FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION (See Section 10; rule 13)
TITLE OF THE INVENTION
Testing Apparatus And Method For Simulating Gear Sltuck Phenomenon Observed In A Vehicle Transmission


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
INVENTOR
Mr. Patel Hiralkumar Ghanshyambhai
An Indian National
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 particularly describes the invention and the manner
in which it is to be performed


FIELD OF INVENTION
The present invention relates to gear stuck incidences in transmission systems of a vehicle. The present invention more particularly relates to a testing apparatus and method for simulating gear stuck phenomenon observed in a vehicle transmission.
BACKGROUND OF INVENTION
Various automotive vehicles such as road vehicles, off road vehicles, and the like, utilize a transmission for driving and increasing the speed ratios of the vehicles. Such transmissions are controlled by a manual gearshift mechanism in order to select various transmission speeds of the vehicle. The operator manually shifts gears in the transmissions between different speed ratios by sliding the gear shift lever and the shifter sleeve. While torque is transmitted, then a high torque load is enforced on the gear shift lever resisting any such movement. The clutch interrupts or breaks the torque transmission such that the operator is able to move the gear shift lever relative to each other. Thus, the driver actuates the clutch and moves the gears to a neutral position.
Moreover, the vehicles with manual gearshift mechanism generally have a "Gear stuck" problem in the transmissions, which is the common warranty complaint observed in the automotive transmissions. This gear stuck phenomenon is observed when gear shifting is done on the transmission with high pullout force while braking. After dismantling the transmission with gear stuck complaint, it may be found that the shifter sleeve is engaged in the transmission gear, but the selector shifter shaft finger and the gear shift lever are in Neutral position.
Such failures in the transmissions are observed because of inaccurate tolerance specification on drawings, production variations, inaccurate tolerance stacking during development stage and non-optimized stiffness of selector and/or shifter shaft detent spring. This gear stuck phenomenon can be detected only on vehicle,

especially when driving the vehicle and occur on specific gearshift pattern. In present scenario, the demand on higher production rate requires the industries to deliver robust product.to save warranty cost and build goodwill for Original Equipment Manufacturer (OEM).
With reference to the conventional methods, none of the prior arts can manage to overcome such gear stuck failures in the vehicle transmission. In order to address the above specified complexity and constraints in the vehicle transmission, it is necessary to provide a quick and fairly accurate method for checking prototype and production transmission in terms of probability of gear stuck occurrence. Such method should also ensure optimization of tolerances and stiffness of selector or shifter detent spring during development stage and production variation in specified range of performance values. Hence, it is essential to provide a testing apparatus and method for simulating gear stuck phenomenon observed in a vehicle transmission.
OBJECTS OF INVENTION
An object of the present invention is to provide a testing apparatus for simulating gear stuck phenomenon observed in a vehicle transmission, which facilitates faster optimization of selector or shifter shaft detent spring stiffness and dimensional tolerance of internal gearshift mechanism of the transmission.
Another object of the present invention is to provide a testing apparatus for simulating gear stuck phenomenon observed in a vehicle transmission, which ensures stacked tolerances of transmission's internal gearshift mechanism components within specified range and increases transmission production rate.
Yet another object of the present invention is to provide a testing apparatus for simulating gear stuck phenomenon observed in a vehicle transmission, which is easy to handle.

Yet another object of the present invention is to provide a testing method for simulating gear stuck phenomenon observed in a vehicle transmission, which requires less time for testing various automotive transmissions.
SUMMARY OF INVENTION
According to one aspect, the present invention, which achieves the objectives, relates to a testing apparatus for simulating gear stuck phenomenon observed in a vehicle transmission comprising a base frame fixed to ground. A spin stand is mounted on the base frame for supporting a transmission under test as per vehicle installation roll and pitch angle. A vertical member is mounted on the base frame and welded with a coupling flange to restrict rotation of an output shaft of the transmission. A bearing assembly is press fitted in the spin stand for holding an input shaft of the transmission. The bearing assembly is connected to a lever with hook for hanging dead weight in order to generate breaking torque at the input shaft. Hence, it facilitates faster optimization of selector or shifter shaft detent spring stiffness and dimensional tolerance of the transmission to avoid gear stuck.
According to another aspect, the present invention, which achieves the objectives, relates to a testing method for simulating gear stuck phenomenon observed in a vehicle transmission involving: mounting a transmission under test on a spin stand as per vehicle installation roll and pitch angle and filling the transmission with transmission oil. The coupling flange welded to the vertical member is connected to an output shaft of the transmission to restrict rotation of the output shaft while testing. The transmission is engaged in any of the gears after placing the dead weight at one meter height from the ground. Finally, the transmission is disengaged from the gear by applying high pull out force and the above steps are repeated for other gears. If the gear stuck is observed during this testing, then spring stiffness and dimensional tolerance of the transmission can be adjusted to avoid gear stuck phenomenon.

