Patent Publication Number: US-8539930-B2

Title: Rotary combustion apparatus

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is generally directed to engines utilizing rotary combustion architecture and, more particularly, to a rotary engine having a rotor and chamber arrangement with an effective constant diameter chamber and variable valve timing. 
     2. Description of the Related Art 
     Various designs have been proposed for utilizing a chamber and a rotor as compressors, engines, and measurement devices. For example, McMillan, U.S. Pat. No. 1,686,569, describes a rotary compressor; Moreover, Feyens, U.S. Pat. No. 1,802,887 is directed to a rotary compressor; and Luck, U.S. Pat. No. 3,656,875, also describes a rotary piston compressor. 
     Dieter, U.S. Pat. No. 3,690,791, pertains to a rotary engine having a radially shiftable rotor. The rotary engine includes a hollow housing having an irregular but generally cylindrical cavity therein and a shaft journalled through the cavity in off-center relation thereto. The curved walls of the housing define and extend about the cavity, gradually increasing and decreasing in radial distance from the axis of rotation of the shaft, however, the spacing between all working curved wall portions of the cavity lying at opposite ends of all diameters of the aforementioned axis is constant. An elliptical rotor is mounted on the shaft within the cavity for rotation with the shaft and for shifting radially off the axis of rotation of the shaft along a line extending between the vertices of the rotor while fuel mixture and exhaust by-products inlet and outlet and fuel mixture ignition are spaced about the outer periphery of the cavity. Also, the rotor and shaft define a rotary assembly having axially extending air passages therethrough opening through opposite ends of the housing with an air vane structure carried by one end of the rotary assembly operative to pump cooling air through the air passages in response to rotation of the assembly. 
     Furthermore, van Michaels, U.S. Pat. No. 4,519,206, describes multi-fuel rotary power plants using gas pistons, elliptic compressors, internally cooled thermodynamic cycles, and slurry type colloidal fuel from coal and charcoal. These rotary power plants are designed for universal application, such as engines for large industrial compressors, cars, electrical power plants, marine and jet propulsion engines. 
     Lew, U.S. Pat. No. 5,131,270, is directed to a sliding rotor pump-motor-meter for generating and measuring fluid flow and generating power from fluid flow. The design includes two combinations of a cylindrical cavity and a divider member rotatably disposed in the cylindrical cavity about an axis of rotation parallel and eccentric to the geometrical central axis of the cylindrical cavity. The divider member extends across the cylindrical cavity on a plane including the axis of rotation in all instances of rotating movement thereof, and a rotary motion coupler for coupling rotating motions of the two divider members in such a way that a phase angle difference of ninety degrees in the rotating motion is maintained between the two divider members. Fluid moving through the two cylindrical cavities and crossing each plane, including the geometrical central axis and the axis of rotation in each of the two cylindrical cavities, relates to rotating motion of the two divider members. 
     Despite the various designs for engines that utilize a rotor instead of a piston, challenges continue to exist with such designs. For example, rotary engines are typically less efficient than piston engines and involve reciprocating motion, complicating the manufacturing and maintenance of such engines. Existing designs also tend to vibrate as a result of the centrifugal forces created by the rotation of the rotor. Furthermore, related designs generally do not provide for selective control over air and fuel intake of rotary engines because a continuously rotating rotor defines the air and fuel intake amounts. 
     There is a need for a rotary engine that is fuel efficient, produces more power, is easier to manufacture, provides more control over the air and fuel intake, and exhibits less vibration than existing engines. 
     BRIEF SUMMARY OF THE INVENTION 
     In accordance with one embodiment of the invention, a rotary engine is provided that includes a generally cylindrical housing having an outer surface and an inner surface, the inner surface defining at least one chamber having a constant diameter, varying radii about a center of origin, an intake valve port, and an exhaust valve port; a rotor having an axis of rotation and an elongate opening, a first end, and a second end, wherein the first end and the second end are rotatably and sealingly in contact with the inner surface; and a rotor shaft having one end slidably received in the elongate opening of the rotor. 
     In accordance with another embodiment of the invention, a rotary engine is provided that includes a cylindrical housing having at least two end walls, an outer surface, and an inner surface, the inner surface defining a chamber having an intake valve and an exhaust valve; a first shaft having at least two opposing flat surfaces, a first end, and a second end; means for producing a combustive force from igniting fuel and air received in the intake valve port; at least one rotor having a first end, a second end, and an elongated opening adapted to slidably receive the flat surfaces of the first shaft, wherein the rotor is operable to rotate in response to the combustive force, and the first end and the second end of the rotor are rotatably and sealingly in contact with the inner surface of the housing; a second shaft having at least one opening extending laterally therethrough, a first end, and a second end, wherein the first end is rotatably mounted on an end wall of the housing, and the opening is positionable adjacent the intake valve of the chamber; a third shaft having at least one opening extending laterally therethrough, a first end, and a second end, wherein the first end is rotatably mounted on an end wall of the housing and the opening is positionable adjacent the exhaust valve of the chamber; and means for rotating the second shaft and the third shaft, respectively aligning the openings in the second shaft and the third shaft with the intake valve port and the exhaust valve port, in an alternating pattern. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
         FIG. 1  is a cross-sectional view of a rotary engine provided in accordance with one embodiment of the present invention; 
         FIG. 2A  is a planar view of a method of generating a shape of an inner surface of a rotor housing of the rotary engine illustrated in  FIG. 1 ; 
         FIG. 2B  is a view of the inner surface generation of  FIG. 2A ; 
         FIG. 2C  is a view of the inner surface formed in accordance with an alternative generation method; 
         FIG. 3A  is an isometric view of a rotor shaft provided in accordance with one embodiment of the present invention; 
         FIGS. 3B-3E  are top, side, and corresponding cross-section views of a rotor shaft with a plurality of bearings provided in accordance with one embodiment of the present invention; 
         FIG. 4A  is an isometric view of a rotor shaft provided in accordance with one embodiment of the present invention; 
         FIGS. 4B-4E  are top, side, and corresponding cross-section views of a rotor shaft with a plurality of bearings provided in accordance with one embodiment of the present invention; 
         FIG. 5A  is an isometric view of a rotor shaft provided in accordance with one embodiment of the present invention; 
         FIGS. 5B-5E  are top, side, and corresponding cross-section views of a rotor shaft with a plurality of bearings provided in accordance with one embodiment of the present invention; 
         FIG. 6A  is a cross-sectional view of a valve of a rotary engine in an open configuration, provided in accordance with an embodiment of the present invention; 
         FIG. 6B  is a cross-sectional view of a valve of a rotary engine in a closed configuration, provided in accordance with an embodiment of the present invention; 
         FIG. 7  is an isometric view of a rotor shaft and two valve shafts provided in accordance with an embodiment of the present invention; 
         FIG. 8  is a side view of a valve shaft, illustrating a valve shaft opening having a valve seal provided in accordance with an embodiment of the present invention; 
         FIG. 9A  is a partial top view of a rotary engine provided in accordance with another embodiment of the invention, illustrating a rotor shaft, two valve shafts, and intermittent rotating gears; 
         FIG. 9B  is a partial front view of the rotary engine of  FIG. 9A ; 
         FIGS. 10A-10C  are a series of partial front views of intermittent rotating gears provided in accordance with yet another embodiment of the present invention; 
         FIG. 11  is a side view of a rotor provided in accordance with one embodiment of the present invention; 
         FIG. 12  is a side view of two rotors provided in accordance with another embodiment of the present invention; 
         FIG. 13  is a top view of the rotor of  FIG. 11 ; 
         FIG. 14  is a cross-sectional view of a rotary engine according to another embodiment of the present invention; 
         FIG. 15  is a side view of a rotor provided in accordance with yet another embodiment of the present invention; 
         FIGS. 16A-16P  are a series of cross-sectional views of a rotary engine provided in accordance with an embodiment of the present invention and illustrating an operating cycle; 
         FIGS. 17A-17E  are an isometric, front side, cross-sectional first end, second side, and cross-sectional second end views, respectively, of a rotor and shaft configuration formed in accordance with an alternative embodiment of the present invention; 
         FIGS. 18A-18C  are a series of cross-sectional views of an alternative embodiment of the rotary engine utilizing the rotor and shaft configuration of  FIGS. 17A-17E ; 
