WO2018025191A1

WO2018025191A1 - Exhaust gas recirculation system for an internal combustion engine

Info

Publication number: WO2018025191A1
Application number: PCT/IB2017/054714
Authority: WO
Inventors: Thiruvallur LOGANATHAN BALASUBRAMANIAN; Varadha IYENGAR LAKSHMINARASIMHAN
Original assignee: Tvs Motor Company Limited
Priority date: 2016-08-03
Filing date: 2017-08-02
Publication date: 2018-02-08

Abstract

The present invention relates to an internal combustion engine (5) comprising of a camshaft (35). The camshaft (35) comprises of an elevated portion (62, 102) formed on either one of an EGR lobe (55) and an EGR pin (91). The EGR lobe (55) or the EGR pin (91) rotates along an arm (56) mounted over the camshaft (35). The further rotation of the EGR lobe (55) or the EGR pin (91) causes the lifting portion (62, 102) to come in contact with the exhaust side roller (43) and exhaust side arm (45), which further causes the lifting portion (62, 102) to lift the exhaust side roller (43) and the exhaust side arm (45) resulting in an opening of the exhaust valve (33). The opening of the exhaust valve (33) and the inlet valve (34) are overlapped for an efficient exhaust gas recirculation.

Description

EXHAUST GAS RECIRCULATION SYSTEM FOR AN INTERNAL

COMBUSTION ENGINE

FIELD OF INVENTION 001] The present invention relates to an internal combustion engine and more particularly to an exhaust gas recirculation system to reduce NOx from exhaust gases produced from the internal combustion engine.

BACKGROUND OF INVENTION

[0001] Generally, an internal combustion engine is functionally connected to a rear wheel of a vehicle to provide a forward motion to it. The internal combustion engine comprises of a cylinder bore where the combustion occurs to provide the needed power for the forward motion of the vehicle. The internal combustion (IC) engine, among other components, has a cylinder on top of which a cylinder head is mounted, and receives a reciprocating piston from the bottom. On combustion of the air-fuel mixture, the piston transfers the energy generated during combustion to a crankshaft through a connecting rod thereby driving the crankshaft. In this way, the reciprocatory motion of the piston is converted to rotary motion of the crankshaft. The crankshaft rotation then in turn powers the vehicle.

[0002] However, there are exhaust gases generated due to the combustion process occurring in the internal combustion engine. The exhaust gas generated after the combustion in internal combustion engine is actually a combination of different gases like N₂, C0₂, CO, H₂0, NO, and N0₂ etc. Most of the gases generated like NO, and N0₂ (combined called as NOx) are harmful and are considered as major pollutants. The exhaust gases generated leave the internal combustion engine through an exhaust port disposed on the cylinder head. An exhaust pipe is connected to the exhaust port, which carries the exhaust from the internal combustion, transferring it to the muffler region from where it is finally released into the atmosphere. Various mechanisms and devices are incorporated for treating of exhaust gases. One such element used is the catalytic converter which tries oxidizing the exhaust gases to convert it into harmless gasses. Another such mechanism is exhaust gas recirculation (EGR) which tries reducing the production of NOx (NO, and N0₂) during combustion of fuel air mixture.

[0003] Various mechanisms for EGR to reduce the NOx in the exhaust gases are already known. One of the existing technologies utilizes secondary air injection (SAI), optimized catalytic converter for treating exhaust gases coming out of the combustion chamber. This particular method of injecting secondary air can though decrease the CO component, but above mentioned configuration leads to high NOx emission. In one of the other known process EGR works by recirculation a portion of exhaust gasses generated by the internal combustion engine back to its cylinder. This dilutes the 02 in the incoming air stream and provides gases inert to combustion to act as absorbents of combustion heat to reduce peak in-cylinder temperatures. In yet another known process, spark timing optimization with optimized EGR flow rates is used to reduce NOx while maintaining fuel consumption at a pre-determined level.

[0004] All the above mentioned known mechanisms require an extra element to be added in the system which makes the whole arrangement bulky, complicated and prone to more failure modes. As explained above, implementation of any known processes, be it SAI, spark timing optimization or optimized catalytic converters either make the system bulky and complicated or increase the probability of greater failure modes. All the above said technologies require loads of maintenance as well. None of the above said technology suggests an easy and simple way of implementation of the EGR mechanism which is not bulky or complicated. There is no known art in which even after the addition of an extra element the chances of failures do not increase. Nor is there a known art which completely eliminates the need of extra elements which are to be added in the system. [0005] Furthermore, all the above methods of exhaust gas recirculation require an external tapping of exhaust gas and a flow path for introducing this tapped exhaust gas back to the cylinder of the engine. This further adds to the manufacturing cost and introduces many failure points due to extra elements added to achieve the objective. Hence, there is a requirement for introducing exhaust gases into engine cylinder to reduce NOx which is simple, eliminates the requirement of extra parts or uses lesser number of external parts without making the system complicated and is cost effective as well. BRIEF DESCRIPTION OF DRAWINGS

[0006] The detailed description of the present subject matter is described with reference to the accompanying figures. Same numbers are used throughout the drawings to reference like features and components.

[0007] Figure 1 illustrates a right side view of an exemplary two-wheeled vehicle, in accordance with an embodiment of the present subject matter.

[0008] Figure 2 illustrates a plain enlarged view of right side of a cylinder head of the internal combustion engine of the exemplary two-wheeled vehicle in accordance with an embodiment of the present subject matter.

[0009] Figure 3 illustrates a cross sectional view of the right side of the cylinder block of the internal combustion engine in accordance with an embodiment of the present subject matter.

[00010] Figure 4 illustrates a cross sectional view of the cylinder head of the internal combustion engine in accordance with an embodiment of the present subject matter. [00011] Figure 5 illustrates an isometric top view of the camshaft of the internal combustion engine in accordance with an embodiment of the present subject matter.

