FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
PROVISIONAL SPECIFICATION
(See Section 10; rule 13)
TITLE OF THE INVENTION Method Of Measuring Frictional Force Of Individual Component In Steering
System
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
Jadhav Narayan D
Rajesh Powar
Gopalakrishna K.
An 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 particularly describes the invention.

FIELD OF INVENTION
This invention relates to a method for measuring frictional force in steering system and more particularly it relates to method of measuring frictional force contributed by individual component in a steering system.
BACKGROUND OF THE INVENTION
The steering system comprises; steering linkage, steering gear, and steering column and wheel. As the steering wheel is turned by the driver effort and multiplied by steering gear box, the steering linkage turns the wheels to control the vehicle's direction. During this process effort is required to overcome the internal friction in linkages of the steering system. Effort at steering wheel increases with friction in steering linkages, developing a steering system which will require minimum effort is achieved by studying and developing the effort loosed in component due to friction. The present method is used for measuring effort at each component.
BRIEF DESCRIPTION OF INVENTION
This innovative method for measuring friction uses instrumented steering wheel which consist torque meter fitted instead of steering wheel which measures effort applied by driver on steering wheel and also measures steering wheel turning angle. During trail the friction between the wheel and ground is kept zero friction which is achieved by turning pad in-between the wheels and road surface or The vehicle axle can be lifted from a ground to avoid the direct contact of tyre and road. The said instrumented wheel is rotated manually full RHS, then LHS turn with gradual and continuous force and back to straight ahead position of steering wheel, with number of Steps explained below in more details for measuring friction of individual component in the steering system.


In accordance with the present invention, method of measuring frictional force in
steering system comprises;
-Applying force at steering wheel manually from straight ahead position for one
complete cycle,
-Measuring the frictional force in total steering system,
-Disconnecting each component one by one and measuring the frictional force after
the disconnection,
-Calculating the frictional force for acquired data,
-Plotting the graph of angular displacement vs. frictional force to find out frictional
loss,
-Measuring the frictional force front the plotted graph,
-Plotting graph for all configurations after each component disconnected,
-Measuring the frictional force for each configuration for calculating frictional force
for each individual component,
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.
Figure-01 shows the schematic view of twin steer axle system. Figure-02 shows the angular displacement Vs. Frictional torque. Figure-03 shows the details of steering system Figure -04 shows the front RHS & LHS wheel system Figure-05 shows the second RHS & LHS wheel system
Now referring to figure-01, twin steer axle system comprises steering wheel (1) which is mounted on steering column (2). Said steering column (2) is connected to steering gear box (4) with the help of universal joint (3). The said gear box output is given to drag link (9) and relay rod (8) by drop arm (5). The connection of said drop arm (5) to


said drag link(9) is done by using drag link ball joint (6) and connection of said drop arm (5) to said relay rod(8) is done by using relay rod ball joint (7), the said drag link is connected to steering arm (12) with drag link ball joint (10) to steer the Front RHS wheel and to achieve steering of LHS wheel the tie rod (14) is used to connect RHS steering arm (12) to LHS steering arm (16) with help of tie rod ball joint(13 & 15) for steering the spindle (17). In same manner the Rear axle wheels are steered which is connected to drop arm (5) with relay rod (8) the connection is done by relay rod ball joint (7). The effort is transmitted to relay arm (21) connected using ball joint (18) relay arm is also assisted with power cylinder (22) with ball joint (20), said power cylinder is mounted with help of ball joint (23) on chassis. Second drag link (24) is connected to Relay arm (21) with drag link ball joint (19) and other end is connected to steering arm (26) with drag link ball joint (25) for achieving the steering of rear RHS wheel and to achieve steering of Rear LHS wheel the tie rod (28) is used to connect RHS steering arm (26) to LHS steering arm (30) with help of tie rod ball joint (27 & 29) for steering the spindle (31) connected with Rear LHS wheel.
Preparation of the vehicle
The vehicle shall conform in all its parts, components and systems to the design and/or production series as applicable.
The vehicle is fitted with instrumented steering wheel which gives torque value with respect to steering wheel angle.
All the ball joints of steering linkages and wheel joints is well lubricated as
recommended by the manufacturer.
The vehicle is un-laden to the weight specified by the manufacturer and the load
distribution between the axles should be as recommended by the manufacturer.
The vehicle is fitted with tyres which have not covered more than 10 percent of its
expected life. Tread depth measurement can be used to assess the tyre life. The tyres


shall be inflated in the cold condition to the pressures specified by the vehicle manufacturer.
If the vehicle is fitted with power assisted steering, the pressure setting of the assistance shall be as per the recommendations of the vehicle manufacturer.
The steering geometry shall be within the limits specified by the manufacturer.
TEST CONDITIONS
The fitment and operation of all instruments shall be such as not to hamper the freedom of the driver to have proper control of the vehicle at all the times.
The pad is provided under the steered wheels is friction less and free to steer full lock angle of vehicle.
Proper working of steering effort instrumented steering wheel and data acquisition system is ensured by checking it.
Front wheels for straight ahead position is checked and straight ahead on steering wheel is marked.
Steering wheel diameter is measured for calculation.
Method of measurement.
In accordance with the present invention, method of measuring frictional force in
steering system comprises;
-Applying force at steering wheel manually from straight ahead position for one
complete cycle
-Measuring the frictional force in total steering system,


