FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See Section 10; rule 13)
TITLE OF THE INVENTION
Method of Testing Durability of Power Train Aggregates and 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
Santosh Gosavi, Girish Chavan, both 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 Complete specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF INVENTION
This invention relates to testing of automotive components and more particularly to a method of testing powertrain durability.
BACKGROUND OF INVENTION
Power train durability testing has always been a challenge in view of its complexity and dependability on various external parameters like driving style road traffic conditions, loading conditions and internal parameters like speed torque fluctuations during various events like gear shifting and coasting.
Testing the vehicle in field is both costly and time consuming. In conventional methods used for testing power train aggregates on a rig, the engine design torque is used to calculate torque on various powertrain components using reduction gear ratios. The components are then tested continuously for this torque value. The present method does not consider the fluctuations in toque which are observed in field and often results in over-designing of components.
KR20030044151 discloses a method for endurance testing of powertrain of a vehicle. In this method information of road is extracted as a 3-D data using Global Positioning System (GPS) and a virtual road is created. The vehicle is run on the virtual road so as to extract grade resistance and traveling resistance in the field is calculated using the grade resistance. Torque on driven shaft is extracted from traveling resistance and this torque data is used to calculate equivalent lifespan of a vehicle. As torque data is found out from simulation, it is based on certain approximations and is less accurate than the data obtained from an instrumented vehicle tested in field.
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OBJECTS OF THIS INVENTION
The main object of this invention is to provide a method for durability testing of powertrains, which will be able to give more realistic testing conditions like field.
Another object of this invention is to provide a method for testing of powertrain durability in least time.
Yet another object of this invention is to provide a method for testing of powertrain durability, the results of which can be used to optimize design of powertrain components.
Yet another object of this invention is to provide a method for testing of powertrain durability which is simple and cost effective.
STATEMENT OF INVENTION
Method of testing durability of power train aggregates and system comprises of following steps:
a) Identifying customer usage profile and operating duty cycle of a vehicle;
b) Instrumentation of vehicle power train for measuring various parameters;
c) Acquiring road torque data by driving instrumented vehicle as per defined customer usage profile;
d) Removing the anomalies and unwanted signals from the acquired raw data;
e) Filtering the data to remove high frequency signals;
f) Determining the gear usage distribution;
g) Removing spikes generated during clutch disengagement period;
h) Determining the engine torque form measured gearbox output torque;
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i) Determining the distance traveled by vehicle;
j) Formulating 3-D matrix of Engine Torque Vs Angular Speed of engine Vs
Distance traveled by vehicle;
k) Reducing the 3-D matrix to a 2-D matrix of Torque Vs Number of revolutions;
1) Analyzing the data to determine the gear shifting pattern;
m) Finding the dominant values of input torque, engine rpm and gear position;
n) Defining test cycles for power train aggregates and system.
Method of testing durability of power train aggregates and system wherein non-damaging torque values and associated distance are determined and then removed from the said 3-D matrix and using the reduced matrix accelerated test cycles for power train aggregates and system are defined.
Method of testing durability of powertrain aggregates and system wherein vehicle powertrain is instrumented to measure torque, speed and temperature at various locations, torque and angular speed is measured at the rear drive shaft, propeller shaft and front drive shaft using strain gauges and radio frequency (RF) telemetry system, engine rpm is measured at the flywheel and oil temperatures are measured at engine & gearbox and rear axle differential.
Method of testing durability of powertrain aggregates and system wherein the said data is analyzed by Markov or From-To analysis.
Method of testing durability of powertrain aggregates and system as mentioned in step (m) wherein dominant values are obtained by plotting the distribution of torque, rpm and gear position against time respectively.
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BRIEF DESCRIPTION OF INVENTION
Method of testing durability of powertrain aggregates and system in accordance with this invention consists of measurement of various external parameters like driving style, road traffic conditions, loading conditions and internal parameters like speed and torque fluctuations and shock loads during various events like gear up/down shift and coasting in actual service usage. This is called as Road Torque Data Collection (RTDC). RTDC involves the vehicle instrumentation for measurement of critical Powertrain parameters like torque, speed and temperature at various locations along the driveline. Once the Road Torque Data (RTD) is collected different analysis tools are being used to draw on engineering results and conclusions out of the raw data. This helps in understanding the working environment of the complete powertrain as a system as well as aggregates. This further helps in deriving the accelerated life test schedules for powertrain system and its aggregates.
BRIEF DESCRIPTION OF DRAWINGS
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 1 shows typical instrumentation for powertrain road torque data collection. Figure 2 shows process flowchart of powertrain durability testing Figure 3 shows a 3-D plot of Engine Torque (Nm) Vs Engine rpm Vs Distance traveled by vehicle.
Figure 4 shows a 2-D matrix of Engine torque (Nm) Vs Number of revolutions. Figure 5 shows Gearshift Matrix using Markov Analysis
Figures 6.1, 6.2 and 6.3 respectively show the distribution of torque, rpm and gear position against time. Figure 7 shows sample test specifications for powertrain durability testing.
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DETAILED DESCRIPTION OF INVENTION
Method of testing powertrain durability consists of following major steps -
1. Identification of customer usage profile and operating duty cycle of the given vehicle through market survey and quality function deployment process.
