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

COMPLETE SPECIFICATION
(See section 10 and rule 13)

A TRANSMISSION SYNCHRONIZER FOR A VEHICLE;

MAHINDRA & MAHINDRA LIMITED, A COMPANY REGISTERED UNDER THE INDIAN COMPANIES ACT, 1913, HAVING ADDRESS AT MAHINDRA & MAHINDRA LTD., MAHINDRA RESEARCH VALLEY. MAHINDRA WORLD CITY, PLOT NO.41/1, ANJUR P.O., CHENGALPATTU, KANCHIPURAM DISTRICT, TAMILNADU – 603004, INDIA

THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE NATURE OF THIS INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED
 
FIELD OF THE INVENTION
The present invention relates to a transmission synchronizer for a vehicle.
BACKGROUND OF THE INVENTION
Synchronizers are known from the prior art with hubs associated with transmission shafts. Spring struts are typically adjustable on the hub and are adjusted by a slide sleeve to activate the synchronizer ring during the shift process. The synchronizer ring can then interact with the gear to synchronize the speed of the synchronizer ring with the corresponding gear. After the speeds are synchronized, the slide sleeve is further adjusted so that torque is transmitted from the hub located on the transmission shaft to the corresponding gears.
Generally, the gear shift travels are same for even/reverse and odd gear shifting. This makes the gear shift travel symmetric for the odd and even/reverse gear engagement. Due to symmetric gear shift travel arrangement, the gearbox face packaging constraints.
Additionally, the synchronizer strut in the gearbox is always preloaded under the sleeve. Considering, the same design practices for the asymmetric gear shift travel arrangement, a larger sleeve will be required to hold the strut in the preloaded condition. Thus, the increased sleeve and the strut may foul with the neighboring parts and increases the weight of the gearbox.
SUMMARY OF THE INVENTION
An objective of the present invention is to provide a synchronizer with shorter sleeve for asymmetric gear shift travel arrangement.
In an embodiment, the present invention provides a transmission synchronizer for a vehicle comprising a main shaft with a gear shift mechanism. The gear shift mechanism located intermediate of a top gear and a reverse gear mounted on the main shaft, the top gear and the reverse gear having an externally splined tooth surface formed thereon. An idle gear disposed on an idle shaft positioned parallel to the main shaft, said idle gear configured to rotate the reverse gear in a direction opposite to the top gear. A hub fixed on the main shaft intermediate the top gear and reverse gear and the hub having an externally splined tooth surface, the hub having at least an axial guide slot formed on the outer circumference of the hub. A spring mounted strut confined within each of the guide slot and adapted for radial and axial movement therein. A shift sleeve configured to be coupled to the gear shift mechanism, the shift sleeve having an internal splined tooth surface adapted to mesh with the hub externally splined tooth surface, wherein the shift sleeve has an axial length less than the axial length of the hub and the shift sleeve has a protruded profile formed circumferentially in the internal splined tooth surface of the shift sleeve.
According to an embodiment of the present invention, the main shaft accommodates a blocker ring intermediate the top gear and the hub, said blocker ring adapted for rotational movement with the main shaft.
According to an embodiment of the present invention, the protruded profile is a raised hump formed on the shift sleeve at one end, the raised hump configured to provide smooth engagement and disengagement of the strut with the shift sleeve.
According to an embodiment of the present invention, the length of guide slot is less than the axial length of the hub.
According to an embodiment of the present invention, the shift sleeve slides axially relative to the hub in a top gear direction for selectively engaging the rotating top gear with the main shaft, wherein the protruded profile of the shift sleeve depresses the struts and the shift sleeve, the strut travels in the top gear direction, the strut configured to move the blocker ring towards the top gear so as to effect frictional engagement of the blocker ring with the top gear for generating torque therebetween.
According to an embodiment of the present invention, the shift sleeve slides axially relative to the hub in a reverse gear direction for selectively engaging the rotating reverse gear with the main shaft, wherein the shift sleeve disengages the strut and the strut is uncovered entirely.
In this respect, it is to be understood that the transmission synchronizer for a vehicle is not limited in its applications to the details of construction and arrangements of the components set forth in the following description or illustration. Those skilled in the art will appreciate that the concept of this disclosure may be readily utilized as a basis for the design of other structures, methods, and systems for carrying out the several purposes of the transmission synchronizer for a vehicle.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are included to provide a further understanding of the invention are incorporated in and constitute a part of this specification, illustrate an embodiment of the invention and together with the description serve to explain the principles of the invention. They are meant to be exemplary illustrations provided to enable persons skilled in the art to practice the disclosure and are not intended to limit the scope of the appended claims.
Figure 1 is a side view showing an embodiment of a transmission synchronizer for a vehicle;
Figure 2 is another side view showing an embodiment of the transmission synchronizer of Figure 1;
Figure 3 is a schematic cross sectional view of the transmission synchronizer of Figure 1 according to an embodiment of the present invention in neutral position;
