DESC:TECHNICAL FIELD
[0001] The present invention generally relates to a hybrid vehicle incorporating an internal combustion engine and an electric motor. More particularly, the present invention relates to an automatic transmission system for the hybrid vehicle.
BACKGROUND
[0002] Generally, two-wheeled vehicles are powered by an internal combustion engine. However, due to depleting crude oil reserves and with strict environmental norms it has become desirable to design two wheeled vehicles with alternate sources of energy. Two-wheeled Hybrid vehicles (hybrid vehicle) were developed as one such solution to the problem. Generally, the hybrid vehicle comprises of an internal combustion engine, and an electric motor for powering the vehicle from both sources. The internal combustion engine installed on such hybrid vehicle uses fuel as any other conventional internal combustion engine. The electric motor is powered by an auxiliary power source such as a battery system located in the hybrid vehicle. The internal combustion engine and the electric motor can be used in conjunction or independently to derive power for the hybrid vehicle based on different user modes. A transmission system is configured to transfer the rotary motion from the internal combustion engine and the electric motor to drive the hybrid vehicle. The critical issues in the design of the hybrid vehicle mainly involve optimization of the transmission system to improve efficiency, better operability and reduce transmission losses.
BRIEF DESCRIPTION OF THE DRAWINGS
[0003] The detailed description is described with reference to the accompanying figures. The same numbers are used throughout the drawings to reference like features and components.
[0004] Fig. 1 illustrates the side view of a two-wheeled hybrid vehicle employing an embodiment of the present invention.
[0005] Fig. 2 illustrates rear portion of the two-wheeled hybrid vehicle employing the embodiment of the present invention.
[0006] Fig. 3 illustrates the side view of an IC engine according to the embodiment of the present invention.
[0007] Fig. 4 illustrates the cross sectional view (X-X) of the IC engine according to the embodiment of the present invention.
[0008] Fig. 5a illustrates a simplified layout of the automatic transmission system, operating in a low-speed transmission path according to the embodiment of the present invention.
[0009] Fig. 5b illustrates a simplified layout of the automatic transmission system, operating in a high-speed transmission path according to the embodiment of the present invention.
DETAILED DESCRIPTION
[00010] Various features and embodiments of the present invention here will be discernible from the following further description thereof, set out hereunder. In the ensuing exemplary embodiments, the vehicle is a two wheeled hybrid vehicle (hybrid vehicle). However it is contemplated that the disclosure in the present invention may be applied to any hybrid vehicle capable of accommodating the present subject matter without defeating the spirit of the present invention. The detailed explanation of the constitution of parts other than the present invention which constitutes an essential part has been omitted at suitable places.
[00011] A transmission system of a hybrid vehicle is essential as it transmits rotary motion from an internal combustion engine and an electric motor to a rear wheel to drive the hybrid vehicle. Typically, the transmission system in the hybrid vehicle includes transmission stages, drive shafts, and the final drive to a rear wheel. The internal combustion engine and the electric motor can be configured in uniquely different ways, but essentially can be classified according to the type powertrain system it has, which determines how the internal combustion engine and the electric motor interact with each other. There are two types namely, series configuration and parallel configuration. In series configuration, a battery system is charged by the internal combustion engine, which in turn powers the electric motor to drive the hybrid vehicle. In parallel configuration, the internal combustion engine and the electric motor work in together to generate the power that drives the hybrid vehicle. Both configurations are usually used and can be designed to enable the internal combustion engine and electric motor to provide power independently or in conjunction with one another with different modes of operation.
