Abstract:
This invention relates to an internal combustion engine for a motorcycle, with two or more single cylinders arranged in a plane approximately normal to a crankshaft, each cylinder accommodating a reciprocating piston and the pistons acting via connecting rods on the same crank of the crankshaft supported in a crankcase. To reduce manufacturing expense, the engine is to be provided with modular components for universal use with at least two different cylinder arrangements (V-type, W-type).

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of application Ser. No. 09/309,583, filed May 11, 1999, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to an internal combustion engine for a motorcycle, with two or more single cylinders arranged in a plane approximately normal to a crankshaft, each cylinder accommodating a reciprocating piston and the pistons acting via connecting rods on the same crank of the crankshaft supported in a crankcase. 
     DESCRIPTION OF THE PRIOR ART 
     In U.S. Des. Pat. No. 294,264 an internal combustion engine for motorcycles is described which includes two cylinders arranged radially to a crankshaft in V-type fashion, each cylinder acting on a crank via a connecting rod. This type of engine features great compactness and a very short overall length, so that it can be mounted transversely in a motorcycle. For reasons of layout and space the cubic capacity per cylinder is limited. The total cubic capacity could only be increased by adding more cylinders, which would increase the engine&#39;s overall length, however. 
     Another alternative known in the art is the use of three cylinders which are radially positioned relative to the engine crankshaft, where the pistons sliding in the cylinders act on a common crank of the crankshaft by means of individual connecting rods. Such an internal combustion engine whose cylinders are arranged in the shape of a W, is described in U.S. Pat. No. 5,765,451. Engines with W-type cylinder arrangement, where the cylinders are positioned essentially in a plane normal to the crankshaft, will also permit a most compact design with very short overall length. Compared to the V-engine, the additional cylinder will improve the engine&#39;s running characteristics and significantly increase its cubic capacity while the small size will be maintained. The large piston-swept volume will permit high engine performance at comparatively low rpm, combined with a typical, full, comparatively low-frequency engine sound. 
     The different properties of V- and W-engines will appeal to different groups of consumers. 
     To meet the demand for V-engines on the one hand and W-engines on the other, separate production and distribution systems would have to be set up under conventional conditions, which would require considerable production and logistics efforts and involve high manufacturing costs. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to avoid the above disadvantages and to reduce the manufacturing costs for an internal combustion engine of the afore-mentioned type. 
     In the invention this object is achieved by using modular components for universal use with at least two different cylinder arrangements. Preferably, the crankcase has a body, which, apart from the flange face for the cylinders, is designed for at least a first and a second cylinder arrangement, the body comprising at least main bearing walls and crankcase side walls. The body may further include a balancer shaft housing configured as an integral part of the crankcase and including balancer shaft bearing walls, and a manual transmission housing including gearshaft bearing walls. 
     The first cylinder arrangement is formed by at least two cylinders arranged in the shape of a V and the second cylinder arrangement is formed by at least three cylinders arranged in the shape of a W. 
     Production simplicity and cost-efficiency in manufacturing an internal combustion engine with at least three cylinders in W-type arrangement are considerably improved by providing that at least one component of the group consisting of cylinder head, cylinder, piston, connecting rod, valve train be identical with that of a corresponding engine whose cylinders are arranged in a V. 
     It is further provided preferably that at least one component of the group consisting of balancer shaft, counterweight, starter, generator, clutch, torque limiter, manual transmission, oil pump, water pump be identical with that of a corresponding engine whose cylinders are arranged in a V. If components of identical type can be used for V- and W-engines, the production process will be simplified considerably, as components may be manufactured and assembled on the same production line. Due to the modular design and component sharing principle large piece numbers will be made possible and manufacturing costs will be reduced. Cost-efficiency will be further improved if at least one component of the group consisting of oil pan, oil cooler, dry sump lubrication, intermediate gear, belt and chain is identical with that of an engine whose cylinders are arranged in a V. Depending on the engine type, carburetor or injection device for multi-point injection or direct injection may be identical in type. 
     In order to keep production costs for the crankcase down, the proposal is put forward that the body of the crankcase for the W-engine be given the same tooling as that of a corresponding engine with V-type cylinder arrangement. Apart from the cylinder flange the crankcases for both V- and W-engines may be tooled on the same production line. 
     The large number of shared components has the additional advantage that available production capacities may be fully utilized and downtimes minimized. 
     V-engines usually have exhaust flange faces that are positioned on the outer side faces of the cylinder heads. To permit the use of identical cylinders and cylinder heads in V-engines and W-engines the proposal is put forward that each cylinder head have a front-side exhaust flange face which is preferably located in a plane normal to the crankshaft axis. The exhaust pipes may thus depart from the front of the engine, which will permit a close spacing of cylinders and reduce the space required by the engine to a minimum. 
     To permit the use of one and the same crankcase for several engine types, the crankcase features an intermediate gear flange face for connection of an intermediate gear. The intermediate gear, which is configured as a reduction gear, may be designed to be shiftable to enable changing of the reduction ratio. 
     It may further be provided that the intermediate gear configured as reduction gear be shiftable to enable changing of the reduction ratio, a special advantage being obtained by providing the crankcase with an oil pan flange on its lower side for carrying an oilpan. The oil tank/oil cooler unit forms part of the dry sump lubrication of the engine. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will now be further described with reference to the accompanying drawings, in which 
     FIG. 1 is a cross-section through an internal combustion engine according to the invention, with W-type cylinder arrangement, 
     FIG. 2 is a cross-section through an internal combustion engine with V-type cylinder arrangement, 
     FIG. 3 is a longitudinal section through an internal combustion engine according to the invention, along line III—III in FIG. 5, 
     FIGS. 4 and 5 are views of internal combustion engines according to the invention, in two variants, 
     FIG. 6 shows a section of the engine of FIG. 5 along line VI—VI in FIG.  5 . 
