CR Tecnology

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Common Rail Systems by LiebherrHigh-Performance and Fuel-Efficient

2 Common Rail Systems by Liebherr

Since the establishment of the company, Liebherr has focused on concentrating its core compe-tencies within the company in order to directly control decisive technologies. For the development of diesel engines, fuel injection and engine management are becoming increasingly crucial due to increasing emission and consumption requirements. Therefore it logically follows that Liebherr has developed its own engine management system and its own Common Rail fuel injection system in order to have all system expertise available in the area of engine development and production.

The fuel injection technology was developed in house and has been used successfully since the beginning of 2012 in Liebherr diesel engines with 97/68 EC stage IIIB and USA EPA CARB Tier 4 interim emission levels. All engine series from 4-cylinder in-line engines up to 12-cylinder V engines are supported. Starting in 2014, Liebherr will offer the fuel injection system for all engine manufacturers. This applies to both road and non-road applications in the medium and heavy-duty range as well as for stationary engines.

High quality fuel injection systems by Liebherr

3Common Rail Systems by Liebherr

High quality fuel injection systems by Liebherr

The Common Rail System Page 4

Development Page 6

Manufacturing expertise Page 8

Quality and reliability Page 10

Engine management Page 12

Efficient pressure generation and storage

Page 14

Fuel injection characteristics Page 16

Liebherr diesel engines with Common Rail fuel injection system

Page 18

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High-pressure pump

A 2-cylinder in-line pump with an oil lubri-cated crankcase is used for engines with a capacity of up to 2 litres per cylinder. An active high-pressure valve provides protection against overpressure by absorbing undesired pressure peaks.

LiebherrEngine Control Unit

Injector

Injector

Pressure Pipe Connector

Pressure Pipe Connector

High Pressure Pump

Pre-filter

Filter

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High Pressure

Low Pressure

High pressure sensor

Pressure control valve

Volumetric control valve

Electric wiring

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The Common Rail System

Engine management

The engine control unit optimizes injection start and duration in real-time. This makes the opti-mum management of fuel combustion possible in every operating point.

Injector

Injectors with solenoid-drive devel-oped and manufactured in house guarantee injection pressures of up to 2,000 bar and ensure extremely fine fuel spray. The opening and closing flank of the nozzle needle speed can be independently adjusted.

Liebherr’s modular Common Rail System consists of four main components: high-pressure pump, pressure accumulator, injector and electronic control unit. This innovative system supports compliance with applicable and future emission standards for diesel engines and makes high performance possible with the low-est possible fuel consumption. With precise multiple injection at pressures of up to 2,000 bar, constant performance and low emission values are guaranteed over the entire service life of the engine.

Reduced emissions The optimised injection process via a 3-way servo valve in the Common Rail injector and the injection nozzle which is perfectly matched to the cylinder, significantly reduce fuel consumption and the level of raw emissions

Efficiency and economy

Liebherr uses a 2-cylinder in-line pump with oil lubrication for engines with a capacity of up to 2 litres per cylinder. This delivers up to 300 litres of fuel per hour at a pres-sure of 2,000 bar. In conjunction with the engine control unit, the pressure is regulated exclusively by a volume flow control valve which only supplies the pump with pre-cisely the right amount of fuel that the combustion engine requires. Injection only takes place when the solenoid injector is energized by the Liebherr control unit for the injection start calculated in real-time. During each cycle of the injector, a volume of switching leakage, not greater than 30 ml/min at full load, returns to the fuel tank. There is no permanent high-pressure control leakage.

Reliability All components are specifically designed for the highly dynamic loads in off-highway applications. To ensure that development is consistently focused on these require-ments, a detailed product validation plan has been created for the development process. In addition to endurance testing with variable load profiles, this also includes various environmental tests.

Fuel Tank

Pre-filter


Modular design

All components of the Common Rail System are suitably dimensioned for the wide spec-trum of use and are designed as a modular system. For example, the injector is de-signed so that it can be used with different injection amounts both with 4 and 6 cylinder in-line engines as well as in 8 and 12 cylin-der v-engines.


Research and development

The Liebherr fuel injection system was created after a development period of only four years. A fundamental aspect for this was the use of the simultaneous engineering concept. Selected components were completely newly developed in order to create a reliable state-of-the-art complete system. Modern development tools such as the Finite Element Method (FEM) and Computational Fluid Dynam-ics analysis (CFD) contributed towards the constant optimisation of the system and its modules.

Finite Element Method

Many components of a fuel injection system are sub-jected to cyclic loads. When testing with FEM, particular emphasis is placed on determining and then optimising fatigue resistance. Stress and deformation are, of course, also inspected under operating and peak loads and the component geometries are adapted accordingly.