         FIGS. 19A-19C  illustrate a spur gear arrangement in combination with a stepper or servo motor; 
         FIGS. 20A-20C  illustrate yet another embodiment of actuation of intake and exhaust valves; 
         FIGS. 21-23  illustrate alternative embodiments of rotor configurations; 
         FIG. 24  is an illustration of a gasket applied to the housing; 
         FIG. 25  is an alternative embodiment of a rotor in combination with a rounded end seal; 
         FIG. 26  illustrates an alternative configuration of a rotor housing and rotor formed in accordance with the present invention; 
         FIGS. 27-32  illustrate alternative embodiments of a rotor; 
       FIGS.  33  and  34 A- 34 C illustrate alternative embodiments of a rotor shaft; 
       FIGS.  35  and  36 A- 36 B illustrate alternative arrangements of valve shafts; and 
         FIGS. 37-38  illustrate alternative valve seal configurations. 
         FIG. 39  illustrates a third rotor mounted on a shaft according to one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following description, certain specific details are set forth in order to provide a thorough understanding of various disclosed embodiments. However, one skilled in the relevant art will recognize that embodiments may be practiced without one or more of these specific details, or with other methods, components, materials, etc. In other instances, well-known structures or components or both associated with engine components and other devices including but not limited to ignition devices, distributor devices, steam generators, or condensers have not been shown or described in detail to avoid unnecessarily obscuring descriptions of the embodiments. 
     Unless the context requires otherwise, throughout the specification and claims which follow, the word “comprise” and variations thereof, such as, “comprises” and “comprising” are to be construed in an open, inclusive sense, that is, as “including, but not limited to.” 
     Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. 
     Reference throughout this specification to “expansion”, “combustion”, “expansion cycle” or “combustion cycle” is not intended in a limiting sense, but is rather intended to refer to any cycle or state that exhibits expansive or combustive properties, or that is descriptive of converting air and fuel to energy, or in which air and fuel are ignited. “Fluid” as used herein includes liquid, gas, and a mixture of liquid and gas. 
     In one embodiment shown in  FIG. 1 , the present design provides a rotary engine  120  made up of seven major components: a rotor shaft  10 , at least one rotor  20 , rotor seals  30 ,  32 , a rotor housing  40 , a rotary intake valve  70 , a rotary exhaust valve  80 , and rotary valve gears  90 ,  92  shown in  FIG. 7 . The gears  90 ,  92  can include a spur gear or other intermittent gearing known to those skilled in the art. 
     As shown in  FIG. 2A , a series of points  42  determines a unique contour of an inner surface  50  of the rotor housing  40  shown in  FIG. 1 . The points  42  are generated by the ends of a line segment  44 , which has a length equal to the length of the rotor  20 . The other ends of the line segment  44  trace a curve  46  that forms one segment of the contour of the inner surface  50 . The center of rotation of the rotor shaft  10  and the center of rotation of the rotor  20  is the origin  16 . The inner surface  50  of the rotor housing  40  has a variable radius with respect to the origin  16  but a constant diameter, which corresponds to the length of the rotor  20 . The radius of the inner surface  50  of the rotor housing  40  is the distance from the origin  16  of the inner surface  50  to a point  42  on the inner surface  50  of the rotor housing  40 . The radius defined by the inner surface  50  of the rotor housing  40  and the rotor  20  as it rotates and slides about the origin  16  in the rotor housing  40  will vary continuously. When any two opposite radii are added together they will equal the length of the rotor  20 , and hence the diameter of the rotor chamber  52 . 
     As shown in  FIG. 2B , the curve  46  that determines the shape of the inner surface  50  of the rotor housing  40  can be a chord or segment of a circle, a parabola, an ellipse, or any other curve that satisfies the relationship described above and results in a desired performance of the rotary engine  120 . The shape of the curve  46  determines the shape of the inner surface  50  of the rotor housing  40 , which along with the shape of the rotor  20  determines the shape of the chamber  52  shown in  FIG. 1 . 
     As illustrated in  FIG. 1 , the inner surface  50  and at least two end walls  60  of the rotor housing  40  form two rotor chambers  52 ,  54 . The shape of the rotor chamber  52 , where the combustion of the air-fuel mixture occurs, determines the fuel combustion efficiency and hence the fuel efficiency of the rotary engine  120 . Different fuels may require rotor chambers  52 ,  54  of different shapes in order to obtain the most efficient combustion. 
     Referring to  FIGS. 2A and 2B , the center of origin  16  is also where a first axis  41  and a second axis  43 , perpendicular to the first axis  41 , intersect. The inner surface  50  of the rotor housing  40 , shown in  FIG. 1 , is not symmetrical about the first axis  41  and need not be symmetrical about the second axis  43 . As shown in  FIG. 2A , both the first axis  41  and the second axis  43  run through the center of origin  16  of the inner surface  50  of the rotor housing  40  shown in  FIG. 1 . The distance the end point  42  of the line segment  44  travels from the center of origin  16  towards the inner surface  50  as the line segment  44  rotates around the center of origin  16  determines the contour of the inner surface  50  of the rotor housing  40 . The greater this distance, the more radical and less circular the inner surface  50  of the rotor housing  40  becomes. 
     The displacement of the rotary engine  120  is determined by the shape of the inner surface  50  of the rotor housing  40  and the width and shape of the rotor  20 . The displacement is the volume of the rotor chamber  52  that is created by the top surface of the rotor  20  and the inner surface  50  of the rotor housing  40  when the rotor  20  is parallel to the first axis  41  in the rotor housing  40 . 
     The placement of the rotor shaft  10  in the rotor housing  40 , the shape of the inner surface  50 , and the shape of the rotor  20  are major factors in determining the compression ratio of the rotary engine  120 . The compression ratio of the rotary engine is the ratio between the maximum area of increasing volume  56  in the rotor chamber  52  and the minimum area of decreasing volume  58  in the rotor chamber  52 . The distance the center of the rotor  20  moves from the center of the rotor shaft  10  as the rotor  20  rotates around the inner surface  50 , along with the shape of the inner surface  50  and the shape of the rotor  20 , determine the compression ratio of the rotary engine  120 . The greater the distance the center of the rotor  20  moves from center of rotation or origin  16  of the rotor shaft  10 , the greater the compression ratio of the rotary engine. 
     A cooling agent such as water or air, depending on the application for which the engine  120  is used, can be used to cool the rotor housing  40 . Air-cooled or water-cooled designs can be used to obtain maximum performance for different applications of the engine. The illustrated embodiment of  FIG. 1  shows a water-cooled version of the engine  120  having at least one water jacket or chamber  51 . In the air-cooled version, the water chambers  51  would be replaced by air-cooling fins mounted on the exterior of the rotor housing  40 . 
     In one embodiment shown in  FIGS. 3A through 3E , the rotary engine  120  has a rotor shaft  10  made up of have a round or cylindrical shaft body  11  with an enlarged rotor guide  13  section formed thereon. The shaft  11  has a circular cross-sectional configuration with the enlarged rotor guide  13  having a pair of mutually-opposing planar surfaces  12  where the rotor  20  slides back and forth. These flat surfaces  12  provide positive engagement between the rotor  20  and the rotor shaft  10  as the rotor  20  reciprocates when it rotates during the operating cycle. Thus, these flat surfaces  12  guide the rotor  20  in a translational movement that is perpendicular to the axis of the shaft  11  as the shaft  11  is rotating in the rotor chamber  52 . The rotor shaft  10  is rotates about the origin  16  in the chamber  52 . 
     In the embodiment illustrated in  FIGS. 3A-3E , to reduce friction, the rotor shaft  10  can be mounted on a plurality of ball bearings or roller bearings  14  in the end walls  60  of the rotor housing  40 . As shown in  FIG. 1 , the flat surfaces  12  on the rotor guide  13  fit through a rectangular opening  28  in the rotor  20  shown in  FIG. 11 . The rotor shaft bearings  14  fit on the round end sections of the cylindrical shaft  11 . 
     In another embodiment, discussed in more detail below in conjunction with  FIG. 12 , the rotary engine can have two rotors  20 ,  22  mounted on flat surfaces  12  formed on opposing ends of the rotor shaft  10 , as shown in  FIG. 4A . The rotors  20 ,  22  turn the rotor shaft  10  as the rotors  20 ,  22  rotate around their respective rotor chambers  52 ,  54  shown in  FIG. 1 , during the operating cycle. The rotors  20 ,  22  slide back and forth across the flat surfaces  12  of an enlarged rotor guide  13  formed on the cylindrical shaft  11  of the rotor shaft  10 , moving perpendicular to the axis of the rotor shaft  10 . Preferably the rotor guide  13  is integrally formed on the shaft  11 , although it may be a discrete component that is mounted on or attached to the cylindrical shaft  11  in a conventional manner. 
