DESC:FIELD OF INVENTION
This invention relates generally to a motorised gear shifting arrangement. More particularly, the invention relates to a gear shift arrangement for motor vehicles. It may be used in two wheelers like a two wheeler scooter but not limited to the same.

BACKGROUND OF THE INVENTION
Two wheeler scooters and motorcycles are conventionally powered by gasoline engine equipped with a sequential speed change gear box transmission to extend the driving speed range of the vehicle. During the course of driving, depending on the vehicle speed, the rider needs to shift to an appropriate gear to maintain the engine RPM within its operating range. Also, since the engine develops more power at higher RPM, the rider may have to or want to shift to a lower gear to take advantage of the extra power for acceleration.
Gear shifting involves physical movement of internal parts of the gear box to mechanically engage a select path of the drive train for power transmission. Gear shift mechanisms are designed with safeguards to prevent simultaneous engagement of two gears and to ensure that the vibrations and other disturbances of the drive do not cause accidental slip off from the engaged position. This is normally achieved by providing roller or ball detent of adequate stiffness in each distinct engagement position. This causes large initial resistance to gear change which the rider has to overcome. Therefore, gear shift operation requires considerable effort.
Further, while shifting the gear the rider has to also de-clutch the engine. Conventional axial engagement friction disc clutches, commonly used in two wheelers, require considerable force for de clutching as well.
Generally, in scooters, clutch and gear shift controls are hand operated. The rider has to first press a lever to declutch and then twist the handle grip with his wrist movement to effect gear change. With considerable force required for both the operations, frequent shifting does cause definite rider fatigue.
With no hassle of declutching and gear shifting, scooters with Continuously Variable Transmission or CVT as they are commonly called, offer a convincing solution to the problem of driving fatigue on account of gear shifting and are becoming popular. However, CVTs employ a centrifugal clutch and Belt Drive, both of which are inherently prone to slippage and have significantly lower power transmission efficiency as compared to gear drives. The fuel economy of CVT scooters is therefore considerably inferior to the conventional geared scooters.
With rapid developments in the recent years - expansion of cities, improved road infrastructure & connectivity of rural areas– the overall commuting levels have increased exponentially. Two wheelers, with their unique & distinct advantages, continue to be the most preferred and popular means of personal transport. In the emerging scenario, it is imperative that the issues of driving fatigue deserve better solution without compromising fuel economy. The present innovation addresses this requirement.
Indian Patent no 257247 claims a gear shift arrangement consisting of a DC motor coupled to a micro controller. However, the said patent does not detail as to how the requisite torque is provided from the motor to the gear shift linkage within the limited space. In addition, it does not detail the exact working or enablement of the claimed subject matter. It only discloses a motorized gear shift arrangement for motor vehicles, more particularly two wheeler motorcycles. It teaches replacing the conventional gear shift foot pedal, by a motor and describes different drive configurations for connecting the motor to the existing downstream gear shifting linkage mechanism. However, it does not suggest any change in the downstream mechanism per se.
As explained earlier, the arrangement of roller detent, normally used to avoid slip off from an engaged position, causes large initial resistance, which the motor is required to overcome. Accordingly, the capacity of the motor, and in turn of the power source for the motor has to be adequately large giving rise to design constraints.
The present invention proposes to achieve the function of roller detent by a worm and a worm wheel pair wherein the worm acts as a bi-directional lock preventing the worm wheel from rotation due to vibrations or other disturbances of the engine. It may be noted that in worm – worm wheel drive the rotation of the worm causes the wheel to rotate however; the wheel cannot rotate the worm and is thus locked in position when the worm is stationary. Unlike the roller detent, which causes large initial resistance to gear shift, the worm and worm wheel system offers minimal resistance.
Another problem in the existing state of art is that the motor load increases considerably if the male and female features of the mating parts are not in alignment for engaging with each other. While this leads to overloading of the motor, the resulting pressure between the mating parts further delays their realignment and proper engagement.
The present invention proposes to restrict the voltage supply to the motor in the event of obstruction as explained above. This prevents the over load on motor and also reduces the pressure between the clashing parts, thereby allowing the parts to quickly realign for smooth engagement.
The present invention seeks to address the issues cited in the conventional system, thereby significantly reducing the force and energy requirement for gear shift. Apart from enhancement in the operational (energy) efficiency, the invention also helps reducing the size of motor and the power source, thereby making it possible to accommodate the motorised gear shift arrangement in some very popular scooters known for their extremely compact design.

