DESC:FIELD
The present disclosure relates to the field of mechanical engineering. Particularly, the present disclosure relates to the field of transmission systems in vehicles.
BACKGROUND
A transmission system in a vehicle aids in transferring power from an engine to an axle. An important factor that decides the amount of energy transmitted from the engine to the axle is the ratio of the rotational speeds of the shafts, also referred as the transmission ratio. Typically, one of the shafts is the crankshaft and the other is the output shaft connected to the axle.
Continuously Variable Transmission (CVT) is a type of a transmission system in which the transmission ratio can be varied across a range of values. A conventional CVT system involves the use of rollers, which under the influence of a centrifugal force vary the width of the pulley groove holding a V-belt, thereby effectuating a changing transmission ratio. In conventional CVT systems, the variation of transmission ratios is controlled by a centrifugal force of rollers and depends on parameters including speed of an engine, a ramp curve of pulley wall, and weight of rollers. Thus, the conventional centrifugal CVT systems used in scooters can be tuned to only one particular setting of transmission ratio variation for either better fuel economy or better acceleration of vehicle. The transmission ratio variation tuning in the conventional centrifugal CVT systems is a compromise between drivability in terms of vehicle acceleration verses the fuel economy. A better acceleration of the vehicle compromises on the fuel economy and vice versa.
Hence, there is need for a system that alleviates the abovementioned drawbacks of the conventional CVT system.

OBJECTS
Some of the objects of the Continuously Variable Transmission (CVT) system of the present disclosure, which at least one embodiment herein satisfies, are as follows:
An object of the present disclosure is to provide a system for continuously variable transmission with better control on the continuous variable transmission ratios and works independent of parameters including speed of an engine, ramp curve of pulley wall, and weight of rollers.
Another object of the present disclosure is to provide a system for continuously variable transmission with an electronic control unit that offers better trend of variation in transmission ratio.
Other objects and advantages of the present disclosure will be more apparent from the following description when read in conjunction with the accompanying figures, which are not intended to limit the scope of the present disclosure.
SUMMARY
A system for continuously variable transmission for a vehicle, in accordance with the present disclosure, has a first drive coupled with a second drive via a belt. The first drive comprises a first shaft, a first bush having a hollow cylindrical profile mounted on the first shaft, and a pulley mounted on the first shaft. Typically, the first shaft is the crankshaft of an engine. The pulley is defined by a fixed sheave and a movable sheave such that the fixed sheave is mounted on the first shaft adjacent to an operative end of the first shaft, and the movable sheave is slidable on the first bush. A second bush is mounted over the movable sheave such that the second bush abuts the movable sheave. The second bush has first engaging formations configured thereon. A third bush is rotatably mounted over the first shaft such that, the rotation of the third bush is independent of the rotation of the first shaft. The third bush has second engaging formations configured thereon. The second engaging formations complement the first engaging formations and are engageable therewith, thereby facilitating the slidable movement of the movable sheave on the first bush, which in turn varies the distance between the fixed sheave and the movable sheave to obtain different transmission ratios. A motor is operatively coupled with the third bush to facilitate rotation of the third bush. A processor is functionally coupled with the motor. The processor receives engine speed signals, vehicle speed signals, and throttle position signals which are sensed by a plurality of sensors mounted on the vehicle. The processor further processes the signals according to a pre-determined set of rules stored in a repository, coupled to the processor, to obtain processed signals. The processor then generates control signals for optimally operating the motor based on the pre-determined set of rules and the processed signals.
Typically, the first and second engaging formations have helix profile. Preferably, the motor is mounted on a crankcase of the vehicle. In an embodiment, the system for continuously variable transmission for a vehicle includes a stationary bush mounted on the first shaft between the second and the third bush. The stationary bush is configured to support the second and third bush.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWING
A system for Continuously Variable Transmission (CVT), of the present disclosure, will now be described with the help of accompanying drawing, in which:
Figure 1a illustrates a sectional view of a conventional CVT front drive with rollers for centrifugally controlled transmission ratio;
Figure 1b illustrates a sectional view of a conventional CVT rear drive with a centrifugal clutch assembly;
Figure 2 illustrates an isometric view of the system for CVT, in accordance with an embodiment of the present disclosure;
Figure 3a illustrates a sectional view of the system for continuously variable transmission, of the present disclosure, with a low transmission ratio;
Figure 3b illustrates a top view of the system for continuously variable transmission, of figure 3a, with a low transmission ratio;
Figure 4a illustrates a sectional view of the system for continuously variable transmission, of the present disclosure, with a high transmission ratio;
Figure 4b illustrates a top view of the system for continuously variable transmission, of figure 4a, with a high transmission ratio; and
Figure 5 illustrates a block diagram of the intelligence system used in the system for CVT of the present disclosure.
