Unit Injectors

8/4/2019 Unit Injectors

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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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Unit Injectors

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