DESC:FIELD OF INVENTION
[0001] The present invention relates to an internal combustion engine and more particularly to transmission system of an internal combustion engine with continuously variable transmission system.
BACKGROUND OF INVENTION
[0002] In engines with continuously variable transmission system, the fixed one of the two drive sheaves will be generally integrated with starter ring gear and will be mounted on crankshaft by means of a spline joint. Adding to this, ratchet which is used for kick-starting is mounted on crankshaft by spline joint in close proximity of sheave fixed drive. Such a sheave fixed drive has higher number of joints due to more number of parts and less spline width due to which spline achieves a low L/D ratio which may lead to spline washout.
[0003] Further in such a system, kick starting power flows through the thread which leads to the over tightening of nut. In addition, due to low L/D ratio, there is more possibility of tilt during assembly of sheave fixed drive, which may result into edge locking, noise, and loosening during operation of the said sheave fixed drive. Moreover, in these systems, micro movements of sheave fixed drive will get transferred to the combined ratchet nut leading to further loosening. Also, higher entry chamfer is sheave takes place.
[0004] Due to low spline length in sheave, lesser contact area is available. Due to lesser contact area, the part will not withstand higher tightening torque. Also, due to more number of parts and some parts with lesser width, the stresses are higher and won’t withstand and retain higher tightening torque. Due to more number of parts, the number of relative joints is higher, that increases plastic deformation in individual parts, and problem of low axial clamping is created, thereby reducing tightening torque withstanding capacity of the ratchet nut.
[0005] In extreme cases, it may lead to frequent serviceability of crankshaft due to crankshaft washout that leads to increased cost. Ratchet nut loosening due to lower tightening torque, ratchet nut thread wash out, crankshaft spline and thread wash out and sheave spline wearing out are common problems faced in such a sheave. Hence, a sheave fixed drive is desired wherein the spline width is optimum to reduce possibility of tilt during assembly for sheave fixed drive.
SUMMARY OF THE INVENTION
[0006] The proposal is to integrate sheave fixed drive with ratchet and/or spacer if any, into a single component either by casting or by welding. This enables single spline joint on to crankshaft, which helps to make the joint stronger and more durable.
[0007] By integrating sheave fixed drive to ratchet and spacer if any, the internal spline created inside the mounting hole, will have larger length/diameter ratio. This ensures that the integral part be robust against misalignments during assembly with crankshaft.
[0008] Longer spline means that the joint is stronger and durable. Number of loose parts in between the abutment face on the crankshaft and the nut ratchet will be reduced. This results in better clamping torque retention due to lesser no. of butting joints along the crankshaft axis. The same part when integrated with ring gear, it can serve as a single driven part of both electric starter mechanism and kick-starter mechanism. The layout becomes compact. Due to increased spine length, improper seating of spring washer can be avoided. In addition, Problem of low axial clamping force is resolved. Furthermore, less L/D ratio of spacer ratchet is overcome. Hence, in the proposed sheave, the ratchet nut tightening process is more efficient as tilting is reduced and high entry chamfer in sheave is resolved.
BRIEF DESCRIPTION OF DRAWINGS
[0009] Figure 1illustrates a typical two wheeler.
[00010] Figure 2illustrates sectional view of a typical engine of a two wheeler.
[00011] Figure 3 illustrates an exploded view of the driving side of the transmission system.
[00012] Figure 4 illustrates sheave fixed drive according to the first embodiment of the current invention.
[00013] Figure 5 illustrates sectional view of the driving side of transmission according to the first embodiment of the current invention.
[00014] Figure 6 illustrates sheave fixed drive according to the second embodiment of the current invention.
[00015] Figure 7 illustrates sectional view of the driving side of transmission according to the second embodiment of the current invention.
[00016] Figure 8 illustrates sheave fixed drive according to the third embodiment of the current invention.
[00017] Figure 9 illustrates sectional view of the driving side of transmission according to the third embodiment of the current invention.
