Abstract:
An improved piston ring suitable for use in an internal combustion engine is disclosed comprising a plurality of races sized to receive elongate rollers disposed around the circumference thereof. The elongate rollers may be shaped as a prolate ellipsoid or other rounded shape. The piston ring may seat within a groove in fluid communication with an oil channel extending through a piston rod and opening into a rod bearing connecting the piston rod to a crankshaft. A crankshaft has a corresponding oil channel therewith and has an opening positioned to periodically align with the opening in the rod bearing when rotated. Oil is pumped into the oil channel in the crankshaft to force oil over the piston rings. Drain apertures may be formed in another groove formed in the piston to conduct oil away from the piston.

Description:
RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/688,953 filed Jun. 9, 2005 and entitled, “RINGS FOR PISTONS AND METHOD FOR SEALING PISTONS IN CYLINDERS.” 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention pertains to piston rings and, more particularly, to compression rings and oil rings having rollers and related methods and lubrication systems for reducing friction and increasing torque and horsepower transmission, particularly in internal combustion engines.  
       BACKGROUND OF THE INVENTION  
       [0003]     Piston-and-cylinder assemblies are used in a variety of fields, including combustion engines, hydraulics, and pneumatics. Typical assemblies include a piston slideably mounted within a cylinder to fill, pressurize, and evacuate substance in the cylinder. This can include air-fuel mixtures, liquids, and gasses.  
         [0004]      FIG. 1  illustrates a typical assembly  20  in which a piston  22  is slideably received within a cylinder bore  24  formed in a block  26 . A cylinder head  28  is attached to the block  26  to form a chamber  30  between the top surface  32  of the piston  22  and an inside surface  34  of the cylinder head. Because the piston  22  has a diameter slightly smaller than the diameter of the cylinder bore  24 , a space  36  is created therebetween. While this reduces friction between the piston  22  and the wall  38  of the cylinder bore  24 , it enables substance to pass from the chamber  30  to outside the cylinder bore  24 . In other words, when the piston  22  slides upward in the cylinder  24  towards the cylinder head  28 , compression of substance within the chamber  30  will force some of the substance into the space  36  between the piston  22  and the cylinder wall  38 . To prevent this from happening, resilient rings are employed.  
         [0005]     More particularly, the selection of piston rings for an engine or other combustion application is related to the particular type of engine. Because different engines have varying requirements, such as competitive racing engines, truck engines, sport engines, and engines designed for specific fuels such as diesel, aircraft, automobile, as well as alcohols and nitrous oxides; all may require specific differences in materials and design. Piston rings function to contain and maintain in the cylinder chamber  30  a combustion pressure, to prevent oil from getting into the combustion chamber  30 , and to assist in the control of temperature in the engine.  
         [0006]     As shown in  FIG. 1 , there are three rings comprising a top ring known as a compression ring  40 , a second ring or secondary compression ring  42 , and a third ring or oil control ring  44 . The top ring  40  aids in sealing against loss of pressure during the combustion process. It is designed to maintain a high buildup of pressure as the piston arrives at the top of its stroke and when the combustible mixture is ignited, building up additional pressure to force the piston  22  downward. Several design criteria aid in the ability of the piston ring to maintain this pressure, including ring gap, material resiliency, and the size and spacing of the ring  40  with respect to the piston  22  and the cylinder wall  38 .  
         [0007]     The second compression ring  42  is similar to the first compression ring  40  in that it has a ring gap that allows gasses to further penetrate down the space  36  between the piston  22  and the cylinder wall  38 . This passing of the hot gasses is known as blow-by, and can have detrimental affects on the engine. This includes contaminating the oil with carbon particles from the combustion process, raising the acidic level and heating up the oil and speeding up the oxidation process. This in turn allows the carbon particles to wear out all the parts that the oil is expected to lubricate. This ring also serves as an oil scraper to minimize oil above the second ring  42 .  
         [0008]     The oil ring  44  is designed to aid in lubrication of the other rings, pistons, the rod, wrist pins, and cylinder walls while preventing the oil from interfering with the combustion process. The oil ring  44  also assists in the thermal control of the piston  22  by aiding in passing oil to the inside of the piston for cooling as well as lubrication.  