[00012] Typically, a hybrid vehicle having parallel configuration includes a powertrain system which comprises the internal combustion engine, an output driven shaft, the transmission system disposed between the internal combustion engine and the output driven shaft, a transmitting means to transmit the drive from the output driven shaft to the rear wheel, the electric motor drivingly coupled to the transmitting means. The input drive means to the transmission system is operably connected to a crankshaft of the internal combustion engine mounted on a frame of the hybrid vehicle. Generally, the transmission system consists of one or more gear reducing mechanisms of different gear ratios designed to vary the output rotary motion from the transmission system. Additionally, the transmitting means transmits the rotary motion from the output driven shaft and the electric motor to the rear wheel. The transmitting means is usually a positive drive such as sprocket and chain arrangement, or belt drive and pulley arrangement. In a hybrid vehicle of parallel configuration, the electric motor is mounted such that the rotary motion can be transferred to the rear wheel of the hybrid vehicle. In one embodiment, the electric motor may be mounted externally on the hub of the rear wheel with the drive from the electric motor directly connecting the rear wheel. The electric motor is directly powered by a battery system. Typically, in the hybrid vehicle to start the internal combustion engine, cranking is required. Conventionally, a kick-start mechanism or the like is used. An electric start mechanism can also be installed to crank the hybrid vehicle. The kick-start mechanism and/or the electric start mechanism includes various components such as kick-rod, various gear(s), one way clutch, and a centrifugal clutch. The electric start mechanism is managed by a control means of the hybrid vehicle.
[00013] Generally, the hybrid vehicle with parallel configuration can operate in any one of three modes, namely an engine mode, an electric mode, and a hybrid mode. In the engine mode only the internal combustion engine is providing the drive to run the hybrid vehicle. In electric mode, only the electric motor is providing the drive. In hybrid mode both the internal combustion engine and the electric motor are providing the drive to the hybrid vehicle. The hybrid mode operation is usually operated by control systems based on the vehicle speed, which controls the power contribution from the internal combustion engine and the electric motor.
[00014] Conventionally, in the hybrid vehicle in parallel configuration, there is a problem of low acceleration at low speeds of the hybrid vehicle. This is especially profound when the hybrid vehicle is operating in hybrid mode where both the internal combustion engine and the electric motor are running together. Additionally, when the hybrid vehicle is climbing a gradient on the road there is requirement of a lot of acceleration at the rear wheel to pull the hybrid vehicle, and the transmission system may not be able to provide the same. Also, there is a problem of low acceleration when heavy load is required to be pulled by the hybrid vehicle. Hence, the transmission system may not be able to provide sufficient acceleration and the internal combustion engine may get switched off. Generally, to resolve this drawback, additional acceleration has to be provided by the electric motor. This leads to designing the electric motor with increased size and increased capacity. Consequently, such a design change would mean to increase the size of the battery system. Additionally, providing such a high acceleration by the electric motor would result in decrease of battery life as additional current is being drawn by the electric motor. Hence, an electric motor which otherwise is able to provide power to the hybrid vehicle at moderate to high speeds will have to be redesigned to meet the demands of the hybrid vehicle at conditions of low speed, presence of gradient or carrying high load. Also, at these conditions, the internal combustion engine has to do additional work to meet the load, hence increasing fuel consumption and decreasing its efficiency. Hence, there is a need for effective transmission systems.
[00015] The design of transmission system of the hybrid vehicle is critical as it can affect the hybrid vehicle’s mechanical efficiency, fuel consumption, and cost. Additionally, the operation of different modes is complex and controlled by a system which has to operate in many modes of running. Hence, the transmission must be capable of operating smoothly at the entire operating range of the hybrid vehicle at all modes. It is also desirable to vary the acceleration at different speeds of the hybrid vehicle. Particularly, the hybrid mode of operation is of consideration as the problem is more profound in this mode. In addition, there is a need to vary acceleration in order to achieve good efficiency. In this regard, the there are many transmission mechanism known in art to vary the rotary motion. Such systems include single speed reduction with fixed gear ratio, automatic transmission systems, and manual transmission system.
[00016] Manual transmission system has drawbacks where the rider has to manually shift between different gear ratios which would cause additional discomfort to the rider, and also introduce additional components causing layout constraints in the existing design. Automatic transmission systems the advantages of automatically changing the acceleration at various stages in relation to speed of the automobiles. Hence, it is very desirable that, the transmission mechanism in the hybrid vehicle be replaced by an automatic transmission system. Automatic transmission system is known in the art to vary the acceleration at various speeds of an automobile. One such system is the continuously variable transmission system, which has infinite number of stages and can vary the acceleration continuously with respect to the speed of the automobile. But the above system has the drawbacks which include lesser efficiency of the internal combustion engine and frequent serviceability. The present invention is to have an automatic transmission system, capable of automatically varying acceleration at different speeds of the hybrid vehicle without the above drawbacks.
