Abstract:
The present invention is a gasoline engine driven electrical generating system for use in confined space enclosures wherein all routine servicing can be accomplished from the single exposed side. The ambient operating temperature of the confined enclosure is minimized by a combination of component locations, sizing and a thermal siphoning exhaust enclosure. Through the use of an electronic fuel management system, throttle body furl injection and a catalytic converter all current EPA NOX emission standards can be met.

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to a extremely compact EPA certifiable gasoline engine driven electrical generating system (a “genset”) and more particularly, to a compartment contained genset that may be completely single side serviced in situ, having access to all the routine maintenance components and access points. 
   Specialty motorcoaches, like intercity traveling medical facilities, make the most out of the least amount of space. To stay competitive in today&#39;s marketplace motorcoaches use multiple slide out side and rear compartments. While maximizing and increasing interior space these slide outs do restrict the usable space below the motorcoach&#39;s floor deck. The current industry standard size for a genset compartment (for a genset and it&#39;s compartment housing, excluding the muffler) is approximately 34 inches long, 25 inches deep and 26 inches high. This movement toward less usable space below the motorcoach&#39;s floor deck has occurred at the same time as motorcoach retailers have seen an increase in the secondary electrical demands of the motorcoach. 
   Generating more electrical power in a motorcoach can be accomplished two ways. One way is to operate the genset at higher running speeds (which results in an undesired increase in noise, heat output, vibration, mechanical wear and servicing.) Another way is to use larger engines and generators. These brutes can output more power running at lower speeds, but because of their physical volume, require larger housing compartments. Enlarging a genset compartment upwards or downwards necessitates a protuberance in the motorcoach floor or a reduction in the motorcoaches&#39;s ground clearance. Unfortunately, for aesthetical reasons motorcoach designers seek smooth floors and a straight visible door line about the motorcoach. 
   The longer gensets are too large for the existing available spaces along the length of the motorcoach with the slide outs. Since the available space for genset compartments is limited, if a larger genset is installed it will cramp the compartment, hinder access to maintenance points, and result in a higher compartment ambient air temperature which will be forced through the generator housing interior causing premature generator failure. Add to this conundrum, the need for additional mechanical equipment required to pass the updated EPA NOX emission and other regulations, and the problem magnifies. Thus, the need for diminutive, high electrical output gensets evolved. 
   The development of space restricted gensets has an additional problem to overcome. As with all partially enclosed heat generating engines, heat buildup, especially from the exhaust components is a problem. Generator coils and windings have narrow operating temperatures and the cooling air circulated through them must also be relatively free of excess airborne particulate. The gasoline engines themselves are prone to overheating in the enclosed compartments and must possess efficient heat removal capacity. To complicate matters, side access doors often must remain closed when the genset is operating, further restricting air flow and containing residual heat in the compartment. 
   Henceforth, a cool running, quiet, low speed, long life, small genset that can be serviced in situ and capable of meeting current EPA standards while producing a large power output, would fulfill a long felt need in the motorcoach industry. This new invention utilizes and combines known and new technologies in a unique and novel configuration to overcome the aforementioned problems and accomplish this. 
   SUMMARY OF THE INVENTION 
   The general purpose of the present invention, which will be described subsequently in greater detail, is to provide a new genset that is able to fit into a size restricted enclosure of approximately 12.8 cubic feet and provide up to 17 kW of electrical power. It has many of the advantages mentioned heretofore and many novel features that result in a new genset which is not anticipated, rendered obvious, suggested, or even implied by any of the prior art, either alone or in any combination thereof. 
   In accordance with the invention, an object of the present invention is to provide an improved motorcoach genset capable of not returning fuel to the motorcoach&#39;s fuel tank as to comply with EPA regulations. 
   It is another object of this invention to provide an improved genset capable of meeting or exceeding current EPA NOX emission standards. 
   It is a further object of this invention to provide a single side access designed genset for motorcoaches that can be fully serviced in situ. 
   It is still a further object of this invention to provide for a genset that does not generate enough heat in an enclosed operation to overheat the generator or engine under a wide variety of operating conditions. 
   It is yet a further object of this invention to provide a quiet, low speed genset with an enhanced radiative exhaust heat removal capability to maintain lower genset compartment operating temperatures. 
