GB2377970A

GB2377970A - V or horizontally opposed motorcycle engine with overhead camshafts arran ged perpendicular to crankshaft

Info

Publication number: GB2377970A
Application number: GB0114307A
Authority: GB
Inventors: Brian Russell Knight; Brian Richard Mason
Original assignee: Ricardo Consulting Engineers Ltd
Current assignee: Ricardo PLC
Priority date: 2001-06-12
Filing date: 2001-06-12
Publication date: 2003-01-29
Anticipated expiration: 2021-06-12
Also published as: GB0114307D0; GB2377970B; DE10226076A1

Abstract

A motorcycle engine of V or horizontally opposed type has all of the overhead camshafts extending perpendicular to the axis of the crankshaft (4). The engine also includes an auxiliary shaft (22) extending above the crankshaft (4) and parallel thereto and connected to the crankshaft to rotate therewith. The auxiliary shaft (22) carries two drive gears (24), which cooperate with two driven gears (26) which are connected to respective drive pulleys (28, fig.3) and are mounted to rotate about respective axes parallel to the axes of the overhead camshafts associated with each cylinder, respectively. The inner ends of the camshafts carry respective driven pulleys (10), the two driven pulleys associated with each cylinder being connected to be rotated by a respective one of the drive pulleys (24) by respective drive chains (30). The inlet duct and exhaust duct associated with each cylinder is located at the front and rear of the cylinder spaced apart in the axial direction of the crankshaft.

Description

MOTORCYCLE ENGINES

The present invention relates to motorcycle engines of V or horizontally opposed type, that is to say internal combustion engines for motorcycles which 5 comprise two or more cylinders, the axes of which are inclined to one another and which contain respective pistons connected by connecting rods to a common crankshaft. In a V engine the axes of the cylinders or two banks of cylinders are typically inclined to one another by 90 or less and in a horizontally opposed engine they are inclined at 180 .

It is known to provide such engines with one or two overhead camshafts per cylinder and for ease of driving these camshafts it is usual to provide them extending parallel to the crankshaft. This means that the camshaft drive must be provided at the front or rear of the cylinders, with respect to the direction of 15 motion of the motorbike. This means in turn that the inlet and exhaust ducts must be provided on the side surfaces of the cylinders. However, the designer is constrained by the fact that there is relatively little space available on the inside surfaces and providing them on the outside surfaces increases the overall width of the motorbike, which is undesirable. The inlet and exhaust systems of 20 such engines are therefore generally designed primarily with space or packaging considerations rather than efficiency considerations in mind which results in a reduction in the efficiency or power output of the engine.

It is an object of the invention to overcome the above problems referred to and 25 to provide a motorcycle engine of the type referred to above, preferably of V twin type, in which the inlet and exhaust ducts may be provided at the front and

rear of the engine and in which the camshaft drive mechanism is both relatively cheap and relatively simple.

According to the present invention a motorcycle engine of V or horizontally 5 opposed type comprises two or more cylinders, the axes of which are inclined to one another and which contain respective pistons connected by connecting rods to a common crankshaft, each cylinder including one or more inlet valves and one or more exhaust valves, the or each inlet valve of each cylinder communicating with a respective inlet duct and cooperating with an overhead 10 camshaft and the or each exhaust valve of each cylinder communicating with a respective exhaust duct and cooperating with an overhead camshaft, all of the overhead camshafts extending perpendicular to the axis of the crankshaft, the engine further including an auxiliary shaft extending above the crankshaft and parallel thereto and connected to the crankshaft to rotate therewith, the auxiliary 15 shaft carrying two drive gears which cooperate with two driven gears, which are connected to respective drive pulleys and are mounted to rotate about respective axes parallel to the axes of the overhead camshaft(s) associated with each cylinder, respectively, the inner ends of the camshaft(s) carrying respective driven pulleys, the two driven pulleys associated with each cylinder being 20 connected to be rotated by a respective one of the drive pulleys by respective flexible endless drive means, the inlet duct and exhaust duct associated with each cylinder being located at the front and the rear of the cylinder spaced apart in the axial direction of the crankshaft.

25 The inlet and exhaust valves of each cylinder may be operated by a single camshaft, in which event the number of overhead camshafts will be equal to the number of cylinders. It is, however, preferred that there are two overhead

camshafts per cylinder, one operating the or each inlet valve and the other operating the or each exhaust valve. It is also preferred that each drive gear comprises a spur gear and each driven gear comprises a face gear.

5 Thus in the engine in accordance with the invention there are one and preferably two overhead camshafts associated with each cylinder and these extend perpendicular to the crankshaft axis. The camshaft(s) associated with each cylinder are driven from the crankshaft via an auxiliary shaft connected to rotate with the crankshaft, two drive gears on the auxiliary shaft, two driven 10 gears in mesh with the drive gears and respective flexible endless drive means, e.g. a drive chain, which passes around each drive pulley and the or each driven pulley associated with each cylinder. The camshaft drive mechanism is thus relatively simple and includes relatively few components. By virtue of the fact that the camshafts extend perpendicular to the axis of the crankshaft, the 15 camshaft drive mechanisms can be positioned on the inner surfaces of the two cylinder blocks and thus be accommodated wholly within the V space defined by the cylinder blocks. The inlet and exhaust ducts may therefore be provided on the front and rear surfaces of the cylinder blocks and may thus be designed solely with efficiency and power considerations in mind without any space or 20 packaging constraints.

