Abstract:
An improved power generator having a pair of relatively rotatable elements each of which may be selectively driven in an opposite direction and at a desired speed by one of a pair of oppositely rotating prime movers to vary the power output and achieve a greater maxim power at a lower speed than conventional devices to reduce vibration and provide a longer life. The unit is comprised of a number of interconnected housing elements so that it can be compact, easily assembled and mounted. A clutch and brake arrange is incorporated to facilitate starting of the prime movers and to insure that one does not drive the other particularly in the wrong direction. In addition a cooling arrangement is provided that accomplishes the necessary cooling with respect to the amount op power generated.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This invention relates to an power generating apparatus and more particularly to an improved generator that produces a large power output at a lower driven speed, one that can be easily mounted in its operating location and as a unit, one which may be driven by a pair of internal combustion engines each of which has its own starting mechanism, one in which a wide variety of power outputs can be achieved with minimum power input, one in which the powering units and the output element are well cooled and also an arrangement where the driving members and the driven generating apparatus can be easily and compactly coupled together.  
         [0002]     The use of electrical generators powered by a prime mover such as an internal combustion engine are well known. Although various constructions have been proposed, the generator normally is comprised of an armature having a number of ferromagnetic pole teeth around which electrical coils are wound. These coils or more particularly the pole teeth face a plurality of circumferentially spaced permanent magnets and one of the elements, generally the one carrying the magnets is rotated so as to induce a current flow through the coils.  
         [0003]     Such an internal combustion engine driven generator is shown in Japanese Published Application JP Hei 8-80095. As is well known the amount of electrical power generated by such a generator is generally proportional to the speed at which it is driven. Therefore when large electrical power outputs are required, the speed of the driving engine is increased.  
         [0004]     However when the engine speed is increased, the engine noise may become objectionable. This can be avoided if a step up transmission of some type is interposed between the engine and the generator to increase the rotational speed in relation to the engine speed, but the inertial force of the generator is proportional to the square of the speed at which it is driven, putting increased loading on the bearings and causing vibrations both of which will adversely affect the unit life and increase the need for servicing.  
         [0005]     Therefore it is a principal object of the invention to provide a driven generator that can produce greater electrical power without requiring high rotational speeds achieved by either higher engine driving speeds or the use of step up transmissions.  
         [0006]     In the co-pending application Ser. No. 10/904,882 of which I am a co-inventor with other and which is assigned to the assignee hereof there is disclosed an electrical generator having two relatively rotatable elements each of which is driven in its respective direction by a prime mover arrangement so as to increase the power output without increasing the driving speed. However all of the embodiments disclosed therein require separate mounting bases for several of the components that makes the mounting of the assembly complicated and may also suffer detrimental effects if alignment is not maintained.  
         [0007]     Therefore it is a first principal object of this to provide a power generating apparatus that can produce high power outputs and which is formed as a unitary assembly to facilitate mounting and insure the desired alignment of the various components.  
         [0008]     Here it should be noted that although the aforenoted co-pending application produces electrical power output, the same arrangement may be employed for producing power outputted in another form such as fluid power with certain types of pumps.  
         [0009]     By driving the generator elements in opposite directions the power can be increased relative to the driving speed avoiding the problems of vibration and noise. In addition it has been discovered that the driving speeds of the prime movers, if two are employed, can be varied independently thus providing a greater range of outputted power. It is therefore a further object of this invention to provide a power generator having a greater range of power outputs at reduced overall driving speed.  
         [0010]     If the power generator is an electrical power generator. brushes may be required to output the electrical power. If the component with which the brushes contact is continuously rotated then there might be high wear. Therefore it is a further object of the invention to provide an electrical generator that produces high electrical power when required but which also may be operated in a mode where brush wear is reduced to minimize servicing requirements.  
         [0011]     With any power generator, heat dissipation is a problem. Where higher power outputs are obtained by the type of generator shown in the co-pending application, the amount of heat generated can become substantial. It is therefore another principal object of the invention to provide a power generator that has a very effective and compact cooling arrangement.  
