VEHICLE

TECHNICAL FIELD

[0001] The present subject matter relates to a motor vehicle and more particularly but not exclusively to an engine assembly for the motor vehicle.

BACKGROUND

[0002] Generally, a motor vehicle is powered by an internal combustion (IC) engine to act as a power unit for the motor vehicle. The IC engine converts chemical energy into mechanical energy by combustion of air-fuel mixture within a combustion chamber of the IC engine. Combustion of the air-fuel mixture causes a piston to reciprocate in the combustion chamber. The reciprocating to- and-fro motion is translated into a rotatory motion of a crankshaft. The rotational motion of the crankshaft is used for moving the motor vehicle.

[0003] Typically, in order to cater to various power and torque requirements, a gear system with plurality of gear ratios is provided with the IC engine. A selected gear is configured to provide a pre-determined gear ratio. The user can manually shift gear through a gear shaft or depending on user requirements an electronic control unit can perform gear shifting with minimal or no user intervention. Typically, to start the IC engine, it is cranked either manually using a kick-start lever, by a hand-operated lever or through an electric start system that utilizes an electric motor. In the motor vehicle, various systems including the gear system and starting system are packaged within the IC engine. BRIEF DESCRIPTION OF DRAWINGS

[0004] The detailed description is described with reference to the accompanying figures, which is related to a two-wheeled motor vehicle being one embodiment of the present invention. However, the preset invention is not limited to the depicted embodiment(s). In the figures, the same or similar numbers are used throughout to reference features and components. [0005] Fig. 1 illustrates a left-side view of an exemplary motor vehicle, in accordance with an embodiment of the present subject matter.

[0006] Fig. 2 depicts a right-side view of an exemplary internal combustion engine, in accordance with an embodiment of the present subject matter.

[0007] Fig. 3 (a) depicts a right-side perspective view of an exemplary internal combustion engine, in accordance with an embodiment of the present subject matter.

[0008] Fig. 3 (b) illustrates a schematic perspective view of a portion of an IC engine with partially exploded components, in accordance with an embodiment of the present subject matter.

[0009] Fig. 3 (c) illustrates a schematic enlarged view of a portion of an IC engine, in accordance with an embodiment of the present subject matter as depicted in Fig. 3 (b).

[00010] Fig. 3 (d) depicts another enlarged view of a portion of the IC engine, in accordance with an embodiment of the present subject matter.

DETAILED DESCRIPTION

[00011] Generally, the motor vehicles, especially smaller capacity motor vehicles including two-wheeled or three-wheeled type, are provided with a kick-start system or a similar cranking system. Further, in order to set the vehicle into motion, the power from the crankshaft of the internal combustion engine is carried to a wheel of the vehicle, in a controllable way, through a transmission system. The transmission system for the IC engine of a two-wheeled motor vehicle such as a motorcycle generally comprises of a clutch assembly, and a gear system containing gear train. A drive mechanism connects the gear system to at least one wheel. The gear train has multiple gear ratios and depending on speed and torque requirement, a gear ratio is selected.

[00012] Conventionally, incorporation of the various systems like the gear system, starter system etc. on the IC engine makes the IC engine bulkier. For example, various components including clutch assembly, gear system including gear sets, shifting mechanism, lubrication assembly etc. are to be accommodated on the crankcase and with minimal or no interference. Additionally, the conventional gear shifting mechanism is spread out on the crankcase owing to avoidance of interference or for packaging challenges thereby occupying lot of space. For example, the IC engine comprises various parts like a drum stopper that are secured to the crankcase. Such parts are to be disposed away from the rotating parts to avoid any interference. Moreover, some conventional gear shifting mechanism operate at a short angle of rotation thereby requiring high precision manufacturing and assembly. Any variations would affect angle of rotation thereby resulting in over shifting or under shifting offering poor performance feel to user. Also, weight of the overall IC engine increases, as the size of the IC engine is increased to accommodate the aforementioned and other systems. Moreover, the IC engine, especially the crankcase has to made rigid to securely support the various systems. An effect of increase in weight is that a frame assembly supporting the IC engine is also to be made bulkier to securely support the IC engine. Moreover, lot of space is occupied on the motor vehicle by the IC engine. Fuel economy of the motor vehicle is affected due to higher weight. Bulkier configuration of the IC engine may affect the ground clearance of the motor vehicle. For example, in a motorcycle with a fuel tank disposed above the IC engine, the position of the fuel tank cannot be moved beyond a certain height owing to riding posture, visibility, and other design constraints. This may result in the IC engine extending downward affecting the ground clearance rendering the vehicle impractical to ride in city and off-road conditions. It could also damage the components of the IC engine due to pot holes or bumps on roads.

