Patent Publication Number: US-7581518-B2

Title: Coaxial oil pump for barrel engines

Description:
REFERENCE TO RELATED APPLICATION 
   This application claims priority to U.S. Provisional Patent Application Ser. No. 60/773,234, filed Feb. 14, 2006, the entire content of which is incorporated herein by reference. 

   FIELD OF THE INVENTION 
   The invention relates to barrel-type internal combustion engines. More particularly, the invention relates to oil pumps barrel-type internal combustion engines. 
   BACKGROUND OF THE INVENTION 
   Internal combustion engines are widely used for driving a variety of vehicles. Internal combustion engines come in a variety of configurations, which are typically aptly named for the particular orientation or arrangement of the reciprocating pistons and cylinders in the engines. One example of an internal combustion engine is a “V”, type engine, in which the “V” refers to the arrangement of the cylinders in rows that are angled relative to each other to form a V shape. Another type of internal combustion engine that is most relevant to the invention is a barrel-type engine. 
   The barrel engine includes a plurality of cylinders and pistons arranged in the form of a “barrel” in which their axes are parallel to each other and typically arranged along a circle concentric with the drive shaft. Power is transmitted from the reciprocating pistons to a cam plate via a roller or bearing interface. The cam plate&#39;s nominal plane is perpendicular to the piston axes and attached to the drive shaft for movement therewith. The cam plate also has a generally sinusoidal shape, so that the axial reciprocal movement of the pistons causes rotational movement of the cam plate and drive shaft. 
   Barrel engines, like most conventional internal combustion engines, include oil pumps for pumping oil to high friction areas of the engine. The oil pumps are commonly driven by the drive shaft via gears or a pulley/belt arrangement, wherein an input shaft of the pump is arranged along an axis that is parallel to and spaced apart from the drive shaft. 
   SUMMARY OF THE INVENTION 
   According to one aspect of the invention, a barrel internal combustion engine includes a plurality of pistons, a drive shaft, a cam plate and an oil pump. The plurality of pistons is slidably coupled to a plurality of cylinders for reciprocal movement along axes generally parallel with a central axis. The drive shaft is rotatable about the central axis. The cam plate is coupled to the drive shaft for rotation therewith. The cam plate is operatively coupled to the pistons to cause rotation of the drive shaft about the central axis in response to the reciprocal movement of the pistons. The oil pump has a rotatable input member coupled coaxially with the drive shaft for rotation therewith about the central axis for actuating the oil pump. 
   According to another aspect of the invention, a barrel internal combustion includes a plurality of pistons slidably coupled to a plurality of cylinders for reciprocal movement along axes generally parallel with a central axis. A valve assembly controls the intake and exhaust of gases from the plurality of cylinders. A cam shaft is rotatable about the central axis to cause actuation of the valve assembly. The cam shaft has a first plurality of spline teeth. An oil pump is actuated by rotation of an input member. The input member has a second plurality of spline teeth. A drive shaft is rotatably driven about the central axis by the plurality of pistons. The drive shaft has a plurality of spline teeth formed on an end thereof. The spline teeth of the drive shaft engage both the first and second plurality of spline teeth for actuating the cam shaft and the oil pump during rotation of the drive shaft. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
       FIG. 1  is an enlarged front perspective view of a portion of the barrel engine according to one aspect of the invention, with the oil pump shown mounted coaxially with the drive shaft of the barrel engine; 
       FIG. 2  is a cross sectional view of the barrel engine of  FIG. 1 ; 
       FIG. 3  is a front perspective view of a drive shaft in the barrel engine in  FIG. 1 ; 
       FIGS. 4 and 5  are front and rear perspective views of an oil pump for the barrel engine; and 
       FIG. 6  is a schematic view of the oil delivery system for the barrel engine. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The invention improves over conventional barrel engine designs by providing an oil pump having an input shaft that is coaxial with and driven by the drive shaft. This coaxial arrangement eliminates the need for gears or pulleys and belts, thereby simplifying the overall assembly of the barrel engine and reducing the costs associated therewith. 
   Referring to the cross sectional view of  FIG. 2 , a barrel-type internal combustion engine according to the invention is generally indicated at  10 . The engine  10  includes a plurality of cylinders  12  and pistons  14  arranged concentrically about a central drive shaft assembly  20 . The pistons  14  are slidably engaged within the respective cylinders  12  for reciprocal axial movement therein. Power is transmitted from the reciprocating pistons  14  to a cam plate  16  via a roller or bearing interface. The cam plate  16  is coupled to the shaft assembly  20  for rotation therewith about a central rotational axis. The cam plate  16  has a generally sinusoidal shape, such that the reciprocal axial movement of the pistons  14  causes corresponding rotational movement of the cam plate  16  and shaft assembly  20 . 