OBJECT OF THE INVENTION
A basic object of the present invention is to overcome the disadvantages/drawbacks of the known art.

Another objective of the present invention is to provide a gear shift arrangement for motor vehicles.

Another objective of the invention is to eliminate the driver’s fatigue caused by large effort in frequent de-clutching and gear shifting while retaining the performance and fuel economy of a conventional geared scooter.
Another objective of the invention is to design a compact system which can be fitted in limited space available in a two wheeler.
Another objective of the invention is to ensure smooth mating of the engaging parts.
These and other advantages of the present invention will become readily apparent from the following detailed description read in conjunction with the accompanying drawings.

SUMMARY OF THE INVENTION
There is provided a gear shift arrangement for motor vehicles. It may be used in two wheelers like a two wheeler scooter but not limited to the same.
The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.
The engine, according to this invention, requires a significantly low force for actuation of clutch and provides an effortless, sequential gear shift for two wheeler scooters.
According to one aspect of the present invention, there is provided a gear shift arrangement for motor vehicles comprising a motor powered by a power source; a control unit regulating power supply to the motor; a pair of micro switches electrically connected to the control unit and placed at a handle bar for actuating a gear shift; a non contact type sensor for monitoring the gear shift movement; characterized in that a drive train and linkage mechanically engaging the motor through a worm and a worm wheel to a gear shifter rod maintaining a controlled backlash between the worm and worm wheel and said worm bi-directionally locking the worm wheel thereby ensuring stability and the control unit is programmed to momentarily disconnect power supply to the motor in the event of significant impediment to the movement of gear shift linkage as assessed by the excess current drawn by the motor thereby preventing overload on the motor and free relative movement between engaging parts for realignment.
Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention. Reference will now be made to the accompanying diagrams which illustrate, by way of an example, and not by way of limitation, of one possible embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS
The following drawings are illustrative of particular examples for enabling methods of the present invention, are descriptive of some of the methods, and are not intended to limit the scope of the invention. The drawings are not to scale (unless so stated) and are intended for use in conjunction with the explanations in the following detailed description.

Figures 1,2 & 3 explains the internal design arrangement related gear shifting of a reference engine for which the new motorized gear shifting design as per the present invention has been worked out and described herein.
Figures 4, 5 & 6 illustrate the design and actuation mechanism of existing manual shift arrangement of the reference engine housed in a casing attached externally to the engine.
Figure 7 is a pictorial view of the handle bar of the existing scooter illustrating the most popular hand operated gear shift arrangement provided in scooters.
Figures 8, 9, 10 and 11 illustrate the design and layout arrangement of the motorized gear shift mechanism housed in a casing attached externally to the engine.
Figure 12 is a perspective view of the handle bar showing the arrangement for actuation of motorized gear shift by the rider.
Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure.
Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.

