DESC:TECHNICAL FIELD
The present subject matter relates generally to a multi cylinder internal combustion (IC) engine with opposed piston configuration. More particularly, the present subject matter relates to a camshaft transmission system employing a belt drive transmission.
BACKGROUND
[0001] An internal combustion (IC) engine is used to convert thermal energy of air-fuel mixture to mechanical energy in a combustion chamber by transferring this thermal energy to one or more reciprocating pistons inside a cylinder block. The one or more reciprocating pistons transfers this reciprocating motion to a rotary motion of one or more crankshaft by a connecting rod utilizing a slider-crank mechanism. In this operation the precise movement and timing of the opening and closing of inlet aperture and outlet aperture to the combustion chamber is essential for accurate performance of the IC engine. The opening and closing operation must function effectively at a large range of speeds and operations. Generally, this opening and closing is controlled by various components present on the cylinder head and cylinder bore and actuated by one or more camshafts by the transmission of drive from the one or more crankshaft using a camshaft transmission system. In IC engines having opposed piston configuration (hereafter opposed piston engine), the camshaft transmission system is critical in optimum performance, reduction of noise and reduction in vibration. Typical opposed piston engines have two camshafts which make the engine layout complex, utilize increased number of parts and increased weight. Even, in some prior arts using single camshaft system, gear trains are used which increases weight, noise and vibration. Hence, a camshaft transmission system is proposed in the present subject matter in order to alleviate one or more drawbacks highlighted above.

BRIEF DESCRIPTION OF THE DRAWINGS
[0002] The detailed description is described with reference to the accompanying figures. The same numbers are used throughout the drawings to reference like features and components.
[0003] Fig. 1. illustrates a perspective view of a multi cylinder internal combustion (IC) engine having opposed piston configuration employing a camshaft transmission system according to an embodiment of the present subject matter.
[0004] Fig. 2. illustrates the exemplary perspective view of a typical multi cylinder internal combustion (IC) engine having opposed piston configuration, indicating a prior art.
[0005] Fig. 3. illustrates a cut sectional view (X-X) of the multi cylinder IC engine employing an embodiment of the present subject matter.
[0006] Fig. 4. illustrates a perspective view of the multi cylinder internal combustion (IC) engine showing the camshaft transmission system according to an embodiment of the present subject matter.
[0007] Fig. 5. illustrates the perspective view of the camshaft transmission system according to an embodiment of the present subject matter.
[0008] Fig. 6. illustrates the front view of the camshaft transmission system according to an embodiment of the present subject matter.

DETAILED DESCRIPTION
[0009] Various features and embodiments of the present subject matter here will be discernible from the following further description thereof, set out hereunder. According to an embodiment, an internal combustion engine (IC) described here is and opposed piston engine and operates in four cycles. Such an IC engine is installed in a step through type two wheeled vehicle. It is contemplated that the concepts of the present invention may be applied to other types of vehicles within the spirit and scope of this invention. The detailed explanation of the constitution of parts other than the present subject matter which constitutes an essential part has been omitted at suitable places.
[00010] IC engines come in various wide variety and design. Typically, an IC engine comprises a cylinder block having one or more cylinder bores, a piston reciprocating in each cylinder bore, a cylinder head located above the cylinder block and a combustion chamber. The combustion chamber is formed between the cylinder head, a top surface of the piston, and walls of the cylinder bore. A central longitudinal axes of the cylinder bore can be defined called cylinder axes and IC engines can be classified based on arrangement of the cylinder bores and the orientation of the cylinder axes with each other. When cylinder axes are parallel to each other, it is referred as in-line IC engine and in certain other type the cylinder axes are coincident to each other on a horizontal plane or are inclined to each other. Charge is ignited in the combustion chamber which expands imparting reciprocating motion to the piston which is converted to rotary motion of a crankshaft through a connecting rod. Further, the motion from the crankshaft is transmitted to wheels of the vehicle through a drive train. In one type of IC engine (hereafter referred to as opposed piston engine), there can be a common combustion chamber of an opposite facing cylinder bore. The cylinder bore can be either horizontal or inclined with respect to each other (i.e. the cylinder axes are inclined to each other in a substantially horizontal plane) and face each other to form the common combustion chamber. The burning of charge in the common combustion chamber imparts reciprocating motion to piston in each of the cylinder bore which transmits into rotary motion of two respective crankshafts which lie away from each other by two respective connecting rods. The cylinder head of opposed-piston engine houses various components such as camshafts, rocker arms, and rocker arm support shafts.