     In the embodiment illustrated in  FIGS. 4A-4E , to reduce friction, the rotor shaft  10  can be mounted on a plurality of ball bearings or roller bearings  14 ,  15  in the end walls  60  of the rotor housing  40 , shown in  FIG. 1 . As shown in  FIG. 1 , the flat surfaces  12  on the rotor guide  13  fit through a rectangular opening  28  in the rotors  20 ,  22 , shown in  FIG. 12 . The rotor shaft bearing  15  with a larger inner raceway diameter is mounted at the center of the cylindrical shaft body  11 . The larger diameter raceway allows the bearing  15  to slide over the rectangular surfaces  12  of the rotor shaft  10 . The rotor shaft bearings  14  fit on the round end sections of the cylindrical shaft  11 . 
     In the embodiment shown in  FIGS. 5A through 5E , the rotary engine  120  includes the rotor shaft  10  having the round or cylindrical shaft body  11  and rotor guide  13  the opposing flat surfaces  12  formed on the shaft  11  where a plurality of rotors  20 ,  22  (shown in  FIG. 12 ) slide back and forth. Here, the bearing member  15  is not used, and the rotor shaft  10  can be of rectangular cross section with opposing flat surfaces  12  on the rotor guide  13  where the rotors  20 ,  22 , shown in  FIG. 12 , mount on the rotor shaft  10 . These flat surfaces  12  guide the translational movement of the rotors  20 ,  22  on the rotor shaft  11  as the rotors  20 ,  22  rotate in the rotor chambers  52 ,  54  during the operating cycle. These flat surfaces  12  also allow the rotors  20 ,  22  to slide across the flat surfaces  12  of the rotor shaft  11 , moving perpendicular to the axis of the rotor shaft  11  as the rotors  20 ,  22  turn the rotor shaft  11 . 
     The rotor shaft  11  is located at the origin  16  of the inner surface of the rotor housing  50 , which is also the center of rotation for the rotors  20 ,  22 . As illustrated in  FIG. 5B , embodiments of the present invention with rectangular rotor shafts  11  can have bearings with modified inner raceways  18  that fit over the rectangular section of the rotor shaft  11 , i.e., the inside surface of the inner raceway  18  has a rectangular cross-sectional configuration. Bearings with modified inner raceways  18 , illustrated in  FIG. 5B , would be used in embodiments having multiple rotor pairs  20 ,  22 , as shown in  FIG. 12 , to accommodate the flat surfaces  12  of the rotor shaft  11 . A completely rectangular rotor shaft  11  can be used by mounting the rotor shaft  11  in the end walls  60  of the rotor housing  40  using only bearings with the special inner raceway  18 , as shown in  FIG. 5B . 
     In one of the embodiments of the present invention having multiple rotor pairs  20 ,  22 , as shown in  FIG. 12 , bearings with modified inner raceways  18  will be used, which fit over the rectangular sections  12  on the rotor shafts  10  shown in  FIG. 5A . A rectangular enlarged section  13  on the rotor shaft  11  can be used by mounting the rotor shaft  10  in the end walls  60 , shown in  FIG. 1 , of the rotor housing  40  using only bearings with the special inner raceway  18 . 
     To lubricate the flat surfaces  12  of the rotor shaft  10  on which the rotors  20 ,  22  are mounted, a small diameter hole (not shown) may be bored in the origin  16  of the rotor shaft  10  which is the center of rotation for the shaft  10 . Lubricant is pumped through this hole and onto the flat surfaces  12  of the rotor shaft  10  to lubricate the flat surfaces  12  on which the rotors  20 ,  22  move. 
     As further illustrated in  FIG. 1 , the engine  120  has an intake valve port  62  and an exhaust valve port  64  located on opposite sides of the rotor housing  40 . Preferably, the valve ports  62 ,  64  in the rotor housing  40  are rectangular in shape with rounded corners, although other known shapes may be used. The large rectangular shape allows for a greater quantity of air to enter into and exhaust from the chamber  52 , giving the engine  120  better combustion, greater power, and greater fuel efficiency. 
     As illustrated in  FIGS. 6A and 6B , the engine  120  has a rotary intake valve  70  and a rotary exhaust valve  80  mounted on either side of the rotor housing  40 . Two valve shafts  72 ,  82 , illustrated in  FIG. 7 , are associated with the respective rotary valves  70 ,  80 . The valve shafts  72 ,  82  are parallel to and in the same plane as the main rotor shaft  10  and are mounted in the intake valve port  62  and exhaust valve port  64 , respectively, of the rotor housing  40 . Valve shaft openings  74 ,  76 ,  84 ,  86 , are formed perpendicular to the axis of the valve shafts  72 ,  82  and extend entirely through the valve shafts  72 ,  82 , preferably at a right angle to the axis of the valve shafts  72 ,  82 . 
     The length of the valve shaft openings  74 ,  76 ,  84 ,  86  is approximately the same as the width of the rotors  20 ,  22  and can vary in width depending on the diameter of the valve shafts  72 ,  82 . To reduce friction, the valve shafts  72 ,  82  can be mounted on ball bearings or roller bearings located in the end walls  60  of the rotor housing  40 . The intake valve port  62  and the exhaust valve port  64 , located on opposite sides of the rotor housing  40 , are illustrated in  FIGS. 6A and 6B . As the valve shafts  72 ,  82  rotate, the valves  70 ,  80  open and close by aligning the openings  74 ,  76 ,  84 ,  86  in the valve shafts  72 ,  82  with the respective air intake port  62  and exhaust port  64  in the rotor housing  40 . When the openings  74 ,  76 ,  84 ,  86  are aligned with the intake and exhaust ports  62 ,  64  as shown in  FIG. 6A , fluid, gas, liquid, or a mixture of gas and liquid can flow through the rotary valves  70 ,  80  into and out of the chamber. When the holes are not aligned, the valves  70 ,  80  are closed, as shown in  FIG. 6B , and fluid cannot flow into or out of the chamber. 
     In certain embodiments the engine  120  has two rotors  20 ,  22 , shown in  FIG. 12 , that are mounted in parallel on the rotor shaft and located one behind the other in separate rotor chambers  52 ,  54  in the rotor housing  40 , as shown in  FIG. 1 . To provide for the two rotors  20 ,  22 , there are four valve shaft openings  74 ,  76 ,  84 ,  86  cut through the valve shafts  72 ,  82  one behind the other. The valve shaft openings  74 ,  76 ,  84 ,  86  run from side to side through the valve shafts  72 ,  82 . The valve shaft openings  74 ,  76 ,  84 ,  86  form passages for the air and exhaust gases to flow to and from the rotor chambers  52 ,  54 . 
     As illustrated in  FIG. 7 , the four valve shaft openings  74 ,  76 ,  84 ,  86  are identical but oriented at different angles from each other along the axis of the rotary valve shafts  72 ,  82 , and they are perpendicular to the longitudinal axis of the rotary valve shafts  72 ,  82 . 
     The spur gears  92  are mounted on each valve shaft  72 ,  82  that are driven by a single drive gear  90  mounted on the rotor shaft  10 . As the rotor shaft  10  is turned by the rotors  20 ,  22 , the gear  92  engages the valve shafts  72 ,  82  and the valve shafts  72 ,  82  are turned, opening and closing the rotary valves  70 ,  80 . Other suitable gears or timing belts and pulleys can be used to rotate the rotary valve shafts  72 ,  82  continuously. 
     The shape of the valve shaft openings  74 ,  76 ,  84 ,  86  in the valve shafts  72 ,  82 , the width of the valve ports  62 ,  64  in the rotor housing  40 , shown in  FIGS. 6A and 6B , and the speed of rotation of the valve shafts  72 ,  82  determine how long the rotary valves  70 ,  80  will remain open or closed. Hence, these parameters determine the performance of the rotary valves  70 ,  80 . As the rotor  20 , shown in  FIG. 1 , rotates the rotor shaft  10 , the rotor shaft  10  rotates the gear  90  mounted on the rotor shaft  10 . The rotor shaft gear  90  simultaneously rotates the spur gear  92  mounted on the intake valve shaft  72  and the spur gear  92  mounted on the exhaust valve shaft  82 . 
     Preferably, the gears  92  mounted on the intake and exhaust valve shafts  72 ,  82  rotate one time to four rotations of the gear  90  mounted on the rotor shaft  10 . Thus, when the rotor  20  and rotor shaft  10  turn 360 degrees, the intake valve shaft  72  and exhaust valve shaft  82  will turn 90 degrees. The shape of the intake valve port  62  and exhaust valve port  64  in the rotor housing  40 , shown in  FIGS. 6A and 6B , and the shape of the valve shaft openings  74 ,  76  in the intake valve shaft  72  and the valve shaft openings  84 ,  86  in the exhaust valve shaft  82  are such that the intake valve  70  and the exhaust valve  80  will open or close every time the rotor  20  and rotor shaft  10  rotate 180 degrees. By rotating the intake valve shaft  72  and the exhaust valve shaft  82  continuously, the engine  120  will run smoother with less vibration than a conventional piston engine or other rotary engines with standard valving mechanisms. 
     In an embodiment of the present invention illustrated in  FIG. 8 , valve seals  78 ,  88  are mounted in grooves cut around the openings  74 ,  76 ,  84 ,  86  in the valve shafts  72 ,  82 . There are also grooves cut along the top and bottom of the valve shafts  72 ,  82 . These seals  78 ,  88 , preferably made of wear and heat resistant material, are spring loaded to remain in constant contact with the sides of the rotary valve ports  62 ,  64  and automatically adjust for wear. 
     In yet a further embodiment illustrated in  FIGS. 9A and 9B , an intermittent gearing configuration using two continuously rotating single toothed spur gears  94  driving two intermittently rotating gears  96  are used to open and close the intake valve  70  and exhaust valve  80  quickly. The intermittently rotating intake valve shaft  72  and the intermittently rotating exhaust valve shaft  82  will remain in the full open or full closed position longer than the continuously rotating intake valve shaft  72  and the continuously rotating exhaust valve shaft  82 . By remaining open longer, the intake valve  70  and exhaust valve  80  allow more fluid to enter the rotor chamber  52  in a given amount of time and more fluid to be exhausted from the rotor chamber  52  in a given amount of time, thereby increasing the fuel efficiency and decreasing the fuel consumption of the engine  120 . 