   The subject matter of the present invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. However, both the organization and method of operation, together with further advantages and objects thereof, may best be understood by reference to the following description taken in connection with accompanying drawings wherein like reference characters refer to like elements. Other objects, features and aspects of the present invention are discussed in greater detail below. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a front side view of the genset in the genset compartment housing unit showing the general arrangement of all components; 
       FIG. 2  is a top side view of the genset with the alternate embodiment shaft driven cooling fan in the genset compartment housing unit, showing the general arrangement of all components; 
       FIG. 3  is a top side view of the genset without the exhaust header pipe, showing the alternate embodiment shaft driven cooling fan and front side mounted alternator; 
       FIG. 4  is a top side view of the genset without the catalytic converter and exhaust header pipe, showing the preferred embodiment dual electric cooling fans; 
       FIG. 5  is a back side view of the genset in the genset compartment housing unit showing the back side of the housing unit and the radiator; 
       FIG. 6  is a front view of a motorcoach with an installed genset and genset housing unit illustrating the preferred embodiment exhaust system; 
       FIG. 7  is a detailed view of the components of the genset exhaust system&#39;s heat riser components; 
       FIG. 8  is a detailed view of the components of the genset preferred embodiment exhaust system utilizing a bent exhaust pipe rather than a deflector; 
       FIG. 9  is a back side view of the back side plate of the genset compartment housing unit showing the sound silencing louvers; 
       FIG. 10  is a front view of the adjustable alternator bracket; and 
       FIG. 11  is a front side view of the genset as in  FIG. 1  but with the cold air intake duct snorkel tube installed. 
   

   NOTE:  FIGS. 1 ,  2 ,  3 ,  4  and  6  show the genset with the cold air intake duct snorkel tube removed for clarity of illustration. 
   DETAILED DESCRIPTION 
   Pancake style generators are known for their short longitudinal axis style bodies. Here, to accommodate tight space configurations, the front (fan side) of a pancake generator is directly coupled to the back (flywheel end) of a conventional (driver) gasoline engine. To keep the overall dimension along the longitudinal axis of this assembly at the absolute minimum required, the system as discussed herein was invented. 
   The low emission, single side access gasoline engine driven electrical generating system of the present invention, (hereinafter “genset”), comprises a four-stroke four cylinder combustion engine directly coupled to a pancake style electrical generator, capable of delivering 13 KW at 120/240 VAC (50/50 Amp) and 60 Hz while idling at an 1800 rpm engine speed, or with a larger internal displacement engine, (17 KW at 1800 RPM) utilizing: 
   a catalytic converter; 
   a thermal syphoning heat riser; 
   computerized direct throttle body fuel injection system; 
   a pressurized engine coolant containment system; 
   a front side mounted oil filler tube/dipstick combination; 
   a front side mounted fuel cell; 
   a rear side mounted high capacity radiator and high CFM flow fan assembly with dual electric fans or a 90 degree shaft drive; 
   a rear side radiator grill louver system; 
   a front side mounted fuel injection Electronic Control Unit (ECU) receiving input signals from a 
   front mounted hall effect engine speed sensor, 
   front mounted coolant temperature sensor, 
   front mounted intake air temperature sensor 
   front mounted manifold pressure sensor, and 
   top mounted exhaust gas oxygen sensor; 
   a front side mounted throttle plate motor; 
   a front side mounted fuel injector; 
   a front side mounted electrical power management and monitoring panel; 
   long life platinum spark plugs; 
   a catalytic converter; 
   a front side mounted air intake cannister; 
   a front side mounted engine starter; 
   a front side mounted starter solenoid; 
   a front side mounted coil; 
   a front side mounted distributor; 
   a front side mounted wiring harness; and 
   a front side mounted engine alternator driven by the main crankshaft pulley. 
   This improved 13 KW genset was invented primarily to meet the industry standard space restrictions of a genset compartment housing unit which is approximately 34 inches long by 26 inches high by 25 inches deep (12.8 cubic feet) for housing a genset minus catalytic converter and exhaust muffler, on a motorcoach; while passing the EPA NOX emission standards for the genset engine and not compromising the motorcoach engine&#39;s EPA fuel return regulations. The cramped quarters necessitated inventing a new genset design that could be serviced from the front or accessible side of the unit. Much of the technology is known in the industry and although discussed, is not the subject of this invention. 
