Internal combustion engine for a motor vehicle

Abstract

The present subject matter relates to an internal combustion engine (101). The internal combustion engine (101) includes a crankshaft (205) and a clutch shaft (220) supported by a crankcase assembly (201). A shift drum assembly (240) is arranged generally downwardly relative to the clutch shaft (220). A drum stop (260) is configured to engage with the shift drum assembly (240) and is arranged generally rearwardly relative to the shift drum assembly (240) when viewed from a lateral side (RH, LH) of the internal combustion engine (101). A shift shaft (245) is arranged forwardly relative to the shift drum assembly (240) when viewed from the lateral side (RH, LH) of the internal combustion engine (101). The internal combustion engine (101) compactly supports and packages various systems and components thereof without requiring significant reinforcement, thereby preventing the engine assembly from becoming more bulky.

Description

TECHNICAL FIELD

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

[0002] Generally, motor vehicles are powered by an internal combustion (IC) engine to function as a power unit of the motor vehicle. The IC engine converts chemical energy into mechanical energy through combustion of an air-fuel mixture within the combustion chamber of the IC engine. The combustion of the air-fuel mixture results in reciprocating motion of the piston in the combustion chamber. The reciprocating motion is converted into rotational motion of the crankshaft. The rotational motion of the crankshaft is used to move the motor vehicle.

[0003] Typically, to meet various power and torque requirements, a gear system having multiple gear ratios is provided with the IC engine. A selected gear configuration is configured to provide a predetermined gear ratio. The user can manually shift gears through a gear shaft or, depending on the user requirements, an electronic control unit can perform the shifting with minimal or no user intervention. Typically, to start the IC engine, either a kick start lever is used, a hand operated lever is used, or a crank is manually performed using an electric start system with an electric motor. In the motor vehicle, various systems including the gear system and the starting system are encapsulated within the IC engine. BRIEF DESCRIPTION OF DRAWINGS

[0004] The specific embodiments will be described with reference to the drawings, wherein there is shown as an example of one embodiment of the application a two-wheeled motor vehicle. However, the application is not limited to the described embodiments. In the drawings, like or similar numbers refer to like or similar features and components throughout the figures.

[0005] Figure 1 A left side view of an exemplary motor vehicle is shown, in accordance with one embodiment of the present subject matter.

[0006] Figure 2 A right side view of an exemplary internal combustion engine is shown, in accordance with one embodiment of the present subject matter.

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

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

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

[0010] Figure 3(d) illustrates another enlarged view of a portion of the IC engine, according to an embodiment of the present subject matter. DETAILED DESCRIPTION

[0011] Generally, motor vehicles, especially smaller capacity motor vehicles including two or three wheeled types, are provided with kick start systems or similar crank start systems. Further, for the vehicle to move, power from the crankshaft of the internal combustion engine is carried in a controllable manner to the wheels of the vehicle through a transmission system. The transmission system for the IC engine of a two wheeled motor vehicle like a motorcycle generally includes a clutch assembly and a gear system comprising a gear train. A drive mechanism connects the gear system to at least one wheel. The gear train has a plurality of gear ratios and the gear ratio is selected depending on the speed and torque requirements.

[0012] Conventionally, incorporation of various systems like gear system, starting system, etc. on the IC engine makes the IC engine bulkier. For example, various components including the clutch assembly, the gear system comprising the gear train, the gear shift mechanism, the lubrication assembly, etc. are to be housed on the crankcase with minimal or no interference. Additionally, due to the avoidance of interference or to address the packaging challenges, the conventional gear shift mechanism is spread out on the crankcase thereby occupying a large amount of space. For example, the IC engine includes various components like a drum stopper fixed to the crankcase. Such components are to be arranged away from the rotating components to avoid any interference. Further, some conventional gear shift mechanisms operate at a short angle of rotation thereby requiring high precision manufacturing and assembly. Any variation would affect the angle of rotation thereby causing over displacement or under displacement, thereby providing a poor performance feel to the user. Also, as the size of the IC engine increases to accommodate the above and other systems, the weight of the entire IC engine also increases. Further, the IC engine, especially the crankcase, has to be made rigid in order to robustly support the various systems. The effect of the increased weight is that the frame assembly supporting the IC engine is also made bulkier to robustly support the IC engine. Further, a large amount of space on the motor vehicle is occupied by the IC engine. The fuel economy of the motor vehicle is affected due to the increased weight. The bulky configuration of the IC engine affects the ground clearance of the motor vehicle. For example, in a motor two-wheeler having a fuel tank arranged above the IC engine, the position of the fuel tank cannot be moved beyond a certain height due to the riding posture, visibility, and other design constraints. This results in the IC engine extending downwards affecting the ground clearance, thereby making it impractical for the vehicle to be ridden in urban and off-road conditions. The components of the IC engine are also damaged due to potholes or bumps on the road.

