118 , a top  117 , and a bottom  119 . As shown in  FIGS. 7-8 , the interior surface  180  of the cover  134  and the interior surface  182  of the base  136  combine to define an interior volume  155  of the muffler assembly  120 , with the interior surface  180  of the cover  134  at least partially defining the interior volume  155  and the interior surface  182  of the base  136  also at least partially defining the interior volume  155 . The exhaust conduit  122  is attached to the cylinder  103  at a cylinder end  121  and extends into the muffler housing  132  at a muffler end  123 . The muffler end  123  is received within the muffler housing  132  and extends through an exhaust opening  124  formed within the base  136  on the bottom  119  of the housing  132 . Accordingly, the exhaust conduit  122  is in fluid communication with the interior volume  155  of the housing  132 . After exiting the cylinder  103 , the exhaust gases flow through the exhaust conduit  122 , from the cylinder end  121  to the muffler end  123 , and into the internal volume  155  of the muffler assembly  120 . 
     As shown in  FIGS. 3-4 , the base  136  includes a mounting flange  137  that is arranged to align with and contact a corresponding mounting flange  135  of the cover  134  when the cover  134  is attached to the base  136 . The mounting flanges  135 ,  137  extend around a circumference of the base  136  and cover  134 , respectively. The mounting flanges  135 ,  137  may include a recessed channel  139  that receives a gasket (not shown) to form a seal between the mounting flanges  135  and  137  of the base  136  and the cover  134 . 
     Referring to  FIGS. 4-8 , the muffler assembly  120  includes a baffle assembly  140  including one or more internal separators (e.g., baffles). The baffle assembly  140  is positioned within the housing  132  of the muffler assembly  120 . As shown in  FIG. 4 , the baffle assembly  140  includes a bottom portion  142 , a top portion  144 , and a stepped chamber portion  146 . In other embodiments, one or more of the portions may be formed as a single integral piece. The baffle assembly  140  includes flange portions  149  formed on the bottom and top portions  142 ,  144  which are configured to fit between the mounting flanges  135 ,  137  of the cover  134  and base  136  during assembly of the baffle assembly  140  with the muffler assembly  120 . In other embodiments, the baffle assembly  140  is otherwise assembled into the housing  132 . The flange portions  149  provide separation of the chambers (e.g., first chamber  150 , second chamber  152 , third chamber  154 , fourth chamber  156 , outlet chamber  158 ) formed within the baffle assembly  140  and within the interior volume  155  of the housing  132 . The bottom portion  142  includes an interior surface  178  and an outer surface  172 , the top portion  144  includes an interior surface  174  and an outer surface  170 , and the stepped chamber portion  146  includes an interior surface  176  and an outer surface  175 . The stepped chamber portion  146  includes a stepped (e.g., raised) portion  161  that is a distance  163  higher ( FIG. 8 ) than the rest of the top side of the stepped chamber portion  146 . The bottom portion  142  mates with the top portion  144  of the baffle assembly  140  at interior surfaces  178  and  176 , respectively, and the interior surface  176  of the stepped chamber portion  146  mates with the outer surface  170  of the top portion  144  to form the baffle assembly  140 . 
     Referring to  FIGS. 7-8 , when assembled into the muffler housing  132 , the baffle assembly  140  divides the internal volume  155  into multiple internal chambers through which exhaust gases flow upon exiting the cylinder  103 . With the baffle assembly  140  inserted into (e.g., assembled with) the housing  132 , at least five separate chambers are formed. The five chambers within the internal volume  155  are in fluid communication with each other and the exhaust conduit  122 . The first chamber  150  ( FIG. 7 ) is formed by the interior surface  182  of the base  136  and the outer surface  172  of the bottom portion  142 . The first chamber  150  is positioned proximate the bottom  119  of the housing  132  and the exhaust conduit  122  and extends between the left and right sides  116 ,  118 . The interior surface  178  of the bottom portion  142  and the interior surface  174  of the top portion  144  of the baffle assembly  140  form two separate chambers, a second chamber  152  and an outlet chamber  158  ( FIG. 7 ). In the illustrated embodiments, the second chamber  152  is formed in a rounded rectangular shape ( FIG. 8 ), while the outlet chamber  158  is formed in a rounded tubular shape ( FIG. 7 ), as described further herein. The second chamber  152  is positioned proximate the right side  118  of the housing  132  and runs approximately from the front  112  to the rear  114  of the housing  132  ( FIG. 8 ). The outlet chamber  158  also extends from proximate the front  112  to the rear  114  of the housing  132 , but is positioned opposite the second chamber  152  near the left side  116  ( FIG. 7 ). The outlet chamber  158  and second chamber  152  are substantially parallel to each other ( FIG. 7 ). In other embodiments, the chambers  152 ,  158  can be angled relative to each other. 