   The detailed description and operation of the present invention is best understood in conjunction with the accompanying figures. 
   Referring to  FIGS. 1 ,  2  and  6 , it can be seen that the genset  2  utilizes a four cylinder gasoline engine  4  matingly engaged at the flywheel to the fan end of the rotor shaft of a pancake style electrical generator  6 . The length of the complete genset unit is the distance bounded between the face of the engine crankshaft pulley  59  and the face of the generator&#39;s exciter rotor diode cover  98 . This length is approximately 36 and ⅝ inches. The industry standard dimensions for a genset housing  18  to be mechanically affixed to the chassis/undercarriage of a motorcoach  62  so as to fit in a genset compartment  8  is approximately 34 inches (plus or minus ¾ of an inch) by 26 inches in height by 25 inches in depth. Although the 34 inch length limitation discussed above is determined by the motorcoach&#39;s aesthetic appearance, slideouts and frame design, there is slightly more length behind the motorcoach&#39;s body panels and the genset compartment door  74  to allow for this 3 inch protuberance from the genset housing unit  18 . 
   Since the length that will fit comfortably in a genset compartment housing unit  18  is approximately 33, and ½ inches and the length of the present invention is 36 and ⅝ inches, a circular orifice has been cut in the left side plate of the housing unit  88  to accommodate the extension of the generator exciter diode cover  98  outside of the housing unit  18  by approximately three inches. This allows the 34 inch wide genset housing unit  18  to hold and support the 36 and ⅝ inch long genset  2  and still fit into the genset compartment  8 . 
   The genset  2  utilizes a 1274 cc internal displacement Nissan CG13, four cylinder, four cycle gasoline engine  4  coupled to a Marathon four pole, brushless, revolving field electric pancake generator  6  having a synchronous speed of 1800 rpm for a 60 Hz output frequency. (1500 rpm for 50 Hz) To achieve the 17 KW output a nominal 2000 cc internal displacement Nissan engine with a shorter flywheel housing is used, however engines from other manufacturers could be utilized provided their overall dimensions were substantially similar. All genset systems have been designed for single front side access when the genset  2  resides in it&#39;s steel housing unit  18  within a motorcoach&#39;s genset compartment  8 , and most importantly, to minimize the genset length. 
   The genset fuel is drawn from the motorcoach&#39;s fuel tank by an accumulator pump inside the front side mounted fuel cell  116 . The inlet line from the motorcoach&#39;s fuel tank is not visible in the drawings but resides behind the fuel cell  116  and the genset  2 . The sealed fuel cell  116  also contains a high pressure fuel injector pump that moves the fuel to the variable orifice solenoid fuel injector which is mounted on the front side of the intake manifold/throttle body assembly  42  below the front side mounted throttle plate motor  35 . The excess fuel at the injector is forced down a bypass line back to the fuel cell  116 . In this manner there is no fuel returned to the motorcoach&#39;s fuel tank. (New EPA regulations for the year 2004 dictate that there cannot be any fuel returned to a motorcoach&#39;s fuel tank that was drawn out to support auxiliary equipment.) 
   The amount of fuel delivered into the intake manifold/throttle body assembly  42  is determined by a front side mounted Electronic Control Unit (ECU)  28  (also known as an electronic fuel management system). The ECU  28  generates and sends the fuel injector solenoid a pulse length signal based on an algorithmic determination using engine speed (RPM) engine coolant temperature, intake air temperature, intake air manifold absolute pressure and exhaust gas oxygen content. All but the exhaust gas oxygen sensor  38  are front mounted. Use of an ECU allows the engine  4  to run at peak efficiency with very low NOX emissions. 
   The engine speed signal comes from a hall effect sensor  30  mounted on the front side bell housing opening, with the hall effect elements mounted on the 288 teeth of the flywheel. The use of multiple hall effect elements results in a much larger number of sensed “events” per engine revolution. In this manner there is a much quicker and accurate engine speed signal sent to the ECU  28 . This faster signal allows a quicker governed adjustment response from the ECU  28  to adjust fuel injection to compensate for engine load with the fluctuations of electrical load. 