[0013] Typically, there have been attempts in the past to make IC engines compact. Such attempts include, but are not limited to, removal of the kick start system in motor vehicles to reduce components and save space. However, the removal of the kick start system is compensated with a large capacity battery, which eventually increases the weight of the motor vehicle. Further, there can be various situations where the battery is not sufficient to crank the IC engine. For example, over time, the battery loses its charge retention capability and can not be able to start the IC engine, or the battery can be drained due to non-use of the motor vehicle for a long time. This would require the user to push the vehicle to a service center for charging or replacement of the battery, making it a cumbersome, inconvenient and costly process. Some other known solutions include reducing the size of the fuel tank in order to compensate for the increase in size of the IC engine. However, by reducing the size of the fuel tank, the fuel retention capacity of the motor vehicle is reduced, which can cause unwanted range anxiety to the user. In some other known solutions, the diameter of the wheel is increased to address the issues related to the ground clearance. Increasing the diameter of the wheel can change the seat height, vehicle ride dynamics, and any other design parameters of the motor vehicle, which is undesirable.

[0014] Therefore, there is a challenge in providing an improved and compact design of the IC engine accommodating various systems without increasing the size of the IC engine. Further, the present subject matter aims to address the aforementioned and other problems in the known art.

[0015] An internal combustion (IC) engine for a motor vehicle is provided. The IC engine of the present subject matter can be forward inclined or vertical or horizontal type. In an embodiment, a crankshaft is rotatably supported by a crankcase. In an embodiment, 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 proximate to the crankshaft.

[0016] In an embodiment, a shift drum assembly is supported by the crankcase. The shift drum assembly is disposed downwardly relative to the clutch shaft. The shift drum assembly is disposed below the clutch shaft, which is capable of interacting with the clutch shaft. In an embodiment, a drum stopper configured to engage with the shift drum assembly is disposed substantially rearwardly relative to the shift drum assembly. The shift drum assembly and the drum stopper are compactly disposed below the clutch shaft and away from the crankshaft. At the crankshaft accessories, an oil filter assembly, an oil pump assembly have been disposed.

[0017] In an embodiment, a shift shaft is disposed forwardly and downwardly relative to the shift drum assembly. The shift shaft is disposed rearwardly and downwardly relative to the crankshaft. The shift mechanism including the shift drum assembly, the drum stopper, and the shift shaft is compactly packaged in the layout of the IC engine.

[0018] In an embodiment, the drum stopper to be pivoted is arranged downwardly with respect to the shift drum assembly and the shift shaft operating the shift drum assembly is arranged forwardly with respect to the shift drum assembly / forwardly in front of the shift drum assembly. Thus, there is no interference between the drum stopper and the component like shift pawl connected with the shift shaft.

[0019] In an embodiment, a kick start shaft connected to the kick start lever is provided. The user can use the kick start lever to crank start the IC engine. In an embodiment, the drum stopper is arranged substantially between the kick start shaft and the shift drum assembly. Thus, the kick start shaft is arranged rearwardly with respect to the drum stopper.

[0020] In an embodiment, the crankcase assembly comprises a substantially equilateral quadrilateral profile as viewed from a projected lateral side view of the crankcase assembly or the internal combustion engine. Thus, the compact equilateral quadrilateral profile of the crankcase assembly can be compactly packaged in compact motor vehicles wherein the frame assembly needs to be changed or the position of the fuel tank needs to be changed.

[0021] In an embodiment, the internal combustion engine comprises an integral member. The integral member is arranged substantially between a first vertical plane passing through the axis of the drum stopper and a second vertical plane passing through the axis of the kick start shaft. In an embodiment, the integral member is a rib member that provides structural strength in the vicinity of the drum stopper mounting portion and the kick start shaft mounting portion.

[0022] In an embodiment, the IC engine comprises a drum stopper provided with a resilient member. The resilient member is provided to preload the drum stopper to act on the shift drum assembly. One end of the resilient member is preloaded against the integral member. Further, the kick start shaft is provided with a kick shaft stopper configured to abut the integral member at a predetermined angle of rotation of the kick start shaft. Thus, the same integral member serves as a support for the resilient member as well as a stopper for the kick shaft stopper. This eliminates the need for multiple stoppers / supports.

[0023] In an embodiment, the integral member is integrally formed on the crankcase. The need for separate fasteners or fixtures for the integral member is eliminated. In an embodiment, the integral member comprises a base having a cross-sectional area greater than the cross-sectional area of the rest of the integral member. In an embodiment, the base of the integral member abuts the outer peripheral wall of the crankcase. The integral member can have any known geometry including a triangular shape / profile when viewed from the lateral side.

[0024] In one embodiment, an imaginary triangular region having an apex is formed at the axis of the kick start shaft, the clutch shaft, and the shift shaft (different from the triangular profile described above). At least one of the kick stopper and the shift drum assembly is disposed substantially within the triangular region when viewed from the lateral side of the IC engine. Thus, the kick start shaft, the clutch shaft, the shift shaft, the kick stopper, and the shift drum assembly are compactly packaged in the IC engine so as to be packaged within a smaller area of the triangular region as described above.

[0025] In one embodiment, the shift drum assembly includes a star index member disposed at its lateral end. The star index member is configured to engage with a shift pawl connected to the shift shaft, which is disposed forward below the shift drum assembly. In one embodiment, the long axis of the shift pawl is tilted rearward. The rearward tilted shift pawl is disposed away from the oil sump below the crankshaft, which is critical for lubrication. Thus, the need to create an additional volume of the oil sump is avoided.

