DESC:FIELD OF THE INVENTION
[0001] The present invention relates to an internal combustion engine. More particularly, but not exclusively, the present invention relates to a bearing structure rotatably supporting a crankshaft of the internal combustion engine.
BACKGROUND OF THE INVENTION
[0002] Generally, an internal combustion engine for a two-wheeled vehicle includes a crankcase assembly divided into two crankcase halves, a crank chamber being defined and formed by the crankcase halves, a crankshaft housed in the crank chamber and a cylinder block connected to the crankcase. A crankshaft is rotatably attached on a crankcase through a pair of rotary bearings each disposed on a LH and a RH crankcase, a piston slidable in a cylinder bore is connected to a crank pin of the crankshaft through a connecting rod. The crankcase houses the crankshaft assembly, clutch assembly, starter assembly and gearbox assembly and other ancillary systems, which include lubrication system, cooling system and exhaust system, all housed in the main engine body. The crankcase is made of know metals like aluminium.
[0003] The pair of rotary bearings are made of know metals like steel. The pair of rotary bearings is each disposed on each of the crank case halves. The pair of rotary bearings is press fitted/slide fitted into an insert present in the crank case halves. The insert functions as a holding member for the rotary bearings. The insert is made of a known metal like cast iron.

BRIEF DESCRIPTION OF DRAWINGS
[0004] The above and other features, aspects and advantages of the subject matter will be better understood with regard to the following description, appended claims and accompanying drawings where:
[0005] Fig. 1 illustrates a side view of a two-wheeled vehicle.
[0006] Fig. 2 illustrates a side view of an engine assembly for a two wheeled vehicle.
[0007] Fig. 3 illustrates a RH crankcase according to an embodiment of the present invention.
[0008] Fig. 4 illustrates a detailed side view of a crankcase assembly according to an embodiment of the present invention.
[0009] Fig. 5 illustrates a side perspective view of a RH crankcase assembly employing the proposed invention according to an embodiment of the present invention.
[00010] Fig. 6 illustrates a sectional view of an engine assembly taken along XX` plane in Fig. 2.
[00011] Fig. 7 illustrates a detailed view of a sectional view of a crankshaft assembly.
[00012] Fig. 8 illustrates a detailed view of the restraining mechanism employed in the inner wall of the insert in the crankcase assembly.
[00013] Fig. 9 illustrates the elements of the restraining mechanism according to an embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[00014] Typically, an internal combustion engine in a two-wheeled vehicle includes a crankcase assembly divided into two crankcase halves, a crank chamber being defined and formed by the crankcase halves, a crankshaft housed in the crank chamber and a cylinder block connected to the crankcase. A clutch cover is arranged towards the right so that it is adjacent to the crankcase in the vehicle width direction. A counter shaft is arranged in the crankcase halves flanked by transmission cover, the rotation of the crankshaft being transmitted to the counter shaft. A drive shaft is arranged rearward or upward of the counter shaft in the crankcase halves, the driving wheel being attached to the drive shaft through chain and sprocket means. The counter shaft is connected to the drive shaft through a gearbox.
[00015] Typically, an internal combustion engine in a two-wheeled vehicle includes a crankcase assembly including two crankcase halves. The two crankcase halves include a RH crankcase and a LH crankcase. The crankcase assembly defines a crank chamber and the crank chamber is formed by the crankcase halves. A crankshaft is housed in the crank chamber and a cylinder block is connected to the two crankcase halves. A clutch cover is arranged towards the right side of the crankcase assembly, so that the clutch cover remains adjacent to the RH crankcase in the vehicle width direction. Further, a countershaft is arranged in the two crankcase halves flanked by a transmission cover, the rotation of the crankshaft being transmitted to the counter shaft. Furthermore, a drive shaft is arranged rearward or upward of the counter shaft in the two crankcase halves, a driving wheel being attached to the drive shaft through chain and sprocket means. The countershaft is connected to the drive shaft through a gearbox.
