DESC:CONTINUOUS VARIABLE TRANSMISSION SYSTEM FOR ELECTRIC VEHICLE
CROSS REFERENCE TO RELATED APPLICTIONS
The present application claims priority from Indian Provisional Patent Application No. 202321012849 filed on 25-02-2023, the entirety of which is incorporated herein by a reference.
TECHNICAL FIELD
Generally, the present disclosure relates to transmission systems. Particularly, the present disclosure relates to a belt-type continuous variable transmission (CVT) system.
BACKGROUND
In the field of mechanical engineering, the development of transmission systems plays a vital role in improving the efficiency and performance of machinery. Among various types of transmission systems, continuous variable transmission systems have gained prominence due to their ability to provide seamless transition through an infinite number of effective gear ratios between maximum and minimum values. Continuous variable transmission systems capability facilitates optimal engine operation and improved fuel efficiency.
Conventional transmission systems, such as manual or automatic transmissions, are limited by a fixed number of gear ratios. The said limitations often result in less efficient engine performance at certain speeds or under certain conditions. To address such inefficiencies, continuous variable transmission systems have been developed. One common approach involves the use of belt-type CVT systems. In belt-type CVT systems, a belt connects two pairs of discs, one pair being driven and the other driving, with the ability to vary the spacing between the discs in each pair. In belt-type CVT systems variation allows for a continuous range of gear ratios, adapting to different driving conditions without the discrete steps found in traditional transmissions.
Despite advantages, existing belt-type CVT systems encounter challenges, particularly in terms of durability, responsiveness, and the efficiency of the variator mechanism to controls the gap variations between the discs. The variator mechanism, being central to the operation of the CVT, requires accurate control to provide smooth and efficient transmission of power. However, the complexity of belt-type CVT system mechanism can compromise the overall performance and reliability of the transmission system. Furthermore, the effective management of gap variations between the driven and driving discs to achieve optimal gear ratios under varying operational conditions remains a significant challenge.
In light of the above, there exists an urgent need for solutions to overcome the problems associated with conventional systems and/or techniques for optimizing the performance and reliability of belt-type continuous variable transmission systems.
SUMMARY
An object of the present disclosure is to provide a belt-type continuous variable transmission (CVT) system for an electric vehicle with improved efficiency and adaptability to different driving conditions.
In an aspect, the present disclosure provides a belt-type continuous variable transmission (CVT) system. Said system comprises a driven pair of discs with a first variable gap therebetween receiving rotational motion, a driving pair of discs with a second variable gap therebetween, and a variator mechanism simultaneously connected to both pairs of discs. The variator mechanism enables variation of the first variable gap to effect a change in the second variable gap, facilitating the adjustment of transmission ratios dynamically.
The present disclosure provides belt-type CVT system facilitates smooth, stepless transitions between gear ratios to enhanced performance and efficiency of vehicle. Advantageously, the disclosed weighted cam lobes enable maintenance of optimum distance between the discs to improvise efficiency, with minimal slippage between the driving and driven disc, minimizing energy loss and enhancing overall system efficiency.
Additional aspects, advantages, features and objects of the present disclosure would be made apparent from the drawings and the detailed description of the illustrative embodiments constructed in conjunction with the appended claims that follow.
It will appreciated that features of the present disclosure are susceptible to being be combined in various combinations without departing from the scope of the present disclosure as defined by the appended claims.
BRIEF DESCRIPTION OF DRAWINGS
The summary above, as well as the following detailed description of illustrative embodiments, is better understood when read in conjunction with the appended drawings. For the purpose of illustrating the present disclosure, exemplary constructions of the disclosure are shown in the drawings. However, the present disclosure is not limited to specific methods and instrumentalities disclosed herein. Moreover, those in the art will understand that the drawings are not to scale. Wherever possible, like elements have been indicated by identical numbers.
Embodiments of the present disclosure will now be described, by way of example only, with reference to the following diagrams wherein:
FIG. 1 illustrates a schematic diagram of a belt-type continuous variable transmission (CVT) system, in accordance with embodiment of present disclosure.
