WO2009058113A1

WO2009058113A1 - Gear based camshaft drive system and method

Info

Publication number: WO2009058113A1
Application number: PCT/US2007/022840
Authority: WO
Inventors: Roy Meyer; Scott A. Sjovall; Jeffrey J. Bailey; Andrew Eaton
Original assignee: S & S Cycle, Inc.
Priority date: 2007-10-30
Filing date: 2007-10-30
Publication date: 2009-05-07

Abstract

A system and method for driving multiple camshafts in an internal combustion engine is disclosed, the multiple camshafts being driven with a gear based camshaft drive system including a plurality of camshaft driven gears and a pinion drive gear. Preferably, an intermediate drive gear is provided for rotating the camshaft driven gears in response to rotation of the pinion drive gear, the intermediate drive gear being meshed with the pinion gear and being bolted to one of the plurality of camshaft driven gears.

Description

GEAR BASED CAMSHAFT DRIVE SYSTEM AND METHOD

Cross Reference to Related Applications

[0001] Aspects of this application are related to U.S. Patent Application No. 11/667,999, the U.S. National Stage Application of PCT Application PCT/US05/41876. PCT Application PCT/US05/41876, in turn, claims priority to Provisional Patent Application No. 60/628,541 (filed 11/18/2004). This application incorporates by reference U.S. Patent Application No. 1 1/667,999, PCT Application PCT/US05/41876, and Provisional Patent Application No. 60/628,541 in their entirety.

Field of the Invention

[0002) Embodiments of the present invention relate generally to vehicles having internal combustion engines, and more specifically, to motorcycles including a gear based camshaft drive system.

Background of the Invention

[0003] A motorcycle is a two-wheeled vehicle powered by an engine. The wheels are in-line, and at higher speed the motorcycle remains upright and stable by virtue of gyroscopic forces; at lower speeds readjustment of the steering by the rider gives stability. The rider sits astride the vehicle on a seat, with hands on a set of handlebars which are used to steer the motorcycle, in conjunction with the rider shifting his weight through his feet, which are supported on a set of "footpegs" or "pegs" which stick out from the frame. The chassis or frame of a motorcycle is typically made from welded struts, with the rear suspension often being an integral component in the design. [0004] The engine of the motorcycle typically sits under a fuel tank, between the rider's legs. Typically, motorcycle engines displace between about three cubic inches (approximately 50 cubic centimeters) and 140 cubic inches (approximately 2300 cubic centimeters) and have one to four cylinders arranged in a "V" configuration, an in-line configuration or a boxer configuration. In most one-cylinder motorcycle engines, the cylinder points up and slightly forward with a spark plug on top. The most common configuration for two-cylinder motorcycle engines is a "v-twin" where the cylinders form a "V" around the crankshaft, which is oriented transversely (i.e., perpendicular to the direction of travel). Typically, the angle of the V is about 45 degrees. Other known configurations for two-cylinder motorcycle engines include a "parallel twin" (i.e. , in-line configuration) where the cylinders are parallel, and a "boxer twin" (also called a "flat-twin") where the cylinders are horizontally opposed, and protrude from either side of the frame. Four-cylinder engines are most commonly configured in-line, although "V" and square configurations are also known. Although less common, motorcycle engines having three, six, eight and ten cylinders are known. [0005] Motorcycle engines are typically cooled either with air or water. Air-cooled motorcycle engines rely on ambient air flowing over the engine to disperse heat. The cylinders on air-cooled motorcycle engines are designed with fins to aid in this process. It is believed that air-cooled motorcycle engines are cheaper, simpler and lighter than water- cooled motorcycle engines, which circulate water between a water jacket surrounding the combustion chamber(s) and a radiator that disperses heat transferred from the engine via the circulating water. [0006] The operation of motorcycle engines may either be two-stroke or four-stroke. It is believed that two-stroke engines are mechanically simpler and may be lighter than equivalent four-stroke engines. But four-stroke engines are believed to operate more cleanly, be more reliable, and deliver power over a much broader range of engine speeds. [0007] Rotation of the engine crankshaft is transferred to a transmission, via a clutch and a primary drive. Most motorcycle transmissions have five or six forward gears; only a few motorcycle transmissions are fitted with a reverse gear. The clutch is typically an arrangement of plates stacked in alternating fashion, one geared on the inside to the engine, and the next geared on the outside to the engine output shaft. Whether wet (rotating in engine oil) or dry, the plates are squeezed together by a spring, causing friction buildup between the plates until they rotate as a single unit, thereby driving the transmission via the primary drive. Releasing the clutch spring allows the engine to freewheel with respect to the engine output shaft. The primary drive couples the engine output shaft to an input shaft of the transmission and typically includes either a toothed belt or a chain. [0008] A secondary or final drive from the transmission to the rear wheel of a motorcycle typically includes a chain, although final drives may alternatively include a toothed belt or an enclosed torque shaft in combination with right-angle drive gearing. [0009] Motorcycle manufacturers often also produce all-terrain vehicles or ATVs. These have two or more back wheels, usually two front wheels, an open driver's seat and a motorcycle-type handlebar. The 4-wheeled versions are also called "quads," "four- wheelers," "quad bikes" or "quad cycles." ATVs are often used off-road for recreation and utility. Recreational ATVs are generally small, light, two-wheel-drive vehicles, whereas utility ATVs are generally bigger four-wheel-drive vehicles with the ability to haul small loads on attached racks or small dump beds. Utility ATVs may also tow small trailers. Utility ATVs with 6 wheels include an extra set of wheels at the back to increase the payload capacity, and can be either four-wheel-drive (back wheels driving only) or six-wheel-drive. [0010] Other types of vehicles that use similar engine technology may include amphibious all terrain vehicles, snowmobiles, personal watercraft and light-sport aircraft. An amphibious all terrain vehicle (AATV) typically has four, six or eight wheels, uses a skid- steer steering system, and the rider sits inside a chassis. Generally designed to float, AATVs can go through swamps as well as traverse dry land. A snowmobile is a land vehicle that is propelled by one or two rubber tracks, with skis for steering. Snowmobiles are designed to be operated on snow and ice, but may also be operated on grass or pavement. A personal watercraft, or PWC, is a recreational watercraft that the rider sits or stands on, rather than inside of, as in a boat. Typically, personal watercraft have an inboard engine driving a pump jet, and are designed for one to four passengers. Light-sport aircraft, which are single or two- seat lightweight, slow-flying airplanes, include "ultralights" that are essentially an engine propelled hang glider-style wing below which is suspended a three wheeled cart for the pilot. An ultralight is controlled by shifting the pilot's body weight with respect to a horizontal bar in roughly the same way as a hang glider pilot flies.

