A
unit injector
(
UI
) is a high-pressure integrated direct
fuel injection
system for
diesel engines
, combining the
injector
nozzle
and the
injection pump
in a single component. The
plunger pump
used is usually driven by a shared
camshaft
. In a unit injector, the device is typically lubricated and cooled by the fuel itself.
High-pressure injection delivers power and fuel consumption benefits over earlier lower-pressure fuel injection by injecting fuel as a larger number of smaller droplets, giving a much higher ratio of surface area to volume. This provides improved vaporisation from the surface of the fuel droplets and so more efficient combining of atmospheric oxygen with vaporised fuel, delivering more complete and cleaner combustion.
History
[
edit
]
In 1911, a patent was issued in
Great Britain
for a unit injector resembling those in use today to
Frederick Lamplough
.
[1]
Commercial usage of unit injectors in the
U.S.
began in early 1930s on
Winton
engines powering locomotives, boats, even
US Navy
submarines,
[2]
and in 1934, Arthur Fielden was granted U.S. patent No.1,981,913
[3]
on the unit injector design
[4]
later used for the
General Motors
two-stroke diesel engines
. Most mid-sized diesel engines used a single pump and separate injectors, but some makers, such as
Detroit Diesel
[5]
and
Electro-Motive Diesel
became well known for favouring unit injectors, in which the high-pressure pump is contained within the injector itself. E.W. Kettering's 1951 ASME presentation goes into detail about the development of the modern Unit injector.
[6]
Also Cummins PT (pressure-time) is a form of unit injection where the fuel injectors are on a common rail fed by a low-pressure pump and the injectors are actuated by a third lobe on the camshaft. The pressure determines how much fuel the injectors get and the time is determined by the cam.
In 1994,
Robert Bosch GmbH
supplied the first
electronic unit injector
for commercial vehicles, and other manufacturers soon followed. In 1995, Electromotive Diesel converted its
710
diesel engines to electronic fuel injection, using an
EUI
which replaces the UI.
Today, major manufacturers include
Robert Bosch GmbH
,
CAT
,
[7]
Cummins
, ?
[8]
Delphi
, ?
[9]
[10]
Detroit Diesel
,
Electro-Motive Diesel
.
[11]
Design and technology
[
edit
]
The design of the unit injector eliminates the need for high-pressure fuel pipes, and with that, their associated failures, as well as allowing for much higher injection pressure to occur. The unit injector system allows accurate injection timing, and amount of control as in the
common rail
system .
[12]
The unit injector is fitted into the engine
cylinder head
, where the fuel is supplied via integral ducts machined directly into the cylinder head. Each injector has its own pumping element, and in the case of electronic control, a fuel
solenoid valve
as well. The fuel system is divided into the low-pressure (<500
kPa
) fuel supply system, and the high-pressure injection system (<2000
bar
).
[13]
Technical characteristics:
- The special feature of the unit injector system is that an individual pump is assigned to each cylinder
- The pump and nozzle are therefore combined in a compact assembly which is installed directly in the cylinder head
- The unit injector system enables high injection pressures up to 2,200 bar.
Advantages:
- High performance for clean and powerful engine
- High engine power balanced against low consumption and low engine emissions
- High degree of efficiency due to compact design
- Low noise level due to direct assembly in the engine block
- Injection pressures up to 2,200 bar for the ideal combination of air-fuel mixture.
Operation principle
[
edit
]
The basic operation can be described as a sequence of four separate phases: the
filling phase
, the
spill phase
, the
injection phase
, and the
pressure reduction phase
.
A low-pressure
fuel delivery pump
supplies
filtered
diesel fuel
into the
cylinder head
fuel ducts, and into each injector fuel port of constant stroke pump plunger injector, which is
overhead camshaft
operated.
- 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 the electric
solenoid valve
remains de-energized the fuel line is open.
- Spill phase
- The pump element is on the way down, and as long as the solenoid valve remains de-energized the fuel line is open and fuel flows in into the return duct.
- Injection phase
- The pump element is still on the way down, the solenoid is now energised and the fuel line is immediately closed. The fuel cannot pass back into the 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
.
- Pressure reduction phase
- The plunger is still on its way down, the
engine ECU
de-energizes the solenoid when the required quantity of fuel is delivered. The fuel valve opens, fuel can flow back into the return duct, causing the pressure to drop. Which in turn causes the injector nozzle needle to shut; hence no more fuel is injected.
- Summary
- The start of an injection is controlled by the solenoid closing point, and the injected fuel quantity is determined by the closing time, which is the length of time the solenoid remains closed. The solenoid operation is fully controlled by the engine ECU.
Additional functions
[
edit
]
The use of electronic control allows for special functions; such as temperature controlled injection timing, cylinder balancing (smooth idle), switching off individual cylinders under part load for further reduction in emissions and fuel consumption, and multi-pulse injection (more than one injection occurrence during one engine cycle).
Usage & Applications
[
edit
]
Unit injector fuel systems are being used on a wide variety of vehicles and engines;
commercial vehicles
from manufacturers such as
Volvo
,
Cummins
,
Detroit Diesel
,
CAT
,
Navistar International
and passenger vehicles from manufacturers such as
Land Rover
and
Volkswagen Group
, among others, and
locomotives
from
Electromotive Diesel
.
The Volkswagen Group mainstream
marques
used unit injector systems (branded
”Pumpe Duse”
,
[14]
commonly abbreviated to
”PD”
) in their
Suction Diesel Injection
(SDI) and
Turbocharged Direct Injection
(TDI)
diesel engines
,
[15]
however this fuel injection method has been superseded by a common-rail design, such as the new 1.6 TDI.