In the accompanying drawings, an underlined number is employed to represent an item over which the underlined number is positioned or an item to which the underlined number is adjacent. A non-underlined number relates to an item identified by a line linking the non-underlined number to the item. When a number is non-underlined and accompanied by an associated arrow, the non-underlined number is used to identify a general item at which the arrow is pointing.
DETAILED DESCRIPTION
The following detailed description illustrates embodiments of the present disclosure and ways in which they can be implemented. Although some modes of carrying out the present disclosure have been disclosed, those skilled in the art would recognise that other embodiments for carrying out or practising the present disclosure are also possible.
The description set forth below in connection with the appended drawings is intended as a description of certain embodiments of belt-type CVT system of an electric vehicle and is not intended to represent the only forms that may be developed or utilised. The description sets forth the various structures and/or functions in connection with the illustrated embodiments; however, it is to be understood that the disclosed embodiments are merely exemplary of the disclosure that may be embodied in various and alternative forms. The figures are not necessarily to scale; some features may be exaggerated or minimised to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ the present invention.
While the disclosure is susceptible to various modifications and alternative forms, specific embodiment thereof has been shown by way of example in the drawings and will be described in detail below. It should be understood, however, that it is not intended to limit the disclosure to the particular forms disclosed, but on the contrary, the disclosure is to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure.
The terms “comprise”, “comprises”, “comprising”, “include(s)”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a setup, system that comprises a list of components or steps does not include only those components or steps but may include other components or steps not expressly listed or inherent to such setup or system. In other words, one or more elements in a system or apparatus preceded by “comprises... a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or apparatus.
In the following detailed description of the embodiments of the disclosure, reference is made to the accompanying drawings and which are shown by way of illustration specific embodiments in which the disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, and it is to be understood that other embodiments may be utilized and that changes may be made without departing from the scope of the present disclosure. The following description is, therefore, not to be taken in a limiting sense.
The present disclosure will be described herein below with reference to the accompanying drawings. In the following description, well known functions or constructions are not described in detail since they would obscure the description with unnecessary detail.
As used herein, the term “continuous variable transmission (CVT) system” or “continuous variable transmission (CVT) drive” refers to a type of transmission that can change seamlessly through an infinite number of effective gear ratios between maximum and minimum values. This system eliminates the need for gear shifts and provides a smooth acceleration experience. The CVT system is designed to improve the efficiency and performance of a vehicle by automatically selecting the optimal gear ratio for any driving condition.
The term “belt-type CVT drive” or “belt-type CVT system” as used throughout the present disclosure relates to a mechanism considered for transmitting power between an input and an output in a vehicle or machinery by utilizing a belt and a pair of variable-diameter pulleys, which can change effective diameters to vary the gear ratio continuously within a range.
As used herein, the term “input pair of discs” denotes a pair of closely positioned discs within a belt-type CVT drive, considered to receive rotational motion from an external source, typically the engine/motor of a vehicle. The input pair of discs receives rotational input from the vehicle's power source, such as an electric motor or internal combustion engine, and transmit received power into the CVT system. By adjusting gap therebetween the input pair of discs allows the CVT to modify the gear ratio.
As used herein, the term “output pair of discs” denotes a pair of discs within the belt-type CVT drive that are positioned space apart from each other. The output pair of discs receives power (through belt or chain) from the input pair of discs and transfer to the vehicle's drivetrain. Through adjustment of gap, transmission ratio can be modified to optimize power output.
As used herein, the term “variator mechanism” refers to a component within the belt-type CVT drive to alter the variable gaps between the input and output pairs of discs, respectively. The gap adjustment mechanism connected to both pairs of discs and enable regulation of transmission's gear ratios without the need for discrete gear changes.