     The two identical continuously rotating single toothed driver gears  94  are shown mounted on the rotor shaft  10  with their single teeth  95  oriented 180 degrees apart from each other. The first driven gear  96  is attached to the intake valve shaft  72  and the second driven gear  96  is attached to the exhaust valve shaft  82 . These driven gears  96  rotate the intake valve shaft  72  and the exhaust valve shaft  82  to either the open or closed position. Referring to  FIGS. 10   a  to  10   c , as the driver gears  94  mounted on the rotor shaft  10  rotate through a small arc of approximately 20 to 30 degrees, the single tooth  95  of the driver gears  94  engage the driven gears  96  and rotate them 90 degrees. After rotating 90 degrees the driven gear  96  remains locked in position by the single toothed driver gear  94  until the driver gear  94  rotates 360 degrees and engages the driven gear  96  and repeats the cycle. Because the two single toothed driver gears  96  are oriented 180 degrees from each other, they counter balance the force generated by the single tooth of each gear as it rotates. In other embodiments, a single continuously rotating driver gear  94  rotating at half the speed of the rotor shaft  10  with two teeth located 180 degrees from each other could also be used to rotate the driven intermittent rotary valve gears  96 . 
     As illustrated in  FIG. 10A , the driver gear  94  has one tooth which engages a plurality of spaces  100  between a plurality of gear lobes  102  of the intermittent driven gear  96 . The driver gear  94  is a round disc with a single gear tooth protruding from it. Other than the single tooth the driver gear  94  is round and smooth with only the single gear tooth extending from its surface. In the illustrated embodiment of  FIG. 10A to 10C , the driven gear  96  has four spaces  100  that engage the tooth of the driver gear  94 . Between the four spaces  100  that engage the driver gear  94  are four specially shaped gear lobes  102 . These four specially shaped gear lobes  102  engage the smooth round surface  106  of the driver gear  94  during the portion of its rotation when the driver gear  94  tooth  95  is not engaging the space between the gear lobes  102  of the driven gear  96 . An outer surface  104  of the gear lobes  102  of the driven gear  96  engages the round surface  106  of the driver gear  94  as it rotates. This action locks the driven gear  96  into position so that it cannot rotate until the tooth  95  of the driver gear  94  rotates and engages the space  100  between the gear lobes  102  of the driven gear  96 . 
     An embodiment of the engine  120  with intermittent rotation of the intake valve shaft  72  and exhaust valve shaft  82  may vibrate more than an engine with continuous rotation of the intake valve shaft  72  and exhaust valve shaft  82 . However, intermittent rotation of the intake valve shaft  72  and exhaust valve shaft  82  may result in greater operating performance and greater fuel efficiency of the engine  120 . In other embodiments, driver gears  94  and driven gears  96  with several teeth may be used instead of single toothed gears in order to dampen and eliminate the vibration caused by the single toothed driver gear  94  as it engages the driven gear  96 . 
     In one embodiment shown in  FIG. 11 , the design utilizes a rotor  20  shaped like a rectangular block that has rounded ends and is symmetrical along a longitudinal axis  21  and along a lateral axis  23  that is perpendicular to the axis longitudinal  21 . The top, bottom, and side surfaces of the rotor  20  are flat. There are at least two recessed areas  24  in the rounded ends of the rotor  20  and at least two recessed areas in the sides  26  of the rotor  20  for rotor seals  30  and  32 , respectively. There is a large rectangular opening  28  passing from one side of the rotor  20  to the opposing side of the rotor  20 . The rotor  20  mounts on the flat surfaces of the rotor shaft  12 , shown in  FIG. 1 , which runs through the large rectangular opening  28  in the side of the rotor  20 . The rotor shaft  10  passes through this rectangular opening  28 , allowing the rotor  20  to slide across the flat surfaces  12  of the rotor shaft  10 , moving perpendicular to the axis of the rotor shaft  10  as the rotor  20  rotates around the inner surface of the rotor housing  50 . The end seals  30  of the rotor  20  are always in contact with the opposite sides of the inner surface of the rotor housing  50  as the rotor  20  rotates around the inner surface of the rotor housing  50 . The side seals  32  of the rotor  20  are always in contact with the rotor housing end wall  60 , as the rotor  20  rotates around the inner surface of the rotor housing  50   
     Ideally, the rotor  20  has a plurality of round holes  34  in the ends and sides of the rotor  20  to hold the rotor seal springs  38 . Guide pins  36  can be mounted in the middle of these holes  34  to position and guide the rotor seals  30 ,  32 . 
     The top and bottom surfaces of the rotor  20  go through the complete operating cycle with every 720 degrees of rotation of the rotor  20 . This double acting function of the rotor  20  generates a power stroke with every 180 degrees of rotation with a pair of rotors  20 ,  22  oriented 180 degrees opposite each other as shown in  FIG. 12 . 
     As better illustrated in  FIG. 13 , the rotor seals  30 ,  32  are respectively mounted in recessed areas  24  in each end of the rotor  20  and in recessed areas  26  in each side of the rotor  20 . The seals  30 ,  32  are made of special material to reduce friction and wear as well as resist heat and are replaceable. A plurality of springs  38  urges the seals to maintain constant contact with the inner surface  50  and end walls  60  of the rotor housing  40 . This enables the rotor seals  30 ,  32  to automatically compensate and adjust for wear. The side and end rotor seals  30 ,  32  interlock at the corners of the rotor  20  to keep the surfaces of the rotor  20  sealed from each other so that no air, air-fuel mixture, exhaust gases, or other fluid will pass between the chambers  56 ,  58  created by the rotor  20  and illustrated in  FIG. 1 , and the inner surface  50  and end walls  60  as the rotor  20  rotates inside the rotor chamber  52 . 
     Referring to  FIG. 14 , when the engine  120  is operating, a force F acts on a surface of the rotor  20  due to pressure from the combustion of fuel in the chamber  52  formed by the rotor  20  and the inner surface  50  during the combustion and expansion phase of the operating cycle. As the rotor  20  rotates around the inner surface  50 , the rotor  20  also moves along its longitudinal axis with respect to the flat surface of the rotor shaft  12 . The rotor  20  is divided into two segments  110 , 112 , one on each side of the rotor shaft  10 , at the center of which is the center of rotation or origin  16  for the rotor  20  and the rotor shaft  10 . At the time of ignition, the functional surface area of one rotor segment  110  is greater than the functional surface area of the other rotor segment  112  on the other side of the origin  16 . The total force acting on the larger surface of the one rotor segment  110  is greater than the total force acting on the smaller surface of the other rotor segment  112  thus creating an unbalanced force. This unbalanced force acting on the one rotor segment  110  during the expansion cycle causes the rotor  20  to rotate around the inner surface  50 , preferably clockwise, and causes the rotor to turn the rotor shaft  10  in the direction of the larger rotor segment  110 . 
     As the rotor  20  rotates around the inner surface  50  during the expansion phase of the operating cycle, the functional surface area of the one rotor segment  110  increases and the surface area of the other rotor segment  112  decreases. The increase in functional surface area of the one rotor segment  110  and the decrease in functional surface area of the other rotor segment  112  increases the unbalanced force acting on the rotor  20 , resulting in an increase in torque and power as the rotor  20  rotates in the housing  40  during the expansion phase of the operating cycle. 
     The rotary engine  120  is a true rotary engine in that the rotors  20 ,  22 , shown in  FIG. 12 , actually rotate inside the rotor chambers  52 ,  54  and form areas of increasing and decreasing volumes  56 ,  58  within the rotor chambers  52 ,  54  ( FIG. 14 ). The inner surfaces  50  have a unique contour that allows the rotors  20 ,  22  to rotate around the rotor chambers  52 ,  54  with the rotor seals  30  at the ends of the rotors  20 ,  22  always in contact with the inner surfaces of the rotor housing  50 . 
     The engine  120  also has a unique twin rotor design that dynamically balances the forces generated by the individual rotors  20 ,  22  as they rotate around the individual rotor chambers  52 ,  54  of  FIG. 14 . The rotor housing  40  of the engine  120  has two rotor chambers  52 ,  54  located one behind the other and oriented 180 degrees from each other. Individual rotors  20 ,  22  in each rotor chamber  52 ,  54  are mounted on the same rotor shaft  10  as shown in  FIG. 12 . The rotor shaft  10  has flat surfaces  12  on which the rotors  20 ,  22  are mounted. The rotors  20 ,  22  turn the rotor shaft  10  as the rotors  20 ,  22  rotate around the rotor chambers  52 ,  54 . The rotors  20 ,  22  slide across the flat surfaces  12  of the rotor shaft  10  moving perpendicular to the axis of the rotor shaft  10  as the rotors  20 ,  22  rotate around the rotor chambers  52 ,  54 . 
