unit injectors
TRANSCRIPT
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By KUMAR
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1911- Frederick lamplough(UK) 1934-Arthur Fielden(US)-
General Motors
two-stroke diesel
engines
1994-Robert Bosch-1st
electronic Unit Injector
for commercial vehicles
http://en.wikipedia.org/wiki/General_Motorshttp://en.wikipedia.org/wiki/General_Motorshttp://en.wikipedia.org/wiki/General_Motors -
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It combines
the injection pump
and injection nozzle
in one unit (Unit Injector).
This technology is also known as the PUMP-NOZZLE SYSTEM
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filling phase
spill phase
injection phase
pressure reduction phase.
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Fill phase
The constant stroke pump element on the
way up draws fuel from the supply duct in
to the chamber, and as long as
electric solenoid valve remains de-
energized fuel line is open.
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Spill phase
The pump element is on the way down,
and as long as solenoid valve remains
de-energized the fuel line is open and
fuel flows in through into the return
duct.
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Injection phase
The pump element is still on the way down,the solenoid is now energized and fuel line is
now closed.
The fuel can not pass back into return duct,
and is now compressed by the plunger until
pressure exceeds specific "opening" pressure,
and the injector nozzle needle lifts, allowing
fuel to be injected into the combustion
chamber.
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Pressure reduction phase
The plunger is still on its way down, the engine
ECU de-energizes the solenoid when required
quantity of fuel is delivered, the fuel valveopens, fuel can flow back into return duct,
causing pressure drop, which in turn causes the
injector nozzle needle to shut, hence no more
fuel is injected.
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The start of an injection is controlled by the
solenoid closing point.
The injected fuel quantity is determined bythe closing time, which is the length of time
the solenoid remains closed.
The solenoid operation is fully controlled bythe engine ECU.
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The first generation of UIS engines incommercial vehicles were capable of aninjection pressure of1,600 bar.
The most recent stage of development of thesecond system generation achieves 1,800bar.
Since 2004, the third generation has been onthe market. This can realize injectionpressures of up to 2,200 bar.
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Applications: Commercial vehicles
Power output: 80 kW/cylinder
No. of cylinders: 8 (more with 2 ECUs)
Control: Electronic, solenoid valve
Injection pressure:1800 bar
Injected fuel quantity: 400 mm3 per stroke
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exhaust-gas values better than those
prescribed by the EU4 regulations.
good degree of efficiency and hightorque with low fuel consumption .
This means more performance, lowerfuel consumption and reduced exhaust
and noise emissions.
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1.Bosch was the worlds first manufacturerin 1995.
2.The feature of the UPS is that each engine
cylinder has a unit pump of its own.
3.high-pressure pump with integratedsolenoid valve, a short injection fuel-
injectionline, a pressure-delivery connection and aconventional nozzle-and-holder assembly.
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1.pressure is built up by the engine camshaft.
2.The cam is shaped in such a way that thedesired high pressure of the fuel is generated
as quickly as possible in the so-called plungerchamber
3.solenoid valve determines both start and
finish of injection.
4.The triggering duration determines theamount of fuel injected.
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Applications: Commercial vehicles
Power output: 80 kW/cylinder
No. of cylinders: 8 (more with 2 ECUs)
Control: Electronic, solenoid valve
Injection pressure: 1600 bar / 1800 bar Injected
fuel quantity: 150 mm3 / 400 mm3 per stroke
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1.injection pressures of up to 2,200 bar.
2.Engine manufacturers save development costs.
3.damaged pump/valve units are simple toexchange.
4.performances of up to 92 kW per cylinder and
with four to 18 cylinders.
5.A second control unit is required if the numberof cylinders exceeds eight.
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The primary disadvantages of direct injectionengines are complexity and cost.
Direct injection systems are more expensive
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