Abstract:
The present invention provides a method of operating a dynamic exhaust system of a motorcycle engine. The method includes providing a valve in the exhaust system that is movable to direct exhaust gases between a first flow path through the exhaust system and a second flow path through the exhaust system. The method includes actuating the valve at a first speed to redirect exhaust gases from the first flow path to the second flow path and actuating the valve at a second speed greater than the first speed to redirect exhaust gases from the second flow path to the first flow path.

Description:
FIELD OF THE INVENTION 
   This invention relates generally to motorcycles, and more particularly to dynamic exhaust systems for motorcycles. 
   BACKGROUND OF THE INVENTION 
   Various designs of motorcycle dynamic exhaust systems are known in the art. Typically, dynamic exhaust systems are utilized to alter the performance of the motorcycle&#39;s engine and/or the noise emissions from the motorcycle&#39;s engine. In a conventional dynamic exhaust system for a motorcycle, a valve is positioned in a muffler to define a restrictive flow path through the muffler, which may be utilized when it is desirable to decrease the noise emissions of the engine, and a less restrictive flow path, which may be utilized when it is desirable to increase the performance of the engine. The valve is typically moved to direct exhaust gases from the engine through either of the restrictive or less restrictive flow paths. An actuator that is responsive to engine vacuum is commonly utilized to actuate the valve, such that when engine vacuum is high, the actuator actuates the valve to direct the exhaust gases through the restrictive flow path of the muffler to quiet the engine. Also, when the engine vacuum is low, the actuator actuates the valve to direct the exhaust gases through the less restrictive flow path of the muffler to increase the performance of the engine. 
   SUMMARY OF THE INVENTION 
   The present invention provides a method of operating an dynamic exhaust system of a motorcycle engine. The method includes providing a valve in the exhaust system that is movable to direct exhaust gases between a first flow path through the exhaust system and a second flow path through the exhaust system. The method includes actuating the valve at a first speed to redirect exhaust gases from the first flow path to the second flow path and actuating the valve at a second speed greater than the first speed to redirect exhaust gases from the second flow path to the first flow path. 
   The method includes, in another aspect, actuating the valve in the exhaust system in a crossover region of first and second torque characteristics of the first and second flow paths, respectively. 
   The present invention provides, in yet another aspect, a motorcycle including a valve and an actuator supported by an airbox. The actuator is operatively coupled to the valve to move the valve between a first position, in which exhaust gases are directed along the first flow path, and a second position, in which exhaust gases are directed along the second flow path. 
   Other features and aspects of the present invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings, wherein like reference numerals indicate like parts: 
       FIG. 1  is a cross-sectional view of a first construction of a dynamic exhaust system embodying the present invention, illustrating exhaust gases flowing through a first flow path of the exhaust system. 
       FIG. 2  is a cross-sectional view of the dynamic exhaust system of  FIG. 1 , illustrating exhaust gases flowing through a second flow path of the exhaust system. 
       FIG. 3  is a partial cross-sectional view of a second construction of a dynamic exhaust system embodying the present invention, illustrating exhaust gases flowing through a first flow path of the exhaust system. 
       FIG. 4  is a partial cross-sectional view of the dynamic exhaust system of  FIG. 3 , illustrating exhaust gases flowing through a second flow path of the exhaust system. 
       FIG. 5  is a cutaway perspective view of a third construction of a dynamic exhaust system embodying the present invention, illustrating exhaust gases flowing through a first flow path of the exhaust system. 
       FIG. 6  is a cutaway perspective view of the dynamic exhaust system of  FIG. 5 , illustrating exhaust gases flowing through a second flow path of the exhaust system. 
       FIG. 7  is a perspective view of a motorcycle including the dynamic exhaust system of  FIGS. 5 and 6 , illustrating an actuator positioned remotely from the exhaust system. 
       FIG. 8  is a graph illustrating a first torque characteristic of a motorcycle engine representative of exhaust gases flowing through the first flow path of the exhaust system of  FIGS. 5 and 6 , and a second torque characteristic of the motorcycle engine representative of exhaust gases flowing through the second flow path of the exhaust system of  FIGS. 5 and 6 . 
   

   Before any features of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or being carried out in various ways. Also, it is understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including”, “having”, and “comprising” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The use of letters to identify elements of a method or process is simply for identification and is not meant to indicate that the elements should be performed in a particular order. 
