Patent Publication Number: US-2007119408-A1

Title: Rotary machine with major and satellite rotors

Description:
This invention relates generally to rotary machines, and more specifically to rotary internal combustion engines, compressors, pumps, and turbines, for expandable gases or compressible liquids.  
      Rotary internal combustion engines are known, examples of which include the Wankel rotary engine and the Sarich orbital engine. These engines suffer from the disadvantage that they require complicated components and seals, exhibit lower compression ratios than some engines and an orbital rotary motion of the rotor which moves the centre of mass, increasing vibration, making balancing difficult.  
      The present invention seeks to provide a rotary machine which alleviates one or more of the aforementioned disadvantages.  
      According to one aspect of the present invention there is provided a rotary internal combustion engine or pump which includes: at least one main body having a void therein, the void having a peripheral wall; a major rotor member disposed within the void for rotation about a first axis of rotation, the major rotor member including at least one outer peripheral wall portion radially spaced from the rotation axis, the peripheral wall portion including at least one generally arcuate wall section defining at least one bight within the major rotor, the or each bight having a central axis; one or more satellite rotor members, the or each satellite rotor member disposed within the or each bight for rotation about a second axis of rotation which is generally coaxial with the central axis of the or each arcuate bight; one or more control chambers being defined generally at any time during a work cycle by any combination of two or more of a wall of the or each satellite rotor member, the peripheral wall of the void and the peripheral wall of the major rotor member; the engine further including a plurality of ports associated with the or each main body for permitting the flow of a fluid to or from the control chamber.  
      According to another aspect of the present invention there is provided a rotary engine or pump which includes: at least one main body having a void therein, the void having a peripheral wall and at least one generally arcuate wall defining at least one bight having a central axis; a major rotor member disposed within the void for rotation about a first axis of rotation, the major rotor member including a peripheral wall spaced from the rotation axis; one or more satellite rotor members, the or each satellite rotor member disposed within the or each bight for rotation about a second axis of rotation; one or more control chambers being defined generally at any time during a work cycle by any combination of two or more of a wall of the or each satellite rotor member, the peripheral wall of the void and the peripheral wall of the major rotor member; the engine further including a plurality of ports associated with the or each main body or rotor for permitting the flow of a fluid to or from the control chamber.  
      Preferably, the or each major rotor member is operatively connected to an output shaft via a transmission means.  
      In one preferred embodiment, the peripheral wall of the void is a generally trochoid, epitrochoid or cycloid shape, by which is defined one upper lobe and one lower lobe, meeting at a midpoint defining a waist. Other preferred embodiments include up to twelve lobes in the void.  
      In one form, at least part of the peripheral wall portion of the major rotor member is a circular shape (or part thereof) and is sized so that its peripheral wall forms a seal which at many points in the work cycle, defines a division between control chambers assisted by the or each waist.  
      In another form, the major rotor member is generally elliptical in shape. In this embodiment, the lobes are circular in shape so that the control chambers can vary in size to affect the fluid therein.  
      Preferably the major rotor member and satellite rotor member are operatively connected to each other via a gear system, and in one form the gears provide anti-clockwise rotation of the satellite rotor member preferably at one-third the rotation speed of the major rotor member when the major rotor member rotates clockwise. The relative speed of rotation of the major and satellite rotor members generally depends on the number of satellite rotor members associated with a major rotor member, whether the satellite rotor member is generally disposed within and rotating with the major rotor member or disposed generally outside the major rotor member, and/or the number of lobes associated with the void, the shape of the or each satellite rotor. In another preferred form the satellite rotor rotates at 1.25 times the angular speed of the major rotor member.  
      Preferably, the satellite rotor member is generally triangular in shape, wherein each side is generally concave. The degree of concavity may vary, and with greater concavities the or each satellite rotor may take on a spoked appearance. The-satellite rotor member may also include one or more seals generally at its vertices, so that the escape of working fluids from one control chamber to another is minimised.  
