Unit injector

Last updated

Early Lucas electronic diesel unit injector Unit injector early.jpg
Early Lucas electronic diesel unit injector

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.

Contents

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

In 1911, a patent was issued in Great Britain for a unit injector resembling those in use today to Frederick Lamplough. [1]

Napier Deltic opposed-piston two-stroke, sectioned. The unit injectors are low down, below the yellow fuel passages, driven by a camshaft to their left and injecting into the centre of the cylinder liner (pale blue). Napier Deltic Diesel Engine National Railway Museum (4).jpg
Napier Deltic opposed-piston two-stroke, sectioned. The unit injectors are low down, below the yellow fuel passages, driven by a camshaft to their left and injecting into the centre of the cylinder liner (pale blue).

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

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:

Advantages:

Operation principle

Animated cut through diagram of a typical fuel injector (click to see animation) Injector3.gif
Animated cut through diagram of a typical fuel injector (click to see animation)
Delphi E1 UI on the Volvo D13A engine Unit injector.jpg
Delphi E1 UI on the Volvo D13A engine
Delphi E1 unit injector parts Delphi E 1 Unit Injector.JPG
Delphi E1 unit injector parts

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

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

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.

Bosch UI on a Scania R164 V8 engine Bosch Unit Injector.JPG
Bosch UI on a Scania R164 V8 engine

The Volkswagen Group mainstream marques used unit injector systems (branded ”Pumpe Düse”, [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 Düse [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-Düse-Einspritzung”, or ”PDE”.

Hydraulically actuated electronic (HEUI) development and applications

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

Notes

  1. DeLuca, Frank. "History of fuel injection" (PDF). www.disa.it. Archived from the original (PDF) on 16 May 2011. Retrieved 28 November 2009.
  2. "The Winton 201A Diesel Engine". Archived from the original on 26 June 2009. Retrieved 28 November 2009.
  3. "United States Patent 1981913" . Retrieved 28 November 2009.
  4. "A. Fielden Fuel Pump" (PDF). Retrieved 28 November 2009.
  5. Asmus, A.; Wellington, B. (1994). Diesel Engines and Fuel System. Robert Bosch GmbH. ISBN   1-56091-542-0.
  6. 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.
  7. "HEUI Fuel Systems" (PDF). Cat.com. Caterpillar Inc. 1999. Retrieved 4 November 2009.
  8. "Fuel Systems — High-Pressure Injection (HPI) Systems". Cummins.com. Cummins Inc. Retrieved 29 April 2015.
  9. "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.
  10. "Injection Systems and Components - Delphi E3 Diesel Electronic Unit Injector". Delphi.com. Delphi Automotive LLP. — Manufacturer Products : Commercial Vehicle Industry. Retrieved 4 November 2009.
  11. "Denso targets French, US automakers". Europe.autonews.com. 17 October 2005. Retrieved 8 July 2018.
  12. "Pumpe Düse Einspritzung (PDE - UIS)". kfztech.de (in German). Retrieved 15 September 2009.
  13. "The efficient pump injector unit". BoschAutoParts.co.uk. Robert Bosch GmbH — Automotive. Archived from the original on 31 March 2009. Retrieved 30 September 2008.
  14. "1.9 litre TDI engine with Pump Düse" (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)
  15. "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.
  16. "Volkswagen Mk4 turbo diesel "how to" index, for 2004–2005 Jettas' and 2004–2006 New Beetles and Golfs".
  17. "History of the HEUI - Hot Shot's Secret". Archived from the original on 11 December 2017. Retrieved 18 April 2018.

Related Research Articles

<span class="mw-page-title-main">Diesel engine</span> Type of internal combustion engine

The diesel engine, named after the German engineer Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is called a compression-ignition engine. This contrasts with engines using spark plug-ignition of the air-fuel mixture, such as a petrol engine or a gas engine.

<span class="mw-page-title-main">Fuel injection</span> Feature of internal combustion engines

Fuel injection is the introduction of fuel in an internal combustion engine, most commonly automotive engines, by the means of a fuel injector. This article focuses on fuel injection in reciprocating piston and Wankel rotary engines.

<span class="mw-page-title-main">Fuel pump</span> Pump

A Fuel pump is a component used in many liquid-fuelled engines to transfer the fuel from the fuel tank to the device where it is mixed with the intake air.

<span class="mw-page-title-main">Common rail</span> Engine fuel delivery method

Common rail direct fuel injection is a direct fuel injection system built around a high-pressure fuel rail feeding solenoid valves, as opposed to a low-pressure fuel pump feeding unit injectors. 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 vaporization from the surface of the fuel droplets, and so more efficient combining of atmospheric oxygen with vaporized fuel delivering more complete combustion.

<span class="mw-page-title-main">Cummins B Series engine</span> Reciprocating internal combustion engine

The Cummins B Series is a family of diesel engines produced by American manufacturer Cummins. In production since 1984, the B series engine family is intended for multiple applications on and off-highway, light-duty, and medium-duty. In the automotive industry, it is best known for its use in school buses, public service buses in the United Kingdom, and Dodge/Ram pickup trucks.