[00017] Generally in automatic transmission system, the reduction of rotary motion from the engine crankshaft to the rear wheel involves reduction at many stages. It is essential from the point of view of drivability that in automatic transmission optimum gear reduction is possible. But, in case of single speed hybrid vehicle in prior art the reduction had to achieved by a single stage geartrain of one large gear and one small gear. Alternatively, a chain drive and sprocket can be used to achieve the same result. But on introduction of multi speed transmission, the reduction is even more crucial before actual two speed transmission takes place.
[00018] Hence, it is the object of the present invention to provide an automatic transmission system for the hybrid vehicle, which would automatically vary the acceleration based on the speed of the internal combustion engine.
[00019] Another object of the present invention is to provide the automatic transmission system with least modification to the existing layout of the hybrid vehicle.
[00020] Another object of the present invention is to provide the automatic transmission system without modifying design of the electric motor and the battery system.
[00021] Another object of the present invention is that the automatic transmission system can be integrated with the electric motor in order to run the vehicle at various modes of operation.
[00022] Another object of the present invention is to improve fuel economy and drivability of the hybrid vehicle.
[00023] Another object of the present invention is that an electric starter system can be additionally introduced along with a kick starter system for ease of cranking of vehicle during start of the internal combustion engine.
[00024] With the above design changes, the following advantages can be obtained such as automatic transmission to provide different accelerations without the need to manually switch the gears, minimal changes to existing layout, minimal changes to electric motor size and capacity, minimal changes to battery capacity, increased battery life, reduced fuel consumption and improvement of efficiency of the hybrid vehicle, and better optimization and minimal changes required in accommodating starting systems such as kick starter system and electric starter system.
[00025] Additionally, the automatic transmission system and control means of the working of the hybrid mode can be optimized at conditions of low speed, heavy load or gradient surface to improve fuel efficiency and battery efficiency.
[00026] The present invention is a hybrid vehicle, which comprises a frame, a front wheel and a rear wheel mounted to the frame, an internal combustion engine, an electric motor drivingly coupled to the rear wheel and an automatic transmission system comprising a driving shaft adapted to receive rotary motion from the internal combustion engine, a driven shaft whose output is drivingly coupled to the rear wheel and a high-speed transmission geartrain and a low-speed transmission geartrain disposed between the driving shaft and driven shaft configured to transmit, and automatically vary the rotary motion output at the driven shaft based on speed of the internal combustion engine, a first one way clutch is coupled to the output of the driven shaft, said one way clutch configured to only permit transfer of rotary motion from the automatic transmission system to the rear wheel.
[00027] The high-speed transmission geartrain and low-speed transmission geartrain, each having a plurality of gear stages, and each configured to separately transmit rotary motion between the driving shaft and the driven shaft and provide different rotary motion output to the driven shaft, a first centrifugal clutch disposed on the driven shaft, and configured to engage at a particular rotational speed of the internal combustion engine to automatically switch between the high-speed transmission system and low-speed transmission system and a second one way clutch disposed on the driven shaft and located at the output of the first centrifugal clutch, and configured to only permit transfer of rotary motion from the first centrifugal clutch to the driven shaft.
[00028] There is a second centrifugal clutch configured to engage at a particular rotational speed of the internal combustion engine disposed on the driving shaft and configured to only permit transfer of rotary motion of the internal combustion engine to the driving shaft at a particular speed of the internal combustion engine, said particular speed being above the idling speed of the internal combustion engine.
[00029] There is a starting system which is interposed between the driving shaft and the internal combustion engine, said starting system comprising a starter motor, and a third one way clutch disposed between the second centrifugal clutch and the internal combustion engine, and configured to only permit transfer of rotary motion of the internal combustion engine to the driving shaft.
[00030] The present invention along with all the accompanying embodiments and their other advantages would be described in greater detail in conjunction with the figures in the following paragraphs.
