POWER TRANSMISSION SYSTEM FOR HYBRID TWO WHEELED VEHICLE

TECHNICAL FIELD

The subject matter described herein, in general, relates to a hybrid vehicle and in particular, relates to the power transmission system of a hybrid two wheeled vehicle.

BACKGROUND

Conventionally, motorized two wheeled vehicles are driven by an internal combustion engine. However, due to the depletion of crude oil reserves along with the rise in fuel prices and increased sensitivity to limiting hydrocarbon emissions, it has become desirable to find alternate ways and solutions to achieve better fuel economy. One way to achieve the aforesaid is through an electrically driven vehicle. However, such a vehicle has increased body weight and shortened running distance. Such drawbacks have been overcome in hybrid two wheeled vehicles.

Hybrid two wheeled vehicles with two power sources are known in the art. A hybrid two wheeled vehicle employs two power sources i.e. an electric motor and an internal combustion engine. Usually, the internal combustion engine is the main source of power while the electric motor provides supplementary or secondary power to the hybrid two wheeled vehicle. The internal combustion engine and the electric motor in a hybrid two wheeled vehicle can be used in combination with each other or can be used independently. The pollution caused by a hybrid two wheeled vehicle is considerably lesser as compared to the vehicles using only internal combustion engines as power source.

The placement of the different components in a hybrid two wheeled vehicle is a critical task. Typical hybrid two wheeled vehicles have limited space for accommodating the internal combustion engine and the electric motor. Conventionally, in hybrid two wheeled vehicles, the electric motor is assembled as a part of the transmission assembly. In such a layout, the internal combustion engine and the electric motor are connected in series and utilize the same transmission assembly. This layout of the electric motor in the hybrid two wheeled vehicle results in transmission losses and reduced power transmission. Moreover, the accessibility of the electric motor becomes very difficult in such a layout. Further, there is reduced heat dissipation from the electric motor due to improper cooling of the electric motor. Hence, the electric motor operates at a high temperature, thereby resulting in a reduction in the efficiency and lifespan of the electric motor.

SUMMARY

The subject matter described herein is directed to a transmission system of a hybrid vehicle, particularly a hybrid two wheeled vehicle. The power transmission system includes a first power source and a second power source to produce power for driving a drive wheel of the vehicle. The first power source of the present subject matter can be an internal combustion engine and the second power source can be an electric motor. The transmission system further includes a transmission assembly provided on a first side of the vehicle for transmitting power from the first power source to the drive wheel. The second power source is mounted on the drive wheel, either directly or through a power transmitting means, such that the second power source is disposed on a second side of the vehicle.

The mounting of the second power source on the drive wheel reduces transmission losses and enhances the power transmission efficiency. Moreover, in such an arrangement, the second power source becomes easily accessible for servicing. Further, there is increased heat dissipation from the electric motor due to improper cooling of the electric motor. Hence, the electric motor operates at a lower temperature, thereby resulting in an increase in the efficiency and lifespan of the electric motor.

These and other features, aspects and advantages of the present subject matter will be better understood with reference to the following subject matter and appended claims.

This summary is provided to introduce a selection of concepts. This summary is not intended to identify keys features or essential features of the claimed subject matter, nor is it intended to be used for to limiting the scope of the claimed subject matter.

BRIEF DESCRIPTION OF DRAWINGS

The above and other features, aspects, and advantages of the subject matter will be better understood with regard to the following description, and accompanying drawings where:

Fig l(a) illustrates a side view of a hybrid two wheeled vehicle according to one embodiment of the present subject matter.

Fig l(b) illustrates a sectional top view of a hybrid two wheeled vehicle of Fig. l(a).

Fig 2(a) illustrates a left hand side view of a hybrid two wheeled vehicle of Fig.

1, depicting a rear wheel and a transmission assembly.

Fig 2(b) illustrates a right hand side view of a hybrid two wheeled vehicle of Fig.l, depicting the position of an electric motor.

Fig 3(a) shows a top view of a hybrid two wheeled vehicle of Fig. 1 depicting the mounting of an electric motor on the rear wheel.