In
North America
, the
Volkswagen Jetta
,
Golf
, and
New Beetle
TDI 2004?2006 are
Pumpe Duse
[16]
(available in both the MK4 and MK5 generations, with BEW and BRM engine codes respectively, older models use timing belt-driven injection pump).
[
citation needed
]
TDI engines incorporating PD unit injector systems manufactured by the Volkswagen Group were also installed on some cars sold in Europe and other markets where the diesel fuel was conveniently priced, amongst those there were some Chrysler/Dodge cars of the DaimlerChrysler era, e.g. the
Dodge Calibre
(MY07 BKD, MY08 BMR),
Dodge Journey
,
Jeep Compass
,
Jeep Patriot
.
Volkswagen Group major-interest
truck
and diesel engine maker
Scania AB
also uses the unit injector system, which they call “
Pumpe-Duse-Einspritzung
”, or
”PDE”
.
Hydraulically actuated electronic (HEUI) development and applications
[
edit
]
In 1993,
CAT
and
International Truck & Engine Corporation
[17]
introduced "hydraulically actuated electronic unit injection” (HEUI), where the injectors are no longer
camshaft
-operated and could pressurise fuel independently of engine RPM. First available on
Navistar's 7.3L /444 cuin
,
V8
diesel engine
. HEUI uses engine oil pressure to power high-pressure fuel injection, where the usual method of unit injector operation is with the
engine
camshaft.
HEUI applications included the Ford 7.3L and 6.0L
Power stroke
used between May 1993 and 2007. International also used the HEUI system for multiple engines including the
DT 466E
, DT 570,
T-444E
, DT-466?570, MaxxForce 5, 7, 9, 10, MaxxForce DT and VT365 engines.
[
dubious
–
discuss
]
Caterpillar
incorporated HEUI systems in the 3116, 3126, C7, C9 among others and the Daimler-Detroit Diesel Series 40 engine supplied by International also incorporated a HEUI fuel system. Isuzu fitted a HEUI system to their 3.0 LTR 4JX1 engine fitted to the Trooper and its variants. The HEUI system has been replaced by many manufacturers with
common rail
injection solutions, a newer technology, to meet better fuel economy and new emissions standards being introduced.
See also
[
edit
]
Notes
[
edit
]
- ^
DeLuca, Frank.
"History of fuel injection"
(PDF)
.
www.disa.it
. Archived from
the original
(PDF)
on 16 May 2011
. Retrieved
28 November
2009
.
- ^
"The Winton 201A Diesel Engine"
. Archived from
the original
on 26 June 2009
. Retrieved
28 November
2009
.
- ^
"United States Patent 1981913"
. Retrieved
28 November
2009
.
- ^
"A. Fielden Fuel Pump"
(PDF)
. Retrieved
28 November
2009
.
- ^
Asmus, A.; Wellington, B. (1994).
Diesel Engines and Fuel System
. Robert Bosch GmbH.
ISBN
1-56091-542-0
.
- ^
Kettering, E.W. (29 November 1951).
History and Development of the 567 Series General Motors Locomotive Engine
. ASME 1951 Annual Meeting. Atlantic City, New Jersey: Electromotive Division, General Motors Corporation.
- ^
"HEUI Fuel Systems"
(PDF)
.
Cat.com
. Caterpillar Inc. 1999
. Retrieved
4 November
2009
.
- ^
"Fuel Systems ? High-Pressure Injection (HPI) Systems"
.
Cummins.com
. Cummins Inc
. Retrieved
29 April
2015
.
- ^
"Injection Systems and Components ? Delphi E1 Diesel Electronic Unit Injector"
.
Delphi.com
. Delphi Automotive LLP. - Manufacturer Products : Commercial Vehicle Industry. Archived from
the original
on 30 December 2009
. Retrieved
4 November
2009
.
- ^
"Injection Systems and Components - Delphi E3 Diesel Electronic Unit Injector"
.
Delphi.com
. Delphi Automotive LLP. ? Manufacturer Products : Commercial Vehicle Industry
. Retrieved
4 November
2009
.
- ^
"Denso targets French, US automakers"
. Europe.autonews.com. 17 October 2005
. Retrieved
8 July
2018
.
- ^
"Pumpe Duse Einspritzung (PDE - UIS)"
.
kfztech.de
(in German)
. Retrieved
15 September
2009
.
- ^
"The efficient pump injector unit"
.
BoschAutoParts.co.uk
. Robert Bosch GmbH ? Automotive. Archived from
the original
on 31 March 2009
. Retrieved
30 September
2008
.
- ^
"1.9 litre TDI engine with Pump Duse"
(PDF)
. Auburn Hills, MI 48326, USA:
Volkswagen of America, Inc
. October 2003. Self-Study Program - Course Number 841303
. Retrieved
4 November
2009
.
{{
cite web
}}
: CS1 maint: location (
link
)
- ^
"Passenger-car systems - Unit Injector System (UIS)"
.
Bosch.de
. Robert Bosch GmbH - Automotive Technology - Diesel systems. Archived from
the original
on 29 October 2009
. Retrieved
4 November
2009
.
- ^
"Volkswagen Mk4 turbo diesel "how to" index, for 2004?2005 Jettas' and 2004?2006 New Beetles and Golfs"
.
- ^
"History of the HEUI - Hot Shot's Secret"
. Archived from
the original
on 11 December 2017
. Retrieved
18 April
2018
.
References
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]