-Disconnecting each component one by one and measuring the frictional force after
the disconnection,
-Calculating the frictional force for acquired data,
-Plotting the graph of angular displacement vs. frictional force to find out frictional
loss,
-Measuring the frictional force front the plotted graph,
-Plotting graph for all configurations after each component disconnected,
-Measuring the frictional force for each configuration for calculating frictional force
for each individual component
Force is applied at Steering effort wheel used in place of steering wheel (1) by hand from straight ahead position to right full lock angle, then from right full lock to left full lock and again to straight ahead position. This completes one cycle.
The effort during above operation , as indicated by the predetermined number of turns of the steering wheel or steering angle, is recorded in the data acquisition system for calculation.
The force applied must be minimum, gradual and continuous which causes just motion. During self centering effect do not apply force. Let wheel move on its own and as the effect finishes again apply force to complete the cycle.
Repeat the procedure for 3-4 times, steering movement shall be made starting from the right and one from left full turn.
The steering effort shall be calculated from steering torque by dividing it by the steering wheel radius.
The above sequence for test should be followed for the all configuration, given in table 1.


ine steering ettort will be getting reduced as we disconnect parts from steering arm (30) to steering column (2) in steering system.
Acquire the data for displacement and force.
Similarly acquire the data for different combination. Repeat the above steps of test for the details given in Table 1
TABLE 1
Test sequence : -

Step Acquire data for displacement and force on time bases for following configuration in Single steer axle system. Effort in kg
1 Measure friction in total Steering system. Fi
2 Disconnect Front LHS Wheel (17) from tie rod (14) at LHS ball joint (15) in above setup stepl and measure friction in system. F2
3 Disconnect Tie rod (14) at RHS ball joint (13) in above setup step. 2 and measure friction in system. F3
4 Disconnect RHS wheel (11) from drag link (9) from ball joint (10) in above step no. 3 and measure friction in system. F4
5 Disconnect drag link (9) from front ball joint (6) drop arm in above Step No. 4 and measure friction in system. F5
6 Disconnect Gear box (4) from universal joint (3) in above setup step No.5 and measure friction in Column and steering wheel. F6


Similar table can be made for Twin steer axle to measure friction for each individual component in power off condition.

Step Acquire data for displacement and force on time bases for following configuration in Double steer axle system. Effortinkg
1 Measure friction in total Steering system. Fi
2 Disconnect Rear LHS Wheel (31) from tie rod (28) LHS ball joint (29) in above setup stepl and measure friction in system. F2
3 Disconnect Tie rod (28) at RHS ball joint (27) in above setup step. 2 and measure friction in system. F3
4 Disconnect RHS wheel from second drag link (24) from ball joint (25) in above step no. 3 and measure friction in system. F4
5 Disconnect drag link (24) from front ball joint (19) drop arm in above Step No. 4 and measure friction in system. F5
6 Disconnect Power cylinder (22) from ball joint (20) in above setup step No. 5 and measure friction. F6
7 Disconnect relay arm (21) from relay rod (8) from ball joint (18) in above step no. 6 and measure friction in system. F7
8 Disconnect relay rod (8) from ball joint (7) in above step no. 7 and measure friction in system in front steering system F8
9 Disconnect Front LHS Wheel (17) from tie rod (14) LHS ball joint (15) in above setup step 8 and measure friction in system. F9
10 Disconnect Tie rod (14) at RHS ball joint (13) in above setup step. 10 and measure friction in system. Fio
11 Disconnect RHS wheel (11) from drag link (9) from ball joint (10) in above step no. 11 and measure friction in system. Fn
12 Disconnect drag link (9) from front ball joint (6) drop arm in above Step No. 12 and measure friction in system. F12
13 Disconnect Gear box (4) from universal joint (3) in above setup step No. 13 and measure friction in Column and steering wheel. F,3


Friction torque is calculated for data Acquired by using formulae
F= (Torque at the wheel in Nm / 9.81) / Steering wheel radius in meter.
graph is plotted for angular displacement vs. Frictional torque. The said graph gives the hysteresis Losses as shown figure-02 (graph)
Frictional force is measured from the graph plotted ,for example the frictional force in the graph is 13.2 Nm for total steering system i.e. Fl.
Graph is plotted for all configurations with reference table 1 and friction force of individual component is calculated with help of table given below for front steer wheel:

Sr.No Frication at the Component Friction Friction in Kg
1. Total System =F1
2. LHS wheel =F1-F2
3. Tie Rod ball joints =F2-F3
4. RHS wheel =F3-F4
5. Drag link with ball joint =F4-F5
6. The gear box. =F5-F6
7. Steering wheel column. =F6
Similarly plot the graph for the entire configuration with reference table 2 and frication is calculated of individual component with help of table given below for Twin steer axle:
Sr.No Frication at the Component Friction Friction in Kg
1. Total System =F1
2. Rear LHS wheel =F1-F2
3. Rear Tie Rod ball joints =F2-F3
4. Rear RHS wheel =F3-F4

5. Rear Drag link with ball joint =F4-F5
6. Power cylinder assembly. (22,20) =F5-F6
7. Relay arm (21) =F6-F7
8. Relay Rod and ball joints =F7-F8
9. LHS wheel =F8-F9
10. Tie Rod ball joints =F9-F10
11. RHS wheel =F10-Fll
12. Drag link with ball joint =F11-F12
13. The gear box. =F12-F13
14. Steering wheel column. =F13
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.
Dated this 31ST day of March 2008