[00016] The crankshaft is rotatably mounted inside the crank chamber with the help of a pair of bearing assembly. The pair of bearing assembly includes a RH bearing assembly and a LH bearing assembly, each disposed on the RH crankcase and the LH crankcase respectively. The bearing assembly includes a plurality of ball bearings held by an insert. During assembly of each of the insert loaded with bearing assembly into the two crankcase halves, any minimum clearance between the bearing assembly, the insert, and the crankcase is overcome during assembly inside the engine assembly.
[00017] The further clearance between the bearing assembly and the insert may occur only during the operation of the engine assembly under high operating temperatures. During the engine operation under high operating temperatures, the bearing assembly, the insert, and the two crankcase halves tend to expand. The expansion rate is not uniform for the bearing assembly, the insert, and the two crankshaft halves. This is because, the crankcase is made of aluminium, the bearing assembly includes balls made of steel, and the insert is made of cast iron. The cast iron insert and the aluminium crankcase tend to expand more than the expansion of the steel balls in the bearing assembly. Hence, an undesired clearance is created between the insert and the bearing assembly. The steel balls in the bearing assembly have clearance more than required. Therefore, due to lose fitting, the steel balls tend to move freely in the expanded space available and an undesired noise is generated. The bearing assembly tends to move up and down in the radial direction inside the crankcase. Due to this, during cranking of the engine, the crank noise is higher at higher engine operating temperature. The rider, during cranking of the engine, gets a feel of lose parts being present inside the engine assembly.
[00018] Hence, it is an objective of the present invention to reduce crank noise by arresting the movement of the bearing assembly in the radial direction during higher engine operating temperatures.
[00019] According to an embodiment of the present invention, a restraining mechanism is provided in the crankcase assembly of the engine assembly to reduce radial movement of the bearing assembly.
[00020] Each of the RH insert and the LH insert includes a slot capable of accommodating a restraining mechanism.
[00021] According to an embodiment of the present invention, the restraining mechanism includes a preloaded elastic member pressed against a restraining member in assembled condition. Further, the elastic member and the restraining member are held in position inside the slot by a locking member. The locking member is detachably attached to a wall of the crankcase.
[00022] At normal engine operating temperatures, the restraining member and the preloaded elastic member are tightly held inside the slot by the locking member. However, during higher engine operating temperatures, due to thermal expansion of the cast iron insert, a clearance is generated between the bearing assembly outer race and the inner diameter of the insert. The restraining member is now free to move inside the expanded slot disposed in the outer race of the bearing. The restraining member is pushed inside the slot by the preloaded elastic member held tightly by the locking member, the restraining member is pushed until there exists clearance, and therefore, any upward movement in the radial direction of the bearing assembly is restrained by the restraining mechanism.
[00023] Therefore, any clearance between the insert and the bearing assembly is completely occupied by the restraining mechanism and the undesired movement and noise created due to radial movement of the bearing assembly is prevented.
[00024] Further, according to an embodiment of the present invention, the restraining member is not allowed to fall out of the slot by the locking member and instead the restraining member is allowed to move inside the slot due to force exerted by the preloaded compression member. The restraining member is pushed inside the slot until the clearance is available inside the slot, which is created due to expansion of the insert and the crankcase. Hence, the radial movement of the bearing assembly is successfully prevented through the disclosed restraining mechanism. Further, the crank noise is substantially reduced by arresting the movement of the bearing assembly in the radial direction.
[00025] Hence, according to an embodiment of the present invention, a more stable functioning of the crankshaft is provided.
[00026] According to an embodiment of the present invention, the restraining mechanism includes an elastic member, a restraining member and, a locking member. The elastic member is a preloaded spring, the restraining member is a spherical object, for example, the spherical object is a steel ball, and the locking member is attached to the wall of the crankcase through a bolt.
[00027] The present subject matter and its embodiments would now be described in greater detail in conjunction with the figures in the following description.The following description provides a convenient illustration for implementing exemplary embodiments of the invention. However, the description and the appended drawings are only used by those skilled in the art to understand the objects, features, and characteristics of the present invention and not to be used to confine the scope and spirit of the present invention.