CFD simulation Through CFD analysis, flow effects within the compo-nents can be simulated. All flow-carrying components of the Common Rail System were inspected intensively by Liebherr calculation engineers using this method. In this way, for example, the effect of cavitation erosion on the nozzle needles and nozzles could be minimised, which occurs due to the very high flow speeds.

Product validation Product validation is an integral part of the development process of Common Rail Systems. The validation plan is oriented towards excellent system reliability and availabil-ity under demanding environmental conditions, as well as towards a long product service life. It includes many measurements and tests to be performed during develop-ment, which are carried out by Liebherr on the numerous hydraulic and engine test benches.

CFD simulation

CFD simulations were used, for example, to optimise nozzle needle and nozzle geometry. In this way, the areas of fuel recondensation are kept separate from the nozzle walls.

Finite Element Method (FEM)

FEM calculations can be used to rep-resent, for example, which areas of the injector housing are decisive for fatigue resistance. Production processes are adjusted in order to maximise fatigue resistance.

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Autofrettage

With autofrettage, the parts of the Common Rail System subjected to high pressure are autofrettaged at up to 10,000 bar, which makes them fatigue-endurable.

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Manufacturing expertise

Micro-precision manufacturing

Negative imprints of injection spray holes of various injection nozzles, which are pro-duced using the manufacturing processes of Electro Discharge Machining (EDM) and Hydro Erosive Grinding (HEG).

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Injector assembly

The injectors assembled in the clean room are subjected to various tests as early as during assembly, for ex-ample pneumatic tests, to check the fitted O-rings.

Liebherr Common Rail Systems are not only developed but also manufactured in Bulle, Switzerland. The micro-precision parts for the injectors are manufactured at an additional site in Germany. Large investments in modern production and test facilities made fast start-up times for series production possible. The latest knowledge about material flow and other process sequences were taken into account when constructing the facilities.

Micro-precision manufacturing

The geometry of the nozzle hole and its process- reliable manufacturing are especially important for the required fine fuel spray. Therefore Liebherr has introduced Electro Discharge Machining (EDM) and Hydro Erosive Grinding (HEG) manufacturing processes at its own micro-precision manufacturing site.

Assembly in a clean room

To ensure the functional capability of the high-precision parts in the Common Rail System, extreme care is nec-essary during assembly. The parts must be absolutely dust and oil-free, therefore they are cleaned in four sepa-rate washing cycles. High pressure pump, high pressure connectors and injector parts are assembled in a class 7 clean room after acclimatization to ensure absolute assembly precision.

Assembly monitoring

On the assembly line, which is configured for series pro-duction and largely automated, all manual process steps are monitored by the system technology. Operating errors are practically eliminated by the intelligent quality man-agement system (Poka Yoke).


Spray pattern test bench

With the aid of a camera, the test bench measures the geometry of the spray pattern of the injec-tor/nozzle. Due to the very high speed of the injection process, this places high demands on the measurement system as well as on the synchronisation of the measurement and control loop.


Geometry measurements

Modern measurement instruments are used to measure the geometry of the Liebherr Common Rail System parts. The photo to the left shows the evaluation of the round surfaces of the con-trol valve.

Quality and reliability

Injector leak test

With the aid of a camera system, theleak tightness of the nozzle/nozzle needle is checked. In the process, the camera records any drop formation on the nozzle which is subjected to high pressure.

Uncompromising quality assurance is decisive for the high reliability and availabil-ity of the fuel injection systems. Liebherr uses an up-to-date computer-assisted quality management system (CAQ system) that is implemented as early as the production creation process and covers the entire product life cycle. Statistical assessments, FMEA (failure mode and effects analyses) and CIP (Continuous Improvement Processes) are examples of a consistent process philosophy. Many efficient test benches that were specially developed for Liebherr are used to test the highly precise components of the Common Rail System.

Comprehensive controls on incoming material

In the incoming goods department, all purchased parts of the Common Rail fuel injection system are already checked for the highest quality with the aid of highly modern measurement instruments. This includes 3D coordinate measuring devices, roughness and contour measuring systems as well as an opti-cal surface scanner.

Series testing Before delivering the fuel injection systems, the high pres-sure pumps, injectors and high pressure connectors are tested 100 % for functional and service life-relevant qual-ity features, such as flow rate, torque or leakage. The Data Matrix Code (DMC) is used to track the assembled parts and assign them to the corresponding system components.

High-pressure pump test bench

The test schedule, according to which every pump is tested, includes eleven test points with approx. 20 attributes. The pa-rameters measured in the individual test points are evaluated and stored in order to guarantee lasting traceability.

