Claims:WE CLAIM:
1. A camshaft assembly (100) for an internal combustion engine (200), the assembly (100) comprising:
a camshaft (102) having end portions (102a, 102b) supported by cam supporting portions (202a, 202b) of an engine body (202), the camshaft (102) provided with an intake cam (104) and an exhaust cam (106) between the end portions (102a, 102b);
a flange (108) mounted axially onto the camshaft (102) and coupled to a sprocket (110), the flange (108) adapted to rotate the camshaft (102) via drive force received by the sprocket (110); and
a decompression device (112) having a decompression arm (114) pivotally supported onto the flange (108) and coupled to a decompression cam (116) engaged to the exhaust cam (106), the decompression arm (114) adapted to be rotated at a predetermined angle between an open position (118) and a closed position (120) by a centrifugal force generated during rotation of the camshaft (102), wherein in the open position (118) the decompression arm (114) is adapted actuate the exhaust cam (106) via the decompression cam (116) to lift an exhaust valve.

2. The assembly (100) as claimed in claim 1, wherein the flange (108) is located between the sprocket (110) and a first bearing (122) mounted on the camshaft (102), the first bearing (122) being positioned adjacent to the sprocket (110).

3. The assembly (100) as claimed in claim 2, wherein the decompression cam (116) passes through the first bearing (122) for engagement with the exhaust cam (106).

4. The assembly (100) as claimed in claim 3, wherein the decompression cam (116) passes through an inner diametrical surface of the first bearing (122).

5. The assembly (100) as claimed in claim 1, wherein the decompression arm (114) is operated to the closed position (120) when a speed of the engine (200) exceeds a predefined limit, the decompression arm (114) in the closed position (120) retains the decompression cam (116) in a no-lift position.

6. The assembly (100) as claimed in claim 1, wherein the decompression arm (114) is operated to the open position (118) when a speed of the engine (200) is below a predefined limit, the decompression arm (114) in the open position (118) operates the decompression cam (116) to a lift position for actuating the exhaust cam (106) to lift the exhaust valve.

7. The assembly (100) as claimed in claim 1 comprising a second bearing (124) mounted on the camshaft (102) and positioned proximal to a spark plug (204) of the engine (200).

8. The assembly (100) as claimed in claim 1, wherein the flange (108) is press-fitted onto the camshaft (102).

9. The assembly (100) as claimed in claim 1, wherein the decompression arm (114) weighs about 15 grams to about 20 grams.

10. The assembly (100) as claimed in claim 1, wherein the decompression arm (114) is coupled to the decompression cam (116) via a cam pin (126).

11. An internal combustion engine (200) comprising:
an engine body (200); and
a camshaft assembly (100), comprising:
a camshaft (102) having end portions (102a, 102b) supported by cam supporting portions (202a, 202b) of the engine body (202), the camshaft (102) provided with an intake cam (104) and an exhaust cam (106) between the end portions (102a, 102b);
a flange (108) mounted axially onto the camshaft (102) and coupled to a sprocket (110), the flange (108) adapted to rotate the camshaft (102) via drive force received by the sprocket (110); and
a decompression device (112) having a decompression arm (114) pivotally supported onto the flange (108) and coupled to a decompression cam (116) engaged to the exhaust cam (106), the decompression arm (114) adapted to be rotated at a predetermined angle between an open position (118) and a closed position (120) by a centrifugal force generated during rotation of the camshaft (102), wherein in the open position (118) the decompression arm (114) is adapted actuate the exhaust cam (106) via the decompression cam (116) to lift an exhaust valve.

12. The engine (200) as claimed in claim 11, wherein the flange (108) is located between the sprocket (110) and a first bearing (122) mounted on the camshaft (102), the first bearing (122) being positioned adjacent to the sprocket (110).

13. The engine (200) as claimed in claim 12, wherein the decompression cam (116) passes through the first bearing (122) for engagement with the exhaust cam (106).