Fig 3(b) illustrates a sectional front view of a hybrid two wheeled vehicle of Fig.

1 depicting the mounting of an electric motor on the rear wheel.

Fig. 4 shows a sectional top view of the hybrid two-wheeler in accordance with another embodiment of the present subject matter.

Fig. 5 illustrates a sectional top view of the hybrid electric vehicle in accordance with yet another embodiment of the present subject matter.

Fig. 6 illustrates a side view of a hybrid two wheeled vehicle in accordance with yet another embodiment of the present subject matter.

Fig. 7 illustrates a side view of a hybrid two wheeled vehicle in accordance with yet another embodiment of the present subject matter.

DESCRIPTION

The subject matter described herein is directed to a transmission system of a hybrid two wheeled vehicle. The transmission system includes two power sources i.e. an internal combustion engine and an electric motor for producing power. The internal combustion engine and the electric motor can be used together or can be used independently. The transmission system further includes a transmission assembly for

transmitting power from the internal combustion engine to a rear wheel of the hybrid two wheeled vehicle. The transmission assembly is provided on one side of the hybrid two wheeled vehicle and includes a driving sprocket, a transmission chain, a driven sprocket and a gear arrangement to transmit the required power to the rear wheel. The electric motor of the present subject matter is directly mounted on the rear wheel of the hybrid two wheeled vehicle. The transmission assembly and the second power source are disposed on the opposite sides of the hybrid two wheeled vehicle.

This arrangement of the power sources eliminates extra transmission parts between the electric motor and the rear wheel. The present subject matter minimizes transmission losses with the decreased number of parts between the electric motor and the rear wheel and enhances power transmission from the electric motor to the rear wheel. The electric motor is positioned on the hub of the rear wheel in such a way that easy accessibility and maintenance of the electric motor is possible. The mounting of the electric motor on the rear wheel also helps to increase the rate of cooling of the motor by enhancing the rate of heat dissipation from the electric motor. Therefore as a whole, the overall performance of the hybrid two wheeled vehicle is enhanced.

Fig l(a) illustrates a side view of a hybrid two wheeled vehicle according to one embodiment of the present subject matter.

Fig l(b) illustrates a sectional top view of a hybrid two wheeled vehicle of Fig. l(a) depicting the transmission system of the vehicle.

For example, and by no way limiting the scope of the subject matter, the hybrid vehicle of the present subject matter is a hybrid two wheeled vehicle 100. As shown

herein, an electric motor 102 is mounted on the rear wheel 104. The transmission system of the hybrid two wheeled vehicle 100 includes two power sources i.e. an internal combustion engine 106 and the electric motor 102. The electric motor 102 of the present subject matter is disposed on the rear wheel 104 of the two wheeled vehicle 100. In the present embodiment, the rear wheel 104 is the drive wheel of the two wheeled vehicle 100.

In operation, the internal combustion engine 106 acts as a main power source of the hybrid two wheeled vehicle 100 and transmits power to the rear wheel 104 through a fixed transmission assembly disposed on one side of the hybrid two wheeled vehicle 100. The engagement of a clutch 108 facilitates the transmission of power from the internal combustion engine 106 to the rear wheel 104 through the transmission assembly of the transmission system. In the present embodiment, the clutch 108 is a centrifugal clutch. The transmission assembly includes a driving sprocket 110, a driven sprocket 112, and a transmission chain 114. The electric motor 102, on the other hand, acts as a secondary power source and transmits power directly to the rear wheel 104. The electric motor 102 is disposed on the side of the hybrid two wheeled vehicle 100, which is opposite to the side where the transmission assembly is provided.

Fig. 2(a) shows a left hand side view of the hybrid two wheeled vehicle 100 depicting the rear wheel 104 and the transmission assembly. In the present embodiment, for example, the transmission assembly is disposed on the left side of the hybrid two wheeled vehicle 100. When the clutch 108 is in an engaged position, the internal combustion engine 106 operates the driving sprocket 110 of the transmission assembly.

The motion of the driving sprocket 110 is transferred to the driven sprocket 112 through the transmission chain 114. The driven sprocket 112, in turn, is connected to the rear wheel 104 through a gear arrangement 116.