     Referring to  FIG. 14 , the placement of the rotor shaft  10  in the rotor housing  40 , the contour of the inner surface of the rotor housing  50 , and the shape of the rotors  20 ,  22  causes the rotors  20 ,  22  to generate an area of increasing volume  56  and an area of decreasing volume  58  between surfaces of the rotors  20 ,  22  and the inner surface  50 , as the rotors  20 ,  22  rotate in the rotor chambers  52 ,  54 . These areas of increasing volume  56  and decreasing volume  58  in the rotor chambers  52 ,  54  enable the engine  120  to go through its operating cycle of intake, compression, expansion, and exhaust. The engine  120  has rotary intake valves  70  and rotary exhaust valves  80  with valve shafts  72  and  82  that rotate either continuously or intermittently, as depicted in  FIGS. 7 and 9A , depending on the application for which the engine  120  is being used and the performance required. 
     In still another embodiment of the present invention, to increase the power, performance, and efficiency of the engine  120 , the contour of the surfaces of the rotor  20  can be shaped to allow more force to act on the one rotor segment  110  than on the other rotor segment  112  during the expansion phase of the operating cycle. As shown in  FIG. 15 , a contour of a surface  123  of the rotor  20  can be shaped to give the rotor segment  110  a larger surface area than the surface area of the other rotor segment  112 . A larger difference between the surface areas of the rotor segments  110 ,  112  will create a greater imbalance of the forces acting on the rotor  20  and thus a greater torque in the engine  120 . The contour of the surfaces  123  of the rotor  20  against which a force is applied during the expansion phase can be shaped so that a greater force acts on the one rotor segment  110  that has more surface area. Reducing the surface area of the other rotor segment  112  that is exposed to the pressure generated by the combustion of fuel during the expansion phase of the engine  120  operating cycle reduces the force acting on the smaller rotor segment  112 , thus increasing the unbalanced force acting on the surface of the larger rotor segment  110 . This increases the power, torque, and efficiency of the engine  120  during the first portion of the expansion phase of the operating cycle. 
     As illustrated in  FIG. 12 , in one embodiment, the engine  120  has two rotors  20 ,  22  mounted parallel to each other on the same rotor shaft  10 . The combined function of the two rotors  20 ,  22  is to provide a power stoke every 180 degrees of rotation of the rotors  20 ,  22  and the rotor shaft  10  and also to balance the unbalanced forces created by each rotor  20 ,  22  as they rotate around the rotor chambers  52 ,  54 , shown in  FIGS. 1 and 14 . The engine  120  may use pairs of rotors  20 ,  22  to cancel the vibration of the engine. The rotors  20 ,  22  balance the centrifugal forces generated by the unequal masses of the individual rotors  20 ,  22  as they move with respect to the origin  16  while traveling across the flat surfaces  12  of the rotor shaft  10  as they rotate around the inner surface  50  and turn the rotor shaft  10 . 
     The engine  120  with pairs of rotors  20 ,  22  can balance the forces generated by the unbalanced rotating mass of the individual rotors  20 ,  22  as they travel across the flat surfaces  12  of the rotor shaft  10 . As the individual rotor  20  rotates around the inner surface  50 , a second rotor  22  will rotate 180 degrees out of phase from the first rotor  20 . To cancel the forces generated by the unbalanced rotating mass of the first rotor  20  there is a second rotor  22  traveling 180 degrees out of phase with the first rotor  20 . As the rotor  20  travels across the flat surface  12  of the rotor shaft  10  the rotor  20  is divided into two rotor segments  110  and  112 , shown in  FIG. 14 , one on each side of the rotor shaft  10 , which is the origin  16  for the rotor  20 . 
     While the total mass of the rotor  20  is constant just as the total length of the rotor  20  is constant, the unbalanced portion of the rotating mass of each rotor segment  110 ,  112  varies directly as the radius of rotation of the rotating rotor segment  110 ,  112  varies. The radius of rotation and mass of each of these rotor segments  110  and  112  changes as the rotor  20  rotates around the inner surface of the rotor housing  50 . The change in radius and rotating mass of each rotor segment  110 ,  112  causes an unbalanced condition. 
     Referring to  FIG. 12 , the second rotor  22  mounted on the rotor shaft  10  and rotating 180 degrees out of phase from the first rotor  20  counter balances the unbalanced forces generated by the first rotor  20 . As the first rotor  20  moves laterally with respect to the origin  16 , the second rotor  22  moves laterally in the opposite direction and 180 degrees out of phase from the first rotor  20  and cancels the forces generated by the first rotor  20 . The second rotor  22  rotates in the same direction as the first rotor  20 . 
     Referring to  FIGS. 1 ,  6  and  7 , as the rotor  20  rotates in the housing  40 , it performs a self valving function relative to the rotor housing intake port  62  and the rotor housing exhaust port  64  by allowing and denying access to the intake port  62  and exhaust port  64 . As the rotor  20  moves past the intake port  62  and the exhaust port  64 , the rotor  20  allows and denies access to these ports due to the rotational position of the rotor  20  relative to the ports  62 ,  64 . As the rotor  20  rotates around the inner surface  50 , each end of the rotor  20  is rotating toward one of these ports and away from the other port. This action allows access to the port toward which the rotor  20  is rotating, and denies access to the port from which the rotor  20  is rotating away. By denying access to a port, the rotor  20  is actually closing the valve. By allowing access to the port, the rotor  20  is allowing the valve to be open if the valve shaft openings  74 ,  84  are in the open position. 
     Referring to the illustrated embodiment of  FIGS. 16A-16Q , the operating cycle of the engine  120  has four phases; intake, compression, expansion, and exhaust. The operating cycle of one side of a single rotor  20  in an engine  120  is now described. 
     Intake Cycle—0 to 180 degrees of rotation of the rotor  20 . 
     Referring to  FIGS. 16A-16D , during the intake cycle, an air-fuel mixture (the shaded area) is taken into the rotor chamber  52  through the rotary intake valve  70 . The rotation of the rotor  20 , the shape of the rotor chamber  52 , and the position of the rotary intake valve  70  in the rotor chamber  52  create turbulence in the air-fuel mixture to cause the air-fuel mixture to mix thoroughly within the rotor chamber  52  before ignition. 
     Compression Cycle—180 to 360 degrees of rotation of the rotor  20 . 
     Referring to  FIGS. 16E-16H , the air-fuel mixture is compressed as the rotor  20  rotates in the rotor chamber  52 . 
     Expansion Cycle—360 to 540 degrees of rotation of the rotor  20 . 
     Referring to  FIGS. 16I-16L , during the first part of this cycle, illustrated in  FIG. 161 , ignition of an air-fuel mixture takes place in the rotor chamber  52  when the rotor is a few degrees out of alignment with the valves so that rotor segment  110  has a larger surface area than rotor segment  112  as shown in  FIG. 14 . This unequal surface area creates unequal forces that act on the rotor, causing it to rotate about the origin  16  of the rotor  20  and rotor shaft  10 . After ignition, the combusted gas expands during the expansion cycle. In a four-cycle gasoline version of the engine  120 , ignition devices  53 , illustrated in  FIG. 14 , such as a conventional spark plug, and a distributor device (not shown), are used to ignite the air-fuel mixture. The distributor device includes a rotor that is in rotational communication with the rotor shaft  10  via a rotating coupling mechanism, such as gears similar to the gears  90 ,  92  coupled to the rotor shaft  10  and the valve shafts  72 ,  82 , illustrated in  FIG. 7 . In other embodiments, a timing belt and at least two pulleys may be used to rotatably couple a distributor device rotor shaft to the rotor shaft  10  of the engine  120 . The distributor may be mounted on the housing  40  or it can be mounted on other structure proximate to the housing  40 . An electronic distributor device and ignition system (not shown) may also be used to control and ignite the air fuel mixture. 
     A variety of fuels may be used to operate the engine  120 . The type of fuel used will determine the type of ignition device  53  used to ignite the air-fuel mixture. For example to ignite the air-fuel mixture in engines  120  that use gasoline as the fuel, the ignition device  53  illustrated in  FIG. 14  may be a conventional spark plug. In other embodiments, such as, but not limited to, those that use diesel as the fuel, the ignition device  53  may be a glow plug (not shown). It will be understood that various embodiments may not incorporate an ignition device  53 . For example, certain diesel engines may be designed to ignite the air-fuel mixture using heat generated from compressed air. One of skill in the art, having reviewed this disclosure, will appreciate these and other variations that can be made to the device  53  without deviating from the spirit of the invention. 
     Exhaust Cycle—540 to 720 degrees of rotation of the rotor  20 . 
     Referring to  FIGS. 16M-16P , the combusted gas is expelled through the rotary exhaust valve  80  as the rotor  20  rotates around the rotor chamber  52 . 
     Table 1 tabulates the relationships of the two sides of the two rotors  20 ,  22 , in embodiments with rotor pairs, as they rotate around the rotor chamber  52  during the engine  120  operating cycle. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Rotor Operating Cycle Sequence 
               
