Description:FIELD OF THE INVENTION
[001] The present invention generally relates to an internal combustion engine. More particularly, the present invention relates to an internal combustion engine for a motor vehicle.

BACKGROUND OF THE INVENTION
[002] Generally, in conventional motor vehicles with internal combustion engines, the internal combustion engine includes a crankshaft and a camshaft. Generally, a vehicle is provided with either a kick start mechanism or an electric start mechanism or both. In vehicles, which are provided with kick start mechanism, a high kick force is required by a user to start the vehicle by overcoming the starting resistance in the internal combustion engine. This high kick force in turn sometimes cause injury to the feet of the user. Similarly, if an electric start is provided, an electric motor generating a high enough torque to overcome the starting resistance of the engine is required. One of the major contributors to this starting resistance of the engine is the compression buildup of the air-fuel mixture inside the combustion chamber of the engine, since the piston has to move against this compression of the air-fuel mixture.
[003] In order to overcome the high kick force or high torque of the electric motor during the starting of the vehicle, generally a decompression system is attached to a portion of the camshaft in the engine. These decompression systems, during the starting of the vehicle, cause the exhaust valve to open slightly which makes the air-fuel mixture exhaust the combustion chamber, thereby preventing compression buildup in the combustion chamber during starting of the engine.
[004] The conventional decompression system are disposed between a cam lobe and a bearing of the decompression system, and the bearing is in contact with a decompression sprocket at one end of the bearing. Furthermore, the existing design of the decompression system includes a moving arm which is extends up to a length of the stopper spring to stop the movement of the decompression system once the engine is cranked. However, the existing configuration of the decompression system is lengthy and bulky and is feasible to be accommodated in at least three valve cylinder head configuration. These bulky conventional decompression systems cannot be accommodated in engines which have a two valve configuration, i.e., having a single intake valve and a single exhaust valve. Furthermore, conventional decompression systems have a small contact surface area between the lobe responsible for decompression and the exhaust valve, which leads to a delay in response of the exhaust valve.
[005] Thus, there is a need in the art for an internal combustion engine which addresses at least the aforementioned problems.

SUMMARY OF THE INVENTION
[006] In one aspect, the present invention is directed towards an internal combustion engine having a camshaft provided in a cylinder head of the internal combustion engine. The camshaft has an axial hollow cavity. A cam sprocket is connected to the camshaft for driving the camshaft. A first shaft is disposed in the axial hollow cavity of the camshaft and has a depression portion. A first pin is rigidly connected to the first shaft and is configured to rotate the first shaft. A pivot arm is mounted on the cam sprocket and is configured to move pivotally between a first position and a second position based on a rotation speed of the camshaft. The pivot arm has a slot and the slot is configured to engage with the first pin wherein the pivotal movement of the pivot arm causes the first pin to move, thereby rotating the first shaft. A second pin is movably provided in a radial slot provided on the camshaft. The second pin is operably connected to the first shaft, wherein when the pivot arm is in the first position, the first shaft pushes the second pin thereby operating an exhaust valve, and when the pivot arm is in the second position, the second pin engages with the depression portion on the first shaft thereby moving inside the radial slot and disengaging with the exhaust valve.
[007] In an embodiment of the invention, the radial slot of the camshaft extends at an inclination with a central axis of the camshaft.
[008] In a further embodiment of the invention, the second pin has an inner end and an outer end. The inner end is in contact with the first shaft and the outer end is configured to operate the exhaust valve. The inner end has a partially slanted profile and the outer end has a curved profile.
[009] In a further embodiment of the invention, the internal combustion engine has a supporting member that is configured for attaching the camshaft to the cam sprocket.
[010] In a further embodiment of the invention, the internal combustion engine has a supporting flange attached to the supporting member, and the supporting flange pivotably supports the pivot arm.
[011] In a further embodiment of the invention, the internal combustion engine has a torsional spring provided between the supporting flange and the pivot arm. The torsional spring is configured to restrict the movement of the pivot arm beyond the first position in a first rotation direction.
[012] In a further embodiment of the invention, the internal combustion engine has a stopper pin attached to the cam sprocket. The stopper pin is configured to restrict the movement of the pivot arm beyond the second position in a second rotation direction.
[013] In a further embodiment of the invention, the internal combustion engine has a compression spring provided in the radial slot. The compression spring is configured to retain the second pin in the radial slot when the pivot arm is in the second position.
[014] In a further embodiment of the invention, the pivot arm is configured to be in the first position if a rotation speed of the camshaft is below a predetermined rotation speed, and to be in the second position if the rotation speed of the camshaft is higher than the predetermined rotation speed.
[015] In a further embodiment of the invention, the second pin extends in a radially opposite direction to a protruding portion of an exhaust cam lobe.