Fig. 2(b) illustrates a right hand side view of the hybrid two wheeled vehicle 100 of Fig. 1. As shown herein, the electric motor 102 is mounted on the right side of the hybrid two wheeled vehicle 100 within a motor casing 200. The electric motor 102 in the hybrid two wheeled vehicle 100 can be used independently or in combination with the internal combustion engine 106. To improve the power transmission and efficiency of the hybrid two wheeled vehicle 100, the electric motor 102 is mounted directly on the rear wheel 104. The electric motor 102 is directly disposed in close proximity of a hub of the rear wheel 104 by means of flange (not shown in figure), thereby eliminating need of extra transmission parts between the electric motor 102 and the rear wheel 104.

Assembling the electric motor 102 at the rear wheel 104 of the hybrid two- wheeler 100 facilitates the effective power transmission and enhanced efficiency of the hybrid two-wheeler 100. This assemblage also facilitates in appropriate cooling of the electric motor 102 by enhancing the heat dissipation. Moreover, in case of servicing or maintenance, the electric motor 102 is easily accessible as it is mounted directly on the hub of the rear wheel 104 and on the side opposite to that of the transmission assembly.

The casing 200 of the electric motor 102 is supported onto the hybrid two wheeled vehicle 100 by means of a support arm 202. The motor casing 200 includes a plurality of mounting bosses 204 on its outer periphery for fastening the motor casing 200 with the support arm 202. One end of the support arm 202 of the present subject matter has a C-shape section, which is fastened to the mounting bosses 204 of the motor casing

200 through fasteners. The other end of the support arm 202 has two mounting bosses 206 to facilitate the attachment of the support arm 202 to a crankcase 208.

It must be noted here that the aforementioned specifications vis-a-vis the shape of the support arm 202 and the means for mounting support arm 202 to the motor casing 200 and to the crank case 208 are not limited those suggested herein and can be easily altered to suit varying functional and technical requirements.

The motor casing 200, the support arm 202 and the crankcase 208 may be held together via formation of a suitable assemblage in conformity to the present subject matter. By way of example, and in no way limiting the scope of the present subject matter, the motor casing 200, the support arm 202 and the crankcase 208 are held together via fasteners, such as bolts or rivets or studs so as to form an assemblage.

The present subject matter can be embodied in many other ways as would be clear to a person skilled in the art. To give example, in another embodiment, the transmission assembly can include a toothed belt to transfer motion from the driving sprocket 110 to the driven sprocket 112. Similarly, in yet another embodiment, a continuously variable transmission (CVT) can be used as transmission assembly for transmitting motion from the engine 106 to the rear wheel 104.

Fig. 3(a) shows a sectional top view of a hybrid two wheeled vehicle 100 in one embodiment of the present subject matter. For example and by no way limiting the scope of the subject matter, a shaft 300 of the electric motor 102 is attached to the hub of the rear wheel 104 through a power transmitting means. In one preferred embodiment, power transmitting means is a flange 302. In another embodiment, the power transmitting means can be a shaft. The flange 302 rigidly connects the motor shaft 300 with the rear wheel

104 and rotates with the rotation of the motor shaft 300, thereby driving the rear wheel 104. Further, the casing 200 of the motor 102 is supported by the support arm 202 that connects the casing 200 with the crankcase 208 of the hybrid two wheeled vehicle 100.

Fig 3 (b) illustrates a sectional front view of the hybrid two wheeled vehicle 100 depicting the mounting of the electric motor 102 on the rear wheel 104. The motor shaft 300 transmits power from the electric motor 102 to the hub of the rear wheel 104 through the flange 302.

Fig. 4 shows a sectional top view of the hybrid two-wheeled vehicle 400 in accordance with another embodiment of the present subject matter. In the present embodiment, the casing 200 of the electric motor 102 is directly mounted on the rear wheel 104 and houses a brake shoe assembly 402. The rotor 404 of the electric motor 102 is integral with the motor casing 200 while the stator 406 of the electric motor 102 along with the brake shoe assembly 402 is attached to the casing 200 of the electric motor 104.