[00013] Typically, attempts have been made in the past to make the IC engine compact. Such attempts, includes but are not limited to a kick-start system being eliminated in the motor vehicles to reduce components and to save space. However, the removal of kick-start system is compensated by a large capacity battery, which eventually adds to the weight of the motor vehicle. Moreover, there would be various conditions during which a battery might not be sufficient to crank the IC engine. For example, with time battery losses its charge retaining capability and may fail to start the IC engine or battery maybe drained due to non usage of motor vehicle for prolonged duration. This would require the user to push the vehicle to a service center for getting the battery charged or replaced making it a cumbersome, inconvenient and costlier process. Some of the other known solutions include reducing size of fuel tank in order to compensate an increase in size of the IC engine. However, by reducing the size of the fuel tank, a fuel holding capacity of the motor vehicle is reduced which may invoke undesirable range anxiety in the user. In certain other known solutions, a diameter of the wheel is increased to address problem related to ground clearance. Increasing a diameter of the wheel may alter the seat height, vehicle riding dynamics and any other design parameters of the motor vehicle, which is undesirable.

[00014] Thus, there existing a challenge to provide an improved & compact design of an IC engine that accommodates various systems without increasing the size of the IC engine. Further, the present subject is aimed at addressing the aforementioned and other problems in the known art.

[00015] An internal combustion (IC) engine for a motor vehicle is provided. The IC engine of the present subject matter can be forwardly inclined or a vertical type or horizontal type. In one embodiment, a crankshaft is rotatably supported by a crankcase. In one implementation, the crankcase is formed by two crankcase members. A clutch shaft is supported by the crankcase. The clutch shaft is configured to support at least one clutch. The at least one clutch is configured to selectively engage and disengage the clutch shaft with the crankshaft. The clutch shaft is disposed adjacent to the crankshaft.

[00016] In one embodiment, a shift drum assembly is supported by the crankcase. The shift drum assembly is disposed downward to the clutch shaft. The shift drum assembly capable of interacting with the clutch shaft is disposed below the clutch shaft. In one embodiment, a drum stopper, which is configured to engage with the shift drum assembly is disposed substantially rearward to the shift drum assembly. The shift drum assembly and the drum stopper are disposed compactly below the clutch shaft and away from the crankshaft. In proximity to the crankshaft an oil- filter assembly, an oil- pump assembly are already disposed. [00017] In one embodiment, a gearshift shaft is disposed forwardly downward to the shift drum assembly. The gearshift shaft is disposed rearward and downward to the crankshaft. The gearshift mechanism that includes a shift drum assembly, the drum stopper and the gearshift shaft are compactly packaged in the layout of the IC engine.

[00018] In one embodiment, the drum stopper, which is to be pivoted is disposed rearward to the shift drum assembly and the gearshift shaft that operates the shift drum assembly is disposed ahead/ forward to the shift drum assembly. Thus, the there is no interference between the drum stopper and components like the gearshift pawl that get connected to the gearshift shaft.

[00019] In one embodiment, a kick-start shaft is provided which gets connected to a kick-start lever. The user can crank the IC engine using the kick-start lever. In one embodiment, the drum stopper is substantially disposed between the kick-start shaft and the shift drum assembly. Thus, the kick-start shaft is disposed rearward to the drum stopper.

[00020] In one embodiment, the crankcase assembly comprises a substantially equilateral quadrilateral profile as seen from a projected lateral side view thereof or of the internal combustion engine. Thus, the compact equilateral quadrilateral profile of the crankcase assembly can be compactly packaged in a compact motor vehicle with the need for any change in a frame assembly or change in position of a fuel tank.

[00021] In one embodiment, the internal combustion engine comprises an integrated member. The integrated member is disposed substantially between a first vertical plane passing through an axis of the drum stopper and a second vertical plane passing through an axis of the kick-start shaft. In one embodiment, the integrated member is a rib member that provides structural strength near the drum stopper mounting portion and the kick-start shaft mounting portion.