      A preferred embodiment of the rotary machine is suitable for use as an internal combustion engine, and in that embodiment, compression ignition fuels may be used, or spark ignition fuels may be used. One or more spark plugs may be used, for example trailing and leading, as is known in rotary engines (cf Wankel). In one form, three spark plugs may be used. Fuel injection systems may be utilised with the engine, wherein fuels may be injected in the phase just before ignition for maximum efficiency.  
      Preferably, the or each main body includes opposed spaced apart end walls to enclose the control chambers. In one preferred embodiment the end walls carry shafts about which the satellite rotors rotate. In this form the end walls rotate at the same rate as the major rotor and are affixed to the shaft thereof, but allow the satellites to rotate about the shaft to which they are affixed.  
      Preferably, the peripheral wall of the void is roughened slightly, as with a hone or similar tool to increase lubricant retention and to increase feedback control of the satellite rotor member when operated without gears operatively connecting the satellite and major rotor members.  
      Preferably, the or each main body has associated therewith two ports, one port being an inlet port and the other being an exhaust port. The inlet and exhaust ports may be disposed at one end of the cylinder in close proximity to one another. The inlet port is adapted to allow a working fluid such as air or a fuel air mixture into the control chamber at a selected part of the rotation of the rotor members. The exhaust port is adapted to allow egress of spent working fluid from the control chamber and drawn away to, for example an exhaust pipe. In one form the ports may be associated with the or each major rotor, such that each port terminates at the peripheral wall of the major rotor. In other embodiments, more ports per main body may be provided, generally in pairs of inlet and exhaust ports.  
      Known methods of sealing may be employed to reduce combustion or other losses, for example, gas blow-by.  
      Advantageously, in operation, in the case of the internal combustion engine, an explosive force provided by the igniting of the working fluid in the control chamber bears on the shaft upon which the or each satellite rotor is mounted. Generally ignition occurs once the satellite rotation axis rotates past an axis generally extending between the major rotor member&#39;s central rotation axis and the spark plug. In this case generally all torque is provided in the required direction.  
      According to yet another aspect of the present invention there is provided a piston element suitable for use in an internal combustion engine or pump, the piston element when in use operatively mounted disposed for rotation within a void having a cooperating interior peripheral wall, the piston element including: a plurality of working surfaces in the form of peripheral working walls; one or more peripheral link walls, each peripheral link wall connecting adjacent peripheral working walls at each end thereof; a vertex at the junction of each peripheral link wall end and peripheral working wall end; a plurality of seal elements, each seal element disposed at each vertex, so that the seal elements improve sealing with the interior peripheral wall by subtending an angle with the cooperating interior peripheral wall as close to 90° as possible.  
      Preferably a biasing means is provided in the form of a spring to bias the seal elements outwardly towards a cooperating wall of a chamber in which the piston element when in use is disposed. Preferably, the spring is a compression spring which provides a generally linear biasing response. In one preferred embodiment the spring is a helical compression spring.  
      Preferably a carriage is provided for mounting and carrying the or each seal element.  
      Preferably the carriage is disposed within a cooperating housing, allowing the carriage to reciprocate in a direction generally normal to the cooperating surface.  
      Preferably apertures are provided in the piston or rotor in order to house the seal elements. In preferred rotor embodiments the apertures are disposed at the or each vertex of the rotor, and provide a passage between the or each vertex and the cooperating housing for the carriage.  
      Preferably, the or each rotor member is generally triangular in shape, wherein each side is generally concave. The degree of concavity may vary, and with greater concavities the or each satellite rotor may take on a spoked appearance. In preferred embodiments of rotor, each rotor member includes two vertices at the ends of each spoke, and a seal element disposed at each vertex, to minimise the escape of working fluid past the seal elements, especially when the radius of the cooperating surface becomes small.  