Figure 4 is a schematic view of the transmission synchronizer of Figure 1 according to an embodiment of the present invention in reverse gear position;
Figure 5 is a schematic view of the transmission synchronizer of Figure 1 according to an embodiment of the present invention in top gear position;
Figure 6 shows an exploded front view of the transmission synchronizer of Figure 1;
Figure 7 is a perspective view of a sleeve with protruded profile of the transmission synchronizer of Figure 1;
Figure 8 is a front view of the sleeve of figure 7; and
Figure 9 is a cross-sectional view of the sleeve of figure 8 taken along line AA-AA.
Throughout the drawing, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures.
DETAILED DESCRIPTION OF THE INVENTION
The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of the invention as defined by the description. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness.
The terms and words used in the following description 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 the present invention is provided for illustration purpose only.
It is to be understood that the singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise.
Figure 1-6 shows the structural representation of a transmission synchronizer (100) for a vehicle. The transmission synchronizer (100) for a vehicle includes a main shaft (1) with a gear shift mechanism (20). The gear shift mechanism (20) is located intermediate of a top gear (2) and a reverse gear (3) mounted on the main shaft (1). In an embodiment of the present invention, the top gear (2) is any gear with forward gear ratio. In an embodiment of the present invention, the top gear (2) is a fifth gear.
The top gear (2) and the reverse gear (3) have an externally splined tooth surface formed thereon. An idle gear (4) is disposed on an idle shaft (5) positioned parallel to the main shaft (1). The idle gear (4) rotates the reverse gear (3) in a direction opposite to the top gear (2). A hub (6) is fixed on the main shaft (1) intermediate the top gear (2) and reverse gear (3). The hub (6) has an externally splined tooth surface. The hub (6) has at least an axial guide slot (7) formed on the outer circumference thereof. In an embodiment of the present invention, the guide slot (7) has a length that is less than the axial length of the hub (6).
The gear shift mechanism (20) comprises at least a shift rail (21). The shift rail (21) has at least a shift fork (22, 23) attached thereto to facilitate gear shift operation. In an embodiment of the present invention, two forks (22, 23) are used to cause gear shift operation. The first shift fork (22) engages with a shift sleeve (9) of the top gear (2) whereas the second shift fork (23) engages with the idle shaft (5) or idle gear (4). The shift sleeve (9) has a circumferential groove (24) defined on the external surface thereof. The groove (24) is coupled to the first shift fork (22) of the gear shift mechanism (20).
A spring mounted strut (8) is confined within each of the guide slot (7) and adapted for radial and axial movement therein. The strut (8) is configured to be biased by the spring radially outwardly and into engagement with the internal splined tooth surface of the shift sleeve (9).
Referring to Figures1 and 7-9, the shift sleeve (9) has an internal splined tooth surface adapted to mesh with externally splined tooth surface of the hub (6), wherein the shift sleeve (9) has an axial length less than the axial length of the hub (6) and the shift sleeve (9) has a protruded profile (10) formed circumferentially in the internal splined tooth surface of the shift sleeve (9). The protruded profile (10) defines a raised hump with a predetermined pattern configured to provide smooth engagement and disengagement of the strut (8) with the shift sleeve (9). According to an embodiment, the raised hump is having a trapezoid shape curved around its edges. In an embodiment the predetermined pattern of the raised hump is selected from a curved pattern, a flat pattern or a combination thereof. Further, the number and the geometry of the protruded profile (10) on the shift sleeve (9) are optimized based on the requirement of the transmission synchronizer (100) of different vehicles.
The main shaft (1) accommodates a blocker ring (11) intermediate the top gear (2) and the hub (6). The blocker ring is adapted to rotate with the main shaft (1).
During the top gear engagement with the main shaft, the shift sleeve (9) slides axially relative to the hub (6) in a top gear (2) direction for selectively engaging the rotating top gear (2) with the main shaft (1), wherein the protruded profile (10) of the shift sleeve (9) depresses the strut (8) and the shift sleeve (9) such that the strut (8) travels in the top gear (2) direction to move the blocker ring (11) towards the top gear (2) so as to effect frictional engagement of the blocker ring (11) with the top gear (2) for generating torque therebetween.
During the reverse gear engagement with the main shaft, the shift sleeve (9) slides axially relative to the hub (6) in a reverse gear (3) direction and the second shift fork (23) selectively engages the idle gear (4) with the rotating reverse gear (3) on the main shaft (1). Thus, the main shaft (1) rotates in the direction opposite to the top gear (2). The shift sleeve (9) disengages the strut (8), and the strut (8) is uncovered entirely as the shift sleeve (9) slides axially relative to the hub (6).
The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, to thereby enable others, skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omission and substitutions of equivalents are contemplated as circumstance may suggest or render expedient, but such are intended to cover the application or implementation without departing from the spirit or scope of the present invention.
 