[00028] Fig. 1 illustrates a side view of a two-wheeled vehicle, for example, a motorcycle 100 according to an embodiment. The motorcycle 100 according to an embodiment includes a front wheel 101 steered by a handlebar 102 and a rear wheel 103 supported by a swing arm 104. Steering assembly parts including the handlebar 102 and the front wheel 101 are supported for pivotal steering operation on a head pipe 105 at the front end of the vehicle body frame 106. A seat 110 for a driver and a pillion is placed rearward to a fuel tank 114. An engine assembly 113 is disposed below the fuel tank. A front fender 111 is provided above the front wheel 101 to avoid the said vehicle and its occupants from being splashed with mud. Likewise, a rear fender 112 is placed above the rear wheel 103, and to the outer side in the radial direction of rear wheel 103. Rear fender 112 inhibits rainwater or the like from being thrown up by rear wheel 103. The swing arm 104 along with a shock absorber 109 is supported at a front portion thereof for pivotal motion and upward and downward rocking motion on the rear side of a lower portion of the vehicle body frame 106.
[00029] The vehicle body frame 106 includes the head pipe 105, a pair of left and right main frames 107. The head pipe 105 is positioned at a front end portion of the vehicle body frame 106. The main frames 107 extend in a leftwardly and rightwardly branching state obliquely downwardly rearwardly from a lower portion of the head pipe 105.
[00030] Fig. 2 illustrates a side view of an engine assembly for a two wheeled vehicle 100 in accordance with an embodiment of the subject matter. A combustion chamber is covered by a cylinder body 12 and a cylinder head 11. The engine assembly comprises of a carburettor, which supplies the air fuel mixture to the combustion chamber. In another embodiment, a fuel injection system may be used. A crankshaft is rotatably supported inside the crankcase assembly. The crankcase assembly includes a RH crankcase (not shown) and a LH crankcase 13.
[00031] Fig. 3 illustrates a RH crankcase according to an embodiment of the present invention. The RH crankcase 201 is preloaded with a bearing assembly (not shown). The bearing assembly includes a plurality of ball bearings. The bearing assembly is held by an RH insert 202a disposed on the RH crankcase 201. According to an embodiment of the present invention, in order to prevent any clearance occurring between the RH insert 202a and the crankcase 201, a restraining mechanism is provided in the RH insert 202a. To accommodate the restraining mechanism in the RH insert 202a, a slot 204 is provided on the outer periphery of the RH insert 202a. In order to retain the restraining mechanism inside the slot 204, a locking member 203 is provided on an inside wall 205 of the RH crankcase 201. The locking member 203 is detachably attached to the inside wall 205 of the RH crankcase 201. The proposed mechanism provides more stable crankshaft operation.
[00032] Fig. 4 illustrates a detailed side view of a crankcase assembly according to an embodiment of the present invention. The figure illustrates a detailed view of an RH insert 202a according to the present invention. The RH insert 202a is configured to include a slot 204. The slot 204 by virtue of its wedge shape, allows easy movement of parts disposed in it. The slot 204 ensures axial movement of the restraining member inside the slot 204, which also results in restraining of the radial motion of the bearing assembly. Hence, the slot 204 allows easy movement of the restraining member 201 whenever there is expansion of the RH insert 202a at higher engine operation temperatures. The slot 204 is easily machined into the wall of the RH insert 202a. Hence, a more simpler method is employed to prevent radial movement of the bearing assembly at higher engine operation temperatures
[00033] Fig. 5 illustrates a side perspective view of a RH crankcase assembly employing the proposed invention according to an embodiment of the present invention. The RH crankcase 201 includes the RH insert 202a capable of holding the bearing assembly (not shown). The restraining member 301 along with a preloaded elastic member 302 is disposed in the slot 204. The arrangement of the restraining member 301 and the preloaded elastic member 302 inside the slot 204 is kept in place by the locking member 203. The restraining mechanism prevents radial movement of the bearing assembly under high engine operations.
[00034] During high engine operating temperatures, the RH crankcase 201 and the RH insert 202a tend to expand creating more clearance between the bearing outer race required space around the ball bearings and the RH insert 202a. Hence, during engine operation, the plurality of ball bearings inside the bearing assembly tends to move freely, which is undesirable. Hence, the free moving plurality of ball bearing tends to make undesired noise. The free movement of the plurality of ball bearings is prevented according to the proposed invention.
