FORM 2
THE PATENT ACT, 1970,
(39 OF 1970)
&
THE PATENTS RULE, 2003
COMPLETE SPECIFICATION
(SEE SECTION 10; RULE 13)
"ANALOG STARTER RELAY CONTROL UNIT FOR ENGINE OF AUTOMOTIVE VEHICLES"
MAHINDRA & MAHINDRA LIMITED
AN INDIAN COMPANY,
R&D CENTER, AUTOMOTIVE SECTOR,
89, M.I.D.C, SATPUR,
NASHIK-422 007,
MAHARASHTRA, INDIA.
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES AND ASCERTAINS THE NATURE OF THIS INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED

FIELD OF INVENTION:-
The present invention is related to analog starter relay control unit for automotive vehicles. More particularly, the present invention is related to analog starter relay control unit that protect the starter motor against abnormal operating conditions in automotive vehicles.
BACKGROUND & PRIOR ART SEARCH:-
Existing technology on starter relay control unit for engine use microcontroller based Digital control circuit taking one or more external input control signals like engine speed, Alternator pulse output, etc. to control the starter relay energizing time. Typically, a vehicle engine has a starter motor which is energized through a starter relay while the ignition switch is moved to 'start' position. During this time the starter relay energize the solenoid of starter motor so that the pinion is engaged with the ring gear of crank shaft and allows current to flow to the starter motor. The reliability of starter motor is affected due to following application conditions thereby leading to starter motor failure.
- Continuously holding the ignition key in start position even after engine started as the driver of the vehicle is not able to ascertain engine running. This leads to flow of short circuit through ignition key (terminal 50) leading to starter motor failure due to overheating.
- Failure of ignition switch leading to switch get stuck at start position which again gives the same effect of the previous case.
- Continuous cranking of engine for long duration at one time due to the fact that the engine does not start, the commutator and brushes of starter motor will be destroyed due to overheating.
- Inching of vehicle with starter motor. Since the engine is cranked against compression and also has to move vehicle, high current is drawn by the starter motor leading to overheating and failure.
- Prevent engaging of starter pinion while engine is running.

In order to protect the starter motor during the above said application conditions, the present invention provides an innovative and low cost solution as described below.
OBJECTIVES OF THE PRESENT INVENTION:-
Main object of the present invention is to provide innovative analog starter relay control unit for engine of an automotive vehicle.
Another object of the present invention is to provide innovative analog starter relay control unit for engine of an automotive vehicle that protects the starter motor against abnormal operating conditions in automotive vehicles.
Further object of the present invention is to provide cost effective solution for protecting the starter motor of a vehicle against abnormal operating conditions in automotive vehicle.
STATEMENT OF INVENTION:-
Accordingly invention provides an unit analog starter relay control for engine of automotive vehicles comprises a first transistor switch connected between the starter relay out put and ground with base connected to the ground through fourth resistance and the said base connected to collector through a fifth resistance; a second transistor switch connected between the said the base of said first transistor and the ground with the base biased by a grounded third resistance; a third transistor switch connected between the base of said second transistor through a second resistance and a first zenor diode in series and ground with eighth resistance biased grounded base connected to the starter relay out put; a R-C series circuit having grounded first capacitor and first resistance in series connected to the said relay out put through a first diode and the said first capacitor and first resistance series joint connected to the said first zenor diode; and a fourth transistor switch connected between the base of said first transistor and ground with the base to be connected to the generator out put through a second zenor

diode, a sixth resistance and a second diode in series and a grounded second capacitor and a seventh resistance connected to the said series joint of the said sixth resistance and a second diode.
BRIEF DESCRIPTION OF THE FIGURES:-
Further objectives and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein,
Figure 1 shows conventional / existing (prior art) starter relay control unit.
Figure 2 shows the Analog Starter Relay Control Unit to protect starter motor against abnormal operating conditions as per the present invention.
Figure 3 shows the representative Analog Starter Relay control circuit in accordance with the present invention.
Figure 4 shows flow chart on operation of Starter relay control unit while cranking condition.
Figure 5 shows flow chart on operation of Starter relay control unit while engine running condition.
DETAILED DESCRIPTION OF THE PRESENT INVENTION:-
The innovative starting system of the present invention for an engine comprises of ignition switch, starter relay and starter motor, a low cost analog electronic circuit without a micro-controller which is connected in series between the ignition switch and starter relay by which the starter relay input supply is disconnected after predetermined time delay even if the driver of the vehicle attempts to continuously start the vehicle by engaging the ignition switch in start position. Also, the circuit will disable the starter relay engagement while engine is in running condition.