As used herein, the term “gap” refers to the adjustable space or distance between two facing surfaces of either input discs or putout discs of a CVT drive system. The adjustment of gap (between either input discs or putout discs) directly influences the transmission's gear ratio. By altering the gap size, the CVT can modify the contact diameter for the transmission belt or chain, thereby changing the effective gear ratio and efficient transition across a wide range of speeds and loads.
As used herein, the term “weighted cam lobes” refers to specially designed elements/protrusions on rotating disc within the CVT system, wherein weight of cam lobe exerts centrifugal force as the shaft or disc rotates. The cam lobes exert a varying amount of force against another component, such as the disc, based on the rotational speed of the disc. As rotational speed increases, the force exerted by the cam lobes also increases, to reduce the variable gap to modify the transmission gear ratio. Through centrifugal force, the CVT can dynamically adjust the gap between the discs, altering the contact point for the transmission belt or chain and thus, modifying the effective gear ratio for alter power transmission.
As used herein, the term “pushing” refers to the mechanical action exerted by the weighted cam lobes against the disc of the CVT system. Pushing action involves a forceful, directional movement that results in the disc moving towards other disc to reduce variable gap between them. The pushing action is a direct consequence of the increase in rotational speed of the weighted cam lobes, which exerts centrifugal force to enable movement of disc.
As used herein, the term “rotationally disposed” refers to the specific arrangement and orientation of components within the CVT system, whereby these components are positioned in a manner that enables them to rotate/pivot around an axis. The rotationally disposed components, such as the weighted cam lobes, enables dynamic adjustment of the variable gaps between discs to modify transmission gear ratio to adapt demanded torque/speed.
FIG. 1 illustrates a schematic diagram of belt-type CVT system (100), in accordance with embodiment of present disclosure. The belt-type CVT drive (100) comprising the input pair of discs (102), the output pair of discs (104) and variator mechanism (106). The belt-type CVT drive (100) improves efficiency and reliability in power transmission within drivetrain systems of electric vehicles or any other machinery, which use belt-type CVT drive (100) of present disclosure. The rotational motion is imparted to the input pair of discs (102) by a power source of vehicle or other machinery, wherein the power source could be either an engine or an electric motor. The input pair of discs (102) can comprise a first disc (102a) and a second disc (102b), wherein the each of first disc (102a) and second disc (102b) are positioned at a defined distance from one another. The arrangement of the first disc (102a) in relation to the second disc (102b) establishes a variable gap (d1) which is an adjustable space that enables modification of transmission ratio in response to the operational conditions (e.g., increase speed or higher torque demand) of the vehicle. The capability to adjust this variable gap (d1) enables belt-type CVT system (100) to achieve an array of gear ratios, eliminating the necessity for manual gear changes or the incorporation of discrete gear stages. Consequently, the belt-type CVT system (100) present disclosure enhances fuel or energy conservation, facilitates smoother acceleration and/or deceleration to enable optimal efficiency of power source based on current/runtime operational demands. For instance, to increase the speed of vehicle, the variable gap (d1) between the first disc (102a) and the second disc (102b) is modulated to vary the transmission ratio, thereby enabling an increased output speed. Both the first disc (102a) and the second disc (102b) are associated, individually, with two distinctive areas: a primary area (i.e., a regular portion) and a secondary area (i.e., engagement area), which interact with either the transmission belt or the variator mechanism (106) to promote the efficient transfer of power to the output pair of discs (104).
In a further embodiment, the output pair of discs (104) comprises a third disc (104a) and a fourth disc (104b). Mirroring the configuration of the input pair of discs (102), the third disc (104a) together with the fourth disc (104b) defines a second variable gap (d2). This second variable gap (d2) undergoes adjustment step to attained variable gear ratio to align with the current operational requirements of the vehicle, such as the need for enhanced torque (to enable smooth drive on hilly terrain) or increased speed. Dynamic adjustment of second variable gap (d2) can be made in conjunction with modifications to the variable first variable gap (d1), thereby regulating the speed and torque conveyed to wheel by drivetrain of vehicle. The aforesaid manipulation of the second variable gap (d2) has a direct impact on the acceleration and cruising efficiency of vehicle. Additionally, both the third disc (104a) and the fourth disc (104b), individually, are associated with two separate sections: a primary section (i.e., regular portion) and a secondary section (i.e., regular portion), which enable interfacing with the transmission belt or the variator mechanism (106), facilitating the reception of power from the input pair of discs (102).