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 illustrates a top perspective view of an internal combustion engine, in accordance with an embodiment of the present invention.
Figure 2 illustrates a side view of the internal combustion engine, in accordance with an embodiment of the present invention.
Figure 3 illustrates a perspective view of the internal combustion engine, in accordance with an embodiment of the present invention.
Figure 4 illustrates another side view of the internal combustion engine, in accordance with an embodiment of the present invention.
Figure 5 illustrates a front view of the internal combustion engine, in accordance with an embodiment of the present invention.
Figure 6 illustrates a sectional view of the internal combustion engine, in accordance with an embodiment of the present invention.
Figure 7 illustrates an exploded view of the internal combustion engine, in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION
[017] The present invention relates to an internal combustion engine. More particularly, the present invention relates to an internal combustion engine for a motor vehicle. The internal combustion engine of the present invention is typically used in a vehicle such as a two wheeled vehicle. However, it should be understood that the internal combustion engine as illustrated may find its application in a three wheeled vehicle, or a four wheeled vehicle, or other multi-wheeled vehicles, or any non-automotive application using an internal combustion engine as required.
[018] Figures 1 and 2 illustrate a top perspective view and a side view of an internal combustion engine 100. As illustrated in Figure 1 and Figure 2, and further referenced in Figure 3, the internal combustion engine 100 comprises a camshaft 110. The camshaft 110 is provided in a cylinder head 12 of the internal combustion engine 100. The camshaft 110 is configured to be driven by a crankshaft of the internal combustion engine 100 and operate at least an intake valve and an exhaust valve 116 of the internal combustion engine 100. In an embodiment, the camshaft comprises an intake cam lobe (not shown) and an exhaust cam lobe 114 respectively configured to drive the intake valve and the exhaust valve 116 for operation of the internal combustion engine 100. The camshaft 110 has an axial hollow cavity extending along a length of the camshaft 110 along a central axis (X-X’) of the camshaft 110.
[019] For driving the camshaft 110 through the crankshaft, the internal combustion engine 100 comprises a cam sprocket 120. The cam sprocket 120 is connected to the camshaft 110 for driving the camshaft 110. In an embodiment, a cam chain extends between the crankshaft and the cam sprocket 120, wherein the cam chain engages with the cam sprocket 120 thereby driving the camshaft 110.
[020] Further, the internal combustion engine 100, as illustrated in Figure 3 and Figure 4, the internal combustion engine 100 has a first shaft 130. The first shaft 130 is disposed in the axial hollow cavity of the camshaft 110 and is provided movably within the axial hollow cavity of the camshaft 110. The first shaft 130 has a depression portion 132 (shown in Figure 6). For moving the first shaft 130, the internal combustion engine 100 has a first pin 140. The first pin 140 is rigidly connected to the first shaft 130 and is configured to rotate the first shaft 130. In an embodiment, the first pin 140 extends radially outwards from the first shaft 130. Thus, movement of the first pin 140 will cause rotational movement of the first shaft 130.
[021] For causing the movement of the first pin 140, the internal combustion engine 100 further has a pivot arm 150. As illustrated, the pivot arm 150 is mounted on the cam sprocket 120. The pivot arm 150 is configured to move pivotally between a first position and a second position based on a rotation speed of the camshaft 110. As specifically illustrated in Figure 3, the pivot arm 150 having a slot 152. The slot 152 is configured to engage with the first pin 140 wherein the pivotal movement of the pivot arm 150 causes the first pin 140 to move, thereby rotating the first shaft 130. In an embodiment, the pivot arm 150 is configured to be in the first position when the camshaft 110 is rotating at lower speeds, i.e. during the starting of the internal combustion engine 100, and is configured to move into the second position when the camshaft 110 is rotating at higher speeds, i.e. after the starting of the internal combustion engine 100 during the operation of the internal combustion engine 100. Due to the centrifugal force experienced by the pivot arm 150 due to rotation of the cam sprocket 120 and the camshaft 110, the pivot arm 150 has a tendency to move radially outward, which leads to the pivot arm 150 moving into the second position when the camshaft 110 operates at higher speeds.
[022] In an embodiment, the pivot arm 150 is configured to be in the first position if a rotation speed of the camshaft 110 is below a predetermined rotation speed, and to be in the second position if the rotation speed of the camshaft 110 is higher than the predetermined rotation speed. In an embodiment, the predetermined rotation speed of the camshaft 110 corresponds to the conventional rotation speed of the camshaft 110 at which the engine 100 starts.
[023] As further illustrated in Figure 6 and Figure 7, the internal combustion engine 100 has a second pin 160. The second pin 160 is movably provided in a radial slot 112 provided on the camshaft 110. In that, the second pin 160 is operably connected to the first shaft 130, wherein when the pivot arm 150 is in the first position, the first shaft 130 pushes the second pin 160 thereby operating an exhaust valve 116 during the starting of the engine 100. Thus, when the engine 100 is starting, the pivot arm 150 is in the first position, and the first shaft 130 pushes the second pin 160 outwardly of the radial slot 112, thereby rotation of the camshaft 110 leads to operating of the exhaust valve 116 during the starting of the engine 100. Since, the exhaust valve 116 is being operated and kept open for a longer duration during the starting of the engine 100, this leads to the compression pressure of air fuel-mixture being built up inside a combustion chamber (not shown) of the internal combustion engine 100 to be released, thereby providing a decompressing means during the starting of the engine 100. This leads to lower starting resistance of the internal combustion engine 100, which leads to lower kick force required or lower torque requirement of a starter motor for starting the internal combustion engine 100. In an embodiment, the second pin 116 is configured to push a cam rocker 118 (shown in Figure 2) which in turn causes the translational movement of the exhaust valve 116.