Brief Description of the Drawings [0011] The accompanying drawings, which are incorporated herein and constitute part of this specification, illustrate presently preferred embodiments of the invention, and, together with the general description given above and the detailed description given below, serve to explain features of the invention.

[0012] Figure 1 shows a cross-section view of a V-configuration motorcycle engine according to an embodiment of the present invention. [0013] Figure 2 shows an exploded assembly view of a camshaft drive system according to an embodiment of the present invention.

10014] Figure 3 shows a front view of the camshaft drive system of Figure 2. [0015] Figure 4 shows a cross sectional view along V-V of the camshaft drive system of Figure 3.

[0016] Figure 5 shows a motorcycle including an engine with a camshaft drive system according to an embodiment of the present invention.

[0017] Figure 6 shows a method of retrofitting an engine including a belt based camshaft drive system with a retrofit camshaft drive assembly according to an embodiment of the present invention.

Detailed Description of the Preferred Embodiment

[0018] Referring initially to Figure 1, a preferred embodiment of an internal combustion engine 300 uses one or more reciprocating pistons 310 (two are illustrated) and works according to a four-stroke pumping process known as the Otto cycle. According to the preferred embodiment, reciprocating pistons 310a and 310b are disposed in respective cylinders 320a and 320b. Intake valves are opened to allow air (and fuel) to be pulled into the respective cylinder 320a, 320b as the corresponding piston 310a, 31 Ob moves away from cylinder heads 340a and 340b. This is commonly referred to as the intake stroke. The intake valves are closed either before or during movement of the pistons 310a, 310b toward the respective cylinder heads 340a,340b to compress the air (and fuel) in the cylinders 320a, 320b, i.e., the compression stroke. If fuel is not mixed with the air, fuel can be directly injected into the cylinders 320a,320b and a spark is introduced before, at, or after top-dead- center, i.e., when a piston 310 reaches a position closest to its cylinder head 340. The air/fuel charge burns creating increased pressures within the cylinders 320a, 320b, forcing the pistons 310a, 31 Ob away from their cylinder heads 340a, 340b and creating work, /. e. , the power stroke. Exhaust valves open before, at, or after bottom-dead-center, i.e., when a piston 310 reaches a point furthest away from its cylinder head 340, allowing some of the combustion gases to escape. The pistons 310a, 31 Ob then move towards the cylinder heads 340a, 340b pushing out the majority of the remaining combustion gases, i.e., the exhaust stroke. The exhaust valves are closed before, at, or after the pistons 310a, 31 Ob reach top- dead-center, and the intake valves are opened either before or after the exhaust valves are closed. This pumping process repeats over the course of every two rotations of a crankshaft 350 connected to the pistons 310a, 310b.

[0019] Camshafts 360a, 360b and 360c (Figure 2) dictate the movement of the intake valves and the exhaust valves. The camshafts 360a, 360b, 360c force tappets to force pushrods to force rocker arms to force the intake valves and the exhaust valves open against the force of valve springs. This linkage of components is commonly referred to as the valve train. According to one embodiment of the present invention, camshaft 360a comprises an intake camshaft and camshafts 360b, 360c comprise exhaust camshafts. However, other configurations are also contemplated. [0020] The pumping processes associated with the cylinders 320a, 320b are out of phase with respect to one another such that ignition of a charge occurs, alternatingly between the cylinders 320a, 320b, once every rotation of the crankshaft 350. Additional details can be found in PCT/US05/41876.