   DETAILED DESCRIPTION 
     FIGS. 1 and 2  illustrate a first construction of a motorcycle dynamic exhaust system  10  embodying the present invention. The exhaust system  10  includes a muffler  14  coupled to an exhaust pipe  18  in a conventional manner. Although not shown, the exhaust system  10  may incorporate a second exhaust pipe and a second muffler. 
   The muffler  14  incorporates a valve assembly  22   a  to direct the flow of exhaust gases through the muffler  14 . In the illustrated construction, the valve assembly  22   a  includes a valve housing  26  defining a central passageway  30 . A shaft  34  is rotatably supported by the valve housing  26 , and a butterfly valve  38  is coupled to the shaft  34 . The butterfly valve  38  is positioned in the central passageway  30  to selectively restrict the flow of exhaust gases through the passageway  30 , as discussed in more detail below. The shaft  34  extends through an outer shell  42  of the muffler  14 , and a quadrant or a lever  46  is coupled to the shaft  34  to receive a cable  50  for pivoting or rotating the shaft  34  and the butterfly valve  38 . 
   The muffler  14  also includes an inlet tube  54  coupled to the valve housing  26  at an inlet end of the valve housing  26 , and an outlet tube  58  coupled to the valve housing  26  at an outlet end of the valve housing  26 . The inlet tube  54  is supported in the outer shell  42  of the muffler  14  by a tube support member  62 . The muffler  14  further includes a catalyst  66  located within a catalyst tube  70 , which is coupled to the inlet tube  54  via a transition sleeve  74 . A first sleeve  78  surrounds the inlet tube  54  and is coupled between the tube support member  62  and the transition sleeve  74 . A plug  82  is positioned within the inlet tube  54  such that unobstructed flow of exhaust gases through the entire length of the inlet tube  54  is restricted. 
   With continued reference to  FIGS. 1 and 2 , the muffler  14  includes a second sleeve  86  surrounding the outlet tube  58 , such that opposite ends of the second sleeve  86  are pinched into contact with the outer surface of the outlet tube  58 . The muffler  14  also includes a third sleeve  90  surrounding the second sleeve  86 , with one end of the third sleeve  90  being coupled to the tube support member  62  and the opposite end being in abutting contact with the outer shell  42 . 
   As a result of the above-identified internal components of the muffler  14 , the muffler  14  generally defines a plurality of chambers through which exhaust gases may flow. More particularly, the space bounded by the catalyst tube  70 , the transition sleeve  74 , and a portion of the inlet tube  54  upstream of the plug  82  defines a first chamber  94 , while the space bounded by the first sleeve  78 , the inlet tube  54 , the transition sleeve  74 , and the tube support member  62  defines a second chamber  98 . In addition, the space bounded by a portion of the inlet tube  54  downstream of the plug  82  and the closed butterfly valve  38  defines a third chamber  102 , and the space bounded between the second sleeve  86 , the third sleeve  90 , and the tube support member  62  defines a fourth chamber  106 . Further, the space bounded by the second sleeve  86  and the outlet tube  58  defines a fifth chamber  110 , while the space bounded by the closed butterfly valve  38  and the outlet tube  58  defines a sixth chamber  114 . 
   With reference to  FIG. 1 , a first flow path of exhaust gases is shown through the muffler  14  by a sequence of arrows. The butterfly valve  38  is shown pivoted to an open position, in which unobstructed flow of exhaust gases is allowed through the passageway  30  in the valve housing  26 . More particularly, exhaust gases exiting the exhaust pipe  18  enter the first chamber  94  of the muffler  14  and encounter the plug  82 , which redirects the exhaust gases into the second chamber  98  via a plurality of first apertures  118  formed in the inlet tube  54 . The exhaust gases are then directed into the third chamber  102  via a plurality of second apertures  122  formed in the inlet tube  54 . From the third chamber  102 , the exhaust gases may pass unobstructed through the passageway  30  of the valve housing  26  and enter the sixth chamber  114 , thereby bypassing the fourth and fifth chambers  106 ,  110  of the muffler  14 . From the sixth chamber  114 , the exhaust gases may exit the muffler  14 . 