      According to one aspect of the present invention there is provided a piston element, when in use disposed within a chamber having a side wall, the piston element including side wall sections which when in use bear against or are disposed in close proximity to the side wall of the chamber, the side walls of the piston element being biased so as to be urged towards the side walls of the chamber.  
      Preferably the piston element is a rotor mounted for rotation within a chamber of an internal combustion engine or pump.  
      Preferably a biasing means is provided in the form of a spring which provides a generally linear biasing response to the axially spaced portions. The spring may in preferred embodiments be a leaf or coil spring or one or more Belleville washers.  
      In preferred embodiments the adjacent, axially spaced portions are halves of the piston element, or may include a main body and one or more covers.  
      Preferably the side wall sections of the chamber is a side boundary of a cylinder or void in which the piston element moves. 
    
    
      In order to enable a clearer understanding of the invention, drawings illustrating example embodiments are attached, and in those drawings:  
      FIGS.  1 ( i )-( viii ) shows front schematic elevation section views along a diametral plane of a rotary engine of the single satellite rotor type at various stages, in sequence, of its work cycles;  
       FIG. 2  shows a front schematic section elevation view along a diametral plane of a rotary engine of the twin satellite type, where a first control chamber has just commenced the ignition stage of a cycle and a second control chamber has just commenced the compression stage of a cycle;  
      FIGS.  3  to  6  and  6 A show differing schematic elevation views along a diametral plane of the same twin satellite rotor engine at differing stages around the work cycle;  
       FIG. 7  shows a schematic side elevation section view showing gears and inter relationship between rotors and output shafts;  
       FIG. 8  shows a similar schematic side elevation section view to that shown in  FIG. 7 , of an engine which does not require gears to operatively connect to satellite rotors with the major rotor output shaft;  
       FIG. 9 ( i )( ii ) shows plan views of satellite rotors suitable for use with an engine built in accordance with the present invention;  
       FIG. 10  shows a 12-satellite rotor engine in schematic front section elevation view;  
       FIG. 11  shows the same embodiment as in  FIG. 10 , with gears (shown in hidden line script) which operatively connect the satellite rotors to the output shaft of the major rotor;  
       FIG. 12  shows a similar view to that shown in  FIG. 10 , however, with the inclusion of a spark plug and gas flow ports;  
       FIGS. 13 and 14  show similar views of a 12-satellite rotor engine to that shown in  FIGS. 7 and 8 ;  
       FIG. 15  shows another preferred embodiment of the invention, being a pump;  
       FIG. 16  shows a further preferred embodiment of a rotary internal combustion engine made according to the present invention, in schematic section elevation view along a diametral plane, the embodiment having two satellite rotors associated with one major rotor;  
       FIG. 17  is a similar view of the embodiment shown in  FIG. 16 , where the major rotor has advanced 90° from the previous view;  
       FIG. 18  is a yet further embodiment of rotary internal combustion engine (shown without inlet and exhaust ports) where one satellite rotor is at approximately the firing stage of rotation;  
       FIG. 19  is another view of the embodiment shown in  FIG. 18 , again shown without ports, wherein one of the rotors is positioned post-firing;  
       FIG. 20  is a side elevation view of a housing for use with one or more embodiments of the invention, showing the location of inlet, outlet and spark ports;  
       FIG. 21  is a side elevation view of a preferred embodiment of seal for insertion into a satellite rotor;  
       FIG. 22  is a side elevation view of a satellite rotor incorporating a seal, the seal shown in  FIG. 21  and that shown in one aspect of the present invention;  
       FIG. 23  is a partial axial section view of the satellite rotor shown in  FIG. 22 ;  
       FIG. 24  is a partial top view of the satellite rotor shown in  FIG. 23 ;  
       FIGS. 25-28  show a still further preferred embodiment of the invention shown in side elevation cutaway, in sequence, at different stages of the combustion cycles, wherein empty circles indicate a fresh air and/or fuel/air charge being inlet to a control chamber, crosses indicate a spent charge moving its way out towards the exhaust ports, and a closely packed pattern of dots indicates a compressed fuel/air charge undergoing a power stroke;  
       FIG. 29  is the embodiment shown in  FIGS. 25-28 , without the fuel/air charge and at a different angular position of the major rotor;  
       FIG. 30  is a section view of the rotary machine along A-A shown in  FIG. 29 .  