[00012] Figure 6 illustrates an isometric top view the additional EGR lobe used in the camshaft of the internal combustion engine in accordance with an embodiment of the present subject matter. [00013] Figure 7 illustrates a side view of the camshaft of the internal combustion engine in an active state of the EGR mechanism in accordance with an embodiment of the present subject matter.

[00014] Figure 8 illustrates a side of the camshaft of the internal combustion engine in an inactive state of the EGR mechanism in accordance with an embodiment of the present subject matter.

[00015] Figure 9 illustrates a perspective view of the camshaft before cranking of the internal combustion engine in accordance with an embodiment of the present subject matter. [00016] Figure 10 illustrates a perspective view of the camshaft after cranking of the internal combustion engine in accordance with an embodiment of the present subject matter.

[00017] Figure 11 illustrates a graph for the instances of intake valve opening and exhaust valve opening during the decompression operation of the internal combustion engine.

[00018] Figure 12 illustrates a graph for the instances of intake valve opening and exhaust valve opening during the EGR operation of the internal combustion engine in accordance with an embodiment of the present subject matter.

DETAILED DESCRIPTION [00019] Generally, the internal combustion engine is the power unit of the vehicle enabled to provide the required drive. Typically, the internal combustion engine is coupled to the drive wheel, which is generally the rear wheel. Mostly, the internal combustion engine comprises of a cylinder bore where the combustion occurs to provide the needed power for the forward motion of the vehicle. The internal combustion (IC) engine, among other components, comprises of a cylinder on top of which a cylinder head is mounted. The cylinder head is mounted to accommodate and receive the to-and- fro motion of the piston reciprocating from the bottom in an upward direction. On combustion of the air-fuel mixture, the piston transfers the energy generated during combustion to a crankshaft through a connecting rod thereby driving the crankshaft. In this way, the reciprocatory motion of the piston is converted to rotary motion of the crankshaft which in turn powers the vehicle.

[00020] However, the combustion process of the internal combustion engine leads to generation of exhaust gases. The exhaust gas generated after the combustion in internal combustion engine is actually a combination of different gases like N₂, C0₂, CO, H₂0, NO, and N0₂ etc. Most of the gases generated like NO, and N0₂ (combined called as NOx) are harmful and are considered as major pollutants. The exhaust gases generated leave the internal combustion engine through an exhaust port disposed on the cylinder head. An exhaust pipe is connected to the exhaust port, which carries the exhaust from the internal combustion transferring it to the muffler region from where it is finally released into the atmosphere. Various mechanisms and devices are incorporated for treating of exhaust gases. One such element used is the catalytic converter which tries oxidizing the exhaust gases to convert it into harmless gasses. Another such mechanism is exhaust gas recirculation (EGR) which tries reducing the production of NOx (NO, and N0₂) during combustion of fuel air mixture.

[00021] Various mechanisms for EGR to reduce the NOx in the exhaust gases are already known. One of the existing technologies utilizes secondary air injection (SAI), optimized catalytic converter for treating exhaust gases coming out of the combustion chamber. This particular method of injecting secondary air can though decrease the CO component, but above mentioned configuration leads to high NOx emission. In one of the other known process EGR works by recirculation a portion of exhaust gasses generated by the internal combustion engine back to its cylinder. This dilutes the 02 in the incoming air stream and provides gases inert to combustion to act as absorbents of combustion heat to reduce peak in-cylinder temperatures. In yet another known process, spark timing optimization with optimized EGR flow rates is used to reduce NOx while maintaining fuel consumption at a pre-determined level. 0022] All the above mentioned known mechanisms require an extra element to be added in the system which makes the whole arrangement bulky, complicated and prone to even more failure modes. As explained above, implementation of any known processes, be it SAI, spark timing optimization or optimized catalytic converters either make the system bulky and complicated or increase the probability of greater failure modes. All the above said technologies require loads of maintenance as well. None of the above said technology suggests an easy and simple way of implementation of the EGR mechanism which is not bulky or complicated. There is no known art in which even after the addition of an extra element the chances of failures do not increase. Nor is there a known art which completely eliminates the need of extra elements which are to be added in the system. The above described methods of exhaust gas recirculation require an external tapping of exhaust gas and a flow path for introducing this tapped exhaust gas back to the cylinder of the engine. This increases the number of elements being added to the internal combustion engine to achieve the objective. In furtherance to it, the manufacturing cost is increased and maintenance becomes tedious. The chances and number of failure points are also increased due to extra elements added to achieve the objective. Hence, there is a requirement for introducing exhaust gases into engine cylinder to reduce NOx which is simple, eliminated the requirement of extra parts or uses lesser number of external parts without making the system complicated and is cost effective as well.

[00023] Therefore, an objective of the present subject matter is to reduce the NOx being generated through an EGR mechanism. In addition to it there is a need of a system which is simple, uses less number of parts and is cost effective. According to one aspect of the invention a certain duration for which the exhaust port opens is overlapped with the opening of the intake port for a short duration. This overlapping of the intake port and exhaust port leads to the introduction of EGR inside the cylinder during intake cycle. Due to introduction of EGR into the cylinder during the intake cycle, the attainment of high temperature is controlled and therefore NOx formation is reduced. Thus, the present subject matter provides an EGR mechanism which is simple, cost effective and does not requires lot of extra elements to be added to the internal combustion engine.

[00024] In an embodiment, an internal combustion engine comprises of a cylinder block to accommodate the reciprocatory of the piston. The internal combustion (IC) engine, among other components, comprises of a cylinder head mounted over the cylinder block. The cylinder head is mounted to accommodate and receive the to-and-fro motion of the piston reciprocating from the bottom in an upward direction. They cylinder head allows the combustion to occur, hence is also termed as combustion chamber. On combustion of the air-fuel mixture, the piston transfers the energy generated during combustion to a crankshaft through a connecting rod thereby driving the crankshaft. In this way, the reciprocatory motion of the piston is converted to rotary motion of the crankshaft which in turn powers the vehicle.

