Abstract:
A dynamic exhaust system is capable of operating at high temperatures and provides a passive, temperature resistant valve for controlling reflection, restriction and/or rerouting of the exhaust gas flow for sound control and/or emissions control in advanced internal combustion engines, such as cylinder deactivation, variable displacement, hybrid power plant, and cold hydrocarbon traps.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The invention relates generally to sound, performance and emission control in vehicles utilizing advanced technology, such as cylinder deactivation or hybrid power sources wherein discontinuations occur in the exhaust gas flow rate during operation of the engine.  
         [0002]     Conventional internal combustion engines or power sources continuously use all cylinders during operation. Advanced internal combustion engine systems include non-conventional internal combustion power plants, such as cylinder deactivation engines, and are more difficult to acoustically attenuate in the exhaust system, because they have a broader range of noise frequencies and a broader range of gas flow (volume per unit time) to deal with. The use of a muffler valve to achieve greater acoustic attenuation is known, especially with conventional engine systems. Passive valves are traditionally used only on conventional engines at lower temperature locations in the exhaust system downstream of the engine. Recently, expensive systems to achieve noise attenuation in advanced non-conventional engine vehicles have utilized active or semi-active valves to handle variable exhaust flow requirements and to simultaneously withstand increased heat requirements of such advanced engine systems. Such active or semi-active valves, however, involve not only expensive hardware and accessory power systems to actuate such valves, but additionally are associated with expensive control modules with accompanying software control for vehicles incorporating such advanced engine techniques. These more expensive active or semi-active valve systems have recently been used due to the inability of previous passive muffler valve arrangements to withstand the heat requirements in areas along a longitudinal length of the exhaust system where the use of such valves is most optimally applied to noise abatement, performance improvement and/or emission reduction.  
         [0003]     Passive valves have traditionally been used to create dynamic exhaust systems in conventional engines. However, these systems have a continuous response proportional to engine speed, a continuous increase in exhaust system pressure as a function of engine speed, and do not have to deal with conditions that are not continuous with engine speed but rather involve step functions of exhaust flow during operation of the vehicle&#39;s power source. Many advanced engine designs, such as cylinder deactivation systems, create unique exhaust conditions that are not continuous with engine speed or possess larger than normal ranges in exhaust flow wherein cost effective management of sound and/or emissions cannot be met by conventional exhaust system designs.  
         [0004]     For the purposes of this disclosure, a “passive valve” is one in which the motive force to operate the valve comes from the energy (velocity or pressure) in exhaust gas flow. For the case of a gas velocity powered valve, the motive energy comes from the velocity of the gas hitting a component of the valve, such as a head or flapper or other element placed in the exhaust stream. For the case of pressure, the valve is moved by forces exerted from a pressure difference between an upstream and a downstream location on either side of the valve element. In summary, the valve is controlled and moved by conditions on either side of the valve element which has been placed in the exhaust stream.  
         [0005]     A “semi-active valve” in addition to utilizing the motive forces for operation used by a passive valve, additionally utilizes motive force that does not burden the gas flow. This additional motive force is derived from an external pressure differential between the interior of the exhaust system and atmospheric pressure.  
         [0006]     An “active valve” is powered or controlled at least in part by a source other than the exhaust pressure or gas velocity. For example, a vehicle engine controller may send an electrical signal to a solenoid-operated valve whenever appropriate conditions so dictate. The solenoid, in turn, controls a vacuum to an actuator for the valve which is appropriately positioned in the exhaust stream.  
       SUMMARY OF THE INVENTION  
       [0007]     In accordance with the need demonstrated by the prior art, a method of controlling exhaust flow in an exhaust system for a non-conventional internal combustion power source exhibiting, during operation, larger ranges of acoustic frequency, flow rate or pressure in exhaust flows than found in conventional internal combustion power sources places a passive, temperature resistant valve in a path of exhaust gas flow, the valve operative to at least partially alter a characteristic of the exhaust gas flow for the larger ranges.  