[00022] In one embodiment, the IC engine comprises a drum stopper provided with an elastic member. The elastic member is provided to pre-load the drum stopper to act on the shift drum assembly. One end of the elastic member is pre- loaded against the integrated member. Further, the kick-start shaft is provided with a kick-shaft stopper configured to abut the integrated member at a pre determined angle of rotation of the kick-start shaft. Thus, the same integrated member acts as a support for the elastic member and as a stopper from the kick- shaft stopper. This eliminates need for multiple stoppers/ supports. [00023] In one embodiment, the integrated member is integrally formed on the crankcase. Need for using separate fasteners or securing means for the integrated member is eliminated. In one embodiment, the integrated member comprises of a base with a cross-sectional area larger than a cross-sectional area of rest of the integrated member. In one embodiment, the base of the integrated member abuts a peripheral wall of the crankcase. The integrated member may have any known geometrical shape including a triangular shape/profile when viewed from a lateral side.

[00024] In one embodiment, an imaginary triangular region (different from aforementioned triangular profile) with vertices is formed at axes of the kick-start shaft, the clutch shaft, and the gearshift shaft. At least one of the drum stopper and the shift drum assembly is disposed substantially within the triangular region when viewed from lateral side of the IC engine. Thus, the kick-start shaft, the clutch shaft, the gearshift shaft, the drum stopper and the shit drum assembly are compactly packaged in the IC engine in order to be packaged within a smaller region as above defined triangular region.

[00025] In one embodiment, the shift drum assembly comprises a star-index member disposed at a lateral end thereof. The star-index member is configured to engage with a gearshift pawl connected to a gearshift shaft, which is disposed forwardly downward of the shift drum assembly. In one embodiment, a long axis of the gearshift pawl is rearwardly inclined. The rearwardly inclined gearshift pawl is disposed away from oil- sump below the crankshaft, which is critical for lubrication. Therefore, a need for creating additional volume of oil- sump is avoided.

[00026] In one embodiment, the crankcase comprises a peripheral wall. The peripheral wall is disposed substantially orthogonal to an outer lateral surface of the crankcase. The peripheral wall extends along entire periphery of the crankcase (or crankcase member). The peripheral wall comprises a lower wall portion comprising a first portion and a second portion. The second portion is rearward to the first portion and is disposed at an acute angle with respect to the first portion. The gearshift shaft is disposed in proximity to a transition portion between the first portion and the second portion. In one embodiment, a curved profile of the transition portion is effectively used for packaging the gearshift shaft and the corresponding gearshift pawl.

[00027] The IC engine configuration may be implemented in any two-wheeled vehicle or a three-wheeled motor vehicle. However, for the purpose of explanation and by no limitation, the IC engine, corresponding additional advantages and features are described through the following embodiments. Arrows wherever provided on top right comer of the figure represent direction with respect to motor vehicle. Arrow F represents forward direction, arrow R represents rearward direction, arrow UW represents upward direction and arrow DW represents downward direction.

[00028] Fig. 1 illustrates a left-side view of an exemplary motor vehicle 100, in accordance with an embodiment of the present subject matter. The motor vehicle 100 comprises of a frame assembly 105 acting as a structural member of the motor vehicle 100. The frame assembly 105 comprises a head pipe 111, a main tube 112 (schematically shown with dotted line) extending rearwardly downward from the head pipe 111. The motor vehicle comprises a front wheel 109, a rear wheel 110, a fuel tank 121 and seat 106. In one embodiment, the frame assembly 105 includes a main tube 112, a down tube (not shown), and one or more seat rails (not shown) extending rearward from the main tube 112. The head pipe 111 supports a steering shaft (not shown) and a front suspension 114 (only one visible) that is attached to the steering shaft through a lower bracket (not shown). The front suspension 114 supports the front wheel 109. The upper portion of the front wheel 109 is covered by a front fender 115 mounted to the front suspension 114. A handlebar assembly 108 is fixed to upper bracket (not shown) and can rotate in both directions for maneuvering the motor vehicle 100. A head light (not marked), a visor guard (not marked) and instrument cluster (not shown) is arranged on an upper portion of the head pipe 111. The down tube may be located in front of the IC engine 101 and extends slantingly downward from head pipe 111. The IC engine comprises a crankcase assembly 201 (shown in Fig. 2) that supports various components of the IC engine 101. The IC engine 101 comprises at least one side cover 102 on lateral sides to cover components thereat. The main tube 112 is located above the IC engine 101 and extends rearward from head pipe 111. The front of the IC engine 101 is mounted at the front by the down tube and the rear of the IC engine 101 at the rear portion is connected to the main tube 112. In one embodiment, the IC engine 101 is a forwardly inclined type.