[00025] In an embodiment, the internal combustion engine comprises of an inlet port and an exhaust port formed in the cylinder head through which air fuel mixture is sent in and after combustion the exhaust is sent out. The internal combustion engine comprises of an inlet valve and exhaust valve to control the opening and closing of the passage of the exhaust port and inlet port. The opening and closing of the exhaust valve and the inlet valve is based on the kind of stroke occurring in the engine, whether it is an intake stroke, compression stoke or a power stroke. In an embodiment, the exhaust vale and inlet valve are actuated by a rocker arm. The actuation of the rocker arms is controlled by lobes mounted over a camshaft which is driven by the crankshaft through a timing chain and driving and driven sprockets. Such engines are provided with one spark plug which forms an integral part of the internal combustion engine and develops a spark. The spark developed in the combustion chamber of the internal combustion engine ignites the air-fuel mixture and develops the required power.

[00026] The air fuel mixture commonly referred to as 'charge' is in the compressed condition at the near end of the compression stroke. This charge is in swirling and tumbling motion inside the combustion chamber so that when the spark produced by the spark plug ignites the charge, power is developed. Due to the swirling and tumbling motion, the flame inside the combustion chamber propagates in a desired manner and the peak of the developed power occurs at an instant as required by the design. In order to achieve optimum performance, the location of spark plug tip, velocity of the charge, the direction of swirl and tumble are some of the important parameters.

[00027] In an embodiment, the internal combustion engine cycle begins with the intake stroke as the piston is pulled towards the crankshaft. In intake stroke, the inlet valve is open, through which air-fuel mixture is drawn past the valve into the combustion chamber through the inlet port located on top of the combustion chamber. For the intake stroke the exhaust valve is closed and the electrical contact switch is open and the air-fuel mixture is at a relatively low pressure (near atmospheric). At the end of the intake stroke, the piston is located at the BDC and begins to move back towards the TDC. The cylinder and combustion chamber are full of the low pressure air-fuel mixture and, as the piston begins to move to the TDC, the intake valve closes. The opening and closing of the intake valve relies on the slightly lower pressure within in the cylinder during the intake stroke to overcome the strength of the spring holding the valve shut. Modern internal combustion engines use cams and rocker arms for opening and closing of the exhaust valve and inlet valve, since cams and rocker arms provide better control and timing of the opening and closing of the valves. [00028] In furtherance to it, next is a compression stroke in which with both the inlet valve and exhaust valve are closed and the cylinder and combustion chamber form a completely closed vessel and contain the fuel/air mixture. As the piston is pushed to the TDC, the volume is reduced and the air-fuel mixture is compressed during the compression stroke. However, no heat is transferred to the air-fuel mixture during the compression stroke. As the volume is decreased because of the piston's motion, the pressure in the gas is increased, as described by the laws of thermodynamics. During the compression stroke, the electrical contact for spark plug is kept open. [00029] After the compression stroke come a power stroke, in which the electrical contact is opened. When the volume is the smallest, and the pressure the highest, the contact is closed, and a current of electricity flows through the spark plug. The sudden closing of the contact produces a spark in the combustion chamber which ignites the air- fuel mixture. Rapid combustion of the fuel releases heat, and produces exhaust gases in the combustion chamber. Because the inlet and exhaust valves are closed, the combustion of the fuel takes place in a totally enclosed (and nearly constant volume) vessel. The combustion increases the temperature of the exhaust gases, any residual air in the combustion chamber, and the combustion chamber itself. From the ideal gas law, the increased temperature of the gases also produces an increased pressure in the combustion chamber. The high pressure of the gases acting on the face of the piston causes the piston to move to the BDC which initiates the power stroke. Unlike the compression stroke, the hot gas does work on the piston during the power stroke. The force on the piston is transmitted by the piston rod to the crankshaft, where the linear motion of the piston is converted to rotational motion of the crankshaft. The work done on the piston is then used to turn a crankshaft in cylinder's compression stroke. Having produced the igniting spark, the electrical contact remains closed. During the power stroke, the volume occupied by the gases is increased because of the piston motion and no heat is transferred to the air-fuel mixture. As the volume is increased because of the piston's motion, the pressure and temperature of the gas are decreased.

[00030] Lastly, is an exhaust stroke which comes at the end of the power stroke and the piston is located at the far BDC. The exhaust valve is then opened by the cam pushing on the rocker arm to begin the exhaust stroke. The purpose of the exhaust stroke is to clear the cylinder of the spent exhaust in preparation for another intake/ignition cycle. As the exhaust stroke begins, the cylinder and combustion chamber are full of exhaust products at low pressure. Because the exhaust valve is open, the exhaust gas is pushed past the valve and exits the engine. The inlet valve is closed and the electrical contact is open during this movement of the piston. [00031] Generally, the cylinder block accommodates the piston with its reciprocatory motion, such that the motion of the piston is converted into rotational motion of the crankshaft. In an embodiment, the cylinder head is disposed above the cylinder block to allow the combustion to happen. As explained above, the cylinder block also comprises of exhaust port and inlet port through which the exhaust leaves and the air-fuel mixture enters into the internal combustion engine. The cylinder head is provided with exhaust valve and inlet valves which control the opening and closing of the exhaust port and inlet port. In furtherance to it, the cylinder head also comprises of a camshaft, wherein the crankshaft and camshaft extend parallel to each other, and the axis of rotation for the camshaft and crankshaft is similar to each other. The camshaft comprises of an exhaust lobe and inlet lobe disposed on it, which help in the opening and closing of the exhaust valve and the inlet valve. A rocker arm and roller arrangement is provided for the opening and closing of the exhaust valve and inlet valve, wherein the rocker and roller arm is in connection with the exhaust lobe and the inlet lobe, such that the rotation of the lobes helps in rotation of the roller and movement of the rocker arm resulting in opening and closing of the valves.

