Claims:WE CLAIM:
1. A transmission system (100) for an internal combustion engine (12) of a saddle type vehicle (10), the transmission system (100) comprising:
a primary drive gear mounted on a crankshaft (110) of the engine (12);
an input shaft (120) of the engine (12) having a primary driven gear (124) that is meshed with the primary drive gear, and a plurality of auxiliary driven gears (122);
an output shaft (130) of the engine (12) being engaged with the input shaft (120) via the plurality of auxiliary driven gears (122), the output shaft (130) having a first speed driven gear (132) meshed with a first auxiliary driven gear (122A), and a second speed driven gear (134) meshed with a second auxiliary driven gear (122B), the second speed driven gear (134) having fewer gear-teeth than the first speed driven gear (132); and
a kickstart shaft (150) having a kickstart drive gear (152) mounted thereon, the kickstart drive gear (152) being configured to be meshed with the second speed driven gear (134) of the output shaft (130), such that rotation of the kickstart shaft (150) causes rotation of the second speed driven gear (134) thereby rotating the crankshaft (110) through the input shaft (120), the primary driven gear (124) and the primary drive gear.

2. The transmission system (100) as claimed in claim 1, wherein the output shaft (130) further comprises a fourth speed driven gear (138) and a fifth speed driven gear (140), wherein the fourth speed driven gear (138) and the fifth speed driven gear (140) are splined on to the output shaft (130).

3. The transmission system (100) as claimed in claim 1, wherein the first speed driven gear (132) and the second speed driven gear (134) are freewheeling gears on the output shaft (130) of the engine (12).

4. The transmission system (100) as claimed in claims 2 and 3, wherein the fourth speed driven gear (138) has a plurality of protrusions (139) configured to engage with a plurality of recesses (133) on the first speed driven gear (132), and the fifth speed driven gear (140) has a plurality of protrusions configured to engage with a plurality of recesses on the second speed driven gear (134).

5. The transmission system (100) as claimed in claim 1, wherein the kickstart shaft (150) has a kickstart lever (160) capable of being actuated by a rider, such that actuation of the kickstart lever (160) causes the kickstart shaft (150) to rotate.

6. The transmission system (100) as claimed in claim 5, wherein the kickstart shaft (150) has a kickstart ratchet drive (154) that is configured to receive the kickstart drive gear (152), such that on actuation of the kickstart lever (160), the kickstart drive gear (152) slides along the kickstart ratchet drive (154) to mesh with the second speed driven gear (134) of the output shaft (130).

7. The transmission system (100) as claimed in claim 6, wherein ratio of length of the kickstart ratchet drive (154) to length of the kickstart shaft (150) is predetermined.

8. The transmission system (100) as claimed in claim 1, wherein ratio of length of the kickstart ratchet drive (154) to diameter of the kickstart ratchet drive (154) is predetermined.

, Description:FIELD OF THE INVENTION
[001] The present invention relates to a transmission system for an internal combustion engine of a saddle type vehicle.

BACKGROUND OF THE INVENTION
[002] In conventional saddle type vehicles, a kickstart is used to start an internal combustion engine and bring it into operation. Usually, a kick drive gear is meshed with a first driven gear of an output shaft of the internal combustion engine. The rotation of the kick drive gear causes the first driven gear of the output start to rotate, eventually resulting in the rotation of the crankshaft of the engine.
[003] In conventional kick start arrangements, since the first driven gear usually has a maximum number of gear-teeth, the startability of the engine is increased as maximum rotation can be thus effectuated. However, the higher number of gear teeth in the first driven gear, in turn, requires a rider to apply a high effort to kickstart, which generally lies in the range of 40 kgf to 50 kgf.
[004] Further, when the vehicle is in a stand-still condition, that being, the vehicle has been in idling condition for a long time which is common in slow moving traffic signals or when the vehicle has just been started, the effort required by the rider to shift from a neutral gear to a first gear would be quite high. This is because the first driven gear is connected to the kick drive gear, and the probability of engagement of the first driven gear to a fourth driven gear remains low as long as the kick drive gear is connected to the first driven gear. The increase in shifting from neutral to first gear is further increased by the fact that, for the neutral to first gear change to be effectuated, both the first driven gear and the fourth driven gear of the output shaft need to stop rotating, that is, to have zero RPM before engaging.
[005] Attempts have been made to reduce effort required for kickstarting the engine by reconfiguring the starter mechanism using design modifications such as length of the shaft. However, the startability of the internal combustion engine is negatively affected due to factors such as change in the compression ratio, change in length and diameter of a kickstart shaft or change in a gear ratio of meshed gears.
[006] Thus, there is a need in the art for a transmission system for an internal combustion engine which addresses the aforementioned problems.