[0026] In one embodiment, the crankcase includes an outer peripheral wall. The outer peripheral wall is disposed substantially normal to the outer lateral surface of the crankcase. The outer peripheral wall extends along the entire periphery of the crankcase (or crankcase member). The outer peripheral wall includes a lower wall portion, which includes a first portion and a second portion. The second portion is rearward with respect to the first portion and is disposed at an acute angle with respect to the first portion. The shift shaft is disposed in the vicinity of the transition portion between the first portion and the second portion. In one embodiment, the curved profile of the transition portion is effective for packaging the shift shaft and the corresponding shift pawl.

[0027] The IC engine configuration can be implemented in any two-wheeled or three-wheeled motor vehicle. However, for the purpose of explanation and not limitation, the IC engine, the corresponding additional advantages and features are described through the following embodiments. The arrows provided anywhere in the upper right corner of the figures represent the directions with respect to the motor vehicle. The arrow F represents the forward direction, the arrow R represents the rearward direction, the arrow UW represents the upward direction, and the arrow DW represents the downward direction.

[0028] Figure 1A left side view of an exemplary motor vehicle 100 is shown in accordance with one embodiment of the present subject matter. The motor vehicle 100 includes a frame assembly 105 that acts as a structural member of the motor vehicle 100. The frame assembly 105 includes a head tube 111, a main tube 112 (shown schematically in phantom) extending downwardly and rearwardly from the head tube 111. The motor vehicle includes front wheels 109, rear wheels 110, a fuel tank 121, and a seat 106. In one embodiment, the frame assembly 105 includes the main tube 112, a down tube (not shown), and one or more seat rails (not shown) extending rearwardly from the main tube 112. The head tube 111 supports a steering shaft (not shown) and front suspensions 114 (only one is visible) attached to the steering shaft by lower brackets (not shown). The front suspensions 114 support the front wheels 109. The upper portion of the front wheels 109 is covered by front fenders 115 mounted to the front suspensions 114. A handlebar assembly 108 is fixed to an upper bracket (not shown) and can be rotated in two directions for steering the motor vehicle 100. The upper portion of the head tube 111 is provided with headlamps (not designated), a fairing (not designated), and an instrument panel (not shown). The down tube can be located in front of an IC engine 101 and extends obliquely downwardly from the head tube 111. The IC engine includes a crankcase assembly 201 (shown in Figure 2 FIG. 6) that supports various components of the IC engine 101. The IC engine 101 includes at least one side cover 102 on a lateral side to cover the components thereat. The main tube 112 is located above the IC engine 101 and extends rearwardly from the head tube 111. The front of the IC engine 101 is mounted at the front by the down tube, while the rear of the IC engine 101 at the rear is connected to the main tube 112. In one embodiment, the IC engine 101 is of a forward inclined type.

[0029] In one embodiment, a fuel tank 121 is mounted on the horizontal portion of the main tube 112. A seat rail is coupled to the main tube 112 and extends rearward to support the seat 106. A swing arm (not shown) is connected to the frame assembly 105 to swing vertically, and the rear wheel 110 is connected to the rear end of the rear swing arm. Typically, the rear swing arm is supported by a single rear suspension or two suspensions 117 (as shown in the present embodiment) arranged on either side of the motor vehicle 100. A tail lamp unit (not shown) is arranged at the end of the motor vehicle behind the seat 106. The rear wheel 110 is disposed substantially below the seat 106 and is rotated by the driving force of the IC engine 101, which is transmitted from the IC engine 101 through a chain transmission mechanism (not shown). In another embodiment, a belt transmission, a continuously variable transmission, or an automatic transmission can be used. Further, an electric motor can be provided to assist the IC engine 101 or to drive the motor vehicle 100 independently of the IC engine. An exhaust system 104 is connected to the IC engine 101 for discharging exhaust gas generated due to combustion of the 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 arranged adjacent to the rear wheel 110 (a portion of the exhaust system 104 is arranged adjacent to the rear wheel 110 and is shown schematically in dotted lines).

[0030] Figure 2 A right side view of the IC engine without a side cover 102 is shown in accordance with one embodiment of the present subject matter. The IC engine 101 includes a cylinder head assembly 103 having a cylinder head (not shown) and a cylinder head cover (not shown) mounted on top of the cylinder head. In one 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 embodiments, the internal combustion engine 101 can include more than one cylinder head, for example, multiple cylinders. In one embodiment, the cylinder head of the present subject matter includes one or more ports (not shown in this figure). For example, the exhaust port (not shown in this figure) of the internal combustion engine 101 is capable of discharging / venting exhaust gas generated due to combustion of the air-fuel mixture, which is combusted inside the combustion chamber (not shown) of the internal combustion engine 101. The gas discharged from the exhaust port is transmitted through an exhaust pipe system, which is connected to the cylinder head through a flange member (not shown).

[0031] In an embodiment, the cylinder block is supported by a crankcase assembly 201. In an 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 a plurality of apertures. Through the plurality of apertures, the crankcase assembly 201 rotatably supports a plurality of components of the IC engine, including a crankshaft 205. The crankshaft 205, in turn, is connected to pistons (not shown) that are capable of moving back and forth within combustion chambers (not shown) defined by the cylinder head and the cylinder block. In an embodiment, the reciprocating motion of the pistons is converted into rotational motion of the crankshaft 205 by connecting rods 210. In the depicted embodiment, a filter assembly 225 is mounted to the crankshaft 205 and disposed towards one lateral side thereof. An oil pump assembly 230 is mounted. Further, the IC engine 101 includes a clutch assembly 215 (shown schematically in dashed lines) that is disposed on a lateral side of the crankcase assembly 201 and is supported by a clutch shaft 220.