[00032] An exhaust side roller is in connection with the exhaust lobe and an inlet side roller is in connection with the inlet lobe. The exhaust lobe and inlet lobe rotate and move along the axis of the rotation of the camshaft. This is in turn results into the rotation of the exhaust side roller and inlet side roller, which in turn are connected to an exhaust side arm and an inlet side arm. The exhaust side arm and inlet side arm are connected to the exhaust valve and the inlet valve, such that with the rotation of the exhaust side roller and inlet side roller the exhaust side arm and inlet side arm also move resulting in movement of the exhaust valve and inlet valve. Thus, the movement of the exhaust valve and inlet valve results in opening and closing of the exhaust port and inlet port depending upon the type of stroke the internal combustion engine is going through.

[00033] Mostly, the internal combustion engine is also enabled with an auto decompression mechanism which enables the pressure to be released from the engine when it is about to be cranked. However, as per the present subject matter, the timing of opening of the exhaust valve and inlet valve is to be matched for a certain short duration for introduction of EGR. In this method of introducing EGR into the internal combustion engine, an additional EGR lobe is added onto the camshaft beside the exhaust lobe. Both the lobes have a flat portion and a lifting portion. The flat portion doesnDt interfere in the valve opening whereas the lifting portion of the lobes lifts the roller and opens the exhaust port. During cranking, lifting portion of the exhaust lobe protrudes out of the regular peripheral profile of the arm. Once engine has cranked, this lifting portion hides and a flat portion surfaces which has no protrusion above the regular peripheral profile.

[00034] During EGR, the additional roller termed as EGR roller, becomes active. Before cranking of engine, when EGR is not desired, the flat portion of the EGR roller surfaces along the peripheral profile of the arm. When EGR is desired, the lifting portion of the EGR roller surfaces outside the peripheral profile of the arm to open the exhaust valve only after the first speed of the internal combustion engine is more than the idling speed, wherein the first speed lies in a range of 1000-1500 rpm. [00035] Hence, according to the present invention, an internal exhaust gas recirculation is used to reduce NOx emissions and is achieved by opening exhaust valve for small duration during suction stroke or by having a predetermined overlap between the above intake stroke and exhaust stroke. According to one embodiment of the present invention, the opening of exhaust valve for small duration during suction stroke is achieved by including a separate EGR lobe on the cam shaft. Thus the present subject matter is simple, cost effective and nor does increases the probability of failure modes and extra maintenance.

[00036] According to the second embodiment of the present invention, the opening of exhaust valve for small duration during suction stroke is achieved by using an additional EGR pin comprising of a lifting portion used to life the exhaust valve. In an embodiment, the auto decompression mechanism within a camshaft assembly is modified to allow exhaust gas flow inside the internal combustion engine after decompression has taken place and engine has cranked. Generally, the arm comprises of a decompression pin which helps in the decompression mechanism. Whereas, as per the present subject matter, a second pin is added onto the arm for EGR. Hence, one decompression pin is used for decompression and other EGR pin is used for exhaust gas recirculation. The pins are further located in such a way that decompression pin is activated before cranking of the engine and the internal EGR cam pin is activated after the first speed of the internal combustion engine is more than the idling speed, wherein the first speed lies in a range of 1000-1500 rpm. During starting of an engine, internal EGR cam pin is inactive and only decompression pin is active, when the speed is less than the first speed. At higher speeds when the engine has cranked, EGR cam pin is active and decompression cam pin becomes inactive.

[00037] In an embodiment, the arm mounted over the cam shaft comprises of a first relief to accommodate a decompression pin to help in the decompression mechanism when the engine is about to be cranked. The decompression pin comprises of a decompression support arm formed perpendicularly at its top which moves with the arm and helps in rotation of the decompression pin rotate. The decompression pin is located in a first relief formed in the arm such that the decompression pin moves along the arm and after a while the first relief itself blocks the further rotation of the arm through the decompression support arm. The decompression pin explained above comprises of a partial cylindrical portion and a partial plain portion. The cylindrical portion functions as the lifting portion which is used to life the rocker side roller. Hence, the exhaust side roller moves along the periphery of the decompression pin and gets lifted by the lifting portion of the decompression pin to allow the decompression mechanism to happen, and gets back to its original position when the plain surface of the decompression pin is in action. In another embodiment, the second relief is accommodated with another separate pin also termed as EGR pin. The EGR pin comprises of a partial cylindrical surface which acts as the elevated portion, whereas the remaining partial surface is a plain surface. When the internal combustion engine reaches the idling speed, the spring connecting the arm and the camshaft experiences a centrifugal force due to which the arm also experiences an outward centrifugal force resulting in the movement of the arm. As the arm rotates, so does the EGR pin with it, and with that rotation the cylindrical shaped lifting portion comes into action resulting in the lifting of the exhaust side roller arm which is in partial connection with the exhaust lobe and the EGR pin. The lifting of the exhaust side roller arm results in the movement of the exhaust side arm which in turn opens up the exhaust valve. In an embodiment, a divider is provided in the arm between the first relief and the second relief, so that the two arms do not interfere with each other and it also provides a surface to the arm for support so that the pins do not rotate more than what is required. The present figure shows the camshaft before cranking of the engine, when the cylindrical shaped lifting portion of the decompression pin is in action and the plain flat portion for the EGR pin is in action. [00038] In an embodiment, the cylindrical shaped lifting portion of the EGR pin comes into action when the EGR mechanism is activated. It is only after the first speed of the internal combustion engine is more than the idling speed (first speed lies in a range of 1000-1500 rpm), then the arm experiences an outward centrifugal force because of the spring through which it is attached to camshaft, which in turn results in rotation of the arm. In an embodiment, the EGR pin rotates with the arm, such that the cylindrical shaped lifting portion is exposed and in contact with the exhaust side roller resulting in movement of the exhaust side arm and opening of the exhaust valve. In an embodiment, the EGR support arm formed on the EGR pin also moves along with it, however after a short duration it reaches and end of the second relief and rests there to keep the lifting portion in that position and keep the exhaust side roller to be lifted for that particular duration. During the duration when the exhaust side roller is lifted, the exhaust valve is also open for that certain duration overlapping with duration of inlet opening and allowing the EGR mechanism to take place.