            
           
           
               
               
               
               
            
               
                 Rotor 1 Side 1 
                 Rotor 1 Side 2 
                 Rotor 2 Side 1 
                 Rotor 2 Side 2 
               
               
                   
               
               
                 Intake 
                 Exhaust 
                 Expansion 
                 Compression 
               
               
                 Compression 
                 Intake 
                 Exhaust 
                 Expansion 
               
               
                 Expansion 
                 Compression 
                 Intake 
                 Exhaust 
               
               
                 Exhaust 
                 Expansion 
                 Compression 
                 Intake 
               
               
                   
               
            
           
         
       
     
     Table 2 tabulates the rotary input and exhaust valve functions as a single rotor  20  rotates around the rotor chamber  52 . 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 2 
               
             
            
               
                   
                   
               
               
                   
                   
                   
                 Combined Rotor 
               
               
                   
                 Rotor Side 1 
                 Rotor Side 2 
                 Sides 1 &amp; 2 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Rotor 
                 Input 
                   
                 Input 
                   
                 Input 
                   
               
               
                 Rotation 
                 Valve 
                 Exhaust 
                 Valve 
                 Exhaust 
                 Valve 
                 Exhaust 
               
               
                   
               
               
                  0 to 180 
                 Open 
                   
                   
                 Open 
                 Open 
                 Open 
               
               
                 180 to 360 
                   
                 Closed 
                 Open 
                   
                 Open 
                 Closed 
               
               
                 360 to 540 
                 Closed 
                   
                   
                 Closed 
                 Closed 
                 Closed 
               
               
                 540 to 720 
                   
                 Open 
                 Closed 
                   
                 Closed 
                 Open 
               
               
                   
               
            
           
         
       
     