14. The engine (200) as claimed in claim 13, wherein the decompression cam (116) passes through an inner diametrical surface of the first bearing (122).

15. The engine (200) as claimed in claim 11, wherein the decompression arm (114) is operated to the closed position (120) when a speed of the engine (200) exceeds a predefined limit, the decompression arm (114) in the closed position (120) retains the decompression cam (116) in a no-lift position.

16. The engine (200) as claimed in claim 11, wherein the decompression arm (114) is operated to the open position (118) when a speed of the engine (200) is below a predefined limit, the decompression arm (114) in the open position (118) operates the decompression cam (116) to a lift position for actuating the exhaust cam (106) to lift the exhaust valve.

17. The engine (200) as claimed in claim 11 comprising a second bearing (124) mounted on the camshaft (102) and positioned proximal to a spark plug (204) of the engine (200).

18. The engine (200) as claimed in claim 11, wherein the flange (108) is press-fitted onto the camshaft (102).

19. The engine (200) as claimed in claim 11, wherein the decompression arm (114) is coupled to the decompression cam (116) via a cam pin (126).

Dated this 28th day of February 2022
TVS MOTOR COMPANY LIMITED
By their Agent & Attorney

(Nikhil Ranjan)
of Khaitan & Co
Reg No IN/PA-1471 , Description:FORM 2
THE PATENTS ACT, 1970
(39 OF 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]

TITLE OF INVENTION
Camshaft Assembly for an Internal Combustion Engine and the Internal Combustion Engine Thereof

APPLICANT
TVS MOTOR COMPANY LIMITED, an Indian company, having its address at “Chaitanya”, No.12 Khader Nawaz Khan Road, Nungambakkam, Chennai 600 006, Tamil Nadu, India.

PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF THE INVENTION
[001] The present invention relates to an internal combustion engine of a vehicle. More particularly, relates to a camshaft assembly for the internal combustion engine of the vehicle.

BACKGROUND OF THE INVENTION
[002] Typically, an internal combustion engine is mounted on a vehicle to provide motive force required for movement of the vehicle. The engine is adapted to receive fuel or fuel-air mixture from an intake system, which is compressed and thereafter ignited for generating the motive force. In recent past, due to demand for improvement in performance of the engine, it is desirable to maintain a relatively high compression ratio. The higher compression ratio results in a greater power output or an increase in the motive force generated by the engine. However, engines that are designed to operate in a high compression ratio give rise to rather large forces that an operator must overcome to enable manual starting.
[003] In order to overcome the forces, devices to lower the forces within the engine during manual starting procedure are provided. One such device for lowering the forces is a decompression device assembled on a camshaft of the engine. The decompression device comprises a decompression arm, which is adapted to lift an exhaust valve of the engine during manual starting procedure for lowering the forces within the engine. In conventional decompression devices, proper actuation of the decompression arm is ensured by pivoting arm which is either provided as a separate part or in a camshaft lobe or in a sprocket. Such a construction in the conventional decompression device requires additional part and thereby increasing the space requirement in the engine. Consequently, the space between camshaft bearings compromises bearing support in the cylinder head.
[004] In view of the above, there is a need for a camshaft assembly for an internal combustion engine, which addresses one or more limitations stated above.