         [0012]     Where the generator is driven by one or more internal combustion engines. It is also desirable that the engine or engines are also well cooled. In accordance with another feature of the invention to provide cooling for the power generator that also is effective to cool the powering prime mover arrangement.  
         [0013]     If the power generator is driven by one or more internal combustion engines, it is desirable that the powering engine or engines have self starters. When this is done, however, it is desirable that the starter or starters do not place a load on the system once the apparatus has started. It is therefore a further principal object of the invention to provide an improved engine driven power generator that embodies at least one electric starter motor that is disengaged when the apparatus has started.  
       SUMMARY OF THE INVENTION  
       [0014]     A first feature of the invention is adapted to be embodied in a power generating apparatus comprised of a pair of prime movers. There is also a power generating device comprised of a pair of relatively moveable elements adapted to generate a source of power upon movement of one of said elements relative to the other. Each of the prime movers is adapted to move the elements in opposite directions. In accordance with the invention, a housing arrangement encloses the prime movers and the power generating device for mounting as a single unit.  
         [0015]     In accordance with another feature of the invention as set forth in the preceding paragraph, the power generating device comprised an electrical generator.  
         [0016]     Another feature of the invention also is adapted to be embodied in a power generating apparatus comprised of a pair of prime movers in the form of internal combustion engines. There is also a power generating device comprised of a pair of relatively moveable elements each driven by one of the engines and together adapted to generate a source of power upon movement of one of said elements relative to the other. Each of the engines is provided with a respective starting system.  
         [0017]     Another feature of the invention is embodied in a power generating apparatus as set forth in the preceding paragraph and the respective starting systems comprise electric motors that drive the engines through one way clutches.  
         [0018]     In accordance with yet another feature as set forth in the immediately preceding paragraph the one way clutches also act as one way brakes. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]      FIG. 1  is a side elevational view of a first embodiment of the invention, with portions broken away and shown in section.  
         [0020]      FIG. 2  is an enlarged cross sectional view of the left hand area of the embodiment shown in  FIG. 1 .  
         [0021]      FIG. 3  is an enlarged cross sectional view of the right hand area of the embodiment shown in  FIG. 1 .  
         [0022]      FIG. 4  is a cross sectional view taken along the line  4 - 4  in  FIG. 2 .  
         [0023]      FIG. 5  is a cross sectional view taken along the line  5 - 5  in  FIG. 3 . 
     
    
     DETAILED DESCRIPTION  
       [0024]     Referring now in detail to the drawings and initially primarily to  FIG. 1 , the reference numeral  11  indicates generally a power generating unit and specifically in this embodiment an electricity generating unit. The power generating apparatus  11  is made up of a prime mover arrangement, indicated generally by the reference numeral  12 , that is in the illustrated embodiment comprised of spaced left  13  and right  14  four-stroke cycle internal combustion engines.  
         [0025]     Disposed between the engines  13  and  14  is a power generator  15 , specifically in this embodiment an electric generator that is driven by the prime mover arrangement  12  in a manner to be described. This assembly is mounted on a fixed member  16  in the form of a pedestal, for directly supporting the prime mover arrangement  12 . The power generator  15  is supported through the prime mover arrangement  12  on the fixed member  16 .  
         [0026]     The power generator  15  includes a first, generally cup shaped element  17  journalled for rotation about a horizontal axis  18  and supporting a plurality of circumferentially spaced permanent magnets  19 . Cooperating with these magnets  19  is a second element  21  also rotatable about the axis  18  and supporting a plural number of generator coils  22  wound around circumferentially spaced pole teeth  23 . The magnets  19  and the coils  22  closely face each other about the axis  18 . The first rotated element  17  and the second rotated element  21  are supported on the side of the fixed member  16  for rotation about the axis  18 .  
         [0027]     The first rotated generator element  17  includes a hub part  24  detachably taper-fit to and supported with the free end of a crankshaft portion  25  of the left engine  13  along with the magnets  19  held to the inside round surface of the yoke  16 , removably attached to the first rotational crankshaft  25  by a fastener  26  provided at the free end of the first crankshaft  25 .  