DETAILED DESCRIPTION
The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary embodiments of the invention as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein can be made without departing from the scope and spirit of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.
The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.
It is to be understood that the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise.
By the term “substantially” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those of skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.
The motorised gear shift mechanism according to this invention requires significantly low force, power and energy for gear shifting. This is achieved by doing away with the conventional roller detent mechanism for retaining the parts firmly in their respective positions corresponding to each engaged position. Instead, the function is accomplished by worm and worm wheel pair wherein the worm act as a bidirectional lock preventing the worm wheel from rotation due to vibrations or other disturbances of the engine. It may be noted that in worm – worm wheel drive the rotation of the worm causes the wheel to rotate however; the wheel cannot rotate the worm and is thus locked in position when the worm is stationary. Unlike the roller detent, which causes large initial resistance to gear shift, the worm and worm wheel system offers no resistance.
The electronic control unit of the present innovation, apart from controlling the direction and extent of rotation, is programmed to momentarily restrict the voltage supplied to the motor in the event of obstruction to its movement. This reduces the pressure between the clashing parts, thereby allowing them to realign for smooth engagement.
The above measures reduce the momentary high loads typically experienced during the initial and engaging phases of gear shift and permit application of a low capacity motor.
Apart from the detent function, the worm – worm wheel drive also provides the most compact transmission which helps accommodating the system in an extremely limited space. Further, since it also provides large reduction ratio, it facilitates application of high speed motor which is smaller.
For reduction in the clutch actuation force, the present clutch has been improvised based on known technology. The initial built-in pressure between the friction drive and driven plates, which the rider has to overcome for de-clutching, is reduced taking advantage of centrifugal action to build up the pressure, as the engine revs up to ensure requisite torque capacity of the clutch in the operation. For gear shifting, the rider also releases the throttle, which reduces the engine RPM and the associated high pressure build up between the plates allowing soft actuation of clutch.
The Figures 1-7 explain the typical manual gear shifting mechanism of scooters.
Figure 1 shows the relevant internal design configuration of the four gear engine being considered for the invention, explaining the arrangement for engaging each of the gears – one at a time.
Driven Gears (1-I to 1-IV) are coaxially mounted on the Drive Shaft (2) and, as such, are free to rotate on the Shaft.
Gear Shifter Rod Complete (3), consisting of Spider (3a) and Rod (3b), is rotationally fixed to the Drive Shaft (2), as shown more clearly in Figure 2, and can slide along its axis “A-A”.
As shown in Figure 3, axial slots are provided in the bores of all the gears for engagement with the Spider lugs. By sliding the Gear Shifter Rod Complete (3), each of the gear can be rotationally engaged with the Spider, and in turn with the Drive Shaft, allowing the power transmission from the particular Gear.
There are 5 distinct axial positions of the Spider (3a) – marked “N” corresponding to neutral, wherein the Spider is safely clear of any engagement with the adjoining gear lugs (and thus no power transmission in this position) and 4 positions marked 1, 2, 3 and 4, corresponding to engagement with gears 1-I, 1-II, 1-III and 1-IV respectively.
One end of the Gear Shifter Rod is projected out from the engine case to provide access for external actuation.
Referring to Figure 4, a conventional Gear Shifter Unit is shown as externally mounted on the engine case.
As shown in Figure 5, it houses and guides Shaft (5) such that the Shaft is free to rotate on axis “B-B”. Pulley (6) and Lever (7) are firmly fixed to Shaft (5) and so rotate along with it. Key (8) is pivotally connected to Lever (7) and is in engagement with a circumferential slot on Gear Shifter Rod (3b). By virtue of this configuration, the sliding of Gear Shifter Rod Complete (3), required for engaging a specific gear can be accomplished by rotating the pulley (6).
To ensure correct axial positioning of the Spider (3a) in each of its 5 distinct positions of interest (4 positions corresponding to engagement with each of the 4 Gears and one neutral position) a spring loaded roller detent is provided which engages with corresponding 5 “V” grooves on the periphery of Pulley (6).
In Figure 6, a conventional Detent Assembly is shown, consisting of Roller (9) fixed to Latch (10) with Pin (11) is pivotally fixed on Gear Shifter Housing (4). Compression Spring (12) forces the Roller (9) against the periphery of Pulley (6).
Figure 7 shows the conventional complimentary arrangement at the handle bar through which the rider manipulates gear shift. Hand Grip (13) is guided in the Handle bar casing (14) and is free to rotate on its axis “C-C” along with Pulley (15) which is fixed to the tube of Hand Grip and thus rotates along with it. Flexible cables (16-I & 16-II) create rotational coupling of Pulley (15) and Pulley (6) (shown in Figure 5) and thus the rider is able to affect gear shift by rotating the hand grip. According to this arrangement, the handle grip has a progressively twisted angular position for each gear.
In the present invention, conceptually no change has been made in the internal arrangement of the engine explained in Figures 1, 2 and 3.
Figure 8, shows the external view of the Motorised Gear Shift Unit (42) at the engine as per the present invention.
Referring to Figure 9, shows the aforesaid Motorised Gear Shift Unit (42) as per the present invention, wherein a Housing (21) houses and guides a Shaft (22) such that the Shaft is free to rotate on axis “B-B”. Disc A (23), and Lever (7) are firmly fixed to Shaft (22) and so rotate along with it. Key (8) is pivotally connected to Lever (7) and is in engagement with a circumferential slot on Gear Shifter Rod (3b) as in the original design shown in Figure 5. By virtue of this configuration, the sliding of Gear Shifter Rod Complete (3), required for engaging a specific gear can be accomplished by rotating the Disc A (23).