[00031] Fig. 1 illustrates a left side view of a hybrid vehicle (100), in accordance with an embodiment of the present invention. The vehicle (100) illustrated, has a step-through type frame assembly (102). The step-through type frame assembly (102) includes a head tube (106), a down tube (120) and a pair of side tubes (119) (only one shown). One end of the down tube (120) extends downwardly and rearwardly and connected with the pair of side tubes (119), while at the other end there is a head tube (106) which is configured to rotatably support a steering tube (not shown) and further connected to the front suspension system (104) at the lower end. A handlebar support member (not shown) is connected to an upper end of the steering tube (not shown) and supports a handlebar assembly (109). Two telescopic front suspension system (104) (only one is shown) is attached to a bracket (not shown) on the lower part of the steering tube (not shown) on which is supported the front wheel (103). The upper portion of the front wheel (103) is covered by a front fender (105) mounted to the lower portion of the steering tube (not shown). The pair of side tubes (119) is inclined downwards and connected to the down tube (120) at one end and extending rearward in a substantially inclined direction at the other end. A plurality of cross pipes (not shown) is secured in between the pair of side-tubes (119) to support vehicular attachments including a seat assembly (111), a utility box (not shown), and a fuel tank assembly (not shown). The utility box (not shown) and fuel tank assembly (not shown) are covered and located below the seat assembly (111).
[00032] The frame assembly (102) is covered by plurality of body panels, mounted and covering it, including a front panel (107), a leg shield (110), an under-seat cover (115), and a left and a right side panel (112). A glove box may be mounted to a leg shield (110). A floorboard (121) is provided at the step-through space provide above the main tube (120). A rear fender (115) is covering at least a portion of the rear wheel (116) and it is positioned below the fuel tank assembly (not shown). The vehicle (100) comprises of plurality of electrical and electronic components including a headlight (108), a taillight (113), a transistor controlled ignition (TCI) unit (not shown), a starter motor (not shown). The rear wheel (116) is mounted to the step-through type frame assembly (102) through one or more rear suspension(s) (114) provided in the rear portion of the vehicle (100) for comfortable ride.
[00033] Fig. 2 illustrates a rear view of the IC engine and includes an internal combustion engine (101). The IC engine (101) is mounted on a swing arm (209), which is swingably connected to the step-through type frame assembly (102) using a toggle link. The IC engine (101) comprises an automatic transmission system (401). The IC engine (101) is connected to the rear wheel (116) through a transmitting means (205), such as in the present embodiment may be pulleys (208a) present on the IC engine (101) and the rear wheel (116), which can be linked to each other through a belt drive (208). In another example, it maybe sprockets linked to each other through a chain drive.
[00034] The electric motor (202) is disposed towards the rear of the hybrid vehicle (100) and drivingly coupled to the rear wheel (116). In the embodiment of the present invention, the electric motor (202) is hub mounted on the rear wheel (116). Hence, the electric motor (202) is directly connected to the rear wheel (116) without the use of any transmission means. A battery system (not shown) is disposed at convenient location in the hybrid vehicle (100) which supplies power the drive the electric motor (202).
[00035] Fig. 3 illustrates the side view of the IC engine (101) in accordance with the embodiment of the present invention. The IC engine (101) houses the internal combustion engine (101) and the automatic transmission system (401). The internal combustion engine is made up of a cylinder head assembly (205), cylinder block (206) and crankcase (302).
[00036] Fig. 4 illustrates a cross sectional view (X-X) of the internal combustion engine (101) showing the main parts which include a reciprocating piston (419), a cylinder block (206), a rotatable crankshaft (421), an engine starting system and the automatic transmission system (401) according to the embodiment of the present invention, which transmits rotary motion from the crankshaft (421) to the output of the IC engine (101). The left side of the crankshaft is coupled to the driving shaft (403) of the automatic transmission system. The cylinder head assembly (205) consists of at least one inlet valve (not shown) and at least one outlet valve (not shown) which are operated by means of rocker arms (not shown) and a camshaft (417) which consists of at least one inlet cam lobe (not shown) and at least one outlet cam lobe (not shown) which actuates the rocker arms (not shown) when required. A cam-chain (418) is meshed between gears (423) in the crankshaft (421) and camshaft (417) in order to drive the camshaft in the cylinder head (205). The inlet air fuel mixture from the carburetor (207) is connected to an inlet portion of the engine in the cylinder head (205) and an exhaust system including a muffler (204) is connected to the outer portion of the cylinder head (205). The crankcase (302) houses the crankshaft (421), starter assembly (402a, 402b) and automatic transmission system (401) and other ancillary systems which include lubrication system (not shown), cooling system (not shown) and exhaust system (not shown) all housed in the crankcase (302).