[00029] In one embodiment, the fuel tank 121 is mounted on a horizontal portion of the main tube 112. Seat rails are joined to main tube 112 and extend rearward to support the seat 106. A swing arm (not shown) is connected to the frame assembly 105 to swing vertically, and a rear wheel 110 is connected to rear end of the rear swing arm. Generally, the rear swing arm is supported by a mono rear suspension or two suspensions 117 (as illustrated in the present embodiment) disposed on either side of the motor vehicle 100. A tail light unit (not shown) is disposed at the end of the motor vehicle at the rear of the seat 106. The rear wheel 110 is arranged substantially below the seat 106 and rotates by a driving force of the IC engine 101 transmitted through a chain drive (not shown) from the IC engine 101. In another embodiment, a belt drive, a continuously variable transmission or an automatic transmission may be used. Further, an electric motor may be provided to assist the IC engine 101 or to independently drive the motor vehicle 100 in conjunction with an IC engine. An exhaust system 104 is connected to the IC engine 101 for expelling exhaust gases generated due to combustion of air-fuel mixture. In one embodiment, at least a portion of the exhaust system 104 extends towards one lateral side of the motor vehicle 100 and is disposed adjacent to the rear wheel 110 (a portion of the exhaust system 104 disposed adjacent to the rear wheel 110 and is schematically shown in dotted line).

[00030] Fig. 2 depicts a right-side view of the IC engine without a side cover 102, in accordance with an embodiment of the present subject matter. The IC engine 101 comprises a cylinder head assembly 103 having a cylinder head (not shown) and a cylinder head cover (not shown) mounted atop the cylinder head. In an embodiment, the internal combustion engine 101 is a single cylinder engine. More particularly, in one embodiment, the internal combustion engine 101 is a four- stroke internal combustion engine 101. In other alternative embodiment, the internal combustion engine 101 can include more than one cylinder head, say a plurality of cylinders. In an embodiment, the cylinder head of the present subject matter includes one or more ports (not shown in this figure). For example, an exhaust port (not seen in this figure) of the internal combustion engine 101 enables exiting/expelling out the exhaust gases arising out of the combustion of the air-fuel mixture that occurs inside the combustion chamber (not shown) of the internal combustion engine 101. The gases exiting from the exhaust port are transported through the exhaust pipe system which is connected to the cylinder head through a flange member (not shown).

[00031] In one embodiment, the cylinder block is supported by a crankcase assembly 201. In one embodiment, the crankcase assembly 201 is formed by two or more crankcase-members. In the depicted embodiment, the crankcase assembly 201 is formed by a left-crankcase member 202 and a right-crankcase member 203 (also shown in Fig. 3). The crankcase assembly 201 is provided with plurality of apertures. Through the plurality of apertures, the crankcase assembly 201 rotatably supports plurality of components of the IC engine including a crankshaft 205. The crankshaft 205 is in turn connected to a piston (not shown) that is capable of moving to-and-fro inside a combustion chamber (not shown) defined by the cylinder head and the cylinder block. In one embodiment, the reciprocating motion of the piston is converted into a rotational motion of the crankshaft 205 through a connecting rod 210. In the depicted embodiment, a filter assembly 225 is mounted to the crankshaft 205 and is disposed towards one lateral side thereof. An oil- pump assembly 230 is mounted Further, the IC engine 101 comprises a clutch assembly 215 (schematically shown in dotted line) disposed on lateral side of the crankcase assembly 201 and supported by a clutch shaft 220.

[00032] In one embodiment, a drive shaft 235 is disposed substantially adjacent to the clutch shaft 220. In the depicted embodiment, a shift drum assembly 240 is disposed substantially below the clutch shaft 220. A gearshift shaft 245 is rotatably supported by the crankcase assembly 201 and the gearshift shaft 245 is configured to rotate the shift drum assembly 240 by a pre-determined angle. In one implementation, the gearshift shaft 245 is a spindle. Plurality of shift forks (not shown) engage with the shift drum assembly 240 and the plurality shift forks are configured to perform engagement of a pre-determined gear ratio attained by the rotation of the shift drum assembly 240. In one embodiment, the shift drum assembly 240 comprises a star-index member 250 that is provided at lateral end of the shift drum assembly 240. A gearshift pawl 255 is secured to one lateral end of the gearshift shaft 245 (as illustrated in the Fig. 2). Other end (not shown) of the gearshift shaft 245 is functionally connected to a gearshift lever (not shown). User of the motor vehicle can perform gearshift operation by actuation of the gearshift lever. Actuation of the gearshift lever causes angular rotation of the gearshift shaft 245. Rotation of the gearshift shaft 245 causes rotation of the gearshift pawl 255. The gearshift pawl 255 is configured to perform rotation of the shift drum assembly 240 through the star-index member 250.