DETAILED DESCRIPTION
A conventional system for continuously variable transmission uses a centrifugal force to facilitate variable transmission. Conventionally, in such systems, rollers are configured to create a centrifugal force, which in turn vary the distance between two faces of a pulley, to vary the transmission ratios.
Figure 1a illustrates a sectional view of a front drive of the conventional system to achieve a continuously variable transmission. The conventional centrifugally controlled CVT system comprises a front drive 100a. The front drive 100a includes a front fixed sheave (also referred as fixed sheave) 102 and a front movable sheave (also referred as movable sheave) 104 mounted on a crankshaft 106 extending from an engine. Figure 1a illustrates two extreme positions of the movable sheave 104, i.e., the low transmission ratio position of the movable sheave 104a and the high transmission ratio position of movable sheave 104b. The fixed sheave 102 is locked in position by a lock nut 134. As illustrated in the figure 1a, the fixed sheave 102 and the movable sheave 104 define the walls of the groove of a front pulley 130. The structure of the fixed sheave 102 and the movable sheave 104 form a seat for a V-belt 108 with a given pulley angle. The axial movement of the movable sheave 104 while varying the distance between the fixed sheave 102 and movable sheave 104, i.e., altering the width of the pulley, maintains a constant pulley angle. This axial movement of the movable sheave 104 effectuates a varying radius of rotation of the V-belt 108 from the axis of rotation of the crankshaft 106 (also known as the pitch diameter). The movable sheave 104 is disposed on a bush 114 that is disposed over the crankshaft 106. One side of the movable sheave 104 acts as a seat for the V-belt 108 while the other side is demarked as a profile 116. Rollers 110 are continuously in contact with the movable sheave 104 on its side bearing the profile 116. This contact is maintained by a ramp plate 112. With the low speed of the engine, the rollers 110 are subjected to less centrifugal force and due to the acting force of the ramp plate 112, the rollers 110 stay closer to the axis of the crankshaft 106. This results in the movable sheave 104 being placed away from the fixed sheave 102 and hence, a low transmission ratio is attained. When the speed of the engine increases, the centrifugal force causes the rollers 110 to roll along the profile 116 while pushing the movable sheave 104. This push results in the axial motion of the movable sheave 104 towards the fixed sheave 102 thus, reducing the distance between the movable sheave 104 and the fixed sheave 102. This results in increased radius of rotation of the V-belt 108 from the center of the crankshaft 106, and hence, a higher transmission ratio is attained.
Figure 1b illustrates a sectional view of a conventional CVT rear drive with a centrifugal clutch assembly, hereinafter referred as a rear drive 100b. The rear drive 100b includes a clutch assembly 118 mounted on a driven shaft 120. A rear pulley 132 is defined by a rear movable sheave 124 and a rear fixed sheave 126. The rear movable sheave 124, mounted on the driven shaft 120, is connected to the clutch assembly 118 via a spring 122. Figure 1b illustrates the extreme positions of the rear movable sheave 124, i.e., the high transmission ratio position 124a, and the low transmission ratio position 124b of the rear movable sheave 124. The spring 122 and a torque groove cam 128 on the rear movable sheave 124 provide the reactionary force to the V-belt 108 for the transmission and act against the axial thrust generated by the rollers 110 in the movable sheave 104. The rollers 110, due to centrifugal force, generates an axial force which overcomes the force of the spring 122, and the thrust generated by the torque groove cam 128, and rolls over outwards pushing the movable sheave 104 axially forward to reposition the V-belt 108, thus changing the transmission ratio.
The main disadvantage of using the abovementioned conventional CVT system is the inability to obtain a better trend of variation in the transmission ratio. The conventional CVT offers a fixed trend of variation which affects the drivability.