         [0028]     The second rotated generator element  21  includes a second rotational crankshaft  27  of the right engine  14  also rotatable about the axis  18 . Fixed to the end of the crankshaft  27  is the core  28  of second generator element which is made of laminated magnetic steel plates around which the coils  22  are wound. As best seen in  FIG. 3  these laminations of the core  28  are detachably taper-fit to the free end of the second rotational crankshaft  27  by a threaded fastener  29 .  
         [0029]     The first and second rotated elements  17  and  21  are placed so that both free ends of the first crankshaft  25  and the second crankshaft  27  closely face each other in the direction of the axis  18 . The prime mover arrangement  12  includes the left engine  13  for rotary-driving the first rotated element  17  in one direction A about the axis  18  and the right engine  14  drives the second rotated element  21  in the opposite direction B about the axis  18 . The fixed member  16  has spaced lugs for supporting the left engine  13  and the right engine  14  separately from each other.  
         [0030]     The end of the first element  21  carrying the magnets  19  and driven by the left engine  13  extends in the direction of the axis  18 , further than the free end of the first crankshaft  25  toward the second crankshaft  27 . In a like manner an end of the core  28  and the coils  22  on the second crankshaft  27  of the right engine  14  projects more than the free end of the second crankshaft to provide a more compact arrangement. In addition the second crankshaft  27  extends a greater distance from its cylinder bore than that of the first crankshaft  25  from its cylinder bore for a reason that will become apparent as this description proceeds.  
         [0031]     The power generating apparatus  11  includes a first starting device, indicated generally at  31 , for starting the left engine  13  by rotating it in the direction A about the axis  18 . There also is a second starting device  32  for starting the right engine  14  by rotating it in the opposite direction B.  
         [0032]     The starting arrangement for the prime mover arrangement  12  also includes a first one-way brake  31  interposed between the left engine  13  and the first starting device  31  to permit the rotation of the first rotated element  17  only in the one direction A through the left engine  13 . In a like manner, a second one-way brake  32  is interposed between the right engine  14  and the second starting device  32  to permit the rotation of the second rotated element  21  only in the opposite direction B through the right engine  14 . Alternatively, only one of the first and second one-way brakes  31  and  32  may be provided.  
         [0033]     Each of the engines  13  and  14  includes a crankcase  35  made by aluminum alloy casting and supported a respective lug of the fixed member  16 . In addition each engine  13  and  14  has its crankshaft  25  and  27  supported with a plural number (a pair) of bearings  36 ,  37  in the respective crankcase  35  for respective rotation about the axis  18 .  
         [0034]     Each engine  13  and  14  has a cylinder block  38  formed by aluminum alloy casting and projecting vertically upward from the crankcase  35  and which forms a respective cylinder bore in which a piston  39  reciprocates. As is common in the engine art, a connecting rod  41  connects the pistons  39  to their respective crankshaft  38  for its rotation.  
         [0035]     The piston  39  and cylinder block  38  of each engine form a respective combustion chamber  42 . As is well known in the art intake and exhaust passages serve the combustion chambers  42  to admit a combustible charge (formed in any desired manner) to them and to discharge the burnt charge to the atmosphere through a suitable exhaust system. One such flow passage is shown at  43  along with a respective flow controlling valve  44  that is operated in any desired manner.  
         [0036]     The charge in the combustion chambers  42  of the left and right engines  13  and  14  is ignited, for example, by a spark plug  45  that is fired by a respective ignition system  46  (only one of which is shown in conjunction with the left engine  13 . These ignition systems  46  are operated in any desired manner and may receive inputs from one or more sensors, indicated schematically at  47 . Again it is to be understood that the engines  13  and  14  may have any desired configuration and/or type except as will be hereinafter described.  
         [0037]     The speed of each engine  13  and  14  may also be controlled in any desired manner, such as by well known throttle valves in their induction systems, and independently of each other, as will be described later in more detail.  
         [0038]     As previously mentioned, the construction of the left and right engines  13  and  14  and their operation and speed control may be of any type and although spark ignited engines have been shown either or both may be Diesel or rotary type if desired. However, in accordance with the invention, the crankcase  35  and the cylinder block  38  of each engine  13  and  14  constitute a portion of an outer shell assembly, indicated generally at  48 . The cylinder block  38  and one part, indicated at  49 , of the crankcase  35  of the left engine  13  are respectively of the same size and shape as the cylinder block  38  and the one part  49  of the crankcase  35  of the right engine  14 .  