It is also preferred that the engine includes a balancer shaft connected to the crankshaft to rotate in synchronism therewith but in the opposite sense and further that, in the case of a V engine, the balancer shaft is also accommodated 25 within the V space defined by the cylinder blocks. The auxiliary shaft may be driven directly by the crankshaft or indirectly via the balancer shaft.

Further features and details of the invention will be apparent from the following description of one specific embodiment of twin motorcycle engine in

accordance with the invention which is given by way of example with reference to the accompanying drawings, in which: Figure 1 is a front diagrammatic view of the essential components of the engine, partly in section; Figure 2 is a plan view of the auxiliary shaft in the direction of the arrow 2 in Figure 1; 10 Figure 3 is a scrap view in the direction of the arrow 3 in Figure 1 showing the camshaft drive arrangement; Figure 4 is a scrap view of the auxiliary shaft in the direction of the arrow 4 in Figure 1; and Figure S is a diagrammatic section view of the engine on its longitudinal central 1 5 plane.

The engine comprises two cylinders 2, whose axes 3 intersect at an angle of, in this case, 90 . Each cylinder contains a piston connected by a respective connecting rod to a common crankshaft 4. Each cylinder includes two exhaust 20 valves, which communicate with a common respective exhaust duct 6 at the front of the engine, with respect to its direction of travel when incorporated in a motorcycle. Each cylinder also includes two inlet valves which communicate with a common respective inlet duct at the rear of the engine. The two exhaust valves and two inlet valves are operated by respective overhead camshafts, 25 whereby there are two such camshafts associated with each cylinder, the axes 8 of both of which extend perpendicular to the axis of the crankshaft. Connected to one end of each camshaft is a respective camshaft drive pulley 10.

The crankshaft 4 carries a toothed gearwheel 12 which is in mesh with a similar gearwheel 14 carried by a rotary balancer shaft 16 of known "Heron" type extending above and parallel to the crankshaft. The balancer shaft thus rotates 5 in the opposite sense to the crankshaft and serves to eliminate or reduce the instability of the motorcycle caused by the asymmekica1 loads acting, in use, on the interior of the cylinders and the reaction torque caused by acceleration of the crankshaft, both of which tend to cause the motorcycle to topple over. The balancer shaft 16 also carries a further gearwheel 18 in mesh with a further 10 gearwheel 20 carried by a rotary auxiliary shaft 22. The auxiliary shaft extends parallel to and above the balancer shaft 16 and rotates in the same sense as the camshaft. The auxiliary shaft 22 carries two spaced gearwheels 24, each of which is in 15 mesh with an annular array of teeth on the end surface of a respective gearwheel 26 of known ' face" type. The gearwheels 26 are mounted to rotate about respective axes which are inclined at the same angle as the axes of the cylinders 2, in this case 90 . A portion 28 of each gearwheel 26 is constructed as a pulley, in this case of toothed type. respective drive chain 30 passes round 20 each pulley 28 and the two associated camshaft drive pulleys 10. Drive is thus transmitted from the crankshaft via the shafts 16 and 22, the gearwheels 24 and 26 and the drive chains 30 to the four overhead camshafts.

The camshaft drive mechanism is thus compact and includes relatively few 25 components and is accommodated wholly on the inner side surface of the two cylinders. The balancer shaft is also wholly accommodated within the space defined by the V shape of the cylinders. The inlet and exhaust ducts may thus

be provided on the front and rear surfaces of the cylinders, thereby permitting them to be designed solely with efficiency and power considerations in mind without being limited by space and packaging constraints.

s

Claims

- CLAIMS

1. A motorcycle engine of V or horizontally opposed type comprising two 5 or more cylinders, the axes of which are inclined to one another and which contain respective pistons connected by connecting rods to a common crankshaft, each cylinder including one or more inlet valves and one or more exhaust valves, the or each inlet valve of each cylinder communicating with a respective inlet duct and cooperating with an overhead camshaft and the or each 10 exhaust valve of each cylinder communicating with a respective exhaust duct and cooperating with an overhead camshaft, all of the overhead camshafts extending perpendicular to the axis of the crankshaft, the engine further including an auxiliary shaft extending above the crankshaft and parallel thereto and connected to the crankshaft to rotate therewith, the auxiliary shaft carrying 15 two drive gears which cooperate with two driven gears, which are connected to respective drive pulleys and are mounted to rotate about respective axes parallel to the axes of the overhead camshaft(s) associated with each cylinder, respectively, the inner ends of the camshaft(s) carrying respective driven pulleys, the two driven pulleys associated with each cylinder being connected to 20 be rotated by a respective one of the drive pulleys by respective flexible endless drive means, the inlet duct and exhaust duct associated with each cylinder being located at the front and the rear of the cylinder spaced apart in the axial direction of the crankshaft.

25

2. An engine as claimed in Claim 1 in which there are two overhead

camshafts associated with each cylinder.

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3. An engine as claimed in claim 1 or 2 in which each drive gear comprises a spur gear and each driven gear comprises a face gear.

4. An engine as claimed in any one of the preceding claims including a 5 balancer shaft extending above the crankshaft and parallel thereto and connected to the crankshaft to rotate therewith but in the opposite direction.