DESC:TECHNICAL FIELD
[0001] The present subject matter relates generally to a two-wheeled or three-wheeled vehicle and more particularly to a gear transmission system for an internal combustion engine for the two-wheeled or three-wheeled vehicle.
BACKGROUND
[0002] Generally, a motor vehicle like a two-wheeled or three wheeled vehicle comprises of a frame assembly extending rearwardly from a head tube. The frame assembly acts as a skeleton and a structural member for the vehicle that supports the vehicle loads. A front wheel is connected to a front portion of the frame assembly through one or more front suspension(s). The frame assembly extends towards a rear portion of the vehicle. A rear wheel is connected to a frame assembly through one or more rear suspension(s). The frame assembly comprises of an engine assembly mounted to it. The engine assembly is functionally connected to the rear wheel, which provides forward motion to the vehicle.
[0003] An engine assembly is mounted to the frame assembly of the vehicle. In a two-wheeled or three wheeled vehicle, the engine assembly is disposed in a front portion of the vehicle. In case of an internal combustion (IC) engine, there are one or more cylinder bore(s), where combustion happens. The internal combustion (IC) engine, among other components, has a cylinder on top of which a cylinder head is mounted, and receives a reciprocating piston from the bottom. On combustion of the air-fuel mixture, the piston transfers the energy generated during combustion to a crankshaft through a connecting rod thereby driving the crankshaft. In this way, the reciprocatory motion of the piston is converted to rotary motion of the crankshaft. The crankshaft rotation then powers the vehicle.
[0004] Vehicles with an internal combustion engine commonly have a geared transmission system to carry the power generated by an internal combustion (IC) engine, in a controllable way, to a wheel of the vehicle. The gear transmission system comprises a system of interlocking gears such that by operating a gear shift lever manually, the driver can choose one of the several ratios of speed between the input shaft and the output shaft. To allow smooth and gradual shifting of gears, a clutch is provided to isolate the engine from the transmission momentarily. When the driver releases the clutch lever manually, the discs in the clutch assembly are squeezed with each other and thus the transmission is engaged with the engine.
[0005] The rider can decide on the need to change the gear position based on the engine speed or vehicle speed indication provided on the instrument cluster. However, problem arises when the rider faces difficulty in changing the gear. The system being mechanical in nature, undergoes wear & tear owing to friction between parts. There have been instances when the gear system has become very hard with usage, wear & tear and the rider faces problems while shifting the gear. This problem has specially been prone to all gear kick start vehicles.
[0006] Generally, a kick start driven gear is provided in a vehicle to initiate the engine and gear transmission in process when a vehicle is started. A set of helical gears is provided in the gear transmission system for an easy operation and running condition. However, during operation of a vehicle, when the rider changes the gear there is an inward axial force which the helical gears exert on the kick start idler gear. This inward axial force pushes the kick start idler gear attached to a clutch shaft resulting in a float reduction of the clutch shaft with continuous running of the vehicle. This float reduction is the prime reason for the stiffness and hardness faced by the rider in shifting the gear.
[0007] Thus the present system provides a gear transmission system which is easy to operate. In furtherance to it the present subject matter aims to remove the stiffness or hardness faced by the rider while changing the gears.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The detailed description of the present subject matter is described with reference to the accompanying figures. Same numbers are used throughout the drawings to reference like features and components.
[0009] Fig. 1 illustrates a right side view of an exemplary two-wheeled vehicle, in accordance with an embodiment of the present subject matter.
[00010] Fig. 2 illustrates a side view of the engine assembly for the two wheeled vehicle as shown in Fig. 1, in accordance with an embodiment of the present subject matter.
[00011] Fig. 3 illustrates a sectional view of the gear transmission box of the engine assembly as shown in Fig. 2, in accordance with an embodiment of the present subject matter.
[00012] Fig. 4 illustrates an enlarged top view of the gear transmission assembly for the engine assembly as shown in Fig. 2, in accordance with an embodiment of the present subject matter.
[00013] Fig. 5 illustrates an enlarged sectional view of the gear transmission box for the engine assembly, in accordance with the embodiment of Fig. 4.
[00014] Fig. 6 illustrates another isometric view of the gear transmission system with selected parts, in accordance with an embodiment of the present subject matter.