VALVE TRAIN [0021 ] The phrase "valve train," as it is used herein, cumulatively refers to the combination of relatively dynamic features (e.g. , camshafts, tappets, pushrods, rocker arm, poppet valves, and return springs) of the internal combustion engine 300 that control the flow of combustion components and combustion products with respect to a combustion chamber.

Tri-cam Layout Including A 2:1 Ratio (Two Exhaust Cams Per One Intake Cam) [0022] According to preferred embodiments, the motorcycle 200 includes a multi-cam system for the internal combustion engine 300 that provides improved valve train geometry in a simple configuration. Preferably, at least three camshafts are used. Most preferably, two exhaust camshafts and one intake camshaft are used such that the pushrods for the exhaust valves and the pushrods for the intake valves are approximately parallel to the center axes of the cylinders 320a, 320b.

[0023] A three camshaft valve train according to preferred embodiments is for use in an internal combustion engine with reciprocating pistons and pushrods; in particular a v-twin pushrod engine. Most specifically, a motorcycle v-twin pushrod engine is disclosed. The three camshafts include two outboard camshafts and one inboard camshaft with respect to the V-configured engine. This allows for the angle of the pushrods that are operated by the outboard camshafts to be generally parallel to the central axes of the cylinders 320a, 320b, and allows for the angle of the pushrods that are operated by the inboard camshaft to be nearly parallel to the central axes of the cylinders 320a, 320b.

[0024] Conventional v-twin motorcycle pushrod engines having one or two camshafts drive the pushrods at angles that require large forces to open the inboard and outboard valves. Some of the energy in opening the valves is lost in the vector components perpendicular to the center axes of the cylinders 320a, 320b; for example, it is desirable for the reciprocating forces of the pushrods to be axially oriented parallel to the center axes of the cylinders 320a, 320b. According to preferred embodiments of the internal combustion engine 300, this energy loss can at least be reduced for the pushrods that are inboard of the V-configuration angle, and can be minimized for pushrods that are outboard of the V-configuration angle. [0025] Another disadvantage of conventional single camshaft v-twin motorcycle pushrod engines is their width, which requires a wider stance by the motorcycle rider. Preferred embodiments of the internal combustion engine 300 provide a narrower engine case, which increases motorcycle rider comfort, by disposing the pairs of intake and exhaust valves for each cylinder 320a, 320b in a plane perpendicular to the axis of the crankshaft 350. Another disadvantage of quad-camshaft v-twin motorcycle pushrod engines is the complexity of the valve train and the high amounts of friction in the valve train. Preferred embodiments of the internal combustion engine 300 have fewer parts and there is less friction as compared to conventional quad-camshaft engines. [0026] According to preferred embodiments of a tri-camshaft valve, train for use in a pushrod v-twin internal combustion engine 300 of a motorcycle 200, two outboard camshafts and one inboard camshaft are disposed in a V configured engine. The three camshafts 360a, 360b, 360c force the tappets to force the pushrods to force the rocker arms to force the valves open against the force of the valve return springs. Using two outboard camshafts 360b, 360c allows for the associated pushrods to be run at an angle that minimizes energy loss in opening the corresponding valves. Using one inboard camshaft 360a for both cylinders 320a, 320b reduces the energy loss in opening the inboard valves by improving the angle of the inboard pushrods as compared to conventional single or twin camshaft engine designs. Energy loss is minimized or reduced by running the pushrods at angles that minimize or reduce the force vector components perpendicular to the center axes of the cylinders 320a, 320b. It is believed that preferred embodiments of the internal combustion engine 300 provide increased net power output, improved durability, and better valve train dynamics. [0027] According to a most preferred embodiment, a pushrod v-twin motorcycle engine having offset cylinders, provides parallel orientation of all of the pushrods with respect to their corresponding cylinder, thereby minimizing or eliminating force vector components of the pushrods that are perpendicular to the central axis of the corresponding cylinder.

CAMSHAFT DRIVE

[0028] The phrase "camshaft drive," as it is used herein, cumulatively refers to the combination of relatively dynamic features of the internal combustion engine 300 that convey rotation from the power system to the valve train. The system of three camshafts 360a, 360b, 360c according to preferred embodiments are preferably driven by a plurality of gears. Exemplary systems that drive camshafts with gears include S&S Cycle's Pro Stock Billet Engines, as described for example in S&S Cycle's 2007 Racing catalogue, which is incorporated by reference herein in its entirety.

[0029] According to preferred embodiments, a gear based camshaft drive system for an internal combustion engine, especially a motorcycle engine such as a pushrod v-twin engine having three or more camshafts, is low cost, easily manufacturable and produces a minimal amount of noise.