[00039] Thus, the present subject matter provides an EGR mechanism for internal combustion engine to reduce the amount of NOx being produced. The EGR described above matter eliminated the need of extra parts to be added to the internal combustion engine. Thus, the present subject matter provides an advantage of being simple and cost effective. In addition to it, it also reduces the probability of failure points for the EGR mechanism and the internal combustion engine. [00040] The aforesaid and other advantages of the present subject matter would be described in greater detail in conjunction with the figures in the following description.

[00041] Arrows provided in the top right corner of each figure depicts direction with respect to the vehicle, wherein an arrow F denotes front direction, an arrow R indicated R direction, an arrow Up denotes upward direction, an arrow Dw denoted downward direction, an arrow Rh denotes right side, an arrow Lh denoted left side, as and where applicable.

[00042] Fig. 1 illustrates a right side view of an exemplary two-wheeled vehicle (10), in accordance with an embodiment of the present subject matter. The vehicle (10) includes a frame assembly (not shown) that extends from a head tube (not shown), which is disposed in the front portion of the vehicle (10). The frame assembly includes a mainframe (not shown) comprising a main tube extending rearward from a rear portion of the head tube and a down tube (not shown) that extends rearwardly downward from the head tube. The frame assembly may further comprise a sub-frame formed by a pair of rear tubes (not shown) that extend obliquely rearward from the main frame. An internal combustion engine (5) is supported by the main frame of the frame assembly. The internal combustion engine (5) acts as the power unit of the vehicle (10), wherein the power unit may also include a traction/electrical motor (not shown). A front portion of a swing arm assembly is swingably connected to the main frame of the frame assembly and rear portion of the swing arm assembly rotatably supports a rear wheel (3). The rear wheel (3) is functionally coupled to the internal combustion engine (5) through a transmission system. A rear fender (4) disposed upwardly of the rear wheel (3) covers at least a portion of the rear wheel (3). Further, the swing arm assembly is coupled to the frame assembly through one or more rear suspension(s). A pair of front forks (7) supports a front wheel (6) and is steerably supported by the head pipe. A handlebar assembly (1) is connected to an upper portion of the pair of front fork (7). Further, a front fender assembly (11) covers at least a portion of the front wheel (6) and the front fender assembly (11) is mounted to the front forks (7). [00043] A fuel tank (9) is mounted to the main tube of the frame assembly and disposed rearwardly of the handlebar assembly (1). A seat assembly (2) is disposed rearwardly of the fuel tank assembly (1) and supported by the pair of rear tubes. Further, the vehicle (10) comprises a visor assembly (12) that is disposed forwardly over the headlamp (8). A tail cover assembly (13) is disposed rearwardly of the side panel assembly (not shown) and extends along the pair of rear tubes thereby covering at least a portion of the pair of rear tubes. The tail cover assembly (13) extends towards a rear portion of the frame assembly and the tail cover assembly (13) is adapted to accommodate a pillion handle (14) attached to its side. [00044] Figure 2 illustrates a plain enlarged view of right side of a cylinder block (25) of the internal combustion engine (5) of the exemplary two- wheeled vehicle (10) in accordance with an embodiment of the present subject matter. Generally, the internal combustion engine (5) comprises of a cylinder block (25) which accommodates a reciprocating piston (shown in Fig. 3) and a cylinder head (24) where the combustion of the air-fuel mixture occurs. In furtherance to it, a carburetor (26) is also provided which supplies the air-fuel mixture to the internal combustion engine (5). The cylinder head (24) comprises of an inlet port (21) through which the air-fuel mixture enters the internal combustion engine (5) and an exhaust port (22) through which the exhaust generated after combustion leaves the internal combustion engine (5). An inlet pipe (23) connects the carburetor (26) and the inlet port (21) to form the intake system to supply the air-fuel mixture into the internal combustion engine (5). The exhaust generated after combustion of the air-fuel mixture leaves the internal combustion engine (5) through an exhaust pipe connected to the exhaust port (22) disposed on the cylinder head (24).