In order to protect the starter motor during the above said application conditions, the invention provides an innovative and low cost solution by which the power supply to the starter relay is disconnected after a predetermined delay which is decided by a series RC circuit, wherein the capacitor charging time constant determines the starter relay "ON" time.
The representative Analog Starter Relay control circuit is shown in figure 3 and described below: -
An analog starter control relay unit for engine of automotive vehicles comprises a first transistor switch T1 connected between the starter relay out put and ground with base connected to the ground through fourth resistance R4 and the said base connected to collector through a fifth resistance R5. A second transistor switch T2 connected between the said the base of said first transistor T1 and the ground with the base biased by a grounded third resistance R3. A third transistor switch T3 connected between the base of said second transistor T2 through a second resistance R2 and a first zenor diode Z1 in series and ground with eighth resistance R8 biased grounded base connected to the starter relay out put. A R-C series circuit having grounded first capacitor C1 and first resistance R1 in series connected to the said relay out put through a first diode D1 and the said first capacitor C1 and first resistance R1 series joint connected to the said first zenor diode Z1. A fourth transistor switch T4 connected between the base of said first transistor T1 and ground with the base to be connected to the generator out put through a second zenor diode Z2 , a sixth resistance R6 and a second diode Z2 in series and a grounded second capacitor C2 and a seventh resistance R7 connected to the said series joint of the said sixth resistance and a second diode D2.
a) Starter relay control while cranking
In the representative electronic circuit shown in Figure 3, Transistor T1 is used in series between the starter relay output and ground. When the ignition

switch is rotated towards "START" position, the power supply from the ignition switch enables the Transistor T1 "ON" by the base trigger through the diode and resistor circuit. At the same time, the RC circuit (R1 & C1) shown will charge the capacitor "C1" with a time constant based on the R1 & C1 values. While the capacitor voltage reaches the threshold level, exceeding the break down voltage level of the zener diode (Z1), the transistor T2 will be switched ON, there by switching "OFF" the transistor T1 which will cut off the starter relay output, there by disabling the starter relay. The starter relay enable duration depends on the time constant of R1&C1 which can be tuned to achieve required cranking time. In order to discharge the capacitor C1 for the next cycle and to have the consistent cranking time, transistor T3 is used which will discharge capacitor C1 so that the time constant for each cranking cycle can be maintained constant.
Referring to figure 4, as the proposed circuit use the ignition switch output (T50) supply for its operation, without requiring any additional interface signals, the hardware can be integrated into the starter relay. Hence, the starter relay with analog control circuit can be adopted in the existing vehicle wiring without any modifications.
b) Starter relay control while engine running
By giving Alternator "W" output signal (which is a pulse having frequency depending on engine speed) to additional transistor (T4) switching circuit, the transistor T1 can be switched off in order to disable starter relay, thereby avoiding starter pinion reengaging while engine is in running condition. The R6, R7 & C2 network is used to adjust the threshold level of voltage generated during cranking and steady state engine running. Those values are adjusted in such a way that the voltage at cathode of zener diode Z2 will be above the zener break down voltage which will switch ON T4. This in turn switch OFF T1, disabling the starter relay. During cranking, while the engine speed is below than idling speed, the voltage across C7 will be less than zener break down of 22. Hence, transistor T4 will not get switched ON, and

T1 transistor drive will not get affected as. understood from the working flowchart as shown in Figure 5.
The technical advantages achieved by this invention are:
- It protects the starter motor against abnormal operating conditions in automotive vehicles.
- The invention can be integrated with the starter relay with alternator "W" terminal signal input to avoid reengaging of starter pinion while engine is in running condition.
- The invention controls the energizing time of the starter motor relay of a vehicle using low cost simple RC circuit without a microcontroller to control the starter relay "ON" time.
- It is a cost effective solution of protecting the starter motor
It should be understood that the present invention is not to be limited by the exact details of the illustrated embodiment. However, it is to be taken as the preferred example of the invention and that various changes may be resorted to by a person skilled in the art without departing from the spirit of the invention. Also, the terminologies used herein are for the purpose of description and should not be regarded as limiting.

WE CLAIM:-
1. An analog starter control relay unit for engine of automotive vehicles comprises a first transistor switch connected between the starter relay out put and ground with base connected to the ground through fourth resistance and the said base connected to collector through a fifth resistance; a second transistor switch connected between the said the base of said first transistor and the ground with the base biased by a grounded third resistance; a third transistor switch connected between the base of said second transistor through a second resistance and a first zenor diode in series and ground with eighth resistance biased grounded base connected to the starter relay out put; a R-C series circuit having grounded first capacitor and first resistance in series connected to the said relay out put through a first diode and the said first capacitor and first resistance series joint connected to the said first zenor diode; and a fourth transistor switch connected between the base of said first transistor and ground with the base to be connected to the generator out put through a second zenor diode, a sixth resistance and a second diode in series and a grounded second capacitor and a seventh resistance connected to the said series joint of the said sixth resistance and a second diode.
2. An analog starter control relay unit as claimed In claim 1 wherein the said first transistor, second transistor and fourth transistor are of NPN type and the said third transistor is PNP type.
3. An analog starter control relay unit as claimed in claims 1 and 2 wherein value of the first capacitor and first resistance selected to achieve required cranking time
4. An Improved starting system of automobile engine comprises of ignition
switch, starter relay and starter motor, the improvement involves providing
an analog starter control relay unit of claim 1 connected in series
between the ignition switch and starter relay.