         [0039]     Each of the crankcase portions  49  of the left and right engines is completed to form the respective crankcase  35  by a second crankcase member, each indicated by the reference number  51 . These portions of each crankcase assembly  35  are generally the same but that of the right engine  14  is slightly different because of the greater length of the crankshaft  27  than that of the crankshaft  25  of the left engine  13 .  
         [0040]     The second crankcase parts  51  are each fixed to respective cylinder blocks  38  along oppositely inclined faces  52  thereof that mate with like inclined faces of the cylinder blocks  38  by respective threaded fasteners  53  that are received in tapped holes in the cylinder blocks  38 .  
         [0041]     Facing outer ends  54  of the second crankcase parts  51  are enlarged and cylindrical in shape. Because of the longer length of the crankshaft  27  from that of the crankshaft  25  the second crankcase part  51  of the right engine  14  is longer than the corresponding part  51  of the left engine  13 . Nevertheless the facing ends  54  are still spaced from each other in the direction of the axis  18 .  
         [0042]     To fill this gap and to provide additional rotational support for the longer crankshaft  27  a cylindrical bridging member  55  is interfitted between the crankcase portions  51 . The bridging member  55  has a wall  56  that supports another bearing  57  is provided so that the crankcase  35  provides further support for the crankshaft  27 .  
         [0043]     The opposing portions  54  of the outer shell members  48  of the first and second engines  13 ,  14  are removably secured to each other with the bridging member  55  sandwiched between them using a plural number of (four) fasteners  58 . These fasteners  58  pass through bosses  59  formed in one of the portions (that of the left engine  13  as shown) and received in tapped bosses  62  in the other portion.  
         [0044]     Both the opposing portions  54  and the bridging member  55  are made in a cylindrical shape to face each other on the axis  18 . The projecting ends of the opposing portions  54  are made in complementarily stepped shapes to detachably fit to the bridging member  55  and to control the spacing between the ends of the crankshafts  25  and  27 .  
         [0045]     The entire power generator  15  is housed in the internal space of the opposing portions  54  and the bridging member  55 . The first and second engines  13  and  14 , and the first and second rotated elements  17  and  21  may be separated from each other in the direction of the axis  18  as the fastening pieces  58  are unfastened. As they are separated, the first and second rotated elements  17  and  21  are exposed respectively out of the power generator  15 . On the other hand, as the second rotated element  21  is attracted toward the magnets  19  with the magnetism of the magnets  19  of the power generator  15 , the mutual fitting of the opposing portions  54  up to the desired dimension is assisted.  
         [0046]     One part  51  of the crankcase  35  is coupled to the cylinder block  38  of each of the engines  13  and  14  to form a single body that supports the respective crankshaft  25  and  27  between the bearings  36  and  37 . The cylinder block  38  crankcase part  49  of each of the engines  13  and  14  carries the bearing  36 . The crankcase part  51  of the crankcase  35  of each engine  13  and  14  carries the bearing  37 .  
         [0047]     As has also been noted, the mating surface  52  of the respective parts  49  and  51  of each of the crankcases  35  slants downwardly in a straight line so as to be more distant from the facing outer end  54  in the direction of the axis  18 . Also as has been noted, the one parts  49  and  51  of the crankcase  35  are removably secured to each other using a plural number of threaded fasteners  53  with their axes extending perpendicular to the mating surfaces including the surface  52 .  
         [0048]     Referring now primarily to  FIG. 3 , the power generator  15  includes a plurality of slip rings  62  (three in the illustrated embodiment), located on the axis  18 , supported with and rotating together with the second crankshaft  27 . These slip rings  62  thus also rotate in unison with the core  28  of the generator  15  and are electrically connected to respective ends of the windings of the coils  22 , as is well known in the art.  