[00035] Whenever, there is expansion in the RH crankcase 201 and the RH insert 202a, the restraining member 301 tends to move further into the slot 204. The wedge shape of the slot and the preloaded elastic member 302 aid the forward movement of the restraining member 301 into the slot 204. Hence, the restraining member 301 occupies any clearance created in the RH insert 202a and bearing outer race. Therefore, the radial movement of the plurality of ball bearings and the bearing assembly is prevented.
[00036] Further, the locking member 203 holds the preloaded elastic member 302 and the restraining member 301 in place during assembly. The locking member 203 is detachable attached to the inside wall of the RH crankcase 201. A provision 203a is created on the inside wall of the RH crankcase 201. The locking member 203 is attached through locking means 203b, for example, a bolt.
[00037] Fig. 6 illustrates a sectional view of an engine assembly taken along XX` plane in Fig. 2. From the figure, it is observed that a plurality of ball bearings 501 is disposed on either side of the crankshaft 502. The plurality of ball bearings 501 aid easy movement of the crankshaft 502. The RH insert 202a is provided with a restraining mechanism 500 according to an embodiment of the present invention. The restraining mechanism 500 includes the locking member 203 bolted to the inside wall of the RH crankcase through a locking means 203b.
[00038] Fig. 7 illustrates a detailed view of a sectional view of a crankshaft assembly. The pluralities of ball bearings 501 are inserted in the RH insert 202a disposed on either side of the crankshaft 502. The RH insert 202a is fitted in the two halves of the crankcase assembly. At higher engine operating temperatures, to prevent the radial movement of the plurality of ball bearings inside the RH insert 202a, a restraining mechanism is pre-assembled into the crankcase inside wall. The restraining mechanism includes an elastic member 302 pressed against a restraining member 301. The locking member 203 tightly holds the preloaded elastic member 302 and the restraining member 301 in place inside the slot created in the inside wall of the RH crankcase. The restraining mechanism is disposed on each of the RH insert and the LH insert.
[00039] Fig. 8 illustrates a detailed view of the restraining mechanism employed in the inner wall of the insert in the crankcase assembly. The figure illustrates a restraining mechanism disposed in the RH insert 202a. The restraining member 301 is disposed in the slot 204. The restraining member 301 is at a first position 301-1 at a predetermined temperature during normal working condition of the engine assembly, wherein a first end of the preloaded elastic member 302 is pressed against the restraining member 301. Under higher engine operating temperatures greater than the predetermined temperature, the crankcase assembly expands and the slot 204 in the RH insert 202a tends to expand. One of the sides 204c of the RH insert 202a expands from position A to position B with an expansion angle O there within. The restraining member 301, by virtue of the shape of the slot 204 including a varying cross section and tension exerted by the preloaded elastic member 302, tends to slide inwards into the slot 204 and attains the second position 301-2 from the first position 301-1. Therefore, the restraining member 301 fills the clearance created due to expansion of the crankcase assembly, and the RH insert 202a. Therefore, the second position 301-2 of the restraining member 301, under higher temperatures does not allow the RH bearing assembly 503 to move in the radial direction and therefore, free movement of the plurality of ball bearings 501 is also restricted. Therefore further, any noise emanating due to movement of the plurality of ball bearings and the RH bearing assembly 503 is prevented. Furthermore, a more reliable and stable operation of the crankshaft assembly is achieved, which results in better engine assembly operation.
[00040] According to an embodiment of the present invention, the at least a slot 204 includes a varying cross-section with a wider cross-section on a side closer 204a to the locking member 203 compared to another side 204a away from the locking member 203.
[00041] According to an embodiment of the present invention, the expansion angle O is approximately 3 degrees.
[00042] At higher engine operating temperatures greater than the predetermined temperature a similar movement of the restraining member 301 from the first position 301-1 to the second position 301-2 occurs in the LH insert 202b as well.
[00043] According to an embodiment of the present invention, the temperature ranges from 0-60 degree centigrade and the predetermined temperature above the temperature is approximately 60-100 degree centigrade.