[024] Once the engine 100 has started, and camshaft 110 is rotating at sufficiently high speeds, the exhaust valve 116 needs to be operated normally, i.e. the second pin 160 is required to be disengaged with the exhaust valve 116 to prevent any unnecessary leakage of compression pressure. As explained hereinbefore, when the camshaft 110 is rotating at higher speeds, due to the centrifugal force experienced by the pivot arm 150 due to rotation of the cam sprocket 120 and the camshaft 110, the pivot arm 150 moves into the second position. Herein, when the pivot arm 150 is in the second position, the pivotal movement of the pivot arm 150 from the first position to the second position cause the first pin 140 to move, thereby rotating the first shaft 130. When the first shaft 130 is thus rotated, the second pin 160 engages with the depression portion 132 on the first shaft 130 thereby moving inside the radial slot 112 and disengaging with the exhaust valve 116. Thus, when the pivot arm 150 is in the second position, the second pin 160 is disengaged with the exhaust valve 116 and the exhaust valve 116 is operated only by the exhaust cam lobe 114 of the camshaft 110.
[025] In the embodiment depicted in Figure 6, the radial slot 112 of the camshaft 110 extends at an inclination with a central axis (X-X’) of the camshaft 110. The inclination of the radial slot 112 and movement of the second pin 160 along the inclined radial slot 112 allows for a higher surface area of contact between the second pin 160 and the cam rocker 118, thereby providing improved operation of the cam rocker 118 and thereby the exhaust valve 116, which reduces the delay in response of the exhaust valve 116 to the movement of the second pin 160. In an embodiment, the inclination of the radial slot 112 with the central axis (X-X’) of the camshaft 110 ranges between 25 to 45 degrees.
[026] Further, in an embodiment, the internal combustion engine 100 comprises a compression spring 180 provided in the radial slot 112. The compression spring 180 is configured to retain the second pin 160 in the radial slot 112 when the pivot arm 150 is in the second position, and the second pin 160 is engaged with the depression portion 132 in the first shaft 130. Thus, the provision of the compression spring 180 ensures that when the second pin 160 slides inside the radial slot 112 when the camshaft 110 is at high speeds, the second pin 160 remains inside the radial slot 112 by balancing the centrifugal forces experienced by the second pin 160. This prevents accidental sliding out of the second pin 160 and ensures that the second pin 160 does not engage with the cam rocker 118 once the pivot arm 150 is in the second position, even when the camshaft 110 is rotating at very high speeds. In an embodiment,
[027] As further illustrated in the embodiment depicted in Figure 6, the second pin 160 comprises an inner end 160A and an outer end 160B. Herein, the inner end 160A of the second pin 160 is in contact with the first shaft 130 and the outer end 160B configured to operate the exhaust valve 116. In that, the inner end 160A has a partially slanted profile. The partially slanted profile of the inner end 160A of the second pin 160 allows the second pin 160 to smoothly engage and disengage with the depression portion 132. Further, the outer end 160B of the second pin 160 has a curved profile. The outer end 160B having the curved profile further increases the contact surface area between the second pin 160 and the cam rocker 118, while also ensuring that lower friction levels.
[028] In a further embodiment, as illustrated in Figure 7, the internal combustion engine 100 comprises a supporting member 170. The supporting member 170 is configured for attaching the camshaft 110 to the cam sprocket 120. Further, for allowing the pivotal movement of the pivot arm 150 between the first position and the second position, the internal combustion engine 100 has a supporting flange 172. The supporting flange 172 is attached to the supporting member 170, and the supporting flange 172 pivotably supports the pivot arm 150. Further for ensuring that the pivot arm 150 moves only between the first position and the second position, the internal combustion engine 100 comprises a torsional spring 176. The torsional spring 176 is provided between the supporting flange 172 and the pivot arm 150. The torsional spring 176 configured to restrict the movement of the pivot arm 150 beyond the first position in a first rotation direction. The torsional spring 176 is preloaded in a manner that any rotational motion of the pivot arm 150 in the first rotation direction beyond the first position is restricted due to the torsion force applied by the torsional spring 176 on the pivot arm 150.
[029] Further, the internal combustion engine 100 comprises a stopper pin 178. The stopper pin 178 is attached to the cam sprocket 120. The stopper pin 178 is configured to restrict the movement of the pivot arm 150 beyond the second position in a second rotation direction. Thus, at high camshaft 110 rotation speeds, once the pivot arm 150 moves to the second position, provision of the stopper pin 178 ensures that the pivot arm 150 comes in contact with the stopper pin 178, which restricts any further movement of the pivot arm 150 beyond the second position irrespective of the further increase in speed of the camshaft 110.
[030] In a further embodiment, as illustrated in Figure 7 and referenced in Figure 3, the second pin 160 extends inside the radial slot 112 in a radially opposite direction to a protruding portion 114A of the exhaust cam lobe 114. Such a disposition ensures that both the protruding portion 114A of the exhaust cam lobe 114 as well as the second pin 160 alternately operate the exhaust valve 116 during the starting of the engine 100, thus achieving maximum decompression by allowing the exhaust valve 116 to stay open for longer and ensuring that a large amount of air-fuel mixture escapes the combustion chamber during the starting of the engine 100.
[031] Advantageously, the present invention provides an internal combustion engine in which the provision of the pivot arm, the first pin, the first shaft and the second pin allow for air fuel mixture to be released from the combustion chamber of the engine during the starting of the engine, thus providing a decompression system which reduces the kick force or starting torque required to start the engine. Further, the present invention also ensures that the second pin is disengaged with the exhaust valve once the engine is started thus preventing any unnecessary leakage of combustion gases from the combustion chamber.
[032] Further, the present invention provides decompression using a compact and non-complex system which ensures that engine dimensions do not need to be increased to accommodate a decompression configuration. The provision of the first shaft within the axial hollow cavity of the camshaft also ensures further compactness, and allows for the internal combustion engine of the present assembly to be used in integral type cylinder heads (wherein cylinder head is a part of cylinder body itself). Further, the present invention ensures that a decompression configuration can be provided in engines with a single exhaust valve and a single intake valve, and thus the requirement of provision of three separate valves is eliminated.
[033] Furthermore, the present invention ensures that the contact area between the second pin and the cam rocker is high, which not only reduces delay in response of the exhaust valve, but also reduces contact stress on the second pin as well as the cam rocker.
[034] 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.