     Embodiments of the engine  120  may have multiple pairs of rotors  20 ,  22 , mounted on the rotor shaft  10  to provide increased power with smoother operation. These pairs of rotors  20 ,  22  can be oriented in such a manner as to give continuous maximum power during each 360 degree rotation of the rotor shaft  10 . For example, an engine  120  with four rotors would have two pairs of rotors  20 ,  22  oriented ninety degrees from each other. An engine  120  having six rotors would have three pairs of rotors  20 ,  22  oriented sixty degrees from each other. 
     In still another embodiment, the engine  120  can incorporate a pre-combustion chamber to increase the efficiency and decrease fuel consumption of the engine by thoroughly mixing the air-fuel mixture before the intake cycle of the engine  120 . The pre-combustion chamber would mix the air-fuel mixture before it enters the combustion chamber. The air-fuel mixture from the pre-combustion chamber would feed directly into the combustion chamber. The pre-combustion chamber would have a similar rotor and housing inner surface configuration as that for rotor chambers  52 ,  54  of the engine  120 . 
     Additionally, or alternatively, the engine  120  can incorporate a super-charger chamber to increase power and performance. The supercharger chamber would be similar to the pre-combustion chamber but would compress the air-fuel mixture before it enters the rotor chambers  52 ,  54  of the engine  120 . This super-charger chamber would have a similar rotor and housing inner surface configuration as that for the rotor chambers  52 ,  54  of the engine  120 . The super-charger may also serve as a pre-combustion chamber to thoroughly mix the air-fuel mixture as described above before it compresses the air-fuel mixture. 
     Additionally, or alternatively, a turbo-charger can be used to increase the power and performance of the engine  120  by increasing the amount of air entering the rotor chambers  52 ,  54  of the engine  120 . The exhaust gases of the engine  120  can drive the turbo-charger. The intake and exhaust ports  62 ,  64  of the engine  120  are located in close proximity so that turbo-chargers can be mounted without difficultly on the engine. 
     Additionally, or alternatively, the engine  120  can readily accommodate a post-combustion chamber that burns the unburned fuel  300  contained in the exhaust gases from the main rotor chambers  52 ,  54  of the engine  120  as shown in  FIG. 39 . The post-combustion chamber would have a similar rotor and rotor chamber as the main rotor  20  and rotor chamber  52  of the engine  120 . The post-combustion chamber will increase fuel efficiency of the engine  120  by gaining additional power by burning the unburned fuel  300  exhausted from the main rotor chambers  52 ,  54 . These unburned gases only need to produce enough power to rotate the rotor with sufficient speed so as to not affect the performance of the engine and therefore not consume any power from the engine. The effect of the post-combustion chamber will be to decrease the exhaust emissions of the engine  120  while providing additional power. 
     Furthermore, the design of the engine  120  can be used for the basis of an air compressor using single or multiple rotors. As the rotor  20  rotates around the rotor chamber  52 , the shape of the inner surface  50  and the rotor  20  create increasing and decreasing volumes within the rotor chamber  52 . During the intake cycle of the compressor the volume of the air chamber formed by the rotor  20  and the inner surface  50  increases in volume thus drawing air into the rotor chamber  52 . During the compression cycle of the compressor the volume of the rotor chamber  52  formed by the rotor  20  and the inner surface  50  decreases in volume thus compressing the air in the rotor chamber  52 . The compressor would not require any intake valves  70  or exhaust valves  80  due to the self-valving action of the rotor  20  as it rotates around the rotor chamber  52 , although one-way exhaust valves may be used to increase the efficiency of the compressor. 
     In such an embodiment, as the rotor  20  passes air intake port  62 , the compressor would draw air into the rotor chamber  52  to be compressed. Air would continue to be drawn into the compressor as the rotor  20  rotates in the rotor chamber  52  for 180 degrees. At this time the opposite end of the rotor  20  would pass the air intake port  62  in the rotor housing  40  thus sealing the rotor chamber  52 . An end of the rotor  20  would pass the exhaust port  64  in the rotor chamber  52  thus opening the port  64  for the compressed air to be exhausted. The compression phase of the cycle would begin as the rotor  20  rotates around the rotor chamber  52 , which gets smaller as the rotor  20  rotates around the inner surface  50 . As the rotor  20  reaches the point of maximum compression the compressed air in the compressor chamber is exhausted out of the compression chamber through a one-way valve in the exhaust port  64 . 
     A more complex version of the compressor may use the rotary exhaust valve design of the engine  120  to gain additional efficiency. Such compressors can be developed using multiple compression chambers feeding one in to the other. In this design rotary intake valves  70  and exhaust valves  80  will control access to the compression chambers to increase the efficiency of the compressor. 
     Additionally, or alternatively, the engine  120  may operate through two cycles. A glow plug may be used as the ignition device  53 , illustrated in  FIG. 14 , in a two-cycle combustion engine  120 . In yet other embodiments of a two-cycle engine  120 , steam or compressed air may be used as the expansion medium, where the engine  120  operates in the expansion and exhaust cycles. There are various methods of generating steam, including several types of steam generators that have been used effectively in the past and continue to be improved upon with new technology. Steam expands into the rotor chamber  52  during the first portion of the expansion cycle, illustrated in  FIG. 161 . The intake valve  70  is then closed and the steam continues to expand in the rotor chamber  52  as the rotor rotates around the rotor housing, as illustrated in  FIGS. 16J-16L . At the end of the expansion cycle, the steam is exhausted from the rotor housing through the exhaust port  64 , as illustrated in  FIGS. 16M-16P . It will be understood that various embodiments may not incorporate the rotary exhaust valve  80 . For example, the self-valving action of the rotor  10  relative to the location of the exhaust port  64  may be sufficient to eliminate the need for the rotary exhaust valve  80 . From the exhaust port  64 , the expanded steam would travel to a condenser (not shown) or to other expansion chambers prior to the condenser. 
     In still other embodiments, the engine  120  according to the present invention is well-suited to be used for a hybrid automobile application such as, but not limited to, a gasoline-electric hybrid, because the engine  120  is lighter and smaller than a comparable internal combustion piston engine, resulting in a high power-to-weight ratio. In addition, the foregoing embodiments can be adapted for use as vacuum and fluid pumps where the main rotor is driven by an external prime mover or by one or more rotors in the same housing. 
     A further embodiment of the invention is illustrated in accompanying  FIGS. 17A-17E  and  18 A- 18 C. In  FIG. 17A  is shown a modified rotor shaft  130  having a substantially cylindrical body  132  with a circular cross-sectional configuration and a shaft  134  extending from each end  136  of the rotor shaft  130 . A pair of transverse openings  138  is formed through the body  132  that are sized and shaped to receive a rotor in slidable engagement, which is shown in  FIGS. 18A-18C . More particularly, the openings  138  as shown in this embodiment have a rectangular cross-sectional configuration to match the cross-sectional configuration of a corresponding rotor. It is to be understood that other cross-sectional configurations can be used. This embodiment depicts two openings because the rotor shaft  130 , 131  will be used in a two-chamber housing having two rotors. 
       FIGS. 17B-17E  are illustrations of the shaft  130  where ball or roller bearings  14  are mounted at each end and in the center of the shaft  130  to support the shaft  130  in the housing (not shown).  FIG. 17C  is a cross-section of the shaft  130  taken along lines C-C in  FIG. 17B , and  FIG. 17E  is a cross section of the shaft  130  taken along lines E-E of  FIG. 17D . 
     In  FIGS. 18A-18C  a rotary engine housing  144  is shown in cross section to include a chamber  146  having a shaft  130  rotatably mounted therein. The transverse opening  138  in the shaft receives a rotor  148  in slidable engagement. The rotor  148  can then slide within the shaft  130  to accommodate the changing relative positions of the rotor and housing as the rotor  148  rotates the rotor shaft  130 . 
     Various other embodiments of the invention are described hereinbelow. 
     For example, the centerline of the intake valve port  62  and the centerline of the exhaust valve port  64  in the rotor housing  40  can be located on the centerline of the rotor shaft  10  as shown in  FIG. 1  or above or below the centerline of the rotor shaft  10 . Locating the centerline of the intake valve  62  below the center line of the rotor shaft  10  allows the intake air fuel mixture to enter the combustion chamber  52  at a point below the centerline of the rotor shaft  10  which may enhance the performance of the rotary engine. Locating the centerline of the exhaust valve port  64  below the center line of the rotor shaft  10  allows the engine exhaust to exit the combustion chamber  52  at a point below the centerline of the rotor shaft  10  which may enhance the performance of the rotary engine. 
     The curve of the inner surface  50  of the rotor housing  40  generated for a rotor  20  with round end seals  30  will be slightly different but essentially the same as the curve of the inner surface  50  of the rotor housing  40  generated for a rotor with end seals  30  that come to a point. The generation of the curve of the inner surface  50  of the rotor housing  40  is done using essentially the same method but in a slightly different manner. 
     As shown in  FIG. 2C  a series of points  42  determine a unique contour of an inner surface  50  of the rotor housing  40 , shown in  FIG. 1 . The points  42  are generated by the round end of the rotor at one end of a line segment  44 , which is equal to the length along the horizontal axis of the rotor and the round end of the rotor at the other end of the line segment  44 , and which traces along a curve  46  that forms one segment of the contour of the inner surface  50  and passes through an origin  16 . The center of rotation of the rotor shaft  10  and the center of rotation of the rotor  20  is the origin  16 . The inner surface  50  of the rotor housing  40  has a variable radius and a variable diameter. As shown in  FIG. 2C  the diameter of the inner surface  50  of the rotor housing  40  is greater along the first axis  41  than the diameter of the inner surface  50  of the rotor housing  40  along the second axis  43 , which is perpendicular to the first axis  41 . 
