FORM-2
THE PATENTS ACT, 1970
(39 of 1970)
COMPLETE SPECIFICATION
(Section 10)
“AN ANALOGUE EXHAUST GAS RECIRCULATION CONTROLLER”
MAHINDRA & MAHINDRA LIMITED.
Mahindra Towers,
Worli,
MUMBAI-400 018, Maharashtra State, India
An Indian Company registered under the provisions
of The Companies Act, 1956
The following specification particularly describes the nature of this invention and the manner in which it is to be performed:-


Present invention relates to emission control devices for use with internal combustion engines. More particularly, it is directed to an analogue electronic controller to govern the operation of the exhaust gases re-circulation device pertaining to automotive vehicles.
In the prior art, exhaust gas re-circulation is a technique commonly used for controlling the generation of undesirable pollutant gases and particulate matter in the operation of internal combustion engines.
Conventionally, exhaust gas re-circulation (EGR) valve is used for returning a part of exhaust gas to the engine intake manifold for reducing Nox contained in the exhaust gas of an internal combustion engine.
It is also known that the amount of obnoxious constituents in the exhaust gases of an automotive diesel engine can be brought down if a certain proportion of the exhaust gases from the exhaust manifold of the engine is fed back in the air-fuel mixture going into the intake manifold of the engine.
It is also known that generally a piping arrangement of suitable size is provided in an automotive diesel engine to connect the exhaust and intake manifolds to each other. A suitably designed vacuum controlled valve is installed in the said piping, which allows admission of controlled amount of exhaust gas into the intake manifold.
The controller of the valve receives the signals from various sensors fitted on the engine, imposes control logic and sends out electrical signals into pneumatic signals and sends them to the said EGR valve.
At present, when the vehicle is switched on, the controller checks all inputs like signals received from various sensors and the control programme is built into the controller. The controller is then ready to operate. The EGR valve is designed to be normally open at a certain combination of low speed and low-load conditions so that the
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full amount of predetermined proportion of the exhaust gas is admitted into the intake manifold of the engine. As the vehicle picks up speed, the EGR valve gradually closes according to the built-in logic of the controller and gets fully closed at another predetermined combinations of high speed and load conditions.
Typically, Engine parameters like engine temperature, potentiometer voltage of fuel injector pump, engine RPM and the feedback from the EGR valve are sensed and processed by the controller. But, failure of any of the sensors forces the controllers to suspend the normal control action of the EGR valve, resulting in its closure. However the failure of the EGR system does not render the vehicle inoperative. But such vehicles running on the road do pose danger to the environment by emitting Nox.
The present invention provides for an analogue electronic EGR controller as described hereunder.
The FIP (Fuel injecting pump) Potentiometer signal has the most significance impact on the basic EGR technique as with the change in the throttle position of the Fuel Injection Pump the output analogue signal from the rotary potentiometer is changed, the signal being voltage signal varying from .45 volts to 3.55 volts. Accordingly, the EGR controller of this invention uses only FIP signal, which is one of the main feature of this invention.
Another object of the present invention is that, the electronic circuit of this controller is analogue type as against microprocessor type, which makes the circuit adjustments easily possible during manufacturing of the EGR controller to suit individual application.
Therefore, an embodiment of the present invention is described with reference to the block diagrams in the accompanying drawings.
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Fig. 1 shows the EGR controller of this invention comprising functional blocks 1 to 9 as described below:
Fig.2 shows the percentage opening of EGR vale. Fig.3 shows the output voltage.
BLOCK 1: Power supply
This block provides a regulated supply voltage for the operation of all the other blocks and gives a stabilised voltage for use by the rest of the blocks consists of a voltage divider network to provide field ground reference for the ramp generator of block 2. This reference voltage is used as the ground for the ramp generator and is used to provide bias current to Block 2.
BLOCK 2: Ramp Generator
A Ramp signal is generated by charging and discharging of capacitors with the help of Integrated Circuits and resistors which also are the frequency and amplitude determining components. The Ramp signal output from this block is fed to Coupling block 3.
BLOCK 3: Coupling Block
The coupling block connects the ramp signal of Block 2 to the pulse width modulator block 5. An RC circuit in the block removes the DC offset. The combination of resistors forms a voltage dividing circuit, this combination is used to adjust the amplitude of the ramp signal, which is turn is used to adjust the "higher cut-off Point".
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BLOCK 4: DC Offset Adder
This block generates a DC voltage, which is added to the ramp signal of Block 2 and then is given to the pulse width modulator block 5. A resistor circuit is used to set the voltage value of DC offset to be added. This DC voltage value corresponds to the lower Cut-off Point shown in fig. 2. The offset added ramp signal is given to the PWM (pulse width modulator) of Block 5.
BLOCK 5: PWM Generator
This block generates the pulse width modulated signal, which ultimately drives the electrical coil of the pneumatic modulator.
This block, consisting of integrated circuit, generates the PWM signal that takes the DC-offset ramp signal from DC Offset Adder Block 4 as one input and from buffer amplifier of Buffer Amplifier Block 6 as another input and manipulates the pneumatic modulator coil in the Switching Block 9.
BLOCK 6: Buffer amplifier
This block receives the FIP POT signal from the rotary potentiometer installed on the Fuel injection pump and provides isolation for the Fuel Injector Pump (FIP) potentiometer(POT) signal from the rest of the circuit and prevents electrical loading of the FIP POT signal. An IC is used in unity gain mode to isolate the input FIP POT signal from the FIP potentiometer. This stage provides the necessary isolation for FIP POT signal from the FIP potentiometer and prevents electrical loading of the said FIP potentiometer.