[00015] Fig. 7 illustrates a sectional view of engine assembly for a conventional design depicting the gear transmission system.
DETALIED DESCRIPTION
[00016] Typically, a saddle type motor vehicle is operated through an engine assembly mounted to the frame assembly in a front portion and a fuel tank disposed above the engine assembly. Conventionally, internal combustion engine assembly includes a crankcase, a cylinder block coupled to the crankcase, and a cylinder head mounted on the upper part of the cylinder block. Air fuel mixture is supplied to the engine assembly by means of a carburetor. Thereafter combustion of the air fuel mixture takes place so that a piston disposed in the engine assembly is set into motion. The piston is operated in a linear motion, after which said liner motion is converted to a rotational motion, wherein said rotational motion is transferred to the rear wheel finally resulting into motion of the vehicle. This mechanism also results in generation of power and torque by the engine assembly.
[00017] Conventionally, a saddle type vehicle is provided with a gear transmission system which transmits the power generated by the internal combustion engine, in a controllable way, to a wheel of the vehicle. The gear transmission system has primarily two functions. Firstly, it disconnects the engine from the wheel to enable gearing to boost the engine's effective torque. Secondly, it also disconnects the engine from the wheel when the vehicle is stopped thus permitting the engine to run without driving the vehicle.
[00018] Generally, the gear transmission system includes a clutch, a gearbox and a drive means. It is housed on an input shaft and an output shaft operatively connected with each other through the gearbox and deriving power from the crankshaft. The clutch is located at one end of the input shaft to momentarily disconnect the gearbox from the engine to ensure gradual shifting of gears. When the clutch is engaged, it transmits force from the engine and rotates the wheel. When the clutch is disengaged, the transmission of rotational force is cut off and the wheel tends to stop. The gearbox comprises a set of interlocking gears with multiple gear ratios. The rider can switch between the gear ratios as the speed of the vehicle varies by operating a gear shift means manually.
[00019] However, such known gear transmission systems face some prominent problems while changing the gear. The rider finds it hard to change the gear and experiences some stiffness in this respect. Such issues are more prominent in an all gear kick start vehicles. Mostly, a kick start driven gear is provided in a vehicle to initiate the engine and gear transmission in process when a vehicle is started. A set of helical gears is provided in the gear transmission system for an easy operation and running condition. However, during operation of a vehicle, when the rider changes the gear, the rider actuates a clutch lever, because of which there is an inward axial force which the helical gears exert on the kick start idler gear. This inward axial force pushes the kick start idler gear attached to a clutch shaft resulting in a float reduction of the clutch shaft with continuous running of the vehicle. This float reduction is the prime reason for the stiffness and hardness faced by the rider in shifting the gear.
[00020] Fig. 7 (prior art) illustrates a sectional view of a conventional gear transmission box (18a), used prior to application of the present subject matter. The conventional gear transmission box (18a) used prior to the present subject matter comprised of a clutch shaft (21), driven shaft (22), primary drive gear (not shown), a primary driven gear (20), clutch assembly (19), a kick start idler gear (23) and intermediate gears (24) attached on the clutch shaft (21) and the driven shaft (22). The power and torque of the internal combustion engine is transferred through the primary drive gear to the primary driven gear (20). The primary driven gear (20) is connected to the clutch shaft (21) through the intermediate gears (24) such that the power and torque coming from the engine assembly (4) is transferred to the clutch shaft (21) as well. This in turn results in rotation of the clutch shaft (21) and in rotation of the intermediate gears (24) attached on the clutch shaft as well. The gears on the clutch shaft (21) are in mesh with the gears attached to the driven shaft (22). This helps in transfer of the power to the driven shaft (22) which then rotates depending upon the gear ratio and since the driven shaft (22) is connected to the rear wheel, it helps in transfer of that torque to the rear wheel (11) as well. In furtherance to it the clutch shaft (21) is connected to the clutch assembly (19) such that when the rider feels the need to change the gear he can use the clutch lever to disengage the primary drive and primary driven gear (20) and move the clutch shaft (21) through the clutch assembly (19). The way gears in the clutch shaft (21) and driven shaft (22) are in mesh changes with the increase or decrease in speed and how the rider changes the gear according to it.
