WO2016199156A1

WO2016199156A1 - An engine with motorised gear shifting and low force actuation clutch for two wheelers

Info

Publication number: WO2016199156A1
Application number: PCT/IN2015/000297
Authority: WO
Inventors: Girish Marathe
Original assignee: Lml Ltd.
Priority date: 2015-06-08
Filing date: 2015-07-27
Publication date: 2016-12-15

Abstract

A motorized gear shifting mechanism consisting of, a DC motor (27) powered by the vehicle's power source, an electronic unit to control the power supply to the motor, a pair of micro switches - one for upward shift and one for downward shift, conveniently located at the handle bar through which the operator signals the electronic unit to effect upward / downward gear shift; a set of sensors to monitor the gear shift movement and generate a signal for the control unit to switch off the motor driven by the motor and a geared transmission mechanism for connecting the motor with the gear shift linkage of the engine; soft actuation clutch.

Description

TITLE OF THE INVENTION

An Engine with Motorised Gear Shifting and low force actuation clutch for two wheelers

FIELD OF INVENTION

This invention relates to gear shifting arrangement for motor vehicles, more particularly, but not exclusively, to two wheeler scooters.

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 is achieved by providing roller or ball detent of adequate stiffness in each distinct engagement position. Since the rider has to overcome this locking force, gear shift operation requires considerable effort. Further, white 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 arid 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. Therefore, the present Invention not only solves the lacunae of the prior art but is also novel and inventive over the same.

OBJECT OF THE INVENTION The object of the invention is to eliminate the driver's fatigue caused by large effort in frequent de-clutching and gear shifting white 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 the scooter.

SUMMARY OF THE INVENTION

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.

A motorized gear shift mechanism is designed. It comprises of a pair of switches, one for upward shift and one for downward shift, conveniently placed at the handle bar for easy actuation by the rider. A DC motor is provided as a power source for the gear shift and is coupled to the existing gear shift linkage through a worm & worm wheel reduction drive to match the speed / torque characteristics of the motor with the application requirement The motor rotates in either direction depending oh whether the upward or downward shift switch is momentarily actuated by the rider and uses the battery / magneto of the vehicle as the power source. A set of sensors are deployed to monitor the actuation and a control unit is provided to switch off the motor.

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.

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

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, 11 and 13 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.

DETAILED DESCRIPTION

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 (1-1 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 rotafjonally 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 1-1, 1-11, 1-111 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 pivotaliy 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 pivotaliy 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 (16-1 & 16-11) create rotational coupling of Pulley (15) and Pulley (6) (shown in Figure 5) and thus the rider is able to effect 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 at the engine as per the present invention.

Referring to Figure 9, shows the aforesaid Motorised Gear Shift Unit 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) & Disc B (24), shown more clearly in Figure 10, and Lever (7) are firmly fixed to Shaft (22) and so rotate along with it. Disc C (25) is coaxially placed between Discs A & B and is rotationally coupled to them through Damper Spring (26). 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 C (25). Figure 11 illustrates the drive from the DC Motor (27) to Disc C (25) 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 4^th 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.

Figure 13 is a view of Discs A, B and C along the axis of their rotation (B-B in Figure 9). A set of Micro Switches are suitably positioned along the periphery of the discs and are actuated by the slotted cam profiles provided thereon. Through this actuation, the switches monitor the rotational position of the Discs and signal the control unit to switch off the motor precisely when the Discs have attained their 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.

Claims

Claims:

1. A motorized gear shifting mechanism consisting of. a DC motor (27) powered by the vehicle's power source; a control unit to control the power supply to the motor; a pair of micro switches - one for upward shift and one for downward shift, conveniently located at the handle bar through which the operator signals the electronic unit to effect upward / downward gear shift; a set of sensors to monitor the gear shift movement and generate a signal for the control unit to switch off the motor driven by the motor and a geared transmission mechanism for connecting the motor with the gear shift linkage of the engine.

2. A motorized gear shifting mechanism as claimed in Claim 1 , wherein the geared transmission mechanism consists of a worm and worm wheel drive with large reduction ratio to provide the requisite torque to the gear shift linkage within the limited space available;

3. A motorized gear shifting mechanism as claimed in Claim 1 , wherein the worm screw in the drive train acts as a bidirectional lock for the worm wheel ensuring a stable engagement position;

4. A motorized gear shifting mechanism as claimed in Claim 1 consisting of a Damper Spring (26) to absorb the shock in the event of momentary obstruction to the movement of the Spider (3a) due to collusion with the face of the mating gear;

5. A motorized gear shifting mechanism as claimed in Claim 1 consisting of a set of Micro Switches that are suitably positioned along the periphery of the discs and are actuated by the slotted cam profiles provided thereon in order to signal the control unit to switch off the motor precisely when the Discs have attained their desired new position;

6. An engine for two wheeler application equipped with a motorised gear shift arrangement as per claim 1 and a soft actuation clutch, to substantially reduce the effort required for gear shifting and the resulting rider fatigue.