Patent Publication Number: US-2009223479-A1

Title: Inline crankshaft journal

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to the journaling of piston connecting rods to crankshafts in general and more particularly to the inline journaling of two connecting rods to a single crankpin of a crankshaft. 
     2. Discussion of the Related Art 
     Engines have become a common element in industry and in everyday lives to provide power for operating a wide range of machinery. The most common of these engines are steam and internal combustion piston driven engines. In its simplest form, a piston driven engine comprises one or more pistons that are linearly driven within a substantially closed cylinder by a pressurized gas such as steam or post-combustion gasses. The piston is rotatably connected with one end of a connecting rod with the opposite end of the connecting rod being rotatably connected to a crank throw on a crankshaft. Each crank throw has a crankpin whose axis is offset from that of the crankshaft. The end of the connecting rod opposite from the piston is rotatably connected to the crankpin. In this manner, the cyclical linear motion of the piston causes the connecting rod to rotationally drive the crankpin about the rotational axis of the crankshaft. The linear motion of the piston is thus transformed into the rotational motion of the crankshaft. 
     Whether engines are of either single- or multi-cylinder design, the power strokes of the individual piston(s) impart a significant side load on the crankshaft. This load is not constant but rather pulses in concert with the power strokes of the pistons thereby also inducing a cyclic and vibrational load to the crankshaft. In engines where all cylinders are in a straight line, the crankshaft becomes relatively long with each cylinder&#39;s connecting rod being journaled to a dedicated crank throw with the side load and vibration forces being significant. Various means have been utilized to dampen and counteract these side loads and induced vibration. Multiple bearings are used along the length of the crankshaft to support the crankshaft instead of just one at each end. Counter weights are also built into the crankshaft to impart a degree of rotational stability to the crankshaft and thereby reducing the effects of the side loads and vibration. 
     By adopting more compact engine configurations such as the “V” orientation of cylinders or of horizontally opposing the cylinders (in lieu of a “straight” orientation), the length of a crankshaft has been able to be shortened thereby reducing the problems inherent with a long crankshaft. In these configurations, the number of crank throws can be halved with corresponding opposite cylinders and their respective connecting rods being journaled to and sharing the same crank throw. In one configuration, substantially identical connecting rods are journaled to the crankpin in a side-by-side configuration where a first connecting rod occupies a position at one end of the crankpin and a second connecting rod occupies a position at the other end of the crankpin. Alternatively, a first of the connecting rods can be forked such that each leg of the fork is journaled to respective outermost ends of the crankpin. The second connecting rod is positioned between the legs of the first connecting rod and is journaled to a middle portion of the crankpin. In this manner, the opposed connecting rods operate in substantially the same plane. 
     Operation of opposed connecting rods in the same plane such as presented by the forked connecting rod configuration is advantageous to further minimize the vibration effects. However, forked connecting rods are more expensive to fabricate and require more parts and assembly time than the side-by-side connecting rod configuration. Additionally, since all connecting rods are not identical in this configuration with half of the connecting rods being forked and half being of single leg configuration, manufacturers must implement multiple fabrication lines and develop a plurality of tracking procedures with increased inventory which all unnecessarily lead to increased costs. Thus, what is desired is a system of piston engine connecting rods where the individual connecting rods are of identical configuration and where connecting rods journaled to a single crankpin operate in the same plane. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to an inline crankshaft journaling configuration that satisfies the need for opposing connecting rods that load the crankpin in a substantially coplanar manner. The crankshaft and connecting rod configuration for use in piston engines comprises a crankshaft having a separable crank throw wherein the separable crank throw includes a pair of laterally separated throw arms supporting a crankpin therebetween. A pair of coplanar connecting rods is in rotational engagement with the crankpin. Each rod has a small end configured for rotational attachment to a piston and a large end configured for the rotational engagement with the crankpin. At least one retention ring engages a portion of the large end of each connecting rod for maintaining the large ends of the connecting rods in rotational engagement with the crankpin. 
     Another aspect of the present invention is crankshaft and connecting rod configuration for use in piston engines having a crankshaft with a separable crank throw including a crankpin supported at each end thereof by a throw arm. First and second connecting rods are opposingly positioned with respect to the crankpin, each rod including a small end configured for rotational attachment to a piston and a large end configured for rotational engagement with the crankpin. At least one retention ring engages a portion of the large end of each connecting rod for maintaining the large ends in rotational engagement with the crankpin. 
     Yet another aspect of the present invention is a connecting rod kit for use in piston engines. The kit includes a pair of connecting rods, each rod having a shaft with a small end at one end of the shaft configured for rotational attachment to a piston and a large end at an opposite end of the shaft. The large end comprising a cannular segment having a concave inner surface and a convex outer surface wherein the cannular segment defines an axis substantially perpendicular to the shaft. The kit further includes at least one retention ring for engaging the convex surface of the large end of each rod such that the cannular segments of each connecting rod are substantially coaxial. 
     These and other features, aspects, and advantages of the invention will be further understood and appreciated by those skilled in the art by reference to the following written specification, claims and appended drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a fuller understanding of the nature of the present invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is an exploded perspective view of a crankshaft and connecting rod journaling arrangement embodying the present invention, wherein two inline connecting rods are journaled to the same crankpin of a crankshaft; 
         FIG. 2  is a partial cross section of the crankshaft illustrating the connecting rods journaled to the same crankpin; 
         FIG. 3  is a cross-sectional view of the journaled connection rods shown in  FIG. 2  and taken along the line  3 - 3 ,  FIG. 2 . 
     
    
    
     Like reference numerals refer to like parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     For purposes of description herein, the terms “upper”, “lower”, “left”, “rear”, “right”, “front”, “vertical”, “horizontal”, and derivatives thereof shall relate to the invention as oriented in  FIG. 1 . However, one will understand that the invention may assume various alternative orientations and step sequences, except where expressly specified to the contrary. While the present invention has been shown and described in accordance with preferred and practical embodiments thereof, one will also recognize that departures from the instant disclosure are fully contemplated within the spirit and scope of the invention. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise. 
     Turning to the drawings,  FIG. 1  shows a combined crankshaft and connecting rod configuration  20  which is one of the preferred embodiments of the present invention and illustrates its various components. Crankshaft and connecting rod configuration  20  is intended for use in piston engines. The disclosed configuration  20  is particularly adaptable to engines wherein two pistons  16  are in a substantially horizontally opposed configuration and positioned to act on a single crankpin  40  of crankshaft  30 . In general, each piston  16  is rotatably connected through wrist pin  18  to a connecting rod  50 . In turn, connecting rods  50  are retained in rotational engagement with crankpin  40  of crankshaft  30  by at least one and preferably two retention rings  70  to transform the linear reciprocation of pistons  16  into the rotation of crankshaft  30 . 
       FIGS. 1-3  illustrate in detail the unique features of crankshaft and connecting rod configuration  20 . A crankshaft  30  is supported within an engine (not shown) at journal points  32 . Journal points  32  define an axis of rotation “A” about which crankshaft  30  rotates. Crankshaft  30  includes at least one crank throw defined by two throw arms  34  supporting crankpin  40  therebetween. Each throw arm  34  typically includes a counterweight  36  diametrically opposite from crankpin  40  to reduce operational vibration in crankshaft  30  in a manner well known in the industry. As further illustrated in  FIGS. 1 and 3 , crankpin  40  is separable from throw arms  34  and is thus removable from crankshaft  30  for convenient replacement and ease of assembly of connecting rods  50  to crankpin  40 . However, crankpin  40  is closely received in crankpin apertures  35  of throw arms  34  such that crankpin  40  does not rotate in crankpin apertures  35 . Crankpin  40  defines throw axis “B”, and as crankshaft  30  rotates about axis “A”, throw axis “B” rotates about axis “A” at a fixed radial distance. This fixed radial distance defines the stroke of piston  16  as is commonly known in the art. 
     Alternatively, as illustrated in the cross-section of  FIG. 4 , crankpin  140  can be integrally and rigidly formed with one of throw arms  134  (lower arm) and is thus not separable therefrom. A free end of crankpin  140  is then closely received in an opposing throw arm  134  (upper arm) to define the crank throw to which connecting rods  150  are rotatably assembled. The configuration of connecting rods  150  and other associated features are identical to connecting rods  50 . Like features of the configuration of  FIG. 3  are like numbered in  FIG. 4  preceded by the numeral “1”. 
     Referring again to  FIGS. 1-3 , connecting rods  50  have a central shaft  56  of a predefined length to accommodate the desired piston stroke within the engine cylinder (not shown). Connecting rod  50  has a first end (known in the industry as the ‘small’ end)  52  configured for rotational attachment to piston  16 . The manner of this attachment is well known in the industry and typically involves wrist pin  18  being non-rotationally affixed in aperture  54  of small end  52  and further wherein wrist pin  18  extends between opposing apertures  17  in piston  16  and freely rotates therein. The second end  58  of connecting rod  50  (known as the ‘large’ end in the industry) is formed as a cannular segment having an inner concave surface  60  and an outer convex surface. Concave surface  60  has a radius that corresponds to the diameter of crankpin  40  so as to permit concave surface  60  to rotate about the surface of crank pin  40 . A first friction reduction sleeve  42  can be interposed between crankpin  40  and concave surface  60  to prevent galling and to decrease the friction resulting from the rotation of concave surface  60  with respect to crank pin  40 . Sleeve  42  can be fabricated of a soft metal or a plastic resin depending on the particular engine type in which it is incorporated. 
     Since pistons  16  are substantially in-line and horizontally opposed one to the other, connecting rods  50  are likewise substantially in-line with one connecting rod  50  on one side of crankshaft  30  and the other connecting rod  50  on the opposite side and are identical one to the other. Preferably, shafts  56  of each connecting rod  50  are aligned such that they are co-planar. In this manner, the forces generated by the reciprocal movement of the opposing pistons  16  operate on the same axial position of crankshaft  30  and greatly reduce the asymmetric vibrational aspects of prior art connecting rods positioned in a side-by-side configuration as practiced in the prior art. Thus, cannular segmented large ends  58  of opposed connecting rods  50  are also diametrically opposed one to the other and do not fully encompass the full diameter of crankpin  40 . 
     Retention ring  70  has an inner surface engaging the outer convex surface of cannular segmented large end  58  of both connecting rods  50  to maintain the respective concave surfaces  60  in rotational engagement with crankpin  40 . In the most preferred embodiment, a retention ring  70  is positioned at each end of cannular segmented large ends  58  and comprises a ring  72  of high strength material to withstand the cyclic forces transferred between crankshaft  30  and reciprocating pistons  16 . Each retention ring  70  also includes an inner friction reduction sleeve  74  of a material similar to friction reduction sleeve  42  on crankpin  40 . 
     Alternatively, retention ring  70  can be comprised of two arcuate segments (not shown) that are fastenable one to the other in a manner similarly practice with respect to the fastening of large ends of connecting rods in the prior art. The arcuate ring segments are thus fastened about the convex surfaces of cannular segmented large ends  58  without requiring the separation of crankpin  40  from one or both throw arms  34  in crankshaft  30  as described above. 
     The arcuate measure of each cannularly segmented large end  58  is defined by first and second cannular edges  62  and  64  and is illustrated in  FIG. 2  as angle “C”. Angle “C” for each cannularly segmented large end  58  is necessarily less than 180 degrees since the opposing connecting rods rotate about crankpin  40  in opposite directions as crankpin  40  rotates about crankshaft  30  axis “A”. A gap  63  is defined between corresponding cannular edges  62  and  64  of opposed connecting rods  50  thus allowing for the respective rotational movement of each connecting rod  50  without adjacent cannular edges  62  and  64  of opposed segments  58  contacting one another. The maximum angle “C” is a trigonometric function of the radial distance (r) of axis “A” from axis “B” and the effective length (l) of connecting rod  50  (as measured from the axis of wrist pin  18  to axis “B”) and is represented by the equation: 
         C max=2*arc sin( r/l ) 
     To assemble the disclosed crankshaft and connecting rod configuration  20 , friction reduction sleeve  42  is sleeved over crankpin  40 . Two connecting rods  50  are placed such that their respective concave surfaces  60  are oppositely engaged with the outer surface of friction reduction sleeve  42 . A retention ring is sleeved over the convex surfaces of corresponding axial ends of cannular segmented large ends  58  of both connecting rods  50  to maintain concave surfaces  60  in rotational engagement with crankpin  40  and sleeve  42 . The ends of crankpin  40  are then pressed into crankpin apertures  35  of throw arms  34 . 
     Alternatively, one end of crankpin  40  can be pressed into crankpin aperture  35  of a first throw arm  34  prior to assembly of connecting rods  50  and thus mirrors the configuration illustrated by  FIG. 4  where crankpin  140  is integrally formed with a first throw arm  134 . In this configuration, friction reduction sleeve  42  is sleeved over crankpin  40  and a first retention ring is telescoped over the combined crankpin  40  and friction reduction sleeve  42 . Two connecting rods  50  are placed such that their respective concave surfaces  60  engage an outer surface of friction reduction sleeve  42 . The respective first ends of the opposed cannular segments  58  of both connecting rods  50  at the first retention ring  70  are then pressed into the annular space defined by the inner surface of retention ring  70  and the outer surface of sleeve  42 . A second retention ring is then pressed over the convex surfaces of axially opposite ends of cannular segments  58  thereby securing both axial ends of cannular segments  58  in rotational engagement with crankpin  40 . The free end of crankpin  40  can then be pressed into the second throw arm  34  thereby completing the crank throw assembly having a coplanar connecting rod configuration. 
     Those practiced in the art will readily recognize that the above disclosure can be incorporated in steam or internal combustion engines and that an engine incorporating the above disclosure can comprise one or more like configured throws as known in the art where adjacent throws are angularly offset one from the other to facilitate sequential power strokes of the different pistons. 
     The above description is considered that of the preferred embodiments only. Modifications of the invention will occur to those skilled in the art and to those who make or use the invention. Therefore, it is understood that the embodiments shown in the drawings and described above are merely for illustrative purposes and are not intended to limit the scope of the invention, which is defined by the following claims as interpreted according to the principles of patent law, including the doctrine of equivalents.