   With reference to  FIG. 2 , a second flow path of exhaust gases is shown through the muffler  14  by a sequence of arrows. The butterfly valve  38  is shown pivoted to a closed position, in which exhaust gases are not allowed to flow through the passageway  30  in the valve housing  26 . More particularly, exhaust gases pass through the first, second, and third chambers  94 ,  98 ,  102  as described above with reference to  FIG. 1 . However, since the butterfly valve  38  is closed, exhaust gases in the third chamber  102  are directed into the fourth chamber  106  via the plurality of second apertures  122 . From the fourth chamber  106 , the exhaust gases are directed into the fifth chamber  110  via a plurality of third apertures  126  formed in the second sleeve  86 . Further, the exhaust gases in the fifth chamber  110  are directed into the sixth chamber  114  via a plurality of fourth apertures  130  formed in the outlet tube  58 . From the sixth chamber  114 , the exhaust gases may exit the muffler  14 . 
     FIGS. 3 and 4  illustrate a second construction of a motorcycle dynamic exhaust system  134  of the present invention. The exhaust system  134  is a dual exhaust system  134  including a first muffler  138  and a second muffler  142 . In the illustrated construction, the first muffler  138  is a conventional multi-chamber muffler  138  while the second muffler  142  is a high-performance single chamber muffler  142 . However, alternate constructions of the exhaust system  134  may utilize two high-performance single chamber mufflers  142  or two conventional multi-chamber mufflers  138 . 
   In the illustrated construction, a valve  22   b  is positioned in the exhaust system  134  upstream of the second muffler  142 . The valve  22   b  is substantially similar to the valve  22   a  shown in  FIGS. 1 and 2 . As shown in  FIGS. 3 and 4 , the exhaust system  134  also includes a first exhaust pipe  146  coupled to the first muffler  138 , and a second exhaust pipe  150  coupled to and merged with the first exhaust pipe  146 . The first and second exhaust pipes  146 ,  150  may be connected to respective exhaust ports of a motorcycle engine (e.g., a V-twin engine, not shown) to receive exhaust gases. The exhaust system  134  further includes a third exhaust pipe  154  coupled to and merged with the second exhaust pipe  150 . The third exhaust pipe  154  is also coupled to the valve  22   b , which, in turn, is coupled to the second muffler  142 . 
   With reference to  FIG. 3 , a first flow path of exhaust gases is shown through the exhaust system  134  by a sequence of arrows. The butterfly valve  38  is shown pivoted to an open position, in which unobstructed flow of exhaust gases is allowed through the valve  22   b . More particularly, exhaust gases may be redirected from the second exhaust pipe  150  to the third exhaust pipe  154 , thereby utilizing both of the first and second mufflers  138 ,  142 . 
   With reference to  FIG. 4 , a second flow path of exhaust gases is shown through the exhaust system  134  by a sequence of arrows. The butterfly valve  38  is shown pivoted to a closed position, in which exhaust gases are not allowed to flow through the valve  22   b . More particularly, exhaust gases may not be redirected from the second exhaust pipe  150  to the second muffler  142 , thereby only utilizing the first muffler  138  in the exhaust system  134 . 
     FIGS. 5 and 6  illustrate a third construction of a motorcycle dynamic exhaust system  158  of the present invention. The exhaust system  158  includes a muffler  162  coupled to an exhaust pipe (not shown) in a conventional manner. Although not shown, the motorcycle may include a dual exhaust system utilizing a second exhaust pipe and a second muffler. 
   Like the muffler  14  of  FIGS. 1 and 2 , the muffler  162  incorporates a valve  22   c  therein to direct the flow of exhaust gases through the muffler  162 . The valve  22   c  is substantially similar to the valve  22   a  shown in  FIGS. 1 and 2 . As shown in  FIGS. 5 and 6 , the valve  22   c  is coupled to a first or inlet tube  166  of the muffler  162 . The inlet tube  166  is supported by a first wall  170  and a second wall  174 , which divide the interior space of the muffler  162  as bounded by an outer shell  178  into a first chamber  182 , a second chamber  186 , and a third chamber  190 . The muffler  162  also includes a second or connecting tube  194  supported by the first and second walls  170 ,  174  that communicates the first and third chambers  182 ,  190 . Further, the muffler  162  includes a third or outlet tube  198  supported by the first and second walls  170 ,  174  that communicates the third chamber  190  with the atmosphere. 
   With reference to  FIG. 5 , a first flow path of exhaust gases is shown through the exhaust system  158  by a sequence of arrows. The butterfly valve  38  is shown pivoted to an open position, in which unobstructed flow of exhaust gases is allowed through the valve  22   c . As such, exhaust gases from the inlet tube  166  are allowed to discharge directly into the third chamber  190  (i.e., bypassing the first chamber  182 ), where the exhaust gases may flow through the outlet tube  198  and exit the muffler  162 . 