SUMMARY OF THE INVENTION
[005] In one aspect, a camshaft assembly for an internal combustion engine is provided. The assembly comprises a camshaft having end portions supported by cam supporting portions of an engine body, and provided with an intake cam and an exhaust cam between the end portions. A flange is mounted axially onto the camshaft and is coupled to a sprocket. The flange is adapted to rotate the camshaft via drive force received by the sprocket. A decompression device having a decompression arm is pivotally supported onto the flange and coupled to a decompression cam engaged to the exhaust cam. The decompression arm is adapted to be rotated at a predetermined angle between an open position and a closed position by a centrifugal force generated during rotation of the camshaft. In the open position the decompression arm is adapted actuate the exhaust cam via the decompression cam to lift an exhaust valve.
[006] In an embodiment, the flange is located between the sprocket and a first bearing mounted on the camshaft, the first bearing being positioned adjacent to the sprocket.
[007] In an embodiment, the decompression cam passes through the first bearing for engagement with the exhaust cam.
[008] In an embodiment, the decompression cam passes through an inner diametrical surface of the first bearing.
[009] In an embodiment, the decompression arm is operated to the closed position when a speed of the engine exceeds a predefined limit. The decompression arm in the closed position retains the decompression cam in a no-lift position.
[010] In an embodiment, the decompression arm is operated to the open position when the speed of the engine is below a predefined limit. The decompression arm in the open position operates the decompression cam to a lift position for actuating the exhaust cam to lift the exhaust valve.
[011] In an embodiment, a second bearing is mounted on the camshaft and positioned proximal to a spark plug of the engine.
[012] In an embodiment, the flange is press-fitted onto the camshaft.
[013] In an embodiment, the decompression arm weighs about 15 grams to about 20 grams.
[014] In an embodiment, the decompression arm is coupled to the decompression cam via a cam pin.
[015] In another aspect, the internal combustion engine is provided. The engine comprises the engine body and the camshaft assembly. The assembly comprises the camshaft having end portions supported by cam supporting portions of the engine body, and provided with the intake cam and an exhaust cam between the end portions. The flange is mounted axially onto the camshaft and is coupled to a sprocket. The flange is adapted to rotate the camshaft via drive force received by the sprocket. The decompression device having the decompression arm is pivotally supported onto the flange and coupled to the decompression cam engaged to the exhaust cam. The decompression arm is adapted to be rotated at the predetermined angle between the open position and the closed position by the centrifugal force generated during rotation of the camshaft. In the open position the decompression arm is adapted actuate the exhaust cam via the decompression cam to lift an exhaust valve.