         [0008]     In another aspect of the invention, an arrangement for controlling exhaust flow in an exhaust system for an internal combustion power source exhibiting, during operation, larger ranges of acoustic frequency, flow rate or pressure in exhaust flows than found in conventional internal combustion power sources includes a passive temperature resistant valve positioned in a path of exhaust gas flow, the valve operative to at least partially alter a characteristic of the exhaust gas flow for the larger ranges. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0009]     The objects and features of the invention will become apparent from a reading of a detailed description, taken in conjunction with the drawing, in which:  
         [0010]      FIG. 1  is a top perspective view of an exhaust system for an advanced internal combustion engine arranged in accordance with the principles of the invention; and  
         [0011]      FIG. 2  sets forth region  2  of  FIG. 1  in more detail. 
     
    
     DETAILED DESCRIPTION  
       [0012]     The invention utilizes the application of a low cost passive valve which can withstand high temperatures allowing the design freedom to locate the valve in the exhaust system at a position where optimum sound attenuation results. This passive, temperature resistant valve is specifically applied to advanced non-conventional power sources which are more challenging to acoustic attenuation.  
         [0013]     Advanced internal combustion power sources for vehicles significantly change their gas flow characteristics during operation. Examples of such advanced non-conventional engine technologies include cylinder deactivation systems, hybrid systems including gas/electric, hydrogen or other types of hybrid source powered vehicles. Use of the passive, temperature resistant valve in such exhaust systems restricts, reflects, and/or routes the exhaust gas stream for the purposes of improving emissions, performance or sound control, or combinations thereof.  
         [0014]     It has been determined by experience that the most effective location for such a passive, temperature resistant valve in the exhaust stream of an advanced internal combustion engine powered vehicle is approximately at the longitudinal midpoint of the exhaust gas flow. It is believed that positioning of the valve at this location most effectively disturbs or breaks up low frequency, long length sound waves being propagated along the exhaust path. This is especially true in cylinder deactivation-type power plants where a portion of the internal combustion cylinders are deactivated under appropriate operating conditions, thereby generating a discontinuity in the gas flow of the exhaust. Other placements of the valve produce acceptable results when the valve is between an engine end of the exhaust system and a longitudinal midpoint thereof. Additionally, it may be acceptable to place the valve closer to the midpoint than to either end of the exhaust system.  
         [0015]     It has additionally been determined that the most effective acoustic attenuation in such exhaust systems is obtained by placing a barrier surface in the gas stream having an approximately perpendicular surface with respect to an axial flow direction of the exhaust stream. Such a transverse barrier surface is believed to set up more effective reflections in the sound waves associated with the exhaust to provide better noise cancellation.  
         [0016]     One example of the use of a passive, temperature resistive valve to control sound in an exhaust system of a cylinder deactivation engine-type vehicle is set forth in the perspective view of  FIG. 1 . With reference to  FIG. 1 , an exhaust system  100  for a cylinder deactivation engine system, such as a V-8 internal combustion engine having the capability of deactivating up to four of the eight cylinders at a time is set forth. System  100  includes manifold exhaust conduits  102  and  104 , respectively, for first and second cylinder banks of the engine (not shown). Situated in conduits  102  and  104  are catalytic converters  106  and  108 , respectively, which are, in turn, coupled via exhaust conduits  110  and  112  to a flexible joint and collector element  114 .  
         [0017]     Flexible joint  114  is coupled to an input of a resonator or mini-muffler  116 . Interior to resonator  116  is at least a first conduit which has an outlet at least partially restricted via a passive, temperature resistant valve element  118 . An outlet of resonator  116  is coupled to an intermediate exhaust conduit  120  which passes the exhaust stream to a muffler  122 . An output of muffler  122  is, in turn, coupled to an exhaust system tailpipe  124 . “L” represents a longitudinal length of exhaust system  100 . As mentioned previously, it has been found that the positioning of the restricting valve  118  is optimally placed approximately in the midpoint along axial distance L, or between the midpoint and the engine, or at least nearer to the midpoint, or L/2 than to either endpoint of the exhaust system apparatus.  