[0030] Turning the camshafts 360a, 360b, 360c requires torque that is supplied by the crankshaft 350 via a gear based camshaft drive system. Torque may be transferred to the camshaft drive system directly from the crankshaft 350, as shown in Figure 4, or indirectly by a pinion shaft or the like. The term "drive shaft" as used herein should thus be understood to refer to a mechanism used to transfer torque from the crankshaft 350 to the gear based camshaft drive system, such as the crankshaft 350 itself, an intermediate pinion shaft(s), or a similar configuration. [0031 ) According to a preferred embodiment as shown in Figure 2, the gear based camshaft drive system includes a plurality of camshaft driven gears 101 , 102, 103, a pinion drive gear 1 10, and an intermediate gear 120. The camshaft drive gears 101, 102, 103, pinion drive gear 1 10, and intermediate gear 120 may be rotatably supported on a cam chest intermediate plate 422 so as to provide easy removal of the whole assembly as a unit. This configuration provides improved crankcase access over conventional designs. In this regard, along with the above referenced gears, the camshafts 360a, 360b , 360c may also be removably supported by the cam chest intermediate plate 422. [0032] As shown in Figure 2, the camshaft driven gears 101 , 102, 103 are arranged such that a first camshaft driven gear 101 is meshed with a second camshaft driven gear 102, and the second camshaft driven gear 102 is meshed with third camshaft driven gear 103. In this regard, rotation of any one of camshaft gears 101, 102, 103 causes a corresponding rotation of the other of camshaft gears 101, 102, 103. Because the camshaft driven gears 101, 102, 103 will cause rotation of camshafts 360a, 360b, 360c, which in turn control the timing of the engine 300, the relative size (e.g., diameter) of the camshaft gears 101, 102, 103 is determined based on the desired engine timing. According to one preferred embodiment, all three camshaft driven gears 101 , 102, 103 are fifty-four tooth gears having approximately the same gear diameter, i.e., a 1 :1 ratio. The gear diameter may be, for example, about 2.905". |0033] In the v-twin engine configuration shown in Figure 2, the camshaft drive system is situated such that the pinion drive gear 110 rotates on a pinion axis 111 substantially parallel to, and preferably the same as, a crankshaft axis. Similarly, the first, second and third camshaft driven gears 101 , 102, 103 rotate on first, second and third axes 201, 202, 203 respectively. The first, second and third axes 201, 202, 203 are preferably parallel to one another, as well as to pinion axis 111.

[0034] To transfer torque from the pinion drive gear 110 to the camshaft driven gears 101, 102, 103, an intermediate drive gear 120 may be provided, or the pinion drive gear 110 may directly transfer torque to one of camshaft drive gears 101, 102, 103 without an intermediate drive gear 120. In the embodiment shown in Figure 2, the intermediate drive gear 120 is meshed with pinion drive gear 110, and rotates about an intermediate gear axis, such that rotation of the pinion drive gear 110 causes rotation of the intermediate drive gear 120. The intermediate gear axis may be substantially identical to one of axes 201, 202, 203. Preferably, the intermediate gear axis is the same as the second axis 202 about which the second camshaft driven gear 102 rotates.

[0035] According to one embodiment of the present invention, the intermediate drive gear 120 is coupled to one of camshaft driven gears 101, 102, 103. In this regard, the intermediate drive gear 120 may be mechanically coupled to one of the camshaft driven gears 101, 102, 103 using a fastening device such as a bolt, socket head cap screw, hex head cap screw, etc. Alternatively, the intermediate drive gear 120 and corresponding one of camshaft driven gears 101, 102, 103 may form separate portions of one integral gear. Regardless of the type of coupling utilized, the gear based camshaft drive system with intermediate drive gear 120 is designed such that rotation of the pinion drive gear 110 causes rotation of the intermediate drive gear 120, which in turn causes rotation of one of camshaft driven gears 101, 102, 103. Again due to timing constraints of the engine, the relative size (e.g., diameter) of the intermediate drive gear 120 relative to the pinion drive gear 1 10 is set based on the desired engine timing. According to one embodiment of the present invention, the intermediate drive gear 120 ninety-six tooth gear and the pinion drive gear 110 is a forty- eight tooth gear with the intermediate drive gear 110 having approximately twice the gear diameter of pinion drive gear 110, i.e., a 2:1 ratio. [0036] For most configurations, as shown for example in Figure 4, the intermediate drive gear 120 and the pinion drive gear 110 are oriented in a first plane and the camshaft driven gears 101 , 102, 103 are oriented in a second plane substantially parallel to the first plane. In some embodiments the first plane will be outside of the second plane relative to a flywheel of the engine 300. In other embodiments, the first plane will be inside of the second plane relative to the flywheel of the engine 300. [0037] In addition to the novel gear driven camshaft drive system described above, it should be appreciated that the gears 101, 102, 103, 110, 120 described in the embodiments above may have outer surfaces to provide additional enhanced functionality. For example, the second camshaft driven gear 102 maybe spaced from the intermediate drive gear 120 with a spacer portion. While it is contemplated to use a spacer component (e.g., a washer) separate from the gears 102, 120, the configuration shown in Figure 2 includes a second camshaft driven gear 102 with a spacer surface that has an inner portion projected relative to an outer portion. As shown, the inner portion of the spacer surface extends outward from the second axis 202 and the inner portion extending inward toward the second axis 202 from an outer gear tooth edge. This type of configuration reduces the overall part count (i.e., by eliminating separate spacer components) and better ensures that the gears are consistently held substantially parallel to each other.