[00037] The engine starting system as illustrated in Fig. 4 consists of a kick starter system and also an electric start system. The kick starter system consists of a ratchet mechanism where one ratchet (423) is rigidly attached to the driving shaft to crank the engine and the corresponding ratchet (424) is spring loaded and connected to the kick start lever (203) and can move when the kick start lever (203) is pushed with the rider’s foot. When the kick start lever (203) is pushed the spring loaded ratchet (424) move forward and meshes with the ratchet (423) on the driving shaft which in turns cranks the internal combustion engine (101). Once, the rider removes his feet from the kick start lever (203), the loaded spring forces the ratchet (424) back, disengaging it with the ratchet (423) on the driving shaft. Hence, cranking is achieved. The electric starter system operates by means of the starter motor (not shown) which is powered by a secondary battery source or by the battery system. The starting motor (not shown) is connected to a starter gear (402c) freely mounted on the driving shaft (403) and integrally attached to the input member of the third one way clutch (402b). The output member of the third one way clutch (402b) is integrally mounted on the driving shaft (403). When the hybrid vehicle (100) is to be cranked, starter motor (not shown) provides rotary motion which is transmitted to the starter gear (402c). The third one way clutch (402b) permits rotary motion from the starter gear (402c) to the driving shaft (403) but not from the driving shaft (403) back to the starter gear (402c). Hence, when the starter motor (not shown) transmits rotary motion to the starter gear (402c), the third one way clutch (402b) transmits the motion to the driving shaft (403) and consequently this rotary motion is used to crank the internal combustion engine (101). Once, the speed of the internal combustion engine (101) picks up and the rotational speed of the internal combustion engine (101) exceeds the rotary speed of the starter motor (not shown), the third one way clutch (402b) prevents this rotary motion of the internal combustion engine (101) back to the starter motor (not shown) and it is disengaged.
[00038] The second centrifugal clutch (402a) is disposed on the driving shaft (403). The second centrifugal clutch (402a) is configured to engage at a particular rotational speed of the internal combustion engine. This rotational speed is usually just above idling rotational speed configured and designed for the internal combustion engine. Hence, if the throttle is not operated by the rider, rotational speed of the internal combustion engine decreases to idling speed and the powertrain system of the hybrid vehicle is disengaged from the internal combustion engine. Once, throttle is operated, the second centrifugal clutch (402a) engages, and the rotary motion is transmitted to the rest of the powertrain system.
[00039] The automatic transmission system (401) shown in Fig. 4 comprises a driving shaft (403) configured to receive rotary motion from the internal combustion engine (101), including a first drive gear (404) mounted on it, a driven shaft (409) whose output has the drive pulley (208a) and is drivingly coupled to the rear wheel (116) by the hybrid transmission means (208). An intermediate shaft (416) is disposed between the driving shaft (403) and the driven shaft (409), including a first driven gear (405) mounted on it and engaged with the first drive gear (404) in the driving shaft (403). The intermediate shaft (416) along with the first drive gear (404) and first driven gear (405) provides the necessary first step reduction of the rotary motion from the crankshaft before it is further reduced by the geartrains of the automatic transmission system. This is essential as the present automatic transmission system is being implemented in a IC engine designed for single speed transmission. Hence, when implementing an automatic two speed transmission in a single speed layout, a part of the single speed reduction should be achieved before it is subjected to automatic two speed reduction. Hence, the intermediate shaft is disposed between the driving shaft and driven shaft, and said first drive gear (404) and first driven gear (405) provide the necessary first stage reduction. Further, the intermediate shaft enables the mounting of a first low-speed gear (415) forming part of the low-speed transmission geartrain and mounting of a first high-speed gear (406) forming part of the highed transmission geartrain.
