Claims:WE CLAIM:
1. A crankshaft web (110) of a crankshaft assembly (100) for an internal combustion engine (12), comprising:
a recess (150) configured to receive a connecting rod (160), the recess (150) disposed between a centre (112) of the crankshaft web (110) and a peripheral end (114) on the crankshaft web (110);
a first peripheral portion (120) extending between a first end (120A) and a second end (120B), the first peripheral portion (120) disposed at a diametrically opposite end to the peripheral end (114), and configured to counter rotational mass of the connecting rod (160);
a second peripheral portion (122) extending between the first end (120A) of the first peripheral portion (120) and the peripheral end (114); and
a third peripheral portion (124) extending between the second end (120B) of the first peripheral portion (120) and the peripheral end (114), wherein mass of the first peripheral portion (120) is greater than mass of the second peripheral portion (122) or the third peripheral portion (124).

2. The crankshaft web (110) as claimed in claim 1, wherein the first end (120A) of the first peripheral portion (120) forms a first angle of (?1) at the centre (112) of the crankshaft web (110) with respect to a transverse axis (X-X’) of the crankshaft web (110), and the second end (120B) of the first peripheral portion (120) forms a second angle of (?2) at the centre (112) of the crankshaft web (110) with respect to the transverse axis (X-X’) of the crankshaft web (110).

3. The crankshaft web (110) as claimed in claim 2, wherein the first angle (?1) and the second angle (?2) range between 20 degrees to 75 degrees.

4. The crankshaft web (110) as claimed in claim 1, wherein the first peripheral portion (120), the second peripheral portion (122) and the third peripheral portion (124) protrude to form a first flange (120’), a second flange (122’) and a third flange (124’), respectively.

5. The crankshaft web (110) as claimed in claim 4, wherein first flange (120’) has a first inner diameter (ID1) and a first outer diameter (OD1), and the second flange (122’) and the third flange (124’) have a second inner diameter (ID2) and a second outer diameter (OD2).

6. The crankshaft web (110) as claimed in claim 5, wherein the first outer diameter (OD1) is equal to the second outer diameter (OD2), and the first inner diameter (ID1) is less than the second inner diameter (ID2), thence the first flange (120’) has a greater breadth than the second flange (122’) or the third flange (124’).

7. The crankshaft web (110) as claimed in claim 5, wherein the first outer diameter (OD1) is equal to the second outer diameter (OD2), and the first inner diameter (ID1) is equal to the second inner diameter (ID2).

8. The crankshaft web (110) as claimed in claim 4, wherein the second flange (122’) and the third flange (124’) have a second flange thickness (tf2).

9. The crankshaft web (110) as claimed in claims 4 and 8, wherein a first flange thickness (tf1) of the first flange (120’) is greater than the second flange thickness (tf2) of the second flange (122’) or the third flange (124’).

10. The crankshaft web (110) as claimed in claim 4, comprising a first inner wall (132) extending from the first end (120A) of the first flange (120’) to the second flange (122’) defining a first web region (142) having a first web thickness (tw1), wherein at least a portion of the first inner wall (132) abuts the recess (150).

11. The crankshaft web (110) as claimed in claim 4, comprising a second inner wall (134) extending from the second end (120B) of the first flange (120’) to the third flange (124’) defining a second web region (144) having a second web thickness (tw2), wherein at least a portion of the second inner wall (134) abuts the recess (150).

12. The crankshaft web (110) as claimed in claims 10 and 11, wherein the second web thickness (tw2) is equal to the first web thickness (tw1).

13. The crankshaft web (110) as claimed in claims 4, 10 and 11, wherein the first inner wall (132), the second inner wall (134) and the first flange (120’) define a third web region (146) having a third web thickness (tw3).

14. The crankshaft web (110) as claimed in claims 12 and 13, wherein the third web thickness (tw3) is greater than the first web thickness (tw1) or the second web thickness (tw2).

15. The crankshaft web (110) as claimed in claims 8 and 12, wherein the second web thickness (tw2) or the first web thickness (tw1) is lower than the second flange thickness (tf2).

16. The crankshaft web (110) as claimed in claims 8 and 13, wherein the third web thickness (tw3) is greater than or equal to the second flange thickness (tf2).

17. The crankshaft web (110) as claimed in claims 9 and 13, wherein the first flange thickness (tf1) greater than the third web thickness (tw3).

18. The crankshaft web (110) as claimed in claim 1, wherein the recess (150) is configured to receive the connecting (160) rod by means of a needle cage (152) and a crankpin (154).