BRIEF DESCRIPTION OF THE DRAWINGS
[016] Reference will be made to embodiments of the invention, examples of which may be illustrated in accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.
Figure 1 is a schematic view of a vehicle, in accordance with an embodiment of the present invention.
Figure 2 is a perspective view of a top portion of an internal combustion engine, in accordance with an embodiment of the present invention.
Figure 3 is a sectional view of the top portion of the internal combustion engine depicting a camshaft assembly, in accordance with an embodiment of the present invention.
Figure 4 is a schematic view of the camshaft assembly having a decompression device, in accordance with an embodiment of the present invention.
Figure 5 is an exploded view of the camshaft assembly having the decompression device, in accordance with an embodiment of the present invention.
Figure 6 is a schematic view of a decompression arm in a closed position, in accordance with an embodiment of the present invention.
Figure 7 is a schematic view of the decompression arm in an open position, in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION
[017] Various features and embodiments of the present invention here will be discernible from the following further description thereof, set out hereunder.
[018] Figure 1 illustrates a schematic view of a vehicle 206, in accordance with an embodiment of the present invention. As an example, the vehicle 206 is a two-wheeled vehicle. In the present embodiment, the vehicle 206 is a motorcycle. The vehicle 206 comprises an internal combustion engine 200 which acts as a prime mover to provide motive force for movement of the vehicle 206. The vehicle 206 comprises a front wheel 208, a rear wheel 210, a frame member (not shown), a seat 212 and a fuel tank 214. The frame member comprises a head pipe (not shown), a main tube (not shown), a down tube (not shown), and a seat rail (not shown). The head pipe supports a steering shaft (not shown) and a telescopic suspension unit 216 attached to the steering shaft through a lower bracket (not shown). The telescopic suspension unit 216 supports the front wheel 208.
[019] Further, the upper portion of the front wheel 208 is covered by a front fender 218 mounted to the lower portion of the telescopic suspension unit 216 at the end of the steering shaft. A handlebar 220 is fixed to upper bracket (not shown) and can rotate about the steering shaft for turning the vehicle 206. A headlight 222, a visor guard (not shown) and instrument cluster 224 is arranged on an upper portion of the head pipe. The frame member comprises a down tube (not shown) that may be positioned in front of the engine 200 and extends slantingly downward from head pipe. The main tube of the frame member is located above the engine 200 and extends rearward from head pipe.
[020] The fuel tank 214 is mounted on the main tube. Seat rails are joined to main tube and extend rearward to support the seat 212. A rear swing arm (not shown) is connected to the frame member to swing vertically, and the rear wheel 210 is connected to rear end of the rear swing arm. Generally, the rear swing arm is supported by a mono rear suspension 226 (as illustrated in the present embodiment) or through two suspensions on either side of the vehicle 206. A taillight unit 228 is disposed at the end of the vehicle 206 and at the rear of the seat 212. A grab rail 230 is also provided to the seat rails. The rear wheel 210 arranged below the seat 212 rotates by the motive force of the engine 200 transmitted through a chain drive (not shown) or any other endless transmission means as per requirement.
[021] Further, a rear fender 232 is disposed above the rear wheel 210. An exhaust pipe 234 of the vehicle 206 extends vertically downward from the engine 200 and then extends below the engine 200, longitudinally along length of the vehicle 206 before terminating in a muffler 236. The muffler 236 is typically disposed adjoining the rear wheel 210.
[022] Further, the engine 200 comprises an engine body 202 adapted to be mounted onto the frame member (not shown) of the vehicle 206. In the present embodiment, the engine body 202 is defined with plurality of mounting provisions (not shown). The mounting provisions are bolted or fastened onto the frame member for mounting the engine 200 onto the vehicle 206. In an embodiment, the engine 200 is aligned vertically with respect to the longitudinal axis of the vehicle 206.
[023] Referring to Figure 2 in conjunction with Figure 1, the engine 200 comprises a cylinder head 238 provided over at least one engine cylinder (not shown). The cylinder head 238 comprises an intake valve (not shown) and an exhaust valve (not shown) for each engine cylinder. The intake valve is adapted to route air or fuel-air mixture into the engine cylinder for combustion and the exhaust valve is adapted to route exhaust gases from the engine cylinder to atmosphere.