[00045] Figure 3 illustrates a cross sectional view of the right side of the cylinder block (25) of the internal combustion engine (5) in accordance with an embodiment of the present subject matter. In an embodiment, the cylinder block (25) accommodates the piston (31) with its reciprocatory motion, such that the motion of the piston (31) is converted into rotational motion of the crankshaft (32). In an embodiment, the cylinder head (24) is disposed above the cylinder block (25) to allow the combustion to happen. As explained above, the cylinder block (25) also comprises of exhaust port (22) and inlet port (21) through which the exhaust leaves and the air-fuel mixture enters into the internal combustion engine (5). The cylinder head (24) is provided with an exhaust valve (33) and inlet valve (34) which controls the opening and closing of the exhaust port (22) and inlet port (21). In furtherance to it, the cylinder head (24) also comprises of a camshaft (35), wherein the crankshaft (32) and camshaft (35) extend parallel to each other, and the axis of rotation for the camshaft (35) and crankshaft (32) is similar to each other. The camshaft (35) comprises of an exhaust lobe (shown in Fig. 4) and inlet lobe (shown in Fig. 4) disposed on it, which help in the opening and closing of the exhaust valve (33) and the inlet valve (34). A rocker arm and roller arrangement (shown in Fig. 4) is provided for the opening and closing of the exhaust valve (33) and inlet valve (34), wherein the rocker and roller arm is in connection with the exhaust lobe and the inlet lobe, such that the rotation of the lobes helps in rotation of the roller and movement of the rocker arm resulting in opening and closing of the valves (33, 34). [00046] Figure 4 illustrates a cross sectional view of the cylinder head (24) of the internal combustion engine (5) in accordance with an embodiment of the present subject matter. The camshaft (35) can be seen to be comprising of the exhaust lobe (41) and the inlet lobe (42). An exhaust side roller is in connection (43) with the exhaust lobe (41) and an inlet side roller (44) is in connection with the inlet lobe (42). The exhaust lobe (41) and inlet lobe (42) rotate and move along the axis of the rotation of the camshaft (35). This is in turn results into the rotation of the exhaust side roller (43) and inlet side roller (44), which in turn is connected to an exhaust side arm (45) and an inlet side arm (46). The exhaust side arm (45) and inlet side arm (46) are connected to the exhaust valve (33) and the inlet valve (34), such that with the rotation of the exhaust side roller (43) and inlet side roller (44) the exhaust side arm (45) and inlet side arm (45) also move resulting in movement of the exhaust valve (33) and inlet valve (34). Thus, the movement of the exhaust valve (33) and inlet valve (34) result in opening and closing of the exhaust port (22) and inlet port (21) depending upon the type of stroke the internal combustion engine is going through. [00047] Figure 5 illustrates an isometric top view of the camshaft (35) of the internal combustion engine (5) in accordance with an embodiment of the present subject matter. In an embodiment, the camshaft (35) comprises of an exhaust bearing (51) and an inlet bearing (52) placed on either sides of the camshaft (35). In furtherance to it, the camshaft (35) is provided with the exhaust lobe (41) and inlet lobe (42) which has an oval shaped profile with a plain portion and a lifting portion. The exhaust lobe (41) and inlet lobe (42) are disposed on the camshaft (35) between the exhaust bearing (51) and inlet bearing (52). The external side roller (43) and internal side roller (44) are mounted over the external lobe (41) and internal lobe (42). Therefore, the rollers (43, 44) rotate along the lobes (41, 42), and when the lifting portion comes the rollers (43, 44) also follow the same profile resulting in lifting of the exhaust side arm (45) and inlet side arm (46) which in turn lifts the exhaust valve (33) and inlet valve (34). Further, the camshaft (35) also comprises of the arm (56) disposed over it being connected by a spring (not shown). In an embodiment, an EGR lobe (55) is also provided over the camshaft (35) between the arm (56) and the exhaust lobe (41). The EGR lobe (55) provided on the camshaft (35) helps in introduction of EGR into the internal combustion (5) engine by enabling the opening of exhaust valve (33) for a short duration during the time when the inlet valve (34) is also open. The arm (56) provided over the camshaft (35) comprises of an arm pin (shown in Fig. 7) connecting the EGR lobe (55) and the arm (56). Moreover, the arm (56) is connected to the camshaft (35) through a spring which experiences a centrifugal force along with the rotation of the camshaft (35). It further results in the arm (56) also experiencing an outward centrifugal force which leads to an outward movement of the arm pin. Thus, the EGR lobe (55) connected to the arm (56) also moves and the lifting portion (shown in Fig. 6) of the EGR lobe (55) protrudes out. The end portion of the exhaust side rocker arm (45) gets in touch with the lifting portion of the EGR lobe (55) and is lifted in an upward direction resulting in an opening of the exhaust valve (33) for a short duration at the same time when the inlet valve (34) is opened. In an embodiment, the camshaft (35) and arm (56) have been connected in such a fashion that the spring described above experiences a substantial force only after the internal combustion engine (5) has crossed at least a first speed to be more than the idling speed. Therefore, as per the present subject matter the EGR lobe (55) comes into action and moves only after the first speed of the internal combustion engine is more than the idling speed, wherein the first speed lies in a range of 1000-1500 rpm.

[00048] Figure 6 illustrates an isometric top view the additional EGR lobe (55) mounted over the camshaft (35) of the internal combustion engine (5) in accordance with an embodiment of the present subject matter. In an embodiment, the EGR lobe (55) is a substantial oval shaped structure comprising of a flat portion and a lifting portion (62). When the EGR lobe (55) is rotated along with the arm (56) the lifting portion (62) comes into contact with an end of the exhaust side arm (45) to lift it so that the exhaust valve (33) is also lifted. In an embodiment, the EGR lobe (55) is provided with an opening (61) which accommodates the arm pin (shown in Fig. 7) such that the outward motion of the arm (56) is transferred to the EGR lobe (55) and it also follows the same profile to lift the exhaust side arm (45).

[00049] Figure 7 illustrates a side view of the camshaft (35) of the internal combustion engine (5) in an active state of the EGR mechanism in accordance with an embodiment of the present subject matter. In an embodiment, the arm (56) can be seen to be mounted over the camshaft (35) through a spring (not shown). The arm comprises of an arm pin (72) which connects the arm (56) and EGR lobe (55). In an embodiment, the present scenario depicts the camshaft (35) in an active state of EGR. The spring through which the arm (56) is connected to the camshaft (35) is under maximum centrifugal force due to which the arm (56) also experiences that force in an outwardly direction. Due to force experienced by the arm (56) it moves resulting in movement of the arm pin (72) also in an outward direction. Since, the arm pin (72) is connected to the EGR lobe (55), it also results in the movement of the EGR lobe (55) and the lifting portion (62) comes up to come in contact with the end of the exhaust side arm (45) to lift it, resulting in the lifting of the exhaust valve (33) as well. Therefore, as the present embodiment, the lifting portion (62) can be seen to be protruding outwards, so that it can come in contact with an end of the exhaust side arm (45) and lift it. In an embodiment, it is only after the internal combustion engine has crossed at least a first speed to be more than the idling speed when the spring experiences a substantial amount of force to move the arm (56) along with EGR lobe (55). Therefore, an active state of EGR achieved by protruding of the lifting portion (62) of the EGR lobe (55) is enabled after the first speed of the internal combustion engine is more than the idling speed, wherein the first speed lies in a range of 1000-1500 rpm.

