FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
THE PATENTS RULES, 2003


COMPLETE SPECIFICATION
(See Section 10; rule 13)
TITLE OF THE INVENTION A Device For Testing Durability Of High Tension Cables
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
Mr. Avinash R. Galugade and
Anant G. Wanpal
Both are 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 and the manner
in which it is to be performed.


FIELD OF INVENTION
This present invention relates to a device for testing durability and validity of high tension cables and is particularly applicable to durability testing of high tension cables used in automobiles.
BACKGROUND OF INVENTION
The high tension (HT) cable is generally used to connect the output of an ignition coil to the spark plug. The basic function of an HT cable is to deliver the high voltage developed across the secondary of the ignition coil to the spark plug in order to generate sparking required for ignition.
The timing signal for the spark ignition is generated by an Engine Management System Electronic Control Unit (EMS ECU) based on feedback signals from various sensors like engine rpm sensor, temperature sensor, vehicle speed sensor, lambda sensor, throttle position sensor etc. The status of signals from these sensors needs to be within the acceptable limits defined for satisfactory operation of the engine and the vehicle. Only then is the EMS ECU able to generate the ignition timing pulse.
The sensor inputs to the EMS ECU can be simulated by one of the following means:-
(a) Building independent set-ups for each sensor to obtain the required signal from the sensor. This would be a highly tedious and time consuming task.
(b) Simulating the signal outputs of the sensors with the use of signal generator or similar equipment having such capability. Hence, an additional test equipment is required for validation.
The above said system is costly and quite tedious to generate output signal. The present invention is aimed towards elimination of the use of EMS ECU and thereby its related sensors by the use of a simple circuit. The hardware was designed to
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generate an output equivalent to that of the EMS ECU to create the ignition spark required for validation of high tension cable.
OBJECTS OF INVENTION
The main object of this invention is to provide an apparatus for durability testing of high tension cables of automobile.
Another object of the present invention is to provide an apparatus for durability testing of high tension cables of automobile which simplifies the set-up required for durability testing of high tension cable.
Another object of the present invention is to provide an apparatus for durability testing of high tension cables of automobile which substitutes the vehicle components responsible for ignition spark generation with an alternative circuit performing the same function thereby resulting in minimizing the time, effort and cost involved in the set-up for the test.
Durability testing and validation is carried out prior to assembly of the high tension cables with automobiles.
STATEMENT OF INVENTION
The present invention relates to a device for testing durability of high tension cables of automobiles comprising; a timing pulse generator, ignition coil, ignition coil driver for driving the primary of said ignition coil, at least two high tension cables connected to two spark plugs wherein said timing pulse generator is interfaced with an integrated circuit of said ignition coil driver, said ignition coil driver having a transistor stage and high voltage power driver, is interfaced with ignition coil, said ignition coil is interfaced with the spark plug through the High tension cables, said
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spark plugs are being mounted separately facing earthed terminal to generate high voltage on ignition.
BRIEF DESCRIPTION OF INVENTION
In accordance with the present invention, a device for durability testing of high tension cable of automobile comprises :
Timing pulse generator (19), ignition coil driver (20) to drive the primary of the ignition coil, ignition coil (51), at least two high tension cable (56,57) , two spark plugs (52,53) and isolated earthed terminals (54,55) arranged in bakelite plate (58), said timing pulse generator (19) having at least four resistor ( 22,23,24 and 25), at least two capacitor (26,27), at least two diodes ( 28,29) all are interface with integrated circuit (21).
Ignition coil driver (20) having transistor stage and high voltage power driver (37). Said transistor stage comprising at least four resistor ( 32,34,36.39), a transistor (31) , at least four capacitors (33,35,38,40) which are earthed.
Said transistor stage is interfaced with high voltage power driver (37) .
Wherein output of said timing pulse generator (19) which is pulse waveform is fed to the said ignition coil driver.
Output of ignition coil driver (20) is fed to said ignition coil (51) which is interfaced with said spark plugs (52,53) through HT cables (56,57) .
BRIEF DESCRIPTION OF DRAWINGS
Figure-01 shows the block diagram of invention
Figure-02 shows timing pulse waveform at the output of IC 555.
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Figurue-03 shows high voltage pulses generated between the spark plug and earth
terminals.
Figure-04 shows the detailed circuit diagram of the invention.
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,
Now referring to figure-01 to 04. In accordance with the present invention, the device for durability testing of high tension cable of automobile comprises : Timing pulse generator, ignition coil driver to drive the primary of the ignition coil, ignition coil (51), at least two high tension cable (56,57) , two spark plugs (52,53) and isolated earthed terminals (54,55) arranged in bakelite plate (58),
The timing pulse generator has at least four resistor ( 22,23,24 and 25) , at least two capacitor (26,27), at least two diodes ( 28,29) all are interfaced with integrated circuit (21).
Ignition coil driver (20) having transistor stage and high voltage power driver (37). Said transistor stage comprising at least four resistor ( 32,34,36,39) , a transistor (31) at least four capacitors (33,35,38,40) which are earthed.
Said transistor stage is interfaced with high voltage power driver (37) .
Wherein output of said timing pulse generator which is pulse waveform is fed to the said ignition coil driver.
Output of ignition coil driver is fed to said ignition coil (51) which is interfaced with said spark plugs (52,53) through HT cables (56,57).
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The said spark plugs (52 & 53) and said earth terminals (54 & 55) were mounted facing each other on a bakelite plate (58). The gap between the said spark plug terminal and the earth terminal was set to 8 - 10 mm to generate the high voltage spark of the order of 15 to 20 kV. A high voltage of this magnitude could not be achieved by merely using a spark plug with a gap to its maximum possible extent. Hence, modified spark plugs and separate earth terminals have been used in the set¬up.