Leak test bench Injectors, pressure pipe connections and high pressure pumps are subjected to a leak test on the leak test bench at multiple stages up to 2,000 bar. This ensures that there is no leakage to the outside or within the system on the high-pressure sealing surfaces.

Highest quality standards

Quality assurance at the Bulle site is certified according to DIN EN ISO 9001/2008 and operates in accordance with VDA standards (reliability control group).


Solenoid drive

A solenoid drive opens and closes the Common Rail injector nozzle. It is controlled by the Liebherr engine control unit.


Engine management

Engine control unit

The engine control unit is developed together with the Liebherr Compe-tence Center for electronics in Lindau. The circuit boards are assembled on their own production equipment.

Application / diagnostics program

With the diagnostic software, which is developed by Liebherr the engine parameters can be optimally ad-justed to the application and errors can be read out and analysed. The diagnostics software is efficient and easy to use.

The Liebherr engine management system records numerous physical engine variables for the optimal control of the fuel injection system. The engine data is processed in the control unit using configurable mathematical models. In this way, the control system can be easily adjusted to different numbers of cylinders and capacities. In addition to the engine control unit, Liebherr also offers an application and diagnostics program in order to provide both the implementer as well as the service operator with optimal support.

Optimal control and monitoring

Comprehensive functions and configuration possibilities of the engine control unit ensure optimal control of the fuel injection system for reliable engine operation. The fuel injection timing and the fuel amount are calculated indi-vidually for each cylinder, so that the injector’s solenoid valve can be correspondingly actuated. The control signal and number of injections will be adapted to the require-ments of the corresponding engine or the application.

Engine system monitoring

The 97/68 EC and USA EPA CARB emissions standards make engine system monitoring necessary. The Liebherr engine management adopts permanently to monitoring and controlling various exhaust gas after-treatment sys-tems such as particulate filters or SCR catalytic convert-ers and exhaust gas recycling.

Highest safety standards

The Liebherr engine control unit was developed according to the requirements of off-highway applications as well as international standards such as ISO15998/ISO13849 and ISO61508 SIL2. All electronic compo-nents fulfil high requirements for reliability, service life and safety and are well suited for rough application areas. For the specific requirements of mining devices, the plugs correspond with degree of protection IP6k9k, both in a connected and disconnected state.

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Pressure generation

At maximum pump speed, 300 litres of fuel are aspirated, condensed and delivered through the high pressure connectors into the injectors every hour.

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Flow curves

The high pressure pump for engines with a capacity of up to a 2 litres per cylinder supplies up to 300 l/h at a pressure of 2,000 bar.

High degree of pump efficiency

The hydraulic degree of efficiency of the CRS system high pressure pump for engines with a capacity of up to 2 litres per cylinder is above 80% at a pressure of 2,000 bar.

Efficient pressure generation and storage

To ensure good pressure stability between injection cycles, the pressure generat-ed by the pump is stored temporarily in so-called high pressure connectors. In the Liebherr Common Rail System, this pressure accumulator has a non-return valve with a choke, which minimises the expansion of the pressure waves, increasing injection performance. Depending on customer requirements and the conditions of the engine installation space, Liebherr also offers a fuel injection system with a conventional continuous rail.

Volume flow regulating valve

A special feature of the Liebherr system is the volume flow control valve that exclusively controls the pressure and only supplies the pump with precisely the right amount of fuel that the combustion engine requires. The system’s pressure sensor is fitted in addition to an active control valve directly on the pump.

System integration The link between the mechanics, electronics and com-bustion is formed by system integration, which develops all required injection and pressure control functions as well as diagnostics and correction algorithms, equipping them with a data set and validating them.

Engine speed [rpm]

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3-way servo valve

The injector has an additionalhydraulic intermediate valve with whichthe nozzle needle can be closedvery quickly and, independently of that,can be opened with adjustable speed.


Injection rates

The diagram on the left shows the fuel supply during the injection process at various opening speeds of the servo valve depending on a set pressure between 200 and 2,000 bar. Closing takes place independently.

Quantity characteristic map

At pressures from 200 to 2,000 bar, the quantity characteristic curves of the Liebherr injectors are set apart by a very high linearity, i.e. even injection amounts, as shown in the diagram on the left.

Fuel injection characteristics

With the Common Rail technique, multiple injections per combustion cycle are possible. A stable multiple injection of the Liebherr system, together with the high injection pressure of 2,000 bar, guarantees a highly efficient combus-tion. Therefore, it is possible to minimise soot particles and NOx emissions already inside the engine. The most complete fuel combustion possible ensures maximum energy use, which thereby reduces fuel consumption.