[0038] In contrast to the spacer surface of the second camshaft driven gear 102, the first and third camshaft driven gears 101 , 103 preferably include a recessed surface as similarly shown in Figure 2. This recessed surface may include an inner portion recessed relative to an outer portion, wherein the inner portion extends outward from the axis about which the gear rotates and the outer portion extending inward toward this same axis from an outer gear tooth edge of the gear. By providing gears 101, 103 with a recessed surface, certain weight savings can be achieved with respect to conventional systems. Minimizing gear weight significantly decreases the amount of force necessary to change the rotational velocity of the gears, which is particularly advantages for high performance applications (e.g., racing motors) wherein the engine RPMs go through rapid periods of acceleration and deceleration. Further weight savings can be achieved by utilizing gears 101 , 102, 103 , 110 and/or 120 with through holes, such as the six weight saving through holes 122 provided in intermediate drive gear 120.

[0039] One or more of gears 101, 102, 103, 110 may further include shaft engaging surface for engaging camshafts 360b, 360a, 360c and drive shaft (e.g., crankshaft 350) respectively. For example, the camshaft driven gears 101, 102, 103 may include a notched center hole adapted to receive and engage a projection the corresponding camshaft 360b, 360a, 360c respectively. Similarly, the pinion drive gear 110 may include a center hole with a flat comprising a drive shaft engaging surface. The flat in the center hole of pinion drive gear 1 10 is adapted to receive and engage a corresponding flat or projection extending from a first end of the drive shaft (e.g., crankshaft 350) toward a second end of the drive shaft.

[0040] It should further be appreciated that one or more of gears 101 , 102, 103, 110 and/or 120 may be supported using a bearing support structure or the like. One exemplary bearing support structure is shown in Figures 2 & 4. The exemplary bearing support structure shown preferably includes a base 42 that is removable from the engine 300, such as a base 42 coupled to a cam chest intermediate plate 422. The base 42 may be removable from the engine 300 in that it may be separately removable from cam chest intermediate plate 422 as shown, or it may be permanently coupled to (e.g. , an integral part of or welded to) cam chest intermediate plate 422 that is removable from engine 300. [0041] The base 42 may include two opposing projections 31 , 32 adapted to securely retain the bearing support structure to cam chest intermediate plate 422 and to properly align the various gears (e.g., pinion drive gear 110) supported thereby. In the embodiment shown in Figure 2, the first projection 32 extends from a first surface of the base 42 and the second projection 31 opposite the first projection 32 extends from a second surface of the base 42. As can be seen in the cross sectional view of Figure 4, the first projection 32 serves to space the pinion drive gear 110 relative to the cam chest intermediate plate 422, whereas the second projection 31 serves to align the base 42 within the cam chest intermediate plate 422. [0042] Preferably, the bearing support structure also includes one or more bearing assemblies 33 (e.g., a needle roller bearing assembly) with a corresponding spacer 39 (e.g. , a bearing race), wherein the bearing assembly 33 and spacer 39 collectively support the drive shaft (e.g., crankshaft 350) within a drive shaft orifice of the bearing support structure. Other possible configurations are also contemplated.

[0043] It should be appreciated that any one of the aforementioned embodiments may be provided as an Original Equipment Manufacturer (OEM) part or an aftermarket retrofit part. One method of retrofitting an engine 300 including a belt based camshaft drive system (see belt 520 in Figure 5 of PCT/US2005/041876) with a retrofit camshaft drive assembly will now be described in reference to Figure 6. As shown in step 1000, a gear based camshaft drive system is provided, the gear based camshaft drive system including a pinion drive gear 1 10, an intermediate drive gear 120, a plurality of camshaft driven gears 101 , 102, 103, and a cam chest intermediate plate 422. By way of example, the gears 110, 120, 101, 102, 103 may be packaged in a retrofit camshaft drive assembly and the cam chest intermediate plate 422 may come from an OEM engine formerly including a belt based camshaft drive system.

[0044] In step 1010, a plurality of lubrication channels 11 (Figure 2) are provided within the cam chest intermediate support plate 422. The plurality of lubrication channels 11 maybe provided, for example, by drilling holes in an OEM cam chest intermediate support plate formerly used in conjunction with a belt based camshaft drive system. Particularly, belt based camshaft drive systems do not include a lubrication system for lubricating the belt. To the contrary, lubrication is to be avoided if possible because it may cause undesirable slippage of the belt. Gear based camshaft drive systems, by contrast, typically require some lubrication between intermeshing gear teeth. The inventors have discovered that lubrication can easily be provided as part of a retrofit assembly by providing lubrication channels 11 within the cam chest intermediate support plate 422, thereby fluidly connecting the cam chest with the gear retaining region. Other lubrication techniques are also contemplated. [0045] In step 1020, the intermediate drive gear 120 is mechanically coupled to second camshaft driven gear 102. Mechanical coupling may comprise, for example, bolting the intermediate drive gear 120 to the second camshaft driven gear 102 with bolts, socket head cap screws, hex head cap screws, or the like. Mechanical coupling may also comprise forming an integral gear with a first portion comprising the intermediate drive gear 120 and a second portion comprising the second camshaft driven gear 102.