     A third chamber  154  (e.g., stepped chamber  154 ) is formed by the outer surface  170  of the top portion  144  and the interior surface  176  of the stepped chamber portion  146  ( FIG. 8 ). The third chamber  154  is positioned directly above the second chamber  152  ( FIGS. 7-8 ). A fourth chamber  156  is formed by the outer surface  175  of the stepped chamber portion  146  and an interior surface  180  of the cover  134 . The fourth chamber  156  is positioned directly above both of the third chamber  154  and the outlet chamber  158  ( FIG. 7 ). As such, the fourth chamber  156  is positioned proximate the top  117  of the housing  132  and extends between the left and right sides  116 ,  118  ( FIG. 7 ). 
     Referring to  FIG. 7 , an outlet tube  148  defines the outlet chamber  158  through which the exhaust gases ultimately exit after flowing through the muffler assembly  120 . The outlet tube  148  extends from proximate the rear  114  of the housing  132  through the front  112  of the housing  132  to an end  151  positioned outside the housing  132 . In other embodiments, the outlet tube  148  can be otherwise positioned (e.g., extending through rear  114  of the housing  132 ). The cover  134  and base  136  of the housing  132  form an outlet opening  110  through which the outlet tube  148  partially extends. According to an exemplary embodiment, the outlet tube  148  is circular in cross-section. Accordingly, each of the top portion  144  and bottom portion  142  include semi-circular pieces which mate together to form the tubular shape of the outlet tube  148  and outlet chamber  158 . The circular cross-section of the outlet tube  148  facilitates noise reduction in the muffler assembly  120 . For example, the overall sound pressure level, which indicates how high the noise levels are at a specific location, is reduced by using the tubular (e.g., rounded surface) outlet structure as shown in  FIGS. 5-6  in place of a more rectangular or flat surface outlet structure. In other embodiments, the outlet tube  148  can be oval, oblong, or other curve shapes in cross-section such that the outlet tube  148  has a curved surface (e.g., curved surfaces  162  shown in  FIGS. 5-7 ). 
     The baffle assembly  140  includes multiple perforated areas including multiple perforations (e.g., apertures). As described further herein, the exhaust gases entering the muffler assembly  120  move through chambers formed by the bottom, top, and stepped chamber portions  142 ,  144 ,  146  via the various perforations formed in the baffle assembly  140  and exit the muffler assembly  120  through the outlet tube  148 . The bottom portion  142  of the baffle assembly  140  includes a first perforated area  141  including first perforations  171  extending from the first chamber  150  to the second chamber  152 . The first perforated area  141  is positioned proximate the front  112  and the right side  118  of the housing  132 . The top portion  144  includes a second perforated area  143  positioned above and directly opposite the first perforated area  141  within the second chamber  152 . Accordingly, the second perforated area  143  is positioned proximate the rear  114  and the right side  118  of the housing  132 . The second perforated area  143  includes second perforations  173  extending between the second chamber  152  and the third chamber  154  (e.g., stepped chamber). The stepped chamber portion  146  includes a third perforated area  145  positioned directly opposite the second perforated area  143  within the third chamber  154  (e.g., stepped chamber). As such, the third perforated area  145  is positioned proximate the front  112  and the right side  118  of the housing  132 . The stepped portion  161  of the stepped chamber portion  146  does not include any perforations. The third perforated area  145  includes third perforations  179  extending between the third chamber  154  and the fourth chamber  156 . The positioning of the stepped portion  161  relative to the third perforated area  145  provides for a longer and more difficult flow path for the fluid moving through the third chamber  154 , and thus, increases noise dampening in that chamber  154 . As shown in  FIGS. 7-8 , all of the first, second, and third perforations  171 ,  173 , and  179  are substantially perpendicular to the surfaces through which the perforations extend. In other embodiments, the first, second, and third perforations  171 ,  173 , and  179  may extend through the surfaces at another angle. 
     The fourth (e.g., final) perforated area  147  is positioned on the outlet tube  148  of the top portion  144  and includes fourth perforations  177  extending between the fourth chamber  156  and the outlet chamber  158 . The fourth perforated area  147  is positioned proximate the rear  114  of the housing  132  near the left side  116 . This positioning of the fourth perforated area  147  (e.g., opposite side from the end  151  of the outlet tube  148 ) of the housing  132  provides as much length (e.g., flow path length) as possible between the fourth perforated area  147  and the end  151  of the outlet tube  148 , which is located opposite the fourth perforated area  147  on the front  112  of the housing  132 . Providing the longest possible flow path between the fourth perforated area  147  and the end  151  of the outlet tube  148  facilitates dampening of the engine noise prior to the exhaust gases exiting the muffler assembly  120 . Furthermore, the fourth perforated area  147  is the only perforated area positioned proximate the left side  116  of the housing  132 , while the three other perforated areas (e.g., first, second, and third areas  141 ,  143 ,  145 ) are positioned opposite the fourth perforated area  147  proximate the right side  118 . This relative positioning further facilitates optimal noise dampening through the muffler assembly  120 . 
