DESC:FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003

COMPLETE SPECIFICATION
[See section 10, Rule 13]

A SYNCHRONIZED GEAR BOX

MAHINDRA & MAHINDRA LIMITED, HAVING ITS REGISTERED OFFICE AT MAHINDRA RESEARCH VALLEY, MAHINDRA WORLD CITY, PLOT NO: 41/1, P.O. – ANJUR, CHENGALPATTU – 603004, DISTT. – KANCHEEPURAM, TAMIL NADU, INDIA

THE FOLLOWING SPECIFICATION DESCRIBES THE INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a manual gearbox of a motor vehicle and more particularly to the synchronized gearbox of a motor vehicle.

BACKGROUND OF THE INVENTION
Automobiles has revolutionized the transportation industry widely. In motor vehicles, the transmission generally is connected to the engine crankshaft via a flywheel or clutch or fluid coupling, partly because internal combustion engines cannot run below a particular speed. The output of the transmission is transmitted via. the driveshaft to one or more differentials to drive the wheels. The transmission system allows the driver to drive the vehicle with respect to the varying speed and torque requirements pertaining to the road conditions.

With the growing technology, the synchronized gearbox was developed in which synchronizer device adjusts the speed of the shaft and the gearwheel, in which the sleeve is moved by the shift fork connected to the gear shift knob towards the gear to be engaged. When there remains a speed difference between the sleeve/ hub system and the gear wheel, the sleeve is blocked by the blocker ring and the synchronizer ring creates a friction torque and when the speed is synchronized, the sleeve can be moved further and engaged into the spline of the engagement ring at the gear wheel.

Generally, in a manual transmission vehicle, it is observed that drivers always keep one hand on the gear shift knob for shifting the gears, as per requirement for driving the vehicle. It is observed that the gearshift knob vibrates continuously in the gear engaged condition by moving back and forth which shakes the hand kept over it and thereby causes inconvenience to the Driver while driving the vehicle. It is also observed that the vibration of the gearshift knob increases as the revolutions per minute (rpm) of the engine increases. The gearshift knob vibration depends upon the various factors such as unbalancing of the engine due to rotating or reciprocating components which generate bending vibrations in the drive train, play in the gear shift lever and also the wobbling of the sleeve in gear engaged condition.

Therefore, there is a requirement to solve atleast one of the aforementioned problems.

SUMMARY OF THE INVENTION
The present invention provides a synchronized gearbox, where the synchronized gearbox comprises an input shaft, an output shaft, a synchronizer hub having splines mounted on the shaft, an engaging sleeve having group of internal teeth which is axial displaceably mounted on the synchronizer hub splines, an outer and an inner synchronizer ring placed on both side of the synchronizer hub, a first gear and a second gear which are rotatably mounted on the shaft at both sides of the synchronizer hub and which are locked relative to the synchronizer hub by axial displacement of the engaging sleeve from a neutral position to an engaged position, a gear shift fork connected with the engaging sleeves at one end and to a gear shift knob at another end, the gear shift knob is operated to shift transmission from one gear to another gear. According to the present invention, the width of synchronizer hub splines is increased in such a manner that the overlapping area between the engaging sleeve and the synchronizer hub also increases. The increased overlapping area between the engaging sleeve and the synchronizer hub changes or shifts the pivot point of the engaging sleeve in gear shifted condition which provides the additional support. Further, the increased overlapping area between the engaging sleeve and the synchronizer hub reduces the angular displacement of the engaging sleeve with respect to the synchronizer hub pivot and thereby reduces the gearshift knob vibration occurring due to engaging sleeve wobbling while driving the vehicle in gear engaged condition.