[00033] Further, a drum stopper 260 is provided to keep the shift drum assembly 240 in a selected orientation corresponding to a selected gear ratio so that it does not shift from a pre-determined orientation. The drum stopper 260 is elastically pre-loaded in order to exert a force to keep the shift drum assembly 240 in a desired position. In one embodiment, the drum stopper 260 is compactly packaged adjacently rearward to the shift drum assembly 240 (and the star-index member 250), when viewed from lateral side. Further, the gearshift shaft 245 is disposed forwardly downward of the shift drum assembly 240. Thus, the gearshift pawl 255 is disposed at an angle towards the shift drum assembly 240. In the depicted embodiment, the gearshift pawl 255 is disposed at a rearward inclination.

[00034] In one implementation, a kick-start shaft 265 is rotatably supported on the crankcase assembly 201. The kick-start shaft 265 is functionally connected to a kick-start lever (not shown) to perform cranking of the IC engine 101. The kick- start shaft 265 is disposed at a substantially rearward and a downward portion of the crankcase assembly 201. The kick-start shaft 265 is configured to rotate the crankshaft 205 through plurality of intermediary gears that are rotatably supported on one or more shafts of the IC engine 101. In one embodiment, the IC engine 101 may be provided with only an electric starter, like a starter motor. Thus, the features of the present subject are still applicable excluding the kick-starter shaft. [00035] In one embodiment, the kick-start shaft 265, the clutch shaft 220, the shift drum assembly 240, the drum stopper 260 and the gearshift shaft 245 are compactly packaged within the layout of the IC engine 101. In one embodiment, the gearshift shaft 245 is disposed substantially at a mid-portion of the crankcase assembly (201), in a longitudinal direction F-R. The gearshift shaft 245 comprises an axis extending substantially in a lateral direction RH-LH. In one embodiment, considering an imaginary vertical plane, referred to as a mid-plane MP, the crankshaft 205, components mounted to crankshaft and oil pump assembly 230 are substantially disposed on one side to the mid-plane MP, when viewed from lateral side RH/ LH. In one embodiment, the mid-plane MP passes through the gearshift shaft 245. The clutch shaft 220, the drive shaft 235, the kick-start shaft 265, the shift drum assembly 240, the drum stopper 260, and a major portion of the clutch assembly 215 and the gearshift pawl 255 are disposed rearward to the mid-plane MP. Thus, heavy components like crankshaft 205 that supports the connecting rod 210 and the piston are disposed in a substantially first half portion with reference to the mid-plane MP. As the first half portion of the crankcase assembly 201 has to support the cylinder block, cylinder head assembly and major portion of the oil in oil sump. In one embodiment, the first portion The improved crankcase assembly 201 of the IC engine 101 as per the present subject matter, optimally supports the various systems and components without any undesirable reinforcement at any region of the crankcase assembly 201 thereby maintaining a balanced distribution of mass as well as a compact layout of the IC engine. The compact layout achieved by the present configuration as per an embodiment, enables obtaining a substantially equilateral quadrilateral ABCD of the crankcase assembly 201 design as seen from a direction parallel to an axis of the crankshaft axis205 or as seen form a projected view/ projected lateral direction of the IC engine 101. In one embodiment, the mid-plane MP is configured to provide a mass distribution on either side of the mid-plane MP to be within a range of 45 to 55 % of a total mass of the internal combustion engine 101. This provides substantially equal distribution of mass about the first half portion and the second half portion of the IC engine 101.

[00036] Further, an imaginary triangular region TR with vertices formed at axes of the kick-start shaft 265, the clutch shaft 220, and the gearshift shaft 245 are considered. The drum stopper 260 and the shift drum assembly 240 are disposed substantially within the triangular region TR when viewed from a lateral side RH or LH of the IC engine 101.