[00040] A low-speed transmission geartrain (Fig. 5a.), including the first low-speed gear (415) mounted on the intermediate shaft, which is engaged with a second low-speed gear (412) freely mounted on the driven shaft (409). A high-speed transmission geartrain (Fig. 5b.), including a first high-speed gear (406) mounted on the intermediate shaft, which is engaged with a second high-speed gear (411) freely mounted on the driven shaft (409). A first centrifugal clutch (410) is disposed on the driven shaft whose one end is rigidly attached to the freely mounted second high-speed gear (411), and configured to engage at another particular rotational speed of the hybrid vehicle (100). This first centrifugal clutch (410) is configured to engage at higher speeds of the hybrid vehicle (100). A first one way clutch (413) having an first input member (413a) and an first output member (413b) disposed on the driven shaft (409), such that the first input member (413a) is rigidly attached to the freely mounted second low-speed gear (412) and the first output member (413b) is rigidly mounted on the driven shaft (409), and said first one way clutch (413) is configured to engage when the rotational speed of a positive direction of the first input member (413a) exceeds the rotational speed of a positive direction of the first output member (413b). A second one way clutch (407) having an second input member (407a) and an second output member (407b) disposed on the driven shaft (409), such that the second input member (407a) is rigidly attached to the freely mounted other end of the first centrifugal clutch (410) and the second output member (407b) is rigidly mounted on the driven shaft (409), and said second one way clutch (407) is configured to engage when the rotational speed of a positive direction of the second input member (407a) exceeds the rotational speed of a positive direction of the second output member (407b).
[00041] Fig. 5a and Fig. 5b. illustrates the simplified layout of the working of the automatic transmission system according to the embodiment of the present invention. The present invention is envisaged to automatically switch between two transmission paths, having different gear meshing stages. Each of the high-speed transmission geartrain (502) and low-speed transmission geartrain (501) has a different gear ratio and can automatically shift between the different geartrains so as to vary the rotary motion output at the driven shaft based on the internal combustion engine rotational speed. Fig. 5a along with the arrows shows the direction of transfer of rotary motion along low-speed transmission geartrain.
[00042] Consider condition where the hybrid vehicle is operating at low speed. Here, the first centrifugal clutch (410) is disengaged as the rotary speed of the hybrid vehicle is low. In this condition, the direction of rotary motion along the low-speed transmission geartrain is taken as illustrated in Fig. 5a. Here, the gear ratio between the first low-speed gear (415) and second low-speed gear (412) is higher than the gear ratio in the high-speed transmission geartrain. The rotary motion is transmitted from the driving shaft (403) to the intermediate shaft (416) through the first drive gear (404) which is meshed with the first driven gear (405). The motion in turn is transmitted to the first low-speed gear (415) and the first high-speed gear (412). Since, the first low-speed gear (415) is in a constant meshing relationship with the second low-speed (412) gear the rotary motion is transferred to the second low-speed gear (412) and to the driven shaft (409). The first one way clutch (413) permits the transfer of this rotary motion and out to the driving pulley (208a) which is transmitted to the driven pulley (208b) and drives the rear wheel (116). The rotation of the driven shaft (409) by the second low-speed gear (412) is prevented from getting transmitted back to the first centrifugal clutch (410) as the second one way clutch (407) prevents any motion from getting transmitted back. Hence, the rear wheel (116) runs at a higher acceleration because the transmission occurs through the low-speed transmission geartrain.
[00043] Consider condition where the hybrid vehicle is operating at high speed. Here, the first centrifugal clutch (410) is engaged as the rotary speed of the hybrid vehicle (100) is high. In this condition, the direction of rotary motion along the high-speed transmission geartrain is taken as illustrated in Fig. 5b. Here, the gear ratio between the first high-speed gear (406) and second high-speed gear (411) is lower than the gear ratio in the low-speed transmission path. The rotary motion is transmitted from the driving shaft (403) to the intermediate shaft (416) through the first drive gear (404) which is meshed with the first driven gear (405). The motion in turn is transmitted to the first high-speed gear (406) and the first low-speed gear (411). Since, the first high-speed gear (406) is in a constant meshing relationship with the second high-speed gear (411) the rotary motion is transferred to the second high-speed gear (411). The second high-speed gear (411) is integrally mounted on the one side of the first centrifugal clutch (410) freely mounted on the driven shaft (409). Since, the first centrifugal clutch (410) is engaged; the rotary motion is transmitted through the first centrifugal clutch (410). The other end of the centrifugal clutch (410) is integrally connected to the second one way clutch (407), the other end is integrally mounted to the driven shaft (409). Hence, the second one way clutch (407) permits the transfer of this rotary motion and out to the driving pulley (208a) which is transmitted to the driven pulley (208b) and drives the rear wheel (116). The rotation of the driven shaft (409) by the second high-speed gear (411) is prevented from getting transmitted back to the low-speed transmission geartrain as the first one way clutch (413) prevents any motion from getting transmitted back. Hence, the interference between the motions of the two paths is prevented and the transmission occurs due to the high-speed transmission geartrain only. The rear wheel (116) runs at a lower acceleration because the transmission occurs through the high-speed transmission geartrain.