Stable multiple injection

With multiple injection, pre-injection is very important for quiet engine operation, the main injection is important for opti-mal power development/maximum torque and post-injection is important for reduction of emissions. Liebherr adapts the vari-ous injection processes specifically to every engine and appli-cation. The 3-way servo valve ensures that the injection spray is established moderately. Finally, the injection process is com-pleted by closing the nozzle needle very quickly. This results in a very clear boundary for the individual injections and a precisely measured fuel amount - both of which are decisive factors for an optimal combustion process.

High degree of efficiency

An efficient energy conversion from high pressure generation up to the injection pressure is decisive for a high degree of efficien-cy of the injection system. Liebherr uses many design measures in order to connect the injector nozzles throttle-free, if possible, to the high pressure pipe system, for example hole filters.

Minimum switching leakage

Liebherr injectors are set apart by their very small amount of switching leakage. In the case of system injectors for engines with a capacity of up to 2 litres per cylinder, at full load, it is a maximum of 30 ml/min. This provides the following advantages.• higher degree of efficiency and therefore lower fuel consumption• lower leakage temperatures, therefore lower cooling

requirements• good tolerance of various fuel qualities• optimal preconditions for start-stop operation – as the

system pressure remains when the engine is shut off, restarting is accelerated


6-cylinder in-line engine D936/9464-cylinder in-line engine D934/944


Liebherr offers two versions of the Common Rail System. The fuel injection system for engines with a capacity of up to 2 litres per cylinder is available for all engine manufacturers starting in 2014. Starting in 2016, the program will be expanded with a system for engines with a capacity of up to 5 litres per cylinder.

Liebherr’s Common Rail fuel injection system is suitable for engines in road and non-road applications in the medium and heavy-duty area as well as for stationary engines.

Product range

8-cylinder V-engine D9508 12-cylinder V-engine D9512

Common Rail System for engines with a capacity of up to 2 litres per cylinder

System pressure 250-2,000 bar

Control leakage / injector 30 ml/min at 2,000 bar

Number of cylinders 4-12

Number of injection cycles 3

Pump delivery volume 300 l/h

Injection volume 5-300 mg

Nozzle flow rate 600-1,300 ml / 30 sec

Emission standards97/68 EC stage IIIB and EPA CARB Tier 4i97/68 EC stage IV and EPA CARB Tier 4fEURO VI

Common Rail System for engines with a capacity of up to 5 litres per cylinder

System pressure 250-2,000 bar

Control leakage / injector 40 ml/min at 2,000 bar

Number of cylinders 8-20

Number of injection cycles 3

Pump delivery volume 900 l/h

Injection volume 10-1,000 mg

Nozzle flow rate 1,400-4,000 ml / 30 sec

Emission standardsUSA EPA CARB Tier 297/68 EC stage III

Liebherr-Component Technologies

Liebherr-Component Technologies AG, based in Bulle, Switzerland, is responsible for all activities of the components division of the Liebherr group. The companies and business areas belonging to this division are specialised in the development, design, manufacture and reconditioning of high-performance components in the field of mechanical, hy draulic and electrical drives and control technology. The sale of components to customers outside the Liebherr group of companies is managed centrally by Liebherr-Components AG in Nussbaumen, Switzerland.

Biberach: large diameter bearings, gearboxes, rope winches, switchgear, electronics, electrical machines

Lindau: electronics, power electronics

Bulle: diesel engines, gas engines, splitter boxes, axial piston units, injection systems

Ettlingen: remanufactured components

Kirchdorf: hydraulic cylinders

Monterrey: large diameter bearings

Many Years of ExperienceLiebherr has decades of experience in the manufacture of high-quality components used in cranes and construc-tion machines, in the mining industry, maritime applica-tions, wind turbines, in vehicle technology or in aerospace and transportation technology.

The Right Solution for Every NeedA high degree of vertical integration and the use of flexi-ble, state-of-the-art production systems allow Liebherr to offer its customers tailor-made solutions. Liebherr is your partner for joint success – from the product idea to devel-opment, manufacture and first installation right through to series production. For the various components of the drivetrain, Liebherr also offers remanufacturing in various degrees in a dedicated factory.

System Solutions from a Single SourceComponents from Liebherr are perfectly matched to each other with regard to operation. Depending on the require-ment, individual components from the wide product range can be expanded through to the complete drivetrain. This results in impressive system solutions which can be inte-grated into a variety of applications.

Highest Quality Standards and Long Service Life All components meet the very highest demands for func-tional reliability and durability, even under extreme loads and harsh conditions. Elaborate quality management and extensive analysis and test procedures are practised throughout the entire development and production process, guaranteeing reliability and long component service life.

www.liebherr.com

Dalian: gearboxes

Liebherr-Components AGPostfach 222, CH-5415 Nussbaumen AG +41 56 296 43-00, Telefax +41 56 296 43-01www.liebherr.com, E-Mail: [email protected]

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