[00021] However, the primary gears generally comprise of helical gears and due to the axial forces which act in an inward direction push the kick start idler gear (23) that is pressed on the clutch shaft (21) resulting in float reduction of the clutch shaft (21). This in turn also creates a problem for the rider while changing the gears as it becomes very hard while doing so.
[00022] The present subject matter overcomes the above stated problems of the gear transmission system in the prior art. One of the objectives of the present subject matter is to provide a two wheeled or three wheeled vehicle with a gear transmission system in which it is easy for the rider to switch gears. The present subject matter achieves the following objective without changing the existing helical gear system to spur gear system. As the use of spur gears offers poor engagement that exerts large amount of stress on the teeth of the gear. Moreover, spur gears tend to produce noise at high speeds. In furtherance to it the present subject matter needs no change in design of the clutch shaft or removal of lugs from the kick start idler gear or the primary driven gear. Thus, the present subject matter enables use of helical gear that offer improved performance compared to spur gears.
[00023] In an embodiment in accordance with the present subject matter, a two-wheeled vehicle employed with a gear transmission system including a kick start idler gear is provided. The gear transmission system is provided in such a way that the rider dose not finds it hard to change the gear.
[00024] In an embodiment, a kick start idler gear is provided to help in starting of the engine. As soon as the rider kick starts the vehicle the primary driven gear provided is turned by a means of a kick idling gear and a kick pinion which in turn helps in starting of the internal combustion engine. Generally, a vehicle also comprises of a gear transmission box which helps in transferring of torque and power generated by the internal combustion engine to the rear wheel. In an embodiment, the gear transmission box comprises of a clutch shaft, driven shaft, clutch assembly, intermediate gears, and primary drive gears. The vehicle is provided with a primary drive gear which helps in transfer of power and transmission generated by the internal combustion engine to the gear transmission box through primary drive gears.
[00025] In an embodiment, the clutch assembly is connected to the clutch shaft on which the intermediate gears are provided. While the internal combustion engine is running the power and torque generated by it is transferred through the primary drive gear to the primary driven gear. In furtherance to it the primary driven gears are connected to the clutch shaft such that it transfers the power to the clutch shaft resulting in its rotation and rotation of the intermediate gears attached to it as well. In an embodiment, the intermediate gears on the clutch shaft are in mesh with the gears on the driven shaft such that the driven shaft moves with different speed as that of the clutch shaft based on ratio of engaging gear. The driven shaft is connected to the rear wheel such that the motion is supplied to the rear wheel through the driven shaft. When the rider feels the need to change the gear as per the speed requirement, he uses clutch assembly to disengage the primary drive and primary driven gears and change the arrangement in which the gears of clutch shaft and driven shaft are in contact. As per the speed requirement the gear arrangement is changed by the rider and the same process of speed and power transfer from the engine assembly is repeated.
[00026] However, there are occasions when the rider finds it hard and inconvenient to change the gear. The prime reason for this problem is the float reduction in the clutch shaft with continuous running of the vehicle. The primary gears generally comprise of helical gears and due to the inward acting axial forces of the helical gears the kick start idler gear is pushed such that it is pressed on the clutch shaft resulting in its float reduction. Therefore in order to stop the kick start idler gear from being pushed further inside and reduce the float reduction a gear spacer is disposed over the primary driven gear. The placement of the gear spacer in that region results in transfer of the inward axial force to the ball bearing through gear spacer and not the kick start idler gear. This in furtherance stops the float reduction caused and solves the problem of hard gear shifting.
[00027] The present subject matter enhances the ease and smoothness for the rider while shifting gears. It also curbs the problem of float reduction occurring in the gear transmission assembly. In furtherance to it the present subject matter does not requires the helical gears to be replaced with spur gears, nor does it requires change in design of the clutch shaft. From the vehicle perspective the present subject matter improves the engine durability and has no impact on the assembly or service time.
[00028] The engine assembly is provided with a gear spacer mounted to the clutch shaft and the gear spacer is capable of providing a spacing between the idler gear and the primary driven gear, which is maintained by the gear spacer, thereby maintaining a pre-determined distance therebetween.