19. The crankshaft web (110) as claimed in claim 1, wherein moment of inertia to mass ratio of the crankshaft web (110) ranges between 9-11.5 cm2.
, Description:FIELD OF THE INVENTION
[001] The present invention relates to a crankshaft assembly for an internal combustion engine.

BACKGROUND OF THE INVENTION
[002] In conventional motor vehicles, especially saddle-type vehicles with a single cylinder internal combustion engine, a crankshaft assembly performs multiple functions. The first of those functions is to convert reciprocating motion of the piston in rotational motion. In addition to that, the crankshaft assembly also performs the functions of balancing the unbalanced rotating and reciprocating masses, and balancing the unbalanced forces caused due to a power stroke of the internal combustion engine.
[003] Especially pertaining to the functions of balancing of unbalanced rotating masses, and balancing of unbalanced forces caused due to a power stroke of the internal combustion engine, the mass and inertia of the crankshaft assembly play a vital role. If the inertia of the crankshaft is low, a high level of fluctuation in the idle speed RPM of the engine is caused. Such fluctuations in the idle speed RPM are known as idle speed instability and are undesirable in operation of the internal combustion engine. Idle speed instability leads to high levels of jerk and vibration at low speeds, forcing the rider to operate the vehicle at higher RPMs. Conversely, if the mass of the crankshaft assembly is increased to increase the inertia, it leads to a heavier internal combustion engine, affecting the fuel efficiency and the overall weight of the vehicle.
[004] In conventional crankshaft assemblies, the crank webs are configured in a manner that mass is unevenly distributed throughout the crank web. The conventional configurations of the crank webs have more mass concentrated towards the centre of the webs, and lesser mass concentrated on the periphery of the web. As is known, that the moment of inertia of a disc is given by MR2/2, wherein R denotes the effective radius of the disc. Due to the distribution of the mass in conventional crank web configurations, the effective radius is lower, and hence the moment of inertia is lower.
[005] Attempts have been made to increase the moment of inertia of a crank web by attachment of an additional part to the crank web such as inertia disc or flywheel to increase crankshaft inertia. In that, the flywheel or inertia disc has a radially outer mass ring and a radially inner fastening flange for fastening to the crankshaft and/or a clutch. However, in this disposition, to increase the moment of inertia of the crankshaft assembly, greater mass has to be provided on the inertia disc or the flywheel, which in turn results an increase in the weight of the crankshaft assembly and the engine. The addition of the inertia disc or the flywheel also negatively impacts the acceleration and fuel efficiency of the vehicle.
[006] Thus, there is a need in the art for a crankshaft web for a crankshaft assembly of an internal combustion engine which addresses at least the aforementioned problems.

SUMMARY OF THE INVENTION
[007] In one aspect, the present invention is directed at a crankshaft web of a crankshaft assembly for an internal combustion engine. The crankshaft web has a recess configured to receive a connecting rod and the recess disposed between a centre of the crankshaft web and a peripheral end on the crankshaft web. A first peripheral portion extends between a first end and a second end, and is disposed at a diametrically opposite end to the peripheral end. The first peripheral portion is configured to counter rotational mass of the connecting rod. A second peripheral portion extends between the first end of the first peripheral portion and the peripheral end. A third peripheral portion extending between the second end of the first peripheral portion and the peripheral end. Herein, mass of the first peripheral portion is greater than mass of the second peripheral portion or the third peripheral portion.
[008] In an embodiment of the invention, the first end of the first peripheral portion forms a first angle of (?1) at the centre of the crankshaft web with respect to a transverse axis of the crankshaft web, and the second end of the first peripheral portion forms a second angle of (?2) at the centre of the crankshaft web with respect to the transverse axis of the crankshaft web. In an embodiment, the first angle (?1) and the second angle (?2) range between 20 degrees to 75 degrees.
[009] In a further embodiment of the invention, the first peripheral portion, the second peripheral portion and the third peripheral portion protrude to form a first flange, a second flange and a third flange, respectively. In an embodiment, the first outer diameter is equal to the second outer diameter, and the first inner diameter is less than the second inner diameter, thence the first flange has a greater breadth than the second flange or the third flange. In an alternative embodiment, the first outer diameter is equal to the second outer diameter, and the first inner diameter is equal to the second inner diameter.
[010] In another embodiment of the invention, the second flange and the third flange have a second flange thickness. In an embodiment, a first flange thickness of the first flange is greater than the second flange thickness of the second flange or the third flange.
[011] In a further embodiment of the invention, the crankshaft web has a first inner wall extending from the first end of the first flange to the second flange defining a first web region having a first web thickness, wherein at least a portion of the first inner wall abuts the recess.
[012] In a further embodiment of the invention, the crankshaft web has a second inner wall extending from the second end of the first flange to the third flange defining a second web region having a second web thickness, wherein at least a portion of the second inner wall abuts the recess.
[013] In a further embodiment of the invention, the second web thickness is equal to the first web thickness.
[014] In a further embodiment of the invention, the first inner wall, the second inner wall and the first flange define a third web region having a third web thickness. In an embodiment, the third web thickness is greater than the first web thickness or the second web thickness.
[015] In a further embodiment of the invention, the second web thickness or the first web thickness is lower than the second flange thickness. In an embodiment, the third web thickness is greater than or equal to the second flange thickness. In an embodiment, the first flange thickness greater than the third web thickness.
[016] In an embodiment of the invention, the recess is configured to receive the connecting rod by means of a needle cage and a crankpin.
[017] In a further embodiment of the invention, moment of inertia to mass ratio of the crankshaft web ranges between 9-11.5 cm2.