In accordance with an aspect, the present invention provides a synchronizing system for a gear box; the synchronizing system comprising a synchronizing hub having splines for mounting an engaging sleeve of the gearbox, an outer and an inner synchronizer ring placed on both side of the synchronizer hub. The width of synchronizer hub splines is increased in such a manner that the overlapping area between the engaging sleeve and the synchronizing hub also increases. The increased overlapping area changes or shifts the pivot point of the engaging sleeve in gear shifted condition. The increased overlapping area between the engaging sleeve and the synchronizer hub reduces the angular displacement of the engaging sleeve with respect to the synchronizer hub pivot and therefore reduces the wobbling of the engaging sleeve.

In accordance with an aspect of the present invention, an increased overlapping area between the engaging sleeve and the synchronizer hub is obtained without making any alteration or change in the size of the gearbox.

BRIEF DESCRIPTION OF THE DRAWINGS
Reference will be made to aspects of the invention, examples of which may be illustrated in the accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in the context of these aspects, it should be understood that it is not intended to limit the scope of the invention to these particular aspects.
Figure 1 shows overlapping of synchronizing hub upon the sleeve in accordance with the conventional gear box of a motor vehicle.
Figure 2 shows the increased overlapping area between synchronizing hub and the sleeve in accordance with an aspect of the present invention.
Figure 3 shows the cross sectional view of the overlapping area between the engaging sleeve and the synchronizing hub in accordance with an aspect of the present invention.

DETAILED DESCRIPTION OF THE INVENTION
The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of exemplary aspects 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 aspects 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 aspects 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. Thus, for example, reference to "a component surface" includes reference to one or more of such surfaces.

It is also to be understood that engaging sleeve means a gear shift sleeve, synchronizer sleeve or sliding sleeve.

The subject matter is now described with reference to the drawings. It may be evident however, that such matter can be practiced with these specific details. In other instances, well-known structures as shown in diagram form in order to facilitate describing the invention.

Figure 1 shows the overlapping of engaging sleeve upon synchronizer hub in accordance with the conventional synchronized gearbox of the motor vehicle where the engaging sleeve is mounted on splines of the synchronizer hub and the point A-B shows the overlapping area between the engaging sleeve and the synchronizer hub. The engaging sleeve is moved by the shift fork or shift knob towards the gear to be engaged.

Figure 2 shows the shows the overlapping of synchronizing hub upon the engaging sleeve in accordance with an aspect of the present invention. In the figure, X and Y show the increased overlapping area between the engaging sleeve and the synchronizer hub in accordance with the present invention. In comparison with the prior art, the width of the spline of the synchronized hub is increased in such a manner that the overlapping area (X-Y) between the engaging sleeve and the synchronizer hub also increases without altering the size of the gearbox. The present invention provides a solution to the problem of gear shift knob vibration occurring due to sleeve wobbling by increasing the width of synchronizer hub spline so as to increase the overlapping area (X-Y) between the engaging sleeve and the synchronizer hub. The increased overlapping area changes or shifts the pivot point of the engaging sleeve which provides the additional support and reduces the angular displacement of the engaging sleeve with respect to the synchronizer hub pivot and therefore, reduces the engaging sleeve wobbling and gearshift knob vibration while driving the vehicle in gear engaged condition.

Figure 3 shows the cross-sectional view of overlapping between the synchronizing hub and the engaging sleeve in accordance with an aspect of the present invention. A synchronizer hub having splines and is mounted on the shaft, an engaging sleeve having group of internal teeth which is axial displaceably mounted on the synchronizer hub splines, an outer and an inner synchronizer ring placed on both side of the synchronizer hub, a first gear and a second gear which are rotatably mounted on the shaft at both sides of the synchronizer hub and which is locked relative to the synchronizer hub by axial displacement of the engaging sleeve from a neutral position to an engaged position. In accordance with the present invention, the width of the splines is increased in such manner that the overlapping area between the engaging sleeve and the synchronizer hub also increases which changes or shifts the pivot point of the synchronizer hub along the shaft of the synchronized gearbox and thus reduces the angular displacement of the engaging sleeve with respect to the synchronizer hub pivot.