A system for continuously variable transmission, of the present disclosure, will now be described with reference to figure 2 to figure 5.
Figure 2 illustrates an isometric view of the system for CVT in accordance with an embodiment of the present disclosure. Figure 3a illustrates a sectional view of a system for continuously variable transmission, of the present disclosure, with a low transmission ratio. Figure 3b illustrates a top view of the system for continuously variable transmission with a low transmission ratio of figure 3a. Figure 4a illustrates a sectional view of system for continuously variable transmission with a high transmission ratio of the present disclosure. Figure 4b illustrates a top view of the system for continuously variable transmission with a high transmission ratio of figure 4a. Figure 5 illustrates a block diagram of the intelligence system used in the system for CVT of the present disclosure.
A system for continuously variable transmission 200, herein after referred as the system 200, comprises a first shaft 106, a pulley defined by a fixed sheave 102 and a movable sheave 104, a first bush 214, a second bush 204, a third bush 205, a stationary bush 206, an electric motor 202, and an electronic control unit 302, which is a processor.
As shown in figure 2 through figure 4b, the movable sheave 104 is slidable on the first bush 214. The first bush 214 is a sleeve, having a hollow cylindrical profile, disposed over the first shaft 106. Typically, the first shaft 106 is a crankshaft of an engine. The stationary bush 206 is mounted on the first shaft 106 operatively between the second bush 204 and the third bush 205 and is configured to support the second bush 204 and the third bush 205. The second bush 204 is mounted on the movable sheave 104 such that, the second bush 204 abuts the movable sheave 104. Further, the second bush 204 is disposed on a first bearing 212 which is also mounted over the movable sheave 104. The second bush 204 has first engaging formations 204a configured thereon. The first shaft 106 is rotatably coupled with a crankcase 208 via a second bearing 210.
The system 200 includes the use of the electric motor 202 mounted on the crankcase 208. The electric motor 202 is coupled with a gear. The teeth profile of the gear is one of spur, helical or warm type. The gear is operatively coupled with the third bush 205 to drive the third bush 205. The third bush 205 has a wheel like structure with spur or helical shaped gear teeth provided on its outer periphery to complement the profile of the gear that is coupled with the electric motor 202. A second engaging formation 205a is configured on a side of the third bush 205 and extends outwardly from the surface thereof. The configuration of the second engaging formations 205a corresponds with the configuration of the first engaging formations 204a, thereby creating a symmetrical mating relationship with one another. In accordance with one embodiment, the first engaging formations 204a and the second engaging formations 205a assume a helix profile configuration. In another embodiment the first engaging formations 204a and the second engaging formations 205a are in a threaded relationship.
The rotational motion of the third bush 205 is translated into a linear motion of the second bush 204. The first engaging formations 204a and the second engaging formations 205a facilitate the translation of the rotational motion of the third bush 205 into a linear motion of the second bush 204. This linear motion is axial in nature and is further responsible for the linear motion of the movable sheave 104. Therefore, the rotation of the third bush 205 results in the axial motion of the movable sheave 104 thus, providing a continuous variation in the transmission ratios. The rotation of the third bush 205 is governed by the electric motor 202, which has been described in subsequent sections of the present disclosure.
The working of the proposed embodiment will hereinafter be described with specific reference to figure 3a through figure 4b. As shown in figure 3b, under lower engine speeds, the second engaging formation 205a provided on the third bush 205 symmetrically engages with the first engaging formations 204a of the second bush 204 during which the movable sheave 104 is positioned away from the fixed sheave 102. With the increase in engine speed, the electric motor 202 is actuated, thereby rotating the third bush 205 and the second engaging formations 205a. The rotation of the third bush 205 causes a linear movement in the movable sheave 104, thereby moving the movable sheave 104 proximate to the fixed sheave 102 as illustrated in figure 4b. As the movable sheave 104 gets closer to the fixed sheave 102, the V-belt 108 gradually moves away from the axis of the first shaft 106, which is the crankshaft of the engine, finally reaching the higher transmission ratio position.