BLOCK 7: Clamping Block
This block is used to clamp the buffered FIP POT signal to the value corresponding to the Lower Cut-off Point.
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The combination of zener diode, resistor and variable resistor in this block is used to adjust the overall zener voltage drop. This voltage in turn is used to clamp the buffered POT signal from FIP potentiometer to the value corresponding to the lower cut-off point.
BLOCK 8: Higher Cut-off Block
This block receives the FIP POT Signal from the rotary potentiometer installed on the Fuel injection pump and functions as a voltage comparator, which compares the voltage value that corresponds to the Higher Cut-off Point shown in fig. 3 with the FIP POT signal.
The Voltage comparator compares the value of voltage set by the combination of resistor and the variable resistor with that provided by the POT signal from FIP potentiometer. A resistor circuit is used to set the voltage value to correspond to the higher cut-off point shown in fig. 2. Resistors also provide the necessary bias current.
When the POT signal voltage value exceeds the set voltage value, the pneumatic modulator operated by the coil is switched off closing the EGR valve completely.
BLOCK9: Switching Block
This block provides the signals used for switching on and off the pneumatic modulator coil for which a power transistor is used. The Pneumatic modulator coil in turn controls the quantity of vacuum (exhaust) that is fed to the EGR valve.
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Working of the invention:
The input analogue signal is derived from the rotary Potentionmeter installed on the FIP (Fuel injection pump).
With the change in the throttle position of the FIP, the output analogue signal from this rotary potentiometer is changed. This FIP signal is a voltage signal. Varying from .45 to 3.55 volts. This input signal from rotary potentiometer is given to Block 6, that is buffer amplifier.
The output of the buffer amplifier is given to the Block 5 that is Pulse width modulator generator. This signal is compared with signal from Block 4.
Block 4 is combined signal from DC offset adder Block 4 and coupling circuit Block 3.
The output from the Block 5 is pulse width modulator signal that is given to the pneumatic modulator coil |g& The Pneumatic modulator coil in turn controls the vacuum of the EGR vale.
The pneumatic modulator is getting control signal, which is PWM signal controller. The output from this pneumatic modulator is modulator vacuum. The EGR valve opening is defined by this vacuum. Thus, the EGR valve is controlled.
Therefore, an analogue EGR controller to operate the exhaust gases recirculation in automotive vehicles comprises a power supply block 1 to provide a regulated supply voltage for the operation of all other blocks. A ramp generator block 2 a ramp generator block to generate a Ramp signal by charging and discharging of capacitors with the help of Integrated Circuits and resistors which also are the frequency and amplitude determining, output of which is fed to block 3. A coupling block 3, which connects the ramp signal to modulate block 5.
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A DC offset block 4 generates a DC voltage, which added to the signal of block 5, and a PWM generator, which generates PWM signal, which ultimately drives the electrical coil of the pneumatic modulator. A buffer amplifier block 6 to receive the FIP POT signal from the rotary potentiometer installed on the Fuel Injection Pump of the engine and prevent electrical loading of the POT signal.
A clamping block 7 a clamping block for adjusting the over all zener voltage to clamp the buffered FIP POT signal to the value corresponding to the Lower Cut-off Point
A higher cut-off point block 8 acts as a voltage comparator and compares the voltage that corresponds to the higher cut-off point with the FIP POT signal received from the FIP potentiometer installed on the FIP of the engine.
A switching block 9, which provides the signals, used for switching on and off the pneumatic modulator coil , which controls the quantity of vacuum (exhaust), which is fed to the EGR valve.
The said isolated input signal from FIP potentiometer is compared with RAMP signal in pulse width modulator to give output, which operates the pneumatic modulator, and the variable output vacuum of the said pneumatic modulator controls opening and closing of EGR valve.
The said rotary potentiometer installed on the fuel injection pump for generation of analogue signal, the signal being voltage signal varying from .45 volts to 3.55 volts.
The said higher cut-off point block is used to act as a voltage comparator to compare the set voltage value with the FIP potentiometer signal, the POT signal voltage value exceeds the set voltage value the pneumatic modulator coil is switched off closing the EGR valve completely.
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To sum up the following advantages are achieved:
1. With only one sensor on the engine and the analogue nature, the EGR controller of this invention becomes highly cost effective as compared with the existing EGR controller.
2. With only one sensor on the engine, enables the manufactures to use this EGR controller ion their vehicles resulting in a greater benefit of emission-control to the society at large.
3. The response time of this EGR controller is of the order of 10 microseconds. This response time results in quicker EGR valve positioning which, in turn, will minimize the Nox and particulate contents of exhaust gases.
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WE CLAIM:
1. An analogue exhaust gas re-circulation controller to operate the exhaust gases re-circulation in automotive vehicles comprising a rotary potentiometer installed on fuel injection pump in such a way that the change of throttle position of said pump alters the output analogue signal of said potentiometer; the said analogue signal of potentiometer is connected to the buffer amplifier; a ramp generator circuit through a DC offset adder circuit and out of said buffer amplifier through a clamping circuit connected to a pulse width modulator circuit by means of a coupling circuit; out put of the said pulse width modulator is connected to the switching block which actuates exhaust gas re-circulation valve; and a higher cut of voltage circuit with comparator is connected between the out of the said potentiometer and switching block.
2. A controller as claimed in claim 1 wherein the said buffer amplifier, ramp generator, DC offset adder circuit, clamping circuit, pulse width modulator are powered by a power supply circuit.
3. A controller as claimed in claims 1 and 2 wherein the analogue out of the said rotary potentiometer is .45 to 3.55 volts.
4. A controller as claimed in claims 1, 2 and 3 wherein the said analogue signal value exceeds set value the said exhaust gas re-circulation valve is switched off.