Patent Publication Number: US-2013227834-A1

Title: Coil spring genset vibration isolation system

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional of U.S. patent application Ser. No. 12/080,206 filed on Apr. 1, 2008, which is incorporated herein by reference. 
    
    
     BACKGROUND 
     The present application relates to electric power generation and the like and more particularly, but not exclusively, relates to a method, system and arrangement for reducing vibration associated therewith. 
     Recreational vehicles are an increasingly popular consumer item due at least in part to the many modern conveniences that may be installed in them. Often, the vehicle carries an electric power genset to electrically power such devices, including, for example, air conditioners, heaters, lighting, entertainment equipment, electronic devices, kitchen appliances and so forth. Frequently, operation of these gensets imparts an undesirable level of vibration in the vehicle cabin. Along with this vibration often comes undesired noise. Accordingly, there is a demand for further contributions in this area of technology. 
     SUMMARY 
     One embodiment of the present application includes a unique technique to reduce vibration and/or noise cause by an electric power genset. Other embodiments include unique apparatus, devices, systems, and methods of genset mounting to reduce vibration and/or noise. Further embodiments, forms, objects, features, advantages, aspects, and benefits of the present application shall become apparent from the detailed description and figures included herewith. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like reference numerals designate corresponding parts throughout the different views. 
         FIG. 1  is a diagrammatic view of a vehicle carrying an electric power generation system. 
         FIG. 2  is a perspective, assembly view of an illustrative electric power generation system. 
         FIG. 3  is a perspective view of the components of the electric power generation system. 
         FIG. 3A  is a detailed view of a portion of an isolation subsystem of the electric power generation system illustrated in  FIGS. 1-3 . 
         FIG. 4  is a perspective view of the components of the electric power generation system illustrated in  FIGS. 1-3 . 
         FIG. 4A  is a detailed view of a portion of an isolation subsystem of the electric power generation system illustrated in  FIG. 4 . 
         FIG. 5  is a side plan view of the electric power generation system illustrating the vertical orientation of coil springs of the isolation subsystem. 
         FIG. 6  is a side plan view of the electric power generation system illustrating the vertical orientation of coils springs of the isolation subsystem that corresponds to the view line  6 - 6  in  FIG. 5  and has a view plane perpendicular to the view plane of  FIG. 5 . 
         FIG. 7  is a top view of the electric power generation system illustrating the horizontal positioning of the coil springs of the isolation subsystem that corresponds to the view line  7 - 7  in  FIG. 5  and has a view plane perpendicular to the view planes of  FIG. 5  and  FIG. 6 . 
         FIG. 8  is a diagrammatic view illustrating one form of the geometric positioning of coil springs for the vibration isolation subsystem. 
     
    
    
     DETAILED DESCRIPTION OF REPRESENTATIVE EMBODIMENTS 
     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is intended, and any alteration or further modification of the illustrated device, and any further application of any principle of the invention as illustrated or described herein is contemplated as would normally occur to one skilled in the art to which the invention relates. 
       FIG. 1  illustrates vehicle  10  in the form of a motor coach  12 . Motor coach  12  includes interior living space  14  and is propelled by coach engine  16 . Coach engine  16  is typically of a reciprocating piston, internal combustion type. To complement living space  14 , motor coach  12  carries various types of electrical equipment  18 , such as an air conditioner  20 . Equipment  18  may further include lighting, kitchen appliances, entertainment devices, and/or such different devices as would occur to those skilled in the art. 
     Motor coach  12  carries an electric power generation system or unit  22  to selectively provide electricity to equipment  18 . Correspondingly, equipment  18  electrically loads the electric power generation system  22 . In one form, electric power generation system  22  is located in a storage bay or other dedicated space  24  of motor coach  12 . The storage bay  24  may include a vented door that provides access to the electric power generation system  22 . In another form, system  22  is positioned between support rails of a chassis for coach  12 . 
     Although illustrated as a motor coach  12 , it should be appreciated by those skilled in the art that the electric power generation system  22  disclosed herein can be utilized in other types of vehicles such as pull along campers, marine craft, truck trailers, travel trailers, work vehicles, and larger recreational vehicles. In addition, the electric power generation system  22  can be utilized in commercial settings, residential settings, and as a portable unit. 