   The engine coolant temperature sensor  32  is front side mounted into the engine cylinder head below the distributor  40 . The intake air temperature sensor  34  and the manifold absolute pressure sensor  36  are each front side mounted in the intake manifold/throttle body assembly  42 . The exhaust gas oxygen sensor  38  is mounted on the short exhaust header pipe  44  at the rear top side of the engine  4  before the catalytic convertor  46 . The short header exhaust pipe  44  is bent to rise near the top of the engine  2  so as to allow access to the sensor from the front side. 
   An emergency low oil pressure shutdown sensor  48  is mounted in a hole extending into the oil gallery that is tapped into the front side of the engine block. 
   The engine  4  draws its air through an intake cannister  50  that is front side mounted in close proximity (approximately eight inches) to the muffler  52 . A cold air intake snorkel tube  132  is connected at one end to the intake cannister  50  by a standard gear clamp  134  and extends through a duct orifice  136  in left side plate  88 . In this manner, residual, radiant heat from the muffler  52  and engine  4  is not drawn into the running engine  2  where it could used in the combustion cycle, thereby affecting the NOX emissions. This feature, in conjunction with the exhaust heat riser system  10 , helps to maintain an ambient air temperature genset compartment  8 . Tests have shown with an outside ambient air temperature of 70 degrees F. the air temperature at the entrance to the intake cannister  50  is 74 degrees F. 
   The genset  2  utilizes a sealed pressurized coolant system operating at approximately 18 to 21 psi. This raises the boiling point of the coolant and eliminates the need for a radiator expansion header tank and a radiator filler cap. (It is noted that the use of this type of coolant system is also facilitated because the engine  4  runs at a constant rpm and in a narrow coolant temperature range such that there are no rapid fluctuations in coolant volume or coolant system pressure.) The pressurized accumulator tank  10  has an inlet line feeding from the top of the radiator  12  and an outlet line  14  that ties into the inlet of the water pump. The accumulator tank  10  is partially full and essentially “sits” on the system as a pressure and volume surge compensator. 
   Referring to  FIGS. 3 ,  4  and  5  it is illustrated that the cooling system radiator  16  is a high heat removal capacity radiator (sized approximately 35% larger than one designed for conventional automotive use with a similarly sized engine) that is mounted in the genset compartment housing unit  18  behind the genset  2  such that their longitudinal axes are parallel. This unconventional placement helps to reduce the overall length of the genset  2 . Air is moved through the radiator cooling fins  20  in either of two fan configurations. 
   The preferred embodiment ( FIG. 4 ) utilizes two substantially similar electric 1250 cfm capacity fans  22  housed between the genset  2  and the radiator  16  that directs the flow of air away from the genset  2  and through the radiator fins  20 . The electric fans  22  have an automatic cutout temperature switch that only allows the fans  22  to run when the coolant temperature exceeds 170 degrees F. This configuration is quieter and the dual fans  22  offer limited protection from overheating by virtue of their partial redundancy. The alternate embodiment ( FIG. 3 ) utilizes a single larger 2400 cfm capacity fan  24  mechanically coupled to one end of an right angled shaft drive  54  having a driven pulley  56  mounted at it&#39;s distal end which is rotated by a belt  58  looped around the crankshaft driver pulley  59 . This alternate embodiment arrangement operates whenever the genset  2  operates. It&#39;s drawback is that the right angled shaft drive  54  is loud and susceptible to belt slippage or belt failure. 
   Since most electrical generators should not operate continually in elevated ambient air temperatures exceeding 104 degrees F., it is important that the air temperature in the compartment  8  be maintained as low as practical. Thus, removing the hot air from the radiator  60  or exhaust before it accumulates in the compartment  8  is essential. 
