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 For Measuring Frictional Force In Automotive Drive Line
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
Saurabh Kumar Singh
Prashant Vishe
Kapila Gopalakrishna
all 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 Method for measuring frictional force in automotive drive line

FIELD OF INVENTION
The present invention relates to the overall power train frictional force measurement for automotive vehicles and more particularly it relates to the method of measuring frictional force in automotive drive line.
BACKGROUND OF INVENTION
Generally, there are three types of variable forces tending to oppose the motion of the vehicle moving at a uniform speed on a surface with almost zero gradient. The three types of variable forces are Aerodynamic Drag, Tyre rolling resistance and Frictional forces developed in the vehicle driveline. The tractive effort at the wheels of vehicle must exactly balance the sum of all three types of variable forces which is tending to oppose the motion of the vehicle. Otherwise, if the said tractive effort is greater, the vehicle will accelerate and if it is smaller, it will decelerate until a balance is achieved. Usually, for all practical purposes the frictional torque produced in the drive train of a vehicle is neglected for simplification. The overall drive train frictional torque produced can be further subdivided into two components one of them being speed dependent and the other being speed independent. Here an attempt has been made to estimate this frictional torque value to enable it to be quantified for more realistic calculations and estimates thereof.
OBJECTS OF INVENTION
The main object of the present invention is to provide a method of measuring the frictional force in automotive drive line.
Yet another object of the present invention is to provide a method of measuring the frictional forces for power train which is simple and less time consuming procedure.


BRIEF DESCRIPTION OF INVENTION
The proposed method involves real time acquisition of torque and speed at the wheel end as well as at the propeller shaft when all the powered wheels are lifted (or jacked up) to avoid contact with the ground.
The complete drive line is warmed up by running it at different gears at varying speed for some time. Now the speed is increased up to maximum. Data acquisition system is provided for recording real time data with reference to wheel end torque and rpm. The Gear transmission is brought to neutral (Coasting mode) and the clutch pedal is completely released, so that the engine is disconnected. Data is recorded until the wheels come to a stand still or their speed reduces to a constant minimum.
The wheel end torque is converted to an equivalent force value and plot a graph of wheel end force (N) and the vehicle speed (kmph) is plotted.
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 flow diagram of the invention
Figure-02 shows the graph of force opposing the straight motion of the vehicle Vs. speed.
Now referring to figure -01 & 02, the method for measuring the frictional force in automotive drive line comprises; lifting the power wheel so that there is no contact between the wheel and ground; warming up the complete drive line for at least 15 minute by running it at different gears at varying speed; increasing the speed up to


maximum RPM; Starting the data acquisition system provided for recording real time data with reference to wheel end torque and rpm;
Bringing the Gear transmission to neutral (Coasting mode) and simultaneously releasing the clutch pedal completely so that the engine is disconnected;
Recording the data until the wheels come to a stand still or their speed reduces to a constant minimum;
Converting the wheel end torque to an equivalent force value and plotting a graph of wheel end force (N) and the vehicle speed (kmph).
Instruments used:
Wheel Force Transducer (WFT) is used for measuring wheel torque and speed. Data Acquisition System is provided for recording real time data with reference to wheel end torque and rpm, Binfeld Torque Telemetry System, Magnetic Pickup for Propeller Shaft RPM.
Vehicle Preparation:
Recommended tyre pressure Vehicle should be as per specification
Procedure:
The test is conducted inside a closed chamber with vehicle in a static condition to avoid any possible effect of aerodynamic drag.
Vehicle should be jacked up/lifted so that all the driven wheels are lifted off the ground and there is no contact between the tyres and the ground. This is done to ensure isolation of the wheels from the tyre rolling resistance effects.


Due to isolation from the atmospheric drag and tyre rolling resistance the only source of resisting torque left is the inherent frictional torque in the vehicle driveline.
Initial warm-up for the complete driveline is necessary before starting the measurements. Therefore, start the vehicle and run it in different gears at varying speeds for about 15 minutes.
Now start the test by increasing the speed upto the maximum rpm.
Start the data acquisition system. Data Acquisition system (DAS) should be able to record real time data with reference to wheel end torque and rpm
Bring the Gear transmission to neutral (Coasting mode) and release the clutch pedal completely so that the engine is disconnected. In the absence of driving engine torque (positive Te) (refer fig. 1) the torque available at the wheel end is only the resisting frictional torque (negative Tf) under which the rotating wheel experiences a gradual reduction in its speed from maximum to minimum rpm. Thus, the decrease in torque and speed with time is a function of overall drive train frictional losses.
Record the data until the wheels come to a stand still or their speed reduces to a constant minimum.
Convert the wheel end torque to an equivalent force value and plot a graph of wheel end force (N) and the vehicle speed (kmph).
Carry out curve fitting to fit the data according to the curve "Y = a + bx2"and estimate the values for the coefficients "a" and "b". Coefficient "a" represents the magnitude of constant frictional force (N) in the drive line whereas "b" represents speed dependent component of this driveline frictional force.
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