[024] In an embodiment, each of the intake valve and the exhaust valve may be spring loaded for ensuring that the intake valve and the exhaust valve return to a no-lift condition (not shown) from a lift condition (not shown). In an embodiment, the lift condition of each of the intake valve and the exhaust valve is an open position. Thus, in the lift condition the intake valve routes air or fuel mixture into the engine cylinder, while the exhaust valve discharges exhaust gas from the engine cylinder. Also, in the no-lift condition, each of the intake valve and the exhaust valve is in a closed position. Thus, in the no-lift condition, the intake valve restricts flow of air or fuel-air mixture into the engine cylinder, while the exhaust valve prevents discharge of the exhaust from the engine cylinder.
[025] A spark plug 204 is also provided on the cylinder head 238. The spark plug 204 is adapted to ignite the air or fuel-air mixture routed via the intake valve, thereby facilitating combustion within the engine cylinder and generation of motive force. Further, for controlling movement or actuation of the intake valve and the exhaust valve, the engine 200 is provided with a camshaft assembly 100. The camshaft assembly 100 is mounted on the engine body 202 (for e.g. as shown in Figure 3) and positioned in the cylinder head 238.
[026] Referring to Figure 4 in conjunction with Figures 1-3, the camshaft assembly 100 comprises a camshaft 102 having end portions 102a, 102b supported by cam supporting portions 202a, 202b of the engine body 202. In an embodiment, the cam supporting portions 202a, 202b of the engine body 202 may be bearing surfaces adapted to support the end portions 102a, 102b of the camshaft 102. The camshaft 102 is also provided with an intake cam 104 and an exhaust cam 106 between the end portions 102a, 102b. The intake cam 104 is adapted to engage and control actuation of the intake valve. The intake cam 104 is defined with a cam lobe (not shown) which engages and controls actuation of the intake valve. Also, the exhaust cam 106 is adapted to engage and control actuation of the exhaust valve. Additionally, the exhaust cam 106 is also defined with a cam lobe (not shown) that engages and controls actuation of the exhaust valve. In an embodiment, the intake cam 104 and the exhaust cam 106 engage with the intake valve and the exhaust valve via a poppet assembly (not shown).
[027] Further, a flange 108 is mounted axially (i.e. along axis A-A’) onto the camshaft 102 and coupled to a sprocket 110. The sprocket 110 may be coupled to a crankshaft (not shown) of the engine 200 via an endless transmission means (not shown) for receiving a drive force. As such, the flange 108 rotate the camshaft 102 via the drive force received by the sprocket 110. In the present embodiment, for accommodating minimal space on the camshaft 102, the flange 108 is located between the sprocket 110 and a first bearing 122 mounted on the camshaft 102 and positioned adjacent to the sprocket 110. In an embodiment, the dimensions and construction of the sprocket 110 is selected as per operating speed requirements of the camshaft 102.
[028] In the present embodiment, the flange 108 comprises a projection portion 108a (as shown in Figure 5) extending from a collar portion 108b (as shown in Figure 5) that is mounted axially onto the camshaft 102. The projection portion 108a and the collar portion 108b are defined with a slot 108c. The slot 108c engages axially on the camshaft 102. In an embodiment, the flange 108 is press-fitted onto the camshaft 102 and assembled onto the sprocket 110. In an embodiment, the projection portion 108a and the collar portion 108b are integrally formed. In other words, the flange 108 may be a single component formed with the projection portion 108a and the collar portion 108b.
[029] In another embodiment, the flange 108 is defined with mounting provisions 130 that engage with mounting members 132 of the sprocket 110 for mounting the flange 108 with the sprocket 110. In the present embodiment, the mounting provisions 130 are strategically provided at diametrically opposite locations about the slot 108c, for ensuring stable mounting with the sprocket 110. Also, the mounting provisions 130 and the mounting members 132 are slots, that are adapted to receive a fastening member for engagement, thereby ensuring mounting of the flange 108 with the sprocket 110. In an embodiment, the flange 108 is made of a metallic material or a composite material as per design feasibility and requirement.
[030] Further, referring to Figure 5 in conjunction with Figure 4, a decompression device 112 having a decompression arm 114 is pivotally supported onto the flange 108. The decompression device 112 is adapted to reduce the forces within the engine cylinder during manual starting of the engine 200. The decompression arm 114 is pivotally supported onto the flange 108 (or the collar portion 108b) via a pivot pin member 128 (as shown in Figures 7 and 8). The decompression arm 114 is adapted to be rotated at a predetermined angle between an open position 118 (shown in Figure 7) and a closed position 120 (shown in Figure 6) by a centrifugal force generated during rotation of the camshaft 102. In an embodiment, the predetermined angle of rotation of the decompression arm 114 is about 10 degrees to about 20 degrees.