   The genset exhaust system comprises an exhaust manifold, exhaust header pipe  44  with exhaust gas oxygen sensor  38 , flex coupling  58 , catalytic converter  46 , and muffler  60 . All but the catalytic converter  46  and muffler  60  are rear side mounted. The exhaust header pipe  44  is bent into an inverted “U” shaped configuration such that approximate center of the apex of the exhaust header pipe  44  rises to the top of the genset  3 . The exhaust gas oxygen sensor  38  is mounted at the apex of the exhaust header pipe  44  and is thus accessible from the front side. The catalytic converter  46  is located directly beneath the muffler  60  and is also accessible for maintenance from the front side. 
   Looking now at  FIGS. 6 ,  7  and  8  it can be seen that there are two embodiments of the genset exhaust system, differing only in the manner of exhausting the gasses after the exit end of the muffler  60 . The preferred embodiment exhaust system dumps exhaust gases above the roof line  64  of the motorcoach  62  and comprises a heat riser box  66 , heat riser tube  68 , exhaust pipe  70  and muffler  60 . The alternate embodiment exhaust system dumps its exhaust gasses below the motorcoach chassis and does not have a heat riser box  66 , heat riser tube  68  and may include an optional spark arrester. (The spark arrester is a US Forrest Services requirement for bottom exiting muffler exhausts.) Connections to the muffler  60  and catalytic converter  46  are accomplished via “O” ring ball and socket type muffler clamps  72 . 
   The preferred embodiment exhaust system dusts the exhaust gasses above the roof line  64  which reduces the noise level experienced from the ground level but most importantly, utilizes the heat riser box  66  and riser tube  68  which reduces the genset compartment air temperature by about two degrees F. with the compartment door  74  open, and about three degrees F. with the door  74  closed. Although the hot exhaust can be efficiently drawn from the engine  4 , the catalytic converter media and the muffler  60  retain and radiate heat that warms the genset compartment  8 . Radiantly heated air from around the muffler  60  and catalytic converter  46  is partially contained in a 11 inch wide by 26 inch long by 13 inch high heat riser box  66 . The heat riser pipe  68  is mounted on the top side of the heat riser box  66  about a circular orifice  78  in the box  66 . The exhaust pipe  70  is of a smaller diameter than the nominal five inch heat riser pipe  68  and passes through the center of the heat riser pipe  68  such that they share the same longitudinal axis. The exit end of the exhaust pipe  70  terminates in an angled deflector  80  which protrudes slightly beyond the heat riser tube&#39;s exit end, above the motorcoach&#39;s rear roof line  64 , although a simple bent exhaust pipe  82  ( FIG. 8 ) has shown to perform satisfactorily. The exhaust pipe  70  is secured in the approximate longitudinal center of the riser pipe  68  by muffler clamps  72  at the top. A flange  76  adapted to fit onto the heat riser tube  68  secures the assembly to the motorcoach roof. The heated air in the box exits up the riser tube  68  with it&#39;s temperature rising slightly as it passes alongside the exhaust pipe  70 . This creates a thermal siphoning effect in the annulus  84  between the exhaust pipe  70  and the heat riser tube  68  which increases the exiting flow of warm gasses from the heat riser box  66  to the atmosphere above the motorcoach  62 . When the genset  2  is operated in a moving motorcoach  62  this thermal siphoning effect is enhanced. 
   Referring again to  FIG. 1 , the genset compartment housing unit  18  is a three sided steel container with a solid plate bottom  86  that serves to support the genset  2  and connect it to the undercarriage or chassis of the motorcoach  62 . The left side plate  88 , right side plate  90  and rear side plate  92  are bolted together through elongated oval slots that allow slight variations in the housing unit  18  dimensions. This allows compensation for fabrication variances in the motorcoach chassis as well as variances in different manufacturer&#39;s motorcoaches. The housing unit&#39;s bottom plate  86  is slightly above the visible line of the motorcoach body when the genset compartment&#39;s door  74  is closed. There is no front side or top side to the housing unit  18 . The genset  2  is mounted to the floor plate  86  of this housing unit  18  with modified motor mounts. 