         [0018]     With reference to  FIG. 2 , details of a passive temperature resistive valve suitable for use with the invention and its location with respect to a resonator  116  of  FIG. 1  are set forth. An end  220  of an exhaust conduit  222  extending into the resonator  116  from an inlet thereof is conically widened or flanged at end  220 . Similarly, a peripheral edge of conical valve disk  218  is conically flared to the purpose of the curved or flared interface is to promote good gas flow characteristics. Valve disk  218  lies adjacent end  220  of conduit  222 . Alternatively, an unflared or straight-edged conduit and mating disk  218  may be employed. While valve surface  218  is shown substantially closing off an outlet of conduit  222 , it has been found optimum, in the rest position of valve  118  to maintain an opening annular gap between end  220  of conduit  222  and valve disk  218  of on the order of one to two millimeters for optimum noise attenuation.  
         [0019]     Valve disk  218  is mounted on a guide rod  216 , guided in turn in a guide sleeve  214 . Guide sleeve  214  is held by an assembly sleeve  212  mounted in a gastight fashion to the wall of the housing of resonator  116 . External to the resonator  116 , a valve housing  208  holds a conical spring  204  which is retained by a spring suspension member  202 . The other end of spring  204  bears upon a spring guide disk  206  mounted at the end of the guide rod  216 . In this way, spring  204  has a secure support and distributes its force symmetrically and axially to guide rod  216 .  
         [0020]     Between the spring guide disk  206  and the valve housing  208 , a ring  210  of wire net is placed on guide rod  216  to serve as a damping element to abate noise interference which could otherwise be caused by vibrations of valve disk  218 .  
         [0021]     When the quantity of exhaust gas flowing through conduit  222  into the housing of resonator  116  increases sufficiently—e.g., by activating all eight cylinders of the engine coupled to exhaust system  100 , the impact on valve disk  218  is sufficient to force element  218  away from end  220  of conduit  222  against the force of spring  204  to substantially remove restriction of exhaust gas flow. When the exhaust gas flow discontinuously decreases during engine operation, for example, by deactivating four of the eight cylinders of the engine, the force of spring  204  overcomes the exhaust flow force exerted on member  218 , allowing it to travel to the left as shown in  FIG. 2  to substantially restrict the exhaust flow which sets up reflections of the sound waves accompanying the exhaust flow which tend to be of long length and low frequency under such engine operating conditions. This restriction/reflection effect thereby attenuates sound under the four cylinder engine operating condition without the need to resort to unacceptably large muffler volumes that would otherwise be required.  
         [0022]     Other examples of the use of a passive, temperature resistant valve as described above, would include rerouting of exhaust gases under appropriate gas flow conditions to make more effective and dynamic use of conventional muffler systems or emission control systems.  
         [0023]     Valve  118  as set forth in  FIG. 2 , is “temperature resistant”, in that its spring biasing component is housed exteriorly of the actual flow path of exhaust gases in the systems. Additionally, valve  118  contains no membrane elements conventionally required in active and semi-active valve components which are more susceptible to degradation under high temperature.  
         [0024]     Finally, from  FIG. 2 , it will be seen that exhaust gas flow, whether restricted under low flow conditions or unrestricted under high flow conditions continues its path out of conduit  222  into the interior of resonator  116  and then through outlet opening  226  of resonator  116  into intermediate exhaust conduit  120 .  
         [0025]     Hence, the invention enables the restriction, reflection or rerouting of exhaust gases in power plants which significantly change their gas flow characteristics during operation for the purposes of improving emissions or control of sound in the exhaust system. Additionally, the passive valve, appropriately positioned within the exhaust system offers high temperature, e.g., above 700° C., resistance for periods of time which is required in many advanced internal combustion systems.  
         [0026]     The invention has been described with reference to a detailed description of a preferred embodiment. The scope and spirit of the invention are to be determined from appropriate interpretation of the appended claims.