   With reference to  FIG. 6 , a second flow path of exhaust gases is shown through the exhaust system  158  by a sequence of arrows. The butterfly valve  38  is shown pivoted to a closed position, in which exhaust gases are not allowed to flow through the valve  22   c . As such, exhaust gases are directed to the first chamber  182  via the inlet tube  166 , and to the third chamber  190  via the connecting tube  194 . From the third chamber  190 , the exhaust gases may flow through the outlet tube  198  and exit the muffler  162 . 
   With reference to  FIG. 7 , a motorcycle  202  is shown that incorporates the dynamic exhaust system  158  of  FIGS. 5 and 6 .  FIG. 7  schematically illustrates the valve  22   c  positioned toward the bottom of the motorcycle  202 . However, in a motorcycle configured to receive the exhaust systems  10 ,  134 , the valves  22   a ,  22   b  may be positioned relative to the motorcycle in a location appropriate with the configuration of the respective exhaust systems  10 ,  134 . As such, the position of the valve  22   c  as shown in  FIG. 7  is for illustrative purposes only. 
   The illustrated motorcycle  202  is configured with an airbox (the location of which is designated by reference numeral  206 ) in a location on the motorcycle  202  typically associated with a fuel tank. The airbox  206  houses conventional air intake components (e.g., an air filter, not shown) for the engine. The airbox  206  is also configured to receive an actuator  210  for opening and closing the valve  22   c  of the exhaust system  158 . The actuator  210  may be mounted on top of the airbox  206  and protected by a cover (not shown) covering the airbox  206 . 
   The actuator  210  may be a conventional servo-motor having a quadrant or lever  214  for pulling or releasing the cable  50 . The cable  50  is schematically illustrated as extending from the upper portion of the motorcycle  202  to the bottom portion of the motorcycle  202 . However, the cable  50  may extend in any direction on the motorcycle  202  depending on the location of the valve  22   c  in the exhaust system  158 . The cable  50  may also be substantially hidden from view by routing the cable  50  through frame members of the motorcycle  202  and/or hidden from view behind one or more fairings or body panels of the motorcycle  202 . 
   The actuator  210  is electrically connected to an engine control unit  218  (“ECU”) of the motorcycle  202 . In addition to controlling other functions of the motorcycle  202  (e.g., fuel injection, engine timing, etc.), the ECU  218  is configured to control operation of the actuator  210 . In addition, a second cable may be utilized to actuate a second valve. 
   Any of the dynamic exhaust systems  10 ,  134 ,  158  of  FIGS. 1-6  may be utilized to alter the performance of the motorcycle&#39;s engine and/or alter the noise emission characteristics of the motorcycle&#39;s engine. With reference to  FIG. 8 , the engine&#39;s torque output is shown as a function of engine speed (measured in revolutions per minute, or RPM). More particularly, curve A illustrates the engine&#39;s torque output when the exhaust gases are routed through the first flow path of the exhaust system  158 , in which the valve  22   c  is opened. Likewise, curve B illustrates the engine&#39;s torque output when the exhaust gases are routed through the second flow path of the exhaust system  158 , in which the valve  22   c  is closed. 
   As shown in  FIG. 8 , the engine&#39;s torque output may be increased by opening the valve  22   c  during low engine speeds and during high engine speeds. However, maintaining the valve  22   c  open during mid-range engine speeds may also cause a decrease in torque output compared to the engine&#39;s output when the valve  22   c  is closed. Such a decrease in torque output may be caused by reversion of the exhaust gases in the exhaust system  158 . 
   The engine exhibits different operating characteristics, or “torque characteristics,” depending on the position (e.g., open or closed) of the valve  22   c . For example, when the valve  22   c  is in an open position, the engine may exhibit a first torque characteristic defined by curve A. Likewise, when the valve is in a closed position, the engine may exhibit a second torque characteristic defined by curve B. Selective actuation of the valve  22   c  between open and closed positions may allow the engine to exhibit a third torque characteristic defined by curve C that takes advantage of the increase in torque output provided by the first operating characteristic during low engine speeds and high engine speeds, while also taking advantage of the torque output provided by the second operating characteristic during mid-range engine speeds to reduce the effects of the above-described reversion phenomena. 