     As set forth in greater detail below, the electric power generation system  22  includes at least an internal combustion engine and a generator that constitute a “genset”, as designated by reference numeral  31 , giving that term its commonly understood meaning. The genset  31  disclosed herein is mounted such that vibrations that are generated by operation of the genset  31  are substantially minimized or reduced so that people utilizing motor coach  12  do not feel transmitted vibrations from the electric power generation system  22 . 
     Referring to  FIG. 2 , a perspective view of a representative electric power generation system  22  is set forth. The electric power generation system  22  includes a two-piece enclosure  30  comprising a basepan or base  32  and a cover  34 . Enclosure  30  houses a genset  31  as well as various other components of electric power generation system  22 . Base  32  and cover  34  are illustrated as being generally rectangular in shape and cover  34  friction fits over an upper lip  36  of the base  32 . In one example, base  32  is made or formed from diecast aluminum such as, for example, A380 diecast aluminum. However, in other embodiments, base  32  may be made of a different material suitable to reduce or eliminate transmitted vibrations from electric power generation system  22  with an isolation subsystem, as further described hereinafter. Collectively, enclosure  30  and genset  31  comprising a form of electric power generating device  28 . 
     Genset  31  includes at least an internal combustion engine  38  coupled to a generator  40 . A starter  42  is coupled to engine  38 , which is controlled by an engine control unit  44  connected with starter  42 , for starting engine  38 . Referring collectively to  FIGS. 1 and 2 , engine  38  is in fluid communication with a fuel tank  26  of motor coach  12 . Fuel tank  26  supplies fuel to engine  38  so that genset  31  can supply electricity to equipment  18 . Engine  38  may comprise a liquid fueled diesel or gasoline internal combustion engine and/or a gaseous fueled type that uses a propane fuel, for example. In one arrangement, propane fueling of genset  31  uses the same fuel source as cooking equipment of coach  12 . 
     In one form, generator  40  is operable to generate an alternating current (“AC”) output voltage signal and, if necessary, a direct current (“DC”) output voltage signal. When engine  38  is started, it drives or rotates generator  40  to cause generator  40  to produce AC electrical power. The portion of generator  40  that rotates or spins is a revolving field type of alternator, but other types of generators may be used. With appropriate power circuitry, generator  40  can be used to produce DC electrical power that may be used to provide DC power certain types of Dc equipment  18  and/or serve as a source of reserve electrical energy that can be converted to AC power for use with or instead of generator  40 . 
     In one form, the AC output voltage is a standard 120 VAC output signal, but other types of output voltage signals may also be generated. In one example, engine  38  has a horsepower rating between 7.0-27 HP and may include anywhere from 1-3 cylinders. Further, in one form generator  40  is capable of generating output power ranging from 2,800-12,500 Watts. The horsepower rating of engine  38  and power rating of generator  40  may vary from the illustrative examples set forth above in alternative embodiments of the present invention. For the purpose of the present invention, it should be noted that engine  38  provides mechanical energy to generator  40 , which in turn, converts the mechanical energy generated by engine  38  into electrical power used by equipment  18  associated with motor coach  12 . 
     Cover  34  includes a panel opening  46  for receipt of a large service panel  48  in the front of electric power generation system  22 . Cover  34  also includes an air inlet  50  that allows ambient air to enter enclosure  30 . As illustrated, genset  31  also includes a cooling system  52  connected with engine  38 . Cooling system  52  includes a cooling impeller assembly  54  and associated housing assembly  56 . Cooling impeller assembly  54  is powered by engine  38  to help cool engine  38 . Electric power generation system  22  includes an exhaust system  60  connected with an exhaust manifold  62  of engine  38 . Exhaust system  60  includes an exhaust gas inlet pipe  64  connected with exhaust manifold  62  of engine  38 . In addition, exhaust system  60  includes a bracket assembly  66  that connects the exhaust system  60  to a plurality of connection members  68  (See  FIG. 3 ) of generator  40 . Connection members  68  may also be located on engine  38  or other respective components of genset  31 . 