         [0049]     Cooperating with the slip rings  62  are a plurality of brushes  63 , supported by the other part  51  of the crankcase  35  and specifically from a wall  64  thereof that carries the bearing  37 . As is also well known in the art, the slip rings  62  transmit the electrical power from the coils  22  to the brushes  63 .As shown schematically in  FIG. 1 , an electrical wire  65  for conducts the power from the brushes  63  to an electricity receiving device  66  such as an external battery.  
         [0050]     From the foregoing description it should be readily apparent that the construction is very robust and the axial alignment of the various components is maintained with high rigidity. This facilitates the mounting of the complete power generating unit as a unit. However this also results in some problems in connection with the cooling of the engines  13  and  14  and the power generator  15 , each of which generates heat in its operation.  
         [0051]     Therefore, the power generating unit  11  is provided with an air type cooling device, indicated generally by the reference numeral  67 , which is comprised of a plurality of fans. The cooling device  67  includes: a first cooling fan  68  supported with and rotating together with the first generator element  17  and specifically formed integrally with its hub portion  24  and a second cooling fan  69  supported with and rotating together with the second generator element  21  and specifically integrally with the portion connecting it to the crankshaft  27 .  
         [0052]     These fans  68  and  69  cool the electrical generator  15 . The fan  68  operates by drawing atmospheric air through a first air intake opening  71  formed in the lower part of the opposing portion  54  of the crankcase  35  of the left engine  13 . This air passes across the elements of the electrical power generator  15  and the heated air is discharged through a first air discharge opening  72  formed radially outside the first cooling fan  68  in the upper part of the opposing portion  54  of the crankcase  35  of the left engine  13 . This air flow is represented by the arrows C in the drawings.  
         [0053]     In addition, a second air intake opening  73  is formed in the lower part of the facing outer end  54  of the crankcase  35  of the right engine  14 . This permits atmospheric air drawn by the action of the fan  69  to enter and pass through a communication passage  74  formed in the partition wall  56 . The air then passes through the interior of the bridging member  55  to cool the electrical generator and pass out of a second air discharge opening  75  formed radially outside the second cooling fan  69  in the upper part of the bridging member  55  as shown by the arrows D.  
         [0054]     In addition to the aforedescribed cooling system  67  for the electrical generator  15 , it also includes an engine cooling fan  76  secured to the other end of the crankshafts  25  and  27  of the left and right engines  13  and  14 , respectively. A respective cowling  77  is secured to each of the crankcases  35  of the left and right engines  13  and  14  to partially cover each engine cooling fan  76 . An air intake opening  78  is formed in the outer face and lower portion of the cowling  77 . In addition, an air discharge opening  79  is formed in the upper part of the cowling  77  in facing relation to the respective cylinder block  38  to permit cooling air flow in the direction of the arrows E.  
         [0055]     In the illustrated embodiment, the first and second starting devices  31 ,  32  comprise recoil starters each including a respective housing  81  secured to the crankcase  35  of the respective engine  13  and  14  through its cowling  77  by means of threaded fasteners  82 . The starters  31  and  32  each include a respective recoil rope  83  contained in the housing  81  with one end comprising a grip portion (not shown) exposed outside the housing  81 . A respective starter clutch  85  contained in the housing  81  permits the transmission of pulling action of the recoil rope  83  to the crankshaft  38  only when a pulling force is applied.  
         [0056]     The housing  81  is placed to cover the air intake opening  78  of the cowling  77 , and is provided with another air intake opening  85  for air to enter the air cooling system of each of the engines  13  and  14 .  
         [0057]     The one-way brakes  33  and  34  are each interposed between the outer end of each crankshaft  25  and  27  and a stopper plate  87  secured to the cowling  77  using the threaded fasteners  82  and other fastening pieces. If the first element  17  tends to rotate together with the crankshaft  25  in a direction opposite the one direction A, or if the second element  21  tends to rotate together with the crankshaft  27  in a direction opposite the direction B, the first and second one-way brakes  33 ,  34  engage with the crankcase  35  through the stopper plate  87  and the cowling  77 , to act as a one way brake so that the elements are prevented from rotating in the respectively reverse directions.  
         [0058]     On the other hand, when the first and second engines  13 ,  14  operate and both the crankshafts  25  and  27  rotate by themselves in their respective normal directions A and B, the first and second one-way brakes  33 ,  34  and both the starter brakes  84  are released and the crankshafts  25  and  27  can turn freely.  