[031] In an embodiment, the pivot pin member 128 is adapted to engage with one of the mounting members 130 of the flange 108 for pivotally mounting the decompression arm 114 onto the flange 108. In an embodiment, the pivot pin member 128 engages at one end of the decompression arm 114. Alternatively, the pivot pin member 128 may engage at any location along the length of the decompression arm 114 as per design feasibility and requirement.
[032] In an embodiment, the pivot pin member 128 is provided with a shank portion that is adapted to engage with the mounting member 130 on the flange 108. The shank portion may be defined with a stepped profile having a portion 128a with a larger diameter and an engagement portion 128b with a smaller diameter. The engagement portion 128b may be adapted to engage with the mounting member 130 for pivotal connection, while the portion 128a may be adapted to receive with the decompression arm 114, thereby enabling mounting of the decompression arm 114 with the flange 108. In an embodiment, the pivot pin member 128 engages with the mounting member 130 via conventional mounting techniques known in the art such as fastening, clamping and the like.
[033] In another embodiment, a spring member 134 is also mounted along with the decompression arm 114 on the pivot pin member 128. The spring member 134 is adapted to store energy during rotation of the decompression arm 114 to the open position 118 and thereafter release the stored energy for reverting the decompression arm 114 to the closed position 120. In the present embodiment, the spring member 134 is a coil spring member configured with resilience as per design feasibility and requirement of the decompression device 112.
[034] In an embodiment, the decompression arm 114 is an arcuate member having an outer surface conforming to peripheral surface of the camshaft 102. Alternatively, the shape and dimensions of the decompression arm 114 is selected as per design feasibility and requirement of the decompression device 112. In an embodiment, the decompression arm 114 is defined with an outer diametrical surface having dimensions greater than diameter of the camshaft 102.
[035] Further, the decompression arm 114 is coupled to a decompression cam 116 engaged to the exhaust cam 106. Such a construction ensures actuation of the exhaust cam 106 via the decompression cam 116, when the decompression arm 114 is operated to the open position 118 from the closed position 120. The decompression arm 114 is operated to the open position 118 when a speed of the engine 200 is below a predefined limit. This is due to the centrifugal force that is exerted on the decompression arm 114 during lower speed of the engine 200. At this scenario, the decompression arm 114 operates the decompression cam 116 to a lift position for actuating the exhaust cam 106 to lift the exhaust valve. The decompression arm 114 is operated to the closed position 120 when speed of the engine 200 exceeds a predefined limit. At this scenario, due to the higher speed of rotation of the crankshaft, the centrifugal force acting on the decompression arm 114 is nullified, thereby operating the decompression arm 114 to the closed position 120. In the closed position 120, the decompression arm 114 retains the decompression cam 116 in a no-lift position.
[036] In an embodiment, the predefined limit of speed of the engine 200 for exerting centrifugal force on the decompression arm 114 is about 500 RPM to about 1000 RPM. In another embodiment, the predefined limit of the speed of the engine 200 can be adjusted as per design feasibility and requirement.
[037] In an embodiment, the decompression cam 116 is a pin-like member that connects the decompression arm 114 at one end and the other end with the exhaust cam 106. The end connecting with the decompression arm 114 may be via a cam pin 126. In other words, the decompression cam 116 and the decompression arm 114 comprises a groove or an opening (not shown) for receiving the cam pin 126. As such, during movement of the decompression arm 114 from the closed position 120 to the open position 118, the decompression cam 116 is axially rotated to a lift position (not shown) from a no-lift position (not shown). The decompression can 116 in the lift position operates or lifts the exhaust valve to relieve pressure within the engine cylinder, thereby facilitating an operator for manual starting.
[038] In an embodiment, the decompression cam 116 comprises a bulged portion 116a and a flat portion 116b. The bulged portion 116a is provided with an outer surface that extends or protrudes beyond peripheral surface of the cam lobe of the exhaust cam 106. As such, in the lift position of the decompression cam 116, the bulged portion 116a faces towards the exhaust valve and lifts the exhaust valve to relieve the pressure within the engine cylinder. In the no-lift position, the bulged portion 116a disengages from the exhaust valve and the flat portion 116b faces towards the exhaust valve. In an embodiment, the shape and dimensions of the bulged portion 116a and the flat portion 116b is selected as per design feasibility and requirement.
