Lubrication system and method of lubricating an internal-combustion engine

#The invention relates generally to lubrication systems for internal-combustion engines, and more specifically to lubrication systems for use in motorcycle engines.

#One example of a lubrication system for use with an internal-combustion engine is disclosed in U.S. Pat. No. 5,588,405 issued to Atsushi Sawa. The engine includes a gearbox incorporated into the crankcase. Oil ducts deliver lubricating oil to the camshaft and to the gears within the gearbox. The oil is circulated within the engine between the crankshaft, various oil-consuming devices, and an oil sump by an oil pump.

#Additional lubrication is required in engines that have manual gearboxes. In particular, in manual gearboxes the gears are moved or shifted by gearshift sleeves and gearshift forks. The gearshift sleeves are moved axially along one or more shafts by one or more gearshift forks. Friction between the gearshift sleeves, the gearshift forks, and the shafts can cause premature wear in the gearbox. It is therefore desirable not only to supply lubricating oil to the gears and to the shafts within the gearboxes but also to supply lubricating oil to the gearshift sleeves and to the gearshift forks.

#The present invention is further described with reference to the accompanying drawings, which show a preferred embodiment of the present invention. However, it should be noted that the invention as disclosed in the accompanying drawings is illustrated by way of example only. The various elements and combinations of elements described below and illustrated in the drawings can be arranged and organized differently to result in embodiments which are still within the spirit and scope of the present invention.

#In the drawings, wherein like reference numerals indicate like parts:

#FIG. 1 is a section view of an internal-combustion engine with a gearbox incorporated in the crankcase;

#The present invention is described herein as including a four-stroke two-cylinder engine. However, the present invention can be used with almost any number of cylinders, such as one, two, three, four, five, and six cylinders with equal effectiveness. Similarly, the present invention can be used with two-stroke engines. Reference is made to engines having a V-shape. One having ordinary skill in the art will appreciate that the present invention can be used with V-shaped engines and with in-line or straight engines with equal effectiveness. Also, the present invention is described herein as including a five-speed gearbox or a five-speed transmission. However, the present invention can be used with almost any number of gearing options, including one, two, three, four, five, and six speed transmissions with equal effectiveness. Similarly, the present invention can be used with equal effectiveness to provide lubrication to gearboxes or to transmissions with any configuration, including manual or automatic transmission. As such, the present invention can include embodiments in which the configuration of the engine includes any conventional motorcycle engine and is not limited to the embodiments referred to herein. For simplicity only, the following description will continue to refer to five-speed, four-stroke, two-cylinder, V-shaped engines.

#Referring to FIGS. 1-3, a crankcase 11 of an internal-combustion engine E has a lower crankcase half 10 and an upper crankcase half 12. The internal-combustion engine E is constructed in the form of a water-cooled, V-shaped engine. In the illustrated embodiment, the internal-combustion engine E is preferably the prime mover for a motorcycle M, as shown in FIG. 4, however, other engine applications are also contemplated. A gearbox sump 33 is located in the lower crankcase half 10. Oil which drains off or is flung off of the gears 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, the sliding sleeves 54, 56, 60, the gearshift forks 64, 66, 68, the gearbox input shaft 36, the gearbox output shaft 40, and the other engine components within the gearbox 34 drains into the gearbox sump 33. From the gearbox sump 33 the oil drains or is moved to the oil sump (not shown). From the oil sump, the oil is drained or pumped to the various oil consuming devices (not shown) within the engine E. Oil that is not consumed by the various oil-consuming devices is returned to the oil sump. In this way, oil is cycled through the engine E along a lubrication cycle (not shown) from the oil sump to the various oil-consuming devices and back to the oil sump.

#A first and a second cylinder 14, 16 are located in the upper crankcase half 12 and are arranged in a V configuration. A cooling water chamber 18 is located adjacent the cylinder 14 in the upper crankcase half 12. A crankshaft 21 is received in the opening 20. A first cylinder head 22 and a second cylinder head 24 are coupled to the first and second cylinders 14, 16, respectively. Cylinder head fasteners (not shown) extend into the fastener openings 26 and hold the first and second cylinder heads 22, 24 on the first and second cylinders 14, 16. FIG. 1 also shows the lower halves of camshaft thrust bearings 28, 30 located on the first cylinder head 22. The camshaft thrust bearings 28, 30 open and close the intake and exhaust valves (not shown).