[00011] Typically, the most common layout configuration of the opposed piston engine is where cylinder bores faces each other horizontally with the cylinder axis and centre of both the crankshaft located horizontal and coincidently with respect to the horizontal plane. Other configurations include cylinder bore inclined to each other at some angle with respect to the horizontal plane. In the latter configuration, the centre of both the crankshafts lies on another axis parallel to the horizontal axis. But all the above layout configuration faces drawbacks of friction loss and decreased efficiency. In the above configurations, since a crankshaft axis of both the crankshaft coincide with the both the cylinder axis, maximum work cannot be extracted when the piston is at top dead centre (the position closest to the common combustion chamber). This is due to friction generated due to vertical position of crankshaft and connecting rod which prevents maximum extraction of work. This increases friction loss and reduces thermal efficiency of the opposed piston engine.
[00012] Generally, opposed piston engines having two cylinder bores is particularly suitable for application to two wheeled vehicles. The two pistons move in opposite directions in the common combustion chamber, moving the two crankshaft, and the cylinder head components are synchronized using suitable camshaft transmission systems which convert both the movements of the crankshafts to drive the camshafts. The camshaft transmission system drives the camshafts which in turn actuates two rocker arms supported on two rocker shafts respectively. The rocker arms operate a sleeve each for each cylinder bore to open and close the inlet and exhaust apertures to access the common combustion chamber. Each of the sleeves is enclosed in the cylinder bore and the piston reciprocates inside the sleeve. The sleeve is capable of sliding and the stroke movement of the sliding sleeve is actuated by each of the rocker arm. While a forward stroke is actuated by the rocker arm, the return stroke of the sleeve is actuated by the bias force of an elastic member such as a spring.
[00013] The cam transmission system is a very important aspect in the effective design of the opposed piston engine as it results in reduced noise, and low vibration operation. In typical opposed piston engines having two cylinder bores, there are two camshafts actuating each rocker arm which actuates the sleeve valve of each of the cylinder bore. Further, the drive from the two crankshafts is transmitted to the two camshafts by gear train transmission systems. Such an arrangement requires a complex mechanism especially when the engine is reciprocating in four cycles, because here the camshafts are running at half crankshaft speed and thus requires large driving wheels. Even with the aid of using special gearing systems such as scissor gear layout weight and noise cannot be reduced. Hence, it desirable to avoid the use of complex gear train systems to drive the two camshafts and transfer the power from secondary crankshaft to primary crankshaft.
[00014] The present subject matter aims to address the drawbacks of camshaft transmission system and reduce friction generated due to layout configuration of cylinder bore and crankshaft. The present subject matter relates to providing an opposed piston engine having offset crankshaft arrangement and a single camshaft operating two rocker arms. The drive to the single camshaft is achieved by a belt drive. A toothed belt is used to drive both the crankshaft and the camshaft. One pulley is assembled on the camshaft and two pulleys are assembled on both the crankshafts with proper alignment to achieve optimum sleeve valve timing. Further, an automatic tensioner, is assembled in between the two crankshafts to avoid belt skipping and also to reduce the belt noise. The offset crankshaft arrangement describes an opposed piston layout configuration wherein the cylinder axis of the both the cylinder bore are horizontal and coincidental and the centre of the both the crankshafts are offset from the crankshaft axis by a fixed value in either direction. In one embodiment, if centre of one crankshaft is offset from the crankshaft axis in the top direction, then the centre of the other crankshaft is offset from the crankshaft axis in the bottom direction. It is seen that, replacing gear train with belt drive can still give rise to problems such as increased frictional loss due to transmission as compared to gear train systems and hence overall reduce efficiency of the opposed-piston engine. But it is another object of the present invention to design the belt drive to reduce frictional transmission losses to the least permissible level in order to achieve the transmission efficiency that is observed in gear train systems described in prior art.
[00015] With the above design changes, the belt layout system ensures low noise during operation and lesser vibration. The belt can be made up of reinforced rubber which is much more resistant to stretching over time. Further, the belt has weight much lesser than gear train system or chain drive system and one can achieve a reduction of 6 kilograms by replacing gear train system by belt drive system. Accurate sliding movement of sleeve can be achieved even at higher speeds of revolution.
[00016] The present subject matter along with all the accompanying embodiments and their other advantages would be described in greater detail in conjunction with the figures in the following paragraphs.