     Exhaust gas inlet pipe  64  is connected with a muffler  70  of exhaust system  60 . Muffler  70  silences operation of engine  38  and may be used to provide emissions treatment of exhaust gas exiting engine  38  as desired. An exhaust gas outlet pipe  72  is connected with an output of muffler  70 . Exhaust gas outlet pipe  72  protrudes through an aperture  74  (See  FIG. 4 ) in base  32  and may be connected with an exhaust pipe (not shown) of motor coach  12 . 
     Referring collectively to  FIGS. 3 and 3A , electric power generation system  22  includes a vibration isolation subsystem  80  in the form of a support mechanism  81 . In one form, vibration isolation subsystem  80  supports the mass of engine  38 , generator  40 , cooling system  52 , and exhaust system  60 . In other forms, vibration isolation subsystem  80  supports at least engine  38  and generator  40 . Vibration isolation subsystem  80  substantially reduces or eliminates the transmitted vibration of genset  31  during operation. Computer analysis of vibration isolation subsystem  80  reveals that the transmitted vibratory energy of genset  31  is reduced over 100 times from prior elastomer based isolation systems. 
     Vibration isolation subsystem  80  includes at least a first support tower or boss  82 , a second support tower or boss  84  and a third support tower or boss  86 , but may include additional support towers in alternative forms. These bosses  82 ,  84 , and  86  are alternatively designated support members or pillars  87 . Support towers  82 ,  84 , and  86  protrude upwardly from a lower surface  88  of base  32 . As set forth in greater detail below, support towers  82 ,  84 , and  86  protrude upwardly at predetermined heights in order to properly support the mass of genset  31  such that genset  31  is properly supported to reduce transmitted vibrations of genset  31  during operation. The support towers  82 ,  84 , and  86  are geometrically positioned, both vertically and horizontally, such that the mass of genset  31  is supported in a manner that reduces or eliminates the transmitted vibratory energy generated by operation of genset  31 . Although three support towers  82 ,  84 , and  86  are illustrated in this form, it should be appreciated that in other forms more than three support towers and corresponding elements described below may be used. 
     Support towers  82 ,  84 , and  86  are illustrated has having a generally cylindrical shape in  FIGS. 3 and 3A . Other shapes such as rectangular-shaped, and so forth are envisioned. An upper surface  90  of each respective support tower  82 ,  84 , and  86  includes a dome-shaped retaining member  92  that protrudes upwardly a predetermined distance from upper surface  90  to receive a respective vibration isolation device  91  (partially shown in  FIGS. 3 and 3A ). For the depicted embodiment, device  91  includes spring dampening sleeve  94  positioned over each retaining member  92  of the support towers  82 ,  84 , and  86 . Spring dampening sleeve  94  includes a lower surface that rests on upper surface  90  of support towers  82 ,  84 , and  86 . In one form, spring dampening sleeve  94  comprises an elastomer-based sleeve, such as a Buna-N based durometer elastomer, but could be manufactured from other suitable material as well. Spring dampening sleeve  94  has been found to reduce high frequency noise that is generated during operation of genset  31 . 
     In addition to sleeve  94 , vibration isolation devices  91  also each include a flat washer  98  and three springs  102  (more specifically designated springs  102   a ,  102   b , and  102   c ). An outside upper rim surface  96  of spring dampening sleeve  94  is configured to receive a flat washer  98  that fits over a dome-shaped portion  100  of spring dampening sleeve  94 . Flat washer  98  fits over dome-shaped portion  100  of spring dampening sleeve  94  and rests on outside upper rim  96 . Flat washer  96  protects spring dampening sleeves  94  from damage that may be caused by vibration of a plurality of coil springs  102   a - c  that are positioned on an upper surface of each respective flat washer  98 . As set forth in detail below, coil springs  102   a - c  support the weight or mass of genset  31  on support towers  82 ,  84 , and  86 . Coil springs  102   a - c  may be manufactured using several materials, such as coated chrome silicon or 17-7 stainless steel, for example. 