Figure 5 illustrates a block diagram of an intelligence system 300 used in the system for CVT of the present disclosure. The actuation of the electric motor 202 is controlled by the intelligence system 300. The intelligence system 300 comprises the electronic control unit 302 (also referred as the processor), an engine speed module 306, a vehicle speed module 308 and a throttle position module 310. The IS 300 further comprises a system repository 304 configured to store a pre-determined set of rules. The electronic control unit 302 cooperates with the system repository 304 and possesses the functional elements to provide system processing commands based on the rules. The engine speed module 306 comprises sensors connected to the engine to measure the speed of the engine. The vehicle speed module 308 comprises sensors connected to the axle to measure the rotational speed of the axle. The throttle position module 310 comprises sensors to sense the position of the throttle.
The electronic control unit 302 receives engine speed signals, vehicle speed signals and throttle position signals sensed by the plurality of sensors mounted on the vehicle, i.e., sensors of the engine speed module 306, the vehicle speed module 308 and the throttle position module 310 respectively. Further, the electronic control unit 302 processes the signals according to a pre-determined set of rules stored in the repository 304 to obtain processed signals. Furthermore, the electronic control unit 302 generates control signals for optimally operating the electric motor 202. The generation of control signals is based on the predetermined set of rules and the processed signals. The system repository 304 consists of a predetermined set of rules which maps the signals provided by the electronic control unit 302 to a transmission ratio.
The mapped transmission ratio is inputted back to the electronic control unit 302 which calculates the stroke value ‘S’ needed to achieve the desired transmission ratio. This stroke value ‘S’ is inputted to an actuator module 312 which controls the operation of the electric motor 202. Thus the system 200 is able to control the axial movement of the movable sheave 104, and thus achieve the desired transmission ratio.
TECHNICAL ADVANCEMENTS
The present disclosure described herein above has several technical advantages including, but not limited to, the realization of:
• a system for continuously variable transmission to provide better control on the continuous variable transmission ratios and to work independent of parameters including ramp curve of pulley wall, weight of rollers and bush length;
• a system for continuously variable transmission with an electronic control to offer better trend of variation in transmission ratio; and
The disclosure has been described with reference to the accompanying embodiments which do not limit the scope and ambit of the disclosure. The description provided is purely by way of example and illustration.
The embodiments herein and the various features and advantageous details thereof are explained with reference to the non-limiting embodiments in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
The foregoing description of the specific embodiments so fully revealed the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
Throughout this specification the word “comprise”, or variations such as “comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
The use of the expression “at least” or “at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.
Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.
While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation. ,CLAIMS:1. A system for continuously variable transmission for a vehicle, said system having a first drive coupled with a second drive via a belt, said first drive comprising:
a first shaft;
a first bush having a hollow cylindrical profile mounted on said first shaft;
a pulley mounted on said first shaft, said pulley defined by a fixed sheave and a movable sheave, wherein said fixed sheave is mounted on said first shaft adjacent to an operative end thereof, and said movable sheave is slidable on said first bush;
a second bush mounted over said movable sheave such that said second bush abuts said movable sheave, said second bush having a first engaging formations configured thereon;
a third bush rotatably mounted over said first shaft such that the rotation of said third bush is independent of the rotation of said first shaft, said third bush having second engaging formations configured thereon, said second engaging formations complement said first engaging formations and are engageable therewith, thereby facilitating the slidable movement of said movable sheave on said first bush which in turn varies the distance between said fixed sheave and said movable sheave to obtain different transmission ratios;
a motor operatively coupled with said third bush to facilitate rotation of said third bush; and
a processor functionally coupled with said motor, said processor configured to:
- receive engine speed signals, vehicle speed signals, and throttle position signals sensed by a plurality of sensors mounted on said vehicle;
- process said signals according to a pre-determined set of rules stored in a repository coupled to said processor to obtain processed signals; and
- generate control signals for optimally operating said motor based on said pre-determined set of rules and said processed signals.
2. The system as claimed in claim 1, wherein said first shaft is a crankshaft of said vehicle.
3. The system as claimed in claim 1, wherein said first engaging formations and said second engaging formations have a helix profile.
4. The system as claimed in claim 1, wherein said motor is mounted on a crankcase of said vehicle.
5. The system as claimed in claim 1, which includes a stationary bush mounted on said first shaft operatively between said second bush and said third bush, said stationary bush configured to support said second bush and said third bush.