[00017] Fig. 1a illustrates the isometric view of the IC engine (100) having camshaft transmission system, according to an embodiment of the present subject matter. According to one embodiment, the IC engine (100) is a twin-cylinder IC engine with common combustion chamber commonly known as opposed-piston engine (100). The opposed piston engine (100) comprises a cylinder block (101) located in the centre, a first LH crankcase (103), a second LH crankcase (105) (first LH crankcase and second LH crankcase collectively called LH crankcase), a first RH crankcase 102, a second RH crankcase 104 (first RH crankcase and second RH crankcase collectively called RH crankcase), a CVT cover (106), and a rear transmission case (107).
[00018] Fig. 3 illustrates a cross-sectional view (X-X) of the opposed piston engine (100). The opposed piston engine (100) includes the cylinder block (101) located at the center of the opposed piston engine (100) having a first cylinder bore (202), and second cylinder bore (203) with its ends forming a common combustion chamber (201). There is stopper (224) in the combustion chamber (201) which physically separates the first cylinder bore (202) and second cylinder bore (203). The angle between the first cylinder bore (202) and the second cylinder bore (203) is 180° and positioned along a horizontal plane. The cylinder bore axis can be understood as a central longitudinal axis of the cylinder bore. Fig. 2 illustrates the exemplary perspective view of a typical multi cylinder internal combustion engine having opposed piston configuration, indicating a prior art. In the prior art, the multi cylinder internal combustion engine having opposed piston configuration has a cylinder bore angle inclined with respect to each other less than 180 degrees. Here, the camshaft transmission system includes a gear train system (refer 306 & 308 in Fig. 2) which drives two camshafts each controlling one rocker arm. Due to disadvantages of increased weight, higher noise and increased vibrations in the prior art, a new camshaft transmission system is proposed. Further, in the prior art, the included angle between the two cylinder axes is inclines at an angle less than 180°. It is another object to propose an offset crankshaft configuration which eliminates the drawback of friction losses as highlighted in paragraph [00013]. Hence, as compared to the prior art in Fig. 2, referring to Fig. 3 it is illustrated that the opposed piston engine according to the present subject matter has both its cylinder axes (A) horizontal and coincident and further the centre of the both the crankshafts (206, 207) are offset from a crankshaft axis (see B, C) by a fixed value in either direction (see offset O). In one embodiment, if centre of one crankshaft is offset from the crankshaft axis in the top direction, then the centre of the other crankshaft is offset from the crankshaft axis in the bottom direction. In one embodiment, the first crankshaft (206) has its centre offset from the cylinder axes above the horizontal plane, and the second crankshaft (207) has its centre offset from the cylinder axes below the horizontal plane.
[00019] Further referring to Fig. 3, the first cylinder bore (202) is enclosed by the second RH and second LH crankcases (105,104). The second RH and second LH crankcases (105,104) houses a first crankshaft (206), which is connected to a first piston (208), reciprocating in the first cylinder bore (202), through a first connecting rod (204). Similarly, the second cylinder bore (203) is enclosed by the first RH and first LH crankcases (103,102). The first RH and first LH crankcases (103,102) houses a second crankshaft (207), which is connected to a second piston (209), reciprocating in the second cylinder bore (203), through a second connecting rod (205). In the embodiment, in which the opposed piston engine (100) is disposed in a horizontal direction, the crankshaft end of the cylinder bore (202, 203) is an inner dead centre of the cylinder bore (202, 203). During operation of the opposed piston engine (100), the first piston (208) and the second piston (209) are facing the common combustion chamber (201) in the respective cylinder bores (202 and 203) at the end of a compression stroke of the opposed piston engine (100). At the end of the compression stroke, i.e., when the compression of charge is almost complete, the top surface of the first piston (208) and the top surface of the second piston (209) are adjacent to each other. The first piston (208) and the second piston (209) have a crown portion (208a, 209a) facing the common combustion chamber (201) and a skirt portion (209b, 208b) connected to the first connecting rod (204) and second connecting rod (205) respectively. The shape and profile of the crown portion (208a, 209a) can be suitably designed to alter the combustion properties and decide the capacity of the opposed piston engine (100). In an implementation, the common combustion chamber (201), when formed, includes compressed charge. Further, one ignition element (217) is provided in the common combustion chamber (201) to achieve combustion of the compressed charge in the common combustion chamber (201). In one example, in case of a spark ignition engine, the ignition element (217) can be a spark plug, whereas in case of a compression ignition engine, the ignition element (217) can be a glow plug. The ignition element (217) is disposed in a through-opening in a lateral wall of the common combustion chamber (201). The ignition element (217) is disposed in the common combustion chamber (201) in such a way that substantially complete combustion of the charge can be achieved in the common combustion chamber (201). In another embodiment, the opposed piston engine (100) can include more than one ignition elements (217) disposed in the common combustion chamber (201). It will be understood that, in other embodiments, a number of ignition elements can be provided in the common combustion chamber (201), so as to achieve a substantially complete combustion of the charge in the common combustion chamber (201).