     Referring to  FIGS. 4 and 4A , genset  31  includes a plurality of spring retention members  110  that extend off of or are otherwise connected to genset  31 . Spring retention members  110  may be connected to a gearcase  112  of generator  40 , an engine block  114  of engine  38 , or at a variety of other predetermined locations of genet  31 . Although not illustrated, in one form, genset  31  includes three spring retention members  110  that are located on various parts of genset  31 . Spring retention members  110  are oriented or positioned at predetermined locations on genset  31  such that an upper end  115  of coil springs  102   a - c  fit within a pocket  116  of spring retention members  110 . Spring retention members  110  are positioned on genset  31  such that pockets  116  line-up with each respective support tower  82 ,  84 , and  86 . Although spring retention member  110  is illustrated as a cast part of genset  31 , it should be appreciated that in other forms spring retention member  110  may comprise a bolt-on bracket member that is connected to genset  31 . 
     Referring to  FIG. 5 , in one form, genset  31  comprises an engine  38 , generator  40  (not visible), cooling system  52 , and exhaust system  60 . All of these respective components of genset  31  have a predetermined mass or weight when assembled or connected to one another or otherwise assembled. Genset  31  is positioned on base  32  such that genset  31  rests on top of isolation subsystem  80 . Genset  31  rests on top of coil springs  102   a - c  and gravity forces genset  31  to remain on top of isolation subsystem  80 . In particular, genset  31  is positioned on top of coil springs  102   a - c  such that upper portion  115  of each respective coil spring  102   a - c  fits within a respective spring pocket  116  of each spring retention member  110  associated with genset  31 . See  FIG. 3 . Although upper portion  115  of coil spring  102   a  is illustrated as fitting within an inside diameter of spring pocket  116 , in another representative form, spring retention member  110  may include a retaining member  92  (See  FIG. 3A ) that fits within an inside diameter of coil spring  102   a . The height of springs  102   a - c  are designed such that changes in the height of two respective coil springs force resultant changes in the height of the other coil spring to keep the coil springs  102   a - c  in-plane with the center of gravity of genset  31 . 
     As illustrated in  FIGS. 5-7 , which more clearly illustrates the orientation of coil springs  102   a - c , genset  31  has a known center of gravity  120  which is represented as a cross-hair in  FIGS. 5-7 . The center of gravity  120  represents the average location of the weight of genset  31 . As previously set forth, when installed on top of isolation subsystem  80 , genset  31  rests on top of upper surface  115  of coil springs  102   a - c . In addition, the location of support towers  82 ,  84 , and  86  in base  32 , and hence coil springs  102   a - c , is such that a reference plane  122  (See  FIG. 6 ) through upper portion  115  of coil springs  102   a - c  coincides with the center of gravity  120  of the mass of genset  31  as it rests on springs  102 . It should be appreciated that the exact position of genset  31  may vary with movement and force applied such as when one or more of springs  102   a - c  are dynamically compressed. Accordingly, the location of intersection of reference plane  122  through one or more of springs  102   a - c , may vary during operation while still passing through the center of gravity of genset  31 . Alternatively or additionally, the point of spring intersection by reference plane  102  may vary from one apparatus to the next, while still remaining coincident with the center of gravity  120  of genset  31 . In further embodiments, it should be appreciated that the reference plane intersection through center of gravity  120  may not always (or ever) be exactly coincident, but instead is approximate—being within an acceptable tolerance range. In one preferred form, this tolerance range is plus or minus ten percent (+/−10%) of the distance spanned by any of the springs  102   a - c  between the respective support tower  82 ,  84 , or  86  and the genset (or other vibration isolator) while the genset is at rest thereon. In a more preferred form, this tolerance range is plus or minus five percent (+/−5%). In an even more preferred form, this tolerance range is plus or minus one percent (+/−1%). 
     In other representative forms, reference plane  122  can pass through any portion of coil springs  102   a - c . In one nonlimiting form, support towers  82 ,  84 , and  86  are positioned as high as possible so that coil springs  102   a - c  can be located as high as possible while still approximately lying in reference plane  122 . 