[0032] In an 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 shift shaft 245 is rotatably supported by the crankcase assembly 201, and the shift shaft 245 is configured to rotate the shift drum assembly 240 by a predetermined angle. In an implementation, the shift shaft 245 is a spindle. A plurality of shift forks (not shown) engage with the shift drum assembly 240, and the plurality of shift forks are configured to effectuate engagement of a predetermined gear ratio effected by rotation of the shift drum assembly 240. In an embodiment, the shift drum assembly 240 includes a star indexing member 250 that is provided at a lateral end of the shift drum assembly 240. A shift pawl 255 is fixed to one lateral end of the shift shaft 245 (as shown in FIG. 2). The other end (not shown) of the shift shaft 245 is functionally connected to a shift lever (not shown). A user of the motor vehicle can perform a shift operation by actuation of the shift lever. Actuation of the shift lever causes angular rotation of the shift shaft 245. Rotation of the shift shaft 245 causes rotation of the shift pawl 255. The shift pawl 255 is configured to effectuate rotation of the shift drum assembly 240 by the star indexing member 250. Figure 2

[0033] ​Further, drum stopper 260 is provided to retain the shift drum assembly 240 in a selected orientation corresponding to a selected gear ratio such that it does not displace from the predetermined orientation. The drum stopper 260 is elastically preloaded so as to exert a force to retain the shift drum assembly 240 in the desired position. In one embodiment, the drum stopper 260 is compactly packed adjacent behind the shift drum assembly 240 (and the star indexing member 250) when viewed from the lateral side. Further, the shift shaft 245 is disposed forward and downward of the shift drum assembly 240. Accordingly, the shift pawl 255 is disposed at an angle towards the shift drum assembly 240. In the depicted embodiment, the shift pawl 255 is disposed rearwardly inclined.

[0034] In one implementation, the 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 the cranking of the IC engine 101. The kick start shaft 265 is disposed at a generally rearward and downward portion of the crankcase assembly 201. The kick start shaft 265 is configured to rotate the crankshaft 205 through a plurality of intermediate gears rotatably supported on one or more shafts of the IC engine 101. In one embodiment, the IC engine 101 can be provided with only an electric starter, like a starter motor. Accordingly, the features of the present subject matter are still applicable except for the kick starter shaft.

[0035] In one embodiment, the kick start shaft 265, the clutch shaft 220, the shift drum assembly 240, the drum stop 260 and the shift shaft 245 are compactly packaged within the layout of the IC engine 101. In one embodiment, the shift shaft 245 is disposed substantially in the middle portion of the crankcase assembly (201) in the longitudinal direction F-R. The shift shaft 245 comprises an axis that extends substantially in the lateral direction RH-LH. In one embodiment, an imaginary vertical plane called the mid-plane MP is envisaged, when viewed from the lateral side RH / LH, the crankshaft 205, the components mounted to the crankshaft and the oil pump assembly 230 are disposed substantially on one side of the mid-plane MP. In one embodiment, the mid-plane MP passes through the shift shaft 245. The clutch shaft 220, the drive shaft 235, the kick start shaft 265, the shift drum assembly 240, the drum stop 260 and the major portion of the clutch assembly 215 and the shift ratchet 255 are disposed behind the mid-plane MP. Thus, the heavier components such as the crankshaft 205 that supports the connecting rods 210 and the pistons are disposed in substantially the first half with respect to the mid-plane MP. Since the first half of the crankcase assembly 201 has to support the major portion of the cylinder block, the cylinder head assembly and the oil in the oil sump. In one embodiment, the first portion of the crankcase assembly 201 of the IC engine 101 according to the present subject matter optimally supports the various systems and components without any undesirable stiffening in any region of the crankcase assembly 201, thereby maintaining the mass balance distribution of the IC engine and the compact layout. The compact layout achieved by the present configuration according to the embodiment, enables a substantially equilateral quadrilateral ABCD of the crankcase assembly 201 design, as seen from the direction of the axis parallel to the crankshaft axis 205, or as seen from the projected view / projection 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, such that the mass distribution is in the range of 45% to 55% of the total mass of the internal combustion engine 101. This provides a substantially equal mass distribution with respect to the first half and the second half of the IC engine 101.

[0036] Further, an imaginary triangular region TR is envisaged, having vertices formed at the axis of the kick start shaft 265, the clutch shaft 220 and the shift shaft 245. The drum stop 260 and the shift drum assembly 240 are disposed substantially within the triangular region TR, when viewed from the lateral side RH or LH of the IC engine 101.

[0037] Figure 3(a) depicts an isometric view of the crankcase, according to one embodiment of the present subject matter. Figure 3(b) depicts an isometric view of the crankcase, according to one embodiment of the present subject matter, wherein the partially exploded components are shown. The crankcase assembly 201 includes an outer lateral surface 301, which is typically uneven with undulations. An outer peripheral wall 302 is arranged so as to form a boundary of the crankcase assembly 201, particularly the right crankcase member 203. In one embodiment, the outer peripheral wall 302 is raised from the outer lateral surface 301 of the crankcase assembly 201. In one embodiment, the side cover 102 is supported on the outer peripheral wall 302. A plurality of apertures are selectively provided along the outer peripheral wall 302 for securing the side cover 102 to the crankcase assembly 201 by fasteners.