Thus, when a current is supplied to the electric motor 102, the casing 200 rotates along with the rotor 404. The rotational motion of the casing 200 is in turn transferred to the rear wheel 104, thereby resulting in the rotational motion of the rear wheel 104. In the present embodiment, the brake shoe assembly 402 is housed in the casing 200 on the side away from the hub of the rear wheel 104. In one preferred embodiment, the casing 200 and the hub of the rear wheel 104 can be integrated and made as a single piece of equipment. In another embodiment, the casing 200 and the hub of the rear wheel 104 are attached to each other through fasteners, such as bolts, rivets, screws etc.

In the first mode, the engagement of the clutch 108 facilitates the transmission of power from the internal combustion engine 106 to the rear wheel 104. When the clutch

108 is in an engaged position, power from the internal combustion engine 106 drives the driving sprocket 110 of the power transmission assembly. The driving sprocket 110 drives the driven sprocket 112 through the transmission chain 114. The driven sprocket 112 in turn drives the rear wheel 104 through the gear arrangement 116. A one way clutch 408 is disposed between the axle of the rear wheel and the gear arrangement 116 such that the one way clutch 408 disengages the axle from transmission assembly, when the hybrid two wheeled vehicle 400 operates under the second mode, i.e. Electric Vehicle (EV) mode. In EV mode, the hybrid two wheeled vehicle 400 is operated by the electric motor 102. The EV mode of the hybrid two wheeled vehicle 400 is the mode in which no power transmission takes place from the internal combustion engine 106 to the rear wheel 104. In the EV mode, the electric motor 102 is the only power source, which drives the rear wheel 104. However, during the third mode, the internal combustion engine 106 and the electric motor 102 together transmit power to the rear wheel 104. .

Fig. 5 illustrates top sectional view of the hybrid two wheeled vehicle 500 in accordance with yet another embodiment of the present subject matter. The brake shoe assembly 402 of the present embodiment is disposed in the electric motor 102, in the proximity to the hub of the rear wheel 104. In the present embodiment, the casing 200 is made integral with the hub of the rear wheel 104.

Fig. 6 illustrates a side view of a hybrid two wheeled vehicle 600 in accordance with yet another embodiment of the present subject matter. The engine 106 of the present subject matter is connected to the rear wheel 104 of the vehicle 600 through a swing arm 602. A toggle link mechanism 604 is provided at the front end of the swing arm 602. The toggle link mechanism 604 allows the engine 106 to swing motion with respect to the

frame of the vehicle 600. The vibrations occurring within the vehicle 600 are overcome by providing rear shock absorbers 606, which connect the frame of the vehicle 600 with the rear end of the swing arm 602.

In another embodiment of the present subject matter as described in Fig. 7, a fixed link 700 is provided to fix the engine 106 with respect to the frame of the vehicle 600 through the swing arm 602. The other aspects of the present embodiment are as described in Fig. 6.

The embodiments illustrated above are described in the context of a hybrid two wheeler. It must be noted that the subject matter is not limited only to such embodiments. Thus, the hybrid two wheeled vehicle may be a step through scooter, a motorcycle or any other two- wheeled vehicle as obvious to a person skilled in the art.

The previously described versions of the subject matter and its equivalent thereof have many advantages, including those which are described below.

The present subject matter achieves enhanced transmission efficiency by substantially eliminating transmission losses from the electric motor to the rear wheel of the hybrid two wheeled vehicle.

The mounting of the electric motor in a manner that is coaxial with the rear wheel 104 facilitates accessibility of the electric motor.

The rate of heat dissipation from the electric motor also increases considerably, thereby achieving better cooling. In other words, the present subject matter facilitates the working of the electric motor at a lower temperature and in a more efficient manner. This also prolongs the lifespan of the electric motor. Moreover, the present subject matter enhances the overall performance of the hybrid two wheeled vehicle.

Although the subject mater has been described in considerable detail with reference to certain preferred embodiments thereof, other embodiments are also possible. As such the sprit and the scope of the subject matter should not be limited to the description of the preferred embodiment contained therein.