[00018] Figure 10 illustrates sheave fixed drive according to the fourth embodiment of the current invention.
[00019] Figure 11 illustrates sectional view of the driving side of transmission according to the fourth embodiment of the current invention.
DETAILED DESCRIPTION OF THE INVENTION
[00020] Face (sheave) fixed drive (30) (shown in Figure 3) is a part of continuously variable transmission (CVT) drive mechanism in which a half pulley is formed in thick sheet or cast to profile, which is further fixed on to crankshaft. It rotates integrally with crankshaft without any relative axial or radial movement w.r.t crankshaft.
[00021] Face (sheave) movable drive (28) (shown in Figure 3) is a part of CVT drive mechanism, and is a half pulley cast to profile, which is slidably mounted on crankshaft. It (Face (sheave) movable drive (28)) rotates along with the crankshaft (25) but will have relative axial movement w.r.t sheave fixed drive. An axial ratchet is fitted on crankshaft by means of spline joint used for cranking the engine by use of a kick starter mechanism and in the end to fix the whole assembly a ratchet nut is deployed.
[00022] The kick-starter ratchet is an axial ratchet fitted slidably and rotatably (simultaneously) on a pin on kick-starter assembly, integral with the final gear of kick-starter. Whenever kick-lever is actuated, the kick-starter ratchet moves axially along the pin, engages with the ratchet crankshaft, rotates the crankshaft keeping the engagement, and retracts back when the engine cranks.
[00023] The ratchet nut is a threaded nut used to secure all the CVT drive parts, Timing sprocket, ratchet and spacers if any axially along the crankshaft axis. A ring gear is large thin spur/helical gear mounted axially on crankshaft by means of spline joint, used for cranking the engine by use of electric starter mechanism. This part can either be an independent part or integrated on sheave fixed drive. This is further described in more detail in separate embodiments of the current invention.
[00024] The ring gear is press-fitted radially or integrally formed on the sheave fixed drive; and ratchet crankshaft is welded axially or integrally casted with the sheave fixed drive. Spacers if any can also be integrated with this part. Internal spline is cut on the central mounting hole. This integral part will be assembled along crankshaft spline, butting against spacer CVT drive and secured by nut ratchet at the end.
[00025] When the ratchet kick-starter engages rotatably with the integral ratchet of the sheave fixed drive, the starting torque is transmitted through the spline joint to the crankshaft. Alternately, when the final drive gear of electric starter mechanism engages with the ring gear on the periphery of sheave fixed drive, ring gear will be driven and the torque gets transmitted to crankshaft through the spline. By any of the above mentioned two means the engine can be cranked, while the driven part on the crankshaft is only one part – Integral sheave-ratchet-ring gear.
[00026] Figure 1 shows a typical two-wheeled vehicle 1 with a rear wheel 2, engine 3, air filter 4, front wheel 5, floorboard6, utility box 7, side panel 9, front shock absorber 10, rear shock absorber 11, grab rail 12, tail lamp 13 and rider seat 14. The direction of arrow “F” shows the front direction of the vehicle and direction of arrow “R” shows the rear direction of the vehicle.
[00027] Figure 2 shows drive shaft 25, cylinder block 26, ramp plate 27, movable sheave of drive pulley 28, weight rollers 29, fixed sheave of drive pulley 30 and CVT belt 31. Ramp plate 27 provides sliding surface to weight rollers 29 for varying CVT ratio. Weight rollers 29 slides between ramp plate 27 and movable sheave of driver pulley 28 for varying CVT ratio.
[00028] Figure 3 shows drive shaft 25, ramp plate 27, movable sheave of driver pulley 28, weight rollers (6 No.s) 29, fixed sheave of drive pulley 30, V- belt 31, CVT drive side 41, CVT driven side 42, spacer for fixed sheave of driver pulley 43, axial fan 44, spacer for ratchet nut 45, ratchet nut 46, nut 47.