   The shaft assembly  20 , in one embodiment of the invention. Includes a drive shaft  30  and a cam shaft  28 . The drive  30  and cam  28  shafts are coupled in a splined arrangement, which couples the shafts  28 ,  30  in the rotational direction and allows assembly or disassembly in the axial direction. As shown in  FIG. 3 , the drive shaft  30  extends axially between opposite first  32  and second  34  ends. The first end  32  includes outwardly extending spline teeth for coupling the drive shaft  30  to a primary driven device, such as a transmission. A middle portion  36  of the drive shaft  30  includes outwardly extending spline teeth for engaging the cam plate  16 . The second end  34  of the drive shaft  30  is defined by a reduced diameter portion having outwardly extending spline teeth  35 . A main bearing or bearing surface  31  is provided close to the second end  34 . A thrust bearing or bearing surface is shown at  39 . As will be clear to those of skill in the art, the splined portions may be formed differently than shown, and the drive shaft configuration may be different than shown. 
   In  FIGS. 1 and 2 , an oil pump  40  for delivering oil throughout the engine  10  is shown coupled to the second end  34  of the drive shaft  30 . The oil pump  40  is illustratively shown as a geroter-type pump. It should, however, be readily appreciated by persons having ordinary skill in the art that other types of pumps operable by rotation of an input member may be used. Referring to  FIGS. 1 ,  4  and  5 , the oil pump  40  includes a housing  29  that extends between opposite first  41  and second  43  ends. The housing  29  includes a cylindrically shaped first inner surface  45  adjacent the first end  41 . The housing  29  includes a cylindrically shaped second inner surface  47  adjacent the second end  43 . In the illustrated embodiment, the first inner surface  45  has a larger diameter than the second inner surface  47 . The first  45  and second  47  inner surfaces are generally coaxially aligned and define a continuous center bore that extends through the housing  29 . 
   The oil pump  40  includes a cylindrically shaped external rotor  49 . The external rotor  49  has a smaller outer diameter than the first inner surface  45 . The external rotor  49  rolls along the first inner surface  45  in an eccentric manner relative to the center axis of the center bore. The external rotor  49  includes a plurality of inner teeth  51  that extend radially inwardly toward a center aperture  53 . An internal rotor or input member  42  is disposed in the center aperture  53 . The input member  42  includes a plurality of outer teeth  55  for engaging the inner teeth  51  of the external rotor  49 . The input member  42  includes a center bore  44  for receiving the second end  34  of the drive shaft  30  coaxially therethrough. The walls defining the center bore  44  of the input member  42  include a plurality of spline teeth complementary with the spline teeth of the second end  34  of the drive shaft  30 . The input member  42  rotates with the drive shaft  30  about the rotational axis. The internal rotor  42  has one less tooth than the external rotor  49 , so that the number of rotations of the external rotor  49  is reduced relative to the internal rotor  42 . The rotation of the internal rotor  42  causes eccentric or wobbling rotation of the external rotor  49  along the first inner surface  45 . Oil is compressed between the external rotor  49  and the first inner surface  45  and directed through an outlet (not shown) in the housing  29  for distribution to various parts of the engine. 
   A main bearing  57  is supported by the oil pump  40  and is disposed in the second inner surface  47  of the housing  29 . The main bearing  57  includes a bearing surface for mating with the bearing surface  31  on the drive shaft and a thrust surface for mating with the thrust bearing surface  39 . 
   As shown in  FIG. 6 , oil feed lines extend between the oil pump  40  and various high friction areas of the engine, such as the bearings. At least one of the feed lines may be directed through an oil cooler  64 , where heat generated by the engine  10  is exchanged with engine coolant passing through the oil cooler  64 . At least one supply line extends between an oil pan  66  and the oil pump  40 . An oil filter  68  is coupled to the feed line between the oil pump  40  and the oil cooler  64  for filtering particulate from the oil flow passing therethrough. 
   Still referring to  FIG. 6 , the reciprocating movement of the pistons  14  causes rotational movement of the cam plate  16  and, in turn, the shaft assembly  20 . The input member  42  rotates with the drive shaft  30  of the shaft assembly  20 . The oil pump  40  is driven by the rotation of the input member  42  with the drive shaft  30 . Oil is supplied from the pan  66  to the oil pump  40  via the supply line. Oil is delivered by the oil pump  40  via the feed lines to the high friction areas of the engine  10 . Oil is gravity fed back to the pan  66 , where it is recirculated during continued operation of the engine  10 . As will clear to those of skill in the art, the positioning of the oil pump in a coaxial relationship with the drive shaft, and the location of the oil pump, is advantageous and makes use of space that may otherwise be wasted. It also provides for the oil pump to be directly driven, thereby eliminating intermediate parts. 
   The invention has been described in an illustrative manner. It is, therefore, to be understood that the terminology used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the invention are possible in light of the above teachings. Thus, within the scope of the appended claims, the invention may be practiced other than as specifically described.