[0038] In one embodiment, the crankcase assembly 201 includes an outer peripheral wall 302. The outer peripheral wall 302 is substantially orthogonal to the outer lateral surface 301 of the crankcase assembly 201. The outer peripheral wall 302 includes a lower wall portion, which includes 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 arranged at an acute angle with respect to the first portion 303. The shift shaft 245 is arranged in the vicinity of the transition between the first portion 303 and the second portion 304. The second portion 304 is substantially upward. The first portion 303 supports the oil drain plug 270 (shown in Figure 2 In one embodiment, the crankcase assembly 201 includes an outer peripheral wall 302. The outer peripheral wall 302 is substantially orthogonal to the outer lateral surface 301 of the crankcase assembly 201. The outer peripheral wall 302 includes a lower wall portion, which includes 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 arranged at an acute angle with respect to the first portion 303. The shift shaft 245 is arranged in the vicinity of the transition between the first portion 303 and the second portion 304. The second portion 304 is substantially upward. The first portion 303 supports the oil drain plug 270 (shown in

[0039] In the depicted embodiment, the crankshaft bearing 314 corresponding to the crankshaft 205 (shown in Figure 2 Similarly, in the current illustration, the clutch shaft bearing 320 and the drive shaft bearing 335 corresponding to the clutch shaft 220 and the drive shaft 235 (shown in Figure 2 Further, the crankcase assembly 201 is provided with a kick shaft aperture 365 corresponding to the kick start shaft 265 (shown in Figure 2 The kick shaft stop 305 is provided at one end of the kick start shaft 265, which rotates along with the kick start shaft 265. In the non-operational state of the kick start shaft 265, the kick shaft stop 305 abuts against the first rib 370, which acts as a stopper. During operation of the kick start shaft 265 due to kick operation of the kick start lever by the user, the kick shaft stop 305 rotates. In the depicted embodiment, the kick shaft stop 305 rotates in the anti-clockwise direction, as viewed from the right lateral side RH of the crankcase assembly 201.

[0040] In one embodiment, the kick shaft stop 305 includes an aperture 308 that enables the kick shaft stop 305 to be secured to the kick start shaft 265. The kick shaft stop 305 includes a first engagement portion 306 and a second engagement portion 307. The first engagement portion 306 abuts the first rib 370 to limit the rotation of the kick start shaft 265 in the clockwise direction when released by the user. The crankcase assembly 201 is provided with an integral member 310. The second engagement portion 307 in the direction of operation (counterclockwise direction) engages with the integral member 310 to limit the rotation of the kick start shaft 265 beyond a certain predetermined angle.

[0041] The shift drum assembly 240 is disposed substantially downwardly with respect to the clutch shaft 220. In one embodiment, a drum stop 260 is disposed rearwardly with respect to the shift drum assembly 240. The drum stop 260 includes an arm portion 340, a roller 341, a pivot portion 342, and a slot portion 343. The roller 341 is rotatably disposed at one end of the arm portion 340. The pivot portion 342 is disposed at the other end of the arm portion 340. The slot portion 343 is disposed adjacent to the pivot portion 342 and is configured to house a resilient member 380, such as a torsion spring, to preload the drum stop 260. The crankcase assembly 201 is provided with a cylindrical protrusion 375 for pivotably mounting the drum stop 260 via the pivot portion 342.

[0042] In one embodiment, the drum stop 260 is compactly disposed between the shift drum assembly 240 (shown similar element star indexing member 250) and the kick start shaft 265. In one embodiment, the integral member 310 is disposed adjacent to the drum stop 260. In one embodiment, the resilient member 380 is a torsion spring housed on the slot portion 343. One end of the resilient member 380 engages with the arm portion 340 and the other end of the resilient member 380 is configured to abut the integral member 310. In one embodiment, the integral member 310 is formed in the shape of a triangle when viewed from the lateral side RH or LH of the IC engine 101.

[0043] Figure 3(c) illustrates a schematic enlarged view of a portion of the IC engine, in accordance with one embodiment of the present subject matter as depicted in Figure 3(b). In one embodiment, the integral member 310 includes a stop portion 316 and a reinforcement portion 317. In accordance with one embodiment, the stop portion 316 is provided on the outer lateral surface of the crankcase assembly 201. The reinforcement portion 317 is provided on the stop portion 316. In one embodiment, both the stop portion 316 and the reinforcement portion 317 are integrally formed. The integral member 310 formed by the stop portion 316 and the reinforcement portion 317 abuts the outer peripheral wall 302 of the crankcase assembly 201.