In yet another embodiment, a set of springs (114) may be employed to maintain the second variable gap (d2) through the application of a directed force by pressing the third disc (104a) towards the fourth disc (104b). In a further embodiment, springs (114) are rotatably positioned in opposition to the third disc (104a) with the express purpose of automatically modulating the second variable gap (d2) between the output pair of discs (104). Said springs (114) apply a directed force upon the third disc (104a), to push the third disc (104a) towards the fourth disc (104b). The spring induce pushing counteracts any centrifugal force-induced outward movement of the third disc (104a) that may arise during high-speed operation. In the absence of the corrective force exerted by said springs (114), an unintended outward displacement of the third disc (104a) could occur, which would inappropriately widen the second variable gap (d2) and potentially induce slippage of the transmission belt. Such slippage hinders the effective transference of power from the motor or engine to the wheels, thereby detrimentally affecting the acceleration and responsive performance characteristics. By exerting a pushing force, said springs (114) enables that the belt maintains optimal engagement with the output pair of discs (104), effectively mitigating the possibility of belt slippage. Moreover, said springs (114) maintain a consistent interaction between belt and output pair of discs (104), preventing outward movement of the third disc (104a) and thus facilitating uninterrupted power transmission.
In another embodiment, a pair of weighted cam lobes (108) can be rotationally disposed onto the first disc (102a) of the driven pair of discs (102). The weighted cam lobes (108) exert centrifugal force onto the first disc (102a) to push the first disc (102a) to move towards the second disc (102b). The movement of the first disc (102a) towards the second disc (102b) results in a reduction of the first variable gap (d1) between the driven pair of discs (102). When rotational speed of the weighted cam lobes (108) is increased from a base speed of 1000 revolutions per minute (RPM) to 2000 RPM. This increase in speed enhances the centrifugal force exerted by the lobes, thereby reducing the first variable gap (d1) from, for example, 10 mm to 5 mm. This reduction in the gap directly translates to a variation in the transmission ratio, enabling the CVT system (100) to adapt to different driving conditions, such as transitioning from a state of acceleration to cruising speed without the need for manual gear changes. Furthermore, the weighted cam lobes (108) can be associated with a controlling mechanism to lock the weighted cam lobes (108) in a specific orientation.
In another embodiment, the weighted cam lobes (108) can be positioned (at regular portion) to engage with the periphery of the first disc (102a) through a mounting mechanism, which allows the weighted cam lobes (108) to pivot or rotate slightly about their axis while remaining in constant, controlled contact with the surface (of regular portion) of first disc (102a). As the rotational speed of the first disc (102a) increases, the weighted cam lobes (108), by virtue of their mass, experience an increase in centrifugal force for pushing the first disc (102a) towards the second disc (102b), thus reducing the gap (d1). In the absence of sufficient centrifugal force—such as at lower rotational speed of first disc (102a), weighted cam lobes (108) are less effective in exerting the necessary force on the first disc (102a). As a result, the first disc (102a) may move away from the second disc (102b), leading to increase first variable gap (d1). The uncontrolled enlargement of the first variable gap (d1) can result in non-continuous power transmission, leading to inefficiencies such as slippage of the transmission belt, which enable transmission of power from input pairs of disc (102) to the output pair of discs (104). Belt slippage may also induce vibration, which may increase wear and tear on the belt and input pairs of disc (102) to the output pair of discs (104).