         [0009]     Referring next to  FIG. 2 , conventional ring terminology is illustrated. This includes the scuff band A, which is one or more raised bands of piston material used in some piston designs to reduce scuffing. The groove depth B is the distance between the back of the ring groove and the cylinder wall with the piston centered. The groove root diameter C represents the piston diameter measured at the back of the groove. This may vary between grooves on the same piston.  
         [0010]     The land diameter D is the diameter of a given land. This can also vary by design from the top to the bottom of the piston. The land clearance E is the difference in diameter between the cylinder bore and the land diameter. “E” represents one-half of the total.  
         [0011]     The skirt clearance F is the difference in diameter between the cylinder bore and the piston skirt diameter. In this case “F” represents one-half the total difference. The skirt groove G is a ring groove cut below the pin bore to carry an oil ring. The pin bore offset H is the distance the pin bore is offset from center and the groove spacer I is used on re-grooved pistons to return a ring groove to specifications or, in some performance applications, to facilitate the use of narrower ring sets than for which the grooves were originally designed.  
         [0012]      FIG. 3  illustrates ring terms and measurements wherein the free gap A is the ring end clearance when the ring is uncompressed. The compressed gap B, also known as the ring gap, is the end gap measured when the ring is installed.  
         [0013]     The radial wall thickness C is the distance between the inside and outside faces of the ring wall. The ring diameter D is the diameter of the ring measured with the ring installed on the piston, and the inside diameter E is measured with the ring installed on the piston. The ring sides F is the top and bottom surfaces of the ring. The ring face G is the part of the ring that is in contact with the cylinder wall. The side clearance H is the clearance between the ring groove and the ring side F.  
         [0014]     The ring width I represents the thickness of the ring between the top and bottom faces F. Torsional twist J as shown in  FIG. 3D  is a result of an imbalance in the compression of the upper and lower sides F of the ring, causing the ring to twist when compressed. This torsional twist is accounted for when attempting to seal both the ring in the groove and the ring to the cylinder wall. Finally, the back clearance K is the distance between the inside diameter of the ring and the bottom of the ring groove when the ring is installed on the piston.  
         [0015]     In the design of combustion engines, there are certain applications in which high power and torque in the 1000-2000 rpm range is desired. Because most engines are designed to operate at a higher rpm range, the low performance in the 1000-2000 rpm range is largely due to friction, and most of it caused by ring friction. Various designs have been proposed for reducing ring friction while maintaining performance levels. For example, U.S. Pat. No. 4,596,179, is directed to a reciprocating machine having a cylinder, a piston performing reciprocating movement within the cylinder and rollers mounted on each side portion of the piston in rolling contact with the cylinder. As shown in  FIG. 1  of this patent, the rollers are mounted below the rings and are designed to maintain the piston in alignment with the cylinder and prevent friction resulting from side thrust and lateral oscillating movements of the connecting rod as exerted on the piston. The use of these rollers would be inappropriate for sealing the piston in the cylinder because their design permits large amounts of blow-by.  
         [0016]     U.S. Pat. No. 4,442,759 describes a piston and cylinder in a hydraulic power booster having rollers mounted in a piston groove and maintained in radial contact with the cylinder wall by way of a leaf spring. These rollers are received in grooves in the cylinder wall to prevent torsional twisting of the piston due to forces exerted on a spindle coupled thereto. These rollers would be ineffective in preventing blow-by and sealing a combustion chamber.  
       BRIEF SUMMARY OF THE INVENTION  
       [0017]     The disclosed embodiments are directed to a rolling compression ring for use with a piston in a combustion engine, to a combination piston and roller compression ring taken alone and when mounted within a cylinder block, an engine formed from the same, and methods of forming a ring, a piston, a piston and ring combination, a short block and engine formed therefrom, including a lubrication system.  