   More particularly, for the engine to exhibit the third torque characteristic and follow curve C, the valve  22   c  is selectively controlled according to engine speed to cause the engine to switch or transition between exhibiting the first torque characteristic and exhibiting the second torque characteristic. For example, the valve  22   c  may be actuated from an open position to a closed position in a first crossover region, designated R 1  in  FIG. 8 . The first crossover region R 1  may be centered about a first intersection or crossover point (designated P 1 ) of curve A and curve B. Crossover point P 1  correlates with the engine speed at which the engine outputs substantially the same amount of torque whether it is exhibiting the first torque characteristic or the second torque characteristic. As shown in  FIG. 8 , crossover point P 1  occurs at about 3800 RPM, and the crossover region R 1  may extend between about 3600 RPM and about 4000 RPM. However, differently-configured engines may exhibit different torque characteristics than those defined by curve A and curve B. As such, crossover point P 1  may occur at a higher or a lower engine speed than 3800 RPM, and the crossover region R 1  may be wider (i.e., encompass a greater range of engine speeds) or more narrow (i.e., encompass a smaller range of engine speeds) than that illustrated in  FIG. 8 . 
   For the engine to continue exhibiting the third torque characteristic and following curve C, the valve  22   c  is actuated from the closed position back to the open position in a second crossover region, designated R 2  in  FIG. 8 . The second crossover region R 2  may be centered about a second intersection or crossover point (designated P 2 ) of curve A and curve B. As shown in  FIG. 8 , crossover point P 2  occurs at about 5300 RPM, and the crossover region R 2  may extend between about 5100 RPM and about 5500 RPM. However, differently-configured engines may exhibit different torque characteristics than those defined by curve A and curve B. As such, crossover point P 2  may occur at a higher or a lower engine speed than 5100 RPM, and the crossover region R 2  may be wider (i.e., encompass a greater range of engine speeds) or more narrow (i.e., encompass a smaller range of engine speeds) than that illustrated in  FIG. 8 . 
   More particularly, the ECU  218  may be configured to trigger the actuator  210 , which in turn may actuate the valve  22   c , when the engine speed reaches the crossover points P 1 , P 2  in the respective crossover regions R 1 , R 2 . However, with respect to the crossover region R 1 , the ECU  218  may trigger the actuator  210  at an engine speed within the crossover region R 1  but at a lower speed or a higher speed than the crossover point P 1 . Likewise, with respect to the crossover region R 2 , the ECU  218  may trigger the actuator  210  at an engine speed within the crossover region R 2  but at a lower speed or a higher speed than the crossover point P 2 . 
   The ECU  218  may also trigger the actuator  210  slightly before the engine speed reaches the crossover point P 1 , or slightly before the engine speed reaches the crossover point P 2  to take into account the mechanical lag associated with the actuator  210 , cable  50 , and valve  22   c . In addition, the ECU  218  may be configured to automatically make slight corrections to the engine speed when the valve  22   c  is actuated based upon input received by the ECU  218  from various engine or motorcycle sensors. Further, one or more conditions may need to be satisfied in order for the ECU  218  to trigger the actuator  210 . For example, a condition that the engine must be operating at 75% of full throttle or more may need to be satisfied in order for the ECU  218  to trigger the actuator  210 . 
   The ECU  218  may also be configured to trigger the actuator  210 , and thus the valve  22   c , according to the speed of the motorcycle  202 . It may be desirable to trigger the actuator  210  according to the speed of the motorcycle  202  to alter the noise emission characteristics of the engine. For example, it may be desirable to operate the engine below a pre-determined sound level during mid-range cruising speeds (e.g., between 10 miles per hour and 50 miles per hour, or MPH). As a result, the ECU  218  may be configured to actuate the valve  22   c  from the open position to the closed position at about 10 MPH. In the closed position, the valve  22   c  directs exhaust gases along a second flow path longer than the first flow path to provide additional muffling of the sound pulses of the exhaust gases. At about 50 MPH, the ECU  218  may be configured to actuate the valve  22   c  back to the open position from the closed position. In the open position, the valve  22   c  directs exhaust gases along the first flow path to decrease the amount of muffling of the sound pulses of the exhaust gases. The ECU  218  may also be configured to trigger the actuator  210  at other motorcycle speeds depending on the desired sound levels or noise emission characteristics of the engine. 
   Various aspects of the invention are set forth in the following claims.