     In another representative form, support towers  82 ,  84 , and  86 , coil springs  102   a - c  and spring retention members  110  are specially oriented in relation to genset  31  such that the mass or weight of genset  31  is approximately equally supported by each respective coil spring  102   a - c . In one nonlimiting form, the mechanical load distributed among isolation devices  91  is the same within a tolerance of plus or minus 10 percent (+/−10%). In one form, coil springs  102   a - c  are relatively soft coil springs, equally loaded with a stiffness ratio (axially and laterally) of 1:1. Coil springs  102   a - c , in alternative forms, may include dead coils to allow for softer coil springs. In addition, coil springs  102   a - c  may comprise hourglass shaped coil springs such that in a surge condition, the upper and lower coils of the springs would be dead and stop the surge. The vertical heights of coil springs  102   a - c  may be increased or decreased to allow for variations in geometry limitations. 
     Referring to  FIG. 8 , which illustrates a top view of coil springs  102   a - c  in relation to the center of gravity  120  of genset  31 , in one form three coil springs  102   a - c  are used in isolation subsystem  80 . In this illustrative example, the three coil springs  102   a - c  are spaced apart from one another by 120 degrees (120°) and approximately at the same vertical level as the center of gravity  120 . In addition, coil springs  102   a - c  are located an equal lineal distance from the center of gravity  120  of the genset  31 . Although not illustrated, in other examples four coil springs may be used that are spaced 90° apart an equal distance from the center of gravity  120 . Yet in another example, five or more coil springs may be used to support the mass of genset  31 . 
     Referring back to  FIGS. 5-7 , in other forms, coil springs  102   a - c  may be used that are not positioned equally spaced apart from the center of gravity  120 . Further, coil springs  102   a - c  also may not be spaced apart 120° from the center of gravity  120  of the genset  31  or at the same vertical height. As illustrated in  FIG. 6 , in this form, the tops or upper surface  115  of coil springs  102   a - c  are in-plane with the center of gravity  120  of the mass of the genset  31  as it rests on the springs. In addition, each of the coil springs  102   a - c  are arranged in relation to genset  31  so that each coil spring  102   a - c  is approximately equally loaded, both axially and vertically, by the mass of genset  31 . For example, in the example illustrated in  FIGS. 5-7 , coil spring  102   a  has a vertical load of 26.9 pounds and an axial load of 26.9 pounds, coil spring  102   b  has a vertical load of 27.0 pounds and an axial load of 27.0 pounds, and coil spring  102   c  has a vertical load of 26.9 pounds and an axial load of 26.9 pounds. 
     Referring to  FIG. 3 , as set forth above vibration isolation subsystem  80  includes support members  82 ,  84 , and  86  that protrude upwardly from lower surface  88  of base  32 . Support members  82 ,  84 , and  86  are three-dimensionally oriented, both vertically and horizontally, in base  32  such that an upper surface  115  of coil springs  102   a - c  lie in plane with the center of gravity  120  of genset  31 . In addition, the three-dimensional orientation of support members  82 ,  84 , and  86  is such that the mass or weight of genset  31  is approximately equally distributed on coil springs  102   a - c.    
     Many embodiments of the present application are envisioned. In one form, a system is disclosed that includes an electrical power generation unit having an internal combustion engine coupled to a generator. The system also includes a base having a first support tower, a second support tower, and a third support tower. Each support tower protrudes upwardly from the base a predetermined distance. A coil spring is positioned between an upper surface of each support tower and a respective lower surface of the electrical power generation unit. Each said support tower is oriented on the base such that each coil spring is equally loaded by the weight of the electrical power generation unit. 
     In another form, a system is disclosed that includes an electric power generating device including an internal combustion engine coupled to an electric power generator, the electric power generating device including three mounting sites; a support mechanism to engage the electric power generating device and bear mechanical load thereof, the support mechanism including: a base including three support pillars, the support pillars each extending away from the base and each providing a corresponding mount at a predetermined distance from the base; and three vibration isolation devices each positioned between a respective one of the three mounting sites and the corresponding mount of a respective one of the support pillars, where a reference plane through each of the vibration isolation devices approximately intersects a center of gravity of the electric power generating device. 
     In yet another form, an apparatus is disclosed that includes a genset for generating electric power. The apparatus also includes a base including a plurality of bosses that protrude upwardly each a respective predetermined height from a surface of the base. A plurality of coil springs are positioned between an upper surface of each of the bosses and a respective mounting member of the genset, wherein the bosses and the mounting members are positioned in relation to the genset such that each respective coil spring is approximately equally loaded by the weight of the electric power generation unit. 