    
    
      Referring to  FIG. 1  there is shown a rotary internal combustion engine generally indicated at  10  comprising an engine body  11  having a housing wall  8 . The engine body  11  is in the form of a rotor block  9  containing a major rotor member  14 , a satellite rotor member  12 .  
      The rotor block is operatively connected to end plates (not shown in this embodiment but similar to  151  and  153  on a second embodiment shown in  FIG. 7 ), the block  9  and plates  51  ( 151 ) and  53  ( 153 ) enclosing an engine body void  15 . The end plates are held in place, sealed against the main body  9  by four bolts  77  ( 177  in  FIG. 7 ). Furthermore, the end plates  51  ( 151 ) and  53  ( 153 ) rotate around the block  9  in unison with the major rotor  14 , carrying with it the rotors  12  and  14  (or  112  and  114 ) via their respective axles. The satellite rotor  12  rotates at a different rate than the major rotor, and hence there is sealed slipping contact between end plates  51  and  53  and satellite rotors  12 . The end plates  51  and  53  also carry shafts for a gear train (shown at  160  for a second embodiment in  FIG. 7 ), the gear train dictating the relative rotation between satellite rotors  12  and major rotor  14 .  
      An upper peripheral wall  32  further defines an upper lobe of the void, as well as a lower peripheral wall  34 , defining a lower lobe of the void  15 , and a waist  42  and  44  is disposed between the two lobes. The peripheral walls  32  and  34  define generally trochoid, epitrochoid or cycloid shapes, more particularly defined by the following mathematical equations:  
      Ordinate  
         y   a     =         (       R   3     -     R   2       )     ⁢           ⁢   cos   ⁢           ⁢   θ     +       R   2     ⁢     cos   ⁡     (     θ   3     )               
 
      Abscissa:  
         x   a     =         (       R   3     -     R   2       )     ⁢           ⁢   sin   ⁢           ⁢   θ     +       R   2     ⁢     sin   ⁡     (     θ   3     )               
 
      Definitions of θ, R 1 , R 2  and R 3  may be found in  FIG. 3 ,  FIG. 10  and below:  
      θ indicates angular displacement of the rotors in a clockwise direction; starting at zero in the 12 o&#39;clock position.  
      R 1  indicates the radius (distance from centre to convex circular peripheral wall) of the major rotor member  
      R 2  indicates the radius (distance from centre to vertex) of the or each satellite rotor member.  
      R 3  indicates distance from major rotor centre the inside peripheral wall of the void at θ=0.  
      The major rotor members  14  and satellite rotor member  12  are disposed within the void  15 . The major rotor member  14  is mounted on a shaft  16 . A gear train (not shown in this embodiment but similar to that shown generally at  160  in another preferred embodiment shown in  FIG. 7 ) operatively connects the major  14  and satellite rotor members  12 , in the embodiment at  FIG. 1  rotating the satellite rotor member  12  at one third the rotation rate of the major rotor member  14 , the two rotors having opposite-handed rotations.  
      The major rotor member  14  has a peripheral wall  7  which is generally circular (or circular in part) and includes a generally arcuate wall  13  which defines a bight  17  within the major rotor  14 . The satellite rotor  12  is disposed for rotation at least partly within bight  17  and mounted on shaft  18 .  
      Two ports are provided at  30  and  28  for the purpose of allowing the flow of a working fluid to  30  and from  28  the control chamber respectively. In  FIG. 1 , port  30  is an inlet port and port  28  is an exhaust port.  