[00044] Many modifications and variations of the present subject matter are possible in the light of above disclosure. Therefore, within the scope of claims of the present subject matter, the present disclosure may be practiced other than as specifically described.
,CLAIMS:We Claim:
1. A hybrid vehicle (100) comprising:
a step-through type frame assembly (102) extending from a front portion (F) to a rear portion (R) of the hybrid vehicle (100);
a front wheel (103) and a rear wheel (116) mounted to the step-through type frame assembly (102) on the front portion (F) and rear portion (R) of the hybrid vehicle (100) respectively;
an electric motor (202) drivingly coupled to the rear wheel (116);
an internal combustion engine (101) swingably mounted to the step-through type frame assembly (102) on the rear portion (R) of the hybrid vehicle (100), and said internal combustion engine (101) enclosing a transmission system (401);
said transmission system (401) comprising:
a driving shaft (403) adapted to receive rotary motion;
a driven shaft (409) whose output is drivingly coupled to the rear wheel (116); and
a first one way clutch (413) coupled to the output of the driven shaft (409), said first one way clutch (413) configured to only permit transfer of rotary motion from the output of the driven shaft (409) to the rear wheel (116); and
a belt drive transmission (208) coupling the internal combustion engine (101) to the rear wheel (116);
wherein the transmission system (401) further comprises:
a high-speed transmission geartrain (502) and a low-speed transmission geartrain (501) between the driving shaft (403) and driven shaft (409), said high-speed transmission geartrain (502) and a low-speed transmission geartrain (501) configured to separately transmit rotary motion between the driving shaft (403) and the driven shaft (409) and provide different rotary motion output to the driven shaft (409);
a first centrifugal clutch (410) disposed on the driven shaft (409);
a second one way clutch (407) disposed on the driven shaft (409); and
said first centrifugal clutch (410), and said second one way clutch (407) configured to automatically switch between the high-speed transmission geartrain (502) and the low-speed transmission geartrain (501) based on speed of the internal combustion engine (101).

2. The hybrid vehicle as claimed in claim 1, wherein transmission system (401) comprises an intermediate shaft (416), a first driven gear (405) mounted on said intermediate shaft (416), and said first driven gear (405) meshing with a first drive gear (404) disposed on the driving shaft (403) whereby the driving shaft (403) transfers rotary motion to the intermediate shaft (416).
3. The hybrid vehicle as claimed in claim 2, wherein said low-speed geartrain (501) comprises a first low-speed gear (415) integrally mounted on the intermediate shaft (416) meshing with a second low-speed gear (412) integrally mounted on the driven shaft (409), and said high-speed geartrain (502) comprises a first high-speed gear (406) integrally mounted on the intermediate shaft (416) meshing with a second high-speed gear (411) freely mounted on the driven shaft (409).
4. The hybrid vehicle as claimed in claim 3, wherein one end of the first centrifugal clutch (410) is freely mounted on the driven shaft (409) and integrally mounted to the second high-speed gear (411), and other end of the first centrifugal clutch (410) is integrally mounted on the driven shaft (409) through the second one way clutch (407).
5. The hybrid vehicle as claimed in claim 1, wherein the belt drive transmission (208) comprises a driving pulley (208a) integrally mounted on one end of the driven shaft (409), a driven pulley (208b) integrally mounted on the rear wheel (116) and a belt drive (208) meshed between the driving pulley (208a) and the driven pulley (208b).
6. The hybrid vehicle as claimed in claim 4, wherein a first one way clutch (413) is mounted on the driven shaft (409) disposed before the driving pulley (208a).
7. The hybrid vehicle as claimed in claim 1, wherein a starting system is interposed on driving shaft, said starting system comprising:
a second centrifugal clutch (402a) configured to engage at a particular rotational speed of the driving shaft (403); and
`a third one way clutch (402b) disposed between the first centrifugal clutch and a crankshaft of the internal combustion engine (101).