BRIEF DESCRIPTION OF THE DRAWINGS
[018] 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 right-side view of an exemplary motor vehicle, in accordance with an embodiment of the invention.
Figure 2 illustrates an exploded view of the crankshaft assembly, in accordance with an embodiment of the invention.
Figure 3A illustrates a side view of the crankshaft assembly, in accordance with an embodiment of the invention.
Figure 3B illustrates a front view of the crankshaft assembly, in accordance with an embodiment of the invention.
Figure 4 illustrates the front view of the crankshaft web of the crankshaft assembly, in accordance with an embodiment of the invention.
Figure 5 illustrates a perspective view of the crankshaft web of the crankshaft assembly, in accordance with an embodiment of the invention.
Figure 6A illustrates a sectional view along a section L-L of the crankshaft web, in accordance with an embodiment of the invention.
Figure 6B illustrates the front view of the crankshaft web with the section L-L depicted therein, in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION
[019] The present invention relates to a crankshaft assembly for an internal combustion engine. More particularly, the present invention relates to a crankshaft web of a crankshaft assembly for an internal combustion engine.
[020] Figure 1 illustrates an exemplary motor vehicle 10, in accordance with an embodiment of the invention. The motor vehicle 10 comprises an Internal combustion engine 12 that is vertically disposed. Preferably, the Internal combustion engine 12 is a single-cylinder type Internal combustion engine. The motor vehicle 10 comprises a front wheel 14, a rear wheel 16, a frame member, a seat assembly 18 and a fuel tank 20. The frame member includes a head pipe 22, a main tube 24, a down tube (not shown), and seat rails (not shown). The head pipe 22 supports a steering shaft (not shown) and two telescopic front suspensions 26 (only one shown) attached to the steering shaft through a lower bracket (not shown). The two telescopic front suspensions 26 support the front wheel 14. The upper portion of the front wheel 14 is covered by a front fender 28 mounted to the lower portion of the telescopic front suspension 26 at the end of the steering shaft. A handlebar 30 is fixed to upper bracket (not shown) and can rotate to both sides. A head light 32, a visor guard (not shown) and instrument cluster (not shown) is arranged on an upper portion of the head pipe 22. The frame member comprises a down tube (not shown) that may be located in front of the Internal combustion engine 12 and extends slantingly downward from head pipe 22. The main tube 24 of the frame member is located above the Internal combustion engine 12 and extends rearward from head pipe 22. The Internal combustion engine 12 is mounted at the front to the down tube and a rear of the Internal combustion engine 12 is mounted at the rear portion of the main tube 24. In an embodiment, the Internal combustion engine 12 is mounted vertically, with a cylinder block extending vertically above a crankcase. In an alternative embodiment, the Internal combustion engine 12 is mounted horizontally (not shown) with the cylinder block extending horizontally forwardly from the crankcase. In an embodiment, the cylinder block is disposed rearwardly of the down tube.
[021] The fuel tank 20 is mounted on the horizontal portion of the main tube 24. Seat rails are joined to main tube 24 and extend rearward to support a seat assembly 18. A rear swing arm 34 is connected to the frame member to swing vertically, and the rear wheel 16 is connected to rear end of the rear swing arm 34. Generally, the rear swing arm 34 is supported by a mono rear suspension 36 (as illustrated in the present embodiment) or through two suspensions on either side of the motor vehicle 10. A taillight unit 33 is disposed at the end of the motor vehicle 10 and at the rear of the seat assembly 18. A grab rail 35 is also provided on the rear of the seat rails. The rear wheel 16 arranged below seat 18 rotates by the driving force of the Internal combustion engine 12 transmitted through a chain drive (not shown) from the Internal combustion engine 12. A rear fender 38 is disposed above the rear wheel 16.
[022] Further, an exhaust pipe 40 of the vehicle extends vertically downward from the Internal combustion engine 12 up to a point and then extends below the Internal combustion engine 12, longitudinally along the vehicle length before terminating in a muffler 42. The muffler 42 is typically disposed adjoining the rear wheel 16.