[00020] In addition, the cylinder block (200) includes one or more inlet apertures (212) that are connected to a fuelling system including a throttle body (not shown in figure) of the opposed piston engine (100), for inducting charge into the common combustion chamber (201) for combustion. For example, the fuelling system may include a carburetor or a fuel injection system. Additionally, the cylinder block (200) includes one or more exhaust ports (213) in the cylinder block (200) to allow combustion products to escape from the common combustion chamber (201), subsequent to the combustion of charge. In an implementation, to control the induction of charge into the common combustion chamber (201) and expulsion of combustion products from the common combustion chamber (201) the opposed piston engine (100) includes a first sleeve (210) and a second sleeve (211) disposed in the first cylinder bore (202) and in the second cylinder bore (203), respectively. The sleeves (210, 211) may serve as a liner for the first cylinder bore (202) and the second cylinder bore (203), respectively. In an embodiment, the first sleeve (210) and the second sleeve (211) are disposed in the respective cylinder bore (202, 203) such that the sleeve (210, 211) is capable of sliding in the respective cylinder bore (202, 203) along a direction of the cylinder bore axis. In an embodiment, the first sleeve (210) is provided with one or more inlet openings (not shown) for allowing charge to be inducted into the first cylinder bore (202) by regulating opening and closing of the inlet apertures (212). In a similar manner as described above, the actuation of the second sleeve (211) can be achieved to control the expulsion of the combustion products from the opposed piston engine (100) by regulating the exhaust aperture (212). In an implementation, the opposed piston engine (100) can include an actuation assembly to achieve actuation of the first sleeve (211) and second sleeve (210). In said embodiment, the actuation assembly actuates the first sleeve (210) to align the inlet openings in the first sleeve (210) with the inlet apertures (212) to open, and allow entry of charge into the first cylinder bore (202). The first sleeve (211) is spring loaded (214) on one end to keep the inlet apertures (212) closed, until the first sleeve (210) is actuated to open the inlet aperture (212). In a similar manner, the actuation assembly actuates the second sleeve (211) to align the exhaust openings in the second sleeve (211) with the exhaust apertures (213) to open the and allow exit of exhaust gases into the second cylinder bore (203). The second sleeve (211) is also spring loaded (215) on one end to keep the exhaust apertures (213) closed, until the second sleeve (211) is actuated to open the exhaust ports (213).
[00021] Further, the first crankshaft (206) meshes with a transmission assembly and serves as a power-take-off shaft, i.e., the shaft from which the drive is finally obtained. In an embodiment, the first crankshaft (206) can be the power-take-off shaft, and the first crankshaft (206) is connected to a transmission assembly (not shown). The transmission assembly (not shown) can be a continuously variable transmission (CVT) assembly, for further providing a drive, for example, to the two wheeled vehicle on which the opposed piston engine (100) is mounted and implemented.
[00022] Fig. 4 illustrates the perspective view of the camshaft transmission system enveloped within the opposed piston engine (100) according to one embodiment of the present invention. The camshaft transmission system is enveloped between the LH crankcase (103,105) and the RH crankcase (102,104). As illustrated in Fig. 4, on removal of the LH crankcase (103,105) the various components of the camshaft transmission system are accessible.
[00023] Fig. 5 illustrates the perspective view of the camshaft transmission system according to an embodiment of the present subject matter. The actuation assembly comprises a first rocker arm (507) having a first roller follower (507a), a second rocker arm (506) having a second roller follower (506a), a camshaft (508), and a cam lobe (508a) attached to the camshaft (508). The first rocker arm (507) and the second rocker arm (506) are connected to the first sleeve (210) and second sleeve (211) and pivoted by a first support shaft (507a) and second support shaft (506b) respectively. The first support shaft (507a) and second support shaft (506b) is connected between the inner surface of the RH crankcase (102,104) and LH crankcase (103,105).