In accordance with another aspect of the present invention, the synchronized gearbox comprises an input shaft, an output shaft, a synchronizer hub having splines and is mounted on the shaft of the gearbox, an engaging sleeve having group of internal teeth which is axial displaceably mounted on the synchronizer hub splines, an outer and an inner synchronizer ring placed on both side of the synchronizer hub, a first gear and a second gear which are rotatably mounted on the shaft at both sides of the synchronizer hub and which are locked relative to the synchronizer hub by axial displacement of the engaging sleeve from a neutral position to an engaged position, a gear shift fork connected with the engaging sleeves at one end and to a gear shift knob at another end, the gear shift knob is operated to shift transmission from one gear to another gear. The width of synchronizer hub splines is increased in such a manner that the overlapping area between the engaging sleeve and the synchronizer hub increases. The increased overlapping area changes the pivot point of the engaging sleeve in gear shifted condition and provides an additional support thereto. Further, the increased overlapping area reduces the angular displacement of the engaging sleeve with respect to the synchronizer hub pivot and therefore, reduces the gearshift knob vibration occurring due to engaging sleeve wobbling while driving the vehicle in gear engaged condition.

In accordance with the present invention, the increment in the engaging sleeve to hub overlap area is obtained without making any alteration or change in the size of the gearbox. The increase in width of the spline of the synchronizer hub further reduces the noise and vibration occurring in the gearbox while shifting the gear.

In accordance with another aspect, the present invention provides a synchronizing system for the synchronized gear box; the synchronizing system comprising a synchronizing hub having splines for mounting an engaging sleeve of the gearbox; an outer and an inner synchronizer ring placed on both side of the synchronizer hub. The width of synchronizer hub splines increases an overlapping area between the engaging sleeve and the synchronizer hub. The increase in overlapping area between the engaging sleeve and the synchronizer hub changes or shifts the pivot point of the engaging sleeve in gear shifted condition and further reduces the angular displacement of the engaging sleeve with respect to the synchronizer hub pivot in order to reduce the wobbling of the engaging sleeve.

In accordance with an aspect of the present invention, the synchronizer gearbox with increased engaging sleeve to hub overlap area is obtained without making any changes in the size of the gearbox and therefore, the synchronizer system of the present invention can be installed in the conventional gearbox so as to eliminate the gearshift knob vibration.

In accordance with a non-limiting aspect of the present invention, when an overlapping area between the engaging sleeve and the synchronizer hub of the gearbox is increased to at least 5.2 mm in gear engaged condition, the wobbling of the engaging sleeve and gear knob vibrations are reduced.

In accordance with the present invention, the present synchronizing device is installed into the conventional gear box, where the overlapping area between the engaging sleeve and the synchronizer is increased by increasing the width of the splines of the synchronizer hub or replacing the conventional synchronizer hub with a synchronizer hub of the present invention having increased with of the splines, subjected to the design parameters of the gearbox. Further, the increment or change in overlapping area between the engaging sleeve and the synchronizer hub to be obtained depends upon the angular displacement of the engaging sleeve to the synchronizer hub.

ADVANTAGES
Following are the advantages of the present invention:
1. The present invention provides a solution to the problem of gearshift knob vibration during operation of the vehicle.
2. The present invention may be adapted to the conventional gearbox without changing or altering the design parameters thereto.
3. The present invention improves the gear shifting of the gearbox with reduced noise and vibration and therefore, increases the efficiency of the gearbox.