Figure 10 illustrates the drive from the DC Motor (27) to Disc A (23) as per the present invention. A geared transmission with large reduction ratio is used. The resulting slow movement of the Spider helps smooth engagement with the mating gear lugs largely eliminating jerks and vibrations in the motion. The transmission consists of Worm & Worm Wheel pair as it offers a compact solution for large reduction ratio and prevents reverse motion in the event of Spider colliding with the gear’s face. The transmission is housed in the Gear Shifter Housing.
Figure 12 shows an arrangement, as per present invention, at the handle bar through which the rider can effortlessly manipulate gear shift. Hand grip (31) is guided in the Handle Bar casing (32) and is free to rotate on its axis “C-C”. Switch Actuator (34) and Spring Actuator (33) are mounted on the extension tube of the Hand Grip & fixed in their respective positions by means of spring pins, thereby rotating along with the Hand Grip.
As illustrated in View X of Figure 12, a typical torsion Spring arrangement is provided to define a Home position for the Hand Grip, allow its limited twist in either direction and make it return to the Home position when the twisting force is removed. So, unlike in the existing manual arrangement, wherein the Hand Grip progressively changes its angular position from N to 4th Gear, in the proposed arrangement the Hand Grip is always in the same angular position irrespective of the engaged gear.
As shown in view Y of Figure 12, two Micro Switches are fixed on the Handle Bar Casing and are so positioned that when the Hand Grip is rotated in clockwise direction from the home position, the Switch Actuator (34) actuates Switch A. Likewise, reversing the direction of rotation causes actuation of Switch B.
Momentary actuation of either Switch A or B by Twisting the Hand Grip generates a signal and accordingly the Control Unit starts the DC motor in appropriate direction moving together Disc C, Discs A & B, Lever (7) and Gear Shifter Rod (3). In the event of momentary obstruction to the movement of the Spider due to collusion with the face of the mating gear, the Damper Spring (26), by virtue of its ability to compress, absorbs the shock.
As shown in Figure 11 a non contact type sensor (43) monitors the rotational position of Disc A and signals the control unit to switch off the motor precisely when the Disc has attained its desired new position. With the Motor switched off, the worm screw in the drive train acts as a bidirectional lock for the worm wheel ensuring a stable engagement position against rocking due to vibrations or other operational disturbances.
The figures and the description above provide details of one particular design which is also specific to the design and configuration of the base engine being considered. It would be obvious to those skilled in the art that, based on the concepts, ideas and issues described herein, several variations of the proposed design for the design and configuration of the base engine being considered as well as for engines with distinctly different design and configuration, are possible without deviating from the scope of this invention.
Although the embodiments herein are described with various specific embodiments, it will be obvious for a person skilled in the art to practice the embodiments herein with modifications. However, all such modifications are deemed to be within the scope of the invention. It is also to be understood that the description is intended to cover all of the generic and specific features of the embodiments described herein and all the statements of the scope of the embodiments which as a matter of language might be said to fall there between. ,CLAIMS:We claim:
1. A gear shift arrangement for motor vehicles comprising:
a motor powered by a power source;
a control unit regulating power supply to the motor;
a pair of micro switches electrically connected to the control unit and placed at a handle bar for actuating a gear shift;
a non contact type sensor for monitoring the gear shift movement;
characterized in that a worm and a worm wheel drive with controlled backlash mechanically connecting the motor to a gear shifter rod and said worm bi-directionally locking the worm wheel thereby ensuring stability of the engaged position and
the control unit programmed to momentarily disconnect power supply to the motor in event of misalignment between a male and a female element of a pair of engaging parts thereby preventing overload on the motor and allowing the engaging parts to realign for free relative movement.
2. The gear shift arrangement as claimed in claim 1 wherein the motor is a high speed DC motor.
3. The gear shift arrangement as claimed in claim 1 wherein the power source is an existing power source in a vehicle.
4. The gear shift arrangement as claimed in claim 1 wherein the pair of micro switches is adapted for manual actuation.
5. The gear shift arrangement as claimed in claim 1 wherein non-contact type sensor is adapted for monitoring actuation of a gear shift.
6. The gear shift arrangement as claimed in claim 1 wherein the micro switches are configured for upward and downward gear shift.
7. The gear shift arrangement as claimed in claim 1 wherein the worm and worm wheel drive having large reduction ratio to provide requisite torque to a drive train and linkage within the limited available space.
8. A method of gear shifting for motor vehicles comprising:
powering a motor through a power source;
signalling an upward or downward gear shift using a pair of micro switches placed at a handle bar;
regulating power supply to the motor using a control unit;
actuating a gear shift using a pair of micro switches electrically connected to the control unit and placed at a handle bar;
monitoring the gear shift movement using non contact type sensor;
characterized in that a worm and a worm wheel drive with controlled backlash mechanically connecting the motor to a gear shifter rod and said worm bi-directionally locking the worm wheel thereby ensuring stability of the engaged position and
the control unit programmed to momentarily disconnect power supply to the motor in event of misalignment between a male and a female element of a pair of engaging parts thereby preventing overload on the motor and allowing the engaging parts to realign for free relative movement.