     In another embodiment as shown in  FIGS. 19A-19C  the spur gear  92  mounted on the intake valve shaft  72  and the spur gear  92  mounted on the exhaust valve shaft  82  mesh with other spur gears (not shown) mounted on the shaft of an electric stepper or servo motors  150 . This allows the timing of the intermittent opening and closing of the intake and exhaust valves  74 ,  76 ,  84 ,  86  to be controlled electronically. 
     In another embodiment as shown in  FIGS. 20A-20C  the intake and exhaust valve shafts  72 ,  82  of a two rotor engine have the same center line but can be rotated independent of each other using electric stepper or servo motors  150 . This allows for the timing of the intermittent opening and closing of the intake and exhaust valves  74 ,  76 ,  84 ,  86  to be rotated independent from each other and controlled electronically. 
     In another embodiment shown in  FIG. 21 , a rotor  152  can have flat top and bottom surfaces that curve symmetrically from the center lateral axis  154  to the tip of each rotor  152 . The curve of the top and bottom surfaces  156 ,  158  can be any curve with a slightly larger diameter than that of the circular portion of the inner surface of the rotor housing  50 . These curves will meet at the tip of the rotor seal  30  at the point the rotor seal  30  comes in contact with the inner surface of the rotor housing  50 . This rotor shape will facilitate the clearing of exhaust fumes from the combustion chamber  52  during the exhaust phase of the engine&#39;s operating cycle by reducing the area of decreasing volume  58  in the rotor chamber to a minimum. This rotor shape also will increase the compression ratio of the engine for a given offset between the center of rotation of the rotor and the center of the circular portion of the inner surface of the rotor housing. 
     In another embodiment shown in  FIG. 22  there can be a curved indentation or hollowed out area  160  in the top and bottom surface  162 ,  164  of the rotor  166 . The air fuel mixture will be concentrated in this area when ignition takes place during the expansion phase of the engine&#39;s operating cycle, causing the combustion to be more complete. 
     In  FIG. 23  there is shown a number of horizontal holes  168  running from one side of the rotor  170  to the other side, which will decrease the weight of the rotor  170 . The decrease in the weight of the rotor  170  will decrease the inertia of the rotor  170  which will make it more responsive to acceleration and deceleration as it rotates about the inside of the rotor housing  50 . The decrease in the weight of the rotor  170  will decrease the unbalanced force generated by the unbalanced weight of the rotor  170  as it rotates about the inner surface of the rotor housing  50 . This in turn will decrease the vibration of the engine. 
     As shown in  FIG. 24 , rotor housing end walls  60  and the rotor housing  40  will be sealed by using a gasket  172  similar to that of a head gasket of an internal combustion piston engine. This gasket  172  will allow coolant to circulate through the end wall of the rotor housing  60  and the rotor housing  40  and provide an air tight seal of the combustion chamber  52 . 
     In another embodiment shown in  FIG. 25 , the seals  174  at the end of the rotor  20  can have a round or curved surface. The curved top and bottom surfaces of the rotor tip seals  30  will be symmetrical along the longitudinal axis  21  of the rotor  20 . The curve of the top and bottom surfaces of the rotor end seals  174  would meet just beyond the point at which the rotor end seal  174  comes in contact with the inner surface of the rotor housing  50  if the end of the rotor seal  174  were not rounded to meet the inner surface of the rotor housing  50 . This rounded or curved shape will cause the rotor end seals  174  to be rounded at the end which will reduce the wear on the end of the rotor seals  174  since the point at which the seals contact the inner surface of the rotor housing  50  will change as the rotor rotates about the inner surface of the rotor housing  50 . 
     In another embodiment as shown in  FIG. 26  the width  176  of the rotor housing  40  and rotor  20  inside the rotor housing  40  can be adjusted along with the shape of the inner surface of the rotor housing  50  to the achieve maximum performance of the rotary engine. 
     In the case of an engine with a supercharger chamber the width  176  of the rotor housing  40  and rotor  20  for the supercharger chamber would be made so that the supercharger chamber gives the engine maximum performance. The width  176  of the supercharger chamber is independent of the width  176  of the rotor  20  and rotor housing  40  of the engine. 
     In the case of an engine with a post-combustion chamber, the width  176  of the rotor housing  40  and rotor  20  inside the rotor housing  40  can be made so that the unburned fuel in the exhaust emissions are burned as completely as possible. The width  176  of the post-combustion chamber is independent of the width  176  of the rotor  20  and rotor housing  40  of the engine. 
     In another embodiment as shown in  FIGS. 27 and 28 , the rotor end seals and the rotor side seals have additional sealing material  182  mounted in enlarged grooves  178 ,  180 , which are located around the perimeter of the rotor end seals  185  and the rotor side seals  184 . This material  182  seals the small seam that may exist between the rotor  20  and the rotor end seals  182  and the rotor side seals  184 . This material serves as a gasket to seal off the small areas around the rotor side seals  184  and rotor end seals  185  that may exist between the rotor  20  and the rotor end seals  185  and rotor side seals  184 . This material will be elastic and made of heat and wear resistant material. 
     In another embodiment as shown in  FIGS. 29-31 , a rotor  188  can be split horizontally into two identical halves  186 . This configuration allows the two halves  186  of the rotor  188  to be held together by either a pin or a bolt  190  running parallel to the rotor shaft. When installed, the split rotor  186  is mounted on and held together in the correct position on the flat surface  12  of the rotor shaft  10 . This method of fabrication eliminates the need to slide the rotor over the rotor shaft  10  to get it into position for assembly of the engine. This allows for rotary engines to have any number of multiple pairs of rotors  188  mounted on round rotor shafts  10 . 
     In another embodiment as shown in  FIG. 32  a rotor  192  can be split horizontally into two identical halves  194 ,  196 . This configuration allows the two halves  194 ,  196  of the rotor  192  to be held together by a set of screws or bolts running from one half of the split rotor  192  to the other half of the split rotor  192  perpendicular to the longitudinal axis  21  of the split rotor  192 . When installed, the split rotor  192  is mounted on and held together in the correct position on the flat surface  12  of the rotor shaft  10 . This method of fabrication allows rotary engines to have any number of multiple pairs of rotors  192  mounted on round rotor shafts  10 . 
     In FIGS.  33  and  34 A- 34 C, the rotor shaft  200  is a round shaft with flat surfaces  12  on opposite sides of the rotor shaft  200  where multiple pairs of rotors can be mounted by using the split rotors described above. As shown in  FIG. 1 , the flat surfaces  12  on the rotor shaft  10  accommodate the flat inner surfaces  12  of the rotors once they are mounted on the rotor shaft  10 . Each pair of rotors  188 ,  192  are oriented at equal degree intervals from each other along the rotor shaft  200 . Each pair of rotors can be next to each other on the rotor shaft  200  or they can be oriented so that a rotor of a different pair is located between them. The rotor shaft  200  can be mounted on a plurality of ball bearings or roller bearings  202  mounted in the end walls  60  of the rotor housing  40 , shown in  FIG. 1 . 
     In another embodiment shown in  FIG. 35 , four rotary valve shafts are mounted on the rotor housing  40 . The intake valves  204  and the exhaust valves  206  are located on opposite sides of the rotor housing  40 . The four valve shafts increase the intake  204  and exhaust  206  valve cross sectional area. The additional valve area increases the amount of air and exhaust that can enter and exit the engine, which will result in better engine performance. Locating the input  62  and exhaust  64  ports above and below the horizontal plane of the rotor shaft  10  allows flexibility in the timing of the opening and closing of the input  204  and exhaust  206  valves for better engine performance. 
     In the embodiment shown in  FIGS. 36A-36B  large rotary valve shafts  208 ,  210  are mounted on the rotor housing  40 . The intake valve  212  and the exhaust valve  214  are located on opposite sides of the rotor housing  40  and in the same plane as the rotor shaft  10 . The centerline of the intake valve port  62  and the centerline of the exhaust valve port  64  in the rotor housing  40  are located on a centerline passing through the rotor shaft  10 . The large valve shafts  208 ,  210  increase the intake valve  212  and exhaust valve  214  cross sectional area. The additional valve area increases the amount of air and exhaust that can enter and exit the engine, which will result in better engine performance. 
     In  FIG. 37  valve seals  216  are mounted in grooves  218  cut around the diameter of the valve shaft  220 , which intersect channels  222  cut along the top and bottom of the valve shaft  220 . Spring loaded valve seals  216  interlock with each other at the intersection of the grooves. There can be multiple grooves with seals in them to insure a tight seal around the valve shafts  220 . 
     In another embodiment illustrated in  FIG. 38  valve seals  224  are mounted in wide grooves  226  cut into the top and bottom of the valve shaft  228 . These grooves  226  are oriented at ninety degrees from the valve openings  230  in the valve shaft  228 . The valve seals  224 , which are wider than the valve openings in the rotor housing  40 , are mounted in these grooves  226  in the valve shaft  228 . Valve seal springs (not shown) are mounted in holes passing through the valve shaft  228  on either side of the valve opening  230  and push against the valve seals  224  and hold them in place. These valve seals  224  can move in and out independently from the center of the valve shaft. 
     In another embodiment illustrated in  FIG. 38 , valve seals  224  are joined together with small shafts  232  mounted in holes passing through the valve shaft  228  on either side of the valve opening  230  so they move as a unit. As the pressure due to combustion or compression in the rotor chamber  52  increases to the point of moving the valve seal  224  away from the inside wall of the valve port  62 ,  64  thus overcoming the air tight seal of the valve  70 ,  80  the part of the valve seal  224  on the other side of the valve shaft  228  will be pressed against the out side wall of the valve port  62 ,  64  thus increasing the force of the seal  224  against that wall and preserving the airtight seal of the valve  70 ,  80 . The force trying to move the valve seal  224  away from the inside wall of the valve port  62 ,  64  will be applied to the part of the valve seal  224  on the other side of the valve shaft  228  and will keep that part of the valve seal  224  from moving away from the outer wall of the valve port  62 ,  64 . 
     All of the above U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet, are incorporated herein by reference, in their entirety. 
     From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims.