The invention relates to connecting rods for two cycle internal combustion engines.

In two cycle internal combustion engines, the ^' side faces of the connecting rods at their crank ends are typically silver plated to bear the -fric- tional rubbing contact with the crankar s or discs of the crankshaft. The expense of silver plating is objectionable.

Accordingly, the present invention provides a two cycle internal combustion engine comprising a piston reciprocal in a cylinder between a crank¬ case chamber .and a combustion chamber, said crankcase chamber containing a fuel-air-lubricant mixture for lubricating said engine and for supplying a combus- tible mixture to said combustion chamber, said en¬ gine having a crankshaft rotatably journaled therein along a crankshaft centerline, said crankshaft having a plurality of crankarms extending radially relative to said centerline, said crankarms having facing crankfaces, a crankpin extending axially between a pair of said crankarms perpendicularly from said crankfaces and parallel to and eccentrically offset from said crankshaft centerline, said piston having a connecting rod rotatably journaled on said crankpin, said connecting rod having side faces normally engaging said crankfaces of said crankarms, said side faces of said connecting rod having grooves formed therein dragging lubricant from said mixture along said crank¬ faces of said crankarms and providing a hydrodynamic bearing with a layer of- lubricant separating said side

faces of said connecting rod from said crankfaces of said crankarms such that said side faces of said connecting rod ride on a layer of lubricant in said mixture and eliminate the need to silverplate said side faces of said connecting rod, wherein the rotary motion of said crankshaft itself supplies said lubri¬ cant to said grooves without the need of an auxiliary pump for pumping lubricant to said grooves.

The present invention eliminates the need to silver plate the side faces of the connecting rods. In apreferred embodiment, grooves or reliefs are cut on the side faces of the connecting rod, with a very low angle to the side face, and with radiused corners, to provide a hydrodynamic-bearing and allow the side face of the connecting rod to ride on a layer of lubricant.

In the drawings:

Figure 1 is a sectional view of a two cycle internal combustion engine; Figure 2 is a perspective view of a connecting rod;

Figure 3 is an enlarged end view of a portion of the connecting rod of Figure 2;

Figure 4 is a sectional view taken along line 5-5 of Figure 3 prior to buffing;

Figure 5 is a sectional view ^' taken along 5-5 of Figure 3.

Figure 1 shows a two cycle internal com¬ bustion engine 2 having a plurality of pistons 4 each reciprocal in a cylinder 6 between a crankcase cham¬ ber 8 and a combustion chamber 10. Crankcase chamber 8 a fuel-air-lubricant mixture for lubricating the engine and for supplying a combustible mixture through transfer passage 12 and intake port 14 to combustion chamber 10. The mixture is supplied to crankcase chamber

through one-way reed valves 16 from a carburetor, schematically shown at 18, or by means of fuel in¬ jection. FIG. 1 shows a portion of one bank of cylinders 'in a V-engine, for example, disclosed in 5 U.S. Patent Nos. 4,244,332, 4,305,351 and 4,702,202. The present invention has broad application to various ty es of two cycle engines having a lubricant mixture in the crankcase.

Piston 4 moves to the left during its intake

10 stroke, drawing a fuel-air-lubricant mixture through, one-way reed valves 16 into crankcase chamber 3, Piston movement to the ^' left also compresses the mix¬ ture in combustion chamber 10 for ignition by spark plug 20, which combustion drives piston 4 to the right,

15 generating its power stroke. During movement of pis¬ ton 4 to the right, the mixture in crankcase chamber 8 is blocked by one-way reed valves 16 from exiting the crankcase, and instead is driven through transfer passage 12 to intake port 14 in combustion chamber 10

20 for compression during the intake stroke, and so on to repeat the cycle, all as is well known. The com¬ bustion products are exhausted at port 22.

The engine has a crankshaft 24 rotatably journaled therein at main bearings 26, 28, 30. and so

25 on, along a crankshaft center line 32, Crankshaft 24 has a plurality of sealing discs such as 34 and 36 which separate and isolate adjacent crankcase chambers and which also provide crankarms having facing crankfaces such, as 38 and 40. Crankarm disc

30 36 has an outer circumferential seal ring 42, FIG. 2, separating and isolating crankcase chamber 8 from crankcase chamber 44, as standard in the art. Crank¬ arm discs 34 and 36 extend radially outwardly from crankshaft center line 32.

35 • A crank pin 46, FIG. 2, extends axially between crankarms 34 and 35 integrally and perpendic¬ ularly from crankfaces 38 and 40 and parallel to and

eccentrically offset from center line 32. Piston 4 has a connecting rod 48 having a left end rotatably journaled to the piston by piston pin 50, and having a right end rotatably journaled on crankpin 46, 5 with roller or needle hearings 52 if desired, for which further reference may be had to McCormick U.S. Patent 4,436,443, incorporated herein by reference. The connecting rod has an end cap 54 mounted to saddle portion 56 by bolts 58. 10 Connecting rod 48 has sidefaces 60 and 62 engaging respective crankfaces 38 and 40 of re¬ spective crankarm discs 34 and 36. Because of the rotary frictional rubbing of the surfaces, sidefaces 60 and 62 of the connecting rod are typically silver 15 plated.

In the present invention, sidefaces 60 and 62 of the connecting rod have grooves 64 formed therein, Figs. 2 and 3. ^" Th.e grooves drag lubricant from the fuel-air-luhricant mixture in crankcase chamber 8 20. along crankfaces. 38 and 40 of crankarm discs 34 and 36, and provide a hydrodynamic bearing with a layer of lubricant separating sidefaces- 60. and 62 of connect¬ ing rod 48 from crankfaces.38 and 40. of crankarm discs 34 and 36. Sidefaces. 60. and 62 of connecting rod 48 25 ride on a layer of lubxicant in the mixture.. This- eliminates, the need to silver plate sidefaces 60 and 62 of connecting rod 48.

Grooves 64 extend radially outwardly relative to crankpin 46. τh.e grooves provide a hydrodynamic 30. bearing which. hears, substantially only radial loading and shearing of the lubricant film, and substantially no axial loading.

Grooves. 64 are ground into the sidefaces of the connecting rod with, a very low grinding profile. 35 in the preferred embodiment, a very shallow angle 66,

FIG, 4, is formed between the groove wall 68 and the connecting rod sideface 60. Angle 66 is exaggerated in FIG. 4, for illustration, but is preferably about 1.5 . After grinding, the junction 70 of groove wall 68 and connecting rod sideface 60 is buffed to pro-^ vide a rounded corner 72, FIG. 5, to enhance the hydrodynamic bearing effect.