[00029] The gear spacer can be mounted on the primary driven gear. For example, the primary driven gear is concentrically mounted on to an extended portion of the primary driven gear whereby the gear spacer does not require additional mounting space on the clutch shaft.
[00030] The gear spacer is sandwiched between the primary driven gear and the first bearing, wherein the first gear is disposed in proximity to the primary driven gear, in axial direction. In other terms, the gear spacer is between the primary driven gear and the first gear maintaining the desired space. The axial forces from the primary driven gear are exerted on the first bearing.
[00031] The gear spacer is having one axial face abutting the primary driven gear and other axial face of the gear spacer is abutting an inner race of the first bearing. The gear spacer can be adapted to be abutting an outer race of the first bearing.
[00032] Preferably, the first bearing is having a diameter larger than a diameter of the second bearing and the first bearing is press fitted to the crankcase whereby the first bearing is capable of withstanding axial forces acting thereon.
[00033] The gear spacer can a substantial circular profile so that it is concentrically mounted to the primary driven gear. However, the gear spacer can have a partial circular profile.
[00034] The primary gear can have a stepped portion and the gear spacer can be mounted at the stepped portion of the primary driven gear, wherein the stepped portion ca be an L-shaped portion. Moreover, the gear spacer is provided with an axial width being at least equal to a width of the stepped portion whereby it can be at least seated thereat without affecting radial clearance.
[00035] The aforesaid and other advantages of the present subject matter would be described in greater detail in conjunction with the figures in the following description.
[00036] Fig. 1 illustrates a right side view of an exemplary two-wheeled vehicle (50), in accordance with an embodiment of the present subject matter. The vehicle (50) includes a frame assembly (5) that extends from a head tube (not shown), which is disposed in the front portion of the vehicle (50). The frame assembly (5) includes a mainframe (not shown) comprising a main tube extending rearward from a rear portion of the head tube and a down tube (not shown) that extends rearwardly downward from the head tube. The frame assembly (5) may further comprise a sub-frame formed by a pair of rear tubes (not shown) that extend obliquely rearward from the main frame. An engine assembly (4) is supported by the main frame of the frame assembly (5). The engine assembly (4) acts as the power unit of the vehicle (50), wherein the power unit may also include a traction/electrical motor (not shown). A front portion of a swing arm assembly (not shown) is swingably connected to the main frame of the frame assembly (5) and rear portion of the swing arm assembly (not shown) rotatably supports a rear wheel (11). The rear wheel (11) is functionally coupled to the engine assembly (4) through a transmission system. A rear fender (14) disposed upwardly of the rear wheel (11) covers at least a portion of the rear wheel (11). Further, the swing arm assembly (not shown) is coupled to the frame assembly (5) through one or more rear suspension(s). A pair of front forks (8) supports a front wheel (10) and is steerably supported by the head pipe. A handlebar assembly (2) is connected to an upper portion of the pair of front fork (8). Further, a front fender assembly (9) covers at least a portion of the front wheel (10) and the front fender assembly (9) is mounted to the front forks (8).
[00037] A fuel tank (3) is mounted to the main tube of the frame assembly (5) and disposed rearwardly of the handlebar assembly (2). A seat assembly (12) is disposed rearwardly of the fuel tank (3) and supported by the pair of rear tubes. Further, the vehicle (50) comprises a visor assembly (6) that is disposed forwardly over the headlamp (7). A tail cover assembly (16) is disposed rearwardly of the side panel assembly (not shown) and extends along the pair of rear tubes thereby covering at least a portion of the pair of rear tubes. The tail cover assembly (16) extends towards a rear portion of the frame assembly (5) and the tail cover assembly (16) is adapted to accommodate a pillion handle (13) attached to its side. An exhaust emission system (17) is disposed extending substantially rearwardly from an exhaust pipe (not shown) emerging out of an exhaust port (not shown) of the engine assembly (4).