[00050] Figure 8 illustrates a side of the camshaft (35) of the internal combustion engine (5) in an inactive state of the EGR mechanism in accordance with an embodiment of the present subject matter. As explained above, the present subject matter comprises of a camshaft (35) on which the arm (56) is mounted. The camshaft (35) also comprises of the external lobe (41), internal lobe (42) and the EGR lobe (55) mounted on it. In an embodiment, the EGR lobe (55) is connected to the arm (56) through an arm pin (72) formed on the arm (56). As per the present subject matter, the spring which connects the arm (56) and the camshaft (35) is under no centrifugal force. Thus, the arm (56) also does not experiences any force resulting in no movement of arm pin (72) or the EGR lobe (55) connected to it. Therefore, the EGR lobe (55) remains mounted as it is and the lifting portion (62) does not protrudes out to lift the exhaust side arm (45). Hence, the EGR is not in an active state and the exhaust valve (33) does not opens for a short duration when the inlet valve (34) is also open, allowing the EGR mechanism to occur. [00051] Figure 9 illustrates a perspective view of the camshaft (35) before cranking of the internal combustion engine (5) in accordance with an embodiment of the present subject matter. In an embodiment, the arm (56) mounted over the cam shaft (35) comprises of a first relief (93) to accommodate a decompression pin (90) to help in the decompression mechanism when the engine (5) is about to be cranked. The decompression pin (90) comprises of a decompression support arm (96) formed perpendicularly at its top which moves with the arm and helps in rotation of the decompression pin (90) rotate. The decompression pin (90) is located in a first relief formed in the arm (56) such that the decompression pin (90) moves along the arm (56) and after a while the first relief (93) itself blocks the further rotation of the arm through the decompression support arm (96). The decompression support arm (96) moves with the decompression pin (90) to reach the other side of the first relief (93) and rests on the surface to contain the decompression pin (90) in the position for a short duration. The exhaust side roller (43) remains in contact with the exhaust lobe (41); however, a partial portion of the exhaust side roller (43) also remains in contact with the decompression pin (90). The decompression pin (90) explained above comprises of a partial cylindrical portion and a partial plain portion. The cylindrical portion functions as the lifting portion (92) which is used to life the rocker side roller. Hence, the exhaust side roller (45) moves along the periphery of the decompression pin (90) and gets lifted by the lifting portion (92) to allow the decompression mechanism to happen, and later gets back to its original position when the plain surface (shown in Fig. 10) of the decompression pin (90) is in action. In another embodiment, the second relief (94) is accommodated with another separate pin termed as EGR pin (91). The EGR pin (91) comprises of a partial cylindrical surface which acts as the lifting portion (shown in Fig. 10), whereas the remaining partial surface is a flat portion (98). When the internal combustion engine (5) reaches the idling speed, the spring connecting the arm (56) and the camshaft (35) experiences a centrifugal force due to which the arm (56) also experiences an outward centrifugal force resulting in the movement of the arm (56). As the arm rotates (56), so does the EGR pin (91) rotates with it, and with that rotation the cylindrical shaped lifting portion (shown in Fig. 10) comes into action resulting in the lifting of the exhaust side arm (45) which is in partial connection with the exhaust lobe (41) and the EGR pin (91). The lifting of the exhaust side roller arm (45) results in the movement of the exhaust side arm (41) which in turn opens up the exhaust valve (33). In an embodiment, a divider (95) is provided in the arm (56) between the first relief (93) and the second relief (96), so that the two supporting arms (96, 97) do not interfere with each other and it also provides a surface to the arm for support so that the pins (90, 91) do not rotate more than what is required. The present figure shows the camshaft (35) before cranking of the engine (5), when the cylindrical shaped lifting portion (92) of the decompression pin (90) is in action and the plain flat portion (98) for the EGR pin (91) is in action. [00052] Figure 10 illustrates a perspective view of the camshaft (35) after cranking of the internal combustion engine (5) in accordance with an embodiment of the present subject matter. In an embodiment, the cylindrical shaped lifting portion (102) of the EGR pin (91) comes into action when the EGR mechanism is activated. It is only after the internal combustion engine (5) has crossed at least the first idling speed and is more than the idling speed, then the arm (56) experiences an outward centrifugal force because of the spring through which it is attached to camshaft (35), which in turn results in rotation of the arm (56). In an embodiment, the EGR pin (91) rotates with the arm (56), such that the cylindrical shaped lifting portion (102) is exposed and in is contact with the exhaust side roller (43) resulting in movement of the exhaust side arm (45) and opening of the exhaust valve (33). In an embodiment, the EGR support arm (97) formed on the EGR pin (91) also moves along with it, however after a short duration it reaches and end of the second relief (94) and rests there to keep the lifting portion (102) in that position and keep the exhaust side roller (43) to be lifted for that particular duration. During the duration when the exhaust side roller (43) is lifted, the exhaust valve (33) is also open for that certain duration overlapping with duration of inlet valve (34) opening and allowing the EGR mechanism to take place. The present figure illustrates that exact stage when the first speed of the internal combustion engine (5) is more than the idling speed, wherein the first speed lies in a range of 1000-1500 rpm, and lifting portion (102) of the EGR pin (91) is in action allowing the EGR mechanism to occur.

[00053] Figure 11 illustrates a graph for the instances of intake valve (34) opening and exhaust valve (33) opening during the decompression operation of the internal combustion engine (5). The objective of the present subject matter is to overlap the duration of exhaust valve (33) opening with duration of the inlet valve (34) opening for a short period of time. This overlapping enables the introduction of EGR into the internal combustion engine (5) which reduces the production of NOx after combustion of the air-fuel mixture. As per the present subject matter, area (200) shows exhaust valve (33) opening with respect to crank angle, whereas area (400) depicts the inlet valve (34) opening with respect to crank angle. As explained above, decompression allows the exhaust valve (33) to open for release of the exhaust, after which it closes and the inlet valve (34) opens for introduction of air-fuel mixture. At a later stage area (200S) depicts the second opening instance of the exhaust valve (33) over the progression of crank angle. However, there in no definite overlapping between the exhaust valve (33) opening and inlet valve (34) opening which would achieve the objective of the present subject matter.