         [0018]     In accordance with one embodiment of the invention, a piston ring is provided that includes an annular body having a plurality of races formed therein, a plurality of ellipsoid rollers retained within respective races in the annular body. Preferably, the ellipsoid rollers have an arcuate sidewall of a radius that corresponds closely to the radius of the annular body, and the races have ellipsoid-shaped seats in which the rollers are mounted.  
         [0019]     In accordance with a version of the foregoing embodiment, at least one oil passageway is formed in the body for allowing oil to pass between an interior side of the annular body and a face of the annular body, particularly to the area between the rollers and the seats.  
         [0020]     In accordance with a version of the foregoing embodiment, the end walls of each of the rollers is convex to reduce friction between the rollers. Ideally, there is a 0.01 inch gap between rollers when seated in the races of the annular body.  
         [0021]     In accordance with a version of the foregoing embodiment, the rollers are spaced apart a sufficient distance to not block an oil passageway formed in the annular body, thus forming a rolling oil ring.  
         [0022]     In accordance with another embodiment of the invention, a piston and ring combination is formed using the embodiment of the ring described above and the various aspects thereof.  
         [0023]     In accordance with another embodiment of the invention, a short block and engine are formed using the piston and ring combination from the embodiment described above.  
         [0024]     In accordance with another embodiment of the invention, a method of forming a ring is provided that includes providing an annular body having a plurality of races formed therein and a plurality of rollers retained within the respective races in the body. Ideally, the races are formed as ellipsoid-shaped seats and the rollers are formed having convex sidewalls with ellipsoid curvature to match the curvature of the seat and to match the curvature of the annular body.  
         [0025]     In accordance with a version of the foregoing embodiment, at least one oil passageway is formed in the annular body for allowing oil to pass between the face of the annular body and a backside of the annular body and between the seats and the rollers.  
         [0026]     In accordance with a version of the foregoing embodiment, the rollers are formed to have end walls that are convex to reduce friction between rollers.  
         [0027]     In accordance with still yet a further aspect of the foregoing embodiment, the ellipsoid-shaped seats are formed so that there is a gap of at least 0.01 inch between rollers when a compression ring is formed and a larger gap between rollers when an oil ring is formed.  
         [0028]     In accordance with another embodiment of the invention, a method for forming a piston in combination with the method of forming a ring above is provided that includes forming a groove in the piston to receive the ring.  
         [0029]     In accordance with a version of the foregoing embodiment, the method includes forming oil passageways in the piston to accommodate oil passing through the ring. In accordance with another embodiment of the invention, a method of forming a short block and a corresponding engine is provided that includes forming a piston and ring combination as described above and further including forming oil passageways in a connecting rod in combination with the piston and ring to lubricate the same.  
         [0030]     The rings formed in accordance with the present invention provide substantially reduced friction between the piston and the cylinder wall, which increases performance at all rpms and allowing further reduction in the speed of the engine. Reducing friction also eliminates heat increases caused thereby. In addition, improved lubrication and oil control is provided for protection of the bearings and various moving parts in the engine as a result of use of the rings of the present invention. In addition, cooler and cleaner oil is provided, contaminant buildup is reduced above and below the ring, and increased pressure of the ring against the wall through all four cycles of the engine is provided, increasing performance at all speeds. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING  
       [0031]     The foregoing advantages and features of the present invention will be more readily appreciated as the same become better understood from the following detailed description when taken in conjunction with the accompanying drawings, wherein:  
         [0032]      FIG. 1  is a partial cross-sectional view of a piston mounted in a cylinder in a known combustion engine arrangement;  