BRIEF DESCRIPTION OF DRAWINGS
The invention will be discussed in greater detail with reference to the accompanying Figures.
FIG. 1 shows a block diagram of a testing apparatus for simulating gear stuck phenomenon observed in a vehicle transmission, in accordance with an exemplary embodiment of the present invention;
FIG. 2 illustrates a cross-sectional front view of the testing apparatus for simulating gear stuck phenomenon observed in the vehicle transmission, in accordance with an exemplary embodiment of the present invention; and
FIG. 3 illustrates a side view of the testing apparatus for simulating gear stuck phenomenon observed in the vehicle transmission, in accordance with an exemplary embodiment of the present invention.
DETAILED DESCRIPTION OF INVENTION
Referring to FIG. 1, a block diagram of a testing apparatus for simulating gear stuck phenomenon observed in a vehicle transmission (4) is illustrated, in accordance with an exemplary embodiment of the present invention. The testing apparatus can be adapted for testing prototype and production lot automotive transmission (4) with mechanical gearshift mechanism. The testing apparatus comprises a rigid base frame (1) that is fixed to ground for supporting components of the testing apparatus. A spin stand (2) is adapted for mounting the vehicle transmission (4) under test.
In addition, input end of the transmission (4) on the spin stand (2) is coupled to a torque-generating device (100) whereas output end of the transmission (4) is connected to a limiting device (200) to restrict the rotation of a transmission output shaft (6) as shown in FIG. 2. The limiting device (200) can be supported by a vertical

member (3), which is mounted on the base frame (1). The torque-generating device (100) can generate torque at the input of the transmission (4), which facilitates accurate simulation of gear stuck phenomenon observed in the transmission.
Referring to FIG. 2, a cross-sectional front view of the testing apparatus for simulating gear stuck phenomenon observed in the vehicle transmission (4) is illustrated, in accordance with an exemplary embodiment of the present invention. Note that the same reference numbers are assigned to identical components in FIGS. 1-3. The spin stand (2) is mounted on the base frame (1) for supporting the transmission (4) under test as per vehicle installation roll and pitch angle. The transmission (4) is usually provided with an input shaft (8) and an output shaft (6). The vertical member (3) is supported by the base frame (1) and welded with a coupling flange (5).
The coupling flange (5) is coupled to the output shaft (6) of the transmission (4) in order to restrict rotation of the output shaft (6) of the transmission (4). A bearing assembly (7) is press fitted in the spin stand (2) for holding the input shaft or clutch shaft (8) of the transmission (4) at its one end. Another end of the bearing assembly (7) is connected to a lever (9), as shown in FIG. 3. The lever (9) is mounted perpendicular to the axis of the input shaft (8) of the transmission (4). The lever (9) is preferably 1 meter long and has suitable attachment, but not limited to hook (10), that is used to hang dead weight (11).
Moreover, the dead weight (11) hanging in the lever hook (10) can generate breaking torque at the input shaft (8) of the transmission (4) through the bearing assembly (7). The dead weight (11) should be sufficient to generate transmission input torque of 15 - 30 % of maximum torque developed by the vehicle engine. Thus, the gear stuck phenomenon observed on the automotive transmission (4) with mechanical gearshift mechanism can be simulated and corrected by rapidly optimizing selector or shifter shaft detent spring stiffness and dimensional tolerance of the transmission (4) in order to deliver robust product. Such testing arrangement being very small and