[023] Figure 2 illustrates an exploded view of a crankshaft assembly 100 in accordance with an embodiment of the invention. As illustrated in the figure, the crankshaft assembly 100 has at least one crankshaft web 110 connected to a crank shaft. Herein the crankshaft web 110 is configured for receiving a connecting rod 160. In that, one end of the connecting rod 160 is connected to a piston (not shown) and the other end of the connecting rod 160 is received by the crankshaft web 110, thereby converting the reciprocating motion of the piston into a rotational motion of the crank shaft. In the embodiment illustrated in the Figure 2, the crankshaft assembly 100 has a pair of crankshaft webs 110 wherein each of the crankshaft webs 110 are connected to a crank shaft half. Each of the crankshaft web 110 has a recess 150 therein that is configured to receive the connecting rod 160 via a needle cage 152 and a crankpin 154. The crankpin 154 and the needle cage 152 assist in converting the reciprocating motion of the piston into rotational motion of the crankshaft web 110, and resultantly the crankshaft assembly 100. During the rotation of the crankshaft web 110, the connecting rod 160 has a reciprocating mass that reciprocates with the piston and a rotating mass that rotates with the crankshaft web 110.
[024] Figure 3A illustrates a side view of the crankshaft assembly 100 and Figure 3B illustrates a front view of the crankshaft assembly 100 in accordance with an embodiment of the invention. As illustrated in Figure 3B, the recess 150 on the crankshaft web 110 to receive the connecting rod 160 is disposed between a centre 112 of the crankshaft web 110 and a peripheral end 114 on the crankshaft web 110. In an embodiment, the recess 150 is a circular recess. Further, the crankshaft web 110 has a first peripheral portion 120 that extends between a first end 120A and a second end 120B. Herein, the first peripheral portion 120 is disposed at a diametrically opposite end to the peripheral end 114. The first peripheral portion 120 is positioned at the diametrically opposite end to the peripheral end 114 such that the first peripheral portion 120 is configured to counter and balance rotational mass of the connecting rod 160.
[025] As further illustrated in Figure 3B, the crankshaft web 110 further has a second peripheral portion 122 that extends between the first end 120A of the first peripheral portion 120 and the peripheral end 114. The crankshaft web 110 further has a third peripheral portion 124 that extends between the second end 120B of the first peripheral portion 120 and the peripheral end 114. Herein, the crankshaft web 110 is configured in a manner that mass of the first peripheral portion 120 is greater than mass of the second peripheral portion 122 or the third peripheral portion 124. Firstly, such a configuration of the crankshaft web 110 ensures that the higher mass of the first peripheral portion 120 can effectively counter and balance rotational mass of the connecting rod 160. Secondly, the configuration of the crankshaft web 110 ensures that mass of crankshaft web 110 is concentrated towards periphery of the crankshaft web 110.
[026] The effect of this concentration of mass towards periphery of the crankshaft web 110 is that a moment of inertia of the crankshaft web 110 is increased. For instance, if the crankshaft web 110 has the shape of a circular disc, the moment of inertia about a central axis of the circular disc is calculated as MR2/2, wherein M represents the mass of the disc and R represents effective radius of gyration of the disc about the central axis of the circular disc. The effect of concentration of mass towards periphery of the crankshaft web 110 by means of the first peripheral portion 120, the second peripheral portion 122 and the third peripheral portion 124 results in an increment in the effective radius of the crankshaft web 110, thereby increasing the moment of inertia of the crankshaft web 110.
[027] Figure 4 illustrates a front view of the crankshaft web 110 in accordance with an embodiment of the invention. As illustrated in Figure 4, the first end 120A of the first peripheral portion 120 forms a first angle of (?1) at the centre 112 of the crankshaft web 110 with respect to a transverse axis (X-X’) of the crankshaft web 110. Further, the second end 120B of the first peripheral portion 120 forms a second angle of (?2) at the centre 112 of the crankshaft web 110 with respect to the transverse axis (X-X’) of the crankshaft web 110. In an embodiment of the invention, the first angle (?1) and the second angle (?2) range between 20 degrees to 75 degrees.