         [0033]      FIG. 2  is a side cross-sectional schematic of a piston and cylinder illustrating various features and aspects of known pistons and ring configurations;  
         [0034]      FIGS. 3A-3E  illustrate conventional features and dimensions of known rings;  
         [0035]      FIG. 4  is a top plan view of a rolling compression ring formed in accordance with the present invention;  
         [0036]      FIG. 5  is a broken view of a section of the rolling compression ring of  FIG. 4 ;  
         [0037]      FIG. 6  is a side view of  FIG. 4 ;  
         [0038]      FIG. 7A  is a partial cross-sectional side view of the rolling compression ring of  FIG. 4 , and  FIG. 7B  is an isometric illustration of a bearing formed in accordance with the present invention;  
         [0039]      FIG. 8  is a top plan view of a rolling oil ring formed in accordance with the present invention;  
         [0040]      FIG. 9  is a side view of a portion of the rolling oil ring of  FIG. 9 ;  
         [0041]      FIG. 10  is a cross-sectional illustration of the rolling oil ring of  FIG. 8 ;  
         [0042]      FIG. 11  is a side view of a piston and cylinder formed in accordance with another embodiment of the invention;  
         [0043]      FIG. 12  is a side view of a piston formed in accordance with a further embodiment of the invention;  
         [0044]      FIG. 13  is a side view of a piston and connecting rod formed in accordance with still yet another embodiment of the invention;  
         [0045]      FIG. 14  is a front view of a portion of the connecting rod of  FIG. 13 ;  
         [0046]      FIG. 15  is a front view of a wrist pin having oil grooves formed therein in accordance with an embodiment of the present invention; and  
         [0047]      FIG. 16  is a front view of a piston and connecting rod incorporating the wrist pin of  FIG. 15 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0048]     Referring initially to  FIGS. 4-7 , shown therein is one embodiment of the invention in the form of a rolling compression ring  50  having a body  52  with a top wall  54 , a bottom wall  56  and a back wall  58  that is preferably integrally formed with the top and bottom rims  5  and,  6 . An interior side  60  of the ring  50  has a plurality of races  62  formed therein.  
         [0049]     As shown in  FIG. 5 , the body  52  of the ring has an opening  64  formed therein that permits the ring  50  to be expanded in its diameter to fit over a piston. The opening is formed by two L-shaped notches  66 ,  68  formed on the ends of the ring  50 . These notches  66 ,  68  on the compression ring  50  are used with the embodiment depicted in  FIGS. 13 and 14 , as will be described in more detail herein. This configuration enables the ring  50  to seal with oil pressure from behind. More particularly, as shown in  FIGS. 6 and 7 , openings  70  are formed in each of the races  62  to permit the passage of oil therethrough.  
         [0050]     In one embodiment, the body  52  of the ring  50  is formed of a suitable material such as gray iron, steel, or the like, and the races  62  formed therein may be laser hardened. Bearings  72  that ride in each of the races  62  may be formed from chrome steel. In use, the upper rim  5  of the ring  50  is typically not heat treated and is formed to rest approximately 1/50,000 inch or less from a cylinder wall. That is, when the compression ring is used as the top ring on a piston it is formed to have this clearance. However, when used as a center compression ring, both the top and bottom rims  5 ,  6  are typically approximately 1/5000 inch from the cylinder wall to permit drainage of oil. The lower rim  6  of a top compression ring is also typically formed to have a clearance 1/5000 inch from the cylinder wall.  
         [0051]     As can be seen from  FIGS. 4-6 , the races  62  may have a concave shape, such as a semi-prolate ellipsoid shape. The bearing  72  or a portion thereof, has a matching shape. As viewed from the top in  FIG. 4 , the radius of curvature of the bearing  72  is similar to the radius of curvature of the exterior edge of the body  52 . As shown in  FIG. 7B , the race  72  is in the shape of a prolate ellipsoid. In other embodiments, the bearing  72  is barrel shaped having a radius of curvature corresponding substantially to the radius of the body  52 .  
         [0052]     Turning next to  FIGS. 8-10 , shown therein is an illustration of a rolling oil ring  76  having a body  78  formed to have a top wall  80 , bottom wall  82 , and back wall  84 . Races  86  are formed in the body  78  to accommodate bearings  88  that have a shortened length to permit oil drainage through enlarged openings  90  formed in the body  78 . Bearings having a shortened length may be accomplished by truncating the ends of ellipsoid or prolate shapes.  