[0044] In one embodiment, the unitary member 310 includes a triangular profile 313 (shown in Fig. 3(d)). The unitary member 310 includes a base 311 (shown in Fig. 3(d)) abutting the outer peripheral wall 302 and an apex 312 (shown in Fig. 3(d)) extending inwardly (in the upward direction in the depicted embodiment) from the outer peripheral wall 302. As shown, in one implementation, the stop portion 316 is configured to have a larger cross-sectional area compared to the reinforcing portion 317 when viewed from the lateral side RH / LH of the IC engine 101. The unitary member 310 with two different cross-sectional areas is optimally configured to provide structural integrity with minimal material usage. In one embodiment, the stop portion 316 with the larger cross-sectional area stops the kickdown shaft stop 305 and supports the resilient member 380 (shown in Fig. 3(a)). The reinforcing portion 317 integral with the stop portion 316 provides reinforcement to the stop portion 316 to withstand the load from the kickdown shaft stop 305 and the resilient member 380 acting on the stop portion 316. In one implementation, the resilient member 380, specifically one end of the resilient member (i.e. one end of the torsion spring) is supported at the apex 312 or at one side of the stop portion 316. The kickdown shaft stop 305 stops on the other side of the stop portion 316. In one embodiment, the triangular profile 313 (where the profile narrows towards the apex 312 into the crankcase assembly 201 with the base 311 towards the outer peripheral wall 302) occupies an optimal minimum space in the crankcase assembly 201. This optimized structure with minimum space requirement enables a compact layout configuration of the drum stop 260 between the shift drum assembly 240 and the kickdown shaft 265, where the shift drum assembly 240 is disposed in the downward portion of the crankcase assembly 201.

[0045] Fig. 3(d) shows another enlarged view of a portion of the IC engine, according to one embodiment of the present subject matter. The kickdown shaft 265, the kickdown shaft stop 305 and the drum stop 260 are compactly housed within a small layout space at the rearward and downward portion of the crankcase assembly 201. As shown, the crankshaft 205, the clutch shaft 220 and the drive shaft 235 are disposed generally upwardly with respect to the shift drum assembly 240. The drum stop 260 is disposed generally away from the area occupied by the clutch 221 (shown in Fig. 3(b)) which is one of the largest components disposed on the outer lateral side of the crankcase assembly 201. Due to the drum stop 260 being disposed at the rearward and downward portion on the crankcase assembly 201, the shift pawl 255, the oil pump assembly 230 (shown in Fig. 3(b)) and the kickdown shaft stop 305 are disposed generally away from the drum stop 260 when viewed from the lateral side RH / LH. Figure 2 Figure 2 Fig. 3(d) shows another enlarged view of a portion of the IC engine, according to one embodiment of the present subject matter. The kickdown shaft 265, the kickdown shaft stop 305 and the drum stop 260 are compactly housed within a small layout space at the rearward and downward portion of the crankcase assembly 201. As shown, the crankshaft 205, the clutch shaft 220 and the drive shaft 235 are disposed generally upwardly with respect to the shift drum assembly 240. The drum stop 260 is disposed generally away from the area occupied by the clutch 221 (shown in Fig. 3(b)) which is one of the largest components disposed on the outer lateral side of the crankcase assembly 201. Due to the drum stop 260 being disposed at the rearward and downward portion on the crankcase assembly 201, the shift pawl 255, the oil pump assembly 230 (shown in Fig. 3(b)) and the kickdown shaft stop 305 are disposed generally away from the drum stop 260 when viewed from the lateral side RH / LH. Figure 2 ​The other components such as the drum stop 260, the star indexing member 250, the shift pawl 255, the elastic member 380, the one-piece member 310, and the like are compactly packaged in the IC engine 101. Further, the drum stop 260 engaged with the star indexing member 250 restricts over displacement and assists in shifting through the plurality of valleys 352 provided on the star indexing member 250. Further, due to the short distance between the shift shaft 245 and the shift drum assembly 240, the user experiences a distinct shift feel or feedback due to a larger angle of rotation which is necessary for perceivable shift feedback. During shifting, the shift pawl 255 rotates due to the rotation of the shift shaft 245. The rotation of the shift shaft 245 can be in the clockwise or anticlockwise direction. Correspondingly, the shift pawl 255 rotates the star indexing member 250 through the plurality of pins 351 provided on the indexing member 250. In one embodiment, a pair of pins out of the plurality of pins 351 enable the rotation of the star indexing member 250. The rotation of the star indexing member 250 rotates the shift drum assembly 240, causing the movement of the fork, thereby causing shifting. When the shifting operation is not performed, the rollers 341 of the drum stop 260 rest at the valleys. When the shifting operation is performed, the rotation of the star indexing member causes the rollers 341 to slide from the valley 352 to the peak formed between two valleys 352. After the peak, the rollers 341 assist in the rotation of the star indexing member 250 while rolling towards the valley 352. When the valley 352 is reached, the star indexing member 250 is held at a predetermined position until the next shifting operation. In one implementation, the shift shaft 245 is rotated by an angle in the range of 14 to 18 degrees, thereby causing an angular rotation of about 72 degrees of the shift drum assembly 240. The user experiences a better or different shift feedback feel when compared to the rotation of the shift shaft by a single digit angle.

[0046] The drum stop 260 has a pivot portion 342 (shown in Fig. 3(b)) arranged like a torsion spring around the one-piece member 310 and the elastic member 380; the torsion spring is arranged around the drum stop 260 and configured to engage with the one-piece member 310 on one side thereof. In one embodiment, the one-piece member 310 is compactly arranged substantially between a first vertical plane PI and a second vertical plane P2, wherein the first vertical plane PI passes through the axis (axis of rotation) of the drum stop 260 and is parallel to the crankshaft axis, and the second vertical plane P2 passes through the axis of the kick start shaft 265 and is parallel to the crankshaft axis. In one implementation, a first distance between the first vertical plane PI and the second vertical plane P2 is less than the length of the drum stop 260. Further, a third vertical plane P3 passes through the shift drum assembly 240 and is parallel to the crankshaft axis, and a second distance between the first vertical plane PI and the third vertical plane P3 is less than the length of the drum stop 260. Thus, the small distance between the planes PI and P2, and between the planes PI and P3 represents the compact packaging of the components in the IC engine 101.

