FIELD OF THE INVENTION
The invention relates to an apparatus for measuring backlash in gears a differential assembly.
BACKGROUND OF THE INVENTION
Differential assembly transfers torque from engine to wheels whereby the differential assembly divides power between the wheels as per vehicle requirement and road condition. A propeller shaft connects the engine with the differential assembly. Differential assembly comprises a pinion gear intermeshed with a ring gear, and the propeller shaft is interconnected with the pinion gear. When the propeller shaft rotates, the pinion gear rotates causing the ring gear to transfer power through axle shaft to the wheels.
One of the parameters for efficient functioning of the differential assembly is ring and pinion gear backlash, which is basically space between meshing teeth of the pinion and ring gear. Accordingly, it is critical to measure the backlash of the gears at regular intervals to ascertain whether the differential can be corrected by mere adjustment or more extensive service is required.
However, for backlash measurement, the entire differential assembly is required to be removed from the vehicle which requires removal of tyres, axle shaft, differential oil and other associated components. Removal of the differential assembly is thus time consuming and tedious. Also, down time of the vehicle, especially during a routine check-up increases.

[005] In view of the above, there is a need for addressing at-least aforementioned problems while measuring backlash in gears of the differential assembly.
SUMMARY OF THE INVENTION
[006] In one aspect, the present invention provides an apparatus for measuring backlash in gears of a differential assembly, the apparatus comprising a test shaft extending form a first end to a second end, a test gear provided at the first end of the test shaft, and at the second end the test shaft rotatably interconnected with a pinion shaft having a pinion gear meshed with a ring gear of the differential assembly such that the test shaft and the test gear have the same rotary motion as the pinion shaft and the pinion gear; a bracket adaptable to a vehicle; and a measuring unit adapted to the bracket and configured to engage with the test gear for determining displacement of the test gear, and thereby measure the backlash between the pinion gear and the ring gear.
BRIEF DESCRIPTION OF THE DRAWINGS
[007] Reference will be made to embodiments of the invention, examples of which may be illustrated in accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.
Figure 1 shows an apparatus for measuring backlash in gears of a differential assembly in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION
[008] The present invention is directed towards an apparatus for measuring backlash in gears of a differential assembly of a vehicle. The apparatus is adaptable to the differential assembly for measuring backlash in gears without uninstalling or removing the differential assembly from the vehicle.
[009] Figure 1 shows an apparatus 100 for measuring backlash in gears of a differential assembly 150 in accordance with an embodiment of the invention. In an embodiment, the apparatus measures backlash of ring gear and pinion gear of the differential assembly. The apparatus comprises a test shaft 110, and a measuring unit 120. As shown, the test shaft is coupled with the differential assembly. The test shaft extends from a first end to a second end. At the first end the test shaft comprises of a test gear 112. At the second end, the test shaft has a mounting flange 114. The mounting flange enables the test shaft to be coupled with a flange of the differential assembly, and interconnect with a pinion shaft of the differential assembly. In this regard, propeller shaft connected with the differential assembly is first removed, and thereafter the test shaft is coupled with the differential assembly. Advantageously, no other components of the differential assembly or axle assembly are required to be removed for adapting the apparatus to the vehicle. In an embodiment, the test shaft is interconnected with the pinion shaft of the differential assembly, and the test shaft is manually rotatable causing the pinion shaft to rotate. The pinion shaft has a pinion gear meshed with a ring gear, and rotation of the test shaft causes the pinion gear .and the ring gear to

rotate. Accordingly, the test shaft and the test gear have the same rotary motion as the pinion shaft and the pinion gear. In this regard, any misalignment in the meshing of the pinion gear and the ring gear causes the pinion shaft and the test shaft to offset from its normal position causing the test gear to also misalign. Accordingly, any backlash in the pinion gear and ring gear is translated on the test gear of the test shaft which causes the test gear to displace. By measure such displacement of the test gear, backlash of the pinion gear the ring gear can be determined.
[010] Further, as shown in the figure, the measuring unit is configured to engage with the test gear for determining position of the test gear of the test shaft. As shown, the measuring unit is adapted to a bracket 130 via an arm assembly 140. In an embodiment, the mounting bracket is a magnetic mounting bracket. Accordingly, the bracket can simply be adapted to a metallic part of a vehicle. Thus, adapting the measuring unit to the vehicle is simple. In an embodiment of the invention, the measuring unit is a dial gauge. The dial indicator gauge comprises of an indicator and a plunger. The indicator can be digital or analog. The plunger is positioned to engage with the teeth of the test gear. As the test gear is rotated, the plunger is pressed towards the dial gauge, and distance indicated on the indicator is indicative of the displacement of the test gear, and thereby the backlash of the pinion gear the ring gear.
[011] The arm assembly comprises a first arm 142 and a second arm 144. The first arm is pivotally mounted on the bracket. The second arm, at one end is pivotally adapted to the first arm, and the measuring unit is mounted at other end

of the second arm. The arm assembly allows precise alignment of the measuring unit with respect to the pinion wheel.
[012] For every scheduled maintenance of the vehicle or to measure backlash of gears of the differential assembly, the vehicle is parked in an inspection pit. Once parked, it is first ensured that gear lever is in neutral condition after which parking brake of the vehicle is applied. Thereafter, propeller shaft is removed from differential flange of the differential assembly. The propeller shaft is supported by a belt. Upon removal of the propeller shaft, the apparatus of the present invention is installed, whereby the test shaft of the apparatus is coupled via mounting flange to the differential flange. The measuring unit is adapted to vehicle under body via the mounting bracket which is magnetically adapted to the vehicle under body. The measuring unit is aligned with the test gear, and the test shaft is rotated manually in forward and reverse directions, and displacement of the test gear is measured. The displacement measured by the measuring unit is indicative of the backlash of gears of the differential assembly.
[013] Advantageously, the present invention does not require removal of the differential assembly and associated components for measuring backlash of gears of the differential assembly. Accordingly, down-time of the vehicle is reduced, and thus the present inventions saves time and is also cost effective.
[014] While the present invention has been described with respect to certain embodiments, it will be apparent to those skilled in the art that various changes and modification may be made without departing from the scope of the invention as defined in the following claims.

WE CLAIM:
1. An apparatus (100) for measuring backlash in gears of a differential
assembly (150), the apparatus comprising:
a test shaft (110) extending form a first end to a second end, a test gear
(112) provided at the first end of the test shaft, and at the second end the
test shaft rotatably interconnected with a pinion shaft having a pinion gear
meshed with a ring gear of the differential assembly such that the test shaft
and the test gear have the same rotary motion as the pinion shaft and the
pinion gear;
a bracket (130) adaptable to a vehicle; and
a measuring unit (120) adapted to the bracket and configured to engage
with the test gear for determining displacement of the test gear, and
thereby measure the backlash between the pinion gear and the ring gear.
2. The apparatus as claimed in claim 1, wherein the bracket is a magnetic bracket.
3. The apparatus as claimed in claim 1, wherein the measuring unit is adapted to the mounting bracket via an arm assembly (140).
4. The apparatus as claimed in claim 3, wherein the arm assembly comprises of:
a first arm (142) pivotally adapted to the bracket;
a second arm (144) pivotally adapted to the first arm at one end and having
the measuring unit pivotally adapted at other end.

5. The apparatus as claimed in claim 1, wherein at the first end the test shaft has a mounting (114) flange adaptable to a flange of the differential assembly.
6. The apparatus as claimed in claim 1, wherein the test gear has teeth corresponding to teeth of the pinion gear.