[0046] In step 1030, gear teeth of an intake camshaft driven gear (e.g., second camshaft driven gear 102) are meshed with gear teeth of two exhaust camshaft driven gears (e.g., first and third camshaft driven gears 101, 103). Similarly, in step 1040, gear teeth of the pinion drive gear 1 10 are meshed with gear teeth of the intermediate drive gear 120. [0047] The aforementioned steps 1000 to 1040 can be referred to generally as a series of assembly steps. While the order of the steps may vary and various steps may be combined in whole or in part, the subsequent steps 1050 to 1080 would not generally be performed until all of steps 1000 to 1040 have been completed. In step 1050, for example, an assembled engine 300 rotates a pinion drive gear 110 with a drive shaft (e.g., crankshaft 350). Step 1050 may comprise direct rotation if the drive shaft comprises a crankshaft 350 and the crankshaft 350 is directly coupled to the pinion drive gear 110. Alternatively, step 1050 may comprise indirect rotation if the drive shaft comprises a pinion shaft or the like such that the pinion drive gear 110 is not directly coupled to the crankshaft 350.

[0048] Given the arrangement of the gears 110 and 120, rotation of the pinion drive gear 110 in step 1050 causes a corresponding rotation of the intermediate drive gear 120. Similarly, because the intermediate drive gear 120 is mechanically coupled to the second camshaft driven gear 102, rotation of the intermediate drive gear 120 in step 1060 causes a corresponding rotation of the second camshaft driven gear 102 in step 1070. However, because the intermediate drive gear 1020 is significantly larger (e.g., about twice the diameter) than the pinion drive gear 110, rotation of the second camshaft gear 103 in step 1070 involves a significantly lower rotational velocity (e.g., about half) than pinion drive gear 1 10. [0049] Finally, in step 1080 rotation of the first and third camshaft driven gears 101 , 103 is caused by rotation of the second camshaft driven gear 102. Thus, rotation of the crankshaft 350 ultimately results in rotation ofthree camshaft driven gears 101 , 102, 103, which in turn cause a corresponding rotation of three camshafts 360b, 360a, 360c respectively. This rotation can be achieved without use of a belt, thereby eliminating disadvantages related to the use of a belt based camshaft drive system. VEHICLES INCLUDING AN INTERNAL COMBUSTION ENGINE

[0050] Vehicles according to preferred embodiments include a chassis and a propulsion system driving the vehicle. Preferably, the chassis provides a platform that is suitable for an intended environment (e.g., land, air, water, etc.) and may support an operator, and the propulsion system includes an internal combustion engine 300, a transmission (e.g. , providing one or more engine speed changing ratios), and an output device. Examples of vehicle types using propulsion systems according to the preferred embodiments may include motorcycles, all terrain vehicles, utility vehicles, riding lawn mowers, passenger cars, cargo trucks, snowmobiles, half-tracks, tracked vehicles, amphibious vehicles, personal watercraft, boats, and light-sport aircraft such as an ultralight.

[0051] Classification as a particular type of vehicle may be made on the basis of characteristics such as the nature of how the chassis receives the operator (e.g., operator rides-on, operator is enclosed within, etc.), the control interface between the vehicle and the operator (e.g., handle bars versus steering wheel, accelerator pedal versus twist grip, etc.), and the interaction of the output device with the intended operating environment (e.g. , one or more ground-engaging driven wheel(s), traction belt, propeller, etc.). [0052] Referring to Figure 5, various features and advantages of the present invention will now be explained with respect to the motorcycle 200, but are also applicable to the other types of the vehicle. [0053] The motorcycle 200 preferably includes a frame, a fork supporting a front wheel, a swing arm supporting a rear wheel, a seat, a fuel tank, an oil tank and a power train. [0054] The fork is pivotally supported with respect to the frame and connected with a set of handlebars for steering the motorcycle 200. The rear wheel is driven by the power train. The seat provides support for the operator, and tank(s) supply fuel and oil to the power train. [0055] The power train conveys rotation to the rear wheel via a secondary driven by the output of a transmission. The secondary may include a chain drive secondary, a shaft drive secondary or a belt drive secondary. Preferably, the secondary includes a chain coupling a driving sprocket fixed to an output from the transmission and a driven sprocket fixed to the rear wheel. [0056] The internal combustion engine 300 conveys rotation to the transmission via a primary and a clutch. The primary may include a belt drive primary or a chain drive primary. [0057] While the present invention has been disclosed with reference to certain preferred embodiments, numerous modifications, alterations, and changes to the described embodiments are possible without departing from the sphere and scope of the present invention, as defined in the appended claims. Accordingly, it is intended that the present invention not be limited to the described embodiments, but that it have the full scope defined by the language of the following claims, and equivalents thereof.