SUMMARY OF THE INVENTION
[007] In an aspect, the present invention is directed towards a transmission system for an internal combustion engine of a saddle type vehicle. The internal combustion engine has a crankshaft, an input shaft and an output shaft. A primary drive gear is mounted on the crankshaft of the internal combustion engine. The input shaft has a primary driven gear and a plurality of auxiliary driven gears. The primary drive gear is meshed with the primary driven gear of the input shaft. Further, the output shaft has a first speed driven gear that is meshed with a first auxiliary driven gear of the input shaft; and a second speed driven gear that is meshed with a second auxiliary driven gear of the input shaft. The second speed driven gear has fewer gear-teeth than the first speed driven gear. A kickstart shaft is mounted on the transmission system for an internal combustion engine and the kickstart shaft has a kickstart drive gear. The kickstart drive gear is configured to mesh with the second speed driven gear of the output shaft. Rotation of the kickstart shaft causes rotation of the second speed driven gear, thereby rotating the crankshaft through the input shaft, the primary driven gear and the primary drive gear.
[008] In an embodiment of the invention, the output shaft has a fourth speed driven gear and a fifth speed driven gear, wherein the fourth speed driven gear and the fifth speed driven gear are splined on to the output shaft.
[009] In a further embodiment of the invention, the first speed driven gears and the second speed driven gears are freewheeling gears on the output shaft.
[010] In a further embodiment of the invention, the fourth speed driven gear has a plurality of protrusions configured to engage with a plurality of recesses on the first speed driven gear, and the fifth speed driven gear has a plurality of protrusions configured to engage with a plurality of recesses on the second speed driven gear.
[011] In a further embodiment of the invention, the kickstart shaft has a kickstart lever capable of being actuated by a rider of the vehicle, such that actuation of the kickstart lever causes the kickstart shaft to rotate.
[012] In a further embodiment of the invention, the kickstart shaft has a kickstart ratchet drive that is configured to receive the kickstart drive gear, such that on actuation of the kickstart lever, the kickstart drive gear slides along the kickstart ratchet drive to mesh with the second speed driven gear of the output shaft.
[013] In a further embodiment of the invention, the ratio of length of the kickstart ratchet drive to length of the kickstart shaft is predetermined.
[014] In a further embodiment of the invention, the ratio of length of the kickstart ratchet drive to the diameter of the kickstart ratchet drive is predetermined.