[00024] The first rocker arm (507) and second rocker arm (506) comprises a first roller follower (507a) and a second roller follower (506a) which is actuated by the cam lobe (508a). The camshaft (508) is operably connected to the two crankshafts (206, 207) to rotate half the revolutions as that of the crankshaft (206, 207). The camshaft (508) comprises a cam-lobe (508a) whose outer profile is designed to operate and control both the first rocker arm (507) and second rocker arm (506) respectively. The rotation of the camshaft (508) actuates the movement of the first sleeve (210) and the second sleeve (211) to control inlet aperture (212) and exhaust aperture (213). The camshaft transmission system comprises an endless belt (501) capable of transmitting the drive from the first crankshaft (206) and second crankshaft (207) to the camshaft (508). The endless belt (501) is loaded on a set of pulleys within suitable tension on which in endless transmission is possible. The first crankshaft (206) comprises the first pulley (504), the second crankshaft (207) comprises the second pulley (505), and the camshaft (508) is connected to a third pulley (502), and around the first pulley (504), second pulley (505) and third pulley (502) the endless belt (501) is loaded with a prerequisite tension (300 to 500 Newton Metre). An automatic tensioner (503) is mounted on the inner surface of the RH crankcase (102,104) to subject the endless belt (501) to a constant tension and to maintain the endless belt tension to a constant value. Referring to Fig. 4, the automatic tensioner (503) comprises a roller surface (503a), tensioner mounting bracket (503b), a torsion spring (503e) whose one end is rigidly connected to the tensioner mounting bracket (503b) through a base support (503g) and whose other end is attached to the roller surface (503a) exerting a positive bias force on the endless belt (501) providing constant tension. The torsion spring (503e) is enclosed inside a roller surface (503a) and the other end of the torsion spring (503e) is attached to the base support (503g) which is connected to the tensioner mounting bracket (503b) by a central fastener (503d) and a washer (503c). The resulting assembly is connected to the inner surface of the RH crankcase (102,104) by plurality of fasteners (503f) located on the outer periphery of the tensioner mounting bracket (503b).
[00025] Fig. 6. illustrates the front view of the camshaft transmission system according to the embodiment of the present invention. The endless belt (501) is loaded around the first pulley (504), second pulley (505) and third pulley (502). Since transmission by endless belt (501) is not a complete positive drive there are transmission losses, hence the endless belt (501) is designed to minimize transmission losses to the best optimum value. In one embodiment, a toothed belt is used which is capable of meshing with corresponding toothed first pulley (504), second pulley (505) and third pulley (502). Further, the automatic tensioner (503) is disposed between the first crankshaft (206) and second crankshaft (207) and located at distance (D) of one forth of the centre distance from the second crankshaft (207) in the horizontal direction. The location of the automatic tensioner (503) is advantageously so located to increase the wrap angle of second pulley (505) to avoid slippage. It is seen that, in the first pulley (504) the slippage is avoided by the exertion of load by the rear wheel of the two wheeled vehicle through the transmission system. Further, the distance of one forth of the centre distance from the second crankshaft (207) provides least belt friction to improve efficiency. It also aids in maintaining ideal tension (300 to 500 Newton Metre) in the endless belt (501) as there are chances of potential loss of belt tension near the second crankshaft (207) due to no application of load. The arrangement also provides compact layout to accommodate the automatic tensioner (503) within the LH crankcase (103,105). Furthermore, the system is designed to be a wet belt system and hence exposed to oil lubrication to enable reduced friction movement. The life of the automatic tensioner (503) is increased by ensuring least transfer load to the torsion spring (503e) enhancing the life of the torsion spring (503e) and base support (503g). The location also serves to avoid automatic tensioner (503) belt skipping. The design of camshaft transmission system within the layout of the inner surface of the RH crankcase (102,104) for the offset crankshaft configuration is important. By ensuring the position of the automatic tensioner (503) to be located at distance of one forth of the centre distance from the second crankshaft (207) in the horizontal direction the frictional transmission losses are restricted to be within permissible levels which is an important aspect of the present subject matter.
[00026] It will be appreciated that the present subject matter and its equivalent thereof offers many advantages, including those which have been described forthwith. The camshaft transmission system according to the present subject matter is capable of reduction of 6 kilograms from the original weight of a typical opposed piston engine employing two camshafts or an opposed-piston engine adopting gear train system for a single camshaft. The noise generated by the opposed piston engine according the present subject matter is about 65 decibels which is within permissible limits required to improve efficiency and meet governmental norms. Further, vibrations are reduced due to automatic tensioner and optimum location of the automatic tensioner.