[0047] The drum stopper has a long axis S-S' that is substantially vertical and parallel to the plane PI or P2 or P3, thereby occupying less space. Further, when the axis of the roller 341 (shown in (b) of FIG. 3) and the axis of the star indexing member 250 are envisaged for prescribed effective operation, a perpendicular is maintained between the drum stopper 260 and the star indexing member 250. Further, the kick shaft stopper 305 in the actuated state of the kick start lever has a second engagement portion 307 that engages on the other side of the unitary member 310. The kick shaft stopper 305 in the actuated state is represented by a dashed line, while the kick shaft stopper 305 in the non-actuated state is represented by a solid line.

[0048] Further, in one embodiment, the drum stopper 260 and the shift pawl 255 are substantially disposed in the second half of the crankcase assembly 201 and substantially on one side of the imaginary line 309 that passes through the uppermost portion of the star indexing member 250 and is orthogonal to the plane PI or P2 or P3. In one implementation, the second half is the rear half. In one embodiment, the shift pawl 255 is connected to the shift shaft 245, and the long axis P-P' of the shift pawl 255 is tilted rearward. Thus, the shift 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.

[0049] Further, as shown in FIG. 3(a) and FIG. 3(d), in one implementation, the unitary stopper 360 has a triangular profile 313 when viewed from the lateral side RH / LH. The unitary stopper 360 protrudes outwardly from the outer lateral surface 301 of the crankcase assembly 201. The triangular profile 313 is shown schematically in dashed lines. The base 311 of the unitary member 310 abuts the outer peripheral wall 302, and the apex 312 opposite 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 the rest of the unitary member 310. In one embodiment, the unitary member 310 is integrally formed with the crankcase assembly 201, i.e., the right crankcase member 203. The larger base provides the structural strength required to bear the forces acting on it from the resilient member 380 and the kick shaft stopper.

[0050] While certain features of the claimed subject matter have been illustrated and described, numerous modifications, substitutions, changes, and equivalents will occur to those skilled in the art. Therefore, it is to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the claimed subject matter.

[0051] List of reference signs:

[0052] 100 vehicle

[0053] 101 internal combustion engine

[0054] 102 side cover

[0055] 103 cylinder head assembly

[0056] 104 exhaust system

[0057] 105 frame assembly

[0058] 106 seat

[0059] 108 handlebar assembly

[0060] 109 front wheel

[0061] 110 rear wheel

[0062] 111 head tube

[0063] 112 main tube

[0064] 114 front suspension

[0065] 115 front fender

[0066] 117 rear suspension

[0067] 121 fuel tank

[0068] 201 crankcase

[0069] 202 left crankcase member

[0070] 203 right crankcase member

[0071] 205 crankshaft

[0072] 210 connecting rod

[0073] 215 clutch assembly

[0074] 220 clutch shaft

[0075] 225 oil filter assembly

[0076] 230 oil pump assembly

[0077] 235 drive shaft

[0078] 240 shift drum assembly

[0079] 245 shift shaft

[0080] 250 star indexing member

[0081] 255 shift pawl

[0082] 260 drum stopper

[0083] 265 kick start shaft

[0084] 270 oil drain plug

[0085] 301 outer lateral surface

[0086] 302 outer peripheral wall

[0087] 303 first portion

[0088] 304 second portion

[0089] 305 kick shaft stop

[0090] 306 first engagement portion

[0091] 307 second engagement portion

[0092] 308 aperture

[0093] 309 imaginary line

[0094] 310 unitary member

[0095] 311 base

[0096] 312 apex

Claims

1. An internal combustion engine (101) for a motor vehicle (100), the internal combustion engine (101) comprising: a crankshaft (205) supported by a crankcase assembly (201); a clutch shaft (220) configured to support at least one clutch (221) configured to engage and disengage the clutch shaft (220) with the crankshaft (205); a shift drum assembly (240) arranged generally downwardly with respect to the clutch shaft (220); a drum stop (260) configured to engage with the shift drum assembly (240) and arranged generally rearwardly with respect to the shift drum assembly (240) when viewed from a lateral side (RH, LH) of the internal combustion engine (101); and a shift shaft (245) arranged forwardly with respect to the shift drum assembly (240) when viewed from the lateral side (RH, LH) of the internal combustion engine (101).

2. The internal combustion engine (101) for a motor vehicle (100) as claimed in claim 1, wherein the internal combustion engine (101) comprises a kick start shaft (265), the drum stop (260) being arranged generally between the kick start shaft (265) and the shift drum assembly (240).

3. The internal combustion engine (101) for a motor vehicle (100) as claimed in claim 1, wherein the crankcase assembly (201) comprises an integral member (310) arranged generally between a first vertical plane (PI) passing through an axis of the drum stop (260) and a second vertical plane (P2) passing through an axis of the kick start shaft (265).