   Referring to  FIGS. 5 and 9 , it can be seen that the rear side plate  92  has cutouts  94  that allow the flow of air passing across the radiator fins  20  to exit. There are flexible but resilient flap style louvers  96  that are attached with mechanical fasteners  118  to the rear side plate  92  cover the external side of the cutouts  94 . These serve to quiet the genset noise and prevent the ingress of particulate contaminants to the genset compartment  8  while the motorcoach  62  is moving. The louvers  96  are opened by the differential in air pressure between the sides of the louvers  96  caused when the cooling system fan/s are running. There are three separate louvers  96  in the preferred embodiment however, testing has shown that there is a wide variation in the number and sizes of louvers  96  that will work and not reduce the flow of cooling air from the fans enough to cause temperature problems. 
   The right side plate  90  of the housing unit  18  has a cutout covered by a removable plate that allows access to the alternator pulley and water pump pulley, as well as the water pump and starter motor. The left side plate  88  has a circular cutout to accommodate the extension of the generator exciter diode cover  98  outside of the housing unit  18  by approximately three inches. There is a 13 inch by 14 inch raised protective plate  100  around the exciter diode cover circular cutout that bolts to the left side plate  88  of the housing unit  18 . The left side plate  88  also has a duct orifice  136  through which cold air intake duct snorkel tube  132  passes. 
   In order to facilitate single side servicing of the engine  4 , a front side oil filler tube/dipstick combination  102  has been incorporated. It has an inner diameter sufficient to allow the checking, addition and removal of oil from the front side of the genset  2 . Although the height of the genset  2  while residing on the housing compartment unit  18  allows topside clearance to access the spark plugs, platinum long life plugs have been utilized to reduce the intervals between checking/changing. The engine starter  104  and starter solenoid  106  are front mounted as well as the coil  108 , distributor  110  and wiring harness (not shown). 
   The dc power to start the genset  2  is drawn from electrical leads off of the motorcoach&#39;s battery. Once started and operational, the genset  2  has its own alternator  112  to provide for its dc power needs. 
     FIG. 10  illustrates the alternator bracket  114 . To allow access and proper operation of the alternator  112 , a special bracket  114  has been developed that bolts into the front side of the engine block and is adapted to withstand the additional torque of using a belt looped between the main crankshaft pulley  59  and the alternator pulley to drive the alternator  112 . This bracket  114  is of a generally planar configuration with several orifices  115  drilled therein for mounting of an alternator shield  117  and for the mechanical attachment to the engine block. At one end of the bracket  114  is a tab  116  residing normal to the longitudinal plane of the bracket  114  defining a hole therein adapted for threaded engagement with one end of an adjusting shaft  118 . The other end of the adjusting shaft is mechanically affixed to a pulley support  120  that is adjacent the same planar surface of the bracket  114  upon which resides the tab  116 . The pulley support  120  is adapted to retain the pulley  122  by the pulley axle  124  yet allow the pulley  122  to freely rotate about this axle  124 . The pulley axle  124  extends through the pulley support  120  and through a slotted orifice  126  in the pulley bracket  114 . The pulley axle  124  is threadingly engaged with a mechanical fastener arrangement  128  on the opposite planar side of the bracket  114 . 
   In operation, the mechanical fastener  128  is loosened and the adjusting shaft  118  is rotated so as to cause the pulley support  120  to change its position along the slotted orifice  126  in the bracket  114 , thereby adjusting the pulley position in relation to the crankshaft pulley  59 . This increases or decreases the alternator belt tension. When the desired tension is reached the mechanical fastener  128  is tightened down onto into frictional engagement with the bracket  114  thereby holding the pulley  120  at that location. 
   Lastly, the power management system  130 , is mounted on the front side of the genset  2 . It has on it several fault warning and status indicators, such as those related to alternator operation, power to main circuit breakers, power from main circuit breakers, cooling and oil pressure as well as 120/240 V 50 A auxiliary power receptacle connectors. 
   This improved single side servicing accessed genset  2  is capable of a 13 KW electrical output while running quietly at 1800 rpm, maintaining a low compartment  8  operating temperature and fitting into a housing unit  18  having the maximum dimensions of 34 inches long by 26 inches high by 25 inches deep and suitably adapted for installation underneath a motorcoach  62 . 
   The above description will enable any person skilled in the art to make and use this invention. It also sets forth the best modes for carrying out this invention. There are numerous variations and modifications thereof that will also remain readily apparent to others skilled in the art, now that the general principles of the present invention have been disclosed.