[00027] Many modifications and variations of the present subject matter are possible in the light of above disclosure. Therefore, within the scope of claims of the present subject matter, the present disclosure may be practiced other than as specifically described.
,CLAIMS:We Claim:
1. A multi-cylinder internal combustion engine (100) having opposed piston configuration, said multi-cylinder internal combustion engine (100) comprising:
a cylinder block (101);
a first cylinder bore (202) and a second cylinder bore (203) enclosed within the cylinder block (202) along a central axis (A);
a proximal end (202a) of the first cylinder bore (202) is facing a proximal end (203a) of the second cylinder bore (203) to form a common combustion chamber (201);
a first sleeve (210) and a second sleeve (211) slidably operable in the first cylinder bore (202) and second cylinder bore (203) respectively to regulate the entry of air fuel mixture;
a first piston (208) reciprocating within the first sleeve (210), said first piston (208) driving a first crankshaft (206), and said first crankshaft (206) is disposed at a distal end (202b) of the first cylinder bore (202);
a second piston (209) reciprocating within the second sleeve (211), said second piston (209) driving a second crankshaft (207), and said second crankshaft (207) is disposed at a distal end (203b) of the second cylinder bore (203); and
a first rocker arm (507) and second rocker arm (506) to control the operation of the first sleeve (210) and second sleeve (211) respectively;
wherein,
said first crankshaft (206) has its centre (O) offset from the central axis (A), and said second crankshaft (207) having its centre (O1) offset from the central axis (A) in a direction opposite to the centre offset (O) of the first crankshaft (207);
said first rocker arm (507) and said second rocker arm (506) being operated by a cam-lobe (508a), said cam-lobe (508a) located on a camshaft (508); and
said camshaft (508) capable of being driven by a belt (501) obtaining the drive from the first crankshaft (206) and second crankshaft (207).
2. The multi-cylinder internal combustion engine (100) as claimed in claim 1, wherein said second crankshaft (207) is having its centre (O1) offset below the central axis (A), and said first crankshaft (206) has its centre (O) offset above the central axis (A).
3. The multi-cylinder internal combustion engine (100) as claimed in claim 1, wherein the first crankshaft (206) comprises a first pulley (504), the second crankshaft (207) comprises a second pulley (505), and the camshaft (508) comprises a third pulley (502), and said belt (501) operably connecting the first pulley (504), the second pulley (505) and the third pulley (502).
4. The multi-cylinder internal combustion engine (100) as claimed in claim 1, wherein an automatic tensioner (503) is mounted on the inner surface of the RH crankcase (102,104) disposed between the first crankshaft (206) and second crankshaft (207) to subject the belt (501) to a constant tension.
5. The multi-cylinder internal combustion engine (100) as claimed in claim 4, wherein said automatic tensioner (503) is located at distance (D) of one forth of the centre distance (O-O1) from the centre of the second crankshaft (O1) in the horizontal plane to increase the wrap angle of second pulley (505) and reduce belt friction.
6. The multi-cylinder internal combustion engine (100) as claimed in claim 3, wherein the belt (501) is loaded with a prerequisite tension of between 300 to 500 Newton Metre around the first pulley (504), second pulley (505) and third pulley (502).
7. The multi-cylinder internal combustion engine (100) as claimed in claim 1 or claim 3, wherein said automatic tensioner (503) comprises
a roller surface (503a) in contact with the belt (501);
a tensioner mounting bracket (503b) connected to the inner surface of the RH crankcase (102,104) by a plurality of fasteners (503f) located on the outer periphery of the tensioner mounting bracket (503b); and
a torsion spring (503e) whose one end is rigidly connected to the tensioner mounting bracket (503b) through a base support (503g) and whose other end is attached to the roller surface (503a) exerting a positive bias force on the endless belt (501) providing constant tension.
8. The multi-cylinder internal combustion engine (100) as claimed in claim 1 or claim 2, wherein lubricating oil is circulated around the belt (501), the first pulley (504), second pulley (505) and third pulley (502) to enable reduced friction movement.
9. The multi-cylinder internal combustion engine (100) as claimed in claim 1, wherein the belt (501) is a toothed belt drive which is capable of meshing with corresponding toothed first pulley (504), second pulley (505) and third pulley (502).
10. The multi-cylinder internal combustion engine (100) as claimed in any of the preceding claims, wherein said multi-cylinder internal combustion engine (100) is used in a two wheeled vehicle.