FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
PROVISIONAL SPECIFICATION
(See Section 10; rule 13)
TITLE OF THE INVENTION Improved Differential Assembly
APPLICANTS
TATA MOTORS LIMITED, an Indian company
having its registered office at Bombay House,
24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001 Maharashtra, India
INVENTORS
Mr .Anand Swichalappa Damami, Mr.Amit Suhas Barve & Mr. Prafulla Vijay Wankhede
All Indian Nationals
of TATA MOTORS LIMITED,
an Indian company having its registered office
at Bombay House, 24 Homi Mody Street, Hutatma Chowk,
Mumbai 400 001 Maharashtra, India
PREAMBLE TO THE DESCRIPTION
The following specification describes the invention


FIELD OF INVENTION
This invention relates to differential assernbly of automobile and more particularly it relates to open type differential assembly with ease of manufacturing, reduced part count & provision of fixing of speed detect gear on differential.
BACKGROUND OF INVENTION
Differential is very much essential in all automobile on live axles which helps to maintain speed deferential between left & right side axle during cornering of the vehicle. Also it helps in torque multiplication because of final drive gear fixed on differential housing.
Figure 1 shows conventional differential assembly which consists of closed type differential housing (a), Final drive gear (b), bevel gear (c), bevel pinion (d), spider with two circlips (e) & speed detect gear (f). Wherein said bevel gear (c) and bevel pinion (d) are provided inside differential housing, said bevel pinion is located with spider with circlip (e). Said final drive gear (b) is bolted and speed detect gear (f) is press fitted on differential housing.
The conventional closed type differential housing requires special tooling & machining operations during manufacturing which are costly.
The conventional differential design uses final drive gear which is annular in shape & has transition fit on housing. To fix the final drive gear on differential housing requires indexing of bolt holes & requires more time.
Also it uses more No of parts to retain spider inside the differential. Considering the size of the circlips, assembly of circlips is time consuming.
The conventional speed detect gear is forged or machined toothed wheel which is to be press fitted on differential. This tooth wheel carries more material, & requires special equipments for assembly.


OBJECTS OF INVENTION
The main object of this invention is to provide improved differential design which calls for simple manufacturing process.
Another object of this invention is to provide improved differential assembly with reduced number of parts.
Yet another object of this invention is to provide improved differential assembly with speed detect gear which is simple in construction & cost effective.
BRIEF DESCRIPTION OF INVENTION
Improved differential assembly in accordance with this invention basically comprises of open type differential housing, final drive gear with support for bevel gears, spider with a provision for spring dowel, speed detect gear, bevel gears and bevel pinions . Wherein said final drive gear is precisely located inside said differential housing, said bevel gear and pinions are located with spider and spring dowel. Said speed detect gear is press fitted on said differential housing.
As the said differential housing is of open type, it is easy to manufacture the same. As differential housing and final drive gear are precision fitted the special equipments are not required to fit the said units. Said speed detect gear is made up of sheet metal which contributes drastically in weight reduction and makes the manufacturing process simple. Said speed detect gear can be easily fitted on said differential by simple readily available equipments.
BRIEF DESCRIPTION OF DRAWINGS
Fig. 1 shows Conventional differential assembly
Fig.2 shows improved differential assembly in accordance with this invention
Fig.3 shows Open type differential housing used in this invention


Fig.4 shows Final Drive gear used in this invention Fig.5 shows Spider used in this invention Fig-6 shows Speed detect gear
DETAILED DESCRIPTION OF INVENTION
Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment of the invention only, and not for the purpose of limiting the same,
Referring to figs. 2 to 6
Improved differential assembly in accordance with this invention basically comprises of open type differential housing (1), final drive gear with support for bevel gear (2), spider with a provision for spring dowel (5), speed detect gear (6), bevel gears (3) and bevel pinions (4) . Wherein said final drive gear is precisely located inside said differential housing (1), said bevel gear and pinions are located with spider and spring dowel (5). Said speed detect gear is push fitted on said differential housing.
As shown in the figure (3), Said open type differential housing comprises of spigot bore (7) which is larger than close type differential housing. The bore size is selected such a way that it makes manufacturing easy & helps in precision location fit of final drive gear. The speed detect gear holding diameter (8) is achieved such a way it suits push fit of speed detect gear.
As shown in the figure (4), said final drive gear with support for bevel gear comprises of cylindrical spigot (9) which supports bevel gear inside differential housing & maintains the symmetry of differential about spider axis. The outer diameter of spigot (10) is selected such a way that it maintains precision location fit with differential housing.
As shown in the figure (5), said spider has a cross hole (11) to carry spring dowel which arrest spider inside differential.


As shown in the figure (6), said speed detect gear is made up of 1.25 mm thick sheet metal which carries bend lugs (12) to suit electronic speed sensor unit. The bore diameter (13) is designed such a way to achieve push fit
"Open type differential housing". The major advantage of this is more accessibility to internal surfaces of the housing which makes it easy to manufacture." Final Drive gear "is designed such a way that it supports the bevel gear & maintains the symmetry about spider shaft." Final drive gear" has precision location fit with differential housing which eliminates special equipments like press to assemble final drive gear on differential & is easy to index. This design calls for "spring Dowel" to locate spider which eliminates two circlips. This reduces part count, complexity in assembly of two circlips & extra length of spider to hold circlips. "Sheet metal speed detect gear" is designed with specific tolerances & material that it can directly be press fitted on differential housing with hand tools. This replaces forged/machined slotted wheel which has higher cost. Also It eliminates the special equipments like hydraulic press to assemble forged / machined wheel on differential housing.
The foregoing description is a specific embodiment of the present invention. It should be appreciated that this embodiment is described for purpose of illustration only, and that numerous alterations and modifications may be practiced by those skilled in the art without departing from the spirit and scope of the invention. It is intended that all such modifications and alterations be included insofar as they come within the scope of the invention as claimed or the equivalents thereof.