      The satellite rotor member  12  is generally triangular in shape, each of the sides being generally concave. The satellite rotor member  12  has three vertices  4 ,  5 , 6  which are substantially always in sealing contact with either the inner peripheral wall of the void  32  or  34  or the periphery of the bight in which it rotates. Thus a number of separate control chambers are formed as appropriate by: the walls of the satellite rotor  36 ,  38  and  40  and the bight  17  walls; and the void periphery,  32 ,  34 . Examples of the control chambers are shown at  70 ,  72 ,  74 ,  76 ,  78 ,  80 ,  82 ,  84 , and  86 . The satellites  12  are generally shaped to provide a balance between clearance with the contours of the void interior periphery  7  and a high compression ratio by providing a chamber as small as possible when at the commencement of the power stroke (generally TDC in Otto cycle parlance).  
      A spark plug is provided at  26  for ignition of the working fluid. Cooling is provided by apertures (not shown) in the walls of main body  9 , for passage of coolant.  
      To describe the rotary machine in operation, we will follow a control chamber through a working cycle, stepping through FIGS.  1 ( i ) to  1 ( viii ) in sequence. The working cycle is based on the well-known Otto cycle of inlet, compression, power and exhaust stages.  
      In operation the major rotor  14  rotates clockwise about its shaft  16  and in  FIG. 1 ( i ) control chamber  70  is in fluid communication with the inlet port  30 , and a working fluid is being drawn and/or forced into the control chamber  70  through the inlet port  30 . The satellite rotor member  12  rotates anticlockwise about its shaft  18 , and by the position shown in  FIG. 1 ( ii ), the vertex at  5  has closed off the inlet port to the control chamber, now denoted by  72 , the control chamber is not in fluid communication with the inlet port  30  and the compression cycle has commenced for this chamber.  
      Advantageously, in operation, in the case of the internal combustion engine, an explosive force provided by the igniting of the working fluid in the control chamber bears on the shaft upon which the or each satellite rotor is mounted. Generally ignition occurs once the satellite rotation axis rotates past an axis generally extending between the major rotor member&#39;s central rotation axis and the spark plug. In this case generally all torque is provided in the required direction.  
       FIG. 1 ( iii ) shows the compression cycle in a more advanced state, at  FIG. 1 ( iv ) shows it nearly complete.  FIG. 1 ( v ) shows the compression cycle complete, and the control chamber, now denoted by numeral  78 , assumes its smallest volume of the work cycle.  
       FIG. 1 ( vi ) shows the initial portion of the work cycle, where the power portion of the work cycle commences. This is where the spark plug  26  ignites the working fluid.  
      FIGS.  1 ( vii ) and  1 ( viii ) show the power cycle more and more advanced, until finally, we return to  FIG. 1 ( i ) where the control chamber, now denoted by numeral  86 , is in fluid communication with the exhaust port  28 , the power cycle ceases and the exhaust cycle begins.  
      Advantageously, the triangular shape of the satellite rotor allows only fresh air/charge to mix with fresh air/charge, and does not dump fuel/air charge or fresh air into the exhaust outlet. Similarly with spent charge—only spent charge within a control chamber will mix with spent charges or be dumped straight to the exhaust outlet port. This becomes particularly effective and advantageous in multi-satellite embodiments, when the interactions are complex.  
      Other features of the triangular satellite rotor member are that one chamber defined by walls of the satellite always undergoes a storage function. That is, only two of the chambers defined by the satellite are undergoing part of the Otto cycle. The other chamber is undergoing storage. However, as mentioned, when the storage chamber rejoins the Otto cycle, the spent and fresh charges do not mix, even to go down the exhaust, (or arguably worse, to send a spent charge back into the inlet). Similar advantages are gained by using a pentagonal-shaped satellite rotor (not shown).  
      More space in the engine block may be utilised than that utilised by other rotary engines. This allows higher compression ratios and greater working volumes to be used.  