The timing pulse from the said EMS ECU was generated using an IC 555 (21) timer circuit and a power output stage to drive the primary winding of the ignition coil (51). The timing pulse with following parameters is generated by using IC 555 (21) in astable mode of operation (as shown in figure-02) :-ON time : 1.6 mseconds, OFF time : 23 mseconds Amplitude :+3.8 V.
The said resistor - capacitor network comprising of resistors (22) and (25) & capacitor (26) defines the ON & OFF time intervals of the pulses. Pin ( 5 ) of integrated circuit "IC" (21) is connected to ground through capacitor (27) for noise immunity. Resistors (23) and (24) are connected to the output pin of IC (21) as pull-up resistors to increase the drive for the subsequent power output stage. The trigger and threshold inputs (pin nos. 2 & 6 respectively of IC (21)) are connected together and to capacitor (26).
The diodes (28) and (29) are hardwired so as to provide two independent paths for charging and discharging capacitor (26). This thereby facilitates selection of the correct values of resistors (22) and (25) and capacitor (26) to achieve the desired ON and OFF timings of the pulses. The capacitor (26) charges towards the supply voltage through resistor (22) and diode (29). As soon as the charge on the capacitor reaches 2/3rd of the supply voltage, the capacitor (26) begins to discharge through resistor (25) and diode (28). The output of IC (21) switches to LOW. As soon as the
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voltage across the capacitor (26) reaches l/3r of the supply voltage, it again starts charging through resistor (22) and diode (29). The output of IC (21) switches to HIGH. This cycle continues to repeat with the capacitor alternately charging and discharging thereby resulting in a continuous stream of rectangular pulses at the output of IC (21).
The ON and OFF timings of the output waveform depend upon the values of resistors (22) and (25) and capacitor (26). The timings are calculated as follows :-
On time "Ton" = 0.693 * R22 * C26 Off time "Toff' = 0.693 * R25 * C26
The circuit for the ignition coil driver stage is supplied with 13.5 Voltage direct current (d.c). and is configured around a high voltage power driver (37) which is Insulated gate bipolar junction transistor ( IGBT) for ignition coil driver applications.
The timing pulse from integrated circuit "IC" (21) is applied to the power driver through a pre-amplifier stage. As the input to the high voltage power driver (37) requires higher current (greater than 20 mA) transistor (31) is used as pre-driver.
The resistors (23) & (24) act as biasing resistors while resistor (32) acts as transistor 1 collector & base bias to transistor 2. Resistors (34) & (36) constitute a divider network with a small time constant provided by capacitor (35). Capacitors (33) & (40) act as decoupling capacitors.
When the said high voltage power driver (37) is turned on, the integrated timer is started. If a valid falling edge has not been received after the time "Tssd", the said high voltage power driver (37) is automatically turned off slowly such that the controlled voltage "VCssd" is not exceeded when operated with the defined load. The soft shutdown is activated until the coil current has reached 0. If a valid falling
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edge is received after the time "Tssd", the edge is ignored and the soft shutdown is completed. The high voltage power driver (37) will not turn on again until a valid rising edge at the input is detected. The said time "Tssd" is adjusted by the value of the external capacitor (38) connected to the CSSD pin ( 6) of the high voltage power driver (37).
The current in the primary of the ignition coil (51) rises exponentially with time and is dependent on the power supply voltage & winding resistance & inductance of the coil. The dwell time or the charging time of the ignition coil (51) is adjusted to the desired timing pulse width using the timer circuit. The peak current thus achieved must be limited within the specification for the ignition coil (51) for safe operation.
The power output of the high voltage power driver (37) is connected to the primary side of ignition coil (51) which is supplied with a supply voltage of 13.5 Volt direct current (dc). The high voltage power driver (37) switches ON and OFF the primary winding of the ignition coil (51) at the rate defined by the timing pulse generator stage. The turning off of the high voltage power driver (37) induces a high voltage of the order of 15 to 20 kilovolts (as shown in figure-03) into the secondary winding of the ignition coil (51). The high voltage is then directed through the high tension cables (56 & 57) to the spark plugs to be released in the form of high voltage spark between the spark plug terminals (52 & 53) and earth terminals (54 & 55).
The test will give the information about the performance of Ht cables like degradation in resistance, failure of insulation etc.
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The details of the circuit components are as follows :-


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
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1. A device for testing durability of high tension cables of automobiles comprising; a timing pulse generator, ignition coil, ignition coil driver for driving the primary of said ignition coil, at least two high tension cables connected to two spark plugs wherein said timing pulse generator is interfaced with an integrated circuit of said ignition coil driver, said ignition coil driver having a transistor stage and high voltage power driver, is interfaced with ignition coil, said ignition coil is interfaced with the spark plug through the High tension cables, said spark plugs are being mounted separately facing earthed terminal to generate high voltage on ignition.
2. The device as claimed in claim 1, wherein said timing pulse generator has at least four resistors, two capacitors, and two diodes interfacing with said integrated circuit of said ignition coil driver.
3. The device as claimed in claims 1 & 2, wherein said transistor stage is interfaced with high voltage power driver.
4. The device as claimed in claims 1& 3, wherein said transistor stage having a transistor, at least four resistors, and four earthed capacitors
5. The device as claimed in claims 2 and 3, wherein said diodes are hard wired.
6. A device for testing durability of high tension cables of automobiles substantially as herein described and illustrated with particular reference to the fieures in the drawings.