[00029] Figure 4 illustrates sheave fixed drive according to the first embodiment of the current invention. Figure 4 shows fixed sheave of drive pulley 30, ring gear 51, sheave fixed drive 52, and fan fixed drive 53, insert 54 and ratchet 56. According to the invention, the sheave fixed drive 52 and the fan fixed drive 53 are made up of aluminium and this whole integrated part is press fit or en moulded with the said ring gear 51 and insert54 wherein the said ring gear 51 and insert 54 are made up of steel. The whole sheave is as cast.
[00030] Figure 5 illustrates sectional view of the driving side of transmission according to the first embodiment of the current invention. Figure 5 shows ring gear 51, sheave fixed drive 52, fan fixed drive 53, insert 54, gear kick starter driven 55, ratchet 56 and spacer movable drive 57. In this case, the insert 54 and the ratchet 56 are not integrated.
[00031] Figure 6 illustrates sheave fixed drive according to the second embodiment of the current invention. Figure 6 shows fixed sheave of drive pulley 30, ring gear 51, sheave fixed drive 52, and fan fixed drive 53, insert 54, and ratchet 56. According to the invention, the sheave fixed drive 52 and the fan fixed drive 53 are made up of aluminium as a single piece; insert 54 and ratchet 56 are made up of aluminium as a single piece; ring gear 51 is made up of steel and then sheave fixed drive 52, and fan fixed drive 53 as a single piece is press fit or en-molded with the said ring gear 51 and the whole ring gear 51, sheave fixed drive 52, and fan fixed drive 53, insert 54, and ratchet 56 are made as cast.
[00032] Figure 7 illustrates sectional view of the driving side of transmission according to the second embodiment of the current invention. Figure 7 shows ring gear 51, sheave fixed drive 52, fan fixed drive 53, insert 54, gear kick starter driven 55, ratchet 56 and spacer movable drive 57. In this embodiment of the current invention, the insert 54 and the ratchet 56 has been integrated into one piece.
[00033] Figure 8 illustrates sheave fixed drive according to the third embodiment of the current invention. Figure 8 shows fixed sheave of drive pulley 30, ring gear 51, sheave fixed drive 52, and fan fixed drive 53, spacer 58. According to the invention, all the ring gear 51, sheave fixed drive 52, and fan fixed drive 53, spacer 58, and ratchet 56 are made up of steel. In this current embodiment, the ring gear 51 and sheave fixed drive 52 are made as one single piece; spacer 58, and ratchet 56 are formed as another single piece. The two single pieces namely the ring gear 51 with sheave fixed drive 52, and insert 54 with ratchet 56 are arc welded whereas the sheave fixed drive 52, and fan fixed drive 53 are spot welded.
[00034] Figure 9 illustrates sectional view of the driving side of transmission according to the third embodiment of the current invention. Figure 9 shows ring gear 51, sheave fixed drive 52, fan fixed drive 53, spacer 58, gear kick starter driven 55, ratchet 56 and spacer movable drive 57. In this embodiment of the current invention, the spacer 58 and the ratchet 56 are not integrated.
[00035] Figure 10 illustrates sheave fixed drive according to the fourth embodiment of the current invention. Figure 10 shows fixed sheave of drive pulley 30, ring gear 51, sheave fixed drive 52, and fan fixed drive 53, spacer 58, and ratchet 56. According to the invention, the ring gear 51 and sheave fixed drive 52 are formed as a single piece and this single piece of ring gear 51 with sheave fixed drive 52 is arc welded with insert 54. Furthermore, sheave fixed drive 52, and fan fixed drive 53 are spot welded.