[00038] Fig. 2 illustrates a side view of the engine assembly (4) of the two wheeled vehicle (50) as shown in Fig. 1, in accordance with an embodiment of the present subject matter. In an embodiment, the engine assembly (4) comprises of a gear transmission box (18) provided to transfer the power and torque of the engine assembly (4) to the rear wheel (11) so that the vehicle (50) is driven. The engine assembly (4) includes a crankcase (30) that rotatably supports various parts of the engine assembly (4) including a crankshaft (34). A primary drive gear (33) is secured to the crankshaft (34), wherein the primary drive gear (33) is preferably a helical gear. The primary drive gear (33) is connected to a primary driven gear (20) (shown in Fig. 2), wherein the primary driven gear (20) is also a helical gear that engages with the primary drive gear (33). A clutch assembly (19) is mounted to the clutch shaft (21). The crankcase (30) supports a cylinder body (35) and a cylinder head (36), wherein a piston (not shown) is reciprocatingly movable inside a cylinder portion defined by the cylinder body (35).
[00039] Fig. 3 illustrates a sectional view of the gear transmission box (18) of the engine assembly (4), taken along axis A-A’, as shown in Fig. 2, in accordance with an embodiment of the present subject matter. In an embodiment, the gear transmission box (18) comprises of a gear transmission assembly (26) including a clutch assembly (19), primary drive gear (33) (shown in Fig. 2), and primary driven gear (20), clutch shaft (21), driven shaft (22) and intermediate gears (24) attached on the clutch shaft (21) and the driven shaft (22). A gear spacer (25) is mounted to the clutch shaft (21), and the gear spacer (25) is capable of providing a spacing between the idler gear (23) and the primary driven gear (20). The idler gear can be a kick start idler gear (23) and is also provided on the clutch shaft (21) with a gear spacer (25) being attached to the primary driven gear (20) and being disposed adjacent to the kick start idler gear (23), in an implementation.
[00040] Fig. 4 illustrates an isometric view of the gear transmission assembly (26) of the two wheeled vehicle (50) as shown in Fig. 1, in accordance with an embodiment of the present subject matter. The gear transmission assembly (26) can be seen to be comprising of the primary driven gear (20) and the intermediate gears (24) attached on the clutch shaft (21) connected to it. In furtherance to it the intermediate gears (24) on the driven shaft (22) are in mesh with the gears on the clutch shaft (21). The gear spacer (25) is placed over the primary driven gear (20) adjacent to the kick start idler gear (23) to absorb the axial inward force caused due to the helical gears.
[00041] Fig. 5 illustrates a sectional view of the gear transmission assembly (26) of the engine assembly (4) as shown in Fig. 2, in accordance with an embodiment of the present subject matter. In an embodiment, the gear spacer (25) is placed over the primary driven gear (20). The gear spacer (25) is disposed beside the kick start idler gear (23) just adjacent to it. The gear spacer (25) is placed in that location to absorb the inward axial force caused by helical gears that includes the primary driven gear (20). The gear spacer (25) is having one axial face abutting the primary driven gear (20) and other axial face of the gear spacer (25) is abutting an inner race (38) of the first bearing (28). The gear spacer (25) transfers the force to the ball bearing inner race, which is first bearing (28), and does not allow it to be transferred to the kick start idler gear (23) which in turn keeps the assembly intact and curbs the problem of float reduction of the clutch shaft (21). Hence, it enhances the ease and smoothness while shifting gears for the rider. The first bearing (28) is having a diameter larger than a diameter of the second bearing (27) (as depicted in Fig. 4) and the first bearing (28) is press fitted to the crankcase (30), wherein the first bearing (28) is capable of withstanding axial forces acting thereon.
[00042] The gear spacer (25) is mounted at a stepped portion of the primary driven gear (20) (as shown in Fig. 5), wherein the stepped portion can be L-shaped portion. The gear spacer (25) is seated at the stepped portion concentrically on the primary driven gear (20). The gear spacer (25) is provided with an axial width being at least equal to a width of the stepped portion.