     The fourth perforated area  147  is formed on a curved surface  162  of the outlet tube  148 . Accordingly, at least a portion of the fourth perforations  177  are formed such that fluid that flows through the perforations  177  on the outlet tube  148  is coming in at various angles relative to the curved surface  162  of the outlet tube  148 . The various angles of fluid flow into the outlet chamber  158  results in optimized mixing of the fluid moving through the outlet chamber  158  (e.g., gases moving toward and mixing with other gases entering the chamber) and as such, results in more attenuation of noise relative to the use of flat surface perforations. 
     In operation, exhaust gases flow into the exhaust conduit  122  of the muffler assembly  120 . The exhaust conduit  122  is fluidly coupled to the interior volume  155  of the housing  132  such that exhaust gases flow into the housing  132  of the muffler assembly  120  for noise dampening. Once inside the housing  132 , the exhaust gases move from the exhaust conduit  122  toward the outlet tube  148  via multiple sets of perforations and chambers, thereby reducing the resultant noise of the exhaust gases exiting the engine  100 . The incoming exhaust gases complete at least four passes (e.g., travel through at least four perforated areas) through the baffle assembly  140  prior to exiting the muffler assembly  120 . 
     Referring to  FIG. 9 , a schematic of the fluid flow through the muffler assembly  120  is illustrated. During a first pass  202 , the incoming exhaust gases flow from the exhaust conduit  122  into a first chamber  150  and through the first perforated area  141  formed in the baffle assembly  140 . As noted above, the first perforated area  141  is positioned toward the front  112  and proximate the right side  118  of the housing  132  ( FIG. 7 ). The gases enter the second chamber  152  through the first perforated area  141  and move toward the second perforated area  143  positioned at the opposite end of the second chamber  152  (e.g., toward the back  114  of the muffler assembly  120 ). 
     Next, the gases flow through the second perforated area  143  in a second pass  204 . The gases move into the third chamber  154  (e.g., stepped chamber  154 ) and back toward the front  112  of the muffler assembly  120  and toward the third perforated area  145  ( FIG. 8 ). As such, the gases moving through the third chamber  154  (e.g., from proximate the rear of the housing  132  to the front  112 ) are substantially opposite in direction to the gases moving through the second chamber  152  (e.g., from proximate the front  112  of the housing  132  to the rear  114 ). 
     The gases then flow through the third perforated area  145  in a third pass  206 . The gases move into the fourth chamber  156  and toward the left side of the housing  132  to the fourth perforated area  147  ( FIG. 7 ). Accordingly, the gases moving in the fourth chamber  156  (e.g., from proximate the right side  118  of the housing  132  to the left side  116 ) are substantially perpendicular in direction to the gases moving through the third chamber  154  (e.g., from proximate the rear of the housing  132  to the front  112 ). 
     Finally, the gases flow through the fourth perforated area  147  in a fourth (e.g., final) pass  208 . The fourth perforated area  147  (e.g., final perforated area  147 ) is formed on the outlet tube  148  and the fourth perforations  177  extend between the fourth chamber  156  and the outlet chamber  158 . Once the gases move into the outlet chamber  158 , the gases are directed toward the end  151  of the outlet tube  148  and are expelled out of the muffler assembly  120 . In the outlet chamber  158 , the gases move approximately from the rear  114  to the front  112  of the housing ( FIG. 7 ). Accordingly, the gases moving through the outlet chamber  158  are substantially opposite in direction to the gases flowing through the second chamber  152  and are substantially parallel in direction to the gases flowing through the third chamber  154  ( FIGS. 7-8 ). Further, the gases moving through the outlet chamber  158  are substantially perpendicular to the gases moving through the fourth chamber  156  ( FIG. 7 ). 
     The four noise dampening passes  202 ,  204 ,  206 , and  208  are arranged in counter flow arrangements to the adjacent noise dampening passes so that the exhaust gases moving through the four passes travels in a first direction in a second chamber  152 , is redirected in a second opposite direction in the third chamber  154 , takes a substantially perpendicular turn in the fourth chamber  156 , and returns to the first direction in the outlet chamber  158 . Fluid flow passes are considered to be substantially the same direction when one fluid flow pass falls within plus or minus 25 degrees of the bearing of the referenced fluid flow pass in the same direction of travel. Fluid flow passes are considered to be substantially the opposite direction when one fluid flow pass falls within plus or minus 25 degrees of the bearing of the referenced fluid flow pass in the opposite direction of travel. Fluid flow passes are considered to be substantially perpendicular in direction when one fluid flow pass falls within plus or minus 10 degrees of 90 degrees from the referenced fluid flow pass. 