      As will be noted by an examination of the geometry of the machine, in this first embodiment, there is provided one power cycle per rotation of the major rotor member, and thus the satellite rotor  12  rotates around the major rotor member ⅓ of a rotation per rotation of the major rotor member. However, numerals on the satellite rotor member are only valid for a single sequential reading of the cycle from  1 ( i ) to  1 ( viii ) thus the reader should not “loop” the cycle from  1 ( viii ) to  1 ( i ) because the vertices  4 ,  5  and  6  index around the rotor at each completion of a single major rotor member  14  rotation. It can be seen that an “empty” chamber rotates around the main body  9 , doing no work on the fluid.  
      Referring to FIGS.  2  to  8  there is shown a rotary machine according to another embodiment of the invention, a twin satellite engine. Like features of the embodiments of those described in the first embodiment are denoted by like numerals. The embodiment in these latter Figures has two satellite rotor members,  112  and  112 B, providing two power cycles per rotation of the major rotor member  114 , providing greater potential for balance and efficiency. Similarly to the first embodiments, the satellite rotors  112  and  112 B rotate ⅓ revolution for every single rotation of the major rotor member  114 . The rotation of the satellites  112  and  112 B is governed by gear trains shown at  160  in  FIG. 7 .  
       FIG. 6A  shows the elevation section schematic view, of a second embodiment, showing in dashed script, gearing which operatively connects the satellite rotor members to the major rotor member. However, another embodiment shown in  FIG. 8 , is a rotary machine having no gears (previously shown at  160  in  FIG. 7 ) linking the rotation of the satellite with the major rotor member  114 . By the concept of advanced feedback, it is believed that the satellites  112  and  112 B will not necessarily require gears to link their rotation to that of the major rotor member  114 . This is because the pressure across one face of the satellite which forms part of a control chamber undergoing a power cycle (eg.  180  in  FIG. 2 ), will be generally constant thus not allowing rotation more or less than that which would normally occur when being governed by gears  160 . That is, if any combusted (or other) gas attempts to flow outwards from the control chamber for example between a seal ( 95 ,  96  or  97 ) and the peripheral wall  132 , it will be restricted because there will be no inward flow from any other orifice (eg. the seal/major rotor interface at  99  to replace the flow). This advanced feedback system thus created is enhanced by the roughening or honing of the peripheral wall of the void  132  and  134 . Thus, the mass, cost and complexity of the rotary machine will be significantly reduced by removing the gear train  160 .  
       FIG. 9 ( i ) shows a detail view of a satellite rotor member suitable for use with a  12  satellite rotary machine as shown in FIGS.  10  to  14 . The satellite rotor  212  has generally three working sides, and is generally triangular in shape. However its vertices are flattened out and thus form snub- or squared ends, instead of points, and at each squared vertex is disposed a seal  96 ,  97 . Advantageously, this snub-satellite can increase the sealing angle subtended by the seal and void wall, to create a better seal.  
       FIG. 9 ( ii ) shows a satellite rotor member suitable for use with a 1- or 2-satellite rotary machine, generally triangular in shape, having three seals generally disposed thereon, one at each vertex.  
      FIGS.  10  to  14  show a 12-rotor embodiment of a machine according to the present invention, like features being are denoted by like numerals in those embodiments previously described.  
      The peripheral wall comprises 12 lobes  232  which are defined by the following mathematical equations on a Cartesian plane: 
 
 y   α   =R  cos θ+ R   2   1  cos(α−3θ) 
 
 x   α   =R  sin θ+ R   2   1  sin(α−3θ) 
 
      where: α is defined in  FIG. 9 ( i ), and in this embodiment is 0.0873 rad. 
          R=R 3 −R 2  (R 2  and R 3  previously defined).        

      Whereas the previous embodiments ( FIGS. 1-8 ) exhibited power cycles which utilised approximately 180° of major rotor member  114  rotation, the present embodiment&#39;s power cycle utilises only approximately 30° of major rotor member  214  rotation for a full power stage. Advantageously, however there are six power stages occurring simultaneously, and each satellite rotor member powers six times per rotation of the major rotor member  214 , leading to smoother power delivery than other embodiments.  