simple set up can be manufactured at low cost and transported to any other location easily.
Referring to FIG. 3, a side view of the testing apparatus for simulating gear stuck phenomenon observed in the vehicle transmission (4) is illustrated, in accordance with an exemplary embodiment of the present invention. While preparing of test setup, the rigid frame (1) is fixed to the ground using suitable means. The spin stand (2) is mounted on the rigid frame (1) by fastening means. After ensuring the preparation of the test transmission (4) as per material and assembling sequence, the test transmission (4) can be mounted on the spin stand (2). Then, the test transmission (4) is filled with appropriate type and quantity of transmission oil.
Thereafter, the vertical member (3) is mounted on the frame (1). The coupling flange
(5) welded to the vertical member (3) is connected and/or coupled to the output shaft
(6) of the transmission (4) to prevent the rotation of output shaft (6) while testing. The dead weight (11) is approximately positioned at one meter height from the ground and the test transmission (4) is engaged in lsl gear. Then, the transmission (4) is disengaged from the 1st gear by sudden application of high pull out force, approximately 3-4 times average pull out force recorded on the vehicle by hand. The pull out force is force to remove gearshift lever from any gear to the neutral position.
Again, the dead weight (11) is approximately positioned at one meter height from ground. The test transmission (4) is engaged in the 1st gear and try to disengage with high pull out force- Repeat this process about 25 times to make a mean value of tolerance. The above described procedure should be repeated while engaging the test transmission (4) in 3rd and 5th gear. If the gear stuck is observed during this testing, then the selector shifter shaft detent spring stiffness, production process and/or quality improvements should be taken care. In order to avoid gear stuck phenomenon on transmission production process, spring stiffness, tolerance control should be

increased or decreased by tightening tolerance or by shifting mean value of tolerance to keep tolerance band same or process control to achieve design specified tolerance.
Such testing is done quicker due to the very simple set up and testing procedure and thereby saves time, which is essential for reducing production cycle time. The testing process also provides fairly accurate results and requires no special testing skills and/or high investment, thus effectively reducing overhead cost for the product. The detection of gear stuck problem during transmission production, i.e. before fitment on the vehicle, can help reduce warranty cost faced by OEM. The testing apparatus is made common for wide range of automotive transmission with mechanical gearshift mechanism without any change.
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 in, so far as they come within the scope of the invention as claimed or the equivalents thereof.

WE CLAIM
1. A testing apparatus for simulating gear stuck phenomenon observed in a
vehicle transmission, comprising:
a base frame fixed to ground;
a spin stand mounted on said base frame for supporting a transmission under test as per vehicle installation roll and pitch angle;
a vertical member mounted on said base frame and welded with a coupling flange to restrict rotation of an output shaft of said transmission; and
a bearing assembly press fitted in said spin stand for holding an input shaft of said transmission, wherein said bearing assembly is connected to a lever with hook for hanging dead weight in order to generate breaking torque at said input shaft of the said transmission.
2. The testing apparatus as claimed in claim 1, wherein said lever is mounted perpendicular to axis of said input shaft of the said transmission.
3. The testing apparatus as claimed in claim 1, wherein said dead weight attached to said lever generates transmission input torque of 15 to 30% of maximum torque produced by a vehicle engine.
4. A testing method for simulating gear stuck phenomenon observed in a vehicle transmission, comprising:
mounting a transmission under test on a spin stand as per vehicle installation roll and pitch angle and filling said transmission with transmission oil;
press fitting a bearing assembly in said spin stand to hold input shaft of said transmission;
connecting a lever to said bearing assembly;
hanging a dead weight at the other end of said lever;
connecting a coupling flange welded to a vertical member, to an output shaft of said transmission to restrict rotation of said output shaft while testing;

engaging said transmission in any of the gears after placing dead weight at one meter height from the ground; and
disengaging said transmission from the gear by applying high pull out force and repeating the above steps for other gears.

5. The method as claimed in claim 4, wherein said dead weight generates breaking torque at an input shaft of said transmission, about 15 to 30% of maximum torque produced by a vehicle engine.
6. The method as claimed in claim 4, wherein said spin stand and said vertical member are mounted on a base frame.
7. The method as claimed in claim 4, wherein the high pull out force is force to remove a gearshift lever from any gear to a neutral position.