EXAMPLE:
A synchronizing device of the present invention was used in the below manner.
A conventional gearbox having six speed gears was tested using tolerance stack loop method. The overlapping area between the engaging sleeve and the synchronizer hub in gear engaged condition was measured as follows:
Gear Position Overlapping Area (in mm)
1st 3.14
2nd 3.30
3rd & 4th 3.57
5th & 6th 4.44

Post engagement of the gear, the engaging sleeve was found to be wobbling and gear shift knob was observed to be vibrating with the above-mentioned overlapping area dimensions. Therefore, the present synchronizing system was used to increase the overlapping area between the engaging sleeve and the synchronizer hub in gear engaged condition by following dimensions:
Gear Position Overlapping Area (in mm)
1st 5.19
2nd 5.35
3rd & 4th 5.62
5th & 6th 6.49

It was observed that engagement sleeve wobbling was reduced and further, no vibrations were felt on the gear shift knob due to the increase in engaging sleeve to synchronizing hub overlapping area. Thus, it was proved that an increase in the overlapping area between the engaging sleeve and the synchronizer hub reduces the sleeve wobbling and vibrations.

Many modifications may be made without departing from the basic spirit of the present invention. Accordingly, it will be appreciated by those skilled in the art that the invention may be practiced other than that has been specifically described herein.
,CLAIMS:WE CLAIM
1. A synchronized gear box, comprising:
an input shaft;
an output shaft;
a synchronizer hub having splines, the synchronizer hub is mounted on the shaft;
an engaging sleeve having group of internal teeth, the engaging sleeve is axial displaceably mounted on the synchronizer hub splines through the internal teeth,
an inner and an outer synchronizer ring placed on both side of the synchronizer hub;
a first gear and a second gear rotatably mounted on the shaft of the synchronizer hub; and
a gear shift fork connected with the engaging sleeves;
wherein width of the splines of the synchronizer hub is increased in such a manner that the overlapping area between the engaging sleeve and the synchronizer hub increases without altering or changing the size of the gearbox, where the increased overlapping area changes the pivot point of the engaging sleeve in gear shifted condition to reduce wobbling of the engaging sleeve.

2. The synchronized gear box as claimed in claim 1, wherein the increased overlapping area between the engaging sleeve and the synchronizer hub reduces the angular displacement of the engaging sleeve with respect to the synchronizer hub pivot.

3. The synchronized gear box as claimed in claim 1, wherein the gear shift fork is connected to a gear shift knob which is operated to shift the transmission from one gear to another gear.

4. The synchronized gear box as claimed in claim 1, wherein the first gear and the second gear are locked relative to the synchronizer hub by axial displacement of the engaging sleeve from a neutral position to an engaged position.

5. The synchronized gear box as claimed in claim 1, where the increase in width of the splines of the synchronizer hub reduces the noise and vibration occurring in the gearbox while shifting the gear.

6. The synchronized gear box as claimed in claim 1, wherein the engaging sleeve to synchronizer hub overlapping area depends upon the angular displacement of the engaging sleeve with respect to the synchronizer hub pivot.

7. The synchronized gear box as claimed in claim 1, wherein the overlapping area between the engaging sleeve and the synchronizer hub is at least 5.2 mm.

8. A synchronizing system for a gear box comprising:
a synchronizing hub having splines for mounting an engaging sleeve of the gearbox; and
an inner and an outer synchronizer ring placed on both side of the synchronizer hub;
wherein the width of the splines of synchronizer hub increases an overlapping area between the engaging sleeve and the synchronizer hub of the gearbox without altering or changing the size of the gearbox, resulting in changing or shifting of a pivot point of the engaging sleeve in gear shifted condition to reduce wobbling of the engaging sleeve.

9. The synchronizing system for a gear box as claimed in claim 8, wherein the increased overlapping area between the engaging sleeve and the synchronizer hub reduces the angular displacement of the engaging sleeve with respect to the synchronizer hub pivot.

10. The synchronizing system for a gear box as claimed in claim 1, wherein the overlapping area between the engaging sleeve and the synchronizer hub is at least 5.2 mm.
Dated this 30th day of August, 2018
For Mahindra & Mahindra Limited.
By their Agent

(GIRISH VIJAYANAND SHETH) (IN/PA 1022)
KRISHNA & SAURASTRI ASSOCIATES LLP