      Section end elevation views of the rotary engine according to the 12-rotor embodiment are shown in FIGS.  13  to  14 .  FIG. 13  shows the section view without the gear train, the system relying on advanced feedback outlined above for rotation of the satellite rotors, and  FIG. 14  showing gears  260  and ring gears.  
      A further embodiment of the rotary machine is shown at  FIG. 15  and takes the form of a pump. In order to force fluid from the inlet port  330  to the outlet port  328 , the major rotor is driven clockwise by a power source (not shown) and the satellite rotors  312  and  312 B utilise the downstream face  338  to force the fluid into the outlet port  328 . Pipe work (not shown) directs fluid to desired locations from port  328 .  
      Yet another form of the invention is shown in  FIG. 16 . In this embodiment, the main rotor  414  is generally elliptical in shape, its peripheral wall defined by the following:  
       y   =       A   ⁢           ⁢   cos   ⁢           ⁢   θ     +       R   2     ⁢     cos   ⁡     (     π   +   α   +       5   3     ⁢   θ       )               
       x   =       A   ⁢           ⁢   sin   ⁢           ⁢   θ     +       R   2     ⁢     sin   ⁡     (     π   +   α   +       5   3     ⁢   θ       )               
 
      where A is defined in  FIG. 16  and α is as defined in  FIG. 9 .  
      In this form, the peripheral wall  432  and  434  of the void  415  is generally circular, and similarly the walls of the bights  417  are circular, or part thereof. This embodiment further has two satellite rotor members  412  and  412 B, associated with the main rotor  414 .  
      In operation the major rotor  414  is, say, rotating clockwise, and the satellite rotors  412  and  412 B thus rotate anticlockwise at ⅓ the rotation rate of the major rotor. Four control chambers are formed at all times in the work cycle of the engine. In the view shown in  FIG. 16 , two chambers,  485  and  488  are assuming their smallest possible volume. The working fluid in  488  is about to be, or is, ignited by spark plug  426 B mounted in side plate (not shown). Chamber  487  is virtually at the end of the inlet stage, and is still in fluid communication with the inlet port  428 . Chamber  485  is virtually at the completion of the exhaust stage, and is in fluid communication with exhaust port  430 . Chamber  486  is virtually at the end of a power stage.  
       FIG. 17  shows each chamber at a later stage than shown in  FIG. 16 , each chamber now denoted by its  FIG. 16  number followed by an “A”. As will be seen from the Figure, chamber  487 A is in compression stage,  488 A is in power stage,  485 A is in inlet stage and  486 A is in exhaust stage.  
      As will be noted, this latter embodiment shown in  FIGS. 16 and 17  has two power strokes for every rotation of the major rotor member  414 , made possible in part by the rotating ports  428  and  430  and two spaced-apart spark plugs  426  and  426 B.  
      The embodiment shown in  FIGS. 18 and 19  is of a triple-satellite engine or pump according to another preferred embodiment of the invention, the engine including four lobes within the main void. Again, like numerals denote like parts in relation to the other engine or pump embodiments described herein. In addition, operation is similar to that of the other engine or pump embodiments.  
       FIGS. 25-29  show yet another preferred embodiment of the invention, being an engine or pump having four satellite rotors and four lobes within the main void. Operation and structure are similar to other engine or pump embodiments described herein, and like numerals denote like parts. Satellite rotors in this embodiment rotate at 1 and ⅓ times the angular speed of the major rotor.  
      Referring to  FIG. 22  there is shown a piston element having a seal assembly generally indicated at  345  suitable for use with a rotary engine or pump as described above. The seal assembly  345  is mounted on a satellite rotor  312  generally as described above, the satellite rotor  312  having a generally triangular main body. The main body has three major walls which are concave, the degree of concavity being such that the satellite rotor. 312  takes on a spoked appearance. A seal assembly is disposed within each spoke.  