         [0053]     As in the previous embodiment, the radius of curvature of the races  86  is substantially the same as the radius of curvature of the exterior edge  92  of the body  78 , and the bearings  88  are typically formed accordingly. In one embodiment, the upper rim  5  is designed to have a clearance of approximately 1/5000 inch from the cylinder wall, and the lower rim  6  is configured to have a clearance of approximately 1/5000 inch from the wall.  
         [0054]      FIG. 11  shows a first oil plan formed in accordance with the present. The illustrated system provides a means for distributing oil to piston rings, such as the piston rings described hereinabove In the illustrated embodiment, a piston and connecting rod assembly  94  is shown in relation to a cylinder wall  96 . More particularly, a piston  98  is shown coupled to a connecting rod  100  via a wrist pin  102  in a conventional fashion. Three ring grooves are formed in the piston  98 , which are a top ring groove  104 , a second ring groove  106 , and a third ring groove  108 . Mounted in each of these grooves may be rolling rings formed in accordance with the present invention as described above. Alternativley, two or more of the grooves may be occupied by a conventional piston compression or oil ring. In one embodiment, a rolling compression ring  110  is mounted in the top ring groove  104 , a middle rolling compression ring  112  is mounted in the second ring groove  106 , and an oil ring  114 , preferably a rolling oil ring is mounted in the third ring groove  108 .  
         [0055]     An oil passageway  116  is formed in the body of the piston to communicate between an interior of the piston and one of the ring grooves, such as the second ring groove  106 . Oil drain holes  120  may be formed in the body of the piston to communicate between the interior  118  of the piston and the third ring groove  108 .  
         [0056]     The piston  98  typically includes piston pin oil passageway  122  to provide oil to the wrist pin  102 , which allow drainage of oil in the present invention.  
         [0057]     In some embodiments, the cylinder wall  96  is nickel plated and may include an optional trim area  24  for the top rim  5  of the compression ring  110  and the bottom rim  6  of the oil ring  114 . This trim area  124  is a raised file-like area of the cylinder wall (about 1/100,000 inch) for trimming the rings in order to keep them from touching the cylinder wall  96 . In some embodiments, the body of the piston  98  is hypereutectic to provide a close fit between the piston  98  and the cylinder wall  96 .  
         [0058]     In this embodiment, a conventional oil ring system is used for the wrist pin  102  where oil is collected by the oil ring  114  and passed through the openings  120  to an oil passage  126  formed in the top of the connecting rod  100  that communicates with the wrist pin  102 . Oil is directed to the oil passageway  116  in the second ring groove  106  to enter behind the ring, then over it and to the bearing in the middle rolling compression ring, and then out through the oil drain holes  120 .  
         [0059]     Turning next to  FIG. 12 , shown therein is an alternative piston-connecting rod arrangement  128  in which a piston  130  is coupled to a connecting rod  132  via a wrist pin  134 . The piston  130  includes a top ring groove  136 , second ring groove  138 , and third oil ring groove  140  in which are mounted, respectively, a top compression ring  142 , a second compression ring  144 , and an oil ring  146 , all of which may be formed in accordance with the teachings of the present invention.  
         [0060]     In this embodiment, the piston  130  has the ends  148  of the wrist pin  134  sealed and an oil passageway  150  leads from the wrist pin  134  through the piston  130  to an outlet  152  formed between the top ring groove  136  and the second ring groove  138 . Another oil passageway  154  is formed in the connecting rod  132  to communicate between a rod bearing  156  and the wrist pin  134 . An opening  158  in the rod bearing aligns with an oil hole (not shown) in the crankshaft (not shown) once every revolution. Oil is pumped through the passageway  154  and the connecting rod  132  to the wrist pin  134 , where it then passes through the oil passageway  150  in the piston  130  to the outlet  152 . The oil then is dispersed to the bearings  160  in each of the three rings  142 ,  144 ,  146 . Note should be taken that the top compression ring  142  and second compression ring  144  do not have oil passageways as does the oil ring  146 , which has passageways  162  communicating with the third oil ring groove  140 . Oil passes herethrough to the drain openings  164  and back to the oil pan. The advantage here is that there is positive oil flow producing more oil to the components, the oil is cooler, resulting in better heat transfer and removal of contaminants.  