         [0059]     Because of this arrangement each of the engines  13  or  14  may be started independently of the other without causing the other engine to be driven in a reverse direction from its normal rotation. In a like manner if both engines  13  and  14  are being operated either one may be stopped without causing the other to be driven in a reverse direction.  
         [0060]     When both of the engines  13  and  14  are operated, the left engine  13  rotary-drives the first rotated element  17  in one direction A while the right engine  14  rotary-drives the second rotated element  21  in the opposite direction B from the one direction A. As a result, the magnets  19  and the coils  22  rotate in opposite directions to magnify the electrical power relative to machines where only one of the elements is rotated and the other is fixed. Thus electric current is generated in the coils  22  and outputted as a three-phase alternate current through the slip rings  62 , the brushes  63 , and the electrical wire  65  to the electricity receiving device  66 .  
         [0061]     In the above case, it is made possible to regulate the rotary speeds (R 1  and R 2 ) of the first and second engines  13  and  14  respectively by the operation of by way of example the firing of the spark plugs  45  or throttle valves of the first and second engines  13  and  14  by the operation of the controller  46 , at the respective absolute rotary speeds R 1  and R 2 .  
         [0062]     To put it more specifically, the rotary speeds of the first and second engines  13 ,  14  may be optionally and individually chosen to be at any of low speed (3000 rpm in the eco-mode), high speed (5000 rpm), and normal speed (4000 rpm). This choice makes it possible for example to operate the power generating apparatus  11  in a state in which the absolute rotary speed R 2  of the second rotated element  21  is higher than the absolute rotary speed R 1  of the first rotated element  17 . It is also possible to operate only one of the first and second engines  13  and  14 .  
         [0063]     As has been noted, the rotary motion of the crankshaft  25  of the left engine  13  is transmitted to the first cooling fan  68  which causes air present below the power generator  15  of the power generating apparatus  11  to be drawn through the first air intake opening  71  to the interior of the opposing portion  54  of the crankcase  35  of the left engine  13  to air-cool the first rotated element  17  and the magnets  19 , then is discharged to the atmosphere through the first air discharge opening  72  in upper part of the power generator  15  as shown by the arrows C in  FIGS. 2 and 4 . Thus if only the engine  13  is operated there will be enough air flow to cool the electrical generator, considering it will not produce maximum power and accordingly maximum heat.  
         [0064]     In a similar manner,. the rotary motion of the crankshaft  27  of the right engine  14  drives the second cooling fan  69  which causes air present below the power generator  15  of the power generating apparatus  11  to be drawn through the second air intake opening  73  to the interior of the crankcase portion  54  to air-cool the slip rings  62  and the brushes  63 . After that, the air is drawn through the communication passage  74  to the interior of the projecting end  59  of the bridging portion to cool the second rotated element  21  and the coils  22 , then through the second air discharge opening  75  to the atmosphere as shown by the arrows D in  FIGS. 3 and 5 . Thus if only the engine  14  is operated there will be enough air flow to cool the electrical generator, considering it will not produce maximum power and accordingly maximum heat.  
         [0065]     When both engines  13  and  14  are operated the greater heat generated by the generator  15  will be dissipated adequately by the operation of both cooling air flows. In this regard it should be noted that when only the engine  13  is operated the slip rings  62  will not be rotated so there will be no significant heating in this area to require cooling.  
         [0066]     In a similar manner, the cooling systems  67  for the engines  13  and  14  comprised of the fans  76  only operate when necessary, that is when the respective engine  13  and/or  14  is started and running. Along with the rotary motions of either or both of the crankshafts  25  and  27  the respective engine cooling fans  76  will rotate. This causes external air to be drawn through the other air intake openings  85  to the interior of respective housings  81  of the first and second starting devices  31  and  32  to air-cool the starter clutches  84 . After that, the air is drawn through the air intake openings  78  to the interior of the cowlings  77  to air-cool the first and second one-way brakes  33 ,  34 , then discharged through the air intake openings  78  of the cowlings  77  toward the cylinders  38  to air-cool the cylinder block  38  as shown by the arrows E in  FIGS. 2 and 3 . Incidentally, because the first and second one-way brakes  33  and  34  normally do not contact the crankshafts  25  and  27 , the air-cooling described above is not always necessary.  