     FIG. 7 is a cross-section through an internal combustion engine according to the invention, with W-type cylinder arrangement, in a further embodiment, 
     FIG. 8 is an oblique view of the combustion chamber top face in the cylinder head, 
     FIG. 9 is a schematical representation of the camshaft drive of this internal combustion engine, 
     FIG. 10 is a side view of the complete motorcycle. 
    
    
     In all embodiments identical components bear the same reference numbers. Cylinder arrangements in the shape of a V or W generally bear the references V or W. 
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1 shows an internal combustion engine with W-type arrangement of cylinders  1 . Each cylinder  1  accommodates a reciprocating piston  2  which is connected to a crankshaft  4  via a connecting rod  3 . Each cylinder  1  carries a cylinder head  5 , which is configured as single cylinder head and houses the valve train  6  including camshaft  7 , charge exchange valves  8  and rocker arms  9 . Each cylinder head  5  has an exhaust flange face  10  on the engine front, which is essentially positioned in a plane normal to the crankshaft axis  4 ′. The exhaust port leading towards the exhaust flange face  10  bears reference number  11 . Each intake pipe  12  is provided with a carburetor  13 . The combustion chamber  14  of each cylinder  1  has two spark plugs  15 , as is shown in FIG.  3 . 
     The crankshaft  4  is supported in the crankcase  16 . The two-part crankcase  16  is divided in a normal plane  29  relative to the crankshaft axis  4 ′. The crankcase  16  further houses a balancer shaft  17  with counterweight  18 . Reference number  19  refers to a manual transmission. 
     FIG. 2 shows an internal combustion engine with two cylinders  1  arranged in a V. To keep production costs down the W-type engine presented in FIGS.  1  and  3 - 5  is designed such that components such as cylinder head  5 , cylinder  1 , piston  2 , valve train  6 , balancer shaft  17 , counterweight  18   a , starter  23 , generator  25 , clutch  27 , torque limiter  28 , manual transmission  19 , oil pump  24 , water pump  26  and/or carburetor  13  or injection device are essentially identical with those of the engine shown in FIG. 2 whose cylinders  1  are arranged in a V. In this embodiment oil pump  24  and water pump  26  are located on the same shaft. The above components can thus be manufactured in one and the same production facility. 
     Moreover, components such as the oil pan  21 , oil cooler  21 ′, intermediate gear  20 , belt and/or chain may be shared by V-type and W-type engines. 
     FIG. 4 shows a variant of an internal combustion engine with cylinders  1  arranged in a W, including an intermediate gear  20  configured as a reduction gear. FIG. 5 presents an internal combustion engine with cylinders  1  arranged in a W, where the crankcase  16  is provided with an oil pan flange  167  on its lower side for carrying an oilpan  21  configured as oil tank/oil cooler unit  210 . Reference  21 ″ refers to cooling fins of the oil cooler  21 ′. FIG. 6 presents a section of this engine as seen from below. 
     The crankcase  16  of the W-engine is designed such that the crankcase body  160 , i.e., crankcase  16  except for flange faces  22  for cylinders  1 , can be worked with the same tools and tool settings as the crankcase  16   a  of the engine shown in FIG. 2, whose cylinders  1  are arranged in a V. The corresponding flange face of the V-engine for cylinders  1  is referred to as  22   a  in FIG.  2 . 
     The crankcase body  160  comprises crankcase side walls  161 , main bearing walls  162 , balancer shaft housing  163 , balancer shaft bearings  164 , manual transmission housing  165 , gearshaft bearing walls  166 . 
     In the invention the majority of components of both V- and W-engines can be manufactured on the same production line and production efforts and costs can be reduced considerably. 
     FIGS. 7 to  9  show another variant of an internal combustion engine with W-type cylinders  1 . The intake and exhaust valves of each cylinder  1  are actuated via push rods  61 ,  62  and rocker arms  63 ,  64  by means of an intake camshaft  65  and an exhaust camshaft  66  per cylinder  1 , as is shown in FIG. 9, each of said camshafts lying below the cylinder. In the engine shown here, with two intake valves  67  and one exhaust valve  68  per cylinder  1 , the rocker arm  63  for the intake valves  67  is configured as a forked rocker. 
     The intake camshafts  65  and exhaust camshafts  66  are driven via a traction means  69 ,  70 , such as a cam chain or belt. At least the means  69  driving the intake camshaft  65  is provided with a pivoted cam chain guide  71 . By rotating the cam chain guide  71  about a pivot  72  the timing of the intake valves  67  may be phase-shifted. The rotation is effected by a hydraulically operated actuating device or a solenoid actuator  73 . 
     As is seen in FIG. 7, each cylinder  1  of the internal combustion engine shown is provided with an injection device  75  opening into an intake port  74 , which device  75  is positioned in the rocker arm bearing block  76  or the valve cover  77  covering the top of the cylinder head  5 . 
     Integrated into the rocker arm bearing blocks  76  or the valve covers  77  are preferably oval throttle valves  78  of the intake ports  74 . In the variant shown in FIG. 7 the intake ports  74  are arranged in the cylinder heads  5  in such a way that reverse tumble flows will be initiated in the combustion chambers. 
     As is seen in FIG. 8, two spark plugs  15  are provided for each cylinder  1 . 
     This variant is also characterized by the modular design of the internal combustion engine, which means that major components can be used both in engines with V-type and W-type cylinder arrangements.