      The satellite rotor element  312  rotates about its central axis  319  and each spoke on the rotor  312  generally has two vertices, and a seal element disposed within a respective aperture, each aperture itself disposed at each vertex. At least one seal element maintains sealed contact with cooperating walls (not shown in this Figure, but the walls are as above described, such as for example, void periphery  32 ,  34 , and bight periphery  13  and like variants) to define a control chamber (also not shown in this Figure).  
      Two vertices per spoke are generally used in order to maintain sealed contact between rotor and cooperating wall when radii of cooperating walls becomes small. However, satellite rotors with one vertex per spoke may be utilised with this seal assembly. The two-vertex system has sealing advantages over a single-vertex seal when radii become small, because the angle between the plane of the seal and the plane of the cooperating wall may be maintained in a range above approximately 30°. When seal angles fall below approximately this figure, sealing becomes ineffective. 90° between seal and wall is the ideal angle for sealing, however, with this style of rotary engine the sealing angles vary around the work cycle.  
      The seal assembly  345  includes a pair of seal elements  347 ,  349  mounted to a carriage  359 , the carriage  359  mounted within a housing  363  for reciprocation along a respective spoke. The carriage  359  is operatively connected to a biasing means  355  in the form of a helical compression spring  357 . This is so that the seal elements  396 ,  397  are biased outwards to extend from the apertures  361  in the vertices of their respective spoke to maintain sealing contact with the corresponding wall throughout a range of seal element  396 ,  397  wear.  
      Referring to  FIG. 23  there is shown a section view in side elevation of a rotor element  412 , the rotor element having a main body including two portions  413  and  415 , each portion adjacent one another, but spaced axially along a shaft  418  about which it rotates. Disposed between the two portions  413  and  415  is a biasing means  471  in the form of a leaf spring. In this manner, end faces of the rotor may sealingly engage with side walls of an engine in which the rotor is disposed, the rotor end walls maintaining sealing engagement with the side walls of the engine notwithstanding thermal expansion or contraction of the engine.  
      Referring to  FIG. 30  there is shown a preferred embodiment of an internal combustion engine, similar to other previously described preferred embodiments, with the same number of satellite rotors  612  and a major rotor cooperating therewith. The  FIG. 30  shows side walls  651  and  653  which, along with void peripheral wall  634 , enclose a plurality of control chambers. The side walls  651  and  653  are mounted to major rotor shaft  616  and rotate therewith. The side walls  651  and  653  are held together by, in this embodiment, four bolts, one of which is shown at  677  each bolt passing through cooperating holes in major rotor  614 . (When there are twelve “cylinders” there are twelve bolts). In this way, axles  618  which support the satellite rotors  612  are mounted to the side walls  651  and  653  and maintain the satellite rotors on their orbit, their own rotation about their own axis  618  being spaced from the major rotor&#39;s axis of rotation  616 .  
      The side walls  651  and  653  are sealably connected to rotor block  609  by seals  635 , and when in operation, rotate past rotor block  609 . In this manner, the engine housing, including end walls  650  and  652  is stationary, and may be bolted to known engine mounts, while the actual work is being performed inside the motor block, with the side  651  and  653  walls rotating with the major rotor and shaft, the satellite rotors rotating about their own axis  618  as well as orbiting about the major rotor&#39;s axis  616 . Gear train  660  also rotates with side walls  651  and  653 .  
      A sump is provided at  660  and  661  to provide lubrication and cooling. Water and/or oil may be used for cooling. A pump is utilised to draw oil from the sump and spray oil from the general area of the end walls  650  and  652  onto the rotating side walls  651  and  653  and gears  660  for cooling and lubrication.  
      Finally, it is to be understood that various alterations, modifications and/or additions may be incorporated into the various constructions and arrangements of parts without departing from the spirit or ambit of the invention.