In an embodiment, the variator mechanism (106) is configured to engage simultaneously with the first disc (102a), the second disc (102b), the third disc (104a), and the fourth disc (104b), each through their respective engagement portions. The variator mechanism (106) is operative to induce an alteration in the first variable gap (d1), which initiates corresponding alteration in the second variable gap (d2). Consequently, the variator mechanism (106) is capable of facilitating a direct correlation between any changes in the first variable gap (d1) and the second variable gap (d2), thereby enabling a continuous and seamless transition of transmission ratios. In another disclosed embodiment, the variator mechanism (106) comprises belt that is equipped with a first roller, which is accommodated within the first variable gap (d1), and a second roller, which is disposed within the second variable gap (d2). The variator mechanism (106) enables the first roller, in conjunction with the weighted cam lobes (108), to regulate the transmission ratio by manipulating the engagement of belt with input pair of discs (102) based on the first variable gap (d1). Correspondingly, the second roller facilitates the synchronous adjustment of second variable gap (d2) to maintain transmission ratios based on varying power demands and driving conditions, ensuring an optimal balance between acceleration, torque, and fuel efficiency. For instance, upon the actuation of the accelerator by the vehicle operator, the belt-type CVT drive (100) enables an incremental enlargement of the first variable gap (d1) between the first disc (102a) and the second disc (102b). Concurrently, the variator mechanism (106) adjusts the second variable gap (d2) between the third disc (104a) and the fourth disc (104b), based on first variable gap (d1). The dual adjustment of the first variable gap (d1) and the second variable gap (d2) repositions the driving belt to a state that elevates the transmission ratio, facilitating an increase in vehicle velocity without necessitating a proportional increment in power output from the source, such as an engine or electric motor.
In a specific aspect, an electric vehicle (EV) comprising the belt-type CVT drive (100), utilizes a motor to impart rotational motion to the input pair of discs (102). As the EV transitions from a stationary state, the weighted cam lobes (108) reduces the first variable gap (d1), reducing effective contact area at which the belt engages with the input pair of discs (102), thereby reducing the gear ratio to maximize torque for accelerated propulsion. Conversely, as the EV attains cruising velocity, the weighted cam lobes (108) expand the first variable gap (d1), thereby increasing the gear ratio to enhance the speed of the vehicle. Correspondingly, the variator mechanism (106) adapts the second variable gaps (d2) in accordance with the newly established first variable gap (d1). Moreover, variator mechanism (106) allows a synchronized adjustment of both gaps (d1 and d2), provides changes in the driving conditions to meet with an immediate and appropriate response in the transmission ratio. The ability of the variator mechanism (106) to simultaneously affect both gaps provides a high level of efficiency in power transmission, optimizing the vehicle performance across a wide range of speeds and conditions.
In an embodiment, the belt is disposed between internal surfaces of each of the driven pair of discs (102) and the driving pair of discs (104), and wherein a friction-improving material (e.g., metal or ceramic dispersed polymeric composite) is disposed on the internal surface corresponding to each of the driven pair of discs (102) and the driving pair of discs (104), significantly improves the belt-type CVT system (100) power transmission efficiency and reliability. The presence of friction-improving material improves the grip between the belt and the discs, reducing slippage, improving the transfer of torque from the engine to the drivetrain and increasing the efficiency of power transmission. The friction-improving material characteristic is important for maintaining performance under varying load conditions and contributes to the smooth acceleration and deceleration of the vehicle. The friction-improving material reduce or eliminates belt slippage under high torque conditions and also delivers consistent power output, improving vehicle performance and energy economy.
In an embodiment, the belt-type CVT system (100), wherein the belt comprises multiple stiffening ribs disposed along a lateral direction of the belt. The multiple stiffening ribs improvise the structural integrity of the belt through maintain shape of belt under varying loads and operational conditions, thereby improving the reliability of the belt-type CVT system (100). The ribs can be disposed at regular intervals along the entire length of the belt to enable uniform distribution of stiffness and strength across span of belt.
In an embodiment, the belt-type CVT system (100), wherein the variator mechanism (106) comprises a tensioning arrangement, and wherein the tensioning arrangement enables the adjustment of tension associated with the belt. The tensioning arrangement provides the belt to operate at optimal tension range for maintaining efficient power transfer. The tensioning arrangement enables belt to remain in proper engagement with each discs (102 and 104) and also prevents slippage that could compromise the efficiency and responsiveness of the transmission.