List of Reference Numerals
12: Cylinder head
100: Internal Combustion Engine
110: Camshaft
112: Radial Slot
114: Exhaust Cam Lobe
114A: Protruding Portion of the Exhaust Cam Lobe
116: Exhaust Valve
118: Cam Rocker
120: Cam Sprocket
130: First Shaft
132: Depression Portion
140: First Pin
150: Pivot Arm
152: Slot
160: Second Pin
160A: Inner End of the Second Pin
160B: Outer End of the Second Pin
170: Supporting Member
172: Supporting Flange
176: Torsional Spring
178: Stopper Pin
180: Compression Spring , Claims:WE CLAIM:
1. An internal combustion engine (100), comprising:
a camshaft (110), the camshaft (110) provided in a cylinder head (12) of the internal combustion engine (100), the camshaft (110) having an axial hollow cavity;
a cam sprocket (120), the cam sprocket (120) being connected to the camshaft (110) for driving the camshaft (110);
a first shaft (130), the first shaft (130) being disposed in the axial hollow cavity of the camshaft (110), the first shaft (130) having a depression portion (132);
a first pin (140), the first pin (140) rigidly connected to the first shaft (130) and configured to rotate the first shaft (130);
a pivot arm (150), the pivot arm (150) mounted on the cam sprocket (120) and being configured to move pivotally between a first position and a second position based on a rotation speed of the camshaft (110), the pivot arm (150) having a slot (152), the slot (152) being configured to engage with the first pin (140) wherein the pivotal movement of the pivot arm (150) causes the first pin (140) to move, thereby rotating the first shaft (130); and
a second pin (160), the second pin (160) being movably provided in a radial slot (112) provided on the camshaft (110), the second pin (160) operably connected to the first shaft (130), wherein when the pivot arm (150) is in the first position, the first shaft (130) pushes the second pin (160) thereby operating an exhaust valve (116), and when the pivot arm (150) is in the second position, the second pin (160) engages with the depression portion (132) on the first shaft (130) thereby moving inside the radial slot (112) and disengaging with the exhaust valve (116).