[028] Figure 5 illustrates a perspective view of the crankshaft web 110 in accordance with an embodiment of the invention. As illustrated in Figure 5, to facilitate the concentration of mass on periphery of the crankshaft web 110, the first peripheral portion 120, the second peripheral portion 122 and the third peripheral portion 124 protrude to form a first flange 120’, a second flange 122’ and a third flange 124’ respectively. As further illustrated in Figure 5, the first flange 120’ has a first inner diameter (ID1) and a first outer diameter (OD1), and the second flange 122’ and the third flange 124’ have a second inner diameter (ID2) and a second outer diameter (OD2). Herein, the first outer diameter (OD1) is equal to the second outer diameter (OD2), and the first inner diameter (ID1) is less than the second inner diameter (ID2). As a result of this, the first flange 120’ has a greater breadth than the second flange 122’ or the third flange 124’. The first flange 120’ having a greater breadth than the second flange 122’ or the third flange 124’ thereby results in the mass of the first peripheral portion 120 being greater than mass of the second peripheral portion 122 or the third peripheral portion 124. In an alternative embodiment of the invention, the first outer diameter (OD1) is equal to the second outer diameter (OD2), and the first inner diameter (ID1) is equal to the second inner diameter (ID2).
[029] Figure 6A illustrates a side-sectional view along a section L-L of the crankshaft web 110 of the crankshaft assembly 100, and Figure 6B illustrates the front view of the crankshaft web 110 with the section L-L depicted therein. As illustrated in Figure 6A, the first flange 120’ has a first flange thickness (tf1), and the second flange 122’ and the third flange 124’ have a second flange thickness (tf2). In an embodiment, the first flange thickness (tf1) of the first flange (120’) is greater than the second flange thickness (tf2) of the second flange (122’) or the third flange (124’). This further facilitates mass of the first peripheral portion 120 being greater than the second peripheral portion 122 or the third peripheral portion 124.
[030] As further illustrated in Figure 6B, the crankshaft web 110 further has a first inner wall 132 that extends from the first end 120A of the first flange 120’ to the second flange 122’. The first inner wall 132 defines a first web region 142. The first web region 142 has a first web thickness (tw1). As can be seen in Figure 6B, at least a portion of the first inner wall 132 abuts the recess 150. Similarly, the crankshaft web 110 has a second inner wall 134 that extends from the second end 120B of the first flange 120’ to the third flange 124’. The second inner wall 134 defines a second web region 144. The second web region 144 has a second web thickness (tw2). As can be seen in Figure 6B, at least a portion of the second inner wall 134 abuts the recess 150. As illustrated in the embodiment depicted by Figure 6A, the second web thickness (tw2) is equal to the first web thickness (tw1), that is thickness of the first web region 142 and the second web region 144 are equal.
[031] As further illustrated in Figure 6B, the first inner wall 132, the second inner wall 134 and the first flange 120’ of the crankshaft web 110 define a third web region 146 having a third web thickness (tw3). Further, in an embodiment, the third web thickness (tw3) is greater than the first web thickness (tw1) or the second web thickness (tw2), that is thickness of the third web region 146 is greater than thickness of the first web region 142 or the second web region 144.
[032] Figure 6A further illustrates that the second web thickness (tw2) or the first web thickness (tw1) is lower than the second flange thickness (tf2). Further, the third web thickness (tw3) is greater than or equal to the second flange thickness (tf2). Furthermore, the first flange thickness (tf1) greater than the third web thickness (tw3). The configuration of the crankshaft web 110 in which the thickness of the first flange 120’, the second flange 122’, the third flange 124’, the first web region 142, second web region 144, and the third web region 146 are interrelated as explained hereinbefore, results in the distribution of mass of the crankshaft web 110 in a manner that effective radius of the crankshaft web 110 is increased. The increase in effective radius resultantly increases the moment of inertia of the crankshaft web 110 without having to increase mass of the crankshaft web 110. In an embodiment of the invention, moment of inertia to mass ratio of the crankshaft web 110 ranges between 9-11.5 cm2.
[033] Advantageously, the configuration of the crankshaft web in the present invention provides for an increment in the moment of inertia of the crankshaft assembly without having to increase the mass of the crankshaft assembly. The increment in moment of inertia of the crankshaft assembly. The high moment of inertia of the crankshaft assembly reduces the level of fluctuation of idle speed RPM.
[034] Further, the higher mass of the first peripheral portion ensures that the rotational mass of the connecting rod is adequately balanced, reducing torsional vibration in the crankshaft assembly.
[035] Furthermore, the present invention ensures that the mass of the crankshaft assembly is not increased for increasing the moment of inertia of the crankshaft assembly, thereby not increasing the mass of the engine and hence providing better fuel efficiency and acceleration.
[036] 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.