BRIEF DESCRIPTION OF THE DRAWINGS
[015] 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 left side view of an exemplary saddle type vehicle in accordance with an embodiment of the invention.
Figure 2 illustrates a perspective view of an internal combustion engine of the vehicle, in accordance with an embodiment of the invention.
Figure 3 illustrates a perspective view of the internal combustion engine of the vehicle with two axes A-A and C2-C2, in accordance with an embodiment of the invention.
Figure 4 illustrates a sectional view of a transmission system for the internal combustion engine along the C2-C2 axis, in accordance with an embodiment of the invention.
Figure 5 illustrates a sectional view of the transmission system for the internal combustion engine along the A-A axis, in accordance with an embodiment of the invention.
Figure 6 illustrates a perspective view of an output shaft of the internal combustion engine, in accordance with an embodiment of the invention.
Figure 7a illustrates a first speed driven gear, a second speed driven gear, a fourth speed driven gear and a fifth speed driven gear mounted on the output shaft, in accordance with an embodiment of the invention.
Figure 7b illustrates the first speed driven gear engaged with the fourth speed driven gear, in accordance with an embodiment of the invention.
Figures 8a and 8b illustrate a front perspective view and a rear perspective view of the first speed driven gear respectively, in accordance with an embodiment of the invention.
Figure 8c, 8d and 8e illustrate a perspective view, a rear perspective view and a front view of the fourth speed driven respectively, in accordance with an embodiment of the invention.
Figure 9 illustrates a perspective view of a kickstart shaft, in accordance with an embodiment of the invention.
Figure 10 illustrates an exploded perspective view of the kickstart shaft, in accordance with an embodiment of the invention.
Figure 11 illustrates a sectional top view of the transmission system of the internal combustion engine, in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION
[016] The present invention relates to a transmission system for an internal combustion engine for a vehicle. More particularly, the present invention relates to a transmission system for an internal combustion engine of a saddle type vehicle.
[017] Figure 1 illustrates an exemplary saddle-type vehicle 10, in accordance with an embodiment of the invention. The saddle type vehicle 10 comprises an internal combustion engine 12 that is vertically disposed. In an embodiment, the internal combustion engine 12 is a single-cylinder type IC engine. The saddle type vehicle 10 further comprises a front wheel 14, a rear wheel 16, a frame member (not shown), a seat 18 and a fuel tank 20. The frame member includes a head pipe 22, a main frame, rear down tubes, 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) are arranged on an upper portion of the head pipe 22. The frame member comprises a down tube 44 that may be located in front of the internal combustion engine 12 and extends slantingly downward from head pipe 22. The main frame 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 44 and a rear of the internal combustion engine 12 is mounted at the rear portion of the main frame. In an embodiment, the internal combustion engine 12 is mounted vertically, with a cylinder block (not shown) extending vertically above a crankcase (not shown). In an alternative embodiment, the internal combustion engine 12 is mounted horizontally with the cylinder block extending horizontally forwardly from the crankcase. In an embodiment, the cylinder block is disposed rearwardly of the downtube.
[018] The fuel tank 20 is mounted on the horizontal portion of the main frame. The seat rails are joined to main frame and extend rearward to support the seat 18. A rear swing arm 34 is connected to the frame member to swing vertically, and a 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 or through two suspensions 36 on either side of the saddle type vehicle 10 (as illustrated in the present embodiment). A taillight unit 33 is disposed at the end of the saddle type vehicle 10 and at the rear of the seat 18. A grab rail 37 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.
[019] Further, an exhaust pipe (not shown) of the vehicle 10 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 (not shown). The muffler is typically disposed adjoining the rear wheel 16.
[020] Figure 2 illustrates a perspective view of the internal combustion engine 12 of the vehicle 10. As illustrated in Figure 2, and further illustrated in Figure 3, a kickstart lever 160 is attached at the internal combustion engine 12. The kickstart lever 160 is configured to be actuated by a rider of the vehicle 10. The actuation of the kickstart lever 160 results in the rotation of a kickstart shaft 150 (shown in Figure 4). In an embodiment depicted in Figure 2, the kickstart lever 160 is disposed on a right hand side of the internal combustion engine 12.
[021] Reference is made to Figure 4 which illustrates a sectional view of a transmission system 100 for the internal combustion engine 12 along C2-C2 axis (illustrated in Figure 3), and Figure 5 which illustrates a sectional view of the transmission system 100 along A-A axis (illustrated in Figure 3). As illustrated in Figures 4 and 5, the transmission system 100 comprises of a primary drive gear (not shown) mounted on a crankshaft 110 (shown in Figure 11) of the internal combustion engine 12. Further, the transmission system 100 has an input shaft 120. The input shaft 120 has a primary driven gear 124 that is meshed with the primary drive gear. The input shaft 120 further has a plurality of auxiliary driven gears 122. The plurality of auxiliary driven gears 122 have a first auxiliary driven gear 122A (shown in Figure 11) and a second auxiliary driven gear 122B (shown in Figure 11).
[022] The transmission system 100 further has an output shaft 130 that is engaged with the input shaft 120 via the plurality of auxiliary driven gears 122. Herein, the output shaft 130 has a first speed driven gear 132 that is meshed with a first auxiliary driven gear 122A, and a second speed driven gear 134 that is meshed with a second auxiliary driven gear 122B. Herein, the second speed driven gear 134 has fewer gear-teeth than the first speed driven gear 132. This means that while the first speed driven gear 132 corresponds to operation of the vehicle 10 in the first gear, the second speed driven gear 134 corresponds to operation of the vehicle 10 in the second gear. In an embodiment, the first speed driven gear 132 has thirty-five gear teeth, which the second speed driven gear 134 has twenty-six gear teeth.