2. Vehicle Powertrain is instrumented as shown in Figure 1 to measure torque, speed and temperature at various locations. Torque and angular speed is measured at the rear drive shaft (1), propeller shaft (3) and front drive shaft (9) using strain gauges and RF Telemetry system. Engine rpm is measured at the flywheel (8). Oil temperatures are measured at engine & gearbox (7) and rear axle differential (2).
3. Instrumented vehicle is driven on service roads as per the defined customer usage profile and road torque data is acquired.
4. The acquired data is then processed through following steps of analysis to develop the test schedules for aggregate level rig testing, system level and vehicle level testing. The flowchart of the process is as shown in Figure 2.
a. Anomaly Correction - Usually the acquired raw data is infected with unwanted
signals and anomalies like noise, spikes and drifts. These anomalies are then
removed out of the raw data using appropriate known tools.
b. Frequency Analysis and Filtering - The clean raw data is then processed to
determine the frequency spectrum and bandwidth of the various signals. For
durability testing usually the low frequency and high amplitude signals are
more vital and accordingly high frequency signal are filtered out of the data.
c. Gear Detection and Decomposition - Gear against time file is generated by
calculating the gear ratio by dividing the engine speed by gearbox output speed.
d. Gear File Smoothing - The computed gear file contains spikes for the clutch
disengaged period. Gear file smoothing function removes these spikes using
clutch settling time.
e. Determining Engine Torque - Road torque data measures the torque on drive
or propeller shafts at the output of the gearbox. The engine torque is calculated
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by dividing the measured gearbox output torque with the gear ratios considering specific transmission efficiency.
f. Determining Distance Traveled - The distance traveled by the vehicle is
calculated either using global positioning system parameters or from measured
wheel speed and wheel dynamic radius.
g. Joint Probability Distribution - For the durability testing of Powertrain
aggregates the torque, rpm and distance traveled are important. Using Joint
Probability Distribution function the 3-D matrix of Torque Vs Angular Speed
Vs Distance is prepared as shown in the Figure 3. This matrix elaborates the
relationship between torque level and angular speed.
h. Rotating Rainflow Counting - The 3-D matrix of Torque Vs Angular Speed Vs Distance is further reduced into 2-D matrix of Torque Vs Number of revolutions as shown in the Figure 4.
i. Markov Analysis - The computed gear file is analyzed to map the gearshift matrix using Markov or From-To analysis as shown in Figure 5. This gear shift matrix elaborates the shifting pattern and the number of shifts for the determined distance and types of roads.
j. Time at Level Analysis - This tool is used to plot the distribution of torque, rpm and gear position against time as shown in figure 6.1 6.2 and 6.3 respectively. The output of this analysis indicates the dominant levels of torque, rpm and gear positions.
5. Accelerated Life Test Cycle Development: The damage for each gear is calculated using the DIN (Deutsches Institut fur Normung i.e. the German Institute of Standardization) gear life calculation method for all the combinations of torque and rpm obtained out of joint probability analysis. The non-damaging torque values and associated distance are removed out of the 3-D matrix of Torque Vs Angular Speed Vs Distance. With this reduced matrix the test schedule of block loading program for powertrain aggregate and system is prepared. A sample test schedule is as shown in
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Figure 7. It shows step loading program for gearbox testing on the test rig. It consists of various torque levels and associated testing time derived out of the above reduced 3-D matrix.
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
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WE CLAIM
1. Method of testing durability of powertrain aggregates and system comprising of
following steps:
a) Identifying customer usage profile and operating duty cycle of a vehicle;
b) Instrumentation of vehicle powertrain for measuring various parameters;
c) Acquiring road torque data by driving instrumented vehicle as per defined customer usage profile;
d) Removing the anomalies and unwanted signals from the acquired raw data;
e) Filtering the data to remove high frequency signals;
f) Determining the gear usage distribution;
g) Removing spikes generated during clutch disengagement period;
h) Determining the engine torque from measured gearbox output torque;
i) Determining the distance traveled by vehicle;
j) Formulating 3-D matrix of Engine Torque Vs Angular Speed of engine Vs
Distance traveled by vehicle; k) Reducing the 3-D matrix to a 2-D matrix of Torque Vs Number of revolutions; 1) Analyzing the data to determine the gear shifting pattern; m) Finding the dominant values of input torque, engine rpm and gear position; n) Defining test cycles for powertrain aggregates and system.
2. Method of testing durability of powertrain aggregates and system as claimed in claim 1 wherein non-damaging torque values and associated distances are determined and then removed from the said 3-D matrix and the reduced matrix is used to define accelerated test cycles for powertrain aggregates and system.
3. Method of testing durability of powertrain aggregates and system as claimed in claims 1 and 2 wherein vehicle powertrain is instrumented to measure torque, speed and temperature, torque and angular speed is measured at the rear drive shaft, propeller shaft and front drive shaft, engine rpm is measured at the flywheel, and oil temperatures are measured at engine and gearbox and rear axle differential.
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4. Method of testing durability of powertrain aggregates and system as claimed in claim 1(1) wherein the said data is analyzed by Markov or From-To analysis.
5. Method of testing durability of powertrain aggregates and system as claimed in claims l(m) wherein dominant values are obtained by plotting the distribution of torque, rpm and gear position against time.
6. Method of testing durability of powertrain aggregates and system substantially as
herein described with reference to accompanying drawings.

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