In the description of the present invention, it is also to be noted that, unless otherwise explicitly specified or limited, the terms “disposed,” “mounted,” and “connected” are to be construed broadly, and may for example be fixedly connected, detachably connected, or integrally connected, either mechanically or electrically. They may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood in specific cases to those skilled in the art.
Modifications to embodiments and combination of different embodiments of the present disclosure described in the foregoing are possible without departing from the scope of the present disclosure as defined by the accompanying claims. Expressions such as “including”, “comprising”, “incorporating”, “have”, “is” used to describe and claim the present disclosure are intended to be construed in a non- exclusive manner, namely allowing for items, components or elements not explicitly described also to be present. Reference to the singular is also to be construed to relate to the plural where appropriate.
Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the present disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.

,CLAIMS:WE CLAIM:
1. A belt-type continuous variable transmission (CVT) system (100), the belt-type CVT system (100) comprising:
- a driven pair of discs (102) having a first variable gap (d1) therebetween, wherein the driven pair of discs (102) receive rotational motion;
- a driving pair of discs (104) having a second variable gap (d2) therebetween; and
- a variator mechanism (106) simultaneously connected to the driven pair of discs (102) and the driving pair of discs (104), wherein the variator mechanism (106) enables a variation of the first variable gap (d1) to create a variation in the second variable gap (d2).
2. The belt-type CVT system (100) as claimed in claim 1, wherein:
- the driven pair of discs (102) comprise a first disc (102a) and a second disc (102b), wherein the first disc (102a)and the second disc (102b) have the first variable gap (d1) therebetween; and
- the driving pair of discs (104) comprise a third disc (104a)and a fourth disc (104b), wherein the third disc (104a) and the fourth disc (104b)have the second variable gap (d2) therebetween;
- wherein the first disc(10ab), the second disc (102b), the third disc (104a), and/or the fourth disc (104b) comprises a regular portion and an engagement portion connected to the regular portion.
3. The belt-type CVT system (100) as claimed in claim 2, wherein the belt-type CVT system (100) comprises a pair of weighted cam lobes (108) rotationally disposed against the first disc (102a) and wherein an increase in a rotational speed associated with the pair of weighted cam lobes (108) causes pushing of the first disc (102a) towards the second disc (102b) to reduce the first variable gap (d1) between the driven pair of discs (102).
4. The belt-type CVT system (100) as claimed in claim 3, wherein the belt-type CVT system (100) comprises a pair of springs (110) rotatably disposed against the third disc (104a) and wherein the pair of springs (110) causes pushing of the third disc (104a) towards the fourth disc (104b) to reduce the second variable gap (d2) between the driving pair of discs (104).
5. The belt-type CVT system (100) as claimed in claim 4, wherein each spring of the pair of springs (110) is a helical spring.
6. The belt-type CVT system (100) as claimed in claim 1, wherein the variator mechanism (106) comprises a belt and wherein the belt comprises:
- a first roller received within the first variable gap (d1); and
- a second roller received within the second variable gap (d2).
7. The belt-type CVT system (100) as claimed in claim 6, wherein the belt is disposed between internal surfaces of each of the driven pair of discs (102) and the driving pair of discs (104) and wherein a friction-enhancing material is disposed on the internal surface corresponding to each of the driven pair of discs (102) and the driving pair of discs (104).
8. The belt-type CVT system (100) as claimed in claim 6, wherein the belt comprises multiple stiffening ribs disposed along a lateral direction of the belt.
9. The belt-type CVT system (100) as claimed in claim 6, wherein the variator mechanism (106) comprises a tensioning arrangement and wherein the tensioning arrangement enables to adjust a tension associated with the belt.
10. The belt-type CVT system (100) as claimed in claim 9, wherein the tensioning arrangement comprise: a hydraulic actuator, a pneumatic actuator, or an electric motor.