[00054] Figure 12 illustrates a graph for the instances of intake valve (34) opening and exhaust valve (33) opening during the EGR operation of the internal combustion engine (5) in accordance with an embodiment of the present subject matter. The area (200) depicts the exhaust valve (33) opening with respect to the crank angle, whereas area (400) depicts the inlet valve (34) opening with respect to crank angle. Generally, the intake valve (34) opens only after the exhaust valve (33) is closed, so that there is no exhaust left in the internal combustion engine (5) and there is no chance of mixture with the air-fuel mixture. However, it is the objective of the present subject matter to provide a definite overlap between the duration of exhaust valve (33) opening with duration of the inlet valve (34) opening for a short period of time for an efficient EGR mechanism. As the present subject matter, after implementation of the EGR mechanism there is a definite overlap between the second instance (200S) of exhaust valve (33) opening and area (400) which depicts the inlet valve opening. Thus, the exhaust valve (33) opens again even when the inlet valve (34) is open resulting in an efficient EGR to happen and mixing the exhaust with the air-fuel mixture to reduce the NOx produced.

[00055] Thus, the present subject matter provides an internal combustion engine with an efficient EGR mechanism which can be used to reduce the amount of NOx produced. The camshaft is provided with an additional EGR lobe which comprises of a lifting portion which enables the opening of the exhaust valve for a short duration by lifting the exhaust side roller after the internal combustion has crossed the idling speed. In another embodiment, the arm mounted over the camshaft is provided with an EGR pin comprising of a lifting portion to enable the opening of the exhaust side valve by lifting the exhaust side roller after the internal combustion engine has crossed the idling speed. Such an arrangement helps in making the whole system simpler and cost effective. It also reduces the number of parts being used, reduces the probability of failure points and improves the maintainability.

[00056] It is to be understood that the aspects of the embodiments are not necessarily limited to the features described herein. Many modifications and variations of the present subject matter are possible in the light of above disclosure. Therefore, within the scope of claims of the present subject matter, the present disclosure may be practiced other than as specifically described.

Claims

I/We claim:

1. An internal combustion engine (5) for a two-wheeled vehicle (10), comprising:

a cylinder block (25) comprising a cylinder to accommodate a reciprocating piston (31) for combustion of fuel;

a cylinder head (24) disposed over said cylinder block (25) to receive said reciprocation piston (31);

an inlet port (21) formed on said cylinder head (24) to allow entry of air-fuel mixture in said internal combustion engine (5);

an exhaust port (22) formed on said cylinder head (24) to allow exhaust formed after combustion to leave said internal combustion engine (5);

an exhaust valve (33) and an inlet valve (34) disposed in said cylinder head (24) enabling opening and closing of said exhaust port (22) and said inlet port (21); a camshaft (35) comprising an inlet lobe (42) to actuate said intake valve (34) through an intake side roller (44) and an intake side arm (46); an exhaust lobe (41) to actuate said exhaust valve (33) through an exhaust side roller (43) and an exhaust side arm (45); an arm (56) connected to said camshaft (35) through a spring enabling decompression of said internal combustion (5) through a decompression pin (91) formed therein; and

a lifting portion formed (62) on an EGR lobe (55) mounted over said camshaft (35) enabling an opening of said exhaust valve (33) to allow recirculation of exhaust gas after a first speed of said internal combustion engine (5) is more than an idling speed of said engine (5).

2. The internal combustion engine (5) as claimed in claim 1, wherein said EGR lobe (55) is mounted over said camshaft (35) between said arm (56) and said exhaust lobe (41).

3. The internal combustion engine (5) as claimed in claim 1, wherein said arm (56) comprises of an arm pin (72) extending in an outward direction from a surface of said arm (56).

4. The internal combustion engine (5) as claimed in claim 1, wherein said EGR lobe (55) comprises of an opening (61) to accommodate said arm (56) resulting in a connection of said EGR lobe (55) and said arm (56).

5. The internal combustion engine (5) as claimed in claim 1, wherein rotation of said arm (56) is actuated through said spring after said internal combustion engine (5) has crossed the idling speed.

6. The internal combustion engine (5) as claimed in claim 1, wherein said EGR lobe (55) is rotated with said arm (56) resulting in contact being established between said lifting portion (62) and said exhaust side arm (45), wherein further rotation of said EGR lobe (55) causes lifting of said exhaust side arm (45) through said lifting portion (62).

7. The internal combustion engine (5) as claimed in claim 1 , wherein lifting of said exhaust side arm (45) through said lifting portion (62) results in opening of said exhaust valve (33) during same duration of opening of said inlet valve (34) resulting in recirculation of exhaust gas.

8. An internal combustion engine (5) for a two-wheeled vehicle (10), comprising:

a lifting portion (102) formed on an EGR pin (91) accommodated between said camshaft (35) and a second relief (94) formed on said arm (56), wherein said lifting portion (102) enables an opening of said exhaust valve (33) to allow recirculation of exhaust gas after a first speed of said internal combustion engine (5) is more than an idling speed of said engine (5).

9. The internal combustion engine (5) as claimed in claim 8, wherein said EGR pin (91) comprises of an EGR support arm (97) formed perpendicularly over said EGR pin (91).

10. The internal combustion engine (5) as claimed in claim 8, wherein said EGR pin (91) comprises of a partial cylindrical shapes structure functioning as said lifting portion (102) and a flat portion (98).

11. The internal combustion engine (5) as claimed in claim 8, wherein said EGR support arm (97) is located in said second relief portion (94).

12. The internal combustion engine (5) as claimed in clam 8, wherein rotation of said arm (56) results in movement of said EGR support arm (97) enabling rotation of said EGR pin (91).

13. The internal combustion engine (5) as claimed in claim 8, wherein rotation of said EGR pin (91) results in contact being established between said lifting portion (102) and said exhaust side roller (43), wherein further rotation of said EGR pin (91) causes lifting of said exhaust side roller (43) through said lifting portion (102).

14. The internal combustion engine (5) as claimed in claim 8, wherein lifting of said exhaust side roller (43) through said lifting portion (102) results in opening of said exhaust valve (33) during same duration of opening of said inlet valve (34) resulting in recirculation of exhaust gas.

15. The internal combustion engine (5) as claimed in claim 1 or 8, wherein said first speed of said internal combustion engine (5) is in a range of 1000 rpm to 1500 rpm.