[039] The decompression cam 116 passes through the first bearing 122 for engagement with the exhaust cam 106. In an embodiment, the decompression cam 116 passes through an inner diametrical surface 122a of the first bearing 122. Such a construction ensures that size of the decompression device 112 conforms to the size of the camshaft 102, thereby mitigating need for additional space in the engine 200. Further, the camshaft assembly 100 comprises a second bearing 124 mounted on the camshaft 102 and positioned proximal to the spark plug 204. The second bearing 124 acts as a mounting surface for the camshaft 102 on the engine 200.
[040] In an embodiment, the decompression arm 114 weighs about 15 grams to about 20 grams. In another embodiment, the projection portion 108a of the flange 108 controls movement via the shape of the projections. In other words, the contour of the projection portion 108a controls the extent of movement of the decompression arm 114. As such, the shape of the projection portion 108a is selected as per design feasibility and requirement.
[041] Referring to Figures 6 and 7 in conjunction with Figures 4 and 5, when the operator tries to manually start the engine 200 via a kick-start mechanism (not shown), the torque provided by the operator to a kick-lever (not shown) is transferred to the crankshaft, which in-turn is transferred to the camshaft 102 via the sprocket 110. As such, the camshaft 102 rotates axially about the axis A-A’. During such a rotation of the camshaft 102, centrifugal force is exerted on the decompression arm 114 due to pivotal connection with the flange 108. Thus, the decompression arm 114 moves away from the camshaft 102 (as shown in Figure 7), thereby operating the decompression arm 114 to the open position 118 from the closed position 120. In this scenario, the decompression cam 116 being connected to the decompression arm 114 via the cam pin 126 rotates about its axis. During such a axial rotation of the decompression cam 116, the bulged portion 116a faces and engages the exhaust valve. Due to the bulge that protrudes from the peripheral surface of the exhaust cam 106, the bulged portion 116a lifts the exhaust valve. The lift of the exhaust valve discharges the charge contained within the engine cylinder, thereby relieving pressure within the engine cylinder. As such, the effort required for the operator to manually kick-start the engine 200 gradually reduces. In an embodiment, the torque provided by the operator during kick-starting of the engine 200 is less than the idling speed or operational speed of the engine 200. In an embodiment, the lift of the exhaust valve via the bulged portion 116a is less than the lift via the exhaust cam 106.
[042] Upon starting of the engine 200, the speed of the engine 200 increases beyond the predefined limit. At this stage, the speed of rotation of the camshaft 102 nullifies the centrifugal force acting on the decompression arm 114 and exerts additional force on the decompression arm 114 to revert to the closed position 120 from the open position 118. As such, lift-off of the exhaust valve is prevented during normal operation of the engine 200.
[043] The claimed invention as discussed above are not routine, conventional, or well understood in the art, as the claimed aspects enable the following solutions to the existing problems in conventional technologies. Specifically, the claimed aspects of the flange 108 supporting the decompression arm 114 provides the technical advancement of ensuring proper or optimal actuation of the decompression device 112 without the necessity of separate or additional parts in the assembly 100, while providing technical solution to the technical problem. Consequently, making the design of the assembly 100 compact in the engine 200. Additionally, as the flange 108 itself limits the actuation of the decompression arm 114 while also acting as a drive force transfer member to the camshaft 102, reduces the part count in the engine 200.
[044] While the present invention has been described with respect to certain embodiments, it will be apparent to those skilled in the art that various changes and modification may be made without departing from the scope of the invention as defined in the following claims.

Reference numerals
100 - Camshaft assembly
102 - Camshaft
102a, 102b - End portions of camshaft
104 - Intake cam
106 - Exhaust cam
108 - Flange
110 - Sprocket
112 - Decompression device
114 - Decompression arm
116 - Decompression cam
116a - Bulged portion
116b - Flat portion
118 - Open position
120 - Closed position
122 - First bearing
124 Second bearing
126 - Cam pin
128 - Pivot pin member
130 - Mounting provisions on flange
132 - Mounting members on sprocket
134 - Spring member
200 - Transmission cover
202 - Engine body
202a, 202b - Cam mounting portions
204 - Sparkplug
206 - Vehicle
208 - Front wheel
210 - Rear wheel
212 - Seat
214 - Fuel tank
216 - Telescopic suspension unit
218 - Front fender
220 - Handlebar
222 - Headlight
224 - Instrument cluster
226 - Mono rear suspension
228 - Taillight unit
230 - Grab rail
232 - Rear fender
234 - Exhaust pipe
236 - Muffler
238 - Cylinder head