[023] Further, reference is made to Figure 6, wherein as illustrated, in an embodiment, the output shaft 130 further has a fourth speed driven gear 138 and a fifth speed driven gear 140. In that, the fourth speed driven gear 138 and the fifth speed driven gear 140 are splined on to the output shaft 130. This means that the rotation of the fourth speed driven gear 138 and the fifth speed driven gear 140 will cause rotation of the output shaft 140. Moreover, the fourth speed driven gear 138 and fifth speed driven gear 140 are capable of moving sideways along the output shaft 130.
[024] In this embodiment, the first speed driven gear 132 and the second speed driven gear 134 are freewheeling gears on the output shaft 130 of the engine 12. This means that the rotation of the first speed driven gear 132 and the second speed driven gear 134 cannot cause rotation of the output shaft 130, till the freewheeling gears are engaged with their respective splined gears, namely the fourth speed driven gear 138 and the fifth speed driven gear 140. To facilitate the engagement of the freewheeling gears with the splined gears, the fourth speed driven gear 138 has a plurality of protrusions 139 (shown in Figure 8c and Figure 8e) configured to engage with a plurality of recesses 133 (shown in Figure 8a and Figure 8b) on the first speed driven gear 132. Similarly, the fifth speed driven gear 140 has a plurality of protrusions configured to engage with a plurality of recesses on the second speed driven gear 134. The fourth speed driven gear 138 and the fifth speed driven gear 140 moves sideways along the output shaft to suitably engage or disengage with the first speed driven gear 132 and the second speed driven gear 134 respectively, by allowing for their respective protrusions to slide in and out of the corresponding recesses.
[025] As further illustrated in Figure 4 and Figure 5, the transmission system 100 further has a kickstart shaft 150. The kickstart shaft 150 has a kickstart drive gear 152 mounted thereon. Reference is made to Figure 11, wherein as illustrated, the kickstart drive gear 152 is configured to be meshed with the second speed driven gear 134 of the output shaft 130. This means that rotation of the kickstart shaft 150, which is effected by actuation of the kickstart lever 160, causes rotation of the second speed driven gear 134 thereby rotating the crankshaft 110 through the input shaft 120, the primary driven gear 124 and the primary drive gear.
[026] In operation, the rotation of the kickstart shaft 150 by the actuation of the kickstart lever 160 causes the kickstart drive gear 152 to rotate which in turn, being meshed with the second speed drive gear 134 causes the output shaft 130 to rotate. The rotational motion is further transferred from the output shaft 130 to the input shaft 120 as the second speed driven gear 134 of the output shaft 130 is meshed with the second auxiliary driven gear 122B of the input shaft 120. Thereafter, since the primary driven gear 124 on the input shaft 120 is meshed with the primary drive gear of the crankshaft 110, the crankshaft 110 is rotated. The rotation of the crankshaft 110 resultantly moves a piston (not shown) of the engine 12 causing the engine 12 to start.
[027] Reference is made to Figure 9 and Figure 10, which illustrate that the kickstart shaft 150 comprises of a kickstart ratchet drive 154. The kickstart ratchet drive 154 has a tooth profile that is configured to receive a kickstart drive gear 152. The actuation of the kickstart lever 160 causes the kickstart drive gear 152 to slide along the kickstart ratchet drive 154, and thereby engage with the second speed driven gear 134. As the kickstart lever 160 is released, the kickstart gear 152 is caused to return to an initial position, thereby disengage with the second speed driven gear 134. The kickstart shaft 150 transfers torque and rotational motion to the kickstart rachet drive 154 and resultantly to the kickstart drive gear 152. In an embodiment of the invention, the ratio of length of the kickstart ratchet drive 154 to length of the kickstart shaft 150 is predetermined. In another embodiment of the invention, the ratio of length of the kickstart ratchet drive 154 to the diameter of the kickstart ratchet drive 154 is predetermined. Any increase in the length of the kickstart ratchet drive 154 is accompanied with a corresponding increase in the diameter of the kickstart ratchet drive 154, which prevents wobbling and vibration in the kickstart drive gear 152.
[028] The engagement of the kickstart gear 152 at the second speed driven gear reduces the effort required by the rider of the vehicle 10 to kickstart the vehicle, which is attributable to gear ratio achieved by the second speed driven gear 134 and the kickstart drive gear 152, due to the second speed driven gear 134 having fewer teeth. Further, effort required by the rider of the vehicle 10 to shift from a neutral gear to the first gear is significantly reduced as engagement probability between the first speed driven gear 132 and the fourth speed driven gear 138 is increased, as the first speed driven gear 132 is not meshed with the kickstart lever 152.
[029] Advantageously, the present invention provides a transmission system for an internal combustion engine of a saddle type vehicle wherein, an effort by a rider is significantly reduced while kickstarting the internal combustion engine. Effort required by the rider to kickstart the vehicle is further reduced by the fact that a higher ratio of length of the kickstart ratchet drive to the diameter of the kickstart ratchet drive is achieved in the present invention.
[030] Further, effort required by the rider while shifting from a neutral gear to a first gear is significantly reduced without affecting startability of the internal combustion engine. In addition, the effort required by the rider to shift from the first gear to the second gear is also not increased, as by the time the second gear is actuated by engaging the second speed driven gear with the fifth speed driven gear, the kickstart drive gear is already disengaged with the second speed driven gear, hence maintaining a higher probability of engagement with the fifth speed driven gear.
[031] 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.