[00036] Figure 11 illustrates sectional view of the driving side of transmission according to the fourth embodiment of the current invention. Figure 11 shows ring gear 51, sheave fixed drive 52, fan fixed drive 53, spacer 58, gear kick starter driven 55, ratchet 56. In this embodiment of the current invention, the spacer 58 and the ratchet 56 are integrated into one piece. The ring gear 51 and the said sheave fixed drive 52 are integrated into a first piece; the said spacer 58 is arc welded with the said first piece; the said sheave fixed drive 52 and the said fan fixed drive 53 are spot welded; all elements being made up of steel; the whole fixed sheave of drive pulley 30 being as cast.
[00037] In all the cases as described herein holding of sheave with spacer having larger L/D ratio, gear hobbing and machining is easier. According to the proposed invention, a low spline length in sheave is avoided. In addition, number of parts has been reduced thereby reducing the number of relative joints that reduces plastic deformation in individual parts, thereby enhancing tightening torque withstanding capacity of the ratchet nut. Due to increased spine length, improper seating of spring washer can be avoided. Also, Problem of low axial clamping force is resolved. Furthermore, less L/D ratio of spacer ratchet is overcome. Hence, in the proposed sheave, the ratchet nut tightening process is more efficient as tilting is reduced and high entry chamfer in sheave is resolved.
,CLAIMS:We claim:
1. A continuously variable transmission system for a two wheeled vehicle, said continuously variable transmission system comprising:
a drive shaft (25) capable of rotating about an axis (X-X’);
a drive pulley system (41) comprising of
a movable sheave (28) capable of rotating about an axis (X-X’) and translating in said axial direction (X-X’); and
a fixed sheave (30) comprising of a ring gear (51), a sheave fixed drive (52) having an annular shape with an inner profile (48) and an outer profile (49), a fan fixed drive (53) consisting of plurality of profile made to drag and divert atmospheric air and joined together by atleast one of the methods amongst welding and casting on said sheave fixed drive (52) wherein said fixed sheave of drive pulley (30) is capable to rotate about the axis X-X’ as and axial movement with respect to said drive shaft (25) is inhibited;
a CVT belt (31), capable of sliding and moving between said movable sheave (28) of drive pulley (41) and said fixed sheave (30) of drive pulley (41);
wherein a ratchet (56) and spacer (54) are integrally formed and the integral piece is as cast joined to said inner profile (48) of said sheave fixed drive (52) and said outer profile (49) of said sheave fixed drive (52) is as cast joined to ring gear (51) to form an integrated sheave structure (30).
2. A continuously variable transmission system for a two wheeled vehicle, said continuously variable transmission system comprising:
a drive shaft (25) capable of rotating about an axis (X-X’);
a drive pulley comprising of
a movable sheave (28) capable of rotating about an axis (X-X’) and translating in said axial direction (X-X’); and
a fixed sheave (30) comprising of a ring gear (51), a sheave fixed drive (52) having an annular shape with an inner profile (48) and an outer profile (49), a fan fixed drive (53) consisting of plurality of profile made to drag and divert atmospheric air and joined together by atleast one of the methods amongst welding and casting on said sheave fixed drive (52) wherein said fixed sheave of drive pulley (30) is capable to rotate about the axis X-X’ as and axial movement with respect to said drive shaft (25) is inhibited;
a CVT belt (31), capable of sliding and moving between said movable sheave of drive pulley (28) and said fixed sheave of drive pulley (30);
wherein an insert (58) is as cast joined to said inner profile (48) of said sheave fixed drive (52) and said outer profile (49) of said sheave fixed drive (52) is as cast joined to ring gear (51) to form an integrated sheave structure (30).
3. The continuously variable transmission system for a two wheeled vehicle as Claimed in Claim 1 such that said ring gear (51) and said sheave fixed drive (52) are integrated into a first piece; said spacer (58) is arc welded with said first piece; said sheave fixed drive (52) and said fan fixed drive (53) are spot welded and all elements are made up of steel and the whole fixed sheave of drive pulley (30) being as cast.

4. The continuously variable transmission system for a two-wheeled vehicle as Claimed in Claim 1 wherein the ratchet (56) is integrated with said spacer (58).