2. The internal combustion engine (100) as claimed in claim 1, wherein the radial slot (112) of the camshaft (110) extends at an inclination with a central axis (X-X’) of the camshaft (110).

3. The internal combustion engine (100) as claimed in claim 1, wherein the second pin (160) comprises an inner end (160A) and an outer end (160B), the inner end (160A) being in contact with the first shaft (130) and the outer end (160B) configured to operate the exhaust valve (116), the inner end (160A) having a partially slanted profile and the outer end (160B) having a curved profile.

4. The internal combustion engine (100) as claimed in claim 1, comprising a supporting member (170), the supporting member (170) being configured for attaching the camshaft (110) to the cam sprocket (120).

5. The internal combustion engine (100) as claimed in claim 4, comprising a supporting flange (172), the supporting flange (172) being attached to the supporting member (170), and the supporting flange (172) pivotably supporting the pivot arm (150).

6. The internal combustion engine (100) as claimed in claim 5, comprising a torsional spring (176) provided between the supporting flange (172) and the pivot arm (150), the torsional spring (176) configured to restrict the movement of the pivot arm (150) beyond the first position in a first rotation direction.

7. The internal combustion engine (100) as claimed in claim 1, comprising a stopper pin (178) attached to the cam sprocket (120), the stopper pin (178) configured to restrict the movement of the pivot arm (150) beyond the second position in a second rotation direction.

8. The internal combustion engine (100) as claimed in claim 1, comprising a compression spring (180) provided in the radial slot (112), the compression spring (180) being configured to retain the second pin (160) in the radial slot (112) when the pivot arm (150) is in the second position.

9. The internal combustion engine (100) as claimed in claim 1, wherein the pivot arm (150) is configured to be in the first position if a rotation speed of the camshaft (110) is below a predetermined rotation speed, and to be in the second position if the rotation speed of the camshaft (110) is higher than the predetermined rotation speed.

10. The internal combustion engine (100) as claimed in claim 1, wherein the second pin (160) extends in a radially opposite direction to a protruding portion (114A) of an exhaust cam lobe (114).

Dated this 11th day of March 2024

TVS MOTOR COMPANY LIMITED
By their Agent & Attorney

(Nikhil Ranjan)
of Khaitan & Co
Reg No IN/PA-1471