[00037] Fig. 3 (a) depict a perspective view of a crankcase, in accordance with an embodiment of the present subject matter. Fig. 3 (b) depicts a perspective view of a crankcase with partially exploded components, in accordance with an embodiment of the present subject matter. The crankcase assembly 201 comprises an outer lateral surface 301, which is typically non-uniform with undulation. A peripheral wall 302 is disposed in order to form a boundary for the crankcase assembly 201 (especially the right crankcase member 203). In one embodiment, the peripheral wall 302 is elevated from the outer lateral surface 301 of the crankcase assembly 201. In one embodiment, a side cover 102 is supported on the peripheral wall 302. Plurality of apertures are provided selectively along the peripheral wall 302 for securing the side cover 102 to the crankcase assembly 201 through fasteners.

[00038] In one embodiment, the crankcase assembly 201 comprises the peripheral wall 302. The peripheral wall 302 is substantially orthogonal to the outer lateral surface 301 of the crankcase assembly 201. The peripheral wall 302 comprises a lower wall portion comprising a first portion 303 and a second portion 304. In one embodiment, the first portion 303 is a substantially horizontal portion. The second portion 304 is disposed at an acute angle with respect to the first portion 303. The gearshift shaft 245 is disposed in proximity to a transition portion between the first portion 303 and the second portion 304. The second portion 304 is substantially upward. The first portion 303 supports an oil- drain plug 270 (shown in Fig. 2), which may include an additional oil- filtering member. The shift drum assembly 240 and the drum stopper 260 are disposed away from the crankshaft 205, the oil- filter assembly 225 and the oil- pump assembly 230.

[00039] In the depicted embodiment, a crankshaft bearing 314 that is corresponding to the crankshaft 205 (shown in Fig. 2) is depicted. Similarly, a clutch shaft bearing 320 and a drive shaft bearing 335 corresponding to the clutch shaft 220 and drive shaft 235 (shown in Fig. 2) are shown in the current illustration. Further, the crankcase assembly 201 is provided with a kick shaft aperture 365 corresponding to the kick-start shaft 265 (shown in Fig. 2). One end of the kick-start shaft 265 is provided with a kick-shaft stopper 305, which rotates along with the kick-start shaft 265. In a non-operational condition of the kick-start shaft 265, the kick-shaft stopper 305 abuts against a first rib 370, which acts a stopper. During operation of the kick-start shaft 265 due to kicking operation of a kick-start lever by user, the kick-shaft stopper 305 rotates. In the depicted embodiment, the kick-shaft stopper 305 rotates in an anti-clock wise direction as viewed from the right lateral side RH of the crankcase assembly 201.

[00040] In one embodiment, the kick-shaft stopper 305 comprises an aperture 308 that enables securing of the kick-shaft stopper 305 to the kick-start shaft 265. The kick-shaft stopper 305 comprises a first engaging portion 306 and a second engaging portion 307. The first engaging portion 306 abuts the first rib 370 in order to restrict rotation of the kick-start shaft 265 in a clock-wise direction, when released by the user. The crankcase assembly 201 is provided with an integrated member 310. The second engaging portion 307 in an operational direction (anti clockwise direction) engages with an integrated member 310 to restrict rotation of the kick-start shaft 265 beyond a certain pre-determined angle.

[00041] The shift drum assembly 240 is disposed substantially downward to the clutch shaft 220. In one implementation, the drum stopper 260 is disposed rearward to the shift drum assembly 240. The drum stopper 260 comprises an arm portion 340, a roller 341, a pivot portion 342, and a groove portion 343. The roller 341 is rotatably disposed at one end of the arm portion 340. The pivot portion 342 is disposed at other end of the arm portion 340. The groove portion 343 is disposed in proximity to the pivot portion 342 and is configured to accommodate an elastic member 380 like a torsion spring in order pre-load the drum stopper 260. The crankcase assembly 201 is provided with a cylindrical protrusion 375 for pivotably mounting the drum stopper 260 through the pivot portion 342.

[00042] In one embodiment, the drum stopper 260 is compactly disposed between the shift drum assembly 240 (analogous element star-index member 250 shown) and the kick-start shaft 265. In one embodiment, the integrated member 310 is disposed adjacent to the drum stopper 260. The elastic member 380, in one implementation, is a torsion spring accommodated on the groove portion 343. One end of the elastic member 380 engages with the arm portion 340 and other end of the elastic member 380 is configured to abut the integrated member 310. In one embodiment, the integrated member 310 is formed in the shape of a triangle, when viewed from a lateral side RH or LH of the IC engine 101.