LIST OF REFERENCE NUMERALS
100 - Transmission synchronizer
1 - Main shaft
2 - Top gear
3 - Reverse gear
4 - Idle gear
5 - Idle shaft
6 - Hub
7 - Guide slot
8 - Strut
9 - Shift sleeve
10 - Protruded profile
11 - Blocker ring
20 - Gear shift mechanism
21 - Shift rail
22 - First shift fork
23 - Second shift fork
24 - Circumferential groove on sleeve
, Claims:[Claim 1]
A transmission synchronizer (100) for a vehicle comprising:
a main shaft (1), having a top gear (2) and a reverse gear (3) mounted thereon, the top gear (2) and the reverse gear (3) having an externally splined tooth surface formed thereon, the main shaft (1) having a gear shift mechanism (20) positioned between the top gear (2) and the reverse gear (3);
an idle gear (4) disposed on an idle shaft (5) positioned parallel to the main shaft (1), said idle gear (4) configured to rotate the reverse gear (3) in a direction opposite to the top gear (2);
a hub (6) fixed on the main shaft (1) between the top gear (2) and reverse gear (3), the hub (6) having an externally splined tooth surface, the hub (6) having at least an axial guide slot (7) formed on the outer circumference thereof;
a spring mounted strut (8) confined within each of the guide slots (7) on the hub (6) and adapted for radial and axial movement therein;
a shift sleeve (9) configured to be coupled to the gear shift mechanism (20), the shift sleeve (9) having an internal splined tooth surface adapted to mesh with the hub (6) externally splined tooth surface, wherein
the shift sleeve (9) has an axial length less than the axial length of the hub (6) and the shift sleeve (9) has a protruded profile (10) formed circumferentially in the internal splined tooth surface of the shift sleeve (9).
[Claim 2]
The transmission synchronizer (100) as claimed in claim 1, wherein the main shaft (1) accommodates a blocker ring (11) between the top gear (2) and the hub (6), said blocker ring (11) facilitate rotational movement with the main shaft (1).
 
[Claim 3]
The transmission synchronizer (100) as claimed in claims 1, wherein the gear shift mechanism (20) includes at least a shift rail (21) that has at least a shift fork (22, 23) attached thereto to facilitate gear shifting.
[Claim 4]
The transmission synchronizer (100) as claimed in claim 1 or 3, wherein the shift sleeve (9) has a circumferential groove (24) on the external surface, the circumferential groove (24) is coupled to the first shift fork (22) of the gear shift mechanism (20).
[Claim 5]
The transmission synchronizer (100) as claimed in claim 1, wherein the protruded profile (10) is a raised hump formed on the shift sleeve (9) at one end, the raised hump configured to provide smooth engagement and disengagement of the strut (8) with the shift sleeve (9).
[Claim 6]
The transmission synchronizer (100) as claimed in claim 1, wherein the guide slot (7) has a length that is less than the axial length of the hub (6).
[Claim 7]
The transmission synchronizer (100) as claimed in claim 1, wherein the spring mounted strut (8) has a spring disposes the strut (8) radially outwardly to engage with the internal splined tooth surface of the shift sleeve (9).
[Claim 8]
The transmission synchronizer (100) as claimed claim 1, wherein the shift sleeve (9) slides axially relative to the hub (6) in a top gear (2) direction for selectively engaging the rotating top gear (2) with the main shaft (1).
 
[Claim 9]
The transmission synchronizer (100) as claimed claim 8, wherein the protruded profile (10) of the shift sleeve (9) depresses the struts (8) and the shift sleeve (9) such that the strut (8) travels in the top gear (2) direction to move the blocker ring (11) towards the top gear (2) so as to effect frictional engagement of the blocker ring (11) with the top gear (2) for generating torque therebetween.
[Claim 10]
The transmission synchronizer (100) as claimed in claim 1, wherein the gear shift mechanism (20) selectively engages the idle gear (4) with the reverse gear (3) on the main shaft (1) and the shift sleeve (9) slides axially relative to the hub (6) in a reverse gear (3) direction, the axial movement of the shift sleeve (9) disengages the strut (8) and the strut (8) is uncovered entirely.