         [0061]      FIGS. 13 and 14  illustrate yet another arrangement  166  of a piston  168  coupled to a connecting rod  170  through a wrist pin  172 . The piston  168  in this embodiment includes the top ring groove  174 , second ring groove  176 , and the third oil ring groove  178  that are configured to receive respectively the top compression ring  180 , second compression ring  182 , and oil ring  184 , all of which may be formed in accordance with the teachings of the present invention and include the unique bearings  186  as described above.  
         [0062]     In this embodiment, the piston  168  has oil passageways  188  communicating with the wrist pin  172  and the grooves  174  and  176 . Corresponding oil passageways  190  are formed in the rings  180  and  182 . In addition, an oil passageway  192  is formed in the connecting rod to communicate between the wrist pin  172  and the bearing  194  between the connecting rod  170  and the crankshaft  196 , which includes a corresponding oil passageway  198 . The oil passageway  192  may include an enlarged portion  193  that has the affect of giving more time for the oil to pass from the crankshaft  196  through the bearing  194 . This may be accomplished by countersinking the crankshaft  196  and the bearing  194 , as well as the connecting rod  170 .  
         [0063]     In this embodiment, pressurized oil from the crankshaft passageway  198  passes through the rod passageway  192  to the wrist pin  172 , which is sealed at its ends  200 . From the wrist pin  172 , the pressurized oil passes through the piston  168  via the oil passageways  188  formed therein and thence through each of the ring passageways  190  to the bearings  186  in each of the rings  180 ,  182 . A gap above and below the rings with respect to the pistons  168  is made small enough to trap the oil and force each of the rings  180 ,  182  against a cylinder wall. Notches in the rings  180 ,  182  (L-shaped notches  66 ,  68  described above) are urged to close together, forcing oil to move around the ring bearings  186 . Oil is then collected by the oil ring  184  where it passes through a ring passageway  208  and holes  202  formed in the groove  178  into the oil passageway  122 . The advantages of this embodiment of the invention is to direct cooler and cleaner oil to the ring bearings. In addition, contaminant buildup is reduced above and below the rings  180 ,  182 ,  184 . In addition, increased pressure of the ring against the wall through all four cycles of the piston stroke enhances performance.  
         [0064]     Referring to  FIGS. 15-16 , in an alternative embodiment, the wrist pin  172  includes grooves  204   a - 204   c . The ends  200  of the wrist pin  172  may be plugged or sealed by means of threaded plugs inserted in the ends  200 . Apertures  206   a - 206   c  pass through the wall of the wrist pin  172  into the grooves  204   a - 204   c . The groove  204   b  aligns with the oil passageway  192  to allow oil to enter the wrist pin  172 . Grooves  204   a ,  204   c  align with oil passageways  188  to allow oil to flow from the wrist pin  172  to the grooves  174 ,  176 . As in the embodiment of  FIG. 13 , oil drains through the apertures  164  in groove  178  into the passageways  122  formed in the piston.  
         [0065]     The size of the rings  180 ,  182 ,  184  may be varied to control the distribution and flow of oil at the boundary between the piston and cylinder. For example, in one embodiment the top rim  5  of ring  180  is slightly larger in diameter than the bottom rim  6  of ring  180  the top and bottom rims  5 ,  6  of rings  182 ,  184 . The larger top rim  5  of the ring  180  is not hardened in some embodiments such that the larger rim  5  of the ring  180  will wear down to conform to the walls of the cylinder.  
         [0066]     In the preferred embodiment, top rim  5  of ring  180  has a diameter such that the gap between the rim  5  and the cylinder wall is about 1/50,000 to 1/100,000 inch. The bottom rim  6  of ring  180  and both rims  5 ,  6  of rings  182 ,  184  have a diameter such that there is about a 1/5,000 in. gap between the rims  5 ,  6  and the walls of the cylinder.  
         [0067]     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.  
         [0068]     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.  
         [0069]     While the preferred embodiment of the invention has been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of the preferred embodiment. Instead, the invention should be determined entirely by reference to the claims that follow.