[00043] Fig. 3 (c) illustrates a schematic enlarged view of a portion of an IC engine, in accordance with an embodiment of the present subject matter as depicted in Fig. 3 (b). The integrated member 310 in one embodiment, comprises a stopper portion 316 and a reinforcing portion 317. The stopper portion 316, according to one implementation, is provided on the outer lateral surface of the crankcase assembly 201. The reinforcing portion 317 is provided on the stopper portion 316. In one embodiment, both the stopper portion 316 and the reinforcing portion 317 are integrally formed. The integrated member 310 formed by the stopper portion 316 and the reinforcing portion 317 abuts the peripheral wall 302 of the crankcase assembly 201.

[00044] In one embodiment, the integrated member 310 comprises a triangular profile 313 (shown in Fig. 3 (d)). The integrated member 310 comprises a base 311 (shown in Fig. 3 (d)) that abuts the peripheral wall 302 and a vertex 312 (shown in Fig. 3 (d)) extends inward (in upward direction in the depicted embodiment) from the peripheral wall 302. As illustrated, in one implementation, the stopper portion 316 is configured to have a larger cross-sectional area when compared to a cross-sectional area of the reinforcing portion 317, when viewed from the lateral side RH/ LH of the IC engine 101. The integrated member 310 with two different cross-sectional areas is optimally configured to provide structural integrity with minimal usage of material. In one embodiment, the stopper portion 316 with the larger cross-sectional area stops the kick-shaft stopper 305 and to support the elastic member 380 (shown in Fig. 3 (a)). The reinforcing portion 317 integrated with the stopper portion 316 provides reinforcement to the stopper portion 316 to withstand the load acting on it from the kick-shaft stopper 305 and the elastic member 380. In one implementation, the elastic member 380, specifically one end of the elastic member (say, one end of a torsion spring) is supported at the vertex 312 or one side of the stopper portion 316. The kick-shaft stopper 305 is stopped on the other side of the stopper portion 316. In one embodiment, the triangular profile 313, with the base 311 towards the peripheral wall 302 and the narrowing profile towards the vertex 312 into the crankcase assembly 201, occupies optimally minimal space in the crankcase assembly 201. This optimal structure with minimal space requirement enables compact layout configuration of the drum stopper 260 between a shift drum assembly 240 disposed in a downward portion of the crankcase assembly 201 and the kick-start shaft 265.

[00045] Fig. 3 (d) depicts another enlarged view of a portion of an IC engine, in accordance with an embodiment of the present subject matter. The kick-start shaft 265, the kick-shaft stopper 305, and the drum stopper 260 are compactly accommodated within a small layout space at a rearward and downward portion of the crankcase assembly 201. As shown in Fig. 2, the crankshaft 205, the clutch shaft 220, and the drive shaft 235 are disposed substantially upward with respect to the shift drum assembly 240. The drum stopper 260 is disposed substantially away from the region occupied by the clutch 221 (shown in Fig. 2), which is one of the largest components disposed on the outward lateral side of the crankcase assembly 201. As the drum stopper 260 is disposed at a rearward and downward portion on the crankcase assembly 201, when viewed from the lateral side RH/ LH, the other components like the gearshift pawl 255, the oil- pump assembly 230 (shown in Fig. 2) are compactly packaged in the IC engine 101. Furthermore, the drum stopper 260 engaging with the star-index member 250 restricts over-shifting and assists in gear shifting through a plurality of valley portions 352 provided on the star-index member 250. Further, due to shorter distance between the gearshift shaft 245 and the shift drum assembly 240, the user experiences a distinct gear shifting feel or feedback due to larger angle of rotation which is necessary for perceivable feedback of gear shifting. During gear shifting, the gearshift pawl 255 is rotated due to rotation of the gearshift shaft 245. The rotation of the gearshift shaft 245 can be in either clockwise or anti-clockwise direction. Correspondingly, the gearshift pawl 255 rotates the star-index member 250 through plurality of pins 351 provided on the start index 250. In one embodiment, a pair of pins of the plurality of pins 351 enable rotation of the star-index member 250. Rotation of the star-index member 250 rotates the shift drum assembly 240 causing movement of the forks thereby causing gear shifting. The roller 341 of the drum stopper 260 sits at the valley portion when change gear operation is not being performed. When gearshift operation is performed, rotation of the star-index member causes the roller 341 to slide from the valley portion 352 to a peak portion formed between two valley portions 352. Subsequent to the peak portion the roller 341 assists rotation of the star-index member 250 while rolling towards the valley portion 352. Upon reaching the valley portion 352, the star-index member 250 is held in the pre-determined position till next gearshift operation. In one implementation, the gearshift shaft 245 is rotated by an angle in range of 14-18 degrees thereby causing about 72 degrees angular rotation of the shift drum assembly 240. The user experiences a better or distinct gearshift feedback feel when compared to a rotation of the gearshift shaft in single digit angles.