     In still another form, a method is disclosed that includes: providing a genset; providing a base having a plurality of support members protruding upwardly from a lower portion of the base; placing a coil spring on top of each the support member; and positioning the genset on top of the coil springs, wherein the support members are positioned in the base such that each coil spring is approximately equally loaded by the genset. 
     Yet another form is directed to a system comprising: means for providing a genset; providing a base having a plurality of support members protruding upwardly from a lower portion of the base; means for placing a coil spring on top of each the support member; and means for positioning the genset on top of the coil springs, wherein the support members are positioned in the base such that each coil spring is approximately equally loaded by the genset. 
     In another form, a system is disclosed comprising a genset; a base; a vibration isolation subsystem including a plurality of support members each three-dimensionally oriented about a center of gravity of the genset in the base. Each of the support members includes a coil spring positioned between an upper surface of the support member and a spring retention member of the genset. The three-dimensional orientation of the support members in the base is such that each coil spring is approximately equally loaded by the genset. 
     A further form includes: an electric power generating device including an internal combustion engine coupled to an electric power generator, the electric power generating device including at least three mounting sites; and a support mechanism to engage the electric power generating device and bear mechanical load thereof. The support mechanism includes: a base including three support pillars, the support pillars each extending away from the base and each providing a corresponding mount at a predetermined distance from the base; and three vibration isolation devices each positioned between a respective one of the three mounting sites and the corresponding mount of a respective one of the support pillars, the vibration isolation devices each bearing one third of the mechanical load of the electric power generating device with a tolerance of plus or minus 10% and suspending at least a portion of the electric power generating device between the support pillars above the base. 
     Still a further form comprises: an electric power generating device including at least a portion of an internal combustion engine and an electric power generator mechanically coupled to the internal combustion engine, the electric power generating device including three mounting sites and a support mechanism to engage the electric power generating device and bear mechanical load thereof. The support mechanism includes: a base including three support members, the support members each extending from the base and each providing a corresponding mount; and three vibration isolation devices each positioned between a respective one of the three mounting sites and the corresponding mount of a respective one of the support members, the vibration isolation devices each bearing a respective portion of the mechanical load of the electric power generating device, the support mechanism being configured to define a plane coincident with a center of gravity of the electric power generating device that passes between the respective one of the mounting sites and the corresponding mount of each of the support members. 
     Another form comprises: providing a genset including an internal combustion engine coupled to an electric power generator that has three mounting sites; supporting the mechanical load of the genset with a support mechanism that includes a base and three support pillars each extending away from the base, the pillars each providing a corresponding mount at a predetermined distance from the base; reducing vibration with three vibration isolation devices each positioned between a respective one of the three mounting sites and the corresponding mount of a respective one of the support pillars; and positioning the three vibration isolation devices such that changes in the position of two of the vibration isolation devices causes a resultant change in another of the vibration isolation devices to keep the vibration isolation devices approximately in-plane with a center of gravity of the genset. 
     In yet another form, a method is disclosed that includes: providing a genset; providing a base having a plurality of support members protruding upwardly from a lower portion of said base; placing a coil spring on top of each said support member; and positioning said genset on top of said coil springs, where said coil springs are vertically oriented in relation to said base such that a respective portion of each said coil spring lies in a plane coincident with a center of gravity of the genset. 
     Any theory, mechanism of operation, proof, or finding stated herein is meant to further enhance understanding of the present invention and is not intended to make the present invention in any way dependent upon such theory, mechanism of operation, proof, or finding. It should be understood that while the use of the word preferable, preferably or preferred in the description above indicates that the feature so described may be more desirable, it nonetheless may not be necessary and embodiments lacking the same may be contemplated as within the scope of the invention, that scope being defined by the claims that follow. In reading the claims it is intended that when words such as “a,” “an,” “at least one,” “at least a portion” are used there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. Further, when the language “at least a portion” and/or “a portion” is used the item may include a portion and/or the entire item unless specifically stated to the contrary. While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the selected embodiments have been shown and described and that all changes, modifications and equivalents that come within the spirit of the invention as defined herein or by any of the following claims are desired to be protected.