     Referring to  FIG. 10 , a noise dampening assembly  300  is shown, according to an exemplary embodiment. The noise dampening assembly  300  includes the cover  134  of the muffler assembly  120 , a retainer  190 , and a noise dampening material  192 . The noise dampening material  192  is made from fiberglass. In other embodiments, the noise dampening material  192  may include other materials that act to dampen noise. The noise dampening material  192  is held into place within the cover  134  by the retainer  190 . The retainer  190  is made from a metallic material and is perforated to allow sound waves in the fourth chamber  156  to communicate with and be absorbed by the noise dampening material  192 . The retainer  190  can be tuned to a certain frequency to allow for further noise attenuation (e.g., by changing the relative size and location of the individual perforations or changing the material of the retainer). The retainer  190  and noise dampening material  192  are attached to the underside of the cover  134  at fastener locations  194 . The retainer  190  is spot-welded to the cover  134  to retain the noise dampening material  192  therein. In other embodiments, the retainer  190  is attached to the housing  132  of the muffler assembly  120  using other means of attachment (e.g., bolted). 
     In an exemplary embodiment, the noise dampening assembly  300  is positioned within the cover  134  of the housing  132  and as such, is positioned within the fourth chamber  156  to provide noise dampening within the muffler assembly  120 . As fluid flows through the third perforated area  145  and into the fourth chamber  156 , the noise from the fluid will be absorbed by the noise dampening assembly  300  as the fluid passes through the fourth chamber  156 . In addition to noise reduction, the noise dampening assembly  300  may also provide temperature reduction on the outer surface of the housing  132  due to the separation of relatively hot exhaust gases from the top surface of the housing  132 . In other embodiments, in addition, a similar noise dampening assembly may also be included in the base  136  of the housing  132 . 
     The dimensions and placement of the chambers, perforations, and other components described herein are configured to facilitate the dampening of noise through the muffler assembly  120 . Specifically, the perforations formed in the baffle assembly  140  are positioned such that the length of the flow path through the muffler assembly  120  is as long as possible. Using the lengthened flow path created within the baffle assembly  140  and the multiple turns of the fluid flow path, the noise attenuation through the muffler assembly  120  is facilitated. As the exhaust gases move through the muffler assembly  120 , the exhaust noise is dampened, and the longer the flow path or more surfaces that the exhaust gases come into contact with while moving through the muffler assembly  120 , the more noise attenuation occurs. 
     Furthermore, the use of four passes of sound filtering results in an additional pass as compared with most conventional mufflers (e.g., three pass mufflers). The additional pass creates an additional point of noise dampening. In addition, the use of a stepped chamber portion  146  with a stepped portion  161  creates a more torturous path for the fluid flow through the muffler assembly  120  and allows room for the fluid flow to develop after flowing through the perforations (e.g., second set perforated area  143 ). Thus, the stepped chamber portion  146  also acts to improve the attenuation of noise through the muffler assembly  120 . 
     As described herein, the muffler assembly can result in up to 3 decibels (dB) less of noise generation as compared to a conventional muffler. Specifically, in tests run by the Applicant, the noise generated by a conventional muffler was compared to the noise generated from the muffler described herein. The comparison of noise generation from the conventional to the described muffler showed a decrease from approximately 100 dB to 97.5 dB, resulting in a 2.5 dB drop in noise production. 
     The construction and arrangement of the apparatus, systems and methods as shown in the various exemplary embodiments are illustrative only. Although only a few embodiments have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.). For example, some elements shown as integrally formed may be constructed from multiple parts or elements, the position of elements may be reversed or otherwise varied and the nature or number of discrete elements or positions may be altered or varied. Accordingly, all such modifications are intended to be included within the scope of the present disclosure. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes, and omissions may be made in the design, operating conditions and arrangement of the exemplary embodiments without departing from the scope of the present disclosure. 
     As utilized herein, the terms “approximately,” “about,” “substantially,” and similar terms are intended to have a broad meaning in harmony with the common and accepted usage by those of ordinary skill in the art of outdoor power equipment. It should be understood by those of skill in the art who review this disclosure that these terms are intended to allow a description of certain features described and claimed without restricting the scope of these features to the precise numerical ranges provided. Accordingly, these terms should be interpreted as indicating that insubstantial or inconsequential modifications or alterations of the subject matter described and are considered to be within the scope of the disclosure.