[00046] The drum stopper 260 has the pivot portion 342 (shown in Fig. 3 (b)) which is disposed in proximity to the integrated member 310 and the elastic member 380 like a torsion spring; The torsion spring is disposed about the drum stopper 260 and is configured to engage with the integrated member 310 on one side thereof. In one embodiment, the integrated member 310 is compactly disposed substantially between a first vertical plane PI passing through an axis (axis of rotation) of the drum stopper 260 and parallel to the crankshaft axis and a second vertical plane P2 passing through an axis of the kick-start shaft 265 and parallel to the crankshaft axis. In one implementation, a first distance between the first vertical plane PI and the second vertical plane P2 is smaller than a length of the drum stopper 260. Further, a third vertical plane P3 is passing through said shift drum assembly 240 and parallel to the crankshaft axis and a second distance between the first vertical plane PI and the third vertical plane P3 is smaller than a length of the drum stopper 260. Thus, the smaller distance between the planes PI & P2, PI & P3 signifies the compact packaging of the components in the IC engine 101.

[00047] The drum stopper has a long axis S-S’ that is substantially vertical parallel to plane PI or P2 or P3 thereby occupying less space. Further, perpendicularity is maintained between drum stopper 260 and the star-index member 250, when considering an axis of the roller 341 (shown in Fig. 3 (b)) and an axis of the star-index member 250 for effective operation as prescribed. Further, the kick-shaft stopper 305 in an actuated condition of the kick-start lever, has the second engaging portion 307 engaging on other side of the integrated member 310. The kick-shaft stopper 305 in actuated condition is illustrated in dotted line and in a non-actuated condition is illustrated in solid line.

[00048] Further, in one embodiment, the drum stopper 260 and the gearshift pawl 255 are disposed in a substantially in a second half portion of the crankcase assembly 201 and substantially on one side of an imaginary line 309 passing through an upper most portion of the star-index member 250 & orthogonal to planes PI or P2 or P3. In one implementation, the second half portion is a rear half portion. In one embodiment, the gearshift pawl 255 is connected to a gearshift shaft 245, and a long axis P-P’ of the gearshift pawl 255 is rearwardly inclined. Thus, the gearshift pawl 255 is disposed rearward to eliminate any interference with the oil- pump assembly 230, the oil- filter assembly 225 and the oil- drain plug 270.

[00049] Further, as illustrated in Fig. 3 (a) and Fig. 3 (d), in one implementation, the integrated stopper 360 is having a triangular profile 313 when viewed from the lateral side RH/ LH. The integrated stopper 360 protrudes outward from the outer lateral surface 301 of the crankcase assembly 201. A triangular profile 313 is schematically shown in dotted line. A base 311 of the integrated member 310 is abutting the peripheral wall 302 and a vertex 312 opposite to the base 311 is disposed between the drum stopper 260 and the kick-shaft stopper 305. In one embodiment, the base 311 comprises a larger cross-sectional area compared to rest of the integrated member 310. In one embodiment, the integrated member 310 is integrally formed with the crankcase assembly 201 (say right-crankcase member 203). The larger base provides the structural strength required to withstand force acting thereon from the elastic member 380 and the kick-shaft stopper.

[00050] While certain features of the claimed subject matter have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes that fall within the true spirit of the claimed subject matter.

List of reference signs:

100 vehicle

101 internal combustion engine

102 side cover 103 cylinder head assembly

104 exhaust system

105 frame assembly

106 seat

108 handlebar assembly 109 front wheel

110 rear wheel

111 head pipe

112 main tube

114 front suspension 115 front fender

117 rear suspension

121 fuel tank

201 crankcase

202 left-crankcase member 203 right-crankcase member

205 crankshaft

210 connecting rod

215 clutch assembly

220 clutch shaft 225 oil-fdter assembly

230 oil pump assembly

235 drive shaft

240 shift drum assembly

245 gearshift shaft 250 star-index member

255 gearshift pawl

260 drum stopper

265 kick-start shaft

270 oil-drain plug 301 outer lateral surface

302 peripheral wall

303 first portion

304 second portion

305 kick-shaft stopper 306 first engaging portion

307 second engaging portion

308 aperture

309 imaginary line

310 integrated member 311 base

312 vertex