<span class="mw-page-title-main">Injection pump</span> Component of a diesel engine

An injection pump is the device that pumps fuel into the cylinders of a diesel engine. Traditionally, the injection pump was driven indirectly from the crankshaft by gears, chains or a toothed belt that also drives the camshaft. It rotates at half crankshaft speed in a conventional four-stroke diesel engine. Its timing is such that the fuel is injected only very slightly before top dead centre of that cylinder's compression stroke. It is also common for the pump belt on gasoline engines to be driven directly from the camshaft. In some systems injection pressures can be as high as 620 bar (8992 psi).

<span class="mw-page-title-main">PACE Award</span> Annual Automotive News award

The PACE Award is an annual award from Automotive News. The focus of the award is an innovation (i) developed primarily by a supplier, (ii) that is new to the automotive industry, (iii) that is in use, and (iv) that "changes the rules of the game". Awards have been given for products, materials, processes, capital equipment, software and services. A panel of independent judges from industry, finance, research, and academia choose finalists from the initial applicants, make site visits to evaluate the innovation, and then gather to select winners, independent of the sponsors. Winners to date include suppliers from Japan, Korea, China, the US, Canada, Brazil, Germany, France, Italy, Poland and other European countries. Among the most awarded companies over the years are BorgWarner, Delphi Automotive, Federal-Mogul, Valeo and PPG Industries as well as Robert Bosch GmbH, Gentex Corporation, and Siemens.

<span class="mw-page-title-main">Volkswagen Constellation</span> Motor vehicle

The Volkswagen Constellation is the flagship truck produced by the Brazilian manufacturer Volkswagen Truck & Bus since 2005. The line covering the 13-57 tonne gross combination mass (GCM) segment. It is produced at Resende in Brazil, and is primarily for the South American market.

<span class="mw-page-title-main">Unit pump</span> Modular high-pressure diesel injection system used in commercial vehicle diesel engines

The Unit Pump system is a modular high-pressure diesel injection system, which is closely related to the unit Injector system, and is designed for use in commercial vehicle diesel engines.

<span class="mw-page-title-main">Electronic Diesel Control</span> Diesel engine fuel injection control system

Electronic Diesel Control is a diesel engine fuel injection control system for the precise metering and delivery of fuel into the combustion chamber of modern diesel engines used in trucks and cars.

<span class="mw-page-title-main">TDI (engine)</span> Branded engine design

TDI is the Volkswagen Group's term for its current common rail direct injection turbodiesel engine range that have an intercooler in addition to the turbo compressor.

An electronically controlled unit injector (EUI) is a unit injector (UI) with electronic control. It performs the same function as a conventional unit injector in an internal combustion engine, such as in an on-road or off-road vehicle or a diesel-electric locomotive. The pressurized delivery of fuel is camshaft-driven, but the timing of the injector's internal operations are controlled by the engine control unit so as to achieve certain advantages.

<span class="mw-page-title-main">4 VD 14,5/12-1 SRW</span> Reciprocating internal combustion engine

The 4 VD 14,5/12-1 SRW is an inline four-cylinder diesel engine produced by the VEB IFA Motorenwerke Nordhausen from 1967 to 1990. The engine was one of the standard modular engines for agricultural and industrial use in the Comecon-countries. Approximately one million units were made.

Manifold injection is a mixture formation system for internal combustion engines with external mixture formation. It is commonly used in engines with spark ignition that use petrol as fuel, such as the Otto engine, and the Wankel engine. In a manifold-injected engine, the fuel is injected into the intake manifold, where it begins forming a combustible air-fuel mixture with the air. As soon as the intake valve opens, the piston starts sucking in the still forming mixture. Usually, this mixture is relatively homogeneous, and, at least in production engines for passenger cars, approximately stoichiometric; this means that there is an even distribution of fuel and air across the combustion chamber, and enough, but not more air present than what is required for the fuel's complete combustion. The injection timing and measuring of the fuel amount can be controlled either mechanically, or electronically. Since the 1970s and 1980s, manifold injection has been replacing carburettors in passenger cars. However, since the late 1990s, car manufacturers have started using petrol direct injection, which caused a decline in manifold injection installation in newly produced cars.

<span class="mw-page-title-main">Volkswagen-Audi V8 engine</span> Reciprocating internal combustion engine

The Volkswagen-Audi V8 engine family is a series of mechanically similar, gasoline-powered and diesel-powered, V-8, internal combustion piston engines, developed and produced by the Volkswagen Group, in partnership with Audi, since 1988. They have been used in various Volkswagen Group models, and by numerous Volkswagen-owned companies. The first spark-ignition gasoline V-8 engine configuration was used in the 1988 Audi V8 model; and the first compression-ignition diesel V8 engine configuration was used in the 1999 Audi A8 3.3 TDI Quattro. The V8 gasoline and diesel engines have been used in most Audi, Volkswagen, Porsche, Bentley, and Lamborghini models ever since. The larger-displacement diesel V8 engine configuration has also been used in various Scania commercial vehicles; such as in trucks, buses, and marine (boat) applications.

References