         [0067]     As has been noted, it is possible to individually change the absolute rotary speeds R 1 , R 2  of the first and second rotated elements  17  and  21  by respectively changing the rotary speeds of the first and second engines  13  and  14  or even stop one of them while the other continues to operate to set the power generating apparatus  11  to an intended state of operation. Because the first and second elements  17  and  21  are rotated in opposite directions from each other, the relative speed between the both elements  17  and  21  can be increased, even with the respective rotation speed of the elements  17  and  21  is small. Therefore, the generation output can be drastically increased to be doubled, for example, compared to the prior art where only one of the elements is rotated at the same rotation speed as above. Such an increase in the generation output derives not simply from a high rotation speed of the rotors, but from the first and second rotors  17  and  21  being rotated in opposite directions. In other words, since the generation output can be increased even when the engines  13  and  14  for driving the first and second elements  17  and  21  is driven at a lower speed, which can be achieved while suppressing noise from the engines  13  and  14 .  
         [0068]     In addition since an increase in the generation output does not rely solely on an increase in the rotation speed of the elements  17  and  21  as described above, the rotation speed of the elements  17  and  21  can be kept low so as not to cause large vibrations in the elements  17  and  21 , thereby preventing problems with the service life of the generating apparatus  11  while achieving an increase in the generation output.  
         [0069]     Since the brushes  63  and slip rings  62  are associated with the element  21  driven by the engine  14  it would be preferable either not operate the engine  14  or to run it at a lower speed than the engine  13  to reduce wear on these components.  
         [0070]     In the case single-phase alternating current is to be outputted with the power generating apparatus  11 , the number of the slip rings  22  may be two. To output in two kinds, three-phase alternating and single-phase alternating, five slip rings  22  in all suffice.  
         [0071]     The opposing portions  54 , of the outer shell assemblies  48  of the first and second engines  13  and  14  opposing each other on the axis  18  are secured to each other. As a result, the first and second engines  13  and  14  are joined together more directly, so that a common framework for supporting the first and second engines  13 ,  14  may be dispensed with, and bringing the power generating apparatus  11  to an intended state of operation may be accomplished with a simple construction and the rigidity of the power generating apparatus  11  as a whole may be achieved without an increase in the weight of the power generating apparatus  11 . Also because the opposing portions  54  and bridging member  55  are made in a cylindrical shape the rigidity of the power generating apparatus  11  as a whole may be accomplished without employing a separate reinforcing member. This also facilitates assembly and disassembly and the interposition of the electrical generator  15  adds to its protection and the overall strength and compactness.  
         [0072]     It should be noted that the aforedescribed structure well meets the objects of the invention. However those skilled in the art will readily understand that various modifications may be made without departing from the scope of the invention, as set out in the appended claims. For example only, the power generator  15  may be directly supported with the fixed member  16  and /or, the power generator  15  may be a liquid pump where the first rotated element  17  comprises a pump housing, and the second rotated element  21  is an impeller. Furthermore, the engines  13  and  14  and the power generator  15  need not be placed on the same axis  18 . Also, the fixed member  16  may or may not be a common framework for the first and second engines  13  and  14 . Furthermore, the power generator  15  may be connected to interlock with the first and second engines  13  and  14  through an interlocking means such as a V-belt girdling mechanism. The magnets  19  may be constituted with coils energized through slip rings from outside. The axis  18  may be vertical or tilted.  
         [0073]     As other possible modifications within the general concept of the invention, either or both the first and second engines  31  and  33  may be of the two-cycle type and their specifications may be freely selected in terms of number of cylinders, total displacement, and engine layout such as in-line type, V-type, and the like. The specifications of the engines may be different from each other. Also, the first and second starting devices  31  and  32  may use an electric motor as a drive source. As noted above, those skilled in the art will readily understand that various other modifications than those specifically mentioned may be made without departing from the scope of the invention, as set out in the appended claims.