[00043] Fig. 6 illustrates an isometric view of the gear transmission assembly (26) of the engine assembly (4) as shown in Fig. 4, in accordance with an embodiment of the present subject matter. In an embodiment, the gear spacer (25) is placed over the primary driven gear (20) such that an inner facing side of the gear spacer (25) abuts an outer facing side of the first bearing (28) (as shown in Fig, 4). The gear spacer (25) is disposed beside the kick start idler gear (23) just adjacent to it but abutting the first bearing (28). The gear spacer (25) is placed in that location to absorb the inward axial force caused by helical gears that includes the primary driven gear (20). The first bearing (28) includes an inner race (38) and an outer race (39) (as shown in Fig. 5). The gear spacer (25) transfers the force to the first bearing (ball) (28), specifically to the inner race (38) and does not allow it to be transferred to the kick start idler gear (23) which in turn keeps the gear assembly intact and curbs the problem of float reduction of the clutch shaft (21). Hence, it enhances the ease and smoothness while shifting gears for the rider.
[00044] Many modifications and variations of the present subject matter are possible within the scope of the present subject matter as claimed in claim 1, in the light of above disclosure.
List of reference signs:

50 vehicle
2 handlebar assembly
3 fuel tank
4 engine assembly
5 frame assembly
6 visor assembly
7 headlamp
8 front forks
9 front fender assembly
10 front wheel
11 rear wheel
12 seat assembly
13 pillion handle
14 rear fender
16 tail cover assembly
17 exhaust emission system
18 transmission box
19 clutch assembly
20 primary driven gear
21 clutch shaft
22 driven shaft
23 idler gear
24 intermediate gears
25 gear spacer
26 gear transmission assembly
28 first bearing
27 second bearing
30 crankcase
33 primary drive gear
34 crankshaft
35 cylinder body
36 cylinder head
38 inner race
39 outer race
,CLAIMS:We claim:
1. An engine assembly (4) comprising:
a crankcase (30);
a clutch shaft (21) rotatably supported by said crankcase (30) through a first bearing (28) and a second bearing (27);
a driven shaft (22) rotatably supported by said crankcase (30), said driven shaft (22) connected to said clutch shaft (21) through one or more intermediate gear(s) (24);
a clutch assembly (19) positioned at one end of said clutch shaft (21);
a primary driven gear (20) mounted to said clutch shaft (21), said primary driven gear functionally connected to said clutch assembly (19); and
an idler gear (23) disposed on said clutch shaft (21);
characterized in that,
a gear spacer (25) mounted to the clutch shaft (21), said gear spacer (25) capable of providing a spacing between the idler gear (23) and the primary driven gear (20).
2. The engine assembly (4) as claimed in claim 1, wherein said gear spacer (25) is mounted on said primary driven gear (20), said gear spacer (25) is sandwiched between the primary driven gear (20) and said first bearing (28), disposed in proximity to said primary driven gear (20), in an axial direction.
3. The engine assembly (4) as claimed in claim 1 or claim 2, wherein said gear spacer (25) is having one axial face abutting said primary driven gear (20) and other axial face of the gear spacer (25) is abutting an inner race (38) of said first bearing (28).
4. The engine assembly (4) as claimed in claim 1 or claim 2, wherein said first bearing (28) is having a diameter larger than a diameter of the second bearing (27) and the first bearing (28) is press fitted to said crankcase (30), wherein said first bearing (28) is capable of withstanding axial forces acting thereon.
5. The engine assembly (4) as claimed in claim 1 or claim 2, wherein said idler gear (23) is a kick start idler gear (23) that is mounted to the clutch shaft (21), said kick start idler gear (23) being press fitted to said first bearing (28).
6. The engine assembly (4) as claimed in claim 1 or claim 2, wherein said gear spacer (25) is having a substantial circular profile and said gear spacer (23) is concentrically mounted to the primary driven gear (20).
7. The engine assembly (4) as claimed in claim 1 or claim 2, wherein said gear spacer (25) being mounted at a stepped portion of said primary driven gear (20), and said gear spacer (25) being provided with an axial width being at least equal to a width of the stepped portion.
8. The engine assembly (4) as claimed in claim 1 or claim 2, wherein said clutch assembly (19) exerts axial force being transferred to the primary driven gear (20) is exerted on the first bearing (28) through the gear spacer (25), wherein any axial force being exerted on the idler gear (23) is limited.
9. The engine assembly (4) as claimed in claim 1 or claim 2, wherein said gear spacer (25) being made of a rigid material including any known metal.
10. A two-wheeled or three wheeled vehicle (50) having the engine assembly (4) as claimed in any one of the preceding claims.