[00044] Fig. 9 illustrates the elements of the restraining mechanism according to an embodiment of the present invention. The radial movement of the plurality of ball bearings and the bearing assembly inside the crankcase assembly is prevented by the restraining mechanism 500. The restraining mechanism 500 inserted in the crankcase includes the restraining member 301 and the preloaded elastic member 302. The preloaded elastic member 302 is preloaded during assembly into the slot 204. The locking member 203 enables locking of the restraining member 301 and the preloaded elastic member 302 inside the slot 204. The slot 204 includes varying dimensions. The slot 204 tapers from the inner wall of the RH crankcase 201 towards the RH insert 202a.

[00045] According to an embodiment of the present invention, the restraining member 301 is a spherical object including a steel ball. The preloaded elastic member 302 is a preloaded spring member. Furthermore, the locking member 203 comprises the provision 203a enabling the mounting of the locking member 203 onto the inner wall of the crankcase. Further, the locking member 203 includes a hole 203c adapted to receive at least a part of the preloaded elastic member 302 during assembly of the restraining mechanism 500.
[00046] Although the subject matter has been described in considerable detail with reference to certain embodiments thereof, other embodiments are possible. It is to be understood that the aspects of the embodiments are not necessarily limited to the features described herein.
,CLAIMS:We claim:
1. An engine assembly (113) for a two wheeled vehicle (100), said engine assembly (113) comprising:
a crankcase assembly (15) including a RH crankcase (201) and a LH crankcase (13), said crankcase assembly (15) is capable of housing a crankshaft (502), said crankshaft (502) is rotatably attached to the crankcase assembly (15) through a pair of bearing assemblies (503, 504) each disposed on the LH crankcase (13) and the RH crankcase (201) respectively; and
a RH insert (202a) and a LH insert (202b) each disposed circumferentially around said pair of bearing assemblies (503, 504),
wherein,
said RH insert (202a) and the LH insert (202b) each includes at least a slot (204) of varying cross-section, said at least a slot (204) is capable of accommodating at least one preloaded elastic member (302) pressed against a restraining member (301), said restraining member (301) is at a first position (301-1) at a predetermined temperature and slides further into the slot (204) to attain a second position (301-2) at a temperature greater than the predetermined temperature.
2. The engine assembly (113) as claimed in claim 1, wherein said at least a slot (204) includes a wider cross-section on a side (204a) closer to the locking member (203) as compared to another side (204b) away from said locking member (203).
3. The engine assembly (113) as claimed in claim 1, wherein said restraining member (301) slides from said first position (301-1) to said second position (301-2) whenever one of the sides (204c) of said at least a slot (204) expands from a location ‘A’ to another location ‘B’, said location ‘A’ and said another location ‘B’ includes an expansion angle (O) of approximately 3 degrees there within.
4. The engine assembly (113) as claimed in claim 1, wherein said preloaded elastic member (302) includes a first end (302a) pressed against said restraining member (301) and a second end (302b) pressed against a locking member (203) detachably attached to an inside wall (201a, 201b) of each of the RH crankcase (201) and the LH crankcase (13) respectively.
5. The engine assembly (113) as claimed in claim 1, wherein said second end (302b) is received by a hole (203c) disposed on the locking member (203).
6. The engine assembly (113) as claimed in claim 1, wherein said locking member (203) is detachably attached through a locking means (203b).
7. The engine assembly (113) as claimed in claim 1 or claim 2, wherein said preloaded elastic member (302) is a spring made of a group of metals including steel, said restraining member (301) is a steel ball, and said locking member (203) is made of sheet metal.
8. The engine assembly (113) as claimed in claim 1, wherein said temperature is approximately in the range of 0-60 degrees centigrade.
9. The engine assembly (113) as claimed in claim 1, wherein said pre-determined temperature is approximately in the range of 60-100 degrees centigrade.
10. The engine assembly (113) as claimed in claim 2, wherein said locking member (203) is detachably attached to the inner wall (201a) of the RH crankcase (201) and the LH crankcase (13).