EXEMPLARY PARTS LIST

Bearing Assembly 33

Bearing Support Base 42

Cam Chest Intermediate Support Plate 422

Camshafts 360

Camshaft Driven Gears 101, 102, 103

Crankshaft 350

Cylinder Head 340

Cylinders 320

Internal Combustion Engine 300

Lubrication Channel(s) 11

Motorcycle 200

Pinion Drive Gear 110

Pinion Gear Retention Washer 88

Piston 310

Inner Race 39

Weight Saving Through Holes 122

Claims

What is claimed is:

1. A camshaft drive system for an internal combustion engine, the internal combustion engine including first and second cylinders in a V-configuration, the camshaft drive system comprising: a pinion drive gear rotating on a pinion axis substantially parallel to a crankshaft axis; a first camshaft driven gear rotating on a first axis parallel to the crankshaft axis, the first camshaft driven gear rotating a first camshaft; a second camshaft driven gear rotating on a second axis parallel to the crankshaft axis, the second camshaft driven gear rotating a second camshaft; a third camshaft driven gear rotating on a third camshaft axis parallel to the crankshaft axis, the third camshaft driven gear rotating a third camshaft; and an intermediate drive gear rotating on an intermediate gear axis parallel to the crankshaft axis, the intermediate drive gear being coupled to one of the first, second and third camshaft driven gears, wherein the first camshaft driven gear is meshed with the second camshaft driven gear, wherein the second camshaft driven gear is meshed with the third camshaft driven gear, and wherein the intermediate drive gear is meshed with the pinion drive gear such that rotation of the pinion drive gear causes rotation of the camshaft driven gears via the intermediate drive gear.

2. The camshaft drive system of claim 1, wherein the first and third camshafts comprise exhaust camshafts, and wherein the second camshaft comprises an intake camshaft.

3. The camshaft drive system of claim 2, wherein the intermediate drive gear is coupled to the second camshaft driven gear.

4. The camshaft drive system of claim 3, wherein the intermediate drive gear rotates on the second axis.

5. The camshaft drive system of claim 3, wherein the intermediate drive gear is bolted to the second camshaft driven gear.

6. The camshaft drive system of claim 3, wherein the intermediate drive gear and the second camshaft driven gear comprise separate portions of one integral gear.

7. The camshaft drive system of claim 3, wherein a diameter of the intermediate drive gear is larger than a diameter of the pinion drive gear.

8. The camshaft drive system of claim 7, wherein the diameter of the intermediate drive gear is about two times the diameter of the pinion drive gear.

9. The camshaft drive system of claim 3, wherein a diameter of the intermediate drive gear is larger than a diameter of the first, second and third camshaft driven gears.

10. The camshaft drive system of claim 9, wherein the diameter of the first camshaft driven gear is substantially the same as the diameter of the third camshaft gear.

1 1. The camshaft drive system of claim 10, wherein the diameter of the first camshaft driven gear is substantially the same as the diameter of the second camshaft driven gear.

12. The camshaft drive system of claim 3, wherein a diameter of the first camshaft gear is substantially the same as a diameter of the third camshaft gear.

13. The camshaft drive system of claim 12, wherein a diameter of the second camshaft gear is substantially the same as the diameter of the first camshaft gear.

14. The camshaft drive system of claim 3, wherein the intermediate drive gear and the pinion drive gear are oriented in a first plane, and wherein the first, second and third camshaft driven gears are oriented in a second plane substantially parallel to but different from the first plane.

15. The camshaft drive system of claim 14, wherein the second plane is inside of the first plane relative to a flywheel of the internal combustion engine.

16. The camshaft drive system of claim 15, further comprising a spacer provided between the intermediate drive gear and the second camshaft driven gear.

17. The camshaft drive system of claim 1 , wherein the internal combustion engine is a v-twin motorcycle engine.

18. A motorcycle including the v-twin motorcycle engine of claim 17.

19. The camshaft drive system of claim 1 , wherein each of the first, second and third camshaft driven gears include a notched center hole adapted to receive and engage a projection on the corresponding camshaft.

20. The camshaft drive system of claim 1, wherein the pinion drive gear includes a center hole with a drive shaft engaging surface, and wherein the drive shaft engaging surface is adapted to engage at least one flat extending from a first end of the drive shaft toward a second end of the drive shaft.

21. The camshaft drive system of claim 20, wherein the drive shaft comprises a crankshaft.

22. The camshaft drive system of claim 20, wherein the drive shaft comprises a pinion shaft.

23. The camshaft drive system of claim 1 , further comprising a bearing support including: a base removable from the internal combustion engine; a first projection extending from a first surface of the base; a second projection extending from a second surface of the base opposite the first surface; a drive shaft orifice extending through the base, first projection and second projection; a bearing assembly adapted to support an end of a draft shaft within the drive shaft support; and an inner race positioned between the bearing assembly and the drive shaft for rotatably supporting the pinion shaft within the base.