4. The internal combustion engine (101) for a motor vehicle (100) as claimed in claim 3, wherein the first vertical plane (PI) and the second vertical plane (P2) are arranged with a first distance, the first distance being generally less than a length of the drum stop (260), and wherein a third vertical plane (P3) passing through an axis of the shift drum assembly (240) is arranged at a second distance from the first vertical plane (P3), and the second distance is generally less than the length of the drum stop (260).

5. The internal combustion engine (101) for a motor vehicle (100) as claimed in claim 3, wherein the drum stop (260) is provided with a resilient member (380) preloaded against the integral member (310), and the kick start shaft (265) is provided with a kick shaft stop (305) configured to abut the integral member (310) at a predetermined angle of rotation of the kick start shaft (265).

6. The internal combustion engine (101) for a motor vehicle (100) as claimed in claim 3, wherein the unitary member (310) is formed integrally with the crankcase assembly (201) and comprises a base (311) having a larger cross-sectional area abutting the outer peripheral wall (302) of the crankcase assembly (201), and wherein the unitary member (310) comprises a geometry comprising a triangular profile when viewed from the lateral sides (RH, LH) of the crankcase assembly (201).

7. The internal combustion engine (101) for a motor vehicle (100) as claimed in claim 2, wherein the internal combustion engine (101) comprises a triangular region (TR) having vertices formed at the axis of the kick start shaft (265), the clutch shaft (220) and the shift shaft (245), wherein at least one of the drum stopper (260) and the shift drum assembly (240) is disposed substantially within the triangular region (TR) when viewed from the side of the internal combustion engine (101).

8. The internal combustion engine (101) for a motor vehicle (100) as claimed in claim 1, wherein the crankcase assembly (201) comprises a substantially equilateral quadrilateral profile as seen from a projected lateral side view of the internal combustion engine (101).

9. The internal combustion engine (101) for a motor vehicle (100) as claimed in claim 1, wherein the shift drum assembly (240) comprises a star-shaped indexing member (250) disposed at its lateral ends, the star-shaped indexing member (250) being configured to engage with a shift pawl (255) connected to the shift shaft (245), and a long axis (P-P’) of the shift pawl (255) is disposed in one of a forward tilt or a rearward tilt when viewed from the lateral sides (RH, LH) of the internal combustion engine (101).

10. The internal combustion engine (101) for a motor vehicle (100) as claimed in claim 1, wherein the crankcase assembly (201) comprises an outer peripheral wall (302) disposed substantially normal to an outer lateral surface (301) of the crankcase assembly (201), the outer peripheral wall (302) comprising a lower wall portion comprising a first portion (303) and a second portion (304), the second portion (304) being disposed at an acute angle with respect to the first portion (303) and rearwardly with respect to the first portion (303), the shift shaft (245) being disposed proximate a transition portion between the first portion (303) and the second portion (304).

11. The internal combustion engine (101) for a motor vehicle (100) as claimed in claim 1, wherein the crankcase assembly (201) comprises an integral member (310), the integral member (310) comprising a stop portion (316) and a reinforcement portion (317), the stop portion (316) comprising a cross-sectional area substantially greater than a cross-sectional area of the reinforcement portion (317), the stop portion (316) being arranged on an outer lateral surface (301) of the crankcase assembly (201) and the reinforcement portion (317) being arranged on the stop portion (317).

12. The internal combustion engine (101) for a motor vehicle (100) as claimed in claim 1, wherein the drum stop (260) and the shift pawl (255) are arranged on one side of an imaginary line (309) passing through an uppermost portion of a star indexing member (250) of the shift drum assembly (240) and the imaginary line (309) is arranged normal to a first vertical plane (PI) passing through an axis of the drum stop (260).

13. The internal combustion engine (101) for a motor vehicle (100) as claimed in claim 1, wherein the internal combustion engine (101) comprises a mid-plane (MP) arranged normal to an axis of the shift shaft (245), a major portion of the clutch shaft (220), the drive shaft (235), the kick start shaft (265), the shift drum assembly (240), the drum stop (260), and the clutch assembly (215) and the shift pawl (255) connected to the shift shaft (245) are arranged on one side of the mid-plane (MP) and wherein the mid-plane (MP) passes through the shift shaft (245) and is arranged normal to the axis of the shift shaft (245).

14. The internal combustion engine (101) for a motor vehicle (100) as claimed in claim 13, wherein the mid-plane (MP) is configured to provide a mass distribution on either side of the mid-plane (MP) in a range of 45% to 55% of a total mass of the internal combustion engine (101).

15. A crankcase assembly (201) for the internal combustion engine (101) as claimed in any one of claims 1 to 14, the crankcase assembly (201) comprising: a left crankcase member (202); and a right crankcase member (203), wherein, at least one of the left crankcase member (202) and the right crankcase member (203) comprises an outer lateral surface (301) and an outer peripheral wall (302), wherein, an integral member (310) is arranged on the outer lateral surface (301) and abuts the outer peripheral wall (302); the integral member (310) comprises a portion configured to limit rotation of a kick start shaft (265) of the internal combustion engine (101) beyond a predetermined angle, and the integral member (310) comprises a reinforcement portion (317) arranged on the portion configured to limit rotation of the kick start shaft (265) beyond the predetermined angle. The one-piece member (310) comprises a further portion configured to support a resilient member (380) arranged to preload the drum stop (260) of the internal combustion engine (101).

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