24. The camshaft drive system of claim 23, wherein the bearing support is removably coupled to one of a crankcase and an intermediate support plate.

25. The camshaft drive system of claim 24, wherein the bearing support is removably coupled to the intermediate support plate.

26. The camshaft drive system of claim 24, wherein the bearing support is bolted to one of the crankcase and the intermediate support plate.

27. The camshaft drive system of claim 26, wherein three bolts removably couple the bearing support to one of the crankcase and the intermediate support plate.

28. The camshaft drive system of claim 25, wherein the intermediate support plate includes a plurality of channels adapted to lubricate the camshaft drive system.

29. The camshaft drive system of claim 1 , further comprising: a pinion shaft operatively coupled to a crankshaft such that rotation of the crankshaft causes a corresponding rotation of the pinion shaft, wherein the pinion drive gear is removably coupled to the pinion shaft.

30. The camshaft drive system of claim 24, further comprising: a bolt adapted to removably couple the pinion drive gear to the pinion shaft, wherein the pinion shaft includes a threaded surface adapted to receive the bolt.

31. The camshaft drive system of claim 1 , wherein the pinion drive gear is removably coupled to a crankshaft.

32. The camshaft drive system of claim 31 , further comprising: a bolt adapted to removably couple the pinion drive gear to the crankshaft, wherein the crankshaft includes a threaded surface adapted to receive the bolt.

33. The camshaft drive system of claim 1, wherein the intermediate drive gear includes a plurality of weight reduction through holes.

34. The camshaft drive system of claim 3, wherein the intermediate drive gear includes six weight reduction through holes.

35. The camshaft drive system of claim 1, wherein the first camshaft driven gear includes a surface facing the pinion driven gear, and wherein an inner portion of the surface is recessed relative to an outer portion of the surface, the inner portion extending outward from the first axis and the outer portion extending inward toward the first axis from an outer gear tooth edge.

36. The camshaft drive system of claim 35, wherein the third camshaft driven gear includes a surface facing the pinion driven gear, and wherein an inner portion of the surface is recessed relative to an outer portion of the surface, the inner portion extending outward from the third axis and the outer portion extending inward toward the third axis from an outer gear tooth edge.

37. The camshaft drive system of claim 1 , wherein the second camshaft driven gear includes a spacer surface facing the pinion driven gear, and wherein an inner portion of the spacer surface is projected relative to an outer portion of the surface, the inner portion extending outward from the second axis and the outer portion extending inward toward the second axis from an outer gear tooth edge.

38. The camshaft drive system of claim 1 , wherein the pinion drive gear includes a countersink adapted to receive a pinion gear retention washer.

39. A method of rotating camshafts in an internal combustion engine, comprising: rotating a pinion gear with a drive shaft operatively connected to a crankshaft; rotating an intermediate drive gear with the pinion gear; rotating a second camshaft gear with the intermediate drive gear; and rotating both a first camshaft gear and a third camshaft gear with the second camshaft gear.

40. The method of claim 39, further comprising bolting the intermediate drive gear to the second camshaft gear.

41. The method of claim 39, further comprising meshing gear teeth of the second camshaft gear with gear teeth of both the first camshaft gear and the third camshaft gear.

42. The method of claim 39, further comprising meshing gear teeth of the pinion gear with the intermediate drive gear.

43. The method of claim 39, further comprising replacing a belt drive system with a gear drive system including: the pinion gear; intermediate drive gear; first camshaft gear; second camshaft gear; and third camshaft gear.

44. The method of claim 39, further comprising providing an intermediate plate between a crankcase and the gears, the intermediate plate including a plurality of holes for lubricating the gears.

45. The method of claim 44, further comprising drilling the plurality of holes into the intermediate plate.

46. The method of claim 44, further comprising removing a seal adapted to seal a crankcase relative to the intermediate plate.

47. A retrofit camshaft drive assembly, comprising: a pinion drive gear rotating on a pinion axis substantially parallel to a crankshaft axis; a first camshaft driven gear rotating on a first axis parallel to the crankshaft axis, the first camshaft driven gear rotating a first camshaft; a second camshaft driven gear rotating on a second axis parallel to the crankshaft axis, the second camshaft driven gear rotating a second camshaft; a third camshaft driven gear rotating on a third camshaft axis parallel to the crankshaft axis, the third camshaft driven gear rotating a third camshaft; and an intermediate drive gear rotating on an intermediate gear axis parallel to the crankshaft axis, the intermediate drive gear being coupled to one of the first, second and third camshaft driven gears; and a removable bearing support adapted to support an end of a crankshaft, wherein the first camshaft driven gear is meshed with the second camshaft driven gear, wherein the second camshaft driven gear is meshed with the third camshaft driven gear, wherein the intermediate drive gear is meshed with the pinion drive gear such that rotation of the pinion drive gear causes rotation of the camshaft driven gears via the intermediate drive gear, and wherein the retrofit camshaft drive assembly is adapted to replace a belt drive system in a motorcycle engine.